Photosensitive discoloring nanometer microsphere material and preparation method thereof

Abstract

The application discloses a photosensitive color-changing nanomicrosphere material and a preparation method thereof. The material is a core-shell structure, the inner core of which is composed of nanocrystalline grains of two spiropyran compounds represented by formula (a) and formula (b), and the outer shell is coated with modified acrylate material; the mass ratio of the inner core to the outer shell is (1-2):(3-5), and the microsphere particle size is 7-15 nm. The photosensitive color-changing nanomicrosphere can respectively change the red and green color under the conditions of ultraviolet and visible light, and effectively filter light of specific wavelengths. The photosensitive color-changing nanomicrosphere can be applied to color correction optical components, play a role of filtering complementary colors, improve the accuracy and saturation of color, and improve the color discrimination ability, and has a remarkable effect in color correction. Wherein R=C 16 H 33 ; wherein R=C 16 H 33 .

Description

Technical Field

[0001] This invention relates to the field of photosensitive color-changing nanomaterials technology, specifically to a photosensitive color-changing nanocomposite microsphere material containing a composite spiropyran compound and its preparation method. Background Technology

[0002] With the rapid development of modern technology, the demand for materials with special properties is increasing. Photochromic materials, as special materials that change color under illumination of specific wavelengths of light, have attracted widespread attention. In many fields, such as optical devices, sensors, and anti-counterfeiting labels, photochromic materials have demonstrated enormous application potential.

[0003] Traditional photochromic materials face numerous challenges in practical applications. Firstly, they exhibit poor stability, easily decomposing and fading under prolonged use or exposure to various environmental factors, significantly limiting their lifespan and application range. For instance, in outdoor environments, changes in light intensity, temperature, and humidity can cause a rapid decline in the performance of photochromic materials. Secondly, color change typically occurs under ultraviolet light irradiation, such as changing from colorless to red, blue, or gray. Color change under visible light is more difficult, especially the integrated control of color-changing properties between two different spiropyran compounds—achieving specific alternating red and green colors under different lighting conditions—which presents considerable challenges. Summary of the Invention

[0004] The purpose of this invention is to provide a photosensitive color-changing nanocomposite microsphere material and its preparation method. This material is a core-shell structured nanosphere, with its core composed of nanocrystals of two different spiropyran compounds of formulas (a) and (b), and its outer shell coated with a modified acrylate material. The mass ratio of the core to the shell is (1-2):(3-5). The outer diameter of the nanosphere is 7-15 nm, the diameter of the spiropyran core is 4-9 nm, and the thickness of the shell is 1.5-3 nm. The two spiropyran compounds can undergo red-green color changes under ultraviolet and visible light conditions, effectively filtering light of specific wavelengths. It can be applied to color correction optical components, acting as a filter and color complement, enhancing the purity of the red-green spectral color and the dimension of the color perception vector space through complementary and synergistic color changes. This adjusts the color balance of light entering the eye or optical components, avoiding visual fatigue caused by prolonged use of a single color, improving color accuracy and saturation, and enhancing color discrimination ability, demonstrating a significant effect in color correction.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] A photosensitive color-changing nanosphere material has a core-shell structure. Its core is composed of nanocrystals of two spiropyran compounds as shown in formula (a) and formula (b), and its shell is coated with a modified acrylate material. The mass ratio of the core to the shell is (1-2):(3-5), and the microsphere particle size is 7-15 nm.

[0007] The modified acrylate material is polymerized from polyvinyl butyral and acrylate monomers or styrene monomers in a mass ratio of (0.5-1.5):(2-5).

[0008] The mass ratio of the two spiropyran compounds of formula (a) and formula (b) is 1:(0.3–3);

[0009]

[0010] Where R = C 16 H 33 ;

[0011]

[0012] Where R = C 16 H 33 .

[0013] In the photosensitive color-changing nanosphere material described above, preferably, the acrylate monomer is selected from at least one of styrene methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, epoxy acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methyl methacrylate, pentaerythritol tetraacrylate, ethoxylated nonylphenol acrylate, ethoxylated bisphenol A diacrylate, polyethylene glycol methacrylate, bisphenol A epoxy acrylate, bisphenol A-dimethicone glycidyl acrylate, triethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate.

[0014] In the photosensitive color-changing nanosphere material described above, preferably, the styrene monomer is selected from styrene or methylstyrene.

[0015] On the other hand, the present invention provides a method for preparing photosensitive color-changing nanocomposite microspheres as described above, the method comprising the following steps:

[0016] I. Preparation of the color-changing solution: Prepare a spiropyran color-changing solution by mixing spiropyran color-changing powder (a), spiropyran color-changing powder (b), and solvent in a mass ratio of (0.5-1.5):(0.5-1.5):(100-200);

[0017] II. Oil-phase color-changing solution: Polyvinyl butyral and acrylate monomers or styrene monomers are added to spiropyran color-changing solution to obtain oil-phase color-changing solution; wherein the mass ratio of polyvinyl butyral, spiropyran color-changing powder and acrylate monomers is (0.5~1.5):(0.5~1.5):(2~5);

[0018] III. Preparation of O / W type emulsion: Prepare an aqueous phase solution by mixing emulsifier and pure water at a mass ratio of (1-3):(200-500); homogenize and emulsify the aqueous phase solution and the oil phase solution to obtain an O / W type emulsion; wherein the mass ratio of the oil phase solution to the aqueous phase solution is (1-2):(1-3);

[0019] IV. Preparation of core-shell nanospheres: Carbodiimide crosslinking agent and initiator are added to O / W type emulsion, and the reaction is carried out at 25-40℃ for 15-40 minutes. Spiropyran crystal nuclei are coated in polyacrylate shell to form a nano core-shell structure. The temperature is raised to 45-65℃ for 6-12 hours for polymerization. After filtration, washing and drying, nanocolor-changing microsphere powder is obtained.

[0020] In the preparation method described above, preferably, the solvent in step I is selected from at least one of isopentane, n-hexane, n-pentane, cyclohexane, and petroleum ether.

[0021] In the preparation method described above, preferably, the emulsifier in step III is selected from non-foaming isomeric alcohol FT-625, diethyl phthalate, stearyl alcohol polyether-21, oleyl alcohol polyether-10, stearate ester PEG-100 and organosilicone oil emulsifiers.

[0022] In the preparation method described above, preferably, the organosilicone oil emulsifier is selected from at least one of dimethyl silicone oil emulsifier, polydimethylsiloxane PEG-3, polydimethylsiloxane PEG-10, organosilicone emulsifier KF-6038, and Shin-Etsu KF-6017 emulsifier from Japan.

[0023] In the preparation method described above, preferably, the carbodiimide crosslinking agent in step IV is selected from polyethylene glycol monomethyl ether MPEG350, N,N-dimethylethanolamine, carbodiimide CDI-1171, carbodiimide XL-701, and carbodiimide INV-2000; and its amount is 1-3 wt% of polyvinyl butyral.

[0024] In the preparation method described above, preferably, the initiator in step IV is selected from at least one of benzoyl peroxide, diisopropyl peroxide dicarbonate, and azobisisobutyronitrile, and its amount is 0.3 to 0.6 wt% of the amount of acrylate monomer or styrene monomer.

[0025] In one aspect, the present invention provides a spiropyran compound having the chemical structure shown in formula (a):

[0026]

[0027] Where R = C 16 H 33 .

[0028] In another aspect, the present invention provides a method for preparing a compound of formula (a), the method comprising the following steps:

[0029] Under I.N2 protection, 4-hydroxy-isophthalaldehyde was mixed with anhydrous ethanol and heated to reflux in an oil bath at 90–220 °C. An ethanol solution of 3,3-dimethyl-1′-hexadecyl-2-methyleneindole was added dropwise, and the reaction solution turned purple. The mixture was heated to reflux for 4–8 hours. After evaporating the ethanol, ether was added with stirring to completely dissolve the purple-red viscous substance. Water was then added with stirring, and the mixture was allowed to stand before separating the water. The ether and a small amount of water were evaporated again to remove the water, yielding a pale purple solid spiropyran compound c. The weight ratio of 4-hydroxy-isophthalaldehyde, 3,3-dimethyl-1′-hexadecyl-2-methyleneindole, and anhydrous ethanol was (0.5–1):(2–5):(20–50).

[0030]

[0031] II. Take an appropriate amount of the spiropyran compound C and malonylurea prepared in step I above and add them to a reaction vessel containing chloroform. Under N2 protection, stir until completely dissolved. Add a chloroform solution of pyridine dropwise. After heating the reactants to reflux in an oil bath, cool to room temperature, adjust the pH to neutral with dilute hydrochloric acid, wash twice with water, extract the organic layer, and evaporate to dryness to obtain a green solid powder. The weight ratio of malonylurea, spiropyran compound C, pyridine, and chloroform is (0.5–1):(0.7–1.5):(5–20):(50–150). The pyridine content in the pyridine solution is 3–5%.

[0032] The preparation method of the spiropyran compound (b) of the present invention can refer to the method described in patent ZL201711112631.2 "A Photochromic Optical Material".

[0033] This invention addresses the issue from four aspects: raw material selection and synthesis, nanocrystal preparation, coating process optimization, and color-changing performance control. Firstly, in terms of raw material selection, modified acrylate polymers are used, which can form chemical bonds or intermolecular forces with the surfaces of various materials. Furthermore, the presence of polar groups makes the modified acrylates more polarly compatible with spiropyran compounds, improving their compatibility and bonding strength with spiropyran nanocrystals. Simultaneously, it slows down the polymerization reaction rate, facilitating the formation of a uniform coating layer and thus enabling control over the uniformity of the coating layer. Secondly, in terms of nanocrystal preparation, the particle size and distribution are precisely controlled; and the reaction conditions during the coating process are strictly controlled, such as temperature, pressure, and reaction time. Finally, the color-changing performance is controlled and combined under different light conditions to overcome the shortcomings of traditional materials and meet the increasingly diverse application needs of materials.

[0034] The beneficial effects of this invention are as follows:

[0035] Firstly, the spiropyran compound (a) synthesized in this invention appears green under normal indoor light but becomes colorless after ultraviolet irradiation. Conversely, the spiropyran compound (b) appears colorless under normal indoor light but turns red after ultraviolet irradiation. The two color-changing compounds exhibit a significant complementary color effect. By precisely controlling the structure and optical properties of the materials, red and green colors can be complementary. Using these compounds to prepare optical materials can improve color accuracy and saturation, resulting in more realistic and vivid images.

[0036] Secondly, this material has excellent light filtering properties. When used to prepare optical materials, it can effectively filter light of specific wavelengths, adjust the color balance of light entering the eye or optical equipment, and in the calibration of optical components, the alternating red and green color enhancement can regulate the visual nerves and avoid visual fatigue caused by long-term use of a single color.

[0037] Third, it has wide applicability. The nanocrystal nuclei have uniform and controllable size, the modified shell is transparent and stable, and the optical properties are good. Moreover, the preparation process is simple, efficient, energy-saving, and low-pollution, and it has the characteristics of low dosage, low cost, and wide range of applications. Attached Figure Description

[0038] Figure 1 Infrared spectrum of spiropyran color-changing powder (a) prepared for Example 1.

[0039] Figure 2 The 1H NMR spectrum of the spiropyran color-changing powder (a) prepared for Example 1.

[0040] Figure 3 Transmission electron microscope image of the photosensitive color-changing nanocomposite microspheres prepared in Example 1.

[0041] Figure 4 The infrared spectrum of the photosensitive color-changing nanocomposite microspheres prepared in Example 1.

[0042] Figure 5 Absorption spectrum of spiropyran color-changing powder (a) prepared for Example 1.

[0043] Figure 6 Absorption spectrum of spiropyran color-changing powder (b) prepared for Example 1.

[0044] Figure 7 The absorption spectrum of the photosensitive color-changing nanocomposite microspheres prepared in Example 1 is shown. Detailed Implementation

[0045] The present invention will be further described below through specific embodiments, but this does not imply a limitation on the scope of protection of the present invention.

[0046] The spiropyran photochromic compounds in the following examples and comparative examples were prepared by the following method: Preparation Example 1

[0047] I. Preparation of spiropyran photochromic compounds (a)

[0048] Under N2 protection, 250 g of 4-hydroxy-isophthalaldehyde was mixed with 11 kg of anhydrous ethanol and heated to reflux in an oil bath at 180 °C. An ethanol solution containing 1400 g of 3,3-dimethyl-1′-hexadecyl-2-methyleneindole was added dropwise, and the reaction solution turned purple. The mixture was heated to reflux for 5.5 hours. After evaporating the ethanol, ether was added with stirring to completely dissolve the purple-red viscous substance. Water was then added with stirring, and the mixture was allowed to stand before separating the liquid to remove the water. The mixture was then evaporated to dryness to remove the ether and a small amount of water, yielding a pale purple solid spiropyran compound (c).

[0049] The specific reaction formula is as follows:

[0050]

[0051] B. Take 100g of compound (c) and 45g of malonylurea and add them to 8500g of chloroform. Under N2 protection, stir until completely dissolved. Add 920g of chloroform solution of pyridine dropwise. After heating the reaction mixture under reflux in an oil bath, cool it to room temperature, adjust the pH to neutral with a small amount of dilute hydrochloric acid, wash twice with water, extract the organic layer, and evaporate to dryness to obtain 127g of green solid powder, namely spiropyran photosensitive color-changing compound (a).

[0052] The specific reaction formula is as follows:

[0053]

[0054] Fourier transform infrared (FT-IR) spectroscopy was performed on the spiropyran photochromic compound (a) prepared in Preparation Example 1. The results are as follows: Figure 1 As shown. Figure 1Spectral analysis shows that 3395 cm -1 and 3250cm -1 The absorption peaks at 2919 and 2846 cm⁻¹ are caused by the stretching and bending vibrations of the amino group. -1 The absorption peak at 1640 cm⁻¹ is due to the stretching vibrations of the methyl and methylene groups; the absorption peak at 1460 cm⁻¹ is due to the stretching and bending vibrations of the amide carbonyl group; 1 The absorption peak at 1103 cm⁻¹ is caused by the stretching vibration of the carbon-carbon double bond. 1 The absorption peak is generated by the stretching vibration of CO.

[0055] 1H NMR (δ) analysis: The spiropyran photochromic compound (a) prepared in Preparation Example 1 was analyzed by 1H NMR spectroscopy, such as... Figure 2 As shown, 8.20 (s, 1H) represents a hydrogen atom on the double bond between malonylurea and the benzene ring; 8.07 (d, 1H), 7.53 (d, 1H), and 7.08 (d, 1H), with δ = 7.08–8.07 ppm, represent three hydrogen atoms on the connected benzene ring; 7.49 (d, 1H), 7.18 (t, 1H), and 6.85 (t, 1H), with δ = 6.85–7.49 ppm, represent three hydrogen atoms on the indole benzene ring; 1.622 (s, 6H) represents six hydrogen atoms on the two substituted methyl groups on the five-membered ring; 1.55 (multiple peak, 2H) represents two hydrogen atoms on the long chain position connected to the nitrogen atom; 1.26 (broad peak, 26H) represents hydrogen atoms on multiple methylene groups on the long chain; and 0.89 (t, 3H) represents three hydrogen atoms on the terminal methyl group of the long chain, which partially overlap.

[0056] II. Preparation of Spiropyran Photochromic Compounds (b)

[0057] A solution of 250 g of 2-hydroxy-1-naphthaldehyde in ethanol was heated in an oil bath to 60 °C under nitrogen protection and refluxed. A solution of 25 g of 3,3-dimethyl-1′-hexadecyl-2-methyleneindole in ethanol was added dropwise, and the mixture was refluxed for another 9 hours. The mixture was then cooled to room temperature, the solvent was evaporated, and the solution was concentrated to 40%. The solution was sealed and placed in an ice bath at -2 °C for 15 hours. The solution was then filtered, eluted, and dried to obtain the spiropyran photochromic compound (b).

[0058] Example 1: Preparation of photosensitive color-changing nanospheres

[0059] (1) Dissolve 2.5g of spiropyran color-changing powder (a) and 1.8g of spiropyran color-changing powder (b) in a mixed solvent of 45g of isopentane and 130g of petroleum ether to obtain a spiropyran solution.

[0060] (2) Add 4.2g of polyvinyl butyral and 14.5g of methyl methacrylate monomer to the above spiropyran solution to obtain an oil phase solution.

[0061] (3) Add 1.8g of organosilicon emulsifier KF-6038 to 650g of pure water, and homogenize and emulsify the aqueous phase solution and the oil phase solution to obtain an O / W type emulsion.

[0062] (4) Preparation of core-shell nanospheres: 0.07g of carbodiimide XL-701 and 0.06g of diisopropyl peroxide dicarbonate were added to the O / W type emulsion and reacted at 26℃ for 30 minutes. The spiropyran crystal nuclei were coated in the polyacrylate shell to form a nano core-shell structure. The temperature was raised to 55℃ for 10 hours for polymerization. After filtration, washing and drying, photosensitive color-changing nanosphere powder was obtained.

[0063] Structure and morphology examination: The product prepared in Example 1 was observed using a JEM-2100 transmission electron microscope. Figure 3 As shown, the spherical morphology reveals a dark green core composed of numerous uniformly sized, monodisperse spiropyran nuclei. The transparent layer is a modified acrylate shell, which can be attributed to a composite core-shell structure formed by the aggregation of spiropyran nanocrystals into nuclei and their encapsulation by acrylate. Since the acrylate outer shell is a colorless and transparent material, it appears as a white outline in the transmission electron microscope image. Calculations using the Scherrer equation (D = K / βcoSθ) and Zeta potential analysis yielded the spiropyran crystal particle size and the dimensions of the nanocomposite microspheres. The diameter of the spiropyran core is approximately 7.5 nm, the thickness of the acrylate shell is approximately 2.6 nm, and the overall diameter of the composite microspheres is approximately 12.7 nm.

[0064] Fourier transform infrared (FT-IR) spectroscopy was performed on the product prepared in Example 1. Figure 4 Analysis of the mid-curve shows that at 3395cm- 1 and 3250cm- 1 The absorption peaks at 2915 and 2846 cm⁻¹ are generated by the stretching and bending vibrations of the amino group, indicating the presence of spiropyran compounds; 1 The absorption peaks are produced by the stretching vibrations of the methyl and methylene groups; 1733 cm⁻¹, 1610 cm⁻¹. 1 cm and 1090cm -1 The strong peak at position C=O is a characteristic absorption peak of acrylate, indicating that the nanocomposite microspheres prepared in Example 1 are not a single spiropyran substance; 810.60 -1 The absorption peak at cm is generated by the skeletal vibration of the benzene ring in the molecule.

[0065] Example 2: Preparation of photosensitive color-changing nanospheres

[0066] (1) Dissolve 1.3g of spiropyran color-changing powder (a) and 1.2g of spiropyran color-changing powder (b) in 180g of petroleum ether solvent to obtain spiropyran solution.

[0067] (2) Add 6g of polyvinyl butyral and 14.5g of pentaerythritol tetraacrylate monomer to the above spiropyran solution to obtain an oil phase solution.

[0068] (3) Add 1.8g of polydimethylsiloxane PEG-10 emulsifier to 620g of pure water, and homogenize and emulsify the aqueous phase solution and the oil phase solution to obtain an O / W type emulsion.

[0069] (4) Preparation of core-shell nanospheres: 0.08g of carbodiimide CDI-1171 and 0.07g of diisopropyl peroxide dicarbonate were added to the O / W type emulsion and reacted at 35℃ for 35 minutes. Spiropyran crystal nuclei were coated in polyacrylate shell to form a nano core-shell structure. The temperature was raised to 55℃ for 10 hours for polymerization. After filtration, washing and drying, photosensitive color-changing nanosphere powder was obtained.

[0070] Example 3: Preparation of photosensitive color-changing nanospheres

[0071] (1) Dissolve 3.0g of spiropyran color-changing powder (a) and 3.0g of spiropyran color-changing powder (b) in a mixed solvent of 190g of isopentane and 230g of n-pentane to obtain a spiropyran solution.

[0072] (2) Add 5.5g of polyvinyl butyral and 16.5g of hydroxypropyl methacrylate monomer to the above spiropyran solution to obtain an oil phase solution.

[0073] (3) Add 1.9g of organosilicon emulsifier KF-6038 to 750g of pure water, and homogenize and emulsify the aqueous phase solution and the oil phase solution to obtain an O / W type emulsion.

[0074] (4) Preparation of core-shell nanospheres: 0.06g of carbodiimide CDI-1171 and 0.09g of diisopropyl peroxide dicarbonate were added to the O / W type emulsion and reacted at 30℃ for 30 minutes. Spiropyran crystal nuclei were coated in polyacrylate shell to form a nano core-shell structure. The temperature was raised to 55℃ for 10 hours for polymerization. After filtration, washing and drying, photosensitive color-changing nanosphere powder was obtained.

[0075] Example 4: Preparation of photosensitive color-changing nanospheres

[0076] (1) Dissolve 4.0g of spiropyran color-changing powder (a) and 3.5g of spiropyran color-changing powder (b) in a mixed solvent of 180g of n-pentane and 350g of petroleum ether to obtain a spiropyran solution.

[0077] (2) Add 4.5g of polyvinyl butyral and 16.5g of epoxy acrylate monomer to the above spiropyran solution to obtain an oil phase solution.

[0078] (3) Add 2.0g of polydimethylsiloxane PEG-10 to 750g of pure water, and homogenize and emulsify the aqueous phase solution and the oil phase solution to obtain an O / W type emulsion.

[0079] (4) Preparation of core-shell nanospheres: 0.07g of carbodiimide XL-701 and 0.08g of diisopropyl peroxide dicarbonate were added to the O / W type emulsion and reacted at 33℃ for 35 minutes. The spiropyran crystal nuclei were coated in the polyacrylate shell to form a nano core-shell structure. The temperature was raised to 55℃ for 10 hours to polymerize. After filtration, washing and drying, photosensitive color-changing nanosphere powder was obtained.

[0080] Example 5: Preparation of photosensitive color-changing nanospheres

[0081] (1) Dissolve 1.5g of spiropyran color-changing powder (a) and 1.5g of spiropyran color-changing powder (b) in 180g of petroleum ether solvent to obtain spiropyran solution.

[0082] (2) Add 5.5g of polyvinyl butyral and 13.0g of hydroxypropyl methacrylate monomer to the above spiropyran solution to obtain an oil phase solution.

[0083] (3) Add 2.2g of polydimethylsiloxane PEG-10 to 620g of pure water, and homogenize and emulsify the aqueous phase solution and the oil phase solution to obtain an O / W type emulsion.

[0084] (4) Preparation of core-shell nanospheres: 0.07g of carbodiimide CDI-1171 and 0.06g of diisopropyl peroxide dicarbonate were added to the O / W type emulsion and reacted at 35°C for 30 minutes. Spiropyran crystal nuclei were coated in polyacrylate shell to form a nano core-shell structure. The mixture was then heated to 55°C and polymerized for 10 hours. After filtration, washing and drying, photosensitive color-changing nanosphere powder was obtained.

[0085] Example 6: Preparation of photosensitive color-changing nanospheres

[0086] (1) Dissolve 2.2g of spiropyran color-changing powder (a) and 3.1g of spiropyran color-changing powder (b) in a mixed solvent of 110g of isopentane and 220g of petroleum ether to obtain a spiropyran solution.

[0087] (2) Add 6.0g of polyvinyl butyral and 13.5g of epoxy acrylate monomer to the above spiropyran solution to obtain an oil phase solution.

[0088] (3) Add 2.5g of organosilicon emulsifier KF-6038 to 650g of pure water, and homogenize and emulsify the aqueous phase solution and the oil phase solution to obtain an O / W type emulsion.

[0089] (4) Preparation of core-shell nanospheres: 0.08g of carbodiimide XL-701 and 0.07g of diisopropyl peroxide dicarbonate were added to the O / W type emulsion and reacted at 26℃ for 30 minutes. Spiropyran crystal nuclei were coated in polyacrylate shell to form a nano core-shell structure. The temperature was raised to 55℃ for 10 hours for polymerization. After filtration, washing and drying, photosensitive color-changing nanosphere powder was obtained.

[0090] Example 7: Photosensitive color-changing performance test

[0091] The color-changing powder samples prepared in the preparation examples and embodiments were dissolved in a dichloromethane solution containing 10% styrene, with a color-changing powder concentration of 0.2 wt%. The powder was dispensed into multiple glass test tubes, labeled, and placed in a test chamber. The sunlight simulator light source was turned on, and the color change of the sample and the time required were recorded. The simulator light source was turned off, and the color change of the sample and the time required were recorded again. The test results are shown in Table 1.

[0092] Test results:

[0093] 1. Spiropyran color-changing powder solution A appears green under normal indoor light, becomes colorless after ultraviolet irradiation, and gradually returns to green after a few minutes back indoors. This color-changing solution changes color under visible light.

[0094] 2. Spiropyran color-changing powder solution B is colorless under normal indoor light, turns red after ultraviolet irradiation, and gradually returns to colorless after irradiation is stopped. This color-changing solution changes color under ultraviolet irradiation.

[0095] 3. The photosensitive color-changing nanosphere solution appears green under normal indoor light, gradually turning yellow and finally red after ultraviolet irradiation. This microsphere solution can change color not only under ultraviolet irradiation but also under visible light, meaning it can automatically achieve complementary red-green color changes under different light conditions.

[0096] Table 1. Results of Photochromic Change in Detected Samples

[0097]

[0098] Example 8: Ultraviolet-Visible Absorption Spectroscopy Detection

[0099] Spiropyran color-changing powder a, spiropyran color-changing powder b, and photosensitive color-changing nanospheres prepared in Preparation Example 1 and Example 1 were dissolved in a dichloromethane solution containing 10% styrene, with a color-changing powder concentration of 0.1 wt%. The solutions were dispensed into multiple glass test tubes, labeled, and then subjected to irradiation detection. Irradiation was performed at room temperature for 15 min, with the solution 20 cm away from the light source. The absorption spectra of the solutions before and after irradiation were recorded. The results showed that... Figure 5 , Figure 6 and Figure 7 As shown. The test results indicate:

[0100] 1. Spiropyran color-changing powder A solution has a strong absorption peak in the ultraviolet region in the range of 200-280nm, the absorption peak in the ultraviolet region in the range of 300-380nm gradually weakens, the absorption peak in the blue light region in the range of 400-480nm gradually strengthens, there is some absorption in the red light region in the range of 600-750nm, and there is basically no absorption in the green light region in the range of 540-590nm.

[0101] 2. Spiropyran color-changing powder B solution has a strong absorption peak in the ultraviolet region below 330nm, the absorption gradually weakens in the spectral region of 350-490nm, there is a small amount of absorption in the green light region of 510-560nm, and there is basically no absorption in the red light region above 640nm.

[0102] 3. The solution of photosensitive color-changing nanospheres has a strong absorption peak in the ultraviolet region below 350nm, some absorption in the spectral range of 360-490nm, and almost no absorption in the spectral range of 500-780nm. This indicates that the transmittance of the green and red light bands is high, and the sensitivity to red and green colors is relatively high.

[0103] The photosensitive color-changing nanospheres were prepared into a coating liquid, which can improve the resolution of red and green colors under different lighting conditions.

Claims

1. A photosensitive color-changing nanomicrosphere material, characterized in that, The material is a core-shell structure, the inner core is composed of nanocrystalline of two spiropyran compounds of formula (a) and formula (b), and the outer shell is coated with a modified acrylate material; the mass ratio of the inner core to the outer shell is (1-2):(3-5), and the particle size of the microspheres is 7-15 nm; The modified acrylate material is polymerized from polyvinyl butyral and an acrylate monomer, or from polyvinyl butyral and a styrene monomer, and the mass ratio of the two is (0.5-1.5):(2-5); The mass ratio of the two spiropyran compounds of formula (a) and formula (b) is 1:(0.3-3); where R = C 16 H 33 ; where R = C 16 H 33 .

2. The photosensitive photochromic nanomicrosphere material according to claim 1, wherein, The acrylate monomer is at least one selected from methyl acrylate, ethyl acrylate, butyl acrylate, epoxy acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methyl methacrylate, pentaerythritol tetraacrylate, ethoxylated nonyl phenol acrylate, ethoxylated bisphenol A diacrylate, polyethylene glycol methacrylate, bisphenol A epoxy acrylate, bisphenol A-glycidyl dimethacrylate, triethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate; The styrene monomer is selected from styrene or methylstyrene.

3. The method for preparing photosensitive color-changing nanocomposite microspheres as described in claim 1 or 2, characterized in that, The method comprises the following steps: I. Preparation of color-changing solution: prepare a spiropyran color-changing solution by mixing spiropyran compound (a), spiropyran compound (b), and a solvent in a mass ratio of (0.5-1.5):(0.5-1.5):(100-200); II. Oil phase color-changing solution: add polyvinyl butyral and an acrylate monomer or a styrene monomer to the spiropyran color-changing solution to obtain an oil phase color-changing solution; the mass ratio of polyvinyl butyral, spiropyran compound, and acrylate monomer is (0.5-1.5):(0.5-1.5):(2-5); III. Preparation of O / W emulsion: prepare an aqueous phase solution by mixing an emulsifier and pure water in a mass ratio of (1-3):(200-500); homogeneously emulsify the aqueous phase solution and the oil phase solution to obtain an O / W emulsion; the mass ratio of the oil phase solution to the aqueous phase solution is (1-2):(1-3); IV. Preparation of core-shell nano-microspheres: add a carbodiimide crosslinking agent and an initiator to the O / W emulsion, and incubate at 25-40°C for 15-40 minutes; the spiropyran crystal nucleus is coated in a polyacrylate shell to form a nano core-shell structure; polymerize at 45-65°C for 6-12 hours; filter, wash, and dry to obtain nano color-changing microsphere powder.

4. The production method according to claim 3, wherein The solvent in step I is at least one selected from isopentane, n-hexane, n-pentane, cyclohexane, and petroleum ether.

5. The production method according to claim 3, wherein The emulsifier in step III is at least one selected from foam-free isomeric alcohol FT-625, diethyl phthalate, stearyl polyether-21, oleyl polyether-10, stearate PEG-100, and silicone oil emulsifiers.

6. The production method according to claim 5, wherein The silicone oil emulsifier is at least one selected from dimethyl silicone oil emulsifier, polydimethylsiloxane PEG-3, polydimethylsiloxane PEG-10, silicone emulsifier KF-6038, and Japan Shin Etsu KF-6017 emulsifier.

7. The production method according to claim 3, wherein The carbodiimide cross-linking agent in step IV is selected from polyethylene glycol monomethyl ether MPEG350, N, N-dimethylethanolamine, carbodiimide CDI-1171, carbodiimide XL-701 and carbodiimide INV-2000; the amount is 1-3 w t%.

8. The production method according to claim 3, wherein The initiator in the step IV is selected from at least one of dibenzoyl peroxide, diisopropyl peroxydicarbonate and azobisisobutyronitrile, and is used in an amount of 0.3 to 0.6 times the amount of the acrylate monomer or the styrene-based monomer w t%.

9. A spiropyran compound, characterized by, The chemical structure is shown as formula (a): where R = C 16 H 33 .

10. The method for preparing the compound of formula (a) as described in claim 9, characterized in that, The method comprises the following steps: I. 4-hydroxyisophthalaldehyde is mixed with anhydrous ethanol under N2 protection, heated to reflux in an oil bath at 90-220°C, and 3,3-dimethyl-1'-hexadecyl-2-methyleneindole ethanol solution is added dropwise. The reaction solution becomes purple, and heating is continued for 4-8 hours. After the ethanol is evaporated, purple-red sticky material is completely dissolved by adding ether, and then water is added. After standing, the water is removed by separation. The ether and a small amount of water are evaporated again to obtain a light purple solid spiropyran compound c; wherein the weight ratio of 4-hydroxyisophthalaldehyde, 3,3-dimethyl-1'-hexadecyl-2-methyleneindole and anhydrous ethanol is (0.5-1):(2-5):(20-50); II. A certain amount of spiropyran compound c prepared in step I above and malonyl urea are added to a reaction container containing chloroform, stirred under N2 protection until completely dissolved, and then pyridine chloroform solution is added dropwise. After the reaction is heated to reflux in an oil bath, it is cooled to room temperature, the pH is adjusted to neutral with dilute hydrochloric acid, washed with water twice, the organic layer is extracted and evaporated to dryness, and a green solid powder is obtained; the weight ratio of malonyl urea, spiropyran compound c, pyridine and chloroform is (0.5-1):(0.7-1.5):(5-20):(50-150); the content of pyridine in the pyridine solution is 3-5%.

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