Thermal recording device

Abstract

To provide a heat-sensitive recording material that is excellent in the long-term preservation of printed matter.SOLUTION: The present disclosure provides a heat-sensitive recording material which comprises, on a supporting body in the following order, at least a primer coating layer that contains hollow particles, an adhesive, and an inorganic pigment I, and a heat-sensitive recording layer that contains a leuco dye, a color developer, and an inorganic pigment II. The color developer is a compound represented by the general formula (1) (where R1-R5 each represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group or an arylamino group).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Thermal recording media that record colored images using the heating-induced color reaction between colorless or light-colored leuco dyes and phenols or organic acids are widely used. Because such thermal recording media form colored images simply by heating, they offer advantages such as compact recording devices, easy maintenance, and low noise generation. Therefore, thermal recording media are widely used as information recording materials in various applications, including label printers, automatic ticket vending machines, CD / ATM machines, order slip output machines in restaurants, and data output machines for scientific research equipment.

[0003] Generally, color developers containing phenolic hydroxyl groups have drawbacks such as poor thermal responsiveness and poor water resistance of the printed area. Furthermore, phenolic compounds such as bisphenol A have endocrine problems. As a result, demand for thermal recording paper using non-phenolic color developers is increasing, particularly in Europe, and various new non-phenolic color developers are being developed.

[0004] For example, Patent Document 1 proposes a thermal recording material using 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, a type of non-phenolic color developer, as a color developer. It has been reported that the printed area has excellent water resistance and the background exhibits high heat stability. However, it has been found that while such color developers have excellent heat resistance to background clouding at 90°C, the long-term preservation of the print is poor. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6529197 [Overview of the project] [Problems that the invention aims to solve]

[0006] The main objective of this invention is to provide a thermal recording material that offers excellent long-term storage of printed information. [Means for solving the problem]

[0007] The present inventors, after diligent research to solve the above-mentioned problems, discovered that the above-mentioned problems can be solved by combining a specific color developer with an inorganic pigment having an oil absorption capacity of 130 ml / 100 g or less, and thus completed the present invention. That is, the present invention relates to the following thermal recording material.

[0008] Item 1: A thermal recording body having, in this order, a base coat layer containing at least hollow particles, an adhesive and an inorganic pigment I, and a thermal recording layer containing a leuco dye, a color developer and an inorganic pigment II, wherein the color developer is the following general formula (1): [ka] (In the formula, R 1 ~R 5 A thermal recording body characterized by containing a compound represented by (), which is the same or different, representing a hydrogen atom, halogen atom, nitro group, amino group, alkyl group, alkoxy group, aryloxy group, alkylcarbonyloxy group, arylcarbonyloxy group, alkylcarbonylamino group, arylcarbonylamino group, alkylsulfonylamino group, arylsulfonylamino group, monoalkylamino group, dialkylamino group, or arylamino group, and containing an inorganic pigment II with an oil absorption of 130 ml / 100 g or less. Item 2: The thermal recording body according to Item 1, wherein the content of the inorganic pigment I is 60% by mass or less of the total solid content of the undercoat layer. Item 3: The thermal recording body according to item 1 or 2, wherein the oil absorption amount of the inorganic pigment I is 130 ml / 100 g or less. Item 4: A thermal recording body according to any one of items 1 to 3, wherein the oil absorption amount of the inorganic pigment II is 65 ml / 100 g or less. Item 5: The heat-sensitive recording body according to any one of Items 1 to 4, wherein the inorganic pigment II is at least one selected from the group consisting of calcium carbonate, aluminum hydroxide, and clay. Item 6: The heat-sensitive recording body according to any one of Items 1 to 5, wherein the content ratio of the hollow particles is 5 to 40% by mass of the total solid content of the undercoat layer. Item 7: The heat-sensitive recording body according to any one of Items 1 to 6, wherein the average particle diameter (D50) of the hollow particles is 3 to 15 μm. Item 8: The heat-sensitive recording body according to any one of Items 1 to 7, wherein the maximum particle diameter (D100) of the hollow particles is 10 to 30 μm. Item 9: The heat-sensitive recording body according to any one of Items 1 to 8, wherein the ratio D100 / D50 of the maximum particle diameter (D100) to the average particle diameter (D50) of the hollow particles is 1.8 to 3.0. Item 10: The heat-sensitive recording body according to any one of Items 1 to 9, wherein the volume percentage of the hollow particles having a particle diameter of 2.0 μm or less is 1% or less. Item 11: The heat-sensitive recording body according to any one of Items 1 to 10, wherein the hollow ratio of the hollow particles is 80 to 98%. Item 12: The heat-sensitive recording body according to any one of Items 1 to 11, wherein the adhesive of the undercoat layer contains a binder resin having a glass transition temperature of -10°C or lower. Item 13: The heat-sensitive recording body according to any one of Items 1 to 12, wherein the adhesive of the undercoat layer contains a binder resin having a glass transition temperature of -30°C or lower. Item 14: The heat-sensitive recording body according to any one of Items 1 to 13, wherein the compound represented by the general formula (1) is at least one selected from the group consisting of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 2-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, and 4-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate. Item 15: The heat-sensitive recording body according to any one of Items 1 to 14, which has an adhesive layer on at least one surface of the support.

Advantages of the Invention

[0009] The thermal recording material of the present invention offers excellent long-term storage of printed information. [Modes for carrying out the invention]

[0010] In this specification, the expression "includes" includes the concepts of "includes," "consisting only of substance," and "consisting only of."

[0011] In this specification, numerical ranges represented by "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits, respectively.

[0012] The latex in this invention includes a gel or dried film state formed by drying the dispersion medium.

[0013] The present invention relates to a thermal recording body having, in this order, a base coat layer containing at least hollow particles, an adhesive, and an inorganic pigment I, and a thermal recording layer containing a leuco dye, a color developer, and an inorganic pigment II, wherein the color developer is the following general formula (1): [ka] (In the formula, R 1 ~R 5 The compound contains a compound represented by ( ), which is identical or different to a hydrogen atom, halogen atom, nitro group, amino group, alkyl group, alkoxy group, aryloxy group, alkylcarbonyloxy group, arylcarbonyloxy group, alkylcarbonylamino group, arylcarbonylamino group, alkylsulfonylamino group, arylsulfonylamino group, monoalkylamino group, dialkylamino group, or arylamino group, and is characterized by containing a pigment with an oil absorption of 130 ml / 100 g or less as inorganic pigment II.

[0014] [Support] The support material in this invention is not particularly limited in terms of type, shape, dimensions, etc. For example, it can be appropriately selected and used from among high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film, and various transparent supports. The thickness of the support material is not particularly limited, and is usually around 20 to 200 μm. The density of the support material is also not particularly limited, and is typically 0.60 to 0.85 g / cm³. 3 A certain degree is desirable.

[0015] [Undercoat layer] The thermal recording material of the present invention has a primer layer between the support and the thermal recording layer. The primer layer contains hollow particles, an adhesive, and an inorganic pigment I.

[0016] (hollow particles) The hollow particles are preferably made of organic resin from the viewpoint of improving cushioning properties. The undercoat layer containing hollow particles has high heat insulation properties, which prevents the diffusion of heat applied to the thermal recording layer and can improve the sensitivity of the thermal recording material.

[0017] Hollow particles made of organic resin can be classified into foamed and non-foamed types depending on the manufacturing method. Of these two types, foamed hollow particles generally have a larger average particle diameter and a higher hollowness ratio than non-foamed hollow particles. Therefore, foamed hollow particles provide better sensitivity and image quality than non-foamed hollow particles.

[0018] Non-foaming hollow particles can be manufactured by polymerizing seeds in a solution, then polymerizing another resin to surround the seeds, and finally swelling and dissolving the internal seeds to remove them, thereby forming a cavity inside. When swelling and dissolving the internal seeds, an alkaline aqueous solution is used. Non-foaming hollow particles with a relatively large average particle size can also be obtained by alkali-swelling core particles coated with a shell layer that does not swell with alkali, and then subjecting these core-shell particles to alkali swelling treatment.

[0019] Foamed hollow particles can be manufactured by creating particles in which a volatile liquid is sealed inside a resin, and then heating the resin to soften it while simultaneously vaporizing and expanding the liquid inside the particles.

[0020] Foamed hollow particles, by heating and expanding the internal liquid during the manufacturing process, have a high hollowness ratio and thus high thermal insulation properties. This can increase the sensitivity of the thermal recording material and improve the recording density. Improved sensitivity is particularly important when developing colors in the midtone region where the thermal energy applied to the thermal recording layer is small. Furthermore, forming the thermal recording layer via a highly thermally insulating undercoat layer prevents the diffusion of heat applied to the thermal recording layer, resulting in excellent image uniformity and improved image quality. Therefore, in this embodiment, it is preferable to use foamed hollow particles that are excellent in improving the thermal insulation properties of the undercoat layer.

[0021] Resins that can be used for foamed hollow particles include thermoplastic resins such as styrene-acrylic resin, polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, polyvinyl chloride resin, polyvinylidene chloride resin, acrylic resin (for example, acrylic resin with acrylonitrile as a component), styrene resin, vinylidene chloride resin, and copolymer resins mainly composed of polyvinylidene chloride and acrylonitrile. Common gases contained inside foamed hollow particles include propane, butane, isobutane, and air. Among the various resins listed above, acrylonitrile resin and copolymer resins mainly composed of polyvinylidene chloride and acrylonitrile are preferred for use in hollow particles from the viewpoint of strength to maintain the shape of the foamed particles.

[0022] In this invention, the maximum particle diameter of the hollow particles is preferably 10 to 30 μm, more preferably 10 to 25 μm. The maximum particle diameter is also referred to as D100. When the maximum particle diameter of the hollow particles is 10 μm or more, the cushioning properties of the undercoat layer are improved, which improves the adhesion of the thermal recording material to the thermal head during printing, resulting in a high-quality thermal recording material. This high quality can lead to an improvement in the recording density in the midtones, which are colored with lower energy than that that gives the maximum recording density (Dmax). On the other hand, when the maximum particle diameter of the hollow particles is 30 μm or less, the smoothness of the undercoat layer is improved, which allows for a more uniform thermal recording layer provided via the undercoat layer, resulting in a thermal recording material that is less prone to white spots in the image.

[0023] In this invention, the average particle diameter of the hollow particles is preferably 3 to 15 μm, more preferably 5 to 15 μm. Here, the average particle diameter is the median diameter, which is the diameter at which the volume occupied by the larger particles and the smaller particles are equal when the particles are divided into two groups by particle diameter, i.e., the particle diameter at which the 50% volume frequency occurs, and is also referred to as D50. When the average particle diameter of the hollow particles is 3 μm or more, the cushioning properties of the undercoat layer are improved, which improves the adhesion of the thermal recording material to the thermal head during printing, resulting in a high-quality thermal recording material. This high quality can lead to an improvement in the recording density in the midtones, which are colored with lower energy than that that gives the maximum recording density (Dmax). On the other hand, when the average particle diameter of the hollow particles is 15 μm or less, the smoothness of the undercoat layer is improved, which allows for the uniformization of the thermal recording layer provided via the undercoat layer, resulting in a thermal recording material that is less prone to white spots in the image.

[0024] The maximum particle diameter (D100) and average particle diameter (D50) of hollow particles can be measured using a laser diffraction particle size distribution analyzer. Alternatively, the particle diameters can be measured from particle images (SEM images) using an electron microscope and the average value of 10 measurements can be presented.

[0025] The ratio D100 / D50, which is the ratio of the maximum particle diameter (D100) to the average particle diameter (D50) of hollow particles, is an indicator of the degree of particle size distribution. This ratio D100 / D50 is preferably 1.8 to 3.0, and more preferably 2.0 to 2.8. When the D100 / D50 of hollow particles is 1.8 or higher, the hollow particles foam sufficiently, the maximum particle diameter becomes sufficiently large, the hollowness ratio increases, and the heat insulation of the undercoat layer can be improved. On the other hand, when the D100 / D50 of hollow particles is 3.0 or lower, the size of the hollow particles becomes uniform, the smoothness of the undercoat layer increases, and white spots in the image can be suppressed.

[0026] In the particle size distribution determined by a laser diffraction particle size distribution analyzer, it is preferable that the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is 1% or less. Furthermore, it is preferable that the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is 0.5%. below It is preferable that it is present, and more preferable that it is not present. Hollow particles with a particle size of 2 μm or less are considered to have an extremely small contribution to heat insulation because their particle size is too small to provide a sufficient hollow region. By setting the volume percentage of hollow particles with a particle size of 2 μm or less in the undercoat layer to 1% or less, the recording density, image quality, etc. can be improved.

[0027] The hollow particles preferably have a hollowness ratio of 80-98%, and more preferably 90-98%. When the hollowness ratio of the hollow particles is 80% or higher, high heat insulation can be imparted to the undercoat layer containing the hollow particles. On the other hand, when the hollowness ratio of the hollow particles is 98% or lower, the strength of the film surrounding the hollow portion can be improved, resulting in hollow particles that do not collapse during the formation of the undercoat layer.

[0028] The hollowness ratio of hollow particles is determined by measuring the true specific gravity using the IPA method and then calculating the true specific gravity value as follows. (1) Sample pretreatment Dry the sample at 60°C overnight to obtain the sample. (2) Reagents • Isopropyl alcohol (IPA: reagent grade 1) (3) Measurement method • Weigh the volumetric flask accurately (W1). • Place approximately 0.5g of the dried sample into a volumetric flask and weigh it accurately (W2). Add approximately 50 mg of IPA and shake thoroughly to completely remove any air from outside the capsule. • Add IPA to the mark and refine (W3). • As a blank, add only IPA to a volumetric flask up to the mark and perform a detailed analysis (W4). (4) Calculation of true specific gravity True specific gravity = {(W2-W1)×((W4-W1) / 100)} / {(W4-W1)-(W3-W2)} (5) Calculation of the hollow ratio Hollowness ratio (%)={1-1 / (1.1 / true specific gravity)}×100

[0029] Furthermore, the hollow ratio is given by the following equation (d 3 / D 3 This value can also be obtained by multiplying by ) × 100. In this formula, d represents the inner diameter of the hollow particle, and D represents the outer diameter of the hollow particle.

[0030] Since the hollow particles in this invention have a relatively large particle size, their proportion in the undercoat layer can be reduced. The proportion of hollow particles is preferably 5 to 40% by mass, and more preferably 5 to 35% by mass, of the total solid content of the undercoat layer. When the proportion of hollow particles is 5% by mass or more, the thermal insulation properties of the undercoat layer can be improved. On the other hand, when the proportion of hollow particles is 40% by mass or less, problems in terms of coating properties, etc., are less likely to occur, a uniform undercoat layer can be easily formed, and the recording density can be improved. In addition, the coating strength of the undercoat layer can be increased.

[0031] (glue) Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or water-insoluble polymer latex such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. Among these, it is preferable to use an adhesive containing latex. The content of the adhesive can be selected from a wide range, but generally it is preferable to have about 20 to 70% by mass of the total solid content of the undercoat layer, and more preferably about 25 to 60% by mass.

[0032] The adhesive preferably contains a binder resin with a glass transition temperature (Tg) of -10°C or lower. A glass transition temperature of -10°C or lower allows for improved image quality even in the low-energy range. A glass transition temperature of -30°C or lower is more preferable, as it further improves image quality in the low-energy range. On the other hand, a temperature of -40°C or higher is preferable because stickiness occurs below -50°C, which is undesirable.

[0033] (Inorganic Pigments I) The undercoat layer in the present invention contains an inorganic pigment I. From the viewpoint of increasing the recording density and improving the long-term storage stability, the oil absorption of the inorganic pigment I is preferably 130 ml / 100 g or less, more preferably 125 ml / 100 g or less, and still more preferably 110 ml / 100 g or less. On the other hand, from the viewpoint of effectively reducing printing defects such as the occurrence of head caking and sticking, it is preferably 40 ml / 100 g or more, and more preferably 80 ml / 100 g or more. Here, the oil absorption is a value determined according to the method of JIS K 5101.

[0034] As the inorganic pigment I, various types can be used, but preferably calcined kaolin, clay, etc. From the viewpoint of improving the long-term storage stability, the content ratio of the inorganic pigment I is preferably 60% by mass or less, more preferably 50% by mass or less, based on the total solid content of the undercoat layer. On the other hand, from the viewpoint of effectively reducing printing defects such as the occurrence of head caking and sticking, it is preferably 20% by mass or more, and more preferably 25% by mass or more, based on the total solid content of the undercoat layer.

[0035] The undercoat layer is formed on the support by, for example, applying an undercoat layer paint prepared by mixing hollow particles, an adhesive, an inorganic pigment I, and optionally an auxiliary agent or the like with water as a medium, and then drying. The coating amount of the undercoat layer paint is not particularly limited, but is preferably about 2 to 20 g / m 2 in terms of dry mass, and more preferably about 2 to 12 g / m 2 in terms of dry mass.

[0036] [Thermosensitive recording layer] (Leuco dye) The thermosensitive recording layer in the thermosensitive recording medium of the present invention can contain various known colorless or light-colored leuco dyes. Specific examples of such leuco dyes are given below.

[0037] Specific examples of leuco dyes include, for example, blue dyes such as 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl)-6-dimethylaminophthalide, and fluorane; and green dyes such as 3-(N-ethyl-Np-tolyl)amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, and rhodamine B-anilinolactam. Chromogenic dyes, such as 3,6-bis(diethylamino)fluoran-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexyl)amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3 -di(n-butyl)amino-6-methyl-7-anilinofluorane, 3-di(n-pentyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-(N-isoamyl-N-ethylamino)-7-(o-chloroanilino)fluorane, 3-(N-ethyl-N-2-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3- (Nn-hexyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-N-methylamino]-6-methyl-7-anilinofluorane, 3-diethylamino-7-(2-chloroanilino)fluorane, 3-di(n-butylamino)-7-(2-chloroanilino)fluorane, 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-2,4,5-Trichlorophenylleucoauramine, 3-Diethylamino-7-butylaminofluorane, 3-Ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-Cyclohexyl-methylamino-6-methyl-7-anilinofluorane, 3-Diethylamino-6-chloro-7-(β-ethoxyethyl)aminofluorane, 3-Diethylamino-6-chloro-7-(γ-chloropropyl)aminofluorane, 3-Diethylamino-6-methyl-7-anilinofluorane, 3-(N-I Soamyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-dibutylamino-7-chloroanilinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-(p-toluidino)fluorane, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-diethylamino -6-chloro-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 2,2-bis{4-[6'-(N-cyclohexyl-N-methylamino)-3'-methylspiro[phthalide-3,9'-xanthene-2'-ylamino]phenyl}propane, 3-diethylamino-7-(3'-trifluoromethylphenyl)aminofluorane, etc. Chromolytic dyes, 3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3-p-(p-dimethylaminoanilino)anilino-6-methyl-7-chlorofluorane, 3-p-(p-chloroanilino)anilino-6-methyl-7-chlorofluorane, 3,Examples include dyes with absorption wavelengths in the near-infrared region, such as 6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide. Of course, the examples are not limited to these, and two or more compounds can be used in combination as needed.

[0038] The content of such leuco dye is not particularly limited, but is preferably about 3 to 30% by mass, more preferably about 5 to 25% by mass, and even more preferably about 7 to 20% by mass, of the total solid content of the thermal recording layer. By setting it to 3% by mass or more, the color development ability can be enhanced and the recording density can be improved. By setting it to 30% by mass or less, the heat resistance can be improved.

[0039] (Color developer) The present invention contains a compound represented by the above general formula (1) as a color developer. By combining this compound with inorganic pigment II, excellent long-term storage properties of printed materials can be achieved.

[0040] R 1 ~R 5 Examples of halogen atoms include fluorine atoms, chlorine atoms, and bromine atoms, with fluorine atoms and chlorine atoms being preferred.

[0041] The alkyl group may be linear, branched, or cyclic, preferably linear or branched alkyl groups, and more preferably linear alkyl groups. Typically, it is an alkyl group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably an alkyl group having 1 to 4 carbon atoms.

[0042] The alkoxy group may be linear, branched, or cyclic, preferably a linear or branched alkoxy group, and more preferably a linear alkoxy group. Typically, it is an alkoxy group having 1 to 12 carbon atoms, preferably an alkoxy group having 2 to 8 carbon atoms, more preferably an alkoxy group having 2 to 6 carbon atoms, and even more preferably an alkoxy group having 2 to 4 carbon atoms.

[0043] The alkylcarbonyloxy group may be linear, branched, or cyclic, preferably a linear or branched alkylcarbonyloxy group, and more preferably a linear alkylcarbonyloxy group. Furthermore, an alkylcarbonyloxy group having 1 to 10 carbon atoms is preferred.

[0044] The alkylcarbonylamino group may be linear, branched, or cyclic, preferably a linear or branched alkylcarbonylamino group, and more preferably a linear alkylcarbonylamino group. Furthermore, alkylcarbonylamino groups having 1 to 10 carbon atoms are preferred.

[0045] The alkylsulfonylamino group may be linear, branched, or cyclic, preferably a linear or branched alkylsulfonylamino group, and more preferably a linear alkylsulfonylamino group. Furthermore, alkylsulfonylamino groups having 1 to 10 carbon atoms are preferred.

[0046] An aryl group refers to a monocyclic or polycyclic group consisting of a 5- or 6-membered aromatic hydrocarbon ring. Examples of aryl groups include phenyl, naphthyl, and biphenyl groups.

[0047] The aryloxy group is preferably an aryloxy group having 6 to 12 carbon atoms. The arylcarbonyloxy group is preferably an arylcarbonyloxy group having 6 to 12 carbon atoms. The arylcarbonylamino group is preferably an arylcarbonylamino group having 6 to 12 carbon atoms. The arylsulfonylamino group is preferably an arylsulfonylamino group having 6 to 12 carbon atoms.

[0048] The monoalkylamino group may be linear, branched, or cyclic, preferably a linear or branched monoalkylamino group, and more preferably a linear monoalkylamino group. Furthermore, a monoalkylamino group in which the alkyl group has 1 to 10 carbon atoms is preferred.

[0049] The dialkylamino group may be linear, branched, or cyclic, preferably a linear or branched dialkylamino group, and more preferably a linear dialkylamino group. Furthermore, a dialkylamino group in which the alkyl group has 1 to 10 carbon atoms is preferred.

[0050] Examples of arylamino groups include monoarylamino groups and diarylamino groups, preferably monoarylamino groups having 6 to 12 carbon atoms.

[0051] A specific example of a compound represented by general formula (1) is R 1 ~R 5 is an alkyl group or a hydrogen atom, preferably R 1 ~R 5 is a linear alkyl group having 1 to 8 carbon atoms or a hydrogen atom, more preferably R 1 ~R 5 R is a linear alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and more preferably R 1 ~R 5 This is a methyl group or a hydrogen atom.

[0052] Other specific examples of compounds represented by general formula (1) include R 1 , R 2 , R 4 and R 5 is a hydrogen atom and R 3 The group is a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group (preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, even more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group).

[0053] The substituents attached to one of the benzene rings in the diphenylurea structure in general formula (1) can be in the ortho, meta, or para position relative to the aminocarbonyl group on the benzene ring, preferably in the ortho or meta position, and more preferably in the meta position.

[0054] The compound represented by general formula (1) is not particularly limited, but at least one selected from the group consisting of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 2-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, and 4-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate is preferred. Among these, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate is preferred.

[0055] The content of the compound represented by general formula (1) is not particularly limited and can be adjusted according to the leuco dye used. Generally, it is preferable to have 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1 part by mass or more, even more preferably 1.2 parts by mass or more, and particularly preferable 1.5 parts by mass or more, per 1 part by mass of leuco dye. On the other hand, the content of the compound represented by general formula (1) is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferable 3.5 parts by mass or less, per 1 part by mass of leuco dye. By having 0.5 parts by mass or more, recording performance can be improved. On the other hand, by having 10 parts by mass or less, background blur in high-temperature environments can be effectively suppressed.

[0056] Other color developers may be included as long as they do not impair the effects of the present invention. Specific examples of other color developers include, for example, 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenyl, 4,4'-cyclohexylidenediphenol, 1,1-bis(4-hydroxyphenyl)-ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, and 4,4'-bis (p-Tolylsulfonylaminocarbonylamino)diphenylmethane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2'-bis[4-(4-hydroxyphenyl)phenoxy]diethyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,4'-dihydroxydiphenyl Lufon, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4-hydroxy-4'-allyloxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone, bis(p-hydroxyphenyl)acetate butyl, bis(p-hydroxyphenyl)acetate methyl, hydroquinone monobenzyl ether, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxy-4' -Methyldiphenylsulfone, 4-allyloxy-4'-hydroxydiphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, 4-hydroxybenzophenone, 4-dimethyl hydroxyphthalate, 4-methyl hydroxybenzoate, 4-propyl hydroxybenzoate, 4-sec-butyl hydroxybenzoate, 4-phenyl hydroxybenzoate, 4-benzyl hydroxybenzoate, 4-benzyl ester hydroxybenzoate, 4-tolyl hydroxybenzoate, 4-chlorophenyl hydroxybenzoate, 4,Phenolic compounds such as 4'-dihydroxydiphenyl ether, or benzoic acid, p-chlorobenzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3,5-di-tert-butylsalicylic acid, 4-[2-(p-methoxyphenoxy)ethyloxy]salicylic acid Aromatic carboxylic acids such as salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, and 4-{3-(p-tolylsulfonyl)propyloxy]zinc salicylate, and their phenolic compounds, salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, and thiocyanate. Examples include organic acidic substances such as zinc antipyrine complexes, complex zinc salts of terephthalaldehyde and other aromatic carboxylic acids, thiourea compounds such as Np-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea, Np-toluenesulfonyl-N'-p-butoxycarbonylphenylurea, Np-tolylsulfonyl-N'-phenylurea, and N,N'-di-m-chlorophenylthiourea, organic compounds having an -SO2NH- bond in the molecule such as N-(p-toluenesulfonyl)carbamoylate p-cumylphenyl ester, N-(p-toluenesulfonyl)carbamoylate p-benzyloxyphenyl ester, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, and N-(o-toluyl)-p-toluenesulfamide, and inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and aluminum silicate.

[0057] Other color developers include urea urethane compounds such as 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4,4'-bis[(2-methyl-5-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, and 4-(2-methyl-3-phenoxycarbonylaminophenyl)ureido-4'-(4-methyl-5-phenoxycarbonylaminophenyl)ureidodiphenylsulfone, represented by the following general formula (2); diphenyl sulfone crosslinked compounds represented by the following general formula (3); and 4,4'-bis(3-tosylureido)diphenylmethane. [ka] [ka] (In the formula, n=1~6)

[0058] The content ratio of other color developers is not particularly limited, but is preferably 0.5 parts by mass or less, and more preferably 0.3 parts by mass or less, per 1 part by mass of the compound represented by general formula (1).

[0059] (Inorganic Pigments II) The thermal recording layer in the present invention contains an inorganic pigment II with an oil absorption capacity of 130 ml / 100 g or less. The oil absorption capacity of inorganic pigment II is preferably 125 ml / 100 g or less, more preferably 100 ml / 100 g or less, and most preferably 65 ml / 100 g or less. This significantly improves long-term storage. On the other hand, from the viewpoint of effectively reducing printing defects such as head residue and sticking, 30 ml / 100 g or more is preferred. The thermal recording layer in the present invention may contain a pigment with an oil absorption capacity exceeding 130 ml / 100 g, as long as it does not impair the effects of the present invention. The content of the pigment with an oil absorption capacity exceeding 130 ml / 100 g is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, and even more preferably 0.1 parts by mass or less, per 1 part by mass of pigment with an oil absorption capacity of 130 ml / 100 g or less. It is particularly preferable that no pigment with an oil absorption capacity exceeding 130 ml / 100 g is contained. Here, the oil absorption amount is a value determined according to the method of JIS K 5101.

[0060] Various types of inorganic pigments can be used as inorganic pigment II, but specific examples include calcium carbonate such as light calcium carbonate, aluminum hydroxide, clay such as kaolin, and talc. Among these, it is preferable that inorganic pigment II is at least one selected from the group consisting of calcium carbonate, aluminum hydroxide, and clay. The type of inorganic pigment II may be different from or the same as inorganic pigment I. The content ratio of inorganic pigment II can be selected from a wide range, but it is preferably 10 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 35% by mass of the total solid content of the thermal recording layer.

[0061] In the present invention, the thermal recording layer may further contain a preservation improver, mainly to further enhance the preservation of the color image. Examples of such preservation improvers include 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1-bis(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisphenol, and 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisphenol At least one compound selected from phenolic compounds such as 4-benzyloxyphenyl-4'-(2-methyl-2,3-epoxypropyloxy)phenylsulfone, 4-(2-methyl-1,2-epoxyethyl)diphenylsulfone, and 4-(2-ethyl-1,2-epoxyethyl)diphenylsulfone, as well as isocyanuric acid compounds such as 1,3,5-tris(2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl)isocyanuric acid, can be used. Of course, it is not limited to these, and two or more compounds can be used in combination as needed.

[0062] When using a preservation improver, the amount used should be sufficient to improve preservation, and is usually about 1 to 25% by mass of the total solid content of the thermal recording layer, and more preferably about 5 to 20% by mass.

[0063] The thermal recording layer in the present invention may also contain a sensitizer. This can increase the recording sensitivity. Examples of sensitizers include stearic acid amide and benzalkonium methoxycarbonyl-N-stearate. MidoN-benzoyl stearate, N-eicosanoate, ethylenebisstearate, behenamide, methylenebisstearate, N-methylol stearate, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenyl sulfone, p-benzyl benzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, dibenzyl oxalate, p-tolylbiphenyl ether, di(p-methoxyphenoxyethyl) ether, 1,2-di(3-methylphenoxy)ethane, 1,2-di(4-methylphenoxy) Examples include ethane, 1,2-di(4-methoxyphenoxy)ethane, 1,2-di(4-chlorophenoxy)ethane, 1,2-diphenoxyethane, 1-(4-methoxyphenoxy)-2-(3-methylphenoxy)ethane, p-methylthiophenylbenzyl ether, 1,4-di(phenylthio)butane, p-acetoluidide, p-acetophenetidide, N-acetoacetyl-p-toluidine, 1,2-diphenoxymethylbenzene, di(β-biphenylethoxy)benzene, p-di(vinyloxyethoxy)benzene, 1-isopropylphenyl-2-phenylethane, di-o-chlorobenzyl adipate, 1,2-bis(3,4-dimethylphenyl)ethane, 1,3-bis(2-naphthoxy)propane, diphenyl, benzophenone, etc. Among these, 1,2-di(3-methylphenoxy)ethane is preferred from the viewpoint of obtaining a sensitizing effect without reducing long-term storage properties. These can be used in combination to the extent that it does not cause problems. The content ratio of the sensitizer should be an amount effective for sensitization, and usually, 2 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass, of the total solid content of the thermal recording layer.

[0064] Other components of the thermal recording layer include adhesives, and if necessary, auxiliary agents such as crosslinking agents, waxes, metal soaps, water-resistant agents, dispersants, colored dyes, and fluorescent dyes may be used.

[0065] Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or water-insoluble polymer latex such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. Among these, polyvinyl alcohol and latex are preferred. The content of the adhesive can be selected from a wide range, but generally it is preferably about 5 to 30% by mass, and more preferably about 10 to 20% by mass, of the total solid content of the thermal recording layer.

[0066] By incorporating a crosslinking agent into the thermal recording layer, the water resistance of the thermal recording layer can be improved. Examples of crosslinking agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylates, dimethylolurea compounds, aziridine compounds, and blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, and potassium tetraborate; boric acid, boric acid triesters, boron-based polymers, hydrazide compounds, and glyoxylates. These may be used individually or in combination of two or more. The amount of crosslinking agent used is preferably about 1 to 5% by mass of the total solid content of the thermal recording layer.

[0067] The thermal recording layer is formed on the undercoat layer by, for example, using water as the dispersion medium, dispersing leuco dyes and color developers separately or together with sensitizers or preservatives as needed using various stirring and wet grinding machines such as ball mills, co-ball mills, attritors, and vertical and horizontal sand mills, along with water-soluble synthetic polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, styrene-maleic anhydride copolymer salts, and other surfactants to obtain dispersions, then finely grinding them to an average particle size of 2 μm or less, and mixing in inorganic pigment II, and, if necessary, adding adhesives, auxiliary agents, etc. The coating for the thermal recording layer is applied and dried. The amount of thermal recording layer applied is not particularly limited, and the amount applied after drying is 1 to 12 g / m². 2 A suitable amount is 2-10 g / m². 2 More preferably, 2.5-8 g / m 2 More preferably, 3-5.5 g / m 2 This is particularly preferable. The thermal recording layer can be formed in two or more layers as needed, and the composition and coating amount of each layer may be the same or different.

[0068] [Protective layer] In thermal recording media, a protective layer may be provided on the thermal recording layer as needed. The protective layer preferably contains a pigment and an adhesive. Furthermore, the protective layer may contain a lubricant such as polyolefin wax or zinc stearate to prevent sticking to the thermal head, and may also contain an ultraviolet absorber. Additionally, providing a glossy protective layer can enhance the added value of the product.

[0069] The pigments contained in the protective layer are not particularly limited and include, for example, inorganic pigments such as amorphous silica, kaolin, clay, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium dioxide, magnesium carbonate, aluminum hydroxide, colloidal silica, and synthetic layered mica, as well as plastic pigments such as urea-formaldehyde resin fillers.

[0070] The adhesive contained in the protective layer is not particularly limited, and water-soluble or water-dispersible aqueous adhesives can be used. The adhesive can be appropriately selected from those that can be used in the thermal recording layer. Among these adhesives, various modified polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol are more preferably used.

[0071] The protective layer is formed on the thermal recording layer by applying a protective coating, prepared by mixing a pigment, adhesive, and auxiliary agents as needed with water as the dispersion medium, and then drying it. The amount of protective coating applied is not particularly limited, but is approximately 0.3 to 15 g / m² by dry mass. 2 A suitable amount is 0.3-10 g / m². 2 A more preferable degree is 0.5-8 g / m 2 A more preferable degree is 1-8 g / m 2 A particularly favorable degree is 1-5 g / m 2 A higher degree is preferable. The protective layer can be formed in two or more layers as needed, and the composition and application amount of each layer may be the same or different.

[0072] [Other layers] In the present invention, it is preferable to have an adhesive layer on at least one side of the support. This can increase the added value of the thermal recording material. As the adhesive layer, for example, by applying an adhesive, re-wettable adhesive, delayed-tack type adhesive, etc. to one side, adhesive paper, re-wettable adhesive paper, delayed-tack paper, etc. can be made. Alternatively, by using the side of the support opposite to the thermal recording layer and giving it functions as thermal transfer paper, inkjet recording paper, carbonless paper, electrostatic recording paper, xenography paper, etc., it is possible to make recording paper that can record on both sides. Of course, it is also possible to make a double-sided thermal recording material. Furthermore, a back layer can be provided to suppress the penetration of oil and plasticizer from the back surface of the thermal recording material, to control curl, and to prevent static charge. It is also possible to make a linerless label that does not require release paper by applying a release layer containing silicone on the protective layer and applying an adhesive to one side.

[0073] [Thermal recording media] A thermal recording material can be manufactured by forming the above-mentioned layers on a support. Any known coating method can be used to form the above-mentioned layers on the support, such as the air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, curtain method, slot die method, slide die method, or extrusion method. In addition, each coating may be applied and dried one layer at a time to form each layer, or the same coating may be applied in two or more layers. Furthermore, simultaneous multilayer coating, in which two or more layers are applied at the same time, may be performed. In addition, after each layer has been formed, or at any stage after all layers have been formed, a smoothing process can be performed using a known method such as a supercalender or softcalender. [Examples]

[0074] The present invention will be described in more detail by reference to examples, but the present invention is not limited thereto. Unless otherwise specified, "parts" and "%" refer to "parts by mass" and "mass%", respectively. Particle sizes such as average particle diameter and maximum particle diameter were measured using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation). Here, the average particle diameter is the median diameter (D50).

[0075] The hollow particles used in the examples and comparative examples are as follows: Hollow particle A: Average particle diameter (D50) 5.0 μm, maximum particle diameter (D100) 13.5 μm, hollowness ratio 90%, percentage of particles 2 μm or smaller 0.2 volume%, solid content concentration 15.0% Hollow particle B: Average particle size (D50) 11 μm, maximum particle size (D100) 23 μm, hollowness ratio 93%, percentage of particles smaller than 2 μm 0 volume%, solid content concentration 15.0% Hollow particle C: Lowpeak SN-1055 (manufactured by Dow), average particle size (D50) 1.0 μm, maximum particle size (D100) 1.8 μm, hollowness ratio 55%, solid content concentration 26.5% The average particle diameter (D50) and maximum particle diameter (D100) of each hollow particle were measured using a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) at a refractive index of 1.70-0.01i.

[0076] The latex used in the examples and comparative examples is as follows: Latex A: Styrene-butadiene copolymer latex (development product) (Tg: -35℃, particle size 300nm, solids content 48%) Latex B: Styrene-butadiene copolymer latex (development product) (Tg: -10℃, particle size 190nm, solids content 48%) Latex C: Styrene-butadiene copolymer latex (product name L-1571, manufactured by Asahi Kasei Corporation, Tg=-3℃, particle size 190nm, solids content 48%)

[0077] The inorganic pigment II used in the examples and comparative examples is as follows: Calcium carbonate: Product name: Brilliant-15, manufactured by Shiraishi Kogyo Co., Ltd., oil absorption capacity 56ml / 100g Calcium carbonate: Product name: Callite KT, manufactured by Shiraishi Kogyo Co., Ltd., oil absorption capacity 120ml / 100g Aluminum hydroxide: Product name: Hygiene Light H-42, manufactured by Showa Denko Corporation, oil absorption capacity 43ml / 100g Clay: Product name: HYDRAGLOSS90, manufactured by KaMin LLC, oil absorption capacity 46ml / 100g Amorphous silica: Product name: NipSeal E743, manufactured by Tosoh Silica Co., Ltd., oil absorption capacity 160ml / 100g

[0078] (Example 1) (1) Preparation of coating liquid for the undercoat layer Hollow particle A 100 parts, calcined kaolin (product name Ansilex 93, manufactured by BASF, oil absorption capacity 104 ml / 100 g) 38 parts, latex A7 9.2 parts, 32 parts of a 25% solution of oxidized starch, 1.1 parts of carboxymethylcellulose (product name: Cellogen AG Gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 100 parts of water were mixed and stirred to obtain a coating solution for the undercoat layer.

[0079] (2) Preparation of leuco dye dispersion (Solution A) 40 parts of 3-di-(n-butyl)amino-6-methyl-7-anilinofluorane, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (Imex Co., Ltd., sand grinder) until the average particle size was 0.5 μm to obtain a leuco dye dispersion (Solution A).

[0080] (3) Preparation of color developer dispersion (Solution B) 40 parts of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (AIMEX, sand grinder) until the average particle size was 1.0 μm to obtain a color developer dispersion (Solution B).

[0081] (4) Preparation of sensitizer dispersion (Solution C) 40 parts of 1,2-di(3-methylphenoxy)ethane (product name: KS-232, manufactured by Sanko Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the average particle size was 1.0 μm to obtain a sensitizer dispersion (Solution C).

[0082] (5) Preparation of coating solution for thermal recording layer A coating solution for a thermal recording layer was obtained by mixing and stirring 29.5 parts of solution A, 63.6 parts of solution B, 45.5 parts of solution C, 70 parts of a 10% aqueous solution of fully saponified polyvinyl alcohol (product name: PVA117, degree of saponification: 99 mol%, average degree of polymerization: 1700, manufactured by Kuraray Co., Ltd.), 20.8 parts of styrene-butadiene copolymer latex (product name: L-1571, manufactured by Asahi Kasei Corporation, solid content concentration 48%), 20 parts of calcium carbonate (product name: Brilliant-15, manufactured by Shiraishi Kogyo Co., Ltd., oil absorption capacity 56 ml / 100 g), 2 parts of dihydrazide adipic acid (manufactured by Otsuka Chemical Co., Ltd.), and 150 parts of water.

[0083] (6) Preparation of coating liquid for protective layer A protective coating solution was obtained by mixing and stirring a composition consisting of 317 parts of a 12% aqueous solution of diacetone-modified polyvinyl alcohol (product name: DF-10, manufactured by Nippon Vi-Vegetable Vinegar Co., Ltd.), 60 parts of kaolin (product name: HYDRAGLOSS90, manufactured by KaMin LLC), 0.5 parts of polyethylene wax (product name: Chemipearl W-400, manufactured by Mitsui Chemicals, Ltd., solid content concentration 40%), 5 parts of zinc stearate (product name: Hydrin Z-8-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36%), and 300 parts of water.

[0084] (7) Preparation of thermal recording media Basis weight 60g / m 2 On one side of the high-quality paper, a coating liquid for the undercoat layer, a coating liquid for the thermal recording layer, and a protective coating are applied. for layers The coating amount after drying of the coating solution was 4.5 g / m². 2 3.8g / m 2 2.3g / m 2The material was coated and dried in such a manner to sequentially form a primer layer, a thermal recording layer, and a protective layer, and then the surface was smoothed with a supercalender to obtain a thermal recording body.

[0085] (Example 2) Thermal sensor in Example 1 record A thermal recording body was obtained in the same manner as in Example 1, except that aluminum hydroxide (product name: Hygierite H-42, manufactured by Showa Light Metal Co., Ltd., oil absorption capacity 43 ml / 100 g) was used instead of calcium carbonate in the preparation of the layer coating solution.

[0086] (Example 3) Thermal sensor in Example 1 record A thermal recording body was obtained in the same manner as in Example 1, except that clay (product name: HG90, manufactured by Kamin, oil absorption capacity 46 ml / 100 g) was used instead of calcium carbonate in the preparation of the layer coating solution.

[0087] (Example 4) Thermal sensor in Example 1 record A thermal recording body was obtained in the same manner as in Example 1, except that calcium carbonate (product name: Callite KT, manufactured by Shiraishi Kogyo Co., Ltd., oil absorption capacity 120 ml / 100 g) was used instead of calcium carbonate (product name: Brilliant-15, manufactured by Shiraishi Kogyo Co., Ltd., oil absorption capacity 56 ml / 100 g) in the preparation of the layer coating solution.

[0088] (Example 5) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the undercoat layer coating liquid in Example 1, 79.2 parts of latex B were used instead of 79.2 parts of latex A.

[0089] (Example 6) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the undercoat layer coating liquid in Example 1, 79.2 parts of latex C were used instead of 79.2 parts of latex A.

[0090] (Example 7) A thermal recording body was obtained in the same manner as in Example 1, except that in the preparation of the undercoat layer coating liquid in Example 1, 100 parts of hollow particle B were used instead of 100 parts of hollow particle A.

[0091] (Example 8) In preparing the undercoat coating solution for Example 1, a thermal recording body was obtained in the same manner as in Example 1, except that the amount of calcined kaolin was changed from 38 parts to 66 parts, the amount of latex A was changed from 79.2 parts to 20.8 parts, and the amount of water was changed from 100 parts to 130 parts.

[0092] (Example 9) In the preparation of the undercoat coating liquid for Example 1, the amount of calcined kaolin was changed from 38 parts to 66 parts, latex A was changed from 79.2 parts to 20.8 parts to 20.8 parts to 20.8 parts to 20.8 parts to 20.8 parts to 20.6 death, A thermal recording material was obtained in the same manner as in Example 1, except that the amount of water was changed from 100 parts to 180 parts.

[0093] (Comparative Example 1) In the preparation of the thermal recording layer coating solution in Example 1, calcium carbonate is used. teenager A thermal recording body was obtained in the same manner as in Example 1, except that amorphous silica (product name: NipSeal E743, manufactured by Tosoh Silica Co., Ltd.) was used.

[0094] (Comparative Example 2) (8) Preparation of color developer dispersion (Solution D) 4-Hydroxy-4 ’ - Isopropoxydiphenylsulfone (Trade name: D-8, Nippon Soda) Company-made 40 parts of ), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the average particle size was 1.0 μm to obtain a color developer dispersion (Solution D).

[0095] In the preparation of the thermal recording layer coating solution of Comparative Example 1, the developer dispersion B Instead of liquid, use a developer dispersion. D A thermal recording material was obtained in the same manner as in Comparative Example 1, except that a liquid was used.

[0096] The above examples and comparative examples were evaluated using the following method. The results are shown in Table 1.

[0097] [Recording density] Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was recorded with applied energy of 0.13 mJ / dot (mid-tone color density) and 0.18 mJ / dot (high-gradation color density). The resulting printed areas were measured using a spectrophotometer (X-Rite504, manufactured by X-Rite Corporation). A higher value indicates a higher print density. The evaluation criteria for mid-tone color density were as follows: Color density of 0.90 or higher: Excellent performance, capable of handling high-speed printing. Color density of 0.80 or higher: Required for practical purposes. Color density less than 0.80: Low sensitivity, resulting in many defects such as whiteout, and posing practical problems. The evaluation criteria for high-gradation color density were as follows: Color intensity of 1.30 or higher: Excellent. Color intensity of 1.20 or higher: Required for practical purposes. Color density less than 1.20: The print density is low and undesirable in practical terms.

[0098] [Long-term preservation of printed text] Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was printed with applied energy of 0.13 mJ / dot (mid-tone color density) and 0.18 mJ / dot (high-gradation color density). After standing for 3 months in an environment of 23°C, 50% RH, and darkness, the optical density of the mid-tone color density and high-gradation color density areas was measured using a spectrophotometer (X-Rite504, manufactured by X-Rite Corporation). In addition, the remaining percentage of the recording area was calculated using the following formula. Remaining percentage (%) = (Recording density after processing / Recording density before processing) × 100 The evaluation criteria were as follows: Survival rate of 95% or higher: Excellent. Survival rate of 85% or higher: Excellent Remaining percentage of 80% or more: No practical problems. Retention rate less than 80%: The recording density after processing is low, which poses practical problems.

[0099] [90℃ heat resistance] Samples of each thermal recording material, colored using a label printer (product name: L-2000, manufactured by Ishida Corporation), were left to stand in a 90°C chamber for 1 hour. The optical density of the blank paper area after processing was measured using a spectrophotometer (X-Rite504, manufactured by X-Rite Corporation). The evaluation criteria were as follows: Density of the white areas after processing: 0.10 or less: Excellent. Density of the white areas after processing: 0.20 or less: No practical problems. If the density of the white areas after processing exceeds 0.20, the background cover is too strong, posing a practical problem.

[0100] [Table 1]

[0101] As can be seen from Table 1, the recording density of the thermal recording materials in Examples 1 to 8 was excellent, and the long-term preservation of the prints was at a level that posed no practical problems. Although the midtone density of the thermal recording material in Example 9 was low, the long-term preservation of the prints was at a level that posed no practical problems. On the other hand, Comparative Example 1 had significantly inferior long-term preservation of the prints. Comparative Example 2 showed excellent recording density and long-term preservation of the prints by changing the color developer, but the density of the white paper area with 90°C heat resistance was inferior.

Claims

1. A thermal recording body having, in this order, a base coat layer containing at least hollow particles, an adhesive, and an inorganic pigment I on a support, and a thermal recording layer containing a leuco dye, a color developer, and an inorganic pigment II, wherein the color developer is the following general formula (1): 【Chemistry 1】 (In the formula, R １ ~R ５ A thermal recording body characterized by containing a compound represented by (which is the same or different as a hydrogen atom, halogen atom, nitro group, amino group, alkyl group, alkoxy group, aryloxy group, alkylcarbonyloxy group, arylcarbonyloxy group, alkylcarbonylamino group, arylcarbonylamino group, alkylsulfonylamino group, arylsulfonylamino group, monoalkylamino group, dialkylamino group, or arylamino group), and containing calcium carbonate with an oil absorption of 100 ml / 100 g or less as inorganic pigment II.

2. The thermal recording body according to claim 1, wherein the content of the inorganic pigment I is 60% by mass or less of the total solid content of the undercoat layer.

3. The thermal recording body according to claim 1 or 2, wherein the oil absorption amount of the inorganic pigment I is 130 ml / 100 g or less.

4. The thermal recording body according to claim 1 or 2, wherein the oil absorption amount of the inorganic pigment II is 65 ml / 100 g or less.

5. The thermal recording body according to claim 1 or 2, wherein the content of the hollow particles is 5 to 40% by mass of the total solid content of the undercoat layer.

6. The thermal recording body according to claim 1 or 2, wherein the average particle diameter (D50) of the hollow particles is 3 to 15 μm.

7. The thermal recording body according to claim 1 or 2, wherein the maximum particle diameter (D100) of the hollow particles is 10 to 30 μm.

8. The thermal recording body according to claim 1 or 2, wherein the ratio D100 / D50 of the maximum particle diameter (D100) to the average particle diameter (D50) of the hollow particles is 1.8 to 3.

0.

9. The thermal recording body according to claim 1 or 2, wherein the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is 1% or less.

10. The thermal recording body according to claim 1 or 2, wherein the hollowness ratio of the hollow particles is 80 to 98%.

11. The thermal recording body according to claim 1 or 2, wherein the adhesive of the undercoat layer contains a binder resin having a glass transition temperature of -10°C or lower.

12. The thermal recording body according to claim 1 or 2, wherein the adhesive of the undercoat layer contains a binder resin having a glass transition temperature of -30°C or lower.

13. The thermal recording body according to claim 1 or 2, wherein the compound represented by the general formula (1) is at least one selected from the group consisting of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 2-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, and 4-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate.

14. The thermal recording body according to claim 1 or 2, having an adhesive layer on at least one side of the support.

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