JP2008246737A - Reversible thermosensitive recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reversible thermosensitive recording material, by which high print density is obtained and, at the same time, in which the change of surface conditions due to repeated printing/erasion is little and which has a favorable repetition durability. <P>SOLUTION: In this reversible thermosensitive recording material, which is formed by providing a thermosensitive recording layer, the transparency or color tone of which reversibly is changed by controlling thermal energy, and a protective layer on one side of a support, the protective layer includes dry process silica under the condition that preferable average primary particle diameter of the dry process silica is ≥5 and <25 nm and preferable average secondary particle diameter of the dry process silica is ≥0.1 and ≤6 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 having little change in surface state due to repeated printing and erasing and 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 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. Methods, a method of adding silica coated with organoclay and calcium, a method of adding a scaly pigment mainly composed of silica, 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.
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-A-8-175012 JP 2006-342918 A JP 2006-082299 A

  An object of the present invention is to provide a reversible thermosensitive recording material having a high printing density, little change in the surface state due to repeated printing and erasing, and good repeated durability.

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

  A reversible thermosensitive recording material provided with a thermosensitive recording layer and a protective layer in which transparency or color tone reversibly changes by controlling thermal energy on one side of the support, characterized in that the protective layer contains dry process silica. It is a reversible thermosensitive recording material.

  The average primary particle diameter of the dry process silica is preferably 5 nm or more and less than 25 nm.

  The average secondary particle diameter of the dry process silica is preferably 0.1 μm or more and 6 μm or less.

  The protective layer preferably contains an ultraviolet curable resin and / or a thermosetting resin, and the thermosetting resin is particularly preferably crosslinked with an isocyanate.

  With the reversible thermosensitive recording material of the present invention, it is possible to obtain a reversible thermosensitive recording material having a high printing density, little change in surface state due to repeated printing and erasing, and good repeated durability.

  The reversible thermosensitive recording material of the present invention will be described in detail below. The reversible thermosensitive recording material of the present invention is a reversible thermosensitive recording material in which a thermal recording layer and a protective layer whose transparency or color tone is reversibly changed by controlling thermal energy are provided on one side of a support. It contains a dry process silica. With this configuration, there are few changes such as changes in surface gloss and cracking due to repeated printing and erasing, printing density is not lowered, erasing defects are difficult to occur, and repeated durability is good. A reversible thermosensitive recording material can be obtained.

  The dry process silica according to the present invention is also referred to as gas phase process 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. The dry silica is usually secondary particles in which primary particles, that is, unaggregated single particles aggregate in a bead shape, and particles connected in a bead shape form a network structure. For example, various grades are commercially available as Aerosil from Nippon Aerosil Co., Ltd. and Leorosil from Tokuyama Co., Ltd.

  The reason why the dry durability is improved by including dry process silica in the protective layer, with less change such as change in surface gloss and cracking due to repeated printing and erasing. It is estimated as follows. Dry silica, unlike many other organic and inorganic pigments, has a network structure in which primary particles are highly connected in a bead shape. For this reason, it is easy to form a matrix structure in the protective layer resin, and the reinforcing effect is high. Further, since the mesh structure can be deformed flexibly, it is considered that the mesh structure is not easily broken by deformation during printing / erasing. Moreover, since the primary particles have a solid structure, it is difficult to absorb the resin component of the protective layer, and a high-density protective layer can be formed. On the other hand, when silica other than the dry method, such as wet colloidal silica, precipitation method or gel method silica, is included in the protective layer, these wet method silicas are generally spherical in shape and have little reinforcing effect. Repeated durability is inferior to silica. In addition, organic and inorganic pigments other than dry-process silica are similarly poor in durability.

  In addition, by including dry process silica in the protective layer, a higher color density can be obtained as compared with the case where other pigments are included. Dry process silica has a large network void formed by connecting primary particles in a bead shape, and the protective layer resin sufficiently enters the void in the network structure to fill the void, thus obtaining a highly transparent protective layer. It is difficult to conceal the color of the heat-sensitive recording layer. In particular, when the average primary particle diameter is less than 25 nm, high color developability can be obtained. Further, when the average primary particle diameter is 5 nm or more, the reinforcing effect is high, and higher repetition durability is obtained. Therefore, it is particularly preferable that the average primary particle diameter is 5 nm or more and less than 25 nm, since both the repeated durability and the color developability are improved. The average primary particle size of the dry method silica referred to in the present invention is obtained by observing the dry method silica with an electron microscope, and determining the particle size of 100 arbitrary primary particles, and obtaining the simple average (number average). Value. Here, each particle diameter is represented by a diameter assuming a circle equal to the projected area.

  The dry process silica according to the present invention preferably has an average secondary particle size of 0.1 μm or more and 6 μm or less. When the average secondary particle diameter is 0.1 μm or more, high repeated durability is obtained. If the average secondary particle diameter is less than 0.1 μm, the repeated durability may be insufficient. Further, when the average secondary particle diameter is 6 μm or less, the surface smoothness is not impaired, the contact property with the print head is improved, and high color development sensitivity is obtained. When high sensitivity is not required, the average secondary particle diameter can be made larger than 6 μm for the purpose of keeping the surface gloss low. In this case, it is possible to obtain a reversible thermosensitive recording material in which the gloss change of the printed part is small compared to the case where a pigment other than dry silica is used. The average secondary particle diameter of the dry process silica referred to in the present invention is a value obtained by measuring a dilute dispersion of dry process silica with a laser diffraction / scattering particle size distribution measuring device.

  The average secondary particle diameter of the dry process silica according to the present invention can be adjusted by pulverization as necessary. The pulverization is performed by a known mechanical pulverizer, for example, a media mill such as a ball mill, a bead mill, or a sand grinder, a pressure disperser such as a high pressure homogenizer or an ultra high pressure homogenizer, an ultrasonic disperser, and a thin film swirl disperser. Can do.

  The dry process silica contained in the protective layer according to the present invention can be used regardless of whether the surface is hydrophilic or hydrophobic. The surface of dry-process silica that has not been surface-treated is usually hydrophilic. It is also possible to modify the hydrophobic surface by subjecting such hydrophilic surface dry silica to a surface treatment. For the hydrophobic surface treatment, a conventionally known method such as a silane coupling agent, an alkoxysilane compound, an organic silicone compound treatment with a silicone oil, a wax treatment or the like can be used. By appropriately adjusting the surface property of the dry process silica, the adhesiveness with the resin constituting the protective layer can be improved, and better repeated durability can be obtained.

  The blending amount of the dry process silica in the protective layer is preferably 3% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, particularly preferably relative to the resin contained in the protective layer. It is 5 mass% or more and 15 mass% or less. If the blending amount of the dry process silica is less than 3% by mass, sufficient repeated durability may not be obtained. Further, when the blending amount exceeds 30% by mass, sufficient repeated durability may not be obtained.

  In the present invention, the resin used in the protective layer is not particularly limited, but preferably contains an ultraviolet curable resin and / or a thermosetting resin. When these resins are used, particularly good printing / erasing durability can be obtained.

  In order to improve the function of the protective layer resin, a plurality of monomers and oligomers can be mixed. UV curable resins include urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, vinyl, unsaturated polyester oligomers, various monofunctional and polyfunctional acrylates, methacrylates, vinyl esters, ethylene derivatives. And monomers such as allyl compounds. Particularly preferred are tri- or higher functional polymerizable monomers and oligomers. Examples of multifunctional monomers and oligomers include trimethylolpropane triacrylate, pentaerythritol triacrylate, glycerin propyloxy addition triacrylate, trisacryloyloxyethyl phosphate, pentaerythritol tetraacrylate, trimethylolpropane propylene oxide 3 mol adduct Triacrylate, glyceryl propoxytriacrylate, dipentaerythritol polyacrylate, polyacrylate of dipentaerythritol caprolactone adduct, propionic acid / dipentaerythritol triacrylate, hydroxypivalaldehyde-modified dimethylolpropane triacrylate, propionic acid / Dipentaerythritol tetraacrylate, ditrimethylo Propane tetraacrylate, pentaacrylate of dipentaerythritol propionate, trimethylolpropane triacrylate added urethane prepolymer, dipentaerythritol hexaacrylate (DPHA), include ε- caprolactone adducts of DPHA.

  In the case of curing using ultraviolet rays, a photopolymerization initiator and a photopolymerization accelerator can be used. Photopolymerization initiators can be broadly classified into radical reaction types and ion reaction types, and radical reaction types are further divided into photocleavage types and hydrogen abstraction types. Examples of photopolymerization initiators include isobutyl benzoin ether, isopropyl benzoin ether, benzoin ethyl ether benzoin methyl ether, 1-phenyl-1,2-propanedione-2- (o-ethoxycycarbonyl) oxime, 2,2- Dimethoxy-2-phenylacetophenone benzyl, hydroxycyclohexyl phenyl ketone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzophenone, chlorothioxanthone, 2-chlorothioxanthone, isopropylthioxanthone, 2-methyl Examples thereof include thioxanthone and chlorine-substituted benzophenone, and are used alone or as a mixture of two or more thereof, but are not limited thereto. Further, as the photopolymerization accelerator, those having an effect of improving the curing rate with respect to hydrogen abstraction type photopolymerization initiators such as benzophenone series and thioxanthone series are preferable. For example, aromatic tertiary amines and fats are used. There is a group of 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 combination 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 or less, based on the total mass of the resin component of the protective layer. It is.

  Examples of thermosetting resins include phenoxy resins, polyvinyl butyral resins, cellulose acetate propionate, cellulose acetate butyrate, acrylic polyols, polyester polyols, polyurethane polyols, and other resins having groups that react with crosslinking agents such as hydroxyl groups and carboxyl groups. Alternatively, a resin obtained by copolymerizing a monomer having a hydroxyl group or a carboxyl group and another monomer can be used. Among them, acrylic polyol resin, polyester polyol resin, and polyurethane polyol resin are preferable. When the hydroxyl value is 70 (KOHmg / g) or more, durability, coating film surface hardness, and crack resistance can be improved. Especially preferably, it is 90 (KOHmg / g) or more. The magnitude of the hydroxyl value affects the crosslink density, and therefore affects the chemical resistance and physical properties of the coating film. Acrylic polyol resins have different characteristics depending on the structure, and the hydroxyl monomers are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 4 -Hydroxybutyl acrylate, 4- (hydroxymethyl) cyclohexylmethyl acrylate, and the like are used. In particular, the use of a monomer having a primary hydroxyl group is preferable because the coating has good crack resistance and durability.

  Examples of the thermal crosslinking crosslinking agent include isocyanates, amino resins, phenol resins, amines, and epoxy compounds. Of these, isocyanates are preferable, and polyisocyanate compounds having a plurality of isocyanate groups are particularly preferable. Specific examples include hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), xylylene diisocyanate (XDI), and trimethylols thereof. Examples thereof include adduct types such as propane, burette types, isocyanurate types, and blocked isocyanates. The addition amount of the crosslinking agent to the resin is preferably such that the ratio of the functional group of the crosslinking agent to the number of active groups contained in the resin is 0.01 or more and 2.00 or less, and if less than 0.01, the heat strength is insufficient. In addition, if it exceeds 2.00, the coloring / decoloring characteristics may be adversely affected. Furthermore, you may use the catalyst used for this kind of reaction as a crosslinking accelerator. Examples of the crosslinking accelerator include tertiary amines such as 1,4-diazabicyclo [2.2.2] octane, metal compounds such as organotin compounds, and the like.

  In the protective layer of the present invention, pigments other than dry process silica can also be added within a range that does not interfere with the purpose of the present invention, for example, aluminum, zinc, calcium, magnesium, barium, titanium and other carbonates, oxides, Inorganic pigments including hydroxides, sulfates, etc. and clays such as wet process silica, zeolite, kaolin, calcined kaolin, talc, starch, styrene resin, polyolefin resin, urea-formalin resin, melamine resin, acrylic resin, Paraffin, natural wax, synthetic wax and the like 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 by controlling thermal energy. 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 1, 2, and 3 are preferable, and in particular, a compound represented by the general formula 1 is 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 1, 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 contain 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 50 carbon atoms, preferably a hydrocarbon group having 6 to 36 carbon atoms, and more preferably a hydrocarbon group having 8 to 24 carbon atoms. R ¹ and R ² mainly represent an alkylene group or an alkenylene group, and R ³ mainly represents an alkyl group or an alkenyl group. 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.

X ¹ and X ² in the general formula 1 include a divalent group having a —CONH— bond that does not include a hydrocarbon group at both ends as a minimum structural unit. Specific examples thereof include diacylamine (—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 2 and 3 is also preferably used.

In general formula 2, 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 the 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 3, 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. 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 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 and 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.

  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 ° C. to 200 ° C. are preferred, and those having a melting point of 80 ° C. 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, an intermediate layer composed of an ultraviolet absorber, an antioxidant, or the like is provided between the heat-sensitive recording layer and the protective layer for the purpose of improving weather resistance or the like. A coat layer may be provided. In addition, a backcoat layer may be provided on the surface opposite to the surface on which the heat-sensitive recording layer is provided for the purpose of preventing curling or charging, or a layer capable of magnetically recording information may be provided. For example, a material that can be electrically and optically recorded with information may be included between another substrate and another 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, U comma coater, AKKU coater, smoothing coater, micro gravure coater, reverse roll coater, 4 roll roll coater, 4 roll roll coater , Coaters such as dip coaters, rod coaters, kiss coaters, gate roll coaters, squeeze coaters, slide coaters, die coaters, etc., and various printing machines such as lithographic, letterpress, intaglio, flexo, gravure, screen, hot melt, etc. I can do it. 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 dispersion of 100 parts of polyester polyol (Dainippon Ink Chemical Co., Ltd., trade name: Burnock 11-408, active ingredient 70 mass%) and 950 parts of methyl ethyl ketone is dispersed with a glass bead for 5 hours with a paint shaker to obtain a dispersion. It was. 130 parts of an isocyanate compound (trade name: Takenate D-110N, active ingredient 75 mass%) manufactured by Mitsui Chemicals Polyurethane Industry Co., Ltd. and 62 parts of methyl ethyl ketone are added to the dispersion thus obtained and mixed well. Was prepared.

(B) Application of heat-sensitive recording layer coating solution The coating solution obtained in (A) was applied to a white polyethylene terephthalate (PET) sheet having a thickness of 250 μm so that the dry coating amount was 10 g / m ² . Drying was performed at 100 ° C. for 5 minutes to form a heat-sensitive recording layer.

(C) Preparation of protective layer coating liquid 15 parts of dipentaerythritol hexaacrylate which is an acrylate-based oligomer, 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), light 1 part of 1-hydroxycyclohexyl phenyl ketone as a polymerization initiator and 85 parts of methyl ethyl ketone were mixed. The mixed solution thus obtained was treated with a bead mill, and the average secondary particle diameter of dry silica was adjusted to 3 μm to prepare a protective layer coating solution.

(D) Coating of protective layer coating solution On the heat-sensitive recording layer coating surface of the coating sheet prepared in (B), the coating solution obtained in (C) was applied so that the dry coating amount was 3 g / m ^2. Then, after drying at 120 ° C. for 1 minute, the film was cured by passing through an ultraviolet lamp with an irradiation energy of 80 W / cm at a conveyance speed of 9 m / min to provide a protective layer, whereby the reversible thermosensitive recording material of Example 1 was obtained. .

  In Example 1 (C), instead of using 1.5 parts of dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), Example was used except that 3.0 parts were used. In the same manner as in Example 1, a reversible thermosensitive recording material of Example 2 was obtained.

  In Example 1 (C), instead of using 1.5 parts of dry-process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), Example was used except that 4.5 parts were used. In the same manner as in Example 1, a reversible thermosensitive recording material of Example 3 was obtained.

  In Example 1 (C), instead of using 1.5 parts of dry-process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), Example was used except that 0.75 parts was used. In the same manner as in Example 1, a reversible thermosensitive recording material of Example 4 was obtained.

  In Example 1 (C), instead of using 1.5 parts of dry-process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), Example was used except that 0.45 parts were used. In the same manner as in Example 1, a reversible thermosensitive recording material of Example 5 was obtained.

  In Example 1 (C), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 6 was obtained in the same manner as in Example 1 except that 1.5 parts (trade name: AEROSIL200, average primary particle size 12 nm) were used.

  In Example 1 (C), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 7 was obtained in the same manner as in Example 1 except that 4.5 parts (trade name: AEROSIL200, average primary particle size 12 nm) were used.

  In Example 1 (C), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 8 was obtained in the same manner as in Example 1 except that 0.75 part (trade name: AEROSIL200, average primary particle size 12 nm) was used.

  In Example 1 (C), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 9 was obtained in the same manner as in Example 1 except that 1.5 parts (trade name: AEROSIL90G, average primary particle diameter 20 nm) were used.

  In Example 1 (C), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 10 was obtained in the same manner as Example 1 except that 4.5 parts (trade name: AEROSIL90G, average primary particle diameter 20 nm) were used.

  In Example 1 (C), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 11 was obtained in the same manner as in Example 1 except that 0.75 part (trade name: AEROSIL90G, average primary particle diameter 20 nm) was used.

  In Example 1 (C), instead of adjusting the average secondary particle size of dry silica to 3 μm, the reversible feeling of Example 12 was the same as Example 1 except that the average secondary particle size was adjusted to 6 μm. A thermal recording material was obtained.

  In Example 1 (C), instead of adjusting the average secondary particle diameter of dry silica to 3 μm, the reversible feeling of Example 13 was the same as Example 1 except that the average secondary particle diameter was adjusted to 1 μm. A thermal recording material was obtained.

  In Example 1 (C), instead of adjusting the average secondary particle size of dry-process silica to 3 μm, the average secondary particle size was adjusted to 0.1 μm. A reversible thermosensitive recording material was obtained.

  In Example 1 (C), instead of using 15 parts of dipentaerythritol hexaacrylate, urethane acrylate-based ultraviolet curable resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: Unidic 17-813 active ingredient 80% by mass) ) A reversible thermosensitive recording material of Example 15 was obtained in the same manner as Example 1 except for using 18.8 parts.

  In Example 1 (C), instead of using 15 parts of dipentaerythritol hexaacrylate, an epoxy acrylate-based ultraviolet curable resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: Unidic V-5500, 100% by mass of active ingredient) ) A reversible thermosensitive recording material of Example 16 was obtained in the same manner as in Example 1 except that 15 parts were used.

(E) Preparation of protective layer coating liquid Polyester polyol (Dainippon Ink Chemical Co., Ltd., trade name: Bernock 11-408, active ingredient 70% by mass) 100 parts, methyl ethyl ketone 800 parts, dry silica (Nippon Aerosil ( Co., Ltd., trade name: AEROSIL300, average primary particle diameter 7 nm) was mixed and treated with a bead mill, and the average secondary particle diameter of the dry silica was adjusted to 3 μm. To this mixed solution, 140 parts of an isocyanate compound (trade name: Takenate D-110N, active ingredient 75% by mass, manufactured by Mitsui Chemicals Polyurethane Industry Co., Ltd.) and 50 parts of methyl ethyl ketone were added and mixed well to prepare a protective layer coating solution.

(F) a protective layer coating solution of the coating in Example 1 (B) coated sheet of heat-sensitive recording layer coating surface on prepared in the coating liquid dry coating amount is 3 g / m ² obtained in (E) And dried at 120 ° C. for 1 minute and then cured by heating at 50 ° C. for 24 hours to provide a protective layer, whereby the reversible thermosensitive recording material of Example 17 was obtained.

(G) Preparation of intermediate layer coating solution 50 parts of UV absorber (Ciba Specialty Chemicals Co., Ltd., trade name: Tinuvin 328), polyester polyol (Dainippon Ink Chemical Co., Ltd., trade name: Burnock 11) A mixture of 100 parts of -408, 70% by weight of active ingredient) and 800 parts of methyl ethyl ketone was dispersed with glass beads for 5 hours with a paint shaker to obtain a dispersion. 140 parts of an isocyanate compound (trade name: Takenate D-110N, active ingredient 75 mass%) manufactured by Mitsui Chemicals Polyurethane Industry Co., Ltd. and 50 parts of methyl ethyl ketone are added to the dispersion thus obtained and mixed well to prepare an intermediate layer coating solution. did.

(H) in the intermediate layer coating solution of the coating in Example 1 (B) coated sheet of heat-sensitive recording layer coating surface on prepared in the coating liquid dry coating amount is 2 g / m ² obtained in (G) After coating at 120 ° C. for 1 minute, the coating was further cured by heating at 50 ° C. for 24 hours to provide an intermediate layer.

(I) Preparation of protective layer coating solution 15 parts of dipentaerythritol hexaacrylate which is an acrylate oligomer, dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle size 7 nm), light 1 part of 1-hydroxycyclohexyl phenyl ketone as a polymerization initiator and 85 parts of methyl ethyl ketone were mixed. The mixed solution thus obtained was treated with a bead mill, and the average secondary particle diameter of dry silica was adjusted to 3 μm to prepare a protective layer coating solution.

(J) Coating of protective layer coating solution On the intermediate layer coating surface of the coating sheet prepared in (H), apply the coating solution obtained in (I) so that the dry coating amount is 3 g / m ^2. After drying at 120 ° C. for 1 minute, the film was cured by passing through an ultraviolet lamp with an irradiation energy of 80 W / cm at a conveyance speed of 9 m / min to provide a protective layer, whereby the reversible thermosensitive recording material of Example 18 was obtained.

  In Example 18 (I), instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 19 was obtained in the same manner as in Example 18 except that 1.5 parts (trade name: AEROSIL200, average primary particle size 12 nm) were used.

  In Example 18 (I), instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 20 was obtained in the same manner as Example 18 except that 1.5 parts (trade name: AEROSIL90G, average primary particle diameter 20 nm) were used.

  Example 1 (C) was carried out in the same manner as in Example 1 except that the average secondary particle size was adjusted to 7 μm instead of adjusting the average secondary particle size of the dry process silica to 3 μm. The reversible thermosensitive recording material of Example 21 was obtained.

  Instead of adjusting the average secondary particle size of the dry silica in Example 1 (C) to 3 μm, the same procedure as in Example 1 was performed except that the average secondary particle size was adjusted to 0.08 μm. Thus, a reversible thermosensitive recording material of Example 22 was obtained.

  In Example 1 (C), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (manufactured by Nippon Aerosil Co., Ltd.) A reversible thermosensitive recording material of Example 23 was obtained in the same manner as in Example 1 except that 1.5 parts (trade name: AEROSIL 50, average primary particle size 30 nm) were used.

  In Example 1 (C), instead of using 1.5 parts of dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), dry process silica (made by Degussa, Germany, trade name) : AEROSIL R812, average primary particle diameter 7 nm, trimethylsilyl group surface-treated product) A reversible thermosensitive recording material of Example 24 was obtained in the same manner as in Example 1 except that 1.5 parts were used.

  In Example 1 (A), Example was carried out in the same manner as in Example 1 except that 100 parts of Exemplified Compound (1-7) was used instead of 100 parts of Exemplified Compound (1-3) as a reversible developer. 25 reversible thermosensitive recording materials were obtained.

  In Example 1 (A), instead of using 100 parts of Exemplified Compound (1-3) as a reversible developer, 100 parts of Exemplified Compound (1-7) was used, and in (C), dry method silica (Nippon Aerosil) Instead of using 1.5 parts by product, product name: AEROSIL300, average primary particle size 7 nm), dry silica (product name: AEROSIL200, average primary particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd.) 1.5 A reversible thermosensitive recording material of Example 26 was obtained in the same manner as Example 1 except that the parts were used.

  In Example 1 (A), instead of using 100 parts of Exemplified Compound (1-3) as a reversible developer, 100 parts of Exemplified Compound (1-7) was used, and in (C), dry method silica (Nippon Aerosil) Instead of using 1.5 parts by product, product name: AEROSIL300, average primary particle size 7 nm), dry silica (product name: AEROSIL90G, average primary particle size 20 nm, manufactured by Nippon Aerosil Co., Ltd.) 1.5 A reversible thermosensitive recording material of Example 27 was obtained in the same manner as in Example 1 except that the parts were used.

Comparative Example 1
Example 1 (C) was the same as Example 1 except that 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle size 7 nm) was not added but not added. Thus, a reversible thermosensitive recording material of Comparative Example 1 was obtained.

Comparative Example 2
In Example 1 (C), instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), wet process silica (manufactured by Fuji Silysia Chemical Co., Ltd.) , Trade name: Silo Hovic 200) Using 1.5 parts of wet method silica and treating with a bead mill so that the average secondary particle diameter of the silica is 3 μm, the reversibility feeling of Comparative Example 2 is the same as Example 1. A thermal recording material was obtained.

Comparative Example 3
In Example 1 (C), instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), wet process silica (manufactured by Fuji Silysia Chemical Co., Ltd.) , Trade name: silo hovic 200) 4.5 parts of wet process silica was used in the same manner as in Example 1 except that it was treated with a bead mill so that the average secondary particle diameter was 3 μm. A thermal recording material was obtained.

Comparative Example 4
In Example 1 (C), instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), wet process silica (manufactured by Fuji Silysia Chemical Co., Ltd.) , Trade name: Silo Hovic 200) 0.75 parts, and reversible feeling of Comparative Example 4 in the same manner as in Example 1 except that the wet secondary silica was treated with a bead mill so that the average secondary particle diameter was 3 μm. A thermal recording material was obtained.

Comparative Example 5
In Example 1 (C), instead of using 15 parts of dipentaerythritol hexaacrylate, urethane acrylate ultraviolet curable resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: Unidic 17-813 active ingredient 80% by mass) 18 .8 parts, instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle size 7 nm), wet process silica (manufactured by Fuji Silysia Chemical Co., Ltd., product) Name: Silo Hovic 200) Reversible thermosensitive recording of Comparative Example 5 in the same manner as in Example 1 except that 1.5 parts was used and the bead mill was processed so that the average secondary particle diameter of the wet process silica was 3 μm. Obtained material.

Comparative Example 6
In Example 1 (C), instead of using 15 parts of dipentaerythritol hexaacrylate, an epoxy acrylate-based ultraviolet curable resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: Unidic V-5500, 100% by mass of active ingredient) ) 15 parts of dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), instead of using 1.5 parts of wet process silica (manufactured by Fuji Silysia Chemical Co., Ltd., product) Name: Silo Hovic 200) Reversible thermosensitive recording of Comparative Example 6 in the same manner as in Example 1 except that 1.5 parts was used and the bead mill was used so that the average secondary particle diameter of the wet process silica was 3 μm. Obtained material.

Comparative Example 7
In Example 17 (E), instead of using 1.5 parts by dry process silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), wet process silica (Fuji Silysia Chemical Co., Ltd.) was used. , Trade name: Silo Hovic 200) Using 1.5 parts of wet method silica and treating with a bead mill so that the average secondary particle diameter of silica is 3 μm, the reversibility feeling of Comparative Example 7 is the same as Example 17. A thermal recording material was obtained.

Comparative Example 8
In Example 18 (I), instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), wet process silica (manufactured by Fuji Silysia Chemical Co., Ltd.) , Trade name: Silo Hovic 200) Using 1.5 parts, the reversibility feeling of Comparative Example 8 was the same as Example 18 except that the wet secondary silica was treated with a bead mill so that the average secondary particle diameter was 3 μm. A thermal recording material was obtained.

Comparative Example 9
In Example 1 (C), instead of using 1.5 parts by dry process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), wet process silica (manufactured by Mizusawa Chemical Co., Ltd.) The product of Comparative Example 9 is the same as Example 1 except that 1.5 parts of the product name: Mizukasil P-527) is used and treated with a bead mill so that the average secondary particle diameter of the wet process silica is 1.5 μm. A reversible thermosensitive recording material was obtained.

Comparative Example 10
A reversible thermosensitive recording material of Comparative Example 10 was obtained in the same manner as in Example 1 except that the protective layer coating solution prepared in (K) below was used.

(K) Preparation of protective layer coating solution 15 parts of dipentaerythritol hexaacrylate, which is an acrylate oligomer, colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex MEK-ST, solid content concentration 30% by mass) 5 1 part of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator and 85 parts of methyl ethyl ketone were mixed to prepare a protective layer coating solution.

Comparative Example 11
In Example 1 (C), instead of using 1.5 parts of dry-process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL300, average primary particle diameter 7 nm), calcium carbonate (manufactured by Shiroishi Kogyo Co., Ltd., product) Name: Univers 70) A reversible thermosensitive recording material of Comparative Example 11 was obtained in the same manner as in Example 1 except that 1.5 parts was used and the bead mill was used so that the average secondary particle diameter of calcium carbonate was 2 μm. It was.

Comparative Example 12
In Example 1 (C), instead of using 1.5 parts of dry-process silica (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL300, average primary particle diameter 7 nm), aluminum hydroxide (manufactured by Showa Denko KK) The product of Comparative Example 12 was prepared in the same manner as in Example 1 except that 1.5 parts of trade name: Hygielite H-42) was used and processed with a bead mill so that the average secondary particle diameter of aluminum hydroxide was 0.7 μm. A reversible thermosensitive recording material was obtained.

Comparative Example 13
In Example 1 (A), instead of using 100 parts of Exemplified Compound (1-3) as a reversible developer, 100 parts of Exemplified Compound (1-7) was used, and in (C), dry method silica (Nippon Aerosil) A reversible thermosensitive recording material of Comparative Example 13 was obtained in the same manner as in Example 1 except that 1.5 parts was not added without adding 1.5 parts (trade name: AEROSIL 300, manufactured by Co., Ltd.). .

Comparative Example 14
In Example 1 (A), instead of using 100 parts of Exemplified Compound (1-3) as a reversible developer, 100 parts of Exemplified Compound (1-7) was used, and in (C), dry method silica (Nippon Aerosil) Instead of using 1.5 parts by product, product name: AEROSIL300, average primary particle size 7 nm), 1.5 parts by weight of wet method silica (manufactured by Fuji Silysia Chemical Co., Ltd., product name: Silo Hovic 200) A reversible thermosensitive recording material of Comparative Example 14 was obtained in the same manner as in Example 1 except that the wet secondary silica was treated with a bead mill so that the average secondary particle diameter of the wet method silica was 3 μm.

Comparative Example 15
In Example 1 (A), instead of using 100 parts of Exemplified Compound (1-3) as a reversible developer, 100 parts of Exemplified Compound (1-7) was used, and in (C), dry method silica (Nippon Aerosil) Co., Ltd., trade name: AEROSIL 300, average primary particle diameter 7 nm), instead of using 1.5 parts calcium carbonate (Shiraishi Kogyo Co., Ltd., trade name: Univers 70) 1.5 parts calcium carbonate A reversible thermosensitive recording material of Comparative Example 15 was obtained in the same manner as in Example 1 except that the average secondary particle size was 2 μm.

Test Table 1 shows the results of repeated durability tests. Regarding the evaluation method of repeated durability, the reversible thermosensitive recording material obtained in the above examples and comparative examples was punched into a credit card, and a card printer. Product name: KU-R-28152V (manufactured by Panasonic Communications Co., Ltd.) Was printed 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 the conditions, the printing energy was set to about 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, erasure printing was repeated 200 times at 2-minute intervals.

  The print density of the first and 200th prints was measured using the Macbeth densitometer RD914 black density. In addition, the erase density was measured only in the same manner as the print density after only erasing the first and 200th printed matter.

The state of the printed portion was determined by visually observing the first and 200th states and using the following criteria.
(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 heat-sensitive recording layer is damaged, and the printed image is missing.

The printed mark was erased from the 200th printed matter, visually observed from an angle of 60 ° with respect to the printed surface, evaluated for the difference in appearance between the printed portion and the non-printed portion, and judged according to the following criteria.
(Double-circle): The difference in the external appearance of a printing part and a non-printing part cannot be visually recognized.
○: The printed part is higher in gloss than the non-printed part.
Δ: The printed part is not peeled off, but the surface is rough and the deterioration is visible.
X: Peeling has occurred in the printed part.

  As is clear from Table 1, the reversible thermosensitive recording materials of Examples 1 to 27 had a high printing density and a small decrease in printing density due to repeated printing and erasing. Furthermore, there was no image deterioration due to repeated printing and erasing, printing marks were hardly formed, and good repeated durability was exhibited.

  In the comparison of Examples 1, 6, 9, and 23 in which the average primary particle diameter of the dry silica is different, Examples 1, 6, and 9 in which the average primary particle diameter is 5 nm or more and less than 25 nm are high in print density and good. Repeated durability was shown.

  Further, in Examples 1, 12 to 14, 21 and 22 in which the average secondary particle diameter of the dry silica is different, Examples 1 and 12 to 14 having an average secondary particle diameter of 0.1 μm or more and 6 μm or less are The printing density was high and good repeated durability was exhibited.

  On the other hand, as is clear from Table 1, the reversible thermosensitive recording materials of Comparative Examples 1, 4, 10, 11, 13, and 15 have a large decrease in print density due to repeated printing and erasing, and further repeated printing and erasing. As a result, the image was easily deteriorated and the print marks were easily attached. In addition, the reversible thermosensitive recording materials of Comparative Examples 2, 3, 5-9, 12, and 14 have no print density as compared with the reversible thermosensitive recording materials of the examples, although there is no image loss due to repeated printing and erasing. It was low, and the crack of the protective layer and the rough surface were liable to occur, and the repeated durability was inferior.

  The reversible thermosensitive recording material of the present invention can be used as a reversible thermosensitive recording material having a high printing density and good repeated durability.

Claims (5)

  A reversible thermosensitive recording material provided with a thermosensitive recording layer and a protective layer in which transparency or color tone reversibly changes by controlling thermal energy on one side of the support, characterized in that the protective layer contains dry process silica. Reversible thermosensitive recording material.   2. The reversible thermosensitive recording material according to claim 1, wherein the dry primary silica has an average primary particle size of 5 nm or more and less than 25 nm.   The reversible thermosensitive recording material according to claim 1 or 2, wherein the dry secondary silica has an average secondary particle size of 0.1 µm or more and 6 µm or less.   The reversible thermosensitive recording material according to claim 1, wherein the protective layer contains an ultraviolet curable resin and / or a thermosetting resin.   The reversible thermosensitive recording material according to claim 4, wherein the thermosetting resin is crosslinked with isocyanate.