JP3193166B2 - Reversible thermosensitive recording material - Google Patents

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, this method reversibly changes the transparency of the heat-sensitive recording material by heat energy,
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.

As described above, in the prior art, there is a reversible thermosensitive recording material which has a good image contrast, can form and erase an image, and can maintain a stable image with time in an environment of daily life. do not do.

[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]

The present inventors have conducted research to solve this problem, and as a result, they have found that a colorless or pale-colored electron-donating dye precursor can be reversibly changed in color tone by heating, that is, color development. The present inventors have found that an electron-accepting compound represented by the following general formula 2 that causes decoloration is present, and the present invention has been completed.

[0011]

Embedded image

In Formula 1 , n is an integer of 1 or more and 3 or less;
And 1 represent 0 or 1. R ¹ represents a substituent selected from an alkyl group , an alkenyl group , an alkoxy group , and a halogen atom, or a hydrogen atom. R ² and R ³ represent a lower alkyl group or a hydrogen atom, and may be the same or different from each other. R ⁴ represents an aliphatic hydrocarbon group having 6 to 22 carbon atoms . X represents a divalent group having at least one hetero atom, and Ar represents a divalent aromatic group.

Further, among the compounds represented by Chemical Formula 2, it is preferable that the number of carbon atoms of R ⁴ is large, and those having R ⁴ of 5 or less do not have a sufficient decoloring effect. Since R ⁴ having 23 or more carbon atoms has a high production cost, R ⁴ is particularly preferably an aliphatic hydrocarbon group having 6 to 22 carbon atoms.

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

N-hexyl-p-hydroxycinnamamide, N-cyclohexyl-p-hydroxycinnamamide, N-cyclohexylmethyl-p-hydroxycinnamamide, N-octyl-p-hydroxycinnamamide, Dodecyl-p-hydroxycinnamamide,
N- (2-decenyl) -p-hydroxycinnamamide, N-tetradecyl-p-hydroxycinnamamide, N-octadecyl-p-hydroxycinnamamide, N-docodecyl-p-hydroxycinnamamide,
N-octacosyl-p-hydroxycinnamamide, N
-(2-ethylhexyl) -p-hydroxycinnamamide, N- (8-octadecenyl) -p-hydroxycinnamamide, N-hexyl-o-hydroxycinnamamide, N-octyl-o-hydroxycinnamamide , N-dodecyl-m-hydroxycinnamamide, N
-Tetradecyl-o-hydroxycinnamamide, N-
Octadecyl-m-hydroxycinnamamide, N-hexyl-2,4-dihydroxycinnamamide, N-octyl-2,4-dihydroxycinnamamide, N-dodecyl-3,4-dihydroxycinnamamide, N- Tetradecyl-3,4-dihydroxycinnamamide, N
-Octadecyl-3,4-dihydroxycinnamamide, N-hexyl-p-hydroxy-α-methylcinnamamide, N-octyl-p-hydroxy-α-methylcinnamamide, N-dodecyl-p-hydroxy- β-
Methylcinnamamide, N-tetradecyl-p-hydroxy-β-methylcinnamamide, N-octadecyl-
p-hydroxy-α-methylcinnamamide,

N- (p-hexylphenyl) -p-hydroxycinnamamide, N- (p-cyclohexylphenyl) -p-hydroxycinnamamide, N- (p-octylphenyl) -p-hydroxycinnamamide , N
-(P-dodecylphenyl) -p-hydroxycinnamamide, N- (p-tetradecylphenyl) -p-hydroxycinnamamide, N- (p-octadecylphenyl) -p-hydroxycinnamamide, N- (M-hexylphenyl) -p-hydroxycinnamamide, N-
(O-octylphenyl) -p-hydroxycinnamamide, N- (m-dodecylphenyl) -p-hydroxycinnamamide, N- (o-tetradecylphenyl)-
p-hydroxycinnamamide, N- (m-octadecylphenyl) -p-hydroxycinnamamide, N-
(O-tetradecylphenyl) -m-hydroxycinnamamide, N- (m-octadecylphenyl) -m-hydroxycinnamamide, N- (p-dodecylphenyl) -3,4-dihydroxycinnamamide, N − (P
-Tetradecylphenyl) -3,4-dihydroxycinnamamide, N- (p-dodecylphenyl) -p-hydroxy-β-methylcinnamamide, N- (p-octadecylphenyl) -p-hydroxy-α- Methyl cinnamamide,

N- (p-hexyloxyphenyl) -p
-Hydroxycinnamamide, N- (p-cyclohexyloxyphenyl) -p-hydroxycinnamamide,
N- (p-octyloxyphenyl) -p-hydroxycinnamamide, N- (p-dodecyloxyphenyl)
-P-hydroxycinnamamide, N- {p- (2-decenyl) oxyphenyl} -p-hydroxycinnamamide, N- (p-tetradecyloxyphenyl) -p-
Hydroxycinnamamide, N- (p-octadecyloxyphenyl) -p-hydroxycinnamamide, N-
(M-hexyloxyphenyl) -p-hydroxycinnamamide, N- (o-octyloxyphenyl) -p
-Hydroxycinnamamide, N- (m-dodecyloxyphenyl) -p-hydroxycinnamamide, N-
(O-tetradecyloxyphenyl) -p-hydroxycinnamamide, N- (m-octadecyloxyphenyl) -p-hydroxycinnamamide, N- (o-tetradecyloxyphenyl) -m-hydroxycinnamamide , N- (m-octadecyloxyphenyl) -m-
Hydroxycinnamamide, N- (p-dodecyloxyphenyl) -3,4-dihydroxycinnamamide, N
-(P-tetradecyloxyphenyl) -3,4-dihydroxycinnamamide, N- (p-dodecyloxyphenyl) -p-hydroxy-β-methylcinnamamide, N- (p-octadecyloxyphenyl)- p-hydroxy-α-methylcinnamamide,

N- (p-hexylthiophenyl) -p-
Hydroxycinnamamide, N- (p-cyclohexylthiophenyl) -p-hydroxycinnamamide, N-
(P-octylthiophenyl) -p-hydroxycinnamamide, N- (p-dodecylthiophenyl) -p-hydroxycinnamamide, N-Δp- (2-decenyl)
Thiophenyl {-p-hydroxycinnamamide, N-
(P-tetradecylthiophenyl) -p-hydroxycinnamamide, N- (p-octadecylthiophenyl)
-P-hydroxycinnamamide, N- (m-hexylthiophenyl) -p-hydroxycinnamamide, N-
(O-octylthiophenyl) -p-hydroxycinnamamide, N- (m-dodecylthiophenyl) -p-hydroxycinnamamide, N- (o-tetradecylthiophenyl) -p-hydroxycinnamamide, N- (m
-Octadecylthiophenyl) -p-hydroxycinnamamide, N- (o-tetradecylthiophenyl) -m
-Hydroxycinnamamide, N- (m-octadecylthiophenyl) -m-hydroxycinnamamide, N-
(P-dodecylthiophenyl) -3,4-dihydroxycinnamamide, N- (p-tetradecylthiophenyl) -3,4-dihydroxycinnamamide, N- (p
-Dodecylthiophenyl) -p-hydroxy-β-methylcinnamamide, N- (p-octadecylthiophenyl) -p-hydroxy-α-methylcinnamamide,

N- (p-hexylcarbonylphenyl)
-P-hydroxycinnamamide, N- (p-octylcarbonylphenyl) -p-hydroxycinnamamide, N- (p-dodecylcarbonylphenyl) -p-hydroxycinnamamide, N- (p-tetradecylcarbonyl Phenyl) -p-hydroxycinnamamide, N
-(P-octadecylcarbonylphenyl) -p-hydroxycinnamamide, N- (m-hexylcarbonylphenyl) -p-hydroxycinnamamide, N- (o
-Octylcarbonylphenyl) -p-hydroxycinnamamide, N- (m-dodecylcarbonylphenyl)
-P-hydroxycinnamamide, N- (o-tetradecylcarbonylphenyl) -p-hydroxycinnamamide, N- (m-octadecylcarbonylphenyl)-
p-hydroxycinnamamide, N- (o-tetradecylcarbonylphenyl) -m-hydroxycinnamamide, N- (m-octadecylcarbonylphenyl) -m
-Hydroxycinnamamide, N- (p-dodecylcarbonylphenyl) -3,4-dihydroxycinnamamide, N- (p-tetradecylcarbonylphenyl)-
3,4-dihydroxycinnamamide, N- (p-dodecylcarbonylphenyl) -p-hydroxy-β-methylcinnamamide, N- (p-octadecylcarbonylphenyl) -p-hydroxy-α-methylcinnamamide ,

N- (p-hexylaminophenyl) -p
-Hydroxycinnamamide, N- (p-dicyclohexylaminophenyl) -p-hydroxycinnamamide, N- (p-octylaminophenyl) -p-hydroxycinnamamide, N- (p-dodecylaminophenyl)- p-hydroxycinnamamide, N- (p-tetradecylaminophenyl) -p-hydroxycinnamamide, N- (p-octadecylaminophenyl) -p-
Hydroxycinnamamide, N- (m-hexylaminophenyl) -p-hydroxycinnamamide, N- (o
-Octylaminophenyl) -p-hydroxycinnamamide, N- (m-dodecylaminophenyl) -p-hydroxycinnamamide, N- (o-tetradecylaminophenyl) -p-hydroxycinnamamide, N-
(M-octadecylaminophenyl) -p-hydroxycinnamamide, N- (o-tetradecylaminophenyl) -m-hydroxycinnamamide, N- (m-octadecylaminophenyl) -m-hydroxycinnamamide, N- (p-dodecylaminophenyl) -3,4-
Dihydroxycinnamamide, N- (p-tetradecylaminophenyl) -3,4-dihydroxycinnamamide, N- (p-dodecylaminophenyl) -p-hydroxy-β-methylcinnamamide, N- (p -Octadecylaminophenyl) -p-hydroxy-α-methylcinnamamide,

N- (p-hexylsulfinylphenyl) -p-hydroxycinnamamide, N- (p-octylsulfinylphenyl) -p-hydroxycinnamamide, N- (p-dodecylsulfinylphenyl)-
p-hydroxycinnamamide, N- {p- (2-decenyl) sulfinylphenyl} -p-hydroxycinnamamide, N- (p-tetradecylsulfinylphenyl) -p-hydroxycinnamamide, N- (p -Octadecylsulfinylphenyl) -p-hydroxycinnamamide, N- (m-hexylsulfinylphenyl) -p-hydroxycinnamamide, N- (o-octylsulfinylphenyl) -p-hydroxycinnamamide, N- ( m-dodecylsulfinylphenyl)-
p-hydroxycinnamamide, N- (o-tetradecylsulfinylphenyl) -p-hydroxycinnamamide, N- (m-octadecylsulfinylphenyl)
-P-hydroxycinnamamide, N- (o-tetradecylsulfinylphenyl) -m-hydroxycinnamamide, N- (m-octadecylsulfinylphenyl) -m-hydroxycinnamamide, N- (p-dodecylsulfinyl) Phenyl) -3,4-dihydroxycinnamamide, N- (p-tetradecylsulfinylphenyl) -3,4-dihydroxycinnamamide, N-
(P-dodecylsulfinylphenyl) -p-hydroxy-β-methylcinnamamide, N- (p-octadecylsulfinylphenyl) -p-hydroxy-α-methylcinnamamide,

N- (p-hexylsulfonylphenyl) -p-hydroxycinnamamide, N- (p-octylsulfonylphenyl) -p-hydroxycinnamamide, N- (p-dodecylsulfonylphenyl)-
p-hydroxycinnamamide, N- {p- (2-decenyl) sulfonylphenyl} -p-hydroxycinnamamide, N- (p-tetradecylsulfonylphenyl) -p-hydroxycinnamamide, N- (p -Octadecylsulfonylphenyl) -p-hydroxycinnamamide, N- (m-hexylsulfonylphenyl) -p-hydroxycinnamamide, N- (o-octylsulfonylphenyl) -p-hydroxycinnamamide, N- ( m-dodecylsulfonylphenyl)-
p-hydroxycinnamamide, N- (o-tetradecylsulfonylphenyl) -p-hydroxycinnamamide, N- (m-octadecylsulfonylphenyl)
-P-hydroxycinnamamide, N- (o-tetradecylsulfonylphenyl) -m-hydroxycinnamamide, N- (m-octadecylsulfonylphenyl) -m-hydroxycinnamamide, N- (p-dodecylsulfonyl) Phenyl) -3,4-dihydroxycinnamamide, N- (p-tetradecylsulfonylphenyl) -3,4-dihydroxycinnamamide, N-
(P-dodecylsulfonylphenyl) -p-hydroxy-β-methylcinnamamide, N- (p-octadecylsulfonylphenyl) -p-hydroxy-α-methylcinnamamide and the like.

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

The generally 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- (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 compounds 4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenylleucouramine, N-2,4,5-trichlorophenylleucouramine, etc.

(3) Xanthene compounds rhodamine B anilinolactam, rhodamine B-p-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- (3,4-dichloroanilino) fluoran, 3 -Diethylamino-7
-(2-chloroanilino) fluoran,

3-Diethylamino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl- 7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Phenethylfluoran, 3-diethylamino-7- (4
-Nitroanilino) fluoran, 3-dibutylamino-
6-methyl-7-anilinofluoran, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamyl) amino-6 Methyl-7-anilinofluoran, 3- (N-
Methyl-N-cyclohexyl) amino-6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-tetrahydrofuryl) amino-6-methyl-7-anilinofluoran and the like,

(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 in combination of two or more.

Next, a specific method for producing the reversible thermosensitive recording material according to 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 according to the present invention, a colorless or pale-color dye precursor and the electron-accepting compound according to the present invention as main components are coated on a support. To form a reversible thermosensitive recording layer.

In general, the colorless or pale-color dye precursor and the electron-accepting compound according to the present invention are 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.

Further, a binder can be added 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 Latexes such as esters, styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene copolymers, ethylene / vinyl acetate copolymers, and the like, but are not limited thereto. No.

Further, 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, but is not limited thereto.

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, a material capable of recording information electrically, magnetically and optically on the surface of the reversible thermosensitive recording layer and / or on the surface opposite to the surface on which the other layer and / or the reversible thermosensitive recording layer is provided. 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 prepared by mixing each dispersion obtained by pulverizing each color-forming component, coating and drying the dispersion on a support, and dissolving each color-forming component in a solvent. It can be obtained by, for example, a method of mixing a solution and coating and drying the solution on a support. In this case, for example, each color-forming component may be contained one layer at a time 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, etc., in addition to head abrasion prevention, anti-sticking, zinc stearate, higher fatty acid metal salts such as calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearamide, Waxes such as caster wax, and a dispersant such as dioctyl sodium sulfosuccinate, a surfactant, a fluorescent dye, and the like can also be contained.

[0041]

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 erasing of the heat-sensitive recording material of the present invention is not clear yet, it is 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 a 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 a molten state, the dye precursor molecule and the electron accepting compound molecule according to the present invention dissolve at a certain ratio to each other, and the color forming state is formed. Becomes Therefore, when the color-developing molten mixture is slowly cooled, the electron-accepting compound according to the present invention and the dye molecules become insoluble with each other and phase-separate as the temperature decreases,
Decolorize. On the other hand, when cooling rapidly, before phase separation,
That is, since the solidified state is maintained in the color-developed state, the color-developed state is fixed and the color-developed state is stably maintained even after the solidification.

As described above, the reversible thermosensitive recording material according to the present invention produces a compatible state and a phase-separated state between a dye molecule and the electron-accepting compound according to the present invention, and develops 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 hot air, radiant heat from an electric heater, or the like.

[0045]

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

Example 1 (A) Preparation of a reversible heat-sensitive coating solution 40 parts of 3-di-n-butylamino-6-methyl-7-anilinofluoran, a dye precursor, was added to a 2.5% aqueous solution of polyvinyl alcohol. 90 parts together with a ball mill for 24 hours to obtain a dye precursor dispersion. Next, 100 parts of N-octadecyl-p-hydroxycinnamamide was added to 2.5 parts.
The mixture was pulverized with a ball mill for 24 hours together with 400 parts of a 50% aqueous solution of polyvinyl alcohol to obtain a dispersion. After mixing the above two dispersions, a 10% aqueous solution of polyvinyl alcohol 200
And 400 parts of water were added and mixed well to prepare a reversible thermosensitive coating liquid.

(B) Preparation of reversible thermosensitive recording material The reversible thermosensitive coating liquid prepared in (A) was applied to a polyethylene terephthalate (PET) sheet at a solids coating amount of 4 g / m ^2.
And dried and then treated with a super calender to obtain a reversible thermosensitive recording material.

Example 2 In place of the dispersion of N-octadecyl-p-hydroxycinnamamide used in Example 1, N- (p-tetradecylphenyl) -p-hydroxycinnamamide 100 was used.
A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that a dispersion obtained by pulverizing a part by a ball mill for 24 hours together with 400 parts of a 2.5% aqueous polyvinyl alcohol solution was used.

Example 3 In place of the dispersion of N-octadecyl-p-hydroxycinnamamide used in Example 1, 100 parts of N- (p-tetradecyloxyphenyl) -p-hydroxycinnamamide was added. 2.5% polyvinyl alcohol aqueous solution 400
A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that a dispersion obtained by pulverizing with a part in a ball mill for 24 hours was used.

Example 4 In place of the dispersion of N-octadecyl-p-hydroxycinnamamide used in Example 1, 100 parts of N- (p-octadecyloxyphenyl) -p-hydroxycinnamamide was added to 2. 5% polyvinyl alcohol aqueous solution 400
A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that a dispersion obtained by pulverizing with a part in a ball mill for 24 hours was used.

Comparative Example 1 In place of the dispersion of N-octadecyl-p-hydroxycinnamamide used in Example 1, 100 parts of a salt of gallic acid and stearylamine was added together with 400 parts of a 2.5% aqueous solution of polyvinyl alcohol. Example 1 was repeated except that a dispersion obtained by pulverizing with a ball mill for 24 hours was used.

Comparative Example 2 In place of the N-octadecyl-p-hydroxycinnamamide dispersion used in Example 1, 2,2-bis (4-
100 parts of (hydroxyphenyl) propane were mixed with 400 parts of a 2.5% aqueous solution of polyvinyl alcohol in a ball mill.
The procedure was the same as in Example 1, except that the dispersion obtained by grinding for 4 hours was used.

Comparative Example 3 Instead of the N-octadecyl-p-hydroxycinnamamide dispersion used in Example 1, 100 parts of benzyl 4-hydroxybenzoate was mixed with 400 parts of a 2.5% aqueous solution of polyvinyl alcohol by a ball mill. The procedure was the same as in Example 1, except that a dispersion obtained by grinding for 24 hours was used.

Test 1 (color density = thermal response) The thermal recording materials obtained in Examples 1-4 and Comparative Examples 1-3 were applied to a thermal facsimile printing tester manufactured by Okura Electric with a print head KJT-256-8MGF1 manufactured by Kyocera. TH-PMD
Were printed under the conditions of an applied pulse of 1.0 millisecond and an applied voltage of 26 volts, 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 4 and Comparative Examples 1 to 3 were attached to a print head KJT-256-8MGF1 manufactured by Kyocera and a thermal facsimile manufactured by Okura Electric. Printing tester TH-PMD
, And printing was performed under the conditions of an applied pulse of 1.0 millisecond and an applied voltage of 26 volts, and stored for 96 hours in an atmosphere of a temperature of 25 ° C. and a relative humidity of 60%. The density was measured, and the image residual ratio was calculated by the following equation (1). The results are shown in Table 1.

[0056]

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

Test 3 (Erasability of Image) The thermal recording materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were applied to a thermal facsimile printing tester TH-Okura Electric with a print head KJT-256-8MGF1 manufactured by Kyocera. PMD
Was applied under the conditions of an applied pulse of 1.0 millisecond and an applied voltage of 26 volts, and was heated at 120 ° C. for 1 second using a heat stamp, and the concentration was measured in the same manner as in Test 1. The results are shown in Table 1.

[0058]

[Table 1]

In Table 1, .largecircle. 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 the contrast is insufficient when the density of the erased portion is 30% or more and less than 80% of the density of the color-developed portion, and X indicates that no reversibility is observed when the density of the erased portion is 80% or more of the density of the color-developed portion.

[0060]

As shown in Table 1, it is usually represented by a colorless or light-colored electron-donating dye precursor and the above-mentioned general formula 2 which causes a reversible color change in the dye precursor upon heating. By using a reversible thermosensitive recording material containing an electron-accepting compound, a reversible thermosensitive recording material capable of forming and erasing images with good contrast and maintaining a stable image over time in an environment of daily life is provided. I got it.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/28-5/34 CA (STN) REGISTRY (STN)

Claims (1)

(57) [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 upon heating. Reversible thermosensitive recording material. Embedded image (In Formula 1, n is an integer of 1 to 3, and m and l are 0.
Or represents 1. R ¹ represents a substituent selected from an alkyl group , an alkenyl group , an alkoxy group , and a halogen atom, or a hydrogen atom. R ² and R ³ represent a lower alkyl group or a hydrogen atom, and may be the same or different from each other. R ⁴
Represents an aliphatic hydrocarbon group having 6 to 22 carbon atoms . X
Represents a divalent group having at least one heteroatom,
r represents a divalent aromatic group. )