Powder with reversible photochromic performance and preparation method and application thereof

Abstract

The invention provides powder with reversible photochromic performance as well as a preparation method and application thereof, and the powder with reversible photochromic performance is a photochromic microcapsule and consists of a core material and a wall material, the core material accounts for 30%-50% of the total weight of the microcapsule, and the wall material accounts for 50%-70% of the total weight of the microcapsule; the core material is an indoline spiroheterocyclic compound, and the wall material is a biocompatible polymer. The core material is an indoline spiroheterocyclic compound, and the wall material is a biocompatible polymer; the powder is prepared by taking indoline spiropyran as a photochromic core material through a microcapsule coating process, has reversible response characteristics of developing under ultraviolet irradiation and decolorizing under strong light irradiation, and can be compounded with a tattooing pigment matrix to obtain a tattooing product with active developing and decolorizing regulation and control functions. The problem that the photochromic tattoo pigment is irreversible in color change is solved, and meanwhile the photochromic tattoo pigment has good stability and biocompatibility.

Description

Technical Field

[0001] This invention relates to the field of photochromic materials, and particularly to a powder with reversible photochromic properties, its preparation method, and its application. Background Technology

[0002] Photochromic materials, capable of reversible color changes under different wavelengths of light, are widely used in decoration, anti-counterfeiting, and sensing. In the tattoo industry, photochromic tattoo inks can meet the needs of personalized dynamic decoration. However, existing domestic products have significant drawbacks: most photochromic tattoo inks, after developing color under ultraviolet light, cannot revert to an invisible state under other light conditions; the color-changing process is irreversible, limiting their application scenarios.

[0003] While imported photochromic powders currently offer some degree of reversibility, their direct application in tattoo inks presents several challenges: first, poor powder stability, making them susceptible to degradation due to skin secretions (such as oil and sweat); second, insufficient biocompatibility, as unencapsulated photochromic molecules may irritate the skin; and third, inaccurate color development / decolorization responses, prone to false triggering under normal ambient light. Therefore, developing a photochromic powder with high stability, good biocompatibility, and precise reversible response, along with its application technology in tattoo inks, has become an urgent need in this field.

[0004] To address the problems existing in current technologies, such as irreversible color change, poor stability, and insufficient biocompatibility when photochromic powders are applied to tattoo inks. Summary of the Invention

[0005] Objective of the Invention: To address the problems of irreversible color change, poor stability, and insufficient biocompatibility of existing photochromic powders when applied to tattoo pigments, this invention provides a powder with reversible photochromic properties, enabling active regulation of color development under ultraviolet irradiation and color fading under strong light irradiation; it also provides a preparation method to improve the stability and biocompatibility of the powder; and further provides its application in tattoo pigments to solve the problem of irreversible color change in existing domestic tattoo pigments.

[0006] The technical solution of the present invention:

[0007] A powder with reversible photochromic properties, wherein the powder with reversible photochromic properties is a photochromic microcapsule, which is composed of a core material and a wall material; by weight percentage, the core material accounts for 30%-50% of the total weight of the microcapsule, and the wall material accounts for 50%-70%; the core material is an indoline spiroheterocyclic complex, and the wall material is a biocompatible polymer.

[0008] The biocompatibility of the wall material and the photoresponsiveness of the core material described in this invention work synergistically. The wall material ensures that the microcapsules are non-irritating to the skin, while the core material provides a reversible color-changing function. The combination of the two enables the powder to achieve both photochromism and biocompatibility.

[0009] In some specific embodiments, the indoline spiroheterocyclic complex is at least one of a spiropyran compound containing -CH3 and 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, spiro[1,3,3-trimethylindole-(6'-nitrobenzodihydrofuran)], or 1,3,3-trimethylindole-β-naphthyldihydrofuran.

[0010] In some specific implementation methods...

[0011] The spiropyran compound containing -CH3 accounts for 50wt%-70wt% of the indoline spiroheterocyclic complex; sufficient methylspiropyran ensures the stability of the spirocyclic structure, and an appropriate amount of monomer supplements the conjugated system. The two work synergistically to improve the photochromic cycling efficiency.

[0012] In some specific embodiments, the biocompatible polymer is at least one of polyethylene glycol, polyvinyl alcohol, and polymethyl methacrylate.

[0013] The method for preparing the spiropyran compound containing -CH3 according to the present invention includes the following steps:

[0014] (1) Add 5-nitrosalicylic aldehyde and 1,3,3-trimethyl-2-methyleneindoline to a round-bottom flask, add anhydrous ethanol, and stir until well mixed;

[0015] (2) Then piperidine was slowly added dropwise, the temperature was raised to 80-90℃ and refluxed for 2-3 hours, cooled, left overnight, filtered and dried to obtain a spiropyran compound containing -CH3.

[0016] The method for preparing the core material of the present invention includes the following steps:

[0017] S1: Core material solution preparation: Dissolve the indoline spiroheterocyclic complex in ethanol solution for later use;

[0018] S2: Preparation of wall material solution: Dissolve the biocompatible polymer in pure water, heat to 40-50℃ and stir until completely dissolved to obtain the wall material solution for later use;

[0019] S3: Emulsification and dispersion: The core material solution from step S1 is slowly added to the wall material solution from step S2, and the mixture is emulsified and stirred at a speed of 1000-2000 r / min for 30-60 minutes to form an emulsion;

[0020] S4: Microcapsule curing: Add a crosslinking agent to the emulsion in step S3. The amount of crosslinking agent is 2%-5% of the weight of the wall material. Stir and react at 30-40℃ for 2-4 hours to allow the wall material to crosslink and cure.

[0021] S5: Post-processing: Centrifuge the reacted system to separate the precipitate, wash it with pure water 3-5 times, freeze-dry it and pass it through a 100-200 mesh sieve to obtain the powder with reversible photochromic properties.

[0022] In some specific embodiments, the crosslinking agent in step S4 is one of glutaraldehyde, citric acid, or carbodiimide.

[0023] The present invention provides an application of the powder with reversible photochromic properties, characterized in that the powder is applied to tattoo pigments, wherein the tattoo pigment raw materials, by weight percentage, comprise: 10%-20% of the powder with reversible photochromic properties, 20%-40% of the humectant, 2%-8% of the thickener, 3%-7% of the dispersant, 0.5%-2% of the preservative, 0.5%-1.5% of the pH stabilizer, 0.3%-1% of the antioxidant, 2%-5% of the anti-allergic component, and the balance being pure water.

[0024] In some specific embodiments, the humectant is at least one of glycerin, propylene glycol, and diglycerin; the thickener is at least one of carbomer 940 and sodium hyaluronate; the dispersant is modified polyacrylate; the preservative is a compound of p-hydroxyacetophenone and 1,2-hexanediol; and the pH stabilizer is ammonium zirconium carbonate.

[0025] In some specific embodiments, the antioxidant is vitamin E; the anti-allergic component is a mixture of Centella asiatica extract, licorice root extract, witch hazel extract, and comfrey extract.

[0026] This invention discloses a powder with reversible photochromic properties. The spiropyran containing -CH3 forms a "stability-color development" balance with the monomer. The former ensures thorough decolorization, while the latter enhances color vibrancy. The synergy between the two improves the efficiency of the photochromic cycle. The wall material achieves a synergistic effect of "hydrophilicity-mechanical strength-corrosion resistance," with PEG ensuring dispersibility and PVA / PMMA providing structural support and barrier protection, isolating the core material from skin secretions and oxygen, thus preventing oxidation or degradation. This invention achieves precise control of tattoo pigment's "UV color development and strong light decolorization" through a three-level synergy of "core material functional complementarity - wall material barrier protection - auxiliary material performance optimization," while also possessing high stability and excellent biocompatibility. This solves the problems of irreversible color change, poor stability, and high irritation associated with existing technologies.

[0027] Beneficial effects:

[0028] This invention provides a powder with reversible photochromic properties, which has the following beneficial effects:

[0029] Excellent reversibility: This powder is prepared by microencapsulation process using indoline spiroheterocycle as the photochromic core material. The molecular isomerization reaction enables active regulation of ultraviolet color development and strong light decolorization, solving the problem of irreversible color change in existing domestic products.

[0030] High stability: The powder can be cycled more than 1000 times to decolorize without significant performance degradation;

[0031] Good biocompatibility: The wall material is made of biocompatible polymers, combined with anti-allergy ingredients and pH adjustment to reduce the risk of skin irritation. No allergic reaction was observed in the skin patch test.

[0032] Convenient application: The powder preparation process is simple and controllable, it has good compatibility with tattoo pigment matrix, can be directly compounded and used, and is suitable for large-scale production. Detailed Implementation

[0033] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0034] The carbomer 940 used in this invention was purchased from Shandong Tianqi Pharmaceutical Co., Ltd.; the modified polyacrylate was purchased from Guangdong Aona Polymer Co., Ltd., product number F498; the licorice root extract was purchased from Xi'an Ruilin Biotechnology Co., Ltd., product number RLGC; the witch hazel extract was purchased from Shaanxi Baitaiyuan Chuang Biotechnology Co., Ltd., product number BTYC-201; the comfrey extract was purchased from Xi'an Haoyu Kangze Biotechnology Co., Ltd., product model: HY-15665; and the centella asiatica extract was purchased from Shaanxi Yilin Biotechnology Co., Ltd., product model: YL-JXC241121.

[0035] Preparation of spiropyran compounds containing -CH3:

[0036] (1) Add 5g of 5-nitrosalicylic acid and 5.2g of 1,3,3-trimethyl-2-methyleneindoline to a round-bottom flask, add 50ml of anhydrous ethanol, and stir well;

[0037] (2) Then slowly add 0.5g piperidine, heat to 80℃ and reflux for 3h, cool, let stand overnight, filter and dry to obtain a spiropyran compound containing -CH3.

[0038] Indoline spiroheterocyclic monomers: 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, spiro[1,3,3-trimethylindole-(6'-nitrobenzodihydropyran)], 1,3,3-trimethylindole-β-naphthyldihydrofuran;

[0039] Biocompatible polymers: polyethylene glycol (PEG, molecular weight 2000), polyvinyl alcohol (PVA, degree of polymerization 1700), polymethyl methacrylate (PMMA, molecular weight 10000);

[0040] Crosslinking agents: glutaraldehyde (25% aqueous solution), citric acid (analytical grade), carbodiimide (EDC, analytical grade);

[0041] Tattoo ink additives: glycerin, propylene glycol, diglycerin, carbomer 940, sodium hyaluronate, modified polyacrylate, p-hydroxyacetophenone, 1,2-hexanediol, ammonium zirconium carbonate, vitamin E, anti-allergy ingredients (Centella asiatica extract: licorice extract: witch hazel extract: limonene extract = 1:1:1:1).

[0042] Example 1:

[0043] S1: Core material solution preparation: Mix 3g of spiropyran compound containing -CH3 with 3g of 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, then dissolve in 60mL of anhydrous ethanol solution and stir until completely dissolved.

[0044] S2: Preparation of wall material solution: Dissolve 14g of polyvinyl alcohol in 86mL of pure water, stir at 45℃ until completely dissolved, and obtain the wall material solution for later use;

[0045] S3: Emulsification and dispersion: The core material solution from step S1 is slowly added to the wall material solution from step S2, and emulsified and stirred at 1500 r / min for 45 minutes to form an emulsion;

[0046] S4: Microcapsule curing: Add 0.36g of glutaraldehyde to the emulsion in step S3, stir at 35°C for 3 hours to crosslink and cure the wall material;

[0047] S5: Post-processing: Centrifuge the reaction system at 8000 r / min for 12 minutes, wash the precipitate with pure water 4 times, freeze-dry at -40℃ for 36 hours, and pass through a 150-mesh sieve to obtain the powder with reversible photochromic properties.

[0048] Tattoo ink preparation: (by weight percentage)

[0049] A powder with reversible photochromic properties is prepared by mixing 15% glycerin, 15% propylene glycol, 3% diglycerin, 1.5% carbomer 940, 0.5% sodium hyaluronate, 5% modified polyacrylate, 0.5% p-hydroxyacetophenone, 0.5% 1,2-hexanediol, 0.8% ammonium zirconium carbonate, 0.5% vitamin E, 3% anti-allergy ingredient, and pure water to 100%.

[0050] Example 2:

[0051] S1: Core material solution preparation: Mix 6g of spiropyran compound containing -CH3 with 4g of 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, then dissolve in 100mL of anhydrous ethanol solution and stir until completely dissolved.

[0052] S2: Preparation of wall material solution: Dissolve 10g of polyvinyl alcohol in 90mL of pure water, stir at 45℃ until completely dissolved, and obtain the wall material solution for later use;

[0053] S3: Emulsification and dispersion: The core material solution from step S1 is slowly added to the wall material solution from step S2, and emulsified and stirred at 1000 r / min for 60 minutes to form an emulsion;

[0054] S4: Microcapsule curing: Add 0.5g of glutaraldehyde to the emulsion in step S3, stir at 35°C for 3 hours to crosslink and cure the wall material;

[0055] S5: Post-processing: Centrifuge the reaction system at 8000 r / min for 12 minutes, wash the precipitate with pure water 4 times, freeze-dry at -40℃ for 36 hours, and pass through a 150-mesh sieve to obtain the powder with reversible photochromic properties.

[0056] Tattoo ink preparation: (by weight percentage)

[0057] A powder with reversible photochromic properties, comprising 10%, 15%, 10%, 10%, 3%, 3%, 940% carbomer, 3%, sodium hyaluronate, 5%, modified polyacrylate, 0.5%, 1,2-hexanediol, 0.8%, ammonium zirconium carbonate, 0.5%, and 3%, is prepared by adding pure water to 100% using a conventional mixing process.

[0058] Example 3:

[0059] S1: Core material solution preparation: Mix 7g of spiropyran compound containing -CH3 with 3g of 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, then dissolve in 100mL of anhydrous ethanol solution and stir until completely dissolved.

[0060] S2: Preparation of wall material solution: Dissolve 15g of polymethyl methacrylate in 85mL of water, heat to 50℃ and stir until completely dissolved to obtain a wall material solution for later use;

[0061] S3: Emulsification and dispersion: The core material solution from step S1 is slowly added to the wall material solution from step S2, and emulsified and stirred at 2000 r / min for 30 minutes to form an emulsion;

[0062] S4: Microcapsule curing: Add 0.3g of carbodiimide to the emulsion in step S3, stir at 40°C for 2 hours to crosslink and cure the wall material;

[0063] S5: Post-processing: Centrifuge the reaction system at 8000 r / min for 12 minutes, wash the precipitate with pure water 4 times, freeze-dry at -40℃ for 36 hours, and pass through a 150-mesh sieve to obtain the powder with reversible photochromic properties.

[0064] Tattoo ink preparation: (by weight percentage)

[0065] A powder with reversible photochromic properties is prepared by mixing 15% glycerin, 15% propylene glycol, 3% diglycerin, 3% carbomer 940, 5% sodium hyaluronate, 5% modified polyacrylate, 0.5% p-hydroxyacetophenone, 0.5% 1,2-hexanediol, 0.8% ammonium zirconium carbonate, 0.5% vitamin E, 3% anti-allergy ingredient, and pure water to 100%.

[0066] Example 4:

[0067] S1: Core material solution preparation: Mix 2g of spiropyran compound containing -CH3 with 8g of 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, then dissolve in 100mL of anhydrous ethanol solution and stir until completely dissolved.

[0068] S2: Preparation of wall material solution: Dissolve 10g of polyvinyl alcohol in 90mL of pure water, stir at 45℃ until completely dissolved, and obtain the wall material solution for later use;

[0069] S3: Emulsification and dispersion: The core material solution from step S1 is slowly added to the wall material solution from step S2, and emulsified and stirred at 1000 r / min for 60 minutes to form an emulsion;

[0070] S4: Microcapsule curing: Add 0.5g glutaraldehyde to the emulsion in step S3, stir at 35℃ for 3 hours to crosslink and cure the wall material;

[0071] S5: Post-processing: Centrifuge the reaction system at 8000 r / min for 12 minutes, wash the precipitate with pure water 4 times, freeze-dry at -40℃ for 36 hours, and pass through a 150-mesh sieve to obtain the powder with reversible photochromic properties.

[0072] Tattoo ink preparation: (by weight percentage)

[0073] A powder with reversible photochromic properties, comprising 10%, 15%, 10%, 10%, 3%, 3%, 940% carbomer, 3%, sodium hyaluronate, 5%, modified polyacrylate, 0.5%, 1,2-hexanediol, 0.8%, ammonium zirconium carbonate, 0.5%, and 3%, is prepared by adding pure water to 100% using a conventional mixing process.

[0074] The preparation of the tattoo pigment in Comparative Example 1 was basically the same as in Example 1, except that the "powder with reversible photochromic properties" in Example 1 was replaced with "a mixture of -CH3 spiropyran compound and 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran in a mass ratio of 1:1 as a powder with reversible photochromic properties".

[0075] Comparative Example 2:

[0076] S1: Core material solution preparation: Mix 3g of spiropyran compound containing -CH3 with 3g of 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, then dissolve in 60mL of anhydrous ethanol solution and stir until completely dissolved.

[0077] S2: Preparation of wall material solution: Dissolve 4g of polyvinyl alcohol in 96mL of pure water, stir at 45℃ until completely dissolved, and obtain the wall material solution for later use;

[0078] S3: Emulsification and dispersion: The core material solution from step (1) is slowly added to the wall material solution from step (2), and emulsified and stirred at 1500 r / min for 45 minutes to form an emulsion;

[0079] S4: Microcapsule curing: Add 0.36g glutaraldehyde to the emulsion in step (3), stir at 35°C for 3 hours to crosslink and cure the wall material;

[0080] S5: Post-processing: Centrifuge the reaction system at 8000 r / min for 12 minutes, wash the precipitate with pure water 4 times, freeze-dry at -40℃ for 36 hours, and pass through a 150-mesh sieve to obtain the powder with reversible photochromic properties.

[0081] Tattoo ink preparation: (by weight percentage)

[0082] The following ingredients were prepared using conventional mixing processes: 15% powder, 15% glycerin, 10% propylene glycol, 3% diglycerin, 0.3% carbomer 940, 1.5% sodium hyaluronate, 0.5% sodium hyaluronate, 5% modified polyacrylate, 0.5% p-hydroxyacetophenone, 0.5% 1,2-hexanediol, 0.8% ammonium zirconium carbonate, 0.5% vitamin E, 3% anti-allergy ingredient, and purified water to 100%.

[0083] Performance testing experiments:

[0084] 1. Photochromic performance test:

[0085] Test conditions: The color rendering light source is 365nm ultraviolet light (intensity 1.5mW / cm²). 2 The achromatic light source is 550nm green light (intensity 10mW / cm²). 2 A spectrophotometer and a photometer were used for color measurement (using a colorimeter), recording the color development / decolorization time and the color intensity retention rate after 1000 cycles; the color development time is the time taken for the photochromic material to develop color under 365nm ultraviolet light (intensity 1.5mW / cm²). 2 The time required for the material to transition from an achromatic state to a chromatic state (with absorbance reaching its maximum stable value) under irradiation at 550 nm green light (intensity 10 mW / cm²); the achromatic time is the time required for the material to transition from an achromatic state to a chromatic state (with absorbance reaching its maximum stable value ... 2 Under irradiation, the time required for the colorimetric state to recover to the achromatic state (absorbance drops to the initial achromatic state level); color intensity retention rate = maximum colorimetric absorbance in the 1000th cycle / maximum colorimetric absorbance in the 1st cycle × 100%.

[0086] 2. Biocompatibility testing:

[0087] Testing Method: Fifty healthy adults aged 18-45 (25 males and 25 females) were selected, excluding those with skin abnormalities (such as eczema, sunburn, trauma) and those with allergies (history of contact dermatitis, asthma, etc. within the past 3 months). Allergy determination was based on the ICDRG criteria: after removing the patch 24 hours later, the appearance of clear erythema with edema / papules (Grade 2, weak positive), erythema with edema and vesicles (Grade 3, strong positive), or severe erythema with exudation (Grade 4, extremely strong positive) on the skin was considered an allergy. Mild suspected erythema (Grade 1) or no reaction (Grade 0) was not included in the allergy statistics.

[0088] 3. Stability Test:

[0089] Test conditions: The tattoo ink was stored at 37°C and 60% relative humidity for 30 days to observe whether it separated into layers and the powder dispersibility.

[0090] Table 1: Test Results Table

[0091]

[0092]

[0093] The data above show that the powders with reversible photochromic properties prepared in Examples 1-3 of this invention exhibit high stability, good biocompatibility, and precise reversible response. Specifically, compared to Example 4, Example 4 contains only 20% spiropyran compounds with -CH3 content, resulting in insufficient photochromic active ingredients, which leads to prolonged color development / decolorization time, decreased cycle stability, and slight stratification after storage due to the imbalance in the core material ratio. Compared to Comparative Example 1, Example 2 was not microencapsulated and lacked wall material protection, resulting in rapid surface energy differences in the powder. Rapid aggregation and severe delamination after storage, with the core material directly exposed and in direct contact with the skin. The unmodified spiroheterocyclic compounds in the core material cause slight skin irritation, resulting in allergic reactions in three individuals. The photochromic molecular structure is rapidly destroyed by skin secretions, and the core material completely fails after 500 cycles, with prolonged decolorization time. Compared with Comparative Example 2, Example 2 has insufficient wall material, which cannot completely cover the core material, resulting in partial core material exposure and causing allergic reactions in a small number of individuals. It also exhibits poor dispersibility, reduced color development / decolorization efficiency, decreased cycle stability, and poor overall stability.

[0094] This invention significantly improves the response efficiency, cycle stability, and storage stability of photochromic powder by controlling the proportion of spiropyran compounds containing -CH3, the weight ratio of core material to wall material, and the microcapsule encapsulation process. It also exhibits excellent biocompatibility, fully meeting the application requirements of tattoo pigments.

[0095] This invention can also be implemented in various other ways. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A powder having reversible photochromic properties, characterized in that, The powder with reversible photochromic performance is a photochromic microcapsule composed of a core material and a wall material; the core material accounts for 30-50% of the total weight of the microcapsule, and the wall material accounts for 50-70% of the total weight of the microcapsule, both in terms of weight percentage; the core material is an indolinespiroheterocyclic complex, and the wall material is a biocompatible polymer.

2. The powder having reversible photochromic properties according to claim 1, characterized in that, The indolinespiroheterocyclic complex is at least one of a spiropyran compound containing-CH3 and 1,3,3-trimethylindole-8'-methoxybenzodihydrofuran, spiro[1,3,3-trimethylindole-(6'-nitrobenzodihydropyrane)], 1,3,3-trimethylindole-β-naphthyl dihydrofuran.

3. The powder having reversible photochromic properties according to claim 1, wherein The spiropyran compound containing-CH3 accounts for 50-70wt% of the indolinespiroheterocyclic complex.

4. The powder having reversible photochromic properties according to claim 1, wherein The biocompatible polymer is at least one of polyethylene glycol, polyvinyl alcohol, and polymethyl methacrylate.

5. The powder having reversible photochromic properties according to claim 2, wherein The preparation method of the spiropyran compound containing-CH3 includes the following steps: (1) 5-nitrosalicylaldehyde and 1,3,3-trimethyl-2-methyleneindoline are added to a round-bottom flask, and anhydrous ethanol is added and stirred uniformly; (2) Then piperidine is slowly dropped, heated to 80-90℃ for refluxing for 2-3h, cooled, left overnight, filtered, and dried to obtain the spiropyran compound containing-CH3.

6. The method for preparing the powder having reversible photochromic properties according to any one of claims 1 to 5, characterized in that, The preparation method of the core material includes the following steps: S1: Core material solution preparation: the indolinespiroheterocyclic complex is dissolved in an ethanol solution for standby; S2: Wall material solution preparation: the biocompatible polymer is dissolved in pure water, heated to 40-50℃ and stirred until completely dissolved to obtain a wall material solution for standby; S3: Emulsification and dispersion: the core material solution of step S1 is slowly added to the wall material solution of step S2, emulsified and stirred at a speed of 1000-2000r / min for 30-60min to form a emulsion; S4: Microcapsule solidification: a crosslinking agent is added to the emulsion of step S3, the amount of the crosslinking agent is 2-5% of the weight of the wall material, and the emulsion is stirred and reacted at 30-40℃ for 2-4h to make the wall material crosslink and solidify; S5: Post-treatment: the system after reaction is centrifuged and separated, the precipitate is washed with pure water for 3-5 times, and then dried in a freezer and sieved through a 100-200 mesh sieve to obtain the powder with reversible photochromic performance.

7. The method of claim 6, wherein the powder having reversible photochromic properties is prepared by the steps of: a) dissolving a photochromic compound in a solvent; b) adding a polymer to the solution; c) removing the solvent; and d) drying the resulting mixture. The crosslinking agent in step S4 is one of glutaraldehyde, citric acid, or carbodiimide.

8. Use of a powder having reversible photochromic properties according to any one of claims 1 to 5, characterized in that, The powder is applied to tattoo pigments, and the raw materials of the tattoo pigments account for 100% by weight, including: 10-20% of the powder with reversible photochromic performance, 20-40% of a humectant, 2-8% of a thickening agent, 3-7% of a dispersing agent, 0.5-2% of a preservative, 0.5-1.5% of a pH stabilizer, 0.3-1% of an antioxidant, 2-5% of an anti-allergic ingredient, and the balance of pure water.

9. Use of the powder having reversible photochromic properties according to claim 8, characterized in that, The humectant is at least one of glycerol, propylene glycol, and diglycerol; the thickening agent is at least one of carbomer 940 and sodium hyaluronate; the dispersing agent is a modified polyacrylic acid salt; the preservative is a compound of p-hydroxyacetophenone and 1,2-hexanediol; and the pH stabilizer is ammonium zirconium carbonate.

10. Use of the powder having reversible photochromic properties according to claim 8, characterized in that, The antioxidant is vitamin E; the anti-allergic component is a mixture of Centella asiatica extract, liquorice root extract, witch hazel extract, and Alkanna tinctoria extract. The antioxidant is vitamin E; the anti-allergic component is a mixture of Centella asiatica extract, liquorice root extract, witch hazel extract, and Alkanna tinctoria extract.

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