Thermal recording device

Abstract

To provide a thermosensitive recording body which is excellent in alcohol resistance, plasticizer resistance and heat resistant ground fogging properties of a recording part.SOLUTION: There is provided a thermosensitive recording body which has an undercoat layer containing at least hollow particles, an adhesive and an inorganic pigment I and a thermosensitive recording layer containing a leuco dye, a developer and an inorganic pigment II in this order on a support, wherein the thermosensitive recording body contains 5-(N-3-methylphenyl-sulfonamide)-N',N' '-bis-(3-methylphenyl)-isophthalic acid diamide as the developer and a pigment having an oil absorption amount of 130 ml / 100 g or less as the inorganic pigment II.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a thermal recording material that utilizes the color development reaction between a leuco dye and a color developer. [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] Because the color reaction is reversible, it is known that the colored image fades over time. This fading reaction is accelerated in high-temperature, high-humidity environments and proceeds rapidly upon contact with oils, plasticizers, etc., sometimes causing the recorded image to fade to the point of being unreadable. In recent years, disinfection and sterilization with alcohol have become commonplace in daily life, especially for the prevention of infectious diseases. In other words, there is a growing demand for improved performance of thermal recording materials, such as preventing the white areas from developing color and the printed areas from fading when in contact with alcohol.

[0004] For example, Patent Document 1 proposes a thermal recording material using a diarylurea derivative as a color developer. However, the thermal recording material described in Patent Document 1 has insufficient resistance to alcohol and plasticizers, and there is room for improvement. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2019 / 044462 [Overview of the project]

Problems to be Solved by the Invention

[0006] The main object of the present invention is to provide a thermal recording medium excellent in alcohol resistance, plasticizer resistance, and heat-resistant ground coating coverage of a recording layer.

Means for Solving the Problems

[0007] In view of the above prior art, the present inventors have conducted intensive studies and as a result, have arrived at a solution to the above problems. That is, the present invention relates to the following thermal recording medium.

[0008] Item 1: A thermal recording medium having, in this order, a primer layer containing at least hollow particles, an adhesive, and inorganic pigment I, and a thermal recording layer containing a leuco dye, a developer, and inorganic pigment II, on a support, wherein the developer contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and the inorganic pigment II contains a pigment having an oil absorption of 130 ml / 100 g or less. Item 2: The thermal recording medium according to Item 1, wherein the inorganic pigment II contains a pigment having an oil absorption of 65 ml / 100 g or less. Item 3: The thermal recording medium according to any one of Items 1 or 2, wherein the inorganic pigment II contains at least one selected from calcium carbonate, aluminum hydroxide, and clay. Item 4: The thermal recording medium according to any one of Items 1 to 3, wherein the inorganic pigment I contains a pigment having an oil absorption of 130 ml / 100 g or less. Item 5: The thermal recording medium according to any one of Items 1 to 4, wherein the inorganic pigment I contains at least one selected from calcium carbonate, aluminum hydroxide, and clay. Item 6: The thermal recording medium according to any one of Items 1 to 5, wherein the content ratio of the inorganic pigment I is 50 parts by mass or less of the total solid content of the primer layer. Item 7: The heat-sensitive recording medium according to any one of Items 1 to 6, wherein the hollow particles have a maximum particle diameter (D100) of 10 to 30 μm, an average particle diameter (D50) of 4.0 to 15 μm, a ratio D100 / D50 of the maximum particle diameter (D100) to the average particle diameter (D50) of 1.8 to 3.0, and a volume percentage of particles with a particle diameter of 2.0 μm or less of 1% or less. Item 8: The heat-sensitive recording medium according to any one of Items 1 to 7, wherein the hollow ratio of the hollow particles is 80 to 98%. Item 9: The heat-sensitive recording medium according to any one of Items 1 to 8, wherein the adhesive of the undercoat layer contains a binder resin having a glass transition temperature of -10°C or lower. Item 10: The heat-sensitive recording medium according to any one of Items 1 to 9, wherein the adhesive of the undercoat layer contains a binder resin having a glass transition temperature of -30°C or lower. Item 11: The heat-sensitive recording layer contains, as a second developer, the following general formula (1):

Chemical formula

Chemical formula

Chemical formula

[0009] The thermal recording material of the present invention exhibits excellent resistance to alcohol and plasticizers in the recording area, as well as excellent resistance to heat-induced surface clouding. Furthermore, it can also increase the color intensity. [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 hollow particles, an adhesive, and an inorganic pigment I, and a thermal recording layer containing a leuco dye, a developer, and an inorganic pigment II on a support, wherein the developer contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and the inorganic pigment II contains a pigment with an oil absorption capacity of 130 ml / 100 g or less.

[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 an 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, and even more preferably 10 to 20 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 4.0 to 15 μm, more preferably 4.5 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 4.0 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 at a 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, the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is preferably 1% or less. Furthermore, the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is preferably 0.5% or less, and it is more preferable that they are not present at all. Hollow particles with a particle diameter of 2 μm or less are considered to have an extremely small contribution to thermal insulation because their particle size is too small to provide a sufficient hollow region. By reducing the volume percentage of hollow particles with a particle diameter 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 Void ratio (%) = {1 - 1 / (1.1 / true specific gravity)} × 100

[0029] In addition, the void ratio is a value that can also be obtained by the following formula (d 3 / D 3 ) × 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 the present invention have a relatively large particle diameter, the content ratio in the undercoat layer can be reduced. The content ratio of the hollow particles is preferably 3 to 40% by mass, and more preferably 5 to 35% by mass, based on the total solid content of the undercoat layer. When the content ratio of the hollow particles is 3% by mass or more, the heat insulation property of the undercoat layer can be improved. On the other hand, when the content ratio of the hollow particles is 40% by mass or less, problems are less likely to occur in terms of coating properties and the like, it is easy to form a uniform undercoat layer, and the recording density can be improved. In addition, the film strength of the undercoat layer can be enhanced.

[0031] (Adhesive) 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, ethylcellulose, and carboxymethylcellulose, 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, and 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 Pigment I) The undercoat layer in the present invention contains inorganic pigment I. From the viewpoint of increasing the recording density and improving alcohol resistance and plasticizer resistance, it is preferable that the inorganic pigment I contains a pigment with an oil absorption amount of 130 ml / 100 g or less. More preferably, the oil absorption amount of inorganic pigment I is 125 ml / 100 g or less, and even more preferably 110 ml / 100 g or less. On the other hand, from the viewpoint of effectively reducing printing problems such as head residue generation and sticking, it is preferable that it is 40 ml / 100 g or more, and more preferably 80 ml / 100 g or more. Here, the oil absorption amount is a value determined according to the method of JIS K 5101.

[0034] Various inorganic pigments can be used as inorganic pigment I, but specific examples include calcium carbonate such as light calcium carbonate, aluminum hydroxide, calcined kaolin, clay such as kaolin, and talc. Among these, it is preferable that inorganic pigment I is at least one selected from the group consisting of calcium carbonate, aluminum hydroxide, and clay. From the viewpoint of improving color sensitivity, the content of inorganic pigment I is preferably 60% by mass or less, and more preferably 50% by mass or less, of the total solid content of the undercoat layer. On the other hand, from the viewpoint of effectively reducing printing problems such as head clogging and sticking, it is preferably 20% by mass or more, and more preferably 25% by mass or more, of the total solid content of the undercoat layer.

[0035] The undercoat layer is formed on the support by applying an undercoat coating, prepared by mixing hollow particles, an adhesive, and an inorganic pigment I, along with auxiliary agents as needed, using water as a medium, and then drying it. The amount of undercoat coating applied is not particularly limited, but is 2 to 20 g / m² by dry mass. 2 A suitable amount is 2-12 g / m². 2 A more moderate degree is preferable.

[0036] [Thermal recording layer] (Leuco dye) The thermal recording layer in the thermal recording material of the present invention may contain various known colorless or light-colored leuco dyes. Specific examples of such leuco dyes are listed 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 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide as a color developer. By combining this compound with inorganic pigment II, excellent alcohol resistance, plasticizer resistance, and heat resistance to surface clouding can be achieved in the recording area.

[0040] The content of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide 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 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is preferable to 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, and the alcohol resistance and plasticizer resistance of the recording part can be improved. On the other hand, by having 10 parts by mass or less, background clouding in high-temperature environments can be effectively suppressed.

[0041] Other color developers (secondary color developers) may be included as long as they do not impair the effects of the present invention. Specific examples of secondary 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 -Tolysulfonylaminocarbonylamino)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 sulfone Hon, 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.

[0042] In the present invention, the second color developer is preferably a urea urethane compound such as 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone represented by the following general formula (1), 4,4'-bis[(2-methyl-5-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4-(2-methyl-3-phenoxycarbonylaminophenyl)ureido-4'-(4-methyl-5-phenoxycarbonylaminophenyl)ureidodiphenylsulfone, a diphenyl sulfone crosslinked compound represented by the following general formula (2), an N,N'-diarylurea compound represented by the following general formula (3), a compound represented by the following general formula (4), and 4,4'-bis(3-tosylureido)diphenylmethane. This allows the effects of the present invention to be fully realized. [ka] [ka] (In the formula, n represents an integer from 1 to 6.) [ka] (In the formula, R 0 R represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and the aralkyl group and aryl group may be substituted with an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom, and multiple R 0 They may be the same or different. 1 A represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and multiple A 1 They may be the same or different. [ka] (In the formula, R 1 ~R 5(These terms, whether identical or distinct, represent 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.)

[0043] In the general formula (3) of the N,N'-diarylurea compound contained as the second color developer, R 0 The C1-C12 alkyl group can be linear, branched, or alicyclic, preferably a C1-C6 alkyl group, more preferably a C1-C3 alkyl group. Examples of C1-C12 alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, cyclopentyl, hexyl, cyclohexyl, 2-ethylhexyl, and lauryl groups. The alkyl group here also includes the alkyl portion of an alkoxy group having C1-C12.

[0044] An aralkyl group refers to an arylalkyl group. Examples of aralkyl groups with 7 to 12 carbon atoms include the benzyl group, 1-phenylethyl group, 2-phenylethyl group, and 3-phenylpropyl group.

[0045] An aryl group refers to a monocyclic or polycyclic group consisting of a 5- or 6-membered aromatic hydrocarbon ring. Examples of aryl groups with 6 to 12 carbon atoms include the phenyl group, 1-naphthyl group, and 2-naphthyl group. The aryl portion of an aralkyl group is also included in the definition of an aryl group.

[0046] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0047] In general formula (3), multiple R 0The substitution position of -SO3- may be the same or different. The substitution position is preferably at position 3, 4, or 5, with position 3 being more preferred. Furthermore, the number of substituents on the aralkyl group with 7 to 12 carbon atoms and the aryl group with 6 to 12 carbon atoms of R2 is not particularly limited, and can be, for example, 1 to 4.

[0048] A 1 The alkyl group having 1 to 4 carbon atoms may be linear or branched, and examples include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, and t-butyl group.

[0049] Multiple A 1 The substitution position may be the same or different. The substitution position is preferably the 3rd, 4th, or 5th position.

[0050] The N,N'-diarylurea compound represented by general formula (3) is not particularly limited, but includes N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(4-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(2-naphthalenesulfonyloxy)phenyl]urea, and N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl At least one selected from the group consisting of [dioxy)phenyl]urea, N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methylphenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(ethanesulfonyloxy)phenyl]urea, and N,N'-di-[2-(p-toluenesulfonyloxy)]phenylurea is preferred. Among these, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea is preferred.

[0051] R 1 ~R 5 Examples of halogen atoms include fluorine atoms, chlorine atoms, and bromine atoms, with fluorine atoms and chlorine atoms being preferred.

[0052] 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.

[0053] 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.

[0054] The alkylcarbonyloxy group may be linear, branched, or cyclic, preferably a linear or branched alkylcarbonyloxy group, and more preferably a linear alkylcarbonyloxy group. Furthermore, alkylcarbonyloxy groups having 1 to 10 carbon atoms are preferred.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Examples of arylamino groups include monoarylamino groups and diarylamino groups, preferably monoarylamino groups having 6 to 12 carbon atoms.

[0062] A specific example of a compound represented by general formula (4) 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.

[0063] Other specific examples of compounds represented by general formula (4) include R 1 , R 2 , R 4 and R 5 is a hydrogen atom and R 3The 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).

[0064] The substituents attached to one of the benzene rings in the diphenylurea structure in general formula (4) 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.

[0065] The compound represented by general formula (4) 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.

[0066] The content of the second developer is not particularly limited, but is preferably 0.2 to 3 parts by mass per 1 part by mass of the leuco dye, and the content of the second developer is preferably about 0.2 to 0.5 parts by mass per 1 part by mass of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, which is the first developer.

[0067] (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 alcohol resistance and plasticizer resistance. 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 the 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.

[0068] 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, calcined kaolin, 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.

[0069] 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.

[0070] 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.

[0071] 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, benzamyl methoxycarbonyl-N-stearate, N-benzoyl stearate amide, N-eicosanoic acid amide, ethylenebisstearate amide, behenic acid amide, methylenebisstearate amide, N-methylol stearate amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenyl sulfone, benzyl p-benzyloxybenzoate, 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-methylphenoxyethyl) Examples include xy)ethane, 1,2-di(4-methylphenoxy)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 is usually preferably about 2 to 25% by mass, more preferably about 5 to 20% by mass, and even more preferably about 5 to 15% by mass, of the total solid content of the thermal recording layer.

[0072] 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.

[0073] 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.

[0074] 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, 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 10% by mass, and more preferably about 1 to 5% by mass, of the total solid content of the thermal recording layer.

[0075] 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 A more preferable degree is 2.5-8 g / m 2 A more preferable degree is 3-5.5 g / m 2 The degree 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.

[0076] [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.

[0077] 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. The pigment content is preferably about 20 to 80% by mass, and more preferably about 30 to 75% by mass, of the total solid content of the protective layer.

[0078] 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. The content of the adhesive is preferably about 10 to 70% by mass, and more preferably about 20 to 50% by mass, of the total solid content of the protective layer.

[0079] 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 degree of 1-5 g / m is particularly preferable. 2A 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.

[0080] [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.

[0081] [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]

[0082] 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).

[0083] The hollow particles used in the examples and comparative examples are as follows: Hollow particle A: Median 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: Median diameter (D50) 11 μm, maximum particle diameter (D100) 23 μm, hollowness ratio 93%, percentage of particles smaller than 2 μm 0% by volume, solid content concentration 15.0% Hollow particle C: Lowpeak SN-1055 (manufactured by Dow), median diameter (D50) 1.0 μm, maximum particle diameter (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.

[0084] The latex used in the examples and comparative examples is as follows: Latex A: Styrene-butadiene latex (development product) (Tg: -35℃, particle size 300nm, solids content 48%) Latex B: Styrene-butadiene latex (development product) (Tg: -10℃, particle size 190nm, solids content 48%) Latex C: Styrene-butadiene latex (product name L-1571, manufactured by Asahi Kasei Corporation, Tg=-3℃, particle size 190nm, solids content 48%)

[0085] (Example 1) (1) Preparation of coating liquid for the undercoat layer A coating solution for the undercoat layer was obtained by mixing and stirring 100 parts of hollow particles A, 38 parts of calcined kaolin (product name: Ansilex 93, manufactured by BASF, oil absorption capacity 105 ml / 100 g), 79.2 parts of latex A, 32 parts of a 25% solution of oxidized starch, 1.1 parts of carboxymethylcellulose (product name: Selogen AG gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 100 parts of water.

[0086] (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).

[0087] (3) Preparation of color developer dispersion (Solution B) 40 parts of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, 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 1.0 μm to obtain a color developer dispersion (Solution B).

[0088] (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).

[0089] (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.

[0090] (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.

[0091] (7) Preparation of thermal recording media Basis weight 60g / m 2 On one side of a sheet of high-quality paper, apply the primer coating liquid, the thermal recording layer coating liquid, and the protective recording layer coating liquid, with a dry application amount of 4.5 g / m² each. 2 3.8g / m 2 2.3g / m 2 The material was applied 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.

[0092] (Example 2) 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 thermal coating solution for the thermal layer in Example 1.

[0093] (Example 3) 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 thermal coating solution for the thermal layer in Example 1.

[0094] (Example 4) 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 thermal coating solution for the thermal layer in Example 1.

[0095] (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.

[0096] (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.

[0097] (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.

[0098] (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.

[0099] (Example 9) 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, latex C was changed from 79.2 parts to 20.8 parts to latex A, hollow particle C was changed from 100 parts to 56.6 parts to hollow particle A, and the amount of water was changed from 100 parts to 180 parts.

[0100] (Comparative Example 1) 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., oil absorption capacity 150-170 ml / 100 g) was used instead of calcium carbonate in the preparation of the thermal coating solution for the thermal layer in Example 1.

[0101] (Comparative Example 2) (8) Preparation of color developer dispersion (Solution D) 40 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone (trade name: D-8, manufactured by Nippon Soda 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 color developer dispersion (Solution D).

[0102] A thermal recording body was obtained in the same manner as in Example 1, except that developer dispersion solution D was used instead of developer dispersion solution B in the preparation of the thermal coating solution for Comparative Example 1.

[0103] The above examples and comparative examples were evaluated using the following method. The results are shown in Table 1.

[0104] [Recording density] A thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.) was used to record each thermal recording material with an applied energy of 0.16 mJ / dot (intermediate color density). The resulting printed areas were measured using a spectrophotometer (X-Rite504, manufactured by X-Rite Co., Ltd.). 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.

[0105] [Alcohol-resistant] Samples of each thermal recording material, colored using a label printer (product name: L-2000, manufactured by Ishida Corporation), were immersed in a 75% by volume ethanol solution for 30 minutes. The optical density of the printed area after treatment was measured using a spectrophotometer (X-Rite504, manufactured by X-Rite Corporation). The evaluation criteria were as follows: After processing Printing section A concentration of 1.00 or higher indicates excellent performance. After processing Printing section Concentration of 0.80 or higher: No practical problems. After processing Printing section Density less than 0.80: The print disappears, posing a practical problem.

[0106] [Plasticizer resistance] A polycarbonate pipe (40mm in diameter) is wrapped three times with plastic wrap (product name: Hi-S Soft, manufactured by Nippon Carbide Industries Co., Ltd.), and each thermal recording element, which has been colored using a label printer (product name: L-2000, manufactured by Ishida Co., Ltd.), is placed on top of it. Then, three more layers of plastic wrap are wrapped around it, and it is left to stand for 24 hours in a 40°C environment. Printing section The optical density was measured using a spectrophotometer (X-Rite504, manufactured by X-Rite Corporation). The evaluation criteria were as follows: After processing Printing section A concentration of 1.00 or higher indicates excellent performance. After processing Printing section Concentration of 0.80 or higher: No practical problems. After processing Printing section Density less than 0.80: The print disappears, posing a practical problem.

[0107] [100℃ 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 100°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.

[0108] [Table 1]

[0109] As can be seen from Table 1, the thermal recording materials of Examples 1 to 9 exhibit excellent alcohol resistance and plasticizer resistance, as well as excellent heat-resistant surface fogging. On the other hand, Comparative Example 1 had poor alcohol resistance for printing and significantly poor plasticizer resistance. By changing the color developer, Comparative Example 2 had significantly poor alcohol resistance, and although its plasticizer resistance was slightly better than that of Comparative Example 1, it was not suitable for practical use. In addition, the density of the white paper area at 100°C was significantly poor.

Claims

1. A thermal recording body having, in this order, a base coat layer containing hollow particles, an adhesive, and an inorganic pigment I on a support, and a thermal recording layer containing a leuco dye, a developer, and an inorganic pigment II, wherein the developer contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and the inorganic pigment II contains a pigment with an oil absorption capacity of 130 ml / 100 g or less.

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

3. The thermal recording body according to claim 1 or 2, wherein the inorganic pigment II contains at least one selected from calcium carbonate, aluminum hydroxide, and clay.

4. The thermal recording body according to claim 1 or 2, wherein the inorganic pigment I contains a pigment with an oil absorption capacity of 130 ml / 100 g or less.

5. The thermal recording body according to claim 1 or 2, wherein the inorganic pigment I contains at least one selected from calcium carbonate, aluminum hydroxide, and clay.

6. The thermal recording body according to claim 1 or 2, wherein the content of the inorganic pigment I is 50 parts by mass or less of the total solid content of the undercoat layer.

7. The thermal recording body according to claim 1 or 2, wherein the hollow particles have a maximum particle diameter (D100) of 10 to 30 μm, an average particle diameter (D50) of 4.0 to 15 μm, a ratio of the maximum particle diameter (D100) to the average particle diameter (D50) D100 / D50 of 1.8 to 3.0, and a volume percentage of particles with a particle diameter of 2.0 μm or less of 1% or less.

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

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

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

11. The thermal recording layer uses the following general formula (1) as a second color developer: 【Chemistry 1】 A urea urethane compound represented by the following general formula (2): 【Chemistry 2】 (In the formula, n represents an integer from 1 to 6.) A diphenylsulfone crosslinked compound represented by the following general formula (3): 【Transformation 3】 (In the formula, R ０ R represents an alkyl group having 1 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and the aralkyl group and aryl group may be substituted with an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom, and multiple R ０ They may be the same or different. A １ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and multiple A １ These may be the same or different.) N,N'-diarylurea compounds represented by the following general formula (4): 【Chemistry 4】 (In the formula, R １ ~R ５ The thermal recording body according to claim 1 or 2, comprising a compound represented by ( ) which is the same or different from 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, and at least one selected from 4,4'-bis(3-tosylureido)diphenylmethane.

12. The thermal recording body according to claim 11, wherein the second color developer is contained in an amount of 0.2 to 3 parts by mass per 1 part by mass of leuco dye.

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

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