JPH0811433A - Reversible thermal recording medium - Google Patents

Abstract

PURPOSE:To eliminate color forming deficiency, deterioration of an image with the elapse of time, and discoloration of a background part at the time of the formation of a protective layer by forming a reversible thermal recording medium by successively laminating a thermal color forming recording layer, an ultraviolet absorbing layer and the protective layer on a support. CONSTITUTION:A thermal color forming recording layer containing an electron donating color forming compd., an electron acceptive compd. and a resin binder as main components and forming a developed color state by heating and melting and forming an erased color state at temp. lower than color forming temp. is provided on a support. A ultraviolet absorbing layer is provided on this thermal recording layer and a protective layer composed of a ultraviolet curable resin is laminated thereon to form a reversible thermal recording medium. The ultraviolet curable resin for forming the protective layer is obtained by using a monomer or oligomer generating polymerization reaction by the irradiation with ultraviolet rays and cured to become a resin. The ultraviolet absorbing layer is composed of a resin containing an ultraviolet absorber and can be formed by applying a soln. prepared by dissolving a resin and an ultraviolet absorber in a solvent to the thermal recording layer to dry the same.

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 medium utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound.

[0002]

2. Description of the Related Art Conventionally, heat-sensitive recording utilizing a color-forming reaction between an electron-donating color-forming compound (hereinafter also referred to as a color-developing agent) and an electron-accepting compound (hereinafter also referred to as a color-developing agent). The medium is widely known, and the output of electronic calculators, facsimiles, vending machines, printers of scientific measuring machines, C
Widely used in RT medical measurement printers. However, all the conventional products have irreversible color development, and it is not possible to repeat the color development and the color erasing alternately. On the other hand, according to the patent publication, there have been proposed some thermal recording media that utilize color reaction between a color former and a color developer to reversibly perform color development and decolorization. For example, Japanese Unexamined Patent Publication (Kokai) No. 60-193691 discloses a developer using a combination of gallic acid and phloroglucinol as a developer. The color-developing material obtained by thermally coloring this material is decolorized with water or steam. But,
In the case of this heat-sensitive recording medium, there is a problem in that it is difficult to make it water resistant and there is a problem in recording storability, and furthermore, there is a problem that the erasing device for erasing the color developing body becomes large. JP-A-6
No. 1-237684 discloses a rewritable optical recording medium using a compound such as phenolphthalene, thymolphthalene or bisphenol as a developer. This product forms a color-forming material by heating and gradually cooling it, while it can be decolored by heating the color-forming material once to a temperature higher than the coloring temperature and then rapidly cooling it. However, in the case of this recording medium, the coloring and erasing steps are complicated, and some color is still seen in the erasable body obtained by erasing the chromophore, and a colored image with good contrast is obtained. I can't.

JP-A-62-140881 and JP-A-62-14088
No. 138568 and JP-A No. 62-138556 disclose homogeneous compatible solutions of a color former, a developer and a carboxylic acid ester. This product shows a completely colored state at a low temperature and a completely decolored state at a high temperature, and can maintain the colored or decolored state at an intermediate temperature between them, and by printing with a thermal head on this medium, the colored background White characters (decolored body) can be recorded on (colored body). Therefore, in the case of this recording medium, since the image to be recorded is a negative image, its use is limited, and it is necessary to keep the image within a specific temperature range for storing the recorded image. JP-A-2-188294 and JP-A2-1
No. 88293, salts of gallic acid and higher aliphatic amines that reversibly develop and reduce color, and salts of bis (hydroxyphenyl) acetic acid or butyric acid and higher aliphatic amines are used as color developers. The one used is shown. This product can be thermally colored in a specific temperature range and decolorized by heating at a higher temperature than that, but since its color developing action and color reducing action occur competitively, these actions are thermally controlled. Difficult to obtain a good image contrast. As described above, the conventional reversible thermosensitive recording medium utilizing the reaction between the color former and the color developer has various problems and is still unsatisfactory.

The present inventors previously used a compound such as an organic phosphoric acid having a long-chain aliphatic group, a carboxyl compound, a phenol compound or a hydroxyphosphonic acid as a color developer,
By combining this with a fluoran compound or the like as a color former, it is possible to easily perform the coloring and decoloring only by heating, and it is possible to maintain the colored and decolored states at room temperature, A reversible thermochromic composition having a decoloring temperature lower than the coloring temperature and capable of repeatedly forming and erasing an image many times by temperature change, and reversible thermosensitive recording containing the same in a recording layer Proposed medium. This reversible thermosensitive recording medium does not cause problems such as a decrease in color density and defective erasing even when it is repeatedly used a number of times, and can be used a number of times that is unthinkable from the prior art. However, when performing high-speed recording, it is necessary to supply a predetermined amount of heat energy in a short time, so the temperature of the thermal head inevitably rises, and the degree of surface wear when high-speed recording is repeated many times It is incomparably larger than when recording several times at low speed. Therefore, in order to take full advantage of the recording medium even under severe conditions such as high-speed recording, it is necessary to install a protective layer in order to prevent the recording layer from being damaged by heat or abrasion.

As described above, since the protective layer is intended to protect the recording layer under high temperature and high speed conditions, the material used for the protective layer is preferably a material having high thermal and mechanical resistance. Therefore, conventionally known methods include the use of heat-resistant resins such as ultraviolet curable resins, electron beam curable resins, and thermosetting resins (Japanese Patent Laid-Open No. 4-247).
985, JP-A-5-42762). Among them, the formation of a protective layer using an ultraviolet curable resin is considered to be an effective method because a protective layer excellent in heat resistance and mechanical durability can be formed relatively easily. However,
These reversible thermosensitive recording media are not always stable to ultraviolet rays and have a problem that discoloration of the background portion occurs when they are irradiated with ultraviolet rays. Improvement of the light resistance of a reversible thermosensitive recording medium against ultraviolet rays has been attempted by incorporating an ultraviolet absorber in the recording layer (Japanese Patent Laid-Open No. 6-1066).
issue). However, the amount of ultraviolet light required for curing the resin by ultraviolet light is considerably larger than that of ordinary sunlight, and in order to prevent discoloration of the background part,
It is necessary to contain a large amount of ultraviolet absorber in the recording layer, which causes a problem that the color developing material becomes unstable.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above problems found in the prior art in a reversible thermosensitive recording medium utilizing the reaction between a color former and a color developer, resulting in poor color formation or aging. The purpose is to provide a reversible thermosensitive recording medium that does not cause image deterioration and that can form a clear recorded image repeatedly for a long period of time even under severe conditions such as high-speed recording. It is an object of the present invention to provide a reversible heat-sensitive recording medium having a protective layer in which the background portion is not discolored when the protective layer is formed.

[0007]

As a result of intensive studies to solve the above problems, the present inventor has found that by providing an ultraviolet absorbing layer between the thermochromic thermosensitive recording layer and the protective layer, The inventors have found that the problems can be solved and have completed the present invention. That is, according to the present invention, an electron-donating color-forming compound, an electron-accepting compound, and a resin binder are contained as main components on a support, and a colored state is formed by heating and melting at a temperature lower than the coloring temperature. A reversible thermosensitive recording medium having a thermochromic thermosensitive recording layer capable of forming a decolored state, and a protective layer made of an ultraviolet curable resin on the recording layer, wherein an ultraviolet absorbing layer is provided between the recording layer and the protective layer. And a reversible thermosensitive recording medium.

The reversible thermosensitive recording medium of the present invention instantly develops color upon heating, and the state of color development is stable even at room temperature. On the other hand, the recording layer in the color-developed state can be instantly decolored by heating below the color-developing temperature, and the color-erased state is stable even at room temperature. The principle of color development and color erasure of the reversible thermosensitive recording medium of the present invention, that is, image formation and image erasure will be described with reference to the graph shown in FIG. The vertical axis of the graph represents the color density and the horizontal axis represents the temperature. The solid line 1 represents the image forming process by heating and the broken line 3
Shows an image erasing process by heating. A is the density in the completely erased state, B is the density in the completely colored state when heated to a temperature of T ₁ or higher, C is the density at the temperature of T ₀ or lower in the completely colored state, and D is T _0. It shows the concentration when erased by heating at a temperature between T _{1 and} T ₁ . The reversible thermosensitive recording medium of the present invention is in a colorless state (A) at a temperature of T ₀ or lower. To perform recording, heating with a thermal head or the like to a temperature of T ₁ or higher is performed, and color development (B) is performed to form a recorded image. This recorded image is the solid line 2
Accordingly, even if the temperature is returned to T ₀ or lower, the state (C) is maintained as it is, and the recording memory property is not lost. Next, in order to erase the recorded image, the formed recorded image may be heated to a temperature between T _{0 and} T _{1 which} is lower than the coloring temperature, and the state becomes colorless (D). This state is maintained as it is even if the temperature is returned to T ₀ or lower (A). That is, the process of forming the recorded image reaches C by the path of the solid line ABC and the recording is held. During the process of erasing the recorded image, the erased state is maintained up to A by the path of the broken line CDA. The behavioral characteristics of formation and erasure of the recorded image are reversible and can be repeated many times.

FIG. 2 is an explanatory view showing an example of image formation and image erasure, in which 1 is a support and 2 is a reversible thermosensitive recording layer. The image forming steps (A) → (B) are achieved by recording and printing at a temperature of T ₁ or higher in FIG. 1 by a heat source for image formation, for example, the thermal head 4. Next, the image erasing step (B) → (A) is achieved by heating the image erasing heat source, for example, the heating roller 5 to a temperature between T _{0 and} T ₁ . In FIG. 2, 3 indicates a color image.
The reversible thermosensitive recording medium of the present invention contains a color former and a developer as essential components. Then, the color development of the reversible thermosensitive recording medium of the present invention is obtained by cooling the color-forming material composition formed by the eutectic reaction of the developer and the color-forming agent constituting the recording layer by heating to room temperature. Is. This color former composition has an erasing temperature region on the lower temperature side than the melting temperature,
In order to cool from the melted colored state to the room temperature while maintaining the color development, it is generally preferable to perform rapid cooling. When gradually cooled, some color disappears when passing through the color-erasing temperature range, and the density often decreases.

It is considered that in the color former composition, the molecules of the color former and the developer interact with each other to open the lactone ring of the color former to develop a color. The composition in the melted state and the rapidly cooled state contains, in addition to the chromophore molecule, the developer molecule and the chromophore molecule which are not directly involved in the formation of the chromophore. In the reversible thermosensitive recording medium of the present invention, the color former composition at room temperature is in a solidified state due to the cohesive force between these molecules.
Further, although the aggregate structure of the color former composition shows some regularity, it may be very regular or not very regular. This depends on the combination and amount ratio of the color developer and the color developer or the cooling conditions. The formation of such an aggregated structure works between the long-chain structure portion of the developer molecule forming the chromophore and the excess long-chain structure portion of the developer molecule not forming the chromophore. It is presumed that the cohesive force mainly acts. The formation of such an aggregated structure is related to the decoloring phenomenon of the color former composition.

The color-forming material composition can be decolored by heating its color-developed state to a specific temperature range.
In this decoloring process, the aggregate structure of the color-developed state changes, and eventually the developer molecules are separated and crystallized from the color-forming composition to form crystals of the developer alone, resulting in a stable decolored state. X
In the reversible thermosensitive recording medium of the present invention confirmed by the lines, it is clear that the long-chain portion of the color developer plays a large role in the formation of the color-developed state and the decoloring process thereof. This is a characteristic of the color former composition formed on the reversible thermosensitive recording medium of the present invention. Therefore, the decolorization temperature can be controlled by the length of the long chain portion of the color developer, and it is recognized that the longer the chain length, the higher the color development and decolorization temperature shifts. This is because the aggregation and motility of the developer molecule change depending on the length of the long chain portion.

The thermochromic composition constituting the recording layer in the present invention is basically a composition in which the above-mentioned color developer having a long chain structure and the color developer are combined, and Preferred color formers are present. The combination of the color developer and the color-developing agent used for the thermochromic composition is a composition in a color-developed state obtained by heating both of them at a melting temperature or higher, and a decoloring which occurs when the temperature is lower than the melting temperature. It is appropriately selected depending on the ease of use, that is, the decoloring property and the characteristics such as the color tone of the coloring state. Among them, the decoloring property can be judged by the presence or absence of an exothermic peak appearing in the temperature rising process in the differential thermal analysis (DTA) or the differential scanning calorimetry (DSC) of the composition in the colored state obtained by the combination. This exothermic peak corresponds to the decoloring phenomenon that characterizes the present invention, and serves as a criterion for selecting a combination having a good decoloring property. In the reversible thermosensitive recording medium of the present invention, the reversible decoloring behavior can be maintained even if the third substance is present in the recording layer and, for example, a polymer compound is present.

In the reversible thermosensitive recording medium of the present invention, the long-chain developer used in combination with the color former basically has a structure showing a color-developing ability capable of developing the color in the molecule. It is a compound that also has a long aliphatic chain structure portion that controls the cohesive force between molecules, and is an organic phosphoric acid compound, an aliphatic carboxylic acid compound, or a phenol compound having an aliphatic group having 12 or more carbon atoms, or 10 to 10 carbon atoms. 1
It is a metal salt of mercaptoacetic acid having an aliphatic group of 8. The aliphatic group includes a linear or branched alkyl group and alkenyl group, and may have a substituent such as halogen, an alkoxy group and an ester group.

As the organic phosphoric acid compound, a compound represented by the following general formula (1) is used. R ₁ -PO (OH) ₂ (1) Specific examples of (wherein, R ₁ represents a number of 12 or more aliphatic groups carbons) organic phosphoric acid compound represented by the general formula (1), for example, the following Is mentioned. Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, hexacosylphosphonic acid, octacosylphosphonic acid and the like.

As the aliphatic carboxylic acid compound, α-hydroxy fatty acids represented by the following general formula (2) are used. R ₂ —CH (OH) —COOH (2) (wherein R ₂ represents an aliphatic group having 12 or more carbon atoms) Examples of the α-hydroxyaliphatic carboxylic acid compound represented by the general formula (2) include: The following are listed. α-hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid,
α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid and the like.

The aliphatic carboxylic acid compound is an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms substituted with a halogen element and having a halogen element at at least the α-position or β-position carbon. Is also used. Specific examples of such compounds include, for example, the following. 2-chlorooctadecanoic acid, heptadecaflornonadecanoic acid, 2-bromohexadecanoic acid, 2-bromoheptadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid, 2-bromodocosanoic acid, 2-bromotetracosanoic acid , 3-bromooctadecanoic acid, 3-bromoeicosanoic acid, 2,3-dibromooctadecanoic acid, 2-flordodecanoic acid, 2-fluorotetradecanoic acid, 2-fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2-fluoroeicosane Acid, 2-flordocosanoic acid, 2-iodohexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, perfluorooctadecanoic acid and the like.

The aliphatic carboxylic acid compound is an aliphatic carboxylic acid compound having an oxo group having 12 or more carbon atoms in the carbon chain, and at least the carbon at the α-position, β-position or γ-position is oxo. The underlying one is also used. Specific examples of such compounds include, for example, the following. 2-oxododecanoic acid,
2-oxotetradecanoic acid, 2-oxohexadecanoic acid, 2-oxooctadecanoic acid, 2-oxoeicosanoic acid, 2-oxotetracosanoic acid, 3-oxododecanoic acid, 3-oxotetradecanoic acid, 3-oxohexadecanoic acid, 3-oxooctadecanoic acid, 3-oxoeicosanoic acid, 3-oxotetracosanoic acid, 4-oxohexadecanoic acid, 4-oxoheptadecanoic acid, 4-oxooctadecanoic acid, 4-oxodocosanoic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (3) is also used. (Where R ₃ represents an aliphatic group having 12 or more carbon atoms,
X represents an oxygen atom or a sulfur atom, and n represents 1 or 2, but Xn may be a —SO ₂ — group. Specific examples of the dibasic acid represented by the general formula (3) include
For example, the following may be mentioned. Dodecylmalic acid, tetradecylmalic acid, hexadecylmalic acid, octadecylmalic acid, eicosylmalic acid, docosylmalic acid, tetracosylmalic acid, dodecylthiomalic acid, tetradecylthiomalic acid, hexadecylthiomalic acid, octadecyl Thiomalic acid, eicosylthiomalic acid, docosylthiomalic acid, tetracosylthiomalic acid, dodecyldithiomalic acid, tetradecyldithiomalic acid, hexadecyldithiomalic acid, octadecyldithiomalic acid, eicosyldithiomalic acid, Docosyl dithiomalic acid, tetracosyl dithiomalic acid, dodecyl sulfone butanedioic acid, tetradecyl sulfone butanedioic acid,
Hexadecyl sulfone butanedioic acid, octadecyl sulfone butanedioic acid, eicosyl sulfone butanedioic acid, docosyl sulfone butanedioic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (4) is also used. (However, R ₄ , R ₅ , and R ₆ represent a hydrogen atom or an aliphatic group, and at least one of them is an aliphatic group having 12 or more carbon atoms) of the dibasic acid represented by the general formula (4) As a specific example,
For example, the following are mentioned. Dodecyl butanedioic acid, tridecyl butanedioic acid, tetradecyl butanedioic acid,
Pentadecyl butanedioic acid, octadecyl butanedioic acid, eicosyl butanedioic acid, docosyl butanedioic acid, 2,3-dihexadecyl butanedioic acid, 2,3-dioctadecyl butanedioic acid, 2-methyl-3-dodecyl butane Diacid, 2-methyl-3-tetradecylbutanedioic acid, 2-methyl-3-
Hexadecyl butanedioic acid, 2-ethyl-3-dodecyl butanedioic acid, 2-propyl-3-dodecyl butanedioic acid, 2
-Octyl-3-hexadecylbutanedioic acid, 2-tetradecyl-3-octadecylbutanedioic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (5) is also used. (However, R ₇ and R ₈ represent a hydrogen atom or an aliphatic group,
At least one of them is an aliphatic group having 12 or more carbon atoms.) Specific examples of the dibasic acid represented by the general formula (5) include:
For example, the following are mentioned. Dodecylmalonic acid,
Tetradecylmalonic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid, tetracosylmalonic acid, didodecylmalonic acid, ditetradecylmalonic acid, dihexadecylmalonic acid, dioctadecylmalonic acid, Dieicosylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, methyleicosylmalonic acid, methyldocosylmalonic acid, methyltetracosylmalonic acid, ethyloctadecylmalonic acid, ethyleicosylmalonic acid, ethyldocosylmalonic acid, Ethyltetracosylmalonic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (6) is also used. (However, R ₉ represents an aliphatic group having 12 or more carbon atoms,
n represents 0 or 1, m represents 1, 2 or 3, m is 2 or 3 when n is 0, and m is 1 or 2 when n is 1) ) As a specific example of the dibasic acid,
For example, the following are mentioned. 2-dodecyl-pentanedioic acid, 2-hexadecyl-pentanedioic acid, 2-octadecyl-pentanedioic acid, 2-eicosyl-pentanedioic acid, 2-docosyl-pentanedioic acid, 2-dodecyl-hexanedioic acid, 2- Pentadecyl-hexanedioic acid, 2-octadecyl-hexanedioic acid, 2-eicosyl-hexanedioic acid, 2-docosyl-hexanedioic acid and the like.

As the aliphatic carboxylic acid compound, a tribasic acid such as citric acid acylated with a long chain fatty acid can also be used. Specific examples thereof include the following.

As the phenol compound, a compound represented by the following general formula (7) is used.

Embedded image (However, Y is -S-, -O-, -CONH-, or-
Represents COO-, R ₁₀ represents a number of 12 or more aliphatic group having a carbon, n is an integer of 1, 2 or 3). Specific examples of the phenol compound represented by the general formula (7) include the following. p- (dodecylthio) phenol, p- (tetradecylthio) phenol, p- (hexadecylthio) phenol, p- (octadecylthio) phenol, p- (eicosylthio) phenol, p- (docosylthio) phenol, p- (tetracosylthio) phenol Ruthio) phenol, p- (dodecyloxy)
Phenol, p- (tetradecyloxy) phenol,
p- (hexadecyloxy) phenol, p- (octadecyloxy) phenol, p- (eicosyloxy)
Phenol, p- (docosyloxy) phenol, p-
(Tetracosyloxy) phenol, p-dodecylcarbamoylphenol, p-tetradecylcarbamoylphenol, p-hexadecylcarbamoylphenol,
p-octadecylcarbamoylphenol, p-eicosylcarbamoylphenol, p-docosylcarbamoylphenol, p-tetracosylcarbamoylphenol, hexadecyl gallate, octadecyl gallate, eicosyl gallate, docosyl gallate, Tetracosyl gallate and the like.

An organic phosphoric acid compound represented by the following general formula (8)
It is also possible to use an α-hydroxyalkylphosphonic acid represented by (However, R ₁₁ is an aliphatic group having ₁₁ to 29 carbon atoms.) Specific examples of the α-hydroxyalkylphosphonic acid represented by the general formula (8) include α-hydroxydodecylphosphonic acid and α-hydroxytetracarboxylic acid. Decylphosphonic acid, α-
Examples thereof include hydroxyhexadecylphosphonic acid, α-hydroxyoctadecylphosphonic acid, α-hydroxyeicosylphosphonic acid, α-hydroxydocosylphosphonic acid, and α-hydroxytetracosylphosphonic acid.

As the metal salt of mercaptoacetic acid, a metal salt of alkyl or alkenyl mercaptoacetic acid represented by the general formula (9) is used. (R ₁₂ —S—CH ₂ —COO) ₂ M (9) (wherein R ₁₂ represents an aliphatic group having 10 to 18 carbon atoms, and M represents tin, magnesium, zinc or copper) General formula (9 Specific examples of the mercaptoacetic acid metal salt represented by the formula (1) include the following. Decyl mercapto acetic acid tin salt, dodecyl mercapto acetic acid tin salt,
Tetradecylmercaptoacetic acid tin salt, hexadecylmercaptoacetic acid tin salt, octadecylmercaptoacetic acid tin salt, decylmercaptoacetic acid magnesium salt, dodecylmercaptoacetic acid magnesium salt, tetradecylmercaptoacetic acid magnesium salt, hexadecylmercaptoacetic acid magnesium salt, octadecylmercaptoacetic acid magnesium salt Salt, decylmercaptoacetic acid zinc salt, dodecylmercaptoacetic acid zinc salt, tetradecylmercaptoacetic acid zinc salt, hexadecylmercaptoacetic acid zinc salt, octadecylmercaptoacetic acid zinc salt, decylmercaptoacetic acid copper salt, dodecylmercaptoacetic acid copper salt, tetradecylmercaptoacetic acid Copper salt,
Hexadecyl mercapto acetic acid copper salt, octadecyl mercapto acetic acid copper salt, etc.

The color-forming composition formed in the reversible thermosensitive recording layer of the present invention is basically formed by combining a color-developing agent with the color-developing agent. The color former used in the present invention has an electron donating property and is itself a colorless or light-colored dye precursor, and is not particularly limited, and may be a conventionally known one such as a triphenylmethanephthalide-based compound and a fluoran-based compound. And phenothiazine compounds, leuco auramine compounds, indolinophthalide compounds and the like. Specific examples of the color former are shown below. As a preferred color former used in the present invention, there is a fluoran compound represented by the following general formula (10).

Embedded image (Wherein, R ₁₃ represents a hydrogen atom, an alkyl group, an allyl group, a cyclic alkyl group, or an alkoxyalkyl group, R ₁₄
Represents an alkyl group, a cyclic alkyl group, an allyl group, an alkoxyalkyl group, or an optionally substituted phenyl group. X represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, an alkoxyalkyl group, or a halogen atom. Y represents a lower alkyl group, an amino group, a substituted amino group, a cyano group, or a halogen atom. )

Specific examples of the compound represented by the general formula (10) include the following compounds. 2-anilino-3-methyl-6- (Nn-hexyl-N-iso-amylamino) fluorane, 2-anilino-3-methyl-6-
(Di-n-hexylamino) fluorane, 2-anilino-3-methyl-6- (di-n-amylamino) fluorane, 2-anilino-3-methyl-6- (di-n-octylamino) fluorane, 2 -Anilino-3-methyl-6
-(Di-n-butylamino) fluorane, 2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane, 2-anilino-3-methyl-6-
(Nn-octyl-N-ethylamino) fluorane,
2-anilino-3-methyl-6- (Nn-octyl-
N-iso-propylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-Nn-propylamino) fluorane, 2-anilino-3-methyl-
6- (Nn-amyl-Nn-butylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane, 2-anilino-3
-Methyl-6- (N-n-amyl-N-methylamino)
Fluoran, 2-anilino-3-methyl-6- (N-i
so-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane, 2-anilino-3-methyl-6- (Nn-) Butyl-N-n-propylamino) fluorane, 2-anilino-3-methyl-6- (N
-Ethyl-N-sec-butylamino) fluorane, 2
-Anilino-3-methyl-6- (Nn-butyl-N-
iso-propylamino) fluorane, 2-anilino-
3-Methyl-6- (Nn-butyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N
-Isobutyl-N-methylamino) fluorane.

2-anilino-3-methyl-6- (N-cyclohexyl-Nn-tetradecylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-Nn-dodecylamino) Fluoran, 2-anilino-3-methyl-6- (N-cyclohexyl-Nn
-Decylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-Nn-octylamino) fluorane, 2-anilino-3-methyl-6- (N
-Cyclohexyl-Nn-hexylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-Nn-amylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-) N-is
o-amylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-Nn-butylamino) fluorane, 2-anilino-3-methyl-6- (N
-Cyclohexyl-Nn-propylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-N-ethylamino) fluorane, 2-anilino-
3-Methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2-anilino-3-methyl-6-
(Dicyclohexylethylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexylethyl-Nn-hexylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexylethyl-N-
n-amylamino) fluorane, 2-anilino-3-methyl-6- (dicyclohexylmethylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexylmethyl-Nn-hexylamino) fluorane, 2
-Anilino-3-methyl-6- (N-cyclohexylmethyl-Nn-amylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexylmethyl-N
-N-butylamino) fluorane, 2-anilino-3-
Methyl-6- (N-cyclohexylmethyl-N-cyclohexylamino) fluorane.

2-anilino-3-methyl-6- (diallylamino) fluorane, 2-anilino-3-methyl-6
-(Nn-octyl-N-allylamino) fluorane, 2-anilino-3-methyl-6- (Nn-hexyl-N-allylamino) fluorane, 2-anilino-3
-Methyl-6- (Nn-amyl-N-allylamino)
Fluorane, 2-anilino-3-methyl-6- (N-ethyl-N-allylamino) fluorane, 2-anilino-
3-Methyl-6- (N-2-ethoxypropyl-N-ethylamino) fluorane, 2-anilino-3-methyl-
6- (diethoxyethylamino) fluorane, 2-anilino-3-methyl-6- (N-ethoxyethyl-Nn)
-Hexylamino) fluorane, 2-anilino-3-methyl-6- (N-ethoxyethyl-Nn-amylamino) fluorane, 2-anilino-3-methyl-6- (N
-Ethoxyethyl-N-iso-amylamino) fluorane, 2-anilino-3-methyl-6- (N-ethoxyethyl-Nn-butylamino) fluorane, 2-anilino-3-methyl-6- (N- Ethoxyethyl-N-ethylamino) fluorane, 2-anilino-3-methyl-
6- (N-ethoxymethyl-Nn-hexylamino)
Fluorane, 2-anilino-3-methyl-6- (N-ethoxymethyl-Nn-amylamino) fluorane, 2
-Anilino-3-methyl-6- (N-ethoxymethyl-
N-iso-amylamino) fluorane, 2-anilino-3-methyl-6- (Nn-hexadecylamino) fluorane, 2-anilino-3-methyl-6- (Nn-)
Octylamino) fluorane, 2-anilino-3-methyl-6- (Nn-hexylamino) fluorane, 2-
Anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-anilino-3-methyl-6-
(N-methyl-p-toluidino) fluorane,

2-anilino-3-methoxy-6- (di-
n-hexylamino) fluorane, 2-anilino-3-
Methoxy-6- (di-n-amylamino) fluorane,
2-anilino-3-methoxy-6- (Nn-hexyl-N-iso-amylamino) fluorane, 2-anilino-3-methoxy-6- (N-cyclohexyl-Nn
-Hexylamino) fluorane, 2-anilino-3-ethoxy-6- (di-n-amylamino) fluorane, 2
-Anilino-3-ethoxy-6- (di-n-butylamino) fluorane, 2-anilino-3-ethoxy-6-diethylaminofluorane, 2-anilino-3-ethoxy-6- (N-cyclohexyl-N- n-hexylamino) fluorane, 2-anilino-3-ethoxy-6-
(N-cyclohexyl-Nn-amylamino) fluorane, 2-anilino-3-ethoxyethyl-6- (di-
n-amylamino) fluorane, 2-anilino-3-ethoxyethyl-6- (di-n-butylamino) fluorane, 2-anilino-3-ethoxyethyl-6-diethylaminofluorane, 2-anilino-3-ethoxymethyl -6- (Di-n-butylamino) fluorane, 2-anilino-3-ethoxymethyl-6- (N-cyclohexyl-Nn-hexylamino) fluorane, 2-anilino-3-ethoxymethyl-6- ( Di-n-amylamino)
Fluoran, 2-anilino-3-methoxymethyl-6-
(N-cyclohexyl-Nn-hexylamino) fluorane, 2-benzylamino-3-methyl-6- (di-
n-butylamino) fluorane, 2-benzylamino-
3-methyl-6- (di-n-amylamino) fluorane, 2-benzylamino-3-methyl-6- (N-cyclohexyl-Nn-hexylamino) fluorane, 2
-(M-Trichloromethylanilino) -3-methyl-6
-Diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-
Methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2- (2,4-dimethylanilino)-
3-Methyl-6- (Nn-hexyl-N-iso-amylamino) fluorane, 2- (2,4-dimethylanilino) -3-methyl-6- (di-n-hexylamino)
Fluoran, 2- (2,4-dimethylanilino) -3-
Methyl-6- (di-n-amylamino) fluorane, 2
-(2,4-Dimethylanilino) -3-methyl-6-
(Di-n-butylamino) fluorane, 2- (2,4-
Dimethylanilino) -3-methyl-6-diethylaminofluorane, 2- (N-ethyl-p-toluidino) -3
-Methyl-6- (N-ethylanilino) fluorane, 2
-(N-methyl-p-toluidino) -3-methyl-6-
(N-propyl-p-toluidino) fluorane,

2-anilino-6- (di-n-hexylamino) fluorane, 2-anilino-6- (Nn-hexyl-N-iso-amylamino) fluorane, 2-anilino-6- (di-n) -Amylamino) fluoran, 2
-Anilino-6-diethylaminofluorane, 2-anilino-6- (Nn-hexyl-N-ethylamino) fluorane, 2-anilino-6- (N-cyclohexyl-
N-n-hexylamino) fluorane, 2-anilino-
6- (N-cyclohexyl-Nn-amylamino) fluorane, 2-anilino-6- (N-cyclohexyl-
N-methylamino) fluorane, 2-anilino-6-
(Diethoxyethylamino) fluorane, 2-anilino-6- (N-ethoxyethyl-N-iso-amylamino) fluorane, 2-anilino-6- (N-ethoxyethyl-Nn-amylamino) fluorane, 2- Anilino-6- (N-ethoxyethyl-Nn-butylamino) fluorane, 2-anilino-6- (Nn-octylamino) fluorane, 2-anilino-6- (Nn-)
Hexylamino) fluorane, 2-anilino-6- (N
-N-amylamino) fluorane, 2- (N-methylanilino) -6- (N-ethyl-p-toluidino) fluorane, 2- (o-chloroanilino) -6-diethylaminofluorane, 2- (o-bromoanilino)- 6-diethylaminofluorane, 2- (o-chloroanilino)-
6-dibutylaminofluorane, 2- (o-fluoroanilino) -6-dibutylaminofluorane, 2- (p-chloroanilino) -6- (Nn-octylamino) fluorane, 2- (p-chloranilino)- 6- (N-n-
Palmitylamino) fluorane, 2- (p-chloroanilino) -6- (di-n-octylamino) fluorane,
2- (m-trifluoromethylanilino) -6-diethylaminofluorane, 2- (p-acetylanilino) -6
-Diethylaminofluorane, 2- (p-acetylanilino) -6- (Nn-hexyl-N-iso-hexylamino) fluorane, 2- (p-acetylanilino)
-6- (di-n-hexylamino) fluorane, 2-
(P-Acetylanilino) -6- (Nn-hexyl-
N-n-amylamino) fluorane, 2- (p-acetylanilino) -6- (di-n-amylamino) fluorane, 2- (p-acetylanilino) -6- (Nn-amyl-N-) n-butylamino) fluorane, 2- (p-
Acetylanilino) -6- (N-cyclohexyl-N-
n-hexylamino) fluorane, 2- (p-acetylanilino) -6- (N-ethoxyethyl-N-iso-
Amylamino) fluorane, 2- (p-acetylanilino) -6- (N-ethoxyethyl-Nn-amylamino) fluorane,

2-benzylamino-6- (N-ethyl-
p-toluidino) fluorane, 2-benzylamino-6
-(N-methyl-2,4-dimethylanilino) fluorane, 2-benzylamino-6- (N-ethyl-2,4-
Dimethylanilino) fluorane, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluorane, 2
-(O-Methoxybenzoylamino) -6- (N-methyl-p-toluidino) fluorane, 2-dibenzylamino-6- (di-n-butylamino) fluorane, 2-dibenzylamino-6- (di -N-amylamino) fluorane, 2-dibenzylamino-6- (di-n-hexylamino) fluorane, 2-dibenzylamino-6- (N
-N-hexyl-N-iso-amylamino) fluorane, 2-dibenzylamino-6- (di-n-propylamino) fluorane, 2-dibenzylamino-6- (N-
Cyclohexyl-N-n-amylamino) fluorane,
2-dibenzylamino-6- (N-cyclohexyl-N
-N-hexylamino) fluorane, 2-dibenzylamino-6- (N-methyl-p-toluidino) fluorane, 2-dibenzylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (di -P-methylbenzylamino) -6- (N-ethyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6-diethylaminofluorane, 2-dibenzylamino-4-methyl-6- ( Di-n-propylamino) fluorane, 2-
Dibenzylamino-4-methyl-6- (di-n-butylamino) fluorane, 2-dibenzylamino-4-methyl-6- (di-n-amylamino) fluorane, 2-dibenzylamino-4-methoxy -6- (N-methyl-P
-Toluidino) fluorane, 2-benzylamino-4-
Methyl-6- (N-ethyl-P-toluidino) fluorane, 2- (α-phenylethylamino) -4-methyl-
6-Diethylaminofluorane, 2- (p-toluidino) -3- (t-butyl) -6- (N-methyl-p-toluidino) fluorane, 2- (α-phenylethylamino) -6- (N- Ethyl-p-toluidino) fluorane, 2- (o-methoxycarbonylanilino) -6-diethylaminofluorane,

2-Methylamino-6- (N-methylanilino) fluorane, 2-methylamino-6- (N-ethylanilino) fluorane, 2-methylamino-6- (N
-Propylanilino) fluorane, 2-ethylamino-
6- (N-methyl-p-toluidino) fluorane, 2-
Ethylamino-6- (N-ethyl-p-toluidino) fluorane, 2-methylamino-6- (N-methyl-2,
4, -Dimethylanilino) fluorane, 2-ethylamino-6- (N-ethyl-2,4, -dimethylanilino)
Fluorane, 2-dimethylamino-6- (N-methylanilino) fluorane, 2-dimethylamino-6- (N-
Ethylanilino) fluorane, 2-diethylamino-6
-(N-methyl-p-toluidino) fluorane, 2-diethylamino-6- (N-ethyl-p-toluidino) fluorane, 2-dipropylamino-6- (N-methylanilino) fluorane, 2-dipropylamino- 6- (N
-Ethylanilino) fluorane, 2-acetylamino-
3-Methyl-6-diethylaminofluorane, 2-acetylamino-3-methyl-6- (di-n-butylamino) fluorane, 2-acetylamino-3-methyl-6
-(Di-n-amylamino) fluorane, 2-acetylamino-3-methyl-6- (di-n-hexylamino)
Fluoran, 2-acetylamino-6- (N-methyl-
p-toluizino) fluoran,

2-amino-6-diethylaminofluorane, 2-amino-6- (di-n-butylamino) fluorane, 2-amino-6- (di-n-amylamino) fluorane, 2-amino-6- (Di-n-hexylamino)
Fluoran, 2-amino-6- (N-cyclohexyl-
N-n-amylamino) fluorane, 2-amino-6-
(N-methylanilino) fluorane, 2-amino-6-
(N-ethylanilino) fluorane, 2-amino-6-
(N-propylanilino) fluorane, 2-amino-6
-(N-methyl-p-toluidino) fluorane, 2-amino-6- (N-ethyl-p-toluidino) fluorane, 2-amino-6- (N-propyl-p-toluidino) fluorane, 2-amino- 6- (N-methyl-p-
Ethylanilino) fluorane, 2-amino-6- (N-
Ethyl-p-ethylanilino) fluorane, 2-amino-6- (N-propyl-p-ethylanilino) fluorane, 2-amino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-amino- 6- (N-ethyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-propyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-methyl-p -Chloranilino) fluorane, 2-amino-6- (N-ethyl-p-chloroanilino) fluorane, 2-amino-6-
(N-propyl-p-chloroanilino) fluorane,
2-Amino-3-methyl-6-diethylaminofluorane, 2-amino-3-methyl-6- (di-n-butylamino) fluorane, 2-amino-3-methyl-6- (di-n-amylamino) ) Fluoran, 2-amino-3-methyl-6- (di-n-hexylamino) fluoran, 2
-Amino-3-methoxy-6- (di-n-butylamino) fluorane, 2-amino-3-methoxy-6- (di-n-amylamino) fluorane, 2-amino-3-methoxy-6- (di -N-hexylamino) fluorane,

1,3-Dimethyl-6-diethylaminofluorane, 1,3-dimethyl-6- (di-n-butylamino) fluorane, 1,3-dimethyl-6- (di-n-)
Amylamino) fluorane, 1,3-dimethyl-6-
(Di-n-hexylamino) fluorane, 1,3-dimethyl-6- (N-cyclohexyl-Nn-butylamino) fluorane, 2,3-dimethyl-6-dimethylaminofluorane, 2-methyl-6 -Dimethylaminofluorane, 2-methyl-6-diethylaminofluorane, 2
-Methyl-6- (di-n-propylamino) fluorane, 2-methyl-6- (di-n-butylamino) fluorane, 2-methyl-6- (di-n-amylamino) fluorane, 2-methyl- 6- (di-n-hexylamino)
Fluoran, 2-methyl-6- (N-cyclohexyl-
N-n-amylamino) fluorane, 2-methyl-6-
(N-cyclohexyl-N-methylamino) fluorane, 3-diethylamino-6- (m-trifluoromethylanilino) fluorane, 3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-methyl- 6- (N
-Ethyl-p-toluidino) fluorane, 4-methoxy-6- (N-ethyl-p-toluidino) fluorane, 2
-Cyano-6-diethylaminofluorane, 2-cyano-6- (di-n-butylamino) fluorane, 2-cyano-6- (di-n-amylamino) fluorane, 2-cyano-6- (di-n -Hexylamino) fluorane, 2
-Cyano-6- (N-cyclohexyl-Nn-hexylamino) fluorane, 2-cyano-6- (N-cyclohexyl-Nn-decylamino) fluorane.

2-chloro-6-diethylaminofluorane, 2-bromo-6-diethylaminofluorane, 2-
Chlor-6-dipropylaminofluorane, 2-chloro-6-dibutylaminofluorane, 3-chloro-6-cyclohexylaminofluorane, 3-bromo-6-cyclohexylaminofluorane, 2-chloro-6- ( N-
Ethyl-N-isoamylamino) fluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2-
Anilino-3-chloro-6-diethylaminofluorane, 2- (o-chloroanilino) -3-chloro-6-cyclohexylaminofluorane, 2- (m-trifluoromethylanilino) -3-chloro-6-diethylamino Fluoran, 2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluorane, 2-ethoxyethylamino-3-chloro-6-dibutylaminofluorane, 2-benzylamino-4-chloro-6 -(N-ethyl-p-toluidino) fluorane, 2-dibenzylamino-4-chloro-6- (N-ethyl-p-toluidino)
Fluoran, 2- (α-phenylethylamino) -4-
Chlor-6-diethylaminofluorane, 2- (N-benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluorane and the like.

Besides the general formula (10), there are many fluoran compounds preferable as the color former used in the present invention, and the following compounds are specifically exemplified. 2-anilino-3-
Methyl-6-pyrrolidinofluorane, 2-anilino-3
-Chlor-6-pyrrolidinofluorane, 2-anilino-
3-Methyl-6- (N-ethyl-N-tetrahydrofurfurylamino) fluorane, 2-mesidino-3-methyl-4 ', 5'-benzo-6-diethylaminofluorane, 2- (m-trifluoromethyl) Anilino) -3-methyl-6-pyrrolidinofluorane, 2- (α-naphthylamino) -3,4-benzo-4′-bromo-6- (N-benzyl-N-cyclohexylamino) fluorane, 2 −
Piperidino-6-diethylaminofluorane, 2- (N
-N-propyl-p-trifluoromethylanilino) -6
-Morpholinofluorane, 2- (di-Np-chlorophenyl-methylamino) -6-pyrrolidinofluorane, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpho Rinofluorane, 1,2-benzo-6-diethylaminofluorane, 1,2-benzo-
6- (N-ethyl-N-isoamylamino) fluorane, 1,2-benzo-6-dibutylaminofluorane,
1,2-benzo-6- (di-n-amylamino) fluorane, 1,2-benzo-6- (di-n-hexylamino) fluorane, 1,2-benzo-6- (N-methyl-)
N-cyclohexylamino) fluorane, 1,2-benzo-6- (N-ethyl-Nn-octylamino) fluorane, 1,2-benzo-6- (N-ethyl-p-toluidino) fluorane, 1, 2-benzo-6-diallylaminofluorane, 1,2-benzo-6- (N-ethoxyethyl-N-ethylamino) fluorane and the like.

There are many compounds other than the fluorane compound which are preferable as the color former used in the present invention, and the following compounds are specifically mentioned. Benzoleucomethylene blue, 2- [3,6-bis (diethylamino)]-6-
(0-chloranilino) xanthyl lactam benzoate,
2- [3,6-bis (diethylamino)]-9- (0-
Chloranilino) xanthyl lactam benzoate, 3,3
-Bis (p-dimethylaminophenyl) -phthalide,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (P
-Dimethylaminophenyl) -6-chlorophthalide;
3,3-bis (p-dibutylaminophenyl) phthalide, 3- (2-methoxy-4-dimethylaminophenyl) -3- (2-hydroxy-4,5-dichlorophenyl) phthalide, 3- (2- Hydroxy-4-dimethylaminophenyl) -3- (2-methoxy-5-chlorophenyl) phthalide, 3- (2-hydroxy-4-dimethoxyaminophenyl) -3- (2-methoxy-5-chlorophenyl) phthalide , 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-methoxy-5-nitrophenyl) phthalide, 3- (2-hydroxy-4-diethylaminophenyl) -3- (2-methoxy-5) -Methylphenyl) phthalide, 3- (2-methoxy-4-dimethylaminophenyl) -3- (2-hydroxy-4-)
Chlor-5-methoxyphenyl) phthalide, 3,6-bis (dimethylamino) fluorenspiro (9,3 ′)-
6'-dimethylaminophthalide, 6'-chloro-8'-
Methoxy-benzoindolino-spiropyran, 6'-bromo-2'-methoxy-benzoindolino-spiropyran and the like.

In the reversible thermosensitive recording medium of the present invention, it is necessary to select an appropriate ratio of the color former and the developer in the recording layer depending on the physical properties of the compound used. The range is generally in the range of 1 to 20 and preferably 2 to 10 for the color developer to the color developer in a molar ratio. A single color developer or a color developer may be used or a mixture of two or more kinds may be used, but the decolorizing property changes depending on the ratio of the color developer and the color developer, and there are relatively many color developers. In this case, the decolorization start temperature becomes low, and when it is relatively small, the decolorization becomes sharp with respect to the temperature. Therefore, it is desirable that this ratio be appropriately selected according to the use and purpose.

The thermochromic composition constituting the recording layer is basically composed of a color developer and a color developer, but for the purpose of improving various characteristics such as decoloring property and storability, Additives that have the effect of controlling the crystallization of the coloring agent can be included. The reversible thermosensitive recording medium of the present invention is one in which a recording layer containing a thermochromic composition is provided on a support, and the reversible thermosensitive recording medium has a basic structure in which a support is provided in the lowermost layer. The recording layer, the intermediate layer, and the protective layer are sequentially laminated. The support used here is paper, synthetic paper, a plastic film or a composite thereof, a glass plate, and the like, as long as it can hold the recording layer.

The recording layer may be in any form as long as the thermochromic composition is present. For example, the developer and the color former may be mixed and melted to form a film, which may be cooled to form the recording layer. good. However, it is usually preferable to sufficiently disperse the color developer and the color developing agent in the binder resin to form a recording layer, and a reversible thermosensitive recording medium having a long life can be obtained by this method. Examples of the binder resin include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic acid esters, Polymethacrylic acid esters, acrylic acid copolymer, maleic acid copolymer,
Chlorinated vinyl chloride resin, a mixture of the above binder resins, and the like are used. The color-developing agent and the color-developing agent can be used as they are or by being encapsulated in microcapsules. Microencapsulation of the color developer and the color developer may be performed by a known method such as a coacervation method, an interfacial polymerization method, an in situ polymerization method.

The recording layer is formed according to a conventionally known method.
It can be carried out by uniformly dispersing or dissolving the color former and the developer together with the binder resin in the organic solvent, and coating and drying the same on the support. The role of the binder resin in the recording layer is to prevent the thermochromic composition from aggregating due to repeated coloring and decoloring, and to keep the thermochromic composition uniformly dispersed. In particular,
Since the composition often aggregates and becomes non-uniform when heat is applied during color development, it is preferable that the binder resin has high heat resistance. The reversible thermosensitive recording medium of the present invention, if necessary,
For the purpose of improving coating properties or recording properties, various additives used in ordinary thermal recording paper, such as dispersants, surfactants, polymeric cationic conductive agents, fillers, color image stabilizers, and antioxidants. Agents, light stabilizers, lubricants and the like can be added to the recording layer.

In the reversible thermosensitive recording medium of the present invention, a protective layer made of an ultraviolet curable resin is provided on the thermochromic thermosensitive recording layer via an ultraviolet absorbing layer. The type of the ultraviolet curable resin is not limited, and various conventionally known resins can be used. As a solvent for this resin, an organic solvent such as tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, toluene or benzene is preferably used. Further, instead of these solvents, a liquid photopolymerizable monomer can be used as a reactive diluent for easy handling. Liquid photopolymerizable monomers include 2-ethylhexyl acrylate, cyclohexyl acrylate, butoxyethyl acrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol. Examples thereof include triacrylate and ethyl methacrylate.

The UV-curable resin used for forming the protective layer may be any monomer or oligomer (or prepolymer) which undergoes a polymerization reaction upon irradiation with UV rays and is cured to become a resin. Examples of such monomers or oligomers include (poly) ester acrylate, (poly) urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, melamine acrylate, and polyphosphazene methacrylate. (Poly) ester acrylate is obtained by reacting polyhydric alcohol such as 1,6-hexanediol, propylene glycol (as polypropylene oxide) and diethylene glycol with polybasic acid such as adipic acid, phthalic anhydride and trimellitic acid and acrylic acid. It is a thing. The structural examples are shown in (a) to (c).

(A) Adipic acid / 1,6-hexanediol / acrylic acid

Embedded image (B) phthalic anhydride / polypropylene oxide / acrylic acid

[Chemical 4] (C) Trimet acid / diethylene glycol / acrylic acid

Embedded image

The (poly) urethane acrylate is obtained by reacting a compound having an isocyanate group such as tolylene diisocyanate (TDI) with an acrylate having a hydroxyl group. An example of the structure is shown in (d). HEA is 2-hydroxyethyl acrylate, HD
O is an abbreviation for 1,6-hexanediol and ADA is an abbreviation for adipic acid. (D) HEA / TDI / HDO / ADA / HDO / TD
I / HEA

[Chemical 6]

Epoxy acrylates are roughly classified into bisphenol A type, novolac type and alicyclic type, and the epoxy groups of these epoxy resins are esterified with acrylic acid to make a functional group an acryloyl group.
Examples of the structure are shown in (e) to (g). (E) Bisphenol A-epichlorohydrin type / acrylic acid

[Chemical 7] (F) Phenol novolac-epichlorohydrin type /
Acrylic acid

Embedded image (G) Alicyclic / acrylic acid

[Chemical 9]

Polybutadiene acrylate has a terminal OH
Isocyanate or 1,2 polybutadiene
-Mercaptoethanol or the like is reacted, and then acrylic acid or the like is further reacted. Its structural example (h)
Shown in (H)

[Chemical 10] The silicone acrylate is, for example, methacryl-modified by a condensation reaction (de-methanol reaction) between an organofunctional trimethoxysilane and a silanol group-containing polysiloxane, and a structural example thereof is shown in (i). (I)

[Chemical 11]

The ultraviolet absorbing layer is made of a resin containing an ultraviolet absorber. As a general forming method, it is formed by dissolving a resin and an ultraviolet absorber in a solvent and applying and drying. Examples of the solvent include water, aliphatic lower alcohols such as methanol isopropanol, ketones such as acetone, 2-butanone and cyclohexane, N,
Aliphatic amides such as N-dimethylformamide and N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, cyclic amides such as N-methyl-2-pyrrolidone, amines such as n-butylamine and pyridine, and tetrahydrofuran Such as cyclic ethers, linear ethers such as ethylene glycol, ethyl acetate, isopropyl acetate,
Esters such as isobutyl acetate, aliphatic halogen hydrocarbons such as chloroform and dichloroethane, n-hexane,
Hydrocarbons such as benzene and toluene, chlorobenzene,
Aromatic halogenated hydrocarbons such as dichlorobenzene are exemplified.

As the resin, for example, polymethylmethacrylate, polyethylmethacrylate, polyisopropylmethacrylate, polyisobutylmethacrylate, poly-n-butylmethacrylate, polyphenylmethacrylate, polybenzylmethacrylate, poly (2-phenylethylmethacrylate), polystyrene. , Poly (p
-Methylstyrene), poly (pt-butylstyrene), polyacenaphthylene, poly (2-vinylpyridine), polycarbonate, polyacrylate, polystyrene, poly (2-phenylene ether sulfone), poly (N-vinylcarbazole) ), Styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-butyl methacrylate copolymer, polyurethane, polyamide, polyetherimide, poly (1-naphthyl methacrylate), poly (5-indolyl methacrylate), poly (4-oxazolyl methacrylate), poly (3-phenanthryl methacrylate), poly (7,
7'-dimethyl-2-norbornyl methacrylate),
Poly (3-ethylmethacrylate), poly (methylthiomethacrylate), poly (2-thiomethoxyethylmethacrylate), poly (pN, N-dimethylaminostyrene), poly (pN, -dimethylaminotolylmethacrylate), Poly (9-phenanthrylmethyl methacrylate), poly [2- (9-phenanthryl) ethyl methacrylate], polyethylene, polypropylene, alkyd resin, phenol-formaldehyde resin, epoxy resin, phenoxy resin, polyvinyl alcohol, vinyl alcohol-vinyl butyral. Copolymer, vinyl alcohol-vinyl acetate copolymer, polyvinyl formal, polyvinyl butyral, polyvinyl chloride, chlorinated polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate Vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, vinyl chloride-vinylidene chloride copolymer, chlorinated polyolefin, poly-p-vinylphenol, poly (2,6-dimethyl-p-phenylene) Oxide), polytrifluoromethylmethacrylate, polyvinylidene fluoride, nitrocellulose, cellulose acetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate, methylcellulose, ethylcellulose, hydroxyethylcellulose, silicone resin, maleic anhydride resin, styrene- Examples thereof include maleic anhydride copolymers and isobutylene-maleic anhydride copolymers.

As the ultraviolet absorber, those known in the art may be used. The binder resin used in the recording layer, the decomposition wavelength of the electron-donating color-forming compound, and the absorption capacity (wavelength, absorption amount) of the ultraviolet absorber. , Selected in consideration of the solubility in the resin liquid. For example, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2
-Hydroxy-4-n-octoxybenzophenone, 2
-Hydroxy-4-dodecyloxybenzophenone,
2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxy-2 ′
-Carboxybenzophenone, 2-hydroxy-4-oxybenzylbenzophenone, 2-hydroxy-4-chlorobenzophenone, 2-hydroxy-5-chlorobenzophenone, 2-hydroxy-4-methoxy-4'-methylbenzophenone, 2-hydroxy- 4-n-heptoxybenzophenone, 2-hydroxy-3,6-dichloro-4-methoxybenzophenone, 2-hydroxy-
3,6-dichloro-4-ethoxybenzophenone, 2-
Benzophenone-based UV absorbers such as hydroxy-4- (2-hydroxy-3-methylacryloxy) propoxybenzophenone and benzophenone-2-hydroxy-4-methoxy-5-sulfonic acid sodium salt, 2-
(2'-Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-ditertiarybutylphenyl) benzotriazole, 2-
(2'-Hydroxy-3'-tert-butyl-5-methylphenyl) benzotriazole, 2- (2'-hydroxy-4'-octoxyphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-ditertiarybutylphenyl) -5-chlorobenzotriazole,
2- (2'-hydroxy-3'-tert-butyl-
5'-Methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'-ethoxyphenyl) benzotriazole and other benzotriazole ultraviolet absorbers, phenyl salicylate, p-octylphenyl salicylate, p-tersia Salicylic acid phenyl ester UV absorbers such as ributylphenyl salicylate, carboxyphenyl salicylate, methylphenyl salicylate, dodecylphenyl salicylate, or p-methoxybenzylidene malonic acid dimethyl ester, 2-ethylhexyl-2-cyano-3,3'-diphenyl Acrylate, ethyl-2-cyano-3,3'-
Diphenyl acrylate, 3,5-ditertiary butyl-4-hydroxybenzoic acid, resorcinol monobenzoate rearranged by ultraviolet light to form benzophenone,
Examples thereof include 2 ', 4'-ditertiarybutylphenyl-3,5-ditertiarybutyl-4-hydroxybenzoate, but are not limited thereto. These ultraviolet absorbers may be used alone or in admixture of two or more. The thickness of the ultraviolet absorbing layer in the present invention is 1 to 5 μm.
m is preferable, and if it is thinner than this, ultraviolet rays are not sufficiently absorbed, and if it is thicker than this, the thermal sensitivity of the recording layer is lowered, which is not preferable.

In the present invention, an intermediate layer may be formed in order to prevent the organic solvent from penetrating into the recording layer and destroying the recording layer when the ultraviolet absorbing layer is formed. The resin used for the intermediate layer is not particularly limited, and various conventionally known water-soluble and water-insoluble polymers are used. Specific examples of the water-soluble polymer include polyvinyl alcohol; modified polyvinyl alcohol; starch and its derivatives; cellulose derivatives such as methylcellulose, methoxycellulose, and hydroxyethylcellulose; casein; gelatin; polyvinylpyrrolidone; styrene / maleic anhydride copolymers; Diisobutylene / maleic anhydride copolymer; polyacrylamide;
Modified polyacrylamide; methyl vinyl ether / maleic anhydride copolymer; carboxy-modified polyethylene; polyvinyl alcohol / acrylamide block copolymer; melamine-formaldehyde resin; urea-formaldehyde resin and the like. These water-soluble polymers are used in the form of aqueous solutions. Specific examples of the water-insoluble polymer include polyvinyl acetate, polyurethane, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, polyacrylic acid, polyacrylic ester, vinyl chloride / vinyl acetate copolymer. Examples include a combination; polybutyl methacrylate; ethylene / vinyl acetate copolymer and the like.
These water-insoluble polymers are used in the form of aqueous emulsion. The polymers may be used alone or as a mixture, and if necessary, a curing agent may be added to cure the resin.

In the present invention, the protective layer may contain an organic or inorganic filler and a lubricant in order to improve the head matching property of the thermal recording medium. As the organic filler, polyolefin particles, polystyrene particles, urea-
Examples thereof include formaldehyde resin particles and plastic micro hollow spheres. As the inorganic filler, aluminum hydroxide, heavy and light calcium carbonate, zinc oxide,
Titanium oxide, barium sulfate, silica gel, colloidal silica (particle size 10 to 50 mμ), alumina sol (particle size 10
Up to 200 mμ), activated clay, talc, kaolinite, calcined kaolinite, diatomaceous earth, synthetic kaolinite, zirconium compound, glass micro hollow spheres, and the like.
Lubricants are mainly waxes such as stearic acid amide, zinc stearate, palmitic acid amide, oleic acid amide, lauric acid amide, ethylenebisstearylamide, methylenebisstearylamide, methylolstearylamide, paraffin wax, polyethylene wax, Examples thereof include higher alcohols, higher fatty acids, higher fatty acid esters, silicone compounds, and the like, but are not limited to these. These fillers and lubricants
They are used alone or in combination of two or more.

In the present invention, an undercoat layer may be interposed between the support and the recording layer, if desired. The undercoat layer is used for the purpose of improving heat insulation, improving the adhesion between the support and the recording layer, improving the resistance of the support to the solvent when the recording layer is formed, and preventing the heat-melting ink from being absorbed by the support when heat is applied. Is installed. One of the important roles of the undercoat layer is to improve the heat insulating property, and this is to make the applied heat energy useful for forming and erasing recording without waste. By providing the heat-insulating undercoat layer, coloring and decoloring can be performed sharply. The heat insulating undercoat layer may be formed by coating fine hollow particles made of an organic or inorganic material on a support. Specifically, the heat insulating undercoat layer is made of glass, ceramics, plastic or the like and has a particle size of about 10 to 50 μm. The fine hollow body may be well dispersed in a solvent together with a binder resin, and uniformly coated and dried on the support. When the support is a substance that easily absorbs liquid such as paper, it is sufficient to form an undercoat layer that is impermeable to liquid, and when a support soluble in a recording layer forming solvent is used. For the above, an undercoat layer insoluble in the solvent may be provided on the support.

The formation of a recorded image is not particularly limited by a hot pen, a thermal head, laser heating, etc. depending on the purpose of use. Similarly, the erasing of the recorded image is not particularly limited as long as the erasing temperature conditions such as the heating roller, the sheet heating element, the constant temperature bath, the warm air, and the thermal head are given. Further, so-called overwriting is possible in which the recorded image is erased by the thermal head set to the erasing temperature and at the same time the recorded image is formed by another thermal head set to the recording temperature.

[0056]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following, all parts and% are based on weight.

Example 1 [Preparation of Recording Layer] A polyester film having a thickness of about 100 μm was coated with a solution having the following composition using a 1.0 mm wire bar and immediately dried at 150 ° C. to obtain a recording layer in a colored state. . Then, heat erasing was performed for 10 minutes in a constant temperature bath at 80 ° C. to obtain a reversible thermosensitive recording medium. 2- (o-chloroanilino) -6-dibutylaminofluorane 5 parts docosylphosphonic acid 18 parts polymethylmethacrylate 33 parts 3,4-dihydro-2H-bilane 225 parts [Preparation of intermediate layer] Reversible thermosensitive recording On the recording layer of the medium 1
A 0% polyvinyl alcohol aqueous solution was applied using a 0.15 mm wire bar and dried at 70 ° C. to form an intermediate layer. [Preparation of UV Absorbing Layer]
It was applied using a wire bar of mm and dried at 70 ° C. to form an ultraviolet absorbing layer. Vinyl chloride-vinyl acetate copolymer 10 parts (VYHH manufactured by Union Carbide) 2-hydroxy-4-n-octoxybenzophenone 1 part Methyl ethyl ketone 90 parts [Preparation of protective layer] Apply using a wire bar, dry at 70 ° C, then 80W / c
When the protective layer was formed by irradiating with a UV lamp of m for curing, a reversible thermosensitive recording medium without discoloration of the background was obtained. 75% butyl acetate solution of urethane acrylate UV curable resin (Dainippon Ink and Chemicals, Unidick C7-157) 150 parts Calcium carbonate (Shiraishi Calcium Co .: Callite SA) 2 parts Polyethylene wax 1 part Methyl ethyl ketone 50 parts

Example 2 After preparing a recording layer in the same manner as in Example 1, the following composition was applied using a wire bar of 0.15 mm and dried at 70 ° C. to form an ultraviolet absorbing layer. Polyvinyl acetate 10 parts 2-Hydroxy-4-n-octoxybenzophenone 1 part Ethyl acetate 50 parts When a protective layer was prepared in the same manner as in Example 1, a reversible thermosensitive recording medium having no background discoloration was obtained.

Comparative Examples 1 and 2 When the protective layer was formed without providing the ultraviolet absorbing layer in Examples 1 and 2, discoloration of the background occurred in yellow-red.

[0060]

EFFECTS OF THE INVENTION The reversible thermosensitive recording medium of the present invention is provided with an ultraviolet absorbing layer between a thermochromic thermosensitive recording layer and a protective layer made of an ultraviolet curable resin, thereby preventing color development failure and image deterioration with time. Moreover, even under severe conditions such as high-speed recording, clear recorded images can be repeatedly formed for a long period of time, and there is no discoloration of the background, which is excellent in light resistance.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between color density and temperature of a reversible thermosensitive recording medium of the present invention, and is an explanatory view of the principle of color development and color erasing. The solid line (A → B → C) indicates the image forming process by the broken line (C →
D → A) shows an image erasing process.

FIG. 2 is a diagram illustrating an image forming process and an image erasing process.

[Explanation of symbols]

 1 Support 2 Reversible Thermal Recording Layer 3 Colored Image 4 Thermal Head 5 Heating Roller

Claims (1)

[Claims] 1. An electron-donating color-forming compound on a support,
A heat-developable heat-sensitive recording layer containing an electron-accepting compound and a resin binder as main components, capable of forming a color-developed state by heating and melting, and capable of forming a decolored state at a temperature lower than the color-developing temperature, is further provided on the recording layer. A reversible thermosensitive recording medium having a protective layer made of an ultraviolet curable resin, wherein an ultraviolet absorbing layer is provided between the recording layer and the protective layer.