Light control device and light control method

Abstract

To provide a new light control device and light control method employing plasmon resonance particles.SOLUTION: A light control device having a first substrate 1, a second substrate 2, and a liquid crystal layer 3 sandwiched between the first substrate 1 and the second substrate 2. The liquid crystal layer 3 includes a liquid crystal component having an alignment direction of liquid crystal molecules 8 reversibly changing in response to external stimulation, and plasmon resonance particles 9 having surface plasmon resonance absorption characteristics reversibly changing in accordance with the alignment direction of the liquid crystal molecules 8.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a light control device and a light control method. [Background technology]

[0002] Display devices using surface plasmon resonance (SPR) have been proposed. For example, Patent Document 1 discloses a display device having a dimming layer that includes mobile fine particles that exhibit color development in a dispersed state and heterogeneous particles that have different properties from the mobile fine particles, with the aim of providing a display device that has high resolution and is capable of full-color display. Metal colloidal particles with plasmon color development are used as the mobile fine particles.

[0003] Patent Document 2 proposes a precious metal particle dispersion in which precious metal particles with plasmon coloring properties are dispersed in silicone oil, and a display method using this dispersion. Patent Document 3 discloses a photochromic composition containing metal nanoparticles that exhibit color based on surface plasmon absorption, exhibiting a color corresponding to their aggregation state, and a reversible change material containing the metal nanoparticles and reversibly changing the aggregation state of the metal nanoparticles in response to an external stimulus. The reversible change material used is a material containing a liquid and a stimulus-responsive polymer gel that swells or shrinks by reversibly absorbing and desorbing the liquid in response to an external stimulus. Patent Document 4 discloses a surface plasmon light modulation element that aims to achieve a large modulation depth. The element has a dielectric block arranged so that modulated light passes through the block and is incident on one surface at a total reflection angle, and a dielectric layer made of a material with a lower refractive index than the dielectric block is interposed between the dielectric block and a metal film. Patent Document 5 and Non-Patent Document 1 will be discussed later. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-350111 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-019493 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-343650 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-292758 [Patent Document 5] Japanese Patent Publication No. 2020-196945 [Non-patent literature]

[0005] [Non-Patent Document 1] J.Milette, V.Toader, L.Reven, R. Bruce Lennox, Journal of Materials Chemistry,2011,21,9043 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure has been made in view of the above background, and aims to provide a dimming device and a dimming method that have a high degree of design freedom and are capable of saving power according to needs. [Means for solving the problem]

[0007] The present disclosure provides the following dimming device and dimming method. [1]: A light-controlling device comprising a first substrate, a second substrate, and a liquid crystal layer sandwiched between the first substrate and the second substrate, wherein the liquid crystal layer has a liquid crystal component whose orientation direction of liquid crystal molecules reversibly changes in response to an external stimulus, and plasmon resonance particles whose surface plasmon resonance absorption characteristics reversibly change in response to the orientation direction of the liquid crystal molecules. [2]: The light-controlling device according to [1], wherein the plasmon resonant particles include at least one of metal nanoparticles and nanocomposite particles containing the metal nanoparticles. [3]: The light-controlling device according to [2], wherein the nanocomposite particles are particles in which the surfaces of the metal nanoparticles are coated with a liquid crystalline compound. [4]: The liquid crystal layer reversibly changes between an isotropic phase and a liquid crystal phase depending on the temperature; The light-controlling device according to any one of [1] to [3], wherein the surface plasmon resonance absorption is in the isotropic phase>liquid crystal phase, and includes a case where the surface plasmon resonance absorption is zero in the liquid crystal phase. [5]: the surface plasmon resonance absorption is in the near-infrared light band; The light-adjusting device according to any one of [1] to [4], wherein the visible light transmittance changes by 10% or less regardless of the alignment direction of the liquid crystal molecules. [6]: The light-adjusting device according to any one of [1] to [5], further comprising a heater mechanism. [7]: A dimming method in which a liquid crystal layer in which the orientation direction of liquid crystal molecules reversibly changes in response to an external stimulus contains plasmon resonance particles whose surface plasmon resonance absorption characteristics reversibly change in response to the orientation direction of the liquid crystal molecules, and optical characteristics are modulated by the surface plasmon resonance absorption characteristics. [Effects of the Invention]

[0008] The present disclosure has the excellent effect of providing a dimming device and a dimming method that have a high degree of design freedom and can also save power according to needs. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a light control window according to a first embodiment. [Figure 2] 1A is a schematic diagram illustrating the visible light transmission state of a liquid crystal layer in a low temperature region, and FIG. 1B is a schematic diagram illustrating the visible light blocking state of a liquid crystal layer in a high temperature region. [Figure 3] FIG. 6 is a schematic cross-sectional view illustrating a light control window according to a second embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view illustrating a light control window according to a third embodiment. [Figure 5] FIG. 10 is a schematic cross-sectional view illustrating a light control window according to a fourth embodiment. [Figure 6] FIG. 13 is a schematic explanatory view for explaining a partition according to a fifth embodiment. [Figure 7] 10 is a schematic diagram for explaining a display panel according to a sixth embodiment. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7 . [Figure 9] FIG. 10 is a graph showing the spectroscopic characteristics of the light-adjusting device according to Example 1 in a low-temperature region. [Figure 10] FIG. 10 is a diagram showing the spectroscopic characteristics of the light-adjusting device according to Example 1 in a high-temperature region. [Figure 11] 10 is a plot of spectroscopic characteristics of the light-adjusting device according to Example 2 at low and high temperatures. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and other embodiments are also included in the scope of the present disclosure as long as they are consistent with the spirit of the present disclosure. In addition, each embodiment can be combined arbitrarily. In this specification, a numerical range specified using "to" includes the numerical values ​​written before and after "to". In this specification, visible light refers to light with a wavelength in the range of 380 to 780 nm, and infrared light refers to light with a wavelength in the range of 780 to 2500 nm. Visible light transmittance refers to the transmittance measured at a wavelength in the range of 380 to 780 nm, and infrared light transmittance here refers to the transmittance measured in the near-infrared band at a wavelength in the range of 780 to 2500 nm, and can be measured in accordance with JIS R 3106 (2019). Transmittance refers to the ratio of the amount of light that passes through the light-control window to the amount of light that enters the window.

[0011] The light-modulating device of the present disclosure includes a first substrate, a second substrate, and a liquid crystal layer sandwiched between these substrates. The liquid crystal layer includes liquid crystal molecules whose orientation direction is reversibly changed in response to an external stimulus and plasmon resonance particles whose surface plasmon resonance absorption characteristics are reversibly changed depending on the orientation direction of the liquid crystal molecules. In other words, the liquid crystal layer includes a liquid crystal component whose phase is reversibly changed in response to an external stimulus and plasmon resonance particles added to the liquid crystal component whose surface plasmon resonance absorption characteristics are reversibly changed. The type of liquid crystal component is not limited, but examples include nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, and ferroelectric liquid crystal. Among these, nematic liquid crystal is preferred due to its relatively wide liquid crystal temperature range and low viscosity.

[0012] A reversible change in the orientation of liquid crystal molecules can be induced by a liquid crystal-isotropic phase transition, or by a phase transition within a liquid crystal phase, such as a nematic-smectic or smectic-cholesteric phase transition.

[0013] In this specification, "dimming" is not limited to narrowly defined changes in light transmittance or color, but generally refers to modulating optical properties (having optical effects). Suitable examples include adjusting light transmittance, reflectance, color, and emitted light intensity. The dimming of this dimming device utilizes reversible changes in surface plasmon resonance absorption properties triggered by reversible phase changes of liquid crystal components. In addition to the above principle, this dimming device may also utilize other dimming methods.

[0014] Plasmon resonance is a phenomenon in which free electrons in plasmon resonant particles move collectively in resonance with the vibration of the electric field of light. Light is strongly absorbed and scattered near the resonant frequency. The plasmon resonance frequency and scattered light characteristics can be controlled by the type, size, shape, surface modification, and dispersion state of the plasmon resonant particles in the liquid crystal component. Plasmon resonance generally occurs on the surface of metal nanoparticles with particle sizes in the submicron to nanometer order. Plasmon resonant particles with multiple, nearly uniform particle sizes selectively absorb and scatter light of specific wavelengths due to plasmon resonance. By creating resonance in the visible light region, visible light reflection functionality can be achieved, and by creating resonance in the infrared region, infrared reflection functionality can be achieved.

[0015] By selecting the particle size and shape, plasmon resonance (absorption) can be achieved over a wide wavelength range. For example, Cytodiagnostics' 100 nm gold particles have both long and short axis resonances, allowing plasmon resonance (absorption) to be achieved over a wide wavelength range. Furthermore, some non-uniform gold rods with different aspect ratios can exhibit two or more peaks in plasmon resonance (absorption).

[0016] Light control due to reversible changes in surface plasmon resonance absorption properties is achieved by reversible changes in scattering / non-scattering or scattering intensity difference (hereinafter, these are also referred to as changes in scattering properties, etc.). Changes in scattering properties, etc. are thought to be caused by changes in the dispersion state of plasmon resonance particles due to phase changes in the liquid crystal components. The dispersion state can be, for example, aggregation and dispersion of plasmon resonance particles.

[0017] The orientation change of the liquid crystal molecules is not limited to any particular type, as long as it reversibly changes the absorption characteristics of the plasmon resonance particles. However, a reversible change due to a phase transition between an isotropic phase and a liquid crystal phase is preferred because it can drastically change the orientation of the liquid crystal molecules. A design in which the surface plasmon resonance absorption is greater than that of the isotropic phase is preferred. The above inequality also includes the case where the surface plasmon resonance absorption of the liquid crystal phase is zero.

[0018] The type of plasmon resonance particles is not limited, but examples include metal nanoparticles, carbon nanoparticles, and nanocomposite particles containing metal nanoparticles. Among these, it is preferable to include at least one of metal nanoparticles and nanocomposite particles containing metal nanoparticles. Examples of metal nanoparticles include platinum nanoparticles, silver nanoparticles, palladium nanoparticles, copper nanoparticles, gold nanoparticles, and alloy nanoparticles of these metals. Examples of carbon nanoparticles include graphene and fullerene. Examples of nanocomposite particles containing metal nanoparticles include particles in which the surface of the metal nanoparticles is partially or entirely coated with an organic compound. The plasmon resonance particles can be used alone or in combination of two or more types.

[0019] Metal nanoparticles can be produced by a solution plasma method, a wet method (reduction method using chloroauric acid), a laser ablation method, a microwave plasma method, or the like. The solution plasma method is a method for producing metal nanoparticles by supplying a pulsed power source to a metal electrode placed in a solution to generate plasma by causing glow discharge, arc discharge, corona discharge, or the like. Commercially available metal nanoparticles may also be used. Specific examples include gold nanoplates such as Au-WPPLC1-C, Au-WPPLC2-C, and Au-WPPLC3-C, and silver nanoplates (AzScience Co., Ltd.).

[0020] In nanocomposite particles in which metal nanoparticles are coated with an organic compound, at least a portion of the surface of the metal nanoparticles is coated with the organic compound. The molecular weight of the organic compound is not particularly limited, and it may be any of a low molecular weight compound, a medium molecular weight compound, and a high molecular weight compound. Suitable organic compounds are those having a group or atom that coordinates with a metal atom. Examples of groups that coordinate with a metal atom include a thiol group, a disulfide group, an amino group, a carboxy group, and a hydroxy group. Examples of compounds that coordinate with a metal atom include liquid crystal molecules having a heterocycle containing a nitrogen atom, a sulfur atom, or the like. Examples of heterocycles include pyridine, pyrimidine, pyrrole, imidazole, pyrazine, pyrrolidine, piperidine, furan, and thiophene.

[0021] The organic compound is preferably a compound that is compatible with the liquid crystal component that forms the liquid crystal layer, and examples of such compounds include liquid crystal compounds having structures such as biphenyl, phenyl benzoate, cyclohexyl benzene, azoxy benzene, azobenzene, azomethine, terphenyl, biphenyl benzoate, cyclohexyl biphenyl, phenyl pyridine, cyclohexyl pyrimidine, and cholesterol.

[0022] Suitable examples of liquid crystal compounds include low-molecular-weight liquid crystal compounds such as 4'-(n-mercaptododecyloxy)biphenyl-4-carbonitrile (12CB-SH), which have introduced groups or atoms that coordinate to metal atoms, and side-chain polymer liquid crystal compounds such as poly[(4-(4-(methoxyphenyloxycarbonyl)phenoxy))butyl methacrylate] (S2-PMA(4OPB)). Note that a liquid crystal compound refers to a compound that can form a liquid crystal phase before bonding to metal nanoparticles. It may also be a compound that can form a liquid crystal phase in the form of nanocomposite particles.

[0023] The average particle diameter of the plasmon resonance particles is not limited, but is, for example, 1 to 300 nm, preferably 3 to 200 nm, and more preferably 5 to 100 nm. The average particle diameter of the plasmon resonance particles can be measured by dynamic light scattering (DLS) and is defined as the median diameter (D50), which is the particle diameter showing the 50% integrated value of the integrated distribution curve. Regarding surface plasmon resonance absorption characteristics, a broad particle size distribution of nanoparticles is preferable for achieving a wide range of absorption, while a narrow particle size distribution of nanoparticles is preferable for achieving absorption in a narrow wavelength range. From the viewpoint of achieving excellent surface plasmon resonance absorption characteristics, it is preferable that 90% or more of the particles exist within a range of ±50 nm of the average particle diameter, and it is even more preferable that 90% or more of the particles exist within a range of ±20 nm of the average particle diameter. The shape of the plasmon resonance particles is not limited, but examples include rods, spheres, ellipses, sheets, and the like. Among these, rods and sheets are preferred.

[0024] An example of a liquid crystal layer in which the orientation direction of liquid crystal molecules changes in response to an external stimulus is a liquid crystal layer in which the orientation direction of liquid crystal molecules changes reversibly at a predetermined temperature or within a predetermined temperature range. Examples of methods using temperature as the external stimulus include using the ambient temperature, adjusting the temperature of the liquid crystal layer by turning on and off the applied voltage, adjusting the temperature of the liquid crystal layer by irradiating it with light, and adjusting the temperature of the liquid crystal phase by providing a heater mechanism. The external stimulus may be any stimulus that can reversibly change the orientation direction of the liquid crystal molecules in the liquid crystal layer, and examples include temperature, light, and voltage. Specific examples of this light-controlling device are described below.

[0025] First Embodiment The dimming device of the first embodiment is a self-active dimming window that does not require electrodes or wiring and does not use an electric field, and is a visible light dimming window. In this dimming window, the orientation direction of liquid crystal molecules reversibly changes in response to an external stimulus, and the absorption characteristics of plasmon resonance particles reversibly change depending on the orientation direction of the liquid crystal molecules. In the first embodiment, temperature is used as the external stimulus. The dimming device of the first embodiment can provide an autonomous window that suppresses the entry and exit of visible light from the outside air when the temperature is above a predetermined level, and actively lets visible light from the outside air into the room when the temperature is below the predetermined level. The dimming device may be equipped with a heater mechanism, which can be used instead of or in combination with the autonomous system to control light by turning the heater on and off.

[0026] This dimming device can provide an autonomous window that, for example, suppresses the inflow and outflow of visible light from the outside air during high temperatures such as summer, and actively lets in visible light from the outside air during low temperatures such as winter. This makes it possible to provide a comfortable space in buildings and vehicles that autonomously reduces glare from the outside air during high temperatures such as summer, and adjusts the amount of light allowed in.

[0027] FIG. 1 shows a schematic cross-sectional view of an example of a light control window, which is a light control device according to the first embodiment. The light control window 10 comprises a first substrate 1, a second substrate 2, and a liquid crystal layer 3. The second substrate 2 is disposed on the outside air side, and is disposed opposite the first substrate 1 with a gap therebetween via a spacer 4. The liquid crystal layer 3 is sandwiched between the first substrate 1 and the second substrate 2. Note that the outside air referred to in this specification refers to the side opposite the side whose temperature is to be controlled, and may also refer to a window separating two rooms. In the case of a window separating two rooms, the side whose temperature is to be controlled is the inside of the room, and the opposite side is the outside air.

[0028] The liquid crystal layer 3 contains liquid crystal molecules that form a liquid crystal phase and plasmon resonance particles that absorb light in the visible light range. In the liquid crystal layer of the first embodiment, the dispersibility of the plasmon resonance particles changes when a phase change between the liquid crystal phase and the isotropic phase is triggered, resulting in a reversible change in the surface plasmon resonance absorption characteristics. Specifically, at a temperature higher than a predetermined temperature or a predetermined temperature range, the plasmon resonance particles disperse, resulting in a decrease in visible light transmittance. On the other hand, at a temperature lower than the predetermined temperature or a predetermined temperature range, the plasmon resonance particles aggregate, resulting in a loss or decrease in absorption characteristics, resulting in a higher visible light transmittance than in the high-temperature range. As a result, the inflow and outflow of visible light from the outside air is suppressed during high temperatures such as summer, and visible light from the outside air can be actively introduced into the room during low temperatures such as winter.

[0029] Fig. 2(a) is a schematic diagram illustrating a state in which visible light is transmitted through the liquid crystal layer in the low temperature region, and Fig. 2(b) is a schematic diagram illustrating a state in which visible light is blocked through the liquid crystal layer in the high temperature region. Note that blocking of visible light also includes a state in which the transmittance of visible light is lower in the high temperature region than in the low temperature region.

[0030] 2(a), in the low temperature region, the liquid crystal molecules 8 are, for example, homogeneously oriented (oriented in a direction substantially horizontal to the main surface of the first substrate 1, etc.). At this time, as shown in the figure, the dispersibility of the plasmon resonance particles 9 decreases, and some particles exist in an aggregated state.

[0031] On the other hand, in the high temperature region, as shown in Figure 2(b), the liquid crystal layer 3 becomes isotropic and the liquid crystal molecules 8 become randomly oriented. In conjunction with this random orientation, the dispersibility of the plasmon resonance particles 9 increases in the liquid crystal layer 3. Accordingly, in the high temperature region, the absorption of visible light by the plasmon resonance particles 9 increases, and the transmittance of visible light decreases.

[0032] In the first embodiment, a liquid crystal layer in which the liquid crystal molecules are homogeneously aligned has been described, but the liquid crystal layer may also be formed using a liquid crystal component having liquid crystal molecules with homeotropic alignment, i.e., alignment approximately perpendicular to the substrate surface. When used in a car sunroof, the liquid crystal molecules are preferably homeotropically aligned. When used in a residential window, in order to efficiently let visible sunlight into the room in the low temperature range, a liquid crystal component in which the liquid crystal molecules are tilted relative to the perpendicular direction to the main surface of the first substrate 1, etc., may be used so that the average incident angle of sunlight depending on the latitude of the installation location and the long axis direction (alignment direction) of the liquid crystal component in the low temperature range are approximately aligned. The alignment control of the liquid crystal component can be adjusted, for example, by an alignment film.

[0033] To obtain the desired visible light transmittance reduction profile, the type of plasmon resonant particle is selected according to the absorption wavelength in the visible light range. Nanoparticles with the desired plasmon absorption in the visible light range can be obtained by adjusting the particle size, shape, and type. Examples include gold nanorods Au-WPP08-C (665 nm, Az Science), gold nanorods Au-WPP1-C (725 nm, Az Science), silver nanoplates AgPLY-24-004 (410 nm, Ito Laboratory), silver nanoplates AgPLM-25-004 (525 nm, Ito Laboratory), and silver nanoplates AgPLN-25-003 (650 nm, Ito Laboratory).

[0034] The content of the plasmon resonance particles 9 can be appropriately designed as long as the surface plasmon resonance absorption characteristics can be reversibly changed in conjunction with the reversible change in orientation of the liquid crystal component, and is, for example, about 0.1 to 5 parts by mass per 100 parts by mass of the liquid crystal component.

[0035] With this dimming device, the conditions under which the alignment of the liquid crystal molecules changes can be adjusted by changing the type of liquid crystal component. This allows for the design of dimming devices with a high degree of freedom depending on the application. For example, by setting the temperature at which the alignment of the liquid crystal molecules changes to 25°C, the visible light transmittance inside a building can be adjusted. For use in a sunroof, for example, it can be set to around 30°C. Furthermore, by providing a heater mechanism, the dimming temperature can be set higher.

[0036] The liquid crystal component includes one or more liquid crystal compounds. Known materials can be used as the liquid crystal component. Examples include biphenyls, phenylbenzoates, cyclohexylbenzenes, azoxybenzenes, azobenzenes, azomethines, terphenyls, biphenylbenzoates, cyclohexylbiphenyls, phenylpyridines, cyclohexylpyrimidines, and cholesterols.

[0037] An alignment film 11 can be provided as needed on the outermost surface of the first substrate 1 or the second substrate 2 facing the liquid crystal layer 3 to control the alignment of the liquid crystal component. The alignment film 11 may be provided on either the first substrate 1 or the second substrate 2, or on both as shown in FIG. 1. There are no limitations on the type of alignment film 11, but a horizontal alignment film is preferred when the liquid crystal phase is to be homogeneously aligned at low temperatures, a vertical alignment film is preferred when homeotropic alignment is to be achieved, and an alignment film with a tilt angle is preferred when the liquid crystal component is to be tilted relative to the substrate surface.

[0038] The alignment film 11 can be formed, for example, by coating an alignment film on the surfaces of the first substrate 1 and the second substrate 2 facing the liquid crystal layer 3 and then performing a rubbing treatment. Alternatively, the alignment film may be formed by coating the alignment film and then irradiating it with polarized UV light to exert an alignment control force. Alternatively, an alignment film whose orientation changes depending on temperature may be used. For example, a temperature-variable alignment film that becomes oil-repellent (large tilt) at low temperatures and oil-philic (small tilt) at high temperatures is suitable. The alignment film may be used to reversibly change the orientation of the liquid crystal component, instead of or in addition to controlling the orientation based on the phase transition temperature of the liquid crystal component, thereby controlling the transmittance of visible light.

[0039] The contrast between the low-temperature transmittance and the high-temperature transmittance can be appropriately designed depending on the desired amount of transmittance reduction. If it is desired to block visible light at high temperatures, the contrast ratio is set high. For example, the contrast ratio is set to 5 or more. On the other hand, if it is desired to gradually reduce the transmittance at high temperatures while maintaining transparency at both low and high temperatures, the contrast ratio is set low. For example, the contrast ratio is set to 1.5 or less. By setting the contrast ratio in this range, it is possible to provide a comfortable space by controlling light while maintaining transparency.

[0040] The first substrate 1 and the second substrate 2 can each independently be made of a known glass plate, plastic sheet, or the like. Examples of glass plates include float glass, polished glass, figured glass, wired glass, striped glass, heat-absorbing glass, laminated glass made thereof, and tempered glass (air-cooled tempered glass, chemically tempered glass). The material of the glass plate is not limited, and examples include soda-lime glass, borosilicate glass, aluminosilicate glass, and alkali-free glass. Examples of plastic sheets include acetylcellulose resins such as triacetylcellulose (TAC), polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin resins such as polyethylene (PE), polypropylene (PP), polystyrene, polymethylpentene, and EVA, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, acrylic resins, polyurethane resins, polysulfone (PEF), polyethersulfone (PES), polycarbonate (PC), polysulfone, polyether (PE), polyether ketone (PEK), (meth)acrylonitrile, cycloolefin polymer (COP), and cycloolefin copolymer. Among these, resins such as polycarbonate, cycloolefin polymer, and polyethylene terephthalate are superior in terms of visible light transmittance.

[0041] The visible light transmittance of each of the first substrate 1 and the second substrate 2 is preferably 80% or more, more preferably 89% or more, and even more preferably 95% or more. The visible light transmittance of these substrates may be the same or different. The thickness of these substrates may be selected appropriately depending on the application. The light control window may be configured to be rotatable relative to the support so that the orientation direction of the liquid crystal component in the low temperature region and the direction of incident light are approximately aligned.

[0042] There are no particular limitations on the thickness of the first substrate 1 and the second substrate 2, and the thickness may be selected depending on the strength, size, heat insulating performance, etc. required for the double glazing. For example, it is 0.2 to 10 mm. The first substrate 1 and the second substrate 2 may have the same thickness, or glass plates of different thicknesses may be combined.

[0043] The first substrate 1 and the second substrate 2 may each have an ultraviolet absorbing film or an ultraviolet reflective film formed thereon, or the substrate itself may have an ultraviolet absorbing function. The liquid crystal component may also contain an ultraviolet absorbing agent or an ultraviolet reflective agent. It is preferable that the outside air side of the liquid crystal layer 3, i.e., the side exposed to sunlight, has an ultraviolet absorbing or reflecting function.

[0044] The liquid crystal layer 3 can be formed by a known method. For example, a composition containing plasmon resonance particles and a liquid crystal component can be formed between the first substrate 1 and the second substrate 2 by a normal vacuum injection method, an ODF method, or the like.

[0045] The spacer 4 may be any material that can maintain a predetermined distance between the substrates and seal them. For example, it may be made of resin, glass, or metal. To maintain the gap between the first substrate 1 and the second substrate 2, a gap-maintaining member (not shown) may be provided independently for each substrate.

[0046] The present light control window 10 is provided with a liquid crystal layer 3 that can increase the transmittance of visible light in low temperature regions, and therefore can actively take in visible light from the outside air when temperatures are low, such as in winter.

[0047] On the other hand, the liquid crystal layer 3 is provided, which can reduce the transmittance of visible light in high-temperature regions, so it is possible to adjust the amount of visible light entering the room during high temperatures such as summer, thereby adjusting the amount of light entering. The switchable window 10 is suitable for energy-saving homes, stores, and car windows that are environmentally friendly and highly sustainable. It may also be used in combination with other switchable light methods, such as infrared light control film, heat-absorbing glass, or heat-reflecting glass.

[0048] Second Embodiment Next, an example of a light control device different from that of the first embodiment will be described. In the following figures, the same elements as those in the above embodiment will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate. The basic configuration of the light control device of the second embodiment is the same as that of the light control window of the first embodiment, except for the following points. While the first embodiment described an example of a visible light control window, the second embodiment differs in that it is an infrared light control window that controls light in the near-infrared light band. The light control window of the second embodiment can provide an autonomous window that suppresses the entry and exit of heat from the outside air during high temperatures such as summer, and actively takes in heat from the outside air during low temperatures such as winter. This can reduce the energy consumed for air conditioning in buildings, vehicles, etc.

[0049] 3 shows a schematic cross-sectional view of an example of a light control window, which is a light control device according to the second embodiment. As in the first embodiment, the light control window 10 comprises a first substrate 1, a second substrate 2, a liquid crystal layer 3, and a spacer 4. A third transparent substrate 6 is disposed on the outer side of the first substrate 1, facing the first substrate 1 with a spacer 5 interposed therebetween. A thermal conduction adjusting layer 7 is provided in the gap between the first substrate 1 and the third transparent substrate 6.

[0050] To ensure transparency, the light control window 10 preferably has a visible light transmittance of 70% or more. From this perspective, a visible light transmittance of 80% or more is more preferable, and 90% or more is even more preferable. Furthermore, to ensure the visible light transparency of the light control window, the change in visible light transmittance is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less, regardless of the orientation direction of the liquid crystal molecules.

[0051] The liquid crystal layer 3 contains liquid crystal molecules that form a liquid crystal phase and plasmon resonance particles that absorb light in the near-infrared region. In the liquid crystal layer of the second embodiment, as in the first embodiment, the dispersibility of the plasmon resonance particles changes when a phase change between the liquid crystal phase and the isotropic phase is triggered, resulting in a reversible change in the surface plasmon resonance absorption characteristics. Specifically, at a temperature higher than a predetermined temperature or a predetermined temperature range, the plasmon resonance particles disperse, resulting in a decrease in infrared light transmittance. On the other hand, at a temperature lower than the predetermined temperature or a predetermined temperature range, the plasmon resonance particles aggregate, resulting in a loss or decrease in absorption characteristics, resulting in a higher infrared light transmittance than in the high-temperature region. As a result, the transfer of heat from the outside air is suppressed during high temperatures such as summer, and heat from the outside air can be actively introduced into the room during low temperatures such as winter.

[0052] The mechanism by which infrared light is transmitted through the liquid crystal layer in the low temperature region and blocked by the liquid crystal layer in the high temperature region is the same as that shown in FIG. 2 of the first embodiment. That is, in the high temperature region, as shown in FIG. 2(b), the liquid crystal layer 3 becomes an isotropic phase and the liquid crystal molecules 8 are randomly oriented. In conjunction with this random orientation, the dispersibility of the plasmon resonance particles 9 in the liquid crystal layer 3 increases. As a result, the absorption of infrared light by the plasmon resonance particles 9 increases in the high temperature region, and the transmittance of infrared light decreases. Note that the infrared light transmittance in the high temperature region is lower than that in the low temperature region, and the infrared light is blocked.

[0053] The type of liquid crystal layer, alignment control of liquid crystal molecules (alignment film, etc.), and type of liquid crystal component are the same as those in the first embodiment. Also, the content of plasmon resonance particles 9 is the same as that in the first embodiment.

[0054] The plasmon resonance particles 9 of the second embodiment are preferably particles that have low absorption in the visible light range and high absorption in the infrared light range. This can suppress the reduction in transmittance in the visible light range due to the plasmon resonance particles. Nanoparticles with plasmon absorption in the near-infrared range can be obtained by adjusting the particle size, shape, and type. Other examples include silver nanoplates Ag-WS5-C (800 nm, Az Science), Ag-PLI (850 nm, Ito Laboratory), gold nanorods Au-WP7-C (1250 nm, Az Science), gold nanorods Au-WPP2-C (900 nm, Az Science), gold nanorods Au-WP4-C (900 nm, Az Science), gold nanorods Au-WP5-C (1050 nm, Az Science), gold nanorods Au-WS5-C (900 nm, Az Science), and the particles described in Patent Document 5.

[0055] According to the light-controlling device of the second embodiment, the conditions under which the alignment of the liquid crystal molecules changes can be adjusted by changing the type of liquid crystal component. This allows for a high degree of design freedom depending on the application. For example, by setting the temperature at which the alignment of the liquid crystal molecules changes to 25°C, the cooling costs and energy required for a building can be reduced. For use in a sunroof, for example, a setting of around 30°C is sufficient. Furthermore, by providing a heater mechanism, the dimming temperature can be set higher.

[0056] The contrast between the low-temperature transmittance and the high-temperature transmittance in the near-infrared region is preferably 2 or more, more preferably 4 or more, and even more preferably 5 or more, and in the visible light region is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.1 or less. By setting the contrast in this range, it is possible to suppress the inflow and outflow of heat while maintaining transparency.

[0057] The types, transmittances, suitable thicknesses, and UV absorbing films that may be provided on the first substrate 1, second substrate 2, and third transparent substrate 6 are the same as those described in the first embodiment.

[0058] The switchable window 10 is designed so that the thermal conductivity in the thickness direction D1 on the first substrate 1 side is lower than the thermal conductivity in the thickness direction D2 on the second substrate 2 side on both sides of the liquid crystal layer 3. In other words, the switchable window 10 is designed so that the thermal insulation properties are higher on the indoor side than on the outdoor side. Note that in this switchable window, it is sufficient that the transmittance of infrared light is lower in the high-temperature region than in the low-temperature region across the entire infrared light range (780 to 2500 nm); it is not necessary for each wavelength to satisfy the above condition. Furthermore, the thermal conductivity referred to here is the thermal conductivity when considered across the entire thickness directions D1 and D2; there may be some areas where the thermal conductivity is reversed in the thickness directions D1 and D2.

[0059] The description of the first embodiment is used for the method of forming the liquid crystal layer 3. The description of the first embodiment is also used for the configuration and manufacturing method of the spacers 4 and 5.

[0060] The thermal conduction adjusting layer 7 serves to lower the thermal conductivity in the thickness direction (D1 in FIG. 3) on the first substrate 1 side on both sides of the liquid crystal layer 3 compared to the thermal conductivity in the thickness direction (D2 in FIG. 3) on the second substrate 2 side. There are no particular limitations on the thermal conduction adjusting layer 7 as long as it has this function. The thermal conduction adjusting layer 7 may be a layer filled with various gases, including air and rare gases such as Ar and Kr. It may also be a reduced pressure layer or a vacuum. It may also be a liquid.

[0061] The thickness (width) of the heat conduction adjusting layer 7 is not particularly limited and can be selected depending on the required thickness of the entire glass, heat insulating performance, etc. For example, it is 5 μm to 20 mm.

[0062] The switchable window 10 includes a liquid crystal layer 3 that can increase the transmittance of infrared light in low-temperature regions, allowing infrared light from the outside air to be actively introduced during low temperatures, such as in winter. Furthermore, the thermal conductivity in the thickness direction on the first substrate 1 side of the liquid crystal layer 3 is lower than the thermal conductivity in the thickness direction on the second substrate 2 side, preventing a drop in the indoor temperature and improving heating efficiency. While infrared light, which is radiant heat from the sun, warms the room by passing through the glass, the thermal conductivity in the thickness direction on the first substrate 1 side of the liquid crystal layer 3 is lower than the thermal conductivity in the thickness direction on the second substrate 2 side, making the liquid crystal layer 3 more susceptible to the temperature of the outside air than the room.

[0063] On the other hand, the liquid crystal layer 3, which can reduce infrared light transmittance in high-temperature regions, can reduce infrared light from outside during high temperatures, such as in summer. Furthermore, by configuring both sides of the liquid crystal layer 3 so that the thermal conductivity in the thickness direction on the first substrate 1 side is lower than the thermal conductivity in the thickness direction on the second substrate 2 side, for example, cooling efficiency can be improved. In other words, even when the indoor side of this switchable window is cold due to indoor cooling temperatures, the liquid crystal layer 3 is designed to easily adjust the temperature in response to the influence of the outside temperature, thereby suppressing infrared light. The switchable window 10 of the second embodiment has excellent visible light transmittance and can effectively prevent heat loss through the window, making it suitable for environmentally friendly, sustainable, energy-saving homes, store windows, and car windows. It may also be used in combination with other light control methods, such as infrared light control film, heat-absorbing glass, or heat-reflecting glass.

[0064] Third Embodiment The switchable window, which is a light control device according to the third embodiment, has a basic configuration similar to that of the switchable window of the second embodiment, except for the following points. That is, as shown in FIG. 4, the switchable window 10 of the third embodiment differs in that it does not have a third transparent substrate 6, a thermal conduction adjusting layer 7, etc. Furthermore, on both sides of the liquid crystal layer 3, the thickness of the first substrate 1 is designed to be thicker than the thickness of the second substrate 2 so that the thermal conductivity in the thickness direction on the first substrate 1 side is lower than the thermal conductivity in the thickness direction on the second substrate 2 side. With this configuration, the switchable window 10 of the third embodiment can achieve the same effects as the second embodiment. Another advantage is that manufacturing costs can be reduced.

[0065] In addition, instead of or in addition to making the thickness of the first substrate 1 thicker than the thickness of the second substrate 2, the materials of the first substrate 1 and the second substrate 2 may be changed on both sides of the liquid crystal layer 3 so that the thermal conductivity in the thickness direction on the first substrate 1 side is lower than the thermal conductivity in the thickness direction on the second substrate 2 side.

[0066] <Fourth embodiment> An example of a switchable window, which is a light control device according to the fourth embodiment, will now be described. The switchable window according to the fourth embodiment has the same basic configuration as the switchable window according to the third embodiment, except for the following points. That is, as shown in FIG. 5, the switchable window 10 according to the fourth embodiment differs in that a heat conduction adjusting film 7a is formed on the outer main surface of the first substrate 1 on both sides of the liquid crystal layer 3 so that the thermal conductivity in the thickness direction on the first substrate 1 side is lower than the thermal conductivity in the thickness direction on the second substrate 2 side. Another difference is that the first substrate 1 and the second substrate 2 have the same thickness. The thicknesses and materials of the first substrate 1 and the second substrate 2 may be different. For example, the thicknesses of the first substrate 1 and the second substrate 2 are preferably 0.5 mm to 10 mm, more preferably 1 mm to 5 mm, and even more preferably 1.3 mm to 3 mm.

[0067] Examples of the heat conduction adjusting film 7a include an infrared light reflective film and a transparent heat insulating layer. Examples of the infrared light reflective film include a film having a cholesteric liquid crystal phase and the reflective layer described in Patent Document 4. Furthermore, an anti-reflection surface for infrared light may be formed on the outer main surface of the first substrate 1 by etching with hydrogen fluoride, or a heat ray reflective film (heat shielding film) such as a Low-E film may be formed. Examples of the Low-E film include a laminate film in which a metal layer such as silver or ITO is sandwiched between dielectric layers, or a fluorine-doped tin oxide film. Examples of the transparent heat insulating layer include a resin sheet such as PET. An aerogel layer may also be formed. Methods for forming the heat conduction adjusting film 7a include, for example, a barcode method, a reverse coating method, a gravure coating method, a die coating method, a roll coating method, a screen method, an inkjet method, a vacuum deposition method, and a sputtering method.

[0068] The light control window according to the fourth embodiment provides the same effects as those of the previous embodiments.

[0069] Fifth Embodiment An example in which the light-adjusting device of the fifth embodiment is applied to a partition will be described. FIG. 6 shows an example of a schematic cross-sectional view of a partition according to the fifth embodiment. A partition 20 has a partition plate 21. As in the first embodiment, the partition plate 21 has a first substrate 1, a second substrate (not shown), and a liquid crystal layer (not shown) sandwiched between these substrates. The liquid crystal layer according to the fifth embodiment contains plasmon resonance particles that absorb visible light. In addition, housings 22 that support the partition plate 21 are provided on both ends of the partition plate 21. A heater mechanism is provided within this housing.

[0070] When the heater is off, the partition 20 functions as a normal window with high visible light transmittance. On the other hand, when the heater is turned on and the partition plate 21 reaches a predetermined temperature, the alignment of the liquid crystal molecules in the liquid crystal layer 3 changes, causing a decrease in visible light transmittance, darkening the partition plate 21, and making it impossible to see the scenery through the partition plate 21.

[0071] According to the partition of the fifth embodiment, the visibility / invisibility beyond the partition board 21 can be reversibly controlled by turning the heater on and off. As a result, it can be used as a transparent partition that provides a high level of openness normally, but when a partition is needed, the heater can be operated to provide privacy, for example.

[0072] Sixth Embodiment An example in which the light-adjusting device of the sixth embodiment is applied to a display panel will be described. Fig. 7 is a schematic explanatory diagram of the display panel of the sixth embodiment, and Fig. 8 is a cross-sectional view taken along the line VIII-VIII in Fig. 7. The display panel 30 displays information at desired times and is non-displaying at other times. The display panel 30 in the figure displays a no-entry mark when entry is prohibited, and is non-displaying and acts as a transparent display panel when entry is permitted.

[0073] The display panel 31 has a first substrate 1, a liquid crystal layer (not shown), and a second substrate (not shown). The basic configuration is the same as in the first embodiment. Support portions 32 equipped with heater mechanisms are provided on both the left and right ends of the display panel 31. The liquid crystal layer is arranged in a first region 33 and a second region 34 separated by a transparent wall 36 between the first substrate 1 and the second substrate. The first region 33 is filled with a liquid crystal layer 3 that appears white when information is displayed, and the second region 34 is filled with a liquid crystal layer 3 that appears red when information is displayed. A gap 35 is provided outside the first region 33 between the first substrate 1 and the second substrate 2. A transparent resin may be filled in place of the gap 35.

[0074] The display panel 30 can reversibly switch between displaying and hiding marks by turning on and off the heater of the support part 32. As a result, it can be used as a transparent bulletin board with a high degree of openness in normal times, and when information needs to be conveyed, the heater can be turned on to display it. Because the display panel 30 is a transparent bulletin board when not in use, it can provide an open space without spoiling the view. [Example]

[0075] The present disclosure will be explained in more detail below based on examples. However, the present disclosure is not limited to these examples. Unless otherwise specified, "parts" in the examples means "parts by mass" and "%" means "% by mass". Blank spaces in the tables indicate that no ingredients were blended.

[0076] <Synthesis Example 1 of Nanocomposite Particles> The following compound (1) (hereinafter also referred to as 12CB-SH) was synthesized according to the method described in Non-Patent Document 1 as a liquid crystalline compound that partially or entirely coats the metal nanoparticles of the nanocomposite particles and functions as a ligand. [ka] (1)

[0077] First, 4'-hydroxybiphenyl-4-carbonitrile (1 equivalent) and 1,12-dibromododecane (10 equivalents) were placed in a round-bottom flask equipped with a condenser and dissolved in acetone. Potassium carbonate (8 equivalents) was then added. The resulting suspension was heated and stirred at reflux for 19 hours and then filtered before cooling. The filtrate was concentrated under reduced pressure, and the residue was added to warm hexane. The precipitate was separated by filtration and purified by recrystallization from hot ethanol to yield 4'-(12-bromododecyloxy)biphenyl-4-carbonitrile.

[0078] 4'-(12-Bromododecyloxy)-biphenyl-4-carbonitrile (1 equivalent) was dissolved in ethanol in a round-bottom flask equipped with a condenser. Thiourea (2.3 equivalents) was then added and the mixture was heated and stirred at reflux for 19 hours. The reaction mixture was cooled to room temperature and filtered. The filtrate was concentrated and purified by recrystallization from ethanol to give 2-(12-((4'-cyanobiphenyl-4-yl)oxy)dodecyl)isothiouronium bromide.

[0079] Next, 2-(12-((4'-cyanobiphenyl-4-yl)oxy)dodecyl)isothiouronium bromide (1 equivalent) and potassium hydroxide (1.3 equivalents) were placed in a round-bottom flask equipped with a condenser and dissolved in a mixture of ethanol and water (volume ratio 1:3), and heated and stirred at reflux for 7 hours. After that, the mixture was cooled to room temperature, and acetic acid was added to adjust the pH of the solution to 4, and heated and stirred at reflux for 2 hours. The solvent was evaporated under reduced pressure, and the product was extracted into the chloroform layer using water and chloroform. The solvent was evaporated under reduced pressure to obtain the target product (compound (1)) as a white powder.

[0080] Silver nanosheets (Ag-NS) manufactured by Dai Nippon Toryo Co., Ltd. were used as metal nanoparticles. These metal nanoparticles have a peak absorption characteristic at a wavelength of 600 nm when dispersed in a solvent. 20 mg of the Ag-NS (2 mL of dispersion), 16 mg of the compound (1) obtained above, and 18 mL of 1-methoxy-2-propanol were weighed and stirred at room temperature for 20 hours to obtain nanocomposite particles whose surfaces were coated with compound (1). After the reaction was completed, the solvent was evaporated under reduced pressure, and the Ag-NS was dispersed in 1-methoxy-2-propanol. hexane was added to the resulting precipitate, which was then centrifuged to remove unreacted compound (1), yielding nanocomposite particles according to Synthesis Example 1.

[0081] <Synthesis Example 2 of Nanocomposite Particles> The following compound (2) was synthesized as a polymer liquid crystalline compound that acts as a ligand and is an organic compound that coats part or all of the metal nanoparticles of the nanocomposite particles. [ka] (2)

[0082] First, (4-(4-(methoxyphenyloxycarbonyl)phenoxy))butyl methacrylate (200 equivalents), bis[2-(2'-bromoisobutyryloxy)ethyl]disulfide (1 equivalent), copper(I) chloride (2 equivalents), and 1,1,4,7,10,10-hexamethyltriethylenetetramine (2 equivalents) were placed in a round-bottom flask and dissolved in anisole. After freeze-degassing, the mixture was heated and stirred at 80°C for 20 hours. The mixture was then cooled to room temperature, and the solvent was removed under reduced pressure. The resulting reaction product was dissolved in chloroform and reprecipitated in hexane. The product was then reprecipitated in diethyl ether, and the solid was filtered and dried to obtain the target product (compound (2)). The number-average molecular weight Mn was 21,800, and the weight-average molecular weight Mw was 28,200.

[0083] Silver nanosheets (Ag-NS) manufactured by Dai Nippon Toryo Co., Ltd. were used as the metal nanoparticles, as in Synthesis Example 1 above. 15 mg of the Ag-NS (1.5 mL of dispersion), 153 mg of the compound (2) obtained above, and 10 mL of chloroform were weighed out and stirred at room temperature for 120 hours to obtain nanocomposite particles in which the surface of Ag-NS was coated with compound (2). After the reaction was completed, methanol was added, and the resulting precipitate was centrifuged to remove the solvent and unreacted compound (2), yielding nanocomposite particles according to Synthesis Example 2.

[0084] <Preparation of composition for forming liquid crystal layer> (Example 1) Mixed liquid crystal E-8 (manufactured by LCC Corporation, #650, NI transition temperature 72°C) was used as the liquid crystal component. 0.1 parts by mass of the nanocomposite particles of Synthesis Example 1 were blended with 100 parts by mass of mixed liquid crystal E-8 to prepare a composition for forming liquid crystal layer 3. Next, this composition was injected at 65°C into a liquid crystal cell having a gap of 200 μm, thereby producing a 200 μm liquid crystal cell 1 injected with the composition of Example 1.

[0085] (Example 2) A composition for forming liquid crystal layer 3 was prepared by blending 1 part by mass of the nanocomposite particles according to Synthesis Example 2 with 100 parts by mass of mixed liquid crystal E-8. Next, this composition was injected at 73°C into a liquid crystal cell having a gap of 200 μm, thereby producing liquid crystal cell 2 of 200 μm injected with the composition of Example 2.

[0086] <Evaluation and Results> For the liquid crystal cell 1, optical changes were confirmed by measuring the spectral transmittance at room temperature and 80°C. Figure 9 shows the spectral transmittance from 300 to 800 nm at room temperature, and Figure 10 shows the spectral transmittance at the same wavelengths at 80°C. It was confirmed that the total light transmittance was 73% at room temperature, but decreased to 26% at 80°C. It was also confirmed that the absorption characteristics changed with temperature, that the plasmon absorption characteristics could be reversibly induced, and that repeated reversibility could be achieved.

[0087] Figure 11 shows a plot of the spectral transmittance of the liquid crystal cell 2 when it was repeatedly heated to room temperature and 80°C. In this figure, the spectral transmittance was measured at each temperature using a temperature program of low temperature (room temperature) → high temperature (80°C) → low temperature 2 (room temperature) → high temperature 2 (80°C) → low temperature 3 (room temperature). It was confirmed that the total light transmittance was 78% at room temperature, but 36% at 80°C. Furthermore, as shown in the figure, it was confirmed that the absorption characteristics changed with temperature, that the plasmon absorption characteristics could be reversibly induced, and that repeated reversibility could be obtained. [Explanation of symbols]

[0088] 1: first substrate, 2: second substrate, 3: liquid crystal layer, 4: spacer, 5: spacer, 6: third transparent substrate, 7: thermal conduction adjusting layer, 8: liquid crystal molecules, 9: plasmon resonance particles, 10: light control window, 11: alignment film, 20: partition, 21: partition board, 22: housing, 30: display panel, 31: display board, 32: support part, 33: first region, 34: second region, 35: gap, 36: transparent wall

Claims

1. a first substrate, a second substrate, and a liquid crystal layer sandwiched between the first substrate and the second substrate; The liquid crystal layer has a liquid crystal component in which the orientation direction of the liquid crystal molecules reversibly changes in response to an external stimulus, and plasmon resonance particles in which the surface plasmon resonance absorption characteristics reversibly change in response to the orientation direction of the liquid crystal molecules.

2. The light-modulating device of claim 1 , wherein the plasmon resonant particles comprise at least one of metal nanoparticles and nanocomposite particles comprising the metal nanoparticles.

3. The light-modulating device according to claim 2 , wherein the nanocomposite particles are particles in which the surfaces of the metal nanoparticles are coated with a liquid crystalline compound.

4. the liquid crystal layer reversibly changes between an isotropic phase and a liquid crystal phase depending on temperature; The light-adjusting device according to claim 1 , wherein the surface plasmon resonance absorption is in an isotropic phase>liquid crystal phase, including a case where the surface plasmon resonance absorption is zero in the liquid crystal phase.

5. the surface plasmon resonance absorption is in the near-infrared light band, The light-modulating device according to claim 1 , wherein the visible light transmittance changes by 10% or less regardless of the orientation direction of the liquid crystal molecules.

6. The light control device of claim 1 , further comprising a heater mechanism.

7. A light control method in which a liquid crystal layer in which the orientation direction of liquid crystal molecules reversibly changes in response to an external stimulus contains plasmon resonance particles whose surface plasmon resonance absorption characteristics reversibly change in response to the orientation direction of the liquid crystal molecules, and optical characteristics are modulated by the surface plasmon resonance absorption characteristics.

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