JP2010126549A - Thermochromic composition and thermochromic microcapsule - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermochromic composition that has excellent developed color density stability over time and is reversibly thermochromic. <P>SOLUTION: In the thermochromic composition including an electron-donating color-developing organic compound, an electron-accepting compound, and a desensitizer, one or a plurality of compounds that are represented by specific general formula having two aromatic rings and have a melting point of 150°C or lower are used as the electron-accepting compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermochromic composition having reversibility and a thermochromic microcapsule encapsulating the thermochromic composition.

  Thermochromic compositions containing an electron-donating color-forming organic compound, an electron-accepting compound, and a desensitizer have already been proposed and put into practical use. Recently, in order to obtain a higher quality thermochromic composition, it has been proposed to use any one or more components as a specific compound. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 6-88070), as a thermochromic composition that is excellent in terms of color density, ground color development, and discoloration color difference, an electron-donating color-forming organic compound, electron-accepting property is disclosed. There has been proposed a thermochromic composition containing a compound and at least one desensitizer selected from carbazole derivatives represented by a specific general formula. In Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-297277), as a reversible thermochromic composition having improved fastness, particularly water resistance, high color density during color development, and low toxicity, And a composition comprising a developer having a specific general formula has been proposed.

  In Patent Document 3 (Japanese Patent Application Laid-Open No. 2001-294833), a reversible thermochromic UV curable ink that exhibits permanent UV reversibility without impairing the color change sensitivity and has efficient UV curability. As a reversible thermochromic composition and a microcapsule pigment encapsulating a light fastness-imparting agent represented by a specific general formula are dispersed in a photopolymerizable composition containing an ultraviolet absorber and a photopolymerization initiator. Inks have been proposed. Patent Document 4 (Japanese Patent Application Laid-Open No. 2001-31884) discloses an electron-donating color-changing organic compound, a bisphenol compound having a molecular weight of 250 or more, represented by a specific general formula as a reversible thermochromic pigment rich in heat resistance. A pigment containing an electron-accepting compound and a color-change temperature adjusting agent has been proposed. In Patent Document 5 (Japanese Patent Laid-Open No. 2003-119309), a reversible thermochromic foam comprising a reversible thermochromic microcapsule pigment encapsulating the pigment described in Patent Document 4, a polyolefin resin, and a foaming agent. Has been proposed.

JP-A-6-88070 JP 2000-297277 A Japanese Patent Laid-Open No. 2001-294783 JP 2001-31884 A JP 2003-119309 A

  The thermochromic composition not only has the property of developing / decoloring at a predetermined temperature, but also has the property that its density (color density) does not easily change over time after color development, that is, the color density. It is sometimes required to have stability over time. For example, in applications where the thermochromic composition is colored for a long period of time (for example, decoration of tableware such as cups and mugs), the color density of the thermochromic composition is low and the stability over time is predetermined. It is not preferable because the appearance and the characters are difficult to see. Accordingly, the thermochromic composition used in the above applications is required to have high color density stability over time.

  The present invention has been made in view of such a situation, and an object thereof is to provide a thermochromic composition having excellent color density stability over time.

  The present invention includes an electron-donating color-forming organic compound, an electron-accepting compound, and a desensitizer. The electron-accepting compound is represented by any one of the following general formulas (1) to (3) and has a melting point. A thermochromic composition comprising one or more compounds having a temperature of 150 ° C. or lower is provided.

(In the general formulas (1) to (3), R ₁ and R ₂ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a phenyl group, or a cyclohexyl group; , Y and Z are each independently a halogen, an OH group, an alkoxy group, an alkoxyallyl group, an allyl group, a linear or branched alkyl group having 1 to 4 carbon atoms, a phenyl group, or a cyclohexyl group; Is a C5-C8 cycloalkane which may have a substituent or a fluorene ring which may have a substituent.

  The thermochromic composition of the present invention is an electron-accepting compound, that is, a compound represented by a specific chemical formula and having a melting point of 150 ° C. or lower (hereinafter referred to as “low-melting color developer for convenience”). Is used). By using a low melting point developer, a reversible thermochromic composition having excellent color developability and decoloring property and excellent color density stability with time can be obtained.

  In the present invention, the thermochromic composition is a compound represented by any one of the above general formulas (1) to (3) as a developer and having a melting point higher than 150 ° C. There is provided a thermochromic composition further comprising a “high melting point developer”. One or more high melting point developers may be included.

  As long as the low-melting color developer is contained, the thermochromic composition of the present invention exhibits excellent color density density stability over time even when a high-melting color developer is contained. By using a high melting point developer, it is possible to utilize the characteristics (for example, high color developability or high decoloring property) and to improve the color density stability over time by using the low melting point developer. .

  The present invention also provides a thermochromic microcapsule in which the thermochromic composition of the present invention is encapsulated in a microcapsule. When the thermochromic composition is encapsulated in the microcapsules, the microcapsules are less susceptible to the influence of substances present in the surroundings.

  The thermochromic composition of the present invention exhibits excellent color density stability over time by using a compound represented by the above-mentioned specific general formula and having a melting point of 150 ° C. or less as a developer. Therefore, the thermochromic composition of the present invention is suitable for applications in which a colored state is maintained for a long time. For example, textile products, inks, paints, pottery, glass products, plastic moldings, packaging materials, recording materials And as a colorant for imparting reversible thermochromic properties to printed matter.

  The thermochromic composition of the present invention (hereinafter sometimes simply referred to as “composition”) includes an electron-donating color-forming organic compound, an electron-accepting compound, and a desensitizer, It contains at least one compound represented by a specific general formula and having a melting point of 150 ° C. or lower. Below, the component which comprises the thermochromic composition of this invention is demonstrated.

[Electron-donating colored organic compound]
The electron-donating color-forming organic compound is also called a color former and reacts with the electron-accepting compound to give a color. A known compound may be arbitrarily used as the electron-donating color-forming organic compound. Specifically, fluorans, fluorenes, diphenylmethane phthalides, diphenylmethane azaphthalides, indolyl phthalides, phenyl indolyl phthalides, phenyl indolyl azaphthalides, styrylquinolines, diazarhodamine Lactones, pyridine compounds, quinazoline compounds, bisquinazoline compounds, ethylenophthalide compounds, and ethylenoazaphthalide compounds are examples of electron donating color-forming organic compounds. Two or more kinds of electron-donating color-forming organic compounds may be used in combination.

The electron donating color-forming organic compound is preferably
2- (2-chloroanilino) -6-dibutylaminofluorane,
3,6-bis (diphenylamino) fluorane

  The content of the electron-donating color-forming organic compound is preferably 0.1% by weight to 50% by weight, based on the total weight of the composition, and 0.8% by weight to 15% by weight. More preferably. When the content of the electron-donating color-forming organic compound is small, the color density may be low. When the content is high, the background color (color density in the decolored state) may be large. is there.

[Electron-accepting compound]
The electron-accepting compound is also called a color developer and is a compound that reacts with an electron-donating color-forming organic compound to give a color. Specifically, the electron-accepting compound is a compound having an active proton, a pseudo-acidic compound, or an electron empty compound. A compound having pores. Furthermore, in the present invention, a compound (low melting color developer) represented by any one of the following general formulas (1) to (3) and having a melting point of 150 ° C. or lower is used as the electron accepting compound.

In the general formulas (1) to (3), R ₁ and R ₂ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a phenyl group, a cyclohexyl group, Y and Z are each independently halogen, OH group, alkoxy group, alkoxyallyl group, allyl group, linear or branched alkyl group having 1 to 4 carbon atoms, phenyl group, or cyclohexyl group, and C is , A C5-C8 cycloalkane which may have a substituent or a fluorene ring which may have a substituent.

  In the general formula (2), an arc containing C means that the carbon atom bonded to the two aromatic rings is a carbon atom constituting the cycloalkane. Accordingly, in the general formula (2), when C is a cycloalkane having 6 carbon atoms (that is, cyclohexane), the general formula (2) is represented by the following formula.

  More specifically, p-cumylphenol, bis (4-hydroxyphenyl) ethane, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4′-methoxydiphenylsulfone, 2,2′-diallyl -4,4'dihydroxydiphenylsulfone and 1,1-bis (4-hydroxyphenyl) cyclohexane are preferably used as the electron-accepting compound. In particular, 2,2′-diallyl-4,4′dihydroxydiphenylsulfone and 4-hydroxy-4′-isopropoxydiphenylsulfone are excellent in heat resistance, for example, kneaded into a thermoplastic resin. Is suitable.

  When a low-melting color developer is used as the electron-accepting compound, it is possible to obtain a composition having excellent color density stability over time. The reason for this is not clear, but it is considered that the developer having a low melting point is less likely to cause crystal separation from the electron-donating color-forming organic compound.

  A compound represented by any one of the above three general formulas and having a melting point of 150 ° C. or lower may be used alone or in combination. By mixing a plurality of types of compounds, a thermochromic composition having better characteristics can be obtained utilizing the characteristics of each compound.

  Alternatively, as long as at least one compound having the specific general formula and the specific melting point is used, the compound represented by any one of the above three general formulas and having a melting point exceeding 150 ° C. Colorants) may be used as electron accepting compounds. High melting point compounds are generally excellent in heat resistance. Therefore, by using a combination of a low melting point compound and a high melting point compound, it is possible to obtain a composition having excellent color density stability over time and excellent heat resistance.

  Specific examples of the high melting point compound include 4-hydroxy-4′-propoxydiphenylsulfone, 1,1-bis (4-hydroxyphenyl) -1-isobutylethane, and 2,2-bis (4-hydroxyphenyl) propane. 4-hydroxy-4′-allyloxydiphenyl sulfone, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, and biscresol fluorene are preferably used. In particular, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, biscresol fluorene, 4-hydroxy-4′-allyloxydiphenyl sulfone, 1,1-bis (4-hydroxyphenyl) cyclohexane and 4- Hydroxy-4'-propoxydiphenyl sulfone is excellent in heat resistance, and is suitable for use in, for example, kneading into a thermoplastic resin.

  The content of the electron-accepting compound is preferably 0.05% to 98% by weight, more preferably 0.5% to 77% by weight, based on the weight of the entire composition. preferable. When the content of the electron-accepting compound is small, the color density may be low, and when the content is high, the background color may be large. The electron-accepting compound is preferably contained in an amount of 0.1 to 100 parts by weight, and 0.5 to 20 parts by weight, based on 1 part by weight of the electron-donating color-forming organic compound More preferably.

  When both the low-melting color developer and the high-melting color developer are included, the weight ratio of both is 1:99 to 99: 1 (low-melting color developer: high-melting color developer). It is preferable to mix, and it is more preferable to mix so that it may become 10: 90-90: 10. If the proportion of the low melting point developer is too large, heat resistance by the high melting point developer may not be obtained. If the proportion of the low melting point developer is too small, good color density stability over time can be obtained. There may not be.

[Desensitizer]
The desensitizer is a compound that can dissolve the electron-donating color-forming organic compound and the electron-accepting compound, and can control the color reaction by the solidification or melting characteristics thereof. In the present invention, for example, by selecting a widely used desensitizer, the color can be changed at -10 ° C to 60 ° C. Specifically, a hardly volatile hydrophobic organic medium (or solvent or solvent) is used as a desensitizer.

  More specifically, examples of the desensitizer include aliphatic monohydric alcohols having 10 or more carbon atoms, fatty acids having 10 or more carbon atoms, fatty acid monoamides having 6 or more carbon atoms, and ester compounds having 13 or more carbon atoms in total. it can

Further, it is composed of an arbitrary combination of an aliphatic, aromatic and alicyclic monobasic acid and any one of an aliphatic, aromatic and alicyclic monohydric alcohol used as a general-purpose desensitizer. An ester compound having a total carbon number of 13 or more and having the following form can be used in the present invention.
-The general-purpose desensitizer acid is a polybasic acid.
-The general-purpose desensitizer alcohol is a polyhydric alcohol.
-The general-purpose desensitizer acid is a polybasic acid and the alcohol is a polyhydric alcohol.

  Alternatively, an aliphatic ketone compound having a total carbon number of 10 or more and an aliphatic ether compound having a total carbon number of 10 or more, which are general-purpose desensitizers, can be used in the present invention.

  Even more specifically, as a desensitizer, methyl laurate, lauric acid amide, methyl myristate, palmitic acid amide, methyl palmitate, myristic acid amide, stearic acid methyl, stearic acid amide, methyl behenic acid, and behenine Mention may be made of acid amides.

  The content of the desensitizer is preferably 1% by weight to 99% by weight, and more preferably 19% by weight to 99% by weight, based on the weight of the entire composition. When the content of the electron-donating color-forming organic compound is small, the background color may increase, and when the content is large, the color density may decrease. Further, the desensitizer is preferably contained in an amount of 1 to 500 parts by weight, more preferably 5 to 100 parts by weight, with respect to 1 part by weight of the electron donating color-forming organic compound. .

  The thermochromic composition of this invention may contain the other component contained in a normal thermochromic composition. Hereinafter, other components will be described.

[Ultraviolet absorber]
The composition of the present invention may contain an ultraviolet absorber. The ultraviolet absorber selectively absorbs ultraviolet rays contained in sunlight. Ultraviolet rays cause the color former to deteriorate by photoreaction. UV absorbers are used to prevent this.

  UV absorbers are broadly classified into benzophenone, benzotriazole, cyanoacrylate, triazine, salicylic acid, oxalic anilide, malonic ester, benzoic acid, cinnamic acid, and dibenzoylmethane. The More specifically, benzotriazole-based Tinuvin 326, triazine-based Tinuvin 40 (both manufactured by Ciba Specialty Chemicals), and benzophenone-based Siasorb UV531 (manufactured by Cytec Industries) can be used.

  The content of the ultraviolet absorber is preferably up to 96% by weight, more preferably up to 61% by weight, based on the weight of the entire composition. When the content of the ultraviolet absorber is large, the color density may be lowered, discoloration may not be sharp, and / or discoloration temperature hysteresis may be increased. Moreover, it is preferable that an ultraviolet absorber is contained in the quantity up to 50 weight part with respect to 1 weight part of electron-donating colorable organic compounds, and it is more preferable that it is contained in the quantity up to 10 weight part.

[Ultraviolet scattering agent]
The composition of the present invention may contain an ultraviolet scattering agent. The ultraviolet scattering agent physically reflects or scatters ultraviolet rays contained in sunlight. As a result, the action of ultraviolet rays on the color former is prevented. The ultraviolet scattering agent is, for example, metal oxide fine particles such as zinc oxide, titanium oxide, α-iron oxide, and cerium oxide.

[Light stabilizer]
The composition of the present invention may contain a light stabilizer. The light stabilizer prevents the coloring agent from deteriorating due to the reaction between the radicals generated by ultraviolet rays and the coloring agent. Specifically, hindered phenols or hindered amines may be used as light stabilizers.

[Others]
As a component other than the components shown above, any of antioxidants (phenolic, phosphorous, and sulfur-based), infrared absorbers, fluorescent brighteners, non-thermochromic dyes, and non-thermochromic pigments One or more components may be included.

  Next, the manufacturing method of the thermochromic composition of this invention is demonstrated. The composition of the present invention can be produced by heating and dissolving an electron-donating color-forming organic compound, an electron-accepting compound, a desensitizer, and, if necessary, other components. The temperature at that time is selected so that the component having the highest melting point among all the components is dissolved, and is generally in the range of 120 ° C to 180 ° C.

  Alternatively, the thermochromic composition of the present invention may be encapsulated in microcapsules. Due to the microencapsulation, the problems that occur when the thermochromic composition is used as it is, for example, in an ink or plastic molding, that is, 1) the migration of components to repeat the solid-liquid state change during discoloration. 2) In particular, in the case of ink, vehicle components (resins, solvents, etc.) tend to affect the discoloration and may have an adverse effect. Is avoided or reduced. This is because the microencapsulation blocks the contact with the surrounding atmosphere during use, thereby preventing the influence of substances present in the vicinity.

  Microencapsulation of the thermochromic composition can be performed according to the following procedure. First, the capsule wall raw material and the thermochromic composition are uniformly dissolved in the desensitizer using a dissolution aid as necessary. The solubilizing agent can uniformly dissolve the thermochromic composition and the capsule wall raw material, and does not impair the thermochromic performance or needs to be removed in a subsequent process. Specifically, an ester solvent, a ketone solvent, an ether solvent, a glycol ether solvent, a hydrocarbon solvent, an aromatic solvent, a nitrogen-containing solvent, a silicon solvent, and a halogen-containing solvent are dissolved. Can be used as an agent. More specifically, ethyl acetate, acetone, and methyl ethyl ketone are preferably used.

  The capsule wall raw material includes a resin main component and a crosslinking agent. The resin main component is a compound that reacts with a crosslinking agent at the interface of an O / W emulsion having a capsule inclusion as a dispersed phase to form a capsule wall. The crosslinking agent is a compound that reacts with the resin main component at the interface of the O / W emulsion having the capsule inclusion as a dispersed phase to form a capsule wall.

  Examples of combinations of the resin main agent and the crosslinking agent are as follows.

  Next, a solution containing the capsule wall raw material and the thermochromic composition is added to the aqueous emulsifier solution heated to 30 to 60 ° C. while being subjected to medium shear stirring. After the addition, high shear stirring is performed to obtain an O / W emulsion having an average particle size of several μm. An emulsifier is an amphiphilic substance that is adsorbed on the interface of an O / W emulsion having a capsule inclusion as a dispersed phase to stabilize the system. Specifically, the emulsifier is a natural water-soluble polymer, a synthetic water-soluble polymer, a low molecular surfactant, and inorganic fine particles. The emulsifiers according to the combination of the resin main agent and the crosslinking agent are as follows.

  The aqueous emulsifier solution is preferably an aqueous solution containing 0.1 to 15% by weight of an emulsifier, and more preferably an aqueous solution containing 0.5 to 8% by weight of an emulsifier. If the concentration of the emulsifier is too high, foaming may occur, and if it is too low, the particle size may increase or emulsification may not be possible.

  After high-shear stirring, switch to low-shear stirring and slowly drop the aqueous crosslinking agent solution. After dropping, the reaction is carried out at 60-90 ° C. for 3-12 hours, and then cooled to room temperature. Thereby, a slurry in which microcapsules are dispersed can be obtained.

The preferred amounts of the above raw materials and additives used in microencapsulation (more preferred amounts in parentheses) are as follows.
Thermochromic composition: 5 to 50 parts by weight (10 to 40 parts by weight)
Dissolving aid: 0 to 100 parts by weight (0 to 40 parts by weight)
Emulsifier aqueous solution: 100 parts by weight Resin main ingredient: 1-50 parts by weight (2-10 parts by weight)
Cross-linking agent: 0.5 to 25 parts by weight (1 to 5 parts by weight)

  If the amount of the thermochromic composition is too large, emulsification may not be possible, and if it is too small, the productivity may deteriorate. If the amount of the solubilizing agent is too large, the productivity may be deteriorated, and if it is too small, the color density may be lowered. If the amount of the resin main component is too large or too small, the reaction may be insufficient and the capsule strength and heat resistance may be reduced. Similarly, if the amount of the crosslinking agent is too large or too small, the reaction may be insufficient and the strength and heat resistance of the capsule may be reduced.

  The thermochromic composition of the present invention can be used to impart reversible thermochromic properties to plastic molded articles such as polyethylene and polypropylene, printing inks, inks, paints, packaging materials, fibers, recording materials, and the like. it can. Or you may use the thermochromic composition of this invention as a coloring agent of a writing instrument and a drawing material (for example, crayon). In that case, the line drawing and painting written or drawn with them can be thermochromic.

  The thermochromic composition of the present invention may be provided in a form encapsulated in microcapsules. Even when microencapsulated, the above-mentioned article can be imparted with thermochromic properties. In particular, the microencapsulated thermochromic composition is preferable for imparting thermochromic properties to aqueous emulsion inks, solvent volatile drying inks, two-component curable epoxy resin inks, printing pastes, and ultraviolet curable inks. Used.

(Examples 1 to 26, Comparative Examples 1 to 20)
A thermochromic composition was prepared using an electron-donating color-forming organic compound (color former), an electron-accepting compound (developer) and a desensitizer shown in Tables 3-6. Specifically, these three components were heated and dissolved at a temperature in the range of 120 to 180 ° C.

(Preparation of measurement sample)
A thermochromic composition heated to 70-100 ° C. A sample for measurement was prepared by dropping 0.05 g onto 5C filter paper and impregnating it by heating at 70 ° C. for 10 minutes. However, for the sample for measuring a thermochromic composition using an electron-accepting compound having a melting point of 100 ° C. or higher, the impregnation condition was 100 ° C. for 10 minutes.

Using the color difference meter CR-300 manufactured by Konica Minolta (formerly Minolta), the white color proofing of the initial color development state and ground color development state of the obtained measurement sample and the color development state (color density) after storage Evaluation was made by determining the color difference from the plate. The color difference is expressed by the following formula. In the formula, L ^* represents a lightness index, and a ^* and b ^* represent a chromaticness index. Details are described in the instruction manual of the device (especially page 77). It can be said that the larger the ΔE ^{*, the} higher the color density or background color density.

Measurement of ΔE ^* in the colored state was performed in a -5 ℃ cooler box, the measurement of the ΔE ^* in the background color development (color erasing) state was carried out on a 100 ℃ hot plate. The color development state after storage was evaluated by measuring ΔE ^* after storing at 32 ° C. for 4 days. From the ΔE ^* before and after storage, the rate of change in color density was calculated according to the following formula.

Furthermore, from the change rate value (absolute value), the temporal stability of the color density was evaluated according to the following criteria.
Good (O): | Change rate | ≦ 10
Bad (×): | Change rate |> 10

Tables 3 to 6 show the evaluation results of the measurement samples prepared using the discoloration compositions of the examples and the comparative examples. In each Example and each Comparative Example, the melting point of the electron-accepting compound was measured using TG / DTA6220 manufactured by SII Nanotechnology. The measurement was performed at an N ₂ flow rate of 200 ml / min and a heating rate of 10 ° C./min, and the melting start temperature appearing on the DTA curve was taken as the melting point.

(Examples 27 to 34, Comparative Examples 21 to 24)
Microcapsules were prepared using the compositions selected from the thermochromic compositions prepared in Examples 1 to 26 and Comparative Examples 1 to 20 as inclusions. The materials and amounts used for the production of the microcapsules are as follows.

  Using these materials, the thermochromic composition and the resin main agent are uniformly dissolved in the solubilizer, and then this solution is added to the aqueous emulsifier solution heated to 60 ° C. with medium shear stirring. did. Next, high shear stirring was performed to obtain an O / W emulsion having an average particle size of several μm. Then, low shear stirring was performed and the aqueous crosslinking agent solution was gradually added dropwise. After dropping, the mixture was reacted at 60 ° C. for 1 hour and 90 ° C. for 1 hour, cooled to room temperature, and a slurry in which microcapsules were dispersed was obtained.

A microencapsulated thermochromic composition in which a sample for measurement was cooled to room temperature, One filter paper was coated with a doctor blade (200 μm) and dried at room temperature for 2 hours. Using this sample, the measurement of the ΔE ^* in the colored state and the background color development (color erasing) state, the measurement of ΔE ^* in the colored state after storage was performed. These measurements were made by the method described in connection with Examples 1-26. Table 8 shows the initial color development and ground color development of each example and each comparative example, the rate of change in color density after storage, and the color density stability over time.

All the examples and comparative examples are reversible thermochromic compositions that can develop a black color at a temperature lower than that at a color change temperature of about 30 ° C. and repeat the change to become colorless at a higher temperature. In Examples 1 to 4 using an electron-accepting compound having a melting point ≦ 150 ° C., the absolute value of the rate of change after storage was 10 or less, indicating excellent color density stability over time. In Comparative Examples 1 to 6 using only an electron-accepting compound having a melting point> 150 ° C., the absolute value of the change rate of ΔE ^* after storage exceeded 10 and the color density greatly changed over time. The stability was low.

In Examples 5 to 8, in which stearamide was added as a desensitizer to the thermochromic compositions of Examples 1 to 4, the absolute values of the rate of change after storage were all 10 or less, and excellent color density It showed stability over time. In Comparative Examples 7 to 12, in which stearamide was added as a desensitizing agent to the thermochromic compositions of Comparative Examples 1 to 6, the absolute values of the rate of change of ΔE ^* after storage all exceeded 10. Over time, the color density changed greatly and the stability was low.

Examples 9 to 15 in which two types of electron accepting compounds having a melting point ≦ 150 ° C. were used in combination, or an electron accepting compound having a melting point ≦ 150 ° C. and an electron accepting compound having a melting point> 150 ° C. were used as ΔE ^* after storage ^. The absolute values of the rate of change were 10 or less, indicating excellent color density stability over time. In Comparative Examples 13 to 17 in which two types of electron accepting compounds having melting points> 150 ° C. were used in combination, the absolute value of the change rate of ΔE ^* after storage exceeded 10 and the color density increased with time. Changed and less stable.

In Examples 16 to 18, in which two types of electron-accepting compounds having a melting point ≦ 150 ° C. and one type of electron-accepting compound having a melting point> 150 ° C. were used in combination, the absolute value of the change rate of ΔE ^* after storage was All were 10 or less and showed excellent color density stability over time. In Comparative Example 18 in which three types of electron accepting compounds having melting points> 150 ° C. were used in combination, the absolute value of the rate of change of ΔE ^* after storage exceeded 10, and the color density greatly changed over time and was stable. The sex was low.

In Examples 20-22 and 24-26, in which a developer having a melting point ≦ 150 ° C. was used alone or in combination of two, and an ultraviolet absorber was added, the absolute value of the change rate of ΔE ^* after storage was 10 or less. Yes, it showed excellent color density stability over time. In Comparative Example 20 using a developer having a melting point> 150 ° C. and adding a UV absorber, the absolute value of the rate of change of ΔE ^* after storage exceeds 10, and the color density increases with time. Changed and less stable. In Example 23 in which two kinds of electron-donating color-forming organic compounds were used in combination and an electron-accepting compound having a melting point ≦ 150 ° C. was used, the absolute value of the change rate of ΔE ^* after storage was 10 or less. Excellent color density stability over time was exhibited. In Comparative Example 19 in which two kinds of electron-donating color-forming organic compounds were used in combination and an electron-accepting compound having a melting point> 150 ° C. was used, the absolute value of the change rate of ΔE ^* after storage exceeded 10 and the time As time passed, the color density changed greatly and the stability was low.

Examples 27 to 34 in which a thermochromic composition (Examples 1, 3, 5, 7, 23 to 26) having good color density stability with time was microencapsulated had a change rate of ΔE ^* after storage. The absolute values of these were all 10 or less, indicating excellent color density stability over time. In Comparative Examples 21 to 24, in which the thermochromic compositions of Comparative Examples 5, 11, 19, and 20 were microencapsulated, the absolute values of the rate of change of ΔE ^* after storage all exceeded 10, As time passed, the color density changed greatly and the stability was low.

  The thermochromic composition of the present invention can be reversibly discolored and has excellent color density stability over time, so that it can be used for textiles, inks, paints, ceramics, glass products, plastic moldings, packaging materials, Can be used as a colorant for imparting reversible thermochromic properties to recording materials and printed matter

Claims (4)

It contains an electron-donating color-forming organic compound, an electron-accepting compound, and a desensitizer. The electron-accepting compound is represented by any one of the following general formulas (1) to (3) and has a melting point of 150 ° C. or lower. A thermochromic composition comprising one or more compounds which are:

(In the general formulas (1) to (3), R ₁ and R ₂ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a phenyl group, or a cyclohexyl group; , Y and Z are each independently a halogen, an OH group, an alkoxy group, an alkoxyallyl group, an allyl group, a linear or branched alkyl group having 1 to 4 carbon atoms, a phenyl group, or a cyclohexyl group; Is a C5-C8 cycloalkane which may have a substituent or a fluorene ring which may have a substituent.   The thermochromic composition according to claim 1, comprising 2,2'-diallyl-4,4'dihydroxydiphenylsulfone or 4-hydroxy-4'-isopropoxydiphenylsulfone as the electron-accepting compound.   The heat according to claim 1 or 2, further comprising at least one compound represented by any one of the general formulas (1) to (3) and having a melting point higher than 150 ° C as the electron-accepting compound. Discoloring composition.   A thermochromic microcapsule containing the thermochromic composition according to any one of claims 1 to 3.