JP2020052178A - Optical device - Google Patents

Abstract

To provide an optical device including a variable refractive index layer (nanoparticle dispersion layer) having a high maximum refractive index while suppressing viscosity low.SOLUTION: An optical device 1 includes: a first substrate 10 having optical transparency; a second substrate 20 having optical transparency arranged opposite to the first substrate 10; a first electrode 30 arranged on a side of the second substrate 20 of the first substrate 10; an uneven structure 50 arranged on a side of the second substrate 20 of the first substrate 10; a second electrode 40 arranged on a side of the first substrate 10 of the second substrate 20; and a variable refractive index layer 60 which is arranged between the uneven structure 50 and the second electrode 30 and of which refractive index is changed according to a voltage applied between the first electrode 30 and the second electrode 40. The variable refractive index layer 60 includes an insulating liquid 61, a plurality of first nanoparticles 62a and a plurality of second nanoparticles 62b which are dispersed in the insulating liquid 61. Each of the first nanoparticles 62a and the second nanoparticles 62b are charged with the same polarity.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical device, and more particularly, to an optical device that can distribute incident light.

  Conventionally, a light distribution device capable of distributing incident light has been proposed as an optical device. Such an optical device is used for a window of a building or a car. For example, by installing an optical device in a window of a building, it is possible to change the traveling direction of external light such as sunlight entering from the outside and introduce the external light toward the ceiling in the room.

  As this kind of light distribution device, a device using a liquid crystal layer is known. For example, Patent Literature 1 discloses a first transparent substrate and a second transparent substrate facing each other, a first transparent electrode layer and an uneven structure disposed on the second transparent substrate side of the first transparent substrate, and a second transparent substrate. A liquid crystal optical element including a second transparent electrode layer disposed on the first transparent substrate side and a liquid crystal layer disposed between the first transparent electrode layer and the second transparent electrode layer is disclosed. In a light distribution device using a liquid crystal layer, the liquid crystal layer is used as a variable refractive index layer, and the refractive index of the liquid crystal layer is changed according to the voltage applied to the first transparent electrode layer and the second transparent electrode layer. A light distribution mode in which the traveling direction of the light incident on the light distribution device is changed, and a transparent mode in which the light incident on the light distribution device is transmitted straight without changing the traveling direction.

JP 2015-41006 A

  In recent years, a light distribution device using a nanoparticle dispersion layer (nanoparticle dispersion liquid) in which nanoparticles such as transparent zirconium oxide particles are dispersed in an insulating liquid instead of using a liquid crystal layer as the refractive index variable layer has been developed. Are being considered. In a light distribution device using a nanoparticle dispersion layer, the traveling direction of light incident on the light distribution device is changed by changing the refractive index of the nanoparticle dispersion layer by electrophoresis of the nanoparticles in the nanoparticle dispersion layer. ing.

  In the light distribution device using the nanoparticle dispersion layer, the light distribution control range (range of the light distribution angle), that is, the light incident on the light distribution device, is increased by increasing the refractive index difference between the uneven structure and the nanoparticle dispersion layer. The range in which the angle at which the light is reflected by the concavo-convex structure can be increased or decreased can be expanded. Therefore, the higher the maximum refractive index of the nanoparticle dispersion layer, the better.

  However, when trying to increase the maximum refractive index of the nanoparticle dispersion layer using transparent zirconium oxide particles as the nanoparticles, the nanoparticle concentration in the nanoparticle dispersion layer increases, and the viscosity of the nanoparticle dispersion layer increases. . As a result, the movement of the zirconium oxide particles in the dispersion is slowed, and the responsiveness when changing the refractive index of the nanoparticle dispersed layer is deteriorated.

  In addition, a zirconia particle dispersion in which only zirconium oxide particles (zirconia particles) were dispersed was actually prepared as a nanoparticle dispersion layer, and the refractive index was measured by changing the concentration of the zirconium oxide particles. As shown, the measured value was lower than the calculated value, and it was also found that even if the concentration of the zirconium oxide particles was increased, a nanoparticle dispersed layer having a predetermined refractive index could not be obtained. In particular, when trying to obtain a nanoparticle dispersed layer having a refractive index of 1.7 or more, the concentration of zirconium oxide particles increases, and the viscosity of the nanoparticle dispersed layer becomes extremely high. That is, it is difficult to obtain a nanoparticle dispersed layer having a refractive index of 1.7 or more while keeping the viscosity low by using only zirconium oxide particles.

  Therefore, instead of the zirconium oxide particles, it is conceivable to use titanium oxide particles having a higher refractive index than the zirconium oxide particles, but since the titanium oxide particles have a high light scattering property, the haze of the nanoparticle dispersion layer becomes high, The transparency of the optical device in the transparent state (in the transparent mode) is reduced.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical device having a variable refractive index layer (nanoparticle dispersed layer) having a high maximum refractive index while suppressing the viscosity to be small. I do.

  In order to achieve the above object, one aspect of the optical device according to the present invention is a first substrate having light transmittance, and a second substrate having light transmittance disposed opposed to the first substrate, A first electrode arranged on the second substrate side of the first substrate, an uneven structure arranged on the second substrate side of the first substrate, and an irregular structure arranged on the first substrate side of the second substrate; A second electrode, a refractive index variable layer disposed between the concave-convex structure and the second electrode, the refractive index of which changes according to a voltage applied between the first electrode and the second electrode. Comprising, the refractive index variable layer has an insulating liquid, a plurality of first nanoparticles and a plurality of second nanoparticles dispersed in the insulating liquid, the first nanoparticles and the second Each of the two nanoparticles is charged with the same polarity.

  According to the present invention, it is possible to realize an optical device having a refractive index variable layer (nanoparticle dispersed layer) having a high maximum refractive index while keeping the viscosity low.

FIG. 2 is a cross-sectional view of the optical device according to the embodiment. It is an expanded sectional view of the optical device concerning an embodiment. It is a figure which shows the relationship between the density | concentration (ratio) of the titania particle in the mixed dispersion liquid of a zirconia particle and a titania particle, and a mixed dispersion liquid. FIG. 3 is a diagram for describing a first optical action of the optical device according to the embodiment. FIG. 4 is a diagram for describing a second optical action of the optical device according to the embodiment. FIG. 9 is a diagram for explaining a third optical action of the optical device according to the embodiment. FIG. 9 is a diagram for describing a first optical action of an optical device according to a modification. FIG. 11 is a diagram for explaining a second optical action of the optical device according to the modification. FIG. 11 is a diagram for explaining a third optical action of the optical device according to the modification. It is a figure which shows the relationship between the density | concentration of a zirconia particle in a zirconia particle dispersion liquid, and the refractive index of a zirconia particle dispersion liquid.

  Hereinafter, embodiments of the present invention will be described. Each of the embodiments described below shows a specific example of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, connection forms, and the like shown in the following embodiments are merely examples and do not limit the present invention. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present invention are described as arbitrary components.

  Each drawing is a schematic diagram, and is not necessarily shown exactly. Therefore, the scale and the like do not always match in each drawing. In each of the drawings, substantially the same components are denoted by the same reference numerals, and redundant description will be omitted or simplified.

  In this specification and the drawings, the X axis, the Y axis, and the Z axis represent three axes of a three-dimensional orthogonal coordinate system. In the present embodiment, the Z axis direction is a vertical direction, and the Z axis direction is perpendicular to the Z axis. Direction (direction parallel to the XY plane) is the horizontal direction. The X axis and the Y axis are axes orthogonal to each other and both are orthogonal to the Z axis. The plus direction in the Z-axis direction is defined as vertically downward. In the present specification, the “thickness direction” means the thickness direction of the optical device, and is a direction perpendicular to the main surfaces of the first substrate 10 and the second substrate 20 (in the present embodiment, the Y-axis direction). That is.

(Embodiment)
First, the configuration of the optical device 1 according to the embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an optical device 1 according to the embodiment. FIG. 2 is an enlarged sectional view of the optical device 1 and shows an enlarged view of a region II surrounded by a broken line in FIG.

  The optical device 1 is a light control device that controls light incident on the optical device 1. Specifically, the optical device 1 controls a traveling direction of light incident on the optical device 1. In the present embodiment, the optical device 1 is a light distribution device that can change the traveling direction of incident light (for example, distribute light) and emit the light.

  As shown in FIGS. 1 and 2, the optical device 1 includes a first substrate 10, a second substrate 20, a first electrode 30, a second electrode 40, an uneven structure 50, a refractive index variable layer 60, Is provided.

  In the optical device 1, a first electrode 30, an uneven structure 50, a refractive index variable layer 60, and a second electrode 40 are arranged in this order along a thickness direction between a pair of a first substrate 10 and a second substrate 20. Configuration.

  As shown in FIG. 1, in the optical device 1, the first substrate 10, the first electrode 30, and the concavo-convex structure 50 form a first laminated substrate 100, and the second substrate 20 and the second electrode 40 The two-layer substrate 200 is configured.

  The first laminated substrate 100 and the second laminated substrate 200 are arranged to face each other with a gap therebetween, and the entire periphery of the outer peripheral end is sealed. Thereby, the variable refractive index layer 60 filled between the first laminated substrate 100 and the second laminated substrate 200 can be confined. For example, a sealing member such as an adhesive is formed in a frame shape on the inner surface along the outer peripheral edge of the first laminated substrate 100 and the second laminated substrate 200, or the first substrate 10 and the second substrate 20 are welded by laser. By doing so, the outer peripheral ends of the first laminated substrate 100 and the second laminated substrate 200 can be sealed.

  Hereinafter, each component of the optical device 1 will be described in detail with reference to FIGS. 1 and 2.

[First substrate, second substrate]
As shown in FIGS. 1 and 2, the first substrate 10 is a base material of the first multilayer substrate 100, and the second substrate 20 is a base material of the second multilayer substrate 200.

  The first substrate 10 and the second substrate 20 are light-transmitting substrates (light-transmitting substrates). The first substrate 10 and the second substrate 20 are preferably transparent substrates.

  As the first substrate 10 and the second substrate 20, for example, a resin substrate made of a resin material or a glass substrate made of a glass material can be used. Examples of the material of the resin substrate include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), acrylic, and epoxy. Examples of the material for the glass substrate include soda glass, non-alkali glass, and high refractive index glass. The resin substrate has an advantage that scattering at the time of destruction is small. On the other hand, the glass substrate has the advantages of high light transmittance and low moisture permeability.

  The first substrate 10 and the second substrate 20 may be made of the same material or different materials, but are preferably made of the same material. Further, the first substrate 10 and the second substrate 20 are not limited to the rigid substrate, but may be a flexible substrate or a film substrate. In the present embodiment, a transparent resin substrate (PET substrate) made of PET is used as each of the first substrate 10 and the second substrate 20.

  The thickness of the first substrate 10 and the second substrate 20 is, for example, 5 μm to 3 mm, but is not limited thereto. In the present embodiment, each of the first substrate 10 and the second substrate 20 has a thickness of 50 μm.

  In addition, the shape of the first substrate 10 and the second substrate 20 in plan view is, for example, a square or a rectangular shape, but is not limited thereto, and may be a polygon other than a circle or a quadrangle. May be employed.

[First electrode, second electrode]
As shown in FIGS. 1 and 2, the first electrode 30 and the second electrode 40 are electrically paired, and are configured to apply an electric field to the refractive index variable layer 60. The first electrode 30 and the second electrode 40 are also arranged in a pair, and are arranged so as to face each other.

  The first electrode 30 is arranged on the second substrate 20 side of the first substrate 10. Further, the second electrode 40 is arranged on the first substrate 10 side of the second substrate 20. Specifically, the first electrode 30 is formed on the main surface of the first substrate 10 on the second substrate 20 side, and the second electrode 40 is formed on the main surface of the second substrate 20 on the first substrate 10 side. Is formed.

  In the present embodiment, a pair of the first electrode 30 and the second electrode 40 is provided between the first substrate 10 and the second substrate 20 so as to sandwich at least the uneven structure 50 and the refractive index variable layer 60. Are located. Specifically, the first electrode 30 is disposed between the first substrate 10 and the uneven structure 50, and the second electrode 40 is disposed between the second substrate 20 and the refractive index variable layer 60. ing.

  The thickness of each of the first electrode 30 and the second electrode 40 is, for example, 5 nm to 2 μm, but is not limited thereto. In the present embodiment, each of the first electrode 30 and the second electrode 40 has a thickness of 100 nm.

  Further, the shape of the first electrode 30 and the second electrode 40 in plan view is, for example, a square or a rectangular shape like the first substrate 10 and the second substrate 20, but is not limited thereto. In the present embodiment, the first electrode 30 and the second electrode 40 are solid electrodes in a plan view shape or a rectangular shape formed on substantially the entire surface of each of the first substrate 10 and the second substrate 20.

  The first electrode 30 and the second electrode 40 are light-transmitting electrodes and transmit incident light. The first electrode 30 and the second electrode 40 are, for example, transparent electrodes made of a transparent conductive layer. Examples of the material of the transparent conductive layer include a conductive metal-containing resin such as ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide), and a resin containing a conductive material such as silver nanowires and conductive particles. Alternatively, a metal thin film such as a silver thin film can be used. In addition, the first electrode 30 and the second electrode 40 may have a single-layer structure thereof, or may have a laminated structure thereof (for example, a laminated structure of a transparent metal oxide and a metal thin film).

  The first electrode 30 and the second electrode 40 are configured to enable electrical connection with an external power supply. For example, each of the first electrode 30 and the second electrode 40 is pulled out to the outside of the sealing resin that seals the refractive index variable layer 60, and the drawn portions are used as electrode terminals for connecting to an external power supply. Is also good.

[Uneven structure]
As shown in FIGS. 1 and 2, the concave-convex structure 50 is a concave-convex layer having a concave-convex surface, and has a configuration in which a plurality of convex portions 51 of a micro-order size or a nano-order size are arranged.

  The uneven structure 50 is arranged on the second substrate 20 side of the first substrate 10. In the present embodiment, the concavo-convex structure 50 is arranged on the second substrate 20 side of the first electrode 30. Specifically, the concavo-convex structure 50 is provided on the main surface of the first electrode 30 on the second substrate 20 side.

  In the present embodiment, the concavo-convex structure 50 is provided on the first electrode 30 so that the plurality of protrusions 51 protrude toward the refractive index variable layer 60 side. In this case, an adhesion layer may be formed between the first electrode 30 and the uneven structure 50. The surface of the concavo-convex structure 50 on the first electrode 30 side (the surface of the projection 51 on the first electrode 30 side) is a flat surface.

  Further, the plurality of convex portions 51 are formed in a stripe shape. Specifically, each of the plurality of protrusions 51 has a trapezoidal cross-sectional shape, is a substantially rectangular column shape extending in the X-axis direction, and is arranged at equal intervals along the Z-axis direction. . Further, all the convex portions 51 have the same shape, but the present invention is not limited to this.

  Each of the protrusions 51 has, for example, a height of 100 nm or more and 100 μm or less and an aspect ratio (height / lower bottom) of about 0.5 to 10, but is not limited thereto. As an example, each protrusion 51 has a height of about 10 μm, a lower bottom of about 5 μm, and an upper bottom of about 2 μm.

  The interval between two convex portions 51 adjacent in the Z-axis direction is, for example, 0 to 100 mm. That is, the two convex portions 51 adjacent to each other in the Z-axis direction may be arranged at a predetermined interval without contacting the bottom portion, or may be arranged with the bottom portion contacting (with an interval of zero). It is preferable that the interval between two adjacent protrusions 51 in the Z-axis direction be equal to or smaller than the bottom of the protrusion 51. As an example, in the case of the protrusions 51 of the above size (height: 10 μm, lower base: 5 μm, upper base: 2 μm), the interval between two adjacent protrusions 51 is about 2 μm. In the concavo-convex structure 50, the adjacent convex portions 51 are connected to each other at the root portion by the adhesive layer. However, the present invention is not limited to this, and the plural convex portions 51 may be formed separately from each other.

  Each of the plurality of convex portions 51 has a pair of side surfaces. In the present embodiment, the cross-sectional shape of each protrusion 51 is a tapered shape that tapers along the direction from the second substrate 20 toward the first substrate 10 (Y-axis minus direction). Therefore, each of the pair of side surfaces of each convex portion 51 is an inclined surface inclined at a predetermined inclination angle with respect to the thickness direction, and the interval between the pair of side surfaces in each convex portion 51 (the width of the convex portion 51). Gradually decreases from the second substrate 20 toward the first substrate 10. The inclination angles of the two side surfaces of each protrusion 51 may be the same or different. In the present embodiment, the inclination angles (base angles) of the two side surfaces of each protrusion 51 are the same.

  A pair of side surfaces of each convex portion 51 is a surface in contact with the refractive index variable layer 60, and light incident from the first substrate 10 receives an optical action on the pair of side surfaces of the convex portion 51.

  Specifically, on each of the pair of side surfaces of the convex portion 51, the light incident from the first substrate 10 is refracted and transmitted according to the refractive index difference between the convex portion 51 and the refractive index variable layer 60. It is transmitted as it is without refraction, or it is totally reflected. That is, the pair of side surfaces of the protrusion 51 can be a refraction surface or a total reflection surface depending on the difference in the refractive index between the protrusion 51 and the refractive index variable layer 60 and the angle of incidence of light. Thereby, the concave-convex structure 50 (convex portion 51) distributes the light incident from the first substrate 10.

  As a material of the concavo-convex structure 50 (convex portion 51), for example, a translucent resin material such as an acrylic resin, an epoxy resin, or a silicone resin can be used. The uneven structure 50 can be formed by, for example, laser processing or imprint. In the present embodiment, the concavo-convex structure 50 is formed using an acrylic resin having a refractive index of about 1.5. Note that the refractive index of the uneven structure 50 is not limited to 1.5.

  The concave-convex structure 50 may be made of only an insulating resin material as long as an electric field can be applied to the refractive index variable layer 60 by the first electrode 30 and the second electrode 40. May be provided. In this case, as the material of the uneven structure 50, a conductive polymer such as PEDOT, a resin containing a conductor (a conductor-containing resin), or the like can be used.

[Refractive index variable layer]
As shown in FIGS. 1 and 2, the variable refractive index layer 60 is a nanoparticle dispersion layer in which an infinite number of nanoparticles are dispersed in an insulating liquid 61. In the present embodiment, a plurality of types of nanoparticles are dispersed in the insulating liquid 61. Specifically, two kinds of nanoparticles, that is, first nanoparticles 62a and second nanoparticles 62b having different refractive indices, are dispersed in the insulating liquid 61. As described above, the refractive index variable layer 60 includes the insulating liquid 61 and the plurality of first nanoparticles 62a and the plurality of second nanoparticles 62b dispersed in the insulating liquid 61.

  The insulating liquid 61 is a transparent liquid having an insulating property, and is a solvent serving as a dispersion medium in which the first nanoparticles 62a and the second nanoparticles 62b are dispersed as a dispersoid. As the insulating liquid 61, for example, a liquid having a refractive index (solvent refractive index) of about 1.3 to about 1.5 can be used. In the present embodiment, an insulating liquid 61 having a refractive index of about 1.4 is used.

Note that the kinematic viscosity of the insulating liquid 61 is preferably 100 mm ² / s or less. The insulating liquid 61 preferably has a low dielectric constant (less than or equal to the dielectric constant of the uneven structure 50). Specifically, the dielectric constant of the uneven structure 50 is preferably higher than the dielectric constant of the insulating liquid 61. Further, the insulating liquid 61 preferably has non-flammability (high flash point whose flash point is 250 ° C. or higher) and low volatility. Specifically, the insulating liquid 61 is a hydrocarbon (such as an aliphatic hydrocarbon, naphtha, or other petroleum-based solvent), a low-molecular-weight halogen-containing polymer, or a mixture thereof. As an example, the insulating liquid 61 is a hydrocarbon halide such as hydrogen fluoride. Note that, as the insulating liquid 61, silicone oil or the like can be used.

  Each of the first nanoparticles 62a and the second nanoparticles 62b dispersed in the insulating liquid 61 is a fine particle having a nano-order size. Specifically, assuming that the wavelength of the incident light is λ, the particle size of the first nanoparticles 62a and the second nanoparticles 62b is preferably λ / 4 or less. By reducing the particle size of the first nanoparticles 62a and the second nanoparticles 62b to λ / 4 or less, light scattering at the first nanoparticles 62a and the second nanoparticles 62b is reduced, and the first nanoparticles 62a and the An average refractive index between the second nanoparticles 62b and the insulating liquid 61 can be obtained. Note that the smaller the particle size of the first nanoparticles 62a and the second nanoparticles 62b, the better, preferably 100 nm or less, more preferably several nm to several tens nm.

  The first nanoparticles 62a and the second nanoparticles 62b are charged charged particles. The first nanoparticles 62a and the second nanoparticles 62b are charged with the same polarity. That is, the first nanoparticles 62a and the second nanoparticles 62b are both positively (positively) charged or both are negatively (negatively) charged. In the present embodiment, the first nanoparticles 62a and the second nanoparticles 62b are both positively charged.

  The first nanoparticle 62a may be charged by the material itself of the first nanoparticle 62a having an electric charge, or the surface of the first nanoparticle 62a may be modified or the first nanoparticle 62a may be added to the insulating liquid 61. It may be charged by adjusting the PH of the entire refractive index variable layer 60 including the insulating liquid 61 after the dispersion of the second nanoparticles 62b. The same applies to the second nanoparticles 62b.

  The charge amount of the first nanoparticles 62a and the charge amount of the second nanoparticles 62b may be the same or different. In the present embodiment, the charge amount of the first nanoparticles 62a and the charge amount of the second nanoparticles 62b are the same.

  Each of the first nanoparticles 62a and the second nanoparticles 62b is made of a high refractive index material. Specifically, the refractive indices of the first nanoparticles 62a and the second nanoparticles 62b are both higher than the refractive index of the insulating liquid 61. In the present embodiment, the refractive indexes of the first nanoparticles 62a and the second nanoparticles 62b are higher than the refractive index of the concavo-convex structure 50.

  In addition, as described above, the first nanoparticles 62a and the second nanoparticles 62b have different refractive indexes. In this case, the refractive index of the second nanoparticles 62b may be higher or lower than the refractive index of the first nanoparticles 62a, but in the present embodiment, the refractive index of the second nanoparticles 62b is It is higher than the refractive index of the nanoparticles 62a.

  As the first nanoparticles 62a and the second nanoparticles 62b, inorganic fine particles such as metal oxide fine particles or metal particles can be used.

In the present embodiment, the first nanoparticles 62a are made of a material having a high transmittance. Specifically, the first nanoparticles 62a are transparent particles. For example, the first nanoparticle 62a, zirconium oxide having a refractive index of 2.13 _(ZrO 2), aluminum oxide _{(Al 2 O} 3) having a refractive index of 1.76, the refractive index 1.9 to 2.1 Transparent metal oxide fine particles composed of zinc oxide (ZnO) or the like can be used.

On the other hand, the second nanoparticles 62b are made of a material having a lower transmittance than the first nanoparticles 62a. Specifically, the second nanoparticles 62b are scattering particles that scatter and reflect light. For example, as the second nanoparticles 62b, metal oxide fine particles or non-transparent white metal particles made of titanium oxide (TiO ₂ ) having a refractive index of 2.52 to 2.72 can be used.

  In the present embodiment, transparent zirconia particles (zirconium oxide particles) made of zirconium oxide are used as the first nanoparticles 62a, and titania particles (oxidized particles) made of titanium oxide are used as the second nanoparticles 62b. Titanium particles).

  In the variable refractive index layer 60, the first nanoparticles 62a and the second nanoparticles 62b are dispersed throughout the insulating liquid 61 so as to have a desired refractive index. In the present embodiment, the refractive index (average refractive index) of the entire refractive index variable layer 60 has an uneven structure in a state where the first nanoparticles 62 a and the second nanoparticles 62 b are uniformly dispersed in the insulating liquid 61. The refractive index is set substantially equal to 50. Specifically, the refractive index of the entire refractive index variable layer 60 is adjusted to be about 1.5. The refractive index of the entire refractive index variable layer 60 can be adjusted by adjusting the concentration (amount) of the first nanoparticles 62a and the second nanoparticles 62b dispersed in the insulating liquid 61.

  Here, referring to FIG. 3, in the refractive index variable layer 60 in which the first nanoparticles 62a and the second nanoparticles 62b are dispersed in the insulating liquid 61, the ratio of the first nanoparticles 62a and the second nanoparticles 62b is determined. The refractive index of the entire refractive index variable layer 60 when changed will be described.

  FIG. 3 shows the refractive index when zirconia particles are used as the first nanoparticles 62a and titania particles are used as the second nanoparticles 62b. In FIG. 3, the horizontal axis represents the concentration of titania particles (second nanoparticles 62b), and the vertical axis represents zirconia particles (first nanoparticles 62a) and titania particles (second nanoparticles 62b). It shows an average refractive index in a state of being uniformly dispersed in the insulating liquid 61. In FIG. 3, the concentration (volume concentration) of the whole particles in the mixed dispersion of zirconia particles and titania particles is fixed at 30 vol%. Therefore, when the content of the titania particles is 30 vol%, no zirconia particles are contained.

  As shown in FIG. 3, by mixing the zirconia particles (first nanoparticles 62 a) and the titania particles (second nanoparticles 62 b), the concentration of the whole particles when the zirconia particles and the titania particles are mixed is not so large. It can be seen that a mixed dispersion having a relatively high refractive index (refractive index variable layer 60) can be realized without increasing the refractive index.

  FIG. 3 shows only the case where the refractive index of the mixed dispersion of zirconia particles and titania particles is larger than 1.6, but the mixed dispersion is diluted to obtain particles of zirconia particles and titania particles. By lowering the overall concentration, a mixed dispersion having a refractive index of 1.6 or less (for example, 1.5 or the like) can be obtained even when both the zirconia particles and the titania particles are included. That is, not only the refractive index variable layer 60 whose refractive index is larger than 1.6 but also the refractive index variable layer 60 whose refractive index is 1.6 or less can be realized.

  From the viewpoint of changing the refractive index by causing the first nanoparticles 62a and the second nanoparticles 62b to migrate in the insulating liquid 61 (response), the viscosity of the refractive index variable layer 60 is 100 mPa.・ It is good to be about s. In this case, the concentration of the first nanoparticles 62a and the second nanoparticles 62b in the entire refractive index variable layer 60 is preferably 30% or less, more preferably 25% or more and 30% or less.

  Further, from the viewpoint of suppressing the haze of the refractive index variable layer 60, it is preferable that the concentration of the first nanoparticles 62a as the transparent particles is higher than the concentration of the second nanoparticles 62b as the scattering particles. That is, as for the first nanoparticles 62a and the second nanoparticles 62 mixed in the refractive index variable layer 60, it is better that the ratio of the first nanoparticles 62a is higher.

  The refractive index variable layer 60 thus configured is disposed between the concave-convex structure 50 and the second electrode 40. Specifically, the refractive index variable layer 60 is in contact with the uneven structure 50. That is, the contact surface of the variable refractive index layer 60 with the uneven surface of the uneven structure 50 is the interface between the variable refractive index layer 60 and the uneven surface of the uneven structure 50. Although the variable refractive index layer 60 is also in contact with the second electrode 40, another layer (film) may be interposed between the variable refractive index layer 60 and the second electrode 40.

  The refractive index of the refractive index variable layer 60 changes according to the voltage applied between the first electrode 30 and the second electrode 40. Specifically, the refractive index variable layer 60 is disposed between the first electrode 30 and the second electrode 40, and a voltage is applied between the first electrode 30 and the second electrode 40. An electric field is applied to the variable refractive index layer 60. For example, a DC voltage is applied between the first electrode 30 and the second electrode 40.

  Since the first nanoparticles 62a and the second nanoparticles 62b dispersed in the insulating liquid 61 are charged, when an electric field is applied to the refractive index variable layer 60, the first nanoparticles 62a and the second nanoparticles 62b become , Migrates in the insulating liquid 61 according to the electric field distribution and is unevenly distributed in the insulating liquid 61. In the present embodiment, since the charge amount and the particle size of the first nanoparticles 62a and the second nanoparticles 62b are substantially the same, when an electric field is applied to the refractive index variable layer 60, the first nanoparticles 62a The second nanoparticles 62b migrate in the insulating liquid 61 with the same behavior. That is, one of the first nanoparticles 62a and the second nanoparticles 62b does not migrate with a delay.

  When the first nanoparticles 62a and the second nanoparticles 62b are unevenly distributed in the insulating liquid 61, the particle distributions of the first nanoparticles 62a and the second nanoparticles 62b in the refractive index variable layer 60 change, so that refraction occurs. The concentration distribution of the first nanoparticles 62 a and the second nanoparticles 62 b can be provided in the rate variable layer 60. As a result, the refractive index distribution in the refractive index variable layer 60 changes. That is, the refractive index of the refractive index variable layer 60 partially changes. As described above, the refractive index variable layer 60 functions as a refractive index adjusting layer that can mainly adjust the refractive index for light in the visible light region.

  The variable refractive index layer 60 thus configured is disposed between the first laminated substrate 100 and the second laminated substrate 200. Specifically, the insulating liquid 61 in which the first nanoparticles 62a and the second nanoparticles 62b are dispersed is sealed between the first laminated substrate 100 and the second laminated substrate 200.

  The thickness of the variable refractive index layer 60 (that is, the gap between the first laminated substrate 100 and the second laminated substrate 200) is, for example, 1 μm to 1 mm, but is not limited thereto. As an example, when the height of the protrusion 51 of the uneven structure 50 is 10 μm, the thickness of the variable refractive index layer 60 is, for example, 40 μm.

[Method of Manufacturing Optical Device]
Next, a method for manufacturing the optical device 1 will be described with reference to FIGS.

  First, for example, a PET substrate is used as the first substrate 10, an ITO film is formed as the first electrode 30 on the PET substrate, and a plurality of acrylic films (refractive index: 1.5) are formed on the ITO film. The first laminated substrate 100 is manufactured by forming the concave-convex structure 50 including the convex portions 51 by an imprint method.

  Next, using a PET substrate as the second substrate 20, for example, the second electrode 40 made of an ITO film is formed on the PET substrate, thereby manufacturing the second laminated substrate 200.

  Next, between the first laminated substrate 100 and the second laminated substrate 200, as the refractive index variable layer 60, while filling the insulating liquid 61 in which the first nanoparticles 62a and the second nanoparticles 62b are dispersed, By joining the outer peripheral portions of the first laminated substrate 100 and the second laminated substrate 200, the variable refractive index layer 60 is sealed between the first laminated substrate 100 and the second laminated substrate 200.

  Thus, the optical device 1 having the structure shown in FIG. 1 can be manufactured.

[Optical action of optical device]
Next, the optical action of the optical device 1 according to the embodiment will be described with reference to FIGS. 4A to 4C. FIG. 4A is a view for explaining a first optical action of the optical device 1 according to the embodiment, and FIG. 4B is a view for explaining a second optical action of the optical device 1; FIG. 3 is a diagram for explaining a third optical action of the optical device 1.

  The optical device 1 can be realized as a window with a light distribution control function, for example, by being installed in a window of a building. The optical device 1 is attached to a window of a building via an adhesive layer, for example. In this case, the optical device 1 is installed on the window such that the longitudinal direction of the convex portion 51 of the concave-convex structure 50 is horizontal. For example, sunlight enters the optical device 1 installed in the window. In the present embodiment, the optical device 1 is installed such that the first substrate 10 provided with the uneven structure 50 is located on the light incident side (outside of the building). The light (sunlight) that has entered from above can be transmitted and emitted from the second substrate 20 to the inside of the building of the optical device 1 (for example, indoors).

  At this time, the light incident on the optical device 1 receives an optical action from the optical device 1 when transmitting the optical device 1. Specifically, the optical device 1 changes its optical action by a change in the refractive index of the refractive index variable layer 60. For this reason, the light incident on the optical device 1 receives a different optical action according to the refractive index of the variable refractive index layer 60, and the traveling direction is controlled according to the refractive index of the variable refractive index layer 60.

  In the present embodiment, the optical device 1 can control the traveling direction of light incident on the optical device 1 according to the voltage applied between the first electrode 30 and the second electrode 40. Specifically, depending on the voltage applied between the first electrode 30 and the second electrode 40, the first nanoparticles 62a and the second nanoparticles 62b in the refractive index variable layer 60 (nanoparticle dispersion layer) are changed. The particle distribution changes, which causes the refractive index of the refractive index variable layer 60 to partially change. As a result, the optical action of the optical device 1 changes. Hereinafter, the optical action of the optical device 1 will be described in detail.

  First, the first optical action of the optical device 1 will be described with reference to FIG. 4A. When no potential is applied to the first electrode 30 and the second electrode 40, that is, when no voltage is applied between the first electrode 30 and the second electrode 40 (when no voltage is applied), The device 1 is in a first optical mode, and gives a first optical action to incident light.

  In the first optical mode, no electric field is applied to the refractive index variable layer 60, and therefore, as shown in FIG. 4A, in the refractive index variable layer 60, the first nanoparticles 62a and the second nanoparticles 62b It is distributed throughout. That is, the first nanoparticles 62a and the second nanoparticles 62b are in a uniform dispersion state in the insulating liquid 61.

  At this time, in the present embodiment, as described above, the refractive index of the refractive index variable layer 60 in a state where the first nanoparticles 62a and the second nanoparticles 62b are dispersed throughout the insulating liquid 61 is as shown in FIG. As shown in the figure, the refractive index is uniform (constant) throughout the variable refractive index layer 60 and is about 1.5. The refractive index of the concave-convex structure 50 is about 1.5. Therefore, when no voltage is applied between the first electrode 30 and the second electrode 40 (in the case of the first optical mode), the refractive index of the entire refractive index variable layer 60 is substantially the same as the refractive index of the uneven structure 50. Becomes As a result, the refractive index difference between the concave-convex structure 50 (convex portion 51) and the refractive index variable layer 60 almost disappears (refractive index difference Δn ≒ 0).

  In this case, as shown in FIG. 4A, when light L enters the optical device 1 from an oblique direction, there is no difference in the refractive index at the interface between the concave / convex structure 50 (the convex portion 51) and the refractive index variable layer 60. The light L incident on the optical device 1 is not refracted at the interface between the refractive index variable layer 60 and the side surface of the convex portion 51 and does not change its traveling direction. For this reason, in the first optical mode, the light L incident on the optical device 1 travels straight through the optical device 1 and exits the optical device 1 without being bent in the optical device 1.

  As described above, when no voltage is applied between the first electrode 30 and the second electrode 40, the optical device 1 transmits the light incident on the optical device 1 in a straight line. Specifically, the optical device 1 allows the light incident on the first substrate 10 to travel straight and transmits through the second substrate 20. That is, the first optical mode is a transparent mode, and in the first optical mode, the optical device 1 is in a transparent state. In this case, the light that has entered the first substrate 10 passes straight through without being distributed by the optical device 1 and exits from the second substrate 20.

  Although not shown in detail, an interface on the light incident side of the first substrate 10, an interface between the first substrate 10 and the first electrode 30, an interface between the first electrode 30 and the uneven structure 50, a refractive index variable layer Where there is a difference in the refractive index at the interface between the members, such as the interface between 60 and the second electrode 40, the interface between the second electrode 40 and the second substrate 20, or the interface on the light emission side of the second substrate 20 In, the light incident from the first substrate 10 is refracted at the interface. However, the first substrate 10 and the second substrate 20 are made of the same material (that is, the same refractive index), and the first electrode 30 and the second electrode 40 are made of the same material (that is, the same refractive index). For this reason, in the first optical mode (transparent mode), the light incident from the first substrate 10 and emitted from the second substrate 20 is incident on the first substrate 10 and emitted from the second substrate 20. Is the same as the emission angle. That is, the angle in the traveling direction of the light L does not change before the light L enters the optical device 1 and after the light L exits from the optical device 1.

  In the first optical mode, the refractive index of the entire refractive index variable layer 60 and the refractive index of the concavo-convex structure 50 are substantially the same if the refractive index difference between the variable refractive index layer 60 and the concavo-convex structure 50 is 0.01 or less. , More preferably 0.005 or less (Δn ≦ 0.005). If the refractive index difference between the variable refractive index layer 60 and the uneven structure 50 exceeds 0.005, light may be scattered at the interface between the variable refractive index layer 60 and the uneven structure 50, and haze may be generated.

  Next, a second optical operation of the optical device 1 will be described with reference to FIG. 4B. When the first voltage is applied between the first electrode 30 and the second electrode 40 (when the first voltage is applied), the optical device 1 enters the second optical mode, and the second mode is applied to the incident light. Gives optical action. Specifically, a DC voltage is applied between the first electrode 30 and the second electrode 40. In this case, the voltage (potential difference) applied between the first electrode 30 and the second electrode 40 is, for example, about several V to several tens V (for example, 20 V).

  In the second optical mode, an electric field is applied to the variable refractive index layer 60 by applying a DC voltage between the first electrode 30 and the second electrode 40. The nanoparticles 62a migrate in the insulating liquid 61 according to the electric field distribution. That is, the first nanoparticles 62 a electrophoreses inside the insulating liquid 61.

  Specifically, when the first nanoparticles 62a and the second nanoparticles 62b are positively charged, a negative potential is applied to the first electrode 30 and a positive potential is applied to the second electrode 40, as shown in FIG. 4B. Is applied, the positively charged first nanoparticles 62a and second nanoparticles 62b migrate toward the first electrode 30 and are aggregated and unevenly distributed on the concave-convex structure 50 side in the refractive index variable layer 60. At this time, the first nanoparticles 62a and the second nanoparticles 62b migrating toward the first electrode 30 enter the concave portion of the concavo-convex structure 50, that is, the region between the two adjacent convex portions 51, and are accumulated. The concentration of the first nanoparticles 62a and the second nanoparticles 62b in the concave portions of the concave-convex structure 50 increases.

  As described above, since the first nanoparticles 62a and the second nanoparticles 62b are unevenly distributed on the concave-convex structure 50 side in the refractive index variable layer 60, the particle distribution of the first nanoparticles 62a and the second nanoparticles 62b is changed. In addition, the refractive index distribution in the refractive index variable layer 60 is not uniform. Specifically, in the refractive index variable layer 60, the first nanoparticle 62a and the second nanoparticle 62b are gathered and the concentration of the first nanoparticle 62a and the second nanoparticle 62b is increased, and the uneven structure 50 side Of the first electrode 60a (high-concentration area) and the second electrode 40 side where the first nanoparticles 62a and the second nanoparticles 62b are eliminated and the concentrations of the first nanoparticles 62a and the second nanoparticles 62b are reduced. And the second region 60b (low concentration region).

  In this case, since the refractive index of the first nanoparticles 62a and the second nanoparticles 62b is higher than the refractive index of the insulating liquid 61, the refractive index of the first region 60a on the concave-convex structure 50 side of the refractive index variable layer 60 is: It becomes higher than the refractive index of the second region 60b of the refractive index variable layer 60 on the second electrode 40 side. Accordingly, in the refractive index variable layer 60, a first region 60a having a high refractive index on the concave-convex structure 50 side and a second region 60b having a low refractive index on the second electrode 40 side are generated.

  In the present embodiment, since the refractive index of the entire refractive index variable layer 60 when no voltage is applied is about 1.5, the first region on the concave-convex structure 50 side of the variable refractive index layer 60 when the first voltage is applied. The refractive index of the second region 60b on the side of the second electrode 40 of the variable refractive index layer 60 has a refractive index of about 1.8 in the thickness direction. 5 to about 1.4.

  Thereby, as described above, since the refractive index of the uneven structure 50 is about 1.5, in the case of the second optical mode (the first voltage is applied between the first electrode 30 and the second electrode 40). ), Between the refractive index (about 1.5) of the uneven structure 50 and the refractive index (about 1.5 to about 1.8) of the first region 60a of the refractive index variable layer 60 on the uneven structure 50 side. Causes a refractive index difference.

  In this case, as shown in FIG. 4B, when light L enters the optical device 1 from an oblique direction, there is a difference in the refractive index at the interface between the concavo-convex structure 50 (the convex portion 51) and the refractive index variable layer 60. The light L is refracted at the interface between the lower side surface of the convex portion 51 and the refractive index variable layer 60, and then is totally reflected at the interface between the upper side surface of the lower adjacent convex portion 51 and the refractive index variable layer 60. Then, the traveling direction is bent in the direction in which the optical device 1 rebounds and is emitted to the outside of the optical device 1. That is, the light L incident on the optical device 1 is distributed by the optical device 1 at an angle different from that when no voltage is applied.

  As described above, when the first voltage is applied between the first electrode 30 and the second electrode 40, the optical device 1 distributes light incident on the first substrate 10 and causes the second substrate 20 to disperse. Let through. That is, the second optical mode is a light distribution mode, and in the second optical mode, the optical device 1 is in the first light distribution state. In this case, the light incident on the first substrate 10 is reflected by the concave-convex structure 50 of the optical device 1, changes its traveling direction, and exits from the second substrate 20 as described above. That is, in the second optical mode, the optical device 1 distributes light incident on the optical device 1 at the first angle.

  Although not shown in detail, also in the case of the second optical mode, the interface on the light incident side of the first substrate 10, the interface between the first substrate 10 and the first electrode 30, the first electrode 30 and the concavo-convex structure 50 , An interface between the variable refractive index layer 60 and the second electrode 40, an interface between the second electrode 40 and the second substrate 20, or an interface on the light emission side of the second substrate 20. As described above, in a portion where the refractive index difference exists, the light incident from the first substrate 10 is refracted at the interface.

  Further, when the potential applied to the first electrode 30 and the second electrode 40 is set to zero and no voltage is applied, the first nanoparticles 62a and the second nanoparticles 62b migrate in the insulating liquid 61, and FIG. As shown in (1), the first nanoparticles 62a and the second nanoparticles 62b return to a state in which they are uniformly dispersed throughout the insulating liquid 61.

  On the other hand, when a second voltage having a reverse voltage (reverse bias) to the first voltage is applied between the first electrode 30 and the second electrode 40 (when a second voltage is applied), the optical device 1 The third optical mode is different from the first optical mode (when no voltage is applied) and the second optical mode (when the first voltage is applied), and gives a third optical action to incident light.

  Hereinafter, the third optical action of the optical device 1 will be described with reference to FIG. 4C. When a second voltage opposite to the first voltage is applied between the first electrode 30 and the second electrode 40 (when a second voltage is applied), the optical device 1 enters the third optical mode, A third optical action is given to the incident light. Specifically, a DC voltage having a reverse bias to the first voltage is applied as a second voltage between the first electrode 30 and the second electrode 40. For example, if the first voltage is + 20V, the second voltage is -20V.

  In the third optical mode, similarly to the second optical mode, an electric field is applied to the refractive index variable layer 60 according to the voltage applied between the first electrode 30 and the second electrode 40. At 60, the charged first nanoparticles 62a and second nanoparticles 62b electrophorese in the insulating liquid 61 according to the electric field distribution.

  Specifically, as shown in FIG. 4C, when a positive potential is applied to the first electrode 30 and a negative potential is applied to the second electrode 40, the positively charged first nanoparticles 62a and second nanoparticles 62b become , Migrate toward the second electrode 40, and are aggregated and unevenly distributed on the second electrode 40 side in the refractive index variable layer 60.

  As described above, since the first nanoparticles 62a and the second nanoparticles 62b are unevenly distributed on the second electrode 40 side in the refractive index variable layer 60, the particle distribution of the first nanoparticles 62a changes, and the refractive index variable layer The refractive index distribution in 60 becomes non-uniform. Specifically, the second electrode 40 in which the first nanoparticles 62a and the second nanoparticles 62b are gathered in the refractive index variable layer 60 and the concentration of the first nanoparticles 62a and the second nanoparticles 62b is increased. Region 60a (high-concentration region) and the uneven structure 50 side where the first nanoparticles 62a and the second nanoparticles 62b are eliminated and the concentrations of the first nanoparticles 62a and the second nanoparticles 62b are reduced. And the second region 60b (low concentration region).

  In this case, since the refractive index of the first nanoparticles 62a and the second nanoparticles 62b is higher than the refractive index of the insulating liquid 61, the refractive index of the first region 60a on the second electrode 40 side of the refractive index variable layer 60 is The refractive index is higher than the refractive index of the second region 60b of the refractive index variable layer 60 on the side of the concave-convex structure 50. In other words, the refractive index of the second region 60b on the concave-convex structure 50 side of the variable refractive index layer 60 is lower than the refractive index of the first region 60a on the second electrode 40 side of the variable refractive index layer 60. Therefore, in the refractive index variable layer 60, a first region 60a having a high refractive index on the side of the second electrode 40 and a second region 60b having a low refractive index on the side of the uneven structure 50 are generated.

  In the present embodiment, the refractive index of the entire refractive index variable layer 60 when no voltage is applied is about 1.5. The refractive index of the region 60a is distributed in the thickness direction from about 1.4 to about 1.8, and the refractive index of the second region 60b of the refractive index variable layer 60 on the side of the uneven structure 50 is about 1.4 in the thickness direction. Distributed in

  Accordingly, as described above, since the refractive index of the concavo-convex structure 50 is about 1.5, in the case of the third optical mode (the second voltage is applied between the first electrode 30 and the second electrode 40). ), The refractive index difference between the refractive index (about 1.5) of the uneven structure 50 and the refractive index (about 1.4) of the second region 60b of the refractive index variable layer 60 on the uneven structure 50 side. Occurs.

  In this case, as shown in FIG. 4C, when light L enters the optical device 1 from an oblique direction, there is a difference in the refractive index at the interface between the concavo-convex structure 50 (the convex portion 51) and the refractive index variable layer 60. The light L is incident on the concave-convex structure 50 (convex portion 51), and at the interface between the upper side surface of the convex portion 51 (particularly, the side surface of the convex portion 51 from the first electrode 30 side) and the refractive index variable layer 60. After the traveling direction is bent in the direction of total reflection and rebound, the light is refracted at the interface between the upper side surface of the convex portion 51 and the refractive index variable layer 60 and is emitted to the outside of the optical device 1. That is, the light L incident on the optical device 1 is distributed by the optical device 1 at an angle different from that when no voltage is applied and when the first voltage is applied.

  Thus, even when the second voltage is applied between the first electrode 30 and the second electrode 40, the optical device 1 distributes light incident on the first substrate 10 and Through. That is, the third optical mode is also a light distribution mode like the second optical mode, and in the third optical mode, the optical device 1 is in the second light distribution state. In this case, the light incident on the first substrate 10 is reflected by the concave-convex structure 50 of the optical device 1, changes its traveling direction, and exits from the second substrate 20 as described above. That is, in the third optical mode, the optical device 1 distributes the light incident on the optical device 1 at a second angle different from the first angle in the second optical mode.

  Although not shown in detail, also in the case of the third optical mode, the interface on the light incident side of the first substrate 10, the interface between the first substrate 10 and the first electrode 30, the first electrode 30 and the uneven structure 50 , An interface between the variable refractive index layer 60 and the second electrode 40, an interface between the second electrode 40 and the second substrate 20, or an interface on the light emission side of the second substrate 20. In the area where the refractive index difference exists, the light incident from the first substrate 10 is refracted at the interface. However, when the surfaces of the members are all parallel surfaces and the medium (air in the present embodiment) on the entrance side and the exit side of the optical device 1 is the same, the light enters from the first substrate 10 and In the third optical mode (transparent mode), the light emitted from the two substrates 20 has the same incident angle when entering the first substrate 10 and the exit angle when exiting from the second substrate 20. That is, the angle of the traveling direction is the same and does not change.

  Further, when the potential applied to the first electrode 30 and the second electrode 40 is set to zero and no voltage is applied, the first nanoparticles 62a and the second nanoparticles 62b migrate in the insulating liquid 61, and FIG. As shown in (1), the first nanoparticles 62a and the second nanoparticles 62b return to a state in which they are uniformly dispersed throughout the insulating liquid 61. On the other hand, when the voltage applied between the first electrode 30 and the second electrode 40 is switched from the second voltage to the first voltage, the first nanoparticles 62a and the second nanoparticles 62b move in the insulating liquid 61 in the opposite direction. Then, as shown in FIG. 4B, the first nanoparticles 62 a and the second nanoparticles 62 b return to a state where they are uniformly dispersed throughout the insulating liquid 61.

  The optical device 1 configured as described above is an active-type optical control device that can change the optical action by controlling the refractive index matching between the concave-convex structure 50 and the refractive index variable layer 60 by an electric field. That is, by controlling the voltage applied between the first electrode 30 and the second electrode 40, the optical device 1 can be switched to a plurality of optical modes. In the present embodiment, switching of the optical device 1 to three modes of a first optical mode (transparent mode), a second optical mode (first light distribution mode), and a third optical mode (second light distribution mode). Can be.

  In a case where the optical device 1 configured as described above is installed in a window of a building, in the first optical mode, sunlight traveling from the outside toward the room can be directed straight toward the floor, and the second optical mode and the second optical mode can be used. In the three-optical mode, it is possible to distribute sunlight traveling from the outside to the room toward the ceiling. That is, the second optical mode and the third optical mode are lighting modes in which sunlight can be collected on the ceiling in the room.

  In addition, by switching the voltage applied between the first electrode 30 and the second electrode 40 stepwise, a plurality of intermediate modes are set between the first optical mode and the second optical mode or the third optical mode. Alternatively, a plurality of intermediate modes can be set between the second optical mode and the third optical mode. Alternatively, the light distribution state is gradually changed between the first optical mode and the second optical mode or the third optical mode by changing the voltage applied between the first electrode 30 and the second electrode 40 in an analog manner. Or the light distribution state can be gradually changed between the second optical mode and the third optical mode.

[Summary]
As described above, according to the optical device 1 according to the present embodiment, the uneven structure 50 and the refractive index variable layer 60 are disposed between the first electrode 30 and the second electrode 40. The insulating liquid 61 in which the first nanoparticles 62a and the second nanoparticles 62b charged with the same polarity are dispersed is used.

  With this configuration, when a voltage is applied between the first electrode 30 and the second electrode 40, the first nanoparticles 62 a and the second nanoparticles 62 b migrate within the insulating liquid 61, so that the refractive index variable layer The refractive index of 60 can be changed. Specifically, the particle distribution of the first nanoparticles 62a and the second nanoparticles 62b in the variable refractive index layer 60 changes, and the refractive index distribution of the variable refractive index layer 60 changes. Thus, the difference in the refractive index between the concave-convex structure 50 and the variable refractive index layer 60 changes, so that the traveling direction of the light incident on the optical device 1 can be controlled.

  Moreover, in the optical device 1 according to the present embodiment, the second nanoparticles 62b are dispersed in the insulating liquid 61 in addition to the first nanoparticles 62a. That is, a plurality of types of nanoparticles are dispersed in the insulating liquid 61.

  Thereby, by adjusting the ratio of the first nanoparticles 62a and the second nanoparticles 62b, the viscosity of the refractive index variable layer 60 when the first nanoparticles 62a and the second nanoparticles 62b are in a uniform dispersion state. And the refractive index can be adjusted. Therefore, it is possible to easily realize the optical device 1 having the refractive index variable layer 60 having a high maximum refractive index while keeping the viscosity low.

  In this case, in the optical device 1 according to the present embodiment, the first nanoparticles 62a are transparent particles, the second nanoparticles 62b are scattering particles, and the refractive index of the second nanoparticles 62b is the first nanoparticle 62a. Is higher than the refractive index.

  Thereby, compared with the case where the refractive index variable layer 60 is constituted only by the first nanoparticles 62a having a lower refractive index than the second nanoparticles 62b, the refractive index variable layer 60 having a small viscosity and a high maximum refractive index is provided. The optical device 1 can be easily realized. In the present embodiment, zirconia particles having a refractive index of 2.13 are used as the first nanoparticles 62a, and titania particles having a refractive index of 2.52 to 2.72 are used as the second nanoparticles 62b. I have.

  In the optical device 1 according to the present embodiment, the concentration of the first nanoparticles 62a is higher than the concentration of the second nanoparticles 62b.

  Accordingly, the ratio of the first nanoparticles 62a, which are transparent particles, to the insulating liquid 61 is larger than the ratio of the second nanoparticles 62b, which are scattering particles, to the insulating liquid 61. Haze can be reduced. Therefore, even if the second nanoparticles 62b, which are scattering particles, are mixed in the refractive index variable layer 60, it is possible to suppress a decrease in the transparency of the optical device 1 in the transparent state.

  In the optical device 1 according to the present embodiment, the particle concentration including the first nanoparticles 62a and the second nanoparticles 62b is 30% or less.

  Thereby, the viscosity of the refractive index variable layer 60 can be set to a value suitable for electrophoresing the first nanoparticles 62a and the second nanoparticles 62b. Therefore, the optical device 1 having excellent light distribution performance can be realized.

(Modification)
Next, an optical device 1A according to a modification will be described with reference to FIGS. 5A to 5C. FIG. 5A is a view for explaining a first optical action of the optical device 1A according to the modification, and FIG. 5B is a view for explaining a second optical action of the optical device 1A. FIG. 5C is a view for explaining a third optical action of the optical device 1A.

  As shown in FIGS. 5A to 5C, the optical device 1 </ b> A according to the present modified example includes a first substrate 10, a second substrate 20, , A second electrode 40, an uneven structure 50, and a refractive index variable layer 60.

  The difference between the optical device 1A in this modification and the optical device 1 in the above embodiment is the refractive index of the refractive index variable layer 60 when no voltage is applied. Specifically, in the optical device 1 according to the above embodiment, the refractive index of the refractive index variable layer 60 and the refractive index of the concavo-convex structure 50 when no voltage is applied are the same. In the optical device 1A, the refractive index of the refractive index variable layer 60 when no voltage is applied is different from the refractive index of the uneven structure 50.

  Also in the optical device 1A according to this modification, the traveling direction of light incident on the optical device 1A can be controlled according to the voltage applied between the first electrode 30 and the second electrode 40. Specifically, depending on the voltage applied between the first electrode 30 and the second electrode 40, the first nanoparticles 62a and the second nanoparticles 62b in the refractive index variable layer 60 (nanoparticle dispersion layer) are changed. The particle distribution changes, which causes the refractive index of the refractive index variable layer 60 to partially change. As a result, the optical action of the optical device 1A changes. Hereinafter, the optical action of the optical device 1A will be described in detail.

  First, the first optical action of the optical device 1A will be described with reference to FIG. 5A. When no potential is applied to the first electrode 30 and the second electrode 40, that is, when no voltage is applied between the first electrode 30 and the second electrode 40 (when no voltage is applied), The device 1A enters the first optical mode and gives the first optical action to the incident light.

  In the first optical mode, an electric field is not applied to the refractive index variable layer 60. Therefore, as shown in FIG. 5A, in the refractive index variable layer 60, the first nanoparticles 62a and the second nanoparticles 62b It is distributed throughout. That is, the first nanoparticles 62a and the second nanoparticles 62b are in a uniform dispersion state in the insulating liquid 61.

  At this time, in the present modification, the refractive index of the refractive index variable layer 60 in a state where the first nanoparticles 62a and the second nanoparticles 62b are dispersed throughout the insulating liquid 61 is, as shown in FIG. It is uniform (constant) throughout the variable layer 60 and is about 1.6. The refractive index of the concave-convex structure 50 is about 1.5. Therefore, when no voltage is applied between the first electrode 30 and the second electrode 40 (in the case of the first optical mode), the refractive index of the refractive index variable layer 60 as a whole is smaller than the refractive index of the concavo-convex structure 50. Therefore, a difference in refractive index occurs between the refractive index of the uneven structure 50 and the refractive index variable layer 60.

  In this case, as shown in FIG. 5A, when light L enters the optical device 1A from an oblique direction, there is a difference in the refractive index at the interface between the concave-convex structure 50 (the convex portion 51) and the refractive index variable layer 60. The light L is refracted at the interface between the lower side surface of the convex portion 51 and the refractive index variable layer 60, and then totally reflected at the interface between the upper side surface of the convex portion 51 and the variable refractive index layer 60, and bounces off. The traveling direction is bent in the direction, and the light exits the optical device 1A. That is, the light L incident on the optical device 1A is distributed by the optical device 1A.

  As described above, when no voltage is applied between the first electrode 30 and the second electrode 40, the optical device 1A distributes light incident on the first substrate 10 and transmits the light through the second substrate 20. . That is, the first optical mode is the first light distribution mode, and in the first optical mode, the optical device 1A is in the light distribution state. In this case, the light incident on the first substrate 10 is reflected by the concave-convex structure 50 of the optical device 1A, changes its traveling direction, and emerges from the second substrate 20, as described above. That is, in the first optical mode, the optical device 1A distributes light incident on the optical device 1A at the first angle.

  Next, a second optical operation of the optical device 1A will be described with reference to FIG. 5B. When a potential is applied to the first electrode 30 and the second electrode 40, that is, when a first voltage is applied between the first electrode 30 and the second electrode 40 (when a first voltage is applied), The optical device 1A is in the second optical mode and gives a second optical action to incident light. Specifically, a DC voltage of, for example, several V to several tens V is applied between the first electrode 30 and the second electrode 40 as the first voltage.

  In the second optical mode, an electric field is applied to the variable refractive index layer 60 by applying a DC voltage between the first electrode 30 and the second electrode 40. The nanoparticles 62a and the second nanoparticles 62b migrate in the insulating liquid 61 according to the electric field distribution.

  Specifically, when the first nanoparticles 62a and the second nanoparticles 62b are positively charged, a negative potential is applied to the first electrode 30 and a positive potential is applied to the second electrode 40, as shown in FIG. 5B. Is applied, the positively charged first nanoparticles 62a and second nanoparticles 62b migrate toward the first electrode 30 and are aggregated and unevenly distributed on the concave-convex structure 50 side in the refractive index variable layer 60. At this time, the first nanoparticles 62a and the second nanoparticles 62b migrating toward the first electrode 30 enter the concave portion of the concavo-convex structure 50, that is, the region between the two adjacent convex portions 51, and are accumulated. The concentration of the first nanoparticles 62a and the second nanoparticles 62b in the concave portions of the concave-convex structure 50 increases.

  As described above, since the first nanoparticles 62a and the second nanoparticles 62b are unevenly distributed on the concave-convex structure 50 side in the refractive index variable layer 60, the particle distribution of the first nanoparticles 62a and the second nanoparticles 62b is changed. In addition, the refractive index distribution in the refractive index variable layer 60 is not uniform. Specifically, in the refractive index variable layer 60, the first nanoparticle 62a and the second nanoparticle 62b are gathered and the concentration of the first nanoparticle 62a and the second nanoparticle 62b is increased, and the uneven structure 50 side Of the first electrode 60a (high-concentration area) and the second electrode 40 side where the first nanoparticles 62a and the second nanoparticles 62b are eliminated and the concentrations of the first nanoparticles 62a and the second nanoparticles 62b are reduced. And the second region 60b (low concentration region).

  Specifically, at the time of the first voltage application, the refractive index of the first region 60a on the concave-convex structure 50 side of the variable refractive index layer 60 is distributed in the thickness direction at about 1.8 to about 1.5, The refractive index of the second region 60b of the refractive index variable layer 60 on the second electrode 40 side is distributed in the thickness direction at about 1.5 to about 1.4.

  Thereby, as described above, since the refractive index of the uneven structure 50 is about 1.5, in the case of the second optical mode (the first voltage is applied between the first electrode 30 and the second electrode 40). ), Between the refractive index (about 1.5) of the uneven structure 50 and the refractive index (about 1.5 to about 1.8) of the first region 60a of the refractive index variable layer 60 on the uneven structure 50 side. Causes a refractive index difference. At this time, the refractive index difference between the refractive index of the concave-convex structure 50 and the refractive index of the first region 60a on the concave-convex structure 50 side of the refractive index variable layer 60 becomes larger than in the first optical mode.

  In this case, as shown in FIG. 5B, when light L is incident on the optical device 1A from an oblique direction, there is a difference in the refractive index at the interface between the concave-convex structure 50 (the convex portion 51) and the refractive index variable layer 60. Similarly to the case of the first optical mode, the light L incident on the optical device 1A is refracted at the interface between the lower side surface of the convex portion 51 and the refractive index variable layer 60, and The light is totally reflected at the interface with the upper side surface of the convex portion 51, and its traveling direction is bent in the direction of rebound and exits the optical device 1A. That is, the light L incident on the optical device 1A is distributed by the optical device 1A.

  However, in the second optical mode, light is distributed at an angle different from that in the first optical mode. Specifically, light is distributed at a steeper angle in the second optical mode than in the first optical mode. That is, the reflection angle when the light L incident on the optical device 1A is totally reflected by the side surface of the convex portion 51 is smaller in the second optical mode than in the first optical mode. Thereby, the angle of rebound (light distribution angle) when the incident light L is totally reflected on the side surface of the convex portion 51 and rebounds upward is smaller in the case of the second optical mode than in the case of the first optical mode. The emission angle when the light is emitted from the second substrate 20 is larger in the case of the second optical mode than in the case of the first optical mode.

  As described above, when the first voltage is applied between the first electrode 30 and the second electrode 40, the optical device 1A transmits light incident on the first substrate 10 to the first electrode 30 and the second electrode Light is distributed at a steeper angle than when no voltage is applied between the second substrate 20 and the second substrate 20. That is, the second optical mode is a light distribution mode like the first optical mode, but the second optical mode is a second light distribution mode that distributes light more steeply than the first optical mode, In the two-optical mode, the optical device 1A is in the second light distribution state. In the second optical mode, the light incident on the first substrate 10 is reflected by the concave-convex structure 50 of the optical device 1 </ b> A, changes its traveling direction greatly, and exits from the second substrate 20. That is, in the second optical mode, the optical device 1 distributes the light incident on the optical device 1A at a second angle different from the first angle in the first optical mode.

  Next, a third optical operation of the optical device 1A will be described with reference to FIG. 5C. When a potential different from that in the second optical mode is applied to the first electrode 30 and the second electrode 40, that is, a second voltage different from the first voltage between the first electrode 30 and the second electrode 40. When a voltage is applied (when a second voltage is applied), the optical device 1A enters a third optical mode, and gives a third optical action to incident light. Specifically, a DC voltage that is a reverse voltage (reverse bias) to the DC voltage in the second optical mode is applied as a second voltage between the first electrode 30 and the second electrode 40. . The second voltage (potential difference) applied between the first electrode 30 and the second electrode 40 is, for example, about several volts to several tens of volts.

  In the third optical mode, an electric field is applied to the refractive index variable layer 60 by applying a DC voltage between the first electrode 30 and the second electrode 40. In the layer 60, the charged nanoparticles 62 migrate in the insulating liquid 61 according to the electric field distribution.

  However, in the third optical mode, unlike the second optical mode, a positive potential is applied to the first electrode 30 and a negative potential is applied to the second electrode 40, so that the positively charged first nanoparticles 62a and The second nanoparticles 62b migrate toward the second electrode 40, and are aggregated and unevenly distributed on the side of the second electrode 40 in the refractive index variable layer 60. At this time, the first nanoparticles 62a and the second nanoparticles 62b that have migrated toward the second electrode 40 accumulate in layers on the surface of the second electrode 40.

  Thereby, the particle distribution of the first nanoparticles 62a and the second nanoparticles 62b changes, and the refractive index distribution in the refractive index variable layer 60 becomes non-uniform as in the second optical mode. Specifically, in the refractive index variable layer 60, the first area 60a (high area) on the second electrode 40 side where the first nanoparticles 62a and the second nanoparticles 62b have gathered and the concentration of the nanoparticles 62 has increased. Concentration region) and the first electrode 30 side (the concavo-convex structure 50 side) where the first nanoparticles 62a and the second nanoparticles 62b disappear and the concentrations of the first nanoparticles 62a and the second nanoparticles 62b decrease. The second region 60b (low-density region) occurs.

  Specifically, the refractive index of the first region 60a on the second electrode 40 side is distributed in the thickness direction from about 1.5 to about 1.8, and the refractive index of the refractive index variable layer 60 on the side of the concavo-convex structure 50 is about The refractive index of the two regions 60b is distributed at about 1.5 in the thickness direction.

  Furthermore, when the second voltage is applied, the refractive index in the vicinity of the concave-convex structure 50 in the second region 60 b on the concave-convex structure 50 side of the refractive index variable layer 60 is substantially equal to the refractive index of the concave-convex structure 50 on average. Voltage is controlled. As a result, the refractive index difference between the second region 60b of the variable refractive index layer 60 on the concave-convex structure 50 side and the concave-convex structure 50 (the convex portion 51) is almost eliminated (refractive index difference ΔnΔ0).

  In this case, as shown in FIG. 5C, when light L enters the optical device 1A from an oblique direction, there is no difference in the refractive index at the interface between the concave-convex structure 50 (the convex portion 51) and the refractive index variable layer 60. The light L incident on the optical device 1A is not refracted at the interface between the refractive index variable layer 60 and the side surface of the convex portion 51 and the traveling direction does not change. For this reason, in the third optical mode, the light L that has entered the optical device 1A travels straight through the optical device 1A and exits the optical device 1A without being bent in the optical device 1A.

  As described above, when the second voltage is applied between the first electrode 30 and the second electrode 40, the optical device 1A causes the light incident on the first substrate 10 to go straight and the second substrate 20 to move. Let through. That is, the third optical mode is a transparent mode, and in the third optical mode, the optical device 1 is in a transparent state. In this case, the light that has entered the first substrate 10 passes straight through without being distributed by the optical device 1 </ b> A, and exits from the second substrate 20.

  Although not shown in detail, also in the case of the third optical mode, the interface on the light incident side of the first substrate 10, the interface between the first substrate 10 and the first electrode 30, the first electrode 30 and the uneven structure 50 , An interface between the variable refractive index layer 60 and the second electrode 40, an interface between the second electrode 40 and the second substrate 20, or an interface on the light emission side of the second substrate 20. In the area where the refractive index difference exists, the light incident from the first substrate 10 is refracted at the interface. However, when the surfaces of the members are all parallel surfaces and the medium (air in the present embodiment) on the entrance side and the exit side of the optical device 1 is the same, the light enters from the first substrate 10 and In the third optical mode (transparent mode), the light emitted from the two substrates 20 has the same incident angle when entering the first substrate 10 and the exit angle when exiting from the second substrate 20. That is, the angle of the traveling direction is the same and does not change.

  In the third optical mode, the refractive index of the second region 60b of the refractive index variable layer 60 on the side of the concave-convex structure 50 and the refractive index of the concave-convex structure 50 are substantially the same. The average refractive index difference between the first and second uneven structures 50 (projections 51) is 0.010 or less, more preferably 0.005 or less (Δn ≦ 0.005).

  Further, when the potential applied to the first electrode 30 and the second electrode 40 is set to zero and no voltage is applied, the first nanoparticles 62a and the second nanoparticles 62b migrate in the insulating liquid 61, and FIG. As shown in (1), the first nanoparticles 62a and the second nanoparticles 62b return to a state in which they are uniformly dispersed throughout the insulating liquid 61.

  As described above, the optical device 1 </ b> A according to the present modification also has the same effect as the optical device 1 according to the above-described embodiment. For example, the optical device 1A having the refractive index variable layer 60 having a high maximum refractive index while suppressing the viscosity to be small can be realized.

(Other modifications)
As described above, the optical device according to the present invention has been described based on the embodiments and the modifications, but the present invention is not limited to the above embodiments and the modifications.

  For example, in the above embodiment, the first nanoparticles 62a and the second nanoparticles 62b are positively charged, but the invention is not limited thereto. That is, the first nanoparticles 62a and the second nanoparticles 62b may be negatively charged.

  Further, in the above-described embodiment and modified examples, in the second optical mode, a negative potential is applied to the first electrode 30 and a positive potential is applied to the second electrode 40, but the invention is not limited thereto. For example, if a predetermined voltage (potential difference) is applied between the first electrode 30 and the second electrode 40, a positive potential is applied to both the first electrode 30 and the second electrode 40 in the second optical mode. Alternatively, a negative potential may be applied.

  Further, in the above-described embodiment and the modified example, the convex portion 51 configuring the concave-convex structure 50 is a long rectangular column having a trapezoidal cross section, but is not limited thereto. For example, the protrusion 51 may be a long triangular prism having a triangular cross section (for example, an isosceles triangle). Further, the cross-sectional shape of the side surface of the convex portion 51 is not limited to a straight line, but may be a curved line or a sawtooth shape. Further, each of the plurality of protrusions 51 is not limited to one long member extending in the X-axis direction, and may be partially divided in the X-axis direction.

  Further, in the above-described embodiment and modified examples, the height of the plurality of convex portions 51 is fixed, but is not limited thereto. For example, the heights of the plurality of protrusions 51 may be randomly different. Alternatively, the intervals between the convex portions 51 may be randomly different, and both the height and the intervals may be random.

  Further, in the above-described embodiments and modified examples, sunlight is illustrated as light incident on the optical devices 1 and 1A, but the present invention is not limited to this. For example, the light incident on the optical devices 1 and 1A may be light emitted from a light emitting device such as a lighting fixture.

  Further, in the above-described embodiment and modified examples, the optical devices 1 and 1A are arranged on the window so that the longitudinal direction of the convex portion 51 is in the X-axis direction, but the present invention is not limited to this. For example, the optical devices 1 and 1A may be arranged in a window such that the longitudinal direction of the convex portion 51 is in the Z-axis direction.

  In addition, in the above-described embodiment and the modified example, the optical devices 1 and 1A are attached to windows, but the optical devices 1 and 1A may be used as windows of buildings. Further, the optical devices 1 and 1A are not limited to being installed in a window of a building, but may be installed in, for example, a window of a car.

  In addition, a form obtained by applying various modifications conceived by those skilled in the art to the above-described embodiments and modifications, or a component in each of the above-described embodiments and modifications without departing from the spirit of the present invention. The present invention also includes a mode realized by arbitrarily combining the functions and the functions.

DESCRIPTION OF SYMBOLS 1, 1A Optical device 10 First substrate 20 Second substrate 30 First electrode 40 Second electrode 50 Concavo-convex structure 60 Refractive index variable layer 61 Insulating liquid 62a First nanoparticle 62b Second nanoparticle

Claims (12)

A first substrate having optical transparency,
A second substrate having light transmissivity disposed opposite to the first substrate,
A first electrode disposed on the second substrate side of the first substrate,
An uneven structure arranged on the second substrate side of the first substrate,
A second electrode disposed on the first substrate side of the second substrate,
A refractive index variable layer arranged between the uneven structure and the second electrode, the refractive index of which changes according to a voltage applied between the first electrode and the second electrode,
The refractive index variable layer, having an insulating liquid, a plurality of first nanoparticles and a plurality of second nanoparticles dispersed in the insulating liquid,
Each of the first nanoparticles and the second nanoparticles are charged with the same polarity,
Optical device. The first nanoparticles are transparent particles,
The second nanoparticles are scattering particles,
The refractive index of the second nanoparticles is higher than the refractive index of the first nanoparticles,
The optical device according to claim 1. The concentration of the first nanoparticles is greater than the concentration of the second nanoparticles,
The optical device according to claim 2. The particle concentration including the first nanoparticles and the second nanoparticles is 30% or less,
The optical device according to claim 1. When no voltage is applied between the first electrode and the second electrode, the refractive index of the refractive index variable layer is substantially the same as the refractive index of the uneven structure,
The optical device according to claim 1. When no voltage is applied between the first electrode and the second electrode, the optical device transmits light incident on the optical device in a straight line,
The optical device according to claim 5. When a first voltage is applied between the first electrode and the second electrode, the optical device distributes light incident on the optical device at a first angle,
The optical device according to claim 5. When a second voltage that is a reverse voltage to the first voltage is applied between the first electrode and the second electrode, the optical device defines light incident on the optical device as a first angle. Distribute light at different second angles,
The optical device according to claim 5. When no voltage is applied between the first electrode and the second electrode, the refractive index of the refractive index variable layer is higher than the refractive index of the uneven structure,
The optical device according to claim 1. When no voltage is applied between the first electrode and the second electrode, the optical device distributes light incident on the optical device at a first angle,
The optical device according to claim 9. When a first voltage is applied between the first electrode and the second electrode, the optical device distributes light incident on the optical device at a second angle different from the first angle,
The optical device according to claim 10. When a second voltage that is a reverse voltage to the first voltage is applied between the first electrode and the second electrode, the optical device transmits light incident on the optical device in a straight line,
The optical device according to claim 10.

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