JP2007076051A - Reversible thermosensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practically high reversible thermosensitive recording medium enabling to obtain favorable resistance against light without forming a special ultraviolet absorbing layer by a method wherein ultraviolet absorbing inorganic particles are included in an upper portion in a recording layer. <P>SOLUTION: In the reversible thermosensitive recording medium having a reversible thermosensitive recording layer which includes resin, an electron donative colorable compound and an electron acceptive compound and can relatively form a color-developed state and a decolorized state caused by the difference between heating temperatures and/or between cooling speeds after heating, and at least a protective layer on a support, the reversible thermosensitive recording layer includes ultraviolet absorbable inorganic particles having particle diameters ranging from 10 nm to 100 nm and, and, quantities of the ultraviolet absorbable inorganic particles included in the reversible thermosensitive recording layer are relatively greater at its upper portion than those included at its lower portion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reversible thermosensitive recording medium using ultraviolet absorbing inorganic fine particles, and in particular, to improve the light resistance, durability, and heat resistance of a dye precursor (leuco dye) contained in a reversible thermosensitive recording layer. The present invention relates to a reversible thermosensitive recording medium containing an inorganic ultraviolet shielding agent.

  2. Description of the Related Art Conventionally, heat-sensitive recording media using a color developing 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, all of these conventional recording media in practical use have irreversible color development, and once recorded images cannot be erased and used repeatedly.

  On the other hand, according to the patent publication, a recording medium capable of reversibly developing and erasing has also been proposed. For example, a recording medium using a combination of gallic acid and phloroglucinol as a developer (Patent Document 1), A developer using a compound such as phenolphthalein or thymolphthalein as a developer (Patent Document 2), a developer containing a homogeneous solution of a color former, a developer and a carboxylic acid ester (Patent Document 3, Patent) Document 4 and Patent Document 5), one using an ascorbic acid dielectric as a developer (Patent Document 6), one using a salt of bis (hydroxyphenyl) acetic acid or gallic acid and a higher aliphatic amine as the developer (Patent Document 7 and Patent Document 8) are disclosed.

Furthermore, the present inventors previously used an organic phosphoric acid compound, aliphatic carboxylic acid compound or phenol compound having a long-chain aliphatic hydrocarbon group as a developer in Patent Document 9, and this and a leuco dye as a color former. By combining with, color development and color erasure can be easily performed under heating and cooling conditions, and the color development state and color erasure state can be kept stable at room temperature, and color development and color erasure are repeated. A reversible thermosensitive coloring composition and a reversible thermosensitive recording medium using the same for a recording layer have been proposed.
Thereafter, it has been proposed to use a phenol compound having a long-chain aliphatic hydrocarbon group having a specific structure (Patent Document 10).

Thus, a reversible thermosensitive recording medium that can repeat color development and decoloration has been proposed.
However, this type of recording medium requires storage characteristics (temperature / humidity / light) and high-speed erasing characteristics, but coloring of the background portion with light is a major problem.
In order to improve the coloring of the background portion by light, it has been proposed in Patent Document 11 to provide an ultraviolet absorbing layer containing an ultraviolet absorber between the recording layer and the protective layer, but depending on the added ultraviolet absorber. There is a problem of a decrease in color density, and there is further coloring of the background portion due to long-time exposure, which is not sufficient.
Further, Patent Document 12 discloses a proposal for containing ultraviolet absorbing inorganic fine particles of 0.1 μm or less in an intermediate layer or a protective layer provided on a recording layer. There are problems such as.

Japanese Patent Laid-Open No. 60-193691 Japanese Patent Laid-Open No. Sho 61-237684 JP-A-62-138556 JP-A-62-138568 JP-A-62-140881 Japanese Patent Laid-Open No. 63-173684 JP-A-2-188293 JP-A-2-188294 JP-A-5-124360 Japanese Patent Laid-Open No. 6-210954 JP-A-8-11433 Japanese Patent Application Laid-Open No. 10-100541

  An object of the present invention is to provide a reversible thermosensitive recording medium having good light resistance even when the layer structure is simplified.

（式中、Ｘ_１及びＸ_２は直接結合手または−ＮＨ−，−ＣＯ−，−ＳＯ_２−，−Ｓ−からなる２価の基を示す。ただし、Ｘ_１及びＸ_２は同時に直接結合手であることはない。
Ｒ_１は炭素数１〜２２の２価の炭化水素基を表し、Ｒ_２は炭素数８〜３０の飽和脂肪族基を表す。また、ｐは０〜４の整数を表し、ｐが２〜４のとき繰り返されるＲ_１およびＸ_２は同一でも、異なっても良い。また、ｐが０のとき、Ｘ_１は直接結合手ではない。さらに、ｑは１〜３の整数を表す。）
本発明の第５は、請求項１〜４のいずれかに記載の可逆性感熱記録媒体と情報記憶部とを積層したことを特徴とする情報表示記録部材に関する。
本発明の第６は、請求項１〜４のいずれかに記載の可逆性感熱記録媒体表面に、接着剤層又は粘着剤層を設けたことを特徴とする可逆性感熱記録ラベルに関する。
本発明の第７は、請求項１〜４のいずれかに記載の可逆性感熱記録媒体を用いて、画像の形成及び／又は消去を行なうことを特徴とする画像処理方法に関する。
本発明の第８は、サーマルヘッドを用いて前記可逆性感熱記録媒体に画像を形成することを特徴とする請求項７に記載の画像処理方法に関する。
本発明の第９は、サーマルヘッドを用いて画像を消去することを特徴とする請求項７に記載の画像処理方法に関する。
本発明の第１０は、請求項７〜９のいずれかに記載の画像処理方法を用いて、画像の形成及び／又は消去を行なうことができるように設定されていることを特徴とする画像処理装置に関する。 As a result of various studies for preventing coloration of the recording medium by the light resistance test, the present inventors newly provided an ultraviolet absorbing layer or the like by containing ultraviolet absorbing inorganic fine particles on the upper side of the recording medium. As a result, it was found that deterioration of the recording layer due to ultraviolet rays could be prevented. That is,
In the first aspect of the present invention, a resin, an electron-donating color-forming compound, and an electron-accepting compound are contained on a support, and a relatively colored state is caused by a difference in heating temperature and / or cooling rate after heating. A reversible thermosensitive recording medium having at least a reversible thermosensitive recording layer and a protective layer capable of forming a decolored state, wherein the reversible thermosensitive recording layer contains ultraviolet-absorbing inorganic fine particles having a particle diameter of 10 nm to 100 nm, and The present invention relates to a reversible thermosensitive recording medium characterized in that the ultraviolet-absorbing inorganic fine particles are contained more in the upper part than in the lower part of the reversible thermosensitive recording layer.
A second aspect of the present invention relates to the reversible thermosensitive recording medium according to claim 1, wherein the ultraviolet absorbing inorganic fine particles cover the surface portion of the recording layer.
A third aspect of the present invention relates to the reversible thermosensitive recording medium according to claim 1, wherein the ultraviolet absorbing inorganic fine particles are contained in the reversible thermosensitive recording layer in an amount of 5 to 40% by weight.
The fourth aspect of the present invention is that the electron-accepting compound is a phenol compound having a saturated aliphatic group having 8 or more carbon atoms represented by the following formula (1): The present invention relates to a thermal recording medium.

(Wherein, X ₁ and X ₂ represent a direct bond or a divalent group consisting of —NH—, —CO—, —SO ₂ —, —S—, wherein X ₁ and X ₂ are directly bonded simultaneously. It is never a hand.
R ₁ represents a divalent hydrocarbon group having 1 to 22 carbon atoms, and R ₂ represents a saturated aliphatic group having 8 to 30 carbon atoms. P represents an integer of 0 to 4, and R ₁ and X ₂ repeated when p is 2 to 4 may be the same or different. When p is 0, X ₁ is not a direct bond. Furthermore, q represents an integer of 1 to 3. )
A fifth aspect of the present invention relates to an information display recording member characterized in that the reversible thermosensitive recording medium according to any one of claims 1 to 4 and an information storage section are laminated.
A sixth aspect of the present invention relates to a reversible thermosensitive recording label characterized in that an adhesive layer or a pressure-sensitive adhesive layer is provided on the surface of the reversible thermosensitive recording medium according to any one of claims 1 to 4.
A seventh aspect of the present invention relates to an image processing method characterized in that an image is formed and / or erased using the reversible thermosensitive recording medium according to any one of claims 1 to 4.
An eighth aspect of the present invention relates to the image processing method according to claim 7, wherein an image is formed on the reversible thermosensitive recording medium using a thermal head.
A ninth aspect of the present invention relates to the image processing method according to claim 7, wherein the image is erased using a thermal head.
According to a tenth aspect of the present invention, there is provided an image processing which is set so that an image can be formed and / or erased using the image processing method according to any one of claims 7 to 9. Relates to the device.

FIG. 6 is a schematic view of the reversible thermosensitive recording medium of the present invention.
The reversible thermosensitive recording medium of the present invention has a reversible thermosensitive recording layer 2 containing a large amount of ultraviolet-absorbing inorganic fine particles 1 on a support 4 on a support 4, and a protective layer 3 on the reversible thermosensitive recording layer 2. Have
In the present invention, in order to contain the ultraviolet absorbing inorganic fine particles relatively in the recording layer, there is a method utilizing a convection phenomenon in the recording layer at the time of drying, for example, a leuco dye, a developer, A coating liquid in which ultraviolet-absorbing inorganic fine particles are dispersed together with a resin is applied on a support and heated to a high temperature of about 100 ° C., thereby causing convection in the recording layer coating liquid during the drying process, thereby absorbing the ultraviolet light. Inorganic fine particles can be present on the upper surface of the recording layer.
Note that the ultraviolet absorbing inorganic fine particles present in the recording layer can be observed with an H-9000NAR transmission electron microscope (TEM) manufactured by Hitachi, Ltd.
Such ultraviolet-absorbing inorganic fine particles have a pigment (A) having an absorption edge in the ultraviolet UV-A region, that is, an ultraviolet UV-A region having a wavelength of 320 to 400 nm, and an absorption edge on the shorter wavelength side than the ultraviolet UV-A region. It can be classified into two groups of pigment (B).
Specific examples of the inorganic pigment (A) include zinc sulfide, titanium oxide, indium oxide, cerium oxide, tin oxide, molybdenum oxide, zinc oxide, and gallium nitride.
Specific examples of the inorganic pigment (B) include silica, alumina, silica-alumina, antimony oxide, magnesium oxide, zirconium oxide, barium oxide, calcium oxide, strontium oxide, silicon nitride, aluminum nitride, boron nitride, barium sulfate. Etc.

The addition amount of the ultraviolet absorbing inorganic fine particles used in the present invention is preferably 5 to 40% by weight, particularly preferably 10 to 40% by weight in the recording layer.
When the UV-absorbing inorganic fine particles are substantially added in an amount of more than 40% by weight in the recording layer, the UV-absorbing inorganic fine particles can cover the surface portion of the recording layer when observed with a TEM. A decrease in image density occurs. When the amount added was less than 5% by weight, it was too small to cover the surface of the recording layer, so that the light resistance was lowered and the recording layer was colored.
Furthermore, in the present invention, by using UV-absorbing inorganic fine particles having a particle diameter of 10 to 100 nm, the fine particles become substantially transparent in the visible region, and there is no adverse effect on the reduction in image density as described above. Ultraviolet-absorbing inorganic fine particles having a particle diameter of 10 to 70 nm are particularly preferred.
If the particle diameter of the ultraviolet absorbing inorganic fine particles exceeds 100 nm, light scattering occurs due to the particles, causing a problem of image density reduction. On the other hand, if the particle diameter is less than 10 nm, the particles tend to aggregate and are stable. There is a problem that dispersion becomes difficult.

The present invention is described in detail below.
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. This basic coloring / decoloring phenomenon will be described.
FIG. 1 shows the relationship between the color density of this recording medium and the temperature.
Introduction gradually heated the recording medium in the decolored state (A), leuco dye and the developer are mixed melt at temperatures T ₁ begins to melt, coloring occurs a molten color developed state (B).
When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature and a fixed 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 recording medium of the present invention, the color development 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 contact each other and form a solid state. Often doing. 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 this aggregated 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. It is done.
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. 1, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

The reversible thermosensitive recording layer of the present invention basically comprises a composition comprising the following electron donating color developing compound, electron accepting compound and resin.
As the leuco dye used in the reversible thermosensitive recording layer, one or more compounds commonly used in this type of reversible thermosensitive recording medium can be used. For example, phthalide compounds, azaphthalide compounds, fluorane compounds It is a known dye precursor.
Examples of these compounds are leuco dyes described in JP-A-5-124360, JP-A-6-210594, JP-A-10-230680 and the like.
Of these, particularly preferred examples include 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-ethyl-p-) Toluidino) fluoran, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- ( - ethyl-2-methylindole-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, and the like.

（式中、Ｘ_１及びＸ_２は直接結合手または−ＮＨ−，−ＣＯ−，−ＳＯ_２−，−Ｓ−からなる２価の基を示す。ただし、Ｘ_１及びＸ_２は同時に直接結合手であることはない。
Ｒ_１は炭素数１〜２２の２価の炭化水素基を表し、Ｒ_２は炭素数８〜３０の飽和脂肪族基を表す。また、ｐは０〜４の整数を表し、ｐが２〜４のとき繰り返されるＲ_１およびＸ_２は同一でも、異なっても良い。また、ｐが０のとき、Ｘ_１は直接結合手ではない。さらに、ｑは１〜３の整数を表す。）
具体的には、Ｒ_１およびＲ_２は置換基を有していてもよい炭化水素基を示し、これらは脂肪族炭化水素基でも芳香族炭化水素基でもよく、また、これらの両方から構成される炭化水素基でもよい。炭化水素基につく置換基としては、水酸基、ハロゲン、アルコキシ基等がある。なお、Ｒ_１は直接結合手でも良い。
また、Ｒ_２の炭素が７以下では発色の安定性や消色性が低下するため、炭素数は８以上が好ましく、１１以上であることがより好ましい。Ｘ_１およびＸ_２は直接結合手またはヘテロ原子を含む２価の基を示し、好ましくは下記に示される基を少なくとも1個以上有する２価の基を表す。 In the present invention, a phenol compound having a saturated aliphatic group having 8 or more carbon atoms represented by the following formula (1) is particularly preferably used as the developer.

(Wherein, X ₁ and X ₂ represent a direct bond or a divalent group consisting of —NH—, —CO—, —SO ₂ —, —S—, wherein X ₁ and X ₂ are directly bonded simultaneously. It is never a hand.
R ₁ represents a divalent hydrocarbon group having 1 to 22 carbon atoms, and R ₂ represents a saturated aliphatic group having 8 to 30 carbon atoms. P represents an integer of 0 to 4, and R ₁ and X ₂ repeated when p is 2 to 4 may be the same or different. When p is 0, X ₁ is not a direct bond. Furthermore, q represents an integer of 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. 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 carbon of R ₂ is 7 or less, the coloring stability and 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 direct bond or a hetero atom, and preferably represents a divalent group having at least one group shown below.

その具体例としては、下記のものが挙げられる。

Specific examples thereof include the following.

（式中のｒ、ｓは、前記のＲ_１およびＲ_２の炭素数を満足する整数を表す。）等が挙げられる。
また、これらの他にもたとえば特開平５−１２４３６０号公報、特開平６−２１０９５４号公報、特開平１０−９５１７５号公報、特開平９−２９０５６３号公報、特開平１１−１８８９６９号公報、特開平１１−９９７４９号公報などに記載の顕色剤を用いることができる。 Specific examples of the phenol compound in the present invention are listed below, but the present invention is not limited thereto. Moreover, a phenol compound can also be used individually or in mixture.

(Wherein, r and s represent integers satisfying the carbon number of R ₁ and R ₂ described above).
Besides these, for example, JP-A-5-124360, JP-A-6-210554, JP-A-10-95175, JP-A-9-290563, JP-A-11-188969, JP Developers described in JP-A No. 11-99749 can be used.

  Examples of the resin used in the present invention include polyvinyl chloride, polyvinyl acetate, vinyl chloride vinyl acetate copolymer, polyvinyl acetal, polyvinyl butyral, polycarbonate, polyarylate, polysulfone, polyether sulfone, polyphenylene oxide, fluorine resin, Polyimide, polyamide, polyamideimide, polybenzimidazole, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polyacrylate ester, polymethacrylate ester, (meth) acrylate ester copolymer , Maleic acid copolymer, epoxy resin, alkyd resin, silicone resin, phenol resin, polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene Emissions oxide, polypropylene oxide, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl E chill cellulose, starch, gelatin and casein, and the like.

Various curing agents and crosslinking agents can also be added for the purpose of increasing the strength of the recording layer film.
Examples of such curing agents and crosslinking agents include compounds having an isocyanate group, polyamide epichlorohydrin resins, compounds having an epoxy group, glyoxal, and zirconium compounds.
Furthermore, the recording layer can be provided using an electron beam curable resin or an ultraviolet curable resin. Examples of such a resin include compounds having an ethylenically unsaturated bond.

Specific examples of these are:
1. 1. Poly (meth) acrylates of aliphatic, alicyclic and aromatic polyhydric alcohols and polyalkylene glycols. 2. Poly (meth) acrylates of polyhydric alcohols obtained by adding polyalkylene oxide to aliphatic, alicyclic, aromatic, or araliphatic polyhydric alcohols. 3. Polyester poly (meth) acrylate 4. Polyurethane poly (meth) acrylate Epoxy poly (meth) acrylate 6. 6. Polyamide poly (meth) acrylate 7. Poly (meth) acryloyloxyalkyl phosphate ester 8. Vinyl-based or diene-based compounds having a (meth) acryloyl group in the side chain or terminal. Monofunctional (meth) acrylate, vinyl pyrrolidone, (meth) acryloyl compound 10. 10. Cyano compounds having an ethylenically unsaturated bond 12. Mono- or polycarboxylic acids having an ethylenically unsaturated bond, and alkali metal salts, ammonium salts, amine salts thereof, etc. 12, ethylenically unsaturated (meth) acrylolamide or alkyl-substituted (meth) acrylamide and multimers thereof 13. Vinyl lactam and polyvinyl lactam compounds 15. Mono- or polyethers having an ethylenically unsaturated bond and esters thereof 15. ester of alcohol having ethylenically unsaturated bond 16. Polyalcohol having ethylenically unsaturated bond and ester thereof 17. Aromatic compounds having one or more ethylenically unsaturated bonds, such as styrene and divinylbenzene. 18. Polyorganosiloxane compound having a (meth) acryloyloxy group in the side chain or terminal. Silicone compound having ethylenically unsaturated bond 20. Examples include multimers of the compounds described in 1 to 19 above, oligoester (meth) acrylate modified products, and the like.

When the recording layer is formed using an ultraviolet curable resin, a photopolymerization initiator is mixed and used.
Photopolymerization initiators include acetophenones such as di- or trichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, benzophenone, Michler ketone, benzoin, benzoin alkyl ether, benzyl dimethyl ketal, tetramethylthiuram monosulfide, thioxanthones, azo compounds , Diaryliodonium salts, triarylsulfonium salts, bis (trichloromethyl) triazine compounds, and the like.

Specific examples of the crosslinked resin used in the present invention include acrylic polyol resins, polyester polyol resins, polyurethane polyol resins, phenoxy resins, polyvinyl butyral resins, cellulose acetate propionate, and cellulose acetate butyrate. A resin having a reactive group, or a resin obtained by copolymerization of a monomer having a group reactive with a crosslinking agent and another monomer may be used, but the present invention is not limited to these compounds.
Furthermore, as the resin to be reacted with the crosslinking agent in the present invention, it is preferable to use a resin having a hydroxyl value of 70 (KOHmg / g) or more. As the resin having a hydroxyl value of 70 (KOHmg / g) or more, an acrylic polyol resin, a polyester polyol resin, a polyurethane polyol resin, and the like are used. Particularly, since the color development stability is good and the decoloring property is good, An acrylic polyol resin is preferably used.
The hydroxyl value is 70 (KOHmg / g) or more, particularly preferably 90 (KOHmg / g) or more. The magnitude of the hydroxyl value affects the crosslink density and thus affects the chemical resistance and physical properties of the coating film. The present inventors have found that durability, coating film surface hardness, and crack resistance are improved when the hydroxyl value is 70 (KOHmg / g) or more. Whether or not the resin is a reversible thermosensitive recording material using a resin having a hydroxyl value of 70 (KOHmg / g) or more can be confirmed by analyzing the amount of residual hydroxyl groups and the amount of ether bonds.

  In addition, acrylic polyol resins have different characteristics depending on the structure. Hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate ( HPMA), 2-hydroxybutyl monoacrylate (2-HBA), 1,4-hydroxybutyl monoacrylate (1-HBA), etc. are used, but it is particularly better to use a monomer having a primary hydroxyl group. Since the crack resistance and durability are good, 2-hydroxyethyl methacrylate is preferably used.

Examples of the crosslinking agent used in the present invention include conventionally known isocyanates, amines, phenols, epoxy compounds and the like. Among these, an isocyanate type crosslinking agent is preferably used.
The isocyanate compound used here is selected from known modified monomers such as urethane modified products, allophanate modified products, isocyanurate modified products, burette modified products, carbodiimide modified products, and blocked isocyanates.
The isocyanate monomer that forms the modified product includes tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), naphthylene diisocyanate (NDI), paraphenylene diisocyanate ( PPDI), tetramethylxylylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), lysine diisocyanate (LDI), isopropylidenebis (4-cyclohexylisocyanate) (IPC) ), Cyclohexyl diisocyanate (CHDI), tolidine diisocyanate (TODI), and the like. It is not limited to the compounds.

Furthermore, you may use the catalyst used for this kind of reaction as a crosslinking accelerator. Examples of the crosslinking accelerator include tertiary amines such as 1,4-diaza-bicyclo [2,2,2] octane, and metal compounds such as organic tin compounds. Further, the total amount of the curing agent may or may not undergo a crosslinking reaction.
That is, an unreacted curing agent may be present. Since this type of crosslinking reaction proceeds over time, the presence of an unreacted curing agent does not indicate that the crosslinking reaction has progressed at all, but an unreacted curing agent is detected. However, this does not mean that there is no resin in a crosslinked state.
Further, as a method for distinguishing whether the polymer in the present invention is in a crosslinked state or in a non-crosslinked state, it can be distinguished by immersing the coating film in a highly soluble solvent. That is, since the polymer in the non-crosslinked state dissolves in the solvent and does not remain in the solute, the presence or absence of the polymer structure of the solute may be analyzed.
Furthermore, according to the present invention, the recording layer contains a color development / decoloration control agent having a linear hydrocarbon group, a hydrogen bond group such as an amide group or a urea group, and the like together with the developer and the leuco dye. As a result, the storage stability of the color image is good, and the erasability at the time of erasing is also improved to obtain good erasability.

Further, according to the present invention, a protective layer containing a resin in a crosslinked state can be provided on the reversible thermosensitive recording layer. As the resin used for the protective layer, the same thermosetting resin, ultraviolet curable resin, and electron beam curable resin as those used for the recording layer are used.
As the resin used in the protective layer, an ultraviolet absorbing polymer having an ultraviolet absorbing group in the molecular structure is particularly preferably used.
Furthermore, according to the present invention, the protective layer can contain the inorganic fine particles having ultraviolet absorbing ability.
Further, in the present invention, inorganic / organic fillers, lubricants and the like used for this type of recording medium may be used in the protective layer.

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, and the like, 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 is used from about several μm to several mm.
Moreover, when providing an under layer on these support bodies, crack generation 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.

The reversible thermosensitive recording label of the present invention is one in which an adhesive layer or a pressure-sensitive adhesive layer is provided on the surface opposite to the surface of the support constituting the reversible thermosensitive recording medium described above.
This reversible thermosensitive recording label includes an adhesive layer or a pressure-sensitive adhesive layer (non-peeling paper type), and a release paper attached under the adhesive layer or pressure-sensitive adhesive layer (peeling paper type). As a material constituting the adhesive layer, a hot melt type material is usually used.
Commonly used materials can be used for the adhesive layer or the pressure-sensitive adhesive layer.
For example, urea resin, melamine resin, phenol resin, epoxy resin, vinyl acetate resin, vinyl acetate-acrylic copolymer, ethylene-vinyl acetate copolymer, acrylic resin, polyvinyl ether resin, vinyl chloride-vinyl acetate Copolymer, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, chlorinated polyolefin resin, polyvinyl butyral resin, acrylic ester copolymer, methacrylic ester copolymer, natural rubber , Cyanoacrylate resins, silicon resins, and the like, but are not limited thereto.
The reversible thermosensitive recording medium of the present invention is an information display produced by combining at least a thermosensitive layer constituting the reversible thermosensitive recording medium as a reversible display unit and a member (information storage unit) having an information storage function. It can be used as a memory member.

Next, the information display storage member will be described.
The members having the information storage unit and the reversible display unit can be roughly classified into the following three items.
(1) A part of a member having an information storage function is used as a support for a reversible thermosensitive recording medium, and a thermosensitive layer is directly formed thereon.
(2) The support surface of a reversible thermosensitive recording medium having a thermosensitive layer formed on a support, which is separately formed, on a member having an information storage function.
(3) The reversible thermosensitive recording label bonded to a member having an information storage function via an adhesive layer or an adhesive layer.
In these cases (1), (2), and (3), it is necessary to set the functions of the information storage unit and the reversible display unit so that the functions of the information storage unit are set. The position can be arbitrarily selected according to the purpose, and it can be provided on the surface of the reversible thermosensitive recording medium opposite to the surface on which the thermosensitive layer is provided, between the support and the thermosensitive layer, or on the thermosensitive layer. It can also be provided in a part of.

The member having the information storage function is not particularly limited, and a general card, disk, disk cartridge, or tape cassette can be used.
Examples of these include thick cards such as IC cards and optical cards, flexible disks, magneto-optical recording disks (MD), disk cartridges with built-in disks that can rewrite storage information such as DVD-RAM, and CD-RWs. Examples thereof include a disc that does not use a disc cartridge, a write-once disc such as a CD-R, an optical information recording medium (CD-RW) that uses a phase change type storage material, and a video tape cassette.
The information display storage member having both the reversible display function and the information storage function will be described in the case of a card, for example, by displaying a part of the information stored in the information storage unit on the reversible thermosensitive recording layer. The owner or the like can confirm information by looking at the card without a special device, and the convenience is greatly improved compared to a card to which the reversible thermosensitive recording medium is not applied.

The information storage unit is not particularly limited as long as it can store necessary information. For example, magnetic recording, contact IC, non-contact IC, or optical memory is useful.
The magnetic recording layer is formed by coating the support using a commonly used metal compound such as iron oxide or barium ferrite and a resin such as vinyl chloride, urethane or nylon, or without using a resin. It forms by methods, such as vapor deposition and sputtering, using the said metal compound. Further, the reversible thermosensitive recording layer in the reversible thermosensitive recording medium used for display can also be used as a storage unit in a manner such as a barcode or a two-dimensional code.

In addition, as an example of using the reversible thermosensitive recording label of (3) above, when the reversible thermosensitive recording layer is difficult to apply as a support, such as a vinyl chloride card with a magnetic stripe, An adhesive layer or a pressure-sensitive adhesive layer can be provided on the entire surface or a part thereof.
By doing so, the convenience of this medium can be improved, such as being able to display a part of the information stored in the magnetism.
The reversible thermosensitive recording label provided with the adhesive layer or the pressure-sensitive adhesive layer is applicable not only to the above-described magnetic PVC card but also to a thick card such as an IC card or an optical card.

FIG. 2 is a diagram showing an example in which a reversible thermosensitive recording label is pasted on an MD disk cartridge.
Further, the reversible thermosensitive recording label can be used in place of a display label on a disk cartridge having a built-in disk capable of rewriting storage information such as a flexible disk, MD, DVD-RAM and the like.
FIG. 3 is a diagram showing an example in which a reversible thermosensitive recording label is pasted on a CD-RW.
Further, in the case of a disc that does not use a disc cartridge such as a CD-RW, a reversible thermosensitive recording label can be directly attached to the disc, or a reversible thermosensitive recording layer can be provided directly on the disc.
By doing so, it is possible to apply to applications such as automatically changing display contents in accordance with changes in the stored contents.
The reversible thermosensitive recording label of the present invention can also be displayed by rewriting a part of the stored information additionally recorded on the CD-R by sticking the reversible thermosensitive recording label on a write-once disc such as a CD-R.

FIG. 4 is a diagram showing an example used as a display label of a video tape cassette.
Further, it may be used as a display label for a video tape cassette.
As a method of providing a thermoreversible recording function on a thick card, a disc cartridge, and a disc, in addition to the method of applying the reversible thermosensitive recording label, a method of directly applying a reversible thermosensitive recording layer on them, There is a method of forming a reversible thermosensitive recording layer on the support and transferring the thermosensitive recording layer onto a thick card, a disc cartridge, or a disc.
When transferring, an adhesive layer such as a hot melt type or an adhesive layer may be provided on the reversible thermosensitive recording layer.
When attaching a reversible thermosensitive recording label or providing a reversible thermosensitive recording layer on a rigid object such as a thick card, disk, disk cartridge, tape cassette, etc., improve the contact with the thermal head. In order to form an image uniformly, it is preferable to provide a cushioning layer or sheet between the rigid substrate and the label or the reversible thermosensitive recording layer.
FIG. 5 shows an example of the image processing apparatus according to the present invention. After the magnetic recording head on the back surface of the recording medium is read and written by the magnetic recording head facing the transport roller 40, the transport facing the ceramic heater 38 is performed. The surface of the recording medium is heated to the erasing temperature by the roller 40, and the image on the reversible thermosensitive recording part is erased. Next, an image is formed on the reversible thermosensitive recording portion by the transport roller 47 facing the thermal head 53.

  According to the present invention, it is possible to provide a highly practical reversible thermosensitive recording medium having good light resistance without providing a special ultraviolet absorbing layer by incorporating ultraviolet absorbing inorganic fine particles in the upper part of the recording layer. did it.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
In the text, “part” or “%” is based on weight unless otherwise specified.

Example 1
[Creation of thermal recording layer]
N- (4-hydroxyphenyl) -N'-octadecylurea 4 parts Acrylic polyol resin (LR503, 50% solid content solution manufactured by Mitsubishi Rayon Co., Ltd.) 12 parts Methyl ethyl ketone 70 parts The above composition was averaged to about 1 μm using a ball mill. Until dispersed. Zinc oxide fine particle dispersion (Sumitomo Osaka Cement Co., Ltd., ZS-303 particle size 30 nm, solid content concentration 30%) 10 parts, 2-anilino-3-methyl-6-dibutylaminofluorane 1.5 parts Then, 2.5 parts of Coronate HL (adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. were sequentially added and stirred well to prepare a thermal recording layer coating solution.
The thermal recording layer coating solution having the above composition was applied to white PET having a thickness of 188 μm using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to form a recording layer having a thickness of about 11.0 μm. Was provided.
[Create protection layer]
Acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd., 50% solid concentration solution) 10 parts isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate HX) 1.4 parts silicone-based acrylic resin (manufactured by Toagosei Co., Ltd., GS-1015) .5 parts methyl ethyl ketone 10 parts or more of the composition was thoroughly stirred to prepare a protective layer coating solution.
A protective layer coating solution having the above composition is applied onto the recording layer using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to provide a protective layer having a thickness of about 3.5 μm. The reversible thermosensitive recording medium of the invention was produced.

Example 2
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the amount of zinc oxide fine particles (particle size 30 nm) used in Example 1 was changed to 2 parts.

Example 3
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the amount of zinc oxide fine particles (particle diameter 30 nm) used in Example 1 was changed to 5 parts.

Example 4
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the addition amount of the zinc oxide fine particles (particle size 30 nm) used in Example 1 was changed to 20 parts.

Example 5
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the amount of zinc oxide fine particles (particle size 30 nm) used in Example 1 was changed to 30 parts.

Comparative Example 1
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the zinc oxide fine particles used in Example 1 were not used.

Comparative Example 2
Comparative Example 1 except that the following intermediate layer solution was applied on the recording layer produced in Comparative Example 1 to a thickness of 2 μm and dried to provide an ultraviolet absorbing layer, and then a protective layer was provided in the same manner as Comparative Example 1. In the same manner, a reversible thermosensitive recording medium was produced.
[Intermediate layer liquid]
Zinc oxide fine particles (ZS-303, manufactured by Sumitomo Osaka Cement Co., Ltd., particle size 30 nm, solid content 30%) 7 parts acrylic polyol resin (LR503, 50% solid content solution manufactured by Mitsubishi Rayon Co., Ltd.) 2 parts adduct type hexamethylene diisocyanate (Nippon Polyurethane Co., Ltd.) Coronate HL 75% ethyl acetate solution) 0.5 parts MEK 5 parts The reversible thermosensitive recording medium produced as described above was observed with an H-9000NAR transmission electron microscope manufactured by Hitachi, Ltd. It has been confirmed that all the reversible thermosensitive recording media have a large amount of fine zinc oxide particles on the upper portion of the recording layer. In particular, in Examples 1, 4, and 5, the surface of the recording layer is covered with the fine zinc oxide particles. Observed.
Next, with the above printing simulator, an image was printed under the condition of a voltage of 17 V, and the color density of the printed portion and the background density of the non-printed portion were measured using a Macbeth densitometer RD914.
Next, a color erasing operation was performed using a heat stamp under the condition of 120 ° C. for 1 second, and the color erasing density of the image area and the density of the background area were measured.
Evaluation of light-resistant storage stability: The written image was irradiated with light of 5000 lux for 100 hours under a fluorescent light source, and the density of the background after irradiation was measured.
The above results are shown in Table 1.

ビーコム社製印字シミュレーターを用い、パルス幅２．０ｍｓｅｃ、電圧１０〜１８Ｖで０．５Ｖ刻みで階調印字をおこなったところ、比較例２の記録媒体は、他の実施例１〜５や比較例１の記録媒体よりも熱感度が低いものであった。

When gradation printing was performed in increments of 0.5 V with a pulse width of 2.0 msec and a voltage of 10 to 18 V using a printing simulator manufactured by BCOM, the recording medium of Comparative Example 2 was the other Examples 1 to 5 and Comparative Examples. The thermal sensitivity was lower than that of recording medium No. 1.

The figure which shows the color development and decoloring characteristic of the reversible thermosensitive coloring composition of this invention. The figure which shows the example which stuck the reversible thermosensitive recording label on the disk cartridge of MD. The figure which shows the example which stuck the reversible thermosensitive recording label on CD-RW. The figure which shows the example used as a display label of a videotape cassette. 1 is a diagram illustrating an example of an image processing apparatus according to the present invention. Schematic of reversible thermosensitive recording medium of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultraviolet-absorbing inorganic fine particle 2 Reversible thermosensitive recording layer 3 Protective layer 4 Support body 34 Magnetic head 38 Ceramic heater 40 Conveying roller 47 Conveying roller 53 Thermal head

Claims (10)

  Containing a resin, an electron-donating color-forming compound, and an electron-accepting compound on the support, forming a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. In a reversible thermosensitive recording medium having at least a reversible thermosensitive recording layer and a protective layer, the reversible thermosensitive recording layer contains ultraviolet absorbing inorganic fine particles having a particle diameter of 10 nm to 100 nm, and the ultraviolet absorbing inorganic fine particles are A reversible thermosensitive recording medium comprising a relatively higher amount in the upper part than in the lower part of the reversible thermosensitive recording layer.   2. The reversible thermosensitive recording medium according to claim 1, wherein the ultraviolet-absorbing inorganic fine particles cover the surface portion of the recording layer.   2. The reversible thermosensitive recording medium according to claim 1, wherein the ultraviolet absorbing inorganic fine particles are contained in the reversible thermosensitive recording layer in an amount of 5 to 40% by weight. 4. The reversible thermosensitive recording medium according to claim 1, wherein the electron accepting compound is a phenol compound having a saturated aliphatic group having 8 or more carbon atoms represented by the following formula (1).

(Wherein, X ₁ and X ₂ represent a direct bond or a divalent group consisting of —NH—, —CO—, —SO ₂ —, —S—, wherein X ₁ and X ₂ are directly bonded simultaneously. It is never a hand.
R ₁ represents a divalent hydrocarbon group having 1 to 22 carbon atoms, and R ₂ represents a saturated aliphatic group having 8 to 30 carbon atoms. P represents an integer of 0 to 4, and R ₁ and X ₂ repeated when p is 2 to 4 may be the same or different. When p is 0, X ₁ is not a direct bond. Furthermore, q represents an integer of 1 to 3. )   An information display recording member, wherein the reversible thermosensitive recording medium according to claim 1 and an information storage unit are laminated.   A reversible thermosensitive recording label comprising an adhesive layer or a pressure-sensitive adhesive layer provided on the surface of the reversible thermosensitive recording medium according to any one of claims 1 to 4.   An image processing method comprising forming and / or erasing an image using the reversible thermosensitive recording medium according to claim 1.   The image processing method according to claim 7, wherein an image is formed on the reversible thermosensitive recording medium using a thermal head.   The image processing method according to claim 7, wherein the image is erased using a thermal head. An image processing apparatus, which is set so that an image can be formed and / or erased using the image processing method according to claim 7.

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