JP2016147412A - Reversible thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermosensitive recording material which can print and erase an image having clear contrast, has less change in surface conditions due to repeated printing and erasure and causes little sticking of a work-up to a thermal head.SOLUTION: There is provided a reversible thermosensitive recording material which comprises: a reversible thermosensitive recording layer which contains a dye precursor which is usually colorless and light-colored and a reversible color developer for forming a relatively color-developed state and a color-faded state due to difference in heating temperature and/or cooling speed after heating on a support; and spherical silica in a protective layer in a reversible thermosensitive recording material in which the protective layer is formed on the reversible thermosensitive recording layer, wherein the spherical silica satisfies the following expression (1): 0.5≤Average particle diameter of spherical silica/Film thickness of protective layer≤4 (1).SELECTED DRAWING: None

Description

  The present invention relates to a reversible thermosensitive recording material whose color tone reversibly changes by controlling thermal energy.

  In recent years, a reversible thermosensitive recording material that can form a temporary image and erase the image when it is no longer needed attracts attention. As a reversible thermosensitive recording material, usually a colorless or light dye precursor and a reversible color developer (hereinafter referred to as reversible developer) that develops color by heating the dye precursor and re-heats it to decolorize it. Also known as colorants), thermal recording materials in which organic low molecular weight substances such as higher fatty acids are dispersed in resins such as vinyl chloride-vinyl acetate, and thermal recordings in which two or more polymers having different refractive indexes are mixed. Materials etc. are known. In particular, a reversible thermosensitive recording material composed of a dye precursor and a reversible developer can form and erase recorded images with high contrast and high sensitivity many times. Have been widely used for the purpose of visualizing information in the card.

  A long-chain aliphatic hydrocarbon group is generally used as a heat-sensitive recording material using a colorless or light-colored dye precursor and a reversible developer that develops color by heating and re-colors the dye precursor by heating. It has been proposed to use a specific phenol compound possessed as a reversible developer (see, for example, Patent Document 1). In a reversible thermosensitive recording material using such a material, the contrast between color development and color erasure is high, and the color development state and color erasure state can be stably maintained at room temperature (for example, Patent Documents 2 and 3). reference).

  When such a reversible thermosensitive recording material is repeatedly printed and erased under practical conditions, the recording surface gradually deteriorates due to repeated heat and force (external force due to conveying force or platen pressure). Accordingly, studies have been made to provide a heat-resistant protective layer in order to improve printing durability, and it has been proposed to provide a protective layer made of one or more thermoplastic resins or thermosetting resins on the thermosensitive recording layer. (For example, refer to Patent Document 4). In addition, it has been proposed to provide a protective layer mainly composed of a curable resin by ultraviolet rays or electron beams (see, for example, Patent Documents 5 and 6). In such a protective layer, various pigments are added for the purpose of further improving the durability of repetition, and silica obtained by hydrophobizing porous synthetic silica having an average particle diameter of 1 to 10 μm is added. A method, a method of adding a scaly pigment mainly composed of silica, a method of adding a dry method silica having an average primary particle size of 5 nm or more and less than 25 nm, and the like are disclosed (for example, see Patent Documents 7 to 9). . However, in the method of adding these pigments, sufficient repeated durability cannot be obtained yet, and further improvement of repeated durability is demanded. Furthermore, there is still a problem that debris adheres to a heat source such as a thermal head due to repeated printing and erasing, and there is room for improvement from the viewpoint of head debris resistance.

Japanese Patent No. 3380277 Japanese Patent No. 311479 Japanese Patent No. 3678932 JP-A-6-8626 JP-A-6-344672 JP-A-8-11433 JP-A-8-175012 JP 2006-82299 A JP 2008-246737 A

  An object of the present invention is to provide a reversible thermosensitive recording material capable of printing and erasing an image having a clear contrast, having little change in surface state due to repeated printing and erasing, and having less residue on the thermal head. That is.

  An object of the present invention is to provide a reversible thermosensitive recording material provided with at least one reversible thermosensitive recording layer whose color tone is reversibly changed by controlling thermal energy and a protective layer on one side of a support, and the protective layer has a spherical shape. This is solved by a reversible thermosensitive recording material characterized by containing silica. That is, the present invention comprises the following (I) to (IV).

(I) A reversible developer that forms a normally colored or light-colored dye precursor and a relatively colored state and a decolored state due to a difference in heating temperature and / or cooling rate after heating on a support. And a reversible thermosensitive recording material comprising a protective layer provided on the reversible thermosensitive recording layer, the protective layer contains spherical silica, and the spherical silica is represented by the following formula ( It is a reversible thermosensitive recording material characterized by satisfying 1).
0.5 ≦ average particle diameter of spherical silica / film thickness of protective layer ≦ 4 Formula (1)

  (II) The spherical silica is more preferably porous spherical silica.

  (III) The protective layer is preferably composed mainly of an ultraviolet curable resin.

  (IV) The ultraviolet curable resin is preferably a dendritic branched compound having a (meth) acrylate group.

  According to the present invention, it is possible to provide a reversible thermosensitive recording material capable of printing and erasing an image having a clear contrast, having little change in surface state due to repeated printing and erasing, and having less residue on the thermal head. .

  The reversible thermosensitive recording material of the present invention will be described in detail below. The reversible thermosensitive recording material of the present invention has a reversible thermosensitive recording layer having a reversible thermosensitive recording layer whose color tone changes reversibly by controlling thermal energy, and a protective layer provided on the reversible thermosensitive recording layer. The thermal recording material is characterized in that the protective layer contains spherical silica.

  The silica according to the present invention has a spherical shape, and the shape is clearly different from normal amorphous silica having an indefinite shape. The shape of the spherical silica is preferably a true sphere, but may be a substantially spherical shape that is slightly deformed. When spherical silica is contained in the protective layer, in order to form a uniform uneven surface on the surface of the protective layer, compared with the case where amorphous silica whose contact point between the protective layer and the thermal head is indefinite is contained. As the friction coefficient is further reduced, it is possible to suppress excessive energy from being applied to the protective layer, to reduce the change in the surface state due to repeated printing and erasing, and to reduce the residue attached to the thermal head. Conceivable.

Further, the spherical silica may be any shape as long as it has a spherical shape, and may be any of nonporous non-hollow silica, porous non-hollow silica, porous hollow silica, etc., but the specific surface area of the spherical silica is 100 m ² / g or more. Porous non-hollow silica or porous hollow silica is preferable, and porous non-hollow silica having a specific surface area of spherical silica of 100 m ² / g or more and 800 m ² / g or less is more preferable. When the specific surface area is in this range, the spherical silica has an appropriate specific gravity. Therefore, when the spherical silica is applied in the protective layer coating solution, the spherical silica can be prevented from settling in the protective layer. It is considered that spherical silica in the protective layer is likely to be appropriately localized on the surface of the protective layer.

  The average particle diameter of such spherical silica is preferably 0.8 μm or more and 15 μm or less, and more preferably 1 μm or more and 10 μm or less. If the average particle diameter is larger than 15 μm, the contact point between the protective layer and the thermal head is excessively reduced in the actual coating process, which may cause a problem of a decrease in printing sensitivity. On the other hand, when the average particle size is smaller than 0.8 μm, the spherical silica embedded in the protective layer increases, and the desired repeated durability cannot be obtained. The pore volume of the spherical silica is preferably 0.5 ml / g or more and 2.5 ml / g or less. When the pore volume exceeds 2.5 ml / g, the compressive strength of the spherical silica is remarkably lowered, and the spherical silica cannot maintain its shape with repeated printing / erasing, and the change in the surface state of the protective layer becomes large.

  Moreover, the oil absorption of the spherical silica is preferably 400 ml / 100 g or less, more preferably 300 ml / 100 g or less. If the amount of oil absorption exceeds 400 ml / 100 g, it may cause problems such as contamination of oil and dust due to the usage environment in actual operation of the reversible thermosensitive recording material.

  Specific examples of spherical silica that can be used in the present invention include trade names: Sunsphere H-31, H-51, H-121, H-32, H-52, H-122, H-33, H-53, L-31, L-51, L-121, NP-30, NP-100 (manufactured by AGC S-Tech Co., Ltd.), trade names: Cyrossphere C-1504, C-1510 (Fuji Silysia Chemical ( Product name: God Ball E-2C, E-6C, E-16C, D-11C, D-25C, B-6C, B-25C, AF-6C, AF-16C, SF-16C, GT-3, G-6C (manufactured by Suzuki Yushi Kogyo Co., Ltd.), trade names: SILICA PEARL 20LB, 20MB, 20CG (manufactured by JGC Catalysts & Chemicals Co., Ltd.) can be mentioned, but are not limited thereto. .

  About these spherical silica, 0.1 to 30 mass% is preferable with respect to the resin component total mass in a protective layer, More preferably, it is 0.5 to 20 mass%.

  In general, spherical fillers include silica, glass, alumina, aluminum nitride, calcium carbonate and other inorganic spherical fillers; polystyrene polymer, polyethylene polymer, polypropylene polymer, urea-formaldehyde polymer, silicone polymer, polymethyl methacrylate acrylate Organic spherical fillers such as (PMMA) polymers, melamine-formaldehyde polymers, polyurethane polymers and the like are mentioned. From the viewpoint of thermal stability (heat resistance) against a heat source such as a thermal head, inorganic spherical fillers are preferable, and spherical silica is particularly preferable. Used.

  In addition, as a resin used for the protective layer according to the present invention, a curable resin such as a thermosetting resin, an electron beam curable resin, or an ultraviolet curable resin may be a main component for the purpose of enhancing durability during repeated use. Particularly, an electron beam curable resin and an ultraviolet curable resin are preferable, and an ultraviolet curable resin is more preferable.

  Examples of the ultraviolet curable resin suitably used in the present invention include urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, polyether (meth) acrylate, vinyl, and unsaturated polyester. Examples of such oligomers include monomers such as various monofunctional and polyfunctional (meth) acrylates, vinyl esters, ethylene derivatives, and allyl compounds.

  These monomers and oligomers used in combination as needed may be used singly or in combination of two or more.

Urethane (meth) acrylate oligomers are obtained, for example, by reacting diisocyanates, polyols, and hydroxy (meth) acrylates, and acryloyl groups (CH ₂ ═CHCO—) or methacryloyl groups as functional groups in the molecule. (CH ₂ = C (CH ₃ ) CO-) and a urethane bond (-NHCOO-).

  Specific examples of diisocyanates include hexamethylene diisocyanate [HDI], isophorone diisocyanate [IPDI], methylenebis (4-cyclohexylisocyanate) [HMDI], trimethylhexamethylene diisocyanate [TMHMDI], tolylene diisocyanate [TDI], 4 4,4'-diphenylmethane diisocyanate [MDI], xylylene diisocyanate [XDI] and the like.

  Specific examples of the polyols include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, and the like. Specific examples of hydroxy (meth) acrylates used for the synthesis of urethane (meth) acrylate include 2-hydroxyethyl acrylate [HEA], 2-hydroxyethyl methacrylate [HEMA], and 2-hydroxypropyl acrylate [HPA]. Glycidol dimethacrylate [GDMA], pentaerythritol triacrylate [PETA], polycaprolactone-modified 2-hydroxyethyl (meth) acrylate, and the like.

  The epoxy (meth) acrylate oligomer is synthesized by a reaction between an epoxy compound such as epichlorohydrin and (meth) acrylic acid. Specific examples of the epoxy (meth) acrylate include bisphenol A type epoxy (meth) acrylate synthesized by the reaction of a reaction product of bisphenol A and epichlorohydrin with (meth) acrylic acid, and the reaction of bisphenol S with epichlorohydrin. Bisphenol S type epoxy (meth) acrylate synthesized by the reaction of the product with (meth) acrylic acid, Bisphenol F type epoxy (meth) synthesized by the reaction of the reaction product of bisphenol F with epichlorohydrin and (meth) acrylic acid ) Phenol novolac type epoxy (meth) acrylate synthesized by the reaction of a reaction product of acrylate, phenol novolac and epichlorohydrin and (meth) acrylic acid.

  Specific examples of the polyester (meth) acrylate oligomer include polyester (meth) acrylate composed of phthalic anhydride, propylene glycol and (meth) acrylic acid, adipic acid, 1,6-hexanediol and (meth) acrylic. Examples include polyester (meth) acrylate composed of acid, polyester (meth) acrylate composed of trimellitic acid, diethylene glycol, and (meth) acrylic acid.

Polyether (meth) acrylate oligomers are prepared by reacting a polyol such as 1,2,6-hexanetriol with ethylene oxide or propylene oxide in the presence of a basic or acidic catalyst (BF ₃ , NaOH), and then Synthesize | combined by making the obtained polyether and (meth) acrylic acid react.

  Specific examples of (meth) acrylate monomers include acrylate, methacrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and neopentyl glycol di (meth) acrylate. 2- (2-ethoxyethoxy) ethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1, 3-butylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol Ruhekisa (meth) acrylate (DPH (M) A), hydroxypivalic acid neopentyl glycol di (meth) acrylate.

  As the ultraviolet curable resin suitably used in the present invention, a dendritic branched compound having a (meth) acrylate group is particularly preferably used. The dendritic branched compound is a compound branched in a dendritic form, and since it can have many (meth) acrylate groups at the molecular end due to the dendritic form, it increases the density of (meth) acrylate groups, It increases the probability of adjacent (meth) acrylate groups and promotes curing during UV irradiation. Since the curing reaction progresses in a short time with high reactivity, it is possible to form a hard layer without being affected by oxygen inhibition during UV curing, and to improve adhesion by suppressing cure shrinkage be able to. As long as it is a dendritic branched compound having a polymerizable functional group such as acryloyloxy group, methacryloyloxy group, acryloyl group, methacryloyl group at the molecular end, it may be a monomer or an oligomer, and is not particularly limited. A dendritic oligomer having a hyperbranched structure in the molecule or a dendritic oligomer having a dendrimer structure in the molecule is preferable, and one kind may be used alone, or two or more kinds may be used in combination.

  Specific examples of dendritic oligomers having a dendrimer structure in the molecule that can be used in the present invention include trade names: Biscote # 1000, Biscote, whose main component is a multi-branched (dendrimer-type) polyester acrylate having an acrylate group at the terminal. # 1020 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) can be mentioned, but is not limited thereto. The biscoat # 1000 and biscoat # 1020 are mainly composed of a multi-branched (dendrimer type) polyester acrylate having an acrylate group at the terminal.

  Specific examples of dendritic oligomers having a hyperbranched structure in the molecule that can be used in the present invention include trade names: STAR-501 (SIRIUS-501, SUBARU-501) (manufactured by Osaka Organic Chemical Industry Co., Ltd.). Can be mentioned. This STAR-501 is mainly composed of a multi-branched (dipentaerythritol hexaacrylate (DPHA) linked) polyacrylate having dipentaerythritol as a core and an acrylate group at the terminal.

  Specific examples of the dendritic oligomer having a hyperbranched structure in the molecule that can be used in the present invention include trade names: CN2300, CN2301, CN2302, CN2303, and CN2304 (manufactured by SARTOMER). The CN2300, CN2301, CN2302, CN2303, and CN2304 are mainly composed of a multi-branched (hyperbranched) polyester acrylate having an acrylate group at the terminal.

  When the protective layer according to the present invention is cured using ultraviolet rays, a photopolymerization initiator or a photopolymerization accelerator can be used. Photopolymerization initiators can be broadly classified into radical reaction types and ion reaction types. Furthermore, radical reaction types are classified into photocleavage types and hydrogen abstraction types. Examples of photopolymerization initiators include benzoin photopolymerization initiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzyldimethyl ketal (also known as 2,2-dimethoxy-2-phenyl) Acetophenone), 2,2-diethoxyacetophenone, 4'-phenoxy-2,2-dichloroacetophenone, 4'-t-butyl-2,2-dichloroacetophenone, 4'-t-butyl-2,2,2- Trichloroacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl-1-propanone, 1- (4-dodecylphenyl)- 2-hydroxy-2-methyl-1-propanone, 1 [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propanone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino- Acetophenone-based photopolymerization initiators such as 1-propanone; benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, 4-hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3, Benzophenone-based photopolymerization initiators such as 3'-dimethyl-4-methoxybenzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2-isopropylthioxanthone, 2,4-dic Thioxanthone photopolymerization initiators such as rothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone; diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, bis (2,4,6-trimethylbenzoyl) Examples thereof include, but are not limited to, acylphosphine oxide photopolymerization initiators such as phenylphosphine oxide. A photoinitiator is used individually or in mixture of 2 or more types.

  Further, as the photopolymerization accelerator, those having an effect of improving the curing rate with respect to a hydrogen abstraction type photopolymerization initiator such as benzophenone or thioxanthone are preferable. For example, aromatic tertiary amines and fats are used. There are those based on the group amines. Specific examples include p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, and the like. These photopolymerization accelerators are used alone or in admixture of two or more.

  The addition amount of these photopolymerization initiator and photopolymerization accelerator is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 10% by mass with respect to the total mass of the resin component of the protective layer. % Or less.

  The method for forming the protective layer in the present invention may be any method as long as it can be applied to the reversible thermosensitive recording layer or the like, but a mixture of spherical silica and resin is applied to the reversible thermosensitive recording layer and heated. dry. As the coating method of the protective layer resin mixture, conventional coating methods such as roll coating using gravure cylinder, doctor knife method, air knife / nozzle coating method, bar coating method, spray coating method, dip coating method, etc. Methods can be used, and these methods may be combined.

  When the protective layer is formed by the above-described coating method, as a method for producing a protective layer resin mixed solution for coating, for example, (1) spherical silica is added and mixed in a solution obtained by dissolving a resin in a solvent, and stirred. (2) After adding spherical silica to the solvent, the resin or resin is dissolved in the solvent in the dispersed liquid using the stirring device or the dispersing device. And a method of adding and mixing the resin solution.

  The stirrer or dispersion device for forming the protective layer resin mixture is not particularly limited as long as it is a normal stirrer or dispersion device, and these can be used to uniformly disperse spherical silica in the dispersion. From the standpoint of obtaining a protective layer resin mixture that is stable to the extent that the shape of the spherical silica is not crushed, it is preferable to use a high-speed stirrer such as a homogenizer or a homomixer.

  In the protective layer according to the present invention, a pigment can be used in the protective layer for the purpose of improving the heat resistance and repeated durability of the resin. As the pigment, organic or inorganic pigments are used alone or in combination. Examples of organic pigments include silicone pigments, fluorine pigments, acrylic pigments, polyurethane pigments, polyamide pigments, epoxy resin pigments, thermosetting resin hollow pigments, and polyethylene waxes. Examples of inorganic pigments include silicon, aluminum, zinc, calcium, magnesium, barium, zirconium, tin, cerium, antimony, titanium, indium, carbonates, oxides, hydroxides, sulfates, etc .; talc, zeolite, kaolin, Examples include calcined kaolin and clay. Inorganic pigments are preferably used from the viewpoints of heat resistance and repeated durability.

  The thickness of the protective layer according to the present invention is preferably in the range of 0.2 to 10 μm, more preferably 0.5 to 5 μm. When the film thickness exceeds 10 μm, not only the effect is saturated, but also the sensitivity of the reversible thermosensitive recording layer tends to decrease. When the film thickness is smaller than 0.2 μm, desired repeated durability cannot be obtained, and the surface of the coating film is easily damaged.

  Here, the film thickness of the protective layer refers to the film thickness of the resin of the protective layer, excluding particles such as the spherical silica. For example, the protective layer is formed using a protective layer coating solution containing spherical silica. When formed, it can be the film thickness of the resin in the region where no spherical silica is present. The film thickness can be measured by observing the laminated section using a scanning electron microscope. The film thickness of the protective layer refers to the average film thickness of the protective layer, preferably the average of five or more film thicknesses, and more preferably the average of ten or more film thicknesses.

In this invention, the film thickness of the said protective layer and the average particle diameter of the spherical silica contained in a protective layer satisfy | fill following formula (1).
0.5 ≦ average particle diameter of spherical silica / film thickness of protective layer ≦ 4 Formula (1)

  The value of the average particle diameter of the spherical silica with respect to the film thickness of the protective layer is not particularly limited as long as it is 0.5 to 4, and can be appropriately selected according to the purpose. If the value is less than 0.5, desired repeated durability cannot be obtained, and if it exceeds 4, spherical silica may fall off the protective layer. The value is more preferably from 0.5 to 3, and particularly preferably from 0.8 to 2, as the range in which the change in the surface state due to repeated printing / erasing is small and the residue attached to the thermal head is less likely to occur.

  Examples of the support according to the present invention include paper, non-woven fabric / woven fabric / knitted fabric, plastic film, resin-coated paper, synthetic paper, metal plate, metal foil, glass, quartz glass, aluminum oxide, silicon oxide, and the like. A composite obtained by combining these can be arbitrarily used depending on the purpose. Examples of the plastic film that can be used in the present invention include polyester film, polyolefin film, polyvinyl alcohol film, polyvinyl chloride film, nylon film, polystyrene film, polyvinylidene chloride film, ethylene-vinyl acetate copolymer film, ethylene-vinyl. Examples include alcohol copolymer films, fluororesin films, silicone resin films, polyimide films, aromatic polyamide films, acrylic resin films, and polycarbonate films. A polyester film is preferable in terms of mechanical strength, smoothness, water resistance, solvent resistance, and heat resistance. These plastic films may be used singly or may be used by laminating two or more of one or more kinds of films by an appropriate method.

  Examples of the polyester film include polyethylene terephthalate (PET), polybutylene terephthalate, poly-1,4-cyclohexanedimethylene terephthalate, polyxylylene terephthalate, polyethylene isophthalate, polyethylene-2,6-naphthalate (PEN). It is done. Preferred polyester films include PET films or PEN films that are excellent in toughness, heat resistance, chemical resistance, dimensional stability, transparency, and electrical insulation.

  The support may be opaque, translucent or transparent. In order to make the background appear white or other specific colors, a white pigment, a colored dye pigment, or air bubbles may be included in the support or on the surface. When the affinity is low when a layer such as a reversible thermosensitive recording layer is provided on the support by coating or bonding, the support is obtained by corona discharge treatment, oxidation reaction treatment (chromic acid, etc.), etching treatment, easy adhesion treatment, etc. A modification treatment may be performed on the surface. There is no restriction | limiting in particular about a shape, a magnitude | size, etc. as a support body concerning this invention. Examples of the shape include a flat plate shape and a roll shape. The size can be appropriately selected according to the use of the reversible thermosensitive recording material.

  The thickness of the support according to the present invention can be appropriately selected according to the use of the reversible thermosensitive recording material, and is not particularly limited, but is preferably 10 μm to 2 mm, and more preferably 20 μm to 1 mm. Used.

  The reversible thermosensitive recording layer according to the present invention uses a material whose color tone reversibly changes by controlling thermal energy. For example, as a heat-sensitive recording material capable of repeating image recording and erasing, a reversible developer that imparts a reversible color tone change by heating to the dye precursor is used to control image formation and erasure by controlling thermal energy. Possible reversible thermosensitive recording materials. Further, these reversible thermosensitive recording layers may be formed by stacking a plurality of reversible thermosensitive recording layers having different colors. Among these, a reversible thermosensitive recording layer containing a dye precursor and a reversible developer is preferable because of excellent image visibility.

  Examples of the normally colorless to light-colored dye precursors according to the present invention include electron-donating color-forming compounds, and known dye precursors generally used for pressure-sensitive recording paper, heat-sensitive recording paper, etc. are appropriately selected depending on the purpose. You can choose. For example, a leuco dye or the like can be suitably used. As the leuco dye, a fluoran compound, an azaphthalide compound, a triphenylmethane (aza) phthalide compound, and an indolyl (aza) phthalide compound can be suitably used. The dye precursors may be used singly or in combination of two or more, and toning can also be performed by mixing dye precursors that develop colors in other colors. Hereinafter, although the specific example of a dye precursor is given, this invention is not limited to this.

  2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6- (di-n-pentylamino) fluorane, 2-anilino-3-methyl-6- (di-n-butyl) Amino) fluorane, 2-anilino-3-methyl-6- (di-n-amylamino) fluorane, 2-anilino-3-methyl-6- (isoamylamino) fluorane, 2-anilino-3-methyl-6- ( N-n-propyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-isobutyl- N-methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- ( -Sec-butyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N-isoamyl) -N-ethylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-N-methyl) Amino) fluorane, 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluorane.

  2- (m-trichloromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trichloromethyl) Anilino) -3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2- (2,4-dimethylanilino) -3-methyl-6-diethylaminofluorane, 2- (2,4 -Dimethylanilino) -3-methyl-6- (di-n-butylamino) fluorane, 2- (m-toluidino) -3-methyl-6-diethylaminofluorane, 2- (m-toluidino) -3- Methyl-6- (di-n-butylamino) fluorane, 2- (p-toluidino) -3-methyl-6-diethylaminofluorane, 2- (p-toluidino) -3- Tyl-6- (di-n-butylamino) fluorane, 2- (N-ethyl-p-toluidino) -3-methyl-6- (N-ethylanilino) fluorane, 2- (N-ethyl-p-toluidino) -3-methyl-6- (Nn-propyl-p-toluidino) fluorane, 2-anilino-6- (Nn-hexyl-N-ethylamino) fluorane, 2- (o-chloroanilino) -6 Diethylaminofluorane, 2- (o-chloroanilino) -6- (di-n-butylamino) fluorane, 2- (m-trifluoromethylanilino) -6-diethylaminofluorane, 2,3-dimethyl-6- Dimethylaminofluorane, 3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-chloro-6-diethylaminofluorane.

  2-bromo-6-diethylaminofluorane, 2-chloro-6- (di-n-propylamino) fluorane, 3-chloro-6-cyclohexylaminofluorane, 3-bromo-6-cyclohexylaminofluorane, 2- Chloro-6- (N-ethyl-N-isoamylamino) fluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2- (o-chloroanilino) ) -3-Chloro-6-cyclohexylaminofluorane, 2- (m-trifluoromethylanilino) -3-chloro-6-diethylaminofluorane, 2- (2,3-dichloroanilino) -3-chloro -6-diethylaminofluorane, 1,2-benzo-6-diethylaminofluorane, 3-diethylamino- - (m-trifluoromethyl) -6-fluoran.

  3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-Ethoxy-4-diethylaminophenyl) -7-azaphthalide, 3- (1-octyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4- Azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindole-3- Yl) -3- (2-methyl-4-diethylaminophenyl) -7-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethyl) Aminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- [4- (Nn-amyl-N-methylamino) phenyl] -4-azaphthalide, 3 -(1-Methyl-2-methylindol-3-yl) -3- (2-hexyloxy-4-diethylaminophenyl) -4-azaphthalide, 3,3-bis (2-ethoxy-4-diethylaminophenyl)- 4-Azaphthalide, 3,3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide.

  2- (p-acetylanilino) -6- (Nn-amyl-Nn-butylamino) fluorane, 2-benzylamino-6- (N-ethyl-p-toluidino) fluorane, 2-benzylamino -6- (N-methyl-2,4-dimethylanilino) fluorane, 2-benzylamino-6- (N-ethyl-2,4-dimethylanilino) fluorane, 2-benzylamino-6- (N- Methyl-p-toluidino) fluorane, 2-benzylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (p-methylbenzylamino) -6- (N-ethyl-p-toluidino) fluorane, 2 -(Α-Phenylethylamino) -6- (N-ethyl-p-toluidino) fluorane.

  2-methylamino-6- (N-methylanilino) fluorane, 2-methylamino-6- (N-ethylanilino) fluorane, 2-methylamino-6- (Nn-propylanilino) fluorane, 2-ethylamino -6- (N-methyl-p-toluidino) fluorane, 2-methylamino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-ethylamino-6- (N-ethyl-2, 4-dimethylanilino) fluorane, 2-dimethylamino-6- (N-methylanilino) fluorane, 2-dimethylamino-6- (N-ethylanilino) fluorane, 2-diethylamino-6- (N-methyl-p-toluidino ) Fluorane, 2-diethylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (di-n-propylamino)- - (N-methylanilino) fluoran, 2- (di -n- propylamino)-6-(N-ethylanilino) fluoran.

  2-amino-6- (N-methylanilino) fluorane, 2-amino-6- (N-ethylanilino) fluorane, 2-amino-6- (Nn-propylanilino) fluorane, 2-amino-6- ( N-methyl-p-toluidino) fluorane, 2-amino-6- (N-ethyl-p-toluidino) fluorane, 2-amino-6- (Nn-propyl-p-toluidino) fluorane, 2-amino- 6- (N-methyl-p-ethylanilino) fluorane, 2-amino-6- (N-ethyl-p-ethylanilino) fluorane, 2-amino-6- (Nn-propyl-p-ethylanilino) fluorane, 2 -Amino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-ethyl-2,4-dimethylanilino) fluorane, 2 Amino-6- (Nn-propyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-methyl-p-chloroanilino) fluorane, 2-amino-6- (N-ethyl-p -Chloroanilino) fluoran, 2-amino-6- (Nn-propyl-p-chloroanilino) fluorane, 1,2-benzo-6- (N-ethyl-N-isoamylamino) fluorane, 1,2-benzo- 6- (Di-n-butylamino) fluorane, 1,2-benzo-6- (N-methyl-N-cyclohexylamino) fluorane, 1,2-benzo-6- (N-ethyl-p-toluidino) fluorane .

  4,4'-bis (dimethylaminophenyl) benzhydrylbenzyl ether, N-chlorophenyl leucooramine, N-2,4,5-trichlorophenyl leucooramine, benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, 3 -Methylspirodinaphthopyrans, 3-ethylspirodinaphthopyrans, 3,3'-dichlorospirodinaphthopyrans, 3-benzylspirodinaphthopyrans, 3-methylnaphthyl (3-methoxybenzo) spiropyrans, 3-propylspiros Benzopyran.

  Multi-color reversible thermosensitive recording materials and full-color reversible thermosensitive recording materials can also be obtained by laminating layers having different color tones or arranging them on a plane. The dye precursor may be subjected to processing such as microencapsulation, resin coating, and composite particle formation with a resin.

  The reversible developer according to the present invention is an electron accepting compound, and is not particularly limited as long as it is a compound having a function of developing the dye precursor. Conventionally known reversible developers include organic phosphorus compounds, aliphatic carboxylic acid compounds, and phenol compounds. The reversible developer preferably used in the present invention is a phenol compound having a long-chain alkyl group from the viewpoint of color developability, decoloring property, image stability, and the like, and particularly represented by the following general formula (1). A compound is preferably used. Note that the present invention is not limited to this. The reversible developer according to the present invention may be used alone or in combination of two or more.

In the general formula (1), X ₁ and X ₂ may be the same or different from each other, and do not contain an oxygen atom, a sulfur atom, or a hydrocarbon atomic group at both ends —CO—, —NH—, Alternatively, it represents a divalent group having a —SO ₂ — bond as the minimum structural unit. R ₁ represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms. R ₂ represents a divalent hydrocarbon group having 1 to 20 carbon atoms. R ₃ represents a monovalent hydrocarbon group having 1 to 50 carbon atoms, preferably a hydrocarbon group having 6 to 36 carbon atoms. R ₁ and R ₂ mainly represent an alkylene group or an alkenylene group, and may contain an aromatic ring. R ₃ mainly represents an alkyl group or an alkenyl group. n represents an integer of 0 to 2, and R ₂ and X _{2 that} are repeated when n is ₂ may be the same or different.

X ₁ and X ₂ in the general formula (1) include a divalent group having a minimum constituent unit of —CO—, —NH—, or —SO ₂ — bond that does not contain a hydrocarbon group at both ends. Specific examples thereof include amide (-CONH-, -NHCO-), urea (-NHCONH-), diacylamine (-CONHCO-), diacylhydrazine (-CONHNHCO-), oxalic acid diamide (-NHCONCONH-), Acylurea (-CONHCONH-, -NHCONHCO-), Semicarbazide (-NHCONHNH-, -NHNHCONH-), Acyl semicarbazide (-CONHNHCONH-, -NHCONHNHCO-), 3-Acylcarbazate (-CONHNHCOO-, -OCONHNHCO-) ), sulfonamide (-NHSO ₂ -, - SO NH-), sulfonyl hydrazide _{(-SO 2 NHNHCO -, - CONHNHSO} 2 -) although groups such like, it is preferably an amide, urea, diacyl hydrazine, oxalic acid diamide.

  Specific examples of the reversible developer represented by the general formula (1) are given below, but the present invention is not limited thereto.

  Np-hydroxyphenyl-N'-octadecylurea, Np-hydroxyphenyl-N'-henicosylurea, Np-hydroxyphenyl-N'-docosylurea, Np-hydroxyphenyl-N'-pentacosyl Urea, Np-hydroxyphenyl-N'-hexacosyl urea, Np-hydroxyphenyl-N'-nonacosyl urea, Np-hydroxyphenyl-N'-triacontyl urea, Np-hydroxyphenyl-N ' -4-oxaoctadecylurea, Np-hydroxyphenyl-N'-12-thiatriacontylurea, N- [2- (p-hydroxyphenyl) ethyl] -N'-octadecylurea, N- [2- (P-hydroxyphenyl) ethyl] -N'-henicosylurea, N- [2- (p-hydroxyphenyl) ethyl ] -N'-docosyl urea, N- [2- (p-hydroxyphenyl) ethyl] -N'-heptacosyl urea, N- [2- (p-hydroxyphenyl) ethyl] -N'-hexacosyl urea, N- [2- (p-hydroxyphenyl) ethyl] -N'-triacontylurea, N- [2- (p-hydroxyphenyl) ethyl] -N'-4-oxaoctadecylurea, N- [2- (p-hydroxy) Phenyl) ethyl] -N'-12-thiatriacontyl urea.

  N- (p-hydroxyphenyl) docosanamide, N- (p-hydroxyphenyl) heptacosanamide, N- (p-hydroxyphenyl) hexacosanamide, N- (p-hydroxyphenyl) nonacosanamide, N- (p -Hydroxyphenyl) triacontanamid, N- (p-hydroxyphenyl) -12-thiatriacontanamid, N- [2- (p-hydroxyphenyl) ethyl] docosanamide, N- [2- (p-hydroxyphenyl) Ethyl] heptacosanamide, N- [2- (p-hydroxyphenyl) ethyl] hexacosanamide, N- [2- (p-hydroxyphenyl) ethyl] nonacosanamide, N- [2- (p-hydroxyphenyl) ) Ethyl] triacontanamid, N- [2- (p-hydroxyphenyl) ethyl ]-12-thia Tria near-end amide.

  N-docosyl-p-hydroxybenzamide, N-heptacosyl-p-hydroxybenzamide, N-hexacosyl-p-hydroxybenzamide, N-nonacosyl-p-hydroxybenzamide, N-triacontyl-p-hydroxybenzamide, N-4-oxa Octadecyl-p-hydroxybenzamide, N-docosyl- (p-hydroxyphenyl) acetamide, N-heptacosyl- (p-hydroxyphenyl) acetamide, N-hexacosyl- (p-hydroxyphenyl) acetamide, N-nonacosyl- (p -Hydroxyphenyl) acetamide, N-triacontyl- (p-hydroxyphenyl) acetamide, N-4-oxaoctadecyl- (p-hydroxyphenyl) acetamide, N-docosyl- [3- (p-hydride) Xylphenyl)] propionamide, N-heptacosyl- [3- (p-hydroxyphenyl)] propionamide, N-hexacosyl- [3- (p-hydroxyphenyl)] propionamide, N-nonacosyl- [3- (p- Hydroxyphenyl)] propionamide, N-triacontyl- [3- (p-hydroxyphenyl)] propionamide, N-4-oxaoctadecyl- [3- (p-hydroxyphenyl)] propionamide.

  N- (p-hydroxybenzoyl) -N'-octadecanohydrazide, N- (p-hydroxybenzoyl) -N'-docosanohydrazide, N- (p-hydroxybenzoyl) -N'-hexacosinohydrazide, N -(P-hydroxybenzoyl) -N'-triacontanohydrazide, N- [3- (p-hydroxyphenyl) propiono] -N'-octadecanohydrazide, N- [3- (p-hydroxyphenyl) propiono ] -N'-docosanohydrazide, N- [3- (p-hydroxyphenyl) propiono] -N'-hexacosinohydrazide, N- [3- (p-hydroxyphenyl) propiono] -N'-triacontano Hydrazide, N- [3- (p-hydroxyphenyl) propiono] -N'-12-thiatriacontanohydrazide.

  Furthermore, specific examples of the reversible developer according to the present invention include the following structural formulas (1-1) to (3-9), but the present invention is not limited thereto. Absent.

  The reversible developer represented by the general formula (1) used in the present invention may be used alone or in combination of two or more, and the reversible developer of the general formula (1) for the dye precursor The amount used is 5 to 5000 mass%, preferably 10 to 3000 mass%.

  In the reversible thermosensitive recording layer according to the present invention, a binder resin may be added to the reversible thermosensitive recording layer for the purpose of improving thermal and / or mechanical strength. Specific examples of the binder resin include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, (meth) acrylic acid amide- (meth) acrylic acid ester copolymer (Meth) acrylic acid amide- (meth) acrylic acid ester- (meth) acrylic acid terpolymer, alkali salt of styrene-maleic anhydride copolymer, alkali salt of ethylene-maleic anhydride copolymer , Polyvinyl acetate, polyurethane, poly (meth) acrylic acid ester, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl (meth) acrylate-butadiene copolymer, ethylene-vinyl acetate copolymer, ethylene -Salt Vinyl copolymers, polyvinyl chloride, ethylene - vinylidene chloride copolymer, polyvinylidene chloride, polycarbonates, polyvinyl butyral, and the like. The role of these binder resins is to keep the materials contained in the reversible thermosensitive recording layer uniformly dispersed without being displaced by heat application for image recording or image erasing. Therefore, it is preferable to use a resin having at least high heat resistance as the binder resin. When heat resistance, water resistance, and adhesiveness are required, a curable resin is particularly preferable.

  Examples of the curable resin include a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. When a thermosetting resin is applied, a liquid containing a crosslinking agent is applied and formed into a film, and then crosslinked by heat. Specific examples of thermosetting resins include epoxy resins, urea resins, xylene-formaldehyde resins, melamine resins, guanamine resins, phenol resins, phenoxy resins, saturated polyester resins, unsaturated polyester resins, and polyol resins. In addition, examples of the curing agent used in these thermosetting resins include organic acids, amines, isocyanates, epoxies, phenols, and the like. It only has to be selected. Among these, a crosslinked resin obtained by thermally curing a polyol compound with an isocyanate compound described in JP-A Nos. 10-230680 and 11-58963 is preferable.

  As oligomers / monomers used for electron beam curable resins or UV curable resins, there are many types of acrylic oligomers / monomers with excellent radiation curing properties, polyene-thiol oligomers / monomers, and photocationic polymerization type epoxy. Examples include oligomers and monomers. Examples of the acrylic monomer include a monofunctional monomer, a bifunctional monomer, and a polyfunctional monomer. A photopolymerization initiator and a photopolymerization accelerator are used particularly in the case of ultraviolet curing.

  Examples of the acrylic oligomer / monomer include polyester acrylate, polyether acrylate, epoxy acrylate, polyurethane acrylate, silicone acrylate, melamine acrylate, polybutadiene acrylate, and the like.

  In the reversible thermosensitive recording layer according to the present invention, a binder resin formed by a reaction between a polyol compound and an isocyanate compound, which are preferable binder resins, will be described. Examples of the polyol compound include poly (meth) acryl polyol, polyester polyol, polycarbonate polyol, polyester polycarbonate polyol, polyether polyol, alkyd polyol, caprolactone polyol, and silicone polyol.

  Poly (meth) acrylic polyol is a copolymer of acrylic acid, methacrylic acid, and esters thereof, which includes a hydroxyl group, and as a copolymer component containing a hydroxyl group, hydroxyethyl acrylate, methacrylic acid are included. Hydroxyethyl acid, hydroxypropyl acrylate, hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate, allyl alcohol and the like are used. Examples of copolymer components other than acrylic acid, methacrylic acid, and esters thereof include styrene, α-methylstyrene, vinyltoluene, acrylamide, methacrylamide and derivatives thereof, vinyl acetate, and maleic anhydride.

  Polyester polyol refers to a condensate of a polybasic acid and a polyhydric alcohol having a hydroxyl group. Polybasic acids used in these are phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid. , Aromatic polybasic acids such as trimesic acid, pyromellitic acid, naphthalenedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,7-dimethyldecanedioic acid, 3,8-dimethyldecanedioic acid, There are aliphatic polybasic acids such as dimer acid, and acid anhydrides obtained from these polybasic acids are also used.

  Polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, propanediol, neopentyl glycol, glycerin, trimethylolethane, trimethylolpropane, diglycerin, pentaerythritol, dipentaerythritol, di In addition to low molecular weight polyols such as acetone glycol and hexanetriol, high molecular weight polyols such as polyethylene glycol, polypropylene glycol and polybutylene glycol are also used. In addition to the polyester polyols obtained from these, hydroxycarboxylic acids, or condensates or ring-opening polymerizations thereof of cyclic lactones such as polybutyrolactone polyols, polycaprolactone polyols, and higher fatty acids in addition to the above polybasic acids and polyhydric alcohols. There are alkyd polyols obtained by condensation. The polyether polyol is a polymer having a main chain composed of an ether bond, and includes polyethylene glycol, polypropylene glycol, polybutylene glycol, and these branched esters.

  Examples of polyether polyols include ethylene oxide and / or propylene oxide adducts of polyhydric alcohols, polytetramethylene glycol, and the like. Examples of the silicone polyol include silicone oils having a siloxane bond in the molecule and a terminal hydroxyl group.

  In addition, fluorine-containing polyols such as hydroxyl-containing fluoroolefin, polyol hydroxyl-terminated polybutadiene, polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, polyurethane and the like can be used. Furthermore, low molecular weight polyols such as diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, pentaerythritol, 1,4-cyclohexanediol, 1,4-dihydroxybenzene, bisphenol A, bisphenol F, and other aliphatic and alicyclic rings Aromatic, aromatic polyhydric alcohols or polyhydric phenols or their condensates may be used as reactive diluents.

  As the polyol compound used in the present invention, poly (meth) acrylic polyol and polyester polyol are preferable from the comprehensive evaluation such as additive dispersibility, coating property, adhesiveness, heat resistance and film strength. The polyol compound used in the present invention may be used alone or in combination with one or more other polyol compounds having different polyol parts or other partial structures or different molecular weights.

  Further, poly (meth) acryl polyols and polyester polyols having a hydroxyl value of 80 (KOHmg / g) or more are preferably used, and particularly preferably 90 (KOHmg / g) or more and 600 (KOHmg / g) or less. Since the magnitude of the hydroxyl value affects the crosslink density, it affects the surface hardness, chemical resistance, durability, etc. of the coating film. Resins with a hydroxyl value of 80 (KOHmg / g) or more react with the polyisocyanate compound to form a binder resin with a high crosslink density, which improves the durability of the reversible thermosensitive recording layer when repeatedly printed and erased. preferable. If the hydroxyl value exceeds 600 (KOHmg / g), the flexibility may be reduced and the coating layer may break during processing.

  A well-known thing can be used as a polyisocyanate compound used for this invention. For example, aromatic aliphatic diisocyanates such as phenylene diisocyanate (PDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), hydrogenated TDI, water XDI, hydrogenated MDI, aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and their derivatives, polyol adducts, and trifunctional or more polyfunctional burette trimers In addition to isocyanate, various oligomers and polymers containing isocyanate may be mentioned. In the present invention, it is preferable to use xylylene diisocyanate or toluene isocyanate as the isocyanate compound because the printing density is improved, and it is more preferable to use xylylene diisocyanate having high background whiteness.

  The polyisocyanate compound used in the present invention may be used alone or in combination of two or more with respect to one or more polyol compounds. When using multiple types of polyisocyanate compound and polyol compound, the combination may be arbitrary.

  The mixture of the polyol compound and the polyisocyanate compound may be used as it is when the mixture is liquid, but it can also be diluted with a non-reactive solvent with the polyisocyanate compound. As the solvent that can be used, a solvent that dissolves the polyol compound and the polyisocyanate compound and disperses and dissolves the dye precursor and the reversible developer is preferable. Specifically, water; alcohols such as methanol, ethanol, n-propanol, 2-propanol, and n-butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; methyl acetate, ethyl acetate, and acetic acid Esters such as butyl, isobutyl acetate, isopropyl acetate, ethyl lactate, and ethylene carbonate, ethers such as diethyl ether, glycol dimethyl ether, glycol diethyl ether, dioxane, dioxolane, and tetrahydrofuran, aromatic carbonization such as benzene, toluene, xylene, and styrene Hydrogen: aliphatic hydrocarbons such as pentane, hexane, cyclohexane, etc .; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, chlorobenzene, dichloroben Halogenated hydrocarbons such as emissions; N, N- dimethylformamide, N, etc. amides such as N- dimethylacetamide can be used. Among them, it is preferable to use an organic solvent that does not have active hydrogen that is reactive with the polyisocyanate compound. Moreover, what is necessary is just to perform the crosslinking reaction of the said polyol compound and a polyisocyanate compound with reaction temperature 30-160 degreeC, and reaction time 0.1 minute-120 hours. Needless to say, a long time is required when the reaction temperature is low, and a short time is required at a high temperature.

  The amount of the binder resin used in the reversible thermosensitive recording layer according to the present invention is preferably such that the mass percentage of the binder resin relative to the total mass of the reversible thermosensitive recording layer is in the range of 35% to 65%. If it is larger than this range, the print density may be significantly reduced. On the other hand, if it is smaller than this range, the heat resistance and mechanical strength of the reversible thermosensitive recording layer may be reduced, the layer may be deformed, and the print density may be reduced. The mass percentage of the binder resin in the reversible thermosensitive recording layer is more preferably 40% to 60%, and particularly preferably 45% to 55%.

  In the reversible thermosensitive recording material of the present invention, the reversible thermosensitive recording layer comprises a compound having at least one group of amide, urethane, urea, diacylhydrazine, and oxalic acid diamide in the molecule as a decoloring accelerator. It is preferable to use a quaternary ammonium salt compound in combination. By using the decolorization accelerator in combination, an intermolecular interaction works between the decolorization accelerator and the reversible developer in the process of forming the erased state, and the erasing speed can be increased.

  As the decoloring accelerator used in the present invention, compounds represented by the following general formulas (4) to (11) are particularly preferable.

R ₄ —CONH ₂ —General formula (4)
R ₄ —NHCONH ₂ —General formula (5)
R ₄ —CONH—R ₅ ... General formula (6)
R ₄ —NHCONH—R ₅ General formula (7)
R ₄ —NHCOCONH—R ₅ —General formula (8)
R ₄ —CONHNHCO—R ₅ —General formula (9)
A-NHCONH-R ₄ ... General formula (10)
^{_{(R 4) 3 N + -R}} 5 Z - ··· formula (11)

However, in the general formula (4) ~ (11), R 4 and R ₅ are as defined, is a saturated or unsaturated hydrocarbon group of good 1 to 24 carbon atoms optionally substituted by one or more identical to each other Represents an optionally branched alkyl group, alkenyl group, aralkyl group or aryl group, and these groups may be substituted by an alkyl group, alkenyl group, hydroxy group, halogen atom, alkoxy group or the like. . Examples of R ₄ and R ₅ include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, dodecyl group, octadecyl group, behenyl group, allyl group, phenyl group, tolyl group, benzyl group and phenyl group. An ethyl group etc. are mentioned. A is a disubstituted acyclic amino group having a nitrogen atom directly bonded to the urea bond, or a nitrogen atom-containing 5- and 6-membered heterocyclic ring. In the case of a heterocyclic ring, the nitrogen atom in the ring is directly bonded to the urea bond. Are connected. When A is a heterocyclic ring, specific examples of the 5-membered ring include pyrrolidine ring, imidazolidine ring, thiazolidine ring, pyrrole ring, imidazole ring and pyrazole ring. Specific examples of the 6-membered ring include piperidine ring, Examples include a morpholine ring, a thiomorpholine ring, and a piperazine ring. Furthermore, the acyclic amino group and heterocyclic ring may be substituted with an alkyl group, an aralkyl group, an aryl group, a hydroxy group, or the like. Z represents an anion, and is halogen, substituted sulfonate, substituted phosphate, substituted borate, or substituted imide, preferably halogen or substituted sulfonate.

  The decoloring accelerators represented by the general formulas (4) to (11) may be used alone or in combination of two or more. The usage-amount with respect to a reversible developer is 0.1-100 mass%, Preferably it is 0.5-50 mass%, Most preferably, it is 1-20 mass%. If the amount used is less than 0.1% by mass, the decoloring promotion effect may not be exhibited, and if it exceeds 100% by mass, the print density may be lowered and the heat stability of the printed image may be lowered. .

  In the reversible thermosensitive recording layer according to the present invention, a heat-fusible substance may be used in combination in order to adjust the color development sensitivity and / or the decoloring temperature. As the heat-fusible substance, those having a melting point of 60 to 200 ° C. are preferable, and those having a melting point of 80 to 180 ° C. are particularly preferable. As the heat-fusible substance, a sensitizer used in general heat-sensitive recording paper can also be used. Examples of heat fusible substances include naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2-bis (3-methylphenoxy) ethane, 2, Polyether compounds such as 2'-bis (4-methoxyphenoxy) diethyl ether and bis (4-methoxyphenyl) ether, carbonic acid or oxalic acid such as diphenyl carbonate, dibenzyl oxalate, bis (p-methylbenzyl) oxalate And diester derivatives.

  The reversible thermosensitive recording layer according to the present invention further comprises an antioxidant such as a hindered phenol antioxidant, a phosphorus antioxidant, a sulfur antioxidant, vitamin A, vitamin for the purpose of improving light resistance and the like. Vitamins such as C and vitamin E, hindered amine light stabilizers, benzophenone UV absorbers, benzotriazole UV absorbers, triazine UV absorbers, benzoate UV absorbers, salicylate UV absorbers, cinnamate UV absorbers An ultraviolet absorber such as an agent may be added, and preferably a hindered phenol antioxidant, a benzotriazole ultraviolet absorber, or a triazine ultraviolet absorber is used. These ultraviolet absorbers and antioxidants may be used in combination as appropriate.

  As these, a polymer containing a monomer having a structural part that expresses each function as a component of polymerization, or a polymer obtained by grafting these structural parts on a polymer main chain can also be used. In addition, these antioxidants, light stabilizers, ultraviolet absorbers and the like may be used alone, or two or more of the same or different may be used in combination. When these antioxidants, light stabilizers, ultraviolet absorbers and the like are used in combination, the amount used with respect to the dye precursor is 0.1 to 200% by mass, preferably 0.5 to 100% by mass, particularly preferably 1 to 50%. % By mass. If the amount used is less than 0.1% by mass, the improvement effect may not be exhibited, and if it exceeds 200% by mass, the print density may be lowered and the heat stability of the printed image may be lowered.

  Examples of pigments that can be added to the reversible thermosensitive recording layer include, for example, carbonates such as aluminum, zinc, calcium, magnesium, barium, and titanium, oxides, hydroxides, sulfates, etc., and zeolite, silica, Inorganic pigments containing clays such as kaolin, calcined kaolin and talc, starch, styrene resin, polyolefin resin, urea-formalin resin, melamine resin, acrylic resin, paraffin, natural wax, synthetic wax and the like can be used. In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate can be used as a lubricant.

  The film thickness of the reversible thermosensitive recording layer according to the present invention is determined by the composition and the desired printing density, and specifically, the range of 0.5 to 20 μm is preferable, and 3 to 15 μm is more preferable. .

  The reversible thermosensitive recording layer according to the present invention comprises a reversible thermosensitive recording layer containing at least a dye precursor and a reversible developer, and if necessary, a binder resin and a decolorization accelerator on at least one surface of the support. It is formed by coating and forming a coating liquid. As a method for including a dye precursor, a reversible developer, a decoloring accelerator, etc. in the reversible thermosensitive recording layer coating solution, each compound is dissolved in a solvent alone or dispersed in a dispersion medium. A method of mixing, a method of mixing each compound and then dissolving or dispersing in a dispersion medium, a method of dissolving each compound by heating, homogenizing, cooling, dissolving in a solvent or dispersing in a dispersion medium, etc. Although it is mentioned, it is not particularly limited. If necessary, a dispersing agent may be used during dispersion.

  For the binder resin, a compound such as a dye precursor and a reversible developer, which are added alone or mixed, and added before or after being dissolved in a solvent or dispersed in a dispersion medium, each compound and the binder resin are mixed and then the solvent is mixed. In the method of dissolving or dispersing in a dispersion medium, each compound is heated and dissolved, homogenized and then cooled, and then added before or after being dissolved in a solvent or dispersed in a dispersion medium. The solvent or dispersion medium is preferably selected so that the binder resin dissolves in the solvent or dispersion medium for the compound such as the dye precursor and the reversible developer. In addition, when a commercially available binder resin is added to the solvent in advance, it may be used together with the binder resin as a solvent or dispersion medium when dissolving or dispersing the compound such as the dye precursor and the reversible developer.

  Specific examples of the solvent or dispersion medium include water; alcohols such as methanol, ethanol, n-propanol, 2-propanol, and n-butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; acetic acid Esters such as methyl, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, ethylene carbonate, ethers such as diethyl ether, glycol dimethyl ether, glycol diethyl ether, dioxane, dioxolane, tetrahydrofuran, benzene, toluene, xylene, Aromatic hydrocarbons such as styrene; aliphatic hydrocarbons such as pentane, hexane, and cyclohexane; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, chlorine Benzene, halogenated hydrocarbons such as dichlorobenzene; N, N- dimethylformamide, N, etc. amides such as N- dimethylacetamide can be used.

  In the present invention, an intermediate layer having some function such as an ultraviolet absorbing layer or a gas barrier layer is provided between any of the reversible thermosensitive recording layer and the protective layer for the purpose of improving weather resistance, etc. For this purpose, an undercoat layer, a light reflecting layer or an air layer may be provided between the support and the reversible thermosensitive recording layer. In particular, the undercoat layer may contain hollow particles. When the reversible thermosensitive recording layer is provided only on one side of the support, a back coat layer may be provided on the other side of the support. These layers may be composed of a single layer or a plurality of layers of two or more layers. Moreover, it is preferable that these layers contain curable resins, such as a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin.

  In the present invention, the intermediate layer may contain an ultraviolet absorber or an antioxidant. Organic absorbers such as benzophenone UV absorbers, benzotriazole UV absorbers, triazine UV absorbers, benzoate UV absorbers, salicylate UV absorbers, and cinnamate UV absorbers as UV absorbers and antioxidants Examples of the ultraviolet absorber include inorganic ultraviolet absorbers such as zinc oxide, cerium oxide, iron oxide, and titanium oxide.

  In the present invention, a protective layer, an intermediate layer, a reversible thermosensitive recording layer, an undercoat layer and the like provided on the support are optionally provided with a leveling agent, a dispersant, a surfactant, a thickener, a hardener. Various additions such as film agents, preservatives, pigments, colored dyes, fluorescent brighteners, UV absorbers, infrared absorbers, antioxidants, antioxidants, pH adjusters, antifoaming agents, lubricants, antistatic agents, etc. An agent can be added.

  The method of laminating each layer in the present invention on a support to form a reversible thermosensitive recording material is not particularly limited, and can be formed by a conventional method. For example, air knife coater, blade coater, bar coater, curtain coater, gravure roll and transfer roll coater, roll coater, comma coater, smoothing coater, micro gravure coater, reverse roll coater, 4 roll roll coater, dip coater, Various coating machines such as a rod coater, a kiss coater, a gate roll coater, a squeeze coater, a slide coater, a die coater and other smearing apparatuses, a planographic plate, a relief plate, an intaglio plate, a flexo, a gravure, a screen, and a hot melt can be used. Furthermore, in addition to the usual drying step, each layer can be held by ultraviolet irradiation or electron beam irradiation, and further by aging by heating or the like. By these methods, it is possible to apply and print one layer at a time or multiple layers simultaneously.

  When any of the above layers contains a curable resin, curing by heating, ultraviolet irradiation, or electron beam irradiation is performed in accordance with the type of resin. Ultraviolet irradiation can be performed using a known ultraviolet irradiation apparatus. Examples of the ultraviolet irradiation device include a light source, a lamp, a power source, a cooling device, a transport device, and the like. Examples of the light source include a mercury lamp, a metal halide lamp, a gallium lamp, a mercury xenon lamp, and a flash lamp. The wavelength of the light source can be appropriately selected according to the ultraviolet absorption wavelength of the photopolymerization initiator and the photopolymerization accelerator. The output and conveying speed of the ultraviolet irradiation are determined according to the irradiation energy necessary for crosslinking the ultraviolet curable resin.

  The reversible thermosensitive recording material of the present invention may be provided with a printing recording layer such as printing such as offset printing or gravure printing; an ink jet recording layer, a thermal transfer image receiving layer, a sublimation thermal transfer image receiving layer. These print and print recording layers may be provided by being laminated with the reversible thermosensitive recording layer, or may be provided on a part of the same surface as the reversible thermosensitive recording layer. Further, it may be provided on a part of or the entire surface opposite to the surface on which the reversible thermosensitive recording layer is provided. An overprint varnish (OP varnish) layer mainly composed of a curable resin may be provided partially or entirely on the print recording layer.

  In the reversible thermosensitive recording material of the present invention, the other layer, the surface on which the reversible thermosensitive recording layer is provided, the surface on the opposite side, etc. are electrically, magnetically and optically. A material capable of recording information may be included. Further, the support may be a multilayer and an IC chip may be sandwiched between them. Further, an antistatic layer can be provided on one side or both sides for the purpose of antistatic. The reversible thermosensitive recording material of the present invention can be attached to another medium through an adhesive layer or the like, or using a heat-fusible resin as a support.

  When the IC chip is encapsulated between the layers of the reversible thermosensitive recording material, for example, it can be encapsulated between the layers of the plastic film or between the paper substrate and the plastic film. It is preferable from the viewpoint of print quality that sealing is performed between layers away from the reversible thermosensitive recording layer. When a non-contact IC chip is encapsulated, it can be encapsulated with an antenna. A cushion layer can be provided for the purpose of preventing the IC chip from being damaged by the pressure during encapsulation. The thickness of the cushion layer is preferably 10 μm or more because cushioning properties are insufficient if it is less than 10 μm. In addition, since a load is applied to the joint between the IC chip and the antenna, the area of the cushion layer is preferably large enough to cover the IC chip and the antenna joint. The cushion layer can be provided on one side or both sides. More preferably, cushion layers are provided on both sides. As the cushion layer, a thermoplastic resin is preferable, and if it is a foamed resin, the cushioning property is better, so that the IC chip can be prevented from being damaged.

  In the reversible thermosensitive recording material of the present invention, in order to form a color-coded recording image, it is sufficient to rapidly cool after heating, and to erase the recorded image, if the cooling rate after heating is slow. good. For example, after heating by an appropriate method, a colored state can be developed by rapidly cooling by pressing a low-temperature metal block or the like. In addition, if the heating is performed for a very short time using a thermal head, laser light, or the like, the cooling is performed immediately after the heating is completed, so that the colored state can be maintained. On the other hand, when heated for a relatively long time with a suitable heat source (thermal head, laser light, heat roll, heat stamp, high-frequency heating, electric heater, radiant heat from a light source such as a tungsten lamp or halogen lamp, hot air, etc.) Since not only the layer but also the support and the like are heated, even if the heat source is removed, the cooling rate is slow, and the color is lost. Therefore, even when the same heating temperature and the same heat source are used, the coloring state and the decoloring state can be arbitrarily developed by controlling the cooling rate.

  Examples of the laser used for heating include, but are not limited to, a semiconductor laser, a YAG laser, and a carbon dioxide gas laser. In order to efficiently perform heating with a semiconductor laser or a YAG laser, a reversible thermosensitive recording layer contains a photothermal conversion material having absorption in the near infrared region, or a photothermal conversion layer containing a photothermal conversion material is reversible. It is preferably provided directly adjacent to the thermal recording layer. Examples of photothermal conversion materials having absorption in the near infrared region include, for example, metal or metalloid layers such as platinum, titanium, silicon, chromium, nickel, germanium, and aluminum, immonium compounds, metal complex compounds, cyanine dyes, squarylium dyes, Photothermal conversion dyes such as naphthoquinone dyes, phthalocyanine compounds, and polymethine compounds can be used, and can be contained in the reversible thermosensitive recording layer in a dispersed state or in a molecular state. Preferable photothermal conversion dyes include phthalocyanine compounds and metal complex compounds in terms of photothermal conversion efficiency, solubility in solvents, dispersibility in resins, and light resistance to ultraviolet light, and phthalocyanine compounds are particularly preferable. When the photothermal conversion layer is provided in the vicinity of the reversible thermosensitive recording layer, a photothermal conversion layer formed of a film such as a copper thin film, indium tin oxide (ITO), or antimony tin oxide (ATO) can also be used.

  Examples of phthalocyanine compounds include naphthalocyanine compounds, metal-free phthalocyanine compounds, iron phthalocyanine compounds, copper phthalocyanine compounds, zinc phthalocyanine compounds, nickel phthalocyanine compounds, vanadyl phthalocyanine compounds, indium chloride phthalocyanine compounds, tin phthalocyanine compounds, and more preferably. Are vanadyl phthalocyanine compounds, zinc phthalocyanine compounds, and tin phthalocyanine compounds. The phthalocyanine compound used in the present invention may have a substituent on the aromatic ring for the purpose of adjusting the absorption wavelength, improving the solubility in a solvent, improving light resistance, and the like. Examples of the substituent include an alkyl ether group, an alkyl thioether group, an aryl ether group, an aryl thioether group, an amide group, an amino group, an alkyl ester group, an aryl ester group, a chlorine atom, and a fluorine atom. When there are two or more substituents on the aromatic ring, they may be the same or different, and the substituents may be bonded to form a ring.

  The amount of the photothermal conversion dye used is preferably set so that the absorbance at the oscillation wavelength of the light source used is 0.2 or more. If it is less than this amount, sufficient heat generation cannot be obtained, and the recording sensitivity is lowered. On the other hand, the photothermal conversion dye has some absorption in the visible region, and if the amount used is too large, the contrast is lowered. It is preferable to set an upper limit for the amount of photothermal conversion dye used so that an average transmittance of 400 nm to 700 nm can be secured by 60% or more. Two or more kinds of photothermal conversion dyes can be mixed and used.

  The photothermal conversion pigment is preferably contained in at least one of the same layer or adjacent layers with respect to the reversible thermosensitive recording layer containing at least the dye precursor and the reversible developer, and contained in the same layer. It is more preferable to obtain good sensitivity.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to this Example. In the examples, the number of parts is based on the mass of the active ingredient. For example, the solvent is the number of parts of the active ingredient, but the solution and the dispersion are the solute and dispersoid contained therein.

Example 1
(A) Preparation of reversible thermosensitive recording layer coating solution As a dye precursor, 20 parts of 2-anilino-3-methyl-6- (di-n-pentylamino) fluorane, and as a reversible developer, structural formula (2 -2) compound 100 parts, as a decoloring accelerator, N, N'-dioctadecylurea 20 parts, N- (1- (4-methyl) piperazinyl) -N'-octadecylurea 0.5 parts, polyester A mixture of 100 parts of polyol (manufactured by DIC Corporation, trade name: Bernock 11-408, active ingredient: 70% by mass) and 950 parts of methyl ethyl ketone was dispersed with glass beads for 12 hours with a paint shaker to obtain a dispersion. To the dispersion thus obtained, 130 parts of an isocyanate compound (manufactured by Mitsui Chemicals, trade name: Takenate D-110N, active ingredient: 75% by mass) and 62 parts of methyl ethyl ketone are added and mixed well, and reversible thermosensitive. A recording layer coating solution was prepared.

(B) Coating of Reversible Thermosensitive Recording Layer Coating Liquid The reversible thermosensitive recording layer coating liquid obtained in (A) is applied to a white polyethylene terephthalate (PET) sheet having a thickness of 250 μm with a dry coating amount of 10 g / m ^2. Then, after drying at 100 ° C. for 1 minute, it was further cured by heating at 50 ° C. for 24 hours to form a reversible thermosensitive recording layer.

(C) Preparation of intermediate layer coating solution 50 parts of 2,2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (2-hydroxyethyl) phenol] as a UV absorber, polyester polyol (DIC) Co., Ltd., trade name: Burnock 11-408) A mixture of 100 parts and 800 parts of methyl ethyl ketone was dispersed with glass beads for 5 hours with a paint shaker to obtain a dispersion. To the dispersion thus obtained, 140 parts of an isocyanate compound (manufactured by Mitsui Chemicals, trade name: Takenate D-110N, active ingredient: 75% by mass) and 50 parts of methyl ethyl ketone were added and mixed well, and the intermediate layer coating solution was added. Was prepared.

(D) Coating of intermediate layer coating liquid On the reversible thermosensitive recording layer coated surface of the coated sheet prepared in (B), the intermediate coating liquid obtained in (C) has a dry coating amount of 2.0 g / After coating to m ² and drying at 100 ° C. for 1 minute, the coating was further cured by heating at 50 ° C. for 24 hours to provide an intermediate layer.

(E) Preparation of protective layer coating solution Dendritic oligomer having a hyper-branch structure (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: SIRIUS-501, active ingredient: 50% by mass), 100 parts, spherical silica (AGC SITEC Product name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption: 150 ml / 100 g), 10 parts of tabular zinc stearate (manufactured by NOF Corporation) , Trade name: Nissan Electol MZ-2) 0.5 part, photopolymerization initiator (manufactured by BASF, trade name: Irgacure 184), and 400 parts of ethyl acetate were mixed. The mixed solution thus obtained was stirred and mixed with a homogenizer to prepare a protective layer coating solution (i).

(F) Coating of protective layer coating liquid On the intermediate layer coating surface of the coating sheet prepared in (D), the dry coating amount of the protective layer coating liquid (i) obtained in (E) is 4 g / m ^2. And dried at 120 ° C. for 1 minute, and then cured by passing through a UV lamp with an irradiation energy of 120 W / cm at a conveyance speed of 10 m / min to provide a protective layer. A thermal recording material was obtained.

Example 2
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-51, average particle size: 5 μm, specific surface area: 300 m ² / g, oil absorption: 150 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Example 3
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-121, average particle size: 12 μm, specific surface area: 300 m ² / g, oil absorption: 150 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Example 4
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-31, average particle size: 3 μm, specific surface area: 800 m ² / g, oil absorption: 150 ml / 100 g) Reversible thermosensitive recording in the same manner as in Example 1, except that 10 parts of (F) protective layer coating solution was applied so that the dry coating amount was 5 g / m ^2. The material was made.

Example 5
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-51, average particle size: 5 μm, specific surface area: 800 m ² / g, oil absorption: 150 ml / 100 g) Reversible thermosensitive recording in the same manner as in Example 1, except that 10 parts of (F) protective layer coating solution was applied so that the dry coating amount was 5 g / m ^2. The material was made.

Example 6
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-121, average particle size: 12 μm, specific surface area: 800 m ² / g, oil absorption: 150 ml / 100 g) Reversible thermosensitive recording in the same manner as in Example 1, except that 10 parts of (F) protective layer coating solution was applied so that the dry coating amount was 5 g / m ^2. The material was made.

Example 7
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-32, average particle size: 3 μm, specific surface area: 700 m ² / g, oil absorption: 300 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Example 8
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-52, average particle size: 5 μm, specific surface area: 700 m ² / g, oil absorption: 300 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Example 9
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-122, average particle size: 12 μm, specific surface area: 700 m ² / g, oil absorption: 300 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Example 10
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (volume: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-33, average particle size: 3 μm, specific surface area: 700 m ² / g, oil absorption: 400 ml / 100 g) Reversible thermosensitive recording in the same manner as in Example 1, except that 10 parts of (F) protective layer coating solution was applied so that the dry coating amount was 3 g / m ^2. The material was made.

Example 11
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere NP-30, average particle size: 4 μm, specific surface area: 40 m ² / g, oil absorption: 30 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Example 12
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere NP-100, average particle size: 10 μm, specific surface area: 50 m ² / g, oil absorption: 35 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Example 13
(G) Preparation of protective layer coating solution Dendritic oligomer having a dendrimer structure (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: Biscote # 1000), spherical silica (manufactured by Fuji Silysia Chemical Co., Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g, oil absorption: 290 ml / 100 g, flat zinc stearate (manufactured by NOF Corporation, trade name: NISSAN ELEC) 0.5 parts of Toll MZ-2), 5 parts of a photopolymerization initiator (manufactured by BASF, trade name: Irgacure 907) and 400 parts of ethyl acetate were mixed. The liquid mixture thus obtained was stirred and mixed with a homogenizer to prepare a protective layer coating liquid (ii).

(H) Coating of protective layer coating liquid On the intermediate layer coating surface of the coating sheet prepared in (D), the dry coating amount of the protective layer coating liquid (ii) obtained in (G) is 4 g / m ^2. And dried at 120 ° C. for 1 minute, and then cured by passing under an ultraviolet lamp with an irradiation energy of 120 W / cm at a conveyance speed of 10 m / min to provide a protective layer. A thermal recording material was obtained.

Example 14
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Fuji Silysia Chemical Co., Ltd., trade name: Cyrossphere C-1510, average particle size: 10 μm, specific surface area: 520 m ² / g, oil absorption : 250 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 13 except that 10 parts were used.

Example 15
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Oil & Fats Co., Ltd., trade name: Godball E-2C, average particle size: 1.2 μm, specific surface area: 520 m ² / g, (Oil absorption amount: 250 ml / 100 g) 12 parts were used, and (H) in the coating of the protective layer coating solution, except that coating was performed so that the dry coating amount was 3 g / m ^2. A reversible thermosensitive recording material was prepared.

Example 16
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Oil & Fats Co., Ltd., trade name: Godball E-6C, average particle size: 2.3 μm, specific surface area: 325 m ² / g, (Oil absorption amount: 120 ml / 100 g) Using 12 parts, (H) In the coating of the protective layer coating solution, the same procedure as in Example 13 was conducted except that the dry coating amount was 3 g / m ^2. A reversible thermosensitive recording material was prepared.

Example 17
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Oil & Fats Co., Ltd., trade name: God Ball D-11C, average particle size: 3.5 μm, specific surface area: 390 m ² / g, (Oil absorption amount: 100 ml / 100 g) Using 8 parts, (H) In the coating of the protective layer coating solution, except that coating was performed so that the dry coating amount was 3 g / m ² , the same as in Example 13 A reversible thermosensitive recording material was prepared.

Example 18
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Yushi Kogyo Co., Ltd., trade name: God Ball B-6C, average particle size: 2.3 μm, specific surface area: 250 m ² / g, (Oil absorption amount: 140 ml / 100 g) Using 8 parts, (H) In the coating of the protective layer coating solution, the same procedure as in Example 13 was performed except that the dry coating amount was 3 g / m ^2. A reversible thermosensitive recording material was prepared.

Example 19
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Yushi Kogyo Co., Ltd., trade name: God Ball B-25C, average particle size: 9 μm, specific surface area: 475 m ² / g, oil absorption : 140 ml / 100 g) Reversible feeling in the same manner as in Example 13 except that 5 parts of (H) protective layer coating solution was applied so that the dry coating amount was 5 g / m ² . A thermal recording material was prepared.

Example 20
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Oil & Fats Co., Ltd., trade name: God Ball SF-16C, average particle size: 4.7 μm, specific surface area: 650 m ² / g, A reversible thermosensitive recording material was prepared in the same manner as in Example 13 except that 10 parts of oil absorption amount: 400 ml / 100 g) was used.

Example 21
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Oil & Fat Co., Ltd., trade name: Godball G-6C, average particle size: 4 μm, specific surface area: 55 m ² / g, oil absorption amount : 30 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 13 except that 10 parts were used.

Example 22
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by JGC Catalysts & Chemicals Co., Ltd., trade name: SILICA PEARL 20LB, average particle size: 5 μm, specific surface area: 120 m ² / g, oil absorption amount: 220 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 13 except that 10 parts were used.

Example 23
(I) Preparation of coating liquid for protective layer Dipentaerythritol penta and hexaacrylate (manufactured by Toagosei Co., Ltd., trade name: Aronix Biscoat M-405, active ingredient: 100% by mass), 100 parts of spherical silica (AGC S) Product name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption: 150 ml / 100 g, 10 parts, flat zinc stearate (Nissan Co., Ltd.) Manufactured, trade name: Nissan Electol MZ-2) 0.5 part, photopolymerization initiator (manufactured by BASF, trade name: Irgacure 184), and 400 parts of ethyl acetate were mixed. The liquid mixture thus obtained was stirred and mixed with a homogenizer to prepare a protective layer coating liquid (iii).

(J) Coating of protective layer coating liquid On the intermediate layer coating surface of the coating sheet prepared in (D), the dry coating amount of the protective layer coating liquid (iii) obtained in (I) is 4 g / m ^2. And dried at 120 ° C. for 1 minute, and then cured by passing through a UV lamp with an irradiation energy of 120 W / cm at a conveyance speed of 10 m / min to provide a protective layer. A thermal recording material was obtained.

Example 24
In preparation of (I) protective layer coating liquid of Example 23, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere NP-30, average particle size: 4 μm, specific surface area: 40 m ² / g, oil absorption: 30 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 23 except that 10 parts were used.

Example 25
In preparation of (I) protective layer coating liquid of Example 23, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g, oil absorption : 290 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 23 except that 10 parts were used.

Comparative Example 1
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption (Amount: 150 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were not used.

Comparative Example 2
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere H-201, average particle size: 20 μm, specific surface area: 800 m ² / g, oil absorption: 150 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that 10 parts were used.

Comparative Example 3
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption Instead of using 10 parts of scaly silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sun Lovely C, average particle size: 5 μm, oil absorption: 95 ml / 100 g) instead of 10 parts of the quantity: 150 ml / 100 g) Produced a reversible thermosensitive recording material in the same manner as in Example 1.

Comparative Example 4
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by Nissan Chemical Industries, Ltd., trade name: Light Star normal particles LA-OS26BK, average particle size: 0.7 μm, specific surface area: 240 m ² / g, A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that 10 parts of the active ingredient was 26%).

Comparative Example 5
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), amorphous silica having an indefinite shape (manufactured by Tosoh Silica Co., Ltd., trade name: Nipseal E-220A, average particle size: 1.5 μm, specific surface area: 135 m ² / g, oil absorption: 230 ml / 100 g) A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that 8 parts were used.

Comparative Example 6
In preparation of (E) protective layer coating liquid of Example 1, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), silicone fine particles (made by Momentive Performance Materials Japan G.K., trade name: Tospearl 130, average particle size: 3 μm, specific surface area: 20 m ² / g, oil absorption: A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that 10 parts of 62 ml / 100 g) were used.

Comparative Example 7
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption: 290 ml / 100 g) A reversible thermosensitive recording material was prepared in the same manner as in Example 13 except that 10 parts were not used.

Comparative Example 8
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g Oil absorption amount: 290 ml / 100 g) Instead of 10 parts, spherical silica (manufactured by Suzuki Yushi Kogyo Co., Ltd., trade name: God Ball GT-3, average particle size: 1 μm, specific surface area: 55 m ² / g, oil absorption amount : 30 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 13 except that 10 parts were used.

Comparative Example 9
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption amount: 290 ml / 100 g) In place of 10 parts, amorphous silica with an indefinite shape (manufactured by Mizusawa Chemical Industry Co., Ltd., trade name: Mizukasil P-527, average particle size: 2 μm, specific surface area: 55 m ² / g, oil absorption: 130 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 13, except that 8 parts were used.

Comparative Example 10
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption amount: 290 ml / 100 g) In place of 10 parts, amorphous amorphous silica having an indefinite shape (manufactured by Fuji Silysia Chemical Co., Ltd., trade name: silo hovic 100, average particle size: 2.7 μm, oil absorption amount) : 240 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 13 except that 8 parts were used.

Comparative Example 11
In the preparation of the protective layer coating solution in Example 13 (G), spherical silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Pyrospher C-1504, average particle size: 4.5 μm, specific surface area: 520 m ² / g , Oil absorption amount: 290 ml / 100 g), except that 10 parts of crosslinked acrylic monodispersed fine particles (manufactured by Soken Chemical Co., Ltd., trade name: Chemisnow MX-300, average particle size: 3 μm) were used. A reversible thermosensitive recording material was prepared in the same manner as in Example 13.

Comparative Example 12
In preparation of (I) protective layer coating liquid of Example 23, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption (Amount: 150 ml / 100 g) A reversible thermosensitive recording material was prepared in the same manner as in Example 23 except that 10 parts were not used.

Comparative Example 13
In preparation of (I) protective layer coating liquid of Example 23, spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere L-31, average particle size: 3 μm, specific surface area: 300 m ² / g, oil absorption In place of 10 parts (amount: 150 ml / 100 g), spherical silica (manufactured by AGC S-Tech Co., Ltd., trade name: Sunsphere NP-200, average particle size: 20 μm, specific surface area: 100 m ² / g, oil absorption: 40 ml / 100 g) A reversible thermosensitive recording material was produced in the same manner as in Example 23 except that 10 parts were used.

  About the reversible thermosensitive recording material obtained in the said Example and comparative example, the lamination | stacking cross section was observed using the scanning electron microscope. According to the observation results, the cross section of the protective layer was an uneven coated surface with protruding spherical particles. The average particle diameter (d) of the particles, the film thickness (t) of the protective layer where no particles are measured, and the ratio of the average particle diameter of the particles to the film thickness of the protective layer where no particles are present (d / t) Are shown in Table 1.

(Test Method 1) Test Method for Repeated Durability The reversible thermosensitive recording material obtained in the above examples and comparative examples was punched into a telephone card shape, and a card reader / writer (trade name: TCP-, manufactured by Star Seimitsu Co., Ltd.). 300II), printing was performed in the erase print mode. The erasure printing is a method in which an image is rewritten by inserting and reciprocating the card once and inserting the card again. The erasing is performed by a ceramic heater (erase bar), and the printing is continuously performed by a thermal head. As conditions, the printing energy is set to two levels of 0.35 mJ / dot and 0.45 mJ / dot, and the erasing energy of the ceramic heater does not disappear due to lack of energy, and the center value of the area where there is no fogging due to over energy. Set. Under these conditions, printing and erasing were repeated 200 times at 2-minute intervals.

(Evaluation method 1) Repeat durability evaluation method (print density)
The print density of the first and 200th prints was measured using the black density of a print densitometer (product name: RD-19, manufactured by GretagMacbeth). The results are shown in Table 2.

(Status of printing section)
The state of the printed portion was determined by visually observing the first and 200th states and using the following criteria. The results are shown in Table 2.
(Double-circle): The printed part is not damaged at all, and a beautiful image is formed.
○: A clean image is formed, but a crack of less than 1 mm is generated in the protective layer.
Δ: Although there is no omission in the printed image, the protective layer has a crack of 1 mm or more.
X: The protective layer is damaged, and the printed image is missing.

(Test method 2) Test method for resistance to head residue The reversible thermosensitive recording material obtained in the above examples and comparative examples was punched into a telephone card shape, and a card reader / writer (manufactured by Star Seimitsu Co., Ltd., trade name: TCP- 300II), printing was performed in the erase print mode. As the conditions, the printing energy was set to 0.45 mJ / dot, and the erasing energy of the ceramic heater was set to the center value of a region where there was no disappearance due to insufficient energy and no fogging due to over energy. Under these conditions, printing and erasing were repeated 200 times at 2-minute intervals.

(Evaluation method 2) Evaluation method of head residue resistance The head residue resistance is measured by observing the head of a card reader / writer (manufactured by Star Seimitsu Co., Ltd., trade name: TCP-300II) with a microscope, and the adhesion of residue is as follows. Judged. Note that the printing failure refers to a state in which debris adheres to the head of the card reader / writer, making it impossible to print on the surface of the reversible thermosensitive recording material, and characters and images cannot be recognized. The results are shown in Table 3.
A: There is no residue on the head, and there is no printing damage.
○: Scrap remains slightly on the head, but there is no printing failure.
Δ: Debris is attached to the head, and printing failure has partially occurred.
X: Waste is attached to the most part of the head, and printing trouble occurs in most of the head.

(Test method 3) Test method for drop-off characteristics of particles The surface of the protective layer of the reversible thermosensitive recording material obtained in the above Examples and Comparative Examples was rubbed with a nail a plurality of times, and a transparent adhesive tape was pasted on it and peeled off. And pasted it on black paper.

(Evaluation Method 3) Evaluation Method of Particle Dropout Characteristics The particle dropout characteristics were determined according to the following criteria. The results are shown in Table 3.
A: No white powder was visible.
○: A small amount of white powder was visible.
Δ: A large amount of white powder was visible.
X: The white powder was visible when rubbed with a nail.

  From Table 2, the average particle diameter (d) of the particles, the film thickness (t) of the protective layer without the particles measured from the observation results, and the ratio of the average particle diameter of the particles to the film thickness of the protective layer without the particles ( The reversible thermosensitive recording materials of Examples 1 to 25 using spherical silica with d / t) of 0.5 to 4 have a high printing density in Test Method 1 and a printing density accompanying repeated printing and erasing. There was little decrease. In addition, the surface of the protective layer was hardly deteriorated by repeated printing and erasing, and good repeated durability was exhibited.

  From Table 3, the average particle diameter (d) of the particles, the film thickness (t) of the protective layer in which no particles are measured, and the ratio of the average particle diameter of the particles to the film thickness of the protective layer in which no particles are present ( The reversible thermosensitive recording materials of Examples 1 to 25 using spherical silica having a d / t) of 0.5 to 4 show that in Test Method 2, the adhesion of the residue to the thermal head is small and the printing trouble is small. Indicated.

  From Table 3, the average particle diameter (d) of the particles, the film thickness (t) of the protective layer in which no particles are measured, and the ratio of the average particle diameter of the particles to the film thickness of the protective layer in which no particles are present ( The reversible thermosensitive recording materials of Examples 1 to 25 using spherical silica having a d / t) of 0.5 to 4 show a result of less dropout of particles from the reversible thermosensitive recording material in Test Method 3. It was.

  As can be seen from the evaluation results of Test Methods 1 to 3, the reversible thermosensitive recording material using spherical silica satisfying “0.5 ≦ average particle diameter of spherical silica / film thickness of protective layer ≦ 4” is as follows. Therefore, it is possible to provide a reversible thermosensitive recording material capable of forming and erasing an image having a clear contrast, causing little change in the surface state due to repeated printing and erasing, and causing less debris adhesion to the thermal head.

  The reversible thermosensitive recording material of the present invention can repeat the formation and erasure of images having clear contrast, and can be compatible with printability. Specific applications include transportation commuter pass, various prepaid cards, magnetic cards such as point cards, IC cards, IC tags, and kanbans and forms used in logistics such as factories and warehouses. It is.

Claims (4)

Contains a normally colorless or light-colored dye precursor on a support and a reversible developer that forms a relatively colored state and a decolored state due to differences in heating temperature and / or cooling rate after heating. A reversible thermosensitive recording layer and a reversible thermosensitive recording material provided with a protective layer on the reversible thermosensitive recording layer, wherein the protective layer contains spherical silica, and the spherical silica is represented by the following formula (1): A reversible thermosensitive recording material characterized by satisfying.
0.5 ≦ average particle diameter of spherical silica / film thickness of protective layer ≦ 4 Formula (1)   The reversible thermosensitive recording material according to claim 1, wherein the spherical silica is porous spherical silica.   The reversible thermosensitive recording material according to claim 1, wherein the protective layer contains an ultraviolet curable resin as a main component.   4. The reversible thermosensitive recording material according to claim 3, wherein the ultraviolet curable resin is a dendritic branched compound having a (meth) acrylate group at the terminal.