JPH0852941A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To ensure the good contrast or stability with the elapse of time of an image by adding a usually colorless electron donating dye precursor and an electron acceptive compd. represented by a specific general formula generating a reversible hue change in the dye precursor by heating. CONSTITUTION:A reversible thermal recording material contains a usually colorless or light-colored electron donating dye precursor and an electron acceptive compd. represented by formula (wherein n is an integer of 1-3, R<1> is a 1-18C divalent hydrocarbon group, X is a divalent group having at least one -CO-NH- group and R<2> is a 1-24C hydrocarbon group) generating a reversible hue change in the dye precursor by heating. By this constitution, the reversible thermal recording material capable of forming and erasing an image in good contrast and capable of holding an image stable with the elapse of time under daily life environment is obtained.

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 heat-sensitive recording material generally comprises a support and a heat-sensitive recording layer containing an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting developer as main components. By heating with a thermal head, a heating pen, a laser beam or the like, a dye precursor and a developer react instantaneously to obtain a recorded image. JP-B-43-4160 and JP-B-45-
No. 14039 is disclosed.

In general, such a heat-sensitive recording material cannot erase the portion of the image once formed and return to the state before the image is formed. Therefore, when further information is recorded, the image is not recorded. There was no choice but to add to the formation part. Therefore, when the area of the heat-sensitive recording portion is limited, there is a problem that the recordable information is limited and it is impossible to record all the necessary information.

In recent years, reversible thermosensitive recording materials capable of repeating image formation and image erasing have been devised in order to deal with such a problem, for example, JP-A-54-119377 and JP-A-63-63. 39377, JP-A-63-4
Japanese Patent No. 1186 describes a heat-sensitive recording material composed of a resin base material and organic low-molecules dispersed in the resin base material. However, since this method reversibly changes the transparency of the heat-sensitive recording material by heat energy, the contrast between the image-formed area and the image-unformed area is insufficient.

Further, in the methods described in JP-A-50-81157 and JP-A-50-105555, since the image to be formed changes according to the ambient temperature, the image forming state and the erasing state. The holding temperatures are different, and these two states cannot be held for an arbitrary period at room temperature.

Further, in Japanese Patent Laid-Open No. 59-120492, the hysteresis characteristic of the color-developing component is utilized to keep the recording material in the hysteresis temperature range, thereby forming an image.
Although a method of 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 region. 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. WO90 /
No. 11898 describes a reversible thermosensitive recording medium composed of a leuco dye and a color-developing and decoloring agent for coloring and decoloring the leuco dye by heating. The color-developing agent is an amphoteric compound having an acidic group for coloring the leuco dye and a basic group for decoloring the colored leuco dye, and the coloring effect by the acidic group or the decoloring effect by the basic group is controlled by controlling thermal energy. One of them is preferentially generated, and coloring and erasing are performed. However, in this method, it is impossible to completely switch the color development reaction and the color removal reaction only by controlling the thermal energy, and since both reactions occur at a certain ratio at the same time, sufficient color development density cannot be obtained, and the color removal Can not be done completely. Therefore, sufficient image contrast cannot be obtained. Also,
Since the decoloring action of the basic group also acts on the color development part at room temperature,
The phenomenon that the density of the color-developed portion decreases with time cannot be avoided.
JP-A-5-124360 describes a reversible thermosensitive recording medium that develops and decolorizes a leuco dye by heating, and an organic phosphoric acid compound, an α-hydroxyaliphatic carboxylic acid, as an electron-accepting compound. Specific phenol compounds such as alkylthiophenol, alkyloxyphenol, alkylcarbamoylphenol, and gallic acid alkylester having a fatty acid dicarboxylic acid and an aliphatic group having 12 or more carbon atoms are exemplified. However, even this recording medium has a low color density, or
The two problems of incomplete decolorization cannot be solved at the same time, and the temporal stability of the image is not satisfactory in practice.

As described above, according to the prior art, a practical reversible thermosensitive recording material having a good image contrast, capable of forming and erasing an image, and capable of holding a stable image over time in the environment of daily life. Is difficult to manufacture.

[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 holding a stable image over time in an environment of daily life. Is to provide.

[0010]

Means for Solving the Problems As a result of research to solve this problem, the present inventors have found that a colorless or light-colored electron-donating dye precursor undergoes reversible color tone change by heating, that is, color development. Further, they have found that there is an electron-accepting compound represented by the following general formula 2 which causes decoloration, and have completed the present invention.

[0011]

Embedded image

(In the formula 2, n is an integer of 1 or more and 3 or less,
R ¹ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and X is
It represents a divalent group having at least one CONH-bond, and R ² represents a hydrocarbon group having 1 to 24 carbon atoms. )

In the compound represented by Chemical formula 2, R ¹ represents a divalent hydrocarbon group having 1 to 18 carbon atoms, preferably a divalent hydrocarbon group having 1 to 12 carbon atoms. R ² represents a hydrocarbon group having 1 to 24 carbon atoms, preferably a hydrocarbon group having 6 to 22 carbon atoms. Further, it is particularly preferable that the sum of carbon numbers of R ¹ and R ² is 11 or more and 35 or less. R ¹ and R ² specifically mainly represent an alkylene group and an alkyl group, respectively, but each may include an aromatic ring, and in the case of R ¹ , only an aromatic ring may be included. On the other hand, X in Formula 2 represents a divalent group having at least one —CONH— bond, and specific examples thereof include amide (—CONH—, —NHCO—), urea (—
NHCONH-), urethane (-NHCOO-, -OC
ONH-), diacylamine (-CONHCO-), diacylhydrazide (-CONHNHCO-), oxalic acid diamide (-NHCOCONH-), acylurea (-C
ONHCONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-),
Semicarbazide (-NHCONHNH-, -NHNHC
ONH-), acyl semicarbazide (-CONHNHC
ONH -, - NHCONHNHCO-), diacyl aminomethane (-CONHCH ₂ NHCO -), 1- acylamino-1- Ureidometan (-CONHCH ₂ NHC
_{ONH -, - NHCONHCH 2 NHCO-)} , it includes groups such as malonamide (-NHCOCH ₂ CONH-).

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

Nn-octadecyl-2- (p-hydroxyphenylsulfonyl) acetamide, Nn-decyl-11- (p-hydroxyphenylsulfonyl) undecane amide, N- (pn-octylphenyl) -6
-(P-hydroxyphenylsulfonyl) hexanamide, N-n-octadecyl-p- (p-hydroxyphenylsulfonyl) benzamide, N- (p-hydroxyphenylsulfonyl) methyl-n-octadecaneamide, N- [6- ( p-hydroxyphenylsulfonyl)
Hexyl] -n-decane amide, N- [p- (p-hydroxyphenylsulfonyl) phenyl] -n-octadecane amide, N- [6- (p-hydroxyphenylsulfonyl) hexyl] -N'-n-decylurea, N- [p
-(P-hydroxyphenylsulfonyl) phenyl]-
N'-n-octadecyl urea, N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-decyl urea, N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n -Octadecyl urea, N-
[10- (3,4-dihydroxyphenylsulfonyl)
Decyl] -N'-n-octadecyl urea, N- [6-
(P-Hydroxyphenylsulfonyl) hexyl] carbamic acid-n-tetradecyl, N- [p- (p-hydroxyphenylsulfonyl) phenyl] carbamic acid-n
-Octadecyl, N-n-octadecylcarbamic acid-
[2- (p-hydroxyphenylsulfonyl) ethyl], Nn-decylcarbamate- [11- (p-hydroxyphenylsulfonyl) undecyl], N- [6
-(P-Hydroxyphenylsulfonyl) hexanoyl] -Nn-octadecanoylamine, N- [2-
(P-Hydroxyphenylsulfonyl) aceto] -N '
-N-octadecanohydrazide, N- [6- (p-hydroxyphenylsulfonyl) hexano] -N'-n-octadecanohydrazide, N- [11- (p-hydroxyphenylsulfonyl) undecano] -N ' -(Pn-
Octylbenzo) hydrazide, N- [11- (p-hydroxyphenylsulfonyl) undecano-N'-n-decanohydrazide, N- [11- (p-hydroxyphenylsulfonyl) undecano-N'-n-tetradecano Hydrazide, N- [11- (p-hydroxyphenylsulfonyl) undecano-N '-(6-phenyl) hexanohydrazide, N- [11- (3,4-dihydroxyphenylsulfonyl) undecano] -N'-n- Octadecanohydrazide, N- [11- (3,4,5-trihydroxyphenylsulfonyl) undecano] -N'-n-octadecanohydrazide, N- [p- (p-hydroxyphenylsulfonyl) benzo]- N'-n-octadecanohydrazide, N- [p- (p-hydroxyphenylsulfonylmethyl) benzo -N'-n-octadecanohydrazide hydrazide, N- [3- (p- hydroxyphenyl sulfonyl) propyl]-N'-n-octadecyl oxamide,
N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-decyloxamide, N- [11-
(P-Hydroxyphenylsulfonyl) undecyl]-
N'-n-octadecyl oxamide, N- [p- (p-
Hydroxyphenylsulfonyl) phenyl] -N'-n
-Octadecyl oxamide, N- [11- (3,4-dihydroxyphenylsulfonyl) undecyl] -N'-
n-octadecyl oxamide, N- [2- (p-hydroxyphenylsulfonyl) acetyl] -N'-n-octadecyl urea, N- [p- (p-hydroxyphenylsulfonyl) benzoyl] -N'-n-octadecyl Urea, N- [6- (p-hydroxyphenylsulfonyl)
Hexyl] -N'-n-octadecanoyl urea, N-
[P- (p-hydroxyphenylsulfonyl) phenyl] -N'-n-octadecanoyl urea, 3- [11-
(P-Hydroxyphenylsulfonyl) undecanoyl] carbazic acid-n-dodecyl, 4- [8- (p-hydroxyphenylsulfonyl) octyl] -1-n-octadecyl semicarbazide, 4- [p- (p-hydroxyphenylsulfonyl) Phenyl] -1-n-octadecyl semicarbazide, 1- [6- (p-hydroxyphenylsulfonyl) hexyl] -4-n-hexadecyl semicarbazide, 4- [8- (p-hydroxyphenylsulfonyl) octyl] -1- n-Octadedecanoyl semicarbazide, 1- [p- (p-hydroxyphenylsulfonyl) benzoyl] -4-n-octadecyl semicarbazide, 1- [11- (p-hydroxyphenylsulfonyl) undecanoyl] -4-n-octadecyl Semicarbazide, 1- [ -(P-Hydroxyphenylsulfonyl) propanamide] -1-n-octadecanoylaminomethane, 1- [11- (p-hydroxyphenylsulfonyl) undecaneamide] -1-n-decanoylaminomethane, 1- [ p- (p-hydroxyphenylsulfonyl) benzamide] -1-n-octadecanoylaminomethane, 1- [6- (p-hydroxyphenylsulfonyl) hexanamide] -1- (N′-n-octadecylureido) methane , 1- [11- (p-hydroxyphenylsulfonyl) undecanamide] -1- (N
'-N-decylureido) methane, 1- [p- (p-hydroxyphenylsulfonyl) benzamide] -1-
(N'-n-octadecyl ureido) methane, 1- {N
′-[10- (p-Hydroxyphenylsulfonyl) decyl] ureido} -1-n-octadecanoylaminomethane, N- [10- (p-hydroxyphenylsulfonyl) decyl] -N′-n-octadecylmalonamide Etc.

The electron-accepting compound according to the present invention may be used alone or in admixture of two or more, and usually, the amount of the electron-accepting compound according to the present invention to be used for a colorless or pale dye precursor is 5 or less. ˜5000 wt%, preferably 10-3000 wt%.

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, heat-sensitive recording paper and the like, but is not particularly limited. Specific examples include the followings, but the present invention is not limited thereto.

(1) Triarylmethane compound 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindole-
3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-)
Yl) -6-Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5 -Dimethylaminophthalide, 3-p
-Dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like,

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

(3) Xanthene compound Rhodamine B anilinolactam, Rhodamine B p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3- Diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3 -Diethylamino-7
-(2-chloroanilino) fluorane,

3-Diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl) tolylamino-
6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-ethyl) tolylamino-6-methyl-7-phenethylfluorane, 3-diethylamino-7 -(4-Nitroanilino) fluorane, 3-dibutylamino-6-methyl-7
-Anilinofluorane, 3- (N-methyl) propylamino-6-methyl-7-anilinofluorane, 3- (N
-Ethyl) isoamylamino-6-methyl-7-anilinofluorane, 3- (N-methyl) cyclohexylamino-6-methyl-7-anilinofluorane, 3- (N-
Ethyl) tetrahydrofurylamino-6-methyl-7-
Anilino Fluoran, etc.

(4) Thiazine-based compounds benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene 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 usually colorless to light-colored dye precursors may be used either individually or in combination 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, usually a colorless or pale color dye precursor and the electron-accepting compound according to the present invention are main components, and these are coated or printed on a support. And a reversible thermosensitive recording layer is formed.

As a method for incorporating a colorless or light-colored dye precursor and the electron-accepting compound according to the present invention into the reversible thermosensitive recording layer, each compound is dissolved in a solvent or dispersed in a dispersion medium. A method of mixing, a method of dissolving each compound in a solvent or dispersing in a dispersion medium, a method of dissolving each compound by heating and homogenizing and then cooling, and a method of dissolving in a solvent or dispersing in a dispersion medium, etc. However, it is 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, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic. Water-soluble polymer 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 Examples include, but are not limited to, latex such as ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, and the like. No.

A heat-fusible substance may be contained in the reversible thermosensitive recording layer as an additive for controlling the color developing sensitivity and the decoloring temperature of the reversible thermosensitive recording layer. 60 ° C
Those having a melting point of ~ 200 ° C are preferable, and especially 80 ° C.
Those having a melting point of ˜180 ° C. are preferred. It is also possible to use a sensitizer which is used in general thermal recording paper. For example, waxes such as N-hydroxymethylstearic acid amide, stearic acid amide and palmitic acid amide, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2. -Bis (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 such as ester or oxalic acid diester derivative may be used in combination.

The support used in the reversible thermosensitive recording material of the present invention is paper, various non-woven fabrics, woven fabrics, synthetic resin films, synthetic resin laminated papers, synthetic papers, metal foils, glass, etc., or a combination thereof. The composite sheet can be arbitrarily used according to the purpose, and may be transparent, semitransparent or opaque. Moreover, it 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 may be provided on the reversible thermosensitive recording layer, or an intermediate layer may 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 a plurality of layers of 2 layers or 3 layers or more. Further, information can be recorded electrically, magnetically, or optically in the reversible thermosensitive recording layer and / or on the surface provided with another layer and / or the reversible thermosensitive recording layer and / or on the opposite surface. The material 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 preventing electrification.

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

The reversible thermosensitive recording layer and / or the protective layer and / or the intermediate layer include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide and hydroxide. Aluminum, pigments such as urea-formalin resin, and other higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearamide, and castor wax, A dispersant such as sodium dioctylsulfosuccinate, a surfactant, a fluorescent dye and the like can be added.

[0034]

The electron-accepting compound according to the present invention has a specific decoloring effect, that is, a reversible effect, although it has the ability to develop the color of the leuco dye. This is totally unexpected, and it is an electron-accepting compound used in a conventional heat-sensitive recording material, that is, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, 4- No such reversible effect is observed with benzyl hydroxybenzoate and the like.

The principle of image formation and erasure of the heat-sensitive recording material of the present invention is not clear yet, but it is considered as follows. When a colorless or light-colored 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 occurs to develop a color.
At this time, it is considered that the electron-accepting compound molecule exists in the extremely close vicinity of the dye molecule that has developed color. Further, when the electron-accepting compound molecule is separated from the color-developed dye molecule, the color-developed dye molecule receives the electron again and becomes in the state of the dye precursor before color development. It is considered that the present invention changes the distance between the molecule of the electron-accepting compound and the molecule of the dye 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, the electron-accepting compound has low compatibility with the dye precursor molecule and the colored dye molecule, and in the coagulated state. It is considered that they are hardly compatible 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 like a heating and melting state, the dye precursor molecule and the electron-accepting compound molecule according to the present invention are mixed with each other at a certain ratio to form a color. It becomes a state. Therefore, when the colored mixture in the molten state is slowly cooled, the electron-accepting compound according to the present invention and the dye molecule become insoluble in each other and phase-separate and disappear when the temperature is lowered. 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 the molecule, it is rapidly crystallized by an intermolecular hydrogen bond. On the other hand, when the material is rapidly cooled, it solidifies before phase separation, that is, in the colored state, so that the colored state is fixed and the colored state is stably maintained even after the solidification.

As described above, the reversible thermosensitive recording material according to the present invention creates a compatible state and a phase separated state between the dye molecule and the electron-accepting compound according to the present invention, and develops a coloring and decoloring state. Conceivable. In order to develop a color, rapid cooling may occur after heating, and for example, heating with a thermal head, laser light or the like is possible. Also, if heated and slowly cooled, the color disappears, for example, heat roll, heat stamp, thermal head, high frequency heating,
It can be performed by using radiant heat from a hot air, an electric heater or a light source such as a halogen lamp.

Next, representative examples of specific synthetic examples of the electron-accepting compound represented by Chemical Formula 2 are shown below.

Synthesis Example 1 Synthesis of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-octadecylurea. Stirrer,
In a flask equipped with a condenser, 20 g of 10- (p-hydroxyphenylsulfonyl) decylamine.HBr salt,
Triethylamine 6.2 g and methyl ethyl ketone 30
0 ml was charged, and the mixture was heated and stirred at 80 ° C. in a nitrogen stream. 18 g of isocyanic acid-n-octadecyl was slowly added dropwise to this solution. After the reaction was aged for 1 hour, the reaction solution was cooled to room temperature. When the reaction solution was poured into ice water, crystals were precipitated. This was filtered under reduced pressure, washed with water, and recrystallized from i-propanol to obtain 22 g of the desired product. Melting point 112 [deg.] C.

Synthesis Example 2 Synthesis of N- [11- (p-hydroxyphenylsulfonyl) undecano] -N'-n-tetradecanohydrazide. In a flask equipped with a stirrer and a condenser, [11-
(P-Hydroxyphenylsulfonyl) undecano] hydrazide (25 g), triethylamine (8.5 g) and dimethylacetamide (300 ml) were charged, and the temperature was 40 ° C under a nitrogen stream.
It was heated and stirred. When 17 g of n-tetradecanoic acid chloride was slowly added dropwise to this solution, white crystals were precipitated. After the reaction was aged for 1 hour, the reaction solution was cooled to room temperature. When the reaction solution was poured into ice water, crystals were precipitated. This was filtered off under reduced pressure, washed with water, and recrystallized from i-propanol to obtain 30 g of the desired product. Melting point 134 [deg.] C.

Synthesis Example 3 Synthesis of N- [p- (p-hydroxyphenylsulfonyl) benzo] -N'-n-octadecanohydrazide. In a flask equipped with a stirrer and a condenser, 44 g of [p- (p-hydroxyphenylsulfonyl) benzo] hydrazide,
30 g of triethylamine and 40 of dimethylacetamide
0 ml was charged, and the mixture was stirred under a nitrogen stream while cooling with ice. When 27 g of n-octadecanoic acid chloride was slowly added dropwise to this solution, white crystals were precipitated. After standing at room temperature for a whole day and night, it was poured into ice water and the precipitated crystals were collected by filtration. Recrystallization from i-propanol gave 49 g of the desired product. Melting point 1
62 ° C.

Synthesis Example 4 Synthesis of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-decyloxamide. Stirrer,
In a flask equipped with a condenser, 20 g of 10- (p-hydroxyphenylsulfonyl) decylamine.HBr salt,
N- (n-decyl) oxamic acid ethyl ester 23.
When 5 g, triethylamine 9.3 g and i-propanol 400 ml were charged and heated under reflux, crystals were precipitated.
After refluxing was continued for 1 hour, the mixture was cooled to room temperature and the precipitated crystals were separated by filtration. Recrystallization from i-propanol gave 16 g of the desired product. Melting point 123 [deg.] C.

[0043]

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

Example 1 (A) Preparation of reversible heat-sensitive coating liquid 40 parts of a dye precursor, 3-di-n-butylamino-6-methyl-7-anilinofluorane, was added to a 2.5% polyvinyl alcohol aqueous solution. It was pulverized together with 90 parts by a ball mill for 24 hours to obtain a dye precursor dispersion liquid. Then N- [10-
(P-Hydroxyphenylsulfonyl) decyl] -N '
100 parts of -n-octadecyl urea was pulverized with 400 parts of a 2.5% polyvinyl alcohol aqueous solution in a ball mill for 24 hours to obtain a dispersion liquid. After mixing the above two kinds of dispersions, 200 parts of 10% polyvinyl alcohol aqueous solution and 4 parts of water
00 parts was added and mixed well to prepare a reversible heat-sensitive coating liquid.

(B) Preparation of reversible heat-sensitive recording material The reversible heat-sensitive coating solution prepared in (A) was applied to a polyethylene terephthalate (PET) sheet to give a solid content of 4 g / m ^2.
To obtain a reversible heat-sensitive recording material.

Example 2 Instead of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-octadecylurea used in Example 1, N- [11- (p-hydroxyphenylsulfonyl) was used. Undecano] -N'-n-tetradecanohydrazide was used to obtain a reversible thermosensitive recording material in the same manner as in Example 1.

Example 3 Instead of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-octadecylurea used in Example 1, N- [6- (p-hydroxyphenylsulfonyl) was used. A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that hexano] -N'-n-octadecanohydrazide was used.

Example 4 Instead of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-octadecylurea used in Example 1, N- [p- (p-hydroxyphenylsulfonyl)) A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that benzo] -N'-n-octadecanohydrazide was used.

Example 5 Instead of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-octadecylurea used in Example 1, N- [11- (p-hydroxyphenylsulfonyl)) A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that [Undecano] -N '-(pn-octylbenzo) hydrazide was used.

Example 6 Instead of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-octadecylurea used in Example 1, N- [10- (p-hydroxyphenylsulfonyl) was used. A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that decyl] -N'-n-decyloxamide was used.

Example 7 Instead of N- [10- (p-hydroxyphenylsulfonyl) decyl] -N'-n-octadecylurea used in Example 1, 1- [11- (p-hydroxyphenylsulfonyl)) Undecanoyl] -4-n-octadecyl semicarbazide was used to obtain a reversible thermosensitive recording material in the same manner as in Example 1.

Comparative Example 1 Instead of N- [2- (p-hydroxyphenylthio) ethyl] -N'-n-octadecylurea used in Example 1, a salt of gallic acid and stearylamine was used. Was performed in the same manner as in Example 1.

Comparative Example 2 Instead of N- [2- (p-hydroxyphenylthio) ethyl] -N'-n-octadecylurea used in Example 1, 2,2-bis (p-hydroxyphenyl) propane was used. Was performed in the same manner as in Example 1 except that was used.

Comparative Example 3 Instead of N- [2- (p-hydroxyphenylthio) ethyl] -N'-n-octadecylurea used in Example 1, p- (n-octadecylthio) phenol was used. Others were the same as in Example 1.

Test 1 (coloring density = thermoresponsiveness) The thermal recording materials obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were used in a thermal facsimile printing tester manufactured by Okura Electric Co. with a print head KJT-256-8MGF1 manufactured by Kyocera. TH-PMD
Was applied under the condition of an applied voltage of 26 V for an applied pulse of 1.1 milliseconds, and the density of the obtained color image was measured using a densitometer Macbeth RD918. The results are shown in Table 1.

Test 2 (Change in color density over time = image stability) The thermal recording materials obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were heat-sensitive facsimiles manufactured by Okura Electric Co. with a print head KJT-256-8MGF1 manufactured by Kyocera. Printing tester TH-PMD
Was applied under the condition of an applied voltage of 26 V for an applied pulse of 1.1 milliseconds and stored in an atmosphere of a temperature of 50 ° C. and a relative humidity of 30% for 14 hours. The density was measured, and the image residual ratio was calculated by the following formula 1. The results are shown in Table 1.

[0057]

[Equation 1] A = (C / B) × 100 A: Image residual ratio (%) B: Image density before test C: Image density after test

Test 3 (Image erasability) The heat-sensitive recording materials obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were used as the heat-sensitive facsimile printing tester TH-manufactured by Okura Electric Co. with a print head KJT-256-8MGF1 manufactured by Kyocera. PMD
Was applied at a voltage of 26 V for an applied pulse of 1.1 ms, and the resulting color image part was heated for 1 second at 120 ° C. using a heat stamp, and then the density was changed in the same manner as in Test 1. It was measured. The results are shown in Table 1.

[0059]

[Table 1]

In Table 1, ∘ indicates that the density of the erased portion is less than 30% of the density of the colored portion and the contrast between the colored portion and the erased portion is good,
Δ indicates that contrast is insufficient when the density of the erased portion is 30% or more and less than 80% of the density of the colored portion, and x indicates that reversibility is not observed when the density of the erased portion is 80% or more of the density of the colored portion.

[0061]

As shown in Table 1, it is usually represented by a colorless or light-colored electron-donating dye precursor and the general formula 2 which causes the dye precursor to reversibly change its color tone by heating. A reversible thermosensitive recording material containing an electron-accepting compound, capable of forming and erasing an image with good contrast, and capable of holding a stable image over time in the environment of everyday life. I was able to get it.

Claims (1)

[Claims] 1. A colorless or light-colored electron-donating dye precursor, and an electron-accepting compound represented by the following general formula 1 which causes a reversible color change in the dye precursor by heating. Reversible thermosensitive recording material. Embedded image (In Formula 1, n is an integer of 1 or more and 3 or less, R ¹ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and X is a divalent group having at least one —CONH— bond. And R ² represents a hydrocarbon group having 1 to 24 carbon atoms.)