JP2007062086A - Reversible thermal recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent reversible thermal recording material which can perform a forming or erasing cycle of a recorded image with sharp contrast and high sensitivity a large number of times and at the same time, enables the compatibility of repetitive durability with low curling properties. <P>SOLUTION: This reversible thermal recording material is formed of a reversible thermal recording layer which contains as main components a normally colorless or pale-color electron-donative dye precursor and a reversible developer responsible for a reversible color tone change in the dye precursor due to a difference of cooling rate after heating, and a single or a plurality of protecting layers formed on the reversible thermal recording layer, on a support. Besides, the thermal recording material is characterized in that at least its one constituent layer contains at least one dendritic branched resin with a functional group selected from the group consisting of an ethylenic unsaturated linkage group, an isocyanate group and a hydroxyl group, at a molecular terminal and that the arborescent branched resin is cured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reversible thermosensitive recording material capable of repeatedly forming and erasing a recorded image many times by controlling thermal energy.

  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. A typical example is a reversible thermosensitive recording material using a normally colorless or light-colored dye precursor, and a reversible developer that develops color by heating and re-colors the dye precursor by heating. It has been known. According to this recording material, a high-contrast and high-sensitivity recorded image can be formed and erased many times, and it is widely used for the purpose of visualizing information in the card in a medium such as an IC card or a magnetic card. It has become. In such a reversible thermosensitive recording material, there are many applications in which recorded images on a large number of media are continuously rewritten. In such a case, it is desired to shorten the time required for erasing and re-forming the recorded image as much as possible. From such a background, in the erasing and printing apparatus, a predetermined thermal energy is applied in a short time by an image recording means (erasing means) such as a thermal head, and as a result, the thermal load on the recording material tends to increase. Therefore, it is also important to improve the sensitivity of the material itself and the latitude of erasure printing conditions (see, for example, Patent Documents 1 to 3).

  As described above, the reversible thermosensitive recording material is composed of an electron donating dye precursor on a substrate and a reversible manifestation that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. A reversible thermosensitive recording layer formed of a binder resin with a main component such as a colorant as a dispersion matrix, and a single layer on the reversible thermosensitive recording layer to ensure image light resistance and durability during repeated erasure printing Alternatively, a plurality of protective layers are generally provided by laminating. In such reversible thermosensitive recording materials that are used repeatedly, the amount of the thermosensitive composition in the reversible thermosensitive recording layer to be formed is desired in order to obtain sufficient contrast color development and good decoloring characteristics. It is necessary to be introduced so as to obtain a color density of 5%, and it is necessary to secure erasing sensitivity, so that the composition ratio of the heat-sensitive composition and the binder resin, the thickness of the reversible heat-sensitive recording layer, etc. The selection range was narrow. Although it depends on the material used, specifically, the composition ratio of the heat-sensitive composition tends to increase, and the thickness of the heat-sensitive layer is limited, so that the strength of the reversible heat-sensitive layer itself It has been difficult to maintain the durability, and the durability is lowered due to the brittle layer.

  In addition, with respect to a single protective layer or a plurality of protective layers formed on the reversible thermosensitive recording layer, in order to ensure durability during repeated use, a material having high heat resistance may be selected, or an inorganic pigment may be added in some cases. It is necessary to add to ensure hardness and matte surface. However, as described above, when the physical strength of the reversible thermosensitive recording layer is low, or depending on the material used for the protective layer, there is a phenomenon that the surface of the printed part is cracked when it is repeatedly applied when excessive energy is applied during erasure printing. Sometimes it became a problem. Furthermore, when a general thermosetting resin, an ultraviolet curable resin for overcoat, or the like is used, a sheet curl is generated due to more or less curing shrinkage, which causes a problem of lower handling properties in the subsequent process.

A dendritic resin is a polymer compound generally called a dendrimer or a hyperbranched polymer, and its molecular structure is not linear but has a three-dimensional structure that branches radially from the core structure. It is. Such a dendritic resin can be used with a low viscosity without using a low molecular component even though it is a polymer, and the terminal functional groups on the surface of the molecule can be arranged at high density. A cured resin obtained by curing a branched resin forms a film having a very high cross-linking density, so that there are some applications in which migration of other low-molecular components and gas barrier properties can be obtained (for example, patents) References 4 and 5, and Non-Patent Documents 1 and 2).
JP-A-6-171225 Japanese Patent Laid-Open No. 6-210954 JP 7-68934 A Japanese Patent Laid-Open No. 10-337963 Japanese Patent Laid-Open No. 2004-323648 J. et al. Am. Chem. Soc. , 1996, 118, 3785 Prog. Polym. Sci. 2000, 25, 453

  An object of the present invention is to provide an excellent reversible thermosensitive recording material capable of forming or erasing a high-contrast, high-sensitivity recorded image many times and at the same time achieving both repeated durability and low curl characteristics. is there.

  The present invention comprises, on a base material, an usually colorless or light-colored electron-donating dye precursor and a reversible developer that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. In a reversible thermosensitive recording layer containing as a main component, and a reversible thermosensitive recording material comprising a single or a plurality of protective layers on the reversible thermosensitive recording layer, the reversible thermosensitive recording layer and the protective layer And at least one layer contains at least one dendritic branch resin having a functional group selected from an ethylenically unsaturated bond group, an isocyanate group, and a hydroxyl group at the molecular end, and is obtained by curing the dendritic branch resin. A reversible thermosensitive recording material is provided.

  Further, the above problem is characterized in that the mass content of the dendritic resin in the cured resin component after crosslinking in the layer using the dendritic resin is 40% or more and 100% or less. This is also preferably achieved by a heat-sensitive recording material.

  According to the present invention, as described above, an excellent reversible thermosensitive recording material capable of forming or erasing a high-contrast, high-sensitivity recorded image many times and having both repeated durability and low curl characteristics. Provided.

  In the present invention, the dendritic resin having the above functional group at the molecular end may be contained in at least one of the reversible thermosensitive recording layer or the protective layer. That is, the dendritic resin has a three-dimensional structure, and has a rigid structure because the atomic density is very high and the degree of freedom is low in the vicinity of the molecular end. Since it is high and cure shrinkage is very small, it is possible to improve mechanical strength and heat resistance, and furthermore, curl can be reduced. From such a viewpoint, it is preferable that the ratio of the dendritic branched resin occupying the cured resin component after crosslinking is 40% or more. If lower than this, the reversible thermosensitive recording material is sufficient. Repetitive durability and low shrinkage of the layer cannot be obtained.

  Hereinafter, the reversible thermosensitive recording material of the present invention will be described in more detail. The reversible thermosensitive recording material according to the present invention is usually a colorless or light-colored electron-donating dye precursor and a reversible developer that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. And a reversible thermosensitive recording layer obtained by forming a coating liquid in which these are dispersed together with a binder resin, and a single protective layer or a plurality of protective layers on the reversible thermosensitive recording layer. Can be obtained. The dendritic branch resin according to the present invention is at least one component of a plurality of compounds constituting the binder resin of the reversible thermosensitive recording layer and / or the resin component of the protective layer, and a plurality of the dendritic branch resins are mixed. May be used. Furthermore, for resin components including dendritic resins, the reaction corresponding to the resin used so that a three-dimensional crosslinked structure having high heat resistance is finally formed after film formation because of the necessity of having repeated durability. It is comprised from what has a crosslinkable functional group, such as superposition | polymerization, by adding a functional compound as a hardening | curing agent, or dendritic branch resin itself.

  Examples of the dendritic branched resin according to the present invention preferably include dendrimers that are sequentially reacted from a core molecule to form a branched structure regularly, and hyperbranched polymers having a random branched structure. There are no particular limitations, and 4th to 7th generations are preferable from the viewpoint of easy synthesis and specificity as a dendrimer. Furthermore, the dendritic resin according to the present invention may have a structure having a plurality of one type of functional group selected from an ethylenically unsaturated bond, an isocyanate group and a hydroxyl group at the molecular end. Those having a base number of 10 or more and 40 or less are preferably used. When the number of functional groups at the molecular end is less than 10, the heat resistance is inferior, and when it exceeds 40, all functional groups do not contribute to the reaction effectively, so the characteristics are not significantly improved. The resin used for the reversible thermosensitive recording layer and / or protective layer may be a reactive monomer, oligomer, or polymer other than the dendritic branched resin, but the cured resin of the dendritic branched resin. It is preferable to apply the composition so that the proportion of the component is 40% or more and 100% or less, and more preferably 60% or more and 100% or less. The dendrimer can be produced by a convergent method or a divergent method. As the convergent method, for example, a method described in Macromolecules, 23, 4726 (1990) or the like may be applied. In the divergent method, Polymer. J. et al. 17, 117 (1985) and the like are preferably applied. As a method for producing a hyperbranched polymer, for example, the method described in Macromolecules, 31, 1716, (1998) may be used.

  In addition, the type of functional group at the molecular end of the dendritic resin may be appropriately selected according to the conditions of use. For example, when the dendritic resin has an ethylenically unsaturated bond at the molecular end, polymerization starts. What is necessary is just to superpose | polymerize and harden | cure on suitable conditions with an agent. Moreover, when it has an isocyanate group, what is necessary is just to thermoset using the compound which has 2 or more functional groups selected from a hydroxyl group, an amino group, or a carboxyl group as a hardening | curing agent. When it has a hydroxyl group, it may be thermally cured using a compound having two or more isocyanate groups as a curing agent. Further, the curing agent having two or more functional groups may be a dendritic resin.

  As the binder resin used for obtaining the reversible thermosensitive recording layer according to the present invention, the following thermoplastic resin or thermosetting resin is applied in combination with the dendritic resin used in the present invention. Is possible. A thermosetting resin is preferable from the viewpoint of heat resistance. In the case of applying a thermosetting resin, a liquid containing a curing agent is applied and formed into a film and then crosslinked by heat.

  Specific examples of the thermoplastic resin 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 ester copolymer, polystyrene, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic ester, poly Methacrylic acid ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, (meth) acrylic acid ester / butadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / Polyvinyl alcohol copolymer, and the like.

  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 thermally curing a polyol resin with an isocyanate compound described in JP-A Nos. 10-230680 and 11-58963 is preferable. Even when the dendritic branched resin used in the present invention is not used as the binder resin used for obtaining the reversible thermosensitive recording layer according to the present invention, it is preferable to use these thermoplastic resins or thermosetting resins. .

  The amount of the binder resin used in the reversible thermosensitive recording layer according to the present invention is such that the mass percentage of the cured resin component including the curing agent with respect to the total mass of the reversible thermosensitive recording layer is in the range of 35% to 65%. It is preferable. 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 reversible 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 reversible thermosensitive recording layer is more preferably from 40% to 60%, and even more preferably from 45% to 55%.

  The film thickness of the reversible thermosensitive recording layer according to the present invention is determined by the composition of the reversible thermosensitive recording layer and the desired color density, and specifically, it is preferably in the range of 0.5 to 20 μm, 15 μm is more preferable. Further, in forming the recording layer, a dispersion liquid in which a composition such as a dye precursor and a reversible developer is mixed with a curable resin and a curing agent as necessary is coated on the substrate. It can also be used after diluted with a non-reactive solvent with a composition such as a curable 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, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate monoethyl ether, diethyl Ethers such as ether, glycol dimethyl ether, glycol diethyl ether, dioxane and tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene, xylene and styrene, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, chlorobenzene, dichlorobenzene and cresol Chlorinated hydrocarbons such as N, N-dimethylformaldehyde, pentane, hexane, etc. can be used, but the binder used is not limited to this It is preferable to use an organic solvent which does not participate in the curing reaction of the resin.

  As the reversible developer used in the present invention, which causes a reversible color change in the dye precursor by heating, known ones can be used. Among them, the one represented by the following general formula (1) is preferable, but the present invention is not limited to this.

In the general formula (1), X and X may be the same or different from each other, and an oxygen atom, a sulfur atom, or a —CONH— bond containing no hydrocarbon atom group at both ends is defined as the minimum structural unit. Represents a divalent group. Specific examples of the divalent group having a —CONH— bond as the minimum structural unit include amide (—CONH—, —NHCO—), urea (—NHCONH—), and urethane (—NHCOO—, —OCONH—). , Diacylamine (-CONHCO-), diacylhydrazine (-CONHNHCO-), oxalic acid diamide (-NHCOCONH-), 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 (- HCOCH ₂ CONH-) has groups and the like. 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. m represents an integer of 0 to 4, and when m is 2 or more, R ² and X which are repeated may be the same or different.

  In the reversible developer represented by the general formula (1) used in the present invention, m is 0, and X is a divalent having a —CONH— bond having no hydrocarbon atom group at both ends as a minimum structural unit. Those which are groups are particularly preferred.

  Although the specific compound represented by General formula (1) below is given, this invention is not limited to this.

  N- [2- (p-hydroxyphenyl) ethyl] carbamic acid-n-octadecyl, N- [6- (p-hydroxyphenyl) hexyl] carbamic acid-n-tetradecyl, N- [p- (p-hydroxyphenyl) ) Phenyl] carbamic acid-n-dodecyl, Nn-octadecylcarbamic acid- [2- (p-hydroxyphenyl) ethyl], Nn-decylcarbamic acid- [11- (p-hydroxyphenyl) undecanyl], Nn-tetradecylcarbamic acid- [p- (p-hydroxyphenyl) phenyl], N- [3- (p-hydroxyphenyl) propionyl] -Nn-octadecanoylamine, N- [6- ( p-hydroxyphenyl) hexanoyl] -Nn-octadecanoylamine, N- [3- (p-hydroxyphenyl) propyl Pionyl] -N- (pn-octylbenzoyl) amine, N- [2- (p-hydroxyphenyl) aceto] -N′-n-dodecanohydrazide, N- [2- (p-hydroxyphenyl) acetate ] -N'-n-octadecanohydrazide, N- [3- (p-hydroxyphenyl) propiono] -N'-n-octadecanohydrazide, N- [3- (3,4-dihydroxyphenyl) propiono ] -N'-n-octadecanohydrazide, N- [2- (p-hydroxyphenyl) aceto] -N'-n-docosanohydrazide, N- [3- (p-hydroxyphenyl) propiono] -N '-N-docosanohydrazide, N- [3- (3,4-dihydroxyphenyl) propiono] -N'-n-docosanohydrazide, N- [6- (p-hydroxyphenyl) he Sano] -N'-n-tetradecanohydrazide, N- [6- (p-hydroxyphenyl) hexano] -N'-n-octadecanohydrazide, N- [6- (p-hydroxyphenyl) hexano] -N '-(pn-octylbenzo) hydrazide, N- [11- (p-hydroxyphenyloxy) undecano-N'-11-dodecenohydrazide, N- [11- (p-hydroxyphenyl) undecano -N'-n-tetradecanohydrazide, N- [11- (p-hydroxyphenyl) undecano-N'-n-octadecanohydrazide, N- [11- (p-hydroxyphenyl) undecano-N'- (6-phenyl) hexanohydrazide, N- [11- (3,4,5-trihydroxyphenyl) undecano] -N′-n-octadecanohydrazide, N— [P- (p-hydroxyphenyl) benzo] -N'-n-octadecanohydrazide, N- [p- (p-hydroxyphenylmethyl) benzo] -N'-n-octadecanohydrazide, N- [ 2- (p-hydroxyphenyl) ethyl] -N′-n-tetradecyloxamide, N- [3- (p-hydroxyphenyl) propyl] -N′-n-octadecyloxamide, N- [3- ( 3,4-dihydroxyphenyl) propyl] -N'-n-octadecyloxamide, N- [11- (p-hydroxyphenyl) undecanyl] -N'-n-decyloxamide, N- [p- (p-hydroxyphenyl) ) Phenyl] -N'-n-octadecyloxamide, N- (p-hydroxyphenyl) -N'-n-dodecylurea, N- [2- (p-hydroxyphenyl) Acetyl] -N'-n-octadecylurea, N- [3- (p-hydroxyphenyl) propionyl] -N'-n-octadecylurea, N- [p- (p-hydroxyphenyl) benzoyl] -N'- n-octadecyl urea, N- [2- (p-hydroxyphenyl) ethyl] -N'-n-dodecanoyl urea, N- [2- (p-hydroxyphenyl) ethyl] -N'-n-octadecanoyl urea N- [p- (p-hydroxyphenyl) phenyl] -N'-n-octadecanoyl urea, 4- [2- (p-hydroxyphenyl) ethyl] -1-n-tetradecyl semicarbazide, 4- [ 2- (p-hydroxyphenyl) ethyl] -1-n-octadecyl semicarbazide, 4- [p- (p-hydroxyphenyl) phenyl] -1-n-tetradecyl Carbazide, 1- [2- (p-hydroxyphenyl) ethyl] -4-n-tetradecyl semicarbazide, 1- [2- (p-hydroxyphenyl) ethyl] -4-n-octadecyl semicarbazide, 1- [p- (P-hydroxyphenyl) phenyl] -4-n-tetradecyl semicarbazide, 1- [2- (p-hydroxyphenyl) acetyl] -4-n-tetradecyl semicarbazide, 1- [3- (p-hydroxyphenyl) Propionyl] -4-n-octadecyl semicarbazide, 1- [11- (p-hydroxyphenyl) undecanoyl] -4-n-decyl semicarbazide, 1- [p- (p-hydroxyphenyl) benzoyl] -4-n-octadecyl Semicarbazide, 4- [2- (p-hydroxyphenyl) ethyl] -1-n-tetrade Canoyl semicarbazide, 4- [2- (p-hydroxyphenyl) ethyl] -1-n-octadecanoyl semicarbazide, 4- [p- (p-hydroxyphenyl) phenyl] -1-n-octadecanoyl semicarbazide 1- [2- (p-hydroxyphenyl) acetamido] -1-n-dodecanoylaminomethane, 1- [2- (p-hydroxyphenyl) acetamido] -1-n-octadecanoylaminomethane, [3- (p-hydroxyphenyl) propanamide] -1-n-octadecanoylaminomethane, 1- [11- (p-hydroxyphenyl) undecanamide] -1-n-decanoylaminomethane, 1- [ p- (p-hydroxyphenyl) benzamide] -1-n-octadecanoylaminomethane, 1- [2- (p-hy Loxyphenyl) acetamido] -1- (3-n-dodecylureido) methane, 1- [2- (p-hydroxyphenyl) acetamido] -1- (3-n-octadecylureido) methane, 1- [3- ( p-hydroxyphenyl) propanamide] -1- (3-n-octadecylureido) methane, 1- [11- (p-hydroxyphenyl) undecanamido] -1- (3-n-decylureido) methane, 1- [ p- (p-hydroxyphenyl) benzamide] -1- (3-n-octadecylureido) methane, 1- {3- [2- (p-hydroxyphenyl) ethyl] ureido} -1-n-octadecanoylamino Methane, 1- {3- [p- (p-hydroxyphenyl) phenyl] ureido} -1-n-octadecanoylaminomethane, N- 2- (p-hydroxyphenyl) ethyl] -N'-n-octadecylmalonamide, N- [p- (p-hydroxyphenyl) phenyl] -N'-n-octadecylmalonamide, N-4-thiahexadeca Noyl-3- (4-hydroxyphenyl) propanoylamide, N-12-thiadcosanoyl-3- (4-hydroxyphenyl) propanoylamide, N-3- (4-hydroxyphenyl) propano-N′-4-oxa Hexadecanohydrazide, N-3- (4-hydroxyphenyl) propano-N′-4-thiahexadecanohydrazide, N-3- (4-hydroxyphenyl) propano-N′-12-oxadocosanohydrazide, N-3- (4-hydroxyphenyl) propano-N'-12-thiadocosanohydrazide, N-3- (4-hydride) Xylphenyl) propano-N'-4-thiahexadecanooxamide, N-3- (4-hydroxyphenyl) propano-N'-12-oxadocosanoxamide, N-3- (4-hydroxyphenyl) propano -N'-12-thiadocosanoxamide, Np-hydroxyphenylethyl-N'-12-thiacoscoxamide, Np-hydroxybenzyl-N'-12-thiadocosylurea, Np- Hydroxybenzyl-N′-12-oxadocosyl urea, 1- (p-hydroxyphenylethyl) -4- (12-thiacosyl) semicarbazide, 1- (p-hydroxybenzyl) -4- (12-thiacosyl) semicarbazide, etc. Can be mentioned.

  The reversible developer represented by the general formula (1) used in the present invention may be used alone or in combination of two or more, and the amount used for a colorless or light dye precursor is usually It is 5-5000 mass%, Preferably it is 10-3000 mass%.

  As generally colorless or light dye precursors used in the present invention, those generally used for pressure-sensitive recording paper, heat-sensitive recording paper and the like are well known. Specific examples include the following, but the present invention is not limited thereto. These dye precursors may be used alone or in combination of two or more.

(1) Triarylmethane compounds 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- ( 4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-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-dimethylindol-3-yl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-n) -Hexyloxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-methylphenyl) -3- (1-ethyl-2-methyl) Indol-3-yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-dimethylamino-2) -Ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-n-octyl-2- Methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide, etc.

(2) Diphenylmethane compounds 4,4′-bis (dimethylaminophenyl) benzhydrylbenzyl ether, N-chlorophenylleucooramine, N-2,4,5-trichlorophenylleucooramine, etc.

(3) Xanthene compounds Rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7 -Phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7-phenoxyfluorane, 3-diethylamino-7- (3,4 Dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (3-methylanilino) fluorane , 3- (N-ethyl) tolylamino-6 -Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-ethyl) tolylamino-6-methyl-7-phenethylfluorane, 3-diethylamino-7- (4-Nitroanilino) fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl) propylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl) ) Isoamylamino-6-methyl-7-anilinofluorane, 3- (N-methyl) cyclohexylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl) tetrahydrofurylamino-6-methyl -7-anilinofluorane, etc.

(4) Thiazine compounds benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like can be mentioned.

(5) Spiro compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyrans, 3,3'-dichlorospirodinaphthopyrans, 3-benzylspirodinaphthopyrans, 3-methylnaphthyl (3-methoxybenzo) ) Spiropyran, 3-propyl spirobenzopyran and the like.

  As the protective layer according to the present invention, a material having mechanical strength and heat resistance such as thermosetting resin or ultraviolet curable resin can be used. In the protective layer, when used in combination with the dendritic resin used in the present invention or when the dendritic resin is not used, a general epoxy resin, urea resin, xylene-formaldehyde resin, melamine resin, Thermosetting resins such as guanamine resins, phenol resins, phenoxy resins, saturated polyester resins, unsaturated polyester resins, and polyol resins, and ethylenically unsaturated bonds as described in, for example, JP-A-6-344672 The ultraviolet curable resin which has can be used. Examples of the curing agent used for the thermosetting resin include organic acids, amines, isocyanates, epoxies, phenols, and the like, and a suitable reactive agent may be selected depending on the type of the thermosetting resin. As for the ultraviolet curable resin, a photoreaction initiator such as trichloroacetophenone, benzophenone, Michler ketone, benzyl, benzoin, benzoin alkyl ether, benzyl dimethyl ketal, etc. can be used in order to efficiently promote the curing with ultraviolet rays. The thickness of the protective layer is preferably 0.5 to 7 μm. If it is thinner than this, formation and erasure of the recorded image cannot be repeated many times, and if it is thicker, the recording sensitivity is lowered. The protective layer may have a plurality of configurations, and the total thickness of the plurality of layers is preferably 3 to 7 μm.

  In addition, the protective layer according to the present invention prevents or reduces sticking and head wear, so that diatomaceous earth, clay, calcined clay, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, oxide Pigments such as silicon, aluminum hydroxide, starch granules, urea-formalin resin particles, melamine resin particles, urethane resin particles, acrylic resin particles, silicone particles, higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, oxidation Waxes such as paraffin, polyethylene, polyethylene oxide, stearamide, and castor wax can be used alone or in combination of two or more. One or more leveling agents, dispersants, surfactants, fluorescent dyes and the like can also be contained.

  Furthermore, the protective layer can contain inorganic metal oxide particles having an ultraviolet shielding property and an organic ultraviolet absorber for the purpose of preventing ultraviolet deterioration of the reversible thermosensitive recording layer. Specific examples of the ultraviolet shielding metal oxide particles include zinc oxide, rutile type titanium dioxide, anatase type titanium dioxide, cerium oxide, and iron oxide hydroxide. What coated with the material may be used. Specific examples of the organic ultraviolet absorber include salicylic acid phenyl ester ultraviolet absorbers such as phenyl salicylate, pt-butylphenyl salicylate, p-octylphenyl salicylate; 2,4-dihydroxybenzophenone, 2-hydroxy-4 Benzophenone ultraviolet absorbers such as -methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone; 2- (2 ' -Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, 2- (2'-hydroxy-4'-octoxy) benzotriazole, 2- ( 2'-hydroxy- Benzotriazole ultraviolet absorbers such as' -t-butyl-5'-methylphenyl) -5-chlorobenzotriazole; 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate, ethyl-2-cyano-3 And acrylate ultraviolet absorbers such as 3,3'-diphenyl acrylate. These may be used alone or in combination of two or more.

  As a base material used in the present invention, paper, various nonwoven fabrics, woven fabric, synthetic resin film, synthetic resin laminated paper, synthetic paper, metal foil, or a composite sheet combining these may be arbitrarily used depending on the purpose. It can be transparent, translucent or opaque. Moreover, it is not limited to these.

  The layer structure of the reversible thermosensitive recording material of the present invention may be provided with a reversible thermosensitive recording layer and one or more protective layers in this order on the substrate. An anchor layer or a heat insulating layer can also be provided between the layers. Further, the surface on which the reversible thermosensitive recording layer is provided and / or the surface on the opposite side may include a material capable of recording information electrically, magnetically, and optically. In addition, a backcoat layer can be provided on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided for the purpose of preventing curling and preventing charging. It is also possible to use a dendritic resin for these anchor layer, heat insulating layer, recording layer, or backcoat layer.

In order to perform color development of the reversible thermosensitive recording material used in the present invention, it is sufficient that rapid cooling occurs after heating, and for example, heating by a thermal head, laser light or the like is possible. Moreover, if it cools slowly after heating, it will erase, and it can carry out by using the radiant heat from light sources, such as a hot roll, a heat stamp, a thermal head, high frequency heating, a hot air, an electric heater, or a halogen lamp. Examples of the laser used for heating include, but are not limited to, a semiconductor laser and a YAG laser. In order to efficiently perform heating with these laser beams, a reversible thermosensitive recording layer contains a photothermal conversion material having absorption in the near infrared region, or a photothermal conversion layer containing the photothermal conversion material is reversible. It is preferably provided directly adjacent to the heat-sensitive recording layer. Examples of photothermal conversion materials having absorption in the near infrared region include layers of metals or metalloids such as platinum, titanium, silicon, chromium, nickel, germanium, and aluminum, IRG002 (trade name) and IRG022 (product) manufactured by Nippon Kayaku. Name) and the like, but include, but are not limited to, immonium compounds, metal complex compounds, cyanine dyes, squarylium dyes, naphthoquinone dyes, phthalocyanine compounds, and the like. Preferable photothermal conversion materials include phthalocyanine compounds and metal complex compounds in terms of photothermal conversion efficiency, solubility in solvents, and dispersibility in resins. Photothermal conversion materials can be used alone or in combination of two or more. The addition amount is suitably 1 mg / m ² to 200 mg / m ² , and preferably 5 mg / m ² to 50 mg / m ² . If the amount is less than this amount, the energy required for image erasure cannot be sufficiently reduced, and the repetition characteristics of print erasure deteriorate. On the other hand, when the amount is larger than this amount, the absorption of the visible portion that the photothermal conversion material is slightly increased becomes too large, and the visibility of the image is lowered.

  The method for forming each layer constituting the reversible thermosensitive recording material of the present invention on the substrate is not particularly limited, and can be formed by a conventional method. For example, smearing devices such as an air knife coater, blade coater, bar coater, curtain coater, roll coater, etc., various printing machines using a flat plate, letterpress, intaglio, flexo, gravure, screen, hot melt, etc. can be used. Furthermore, in addition to the normal drying process, each layer can be held by ultraviolet irradiation or electron beam irradiation as necessary. By these methods, it is possible to apply and print one layer at a time or multiple layers simultaneously.

  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 and percentage in an Example are based on mass.

  To a suspension obtained by mixing 100 parts of a dendrimer having a hydroxyl group represented by the following structural formula and 180 parts of m-xylylene diisocyanate in 260 parts of ethyl acetate, 0.3 part of stannous octylate is added to 20 parts of ethyl acetate. The solution dissolved in was added dropwise with stirring. After completion of the dropwise addition, the mixture was stirred for 1 hour and then at 70 ° C. for 4 hours. Thereby, an isocyanate group-added dendrimer solution having a solid content of 50% and having an isocyanate group at the end was prepared.

  Dye precursor 3-di-n-butylamino-6-methyl-7-anilinofluorane 20 parts, reversible developer N- [3- (p-hydroxyphenyl) propiono] -N ′ A mixture of 100 parts of n-docosanohydrazide, 86 parts of polyester polyol (Takelac U-21 manufactured by Takeda Pharmaceutical Co., Ltd., concentration 70%) and 885 parts of methyl ethyl ketone was dispersed with glass beads for 10 hours with a paint shaker to obtain a dispersion. . Next, 200 parts of the above isocyanate group-added dendrimer solution and 200 parts of methyl ethyl ketone were added to the resulting dispersion and mixed well to prepare a reversible thermosensitive recording layer coating solution. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 62.4%. Using this coating solution, it was applied to a white polyethylene terephthalate (PET) sheet having a thickness of 100 μm so that the thickness after forming the layer was 8 μm, dried at 120 ° C. for 3 minutes, and further at 50 ° C. for 48 hours. Heating was performed to form a reversible thermosensitive recording layer.

  Paint 100 parts of polyester polyol resin solution (Q161-45 manufactured by Mitsui Chemicals, 45% concentration), 10 parts of 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, and 160 parts of methyl ethyl ketone with glass beads. After 3 hours of dispersion with a shaker, 41 parts of an isocyanate compound solution (Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 100%) was mixed well, and the resulting coating solution was applied onto the reversible thermosensitive recording layer. After drying at 120 ° C. for 2 minutes, the mixture was further heated at 50 ° C. for 48 hours to provide a first protective layer having a thickness of 2 μm. Thereafter, a mixed solution of 15 parts of urethane acrylate ultraviolet curable resin (C7-157 manufactured by Dainippon Ink & Chemicals, Inc., concentration 100%) and 85 parts of methyl ethyl ketone was applied, dried at 120 ° C. for 1 minute, and then irradiated energy 80 W. A reversible thermosensitive recording material was prepared by passing under a UV lamp of / cm at a conveyance speed of 9 m / min and curing, and providing a second protective layer having a thickness of 3 μm.

  Dye precursor 3-di-n-butylamino-6-methyl-7-anilinofluorane 20 parts, reversible developer N- [3- (p-hydroxyphenyl) propiono] -N ′ A mixture of 100 parts of n-docosanohydrazide, 86 parts of polyester polyol (Takelac U-21 manufactured by Takeda Pharmaceutical Co., Ltd., concentration 70%) and 885 parts of methyl ethyl ketone was dispersed with glass beads for 10 hours with a paint shaker to obtain a dispersion. . Next, 132 parts of the isocyanate group-added dendrimer solution prepared in Example 1, 41 parts of an isocyanate compound (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd., 75% concentration) and 200 parts of methyl ethyl ketone were added to the obtained dispersion and mixed well. A reversible thermosensitive recording layer coating solution was prepared. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 42.1%. Using this coating solution, it was applied to a white polyethylene terephthalate (PET) sheet having a thickness of 100 μm so that the thickness after forming the layer was 8 μm, dried at 120 ° C. for 3 minutes, and further at 50 ° C. for 48 hours. Heating was performed to form a reversible thermosensitive recording layer. Thereafter, a protective layer was formed in the same manner as in Example 1 to produce a reversible thermosensitive recording material of the present invention.

  Dye precursor 3-di-n-butylamino-6-methyl-7-anilinofluorane 20 parts, reversible developer N- [3- (p-hydroxyphenyl) propiono] -N ′ A mixture of 100 parts of n-docosanohydrazide, 86 parts of polyester polyol (Takelac U-21 manufactured by Takeda Pharmaceutical Co., Ltd., concentration 70%) and 885 parts of methyl ethyl ketone was dispersed with glass beads for 10 hours with a paint shaker to obtain a dispersion. . Next, 120 parts of the isocyanate group-added dendrimer solution prepared in Example 1, 48 parts of isocyanate compound (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 75%) and 200 parts of methyl ethyl ketone were added to the obtained dispersion and mixed well. A reversible thermosensitive recording layer coating solution was prepared. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 38.4%. Using this coating solution, it was applied to a white polyethylene terephthalate (PET) sheet having a thickness of 100 μm so that the thickness after forming the layer was 8 μm, dried at 120 ° C. for 3 minutes, and further at 50 ° C. for 48 hours. Heating was performed to form a reversible thermosensitive recording layer. Thereafter, a protective layer was formed in the same manner as in Example 1 to produce a reversible thermosensitive recording material of the present invention.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 3. Further, 67 parts of a polyester polyol resin solution (Q161-45 manufactured by Mitsui Chemicals, concentration: 45%), 2- (2'-hydroxy-5 ') -T-octylphenyl) benzotriazole (15 parts) and methyl ethyl ketone (120 parts) were dispersed together with glass beads in a paint shaker for 3 hours, and 53 parts of the isocyanate group-added dendrimer solution prepared in Example 1 and an isocyanate compound solution of 3.7 Parts (Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 100%) were mixed well, and the resulting coating solution was applied onto the above reversible thermosensitive recording layer, dried at 120 ° C. for 2 minutes, and further to 50 ° C. For 48 hours to provide a first protective layer having a thickness of 2 μm. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 43.9%. Thereafter, a mixed solution of 15 parts of urethane acrylate ultraviolet curable resin (C7-157 manufactured by Dainippon Ink & Chemicals, Inc., concentration 100%) and 85 parts of methyl ethyl ketone was applied, dried at 120 ° C. for 1 minute, and then irradiated energy 80 W. A reversible thermosensitive recording material of the present invention was prepared by curing under a UV lamp of / cm at a conveying speed of 9 m / min and providing a second protective layer having a thickness of 3 μm.

  Dye precursor 3-di-n-butylamino-6-methyl-7-anilinofluorane 20 parts, reversible developer N- [3- (p-hydroxyphenyl) propiono] -N ′ -A dispersion of 100 parts of n-docosanohydrazide, 87 parts of polyester polyol (Takelac U-21, Takeda Pharmaceutical Co., Ltd., concentration 70%) and 950 parts of methyl ethyl ketone was dispersed together with glass beads for 5 hours in a paint shaker to obtain a dispersion. It was. Next, 144 parts of an isocyanate compound (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 75%) and 62 parts of methyl ethyl ketone were added to the obtained dispersion and mixed well to prepare a reversible thermosensitive recording layer coating liquid. Using this coating solution, it was applied to a white polyethylene terephthalate (PET) sheet having a thickness of 100 μm so that the thickness after forming the layer was 8 μm, dried at 120 ° C. for 3 minutes, and further at 50 ° C. for 48 hours. Heating was performed to form a reversible thermosensitive recording layer.

  Paint 67 parts of polyester polyol resin solution (Q161-45 manufactured by Mitsui Chemicals, 45% concentration), 15 parts of 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, and 120 parts of methyl ethyl ketone together with glass beads. After 3 hours of dispersion with a shaker, 47 parts of the isocyanate group-added dendrimer solution prepared in Example 1 and 3.7 parts of an isocyanate compound solution (Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 100%) were mixed well, The obtained coating solution was applied onto the above reversible thermosensitive recording layer, dried at 120 ° C. for 2 minutes, and further heated at 50 ° C. for 48 hours to provide a first protective layer having a thickness of 2 μm. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 41.0%. Thereafter, a mixed solution of 15 parts of urethane acrylate ultraviolet curable resin (C7-157 manufactured by Dainippon Ink & Chemicals, Inc., concentration 100%) and 85 parts of methyl ethyl ketone was applied, dried at 120 ° C. for 1 minute, and then irradiated energy 80 W. A reversible thermosensitive recording material of the present invention was prepared by curing under a UV lamp of / cm at a conveying speed of 9 m / min and providing a second protective layer having a thickness of 3 μm.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 5. Further, 67 parts of a polyester polyol resin solution (Q161-45 manufactured by Mitsui Chemicals, concentration: 45%), 2- (2'-hydroxy-5 ') -T-octylphenyl) benzotriazole (15 parts) and methyl ethyl ketone (120 parts) were dispersed together with glass beads in a paint shaker for 3 hours, to which 40 parts of an isocyanate group-added dendrimer solution prepared in Example 1 and an isocyanate compound solution of 4.6 were added. Parts (Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 100%) were mixed well, and the resulting coating solution was applied onto the above reversible thermosensitive recording layer, dried at 120 ° C. for 2 minutes, and further to 50 ° C. For 48 hours to provide a first protective layer having a thickness of 2 μm. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 37.1%. Thereafter, a mixed solution of 15 parts of urethane acrylate ultraviolet curable resin (C7-157 manufactured by Dainippon Ink & Chemicals, Inc., concentration 100%) and 85 parts of methyl ethyl ketone was applied, dried at 120 ° C. for 1 minute, and then irradiated energy 80 W. A reversible thermosensitive recording material of the present invention was prepared by curing under a UV lamp of / cm at a conveying speed of 9 m / min and providing a second protective layer having a thickness of 3 μm.

  100 parts of a dendrimer having a hydroxyl group at the molecular end and 53 parts of triethylamine used in Example 1 were dissolved in 200 parts of acetone, and 44 parts of acryloyl chloride was added dropwise with stirring, and the mixture was stirred for 12 hours after completion of the addition. Thereafter, acetone was distilled off, and the reaction product was dissolved in 200 parts of methylene chloride. This was washed with a 10% aqueous ammonium chloride solution and a 1% aqueous sodium hydroxide solution and then dried over magnesium sulfate. As a result, a liquid dendrimer having an acryloyl group at the molecular end was prepared.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 5. Further, 50 parts of a dendrimer having an acryloyl group at the molecular end, 2.5 parts of Irgacure 184 as a photopolymerization initiator, and 80 parts of methyl ethyl ketone were mixed thereon. After applying the solution and drying at 120 ° C. for 1 minute, it is cured by passing it under a UV lamp with an irradiation energy of 80 W / cm at a conveyance speed of 9 m / min, and a protective layer having a thickness of 3 μm is provided, and the reversible of the present invention. A heat-sensitive recording material was prepared. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 100%.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 5. Further, 50 parts of a dendrimer having an acryloyl group at the molecular end prepared in Example 7 and a urethane acrylate UV curable resin (UA from Shin-Nakamura Chemical Co., Ltd.) -122P, concentration 100%) 70 parts, 2.5 parts of Irgacure 184 as a photopolymerization initiator, 180 parts of methyl ethyl ketone were applied, dried at 120 ° C. for 1 minute, and then an ultraviolet lamp with an irradiation energy of 80 W / cm The bottom was cured by passing at a conveyance speed of 9 m / min, and a protective layer having a thickness of 3 μm was provided to produce a reversible thermosensitive recording material of the present invention. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 41.7%.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 5. Further, 50 parts of a dendrimer having an acryloyl group at the molecular end prepared in Example 7 and a urethane acrylate UV curable resin (UA from Shin-Nakamura Chemical Co., Ltd.) -122P, concentration 100%) 85 parts, Irgacure 184 as a photopolymerization initiator, 2.5 parts, and 200 parts of methyl ethyl ketone were applied, dried at 120 ° C. for 1 minute, and then an ultraviolet lamp with an irradiation energy of 80 W / cm The bottom was cured by passing at a conveyance speed of 9 m / min, and a protective layer having a thickness of 3 μm was provided to produce a reversible thermosensitive recording material of the present invention. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 37.0%.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 3, and a protective layer was further formed thereon as in Example 9 to produce a reversible thermosensitive recording material of the present invention.

  After forming to the 1st protective layer similarly to Example 4, the 2nd protective layer was formed like the protective layer of Example 9, and the reversible thermosensitive recording material of this invention was produced.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 5, and 50 parts of a dendrimer having the above hydroxyl group at the molecular end thereon, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole 15 And 120 parts of methyl ethyl ketone were dispersed together with glass beads for 3 hours with a paint shaker, and 50 parts of the isocyanate group-added dendrimer solution prepared in Example 1 was thoroughly mixed with this, and the resulting coating solution was mixed with the above reversible thermosensitive material. This was coated on the recording layer, dried at 120 ° C. for 2 minutes, and further heated at 50 ° C. for 48 hours to provide a first protective layer having a thickness of 2 μm. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 100%. Thereafter, a mixed solution of 15 parts of urethane acrylate ultraviolet curable resin (C7-157 manufactured by Dainippon Ink & Chemicals, Inc., concentration 100%) and 85 parts of methyl ethyl ketone was applied, dried at 120 ° C. for 1 minute, and then irradiated energy 80 W. A reversible thermosensitive recording material of the present invention was prepared by curing under a UV lamp of / cm at a conveying speed of 9 m / min and providing a second protective layer having a thickness of 3 μm.

  100 parts of a dendrimer having a hydroxyl group at the molecular end used in Example 1, 0.049 part of dibutyltin dilaurate and 0.022 part of 2,6-di-t-butyl-p-cresol were dissolved in 200 parts of acetone. -75.4 parts of methacryloyloxyethyl isocyanate was added dropwise with stirring. After completion of the addition, the mixture was stirred at 40 ° C for 4 hours. Thereafter, acetone was distilled off, the reaction product was dissolved in 200 parts of methylene chloride, washed with a 1% aqueous sodium hydroxide solution, and then dried over magnesium sulfate. Thereby, a liquid dendrimer having a methacryloyl group at the molecular end was prepared.

  A reversible thermosensitive recording layer was formed in the same manner as in Example 5. Further, 50 parts of a dendrimer having a methacryloyl group at the molecular end, 2.5 parts of Irgacure 184 as a photopolymerization initiator, and 80 parts of methyl ethyl ketone were mixed thereon. After applying the solution and drying at 120 ° C. for 1 minute, it is cured by passing it under a UV lamp with an irradiation energy of 80 W / cm at a conveyance speed of 9 m / min, and a protective layer having a thickness of 3 μm is provided, and the reversible of the present invention. A heat-sensitive recording material was prepared. At this time, the mass content of the dendrimer component in the cured resin component contributing to crosslinking was 100%.

(Comparative Example 1)
A reversible thermosensitive recording layer was formed in the same manner as in Example 5, and the first and second protective layers were further formed in the same manner as in Example 1 to produce a reversible thermosensitive recording material.

(Comparative Example 2)
A reversible thermosensitive recording layer was formed in the same manner as in Example 5, and then, a mixed solution of 25 parts of urethane acrylate UV curable resin (C7-157 manufactured by Dainippon Ink & Chemicals, Inc., concentration 100%) and 85 parts of methyl ethyl ketone was added. After coating and drying at 120 ° C. for 1 minute, the film is cured by passing through a UV lamp with an irradiation energy of 80 W / cm at a conveyance speed of 9 m / min, and a protective layer having a film thickness of 5 μm is provided. The material was made.

Test 1 (Color density and erasability test)
The reversible thermosensitive recording materials produced in Examples 1 to 11 and Comparative Examples 1 and 2 were subjected to an applied pulse of 1. using Okura Electric thermal facsimile printing tester TH-PMD with Kyocera print head KJT-256-8MGF1. Printing was performed at an applied voltage of 26 volts in 1 millisecond. Further, a part of the mixture was heated at 140 ° C. for 1 second each at 140 ° C. using a heat stamp. The density and erasability (density difference between the color-erased portion and the background portion, three arithmetic average values) of the colored portion thus obtained were measured using a densitometer Macbeth RD918. Regarding the density of the color developing portion, the reversible thermosensitive recording layer used in this example may be 1.0 or more, and if the erasability is 0.01 or less, it is considered that there is no problem. The results are shown in Table 1.

Test 2 (Actual machine repeated erasing print test)
After forming the reversible thermosensitive recording materials obtained in Examples 1 to 11 and Comparative Examples 1 and 2 into a card having a thickness of 760 μm, a printing test mode (printing speed of 69 mm / s, printing speed of Sanwa Newtec printer (ABS-3001KMT)) was used. The printing test was performed with a thermal head resistance value of 450Ω, and then the erasing operation was repeated 500 times at intervals of 3 minutes, and the printing state after completion and the surface state of the recording medium were visually observed and evaluated at the following levels. The results are shown in Table 1.
(Double-circle): The image part is a favorable color development state, and no disappearance is observed.
○: The image portion was in a good color development state, but disappeared a little.
X: Unevenness was observed in the image area, and the remaining disappearance or discoloration was noticeable.

Test 3 (sheet curl evaluation)
When the reversible thermosensitive recording materials obtained in Examples 1 to 11 and Comparative Examples 1 and 2 were cut into a size of 250 mm × 350 mm and placed on a horizontal table with the reversible thermosensitive recording layer on the top surface, The amount of lift due to each warp was measured and evaluated by the arithmetic average value. The results are shown in Table 1.

  An IC or magnetic card using the reversible thermosensitive recording material of the present invention capable of forming and erasing a high-contrast and high-sensitivity recorded image many times is used for the purpose of visualizing information. Furthermore, since it is excellent in handling at the time of post-processing of the material, productivity is improved, and it is used for a long time due to good repeated durability.

Claims (2)

  Mainly contains a colorless or light-colored electron-donating dye precursor on the substrate and a reversible developer that causes a reversible color change in the dye precursor due to the difference in cooling rate after heating. A reversible thermosensitive recording layer, and a reversible thermosensitive recording material comprising a single or a plurality of protective layers provided on the reversible thermosensitive recording layer, wherein at least one of the reversible thermosensitive recording layer and the protective layer. Comprising at least one dendritic resin having a functional group selected from an ethylenically unsaturated bond group, an isocyanate group, and a hydroxyl group at the molecular end, and is obtained by curing the dendritic resin. Reversible thermosensitive recording material.   2. The reversible thermosensitive recording according to claim 1, wherein the mass content of the dendritic resin in the cured resin component after crosslinking in the layer using the dendritic resin is 40% or more and 100% or less. material.