JPS63309490A - Reversible color forming and decoloring material - Google Patents

Abstract

PURPOSE:To obtain a reversible color forming and decoloring material having sensitivity to both heat and water and finding a wide range of application, by using a compatible material which comprises an electron-donative color- reactive organic compound having a lactone ring and a color developer and is capable of solid-liquid changes upon heating and cooling. CONSTITUTION:An electron-donative color-reactive organic compound having a lactone ring, namely, a coloring matter precursor interacts with an electron acceptor to form a color through opening of the lactone ring. This reaction is represented by formula I. When a coexistence element of the compatible material and water is heated to or above the melting point of a solid acid, an interface between the solid acid and water is formed, and molecules of the solid acid are so oriented that polar groups of the solid acid are exposed at the interface. Then, there takes place development into a color of the coloring matter precursor taken into micells of the solid acid due to acceleration of dissociation of the solid acid, concentration of protons in water on the interface or other mechanism. When the compatible material is cooled, free protons disappear as the solid acid is solidified, and the contact with water is interrupted, whereby the coloring matter precursor is decolored.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reversible color-developing and discoloring material, and in particular to a reversible material that can be applied to new display devices, temporary recording materials, sensors, teaching materials, stationery, toys, etc. Related to color-developing and color-developing materials.

[4 Summary of the Invention] The present invention uses an electron-donating color-forming organic compound having a lactone ring as a dye precursor, and uses a hydrophobic solid acid with a small acid dissociation constant as a color developer that also serves as a dispersion medium. , in a reversible color developing and erasing material formed by dissolving the dye precursor and the color developer in a compatible manner, color is developed by adding moisture in a heated and melted state;
It is possible to erase the color by cooling or removing moisture.

[Conventional technology]

BACKGROUND ART Conventionally, various reversible sintering coloring and fading materials have been developed for the purpose of application to various sensors, displays, etc. that utilize color change due to heat or water.

The present inventor has so far developed various materials that exhibit reversible coloring and fading behavior with either heat or water.

First, as a material exhibiting coloring/decoloring behavior by heat, for example, Japanese Patent Application No. 162400/1987 discloses a reversible thermal coloring/decolorizing material containing an electron-donating color-forming organic compound having a lactone ring. . The organic compound used here develops color by opening the lactone ring when it comes into contact with an electron-accepting color developer. When such an electron-donating color-forming organic compound and a suitable color developer are dissolved in a polymer having a long alkyl chain as a medium, it becomes a colored solid at room temperature; When heated to a temperature exceeding the melting point of the polymer, it changes to a colorless and transparent liquid, and conversely, when cooled to a temperature below the freezing point of the polymer, it returns to a colored solid.

Furthermore, as a material exhibiting reversible coloring/decoloring behavior with water, for example, Japanese Patent Application No. 1982-77776 discloses a reversible coloring/decoloring material containing an electron-donating dye precursor having a lactone ring. has been done. Here, the electron-donating color-forming organic compound incorporated into the micelles of the anionic surfactant reacts with electron acceptors such as protons or hydronium ions in water via the micelles. It becomes colored due to the reaction mechanism of , and disappears when water is removed.

[Problem that the invention seeks to solve]

In the conventional materials mentioned above, coloring and fading behavior occurs under the action of either heat or water, but the property of being sensitive to both heat and water at the same time has not yet been achieved, and, for example, the property of being sensitive to both heat and water has not yet been achieved. However, there is a possibility that a color development/decolorization behavior opposite to the conventional one, such as decolorization upon cooling, may be required in practical applications.

Therefore, an object of the present invention is to provide a reversible color-changing and fading material which has a property of being sensitive to heat and water at the same time and has a wider range of uses.

[Means for solving problems]

The present inventor, in the process of researching the color development/discoloration behavior of a dye precursor having a lactone ring, discovered a material that develops color by the simultaneous action of heat and water, leading to the present invention.

That is, the reversible color-developing and discoloring material according to the present invention is composed of a compatible solution that includes an electron-donating color-forming organic compound having a lactone ring and a color developer, and can undergo a solid-liquid change by heating and cooling. It is characterized by the fact that it develops color when water coexists with the heated molten state of the solution.

The electron-donating color-forming organic compound itself is a colorless or light-colored dye precursor (so-called leuco dye).
It develops color by opening the lactone ring.

the electron-donating color-forming organic compound having the lactone ring;
That is, dye precursors can be broadly classified into triphenylmethane phthalides, fluorans, thiofluoranes, indolyl phthalides, rhodamine lactams, azaphthalides, etc., and the following compounds are exemplified.

First, examples of triphenylmethane phthalides include crystal violet lactone and malachite green lactone, and examples of fluorans include 2-(2'-chlorophenylamino)-(i-di-n-butylaminofluoran, 3- Diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-benzyloxyfluorane, 1,2-benz-6-diethylaminofluorane, 3.6-jp -) Cyidino-4,5-dimethylfluoran phenylhydrazide-T-lactam, 3-amino-5-methylfluoran, 2-methyl-3-amino-
6-Methyl-7-methylfluorane, 2.3-butylene-6-di-n-butylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-(balatluidino)-fluorane, 7 -acetamino-3-diethylaminofluorane, 2-bromo-6
-cyclohexylaminofluorane, 2°7-dichloro-3-methyl-6-n-butylaminofluorane, and the like. In addition, examples of thiofluoranes include 3-diethylamino-6-methyl-7-dimethylaminothiofluorane and 3-diethylamino-7-dibenzylaminothiofluorane, and examples of indolylphthalides include 8-(4 -diethylaminophenyl) -8-(1-
ethyl-2-methylindol-8-yl)phthalide,
3.3-bis(1-ethyl-2-methyl-8-yl)phthalide, 3,3-bis(2-phenylindole-3-
yl)phthalide, 3-(4-di-n-butylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 8-[4-(dimethylamino)phenyl)-3
-(N.

Examples include N-bis(4-octylphenyl)aminoophthalide. Furthermore, rhodamine lactams include rhodamine lactone, and azatuclides include 3.
Examples include 3-bis(l-ethyl-2-methylindol-3-yl)-7-azaphthalide.

Further, the color developer used in the present invention is preferably a solid acid, since it is required to be solid at room temperature and have a small acid dissociation constant of 1, that is, to be a weak acid. In cases where such a solid acid is hydrophobic, it is not necessarily convenient to determine its acid dissociation constant, but
For convenience, the appropriate range of the acid dissociation constant in the present invention will be determined by the following method.

First, consider acetic acid as a representative example of a weak acid, although it is not a solid acid. The PKM of acetic acid is approximately 4.76 (K,
= 1.738 Therefore, we will investigate capric acid, which is an even weaker acid than acetic acid and has a high melting point of 31.5°C. PKa of capric acid is 25
approximately 4.89 (K, = 1.288 xlO
-'), and when crystal violet lactone was similarly dissolved therein, it still showed some color development, although it was less pronounced than in the case of acetic acid. Therefore, pK,
It is necessary that the value of is at least 4.9 or more.

As the hydrophobic solid acid having the acid dissociation constant as described above, higher carboxylic acids, higher carboxylic acid salts, long-chain alkyl-substituted phenols, etc. can be used.

The mixing ratio of the dye precursor and solid acid as described above needs to be adjusted to an appropriate value depending on solubility, desired coloring density, etc., but it can actually be selected from a fairly wide range.
The mixing ratio of dye precursor/colorant (weight ratio) ranges from approximately 1/10' to 100/1.

The compatible solution obtained in this way is solid at room temperature, but in order to develop color, it must be poured into water and heated, or the compatible solution can be dissolved in an appropriate solvent and PET
Possible methods include forming a film on a suitable support such as a (polyethylene terephthalate) film, and applying water with a dropper, cotton swab, brush, sprayer, etc. while heating.

[Effect]

The electron-donating color-forming organic compound containing a lactone ring used in the present invention, that is, the dye precursor, generates color by opening the lactone ring through interaction with an electron acceptor. Taking crystal violet lactone as an example, this reaction is expressed as follows.

N(CHs)z According to this mechanism, crystal violet lactone is a color-forming compound that is stabilized by the quinoid resonance structure that is created by opening the lactone ring to produce a carboxyl group by proton attack. becomes.

The electron acceptor in the above formula, that is, the proton, is provided by the following mechanism. In other words, the solid acid used as a color developer that also serves as a dispersion medium for the dye precursor in the present invention has a very small acid dissociation constant, so it cannot release protons if it simply forms a compatible solution with the dye precursor. First, the dye precursor cannot be colored, and even if it is colored, only an extremely weak color appears. Even when such a compatible solution is brought into contact with water at room temperature, the solid acid does not dissociate, so no protons are generated, and therefore the dye precursor does not develop color.

However, when this system of coexistence with water is heated above the melting point of the isomer acid, an interface between the solid acid and water is formed, and the solid acid molecules are oriented so that the polar groups of the solid acid are exposed at this interface. do. Then, the dye precursor incorporated into the solid acid micelles develops a color due to a mechanism such as promoting the dissociation of the solid acid or concentrating protons in water at this interface.

When this compatible solution is cooled, free protons disappear as the solid acid solidifies, and at the same time contact with water is cut off, thereby decolorizing the dye precursor.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on experimental results.

First Example In this example, crystal violet lactone is used as a dye precursor having a lactone ring, and stearic acid is used as a solid acid. A compatible solution prepared from these substances is poured into water and heated to form a liquid phase. This is what causes the color to develop inside.

First, 1 g of crystallba iolet lactone is heated and melted with 50 g of stearic acid at 100°C for 30 minutes with stirring, and then cooled to room temperature. Solid compatibilizer I
I got it. This compatible solution (3) did not develop color even when heated again.

Next, this compatible solution f was put into the same amount of water at room temperature in the form of a lump or in a finely pulverized state.

This compatible solution (3) did not dissolve in water and did not show any color development here either.

Next, the mixture system of the above compatible solution ■ and water is added to the melting point of stearic acid (
When heated above approximately 67°C, stearic acid melts, and when the compatible solution (2) is put into water as a lump, the above mixed system separates into an aqueous layer and an organic layer mainly composed of stearic acid. When the Compatible Other 1 was finely pulverized and added, oil droplets were dispersed in water. At this time, in all cases, blue coloring started from the interface between stearic acid and water, and soon the entire organic layer or the entire oil droplet turned blue.

Next, when the mixed system was cooled to, for example, room temperature, the organic layer or oil droplets solidified and disappeared.

This color development/discoloration behavior appeared reversibly by repeated heating and cooling.

Here, the crystal violet lactone used as a dye precursor is a substance that can also be used in the conventional reversible sintering coloring and fading material mentioned above, and its coloring and fading behavior is such that the color disappears when heated and the color develops when cooled. Met. However, in the reversible color-developing and discoloring material of the present invention, which develops color only when both heat and water act on it, for example, as in this example, water is added to the reaction system in advance, and then heat is applied. By doing so, a color development/discoloration behavior occurs that is opposite to the conventional method, in which color develops when heated and discolors when cooled.

Therefore, it is possible to provide a reversible coloring/discoloring material with a wider range of uses.

Second Example This example uses 2-(2'-chlorophenylamino)-6-di-n-butylaminofluorane as a dye precursor and arachidic acid as a solid acid, and is prepared from these materials. This is an example in which a compatible solution is dissolved in a solvent, then a film is formed on a suitable support, and color is developed by adding water by an appropriate means while heating the support.

Maf, 2-(2'-chlorophenylamino)-6-di-n-butylaminofluorane Ig was added to arachidic acid 100
By heating and melting the mixture with g at 100° C. for 30 minutes with stirring, and then cooling to room temperature, Compatible Solution (2) was obtained as a pale white solid with a slight reddish-purple color.

Next, this compatible solution (Ig) was dissolved in 50 g of chloroform, applied onto a PET film, and dried to form a film.

Next, when the entire coating was heated and a small amount of water was brought into contact with the coating using a dropper or a cotton swab, the contact area developed a reddish-black color. Note that the heating temperature at this time needs to be selected to be higher than the melting point of arachidic acid (78°C), and in this example, it was set to 90°C.

Next, the colored portion was decolored by evaporating the water while the coating was heated or by cooling the coating.

Note that no color development was observed even when this film was brought into contact with water at room temperature.

〔Effect of the invention〕

As is clear from the above explanation, the reversible coloring/discoloring material according to the present invention develops color only when heat and water act simultaneously. Unlike the case of 4H heating, the degree of freedom in control increases; that is, you can add water in advance and heat it later.
Alternatively, it becomes possible to perform control such as applying heat in advance and then adding water afterwards, making it possible to provide a novel display device based on such a principle.

In addition, we have a sensor that detects temperature and humidity at the same time,
For example, it is possible to provide ink that develops color when immersed in warm water, various teaching materials, stationery, toys, etc.

Patent Applicant Sony Corporation Representative Patent Attorney Koike Mimi Ei Tamura - Masaru Sato

Claims (1)

[Claims] Consisting of a compatible solution containing an electron-donating color-forming organic compound having a lactone ring and a color developer that can undergo a solid-liquid change by heating and cooling, and coloring occurs when water coexists in the heated and molten state of the compatible solution. A reversible color-changing and fading material.