JP4617228B2 - Reversible thermosensitive recording medium - Google Patents

Description

  The present invention relates to a reversible thermosensitive recording medium capable of displaying or erasing information such as characters and images by heat and light, and an information recording / display medium using the same.

  In general, a card-like reversible thermosensitive recording medium having a reversible thermosensitive recording layer is known as a display means of an information recording apparatus incorporating a magnetic recording means or an IC chip (Patent Documents 1, 2, and 3).

  Such a card-like reversible thermosensitive recording medium is also called a magnetic card or an IC card. In order to form a reversible thermosensitive recording layer, a solvent is added to the material to form a coating liquid, which is used as a base material. Apply and dry. At that time, the solvent remaining in the formed reversible thermosensitive recording layer may damage the substrate.

  As shown in FIG. 3, in order to prevent damage to the base material layer 12 due to such a cause, the base material layer 12 and the reversible thermosensitive recording layer 13 are prevented from touching the base material layer 12 with the solvent. It is known that a method of providing the barrier layer 14 with a resin excellent in solvent resistance is employed (Patent Document 4).

JP-A-63-41186 Japanese Patent Laid-Open No. 2-188293 JP-A-5-124360 JP 2000-148794 A (see claim 6)

  However, in the above-described conventional reversible thermosensitive recording medium, there are cases where problems such as deterioration or discoloration of the base material layer occur when used in an environment with a lot of ultraviolet rays.

  Further, in the manufacturing process of the reversible thermosensitive recording medium, when an ultraviolet curable resin is employed as a barrier layer having excellent solvent resistance, ultraviolet rays are irradiated as a curing treatment of the barrier layer. However, the ultraviolet rays deteriorate the base material layer or cause discoloration (so-called “color burnt”), which adversely affects the visibility of the product.

  In addition, the layer made of an ultraviolet curable resin is not only used as a barrier layer that does not allow solvent permeation, but may be provided as a protective layer on the outside (surface) of the reversible thermosensitive recording layer. Similarly, the ultraviolet rays deteriorated the base material layer and changed its color during processing.

  Such a problem is particularly likely to occur when the base layer employs an amorphous polyester resin that is easily decomposed by ultraviolet energy as a resin for forming the base layer.

  Incidentally, “color burn” occurs when the base polyester resin is decomposed by the energy of ultraviolet rays. Such “color burn” is a sheet-like reversible thermosensitive recording medium used as a card-like information recording medium as a final product. It also remains and deteriorates its appearance. For example, the white card-like information recording medium is finished in a yellowed state, which has an unfavorable influence on the design (design) and also reduces the appearance and image of the product.

  Therefore, an object of the present invention is to solve the above-mentioned problems, and when the reversible thermosensitive recording medium is exposed to ultraviolet rays in the production process or use environment, an undesirable influence due to molecular decomposition by ultraviolet rays is exerted on the base material layer. In other words, the reversible thermosensitive recording medium is excellent in visibility without discoloration due to UV resistance.

  In addition, another object of the present invention is that, in the reversible thermosensitive recording medium, when an ultraviolet curable resin is employed as a barrier layer or protective layer having excellent solvent resistance, the ultraviolet ray irradiated as the curing treatment is used. It is to prevent discoloration and deterioration of the base material layer.

  In particular, in the reversible thermosensitive recording medium of the present invention, when a base material layer containing an amorphous polyester resin is employed, not only when an ultraviolet curable resin is employed for a barrier layer or a protective layer, Even when an ultraviolet curable resin is not used for the layer or the protective layer, the reversible thermosensitive recording medium is excellent in ultraviolet resistance so that the influence of ultraviolet rays does not reach the substrate layer.

In order to solve the problems noted above, in the present invention, the display on the surface side of the base layer, and one or more layers of the UV curable resin layer, a visible image by chromogenic or transparency change due to temperature change And an erasable reversible thermosensitive recording layer integrally formed, and an ultraviolet opaque layer is provided between the substrate layer and the ultraviolet curable resin layer closest to the substrate layer in the laminate. This is a reversible thermosensitive recording medium.

  In the reversible thermosensitive recording medium of the present invention configured as described above, an ultraviolet opaque layer is provided between the base material layer and the UV curable resin layer closest to the base material layer. When the ultraviolet curable resin layer is irradiated with ultraviolet rays for the curing treatment, the ultraviolet rays are absorbed or reflected by the ultraviolet opaque layer and do not pass through this layer and do not reach the base material layer. Therefore, the influence of ultraviolet rays exposed in the production process does not reach the base material layer, and the reversible thermosensitive recording medium has excellent ultraviolet resistance and excellent visibility without discoloration.

  Further, when the above-described reversible thermosensitive recording medium is provided with an ultraviolet opaque layer made of a polymer type ultraviolet absorber as the ultraviolet opaque layer, the ultraviolet absorber is prevented from bleeding, there is no delamination, and the strength increases with time. Such a configuration is preferable in order to obtain a reversible thermosensitive recording medium having no deterioration, and to make a reversible thermosensitive recording medium having a layer thickness as thin as possible by efficiently absorbing ultraviolet rays.

  As the ultraviolet opaque layer made of a polymer type ultraviolet absorber having such a preferable action, the ultraviolet opaque layer is a polymer copolymer of a monomer having an ultraviolet absorbing molecular structure and a polymerizable monomer, or ultraviolet rays. An ultraviolet opaque layer made of a polyaddition product or a polycondensation product of a monomer having an absorbing molecular structure is preferred.

  In the present invention, the reversible thermosensitive recording medium is provided with an ultraviolet opaque layer between the base material layer and the UV curable resin layer closest to the base material layer. Even when a base material layer containing a resin at a ratio of 100% by weight or less is adopted, not only when using an ultraviolet curable resin as a barrier layer or a protective layer, but also when an ultraviolet curable resin is not used, The reversible thermosensitive recording medium is excellent in ultraviolet resistance by preventing the influence of ultraviolet rays in the usage environment from affecting the base material layer.

  That is, a reversible thermosensitive recording layer capable of displaying and erasing a visible image on the surface side of a base material layer containing an amorphous polyester resin at a ratio of 100% by weight or less by a change in color developability or transparency accompanying a temperature change. And a reversible thermosensitive recording medium in which an ultraviolet-opaque layer is provided between the reversible thermosensitive recording layer and the base material layer in the laminate. Since the influence does not reach the base material layer, the reversible thermosensitive recording medium is excellent in ultraviolet resistance.

  By using the reversible thermosensitive recording medium configured as described above and forming an information recording display medium in which a non-contact IC chip and an antenna are overlapped and integrated thereon, ultraviolet rays exposed in the manufacturing process or the use environment Will not affect the base layer of the reversible thermosensitive recording medium, and the information recording and display medium is excellent in UV resistance and excellent in visibility without discoloration.

  In the reversible thermosensitive recording medium of the present invention, an ultraviolet opaque layer is provided between the reversible thermosensitive recording layer and the base material layer. There are advantages that the reversible thermosensitive recording medium has no adverse effects of substrate molecular decomposition, excellent ultraviolet resistance, no discoloration, and excellent visibility. In particular, even when a base material layer containing an amorphous polyester resin is employed, there is an advantage that the influence of ultraviolet rays does not reach the base material layer, and a reversible thermosensitive recording medium having excellent ultraviolet resistance is obtained.

  Further, in the reversible thermosensitive recording medium of the present invention in which an ultraviolet opaque layer is provided between the substrate layer and the ultraviolet curable resin layer closest to the substrate layer, an ultraviolet curable resin is used as a barrier layer or a protective layer. When used, the substrate layer is not particularly affected by ultraviolet rays exposed in the manufacturing process, and has the advantage of being a reversible thermosensitive recording medium with excellent UV resistance and excellent visibility without discoloration. is there.

  Further, by using a reversible thermosensitive recording medium having such advantages and forming an information recording display medium in which a non-contact IC chip and an antenna are overlapped and integrated thereon, it is exposed in the manufacturing process or use environment. An information recording and display medium that is not affected by ultraviolet rays, has excellent ultraviolet resistance, and has excellent visibility without discoloration.

Embodiments of the present invention and manufacturing methods thereof will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the reversible thermosensitive recording medium according to the first embodiment is provided with two ultraviolet curable resin layers including a barrier layer 2 and a protective layer 3 on the surface side of a base material layer 1 and a temperature. A reversible thermosensitive recording medium A comprising a card-like laminate integrally provided with a reversible thermosensitive recording layer 4 capable of displaying and erasing a visible image by a change in color development or transparency accompanying the change. An ultraviolet opaque layer 5 is provided between the base material layer 1 and the barrier layer 2 which is an ultraviolet curable resin layer closest to the base material layer 1. This embodiment can also be said to be a reversible thermosensitive recording medium A in which an ultraviolet opaque layer 5 is provided between the reversible thermosensitive recording layer 4 and the base material layer 1 in the laminate.

  As shown in FIG. 2, the information recording and display medium B of the second embodiment uses two core sheets 6 and 7 as a base material layer, and similarly to the above, the ultraviolet opaque layer 5 on one side of the one sheet. A barrier layer 2, a reversible thermosensitive recording layer 4, and a protective layer 3, which are sequentially stacked, and a non-contact IC chip 9 integrated with an antenna coil 8 between the other core sheet 7. Are laminated so as to sandwich the inlet sheet 10 embedded therein, and further, an oversheet 11 is stacked, and these are integrated by heating and pressing. When this is punched into a card shape, it becomes an information recording / displaying card, and it can be appropriately manufactured in a required shape as a tag or other information recording / displaying medium.

  The antenna coil 8 may be formed by printing or etching a sheet-like material, or an IC chip (not shown) wired with the antenna coil may be used.

  The information recorded on the card-like information recording and display medium B with the non-contact IC chip of the present invention can read stored information or write new information by a conventionally known method.

  In the first embodiment and the second embodiment having the above-described configuration, the adhesiveness or heat-sealing property is taken into consideration so that the core sheets 6 and 7 which are the materials constituting the base material layer can be easily integrated as a laminate. , Preferably formed of a resin composition containing an amorphous polyester resin in a proportion of 100% by weight or less. More specifically, in addition to those containing one kind of amorphous polyester resin composition, It is preferably formed using a polymer alloy resin composition of amorphous polyester resin or a polymer alloy resin composition of amorphous polyester resin and polycarbonate resin.

  Here, the amorphous polyester resin is obtained from a dehydrated condensate of an aromatic dicarboxylic acid component and a diol component, and is practically used in the manufacturing process of a card or the like such as press fusion. Even if it is heat-processed, it does not cause actual harm such as white turbidity or poor fusion due to crystallization. For example, in addition to low crystallinity on the molecular structure, PBT (polybutylene terephthalate) before crystallization treatment, etc. It is a concept that also includes

  Preferable representative examples of the aromatic dicarboxylic acid component used as the raw material for the amorphous polyester resin include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and the like, in which a part of terephthalic acid is substituted with another dicarboxylic acid. But you can.

  Other dicarboxylic acid components mentioned here include oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, neopentylic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, p-oxybenzoic acid and the like. Can be mentioned. In addition, these other dicarboxylic acid components may be one kind or a mixture of two or more kinds, and the amount of other dicarboxylic acid to be substituted can be appropriately selected.

  In addition, preferable examples of the diol component used as a raw material for the amorphous polyester resin include ethylene glycol, diethylene glycol, triethylene glycol, cyclohexane dimethanol, and the like. It may be substituted with a component.

  Other diol components mentioned here include propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, neopentyl glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol, glycerin, pentaerythritol, trimethylol. And methoxy polyalkylene glycol. These other diol components may be one kind or a mixture of two or more kinds, and the amount of the other diol to be substituted can be appropriately selected.

  Among the amorphous polyester resins used in the present invention, polyethylene terephthalate formed by condensation polymerization of terephthalic acid and ethylene glycol is preferable from the viewpoint of cost, and other than terephthalic acid. A copolyester containing a dicarboxylic acid component and / or a diol component other than ethylene glycol is also preferable.

  As the copolyester, 60 mol% or more of the dicarboxylic acid component is terephthalic acid, the dicarboxylic acid component in which the remaining dicarboxylic acid component is replaced with another dicarboxylic acid component, and 60 mol% or more of the diol component is ethylene glycol. And a copolyester obtained by condensation polymerization of a diol component in which the remaining diol component is substituted with another diol component.

  Further, as the aromatic polyester resin used in the present invention, a mixture of polyethylene terephthalate and the above-mentioned copolymerized polyester may be employed.

  When such a mixture is employed, it is produced by replacing about 30 mol% of ethylene glycol in polyethylene terephthalate with 1,4-cyclohexanedimethanol, particularly as a copolyester, and is substantially amorphous. Aromatic polyester resin is preferably used. For example, a product having a trade name of “PETG” manufactured by Eastman Chemical Co., Ltd. can be used.

  The polycarbonate resin in the polymer alloy resin composition of the amorphous polyester resin and the polycarbonate resin can be widely used as long as it is a polymer having a carbonate bond (—O—CO—O—) in the main chain.

  Polycarbonate resins include those produced from bisphenol A synthesized from phenol and acetone by interfacial polymerization, transesterification, pyridine, etc., bisphenol A and dicarboxylic acid derivatives (eg, tele (iso) phthalic acid dichloride, etc. ) And a polyester carbonate obtained by copolymerization with bisphenol A derivatives (for example, tetramethylbisphenol A etc.).

  In addition, the substrate layer and oversheet of the embodiment can employ the above-described substrate layer as a single layer, and when the required function is achieved without a single layer, for example, an amorphous polyester resin film and You may employ | adopt the laminated body of two or more layers with another kind of different film.

  Furthermore, you may make the base material layer contain additives, such as a coloring agent, a lubricant, a filler, and an impact modifier, as needed. In particular, a plate-like filler such as talc or a polymer that lowers the tensile strength such as polybutylene terephthalate may be blended.

  The thickness of the base material layer is not particularly limited as long as it corresponds to the thickness of the information recording display medium such as a card shape to be created. In the case of a general card, it is preferably 50 μm to 250 μm, and is 75 μm to 200 μm. It is more preferable.

  The UV-impermeable layer in the present invention can be applied to the base material layer (support) by dissolving or dispersing a well-known low-molecular-weight UV absorber in a polymer resin matrix or appropriately diluted. A polymer type ultraviolet absorber can be employed.

  Examples of the low molecular weight ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber. The low molecular weight organic ultraviolet absorber is an organic compound having an ultraviolet absorbing ability in the molecular structure. Specifically, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′- Benzophenones such as dihydroxy-4-methoxybenzophenone, 2- (2′-hydroxy-5-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole Benzotriazole-based, hindered amine-based, triazine-based and benzoate-based compounds. These ultraviolet absorbers may be used alone or in combination of two or more.

  Examples of inorganic ultraviolet absorbers include pigments having absorption in the ultraviolet region, such as titanium oxide, zinc oxide, tin oxide, silica, and alumina. Among these, those having no absorption in the visible light region are more preferable. These ultraviolet absorbers may be used alone or in combination of two or more.

  In addition, as the polymer resin serving as a resin base material for forming the ultraviolet ray opaque layer, a transparent resin having good film forming property is preferable, and a resin having excellent heat resistance and having no decomposability and yellowing is preferable. For example, a polyester resin, a polyurethane resin, an acrylic resin, etc. are mentioned.

  The content of the ultraviolet absorber in the polymer resin is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the polymer resin. If the amount is too small, it is difficult to obtain sufficient weather resistance. If the amount is too large, bleeding occurs and the material becomes brittle and affects adhesiveness, durability, and the like.

  Next, as the polymer type ultraviolet absorber, a polymer having a structure exhibiting an ultraviolet absorbing function in a polymer structure can be used. That is, it is an ultraviolet absorbent comprising a polymer copolymer of a monomer having a UV-absorbing molecular structure and a polymerizable monomer, or a polyaddition or polycondensate of a monomer having a UV-absorbing molecular structure.

  Specifically, a monomer having an ultraviolet absorbing molecular structure such as benzotriazole or benzophenone having a reactive unsaturated ethylene group in the molecular structure was copolymerized with a polymerizable monomer such as methyl methacrylate, styrene or ethylene. A polymer copolymer can be applied, and a monomer having an ultraviolet absorbing molecular structure such as benzotriazole or benzophenone having a hydroxyethyl group in the molecular structure is added to a monomer such as isocyanate, carboxylic acid or carboxylic acid ester, Mention may be made of condensed polymer copolymers.

  Specific examples of the monomer having the ultraviolet absorption molecular structure described above include 2-hydroxy-4-methacryloxybenzophenone, 2-hydroxy-4-acryloxybenzophenone, 2-hydroxy-4- (2-methacryloxy) ethoxybenzophenone, 2 Benzophenone compounds such as -hydroxy-4- (2-acryloxy) ethoxybenzophenone, 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5) '-Acryloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methacryloxypropylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-acryloxypropylphenyl) ) -2H-benzotriazole What benzotriazole compounds.

  These monomers may be a single component or a plurality of components, and may be copolymerized with a reactive monomer having other functionality such as reactive HALS (hindered amine light stabilizer).

  Moreover, these high molecular weight ultraviolet absorbers may be used alone or in combination of two or more, or may be used in combination with a low molecular weight ultraviolet absorber.

  Such high-molecular-weight ultraviolet absorbers are characterized by better thermal stability and ultraviolet-absorbing performance stability than low-molecular-weight ultraviolet absorbers. This is an excellent effect that a reversible thermosensitive recording medium free from delamination and change with time can be obtained. In addition, since the high-molecular-weight ultraviolet absorber has a higher ultraviolet-absorbing function than the low-molecular-weight type, the thickness of the reversible thermosensitive recording medium having a laminate structure can be reduced.

  The proportion of the structure exhibiting an ultraviolet absorbing function in the polymer structure is preferably about 5 to 60% by weight. If the amount is less than the above range, even if the layer is formed thick, there is not sufficient UV resistance, and if it is added in a large amount exceeding the above range, the film forming property and strength for forming the UV opaque layer are insufficient. To do.

  The thickness of the ultraviolet opaque layer is preferably about 1 to 10 μm, more preferably 1 to 5 μm. This is because if the thickness is less than the predetermined thickness, the effect of ultraviolet absorbing ability is not sufficiently exhibited, and transparency and adhesiveness that are thicker than the predetermined thickness are deteriorated.

  Although it is conceivable to add an ultraviolet absorber to the substrate layer itself, the amount of the ultraviolet absorber to be added must be increased, so that bleeding tends to occur or the transparency of the substrate layer is increased. Since it may damage, it is not preferable. Furthermore, the ultraviolet absorber is decomposed or sublimated due to a change in heat or pressure during sheet production, which is not preferable because sufficient effects may not be exhibited.

  Examples of the ultraviolet curable resin for forming the ultraviolet curable resin layer in the present invention include urethane acrylate and epoxy acrylate. Further, the elongation percentage can be adjusted by adding an oligomer component or a monomer component to polyurethane acrylate, polyester acrylate, epoxy acrylate or the like.

  Examples of the oligomer component include urethane acrylate compounds, urethane (meth) acrylate compounds, epoxy acrylate compounds, and epoxy (meth) acrylate compounds.

In order to reduce the curing shrinkage of the ultraviolet curable resin and improve the strength after curing, an amide group may be introduced into the urethane acrylate molecule, that is, an amino-modified urethane acrylate may be blended.
The thickness of such an ultraviolet curable resin layer is preferably 1 to 10 μm in order to ensure the impermeability (barrier) property of the solvent, and a more preferable layer thickness is 1 to 4 μm.

Next, the reversible thermosensitive recording layer will be described.
The reversible thermosensitive recording layer is made of a material that can display and erase a visible image by reversibly changing the transparency or color development depending on the temperature. The recording material is composed of a resin base material and a recording material.

  As the kind of the resin base material, a transparent synthetic resin having a good film forming property is preferable. For example, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acetic acid. Vinyl-acrylic acid copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, other vinyl acetate compounds, vinyl chloride copolymers, polyvinylidene chloride, vinylidene chloride copolymer, polyester resin, polyurethane resin, acrylic Examples thereof include transparent amorphous resins such as resins, polystyrene resins, ABS resins, and AS resins, and these may be used alone or in admixture of two or more. Furthermore, a crosslinkable resin can also be used.

  As a recording material of a type whose transparency changes, a material in which an organic low molecular weight compound is dispersed as an aggregate having a diameter of about 0.1 to 2.0 μm in a polymer resin matrix can be preferably used. . In this type recording layer, the organic low molecular weight compound dispersed in the polymer resin matrix undergoes a volume change between crystallization and melting, and accordingly, voids are generated between the polymer resin matrix, This utilizes the effect that light scattering occurs.

  Specific examples of the organic low molecular weight compound include known organic low molecular weight compounds such as higher fatty acids having 12 or more carbon atoms, higher fatty acid esters, carboxylic acids, dicarboxylic acids, ketones, ethers, alcohols, esters, sulfides, fatty acid amides, A crystalline low molecular weight compound composed of an aliphatic dibasic acid, an aliphatic dibasic acid ester and a derivative thereof may be used, and these may be used alone or in combination of two or more.

  In the present invention, among the organic low-molecular compounds dispersed in the resin matrix, the fatty acid alkyl ester having 12 or more carbon atoms has a low melting point (mp) and is melted and crystallized by heat treatment at a relatively low temperature. Therefore, it is preferable. Furthermore, in addition to the fatty acid alkyl ester having 12 or more carbon atoms, a high melting point (mp) of an aliphatic dibasic acid having 10 or more carbon atoms is used in combination, and the mixing ratio of the fatty acid alkyl ester and the aliphatic dibasic acid is adjusted. The temperature range to be transparent can be adjusted, and the degree of transparency and cloudiness at a predetermined temperature can be changed.

  Examples of fatty acid alkyl esters having 12 or more carbon atoms include methyl stearate, ethyl stearate, butyl stearate, octyl stearate, stearyl stearate, behenyl stearate, methyl behenate, ethyl behenate, butyl behenate. Octyl behenate, stearyl behenate, behenyl behenate, methyl lignocerate, ethyl lignocerate, and the like.

  Examples of the aliphatic dibasic acid having 10 or more carbon atoms include sebacic acid, dodecanedioic acid, tetradecanedioic acid, and eicosane diacid.

  Examples of the aliphatic dibasic acid having 10 or more carbon atoms include sebacic acid, dodecanedioic acid, tetradecanedioic acid, and eicosane diacid. The fatty acid alkyl ester having 12 or more carbon atoms and the aliphatic dibasic acid having 10 or more carbon atoms may be used alone or in combination of two or more.

  As an example of a recording material of a type that changes color developability, that is, a color tone, an electron donating color developing compound and an electron accepting compound are dissolved or dispersed in a polymer resin base material. An electron-accepting compound that exhibits acid properties or base properties by the action of heat can be a developer or a color reducing agent for an electron-donating color-forming compound having a reversible structure. It is something that uses that.

  For example, after heating to a temperature where the melting temperature of the electron donating color compound and the electron accepting compound is abnormal, the color develops when rapidly cooled, and after heating at a temperature below the melting temperature, the color disappears when gradually cooled. When an electron accepting compound having a long chain alkyl group is used as the developer, the developer itself has a cohesive force due to the structure of the long chain alkyl group. For this reason, depending on the heating conditions and the cooling rate after heating, the leuco dye can be contacted or separated, and when the developer and the leuco dye are brought into contact with each other, the color is developed and the color is erased by separation. .

  Specific examples of electron donating color-forming compounds (so-called leuco dyes) having a lactone ring in the molecular structure and exhibiting color development due to structural changes such as ring opening of the lactone ring by electron emission include crystal violet lactone, 3- ( 4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, etc. Phthalide compounds, 3-diethylamino-6-methyl-7-anilinofluorane, 2- (2-chloroanilino) -6-diethylaminofluorane, 2- (2-chloroanilino) -6-dibutylaminofluorane, 2- Anilino-3-methyl-6 (N-ethylisopentylamino) fluorane, 3-cyclohexylmethylamino-6 -Methyl-7-anilinofluorane, 3-benzylethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-methylpropylamino-6- And fluorane compounds such as methyl-7-anilinofluorane and 3-diethylamino-6-methyl-7-xylidinofluorane.

  As an electron-accepting compound, for example, an organic phosphoric acid compound, aliphatic carboxylic acid compound or phenolic compound having an aliphatic group having 6 or more carbon atoms (a phenolic compound having an aliphatic group having 12 or more carbon atoms is preferred). Is mentioned.

  Specific examples of the electron-accepting compound include dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, α-hydroxydecanoic acid, α-hydroxytetradecanoic acid, and α-hydroxyhexadecane. Acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid, etc. Can be mentioned.

  Examples of phenolic compounds include 4'-hydroxy-4-octadecylbenzanilide, N-octadecyl-4-hydroxybenzamide, N- (4-hydroxyphenyl) -N'-octadecylurea, 4-hydroxyphenylpropiono-behenyl hydrazide. Etc.

  The blending ratio of the electron donating color compound, the electron accepting compound and the polymer resin base material is, for example, preferably 10 to 100 parts by weight, more preferably 20 to 50 parts by weight of the electron accepting compound with respect to 10 parts by weight of the leuco dye. The polymer resin base material is preferably 10 to 200 parts by mass, and more preferably 20 to 100 parts by mass with respect to 10 parts by mass of the leuco dye.

The reversible recording layer is obtained by dispersing an organic low molecular weight compound in a polymer resin matrix and then applying it on a support or the like, or by applying an electron donating color compound and an electron in the polymer resin matrix. It is formed by dissolving or dispersing the receptive compound and then applying it onto a support or the like.
The thickness of the reversible thermosensitive recording layer is preferably 3 μm to 30 μm, but is not particularly limited to this range.

  In the case of the transparent cloudy type, it is preferable to further provide a light reflection layer in order to increase the contrast of the visible image and improve the sharpness. The light reflecting layer is formed by, for example, applying a light-reflective coloring paint mixed with metal deposition such as aluminum or tin, adhesion of vapor-deposited foil or aluminum powder, white pigment, etc. on the UV-curable resin layer or the support. You may do it.

  When the reversible thermosensitive recording layer is formed of a color tone change type, it is preferable to dispose a colored layer instead of the light reflecting layer. The colored layer is formed, for example, by applying a colored paint mixed with a pigment, a dye or the like.

  As shown in FIG. 1, a protective layer 3 is usually provided on the reversible recording layer 4. By providing the protective layer 3, rewrite durability and matching with a thermal head can be improved.

  The protective layer 3 is the outermost layer and is preferably made of a material having excellent scratch resistance and contamination resistance in consideration of contact with a thermal head or other objects. For example, in addition to the ultraviolet curable resin described above, polyethylene terephthalate, polyetherimide, polyetherketone, polyetheretherketone, polysulfone, polyphenylene sulfide, polyacrylate, polyethersulfone, polycarbonate, polyethylene naphthalate, polyimide, acrylic It is preferable to use a resin such as a resin or an electron beam curable resin.

  Examples of the ultraviolet curable resin or electron beam curable resin include, for example, various acrylate monomers, other additives, and the like, which are mainly composed of oligomers such as urethane acrylate and epoxy acrylate, to facilitate handling and workability. Those having adjusted curability and the like can be used.

  The thickness of the protective layer 3 is preferably designed as appropriate according to the type of the resin material, etc., but is generally preferably in the range of 0.5 to 20 μm, more preferably in the range of 2 to 10 μm. Is within. If the thickness of the protective layer is less than 0.5 μm, a sufficient protective effect may not be obtained. If the thickness is more than 20 μm, the contrast of the reversible recording layer may be lowered.

  The reversible thermosensitive recording medium A can also display or erase a visible image using light such as a laser. In that case, the reversible thermosensitive recording layer 4 preferably contains a light absorber. Examples of light absorbers include azo dyes, cyanine dyes, naphthoquinone dyes, anthraquinone dyes, squarylium dyes, phthalocyanine dyes, naphthalocyanine dyes, naphthoquinone dyes, porphyrin dyes, indigo dyes, dithiols. Examples thereof include complex dyes, azulenium dyes, quinoneimine dyes, and quinone dimyne dyes.

  Further, a photothermal conversion layer may be disposed adjacent to the reversible thermosensitive recording layer 4 in place of the above-described light absorber or together with the addition of the light absorber to the reversible thermosensitive recording layer. When using an infrared laser, it is preferable to provide a visible light transmissive photothermal conversion layer made of a material containing an infrared absorbing dye in order to improve the printing sensitivity of the infrared laser.

  As the infrared absorbing dye, one having an absorption peak near the oscillation wavelength of the semiconductor laser light to be used is selected. In general, a semiconductor laser having a wavelength of 300 nm to 1000 nm, preferably 700 to 900 nm can be used. As an infrared absorbing dye, a cyanine dye, a phthalocyanine dye, a polymethine dye having an absorption peak in such a wavelength region, Anthraquinone dyes and the like are preferably used.

  As the resin base material constituting the photothermal conversion layer, those having high visible light permeability and good film forming properties are preferable, and those having excellent heat resistance and not decomposing and not yellowing are preferable. Specific examples include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, polyester-urethane copolymer, and the like. Further, the same polymer resin base material constituting the reversible recording layer may be used. The thickness of the photothermal conversion layer is preferably 0.1 μm to 10 μm, more preferably 0.5 μm to 5 μm, but is not particularly limited to this range.

  The reversible thermosensitive recording medium A or information recording / display medium B is a card-like, sheet-like, or the like that is obtained by superimposing and integrally bonding an oversheet, a core sheet, an inlet sheet, and other sheets formed of the above materials. It can form in the laminated body.

  As such a method of bonding each sheet, a well-known method may be employed if the sheets are uniformly adhered and laminated and integrated, for example, adhesion via an adhesive, heat fusion by heating and pressing, and the like. Can be adopted. If they are stacked in sheet form, they can then be punched into a predetermined size card shape. As the above-described heating and pressing method, a pressing method or a laminating method is appropriately selected and adopted so as to be suitable for the material of the sheet.

  In order to form, for example, a color image on the reversible thermosensitive recording medium A or the information recording / display medium B, it is only necessary to heat the color to a temperature higher than the color development temperature and then rapidly cool it. Specifically, for example, when the recording layer is heated for a short time with a thermal head or laser light, the recording layer is locally heated, so that the heat is immediately diffused and abrupt cooling occurs, so that the colored 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 heat roller, a heat stamp, hot air, a ceramic heater, or the like may be used, or heating may be performed for a long time using a thermal head. In order to heat the recording layer to the color erasing 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 and erasing can be performed only with a thermal head, and so-called overwriting is possible by erasing an image and displaying a new image. The recording apparatus may be a thermal printer having a thermal head, and a thermal transfer printer, a sublimation printer, or the like may be used. It can also be erased by heating to a decoloring temperature range with a heat roller or a heat stamp. Examples of the image display means include a thermal head and a laser device, and examples of the image erasing means include a thermal head, a ceramic heater, a heat roller, a heat stamp, and a hot air machine.

First, a reversible thermosensitive recording medium having the same structure as that of the first embodiment whose layer structure is shown in FIG. 1 was manufactured.
A composition in which a sheet of amorphous polyester resin (Mitsubishi Resin Co., Ltd .: Diafix PA-C, thickness 100 μm) is used as the base material layer 1 and the following materials (1), (2), and (3) are mixed on the surface thereof: A coating solution for forming an ultraviolet opaque layer was prepared, and this was coated with a bar coater. Then, the coating was performed at 100 ° C. for 5 minutes to form an ultraviolet opaque layer 5 having a thickness of 2 μm.

[UV-opaque layer composition]
(1) 50 parts by weight of acrylic resin (Mitsubishi Rayon Co., Ltd .: BR-80)
(2) Benzotriazole UV absorber (Ciba Geigy: Tinuvin 234)
20 parts by weight
(3) 200 parts by weight of toluene

  Next, a coating solution of an ultraviolet curable resin layer (barrier layer) composed of a composition in which the following materials (1), (2), and (3) are mixed is prepared, and this is formed with a bar coater and the ultraviolet opaque layer formed above The ultraviolet curable resin layer (barrier layer) 2 was formed by passing the film at a rate of 5 m / min under a 160 W / cm high-pressure mercury lamp.

[Liquid composition of UV curable resin layer (barrier layer)]
(1) UV curable resin (Toagosei Co., Ltd .: Aronix M1200) 100 parts by weight
(2) 3 parts by weight of a polymerization initiator (manufactured by Ciba Specialty Chemicals: Irgacure 184)
(3) 50 parts by weight of solvent (2-propanol)

  Next, a reversible thermosensitive recording layer was formed by the following steps. That is, 10 parts by mass of crystal violet lactone as a dye precursor, 20 parts by mass of hydroxyphenylpropiono-behenyl hydrazide as an electron accepting compound, 50 parts by mass of a polymer resin base material (Mitsubishi Rayon Co., Ltd .: LR-1503), 150 parts by mass of a solvent (toluene) was mixed and dispersed for 2 hours using a paint shaker to prepare a reversible recording layer dispersion. 5 parts by mass of an isocyanate compound (manufactured by Nippon Polyurethane Industry Co., Ltd .: Coronate L, solid content: 75% by mass) as a curing agent was added to this reversible recording layer dispersion and stirred sufficiently to form a reversible thermosensitive recording layer. A coating solution was prepared.

  The obtained coating liquid was applied on the barrier layer 2 made of the ultraviolet curable resin prepared in the above step with a bar coater and dried at 100 ° C. for 5 minutes to form the reversible thermosensitive recording layer 4.

  Next, the UV curable resin layer (barrier layer) coating solution is applied over the reversible thermosensitive recording layer 4 so that the thickness after drying is 2 μm, and is under a 120 W / cm high-pressure mercury lamp. The sheet was cured by passing at a speed of 10 m / min to form an ultraviolet curable resin layer (protective layer) 3 to produce a sheet-like reversible thermosensitive recording medium of Example 1.

Next, as the core sheets 6 and 7, two non-crystalline polyester resins (Mitsubishi Resin Co., Ltd .: Diafix PG-WHI, thickness 280 μm) are stacked, and this is a reversible thermosensitive recording medium manufactured as described above. And sandwiched between PETG (Mitsubishi Resin Co., Ltd .: Diafix PA-C, thickness 100 μm) as an oversheet amorphous PET copolymer, temperature 130 ° C., pressure 20 kgf / cm ² , holding time 10 minutes Press processing was performed under the conditions to integrate the layers.

  The reversible thermosensitive recording medium comprising the obtained sheet-like laminate was subjected to a measurement test according to the following evaluation items (a), (b) and (c), and the results are shown in Table 1.

(A) Background density The reflection density was measured with a reflection densitometer (X-Rite 928), and the measured value was defined as the background density. By the way, the measured value indicates that yellow is stronger as the numerical value is larger, and closer to transparency as the numerical value is smaller.

(B) Rewrite characteristics Using KU-R28112KFL manufactured by Panasonic Communications as a printer, printing is performed by performing printing and erasing under thermal head printing conditions of 0.5 mJ / dots and heater bar erasing conditions of 128 ° C. (speed: 28 mm / sec). The density after the measurement was measured with a Macbeth reflection densitometer RD-918, and the density after erasure was measured with a reflection densitometer X-Rite.

(C) Visibility When the appearance of the printed image is seen with the naked eye, the card turns yellow and the printed image is difficult to see. did.

  A sheet-like reversible thermosensitive recording medium was produced in exactly the same manner as in Example 1 except that the ultraviolet opaque layer was formed with the following composition.

[UV-opaque layer composition]
(1) Polymer type benzotriazole ultraviolet absorber (manufactured by Nippon Shokubai Co., Ltd .: UV-G714)
100 parts by weight
(2) 300 parts by weight of methyl ethyl ketone

[Comparative Example 1]
A sheet-like reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the ultraviolet-opaque layer was omitted.

  As is clear from the results in Table 1, the sheet-like reversible thermosensitive recording medium having no UV-opaque layer has a poor appearance due to yellowing of the sheet base immediately after production, and the print density is low. Further, the evaluation of visibility was poor because the erase density was high and the printed image was difficult to see.

  On the other hand, in Examples 1 and 2, the sheet background was white and the appearance was good, the printing density was high, the erasing density was low, and the printed image was easy to see, so the visibility evaluation was also good.

  In addition, Example 2 using a polymer type ultraviolet absorber had a lower background density and erasing density than Example 1, and was more excellent.

Sectional drawing which shows the reversible thermosensitive recording medium of 1st Embodiment. Sectional drawing which shows the information recording display medium of 2nd Embodiment Sectional view showing a conventional reversible thermosensitive recording medium

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 12 Base material layer 2, 14 Barrier layer 3 Protective layer 4, 13 Reversible thermosensitive recording layer 5 Ultraviolet opaque layer 6, 7 Core sheet 8 Antenna coil 9 IC chip 10 Inlet sheet 11 Oversheet A Reversible thermosensitive recording medium B Information recording and display medium

Claims (5)

  One or more UV curable resin layers and a reversible thermosensitive recording layer capable of displaying and erasing a visible image by a change in color development or transparency accompanying a temperature change are integrally provided on the surface side of the base material layer. A reversible thermosensitive recording medium comprising a laminate, wherein an ultraviolet opaque layer is provided between a substrate layer in the laminate and an ultraviolet curable resin layer closest to the substrate layer. 2. The reversible thermosensitive recording medium according to claim 1, wherein the ultraviolet opaque layer is an ultraviolet opaque layer made of a polymer ultraviolet absorber. The UV-opaque layer is a UV-opaque layer comprising a polymer copolymer of a monomer having a UV-absorbing molecular structure and a polymerizable monomer, or a polyaddition or polycondensate of a monomer having a UV-absorbing molecular structure. The reversible thermosensitive recording medium according to claim 1 . The reversible thermosensitive recording medium according to any one of claims 1 to 3 , wherein the base material layer is a base material layer containing an amorphous polyester resin in a proportion of 100% by weight or less. Claim 1 in the reversible thermosensitive recording medium according to any one of 4, the information recording display medium which is provided integrally overlaid noncontact IC chip and an antenna.

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