JP2001113829A - Reversible heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible heat-sensitive recording material for forming and erasing with good contrast an image and retaining the image stabilized with time under the environment of daily life. SOLUTION: A reversible heat-sensitive recording material contains usually a colorless or light color electron donative dye precursor and also at least one kind of compounds represented, for instance, by the formula as an electron acceptive compound generating the reversible tone variation for the dye precursor by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording material capable of forming and erasing an image by heating.

[0002]

2. Description of the Related Art A thermosensitive recording material generally comprises a support provided with a thermosensitive recording layer mainly comprising an electron-donating usually colorless or pale-color dye precursor and an electron-accepting developer. By heating with a thermal head, a hot pen, a laser beam or the like, the dye precursor and the color developer react instantaneously to obtain a recorded image. Japanese Patent Publication Nos. 43-4160 and 45-160
It is disclosed in, for example, Japanese Patent Publication No. 14039.

In general, it is impossible for such a heat-sensitive recording material to form an image once and erase that portion and return to the state before image formation. There was no choice but to add to the formation. For this reason, when the area of the heat-sensitive recording portion is limited, there has been a problem that the recordable information is limited and all necessary information cannot be recorded.

In recent years, reversible thermosensitive recording materials capable of repeatedly forming and erasing images have been devised to address such problems. For example, JP-A-54-119377 and JP-A-63-119377 disclose a reversible thermosensitive recording material. 39377, JP-A-63-4
Japanese Patent No. 1186 describes a heat-sensitive recording material composed of a resin base material and an organic low-molecular compound dispersed in the resin base material. However, in this method, the transparency of the heat-sensitive recording material is reversibly changed by heat energy, so that the contrast between the image forming portion and the non-image forming portion is insufficient.

In the methods described in Japanese Patent Application Laid-Open Nos. 50-81157 and 50-105555, since the image to be formed changes according to the environmental temperature, the image forming state and the erasing state are changed. Are different from each other, and these two states cannot be maintained for an arbitrary period at room temperature.

Further, Japanese Patent Application Laid-Open No. Sho 59-120492 discloses that an image forming state is controlled by keeping a recording material in a hysteresis temperature range by utilizing a hysteresis characteristic of a coloring component.
Although a method for maintaining the erased state is described, this method requires a heating source and a cooling source for image formation and erasure, and the temperature range in which the image formation state and the erased state can be maintained is limited to the hysteresis temperature range. However, it is still insufficient for use in the temperature environment of daily life.

On the other hand, JP-A-2-188293, JP-A-2-188294, and International Publication No.
No. 11898 describes a reversible thermosensitive recording medium comprising a leuco dye and a color-reducing agent which causes the leuco dye to develop and decolor the color by heating. The color-developing agent is an amphoteric compound having an acidic group for coloring the leuco dye and a basic group for decolorizing the colored leuco dye, and has a coloring effect by an acidic group or a decolorizing effect by a basic group by controlling thermal energy. One is preferentially generated to perform color development and decoloration. However, in this method, it is impossible to completely switch between the coloring reaction and the decoloring reaction only by controlling the heat energy, and since both reactions occur at a certain ratio at the same time, a sufficient coloring density cannot be obtained. Can't do it perfectly. Therefore, sufficient image contrast cannot be obtained. Also,
Since the decolorizing action of the basic group also acts on the colored portion at room temperature,
The phenomenon that the density of the color-developed portion decreases over time is inevitable.
JP-A-5-124360 describes a reversible thermosensitive recording medium that develops and decolorizes a leuco dye by heating, and as an electron accepting compound, an organic phosphoric acid compound, an α-hydroxy aliphatic carboxylic acid, Specific phenol compounds such as an aliphatic dicarboxylic acid and an alkylthiophenol having an aliphatic group having 12 or more carbon atoms, an alkyloxyphenol, an alkylcarbamoylphenol, and an alkyl gallate are exemplified. However, this recording medium still has a low color density, or
The two problems of incomplete erasure cannot be solved at the same time, and the temporal stability of the image is not practically satisfactory.

As described above, according to the prior art, a practical reversible thermosensitive recording material having good image contrast, capable of forming and erasing an image, and capable of maintaining a stable image over time in an environment of daily life. Does not exist.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermosensitive recording material capable of forming and erasing an image with good contrast and capable of maintaining a stable image over time in an environment of daily life. To provide.

[0010]

Means for Solving the Problems The present inventor has conducted studies to solve this problem, and as a result, a colorless or pale-color electron-donating dye precursor has been reversibly changed in color tone by heating.
That is, the following general formula 5 which causes color development and decoloration
It has been found that the electron accepting compound represented by the formulas (7) to (7) is present, and the present invention has been completed.

[0011]

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In Formula 1, m represents an integer of 1 or more and 3 or less, and n represents an integer of 1 or more and 18 or less. X ¹ represents a divalent group having at least one —CONH— bond. R ¹ represents a hydrocarbon group having 1 to 24 carbon atoms.

[0013]

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In Formula 2, q represents an integer of 1 or more and 3 or less, and r and s represent an integer of 1 or more and 18 or less. Q is an oxygen atom,
Alternatively, it represents a sulfur atom. X ² represents a divalent group having at least one —CONH— bond. R ² has 1 carbon atom
To 24 hydrocarbon groups.

[0015]

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In the formula 3, t represents an integer of 1 or more and 3 or less, and u represents 0 or 1. X ³ represents a single bond, an oxygen atom or a sulfur atom. R ³ represents a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁴ represents a monovalent group represented by the following general formula 4.

[0017]

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In Formula 4, v and y represent 0 or 1, and z represents an integer of 1 or more and 3 or less. X ⁴ represents a single bond, an oxygen atom, a sulfur atom, or a divalent group having at least one —CONH— bond. R ⁵ represents a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁶ represents a hydrocarbon group having 1 to 24 carbon atoms. A represents a divalent group having at least one -CONH- bond.

In the compound represented by formula 5, n is 1 or more and 18
The following integers are represented, and preferably an integer of 1 or more and 10 or less. R ¹ represents a divalent hydrocarbon group having 1 to 24 carbon atoms, preferably a divalent hydrocarbon group having 6 to 22 carbon atoms. Further, the sum of the carbon number of n and the carbon number of R ¹ is 1
The case where the number is 1 or more and 35 or less is particularly preferable. R ¹ specifically mainly represents an alkylene group and an alkyl group, respectively. On the other hand, X ¹ represents a divalent group having at least one —CONH— bond, and specific examples thereof include amide (—CONH—, —NHCO—) and urea (—NHCON—).
H-), urethane (-NHCOO-, -OCONH)
−), Diacylamine (—CONHCO—), diacylhydrazide (—CONHNHCO—), oxalic acid diamide (—NHCONH—), acylurea (—CONH—)
CONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-), semicarbazide (-NHCONHNH-, -NHNHCONH)
-), Acyl semicarbazide (-CONHNHCONH
-, - NHCONHNHCO-), diacyl aminomethane (-CONHCH ₂ NHCO-), 1- acylamino-1- Ureidometan (-CONHCH ₂ NHCONH
-, - NHCONHCH ₂ NHCO-), include groups such as malonamide (-NHCOCH ₂ CONH-).

In the compound represented by Chemical formula 6, r and s are the same or different and each represents an integer of 1 or more and 18 or less, preferably an integer of 1 or more and 10 or less. R ² represents a divalent hydrocarbon group having 1 to 24 carbon atoms, and is preferably a divalent hydrocarbon group having 6 to 22 carbon atoms. Further, the sum of the carbon number of r and the carbon number of R ² is 11
It is particularly preferable that the number be 35 or more and 35 or less. Specifically, R ² mainly represents an alkylene group or an alkyl group, but the group may contain an aromatic ring. On the other hand, X ² −
It represents a divalent group having at least one CONH-bond, and specific examples thereof have the same meaning as X ¹ represented by Chemical Formula 5.

In the compound represented by formula 7, X ³ is a single bond,
It represents an oxygen atom or a sulfur atom, and is preferably a single bond or an oxygen atom. R ³ has 1 carbon atom
To 18 divalent hydrocarbon groups, preferably a divalent hydrocarbon group having 1 to 10 carbon atoms. R ³ is further
The group may contain an aromatic ring.

In the substituent R ^{4 in} Chemical Formula 7, that is, in the substituent represented by Chemical Formula 8, z represents an integer of 1 to 3, and is preferably 1. X ⁴ represents a single bond, an oxygen atom, a sulfur atom, or a divalent group having at least one -CONH- bond, and preferably represents an oxygen atom or a divalent group having at least one -CONH- bond. Either. R ⁵ represents a divalent hydrocarbon group having 1 to 18 carbon atoms, and preferably has the same meaning as R ³ . R ⁶ represents a divalent hydrocarbon group having 1 to 24 carbon atoms, and preferably has the same meaning as R ² . A is a divalent radical having one of at least a -CONH- bond, and specific examples thereof include the same meaning as X ¹ shown in Chemical formula 5.

Specific examples of the electron-accepting compound used in the present invention, which causes the colorless or pale-colored electron-donating dye precursor to cause a reversible color change, include the following compounds. It is not limited to this.

First, as an example represented by the general formula 5,
Compounds of Chemical Formulas 9 and 10 are included.

[0025]

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[0026]

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Next, as an example represented by the general formula 6,
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[0028]

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Finally, examples of the compounds represented by the general formula 7 include compounds represented by the formulas 12 and 13.

[0030]

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[0031]

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The electron-accepting compound according to the present invention may be used alone or as a mixture of two or more kinds. Usually, the amount of the electron-accepting compound according to the present invention to the colorless or pale color dye precursor is 5 to 5%. It is 5,000 to 5000% by weight, preferably 10 to 3,000% by weight.

The usually colorless or light-colored electron-donating dye precursor used in the present invention is typified by those generally used for pressure-sensitive recording paper and heat-sensitive recording paper, but is not particularly limited. Specific examples include, for example, the following, but the present invention is not limited thereto.

(1) Triarylmethane compounds 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3
-Yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-
Phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) ) -6-Dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3-
Yl) -4-azaphthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylamino Phthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like,

(2) Diphenylmethane compounds 4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc.

(3) Xanthene compounds rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3- Diethylamino-7-phenylfluoran, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7-phenoxyfluoran, 3-diethylamino-7- (3 , 4-Dichloroanilino) fluorane, 3-diethylamino-7-
(2-chloroanilino) fluoran,

3-Diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-
7- (3-methylanilino) fluoran, 3- (N-ethyl) tolylamino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3- (N-ethyl ) Tolylamino-6-methyl-7-phenethylfluoran, 3-diethylamino-7
-(4-nitroanilino) fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N
-Methyl) propylamino-6-methyl-7-anilinofluoran, 3- (N-ethyl) isoamylamino-6
-Methyl-7-anilinofluoran, 3- (N-methyl) cyclohexylamino-6-methyl-7-anilinofluoran, 3- (N-ethyl) tetrahydrofurylamino-6-methyl-7-anilino Fluoran, etc.

(4) Thiazine compounds Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.

(5) Spiro compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3 -Methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like.

The above colorless or pale-color dye precursors may be used alone or as a mixture of two or more.

Next, a specific method for producing the reversible thermosensitive recording material of the present invention will be described, but the present invention is not limited thereto.

As a specific example of the method for producing the reversible thermosensitive recording material of the present invention, a colorless or pale color dye precursor and the electron accepting compound according to the present invention are mainly used, and these are coated or printed on a support. To form a reversible thermosensitive recording layer.

The colorless or pale color dye precursor and the electron-accepting compound according to the present invention are usually contained in the reversible thermosensitive recording layer by dissolving each compound alone in a solvent or dispersing it in a dispersion medium. Examples include a method of mixing, a method of mixing and dissolving each compound in a solvent or dispersing in a dispersion medium, and a method of dissolving or dispersing in a solvent after dissolving or dispersing each compound in a solvent after heating and homogenizing each compound. But not specified.

It is also possible to add a binder to the reversible thermosensitive recording layer for the purpose of improving the strength of the reversible thermosensitive recording layer. Specific examples of the binder include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acryl. Water-soluble polymers such as acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic acid Ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl chloride copolymer, polyvinyl chloride, ethylene Vinylidene chloride copolymers, latexes such as polyvinylidene chloride. The role of these binders is to keep the materials of the composition uniformly dispersed without unevenness due to the application of heat for printing and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. Recently, high value-added reversible thermosensitive recording materials such as prepaid cards and stored cards are increasingly used, and with this, high durability products such as heat resistance, water resistance and adhesiveness are required. It is becoming. Curable resins are particularly preferred for such requirements.

Examples of the curable resin include a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin.
Examples of the thermosetting resin include resins that are cured by reacting a hydroxyl group and a carboxyl group with a crosslinking agent such as a phenoxy resin, a polyvinyl butyral resin, and a cellulose acetate propionate resin. Examples of the crosslinking agent at this time include isocyanates, amines, phenols, epoxies and the like.

Monomers used for the electron beam and curing beam resins include monofunctional monomers represented by acrylics, difunctional monomers, polyfunctional monomers and the like. And a photopolymerization accelerator.

In addition, a heat-fusible substance can be contained in the reversible thermosensitive recording layer as an additive for adjusting the color development sensitivity and the decoloring temperature of the reversible thermosensitive recording layer. 60 ° C
Those having a melting point of 200 ° C to 200 ° C
Those having a melting point of -180 ° C are preferred. A sensitizer used in general thermosensitive recording paper can also be used. For example, waxes such as N-hydroxymethyl stearamide, stearamide, palmitamide, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2 -Screw (3-
Polyether compounds such as methylphenoxy) ethane, 2,2'-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate, bis (p-methylbenzyl) oxalate Carbonic acid or oxalic acid diester derivatives such as esters can be added in combination.

As the support used in the reversible thermosensitive recording material of the present invention, paper, various nonwoven fabrics, woven fabrics, synthetic resin films, synthetic resin laminated paper, synthetic paper, metal foil, glass, etc., or a combination thereof are used. The composite sheet can be used arbitrarily according to the purpose, and may be transparent, translucent or opaque. Further, the present invention is not limited to these.

The layer structure of the reversible thermosensitive recording material of the present invention is as follows.
Only the reversible thermosensitive recording layer may be used. If necessary,
A protective layer can be provided on the reversible thermosensitive recording layer, or an intermediate layer can be provided between the reversible thermosensitive recording layer and the support. In this case, the protective layer and / or the intermediate layer may be composed of two or three or more layers. Further, information can be recorded electrically, magnetically and optically in the reversible thermosensitive recording layer and / or on another layer and / or on the surface on which the reversible thermosensitive recording layer is provided and / or on the opposite surface. Materials may be included. Further, a back coat layer may be provided on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided for the purpose of preventing curling and charging.

The reversible thermosensitive recording layer is obtained by mixing each dispersion obtained by finely pulverizing each coloring component, coating the mixture on a support,
It can be obtained by a method of printing and drying, a method of dissolving each coloring component in a solvent, mixing respective solutions obtained, applying the solution on a support, printing and drying. in this case,
For example, each color forming component may be contained one layer at a time to form a multilayer structure.

In the reversible thermosensitive recording layer and / or the protective layer and / or the intermediate layer, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, hydroxide Aluminum, pigments such as urea-formalin resin, in addition, zinc stearate, higher fatty acid metal salts such as calcium stearate, waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide, caster wax, A dispersant such as sodium dioctyl sulfosuccinate, a surfactant, a fluorescent dye, and the like can also be contained.

[0052]

The electron-accepting compound according to the present invention has a specific decoloring effect, that is, a reversible effect, in spite of having the ability to form a leuco dye. This is completely unexpected, and the electron-accepting compounds used in ordinary thermosensitive recording materials, namely, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, Such a reversible effect is not seen at all with benzyl hydroxybenzoate and the like.

Although the principle of image formation and erasure of the reversible thermosensitive recording material of the present invention is not clear yet, it can be considered as follows. Generally, when a colorless or pale color dye precursor is heated together with an electron accepting compound such as a phenolic compound, electron transfer from the dye precursor to the electron accepting compound takes place and color is formed. At this time, it is considered that the electron accepting compound molecule exists very close to the dye molecule that has developed color. When the electron-accepting compound molecule is separated from the dye molecule which has developed color, the dye molecule which has developed color receives electrons again and becomes a state of a dye precursor before color development. It is considered that the present invention changes the distance between the electron-accepting compound molecule and the dye molecule by heating to perform coloring and decoloring.

More specifically, since the electron-accepting compound according to the present invention has a large fatty chain in its structure, it has a low compatibility with the dye precursor molecule and the dye molecule which has developed a color, and in the solidified state, It is considered that they hardly mix with each other. Further, in a state where the dye precursor molecule and the electron accepting compound molecule according to the present invention can freely move, such as in a heated and melted state, the dye precursor molecule and the electron accepting compound molecule according to the present invention dissolve at a certain ratio with each other, and form color. State. Therefore, when the color-forming molten mixture is cooled slowly, the electron-accepting compound according to the present invention and the dye molecules become insoluble with each other and phase-separate and lose color as the temperature decreases. At this time, since the electron-accepting compound according to the present invention contains a bond having a hydrogen bonding ability such as an amide bond in a molecule, the compound is rapidly crystallized by an intermolecular hydrogen bond. On the other hand, when cooling is performed rapidly, the solidified state is obtained before the phase separation, that is, in the state of the color development, so that the color development state is fixed and the color development state is stably maintained after the solidification.

As described above, the reversible thermosensitive recording material according to the present invention is capable of producing a compatible state and a phase-separated state between the dye molecule and the electron-accepting compound according to the present invention so as to develop a color-developing state and a decoloring state. Conceivable. In order to perform color development, rapid cooling may be performed following heating, and for example, heating by a thermal head, laser light, or the like is possible. Also, if you slowly cool after heating, the color will be erased, for example, hot roll, heat stamp, thermal head, high frequency heating,
It can be performed by using radiant heat from a light source such as a hot air, an electric heater or a halogen lamp.

Next, representative examples of specific examples of the synthesis of the electron-accepting compounds represented by Chemical Formula 5, Chemical Formula 6, and Chemical Formula 7 are shown below.

Synthesis Example 1 Synthesis of N- (p-hydroxyphenyl) -N'-octadecylurea In a 1000 ml flask equipped with a stirrer, 10.9 g of p-aminophenol and methyl ethyl ketone (M
EK), and 29.5 g of octadecyl isocyanate was added dropwise while stirring at room temperature. After completion of the dropwise addition, the mixture was stirred at room temperature for 30 minutes and then heated under reflux for 2 hours. After completion of the reaction, the reaction mixture was cooled to room temperature, and the precipitated crystals were collected by filtration. The obtained crystals were washed with 100 ml of MEK and then dried at 50 ° C. under reduced pressure to obtain 38.8 g of the desired product.

Synthesis Example 2 Synthesis of ethyl 2- (p-octadecylcarbamoylaminophenoxy) acetate 12.1 g of the phenol compound obtained in Synthesis Example 1 and ethyl chloroacetate 5 in a 300 ml flask equipped with a stirrer and a condenser. 0.5 g, anhydrous potassium carbonate 6.2 g, and N,
200 ml of N-dimethylformamide (DMF) was charged and heated and stirred in an oil bath at 80 ° C. for 2 hours. After completion of the reaction, the reaction mixture was poured into 500 ml of ice water, and the precipitated crystals were collected by filtration. The obtained crystals were washed with 300 ml of distilled water and then recrystallized from isopropanol (IPA).
13.0 g of the desired product was obtained.

Synthesis Example 3 Hydrolysis of ester obtained in Synthesis Example 2 In a 300 ml flask equipped with a stirrer and a cooler, 13.0 g of the ester, 800 ml of 1,4-dioxane,
Then, an aqueous sodium hydroxide solution in which 3.1 g of sodium hydroxide was dissolved in 50 ml of distilled water was charged, and the mixture was heated and stirred in a 60 ° C. oil bath for 8 hours. The reaction mixture was diluted with 2% dilute hydrochloric acid 10
The mixture was poured into 00 ml, and the precipitated crystals were collected by filtration. The obtained crystals were washed with water until the washing liquid became neutral, and then IPA 500 m
Recrystallization from 1 gave 10.9 g of the desired product.

Synthesis Example 4 Synthesis of Exemplified Compound (1-3) In a 200 ml flask equipped with a stirrer and a condenser, 5.09 g of the carboxylic acid obtained in Synthesis Example 3, 1.44 g of p-aminophenol, N , N'-diisopropylcarbodiimide 1.7 g, 1-hydroxybenzotriazole monohydrate 2.0 g, and tetrahydrofuran (THF) 15
0 ml was charged and heated under reflux for 3 hours. After completion of the reaction, the reaction mixture was allowed to cool to room temperature, and the precipitated crystals were collected by filtration.
The obtained crystals were washed with 40 ml of THF and then recrystallized from 250 ml of 2-methoxyethanol to obtain 4.6 of the desired product.
g was obtained. Melting point 194 [deg.] C.

Synthesis Example 5 Synthesis of diglycolic acid mono (p-hydroxy) anilide In a 300 ml flask equipped with a stirrer, 6.0 g of p-aminophenol, 5.8 g of diglycolic anhydride,
5.5 g of triethylamine and 100 ml of THF were charged and stirred at room temperature for 3 hours. After completion of the reaction, the reaction mixture was poured into 100 ml of 2% dilute hydrochloric acid, and then supersaturated sodium chloride was added, followed by extraction with ethyl acetate. The ethyl acetate layer was dried over anhydrous sodium sulfate and then distilled off under reduced pressure to obtain 5.7 g of the desired product as a powder.

Synthesis Example 6 Synthesis of Exemplified Compound (2-4) In a 300 ml flask equipped with a stirrer, 3.4 g of the carboxylic acid obtained in Synthesis Example 5 and 4.0 g of stearic hydrazide.
5 g, N, N'-diisopropylcarbodiimide 2.3
g, 1-hydroxybenzotriazole monohydrate 2.8
g and 150 ml of THF were charged and heated under reflux for 3 hours. After completion of the reaction, the reaction mixture was allowed to cool to room temperature, and the precipitated crystals were collected by filtration. The obtained crystals were washed with 40 ml of THF, and then recrystallized from 250 ml of IPA to obtain the desired product.
6 g were obtained. Melting point 161 [deg.] C.

Synthesis Example 7 Synthesis of N- (11-bromoundecano) -N'-n-dodecanohydrazide In a 500 ml flask equipped with a stirrer, 26.5 g of 11-bromoundecanoic acid and 21.n-dodecanoic acid hydrazide. 4 g, 2.3 g of N, N'-diisopropylcarbodiimide, 2.8 g of 1-hydroxybenzotriazole monohydrate and 150 ml of THF were charged and heated under reflux for 3 hours. After completion of the reaction, the reaction mixture was allowed to cool to room temperature,
The precipitated crystals were collected by filtration. The obtained crystal is THF40m
After washing with 1 l, recrystallization was performed from 200 ml of IPA to obtain 38.1 g of the desired product.

Synthesis Example 8 N- [11- (p-formylphenoxy) undecano]
Synthesis of -N'-n-dodecanohydrazide In a 300 ml flask equipped with a stirrer, 11.5 g of the bromo compound obtained in Synthesis Example 7, 3.7 g of p-hydroxybenzaldehyde, 5.2 g of anhydrous potassium carbonate, and potassium iodide 0.4 g and N, N-dimethylacedamide (DM
A) 150 ml was charged and heated and stirred in a 100 ° C. oil bath for 6 hours. After completion of the reaction, the reaction mixture was poured into 500 ml of ice water, and the precipitated crystals were collected by filtration. After washing the obtained crystals with distilled water, recrystallization was performed from 200 ml of IPA.
9.2 g of the desired product was obtained.

Synthesis Example 9 Synthesis of Exemplified Compound (3-11) In a 200 ml flask equipped with a stirrer, 4.5 g of the formyl compound obtained in Synthesis Example 8 and 2.0 g of 3- (p-hydroxyphenyl) propionic acid hydrazide. , 3 drops of glacial acetic acid and 100 ml of ethanol, and the mixture was heated under reflux for 3 hours. After completion of the reaction, the precipitated crystals were collected by filtration while hot. The obtained crystals were washed with ethanol and dried under reduced pressure at 60 ° C.
5.4 g of the desired product was obtained. 185 ° C

[0066]

The present invention will be described in more detail with reference to the following examples.

Example 1 (A) Preparation of a reversible thermosensitive coating solution 3- (4-diethylamino-2-ethoxyphenyl)-
3- (1-ethyl-2-methylindol-3-yl)
40 parts of -4-azaphthalide and Exemplified Compound (1-1) 20
0 parts of 8% polyvinyl acetal (Sekisui Chemical Co., Ltd., B
The mixture was pulverized with a paint conditioner together with 9100 parts of a tetrahydrofuran (THF) solution (L-1, acetalization degree: 63 mol%) to prepare a reversible heat-sensitive coating liquid.

(B) Coating of the reversible thermosensitive recording layer After adding 29 parts of Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) to the reversible thermosensitive coating liquid prepared in (A), a polyethylene terephthalate (PET) sheet was added. The smear was applied so that the solid content was 4.0 g / m ² . It was dried at 60 ° C. for 24 hours and treated with a super calender to obtain a reversible thermosensitive recording material.

(C) Coating of protective layer Aronix M80 was coated on the coated sheet prepared in (B).
90 (manufactured by Toagosei Chemical Industry Co., Ltd.) 90 parts, N-vinyl-2-
5 parts of pyrrolidone, 5 parts of Irgacure 500 (manufactured by Nippon Ciba Geigy), and 10 parts of nip seal E220A (manufactured by Nippon Silica) were added, and after stirring, 1.0 g of a protective layer coating liquid was obtained.
/ M ^2, and cured with an ultraviolet irradiation device to obtain a reversible thermosensitive recording material having a protective layer.

Example 2 A reversible thermosensitive recording material was obtained in the same manner as in Example 1, except that the exemplified compound (1-1) was used instead of the exemplified compound (1-1) used in the example 1. Was.

Example 3 A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the exemplified compound (1-1) was used in place of the exemplified compound (1-1) used in Example 1. Was.

Example 4 A reversible thermosensitive recording material was obtained in the same manner as in Example 1, except that the exemplified compound (1-1) was used in place of the exemplified compound (1-1) used in the example 1. Was.

Example 5 A reversible thermosensitive recording material was obtained in the same manner as in Example 1, except that the exemplified compound (1-16) was used instead of the exemplified compound (1-1) used in the example 1. Was.

Example 6 A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the exemplified compound (1-1) used in the example 1 was replaced with the exemplified compound (2-3). Was.

Example 7 A reversible thermosensitive recording material was obtained in the same manner as in Example 1, except that Exemplified Compound (2-4) was used instead of Exemplified Compound (1-1) used in Example 1. Was.

Example 8 A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the exemplified compound (2-8) was used instead of the exemplified compound (1-1) used in the example 1. Was.

Example 9 A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the exemplified compound (3-6) was used instead of the exemplified compound (1-1) used in the example 1. Was.

Example 10 A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the exemplified compound (3-7) was used instead of the exemplified compound (1-1) used in the example 1. Was.

Example 11 A reversible thermosensitive recording material was obtained in the same manner as in Example 1, except that the exemplified compound (3-11) was used instead of the exemplified compound (1-1) used in the example 1. Was.

Example 12 A reversible thermosensitive recording material was obtained in the same manner as in Example 1, except that the exemplified compound (3-15) was used instead of the exemplified compound (1-1) used in the example 1. Was.

Comparative Example 1 Instead of the exemplified compound (1-1) used in Example 1, 1
Example 1 was repeated except that-(p-hydroxyphenylmethylidene) -N'-octadecanohydrazide was used.

Comparative Example 2 Instead of the exemplified compound (1-1) used in Example 1, N
Example 1 was repeated except that-(p-hydroxyphenyl) -6-[(octadecylcarbamoyl) amino] caproic acid amide was used.

Test 1 (Coloring density = thermal response) The reversible thermosensitive recording materials obtained in Examples 1 to 12 and Comparative Examples 1 and 2 were applied to a Kyocera print head KJT-256-8MG.
Okura Electric Thermal Facsimile Printing Tester with F1 TH-
Using a PMD, an applied pulse of 1.1 milliseconds and an applied voltage of 26
Printing was performed under bolt conditions, and the density of the obtained color image was measured using a densitometer Macbeth RD918.

Test 2 (Erasability of Image) The reversible thermosensitive recording materials obtained in Examples 1 to 12 and Comparative Examples 1 and 2 were applied to a Kyocera print head KJT-256-8MG.
Okura Electric Thermal Facsimile Printing Tester with F1 TH-
Using a PMD, an applied pulse of 1.1 milliseconds and an applied voltage of 26
Printing was performed under bolt conditions, and this was printed using a heat stamp.
After heating at 0 ° C. for 1 second, the concentration was measured in the same manner as in Test 1.

Test 3 (Decoloring Start Temperature) The reversible thermosensitive recording materials obtained in Examples 1 to 12 and Comparative Examples 1 and 2 were applied to a Kyocera print head KJT-256-8MG.
Okura Electric Thermal Facsimile Printing Tester with F1 TH-
Using a PMD, an applied pulse of 1.1 milliseconds and an applied voltage of 26
Printing is performed under the condition of bolts, and this is
After heating for 10 seconds from 10 ° C. to 170 ° C. at 10 ° intervals, each concentration was measured in the same manner as in Test 1. The heating temperature at which the optical density of the printed image was lower than 0.15 was defined as the decolorization start temperature.

Test 4 (Time-dependent change in color density = image stability) The reversible thermosensitive recording materials obtained in Examples 1 to 12 and Comparative Examples 1 and 2 were applied to a print head KJT-256-8MG manufactured by Kyocera.
Okura Electric Thermal Facsimile Printing Tester with F1 TH-
Using a PMD, an applied pulse of 1.1 milliseconds and an applied voltage of 2
Printing at 6 volts, temperature 50 ° C, relative humidity 20%
After storing in the atmosphere for 24 hours, the density of the color-developed portion was measured in the same manner as in Test 1, and the image remaining ratio was calculated by the following equation (1).

[0087]

A = (C / B) × 100 A: Image residual ratio (%) B: Image density before test C: Image density after test

Table 1 shows the results of Tests 1 to 4 of Examples 1 to 12 and Comparative Examples 1 and 2.

[0089]

[Table 1]

[0090]

As is clear from Table 1, the colorless or light-colored electron-donating dye precursor and the above-mentioned general formula 5 which causes the dye precursor to undergo a reversible color change upon heating.
A reversible thermosensitive recording material containing at least one electron-accepting compound represented by any one of formulas (1) to (4) enables formation and erasing of images with good contrast, and is stable over time in an environment of daily life. Thus, a reversible thermosensitive recording material capable of holding an excellent image was obtained.

Claims (1)

[Claims] 1. A colorless or pale color electron-donating dye
A reversible color change to the dye precursor by heating
It is represented by the following general formulas (1), (2) and (3).
Reversible containing at least one electron-accepting compound
Thermosensitive recording material. Embedded image(In the formula 1, m is an integer of 1 or more and 3 or less, and n is 1 or more and 18
Represents the following integers. X ¹Has at least -CONH- bonds.
Also represents a divalent group having one or more. R¹Is 1 to 2 carbon atoms
4 represents a hydrocarbon group. )(In the formula 2, q is an integer of 1 or more and 3 or less, and r and s are 1
It represents an integer of 18 or more and 18 or less. Q is an oxygen atom or sulfur
Represents a yellow atom. X^TwoHas at least one -CONH- bond.
Represents a divalent group having at least one divalent group. R^TwoHas 1 to 24 carbon atoms
Represents a hydrocarbon group. )(In the formula 3, t is an integer of 1 or more and 3 or less, and u is 0 or 1.
Represents X^ThreeRepresents a single bond, oxygen atom or sulfur atom
You. R^ThreeRepresents a divalent hydrocarbon group having 1 to 18 carbon atoms;^Four
Represents a monovalent group represented by the following general formula 4. )(In the formula 4, v and y are 0 or 1, and z is 1 or more and 3 or less.
Represents an integer. X^FourIs a single bond, oxygen atom, sulfur atom or
Is a divalent group having at least one -CONH- bond
Represents R^FiveIs a divalent hydrocarbon group having 1 to 18 carbon atoms
And R⁶Represents a hydrocarbon group having 1 to 24 carbon atoms. A is
A divalent group having at least one -CONH- bond
Represent. )