JPH04267190A - Reversible thermochromic material - Google Patents

Abstract

PURPOSE:To improve the properties of a material which becomes discolored reversibly in accordance with temperature change. CONSTITUTION:A reversibly thermal discoloring material contains an electron- donative, color developing organic compound, an electron-receptive chemical compound and a discoloring temperature-adjustable compound, and further R1-PO(OH) or R2-CH(OH)COOH (R1 is 8 to 30C alkyl group; R2 is a 6 to 28C alkyl group). This reversibly thermal discoloring material has improved thermal response, developed color density and discharging properties.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to materials that reversibly change color in response to temperature changes, and more specifically to materials that exhibit reversible thermal changes in which a color develops from a colorless state when heated and discolors when cooled. This invention relates to a reversible thermochromic material with improved responsiveness, coloring density, and color erasing properties.

0002

[Prior Art] Many materials have been proposed as materials exhibiting reversible thermochromic properties, such as metal complex salts, cholesteric liquid crystals, and mixed systems of electron-donating color-forming organic compounds, electron-accepting compounds, and color-changing temperature-regulating compounds. It is used as an indicator for temperature measurement, temperature control, etc., and various sensors that take advantage of its reversible characteristics.
Displays, clothing, ink, toner, writing instruments, teaching materials,
It is used for a wide range of purposes such as toys. In particular, reversible thermochromic materials that require the three components of an electron-donating color-forming organic compound, an electron-accepting compound, and a color-changing temperature regulating compound have the advantage that the color-changing temperature can be set within a wide range and that the color changes greatly. Many inventions have been made because of the advantages of being abundant and non-toxic. (For example, JP 51-44706, JP 51-44709, JP 52-7764, JP 6
3-15877, JP-A-63-251487, JP-A-1
-121394, JP-A-1-174591, etc.)

0
003]

[Problem to be solved by the invention] Many of the conventional ones are
It is a heat-decolorable type that changes color by heating from a state that is colored due to the interaction between an electron-donating color-forming organic compound and an electron-accepting compound.A temperature-regulating compound acts as a desensitizer and the color disappears to colorless. This shows reversible behavior. On the other hand, there are very few reversible thermochromic materials that exhibit heat-coloring type discoloration behavior, in which the color changes reversibly from a colorless state to a colored state upon heating. It lacks practicality due to its poor characteristics. Currently, in order to obtain reversible discoloration from one color to a different color, dyes or pigments are generally added to heat-erasable reversible thermochromic materials, or dyes or pigments are added to the material and then heat-erasable. Although it is coated with a color-type reversible thermochromic material, it is not possible to change color from colorless to colored, and there is also a change in hue due to color mixing of the reversible thermochromic material with dyes and pigments, and coloring of dyes and pigments. However, the scope of application was also limited due to the limitations of color matching and contrast, which prevents the ability to sufficiently hide the color. An object of the present invention is to provide a heat-coloring type reversible thermochromic material that has good thermal responsiveness, good coloring density, and particularly excellent color erasing properties.

0004

[Means for Solving the Problem] As a result of various studies to achieve the above-mentioned object, the present inventors have determined that an electron-donating color-forming organic compound, an electron-accepting compound, and a discoloration temperature regulating compound are essential components. In the reversible thermochromic material, as an electron-accepting compound, an organic phosphoric acid compound represented by the following general formula (1) or an organic acid R1-PO ( OH)2...(1)(However, R1
represents a linear or branched alkyl group having 8 to 30 carbon atoms. ) R2-CH(OH)COOH...(2) (However, R2 represents a linear or branched alkyl group having 6 to 28 carbon atoms.) By using R2-CH(OH)COOH, the color erasing property is significantly improved, and further specific The inventors have discovered that the thermal response and color density can be improved by adding a solvent, leading to the present invention.

[0005] Specific examples of the organic phosphoric acid compound represented by the above general formula (1), which is an electron-accepting compound used in the present invention, include the following, but the present invention is not limited thereto. do not have. Octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, dotecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid,
Examples include octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, and tetracosylphosphonic acid.

Further, specific examples of the organic acid having a hydrogen group at the α-position carbon represented by the general formula (2) include the following, but the present invention is not limited thereto. α-hydroxyoctanoic acid, α-hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, and the like.

The electron-donating color-forming organic compound of the present invention used in combination with the electron-accepting compound is itself a colorless or light-colored dye precursor, such as triphenylmethanephthalide compounds, fluoran compounds, etc. ,
Phenothiazine compounds, leukoolamine compounds,
rhodamine lactam compounds, spiropyran compounds,
There are indolinophthalide compounds, and specific examples 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-dimethylaminophenyl)-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-cyclohexylamino -6-chlorofluorane, 3-dimethylamino-5
, 7-dimethylfluorane, 3-diethylamino-7-
Chlorofluorane, 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'-Tolylfluoromethylphenyl)amino}-
6-diethylaminofluorane, 2-{3,6-bis(
diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam, 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 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-5-chloro-7
-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5
-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-
phenylethylamino)fluoran, 3-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)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3 -diethylamino-6
-Methyl-7-mesitidino-4',5'-benzofluorane and the like. 3-(N-methyl-N-isopropylamino)
-6-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(
N,N-diethylamino)-5-methyl-7-(N,N
-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3-(2' −
Hydroxy-4'-dimethylaminophenyl)-3-(
2'-methoxy(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'-methylphenyl)phthalide, 3-morpholino-7 -(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7
-trifluoromethylanilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,
6-bis(dimethylamino)fluorene spiro(9,3
')-6'-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)fluoran, etc.

The electron-accepting compounds of the present invention may be used alone or in combination of two or more. Similarly, electron-donating color-forming compounds can be used alone or in combination of two or more.

In addition, gallic acid esters such as lauryl gallate and stearyl gallate, parahydroxybenzoic acid esters such as methyl parahydroxybenzoate and propyl parahydroxybenzoate, and protocatechuic acids such as stearyl protocatechuate and benzyl protocatechuate. A thermochromic electron-accepting compound selected from esters, urea, etc. can also be used in combination with the electron-accepting compound of the present invention.

[0010] High boiling point alcohols are used as discoloration temperature regulators.
Examples include lauriuryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, myristic acid. Stearyl, propyl palmitate, ethyl stearate, butyl stearate, glycerin tristearate, glycerin trimyristate, propylene glycol distearate, glycerin monocetyl ether, myristic acid, palmitic acid, lauric acid, These include didecyl ether, didodecyl ether, stearic acid amide, etc.

The low volatility solvent can be selected from those commonly used as pressure sensitive oils. Examples include alkylnaphthalene compounds, diarylalkane compounds, alkylbiphenyl compounds, terphenyl compounds, triallylmethane compounds, and the like. For example, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, 1-methyl-1-dimethylphenyl-1-phenylmethane, 1-methyl-1-ethylphenyl-1-
Phenylmethane, dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, hydrogenated terphenyl,
Examples include tritolylmethane.

[0012] It is necessary to select an appropriate mixing ratio of each component depending on the physical properties of the material used and the conditions of use. Electron-donating color-forming organic compound: Electron-accepting compound:
The mixing ratio of discoloration temperature regulating compound:low volatility solvent is 1.0:0.5~4.0:0.5~5.0:0.2, respectively.
A range of 4.0 is appropriate.

Depending on the purpose, the reversible thermochromic material having the above structure can be used together with a binder, heated and melted and injected into cells, or encapsulated in microcapsules. Encapsulation in microcapsules is preferable from the viewpoints of preventing functional deterioration by protecting the contents and ease of handling. Microencapsulation is a core cell base.
It can be used in the form of microcapsules with a particle size of about 1 to several tens of micrometers by known microencapsulation techniques such as cation method, interfacial polymerization method, and in-situ polymerization method.

The form of the reversible thermochromic material of the present invention varies depending on the use, but for example, microcapsules containing the reversible thermochromic material of the present invention are mixed with a suitable binder to produce paper, synthetic paper, plastic. It is used by applying it onto a substrate such as a film, and if necessary, providing a protective layer on the surface.

[0015]

[Examples] The present invention will be specifically explained below with reference to Examples. Note that parts in the examples represent parts by weight.

Example 1 3-N-methyl-N-cyclohexylamino-6-
Methyl-7-anilinofluorane
5th part
Octadecylphosphonic acid

10 parts myristyl alcohol

5 parts diisopropylnaphthalene (manufactured by Kureha Chemical Co., Ltd., KMC-113)
Approximately 100 parts of reversible thermochromic material consisting of 10 parts
Dissolve uniformly at ℃. 80 parts of 3% aqueous solution of styrene-maleic anhydride copolymer whose pH was adjusted to 4.5
25 parts of the above melt was added dropwise to a mixture heated to ℃, and
Emulsify and disperse the mixture into fine droplets of 1 to 8 μm. Next, while stirring the obtained emulsion, a melamine-formalin prepolymer (manufactured by Sanwa Chemical Co., Ltd., Nikalac M) was added.
11.0 g of X-54) was added and reacted at 70° C. for 3 hours to obtain a microcapsule dispersion having an average particle size of 3.5 μm. Microcapsule dispersion liquid 30 whose color change properties were evaluated
30 parts of 10% polyvinyl alcohol was added to the coating solution, and the amount of adhesion after drying was 5.
The coating was carried out so that the amount of the coating was g/m2. When the thermochromic properties of the reversible thermochromic sheet thus prepared were investigated, the color rapidly changed from colorless to black at a high concentration at 37°C. The color density was measured (Macbeth densitometer D-918) and found to be 1.35. When this product was returned to room temperature, the color completely disappeared. This reversible behavior of color development and decolorization reproduced high-density color development and complete decolorization.

Example 2 Crystal violet lactone

5 parts docosylphosphonic acid

15 parts myristyl alcohol
5 parts stearyl alcohol

5 parts diphenylmethane solvent (
A reversible thermochromic material consisting of 5 parts (manufactured by Nippon Petrochemical Co., Ltd., SAS-296) is uniformly dissolved at about 100°C. 50 parts of a 3% aqueous gelatin solution of styrene-maleic anhydride copolymer whose pH was adjusted to 4.5 was heated at 80°C.
25 parts of the above-mentioned dissolved material was added dropwise into the solution heated to 30°C, and emulsified and dispersed using a mixer to form fine droplets of 1 to 8 μm. Next, while stirring the obtained emulsion, a urea-formalin prepolymer (manufactured by Mitsui Toatsu Chemical Co., Ltd., Euramin P-15) was added.
00) was added and reacted at 70° C. for 3 hours to obtain a microcapsule dispersion having an average particle size of 3.5 μm. Evaluation of thermochromic properties 30 parts of a 10% acrylic emulsion was added to 30 parts of the obtained microcapsule dispersion to prepare a coating solution with a thickness of 100 μm.
A reversible thermochromic sheet was prepared by coating a polyester film with a coating thickness of 1.5 μm and drying, and evaluated it in the same manner as in Example 1. It rapidly changed from colorless to bright blue at 40°C. It developed color. The color density was 1.28. When this product was returned to room temperature, the color completely disappeared as in Example 1, and no deterioration due to repeated use was observed.

Example 3 3-(
N,N-diethylamino)-5-methyl-7-(N,N
A reversible thermochromic sheet was prepared in the same manner as in Example 1, except that α-hydroxyoctadecanoic acid was used in place of octadecyl phosphorane and octadecyl fluorane, and the same evaluation was conducted at 37°C. Color density 1.34
The color became green, and completely disappeared at room temperature. It also showed similar repeatability characteristics.

Example 4 In place of crystal violet lactone in Example 2, 3
A reversible discoloration sheet was prepared in the same manner as in Example 2, except that -diethylamino-7-chlorofluorane and docosylphosphonic acid were replaced with α-hydroxydocosanoic acid, and the same evaluation was conducted.40 Color density 1.14 at °C
It exhibited a bright pink color, which disappeared completely at room temperature. It also showed similar repeatability characteristics.

Comparative Example 1 A reversible thermochromic sheet was prepared in the same manner as in Example 1, except that octatecylphosphonic acid in Example 1 was replaced with stearyl gallate and diisopropylnaphthalene was omitted, and the same evaluation was carried out. When tested, a black color developed at 48° C., but the color density was 1.15. Although this product was returned to room temperature, the color did not disappear completely and the color remained. In addition, deterioration due to repeated use was observed.

Comparative Example 2 A reversible thermochromic sheet was prepared in the same manner as in Example 2, except that docosylphosphonic acid in Example 2 was replaced with methyl parahydroxybenzoate and the diphenylmethane solvent was omitted. When a similar evaluation was performed, a blue color developed at 53° C., but the color density was 1.09. Although this product was returned to room temperature, the color did not disappear completely and the color remained. In addition, deterioration due to repeated use was observed.

Comparative Example 3 A reversible thermochromic sheet was prepared in the same manner as in Example 1 except that octadecylphosphonic acid in Example 1 was replaced with stearyl gallate, and the same evaluation was performed. The color developed black and the color density was as high as 1.34, but when it was returned to room temperature, the color did not disappear completely and the color remained. In addition, deterioration due to repeated use was also observed.

[0023]

As explained above, according to the present invention, the problems of thermoresponsiveness, coloring density, and color erasing properties, which are problems of heat coloring type reversible thermochromic materials, can be solved by using an organic phosphoric acid compound or an organic phosphoric acid compound as an electron accepting compound. This can be improved by using an organic acid having a hydroxyl group at the α-position carbon and further adding a low volatility solvent. The reversible thermochromic material of the present invention has a sensitive thermoresponsiveness and high color density, and is completely erasable when decoloring.
It has many features, such as the ability to set the color change temperature range and select colors arbitrarily, and can withstand repeated use, making it possible to apply it in a wide range of fields by taking advantage of these features.

Claims (3)

[Claims] Claim 1: A reversible thermochromic material containing an electron-donating color-forming organic compound, an electron-accepting compound, and a color-changing temperature regulating compound as essential components, in which the electron-accepting compound is represented by the following general formula (1): A reversible thermochromic material characterized by using an organic phosphoric acid compound. R1-PO(OH)2...(1) (However, R1
represents a linear or branched alkyl group having 8 to 30 carbon atoms. ) [Claim 2] In a reversible thermochromic material comprising an electron-donating color-forming organic compound, an electron-accepting compound, and a color-changing temperature regulating compound as essential components, the electron-accepting compound is represented by the following general formula (2). A reversible thermochromic material characterized by using an organic acid having a hydrogen group at the α-position carbon. R2-CH(OH)COOH...(2) (However, R2 represents a linear or branched alkyl group having 6 to 28 carbon atoms.) 3. The reversible thermochromic material according to claim 1 or 2, which contains a low volatility solvent.