JP3475251B2 - Image forming method using reversible thermosensitive recording medium and image erasing method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to controlling heat energy containing as a main component a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound. and an image forming method using the reversible thermosensitive recording medium capable of erasing and forming a colored image by relates to image erasing how.

[0002]

2. Description of the Related Art Conventionally, electron-donating color-forming compounds (hereinafter referred to as
Thermosensitive recording media utilizing the color-forming reaction between a color former or leuco dye) and an electron-accepting compound (hereinafter also referred to as a developer) are widely known, and can be used in facsimiles, word processors, scientific measuring instruments, etc. Used in printers. However, all of these conventional recording media that have been put to practical use have irreversible color development, and it is not possible to erase an image once recorded and repeatedly use it.

However, according to the patent publication, a recording medium capable of reversibly developing and erasing colors has been proposed. For example, Japanese Patent Laid-Open No. Sho 60-58 uses a combination of gallic acid and phloroglucinol as a developer. No. 193,691; JP-A-61-237684, wherein a compound such as phenolphthalein or thymolphthalein is used as a color developer. A recording layer contains a homogenous solution of a color developer, a color developer and a carboxylic acid ester. JP-A-62-138556 and JP-A-62-1
38568 and JP-A-62-140881, JP-A-63 that uses an ascorbic acid derivative as a developer.
-173684, JP-A-2-188293 and JP-A-2-18 using a salt of bis (hydroxyphenyl) acetic acid or gallic acid and a higher aliphatic amine as a color developer.
No. 8294, etc. are disclosed. However, the conventional reversible thermosensitive recording mediums described above still have problems in terms of compatibility of color development stability and decolorization property, or stability in color density and repetition, and practical recording It is not a satisfactory medium.

The inventors of the present invention first disclosed in Japanese Patent Laid-Open No. 12436/1993.
In JP-A-0, No. 0,058,032, an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having a long-chain aliphatic hydrocarbon group is used as a color developing agent, and by combining this with a leuco dye which is a color developing agent, color development is achieved. Decoloring can be easily performed under heating / cooling conditions, and the colored state and decolored state can be maintained stably at room temperature, and the colored state and decolored state can be stably repeated. A reversible thermosensitive color-developing composition and a reversible thermosensitive recording medium using the same for a recording layer have been proposed. This has a practical level of performance in terms of the balance between color stability and erasability and color density, but it will be improved in terms of compatibility with a wider range of usage environments and the range of application of color erasing conditions. There was room to do it. Since then, it has been proposed to use a specific structure for a phenol compound having a long-chain aliphatic hydrocarbon group (JP-A-6-210954), but this also had a similar problem.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reversible thermosensitive recording medium which retains stable color forming property and decoloring property, can cope with high speed erasing, and is particularly excellent in heat resistant storage stability.
In particular, <br/> side for erasing an image is not durable dents occurred which form the method and shape for forming an image using a good reversible thermosensitive recording medium of the recording medium by repeated use To provide the law .

[0006]

The inventors of the present invention have found that in the reversible coloring and decoloring phenomenon of such a composition of a color developing agent and a color developing agent, the color developing agent of the color developing agent having a long-chain aliphatic group is used. We considered that the balance between the ability to develop color and the cohesive force between molecules is important, and compounds with various structures were investigated. As a result, they have found that the above problems can be solved by using a phenol compound having a specific structure as a color developer, and arrived at the present invention.

That is, according to the present invention, the following image
An image forming method and an image erasing method are provided. (1) Heating at least a part of the surface of a reversible thermosensitive recording medium capable of forming a relatively colored state and a decolored state due to a difference in heating temperature and / or a cooling rate after heating to a temperature above a color development start temperature. And then rapidly cooling to form a color image, wherein the recording medium contains as a main component a reversible thermosensitive coloring composition comprising an electron-donating color-forming compound and an electron-accepting compound. An image forming method comprising a layer provided on a support, wherein the electron-accepting compound is a phenol compound represented by the following general formula (1).

[Chemical 2] (In the formula, n represents an integer of 1 to 3, m represents an integer of 1 to 20, r represents an integer of 0 to 3, and X and Y are a divalent chain structure containing a hetero atom. Group (excluding divalent amino group), R ₁ is a divalent chain having 1 to 20 carbon atoms.
Represents a linear hydrocarbon group, and R ₂ is a chain hydrocarbon group having 2 to 20 carbon atoms (however, a chain hydrocarbon group having 2 to 6 carbon atoms is excluded).
The image forming method according to the represent) (2) wherein, characterized in that a protective layer is provided reversible thermosensitive recording layer (1). (3) The image forming method as described in ( 2 ) above, wherein an intermediate layer is provided between the reversible thermosensitive recording layer and the protective layer. (4) An undercoat layer is provided between the support and the reversible thermosensitive recording layer (1) to ( 3 ).
The image forming method according to any one of 1. ( 5 ) The image forming method described in any one of (1) to ( 4 ) above, wherein a print layer is provided on the recording medium. ( 6 ) The image forming method as described in any one of (1) to ( 5 ) above, wherein a magnetic recording layer is provided on the recording medium. ( 7 ) The image forming method described in any one of (1) to ( 6 ), wherein the recording medium is processed into a card shape or a sheet shape. ( 8 ) The reversible thermosensitive recording layer side surface of the support and / or at least a part of the opposite surface thereof has a printed portion, according to any one of the above (1) to ( 7 ). Image forming method. ( 9 ) The reversible thermosensitive recording medium on which a color image is formed by the image forming method according to any one of (1) to ( 8 ) is heated at a temperature lower than the color formation start temperature to erase the color image. An image erasing method characterized by coloring. (1 0) (1), characterized in that to form a color image by the image forming method according to any one of - (8), and then decolorized by heating the emitting color images at a lower temperature than the coloring start temperature Image forming and erasing method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. First, the compound represented by the general formula (1) will be described in detail. In the compounds represented by the general formula (1), R ₁ shows the divalent chain-like hydrocarbon group having 1 to 20 carbon atoms.

Preferred examples of R ₁ include those shown in Table 1 below.

[Table 1] As a particularly preferred example, R ₁ represents-(CH ₂ ) q-.

R ₂ is a chain hydrocarbon group having 2 to 20 carbon atoms (however, a chain hydrocarbon group having 2 to 6 carbon atoms is excluded).
The be shown. Also, a chain aliphatic hydrocarbon group but it may also have a well also be linear or branched, further unsaturated bond.

Preferred examples of R ₂ include those shown in Table 2 below.

[Table 2] Particularly preferred examples, R ₂ represents - _{(CH 2) s-CH 3} .

When the sum of the integer m and the number of carbon atoms in R ₁ and R ₂ is 7 or less, the stability of color development and the decoloring property are deteriorated. Therefore, the number of carbon atoms is preferably 8 or more, It is more preferably 11 or more. Therefore, q, q ′, q ″, q ′ ″, s, in the formulas specifically exemplified for R ₁ and R ₂ are
It is preferable that s ′, s ″, and s ′ ″ each represent an integer satisfying this carbon number.

X and Y represent a divalent group having a chain structure containing a hetero atom (excluding a divalent amino group), and preferably

[Chemical 3] Represents a divalent group having at least one group represented by. Examples of X and Y include those shown in Table 3 below.

[0014]

[Table 3]

Examples of preferable phenol compounds used in the present invention include compounds represented by the following general formulas (2) to (5).

[Chemical 4]

[Chemical 5]

[Chemical 6]

[Chemical 7] In the formula, q, q ′, q ″, and s each independently represent an integer of 0 to 20. However, the sum of these integers is 8 or more.
Further, Y ′ and Y ″ represent a divalent group containing a hetero atom similar to the above Y, and these may be the same or different.

More specific examples of the phenol compound in the present invention include the compounds shown in Table 4 as examples of the general formula (2) and the general formula (3).
Although not shown here by the structural formula, another general formula (4),
In the case of the compound represented by the general formula (5), the same X and Y as those shown in Table 4 can be mentioned. However, the present invention is not limited to these.

[0017]

[Table 4]

Further, in the present invention, a compound having a divalent group containing a hetero atom and a linear alkyl group having 6 or more carbon atoms as a color-decoloration controlling agent, for example, the following general formula (A)
By using the compound represented by, the storage characteristics and the high-speed erasing characteristics become excellent.

[Chemical 8]

In the above formula, X ₁ , X ₂ and X ₃ represent a group containing a hetero atom, and R ₃ , R ₄ , R ₅ and R ₆ represent a group having 1 to 22 carbon atoms. Moreover, h, i, and k each independently represent 0 or 1, and j represents an integer of 0 to 4. However, h, i, j, and k are never 0 at the same time.
Further, R ₅ and X ₂ repeated when j is 2 or more may be the same or different. In addition, R ₃ , R ₄ ,
R ₅ and R ₆ may include a heterocycle.

R ₃ , R ₄ , R ₅ and R ₆ represent a hydrocarbon group which may have a substituent, which may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or both of them. It may be a hydrocarbon group composed of Further, the aliphatic hydrocarbon group may be linear or branched, and may have an unsaturated bond. Examples of the substituent attached to the hydrocarbon group include a hydroxyl group, a halogen atom, an alkoxy group and the like. Also,
When the sum of the carbon numbers of R ₃ , R ₄ , R ₅ and R ₆ is 7 or less, the stability of color development and the decoloring property are deteriorated. Therefore, the number of carbons is preferably 8 or more, more preferably 11 or more.

Preferred examples of R ₃ and R ₅ include those shown in Table 5 below.

[Table 5]

Preferred examples of R ₄ and R ₆ include those shown in Table 6 below.

[Table 6] In the formula, q, q ′, q ″, and q ′ ″ are R
_It represents an integer satisfying the carbon number of ₃ , R ₄ , R ₅ and R ₆ .

When X ₁ and X ₃ are at the terminal position of the structural formula as an example, preferably

[Chemical 9] Represents a group having at least one group represented by. Examples thereof include those shown in Table 7 below.

[0024]

[Table 7]

Further, X ₁ and X ₂ are 2 including a hetero atom.
Represents a valent group, preferably

[Chemical 10] Represents a divalent group having at least one group represented by. Examples thereof include those shown in Table 8 below.

[0026]

[Table 8]

The preferred structures of the color-decoloration controlling agent used in the present invention are shown in Table 9 below, but the present invention is not limited to these compounds.

[Table 9]

The above R ₃ , R ₄ , R ₅ , R ₆ , X ₁ , X ₂ and X ₃ each represent the same group as described above. Also, j is 0
Is an integer from 4 to 4 and is repeated when j is 2 or more.
₅ , X ₂ may be the same or different. Further, i represents 0 or 1. However, j and i are 0 at the same time
Never be.

Further, particularly preferable structures include those represented by the following general formulas (d) to (i).

[Table 10]

Specific examples of the coloring and decoloring control agent used in the present invention are shown in Table 1 as an example of the general formula (h).
Compounds 1 and 12 are mentioned. In addition, the general formula (i)
The same compounds can be mentioned for.

[0031]

[Table 11]

[0032]

[Table 12]

Further specific examples are shown in Table 11 below.
of CH₃(CH₂) q-NHCONH- (CH₂) q'CH₃ and, CH₃(CH₂) q-NHCONH- (CH₂) q ''-NHCONH- (CH₂) q '' 'CH₃ As examples of compounds represented by
There is a mixture.

[0034]

[Table 13]

[0035]

[Table 14]

The reversible thermosensitive coloring composition used in the present invention is
Basically, it is constituted by combining the electron-accepting compound (that is, the color developing agent) and the electron-donating color-forming compound (that is, the color developing agent). In the present invention, a conventionally known leuco dye can be optionally used as the electron-donating color-developing compound, and in particular, at least one leuco dye represented by the following general formulas (6), (8) and (9). Is preferably used.

[0037]

[Chemical 11] Wherein, R _11, R ₁₂ represents a lower alkyl group, an optionally substituted aryl group or a hydrogen atom, further R _11, R ₁₂
May combine with each other to form a ring. R ₁₃ represents a lower alkyl group, a halogen atom or a hydrogen atom, and R _13
14 represents a lower alkyl group, a halogen atom, a hydrogen atom or a substituted anilino group represented by the following general formula (7).

[Chemical 12] (In the formula, R ₁₅ represents a lower alkyl group or a hydrogen atom,
A represents a lower alkyl group or a halogen atom. Z is 0
Represents an integer of 3; )]

[0038]

[Chemical 13] (In the formula, R _{16 to} R ₁₉ represent an alkyl group or a hydrogen atom, and R ₂₀ represents an alkyl group, an alkoxyl group or a hydrogen atom.)

[0039]

[Chemical 14] (In the formula, R _{21 to} R ₂₄ represent a lower alkyl group or a hydrogen atom, and R ₂₅ and R ₂₆ represent an alkyl group, an alkoxyl group or a hydrogen atom.)

The examples of leuco dyes used in the present invention are shown below, but the present invention is not limited to these. 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6- (di-n-
Butylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane , 2-anilino-
3-Methyl-6- (N-isobutyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N
-N-amyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-sec-butyl-N-
Methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) ) Fluoran, 2-anilino-
3-Methyl-6- (Nn-propyl-N-isopropylamino) fluorane, 2-anilino-3-methyl-6
-(N-cyclohexyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-ethyl-p
-Toluidino) fluorane, 2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluorane, 2
-(M-Trichloromethylanilino) -3-methyl-6
-Diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trichloromethylanilino) -3
-Methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2- (2,4-dimethylanilino)-
3-methyl-6-diethylaminofluorane, 2- (N
-Ethyl-p-toluidino) -3-methyl-6- (N-
Ethylanilino) fluorane, 2- (N-ethyl-p-
Toluidino) -3-methyl-6- (N-propyl-p-
Truizino) Fluoran,

2-anilino-6- (Nn-hexyl-
N-ethylamino) fluorane, 2- (o-chloroanilino) -6-diethylaminofluorane, 2- (o-chloroanilino) -6-dibutylaminofluorane, 2-
(M-Trifluoromethylanilino) -6-diethylaminofluorane, 2,3-dimethyl-6-dimethylaminofluorane, 3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-chloro- 6-diethylaminofluorane, 2-bromo-6-diethylaminofluorane, 2-chloro-6-dipropylaminofluorane,
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
-Diethylaminofluorane, 2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluorane, 1,2-benzo-6-diethylaminofluorane,
3-diethylamino-6- (m-trifluoromethylanilino) fluorane,

3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-octyl-2-methylindole-3) -Yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4-azaphthalide, 3- (1
-Ethyl-2-methylindol-3-yl) -3-
(2-Methyl-4-diethylaminophenyl) -7-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl)-
4-Azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-Nn-amyl-N-
Methylaminophenyl) -4-azaphthalide, 3- (1
-Methyl-2-methylindol-3-yl) -3-
(2-hexyloxy-4-diethylaminophenyl)
-4-azaphthalide, 3,3-bis (2-ethoxy-4)
-Diethylaminophenyl) -4-azaphthalide, 3,
3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,

As the electron-donating compound used in the present invention, that is, the color former, conventionally known leuco dyes can be used alone or in combination, in addition to the above-mentioned fluorane compound and azaphthalide compound. The color former is shown below. 2-
(P-Acetylanilino) -6- (Nn-amyl-N
-N-butylamino) 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-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- (α-phenylethylamino) -6- (N-ethyl-p-toluidino) fluorane, 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-methylamino-6- (N-methyl-2,4, -dimethylanilino) fluorane, 2-ethylamino-6- (N-ethyl-2,4,4. -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-methyl-anilino) fluorane, 2-dipropylamino-6- (N-ethyl-anilino) 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-chloroanilino) fluorane, 2-amino-6- (N-ethyl-p-chloroanilino) fluorane, 2-amino-6- (N- Propyl-p
-Chloroanilino) fluorane, 1,2-benzo-6-
(N-ethyl-N-isoamylamino) fluorane,
1,2-benzo-6-dibutylaminofluorane, 1,
2-benzo-6- (N-methyl-N-cyclohexylamino) fluorane, 1,2-benzo-6- (N-ethyl-toluidino) fluorane, and others.

Specific examples of other color formers preferably used in the present invention are as follows. 2-anilino-3-methyl-6- (N-2-ethoxypropyl-N
-Ethylamino) fluorane, 2- (p-chloroanilino) -6- (Nn-octylamino) fluorane, 2
-(P-chloroanilino) -6- (Nn-palmitylamino) fluorane, 2- (p-chloroanilino) -6
-(Di-n-octylamino) fluorane, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (o-methoxybenzoylamino) -6-
(N-methyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6-diethylaminofluorane, 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- (o-methoxycarbonylamino) -6-diethylaminofluorane,
2-Acetylamino-6- (N-methyl-p-toluidino) fluorane, 4-methoxy-6- (N-ethyl-p
-Toluidino) fluorane, 2-ethoxyethylamino-3-chloro-6-dibutylaminofluorane, 2-dibenzylamino-4-chloro-6- (N-ethyl-p-
Triidino) fluorane, 2- (α-phenylethylamino) -4-chloro-6-diethylaminofluorane,
2- (N-benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluorane, 2
-Anilino-3-methyl-6-pyrrolidinofluorane,
2-anilino-3-chloro-6-pyrrolidinofluorane, 2-anilino-3-methyl-6- (N-ethyl-N
-Tetrahydrofurfurylamino) fluorane, 2-mesidino-4 ', 5'-benzo-6-diethylaminofluorane, 2- (m-trifluoromethylanilino) -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-N-
p-chlorophenyl-methylamino) -6-pyrrolidinofluorane, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpholinofluorane,
1,2-benzo-6- (N-ethyl-N-n-octylamino) fluorane, 1,2-benzo-6-diallylaminofluorane, 1,2-benzo-6- (N-ethoxyethyl-N -Ethylamino) fluorane,

Benzoleucomethylene blue, 2- [3,
6-bis (diethylamino)]-6- (o-chloroanilino) xanthyl benzoate lactam, 2- [3,6-bis (diethylamino)]-9- (o-chloroanilino)
Lactam xanthyl 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-chloro-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 others.

The reversible thermosensitive recording medium used in the present invention has different heating temperatures and / or cooling rates after heating.
It is possible to form a relatively colored state and a relatively decolored state. The basic coloring / decoloring phenomenon of the composition composed of the color former and the developer used in the present invention will be described. Figure 1
Shows the relationship between the color density and temperature of this recording medium. When the temperature of the recording medium that is initially in the color erasing state (A) is raised, color development occurs at the temperature T ₁ at which it begins to melt, resulting in the melt color developing state (B). When the melted and colored state (B) is rapidly cooled, the temperature can be lowered to room temperature in the colored state and the solidified and colored state (C) is obtained. Whether or not this colored state is obtained depends on the rate of temperature decrease from the molten state,
In slow cooling, decoloring occurs in the process of lowering the temperature, and a state of relatively lower density than in the same decoloring state (A) or rapid cooling color development state (C) as in the beginning is formed. On the other hand, when the temperature of the rapidly cooled coloring state (C) is increased again, decoloring occurs at a temperature T ₂ lower than the coloring temperature (D to E), and when the temperature is lowered from here, the same decoloring state (A) as that at the beginning is obtained. Return. The actual color-developing temperature and decoloring temperature vary depending on the combination of the color-developing agent and the color-developing agent used, and can be selected according to the purpose. Further, the density in the melted color state and the color density in the case of rapid cooling do not always match and may be different.

In the recording medium used in the present invention, the color-developed state (C) obtained by rapid cooling from the molten state is a state in which the color-developing agent and the color-developing agent are mixed in a state in which they can react with each other by molecules, and Often form a solid state. This state is a state in which the color developer and the color former are aggregated and the color is maintained, and it is considered that the color formation is stabilized by the formation of this aggregate structure. On the other hand, the decolored state is a state in which both are phase-separated. This state is a state in which molecules of at least one compound are aggregated to form a domain or crystallize, and it is a state in which the color former and the developer are separated and stabilized by aggregation or crystallization. Conceivable. In the present invention, in many cases, more complete decoloring occurs due to phase separation of the two and crystallization of the developer. In both the decolored state from the molten state by slow cooling and the decolored state by heating from the colored state shown in FIG. 1, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

To form a color-developed record on the reversible thermosensitive recording medium according to the present invention, heating with a thermal head or the like to a temperature at which it is once melted and mixed may be followed by rapid cooling. Decoloring is performed by two methods, namely, a method of gradually cooling from a heated state and a method of heating to a temperature slightly lower than the coloring temperature. However, these are the same in the sense that both are phase-separated, or at least one is temporarily kept at a temperature at which crystallization occurs. The reason why the material is rapidly cooled in the formation of the colored state is to prevent the phase separation temperature or the crystallization temperature from being maintained. The quenching and gradual cooling here are relative to one composition, and the boundary changes depending on the combination of the color former and the developer.

The ratio of the color-developing agent to the color-developing agent in the composition varies depending on the combination of the compounds used, but the molar ratio of the color-developing agent to the color-developing agent is 0.1 to 20 in general. Range, preferably in the range of 0.2 to 10,
If the amount of the developing agent is less or more than this range, the density of the color-developed state is lowered, which is a problem. Further, the composition preferably contains a color-decoloring control agent as described above, but the content ratio in that case is preferably 0.1 to 300% by weight, more preferably 1% by weight based on the color developer. ~ 100% by weight.

The reversible thermosensitive recording medium used in the present invention comprises a support having thereon a recording layer containing the above composition as a main component. The support is paper, resin film, synthetic paper, metal foil, glass or a composite of these,
Any material can be used as long as it can hold the recording layer.

The recording layer may be of any type as long as the composition of the present invention is present, but generally a state in which a color former and a developer are finely and uniformly dispersed in a binder resin is used. The color former and the developer may individually form particles, but more preferably, they are dispersed as composite particles. This can be accomplished by once melting or dissolving the color former and developer. To form such a recording layer, each material is dispersed and dissolved in a solvent and then mixed, or each material is mixed and dispersed or dissolved in a solvent, and then applied on a support and dried. Done by. The color former and the color developer can also be used by being encapsulated in microcapsules.

As the binder resin used for forming the recording layer, for example, polyvinyl chloride, polyvinyl acetate,
Vinyl chloride vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid Examples thereof include copolymers, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, and starches. The role of these binder resins is to keep each material of the composition uniformly dispersed without being biased by heat application for recording and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. For example, the binder resin may be crosslinked with heat, ultraviolet rays, electron beams or the like.

The curable resin is, for example, a combination of a cross-linking agent and a resin having an active group which reacts with the cross-linking agent, and is a resin which can be cross-linked and cured by heat, electron beams, ultraviolet rays or the like. The resin used in the heat curing is, for example, a phenoxy resin, a polyvinyl butyral resin, a cellulose acetate propionate, a cellulose acetate butyrate, a resin having a group reactive with a crosslinking agent such as a hydroxyl group or a carboxyl group, or a hydroxyl group or a carboxyl group. There is a resin obtained by copolymerizing a monomer that it has with another monomer. The copolymer resin includes, for example, vinyl chloride-based, acrylic-based, styrene-based resins, and the like, and specifically, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-hydroxypropyl acrylate copolymer,
Examples thereof include vinyl chloride-vinyl acetate-maleic anhydride copolymer.

Examples of the crosslinking agent for thermal crosslinking include isocyanates, amines, phenols and epoxy compounds. For example, the isocyanates are polyisocyanate compounds having a plurality of isocyanate groups, specifically hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI),
Examples thereof include xylylene diisocyanate (XDI) and the like, and adduct type, buret type, isocyanurate type and blocked isocyanates using trimethylolpropane and the like. The amount of the crosslinking agent added to the resin is preferably such that the ratio of the functional groups of the crosslinking agent to the number of active groups contained in the resin is 0.01 to 2.0, and if it is less than this, the thermal strength becomes insufficient, and Addition of more than this adversely affects the coloring and decoloring properties. Furthermore, a catalyst used in this type of reaction may be used as a crosslinking accelerator. Examples of the crosslinking accelerator include tertiary amines such as 1,4-diazabicyclo [2,2,2] octane and metal compounds such as organic tin compounds. When the recording layer contains a resin which is in a crosslinked state with an isocyanate compound, the heat resistance of the recording layer is improved, and the repetitive durability is significantly improved.

Next, examples of the monomers used for the electron beam and ultraviolet ray curing include the followings. Examples of monofunctional monomers Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, Cyclohexyl methacrylate, benzyl methacrylate, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl methacrylate methyl chloride salt, diethylaminoethyl methacrylate, glycidyl methacrylate, methacryl Acid tetrahydrofurfuryl, allyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethyl dimethacrylate Glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol, trimethylolpropane trimethacrylate, methacrylic acid 2-
Ethoxyethyl, 2-ethylhexyl acrylate, 2
-Ethoxyethyl acrylate, 2-ethoxyethoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, dicyclopentenylethyl acrylate, N-vinylpyrrolidone,
Vinyl acetate etc.

Examples of bifunctional monomers 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, tripropylene. Glycol diacrylate, polypropylene glycol diacrylate, bisphenol A ethylene oxide adduct diacrylate, glycerin methacrylate acrylate, neopentyl glycol propylene oxide 2 mol adduct diacrylate, diethylene glycol diacrylate, polyethylene glycol (400) diacrylate, hydroxypivalin Diacrylate of acid and ester of neopentyl glycol,
2,2-bis (4-acryloxydiethoxyphenyl)
Propane, diacrylate of neopentyl glycol diadipate, diacrylate of ε-caprolactone adduct of neopentyl glycol hydroxypivalate, 2
-(2-hydroxy-1,1-dimethylethyl) -5-
Hydroxymethyl-5-ethyl-1,3-dioxane diacrylate, tricyclodecane dimethylol diacrylate, ε-caprolactone adduct of tricyclodecane dimethylol diacrylate, diacrylate of glycidyl ether of 1,6-hexanediol, etc. .

Examples of polyfunctional monomers Trimethylolpropane triacrylate, glycerin propylene oxide addition acrylate, trisacryloyloxyethyl phosphate, pentaerythritol acrylate, triacrylate of propylene oxide 3 mol adduct of trimethylolpropane, dipentaerythritol. Polyacrylate, polyacrylate of dipentaerythritol caprolactone adduct,
Propionate dipentaerythritol triacrylate, hydroxypivalaldehyde-modified dimethylolpropane triacrylate, propionate dipentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, propionate dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, diester Ε-caprolactone adduct of pentaerythritol hexaacrylate and the like.

Examples of oligomers Bisphenol A-diepoxy acrylic acid addition product and the like.

In the case of crosslinking using ultraviolet rays, the following photopolymerization initiators and photopolymerization accelerators are used.
Examples of the photopolymerization initiator include benzoin ethers such as isobutyl benzoin ether, isopropyl benzoin ether, benzoin ethyl ether, and benzoin methyl ether; 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime. Α-acyloxime ester such as; benzyl ketals such as 2,2-dimethoxy-2-phenylacetophenone, benzyl and hydroxycyclohexyl phenyl ketone; diethoxyacetone phenone, 2-hydroxy-2-methyl-1-
Acetophenone derivatives such as phenylpropan-1-one; benzophenone, 1-chlorothioxanthone, 2-
Chlorothioxanthone, isopropylthioxanthone,
Ketones such as 2-methylthioxanthone and 2-chlorobenzophenone may be mentioned. These photopolymerization initiators are
Used alone or in combination of two or more. The addition amount is 0. 1 with respect to 1 part by weight of the monomer or oligomer.
The amount is preferably 005 to 1.0 part by weight, more preferably 0.01 to 0.5 part by weight.

As the photopolymerization accelerator, there are aromatic tertiary amines and aliphatic amines. Specific examples include p-dimethylaminobenzoic acid isoamyl ester and p-dimethylaminobenzoic acid ethyl ester. These photopolymerization accelerators are used alone or in combination of two or more kinds. The addition amount is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 1 part by weight of the photopolymerization initiator.
~ 3 parts by weight.

The ratio of the color-forming component and the binder resin in the recording layer of the present invention is preferably 0.1 to 10 relative to the color-forming component 1. If the ratio is less than this, the thermal strength of the recording layer is insufficient, and if it is more than this. In this case, the color density decreases, which is a problem.

To form the recording layer, a mixture of the above-mentioned color developer, color former, color fading accelerator and binder resin (preferably in a crosslinked state) and coating solvent is uniformly mixed and dispersed. The coating liquid thus prepared is used. Specific examples of the solvent used for preparing the coating liquid include
Water; methanol, ethanol, isopropanol, n-
Alcohols such as butanol and methylisocarbinol; ketones such as acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone and cyclohexanone; N, N-dimethylformamide, N, N
-Amides such as dimethylacetamide; diethyl ether, isopropyl ether, tetrahydrofuran,
Ethers such as 1,4-dioxane and 3,4-dihydro-2H-pyran; glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; 2-methoxyethyl acetate, Glycol ether acetates such as 2-ethoxyethyl acetate and 2-butoxyethyl acetate; Esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and ethylene carbonate; Aromatic carbonization such as benzene, toluene and xylene Hydrogens; Aliphatic hydrocarbons such as hexane, heptane, iso-octane, cyclohexane; methylene chloride, 1,2-dichloroethane,
Halogenated hydrocarbons such as dichloropropane and chlorobenzene; Sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl-2-
Examples thereof include pyrrolidones such as pyrrolidone.

The coating liquid for the recording layer can be adjusted by using a known coating liquid dispersing device such as a paint shaker, a ball mill, an attritor, a three-roll mill, a Keddy mill, a sand mill, a dyno mill and a colloid mill. Further, each material may be dispersed in a solvent by using the above coating liquid dispersion device, or each material may be individually dispersed in a solvent and mixed. Further, it may be dissolved by heating and then precipitated by quenching or cooling.

The coating method for providing the recording layer is not particularly limited, and blade coating, wire bar coating, spray coating, air knife coating, bead coating, curtain coating, gravure coating, kiss coating, etc. A known method can be used.

The method of drying and curing the recording layer is as follows:
Curing treatment is performed if necessary. As long as it is heat-crosslinkable, it may be heat-treated at a relatively high temperature for a short time using a constant temperature bath or at a relatively low temperature for a long time. Further, for UV curing and electron beam curing, known curing devices may be used. For example, as a light source for ultraviolet irradiation, there are a mercury lamp, a metal halide lamp, a gallium lamp, a mercury xenon lamp, a flash lamp, etc., which correspond to the ultraviolet absorption wavelengths of the photopolymerization initiator and the photopolymerization accelerator that are arranged in advance. A light source having an emission spectrum may be used. Further, as the ultraviolet irradiation conditions, the lamp output and the conveying speed may be determined according to the irradiation energy required for crosslinking the resin. As the electron beam irradiation device, either a scanning type or a non-scanning type may be selected according to the purpose of irradiation area, irradiation dose, etc., and the irradiation condition is determined by electron irradiation depending on the dose required to crosslink the resin. It suffices to determine the flow, irradiation width, and transport speed. The thickness of the recording layer is 1 to 20
The range of μm is preferable, and the range of 3 to 10 μm is more preferable.

The reversible thermosensitive recording medium used in the present invention includes:
If necessary, an additive for improving or controlling the coating properties and color development / erasing properties of the recording layer can be used. These additives include, for example, surfactants, conductive agents, fillers, antioxidants, light stabilizers and color development stabilizers.

The reversible thermosensitive recording medium used in the present invention is basically a recording layer on a support, preferably a recording layer containing a resin in the above-mentioned crosslinked state, and optionally a protective layer, preferably a crosslinked layer. Although a protective layer containing a resin in a state is provided, an adhesive layer, an intermediate layer, an undercoat layer, a backcoat layer and the like can be provided in order to improve characteristics as a recording medium. Further, a magnetic recording layer may be provided. Further, each of the above layers and the support may be colored with a coloring agent. In this case, a part or the whole surface of the recording medium may be colored, for example, by printing.
Further, a colorless or light-colored print protective layer containing a resin as a main component may be provided on the colored print layer.

Examples of the resin used for the protective layer include polyvinyl alcohol, styrene-maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin and urea-formaldehyde resin, in addition to the above-mentioned resins in the crosslinked state. . The thickness of the protective layer is 0.1
To 20 μm is preferable, and more preferably 0.3 to
It is 10 μm.

An intermediate layer is provided between the recording layer and the protective layer for the purpose of improving adhesion, preventing alteration of the recording layer by coating the protective layer, and preventing migration of additives in the protective layer to the recording layer. Is also preferable. Further, in order to effectively utilize the applied heat, a heat insulating undercoat layer can be provided between the support and the recording layer. The heat insulation layer can be formed by applying organic or inorganic fine hollow particles using a binder resin. An undercoat layer may be provided for the purpose of improving the adhesiveness between the support and the recording layer and preventing penetration of the recording layer material into the support. For the intermediate layer and the undercoat layer, the same resin as the resin for the recording layer can be used.

A filler may be added to the undercoat layer, the recording layer, the intermediate layer and the protective layer, and the filler can be divided into an inorganic filler and an organic filler. Inorganic fillers include carbonates such as calcium carbonate and magnesium carbonate; silicates such as anhydrous silicic acid, hydrous silicic acid, hydrous aluminum silicate and hydrous calcium silicate; hydroxides such as alumina and iron oxide; zinc oxide. , Indium oxide, alumina, silica, zirconia oxide, tin oxide, cerium oxide, iron oxide, antimony oxide, barium oxide, calcium oxide, barium oxide, bismuth oxide, nickel oxide, magnesium oxide, chromium oxide, manganese oxide, tantalum oxide, Niobium oxide, thorium oxide, hafnium oxide, molybdenum oxide, iron ferrite,
Metal oxides such as nickel ferrite, cobalt ferrite, barium titanate and potassium titanate; metal sulfides or sulfuric acid compounds such as zinc sulfide and barium sulfate; titanium carbide, silicon carbide, molybdenum carbide, tungsten carbide and tantalum carbide. Examples of such metal carbides include metal nitrides such as aluminum nitride, silicon nitride, boron nitride, zirconium nitride, vanadium nitride, titanium nitride, niobium nitride, and gallium nitride. As an organic filler,
Silicone resin, cellulose resin, epoxy resin, nylon resin, phenol resin, polyurethane resin, urea resin, melamine resin, polyester resin, polycarbonate resin, styrene, polystyrene, polystyrene / isoprene, styrene vinyl resins such as styrene-vinylbenzene, vinylidene chloride acrylic , Acrylic urethane, ethylene acrylic, and other acrylic resins, polyethylene resin, benzoguanamine formaldehyde, melamine formaldehyde, and other formaldehyde resins, polymethylmethacrylate resins, vinyl chloride resins, and the like.
In the present invention, the organic filler may be used alone, but may be contained in two or more kinds and may be a composite particle. The shape may be spherical, granular, plate-like, needle-like, or the like. The content of the filler in the layer is 1 in terms of volume fraction.
˜95%, more preferably 5-75%.

Further, a lubricant may be added to the undercoat layer, the recording layer, the intermediate layer and the protective layer. Specific examples of the lubricant include synthetic waxes such as ester wax, paraffin wax and polyethylene wax: hardened castor oil and the like. Vegetable waxes: Animal waxes such as beef tallow oil:
Higher alcohols such as stearyl alcohol and behenyl alcohol: higher fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, cerotic acid: higher fatty acid esters such as sorbitan fatty acid esters: stearamide And amides such as oleic acid amide, lauric acid amide, ethylenebisstearic acid amide, methylenebisstearic acid amide, and methylolstearic acid amide. The content of the lubricant in the layer is 0.1 to 95% in volume fraction,
It is more preferably 1 to 75%.

In the present invention, the intermediate layer and the protective layer may contain an inorganic or organic UV absorber, and the content thereof is 0.5 to 1 with respect to 100 parts by weight of the binder.
A range of 0 parts by weight is preferred.

Specific examples of the inorganic ultraviolet absorber include zinc oxide, titanium oxide, cerium oxide, tin oxide, molybdenum oxide, gallium nitride, silica, alumina, antimony oxide, magnesium oxide, zirconium oxide, barium oxide, and oxide. Examples thereof include calcium, strontium oxide, silicon nitride, aluminum nitride, boron nitride and barium sulfate.

Specific examples of the organic ultraviolet absorber include, for example, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole and 2- (2'-hydroxy-5'-t-butylphenyl). Benzotriazole,
2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- (2'-Hydroxy-5'-octoxyphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) -5-
Chlorobenzotriazole, 2- (2'-hydroxy-
3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5 '
-Ethoxyphenyl) benzotriazole-based UV absorbers such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyl Oxybenzophenone, 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-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-
Benzophenone-based UV absorbers such as sodium 4-methoxybenzophenone-5-sulfonate and sodium 2,2'-dihydroxy 4,4'-dimethoxybenzophenone-sulfonate; phenyl salicylate, p-octylphenyl salicylate, pt-butyl. Phenyl salicylate, carboxyphenyl salicylate, methylphenyl salicylate, dodecylphenyl salicylate, 2
-Salicylate UV absorbers such as ethylhexylphenyl salicylate and homomenthylphenyl salicylate; 2-ethylhexyl-2-cyano-3,3 'diphenyl acrylate, ethyl-2-cyano-3,3'.
A cyanoacrylate-based UV absorber such as diphenyl acrylate; p-aminobenzoic acid, glyceryl p-aminobenzoate, amyl p-dimethylaminobenzoate, p-
P-Aminobenzoic acid type ultraviolet absorbers such as ethyl dihydroxypropylbenzoate; cinnamic acid type ultraviolet absorbers such as p-methoxycinnamate-2-ethylhexyl and p-methoxycinnamate-2-ethoxyethyl; 4; -T-butyl-
4'-methoxy-dibenzoylmethane, urocanic acid,
Examples thereof include ethyl urocanate.

Solvent used for coating liquid of the middle layer and the protective layer,
As a dispersion device for the coating liquid, a coating method, a drying / curing method, and the like, the known methods used for the recording layer can be used.

In order to form a color image using the reversible thermosensitive recording medium according to the present invention, it is sufficient to heat once above the color development temperature and then quench it. Specifically, for example, when the recording layer is heated for a short time with a thermal head or a laser beam, the recording layer is locally heated, so that the heat immediately diffuses and rapid cooling occurs, so that the coloring state can be fixed. On the other hand, in order to erase the color, it may be heated and cooled for a relatively long time using an appropriate heat source, or may be temporarily heated to a temperature slightly lower than the coloring temperature. When heated for a long time, the temperature of a wide range of the recording medium rises and the subsequent cooling slows down, so that decoloring occurs in the process. In this case, as a heating method, a heat roller, a heat stamp, hot air, or the like may be used, or a thermal head may be used to heat for a long time. In order to heat the recording layer to the decoloring temperature range, the applied energy may be slightly lowered from that at the time of recording by adjusting the voltage applied to the thermal head or the pulse width. By using this method, recording / erasing can be performed only by the thermal head, and so-called overwriting is possible. Of course, it can be erased by heating in a decoloring temperature range with a heat roller or a heat stamp.

The reversible thermosensitive recording medium used in the present invention is formed by holding the recording layer on the support exemplified above, and the support used at this time has a thickness as required. Can be used alone or by pasting. That is, a support having an arbitrary thickness of about several μm to several mm is used. Further, these supports may have a magnetic recording layer on the same surface and / or the opposite surface to the reversible thermosensitive recording layer. The reversible thermosensitive recording medium used in the present invention may be attached to another medium via an adhesive layer or the like. The reversible thermosensitive recording medium used in the present invention may be processed into a sheet shape or a card shape, and its shape can be processed into an arbitrary shape, and printing processing can be performed on the surface of the medium. . Further, the reversible thermosensitive recording medium used in the present invention may be used in combination with an irreversible thermosensitive recording layer, in which case the color tone of each recording layer may be the same or different.

[0078]

The present invention will be described in more detail with reference to the following examples. In the examples, "parts" and "%" are based on weight.

Example 1 A composition used in the present invention was prepared by using 2-anilino-3-methyl-6-dibutylaminofluorane as a color former and each compound shown in Table 15 as a color developer. Created like. First, the color former and the developer were weighed so as to have a mixing ratio (molar ratio) of 1: 2, and pulverized and mixed in a mortar.
A glass plate having a thickness of 1.2 mm is heated on a hot plate at a temperature of 2
Heated to 00 ° C. Then, a cover glass was covered on the molten mixture, the melt was spread to a uniform thickness, and immediately the whole glass plate was immersed in the prepared ice water and quenched. Immediately after the temperature was lowered, it was taken out from the ice water and the attached water was removed to obtain a thin film-shaped composition used in the present invention. Next, when the composition sample in the above-mentioned color-developed state was placed on a hot plate heated to the erasing temperature shown in Table 6, all of them were instantly decolorized. Again, this decolorized composition sample was taken 20 times.
When heated to 0 ° C., all exhibited a black color. From this fact, it was confirmed that the composition used in the present invention had a repeating property of color development and decolorization.

[0080]

[Table 15]

Example 2 The following composition was pulverized and dispersed to a particle size of 1 to 4 μm using a ball mill to prepare a recording layer coating solution. 2-anilino-3-methyl-6-dibutylaminofluorane 2 parts Developer shown in Table 15 8 parts Vinyl chloride-vinyl acetate copolymer (VYHH manufactured by Union Carbide) 20 parts Methyl ethyl ketone 45 parts Toluene 45 parts A recording layer coating solution having a composition was applied onto a polyester film having a thickness of 100 μm using a wire bar and dried to prepare a reversible thermosensitive recording medium used in the present invention having a recording layer having a thickness of about 6.0 μm.

The obtained recording medium was printed with a thermal head of 8 dots / mm under the conditions of an applied voltage of 13.3 V and an applied pulse width of 1.2 ms to obtain a colored image. The optical density of this colored image was measured using a Macbeth densitometer RD-914. Next, the color-developed recording medium was heated at an erasing temperature shown in Table 16 for 1 second using a thermal gradient tester, and then the density was measured. Further, this printing and erasing were repeated 10 times. The results are shown in Table 16. From Table 16, it can be seen that the recording medium used in the present invention is erased to the same level as the background density by heating for 1 second. Furthermore, it can be seen that printing and erasing are repeated stably. Also,
The printed sample was kept under a dry condition at 50 ° C. for 24 hours, and the background density and color density before and after storage were measured to examine the storage stability. The results are shown in Table 16. The concentration storage ratio in the table is given by the following formula. Density retention rate (%) = {(color density after storage-background density after storage)
/ (Color density before storage-Background density before storage)} x 100

Comparative Example 1 Eicosylphosphonic acid was used in place of the developer used in the present invention, and 2-anilino-3-methyl-6- (N-ethyl-Np-tolylamino) fluoran was used as a leuco dye. A reversible thermosensitive recording medium was prepared in the same manner as in Example 2 except that it was used.

This recording medium was printed and erased in the same manner as in Example 2. As shown in Table 16, this recording medium does not erase to the initial background density by heating for 1 second, and remains unerased. Further, the color-developed recording medium required heating for 1 minute in order to reduce the color density to 0.16 which is almost equal to the background density.

Comparative Example 2 Reversible thermosensitive recording was carried out in the same manner as in Example 2 except that N- (4-hydroxyphenyl) -N'-n-octadecylurea was used instead of the color developer used in the present invention. A medium was prepared.

This recording medium was printed and erased in the same manner as in Example 2. In addition, as in Example 2, the print sample was
It was kept under drying at 0 ° C. for 24 hours, and the storage stability was examined. Table 16 shows the concentration retention rate after storage. As shown in Table 6, this recording medium is erased to the initial background density by heating for 1 second. However, it can be seen that the image retention rate is extremely low when stored in a dry environment at 50 ° C. for 24 hours.

[0087]

[Table 16]

[0088] Example 3 1) 2-anilino-3-methyl-6-dibutylaminofluorane 2 parts 2) Table 15-No. 2 developer 8 parts 3) Color development / decoloration control agent having the following structure 3 parts

[Chemical 15] 4) 15% tetrahydrofuran (THF) solution of acrylic polyol resin 70 parts Using a ball mill, the average particle size is 0.1 to 3 μm.
It was pulverized and dispersed to m. To the obtained dispersion, 10 parts of Coronate HL (adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Company, was added,
The recording layer coating liquid was prepared by thoroughly stirring. The recording layer coating solution having the above composition was applied on a polyester film having a thickness of 188 μm using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to give a recording layer having a thickness of about 8.0 μm. Was provided to prepare a reversible thermosensitive recording medium used in the present invention.

Example 4 No. 14 in Table 15 was used as the color developer in Example 3. A reversible thermosensitive recording medium was prepared in the same manner as in Example 3 except that the color developer of No. 3 was used.

Example 5 A reversible thermosensitive recording medium was prepared in the same manner as in Example 3, except that the color-decoloring controlling agent in Example 3 was changed to the following compound.

[Chemical 16]

The reversible thermosensitive recording media produced in Examples 3 to 5 as described above were used in a thermal printer manufactured by Okura Electric Co., Ltd.
Printing was performed with a voltage of 13.3 V and a pulse width of 1.2 msec, and the obtained image was measured with a Macbeth densitometer RD-914.
In addition, the color development image is 110 with a thermal gradient tester manufactured by Toyo Seiki Co., Ltd.
The color was erased under the condition of 1 ° C. for 1 second, and the density of the image area and the background density after the color was erased were measured. Next, the erase remaining concentration was calculated from the following formula. These results are shown in Table 17. Unerased density = (density of image area after deletion)-(background density)

[0092]

[Table 17] From the above results, it can be seen that the erasability is good even at a relatively low erasing temperature.

Example 6 A reversible thermosensitive recording medium was prepared by providing a protective layer having the following composition on the recording layer prepared in Example 3. [Preparation of protective layer] 1) Urethane acrylate UV curable resin (C7-157 manufactured by Dainippon Ink and Chemicals, Inc.) 15 parts 2) Ethyl acetate 85 parts The above composition was well dissolved and stirred to prepare a protective layer coating liquid. The coating solution for the protective layer having the above composition was applied onto the recording layer using a wire bar and dried at 90 ° C. for 1 minute, and then passed under an ultraviolet lamp with irradiation energy of 80 W / cm at a conveying speed of 9 m / min. A reversible thermosensitive recording medium used in the present invention was prepared by curing and providing a protective layer having a film thickness of 3 μm.

When the reversible thermosensitive recording medium prepared as described above was repeated 50 times under the above-mentioned coloring and erasing conditions, the reversible thermosensitive recording medium of this example was free from dents and good. The color development and decolorization densities were maintained.

Example 7 An intermediate layer having the following composition was provided on the recording layer prepared in Example 3. [Preparation of intermediate layer] 15% methyl ethyl ketone (MEK) solution of acrylic polyol resin 30 parts (2-hydroxy-4-n-octoxy) benzophenone 4 parts (Viosorb 130 manufactured by Kyodo Chemical Co., Ltd.) Coronate HL 4 parts And apply at 100 ° C for 2
After drying for 1 minute, heat at 60 ° C for 24 hours to obtain a film thickness of approx.
Was provided. Then, a protective layer was provided in the same manner as in Example 6 to obtain a reversible thermosensitive recording medium used in the present invention.

Example 8 An intermediate layer was provided on the recording layer prepared in Example 4 in the same manner as in Example 7. Further, a protective layer was provided in the same manner as in Example 6 to obtain a reversible thermosensitive recording medium used in the present invention.

After the reversible thermosensitive recording media prepared in Examples 7 and 8 were colored under the same coloring conditions as described above,
After irradiating with a fluorescent lamp of 5000 lux for 100 hours, and then erasing under the same erasing conditions as above, and examining deterioration due to light, no change was observed in the image part after light irradiation, and the unerased remaining after erasing Not in good condition.

[0098]

According to the present invention, a high-contrast image can be easily formed and erased. Further, the color-developed image is stable under normal use conditions, has high durability against repeated recording and erasing, and rewritable recording having high practicality can be obtained.

[Brief description of drawings]

FIG. 1 shows the color development of the reversible thermosensitive coloring composition used in the present invention.
It is a figure which shows a decoloring characteristic.

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-9-263052 (JP, A) JP-A-9-193558 (JP, A) JP-A-8-67067 (JP, A) JP-A-2000-263946 (JP, A) JP 2002-248869 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (10)

(57) [Claims] 1. At least a part of the surface of a reversible thermosensitive recording medium capable of forming a relatively colored state and a relatively decolored state depending on a difference in heating temperature and / or a cooling rate after heating, is at least a coloring start temperature. A method for forming a color image by heating to a low temperature and then rapidly cooling the recording medium, wherein the recording medium contains a reversible thermosensitive coloring composition composed of an electron-donating color-forming compound and an electron-accepting compound as a main component. An image forming method comprising a thermal recording layer provided on a support, wherein the electron-accepting compound is a phenol compound represented by the following general formula (1). [Chemical 1] (In the formula, n represents an integer of 1 to 3, m represents an integer of 1 to 20, r represents an integer of 0 to 3, and X and Y are a divalent chain structure containing a hetero atom. Group (excluding divalent amino group), R ₁ is a divalent chain having 1 to 20 carbon atoms.
Represents a linear hydrocarbon group, and R ₂ is a chain hydrocarbon group having 2 to 20 carbon atoms (however, a chain hydrocarbon group having 2 to 6 carbon atoms is excluded).
Represents ) 2. The image forming method according to claim 1, wherein a protective layer is provided on the reversible thermosensitive recording layer. 3. The image forming method according to claim 2 , wherein an intermediate layer is provided between the reversible thermosensitive recording layer and the protective layer. 4. An undercoat layer is provided between the support and the reversible thermosensitive recording layer.
The image forming method according to any one of 3 above. 5. The image forming method according to any one of claims 1 to 4, characterized in that a printed layer on the recording medium. 6. The image forming method according to any one of claims 1 to 5, characterized in that a magnetic recording layer on the recording medium. 7. The image forming method according to any one of claims 1 to 6, wherein the recording medium is characterized in that which has been processed into a card or sheet. 8. A least a portion of the surface of the reversible thermosensitive recording layer side of the support and / or the opposite surface thereof, an image according to any one of claims 1 to 7, characterized by having a printing portion Forming method. 9. A reversible thermosensitive recording medium on which a color image is formed by the image forming method according to any one of claims 1 to 8 is heated at a temperature lower than the color formation start temperature to erase the color image. An image erasing method characterized by: 10. A form colored images by the image forming method according to any one of claims 1-8, and then characterized by decolored by heating the emitting color images at a lower temperature than the coloring start temperature Image formation erasing method.