JP2006248196A - Thermal recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality level thermal recording material which can produce successful glossiness and color development density even by a high energy application part. <P>SOLUTION: This thermal recording material has one or not less than two thermal recording layers and one or not less two adjacent layers which adjoin the thermal recording layers, formed on a support. At least one of the adjacent layers contains an oily phase component particle, and the oily phase component is an oily substance with lower than 40°C melting point or a molten or vitreous substance with no melting point of 40°C or higher. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material excellent in image quality that can ensure good glossiness and color density even in high-energy printing.

The thermal recording system has the advantage that the recording device is simple, reliable and maintenance-free, and has been used more and more in recent years, and more recently, multicolor thermal recording has been actively used. Yes.
The multicolor thermosensitive recording material is one in which a plurality of thermosensitive recording layers are provided on a support.
However, when printing on a multicolor thermosensitive recording material, it is difficult to obtain a sufficient color of each thermosensitive recording layer in the multilayer thermosensitive recording material in which the respective thermosensitive recording layers are stacked, and before obtaining a sufficient color density, There was a problem that color development started.
Also, when coloring the bottom layer, if you print at high speed or perform high energy printing to obtain a high color density, the gloss of the image changes unnaturally at the high energy application section, or the image is distorted The color density may decrease.

In order to solve such problems, an intermediate layer is provided between the heat-sensitive recording layer and the heat-sensitive recording layer, and by adding a thermoplastic substance or the like to this intermediate layer, the thermal fractionation of each heat-sensitive recording layer is improved. A technique to be used is disclosed (see Patent Documents 1 and 2).
However, with this technology, when coloring the bottom layer, if you print at high speed or perform high energy printing to obtain a high color density, the gloss of the image may change unnaturally at the high energy application part. The problem that the image is disturbed and the color density is lowered has not been solved. In addition, when the heat-sensitive recording layer is scratched, there is a problem that foaming occurs around the scratch or cracks occur.
JP-A-5-169802 JP 2003-341229 A

  The present invention has been made under the circumstances as described above, and its purpose is to provide a high-quality heat-sensitive recording material that does not have the above-described problems and can obtain good gloss and color density even at a high energy application part. It is to provide.

  In view of such circumstances, the present inventor has intensively studied, and as a result, has completed the following invention.

  <1> In a heat-sensitive recording material in which one or two or more heat-sensitive recording layers and one or two or more adjacent layers adjacent to the heat-sensitive recording layer are provided on a support, at least one of the adjacent layers is oil phase component particles. And the oil phase component is an oily substance having a melting point of less than 40 ° C., or a molten or glassy substance having no melting point at 40 ° C. or higher.

<2> One or two or more thermosensitive recording layers and one or more adjacent layers adjacent to the thermosensitive recording layer are provided on a support, and at least one of the adjacent layers has an oily substance having a melting point of less than 40 ° C. A method for producing a thermosensitive recording material containing a molten or glassy substance having no melting point at 40 ° C. or higher, wherein the oily substance has a melting point of less than 40 ° C., or a molten state or glass having no melting point at 40 ° C. or higher. A method for producing a heat-sensitive recording material, comprising applying an adjacent layer coating solution containing particles of a substance in a state.
<3> The method for producing a heat-sensitive recording material according to <2>, wherein the particles are emulsion particles.

  <4> In a heat-sensitive recording material in which one or two or more heat-sensitive recording layers containing microcapsules and one or two or more adjacent layers adjacent to the heat-sensitive recording layer are provided on a support, at least one of the adjacent layers A heat-sensitive recording material, wherein the layer comprises polymer compound particles having a melting point, a softening point, or a glass transition point of less than 40 ° C.

  <5> The heat-sensitive recording material according to <4>, wherein the adjacent layer is prepared by applying a latex containing latex particles of a polymer compound.

  <6> The heat-sensitive recording material according to <1>, <4>, or <5>, wherein the heat-sensitive recording layer has two or more heat-sensitive recording layers, and each heat-sensitive recording layer is colored in a different hue.

  <7> The heat-sensitive recording material according to <6>, further comprising an adjacent layer between the heat-sensitive recording layer that develops yellow and the heat-sensitive recording layer that develops magenta.

  <8> Any one of <1> and <4> to <7>, wherein at least one of the thermosensitive recording layers contains a diazonium salt compound and a coupler compound that reacts with the diazonium salt compound to develop a color. The heat-sensitive recording material according to item 1.

  According to the present invention, it is possible to provide a high-quality heat-sensitive recording material capable of obtaining good gloss and color density even at a high energy application portion.

  The thermosensitive recording material of the present invention is a thermosensitive recording material in which at least one thermosensitive recording layer is provided on a support, and one or two or more adjacent layers adjacent to the thermosensitive recording layer are provided. The layer has the characteristics as described above. Further, a protective layer, an undercoat layer, a light transmittance adjusting layer, other layers, and the like can be further provided according to the purpose and necessity.

<Adjacent layer>
In the present invention, the adjacent layer is one or more layers adjacent to the thermosensitive recording layer, and if it is present between the two thermosensitive recording layers, it becomes an intermediate layer, but is not limited to the intermediate layer.
At least one of the adjacent layers contains oil phase component particles or polymer compound particles. The layer containing the particles may be one layer or a plurality of layers, and the position of the layer containing the particles is not particularly limited.

(Oil phase component particles)
The oil phase component of the oil phase component particles used in the present invention is an oily substance having a melting point of less than 40 ° C., or a molten or glassy substance having no melting point at 40 ° C. or higher.

The oil phase component used in the present invention may be any substance as long as it is an oily substance having a melting point of less than 40 ° C., preferably 30 ° C. or less, or a substance in a molten state or glass state having a melting point of 40 ° C. or more. Good. When the melting point is 40 ° C. or higher, the gloss is lowered or the concentration is lowered when high energy is applied. Moreover, even if it contains a substance having a melting point above 40 ° C., it may be present in a dissolved or molten state. Specifically, an organic solvent having a melting point of less than 40 ° C. and a boiling point of 100 ° C. to 300 ° C. is preferable. For example, alkylnaphthalene, alkyldiphenylethane, alkyldiphenylmethane, alkylbiphenyl, alkylterphenyl, chlorinated paraffin, phosphate ester , Maleic acid esters, adipic acid esters, phthalic acid esters, benzoic acid esters, carbonic acid esters, ethers, sulfuric acid esters, sulfonic acid esters, and the like. You may use these in mixture of 2 or more types. Further, as described above, a substance having a melting point of 40 ° C. or higher may be dissolved in these oils so as not to have a melting point. In addition, a low-boiling solvent having a boiling point of 100 ° C. or lower is used in combination as an auxiliary solvent for adjusting the particle size of the emulsion or adjusting the viscosity when preparing the emulsion, or for dissolving a substance having a melting point of 40 ° C. or higher. May be. Further, several substances having a melting point of 40 ° C. or higher are dissolved in an auxiliary solvent of a low boiling point solvent, and then the auxiliary solvent is evaporated to create a eutectic state. This eutectic substance has no melting point or the melting point is lower than 40 ° C. If so, such a substance may be used. Examples of the low boiling point solvent include ethyl acetate, methyl acetate, isopropyl acetate, propyl acetate, butyl acetate, methylene chloride, tetrahydrofuran, acetonitrile, acetone and the like.
The solubility of the oil phase component in water is preferably 1% or less, and particularly preferably 0.5% or less. If the solubility in water is greater than 1%, fogging or discoloration may occur during sample storage.
The median diameter of the oil phase component particles is preferably 1 μm or less, and more preferably 0.5 μm or less.
In addition, in this specification, an average particle diameter represents a median diameter, and means the result measured with the laser diffraction / scattering type particle size distribution measuring apparatus (Horiba, Ltd. product LA-700).

  The addition amount of the oil phase component particles is preferably 5 to 95% by mass of the dry coating amount of the adjacent layer, particularly 10 to 80% by weight, and more preferably 20 to 70% by weight. If this addition amount is less than 5% by weight, the effect of the present invention is small, and if it exceeds 95% by weight, fogging or discoloration may occur during sample storage.

(Polymer compound particles)
The polymer compound particles used in the present invention are polymer compounds having a melting point, a softening point, or a glass transition point of less than 40 ° C., preferably 30 ° C. or less. When the melting point or the like is 40 ° C. or higher, the gloss is lowered or the density is lowered when high energy is applied, which is not preferable.
Specific examples of the polymer compound include polystyrene, polyethylene, polypropylene, polybutadiene, polystyrene polybutadiene copolymer, polyacrylonitrile, acrylic emulsion, and modified polymers thereof. You may use these in mixture of 2 or more types.
The solubility of the polymer compound in water is preferably 1% or less, and particularly preferably 0.5% or less. If the solubility in water is greater than 1%, fogging or discoloration may occur during sample storage.
The median diameter of the polymer compound particles is preferably 1 μm or less, and more preferably 0.5 μm or less.
The polymer compound particles become latex particles in the coating solution, and this latex may be any of cationic, nonionic or anionic, but nonionic or cationic latex is preferred.
The addition amount of the polymer compound particles is preferably 5 to 95% by mass of the dry coating amount of the adjacent layer, particularly 10 to 80% by weight, and more preferably 20 to 70% by weight. If this addition amount is less than 5% by weight, the effect of the present invention is small, and if it exceeds 95% by weight, fogging or discoloration may occur during sample storage.

(Create adjacent layers)
At least one of the adjacent layers contains oil phase component particles or polymer compound particles.
Moreover, this adjacent layer can contain a binder, a crosslinking agent, a lubricant, a surfactant, other additives, and the like according to the purpose and necessity. The adjacent layer is preferably formed between the heat-sensitive recording layer and the heat-sensitive recording layer, or between the heat-sensitive recording layer and the protective layer.

  There is no restriction | limiting in particular as a binder used for the said adjacent layer, According to a system, polyvinyl alcohol, gelatin, polyvinylpyrrolidone, cellulose, these derivatives, etc. can be used. In particular, gelatin and gelatin derivatives have fluidity at a relatively high temperature. However, gelatin and gelatin derivatives lose their fluidity at low temperatures (for example, 35 ° C. or less) and have excellent gelling properties (setting properties). When forming a plurality of layers on the support, when applying each coating solution and drying it, it is possible to apply a plurality of layers one after another, or to apply multiple layers at once by an extrusion die method, etc. Even in the drying method, it is possible to effectively prevent the adjacent two layers from being mixed with each other, to obtain a heat-sensitive recording material capable of forming a high-quality image by improving the surface shape of the resulting heat-sensitive recording material. Therefore, it is suitable for a recording material for medical diagnosis that needs to form a clear image in detail. Furthermore, even if it is dried at a high wind speed, the surface shape does not deteriorate, so that the production efficiency is improved.

  As the gelatin used in the adjacent layer of the present invention, any of unmodified (untreated) gelatin and modified (treated) gelatin can be used without any problem. Examples of the modified gelatin include lime-processed gelatin, acid-processed gelatin, phthalated-processed gelatin, deionized-processed gelatin, and enzyme-processed low-molecular-weight gelatin. Of these, alkali-processed gelatin having a low isoelectric point (for example, lime-processed gelatin) and derivative gelatin (for example, phthalated gelatin) in which an amino group is reacted are preferably used.

  As the binder for the adjacent layer, in addition to the above gelatins, water-soluble binders are also preferable. For example, vinyl acetate-acrylamide copolymer, silicon-modified polyvinyl alcohol, starch, modified starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gum arabic , Casein, styrene-maleic acid copolymer hydrolyzate, styrene-maleic acid copolymer half ester hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyacrylamide derivative, polyvinylpyrrolidone, polystyrene sulfonate soda , Water-soluble polymers such as sodium alginate, and styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, vinyl acetate emuls ® dispersible polymer such emissions, or the like can be used.

  For the purpose of improving the water resistance and the like of the adjacent layer, it is effective to use a crosslinking agent and a catalyst for promoting the reaction in combination. Examples of the crosslinking agent include epoxy compounds, blocked isocyanates, and vinyl sulfone compounds. Aldehyde compounds, methylol compounds, boric acid, carboxylic acid anhydrides, silane compounds, chelate compounds, halides, etc., among which epoxy compounds are particularly preferred. In order to accelerate the crosslinking reaction, a known acid, metal salt or the like may be used as a catalyst. What can adjust pH of the coating liquid for adjacent layer formation to 6.0-7.5 is preferable. Examples of the catalyst include known acids and metal salts, and those that can adjust the pH of the coating solution to 6.0 to 7.5 as described above are preferable.

Examples of the lubricant preferably include zinc stearate, calcium stearate, paraffin wax, and polyethylene wax.
Preferred examples of the surfactant include sulfosuccinic acid-based alkali metal salts and fluorine-containing surfactants so that an adjacent layer can be uniformly formed on the heat-sensitive recording layer. Examples thereof include sodium salts such as (2-ethylhexyl) sulfosuccinic acid and di- (n-hexyl) sulfosuccinic acid, and ammonium salts.

The coating solution for forming the adjacent layer (adjacent layer coating solution) is obtained by mixing the above-described components. Furthermore, you may add a mold release agent, a wax, a water repellent, etc. as needed.
As the form of the coating liquid, an emulsion in which the oil phase component is formed into emulsion particles and dispersed in the aqueous phase or a latex in which the polymer compound is dispersed in the aqueous phase is preferable.
The emulsion particles are prepared by adding an oil phase component to an aqueous phase and emulsifying it by adding mechanical energy (stirring, stirring, or mixing) or electrical energy. Examples of the emulsifier that gives mechanical energy include a stirrer, a colloid mill, and a homogenizer. On the other hand, latex particles are subjected to a polymerization reaction with a monomer emulsion or the like by an emulsion polymerization method, a seed polymerization method, an aqueous solution polymerization method or the like to prepare a polymer particle dispersion. The method for producing the emulsion particles and latex particles is described in detail in the book (for example, “Dispersion / Emulsification System Chemistry” Fumio Kitahara, Kunio Furusawa P36-P76, etc.), and all these methods can be applied to the present invention.
The protective colloid of these particles and the binder are preferably compatible, particularly preferably the same.

  The heat-sensitive recording material of the present invention can be formed, for example, by applying an adjacent layer coating solution on a heat-sensitive recording layer formed on a support by a known coating method. Examples of the known coating method include a method using a bar coater, an air knife coater, a blade coater, a curtain coater and the like.

In the adjacent layer of the heat-sensitive recording material of the present invention, the concentration of the water-soluble binder containing gelatin or the like is 3 to 25% by mass, preferably about 5 to 15% by mass. The dry coating amount of the adjacent layer is 0.5 to 6 g / m ² , preferably 1 to 4 g / m ² . By setting it in such a range, it is possible to prevent mixing of coloring components and adjust sensitivity between recording layers.

<Thermal recording layer>
In the heat-sensitive recording material of the present invention, a heat-sensitive recording layer containing a coloring component and, if necessary, other components such as a binder and a base is provided on a support. Examples of the coloring component include a combination of a diazonium salt compound and a coupler that reacts with the diazonium salt to form a dye, an electron-donating dye precursor, and an electron-accepting compound that reacts with the electron-donating dye precursor to form a color. Combinations and other conventionally known color forming component systems can be used. The diazonium salt compound, the electron donating dye precursor and the like are preferably in the form of being encapsulated in microcapsules.

(Diazonium salt)
In the present invention, as a diazonium salt contained within the above concentration range,
Ar-N ₂ ⁺ · X ⁻ (2)
It is preferable to contain the compound represented by these.

  In the above formula (2), Ar represents a substituted or unsubstituted aryl group. When substituted, examples of the substituent include alkyl group, alkoxy group, alkylthio group, aryl group, aryloxy group, arylthio group, acyl group, alkoxycarbonyl group, carbamoyl group, carboamide group, sulfonyl group, sulfamoyl group, sulfone. Examples include an amide group, a ureido group, a halogen group, an amino group, and a heterocyclic group, and these substituents may be further substituted.

  As said aryl group, a C6-C30 aryl group is preferable, for example, a phenyl group, 2-methylphenyl group, 2-chlorophenyl group, 2-methoxyphenyl group, 2-butoxyphenyl group, 2- (2- Ethylhexyloxy) phenyl group, 2-octyloxyphenyl group, 3- (2,4-di-t-pentylphenoxyethoxy) phenyl group, 4-chlorophenyl group, 2,5-dichlorophenyl group, 2,4,6-trimethyl Phenyl group, 3-chlorophenyl group, 3-methylphenyl group, 3-methoxyphenyl group, 3-butoxyphenyl group, 3-cyanophenyl group, 3- (2-ethylhexyloxy) phenyl group, 3,4-dichlorophenyl group, 3,5-dichlorophenyl group, 3,4-dimethoxyphenyl group, 3- (dibutylaminocarboni Methoxy) phenyl group, 4-cyanophenyl group, 4-methylphenyl group, a 4-methoxyphenyl group, 4-butoxyphenyl,

4- (2-ethylhexyloxy) phenyl group, 4-benzylphenyl group, 4-aminosulfonylphenyl group, 4-N, N-dibutylaminosulfonylphenyl group, 4-ethoxycarbonylphenyl group, 4- (2-ethylhexylcarbonyl) ) Phenyl group, 4-fluorophenyl group, 3-acetylphenyl group, 2-acetylaminophenyl group, 4- (4-chlorophenylthio) phenyl group, 4- (4-methylphenyl) thio-2,5-butoxyphenyl Group, 4- (N-benzyl-N-methylamino) -2-dodecyloxycarbonylphenyl group and the like.
Further, these groups may be further substituted with an alkyloxy group, an alkylthio group, a substituted phenyl group, a cyano group, a substituted amino group, a halogen atom, a heterocyclic group, or the like.

X ⁻ represents an acid anion. The acid anion may be either an inorganic anion or an organic anion.
Preferred examples of the inorganic anion include hexafluorophosphate ion, borohydrofluoric acid ion, chloride ion, and sulfate ion, and among them, hexafluorophosphate ion and borohydrofluoric acid ion are particularly preferable. Examples of the organic anion include polyfluoroalkylcarboxylate ions, polyfluoroalkylsulfonate ions, tetraphenylborate ions, aromatic carboxylate ions, and aromatic sulfonate ions. Among them, Polyfluoroalkyl sulfonate ions, tetraphenylborate ions, and aromatic carboxylate ions are particularly preferred.

  More preferred examples of the diazonium salt compound include diazonium salt compounds as described in paragraphs [0028] to [0049] of Japanese Patent Application No. 2002-006233. However, the present invention is not limited to these.

  The diazonium salt can be produced by a known method. That is, the corresponding aniline can be obtained by diazotization in an acidic solvent using sodium nitrite, nitrosylsulfuric acid, isoamyl nitrite or the like.

  The diazonium salt may be either oily or crystalline, but is preferably in a crystalline state at room temperature from the viewpoint of handleability. These diazonium salts may be used alone or in combination of two or more according to the purpose such as hue adjustment.

The content of the diazonium salt in a single heat-sensitive recording layer is preferably 0.02 to 5 g / m ^2, more preferably 0.1-4 g / m ² from the viewpoint of color density. Further, in order to stabilize the diazonium salt, a complex compound may be formed using zinc chloride, cadmium chloride, tin chloride or the like.

  In particular, the above-described diazonium salt develops a color by reaction with a coupler compound described later, provides a high color density with excellent color developability, and the color developing dye has excellent light resistance. In addition, it has excellent photodegradability in the wavelength range of 350 to 430 nm, such as fluorescent lamps, has high-speed decomposability that can be sufficiently fixed even with short-time light irradiation, and at the same time, coloring due to photodecomposition (stain generation) Therefore, it is very suitable as a color-forming component used in a light-fixing type heat-sensitive recording material, and can form a high-contrast image that is robust and excellent in whiteness of the background portion.

(Coupler compound)
In the present invention, together with the above-described diazonium salt, a coupler compound that reacts with the diazonium salt to cause color development (hereinafter sometimes simply referred to as “coupler”) is contained in the heat-sensitive recording layer.

  Examples of the coupler include JP-B-4-75147, JP-B-6-55546, JP-B-6-79867, JP-A-4-201483, JP-A-60-49991, JP-A-60. No. 242094, JP 61-5983, JP 63-87125, JP 4-59287, JP 5-185717, JP 7-88356, JP 7-7 -96671, JP-A-8-324129, JP-A-9-38389, JP-A-5-185736, JP-A-5-8544, JP-A-59-190866, JP-A-62. -55190, JP-A-60-6493, JP-A-60-259492, JP-A-63-3318546, JP-A-4-65291, For example, see Japanese Laid-Open Patent Application No. 5-1855736, Japanese Laid-Open Patent Application No. Hei 5-204089, Japanese Laid-Open Patent Application No. 8-310133, Japanese Laid-Open Patent Application No. 8-324129, Japanese Laid-Open Patent Application No. 9-156229, Japanese Laid-Open Patent Application No. 9-175017. As specific compound examples, the following exemplified compounds (B-1 to B-24, (1) to (28), II-1 to II-11, and VI-1 to VI-6) are shown below as specific compound examples. Shown in However, the present invention is not limited to these.

  The content of the coupler compound in the heat-sensitive recording layer is preferably 0.5 to 20 parts by mass and more preferably 1 to 10 parts by mass with respect to 1 part by mass of the diazonium salt. If the content is less than 0.5 parts by mass, sufficient color developability may not be obtained, and if it exceeds 20 parts by mass, the coating suitability may be deteriorated.

  The coupler compound (along with other components added as desired) can be used by adding a water-soluble polymer and solid-dispersing it with a sand mill or the like. It can also be used. Here, the solid dispersion or emulsification method is not particularly limited, and a conventionally known method can be used. Details of these methods are described in JP-A-59-190886, JP-A-2-141279, and JP-A-7-17145.

(Other ingredients)
The heat-sensitive recording layer according to the present invention may contain a basic substance, a coloring aid, a binder, an antioxidant and the like as the other components.
The basic substance is contained for the purpose of promoting the coupling reaction between the diazonium salt and the coupler compound. Specifically, one or more conventionally known compounds can be used, and can be appropriately selected from the basic substances described in the above-mentioned publications listed in the section of coupler compounds.
Examples of the basic substance include nitrogen-containing compounds such as tertiary amines, piperidines, piperazines, amidines, formamidines, pyridines, guanidines and morpholines.

  Among them, in particular, N, N′-bis (3-phenoxy-2-hydroxypropyl) piperazine, N, N′-bis (3- (p-methylphenoxy) -2-hydroxypropyl) piperazine, N, N′-bis (3- (p-methoxyphenoxy) -2-hydroxypropyl) piperazine, N, N′-bis (3-phenylthio-2-hydroxypropyl) piperazine, N, N′-bis (3- (β-naphthoxy)- 2-hydroxypropyl) piperazine, N-3- (β-naphthoxy) -2-hydroxypropyl-N′-methylpiperazine, 1,4-bis ((3- (N-methylpiperazino) -2-hydroxy) propyloxy) Piperazines such as benzene, N- (3- (β-naphthoxy) -2-hydroxy) propylmorpholine, 1,4-bis ((3-morpholino- Morpholines such as -hydroxy) propyloxy) benzene and 1,3-bis ((3-morpholino-2-hydroxy) propyloxy) benzene, N- (3-phenoxy-2-hydroxypropyl) piperidine, N-dodecylpiperidine And guanidines such as triphenylguanidine, tricyclohexylguanidine and dicyclohexylphenylguanidine are preferred.

The coloring aid is contained for the purpose of rapid and complete thermal printing with low energy. That is, the color former is a substance that increases the color density during heat recording or controls the color temperature, lowering the melting point of coupler compounds, basic substances or diazonium salts, and lowering the softening point of the capsule wall. By the action, the conditions are set such that a diazonium salt, a basic substance, a coupler compound and the like can easily react.
Examples of the coloring aid include phenol derivatives, naphthol derivatives, alkoxy-substituted benzenes, alkoxy-substituted naphthalenes, aromatic ethers, thioethers, esters, amides, ureidos, urethanes, sulfonamide compounds, hydroxy compounds, and the like.

  The binder can be selected from conventionally known binders, and examples thereof include water-soluble polymers such as polyvinyl alcohol and gelatin, and polymer latex.

  The antioxidant is contained for the purpose of improving fastness to light and heat of a thermochromic image or reducing yellowing due to light of an unprinted portion (non-image portion) after fixing. Examples of the antioxidant include European Patent No. 223739, Patent No. 309401, Patent No. 309402, Patent No. 310551, Patent No. 310552, Patent No. 457416, Patent Published German No. 3435443, JP-A-54-48535, JP-A-62-262047, JP-A-63-113536, JP-A-63-163351, JP-A-2-262654, JP-A-2-71262. And JP-A-3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.

The heat-sensitive recording layer in the present invention may be composed of a layer containing an electron-accepting compound and an electron-donating dye precursor encapsulated in microcapsules as a coloring component. Examples of the electron donating dye precursor and the electron accepting compound that can be used in the present invention include JP-A-6-328860, JP-A-7-290826, JP-A-7-314904, and JP-A-8-324116. JP-A-3-37727, JP-A-9-31345, JP-A-9-111136, JP-A-9-118073, JP-A-11-157221, and the like. Moreover, as a more specific compound, the compound described in paragraph number [0025]-[0031] of Japanese Patent Application No. 2001-360629 is preferable.
The content of the electron-accepting compound in the heat-sensitive recording layer is preferably 5 to 15 parts by mass with respect to 1 part by mass of the electron-donating dye precursor.

(Method of microencapsulation)
As a microcapsule formation method, a conventionally known microcapsule formation method (specifications such as US Pat. Nos. 3,726,804 and 3,796,669) can be used. Specifically, Interfacial polymerization and internal polymerization are suitable. Specifically, a diazonium salt is dissolved in a water-insoluble or insoluble organic solvent together with a microcapsule wall precursor (wall material) to form an oil phase, and this is dissolved in an aqueous solution (water phase) of a water-soluble polymer. It is added and emulsified and dispersed with a homogenizer or the like, and heated to form a polymer film (wall film) that becomes a microcapsule wall at the oil / water interface.
In the present invention, particularly in the preparation of the oil phase, among the oil phase components, the diazonium occupies all the non-volatile oil-soluble components of the oil-soluble components to be included in the microcapsules excluding the capsule wall material component and the surfactant component. The salt concentration is adjusted to 20-70% by mass.

  Examples of the polymer material (wall material) used as the wall film include polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, and styrene. -Methacrylate copolymer resin, gelatin, polyvinyl alcohol and the like. Among these, microcapsules having a wall film made of polyurethane / polyurea resin are preferable.

Hereinafter, a method for producing a diazonium salt-encapsulating microcapsule (polyurea / polyurethane wall) will be described as an example.
First, the diazonium salt is dissolved or dispersed in a hydrophobic organic solvent (including a low-boiling solvent as required) serving as a capsule core to prepare an oil phase (organic solvent solution) serving as a microcapsule core. At this time, a polyvalent isocyanate as a wall material or a surfactant may be further added to the oil phase side for the purpose of uniformly emulsifying and dispersing. Further, additives such as an anti-fading agent and an anti-stain agent may be added.

  In the present invention, in the oil phase (organic solvent solution), among the oil phase components, the oil-soluble components are all non-volatile except for the capsule wall material component (polyvalent isocyanate) and the surfactant and the low boiling point solvent. The concentration of the diazonium salt in the oil-soluble component is adjusted to 20 to 70% by mass. In other words, 20 to 70 mass of the total nonvolatile oil-soluble component of the diazonium salt, the high-boiling organic solvent (boiling point 100 ° C. or higher), and other oil-soluble additives, which are oil-soluble components constituting the oil phase in this example. Adjust to be%.

As said polyvalent isocyanate compound, the compound which has a trifunctional or more than trifunctional isocyanate group is preferable, and a bifunctional isocyanate compound may be sufficient. Specifically, xylene diisocyanate and hydrogenated products thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated products thereof, and diisocyanates such as isophorone diisocyanate are used as main raw materials, and these dimers or trimers (burette or isocyanate). Nurate), other polyfunctional adducts of polyols such as trimethylolpropane and bifunctional isocyanates such as xylylene diisocyanate, adducts of polyols such as trimethylolpropane and bifunctional isocyanates such as xylylene diisocyanate Examples thereof include a compound in which a high molecular weight compound such as polyether having active hydrogen such as polyethylene oxide is introduced, and a formalin condensate of benzene isocyanate.
The compounds described in JP-A-62-212190, JP-A-4-26189, JP-A-5-317694, and Japanese Patent Application No. 8-268721 are also preferable.

  The amount of polyisocyanate used is determined so that the average particle diameter of the microcapsules is 0.3 to 12 μm and the wall thickness is 0.01 to 0.3 μm. The dispersed particle diameter is 0.2 About 10 μm is common.

  As the surfactant, a known surfactant for emulsification can be used, and the addition amount in the case of adding the surfactant is preferably 0.1 to 5% by mass relative to the mass of the oil phase, -2 mass% is more preferable.

In the preparation of the oil phase, the hydrophobic organic solvent that dissolves and disperses the diazonium salt is preferably an organic solvent having a boiling point of 100 to 300 ° C., for example, alkylnaphthalene, alkyldiphenylethane, alkyldiphenylmethane, alkylbiphenyl, alkyl Terphenyl, chlorinated paraffin, phosphate ester, maleate ester, adipate ester, phthalate ester, benzoate ester, carbonate ester, ether, sulfate ester, sulfonate ester, etc. It is done. You may use these in mixture of 2 or more types.
In addition, when the solubility of the diazonium salt in the organic solvent is poor, a low-boiling solvent having high solubility of the diazonium salt may be supplementarily used. Examples of the low-boiling solvent include ethyl acetate and propyl acetate. Isopropyl acetate, butyl acetate, methylene chloride, tetrahydrofuran, acetonitrile, acetone and the like.

  That is, the diazonium salt preferably has an appropriate solubility in a hydrophobic organic solvent and a low boiling point solvent. Specifically, the solubility in the solvent is 5 in that the concentration of the following diazonium salt can be easily adjusted. % Or more is preferable. The solubility in water is preferably 1% or less.

  Subsequently, the prepared oil phase is emulsified and dispersed in the aqueous phase. At this time, an aqueous solution in which a water-soluble polymer is dissolved is used for the aqueous phase, and after the oil phase is added thereto, emulsification and dispersion are performed by means such as a homogenizer. The water-soluble polymer functions as a dispersion medium that makes the dispersion uniform and easy, and stabilizes the emulsified and dispersed aqueous solution. Here again, the same surfactant as described above may be added for the purpose of further uniformly emulsifying and dispersing.

The water-soluble polymer used in the aqueous phase is preferably a water-soluble polymer having a solubility in water of 5% or more at the temperature to be emulsified. For example, polyvinyl alcohol and modified products thereof, polyacrylic acid amide and derivatives thereof , Ethylene-vinyl acetate copolymer, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate- Acrylic acid copolymers, carboxymethylcellulose, methylcellulose, casein, gelatin, starch derivatives, arabic gum, sodium alginate and the like can be mentioned.
The water-soluble polymer preferably has no or low reactivity with an isocyanate compound. For example, a polymer having a reactive amino group in a molecular chain such as gelatin may be modified beforehand. It is desirable to eliminate the reactivity.

In an emulsified dispersion obtained by adding an oil phase to an aqueous phase, a polyisocyanate polymerization reaction occurs at the interface between the oil phase and the aqueous phase to form a polyurea wall.
If a polyol and / or polyamine is further added to the hydrophobic solvent in the aqueous phase or the oil phase, it can react with the polyvalent isocyanate and be used as one of the components of the microcapsule wall. In the above reaction, it is preferable to keep the reaction temperature high or to add an appropriate polymerization catalyst from the viewpoint of increasing the reaction rate.

Specific examples of the polyol or polyamine include propylene glycol, glycerin, trimethylolpropane, triethanolamine, sorbitol, hexamethylenediamine and the like. When a polyol is added, a polyurethane wall is formed.
The polyvalent isocyanate, polyol, reaction catalyst, or polyamine for forming a part of the walling agent is described in detail in Seisho (Polyurethane Handbook edited by Keiji Iwata, Nikkan Kogyo Shimbun (1987)). is there.

The above emulsification can be carried out by appropriately selecting from known emulsifiers such as a homogenizer, a manton gorey, an ultrasonic disperser, a dissolver, and a kedy mill.
After emulsification, the emulsion is heated to 30 to 70 ° C. for the purpose of promoting the capsule wall formation reaction. Further, during the reaction, in order to prevent aggregation between the capsules, it is necessary to add water to reduce the collision probability between the capsules or to perform sufficient stirring. Further, a dispersion for preventing aggregation may be added during the reaction.
During the polymerization reaction, generation of carbon dioxide gas is observed as the polymerization progresses, and the end thereof can be regarded as an approximate end point of the capsule wall formation reaction. Usually, the target diazonium salt-encapsulating microcapsules can be obtained by reacting for several hours.

  On the other hand, in the preparation of a coating solution for forming a heat-sensitive recording layer (coating solution for heat-sensitive recording layer), a coupler that develops color of the diazonium salt is, for example, a water-soluble polymer, an organic base, other color forming aids, etc. Although it can be used in the form of a solid dispersion, it is particularly preferable that the high-boiling point organic solvent containing a surfactant and / or a water-soluble polymer as a protective colloid is first dissolved in a high-boiling organic solvent that is hardly soluble or insoluble in water. It is preferably used as an emulsified dispersion that is mixed with an aqueous molecular solution (aqueous phase) and emulsified with a homogenizer or the like. If necessary, a low boiling point solvent may be used as a dissolution aid.

Furthermore, couplers, organic bases, and the like can be emulsified and dispersed separately, or mixed and then dissolved in a high boiling point organic solvent to be emulsified and dispersed. A preferable emulsified and dispersed particle size is 1 μm or less. The high-boiling organic solvent can be appropriately selected from, for example, high-boiling oils described in JP-A-2-141279. From the viewpoint of emulsion stability, esters are preferred, and tricresyl phosphate is particularly preferred.
Examples of the low-boiling solvent include those similar to the low-boiling solvent in the oil phase.

  Further, as the surfactant contained in the aqueous phase, an anionic or nonionic surfactant that does not cause precipitation or aggregation with a water-soluble polymer can be appropriately selected. For example, sodium alkylbenzene sulfonate, Examples include sodium alkyl sulfate, dioctyl sulfosuccinate sodium salt, polyalkylene glycol (for example, polyoxyethylene nonyl phenyl ether), and the like.

<Support>
As the support, for example, plastic film, paper, plastic resin laminated paper, synthetic paper, and the like can be used, and plastic film, synthetic paper, and plastic resin laminated paper are preferable from the viewpoint of gloss.

<Multicolor thermal recording layer>
The heat-sensitive recording material of the present invention is preferably a heat-sensitive recording material having a plurality of heat-sensitive recording layers on a support and capable of forming a multicolor image by changing the color hue of each heat-sensitive recording layer.
That is, full color image recording can be performed by selecting the color development hues of the respective heat-sensitive recording layers to be the three primary colors in the subtractive color mixing, yellow, magenta, and cyan. In this case, the coloring mechanism of the thermosensitive recording layer (lowermost layer) directly laminated on the support surface is not limited to the diazo coloring system based on the combination of the diazonium salt and the coupler compound, but includes, for example, an electron donating dye and the electron Coloring system combining electron-accepting dyes that react with donor dyes, color developing systems that come into contact with basic compounds, color forming systems that chelate, chelate coloring systems, and reaction with nucleophiles to cause elimination reactions Any color developing system may be used, and two or more diazo color recording layers having different maximum absorption wavelengths and different color hues may be provided on the heat sensitive recording layer.

For example, the layer configuration of the full color thermosensitive recording material may be configured in the following manner. However, the present invention is not limited to these.
Two kinds of diazonium salts having different photosensitive wavelengths are combined in a separate layer in combination with a coupler compound that can react with each diazonium salt when heated to develop a different hue. It may be a full-color heat-sensitive recording material in which a heat-sensitive recording layer (B layer, C layer) and a heat-sensitive recording layer (A layer) obtained by combining an electron-donating colorless dye and an electron-accepting compound are laminated, or The two heat-sensitive recording layers (B layer, C layer), a diazonium salt having a different photosensitive wavelength, and a coupler compound that reacts with the diazonium salt when heated to form a color (A layer) And a full color thermosensitive recording material.

  Specifically, from the support side, an electron-donating colorless dye and an electron-accepting compound, or a diazonium salt having a maximum absorption wavelength shorter than 350 nm and a coupler compound that reacts with the diazonium salt when heated to develop a color. One heat-sensitive recording layer (A layer), a second heat-sensitive recording layer (B layer) containing a diazonium salt having a maximum absorption wavelength of 360 nm ± 20 nm and a coupler compound that reacts with the diazonium salt when heated to produce a color, A third thermosensitive recording layer (C layer) containing a diazonium salt having an absorption wavelength of 400 ± 20 nm and a coupler compound that reacts with the diazonium salt when heated to form a color may be sequentially laminated.

In the case of a multicolor thermosensitive recording material, recording can be performed as follows.
First, the third heat-sensitive recording layer (C layer) is heated to cause the diazonium salt and coupler compound contained in the layer to develop color. Next, the light of 400 ± 20 nm is irradiated to decompose the unreacted diazonium salt contained in the C layer. Next, sufficient heat is applied to the second heat-sensitive recording layer (B layer) to develop a color, thereby causing the diazonium salt and coupler compound contained in the layer to develop a color. At this time, the C layer is also strongly heated at the same time, but the diazonium salt has already decomposed and the color developing ability is lost, so no color is developed. Thereafter, the light of 360 ± 20 nm is irradiated to decompose the diazonium salt contained in the B layer. Finally, the first heat-sensitive recording layer (A layer) is colored by applying sufficient heat. At this time, the C layer and the B layer are also strongly heated at the same time, but since the diazonium salt has already decomposed and the coloring ability is lost, no color is developed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. Hereinafter, “parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively.

Example 1
<Preparation of aqueous solution of phthalated gelatin>
Phthalated gelatin (trade name: MGP gelatin, manufactured by Nippi Collagen Co., Ltd.) 32 parts, 1,2-benzothiazolin-3-one (3.5% methanol solution, manufactured by Daito Chemical Industry Co., Ltd.) 0.9143 Part and 367.1 parts of ion-exchanged water were mixed and dissolved at 40 ° C. to obtain a phthalated gelatin aqueous solution.

<Preparation of alkali-treated gelatin solution>
25.5 parts of alkali-treated low-ion gelatin (trade name: # 750 gelatin, manufactured by Nitta Gelatin Co., Ltd.), 1,2-benzthiazolin-3-one (3.5% methanol solution, Daito Chemical Industry Co., Ltd.) )) 0.5 parts, calcium hydroxide 0.153 parts and ion-exchanged water 143.85 parts were mixed and dissolved at 50 ° C. to obtain an aqueous gelatin solution for preparing an emulsion.

<Preparation of yellow thermosensitive recording layer coating solution a1>
-Preparation of diazonium salt compound-encapsulated microcapsule solution (a1)-
16.1 parts of ethyl acetate, 3.0 parts of the following compound A (diazonium salt compound, maximum absorption wavelength 420 nm), 1.4 parts of the following compound B (diazonium salt compound, maximum absorption wavelength 420 nm), monoisopropylbiphenyl 4.8 Part, 4.8 parts of diphenyl phthalate, and 0.4 part of diphenyl- (2,4,6-trimethylbenzoyl) phosphine oxide (trade name: Lucillin TPO, manufactured by BASF Japan Ltd.), 40 ° C. And uniformly dissolved.
The resulting mixture was mixed with xylylene diisocyanate / trimethylolpropane adduct and xylylene diisocyanate / bisphenol A adduct (trade name: Takenate D119N (50 mass% ethyl acetate solution), Takeda Pharmaceutical Co., Ltd.) 8.6 parts) (mixed) was added and stirred uniformly to obtain a mixed liquid (I-1; oil phase).

  Separately, 16.3 parts of ion-exchanged water and 0.3 part of Scratch AG-8 (50% by mass; manufactured by Nippon Seika Co., Ltd.) were added to 58.6 parts of the phthalated gelatin aqueous solution, and the mixture (II -1; aqueous phase).

The mixed liquid (I-1) was added to the mixed liquid (II-1) obtained above, and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). After adding 20 parts of water to the obtained emulsion and homogenizing it, the mixture was stirred at 40 ° C. to carry out an encapsulation reaction for 3 hours while removing ethyl acetate. Thereafter, 4.1 parts of ion exchange resin Amberlite IRA68 (manufactured by Organo Corp.) and 8.2 parts of Amberlite IRC50 (manufactured by Organo Corp.) were added and further stirred for 1 hour.
Subsequently, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content of the microcapsule solution was 20.0%, whereby a diazonium salt compound-encapsulating microcapsule solution (a) was obtained. As a result of measuring the particle size of the obtained microcapsule using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.37 μm. Further, Tg of the resulting microcapsule polyurethane / urea shell was measured with a viscoelasticity measuring apparatus (DMS6100, manufactured by Seiko Instruments Inc.), and Tg was 95 ° C.

-Preparation of coupler emulsion (a)-
To 33.2 parts of ethyl acetate, 9.9 parts of the following coupler compound (C), 9.9 parts of triphenylguanidine (manufactured by Hodogaya Chemical Co., Ltd.), and 4,4 ′-(m-phenylenediisopropylidene) di 18.8 parts of phenol (trade name: bisphenol M, manufactured by Mitsui Petrochemical Co., Ltd.) and 3,3,3 ′, 3′-tetramethyl-5,5 ′, 6,6′-tetra (1-propyloxy) ) -1,1′-spirobisindane 5.3 parts, 4- (2-ethylhexyloxy) benzesisulfonic acid amide (manac Co., Ltd.) 13.6 parts, 4-n-pentyloxybenzenesulfone 6.8 parts of acid amide (manac Co., Ltd.) and 4.2 parts of calcium dodecylbenzenesulfonate (trade name: Pionein A-41-C (70% methanol solution), Takemoto Yushi Co., Ltd.) Dissolve and mix (III It was obtained.

Separately, 107.6 parts of ion-exchanged water was mixed with 206.0 parts of the alkali-treated gelatin aqueous solution obtained above to obtain a mixed liquid (IV).
Subsequently, the liquid mixture (III) was added to the liquid mixture (IV), and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). The obtained coupler emulsion was heated under reduced pressure to remove ethyl acetate, and then the concentration was adjusted so that the solid content concentration was 26.5% by mass. As a result of measuring the particle size of the obtained coupler emulsion (a) with LA-700 (manufactured by Horiba, Ltd.), the median size was 0.23 μm.
Furthermore, with respect to 100 parts of the coupler emulsion after concentration adjustment, ion-exchanged water was added to SBR latex (trade name: SN-307 (48%), manufactured by Sumika ABS Latex Co., Ltd.) to 26.5%. 9.1 parts of the adjusted concentration was added and stirred uniformly to obtain a coupler emulsion (a).

-Preparation of coating solution for yellow thermosensitive recording layer-
The diazonium salt compound-encapsulating microcapsule liquid (a1) and the coupler emulsion liquid (a) obtained above were mixed so that the mass ratio of the coupler compound / diazonium salt compound was 2.2 / 1, respectively. A recording layer coating solution was obtained.

<Preparation of coating solution for magenta thermosensitive recording layer>
-Preparation of diazonium salt compound-encapsulated microcapsule solution (b1)-
14.0 parts of ethyl acetate, 3.8 parts of the following compound D (diazonium salt compound, maximum absorption wavelength 365 nm), 3.0 parts of isopropyl biphenyl, 3.3 parts of tricresyl phosphate, 3.3 parts of diphenyl phthalate, sulfuric acid 1.1 parts of dibutyl, 0.38 parts of 2,4,6-trimethylbenzoylphenylphosphinic acid ethyl ester, and calcium dodecylbenzenesulfonate (surfactant; trade name: Pionine A-41-C (70% methanol solution) ); 0.15 part of Takemoto Yushi Co., Ltd.) was added and heated to dissolve uniformly.

10.9 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name: Takenate D110N (75% ethyl acetate solution), manufactured by Takeda Pharmaceutical Co., Ltd.) as a capsule wall material is added to the resulting mixture. It stirred uniformly and the liquid mixture (V-1; oil phase) was obtained.
Separately, 26.0 parts of ion-exchanged water was mixed with 56.0 parts of the phthalated gelatin aqueous solution to obtain a mixed liquid (VI-1; aqueous phase).

The mixed solution (V-1) was added to the mixed solution (VI-1) obtained above, and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusyo Co., Ltd.). To the obtained emulsion, 27.3 parts of water was added for homogenization, and the mixture was stirred at 40 ° C. for 3 hours while removing ethyl acetate. Then, 1.16 parts of ion exchange resin Amberlite IRA67 (manufactured by Organo Corporation) and 2.33 parts of SWA100-HG (manufactured by Organo Corporation) were added and further stirred for 1.0 hour.
Subsequently, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content of the microcapsule solution was 18.5%, thereby obtaining a diazonium salt compound-encapsulating microcapsule solution (b1). As a result of measuring the particle size of the obtained microcapsule using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.57 μm. The Tg of the resulting microcapsule polyurethane / urea shell was measured with a viscoelasticity measuring device (DMS6100 manufactured by Seiko Instruments Inc.), and the Tg was 122 ° C.

-Preparation of coupler emulsion (b)-
33.0 parts of ethyl acetate, 6.3 parts of the following coupler compound (E), 14.0 parts of triphenylguanidine (manufactured by Hodogaya Chemical Co., Ltd.), and 4,4 ′-(m-phenylenediisopropylidene) 14.5 parts of diphenol (trade name: bisphenol M (manufactured by Mitsui Petrochemical Co., Ltd.)), 13.5 parts of 1,1 ′-(-p-hydroxyphenyl) -2-ethylhexane, and 3,3 , 3 ′, 3′-tetramethyl-5,5 ′, 6,6′-tetra (1-propyloxy) -1,1′-spirobisindane and 3.5 parts of the following compound (G) And 2.5 parts of tricresyl phosphate and 4.5 parts of calcium dodecylbenzenesulfonate (trade name: Pionein A-41-C (70% methanol solution), Takemoto Yushi Co., Ltd.) are mixed and mixed. A liquid (VII) was obtained.

Separately, 106.3 parts of ion-exchanged water was mixed with 206.3 parts of the alkali-treated gelatin aqueous solution obtained above to obtain a mixed liquid (VIII).
The mixed solution (VII) was added to the mixed solution (VIII), and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). The resulting coupler emulsion was heated under reduced pressure to remove ethyl acetate, and then the concentration was adjusted so that the solid content concentration was 24.5% by mass to obtain a coupler emulsion (b). As a result of measuring the particle diameter of the obtained coupler emulsion (b) using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.23 μm.

-Preparation of coating solution for magenta thermosensitive recording layer-
The diazonium salt compound-encapsulated microcapsule liquid (b1) and the coupler emulsion liquid (b) obtained above were mixed so that the mass ratio of coupler compound / diazonium salt compound was 1.9 / 1. Further, an aqueous solution (5% by mass) of polystyrene sulfonic acid (partially potassium hydroxide neutralized) was mixed in an amount of 0.015 part with respect to 10 parts of the mixed diazonium salt compound-encapsulated microcapsule liquid (b1). A magenta thermosensitive recording layer coating solution was obtained.

<Preparation of coating solution for cyan thermosensitive recording layer>
-Preparation of electron-donating dye precursor-encapsulated microcapsule solution (c1)-
18.1 parts of ethyl acetate, 7.6 parts of the following electron donating dye precursor (H), and a mixture of 1-methylpropylphenyl-phenylmethane and 1- (1-methylpropylphenyl) -2-phenylethane ( Product name: Hysol SAS-310, manufactured by Nippon Petroleum Co., Ltd. (8.0 parts) and the following compound (I) (trade name: Irgaperm 2140, Ciba Geigy Co., Ltd.) (8.0 parts) were added and heated to be uniform. Dissolved in.
To the obtained mixed liquid, 7.2 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name: Takenate D110N (75% by mass ethyl acetate solution), Takeda Pharmaceutical Co., Ltd.) as a capsule wall material, Methylene polyphenyl polyisocyanate (trade name: Millionate MR-200, manufactured by Nippon Polyurethane Industry Co., Ltd.) (5.3 parts) was added and stirred uniformly to obtain a mixed liquid (IX-1).

Separately, 28.8 parts of the phthalated gelatin aqueous solution obtained above were added to 9.5 parts of ion-exchanged water, 0.17 part of Scarph AG-8 (50% by mass), manufactured by Nippon Seika Co., Ltd., and dodecylbenzene. 4.3 parts of sodium sulfonate (10% aqueous solution) was added and mixed to obtain a mixed solution (X-1).
The mixed liquid (IX-1) was added to the mixed liquid (X-1) obtained above, and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). To the obtained emulsion, 50 parts of water and 0.12 part of tetraethylenepentamine were homogenized, and the mixture was stirred at 65 ° C. for 3 hours while removing ethyl acetate. A microcapsule liquid whose concentration was adjusted so that the solid content concentration was 33% was obtained. As a result of measuring the particle size of the microcapsule at this time using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 1.00 μm. The Tg of the resulting microcapsule polyurethane / urea shell was measured with a viscoelasticity measuring device (DMS6100, manufactured by Seiko Instruments Inc.), and the Tg was 170 ° C.

  Furthermore, 3.7 parts of sodium dodecylbenzenesulfonate 25% aqueous solution (trade name: Neoperex F-25, manufactured by Kao Corporation) and 4,4′- An optical brightener (trade name: Kaycoll BXNL, manufactured by Nippon Soda Co., Ltd.) containing 4.3 parts of a bistriazinylaminostilbene-2,2′-disulfone derivative is added and stirred uniformly to provide an electron donating property. A dye precursor-encapsulated microcapsule solution (c1) was obtained.

-Preparation of electron-accepting compound dispersion liquid (c)-
To 11.3 parts of the phthalated gelatin aqueous solution obtained above, 30.1 parts of ion-exchanged water and 4,4 ′-(p-phenylenediisopropylidene) diphenol (trade names: bisphenol P, Mitsui Petrochemical Co., Ltd.) 15 parts) and 2% 2% sodium 2-ethylhexyl succinate aqueous solution were added and dispersed overnight using a ball mill to obtain a dispersion having a solid content concentration of 26.6%.
To 100 parts of this dispersion, 45.2 parts of the alkali-treated gelatin aqueous solution obtained above was added and stirred for 30 minutes, and then ion-exchanged water was added so that the solid content concentration of the dispersion was 23.5%. A receptive compound dispersion (c) was obtained.

-Preparation of coating solution for cyan thermosensitive recording layer-
The electron-donating dye precursor-encapsulated microcapsule liquid (c1) and the electron-accepting compound dispersion liquid (c) obtained as described above have an electron-accepting compound / electron-donating dye precursor mass ratio of 10/1. Thus, a cyan thermosensitive recording layer coating solution was obtained.

-Preparation of coating solution for intermediate layer (adjacent layer)-
<Preparation of alkali-treated gelatin solution>
25.5 parts of alkali-treated low-ion gelatin (trade name: # 751 gelatin, manufactured by Nitta Gelatin Co., Ltd.), 1,2-benzothiazolin-3-one (3.5% methanol solution, Daito Chemical Industry Co., Ltd.) )) 0.7286 parts, calcium hydroxide 0.153 parts, and ion-exchanged water 143.6 parts were mixed and dissolved at 50 ° C. to obtain an aqueous gelatin solution for preparing an emulsion.
<Preparation of liquid mixture I>
A mixture of 1-methylpropylphenyl-phenylmethane and 1- (1-methylpropylphenyl) -2-phenylethane in 2.0 parts of ethyl acetate (liquid at room temperature) (trade name: Hyzol SAS-310, Nippon Oil Corporation )) 4.71 parts, and calcium dodecylbenzenesulfonate (trade name: Pionein A-41-C (70% methanol solution), Takemoto Yushi Co., Ltd.) 0.1 parts are dissolved in a mixed solution I. Got.
<Preparation of emulsion particles for intermediate layer>
13.51 parts of ion-exchanged water was mixed with 15.12 parts of the alkali-treated gelatin aqueous solution obtained above to obtain a mixed solution II. Subsequently, the liquid mixture I was added to the liquid mixture II, and the mixture was emulsified and dispersed at 40 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). The obtained emulsion particle liquid for intermediate layer was heated under reduced pressure to remove ethyl acetate, and then the concentration was adjusted so that the solid concentration was 20%. As a result of measuring the particle diameter of the obtained emulsion for intermediate layer with LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.31 micron.

<Preparation of coating solution for intermediate layer>
Alkali-treated low-ion gelatin (trade name: # 751 gelatin, manufactured by Nitta Gelatin Co., Ltd.) 100 parts, 1,2-benzothiazolin-3-one (3.5% methanol solution, manufactured by Daito Chemical Industry Co., Ltd.) ) 4.825 parts, calcium hydroxide 0.281 parts, boric acid 6.875 parts and ion-exchanged water 513.02 parts were mixed and dissolved at 50 ° C. to obtain a gelatin aqueous solution for preparing an intermediate layer coating solution. .
50.0 parts of the obtained gelatin aqueous solution, 0.35 parts of a 2% aqueous solution of sulfosuccinic acid 2-ethylhexyl ester (trade name: Nissan Rapisol B90), 13.75 parts of boric acid (4.0% by mass aqueous solution), polystyrene sulfonic acid (Partially potassium hydroxide neutralized) 0.66 parts of aqueous solution (5% by mass), 9.95 parts of 4% aqueous solution of the following compound (J) (manufactured by Wako Pure Chemical Industries, Ltd.), the following compound (J ′) A mixed solution III was obtained by mixing 3.32 parts of a 4% aqueous solution and 19.64 parts of ion-exchanged water. 40.0 parts of the 20% intermediate layer emulsion particles were mixed with the mixed solution III to prepare an intermediate layer coating solution.

<Preparation of coating solution for light transmittance adjusting layer>
-Preparation of UV absorber precursor microcapsule solution-
In 71 parts of ethyl acetate, 14.5 parts of [2-allyl-6- (2H-benzotriazol-2-yl) -4-tert-octylphenyl] benzenesulfonate as a UV absorber precursor, 2,2′- 5.0 parts of t-octylhydroquinone, 1.8 parts of tricresyl phosphate, 5.8 parts of α-methylstyrene dimer (trade name: MSD-100, manufactured by Mitsui Chemicals), calcium dodecylbenzenesulfonate (trade name) : Pionein A-41-C (70% methanol solution), Takemoto Yushi Co., Ltd. 0.45 part was mixed and dissolved uniformly.

54.7 parts of xylylene diisocyanate / trimethylolpropane adduct (trade name: Takenate D110N (75% by mass ethyl acetate solution), Takeda Pharmaceutical Co., Ltd.) is added as a capsule wall material to the resulting mixture. And stirred uniformly to obtain a UV absorber precursor mixed solution.
Separately, 8.9 parts of a 30% phosphoric acid aqueous solution and 532.6 parts of ion-exchanged water are mixed with 52 parts of itaconic acid-modified polyvinyl alcohol (trade name: KL-318, manufactured by Kuraray Co., Ltd.) to obtain an ultraviolet absorber precursor. A body PVA aqueous solution was obtained.
The above-mentioned ultraviolet absorbent precursor mixed solution was added to 516.06 parts of the obtained ultraviolet absorbent precursor PVA aqueous solution, and the mixture was emulsified and dispersed at 20 ° C. using a homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). After adding 254.1 parts of ion-exchanged water to the obtained emulsion and homogenizing it, an encapsulation reaction was performed for 3 hours with stirring at 40 ° C. Thereafter, 94.3 parts of ion exchange resin Amberlite MB-3 (manufactured by Organo Corporation) was added thereto, and the mixture was further stirred for 1 hour.

Subsequently, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content concentration of the microcapsule solution was 13.5%. As a result of measuring the particle size of the obtained microcapsule using LA-700 (manufactured by Horiba, Ltd.), the median diameter was 0.23 ± 0.05 μm.
To 859.1 parts of this microcapsule solution, 2.416 parts of carboxy-modified styrene-butadiene latex (trade name: SN-307 (48% aqueous solution), manufactured by Sumitomo Nougatac Co., Ltd.) and 39.5 parts of ion-exchanged water are added. By mixing, an ultraviolet absorbent precursor microcapsule solution was obtained.

-Preparation of coating solution for light transmittance adjusting layer-
1000 parts of the ultraviolet absorber precursor microcapsule solution obtained from the above, fluorinated surfactant (trade name: Megafac F-120 (5% aqueous solution), manufactured by Dainippon Ink & Chemicals, Inc.), 5.2 parts, 7.75 parts of a 4% aqueous sodium hydroxide solution and 73.39 parts of sodium (4-nonylphenoxytrioxyethylene) butyl sulfonate (manufactured by Sankyo Chemical Co., Ltd .; 2.0% aqueous solution) are mixed to transmit light. A coating solution for rate adjusting layer was obtained.

<Preparation of coating solution for protective layer>
-Preparation of PVA solution for protective layer-
160 parts of vinyl alcohol (PVA) -alkyl vinyl ether copolymer (trade name: EP-130, manufactured by Denki Kagaku Kogyo Co., Ltd.), a mixed liquid of sodium alkyl sulfonate and polyoxyethylene alkyl ether phosphate (trade name: Neoscore CM-57 (54% aqueous solution), Toho Chemical Industry Co., Ltd. (8.74 parts) and ion-exchanged water (3832 parts) were mixed and dissolved at 90 ° C. for 1 hour to homogenize the PVA solution for the protective layer. Obtained.

-Preparation of pigment dispersion for protective layer-
In 8 parts of barium sulfate (trade name: BF-21F (barium sulfate content 93% or more), manufactured by Sakai Chemical Industry Co., Ltd.), an anionic special polycarboxylic acid type polymer activator (trade name: Poise 532A ( 40% aqueous solution), manufactured by Kao Co., Ltd.) 0.3 parts and ion-exchanged water 11.7 parts were mixed and dispersed with a dynomill to obtain a barium sulfate dispersion. The particle size at this time was measured using LA-700 (manufactured by Horiba, Ltd.), and as a result, the median diameter was 0.17 μm or less.
Then, 8.1 parts of colloidal silica (trade name: Snowtex O (20% aqueous dispersion), manufactured by Nissan Chemical Co., Ltd.) is added to 45.6 parts of the obtained barium sulfate dispersion, and a protective layer is added. A pigment dispersion was obtained.

-Preparation of matting agent dispersion for protective layer-
An aqueous dispersion of 1,2-benzisothiazolin-3-one (trade name: PROXEL BD, IC) was added to 220 parts of wheat starch (trade name: wheat starch S, manufactured by Shinshin Food Industry Co., Ltd.). 3.81 parts manufactured by Co., Ltd. and 1976.19 parts ion-exchanged water were mixed and dispersed uniformly to obtain a matting agent dispersion for protective layer.

-Preparation of coating solution for protective layer-
To 1000 parts of the PVA solution for protective layer obtained above, 40 parts of the fluorosurfactant (trade name: Megafac F-120 (5% aqueous solution), manufactured by Dainippon Ink & Chemicals, Inc.), (4- Nonylphenoxytrioxyethylene) sodium butyl sulfonate (manufactured by Sankyo Chemical Co., Ltd .; 2.0% aqueous solution), 49.87 parts of pigment dispersion for protective layer obtained from above, for protective layer obtained from above 16.65 parts of matting agent dispersion, 48.7 parts of zinc stearate dispersion (trade name: Hydrin F115 (20.5% aqueous solution), manufactured by Chukyo Yushi Co., Ltd.) and 280 parts of ion-exchanged water are uniformly mixed. A protective layer coating solution was obtained.

<Preparation of support with undercoat layer>
-Preparation of coating solution for undercoat layer-
40 parts of enzyme-degraded gelatin (average molecular weight 10,000, PAGI viscosity = 15 mP, PAGI jelly strength = 20 g) is added to 60 parts of ion-exchanged water, and stirred and dissolved at 40 ° C. to prepare a coating solution for an undercoat layer. An aqueous gelatin solution was prepared.
Separately, 8 parts of water-swelling synthetic mica (aspect ratio 1000; trade name: Somasif ME100, manufactured by Coop Chemical Co., Ltd.) and 92 parts of water were mixed and then wet-dispersed with Viscomil, and the average particle size was 2.0 μm. A mica dispersion was obtained. Water was added to this mica dispersion so that the mica concentration was 5% and mixed uniformly to obtain a mica dispersion.

  120 parts of water and 556 parts of methanol were added to 100 parts of an aqueous gelatin solution for preparing a coating solution for an undercoat layer adjusted to 40% at 40 ° C. and sufficiently stirred and mixed, and then 208 parts of the mica dispersion adjusted to 5%. Then, the mixture was further sufficiently stirred and mixed, and 9.8 parts of a 1.66% polyethylene oxide surfactant was added. And the liquid temperature was hold | maintained at 35-40 degreeC, 7.3 parts of gelatin hardeners which are an epoxy compound were added, and the coating liquid (5.7%) for undercoat layers was obtained.

-Production of support with undercoat layer-
Next, the wood pulp comprising 50 parts of LBPS and 50 parts of LBPK was beaten to 300 cc Canadian freeness with a disc refiner, 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, 1.0 part of aluminum sulfate, polyamide polyamine 0.1 parts of epichlorohydrin and 0.5 parts of cationic polyacrylamide were added in an absolutely dry mass ratio with respect to the pulp, and a base paper having a basis weight of 114 g / m ² was made with a long net paper machine, and then the thickness was determined by a calendering process. The thickness was adjusted to 100 μm.
Subsequently, after corona discharge treatment was performed on both surfaces of the obtained base paper, polyethylene was coated to a resin thickness of 36 μm using a melt extruder to form a resin layer consisting of a mat surface (this surface was designated as “ It's called the back side.) Next, on the surface opposite to the side on which the resin layer is formed, polyethylene containing 10% anatase-type titanium dioxide and a small amount of ultramarine blue is coated using a melt extruder so as to have a thickness of 50 μm. A resin layer composed of a surface was formed (this surface is referred to as “front side”).

After the corona discharge treatment is applied to the resin surface of the back surface, aluminum oxide (trade name: Alumina Sol 100, manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (trade name: Snowtex O, Nissan Chemical Industries, Ltd.) are used as antistatic agents. (Made by Co., Ltd.) was dispersed in water at a ratio of 1/2 (= aluminum oxide / silicon dioxide; mass ratio), and this was applied so that the dry mass was 0.2 g / m ² .
Subsequently, after the corona discharge treatment was performed on the surface of the polyethylene resin layer on the front side, the coating solution for the undercoat layer obtained above was applied so that the mica coating amount was 0.26 g / m ² and dried. A support with an undercoat layer was obtained.

<Preparation of thermal recording material>
Cyan heat-sensitive recording layer coating solution (c1), intermediate layer coating solution, magenta thermosensitive recording layer coating solution (b1), and intermediate layer-use cloth on the surface of the undercoat layer of the undercoat support. Liquid, yellow heat-sensitive recording layer coating liquid (a1), light transmittance adjusting layer coating liquid, and protective layer coating liquid are simultaneously and continuously applied (seven layers are simultaneously coated) and dried at 30 ° C. and 30% RH. And the drying process was performed on 40 degreeC and 30% of drying conditions, respectively, and the multicolor thermosensitive recording material was produced.

At this time, the yellow thermosensitive recording layer coating solution (a1) was used in a magenta thermosensitive recording so that the total coating amount of the diazonium salt compounds (A) and (B) was 0.156 g / m ^{2 in} terms of the solid coating amount. The layer coating solution (b1) is an amount such that the coating amount of the diazonium salt compound (D) is 0.225 g / m ^{2 in} terms of the solid coating amount, and the cyan thermosensitive recording layer coating solution (c1) is electron donating. The coating amount of the dye precursor (H) was applied in such an amount that the solid content coating amount would be 0.355 g / m ² .
In addition, the intermediate layer coating solution is used in an amount such that the solid coating amount of gelatin is 2.064 g / m ² between the coating solution (a) and the coating solution (b). ) And the coating liquid (c), the amount of gelatin solid content coating amount is 2.885 g / m ^2, and the light transmittance adjusting layer coating liquid has a solid content coating amount of 2.35 g / m ^2. The amount of m ² was applied to the protective layer coating solution in such an amount that the solid content was 1.39 g / m ² .

Example 2
Except that tricresyl phosphate (liquid at room temperature) was used instead of 4.71 parts of Hysol SAS-310 Nippon Petroleum Co., Ltd., and ethyl acetate 2.0 was not used when preparing the intermediate layer coating solution in Example 1. A sample was prepared in the same manner as in Example 1.

Example 3
A sample was prepared in the same manner as in Example 1 except that isopropyl biphenyl (liquid at room temperature) was used instead of 4.71 parts of Hysol SAS-310 Japan Petroleum Co., Ltd. during preparation of the intermediate layer coating solution in Example 1. .

Example 4
In Example 1, instead of 4.71 parts of Hysol SAS-310 Japan Petroleum Co., Ltd. when preparing the intermediate layer coating solution, SAS-310, 1.2 parts 2.4 parts tricresyl phosphate, diphenyl phthalate 1.0 A sample was prepared in the same manner as in Example 1, except that a mixture of 0.11 part of diethyl maleate (liquid at room temperature) was used.

Example 5
In Example 1, SBR latex (trade name: SN-307 (48%), Sumika ABS Latex Co., Ltd.) was used instead of mixing 40.0 parts of 20% intermediate layer emulsion particles during preparation of the intermediate layer coating solution. A sample was prepared in the same manner as in Example 1, except that 43.0 parts of ion-exchanged water was used instead of 19.64 parts of ion-exchanged water in the preparation of the intermediate layer coating solution. .

Comparative Example 1
In Example 1, instead of 50.0 parts of the gelatin aqueous solution when preparing the intermediate layer coating solution, 100.0 parts of the gelatin aqueous solution and 23.39 parts of ion-exchanged water 19.64 parts were used. A sample was prepared in the same manner as in Example 1 except that the particles and 4% boric acid solution were not used.

Comparative Example 2
Instead of mixing 40.0 parts of 20% intermediate layer emulsion particles during preparation of the intermediate layer coating solution in Example 1, zinc stearate dispersion (L111: manufactured by Chukyo Yushi Co., Ltd., melting point 117 ° C., particle size) A sample was prepared in the same manner as in Example 1 except that 38.1 parts of 0.15 μm and a solid content of 21% were used, and 21.55 parts were used instead of 19.64 parts of ion-exchanged water.

(Evaluation of color density and gloss of cyan thermal recording layer)
For the multicolor thermosensitive recording materials obtained in Examples 1 to 5 and Comparative Examples 1 and 2, first, the diazonium salt compound in the yellow thermosensitive recording layer was deactivated by an ultraviolet lamp having an emission center wavelength of 420 nm and an output of 40 W, and then The diazonium salt compound in the magenta thermosensitive recording layer was deactivated by an ultraviolet lamp having an emission center wavelength of 365 nm and an output of 40 W.
Next, using a thermal head (KST type, manufactured by Kyocera Corporation), the applied voltage and pulse width to the thermal head are set so that the recording energy per unit area is 100 mJ / mm ^2, and the cyan thermosensitive recording layer. Was heat-printed.
The maximum color density (Dmax) was measured with a red filter using a Macbeth densitometer (reflection densitometer RD918, manufactured by Macbeth Co.). The measurement results are shown in Table 1 below.
In addition, the glossiness of the cyan coloring portion was examined with a measurement angle of 20 degrees of a digital variable glossiness meter UGV-6P (manufactured by Suga Test Instruments Co., Ltd.). The results are shown in Table 1 below.

  According to the present invention, it is possible to provide a heat-sensitive recording material capable of obtaining good gloss and color density even at a high energy application portion.

Claims (8)

  In the heat-sensitive recording material in which one or two or more heat-sensitive recording layers and one or two or more adjacent layers adjacent to the heat-sensitive recording layer are provided on the support, at least one of the adjacent layers contains oil phase component particles, A heat-sensitive recording material, wherein the oil phase component is an oily substance having a melting point of less than 40 ° C, or a molten or glassy substance having a melting point of 40 ° C or higher.   One or two or more heat-sensitive recording layers and one or more adjacent layers adjacent to the heat-sensitive recording layer are provided on a support, and at least one of the adjacent layers is an oily substance having a melting point of less than 40 ° C. or 40 ° C. or more. A method for producing a heat-sensitive recording material comprising a molten or glassy substance having no melting point, wherein said oily substance having a melting point of less than 40 ° C., or a molten or glassy substance having no melting point above 40 ° C. A method for producing a heat-sensitive recording material, comprising applying an adjacent layer coating solution containing the particles.   The method for producing a thermosensitive recording material according to claim 2, wherein the particles are emulsion particles.   In the thermosensitive recording material in which one or two or more thermosensitive recording layers containing microcapsules and one or two or more adjacent layers adjacent to the thermosensitive recording layer are provided on a support, at least one of the adjacent layers includes: A thermosensitive recording material comprising polymer compound particles having a melting point, softening point or glass transition point of less than 40 ° C.   The heat-sensitive recording material according to claim 4, wherein the adjacent layer is prepared by applying a latex containing latex particles of a polymer compound.   6. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer has two or more heat-sensitive recording layers, and each of the heat-sensitive recording layers is colored in different hues.   7. The heat-sensitive recording material according to claim 6, further comprising an adjacent layer between the heat-sensitive recording layer that develops yellow and the heat-sensitive recording layer that develops magenta.   8. The heat-sensitive recording material according to claim 1, wherein at least one of the heat-sensitive recording layers contains a diazonium salt compound and a coupler compound that reacts with the diazonium salt compound to develop a color. .