JP4920376B2 - Reversible thermosensitive recording material - Google Patents

Description

  The present invention relates to a reversible thermosensitive recording material whose transparency or color tone reversibly changes by controlling thermal energy. In particular, the present invention relates to a reversible thermosensitive recording material that has little curling, does not fall off when it is cut, or is bonded to another base material and punched into a card, and has good repeated durability.

  In recent years, a reversible thermosensitive recording material that can form a temporary image and can erase the image when it is no longer needed has attracted attention. As a reversible thermosensitive recording material, a thermosensitive recording material using a colorless or light-colored dye precursor and a reversible color developer that develops color by heating the dye precursor and then re-heats it to erase the color. (See, for example, Patent Documents 1 to 3), a thermal recording material in which organic low-molecular substances such as higher alcohols and higher fatty acids are dispersed in a resin such as polyester, a thermal recording material in which two or more polymers having different refractive indexes are mixed, and the like. It has been 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.

  When such a reversible thermosensitive recording material is repeatedly printed and erased under practical conditions, the recording surface gradually deteriorates due to repeated force (external force due to conveying force or platen pressure). In view of this, in order to improve printing durability, studies have been made to provide a heat-resistant protective layer, and it has been proposed to provide a thermoplastic resin or a thermosetting protective layer on the heat-sensitive recording layer or via an intermediate layer. (For example, refer to Patent Document 4) However, the durability of these resins is not sufficient, and at present, a protective layer mainly composed of a cured resin by ultraviolet rays or electron beams has been used (for example, Patent Documents 5 and 5). 6). In addition, as a countermeasure against cracks on the surface of the protective layer during repeated use, it is disclosed to use epoxy acrylate having a bisphenol A skeleton in the protective layer to control the irradiation energy of ultraviolet rays (see, for example, Patent Document 7).

Due to these protective layers mainly composed of a cured resin by ultraviolet rays or electron beams, a practically constant effect is observed with respect to repeated durability. However, in these protective layers, the shrinkage of the coating layer due to curing is large, and the protective layer is greatly curled toward the surface to which the protective layer is applied, so that the handleability of the reversible thermosensitive recording material is deteriorated. In addition, a protective layer using a cured resin by ultraviolet rays or electron beams is excellent in hardness but weak in impact and inferior in flexibility, or a roll-like reversible thermosensitive recording material is continuously slitted into a small roll shape. When processing or cutting with a cutting processing apparatus such as a guillotine or a punching machine to form a sheet or card, a powder falling phenomenon occurred in which the coating layer peeled off from the support on the cut surface. In addition, an adhesive layer is provided on the opposite surface of the support, and an information recording medium such as an optical memory, a contact IC, or a non-contact IC is provided between the reversible thermosensitive recording material and another substrate, heating, etc. A number of methods have been proposed in which, after laminating, a punching to a card size is used. In the card laminated on such a thick material, the problem of powder falling when punched into the card has been remarkable. Such powder fall has led to a decrease in work efficiency such as an increase in cleaning work during the cutting process. Furthermore, due to the influence of powder falling, the thermal head is not closely attached to the thermal recording layer, white spots are generated in the printed part, the thermal head is damaged, or the fixed information is printed on the reversible thermal recording material. In this case, there was a problem that printing did not get on the powder fallen part and the white part was lost and the appearance was lowered.
Japanese Patent Laid-Open No. 6-210954 JP-A-6-210955 JP-A-7-125428 JP-A-6-8626 JP-A-6-344672 JP-A-8-11433 JP 11-334220 A

  The problem of the present invention is that the curl is low, and it is easy to handle because it does not fall off when it is cut or pasted into a card with another substrate. It is to provide a thermal recording material.

  As a result of studying to solve these problems, the present inventors have found that the above-described problems can be solved by the following invention.

  In a reversible thermosensitive recording material having a thermosensitive recording layer and a protective layer whose transparency or color tone reversibly changes depending on temperature on one side of a support, an ultraviolet ray or electron beam curable resin having the protective layer as a main component A polyfunctional (meta) containing a cured product of the composition, wherein the ultraviolet or electron beam curable resin composition before curing has at least a number average molecular weight of from 4,000 to 50,000 and a double bond equivalent of from 180 to 2,000. ) A reversible thermosensitive recording material comprising an acrylate polymer.

  The polyfunctional (meth) acrylate polymer before curing has a structure formed by polymerizing a monomer having at least an ethylenically unsaturated bond as a main chain, and has one (meth) acryloyl group in the side chain. The above structure is preferable.

In the polyfunctional (meth) acrylate polymer before curing, 50% or more of the total number of (meth) acryloyl groups is preferably a structure represented by the following general formula 1 (Q ¹ represents a hydrogen atom or a methyl group). Q ² represents a divalent linking group, and Q ³ , Q ⁴ , and Q ⁵ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

  The protective layer further contains a polyfunctional (meth) acrylic monomer, and the blending ratio of the polyfunctional (meth) acrylate polymer / polyfunctional (meth) acrylic monomer is 9/1 to 1 in terms of an active ingredient ratio (mass ratio) before curing. It is preferable that it is 3/7.

  It is preferable that the protective layer further contains silica.

  With the reversible thermosensitive recording material of the present invention, curl is low, and there is no powder falling off when cutting or pasting and carding with another base material. Can be obtained.

  The reversible thermosensitive recording material of the present invention will be described in detail below. The reversible heat-sensitive recording material of the present invention is a reversible heat-sensitive recording material comprising a heat-sensitive recording layer and a protective layer in which transparency or color tone reversibly changes depending on temperature on one side of a support. An ultraviolet ray or electron beam curable resin composition is contained as a main component, the ultraviolet ray or electron beam curable resin composition before curing has at least a number average molecular weight of 4,000 to 50,000, and a double bond equivalent of 180 to 2000. It is characterized by comprising the polyfunctional (meth) acrylate polymer which is. In the present invention, the double bond equivalent refers to a value obtained by dividing the number average molecular weight of the polyfunctional (meth) acrylate polymer by the number of (meth) acryloyl groups per molecule. By adopting such a configuration, curl is low, reversibility is excellent because it is easy to handle because it does not fall off when it is cut or pasted into another substrate and carded. A heat-sensitive recording material can be obtained.

  In the present invention, the protective layer contains a cured product of an ultraviolet ray or electron beam curable resin composition as a main component, and the cured product of the ultraviolet ray or electron beam curable resin composition with respect to the total dry solid content in the protective layer. This means that the dry solid content ratio is 50% by mass or more. More preferably, it is 70 mass% or more, Most preferably, it is 80 mass% or more.

  In this invention, the number average molecular weight before hardening of the polyfunctional (meth) acrylate polymer used by a protective layer is 4000 or more and 50000 or less. Preferably they are 5000 or more and 30000 or less, Most preferably, they are 7000 or more and 20000 or less. If the number average molecular weight is less than 4000, when cured by ultraviolet rays or electron beams, the coating layer shrinks greatly, curling occurs, and the handleability deteriorates. On the other hand, if it is larger than 50000, the viscosity of the protective layer coating solution becomes high and handling properties are deteriorated, and the efficiency of the curing reaction by ultraviolet rays or electron beams is deteriorated, so that sufficient coating layer strength cannot be obtained.

  The polyfunctional (meth) acrylate polymer according to the present invention is a compound having two or more (meth) acryloyl groups in the molecule before curing. The higher the number of (meth) acryloyl groups, the higher the hardness of the film after irradiation with ultraviolet light or electron beam, and curling or cutting of reversible thermosensitive recording materials or bonding to another substrate. Therefore, it is possible to combine both the characteristics of powder fall-off when punched into a card and repeated durability, which is preferable. The double bond equivalent before curing of the polyfunctional (meth) acrylate polymer according to the present invention is 180 or more and 2000 or less. More preferably, it is 180 or more and 1000 or less, Most preferably, it is 180 or more and 500 or less. If the double bond equivalent is less than 180, it is difficult to synthesize, and if it is greater than 2000, the hardness of the film cured by ultraviolet rays or electron beams cannot be obtained.

  In the present invention, the polyfunctional (meth) acrylate polymer before curing has a structure formed by polymerizing a monomer having at least an ethylenically unsaturated bond as a main chain, and a (meth) acryloyl group in the side chain. It is preferable to have a structure in which one or more are bonded. With such a structure, a large number of (meth) acryloyl groups can be hung on the main chain. Of course, a (meth) acryloyl group may be bonded to one or both ends of the main chain, and any structure can be used as long as the number of (meth) acryloyl groups in the polymer is 2 or more. Good.

  In the present invention, when the polyfunctional (meth) acrylate polymer is a compound having an aliphatic hydrocarbon as a main component, an ultraviolet ray or an electron beam as compared with a compound having an aromatic hydrocarbon or an alicyclic hydrocarbon as a main component. This is preferable because the coating layer after curing is excellent in hardness and also has the flexibility of the coating layer, so that curling is small and powder falling off at the time of cutting or punching is reduced. The main component of aliphatic hydrocarbon is the dry solid of the portion excluding aromatic hydrocarbons and alicyclic hydrocarbons (aliphatic hydrocarbon part) with respect to the total dry solid content of the polyfunctional (meth) acrylate polymer. The fraction is 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more.

  As the monomer having an ethylenically unsaturated bond, as a monomer consisting only of an aliphatic hydrocarbon group, methyl, ethyl, propyl, butyl, 2-ethylhexyl, isooctyl, isononyl, isodecyl, dodecyl, lauryl, tridecyl, Alkyl (meth) acrylates, alkoxyalkyl (meth) acrylates, polyalkylene glycol (meth) acrylates, 2-hydroxys having an alkyl group usually having 20 or less carbon atoms, such as pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl Ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic acid; a divalent or higher carboxyl group such as itaconic acid, fumaric acid, maleic acid, etc. Monomers having these monomers and epoxy group-containing monomers such as acid anhydrides of these compounds, (meth) acrylamide, N-methylol (meth) acrylamide, (meth) acrylonitrile, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, etc. Examples thereof include vinyl ester monomers such as vinyl acetate, vinyl ether monomers, olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene. Examples of the monomer containing an aromatic hydrocarbon or alicyclic hydrocarbon include N-vinyl lactams such as styrene and N-vinylpyrrolidone, and heterocyclic-containing vinyl monomers. These may be used alone or in combination of two or more appropriately selected.

  In the present invention, as a method for introducing a (meth) acryloyl group into the side chain, a compound having a cyclic ether group such as an epoxy group or an oxetane group and a (meth) acryloyl group in a polymer having a carboxyl group in the side chain Or a method in which a compound having a hydroxyl group and a (meth) acryloyl group is reacted to form an ester bond, a polymer having a hydroxyl group in the side chain is reacted with a compound having a (meth) acryloyl group and an isocyanate group, and urethane A method of forming a bond, a method of reacting (meth) acrylic acid with a polymer having a cyclic ether group such as an epoxy group or an oxetane group in a side chain to form an ester bond, a polymer having a hydroxyl group in a side chain (meth) A method of reacting acrylic acid to form an ester bond, having an isocyanate group in the side chain A method in which a compound having a hydroxyl group and an acryloyl group such as hydroxyethyl (meth) acrylate is reacted with a limer to form a urethane bond, a polymer having a silanol group in a side chain, and 3-acryloxypropyltrimethoxysilane Examples of such methods include, but are not limited to, a method in which a silanol group is generated by hydrolysis and a compound having a (meth) acryloyl group is reacted to form a siloxane bond. Among these, when 50% or more of the total number of (meth) acryloyl groups is a structure represented by the following general formula 1, the card is formed by stamping or pasting with another base material at the time of cutting processing. It is preferable because it is less likely to fall off when turned into a powder and is excellent in repeated durability. More preferably, it is 70% or more, and particularly preferably 85% or more.

In the general formula 1, Q ¹ represents a hydrogen atom or a methyl group, and preferably a hydrogen atom. Q < ³ >, Q < ⁴ >, Q < ⁵ > represents a hydrogen atom or a C1-C4 alkyl group. Among these, a hydrogen atom and a methyl group are preferable, and a hydrogen atom is particularly preferable. Q ² represents a divalent linking group. The divalent linking group can be appropriately selected from various divalent organic groups formed by organic atoms (carbon atom, nitrogen atom, oxygen atom, hydrogen atom, etc.). More specifically, for example, a divalent hydrocarbon group (a divalent aliphatic hydrocarbon group, a divalent alicyclic hydrocarbon group, a divalent aromatic hydrocarbon group, or these hydrocarbon groups 2 or more groups combined), polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., a linking group having an ether bond, carbonyl group, oxy group, imino group, thiocarbonyl group, thiooxy group, and these And a group in which two or more groups are combined. Among these, Q ² is preferably a divalent aliphatic hydrocarbon group having 1 to 3 carbon atoms, particularly preferably a methylene group.

In the polyfunctional (meth) acrylate polymer according to the present invention, the method for introducing the structure represented by the general formula 1 into the side chain is not particularly limited, and a conventionally known method can be employed. The compound in which Q ² is a divalent aliphatic hydrocarbon group having 1 to 3 carbon atoms, which is a preferred embodiment in the general formula 1, will be described as an example. For example, (meth) acrylic acid as an essential component, this is polymerized alone, or a monomer having an ethylenically unsaturated bond is appropriately blended and copolymerized to obtain a polymer containing a carboxyl group, A method of carrying out an esterification reaction between a carboxyl group in the polymer and a monomer having an epoxy group such as glycidyl (meth) acrylate and a α, β-unsaturated bond separately prepared, (meth) acrylic acid A monomer containing an epoxy group such as glycidyl is used as an essential component, and this is polymerized alone, or a monomer having an ethylenically unsaturated bond is appropriately blended and copolymerized to obtain a polymer containing an epoxy group. Examples of the method include an esterification reaction between the epoxy group in the polymer and a carboxylic acid having an α, β-unsaturated bond such as (meth) acrylic acid prepared separately. In the former case, as the monomer having an ethylenically unsaturated bond to be copolymerized with a polymer containing a carboxyl group, a monomer not containing an epoxy group among the monomers exemplified above is a copolymerization reaction. It is preferably used because sometimes no cross-linking occurs. In the latter case, as the monomer having an ethylenically unsaturated bond to be copolymerized with a polymer containing an epoxy group, a monomer not containing a carboxyl group is preferably used because crosslinking does not occur during the copolymerization reaction. The An esterification catalyst, a polymerization inhibitor or the like can be used for the reaction between the carboxyl group and the epoxy group.

  The polyfunctional (meth) acrylate polymer according to the present invention is formed by ring-opening / polymerizing an alkylene glycol component such as polyethylene glycol and polypropylene glycol in the main chain and a compound having an epoxy group within the range that does not interfere with the object of the present invention. Components, polyurethane components, polyester components, silicone components, melamine components, and the like.

  The polyfunctional (meth) acrylate polymer according to the present invention is preferably contained in an amount of 30% by mass or more, more preferably, in an active ingredient ratio relative to the total ultraviolet ray or electron beam curable resin composition in the protective layer before curing. Is 50 mass% or more. As the ultraviolet ray or electron beam curable resin composition other than the polyfunctional (meth) acrylate polymer, it is preferable to blend a polyfunctional (meth) acrylic monomer. By using a polyfunctional (meth) acrylic monomer in combination, it is possible to further improve the coating layer strength while suppressing powder falling during curling and cutting. The blending ratio of the polyfunctional (meth) acrylate polymer / polyfunctional (meth) acrylic monomer is preferably 9/1 to 3/7 in terms of the effective component ratio (mass ratio) before curing. When the blending ratio exceeds 9/1, the effect of adding a polyfunctional (meth) acrylic monomer is reduced, and the effect of improving the strength tends to be reduced. If it is less than 3/7, the excellent curling property of the polyfunctional (meth) acrylate polymer according to the present invention and the powder-proofing property at the time of punching are likely to be impaired.

  Examples of the polyfunctional (meth) acrylic monomer include 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, neo Bifunctional monomers such as pentyl glycol diacrylate, pentaerythritol diacrylate, dipentaerythritol diacrylate, polyethylene glycol diacrylate or hydroxypivalate ester neopentyl glycol diacrylate, or pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipenta Erythritol hexaacrylate, dipentaerythritol pentaacrylate, tripentaerythritol Loctaacrylate, tripentaerythritol heptaacrylate, tripentaerythritol hexaacrylate, or the like, or trimethylolpropane triacrylate, ditrimethylolpropane hexaacrylate, ditrimethylolpropane pentaacrylate, etc. Examples thereof include trifunctional or higher functional monomers such as ester compounds of polyhydric alcohol and (meth) acrylic acid, such as compounds substituted with a methacryloyl group.

  In the protective layer of the present invention, an ultraviolet ray or electron beam curable monofunctional monomer may be blended for the purpose of adjusting the viscosity of the protective layer coating solution. Examples of the ultraviolet or electron beam curable monofunctional monomer include n-butyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, trimethylolpropane acrylate, pentaerythritol acrylate, 2-ethylhexyl acrylate, acryloylmorpholine, and isobornyl acrylate. Or monofunctional monomers, such as 2-hydroxyethyl acryloyl phosphate, are mentioned. In addition, the polyfunctional oligomer outside the range of the number average molecular weight and double bond equivalent defined in the present invention is included as a component other than the polyfunctional (meth) acrylate polymer according to the present invention within a range not impeding the purpose of the present invention. May be. Examples of the polyfunctional oligomer include polyurethane (meth) acrylate, polyester (meth) acrylate, polyether (meth) acrylate, silicone (meth) acrylate, melamine (meth) acrylate, and the like.

  The solvent used in the synthesis or preparation of the polyfunctional (meth) acrylate polymer according to the present invention can be appropriately selected depending on the kind of polyfunctional (meth) acrylate polymer, the production method, and the like, but an organic solvent is usually used. Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone, and esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, and glycol acetate monoethyl ether. , Diethyl ether, glycol dimethyl ether, glycol diethyl ether, dioxane, tetrahydrofuran, and other ethers, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and other alcohols, benzene, toluene, xylene, styrene, and other aromatic hydrocarbons , Chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, chlorobenzene, dichlorobenzene, cresol, N, N-dimethyl Le formaldehyde, pentane, hexane, or the like mixtures thereof.

  When the protective layer of the present invention is crosslinked and cured by ultraviolet irradiation, it is preferable to incorporate a photoinitiator in the protective layer in order to promote the curing efficiently. Examples of the photoinitiator include benzophenone, methyl benzoylbenzoate, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- ( Examples include 4- (methylthio) phenyl-2-) morpholinopropane-1, benzoin isobutyl ether, benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal, 2-chlorothioxanthone, and 2,4-diethylthioxanthone. The addition amount of the photoinitiator 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 dry solid content of the ultraviolet ray or electron beam curable resin composition. It is as follows.

  The protective layer of the present invention preferably contains silica for the purpose of adjusting surface gloss, improving repeated durability, improving scratch resistance and the like.

  The silica particles can be appropriately selected from known silica particles (particles made of silicon dioxide). For example, wet method silica, gas phase method silica, colloidal silica and the like can be mentioned.

  Wet process silica is classified into precipitated silica and gel process silica depending on the production method. Precipitated silica is produced by reacting sodium silicate and sulfuric acid under alkaline conditions, and the silica particles that have grown are agglomerated and settled, and are then commercialized through filtration, water washing, drying, pulverization and classification. Gel silica is produced by reacting sodium silicate and sulfuric acid under acidic conditions. During the ripening, the fine particles dissolve and reprecipitate so as to bind other primary particles, so that the distinct primary particles disappear and form relatively hard aggregated particles having an internal void structure. Vapor phase silica is also called dry silica and is generally made by flame hydrolysis. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or silicon tetrachloride instead of silicon tetrachloride. Can be used in a mixed state. Colloidal silica is produced by removing impurities from a silicic acid compound by various methods to obtain an anhydrous silicic acid sol, and adjusting the pH and concentration to maintain stability.

  The wet method silica and the vapor phase method silica are used after being dispersed or pulverized in the same organic solvent used in the synthesis or preparation of the polyfunctional (meth) acrylate polymer according to the present invention. At the time of dispersion or pulverization, a solution of a polyfunctional (meth) acrylate polymer, a polyfunctional (meth) acrylic monomer, or the like may be added to these organic solvents. As a dispersion or pulverization method, a known method can be adopted. For example, silica and an organic solvent and an appropriate dispersant are added and mixed with ordinary propeller stirring, turbine stirring, homomixer stirring, etc., and further, a media mill such as a ball mill, a bead mill, a sand grinder, Dispersion or pulverization can be performed using a pressure disperser such as a high-pressure homogenizer or an ultra-high-pressure homogenizer, an ultrasonic disperser, a thin film swirl disperser, or the like.

  The silica used in the protective layer is a dispersion obtained after the above dispersion or pulverization treatment. Furthermore, the polyfunctional (meth) acrylate polymer, polyfunctional (meth) acrylic monomer, etc. of the present invention is added to these dispersions. From the viewpoint of the temporal stability of the protective layer coating solution prepared in this manner, hydrophobized silica is preferably used. In particular, when the organic solvent used in the preparation of the polyfunctional (meth) acrylate polymer is a non-alcoholic organic solvent such as methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, toluene, etc., when hydrophobized silica is used. The stability with time of the protective layer coating solution is significantly improved. In the case of silica that has not been hydrophobized, the dispersion state of the silica in the protective layer coating liquid immediately after preparation is good, but the silica settles with time, and the dispersion state of the silica is based on a simple treatment such as stirring. The problem of not returning easily occurs. On the other hand, silica that has been subjected to a hydrophobization treatment is preferable because it can be returned to its original dispersed state by simple treatment such as stirring even if silica sedimentation occurs over time. As the hydrophobizing treatment of silica, a conventionally known method such as a silane coupling agent, an organosilicone compound treatment with an alkoxysilane compound, or a wax treatment can be used.

  The amount of silica is preferably 20% by mass or less, more preferably 3% by mass to 15% by mass, and particularly preferably 5% by mass to 10% by mass with respect to the total dry solid content of the protective layer. is there.

  In the protective layer of the present invention, pigments other than silica can be added as long as the object of the present invention is not hindered. For example, carbonates such as aluminum, zinc, calcium, magnesium, barium, and titanium, oxides, hydroxides Products, sulfates, etc., and inorganic pigments including clays such as zeolite, kaolin, calcined kaolin, talc, starch, styrene resin, polyolefin resin, urea-formalin resin, melamine resin, acrylic resin, paraffin, natural wax, synthesis Wax etc. can be used. Further, higher fatty acid metal salts such as zinc stearate and calcium stearate can be used as a lubricant. Further, a singlet oxygen scavenger, a superoxide anion scavenger, and the like can be used.

  The thickness of the protective layer according to the present invention is preferably in the range of 0.1 to 10 μm, and 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 thermosensitive recording layer tends to decrease. When the film thickness is smaller than 0.1 μm, it is difficult to obtain the expected coating layer strength, and the coating layer is easily damaged.

  The heat-sensitive recording layer according to the present invention uses a material whose transparency or color tone reversibly changes depending on the temperature. For example, as a heat-sensitive recording material that can repeat image recording and erasing, a reversible developer that gives the dye precursor a reversible color change by heating is used to form and erase images by controlling thermal energy. Reversible thermosensitive recording material, low molecular weight organic dispersion in a resin matrix, heat turbid reversible thermosensitive recording material that gives a transparent state and a cloudy state by heat, and two or more polymers having different refractive indexes Examples thereof include mixed heat-sensitive recording materials. In addition, these heat-sensitive recording layers may be stacked with a plurality of heat-sensitive recording layers having different color tones. Among these, a heat-sensitive recording layer containing a dye precursor and a reversible developer is preferable because of excellent image visibility. Specific examples of the dye precursor according to the present invention include the following, for example, but the present invention is not limited thereto.

  3-diethylamino-7-o-chlorophenylaminofluorane, 3-diethylamino-7-m-chlorophenylaminofluorane, 3-diethylamino-7-p-chlorophenylaminofluorane, 3-diethylamino-7-o-fluorophenylamino Fluorane, 3-diethylamino-7-m-fluorophenylaminofluorane, 3-diethylamino-7-p-fluorophenylaminofluorane, 3-di-n-butylamino-7-m-chlorophenylaminofluorane, 3 -Di-n-butylamino-7-p-chlorophenylaminofluorane, 3-di-n-butylamino-7-o-fluorophenylaminofluorane, 3-di-n-butylamino-7-m-fluoro Phenylaminofluorane, 3-di-n-butylamino-7-p Fluorophenyl aminofluoran,

  3-diethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-o-chlorophenylaminofluorane, 3-diethylamino-6-methyl-7-m-chlorophenylaminofluorane, 3 -Diethylamino-6-methyl-7-p-chlorophenylaminofluorane, 3-diethylamino-6-methyl-7-o-fluorophenylaminofluorane, 3-diethylamino-6-methyl-7-o-tolylaminofluorane 3-diethylamino-6-methyl-7-m-tolylaminofluorane, 3-diethylamino-6-methyl-7-p-tolylaminofluorane, 3-diethylamino-6-methyl-7-o-trifluoromethyl Phenylaminofluorane, 3-diethylamino-6-methyl-7-m Trifluoromethylphenylaminofluorane, 3-diethylamino-6-methyl-7-p-acetylphenylaminofluorane, 3-diethylamino-6-methoxy-7-phenylaminofluorane, 3-diethylamino-6-ethoxy-7 -Phenylaminofluorane,

  3-di-n-butylamino-6-methyl-7-phenylaminofluorane, 3-di-n-butylamino-6-methyl-7-o-tolylaminofluorane, 3-di-n-butylamino -6-methyl-7-m-tolylaminofluorane, 3-di-n-butylamino-6-methyl-7-p-tolylaminofluorane, 3-di-n-butylamino-6-methyl-7 -O-chlorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-m-chlorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-p-chlorophenylaminofluor Oran, 3-di-n-butylamino-6-methyl-7-o-fluorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-m-fluorophenylaminofluorane 3-di-n-butylamino-6-methyl-7-p-fluorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-o-trifluoromethylphenylaminofluorane, 3-di-n-butylamino-6-methyl-7-m-trifluoromethylphenylaminofluorane, 3-di-n-butylamino-6-methyl-7-p-trifluoromethylphenylaminofluorane, 3-di-n-butylamino-6-methoxy-7-phenylaminofluorane, 3-di-n-butylamino-6-ethoxy-7-phenylaminofluorane,

  3-di-n-pentylamino-6-methyl-7-phenylaminofluorane, 3-di-n-pentylamino-6-methyl-7-m-trifluoromethylphenylaminofluorane, 3-pyrrolidyl-6 -Methyl-7-phenylaminofluorane, 3-piperidyl-6-methyl-7-phenylaminofluorane, 3-N-methyl-N-isopentylamino-6-methyl-7-phenylaminofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-phenylaminofluorane, 3-N-methyl-Nn-butylamino-6-methyl-7-phenylaminofluorane, 3-N- Methyl-Nn-propylamino-6-methyl-7-phenylaminofluorane, 3-N-ethyl-N-isopentylamino-6-methyl-7-phen Ruaminofluorane, 3-N-ethyl-N-isopentylamino-6-methyl-7-o-chlorophenylaminofluorane, 3-N-ethyl-Np-tolylamino-6-methyl-7-phenylamino Fluorane, 3-N-ethyl-N- (4-ethoxybutyl) amino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylamino Fluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroani Lino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane,

  3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3 -(1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3 -(2-Phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole) -3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3 Bis (2-phenylindole-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrole-2-yl) -6-dimethylaminophthalide,

  3- (2-Ethoxy-4-aminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-methylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-ethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl)- 4-Azaphthalide, 3- (2-ethoxy-4-propylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-hexylamino) Phenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-dimethylaminophenyl) -3- (1-ethyl-2-methyl) Ndol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2- Ethoxy-4-dipropylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-dihexylaminophenyl) -3- (1- Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-phenylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide , 3- (2-Ethoxy-4-pyridylphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (3-ethoxy-4-di Chill aminophenyl) -3- (1-ethyl-2-methylindole-3-yl) -4-azaphthalide,

  3- (2-Methyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethyl-4-diethylaminophenyl) -3- ( 1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-propyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4- Azaphthalide, 3- (2-butyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-pentyl-4-diethylaminophenyl) -3 -(1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-hexyl-4-diethylaminophenyl) -3- (1-ethyl-2- Tilindole-3-yl) -4-azaphthalide, 3- (2-cyclohexyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2 -Cyano-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-nitro-4-diethylaminophenyl) -3- (1-ethyl- 2-methylindol-3-yl) -4-azaphthalide, 3- (2-chloro-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-Bromo-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-methyl-4 Diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (2-methylindol-3-yl) -4-Azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-methyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) ) -3- (1-propyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-butyl-2-methylindole-3- Yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-pentyl-2-methylindol-3-yl) ) -4-azaphthalide,

  3- (2-Ethoxy-4-diethylaminophenyl) -3- (1-hexyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- ( 1-heptyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-octyl-2-methylindol-3-yl) -4- Azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-nonyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3 -(1-Isopropyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- 1-isobutyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-isopentyl-2-methylindol-3-yl) -4- Azaphthalide,

  3- (2-Ethoxy-4-diethylaminophenyl) -3- (1-methyl-2-ethylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- ( 1-ethyl-2-propylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-butylindol-3-yl) -4- Azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-pentylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3 -(1-Ethyl-2-hexylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1- Til-2-isopropylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-isobutylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4-azaphthalide,

  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 Examples include benzopyran.

  The dye precursors may be used alone or in combination of two or more. Toning can also be performed by mixing a dye precursor that develops in another hue.

  In the heat-sensitive recording layer composed of the dye precursor and the reversible developer according to the present invention, the reversible developer is a developer that takes into consideration not only image formation by heating but also erasure of the recorded image. Yes, the thermosensitive recording layer using a reversible developer can rewrite the display content repeatedly. Of course, it can also be used for applications in which image formation is performed only once, as is the case with ordinary heat-sensitive recording materials. As the reversible developer, compounds represented by the following general formulas 2, 3, and 4 are preferable, and a compound represented by the general formula 2 is particularly preferably used. Note that the present invention is not limited to this. The reversible developers according to the present invention may be used alone or in combination of two or more.

In General Formula 2, X ¹ and X ² may be the same or different from each other, and may be different oxygen atoms, sulfur atoms, or divalent having a —CONH— bond that does not include a hydrocarbon group at both ends as a minimum structural unit. Represents a group of R ¹ represents a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms. R ² represents a divalent hydrocarbon group having 1 to 18 carbon atoms. A divalent hydrocarbon group having 1 to 4 carbon atoms is preferred. R ³ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, preferably a hydrocarbon group having 6 to 24 carbon atoms, and more preferably a hydrocarbon group having 8 to 24 carbon atoms. Furthermore, the case where the sum of the carbon numbers of R ¹ , R ² and R ³ is 11 or more and 35 or less is particularly preferable. R ¹ , R ² and R ³ mainly represent an alkylene group and an alkyl group, respectively. In the case of R ¹ , it may contain an aromatic ring. f represents an integer of 0 to 4, and R ² and X ² repeated when f is 2 or more may be the same or different.

But X ^1, X ² in the general formula 2 comprises a divalent group of -CONH- bond containing no hydrocarbon atomic group at both ends as minimum unit, and specific examples thereof include Jiashiruamin (-CONHCO -), Diacylhydrazine (-CONHNHCO-), oxalic acid diamide (-NHCONCONH-), acylurea (-CONHCONH-, -NHCONHCO-), semicarbazide (-NHCONHNH-, -NHNHCONH-), acyl semicarbazide (-CONHNHCONH-, -NHCONHNHCO-), diacyl aminomethane (-CONHCH ₂ NHCO -), 1- acylamino-1- Ureidometan _{(-CONHCH 2 NHCONH -, - NHCONHCH} 2 NHCO-), malonamide (-NHCOCH ₂ CONH -), 3- Ashirukarubaji Ester (-CONHNHCOO -, - OCONHNHCO-) although groups such like, preferably a diacyl hydrazine, oxalic acid diamide, acyl semicarbazide.

  Specific examples of the reversible developer according to the present invention include the following structural formulas (1-1) to (1-16), but the present invention is not limited thereto.

  Among specific examples of the reversible developer, particularly preferred compounds are (1-3), (1-4), (1-5), (1-6), (1-7), (1-9). ) And (1-16).

  As the reversible developer, an alcohol compound containing an electron-withdrawing fluorine atom as represented by the following general formulas 3 and 4 is also preferably used.

In General Formula 3, a represents an integer of 0 or 1. T ¹ and T ² each independently represent a member selected from a hydrogen atom, a methyl group and a phenyl group, and T ³ represents a member selected from a hydrogen atom, a methyl group, a phenyl group and a trifluoromethyl group. . T ⁴ and T ⁵ each independently represent a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms, and T ⁶ represents a monovalent linear aliphatic group having 8 to 30 carbon atoms. Y ¹ and Y ² each independently represent a single bond or a member selected from divalent groups represented by the following (2-1) to (2-23), and Y ¹ and Y ² are simultaneously selected. Does not include those that are single bonds. Further, when the divalent groups represented by (2-1) to (2-23) are not bilaterally symmetric, these groups are bonded to the groups adjacent to the compound represented by Formula 3 in the same direction. It may be bonded to the groups on both sides in a horizontally reversed manner.

In General Formula 4, b represents an integer of 1 or 2, and c represents an integer of 1 to 3. T ⁷ and T ⁸ each independently represent a member selected from a hydrogen atom, a methyl group and a phenyl group, and T ⁹ and T ¹⁰ each independently represent a single bond or a divalent hydrocarbon having 1 to 20 carbon atoms. T ¹¹ represents a hydrogen atom or a monovalent linear aliphatic group having 1 to 30 carbon atoms. Y ³ and Y ⁴ each independently represent a single bond or a member selected from divalent groups represented by the following (2-1) to (2-23), and Y ³ and Y ⁴ are simultaneously Does not include those that are single bonds. In addition, when the divalent groups represented by (2-1) to (2-23) are not bilaterally symmetric, these groups are bonded to the groups adjacent to the compound represented by Formula 4 in the same direction. It may be bonded to the groups on both sides in a horizontally reversed manner.

In Y ¹ and Y ³ , preferred divalent groups include (2-18) to (2-23), and (2-18) and (2-21) are particularly preferred.

  Each of the reversible developers according to the present invention may be used alone or in combination of two or more. The amount used is usually 5 to 5000% by mass, preferably 10 to 10%, based on a colorless or pale dye precursor. 3000% by mass.

  A heat-sensitive recording layer comprising a dye precursor and a reversible developer according to the present invention comprises a heat-sensitive recording layer coating containing at least a dye precursor and a reversible developer on at least one surface of a support. It is formed by coating and forming a liquid. As a method for including the dye precursor and the reversible developer in the heat-sensitive recording layer coating solution, each compound is dissolved in a solvent alone or dispersed in a dispersion medium, and then mixed. A method of dissolving in a solvent or dispersing in a dispersion medium after combining, a method in which each compound is heated and dissolved, homogenized and then cooled, dissolved in a solvent or dispersed in a dispersion medium, etc. Absent. If necessary, a dispersing agent may be used during dispersion. As a dispersant when water is used as a dispersion medium, water-soluble polymers such as polyvinyl alcohol and various surfactants can be used. In aqueous dispersion, a water-soluble organic solvent such as ethanol may be mixed. In addition, when an organic solvent typified by hydrocarbons is a dispersion medium, lecithin, phosphate esters, or the like may be used as a dispersant.

  It is also possible to add a binder to the heat-sensitive recording layer for the purpose of improving the strength of the heat-sensitive recording layer according to the present invention. Specific examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic. Acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic ester, styrene / butadiene copolymer Polymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl chloride copolymer, polyvinyl chloride, ethylene / vinylidene chloride Polymers, polyvinylidene chloride, polycarbonates, polyvinyl butyral, and the like. The role of these binders is to keep the materials of the composition uniformly dispersed without being displaced by the application of heat for printing and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. A curable resin is particularly preferable when a highly durable product such as heat resistance, water resistance, and adhesiveness is required.

  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. Curing agents used in these thermosetting resins include organic acids, amines, isocyanates, epoxies, phenols, etc., but select a suitable reactive agent depending on the type of thermosetting resin. Just do it. Among these, a crosslinked resin obtained by thermosetting a polyol resin with an isocyanate compound described in JP-A Nos. 10-230680 and 11-58963 is preferable. As the oligomer / monomer used for the electron beam and the ultraviolet curable resin, the compounds exemplified in the protective layer can be used.

  The amount of binder used in the thermosensitive recording layer according to the present invention is preferably such that the mass percentage of the binder component relative to the total mass of the thermosensitive recording layer is in the range of 35% to 65%. When it is larger than this range, the color density is remarkably lowered. On the other hand, when it is smaller than this range, the heat resistance and mechanical strength of the thermosensitive recording layer are lowered, and the layer is deformed and the color density is lowered. The mass percentage of the binder component in the heat-sensitive recording layer is more preferably from 40% to 60%, particularly preferably from 45% to 55%.

  The film thickness of the heat-sensitive recording layer according to the present invention is determined by the composition of the heat-sensitive recording layer and the desired color density, and specifically, the range of 0.5 to 20 μm is preferable, and 3 to 15 μm is more preferable. . Further, in forming the recording layer, a dispersion obtained by mixing a composition such as a dye precursor and a reversible developer together with a thermosetting resin and a curing agent is applied onto the support. Further, it can be used after diluted with a non-reactive solvent with a thermosetting resin and a curing agent. As the solvent that can be used, a solvent that dissolves the binder resin and disperses / dissolves a composition such as a dye precursor and a reversible developer is preferable. Specifically, the compounds exemplified as the solvent used in the synthesis or preparation of the polyfunctional (meth) acrylate polymer can be used, but are not limited thereto. Among these, it is preferable to use an organic solvent that does not have an active hydrogen group such as a hydroxyl group, an amino group, or a carboxyl group.

  As an additive for adjusting the color development sensitivity and decoloring temperature of the heat-sensitive recording layer, a heat-fusible substance can be contained in the heat-sensitive recording layer. Those having a melting point of 60 to 200 ° C. are preferred, and those having a melting point of 80 to 180 ° C. are particularly preferred. Sensitizers used for general heat-sensitive recording paper can also be used. For example, waxes such as N-hydroxymethyl stearamide, stearamide, and palmitic acid amide, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2 -Polyether compounds such as bis (3-methylphenoxy) ethane, 2,2'-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate, bis (oxalate) ( and carbonic acid or oxalic acid diester derivatives such as p-methylbenzyl) ester. These compounds can also be added in combination.

  In the heat-sensitive recording layer according to the present invention, pigments and the like can be added as long as the object of the present invention is not hindered, and the pigments exemplified in the protective layer can be used. Further, higher fatty acid metal salts such as zinc stearate and calcium stearate can be used as a lubricant.

  In addition to the above components, the protective layer and / or heat-sensitive recording layer according to the present invention, if necessary, a leveling agent, a dispersant, a surfactant, a hardener, a preservative, a dye, a fluorescent dye, an ultraviolet absorber, an oxidation agent Various additives such as an inhibitor, an anti-aging agent, a pH adjuster, and an antifoaming agent can be added. In the present invention, the protective layer and / or the heat-sensitive recording layer may be a multilayer of two or more layers by containing each component one by one or changing the blending ratio for each layer.

  Supports used in the reversible thermosensitive recording material of the present invention include paper, various nonwoven fabrics, woven fabrics, synthetic resin films such as polyethylene terephthalate and polypropylene, paper laminated with synthetic resins such as polyethylene and polypropylene, synthetic paper, metal Foil, glass or the like, or a composite sheet combining these can be arbitrarily used depending on the purpose, but is not limited to these, and these 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. In particular, when water-based coating is applied to films, etc., when the hydrophilicity of the support is small and it is difficult to apply the heat-sensitive recording layer, surface-hydrophilic treatment by corona discharge or the like and water-soluble polymers similar to the binder are supported. Easy adhesion treatment such as application to the body surface may also be performed.

  In the present invention, for the purpose of improving weather resistance or the like, an intermediate layer containing an ultraviolet absorber or an antioxidant is provided between the heat-sensitive recording layer and the protective layer, or color development sensitivity is improved between the heat-sensitive recording layer and the support. For this purpose, an undercoat layer containing hollow particles may be provided. Further, a backcoat layer may be provided on the surface opposite to the surface on which the heat-sensitive recording layer is provided of the support for the purpose of preventing curling or charging, or a layer capable of magnetically recording information may be provided. Further, adhesion processing or the like may be performed, and another material may be pasted together, or a material capable of recording information electrically and optically may be included between the other substrate. Further, printing with UV ink or the like may be performed on an arbitrary layer and / or support in the reversible thermosensitive recording material.

  In the reversible thermosensitive recording material of the present invention, a photothermal conversion material can be contained in any layer and / or support in the reversible thermosensitive recording material in order to perform printing / erasing with a laser beam.

  The method for 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 smearing device such as a rod coater, kiss coater, gate roll coater, squeeze coater, slide coater, die coater, etc., a planographic plate, a relief plate, an intaglio plate, a flexo, a gravure, a screen, a hot melt, etc. can be used. Furthermore, each layer can be held by ultraviolet irradiation or electron beam irradiation in addition to a normal drying process. By these methods, it is possible to apply and print one layer at a time or multiple layers simultaneously.

  In a heat-sensitive recording layer containing a dye precursor and a reversible developer, which is a preferred form for the heat-sensitive recording layer according to the present invention, rapid cooling is subsequently applied to form a color-recorded image of the heat-sensitive recording layer. It only has to occur, and in order to erase the recorded image, the cooling rate after heating should be slow. 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 expressed by controlling the cooling rate.

  In addition, in the case where the thermosensitive recording layer is of a type in which organic low molecules are dispersed in a resin base material, the heat-sensitive recording layer after heating / cooling is arbitrarily formed in a transparent state and a cloudy state, depending on the heating temperature. . For example, when heated to a certain temperature range, the heat-sensitive recording layer becomes transparent, and remains transparent even when returned to room temperature in this state. When heated to a temperature range higher than the above temperature range, the thermosensitive recording layer becomes translucent, and when this state is returned to room temperature, it changes to a cloudy state. As the heating / cooling means, the heating / cooling means exemplified in the heat-sensitive recording layer containing the dye precursor and the reversible developer can be used.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples. In addition, the number of parts in an Example is a mass reference | standard.

(A) Preparation of heat-sensitive recording layer coating solution 20 parts of 3-diethylamino-6-methyl-7-p-tolylaminofluorane as a dye precursor, 100 parts of exemplary compound (1-3) as a reversible developer, A mixture of 87 parts of polyester polyol (trade name “Takelac U-21”, manufactured by Takeda Pharmaceutical Co., Ltd.) and 950 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, 144 parts of an isocyanate compound (trade name “Coronate L”, manufactured by Nippon Polyurethane Industry Co., Ltd.) and 62 parts of methyl ethyl ketone were added and mixed well to prepare a thermal recording layer coating solution.

(B) Application of heat-sensitive recording layer coating solution The coating solution obtained in (A) was applied to a transparent polyethylene terephthalate (PET) sheet having a thickness of 25 μm so that the dry film thickness was 8 μm. After partial drying, the mixture was further heated at 50 ° C. for 48 hours to form a thermosensitive recording layer.

(C) Preparation of protective layer coating solution 1
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a methylene group, and are composed only of aliphatic hydrocarbons. An ethyl acetate / butyl acetate = 1/1 solution of a functional acrylate polymer (number average molecular weight: 12,000, double bond equivalent: 200, solid content concentration: 50 mass%) was obtained. 200 parts of the polyfunctional acrylate polymer solution thus obtained and 5 parts of 1-hydroxycyclohexyl phenyl ketone (trade name “Irgacure 184”, manufactured by Ciba Specialty Chemicals) as a photoinitiator were mixed well, and the solid content concentration was 45 mass. %, A mixed solvent of ethyl acetate / butyl acetate = 1/1 was added to prepare a protective layer coating solution.

(D) Coating of protective layer coating liquid The coating liquid obtained in (C) is coated on the heat-sensitive recording layer coated surface of the coated sheet prepared in (B), dried at 120 ° C. for 1 minute, and then irradiated. The film was cured by passing it under an ultraviolet lamp with an energy of 80 W / cm at a conveying speed of 9 m / min, and a protective layer having a thickness of 3 μm after drying and curing was provided to obtain a reversible thermosensitive recording material of the present invention.

(E) Preparation of coating solution for adhesive layer 30 parts of saturated polyester resin (trade name “PES-355S30”, manufactured by Toagosei Co., Ltd.), 56 parts of toluene, 14 parts of methyl ethyl ketone, and polyhydric alcohol fatty acid ester (trade name “SL”) 02 ", manufactured by Riken Vitamin Co., Ltd.) was mixed well to prepare an adhesive layer coating solution.

(F) Application of adhesive layer coating liquid The adhesive layer coating liquid obtained in (E) was applied to the non-coated surface on the support of the heat-sensitive recording material so that the dry film thickness was 10 μm, and at 80 ° C. It was dried for 3 minutes to provide an adhesive layer.

  In the preparation of the protective layer coating solution of Example 1 (C), a protective layer coating solution was prepared without adding a photoinitiator. (D) In the coating of the protective layer coating solution, the same procedure as in Example 1 was performed, except that the protective layer coating solution thus obtained was used, and instead of irradiation with an ultraviolet lamp, irradiation with an electron beam with an irradiation dose of 10 Mrad was performed. Thus, a reversible thermosensitive recording material of the present invention was obtained.

(G) Preparation of protective layer coating solution 2
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a methylene group, and are composed only of aliphatic hydrocarbons. An ethyl acetate / butyl acetate = 1/1 solution of a functional acrylate polymer (number average molecular weight: 12,000, double bond equivalent: 200, solid content concentration: 50 mass%) was obtained. 120 parts of the polyfunctional epoxy acrylate solution thus obtained, 40 parts of pentaerythritol triacrylate as a polyfunctional (meth) acrylic monomer, 1-hydroxycyclohexyl phenyl ketone (trade name “Irgacure 184”, Ciba Specialty Chemicals, Ltd. as a photoinitiator) 5 parts) was mixed well, and a mixed solvent of ethyl acetate / butyl acetate = 1/1 was added so that the solid content concentration was 45% by mass to prepare a protective layer coating solution.

  In the coating of the protective layer coating liquid of Example 1 (D), the reversible thermosensitive material of the present invention was used in the same manner as in Example 1 except that the coating liquid obtained in (G) Preparation 2 of the protective layer coating liquid was used. A recording material was obtained.

In the preparation 2 of the protective layer coating solution (G) of Example 3, all the structures of the (meth) acryloyl group as the polyfunctional (meth) acrylate polymer are Q ¹ , Q ³ , Q ⁴ , Q ⁵ in the general formula 1. Of the polyfunctional acrylate polymer (number average molecular weight: 5000, double bond equivalent: 200, solid content concentration: 50% by mass), each of which is a hydrogen atom, Q ² is represented by a methylene group, and is composed only of aliphatic hydrocarbons. A protective layer coating solution was prepared using the solution. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In the preparation 2 of the protective layer coating solution (G) of Example 3, all the structures of the (meth) acryloyl group as the polyfunctional (meth) acrylate polymer are Q ¹ , Q ³ , Q ⁴ , Q ⁵ in the general formula 1. Of the polyfunctional acrylate polymer (number average molecular weight: 45000, double bond equivalent: 200, solid content concentration: 50% by mass), each of which is a hydrogen atom, Q ² is represented by a methylene group, and is composed only of an aliphatic hydrocarbon. A protective layer coating solution was prepared using the solution. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

  In Preparation 2 of Example 3 (G) Protective Layer Coating Liquid, the protective layer coating liquid was prepared by changing the number of blended parts of the polyfunctional acrylate polymer solution to 160 parts and 20 parts of pentaerythritol triacrylate. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

  In Preparation 2 of Example 3 (G) Protective Layer Coating Liquid, the protective layer coating liquid was prepared by changing the blending number of the polyfunctional acrylate polymer solution to 80 parts and pentaerythritol triacrylate to 60 parts. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
(Meth) structure acryloyl groups are all, Q ¹ is a methyl group in the general formula 1, Q ² is methylene group, Q ^3, Q ^4, also Q ⁵ are both represented by hydrogen, constituting only aliphatic hydrocarbon A protective layer coating solution was prepared using a solution of the polyfunctional acrylate polymer (number average molecular weight: 12000, double bond equivalent: 200, solid content concentration: 50% by mass). A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a methylene group, and are composed only of aliphatic hydrocarbons. A protective layer coating solution was prepared using a solution of a functional acrylate polymer (number average molecular weight: 12,000, double bond equivalent: 500, solid concentration 50 mass%). A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a methylene group, and are composed only of aliphatic hydrocarbons. A protective layer coating solution was prepared using a solution of a functional acrylate polymer (number average molecular weight: 12,000, double bond equivalent: 1500, solid content concentration: 50 mass%). A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a propylene group, and is composed only of aliphatic hydrocarbons. A protective layer coating solution was prepared using a solution of a functional acrylate polymer (number average molecular weight: 12,000, double bond equivalent: 250, solid concentration 50 mass%). A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
All structures of the (meth) acryloyl group are all represented by Q ¹ , Q ³ , Q ⁴ , and Q ⁵ in the general formula 1 as a hydrogen atom, and Q ² is a (CH ₂ —CH ₂ —O) _n —CH ₂ group (n The average value is about 9), and a solution of a polyfunctional acrylate polymer (number average molecular weight: 12000, double bond equivalent: 500, solid content concentration: 50% by mass) composed only of aliphatic hydrocarbons is used. Thus, a protective layer coating solution was prepared. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In the preparation 2 of the protective layer coating solution (G) of Example 3, all the structures of the (meth) acryloyl group as the polyfunctional (meth) acrylate polymer are Q ¹ , Q ³ , Q ⁴ , Q ⁵ in the general formula 1. Is a hydrogen atom, Q ² is represented by a methylene group, and a polyfunctional acrylate polymer (number average molecular weight: 12,000, double bond equivalent: 200, solid content concentration: 50% by mass) composed only of aliphatic hydrocarbons. A solution of ethyl acetate / butyl acetate = 1/1 was obtained. This polyfunctional acrylate polymer has a structure in which a monomer consisting only of glycidyl (meth) acrylate is polymerized to form a main chain, and the epoxy group of this polymer is reacted with acrylic acid to perform esterification. Have. 120 parts of the polyfunctional epoxy acrylate solution thus obtained, 40 parts of pentaerythritol triacrylate as a polyfunctional (meth) acrylic monomer, 1-hydroxycyclohexyl phenyl ketone (trade name “Irgacure 184”, Ciba Specialty Chemicals, Ltd. as a photoinitiator) 5 parts) was mixed well, and a mixed solvent of ethyl acetate / butyl acetate = 1/1 was added so that the solid content concentration was 45% by mass to prepare a protective layer coating solution.

  In preparation 2 of the protective layer coating solution (G) of Example 3, the epoxy acrylate solution was trade name “Beam Set 3700” (Arakawa Chemical Industries, Ltd., ethyl acetate / butyl acetate mixed solvent, solid concentration 50 mass). %, Number average molecular weight: 10000, double bond equivalent: 200, composed only of aliphatic hydrocarbons) to prepare a protective layer coating solution. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
The structure of the (meth) acryloyl group is all represented by Q ¹ , Q ³ , Q ⁴ , and Q ⁵ in general formula 1 as hydrogen atoms, Q ² as a methylene group, and aliphatic hydrocarbons and aromatic hydrocarbons A solution of a polyfunctional acrylate polymer (number average molecular weight: 12000, double bond equivalent: 500, theoretical dry solid content ratio of aliphatic hydrocarbon: 85 mass%, solid content concentration of 50 mass%) is used. Thus, a protective layer coating solution was prepared. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
The structure of (meth) acryloyl group is a structure in which an acrylic acid is reacted with a polymer having a hydroxyl group in the side chain to form an ester bond, and a polyfunctional acrylate polymer (number average) composed only of aliphatic hydrocarbons. A protective layer coating solution was prepared using a solution having a molecular weight of 12,000, a double bond equivalent of 1500 and a solid content of 50% by mass. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
(Meth) acryloyl group structure is a polyfunctional acrylate polymer composed of only aliphatic hydrocarbons, which is a structure in which hydroxyethyl acrylate is reacted with a polymer having an isocyanate group in the side chain to form a urethane bond. A protective layer coating solution was prepared using a solution of (number average molecular weight: 12000, double bond equivalent: 1500, solid content concentration: 50 mass%). A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

  The protective layer coating solution used in Example 10 / the protective layer coating solution used in Example 17 were mixed at a ratio of 7/3 to prepare a protective layer coating solution. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

  A dispersion of 15 parts of wet silica treated with an organosilicone compound (trade name “Silo Hovic 200”, manufactured by Fuji Silysia Chemical Co., Ltd.) and 85 parts of isopropyl alcohol together with glass beads in a paint shaker for 1 hour. Obtained. (G) In preparation 2 of the protective layer coating solution, 60 parts of the silica dispersion thus obtained was further added to prepare a protective layer coating solution. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

In Example 19 , except that the wet method silica treated with the organosilicon compound was changed to the wet method silica treated with wax (trade name “AZ260”, manufactured by Tosoh Silica Co., Ltd.), the same as in Example 19. A reversible thermosensitive recording material of the present invention was obtained.

The same procedure as in Example 19 was conducted except that the wet process silica treated with the organosilicon compound was changed to an untreated wet process silica (trade name “AY200”, manufactured by Tosoh Silica Co., Ltd.) in Example 19. An inventive reversible thermosensitive recording material was obtained.

  In Preparation 1 of Example 1 (A) Thermosensitive Recording Layer Coating Liquid, Example Compound (1-4) was used instead of Example Compound (1-3) as the reversible developer, and the thermal recording layer coating liquid was used. Was prepared. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 3 except that the thus obtained thermosensitive recording layer coating solution was used.

  In Preparation 1 of Example 1 (A) Thermosensitive Recording Layer Coating Liquid, Exemplified Compound (1-5) was used instead of Illustrative Compound (1-3) as the reversible developer, and the thermal recording layer coating liquid was used. Was prepared. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 3 except that the thus obtained thermosensitive recording layer coating solution was used.

  In Preparation 1 of Example 1 (A) Thermosensitive Recording Layer Coating Liquid, instead of Exemplified Compound (1-3) as the reversible developer, Exemplified Compound (1-6) was used as the thermal recording layer coating liquid. Was prepared. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 3 except that the thus obtained thermosensitive recording layer coating solution was used.

  In Preparation 1 of Example 1 (A) Thermosensitive Recording Layer Coating Liquid, Example Compound (1-7) was used instead of Example Compound (1-3) as the reversible developer, and the thermal recording layer coating liquid was used. Was prepared. A reversible thermosensitive recording material of the present invention was obtained in the same manner as in Example 3 except that the thus obtained thermosensitive recording layer coating solution was used.

  6 parts of stearic acid, 4 parts of eicosane diacid, 2 parts of diisodecyl phthalate, vinyl chloride / vinyl acetate / phosphorus ester copolymer (trade name “Denka Vinyl # 1000P”, manufactured by Denki Kagaku Kogyo Co., Ltd.), tetrahydrofuran A coating solution containing 150 parts and 15 parts of toluene was applied to a 25 μm-thick transparent polyethylene terephthalate (PET) sheet so that the dry film thickness was 5 μm, and dried at 120 ° C. for 3 minutes to produce a thermosensitive recording layer. Formed. Next, using a solution comprising 5 parts of polyamide resin (trade name “CM8000”, manufactured by Toray Industries, Inc.) and 90 parts of methyl alcohol, it was applied onto the heat-sensitive recording layer so that the dry film thickness was 0.3 μm. And dried at 120 ° C. for 3 minutes. Furthermore, using the protective layer coating liquid obtained in (G) Preparation 2 of the protective layer coating liquid, a protective layer and an adhesive layer are provided in the same manner as in Example 1, and the reversible thermosensitive recording material of the present invention. Got.

Comparative Example 1
In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a methylene group, and are composed only of aliphatic hydrocarbons. A protective layer coating solution was prepared using a solution of a functional acrylate polymer (number average molecular weight: 3000, double bond equivalent: 200, solid content concentration 50% by mass). A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

Comparative Example 2
In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a methylene group, and are composed only of aliphatic hydrocarbons. A solution of a functional acrylate polymer (number average molecular weight: 80000, double bond equivalent: 200, solid content concentration: 30% by mass) was obtained. A protective layer coating solution was prepared in the same manner as in (G) Preparation of protective layer coating solution 2 except that 200 parts of the polyfunctional acrylate polymer solution thus obtained was used and the solid content concentration was 40% by mass. A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

Comparative Example 3
In preparation 2 of the protective layer coating solution (G) of Example 3, as the polyfunctional acrylate polymer,
All structures of (meth) acryloyl groups are represented by Q ¹ , Q ³ , Q ⁴ , Q ⁵ in general formula 1 are all hydrogen atoms, Q ² is a methylene group, and are composed only of aliphatic hydrocarbons. A protective layer coating solution was prepared using a solution of a functional acrylate polymer (number average molecular weight: 12000, double bond equivalent: 2500, solid content concentration: 50% by mass). A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

Comparative Example 4
In Preparation 2 of Example 3 (G) Protective Layer Coating Liquid, a polyfunctional acrylate polymer was not used, and the amount of pentaerythritol triacrylate was changed to 100 parts to prepare a protective layer coating liquid. A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

Comparative Example 5
In Preparation 2 of the protective layer coating solution (G) of Example 3, a solution of a monofunctional acrylate polymer (number average molecular weight: 12000, solid content concentration: 50% by mass) instead of the polyfunctional acrylate polymer having a number average molecular weight of 12000 Was used to prepare a protective layer coating solution. A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

Comparative Example 6
To the protective layer coating solution prepared in Comparative Example 2, 60 parts of the silica dispersion used in Example 19 was further added. A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

Comparative Example 7
In preparation 2 of the protective layer coating solution (G) of Example 3, an epoxy acrylate having a bisphenol A skeleton (trade name “epoxy ester 3000A”, Kyoeisha Chemical Co., Ltd.) instead of the polyfunctional acrylate polymer having a number average molecular weight of 12000 )) Was used to prepare a protective layer coating solution. A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer coating solution thus obtained was used.

Test 1 (Curl)
The reversible thermosensitive recording materials obtained in Examples 1 to 26 and Comparative Examples 1 to 7 were cut into 10 cm × 10 cm and stored for 1 day in an environment of 23 ° C. and 50% RH. The sheet after storage was placed on a flat surface, the height was measured from a quadrangular plane, and the maximum height was taken as the curl value. The results are shown in Table 1. Smaller values indicate better curl. When the curl value exceeds 10 mm, it impedes practical handling. In Table 1, the evaluation result x indicates that the sheet is curled into a cylindrical shape and cannot be measured.

Test 2 (powder removal after punching)
For the reversible thermosensitive recording materials obtained in Examples 1 to 26 and Comparative Examples 1 to 7, a polyvinyl chloride film having a thickness of 200 μm was superimposed on the side opposite to the side on which the thermosensitive recording layer was provided on the support, It was sandwiched between two stainless steel mirror plates and thermocompression bonded at 130 ° C. and a pressure of 1.5 MPa for 20 minutes to finish a reversible thermosensitive recording material laminate. The laminate thus obtained was finished to a card size using a punching machine. About the end surface of the completed card | curd, the state of powder fall was determined on the following references | standards by visual observation and microscopic observation. The results are shown in Table 1.
A: Even if the end face is rubbed with a finger, no powder adheres. Even with microscopic observation, the coating layer is almost free from chipping.
○: No powder adheres even if the end face is rubbed with a finger. In microscopic observation, chipping of a small coating layer is observed in some places, but there is no practical problem.
(Triangle | delta): When an end surface is rubbed with a finger, powder will adhere slightly. In microscopic observation, relatively large chipping of the coating layer can be observed continuously.
X: When the end face is rubbed with a finger, white powder adheres. The chipped coating layer on the end face of the card can be confirmed visually.

Test 3 (Repeatability 1)
The card produced in Test 2 was printed in the printing test mode (printing speed 69 mm / s, thermal head resistance 450 Ω) of Sanwa Newtech printer (ABS-3001KMT), and then erased at 100 minutes every 2 minutes. Repeated times. The state of the printed portion at the 100th time was visually observed and judged according to the following criteria. The results are shown in Table 1.
(Double-circle): The printed part is not damaged at all, and a beautiful image is formed.
○: A clear image is formed, but the area around the thermal head is slightly visible.
Δ: Printed, but scratched.
X: The printed part is scratched and the scratched part is not printed.

Test 4 (Repeatability 2)
For the reversible thermosensitive recording materials obtained in Examples 3 and 19 to 21, the number of repetitions was increased to 300 in the repeated durability test of Test 3. The state of the 300th printed portion was visually observed and judged using the above evaluation criteria.

Test 5 (Stability of protective layer coating solution over time)
About the protective layer coating liquid of Examples 19-21, the state of the coating liquid after one week was observed, and it determined by the following references | standards. The results are shown in Table 1.
(Double-circle): Although sedimentation of silica is seen, it returns to the original dispersion state by simple stirring.
○: Although precipitation of silica is observed, the dispersion returns to the original dispersed state by slightly agitation and longer time.
X: A hard silica sediment is formed. Even if stirring is performed carefully, silica agglomerates are not lost and the original state is not restored.

  As is clear from Table 1, the reversible thermosensitive recording materials of Examples 1 to 26 are less curled and have no powder falling off at the time of punching. Excellent durability. From the comparison of Examples 3 to 5 and Comparative Examples 1 and 2, when the number average molecular weight is 4000 to 50000, the balance of the above characteristics is good. From the comparison of Examples 3, 9, 10 and Comparative Example 3, when a polyfunctional (meth) acrylate polymer having a double bond equivalent of 180 to 2000 is used, both powder fall and repeated durability are excellent and preferable. From the comparison of Examples 1, 3, 6, and 7, a polyfunctional (meth) acrylic monomer was further blended in the protective layer, and the blending ratio of the polyfunctional (meth) acrylate polymer / polyfunctional (meth) acrylic monomer was determined before curing. When the active ingredient ratio is 9/1 to 3/7, the balance between powder falling and repeated durability is good. From the comparison between Examples 10 and 16 to 18, when 50% or more of the structure of the (meth) acryloyl group is the structure represented by the general formula 1, the repeated durability is good. From the comparison of Examples 3 and 19-21, when silica is added to the protective layer, repeated durability is further improved. Further, from the comparison of Examples 19 to 21, it is preferable to use hydrophobized silica because the stability with time of the protective layer coating liquid is improved.

  On the other hand, Comparative Example 1 using a polyfunctional (meth) acrylate polymer having a number average molecular weight of 3000 and a double bond equivalent of 200, and Comparative Example 4 using only a polyfunctional (meth) acryl monomer are severely curled and punched. Powder falling occurred during processing. In Comparative Examples 2 and 6 using a polyfunctional (meth) acrylate polymer having a number average molecular weight of 80000 and a double bond equivalent of 200, the viscosity of the coating liquid was high and difficult to handle, and repeated durability deteriorated. In Comparative Example 3 using a polyfunctional (meth) acrylate polymer having a number average molecular weight of 12,000 and a double bond equivalent of 2000 or more, repeated durability deteriorated. In Comparative Example 5 using a monofunctional (meth) acrylate polymer, repeated durability deteriorated. In Comparative Example 7 using an epoxy acrylate having a bisphenol A skeleton, curling was severe and powder falling occurred during punching.

  The reversible thermosensitive recording material of the present invention has little curling and does not cause powder falling due to cutting, punching, or the like, and thus can be used as a reversible thermosensitive recording material having excellent workability and good repeated durability.

Claims (5)

  In a reversible thermosensitive recording material having a thermosensitive recording layer and a protective layer whose transparency or color tone reversibly changes depending on temperature on one side of a support, an ultraviolet ray or electron beam curable resin having the protective layer as a main component A polyfunctional (meta) containing a cured product of the composition, wherein the ultraviolet or electron beam curable resin composition before curing has at least a number average molecular weight of from 4,000 to 50,000 and a double bond equivalent of from 180 to 2,000. ) A reversible thermosensitive recording material comprising an acrylate polymer.   The polyfunctional (meth) acrylate polymer before curing has a structure formed by polymerizing a monomer having at least an ethylenically unsaturated bond as a main chain, and has one (meth) acryloyl group in the side chain. The reversible thermosensitive recording material according to claim 1, which has a combined structure. The reversible thermosensitive recording material according to claim 1 or 2, wherein in the polyfunctional (meth) acrylate polymer before curing, 50% or more of the total number of (meth) acryloyl groups is a structure represented by the following general formula 1. .

(Q ¹ represents a hydrogen atom or a methyl group, Q ² represents a divalent linking group, and Q ³ , Q ⁴ , and Q ⁵ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.   The protective layer further contains a polyfunctional (meth) acrylic monomer, and the blending ratio of the polyfunctional (meth) acrylate polymer / polyfunctional (meth) acrylic monomer is 9/1 to 1 in terms of an active ingredient ratio (mass ratio) before curing. The reversible thermosensitive recording material according to any one of claims 1 to 3, which is 3/7.   The reversible thermosensitive recording material according to any one of claims 1 to 4, wherein the protective layer further contains silica.