Diffuser and lighting device

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

[0001] SUMMARY The present disclosure relates to sky-simulating diffusers and lighting devices.

[0002] Spaces with a claustrophobic feel, such as basements and windowless offices, can cause stress for occupants. Therefore, lighting systems that simulate a blue sky have been proposed to provide a sense of openness in such spaces. Patent Document 1 proposes a lighting system that can recreate a pseudo-sky atmosphere by including a diffuser that is translucent and has light-diffusing properties, and multiple light sources that direct light toward the diffuser.

[0003] Japanese Patent Application Laid-Open No. 2018-170153

[0004] However, according to 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, so when trying to create a change such as cloud movement within the diffuser, it is necessary to use multiple types of light sources and control the incidence methods of these light sources, which is difficult to control and results in a mechanical change in the way the light changes.

[0005] The present disclosure has been made in consideration of the above, and aims to provide a diffuser that can express the transition of clouds and other objects in a plane more naturally than conventional diffusers.

[0006] In order to solve the above-mentioned problems and achieve the objectives, the diffuser of the present disclosure comprises a light diffusion layer having particles that scatter visible light and a stimulus-responsive polymer whose light scattering properties change in response to a stimulus.

[0007] 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.

[0008] A perspective view showing an example of a schematic configuration of an illumination device according to embodiment 1. A cross-sectional view showing an example of a schematic configuration of an illumination device according to embodiment 1. A top view showing an example of a schematic configuration of a light source used in an illumination device according to embodiment 1. A side view showing an example of a schematic configuration of a light source used in an illumination device according to embodiment 1. A diagram showing another example of a schematic configuration of an illumination device according to embodiment 1. A diagram schematically showing the state of an illumination device when a stimulus-responsive polymer is in the form of a polymer chain and has the property of transmitting light incident on a diffuser. A diagram schematically showing the state of an illumination device when a stimulus-responsive polymer is in the form of particles and has the property of transmitting light incident on a diffuser. FIG. 1 is a diagram schematically showing the state of an illumination device when the stimuli-responsive polymer is chain-shaped and has the property of scattering light incident on the diffuser; FIG. 1 is a diagram schematically showing the state of an illumination device when the stimuli-responsive polymer is particulate and has the property of scattering light incident on the diffuser; FIG. 2 is a diagram showing another example of the schematic configuration of an illumination device according to embodiment 1;

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A diffuser and a lighting device according to embodiments of the present disclosure will be described below with reference to the accompanying drawings. The following embodiments are merely examples, and may be modified as appropriate.

[0010] 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 direction that is desired to be visualized by the user as a light-emitting surface simulating the sky.

[0011] 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 as a light emitter. Although not shown, the illumination device 100 may also include a frame that supports the light source 10 and the diffuser 20.

[0012] 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 simulating 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 FIG. 1, the diffuser 20 has a rectangular plate-like structure, and the light source 10 is disposed opposite the end surface f23 of the diffuser 20. The diffuser 20 guides and scatters the light emitted from the light source 10.

[0013] The lighting device 100 according to the first embodiment is installed in a space that has a claustrophobic feeling, such as a basement, a windowless office, etc. In one example, the lighting device 100 is disposed on a wall surface of such a space.

[0014] Hereinafter, light incident on the end surface f23 of the diffuser 20 will be referred to as light Li. Scattered light simulating the sky, emitted from the diffuser 20, will be referred to as light Ls or scattered light Ls. Furthermore, among the scattered light Ls, Rayleigh scattered light will be referred to as Lsr, and Mie scattered light will be referred to as Lsm. Light guided within the diffuser 20 will be referred to as light Lt. Here, "guiding light" refers to propagating light that has entered a certain medium along a predetermined optical path within the medium. Therefore, light Lt does not include light that is scattered or absorbed within the diffuser 20.

[0015] 2, the main light-emitting surface of the diffuser 20 may be the entire main light-emitting surface f21, or may be a partial region of the main light-emitting surface f21. In the diffuser 20, scattered light Ls that simulates the sky can be emitted not only from the main light-emitting surface, but also from the back surface f22 and end surfaces f23-f26.

[0016] <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.

[0017] The light source 10 emits light Li to be incident on the inside 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.

[0018] The light source 10 is disposed opposite at least a portion of the surfaces constituting the diffuser 20, i.e., the main light-emitting surface constituting surface f21, the back surface f22, and the end surfaces f23-f26. In Figures 1 and 2, an example is shown in which the light source 10 is disposed along the end surface f23 of the diffuser 20.

[0019] The light source 10 includes a substrate 11 and light-emitting elements 12. In one example, the substrate 11 is a plate-like 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 that faces the diffuser 20. In Figures 3 and 4, a plurality of light-emitting elements 12 are arranged along the extension direction of the substrate 11.

[0020] 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 plurality of light-emitting elements 12 emits light. The light source 10 is disposed facing the diffuser 20. Specifically, the light source 10 is disposed so that the light-emitting surface f11 faces at least a portion of the surfaces f21-f26 that constitute the diffuser 20. In the example of FIGS. 1 and 2 , the light source 10 is disposed so that the light-emitting surface f11 faces the end surface f23 of the diffuser 20.

[0021] Note that FIG. 1 illustrates an example of the configuration of the lighting device 100, and the configuration of the lighting device 100 is not limited thereto. FIG. 5 illustrates another example of the schematic configuration of the lighting device according to the first embodiment. As shown in FIG. 5, the lighting device 100a may include multiple light sources 10 for one diffuser 20. Here, the light sources 10 are units that can be independently controlled for on / off, light emission intensity, or light emission color. Here, six light sources 10 are disposed on each of 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 has a configuration having only one light source 10 for one diffuser 20, the lighting device 100a may include multiple lighting units.

[0022] Hereinafter, 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.

[0023] As an example, in the configuration of the light source 10 shown in Figures 3 and 4, each light emitting element 12 can be regarded as one 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 configuration of the light source 10 shown in Figure 3, i.e., a configuration including a plurality of light emitting elements 12. Also, in the example of the arrangement of the light source 10 shown in Figure 5, each light source 10 in the figure can be regarded as one light emitting element 12.

[0024] 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 the light Li, or may emit light with a determined correlated color temperature as the light Li. In one example, the correlated color temperature may be 6500 K or 5000 K. The correlated color temperatures of the light Li emitted by each light source 10 may be the same, or may be different from each other or from some of the light sources 10.

[0025] 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 including a white light source and a greenish light source, or may include a light source 10 including a white light source, a green light source, a blue light source, and an orange light source.

[0026] Furthermore, the lighting device 100 may include light sources 10 that include white light sources of 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.

[0027] Here, the difference in color temperature between the high color temperature white light and the low color temperature white light can be, for example, 8800 K. The correlated color temperature of light Li emitted from the high color temperature white light source is, for example, 11500 K or more and 19000 K or less. The correlated color temperature of light Li emitted from the low color temperature white light source is, for example, 5500 K or more and 6050 K or less. Within the above range of correlated color temperatures of the high color temperature white light and the 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 8800 K. For example, the correlated color temperature of the high color temperature white light can be 14400 K, and the correlated color temperature of the low color temperature white light can be 5600 K.

[0028] 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, a plurality of light sources 10 may be provided, and the correlated color temperatures of the light Li emitted by the plurality of light sources 10 may be different.

[0029] The light source 10 may be disposed opposite one end surface f23 that constitutes the end of the main light-emitting surface forming surface f21 as shown in Fig. 1, or may be disposed opposite two or more end surfaces f23-f26 as shown in Fig. 5. In this way, any light source that functions as the light source 10 that emits light Li from one end surface f23-f26 of the diffuser 20 can be considered to be the light source 10 of the lighting device 100 according to the first embodiment.

[0030] 1 and 2, the light source 10, more specifically the light-emitting surface f11 of the light source 10, may be disposed opposite at least one of the end faces f23-f26 that constitute the end of the main light-emitting surface-forming surface f21 of the diffuser 20. In another example, as shown in FIG. 5, a plurality of light sources 10 may be disposed along at least one of the end faces f23-f26 of the diffuser 20.

[0031] The shape of the diffuser 20 is not limited to a rectangular plate. For example, the diffuser 20 may be a rectangle, a polygon, a circle, a barrel, a spool, or any other shape formed by connecting two or more straight lines, by connecting two or more arcs, or by connecting one or more straight lines and one or more arcs.

[0032] When the diffuser 20 has another shape, the light source 10 may be disposed 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. The number of light sources 10 may be one or more. When multiple light sources 10 are disposed, they may be disposed 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, when the main light-emitting surface forming surface f21 and the back surface f22 are polygonal, including a rectangular shape, the side surface is formed of multiple planes. In such a case, one or more light sources 10 may be disposed so as to face one of the multiple planes constituting the side surface. In this case, the one or more light sources 10 may be disposed so as to face the entirety of one plane, or may be disposed so as to face a portion of one plane. Furthermore, one or more light sources 10 may be disposed so as to face each of two or more planes constituting the side surface. In this case, the one or more light sources 10 may be disposed so as to face the entirety of each of the two or more planes, or may be disposed so as to face a portion of each of the two or more planes.

[0033] Furthermore, in consideration of ZEB (Zero Energy Building), light Li from light source 10 can be substituted with 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 predetermined direction can be used. In other words, lighting device 100 may include such a light-collecting member or light guide as light source 10.

[0034] 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.

[0035] The particles 21 scatter visible light. One example of the particles 21 is nanoparticles. A "nanoparticle" is a particle having a size on the order of nanometers (nm). A nanoparticle generally refers to a particle having a size of 1 nm or more and several hundred nm or less. In other words, one example of the particles 21 is a particle having a particle size on the order of nanometers. In this case, the particle size of the particles 21 may be the average particle size.

[0036] The particles 21 may be spherical or have another shape. Also, the diffuser 20 may include multiple types of particles 21.

[0037] 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.

[0038] The particles 21 scatter the light Li incident on the diffuser 20 to form light Ls. The particles 21 also scatter the light Lt propagating through the diffuser 20 to form light Ls.

[0039] Depending on the combination of the particle size of the particles 21 and the light Li incident into 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 mainly cause Rayleigh scattering or a Rayleigh scattering-like scattering phenomenon with respect to visible light.

[0040] The stimuli-responsive polymer 22 is a material whose physical properties change in response to an external stimulus. The external stimulus will be simply referred to as a stimulus hereinafter. The physical properties of the stimuli-responsive polymer 22 exhibit reversible changes when the stimulus exceeds a certain stimulus threshold and when the stimulus is below the threshold.

[0041] The physical properties of the stimuli-responsive polymer 22 that change in response to a stimulus include the refractive index and compatibility with a solvent. The refractive index changes due to a phase transition of the stimuli-responsive polymer 22 around a threshold. Furthermore, a change in compatibility may also cause a change in the conformation of the stimuli-responsive polymer 22. In other words, the stimuli-responsive polymer 22 can be said to be a polymer material whose light-scattering properties change in response to a stimulus.

[0042] The stimulus applied to the stimulus-responsive polymer 22 is, for example, temperature or light. When the stimulus is temperature, the threshold is preferably, for example, 10° C. or higher and 70° C. or lower. When 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.

[0043] The shape of the stimuli-responsive polymer 22 is not particularly limited, and may be particulate, flat, fibrous, polymer chain, or the like.

[0044] In one example, the stimulus-responsive polymer 22 is a solid or a liquid.

[0045] The gel state is also included when the stimulus-responsive polymer 22 is solid. In one example, the stimulus-responsive polymer 22 is an acrylate-based material.

[0046] When the stimuli-responsive polymer 22 is liquid, it also includes a gel state. One example of the stimuli-responsive polymer 22 is a non-ionic hydrophilic (water-soluble) polymer. Specific examples include poly(meth)acrylamide derivatives, polyvinylamide derivatives, polyvinyl methyl ether, and cellulose derivatives. Other examples include polyoxazolidones, polyalkylene oxides, polyvinyl alcohols, polymethacrylic acids, and derivatives thereof. Furthermore, polyethylene glycol / polypropylene glycol block copolymers may 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.

[0047] (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, N-tetrahydrofuryl acrylamide, or the like. 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.

[0048] (Polyvinylamide Derivatives) Examples of polyvinylamide derivatives include polymers obtained by polymerizing N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-methylformamide, N-vinylpropionamide, etc. Preferred are N-vinylacetamide and N-vinyl-N-methylacetamide. Furthermore, the polyvinylamide derivative may be a polyvinylamide copolymer obtained by copolymerizing multiple types of vinylamide monomers or a vinylamide monomer with another monomer.

[0049] (Cellulose Derivatives) Examples of cellulose derivatives that can be used include alkyl-substituted cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, and hydroxyethylmethyl cellulose.

[0050] In another example, the stimulus-responsive polymer 22 is a hydrophobic polymer. Specifically, the stimulus-responsive polymer 22 is a stearyl acrylate-based substance or the like.

[0051] The physical properties of the stimulus-responsive polymer 22 change around the threshold, and the scattering characteristics for the light Lt guided through the diffuser 20 change. In one example, below the threshold, the polymer has a strong tendency to transmit the light Lt, and above the threshold, the polymer exhibits a strong tendency to scatter the light Lt. In this case, the particles 21 mainly cause Rayleigh scattering or a Rayleigh scattering-like scattering phenomenon for visible light, whereas when the stimulus exceeds the threshold, the stimulus-responsive polymer 22 mainly causes Mie scattering for the light Lt.

[0052] Furthermore, the scattering characteristics, i.e., the relationship between the change in physical properties before and after the threshold value, may change depending on the combination with the base material 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.

[0053] In this way, the stimulus-responsive polymer 22 is a material that switches between a first state that mainly causes Mie scattering and a second state that transmits visible light in response to a stimulus, and in response to a stimulus applied to the stimulus-responsive polymer 22, a region in the first state is formed across the entire or part of the diffuser 20.

[0054] The threshold for the stimulus-responsive polymer 22 to respond to a stimulus may have a certain range.

[0055] The substrate 23 is a member that includes the particles 21 and the stimuli-responsive polymer 22 and guides the incident light Li to the interior. In one example, the particles 21 and the stimuli-responsive polymer 22 are dispersed in the substrate 23. The particles 21 and the stimuli-responsive polymer 22 may be fixed to the substrate 23 or may have fluidity. In other words, the substrate 23 is not limited to a solid, and may be a liquid, liquid crystal, or gel-like substance.

[0056] In one example, the substrate 23 is a transparent material. The substrate 23 does not necessarily need to be transparent to all wavelengths of the light Li. For example, the substrate 23 may have absorption at a specific wavelength among the wavelengths of the light Li.

[0057] 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 wavelength range, i.e., a wavelength band. For example, when the incident light Li is white light, the design wavelength may be one or more of 450 nm, 550 nm, and 650 nm.

[0058] When the substrate 23 is solid, the substrate 23 is, for example, a resin plate made of a thermoplastic polymer, a thermosetting resin, a photopolymerizable resin, or the like. 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 the particles 21 and the stimuli-responsive polymer 22 in the uncured or molten material of the substrate 23, and then performing a curing process.

[0059] When the substrate 23 is a liquid, the substrate 23 is, for example, composed of a polar solvent such as water or ethanol, or a non-polar solvent such as oil or an organic solvent.

[0060] For example, the substrate 23 may be formed from an organic molecular dispersion material or an organic-inorganic hybrid material produced by a sol-gel process. Organic-inorganic hybrid materials are also referred to as organic-inorganic nanocomposite materials. For 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 an 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 during such a manufacturing process are also considered to be particles 21.

[0061] Furthermore, the substrate 23 may have minute concaves and convexes formed on its surface that are smaller than the wavelength of blue light. The maximum diameter of the concaves or convexities is preferably on the order of nanometers, for example, between 1 nm and several hundred nm.

[0062] In the above, an example has been shown in which the diffuser 20 is composed of the particles 21, the stimuli-responsive polymer 22, and the substrate 23, but the diffuser 20 may also be a gel composed of the stimuli-responsive polymer 22 and the substrate 23. In this case, the substrate 23 may be a polar solvent such as water or ethanol, and the stimuli-responsive polymer 22 may be a gel composed 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 stimuli-responsive polymer 22 may be a gel composed of a hydrophobic polymer.

[0063] The diffuser 20 may have at least one surface coated with a translucent functional coating such as an anti-reflection coating, an antifouling coating, a heat-shielding coating, or a water-repellent coating. The diffuser 20 may further include two transparent plates sandwiching a light-diffusing layer having particles 21, a stimuli-responsive polymer 22, and a substrate 23. In one example, the light-diffusing layer may be sandwiched between two transparent substrates such as glass plates, taking into account functionality such as impact resistance, water resistance, and heat resistance required for a window. In this case, the diffuser 20 may be an interlayer film for 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.

[0064] 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 cured oxides, holes, and depressions or protrusions on the surface, each having a size on the order of nanometers. Hereinafter, these are collectively referred to as nano-order optical media. Herein, the nano-order optical medium is not particularly limited as long as it causes Rayleigh scattering or a Rayleigh scattering-like scattering phenomenon for light Lt within the substrate 23. Such nano-order optical media include interfaces. Furthermore, the nano-order optical medium may emit light Lt guided within the diffuser 20. In one example, light Lt guided within the diffuser 20 and reaching the end face f25 opposite the end face f23, which is the incident surface, may be emitted as light simulating sunlight. In this disclosure, unless otherwise specified, the term "particles 21" is used as a general term for such nano-order optical media.

[0065] 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 face f23, which is a side face of the diffuser 20, light Ls can be extracted from the main light-emitting surface f21 and the back face f22, which are perpendicular to the end face f23.

[0066] <Generation of Scattered Light Ls that Simulates the Sky> Hereinafter, the principle of generation of scattered light Ls that simulates the sky will be described with reference to FIGS. 6 to 9. FIG.

[0067] First, a case where the stimulus-responsive polymer 22 has a property of transmitting light Li incident on the diffuser 20 will be described. Fig. 6 is a diagram schematically showing the state of an illumination device when the stimulus-responsive polymer is in the form of a polymer chain and has a property of transmitting light incident on the diffuser. Fig. 7 is a diagram schematically showing the state of an illumination device when the stimulus-responsive polymer is in the form of particles and has a property of transmitting light incident on the diffuser.

[0068] 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 as light Lt through the diffuser 20. As shown in Fig. 6 , the light Lt is reflected by the main light-emitting surface constituting face f21 and the back face f22 of the diffuser 20 and is guided.

[0069] 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 is 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 FIG. 6 or in the form of particles as shown in FIG. 7, transmits the light Lt and is therefore not involved in generating scattered light Ls.

[0070] Of the scattered light Ls, light that is incident on the main light-emitting surface f21 at an angle of incidence equal to or smaller 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.

[0071] 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 incident on the diffuser 20. In other words, it can be said that the light source 10 emits light Li with a lower correlated color temperature than the correlated color temperature of the light Ls scattered by the diffuser 20.

[0072] When light Li has a spectral distribution across the entire visible light range, blue light is preferentially scattered. In one example, light source 10 includes a white LED that emits white light Li as light-emitting element 12, so that blue light is scattered as scattered light Ls by particles 21 in diffuser 20. In this way, by appropriately designing light source 10 and diffuser 20, light Ls has a correlated color temperature that indicates blue close to the actual color of the sky.

[0073] Since the amount of light Ls depends on the amount of incident light Li, by appropriately selecting the amount of light from the light source 10 used, it is possible to reproduce a blue sky color while maintaining sufficient brightness as a 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 the particles 21, the thickness of the diffuser 20 can be reduced. According to the configuration of the first embodiment, 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 short, 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.

[0074] Next, a case where the stimuli-responsive polymer 22 has the property of scattering light Li incident on the diffuser 20 will be described. Fig. 8 is a diagram schematically showing the state of an illumination device when the stimuli-responsive polymer is in the form of a polymer chain and has the property of scattering light incident on the diffuser. Fig. 9 is a diagram schematically showing the state of an illumination device when the stimuli-responsive polymer is in the form of particles and has the property of scattering light incident on the diffuser.

[0075] In this case, when the light Lt propagates through the diffuser 20, part of the light Lt collides with the stimuli-responsive polymer 22 in addition to the particles 21, etc. Alternatively, part of the light Lt is obstructed by the particles 21, etc. and the stimuli-responsive polymer 22. The scattering of the light Lt by the particles 21 is similar to the cases described with reference to FIGS. 6 and 7 .

[0076] 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 and becomes 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 forming surface f21.

[0077] The light Ls scattered by the stimuli-responsive polymer 22 has a higher proportion of Mie scattering and a higher 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 affected by the color of the light Li incident from the light source 10. In one example, when the light source 10 includes 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 stimuli-responsive polymer 22 is close to white in color. Therefore, in the examples shown in Figures 8 and 9, clouds floating in a blue sky can be reproduced.

[0078] In another example, when the light source 10 includes an LED with a low correlated color temperature as the light-emitting element 12, the light Ls scattered by the stimulus-responsive polymer 22 approaches a warm color, making it possible to reproduce sunset clouds. In addition, by using multiple types of light sources 10, it is possible to produce a variety of clouds.

[0079] The light Ls scattered by the stimuli-responsive polymer 22 has a high proportion of Mie scattering, and therefore is brighter than the light Ls scattered by the particles 21. Therefore, by appropriately blending the particles 21 and the stimuli-responsive polymer 22, it is possible to express clouds floating in a blue sky.

[0080] As described above, the light scattering properties change as the stimulus applied to the stimulus-responsive polymer 22 crosses a threshold. In one example, the stimulus-responsive polymer 22 exhibits strong light transmission when the stimulus applied is below the threshold, and exhibits strong light scattering when the stimulus applied exceeds the threshold. In other words, the stimulus-responsive polymer 22 switches between a first state in which Mie scattering is mainly caused and a second state in which visible light is transmitted, depending on the stimulus.

[0081] In this way, the light scattering properties of the stimulus-responsive polymer 22 can be changed by turning the stimulus on or off, so that by applying a stimulus to the entire diffuser 20, clouds can be reproduced over the entire diffuser 20. Also, by applying a stimulus to a part of the diffuser 20, clouds can be reproduced in a part of a blue sky.

[0082] Furthermore, the light scattering property of the stimuli-responsive polymer 22 can be adjusted by adjusting the stimulus value, which indicates the magnitude of the stimulus applied to the diffuser 20, to be close to the threshold value of the stimuli-responsive polymer 22. By making such adjustments, it is possible to reproduce a light cloud by varying the strength of the light scattering property, or to create the appearance of clouds slowly appearing or disappearing.

[0083] The diffuser 20 may contain multiple types of stimulus-responsive polymers 22 with different thresholds. In other words, when 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 in which the light Lt is scattered and a second state in which the light Lt is transmitted. The presence of multiple types of stimulus-responsive polymers 22 with different thresholds allows different light-scattering states to be mixed within the diffuser 20 for a single stimulus value. As a result, it becomes possible to express a more complex sky appearance.

[0084] The diffuser 20 may also include 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 include multiple stimulus-responsive polymers 22 that switch between a first state that scatters light Lt and a second state that transmits light Lt, depending on the type of stimuli. In this way, even if multiple types of stimulus-responsive polymers 22 that respond to different stimuli exist, different light-scattering states can be mixed within the diffuser 20 by using different types of stimuli. As a result, it is possible to express a more complex skyscape.

[0085] Furthermore, multiple types of stimulus-responsive polymers 22 with different light-scattering properties may be mixed within the diffuser 20. For example, by mixing a stimulus-responsive polymer 22 with strong light-scattering properties and a stimulus-responsive polymer 22 with weak light-scattering properties within the diffuser 20, it is possible to increase the variety of clouds that can be reproduced. For example, it is possible to reproduce clouds that look like thick cumulonimbus clouds, thin cirrocumulus clouds, and the like.

[0086] 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 may have 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 the light Lt is scattered and a second state in which the light Lt is transmitted. By stacking stimulus-responsive polymers 22 with different thresholds, areas with strong or weak light scattering properties can be created between the main light-emitting surface f21 and the back surface f22 of the diffuser 20. This allows the reproduction of clouds in low or high altitudes, thereby creating a blue sky with a sense of depth.

[0087] In this case, a different light source 10 may be used for each layer of the stimuli-responsive polymer 22, i.e., for each light diffusion layer, thereby reproducing the gradation of the sky.

[0088] The diffuser 20 may be stimulated by a stimulus source or by the installation environment.

[0089] When the stimulus is provided by a stimulus generator, the stimulus generator may be provided outside the lighting device 100 or may be incorporated into the lighting device 100 .

[0090] FIG. 10 is a diagram illustrating another example of the schematic configuration of the lighting device according to the first embodiment. As illustrated 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.

[0091] The stimulus generating unit 30 may be installed on a part of the lighting device 100b, i.e., the diffuser 20, or may be installed on the entire surface. Taking the case where the diffuser 20 has the configuration shown in FIG. 1 as an example, the stimulus generating unit 30 may be installed on any one of the main light-emitting surface constituting surface f21, the back surface f22, and the end surfaces f23-f26 of the diffuser 20, or on multiple surfaces, or may be installed on the entire surface. Furthermore, the stimulus generating unit 30 may be installed on all of these surfaces, or on some of these surfaces.

[0092] In the example of FIG. 10 , 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 only to a portion of the back surface f22. When applying a stimulus only to a portion of the back surface f22, for example, the stimulus generating unit 30 has multiple stimulus generating elements, which are arranged two-dimensionally on the back surface f22. Then, a stimulus is generated from the stimulus generating element at the desired position. This makes it possible to select the position to 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 sequentially so that the position to which the stimulus is applied moves. This allows the position to 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, for example.

[0093] 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 driving 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.

[0094] 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 that 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.

[0095] 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, for example, lighting up a clear blue sky on a rainy day.

[0096] 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. For example, the control circuit includes a processor and a memory. For example, the processor and the memory can transmit and receive data to and from each other via a bus. The processor performs each function by reading and executing a program stored in the memory. For example, the processor includes one or more of a CPU (Central Processing Unit) and a DSP (Digital Signal Processor).

[0097] The memory may include one or more of a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), and an electrically erasable programmable read-only memory (EEPROM®). The computer program stored in the memory may be provided by a recording medium, for example. The recording medium may include one or more of a non-volatile or volatile semiconductor memory, a magnetic disk, a flexible memory, an optical disk, a compact disk, and a digital versatile disk (DVD). 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 a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), and a system large scale integration (LSI).

[0098] When the stimulus source is provided outside the lighting device 100, the stimulus source may 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 may be a temperature control device such as a heat generating device, such as a heater or an infrared irradiator, or a cooling device, such as a fan or a 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 stimulus can be applied to the diffuser 20 by light or temperature using a temperature control device external to the lighting device 100.

[0099] When the 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 varies depending on the stimulus value of the stimulus provided by the installation environment.

[0100] Furthermore, by using stimuli based on the temperature or light of the installation environment, it is possible to utilize changes in season, weather, time of day, etc. as lighting effects. For example, time of day can be morning, noon, or night.

[0101] In conventional technology, when attempting to create a change, such as the movement of clouds, in a diffuser that does not contain particles 21 and a stimulus-responsive polymer 22, it was necessary to use multiple light sources and control the incidence of these light sources. Such control was difficult, and the change was mechanical. However, in embodiment 1, the diffuser 20 includes a light-diffusing layer having particles 21 that scatter visible light and a stimulus-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 respect to visible light, and the stimulus-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. The diffuser 20 forms a region in the first state entirely or partially in response to the stimulus applied to the stimulus-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 stimulus-responsive polymer 22. This scattering phenomenon is essentially the same as that occurring in the natural sky, and therefore the shifting effects of clouds and other objects can be more naturally expressed within the diffuser 20 than in the past.

[0102] Furthermore, the light diffusion layer of the diffuser 20 contains a plurality of stimulus-responsive polymers 22 with different thresholds for the stimulus that switches between the first state and the second state, which has the effect of enabling the representation of changes in a surface, such as clouds, to be expressed by adding shading within the diffuser 20.

[0103] Furthermore, the diffuser 20 has a plurality of stacked light diffusion layers, and the threshold value of the stimulus at which the stimulus-responsive polymer 22 switches between the first and second states is different between adjacent light diffusion layers in the stacking direction. This has the effect of enabling the representation of a moving image such as clouds to be expressed with a sense of depth within the diffuser 20.

[0104] The diffuser 20 further includes two transparent plates sandwiching the light diffusion layer, thereby enabling different effects to be produced depending on the position between the plates in the stacking direction of the diffuser 20. Furthermore, when the diffuser 20 is made of liquid, leakage of the diffuser 20 can be suppressed.

[0105] Furthermore, the lighting device 100 according to the first embodiment includes a diffuser 20 and a light source 10 that emits light Li including visible light to be guided inside the diffuser 20. 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.

[0106] Furthermore, the light source 10 is installed facing the diffuser 20. This allows the light Li emitted from the light source 10 to be incident on the diffuser 20 efficiently.

[0107] Furthermore, the light source 10 emits light Li having a correlated color temperature lower than the correlated color temperature of the light Ls scattered by the diffuser 20. This makes it possible to express a color closer to that of the real sky by utilizing the Rayleigh scattered light Lsr.

[0108] The device further includes a stimulus generator 30 that applies a stimulus to all or part of the diffuser 20, and the stimulus generator 30 is capable of changing the position at which the stimulus is applied when applying a stimulus to part of the diffuser 20. This has the effect of allowing the effect of a moving image such as clouds to move within the diffuser 20.

[0109] Furthermore, the light source 10 and the stimulus generating unit 30 may be controlled separately. By controlling the light source 10 and the stimulus generating unit 30 separately in this way, the range of cloud or transitional expression can be expanded.

[0110] <Modification 1> Modification 1 of the lighting device 100 according to Embodiment 1 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 Modification 1 of Embodiment 1. Note that the same components as those described in Embodiment 1 are denoted by the same reference numerals, and their description will be omitted. In addition to the configuration of Embodiment 1, the lighting device 100c according to Modification 1 further includes a stimulus generating unit 30 that applies a stimulus to the stimulus-responsive polymer 22. 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 back surface f22 side of the diffuser 20. The stimulus generating unit 30 has multiple stimulus generating elements 31a-31f. In one example, the multiple stimulus generating elements 31a-31f are provided across the entire back surface f22 of the diffuser 20. Each of the multiple 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.

[0111] Next, an operation method of the lighting device 100 in Modification 1 will be described with reference to Fig. 11 to Fig. 13. Fig. 12 and Fig. 13 are diagrams schematically showing an example of a lighting method in the lighting device according to Modification 1 of Embodiment 1.

[0112] 11 shows a state in which the stimulus generator 30 does not generate stimuli such as temperature or light. Therefore, 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. Therefore, the lighting device 100c provides illumination that simulates a blue sky.

[0113] 12 shows a state in which one stimulus generating element 31c of the stimulus generating unit 30 generates a stimulus, while the other stimulus generating elements 31a, 31b, 31d-31f do not generate any stimulus. As a result, the light scattering properties of the stimulus-responsive polymer 22c change in the area to which the stimulus generated by the stimulus generating element 31c is applied. In other words, the stimulus-responsive polymer 22c present in the area to which 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. As a result, it appears as if a cloud has appeared only in the area of ​​the stimulus-responsive polymer 22c exhibiting light scattering properties.

[0114] In addition, by providing a plurality of stimulus generating elements 31 that generate stimuli at separate locations, it is possible to express a state in which a plurality of clouds are 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 provide a plurality of stimulus generating positions at separate locations.

[0115] FIG. 13 illustrates a state in which, in addition to the stimulus generating element 31c of the stimulus generating unit 30, the adjacent stimulus generating elements 31b and 31d generate stimuli of different intensities than the stimulus generating element 31c. Here, the stimulus generating elements 31b and 31d generate stimuli weaker than the stimulus generating element 31c. Furthermore, the stimulus generating elements 31a, 31e, and 31f do not generate stimuli. Thus, depending on the strength of the stimulus, the light scattering properties of the stimulus-responsive polymer 22 also vary. In the example of FIG. 13, the stimulus applied to the stimulus-responsive polymers 22b and 22d in the stimulus-applied range by the stimulus generating elements 31b and 31d is weaker than the stimulus applied to the stimulus-responsive polymer 22c in the stimulus-applied range by the stimulus generating element 31c, resulting in weaker light scattering properties of the stimulus-responsive polymers 22b and 22d. Therefore, the area where the stimulus generating element 31c applies a stimulus becomes a thick cloud, while the area where the stimulus generating elements 31b and 31d apply a stimulus becomes a thin cloud. In other words, thick and thin clouds can be expressed.

[0116] Furthermore, by moving the stimulus generating element 31c that generates a stimulus and the stimulus generating elements 31b and 31d that generate a stimulus weaker than that of the stimulus generating element 31c, in one example by moving them left and right on the paper surface of Figure 13, it is possible to express the appearance of clouds slowly appearing, flowing away, and disappearing.

[0117] 11 to 13, when the stimulus generating unit 30 is composed of a plurality of stimulus generating elements 31a-31f, the position at which the stimulus is generated can be moved by operating the stimulus generating elements 31 with an electrical signal so that the stimulus generating element 31 that generates a stimulus is changed among the plurality of 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.

[0118] 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 make the entire surface appear cloudy.

[0119] As described above, according to the first modification, it is possible to move a changing effect such as clouds within the diffuser 20.

[0120] <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.

[0121] Each of the light diffusing layers 210a-210d contains one type of stimulus-responsive polymer 22 with one threshold. In this example, the light diffusing layer 210a contains a stimulus-responsive polymer 22 with a stimulus threshold of "A," the light diffusing layer 210b contains a stimulus-responsive polymer 22 with a stimulus threshold of "B," the light diffusing layer 210c contains a stimulus-responsive polymer 22 with a stimulus threshold of "C," and the 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.

[0122] 14 shows a case where all the light diffusing layers 210a-210d have different stimulus thresholds, but two types of light diffusing layers 210a-210d having different stimulus thresholds may be alternately stacked in the stacking direction. In other words, it is sufficient that the light diffusing layers 210a-210d adjacent to each other in the stacking direction contain stimulus-responsive polymers 22 with different stimulus thresholds. Furthermore, each of the light diffusing layers 210a-210d may contain two or more types of stimulus-responsive polymers 22 with different stimulus thresholds.

[0123] The light diffusion layers 210a to 210d may be separated by a plate, air, or the like, or may be continuous layers.

[0124] 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, so it is possible to freely create layers with strong light scattering properties, weak light scattering properties, or no light scattering properties in the stacking direction of the stimulus-responsive polymer 22. This makes it possible to express clouds in the high sky, clouds at low altitudes, etc.

[0125] As described above, according to the second modification, it is possible to express the transition of clouds or other objects in a plane in a manner that gives a sense of depth within the diffuser 20.

[0126] Although the diffuser 20 and lighting device 100 according to the first embodiment have been described above, the diffuser 20 and lighting device 100 of the present disclosure are not limited to this embodiment, and also include configurations that are realized by combining functions arbitrarily. In other words, the configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and some of the configurations may be omitted or modified without departing from the spirit of the invention.

[0127] 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 surface.

Claims

1. A diffuser comprising a light-diffusing layer having particles that scatter visible light and a stimulus-responsive polymer whose light-scattering properties change in response to a stimulus.

2. The diffuser described in claim 1, characterized in that the particles cause mainly Rayleigh scattering or a Rayleigh scattering-like scattering phenomenon for visible light, the stimulus-responsive polymer is a material that switches between a first state that mainly causes Mie scattering and a second state that transmits the visible light in response to a stimulus, and a region of the first state is formed in whole or in part in response to a stimulus applied to the stimulus-responsive polymer.

3. The diffuser according to claim 2, wherein the light diffusion layer contains a plurality of stimulus-responsive polymers having different thresholds of the stimulus at which the first state and the second state are switched.

4. A diffuser as described in claim 2 or 3, characterized in that it has a plurality of stacked light diffusion layers, and the threshold of the stimulus 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.

5. The diffuser according to any one of claims 1 to 4, further comprising two transparent plates sandwiching the light diffusing layer.

6. A lighting device comprising: a diffuser according to any one of claims 1 to 5; and a light source that emits light including the visible light to be guided inside the diffuser.

7. The lighting device according to claim 6, wherein a plurality of the light sources are provided, and the light emitted by the plurality of light sources has different correlated color temperatures.

8. The lighting device according to claim 6 or 7, wherein the light source is disposed facing the diffuser.

9. The lighting device according to any one of claims 6 to 8, wherein the light source emits light having a correlated color temperature lower than the correlated color temperature of the light scattered by the diffuser.

10. A lighting device as described in any one of claims 6 to 9, further comprising a stimulus generating unit that applies the stimulus to all or part of the diffuser, wherein the stimulus generating unit is capable of changing the position at which the stimulus is applied when applying the stimulus to part of the diffuser.

11. The lighting device according to claim 10, wherein the light source and the stimulus generator are controlled separately.

Images