JP4675041B2 - Thermoreversible color change - Google Patents

Description

  The present invention relates to a thermoreversible discolorant having thermochromic performance.

Conventionally, various coloring materials are used in various fields such as coating fields such as paints, inks, and printing, cosmetics fields, dyeing fields, and plastic fields.
Each coloring material has its own color development performance depending on the chemical and physical properties of the material, and various colors can be expressed by appropriately selecting and combining these coloring materials. Is possible.

  For example, common coloring materials in the coating field include organic pigments, inorganic pigments, metal powder pigments, dyes and the like. By mixing and dispersing one or more of these coloring materials in a binder, a coating material having uniform color development performance can be obtained.

  Examples of other coloring materials include thermoreversible color-changing materials whose hue changes with heat. This thermoreversible color-changing material is a material that exhibits the property of discoloring significantly (thermochromic performance) due to temperature changes. For example, by forming a film with a coating material containing a thermoreversible color-changing material, it is unique due to the color-changing effect. Can be expressed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2000-221885

  As materials showing such thermochromic performance, organic materials, inorganic materials, liquid crystal materials, and the like are known. Among these materials, inorganic materials often contain harmful elements such as mercury and are not very practical because they may cause direct harm to the human body. On the other hand, since organic materials and liquid crystal materials have advantages such as high safety and the ability to freely select the color type and the color change temperature, practical use can be expected.

  However, organic materials and liquid crystal materials have a problem that they are vulnerable to heat. That is, the heat resistance temperature of organic materials and liquid crystal materials is relatively low, and when the temperature reaches a temperature equal to or higher than the heat resistance temperature, the original hue changes, the thermoreversibility is lost, and the color fading may occur. In particular, such a tendency tends to be seen in summer and places where it is greatly affected by sunlight.

  In order to solve the above-mentioned problems, the present inventor has intensively studied, and as a result, thermoreversible having water vapor desorption properties in a temperature range higher than the color change temperature of the thermoreversible color change material and lower than the heat resistant temperature of the thermoreversible color change material. It has been found that sex discoloration has the property of discoloring significantly with temperature change (thermochromic performance), suppresses fading due to heat, maintains thermoreversibility, and exhibits thermochromic performance for a long time. The invention has been completed.

That is, the present invention has the following characteristics.
1. Contains thermoreversible color change material, binder, porous inorganic powder and hygroscopic synthetic resin fine particles, in a temperature range higher than the temperature change temperature of the thermoreversible color change material and lower than the heat resistance temperature of the thermoreversible color change material. Has water vapor adsorption and desorption properties with hysteresis characteristics,
And the amount of water vapor adsorbed / desorbed at a relative humidity of 90% at a temperature 2 ° C. higher than the upper limit of the color change temperature of the thermoreversible color change material (measured based on the weight at a relative humidity of 40%, at a relative humidity of 90% A thermoreversible discolorant, characterized in that the amount of water vapor that can be retained per unit weight of the thermoreversible discolorant is 0.05 g / g or more.
2. Furthermore, it contains a metal oxide (excluding the binder and the porous inorganic powder) . The thermoreversible discolorant described in 1.
3. A reactive functional group-containing synthetic resin binder is used as a binder, and a reactive functional group-containing hygroscopic synthetic resin particle is used as a hygroscopic synthetic resin fine particle. A reactive functional group-containing synthetic resin binder and a reactive functional group are used. 1. A cross-linking agent having a functional group capable of reacting with the reactive functional group of the moisture-absorbing / releasing synthetic resin fine particles. Or 2. The thermoreversible discolorant described in 1.

  The thermoreversible discolorant of the present invention has a property (thermochromic performance) that changes color remarkably with temperature change, suppresses fading due to the influence of heat, maintains thermoreversibility, and exhibits long-term thermochromic performance. be able to.

  Hereinafter, it explains in detail with the best form for carrying out the present invention.

  The thermoreversible color change material of the present invention contains a thermoreversible color change material and has a water vapor desorption property in a temperature range higher than the color change temperature of the thermoreversible color change material and lower than the heat resistance temperature of the thermoreversible color change material. It is characterized by this.

  The color change temperature of the thermoreversible color change material is a temperature at which the thermoreversible color change material described later changes color. The heat-resistant temperature of the thermoreversible color changing material is a temperature at which the thermoreversible color changing material is decomposed at a temperature higher than that, causing discoloration and loss of thermoreversibility.

The thermoreversible color change material of the present invention is characterized in that it has a water vapor desorption property in a temperature range higher than the color change temperature of such a thermoreversible color change material and the heat reversible color change material is lower than the heat resistant temperature.
In the present invention, the thermoreversible discolorant has water vapor desorbing properties, so that moisture that has autonomously absorbed moisture from the atmosphere or a substrate is desorbed in a predetermined temperature range. Is taken away. Therefore, the temperature rise of the thermoreversible color change material can be suppressed, fading of the thermoreversible color change material can be prevented, the thermoreversibility can be maintained, and thermochromic performance can be exhibited over a long period of time.
In addition, although the thermoreversible color change material of the present invention can absorb moisture autonomously, moisture may be forcibly supplied if necessary.

Specifically, as the water vapor desorption property, the water vapor adsorption / desorption amount is preferably 0.05 g / g or more, more preferably 0.1 g / g or more. More specifically, at a relative humidity of 90% in the temperature range higher than the color change temperature of the thermoreversible color change material and lower than the heat resistance temperature of the thermoreversible color change material, 0.05 g / g or more, and further 0.1 g / g. The above is preferable.
When the water vapor adsorption / desorption amount is 0.05 g / g or more, the temperature increase of the thermoreversible color-changing material can be suppressed, and fading of the thermoreversible color-changing material can be further prevented. Therefore, the thermoreversibility of the thermoreversible color change material is maintained, and thermochromic performance can be exhibited over a long period of time.

Furthermore, the thermoreversible color change material of the present invention has a water vapor adsorption / desorption property in a temperature range higher than the color change temperature of the thermoreversible color change material and lower than the heat resistance temperature of the thermoreversible color change material, and has a water vapor adsorption / desorption property. Preferably has hysteresis characteristics.
As shown in FIG. 1, the water vapor adsorption / desorption hysteresis characteristic is an adsorption / desorption isotherm when the relative humidity is on the horizontal axis and the water vapor adsorption / desorption amount is on the vertical axis, and the desorption curve is above the adsorption curve. Is meant to be This adsorption / desorption isotherm is obtained by sequentially raising the relative humidity from a low state to a high state with a constant temperature, and then returning it to a low state again. The thermoreversible color changer per unit weight is obtained. It represents the amount of water vapor that can be retained.

  Specifically, it is first left at a constant temperature in a constant temperature and humidity chamber with a relative humidity of 40% until the weight of the thermoreversible discoloration body is balanced, and the weight after being left is measured. Next, the same operation is performed in a constant temperature and humidity chamber where only the humidity is increased at the same temperature, and measurement is performed up to a relative humidity of 90% while increasing only the humidity step by step. Thereafter, the same operation is repeated while gradually decreasing the humidity at the same temperature, and the weight is measured. By calculating the water vapor adsorption / desorption amount from the weight of the thermoreversible discolorant at each humidity obtained by such measurement, an adsorption / desorption isotherm exhibiting the water vapor adsorption / desorption property can be obtained.

In the present invention, with such a water vapor adsorption / desorption hysteresis characteristic, the desorption rate of water vapor can be moderately suppressed, and the water vapor in the thermoreversible discoloration body can be maintained for a long time. It can be sustained, and fading due to heat of the thermoreversible color-changing material can be further prevented.
Furthermore, this hysteresis characteristic absorbs moisture present in the atmosphere and the base material at low temperatures such as in the nighttime, for example, in summer, and suppresses the rise in temperature due to desorption during the daytime when the temperature is high. It can be demonstrated.

  The water vapor adsorption / desorption amount and the water vapor adsorption / desorption property can be read from an adsorption / desorption isotherm as shown in FIG.

The thermoreversible color change material of the present invention contains a thermoreversible color change material (hereinafter referred to as “component (a)”),
If it has water vapor | steam desorbability, it will not specifically limit.
For example, thermoreversible containing component (a) and binder (hereinafter referred to as “component (b)”), porous inorganic powder and / or hygroscopic synthetic resin fine particles (hereinafter referred to as “component (c)”) Thermoreversible discoloration body comprising a color changeable composition, a thermoreversible discoloration porous body in which the porous body is supported with the component (a), a thermoreversible color change fiber body in which the fiber is supported with the component (a) Etc.
In this invention, it is preferable that it is a thermoreversible color-change body which consists of a thermoreversible color-change composition containing (a) component, (b) component, and (c) component.

The component (a) has thermochromic performance.
Although it does not specifically limit as (a) component, It is preferable to use an organic thermoreversible color-change material from the advantage that the precision of color change is high and a color seed | species and color-change temperature can be selected freely.
Specifically, as the organic thermoreversible color-changing material, (p) an electron-donating color-forming organic compound, an electron-accepting organic compound, a microcapsule containing a polar organic compound (hereinafter referred to as “(p) component”), Alternatively, (q) liquid crystal (hereinafter referred to as “(q) component”) can be preferably used.

  The component (p) is an electron-donating color-forming organic compound (color component), an electron-accepting organic compound (color-developing agent) that expresses another color by binding to it, and a color component with a certain temperature as a boundary. Three components of a polar organic compound (decoloring agent) having the ability to dissolve any of the components by cutting the bond between the colorant and the color former are encapsulated. That is, at a low temperature, a first color is displayed due to the combination of the color component and the color former, and at a high temperature, the bond between the color component and the color developer is broken due to the activity of the decoloring agent, and the second color is changed. It is expressed.

  Specifically, as the electron donating color-forming organic compound contained in the component (p), for example, diaryl phthalides, triaryl methane phthalides, leuco triaryl methanes, leuco xanthenes, leuco phenothiazines, Leucophenoxazines, leucooxazines, leucoin digoids, leucooramines, acyl auramines, aryl auramines, diaryl methanes, diaryl phthalides, polyaryl carbinols, indoline phthalides And azaphthalides, fluorans, thiofluorans, spiropyrans, rhodamine B lactams, chromenopyrazoles, methines, quinazolines, diazaxanthenes, bislactones, fluorenes and the like.

  Examples of the electron-accepting organic compound include 1,2,3-triazoles, phenols, thiourea derivatives, oxyaromatic carboxylic acids, and the like.

  Examples of the polar organic compound include alcohols, alcohol / acrylonitrile adducts, azomethines, and esters.

  In addition to the above-described components, the component (p) may contain a surfactant, a hydrophilic protective colloid substance, and the like as necessary.

  For forming the microcapsules of the component (p), a thermoplastic resin is usually used. As such a thermoplastic resin, a conventionally well-known thing can be used widely. This thermoplastic resin film may contain an organic photochromic compound in a matrix state.

  On the other hand, as the component (q), for example, cholesteric liquid crystal, terphenyl liquid crystal, nematic liquid crystal, or the like can be used. Those encapsulated in microcapsules can also be used.

  The component (b) can be used without any particular limitation as long as it does not hinder the discoloration performance of the component (a). As the component (b), for example, a synthetic resin binder and / or an inorganic binder can be used.

Synthetic resin binders include, for example, ethylene resins, polyester resins, vinyl acetate resins, alkyd resins, vinyl chloride resins, epoxy resins, acrylic resins, acrylic silicon resins, urethane resins, silicon resins, fluororesins, etc. Any resin such as a solvent-soluble resin, a non-water-dispersed resin, a water-soluble resin, a water-dispersed resin, and a solvent-free resin can be used. In particular, the use of one or more resins selected from acrylic resins, urethane resins, silicon resins, and fluororesins is preferred because durability can be increased.
By using a synthetic resin binder, the coating film containing the component (a) can have flexibility. Further, the degree of flexibility can be freely changed by adjusting the glass transition temperature of the synthetic resin.

Examples of the inorganic binder include Portland cement, blast furnace cement, silica cement, fly ash cement, white cement, calcined gypsum, colloidal silica, water-soluble alkali metal silicate, and the like. Can be used.
By using an inorganic binder, the thickness of the coating film can be increased. It is also possible to ensure high water vapor desorption performance and water vapor adsorption / desorption performance.

  When a synthetic resin binder is included as the binder, the synthetic resin binder is preferably a reactive functional group-containing synthetic resin binder. As the reactive functional group of the synthetic resin binder, those capable of reacting with the functional group of the crosslinking agent described later can be used. Examples of such functional group combinations include, for example, carboxyl group and metal ion, carboxyl group and carbodiimide group, carboxyl group and epoxy group, carboxyl group and aziridine group, carboxyl group and oxazoline group, hydroxyl group and isocyanate group, and carbonyl group. A hydrazide group, an epoxy group, an amino group, etc. are mentioned.

  In the present invention, a carboxyl group is particularly preferably used as the reactive functional group of the synthetic resin binder. Examples of carboxyl group-containing synthetic resin binders include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and fumaric acid, and ammonium salts, organic amine salts, and alkali metals. It can be obtained by copolymerizing a carboxyl group-containing monomer such as a salt. These monomers can be used alone or in combination of two or more.

The weight ratio of the component (a) to the component (b) is such that the solid content of the component (a) is 0.1 to 200 parts by weight (preferably 0.5 to 100 parts per 100 parts by weight of the solid content of the component (b). Parts by weight, more preferably 1 to 50 parts by weight).
When the ratio of the component (a) is more than 200 parts by weight, the physical properties of the coating film may be inferior, and when it is less than 0.1 parts by weight, the thermochromic performance may be insufficient.

The component (c) has water vapor adsorption / desorption properties, and is a component that imparts a temperature rise suppression effect due to the latent heat of vaporization of moisture.
Such a component (c) can autonomously absorb moisture present in the air or on a substrate.
In the present invention, since the component (c) has water vapor adsorption / desorption properties, moisture absorbed is desorbed in a predetermined temperature range, and at that time, heat is taken away by the latent heat of vaporization of the moisture, thereby suppressing an increase in temperature. Can do. Therefore, fading of the component (a) is prevented, thermoreversibility is maintained, and thermochromic performance can be exhibited over a long period of time.

  Examples of the component (c) include porous inorganic powder (hereinafter referred to as “(c-1) component”) and / or hygroscopic synthetic resin fine particles (hereinafter referred to as “(c-2) component”).

As the component (c-1), for example, porous inorganic powders such as silica gel, zeolite, sodium sulfate, alumina, activated carbon, and allophane can be used.
In particular, the component (c-1) is preferably one or more selected from silica gel, zeolite, activated carbon, and allophane, and among these, silica gel is most preferable.

The specific surface area of the component (c-1) is preferably 100 m ² / g or more (preferably 200 m ² / g or more, more preferably 300 m ² / g or more), and it is excellent by having such a specific surface area. It becomes possible to exhibit the temperature rise suppressing effect. The specific surface area is a value measured by the BET method.

  The component (c-2) has water vapor adsorption / desorption properties. Specifically, the moisture absorption rate at a temperature of 20 ° C. and a relative humidity of 45% is 10 wt% or more (preferably 20 wt% or more, more preferably 30 wt%). Or more).

The moisture absorption rate at a temperature of 20 ° C. and a relative humidity of 45% means that the sample was dried at 120 ° C. for 1 hour and then absorbed by a constant temperature and humidity chamber at a temperature of 20 ° C. and a relative humidity of 45% for 24 hours. It is a value obtained by measuring the change in weight, and can be determined by the following formula.
Moisture absorption rate (wt%) = {(weight after moisture absorption−weight after drying) / weight after drying} × 100

  As the component (c-2), for example, one kind or two or more kinds of monomers such as various (meth) acrylic acid esters, acrylamides, aromatic vinyls, vinyl esters, and vinyl halides are publicly known. Although it is obtained by copolymerization by a method, it is desirable to have a crosslinked structure from the viewpoint of improving water vapor adsorption and desorption. Such a crosslinked structure can be formed by a method such as introduction of a crosslinkable monomer in the polymerization stage, introduction of a crosslinkable compound after polymerization. As the crosslinkable monomer, divinylbenzene, ethylene glycol di (meth) acrylate, methylenebisacrylamide and the like can be suitably used, and as the crosslinkable compound, a hydrazine-based compound can be suitably used.

  The component (c-2) is preferably reactive functional group-containing hygroscopic synthetic resin fine particles. As such a reactive functional group, those similar to the component (b) can be used. In the present invention, a carboxyl group is particularly preferably used. The method for introducing a carboxyl group into the component (c-2) is not particularly limited. For example, a method by homopolymerization of a monomer having a carboxyl group or copolymerization with another monomer capable of copolymerization, Examples include a method of subjecting a polymer obtained by copolymerizing a cyano group-containing monomer such as (meth) acrylonitrile to a hydrolysis treatment, a method by oxidation of an alkene, an alkyl halide, an alcohol, an aldehyde, or the like. The carboxyl group content of the component (c-2) is preferably 1 mmol / g or more.

  The particle size of the component (c-2) is not particularly limited, but a component having a particle size of about 0.1 to 100 μm can be used.

  Furthermore, it is preferable that (c) component has a hysteresis characteristic in water vapor adsorption / desorption property. By having a hysteresis characteristic, it is possible to moderately suppress the desorption rate of water vapor and to maintain the water vapor in the component (c) for a long time, so that the temperature rise suppressing effect can be maintained, (a) It is possible to further suppress discoloration due to heat of components.

The mixing amount of the component (c-1) is preferably 10 to 600 parts by weight with respect to 100 parts by weight of the solid content of the component (b). When the amount of component (c-1) is less than 10 parts by weight, it is difficult to obtain sufficient adsorption / desorption performance and hysteresis characteristics. If it exceeds 600 parts by weight, the formed coating film tends to be brittle.
The mixing amount of the component (c-2) is 1 to 100 parts by weight, preferably 5 to 50 parts by weight with respect to 100 parts by weight of the solid content of the component (b). If this amount is less than 1 part by weight, the water vapor adsorptivity per unit time tends to decrease. If it exceeds 100 parts by weight, the formed coating film tends to be brittle.

  The component (c) only needs to include one of the component (c-1) and the component (c-2), but includes both the component (c-1) and the component (c-2). A thing can be used conveniently.

  The thermoreversible color change composition of the present invention may further contain a metal oxide (hereinafter also referred to as “component (d)”). By containing (d) component, degradation of (a) component etc. by ultraviolet-ray can be suppressed, and fading of (a) component can be prevented more for a long period of time.

Examples of the component (d) include titanium oxide, zinc oxide, cerium oxide, and iron oxide. Moreover, what coat | covered the surface of these metal oxides with a silica, an alumina, a silicone, a stearate, a laurate, a hexametaphosphate etc. can be used. These can be used alone or in combination of two or more.
(D) The average primary particle diameter of a component becomes like this. Preferably it is 200 nm or less, More preferably, it is 100 nm or less, More preferably, it is 5-50 nm. When the average primary particle size is larger than this value, it may be difficult to sufficiently suppress the fading of the component (a).
In addition, the average primary particle diameter in this invention is a value calculated by observation using a transmission electron microscope.

The weight ratio of the component (d) to the component (b) is such that the solid content of the component (d) is 0.1 to 100 parts by weight (preferably 0.5 to 50 parts per 100 parts by weight of the solid content of the component (b). Parts by weight, more preferably 1 to 30 parts by weight).
When the ratio of the component (d) is more than 100 parts by weight, the color development performance of the component (a) may be deteriorated. When the ratio is less than 0.1 part by weight, the effect of suppressing deterioration of the component (a) and the like. Is difficult to obtain.

Furthermore, in the thermoreversible color change composition, when the reactive functional group-containing synthetic resin binder is used as the component (b) and the reactive functional group-containing hygroscopic synthetic resin fine particles are used as the component (c). It is desirable to use a crosslinking agent (hereinafter referred to as “component (e)”) having a functional group capable of reacting with the reactive functional group of component (b) and component (c). By including such a component (e), a crosslinked structure is introduced, the strength of the formed coating film is improved, and excellent water vapor adsorption / desorption properties can be exhibited.
The component (e) preferably contains two or more of these functional groups in one molecule.
The functional group of the component (e) is not limited as long as it can react with the component (b) and the component (c). In the present invention, a carbodiimide group or an epoxy that is a functional group capable of reacting with a carboxyl group is particularly used. One or more selected from a group, an aziridine group, an oxazoline group and the like are preferably used.

  Specific examples of the component (e) include, for example, those described in JP-A-10-60272, JP-A-10-316930, JP-A-11-60667, and the like as a crosslinking agent containing a carbodiimide group. As a crosslinking agent containing an epoxy group, polyethylene glycol diglycidyl ether, polyhydroxyalkane polyglycidyl ether, diglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc., as a crosslinking agent containing an aziridine group, 2,2-bishydroxymethylbutano -Lutris [3- (1-aziridinyl) propionate], 1,6-hexamethylenediethyleneurea, diphenylmethane-bis-4,4'-N, N'-diethyleneurea and the like as a crosslinking agent containing an oxazoline group, 2-Vinyl-4-methyl-2-oxa Phosphorus, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-polymerizable oxazoline compound of oxazoline each compound and copolymerizable monomer copolymerized with resins.

  The thermoreversible color-changing composition of the present invention contains, in addition to the above-mentioned components, pigments, aggregates, fibers, surfactants, catalysts, antifoaming agents, film-forming aids, leveling agents, plasticizers as necessary. Including additives such as antifreezing agents, pH adjusting agents, antiseptics, antifungal agents, anti-algae agents, antibacterial agents, light stabilizers, dispersants, crosslinking agents, thickeners, moisturizers, flame retardants, and fragrances You can also.

  The thermoreversible color-changing composition of the present invention can be applied to a location that expresses a specific color due to a color-changing effect, and in particular, furniture, toys, daily necessities, artificial flowers, beverage containers, vehicles, walls in the construction field, floor surfaces, It can be applied to roofs, rooftops, etc. Examples of the base material constituting such a part include concrete, inorganic molded board, tile, plastic, metal, wood, paper, etc., and these base materials are those on which some kind of coating has already been formed. May be.

In this invention, it can use by laminating | stacking a thermoreversible discoloration body on these base materials. The laminating method is not particularly limited, but a method of applying and laminating a thermoreversible color change composition to a base material, preparing a thermoreversible color change body in advance, such as a sheet, and then known adhesion to the base material And a method of laminating with an adhesive / adhesive or an adhesive / adhesive tape.
In the method of applying and laminating the thermoreversible color change composition, it may be applied by using a coating device such as a brush, a trowel, a spray, a roller, a roll coater, or a flow coater. It is not limited.
Further, when the layers are laminated, the substrate may be subjected to some ground treatment. Furthermore, after lamination, a top coat can be applied to such an extent that the effects of the present invention are not impaired.

  Examples and Comparative Examples are shown below to clarify the features of the present invention.

  Using the raw materials shown in Table 1, the raw materials were mixed in the raw material composition shown in Table 2, to produce thermoreversible color change compositions 1 to 5, respectively.

(Water vapor adsorption / desorption test)
The obtained thermoreversible color change compositions 1 to 5 were each applied to an aluminum plate having a thickness of 0.5 mm so that the dry film thickness was 500 μm, and the temperature was 25 ° C. and the relative humidity was 55% and 14%. A sample was prepared by drying for days to form a film. The obtained specimen was left in a constant temperature and humidity chamber at a temperature of 25 ° C. and a relative humidity of 40% until the weight was balanced, and the weight after the standing was measured. Next, the same operation was performed in a constant temperature and humidity chamber where only the humidity was increased at the same temperature, and the weight was measured up to a relative humidity of 90% while increasing only the humidity step by step. Thereafter, the same operation was repeated while decreasing only the humidity stepwise at the same temperature, and the weight was measured. By calculating the water vapor adsorption / desorption amount from the weight of the test specimen at each humidity, an adsorption / desorption isotherm showing water vapor adsorption / desorption properties was obtained. The results are shown in FIG.
Further, the water vapor adsorption / desorption amount (g / g) at a temperature of 25 ° C. and a humidity of 90% was obtained from the adsorption / desorption isotherm. The results are shown in Table 2, respectively.
In the present invention, the temperature range higher than the color change temperature of the thermoreversible color change material and lower than the heat resistance temperature of the thermoreversible color change material is set to a temperature 2 ° C. higher than the upper limit value of the color change temperature of the thermoreversible color change material. did. That is, since the upper limit of the color change temperature of the thermoreversible color change material is 23 ° C., the temperature in the water vapor adsorption / desorption test was set at 25 ° C., 2 ° C. higher than that, and the measurement was performed.

Example 1
The thermoreversible color change composition 1 was poured into a mold (150 × 70 × 2 mm) so as to have a dry film thickness of 1 mm, dried at room temperature for 24 hours, and then taken out from the mold to obtain a test body.
The obtained specimen was magenta at a temperature of 15 ° C., became white and transparent at a temperature of 25 ° C., and showed discoloration due to heat.

(Heat resistance test)
The obtained specimen is left in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 90% for 24 hours to absorb moisture, then left in a constant temperature oven at 70 ° C., and the temperature of the specimen after about 10 minutes is measured. It was measured. As a result, the specimen temperature was about 45 ° C., and it did not reach the heat resistance temperature of the thermoreversible color changing material.
Further, the color difference at a temperature of 25 ° C. and a temperature of 15 ° C. before and after the heat resistance test was measured with a color difference meter (SPECTROTOPOMETER CM-3700d, manufactured by Minolta Co., Ltd.). Evaluation is performed by color difference, A: 0.1 or less, B: 0.2 to 0.3, C: 0.4 to 0.5, D: 0.6 to 0.7, E: 0.8 The above five-step evaluation was adopted. The results are shown in Table 2.

(Example 2)
A test specimen was obtained in the same manner as in Example 1 except that the thermoreversible color change composition 1 was replaced with the thermoreversible color change composition 2.
The obtained test body was magenta at a temperature of 15 ° C., became white and transparent at a temperature of 25 ° C., and showed discoloration due to heat.
When the same heat resistance test as in Example 1 was performed on this test body, the test body temperature was about 49 ° C. and did not reach the heat resistance temperature of the thermoreversible color-changing material. As in Example 1, the color difference evaluation before and after the heat resistance test is shown in Table 2.

(Example 3)
A test specimen was obtained in the same manner as in Example 1 except that the thermoreversible color change composition 1 was replaced with the thermoreversible color change composition 3.
The obtained test body was green at a temperature of 15 ° C., became white and transparent at a temperature of 25 ° C., and showed discoloration due to heat.
When the same heat resistance test as that of Example 1 was performed on this test body, the test body temperature was about 46 ° C. and did not reach the heat resistance temperature of the thermoreversible color changing material. As in Example 1, the color difference evaluation before and after the heat resistance test is shown in Table 2.

Example 4
A test body was obtained in the same manner as in Example 1 except that the thermoreversible color change composition 1 was replaced with the thermoreversible color change composition 4.
The obtained specimen was magenta at a temperature of 15 ° C., became white and transparent at a temperature of 25 ° C., and showed discoloration due to heat.
When the same heat resistance test as that of Example 1 was performed on this test body, the test body temperature was about 45 ° C. and did not reach the heat resistance temperature of the thermoreversible color changing material. As in Example 1, the color difference evaluation before and after the heat resistance test is shown in Table 2.

(Reference Example 1)
A test specimen was obtained in the same manner as in Example 1 except that the thermoreversible color change composition 1 was replaced with the thermoreversible color change composition 5.
The obtained specimen was magenta at a temperature of 15 ° C., became white and transparent at a temperature of 25 ° C., and showed discoloration due to heat.
When this test body was subjected to the same heat resistance test as in Example 1, the test body temperature increased to about 69 ° C.

Diagram showing hysteresis characteristics The graph which shows the adsorption / desorption isotherm of the thermoreversible color-change composition 1-5

Claims (3)

Contains thermoreversible color change material, binder, porous inorganic powder and hygroscopic synthetic resin fine particles, in a temperature range higher than the temperature change temperature of the thermoreversible color change material and lower than the heat resistance temperature of the thermoreversible color change material. Has water vapor adsorption and desorption properties with hysteresis characteristics,
And the amount of water vapor adsorbed / desorbed at a relative humidity of 90% at a temperature 2 ° C. higher than the upper limit of the color change temperature of the thermoreversible color change material (measured based on the weight at a relative humidity of 40%, at a relative humidity of 90% A thermoreversible discolorant, characterized in that the amount of water vapor that can be retained per unit weight of the thermoreversible discolorant is 0.05 g / g or more. The thermoreversible discolorant according to claim 1, further comprising a metal oxide (excluding the binder and the porous inorganic powder) . A reactive functional group-containing synthetic resin binder is used as a binder, and a reactive functional group-containing hygroscopic synthetic resin particle is used as a hygroscopic synthetic resin fine particle. A reactive functional group-containing synthetic resin binder and a reactive functional group are used. The thermoreversible discolorant according to claim 1 or 2, further comprising a crosslinking agent having a functional group capable of reacting with the reactive functional group of the moisture-absorbing / releasing synthetic resin fine particles.

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