Thermal recording device

Abstract

To provide a thermosensitive recording medium characterized by high sensitivity, superior heat-resistant background fogging, and superior plasticizer resistance in the printed sections.SOLUTION: Disclosed is a thermosensitive recording medium which has, on a support, a thermosensitive recording layer which contains a leuco dye, developers, and an adhesive. As a first developer in the thermosensitive recording layer, it contains a compound expressed by general formula (1) (where R1 to R5 are the same or different to represent a hydrogen atom or the like), and as a second developer, it comprises 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide or N-[2-(3-phenylureido)phenyl] benzensulfonamide.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, and reports that the printed area has excellent water resistance and the background exhibits high stability against heat.

[0005] Furthermore, Patent Document 2 reports that a thermal recording material using a combination of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate and a urea urethane compound represented by the following general formula (3) as a color developer exhibits excellent printability.

[0006] However, in Patent Documents 1 and 2, for such a developer, the heat-resistant ground fogging has only been evaluated up to 90°C. Further heat resistance is required due to recent market needs, and the 90°C heat resistance is insufficient, and improvement is demanded.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] The main object of the present invention is to provide a thermal recording medium that is highly sensitive, excellent in heat-resistant ground fogging, and excellent in plasticizer resistance of the printed portion.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above object, the present inventors have found that the above problems can be solved by combining a compound represented by the following general formula (1) with a specific developer, and have completed the present invention. That is, the present invention relates to the following thermal recording medium.

[0010] Item 1: In a thermal recording medium having, in this order, an undercoat layer containing at least hollow particles and an adhesive, and a thermal recording layer containing a leuco dye, a developer, and an adhesive on a support, as the first developer of the thermal recording layer, the following general formula (1):

[0011]

Chemical formula

[0012] The thermal recording material of the present invention exhibits high sensitivity, excellent heat resistance to surface fogging, and excellent resistance to plasticizers in the printed area. [Modes for carrying out the invention]

[0013] In this specification, the expression "includes" includes the concepts of "includes," "consisting only of substance," and "consisting only of."

[0014] 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.

[0015] The latex in this invention includes a gel or dried film state formed by drying the dispersion medium.

[0016] The present invention relates to a thermal recording body having, in this order, a primer layer containing hollow particles and an adhesive, and a thermal recording layer containing a leuco dye, a color developer, and an adhesive on a support, wherein the first color developer of the thermal recording layer is the following general formula (1):

[0017] [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 contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide or N-[2-(3-phenylureido)phenyl]benzenesulfonamide as a second developer, and is characterized in that the second developer is present in an amount of 0.4 to 2.5 parts by mass per 1 part by mass of the first developer.

[0018] [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.

[0019] [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 and an adhesive.

[0020] (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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 the mark in a volumetric flask and evaluate it (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

[0033] 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.

[0034] 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.

[0035] (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.

[0036] 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.

[0037] The undercoat layer may contain oil-absorbing pigments with an oil absorption capacity of 70 ml / 100g or more, particularly 80 to 150 ml / 100g. Here, the above oil absorption capacity is determined according to the method of JIS K 5101.

[0038] As the oil-absorbing pigment, various types can be used. Specific examples include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. The average particle diameter of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, particularly preferably about 0.02 to 3 μm. The amount of the oil-absorbing pigment used can be selected from a wide range, but generally, it is preferably about 20 to 60% by mass, more preferably about 25 to 55% by mass, based on the total solid content of the undercoat layer.

[0039] The undercoat layer is formed on the support by, for example, applying a coating liquid for the undercoat layer prepared by mixing hollow particles, an adhesive, and, if necessary, an oil-absorbing pigment, an auxiliary agent, etc. with water as a medium, and then drying. The coating amount of the coating liquid for the undercoat layer is not particularly limited, but is preferably about 2 to 20 g / m 2 in terms of dry mass, more preferably about 2 to 12 g / m 2 in terms of dry mass.

[0040] Examples of the auxiliary agent contained in the coating liquid for the undercoat layer include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate ester, and fatty acid metal salts; waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax; water resistance agents such as hydrazide compounds, boric acid, dialdehyde starch, glyoxylate salts, and epoxy compounds; defoaming agents; coloring dyes; and fluorescent dyes.

[0041] [Thermosensitive recording layer] (Leuco dye) The thermosensitive recording layer in the thermosensitive recording body of the present invention can contain various known colorless or light-colored leuco dyes. Specific examples of such leuco dyes are listed below.

[0042] 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.

[0043] 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.

[0044] (Color developer) In the present invention, the color developer contains a first color developer and a second color developer, and the first color developer contains a compound represented by the above general formula (1).

[0045] R 1 ~R 5 Examples of halogen atoms include fluorine atoms, chlorine atoms, and bromine atoms, with fluorine atoms and chlorine atoms being preferred.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Examples of arylamino groups include monoarylamino groups and diarylamino groups, preferably monoarylamino groups having 6 to 12 carbon atoms.

[0056] 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.

[0057] 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).

[0058] 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.

[0059] 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.

[0060] The content of the first developer 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 first developer 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 using 0.5 parts by mass or more, recording performance can be improved. On the other hand, by using 10 parts by mass or less, background clouding in high-temperature environments can be effectively suppressed.

[0061] The second color developer contains 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide or N-[2-(3-phenylureido)phenyl]benzenesulfonamide. This allows for high sensitivity, excellent heat resistance to surface covering at high temperatures (especially 100°C and 110°C), and resistance to plasticizers. 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide is preferred as the second color developer.

[0062] The content of the second color developer is not particularly limited, but is about 0.4 to 2.5 parts by mass per 1 part by mass of the first color developer, preferably 0.7 to 2.5% by mass, more preferably 0.9 to 2.5 parts by mass, and even more preferably 1.7 to 2.3 parts by mass. By setting the content of the second color developer to 0.4 parts by mass or more, plasticizer resistance can be improved. On the other hand, by setting it to 2.5 parts by mass or less, recording performance can be improved.

[0063] 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 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, and 4-{3-(p-tolylsulfonyl)propyloxy]zinc salicylate, as well as these phenolic compounds, salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, and zinc thiocyanate. Examples include antipyrine complexes, complex zinc salts of terephthalaldehyde and other aromatic carboxylic acids, diarylureas such as N,N'-di[3-(p-toluenesulfonyl)oxy]phenylurea, 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, and N-(o-toluyl)-p-toluenesulfamide, and inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and aluminum silicate.

[0064] 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.

[0065] 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.

[0066] 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, dimethyl terephthalate, 1,2-di(3-methylphenoxy)ethane, stearic acid amide, and diphenyl sulfone are preferred, and dimethyl terephthalate and 1,2-di(3-methylphenoxy)ethane are more preferred from the viewpoint of obtaining a sensitizing effect without reducing the heat-resistant surface coverage at high temperatures. These can be used in combination to the extent that it does not cause problems.The proportion of the sensitizer should be an amount effective for sensitization, and is usually preferably 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.

[0067] Other components of the thermal recording layer include adhesives, and if necessary, auxiliary agents such as pigments, crosslinking agents, waxes, metal soaps, water-resistant agents, dispersants, colored dyes, and fluorescent dyes may be used.

[0068] 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.

[0069] 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.

[0070] 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 pigments, adhesives, auxiliary agents as needed. The thermal recording layer coating solution is then applied and dried. The amount of thermal recording layer applied is not particularly limited, and the amount 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.

[0071] [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.

[0072] 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.

[0073] 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.

[0074] The protective layer is formed on the thermal recording layer by applying a protective coating solution, prepared by mixing a pigment, adhesive, and auxiliary agents as needed, using water as a dispersion medium, and then drying it. The amount of protective coating solution 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.

[0075] [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.

[0076] [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 liquid may be applied and dried one layer at a time to form each layer, or the same coating liquid may be applied in two or more layers. Furthermore, simultaneous multilayer coating may be performed by applying two or more layers at the same time. 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]

[0077] 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).

[0078] The hollow particles used in the examples and comparative examples are as follows: Hollow particle A: 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% 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: Average particle size (D50) 5.0 μm, maximum particle size (D100) 13.5 μm, hollowness ratio 90%, percentage of particles 2 μm or smaller 0.2 volume%, solid content concentration 15.0% 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.

[0079] The latex used in the examples and comparative examples is as follows: Latex A: Styrene-butadiene copolymer latex (product name L-1571, manufactured by Asahi Kasei Corporation, Tg=-3℃, particle size 190nm, 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 (development product) (Tg: -35℃, particle size 300nm, solids content 48%)

[0080] (Example 1) (1) Preparation of coating solution for the undercoat layer A coating solution for the undercoat layer was obtained by mixing and stirring 56.6 parts of hollow particles A, 70 parts of calcined kaolin (product name: Ansilex 93, manufactured by BASF, oil absorption capacity 105 ml / 100 g), 22.9 parts of latex A, 12 parts of a 25% solution of oxidized starch, 6.7 parts of a 15% aqueous solution of fully saponified polyvinyl alcohol (product name: PVA105, degree of saponification: 99 mol%, average degree of polymerization: 500, manufactured by Kuraray Co., Ltd.), and 80 parts of water.

[0081] (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 (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), and 20 parts of water were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the average particle size was 0.5 μm to obtain a leuco dye dispersion (Solution A).

[0082] (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 (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 B).

[0083] (4) Preparation of color developer dispersion (Solution C) 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 (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 C).

[0084] (5) Preparation of sensitizer dispersion (Solution D) 40 parts of dimethyl terephthalate (manufactured by Tokyo Chemical Industry Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 D).

[0085] (6) Preparation of coating solution for thermal recording layer A coating solution for the thermal recording layer was prepared by mixing and stirring 34.1 parts of solution A, 46.7 parts of solution B, 22.7 parts of solution C, 35 parts of solution D, 63.7 parts of a 15% aqueous solution of fully saponified polyvinyl alcohol (product name: PVA110, degree of saponification: 99 mol%, average degree of polymerization: 1000, manufactured by Kuraray Co., Ltd.), 12.8 parts of latex A (product name: L-1571, manufactured by Asahi Kasei Corporation, solid content concentration 48%), 21 parts of calcium carbonate (product name: Brilliant-15, manufactured by Shiraishi Kogyo Co., Ltd., oil absorption capacity 56 ml / 100 g), 1 part of dihydrazide adipic acid (manufactured by Otsuka Chemical Co., Ltd.), and 150 parts of water.

[0086] (7) Preparation of coating solution for protective layer A protective coating solution was obtained by mixing and stirring a composition consisting of 292 parts of a 12% aqueous solution of acetoacetyl-modified polyvinyl alcohol (product name: Gosenex Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 62 parts of kaolin (product name: HYDRAGLOSS90, manufactured by KaMin LLC), 8.3 parts of zinc stearate (product name: Hydrin Z-9-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36%), and 150 parts of water.

[0087] (8) Preparation of thermal recording media Basis weight 60g / m 2 On one side of a sheet of high-quality paper, apply the primer coating, the thermal recording layer coating, and the protective layer coating, with a dry coating amount of 6.5 g / m² each. 2 3.5g / 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.

[0088] (Example 2) In preparing the coating solution for the heat-sensitive layer in Example 1, the amount of dispersion C was changed from 22.7 parts to 34.1 parts, and the amount of calcium carbonate was changed from 21 parts to 16 parts. Otherwise, a heat-sensitive recording body was obtained in the same manner as in Example 1.

[0089] (Example 3) In preparing the coating solution for the heat-sensitive layer in Example 1, a heat-sensitive recording body was obtained in the same manner as in Example 1, except that the amount of dispersion C was changed from 22.7 parts to 45.5 parts, and the amount of calcium carbonate was changed from 21 parts to 11 parts.

[0090] (Example 4) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of dispersion B was changed from 47.7 parts to 22.7 parts, and the amount of dispersion C was changed from 22.7 parts to 47.7 parts.

[0091] (Example 5) (9) Preparation of sensitizer dispersion (Solution E) 40 parts of 1,2-di(3-methylphenoxy)ethane (product name: KS-232, manufactured by Sankosha), 40 parts of a 10% aqueous solution of polyvinyl alcohol (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 E).

[0092] A thermal recording body was obtained in the same manner as in Example 1, except that dispersion E was used instead of dispersion D in the preparation of the coating solution for the thermal layer in Example 1.

[0093] (Example 6) In preparing the coating solution for the heat-sensitive layer in Example 1, a heat-sensitive recording body was obtained in the same manner as in Example 1, except that 64 parts of Highmicron L-271 (main component: stearic acid amide, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 25%) were used instead of 36.4 parts of dispersion D.

[0094] (Example 7) (10) Preparation of sensitizer dispersion (Solution F) 40 parts of diphenyl sulfone (manufactured by Nikka Chemical Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 F).

[0095] A thermal recording body was obtained in the same manner as in Example 1, except that dispersion F was used instead of dispersion D in the preparation of the coating solution for the undercoat layer in Example 1.

[0096] (Example 8) (11) Preparation of color developer dispersion (Solution G) 40 parts of N-[2-(3-phenylureido)phenyl]benzenesulfonamide (product name: NKK-1304, manufactured by Nippon Soda Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 G).

[0097] A thermal recording body was obtained in the same manner as in Example 1, except that dispersion G was used instead of dispersion C in the preparation of the coating solution for the thermal layer in Example 1.

[0098] (Example 9) In preparing the coating solution for the heat-sensitive layer in Example 1, the amount of dispersion B was changed from 47.7 parts to 22.7 parts, and dispersion G was changed from 22.7 parts to 22.7 parts to 22.7 parts of dispersion C. Otherwise, a heat-sensitive recording body was obtained in the same manner as in Example 1.

[0099] (Example 10) In preparing the coating solution for the undercoat layer in Example 4, a thermal recording body was obtained in the same manner as in Example 4, except that 56.6 parts of hollow particles A were replaced with 66.7 parts of hollow particles B, the amount of calcined kaolin (trade name Ansilex 93, manufactured by BASF, oil absorption capacity 105 ml / 100 g) was changed from 70 parts to 30 parts, the amount of latex A was changed from 22.9 parts to 95.8 parts, the amount of 25% solution of oxidized starch was changed from 12 parts to 40 parts, and the amount of water was changed from 80 parts to 0 parts.

[0100] (Example 11) A thermal recording body was obtained in the same manner as in Example 10, except that in the preparation of the coating solution for the undercoat layer in Example 10, 66.7 parts of hollow particles C were used instead of 66.7 parts of hollow particles B.

[0101] (Example 12) A thermal recording body was obtained in the same manner as in Example 10, except that in the preparation of the coating solution for the undercoat layer in Example 10, 95.8 parts of latex B were used instead of 95.8 parts of latex A.

[0102] (Example 13) A thermal recording body was obtained in the same manner as in Example 10, except that in the preparation of the coating solution for the undercoat layer in Example 10, 95.8 parts of latex C were used instead of 95.8 parts of latex A.

[0103] (Comparative Example 1) (12) Preparation of color developer dispersion (Solution H) 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 (trade name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 H).

[0104] A thermal recording body was obtained in the same manner as in Example 1, except that dispersion H was used instead of dispersion B in the preparation of the coating solution for the thermal layer in Example 1.

[0105] (Comparative Example 2) (13) Preparation of color developer dispersion (Solution J) 40 parts of Np-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea (product name: PF201, manufactured by Solenis), 40 parts of a 10% aqueous solution of polyvinyl alcohol (product name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 J).

[0106] In preparing the coating solution for the heat-sensitive layer in Example 1, dispersion J was used instead of dispersion B, the amount of dispersion C was changed from 22.7 parts to 0 parts, and the amount of calcium carbonate was changed from 21 parts to 31 parts. Otherwise, a heat-sensitive recording body was obtained in the same manner as in Example 1.

[0107] (Comparative Example 3) In preparing the coating solution for the heat-sensitive layer in Example 1, a heat-sensitive recording body was obtained in the same manner as in Example 1, except that the amount of dispersion C was changed from 22.7 parts to 0 parts, and the amount of calcium carbonate was changed from 21 parts to 31 parts.

[0108] (Comparative Example 4) In preparing the coating solution for the heat-sensitive layer in Example 1, the amount of dispersion C was changed from 22.7 parts to 11.4 parts, and the amount of calcium carbonate was changed from 21 parts to 26 parts. Otherwise, a heat-sensitive recording body was obtained in the same manner as in Example 1.

[0109] (Comparative Example 5) In preparing the coating solution for the heat-sensitive layer in Example 1, a heat-sensitive recording body was obtained in the same manner as in Example 1, except that the amount of dispersion B was changed from 47.7 parts to 0 parts, the amount of dispersion C was changed from 22.7 parts to 44.7 parts, and the amount of calcium carbonate was changed from 21 parts to 31 parts.

[0110] (Comparative Example 6) (14) Preparation of color developer dispersion (K solution) 40 parts of a diphenylsulfone crosslinked compound represented by the following general formula (2) (trade name: D-90, manufactured by Nippon Soda Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 K).

[0111] [ka] (In the formula, n represents an integer from 1 to 6.)

[0112] A thermal recording body was obtained in the same manner as in Example 1, except that dispersion K was used instead of dispersion C in the preparation of the coating solution for the thermal layer in Example 1.

[0113] (Comparative Example 7) (15) Preparation of color developer dispersion (Solution L) 40 parts of a urea urethane compound represented by the following general formula (3) (trade name: UU, manufactured by Chemipro Chemical Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA205, degree of polymerization 500, degree of saponification 88%, manufactured by Kuraray Co., Ltd.), 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 L).

[0114] [ka]

[0115] A thermal recording body was obtained in the same manner as in Example 1, except that dispersion L was used instead of dispersion C in the preparation of the coating solution for the thermal layer in Example 1.

[0116] The above examples and comparative examples were evaluated using the following method. The results are shown in Table 3.

[0117] [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 0.18 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 1.25 or higher: Suitable for high-speed printing and is excellent. Color intensity of 1.10 or higher and less than 1.25: Required for practical purposes. Color density less than 1.10: Low sensitivity, resulting in many defects such as whiteout, which poses practical problems.

[0118] Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was recorded with an applied energy of 0.25 mJ / dot (maximum color density), and the resulting printed areas were measured with a spectrophotometer (X-Rite504, manufactured by X-Rite Corporation). A higher value indicates a higher print density. The highest color intensity was evaluated based on the following criteria. Color density of 1.40 or higher: Excellent performance, capable of handling high-speed printing. Color intensity of 1.30 or higher but less than 1.40: Required for practical purposes. Color density less than 1.30: Low sensitivity, resulting in many defects such as whiteout, which poses practical problems.

[0119] [Plasticizer resistance] A polycarbonate pipe (40 mm in diameter) was wrapped three times with plastic wrap (product name: Hi-S Soft, manufactured by Nippon Carbide Industries Co., Ltd.), and each thermal recording material, which had been colored using a label printer (product name: L-2000, manufactured by Ishida Co., Ltd.), was placed on top of it. Three more layers of plastic wrap were then wrapped around the recording material, and it was left to stand for 24 hours in a 50°C environment. After processing, the optical density of the recording area was measured with a spectrophotometer (X-Rite 504, manufactured by X-Rite Co., Ltd.), and the retention rate was calculated as (print density after processing) ÷ (print density before processing). The following criteria were used to evaluate the survival rate. Over 65% survival rate after processing: Barcodes can be read, indicating excellent performance. A residual rate of 40% to less than 65% after processing is visually legible and poses no practical problems. Remaining percentage after processing is less than 40%: The printing disappears, posing a practical problem.

[0120] [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:

[0121] [Table 1]

[0122] [110℃ 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 110°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:

[0123] [Table 2]

[0124] [Table 3]

Claims

1. A thermal recording body having, in this order, a base coat layer containing hollow particles and an adhesive on a support, and a thermal recording layer containing a leuco dye, a color developer and an adhesive, wherein the first color developer of the thermal recording layer is the following general formula (1): 【Chemistry 1】 (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. A thermal recording body characterized by containing a compound represented by the general formula (1), containing 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide as a second color developer, the second color developer being present in an amount of 0.4 to 2.5 parts by mass per 1 part by mass of the first color developer, and the compound represented by the general formula (1) being 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.

2. The thermal recording body according to claim 1, wherein the compound represented by the general formula (1) is 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate.

3. The thermal recording body according to claim 1 or 2, wherein the second color developer is contained in an amount of 0.9 to 2.5 parts by mass per 1 part by mass of the first color developer.

4. The thermal recording body according to claim 1 or 2, wherein the thermal recording layer contains at least one sensitizer selected from dimethyl terephthalate, 1,2-di(3-methylphenoxy)ethane, stearic acid amide, and diphenyl sulfone.

5. The thermal recording body according to claim 1 or 2, wherein the thermal recording layer contains at least one sensitizer selected from dimethyl terephthalate and 1,2-di(3-methylphenoxy)ethane.

6. 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.

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

8. 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.

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 -30°C or lower.

10. 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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