WO2026009327A1 - Diffuser and lighting device - Google Patents

Abstract

The objective of the present invention is to provide a diffuser (20) that can express an effect of changing clouds or the like in a plane more naturally than before. The diffuser (20) according to the present disclosure comprises a light diffusion layer having particles (21) that scatter visible light and a stimulus-responsive polymer (22) having light-scattering properties that change in response to a stimulus.

Description

Diffusers and lighting devices

This disclosure relates to a diffuser and lighting device that simulates the sky.

Closure-feeling spaces such as basements and windowless offices can cause stress for occupants. Therefore, lighting systems have been proposed that simulate the blue sky, bringing a sense of openness to such spaces. Patent Document 1 proposes a lighting system that can recreate a pseudo-sky, equipped with a diffuser that is translucent and has the ability to diffuse light, and multiple light sources that direct light into the diffuser.

Japanese Patent Application Laid-Open No. 2018-170153

However, with the above-mentioned conventional technology, the diffuser is a transparent panel containing a light diffusing material inside, or a transparent panel with a diffusing surface. Therefore, if you want to create changes within the diffuser, such as the movement of clouds, you must use multiple types of light sources and control the way these light sources are incident. This type of control is difficult, and there is also the problem that the changes are mechanical.

The present disclosure has been made in light of the above, and aims to provide a diffuser that can more naturally express the transitions of clouds and other objects on a surface than ever before.

In order to solve the above-mentioned problems and achieve the objectives, the diffuser of the present disclosure comprises a light-diffusing layer containing particles that scatter visible light and a stimulus-responsive polymer whose light-scattering properties change in response to a stimulus.

The diffuser according to the present disclosure has the effect of being able to more naturally express the transitions of clouds and other objects within a surface than conventional diffusers.

FIG. 1 is a perspective view showing an example of a schematic configuration of an illumination device according to a first embodiment; FIG. 1 is a cross-sectional view showing an example of a schematic configuration of an illumination device according to a first embodiment; FIG. 1 is a top view showing an example of a schematic configuration of a light source used in an illumination device according to a first embodiment; FIG. 1 is a side view showing an example of a schematic configuration of a light source used in an illumination device according to a first embodiment; FIG. 1 is a diagram showing another example of a schematic configuration of the lighting device according to the first embodiment; FIG. 1 is a diagram schematically illustrating the state of a lighting device when the stimulus-responsive polymer is a polymer chain and has the property of transmitting light incident on the diffuser. FIG. 1 is a diagram schematically illustrating the state of a lighting device when the stimulus-responsive polymer is particulate and has the property of transmitting light incident on the diffuser. FIG. 1 is a diagram schematically illustrating the state of a lighting device when the stimulus-responsive polymer is a polymer chain and has the property of scattering light incident on the diffuser. FIG. 1 is a diagram schematically illustrating the state of a lighting device when the stimulus-responsive polymer is particulate and has the property of scattering light incident on the diffuser. FIG. 1 is a diagram showing another example of a schematic configuration of the lighting device according to the first embodiment; FIG. 1 is a cross-sectional view schematically illustrating an example of a schematic configuration of an illumination device according to a first modification of the first embodiment. FIG. 10 is a diagram schematically illustrating an example of an illumination method in an illumination device according to a first modification of the first embodiment. FIG. 10 is a diagram schematically illustrating an example of an illumination method in an illumination device according to a first modification of the first embodiment. FIG. 10 is a cross-sectional view showing an example of a schematic configuration of a diffuser that configures an illumination device according to a second modification of the first embodiment.

The following describes a diffuser and lighting device according to an embodiment of the present disclosure, with reference to the drawings. The following embodiment is merely an example, and can be modified as appropriate.

In the following embodiments, the main emission direction of the diffuser is the direction in which scattered light simulating the sky is mainly emitted from the diffuser. The main emission direction may be any surface that is intended to be visualized by the user as a light-emitting surface simulating the sky.

Embodiment 1.
Fig. 1 is a perspective view showing an example of a schematic configuration of an illumination device according to embodiment 1. Fig. 2 is a cross-sectional view showing an example of a schematic configuration of an illumination device according to embodiment 1. The illumination device 100 includes a light source 10 and a diffuser 20 serving as a light emitter. Although not shown, the illumination device 100 may also include a frame supporting the light source 10 and the diffuser 20.

The diffuser 20 has a main light-emitting surface forming surface f21, which is a surface including the main light-emitting surface; a back surface f22 facing the main light-emitting surface forming surface f21; and end surfaces f23-f26, which are side surfaces connecting the main light-emitting surface forming surface f21 and the back surface f22. The end surfaces f23-f26 are surfaces that form the end portions of the main light-emitting surface forming surface f21. The area of the main light-emitting surface forming surface f21 from which light that simulates the sky is emitted is the main light-emitting surface. In one example, the light source 10 is provided along at least a portion of the end surfaces f23-f26 of the diffuser 20. In the example shown in Figure 1, the diffuser 20 has a rectangular plate-like structure, and the light source 10 is arranged opposite the end surface f23. The diffuser 20 guides and scatters the light emitted from the light source 10.

The lighting device 100 according to embodiment 1 is installed in a space that feels claustrophobic, such as a basement or a windowless office. In one example, the lighting device 100 is placed on a wall surface of such a space.

Hereinafter, light incident on the end surface f23 of the diffuser 20 is referred to as light Li. The scattered light emitted from the diffuser 20, simulating the sky, is referred to as light Ls or scattered light Ls. Furthermore, of the scattered light Ls, Rayleigh scattered light is referred to as Lsr, and Mie scattered light is referred to as Lsm. Light guided within the diffuser 20 is referred to as light Lt. Here, "guiding light" refers to propagating light that has entered a certain medium along a specified optical path within that medium. Therefore, light Lt does not include light that is scattered or absorbed within the diffuser 20.

In the example shown in Figure 2, the primary light-emitting surface of the diffuser 20 may be the entire primary light-emitting surface f21, or a partial area of the primary light-emitting surface f21. In the diffuser 20, scattered light Ls that simulates the sky can be emitted not only from the primary light-emitting surface, but also from the back surface f22 and end surfaces f23-f26.

<Light source 10>
Fig. 3 is a top view showing an example of a schematic configuration of a light source used in the lighting device according to embodiment 1, and Fig. 4 is a side view showing an example of a schematic configuration of a light source used in the lighting device according to embodiment 1. Note that, here, the top view refers to a view of the light source 10 as seen from the emission direction of light Li from the light source 10.

The light source 10 emits light Li to be incident on the interior of the diffuser 20. The light source 10 has a light-emitting element 12. In one example, the light source 10 is an LED light source that uses a light-emitting diode (LED) element as the light-emitting element 12.

The light source 10 is positioned opposite at least a portion of the surfaces that make up the diffuser 20, namely the main light-emitting surface constituting surface f21, the back surface f22, and the end surfaces f23-f26. Figures 1 and 2 show an example in which the light source 10 is positioned along the end surface f23 of the diffuser 20.

The light source 10 includes a substrate 11 and light-emitting elements 12. In one example, the substrate 11 is a plate-shaped member extending in one direction. The substrate 11 has a wiring layer (not shown) that is electrically connected to the mounted light-emitting elements 12. The light-emitting elements 12 are arranged on the surface of the substrate 11 facing the diffuser 20. In Figures 3 and 4, multiple light-emitting elements 12 are arranged along the extension direction of the substrate 11.

The light source 10 has a light-emitting surface f11 that emits light Li, which is incident light on the diffuser 20. The light-emitting surface f11 is an imaginary surface formed to include the surfaces from which each of the multiple light-emitting elements 12 emits light. The light source 10 is positioned facing the diffuser 20. Specifically, the light source 10 is positioned so that the light-emitting surface f11 faces at least a portion of the surfaces f21-f26 that make up the diffuser 20. In the example of Figures 1 and 2, the light source 10 is positioned so that the light-emitting surface f11 faces the end surface f23 of the diffuser 20.

Note that FIG. 1 shows one example of the configuration of the lighting device 100, and the configuration of the lighting device 100 is not limited to this. FIG. 5 is a diagram showing another example of the schematic configuration of the lighting device according to embodiment 1. As shown in FIG. 5, the lighting device 100a may include multiple light sources 10 for one diffuser 20. Here, the light source 10 is a unit that can be independently controlled for on/off, light emission intensity, or light emission color. Here, six light sources 10 are arranged on each of the four end faces f23-f26 of the diffuser 20, whose main light-emitting surface f21 is made of a square plate-like member. Note that when a lighting unit is configured to have only one light source 10 for one diffuser 20, the lighting device 100a may include multiple lighting units.

In the following, one or more light sources 10 or light-emitting elements 12 that emit light Li, which is incident light that generates light Ls that simulates the sky, toward one diffuser 20, may be collectively referred to as light source 10. Furthermore, the function of the light source 10 that emits light Li will be described using light source 10 as the subject, but this function can be considered as the function of one light source 10 or one light-emitting element 12 included in the lighting device 100, or as the function of a combination of multiple light sources 10 or multiple light-emitting elements 12.

In one example, in the light source 10 configuration shown in Figures 3 and 4, each light emitting element 12 can be considered to be a single light source 10. In this case, it is not precluded that one of the light sources 10 corresponding to each light emitting element 12 in the figures has the light source 10 configuration shown in Figure 3, i.e., a configuration including multiple light emitting elements 12. Also, in the example of the arrangement of light sources 10 shown in Figure 5, each light source 10 in the figure can be considered to be a single light emitting element 12.

As shown in FIG. 2, the light source 10 emits light Li, which is incident light on the diffuser 20. In one example, the light source 10 may emit white light as light Li, or light with a determined correlated color temperature as light Li. In one example, the correlated color temperature may be 6500 K or 5000 K. Furthermore, the correlated color temperatures of the light Li emitted by each light source 10 may be the same, or each or some of the light may be different.

The color of the light Li emitted from the light source 10 may be a color other than white. In one example, the lighting device 100 may include a light source 10 that includes a white light source and a green light source, or a light source 10 that includes a white light source, a green light source, a blue light source, and an orange light source.

The lighting device 100 may also include light sources 10 that include white light sources with different color temperatures. In one example, the lighting device 100 may include light sources 10 that include a white light source with a high color temperature and a white light source with a low color temperature.

Here, the difference in color temperature between the high color temperature white light and the low color temperature white light can be, for example, 8800K. The correlated color temperature of light Li emitted from the high color temperature white light source is, for example, 11500K or higher and 19000K or lower. The correlated color temperature of light Li emitted from the low color temperature white light source is, for example, 5500K or higher and 6050K or lower. Within the above range of correlated color temperatures of high and low color temperature white light, the color temperatures of the high color temperature white light emitted from the high color temperature white light source and the low color temperature white light source are selected so that the difference in color temperature between the high color temperature white light and the low color temperature white light is 8800K. For example, the correlated color temperature of the high color temperature white light can be 14400K, and the correlated color temperature of the low color temperature white light can be 5600K.

As described above, the light source 10 is a component that emits light Li, including visible light, to be guided inside the diffuser 20. Furthermore, multiple light sources 10 may be provided, and the correlated color temperatures of the light Li emitted by the multiple light sources 10 may be different.

In addition to being arranged opposite one end surface f23 that constitutes the end of the main light-emitting surface forming surface f21 as shown in FIG. 1, the light source 10 may also be arranged opposite two or more end surfaces f23-f26 as shown in FIG. 5. In this way, any light source that functions as a light source 10 that emits light Li from one end surface f23-f26 of a single diffuser 20 can be considered to be the light source 10 of the lighting device 100 according to embodiment 1.

In one example, as shown in Figures 1 and 2, the light source 10, or more specifically, the light-emitting surface f11 of the light source 10, may be arranged opposite at least one of the end faces f23-f26 that form the end of the main light-emitting surface-forming surface f21 of the diffuser 20. In another example, as shown in Figure 5, multiple light sources 10 may be arranged along at least one of the end faces f23-f26 of the diffuser 20.

The shape of the diffuser 20 is not limited to a rectangular plate. As an example, the diffuser 20 may be rectangular, polygonal, circular, barrel-shaped, spool-shaped, or any other shape formed by connecting two or more straight lines, two or more arcs, or one or more straight lines and one or more arcs.

If the diffuser 20 has another shape, it is sufficient that the light source 10 is arranged so as to face at least a portion of the side surface connecting the main light-emitting surface forming surface f21 and the back surface f22. Furthermore, there may be one or more light sources 10. If multiple light sources 10 are arranged, they may be arranged so as to face different portions of the side surface connecting the main light-emitting surface forming surface f21 and the back surface f22. In one example, if the main light-emitting surface forming surface f21 and the back surface f22 are polygonal, including rectangular, the side surface will be composed of multiple planes. In such a case, one or more light sources 10 may be arranged so as to face one of the multiple planes that make up the side surface. In this case, the one or more light sources 10 may be arranged so as to face the entirety of one plane, or so as to face a portion of one plane. Furthermore, one or more light sources 10 may be arranged so as to face each of two or more planes that make up the side surface. In this case, the one or more light sources 10 may be arranged so as to face the entirety of each of the two or more planes, or so as to face a portion of each of the two or more planes.

Furthermore, in consideration of ZEB (Zero Energy Building), the light Li from the light source 10 can be substituted with, for example, guided light from outside, such as sunlight. To guide the outside light, a light-collecting member or light guide that captures the outside light and emits it in a specified direction can be used. In other words, the lighting device 100 may be equipped with such a light-collecting member or light guide as the light source 10.

<Diffuser 20>
As shown in Fig. 2, the diffuser 20 is a structure having a light diffusion layer including particles 21, a stimulus-responsive polymer 22, and a substrate 23, and has the ability to scatter light Li. Fig. 2 shows a case where the light diffusion layer is a single layer.

Particles 21 scatter visible light. One example of particles 21 is nanoparticles. A "nanoparticle" is a particle with a size on the order of nanometers (nm). Nanoparticles generally refer to particles with a size of 1 nm or more and several hundred nm or less. In other words, one example of particles 21 is a particle with a diameter on the order of nanometers. In this case, the diameter of particles 21 may be taken as the average diameter.

The particles 21 may be spherical or have another shape. The diffuser 20 may also contain multiple types of particles 21.

The particles 21 are particles made of an inorganic oxide or an organic compound. Examples of inorganic oxides include ZnO, _TiO2 , _ZrO2 , _SiO2 , _{and Al2O3} . Examples of organic compounds include acrylic, styrene, silicone, urethane, and melamine resins.

Particles 21 scatter light Li incident on diffuser 20 to produce light Ls. Particles 21 also scatter light Lt propagating through diffuser 20 to produce light Ls.

Depending on the combination of the particle size of the particles 21 and the light Li incident on the diffuser 20, the light Ls scattered by the particles 21 may include Rayleigh scattered light Lsr. However, the light Ls scattered by the particles 21 is not limited to Rayleigh scattered light Lsr, and may also include Mie scattered light Lsm. In other words, the particles 21 primarily cause Rayleigh scattering or a Rayleigh scattering-like scattering phenomenon with visible light.

The stimuli-responsive polymer 22 is a substance whose physical properties change in response to an external stimulus. The external stimulus will be referred to simply as the stimulus hereinafter. The physical properties of the stimuli-responsive polymer 22 exhibit reversible changes when the stimulus exceeds a certain stimulus threshold and when it is below the threshold.

The physical properties of the stimulus-responsive polymer 22 that change in response to a stimulus include the refractive index and compatibility with the solvent. The refractive index changes due to the phase transition of the stimulus-responsive polymer 22 around a threshold. Changes in compatibility can also cause changes in the conformation of the stimulus-responsive polymer 22. In other words, the stimulus-responsive polymer 22 can be described as a polymeric material whose light scattering properties change in response to a stimulus.

The stimulus applied to the stimulus-responsive polymer 22 may be, for example, temperature or light. If the stimulus is temperature, the threshold is preferably, for example, 10°C or higher and 70°C or lower. If the stimulus is light, a polymer whose physical properties change in response to specific light, such as ultraviolet light, may be used as the stimulus-responsive polymer 22.

The shape of the stimulus-responsive polymer 22 is not particularly limited and may be particulate, flat, fibrous, polymer chain, etc.

In one example, the stimulus-responsive polymer 22 is a solid or liquid.

When the stimulus-responsive polymer 22 is solid, it may be in a gel state. In one example, the stimulus-responsive polymer 22 is an acrylate-based material.

When the stimuli-responsive polymer 22 is liquid, this also includes a gel state. One example of the stimuli-responsive polymer 22 is a non-ionic hydrophilic (water-soluble) polymer. Specific examples that can be used include poly(meth)acrylamide derivatives, polyvinylamide derivatives, polyvinyl methyl ether, and cellulose derivatives. Other examples include polyoxazolidones, polyalkylene oxides, polyvinyl alcohols, polymethacrylic acid, and their derivatives. Furthermore, polyethylene glycol/polypropylene glycol block copolymers may also be used as the stimuli-responsive polymer 22. Examples of polyvinyl alcohol derivatives include partial acetoacetal compounds, partial formal compounds, and partial butyral compounds of polyvinyl alcohol.

(Poly(meth)acrylamide derivatives)
An example of a poly(meth)acrylamide derivative is a poly N-substituted (meth)acrylamide derivative. An example of an N-substituted (meth)acrylamide is a polymer obtained by polymerizing N-cyclopropyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-n-propyl(meth)acrylamide, N-methyl-N-ethylacrylamide, N-methyl-N-isopropylacrylamide, N-methyl-N-n-propylacrylamide, N,N-diethylacrylamide, N-acryloylpiperidine, N-acryloylpyrrolidine, or N-tetrahydrofuryl acrylamide. Furthermore, the poly(meth)acrylamide derivative may be a poly(meth)acrylamide copolymer obtained by copolymerizing multiple types of (meth)acrylamides or (meth)acrylamide with other monomers.

(Polyvinylamide derivatives)
An example of the polyvinylamide derivative is a polymer obtained by polymerizing N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-methylformamide, N-vinylpropionamide, or the like. N-vinylacetamide and N-vinyl-N-methylacetamide are preferred. The polyvinylamide derivative may also be a polyvinylamide copolymer obtained by copolymerizing multiple types of vinylamide monomers or a vinylamide monomer with another monomer.

(cellulose derivatives)
As the cellulose derivative, for example, alkyl-substituted cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, and hydroxyethylmethyl cellulose can be used.

In another example, the stimulus-responsive polymer 22 is a hydrophobic polymer. Specifically, the stimulus-responsive polymer 22 is a stearyl acrylate-based substance, etc.

The physical properties of the stimulus-responsive polymer 22 change around the threshold, causing the scattering characteristics for the light Lt guided through the diffuser 20 to change. In one example, below the threshold, the polymer has a strong tendency to transmit light Lt, but above the threshold, it changes to a tendency to strongly scatter light Lt. In this case, the particles 21 primarily cause Rayleigh scattering or Rayleigh scattering-like scattering phenomena for visible light, whereas when the stimulus exceeds the threshold, the stimulus-responsive polymer 22 primarily causes Mie scattering for the light Lt.

Furthermore, this scattering characteristic, i.e., the relationship between the change in physical properties before and after the threshold value, may change depending on the combination with the substrate 23. In one example, when the threshold value is less than the threshold value, the material may have the property of scattering incident light Li, and when the threshold value is exceeded, the material may have the property of transmitting incident light Li.

In this way, the stimulus-responsive polymer 22 is a material that switches between a first state, which primarily causes Mie scattering, and a second state, which transmits visible light, in response to a stimulus. Depending on the stimulus applied to the stimulus-responsive polymer 22, a region in the first state is formed across the entire or partial diffuser 20.

The threshold at which the stimulus-responsive polymer 22 responds to stimuli may have a certain range.

The substrate 23 is a component that includes particles 21 and a stimulus-responsive polymer 22 and guides incident light Li into the interior. In one example, the particles 21 and the stimulus-responsive polymer 22 are dispersed in the substrate 23. The particles 21 and the stimulus-responsive polymer 22 may be fixed to the substrate 23, or may be fluid. In other words, the substrate 23 is not limited to being solid, and may be a liquid, liquid crystal, or gel-like substance.

In one example, the substrate 23 is a transparent material. The substrate 23 does not necessarily have to be transparent to all wavelengths of the light Li. As one example, the substrate 23 may absorb certain wavelengths of the wavelengths of the light Li.

The substrate 23 preferably has a rectilinear transmittance, which indicates the transmittance at a light guide distance of 5 mm, of 85% or more at the design wavelength, more preferably 95% or more, and even more preferably 98% or more. Here, the design wavelength may be a predetermined wavelength among the wavelengths of the incident light Li. The design wavelength is not limited to one wavelength, but may be multiple wavelengths or a range of wavelengths, i.e., a wavelength band. In one example, when the incident light is white light Li, the design wavelength may be one or more of 450 nm, 550 nm, and 650 nm.

When the substrate 23 is solid, the substrate 23 is, for example, composed of a resin plate using a thermoplastic polymer, a thermosetting resin, or a photopolymerizable resin. Examples of resin plates that can be used include acrylic polymers, olefin polymers, vinyl polymers, cellulose polymers, amide polymers, fluorine-based polymers, urethane polymers, silicone polymers, and imide polymers. For example, the diffuser 20 may be formed by dispersing particles 21 and stimuli-responsive polymer 22 in the uncured or molten material of the substrate 23, and then performing a curing process.

When the substrate 23 is liquid, the substrate 23 is composed of, for example, a polar solvent such as water or ethanol, or a non-polar solvent such as oil or an organic solvent.

In one example, the substrate 23 may be formed from an organic molecular dispersion material or an organic-inorganic hybrid material produced by a sol-gel method. Organic-inorganic hybrid materials are also called organic-inorganic nanocomposite materials. In one example, the substrate 23 is an organic-inorganic hybrid resin or a hybrid resin of a resin and an inorganic oxide. In this case, the substrate 23 contains inorganic oxide produced by sol-gel curing as a substance equivalent to the particles 21. Note that in the present disclosure, microscopic pores produced in the substrate 23 by such a manufacturing process are also considered to be particles 21.

Furthermore, the substrate 23 may have fine irregularities formed on its surface that are smaller than the wavelength of blue light. The maximum diameter of the concave or convex portions is preferably on the nano-order, for example, between 1 nm and several hundred nm.

In the above, an example has been shown in which the diffuser 20 is composed of particles 21, a stimulus-responsive polymer 22, and a substrate 23, but the diffuser 20 may also be a gel composed of the stimulus-responsive polymer 22 and substrate 23. In this case, the substrate 23 may be a polar solvent such as water or ethanol, and the diffuser 20 may be composed of a gel in which the stimulus-responsive polymer 22 is made of a hydrophilic polymer. In another example, the diffuser 20 may be composed of a non-polar solvent such as oil or an organic solvent, and the stimulus-responsive polymer 22 is a gel in which the hydrophobic polymer is made.

The diffuser 20 may have at least one surface coated with a translucent functional coating such as an anti-reflection coating, an anti-fouling coating, a heat-shielding coating, or a water-repellent coating. The diffuser 20 may also include two transparent plates sandwiching a light-diffusing layer having particles 21, a stimuli-responsive polymer 22, and a substrate 23. In one example, taking into account functionality such as impact resistance, water resistance, and heat resistance as a window, the light-diffusing layer may be sandwiched between two transparent substrates such as glass plates. In this case, the diffuser 20 may be an intermediate film in laminated glass. Furthermore, if the substrate 23 is a liquid, sandwiching the light-diffusing layer between two transparent plates can prevent leakage of the liquid from the substrate 23.

The diffuser 20 having the above configuration emits light Ls scattered by the particles 21. However, as described above, the particles 21 include not only nanoparticles but also compositions such as sol-gel-hardened oxides, holes, and depressions or protrusions on the surface, each having a size on the order of nanometers. Hereinafter, these will be collectively referred to as a nano-order optical medium. Herein, the nano-order optical medium is not particularly limited as long as it is an optical medium that causes Rayleigh scattering or a Rayleigh scattering-like scattering phenomenon for light Lt within the substrate 23. Such a nano-order optical medium includes an interface. Furthermore, the nano-order optical medium may emit light Lt guided within the diffuser 20. In one example, light Lt that has been guided within the diffuser 20 and reached end face f25 opposite end face f23, the incident surface, may be emitted as light that reproduces sunlight. In this disclosure, unless otherwise specified, the term "particles 21" is used as a general term for such nano-order optical media.

In Rayleigh scattering, scattered light Lsr is emitted in all directions. Therefore, as shown in Figure 1, even if light Li is incident on the end surface f23, which is the side surface of the diffuser 20, light Ls can be extracted from the main light-emitting surface f21 and back surface f22, which are perpendicular to the end surface f23.

<Generation of scattered light Ls simulating the sky>
The principle of generation of scattered light Ls simulating the sky will be described below with reference to FIGS. 6 to 9. FIG.

First, we will explain the case where the stimulus-responsive polymer 22 has the property of transmitting light Li incident on the diffuser 20. Figure 6 is a diagram that schematically shows the appearance of a lighting device when the stimulus-responsive polymer is in the form of a polymer chain and has the property of transmitting light incident on the diffuser. Figure 7 is a diagram that schematically shows the appearance of a lighting device when the stimulus-responsive polymer is in the form of particles and has the property of transmitting light incident on the diffuser.

As already explained, light Li emitted from the light source 10 enters the diffuser 20 from the end face f23. The incident light Li is guided through the diffuser 20 as light Lt. As shown in Figure 6, light Lt is reflected by the main light-emitting surface forming surface f21 and the back surface f22 of the diffuser 20 and is guided.

As the light Lt propagates through the diffuser 20, some of the light Lt collides with particles 21, etc. Alternatively, some of the light Lt has its path blocked by particles 21, etc. The light Lt that collides with particles 21, etc. is scattered in all directions and becomes scattered light Ls. At this time, the stimulus-responsive polymer 22 in the diffuser 20, whether in the form of a polymer chain as shown in Figure 6 or a particle as shown in Figure 7, transmits the light Lt and is therefore not involved in generating scattered light Ls.

Among the scattered light Ls, light that is incident on the main light-emitting surface f21 at an angle of incidence less than the critical angle is emitted from the main light-emitting surface of the main light-emitting surface f21. The critical angle is the smallest angle of incidence at which total reflection occurs when light travels from a medium with a high refractive index to a medium with a low refractive index.

In this case, if the scattered light Ls is Rayleigh scattered, the shorter the wavelength of the light, the higher the probability of it being scattered. As a result, the correlated color temperature of the scattered light Ls is higher than the correlated color temperature of the light Li that enters the diffuser 20. In other words, it can be said that the light source 10 emits light Li that has a lower correlated color temperature than the correlated color temperature of the light Ls scattered by the diffuser 20.

When light Li has a spectral distribution across the entire visible light range, blue light is preferentially scattered. In one example, the light source 10 is equipped with a white LED that emits white light Li as the light-emitting element 12, and the blue light is scattered as scattered light Ls by the particles 21 in the diffuser 20. In this way, by appropriately designing the light source 10 and diffuser 20, the light Ls has a correlated color temperature that indicates a blue that is close to the actual color of the sky.

Note that the amount of light Ls depends on the amount of incident light Li, so by appropriately selecting the amount of light from the light source 10 used, it is possible to reproduce the blue sky color while maintaining sufficient brightness for the lighting fixture. Furthermore, by appropriately designing the light guide direction and light guide distance of the light Lt within the diffuser 20 and the concentration of particles 21, the thickness of the diffuser 20 can be reduced. According to the configuration of embodiment 1, the thickness of the diffuser 20 can be set to 100 mm or less, 20 mm or less, 10 mm or less, or even 5 mm or less. Furthermore, in the examples of Figures 2 and 3, if the length of the light source 10 in the direction perpendicular to the main light-emitting surface f21 of the diffuser 20 is small, or if the light Li is light with a small irradiation range on the incident surface of the diffuser 20, such as light emitted from a laser light source or focused spot light, the thickness of the diffuser 20 can be set to 1 mm or less.

Next, we will explain the case where the stimulus-responsive polymer 22 has the property of scattering light Li incident on the diffuser 20. Figure 8 is a diagram that schematically shows the appearance of a lighting device when the stimulus-responsive polymer is in the form of a polymer chain and has the property of scattering light incident on the diffuser. Figure 9 is a diagram that schematically shows the appearance of a lighting device when the stimulus-responsive polymer is in the form of particles and has the property of scattering light incident on the diffuser.

In this case, as the light Lt propagates through the diffuser 20, some of the light Lt collides with the stimuli-responsive polymer 22 in addition to the particles 21, etc. Alternatively, some of the light Lt is blocked by the particles 21, etc. and the stimuli-responsive polymer 22. The scattering of the light Lt by the particles 21 is similar to that described in Figures 6 and 7.

Here, the stimuli-responsive polymer 22 exhibits light scattering properties. Therefore, light Lt that strikes the stimuli-responsive polymer 22 is scattered in all directions, becoming scattered light Ls. The scattered light Ls contains a large amount of Mie scattered light Lsm. However, it may also contain Rayleigh scattered light Lsr. Then, the light Ls scattered by the particles 21 and the light Ls scattered by the stimuli-responsive polymer 22 are emitted from the main light-emitting surface of the main light-emitting surface constituent surface f21.

The light Ls scattered by the stimulus-responsive polymer 22 has a higher proportion of Mie scattering and a greater scattering intensity than the light Ls scattered by the particles 21. Unlike Rayleigh scattering, Mie scattering has almost no selectivity for scattering wavelengths, and is therefore strongly influenced by the color of the light Li incident from the light source 10. For example, if the light source 10 has a white LED as the light-emitting element 12, the light Ls scattered by the particles 21, etc. is blue light, but the light Ls scattered by the stimulus-responsive polymer 22 is close to white in color. For this reason, in the example shown in Figures 8 and 9, it is possible to reproduce clouds floating in a blue sky.

In another example, if the light source 10 is equipped with an LED with a low correlated color temperature as the light-emitting element 12, the light Ls scattered by the stimulus-responsive polymer 22 will be closer to a warm color, making it possible to recreate sunset clouds. In addition, by using multiple types of light sources 10, it is possible to create a variety of clouds.

Because the light Ls scattered by the stimulus-responsive polymer 22 has a high proportion of Mie scattering, it is brighter than the light Ls scattered by the particles 21. Therefore, by appropriately combining the particles 21 and the stimulus-responsive polymer 22, it is possible to express clouds floating in a blue sky.

As described above, the light scattering properties change when the stimulus applied to the stimulus-responsive polymer 22 crosses a threshold. In one example, the stimulus-responsive polymer 22 exhibits strong light transparency when the stimulus applied is below the threshold, and exhibits strong light scattering when the stimulus exceeds the threshold. In other words, the stimulus-responsive polymer 22 switches between a first state in which Mie scattering occurs primarily, and a second state in which visible light is transmitted, depending on the stimulus.

In this way, the light scattering properties of the stimulus-responsive polymer 22 can be changed by turning the stimulus on or off, so by applying a stimulus to the entire diffuser 20, clouds can be reproduced across the entire diffuser 20. Also, by applying a stimulus to only a portion of the diffuser 20, clouds can be reproduced in a portion of a blue sky.

Furthermore, by setting the stimulus value, which indicates the magnitude of the stimulus applied to the diffuser 20, near the threshold value of the stimulus-responsive polymer 22, the light scattering properties of the stimulus-responsive polymer 22 can be adjusted. By making such adjustments, it is possible to recreate the appearance of wispy clouds by varying the strength of the light scattering properties, or to create the appearance of clouds slowly appearing and disappearing.

The diffuser 20 may contain multiple types of stimulus-responsive polymers 22 with different thresholds. In other words, if the diffuser 20 is composed of a single light-diffusing layer, the light-diffusing layer may contain multiple stimulus-responsive polymers 22 with different stimulus thresholds that switch between a first state that scatters light Lt and a second state that transmits light Lt. The presence of multiple types of stimulus-responsive polymers 22 with different thresholds makes it possible to mix different light-scattering states within the diffuser 20 for a single stimulus value. As a result, it becomes possible to express a more complex sky appearance.

Furthermore, the diffuser 20 may contain multiple types of stimulus-responsive polymers 22 that respond to different stimuli, such as temperature or light. In other words, if the diffuser 20 is composed of a single light-diffusing layer, the light-diffusing layer may contain multiple stimulus-responsive polymers 22 that switch between a first state that scatters light Lt and a second state that transmits light Lt, and that respond to different types of stimuli. In this way, even if there are multiple types of stimulus-responsive polymers 22 that respond to different stimuli, by using different types of stimuli, it is possible to mix different light-scattering states within the diffuser 20. As a result, it is possible to express a more complex sky appearance.

Furthermore, multiple types of stimulus-responsive polymers 22 with different light-scattering properties may be mixed within the diffuser 20. In one example, by mixing stimulus-responsive polymers 22 with strong light-scattering properties and stimulus-responsive polymers 22 with weak light-scattering properties within the diffuser 20, it is possible to increase the variety of clouds that can be reproduced. In one example, it is possible to reproduce clouds that resemble dense cumulonimbus clouds, thin cirrocumulus clouds, etc.

The diffuser 20 may also have a configuration in which stimulus-responsive polymers 22 with different thresholds are stacked. In one example, the diffuser 20 has multiple stacked light-diffusing layers, and adjacent light-diffusing layers in the stacking direction may have different stimulus thresholds at which the stimulus-responsive polymer 22 switches between a first state in which it scatters light Lt and a second state in which it transmits light Lt. By stacking stimulus-responsive polymers 22 with different thresholds, it is possible to create areas with strong or weak light scattering between the main light-emitting surface constituent surface f21 and the back surface f22 of the diffuser 20. This makes it possible to reproduce clouds in the low or high altitude layers, creating a blue sky with a sense of depth.

In this case, a different light source 10 may be used for each layer of stimulus-responsive polymer 22, i.e., for each light-diffusing layer. This makes it possible to reproduce the gradation of the sky.

The diffuser 20 may be stimulated by a stimulus source or by the installation environment.

If the stimulus is provided by a stimulus generator, the stimulus generator may be provided external to the lighting device 100 or may be incorporated into the lighting device 100.

FIG. 10 is a diagram showing another example of the schematic configuration of the lighting device according to embodiment 1. As shown in FIG. 10, the lighting device 100b further includes a stimulus generator 30, which is a stimulus source, in addition to the light source 10 and the diffuser 20. The stimulus generator 30 is a device that can apply a stimulus such as light or heat to the diffuser 20. When the stimulus is light, an example of the stimulus generator 30 is an ultraviolet irradiation device that generates ultraviolet rays. When the stimulus is heat, an example of the stimulus generator 30 is a temperature control device such as a heat generating device such as a heater or infrared irradiation device, a cooling device such as a fan or water cooling device, or a device that dissipates and absorbs heat such as a Peltier element. Note that when the stimulus is heat, the stimulus generator 30 is a device that applies heat to the diffuser 20 to control its temperature. In this way, the stimulus generator 30 inside the lighting device 100b can apply a stimulus to the diffuser 20 using light or temperature.

The stimulus generating unit 30 may be installed on a portion of the lighting device 100b, i.e., the diffuser 20, or on the entire surface. Taking the example of a diffuser 20 configured as shown in Figure 1, the stimulus generating unit 30 may be installed on one of the main light-emitting surface forming surface f21, the back surface f22, and the end surfaces f23-f26 of the diffuser 20, or on multiple surfaces, or on the entire surface. Furthermore, the stimulus generating unit 30 may be installed on all of these surfaces, or on only some of these surfaces.

10 shows an example in which the stimulus generating unit 30 is provided over the entire back surface f22 of the diffuser 20. In this case, the stimulus generating unit 30 may apply a stimulus to the entire back surface f22, i.e., the diffuser 20, or may apply a stimulus to only a portion of the back surface f22. When applying a stimulus to only a portion of the back surface f22, in one example, the stimulus generating unit 30 has multiple stimulus generating elements that are arranged two-dimensionally on the back surface f22. A stimulus is then generated from the stimulus generating element at the desired position. In this way, it is possible to select the position at which the stimulus is applied, such as the entire back surface f22, a portion, or multiple portions. Furthermore, the positions of the stimulus generating elements that generate a stimulus may be switched in sequence so that the position at which the stimulus is applied moves. This allows the position at which the stimulus is applied to move within the back surface f22. In this way, by moving the position of the stimulus generated by the stimulus generating unit 30 within the diffuser 20, it is possible to reproduce the movement of clouds, etc.

Alternatively, the stimulus generating unit 30 may be made smaller than the area of the back surface f22, and the stimulus generating unit 30 may be made movable in the in-plane direction of the back surface f22 by a drive unit. This allows the stimulus generating unit 30 to generate a stimulus at any position within the plane of the back surface f22. In this way, by moving the position of the stimulus generated by the stimulus generating unit 30 within the diffuser 20, it is possible to reproduce the movement of clouds, etc.

In another example, the stimulus source may be light or heat generated from the light source 10. When the stimulus source is light or heat generated from the light source 10, the light source 10 also functions as the stimulus generator 30. In one example, the light source 10 may be configured to include a light-emitting element 12 that emits light Li, which is the basis of light Lt that is guided within the diffuser 20, and a light-emitting element 12 that emits light that stimulates the stimulus-responsive polymer 22.

Furthermore, by linking weather and other information with the stimulus generation unit 30, it is possible to create a sky that is linked to the actual weather. Weather and other information can be obtained from a server device that provides meteorological information via a network. Alternatively, it is possible to create a sky that is the complete opposite of the actual weather, such as lighting a clear blue sky on a rainy day.

Furthermore, the light source 10 and the stimulus generating unit 30 may be controlled separately. In this case, the light source 10 and the stimulus generating unit 30 are controlled by a control circuit (not shown), for example. The control circuit is connected to the light source 10 and the stimulus generating unit 30 via wiring. In one example, the control circuit includes a processor and memory. In one example, the processor and memory can send and receive data to and from each other via a bus. The processor performs each function by reading and executing programs stored in the memory. In one example, the processor includes one or more of a CPU (Central Processing Unit) and a DSP (Digital Signal Processor).

The memory may include one or more of RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). In one example, the computer program stored in the memory is provided by a recording medium. The recording medium may include one or more of non-volatile or volatile semiconductor memory, magnetic disks, flexible memory, optical disks, compact disks, and DVDs (Digital Versatile Discs). In another example, the program stored in the memory may be provided by a communication medium. When the control circuit is dedicated hardware, the control circuit may include at least one of FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), and system LSI (Large Scale Integration).

If the stimulus source is provided outside the lighting device 100, the stimulus source can be another lighting device. In this case, light or heat generated from the other lighting device is used as the stimulus. Alternatively, the stimulus source can be a temperature control device such as a heat generating device, such as a heater or infrared irradiator, or a cooling device, such as a fan or water cooling device, provided outside the lighting device 100. In this case, heat generated from the stimulus source is used as the stimulus. As described above, a temperature control device external to the lighting device 100 can provide a stimulus to the diffuser 20 using light or temperature.

When a stimulus is provided by the installation environment, the stimulus is heat or light from the installation environment. The light Ls emitted from the main light-emitting surface of the diffuser 20 will differ depending on the stimulus value of the stimulus provided by the installation environment.

Furthermore, by using stimuli such as temperature or light in the installation environment, changes in season, weather, time of day, etc. can be used as lighting effects. Examples of time periods include morning, noon, and night.

In conventional technology, when attempting to create changes such as cloud movement in a diffuser that does not contain particles 21 and stimuli-responsive polymer 22, it was necessary to use multiple light sources and control the way in which these light sources enter. Such control was difficult, and the changes were mechanical. However, in embodiment 1, the diffuser 20 is equipped with a light-diffusing layer containing particles 21 that scatter visible light and a stimuli-responsive polymer 22 whose light-scattering properties change in response to a stimulus. Furthermore, the particles 21 primarily cause Rayleigh scattering or a Rayleigh-scattering-like scattering phenomenon with visible light, and the stimuli-responsive polymer 22 is a material that switches between a first state that primarily causes Mie scattering and a second state that transmits visible light in response to a stimulus. A region in the first state is formed in the diffuser 20, either entirely or partially, depending on the stimulus applied to the stimuli-responsive polymer 22. As a result, when light Li is incident on the diffuser 20, scattered light Ls is emitted from the primary light-emitting surface due to scattering by at least one of the particles 21 and the stimuli-responsive polymer 22. This scattering phenomenon is essentially the same as the phenomenon that occurs in the natural sky. As a result, the shifting effects of clouds and other objects can be more naturally expressed within the diffuser 20 than with conventional methods.

Furthermore, the light diffusion layer of the diffuser 20 contains multiple stimulus-responsive polymers 22 with different stimulus thresholds for switching between the first and second states. This has the effect of enabling the representation of changes within a surface, such as clouds, to be expressed by adding shading within the diffuser 20.

Furthermore, the diffuser 20 has multiple stacked light-diffusing layers, and the stimulus threshold at which the stimulus-responsive polymer 22 switches between the first and second states differs between adjacent light-diffusing layers in the stacking direction. This has the effect of allowing the transitional effects of clouds and other objects to be expressed with a sense of depth within the diffuser 20.

Furthermore, the diffuser 20 further comprises two transparent plates sandwiching the light diffusion layer. This allows different effects to be produced depending on the position between the diffusers 20 in the stacking direction. Furthermore, when the diffuser 20 is made of liquid, leakage of the diffuser 20 can be suppressed.

Furthermore, the lighting device 100 according to embodiment 1 includes a diffuser 20 and a light source 10 that emits light Li, including visible light, to be guided inside the diffuser 20. Furthermore, a plurality of light sources 10 are provided, and the light Li emitted by the plurality of light sources 10 has different correlated color temperatures. This has the effect of enabling a variety of in-plane color tones to be expressed and changed.

Furthermore, the light source 10 is installed facing the diffuser 20. This allows the light Li emitted from the light source 10 to be efficiently incident on the diffuser 20.

Furthermore, the light source 10 emits light Li with a correlated color temperature lower than the correlated color temperature of the light Ls scattered by the diffuser 20. This makes it possible to use Rayleigh scattered light Lsr to express colors that are closer to the real sky.

The device also includes a stimulus generator 30 that applies a stimulus to all or part of the diffuser 20, and when applying a stimulus to part of the diffuser 20, the stimulus generator 30 is able to change the position at which the stimulus is applied. This has the effect of allowing the effect of a changing surface, such as clouds, to be moved within the diffuser 20.

Furthermore, the light source 10 and the stimulus generator 30 may be controlled separately. By controlling the light source 10 and the stimulus generator 30 separately in this way, the range of cloud or transitional expressions can be expanded.

<Modification 1>
A first modification of the lighting device 100 according to the first embodiment will be described below. FIG. 11 is a cross-sectional view schematically illustrating an example of the overall configuration of a lighting device according to the first modification of the first embodiment. Note that the same components as those described in the first embodiment are denoted by the same reference numerals, and their description will be omitted. The lighting device 100c according to the first modification further includes a stimulus generating unit 30 that applies a stimulus to the stimulus-responsive polymer 22 in addition to the configuration of the first embodiment. The stimulus generating unit 30 is a device that generates a stimulus such as temperature or light and applies the stimulus to the diffuser 20. The stimulus generating unit 30 is provided on the rear surface f22 side of the diffuser 20. The stimulus generating unit 30 has a plurality of stimulus generating elements 31a-31f. In one example, the plurality of stimulus generating elements 31a-31f are provided across the entire rear surface f22 of the diffuser 20. Each of the plurality of stimulus generating elements 31a-31f can independently generate a stimulus in response to a signal from a control device (not shown). In the following description, when referring to one or more arbitrary stimulus generating elements among the plurality of stimulus generating elements 31a-31f but not all of them, the stimulus generating elements will be referred to as a stimulus generating element 31.

Next, the operation method of the lighting device 100 in Variation 1 will be described using Figures 11 to 13. Figures 12 and 13 are diagrams that schematically show an example of a lighting method using a lighting device in Variation 1 of Embodiment 1.

Figure 11 shows a state in which the stimulus generating unit 30 is not generating stimuli such as temperature or light. As a result, the stimulus-responsive polymer 22 does not exhibit light scattering properties, and only the particles 21 exhibit light scattering properties. At this time, the light Ls scattered by the particles 21 is Rayleigh scattered or Rayleigh scattered-like light, and has a higher correlated color temperature than the incident light Li. As a result, the lighting device 100c provides illumination that simulates a blue sky.

Figure 12 shows a state in which a stimulus is generated from one stimulus generating element 31c of the stimulus generating unit 30, while the other stimulus generating elements 31a, 31b, 31d-31f do not generate any stimulus. This changes the light scattering properties of the stimulus-responsive polymer 22c in the area where the stimulus generated by the stimulus generating element 31c is applied. In other words, the stimulus-responsive polymer 22c present in the area where the stimulus is applied by the stimulus generating element 31c comes to have light scattering properties. The stimulus-responsive polymer 22c with light scattering properties generates Mie scattered light Lsm with a scattering intensity stronger than that of the particles 21. This makes it appear as if a cloud has appeared only in the area of the stimulus-responsive polymer 22c that exhibits light scattering properties.

Furthermore, by placing multiple stimulus generating elements 31 that generate stimuli at separate locations, it is possible to express the appearance of multiple clouds floating in a blue sky. In one example, by separating the positions of the stimulus generating elements 31 that generate stimuli, it is possible to place multiple stimulus generating positions at separate locations.

Figure 13 shows a state in which, in addition to stimulus generating element 31c of the stimulus generating unit 30, adjacent stimulus generating elements 31b and 31d generate stimuli of a different intensity than stimulus generating element 31c. Here, stimulus generating elements 31b and 31d generate stimuli that are weaker than stimulus generating element 31c. Furthermore, stimulus generating elements 31a, 31e, and 31f do not generate stimuli. In this way, the strength of the stimulus also affects the light scattering properties of the stimulus-responsive polymer 22. In the example of Figure 13, stimulus-responsive polymers 22b and 22d present in the stimulus-applied range by stimulus generating elements 31b and 31d are applied with a weaker stimulus than stimulus-responsive polymer 22c present in the stimulus-applied range by stimulus generating element 31c, and therefore the light scattering properties of stimulus-responsive polymers 22b and 22d are also weaker. As a result, a thick cloud is formed in the stimulus-applied range of stimulus generating element 31c, and a thin cloud is formed in the stimulus-applied range of stimulus generating elements 31b and 31d. This means that it is possible to create both thick and thin clouds.

Furthermore, by moving the stimulus generating element 31c, which generates a stimulus, and the stimulus generating elements 31b and 31d, which generate a weaker stimulus than stimulus generating element 31c, in one example, moving them left and right on the paper surface of Figure 13, it is possible to express the appearance of clouds slowly appearing, flowing, and disappearing.

As shown in Figures 11 to 13, when the stimulus generating unit 30 is made up of multiple stimulus generating elements 31a-31f, the position at which the stimulus is generated can be moved by operating the stimulus generating elements 31 with electrical signals so that the stimulus generating element 31 that generates the stimulus is changed among the multiple stimulus generating elements 31a-31f. Alternatively, the position at which the stimulus is generated can be moved by physically moving the stimulus generating unit 30.

Furthermore, by arranging the stimulus-generating element 31 over the entire back surface f22, it is possible to stimulate the stimulus-responsive polymer 22 to exhibit light scattering properties over the entire diffuser 20, making it possible to create a cloudy sky over the entire surface.

As described above, according to variant example 1, it is possible to move clouds or other in-plane transitions within the diffuser 20.

<Modification 2>
Modification 2 of the lighting device 100 according to Embodiment 1 will be described below. Fig. 14 is a cross-sectional view showing an example of a schematic configuration of a diffuser constituting a lighting device according to Modification 2 of Embodiment 1. The diffuser 20 according to Modification 2 has a plurality of light diffusion layers 210a-210d stacked one on top of the other. Each of the light diffusion layers 210a-210d has particles 21 that scatter visible light and a stimulus-responsive polymer 22 whose light scattering properties change in response to a stimulus. Specifically, the light diffusion layers 210a-210d have a configuration in which the particles 21 and the stimulus-responsive polymer 22 are dispersed in a substrate 23.

Each light diffusing layer 210a-210d contains one type of stimulus-responsive polymer 22 with one threshold. In this example, light diffusing layer 210a contains a stimulus-responsive polymer 22 with a stimulus threshold of "A", light diffusing layer 210b contains a stimulus-responsive polymer 22 with a stimulus threshold of "B", light diffusing layer 210c contains a stimulus-responsive polymer 22 with a stimulus threshold of "C", and light diffusing layer 210d contains a stimulus-responsive polymer 22 with a stimulus threshold of "D". As a result, the diffuser 20 contains stimulus-responsive polymers 22 with two or more different thresholds.

In the example of Figure 14, all of the light diffusion layers 210a-210d have different stimulus thresholds, but two types of light diffusion layers 210a-210d with different stimulus thresholds may be stacked alternately in the stacking direction. In other words, it is sufficient that adjacent light diffusion layers 210a-210d in the stacking direction contain stimulus-responsive polymers 22 with different stimulus thresholds. Furthermore, each light diffusion layer 210a-210d may contain two or more types of stimulus-responsive polymers 22 with different stimulus thresholds.

Furthermore, the light diffusion layers 210a-210d may be separated by a plate, air, etc., or may be continuous layers.

When a stimulus is applied to the diffuser 20, which is made up of stacked light diffusion layers 210a-210d, adjacent layers have different stimulus thresholds, making it possible to freely create layers of stimulus-responsive polymer 22 with strong light scattering properties, weak light scattering properties, or no light scattering properties in the stacking direction. This makes it possible to express clouds in the sky, low in the sky, etc.

As described above, according to variant example 2, it is possible to create a sense of depth within the diffuser 20 by creating a shifting effect on a surface, such as clouds.

The diffuser 20 and lighting device 100 according to embodiment 1 have been described above, but the diffuser 20 and lighting device 100 of the present disclosure are not limited to this embodiment, and the diffuser 20 and lighting device 100 of the present disclosure also include configurations that are realized by combining functions in any desired manner. In other words, the configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and portions of the configuration may be omitted or modified without departing from the spirit of the invention.

10 light source, 11 substrate, 12 light-emitting element, 20 diffuser, 21 particles, 22, 22b-22d stimulus-responsive polymer, 23 substrate, 30 stimulus generating unit, 31, 31a-31f stimulus generating element, 100, 100a-100c lighting device, 210a-210d light diffusion layer, f11 light-emitting surface, f21 main light-emitting surface constituent surface, f22 back surface, f23-f26 end surfaces.

Claims (11)

A diffuser characterized by having a light diffusion layer containing particles that scatter visible light and a stimulus-responsive polymer whose light scattering properties change in response to a stimulus. the particles cause mainly Rayleigh scattering or Rayleigh scattering-like scattering phenomena with respect to visible light,
the stimulus-responsive polymer is a material that switches between a first state in which Mie scattering is mainly caused and a second state in which visible light is transmitted, in response to a stimulus;
The diffuser according to claim 1 , wherein the first state region is formed in whole or in part in response to a stimulus to the stimulus-responsive polymer. The diffuser described in claim 2, characterized in that the light diffusion layer contains a plurality of stimulus-responsive polymers having different stimulus thresholds at which the first state and the second state are switched. a plurality of the light diffusion layers stacked one on top of the other,
A diffuser as described in claim 2 or 3, characterized in that the stimulus threshold at which the stimulus-responsive polymer switches between the first state and the second state is different between adjacent light diffusion layers in the stacking direction. A diffuser as described in any one of claims 1 to 4, further comprising two transparent plates sandwiching the light diffusion layer. A diffuser according to any one of claims 1 to 5;
a light source that emits light including the visible light to be guided inside the diffuser;
A lighting device comprising: The light source is provided in plurality,
7. The lighting device according to claim 6, wherein the light emitted from the plurality of light sources has different correlated color temperatures. The lighting device described in claim 6 or 7, characterized in that the light source is installed facing the diffuser. The lighting device described in any one of claims 6 to 8, characterized in that the light source emits light having a correlated color temperature lower than the correlated color temperature of the light scattered by the diffuser. Further provided is a stimulus generating unit that applies the stimulus to all or part of the diffuser,
10. The lighting device according to claim 6, wherein the stimulus generator is capable of changing the position at which the stimulus is applied when the stimulus is applied to a part of the diffuser. The lighting device described in claim 10, characterized in that the light source and the stimulus generator are controlled separately.