JPH0443074A - Reversible thermochromic material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a material that reversibly changes color in response to temperature changes. More specifically, the present invention relates to a color-changing material that exhibits a reversible thermal change in which a certain color tone changes to a different hue upon heating.

[Prior Art] Conventionally, various reversible color-changing materials have been developed for the purpose of utilizing color change due to heat. In recent years, materials consisting of electron-donating color-forming organic compounds, electron-accepting compounds, and color-changing temperature-regulating compounds have been developed, and are being commercialized by taking advantage of their properties.

Normally, an electron-donating color-forming organic compound and an electron-accepting compound react to form a color, which changes color by heating.A heat-decolorizing type in which a temperature-adjusting compound acts with a desensitizer to become colorless. It exhibits reversible color change behavior from colored to colorless.

Heat-colorable reversible color-changing materials that reversibly change color from colorless to colored by heating have drawbacks in characteristics such as thermal response speed and coloring density.

Currently, in order to obtain reversible discoloration from one color to another, it is generally necessary to add dyes or pigments to heat-erasable or reversible thermochromic materials, or to color the materials with dyes or pigments and then heat-erasable them. Although it is coated with a color-type reversible thermochromic material, there are limitations on color change and contrast, such as changes in hue due to mixing of the reversible thermochromic material with dyes and pigments, and the inability to sufficiently shield the coloring of dyes and pigments. However, the range of application was also limited.

[Problems to be Solved by the Invention] The present invention combines a heat-coloring type reversible color-changing material with good heat responsiveness and coloring density and a heat-erasing type reversible thermochromic material. An object of the present invention is to provide a reversible thermochromic material that reversibly changes color and exhibits excellent contrast without color mixture.

[Means for Solving the Problems] As a result of various studies to achieve the above-mentioned object, the present inventors microcapsulated and combined heat-coloring type and heat-decolorizing reversible thermochromic materials respectively. The present invention was achieved based on the finding that this is effective.

That is, the present invention provides a reversible thermochromic material containing a reversible thermochromic material that develops color when heated and a reversible thermochromic material that discolors when heated, each of which is separately encapsulated in microcapsules. It is a reversible thermochromic material with special characteristics.

According to the present invention, the heat-erasable reversible thermochromic material changes from colored to colorless in response to temperature changes, that is, due to heating, and the heat-colorable reversible thermochromic material changes from colorless to colored.

Cooling causes exactly the opposite change, allowing completely different hues to be reversibly repeated.

Since the hue can be selected from a wide range depending on the electron-donating color-forming organic compound, it is possible to freely change the hue by combining the heat-decolorizing type and the heat-coloring type.

The reversible thermochromic material used in the present invention contains an electron-donating color-forming organic compound, an electron-accepting compound, and a color-changing temperature regulating compound as essential components, and furthermore, the reversible thermochromic material that develops color upon heating has a low Contains a volatile solvent.

The electron-donating color-forming organic compounds used in the present invention may be used alone or in a mixture of two or more, and are themselves colorless or light-colored dye precursors, such as triphenylmethane phthalide compounds, Examples include fluoran compounds, phenothiazine compounds, leucoauramine compounds, rhodamine lactam compounds, spiropyran compounds, and indolinophthalide compounds.

Specific examples of the electron-donating color-forming organic compound include the following.

3.3-bis(p-dimethylaminophenyl) phthalide, 3.3-bis(p-dimethylaminophenyl) 6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p-dimethylamino phenyl) 6-dibutylaminophenyl, 3.3-bis(p-dimethylaminophenyl) 6-chlorophthalide, 3.3-bis(p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-lylolofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6 -Methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ethylamino)6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2 - ((N-(3-1-lifluoromethylphenyl)
amino) -6-dinithylaminofluorane, 2-H
,8-bis(diethylamino)-9-(.

-chloroanilino)xantylbenzoic acid lactam, 3-diethylamino-6-methyl-7-(i-trichloromethylanilino)fluoran, 3-diethylamino-
7-(o-chloroanilino)fluorane, 3-dibutylamino-7-(o-chloroanilino)fluorane, 3-N-methyl-N-amylamino-6-methyl-7
-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-
6-Methyl-7-anilinofluorane, 8-(N,N-diethylamino)-5-methyl-7-
(N,N-dibenzylamino)fluoran, benzoylleucomethylene blue 6°-chloro-8′-methoxy-benzoindolino-spirobilane, 6”-bromo-3°-methoxy-benzoindolino-spirobilane, 3-(2 '-Hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)
Phthalide, 3-(2°-hydroxy-4′-dimethylaminophenyl)-8-<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°-
methylphenyl)phthalide, 3-morpholino-2(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N- Benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 8-')I,7mi)-5-chloro-7-(α -phenylethylamino)fluoran, 3-(N-ethyl-
p-Toluidino)-7-(α-phenylethylamino)
Fluoran, 8-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-
Piperidinofluorane, 2-chloro-3-(N-methyltoluidino)7-(p-
n-butylanilino)fluoran, 3-(N-benzyl-N-cyclohexylamino)-5,6-penzo 7
-α-naphthylamino-4°-bromofluorane, 3-diethylamino-B-methyl-7-mesitidino 4
',5'-benzofluorane etc.

3-(N-methyl-N-isopropylamino)-6-methyl-7-anilinofluorane, 3-dibutylamino-
6-Methyl-7-anilinofluorane, 3,6-bis(dimethylamino)fluorene spiro(9
,3')-8°-dimethylaminophthalide, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N-(2-ethoxypropyl)amino-6-methyl-7- Anilinofluorane, 3-N-
Ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-isobutyl-6-methyl-7-
Anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-
Anilinofluorane, 3-diethylamino-6-methyl-7-(2°.

4′-dimethylanilino)fluorane, etc.

Next, the electron-accepting compound can be selected from color developers commonly used for thermal paper in systems whose color is erased by heating.

For example, phenolic compounds, thiophenolic compounds,
Thiourea derivatives, organic acids, metal salts thereof, and the like can be used, and specific examples thereof include those shown below.

4.4°-isopropylidene bisphenol, 4.4°
-isopropylidene bis(0-methylphenol), 4.4°-secondary butylidene bisphenol, 4,4′-isopropylidene bis(2-tert-butylphenol), 4.4°-cyclohexylidene diphenol, 4 .4'-isopropylidene bis(2-chlorophenol), 2.2'-methylenebis(4-methyl-6-tert-butylphenol), 2.2'-methylenebis(4-ethyl-6-tert-butylphenol), 4.4°-Butylidene bis(B-tert-butyl-
2-methylphenol), 1.1. l-) lis(2-methyl-4-hydroxy-5
-tert-butylphenyl)butane, 1.1.3-
) Lis(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4.4゛-thiobis(8-tert-butyl-2-methylphenol), 4.4°-diphenolsulfone, 4- Isopropoxy-4゛-hydroxydiphenylsulfone, 4-benzyloxy-4゛-hydroxydiphenylsulfone, 4.4°-diphenolsulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate, gallic acid Stearyl, lauryl gallate, octyl gallate, 1.3-bis(4-hydroxyphenylthio)-propane, 1.3-bis(4-hydroxyphenylthio)-2-hydroxypropane, N,N'-diphenylthio Urea, N,N"-di(m-chlorophenyl)thiourea, salicylanilide, 5-chloro-salicylanilide, bis-(4-hydroxyphenyl)acetic acid methyl ester, bis-(4-hydroxyphenyl)acetic acid benzyl ester, 1.3-bis(4-hydroxycumyl)benzene, 1.
4-bis(4-hydroxycumyl)benzene, 2.4°
-diphenolsulfone, 2,2'-diallyl-4,4'-diphenolsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, -zinc acetyloxy-2-naphthoate, 2-acetyloxy-1 -Zinc naphthoate, 2-acetyloxy-
Zinc 3-naphthoate, α,α-bis(4-hydroxyphenyl)-α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A1, tetrabromobisphenol S, etc.

For systems that develop color upon heating, the selection range is narrower than for systems that discolor, and particularly preferred electron-accepting compounds include gallic acid esters such as dodecyl gallate, cetyl gallate, and stearyl gallate, and para-hydroxyl. Examples include parahydroxybenzoic acid esters such as methyl benzoate, ethyl parahydroxybenzoate, and propyl parahydroxybenzoate, protocatechuic acid esters such as stearyl protocatechuate and benzyl protocatechuate, and urea.

Examples of discoloration temperature regulators include high-boiling alcohols, esters, acid amides, carboxylic acids, ethers, and ketones, such as lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, stearyl myristate, Propyl palmitate, ethyl stearate, butyl stearate, glycerin tristearate, glycerin trimyristate, propylene glycol distearate, glycerin monocetyl ether, myristic acid, valmitic acid, lauric acid, didecyl ether, didodecyl ether, Examples include stearic acid amide. The low volatility solvent can be selected from those commonly used as pressure sensitive oils. Examples include alkylnaphthalene compounds, diarylalkane compounds, alkyl biphenyl compounds, terphenyl compounds, and triallylmethane compounds. For example, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, 1-methyl-1
Examples include -dimethylphenyl-1-phenylmethane, 1-methyl-1-ethylphenyl-1-phenylmethane, dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, hydrogenated terphenyl, and tritolylmethane.

It is necessary to select an appropriate mixing ratio of each component depending on the physical properties of the material used, but in reality it can be selected from a fairly wide range.Electron donating color forming organic compound: Electron accepting compound: Discoloration The mixing ratio (weight) of the temperature regulator is 1:
A range of 1 to 10:5 to 50 is suitable.

The mixing ratio of the low-volatile solvent is preferably in the range of 30 to 80% by weight; if it is too small, the improvement in thermal response speed and color density will be small. Furthermore, if the amount is too large, the reversibility of color development and decolorization will be poor, and in particular, decolorization will not be sufficient.

In the reversible thermochromic material having the above structure, it is recommended to encapsulate the heat-decolorizing type and the heat-coloring type separately in microcapsules to prevent functional deterioration due to the separation and protection of the respective contents, and to improve ease of handling. preferable.

Microencapsulation is, for example, coacervation method,
It can be used in the form of microcapsules with a particle size of about 1 to several tens of μS by known techniques such as interfacial polymerization and In5ltu polymerization.

The resulting microcapsules are made by mixing a heat-decolorizing type and a heat-coloring type at a mixing ratio of 1:1 by weight, but they can be used at a ratio that is more preferable depending on the development, color-erasing characteristics, and intended use of each. It is preferable to do so.

The mixture may be used together with appropriate materials such as synthetic resins, waxes, etc. depending on the intended use, but is not limited thereto.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

In addition, parts in Examples represent parts by weight.

Example 1 Preparation of heat-decolorable microcapsules (A) 1 part of 3-diethylamino-7,8-benzfluorane, 2 parts of 4.4°-isopropylidene bisphenol, and 25 parts of n-cetyl alcohol were heated to about 100°C. Dissolve uniformly. pH to 6
．． 4 of the ethylene-maleic anhydride copolymer adjusted to 0
% aqueous solution was heated to 70° C., the above-mentioned dissolved material was added thereto, and the mixture was emulsified and dispersed using a mixer so that the average particle diameter was about 5 μm. Next, melamine-formalin prepolymer (
Product 8 Nikaratsuku MX-54, manufactured by Sanso Chemical Co., Ltd.) 50
% aqueous solution was added to adjust the pH to 4.5, and the pH was adjusted to 7.
The reaction mixture was stirred at 0° C. for 4 hours to obtain a microcapsule dispersion (A).

Preparation of heat-colorable microcapsules (B) 1 part of listal violet lactone, 4 parts of dodecyl gallate, 10 parts of myristyl alcohol, and 15 parts of diisopropylnaphthalene are uniformly dissolved at about 100"C. A microcapsule dispersion (B) was obtained in the same manner as in the preparation of capsules (A).

Evaluation of discoloration properties 20 parts of the obtained microcapsule dispersion (A) and 20 parts of microcapsule dispersion (B) were mixed with 20 parts of lO% polyvinyl alcohol, and the amount of adhesion after drying on high-quality paper was 15.
It was coated so that it became g/+2.

The obtained sample exhibited a bright red color at 20°C, but when heated to 45°C, the red color disappeared and the color changed to bright blue with high concentration. When cooled, the blue color disappeared and returned to its original red color. This reversible thermal color change repeatedly showed the same behavior.

Example 2 Preparation of heat-decolorable microcapsules (C) 1 part of 3-cyclohexylamino-6-chlorofluorane, 2 parts of methyl p-hydroxybenzoate, 2 parts of n-myristyl alcohol
5 parts were uniformly dissolved at about 100°C. 80 parts of a 5% gelatin aqueous solution whose pH was adjusted to 7.0 was heated to 70°C,
Add the above solution and use a mixer until the average particle size is about 5.
It was emulsified and dispersed so that it became μ■. Next, add 80 parts of a 5% gum arabic aqueous solution heated to 70°C, and add 17 parts of 70°C warm water.
Dilute with 0 parts and gradually add dropwise a 10% acetic acid solution while stirring to adjust the pH to 4.3 to generate coacervagedine,
Next, after cooling to 10°C to gel, 1.5 parts of 25% glutaraldehyde was added, the pH was adjusted to 9.0, and stirring was continued for 12 hours to form a microcapsule dispersion (C
) was obtained.

Preparation of heat-colorable microcapsules (D) 1 part of 3-diethylamino-5-methyl-7-dipendylaminofluorane, 5 parts of n-propyl p-hydroxybenzoate, 15 parts of stearyl alcohol, 1 part of diisopropylbiphenyl
0 part is uniformly dissolved at about 100°C.

A microcapsule dispersion (D) was obtained in the same manner as in the preparation of the heat-decolorable microcapsules (C). Evaluation of discoloration properties A sample was prepared in the same manner as in Example 1 by mixing 20 parts of the obtained microcapsule dispersion (C) and 20 parts of the microcapsule dispersion (D) with 10 parts of 10% polyvinyl alcohol.

The obtained sample exhibited a bright orange color at 20°C, but the orange color disappeared and became colorless at 38°C, and the color changed to bright green at 45°C. When cooled, the green color disappeared and the colorless color returned to its original orange color.

This color change was reversible and repeated.

Comparative Example 1 20 parts of heat-erasable microcapsules (A) prepared in Example 1 on high-quality paper colored blue with cyanine blue, 10%
A mixed solution of 10 parts of polyvinyl alcohol was applied so that the amount of adhesion after drying was 15 g/2.

At 20°C, the obtained sample exhibited a dull reddish-purple color due to the color mixture, rather than the blue color of the colored paper, and when heated to 45°C, the color changed to blue. Although the color returned to its original state upon cooling, it did not exhibit the desired clear reversible color change from blue to red.

Comparative Example 2 Heat-colored microcapsules (D) prepared in Example 2 on high-quality paper colored red with Brilliant Carmine 6B (D) 2
A mixed solution of 0 parts and 5 parts of 1O% polyvinyl alcohol was applied in the same manner as in Comparative Example 1.

The obtained sample had a slightly whitish red color at 20°C, but changed to a dull reddish-black color when heated to 45°C. Although it returned to its original state after cooling, the desired clear color change could not be obtained.

[Effects of the Invention] According to the present invention, by combining a reversible thermochromic material that develops color when heated and a reversible thermochromic material that discolors when heated, the color can be reversibly changed from a colored color to a different color in accordance with temperature changes. It is possible to provide a reversible thermochromic material that can be applied to a wide range of applications, which undergoes color change, has a clear hue, has excellent contrast, and can arbitrarily select a hue.

Claims (1)

[Claims] A reversible thermochromic material containing a reversible thermochromic material that develops color when heated and a reversible thermochromic material that discolors when heated, each of which is individually encapsulated in microcapsules. Color changing material.