Top coat layer and thermal recording material

Abstract

To provide a top coat layer that combines transparency and a matte finish. [Solution] The topcoat layer 1 of the present invention contains particles 1a whose primary particles are shaped particles and whose average primary particle diameter is 0.5 μm or more. The particles 1a contain one or more selected from the group consisting of resins containing structural units having polar groups and inorganic oxides. The content of particles 1a is 5% by mass or more with respect to 100% by mass of the total solid content of the topcoat layer 1. The topcoat layer 1 may contain calcium carbonate, but the content of the calcium carbonate is 30% by mass or less with respect to 100% by mass of the total solid content of the topcoat layer 1.

Description

[Technical Field]

[0001] This invention relates to a top coat layer and a thermal recording material. [Background technology]

[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 not only as recording media for fax machines, automatic ticket vending machines, and scientific measuring instruments, but also in a wide range of applications such as thermal recording labels and receipt paper for POS systems in retail stores.

[0003] In particular, when using thermal recording media as labels or films for food containers such as bento boxes, there is a need for thermal recording media with excellent transparency so that the contents can be easily seen. As an example of a thermal recording media with excellent transparency, a thermal recording media has been proposed in which the transparency is further improved by using colloidal silica instead of calcium carbonate, a known filler, as the filler in the top coat layer (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-218024 [Overview of the project] [Problems that the invention aims to solve]

[0005] A thermal recording medium that possesses both a certain degree of transparency and a moderate matte finish offers excellent visibility of its contents, and also excels in aesthetics and design due to its matte finish, which conveys a sense of luxury. However, a thermal recording medium that achieves both transparency and a matte finish, and a topcoat layer that can be used with such a thermal recording medium, have not yet been specifically provided.

[0006] The present invention was conceived under these circumstances, and its objective is to provide a top coat layer that combines transparency and a matte finish. Another objective of the present invention is to provide a thermal recording material that combines transparency and a matte finish. [Means for solving the problem]

[0007] As a result of diligent research to achieve the above objective, the inventors have discovered that a layer containing particles made of a specific material and having a specific shape can achieve a texture that is both transparent and matte. This invention was completed based on these findings.

[0008] In other words, the present invention provides a topcoat layer comprising primary particles that are shaped particles and have an average primary particle diameter of 0.5 μm or more, wherein the particles comprise one or more selected from the group consisting of resins containing structural units having polar groups and inorganic oxides, the content of the particles is 5% by mass or more with respect to 100% by mass of the total solid content of the topcoat layer, and the topcoat layer may also contain calcium carbonate, the content of the calcium carbonate is 30% by mass or less with respect to 100% by mass of the total solid content of the topcoat layer.

[0009] The primary particles described above are preferably spherical or polyhedral particles.

[0010] The glass transition temperature of the above particles is preferably 90°C or higher.

[0011] The resin containing the structural unit having the above polar group is preferably one or more selected from the group consisting of acrylic resins and silicone resins.

[0012] The inorganic oxide mentioned above is preferably one or more selected from the group consisting of silica, aluminosilicate, and alumina.

[0013] The present invention also provides a thermal recording medium including a base material and a thermal recording layer, wherein the base material, the thermal recording layer, and the top coat layer are laminated in this order.

[0014] The base material is preferably a transparent film.

[0015] When the top coat layer is provided on one surface and the base material is provided on the other surface, it is preferable that the opacity is 20% or less, the haze is 40 to 85%, and the 60° glossiness is 40% or less.

Advantages of the Invention

[0016] According to the present invention, a top coat layer having both transparency and a matte feeling can be provided. Further, according to the present invention, a thermal recording medium having both transparency and a matte feeling can be provided.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic cross-sectional view showing an embodiment of the top coat layer of the present invention. [Figure 2] It is a schematic cross-sectional view showing an embodiment of the thermal recording medium of the present invention.

Embodiments for Carrying Out the Invention

[0018] [Top Coat Layer] The top coat layer of the present invention contains particles in which the primary particles are shaped particles. The particles contain one or more selected from the group consisting of a resin containing a structural unit having a polar group and an inorganic oxide. Further, the content ratio of the particles is 5% by mass or more based on 100% by mass of the total solid content of the top coat layer. The top coat layer of the present invention may contain calcium carbonate, and when the top coat layer contains calcium carbonate, the content ratio of the calcium carbonate is 30% by mass or less based on 100% by mass of the total solid content of the top coat layer. By satisfying the above configuration, the top coat layer of the present invention can achieve both appropriate transparency and an appropriate matte feeling.

[0019] In this specification, "standard shape" is used as a term in contrast to "amorphous shape." "Standard-shaped particles" mean that the regularity of the particle shapes is easily recognizable, and that the shape is constant, while "amorphous particles" mean that the regularity of the particle shapes is not easily recognizable, and that the shape is not constant. Specifically, if standard-shaped particles are spherical particles, it means that substantially all particles are spherical. However, standard-shaped particles also include those that have undergone unavoidable deformation during manufacturing, such as those that are partially missing or those that have only a portion of their edges beveled.

[0020] The topcoat layer of the present invention is suitable as a topcoat layer for thermal recording media. Therefore, when used in a thermal recording media described later, the topcoat layer can function as a layer that protects other layers, such as the thermal recording layer described later, from physical loads such as abrasion and / or chemical loads such as water and oil. Furthermore, when used in a thermal recording media described later, the topcoat layer can also function as a layer that improves the printability of the thermal recording media by improving the matching suitability with the thermal head. In addition, when the topcoat layer is a topcoat layer for thermal recording media, particles whose primary particles are fixed-shape particles can function as fillers. For this reason, these particles may be referred to as fillers in this specification.

[0021] Hereinafter, one embodiment of the topcoat layer of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments.

[0022] Figure 1 shows one embodiment of the topcoat layer of the present invention. In the topcoat layer 1 shown in Figure 1, the primary particles, which are shaped particles 1a, are dispersed in a binder 1b. The binder 1b may contain other components described later in a dispersed state, or it may be uniformly dissolved with the other components. The particles 1a may be completely embedded in the binder 1b, or they may be partially embedded and partially exposed. It is preferable that all or some of the total amount of particles 1a are partially exposed from the binder 1b. The partial exposure of particles 1a creates irregularities on the surface of the topcoat layer 1, resulting in a matte finish and texture, which is aesthetically pleasing and can also improve the suitability for matching with thermal heads.

[0023] In the topcoat layer 1, particles 1a may be arranged as secondary particles by aggregating primary particles with each other, or as primary particles separated from each other and arranged as primary particles. From the viewpoint of ensuring high transparency and producing a highly uniform matte finish, it is preferable that particles 1a are arranged as primary particles in the topcoat layer 1. Specifically, it is preferable that 50% or more of the total number of primary particles in the topcoat layer 1 be arranged as primary particles, more preferably 70% or more be arranged as primary particles, and even more preferably 90% or more be arranged as primary particles. The above percentages can be determined, for example, by microscopic observation.

[0024] Particle 1a has a fixed primary particle shape. The topcoat layer 1, by containing such particles 1a, is thought to produce a matte finish while maintaining transparency because light is moderately scattered and transmitted on the surface and / or inside the particles 1a. Examples of the fixed-shape particles include spherical particles, cylindrical particles, and polyhedral particles. Examples of the spherical particles include perfectly spherical particles and ellipsoidal particles. Examples of the polyhedral particles include tetrahedral particles, cubic particles, rectangular parallelepiped particles, pentagonal prism particles, hexagonal prism particles, octahedral particles, dodecahedral particles, icosahedral particles, icostetrahedral particles, and triadahedral particles. The polyhedral particles may also be regular polyhedral particles. Examples of the regular polyhedral particles include regular tetrahedral particles, cubic particles, regular octahedral particles, regular dodecahedral particles, and regular icosahedral particles. Particle 1a may be of one type only, or two or more types may be used.

[0025] The above-mentioned shaped particles are preferably one selected from the group consisting of spherical particles and polyhedral particles, more preferably one selected from the group consisting of perfectly spherical particles, ellipsoidal particles, cubic particles, and rectangular parallelepiped particles, and even more preferably one selected from the group consisting of perfectly spherical particles and cubic particles.

[0026] The aspect ratio of particle 1a is preferably 5 or less, more preferably 3 or less, even more preferably 2 or less, even more preferably 1.5 or less, even more preferably 1.3 or less, even more preferably 1.2 or less, and particularly preferably 1.1 or less. The aspect ratio of particle 1a may be substantially 1. When the aspect ratio is within the above range, light scattering and / or transmission by particle 1a occurs appropriately, making it easier to achieve a more appropriate range for transparency and matte finish. The aspect ratio of the primary particles of particle 1a is preferably within the above range. The above aspect ratio is the ratio of the length in the long axis direction to the length in the short axis direction of particle 1a [length in the long axis direction / length in the short axis direction]. The above aspect ratio can be determined by measuring the lengths in the short axis direction and the long axis direction by microscopic observation, such as with a transmission microscope.

[0027] The average particle diameter of particle 1a is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. Alternatively, the average particle diameter may be 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. The average particle diameter may also be 3 μm or less. When the average particle diameter is 0.5 μm or more, light scattering and / or transmission by particle 1a occurs appropriately, making it easier to achieve a more appropriate range for transparency and matte finish. When the average particle diameter is 10 μm or less, the particles adhere easily to the topcoat layer 1, making it easier to achieve a more appropriate range for matching with the thermal head.

[0028] The average primary particle diameter of particle 1a is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. Alternatively, the average primary particle diameter may be 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. The average primary particle diameter may also be 3 μm or less. When the average primary particle diameter is 0.5 μm or more, light scattering and / or transmission by particle 1a occurs appropriately, making it easier to achieve a more suitable range for transparency and matte finish. Furthermore, when the average primary particle diameter is 10 μm or less, the particles adhere easily to the topcoat layer 1, making it easier to achieve a more suitable range for matching with the thermal head.

[0029] In this specification, "average particle diameter of particle 1a" means the average primary particle diameter when particle 1a mainly exists as a primary particle, and the average secondary particle diameter when particle 1a mainly exists as a secondary particle. Furthermore, unless otherwise specified, the average particle diameter of particle 1a means the particle diameter (D50, median diameter) at 50% of the cumulative value of the particle size distribution measured by the Coulter counter method.

[0030] Particle 1a may be solid or hollow. From the viewpoint of improving transparency, matte finish, and color development efficiency, it is preferable that particle 1a is solid.

[0031] Particle 1a comprises one or more selected from the group consisting of a resin containing a structural unit having a polar group and an inorganic oxide. It is presumed that by having part or all of particle 1a composed of the above-mentioned resin containing a structural unit having a polar group and / or an inorganic oxide, it can have a moderate refractive index and dispersibility, and its transparency and matte finish can be brought into a more appropriate range. The surface of particle 1a may be treated with a hydrophilic treatment or the like.

[0032] The above polar groups are not particularly limited, but examples include carbonyl groups, carboxyl groups, groups containing ester bonds, hydroxyl groups, groups containing urethane bonds, silanol groups, alkoxysilyl groups, and groups containing siloxane bonds. The above polar groups may consist of only one type or two or more types.

[0033] Examples of resins containing the above-mentioned polar group structural unit 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; and silicone resins such as silicone resins and silicone rubbers. The resin containing the above-mentioned polar group structural unit may be a modified resin modified by a known method. Only one type of resin containing the above-mentioned polar group structural unit may be used, or two or more types may be used. In particular, the above-mentioned silicone resin typically has a siloxane bond of (RSiO3 / 2). n (Especially (CH3SiO3 / 2)) n This refers to polyorganosylsesquioxane (especially polymethylsilsesquioxane) having a three-dimensional network-like cross-linked structure represented by ). Furthermore, the above-mentioned silicone rubber typically refers to one having a structure in which linear dimethylpolysiloxanes are cross-linked.

[0034] The resin containing the structural unit having the polar group described above is preferably one or more selected from the group consisting of acrylic resins and silicone resins, and more preferably one or more selected from the group consisting of acrylic resins and silicone resins. These resins may be modified resins that have been modified by known methods.

[0035] 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 another monomer (a monomer other than an acrylic monomer that can copolymerize with an acrylic monomer). Here, the acrylic monomer and the other monomer may 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.

[0036] The salts in the above (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 salt, ethylamine salt, diethylamine salt, and triethylamine salt; polyamine salts such as diethyleneamine salt and diethylenetriamine salt; 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. One type of salt may be used, or two or more types may be used.

[0037] When particle 1a contains a resin containing structural units having the polar groups described above, the glass transition temperature of particle 1a is not particularly limited, but is preferably 90°C or higher, more preferably 95°C or higher, even more preferably 100°C or higher, even more preferably 105°C or higher, and particularly preferably 110°C or higher. The upper limit of the glass transition temperature is not particularly limited and may be 300°C or lower, 250°C or lower, 200°C or lower, or 150°C or lower. When the glass transition temperature is 90°C or higher, particle 1a is less likely to soften even when heated by a thermal head, so that changes in the shape of the particles are suppressed even after printing, and the matte finish of the printed area can be maintained.

[0038] The inorganic oxides mentioned above are not particularly limited, but examples include silica, aluminosilicate, alumina, titanium oxide, and barium titanate. Preferably, the inorganic oxide is one or more selected from the group consisting of silica, aluminosilicate, and alumina, and more preferably, one or more selected from the group consisting of silica and aluminosilicate. Only one type of inorganic oxide may be used, or two or more types may be used.

[0039] The salts in the above aluminosilicate 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. One type of salt may be used, or two or more types may be used.

[0040] The content of particles 1a is 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more, based on 100% by mass of the total solid content of the top coat layer 1. When the above content is 5% by mass or more, a matte finish can be obtained. Furthermore, the content of particles 1a 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 top coat layer 1.

[0041] The topcoat layer 1 preferably further contains a binder. The topcoat layer 1 may also contain other components, such as crosslinking agents, fillers other than particles 1a (other fillers), lubricants, and wetting agents. Each of these components may be used individually or in combination of two or more.

[0042] The topcoat layer 1 preferably contains a binder from the viewpoint of excellent manufacturability. Examples of the binder include resins. The resin may have a water-soluble portion or may not have a water-soluble portion. Examples of the resins 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 latex (SBR) resins; acrylonitrile-butadiene-styrene resins; vinyl acetate resins; polyvinyl alcohol resins such as fully saponified polyvinyl alcohol resins, partially saponified polyvinyl alcohol resins, diacetone-modified polyvinyl alcohol resins, acetoacetyl-modified polyvinyl alcohol resins, sulfonic acid-modified polyvinyl alcohol resins, olefin-modified polyvinyl alcohol resins, nitrile-modified polyvinyl alcohol resins, pyrrolidone-modified polyvinyl alcohol resins, silanol-modified polyvinyl alcohol resins, and cation-modified polyvinyl alcohol resins. The resins may be modified resins modified by known methods.

[0043] The above binder preferably contains an acrylic resin from the viewpoint of excellent transparency. The content of the above binder is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more, based on 100% by mass of the total solids content of the top coat layer 1. Furthermore, the content of the above binder is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less, based on 100% by mass of the total solids content of the top coat layer 1.

[0044] The composition forming the above-mentioned binder may be a solid, an emulsion, or a solution. From the viewpoint of excellent coating properties, it is preferably an emulsion or a solution.

[0045] Examples of the crosslinking agents include inorganic crosslinking agents and organic crosslinking agents. Examples of inorganic crosslinking agents include zirconium carbonate, zirconium ammonium carbonate, and zirconium acetate. Examples of organic crosslinking agents include cationic crosslinking agents such as polyamide epichlorohydrin resins, polyamine epichlorohydrin resins, and polyamide polyamine epichlorohydrin resins; and non-cationic crosslinking agents such as oxazoline group-containing polymers. From the viewpoint of improving the heat resistance of the topcoat layer 1 and enhancing its suitability for thermal heads, inorganic crosslinking agents are preferred, and zirconium carbonate or zirconium ammonium carbonate are more preferred.

[0046] The content of the above crosslinking agent is preferably 0.1% 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 solids content of the topcoat layer 1. 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 solids content of the topcoat layer 1.

[0047] Other fillers mentioned above include, for example, calcium carbonate, magnesium carbonate, colloidal silica, and particles made from resins that do not contain structural units with polar groups (such as polyolefin resin particles).

[0048] If the topcoat layer 1 contains the above-mentioned calcium carbonate, the content of the above-mentioned calcium carbonate in the topcoat layer 1 is 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, and may also be 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on 100% by mass of the total solids content of the topcoat layer 1. When the above-mentioned content is 30% by mass or less, transparency can be maintained. Furthermore, the content of other fillers is preferably within the above range based on 100% by mass of the total solids content of the topcoat layer 1. Furthermore, the topcoat layer 1 does not have to contain other fillers. Furthermore, the content of amorphous particles is preferably within the above range based on 100% by mass of the total solids content of the topcoat layer 1.

[0049] When the topcoat layer 1 contains particles 1a and the other fillers mentioned above as fillers, the total content of the fillers is 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more, based on 100% by mass of the total solids content of the topcoat layer 1. Furthermore, the total content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, based on 100% by mass of the total solids content of the topcoat layer 1.

[0050] The content of particles 1a in the top coat layer 1 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 amount of the filler, and may also be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0051] Examples of the above lubricants include fatty acids such as oleic acid, metal soaps such as zinc stearate, fatty acid amides such as stearate amide, polyolefin waxes such as polyethylene wax, ester waxes such as polystyrene wax and carnauba wax, paraffin wax, silicone oil, and oils such as whale oil. From the viewpoint of improving transparency and matching suitability with thermal heads, the above lubricants preferably contain metal soaps and / or polyolefin waxes, more preferably contain zinc stearate and / or polyethylene wax, and even more preferably contain zinc stearate and polyethylene wax.

[0052] From the viewpoint of further improving transparency, the average particle size of the above lubricant is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.5 μm. In this specification, unless otherwise specified, the average particle size of components other than particle 1a (lubricant, colorant, developer, and other fillers) refers to the particle size at 50% of the cumulative value of the particle size distribution measured by laser diffraction-scattering (D50, median diameter). The average particle size can be measured by laser diffraction-scattering, for example, using the "MT3300EX-II" product name from Microtrac-Bell.

[0053] The average particle size of the above-mentioned metal soaps is preferably 1 to 10 μm, and more preferably 4 to 7 μm, from the viewpoint of further improving transparency and head matching suitability. Generally, as the average particle size of particulate raw materials decreases, light scattering on the particle surface is further suppressed, and therefore transparency tends to improve. However, for the above-mentioned metal soaps, by keeping the average particle size within the above range, transparency can be further improved and head matching suitability can be made more appropriate. Normally, the above-mentioned metal soaps are opaque particulate raw materials with relatively high hiding power, making it difficult to formulate them while ensuring transparency. For this reason, it is presumed that for the above-mentioned metal soaps, rather than improving transparency by decreasing the average particle size, it is more effective to deliberately increase the average particle size to reduce the packing rate of the metal soaps in the topcoat layer 1 and suppress the hiding power, thereby improving transparency. In addition, when the average particle size of the above-mentioned metal soaps is within the above range, a portion is exposed from the topcoat layer 1 and it is easier for them to come into contact with the thermal head, which is also preferable from the viewpoint of improving head matching suitability.

[0054] 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 solids content of the top coat layer 1. 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 15% by mass or less, based on 100% by mass of the total solids content of the top coat layer 1.

[0055] When the top coat layer 1 contains the above-mentioned metal soaps as a lubricant, the content of the metal soaps is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and particularly preferably 20 to 30% by mass, based on 100% by mass of the total amount of the lubricant. When the above content is within the above range, it is easy to improve transparency while maintaining appropriate head matching. Furthermore, the content of the above-mentioned zinc stearate is preferably within the above range, based on 100% by mass of the total amount of the lubricant.

[0056] When the top coat layer 1 contains the above-mentioned metal soaps and polyolefin wax as lubricants, the mass ratio of the polyolefin wax to the metal soaps [parts by mass of polyolefin wax / parts by mass of metal soaps] is preferably 1 to 10, more preferably 1.5 to 6, and even more preferably 2 to 4, from the viewpoint of further improving transparency and head matching suitability. Furthermore, the mass ratio of the polyethylene wax to the zinc stearate is preferably within the above range.

[0057] Examples of the wetting agents mentioned above include surfactants. Known surfactants can be used as appropriate, and examples include anionic surfactants such as sodium dioctyol succinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and alkyl ether sulfates; and nonionic surfactants such as acetylene glycol surfactants and polyoxyalkylene alkyl ethers.

[0058] The coating amount (dry mass) of topcoat layer 1 is 0.1 g / m². 2 ~10g / m 2 Preferably, and more preferably, 1.0 g / m 2 ~5.0g / m 2 That is the case.

[0059] [Method for manufacturing the top coat layer] The topcoat layer of the present invention can be manufactured by known or conventional methods. For example, a method for manufacturing the topcoat layer 1 shown in Figure 1 will be described. First, a coating liquid for forming the topcoat layer 1 is prepared by a conventional method.

[0060] (Preparation process) The method for preparing the above coating solution is not particularly limited, and for example, it can be prepared by pre-dispersing all the materials used in the topcoat layer 1 in the same solvent. Examples of methods for preparing the coating solution that forms the topcoat layer include stirring, ultrasonic treatment, crushing treatment using a ball mill, bead mill, sand mill, high-pressure homogenizer, etc. One of these methods may be used, or two or more may be used.

[0061] (Coating process) The prepared topcoat coating solution is applied directly to the target surface, such as the thermal recording layer or intermediate layer described later. 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. One or more of these methods may be used.

[0062] (drying process) The method for drying the above-mentioned coating liquid is not particularly limited and includes, for example, heat drying, room temperature drying, and vacuum drying. One of these methods may be used, or two or more may be used.

[0063] The top coat layer 1 can be manufactured as described above. The top coat layer of the present invention has both transparency and a matte finish, resulting in an aesthetically pleasing appearance and excellent design. Furthermore, since the particles 1a also function as a filler, when used with the thermal recording material described later, it also exhibits excellent compatibility with the thermal head, resulting in good printability.

[0064] [Thermal recording media] The thermal recording body of the present invention has a structure in which at least a thermal recording layer and the top coat layer of the present invention described above are laminated. The top coat layer is located on one surface of the thermal recording body of the present invention. The thermal recording body of the present invention may also include other layers other than the thermal recording layer and the top coat layer. Examples of these other layers include a substrate, an anchor layer, and an intermediate layer. The substrate functions as a support for the thermal recording layer and the top coat layer, increasing the strength of the thermal recording body of the present invention and improving handling and manufacturability. The anchor layer is a layer provided between the substrate and the thermal recording layer, and can improve the adhesion between the thermal recording layer and the substrate. The intermediate layer is a layer located between the thermal recording layer and the top coat layer, and includes a protective layer that protects the thermal recording layer.

[0065] The thermal recording body of the present invention preferably comprises a substrate as one of the other layers. The thermal recording body of the present invention comprising the substrate preferably has a structure in which the substrate, the thermal recording layer, and the top coat layer are laminated in this order.

[0066] The thermal recording material of the present invention preferably includes an intermediate layer as one of the other layers. The thermal recording material of the present invention, which includes the intermediate layer, preferably has a structure in which a thermal recording layer, an intermediate layer, and a top coat layer are laminated in this order.

[0067] Hereinafter, one embodiment of the thermal recording body of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments.

[0068] Figure 2 shows one embodiment of the thermal recording body of the present invention. The thermal recording body 10 shown in Figure 2 comprises a substrate 2, a thermal recording layer 3, an intermediate layer 4, and a top coat layer 1 in that order. The top coat layer 1 is located on one surface of the thermal recording body 10, and the substrate 2 is located on the other surface of the thermal recording body 10.

[0069] (base material) The base material 2 is preferably a transparent film. Examples of the transparent film include synthetic resin films such as polypropylene film, polyethylene terephthalate film, polystyrene film, and polycarbonate film. The transparent film may be stretched or unstretched. Furthermore, the base material 2 may be a single layer or a multi-layered layer.

[0070] The thickness of the base material 2 is not particularly limited, but is preferably 5 to 150 μm, and more preferably 10 to 100 μm. Furthermore, from the viewpoint of reducing the amount of resin material used and reducing plastic use, the above thickness may be 50 μm or less, or 40 μm or less.

[0071] The opacity of the substrate 2 is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less, from the viewpoint of further improving transparency. The above opacity can be measured by a conventional method, for example, by the method specified in JIS P8149.

[0072] The haze of the substrate 2 is preferably 10% or less, more preferably 5% or less, and even more preferably 3.5% or less, from the viewpoint of further improving transparency. The above haze can be measured by a conventional method, for example, by the method specified in JIS K7136.

[0073] (Thermal recording layer) The thermal recording layer 3 is a layer that develops color through a chemical reaction when heated by a thermal head or the like, forming a recorded image on the thermal recording body 10. The thermal recording layer 3 may contain colorants, color developers, fillers, binders, lubricants, sensitizers, wetting agents, etc. Only one of these components may be used, or two or more may be used.

[0074] The thermal recording layer 3 preferably contains the above-mentioned colorant. Examples of the above-mentioned colorant include leuco dyes. The above leuco dyes include, for example, 2-aniline-3-methyl-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-ethyl-Np-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-Nn-propyl)amino-6-methyl-7-anilinofluorane, and 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. The average particle size of the above-mentioned colorant is preferably 0.1 to 1.0 μm, from the viewpoint of improving transparency and color development efficiency.

[0075] The content of the above-mentioned coloring agent 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 3. Furthermore, the content of the above-mentioned coloring agent is preferably 40% by mass or less, more preferably 30% 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 thermal recording layer 3.

[0076] It is preferable that the thermal recording layer 3 contains the above-mentioned color developer. Examples of the above-mentioned color developer include 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone, 1,1-bis(p-hydroxyphenyl)cyclohexane, 1,1-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2'-methylenebis(4-chlorophenol), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and 4-hydroxy-4'-methyldi Phenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 4-hydroxy-4'-allyloxydiphenylsulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, poly(4-hydroxybenzoic acid), benzyl 4-hydroxybenzoate, 2,4-bis(phenylsulfonyl)phenol, α-{4-[(hydroxyphenyl)sulfonyl]phenyl}-Ω-hydroxypoly(degree of polymerization 1-7)(oxyethyleneoxyethyleneoxy-p-phenylenesulfonyl-p-phenylene), 2,2-bis[(4-methyl-3-phenoxycarbonylaminophenyl)urea]diphenylsulfone, 3,5-bis(α-methylbenzyl)salicylic acid, bis[4-(n-octyloxycarbonylamino)salicylate zinc], 4,4'-Bis(p-tolylsulfonylaminocarbonylamino)diphenylmethane, 4-hydroxybenzenesulfonanilide, 2'-(3-phenylureido)benzenesulfonanilide, 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, 4-tert-butylphenol-formaldehyde polycondensate, N-(p-toluenesulfonyl)N'-(3-p-toluenesulfonyloxyphenyl)urea, 1-phenyl-3-(4-methylphenylsulfonyl)urea, etc. can be used. The average particle size of the above color developer is preferably 0.1 to 1.0 μm from the viewpoint of improving transparency and color development efficiency.

[0077] 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 3. Furthermore, the content of the above-mentioned color developer is preferably 60% by mass or less, more preferably 50% 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 3.

[0078] The thermal recording layer 3 preferably contains the above-mentioned filler. Examples of the above-mentioned filler 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, white carbon, zinc oxide, silicon oxide, colloidal silica, hollow particles, and particles without hollows. The average particle size of the above-mentioned filler is preferably 1.0 μm or less from the viewpoint of improving transparency. In this specification, the average particle size of the above-mentioned filler refers to the particle size (D50, median diameter) at 50% of the cumulative value of the particle size distribution measured by laser diffraction-scattering.

[0079] The content of the above-mentioned filler 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 3. Furthermore, the content of the above-mentioned filler is preferably 40% by mass or less, more preferably 30% 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 thermal recording layer 3.

[0080] The thermal recording layer 3 preferably contains the above-mentioned binder. Examples of the binder include those similar to the binder exemplified in the section on topcoat layer 1. The binder may be a resin having a water-soluble portion or a resin not having a water-soluble portion. The resin may be a modified resin modified by a known method.

[0081] The content of the above-mentioned binder is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the total solid content of the thermal recording layer 3. Furthermore, the content of the above-mentioned binder is preferably 60% by mass or less, more preferably 50% 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 3.

[0082] The thermal recording layer 3 preferably contains the above-mentioned lubricant. Examples of the above-mentioned lubricant include fatty acids such as oleic acid, metal soaps such as zinc stearate, fatty acid amides such as stearate amide, polyolefin waxes such as polyethylene wax, ester waxes such as polystyrene wax and carnauba wax, paraffin wax, silicone oil, whale oil, and other oils. From the viewpoint of improving transparency, the average particle size of the above-mentioned lubricant is preferably 1.0 μm or less, and more preferably 0.5 μm or less.

[0083] The above lubricant preferably contains paraffin wax from the viewpoint of improving transparency. The melting point of the above lubricant is preferably below the color development temperature of the thermal recording layer 3, for example, preferably below 80°C, more preferably below 70°C, even more preferably below 60°C, and particularly preferably below 50°C. When the coating liquid for the thermal recording layer contains a low-melting-point lubricant, when the coating liquid is applied to the substrate 2 and heated to dry, the low-melting-point lubricant is thought to melt and enter into gaps such as irregularities on the particle surface of the other components constituting the thermal recording layer 3, thereby filling the voids. As a result, when the thermal recording layer 3 is formed, the voids in the layer are reduced, and the diffuse reflection of light that may occur in the voids is suppressed, which can improve the transparency of the thermal recording body 10.

[0084] The lubricant content is, for example, 0.1 g / m² as dry mass. 2 ~1.0g / m 2 It is preferable that the paraffin wax content is within the above range.

[0085] The content of the above lubricant is preferably 0.1% 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 thermal recording layer 3. Furthermore, the content of the above lubricant 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 thermal recording layer 3.

[0086] Examples of the sensitizers mentioned above include anilide stearate, 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, diphenylsulfone, p-benzyloxybenzoate benzyl, dibenzyl terephthalate, and p-toluenesulfonamide.

[0087] Examples of the wetting agent include the same ones as those exemplified in the item of the top coat layer 1.

[0088] The coating amount (dry mass) of the heat-sensitive recording layer 3 is, for example, 0.3 g / m 2 ~10 g / m 2 is preferable, and more preferably 2.0 g / m 2 ~6.0 g / m 2 When the coating amount is within the above range, it is easier to make the color developing property more appropriate.

[0089] (Intermediate layer) The intermediate layer 4 has a barrier property against water and oil and has a function of improving the water resistance and chemical resistance of the heat-sensitive recording body 10. The intermediate layer 4 may contain a binder, a crosslinking agent, a wetting agent, etc. These components may each be used alone or two or more of them may be used.

[0090] Examples of the binder include resins. Examples of the binder include the same ones as those exemplified in the item of the top coat layer 1. The binder may be a resin having a water-soluble portion or a resin not having a water-soluble portion. The resin may be a modified resin modified by a known method.

[0091] The above-mentioned binder preferably contains a resin having a water-soluble portion, from the viewpoint of improving the transparency of the thermal recording body 10. Examples of resins having a water-soluble portion include polyvinyl alcohol (PVA), which is a resin having a hydroxyl group as a hydrophilic structural unit, and resins having a carboxyl group as a hydrophilic structural unit (carboxyl group-containing resin). In this specification, "carboxyl group-containing resin" means a resin that contains a carboxyl group in the structural units of the polymer or copolymer that forms the resin. Furthermore, the carboxyl group in the carboxyl group-containing resin may be a free carboxyl group or an acid anhydride group (specifically, a dicarboxylic acid anhydride group). In addition, the acid anhydride group may be partially ring-opened to become a carboxyl group. In the carboxyl group-containing resin, some or all of the carboxyl groups may be neutralized with an alkali.

[0092] The above-mentioned binder preferably contains a carboxyl group-containing resin. The carboxyl group-containing resin is preferably at least one selected from the group consisting of acrylic resins and maleic acid resins, and more preferably an acrylic resin.

[0093] The above-mentioned binder preferably contains a core-shell type resin from the viewpoint of further improving transparency. The above-mentioned core-shell type resin is preferably, for example, a carboxyl group-containing resin with a core-shell structure (core-shell type carboxyl group-containing resin). In this specification, "core-shell type resin" means a resin with a core-shell structure in which hydrophobic core particles are coated with a water-soluble shell polymer. Generally, a core-shell type resin is a resin obtained by forming hydrophobic core particles and a water-soluble shell polymer through a multi-step polymerization reaction, and the resins constituting the core particles and shell polymer are the same as those described above. Therefore, all of the above descriptions of resins can be applied to the resin in the core-shell type resin.

[0094] The above-mentioned core-shell type carboxyl group-containing resin is preferably at least one selected from the group consisting of core-shell type acrylic resins and core-shell type maleic acid resins, and more preferably a core-shell type acrylic resin. Examples of the above-mentioned core-shell type acrylic resins include core-shell type acrylic resins, core-shell type styrene-acrylic resins, core-shell type acrylic-urethane resins, core-shell type acrylamide resins, and core-shell type vinyl acetate-acrylic resins. As the core-shell type resin, for example, a resin commercially available under the name Barrierstar (manufactured by Mitsui Chemicals, Inc.) can be used.

[0095] Water-soluble polyvinyl alcohol and core-shell type acrylic resins have good film-forming properties. Furthermore, when the coating liquid for forming the intermediate layer is applied to the thermal recording layer 3 and dried, the resin with a water-soluble portion penetrates into the thermal recording layer 3, forming a smooth intermediate layer 4. As a result, diffuse reflection of light in the thermal recording layer 3 is further suppressed, which can further improve the transparency of the thermal recording body 10.

[0096] The content of the above-mentioned binder is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on 100% by mass of the total solid content of the intermediate layer 4. Furthermore, the content of the above-mentioned binder is preferably 95% by mass or less, and more preferably 90% by mass or less, based on 100% by mass of the total solid content of the intermediate layer 4.

[0097] The content of the above-mentioned core-shell type resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on 100% by mass of the total amount of binder in the intermediate layer 4. It may also be 95% by mass or more, or 99% by mass or more.

[0098] The intermediate layer 4 preferably contains a crosslinking agent. Examples of the crosslinking agent include those similar to those exemplified in the section on topcoat layer 1. In particular, from the viewpoint of further improving transparency, the crosslinking agent is preferably a cationic crosslinking agent, and more preferably an epichlorohydrin resin. The epichlorohydrin resin is preferably one or more selected from the group consisting of polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and polyamide polyamine epichlorohydrin resin, and more preferably a polyamide epichlorohydrin resin.

[0099] The content of the above crosslinking agent 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 intermediate layer 4. Furthermore, the content of the above crosslinking agent is preferably 40% by mass or less, more preferably 30% 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 intermediate layer 4.

[0100] The amount of the crosslinking agent is preferably 1 to 30 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 15 to 20 parts by mass, relative to 100 parts by mass of the total amount of the binder. Furthermore, the amount of the crosslinking agent is preferably within the above range relative to 100 parts by mass of the total amount of the core-shell type resin.

[0101] Examples of the wetting agents mentioned above include those similar to the wetting agents exemplified in the section on topcoat layer 1.

[0102] For example, the coating amount (dry mass) of the intermediate layer 4 is 0.3 g / m². 2 ~10g / m 2 Preferably, and more preferably, 1.0 g / m 2 ~5.0g / m 2 That is the case.

[0103] When the thermal recording body 10 has a top coat layer 1 on one surface and a substrate 2 on the other surface, the opacity of the thermal recording body 10 is preferably 20% or less, and more preferably 18% or less. The haze of the thermal recording body 10 is preferably 40-85%, and more preferably 60-85%. The 60° gloss of the thermal recording body 10 is preferably 40% or less, and more preferably 35% or less. Furthermore, it is preferable that the opacity of the thermal recording body 10 is 20% or less, the haze is 40-85%, and the 60° gloss is 40% or less, and more preferably that the opacity is 18% or less, the haze is 60-85%, and the 60° gloss is 35% or less. When at least one of the above parameters—opacity, haze, or 60° gloss—is within the above range, transparency and / or matte finish can be improved. Furthermore, if the three parameters mentioned above—opacity, haze, and 60° gloss—are simultaneously within the specified range, the transparency and matte finish can be further enhanced.

[0104] [Method for manufacturing thermal recording media] The thermal recording material of the present invention can be manufactured by known or conventional methods. For example, a method for manufacturing the thermal recording material 10 shown in Figure 2 will be described. First, coating liquids for forming each layer are prepared by a conventional method.

[0105] (Preparation process) The method for preparing the above coating solution is not particularly limited, and for example, it can be prepared by pre-dispersing all the materials used in each layer in the same solvent. Alternatively, in preparing the coating solution for the thermal recording layer, 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. Examples of methods for preparing the above coating solution for the thermal recording layer include stirring, ultrasonic treatment, crushing treatment using a ball mill, bead mill, sand mill, high-pressure homogenizer, etc. One of these methods may be used, or two or more may be used.

[0106] (Coating process) The method of applying the above coating liquid is not particularly limited and includes methods such as direct application to the substrate or application to a release film and then transfer to 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 application using a wire bar is also acceptable. One of these methods may be used, or two or more may be used.

[0107] (drying process) The method for drying the above coating liquid is not particularly limited and includes, for example, heat drying, room temperature drying, and vacuum drying. One of these methods may be used, or two or more may be used. Furthermore, when each layer is formed by transferring it to the substrate 2, drying may be performed after transferring to the substrate 2, or after drying.

[0108] As described above, a thermal recording body 10 can be manufactured by sequentially forming a thermal recording layer 3, an intermediate layer 4, and a top coat layer 1 on one surface of the substrate 2.

[0109] The thermal recording material of the present invention has a top coat layer that combines transparency and a matte finish, resulting in excellent visibility when viewed through the thermal recording material, while also evoking an aesthetic sense such as a high-quality feel based on its matte finish. Furthermore, the top coat layer also has excellent compatibility with thermal heads, thus offering excellent printability. [Examples]

[0110] 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.

[0111] Example 1 (Preparation of thermal recording media) <Thermal recording layer> A thermal recording layer coating solution (solid content 25% by mass) was prepared by conventional methods, containing 35% by mass of 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone (average particle size: 0.4 μm) as a color developer, 14% by mass of kaolin (average particle size: 0.4 μm) as a filler, 28% by mass of styrene-butadiene latex (SBR) (glass transition temperature: -3°C) as a binder, 6% by mass of paraffin (melting point: 46°C, average particle size: 0.2 μm) as a lubricant, 17% by mass of 2-aniline-3-methyl-6-(N-methyl-p-toluidino)fluorane as a leuco dye, and water as a solvent. The above-mentioned thermal recording layer coating solution is applied to one surface of a transparent film (material: polyethylene terephthalate, thickness: 25 μm, opacity: 2.0%, haze: 3.4%, 60° gloss: 138%) using a conventional method, and then dried, resulting in a coating amount of 4.5 g / m². 2 A thermal recording layer of (dry mass) was formed. The values ​​for each material above represent the mass ratio of each material to 100% by mass of the thermal recording layer (dry state).

[0112] <Middle class> An intermediate layer coating solution containing 84% by mass of a core-shell type acrylic resin as a binder, 15% by mass of a polyamide epichlorohydrin resin as a crosslinking agent, 1% by mass of an acetylene glycol-based surfactant as a wetting agent, and water as a solvent was prepared by a conventional method. The above intermediate layer coating solution was applied to the surface of the heat-sensitive recording layer by a conventional method and dried, resulting in a coating amount of 2.0 g / m². 2 An intermediate layer of (dry mass) was formed. The values ​​for each material above represent the mass ratio of each material to 100% by mass of the intermediate layer (dry state).

[0113] <Top coat layer> A topcoat coating solution (solid content 14% by mass) was prepared by conventional means, containing 42.0% by mass of acrylic resin as a binder, 5.0% by mass of zirconium ammonium carbonate as a crosslinking agent, 10.3% by mass of lubricant A and 3.4% by mass of lubricant B as lubricants, 39.2% by mass of filler A as a filler, and water as a solvent. The above topcoat coating solution was applied to the surface of the above intermediate layer by conventional means and dried, resulting in a coating amount of 1.5 g / m². 2 A topcoat layer of (dry mass) was formed. The values ​​for each material listed above represent the mass ratio of each material to 100% by mass of the topcoat layer (dry state).

[0114] Examples 2-7, Comparative Examples 1-6 A thermal recording body was prepared in the same manner as in Example 1, except that the composition of the coating liquid for the top coat layer was changed as shown in Table 1.

[0115] [Table 1]

[0116] Examples 8-14 A thermal recording body was prepared in the same manner as in Example 1, except that the composition of the coating liquid for the top coat layer was changed as shown in Table 2.

[0117] [Table 2]

[0118] [evaluation] The thermal recording materials prepared in the examples and comparative examples were evaluated as follows. The results are shown in Table 3.

[0119] (1) Opacity The opacity of the thermal recording materials prepared in the examples and comparative examples was measured using a reflectance densitometer (manufactured by Tokyo Denshoku Co., Ltd., device name: TC-6DS / A) according to the method specified in JIS P8149.

[0120] (2) Hayes The haze of the thermal recording materials prepared in the examples and comparative examples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., device name: NDH700) according to the method specified in JIS K7136.

[0121] (3) 60° gloss The 60° gloss of the thermal recording materials prepared in the examples and comparative examples was measured using a handheld gloss meter (manufactured by Nippon Denshoku Industries Ltd., device name: PG-1M) according to the method specified in JIS Z8741.

[0122] (4) Parameter evaluation The evaluation was conducted based on the following criteria. [Evaluation Criteria] ◎: (1) The opacity is 18% or less, (2) The haze is 60-85%, and (3) The 60° gloss is 35% or less. ○: (1) The opacity is 20% or less, (2) The haze is 40-85%, and (3) The 60° gloss is 40% or less (excluding those with a ◎ rating). ×: One or more of the following conditions must be met: (1) Opacity is greater than 20%, (2) Haze is less than 40% or greater than 85%, or (3) 60° gloss is greater than 40%.

[0123] (5) Uniformity of the scalp area The scalp area was visually inspected and evaluated based on the following evaluation criteria. [Evaluation Criteria] ○: The matte finish on the scalp area is uniform. ×: The matte finish on the scalp area is uneven and resembles orange peel.

[0124] (6) Surface quality of the printed area The printed area was visually inspected and evaluated based on the following evaluation criteria. [Evaluation Criteria] ○: The matte finish of the printed area is the same as the background. ×: The matte finish of the printed area is less pronounced than the background, giving it a glossy appearance.

[0125] [Table 3]

[0126] As shown in Table 3, the thermal recording materials of the examples using fillers A to G, in which the primary particles are fixed-form particles and composed of specific materials, were able to achieve the target numerical range for all three parameters: opacity, haze, and 60° gloss. Therefore, they were evaluated as thermal recording materials that combine transparency and matte finish. Furthermore, the background surface was evaluated as having excellent aesthetics due to its high uniformity of matte finish. In addition, the printed area had a matte finish that blended seamlessly with the background surface, and the surface quality of the printed area was also evaluated as excellent.

[0127] On the other hand, when calcium carbonate filler H was used, and its content was approximately 33% by mass relative to 100% by mass of the total solid content of the topcoat layer (Comparative Example 1), the opacity could not be brought within the target numerical range, the base material appeared whitish and cloudy, and the transparency was evaluated as insufficient.

[0128] When fillers I and J, composed of polyolefin resin, were used (Comparative Examples 2-3), the haze could not be brought within the target numerical range, the base surface appeared whitish and cloudy, and the transparency was evaluated as insufficient. Polyolefin resin particles are highly hydrophobic because they consist only of non-polar structural units. Because particles composed of such resins have a different degree of light transmission and / or scattering than fillers A-G, it was difficult to satisfy all parameters simultaneously. In addition, the matte finish of the base surface was uneven and observed to be orange peel-like. Therefore, the uniformity of the matte finish of the base surface was low and it was evaluated as having poor aesthetics. It is presumed that because polyolefin resin particles are highly hydrophobic resins that do not have polar groups in their structural units, their dispersibility in the coating liquid is low, and they were unevenly dispersed in the topcoat layer, resulting in the orange peel-like appearance.

[0129] When using filler K, which is an aggregate of styrene-acrylic resin fine particles (primary particles) (secondary particles) (Comparative Example 4), the opacity could not be brought within the target numerical range, the background appeared whitish and cloudy, and the transparency was evaluated as insufficient. Electron microscope observation revealed that the primary particles of filler K were irregularly shaped particles with a primary particle diameter of approximately 0.1 to 0.3 μm. These primary particles aggregate to form roughly spherical secondary particles, resulting in many voids within the secondary particles. Therefore, it is presumed that light is highly diffusely reflected and easily absorbed on the surface and / or within the secondary particles, resulting in reduced light transmittance. Furthermore, a strong gloss was observed only in the printed area, and the surface quality of the printed area was evaluated as inferior. This is presumed to be because filler K has a relatively low glass transition temperature of 85°C, causing it to melt due to the heat of the thermal head during printing, resulting in gloss.

[0130] When filler L, which is amorphous silica, was used (Comparative Example 5), the opacity could not be brought within the target numerical range, the base surface appeared whitish and cloudy, and the transparency was evaluated as insufficient. Filler L is said to form aggregates (secondary particles) in which amorphous silica fine particles (primary particles) are irregularly aggregated. Therefore, it is presumed that light is highly diffusely reflected and easily absorbed on the surface and / or inside the secondary particles, resulting in a decrease in light transmittance. On the other hand, when filler M, which is colloidal silica, was used (Comparative Example 6), although the opacity decreased significantly and the transparency improved, a significant decrease in haze and a significant increase in gloss were observed, and the matte finish was evaluated as insufficient. Filler M consists of spherical particles, which are primary particles, dispersed without almost aggregation, and their average primary particle diameter is on the nano-order, which is very small. Therefore, it is presumed that filler M is completely embedded in the topcoat layer, and the degree of light scattering is insufficient, so although the transparency is excellent, it was difficult to bring the haze and gloss within the target numerical range.

[0131] Furthermore, when printing was performed on the thermal recording media of Examples 1 to 14 using a thermal label printer (manufactured by Teraoka Seiko Co., Ltd., device name: HP-800) set to a printing speed of 115 mm / sec and a duty cycle of 70%, and visually evaluated, it was found that printing with sufficient density was possible. In addition, the retention rate of the printed area was 95% or more for all thermal recording media after 3 days from printing, confirming excellent printability.

[0132] The various raw materials shown in Tables 1 and 2 are as follows: <Lubricant> Lubricant A: Polyethylene wax (average particle size: 0.19 μm) Lubricant B: Zinc stearate (average particle size: 5.5 μm) Lubricant C: Zinc stearate (average particle size: 0.9 μm) <Filler> Filler A: Spherical particles (Material: Acrylic resin, Primary particle shape: Spherical, Average primary particle diameter: 2.0 μm, Glass transition temperature: 110°C) Filler B: Spherical particles (Material: Acrylic resin, Primary particle shape: Spherical, Average primary particle diameter: 2.5 μm, Glass transition temperature: 110°C) Filler C: Spherical particles (Material: Acrylic resin, Primary particle shape: Spherical, Average primary particle diameter: 5.0 μm, Glass transition temperature: 110°C) Filler D: Spherical particles (Material: Silicone resin, Primary particle shape: Spherical, Average primary particle diameter: 2.0 μm) Filler E: Spherical particles (Material: Silica, Primary particle shape: Spherical, Average primary particle diameter: 2.5 μm) Filler F: Spherical particles (Material: aluminosilicate, Primary particle shape: spherical, Average primary particle diameter: 2.1 μm) Filler G: Cubic particles (Material: aluminosilicate, Primary particle shape: cubic, Average primary particle diameter: 2.5 μm) Filler H: Calcium carbonate (Material: Calcium carbonate, Primary particle shape: Irregular, Average primary particle diameter: 0.5 μm) Filler I: Spherical particles (Material: Polyolefin resin, Primary particle shape: Spherical, Average primary particle diameter: 2.5 μm, Softening point: 113°C) Filler J: Spherical particles (Material: Polyolefin resin, Primary particle shape: Spherical, Average primary particle diameter: 3 μm, Softening point: 132°C) Filler K: Fine particle aggregate (Material: Styrene acrylic resin, Primary particle shape: Irregular, Average secondary particle diameter: 1.0 μm, Glass transition temperature: 85°C) Filler L: Amorphous silica (Material: Silica, Primary particle shape: Amorphous, Average primary particle diameter: 40-100 nm, Average secondary particle diameter: 2.0 μm) Filler M: Colloidal silica (Material: Silica, Primary particle shape: Spherical, Average primary particle diameter: 35-55 nm)

[0133] In summary, the configuration of the present invention and its variations are described below. [Note 1] A topcoat layer comprising primary particles that are shaped particles and have an average primary particle diameter of 0.5 μm or more, wherein the particles comprise one or more selected from the group consisting of resins containing structural units having polar groups and inorganic oxides, the content of the particles is 5% by mass or more with respect to 100% by mass of the total solid content of the topcoat layer, and the topcoat layer may also contain calcium carbonate, the content of the calcium carbonate is 30% by mass or less with respect to 100% by mass of the total solid content of the topcoat layer. [Note 2] The topcoat layer according to Note 1, wherein the primary particles are spherical particles or polyhedral particles. [Note 3] The top coat layer according to Note 1 or 2, wherein the particles are arranged as primary particles in the top coat layer. [Note 4] The top coat layer according to any one of Notes 1 to 3, wherein the particles include a resin containing at least the structural units having the polar groups. [Note 5] The top coat layer according to any one of Notes 1 to 4, wherein the glass transition temperature of the particles is 90°C or higher. [Note 6] The top coat layer according to any one of Notes 1 to 5, wherein the resin containing the structural unit having the polar group is one or more selected from the group consisting of acrylic resins and silicone resins. [Note 7] The top coat layer according to any one of Notes 1 to 6, wherein the inorganic oxide is one or more selected from the group consisting of silica, aluminosilicate, and alumina. [Appendix 8] A thermal recording body further comprising a substrate and a thermal recording layer, wherein the substrate, the thermal recording layer, and the top coat layer described in any one of Appendix 1 to 7 are laminated in this order. [Note 9] The thermal recording body described in Note 8, wherein the substrate is a transparent film. [Note 10] The thermal recording body according to Note 8 or 9, wherein the top coat layer is provided on one surface and the substrate is provided on the other surface, the opacity is 20% or less, the haze is 40-85%, and the 60° gloss is 40% or less. [Explanation of symbols]

[0134] 1. Top coat layer 1a particle 1b Binding agent 2 Base material 3. Thermal recording layer 4. Middle Class 10 Thermal recording media

Claims

1. A topcoat layer containing primary particles that are well-formed and have an average primary particle diameter of 0.5 μm or more. The particles include one or more selected from the group consisting of resins containing structural units having polar groups and inorganic oxides. The content ratio of the aforementioned particles is 5% by mass or more, relative to 100% by mass of the total solid content of the top coat layer. The top coat layer may contain calcium carbonate. The topcoat layer wherein the calcium carbonate content is 30% by mass or less with respect to 100% by mass of the total solid content of the topcoat layer.

2. The topcoat layer according to claim 1, wherein the primary particles are spherical particles or polyhedral particles.

3. The topcoat layer according to claim 1, wherein the glass transition temperature of the particles is 90°C or higher.

4. The topcoat layer according to claim 1, wherein the resin containing the structural unit having the polar group is one or more selected from the group consisting of acrylic resins and silicone resins.

5. The topcoat layer according to claim 1, wherein the inorganic oxide is one or more selected from the group consisting of silica, aluminosilicate, and alumina.

6. Furthermore, it comprises a substrate and a thermal recording layer, A thermal recording body in which the substrate, the thermal recording layer, and the top coat layer according to any one of claims 1 to 5 are laminated in this order.

7. The thermal recording body according to claim 6, wherein the substrate is a transparent film.

8. When the top coat layer is provided on one surface and the substrate is provided on the other surface, The opacity is 20% or less. The haze is between 40% and 85%. The thermal recording body according to claim 7, wherein the glossiness at 60° is 40% or less.

Images