JPH0446986A - Reversible heat-sensitive color developing and extinguishing composition - Google Patents

Abstract

PURPOSE:To provide a reversible heat-sensitive color developing and extinguishing composition which can repeat color developing and extinction only by heat and can extinguish the color at low temperature by using a leuco compound, a specific amphoteric compound and a thermofusible sensitizing agent as essential components. CONSTITUTION:A reversible heat-sensitive color developing and extinguishing composition is produced by mixing a leuco compound such as crystal violet lactone, an amphoteric compound which has at least one group selected from the group consisting of a phenolic hydroxy group and a carboxyl group and contains an amino group as its functional group or as a part of the salt thereof, such as 2-hydroxy-3-aminobenzoic acid and a thermofusible sensitizing agent such as montan wax. This composition is dissolved or dispersed in a suitable solvent such as water or an organic solvent to make a paint. The paint is applied to a support such as a plastic card to be used as a recording layer.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a reversible heat-sensitive coloring/discoloring composition.

More specifically, the present invention relates to a reversible heat-sensitive coloring/discoloring composition that develops color when heated for a short time and disappears when heated for a long time.

(Prior Art) Conventionally, reversible coloring/discoloring materials have been disclosed, for example, in Japanese Patent Application Laid-open Nos. 58-191190 and 60-1936.
No. 91, U.S. Patent Specification No. 3666.525, JP-A-54-119377, JP-A-63-39377
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, US Pat. No. 4,028.
No. 118, JP-A-58-81157, JP-A-Sho 50
In the method described in Japanese Patent No. 105555, the image formed varies depending on the temperature, and the image once formed cannot be stored at room temperature, and the image lacks memorability.

Also, JP-A-58-191190, JP-A-60-
No. 193691, U.S. Patent Specification 3°666.52
The device described in No. 5 has a recording layer consisting of a color former, a color developer, and a binder, and if necessary, a low vapor pressure solvent or a heat-melting substance is added, and the color development is Although heat is used to remove color, decoloring is performed using water, water vapor, or some kind of organic solvent, and it is not possible to repeat both coloring and decoloring by controlling thermal energy.

Also, JP-A-54-119377, JP-A-63-
39377 and JP-A-63-41186 have a heat-sensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material. Coloring and decoloring are performed by reversibly changing the transparency of the heat-sensitive layer using thermal energy. In other words, it does not chemically develop or erase color.

In contrast, Japanese patent No. 11! dated April 6, 1990 by the applicant! (Name: "Composition for Reversible Thermosensitive Recording Media") describes a composition that can carry out both coloring and decoloring chemical reactions only by controlling thermal energy.

As a result, this composition can be applied to a base material such as a plastic card for a short period of time (several milliseconds to
The result is that the color develops by heating (several tens of milliseconds), and the color disappears by heating for a long time (about 1 second). Coloring and decoloring can be performed repeatedly, for example, coloring and decoloring can be repeated several thousand times from the screen.

(The problem that the invention attempts to solve!! However, the Japanese patent application dated April 6, 1990 (
The composition described under the name "Composition for Reversible Thermosensitive Recording Media" requires heating at a temperature of 120 to 130° C. for about 1 second in order to erase its color. However, plastics such as polyester or polyvinyl chloride are damaged by repeating this heating at 120 to 130° C. for about 11 seconds several thousand times. For this reason, this composition could not make full use of its properties, and could only repeat coloring and decoloring about 1°O times at most.

Therefore, the present invention provides a reversible heat-sensitive coloring and decoloring composition that decolors at a lower temperature, without damaging plastics.
The purpose is to make it possible to repeat color development and fading several hundred to several thousand times.

(Means for solving the problem) In order to achieve this object, 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 thermofusible sensitizer.

(The composition according to the detailed description of the invention consists of a leuco compound, an amphoteric compound, and a thermofusible sensitizer.

Leuco compounds develop and discolor when heated.
For example, Custarbioresotolactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamine-7-chlorofluoran, 2-(2-fluorophenylamino)-6-dini Thylaminofluorane, 2-(2-fluorophenyl)
-6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5-methyl-7-1-butylfluorane,
3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-butylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-anilino-3-methyl- 6-ethyl-p-1-luidino)-fluorane, 3-pyrrolidino6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-N-methylsilohexylamino-6 -Methyl 7-anilinofluorane, 3-N-ethylpentylamino-6-methyl-
7-anirite fluorane and the like can be mentioned.

The amphoteric compound is one that causes the coloring reaction and decoloring reaction of the leuco compound when heated. That is, the phenolic hydroxyl group or carboxyl group opens the lactone ring of the colorless leuco compound by thermal energy, causing the colorless to colored color to develop. However, when a compound with an opened lactone ring comes into contact with a basic substance, it returns to its original colorless compound with a lactone ring.

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 color erasing reaction are probably caused by
They occur at the same time due to heating. Under heating conditions, the reaction rate of the coloring reaction is faster than the reaction rate of the color erasing reaction, so it can be inferred that the coloring state is maintained after short heating and cooling. It is also assumed that the equilibrium state is a colorless state under heating conditions. Therefore, the color disappears when heated for a long time, and this colorless state is maintained even after cooling to room temperature.

This reaction rate equation is g(t)-A(exp (-t/r
a) It can be expressed as -exp (-t/rb). In the formula, g(t) is the color density, t is the heating time, τ and τ1 are constants determined by the type of amphoteric compound, and A is a constant. Note that Doroku's equation can be derived even if it is assumed that the color-decolorizing reaction has stopped following the color-developing reaction.

This amphoteric compound must have both an acidic group and a basic group in order to cause both a color-forming reaction and a color-erasing reaction upon heating. 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 as a part of the salt compound.

Examples of compounds 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 the following general formula [3].
] Hydroquinoaminoan 2t represented by the following and folic acid are mentioned.

(In the formula, X represents a hydroxyl group or a carboxyl group.) Specifically, the aminophenol or aminobenzoic acid represented by the above general formula [2] includes 2-aminophenol, 3-aminephenol, 4-aminephenol, Aminophenols such as phenol; and aminobenzoic acids such as 2-aminobenzoic acid, 3-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-hydroquine benzoic acid, 2-amino-4
-Hydroquine benzoic acid, 2-hydroquino-4-aminobenzoic acid, 2-hydroquino-6-aminobenzoic acid, aromatic acid, 3-
Amino-4-hydroxybenzoic acid, 3-hydroquino-5
-aminobenzoic acid and the like.

Further, the amphoteric compound having an amino group as part of the salt compound is a salt or complex salt of a compound having a phenolic water flI group or a carboxyl group and a compound having an amino group.

Examples of the compound having a phenolic hydroxyl group or carboxyl group include compounds represented by the following general formula [A] or [B] or esters thereof.

(In the formula, n is an integer of 1 to 3, preferably 2 or Represents 3.

(In the formula, R1 represents a hydrogen atom or a methyl group, and n+ represents an integer of 0 to 6.) Specifically, the compound represented by the above general formula (A) includes 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, etc. (n=1)i3,4-dihydroxybenzoic 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
Examples include 5-dihydroxybenzoic acid, 4,6-dihydroxybenzoic acid, 4-hydroxysalicylic acid, 5-hydroxysalicylic acid, etc. (n=2); and gallic acid, etc. (n=3).

In addition, examples of the ester of the compound represented by the above general formula [A] include hexyl gallate, hebutyl gallate, octyl gallate, nonyl gallate, decyl gallate, undecyl gallate, lauryl gallate, and tridecyl gallate. , tetradecyl gallate, pentadecyl gallate, cetyl gallate, heptadecyl gallate, stearyl gallate, and the like.

In addition, as a compound represented by the above general formula CB), 2
．． 2-bis(4-hydroxyphenyl)ethanoic acid, 2,
2-bis(4-hydroxyphenyl)propionic acid, 3
．． 3-bis(4-hydroxyphenyl)propionic acid,
4.4-bis(4hydroxyphenyl)butanoic acid, 4.
4-bis(4-hydroquinphenyl)hebutanoic acid, 5.
5-bis(hydroxyphenyl)pentanoic acid, 5.5-bis(4-hydroxyphenyl)hexanoic acid, 6.6-bis(4-hydroxyphenyl)hebutanoic acid, 7.7-bis(4-hydroxyphenyl) Examples include butanoic acid, 8,8-bis(4-hydroxyphenyl)octanoic acid, 7.7-bis(4-hydroxyphenyl)octanoic acid, 8,8-bis(4-1 doroquinphenyl)nonanoic acid, and the like.

Examples of the compound having an amino group that forms a salt or a complex salt with the compound having a phenolic hydroxyl group or carboxyl group include compounds represented by the following general formula [C] or CD).

R2NH, (C) (In the formula, R2 represents an alkyl group having 8 or more carbon atoms.) (In the formula, R1 represents a hydrogen atom, an alkyl group, a halogen atom, or an alkoxy group, and R2 represents an alkyl group having 8 or more carbon atoms. Represents an integer.

) Specifically, the aliphatic amine represented by the above general formula (C) includes octylamine, nonylamine, denoramine, undecylamine, laurylamine, tridenolamine, tetradenlamine, hefridenylamine, stearylamine, hexyl Examples include amine, heptylamine, and the like.

In addition, examples of the amine represented by the general formula C'D) include hensylamine, 2-phenylethylamine, 3-phenylethylamine,
Phenylpropylamine, 4-phenylbutylamine,
5-phenylpentylamine, 6-phenylethylamine, 7-phenylheptyloctylamine, 9-phenylnonylamine, 10-phenylethylamine, 11-
Phenylundenylamine, 12-phenyldodecylamine, 13-phenyltridecylamine, 14-phenyltridecylamine, 15-phenylpentatedylamine, 16-phenylhexadicylamine, 17-phenylheptadecylamine, 18-phenyloctadecyl amine, methylbenzylamine, 2-triethylamine,
3-tolylpropylamine, 4-tolylbutylamine,
5-tolylpentylamine, 6-tolylhexylamine, 7-tolylhebutylamine, 8-tolyloctylamine, 9-tolylnonylamine, 10-tolyldecylamine, 11-tolylundecylamine, 12-tolyldodecylamine, 13-tolyltridecylamine, 14-tolyltetradecylamine, 15-tolylpentadecylamine, 16-tolylhexapsylamine, 17-tolylheptadecylamine, 18-tolyl octadecylamine, chlorobenzylamine, 2-chlorophenylethylamine, Examples include fromobenzylamine, 2-bromophenylethylamine, methoxybenzylamine, and ethoxybenzylamine.

In the present invention, the salt or complex salt is preferably a salt of dihydroxybenzoic acid represented by the following general formula (4) and a higher aliphatic amine having an alkyl group having 8 or more carbon atoms, a salt of the following general formula [ A salt of gallic acid and a higher aliphatic amine represented by the following general formula [6], a salt of hydroxybenzoic acid or dihydroxybenzoic acid and an aliphatic amine represented by the following general formula [6], a salt represented by the following general formula [7] A salt of gallic acid and an aliphatic amine, bis(
A salt of hydroxyphenyl)acetic acid or bis(hydroxyphenyl)butyric acid and a higher aliphatic amine, the following general formula [9
] A salt of an aliphatic carboxylic acid having two hydroxyphenyl groups and an aliphatic amine, represented by the following general formula [lO
] Examples include complex salts of gallic acid esters and higher aliphatic amines.

(In the formula, R4 represents an alkyl group having 8 or more carbon atoms,
) (In the formula, represents an alkyl group having 8 or more carbon atoms.

(In the formula, is a hydrogen atom, alkyl group, Halogen ion atom, or an alkoxy group, Ba or 2, n Go teeth ■ Represents an integer of 8.

(In the formula, represents a hydrogen atom, an alkyl group, a halogen atom, or an alkoxy group, and R4 represents the number of 1-18(7)l.) (In the formula, R8 represents a hydrogen atom or a methyl group, and R7 represents a carbon atom number of 8 or more. ) (wherein R1 is a hydrogen atom or a thyl group, R1 is a hydrogen atom, an alkyl group, a halogen atom or an alkoxy group, n is an integer of 1 to 6,
R6 represents an integer of 1 to 18. (In the formula, R1! and R1ff each represent an alkyl group having 8 or more carbon atoms.) It is intended to be produced at low temperatures. Although it is not clear why the mixture of thermofusible sensitizers causes decolorization at low temperatures, it can be assumed that the decolorization temperature is lowered due to a decrease in the melting point. For this reason, the thermofusible sensitizer is preferably a low melting point compound with a melting point of 50 to 150°C.

Examples of such thermofusible sensitizers include montanic acid wax and derivatives thereof; examples include carnauba wax, paraffin wax, microcrystalline wax, polyethylene wax, and polypropylene wax.

Furthermore, N-substituted or unsubstituted fatty acid amides can be used as the thermofusible sensitizer. As N-substituted fatty acid amide,
N-lauryl stearamide, N-oleyl stearamide, N-stearyl erucic acid amide, N-valmityl 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-simyristyloleic acid amide, N,N'-dilauryl adipic acid amide, N
, N'-distearyl adipate amide, N, N'-
Examples include dilauryl sebacic acid amide.

Further, examples of the unsubstituted fatty acid amide include stearic acid amide, oleic acid amide, valmitic acid amide, escaic acid amide, lauric acid amide, or methylolated products thereof.

Furthermore, N-substituted aromatic amides can also be used as thermofusible sensitizers. For example, N-laurylbenzamide, N-stearylbenzamide, N-oleylbenzamide, N,N-distearylbenzamide, N,N-
Dioleylbenzamide, N,N-dilaurylbenzamide, N,N' distearyl terephthalic acid amide, N,
N''-distearylisophthalic acid amide, N,N'-dilauryl isophthalic acid amide, and the like.

Moreover, an aliphatic bisamide can also be used as a thermofusible sensitizer. For example, ethylene bislauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis palmitic acid amide, etc.

Furthermore, aromatic sulfonamides can also be used as thermofusible sensitizers. Such aromatic sulfonamides include benzenesulfonamide, toluenesulfonamide, ethylhenzenesulfonamide, n-probyrhenzenesulfonamide, isophthalbenzenesulfonamide, chlorobenzenesulfonamide, dichlorohenzenesulfonamide, and methoxybenzene. Sulfonamide, ethoxybenzenesulfonamide, isophthalbenzenesulfonamide, octylbenzenesulfonamide,
Examples include laurylbenzenesulfonamide, myristylbenzenesulfonamide, cetylbenzenesulfonamide, and stearylbenzenesulfonamide.

The composition of the present invention can further contain a binder. As such a binder, commonly used polymeric materials that are soluble in water or organic solvents can be used. Examples of such polymer materials include polyvinyl alcohol, methyl cellulose, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl chloride, linear saturated polyester, polymethyl methacrylate, polyethyl methacrylate, and other methacrylic resins alone. or copolymers, polyurethane, polyvinyl alcohol,
Examples include thermoplastic resins such as nitrocellulose.

The composition of the present invention can be obtained by mixing such an amphoteric compound, a thermofusible sensitizer, a leuco compound, and a necessary binder.

The thermofusible sensitizer is 0.1 part by weight of the amphoteric compound.
It is sufficient to mix up to 1.0 parts by weight. If it is less than 0.1 part by weight, the decoloring temperature will not be sufficiently low, and if it exceeds 1.0 parts by weight, the decoloring reaction itself will become 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 amount of the binder may be 5 parts by weight or less per 1 part by weight of the amphoteric compound.

The composition of the present invention can be dissolved or dispersed in a suitable solvent such as water or an organic solvent to form a paint, and this paint can be applied as a recording layer on a suitable support. During coating, liquid property improvers such as thickeners and pigments can be added to the paint. In addition to paper, plastic materials such as plastic cards can be used as the support.

Coating can be done by well-known coating methods such as barcode coating, blade coating, air knife coating, gravure coating, and roll coating. The amount of application is 4 to 1 by weight after drying.
0 g/rrf is preferred.

A protective layer may be provided on this recording layer to protect the recording layer. For example, a protective layer may be formed of 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 when heated for a short time.

The heating required for color development is extremely short; for example,
Heating with a thermal head may be performed for several milliseconds to several hundred milliseconds, and the temperature may be the same as that of a normal single-head, which is usually about 300°C.

Moreover, this recording layer loses its color when heated for a long time. Long-term heating means heating for a long time compared to the time required for color development. The temperature is 8
The temperature may be 0 to 110°C, which is a temperature that does not damage the plastic even when coloring and decoloring are repeated hundreds to thousands of times.

(Example 1) methacrylic resin 5.

0 parts by weight toluene 40.

0 parts by weight B liquid methacrylic resin toluene 7.5 parts by weight 40.0 parts by weight C liquid stearamide 10.0 parts methacrylic resin 2.0 parts by weight toluene
40.0 parts by weight The above liquids A and B were each ground and dispersed in a sand mill for 1 hour, and then 1 part by weight of liquid A, 4 parts by weight of liquid B, and 2 parts by weight of liquid C were thoroughly mixed to produce a paint. .

This paint was applied onto a 250 μm thick white polyvinyl chloride sheet using a Mayer bar and dried to a dry film thickness of 5.5 μm to produce a reversible sheet with no background fog.

(Example 2) A liquid polyvinyl alcohol water Isopropyl alcohol 2.0 weight 1 part 32.0 parts by weight 8.0 parts by weight 81 nights COOH carbonated power runum polyvinyl alcohol water Isopropyl alcohol ■　0　.

10° 32.

8.

0 parts by weight 0 parts by weight 0 parts by weight Liquid C Ethylene bisstearamide 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 liquids A and B were each ground and dispersed in a sand mill for 1 hour, and then 1 part by weight of liquid A, 7 parts by weight of liquid B, and 4 parts by weight of liquid C were thoroughly mixed to produce a paint. .

This paint was applied onto a high-quality paper with a basis weight of 60 g/% using a Mayer bar and dried to a dry film thickness of 8.0 μm to produce a reversible sheet with no background fog.

(Margin below) (Example 3) A liquid polyvinyl butyral 2.

0 parts by weight toluene 0.

0 parts by weight B liquid silicone resin fine powder 0.

0 parts by weight polyvinyl butyral 0.

0 parts by weight toluene 0.

0 parts by weight Liquid C microcrystalline wax 5.0 parts by weight Stearamide 5.0 parts by weight Polyvinyl butyral 2.0 parts by weight Toluene
40.0 parts by weight Above Af! After grinding and dispersing liquids A and B for 1 hour using a sand mill, 1.0 parts by weight of liquid A and B
A paint was prepared by thoroughly mixing 5.0 parts by weight of liquid and 2.5 parts by weight of liquid C. This paint was applied onto a 188 μm thick white polyester sheet using a Mayer bar to a dry film thickness of 70 μm and dried to produce a reversible sheet with no background fog.

(Example 4) A liquid polyester resin 2.

0 parts by weight Toluet hmm 0 parts by weight B liquid polyester resin 0.

0 parts by weight toluene 0.

0 parts by weight C liquid O Cutylbenzene sulfonate 0.

0 parts by weight Po Lyester resin 2.

0 parts by weight toluene 4 0.

0 parts by weight D liquid methacrylic resin 10.0 parts by weight Calcium carbonate 1000 parts by weight Toluene
40.0 parts by weight After grinding and dispersing the above liquids A and B in a sand mill for 1 hour, 1.0 parts by weight of liquid A, 2.5 parts by weight of liquid B, and 1.5 parts by weight of liquid C were thoroughly mixed. and produced paint. This paint was applied onto a white polyester sheet with a thickness of 188 μm using a Mayer bar to a dry film thickness of 6
．． Solution D was coated and dried to a thickness of 0 μm. Then, using a Mayer bar, the solution D was coated and dried to a dry film thickness of 1.5 μm to produce a reversible sheet with no background capri.

(Comparative Examples 1 to 4) Corresponding Examples 1 to 4 except for excluding liquid C of Examples 1 to 4
A reversible sheet was produced in the same manner.

(Evaluation) The sheets of Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated by the following method.

In other words, each sheet is run on a Searl simulator (
Printing conditions: applied voltage 0.40W/dat, pulse width 2.5m5ecON10FF, sir? ) Lt head:
Toshiba's thin film head (348Ω), 7D density: 6d
ot/mm) in a 10 mm width, and the color density was measured using a reflection densitometer (RD-918 manufactured by MACBETH).

Next, it was pressed for 1 second with a heat stamp plate heated to 100° C. to erase the color, and the reflection density at this time was measured in the same manner.

The results are shown in Table 1. In the table, "Hue" refers to the hue at the time of color development, and "Base J""Colordevelopment" and "Decolorization" refer to the reflection density before color development, during color development, and at the time of decolorization, respectively. means.

Furthermore, although each sheet was repeatedly colored and decolored several hundred times, the colored and decolored states were successfully reproduced without any damage to the base material.

Table 1 (Effects) As described above, according to the present invention, color development and
It is possible to obtain a reversible color developing and decoloring composition that can be repeatedly decolored and can be decolored at low temperatures without damaging plastic substrates and the like.

Therefore, it becomes possible to reversibly print or print by coating the surface of a plastic card or the like.

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 part of a salt compound;
and a reversible heat-sensitive coloring/discoloring composition comprising a thermofusible sensitizer. (2) The thermofusible sensitizer is one or two selected from montanic acid wax or its derivatives, N-substituted or unsubstituted higher fatty acid amides, N-substituted aromatic amides, aliphatic bisamides, and aromatic sulfonamides. 2. The reversible heat-sensitive coloring/discoloring composition according to claim 1, which comprises at least one type of compound.