JP2005342918A - Reversible heat-sensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reversible heat-sensitive recording medium which is free from the build-up of head tailings generated due to the repeated use of the medium and shows excellent durability of its surface. <P>SOLUTION: This reversible heat-sensitive recording medium has a recording layer, formed on a support, which contains an electron donative coloring compound and an electron receptive compound and can relatively form a color development state and a decoloration state due to a difference in the heating temperature and/or a cooling rate after heating. In addition, a protective layer is formed on the recording layer and contains at least silica coated with an organoclay and calcium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reversible thermosensitive recording medium utilizing a color development reaction between an electron-donating color-forming compound and an electron-accepting compound, and more specifically, formation and erasure of a color image by controlling thermal energy. The present invention relates to a reversible thermosensitive recording medium capable of performing the above.

  2. Description of the Related Art Conventionally, thermal recording media using a color development reaction between an electron donating color developing compound (hereinafter also referred to as a color former or a leuco dye) and an electron accepting compound (hereinafter also referred to as a developer) are widely known. It is used in printers such as facsimile machines, word processors, and scientific measuring machines. However, any of these conventional recording media in practical use has irreversible color development, and once recorded images cannot be erased and used repeatedly.

  First, we used an organic phosphoric acid compound, aliphatic carboxylic acid compound or phenol compound having a long-chain aliphatic hydrocarbon group as a developer, and combined this with a leuco dye as a color former to develop and decolorize. Can be easily performed under heating and cooling conditions, and the coloring and erasing states can be stably maintained at room temperature, and the reversibility can be stably repeated between coloring and erasing. A coloring composition and a reversible thermosensitive recording medium using the same for a recording layer have been proposed (see Patent Document 1). This has a practical level of performance in terms of the balance between color stability and color erasability and color density, but it can be further improved in terms of compatibility with a wide range of usage environments and color erasing conditions. There was room for it. Thereafter, the use of a specific structure for a phenol compound having a long-chain aliphatic hydrocarbon group has been proposed (see Patent Document 2), and by these proposals, highly practical color-decoloring properties could be obtained.

  On the other hand, in a reversible thermosensitive recording medium, the composition in the recording layer and the thermal decomposition product thereof are deposited on the surface of the protective layer by migration due to repeated printing and erasing by the printer, causing residue of the thermal head to occur and printing. There is a problem that causes defects.

With respect to such a problem of the recording medium, Patent Document 3 proposes improvement of repeated durability by adding particles having an average particle diameter of 1.1 times or more the recording layer thickness. Further, Patent Document 4 proposes to improve the repeated durability by providing a protective layer having a specific glossiness and surface roughness and improving the head matching property. Furthermore, Patent Document 5 proposes using a resin in a crosslinked state in the protective layer. However, even if these reversible thermosensitive recording media are used, it is impossible to completely prevent head stains at the time of repeated printing / erasing, and the number of repeated use may be limited to a small number of times, or There is a problem that the head cleaning needs to be frequently performed. Furthermore, these recording media also have problems such as the surface of the recording medium being easily scratched during repeated use.
JP 05-124360 A JP-A-10-095175 Japanese Patent Laid-Open No. 06-340171 Japanese Patent Laid-Open No. 08-156410 JP 2002-187362 A

  Accordingly, the present invention has been made in view of the above-described problems, and an object thereof is to provide a reversible thermosensitive recording medium that does not cause head scum adhesion even after repeated use and has excellent durability on the surface of the recording medium. .

  That is, as described in claim 1, the object includes an electron-donating color-forming compound and an electron-accepting compound, and relatively develops color due to a difference in heating temperature and / or cooling rate after heating. In a reversible thermosensitive recording medium in which a recording layer capable of forming a state and a decolored state is provided on a support and a protective layer is provided on the recording layer, the protective layer is a silica coated with at least organic clay and calcium It is achieved by a reversible thermosensitive recording medium characterized by containing

  According to the first aspect of the present invention, it is possible to provide a reversible heat-sensitive recording medium that is free from the adhesion of head residue even after repeated use and has excellent durability on the surface of the recording medium.

  The invention according to claim 2 contains an electron-donating color-forming compound and an electron-accepting compound, and forms a relatively colored state and a decolored state due to a difference in heating temperature and / or cooling rate after heating. In a reversible thermosensitive recording medium having a recording layer provided on a support and a protective layer provided on the recording layer, the protective layer contains at least an organic clay and a thermally crosslinkable silicone resin. It can be achieved by a reversible thermosensitive recording medium characterized by the following.

  According to the second aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium which does not cause head residue even after repeated use and has excellent durability on the surface of the recording medium.

  The invention according to claim 3 contains an electron-donating color-forming compound and an electron-accepting compound, and forms a relatively colored state and a decolored state due to a difference in heating temperature and / or cooling rate after heating. A reversible thermosensitive recording medium comprising a recording layer provided on a support and a protective layer provided on the recording layer, wherein the protective layer contains at least an organic clay and an ultraviolet absorbing polymer. This can be achieved by a sexually sensitive recording medium.

  According to the third aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium which does not cause head residue even after repeated use and has excellent durability on the surface of the recording medium.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein one or more kinds selected from the group of acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, and polyvinyl butyral resin are used. A resin is contained in the protective layer.

  According to the fourth aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium that does not peel off even after repeated use and has excellent durability on the surface of the recording medium.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the clay in the organized clay is a layered clay mineral.

  According to the invention described in claim 5, it is possible to provide a reversible thermosensitive recording medium with improved barrier properties and less debris adhesion to the thermal head during repeated use.

  The invention according to claim 6 is the invention according to claim 5, wherein the layered clay mineral is one or more substances selected from the group consisting of montmorillonite, hectorite, saponite, beidellite and mica. And

  According to the sixth aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium with improved barrier properties and less debris adhesion to the thermal head during repeated use.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the organoclay is obtained by organically treating clay with an organic agent, and the organic agent is carbon. It is an organic ammonium ion of several 6 or more.

  According to the seventh aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium with improved barrier properties and less debris adhesion to the thermal head during repeated use.

  The invention according to an eighth aspect is characterized in that, in the invention according to any one of the first to seventh aspects, the organized clay used in the protective layer intercalates a resin.

  According to the eighth aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium with improved barrier properties and less debris adhesion to the thermal head during repeated use.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the resin used in the protective layer is a thermosetting resin in a crosslinked state.

  According to the ninth aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium which does not peel off even after repeated use and has excellent durability on the surface of the recording medium.

  According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the resin is intercalated between the organized clay layers by pulverizing the organized clay and refluxing with an organic solvent. It is characterized by having made it.

  According to the tenth aspect of the present invention, it is possible to provide a reversible thermosensitive recording medium with improved barrier properties and less debris adhesion to the thermal head during repeated use.

  The invention according to claim 11 can be achieved by a reversible thermosensitive recording medium, wherein the organic solvent used in the reflux treatment according to claim 10 is N, N-dimethylformamide (DMF).

  According to the eleventh aspect of the invention, the resin can be intercalated into the organic clay in a good state, the barrier property is improved, and the reversible thermosensitive recording medium is less likely to adhere to the thermal head during repeated use. Can be provided.

  According to a twelfth aspect of the present invention, in the reversible thermosensitive recording medium according to any one of the first to eleventh aspects, any one of an adhesive layer and a pressure-sensitive adhesive layer is provided on a surface opposite to a surface on which an image is formed. It can be achieved by a reversible thermosensitive recording label characterized by having.

  According to invention of Claim 12, it can affix on base sheets, such as a card | curd, and another medium as a reversible thermosensitive recording label which provided the adhesive bond layer or the adhesive layer.

  The invention according to claim 13 includes an information storage unit and a reversible display unit, and the reversible display unit includes the reversible thermosensitive recording medium according to any one of claims 1 to 11. This can be achieved by a reversible thermosensitive recording member.

  According to the invention described in claim 13, the reversible thermosensitive recording member is provided with the reversible display unit and the information storage unit, thereby displaying the information stored in the information storage unit on the reversible display unit. Information can be confirmed without a device, and convenience can be improved.

  According to a fourteenth aspect of the present invention, there is provided image forming means for heating a reversible thermosensitive recording medium to form an image on the reversible thermosensitive recording medium, and heating the reversible thermosensitive recording medium to form the reversible thermosensitive recording medium. 12. A reversible thermosensitive recording medium according to claim 1, wherein the reversible thermosensitive recording medium comprises at least one of image erasing means for erasing the recorded image. This can be achieved by the image processing apparatus.

  According to the fourteenth aspect of the present invention, it is possible to provide an image processing apparatus including an image forming and / or erasing unit that heats a reversible thermosensitive recording medium to form and / or erase an image on the reversible thermosensitive recording medium. That is, it is possible to provide an apparatus capable of recording / erasing with only a thermal head.

  According to the fifteenth aspect of the present invention, the reversible thermosensitive recording medium is heated to form an image on the reversible thermosensitive recording medium, and the reversible thermosensitive recording medium is heated to form the reversible thermosensitive recording medium. 12. An image processing method comprising: erasing a recorded image, wherein the reversible thermosensitive recording medium is the reversible thermosensitive recording medium according to any one of claims 1 to 11. it can.

  According to the fifteenth aspect of the present invention, it is possible to provide an image processing method capable of forming and / or erasing an image on a reversible thermosensitive recording medium by heating the reversible thermosensitive recording medium. Recording and erasing can be performed only with the thermal head, and so-called overwriting becomes possible.

  According to the present invention, it is possible to provide a reversible thermosensitive recording medium that does not cause head residue even after repeated use and has excellent durability on the surface of the recording medium.

  As shown in FIG. 1, the organic clay used in the present invention refers to an organic ammonium ion ionically bonded to the surface of the clay. Originally clay is an inorganic substance and is hydrophilic, but develops hydrophobicity by applying an organic treatment. Thereby, it becomes easy to disperse in an organic solvent or a resin, and dispersibility is improved as compared with a general inorganic filler.

  In addition, by applying a shearing force such as heating and stirring the mixture of resin and organic clay, the resin intercalates (inserts) between the clay layers, which increases the interface between the clay surface and the resin, Heat resistance, mechanical strength, etc. are improved. Further, the intercalation exhibits a barrier property that prevents the low-molecular composition in the recording layer and the thermal decomposition product thereof from being deposited on the surface of the protective layer due to migration. As shown in FIG. 2, this is considered to be caused by the fact that the organized clay dispersed in the protective layer acts as a blocking agent for the recording layer components and their thermal decomposition products.

  In the present invention, the state in which the resin is intercalated between the organic clay layers can be measured by an X-ray diffraction method. When the resin intercalates between the organized clay layers, a measurement result is obtained in which the layer spacing is wider than the layer spacing of the powdered organized clay (the peak shifts to the small angle side). Preferably, the diffraction peak indicating the clay layer interval is in a state of being smaller on the smaller angle side than the powdered organic clay, and more preferably, the diffraction peak indicating the layer interval disappears. Next, a typical X-ray diffraction pattern is shown below. FIG. 3 is a pattern of powdered organic clay (organic montmorillonite). FIG. 4 shows a pattern in which the resin is intercalated between the previous organic clay layers, and the maximum peak is shifted to the small angle side. FIG. 5 shows a pattern in which the intercalation has progressed more than the state shown in FIG. 4, and no maximum peak is recognized.

  Usable organic clays include those obtained by organically treating synthetic or natural layered clay minerals with an organic agent.

  The layered clay mineral may be either synthetic or natural, and examples thereof include montmorillonite, saponite, hectorite, beidellite, stevensite, nontrite and mica.

  Examples of the organicizing agent include 1 to 4 quaternary ammonium ions. Examples include hexyl ammonium ion, octyl ammonium ion, 2-ethylhexyl ammonium ion, dodecyl ammonium ion, lauryl ammonium ion, octadecyl ammonium ion, dioctyl dimethyl ammonium ion, trioctyl ammonium ion, dioctadecyl dimethyl ammonium ion, and trioctadecyl ammonium ion. .

  In the present invention, silica coated with calcium together with the organoclay can be used. As a result, the head matching property is particularly excellent. When silica particles that have not been surface-treated are added to the protective layer, leuco dye coloration occurs on the silica surface, causing color development on the background (background fogging), and erasing when color development / decoloration is repeated Problems such as occurrence of defects occur. On the other hand, even when calcium carbonate, talc, or aluminum hydroxide is used as an inorganic filler other than silica, there are problems such as generation of background density fogging and poor erasure.

  In the present invention, a thermally crosslinkable silicone resin can be used together with the organoclay. The basic skeleton of the thermally crosslinkable silicone resin is a copolymer of a monomer containing a dimethylsiloxane structure and a monomer containing a functional group. The copolymer includes random copolymerization, block copolymerization, graft copolymerization, and the like, and is not particularly limited, but among them, block copolymers and graft copolymers are particularly preferably used. The monomer having a dimethylsiloxane structure preferably has a long chain length, and the molecular weight of the monomer is preferably about 500 to 40,000.

  Examples of the monomer containing a functional group include 2-isopropenyl-2-oxazoline, 2-aziridinylethyl (meth) acrylate, methacrylic acid, glycidyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxylpropyl ( Examples include meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate. Among them, hydroxylethyl (meth) acrylate Hydroxypropyl (meth) acrylate and the like are particularly preferably used.

  Furthermore, other monomers may be copolymerized. For example, monomer groups such as styrene, styrene-butadiene, styrene-isobutylene, ethylene vinyl acetate, vinyl acetate, methacrylonitrile, vinyl alcohol, vinyl pyrrolidone, acrylonitrile, methacrylonitrile; acrylic acid, methyl (meth) acrylate, ethyl (meth ) Acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, ethylhexyl (meth) acrylate, octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) ) Acrylate, lauryl tridecyl (meth) acrylate, tridecyl (meth) acrylate, cetyl stearyl (meth) acrylate, stearyl (meth) acrylate , (Meth) acrylic acid ester groups not containing a functional group such as cyclohexyl (meth) acrylate and benzyl (meth) acrylate.

  Examples of the curing agent used in the heat-crosslinkable silicone resin include isocyanate-based, aziridine-based, epoxy-based, melamine-based, oxazoline-based, carbodiimide-based, and the like, and particularly preferably, an isocyanate-based curing agent. Isocyanate curing agents are polyisocyanate compounds having a plurality of isocyanate groups, such as hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), etc. And adduct type, burette type, isocyanurate type, blocked isocyanates and the like based on these trimethylolpropane. Among these, hexamethylene diisocyanate is particularly preferable, and this adduct type, burette type, and isocyanurate type are preferably used.

  In the present invention, a resin curable with the same curing agent as described above can be used in the protective layer in addition to the above-mentioned thermally crosslinkable silicone resin, and in particular, an acrylic polyol resin, a polyester polyol resin, and a polyurethane polyol resin. It is also preferable to use polyvinyl butyral resin in combination.

  In the present invention, an ultraviolet absorbing polymer can be used in addition to the heat-crosslinking silicone resin. The basic skeleton of the ultraviolet absorbing polymer is a monomer containing an ultraviolet absorbing group or a copolymer of a monomer containing an ultraviolet absorbing group and a monomer containing a functional group. Examples of the polymerization form include linear polymers, long chain branched polymers, short chain branched polymers, star polymers, comb polymers, dendritic polymers, cyclic polymers, and catena polymers. As long as it is a copolymer, any of a block copolymer, a graft copolymer, a star copolymer, and a random copolymer may be used. A copolymer is particularly preferably used.

  Among monomers containing an ultraviolet absorbing group, for example, as a benzotriazole group-containing monomer, 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole, 2- (2 ′ -Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methyl) Phenyl) benzotriazole, 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t -Butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'-t-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydride) Roxy-3 ′, 5′-di-t-butylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-aminophenyl) benzotriazole, 2- (2′-hydroxy-) 5'-t-octylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-benzylphenyl) benzotriazole, 2- [2'-hydroxy-3'-(3 ' ', 4' ', 5' ', 6' '-tetrahydrophthalimido-methyl) -5'-methylphenyl] benzotriazole, 2- [2'-hydroxy-3', 5'-bis (α, α-diethyl Benzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-3′-eudecyl-5′-methylphenyl) benzotriazole, 2- (5′-methyl-2′-hydroxyphenyl) benzotriazole, 2 -[2 ' Hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2- (3 T-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3 , 5-Di-t-amyl-2-hydroxyphenyl) benzotriazole, 2- (2′-hydroxy-5′-t-octylphenyl) benzotriazole, 2- (5-t-butyl-2-hydroxyphenyl) Benzotriazole, 2- (5-t-octyl-2-hydroxyphenyl) benzotriazole, 2- (2′-hydroxy-3′-dodecyl-5′-methylphenyl) Benzotriazole, 2- (2′-hydroxy-3′-undecyl-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′-tridecyl-5′-methylphenyl) benzotriazole, 2- ( 2′-hydroxy-3′-tetradecyl-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′-pentadecyl-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3) '-Hexadecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-4'-(2 ''-ethylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2 '' -Ethylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2' '-ethyloctyl) oxy Phenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(2 ″ -propylhexyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(2 ″ -propylheptyl) oxy Phenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(2 ″ -propyloctyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″ -ethylhexyl) oxyphenyl ] Benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″ -ethylheptyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″ -ethyloctyl) oxyphenyl] ] Benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″ -propylhexyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″ -propiyl) Heptyl) oxy phenyl] benzotriazole, 2- [2'-hydroxy-4 '- (1' '- propyl octyl) oxy phenyl] benzotriazole. Among these, 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′- Hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole and the like are particularly preferably used.

  Furthermore, as the monomer containing an ultraviolet absorbing group, those having a benzophenone moiety exemplified below are preferable. 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4 -N-dodecyloxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4,4'-dimethoxybenzophenone, 2,2,4,4-tetrahydroxybenzophenone, 2-hydroxy-4- Methoxy-2′-carboxybenzophenone, 2-hydroxy-4-oxybenzylbenzophenone, 2-hydroxy-4-chlorobenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-4-methoxyben Phenone-5-sodium sulfonate, 2,2'-dihydroxy-4,4'-dimethoxy-benzophenone - sodium sulfonate. Of these, 2,2,4,4-tetrahydroxybenzophenone and the like are particularly preferably used.

  Examples of the monomer containing a functional group include 2-isopropenyl-2-oxazoline, 2-aziridinylethyl (meth) acrylate, methacrylic acid, glycidyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxyl Examples include propyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate, among which hydroxylethyl (meth) ) Acrylate, hydroxylpropyl (meth) acrylate and the like are particularly preferably used.

  Furthermore, in order to increase the strength of the coating film and improve heat resistance, the following monomers may be copolymerized with a copolymer of a monomer containing an ultraviolet absorbing group and a monomer containing a functional group. For example, monomer groups such as styrene, styrene-butadiene, styrene-isobutylene, ethylene vinyl acetate, vinyl acetate, methacrylonitrile, vinyl alcohol, vinyl pyrrolidone, acrylonitrile, methacrylonitrile; acrylic acid, methyl (meth) acrylate, ethyl (meth ) Acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, ethylhexyl (meth) acrylate, octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) ) Acrylate, lauryl tridecyl (meth) acrylate, tridecyl (meth) acrylate, cetyl stearyl (meth) acrylate, stearyl (meth) acrylate , (Meth) acrylate groups not containing functional groups such as cyclohexyl (meth) acrylate and benzyl (meth) acrylate; ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetra Ethylene glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate, pentacontactor ethylene glycol (meth) acrylate, butylene di (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, Has two or more polymerizable double bonds in one molecule, such as pentadecaethylene glycol di (meth) acrylate and diethylene glycol di (meth) acrylate phthalate Although it is mentioned from a monomer group etc., it is not particularly limited, among them, styrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, Particularly preferred is t-butyl (meth) acrylate. Moreover, 2 or more types can also be used together as needed.

  From the above, specific preferred examples of the ultraviolet absorbing polymer used in the present invention include 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole and 2-hydroxyethyl methacrylate. A copolymer of styrene, a copolymer of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2-hydroxypropyl methacrylate and methyl methacrylate, 2- (2′-hydroxy-3 ′) -T-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-hydroxyethyl methacrylate, methyl methacrylate and t-butyl methacrylate, 2,2,4,4-tetrahydroxy Benzophenone, 2-hydroxypropyl methacrylate, styrene and methyl methacrylate A copolymer consisting of propyl methacrylate, and the like, but not particularly limited.

  By using organically modified clay intercalated with such UV-absorbing polymers in the protective layer, it is possible to reduce the deterioration of the recording layer due to ultraviolet light, especially the deterioration of the leuco dye in the recording layer. A highly practical recording medium excellent in performance can be obtained. By mixing these two types of resins, the reason is not clear, but particularly excellent durability is exhibited.

  In the present invention, an acrylic polyol resin can be used in addition to the organic clay and the ultraviolet absorbing polymer. The acrylic polyol resin is composed of styrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, etc. and 2-hydroxy A copolymer composed of a monomer having a hydroxyl group such as ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate is preferably used, and styrene and methyl methacrylate having high Tg are mainly used. An acrylic polyol resin as a component is preferably used.

  Repeated durability can be further improved by crosslinking the ultraviolet absorbing polymer and the acrylic polyol resin. When the polymer is crosslinked, examples of the curing agent used include isocyanate-based, aziridine-based, epoxy-based, melamine-based, oxazoline-based, carbodiimide-based, and the like, and an isocyanate-based curing agent is particularly preferable. Isocyanate curing agents are polyisocyanate compounds having a plurality of isocyanate groups, such as hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), etc. And adduct type, burette type, isocyanurate type, blocked isocyanates and the like based on these trimethylolpropane. Among these, hexamethylene diisocyanate is particularly preferable, and this adduct type, burette type, and isocyanurate type are preferably used. The hydroxyl value of the resin used at this time is preferably about 30 to 200.

  The matrix resin for the protective layer is not particularly limited. For example, polyester, polycarbonate, polyacetal, polyarylate, polyamide, polyamideimide, polyetherimide, polyphenylene ether, polyphenylene sulfide, polyethersulfone, polyetherketone. , Polyphthalamide, polyether nitrile, polyether sulfone, polybenzimidazole, polycarbodiimide, polysiloxane, polymethyl (meth) acrylate, poly (meth) acrylamide and other acrylic resins, acrylic rubber, poly-4-fluorinated ethylene, fluorine Resin, fluoro rubber, liquid crystal polymer, epoxy resin, melamine resin, urea resin, diallyl phthalate resin, phenol resin, polysilane, silicone resin, urethane resin , Polyethylene, polypropylene, polybutene, polypentene, ethylene-propylene copolymer, ethylene-butene copolymer, polybutadiene, poisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, ethylene-propylene-diene copolymer, ethylene-butene-diene Examples thereof include copolymers, butyl rubber, polymethylpentene, polystyrene, styrene-butadiene copolymers, and styrene-hydrogenated butadiene copolymers. Furthermore, it is more preferable to use a resin that can be thermoset by a crosslinking agent such as an isocyanate compound. Examples of the thermosetting resin include various resins having a functional group such as a hydroxyl group, and examples thereof include polyester polyol, acrylic polyol, and polyurethane polyol. Examples of the curing agent used in these resins include isocyanate-based, aziridine-based, epoxy-based, melamine-based, oxazoline-based, carbodiimide-based, and the like, and particularly preferable are isocyanate-based curing agents. The isocyanate curing agent is a polyisocyanate compound having a plurality of isocyanate groups, specifically hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), xylene diisocyanate (XDI), isophorone diisocyanate (IPDI), etc. And adduct type, burette type, isocyanurate type, blocked isocyanates and the like based on these trimethylolpropane. Among these, hexamethylene diisocyanate is particularly preferable, and this adduct type, burette type, and isocyanurate type are more preferably used.

  The amount of the organic clay used is preferably 0.1 to 100 parts by weight, particularly 0.1 to 20 parts by weight, based on 100 parts by weight of the resin constituting the protective layer. If the amount added is less than this range, sufficient barrier properties may not be obtained. Moreover, when there is much addition amount, the viscosity of a resin composite material will increase, and possibility that a moldability fall and dispersion | distribution of organic clay will become inadequate will become high.

  Next, the coloring / decoloring phenomenon of the present invention will be described.

  The reversible thermosensitive recording medium of the present invention can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. The basic coloring / decoloring phenomenon of the composition comprising the color former and developer used in the present invention will be described.

FIG. 6 shows the relationship between the color density and temperature of the recording medium of the present invention. Introduction gradually heated the recording medium in the decolored state (A), and color development takes place leuco dye and the developer is melted colored state (B) at temperatures T ₁ begins to melt. When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature and a solid color state (C) is obtained.

  Whether or not this color development state is obtained depends on the rate of temperature decrease from the molten state, and in slow cooling, the color disappears during the temperature decrease, and the same color disappearance state (A) or rapid color development state (C ) A relatively low concentration state is formed.

On the other hand, rapidly cooled colored state (C) is again raised gradually and discoloring occurs at a lower temperature T ₂ than the coloring temperature (E from D), returns the beginning when the temperature decreases from here to the same decolored state (A). The actual color developing temperature and color erasing temperature vary depending on the combination of the developer and color former used, and can be selected according to the purpose.

  Further, the density of the melt coloring state and the coloring density when rapidly cooled are not necessarily the same and may be different.

  In the reversible thermosensitive recording medium of the present invention, the colored state (C) obtained by quenching from the molten state is a state in which the developer and the color former are mixed in a state where they can be contacted with each other, and this is a solid state. Often forms a state. This state is a state where the developer and the color former are aggregated to maintain the color development, and it is considered that the color development is stabilized by the formation of the aggregate structure.

  On the other hand, the decolored state is a state in which both phases are separated. This state is a state in which molecules of at least one compound aggregate to form a domain or crystallize, and the color former and developer are separated and stabilized by aggregation or crystallization. Conceivable.

  In many cases, in the present invention, more complete color erasure occurs due to phase separation of the two and crystallization of the developer.

  In both the decoloring by slow cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG. 6, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

  The color image of the present invention may be formed by heating to a temperature at which it is once melt-mixed by a thermal head or the like and then rapidly cooling. Further, decolorization is two methods, a method of slowly cooling from a heated state and a method of heating to a temperature slightly lower than the coloring temperature.

  However, they are the same in the sense that they are phase-separated or at least temporarily held at a temperature at which one crystallizes.

  The reason for rapid cooling in the process of forming the colored state is to prevent the temperature from being maintained at this phase separation temperature or crystallization temperature. The rapid cooling and slow cooling here are relative to one composition, and the boundary thereof changes depending on the combination of the color former and the developer.

  As described above, the recording layer can be erased by controlling the heating temperature and / or the cooling rate after heating. Printing with this heat-sensitive recording layer provides high contrast and excellent image quality.

  As the leuco dye used in the present invention, one or more compounds used in this type of reversible thermosensitive recording medium can be used. For example, known dye precursors such as phthalide compounds, azaphthalide compounds, and fluorane compounds. It is.

  Specific examples of the leuco dye used in the present invention include the following.

2-anilino-3-methyl-6-diethylaminofluorane,
2-anilino-3-methyl-6-di (n-butylamino) fluorane,
2-anilino-3-methyl-6- (Nn-propyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (Nn-amyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-sec-butyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane,
2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluorane,
2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane,
2-anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane,
2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluorane,
2- (m-trichloromethylanilino) -3-methyl-6-diethylaminofluorane,
2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluorane,
2- (m-trichloromethylanilino) -3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane,
2- (2,4-dimethylanilino) -3-methyl-6-diethylaminofluorane,
2- (N-ethyl-p-toluidino) -3-methyl-6- (N-ethylanilino) fluorane,
2- (N-ethyl-p-toluidino) -3-methyl-6- (N-propyl-p-toluidino) fluorane,
2-anilino-6- (Nn-hexyl-N-ethylamino) fluorane,
2- (o-chloroanilino) -6-diethylaminofluorane,
2- (o-chloroanilino) -6-dibutylaminofluorane,
2- (m-trifluoromethylanilino) -6-diethylaminofluorane,
2,3-dimethyl-6-dimethylaminofluorane,
3-methyl-6- (N-ethyl-p-toluidino) fluorane,
2-chloro-6-diethylaminofluorane,
2-bromo-6-diethylaminofluorane,
2-chloro-6-dipropylaminofluorane,
3-chloro-6-cyclohexylaminofluorane,
3-bromo-6-cyclohexylaminofluorane,
2-chloro-6- (N-ethyl-N-isoamylamino) fluorane,
2-chloro-3-methyl-6-diethylaminofluorane,
2-anilino-3-chloro-6-diethylaminofluorane,
2- (o-chloroanilino) -3-chloro-6-cyclohexylaminofluorane,
2- (m-trifluoromethylanilino) -3-chloro-6-diethylaminofluorane,
2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluorane,
1,2-benzo-6-diethylaminofluorane,
3-diethylamino-6- (m-trifluoromethylanilino) fluorane,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
3- (1-octyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -7-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (4-Nn-amyl-N-methylaminophenyl) -4-azaphthalide,
3- (1-methyl-2-methylindol-3-yl) -3- (2-hexyloxy-4-diethylaminophenyl) -4-azaphthalide,
3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3,3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, and the like.

  Examples of the developer used in the heat-sensitive recording layer include those described in, for example, Patent Document 1, Patent Document 2, and Japanese Patent Application Laid-Open No. 6-210954.

  The developer used here is a structure having a color developing ability for developing a leuco dye in the molecule, such as a phenolic hydroxyl group, a carboxylic acid group, or a phosphate group, and a structure that controls the cohesion between molecules, such as a long It is a compound having one or more structures in which chain hydrocarbon groups are linked. The linking moiety may be via a divalent or higher valent linking group containing a hetero atom, and the same linking group and / or aromatic group may be contained in the long-chain hydrocarbon group. Specific examples of such a reversible developer are disclosed in, for example, JP-A-9-290563 and JP-A-11-188969.

  Specific examples of the developer used in the present invention are shown below. In addition, a color developer may be used independently and may be used in mixture of 2 or more types.

式中、Ｘ_１はヘテロ原子を含む２価の基又は直接結合手を示し、Ｘ_２はヘテロ原子を含む２価の基を示す。Ｒ_１は２価の炭化水素基を表わし、Ｒ_２は炭素数１から２２の炭化水素基を表わす。また、ｐは０から４の整数を表わし、ｐが２から４のとき繰り返されるＲ_１及びＸ_２は同一でも、異なっていても良い。また、ｑは１から３を表わす。

In the formula, X ₁ represents a divalent group containing a hetero atom or a direct bond, and X ₂ represents a divalent group containing a hetero atom. R ₁ represents a divalent hydrocarbon group, and R ₂ represents a hydrocarbon group having 1 to 22 carbon atoms. P represents an integer of 0 to 4, and when p is 2 to 4, R ₁ and X _{2 that} are repeated may be the same or different. Q represents 1 to 3;

Specifically, R ₁ and R ₂ represent an optionally substituted hydrocarbon group, which may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and is composed of both of them. It may be a hydrocarbon group. The aliphatic hydrocarbon group may be linear or branched and may have an unsaturated bond. Examples of the substituent attached to the hydrocarbon group include a hydroxyl group, a halogen, and an alkoxy group. R ₁ may be a direct bond.

Further, when the sum of the carbon numbers of R ₁ and R ₂ is 7 or less, the stability of color development and the decoloring property are lowered, so that the carbon number is preferably 8 or more, and more preferably 11 or more. X ₁ and X ₂ each represents a divalent group containing a hetero atom, and preferably represents a divalent group having at least one group represented by Table 1 below.

その具体例としては、下記表２に示すものが挙げられる。

Specific examples thereof include those shown in Table 2 below.

本発明におけるフェノール化合物の具体的な例を表３に挙げるが、本発明はこれらに限定されるものではない。

Although the specific example of the phenolic compound in this invention is given in Table 3, this invention is not limited to these.

  Moreover, a phenol compound can also be used individually or in mixture.

有機リン酸系の顕色剤としては、以下のような化合物が例示できる。

Examples of the organic phosphate developer include the following compounds.

  Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, ditetradecyl phosphate, dihexadecyl phosphate, phosphoric acid Dioctadecyl ester, dieicosyl phosphate, dibehenyl phosphate, etc.

  Examples of the aliphatic carboxylic compound include the following compounds.

  2-hydroxytetradecanoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecanoic acid, 2-hydroxyeicosanoic acid, 2-hydroxydocosanoic acid, 2-bromohexadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid 2-bromodocosanoic acid, 3-bromooctadecanoic acid, 3-bromodocosanoic acid, 2,3-dibromooctadecanoic acid, 2-fluorododecanoic acid, 2-fluorotetradecanoic acid, 2-fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2 -Fluoroeicosanoic acid, 2-fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, perfluorooctadecanoic acid and the like.

  Examples of the aliphatic dicarboxylic acid and tricarboxylic acid compound include the following compounds.

  2-dodecyloxy succinic acid, 2-tetradecyloxy succinic acid, 2-hexadecyloxy succinic acid, 2-octadecyloxy succinic acid, 2-eicosyloxy succinic acid, 2-dodecyloxy succinic acid, 2-dodecylthiosuccinic acid 2-tetradecylthiosuccinic acid, 2-hexadecylthiosuccinic acid, 2-octadecylthiosuccinic acid, 2-eicosylthiosuccinic acid, 2-docosylthiosuccinic acid, 2-tetracosylthiosuccinic acid, 2-hexadecyldithiosuccinic acid, 2-octadecyl dithiosuccinic acid, 2-eicosyl dithiosuccinic acid, dodecyl succinic acid, tetradecyl succinic acid, pentadecyl succinic acid, hexadecyl succinic acid, octadecyl succinic acid, eicosyl succinic acid, docosyl succinic acid, 2,3-dihexadecyl succinic acid, 2 , 3-Dioc Decyl succinic acid, 2-methyl-3-hexadecyl succinic acid, 2-methyl-3-octadecyl succinic acid, 2-octadecyl-3-hexadecyl succinic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid , Dihexadecylmalonic acid, dioctadecylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, 2-hexadecylglutaric acid, 2-octadecylglutaric acid, 2-eicosylglutaric acid, docosylglutaric acid, 2-pentadecyladipine Acid, 2-octadecyl adipic acid, 2-eicosyl adipic acid, 2-docosyl adipic acid, 2-hexadecanoyloxypropane-1,2,3-tricarboxylic acid, 2-octadecanoyloxypropane-1,2 , 3-tricarboxylic acid, etc. .

  The appropriate ratio of the color former to the color developer varies depending on the combination of the compounds used, but the color developer is generally in the range of 0.1 to 20 with respect to the color developer 1 at a molar ratio, preferably 0. The range is from 2 to 10. If the amount of the developer is less or more than this range, the density of the colored state is lowered, which causes a problem. In addition, the color former and the developer can be used in a microcapsule.

  In the heat-sensitive recording layer of the present invention, an additive for improving or controlling coloring and decoloring characteristics such as coating characteristics, decoloring properties, and image stability can be used as necessary. Examples of these additives include a surfactant, a conductive agent, a filler, an antioxidant, a color development / decoloration control agent, a color development stabilizer, and a color disappearance accelerator.

  As the color-decoloring / controlling agent, a compound having a divalent group containing a hetero atom and an alkyl chain having 8 or more carbon atoms, or a compound having an amide group of an N, N′-2 substituent, However, the present invention is not limited to these compounds.

  As the resin (binder resin) used in the heat-sensitive recording layer of the present invention, conventionally known resins are widely used. Among them, resins that can be cross-linked are preferably used from the viewpoint of repeated durability. For example, a resin having a hydroxyl group is used. A resin cured with an isocyanate-based crosslinking agent is particularly preferably used.

  Examples of the resin used in the present invention include olefin polymers such as polyethylene, polybutadiene, polypropylene, polyisoprene and hydrogenated polybutadiene; polymethyl acrylate, polyethyl acrylate, poly (n-butyl acrylate), poly (isobornyl). Acrylate), poly (2-hydroxyethyl acrylate, poly (2-hydroxypropyl acrylate), poly (2-hydroxybutyl acrylate), polymethyl methacrylate, polyethyl methacrylate, poly (n-butyl methacrylate), poly (isobutyl methacrylate) , Poly (sec-butyl methacrylate), poly (tert-butyl methacrylate), poly (isobornyl methacrylate), poly (benzyl methacrylate), poly (2-ethyl) Ruhexyl methacrylate), polycyclohexyl methacrylate, poly (2-hydroxyethyl methacrylate, poly (2-hydroxypropyl methacrylate), poly (2-hydroxybutyl methacrylate), polyacrylic acid, polymethacrylic acid and copolymers thereof. Acrylic polymer; styrene polymer such as polystyrene, poly (α-methylstyrene), poly (4-methylstyrene), poly (4-methoxystyrene), styrene-acrylonitrile copolymer, styrene-butadiene copolymer; Polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl formal, vinyl alcohol-vinyl butyral copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-bi Nyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, poly (2-vinylpyridine), poly (4-vinylpyridine), poly (N-vinylcarbazole) ) Such as polytetrafluoroethylene, polytrifluoroethylene, and polyvinylidene fluoride; nitrocellulose, cellulose acetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate, ethyl cellulose, Cellulosic polymers such as methylcellulose; polytetrahydrofuran; isobutylene-maleic anhydride copolymer; polyisobutyl ether ;; polycarbonate, polyarylate, polysulfone, poly (2,6-di) Chill-p-phenylene oxide), engineering plastics such as polyimide polyamideimide, polyetherimide; polyurethane; polyamide resins such as nylon 6 and nylon 66; polyvinyl alcohol, polyethylene oxide, polypropylene oxide, polysaccharides, polystyrene Water-soluble polymers such as sodium sulfonate; rubber-based polymers such as natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and the like can be used, and two or more kinds can be used in combination as required.

  In addition, a resin having a group that reacts with a crosslinking agent, such as an acrylic polyol resin, a polyester polyol resin, a polyurethane polyol resin, a polyvinyl butyral resin, cellulose acetate propionate, or cellulose acetate butyrate, or a monomer that has a group that reacts with the crosslinking agent Resins obtained by copolymerizing other monomers may be used together with a crosslinking agent.

  Among these resins, preferably used resins include acrylic polyol resins, polyester polyol resins, polyurethane polyol resins, polyvinyl butyral resins, and the like, and particularly heat-crosslinked resins obtained by crosslinking these resins with isocyanate compounds. Preferably used.

  Isocyanate compounds are polyisocyanate compounds having a plurality of isocyanate groups, specifically hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), and the like. Examples thereof include adduct type, burette type, isocyanurate type, and blocked isocyanates by trimethylolpropane.

  Of these, aliphatic isocyanate compounds are preferred in terms of background whiteness, repeated durability, and burrs / cracks.

  The ratio of the hydroxyl group-containing resin and the isocyanate-based crosslinking agent is preferably 0.5 to 1.5 with respect to the hydroxyl group of the resin.

  The weight ratio of the color forming component and the resin in the heat sensitive recording layer is preferably 0.1 to 10 with respect to the color developing component 1, and if it is less than this, the heat intensity of the heat sensitive recording layer is insufficient, and if it is more than this, the color density is high. Decreases and becomes a problem.

  For the formation of the thermosensitive recording layer, a coating solution prepared by uniformly mixing and dispersing a mixture of a developer, a color former, various additives, a binder resin and a coating solvent is used.

  Specific examples of the solvent used for preparing the coating liquid include water; alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Ketones such as N; N-dimethylformamide, amides such as N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, and 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl Glycol ether acetates such as acetate; esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and ethylene carbonate; aromatic hydrocarbons such as benzene, toluene, and xylene; hexane, heptane, iso-octane Aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl Examples include pyrrolidones such as -2-pyrrolidone.

  The coating liquid can be prepared using a known coating liquid dispersing apparatus such as a paint shaker, a ball mill, an attritor, a three-roll mill, a keddy mill, a sand mill, a dyno mill, or a colloid mill. Moreover, each material may be disperse | distributed in a solvent using the said coating-liquid dispersion | distribution apparatus, and each may be disperse | distributed and mixed in a solvent individually. Further, it may be dissolved by heating and deposited by rapid cooling or cooling.

  There are no particular restrictions on the coating method for providing the thermosensitive recording layer, blade coating, wire bar coating, spray coating, air knife coating, bead coating, curtain coating, gravure coating, kiss coating, reverse roll. Known methods such as coating, dip coating, and die coating can be used.

  The thickness of the thermosensitive recording layer is usually 5 to 15 μm.

  A filler may be added to the heat-sensitive recording layer and the protective layer, and the filler can be divided into an inorganic filler and an organic filler.

  Examples of inorganic fillers include carbonates such as calcium carbonate and magnesium carbonate; silicates such as anhydrous silicic acid, hydrous silicic acid, hydrous aluminum silicate, and hydrous calcium silicate; hydroxides such as alumina and iron oxide; Zinc oxide, indium oxide, alumina, silica, zirconia oxide, tin oxide, cerium oxide, iron oxide, antimony oxide, barium oxide, calcium oxide, barium oxide, bismuth oxide, nickel oxide, magnesium oxide, chromium oxide, manganese oxide, oxidation Metal oxides such as tantalum, niobium oxide, titanium oxide, thorium oxide, hafnium oxide, molybdenum oxide, iron ferrite, nickel ferrite, cobalt ferrite, barium titanate and potassium titanate; metal sulfides such as zinc sulfide and barium sulfate Or sulfuric acid compounds; titanium Metal carbides such as carbide, silicon carbide, molybdenum carbide, tungsten carbide, tantalum carbide; metal nitrides such as aluminum nitride, silicon nitride, boron nitride, zirconium nitride, vanadium nitride, titanium nitride, niobium nitride, gallium nitride, etc. Can be mentioned.

  Organic fillers include silicone resins, cellulose resins, epoxy resins, nylon resins, phenolic resins, polyurethane resins, urea resins, melamine resins, polyester resins, polycarbonate resins, styrene resins such as polystyrene, polystyrene / isoprene, polystyrene / vinylbenzene, etc. Acrylic resins such as vinylidene chloride acrylic, acrylic urethane and ethylene acrylic, polyethylene resins, formaldehyde resins such as benzoguanamine formaldehyde and melamine formaldehyde, polymethyl methacrylate resins, vinyl chloride resins and the like. In the present invention, the organic filler can be used alone, but two or more kinds may be included, and composite particles may be used. Examples of the shape include a spherical shape, a granular shape, a plate shape, and a needle shape.

  In addition, a lubricant may be added to the heat-sensitive recording layer and the protective layer. Specific examples of the lubricant include synthetic waxes such as ester wax, paraffin wax, and polyethylene wax: vegetable waxes such as hardened castor oil: beef tallow hardened oil Animal waxes such as: Higher alcohols such as stearyl alcohol and behenyl alcohol: Higher fatty acids such as margaric acid, lauric acid, mystynolic acid, palmitic acid, stearic acid, behenic acid, and fumenic acid: higher fatty acids such as sorbitan fatty acid ester Fatty acid esters: amides such as stearic acid amide, oleic acid amide, lauric acid amide, ethylene bis stearic acid amide, methylene bis stearic acid amide, and methylol stearic acid amide.

  In the present invention, the drying / curing method for forming the heat-sensitive recording layer, the protective layer, etc. is carried out as necessary after coating / drying. A high temperature bath or the like may be used for a relatively short time at a relatively high temperature, or a heat treatment may be performed at a relatively low temperature for a long time. As specific conditions for the crosslinking reaction, it is preferable to heat from about 1 minute to 150 hours under a temperature condition of about 30 ° C. to 130 ° C. from the viewpoint of reactivity. More preferably, heating is performed for about 60 minutes to 120 hours under a temperature condition of 40 ° C to 100 ° C.

  Further, although a PET film is often used as a support, it is difficult to dry at 130 ° C. or higher due to the heat resistance of the PET film. Therefore, it is necessary to provide a crosslinking step separately from the drying step. Furthermore, when the cross-linking temperature is very high, the cross-linking proceeds rapidly, but this causes a problem that the coatability of the layer surface is extremely deteriorated, resulting in poor coating or poor adhesion between the laminated layers. Occurs.

  Therefore, the crosslinking temperature is preferably heated for 2 minutes to 120 hours under a temperature condition of 40 ° C to 100 ° C.

  The support for the reversible thermosensitive recording medium of the present invention is paper, resin film, PET film, synthetic paper, metal foil, glass, or a composite thereof, as long as it can hold the thermosensitive recording layer. Moreover, the thing of the thickness as needed can be used individually or by bonding. That is, it is preferably 60 to 150 μm, and a support having an arbitrary thickness from about several μm to about several mm is used.

  Moreover, when providing the said under layer on these support bodies, crack generation | occurrence | production prevention and generation | occurrence | production of a burr | flash are improved by providing through an contact bonding layer.

  The adhesive layer can be formed by the same coating method as that for each of the above layers.

Next, modifications of the reversible thermosensitive recording medium of the present invention will be described.
In recent years, disc cartridges incorporating thick cards such as IC cards and optical cards, thin sheets such as non-contact IC tags, flexible disks, magneto-optical recording disks (MD), and disks that can rewrite storage information such as DVD-RAM. , CD-RW discs that do not use disc cartridges, CD-R discs, write-once discs, optical information recording media (CD-RW) using phase change storage materials, video tape cassettes, etc. From the surface of the support constituting the reversible thermosensitive recording medium of the present invention on the surface opposite to the surface on which the thermosensitive recording layer is formed, an adhesive layer or a pressure-sensitive adhesive layer is provided as a reversible thermosensitive recording label as a substrate such as a card. You may affix on a sheet | seat or another medium.

  The present invention can also provide a reversible thermosensitive recording member having an information storage unit and a reversible display unit including the reversible thermosensitive recording medium of the present invention. The reversible thermosensitive recording member is provided with a reversible display unit including an reversible thermosensitive recording medium and an information storage unit, so that the information stored in the information storage unit is displayed on the reversible display unit, and there is no special device. You can also check the information, improving convenience. A magnetic recording layer, an IC recording unit, or the like is preferably used as the storage unit used at that time.

  Next, an image processing apparatus and an image processing method for executing image formation and / or image erasure on the reversible thermosensitive recording medium of the present invention will be described.

  In order to form a color image using the reversible thermosensitive recording medium of the present invention, the color image may be rapidly cooled after being heated above the color development temperature. Specifically, for example, when the thermal recording layer is heated for a short time with a thermal head or laser light, the heat-sensitive recording layer is locally heated, so that the heat is immediately diffused and rapid cooling occurs, so that the color development state can be fixed.

  On the other hand, in order to erase the color, it may be heated and cooled for a relatively long time using an appropriate heat source, or may be temporarily heated to a temperature slightly lower than the coloring temperature. When heated for a long time, the temperature of a wide range of the recording medium rises, and the subsequent cooling becomes slow. As a heating method in this case, a hot roller, a hot stamp, hot air, or the like may be used, or heating may be performed for a long time using a thermal head.

  Further, in order to heat the thermosensitive recording layer to the decoloring temperature range, for example, the applied energy may be lowered slightly from the time of recording by adjusting the voltage applied to the thermal head and the pulse width. If this method is used, recording / erasing can be performed only by the thermal head, and so-called overwriting becomes possible. Of course, it can be erased by heating to a decoloring temperature range with a heat roller or a heat stamp.

  Thus, the present invention can provide an image processing apparatus and an image processing method characterized in that image formation and / or image erasure is performed by heating the reversible thermosensitive recording medium of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to examples. All parts in this example are parts by weight, and this example is merely illustrative of the present invention, and the present invention is not limited by these examples. In addition, a part shows a weight ratio.

Example 1
(Create recording layer)
The following composition was pulverized and dispersed to a particle size of 1 to 4 μm with a ball mill.

  9 parts developer with the following structure

下記構造の発色消色制御剤 ４部

4 parts coloring and decoloring control agent with the following structure

アクリルポリオール樹脂（三菱レイヨン社製LR503 固形分濃度50%) ３０部
メチルエチルケトン １００部
得られた分散液に２−アニリノ−３−メチル−６−ジブチルアミノフルオラン３部、日本ポリウレタン社製コロネートＨＬ（アダクト型ヘキサメチレンジイソシアネート ７５％酢酸エチル溶液）６部を加え、よく撹拌し記録層塗工液を調製した。上記組成の記録層塗工液を、厚さ100μｍのポリエステルフィルム上にワイヤーバーを用い塗工し、８０℃で乾燥した後、６０℃で２４時間加熱して、膜厚約８．０μｍの記録層を設けた。
(有機化クレーの分散液の作成)
下記組成物をペイントシェーカーにより、粒径０．５〜０．８μｍまで粉砕分散し、分散液１を得た。
アクリルポリオール樹脂（三菱レイヨン社製LR503 固形分濃度50%) ８部
有機化クレー（Nanocor社製、nanomer I.30T） １部
＊Ｉ.30Ｔ：有機化モンモリロナイト、有機化剤：オクタデシルアンモニウムイオン
Ｎ，Ｎージメチルホルムアミド １５部
(樹脂の有機化クレーへのインターカレート)
分散液１に、Ｎ，Ｎ−ジメチルホルムアミド １００部入れ、３時間還流した。還流後、Ｎ，Ｎ−ジメチルホルムアミドを減圧乾燥して、樹脂がクレー層間にインターカレートした固体状組成物１を得た。
（保護層の作成）
固体状組成物１にメチルエチルケトン １５部を加えて、超音波分散器でよく分散した。得られた分散液にカルシウムコーティングシリカ（水澤化学社製 Ｐ−８３２）１部を加え、ペイントシェーカーにて粒子径約０．７μｍになるまで分散した。この分散液に日本ポリウレタン社製コロネートＨＸ（アダクト型ヘキサメチレンジイソシアネート ７５％酢酸エチル溶液）３部を加え、よく撹拌し保護層塗工液を調製した。上記組成の保護層塗工液を、先に作成した記録層上にワイヤーバーを用い塗工し、８０℃で乾燥した後、６０℃で２４時間加熱して、膜厚約３．０μｍの保護層を設け、本発明の可逆性感熱記録媒体を作製した。

Acrylic polyol resin (LR503, solid content concentration 50%, manufactured by Mitsubishi Rayon Co., Ltd.) 30 parts Methyl ethyl ketone 100 parts 3 parts of 2-anilino-3-methyl-6-dibutylaminofluorane was added to the obtained dispersion, and Coronate HL (manufactured by Nippon Polyurethane Co., Ltd.) 6 parts of adduct type hexamethylene diisocyanate (75% ethyl acetate solution) was added and stirred well to prepare a recording layer coating solution. The recording layer coating solution having the above composition was applied on a polyester film having a thickness of 100 μm using a wire bar, dried at 80 ° C., and then heated at 60 ° C. for 24 hours to obtain a recording film having a thickness of about 8.0 μm. A layer was provided.
(Creation of organic clay dispersion)
The following composition was pulverized and dispersed to a particle size of 0.5 to 0.8 μm using a paint shaker to obtain dispersion 1.
Acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd., 50% solid concentration) 8 parts Organized clay (Nanocor, nanomer I.30T) 1 part * I.30T: Organized montmorillonite, Organizing agent: Octadecyl ammonium ion N, N-dimethylformamide 15 parts
(Intercalation of resin to organic clay)
To dispersion 1, 100 parts of N, N-dimethylformamide was added and refluxed for 3 hours. After refluxing, N, N-dimethylformamide was dried under reduced pressure to obtain a solid composition 1 in which the resin was intercalated between the clay layers.
(Creation of protective layer)
15 parts of methyl ethyl ketone was added to the solid composition 1 and well dispersed with an ultrasonic disperser. 1 part of calcium-coated silica (P-832, manufactured by Mizusawa Chemical Co., Ltd.) was added to the obtained dispersion, and dispersed with a paint shaker until the particle size became about 0.7 μm. To this dispersion, 3 parts of Coronate HX (Adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane was added and stirred well to prepare a protective layer coating solution. The protective layer coating solution having the above composition is coated on the previously prepared recording layer using a wire bar, dried at 80 ° C., and then heated at 60 ° C. for 24 hours to protect the film with a thickness of about 3.0 μm. A layer was provided to produce a reversible thermosensitive recording medium of the present invention.

Example 2
A recording medium was produced in the same manner as in Example 1 except that the following acrylic polyol resin was used instead of LR-503 used in Example 1.
Hydroxyl value: 133, glass transition temperature: 86 ° C., molecular weight 21800, solid content concentration 50% 8 parts [interlayer distance by X-ray diffraction measurement]
The interlayer distance of the organized clay powder (I.30T) was 22 mm by X-ray diffraction.
On the other hand, in the recording media prepared in Examples 1 and 2, by the X-ray diffraction measurement method, the peak of 22 Å measured by the organic clay powder (I.30T) disappeared, and the diffraction intensity moved to the small corner, The maximum is no longer recognized. This means that the clay interlayer distance has increased significantly.

Comparative Example 1
A recording medium was produced in the same manner as in Example 1 except that the organic clay used in Example 1 was not used.

Comparative Example 2
A recording medium was produced in the same manner as in Example 2 except that the organic clay used in Example 2 was not used.
(Evaluation item)
1) Color Decoloration Characteristics The recording media produced in Examples 1 and 2 and Comparative Examples 1 and 2 were printed with a thermal printing device manufactured by Okura Electric Co., Ltd. at a voltage of 13.3 V and a pulse width of 1.2 msec. The density of the printed part was measured with a Macbeth densitometer RD914. Next, this printed sample was erased by heating at 140 ° C. for 1 second with a thermal inclination tester. The density | concentration of the erasure | elimination part and the background part was measured similarly. Next, the erase remaining density was calculated from the following equation.

Erasing remaining density = (Density of image area after erasing)-(Skin density)
The above results are shown in the table below.

２）耐熱バリアー性試験
２００℃に加熱したガラスプレートに記録媒体を１５秒間押し付け、その時のガラスプレートへの汚れ付着の程度を評価し、耐熱バリアー性を評価した。

2) Heat-resistant barrier property test The recording medium was pressed against a glass plate heated to 200 ° C. for 15 seconds, and the degree of dirt adhesion to the glass plate at that time was evaluated to evaluate the heat-resistant barrier property.

  In Comparative Examples 1 and 2 in which no organic clay was added, a large amount of cloudy stains derived from the recording layer adhered to the glass plate. On the other hand, in Examples 1 and 2 to which organic clay was added, no dirt adhered to the glass plate.

3) Repeated durability test The recording medium was colored with the thermal printing apparatus manufactured by Okura Electric Co., Ltd. used in Test 1), and erased in a heat roller heated to 140 ° C. under the condition of a linear speed of 30 mm / second. This printing / erasing was repeated 100 times, and the state of the thermal head after 100 times was observed with an optical microscope.

  As a result, in Comparative Examples 1 and 2 in which no organic clay was added, debris adhered to the heating element of the thermal head and an abnormality occurred in the printed image, whereas the organic clay was added. No. 2 showed no dirt on the thermal head, and the printed image was in good condition.

Example 3
(Dispersion of organic clay)
The following composition was pulverized and dispersed to a particle size of 0.5 to 0.8 μm with a paint shaker to obtain dispersion 2.

Thermally crosslinkable silicone resin GS-1015 (Toagosei Co., Ltd. solid concentration 45%) 8 parts Organized clay (Nanocor, nanomer I.30T) 1 part
* I.30T: Organized montmorillonite, Organizing agent: Octadecyl ammonium ion N, N-dimethylformamide 15 parts
(Intercalation of resin to organic clay)
In dispersion 2, 100 parts of N, N-dimethylformamide was added and refluxed for 3 hours. After refluxing, N, N-dimethylformamide was dried under reduced pressure to obtain a solid composition 2 in which the resin was intercalated between the clay layers.

(Creation of protective layer)
15 parts of methyl ethyl ketone was added to the solid composition 2 and well dispersed with an ultrasonic disperser. To the obtained dispersion, 2 parts of Coronate HX (Adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. was added and stirred well to prepare a protective layer coating solution. The protective layer coating solution having the above composition is coated on the previously prepared recording layer using a wire bar, dried at 80 ° C., and then heated at 60 ° C. for 24 hours to protect the film with a thickness of about 3.0 μm. A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the layer was provided.

Example 4
A recording medium was produced in the same manner as in Example 3 except that the following liquid was used as the organic clay dispersion used in Example 3.
Thermally crosslinkable silicone resin GS-1015 (solid content concentration 45% manufactured by Toagosei Co., Ltd.) 3 parts acrylic polyol resin LR-503 (solid content concentration 50% manufactured by Mitsubishi Rayon Co., Ltd.) 5 parts Organic clay (Nanocor, nanomer I .30T) 1 copy
N, N-dimethylformamide 15 parts [interlayer distance by X-ray diffraction measurement]
The interlayer distance of the organized clay powder (I.30T) was 22 mm by X-ray diffraction.

  On the other hand, in the recording media prepared in Examples 3 and 4, the X-ray diffraction measurement method revealed that the peak of 22 測定 measured with the organic clay powder (I.30T) disappeared, and the diffraction intensity moved to the small corner, The maximum is no longer recognized. This means that the clay interlayer distance has increased significantly.

Comparative Example 3
A recording medium was produced in the same manner as in Example 3 except that the organic clay used in Example 3 was not used.

Comparative Example 4
A recording medium was produced in the same manner as in Example 2 except that the organic clay used in Example 4 was not used.
(Evaluation item)
1) Color-decoloring characteristics The recording media produced in Example 3, Example 4, Comparative Example 3 and Comparative Example 4 were printed with a thermal printing device manufactured by Okura Electric Co., Ltd. at a voltage of 13.3 V and a pulse width of 1.2 msec. did. The density of the printed part was measured with a Macbeth densitometer RD914. Next, this printed sample was erased by heating at 140 ° C. for 1 second with a thermal inclination tester. The density | concentration of the erased part and the background part was measured similarly. Next, the erase remaining density was calculated from the following equation.

Erasing remaining density = (Density of image area after erasing)-(Skin density)
The above results are shown in the table below.

２）耐熱バリアー性試験
２００℃に加熱したガラスプレートに記録媒体を１５秒間押し付け、その時のガラスプレートへの汚れ付着の程度を評価し、耐熱バリアー性を評価した。

2) Heat-resistant barrier property test The recording medium was pressed against a glass plate heated to 200 ° C. for 15 seconds, and the degree of dirt adhesion to the glass plate at that time was evaluated to evaluate the heat-resistant barrier property.

  In Comparative Examples 3 and 4 in which no organic clay was added, a large amount of cloudy stains derived from the recording layer adhered to the glass plate. On the other hand, in Examples 3 and 4 to which organic clay was added, no dirt adhered to the glass plate.

3) Repeated durability test The recording medium was colored with the thermal printing apparatus manufactured by Okura Electric Co., Ltd. used in Test 1), and erased in a heat roller heated to 140 ° C. under the condition of a linear speed of 30 mm / second. This printing / erasing was repeated 100 times, and the state of the thermal head after 100 times was observed with an optical microscope.

  As a result, in Comparative Examples 3 and 4 in which no organic clay was added, debris adhered to the heating element of the thermal head and an abnormality occurred in the printed image, whereas Example 3 in which organic clay was added. , 4, there was no dirt on the thermal head and the printed image was in good condition. Furthermore, there was no scratch on the surface of the recording medium.

Example 5
(Dispersion of organic clay)
The following composition was pulverized and dispersed to a particle size of 0.5 to 0.8 μm with a paint shaker to obtain dispersion 3.

UV-absorbing polymer UV-G300 (Nippon Shokubai Co., Ltd., solid content concentration 43%) 8 parts Organized clay (Nanocor, nanomer I.30T) 1 part * I.30T: Organized montmorillonite, Organizing agent: Octadecyl ammonium Ion N, N-dimethylformamide 15 parts
(Intercalation of resin to organic clay)
To dispersion 3, 100 parts of N, N-dimethylformamide was added and refluxed for 3 hours. After refluxing, N, N-dimethylformamide was dried under reduced pressure to obtain a solid composition 3 in which the resin was intercalated between the clay layers.
(Creation of protective layer)
15 parts of methyl ethyl ketone was added to the solid composition 3 and well dispersed with an ultrasonic disperser. To the obtained dispersion, 2 parts of Coronate HX (Adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. was added and stirred well to prepare a protective layer coating solution. The protective layer coating solution having the above composition was applied onto the previously prepared recording layer using a wire bar, dried at 80 ° C., and then heated at 60 ° C. for 24 hours to form a protective layer having a thickness of about 3 μm. A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that it was provided.

Example 6
In place of UV-G300 used in Example 5, a recording medium was prepared in the same manner as in Example 5 except that ULS-115 (solid content concentration 50%) manufactured by Yushi Co., Ltd., which is also an ultraviolet absorbing polymer, was used. Produced.
[Layer distance by X-ray diffraction measurement]
The interlayer distance of the organized clay powder (I.30T) was 22 mm by X-ray diffraction.

  On the other hand, in the recording media prepared in Examples 1 and 2, by the X-ray diffraction measurement method, the peak of 22 Å measured by the organic clay powder (I.30T) disappeared, and the diffraction intensity moved to the small corner, The maximum is no longer recognized. This means that the clay interlayer distance has increased significantly.

Comparative Example 5
A recording medium was produced in the same manner as in Example 5 except that the organic clay used in Example 5 was not used.

Comparative Example 6
A recording medium was produced in the same manner as in Example 6 except that the organic clay used in Example 6 was not used.

Comparative Example 7
Example 5 is the same as Example 5 except that instead of UV-G300 used in Example 5, acrylic polyol resin LR503 (solid content concentration 50%) manufactured by Mitsubishi Rayon Co., Ltd., which does not have ultraviolet absorbing ability, is used, and no organic clay is used. A recording medium was produced in the same manner.
(Evaluation item)
1) Color-decoloring characteristics The recording media produced in Examples 5, 6, 6, 5, and 7 were subjected to a thermal printing apparatus manufactured by Okura Electric Co., Ltd. with a voltage of 13.3 V and a pulse width of 1. Printing was performed in 2 milliseconds. The density of the printed part was measured with a Macbeth densitometer RD914. Next, this printed sample was erased by heating at 140 ° C. for 1 second with a thermal inclination tester. The density | concentration of the erased part and the background part was measured similarly. Next, the erase remaining density was calculated from the following equation.

Erasing remaining density = (Density of image area after erasing)-(Skin density)
The above results are shown in the table below.

２）耐熱バリアー性試験
２００℃に加熱したガラスプレートに記録媒体を１５秒間押し付け、その時のガラスプレートへの汚れ付着の程度を評価し、耐熱バリアー性を評価した。

2) Heat-resistant barrier property test The recording medium was pressed against a glass plate heated to 200 ° C. for 15 seconds, and the degree of dirt adhesion to the glass plate at that time was evaluated to evaluate the heat-resistant barrier property.

  In Comparative Example 5, Comparative Example 6 and Comparative Example 7 to which no organic clay was added, a large amount of cloudy stains derived from the recording layer adhered to the glass plate. On the other hand, in Examples 5 and 6 to which the organic clay was added, no dirt adhered to the glass plate.

3) Repeated durability test The recording medium was colored with the thermal printing apparatus manufactured by Okura Electric Co., Ltd. used in Test 1), and erased in a heat roller heated to 140 ° C. under the condition of a linear speed of 30 mm / second. This printing / erasing was repeated 100 times, and the state of the thermal head after 100 times was observed with an optical microscope.

  As a result, in Comparative Example 5, Comparative Example 6 and Comparative Example 7 in which no organic clay was added, debris adhered to the heating element of the thermal head and an abnormality occurred in the printed image. In Examples 5 and 6 to which no was added, there was no contamination on the thermal head, and the printed image was also in a good state.

4) Light resistance test A recording medium colored in the same manner as in Test 1) was tested for 100 hours under irradiation conditions of a fluorescent lamp of 5000 lux. As a result, the recording media of Example 5, Example 6, Comparative Example 5 and Comparative Example 6 showed no discoloration in both the background portion and the image portion, whereas the recording medium of Comparative Example 7 showed the background portion and the image portion. In both cases, discoloration was observed, and in particular the discoloration was clearly seen in light brown. (Creation of protective layer)
Example 7
(Creation of organic clay dispersion)
The following composition was pulverized and dispersed to a particle size of 0.5 to 0.8 μm with a paint shaker to obtain dispersion 4.

UV-absorbing polymer UV-G300 (manufactured by Nippon Shokubai Co., Ltd., solid content concentration 43%) 4 parts Acrylic polyol resin LR-503 (manufactured by Mitsubishi Rayon Co., Ltd., solid content concentration 50%) 4 parts Organic clay (manufactured by Nanocor, nanomer I. 30T) 1 part * I.30T: Organized montmorillonite, Organizing agent: Octadecyl ammonium ion N, N-dimethylformamide 15 parts
(Intercalation of resin to organic clay)
To dispersion 4, 100 parts of N, N-dimethylformamide was added and refluxed for 3 hours. After refluxing, N, N-dimethylformamide was dried under reduced pressure to obtain a solid composition 4 in which the resin was intercalated between the clay layers.

(Preparation of protective layer) 15 parts of methyl ethyl ketone was added to the solid composition 4 and well dispersed with an ultrasonic disperser. Coronate HX (adduct type hexamethylene diisocyanate 75% ethyl acetate solution manufactured by Nippon Polyurethane Co., Ltd.) was obtained. 2 parts were added and stirred well to prepare a protective layer coating solution, which was coated on the previously prepared recording layer using a wire bar and dried at 80 ° C. A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that a protective layer having a thickness of about 3.0 μm was provided by heating at 60 ° C. for 24 hours.

Example 8
Instead of UV-G300 used in Example 7, a recording medium was prepared in the same manner as in Example 1 except that ULS-115 (solid content concentration: 50%) manufactured by Yushi Co., Ltd. was also used. Produced.
[Layer distance by X-ray diffraction measurement]
The interlayer distance of the organized clay powder (I.30T) was 22 mm by X-ray diffraction.

  On the other hand, in the recording media prepared in Examples 7 and 8, the peak of 22 さ れ る measured by the organic clay powder (I.30T) disappeared by the X-ray diffraction measurement method, and the diffraction intensity moved to the small corner part. The maximum is no longer recognized. This means that the clay interlayer distance has increased significantly.

Comparative Example 8
A recording medium was produced in the same manner as in Example 1 except that the organic clay used in Example 7 was not used.

Comparative Example 9
A recording medium was produced in the same manner as in Example 2 except that the organic clay used in Example 8 was not used.

Comparative Example 10
Recording was carried out in the same manner as in Example 1 except that 8 parts of acrylic polyol resin LR503 (solid content concentration 50%) manufactured by Mitsubishi Rayon Co., Ltd. and no organic clay were used without using UV-G300 used in Example 7. A medium was made.
(Evaluation item)
1) Color Decoloration Characteristics The recording media produced in Examples 7, 8, 8, 9, and 10 were subjected to a thermal printing apparatus manufactured by Okura Electric Co., Ltd. with a voltage of 13.3 V and a pulse width of 1. Printing was performed in 2 milliseconds. The density of the printed part was measured with a Macbeth densitometer RD914. Next, this printed sample was erased by heating at 140 ° C. for 1 second with a thermal inclination tester. The density | concentration of the erased part and the background part was measured similarly. Next, the erase remaining density was calculated from the following equation.

Erasing remaining density = (Density of image area after erasing)-(Skin density)
The above results are shown in the table below.

２）耐熱バリアー性試験
２００℃に加熱したガラスプレートに記録媒体を１５秒間押し付け、その時のガラスプレートへの汚れ付着の程度を評価し、耐熱バリアー性を評価した。

2) Heat-resistant barrier property test The recording medium was pressed against a glass plate heated to 200 ° C. for 15 seconds, and the degree of dirt adhesion to the glass plate at that time was evaluated to evaluate the heat-resistant barrier property.

  In Comparative Examples 8 to 10 in which no mechanized clay was added, a large amount of white turbid stain derived from the recording layer adhered to the glass plate. On the other hand, in Examples 7 and 8 to which organic clay was added, no dirt adhered to the glass plate.

3) Repeated durability test The recording medium was colored with the thermal printing apparatus manufactured by Okura Electric Co., Ltd. used in Test 1), and erased in a heat roller heated to 140 ° C. under the condition of a linear speed of 30 mm / second. This printing / erasing was repeated 100 times, and the state of the thermal head after 100 times was observed with an optical microscope.

  As a result, in Comparative Examples 1 to 3 in which no organic clay was added, debris adhered on the heating element of the thermal head and an abnormality occurred in the printed image, whereas Example 7 in which organic clay was added. , 8, there was no dirt on the thermal head and the printed image was in good condition.

4) Light resistance test A recording medium colored in the same manner as in Test 1) was tested for 100 hours under irradiation conditions of a fluorescent lamp of 5000 lux. As a result, the recording media of Examples 7, 8 and Comparative Examples 8 and 9 showed no discoloration in both the background portion and the image portion, whereas the recording medium of Comparative Example 10 showed discoloration in both the background portion and the image portion. And the discoloration was clearly seen in the light brown color.

It is a figure which shows the structure of the organized clay used for this invention. It is a schematic diagram of a cross section of a reversible recording medium of the present invention. It is a figure which shows the X-ray-diffraction pattern of a powdery organized clay (organized montmorillonite). It is a figure which shows the X-ray-diffraction pattern of the state which resin intercalated between the layers of the organized clay. It is a figure which shows the X-ray-diffraction pattern of the state which advanced the intercalation rather than the state shown in FIG. It is a figure which shows the color development and decoloring characteristic of the reversible thermosensitive coloring composition of this invention.

Explanation of symbols

A Decoloring state B Melting color state C Solid color state D Decoloring process E Decoloring state

Claims (15)

  A recording layer containing an electron-donating color-forming compound and an electron-accepting compound and capable of forming a relatively colored state and a decolored state due to a difference in heating temperature and / or cooling rate after heating is provided on a support. A reversible thermosensitive recording medium provided with a protective layer on the recording layer, wherein the protective layer contains at least an organoclay and calcium-coated silica.   A recording layer containing an electron-donating color-forming compound and an electron-accepting compound and capable of forming a relatively colored state and a decolored state due to a difference in heating temperature and / or cooling rate after heating is provided on a support. A reversible thermosensitive recording medium comprising a protective layer on the recording layer, wherein the protective layer contains at least an organic clay and a thermally crosslinkable silicone resin. Medium.   A recording layer containing an electron-donating color-forming compound and an electron-accepting compound and capable of forming a relatively colored state and a decolored state due to a difference in heating temperature and / or cooling rate after heating is provided on a support. A reversible thermosensitive recording medium provided with a protective layer on the recording layer, wherein the protective layer contains at least an organic clay and an ultraviolet absorbing polymer.   The protective layer contains at least one resin selected from the group of acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, and polyvinyl butyral resin, according to any one of claims 1 to 3. Reversible thermosensitive recording medium.   The reversible thermosensitive recording medium according to any one of claims 1 to 4, wherein the clay in the organized clay is a layered clay mineral.   6. The reversible thermosensitive recording medium according to claim 5, wherein the layered clay mineral is one or more substances selected from the group consisting of montmorillonite, hectorite, saponite, beidellite, and mica.   The organically modified clay is obtained by organically treating clay with an organic agent, and the organic agent is an organic ammonium ion having 6 or more carbon atoms. A reversible thermosensitive recording medium according to 1.   The reversible thermosensitive recording medium according to any one of claims 1 to 7, wherein the organic clay used in the protective layer intercalates a resin.   The reversible thermosensitive recording medium according to any one of claims 1 to 8, wherein the resin used in the protective layer is a thermosetting resin in a crosslinked state.   The reversible thermosensitive material according to any one of claims 1 to 9, wherein the organic clay is pulverized and the resin is intercalated between the organic clay layers by a reflux treatment using an organic solvent. recoding media.   The reversible thermosensitive recording medium, wherein the organic solvent used for the reflux treatment according to claim 10 is N, N-dimethylformamide (DMF).   The reversible feeling characterized by having either an adhesive layer or an adhesive layer on the surface opposite to the image forming surface of the reversible thermosensitive recording medium according to any one of claims 1 to 11. Thermal record label.   A reversible thermosensitive recording member comprising an information storage unit and a reversible display unit, wherein the reversible display unit includes the reversible thermosensitive recording medium according to any one of claims 1 to 11.   Image forming means for forming an image on the reversible thermosensitive recording medium by heating the reversible thermosensitive recording medium, and image erasing for erasing the image formed on the reversible thermosensitive recording medium by heating the reversible thermosensitive recording medium An image processing apparatus comprising the reversible thermosensitive recording medium according to any one of claims 1 to 11, wherein the reversible thermosensitive recording medium comprises at least one of the following means.   At least forming an image on the reversible thermosensitive recording medium by heating the reversible thermosensitive recording medium, and erasing the image formed on the reversible thermosensitive recording medium by heating the reversible thermosensitive recording medium. An image processing method comprising the reversible thermosensitive recording medium according to claim 1, wherein the reversible thermosensitive recording medium is any one of claims 1 to 11.

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