JP7370350B2 - Lighting devices and diffusers - Google Patents

Description

The present invention relates to a lighting device and a diffuser that emit light scattered by a scattering layer.

Illumination devices that simulate natural light such as a blue sky scatter light output from a light source with a scattering layer, and allow an observer to observe the scattered light.

In the lighting device described in Patent Document 1, the scattering layer is arranged at the bottom of the lighting device, and the light source is arranged at the top of the lighting device. In this lighting device, for example, a filler that generates Rayleigh scattered light is dispersed in the base material of the scattering layer, and the Rayleigh scattered light scattered by the filler is emitted from the lower surface of the scattering layer.

Japanese Patent Application Publication No. 2015-207554

However, since Rayleigh scattered light emits light in all directions, in the illumination device of Patent Document 1, the Rayleigh scattered light emitted in the scattering layer is transmitted not only to the lower surface, which is the target light exit surface. , the light is also emitted from the upper surface, resulting in a significant loss of the amount of Rayleigh scattered light. In order to efficiently utilize Rayleigh scattered light, it is possible to install a reflective layer on the top surface of the diffusing layer and make the light output from the light source enter from the side of the scattering layer. If they come into close contact, the light that has entered the scattering layer directly or the white light that is totally reflected in the scattering layer will be diffused by the reflective layer. In this case, the color of the light emitted from the lower surface of the scattering layer becomes whitish, impairing the color sense unique to Rayleigh scattered light.

The present invention has been made in view of the above, and an object of the present invention is to obtain a lighting device that outputs natural light without impairing the color sense while efficiently utilizing Rayleigh scattered light.

In order to solve the above-mentioned problems and achieve the objectives, the lighting device of the present invention is a lighting device that simulates natural light including blue sky, and includes a light source with a correlated color temperature of 2000 Kelvin or more, and a top surface, a bottom surface, and a side surface. The light emitted by the light source enters from the side, and the scattering layer emits the scattered light generated by Rayleigh scattering the incident light from the bottom surface, and the scattering layer faces the top surface. a reflective layer disposed at a position to reflect scattered light. Further, the lighting device of the present invention includes a low refractive index layer that is disposed between the scattering layer and the reflective layer and has a second refractive index lower than the first refractive index of the scattering layer, and the natural light is , simulated by light emitted from the lower surface of the scattering layer, and the arithmetic mean roughness of the surface of the reflective layer facing the upper surface of the scattering layer is 0.03 μm or more.

The lighting device according to the present invention has the effect of being able to efficiently utilize Rayleigh scattered light while outputting natural light that does not impair the color sense.

A cross-sectional view showing the configuration of a lighting device according to an embodiment. A perspective view showing the configuration of a lighting device according to an embodiment. A perspective view showing the configuration of a reflective layer included in the lighting device according to the embodiment. A cross-sectional view showing an interlayer structure between a reflective layer and a scattering layer of a lighting device according to an embodiment. Diagram for explaining chromaticity of a lighting device according to an embodiment

EMBODIMENT OF THE INVENTION Below, the illuminating device and diffuser concerning embodiment of this invention are demonstrated in detail based on drawing. Note that the present invention is not limited to this embodiment.

Embodiment.
FIG. 1 is a sectional view showing the configuration of a lighting device according to an embodiment. FIG. 2 is a perspective view showing the configuration of the lighting device according to the embodiment. The lighting device 100 includes a diffuser 10, a light source 4, and a partition plate 8. The lighting device 100 is an edge incident lighting device in which a light source 4 is arranged to face a side surface of a plate-shaped diffuser 10.

The light source 4 includes a substrate 41 and one or more light emitting elements arranged on the substrate 41. An example of the light emitting element is an LED (Light Emitting Diode) element 42. In the example of FIG. 2, the light source 4 includes a plurality of LED elements 42 arranged in an array. Light source 4 outputs light from LED element 42 to diffuser 10 .

The diffuser 10 has, for example, a plate shape having rectangular upper and lower surfaces and four side surfaces. In this case, among the four side surfaces of the diffuser 10, the first side and the second side face each other, and the third side face and the fourth side face each other. Note that the upper and lower surfaces of the diffuser 10 may have a shape other than a rectangle, such as a circle.

The diffuser 10 includes a reflective layer 1, a low refractive index layer 2, and a scattering layer 3. The reflective layer 1, the low refractive index layer 2, and the scattering layer 3 are configured using, for example, plate-shaped members. The upper surface of the reflective layer 1, the upper surface of the low refractive index layer 2, and the upper surface of the scattering layer 3 all have the same shape and the same size.

In the diffuser 10, the upper surface of the scattering layer 3 and the low refractive index layer 2 are adjacent to each other, and the upper surface of the low refractive index layer 2 and the lower surface 12 of the reflective layer 1 are adjacent to each other. In other words, in the diffuser 10, the low refractive index layer 2 is provided on the lower surface 12 side (light exit surface 32 side) of the reflective layer 1, and the scattering layer 3 is provided on the lower surface side of the low refractive index layer 2. There is.

1 and 2, the upper surface of the reflective layer 1, the upper surface of the low refractive index layer 2, and the upper surface of the scattering layer 3 are parallel to the XY plane, and the upper surface of the reflective layer 1, the low refractive index layer 2, and the scattering layer 3 are The case where the stacking direction is the Z direction is shown. Among the four side surfaces of the diffuser 10, the first side surface and the second side surface extend in the X direction, and the third side surface and the fourth side surface extend in the Y direction. That is, the reflective layer 1, the low refractive index layer 2, and the scattering layer 3 each have two side surfaces extending in the X direction and two side surfaces extending in the Y direction. In the following description, the side of the diffuser 10 on which the reflective layer 1 is arranged will be referred to as the upper side of the lighting device 100, and the side on which the scattering layer 3 is arranged will be referred to as the lower side of the lighting device 100. be.

The scattering layer 3 is a layer that scatters the light incident from the light source 4. The low refractive index layer 2 is a layer whose refractive index is lower than the refractive index of the scattering layer 3. The reflective layer 1 is a layer that reflects the scattered light 7 generated in the scattering layer 3 toward the scattering layer 3 side.

The scattering layer 3 has a light emitting surface 32 as a lower surface, a back surface 33 as an upper surface, and a side surface connecting the light emitting surface 32 and the back surface 33. The light emitting surface 32 is a surface that emits light. The back surface 33 is a surface (upper surface) opposite to the light exit surface 32 . The back surface 33 and the light exit surface 32 are parallel.

Note that the plate shape of the scattering layer 3 may be other than a flat plate. The plate shape of the scattering layer 3 may be, for example, a curved shape. The plate shape of the scattering layer 3 may be such that one or both of the light exit surface 32 and the back surface 33 are curved. This curved shape may be a convexly curved shape or a concavely curved shape.

One or more of the side surfaces that the scattering layer 3 has is the light incident surface 31 . That is, when the scattering layer 3 has four side surfaces, at least one of the four side surfaces is the light entrance surface 31. In the following description, a case will be described in which one of the side surfaces of the scattering layer 3 is the light entrance surface 31.

The light incident surface 31 is formed at the end of the scattering layer 3 in the X direction, and the light output from the light source 4 is incident thereon. That is, the incident light 5 generated by the light source 4 enters into the scattering layer 3 from the light incidence surface 31 of the scattering layer 3 . The incident light 5 is guided through the scattering layer 3 .

The scattering layer 3 has a base material 34 and a filler 6. The filler 6 is a particle having a size on the order of nanometers (nm), and causes Rayleigh scattering of the incident light 5. The filler 6 is, for example, spherical, but may have another shape. The filler 6 may be a true sphere or an ellipsoid. The particle diameter of the filler 6 is desirably within the range of 1 nm or more and 300 nm or less. When the particle size of the filler 6 is 1 nm or less, the incident light 5 is hardly scattered and Rayleigh scattering hardly occurs. When the particle size of the filler 6 is 300 nm or more, Mie scattering occurs instead of Rayleigh scattering, and the color appearance of Rayleigh scattering is impaired.

Further, it is more desirable that the particle diameter of the filler 6 is within the range of 60 nm or more and 150 nm or less. However, in a case where the filler 6 dispersed in the base material 34 includes a plurality of types of fillers 6, the particle diameter of some of the fillers 6 may not be within the above range. For example, the base material 34 may contain micro-order light scattering particles that are particles other than the filler 6.

The filler 6 is, for example, an inorganic oxide. These inorganic oxides include ZnO (Zinc Oxide), TiO ₂ (Titanium Dioxide), ZrO ₂ (Zirconium Dioxide), SiO ₂ (Silicon Dioxide), and Sb ₂ One or more of O ₅ (Diantimony Pentoxide), Al ₂ O ₃ (Dialuminium Trioxide), and the like. Filler 6 scatters incident light 5 to generate scattered light 7 . In other words, the filler 6 scatters the guided light to generate scattered light 7.

The filler 6 may be, for example, an organic polymer. This organic polymer is one or more of acrylic, styrene, urethane, polyester, polyethylene, melamine, and the like.

The filler 6 is dispersed in the base material 34. Scattering layer 3 is formed by adding filler 6 to base material 34 . The base material 34 is formed from a material that transmits light. The scattering layer 3 is formed using, for example, a base material 34 containing a plurality of types of fillers 6.

The transmittance of the incident light 5 at a light guide distance of 5 mm in the base material 34 (that is, straight transmittance) is preferably 90% or more at the design wavelength. Moreover, it is more preferable that this transmittance is 95% or more. Moreover, it is more preferable that this transmittance is 99% or more. Here, the design wavelength refers to a predetermined wavelength among the wavelengths of the incident light 5 output from the light source 4. The design wavelength is not limited to one wavelength, and may be a plurality of wavelengths. In this case, it is desirable that the above straight transmittance value be satisfied at all design wavelengths. The design wavelength may be, for example, a wavelength within the range of 450 nm to 650 nm. When the light source 4 is a white light source, the design wavelength is, for example, one of 450 nm, 550 nm, and 650 nm.

The base material 34 is solid. The base material 34 is formed from a resin plate using, for example, a thermoplastic polymer, a thermosetting resin, or a photopolymerizable resin. The resin plate may be made of one or more of acrylic polymers, olefin polymers, vinyl polymers, cellulose polymers, amide polymers, fluorine polymers, urethane polymers, silicone polymers, imide polymers, etc. A material or materials can be used. Note that the base material 34 may be a liquid, liquid crystal, gel, sol, or gas.

The scattering layer 3 may be an organic hybrid resin or an inorganic hybrid resin. The organic hybrid resin and the inorganic hybrid resin are, for example, a hybrid resin of a resin and an inorganic oxide. In this case, the filler 6 is an inorganic oxide produced by sol-gel curing based on the substrate 34.

Further, the scattering layer 3 may be formed, for example, by coating one or both of the first surface and the second surface of a solid transparent base material with a thin film containing the filler 6. That is, the filler 6 may not be arranged on the entire base material 34, but may be arranged on the upper surface or the lower surface of the base material 34. In this case, the thin film is the scattering layer 3. Further, a hard coat layer having a hardness of 1H or more may be disposed on at least one of the lower surface, upper surface, and side surface of the scattering layer 3.

A transparent coating such as an abrasion-resistant coat, a weather-resistant coat, an anti-reflection coat, an anti-fouling coat, or a heat-shielding coat is applied to at least one of the light output surface 32, the back surface 33, and the side surfaces, which are the front surface of the diffuser 10. A functional coating or a hard coating may be applied.

The incident light 5 guided through the scattering layer 3 is reflected by the light exit surface 32 and the back surface 33 and is guided. The incident light 5 is guided by, for example, total internal reflection.

The light emitting surface 32 emits the scattered light 7 scattered by the filler 6. It is desirable that the light exit surface 32 has high smoothness. This is because if minute scratches or minute irregularities occur on the light exit surface 32, the light guided within the diffuser 10 will slightly leak out from the light exit surface 32.

The light exit surface 32 is a surface facing toward the observer. In this case, the scattered light 7 emitted from the back surface 33 becomes a loss. In the lighting device 100, in order to utilize the scattered light 7 emitted from the back surface 33, a reflective layer 1 that reflects light is arranged on the back surface 33 side of the scattering layer 3. The reflective layer 1 is, for example, a white reflector. The reflective layer 1 may be a colored reflector such as blue.

In the illumination device 100, incident light 5 emitted from the light source 4 is reflected inside the scattering layer 3 and travels toward the light guide direction. Since the filler 6 is uniformly dispersed in the scattering layer 3, when the incident light 5 hits the filler 6, scattered light 7 is generated. The scattered light 7 includes Rayleigh scattered light.

In this embodiment, since the illumination device 100 has a configuration (edge incidence method) in which the incident light 5 enters from the side surface of the diffuser 10, the light guide distance is from the light incidence surface 31 of the scattering layer 3 to This is the distance to the facing surface 31. When the light guide direction of the incident light is in the thickness direction of the scattering layer, that is, when the lighting device is a direct lighting system, the light guide distance is the length of the scattering layer thickness, so the illumination of this embodiment The light guide distance is shorter than that of the device 100.

As the light guide distance becomes longer as in the lighting device 100, the frequency with which the incident light 5 comes into contact with the filler 6 increases, and the scattered light 7 is efficiently generated. Therefore, in this embodiment, if the diffuser 10 has the same size, the filler concentration required to generate the same amount of scattered light 7 can be lowered.

When the filler concentration in the scattering layer is high, the distance between the particles becomes short, so that particle aggregation is likely to occur. When the size of particle aggregates becomes equal to the wavelength of light, Mie scattering in the scattered light increases. If this happens, the color sense of the Rayleigh scattered light will be impaired, making it impossible to express the desired color. Furthermore, if the light guide distance is increased by increasing the thickness of the scattering layer, the entire lighting device will become larger. The illumination device 100 of the present embodiment has an appropriate filler concentration so that the scattered light 7, which is efficiently emitted Rayleigh scattered light, can be emitted to the lower surface of the scattering layer 3 while suppressing Mie scattering within the scattering layer 3. The incident light 5 is adjusted to enter from the side surface of the diffuser 10. As a result, the observer observes the Rayleigh scattered light generated efficiently by suppressing Mie scattering from the light exit surface 32.

By the way, since the Rayleigh scattered light is emitted in all directions, the scattered light 7 is also emitted on the upper surface of the scattering layer 3, etc. The scattered light 7 emitted from the upper surface (back surface 33) first enters the low refractive index layer 2, but if the incident angle of the scattered light 7 is below a certain level, the low refractive index It is reflected by layer 2 and returned to the lower surface of scattering layer 3. On the other hand, when the scattered light 7 emitted from the upper surface of the scattering layer 3 is incident at an angle higher than a certain angle, it passes through the low refractive index layer 2, is reflected by the reflective layer 1, and reaches the lower surface of the scattering layer 3. It will be returned. The incident angle of the scattered light 7 reflected by the low refractive index layer 2 is determined by the refractive index difference between the scattering layer 3 and the low refractive index layer 2.

The role of the low refractive index layer 2 is to prevent the incident light 5 that has been totally reflected in the scattering layer 3 from being reflected or scattered by the reflective layer 1 . If there is no low refractive index layer 2 and the reflective layer 1 is in direct contact with the upper surface of the scattering layer 3, the incident light 5 that is totally reflected in the scattering layer 3 will be reflected by the reflective layer 1 directly above it. The reflected light is emitted from the light emitting surface 32. Since the reflected light of the incident light 5 has a higher emission intensity than the Rayleigh scattered light generated in the scattering layer 3, when the reflected light of the incident light 5 is emitted from the light output surface 32, the color sense of the Rayleigh scattered light is impaired. It will be done. In this embodiment, since the low refractive index layer 2 is provided between the scattering layer 3 and the reflective layer 1, the incident light 5 is totally reflected in the scattering layer 3 and cannot reach the reflective layer 1.

Further, a light-shielding partition plate 8 is installed below or around the light source 4 in this embodiment, so that the observer cannot directly view the light source 4. That is, the partition plate 8 separates the outside and the inside of the lighting device 100. The partition plate 8 is arranged, for example, on the lower surface side of the scattering layer 3 at the outer periphery of the lower surface.

When the lower surface of the scattering layer 3 is rectangular, the partition plate 8 is arranged on the side of the lower surface of the scattering layer 3 where the light source 4 is arranged. Note that the partition plate 8 may be placed on both the side where the light source 4 is placed and the side where the light source 4 is not placed. For example, the partition plate 8 may be arranged around one circumference of the outer peripheral region of the lower surface of the scattering layer 3. That is, when the lower surface of the scattering layer 3 is rectangular, the partition plates 8 may be arranged on four sides of the lower surface of the scattering layer 3. In this case, the lower surface shape of the partition plate 8 is annular along the outer peripheral region of the lower surface of the scattering layer 3 .

The lighting device 100 is installed, for example, on the ceiling. In this case, the lighting device 100 is installed on the ceiling so that the light exit surface 32 faces the ground side. The observer observes the light emitted from the light emitting surface 32 by looking toward the ceiling. Note that the lighting device 100 may be installed on a wall or the like.

FIG. 3 is a perspective view showing the configuration of a reflective layer included in the lighting device according to the embodiment. FIG. 4 is a cross-sectional view showing an interlayer structure between a reflective layer and a scattering layer of the lighting device according to the embodiment. In FIG. 3, the lower surface 12 of the reflective layer 1 is shown on the upper side.

The lower surface 12 of the reflective layer 1 has fine roughness. Specifically, a plurality of convex portions 11 are provided on the lower surface 12 of the reflective layer 1 . As a result, when the reflective layer 1 is installed directly above the scattering layer 3, the reflective layer 1 and the scattering layer 3 are not completely brought into close contact with each other due to the convex portions 11, which are minute irregularities of the reflective layer 1, and the convex portions It becomes possible to provide an extremely thin low refractive index layer 2 in an area corresponding to the height of 11. As a result, space saving can be realized, so that the lighting device 100 can be downsized.

It is sufficient that the lower surface 12 of the reflective layer 1 has at least three convex portions 11 . Thereby, the scattering layer 3 can support the reflective layer 1 with at least three convex parts 11, so that a gap can be provided between the reflective layer 1 and the scattering layer 3. For example, by arranging the convex portions 11 at the four corners of the lower surface 12 of the reflective layer 1, the low refractive index layer 2 can be provided in the gap between the reflective layer 1 and the scattering layer 3. Note that the reflective layer 1 may have fine roughness on the top surface and side surfaces. That is, the convex portions 11 may also be provided on the upper surface and side surfaces of the reflective layer 1.

The surface roughness Ra, which is the arithmetic mean roughness of the reflective layer 1, is desirably 0.03 μm or more. When the surface roughness Ra is smaller than 0.03 μm, the reflective layer 1 and the scattering layer 3 will come into close contact with each other, and in the region between the reflective layer 1 and the scattering layer 3, the low refractive index layer 2 will be It disappears within the area or the entire surface. Furthermore, in order to further reduce the degree of adhesion between the reflective layer 1 and the scattering layer 3, the surface roughness Ra is desirably 0.2 μm or more.

The refractive index n ₂ of the low refractive index layer 2 is lower than the refractive index n ₃ of the scattering layer 3. The refractive index n ₃ of the scattering layer 3 is the first refractive index, and the refractive index n ₂ of the low refractive index layer 2 is the second refractive index. The refractive index difference between the low refractive index layer 2 and the scattering layer 3 is preferably (n ₃ −n ₂ )≧0.05. When the refractive index difference becomes smaller than 0.05, the incident light 5 that is totally reflected in the scattering layer 3 is not totally reflected depending on the angle of incidence on the low refractive index layer 2, but is transmitted to the low refractive index layer 2 and reflected. It will be reflected by layer 1. In this case, the reflected light of the incident light 5 will reach the observer, and the color sense of the scattered light 7 including the Rayleigh scattered light will be impaired.

When the refractive index difference is (n ₃ −n ₂ )≧0.05, the critical angle of incidence for total reflection within the scattering layer 3 is 75°. At this time, if the incident angle of light emitted from the light source 4 is within 25 degrees, total internal reflection will occur. When the angle of incidence of the light source 4 is larger than 25°, it is possible to change the angle of incidence by narrowing down the angle of incidence with a narrow-angle lens or the like.

Note that it is more desirable for the refractive index difference to be (n ₃ −n ₂ )≧0.3 than (n ₃ −n ₂ )≧0.05. If (n ₃ −n ₂ )≧0.3, total reflection occurs at the incident angle of a general light source such as an LED.

The thickness t of the low refractive index layer 2 is preferably 0<t≦1 mm. When the thickness of the low refractive index layer 2 is 0 mm, that is, when the scattering layer 3 and the reflective layer 1 are in complete contact with each other, the incident light 5 is reflected by the reflective layer 1, resulting in scattered light 7 including Rayleigh scattered light. The low refractive index layer 2 must be thicker than 0 mm because it impairs the color sense. Therefore, the low refractive index layer 2 of this embodiment is thicker than 0 mm. Further, if the thickness of the low refractive index layer 2 is 1 mm or more, when an observer looks at the lighting device 100 from outside the lighting device 100 at an angle close to the side, the inside of the lighting device 100 is visible, and the lighting device 100 looks bad. Therefore, it is desirable that the low refractive index layer 2 of this embodiment is thinner than 1 mm.

In addition, when the light source 4 is an LED, when the incident light 5 from the light source 4 is directly irradiated onto the reflective layer 1, the reflected light from the reflective layer 1 of the incident light 5 reaches the observer, and the Rayleigh scattered light The color sense is impaired. Therefore, in the lighting device 100, when the light source 4 is an LED, the incident light 5 from the light source 4 is prevented from directly irradiating the reflective layer 1.

The thickness of the low refractive index layer 2 may be determined based on the surface roughness Ra or unevenness of the reflective layer 1, or if the material of the low refractive index layer 2 has adhesiveness or adhesiveness, It may be adjusted using the properties of the material of the refractive index layer 2. Further, the thickness of the low refractive index layer 2 may be adjusted using a spacer or the like.

The low refractive index layer 2 is a low refractive index resin such as a fluorine-based polymer, silicone polymer, acrylic polymer, polypropylene, or urethane polymer. Further, the low refractive index layer 2 may be a solid such as glass, or a liquid such as water, methyl alcohol, ethanol, acetone, or acetic acid. Moreover, the low refractive index layer 2 may be a gas such as air, helium, nitrogen, or oxygen, or may be an aerosol, a gel, or the like.

The light source 4 emits light with a correlated color temperature T _ci . The correlated color temperature T _ci is, for example, 6500K (Kelvin). The correlated color temperature T _ci may be 5000K. "Correlated color temperature" means the color temperature of blackbody radiation that appears to be the closest color to the color of the light emitter. The light source 4 may be, for example, a light source that emits white light as light having a correlated color temperature _Tci .

Each of the plurality of LED elements 42 included in the light source 4 is configured to emit light of the same correlated color temperature _Tci . Note that the light source 4 may include multiple types of LED elements 42 that emit light with mutually different correlated color temperatures _Tci . For example, the light emitted by the plurality of LED elements 42 may include three colors of red light, green light, and blue light. In this case, the LED elements 42 of the light source 4 include an LED element 42 that emits red light, an LED element 42 that emits green light, and an LED element 42 that emits blue light.

Further, the light emitted by the plurality of LED elements 42 may include light of three colors: white light, green light, and blue light. In this case, the LED elements 42 of the light source 4 include an LED element 42 that emits white light, an LED element 42 that emits green light, and an LED element 42 that emits blue light.

Further, the light emitted by the plurality of LED elements 42 may include light of four colors: white light, green light, blue light, and orange light. In this case, the LED elements 42 of the light source 4 include an LED element 42 that emits white light, an LED element 42 that emits green light, an LED element 42 that emits blue light, and an LED element 42 that emits orange light. .

Each of the plurality of LED elements 42 may be independently turned on and turned off. Further, each of the plurality of LED elements 42 may be independently controlled in amount of light emitted, or may be controlled in color of emitted light. That is, each of the plurality of LED elements 42 may be independently subjected to at least one of on-off control, light emission amount control, and light emission color control. Through these controls, the lighting device 100 can express not only a blue sky but also a sky in the evening or after sunset.

Furthermore, the light source 4 can emit white light by independently controlling each of the LED elements 42 on and off, controlling the amount of light emitted, and controlling the color of the light emitted. Note that the color of the light output from the light source 4 may be other than white. For example, by independently controlling each of the plurality of LED elements 42 by the control circuit that controls the light source 4, it becomes possible to adjust the spectrum of white light or to emit light other than white. .

The combination of emitted light colors of the LED elements 42 included in the light source 4 is not limited to the above-mentioned combinations. For example, light source 4 may include an LED element 42 that emits light of one or more of white light, green light, and orange light. Alternatively, the light source 4 may include an LED element 42 that emits light in one or more of white light, green light, orange light, and blue light.

Further, the light source 4 can include an LED element 42 that emits white light with a low color temperature and an LED element 42 that emits white light with a high color temperature. Here, the difference in color temperature between white light with a high color temperature and white light with a low color temperature is, for example, 2500K or more. The difference in color temperature between the high color temperature white light and the low color temperature white light may be 4000K or more. Further, the difference in color temperature between white light with a high color temperature and white light with a low color temperature may be 8500K.

The correlated color temperature T _cwh of white light with a high color temperature is, for example, 6500K or more. An example of a correlated color temperature T _cwh of high color temperature white light is 11000K. The correlated color temperature T _cwl of white light with a low color temperature is, for example, 2000K or more. An example of a correlated color temperature T _cwl of white light with a low color temperature is 4000K. However, the color temperature of the incident light 5 entering the light incidence surface 31 or the light emitted by each LED element 42 is larger than the black body locus on the chromaticity diagram (for example, the CIE (Commission Internationale de l'Eclairage) 1931 chromaticity diagram). If it is outside the range and difficult to express using correlated color temperature, the color temperature of the light is not limited to the above value.

The light source 4 includes a light emitting surface that emits light. The light output surface of the light source 4 may be placed at a position opposite to the light input surface 31 or may be placed at a position opposite to the light output surface 32. When the light source 4 is arranged at the position shown in FIG. 1, the scattered light 7 may be emitted from the light exit surface 32, or may be emitted from the side surface facing the light entrance surface 31. Further, the light sources 4 may be arranged on multiple sides of the scattering layer 3. In this case, each light source 4 is arranged at a position facing each light incident surface 31.

Next, the chromaticity of the scattered light 7 emitted by the diffuser 10 of this embodiment will be explained. Here, the chromaticity measured by manufacturing and measuring the first diffuser 10 of the present embodiment, the second diffuser 10 of the present embodiment, and the diffuser of a comparative example will be described. It is assumed that the diffuser of the comparative example includes a scattering layer 3 and a low refractive index layer 2 similar to the diffuser 10 of the present embodiment. Note that in the following description, the first diffuser 10 of the present embodiment, the second diffuser 10 of the present embodiment, and the diffuser of the comparative example may be referred to as three diffusers.

In the first diffuser 10, the scattering layer 3 is a resin plate in which a nanofiller is added to a transparent resin, and a white plate with a surface roughness Ra = 0.03 μm is provided as a reflective layer 1 on the back surface 33 side of the scattering layer 3. is set up.

In the second diffuser 10, the scattering layer 3 is a resin plate in which a nanofiller is added to a transparent resin, and a white plate with a surface roughness Ra=0.2 μm is provided as a reflective layer 1 on the back surface 33 side of the scattering layer 3. is set up.

In the diffuser of the comparative example, the scattering layer 3 is a resin plate in which nanofiller is added to a transparent resin, and a white plate with a surface roughness Ra = 0.02 μm is installed as the reflective layer 1 on the back surface 33 side of the scattering layer 3. has been done.

In all three diffusers, the low refractive index layer 2 is an air layer. The thicknesses of these low refractive index layers 2 depended on the surface roughness Ra of each reflective layer 1, and were all 1 mm or less. Further, in all three diffusers, the difference in refractive index between the scattering layer 3 and the low refractive index layer 2 is (n ₃ −n ₂ )≧0.3. For the three diffusers, a white LED with a correlated color temperature of 6500 K was arranged as a light source 4 so that light could enter from the side surface of the scattering layer 3.

CIE1931 chromaticity emitted from the light exit surface 32 was measured for three diffusers with different surface roughness Ra. FIG. 5 is a diagram for explaining the chromaticity of the lighting device according to the embodiment. FIG. 5 shows the correspondence between the surface roughness Ra of three diffusers and the chromaticity coordinates.

For the three diffusers, the chromaticity was measured at a location 100 mm away from the light source 4 in a plane parallel to the XY plane. FIG. 5 shows the measurement results of chromaticity for three diffusers. In the first diffuser 10 having a surface roughness Ra of 0.03 μm, the chromaticity was (x, y)=(0.261, 0.289), and a bluish emission color was confirmed.

Further, in the second diffuser 10 whose surface roughness Ra is 0.2 μm, the chromaticity is (x, y) = (0.254, 0.276), which is more bluish than the first diffuser 10. It has a strong chromaticity.

In the comparative example diffuser with a surface roughness Ra of 0.02 μm, close contact between the scattering layer 3 and the reflective layer 1 was confirmed, and the reflected light of the incident light 5 emitted from the close contact portion caused the white LED of the light source 4 to be illuminated. The color was similar. The chromaticity of the comparative example diffuser was (x, y)=(0.312, 0.328).

In this embodiment, the illumination device 100 includes the scattering layer 3, the low refractive index layer 2, and the reflective layer 1. Since the surface roughness Ra of 12 is 0.03 μm or more, the diffuser 10 can efficiently utilize Rayleigh scattered light while outputting natural light that does not impair the color sense.

Further, in the embodiment, since the light source 4 is arranged on the side surface of the diffuser 10, the thickness of the lighting device 100 can be suppressed. Further, in the embodiment, since the partition plate 8 is arranged on the light exit surface 32 side of the scattering layer 3, the scattered light 7 is not observed by the observer from any side other than the light exit surface 32.

The configurations shown in the embodiments described above are examples of the contents of the present invention, and can be combined with other known techniques, and the configurations can be modified without departing from the gist of the present invention. It is also possible to omit or change parts.

1 reflective layer, 2 low refractive index layer, 3 scattering layer, 4 light source, 5 incident light, 6 filler, 7 scattered light, 8 partition plate, 10 diffuser, 11 convex portion, 12 lower surface, 31 light incidence surface, 32 light Output surface, 33 back surface, 34 base material, 41 substrate, 42 LED element, 100 lighting device.

Claims (8)

It is a lighting device that simulates natural light including blue sky.
A light source with a correlated color temperature of 2000 Kelvin or more,
The scattering device has a plate shape having an upper surface, a lower surface, and a side surface, and the light emitted by the light source is incident from the side surface, and the scattered light generated by Rayleigh scattering the incident light is emitted from the lower surface. layer and
a reflective layer disposed at a position facing the top surface and reflecting the scattered light;
a low refractive index layer disposed between the scattering layer and the reflective layer and having a second refractive index lower than the first refractive index of the scattering layer;
The natural light is simulated by light emitted from the lower surface,
The surface of the reflective layer facing the upper surface has an arithmetic mean roughness of 0.03 μm or more;
A lighting device characterized by: The light incident from the side surface is reflected and guided by the upper surface and the lower surface within the scattering layer,
The scattering layer performs Rayleigh scattering on the light guided through the scattering layer to generate the scattered light that simulates the natural light.
The lighting device according to claim 1, characterized in that: The reflective layer is a colored reflector.
The lighting device according to claim 1 or 2, characterized in that: further comprising a light-shielding partition plate disposed on the outer periphery of the lower surface;
The lighting device according to any one of claims 1 to 3, characterized in that: The difference between the first refractive index and the second refractive index is 0.05 or more,
The angle of incidence of light incident on the side surface from the light source is within 25°;
The lighting device according to any one of claims 1 to 4. The thickness of the low refractive index layer is greater than 0 and less than 1 mm,
The lighting device according to any one of claims 1 to 5. In the scattering layer, a filler having a particle size of 300 nm or less is dispersed in a transparent resin,
The lighting device according to any one of claims 1 to 6, characterized in that: A diffuser used in a lighting device that simulates natural light including blue sky,
It has a plate shape having an upper surface, a lower surface, and a side surface, and light having a correlated color temperature of 2000 Kelvin or more is incident from the side surface, and scattered light generated by Rayleigh scattering the incident light is emitted from the lower surface. a scattering layer that emits;
a reflective layer disposed at a position facing the top surface and reflecting the scattered light;
a low refractive index layer disposed between the scattering layer and the reflective layer and having a second refractive index lower than the first refractive index of the scattering layer;
The natural light is simulated by light emitted from the lower surface,
The surface of the reflective layer facing the upper surface has an arithmetic mean roughness of 0.03 μm or more;
A diffuser characterized by:

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