A bilayer thermally responsive photonic crystal thin-film device and its fabrication method

Abstract

This invention discloses a double-layer thermo-responsive photonic crystal thin-film device and its fabrication method. The device comprises a thermochromic polymer film, an opal photonic crystal thin film assembled from nanospheres, and a polymer thin film material filled within the opal photonic crystal thin film, forming a sandwich structure. The fabrication method is as follows: First, a photonic crystal template is assembled. A color developer, a leucochromic agent, a solvent, polydimethylsiloxane, a curing agent, and a diluent are mixed and drop-coated onto the surface of a glass substrate. High-temperature thermosetting yields a thermochromic polymer film. The photonic crystal template is then transferred into the polymer film and combined with a blank glass substrate. A polymer precursor solution is infiltrated through the gap between the two glass substrates. After standing and high-temperature thermosetting, the glass substrate is peeled off to obtain the final product. This invention uses a thermochromic polymer film exhibiting melting-darkening or melting-brightening properties as a switch for the optical path of the photonic crystal thin film. The resulting photonic crystal thin film possesses hydrophobicity, corrosion resistance, and high stability.

Description

Technical Field

[0001] This invention relates to a crystalline thin film and its preparation method, and more particularly to a bilayer thermally responsive photonic crystalline thin film device and its preparation method. Background Technology

[0002] Responsive photonic crystals are intelligent responsive materials that dynamically tune electromagnetic wave propagation. They can convert external stimuli such as heat, light, humidity, ion concentration, and magnetic fields into changes in optical signals and structural colors, showing broad application prospects in anti-counterfeiting, sensing, displays, green printing, and photocatalysis. One method for constructing responsive composite materials is the fabrication of responsive photonic crystals based on responsive assembly units. Among these, thermally responsive photonic crystals have great application potential due to their ease of fabrication. Typically, responsive photonic crystals achieve a harmonic response by adjusting the periodic lattice constants of the photonic crystal, such as the material's refractive index, incident light angle, and lattice spacing, to induce a redshift or blueshift of the reflection peak. Therefore, achieving a stimulus response in photonic crystals by adjusting non-array parameters is a significant challenge.

[0003] Among organic thermochromic phase change systems, the three-component organic thermochromic phase change system exhibits better performance and greater promise. This system mainly consists of a chromogenic agent that initiates the thermochromic reaction, a leucotropic agent that provides the thermochromic group, and a solvent that determines the color change temperature. Chromogenic agents are mainly classified into fluoranes, triarylmethanes, and spirocyclic pyrans, such as crystal violet lactone (CVL). Leucotropic agents mainly include phenols, ethers, ketones, and esters, with common examples including bisphenol A, bisphenol S, and alkyl gallate esters. Studies have shown that the intensity of the color change is related to both the color-developing agent and the solvent. Song et al. studied the thermochromic properties of the thermosensitive green / bisphenol AF / dodecyl alcohol solvent system and found that the system has reversible thermochromic properties, appearing green in the crystalline state and colorless in the molten state. Tang et al. studied the crystal violet lactone / gallic acid lauryl ester / dodecyl alcohol solvent system and found that it had no color-changing properties, while crystal violet lactone / gallic acid lauryl ester / tetradecyl alcohol had reversible thermochromic properties, appearing blue in the molten state and colorless in the crystalline state. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a double-layer thermally responsive photonic crystal thin film device with hydrophobicity, corrosion resistance, and high stability;

[0005] The second objective of this invention is to provide a method for fabricating the above-mentioned bilayer thermally responsive photonic crystal thin film device.

[0006] Technical Solution: The dual-layer thermo-responsive photonic crystal thin-film device of the present invention includes a thermochromic polymer film, an opal photonic crystal thin film assembled from nanospheres, and a polymer thin film material filled within the opal photonic crystal thin film. The thermochromic polymer film, the opal photonic crystal thin film, and the polymer thin film material form a sandwich structure. The thermochromic polymer film is formed by curing a thermochromic phase change system and a polymer precursor solution at high temperature. The polymer thin film material is formed by curing a precursor solution composed of polydimethylsiloxane, a curing agent, and a diluent at high temperature.

[0007] The thermochromic polymer film has a thickness of 50-100 μm, and the opal photonic crystal film has a thickness of 10-50 μm.

[0008] The nanospheres have a particle size of 150nm-550nm.

[0009] The nanospheres are made of one of the following: silica, titanium dioxide, tin dioxide, polystyrene, polymethyl methacrylate, cadmium sulfide, zinc oxide, or silica-coated polystyrene, polymethyl methacrylate, or titanium dioxide-coated poly(styrene-methyl methacrylate-acrylic acid) polymer colloidal microspheres, or silica-coated zinc oxide, cadmium sulfide, or titanium dioxide.

[0010] The above-mentioned method for fabricating a bilayer thermally responsive photonic crystal thin-film device includes the following steps:

[0011] (1) Photonic crystal templates were assembled from nanospheres using a vertical deposition method;

[0012] (2) Mix the color developer, leucocyanate, solvent, polydimethylsiloxane, curing agent and diluent, then drop-coat the mixture onto the surface of a glass substrate and heat-cur it at high temperature to obtain a thermochromic polymer film.

[0013] (3) The photonic crystal template from step (1) is transferred onto the thermochromic polymer film to obtain a glass substrate;

[0014] (4) Combine the glass substrate from step (3) with a blank glass substrate, and under capillary force, allow the polymer precursor solution to permeate from the gap between the two glass substrates. Let it stand to allow the polymer precursor solution to permeate into the opal pores, and then heat-cur it at high temperature. The polymer precursor solution includes polydimethylsiloxane, curing agent and diluent.

[0015] (5) Peel off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

[0016] In step (4), the volume ratio of polydimethylsiloxane, curing agent and diluent is 0.1-0.3:0.01-0.03:0.7-0.9.

[0017] In step (1), the concentration of the vertical sedimentation solution is 0.5-2 wt%.

[0018] In step (2), the molar ratio of the color developer, the leucochromic agent and the solvent is 1-3:1-3:50-200.

[0019] In step (2), the mass ratio of the thermochromic phase change system, the diluent polymer, the polydimethylsiloxane and the curing agent is 0.05-0.1:0.6-0.8:0.2-0.3:0.02-0.03.

[0020] The color-developing agents are phenols, sulfonic acids, carboxylic acids, haloalcohols and their derivatives;

[0021] The leucochemical agent is one of triarylmethanes, phenothiazines, fluoranes, spirocyclopyrans, or rhodamine B lactams; the solvent is an alcohol, ether, ketone, phosphate ester, carboxylic acid ester, sulfonate ester, or sulfite ester, etc.; and the diluent is one of an alcohol, hydrocarbon, ether, or ketone.

[0022] Invention Principle: By controlling the temperature-induced thermochromic polymer film, the presence or absence of information in the photonic crystal's optical path can be displayed or hidden. This double-layer thermoresponsive photonic crystal film can be applied to anti-counterfeiting and smart window applications. Compared to traditional responsive photonic crystals, this double-layer photonic crystal achieves stimulus response through non-array parameter control, with no volume change during the response process. Using polymer-encapsulated nanosphere photonic crystals improves the abrasion resistance and solvent resistance of the photonic crystal device, thus broadening its application areas.

[0023] Beneficial Effects: Compared with existing technologies, this invention achieves the following significant effects: 1. Using a thermochromic polymer film with melting-darkening or melting-brightening properties as the switch for the photonic crystal thin film's optical path results in a photonic crystal thin film with hydrophobicity, corrosion resistance, and high stability. 2. It achieves self-cleaning and possesses a color effect that is permanent and angle-dependent. 3. The process is simple and low-cost. 4. Heating can cause the thermochromic film to fade, opening the optical path of the photonic crystal and thus enabling information display. 5. Illumination can raise the device temperature, achieving a deeper color effect, thereby achieving heat insulation and energy saving. The presence of the photonic crystal absorbs most ultraviolet light, providing ultraviolet protection and making it applicable to smart windows. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the fabrication process of the thermally responsive bilayer photonic crystal thin-film device of the present invention.

[0025] Figure 2The images show the SEM image of the polystyrene microsphere template in Example 1, the reflectance spectrum of the diffuse reflectance spectrum detected using the integrating sphere mode, and the corresponding microscope optical photographs.

[0026] Figure 3 The images show the SEM image of the polystyrene microsphere template in Example 2, the reflectance spectrum of the diffuse reflectance spectrum detected using the integrating sphere mode, and the corresponding microscope optical photographs.

[0027] Figure 4 The images show the SEM image of the polystyrene microsphere template in Example 3, the reflectance spectrum of the diffuse reflectance spectrum detected using the integrating sphere mode, and the corresponding microscope optical photographs.

[0028] Figure 5 The images show the SEM image of the polystyrene microsphere template in Example 4, the reflectance spectrum of the diffuse reflectance spectrum detected using the integrating sphere mode, and the corresponding microscope optical photographs.

[0029] Figure 6 Optical photographs of the molten and brightened bilayer thermally responsive photonic crystal film in Example 2 in the molten state and in the crystalline state;

[0030] Figure 7 This is a digital photograph of the polystyrene template in Example 3 as the incident angle changes;

[0031] Figure 8 The reflectance spectrum of the photonic crystal thin film prepared in Example 3 is an angle-dependent reflectance spectrum.

[0032] Figure 9 An optical photograph of the melt-darkening thermochromic phase transition system in Example 4;

[0033] Figure 10 The image shows the reflection spectrum of the thermally responsive photonic crystal thin film in Example 3.

[0034] Figure 11 An optical photograph of the photonic crystal prepared in Comparative Example 1;

[0035] Figure 12 An optical photograph of the photonic crystal prepared in Comparative Example 2;

[0036] Figure 13 This is an optical photograph of the thermochromic system in Comparative Example 3. Detailed Implementation

[0037] The present invention will now be described in further detail.

[0038] Example 1

[0039] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0040] (1) Mix crystal violet lactone, bisphenol A, and cetyl alcohol in a molar ratio of 2:1:100, thermochromic phase change system, diluent, Sylgard 184 polydimethylsiloxane, and Sylgard 184 curing agent in a volume ratio of 0.05:0.7:0.25:0.02, and after ultrasonic dispersion, apply the mixture to the surface of a glass substrate using a pipette. Then, heat-cure the mixture at a high temperature of 90°C for 30 minutes.

[0041] (2) A polystyrene opal photonic crystal template with a particle size of ~183nm was assembled in a constant temperature drying oven at 60℃ and 50% humidity using a vertical deposition method, with a solid content of 0.5wt% in the deposition liquid. The pre-assembled photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0042] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor liquid, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.2:0.02:0.8, into the gap between the two glass substrates. Use a separator with a thickness of 50 μm to control the distance between the glass slides to obtain a polymer film with a thickness of 50 μm. Let it stand for 20 min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90 °C for 30 min. Peel off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

[0043] Figure 1 This is a flowchart illustrating the fabrication process of the thermoresponsive bilayer photonic crystal thin-film device in this embodiment, and it is applicable to all embodiments. The bilayer photonic crystal thin-film device is fabricated using a three-step method: first, a thermochromic polymer film is prepared; then, a polystyrene opal photonic crystal is pre-assembled; a photonic crystal template is transferred onto the thermochromic polymer film; the film is then merged with another glass substrate; finally, a polymer precursor is infused into the gap between the two glass plates; and the film is then thermo-cured at high temperature to obtain the photonic crystal thin film.

[0044] Figure 2 In this embodiment, 'a' represents the SEM image of the ~183nm polystyrene microsphere template used. Figure 2 The upper right corner of 'a' in the graph is the corresponding Fast Fourier Transform spectrum; Figure 2 In the figure, b represents the reflectance spectrum obtained by detecting diffuse reflectance using the integrating sphere mode; Figure 2 In the image, 'c' represents the corresponding microscope optical photograph; in the digital photograph, the thin film appears purple.

[0045] Example 2

[0046] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0047] (1) Mix crystal violet lactone, bisphenol S, and cetyl alcohol in a molar ratio of 2:1:100, thermochromic phase change system, diluent, Sylgard 184 polydimethylsiloxane, and Sylgard 184 curing agent in a volume ratio of 0.1:0.6:0.3:0.03, and ultrasonically disperse the mixture evenly. Then, use a pipette to drop the mixture onto the surface of a glass substrate and heat cure it at a high temperature of 90°C for 30 minutes.

[0048] (2) A polystyrene opal photonic crystal template with a particle size of ~210 nm was assembled in a constant temperature drying oven at 60℃ and 50% humidity using a vertical deposition method, with a solid content of 1 wt% in the deposition liquid. The pre-assembled photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0049] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor liquid, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.2:0.02:0.8, into the gap between the two glass substrates. Use a separator with a thickness of 50 μm to control the distance between the glass slides to obtain a polymer film with a thickness of 50 μm. Let it stand for 20 min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90 °C for 30 min. Peel off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

[0050] Figure 3 In this embodiment, 'a' represents the SEM image of the ~210nm polystyrene microsphere template used. Figure 3 The upper right corner of 'a' in the graph is the corresponding Fast Fourier Transform spectrum; Figure 3 In the figure, b represents the reflectance spectrum obtained by detecting diffuse reflectance using the integrating sphere mode; Figure 3 In the image, 'c' represents the corresponding microscope optical photograph; in the digital photograph, the thin film is green.

[0051] Figure 6 In this embodiment, 'a' is an optical photograph of the bilayer thermally responsive photonic crystal thin film in the molten state. Figure 6 In the image, b is an optical photograph of a bilayer thermally responsive photonic crystal thin film in its crystalline state.

[0052] Example 3

[0053] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0054] (1) Mix crystal violet lactone, bisphenol A, and cetyl alcohol in a molar ratio of 2:1:100, thermochromic phase change system, diluent, Sylgard 184 polydimethylsiloxane, and Sylgard 184 curing agent in a volume ratio of 0.1:0.6:0.3:0.03, and ultrasonically disperse the mixture evenly. Then, use a pipette to drop the mixture onto the surface of a glass substrate and heat cure it at a high temperature of 90°C for 30 minutes.

[0055] (2) A polystyrene opal photonic crystal template with a particle size of ~249 nm was assembled in a constant temperature drying oven at 60℃ and 50% humidity using a vertical deposition method, with a solid content of 2wt% in the deposition liquid. The pre-assembled photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0056] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor liquid, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.2:0.02:0.8, into the gap between the two glass substrates. Use a separator with a thickness of 100μm to control the distance between the glass slides to obtain a polymer film with a thickness of 100μm. Let it stand for 30min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90℃ for 30min. Peel off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

[0057] Figure 4 In the example, 'a' is the SEM image of the ~249nm polystyrene microsphere template used in the embodiment, and the upper right corner of 'a' in '4' is the corresponding fast Fourier transform spectrum. Figure 4 In the figure, b represents the reflectance spectrum obtained by detecting diffuse reflectance using the integrating sphere mode; Figure 4 In the image, 'c' represents the corresponding microscope optical photograph; in the digital photograph, the thin film is orange.

[0058] Figure 7 This is a digital photograph of the polystyrene opal photonic crystal template in this embodiment, taken at varying incident angles (0°, 10°, 30°, 45°, 60°, and 90°). The photograph shows the structural color changing from orange to blue.

[0059] Figure 8 The image shows the reflection spectrum of the photonic crystal film after filling the polystyrene opal photonic crystal with PDMS in this embodiment, from the observation angle of 0° to 80°. The reflection peak is 649nm when the observation angle is 0°. As the observation angle increases, the reflection peak blue shifts. The wavelength of the reflection peak is 495nm when the observation angle is 80°.

[0060] Example 4

[0061] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0062] (1) Mix crystal violet lactone, gallic acid dodecyl ester, tetradecyl alcohol in a molar ratio of 1:6:40, thermochromic phase change system, diluent, Sylgard 184 polydimethylsiloxane and Sylgard 184 curing agent in a volume ratio of 0.05:0.75:0.3:0.03, and ultrasonically disperse evenly. Then, drop the mixture onto the surface of the glass substrate with a pipette and heat cure at a high temperature of 90°C for 30 minutes.

[0063] (2) A polystyrene opal photonic crystal template with a particle size of ~263nm was assembled in a constant temperature drying oven at 60℃ and 50% humidity using a vertical deposition method, with a solid content of 1wt% in the deposition liquid. The pre-assembled photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0064] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor liquid, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.1:0.01:0.9, into the gap between the two glass substrates. Use a separator with a thickness of 100 μm to control the distance between the glass slides to obtain a polymer film with a thickness of 100 μm. Let it stand for 30 min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90 °C for 30 min. Peel off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

[0065] Figure 5 In this embodiment, 'a' represents the SEM image of the ~263nm polystyrene microsphere template used. Figure 5 The upper right corner of 'a' in the graph is the corresponding Fast Fourier Transform spectrum; Figure 5 In the diagram, b represents the reflectance spectrum obtained by detecting diffuse reflectance using the integrating sphere mode. Figure 5 In the image, 'c' represents the corresponding microscope optical photograph; in the digital photograph, the thin film is red.

[0066] Figure 9 The color change of the melt-darkening thermochromic phase change system in this embodiment shows a significant heating color deepening phenomenon under conditions of high chromogenic agent concentration, low solvent concentration, and matching alkyl chain lengths of the chromogenic agent and solvent.

[0067] Example 5

[0068] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0069] (1) Mix crystal violet lactone, bisphenol A, and cetyl alcohol in a molar ratio of 2:1:100, thermochromic phase change system, diluent, Sylgard 184 polydimethylsiloxane, and Sylgard 184 curing agent in a volume ratio of 0.1:0.6:0.3:0.03, and ultrasonically disperse the mixture evenly. Then, use a pipette to drop the mixture onto the surface of a glass substrate and heat cure it at a high temperature of 90°C for 30 minutes.

[0070] (2) A patterned PDMS mask was attached to a glass substrate cleaned with piranha solution. A patterned polystyrene opal photonic crystal template with a particle size of ~210 nm was assembled in a constant temperature drying oven at 60°C and 50% humidity using a vertical deposition method. The solid content of the deposition liquid was 1 wt%. The pre-assembled patterned photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0071] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor liquid, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.1:0.01:0.9, into the gap between the two glass substrates. Use a separator with a thickness of 50 μm to control the distance between the glass slides to obtain a polymer film with a thickness of 50 μm. Let it stand for 20 min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90 °C for 30 min. Peel off the glass substrate to obtain a patterned double-layer thermally responsive photonic crystal film.

[0072] Figure 10 The images show the reflection spectra of the thermoresponsive photonic crystal thin film in this embodiment, in order: the reflection spectrum observed from the thermochromic polymer film side in the crystalline state, the reflection spectrum observed from the photonic crystal thin film side in the crystalline state, the reflection spectrum observed from the thermochromic polymer film side in the molten state, and the reflection spectrum observed from the photonic crystal thin film side in the molten state.

[0073] Comparative Example 1

[0074] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0075] (1) Mix crystal violet lactone, bisphenol A, tetradecyl alcohol in a molar ratio of 2:1:100, thermochromic phase change system, diluent, Sylgard 184 polydimethylsiloxane and Sylgard 184 curing agent in a volume ratio of 0.05:0.75:0.2:0.02, and ultrasonically disperse evenly. Then, drop the mixture onto the surface of the glass substrate with a pipette and heat cure at a high temperature of 90°C for 30 minutes.

[0076] (2) A polystyrene opal photonic crystal template with a particle size of ~210 nm was assembled in a constant temperature drying oven at 80℃ and 50% humidity using a vertical deposition method, with a solid content of 1 wt% in the deposition liquid. The pre-assembled photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0077] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor solution, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.1:0.01:0.9, into the gap between the two glass substrates. Use a separator with a thickness of 50 μm to control the distance between the glass slides to obtain a polymer film with a thickness of 50 μm. Let it stand for 20 min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90 °C for 30 min. Peel off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

[0078] Figure 11 The image shows an optical photograph of the photonic crystal prepared in Comparative Example 1. Due to the excessively high assembly temperature, the deposition time was insufficient, resulting in poor regularity of the obtained photonic crystal film.

[0079] Comparative Example 2

[0080] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0081] (1) Mix crystal violet lactone, bisphenol A, cetyl alcohol in a molar ratio of 2:1:100, thermochromic phase change system, diluent, Sylgard 184 polydimethylsiloxane and Sylgard 184 curing agent in a volume ratio of 0.05:0.75:0.2:0.02, and ultrasonically disperse evenly. Then, use a pipette to drop the mixture onto the surface of the glass substrate and heat cure it at a high temperature of 90°C for 30 minutes.

[0082] (2) A polystyrene opal photonic crystal template with a particle size of ~210 nm was assembled in a constant temperature drying oven at 60℃ and 50% humidity using a vertical deposition method, with a solid content of 3 wt% in the deposition liquid. The pre-assembled photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0083] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor liquid, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.1:0.01:0.9, into the gap between the two glass substrates. Control the distance between the glass slides through a separator with a thickness of 100 μm to obtain a polymer film with a thickness of 100 μm. Let it stand for 20 min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90 °C for 30 min. Peel off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

[0084] Figure 12 The image shows an optical photograph of the photonic crystal prepared in Comparative Example 2. The high concentration of the assembly solution resulted in a large thickness of the photonic crystal film, while the weak bonding between the photonic crystal and the glass substrate led to a large amount of photonic crystal detachment.

[0085] Comparative Example 3

[0086] A bilayer thermally responsive photonic crystal thin-film device, the fabrication method of which includes the following steps:

[0087] (1) Mix crystal violet lactone, octadecyl gallate, tetradecyl alcohol in a molar ratio of 1:6:100, thermochromic phase change system, Sylgard 184 polydimethylsiloxane, Sylgard 184 curing agent and diluent in a volume ratio of 0.05:0.75:0.2:0.02, and ultrasonically disperse evenly. Then, use a pipette to drop the mixture onto the surface of a glass substrate and heat cure it at a high temperature of 90°C for 30 minutes.

[0088] (2) A polystyrene opal photonic crystal template with a particle size of ~263 nm was assembled in a constant temperature drying oven at 60℃ and 50% humidity using a vertical deposition method, with a liquid-solid content of 0.5 wt%. The pre-assembled photonic crystal template was carefully transferred onto the above-mentioned thermochromic polymer film.

[0089] (3) Combine the glass substrate from the previous step with the blank glass substrate. Under capillary force, inject the polymer precursor liquid, which is a mixture of Sylgard184 polydimethylsiloxane, Sylgard184 curing agent and diluent in a volume ratio of 0.1:0.8:0.08, into the gap between the two glass substrates. Control the distance between the glass slides through a separator with a thickness of 100 μm to obtain a polymer film with a thickness of 100 μm. Let it stand for 30 min to allow the polymer solution to completely penetrate into the opal pores. Perform high-temperature thermal curing at a curing temperature of 90 °C for 30 min. Peel off the glass substrate to obtain a double-layer melt-darkening thermally responsive photonic crystal film.

[0090] Figure 13To compare the thermochromic performance of the thermochromic system in Comparative Example 3, Comparative Example 3 could not show the melting and darkening effect due to the high solvent concentration and the mismatch between the alkyl chain lengths of the solvent and the color developer, and the color change was not obvious.

[0091] The experiments above demonstrate that by controlling the deposition conditions of photonic crystals, such as deposition temperature and deposition solution concentration, photonic crystal films with regular structures and distinct structural colors can be obtained. By adjusting the volume ratio of the components in the thermochromic phase transition system, thermochromic polymer films with distinct color changes and good color sensitivity can be prepared. By assembling the polymer film and photonic crystal film with polydimethylsiloxane, a bilayer thermoresponsive photonic crystal film can be prepared with good thermal responsiveness. The color change of the upper thermochromic polymer film under temperature stimulation enables the display and concealment of the lower structural color. Through the synergistic effect of structural color and pigment color, colorful and high-quality smart products can be prepared.

Claims

1. A double-layer thermally responsive photonic crystal thin film device, characterized in that, The thermal color-changing polymer film, the opal photonic crystal film assembled by the nanometer microspheres, and the polymer film material filled in the opal photonic crystal film form a sandwich structure; the thermal color-changing polymer film is formed by curing a thermal color-changing phase change system and a polymer precursor solution at high temperature; the polymer film material is formed by curing a precursor solution composed of polydimethylsiloxane, a curing agent, and a diluent at high temperature; The preparation method of the double-layer thermal response photonic crystal film device comprises the following steps: (1) a photonic crystal template is assembled by nanometer microspheres by using a vertical deposition method; the vertical deposition liquid concentration is 0.5-2 wt%; (2) a color developer, a leuco developer, a solvent, polydimethylsiloxane, a curing agent, and a diluent are mixed, and then are dropped and coated on the surface of a glass substrate, and are heat-cured at high temperature to obtain a thermal color-changing polymer film; the molar ratio of the color developer, the leuco developer, and the solvent is 1-3:1-3:50-200; the mass ratio of the thermal color-changing phase change system, the diluent, polydimethylsiloxane, and the curing agent is 0.05-0.1:0.6-0.8:0.2-0.3:0.02-0.03; the color developer is one of phenols, sulfonic acids, carboxylic acids, and halogenated alcohols and derivatives thereof; the leuco developer is one of triarylmethane, phenothiazine, fluoran, spirocyclic pyran, or rhodamine B lactam; the solvent is one of alcohol, ether, ketone, phosphate, carboxylic acid ester, sulfonate, and sulfite; and the diluent is one of alcohol, hydrocarbon, ether, or ketone; (3) the photonic crystal template in step (1) is transferred into the thermal color-changing polymer film to obtain a glass substrate; (4) the glass substrate in step (3) is combined with a blank glass substrate, polymer precursor solution penetrates from the gap between the two glass substrates under capillary force, and the polymer precursor solution is allowed to penetrate into the opal pores and is heat-cured at high temperature; the polymer precursor solution comprises polydimethylsiloxane, a curing agent, and a diluent; (5) the glass substrate is peeled off to obtain a double-layer thermal response photonic crystal film.

2. The dual-layer thermo-responsive photonic crystal thin film device of claim 1, wherein, The thickness of the thermal color-changing polymer film is 50-100 μm, and the thickness of the opal photonic crystal film is 10-50 μm.

3. The dual-layer thermo-responsive photonic crystal thin film device of claim 1, wherein, The particle size of the nanometer microspheres is 150 nm-550 nm.

4. The dual-layer thermo-responsive photonic crystal thin film device of claim 1, wherein, The nanometer microspheres are one of silica, titanium dioxide, tin dioxide, polystyrene, polymethyl methacrylate, cadmium sulfide, zinc oxide, silica-coated polystyrene, polymethyl methacrylate, or titanium dioxide-coated poly(styrene-methyl methacrylate-acrylic acid) polymer colloidal microspheres, or silica-coated zinc oxide.

5. A method for preparing the double-layer thermally responsive photonic crystal thin film device of claim 1, characterized in that, The preparation method comprises the following steps: (1) a photonic crystal template is assembled by nanometer microspheres by using a vertical deposition method; the vertical deposition liquid concentration is 0.5-2 wt%; (2) mixing the color developer, the leuco developer, the solvent, the polydimethylsiloxane, the curing agent and the diluent, then dropping and coating on the surface of the glass substrate, high-temperature thermal curing to obtain a thermochromic polymer film; the molar ratio of the color developer, the leuco developer and the solvent is 1-3:1-3:50-200; the mass ratio of the thermochromic phase change system, the diluent, the polydimethylsiloxane and the curing agent is 0.05-0.1:0.6-0.8:0.2-0.3:0.02-0.03; the color developer is phenolic, sulfonic acid, carboxylic acid and halogenated alcohol and its derivatives; the leuco developer is one of triarylmethane, phenothiazine, fluoran, spirocyclic pyran or rhodamine B lactam; the solvent is alcohol, ether, ketone, phosphate, carboxylic acid ester, sulfonic acid ester and sulfite, and the diluent is one of alcohol, hydrocarbon, ether or ketone; (3) transferring the photonic crystal template of step (1) into the thermochromic polymer film to obtain a glass substrate; (4) combining the glass substrate of step (3) with a blank glass substrate, under the capillary force, the polymer precursor solution penetrates from the gap between the two glass substrates, and is left to stand, so that the polymer precursor solution penetrates into the opal pores, and is high-temperature thermal cured; the polymer precursor solution includes polydimethylsiloxane, a curing agent and a diluent; (5) peeling off the glass substrate to obtain a double-layer thermally responsive photonic crystal film.

6. The method of claim 5, wherein the method further comprises: In step (4), the volume ratio of the polydimethylsiloxane, the curing agent and the diluent is 0.1-0.3:0.01-0.03:0.7-0.9.

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