JP2000177246A - Reversible thermosensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermosensitive recording medium having good durability without nick of the medium even by a repeating use, good color developability, good preserving characteristics and good rapid erasability. SOLUTION: In the reversible thermosensitive recording medium comprising a reversible heat color developing composition capable for forming a relatively color developed state according to a difference of a heating speed and/or a cooling speed after heating by using an electron donative colorable compound and an electron acceptive compound on a support, an isocyante compound having an ether bond or an ester bond is used as a crosslinker for a resin in the recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound. The present invention relates to a reversible thermosensitive recording medium capable of forming and erasing.

[0002]

2. Description of the Related Art Conventionally, an electron-donating color-forming compound (hereinafter, referred to as an electron donating color compound)
Thermal recording media utilizing a color development reaction between a color former or a leuco dye and an electron-accepting compound (hereinafter also referred to as a developer) are widely known, such as facsimile machines, word processors, and scientific measuring instruments. Used in printers. However, these conventional recording media that have been put into practical use all have irreversible color development, and once recorded images cannot be erased and used repeatedly.

However, according to the patent publication, a recording medium capable of reversibly developing and decoloring has also been proposed. For example, Japanese Patent Application Laid-Open No. Sho 60-1985 uses a combination of gallic acid and phloroglucinol as a color developer. JP-A-1936991, JP-A-61-237684 using a compound such as phenolphthalein or thymolphthalein as a developer, and a recording layer containing a homogeneous compatibilizer of a color former, a developer and a carboxylic acid ester. JP-A-62-138556, JP-A-62-1
38568 and JP-A-62-140881, and JP-A-63-63163 using an ascorbic acid derivative as a developer.
JP-A-173684, JP-A-2-188293 and JP-A-2-18893 using a salt of bis (hydroxyphenyl) acetic acid or gallic acid and a higher aliphatic amine as a developer.
No. 188294 is disclosed.

Further, the present inventors have disclosed in Japanese Patent Laid-Open No.
Japanese Patent No. 24360 discloses an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having a long-chain aliphatic hydrocarbon group as a color developer, which is combined with a leuco dye as a color former to form a color. Colors can be easily performed by heating and cooling conditions, and the color development and decoloration states can be stably maintained at room temperature, and furthermore, color development and decoloration can be repeated stably. A reversible thermosensitive coloring composition and a reversible thermosensitive recording medium using the same in a recording layer have been proposed. Further, thereafter, it has been proposed to use a specific structure for a phenol compound having a long-chain aliphatic hydrocarbon group (Japanese Patent Application Laid-Open No. Hei 6 (1994) -186).
-210954).

[0005] Japanese Patent Application Laid-Open No. 7-52542,
-68933, JP-A-8-132735 and JP-A-8-132735
In each of JP-A-310128, JP-A-9-272262, JP-A-9-270563, JP-A-9-300817, and JP-A-9-300820, high-speed decolorization is performed by adding a specific decolorization accelerator. Improvements in characteristics have been proposed, but have problems such as insufficient erasability and poor image storability.

[0006] Further, printing / printing is repeatedly performed under actual use conditions.
When erasing is performed, problems such as a decrease in image density and dents (deformation of a printed portion) occur, and a reversible thermosensitive recording medium capable of sufficiently exhibiting the coloring and decoloring properties of the developer and leuco dye composition. Was not obtained. This is because printing with a thermal head is performed while applying mechanical force to the recording medium simultaneously with heating to a high temperature, so the structure of the layers that make up the recording medium, such as the recording layer and the protective layer, changes. It is due to being destroyed.

To cope with such a problem of the recording medium, Japanese Patent Application Laid-Open No. Hei 6-340171 proposes improvement of the repetition durability by adding particles having an average particle diameter of 1.1 times or more the thickness of the recording layer. Also, Japanese Patent Application Laid-Open No. 8-156410 proposes an improvement of the repetition durability by improving a head matching property by providing a protective layer having a specific glossiness and surface roughness. However, even if these recording layers and protective layers are used, it is not possible to completely prevent the destruction of the coating layer during repeated printing / erasing, and dents may occur on the surface of the recording medium due to repeated use. As a result, there is a problem that printing is poor and the number of times of repeated use is substantially limited to a small number.

Further, the conventional medium has a problem to be improved in terms of adapting to a wide range of use environments and the range of application of coloring and erasing conditions. For example, when the print image area and the background area are exposed to sunlight or fluorescent light for a long time, the print image area and the background area are discolored, and especially the print image area is completely erased even if the image is erased. However, there was a problem in light storage stability that an afterimage was generated. Even with the use of a phenol compound having a long-chain aliphatic hydrocarbon group (JP-A-6-210954), such a problem of light storage stability did not always bring a satisfactory result. Further, when the reversible thermosensitive recording medium is applied to a card, a display, or the like, no practical technology for forming a medium has been proposed.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reversible thermosensitive recording medium having good durability and having no dents on the recording medium even when used repeatedly. Further, it is another object of the present invention to provide a reversible thermosensitive recording medium having good color development characteristics and storage characteristics and good high-speed erasing characteristics.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve these problems, and as a result, have found that deterioration due to repeated use of a recording medium, that is, destruction of a coating film due to multiple printing / erasing operations. Has found that the recording layer is the largest, and that the heat resistance of the recording layer is improved, whereby the repetition durability of the recording medium is improved.

That is, according to the present invention, first, by using an electron-donating color-forming compound and an electron-accepting compound on a support, a relative difference in heating temperature and / or cooling rate after heating can be obtained. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer containing a reversible thermochromic composition capable of forming a colored state and a decolored state, an ether bond or an ester as a crosslinking agent for the resin in the recording layer A reversible thermosensitive recording medium characterized by using an isocyanate compound having a bond is provided. Secondly, there is provided the reversible thermosensitive recording medium described in the first aspect, wherein an acrylic polyol resin is used as the resin. Thirdly, there is provided the reversible thermosensitive recording medium according to the first or second aspect, wherein a phenol compound having an alkyl chain having 8 or more carbon atoms is used as the electron accepting compound. Fourth, the recording layer further contains a compound having a divalent group containing a hetero atom and an alkyl chain having 6 or more carbon atoms as a coloring / decoloring control agent. The present invention provides a reversible thermosensitive recording medium according to any one of the first to third aspects. Fifthly, the reversible thermosensitive recording medium according to any one of the first to fourth aspects, wherein the recording layer further contains a compound having a second amide group as a decolorizing accelerator. Is done. Sixth, there is provided the reversible thermosensitive recording medium according to any one of the first to fifth aspects, wherein a layer containing an inorganic or organic ultraviolet absorber is provided on the recording layer. Seventh, the reversible thermosensitive recording medium according to any one of the first to sixth aspects, wherein a layer using a resin in a crosslinked state is provided as a protective layer on the recording layer. . Eighth, the first to the above, which have a magnetic recording layer.
A reversible thermosensitive recording medium according to any one of the seventh to eleventh aspects is provided. Ninthly, there is provided the reversible thermosensitive recording medium according to any one of the first to eighth aspects, which is processed into a card shape or a sheet shape. Tenthly, there is provided the reversible thermosensitive recording medium according to any one of the first to ninth aspects, wherein the reversible thermosensitive recording medium has a printed portion on at least a part of the front surface and / or the back surface.

In the reversible thermosensitive recording medium of the present invention,
By making the reversible thermosensitive recording layer contain a resin in a cross-linked state by an isocyanate compound having an ether bond, the heat resistance of the recording layer is improved, and the repeated durability is improved. By providing a protective layer mainly composed of the crosslinked resin on the recording layer containing the crosslinked resin, the durability can be further improved. In addition, there is no powder drop or burrs at the time of cutting. Further, in the present invention, an isocyanate compound having an ether bond is used as a cross-linking agent for the resin, but by using an acrylic polyol resin as the resin at this time, a background density, a color developing property, a decoloring property, and excellent storage stability are obtained. Become.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reversible thermosensitive recording medium of the present invention will be described in detail below. The reversible thermosensitive recording medium of the present invention is characterized in that an isocyanate compound having an ether bond or an ester bond is used as a crosslinking agent for the resin in the reversible thermosensitive recording layer. Examples of the crosslinking agent used in the present invention include compounds obtained by copolymerizing glycols with hexamethylene diisocyanate, compounds obtained by copolymerizing glycols with a hexamethylene isocyanate compound having an isocyanurate bond, and the like. The crosslinking agent to be obtained is not limited to these, and includes an isocyanate compound having an ether bond and the like, and these are used alone or as a mixture. Further, in the present invention, when a mixture of two or more isocyanate compounds is used, hexamethylene diisocyanate, toluene diisocyanate, adduct type such as xylylene diisocyanate compound, buret type, isocyanurate type, block type and the like. Used.

Further, the resin used in the present invention includes:
Although a resin having a hydroxyl group is optionally used, an acrylic polyol resin is particularly preferably used. As the acrylic polyol resin, a copolymer containing styrene, methyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, or the like as a main component is preferably used. These resins and crosslinking agents are dyes, developers,
It is coated on a support together with a coloring and decoloring control agent and a decoloring accelerator to form a recording layer.

Further, according to the present invention, by using an electron-accepting compound, that is, a phenol compound having an alkyl chain having 8 or more carbon atoms as a color developer, a reversible heat-sensitive material having a good contrast between background density and coloring density. A recording medium can be obtained. Preferred examples of the color developer include a compound represented by the following general formula (1).

Embedded image

In the above formula, X ₁ represents a direct bond or an associative group, and X ₂ represents an associative group, wherein the associative groups are —O—, —S—, —NH—, _{-CO -, - SO 2 -,} -
It is a group having CS- or the like and capable of associating by hydrogen bonding within a molecule or between two or more molecules, and examples thereof include groups shown in Table 1 below.

[0017]

[Table 1]

In the general formula (1), R ₁ and R ₂ represent a hydrocarbon group. Here, R ₁ or R ₂ has a linear alkyl chain having 8 or more carbon atoms. At this time, R ₁
And R ₂ represent a hydrocarbon group which may have an aromatic group and may have an unsaturated bond. Also, R ₁ and R ₂
May be branched. Y represents a lower alkyl group, a lower alkoxyl group, or a halogen atom. Further, n is 1 to
3, 1 represents 0 to 3, and when 1 is 2 or more, Y may be the same or plural types, and m represents an integer of 0 to 4,
X ₂ and R ₂ repeated when m is 2 or more may be the same or different. Tables 2 and 3 show examples of preferred developers used in the present invention, but the present invention is not limited thereto.

[0019]

[Table 2]

[0020]

[Table 3]

Further, in the present invention, a color developer compound other than the phenolic compound, for example, a color reversible color developer such as thioureas and sulfonamides may be used. Also,
Color development by acid and base salts as reversible developer /
A developer in which decolorization is controlled may be used.

In the present invention, the use of a compound having a divalent group containing a hetero atom and a straight-chain alkyl group having 6 or more carbon atoms as a color-developing / discoloring controlling agent provides good stability of the colored portion. And excellent in high-speed erasability. In the present invention, the following general formulas (2) to
The compound represented by (4) can be used.

Embedded image

In the above formula, X _{3 to} X ₆ represent an associative group. Here, the associative groups are -O-, -S-, -NH-, -CO
_{-, - SO 2 -, -} CS- , etc. are groups capable of having associative by hydrogen bonding within or more between two molecules molecules have, similarly to Table 1 for X ₃ and X ₄ Groups. Further, Table 4 for X ₅ and X ₆
Are preferred examples.

[0024]

[Table 4]

In the above general formulas (2) to (4), R ₃
To R ₆ represent a hydrocarbon group, and have at least one straight-chain alkyl chain having 6 or more carbon atoms in the molecule. At this time, R _{3 to} R ₆
Represents a hydrocarbon group which may have an aromatic group and may have an unsaturated bond. R _{3 to} R ₆ may be branched. P represents an integer of 0 to _4, and X ₄ and R ₅ repeated when p is 2 or more may be the same or different. Table 5 shows examples of the coloring and decoloring controlling agents preferably used in the present invention, but the present invention is not limited to these.

[0026]

[Table 5]

In the present invention, it has been found that by using a compound having a secondary amide group as a decoloring accelerator, high-speed erasability is excellent. Furthermore, it has been found that by having a second amide group and an alkyl chain having 6 or more carbon atoms and / or an associative group, it is further improved. In this case, examples of the second amide group include groups represented by general formulas (5) to (7) below.

Embedded image

In the above formula, R ₇ to R ₁₁ represent a saturated or unsaturated hydrocarbon group which may have a substituent, and R ₇ and R ₈
May form a ring, the formed ring is a nitrogen atom,
It may be via an oxygen atom or a sulfur atom. further,
Examples of the hydrocarbon group which may have a substituent and is preferably used for R _{7 to} R ₁₁ may be straight-chain or branched, and include —O—, —S—, —CO—, and —COO. -It may be via a group. Further, it may have an aromatic ring or an aliphatic ring. Further, these groups may be substituted with a hydroxyl group, a halogen atom or the like. Here, the associative group is -O-,
-S -, - NH -, - CO -, - SO 2 -, - CS- , etc. a group capable of having associative by hydrogen bonding within or more between two molecules molecules have, for example, the following The groups shown in Table 6 are mentioned as preferred examples.

[0029]

[Table 6]

Tables 7 and 8 show preferred examples of the decolorizing accelerator used in the present invention. However, the decoloring accelerator used in the present invention is not limited to these compounds.

[0031]

[Table 7]

[0032]

[Table 8]

Further, in the present invention, by using an inorganic and / or organic ultraviolet absorber, discoloration and fading due to light irradiation can be prevented. UV absorbers
It is used for the recording layer, the protective layer, the undercoat layer, etc., but is preferably contained in the recording layer and the upper layer than the recording layer, and is also preferably contained in the intermediate layer provided between the protective layer and the recording layer. . As the ultraviolet absorber, inorganic and / or organic ultraviolet absorbers are widely used.

Specific examples of the inorganic ultraviolet absorber include, for example, zinc oxide, titanium oxide, cerium oxide, tin oxide, molybdenum oxide, gallium nitride, silica, alumina, antimony oxide, magnesium oxide, zirconium oxide, barium oxide, oxide Examples include calcium, strontium oxide, silicon nitride, aluminum nitride, boron nitride, barium sulfate, and the like.

Specific examples of the organic ultraviolet absorber include, for example, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-butylphenyl) Benzotriazole,
2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, (2′-hydroxy-5′-octoxyphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5
Chlorobenzotriazole, 2- (2'-hydroxy-
3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5 '
Benzotriazole-based UV absorbers such as -ethoxyphenyl) benzotriazole; 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyl Oxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxy −
2'-carboxybenzophenone, 2-hydroxy-4
-Oxybenzylbenzophenone, 2-hydroxy-4
-Chlorobenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-
Benzophenone ultraviolet absorbers such as sodium 4-methoxybenzophenone-5-sulfonate and sodium 2,2'-dihydroxy-4,4'-dimethoxybenzophenone-sulfonate; phenyl salicylate, p-octylphenyl salicylate, pt-butyl Phenyl salicylate, carboxyphenyl salicylate, methylphenyl salicylate, dodecylphenyl salicylate, 2
Salicylic acid ester ultraviolet absorbers such as -ethylhexylphenyl salicylate and homomenthylphenyl salicylate; 2-ethylhexyl-2-cyano-3,3'diphenylacrylate, ethyl-2-cyano-3,3 '
A cyanoacrylate-based ultraviolet absorber such as diphenyl acrylate; p-aminobenzoic acid, glyceryl p-aminobenzoate, amyl p-dimethylaminobenzoate, p-
P-aminobenzoic acid-based ultraviolet absorbers such as ethyl dihydroxypropyl benzoate; cinnamate-based ultraviolet absorbers such as p-methoxycinnamate-2-ethylhexyl and p-methoxycinnamate-2-ethoxyethyl; -T-butyl-
4'-methoxy-dibenzoylmethane, urocanic acid,
Ethyl urocanate and the like.

Further, in the reversible thermosensitive recording medium of the present invention, the durability can be further enhanced by providing a protective layer mainly composed of a crosslinked resin on the recording layer.

The resin in a cross-linked state is, for example, a combination of a cross-linking agent and a resin having an active group which reacts with the cross-linking agent, and is a resin which can be cross-linked and cured by heat. The resin used here has, for example, a resin having a group that reacts with a crosslinking agent such as a hydroxyl group, a carboxyl group, or a hydroxyl group, a carboxyl group, or the like, such as a phenoxy resin, a polyvinyl butyral resin, a cellulose acetate propionate, or a cellulose acetate butyrate. There is a resin in which a monomer is copolymerized with another monomer. Copolymer resins include, for example, resins of vinyl chloride type, acrylic type, styrene type and the like.
Vinyl alcohol copolymer, vinyl chloride-vinyl acetate-
Examples thereof include a hydroxypropyl acrylate copolymer and a vinyl chloride-vinyl acetate-maleic anhydride copolymer.

Examples of the crosslinking agent for thermal crosslinking include isocyanates, amino resins, amines, phenols, epoxy compounds and the like. For example, the isocyanates are polyisocyanate compounds having a plurality of isocyanate groups, specifically, hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), xylylene diisocyanate (XDI)
And adduct type, burette type, isocyanurate type and blocked isocyanates thereof with trimethylolpropane and the like. As the amount of the crosslinking agent added to the resin, the ratio of the functional group of the crosslinking agent to the number of active groups contained in the resin is 0.0
If it is less than this, the thermal strength is insufficient, and if it is added more than this, the coloring and decoloring properties are adversely affected. Further, a catalyst used in this type of reaction may be used as a crosslinking accelerator. As a crosslinking accelerator, for example, 1,4-diazabicyclo [2,2,
2] Tertiary amines such as octane; metal compounds such as organic tin compounds;

Next, examples of monomers used for curing with electron beams and ultraviolet rays include the following. Examples of monofunctional monomers Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, Cyclohexyl methacrylate, benzyl methacrylate, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl methyl methacrylate methyl chloride, diethylaminoethyl methacrylate, glycidyl methacrylate, methacrylic acid Acid tetrahydrofurfuryl, allyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene dimethacrylate Glycol, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, methacrylic acid, trimethylolpropane trimethacrylate, 2-ethoxyethyl methacrylate, 2-ethylhexyl acrylate, 2-ethoxyethyl acrylate , 2-ethoxyethoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, dicyclopentenylethyl acrylate, N-vinylpyrrolidone, vinyl acetate and the like.

Examples of difunctional monomers 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, tripropylene Glycol diacrylate, polypropylene glycol diacrylate, bisphenol A ethylene oxide adduct diacrylate, glycerin methacrylate acrylate, diacrylate of neopentyl glycol propylene oxide 2 mol adduct, diethylene glycol diacrylate, polyethylene glycol (400) diacrylate, hydroxypivalin Diacrylate of ester of acid and neopentyl glycol,
2,2-bis (4-acryloxydiethoxyphenyl)
Propane, diacrylate of neopentyl glycol diadipate, diacrylate of ε-caprolactone adduct of neopentyl glycol hydroxypivalate, 2
-(2-hydroxy-1,1-dimethylethyl) -5-
Hydroxymethyl-5-ethyl-1,3-dioxane diacrylate, tricyclodecane dimethylol diacrylate, ε-caprolactone adduct of tricyclodecane dimethylol diacrylate, diacrylate of glycidyl ether of 1,6-hexanediol, etc. .

Examples of polyfunctional monomers: Trimethylolpropane triacrylate, glycerin propylene oxide addition acrylate, trisacryloyloxyethyl phosphate, pentaerythritol acrylate, triacrylate of 3 moles of propylene oxide adduct of trimethylolpropane, dipentaerythritol. Polyacrylate, polyacrylate of caprolactone adduct of dipentaerythritol,
Dipentaerythritol triacrylate propionate, dimethylolpropane triacrylate modified with hydroxypivalaldehyde, tetraacrylate of dipentaerythritol propionate, pentaacrylate of ditrimethylolpropane tetraacrylate, pentaacrylate of dipentaerythritol propionate, dipentaerythritol hexaacrylate, dipentaerythritol Ε-caprolactone adduct of pentaerythritol hexaacrylate and the like.

Examples of oligomers Bisphenol A-diepoxyacrylic acid adducts and the like.

When crosslinking is carried out using ultraviolet rays, the following photopolymerization initiator and photopolymerization accelerator are used.
Examples of the photopolymerization initiator include benzoin ethers such as isobutyl benzoin ether, isopropyl benzoin ether, benzoin ethyl ether and benzoin methyl ether; 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime Α-acyloxime esters; benzyl ketals such as 2,2-dimethoxy-2-phenylacetophenone, benzyl, and hydroxycyclohexylphenyl ketone; diethoxyacetone phenone, 2-hydroxy-2-methyl-1-
Acetophenone derivatives such as phenylpropan-1-one; benzophenone, 1-chlorothioxanthone, 2-
Chlorothioxanthone, isopropylthioxanthone,
Ketones such as 2-methylthioxanthone and 2-chlorobenzophenone are exemplified. These photopolymerization initiators,
Used alone or in combination of two or more. The amount of addition is 0.1 to 1 part by weight of the monomer or oligomer.
The amount is preferably from 005 to 1.0 part by weight, more preferably from 0.01 to 0.5 part by weight.

As the photopolymerization accelerator, there are aromatic tertiary amines and aliphatic amines. Specific examples include p-dimethylaminobenzoic acid isoamyl ester and p-dimethylaminobenzoic acid ethyl ester. These photopolymerization accelerators are used alone or in combination of two or more. The addition amount is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 1 part by weight, based on 1 part by weight of the photopolymerization initiator.
３3 parts by weight.

As a light source for ultraviolet irradiation used in the present invention, there are a mercury lamp, a metal halide lamp, a gallium lamp, a mercury xenon lamp, a flash lamp, etc., and the above-mentioned photopolymerization initiator and photopolymerization accelerator absorb ultraviolet rays. A light source having an emission spectrum corresponding to the wavelength may be used. As the UV irradiation conditions, the lamp output and the transport speed may be determined according to the irradiation energy required for crosslinking the resin.

As the electron beam irradiation apparatus, either a scanning type or a non-scanning type may be selected according to the purpose such as an irradiation area and an irradiation dose. The irradiation condition is set to a dose necessary for crosslinking the resin. The electron flow, irradiation width, and transport speed may be determined accordingly.

In the present invention, another developer may be used in combination with the phenol compound. As a color developer used in combination, as disclosed in Japanese Patent Application Laid-Open No. 5-124360, together with typical examples of a phosphoric acid compound, a fatty acid compound and a phenol compound having a long-chain hydrocarbon group, a color is formed in the molecule. It is possible to use a compound having both a structure having a color developing ability capable of coloring the agent and a structure controlling the cohesive force between molecules. Hereinafter, the color developer used in the present invention will be specifically exemplified.

Examples of the organic phosphoric acid type developer include the following compounds. Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, ditetradecyl phosphate, dihexadecyl phosphate, phosphoric acid Dioctadecyl ester, dieicosyl phosphate,
Dibehenyl phosphate and the like.

Examples of the aliphatic carboxylic compound include the following compounds. 2-hydroxytetradecanoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecanoic acid, 2-hydroxyeicosanoic acid, 2-hydroxydocosanoic acid, 2-bromohexadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid 2-bromodocosanoic acid, 3-bromooctadecanoic acid, 3-bromodocosanoic acid, 2,3-dibromooctadecanoic acid,
Fluorododecanoic acid, 2-fluorotetradecanoic acid, 2
-Fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2-fluoroeicosanoic acid, 2-fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, par Fluorooctadecanoic acid and the like.

Examples of the aliphatic dicarboxylic acid and tricarboxylic acid compounds include the following compounds. 2
-Dodecyloxysuccinic acid, 2-tetradecyloxysuccinic acid, 2-hexadecyloxysuccinic acid, 2-octadecyloxysuccinic acid, 2-eicosyloxysuccinic acid, 2-dodecyloxysuccinic acid, 2-dodecylthiosuccinic acid, 2-tetradecylthiosuccinic acid, 2-hexadecylthiosuccinic acid, 2-octadecylthiosuccinic acid, 2
-Eicosylthiosuccinic acid, 2-docosylthiosuccinic acid, 2-tetracosylthiosuccinic acid, 2-hexadecyldithiosuccinic acid, 2-octadecyldithiosuccinic acid, 2
-Eicosyldithiosuccinic acid, dodecylsuccinic acid, tetradecylsuccinic acid, pentadecylsuccinic acid, hexadecylsuccinic acid, octadecylsuccinic acid, eicosylsuccinic acid, docosylsuccinic acid, 2,3-dihexadecylsuccinic acid, 2,3-dioctadecylsuccinic acid, 2-methyl-3
-Hexadecylsuccinic acid, 2-methyl-3-octadecylsuccinic acid, 2-octadecyl-3-hexadecylsuccinic acid, hexadecylmalonic acid, octadecylmalonic acid,
Eicosylmalonic acid, docosylmalonic acid, dihexadecylmalonic acid, dioctadecylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, 2-hexadecylglutaric acid, 2-octadecylglutaric acid, 2-eicosylglutaric acid, docosylglutaric Acid, 2-pentadecyl adipic acid, 2-octadecyl adipic acid, 2-eicosyl adipic acid, 2-docosyl adipic acid, 2-hexadecanoyloxypropane-1,2,3-tricarboxylic acid, 2-octadeca Noyloxypropane-1,2,
3-tricarboxylic acid and the like.

In the present invention, conventionally known leuco dyes can be used arbitrarily as the electron donating compound. In particular, leuco dyes represented by the following general formulas (8), (10) and (11) can be used. It is preferable to use at least one kind.

Embedded image [Wherein, R ₁₂ and R ₁₃ represent a lower alkyl group, an aryl group which may be substituted or a hydrogen atom, and further, R ₁₂ and R ₁₃
May bond to each other to form a ring. R ₁₄ represents a lower alkyl group, a halogen atom or a hydrogen atom;
₁₅ represents a lower alkyl group, a halogen atom, a hydrogen atom or a substituted anilino group represented by the following general formula (9).

Embedded image (Wherein, R ₁₆ represents a lower alkyl group or a hydrogen atom,
A represents a lower alkyl group or a halogen atom. Z is 0
Represents an integer of 1 to 3. )]

[0052]

Embedded image (In the formula, R _{17 to} R ₂₀ represent an alkyl group or a hydrogen atom, and R ₂₁ represents an alkyl group, an alkoxyl group, or a hydrogen atom.)

[0053]

Embedded image (In the formula, R _{22 to} R ₂₅ represent a lower alkyl group or a hydrogen atom, and R ₂₆ and R ₂₇ represent an alkyl group, an alkoxyl group, or a hydrogen atom.)

Examples of leuco dyes used in the present invention are shown below, but the present invention is not limited to these. 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6- (di-n-butylamino) fluoran, 2-anilino-3-methyl-6
-(Nn-propyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluoran, 2-anilino-3
-Methyl-6- (N-isobutyl-N-methylamino)
Fluoran, 2-anilino-3-methyl-6- (Nn
-Amyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-sec-butyl-N-methylamino) fluoran, 2-anilino-3-methyl-6
-(Nn-amyl-N-ethylamino) fluoran,
2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluoran, 2-anilino-3-
Methyl-6- (NN-propyl-N-isopropylamino) fluoran, 2-anilino-3-methyl-6
(N-cyclohexyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-ethyl-p
-Toluidino) fluoran, 2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluoran, 2
-(M-trichloromethylanilino) -3-methyl-6
-Diethylaminofluoran, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluoran, 2- (m-trichloromethylanilino) -3
-Methyl-6- (N-cyclohexyl-N-methylamino) fluoran, 2- (2,4-dimethylanilino)-
3-methyl-6-diethylaminofluoran, 2- (N
-Ethyl-p-toluidino) -3-methyl-6- (N-
Ethylanilino) fluoran, 2- (N-ethyl-p-
Toluidino) -3-methyl-6- (N-propyl-p-
Toluisino) Fluoran,

2-anilino-6- (Nn-hexyl-
N-ethylamino) fluoran, 2- (o-chloroanilino) -6-diethylaminofluoran, 2- (o-chloroanilino) -6-dibutylaminofluoran, 2-
(M-trifluoromethylanilino) -6-diethylaminofluoran, 2,3-dimethyl-6-dimethylaminofluoran, 3-methyl-6- (N-ethyl-p-toluidino) fluoran, 2-chloro- 6-diethylaminofluoran, 2-bromo-6-diethylaminofluoran, 2-chloro-6-dipropylaminofluoran,
3-chloro-6-cyclohexylaminofluoran, 3
-Bromo-6-cyclohexylaminofluoran, 2-
Chloro-6- (N-ethyl-N-isoamylamino) fluoran, 2-chloro-3-methyl-6-diethylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2- (o-chloroanilino ) -3
-Chloro-6-cyclohexylaminofluoran, 2-
(M-trifluoromethylanilino) -3-chloro-6
-Diethylaminofluoran, 2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluoran, 1,2-benzo-6-diethylaminofluoran,
3-diethylamino-6- (m-trifluoromethylanilino) fluoran,

3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-octyl-2-methylindole-3 -Yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4-azaphthalide, 3- (1
-Ethyl-2-methylindol-3-yl) -3-
(2-methyl-4-diethylaminophenyl) -7-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl)-
4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-Nn-amyl-N-
Methylaminophenyl) -4-azaphthalide, 3- (1
-Methyl-2-methylindol-3-yl) -3-
(2-hexyloxy-4-diethylaminophenyl)
-4-azaphthalide, 3,3-bis (2-ethoxy-4
-Diethylaminophenyl) -4-azaphthalide, 3,
3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,

As the electron-donating compound used in the present invention, that is, the color former, in addition to the above-mentioned fluoran compounds and azaphthalide compounds, conventionally known leuco dyes can be used alone or in combination. The coloring agent is shown below. 2- (p-acetylanilino) -6- (Nn-amyl-Nn-butylamino) fluoran, 2-benzylamino-6- (N-ethyl-p-toluidino) fluoran, 2-benzylamino -6- (N-methyl-2,4-
Dimethylanilino) fluoran, 2-benzylamino-
6- (N-ethyl-2,4-dimethylanilino) fluoran, 2-dibenzylamino-6- (N-methyl-p-
Toluidino) fluoran, 2-dibenzylamino-6
(N-ethyl-p-toluidino) fluoran, 2- (di-p-methylbenzylamino) -6- (N-ethyl-p
-Toluidino) fluoran, 2- (α-phenylethylamino) -6- (N-ethyl-p-toluidino) fluoran, 2-methylamino-6- (N-methylanilino)
Fluoran, 2-methylamino-6- (N-ethylanilino) fluoran, 2-methylamino-6- (N-propylanilino) fluoran, 2-ethylamino-6
(N-methyl-p-toluidino) fluoran, 2-methylamino-6- (N-methyl-2,4, -dimethylanilino) fluoran, 2-ethylamino-6- (N-ethyl-2,4, -Dimethylanilino) fluoran, 2-dimethylamino-6- (N-methylanilino) fluoran, 2-dimethylamino-6- (N-ethylanilino)
Fluoran, 2-diethylamino-6- (N-methyl-
p-Toluidino) fluoran, 2-diethylamino-6
-(N-ethyl-p-toluidino) fluoran, 2-dipropylamino-6- (N-methyl-anilino) fluoran, 2-dipropylamino-6- (N-ethyl-anilino) fluoran, 2-amino- 6- (N-methylanilino) fluoran, 2-amino-6- (N-ethylanilino) fluoran, 2-amino-6- (N-propylanilino) fluoran, 2-amino-6- (N-methyl-
p-Toluidino) fluoran, 2-amino-6- (N-
Ethyl-p-toluidino) fluoran, 2-amino-6
-(N-propyl-p-toluidino) fluoran, 2-
Amino-6- (N-methyl-p-ethylanilino) fluoran, 2-amino-6- (N-ethyl-p-ethylanilino) fluoran, 2-amino-6- (N-propyl-p-ethylanilino) fluoran, 2 -Amino-6-
(N-methyl-2,4-dimethylanilino) fluoran, 2-amino-6- (N-ethyl-2,4-dimethylanilino) fluoran, 2-amino-6- (N-propyl-2,4 -Dimethylanilino) fluoran, 2-amino-6- (N-methyl-p-chloroanilino) fluoran, 2-amino-6- (N-ethyl-p-chloroanilino) fluoran, 2-amino-6- (N- Propyl-p
-Chloroanilino) fluorane, 1,2-benzo-6-
(N-ethyl-N-isoamylamino) fluoran,
1,2-benzo-6-dibutylaminofluoran,
2-benzo-6- (N-methyl-N-cyclohexylamino) fluoran, 1,2-benzo-6- (N-ethyl-toluidino) fluoran, and others.

Specific examples of other color formers preferably used in the present invention are as follows. 2-anilino-3-methyl-6- (N-2-ethoxypropyl-N
-Ethylamino) fluoran, 2- (p-chloroanilino) -6- (Nn-octylamino) fluoran, 2
-(P-chloroanilino) -6- (Nn-palmitylamino) fluoran, 2- (p-chloroanilino) -6
-(Di-n-octylamino) fluoran, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluoran, 2- (o-methoxybenzoylamino) -6
(N-methyl-p-toluidino) fluoran, 2-dibenzylamino-4-methyl-6-diethylaminofluoran, 2-dibenzylamino-4-methoxy-6- (N
-Methyl-P-toluidino) fluoran, 2-benzylamino-4-methyl-6- (N-ethyl-P-toluidino) fluoran, 2- (α-phenylethylamino)-
4-methyl-6-diethylaminofluoran, 2- (p
-Toluidino) -3- (t-butyl) -6- (N-methyl-p-toluidino) fluoran, 2- (o-methoxycarbonylamino) -6-diethylaminofluoran,
2-acetylamino-6- (N-methyl-p-toluidino) fluoran, 4-methoxy-6- (N-ethyl-p
-Toluidino) fluoran, 2-ethoxyethylamino-3-chloro-6-dibutylaminofluoran, 2-dibenzylamino-4-chloro-6- (N-ethyl-p-
Toluidino) fluoran, 2- (α-phenylethylamino) -4-chloro-6-diethylaminofluoran,
2- (N-benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluoran, 2
-Anilino-3-methyl-6-pyrrolidinofluoran,
2-anilino-3-chloro-6-pyrrolidinofluoran, 2-anilino-3-methyl-6- (N-ethyl-N
-Tetrahydrofurfurylamino) fluoran, 2-mesidino-4 ', 5'-benzo-6-diethylaminofluoran, 2- (m-trifluoromethylanilino) -3
-Methyl-6-pyrrolidinofluoran, 2- (α-naphthylamino) -3,4-benzo-4′-bromo-6
(N-benzyl-N-cyclohexylamino) fluoran, 2-piperidino-6-diethylaminofluoran,
2- (Nn-propyl-p-trifluoromethylanilino) -6-morpholinofluoran, 2- (di-N-
p-chlorophenyl-methylamino) -6-pyrrolidinofluoran, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpholinofluoran,
1,2-benzo-6- (N-ethyl-Nn-octylamino) fluoran, 1,2-benzo-6-diallylaminofluoran, 1,2-benzo-6- (N-ethoxyethyl-N -Ethylamino) fluoran,

Benzoleucomethylene blue, 2- [3,
6-bis (diethylamino)]-6- (o-chloroanilino) xanthylbenzoate lactam, 2- [3,6-bis (diethylamino)]-9- (o-chloroanilino)
Lactam xanthylbenzoate, 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-
Dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-
Bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3- (2 -Methoxy-
4-dimethylaminophenyl) -3- (2-hydroxy-4,5-dichlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-
Methoxy-5-chlorophenyl) phthalide, 3- (2-
(Hydroxy-4-dimethoxyaminophenyl) -3-
(2-methoxy-5-chlorophenyl) phthalide, 3-
(2-hydroxy-4-dimethylaminophenyl) -3
-(2-methoxy-5-nitrophenyl) phthalide, 3
-(2-hydroxy-4-diethylaminophenyl)-
3- (2-methoxy-5-methylphenyl) phthalide,
3- (2-methoxy-4-dimethylaminophenyl)-
3- (2-hydroxy-4-chloro-5-methoxyphenyl) phthalide, 3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'-dimethylaminophthalide, 6'-chloro-8 '-Methoxy-benzoindolino-spiropyran, 6'-bromo-2'-methoxy-benzoindolino-spiropyran, and others.

The reversible thermosensitive recording medium of the present invention can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. The basic coloring / decoloring phenomenon of the composition comprising the color former and the developer used in the present invention will be described. FIG. 1 shows the relationship between the color density and the temperature of the recording medium. When the temperature of the recording medium in the decolored state (A) is increased at _first , coloring occurs at the temperature T1 at which the recording medium starts to be melted, and the state changes to the molten color developing state (B). When the color is rapidly cooled from the molten color-developed state (B), the temperature can be lowered to room temperature while maintaining the color-developed state, and a solid color-developed state (C) is obtained. Whether or not this coloring state can be obtained depends on
It depends on the rate of temperature drop from the molten state. In slow cooling, decoloration occurs in the process of temperature drop, and the state in which the density is relatively lower than the initial decolored state (A) or rapidly cooled color developing state (C) It is formed. On the other hand, if rapidly cooled colored state (C) is going again heated, discoloring occurs at lower than the coloring temperature the temperature T ₂ (E from D), when the temperature is lowered from this, the same colorless state including (A) Return. The actual color development temperature and decolorization temperature vary depending on the combination of the color developer and color developer used, and can be selected according to the purpose. Further, the density in the molten color-developing state and the color density after quenching are not always the same, and may be different.

In the recording medium of the present invention, the color-developed state (C) obtained by quenching from the molten state is a state in which the developer and the color-developing agent are mixed in a state where they can react with each other between molecules. It often forms a solid state. This state is a state in which the color developer and the color forming agent aggregate to maintain the color development, and it is considered that the color formation is stabilized by the formation of the aggregate structure. On the other hand, the decolored state is a state where both are phase-separated. This state is a state in which molecules of at least one compound are aggregated to form a domain or crystallized, and a state in which the color former and the developer are separated and stabilized by aggregation or crystallization. Conceivable. In many cases, the present invention causes more complete decoloration due to phase separation of the two and crystallization of the color developer. The decoloring by gradual cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG.
In each case, the aggregation structure changes at this temperature, and phase separation and crystallization of the color developer have occurred.

The formation of color recording on the reversible thermosensitive recording medium of the present invention may be performed by heating the mixture to a temperature at which the mixture is melted and mixed by a thermal head or the like and then rapidly cooling the mixture. The decoloring is performed by two methods: a method of gradually cooling from a heating state and a method of heating to a temperature slightly lower than a coloring temperature. However, they are the same in the sense that they both phase-separate or temporarily hold at a temperature at which at least one crystallizes. The rapid cooling in the formation of a color-developed state is for preventing the phase separation temperature or the crystallization temperature from being maintained. Here, the rapid cooling and the slow cooling are relative to one composition, and the boundary changes depending on the combination of the color former and the developer.

The ratio of the color former to the color developer varies in an appropriate range depending on the combination of the compounds used, but the color developer is generally in the range of 0.1 to 20 with respect to the color developer 1 in a molar ratio. Preferably it is in the range of 0.2 to 10. If the amount of the developer is smaller or larger than this range, the density of the color-developed state is reduced, which is problematic. Further, the ratio of the coloring / decoloring control agent is preferably from 0.1% by weight to 300% by weight, more preferably from 3% by weight to 100% by weight, based on the developer. Further, the color former and the developer can be used by being encapsulated in microcapsules.

The ratio of the color-forming component and the resin in the recording layer of the present invention is preferably from 0.1 to 10 with respect to the color-forming component 1. If the ratio is less than this, the thermal strength of the recording layer becomes insufficient. Is a problem because the color density is lowered.

The recording layer is formed by uniformly mixing and dispersing the above-mentioned mixture of the color developer, the color former, the color erasure accelerator, the color elimination control agent, the cross-linked resin and the coating solution solvent. Use the applied coating solution. Specific examples of the solvent used for preparing the coating liquid include water; alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, Ketones such as cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; diethyl ether, isopropyl ether;
Ethers such as tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran; glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; 2-methoxyethyl Glycol ether acetates such as acetate, 2-ethoxyethyl acetate, and 2-butoxyethyl acetate;
Esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and ethylene carbonate; aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as hexane, heptane, iso-octane and cyclohexane And methylene chloride, 1,
Halogenated hydrocarbons such as 2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone;
Examples thereof include pyrrolidones such as N-octyl-2-pyrrolidone.

The coating liquid for the recording layer can be adjusted using a known coating liquid dispersing apparatus such as a paint shaker, a ball mill, an attritor, a three-roll mill, a Keddy mill, a sand mill, a dyno mill, and a colloid mill. In addition, each material may be dispersed in a solvent using the above-described coating liquid dispersion device, or each material may be dispersed alone in the solvent and mixed. Further, it may be heated and dissolved to precipitate by rapid cooling or cooling.

The coating method for providing the recording layer is not particularly limited, and includes blade coating, wire bar coating, spray coating, air knife coating, bead coating, curtain coating, gravure coating, kiss coating, and the like. A known method can be used. The thickness of the recording layer is preferably in the range of 1 μm to 20 μm, and more preferably in the range of 2 μm to 15 μm.

The method for drying and curing the recording layer is as follows:
A curing treatment is performed if necessary. As long as it can be crosslinked by heat, the heat treatment may be performed at a relatively high temperature for a short time using a high temperature bath or the like, or the heat treatment may be performed at a relatively low temperature for a long time. In the case of ultraviolet curing and electron beam curing, a known curing device may be used. For example, as a light source at the time of ultraviolet irradiation, there are a mercury lamp, a metal halide lamp, a gallium lamp, a mercury xenon lamp, a flash lamp, etc., corresponding to the ultraviolet absorption wavelength of a photopolymerization initiator and a photopolymerization accelerator arranged in advance. A light source having an emission spectrum may be used. As the UV irradiation conditions, the lamp output and the transport speed may be determined according to the irradiation energy required for crosslinking the resin. Further, as the electron beam irradiation device, either a scanning type or a non-scanning type may be selected according to the purpose such as an irradiation area and an irradiation dose, and the irradiation condition may be selected according to a dose required for crosslinking the resin. The flow, irradiation width, and transport speed may be determined. The thickness of the recording layer is 1 to 20
The range of μm is preferred, and more preferably 3 to 10 μm.

The support of the reversible thermosensitive recording medium of the present invention is paper, resin film, synthetic paper, metal foil, glass or a composite thereof, and may be any as long as it can hold the recording layer.

In the reversible thermosensitive recording medium of the present invention, an additive for improving or controlling the coating characteristics and the coloring and decoloring characteristics of the recording layer can be used, if necessary. These additives include, for example, surfactants, conductive agents, fillers, antioxidants, light stabilizers, color stabilizers, and the like.

The reversible thermosensitive recording medium of the present invention basically comprises a recording layer containing the above-mentioned crosslinked resin on a support,
A protective layer containing a resin in a cross-linked state is further provided as necessary.However, in order to improve the characteristics as a recording medium, an adhesive layer, an intermediate layer, an undercoat layer, a back coat layer, and the like are provided. Can be. Further, a magnetic recording layer may be provided. Further, each of the above-mentioned layers and the support may be colored with a coloring agent. The recording medium may be partially or entirely colored by, for example, printing. Further, a colorless or light-colored print protection layer containing a resin as a main component may be provided on the colored print layer.

Examples of the resin used for the protective layer include polyvinyl alcohol, styrene-maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin, and urea-formaldehyde resin, in addition to the above-mentioned crosslinked resin. . The thickness of the protective layer is 0.1
The range is preferably from 20 to 20 μm, more preferably from 0.3 to
10 μm.

An intermediate layer is provided between the recording layer and the protective layer for the purpose of improving adhesion between the recording layer and the protective layer, preventing deterioration of the recording layer due to application of the protective layer, and preventing transfer of additives in the protective layer to the recording layer. It is also preferred. In order to effectively use the applied heat, a heat insulating undercoat layer can be provided between the support and the recording layer. The heat insulating layer can be formed by applying organic or inorganic fine hollow particles using a binder resin. An undercoat layer may be provided for the purpose of improving the adhesion between the support and the recording layer and preventing the penetration of the recording layer material into the support. The same resin as the above-mentioned resin for the recording layer can be used for the intermediate layer and the undercoat layer.

A filler may be added to the undercoat layer, the recording layer, the intermediate layer, and the protective layer. The filler can be divided into an inorganic filler and an organic filler. As the inorganic filler, carbonates such as calcium carbonate and magnesium carbonate; silicates such as silicic anhydride, hydrous silicic acid, hydrous aluminum silicate and hydrous calcium silicate; hydroxides such as alumina and iron oxide; zinc oxide , Indium oxide, alumina, silica, zirconia oxide, tin oxide, cerium oxide, iron oxide, antimony oxide, barium oxide, calcium oxide, barium oxide, bismuth oxide, nickel oxide, magnesium oxide, chromium oxide, manganese oxide, tantalum oxide, Niobium oxide, thorium oxide, hafnium oxide, molybdenum oxide, iron ferrite,
Metal oxides such as nickel ferrite, cobalt ferrite, barium titanate and potassium titanate; metal sulfides and sulfate compounds such as zinc sulfide and barium sulfate; titanium carbide, silicon carbide, molybdenum carbide, tungsten carbide and tantalum carbide Metal nitrides such as aluminum nitride, silicon nitride, boron nitride, zirconium nitride, vanadium nitride, titanium nitride, niobium nitride, and gallium nitride. As organic filler,
Silicone resin, cellulose resin, epoxy resin, nylon resin, phenolic resin, polyurethane resin, urea resin, melamine resin, polyester resin, polycarbonate resin, styrene resin such as styrene, polystyrene, polystyrene / isoprene, styrene vinylbenzene, vinylidene chloride And acrylic resins such as acrylic urethane and ethylene acrylic; polyethylene resins; formaldehyde resins such as benzoguanamine formaldehyde and melamine formaldehyde; polymethyl methacrylate resins; and vinyl chloride resins.
In the present invention, the organic filler may be used alone, but may be contained in two or more types, or may be a composite particle. Examples of the shape include a spherical shape, a granular shape, a plate shape, and a needle shape. The content of the filler in the layer was 1 volume fraction.
~ 95%, more preferably 5-75%.

A lubricant may be added to the undercoat layer, the recording layer, the intermediate layer, and the protective layer. Specific examples of the lubricant include synthetic waxes such as ester wax, paraffin wax and polyethylene wax: hardened castor oil and the like. Vegetable waxes: animal waxes such as hardened tallow oil:
Higher alcohols such as stearyl alcohol and behenyl alcohol: higher fatty acids such as margaric acid, lauric acid, mystyrenic acid, palmitic acid, stearic acid, behenic acid, and furomenic acid: higher fatty acid esters such as fatty acid esters of sorbitan: stearamide And amides such as oleic acid amide, lauric acid amide, ethylenebisstearic acid amide, methylenebisstearic acid amide, and methylolstearic acid amide. The content of the lubricant in the layer is 0.1 to 95% by volume fraction,
More preferably, it is 1 to 75%.

Solvents used for coating liquids for the middle layer and the protective layer,
As the coating liquid dispersing apparatus, coating method, drying / curing method, and the like, known methods used for the recording layer can be used.

In order to form a color image using the reversible thermosensitive recording medium of the present invention, the color image is heated once to the color development temperature and then rapidly cooled. In particular,
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 rapid cooling occurs, so that the coloring state can be fixed. On the other hand, in order to erase the color, heating may be performed by using an appropriate heat source for a relatively long time to cool, or heating may be temporarily performed to a temperature slightly lower than the coloring temperature. If the recording medium is heated for a long time, the temperature of a wide area of the recording medium rises, and the subsequent cooling is slowed down. As a heating method in this case, a heat roller, a heat stamp, hot air, 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 decoloring temperature range, the applied energy may be slightly reduced from that at the time of recording, for example, by adjusting the applied voltage and the pulse width to the thermal head. With this method, recording and erasing can be performed only with the thermal head, and so-called overwriting can be performed. Of course, heat roller,
It can also be erased by heating to the decoloring temperature range by a heat stamp.

The reversible thermosensitive recording medium of the present invention is formed by holding the recording layer on the above-mentioned support. The support used at this time has a thickness as required. They can be used alone or bonded together. That is, a support having an arbitrary thickness from about several μm to about several mm is used. Further, these supports may have a magnetic recording layer on the same side and / or the opposite side as the reversible thermosensitive recording layer. The reversible thermosensitive recording medium of the present invention may be attached to another medium via an adhesive layer or the like. The reversible thermosensitive recording medium of the present invention may be processed into a sheet shape or a card shape, the shape can be processed into any shape, and the medium can be printed. Further, the reversible thermosensitive recording medium of the present invention may use an irreversible thermosensitive recording layer in combination. At this time, the color tone of each recording layer may be the same or different.

[0079]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” and “%” are based on weight.

Example 1 1) 2 parts of 2-anilino-3-methyl-6-dibutylaminofluoran 2) 8 parts of a developer having the following structure

Embedded image 3) 70% of a 15% tetrahydrofuran (THF) solution of an acrylic polyol resin The above composition was averaged in a particle size of 0.1 to 3 µ using a ball mill.
m. To the resulting dispersion was added 10 parts of a hexamethylene diisocyanate-based crosslinking agent having an ester bond, and the mixture was stirred well to prepare a recording layer coating solution. The recording layer coating solution having the above composition was applied to a 188 μm-thick polyester film using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to obtain a film thickness of about 8.0 μm.
Was provided to produce a reversible thermosensitive recording medium of the present invention.

The reversible thermosensitive recording medium produced as described above was printed at a voltage of 13.3 V and a pulse width of 1.2 msec with a thermal printing apparatus manufactured by Okura Electric Co., Ltd., and the obtained image was recorded with a Macbeth densitometer RD-914. It was measured. The color density was 0.98. The density of the color image was measured using a thermal gradient tester manufactured by Toyo Seiki Co., Ltd. at 130 ° C. for 1 second, and the density was measured in the same manner. Print and erase the above 3
When it was repeated 0 times, it was in a good state without dents.

Example 2 A hexamethylene diisocyanate-based crosslinking agent having an ether bond was used in place of the crosslinking agent in Example 1,
A reversible thermosensitive recording medium was produced in the same manner as in Example 1.
The reversible thermosensitive recording medium produced as described above was colored and decolored in the same manner as in Example 1, and the density was measured and the state of the dents was observed. As a result, the coloring density was 0.94 and the erasing density was 0.11. No dents were found.

Example 3 Example 1 was repeated except that the dispersion of Example 1 was changed to the following composition.
A reversible thermosensitive recording medium was obtained in the same manner as described above. 1) 2-anilino-3-methyl-6-dibutylaminofluorane 2 parts 2) Color developer having the following structure 8 parts

Embedded image 3) Color-decoloring control agent having the following structure: 3 parts CH_Three(CH_Two)_Four-NHCONH- (CH_Two)₁₇CH_Three  4) 70 parts of 15% tetrahydrofuran (THF) solution of acrylic polyol resin

The reversible thermosensitive recording medium produced as described above was colored in the same manner as in Example 1 and the density was measured. The result was 1.02. Next, the density was measured by erasing in the same manner as in Example 1 except that the temperature was changed to 110 ° C., and it was 0.11. When the above coloring and decoloring were repeated 30 times, no dents were found. Also. The image retention after storing the recording medium colored by the above method in an environment of 50 ° C. for 24 hours was 82%. The concentration retention was calculated by the following equation.

(Equation 1)

Example 4 Example 1 was repeated except that the dispersion of Example 1 was changed to the following composition.
A reversible thermosensitive recording medium was obtained in the same manner as described above. 1) 2-anilino-3-methyl-6-dibutylaminofluorane 2 parts 2) Color developer having the following structure 8 parts

Embedded image 3) 2 parts of decolorization accelerator having the following structure

Embedded image 4) Color-decoloring control agent having the following structure: 3 parts CH_Three(CH_Two)_Four-NHCONH- (CH_Two)₁₇CH_Three  5) 70 parts of 15% tetrahydrofuran (THF) solution of acrylic polyol resin

The reversible thermosensitive recording medium produced as described above was colored and decolored in the same manner as in Example 3, and the color density and decolor density were measured. As a result, the image density was 1.
01, and the decoloring density was 0.10. When printing and erasing were repeated in the same manner as in Example 3, no dents were found. The concentration retention rate at 50 ° C. is 88%.
Met.

Example 5 A protective layer having the following composition was provided on the recording layer prepared in Example 4 to prepare a reversible thermosensitive recording medium. [Preparation of Protective Layer] 1) Urethane acrylate-based UV-curable resin (C7-157, manufactured by Dainippon Ink and Chemicals, Inc.) 15 parts 2) Ethyl acetate 85 parts The above composition was dissolved and stirred well to prepare a protective layer coating solution. The protective layer coating solution having the above composition is coated on the recording layer using a wire bar, dried at 90 ° C. for 1 minute, and passed under an ultraviolet lamp having an irradiation energy of 80 W / cm at a transport speed of 9 m / min. After curing, a protective layer having a thickness of 3 μm was provided to prepare a reversible thermosensitive recording medium of the present invention.

When the reversible thermosensitive recording medium produced as described above was repeated 50 times under the coloring and erasing conditions of Example 3, the reversible thermosensitive recording medium of the present example had no dents or the like. And good color development and decoloring density were maintained.

Example 6 An intermediate layer having the following composition was provided on the recording layer prepared in Example 4. [Preparation of Intermediate Layer] Acrylic polyol resin 15% methyl ethyl ketone (MEK) solution 30 parts (2-hydroxy-4-n-octoxy) benzophenone 4 parts (Viosorb 130 manufactured by Kyodo Chemical Co., Ltd.) Coronate HL 4 parts And apply at 100 ° C for 2 hours.
After drying for 60 minutes, the film is heated at 60 ° C. for 24 hours to have a thickness of about 2 μm.
Was provided. Next, a protective layer was provided in the same manner as in Example 5 to obtain a reversible thermosensitive recording medium of the present invention.

After the reversible thermosensitive recording medium produced as described above was colored under the same coloring conditions as in Example 3, the fluorescent lamp 50 was used.
Irradiation at 100 lux for 100 hours, and then erasing under the same erasing conditions as in Example 3 and examining the deterioration due to light,
No change was observed in the image area after light irradiation, and the image was in a good state without any erasure after erasure.

Comparative Example 1 The following color developer was used in place of the color developer and the decolorization accelerator in Example 1, except that the decolorization accelerator was not used.
In the same manner as in the above, a reversible thermosensitive recording medium was produced. Color developer

Embedded image

The reversible thermosensitive recording medium produced as described above was subjected to color development and color erasing in the same manner as in Example 3, and the color development density and the color erasure density were measured. As a result, the image density becomes 0.
At 98, the decoloring density was 0.20. Further, Example 3
The image retention after storage for 24 hours in a 50 ° C. environment was measured in the same manner as in the above, and it was 32%.

Comparative Example 2 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following decolorization accelerator was used instead of the decolorization accelerator in Example 1. Decoloring accelerator

Embedded image

The reversible thermosensitive recording medium produced as described above was colored and decolored in the same manner as in Example 3, and the color density and the decolor density were measured. As a result, the image density was 0.9.
In No. 6, the decoloring density was 0.18. Further, the image retention after storage in a 50 ° C. environment for 24 hours in the same manner as in Example 3 was 52%.

Comparative Example 3 A vinyl chloride-vinyl acetate resin (VYHH manufactured by Union Carbide) was used instead of the acrylic polyol resin used in Example 10.
A recording layer was prepared using 120 parts of a 15% MEK solution without using a cross-linking agent, and then a polyvinyl chloride-vinyl acetate resin (VY manufactured by Union Carbide Co., Ltd.) was used instead of the protective layer used in Example 5.
Using a MEK solution of HH), a reversible thermosensitive recording medium was produced in the same manner as in Example 5 except that a protective layer having a thickness of about 3 μm was provided by drying at 100 ° C. for 3 minutes.

When the reversible thermosensitive recording medium produced as described above was repeated 50 times under the coloring and erasing conditions of Example 5, the reversible thermosensitive recording medium was large and uniform in image color formation such as formation of dents. And could not be erased.

[0097]

The reversible thermosensitive recording medium of the present invention has excellent durability, and further has excellent coloring properties, high-speed erasability, storage stability and light resistance.

[Brief description of the drawings]

FIG. 1 is a diagram showing color development / decoloration characteristics of a reversible thermosensitive recording medium of the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B41M 5/18 101C 101E 109 (72) Inventor Hiromi Furuya 1-3-6 Nakamagome, Ota-ku, Tokyo Stock F-term in Ricoh Company (reference) 2H026 AA07 AA09 AA28 BB01 BB25 BB28 BB32 CC07 DD03 DD15 DD43 DD53 DD55 FF11 FF25 GG01 4F100 AH02B AH03B AH03H AK01B AK25B AK41 AR00C AR00E AS00 BA30BBA00A00 BA00BA07A00

Claims (10)

[Claims] Claims 1. An electron-donating color-forming compound and an electron-accepting compound are used on a support to form a relatively colored state and a decolored state due to a difference in heating temperature and / or cooling rate after heating. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer containing a reversible thermochromic composition that can be formed,
A reversible thermosensitive recording medium characterized by using an isocyanate compound having an ether bond or an ester bond as a crosslinking agent for the resin in the recording layer. 2. The reversible thermosensitive recording medium according to claim 1, wherein an acrylic polyol resin is used as the resin. 3. The method according to claim 1, wherein the electron accepting compound has 8 carbon atoms.
3. The reversible thermosensitive recording medium according to claim 1, wherein a phenol compound having the above alkyl chain is used. 4. The recording layer according to claim 1, further comprising a compound having a divalent group containing a hetero atom and an alkyl chain having 6 or more carbon atoms as a coloring / erasing control agent. 4. The reversible thermosensitive recording medium according to any one of 3. 5. The reversible thermosensitive recording medium according to claim 1, wherein the recording layer further contains a compound having a second amide group as a color erasure accelerator. 6. The reversible thermosensitive recording medium according to claim 1, wherein a layer containing an inorganic or organic ultraviolet absorber is provided on the recording layer. 7. The recording medium according to claim 1, wherein a layer using a crosslinked resin is provided as a protective layer on the recording layer.
7. A reversible thermosensitive recording medium according to any one of claims 6 to 6. 8. The reversible thermosensitive recording medium according to claim 1, further comprising a magnetic recording layer. 9. The reversible thermosensitive recording medium according to claim 1, which is processed into a card shape or a sheet shape. 10. A printed portion is provided on at least a part of the front surface and / or the back surface.
10. The reversible thermosensitive recording medium according to any one of 9.