WO2022045186A1

WO2022045186A1 - Heat-sensitive recording body and image formation method

Info

Publication number: WO2022045186A1
Application number: PCT/JP2021/031143
Authority: WO
Inventors: 靖浩愛知; 淳二伊藤; 正宣大塚; 彩乃増田
Original assignee: キヤノン株式会社
Priority date: 2020-08-27
Filing date: 2021-08-25
Publication date: 2022-03-03

Abstract

A heat-sensitive recording body comprising a heat-sensitive coloring layer that contains: an electron-donating dye precursor; an electron-accepting compound; a radical polymerizable compound; a photoradical polymerization initiator; and microcapsules, wherein the heat-sensitive recording body is characterized in that the microcapsules are contained in the heat-sensitive coloring layer in a state in which the radical polymerizable compound, the electron-donating dye precursor, and the photoradical polymerization initiator are encapsulated within the microcapsules.

Description

Thermal recording body and image forming method

The present invention relates to a heat-sensitive recorder and an image forming method using the same.

Conventionally, a heat-sensitive recorder using a mechanism for reacting a leuco dye with a color developer to develop a color has been widely used. Thermal recorders do not require consumables such as ink or toner and are relatively inexpensive, so they are widely used as recording media for fax machines, receipts, and other applications. A general heat-sensitive recorder is manufactured by printing or coating a water-containing liquid-coated heat-sensitive color-developing composition on an arbitrary support and then drying to form a heat-sensitive color-developing layer.

Further, a heat-sensitive recorder containing a photocurable composition together with a heat-sensitive color-developing composition in the heat-sensitive color-developing layer is being studied. In the image forming method using this heat-sensitive recorder, the heat-sensitive material does not move in the portion exposed by ultraviolet rays, so that the color does not develop. However, in the portion not exposed by ultraviolet rays, the heat-sensitive material moves and develops color to form an image. can do. For example, a photosensitive layer having a photosensitive / heat-sensitive layer containing microcapsules containing an electron-donating colorless dye and a photocurable composition containing an electron-accepting and polymerizable vinyl monomer and a photopolymerizable initiator. A heat-sensitive recording material (heat-sensitive recording body) has been proposed (Patent Document 1). Since the microcapsules contain an electron-donating colorless dye, which is an electron-donating dye precursor, this heat-sensitive recorder is called "skin fog", which causes unintentional color development during storage before image formation. It is possible to suppress the phenomenon called.

Japanese Unexamined Patent Publication No. 3-72358

However, although the heat-sensitive recorder proposed in Patent Document 1 can cure the photocurable composition by being irradiated with ultraviolet rays, the curing may not be sufficient. Therefore, when heated after irradiation with ultraviolet rays, the electron-donating dye precursor and the electron-accepting compound move, especially in the non-imaging region, and the electron-donating dye precursor and the electron-accepting compound partially come into contact with each other. However, it sometimes developed color.

Therefore, an object of the present invention is to suppress the occurrence of background fog, obtain good color development of an image, and further suppress color development in a non-image forming region even when heated after irradiation with ultraviolet rays. The purpose is to provide a possible thermal recorder. Another object of the present invention is to provide an image forming method using the above-mentioned heat-sensitive recorder.

The above object is achieved by the following invention.

That is, according to the present invention, it is a heat-sensitive recorder provided with a heat-sensitive color-developing layer containing an electron-donating dye precursor, an electron-accepting compound, a radically polymerizable compound, a photoradical polymerization initiator, and microcapsules. A heat-sensitive recorder characterized in that the microcapsules are contained in the heat-sensitive color-developing layer in a state of containing the radical-polymerizable compound, the electron-donating dye precursor, and the photo-radical polymerization initiator. Provided.

Further, according to the present invention, a step of applying a heat pulse to the heat-sensitive recording body by applying a heat pulse to the heat-sensitive recording body and irradiating the heat-sensitive recording body on which the image is formed with ultraviolet rays are performed. Provided is an image forming method characterized by having a step of fixing the heat-sensitive color-developing layer.

According to the present invention, it is possible to suppress the generation of background fog, obtain good color development of an image, and suppress color development in a non-image forming region even when heated after irradiation with ultraviolet rays. A recording body can be provided. Further, according to the present invention, it is possible to provide an image forming method using the above-mentioned heat-sensitive recording body.

It is sectional drawing which shows one Embodiment of the heat-sensitive recording body of this invention.

<Thermal recording body>
Hereinafter, the details of the present invention will be described with reference to preferred embodiments, but the present invention is not limited to the following embodiments. The heat-sensitive recorder of the present invention is a heat-sensitive recorder provided with a heat-sensitive color-developing layer containing an electron-donating dye precursor, an electron-accepting compound, a radically polymerizable compound, a photoradical polymerization initiator, and microcapsules. The microcapsules are contained in the heat-sensitive color-developing layer in a state of containing a radically polymerizable compound, an electron-donating dye precursor, and a photoradical polymerization initiator.

The reason why the effect of the present invention can be obtained by the above configuration is unknown, but the present inventors speculate as follows.

Since the electron-donating dye precursor is encapsulated in the microcapsules, the electron-donating dye precursor is in a state where it is difficult to come into contact with the electron-accepting compound outside the microcapsules. As a result, the occurrence of skin fog can be suppressed.

On the other hand, when heat is applied during image formation, the shell portion of the microcapsules is softened by heating and the electron-accepting compound is further melted, so that the electron-donating dye precursor and the electron-accepting compound can move. .. As a result, the chance of contact between the electron-donating dye precursor and the electron-accepting compound is increased, and an image having good color-developing property can be formed.

Further, when ultraviolet rays are irradiated after image formation by heating, the photoradical polymerization initiator contained in the heat-sensitive color-developing layer is decomposed and radicals are generated. Then, the radicals generated promote the cross-linking reaction of the radically polymerizable compound. Here, in the unheated region (non-image forming region), the radical-polymerizable compound and the photo-radical polymerization initiator are still contained in the microcapsules, so that the cross-linking reaction of the radical-polymerizable compound is external such as oxygen. It progresses in a state where it is not easily inhibited by radical polymerization. As a result, in the non-image forming region, a cured product having a high degree of cross-linking can be formed by the cross-linking reaction of the radically polymerizable compound. The electron-donating dye precursor is immobilized in this strong cured product, and the electron-accepting compound also becomes difficult to penetrate into the cured product. Therefore, even if the heat-sensitive recorder is heated after irradiation with ultraviolet rays, it is difficult for the electron-donating dye precursor and the electron-accepting compound to come into contact with each other in the non-image forming region. Then, it is possible to suppress color development due to contact between the electron-donating dye precursor and the electron-accepting compound in the non-image forming region.

(Microcapsules)
The heat-sensitive color-developing layer contains microcapsules. The microcapsules preferably have a core portion and a shell portion.

The core portion is composed of an electron-donating dye precursor, a radically polymerizable compound, and a photoradical polymerization initiator.

The shell portion may include the core portion and may suppress contact between the electron-donating dye precursor contained in the core portion and the electron-accepting compound existing outside the microcapsule. It should be noted that the "encapsulation" in the present invention does not need to completely enclose the entire electron-donating dye precursor, radically polymerizable compound, and photoradical polymerization initiator inside the shell portion, and one of these. The case where the portion is exposed to the outside of the shell portion is also included. In particular, the electron-donating dye precursor may be partially exposed to the outside of the microcapsules as long as it does not affect the background fog. However, in order to further suppress contact with the electron-accepting compound existing on the outside of the microcapsules, it is preferable that the electron-donating dye precursor is wrapped in a state where it is not exposed to the outside of the shell portion. From the viewpoint of the color development property of the heat-sensitive color-developing layer, the core portion is preferably made of a thermoplastic resin.

Materials constituting the shell portion include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene-methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinylpyrrolidone, and polyvinyl alcohol. Resins such as. In addition, two or more of these materials may be used in combination. Of these materials, polyurethane or polyurea is particularly preferable as the material constituting the shell portion from the viewpoint of color development.

Examples of polyurethane and polyurea include a heavy adduct of a polyhydric isocyanate and a compound containing an active hydrogen group. Examples of the compound having an active hydrogen group include water, a polyhydric alcohol, a polyvalent amine and the like.

Examples of the polyvalent isocyanate include m-phenylenedi isocyanate, p-phenylenedi isocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3 , 3'-dimethoxy-4,4'-biphenyl-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropanediisocyanate, trimethylenediisocyanate , Hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate and other diisocyanates, 4', 4 "-triphenyl Triisocyanate such as methanetriisocyanate, toluene-2,4,6-triisocyanate, tetraisocyanate such as 4,4'-dimethyldiphenylmethane-2,2', 5,5'-tetraisocyanate, hexamethylenediisocyanate and trimethylol Examples thereof include additions of propane, additions of 2,4-tolylene diisocyanate and trimethylolpropane, additions of xylylene diisocyanate and trimethylolpropane, and isocyanate prepolymers such as additions of tolylene diisocyanate and hexanetriol. , Not limited to this.

Further, the content of the shell portion is preferably 3% by mass or more and 25% by mass or less based on the total mass of the microcapsules.

As a method for microencapsulating the electron-donating dye precursor, the radical polymerization compound, and the photoradical polymerization initiator constituting the core portion, a conventionally known method can be used. For example, an oil phase prepared by dissolving or dispersing an electron-donating dye precursor, a radically polymerizable compound, and a photoradical polymerization initiator in an organic solvent that is poorly soluble or insoluble in water, and an aqueous phase in which a water-soluble polymer is dissolved. And is emulsified and dispersed by means such as a homogenizer. Then, a surface polymerization method or the like in which a polymer forming reaction is caused at the oil droplet interface by heating the dispersion liquid to form a shell portion of the polymer substance is preferable. This interfacial polymerization method is preferable because capsules having a uniform particle size can be formed within a short time and a recording material having excellent background fog can be obtained.

As the organic solvent, for example, a low boiling point solvent such as acetate, methylene chloride, or cyclohexanone is preferable. Here, the boiling point of the low boiling point solvent is 160 ° C. or lower. It is preferable to remove the low boiling point solvent by removing the low boiling point solvent at the time of forming the capsule because the fog on the skin and the fixability can be further improved. The content of the low boiling point solvent in the microcapsules is preferably 100% by mass or less based on the content of the electron-donating dye precursor. When the content of the low boiling point solvent is 100% by mass or less, the fixing property of the heat-sensitive color-developing layer can be maintained for a long period of time. The lower limit of the content of the low boiling point solvent is not particularly limited, but for example, it is preferably 0% by mass or more based on the content of the electron-donating dye precursor.

Further, a high boiling point solvent may be contained as the organic solvent. Here, the boiling point of the high boiling point solvent is 180 ° C. or higher. As high boiling point solvents, phosphoric acid ester, phthalate ester, acrylic acid ester, methacrylic acid ester, carboxylic acid ester, fatty acid amide, alkylated biphenyl, alkylated terphenyl, alkylated naphthalene, diarylethane, chlorinated paraffin, alcohol-based Examples thereof include a solvent, a phenol-based solvent, an ether-based solvent, a monoolefin-based solvent, and an epoxy-based solvent. Specifically, tricresyl phosphate, trioctyl phosphate, octyldiphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilaurate phthalate, dicyclohexyl phthalate, butyl olefinate, diethylene glycol benzoate, dioctyl sebacate, Dibutyl sebacate, dioctyl adipate, trioctyl trimeritate, acetyltriethyl citrate, octyl maleate, dibutyl maleate, isoamylbiphenyl, chlorinated paraffin, diisopropylnaphthalene, 1,1'-ditrilethane, monoisopropylbiphenyl, diisopropylbiphenyl, High boiling point solvents such as 2,4-ditershariamilphenol, N, N-dibutyl-2-butoxy-5-tershaliooctylaniline, hydroxybenzoic acid 2-ethylhexyl ester, polyethylene glycol and the like can be mentioned.

From the viewpoint of suppressing color development in the background fog and the non-image forming region, the content of the organic solvent in the microcapsules is preferably 0% by mass or more and 5% by mass or less based on the total mass of the microcapsules.

Further, the content of the high boiling point solvent in the microcapsules is preferably 100% by mass or less based on the content of the electron donating dye precursor. When the content of the high boiling point solvent is 100% by mass or less, the fixing property of the heat-sensitive color-developing layer can be maintained for a long period of time.

By adjusting the content of the high boiling point solvent within the above range, the outflow of the electron-donating dye precursor to the outside of the microcapsules and the inflow of the electron-accepting compound into the microcapsules after irradiation with ultraviolet rays are further increased. The present inventors speculate that this is because it could be suppressed.

The lower limit of the content of the high boiling point solvent is not particularly limited, but for example, it is preferably 0% by mass or more based on the content of the electron-donating dye precursor.

Further, the core portion may contain an antioxidant such as hindered phenol and hindered amine.

Examples of the water-soluble polymer include water-soluble polymers such as polyvinyl alcohol, for example, polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amino-modified polyvinyl alcohol, itaconic acid-modified polyvinyl alcohol, and styrene-anhydrous maleine. Acid Polymers, butadiene-Maleic Anhydrous Copolymers, Ethylene-Maleic Anhydrous Copolymers, Isobutylene-Maleic Anhydrous Polymers, Polyacrylamide, Polyacrylamide Ssulfonic Acid, Polyvinylpyrrolidone, Ethylene-Acrylic Acid Polymers, Examples include gelatin.

A hydrophobic polymer emulsion, latex, or the like can be used in combination with the water-soluble polymer. Examples of the emulsion or latex include a styrene-butadiene copolymer, a carboxy-modified styrene-butadiene copolymer, and an acrylonitrile-butadiene copolymer. At this time, a conventionally known surfactant or the like may be added as needed.

The SP value of the polymerizable monomer of the resin constituting the shell portion and the SP value of the radically polymerizable compound of the resin constituting the core portion preferably satisfy the following relationship.
(SP value of radically polymerizable compound) <(SP value of polymerizable monomer of resin constituting shell portion)

Further, it is more preferable to satisfy the following relationship.
(SP value of radically polymerizable compound) + 1 <(SP value of polymerizable monomer of resin constituting shell portion)

By satisfying this relationship, the material constituting the core portion of the microcapsules can easily stay in the core portion of the microcapsules, so that skin fog can be suppressed for a long period of time.

The SP value is the solubility parameter. This SP value is a value introduced by Hildebrand and defined by regular theory, and is indicated by the square root of the aggregation energy density of the solvent (or solute), and serves as a guideline for the solubility of the two-component solution.

The SP value of the radically polymerizable compound is a value calculated from the evaporation energy and molar volume of atoms and atomic groups by Fedors described in Coating Basics and Engineering (page 53, by Yuji Harasaki, Processing Technology Study Group). ..

The unit of the SP value in the present invention is (cal / cm ³ ) ^1/2 , but by 1 (cal / cm ³ ) ^1/2 = 2.046 × 10 ³ (J / m ³ ) ^1/2 , ( The unit of cal / cm ³ ) ^1/2 can be converted to the unit of (J / m ³ ) ^1/2 .

Further, when a plurality of polymerizable monomers are used in the resin constituting the shell portion and the core portion, the SP value of each polymerizable monomer contains each polymerizable monomer in the total polymerizable monomer. Multiplying by mol% and adding them together is taken as the "SP value of the radically polymerizable compound" used in the above relational expression.

The particle size of the microcapsules is preferably 10 nm or more and 1,000 nm or less, and more preferably 50 nm or more and 300 nm or less. When the particle size of the microcapsules is 10 nm or more and 50 nm or more, respectively, the radical polymerization reactivity becomes high and the color development in the non-image area can be further suppressed. On the other hand, when the particle size of the microcapsules is 1,000 nm or less and 300 nm or less, respectively, unnecessary light scattering in the heat-sensitive color-developing layer can be reduced and the color-developing property can be improved. The particle size of the microcapsules in the present specification means a 50% particle size (D50) based on the volume distribution.

(Electron-donating dye precursor)
The heat-sensitive color-developing layer contains an electron-donating dye precursor (also referred to as a leuco dye). Electron-donating dye precursors are usually colorless or pale in color. The electron-donating dye precursor has a property of donating an electron or receiving a proton such as an acid to develop a color. Specific examples of electron-donating dye precursors are listed below.

Examples of electron-donating dye precursors that develop a red or vermilion color tone include 3,6-bis (diethylamino) fluorane-γ-anilinolactam and 3,6-bis (diethylamino) fluorane-γ- (p-nitro). ) Anilinolactam, 3,6-bis (diethylamino) fluorane-γ- (o-chloro) anilinolactam, 3-dimethylamino-7-bromofluorane, 3-diethylaminofluorane, 3-diethylamino-6-methyl Fluolan, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluorine, 3-diethylamino-7,8-benzofluorine, 3-diethylamino-6 , 8-Dimethylfluorane, 3-diethylamino-6-methyl-7-chlorofluorine, 3-diethylamino-7-tert-butylfluorane, 3- (N-ethyl-N-tolylamino) -7-ethylfluorine , 3- (N-ethyl-N-isobutylamino) -6-methyl-7-chlorofluorane and the like.

Further, 3-cyclohexylamino-6-chlorofluorane and 3-di (n-butyl) amino-6-methyl-7-bromofluorane are examples of electron-donating dye precursors that develop a red or vermilion color. , 3-Di (n-butyl) amino-7,8-benzofluorine, 3-tolylamino-7-methylfluorane, 3-tolylamino-7-ethylfluorane, 2- (N-acetylanilino) -3 -Methyl-6-di (n-butyl) aminofluorane, 2- (N-propionylanilino) -3-methyl-6-di (n-butyl) aminofluorane, 2- (N-benzoylanilino) -3-Methyl-6-di (n-butyl) aminofluorane, 2- (N-carbobtoxyanilino) -3-methyl-6-di (n-butyl) aminofluorane, 2- (N-formylanilino) ) -3-Methyl-6-di (n-butyl) aminofluorane, 2- (N-benzylanilino) -3-methyl-6-di (n-butyl) aminofluorane, 2- (N-allylanilino) ) -3-Methyl-6-di (n-butyl) aminofluorane, 2- (N-methylanilino) -3-methyl-6-di (n-butyl) aminofluorane, 3-diethylamino-7-phenoxyflu Oran, 2-methyl-6- (N-p-tolyl-N-ethylamino) -fluorane and the like can be mentioned.

Examples of electron-donating dye precursors that develop magenta tones include 3,3-bis (1-ethyl-2-methylindole-3-yl) phthalide and 3,3-bis (1-n-octyl-). 2-Methylindole-3-yl) phthalide, 7- (N-ethyl-N-isoamylamino) -3-methyl-1-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole)) -4,3'-phthalide], 7- (N-ethyl-N-isoamylamino) -3-methyl-1-p-methylphenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole] ) -4,3'-phthalide], 7- (N-ethyl-Nn-hexylamino) -3-methyl-1-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) ) -4,3'-phthalide] and the like.

Further, as electron-donating dye precursors that develop colors in magenta tones, 3- (N-ethyl-N-isoamylamino) -7,8-benzofluorine, 3,3-bis (1-n-) Butyl-2-methylindole-3-yl) phthalide, 3- (N-ethyl-N-isoamylamino) -7-phenoxyfluorane and the like can be mentioned.

Examples of electron-donating dye precursors that develop red, vermilion, or magenta tones include 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,8-dimethylfluorane, and 3- (N-ethyl). -N-isoamylamino) -7,8-benzofluorine, 2-methyl-6- (Np-tolyl-N-ethylamino) -fluorane, 3-di (n-butyl) amino-6-methyl- It is preferable to use at least one selected from the group consisting of 7-bromofluorane and 3,3-bis (1-n-butyl-2-methylindole-3-yl) phthalide.

Examples of electron-donating dye precursors that develop a bluish tint include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2-methylphenyl) -3. -(4-Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3-yl) -4-azaphthalide, 3- (1-Ethyl-2-methylindole-3-yl) -3- (4-diethylaminophenyl) phthalide, 3- (1-ethyl-2-methylindole-3-yl) -3- (2-methyl) -4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindole-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-) Ethyl-2-methylindole-3-yl) -3- (2-n-hexyloxy-4-diethylaminophenyl) -4-azaphthalide, 3-diphenylamino-6-diphenylaminofluorane and the like can be mentioned.

As an electron donating dye precursor that develops a cyan color tone, 3- (1-ethyl-2-methylindole-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide is used. , 3- [1,1-bis (p-diethylaminophenyl) ethylene-2-yl] -6-dimethylaminophthalide, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3 , 3'-Bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide and the like.

Examples of electron-donating dye precursors that develop a blue or cyan color tone include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2-methylphenyl). ) -3- (4-Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4 -Azaphthalide, 3- (1-ethyl-2-methylindole-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3) -Il) -3- (2-n-hexyloxy-4-diethylaminophenyl) -4-azaphthalide, 3- [1,1-bis (p-diethylaminophenyl) ethylene-2-yl] -6-dimethylaminophthali It is preferable to use at least one selected from the group consisting of do and 3,3'-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide.

Examples of electron-donating dye precursors that develop a yellowish hue include 4- [2- [2- (butoxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzeneamine, 4-[. 2- [2- (octyloxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzeneamine, 4- [2- [2- (ethoxy) phenyl] -6-phenyl-4-pyridinyl ] -N, N-dimethylbenzeneamine, 4- [2,6-bis (2-ethoxyphenyl) -4-pyridinyl] -N, N-dimethylbenzeneamine, 4- (2,6-diphenyl-4-pyridinyl) ) -N, N-dimethylbenzeneamine, 4- [2,6-bis (2-butoshikiphenyl) -4-pyridinyl] -N, N-dimethylbenzeneamine, 4- [2,6-bis (2-6-bis) Octyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzeneamine, 4- [2- [2- (hexyloxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzeneamine, 4- [2,6-bis (2-hexyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzeneamine, 3,6-dimethoxyfluorane, 1- (4-n-dodecyloxy-3-methoxy) Examples thereof include phenyl) -2- (2-quinolyl) ethylene.

Examples of the electron-donating dye precursor that develops a yellowish hue include 4- [2- [2- (octyloxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzeneamine, 3, It is preferable to use at least one selected from the group consisting of 6-dimethoxyfluorane and 1- (4-n-dodecyloxy-3-methoxyphenyl) -2- (2-quinolyl) ethylene.

Examples of the electron-donating dye precursor that develops a greenish tone include 3- (N-ethyl-Nn-hexylamino) -7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, and the like. 3-Pyrrolidino-7-dibenzylaminofluorane, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3- (N-ethyl-N-p-tolylamino) -7- (N) -Phenyl-N-methylamino) fluorane, 3- [p- (p-anilinoanilino) anilino] -6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3' -(6'-Dimethylamino) phthalide and the like can be mentioned.

As the electron-donating dye precursor that develops a greenish color tone, at least one selected from the group consisting of 3-diethylamino-7-dibenzylaminofluorane and 3-pyrrolidino-7-dibenzylaminofluorane. It is preferable to use.

Examples of electron-donating dye precursors that develop a blackish tone include 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, and 3-. Diethylamino-6-methyl-7- (m-methylanilino) fluorane, 3- (N-isoamyl-N-ethylamino) -7- (o-chloroanilino) fluorane, 3- (N-ethyl-p-toluizino) -6 -Methyl-7-anilinofluolane, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilino Fluolane, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-amyl) amino-6-methyl-7-anilinofluoran, 3- (N-) Isoamyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-ethylamino) -6-methyl-7-anilinofluoran, 3- [N- (3-ethoxypropyl) -N-methylamino) -6-methyl-7-anilino Fluolane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-di (n-butyl) amino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluorane, 2,4-dimethyl-6- Examples thereof include (4-dimethylaminoanilino) fluorane and 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane.

As electron-donating dye precursors that develop a blackish color tone, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane and 3-di (3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-butyl), which have relatively excellent light resistance, are used as electron-donating dye precursors. n-amyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane, 3-diethylamino-6-methyl-7- (2) , 4-Dimethylanilino) fluorane, and 2,4-dimethyl-6- (4-dimethylaminoanilino) fluorane, it is preferable to use at least one selected from the group.

As an electron donating dye precursor having absorption in the near infrared region, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7- Tetrabromophthalide, 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 -Anilino anilino) anilino] -6-methyl-7-chlorofluorine, 3- [p- (p-dimethylaminoanilino) anilino] -6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) ) Fluoren-9-spiro-3'-(6'-dimethylamino) phthalide, bis (p-dimethylaminostyryl) -p-tolylsulfonylmethane, 3- [p- (p-dimethylaminoanilino) anilino]- 6-Methylfluorane, 3-di (n-pentyl) amino-6,8,8-trimethyl-8,9-dihydro- (3,2e) pyridofluorane, 3-di (n-butyl) amino-6 , 8,8-trimethyl-8,9-dihydro- (3,2e) pyridofluorane, 3- (pn-butylaminoanilino) -6-methyl-7-chlorofluorine, 2-mesidino-8 -Diethylamino-benz [C] fluorane and the like can be mentioned.

The content of the electron-donating dye precursor is preferably 3% by mass or more and 18% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, based on the total mass of the microcapsules. By setting the content of the electron-donating dye precursor within the above range, the color-developing property can be further improved and the background fog can be suppressed.

It is preferable that the content of the electron-donating dye precursor in the heat-sensitive color-developing layer is 0.01 g / m ² or more and 2.00 g / m ² or less because an image having a more sufficient optical density can be formed.

(Electron accepting compound)
The heat-sensitive color-developing layer contains an electron-accepting compound (also referred to as a color developer) having a property of developing an electron-donating dye precursor by contact with the color-sensitive color-developing layer. As the electron-accepting compound, it is preferable to use a compound having a property of liquefying or dissolving when the temperature rises. Examples of the electron-accepting compound include phenol compounds, aromatic carboxylic acids, and organic acidic substances such as polyvalent metal salts of these compounds.

Examples of the electron-accepting compound include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidene diphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4, 4'-isopropyridene diphenol, 4,4'-dihydroxydiphenyl ether, 4,4'-cyclohexylidene diphenol, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-Phenylethane, 4,4'-dihydroxydiphenylsulfide, 4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone , 4-Hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone , 4,4'-Bis [(4-Methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone, 4- [4'-(1'-methylethyloxy) phenyl] sulfonylphenol, N- (p-toluene) Sulfonyl) -N'-(3-p-toluenesulfonyloxyphenyl) urea, Np-tolylsulfonyl-p-butoxycarbonylphenylurea, N- (p-toluenesulfonyl) -N'-phenylurea, 4,4 '-Bis (3-tosylureido) diphenylmethane and the like can be mentioned.

Examples of the electron-accepting compound include 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, -sec-butyl 4-hydroxybenzoate, and 4-hydroxybenzoic acid. Phenolic compounds such as phenyl, benzyl 4-hydroxybenzoate, trill 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl ether; benzoic acid, p-tert-butyl benzoic acid, trichlor benzoic acid, Aromatic carboxylic acids such as terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3,5- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid. Examples include organic acidic substances such as salts of these compounds with polyvalent metals such as zinc, magnesium, aluminum and calcium.

The electron-accepting compound may be dispersed in water by a known method, and the dispersion of the electron-accepting compound may be mixed when preparing the coating solution for the heat-sensitive color-developing layer. The electron-donating compound was encapsulated in microcapsules together with the radical-polymerizable compound and the photo-radical polymerization initiator, as in the case of the electron-donating dye precursor, although it depends on the viscosity of the material constituting the core portion. It may be contained in the heat-sensitive color-developing layer in a state.

When the content of the electron-accepting compound in the heat-sensitive color-developing layer is 0.01 g / m ² or more and 10.00 g / m ² or less, an image having a more sufficient optical density can be formed, which is preferable. The content of the electron-accepting compound in the heat-sensitive color-developing layer is preferably 100% by mass or more and 2000% by mass or less with respect to the electron-donating dye precursor. By setting the content of the electron-accepting compound to the electron-donating dye precursor to 100% by mass or more, the color development of the image can be further improved. On the other hand, when the content of the electron-accepting compound with respect to the electron-donating dye precursor is 2000% by mass or less, the deterioration of the texture due to the increase in the film thickness can be suppressed and the film strength can be improved.

(Radical polymerizable compound)
The heat-sensitive color-developing layer contains a radically polymerizable compound.

Examples of the radically polymerizable compound include a radically polymerizable monomer, a radically polymerizable oligomer, and a radically polymerizable polymer, but a radically polymerizable monomer is preferable from the viewpoint of being efficiently cured by ultraviolet rays.

Examples of the radically polymerizable monomer include stearyl acrylate, behenyl acrylate, cyclohexanedimethanol diacrylate, bisphenol A diacrylate, ethoxylated bisphenol A diacrylate, propoxylated bisphenol A diacrylate, hydride bisphenol A diacrylate, and ethoxylated hydride bisphenol. Examples thereof include A-diacrylate, propoxyhydride bisphenol A-diacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate and the like.

Examples of the radically polymerizable oligomer include those in which an acrylate group is bonded to an oligomer such as a urethane oligomer, an epoxy oligomer, or a polyester oligomer. An appropriate linking group may be interposed between the above oligomer and the acrylate group.

Examples of the radically polymerizable polymer include those in which an acrylate group is bonded to a polymer such as an acrylic polymer, a urethane polymer, an epoxy polymer, and a polyester polymer. A suitable linking group may be interposed between the above polymer and the acrylate group.

Among the radically polymerizable monomers, it is preferable that the compound is at least one selected from the group consisting of a pentaerythritol derivative, an isocyanurate derivative, and a trimethylolpropane derivative.

Examples of the pentaerythritol derivative include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ethylene oxide-modified pentaerythritol tri (meth) acrylate, propylene oxide-modified pentaerythritol tri (meth) acrylate, and ethylene oxide-modified pentaerythritol tetra (meth) acrylate. Examples thereof include meth) acrylate, propylene oxide-modified pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and tripentaerythritol (meth) acrylate. Among them, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and tripentaerythritol (meth) acrylate are preferable. In addition, "(meth) acrylate" means methacrylate or acrylate. Commercially available products of the pentaerythritol derivative include, for example, light acrylate PE-3A; manufactured by Kyoeisha Chemical Co., Ltd., light acrylate PE-4A; manufactured by Kyoeisha Chemical Co., Ltd., light acrylate DPE-6A; manufactured by Kyoeisha Chemical Co., Ltd., SR295. ; Sartmer Co., Ltd., Viscort # 300; Osaka Organic Chemical Industry Co., Ltd., MT-3549; Toa Synthetic Co., Ltd., NK Oligo U-6LPA; Shin Nakamura Chemical Co., Ltd., U-15HA; New Nakamura Kagaku Co., Ltd., KAYARAD D-310; Nihonkayaku Co., Ltd., KAYARAD D-310; Nihonkayaku Co., Ltd., KAYARAD D-330; Nihonkayaku Co., Ltd., A-DPH; Nakamura Chemical Co., Ltd., A-TMMT; Shin-Nakamura Chemical Co., Ltd., etc. may be mentioned.

As the isocyanurate derivative, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, and polyfunctional penta having a hydroxyl group in isocyanurate-type polyisocyanate. Examples thereof include a urethane acrylate-type isocyanurate derivative in which an erythritol derivative or a polyfunctional trimethylol derivative is reacted and polyfunctionalized via a urethane bond. Among them, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate and urethane acrylate type isocyanurate derivative are preferable. Commercially available isocyanurate derivatives include, for example, Funkryl FA-731A; Hitachi Chemical Co., Ltd., SR368; Sartmer Co., Ltd., Aronix M-315; Toagosei Co., Ltd., U-15HA; Shin-Nakamura Chemical Co., Ltd. Made by Co., Ltd.

Examples of the trimethylolpropane derivative include trimethylolpropane tri (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane triacrylate, propylene oxide-modified trimethylolpropane, and ditrimethylolpropane tetra. Examples include acrylate. Among them, as the trimethylolpropane derivative, trimethylolpropane tri (meth) acrylate and trimethylolpropane tetraacrylate are preferable. Commercially available products of trimethylolpropane derivatives include, for example, Sunester TMP; manufactured by Sanshin Chemical Industry Co., Ltd., Viscort # 295; manufactured by Osaka Organic Chemical Industry Co., Ltd., Lightester TMP; manufactured by Kyoeisha Chemical Co., Ltd., Acryester. TMP; Mitsubishi Chemical Holdings Co., Ltd., Miramar M410; Toyo Chemicals Co., Ltd., Miramar M300; Toyo Chemicals Co., Ltd., Miramar M301; Toyo Chemicals Co., Ltd., EBECRYL140; Daicel Ornex Co., Ltd., EBECRYL1142; manufactured by Daicel Ornex Co., Ltd., SR355; manufactured by Sartmer Co., Ltd., A-TMPT; manufactured by Shin-Nakamura Chemical Co., Ltd., AD-TMP; manufactured by Shin-Nakamura Chemical Co., Ltd. and the like.

Two or more radically polymerizable compounds may be used in combination. The melting point of the radically polymerizable compound when two or more kinds of radically polymerizable compounds are used means the melting point of the mixture of the radically polymerizable compounds. Further, the SP value of the radically polymerizable compound when two or more kinds of radically polymerizable compounds are used means the SP value of the weight average of the mixture of the radically polymerizable compounds.

The SP value of the radically polymerizable compound and the SP value of the electron-donating dye precursor preferably satisfy the following relationship.
(SP value of radically polymerizable compound) -2 <(SP value of electron donating dye precursor) <(SP value of radically polymerizable compound) +2

By satisfying the above relationship between the SP value of the radically polymerizable compound and the SP value of the electron donating dye precursor, color development in the non-image forming region can be further suppressed. This is because the compatibility between the radically polymerizable compound and the electron donating dye precursor is good in the microcapsules, so that the electron donating dye precursor is more easily confined in the radical polymerization compound during the radical polymerization reaction. It is believed that there is.

The radically polymerizable compound is preferably a compound that is liquid at 25 ° C. Here, the liquid means that the melting point or the glass transition point (Tg) is 25 ° C. or lower.

By using a radically polymerizable compound that is liquid at 25 ° C, color development in the non-image region can be further suppressed.

The content of the radically polymerizable compound in the heat-sensitive color-developing layer is preferably 100% by mass or more and 3500% by mass or less, preferably 300% by mass or more and 2000% by mass or less, based on the content of the electron-donating dye precursor. It is more preferable to have. When it is 100% by mass or more, the fixability is improved, and when it is 300% by mass or more, the fixability is further improved. On the other hand, when the content is 3500% by mass or less, the color development of the image is improved, and when the content is 2000% by mass or less, the color development of the image is further improved.

(Photoradical polymerization initiator)
The heat-sensitive color-developing layer contains a photoradical polymerization initiator. The photoradical polymerization initiator may be any compound that can generate radicals by the action of light. As the photoradical polymerization initiator, a known compound capable of generating a radical can be used. As for the photoradical polymerization initiator in the heat-sensitive color-developing layer (second heat-sensitive color-developing layer) on the lower layer side, the photoradical polymerization initiator in the heat-sensitive color-developing layer (first heat-sensitive color-developing layer) on the upper layer side generates radicals. It is preferable that radicals are generated by light having a longer wavelength than that of light.

Examples of the photoradical polymerization initiator include aromatic ketone compounds, oxime ester compounds, acylphosphine oxide compounds, α-hydroxyketone compounds, thioxanthone compounds, benzophenone compounds, benzoate compounds, aromatic onium salt compounds, organic peroxides, and thio compounds. (Thiophenyl group-containing compounds, etc.), α-aminoalkylphenone compounds, hexaarylbiimidazole compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having carbon halogen bonds, alkylamine compounds, etc. may be mentioned. can. Further, radical generators described in JP-A-2018-355369, JP-A-2018-39265, etc. can also be used. Among them, an α-hydroxyketone compound, an α-aminoalkylphenone compound, an oxime ester compound, an acylphosphine oxide compound, or a benzophenone compound is preferable, and an oxime ester compound is more preferable. The photoradical polymerization initiator may be used alone or in combination of two or more. The content of the photoradical polymerization initiator in the heat-sensitive color-developing layer is preferably 0.1% by mass or more and 30% by mass or less, preferably 1% by mass or more and 25% by mass or less, based on the content of the radically polymerizable compound. Is more preferable. When the first particle and the second particle each contain a photoradical polymerization initiator, these photoradical polymerization initiators may be the same or different.

Examples of the aromatic ketone compound include acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2'-phenylp-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, and the like. Methylbenzoylformate, N, N'-tetramethyl-4,4'-diaminobenzophenone (Michler ketone), 1-hydroxycyclohexylphenylketone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy- 2-Methylpropane, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propane, 2 -(Dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone and the like can be mentioned.

Oxime ester compounds include 1,2-octanedione, 1- [4- (phenylthio) phenyl]-, 2- (O-benzoyloxime), etanone, 1- [9-ethyl-6- (2-methylbenzoyl). ) -9H-Carbazole-3-yl]-, 1- (O-acetyloxime), (9-ethyl-6-nitro-9H-carbazole-3-yl)-(4-((1-methoxypropane-2) -Il) Oxime) -2-Methylphenyl) Metanon-o-acetyloxime, 1- [4-[[4- (2-hydroxyethoxy) phenyl] thio] phenyl-1] -1,2-propanedione-2 -(O-Acetyloxime) and the like can be mentioned.

Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -diphenylphosphine oxide.

Examples of the α-hydroxyketone compound include 2-hydroxy-2-methyl-1-phenyl-1-propanol and 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl]. -Phenyl} -2-methyl-propane-1-one, 1-hydroxycyclohexylphenylketone and the like can be mentioned.

Examples of the α-aminoalkylphenone compound include 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1. -Propane, 2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, and the like can be mentioned.

Examples of the thioxanthone compound include 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, and 2-methylthioxanthone.

Examples of the benzophenone compound include benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4- (4-methylphenylthio) benzophenone, and 4,4'-bis (diethylamino) benzophenone.

Examples of the benzoate compound include ethyl-4- (dimethylamino) -benzoate, ethylhexyl-4-dimethylaminobenzoate, methyl-o-benzoylbenzoate, and p- (dimethylamino) benzoate 3-methylbutyl.

Among the above, commercially available products of the oxime ester compound, which is a preferable photoradical polymerization initiator, include, for example, IRGACURE OXE01, IRGACURE OXE02, IRGACURE OXE03, IRGACURE OXE04 (above, manufactured by BASF), ADEKA ARCULS N-1919, NCI-831. , NCI-930 (all manufactured by ADEKA) and the like.

(Other ingredients)
The heat-sensitive color-developing layer may contain a storage stability improving agent. By including the preservability improving agent in the heat-sensitive color-developing layer, the preservability of the developed image can be further improved. Examples of the storage improving agent include 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane and 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, 4 , 4'-[1,3-phenylenebis (1-methylethylidene)] bisphenol and other phenol compounds; 4-benzyloxyphenyl-4'-(2-methyl-2,3-epoxypropyloxy) phenyl sulfone, 4 -Epoxy compounds such as (2-methyl-1,2-epoxyethyl) diphenyl sulfone, 4- (2-ethyl-1,2-epoxyethyl) diphenyl sulfone; 1,3,5-tris (2,6-dimethyl) Examples thereof include isocyanuric acid compounds such as benzyl-3-hydroxy-4-tert-butyl) isocyanuric acid.

The heat-sensitive color-developing layer can contain a heat sensitizer. By including the heat sensitizer in the heat-sensitive color-developing layer, the recording sensitivity can be improved. Examples of the heat sensitizer include stearate amide, methoxycarbonyl-N-benzyl stearate, N-benzoyl stearate amide, N-eicosanoic acid amide, ethylene bisstea acid amide, behenic acid amide, methylene bisstea acid amide, and 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, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, oxalic acid dibenzyl ester, p-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1, 2 -Di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1 , 2-Diphenoxyetane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluiside, p-acet Phenetidine, 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 and the like. The content of the heat sensitizer in the heat-sensitive color-developing layer may be an amount effective for heat sensitization. Specifically, the total solid content of the heat-sensitive color-developing layer is preferably 2% by mass or more and 40% by mass or less, and preferably 5% by mass or more and 25% by mass or less.

Auxiliary agents such as a storage improver and a heat sensitizer may be mixed with a coating liquid for forming a heat-sensitive color-developing layer in the state of fine particles (solid dispersed fine particles) dispersed in water. Further, these auxiliaries can be dissolved in a solvent and used as an emulsified state by using a water-soluble polymer compound as an emulsifier. Further, the storage stability improving agent and the heat sensitizer may be contained in the particles containing the electron-donating dye precursor and the electron-accepting compound.

The heat-sensitive color-developing layer can contain a polymerization accelerator. Examples of the polymerization accelerator include benzoate compounds and amine compounds.

Examples of the benzoate compound and the amine compound include ethyl-4- (dimethylamino) -benzoate, ethylhexyl-4-dimethylaminobenzoate, methyl-o-benzoylbenzoate, p- (dimethylamino) 3-methylbutyl benzoate, N, N-. Examples thereof include dimethylaminobenzoic acid ethyl ester, N, N-dimethylaminobenzoic acid isoamyl ester, pentyl4-dimethylaminobenzoate, triethylamine, triethanolamine and the like.

The heat-sensitive color-developing layer can contain a sensitizer. The sensitizer may be one that sensitizes the photoradical polymerization initiator by an electron transfer mechanism or an energy transfer mechanism. Examples of the sensitizer include aromatic polycondensate compounds such as anthracene, 9,10-dialkoxyanthracene, pyrene and perylene; aromatic ketone compounds such as acetophenone, benzophenone, thioxanthone and Michler ketone; and phenothiazine and N-aryloxazolidinone. Heterocyclic compounds can be mentioned. The content of the sensitizer in the heat-sensitive color-developing layer is preferably 0.1 part by mass or more and 10 parts by mass or less with respect to 1 part by mass of the photoradical polymerization initiator, and is preferably 1 part by mass or more and 5 parts by mass or less. It is more preferable to do so.

In order to improve the electron transfer efficiency or energy transfer efficiency between the sensitizer and the photoradical polymerization initiator, it is preferable to include a sensitizing aid in the heat-sensitive color-developing layer. Examples of the sensitizing aid include naphthalene compounds such as 1,4-dihydroxynaphthalene, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 4-methoxy-1-naphthol, and 4-ethoxy-1-naphthol; 1 , 4-Dihydroxybenzene, 1,4-dimethoxybenzene, 1,4-diethoxybenzene, 1-methoxy-4-phenol, 1-ethoxy-4-phenol and other benzene compounds can be mentioned. The content of the sensitizing aid in the heat-sensitive color-developing layer is preferably 0.1 part by mass or more and 10 parts by mass or less, and 0.5 parts by mass or more and 5 parts by mass or less with respect to 1 part by mass of the sensitizer. Is preferable.

The heat-sensitive color-developing layer can contain a radical polymerization inhibitor. The photoradical polymerization initiator is slightly decomposed into a radical compound during storage of the heat-sensitive recorder. Since polymerization caused by this radical compound may be caused, it is preferable to include a radical polymerization inhibitor in the heat-sensitive color-developing layer in order to prevent this polymerization.

Examples of the radical polymerization inhibitor include phenolic hydroxyl group-containing compounds, methquinone (hydroquinone monomethyl ether), hydroquinone, quinones such as 4-methoxy-1-naphthol, hindered amine antioxidants, and 1,1-diphenyl-2-picryl. Hydrazyl-free radicals, N-oxyl-free radical compounds, nitrogen-containing heterocyclic mercapto compounds, thioether-based antioxidants, hindered phenol-based antioxidants, ascorbic acids, zinc sulfate, thiocitanoates, thiourea derivatives, various Of saccharides, phosphoric acid antioxidants, nitrites, sulfites, thiosulfates, hydroxylamine derivatives, aromatic amines, phenylenediamines, imines, sulfonamides, urea derivatives, oximes, dicyandiamides and polyalkylene polyamines. Examples thereof include polycondensates, sulfur-containing compounds such as phenothiazine, tetraazaannulene (TAA) -based complexing agents, and hindered amines.

Among them, as the radical polymerization inhibitor, phenols, N-oxyl-free radical compounds, 1,1-diphenyl-2-picrylhydrazyl-free radicals, phenothiazines, quinones, and hindered amines are preferable. Further, N-oxyl-free radical compounds are more preferable. The content of the radical polymerization inhibitor in the heat-sensitive color-developing layer is preferably 1 ppm or more and 5,000 ppm or less on a mass basis with respect to the content of the radically polymerizable compound.

The heat-sensitive color-developing layer can contain a pigment having a high whiteness with an average particle diameter of 10 μm or less. By containing such a pigment, the whiteness of the heat-sensitive color-developing layer can be improved and the uniformity of the image can be improved. Pigments include calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica. Inorganic pigments; organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, and polystyrene resin can be mentioned. The content of the pigment in the heat-sensitive color-developing layer is preferably an amount that does not reduce the color-developing density of the image. Specifically, it is preferably 50% by mass or less in the total solid content of the heat-sensitive color-developing layer.

A binder can be used as a component for forming the heat-sensitive color-developing layer. Further, if necessary, a cross-linking agent, waxes, metal soap, colored dye, colored pigment, fluorescent dye and the like can be contained. Examples of the binder include polyvinyl alcohol and its derivatives; starch and its derivatives; cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose and ethyl cellulose; sodium polyacrylic acid, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymers, and the like. Water-soluble polymer materials such as acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and derivatives thereof; vinyl acetate , Polyacrylic acid, Polyacrylic acid, Polyacrylic acid ester, Vinyl chloride-vinyl acetate copolymer, Polybutyl methacrylate, Ethylene-vinyl acetate copolymer and other emulsions; Examples thereof include latex of a water-insoluble polymer such as a polymer.

By including a cross-linking agent in the heat-sensitive color-developing layer, the water resistance of the heat-sensitive color-developing layer can be improved. Examples of the cross-linking agent include aldehyde compounds such as glioxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxyphosphates, dimethylolurea compounds, aziridine compounds, and organic compounds such as blocked isocyanate compounds; In addition to inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, potassium tetraborate, etc .; examples thereof include boric acid, borate triester, borane polymer, hydrazide compound, glyoxylate and the like. The content of the cross-linking agent in the heat-sensitive color-developing layer is preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the total solid content of the heat-sensitive color-developing layer.

Examples of the wax include waxes such as paraffin wax, carnauba wax, microcrystalline wax, polyolefin wax and polyethylene wax; higher fatty acid amides such as stearate amide and ethylene bisstearic acid amide; higher fatty acid esters and derivatives thereof. can. Examples of the metal soap include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

When the heat-sensitive recording body is a two-color heat-sensitive recording body, it is preferable that the heat-sensitive color-developing layer contains a colored dye or a colored pigment having a color tone that is complementary to the low-temperature color-developing color tone. By incorporating such a colored dye or a colored pigment in the heat-sensitive color-developing layer, the color tone of the heat-sensitive recorder before and after forming an image can be adjusted. Further, if necessary, various auxiliary agents such as an oil repellent, an antifoaming agent, and a viscosity adjusting agent can be contained in the heat-sensitive color-developing layer.

For the heat-sensitive color-developing layer, for example, water is used as a dispersion medium, and a coating liquid for a heat-sensitive color-developing layer containing each component constituting the heat-sensitive color-developing layer is applied onto a support to form a coating layer, and then this coating is applied. It can be formed by drying the layer. For example, a coating liquid for a heat-sensitive color-developing layer is prepared by dispersing microcapsules containing a radically polymerizable compound, an electron-donating dye precursor, and a photoradical polymerization initiator in water and an electron-accepting compound. can do. Then, by applying the coating liquid on the support and drying it, a heat-sensitive color-developing layer can be formed on the support. The amount of the coating liquid to be applied is preferably 2 g / m ² or more and 20 g / m ² or less, more preferably 2 g / m ² or more and 15 g / m ² or less, and 2 g / m ² or more and 10 g in terms of dry mass. It is particularly preferable that it is / m ² or less.

It is preferable to use a surfactant to prepare the above-mentioned microcapsules. Surfactants include anionic surfactants such as sodium alkylsulfonate, sodium alkylbenzenesulfonate, sodium dialkylsulfosuccinate, sodium alkylcarboxylate; polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene polyoxy. Nonionic surfactants such as propylene glycol, sorbitan alkyl ester, polyoxyethylene sorbitan alkyl ester, glycerin alkyl SL, polyoxyethylene hydrogenated castor oil; cations such as alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, alkylbenzyldimethylammonium chloride. Sexual surfactants; amphoteric surfactants such as alkylbetaines and alkyldimethylamine oxides can be mentioned. Further, a polymer-type surfactant such as a sodium salt of a naphthalene sulfonic acid formarin condensate or sodium polyacrylate can be used.

Ionic groups such as sulfonic acid groups, carboxylic acid groups and amino groups; radical polymerizable compounds imparted with surface active ability by binding hydrophilic nonionic groups such as polyoxyethylene groups and polyglyceryl groups to radically polymerizable compounds. Can also be used.

A dispersion aid can also be used to prepare the aforementioned microcapsules. Dispersion aids include polyvinyl alcohol and its variants, polyacrylic acid amides and derivatives thereof, ethylene / vinyl acetate copolymers, styrene / maleic anhydride copolymers, ethylene / maleic anhydride copolymers, isobutylene / anhydrous. Water-soluble polymers such as maleic acid copolymer, polyvinylpyrrolidone, ethylene / acrylic acid copolymer, vinyl acetate / acrylic acid copolymer, carboxymethyl cellulose, methyl cellulose, casein, gelatin, starch derivative, arabiya rubber, sodium alginate, etc. be able to.

The amount of the surfactant and the dispersion aid added is preferably 0.1% by mass or more and 10% by mass or less based on the respective masses of the first particle and the second particle, and 0. It is more preferably 5% by mass or more and 5% by mass or less.

(Middle layer)
When the heat-sensitive color-developing layers are laminated to form a heat-sensitive recording body capable of forming a multicolor image, an intermediate layer can be provided between the heat-sensitive color-developing layers. As the material constituting the intermediate layer, a water-soluble polymer material or a water-insoluble polymer used in a known heat-sensitive recording material can be used. Specific examples of the material constituting the intermediate layer include the same materials as the binder which is a component for constituting the heat-sensitive color-developing layer. In addition, particles with a high void ratio such as silica and calcined kaolin and organic compounds such as plastic pigments, ultraviolet absorbers, hollow particles, foams, and polyethylene wax having a glass transition point or melting point are contained in the intermediate layer as an auxiliary agent. You may.

The intermediate layer is formed by, for example, using water as a dispersion medium, applying a coating liquid for an intermediate layer containing each component constituting the intermediate layer to form a coating layer, and then drying the coating layer. can do. The amount of the coating liquid to be applied is preferably 1 g / m ² or more and 40 g / m ² or less, and more preferably 2 g / m ² or more and 10 g / m ² or less in terms of dry mass.

(Protective layer)
It is preferable to have a protective layer on the heat-sensitive color-developing layer. As the protective layer, a protective layer used in a known heat-sensitive recording body can be used. For example, it is preferable to provide a protective layer containing a water-soluble polymer material and particles. As the water-soluble polymer material and particles, the same materials as those that can be contained in the heat-sensitive color-developing layer can be used. Further, it is also preferable to add a cross-linking agent to impart water resistance to the protective layer.

By including microcapsules containing an ultraviolet absorber and solid dispersed fine particles of an ultraviolet absorber in the protective layer, the light resistance can be significantly improved. Among them, microcapsules having a shell portion made of polyurethane-polyurea resin or aminoaldehyde resin are preferable because they have excellent heat resistance and also exhibit excellent accompanying effects such as suppressing sticking to the thermal head. Further, the microcapsules having a shell portion made of a polyurethane-polyurea resin or an aminoaldehyde resin have a lower refractive index than the microcapsules having a shell portion made of another resin. Further, since the shape is spherical, even if a large amount is added to the protective layer, the concentration decrease due to diffused reflection of light is unlikely to occur, which is preferable.

Further, it is preferable to contain particles in the protective layer because it is possible to prevent dirt from adhering to the thermal head and sticking. The oil absorption of the particles is preferably 50 mL / 100 g or more. The content of the particles in the protective layer is preferably an amount that does not reduce the color development density, and specifically, is preferably 60% by mass or less in the total solid content of the protective layer.

For the protective layer, for example, water is used as a dispersion medium, and a coating liquid for the protective layer containing each component constituting the protective layer is applied onto the heat-sensitive color-developing layer to form a coating layer, and then this coating layer is applied. It can be formed by drying. The amount of the coating liquid to be applied is preferably 0.1 g / m ² or more and 15 g / m ² or less, and more preferably 0.5 g / m ² or more and 8 g / m ² or less in terms of dry mass.

(Resin layer)
A resin layer made of a resin cured by an electron beam or ultraviolet rays can be provided on each of the heat-sensitive color-developing layer, the intermediate layer, and the protective layer. As the resin cured by an electron beam, for example, the resin described in JP-A-58-177392 can be used. Auxiliary agents such as non-electron beam curable resin, particles, defoaming agent, leveling agent, lubricant, surfactant, and plasticizer may be appropriately added to the resin constituting the resin layer. Among them, it is preferable to add particles such as calcium carbonate and aluminum hydroxide; waxes and lubricants such as silicon because sticking to the thermal head can be suppressed.

(Other layers)
By processing the heat-sensitive recording body to give it a higher function, the added value of the heat-sensitive recording body can be increased. For example, by applying an adhesive, a re-wet adhesive, a delayed tack type adhesive, or the like to the back surface, it is possible to obtain an adhesive paper, a re-wet adhesive paper, or a delayed tack paper. Further, by imparting functions such as thermal transfer paper, inkjet recording paper, carbonless copy paper, electrostatic recording paper, and zeography paper to the back surface, it is possible to obtain a recording paper capable of double-sided recording. Furthermore, by arranging a heat-sensitive color-developing layer on the back surface, a double-sided heat-sensitive recorder can be obtained. Further, a back layer may be provided on the back surface of the heat-sensitive recording body in order to suppress the penetration of oil or plasticizer from the back surface, or to control curl or prevent static electricity.

(Layer structure of thermal recording body)
FIG. 1 is a cross-sectional view showing an embodiment of the heat-sensitive recording body of the present invention. The heat-sensitive recording body 100 shown in FIG. 1 includes a sheet-shaped support 101, a heat-sensitive color-developing layer 102 provided on one surface side of the support 101, and a protective layer 103 provided on the heat-sensitive color-developing layer 102. Be prepared. The thermal recording body according to the embodiment of the present invention may not be provided with the protective layer 103 as shown in FIG.

The support 101 may be made of a material capable of forming a coating film using a coating liquid (heat-sensitive color-developing composition) for the heat-sensitive color-developing layer. Examples of the constituent material of the support 101 include paper, synthetic paper, and various plastics. Examples of the plastic include PET (polyethylene terephthalate) and OPP (oriented polypropylene). If necessary, the surface of the support 101 is preferably subjected to a corona discharge treatment, a sandplast treatment, a primer treatment (lamination of the undercoat layer) and the like. By applying these treatments, the wettability of the surface of the support 101 can be improved, the surface can be roughened or easily adhered, and the formability of the coating film by the heat-sensitive color-developing composition can be enhanced. It is possible.

A coating film can be formed by applying or printing a heat-sensitive color-developing composition on the support 101. Examples of means for applying or printing the heat-sensitive color-developing composition include a blade coater, a rod coater, a reverse roll coater, a die coater, an offset printing machine, a gravure printing machine, a flexographic printing machine, a letterpress printing machine, and a silk screen printing machine. be able to. The intermediate layer (including the protective intermediate layer) and the protective layer can be formed by using an intermediate layer composition or an overcoat composition prepared by the same method as the method for preparing a heat-sensitive color-developing composition. A coating film can be formed by applying these intermediate layer compositions and overcoat compositions to predetermined locations. By forming each coating film and then drying it, each layer can be formed, and a target heat-sensitive recording body can be obtained. The coating film may be applied and dried one layer at a time, or the same coating film may be applied and dried in two or more times. Further, simultaneous multi-layer coating may be performed in which two or more coating liquids are simultaneously coated. It is preferable to perform smoothing treatment by a known method such as a super calendar or a soft calendar in an arbitrary process such as after each layer is formed or after all layers are formed. By the surface smoothing treatment, the recording sensitivity can be improved and the uniformity of the formed image can be improved.

<Image formation method>
Next, the image forming method of the present invention will be described. The image forming method of the present invention includes a step of applying a heat pulse to the above-mentioned heat-sensitive recording body by applying a heat pulse (image forming step) and irradiating the heat-sensitive recording body on which the image is formed with ultraviolet rays. Then, it has a step of fixing the heat-sensitive color-developing layer (fixing step).

The temperature of the heat pulse applied to the heat-sensitive recorder in the image forming step can be, for example, 80 ° C. or higher and 120 ° C. or lower. A desired image can be formed by applying a heat pulse to the heat-sensitive color-developing layer of the heat-sensitive recording body in a state where the thermal head is in contact with the heat-sensitive recording body. Specifically, the radically polymerizable compound contained in the heat-sensitive color-developing layer is dissolved by applying a heat pulse and heating. When the radically polymerizable compound is dissolved, the electron-donating dye precursor and the electron-accepting compound come into contact with each other to develop a color-sensitive color-developing layer, and an image can be formed.

In the fixing process, the heat-sensitive recorder on which the image is formed is irradiated with ultraviolet rays. The wavelength of the ultraviolet rays to be irradiated may be a wavelength at which the photoradical polymerization initiator contained in the heat-sensitive color-developing layer can react, and may be, for example, 365 nm or more and 425 nm or less. By irradiating with ultraviolet rays, the radically polymerizable compound can be polymerized and the heat-sensitive color-developing layer can be fixed. If the heat-sensitive color-developing layer is fixed, the heat-sensitive color-developing layer does not develop color even if the heat energy reaching the color-developing start temperature is subsequently applied, so that the color-developing property of the formed image can be maintained for a long period of time. The wavelength of ultraviolet rays in the present specification means the peak wavelength of ultraviolet rays to be irradiated. Further, fixing the heat-sensitive color-developing layer means fixing the color-developing state of the heat-sensitive color-developing layer.

Since the heat-sensitive color-developing layer that develops color with the thermal head heats a minute region in contact with the thermal head in a short time, it is preferable that the heat-sensitive color-developing layer has good thermal responsiveness. Therefore, the content of the organic solvent in the heat-sensitive color-developing layer is preferably 100% by mass or less based on the electron-donating dye precursor. When the content of the organic solvent in the heat-sensitive color-developing layer is within the above range, the thermal responsiveness of the heat-sensitive color-developing layer can be improved and the color development by the thermal head can be improved. The lower limit of the content of the organic solvent in the heat-sensitive color-developing layer is not particularly limited, but is preferably 0% by mass or more based on the content of the electron-donating dye precursor, for example.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. Unless otherwise specified, those described as "parts" and "%" regarding the amount of components are based on mass.

(Example 1)
<Manufacturing of thermal recording body (1)>
[Preparation of raw material composition]
The following materials were mixed and dissolved to prepare [oil phase A] liquid and [aqueous phase B].
[Oil phase A] Liquid: Composition containing electron-donating dye precursor ・ Electron-donating dye precursor (3- (1-ethyl-2-methylindole-3-yl) -3- (4-diethylamino-2) -Methylphenyl) -4-azaphthalide (BLUE220, manufactured by Fukui Yamada Chemical Industry Co., Ltd.) 8 parts ・ Radical polymerizable compound (mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate (SR295, manufactured by Sartmer Co., Ltd.)) 60.9 Part ・ Photo-radical polymerization initiator (Oxym ester compound (Irgacure OXE01, manufactured by BASF Japan)) 6.1 parts ・ Methyl ethyl ketone 111.7 parts ・ Polyvinyl monomer of resin constituting the shell part (xylylene diisocyanate / trimethylol) Propane adduct (Takenate D110N, manufactured by Mitsui Chemicals, Inc.) Solid content 75%) 33.3 parts [Aqueous phase B] Liquid / Polyvinyl alcohol (Kurarepoval 5-88, manufactured by Kuraray) 2.5 parts / Di-2-ethylhexyl sulfosuccinate 1.0 part of sodium acid, sodium polyacrylate (Aron T-50, manufactured by Toa Synthetic) 1.0 part, 0.02 part of radical acid, 0.02 part of sodium tetraborate, 0.02 part of water, 95.5 parts of water

[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
After mixing 80 parts of the [oil phase A] liquid and 100 parts of the [water phase B] liquid, they were emulsified using an ultrasonic homogenizer (UH-600S, manufactured by SMT). Then, after removing the methyl ethyl ketone under reduced pressure using a rotary evaporator, the same amount of water as the removed amount was added, the temperature was raised to 50 ° C. with stirring, and the encapsulation reaction was carried out for 4 hours to obtain a microcapsule particle dispersion. Obtained. The particle size (D50) of the particles in the electron-donating dye precursor-containing microcapsule particle dispersion measured using a particle size distribution measuring device (Nanotrack, manufactured by Microtrac) was 200 nm.
Liquid [C]: Particle dispersion containing an electron-accepting compound

After mixing the following materials, the solution [C] was pulverized and dispersed using a bead mill to obtain an electron-accepting compound-containing particle dispersion.
・ Electron-accepting compound (2,2'-diallyl-4,4'-sulfonyldiphenol (TGSH (H), manufactured by Nippon Kayaku)) 40 parts ・ Dispersant (EFKA7710, manufactured by BASF) 4 parts ・ 56 parts of water

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 6.1 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 6.32 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of BLUE 220 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

[Preparation of kaolin dispersion]
Using corres, 59.5 parts of kaolin, 0.5 part of dispersant, and 40 parts of water were dispersed for 1 hour to obtain a kaolin dispersion. As kaolin, the trade name "HYDRAGLOSS90, KaMin" (manufactured by LLC) was used. As the dispersant, the trade name “Aron T-50” (manufactured by Toagosei, solid content concentration 40%) was used.

[Formation of protective layer]
210 parts of 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol A, 80 parts of 20% aqueous solution of acetoacetyl-modified polyvinyl alcohol B, 100 parts of kaolin dispersion, 5.6 parts of aqueous dispersion of zinc stearate, and polyethylene wax emulsion 2. We prepared 5 copies. These components were mixed and stirred to obtain a coating liquid for a protective layer. As the acetoacetyl-modified polyvinyl alcohol A, the trade name "Gosefimer Z-200" (saponification degree 99.4 mol%, average polymerization degree 1,000, modification degree 5 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used. .. As the acetoacetyl-modified polyvinyl alcohol B, the trade name "Gosefimer Z-100" (saponification degree 99.4 mol%, average polymerization degree 500, modification degree 5 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used. As the aqueous dispersion of zinc stearate, the trade name “Hydrin Z-8-36” (manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36%) was used. As the polyethylene wax emulsion, the trade name "Chemipal W-400" (solid content concentration 40%, manufactured by Mitsui Chemicals) was used.

The obtained protective layer coating liquid is applied onto the heat-sensitive color-developing layer so that the coating amount after drying is 1.5 g / m ² , and dried to form a protective layer, and then the surface is smoothed with a super calendar. I got a heat-sensitive recorder.

(Example 2)
As an electron donating dye precursor, instead of BLUE220, 9- (N-ethyl-N-isopentylamino) spiro [benzo [a] xanthene-12,3'-phthalide] (RED500, manufactured by Fukui Yamada Chemical Industry Co., Ltd.) A heat-sensitive recorder was obtained in the same manner as in Example 1 described above, except that

(Example 3)
As an electron-donating dye precursor, instead of BLUE220, 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzeneamine (YELLOW435, manufactured by Fukui Yamada Chemical Industry Co., Ltd.) ) Was used, and a heat-sensitive recorder was obtained in the same manner as in Example 1 described above.

(Example 4)
A heat-sensitive recorder was obtained in the same manner as in Example 1 described above, except that dipentaerythritol pentaacrylate (SR399, manufactured by Sartmer Co., Ltd.) was used as the radically polymerizable compound instead of SR295.

(Example 5)
A heat-sensitive recorder was obtained in the same manner as in Example 1 above, except that a mixture of urethane acrylate oligoma and pentaerythritol tetraacrylate (UA-306I, Kyoeisha Chemical Co., Ltd.) was used as the radically polymerizable compound instead of SR295. rice field.

(Example 6)
A heat-sensitive recorder was obtained in the same manner as in Example 1 above, except that a mixture of urethane acrylate oligoma and pentaerythritol tetraacrylate (UA-306T, Kyoeisha Chemical Co., Ltd.) was used as the radically polymerizable compound instead of SR295. rice field.

(Example 7)
A heat-sensitive recorder was obtained in the same manner as in Example 1 above, except that an oxime ester compound (Irgacure OXE02, manufactured by BASF Japan) was used instead of Irgacure OXE01 as the photoradical polymerization initiator.

(Example 8)
A heat-sensitive recorder was obtained in the same manner as in Example 1 above, except that an oxime ester compound (NCI-831, manufactured by ADEKA) was used instead of Irgacure OXE01 as the photoradical polymerization initiator.

(Example 9)
Except for the fact that pentane-1,5-diisocyanate / isocyanurate adduct (Takenate D-370N, manufactured by Mitsui Chemicals) was used instead of D110N as the polymerizable monomer of the resin constituting the shell portion of the microcapsules. , A heat-sensitive recorder was obtained in the same manner as in Example 1 described above.

(Example 10)
Example 1 described above, except that a xylylene diisocyanate / isocyanurate adduct (Takenate D131N, manufactured by Mitsui Chemicals) was used instead of D110N as the polymerizable monomer of the resin constituting the shell portion of the microcapsules. A heat-sensitive recorder was obtained in the same manner as above.

(Example 11)
A heat-sensitive recorder was obtained in the same manner as in Example 10 described above, except that tris (2-hydroxyethyl) isocyanurate triacrylate (SR368, manufactured by Sartmer Co., Ltd.) was used as the radically polymerizable compound.

(Example 12)
A heat-sensitive recorder was obtained in the same manner as in Example 11 above, except that an acylphosphine oxide-type photopolymerization initiator (Omnirad TPO, manufactured by iGM Resin) was used instead of Irgacure OXE01 as the photoradical polymerization initiator. rice field.

(Example 13)
As radically polymerizable compounds, instead of SR368, tris (2-hydroxyethyl) isocyanurate triacrylate (SR368, manufactured by Sartmer Co., Ltd.) and urethane acrylate (U-15HA, Shin-Nakamura Chemical Co., Ltd.) are used in a mass ratio. A heat-sensitive recorder was obtained in the same manner as in Example 12 described above, except that it was used as a 1: 1 mixture.

(Example 14)
A heat-sensitive recorder was obtained in the same manner as in Example 13 described above, except that YELLOW 435 was used instead of BLUE 220 as the electron-donating dye precursor.

(Example 15)
Examples described above except that a xylylene diisocyanate / trimethylolpropane adduct (Takenate D110N, manufactured by Mitsui Chemicals) was used instead of D131N as the polymerizable monomer of the resin constituting the shell portion of the microcapsules. A heat-sensitive recorder was obtained in the same manner as in 14.

(Example 16)
A heat-sensitive recorder was obtained in the same manner as in Example 15 described above, except that SR368 was used instead of the mixture of SR368 and U-15HA as the radically polymerizable compound.

(Example 17)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
YELLOW 435, which is an electron-donating dye precursor of the oil phase A solution in Example 16, is added to 3 parts, SR368, which is a radically polymerizable compound, is added to 65.5 parts, and TPO, which is a photoradical polymerization initiator, is added to 6.5 parts. changed. That is, the reduced amount of the electron-donating dye precursor was added to the radically polymerizable compound and the photoradical initiator at a ratio of 10: 1 to make the total amount the same. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 16.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 2.3 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 11.35 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 16 to obtain a heat-sensitive recorder.

(Example 18)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
YELLOW 435, which is an electron-donating dye precursor of the oil phase A solution in Example 17, is added to 15 parts, SR368, which is a radically polymerizable compound, is added to 54.5 parts, and TPO, which is a photoradical polymerization initiator, is added to 5.5 parts. changed. That is, the increase in the electron-donating dye precursor was reduced by a ratio of 10: 1 to the polymerizable compound and the photoradical initiator to make the total amount the same. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 17.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 11.4 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 4.91 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

(Example 19)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
YELLOW 435, which is an electron-donating dye precursor of the oil phase A solution in Example 18, is added to 18 parts, SR368, which is a radically polymerizable compound, is added to 51.8 parts, and TPO, which is a photoradical polymerization initiator, is added to 5.2 parts. changed. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 18.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 13.6 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 4.64 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 18 to obtain a heat-sensitive recorder.

(Example 20)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
In Example 19, YELLOW 435, which is an electron-donating dye precursor of the oil phase A solution, was added to 25 parts, SR368, which is a radically polymerizable compound, was added to 45.4 parts, and TPO, which was a photoradical polymerization initiator, was added to 4.5 parts. changed. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 19.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 18.9 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 4.27 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 19 to obtain a thermal recorder.

(Example 21)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
In Example 20, YELLOW 435, which is an electron-donating dye precursor of the oil phase A solution, is added to 2 parts, SR368, which is a radically polymerizable compound, is added to 66.4 parts, and TPO, which is a photoradical polymerization initiator, is added to 6.6 parts. changed. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 20.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 1.5 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 15.37 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 20 to obtain a thermal recorder.

(Example 22)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
In Example 21, 25 parts of YELLOW 435, which is an electron-donating dye precursor of the oil phase A solution, 59.1 parts of SR368, which is a radically polymerizable compound, and 5.9 parts of TPO, which is a photoradical polymerization initiator. The amount of D110N, which is a polymerizable monomer of the resin constituting the shell portion of the microcapsules, was changed to 13.3 parts, and the amount of methyl ethyl ketone was changed to 116.7 parts. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 21.

[Formation of thermal color layer]
After mixing 13.3 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 18.9 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying is 4.23 g / m ² . It was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm so as to be. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 21 to obtain a thermal recorder.

(Example 23)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
65.5 parts of SR368, which is a polymerizable compound of the oil phase A solution in Example 22, 6.5 parts of TPO, which is a photoradical polymerization initiator, and a polymerizable monomer of the resin constituting the shell part of the microcapsules. D110N was changed to 4.0 parts and methyl ethyl ketone was changed to 119.0 parts. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 22.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 18.9 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 4.21 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 22 to obtain a thermal recorder.

(Example 24)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
66.4 parts of SR368, which is a polymerizable compound of the oil phase A solution in Example 23, 6.6 parts of TPO, which is a photoradical polymerization initiator, and a polymerizable monomer of the resin constituting the shell part of the microcapsules. D110N was changed to 2.7 parts and methyl ethyl ketone was changed to 119.3 parts. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 23.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 18.9 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 4.20 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 23 to obtain a thermal recording body.

(Example 25)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
31.8 parts of SR368, which is a polymerizable compound of the oil phase A solution in Example 24, 3.2 parts of TPO, which is a photoradical polymerization initiator, and a polymerizable monomer of the resin constituting the shell part of the microcapsules. Changed D110N to 53.3 copies. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 24.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 18.9 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 4.31 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 24 to obtain a thermal recorder.

(Example 26)
As the polymerizable monomer of the resin constituting the shell portion of the microcapsules of the oil phase A solution in Example 25, 40 parts of a melamine-formalin initial polymer (Sumirez Resin 513 (manufactured by Sumitomo Chemical Co., Ltd.)) and 120.0 of methyl ethyl ketone were added. I changed to the department. Except for this, a heat-sensitive recorder was obtained in the same manner as in Example 25.

(Example 27)
A heat-sensitive recorder was obtained in the same manner as in Example 26, except that a mixture of SR368 and U-15HA having a mass ratio of 1: 1 was used instead of SR368 as the radically polymerizable compound of the oil phase A solution.

(Example 28)
Instead of TPO, which is the photoradical polymerization initiator of the oil phase A solution in Example 26, the α-hydroxyketone type photopolymerization initiator (Omnirad 184, manufactured by iGM Resin) was changed. Except for this, a heat-sensitive recorder was obtained in the same manner as in Example 26.

(Example 29)
Instead of TPO, which is the photoradical polymerization initiator of the oil phase A solution in Example 26, the α-aminoalkylphenone type photopolymerization initiator (Omnirad 369, manufactured by iGM Resin) was changed. Except for this, a heat-sensitive recorder was obtained in the same manner as in Example 26.

(Example 30)
Instead of TPO, which is the photoradical polymerization initiator of the oil phase A solution in Example 26, a benzophenone-type photopolymerization initiator (Omnirad EMK, manufactured by iGM Resin) was used. Except for this, a heat-sensitive recorder was obtained in the same manner as in Example 26.

(Example 31)
Instead of TPO, which is the photoradical polymerization initiator of the oil phase A solution in Example 26, it was changed to benzoin butyl ether. Except for this, a heat-sensitive recorder was obtained in the same manner as in Example 26.

(Example 32)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
YELLOW 435, which is an electron-donating dye precursor of the oil phase A solution in Example 26, was changed to 12.5 parts, and 12.5 parts of dibutyl phthalate (boiling point: 340 ° C.), which is a high boiling point organic solvent, was added. .. Except for this, an electron-donating dye precursor-containing microcapsule particle dispersion was obtained in the same manner as in Example 26.

[Formation of thermal color layer]
After mixing 10 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 9.5 parts of the electron-accepting compound-containing particle dispersion [C solution], the coating amount after drying becomes 5.10 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of YELLOW 435 was 0.20 g / m ² , and the coating amount of TGSH (H) was 3.0 g / m ² .

Subsequent [preparation of kaolin dispersion (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 26 to obtain a thermal recorder.

(Comparative Example 1)
A heat-sensitive recorder was obtained in the same manner as in Example 26, except that the precursor of the shell portion of the microcapsules of the oil phase A solution was not used.

(Comparative Example 2)
A heat-sensitive recorder was obtained in the same manner as in Example 26, except that the photoradical polymerization initiator of the oil phase A solution was not used.

(Comparative Example 3)
As the photoradical polymerization initiator of the oil phase A solution in Example 26, a mixture of 1-methylpropylphenylphenylmethane and 1- (1-methylpropylphenyl) -2-phenylethane instead of SR368 (manufactured by Nippon Petrochemical). , Nisseki Hysol SAS-310) was used. Except for this, a heat-sensitive recorder was obtained in the same manner as in Example 26.

(Comparative Example 4)
The following materials were mixed and dissolved to prepare a [oil phase D] solution.
[Oil phase D] Liquid: Composition containing electron-accepting compound-Electron-accepting compound (2,2'-diallyl-4,4'-sulfonyldiphenol (TGSH (H), Nippon Kayaku))
8 parts ・ Radical polymerizable compound (Tris (2-hydroxyethyl) isocyanurate triacrylate (SR368, manufactured by Sartmer Co., Ltd.)) 60.9 parts ・ Photoradical polymerization initiator (Omnirad TPO, manufactured by iGM Resin)
6.1 parts ・ 120 parts of methyl ethyl ketone ・ Polymerizable monomer of the resin constituting the shell part of the microcapsule (Melamine-formalin initial polymer (Sumirez Resin 513, manufactured by Sumitomo Chemical Co., Ltd.))
30 copies

[Preparation of microcapsule particle dispersion containing electron-accepting compound]
After mixing 80 parts of the [oil phase D] liquid and 100 parts of the [water phase B] liquid, they were emulsified using an ultrasonic homogenizer (UH-600S, manufactured by SMT). Then, after removing ethyl acetate under reduced pressure using a rotary evaporator, the same amount of water as the removed amount was added, the temperature was raised to 70 ° C. with stirring, the encapsulation reaction was carried out for 2 hours, and the microcapsule particle dispersion was carried out. Got The particle size (D50) of the particles in the electron-donating dye precursor-containing microcapsule particle dispersion measured using a particle size distribution measuring device (Nanotrack, manufactured by Microtrac) was 500 nm.
[E] Liquid: Electron-donating dye precursor-containing particle dispersion liquid

After mixing the following materials, they were pulverized and dispersed using a bead mill to obtain an electron-accepting compound-containing particle dispersion [E].
-Electron-donating dye precursor 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzeneamine (YELLOW435, manufactured by Fukui Yamada Chemical Industry Co., Ltd.)
40 parts, dispersant (EFKA7710, manufactured by BASF) 4 parts, 56 parts of water

[Formation of thermal color layer]
After mixing 10 parts of the electron-accepting compound-containing microcapsule particle dispersion and 0.08 part of the electron-donating dye precursor-containing particle dispersion [E solution], the coating amount after drying becomes 15.7 g / m ² . As described above, it was applied to a synthetic paper (Yupo, manufactured by YUPO) having a thickness of 130 μm. Then, it was dried to form a heat-sensitive color-developing layer. The coating amount of TGSH, which is an electron-accepting compound, was 3.0 g / m ² , and the coating amount of YELLOW 435, which is an electron-donating dye precursor, was 0.2 g / m ² .

Subsequently, [preparation of kaolin dispersion liquid (solution C)] and [formation of protective layer] were carried out in the same manner as in Example 26 to obtain a heat-sensitive recorder.

Table 1 shows the constituent materials of the heat-sensitive color-developing layer of the heat-sensitive recording materials used in Examples 1 to 27 and Comparative Examples 1 to 4 and their contents. Further, the difference between the SP value of the polymerizable monomer of the resin constituting the shell portion and the SP value of the radically polymerizable compound, the difference in the SP value of the electron donating dye precursor and the radically polymerizable compound, and the radically polymerizable compound. The state at 25 ° C. is shown in Table 2. The SP value of SumirezResin513, which is a polymerizable monomer of the resin constituting the shell portion used in Examples 26 and 27 and Comparative Examples 2 to 4, was unknown. Therefore, the difference in SP value between Examples 26 and 27 and Comparative Examples 2 to 4 in Table 2 ((SP value of the polymerizable monomer of the resin constituting the shell portion)-(SP value of the radically polymerizable compound)). The value was not stated in the column of.

<Evaluation (1)>
(Preservation (skin fog))
Using a reflection densitometer (trade name "Xrite530", manufactured by Sakata Inx Engineering), before storage (on the day of production), after storage in a 50 ° C incubator for 1 month, and in a 50 ° C incubator for 3 months. The optical reflection density of the heat-sensitive recorder after storage was measured. The results are shown in Table 3.

<Evaluation (2)>
(Color development)
Using a thermal head (KPE type, manufactured by Kyocera), the applied power and pulse width were set so that the recording energy per unit area was 150 mJ / mm ² , and an image of 2 cm × 2 cm was formed on the heat-sensitive recorder. The optical reflection density of the image formed by using a reflection densitometer (trade name "Xrite530", manufactured by Sakata Inx Engineering) was measured. The results are shown in Table 3.

<Evaluation (3)>
(Light fixability (color development in non-image area))
An ultraviolet irradiation device (GC77 (irradiation wavelength: 365 nm), manufactured by HAMAMATU) equipped with a linear irradiation type UV-LED was used for the heat-sensitive recorder, and ultraviolet rays were irradiated once at a conveyor speed of 100 m / min. Separately, the integrated light intensity under the same conditions was measured with an ultraviolet integrated photometer (C9536-01, manufactured by HAMAMATSU) and found to be 100 mJ / cm ² . After that, using a thermal head (KPE type, manufactured by Kyocera) as in the above-mentioned evaluation of "color development", the applied power and pulse width are set so that the recording energy per unit area is 150 mJ / mm ² . , A 2 cm × 2 cm image was formed on the heat-sensitive recorder. Then, the optical reflection density (OD) of the image formed by using a reflection densitometer (trade name "Xrite530", manufactured by Sakata Inx Engineering) was measured. The evaluation results are shown in Table 3. Further, the heat-sensitive recorder on which the image was formed was stored in an environment of 50 ° C. for 3 days, and the presence or absence of color development in the non-image region before and after the storage for 3 days was visually observed to evaluate the fixing storage stability. As a result, no color development was observed in any of Examples 1 to 32, and good fixing and storage stability was obtained. In the heat-sensitive recorders used in Comparative Examples 1 to 4, color development in the non-image region had already been confirmed before storage, so the fixation storage stability was not evaluated.

Table 4 shows the SP value of the electron-donating dye precursor used in this example. In addition, Table 5 shows the melting point or the glass dislocation point of the SP value of the radically polymerizable compound used in this example. In addition, Table 6 shows the SP value of the precursor of the shell portion of the microcapsules used in this example.

(Comparative Example 5)
[Preparation of microcapsule particle dispersion containing electron-donating dye precursor]
The following materials were mixed and dissolved to prepare a [oil phase F] solution and a [aqueous phase G] solution.
[Oil phase F] Liquid-Electron donating dye precursor (1) having the structure represented by the following formula (1)
12.4 copies

・ Dicyclohexylphthalate 12.4 parts ・ Ethyl acetate 10.4 parts ・ Xylylene diisocyanate / trimethylolpropane adduct (Takenate D110N, manufactured by Mitsui Chemicals) 27 parts ・ Millionate MR200 (manufactured by Tosoh) 3 parts [Aquatic phase G]
・ Polybini alcohol 4.6 parts ・ Water 74 parts

The [oil phase F] solution and the [aqueous phase G] solution were mixed and emulsified and dispersed at 20 ° C. to obtain particles having an average particle size of 2.5 μm. Further, 100 g of water was added, and an encapsulation reaction was carried out at 60 ° C. for 2 hours to obtain an electron-donating dye precursor-containing microcapsule particle dispersion.

[Preparation of electron-accepting compound-containing dispersion]
The following materials were mixed and dissolved to prepare [oil phase G] liquid and [aqueous phase H].
[Oil phase G]
-Hydroxyethyl acrylate monophthalate 8 parts-2,2-dimethoxy-1,2-diphenylethane-1-one 0.8 parts-N-phenylglycine ethyl ester 0.2 parts-Ethyl acetate 3 parts [Aquatic phase H]
・ 7.5 mass% polyvinyl alcohol aqueous solution 9.6 parts ・ 2 mass% sodium dodecyl sulfate 1.6 parts

The [oil phase F] solution and the [aqueous phase G] solution were mixed and emulsified with a homogenizer (manufactured by Nippon Seiki Co., Ltd.) at 10,000 rpm for 5 minutes to obtain an electron-accepting compound-containing dispersion.

[Formation of thermal color layer]
After mixing 4 parts of the electron-donating dye precursor-containing microcapsule particle dispersion and 12 parts of the electron-accepting compound-containing dispersion, a synthetic paper having a thickness of 130 μm so that the coating amount after drying is 8 g / m ² . It was applied to YUPO, made by YUPO). Then, it was dried to form a heat-sensitive color-developing layer.

As in the other examples, when the storage stability was evaluated, the optical reflection concentration at 50 ° C. for 3 months was 0.75, and a heat-sensitive recorder with good storage stability could not be obtained.

(Comparative Example 6)
[Preparation of microcapsule particle dispersion containing diazonium salt]
The following materials were mixed and dissolved to prepare [oil phase I] and [aqueous phase J] liquids.
[Oil phase I]
・ 4-Morpholino-2,5-dibutoxybenzenediazonium (DH-300PF6 manufactured by Daitokemix) 3 parts ・ Isopropylbiphenyl 6 parts ・ Ethyl acetate 10 parts ・ Xylylene diisocyanate / trimethylolpropane adduct (Takenate D110N, manufactured by Mitsui Chemicals) Part 8 [Water Phase J]
・ N-octyl glucoside (ScuraphAG-8 manufactured by Nippon Fine Chemical Co., Ltd.)
0.2 parts, 6 parts by mass gelatin aqueous solution 64 parts

The [oil phase I] solution and the [aqueous phase J] solution were mixed and emulsified and dispersed at 8,000 rpm for 5 minutes using a homogenizer. After adding 20 parts by mass of water to the obtained emulsion, the temperature was raised to 60 ° C. at a heating rate of 1 ° C./min and an encapsulation reaction was carried out at 60 ° C. for 3 hours while stirring. Then, the liquid temperature was lowered to 35 ° C., 6.5 parts by mass of ion exchange resin Amberlite IRA67 (manufactured by Organo) and 13 parts by mass of ion exchange resin Amberlite IRC50 (manufactured by Organo) were added, and the mixture was further stirred for 1 hour. Then, the ion exchange resin was filtered to obtain a capsule solution. Moisture was removed from this liquid to obtain Capsule A. The average particle size (D50) of the capsule was 0.8 μm.

[Preparation of coloring capsules]
・ 80 parts of trimethylolpropane triacrylate ・ 3 parts of 2-hydroxynaphthalene-3-carboxy-2'-methylaniline (DaitoGrounderOL manufactured by Daitokemix) as a coupler ・ 0.5 part of squarylium as a wavelength sensitizing dye ・ Photopolymerization initiator Add 3 parts of 2,4-trichloromethyl (piperonyl) -6-triazine and heat at 50 ° C. for 10 minutes, then add 15 parts by mass of the above capsule A and 10 parts by mass of D-110N from which the solvent has been removed to make it uniform. Mixing gave a hydrophobic liquid component. Next, 180 parts by mass of a 6% by mass gelatin aqueous solution was prepared by adding 6 parts by mass of a 2% by mass sodium dodecylbenzene sulfonate solution. Then, the above-mentioned hydrophobic liquid component is added to the gelatin aqueous solution, and the mixture is emulsified and dispersed for 10 minutes using a homogenizer. A time encapsulation reaction was performed. As a result, a colored capsule slurry (capsule solid content content 40% by mass) liquid having photosensitivity around 650 nm was obtained. The average particle size of the capsule was 5 μm.

[Formation of thermal color layer]
20 parts by mass of the capsule slurry liquid of the coloring capsule, 5 parts by mass of a 20% aqueous solution of polyvinyl alcohol as a binder resin, 2 parts by mass of trimethylolpropane as a heat sensitizer, and 2 parts by mass of 4-dimethylaminopyridine are mixed. Then, it was used as a coating liquid and applied to a polyethylene-coated paper having a thickness of 200 μm by a bar coating method to obtain a heat-sensitive recording material having a heat-sensitive color-developing layer having a dry film thickness of 20 μm.

As in the other examples, when the storage stability was evaluated, the optical reflection concentration at 50 ° C. for 3 months was 0.73, and a heat-sensitive recorder with good storage stability could not be obtained.

From the results of Comparative Examples 5 and 6, when a heat-sensitive recorder in which an electron-donating dye precursor, a radically polymerizable compound, and a photoradical polymerization initiator was encapsulated in microcapsules was used, heat-sensitive recording with good storage stability and photofixability was performed. You can see that it becomes a body.

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are attached in order to publicize the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2020-143832 submitted on August 27, 2020 and Japanese Patent Application No. 2021-135033 submitted on August 20, 2021. All of the contents are incorporated here.

Claims

A heat-sensitive recorder provided with a heat-sensitive color-developing layer containing an electron-donating dye precursor, an electron-accepting compound, a radically polymerizable compound, a photoradical polymerization initiator, and microcapsules.
A heat-sensitive recorder characterized in that the microcapsules are contained in the heat-sensitive color-developing layer in a state of containing the radical-polymerizable compound, the electron-donating dye precursor, and the photo-radical polymerization initiator.
The heat-sensitive recording body according to claim 1, wherein the microcapsule has a core portion and a shell portion.
The heat-sensitive recording body according to claim 2, wherein the shell portion contains polyurea or polyurethane.
The heat-sensitive recorder according to claim 2 or 3, wherein the content of the shell portion is 3% by mass or more and 25% by mass or less based on the total mass of the microcapsules.
The heat-sensitive recorder according to any one of claims 2 to 4, wherein the content of the electron-donating dye precursor is 3% by mass or more and 18% by mass or less based on the total mass of the microcapsules.
The heat-sensitive recorder according to any one of claims 2 to 4, wherein the content of the electron-donating dye precursor is 3% by mass or more and 15% by mass or less based on the total mass of the microcapsules.
The SP value of the polymerizable monomer of the resin constituting the shell portion and the SP value of the radically polymerizable compound are
(SP value of radically polymerizable compound) <(SP value of polymerizable monomer of resin constituting shell)
The heat-sensitive recorder according to any one of claims 2 to 6, which satisfies the relationship of the above.
The SP value of the polymerizable monomer of the resin constituting the shell portion and the SP value of the radically polymerizable compound are
(SP value of radically polymerizable compound) + 1 <(SP value of polymerizable monomer of resin constituting shell)
The heat-sensitive recording body according to any one of claims 2 to 6, wherein the relationship is satisfied.
The SP value of the radically polymerizable compound and the SP value of the electron donating dye precursor are
(SP value of radically polymerizable compound) -2 <(SP value of electron donating dye precursor) <(SP value of radically polymerizable compound) +2
The heat-sensitive recorder according to any one of claims 1 to 8, which satisfies the relationship of.
The heat-sensitive recording according to any one of claims 1 to 9, wherein the photoradical polymerization initiator is an α-hydroxyketone compound, an α-aminoalkylphenone compound, an oxime ester compound, an acylphosphine oxide compound, or a benzophenone compound. body.
The heat-sensitive recorder according to any one of claims 1 to 10, wherein the photoradical polymerization initiator is an oxime ester compound.
The heat-sensitive recorder according to any one of claims 1 to 11, wherein the radically polymerizable compound is a liquid at 25 ° C.
The invention according to any one of claims 1 to 12, wherein the content of the high boiling point solvent having a boiling point of 180 ° C. or higher in the microcapsules is 100% by mass or less based on the content of the electron donating dye precursor. Heat-sensitive recording body.
A step of forming an image by applying a heat pulse to the heat-sensitive recorder according to any one of claims 1 to 13 using a thermal head.
A step of irradiating the heat-sensitive recording body on which the image is formed with ultraviolet rays to fix the heat-sensitive color-developing layer, and a step of fixing the heat-sensitive color-developing layer.
An image forming method characterized by having.