Application of a fluoran-based discoloring dye in improving material's resistance to sunlight

Abstract

The application discloses application of a fluorane-based discoloring dye in improving material light resistance, and belongs to the technical field of fine chemical industry.The application provides a series of fluorane-based discoloring dyes containing different electron-withdrawing groups, and the series of discoloring dyes has good light resistance performance.Therefore, the application mainly designs a fluorane dye containing electron-withdrawing substituents, that is, on the basis of an existing fluorane dye parent structure, electron-withdrawing groups such as nitro, fluorine, chlorine, bromine and iodine are introduced, the electron-withdrawing performance of the electron-withdrawing groups is utilized, the electron cloud distribution state of the dye molecular structure is changed, and the light resistance performance is improved.

Description

TECHNICAL FIELD

[0001] The application relates to application of a fluorane-based color-changing dye to improving the sunlight resistance of materials and belongs to the technical field of fine chemical industry. BACKGROUND

[0002] The thermochromic textile refers to a kind of functional textile material whose color changes with temperature. The temperature range is generally 15-70 DEG C. The color change can be used to monitor body temperature, health status, health care and safety warning in real time.

[0003] Among the thermochromic materials for thermochromic textiles, the fluorane-based leuco dye is considered to be the most promising thermosensitive material, which has the advantages of full color spectrum, high color sensitivity and good stability. However, under the irradiation of light, the thermosensitive dye is prone to oxidation and degradation, and loses the color developing and changing ability. Therefore, the main problem limiting its application in the field of functional textiles is poor light resistance.

[0004] Currently, in the aspect of improving the light resistance of colored textile materials, using anti-ultraviolet finishing agents to treat fabrics is the most common method. For example, in Chinese patent CN114808472A, Zhong Ziheng et al. used specific ultraviolet absorber monomers, structural monomers, and controlled their feeding ratio to prepare polymers with excellent ultraviolet absorption performance by solution polymerization according to a certain method. Then the polymers were coated onto the thermochromic fabric by solvent evaporation method to prepare light-resistant thermochromic fabric. For fluoran dyes, their light resistance is mainly related to their molecular structure. Methods for improving the light resistance of fluoran dyes by designing their molecular structure have been reported in articles. For example, the article Dyes and Pigments 197 (2022) 109924 reported a fluoran dye with good light resistance, which mainly introduced long alkyl chains into the dye molecular structure to change the dye molecular aggregation state and improve its light resistance. In addition, it has been reported that the introduction of electron-withdrawing groups into the dye molecular structure is beneficial to the improvement of its light resistance. For example, in Chinese patent CN202210370546.0, the introduction of polar carboxylate and cyano groups into the dye structure improves the affinity of the dye for polyester fibers and absorbs ultraviolet light, thereby improving the light fastness and color fastness of the dye, and also has excellent alkali washability. In patent CN202010330698.9, a light-resistant and easy-to-wash red azo disperse dye was prepared, which contains cyano and carboxylate groups in its molecular structure, thereby improving the light resistance of the dye molecule. In summary, by using ultraviolet absorbing finishing agents, changing the aggregation state of fluoran dye molecules, and other methods, the light resistance of fluoran dyes and related materials has been improved to some extent. However, after treating fabrics with existing fluoran dye color-changing systems, the colored fabrics have short light resistance time and poor durability, losing their color and color-changing ability after being exposed to sunlight for a week, and still cannot meet the requirements of long-term outdoor use. SUMMARY

[0005]

TECHNICAL PROBLEM

[0006] The existing fluoran dye color-changing system for treating fabrics has short light resistance time and poor durability, losing its color and color-changing ability after being exposed to sunlight for a week, and still cannot meet the requirements of long-term outdoor use.

[0007]

TECHNICAL SCHEME

[0008] In order to solve the problem of poor sunlight resistance of dye molecules, the application provides a series of fluoran-based reversible dyes containing different electron-withdrawing groups, and the series of reversible dyes exhibit good sunlight resistance. Therefore, the application mainly designs a fluoran dye containing electron-withdrawing substituents, that is, on the basis of the existing fluoran dye parent structure, electron-withdrawing groups such as nitro, fluorine, chlorine, bromine and iodine are introduced, the electron-withdrawing properties of the groups are utilized, the electron cloud distribution state of the dye molecular structure is changed, and the sunlight resistance is improved.

[0009] A first object of the application is to provide an application of a fluoran-based reversible dye in improving the sunlight resistance of materials, and the structure general formula of the fluoran-based reversible dye is as follows:

[0010]

[0011] Among them:

[0012] R5, R6, R8, R9, R 11 and R 12 Each is independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane and halogen;

[0013] R7 is independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl), chloro;

[0014] R 10 is independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl), N-cyclohexyl;

[0015] Optionally, 1-2 of R1, R2, R3 and R4 are electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl and substituted heterocycloalkyl; and the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl and carboxyl.

[0016] Preferably, R1, R2, R3 or R4 is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl and carboxyl.

[0017] In an embodiment of the application, the structure general formula of the fluoran-based reversible dye is as follows:

[0018]

[0019] Among them:

[0020] R5, R6, R7, R8, R9 and R 10each independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen;

[0021] Optionally, one or two of R1, R2, R3, and R4are an electron-withdrawing group, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; and the electron-withdrawing group is selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0022] Optionally, one or two of R1, R2, R3, and R4are an electron-withdrawing group, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; and the electron-withdrawing group is selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0023] Optionally, one or two of R1, R2, R3, and R4are an electron-withdrawing group, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; and the electron-withdrawing group is selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0024] A second object of the present application is to provide an application of the spiropyran-based color-changing dye in improving the material's resistance to sunlight, wherein the spiropyran-based color-changing dye has the following general structure:

[0025]

[0026] wherein:

[0027] R5, R6, R7, R8, R9, and R 10 each independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen;

[0028] R1, R2, R3, and R4are Cl.

[0029] In an embodiment of the present application, the material includes textile material, composite material, display material, sensing material, and painting material, etc.

[0030] In an embodiment of the present application, the textile material refers to fibers and fiber products, including fibers, yarns, fabrics, non-woven fabrics, and their composites.

[0031] A third object of the present application is to provide a method for improving the material's resistance to sunlight, wherein the method is to color the material by using the spiropyran-based color-changing dye as the color-changing microcapsule, wherein the spiropyran-based color-changing dye has the following general structure:

[0032]

[0033] wherein:

[0034] R5, R6, R8, R9, R 11 and R 12 each is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane, and halogen;

[0035] R7is independently selected from the group consisting of N,N-diethyl, methoxy, N,N-di(p-tolyl), chloro;

[0036] R 10 is independently selected from the group consisting of N,N-diethyl, methoxy, N,N-di(p-tolyl), N-cyclohexyl;

[0037] Optionally, one to two of R1, R2, R3, and R4are electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0038] In one embodiment of the present application, the fluoran-based color-changeable dye structure is of the general formula:

[0039]

[0040] wherein:

[0041] R5, R6, R7, R8, R9, and R 10 each is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen;

[0042] Optionally, one to two of R1, R2, R3, and R4are electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0043] Preferably, R1, R2, R3, or R4is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0044] Preferably, R1or R3is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0045] The fourth objective of this invention is to provide a method for improving the lightfastness of color-changing materials. This method involves coloring the material using microcapsules containing a fluorane-based color-changing dye as the chromophore. The general structural formula of the fluorane-based color-changing dye is as follows:

[0046]

[0047] In Formula III:

[0048] R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocyclic alkyl, substituted heterocyclic alkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino and halogen;

[0049] R1, R2, R3, and R4 are Cl.

[0050] In one embodiment of the present invention, the dyeing method involves mixing the fluorane color-changing dye as a color-changing microcapsule, a thickener, and a binder to form a thermochromic color paste; then, the thermochromic color paste is used to color the material via screen printing, so as to give the material color-changing properties while also having good color-changing durability.

[0051] In one embodiment of the present invention, the mass ratio of thickener, binder and microcapsules with fluorane color-changing dye as color-changing body in the thermochromic color paste is (1-5):(1-5):(70-90).

[0052] In one embodiment of the present invention, the material after screen printing is dried at 50-100°C to obtain a sun-resistant color-changing material.

[0053] In one embodiment of the present invention, the dyeing conditions are as follows: a thermochromic color paste is prepared by mixing and stirring a thickener (3%), a binder (3%), 80% of the color-changing dye as a color-changing microcapsule, and deionized water for 20 minutes. Cotton or polyester textiles are fixed on a table, and then screen-printed onto the fabric. The printed fabric is then dried in a 70°C oven and cured at 100°C for 2 minutes to obtain the color-changing fabric.

[0054] The fifth objective of this invention is to provide a method for preparing a sun-resistant color-changing material. The method involves coloring the material with fluorane-based color-changing dyes to obtain a color-changing material with sun-resistant properties. The general structural formula of the fluorane-based color-changing dyes is as follows:

[0055]

[0056] in:

[0057] R5, R6, R8, R9, R 11and R 12 each is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane, and halogen;

[0058] R7is independently selected from the group consisting of N,N-diethyl, methoxy, N,N-di(p-tolyl), chloro;

[0059] R 10 is independently selected from the group consisting of N,N-diethyl, methoxy, N,N-di(p-tolyl), N-cyclohexyl;

[0060] R1, R2, R3, and R4optionally 1-2 are electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; the electron- withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0061] In one embodiment of the present application, the fluoran-based color-changeable dye structure is of the general formula:

[0062]

[0063] wherein:

[0064] R5, R6, R7, R8, R9, and R 10 each is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen;

[0065] R1, R2, R3, and R4optionally 1-2 are electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; the electron- withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0066] Preferably, R1, R2, R3, or R4is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0067] Preferably, R1, R2, R3, or R4is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0068] Preferably, R1or R3is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0069] A sixth object of the present application is to provide a method for preparing a lightfast color-changing material, which is coloring a material with microcapsules of the fluorane-based color-changing dye as a color-changing body to obtain a color-changing material having lightfastness, the fluorane-based color-changing dye having the following general structure:

[0070]

[0071] In formula III:

[0072] R5, R6, R7, R8, R9, and R 10 each is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen;

[0073] R1, R2, R3, and R4 are Cl.

[0074] In one embodiment of the present application, the coloring method is using the thermochromic color paste of the microcapsules of the fluorane-based color-changing dye as a color-changing body, a thickening agent, and a binder mixed together; and then using the thermochromic color paste to color the material by silk screen printing to impart good color-changing and color-changing durability properties to the material.

[0075] In one embodiment of the present application, the mass ratio of the thickening agent, the binder, and the microcapsules of the fluorane-based color-changing dye as a color-changing body in the thermochromic color paste is (1-5):(1-5):(70-90).

[0076] In one embodiment of the present application, the material after silk screen printing is dried at 50-100°C to obtain a lightfast color-changing material.

[0077] In one embodiment of the present application, the material includes cotton fabric or polyester textile.

[0078] In one embodiment of the present application, the dyeing conditions are preparing a thermochromic color paste by blending and stirring a thickening agent (3%), a binder (3%), 80% of the microcapsules of the color-changing dye as a color-changing body, and deionized water for 20 min. The cotton fabric or polyester textile is fixed on a table, and then printed using silk screen printing technology. The printed fabric is dried in an oven at 70°C and cured at 100°C for 2 min to obtain a color-changing fabric.

[0079] In one embodiment of the present application, the microcapsules of the color-changing body are using the fluorane-based color-changing dye as a core material and a high-molecular polymer, inorganic particles, or inorganic particle-doped polymer as a wall material.

[0080] A seventh object of the present invention is to provide a lightfast color-changing material prepared according to the above method.

[0081] An eighth object of the present invention is to provide a product containing the above lightfast color-changing material.

[0082] A ninth object of the present invention is to provide a color-changing body microcapsule, which is a color-changing body microcapsule having a fluoran-based color-changing dye as a core material and a polymer, an inorganic particle or an inorganic particle-doped polymer as a wall material, the fluoran-based color-changing dye having the following general structure:

[0083]

[0084]

[0085] wherein:

[0086] R5, R6, R8, R9, R 11 and R 12 each independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane, and halogen;

[0087] R7is independently selected from the group consisting of N,N-diethyl, methoxy, N,N-di(p-tolyl), chloro;

[0088] R 10 is independently selected from the group consisting of N,N-diethyl, methoxy, N,N-di(p-tolyl), N-cyclohexyl;

[0089] optionally 1-2 of R1, R2, R3, and R4are electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl;

[0090] or,

[0091]

[0092] wherein:

[0093] R5, R6, R7, R8, R9, and R 10 each independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen;

[0094] R1, R2, R3 and R4 are optionally 1-2 of the group consisting of an electron- withdrawing group, and the remaining groups are selected from one or more of the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl and substituted heterocycloalkyl; the electron-withdrawing group is selected from one or more of the group consisting of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl and carboxyl;

[0095] or,

[0096]

[0097] wherein:

[0098] R5, R6, R7, R8, R9 and R 10 each is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino and halogen;

[0099] R1, R2, R3 and R4 are Cl.

[0100] In one embodiment of the present application, the microcapsule preparation method is prepared by in-situ polymerization.

[0101] In one embodiment of the present application, the high molecular polymer includes natural polymers (such as carbohydrates, proteins, waxes or lipids), wholly synthetic polymers, semi-synthetic polymers (such as cellulose derivatives), inorganic materials (such as layered double hydroxides, calcium carbonate and phosphate salts, etc.); the inorganic particles include nano titanium dioxide, nano zinc oxide, etc.

[0102] Advantages of the present application:

[0103] The present application optimizes the structure of commercialized fluorophore dyes, provides a preparation method of full color spectrum and good sunlight resistance fluorophore dyes, on the basis of maintaining the color development, color change sensitivity and color change fatigue resistance of the dyes, the sunlight resistance performance is improved, the sunlight resistance time is increased by 4-18 hours, which is increased by 40%-80%, solves the main problem of the application of the temperature-sensitive material in the functional textile field, expands the application field, and is conducive to economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0104] Figure 1 Synthesis route of symmetrical fluorophore color-changing dye;

[0105] Figure 2 Synthesis route of asymmetrical fluorophore color-changing dye;

[0106] Figure 3 Infrared spectrum of Example 3;

[0107] Figure 4 Mass spectrum of Example 3;

[0108] Figure 5 Structure of the fluoran chromic dye of Example 3-;

[0109] Figure 6 Structure of the fluoran chromic dye of the red color of the comparative example. DETAILED DESCRIPTION

[0110] The following describes the preferred embodiments of the present application, and it should be understood that the embodiments are for better explaining the present application, and are not used to limit the present application.

[0111] 1. Experimental materials

[0112] The monomers used in the examples are 4-bromophthalic anhydride and m-hydroxy-N,N-diethyl aniline, respectively, with CAS numbers of 86-90-8 and 91-68-9, purchased from Shanghai Maikelin Biotech Co., Ltd.; other chemicals are commercially available products.

[0113] 2. Test method

[0114] (1) Light fastness test of fluoran dye: the light fastness of the self-made dye phase change material was tested according to the American AATCC TM16 light fastness test standard, the color change was observed, the apparent depth (K / S value) was measured by UltraScanXE computer side color instrument, and then the average value was calculated. D65 light source was used in the test, and the observation angle was 10°.

[0115] (2) Fading rate: the chromic fabric was artificially simulated solar aging using a solar climate test machine, combined with the K / S value of the fabric at different solar times, and calculated according to the following formula,

[0116]

[0117] In the formula, K / S0is the K / S value of the fabric at the initial time, K / S t is the K / S value of the fabric after t hours.

[0118] Example 1: a symmetrical structure fluoran chromic dye with good light fastness and its synthesis method

[0119] Synthesis method of symmetrical structure fluoran chromic dye:

[0120] Under the protection of N2, the appropriate molar ratio of reactant 1 and reactant 2 and an appropriate amount of catalyst were added into a 50 mL three-necked flask, mechanical stirring was continued, the temperature was raised to 160℃, and the reaction was continued for 3 hours, and TLC detection was continued during the reaction. After the reaction was completed, the solid was broken, the solid was washed twice with hot saturated brine, and then an appropriate amount of sodium hydroxide (10%) solution was ultrasonically dissolved, and then 20% hydrochloric acid was added to neutralize, and then sodium sulfate was added to saturation, and then it was left to stand overnight to precipitate, and then it was suction filtered and vacuum dried to obtain a symmetrical fluoran dye.

[0121] wherein the above-mentioned reactant 1 is phthalic anhydride and its derivatives, such as 4-bromophthalic anhydride, 4-chlorophthalic anhydride, 4-nitrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, etc.; reactant 2 is m-hydroxy-N,N-diethyl aniline; the molar ratio between reactant 1 and reactant 2 is in the range of 1.5-2.5:1. The catalyst is one or more than one of di-ni oxide, zinc chloride, concentrated sulfuric acid, and methyl sulfonic acid, and the amount is in the range of 50% of the molar equivalent, and the synthesis route of the symmetrical structure fluoran variable color dye is as shown in Figure 1 .

[0122] Example 2: A synthesis method of an asymmetrical structure fluoran variable color dye with good light resistance

[0123] A synthesis method of an asymmetrical structure fluoran variable color dye with good light resistance, the method comprising the following steps:

[0124] Step (1): In an environment of nitrogen atmosphere, monomer 1 and monomer 2 were accurately weighed in an appropriate molar ratio and added into a three-necked flask, and then a solvent and a catalyst were added and refluxed for 4 hours. After the reaction was completed, the mixture was cooled to 50-60℃, and an appropriate amount of 35% NaOH aqueous solution was added to the mixture. Then the mixture was heated to 90℃, and kept for 6 hours. Finally, the mixture was poured into ice, and the obtained mixture was acidified with concentrated hydrochloric acid, and then the obtained mixture was left to stand at room temperature for 2 hours. The suspension was filtered, the solid was recrystallized from ethanol, and then the solid was dried to obtain intermediate 1.

[0125] Table 1 intermediate 1 and the R group in its structure

[0126]

[0127] Table 2 monomer 1 and the R group in its structure

[0128]

[0129] monomers 1 are m-hydroxy-N,N-diethyl aniline and PDS-1, etc., monomers 2 are 4-bromophthalic anhydride, 4-chlorophthalic anhydride, 4-nitrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, etc.; the solvent is one or more than one of toluene / xylene / chlorobenzene / propionic acid / methyl sulfonic acid; the molar ratio between the anhydride and the aniline is in the range of 1-1.5:1, the catalyst is one or more than one of manganese dioxide, zinc chloride, concentrated sulfuric acid, methyl sulfonic acid, and the amount used is in the range of 50% of the molar equivalent of the reaction;

[0130] Step (2): Intermediate 1 and monomer 3 are weighed in a molar ratio, stirred uniformly in a solvent, and after the catalyst is added dropwise, the mixture is heated to reflux temperature for about 5 h, and the generated water is removed during the process. After the reaction is completed, the organic phase is concentrated, and the residue is recrystallized with ethanol to obtain the target product 2, an asymmetric fluoran-based light-fast dye.

[0131] Table 3 Monomer 3 and the R group in its structure

[0132]

[0133] monomers 1 are m-hydroxy-N,N-diethyl aniline and PDS-1, PDS-2, PDS-3, etc., the solvent is one or more than one of toluene / xylene / chlorobenzene / propionic acid / methyl sulfonic acid; the molar ratio between intermediate 1 and monomer 3 is in the range of 1-1.5:1. The catalyst is one or more than one of manganese dioxide, zinc chloride, concentrated sulfuric acid, methyl sulfonic acid, and the amount used is in the range of 50% of the molar equivalent of the reaction. The synthesis route of the asymmetric fluoran-based color-changing dye is shown in Figure 2 .

[0134] Example 3: Synthesis and purification of fluoran color-changing dye red 1

[0135] According to the synthesis operation steps described in the symmetric fluoran dye, 4-bromophthalic anhydride and m-hydroxy-N,N-diethyl aniline in a molar ratio of 1:3 are added to a 50 mL three-necked flask under N2 protection, and 50% mol equivalent of the catalyst for 4-bromophthalic anhydride is added. Continuous mechanical stirring is performed, and the temperature is raised to 160°C. The reaction is carried out for 3 h, and TLC detection is performed during the reaction. After the reaction is completed, the solid is broken, and the solid is washed twice with hot saturated brine. After the catalyst is removed by dissolving in methanol and filtering, the organic phase is concentrated by rotary evaporation. The mass of the dye added: the mass of the silica = 1:3. The silica column chromatography powder is stirred uniformly, dried by rotary evaporation, and purified by column chromatography to obtain red 1, which is characterized by infrared and mass spectrometry.

[0136] Example 4: Synthesis and purification of fluoran color-changing dye red 2

[0137] Red 2 can be obtained by adjusting the reactant 2 to 4-chlorophthalic anhydride according to the synthesis method in Example 3.

[0138] Example 5: Synthesis and purification of fluoran color change dye Red 3

[0139] Red 3 can be obtained by adjusting the reactant 2 to tetrabromophthalic anhydride according to the synthesis method in Example 3.

[0140] Example 6: Synthesis and purification of fluoran color change dye Red 4

[0141] Red 4 can be obtained by adjusting the reactant 2 to tetrachlorophthalic anhydride according to the synthesis method in Example 3.

[0142] Example 7: Synthesis and purification of fluoran color change dye Red 5

[0143] Red 5 can be obtained by adjusting the reactant 2 to 4-nitrophthalic anhydride according to the synthesis method in Example 3.

[0144] Example 8: Synthesis and purification of fluoran color change dye Red 6

[0145] Red 6 can be obtained by adjusting the reactant 2 to 4-cyanophthalic anhydride according to the synthesis method in Example 3.

[0146] Example 9: Synthesis and purification of fluoran color change dye Yellow 1

[0147] According to the synthesis procedure described in the symmetrical fluoran dye, 4-bromophthalic anhydride and m-methoxyphenol in a molar ratio of 1:2 were added to a 50 mL three-necked flask under N2 protection, and 50% mol equivalent of catalyst for 4-bromophthalic anhydride was added, mechanical stirring was continued, the temperature was raised to 160°C, and the reaction was carried out for 3 h, and TLC detection was continuously performed during the reaction. After the reaction was completed, the solid was broken, the solid was washed twice with hot saturated brine, and after the catalyst was removed by dissolving in methanol and filtering, the organic phase was concentrated by rotary evaporation. The mass of the dye: the mass of silica = 1:2 of silica column chromatography powder was stirred evenly, dried by rotary evaporation, and purified by column chromatography to obtain Yellow 1.

[0148] Example 10: Synthesis and purification of fluoran color change dye Yellow 2

[0149] Yellow 2 can be obtained by adjusting the reactant 2 to 4-chlorophthalic anhydride according to the synthesis method in Example 9.

[0150] Example 11: Synthesis and purification of fluoran color change dye Yellow 3

[0151] Yellow 3 can be obtained by adjusting the reactant 2 to tetrabromophthalic anhydride according to the synthesis method in Example 9.

[0152] Example 12: Synthesis and purification of fluoran color change dye Yellow 4

[0153] Yellow 4 can be obtained by adjusting the reactant 2 to be tetra-chloro-phthalic anhydride according to the synthesis method in Example 9.

[0154] Example 13: Synthesis and purification of fluoran color change dye Yellow 5

[0155] Yellow 5 can be obtained by adjusting the reactant 2 to be 4-nitro-phthalic anhydride according to the synthesis method in Example 9.

[0156] Example 14: Synthesis and purification of fluoran color change dye Yellow 6

[0157] Yellow 6 can be obtained by adjusting the reactant 2 to be 4-cyano-phthalic anhydride according to the synthesis method in Example 9.

[0158] Example 15: Synthesis and purification of fluoran color change dye Blue 1

[0159] According to the synthesis procedure described in symmetrical fluoran dyes, 4-bromo-phthalic anhydride and m-hydroxy-N,N-di-p-tolyl aniline were added into a 50 mL three-necked flask with a molar ratio of 1:2 under N2 protection, and 50% mol equivalent of catalyst for 4-bromo-phthalic anhydride was added, mechanical stirring was continued, the temperature was raised to 160°C, and the reaction was carried out for 3 h, and TLC detection was continuously carried out during the reaction. After the reaction was completed, the solid was broken, the solid was washed twice with hot saturated brine, and after the catalyst was removed by dissolving in methanol and filtering, the organic phase was concentrated by rotary evaporation. The mass of the dye: the mass of silica = 1:3 of silica column chromatography powder was stirred evenly, dried by rotary evaporation, and Blue 1 was obtained by column chromatography separation and purification.

[0160] Example 16: Synthesis and purification of fluoran color change dye Blue 2

[0161] Blue 2 can be obtained by adjusting the reactant 2 to be 4-chloro-phthalic anhydride according to the synthesis method in Example 15.

[0162] Example 17: Synthesis and purification of fluoran color change dye Blue 3

[0163] Blue 3 can be obtained by adjusting the reactant 2 to be tetra-bromo-phthalic anhydride according to the synthesis method in Example 15.

[0164] Example 18: Synthesis and purification of fluoran color change dye Blue 4

[0165] Blue 4 can be obtained by adjusting the reactant 2 to be tetra-chloro-phthalic anhydride according to the synthesis method in Example 15.

[0166] Example 19: Synthesis and purification of fluoran color change dye Blue 5

[0167] Blue 5 can be obtained by following the synthetic procedure of Example 15 by adjusting the reactant 2 to 4-nitrophthalic anhydride.

[0168] Example 20: Synthesis and purification of fluoran color changeable dye Blue 6

[0169] Blue 6 can be obtained by following the synthetic procedure of Example 15 by adjusting the reactant 2 to 4-cyanophthalic anhydride.

[0170] Example 21: Synthesis and purification of fluoran color changeable dye Black 1

[0171] Following the synthetic procedure described in asymmetric fluoran dyes, Step (1): m-Hydroxy-N,N-diethyl aniline and 4-bromophthalic anhydride were accurately weighed in a molar ratio of 1:2 in a three-necked flask under an atmosphere of nitrogen, followed by the addition of solvent and catalyst and refluxing for 4 hours. After completion of the reaction, the mixture was cooled to 50-60°C and 5 mL of 35% aqueous NaOH solution was added to the mixture. The mixture was then heated to 90°C and maintained for 6 hours. Finally, the mixture was poured into ice and the resulting mixture was acidified with concentrated hydrochloric acid and allowed to stand at room temperature for 2 hours. The suspension was filtered, the solid was recrystallized from ethanol and the solid was dried to obtain the intermediate 1-1.

[0172] Step (2): Intermediate 1 and ODB-1 were weighed in a molar ratio, stirred in a solvent and the catalyst was added dropwise. The mixture was then heated to reflux temperature for about 5 h, during which time the water formed was removed. After completion of the reaction, the organic phase was recovered with an appropriate amount of 25% concentrated solvent and the residue was recrystallized from ethanol to obtain Black 1.

[0173] Example 22: Synthesis and purification of fluoran color changeable dye Black 2

[0174] Black 2 can be obtained by following the synthetic procedure of Example 21 by adjusting the monomer 3 to 4-chlorophthalic anhydride.

[0175] Example 23: Synthesis and purification of fluoran color changeable dye Black 3

[0176] Black 3 can be obtained by following the synthetic procedure of Example 21 by adjusting the monomer 3 to tetrabromophthalic anhydride.

[0177] Example 24: Synthesis and purification of fluoran color changeable dye Black 4

[0178] Black 4 can be obtained by following the synthetic procedure of Example 21 by adjusting the monomer 3 to tetrachlorophthalic anhydride.

[0179] Example 25: Synthesis and purification of fluoran color changeable dye Black 5

[0180] Black 5 can be obtained by adjusting monomer 3 to 4-nitrophthalic anhydride following the synthetic procedure of Example 21.

[0181] Example 26: Synthesis and purification of fluoran color change dye Black 6

[0182] Black 6 can be obtained by adjusting monomer 3 to 4-cyanophthalic anhydride following the synthetic procedure of Example 21.

[0183] Example 27: Synthesis and purification of fluoran color change dye Green 1

[0184] Following the synthetic procedure described in asymmetric fluoran dyes, Step (1): m-Hydroxy-N,N-diethyl aniline and 4-bromophthalic anhydride were accurately weighed in a molar ratio of 1:1.5 in a three-necked flask under an atmosphere of nitrogen. Solvent and catalyst were then added and the mixture was refluxed for 4 hours. After the reaction was completed, the mixture was cooled to 50-60°C and 5 mL of 35% aqueous NaOH solution was added to the mixture. The mixture was then heated to 90°C and maintained for 6 hours. Finally, the mixture was poured into ice and the resulting mixture was acidified with concentrated hydrochloric acid and allowed to stand at room temperature for 2 hours. The suspension was filtered, the solid was recrystallized from ethanol and dried to obtain intermediate 1-1.

[0185] Step (2): Intermediate 1 and ODB-2 were weighed in a molar ratio of 1:1.5, stirred in a solvent and the catalyst was added dropwise. The mixture was then heated to reflux temperature for about 5 hours, during which time the water formed was removed. After the reaction was completed, the organic phase was recovered with an appropriate amount of 25% concentrated solvent and the residue was recrystallized from ethanol to obtain Green 1.

[0186] Example 28: Synthesis and purification of fluoran color change dye Green 2

[0187] Green 2 can be obtained by adjusting monomer 3 to 4-chlorophthalic anhydride following the synthetic procedure of Example 27.

[0188] Example 29: Synthesis and purification of fluoran color change dye Green 3

[0189] Green 3 can be obtained by adjusting monomer 3 to tetrabromophthalic anhydride following the synthetic procedure of Example 27.

[0190] Example 30: Synthesis and purification of fluoran color change dye Green 4

[0191] Green 4 can be obtained by adjusting monomer 3 to tetrachlorophthalic anhydride following the synthetic procedure of Example 27.

[0192] Example 31: Synthesis and purification of fluoran color change dye Green 5

[0193] Green 5 can be obtained by adjusting monomer 3 to 4-nitrophthalic anhydride following the synthetic procedure described in Example 27.

[0194] Example 32: Synthesis and purification of fluoran color change dye Green 6

[0195] Green 6 can be obtained by adjusting monomer 3 to 4-cyanophthalic anhydride following the synthetic procedure described in Example 27.

[0196] Example 33: Synthesis and purification of fluoran color change dye Orange 1

[0197] Following the synthetic procedure described in asymmetric fluoran dyes, Step (1): PSD-1 and 4-bromophthalic anhydride were accurately weighed in a 1:1 molar ratio in a three-necked flask under a nitrogen atmosphere, followed by the addition of solvent and catalyst and refluxing for 4 hours. After the completion of the reaction, the mixture was cooled to 50-60°C and an appropriate amount of 35% aqueous NaOH solution was added to the mixture. The mixture was then heated to 90°C and maintained for 6 hours. Finally, the mixture was poured into ice and the resulting mixture was acidified with concentrated hydrochloric acid and allowed to stand at room temperature for 2 hours. The suspension was filtered, the solid was recrystallized from ethanol and the solid was dried to obtain intermediate 1-3.

[0198] Step (2): Intermediate 1 and ODB-3 were weighed in a molar ratio, stirred in a solvent and the catalyst was added dropwise. The mixture was then heated to reflux temperature for about 5 hours, during which time the water formed was removed. After the completion of the reaction, the organic phase was recovered with an appropriate amount of 25% concentrated solvent and the residue was recrystallized from ethanol to obtain Orange 1.

[0199] Example 34: Synthesis and purification of fluoran color change dye Orange 2

[0200] Orange 2 can be obtained by adjusting monomer 3 to 4-chlorophthalic anhydride following the synthetic procedure described in Example 33.

[0201] Example 35: Synthesis and purification of fluoran color change dye Orange 3

[0202] Orange 3 can be obtained by adjusting monomer 3 to tetrabromophthalic anhydride following the synthetic procedure described in Example 33.

[0203] Example 36: Synthesis and purification of fluoran color change dye Orange 4

[0204] Orange 4 can be obtained by adjusting monomer 3 to tetrachlorophthalic anhydride following the synthetic procedure described in Example 33.

[0205] Example 37: Synthesis and purification of fluoran color change dye Orange 5

[0206] Orange 5 can be obtained by adjusting monomer 3 to be 4-nitrophthalic anhydride according to the synthesis method in Example 33.

[0207] Example 38: Synthesis and purification of fluoran color-changing dye Orange 6

[0208] Orange 6 can be obtained by adjusting monomer 3 to be 4-cyanophthalic anhydride according to the synthesis method in Example 33.

[0209] Example 39: Fluoran color-changing dye

[0210] Red fluoran dyes 1'-17' can be obtained by adjusting reactant 2 according to the method in Example 3, and the specific structural formula is shown in the table, wherein R5, R6, R7, R8, R9 and R 10 are hydrogen, and R1, R2, R3 and R4 are selected from different substituents, respectively.

[0211] Table 4 Relationship between red fluoran dyes and R groups in their structures

[0212]

[0213] Example 40: A color-changing microcapsule

[0214] A method for preparing a color-changing microcapsule, comprising the following steps:

[0215] (1) Preparation of a prepolymer: a solution of urea and formaldehyde with a molar ratio of 1:1 is placed in a three-necked flask, and after the urea is dissolved by stirring, triethanolamine is added dropwise to adjust the pH value to 8.5, slowly heated to 75°C, and kept at constant temperature for 1 h to obtain a viscous transparent urea-formaldehyde prepolymer;

[0216] (2) Dispersion of the capsule core: the capsule core used is a thermosensitive dye compound, and the color former: color developer: solvent (mass ratio) = 1:4:40, wherein the solvent tetradecanol: hexadecanol = 4:6. A certain amount of capsule core and water are placed in a three-necked flask, emulsified and dispersed at 1500 r / min for 0.5-1 h under a 70°C water bath, and then transferred into a 20°C water bath for continuous dispersion for 1-0.5 h to form an O / W emulsion;

[0217] (3) Microencapsulation and post-treatment: the prepolymer and the emulsion are mixed in a ratio of 7:1, 0.5wt% of sodium chloride and silicon dioxide are added and uniformly mixed in a mass ratio of 1-2:1, and fully stirred to dissolve. Slowly add acetic acid to adjust the pH to 2.5 at 35°C. Continue to react for 1 h, then heat to 65°C and continue to react for 30 min, cool to room temperature, wash, filter and dry to obtain the microcapsule.

[0218] Example 41: A method for preparing a light-fast color-changing fiber

[0219] The leuco dyes synthesized in Example 3 to Example 39 were used to prepare the thermochromic microcapsules according to the procedure described in Example 40. The thermochromic microcapsules were used to dye cotton fabric. The dyeing procedure was as follows: a thermochromic paste was prepared by mixing thickener (3%), binder (3%), 80% thermochromic microcapsules and deionized water for 20 min. The cotton fabric was fixed and then printed using silk screen printing technique. The printed fabric was dried in an oven at 70°C and cured at 100°C for 2 min to obtain the thermochromic fabric.

[0220] Example 42: A method for preparing a lightfast thermochromic fabric

[0221] The leuco dyes synthesized in Example 3 to Example 39 were used to prepare the thermochromic microcapsules according to the procedure described in Example 40. The thermochromic microcapsules were used to dye polyester fabric. The dyeing procedure was as follows: a thermochromic paste was prepared by mixing thickener (3%), binder (3%), 80% thermochromic microcapsules and deionized water for 20 min. The polyester fabric was fixed and then printed using silk screen printing technique. The printed fabric was dried in an oven at 70°C and cured at 100°C for 2 min to obtain the thermochromic fabric.

[0222] The leuco dyes synthesized in Example 3 to Example 39 were used to prepare the thermochromic microcapsules according to the procedure described in Example 40. The thermochromic microcapsules were used to dye polyester fabric. The dyeing procedure was as follows: a thermochromic paste was prepared by mixing thickener (3%), binder (3%), 80% thermochromic microcapsules and deionized water for 20 min. The polyester fabric was fixed and then printed using silk screen printing technique. The printed fabric was dried in an oven at 70°C and cured at 100°C for 2 min to obtain the thermochromic fabric.

[0223] The leuco dyes synthesized in Example 3 to Example 39 were used to prepare the thermochromic microcapsules according to the procedure described in Example 40. The thermochromic microcapsules were used to dye polyester fabric. The dyeing procedure was as follows: a thermochromic paste was prepared by mixing thickener (3%), binder (3%), 80% thermochromic microcapsules and deionized water for 20 min. The polyester fabric was fixed and then printed using silk screen printing technique. The printed fabric was dried in an oven at 70°C and cured at 100°C for 2 min to obtain the thermochromic fabric.

[0224] The leuco dyes synthesized in Example 3 to Example 39 were used to prepare the thermochromic microcapsules according to the procedure described in Example 40. The thermochromic microcapsules were used to dye polyester fabric. The dyeing procedure was as follows: a thermochromic paste was prepared by mixing thickener (3%), binder (3%), 80% thermochromic microcapsules and deionized water for 20 min. The polyester fabric was fixed and then printed using silk screen printing technique. The printed fabric was dried in an oven at 70°C and cured at 100°C for 2 min to obtain the thermochromic fabric.

[0225] According to the synthesis procedure described in symmetric fluoran dye, under N2 protection, 50 mL three-necked flask was added with proper molar ratio of 4-amino phthalic anhydride and meta-hydroxy-N,N-diethyl aniline, and proper amount of catalyst was added, mechanical stirring was continued, temperature was raised to 160°C, reaction was carried out for 3 h, and TLC detection was continuously carried out during the reaction. After the reaction was completed, the solid was broken, the solid was washed with hot saturated brine twice, and after the catalyst was removed by dissolving with methanol and filtering, the organic phase was concentrated by rotary evaporation. Proper amount of silica column chromatography powder was added, stirring was uniform, rotary evaporation was carried out for drying, and purification by column chromatography separation was carried out to obtain 5-amino fluoran dye.

[0226] Cotton fabric was dyed with 5-amino fluoran dye, and the dyeing conditions were the same as in Example 41. The test results are shown in Table 8 below, and the results show that the light fastness of the example is obviously better than that of the comparative example.

[0227] Comparative Example 3-Comparative Example 5

[0228] Referring to the method of Example 3, red fluoran dye was obtained by adjusting the reactant 2, and the specific structural formula is shown in the table, wherein R5, R6, R7, R8, R9 and R 10 are hydrogen, and R1, R2, R3 and R4 are respectively selected from different substituents.

[0229] The dyes of the examples and comparative examples were dyed on cotton fabric, and the dyeing conditions were the same as in Example 41. The test results are shown in the table below, and the results show that the light fastness of the example is obviously better than that of the comparative example. The light fastness of the dye was compared. Under the same conditions in the light fastness tester, the commercial dye (Comparative Example 1) had a color fading rate of 31.8% when exposed to sunlight for 8 h, while the dye with good light fastness synthesized in Example 7 had a color fading rate of 8.3% in the same time, and the light fastness was improved by 23.5%.

[0230] The performance of the leuco dyes obtained in the examples and comparative examples was tested, and the test results are shown in Tables 7-8 below:

[0231] Table 5 Relationship between red fluoran dye and R group in its structure (comparative example)

[0232]

[0233] Table 6 Relationship between color of new fluoran dye and R group in its structure

[0234]

[0235]

[0236] Table 7 Light fastness performance test of red fluoran dye in Example 39

[0237]

[0238]

[0239] Table 8: Xanthenes dye weatherability test

[0240]

[0241]

[0242] The results show that when R1, R2, R3, and R4 are each independently selected from different electron-withdrawing substituents; when R1 and R3 are each independently selected from different electron-withdrawing substituents, the weatherability of the dye is improved accordingly. Preferably, R5, R6, R7, R8, R9, and R10 are each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen; and R1, R2, R3, and R4 are each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen; and R1, R2, R3, and R4 are each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; and the electron-withdrawing group is selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl. 10 each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen; and R1, R2, R3, and R4 are each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, and substituted heterocycloalkyl; and the electron-withdrawing group is selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0243] Further preferably, R1, R2, R3, or R4 is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0244] Further preferably, R1 or R3 is selected from one of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid group, formyl, acyl, and carboxyl.

[0245] While the application has been disclosed by reference to the preferred embodiments thereof, a worker skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the application. Accordingly, the proper scope of the application is to be interpreted in light of the appended claims and their equivalents.

Claims

1. The application of a fluorane-based color-changing dye in improving the sunlight resistance of textile materials, composite materials, display materials, sensor materials, or painting materials, characterized in that, The general structural formula of the fluorane-based color-changing dyes is as follows: Formula I in: R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, alkenyl, heterocyclic alkyl, acylamino, and halogen; One or two of R1, R2, R3 and R4 are selected as electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, alkenyl and heterocyclic alkyl; the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl and carboxyl.

2. The application according to claim 1, characterized in that, R1, R2, R3, or R4 is selected from one of the following: halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl, and carboxyl.

3. The application according to claim 1 or 2, characterized in that, R1 or R3 is selected from one of the following groups: halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl, and carboxyl.

4. The application of a fluorane-based color-changing dye in improving the sunlight resistance of textile materials, composite materials, display materials, sensor materials, or painting materials, characterized in that, The general structural formula of the fluorane-based color-changing dyes is as follows: Formula III in: R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, alkenyl, heterocyclic alkyl, acylamino, and halogen; R1, R2, R3, and R4 are Cl.

5. The application according to claim 1 or 4, characterized in that, The textile materials refer to fibers and fiber products, including fibers, yarns, fabrics, nonwovens and their composites.

6. A method for improving the sun resistance of color-changing textile materials, composite materials, display materials, sensor materials, or painting materials, characterized in that, The method involves coloring materials using microcapsules containing fluorane-based color-changing dyes as chromosomes. The general structural formula of the fluorane-based color-changing dyes is as follows: Formula I in: R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, alkenyl, heterocyclic alkyl, alkoxy, acylamino, and halogen; One or two of R1, R2, R3 and R4 are selected as electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, alkenyl and heterocyclic alkyl; the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl and carboxyl.

7. The method according to claim 6, characterized in that, R1, R2, R3, or R4 is selected from one of the following: halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl, and carboxyl.

8. The method according to claim 6, characterized in that, R1 or R3 is selected from one of the following groups: halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl, and carboxyl.

9. A method for improving the sun resistance of color-changing textile materials, composite materials, display materials, sensor materials, or painting materials, characterized in that, The method involves coloring materials using microcapsules containing fluorane-based color-changing dyes as chromosomes. The general structural formula of the fluorane-based color-changing dyes is as follows: Formula III In Formula III: R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, alkenyl, heterocyclic alkyl, acylamino, and halogen; R1, R2, R3, and R4 are Cl.

10. The method according to any one of claims 6-9, characterized in that, The coloring process involves mixing fluorescein-based color-changing dyes as color-changing microcapsules, thickeners, and binders to form a thermochromic color paste; then, the thermochromic color paste is used to color the material via screen printing to impart color-changing properties and color-changing durability to the material.

11. A method for preparing a sun-resistant color-changing textile material, composite material, display material, sensing material, or painting material, characterized in that, The method involves coloring materials using microcapsules containing fluorane-based color-changing dyes as chromophores to obtain color-changing materials with lightfastness. The general structural formula of the fluorane-based color-changing dyes is as follows: Formula I in: R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, alkenyl, heterocyclic alkyl, acylamino, and halogen; One or two of R1, R2, R3 and R4 are selected as electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, alkenyl and heterocyclic alkyl; the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl and carboxyl.

12. The method according to claim 11, characterized in that, R1, R2, R3, or R4 is selected from one of the following: halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl, and carboxyl.

13. The method according to claim 11, characterized in that, R1 or R3 is selected from one of the following groups: halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl, and carboxyl.

14. A method for preparing a sun-resistant color-changing textile material, composite material, display material, sensing material, or painting material, characterized in that, The method involves coloring materials using microcapsules containing fluorane-based color-changing dyes as chromophores to obtain color-changing materials with lightfastness. The general structural formula of the fluorane-based color-changing dyes is as follows: Formula III In Formula III: R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, alkenyl, heterocyclic alkyl, acylamino, and halogen; R1, R2, R3, and R4 are Cl.

15. The method according to any one of claims 11-14, characterized in that, The coloring method includes: mixing chromogenic microcapsules, thickeners and binders to form a thermochromic color paste; then using screen printing to dye the material with the thermochromic color paste to obtain a sun-resistant color-changing material.

16. The method according to claim 15, characterized in that, The mass ratio of thickener, binder, and microcapsules containing the fluorane-based color-changing dye in the thermochromic paste is 1-5:1-5:70-90.

17. The method according to claim 15, characterized in that, The material after screen printing is dried at 50-100℃ to obtain a sun-resistant color-changing material.

18. The method according to claim 11 or 14, characterized in that, Textile materials include cotton fabrics or polyester textiles.

19. The method according to claim 6, 9, 11 or 14, characterized in that, The chromosome microcapsules use fluorane-based chromosome dyes as the core material and high-molecular polymers, inorganic particles, or polymers doped with inorganic particles as the wall material.

20. A sun-resistant color-changing textile material, composite material, display material, sensing material, or painting material prepared by the method according to any one of claims 11-19.

21. A product comprising the sun-resistant color-changing textile material, composite material, display material, sensing material, or painting material as described in claim 20.

22. A chromotropic microcapsule, characterized in that, The chromosome microcapsules use fluorane-based chromosome dyes as the core material and polymers, inorganic particles, or polymers doped with inorganic particles as the wall material. The general structural formula of the fluorane-based chromosome dyes is as follows: Formula I in: R5, R6, R7, R8, R9 and R 10 Each is independently selected from hydrogen, alkyl, alkenyl, heterocyclic alkyl, alkoxy, acylamino, and halogen; One or two of R1, R2, R3 and R4 are selected as electron-withdrawing groups, and the remaining groups are selected from one or more of hydrogen, alkyl, alkenyl and heterocyclic alkyl; the electron-withdrawing groups are selected from one or more of halogen, nitro, cyano, tertiary amine cation, trihalomethyl, sulfonic acid, formyl, acyl and carboxyl.

23. The chromotropic microcapsule according to claim 22, characterized in that, The microcapsules were prepared by in-situ polymerization.

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