Method for manufacturing optical control element

Abstract

To provide a novel optical control element.SOLUTION: A method for manufacturing an optical control element is to manufacture an optical control element whose optical characteristics, which are one or more of light transmission characteristics and light reflection characteristics, change according to environmental changes which are one or more of temperature change and light absorption, and the manufacturing method includes: a precursor step of preparing an element precursor comprising a substrate, and a plurality of inorganic particles formed of phase transition material that makes a phase transition according to the environmental changes, having an average particle diameter of 1 nm or more and 1000 μm or less, and spaced apart from each other on a surface of the substrate; and an irradiation step of irradiating the inorganic particles of the element precursor with ultraviolet light.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a light control element. [Background technology]

[0002] It has been proposed to adjust the metal-dielectric phase transition characteristics by irradiating ultraviolet light onto a vanadium oxide film formed on the surface of an alumina substrate (see, for example, Non-Patent Document 1). Non-Patent Document 1 claims that by irradiating ultraviolet light onto a vanadium oxide film, the metal-dielectric phase transition characteristics can be adjusted at a relatively low temperature, such as below 250°C. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] G. Ko and S. Ramanathan, “Effect of ultraviolet irradiation on electrical resistance and phase transition characteristics of thin film vanadium oxide”, Journal of Applied Physics 103, 106104 (2008). Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, elements having a film of a phase-transition material such as vanadium oxide formed on the surface of a substrate undergo a phase transition in response to environmental changes such as temperature change or light absorption, which in turn changes their optical properties, such as light transmission and reflection characteristics. These properties can be utilized to form light-controlling elements. It is believed that applying the technology of Non-Patent Document 1 to such light-controlling elements and adjusting the phase transition properties by irradiating them with ultraviolet light makes it possible to adjust the changes in optical properties. However, in Non-Patent Document 1, the phase-transition material vanadium dioxide is formed as a film, and when used in light-controlling elements, the desired change in optical properties may not be achieved.

[0005] The present disclosure has been made to solve such problems, and a main object of the disclosure is to provide a novel light control element. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above-mentioned object, the inventors discovered that when a phase transition material is separated and arranged as nano- to micro-sized particles, rather than as a film, and irradiated with ultraviolet light, it exhibits a desired change in optical properties, thereby completing the invention of the present disclosure.

[0007] That is, the method for manufacturing a light control element according to the present disclosure includes the steps of: A manufacturing method for manufacturing a light control element whose optical characteristics, which are at least one of light transmission characteristics and light reflection characteristics, change due to an environmental change, which is at least one of temperature change and light absorption, comprising: a precursor step of preparing an element precursor including a substrate and a plurality of inorganic particles formed of a phase transition material that undergoes a phase transition in response to a change in the environment, the inorganic particles having an average particle size of 1 nm to 1000 μm and arranged separately from one another on a surface of the substrate; an irradiation step of irradiating the inorganic particles of the element precursor with ultraviolet light; It includes: [Effects of the Invention]

[0008] The present disclosure provides a novel light control element. For example, it can provide a light control element that exhibits a change in optical properties different from that observed when a phase transition material is formed into a film and irradiated with ultraviolet light. The reason for this effect is presumed to be as follows. For example, when a phase transition material is formed into nano- to micro-sized particles, the surface condition (e.g., the amount of oxygen defects on the surface that become crystal nuclei and the distortion of the crystal structure) differs from that observed when the material is formed into a film, and therefore it is believed that a light control element can be provided that exhibits a change in optical properties different from that observed when the material is formed into a film. It is also believed that the change in optical properties can be finely adjusted, for example, by adjusting the irradiation conditions or whether or not to irradiate ultraviolet light for each particle. It is also believed that the tendency for ultraviolet light irradiation to reduce the variation in the change in optical properties of inorganic particles can be utilized to suppress the variation in the change in optical properties between products. In this way, it is possible to provide a novel light control element that exhibits a desired change in optical properties. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram showing the outline of the configuration of an element precursor 10. [Figure 2] FIG. 2 is an explanatory diagram showing an outline of an irradiation process using an ultraviolet light irradiation device 50. [Figure 3] FIG. 2 is an explanatory diagram illustrating changes in the optical properties of inorganic particles when the temperature is increased and decreased. [Figure 4] Confocal microscope photograph of Experimental Example 1 at a sample temperature of 18°C. [Figure 5] Confocal microscope photographs of the sample in Experimental Example 1 as the temperature was increased. [Figure 6] A graph showing the brightness change of the circled particles in Figure 4. [Figure 7] Representative graphs showing the change in particle brightness in Experiments 1 and 2. [Figure 8] Frequency distribution of the hysteresis width ΔT of particle brightness change in Experimental Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for manufacturing a light control element disclosed herein is a method for manufacturing a light control element whose optical characteristics change in response to environmental changes, such as temperature change and / or light absorption. This manufacturing method includes a precursor process and an irradiation process. Each process will be described below.

[0011] (Precursor process) In the precursor process, an element precursor, which is a precursor of the light control element, is prepared. The element precursor includes a substrate and a plurality of inorganic particles formed on the surface of the substrate. The inorganic particles may be formed on only one surface of the substrate, or may be formed on two opposing surfaces, for example. The inorganic particles are arranged separately from each other on the surface of the substrate. "Separate arrangement" means that the inorganic particles are arranged apart from each other without contacting each other.

[0012] The substrate is, for example, a flat substrate, preferably a plane-parallel substrate. The substrate may be, for example, a glass substrate such as fused silica glass or synthetic quartz glass, a ceramic substrate, or a resin substrate. The substrate is preferably light-transmitting, and is preferably transparent.

[0013] The inorganic particles are made of a phase-transition material that undergoes a phase transition in response to an environmental change, which may be one or more of a temperature change and light absorption. When a phase-transition material undergoes a phase transition in response to an environmental change, it is thought that the dielectric constant changes, the interaction with incident light changes, and optical properties such as transmitted light characteristics and reflected light characteristics change. The temperature change also includes a temperature change caused by the inorganic particles absorbing light. The phase-transition material may be a solid-solid phase-transition material whose crystalline structure changes in response to a change in environmental conditions, or a metal-dielectric phase-transition material. The phase-transition material may be a metal oxide or a metal sulfide. The phase-transition material may be a strongly correlated insulator or a Mott insulator, such as vanadium dioxide (VO2) or chromium hollandite (K2Cr8O 16), or iron-based spin ladder material (BaFe2S3). These may be doped with other atoms or may not be doped; for example, vanadium dioxide may be undoped vanadium dioxide, tungsten-doped vanadium dioxide, or chromium-doped vanadium dioxide.

[0014] The inorganic particles are preferably formed of vanadium dioxide. Vanadium dioxide changes from a dielectric state to a metallic state when the temperature is changed from low to high, and from the metallic state to a dielectric state when the temperature is changed from high to low. In this way, the real part of the relative dielectric constant of vanadium dioxide is inverted before and after the phase transition due to the temperature change. Furthermore, when vanadium dioxide is irradiated with light, it absorbs the incident light and converts it into heat, causing a temperature change.

[0015] The inorganic particles are preferably composed of nanoparticles having a nano-sized particle size (1 nm or more but less than 1000 nm) or microparticles having a micro-sized particle size (1 μm or more but less than 1000 μm). The average particle size of the inorganic particles is 1 nm or more but less than 1000 μm. The average particle size of the inorganic particles may be 10 nm or more, 100 nm or more, 300 nm or more, or 500 nm or more. The average particle size of the inorganic particles is preferably 1 / 10 or more of the target wavelength, and considering applications from visible light to near-infrared wavelengths, 40 nm or more is desirable. The average particle size of the inorganic particles may be 1000 nm or less, 700 nm or less, 650 nm or less, or 350 nm or less. The particle size of the inorganic particles is the equivalent circle diameter (the diameter of a circle having the same area as the projected area of ​​the particle) determined by image analysis using an optical microscope or electron microscope. The average particle size of the inorganic particles is the average particle size based on the number of particles.

[0016] The shape of the inorganic particles may be, for example, a circular or elliptical shape when the light control element is viewed from above, or a shape in which multiple such shapes are connected together.The shape of the inorganic particles may be, for example, a spherical shape, an ellipsoidal shape, a partially missing sphere shape, or a partially missing ellipsoidal shape.Furthermore, the shape of the inorganic particles may be a secondary particle shape in which multiple primary particles such as spheres, ellipsoids, partially missing spheres, or partially missing ellipsoidal spheres are connected together.

[0017] The inorganic particles may have variations in one or more of particle size and particle shape. When the particle size or particle shape of the inorganic particles differs, the phase transition temperature differs due to differences in the surface condition (e.g., the amount of oxygen defects on the surface that become crystal nuclei or the distortion of the crystal structure). Therefore, by having variations in one or more of particle size and particle shape, the phase transition temperature differs for each particle, and it is thought that the optical properties can be changed to a multi-value or continuous value exceeding two. When the inorganic particles have variations in particle size, the standard deviation of the particle size may be 500 nm or less, 400 nm or less, or 300 nm or less. The standard deviation of the particle size may be 100 nm or more, or 200 nm or more. Incidentally, having variations in particle size and particle shape means that the particle size and particle shape are not constant, and two or more particle sizes and particle shapes are sufficient. Incidentally, the inorganic particles do not need to have variations in particle size and particle shape.

[0018] The inorganic particles may be formed over 10% or more of the substrate surface, i.e., the coverage of the substrate surface with the inorganic particles may be 10% or more. This coverage may be 15% or more, or 20% or more. Also, this coverage may be 90% or less, 80% or less, 70% or less, or 65% or less.

[0019] The element precursor may be fabricated, for example, by forming the raw material of the phase transition material or the phase transition material into a film or particles on a substrate and, if necessary, heat-treating the resulting material under a predetermined atmosphere. Examples of phase transition materials include the aforementioned vanadium dioxide, chromium hollandite, and iron-based spin ladder materials. Examples of raw materials for the phase transition material include metals such as vanadium, tungsten, chromium, iron, potassium, and barium, as well as compounds containing these metals. Methods for forming the film or particles include physical vapor deposition (PVD) such as sputtering, vacuum deposition, and ion plating, and chemical vapor deposition (CVD) such as thermal CVD and plasma CVD. When forming the film, the film thickness may be, for example, 1 nm or more, 10 nm or more, or 20 nm or more. The film thickness may be, for example, 300 nm or less, 200 nm or less, or 100 nm or less. Examples of heat-treatment atmospheres include oxygen-containing atmospheres, sulfur-containing atmospheres, and vacuum atmospheres. The heat treatment atmosphere may be, for example, 0.1 Pa or more, or 20 Pa or more. The heat treatment atmosphere may be, for example, 100 Pa or less, or 30 Pa or less. The heat treatment temperature may be, for example, 150°C or more, or 300°C or more. The heat treatment temperature may be, for example, 600°C or less, or 400°C or less. The heat treatment time may be, for example, 1 minute or more and 180 minutes or less, 5 minutes or more and 120 minutes or less, or 10 minutes or more and 90 minutes or less. By appropriately adjusting these conditions, the particle size, particle shape, coverage rate, etc. of the inorganic particles can be adjusted.

[0020] An example of an element precursor is shown in FIG. 1. FIG. 1 is an explanatory diagram showing an outline of the configuration of an element precursor 10. FIG. 1A is a schematic top view of the element precursor 10, and FIG. 1B is a schematic cross-sectional view of the element precursor 10 cut along a plane perpendicular to a substrate 12. As shown in FIG. 1, the element precursor 10 includes a substrate 12 and a plurality of inorganic particles 14 arranged separately from one another on a surface 12a of the substrate 12. The inorganic particles 14 are made of a phase change material such as VO2, and have an average particle size of 1 nm or more and 1000 μm or less. The inorganic particles 14 may have variation in one or more of particle size and particle shape.

[0021] Even in its original state, the element precursor changes its optical properties in response to environmental changes, and functions as a light control element. The change in optical properties due to environmental changes will be explained using Figure 3. Figure 3 is an explanatory diagram illustrating the change in optical properties of inorganic particles when the temperature is increased and decreased. In Figure 3, the change in optical properties (vertical axis) is the change in brightness of inorganic particles extracted from images captured by a confocal microscope. Figure 3 also shows examples of the change in brightness of three inorganic particles, using a solid line, a dashed line, and a dashed-dotted line. As shown in Figure 3, when the light control element (which may be an element precursor) is heated, the brightness of the inorganic particles suddenly becomes darker at a certain temperature and then converges, while when the temperature is decreased, the brightness suddenly becomes brighter at a certain temperature and then converges. Regarding the change in brightness at this time, the inflection point temperature of the brightness change when the temperature is increased is defined as T C,up [℃], and the inflection point temperature of the brightness change when the temperature is lowered is T C,down [℃], and the difference in inflection point temperature during temperature rise and temperature fall, T C,up -T C,down The hysteresis width ΔT [°C] is shown in Figure 3. As shown in Figure 3, the change in optical properties, for example, the inflection point temperature T C,up and T C,down The hysteresis width ΔT, etc., differ for each inorganic particle. This is presumably because the amount of oxygen defects on the surface that become the crystal nuclei and the distortion of the crystal structure differ for each inorganic particle due to differences in particle size and particle shape. When a phase transition material is formed as particles rather than as a film, it is possible to utilize these differences between particles to change the optical properties to multiple values ​​greater than two or continuously. However, in this state, the desired change in optical properties may not be observed. Furthermore, because it is relatively difficult to control the particle size and particle shape of inorganic particles, the change in optical properties may vary greatly from product to product. Therefore, the following irradiation process is performed.

[0022] (irradiation process) In the irradiation step, ultraviolet light is irradiated onto inorganic particles of the element precursor. When the inorganic particles are irradiated with ultraviolet light, the amount of oxygen vacancies and the valence of metal elements (e.g., vanadium) in the phase transition material change, particularly on the surface of the inorganic particles, and it is thought that this causes a change in the generation of crystal nuclei that serve as the starting point for the phase transition. This changes the phase transition characteristics (e.g., phase transition temperature) of the inorganic particles, which in turn changes the optical properties of the inorganic particles, for example, the inflection point temperature T C,up and T C,down It is believed that this makes it possible to adjust the hysteresis width ΔT, etc., and to manufacture an optical control element that exhibits a desired change in optical properties. The hysteresis width ΔT of the change in optical properties corresponds to the hysteresis width of the phase transition (also called the phase transition temperature width).

[0023] In the irradiation step, ultraviolet light may be irradiated onto all of the inorganic particles, or only some of the inorganic particles. The wavelength of the ultraviolet light may be 400 nm or less, but is preferably 300 nm or less, and may be 280 nm or less, or 260 nm or less. It is presumed that irradiation with ultraviolet light having a wavelength of 300 nm or less promotes electron transition due to the high energy of about 5 eV or more, thereby promoting an increase in the amount of oxygen vacancies and a change in the valence of metal elements in the phase transition material. The wavelength of the ultraviolet light may be, for example, 100 nm or more, 200 nm or more, or 250 nm or more. In the irradiation step, the ultraviolet light may be focused and irradiated. By focusing the light, the ultraviolet light can be irradiated spatially and locally. When focusing the ultraviolet light, the spot diameter may be, for example, 10 mm or less, 5 mm or less, or 2 mm or less. The spot diameter may be, for example, 0.1 mm or more, 0.5 mm or more, or 1 mm or more. The irradiation intensity of the ultraviolet light is, for example, 0.1 mW / mm 2 It may be 0.5 mW / mm or more. 2 It may be 1 mW / mm or more. 2 The irradiation intensity of the ultraviolet light may be, for example, 10 mW / mm 2 May be less than 5mW / mm 2 May be less than 2mW / mm 2The ultraviolet light source may be a laser light source. Coherent laser light is suitable for local focusing, allowing for a smaller spot diameter, which in turn increases the light irradiation intensity. Coherent light such as laser light can be focused spatially, and although it depends on the optical device used, in principle, it is possible to focus the light to about half the wavelength. Such focusing is difficult with lamp light sources such as mercury lamps. The ultraviolet light irradiation time may be, for example, 1 minute or more, 5 minutes or more, or 15 minutes or more. The ultraviolet light irradiation time may be, for example, 2 hours or less, 1 hour or less, or 30 minutes or less.

[0024] An example of the irradiation process is shown in FIG. 2. FIG. 2 shows an outline of the irradiation process using an ultraviolet light irradiation device 50. The ultraviolet light irradiation device 50 includes a light source 52, a first lens 54, and a second lens 56. The light source 52 is, for example, a laser diode light source that emits ultraviolet light with a wavelength of 300 nm or less. The first lens 54 and the second lens 56 are both plano-convex lenses made of, for example, ultraviolet-grade fused quartz. The first lens 54 and the second lens 56 are arranged with their convex surfaces 54c and 56c facing each other, in the order of the light source 52, the first lens 54, the second lens 56, and the element precursor 10. The ultraviolet light UV emitted from the light source 52 is collimated by the first lens 54, concentrated by the second lens 56, and irradiated onto the inorganic particles 14 of the element precursor 10. In the irradiation process, ultraviolet light is sequentially irradiated onto the inorganic particles 14 of the element precursor 10 whose optical properties are to be adjusted. In this way, a light control element is obtained. The light control element has the same structure as the element precursor 10, except that the surface condition of the inorganic particles 14 is changed.

[0025] The above irradiation process causes changes in the optical properties of the individual inorganic particles, for example, the above-mentioned inflection point temperature T C,up and T C,downBy adjusting the hysteresis width ΔT, etc., it is possible to manufacture a light control element that exhibits the desired overall change in optical properties. For example, it has been confirmed that UV light irradiation tends to reduce the variation in the change in optical properties of inorganic particles (particularly the variation in the hysteresis width ΔT). Utilizing this tendency, it is thought that it will be possible to suppress the variation in the change in optical properties between products and improve the uniformity of products.

[0026] The light control element may be used, for example, in a window material such as a smart window, or in an optical system for writing to an optical medium such as a CD.

[0027] The above-described manufacturing method for a light control element can provide a novel light control element, as described above. For example, when a phase-transition material is formed into nano- to micro-sized particles and irradiated with ultraviolet light, the surface condition (e.g., the amount of oxygen defects on the surface that become crystal nuclei and the distortion of the crystal structure) differs from that when the material is formed into a film and irradiated with ultraviolet light. Therefore, it is believed that a light control element can be manufactured that exhibits changes in optical properties different from those when the material is formed into a film and irradiated with ultraviolet light. When a phase-transition material is formed into particles, the hysteresis width ΔT of the entire light control element tends to be wider than when the material is formed into a film. This makes it suitable, for example, for changing the optical properties to multiple values ​​greater than two or continuously. Furthermore, it is believed that the optical properties can be finely adjusted, for example, by adjusting the irradiation conditions or whether or not to irradiate with ultraviolet light for each particle. Furthermore, it is believed that, for example, by utilizing the tendency for ultraviolet light irradiation to reduce the variability in the changes in the optical properties of inorganic particles, it is possible to suppress the variability in the changes in optical properties between products and improve product uniformity. Furthermore, when the phase transition material is formed as particles, the hysteresis width ΔT of the entire light control element is wider than when it is formed as a film, so it is possible to manufacture a light control element that has a wider hysteresis width ΔT than when it is formed as a film and a narrower hysteresis width ΔT than when it is formed as particles and irradiated with ultraviolet light.

[0028] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

[0029] The present disclosure may be any of the following [1] to [8]. [1] A method for producing a light control element whose optical characteristics, which are one or more of light transmission characteristics and light reflection characteristics, change in response to an environmental change, which is one or more of temperature change and light absorption, comprising: a precursor step of preparing an element precursor including a substrate and a plurality of inorganic particles formed from a phase transition material that undergoes a phase transition in response to the environmental change, the inorganic particles having an average particle size of 1 nm to 1000 μm and arranged separately from one another on the surface of the substrate; and an irradiation step of irradiating the inorganic particles of the element precursor with ultraviolet light. [2] The method for manufacturing a light control element according to [1], wherein the phase transition material is vanadium dioxide. [3] The method for manufacturing a light control element according to [1] or [2], wherein the environmental change is a temperature change. [4] The method for producing a light control element according to any one of [1] to [3], wherein the ultraviolet light has a wavelength of 300 nm or less. [5] The method for producing a light control element according to any one of [1] to [4], wherein the light source of the ultraviolet light is a laser light source. [6] The method for producing a light control element according to any one of [1] to [5], wherein in the irradiating step, the ultraviolet light is concentrated and irradiated onto only some of the plurality of inorganic particles. [7] The method for producing a light control element according to any one of [1] to [6], wherein the inorganic particles have variation in one or more of particle size and particle shape. [8] The method for producing a light control element according to any one of [1] to [7], wherein in the irradiation step, the variation in the change in optical properties of each of the inorganic particles is reduced. [Example]

[0030] Hereinafter, examples in which a method for manufacturing a light control element according to the present disclosure has been specifically considered will be described as examples. Experimental Example 2 corresponds to an example of the present disclosure, and Experimental Example 1 corresponds to a reference example.

[0031] [Experimental Example 1] Vanadium was sputtered onto a fused quartz substrate to a thickness of 60 nm, and then baked under controlled oxygen partial pressure to produce a device precursor with nanoparticles formed on the substrate surface. Specifically, the base vacuum in the chamber was set at 1×10 -3 After evacuation to below 100 Pa, a mixed gas of argon and oxygen was used as the sputtering gas. The ratio of argon to oxygen was 99.5% and the gas pressure was 0.5 Pa. The substrate temperature during film formation was 350°C. After sputtering, when the substrate temperature fell to below 50°C, the chamber was purged with nitrogen gas and the sample was released into the atmosphere. The firing conditions after sputtering were as follows: the furnace was evacuated to a base vacuum of 2 Pa or less, and then oxygen gas was introduced into the furnace, maintaining the oxygen gas pressure in the furnace at 20 Pa. Then, firing was performed at 600°C for 90 minutes. When the temperature in the furnace fell to below 50°C, the sample was released into the atmosphere. This was the sample for Experimental Example 1.

[0032] [Experimental Example 2] The sample of Experimental Example 1 was irradiated with 3 mW of ultraviolet light over an area 1.5 mm in diameter for 30 minutes using the ultraviolet light irradiation device 50 shown in Figure 2 to produce an optical control element. A laser diode light source with a central wavelength of 255 nm and a full width at half maximum of approximately 15 nm was used as the ultraviolet light source 52. Plano-convex lenses made of ultraviolet-grade fused quartz and with a focal length of 20 mm were used as the first lens 54 and second lens 56. This was used as the sample of Experimental Example 2.

[0033] [Results and Discussion] Figure 4 shows a confocal microscope photograph of the sample in Experimental Example 1 taken at 18°C, specifically an image of the pixels corresponding to the red component in RGB decomposition. It was found that VO2 nanoparticles with an average particle size of about several hundred nm were dispersed on the substrate surface.

[0034] Figure 5 shows the changes in confocal microscope images of the sample from Experimental Example 1 as it was heated. Figure 5 is an enlarged view of the center of Figure 4. The sample was heated from 18°C, then from 40°C to 60°C in 10°C increments, and then from 65°C to 95°C in 3°C increments. Images were taken using a confocal microscope for each temperature increase. The number of particles began to darken at 68°C, and by 92°C, almost all particles had darkened. While individual particles showed abrupt changes in brightness, the brightness change overall was gradual. After the temperature increase, the sample was cooled at specified temperature intervals, and images were taken using a confocal microscope. For both the temperature increase and decrease, the coordinates of the pixel positions where brightness changed were extracted from the images before and after the temperature increase as the coordinates of the particles whose brightness changed, and the brightness change of the particles was determined.

[0035] Figure 6 shows a graph representing the brightness change of the circled particles in Figure 4. Figure 6 also shows the results of fitting the brightness data at each observation temperature with a broken line. Equation (1) was used for fitting. In equation (1), T C is the inflection point temperature in the transition, and α is used to adjust the slope of the temperature change. The light intensity value was normalized between the maximum and minimum values ​​and used for fitting. The inflection point temperature T C T C,up and the inflection point temperature T C T C,down Therefore, the hysteresis width ΔT = T C,up -T C,down Similarly, brightness data was acquired for a plurality of particles in the samples of Experimental Examples 1 and 2, and fitting was performed to determine the hysteresis width ΔT.

[0036]

number

[0037] Figure 7 shows a typical example of a graph showing the change in brightness of individual particles in each sample. Figure 7A shows the sample from Experimental Example 1, and Figure 7B shows the sample from Experimental Example 2. Figure 8 shows the frequency distribution of the hysteresis width ΔT of individual particles for the samples from Experimental Example 1 and Experimental Example 2. As shown in Figure 8, in Experimental Example 2, which was irradiated with ultraviolet light, the variation in the hysteresis width ΔT was significantly reduced, indicating that ultraviolet light irradiation can significantly reduce the variation in the transition temperature width.

[0038] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure. [Explanation of symbols]

[0039] 10 element precursor, 12 substrate, 12a surface, 14 inorganic particles, 50 ultraviolet light irradiation device, 52 light source, 54 first lens, 54c convex surface, 56 second lens, 56c convex surface, UV ultraviolet light.

Claims

1. A manufacturing method for manufacturing a light control element whose optical characteristics, which are at least one of light transmission characteristics and light reflection characteristics, change in response to an environmental change, which is at least one of temperature change and light absorption, comprising: a precursor step of preparing an element precursor including a substrate and a plurality of inorganic particles formed of a phase transition material that undergoes a phase transition in response to an environmental change, the inorganic particles having an average particle size of 1 nm to 1000 μm and arranged separately from one another on a surface of the substrate; an irradiation step of irradiating the inorganic particles of the element precursor with ultraviolet light; A method for manufacturing a light control element, comprising:

2. The method for manufacturing a light control element according to claim 1 , wherein the phase change material is vanadium dioxide.

3. The method for manufacturing a light control element according to claim 1 or 2, wherein the environmental change is a temperature change.

4. 3. The method for manufacturing a light control element according to claim 1, wherein the ultraviolet light has a wavelength of 300 nm or less.

5. The method for manufacturing a light control element according to claim 1 or 2, wherein the ultraviolet light source is a laser light source.

6. The method for manufacturing a light control element according to claim 1 , wherein in the irradiating step, the ultraviolet light is concentrated and irradiated onto only a portion of the plurality of inorganic particles.

7. The method for manufacturing a light control element according to claim 1 , wherein the inorganic particles have variation in one or more of particle size and particle shape.

8. The method for manufacturing a light control element according to claim 1 , wherein the irradiation step reduces variations in optical properties of the inorganic particles.

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