JPH089270B2 - Reversible thermosensitive coloring / erasing composition - Google Patents

Description

Detailed Description of the Invention

(Field of Industrial Application) The present invention relates to a reversible thermosensitive coloring / erasing composition. More specifically, it relates to a reversible thermosensitive coloring / erasing composition that develops color by heating for a short time and decolorizes by heating for a long time. (Prior Art) Conventionally, for reversible coloring and decoloring materials, for example,
JP 58-191190 JP, JP 60-193691 JP, U.S. Pat.No. 3,666,525, JP 54-119377,
It is described in JP-A-63-393770, JP-A-63-41186, US Pat. No. 4,028,118, JP-A-58-81157, JP-A-50-105555, and the like. However, among the above documents, U.S. Pat.
In the methods described in JP-A No. 8, JP-A-58-81157 and JP-A No. 50-105555, the image formed varies with temperature, and the image once formed is stored at room temperature. Cannot be done, and the image lacks in memory. Further, those described in JP-A-58-191190, JP-A-60-193691, and U.S. Pat.No. 3,666,525 are provided with a recording layer composed of a color former, a developer and a binder, A low vapor pressure solvent or a heat-melting substance is added as necessary.The color is developed by using heat, but the color is erased by water, water vapor or some kind of organic solvent. It is not possible to repeat both coloring and erasing under the control of. Further, those described in JP-A-54-119377, JP-A-63-39377, and JP-A-63-41186 include a resin base material and an organic substance dispersed in the resin base material. It has a heat-sensitive layer containing a low-molecular substance as a main component, and reversibly changes the transparency of the heat-sensitive layer by heat energy to perform coloring and decoloring. That is, it does not chemically develop or erase color. On the other hand, the applicant of the present invention filed a Japanese patent application on April 6, 1990 (name “Reversible Thermosensitive Recording Medium Composition”).
Describes a composition in which both color development and color eradication chemical reactions can be carried out only by controlling thermal energy. As a result, the composition is applied to a base material such as a plastic card and is heated by a thermal head or the like for a short time (several milliseconds to several tens of milliseconds) to develop a color, which is heated for a long time (about 1 second). By doing so, the result of erasing is obtained. Coloring and erasing can be repeated, for example, 100 to several thousand times can be repeated. (Problems to be Solved by the Invention) However, the composition described in the Japanese patent application (named “composition for reversible thermosensitive recording medium”) dated April 6, 1990, is 120 It requires heating at a temperature of 130 ° C for about 1 second. However, polyesters or plastics such as polyvinyl chloride are
It will be damaged by repeating heating for about 1 second at a temperature of several tens of times. For this reason, this composition could not fully utilize its characteristics, and it was only possible to repeat coloring and decoloring about 100 times at most. Therefore, the present invention provides a reversible exothermic coloring and decoloring composition that decolors at a lower temperature, and makes it possible to repeat coloring and decoloring hundreds to thousands of times without damaging the plastic. With the goal. (Means for Solving the Problems) To achieve this object, an amphoteric compound having a leuco compound, at least one of a phenolic hydroxyl group and a carboxyl group, and having an amino group as a functional group or as a part of a salt compound, Provided is a reversible thermosensitive coloring / erasing composition containing a large amount of a heat-fusible sensitizer. (Detailed Description of the Invention) The composition according to the present invention comprises a leuco compound, an amphoteric compound,
And a heat-fusible sensitizer. The leuco compound is one that develops and decolorizes by heating, and includes, for example, custal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-ciethylamino-7-chlorofluorane, 2- (2-fluorophenylamino) -6-
Diethylaminofluorane, 2- (2-fluorophenyl) -6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3
-Diethylamino-5-methyl-7-t-butylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-butylanilinofluorane, 3-cyclohexylamino −
6-chlorofluorane, 2-anilino-3-methyl-6
-(N-ethyl-p-toluidino) -fluorane, 3-
Pyrrolidino-6-methyl-7-anilinofluorane, 3
-Pyrrolidino-7-cyclohexylaluminofluorane, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluorane, 3-N-ethylpentylamino-6-methyl-7-anilinofluorane and the like. be able to. The amphoteric compound causes a coloring reaction and a decoloring reaction of the leuco compound by heat. That is, the phenolic hydroxyl group or the carboxyl group opens the lactone ring of the colorless leuco compound by the energy of heat, and develops a colorless to colored color. However, a compound in which the lactone ring is opened returns to a colorless compound having a lactone ring of the group when contacted with a basic substance. Since the amphoteric compound of the present invention has both an acidic group consisting of a phenolic hydroxyl group or a carboxyl group and a basic group consisting of an amino group, the coloring reaction and the decoloring reaction probably occur simultaneously by heating. Under heating conditions, the reaction rate of the color development reaction is faster than the reaction rate of the decolorization reaction. Therefore, it can be inferred that the color development state is maintained by heating and cooling for a short time. Further, it is presumed that the equilibrium state is the decolored state under the heating condition. Therefore, the color is erased by heating for a long time, and this decolored state is maintained even after cooling to room temperature. This reaction rate formula is g (t) = A {exp (−t /
τ _a ) −exp (−t / τ _b ). Where:
g (t) is the color density, t is the heating time, τ _a and τ _b are constants determined by the type of amphoteric compound, and A is a constant. In addition,
A similar formula can be derived even if it is considered that the color-development reaction is followed by the decolorization reaction. This amphoteric compound needs to have both an acidic group and a basic group, because heating causes both a color-developing reaction and a color-erasing reaction. The acidic group is a phenolic hydroxyl group or a carboxyl group. The basic group is an amino group. The basic group may be included as a functional group or may be included as part of the salt compound. Examples of the compound having an amino group as a functional group include amphoteric compounds represented by the following general formula [1]. (In the formula, X represents a hydroxyl group or a carboxyl group, and R
Represents a hydrogen atom or a hydroxyl group. ) Examples of such compounds include aminophenol or aminobenzoic acid represented by the following general formula [2], or hydroxyaminobenzoic acid represented by the following general formula [3]. (In the formula, X represents a hydroxyl group or a carboxyl group.) Specific examples of the aminophenol or aminobenzoic acid represented by the above general formula [2] include aminophenols such as 2-aminophenol, 3-aminophenol and 4-aminophenol; 2-aminobenzoic acid, 3 Examples thereof include aminobenzoic acid such as -aminobenzoic acid and 4-aminobenzoic acid. Examples of the hydroxyaminobenzoic acid represented by the general formula [3] include 2-hydroxy-3-aminobenzoic acid, 2-amino-3-hydroxybenzoic acid, 2-amino-4-hydroxybenzoic acid, 2- Hydroxy-4-aminobenzoic acid, 2-hydroxy-6-aminobenzoic acid, 3
-Amino-4-hydroxybenzoic acid, 3-hydroxy-
5-aminobenzoic acid etc. can be mentioned. The amphoteric compound having an amino group as a part of the salt compound is a salt or complex salt of a compound having a phenolic hydroxyl group or a carboxyl group and a compound having an amino group. Examples of the compound having a phenolic hydroxyl group or a carboxyl group include compounds represented by the following general formula [A] or [B] or esters thereof. (In the formula, n represents an integer of 1 to 3, preferably 2 or 3.) (In the formula, R ₁ represents a hydrogen atom or a methyl group, and n ₁ is 0 to 6
Represents the integer. ) Specific examples of the compound represented by the general formula [A] include 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid and the like (n = 1); 3,4-dihydroxybenzoic acid. Acid, 3,5-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5
-Dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,6-dihydroxybenzoic acid, 4,5-dihydroxybenzoic acid, 4,6-dihydroxybenzoic acid, 4-hydroxysalicylic acid, 5-hydroxysalicylic acid, etc. (n = 2);
Examples thereof include gallic acid (n = 3). As the ester of the compound represented by the general formula [A], hexyl gallate, heptyl gallate, octyl gallate, nonyl gallate, decyl gallate, undecyl gallate, lauryl gallate, tridecyl gallate, Examples include tetradecyl gallate, pentadecyl gallate, cetyl gallate, heptadecyl gallate, stearyl gallate, and the like. Further, as the compound represented by the above general formula [B],
2,2-bis (4-hydroxyphenyl) ethanoic acid, 2,2-
Bis (4-hydroxyphenyl) propionic acid, 3,3-
Bis (4-hydroxyphenyl) propionic acid, 4,4-
Bis (4-hydroxyphenyl) butanoic acid, 4,4-bis (4-hydroxyphenyl) heptanoic acid, 5,5-bishydroxyphenyl) pentanoic acid, 5,5-bis (4-hydroxyphenyl) hexanoic acid, 6 , 6-bis (4-hydroxyphenyl) heptanoic acid, 7,7-bis (4-hydroxyphenyl) heptanoic acid, 8,8-bis (4-hydroxyphenyl) octanoic acid, 7,7-bis (4-hydroxy) Examples include phenyl) octanoic acid and 8,8-bis (4-hydroxyphenyl) nonanoic acid. Examples of the compound having an amino group which forms a salt or a complex salt with the compound having a phenolic hydroxyl group or a carboxyl group include compounds represented by the following general formula [C] or [D]. R ₂ NH ₂ [C] (In the formula, R ₂ represents an alkyl group having 8 or more carbon atoms.) (In the formula, R ₃ represents a hydrogen atom, an alkyl group, a halogen atom or an alkoxy group, and n ₂ represents an integer of 1 to 18.) As the aliphatic amine represented by the general formula [C],
Specific examples include octylamine, nonylamine, decylamine, undecylamine, laurylamine, tridecylamine, tetradecylamine heptadecylamine, stearylamine, hexylamine, heptylamine and the like. Moreover, as the amine represented by the general formula [D], for example, benzylamine, 2-phenylethylamine, 3-
Phenylpropylamine, 4-phenylbutylamine,
5-phenylpentylamine, 6-phenylhexylamine, 7-phenylheptyloctylamine, 9-phenylnonylamine, 10-phenyldecylamine, 11-phenylundecylamine, 12-phenyldodecylamine, 13-phenyltridecylamine , 14-phenyltetradecylamine, 15-phenylpentadecylamine, 16
-Phenylhexadecylamine, 17-phenylheptadecylamine, 18-phenyloctadecylamine, methylbenzylamine, 2-triethylamine, 3-tolylpropylamine, 4-tributylamine, 5-tolylpentylamine, 6-tolylhexylamine, 7-Tolylheptylamine, 8-Tolyloctylamine, 9-Tolylnonylamine, 10-Tolyldecylamine, 11-Tolylundecylamine, 12-Tolyldecylamine, 13-Tolyltridecylamine, 14-Tolyltetradecylamine ,
15-tolylpentadecylamine, 16-tolylhexadecylamine, 17-tolylheptadecylamine, 18-tolyloctadecylamine, chlorobenzylamine, 2-chlorophenylethylamine, fluorobenzylamine, 2-
Examples include bromophenylethylamine, methoxybenzylamine, ethoxybenzylamine and the like. In the present invention, the salt or complex salt is preferably a salt of dihydroxybenzoic acid represented by the following general formula [A] and a higher aliphatic amine having an alkyl group having 8 or more carbon atoms, the following general formula [ 5], a salt of gallic acid and a higher aliphatic amine, a salt of hydroxybenzoic acid or dihydroxybenzoic acid of the following general formula [6] and an aliphatic amine, and a salt of the following general formula [7]. Salt of gallic acid with an aliphatic amine, a salt of bis (hydroxyphenyl) acetic acid or bis (hydroxyphenyl) butyric acid represented by the following general formula [8] with a higher aliphatic amine, the following general formula

[9] A salt of an aliphatic carboxylic acid having two hydroxyphenyl groups and an aliphatic amine, and a salt of a gallic acid ester represented by the following general formula [10] and a higher aliphatic amine. To be (In the formula, R ₄ represents an alkyl group having 8 or more carbon atoms.) (In the formula, R ₅ represents an alkyl group having 8 or more carbon atoms.) (In the formula, R ₆ represents a hydrogen atom, an alkyl group, a halogen atom, or an alkoxy group, n ₂ represents 1 or 2, and n ₃ represents an integer of 1 to 18.) (In the formula, R ₇ represents a hydrogen atom, an alkyl group, a halogen atom or an alkoxy group, and n ₄ represents an integer of 1 to 18.) (In the formula, R ₈ represents a hydrogen atom or a methyl group, and R ₉ represents an alkyl group having 8 or more carbon atoms.) (In the formula, R ₁₀ is a hydrogen atom or a chill group, R ₁₁ is a hydrogen atom,
Alkyl group, halogen atom or alkoxy group, n ₅ is 1
Is an integer of ₆ and n ₆ is an integer of 1 to 18. ) (In the formula, R ₁₂ and R ₁₃ each represent an alkyl group having 8 or more carbon atoms.) The heat-fusible sensitizer of the present invention is for causing this decoloring to occur at a lower temperature. Although the reason for decoloring at low temperature by mixing the heat-fusible sensitizer is not clear, it can be presumed that the decoloring temperature is lowered by lowering the melting point. Therefore, the heat-fusible sensitizer is preferably a low melting point compound having a melting point of 50 to 150 ° C. Examples of such heat-fusible sensitizers include montanic acid wax and its derivatives. For example, carnauba wax, paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax and the like. Further, as the heat-fusible sensitizer, N-substituted or unsubstituted fatty acid amide can be used. Examples of the N-substituted fatty acid amide include N-lauryl stearic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N
-Palmityl stearic acid amide, N-myristyl stearic acid amide, N-lauryl oleic acid amide, N, N
-Dilauryl stearic acid amide, N, N-dioleyl stearic acid amide, N, N-dimyristyl oleic acid amide, N, N'-dilauryl adipic acid amide, N, N'-distearyl adipic acid amide, N , N'-dilauryl sebacic acid amide can be exemplified. Examples of the unsubstituted fatty acid amide include stearic acid amide, oleic acid amide, palmitic acid amide, escaic acid amide, lauric acid amide, and their methylol compounds. Further, an N-substituted aromatic amide can be used as the heat-fusible sensitizer. For example, N-laurylbenzamide, N-stearylbenzamide, N-oleylbenzamide, N, N-distearylbenzamide, N, N-dioleylbenzamide, N, N-dilaurylbenzamide,
Examples thereof include N, N'-distearyl terephthalic acid amide, N, N'-distearyl isophthalic acid amide, and N, N'-dilauryl isophthalic acid amide. Further, an aliphatic bisamide can be used as the heat-fusible sensitizer. For example, ethylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebisoleic acid amide, ethylenebispalmitic acid amide and the like. Furthermore, aromatic sulfonamides can be used as the heat-fusible sensitizer. Examples of such aromatic sulfonamides include benzenesulfonamide, toluenesulfonamide, ethylbenzenesulfonamide, n-propylbenzenesulfonamide, isopropylbenzenesulfonamide, chlorobenzenesulfonamide, dichlorobenzenesulfonamide, methoxybenzenesulfonamide, ethoxybenzene. Sulfonamide, isophthalbenzenesulfonamide, octylbenzenesulfonamide, laurylbenzenesulfonamide, myristylbenzenesulfonamide, cetylbenzenesulfonamide,
Stearyl benzene sulfonamide etc. can be illustrated. The composition of the present invention may further contain a binder. As such a binder, a commonly used polymer material that is soluble in water or an organic solvent can be used. Specific examples of such a polymer material include polyvinyl alcohol, methyl cellulose, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl chloride, linear saturated polyester, methacrylic resin such as polymethyl methacrylate and polyethyl methacrylate alone. Alternatively, a thermoplastic resin such as a copolymer, polyurethane, polyvinyl butyral, or nitrocellulose may be used. The composition of the present invention can be obtained by mixing such an amphoteric compound, a heat-fusible sensitizer, a leuco compound, and a necessary binder. The heat-fusible sensitizer is 0.1 parts by weight per 1 part by weight of the amphoteric compound.
Mixing up to 1.0 parts by weight is enough. If it is less than 0.1 part by weight, the decolorization temperature is not sufficiently low, and if it exceeds 1.0 part by weight, the decolorization reaction itself becomes difficult. The leuco compound is 0.1 to 1 part by weight of the amphoteric compound.
It is desirable to mix 1.0 part by weight. Further, the binder may be 5 parts by weight or less with respect to 1 part by weight of the amphoteric compound. The composition of the present invention can be used as a recording layer by dissolving or dispersing it in water or an appropriate solvent such as an organic solvent to form a coating, and coating the coating on a suitable support. In coating, a liquidity improver such as a thickener or a pigment can be added to the paint. As the support, in addition to paper, a plastic material such as a plastic card can be used. The coating can be performed by a well-known coating method such as bar coating, blade coating, air knife coating, gravure coating roll coating and the like. The coating amount is preferably 4 to 10 g / m ^{2 by} weight after drying. A protective layer may be provided on the recording layer to protect the recording layer. For example, wax, the above-mentioned thermoplastic resin, or a curable resin such as a thermosetting resin or an ultraviolet curable resin. This recording layer develops color by heating for a short time. The heating required for color development is for a very short time, and for example, heating with a thermal head for several milliseconds to several hundreds of milliseconds may be sufficient.
The temperature may be the same as the heating temperature of a normal thermal head,
It is usually around 300 ° C. Further, this recording layer is erased by heating for a long time. The long-time heating means heating for a longer time than the time required for color development, and the "long-time heating" required for this decoloring is only 1 to several seconds. The temperature required for erasing is
A temperature of 80 to 110 ° C is sufficient, and it is a temperature at which the plastic is not damaged even when the coloring and decoloring is repeated hundreds to thousands of times. (Example 1) Methacrylic resin 5.0 parts by weight Toluene 40.0 parts by weight Liquid B Methacrylic resin 7.5 parts by weight Toluene 40.0 parts by weight Solution C Stearic acid amide 10.0 parts by weight Methacrylic resin 2.0 parts by weight Toluene 40.0 parts by weight The above solutions A and B are pulverized and dispersed in a sand mill for 1 hour respectively, and then solution A 1 part by weight, Liquid B 4 parts by weight, liquid C 2
A coating was prepared by thoroughly mixing parts by weight. This paint
A reversible sheet having no background fog was produced by coating and drying on a white polyvinyl chloride sheet having a thickness of 250 μm using a Meyer bar so as to have a dry film thickness of 5.5 μm. (Example 2) Polyvinyl alcohol 2.0 parts by weight Water 32.0 parts by weight Isopropyl alcohol 8.0 parts by weight Calcium carbonate 10.0 parts by weight Polyvinyl alcohol 10.0 parts by weight Water 32.0 parts by weight Isopropyl alcohol 8.0 parts by weight Solution C Ethylenebisstearic acid amide 10.0 parts by weight Polyvinyl alcohol 2.0 parts by weight Water 32.0 parts by weight Isopropyl alcohol 8.0 parts by weight The above solutions A and B are added. After pulverizing and dispersing in a sand mill for 1 hour each, 1 part by weight of solution A, 7 parts by weight of solution B, and solution 4 of solution C
A coating was prepared by thoroughly mixing parts by weight. This paint
A reversible sheet having no background fog was produced by coating and drying on a high-quality paper having a basis weight of 60 g / m ² using a Meyer bar so as to obtain a dry film thickness of 8.0 μm. (Example 3) Polyvinyl butyral 2.0 parts by weight Toluene 40.0 parts by weight Silicone resin fine powder 10.0 parts by weight Polyvinyl butyral 10.0 parts by weight Toluene 40.0 parts by weight Solution C Microcrystalline wax 5.0 parts by weight Stearic acid amide 5.0 parts by weight Polyvinyl butyral 2.0 parts by weight Toluene 40.0 parts by weight Each of the solutions A and B is 1 in a sand mill. After pulverizing and dispersing for an hour, 1.0 part by weight of solution A, 5.0 parts by weight of solution B, solution C
A coating was prepared by thoroughly mixing 2.5 parts by weight. This coating material was applied and dried on a white polyester sheet having a thickness of 188 μm using a Meyer bar so as to have a dry film thickness of 7.0 μm, to produce a reversible sheet having no background fog. (Example 4) Polyester resin 2.0 parts by weight Toluene 40.0 parts by weight Polyester resin 10.0 parts by weight Toluene 40.0 parts by weight Solution C p-octylbenzenesulfonamide 10.0 parts by weight Polyester resin 2.0 parts by weight Toluene 40.0 parts by weight Solution D Methacrylic resin 10.0 parts by weight Calcium carbonate 10.0 parts by weight Toluene 40.0 parts by weight Above solutions A and B The solution was crushed and dispersed in a sand mill for 1 hour each, and then 1.0 part by weight of solution A, 2.5 parts by weight of solution B, and solution C
A paint was prepared by thoroughly mixing 1.5 parts by weight. This coating material was applied and dried on a white polyester sheet having a thickness of 188 μm using a Meyer bar so that a dry film thickness was 6.0 μm. Next, the solution D was applied and dried using a Meyer bar so that the dry film thickness was 1.5 μm, and a reversible sheet free from background fog was produced. (Comparative Examples 1 to 4) Corresponding Examples 1 to 1 except that the liquid C of Examples 1 to 4 was removed.
A reversible sheet was prepared in the same manner as in No. 4. (Evaluation) The sheets of Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated by the following methods. In other words, each sheet is a Sir simulator (printing conditions: applied voltage 0.40 W / dot, pulse width 2.5 msec ON / O
FF, thermal head: Thin film head manufactured by Toshiba Corporation (348
Ω), dot density: 6 dots / mm), and printed on a solid of 10 mm width, and the color density was measured with a reflection densitometer (RD-918 manufactured by MACBBTH). Next, the color was depressed by pressing with a hot stamp plate heated to 100 ° C. for 1 second, and the reflection density at this time was measured by the same method. The results are shown in Table 1. In the table, "hue" means the hue at the time of color development, and "base", "color development", and "decoloration" mean the reflection densities before color development, color development, and color erasure, respectively. In addition, each sheet was repeatedly colored and decolored several hundred times, but the substrate was not damaged and the colored and decolored states were successfully reproduced. (Effects) As described above, according to the present invention, a reversible coloring / erasing composition capable of repeating coloring / decoloring only by heat, and at low temperature without damaging a plastic substrate or the like. It is possible to obtain a composition that can be erased by. For this reason, apply it on the surface of plastic cards,
It becomes possible to reversibly print or print.

Claims (2)

[Claims] 1. A leuco compound, an amphoteric compound having at least one of a phenolic hydroxyl group and a carboxyl group, and having an amino group as a functional group or as a part of a salt compound, and a heat-fusible sensitizer. A reversible thermosensitive coloring / erasing composition. 2. The heat-fusible sensitizer is montanic acid wax or its derivative, N-substituted or unsubstituted higher fatty acid amide,
The reversible thermosensitive decolorizable composition according to claim (1), which is one or more compounds selected from N-substituted aromatic amides, aliphatic bisamides, and aromatic sulfonamides.