Heat-sensitive recording body

Abstract

The present invention provides a heat-sensitive recording body which exhibits excellent boil resistance in a non-printed portion.　A heat-sensitive recording body 1 according to the present invention has a structure in which a heat-sensitive recording layer 4 and a small contact angle layer 5 are laminated in this order on a base material 2. The small contact angle layer 5 is directly laminated on the heat-sensitive recording layer 4. The heat-sensitive recording layer 4 contains a compound represented by formula (1) as a developer. The water contact angle of the small contact angle layer 5 is not more than 40°. In formula (1), each R1 is a C1-12 hydrocarbon group that may have a substituent, and a plurality of R1s may be the same or different. A1 is a C1-4 hydrocarbon group. When there are two or more A1s, the plurality of A1s may be the same or different. Each n represents an integer of 0-4, and a plurality of ns may be the same or different.

Description

Thermal recording device

[0001] This invention relates to a thermal recording material.

[0002] Thermal recording media produce color through a chemical reaction when heated by a thermal head or similar device, resulting in a recorded image. They are used in a wide range of applications, including as recording media for fax machines, automatic ticket vending machines, and scientific measuring instruments, as well as as thermal recording labels used on various products such as food pouches.

[0003] Incidentally, food pouches are sometimes immersed in hot water (boiled) to disinfect their contents. However, the printed portion of a thermal recording medium usually disappears when boiled, and the non-printed portion may change color when boiled. Therefore, boiling food pouches with thermal recording mediums attached has been contraindicated. For this reason, thermal recording mediums are sometimes required to have the property that the printed portion does not disappear even when boiled, i.e., the printed portion is boil-resistant. Similarly, thermal recording mediums are sometimes required to have the property that the non-printed portion does not change color when boiled, i.e., the non-printed portion is boil-resistant.

[0004] As a thermal recording material that exhibits excellent boil resistance in both printed and unprinted areas, for example, a thermal recording material has been proposed in which an underlayer containing hollow particles having a specific porosity, a thermal recording layer containing a specific color developer, and a topcoat layer containing a specific lubricant are laminated in this order on a substrate (see, for example, Patent Document 1).

[0005] Patent No. 7456711

[0006] However, conventional thermal recording media, which are considered to have excellent boil resistance, may gradually discolor after being removed from hot water, even if the non-printed areas do not show a clear change in color. If the degree of discoloration after boiling is severe, the contrast difference between the printed and non-printed areas decreases, leading to problems such as reduced visibility and aesthetics of the printed area. For this reason, there is a need for thermal recording media that can further suppress discoloration of the non-printed areas not only during boiling but also after boiling, that is, thermal recording media with improved boil resistance of the non-printed areas.

[0007] This invention was conceived under these circumstances, and its purpose is to provide a thermal recording material with excellent boil resistance in the non-printed areas.

[0008] As a result of diligent research to achieve the above objective, the inventors of the present invention have found that a thermal recording material having a low contact angle layer with a water contact angle of 40° or less on a thermal recording layer containing a specific color developer exhibits excellent boil resistance in the non-printed areas. The present invention was completed based on these findings.

[0009] In other words, the present invention provides a thermal recording body comprising a substrate, a thermal recording layer, and a low contact angle layer in that order, wherein the low contact angle layer is directly laminated on the thermal recording layer, the thermal recording layer contains a compound represented by the following formula (1) as a color developer, and the water contact angle of the low contact angle layer is 40° or less. (In formula (1), R １ is a hydrocarbon group having 1 to 12 carbon atoms, which may have substituents, and a plurality of R １ They may be the same or different. A １ A is a hydrocarbon group having 1 to 4 carbon atoms. １ If there are two or more A １ n can be the same or different. n represents an integer from 0 to 4, and multiple n values ​​can be the same or different.

[0010] The low-contact stratum corneum described above preferably contains a core-shell type resin as a binder.

[0011] The above-mentioned core-shell type resin preferably includes a core-shell type acrylic resin.

[0012] In the above-described core-shell type resin, it is preferable that the ratio of the mass of the shell portion to the mass of the core portion (mass of the shell portion / mass of the core portion) is 0.5 or more.

[0013] The above low-contact stratum corneum may further contain an epichlorohydrin-based resin.

[0014] The content ratio of the above binder is preferably 80% by mass or more relative to 100% by mass of the total solid content of the low-contact stratum corneum.

[0015] It is preferable that the above heat-sensitive recording layer does not contain a water-soluble resin.

[0016] It is preferable that the above heat-sensitive recording layer contains at least one selected from the group consisting of kaolin, calcined kaolin, aluminum oxide, aluminum silicate, and kaolinite as a filler.

[0017] It is preferable to provide an anchor layer containing an acrylic resin as a binder between the above base material and the above heat-sensitive recording layer.

[0018] It is preferable that the content ratio of the above binder is 50% by mass or more with respect to 100% by mass of the total solid content of the above anchor layer.

[0019] It is preferable that the content ratio of the above acrylic resin is 70% by mass or more with respect to 100% by mass of the total amount of the binder in the above anchor layer.

[0020] The above anchor layer may contain hollow particles as a filler. When the above anchor layer contains the above hollow particles, the content ratio of the above hollow particles is preferably 10% by mass or less with respect to 100% by mass of the total solid content of the above anchor layer.

[0021] The above anchor layer may not contain hollow particles.

[0022] It is preferable to provide a top coat layer on the surface of the above low contact angle layer opposite to the above heat-sensitive recording layer.

[0023] It is preferable that the above base material is any one of laminated paper, non-woven fabric, synthetic resin film, or synthetic paper.

[0024] According to the present invention, it is possible to provide a heat-sensitive recording medium excellent in boil resistance of a non-printing portion.

[0025] It is a schematic cross-sectional view showing one embodiment of the heat-sensitive recording medium of the present invention. It is a schematic cross-sectional view showing another embodiment of the heat-sensitive recording medium of the present invention.

[0026] [Thermosensitive Recording Medium] The thermosensitive recording medium of the present invention includes at least a substrate, a thermosensitive recording layer, and a low contact angle layer. The low contact angle layer is directly laminated on the thermosensitive recording layer. Further, the thermosensitive recording layer contains at least a developer. Furthermore, the developer contains a compound represented by the following formula (1). Also, the water contact angle of the low contact angle layer is 40° or less.

[0027]

[0028] In formula (1), R １ is a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, and a plurality of R １ may be the same or different. A １ is a hydrocarbon group having 1 to 4 carbon atoms. When there are two or more A １ a plurality of A １ may be the same or different. n represents an integer of 0 to 4, and a plurality of n may be the same or different.

[0029] Hereinafter, an embodiment of the thermosensitive recording medium of the present invention will be described in detail based on the drawings, but the present invention is not limited to the following embodiments.

[0030] FIG. 1 is a schematic cross-sectional view showing an embodiment of the thermosensitive recording medium of the present invention. In FIG. 1, the thermosensitive recording medium 1 includes a substrate 2, a thermosensitive recording layer 4, and a low contact angle layer 5 in this order. At this time, the low contact angle layer 5 is laminated so as to directly contact one surface of the thermosensitive recording layer 4.

[0031] FIG. 2 is a schematic cross-sectional view showing another embodiment of the thermosensitive recording medium of the present invention. The thermosensitive recording medium 1 shown in FIG. 2 has a structure in which the thermosensitive recording medium 1 shown in FIG. 1 further includes an anchor layer 3 and a top coat layer 6. Specifically, the anchor layer 3 is a layer provided between the substrate 2 and the thermosensitive recording layer 4. Also, the top coat layer 6 is a layer provided on the surface of the low contact angle layer 5 opposite to the thermosensitive recording layer 4. At this time, the substrate 2 and the anchor layer 3, the anchor layer 3 and the thermosensitive recording layer 4, and the low contact angle layer 5 and the top coat layer 6 are laminated so as to directly contact each other. Further, in the thermosensitive recording medium 1, the top coat layer 6 is located on one surface, and the substrate 2 is located on the other surface.

[0032] (Substrate) The substrate 2 can function as a support in the thermal recording body 1 of the present invention. The thermal recording body 1 is superior in handling and other aspects by having the substrate 2. As the substrate 2, for example, paper such as fine paper, art paper, coated paper, kraft paper, laminated paper obtained by laminating these paper substrates with a thermoplastic resin such as polyethylene, porous materials such as nonwoven fabric, synthetic resin film, and synthetic paper can be used. Examples of resins constituting the above synthetic resin film and synthetic paper include polypropylene, polyethylene, polyethylene terephthalate, polystyrene, and polycarbonate. Only one of the above resins may be used, or two or more may be used. The above synthetic resin film may be stretched or not. Furthermore, the substrate 2 may be a single layer or a multi-layer structure which is the same or has different compositions and thicknesses.

[0033] From the viewpoint of maintaining strength even when boiled, the base material 2 is preferably one of laminated paper, nonwoven fabric, synthetic resin film, or synthetic paper, and more preferably one of synthetic resin film or synthetic paper.

[0034] The thickness of the substrate 2 is not particularly limited, but is preferably 5 μm to 150 μm, and more preferably 10 μm to 100 μm. When the thickness is within the above range, it is easier to achieve more appropriate coating properties and support properties, and handling properties may be better.

[0035] (Anchor layer) The anchor layer 3 is a layer intended to improve the adhesion between the substrate 2 and the thermal recording layer 4. The anchor layer 3 may be omitted if it is not needed, in which case the thermal recording layer 4 can be directly laminated on one side of the substrate 2. The anchor layer 3 includes, for example, a binder. The anchor layer 3 may also contain other components. Examples of these other components include antistatic agents, wetting agents, fillers, etc.

[0036] Examples of the above-mentioned binders include known resins. These binders include acrylic resins such as acrylic resins, styrene-acrylic resins, acrylic-urethane resins, acrylamide resins, and vinyl acetate-acrylic resins; maleic acid resins such as maleic acid resins, styrene-maleic acid resins, and olefin-maleic acid resins; styrene-butadiene rubber (SBR); and polyvinyl alcohol resins (PVA) such as fully saponified polyvinyl alcohol resins and partially saponified polyvinyl alcohol resins. Furthermore, the binder may be starch, casein, gelatin, polyamide, polyacrylamide, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, polyvinyl acetate, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methylvinyl-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyurethane, polystyrene, polyvinylpyrrolidone, acrylonitrile, methyl vinyl ether, etc. The resins may all be modified resins obtained by known methods. These binders can be used individually or in combination of two or more.

[0037] In particular, from the viewpoint of achieving good adhesion even when the base material contains resin, and from the viewpoint of superior stability because it does not swell easily when boiled, the binder preferably contains an acrylic resin.

[0038] The binder content is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on 100% by mass of the total solid content of the anchor layer 3. Furthermore, the binder content is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on 100% by mass of the total solid content of the anchor layer 3.

[0039] The content of the acrylic resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of the total amount of binder in the anchor layer 3. Alternatively, the content of the acrylic resin may be 100% by mass, based on 100% by mass of the total amount of binder in the anchor layer 3.

[0040] In this specification, "acrylic resin" means a resin obtained by homopolymerizing acrylic monomers (monomers having a (meth)acryloyl group) (acrylic resin), and / or a resin obtained by copolymerizing an acrylic monomer with other monomers (monomers other than acrylic monomers that can copolymerize with acrylic monomers). Here, the acrylic monomer and the other monomer may each be one type or two or more types. Also, when simply referred to as "acrylic," unless otherwise specified, it means (meth)acrylic acid (salt) and / or (meth)acrylic acid ester. Here, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid. Also, "(meth)acrylic acid (salt)" means (meth)acrylic acid and / or (meth)acrylic acid salt.

[0041] The salts in the above-mentioned (meth)acrylate salts are not particularly limited and include, for example, ammonium salts such as ammonia; alkanolamine salts such as triethanolamine, diethanolamine, and monoethanolamine; alkylamine salts such as methylamine, ethylamine, diethylamine, and triethylamine; polyamine salts such as diethyleneamine and diethylenetriamine; alkali metal salts such as lithium, sodium, and potassium; alkaline earth metal salts such as magnesium and calcium; and polyvalent metal salts such as zinc and iron. These salts can be used individually or in combination of two or more.

[0042] The composition forming the above resin may be a solid, an emulsion, or a solution. From the viewpoint of excellent handling and coating properties, an emulsion or a solution is preferred.

[0043] Examples of the antistatic agents mentioned above include low-molecular-weight antistatic agents such as surfactants; high-molecular-weight antistatic agents such as acrylic-styrene copolymers; and conductive metal compounds such as tin oxide. These antistatic agents can be used individually or in combination of two or more.

[0044] The content ratio of the antistatic agent is not particularly limited. For example, it may be 1% by mass or more, or 3% by mass or more, based on 100% by mass of the total solid content of the anchor layer 3. Furthermore, the content ratio of the antistatic agent may be 40% by mass or less, or 30% by mass or less, based on 100% by mass of the total solid content of the anchor layer 3.

[0045] Examples of the wetting agents mentioned above include surfactants. Known surfactants can be used as appropriate, including, for example, anionic surfactants such as sodium dioctyol succinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and alkyl ether sulfates; and nonionic surfactants such as acetylene glycol-based surfactants and polyoxyalkylene alkyl ethers. Among these, acetylene glycol-based surfactants such as acetylene glycol and alkylene oxide adducts of acetylene glycol are preferred. These wetting agents can be used individually or in combination of two or more.

[0046] Examples of the above-mentioned fillers include inorganic fillers such as kaolin, calcined kaolin, aluminum oxide, aluminum silicate, heavy calcium carbonate, light calcium carbonate, titanium dioxide, barium sulfate, silica gel, activated clay, talc, clay, kaolinite, diatomaceous earth, white carbon, magnesium carbonate, magnesium oxide, magnesium hydroxide, aluminum hydroxide, and zinc oxide; and organic fillers such as hollow particles and non-hollow particles. The above-mentioned fillers may or may not contain hollow particles. These fillers can be used individually or in combination of two or more types.

[0047] The materials constituting the hollow and non-hollow particles are not particularly limited, and examples include thermoplastic resins. Examples of thermoplastic resins include acrylic resins such as acrylic resins (especially polymethyl methacrylate: PMMA), acrylonitrile resins, acrylic-polyvinylidene chloride resins, acrylic-polyvinylidene chloride-acrylonitrile resins, acrylic-acrylonitrile resins, styrene-acrylic resins, acrylic-urethane resins, acrylamide resins, vinyl acetate-acrylic resins, etc.; polyvinylidene chloride resins such as polyvinylidene chloride resins and polyvinylidene chloride-acrylonitrile resins; polystyrene resins; urea-formaldehyde resins; polyolefin resins such as polyethylene resins and polypropylene resins; polyvinyl chloride resins; polyvinyl acetate resins; and polybutadiene resins. Furthermore, these resins may be modified resins obtained by known methods. These materials constituting the hollow and non-hollow particles can be used individually or in combination of two or more types.

[0048] The average particle diameter of the hollow particles is not particularly limited, but is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 3 μm or more, and especially preferably 5 μm or more. Alternatively, the average particle diameter may be 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. When the average particle diameter is within the above range, it is easier to achieve more appropriate heat insulation, and heat resistance and density of the printed area can be improved. In this specification, "average particle diameter" refers to the particle diameter (D50, median diameter) at 50% of the cumulative value of the particle size distribution measured by laser diffraction and scattering. The average particle diameter can be measured by laser diffraction and scattering, for example, using the product name "MT3300EX-II" manufactured by Microtrac-Bell. Hereinafter, "average particle diameter" refers to the median diameter measured by the above method.

[0049] The content ratio of the above-mentioned filler is not particularly limited. For example, it may be 1% by mass or more, 3% by mass or more, or 5% by mass or more, relative to 100% by mass of the total solid content of the anchor layer 3. Furthermore, the content ratio of the above-mentioned filler may be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less, relative to 100% by mass of the total solid content of the anchor layer 3. Furthermore, the content ratio of the above-mentioned hollow particles is not particularly limited. For example, it may be within the above range relative to 100% by mass of the total solid content of the anchor layer 3. Furthermore, the content ratio of the above-mentioned hollow particles is not particularly limited. For example, it may be 5% by mass or less, 3% by mass or less, or 1% by mass or less, relative to 100% by mass of the total solid content of the anchor layer 3.

[0050] The content ratio of the above-mentioned hollow particles is not particularly limited. For example, it may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or 1% by mass or less, based on 100% by mass of the total amount of the filler. Furthermore, the content ratio may be 0% by mass, based on 100% by mass of the total amount of the filler.

[0051] The coating amount (dry mass) of the anchor layer 3 is preferably, for example, 0.1 g / m². ２ ~10g / m ２ More preferably 0.2 g / m ２ ~5.0 g / m ２ Therefore, when the amount of coating is within the above range, it is easier to achieve more appropriate properties such as heat insulation, cushioning, and adhesion between the substrate 2 and the heat-sensitive recording layer 4. In this specification, "dry mass" refers to the mass of non-volatile components (solids) excluding solvents (volatile components) such as water contained in the coating liquid or its raw materials.

[0052] (Thermal Recording Layer) The thermal recording layer 4 is a layer that develops color through a chemical reaction when heated by a thermal head or the like, and forms a recorded image on the thermal recording body 1. The thermal recording layer 4 contains at least a color developer. The color developer contains at least a compound represented by the following formula (1). By using such a color developer, it is possible to achieve both good color development with high sensitivity and good boil resistance so that the color does not disappear even when boiled. The thermal recording layer 4 may further contain other components as needed. Examples of these other components include dyes, binders, fillers, lubricants, crosslinking agents, wetting agents, sensitizers, etc.

[0053]

[0054] In formula (1), R １ is a hydrocarbon group having 1 to 12 carbon atoms, which may have substituents, and a plurality of R １ They may be the same or different. A １ A is a hydrocarbon group having 1 to 4 carbon atoms. １ If there are two or more A １ n can be the same or different. n represents an integer from 0 to 4, and multiple n can be the same or different.

[0055] In the above formula (1), multiple R １ -SO ３ - is directly bonded to the carbon atoms that make up the benzene ring. Multiple R １ -SO ３ The substitution positions of the - may be the same or different between one benzene ring and the other benzene ring. １ -SO ３ - The substitution position and R on the other benzene ring １ -SO ３ The substitution positions of the hyphens are preferably the same, and more preferably both are at position 3. In this specification, in formula (1) above, the carbon atom on the benzene ring bonded to the nitrogen atom of the urea group (-NH-CO-NH-) is defined as position 1.

[0056] In the above formula (1), the above R １Among the "carbon groups having 1 to 12 carbon atoms that may have substituents," examples of the "carbon groups having 1 to 12 carbon atoms" include linear alkyl groups having 1 to 12 carbon atoms, branched alkyl groups having 3 to 12 carbon atoms, alicyclic alkyl groups having 3 to 12 carbon atoms, aryl groups having 6 to 12 carbon atoms, or monovalent groups having 4 to 12 carbon atoms formed by bonding two or more different groups from these groups. Furthermore, the multiple "carbon groups having 1 to 12 carbon atoms that may have substituents" may be the same or different from each other. Note that in this specification, the above R １ In the phrase "hydrocarbon groups having 1 to 12 carbon atoms," the number of carbon atoms refers to the total number of carbon atoms, including the carbon atoms in the substituents if the substituents contain carbon atoms.

[0057] The above-mentioned "linear alkyl group having 1 to 12 carbon atoms" may be a linear saturated alkyl group or a linear unsaturated alkyl group. Examples of the above-mentioned "linear alkyl group having 1 to 12 carbon atoms" include a methyl group, an ethyl group, an n-propyl group, an allyl group, an n-butyl group, a 3-butenyl group, an n-hexyl group, a lauryl group, and the like.

[0058] The above-mentioned "branched alkyl group having 3 to 12 carbon atoms" may be a branched saturated alkyl group or a branched unsaturated alkyl group. Examples of the above-mentioned "branched alkyl group having 3 to 12 carbon atoms" include i-propyl group, i-butyl group, s-butyl group, t-butyl group, and 2-ethylhexyl group.

[0059] The above-mentioned "alicyclic alkyl group having 3 to 12 carbon atoms" may be either an alicyclic saturated alkyl group or an alicyclic unsaturated alkyl group. Examples of the above-mentioned "alicyclic alkyl group having 3 to 12 carbon atoms" include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, and the like.

[0060] Examples of the above-mentioned "aryl group having 6 to 12 carbon atoms" include unsubstituted aryl groups such as phenyl, 1-naphthyl, and 2-naphthyl groups.

[0061] Examples of the above-mentioned "monovalent groups having 4 to 12 carbon atoms, formed by the bonding of two or more distinct groups" include "monovalent groups having 7 to 12 carbon atoms, formed by the bonding of an aryl group with one or more linear alkyl groups," "monovalent groups having 9 to 12 carbon atoms, formed by the bonding of an aryl group with one or more branched alkyl groups," and "monovalent groups having 4 to 12 carbon atoms, formed by the bonding of an alicyclic alkyl group with one or more linear alkyl groups."

[0062] The above-mentioned "monovalent group having 7 to 12 carbon atoms bonded to an aryl group and one or more linear alkyl groups" is preferably "a monovalent group having 7 to 12 carbon atoms bonded to a phenyl group and one to three linear alkyl groups having 1 to 4 carbon atoms." Specifically, examples include p-tolyl group, m-tolyl group, o-tolyl group, 2,5-dimethylphenyl group, 2,4-dimethylphenyl group, 3,5-dimethylphenyl group, 2,3-dimethylphenyl group, 3,4-dimethylphenyl group, mesitylene group, p-ethylphenyl group, etc. Alternatively, aralkyl groups such as benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, p-methylbenzyl group, m-methylbenzyl group, m-ethylbenzyl group, and p-ethylbenzyl group may also be used. Furthermore, the above-mentioned "monovalent group having 7 to 12 carbon atoms, in which a phenyl group is bonded to 1 to 3 linear alkyl groups having 1 to 4 carbon atoms" may have substituents as described below.

[0063] The above-mentioned "monovalent group having 9 to 12 carbon atoms bonded to an aryl group and one or more branched alkyl groups" is preferably a "monovalent group having 7 to 12 carbon atoms bonded to a phenyl group and one or two branched alkyl groups having 3 to 4 carbon atoms." Specifically, examples include the p-i-propylphenyl group and the p-t-butylphenyl group. Furthermore, the above-mentioned "monovalent group having 7 to 12 carbon atoms bonded to a phenyl group and one or two branched alkyl groups having 3 to 4 carbon atoms" may have substituents as described later.

[0064] The above-mentioned "monovalent group having 4 to 12 carbon atoms bonded to an alicyclic alkyl group and one or more linear alkyl groups" is preferably a "monovalent group having 7 to 12 carbon atoms bonded to an alicyclic alkyl group having 6 to 12 carbon atoms and one to three linear alkyl groups having 1 to 4 carbon atoms." Specifically, examples include a 4-methylcyclohexyl group and a 4-methylcyclooctyl group. Furthermore, the above-mentioned "monovalent group having 7 to 12 carbon atoms bonded to an alicyclic alkyl group having 6 to 12 carbon atoms and one to three linear alkyl groups having 1 to 4 carbon atoms" may have substituents as described later.

[0065] The above-mentioned "substituent" is a group having at least one atom other than carbon and hydrogen atoms (heteroatom). In this specification, the heteroatom in the "substituent" is assumed to be bonded to a carbon atom in the "carbon 1 to 12 hydrocarbon group". Specifically, examples of the above-mentioned "substituent" include halogen atoms, hydroxyl groups, alkoxy groups, oxo groups (=O), etc. Furthermore, the above-mentioned "substituent" may or may not contain a carbon atom. If the above-mentioned "substituent" contains a carbon atom, the number of carbon atoms in the substituent is preferably 1 to 6, and more preferably 1 to 4. There may or may not be multiple above-mentioned "substituents". Furthermore, the substitution position of multiple "substituents" is on one of the benzene rings R １ and R on the other benzene ring １ The R on one of the benzene rings may be the same or different from each other. １ The substitution position of the substituent in and the R on the other benzene ring １ It is preferable that the substitution positions of the substituents in the compound are the same.

[0066] In the above formula (1), the above R １ In particular, a monovalent group having 7 to 10 carbon atoms, formed by bonding a phenyl group to 1 to 3 linear alkyl groups having 1 to 4 carbon atoms, is preferred, and a monovalent group having 7 to 10 carbon atoms, formed by bonding a phenyl group to 1 linear alkyl group having 1 to 4 carbon atoms, is more preferred. Specifically, the above R １The R is preferably a p-tolyl group, m-tolyl group, o-tolyl group, 2,5-dimethylphenyl group, 2,4-dimethylphenyl group, 3,5-dimethylphenyl group, 2,3-dimethylphenyl group, 3,4-dimethylphenyl group, or mesitylene group, with the p-tolyl group being more preferred. １ In that case, the color development and shelf life may be better.

[0067] In the above formula (1), A １ Among the carbon atoms constituting the benzene ring, the above R １ -SO ３ A can bond to a carbon atom that is not bonded to it. Also, A １ If there are two or more A １ The substitution positions may be the same or different between one benzene ring and the other. １ The preferred substitution positions are the 2nd, 4th, 5th, and 6th positions.

[0068] A above １ Examples of hydrocarbon groups having 1 to 4 carbon atoms include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, and t-butyl group.

[0069] In the above formula (1), n ​​is preferably an integer between 0 and 2, more preferably an integer between 0 and 1, and even more preferably 0.

[0070] The compounds represented by formula (1) above include, but are not limited to, the following specific compounds.

[0071] In other words, the compounds represented by the above formula (1) are N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methylphenyl]urea, N,N'-di-[3-(p-xylenesulfonyloxy)phenyl]urea, and N,N'-di-[3-(m-xylenesulfonyloxy)phenyl]urea Examples include N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-methylphenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-ethylphenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-5-methylphenyl]urea, and N,N'-di-[3-(benzenesulfonyloxy)-4-propylphenyl]urea. Among these, the compound represented by formula (1) above is particularly preferred, namely the compound represented by formula (1a) below, i.e., N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0072]

[0073] The above-mentioned color developer may contain the compound represented by formula (1) alone, or it may contain two or more compounds represented by formula (1). Furthermore, the above-mentioned color developer may contain color developers other than the compound represented by formula (1) (other color developers) to the extent that they do not impair the effects of the present invention.

[0074] Other color developers include, for example, 3-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate (trade name: TG-MD), N-3-[(p-toluenesulfonyl)oxy]phenyl-N'-(p-toluenesulfonyl)-urea (trade name: PF-201), N-[2-(3-phenylureido)phenyl]-benzenesulfonamide (trade name: NKK-1304), 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophen Known non-phenol colorants such as [nyl)ureido]diphenylsulfone (trade name: UU), 4,4'-isopropylidenediphenol (BPA), 4,4'-dihydroxydiphenylsulfone (BPS), 4-allyloxy-4'-hydroxydiphenylsulfone (trade name: BPS-MAE), 4-allyloxy-4'-hydroxydiphenylsulfone (trade name: TGSA), 2,2'-diallyl-4,4'-sulfonyldiphenol (trade name: TG-SH) , 4-hydroxy-4'-isopropoxydiphenylsulfone (trade name: D-8), N-(m-tolylaminocarbonyl)-methionine, N-(m-tolylaminocarbonyl)-phenylalanine and N-(phenylaminocarbonyl)-phenylalanine, 1,1-bis(p-hydroxyphenyl)cyclohexane, 1,1-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl) Phenyl)butane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2'-methylenebis(4-chlorophenol), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, poly(4-hydroxybenzoic acid), benzyl 4-hydroxybenzoate, 2,4-bis(phenylsulfonyl)phenol, 3,5-bis(α-methylbenzyl)salicylic acid, bis[4-(n-octyloxycarbonylamino)zinc salicylate], 4,Known color developers include 4'-bis(p-tolylsulfonylaminocarbonylamino)diphenylmethane, 4-hydroxybenzenesulfonanilide, N-(2-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, N-(4-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, 4-[4-(4-{4-[4-(1-methylethoxy)phenylsulfonyl]phenoxy}butoxy)phenylsulfonyl]phenol, and 4-tert-butylphenol / formaldehyde polycondensate.

[0075] The content of the compound represented by formula (1) above is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of the total amount of developer in the thermal recording layer 4. The above total content may be substantially 100% by mass, based on 100% by mass of the total amount of developer in the thermal recording layer 4. When the above total content is within the above range, it is easier to make the boil resistance more appropriate. Furthermore, the content of the compound represented by formula (1a) above is preferably within the above range, based on 100% by mass of the total amount of developer in the thermal recording layer 4.

[0076] The content of the above-mentioned color developer is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on 100% by mass of the total solid content of the thermal recording layer 4. Furthermore, the content of the above-mentioned color developer is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less, based on 100% by mass of the total solid content of the thermal recording layer 4.

[0077] Examples of the above dyes include 2'-bromo-6'-(dibutylamino)-3'-methylspiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one, 3-(1-ethyl-2-methylindole-3-yl)-3-(4-diethylamino-2-methylphenyl)-4-azaphthalide, 6-(dimethylamino)-3,3-bis[4-(dimethylamino)phenyl]-1(3H)-isobenzofuranone, 1,2-dihydro-1-ethyl-8-[N-(4-methylphenyl)-N-ethylamino]-2,2,4-trimethylspiro[11H]-chromeno(2,3-g)quinoline-11,3'-phthalide, 2'-[bis(phenylmethyl)amino]-6'-(diethylamino)-spiro[isobenzofuran-1(3H),9'-(9H)xanthene]-3-one, 3-dibutylamino-6-methyl-7-anilinofluorane, 2-aniline-3methyl-6-(N-methyl-p-toluidino)fluorane, 3-(N-isobutyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-(N-isopentyl-N-ethyl)amino-6-methyl-7-o-chloroanilinofluorane, 3-(N-methyl-N-p-toluidino)-6-methyl -7-anilinofluorane, 3-(N-ethyl-N-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethoxypropyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluorane, 3-(N-methyl-N-n-propyl) Mino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-toluidinofluorane, 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-pyrrolidino-6-methyl-7-anilinofluorane, crystal violet lactone, etc. can be used. These dyes can be used individually or in combination of two or more.

[0078] The average particle size of the above dye is preferably 0.1 to 1.0 μm. Generally, dyes react by melting, so reducing the average particle size tends to improve sensitivity characteristics. On the other hand, increasing the average particle size tends to suppress unexpected color development due to heat during drying. When the average particle size is within the above range, the sensitivity characteristics and color development temperature of the dye can be adjusted more appropriately.

[0079] The content of the above dye is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on 100% by mass of the total solid content of the thermal recording layer 4. Furthermore, the content of the above dye is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of the total solid content of the thermal recording layer 4.

[0080] Examples of the binders mentioned above include those similar to those listed in the section on the anchor layer. Among these, styrene-butadiene rubber (SBR) and acrylic resins are preferred as binders. Furthermore, from the viewpoint of improving boil resistance, it is preferable that the thermal recording layer 4 does not contain water-soluble resins such as PVA. These binders can be used individually or in combination of two or more types.

[0081] The binder content is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of the total solid content of the thermal recording layer 4. Furthermore, the binder content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, based on 100% by mass of the total solid content of the thermal recording layer 4.

[0082] The content of the water-soluble resin is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 1% by mass or less, based on 100% by mass of the total amount of the binder. It is also preferable that the content of the water-soluble resin is 0% by mass, based on 100% by mass of the total amount of the binder.

[0083] Examples of the above-mentioned fillers include those similar to those listed in the section on the anchor layer. In particular, one or more of the above-mentioned fillers are preferably selected from the group consisting of kaolin, calcined kaolin, aluminum oxide, aluminum silicate, and kaolinite, and one or more of the group consisting of kaolin and calcined kaolin are more preferably selected. Generally, in the case of a thermal recording material that has excellent resistance to heating such as boiling (heat resistance), the color development efficiency may be low. For this reason, the anchor layer may contain hollow particles in order to improve the color development efficiency. However, in one embodiment of the present invention, by including these fillers in the thermal recording layer 4, the color development efficiency can be made even more appropriate even if the anchor layer 3 does not contain hollow particles. These fillers can be used individually or in combination of two or more.

[0084] The content of the above-mentioned filler is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on 100% by mass of the total solid content of the thermal recording layer 4. Furthermore, the content of the above-mentioned filler is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the total solid content of the thermal recording layer 4.

[0085] Examples of the above lubricants include hydrocarbon waxes such as paraffin, polyethylene, and polystyrene; ester waxes such as carnauba wax; oils such as silicone oil and whale oil; fatty acids such as oleic acid and stearic acid; and metal soaps such as zinc stearate. These lubricants can be used individually or in combination of two or more.

[0086] The content of the above lubricant is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, based on 100% by mass of the total solid content of the thermal recording layer 4. Furthermore, the content of the above lubricant is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the total solid content of the thermal recording layer 4.

[0087] Examples of the crosslinking agents include inorganic crosslinking agents such as zirconium compounds, and organic crosslinking agents such as epichlorohydrin resins and oxazoline compounds. Examples of the zirconium compounds include zirconium carbonate, zirconium ammonium carbonate, and zirconium acetate. Examples of the epichlorohydrin resins include polyamide epichlorohydrin resins, polyamine epichlorohydrin resins, and polyamide polyamine epichlorohydrin resins. Among these, epichlorohydrin resins are preferred as the crosslinking agent. These crosslinking agents can be used individually or in combination of two or more.

[0088] The content of the above crosslinking agent is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, based on 100% by mass of the total solid content of the thermal recording layer 4. Furthermore, the content of the above crosslinking agent is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the total solid content of the thermal recording layer 4.

[0089] Examples of the wetting agents mentioned above include those similar to those listed in the section on anchor layers. These wetting agents can be used individually or in combination of two or more types.

[0090] Examples of the sensitizers mentioned above include known sensitizers such as higher fatty acid amides like stearate amide, methylol stearate amide, methylene bis-stearate amide, and ethylene bis-stearate amide; higher fatty acid anilides like stearate anilide; aromatic ethers such as 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis(3-methylphenoxy)ethane, and 1,2-bis(4-methoxyphenoxy)ethane; 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 2,6-diisopropylnaphthalene; di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl oxalate, p-benzylbiphenyl, m-terphenyl, diphenylsulfone, p-benzyloxybenzoate benzyl, dibenzyl terephthalate, and p-toluenesulfonamide. The above-mentioned sensitizers are preferably solid at room temperature and pressure (e.g., 25°C, 1 atm), and more preferably have a melting point of 70°C or higher. These sensitizers can be used individually or in combination of two or more.

[0091] For example, the coating amount (dry mass) of the thermal recording layer 4 is 0.3 g / m². ２ ~10g / m ２ Preferably, and more preferably, 2.0 g / m ２ ~6.0 g / m ２ Therefore, if the amount of coating is within the above range, it is easier to achieve more appropriate color development.

[0092] (Low Contact Angle Layer) The low contact angle layer 5 is a layer that is in direct contact with the thermal recording layer 4. Furthermore, the low contact angle layer 5 has a water contact angle of 40° or less. The low contact angle layer 5 is in direct contact with at least a portion of one side of the thermal recording layer 4. Preferably, the low contact angle layer 5 is in direct contact with the entire one side of the thermal recording layer 4. By satisfying these configurations, the low contact angle layer 5 can improve the boil resistance of the thermal recording body 1 (especially the boil resistance of the non-printed portion). This is presumably due to reasons such as the following: The thermal recording body 1, which is a laminate of at least the thermal recording layer 4 and the low contact angle layer 5, requires a certain amount of time to completely dry and cool down even after being removed from the hot water after boiling, because hot water remains attached to and permeates it. For this reason, the thermal recording body 1 remains heated for a while even after being removed from the hot water due to the effects of the attached and permeated hot water and the hot water vapor produced when the hot water evaporates. Generally speaking, the smaller the water contact angle of a surface, the easier it is for water to wet and spread across that surface. Therefore, when the water contact angle of the low-contact-angle layer 5 is small and water spreads easily, it is presumed that the hot water or water vapor that adheres to and penetrates the low-contact-angle layer 5 is quickly adsorbed onto the low-contact-angle layer 5 and spreads, and is easily discharged from the thermal recording layer 4 along the low-contact-angle layer 5. As a result, the temperature of the thermal recording layer 4 decreases easily after being removed from the hot water, and discoloration of non-printed areas is suppressed.

[0093] In the present invention, the water contact angle of the low contact angle layer 5 is measured 30 seconds after dropping 0.025 g of pure water onto the surface of the low contact angle layer 5. A microscope such as a digital microscope can be used for the above measurement, and specifically, it can be measured by the method described in the examples. The above water contact angle can be adjusted by the type and content ratio of the materials constituting the low contact angle layer 5.

[0094] The water contact angle of the low-contact-angle layer 5 is 40° or less, and may be 38° or less, 35° or less, 33° or less, or 30° or less. When the above contact angle is 40° or less, boil resistance (especially boil resistance of non-printed areas) is excellent. Furthermore, the ratio of the water contact angle of the low-contact-angle layer 5 to the water contact angle of the thermal recording layer 4 (water contact angle of the low-contact-angle layer 5 / water contact angle of the thermal recording layer 4) is not particularly limited, but may be, for example, 0.1 to 0.88, 0.2 to 0.85, or 0.3 to 0.8.

[0095] The low-contact angle layer 5 includes, for example, a binder such as a resin. The low-contact angle layer 5 may further contain other components as needed. Examples of these other components include crosslinking agents and wetting agents. By using a binder with high hydrophilicity and film-forming properties, the water contact angle can be reduced.

[0096] Examples of the binders mentioned above include those similar to those listed in the section on the anchor layer. Among these, acrylic resins are preferred as binders. Acrylic resins have highly hydrophilic parts such as carboxyl groups and / or ester bonds, which makes it easier to reduce the water contact angle.

[0097] The binder described above is preferably a core-shell type resin, and more preferably a core-shell type acrylic resin, from the viewpoint of improving the film-forming properties of the low-contact angle layer 5, ensuring strength, and suppressing peeling of the layer due to loads such as boiling. A core-shell type resin is a resin having a structure in which hydrophobic core particles (core part) are coated with a water-soluble shell polymer (shell part), and is typically obtained by stepwise polymerization of monomers with different compositions. In this case, by forming a cross-linking structure in the core particles, or by adjusting the molecular weight and glass transition temperature, the core particles can be made to be easily fused or difficult to fuse during film formation. For example, when the low-contact angle layer 5 is formed using a coating liquid containing a core-shell type resin consisting of a shell part composed of a water-soluble resin component and a core part with a relatively high glass transition temperature, the shell parts mix easily in the coating liquid, making it easy to form a film when drying after coating, thus improving film-forming properties. In addition, since the core part is difficult to melt, the core parts remain scattered in the layer even after the low-contact angle layer 5 is formed, and the water resistance of the layer can be improved due to the hydrophobicity of the core part. These binders can be used individually or in combination of two or more types. Furthermore, in this specification, resins that do not have the above-mentioned shell polymer portion may be specifically referred to as non-core-shell type resins.

[0098] From the viewpoint of making the low-contact-angle layer 5 a hydrophilic and smooth layer and further reducing the water contact angle, it is preferable that the ratio of the mass of the shell portion to the mass of the core portion in the above core-shell type resin is larger. In the above core-shell type resin, the ratio of the mass of the shell portion to the mass of the core portion (mass of the shell portion / mass of the core portion) is preferably 0.5 or more, more preferably 0.7 or more, even more preferably 1 or more, even more preferably 1.5 or more, and particularly preferably 2 or more. Furthermore, the above ratio (mass of the shell portion / mass of the core portion) may be, for example, 50 or less, 30 or less, 20 or less, 10 or less, or 5 or less.

[0099] The above-mentioned core-shell type acrylic resin is the same resin as the one exemplified as the binder in the anchor layer section, and is of the core-shell type. Specifically, examples include core-shell type acrylic resins such as core-shell type acrylic resin, core-shell type styrene-acrylic resin, core-shell type acrylic-urethane resin, core-shell type acryl-amide resin, and core-shell type vinyl acetate-acrylic resin.

[0100] The above-mentioned core-shell type acrylic resin is preferably a core-shell type carboxyl group-containing acrylic resin. The core-shell type carboxyl group-containing acrylic resin is thought to have carboxyl groups in the shell polymer, and with such a structure, the carboxyl groups react with the crosslinking agent, making it easier to form a crosslinked structure, thus potentially improving the strength of the low-contact corner layer 5.

[0101] When the binder contains a resin, the glass transition temperature of the resin is preferably 15 to 48°C, more preferably 20 to 45°C, and particularly preferably 22 to 40°C. Furthermore, the glass transition temperature of the core portion of the core-shell type resin is preferably within the above range. When the glass transition temperature is within the above range, it is considered that the coating fuses appropriately and good film formation is obtained, making it easier to set the water contact angle to an even more appropriate range. In addition, when the glass transition temperature is within the above range, the film formation is excellent, so when boiled, peeling of the layer can be further suppressed.

[0102] The binder content is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the total solid content of the low-contact stratum 5. Furthermore, the binder content may be 95% by mass or more, 97% by mass or more, 99% by mass or more, or even substantially 100% by mass, based on 100% by mass of the total solid content of the low-contact stratum 5. When the binder content is within the above range, it is easier to set the water contact angle to an even more appropriate range.

[0103] The content of the above core-shell type resin is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of the total amount of binder in the low-contact cornea layer 5. The above content may be substantially 100% by mass, based on 100% by mass of the total amount of binder in the low-contact cornea layer 5. Furthermore, the content of the above core-shell type acrylic resin is preferably within the above range, based on 100% by mass of the total amount of binder in the low-contact cornea layer 5.

[0104] Examples of the crosslinking agents mentioned above include those similar to those listed in the section on the thermal recording layer. Among these, epichlorohydrin resins are preferred as the crosslinking agent because they readily form a crosslinked structure with the acrylic resin. These crosslinking agents can be used individually or in combination of two or more.

[0105] The content of the above crosslinking agent may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, based on 100% by mass of the total solids content of the low-contact stratum corneum 5. Furthermore, the content of the above crosslinking agent may be 40% by mass or less, or 30% by mass or less, based on 100% by mass of the total solids content of the low-contact stratum corneum 5. In this specification, the above epichlorohydrin resin is not included in the content as a binder, but is included in the content as a crosslinking agent.

[0106] Examples of the wetting agents mentioned above include those similar to those listed in the section on anchor layers. These wetting agents can be used individually or in combination of two or more types.

[0107] For example, the coating amount (dry mass) of the low-contact corner layer 5 is 0.1 g / m². ２ ~10g / m ２ Preferably, and more preferably, 1.0 g / m ２ ~5.0 g / m ２ Therefore, if the above coating amount is within the above range, it is easier to achieve more appropriate boil resistance.

[0108] (Top coat layer) The top coat layer 6 is a layer intended to improve the matching of the thermal recording body 1 with respect to the thermal head, that is, to improve the slipperiness of the head and suppress the adhesion of debris to the head. The top coat layer 6 may be omitted if it is not necessary. From the viewpoint of improving matching, it is preferable that the thermal recording body 1 has the top coat layer 6 on one end face. The top coat layer 6 may contain, for example, a binder, filler, lubricant, crosslinking agent, wetting agent, etc.

[0109] Examples of the binders mentioned above include those similar to those listed in the section on the anchor layer. Among these, acrylic resins are preferred as the binder. Furthermore, the binder may or may not contain a core-shell type resin. These binders can be used individually or in combination of two or more types.

[0110] The binder content is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on 100% by mass of the total solid content of the topcoat layer 6. Furthermore, the binder content is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, based on 100% by mass of the total solid content of the topcoat layer 6. In addition, the resin content is preferably within the above range based on 100% by mass of the total amount of resin in the topcoat layer 6.

[0111] Examples of the above-mentioned fillers include those similar to those listed in the section on the anchor layer. Among these, inorganic fillers are preferred. In some cases, organic fillers (such as PMMA particles) listed in the section on the anchor layer may also be added. These binders can be used individually or in combination of two or more.

[0112] The content of the above-mentioned filler is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on 100% by mass of the total solid content of the topcoat layer 6. Furthermore, the content of the above-mentioned filler is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, based on 100% by mass of the total solid content of the topcoat layer 6.

[0113] Examples of the lubricants mentioned above include those similar to those listed in the section on the thermal recording layer. These lubricants can be used individually or in combination of two or more types.

[0114] The content of the above lubricant is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on 100% by mass of the total solid content of the top coat layer 6. Furthermore, the content of the above lubricant is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on 100% by mass of the total solid content of the top coat layer 6.

[0115] Examples of the crosslinking agents mentioned above include those similar to those listed in the section on thermal recording layers. In particular, inorganic crosslinking agents are preferred, and zirconium compounds are more preferred, from the viewpoint of improving heat resistance and enhancing suitability for thermal heads by forming a crosslinked structure containing metal ions. These crosslinking agents can be used individually or in combination of two or more.

[0116] The content of the above crosslinking agent is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, based on 100% by mass of the total solid content of the topcoat layer 6. Furthermore, the content of the above crosslinking agent is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the total solid content of the topcoat layer 6.

[0117] Examples of the wetting agents mentioned above include those similar to those listed in the section on anchor layers. These wetting agents can be used individually or in combination of two or more types.

[0118] [Method for Manufacturing a Thermal Recording Body] The method for manufacturing the thermal recording body of the present invention is not particularly limited, and known or conventional methods can be applied. One embodiment of the above method for manufacturing a thermal recording body will be described with reference to Figure 1. First, the thermal recording layer 4 and the low-contact-angle layer 5 can be formed by coating them with a coating solution containing the components contained in each layer. For example, the coating solution for the thermal recording layer can be prepared by dispersing the components contained in the thermal recording layer 4 in a solvent such as water, and the coating solution for the low-contact-angle layer can be prepared by a similar means. Next, the thermal recording layer 4 can be formed by coating the thermal recording layer coating solution on one side of the substrate 2 and drying it, and the low-contact-angle layer 5 can be formed by coating the low-contact-angle layer coating solution on the surface of the thermal recording layer 4 and drying it. In this way, the thermal recording body 1 shown in Figure 1 can be obtained.

[0119] (Preparation Process) The above-mentioned coating solution for the thermal recording layer may be prepared by pre-dispersing all the materials in the same solvent. Alternatively, the dye and developer, which react with each other, may be prepared as separate dispersions and then mixed together to form the coating solution for the thermal recording layer. In this case, the other components may be added to either the dispersion containing the dye or the dispersion containing the developer, or to both. Methods for preparing the above-mentioned coating solution for the thermal recording layer include, for example, stirring, ultrasonic treatment, crushing treatment using a ball mill, bead mill, sand mill, high-pressure homogenizer, etc. The above-mentioned coating solution for the low-contact angle layer can also be prepared by similar means. These methods can be used individually or in combination of two or more.

[0120] (Coating Process) Methods for applying the above-mentioned thermal recording layer coating include, for example, applying it to a release liner and then peeling off the release liner, or, when a substrate is used, applying it directly to one side of the substrate. Examples of coating methods include air knife coating, barrier blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, and gravure coating. Hand coating using a wire bar is also acceptable. The above-mentioned low-contact angle layer coating can also be applied by similar means. These methods can be used individually or in combination of two or more.

[0121] (Drying process) Methods for drying the coating liquid for the thermal recording layer applied as described above include, for example, heat drying, room temperature drying, and vacuum drying. These methods can be used individually or in combination of two or more. The thermal recording layer 4 can be formed by these methods. The low contact angle layer 5 can also be formed by similar means.

[0122] If the thermal recording body of the present invention comprises layers other than the substrate, thermal recording layer, and low-contact-angle layer, the above-described method can be used to form the other layers. For example, the thermal recording body 1 shown in Figure 2 can be manufactured by coating one side of the substrate 2 with an anchor layer coating solution prepared by dispersing the components contained in the anchor layer 3 in a solvent such as water, and drying it to form the anchor layer 3; then laminating the thermal recording layer 4 and the low-contact-angle layer 5 on the anchor layer 3 using the same method as described above; and then coating the surface of the low-contact-angle layer 5 with a topcoat coating solution prepared by dispersing the components contained in the topcoat layer 6 in a solvent such as water, and drying it to form the topcoat layer 6.

[0123] In the method for manufacturing a thermal recording body of the present invention, each layer may be simultaneously coated in multiple layers using, for example, a curtain coater, or it may be formed individually and sequentially. Alternatively, some layers may be simultaneously coated, and some layers may be formed individually and sequentially.

[0124] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples. Unless otherwise specified, the masses mentioned in the examples refer to the mass of each component (i.e., the mass after drying following layer formation).

[0125] Example 1 (Preparation of a thermal recording material) <Anchor layer> 84% by mass of styrene-acrylic resin, which is the binder, 15% by mass of acrylic-styrene copolymer, which is the antistatic agent, 1% by mass of surfactant, which is the wetting agent, and water were mixed to prepare an anchor layer coating solution (solid content concentration 11% by mass) by a conventional method. The obtained anchor layer coating solution was applied to one side of the synthetic paper substrate by a conventional method and dried to a coating amount of 0.4 g / m². ２ An anchor layer of (dry mass) was formed.

[0126] <Thermal recording layer> A dispersion of agent A (solid content concentration 39% by mass) was prepared by mixing 90% by mass of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea (product name "S-176", manufactured by Sanko Co., Ltd.), which is a color developer, with 10% by mass of an acrylic resin, which is a binder, and water, using a conventional method. Next, a dispersion of agent B (solid content concentration 36% by mass) was prepared by mixing 60% by mass of the above dispersion of agent A, with 15% by mass of kaolin, which is a filler, with 23% by mass of styrene-butadiene rubber (SBR), which is a binder, with 2% by mass of polyethylene, which is a lubricant, and water, using a conventional method. Next, 83% by mass of the dye 3-dibutylamino-6-methyl-7-anilinofluorane (ODB-2), 17% by mass of the binder acrylic resin, and water were mixed to prepare a C agent dispersion (solid content concentration 34% by mass) by conventional methods. Next, 82% by mass of the above B agent dispersion, 17% by mass of the above C agent dispersion, 1% by mass of the crosslinking agent polyamide epichlorohydrin resin, and water were mixed to prepare a thermal recording layer coating solution (solid content concentration 24% by mass) by conventional methods. The obtained thermal recording layer coating solution was applied to the surface of the anchor layer by conventional methods and dried, resulting in a coating amount of 4.4 g / m². ２ A thermal recording layer of (dry mass) was formed.

[0127] <Low Contact Corner Layer> A coating solution for a low contact corner layer (solid content concentration 14% by mass), prepared by conventional methods by adding water to an emulsion containing a core-shell type acrylic resin (resin A), is applied to the surface of the thermal recording layer by conventional methods and dried, resulting in a coating amount of 1.6 g / m². ２ A low-contact stratum corneum A of (dry mass) was formed to obtain the thermal recording material of Example 1.

[0128] Examples 2-3 and Comparative Examples 1-6: Thermal recording bodies for Examples 2-3 and Comparative Examples 1-6 were manufactured in the same manner as in Example 1, except that the resins shown in Table 1 were used instead of resin A in the low-contact-angle layer manufacturing process. In Comparative Examples 1-6, the layer formed at the position corresponding to the low-contact-angle layer in the Examples is referred to as a protective layer because it has a high water contact angle, as will be described later.

[0129] Reference Example 1: A laminate consisting of a substrate, an anchor layer, and a thermal recording layer was fabricated in the same manner as in Example 1, except that a low-contact angle layer was not formed.

[0130] [Evaluation] The thermal recording materials prepared in the examples and comparative examples, as well as the laminate prepared in the reference example, were evaluated as follows. The results are shown in Table 1.

[0131] (1) Measurement of water contact angle 0.025 g of pure water was dropped onto the surface of the low contact angle layer, and the contact angle after 30 seconds was measured using a digital microscope (manufactured by Keyence Corporation, device name: VHX-8000). In Reference Example 1, the water contact angle of the thermal recording layer was measured using the same procedure as above.

[0132] (2) Boiling test: The thermal recording material or laminate was immersed in boiling water (100°C) for 1 minute.

[0133] (3) Evaluation of layer delamination and dissolution The heat-sensitive recording material or laminate after the boil test in (2) was visually observed and evaluated based on the following evaluation criteria. [Evaluation Criteria] ○: No layer delamination or dissolution was observed ×: One or more of the following was observed: layer delamination or dissolution

[0134] (4) Measurement of L value The L value of the non-printed area of ​​the thermal recording material or laminate after the boil test in (2) was measured using a spectrophotometer (X-rite Corporation, device name: eXact).

[0135] (5) Evaluation of boil resistance The following evaluation criteria were used to evaluate the boil resistance. [Evaluation Criteria] ○: All of the following items 1 and 2 are met ×: One or more of the following items 1 and 2 are not met Item 1. The evaluation result of (3) is ○ Item 2. The L value measured in (4) is 90 or higher

[0136]

[0137] As shown in Table 1, when the low-contact-angle layer was not laminated (Reference Example 1), the L value of the non-printed area after boiling was the highest (95.07), indicating that the whiteness of the non-printed area was best preserved. This is presumed to be because, in Reference Example 1, the thermal recording layer is located at the edge of the laminate, so the hot water adhering to and penetrating the laminate evaporates quickly after boiling, causing the thermal recording layer to cool easily and thus suppressing color development. Furthermore, even when the low-contact-angle layer was laminated, when the water contact angle of the low-contact-angle layer was 40° or less (Examples 1-3), the L value was high (91.87-93.04), and the whiteness of the non-printed area was maintained, indicating excellent boil resistance of the non-printed area. This is presumed to be because, when the water contact angle of the low-contact-angle layer is low, it has excellent wettability, so hot water and water vapor are quickly adsorbed onto the low-contact-angle layer and spread, and are easily discharged from the thermal recording layer along the low-contact-angle layer, thus suppressing color development. On the other hand, when the water contact angle of the protective layer formed at a position corresponding to the low contact angle layer in the example was greater than 40° (Comparative Examples 1-3), the L value was lower (86.18-87.62) than when the water contact angle was 40° or less, indicating inferior maintenance of whiteness in the non-printed area and inferior boil resistance in the non-printed area.

[0138] Furthermore, when the protective layer was formed only from resins with a glass transition temperature of 50°C or higher (Comparative Examples 4-5), no examples were found where the water contact angle was 40° or less, and peeling of the layer was observed after boiling. The reason for this is not clear, but the following reasons are possible. First, when the protective layer is formed only from resins with relatively high glass transition temperatures, the resin does not fuse well during coating, so it is thought that particulate resin tends to remain in the protective layer. Such a protective layer has an uneven layer and water does not adhere well to it, so hot water that adheres to and penetrates the thermal recording material is not easily absorbed by the protective layer and does not spread easily, so water droplets tend to exist between the thermal recording layer and the protective layer. Therefore, it is thought that blistering and other issues are more likely to occur, and peeling is more likely to occur.

[0139] Furthermore, when the protective layer was formed with PVA, a water-soluble resin (Comparative Example 6), it dissolved in water, making it impossible to accurately measure the water contact angle. Moreover, dissolution of the layer was observed after boiling.

[0140] The various raw materials shown in Table 1 are as follows: Resin A: Core-shell type acrylic resin (glass transition temperature of the core: 30°C) Resin B: Core-shell type acrylic resin (glass transition temperature of the core: 36°C) Resin C: Core-shell type acrylic resin (glass transition temperature of the core: 36°C) Resin D: Non-core-shell type SBR (glass transition temperature: 8°C) Resin E: Non-core-shell type styrene-acrylic resin (glass transition temperature: 4°C) Resin F: Non-core-shell type styrene-acrylic resin (glass transition temperature: 14°C) Resin G: Non-core-shell type acrylic resin (glass transition temperature: 60°C) Resin H: Non-core-shell type acrylic resin (glass transition temperature: 50°C) Resin I: PVA resin (water-soluble resin)

[0141] In summary, the configuration of the present invention and its variations are described below. [Note 1] A thermal recording body comprising a substrate, a thermal recording layer, and a low contact angle layer in this order, wherein the low contact angle layer is directly laminated on the thermal recording layer, the thermal recording layer contains a compound represented by the above formula (1) as a color developer, and the water contact angle of the low contact angle layer is 40° or less. [Note 2] The thermal recording body according to Note 1, wherein the low contact angle layer contains a core-shell type resin as a binder. [Note 3] The thermal recording body according to Note 2, wherein the core-shell type resin contains a core-shell type acrylic resin. [Note 4] The thermal recording body according to Note 2 or 3, wherein in the core-shell type resin, the ratio of the mass of the shell part to the mass of the core part (mass of the shell part / mass of the core part) is 0.5 or more. [Note 5] The thermal recording body according to any one of Notes 1 to 4, wherein the low contact angle layer further contains an epichlorohydrin type resin. [Note 6] The thermal recording body according to any one of Notes 2 to 5, wherein the content of the binder is 80% by mass or more with respect to 100% by mass of the total solid content of the low contact angle layer. [Note 7] The thermal recording body according to any one of Notes 1 to 6, wherein the thermal recording layer does not contain a water-soluble resin. [Note 8] The thermal recording body according to any one of Notes 1 to 7, wherein the thermal recording layer contains one or more selected from the group consisting of kaolin, calcined kaolin, aluminum oxide, aluminum silicate, and kaolinite as a filler. [Note 9] The thermal recording body according to any one of Notes 1 to 8, wherein an anchor layer containing an acrylic resin as a binder is provided between the substrate and the thermal recording layer. [Note 10] The thermal recording body according to Note 9, wherein the content of the binder is 50% by mass or more with respect to 100% by mass of the total solid content of the anchor layer. [Note 11] The thermal recording body according to Note 9 or 10, wherein the content of the acrylic resin is 70% by mass or more with respect to 100% by mass of the total amount of binder in the anchor layer. [Note 12] The thermal recording body according to any one of Notes 9 to 11, wherein the anchor layer may contain hollow particles as a filler, and if the anchor layer contains the hollow particles, the content of the hollow particles is 10% by mass or less with respect to 100% by mass of the total solid content of the anchor layer.[Note 13] The thermal recording body according to any one of Notes 9 to 12, wherein the anchor layer does not contain hollow particles. [Note 14] The thermal recording body according to any one of Notes 1 to 13, wherein the low-contact angle layer is provided with a top coat layer on the side opposite to the thermal recording layer. [Note 15] The thermal recording body according to any one of Notes 1 to 14, wherein the substrate is laminated paper, nonwoven fabric, synthetic resin film, or synthetic paper.

[0142] 1. Thermal recording element 2. Substrate 3. Anchor layer 4. Thermal recording layer 5. Low contact angle layer 6. Top coat layer

Claims

1. A thermal recording body comprising a substrate, a thermal recording layer, and a low contact angle layer in this order, wherein the low contact angle layer is directly laminated on the thermal recording layer, the thermal recording layer contains a compound represented by the following formula (1) as a color developer, and the water contact angle of the low contact angle layer is 40° or less. (In formula (1), R １ is a hydrocarbon group having 1 to 12 carbon atoms, which may have substituents, and a plurality of R １ They may be the same or different. A １ A is a hydrocarbon group having 1 to 4 carbon atoms. １ If there are two or more A １ n can be the same or different. n represents an integer from 0 to 4, and multiple n values ​​can be the same or different.

2. The thermal recording body according to claim 1, wherein the low-contact angle layer includes a core-shell type resin as a binder.

3. The thermal recording body according to claim 2, wherein the core-shell type resin includes a core-shell type acrylic resin.

4. The thermal recording body according to claim 2, wherein in the core-shell type resin, the ratio of the mass of the shell portion to the mass of the core portion (mass of the shell portion / mass of the core portion) is 0.5 or more.

5. The thermal recording body according to claim 4, wherein the low-contact stratum corneum further comprises an epichlorohydrin-based resin.

6. The thermal recording body according to any one of claims 2 to 5, wherein the content of the binder is 80% by mass or more with respect to 100% by mass of the total solid content of the low contact surface layer.

7. The thermal recording body according to claim 6, wherein the thermal recording layer does not contain a water-soluble resin.

8. The thermal recording body according to claim 6, wherein the thermal recording layer comprises one or more selected from the group consisting of kaolin, calcined kaolin, aluminum oxide, aluminum silicate, and kaolinite as a filler.

9. The thermal recording body according to claim 6, further comprising an anchor layer containing an acrylic resin as a binder between the substrate and the thermal recording layer.

10. The thermal recording body according to claim 9, wherein the content of the binder is 50% by mass or more with respect to 100% by mass of the total solid content of the anchor layer.

11. The thermal recording body according to claim 9, wherein the content of the acrylic resin is 70% by mass or more with respect to 100% by mass of the total amount of binder in the anchor layer.

12. The thermal recording body according to claim 9, wherein the anchor layer may contain hollow particles as a filler, and if the anchor layer contains the hollow particles, the content ratio of the hollow particles is 10% by mass or less with respect to 100% by mass of the total solid content of the anchor layer.

13. The thermal recording body according to claim 9, wherein the anchor layer does not contain hollow particles.

14. The thermal recording body according to claim 6, wherein the low-contact angle layer is provided with a top coat layer on the side opposite to the thermal recording layer.

15. The thermal recording body according to claim 6, wherein the substrate is any one of laminated paper, nonwoven fabric, synthetic resin film, or synthetic paper.

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