Method for repeatedly building structural color on thermoplastic and application thereof

Abstract

The application belongs to the technical field of structural color, and discloses a method for repeatedly constructing structural color on thermoplastic plastic and application. Nano-silica microspheres are deposited on a thermoplastic plastic substrate, and an ordered and periodic photonic crystal structure is formed through self-assembly, presenting structural color. The thermoplastic plastic substrate with the deposited photonic crystal is placed into a flat vulcanizing machine for heating and pressing, so that the photonic crystal structure and the structural color presented thereby are firmly attached to the thermoplastic plastic substrate. The thermoplastic plastic substrate with the firmly attached structural color is again placed into the flat vulcanizing machine for heating and pressing, so that the attached structural color is faded, and thus the thermoplastic plastic substrate with faded color can be colored again. The structural color obtained by the application has high color fastness, can be repeatedly colored, has the angle color change characteristic, is simple, fast, effective, green and environment-friendly, and can be applied to the fields of dyeing, decoration and anti-counterfeiting, and provides a feasible method for replacing the use of traditional dyes.

Description

Technical Field

[0001] This invention relates to the field of structural color technology, and more specifically to a method for applying structural colors to thermoplastics with high color fastness and repeatability. Background Technology

[0002] Structural color is a type of color produced by the interaction between light and microscopic structures, such as reflection, refraction, interference, and scattering; therefore, it is also called physical color. Most colors in everyday life are chemical colors, which rely on pigment molecules absorbing certain wavelengths of light and reflecting the rest. Although structural and chemical colors have different generation mechanisms, they both allow the human eye to observe a rich visual effect of color. However, prolonged absorption of light energy by pigment molecules inevitably damages their molecular structure, causing chemical colors to fade. Furthermore, the preparation of artificially synthesized pigments involves various toxic raw materials such as aniline, produces harmful byproducts such as heavy metals, and results in the emission of large amounts of wastewater and waste gas, significantly impacting the environment. Structural colors, due to their unique generation mechanism, have the advantage of being less prone to fading compared to chemical colors, and their preparation is also more environmentally friendly.

[0003] Photonic crystals are microstructures capable of achieving structural colors. They selectively reflect light through photonic band gaps created by the periodic distribution of refractive index, resulting in structural colors. Depending on the angle of incident light, photonic crystals can also reflect different wavelengths of light, displaying different colors, which has applications in anti-counterfeiting and decoration. Most current artificial photonic crystals rely on the self-assembly of various nanospheres, such as silica, polystyrene, or polymethyl methacrylate, to form ordered arrays that interact with light. However, these self-assembled photonic crystals generally suffer from instability and are prone to detachment. Therefore, adhesives are often added to reinforce the photonic crystal structure, or a protective film is applied to maintain the stability of the ordered structure. However, these methods are often time-consuming and introduce substances beyond the raw materials, hindering the large-scale application of structural colors.

[0004] Therefore, developing a structural coloring method with high color fastness and repeatability on thermoplastics is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for constructing structural colors on thermoplastic plastics. The resulting structural colors have high color fastness, can be repeatedly applied, have angle-changing color characteristics, are simple, quick, effective, green and environmentally friendly, and can be applied to dyeing, decoration and anti-counterfeiting fields, providing a feasible method to replace the use of traditional dyes.

[0006] To achieve the above objectives, the present invention provides a method for repeatedly constructing structural colors on thermoplastics, comprising the following steps:

[0007] (1) Preparation of nano-silica microspheres: 3.5~4.5 mL of ammonia water and 48 mL of anhydrous ethanol were mixed evenly and heated at 30°C. 3 mL of tetraethyl orthosilicate and 3 mL of anhydrous ethanol were mixed evenly and heated at 30°C. 3 mL of tetraethyl orthosilicate ethanol solution was added to the ammonia water ethanol solution. The mixture was heated at 30°C and stirred at 300 rpm. After 30 minutes, another 3 mL of tetraethyl orthosilicate ethanol solution was added. The mixture was heated at 30°C and stirred at 300 rpm. After reacting for 5 hours, the mixture was washed three times by centrifugation with deionized water and anhydrous ethanol. The precipitate was dried in an oven and then ground thoroughly to obtain nano-silica microspheres.

[0008] (2) Structural color self-assembly: Nano-silica microspheres are added to deionized water, with a mass fraction of 0.3~0.6wt%, preferably 0.4wt%; the nano-silica microsphere suspension is obtained by ultrasonic dispersion for 15~30min using an ultrasonic disruptor at 500W power; a small amount of nano-silica microspheres are coated on a thermoplastic substrate for pretreatment, which helps the nano-silica microsphere suspension to spread and disperse evenly on the thermoplastic substrate; the nano-silica suspension is coated on the thermoplastic substrate and heated at 50℃ for evaporation deposition, so that the nano-silica microspheres self-assemble into an ordered photonic crystal structure, exhibiting structural color.

[0009] (3) Hot pressing coloring: The thermoplastic substrate with photonic crystal deposited is placed in a flat vulcanizing machine for heating and pressing. First, the substrate is placed in the flat vulcanizing machine and preheated at 190~210℃ for 5 minutes to soften the PC / ABS substrate to a certain extent. Then, the temperature is maintained and the mold is closed and pressurized at 3~5MPa for 45~60s. The substrate is then transferred to the cooling zone and cooled at 3~5MPa for 90~120s to make the photonic crystal structure and its structural color firmly attached to the thermoplastic substrate.

[0010] (4) Hot pressing fading: The thermoplastic substrate with the attached structural color is put back into the flat vulcanizing machine for heating and pressing. First, the thermoplastic substrate is placed in the flat vulcanizing machine and pre-pressed at 250℃ and 3~5MPa for 3 minutes to soften the thermoplastic substrate to a certain extent. Then, the temperature is maintained and the pressure is increased to 10~15MPa for 5~10 minutes. Then, it is transferred to the cooling zone and cooled at 10~15MPa for 5 minutes to remove the attached structural color.

[0011] (5) Recoloring: Use the faded thermoplastic substrate obtained in step (4) as the object of operation, replacing the thermoplastic substrate in steps (2) and (3), and repeat the remaining operations.

[0012] Preferably, the thermoplastic substrate is selected from at least one of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polycarbonate (PC), and acrylonitrile-butadiene-styrene copolymer (ABS).

[0013] Preferably, the structural coloring method provided by the present invention achieves structural colors with high saturation, capable of displaying various colors in the visible spectrum (e.g., red, green, blue). Different structural colors are achieved by depositing nano-sized silica microspheres (180~330nm). More preferably, red is formed by microspheres with a particle size of approximately 302.4nm, green by microspheres with a particle size of approximately 241.6nm, and blue by microspheres with a particle size of approximately 195.8nm.

[0014] In step (3), the thermoplastic substrate is softened in the preheating stage to provide the preconditions for it to enter the photonic crystal structure. The mold closing and pressurization stage allows the thermoplastic substrate to enter the photonic crystal structure. The cooling stage allows the thermoplastic substrate to solidify inside the photonic crystal.

[0015] In step (4), the thermoplastic substrate is softened during the pre-pressing stage, and the softened thermoplastic is embedded and destroyed in the pressurization stage, causing the structural color to fade.

[0016] The hot-press coloring mechanism of this invention utilizes high temperature to heat and soften thermoplastic plastic to give it a certain fluidity, and then uses pressure to press the thermoplastic plastic into a silicon dioxide photonic crystal, so that the thermoplastic plastic and the silicon dioxide photonic crystal can be firmly bonded together to achieve structural coloring.

[0017] As can be seen from the above technical solution, compared with the prior art, the beneficial effects achieved by the present invention include at least the following: The structural coloring method provided by this invention uses a flat vulcanizing machine to combine the photonic crystal structure formed by the self-assembly of nano-silica microspheres with thermoplastic plastic, thereby achieving structural coloring and fading of thermoplastic plastic.

[0018] This invention enables structural colors to adhere stably to thermoplastics, providing high color fastness.

[0019] This invention enables the removal of structural color from thermoplastics and the re-coloring of the removed thermoplastics.

[0020] The structural coloring method provided by this invention is simple and quick to operate, requires little time, and is fast and effective.

[0021] The structural coloring method provided by this invention achieves angle-dependent structural colors, which can be seen from different angles, and has application potential in fields such as anti-counterfeiting and decoration.

[0022] The structural coloring method provided by this invention uses structural color materials that are more environmentally friendly than traditional dyes, while also possessing rich and vibrant colors, and have great potential to replace traditional dyes. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 Optical photographs of PC / ABS substrates and samples with different structural colors attached, wherein (a) is a PC / ABS substrate, (b) is a sample prepared in Example 1, (c) is a sample prepared in Example 2, and (d) is a sample prepared in Example 3.

[0025] Figure 2 The images are scanning electron microscope (SEM) images of the sample surfaces, where (a) is a scanning electron microscope image of the uncolored PC / ABS substrate surface, and (b) is a scanning electron microscope image of the green structural color sample prepared in Example 1 surface.

[0026] Figure 3 The figures are optical photographs of the samples, where (a) is an optical photograph of the faded sample of Example 4, and (b) is an optical photograph of the recolored sample of Example 5.

[0027] Figure 4 Figure 1 shows the scanning electron microscope (SEM) images of the samples, where (a) is the SEM image of the faded sample from Example 4, and (b) is the SEM image of the re-stained sample from Example 5.

[0028] Figure 5 The images are optical photographs of the color fastness test, where (a) and (b) are photographs of the hot-pressed colored sample of Example 1 before and after the color fastness test, (c) and (d) are photographs of the un-hot-pressed colored sample of Comparative Example 1 before and after the color fastness test, (e) and (f) are photographs of the sample of Comparative Example 2 before and after the color fastness test, and (g) and (h) are photographs of the sample of Comparative Example 4 before and after the color fastness test.

[0029] Figure 6The figures are optical photographs of the samples, where (a) is an optical photograph of the sample obtained in Comparative Example 3 and (b) is an optical photograph of the sample obtained in Comparative Example 5.

[0030] Figure 7 Optical photographs of the colored sample obtained in Example 3 at different viewing angles are shown in Figures (a)-(d), which are optical photographs obtained as the viewing angle increases sequentially. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a method for achieving high color fastness and repeatable structural coloring on thermoplastics, comprising the following steps: (1) Nano-silica microspheres are deposited on a thermoplastic substrate and self-assembled to form an ordered periodic photonic crystal structure, exhibiting structural color; (2) The thermoplastic substrate with the photonic crystal deposited is placed in a flat vulcanizing machine for heating and pressing, so that the photonic crystal structure and its structural color are firmly attached to the thermoplastic substrate. (3) The thermoplastic substrate with the firmly attached structural color is placed in a flat vulcanizing machine for reheating and pressing, so that the attached structural color fades, and the faded thermoplastic substrate can be recolored.

[0033] In step (2), the preheating stage softens the thermoplastic substrate, the pressurization stage allows the softened thermoplastic substrate to enter the photonic crystal structure, and the cooling stage allows the thermoplastic substrate to solidify inside the photonic crystal, thereby making the thermoplastic substrate firmly bonded to the structural color.

[0034] In step (3), the preheating stage softens the thermoplastic substrate with the firmly attached structural color, the pressurization stage destroys the softened thermoplastic substrate and embeds the photonic crystal structure, and the cooling stage solidifies the thermoplastic substrate, thereby causing the structural color to disappear from the thermoplastic substrate.

[0035] Example 1 A coloring experiment was conducted on a thermoplastic substrate, including the following steps: (1) Preparation of nano-silica microspheres: 4 mL of ammonia water and 48 mL of anhydrous ethanol were mixed evenly and heated at 30 °C. 3 mL of tetraethyl orthosilicate and 3 mL of anhydrous ethanol were mixed evenly and heated at 30 °C. 3 mL of tetraethyl orthosilicate ethanol solution was added to the ammonia water ethanol solution. The mixture was heated at 30 °C and stirred at 300 rpm. After 30 minutes, another 3 mL of tetraethyl orthosilicate ethanol solution was added. The mixture was heated at 30 °C and stirred at 300 rpm. After reacting for 5 hours, the mixture was washed three times by centrifugation at 9000 rpm with deionized water and anhydrous ethanol. The precipitate was dried in an oven and then ground thoroughly to obtain nano-silica microspheres with a particle size of about 241.6 nm.

[0036] (2) Structural color self-assembly: Nano-silica microspheres were added to deionized water with a mass fraction of 0.4 wt%. The nano-silica microspheres were ultrasonically dispersed for 20 minutes using an ultrasonic disruptor at a power of 500 W to obtain a nano-silica microsphere suspension. A small amount of nano-silica microspheres were coated on a polycarbonate / acrylonitrile-butadiene-styrene copolymer alloy (PC / ABS) substrate for pretreatment, which helped the nano-silica microsphere suspension to spread and disperse evenly on the PC / ABS substrate. The nano-silica suspension was coated on the PC / ABS substrate and heated to 50°C for evaporation deposition, so that the nano-silica microspheres self-assembled into an ordered photonic crystal structure, exhibiting structural color.

[0037] (3) Hot pressing and coloring: The PC / ABS substrate with photonic crystal deposited is placed in a flat vulcanizing machine for heating and pressing. First, the PC / ABS substrate is placed in the flat vulcanizing machine and preheated at 190°C for 5 minutes to soften the PC / ABS substrate to a certain extent. Then, the mold is closed and pressurized for 60 seconds at 190°C and 3MPa. It is then transferred to the cooling zone and cooled at 3MPa for 120 seconds to make the photonic crystal structure and its structural color firmly attached to the PC / ABS substrate.

[0038] like Figure 1 As shown in Figure (b), the colored PC / ABS sample obtained in this embodiment is green.

[0039] like Figure 5 As shown, the colored sample prepared in this embodiment was subjected to an abrasion fastness test. The colored sample was placed with the colored side facing up, covered with bleached cotton cloth, and a 50g weight was applied on it. After moving the bleached cotton strip horizontally by 50 cm, the condition of the colored sample was observed. Figure 5 Figure (a) and Figure 5 Figure (b) shows optical photographs of the colored samples before and after the color fastness test. It can be seen that the color difference between the colored samples before and after the test is small, and the color fastness of the structural color is high.

[0040] Example 2 A coloring experiment was conducted on a thermoplastic substrate, including the following steps: (1) Preparation of nano-silica microspheres: 3.5 mL of ammonia water and 48 mL of anhydrous ethanol were mixed evenly and heated at 30 °C. 3 mL of tetraethyl orthosilicate and 3 mL of anhydrous ethanol were mixed evenly and heated at 30 °C. 3 mL of tetraethyl orthosilicate ethanol solution was added to the ammonia water ethanol solution. The mixture was heated at 30 °C and stirred at 300 rpm. After 30 minutes, another 3 mL of tetraethyl orthosilicate ethanol solution was added. The mixture was heated at 30 °C and stirred at 300 rpm. After reacting for 5 hours, the mixture was washed three times by centrifugation at 7000 rpm with deionized water and anhydrous ethanol. The precipitate was dried in an oven and then ground thoroughly to obtain nano-silica microspheres with a particle size of about 195.8 nm.

[0041] The subsequent steps are the same as steps (2) and (3) in Example 1.

[0042] like Figure 1 As shown in Figure (c), the colored PC / ABS sample obtained in this embodiment is blue.

[0043] Example 3 A coloring experiment was conducted on a thermoplastic substrate, including the following steps: (1) Preparation of nano-silica microspheres: 4.3 mL of ammonia water and 48 mL of anhydrous ethanol were mixed evenly and heated at 30 °C. 3 mL of tetraethyl orthosilicate and 3 mL of anhydrous ethanol were mixed evenly and heated at 30 °C. 3 mL of tetraethyl orthosilicate ethanol solution was added to the ammonia water ethanol solution. The mixture was heated at 30 °C and stirred at 300 rpm. After 30 minutes, another 3 mL of tetraethyl orthosilicate ethanol solution was added. The mixture was heated at 30 °C and stirred at 300 rpm. After reacting for 5 hours, the mixture was washed three times by centrifugation at 7000 rpm with deionized water and anhydrous ethanol. The precipitate was dried in an oven and then ground thoroughly to obtain nano-silica microspheres with a particle size of about 302.4 nm.

[0044] The subsequent steps are the same as steps (2) and (3) in Example 1.

[0045] like Figure 1 As shown in Figure (d), the colored PC / ABS sample obtained in this embodiment is red.

[0046] Example 4 A fading test is performed on the colored sample, including the following steps: The colored PC / ABS sample obtained according to Example 1 was placed again in a flat vulcanizing machine for heating and pressing. First, the thermoplastic substrate was placed in the flat vulcanizing machine and pre-pressed at 250°C and 5MPa for 3 minutes to soften the thermoplastic substrate to a certain extent. Then, the pressure was increased at 250°C and 10MPa for 5 minutes, and then transferred to the cooling zone and cooled at 10MPa for 5 minutes to remove the attached structural color.

[0047] like Figure 3 As shown in Figure (a), the structural color on the fading experimental sample prepared in this embodiment has disappeared, and it is similar in appearance to the initial substrate.

[0048] like Figure 4 As shown in Figure (a), the scanning electron microscope image of the fading experimental sample prepared in this embodiment shows that the original photonic crystal structure has been destroyed and embedded by the PC / ABS substrate.

[0049] Example 5 The recoloring experiment for faded samples includes the following steps: (1) The nano-silica microspheres prepared in Example 1 were added to deionized water, and the mass fraction of the nano-silica microspheres in the deionized water was 0.4 wt%. The nano-silica microsphere suspension was obtained by ultrasonic dispersion for 20 minutes using an ultrasonic disruptor at a power of 500W. A small amount of nano-silica microspheres were coated on the bleached PC / ABS substrate prepared in Example 4 for pretreatment, which helped the nano-silica microsphere suspension to spread and disperse evenly on the bleached PC / ABS substrate. The nano-silica suspension was coated on the bleached PC / ABS substrate and heated to 50°C for evaporation deposition, so that the nano-silica microspheres self-assembled into an ordered photonic crystal structure and exhibited structural color.

[0050] (2) The PC / ABS substrate with the photonic crystal deposited is placed in a flat vulcanizing machine for heating and pressing. First, the PC / ABS substrate is placed in the flat vulcanizing machine and preheated at 190°C for 5 minutes to soften the PC / ABS substrate to a certain extent. Then, the temperature is maintained at 190°C and the mold is closed and pressurized at 3MPa for 60 seconds. The substrate is then transferred to the cooling zone and cooled at 3MPa for 120 seconds to ensure that the photonic crystal structure and its structural color are firmly attached to the PC / ABS substrate.

[0051] like Figure 3 As shown in Figure (b), the colored sample obtained in this embodiment regained its color.

[0052] like Figure 4 As shown in Figure (b), the scanning electron microscope image of the colored sample prepared in this embodiment shows that the photonic crystal structure is reattached to the PC / ABS substrate.

[0053] Comparative Example 1 According to Example 1, a PC / ABS sample with photonic crystal deposited was prepared without hot pressing and coloring.

[0054] like Figure 5 As shown in Figures (c) and (d), the structural color was easily wiped off by the cotton cloth during the color fastness test because the photonic crystal was simply deposited on the PC / ABS substrate without hot pressing, resulting in weak adhesion between the two.

[0055] Comparative Example 2 A coloring experiment was conducted on a thermoplastic substrate, including the following steps: The PC / ABS substrate with photonic crystal deposited as prepared in Example 1 was subjected to hot pressing and coloring. The PC / ABS substrate with photonic crystal deposited was placed in a flat vulcanizing machine for heating and pressing. First, the PC / ABS substrate was placed in the flat vulcanizing machine and preheated at 170°C for 5 minutes to soften the PC / ABS substrate to a certain extent. Then, the mold was closed and pressurized at 3MPa for 60 seconds at 170°C, and then transferred to the cooling zone and cooled at 3MPa for 120 seconds.

[0056] Due to insufficient preheating and pressurization temperatures, the bonding between the PC / ABS substrate and the photonic crystal structure in the colored sample prepared in this comparative example was weak. The PC / ABS failed to penetrate well into the photonic crystal structure and cure properly, resulting in low color fastness of the colored sample. Figure 5 As shown in Figures (e) and (f), wiping with cotton cloth during the color fastness test disrupted the photonic crystal structure composed of nano-silica microspheres, causing the color of the colored sample to be wiped away.

[0057] Comparative Example 3 A coloring experiment was conducted on a thermoplastic substrate, including the following steps: The PC / ABS substrate with photonic crystal deposited as prepared in Example 1 was subjected to hot pressing and coloring. The PC / ABS substrate with photonic crystal deposited was placed in a flat vulcanizing machine for heating and pressing. First, the PC / ABS substrate was placed in the flat vulcanizing machine and preheated at 230°C for 5 minutes to soften the PC / ABS substrate to a certain extent. Then, the mold was closed and pressurized at 3MPa for 60 seconds at 230°C, and then transferred to the cooling zone and cooled at 3MPa for 120 seconds.

[0058] Due to excessively high preheating and pressurization temperatures, the PC / ABS substrate of the colored sample prepared in this comparative example exhibited excessive bonding with the photonic crystal structure. During the hot-pressing process, the PC / ABS substrate damaged and partially embedded the photonic crystal structure, resulting in a pale color and some areas lacking color. Figure 6 Figure (a) in the middle.

[0059] Comparative Example 4 A coloring experiment was conducted on a thermoplastic substrate, including the following steps: The PC / ABS substrate with photonic crystal deposited as prepared in Example 1 was subjected to hot pressing and coloring. The PC / ABS substrate with photonic crystal deposited was placed in a flat vulcanizing machine for heating and pressing. First, the PC / ABS substrate was placed in the flat vulcanizing machine and preheated at 190°C for 5 minutes to soften the PC / ABS substrate to a certain extent. Then, the mold was closed and pressurized at 3MPa for 30 seconds at 190°C, and then transferred to the cooling zone and cooled at 3MPa for 120 seconds.

[0060] Due to insufficient time for mold clamping and pressurization, the substrate of the colored sample prepared in this comparative example has weak bonding with the photonic crystal structure, resulting in low color fastness. Figure 5 As shown in Figures (g) and (h), wiping with cotton cloth during the color fastness test disrupted the photonic crystal structure composed of nano-silica microspheres, causing the color of the colored sample to be wiped away.

[0061] Comparative Example 5 A coloring experiment was conducted on a thermoplastic substrate, including the following steps: The PC / ABS substrate with photonic crystal deposited as prepared in Example 1 was subjected to hot pressing and coloring. The PC / ABS substrate with photonic crystal deposited was placed in a flat vulcanizing machine for heating and pressing. First, the PC / ABS substrate was placed in the flat vulcanizing machine and preheated at 190°C for 5 minutes to soften the PC / ABS substrate to a certain extent. Then, the mold was closed and pressurized at 3MPa for 120 seconds at 190°C, and then transferred to the cooling zone to cool at 3MPa for 120 seconds.

[0062] Due to the excessively long molding and pressing time, the PC / ABS substrate and photonic crystal structure of the colored sample prepared in this comparative example were over-bonded. During the hot-pressing process, the PC / ABS substrate damaged and partially embedded the photonic crystal structure, resulting in a pale color and some areas without color. Figure 6 Figure (b) in the middle.

[0063] Comparative Example 6 A fading test is performed on the colored sample, including the following steps: The hot-pressed colored PC / ABS sample obtained according to Example 1 was placed again in a flat vulcanizing machine for heating and pressing. First, the thermoplastic substrate was placed in the flat vulcanizing machine and pre-pressed at 250°C with a pressure of 5 MPa for 3 minutes to soften the thermoplastic substrate to a certain extent. Then, the pressure was increased to 10 MPa at 250°C for 3 minutes, and then transferred to the cooling zone with a pressure of 10 MPa for 5 minutes to cool it down, so that the attached structural color faded.

[0064] Due to insufficient pressurization time, the PC / ABS substrate in the fading sample prepared in this comparative example did not fully destroy and embed the photonic crystal structure, resulting in the structural color on the sample not fading completely.

[0065] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for repeatedly constructing structural colors on thermoplastics, characterized in that, include: (1) Add nano-silica microspheres to deionized water, disperse by ultrasonication to prepare nano-silica suspension, coat it on thermoplastic substrate, heat and evaporate to deposit, and obtain substrate with photonic crystal deposited. (2) The substrate with the photonic crystal deposited is placed in a flat vulcanizing machine and preheated, pressurized and cooled in sequence to obtain a substrate with structural color attached. (3) Place the substrate with the structural color into a flat vulcanizing machine and perform preheating, pressurization and cooling treatment in sequence to obtain the faded substrate; (4) Take the faded base as the object of operation and repeat steps (1)-(2) to achieve recoloring.

2. The method according to claim 1, characterized in that, In step (1), the nano-silica microspheres are 180-330 nm in size.

3. The method according to claim 1, characterized in that, In step (1), the nano-silica microspheres are prepared by the sol-gel method.

4. The method according to claim 1, characterized in that, In step (1), the ultrasonic dispersion is performed at 500W for 15-30 minutes.

5. The method according to claim 1, characterized in that, In step (1), the concentration of the nano-silica suspension is 0.3~0.6wt%.

6. The method according to claim 1, characterized in that, In step (1), the thermoplastic substrate is selected from at least one of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polycarbonate, and acrylonitrile-butadiene-styrene copolymer.

7. The method according to claim 1, characterized in that, In step (1), the heating evaporation deposition is a heating evaporation deposition at 50°C.

8. The method according to claim 1, characterized in that, In step (2), the preheating, pressurizing and cooling process includes: first preheating at 190~210℃ for 5 minutes, then maintaining the temperature and pressing the mold at 3~5MPa for 45~60 seconds, and finally transferring to the cooling zone and maintaining the pressure at 3~5MPa for 90~120 seconds for cooling.

9. The method according to claim 1, characterized in that, In step (3), the preheating, pressurization and cooling process includes: first, pre-pressing the mold at 250℃ and 3~5MPa for 3 minutes, then maintaining the temperature and pressurizing at 10~15MPa for 5~10 minutes, and finally transferring to the cooling zone and maintaining 10~15MPa for 5 minutes for cooling.

10. The application of the method according to any one of claims 1-9 in the fields of dyeing, decoration and anti-counterfeiting.

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