JPH06227125A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To form an image by an excellent contrast, to erase it and to keep the stability of the image by using an electron-accepting compound which causes a reversible change in color tone in an electron-donating dye precursor by heating and which is expressed by a specific general formula. CONSTITUTION:A reversible thermal recording material is constructed of an electron-donating dye precursor being colorless or light-colored ordinarily and an electron-accepting compound causing a reversible change in color tone in the electron-donating dye precursor by heating. The electron-accepting compound to be used is expressed by a general formula shown. In the formula, (n) and (m) denote integers of 0 or 1 and R<1> and R<2> aliphatic hydrocarbon or hydrogen atoms respectively. When (n) and (m) denote 1 respectively, R<1> and R<2> denote only aliphatic hydrocarbon groups respectively. The case in which R<1> and R<2> are hydrogen atoms simultaneously is excluded herein. Moreover, X and y denote bivalent groups each having one hetero atom at least.

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 forming portion and the image non-forming portion 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 / reducing agent is an amphoteric compound having an acidic group for coloring a leuco dye and a basic group for decoloring a leuco dye that has formed a color, and a coloring action by an acidic group or a decoloring action by a basic group 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.

As described above, according to the conventional technique, there is a reversible thermosensitive recording material having a good image contrast, capable of forming / erasing an image, and capable of holding a stable image over time in the 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 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]

[Chemical 2]

(In the formula 2, n and m represent an integer of 0 or 1. R ¹ and R ² represent an aliphatic hydrocarbon group or a hydrogen atom, provided that when n is 1, R ¹ is a fat. R ² represents only an aliphatic hydrocarbon group, and when m is 1, R ² represents only an aliphatic hydrocarbon group, and R ¹ and R ² are not hydrogen atoms at the same time. Represents a divalent group having at least one hetero atom.)

Among the compounds represented by Chemical formula ² , R ¹ and R ²
Among the aliphatic hydrocarbon groups represented by, it is preferable that at least one group has a large number of carbon atoms, and those having 5 or less carbon atoms do not have sufficient decoloring effect and have 23 or more carbon atoms. Is expensive to manufacture. Therefore, among the aliphatic hydrocarbon groups represented by R ¹ and R ^{2, those in} which at least one group has 6 to 22 carbon atoms are particularly preferable. X and Y in Formula 2 specifically represent an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or the like.

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.

N- (pn-hexylphenyl) -N '
-Phenylthiourea, N- (p-cyclohexylphenyl) -N'-phenylthiourea, N- (pn-octylphenyl) -N'-phenylthiourea, N- [p-
(2-decenyl) phenyl-N'-phenyl] thiourea, N- (pn-dodecylphenyl) -N'-phenylthiourea, N- (pn-tetradecylphenyl)-
N'-phenylthiourea, N- (pn-octadecylphenyl) -N'-phenylthiourea, N- (mn-
Dodecylphenyl) -N'-phenylthiourea, N-
(M-n-octadecylphenyl) -N'-phenylthiourea, N- (p-cyclohexyloxyphenyl)-
N'-phenylthiourea, N- (pn-decyloxyphenyl) -N'-phenylthiourea, N- (pn-
Dodecyloxyphenyl) -N'-phenylthiourea,
N- (pn-tetradecyloxyphenyl) -N'-
Phenylthiourea, N- (pn-octadecyloxyphenyl) -N'-phenylthiourea, N- (mn-
Dodecyloxyphenyl) -N'-phenylthiourea,
N- (mn-octadecyloxyphenyl) -N'-
Phenylthiourea, N- (pn-decylthiophenyl) -N'-phenylthiourea, N- (pn-dodecylthiophenyl) -N'-phenylthiourea, N- (p
-N-tetradecylthiophenyl) -N'-phenylthiourea, N- (pn-octadecylthiophenyl)-
N'-phenylthiourea, N- (mn-dodecylthiophenyl) -N'-phenylthiourea, N- (mn-
Octadecylthiophenyl) -N'-phenylthiourea, N- [p- (2-decenyl) carbonylphenyl]
-N'-phenylthiourea, N- (pn-dodecylcarbonylphenyl) -N'-phenylthiourea, N-
(Pn-tetradecylcarbonylphenyl) -N'-
Phenylthiourea, N- (pn-octadecylcarbonylphenyl) -N'-phenylthiourea, N- (m-
n-dodecylcarbonylphenyl) -N'-phenylthiourea, N- (m-n-octadecylcarbonylphenyl) -N'-phenylthiourea, N- [p- (2-decenyl) sulfonylphenyl] -N'-phenylthiourea , N- (pn-dodecylsulfonylphenyl) -N
'-Phenylthiourea, N- (pn-tetradecylsulfonylphenyl) -N'-phenylthiourea, N-
(Pn-octadecylsulfonylphenyl) -N'-
Phenylthiourea, N- (mn-dodecylsulfonylphenyl) -N'-phenylthiourea, N- (mn-
Octadecylsulfonylphenyl) -N'-phenylthiourea,

N, N'-bis (pn-hexylphenyl) thiourea, N, N'-bis (p-cyclohexylphenyl) thiourea, N, N'-bis (pn-octylphenyl) thio Urea, N, N'-bis [p- (2-decenyl) phenyl] thiourea, N, N-bis (p-dodecylphenyl) thiourea, N, N'-bis (pn-tetradecylphenyl) Thiourea, N, N'-bis (pn
-Octadecylphenyl) thiourea, N, N'-bis (mn-dodecylphenyl) thiourea, N, N'-bis (mn-octadecylphenyl) thiourea, N-
(P-Tolyl) -N '-(pn-octadecylphenyl) thiourea, N- (pn-tetradecylphenyl)
-N '-(pn-octadecylphenyl) thiourea,
N- (pn-octadecylphenyl) -N '-(m-
n-octadecylphenyl) thiourea, N, N'-bis (pn-hexyloxyphenyl) thiourea, N, N
′ -Bis (p-cyclohexyloxyphenyl) thiourea, N, N′-bis (pn-octyloxyphenyl) thiourea, N, N′-bis [p- (2-decenyl)
Oxyphenyl] thiourea, N, N'-bis (pn-
Dodecyloxyphenyl) thiourea, N, N'-bis (pn-tetradecyloxyphenyl) thiourea,
N, N'-bis (pn-octadecyloxyphenyl) thiourea, N, N'-bis (mn-dodecyloxyphenyl) thiourea, N, N'-bis (mn-octadecyloxyphenyl) ) Thiourea, N- (pn-butoxyphenyl) -N '-(pn-tetradecylphenyl) thiourea, N- (p-methoxyphenyl) -N'
-(Pn-octadecyloxyphenyl) thiourea,
N- (pn-tetradecyloxyphenyl) -N'-
(Pn-octadecyloxyphenyl) thiourea, N
-(Pn-octadecyloxyphenyl) -N'-
(Mn-octadecyloxyphenyl) thiourea,
N, N'-bis (pn-hexylthiophenyl) thiourea, N, N'-bis (p-cyclohexylthiophenyl) thiourea, N, N'-bis (pn-octylthiophenyl) thio Urea, N, N'-bis [p- (2-decenyl) thiophenyl] thiourea, N, N'-bis (p-
n-dodecylthiophenyl) thiourea, N, N'-bis (pn-tetradecylthiophenyl) thiourea, N,
N'-bis (pn-octadecylthiophenyl) thiourea, N, N'-bis (mn-dodecylthiophenyl) thiourea, N, N'-bis (mn-octadecylthiophenyl) thio Urea, N- (pn-tetradecylthiophenyl) -N '-(pn-octadecylthiophenyl) thiourea, N- (pn-octadecylthiophenyl) -N'-(mn- Octadecylthiophenyl) thiourea, N, N'-bis (pn-hexylcarbonylphenyl) thiourea, N, N'-bis (p-cyclohexylcarbonylphenyl) thiourea, N, N'-
Bis (pn-octylcarbonylphenyl) thiourea, N, N'-bis (pn-decylcarbonylphenyl) thiourea, N, N'-bis (pn-dodecylcarbonylphenyl) thiourea, N , N'-bis (pn-
Tetradecylcarbonylphenyl) thiourea, N, N '
-Bis (pn-octadecylcarbonylphenyl) thiourea, N, N'-bis (mn-dodecylcarbonylphenyl) thiourea, N, N'-bis (mn-octadecylcarbonylphenyl) thiourea, N- (pn-
Tetradecylcarbonylphenyl) -N '-(pn-
Octadecylcarbonylphenyl) thiourea, N- (p
-N-octadecylcarbonylphenyl) -N '-(m
-N-octadecylcarbonylphenyl) thiourea,
N, N'-bis (pn-hexylsulfonylphenyl) thiourea, N, N'-bis (pn-octylsulfonylphenyl) thiourea, N, N'-bis [p- (2
-Decenyl) sulfonylphenyl] thiourea, N, N '
-Bis (pn-dodecylsulfonylphenyl) thiourea, N, N'-bis (pn-tetradecylsulfonylphenyl) thiourea, N, N'-bis (pn-octadecylsulfonylphenyl) thiourea , N, N-bis (mn-dodecylsulfonylphenyl) thiourea,
N, N'-bis (mn-octadecylsulfonylphenyl) thiourea, N- (pn-tetradecylsulfonylphenyl) -N '-(pn-octadecylsulfonylphenyl) thiourea, N- (p -N-octadecylsulfonylphenyl) -N '-(m-n-octadecylsulfonylphenyl) thiourea, N- (pn-octadecylphenyl) -N'-(pn-octadecyloxyphenyl) thiourea, N -(Pn-octadecylphenyl) -N '-(pn-octadecylthiophenyl)
Thiourea, N- (pn-octadecylphenyl) -N
'-(Pn-octadecylcarbonylphenyl) thiourea, N- (pn-octadecylphenyl) -N'-
(Pn-octadecylsulfonylphenyl) thiourea, N- (mn-octadecylphenyl) -N'-
(Pn-octadecyloxyphenyl) thiourea and the like.

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

The usually colorless to light-colored electron-donating dye precursor used in the present invention is represented by those generally used for pressure-sensitive recording paper, heat-sensitive recording paper, etc., 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 compounds 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-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl- 7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Phenethylfluorane, 3-diethylamino-7- (4
-Nitroanilino) fluorane, 3-dibutylamino-
6-methyl-7-anilinofluorane, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6- Methyl-7-anilinofluorane, 3- (N-
Methyl-N-cyclohexyl) amino-6-methyl-7
-Anilinofluorane, 3- (N-ethyl-N-tetrahydrofuryl) amino-6-methyl-7-anilinofluorane, etc.

(4) Thiazine-based compounds benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue, etc.

(5) Spiro compound 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 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 are mainly contained, and these are coated on a support. And a reversible thermosensitive recording layer is formed.

As a method of incorporating a colorless or light-colored dye precursor and an electron-accepting compound according to the present invention into a 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, latexes such as esters, styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene copolymers, ethylene / vinyl acetate copolymers. 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 for 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 depending on 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 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, in the reversible thermosensitive recording layer and / or on the surface opposite to the surface on which another layer and / or the reversible thermosensitive recording layer is provided, a material capable of electrically, magnetically and optically recording information 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 preventing electrification.

The reversible thermosensitive recording layer is obtained by finely pulverizing each color-forming component, mixing each dispersion, coating and drying on a support, and each color-forming component dissolved in a solvent. It can be obtained by a method in which the solutions are mixed, coated on a support and dried. 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. In addition to pigments such as aluminum and urea-formalin resin, zinc stearate, higher fatty acid metal salts such as calcium stearate, paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearic acid amide, and the like for the purpose of preventing head wear and sticking. Waxes such as castor wax may also be contained in addition to a dispersant such as sodium dioctylsulfosuccinate, a surfactant, and a fluorescent dye.

[0035]

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, 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 dye molecule that has developed color, and in the coagulated state. It is considered that they are hardly compatible with each other. Further, in a state in which the dye precursor molecule and the electron-accepting compound molecule according to the present invention can freely move like a molten 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, and a coloring state is obtained. Becomes 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 as the temperature decreases.
Erase. On the other hand, if cooling is performed rapidly, before phase separation,
That is, since the solidified state remains solid, the colored state is fixed, and the solidified state is maintained even after 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 hot air, radiant heat from an electric heater, or the like.

[0039]

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 3-di-n-butylamino-6-methyl-7-anilinofluorane, which is a dye precursor, 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- (pn
-Octadecylphenyl) -N'-phenylthiourea 1
00 copies 2. 5% polyvinyl alcohol aqueous solution 400
And a ball mill for 24 hours to obtain a dispersion liquid.
After mixing the above two kinds of dispersions, 200 parts of a 10% polyvinyl alcohol aqueous solution and 400 parts of water were 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 liquid 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 the N- (pn-octadecylphenyl) -N'-phenylthiourea dispersion used in Example 1, N was used.
Example except that 100 parts of-(pn-octadecyloxyphenyl) -N'-phenylthiourea was crushed with 400 parts of a 2.5% aqueous polyvinyl alcohol solution by a ball mill for 24 hours, and used. A reversible thermosensitive recording material was obtained in the same manner as in 1.

Example 3 Instead of the N- (pn-octadecylphenyl) -N'-phenylthiourea dispersion used in Example 1,
100 parts of N, N'-bis (pn-octadecylphenyl) thiourea was added to a 2.5% aqueous solution of polyvinyl alcohol 4
A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the dispersion liquid obtained by pulverizing with 00 parts by a ball mill for 24 hours was used.

Example 4 Instead of the N- (pn-octadecylphenyl) -N'-phenylthiourea dispersion used in Example 1,
Example 1 except that 100 parts of N, N'-bis (pn-octadecyloxyphenyl) thiourea was pulverized with 400 parts of a 2.5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a dispersion. A reversible thermosensitive recording material was obtained in the same manner as.

Comparative Example 1 Instead of the N- (pn-octadecylphenyl) -N'-phenylthiourea dispersion used in Example 1, 100 parts of a salt of gallic acid and stearylamine was added at 2.5%. Example 1 except that the dispersion obtained by grinding with a ball mill for 24 hours together with 400 parts of an aqueous polyvinyl alcohol solution was used.
Same as.

Comparative Example 2 Instead of the N- (pn-octadecylphenyl) -N'-phenylthiourea dispersion used in Example 1,
2,2-bis (4-hydroxyphenyl) propane 10
Example 1 was repeated except that 0 part was used together with 400 parts of a 2.5% aqueous polyvinyl alcohol solution and ground for 24 hours in a ball mill.

Comparative Example 3 Instead of the N- (pn-octadecylphenyl) -N'-phenylthiourea dispersion used in Example 1, 4
100 parts of benzyl hydroxybenzoate were ball milled together with 400 parts of 2.5% aqueous polyvinyl alcohol solution.
The same procedure as in Example 1 was performed except that the dispersion liquid obtained by pulverizing for 4 hours was used.

Test 1 (coloring density = thermoresponsiveness) The thermal recording materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were applied to a thermal facsimile printing tester manufactured by Okura Electric Co. with a print head KJT-256-8MGF1 manufactured by Kyocera. TH-PMD
Was applied for 1.0 millisecond with an applied pulse of 26 volts, and the density of the resulting color image was measured using a densitometer Macbeth RD918. The results are shown in Table 1.

Test 2 (Change in Color Density with Time = Image Stability) The thermal recording materials obtained in Examples 1 to 4 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 with an applied pulse of 1.0 msec and stored in an atmosphere of a temperature of 25 ° C. and a relative humidity of 60% for 96 hours. The density was measured, and the image residual ratio was calculated by the following formula 1. The results are shown in Table 1.

[0050]

[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 4 and Comparative Examples 1 to 3 were used as a thermal facsimile printing tester TH-manufactured by Okura Electric Co. with a print head KJT-256-8MGF1 manufactured by Kyocera. PMD
Was applied under the condition of an applied voltage of 26 V with an applied pulse of 1.0 msec, and the printed sample was heated at 120 ° C. for 1 second using a heat stamp, and then the density was measured in the same manner as in Test 1. The results are shown in Table 1.

[0052]

[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.

[0054]

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. [Chemical 1] (In formula 1, n and m represent 0 or an integer of ^1. R ¹
And R ² represents an aliphatic hydrocarbon group or a hydrogen atom. However, when n is 1, R ¹ represents only an aliphatic hydrocarbon group, and when m is 1, R ² represents only an aliphatic hydrocarbon group. Furthermore, the case where R ¹ and R ² are simultaneously hydrogen atoms is excluded. Further, X and Y represent a divalent group having at least one hetero atom. )