JP7486675B1 - Light scattering body and lighting device - Google Patents

Abstract

The light-scattering body (10) comprises a light-transmitting resin layer (3), a light-scattering layer (2a, 2b) formed on the surface of the light-transmitting resin layer (3) and containing a light-transmitting resin (4) and light-scattering particles (5) that are dispersed inside the light-transmitting resin (4) without agglomerating and that Rayleigh-scatter incident visible light to generate Rayleigh scattered light, and an electrically conductive heat transfer layer (1a, 1b) formed on at least one surface of the light-scattering layer (2a, 2b) and the light-transmitting resin layer (3).

Description

The present disclosure relates to a light scatterer and an illumination device.

A lighting device has been proposed that includes a light-transmitting substrate and a light-scattering layer that is arranged on one side of the substrate and has a plurality of light-scattering particles that change the direction of light (see, for example, Patent Document 1). In the lighting device described in this document, Rayleigh scattered light generated by the light-scattering particles inside the light-scattering layer is emitted from the bottom surface of the light-scattering layer to the outside via the light-transmitting substrate.

International Publication No. 2014/084012 (see, for example, paragraph 0061)

However, in the device of Patent Document 1, when the light output from the light source is scattered by the light scattering particles inside the light scattering layer, the light scattering particles absorb part of the light and generate heat. A translucent substrate is placed in contact with the underside of the light scattering layer, so the heat generated inside the light scattering layer is difficult to dissipate.

The present disclosure aims to efficiently dissipate heat generated by light scattering.

The light scattering body of the present disclosure is characterized in that it comprises: a plate-like light-transmitting resin layer having side surfaces and a surface, which guides visible light incident from the side surfaces in a light guide direction along the surface ; a first light-scattering layer having a first surface in contact with the surface and a second surface opposite to the first surface , which contains a light-transmitting resin and light-scattering particles that are dispersed within the light-transmitting resin without agglomerating and which Rayleigh scatter the visible light incident from the surface through the first surface to generate Rayleigh scattered light; a first conductive heat transfer layer having a third surface in contact with the second surface of the first light -scattering layer and a fourth surface opposite to the third surface, which is made of an inorganic oxide that transmits visible light, and which emits the Rayleigh scattered light incident from the second surface through the third surface from the fourth surface; and a conductive heat transfer jig in contact with an end of the fourth surface of the first conductive heat transfer layer.

The light scattering material disclosed herein can efficiently dissipate heat generated by light scattering.

1 is a cross-sectional view showing a schematic configuration of a light scattering body and an illumination device according to an embodiment. 1 is a perspective view showing a schematic configuration of a light scattering body and an illumination device according to an embodiment; 11 is a cross-sectional view that shows a schematic diagram of a light scattering body and an illumination device according to a first modified example of an embodiment. FIG. 11 is a cross-sectional view that illustrates a schematic light-scattering body and an illumination device according to a second modified example of an embodiment. FIG. 13 is a cross-sectional view that illustrates a schematic light-scattering body and an illumination device according to a third modified example of an embodiment. FIG. 13 is a cross-sectional view that illustrates a schematic light-scattering body and an illumination device according to a fourth modified example of an embodiment. FIG. FIG. 1 shows an apparatus for evaluating light scatterers. FIG. 13 is a table showing the evaluation results of the light scattering body.

Below, light scattering bodies and lighting devices according to embodiments are described with reference to the drawings. The following embodiments are merely examples, and it is possible to combine the configurations of the embodiments as appropriate and to modify the embodiments as appropriate.

<Embodiment>
Fig. 1 is a cross-sectional view that shows a schematic configuration of a light scatterer 10 and an illumination device 20 according to an embodiment. Fig. 2 is a perspective view that shows a schematic configuration of a light scatterer and an illumination device according to an embodiment. The illumination device 20 includes a light scatterer 10 as a light emitter, a light source 6 that emits light, conductive heat transfer jigs 9a and 9b, and a reflective layer (or reflector) 11. The illumination device 20 is an edge incidence type illumination device in which the light source 6 is disposed to face a side surface of the plate-shaped light scatterer 10.

The light scatterer 10 is, for example, a plate-like shape having a rectangular surface (top and bottom surfaces in FIG. 1) and four side surfaces (also referred to as "first to fourth side surfaces") connecting the top and bottom surfaces. In this case, of the four side surfaces of the light scatterer 10, the first side surface and the second side surface face each other, and the third side surface and the fourth side surface face each other. The top and bottom surfaces of the light scatterer 10 may be shapes other than rectangular, for example, circular.

The light scattering body 10 includes conductive heat transfer layers 1a and 1b (first conductive heat transfer layer, second conductive heat transfer layer), light scattering layers 2a and 2b (first light scattering layer, second light scattering layer), and a translucent resin layer 3. Each of the conductive heat transfer layers 1a and 1b, the light scattering layers 2a and 2b, and the translucent resin layer 3 is, for example, composed of a plate-shaped member. The conductive heat transfer layers 1a and 1b, the light scattering layers 2a and 2b, and the translucent resin layer 3 may be composed of a film-shaped member or a thin-film-shaped member. The surfaces of the conductive heat transfer layers 1a and 1b (upper and lower surfaces in FIG. 1), the surfaces of the light scattering layers 2a and 2b (upper and lower surfaces in FIG. 1), and the surfaces of the translucent resin layer 3 (upper and lower surfaces in FIG. 1) are all the same shape and size.

The figure shows the coordinate axes of the XYZ Cartesian coordinate system. In the figure, the conductive heat transfer layers 1a, 1b, the light scattering layers 2a, 2b, and the translucent resin layer 3 are parallel to the XY plane, and the stacking direction of the conductive heat transfer layers 1a, 1b, the light scattering layers 2a, 2b, and the translucent resin layer 3 is the Z direction. Of the four side surfaces of the light scatterer 10, the first and second side surfaces extend in the X direction, and the third and fourth side surfaces extend in the Y direction. That is, the conductive heat transfer layers 1a, 1b, the light scattering layers 2a, 2b, and the translucent resin layer 3 each have two side surfaces extending in the X direction and two side surfaces extending in the Y direction.

The plate shapes of the conductive heat transfer layers 1a, 1b, the light scattering layers 2a, 2b, and the translucent resin layer 3 may be shapes other than flat. The plate shapes of the conductive heat transfer layers 1a, 1b, the light scattering layers 2a, 2b, and the translucent resin layer 3 may be, for example, curved. The plate shapes of the conductive heat transfer layers 1a, 1b, the light scattering layers 2a, 2b, and the translucent resin layer 3 may be shapes in which either the light exit surface or the back surface, or both, are curved. This curved shape may be a convex curved shape or a concave curved shape.

One or more of the side surfaces of the light scattering body 10 are light incident surfaces 101. That is, when the light scattering body 10 has four side surfaces, at least one of the four side surfaces is the light incident surface 101. In the following explanation, a case where one of the side surfaces of the light scattering layers 2a, 2b is the light incident surface 101 will be described.

The light scatterer 10 has a back surface 102 which is the surface on the reflective layer 11 side (top surface in FIG. 1), a light exit surface 103 which is the surface (bottom surface in FIG. 1) on which an observer (i.e., a person who looks at the light scatterer 10 or the outgoing light emitted from the light scatterer 10, also called an "observer" or "user") observes the outgoing light, and a light entrance surface 101 which is a side surface connecting the back surface 102 and the light exit surface 103. The light exit surface 103 is the surface from which light exits. The back surface 102 is the surface (top surface) opposite the light exit surface 103. The back surface 102 and the light exit surface 103 are parallel.

The light source 6 includes a base 61 and one or more light-emitting elements arranged on the base. An example of the light-emitting element is an LED (Light Emitting Diode) element 62. In the example of FIG. 2, the light source 6 includes a plurality of arranged LED elements 62. The plurality of LED elements 62 are on/off controlled, or both on/off controlled and light emission intensity controlled, by a known drive control circuit (not shown). The light source 6 outputs light from the LED elements 62 toward the light entrance surface 101 of the light scatterer 10. The number of the plurality of LED elements 62 is not limited to the number shown in the figure. In addition, although the figure shows an arrangement of one row of LED elements 62, the light source 6 may include an arrangement of two or more rows of LED elements 62.

The light incident surface 101 is formed at the X-direction end of the light scattering layers 2a, 2b (or at the end of the light scattering layers 2a, 2b and the translucent resin layer 3), and the light output from the light source 6 is incident thereon. That is, the incident light 7 generated by the light source 6 is incident on the light scattering layers 2a, 2b from the light incident surfaces (i.e., the light incident surfaces 101) of the light scattering layers 2a, 2b. The incident light 7 travels through the light scattering layers 2a, 2b and the translucent resin layer 3.

The light scattering layers 2a and 2b are layers that Rayleigh scatter the incident light 7, which is light output from the light source 6 and incident into the light scattering layers 2a and 2b. The light scattering layers 2a and 2b have a translucent resin 4 and a plurality of light scattering particles 5. The light scattering particles 5 are particles having a size on the order of nanometers [nm], and Rayleigh scatter the incident light 7. The light scattering particles 5 are, for example, spherical, but may be of other shapes. The light scattering particles 5 may be, for example, spherical or ellipsoidal.

The particle diameter of the light scattering particles 5 is preferably in the range of 1 nm or more and 500 nm or less. The reason why a particle diameter of 1 nm or more is preferable is that if the particle diameter of the light scattering particles 5 is less than 1 nm, the incident light 7 is hardly scattered and almost no Rayleigh scattering occurs. The reason why a particle diameter of 500 nm or less is preferable is that if the particle diameter of the light scattering particles 5 exceeds 500 nm, Mie scattering occurs instead of Rayleigh scattering, and the color feeling of Rayleigh scattering is impaired.

Moreover, it is more preferable that the particle diameter of the light scattering particles 5 is within the range of 50 nm to 400 nm. However, in cases where the light scattering particles 5 dispersed in the light scattering layers 2a and 2b contain multiple types of particles, the particle diameter of some of the particles may not be within the range of 50 nm to 400 nm. For example, the light scattering layers 2a and 2b may contain one or both of nano-order particles and micro-order particles, which are particles other than the light scattering particles 5.

By increasing the light guide distance as in the lighting device 20, the frequency with which the incident light 7 comes into contact with the light scattering particles 5 increases, and Rayleigh scattered light is generated efficiently. Therefore, the light scattering body 10 according to the present embodiment can increase the intensity of the Rayleigh scattered light even when the concentration of light scattering particles is low. In other words, the light scattering body 10 according to the present embodiment can reduce the concentration of light scattering particles required to generate Rayleigh scattered light of the same intensity, compared to a conventional light scattering body of the same size.

When the concentration of the light scattering particles 5 in the light scattering layers 2a and 2b is high, the distance between the particles becomes closer, so that the particles are more likely to aggregate. When the size of the aggregates of the light scattering particles 5 becomes equal to or larger than the wavelength of the light, the proportion of Mie scattering in the scattered light increases. When this happens, the color of the Rayleigh scattered light is hindered, and the desired color cannot be expressed. The lighting device 20 according to this embodiment employs a structure in which the filler concentration is appropriately adjusted and the incident light 7 is made incident from the side of the light scatterer 10 in order to suppress the Mie scattering occurring in the light scattering layers 2a and 2b while enabling the efficiently emitted Rayleigh scattered light to be emitted from the underside of the light scattering layer 2b. As a result, the observer can observe the efficiently generated Rayleigh scattered light with the Mie scattering suppressed from the light exit surface 103.

The light scattering particles 5 are, for example, inorganic oxides. The inorganic oxides of the light scattering particles 5 are, for example, any one of ZnO (zinc oxide), TiO ₂ (titanium dioxide (IV)), ZrO ₂ (zirconium dioxide), SiO ₂ (silicon dioxide), Sb ₂ O ₅ (antimony pentoxide), Al ₂ O ₃ (dialuminum trioxide), and the like, or a combination of two or more of them. The light scattering particles 5 scatter the incident light 7 to generate Rayleigh scattered light. In other words, the light scattering particles 5 scatter the incident light 7, which is guided light, to generate Rayleigh scattered light.

The light scattering particles 5 may be, for example, an organic polymer. The organic polymer of the light scattering particles 5 may be, for example, any one of acrylic, styrene, urethane, polyester, polyethylene, melamine, phenol, epoxy, polyamide, etc., or a combination of two or more thereof.

The transmittance (i.e., rectilinear transmittance) of the incident light 7 at a light guide distance of 5 mm of the light scatterer 10 is preferably 80% or more at the design wavelength. Moreover, the transmittance is more preferably 85% or more. Moreover, this transmittance is even more preferably 90% or more. Here, the design wavelength refers to a predetermined wavelength among the wavelengths of the incident light 7 output from the light source 6. The design wavelength is not limited to one wavelength, and may be multiple wavelengths. In this case, it is desirable that the above-mentioned rectilinear transmittance value is satisfied at all of the design wavelengths. The design wavelength may be, for example, a wavelength in the range from 400 nm to 800 nm. When the light source 6 is a white light source, the design wavelength is, for example, any one of 450 nm, 550 nm, and 650 nm, or a combination of two or more.

The light-transmitting resin layer 3 is a solid. The light-transmitting resin layer 3 is preferably composed of one or more of the following materials: a thermoplastic polymer, a thermosetting resin, a photopolymerizable resin, an acrylic polymer, an olefin polymer, a vinyl polymer, a cellulose polymer, an amide polymer, a fluorine polymer, a urethane polymer, a silicone polymer, an imide polymer, etc.

The refractive index of the base material of the light scattering layers 2a and 2b and the refractive index of the light-transmitting resin layer 3 are preferably 1 or more and 1.7 or less. Furthermore, it is more preferable that these refractive indices are 1.3 or more and 1.6 or less.

Examples of dispersion devices for dispersing the light scattering particles 5 in the translucent resin 4 include general agitators equipped with a mechanism such as a propeller blade, turbine blade, or battle blade at the tip, or a high-speed rotating centrifugal radial agitator equipped with a toothed disk-shaped impeller mechanism with a circular saw blade bent up and down alternately at the tip. Examples of dispersion devices include ultrasonic emulsification dispersion devices that generate ultrasonic energy in a concentrated manner to perform dispersion processing, bead mill devices that fill a container with beads and rotate it to grind and disperse the raw materials, and revolution rotation agitators that disperse the raw materials by the shear force of the container as it rotates and revolves. However, usable dispersion devices are not limited to these devices.

The light scattering layers 2a and 2b may be thin films formed by coating both sides (also called the "first surface" and "second surface") of the light-transmitting resin layer 3 with a material containing light-transmitting resin 4 and light-scattering particles 5. The light scattering layers 2a and 2b may also be composed of films containing light-transmitting resin 4 and light-scattering particles 5 and bonded to both sides of the light-transmitting resin layer 3. The light scattering layers 2a and 2b may also be composed of thin plates containing light-transmitting resin 4 and light-scattering particles 5 and bonded to both sides of the light-transmitting resin layer 3.

Thin-film coatings can be formed by known wet processes. Specifically, thin-film coatings can be formed by coating methods such as spin coating, dipping, doctor blade, ejection coating, and spray coating, and by printing methods such as inkjet, letterpress printing, intaglio printing, screen printing, and microgravure coating.

The light scattering layers 2a and 2b contain a light-transmitting resin 4 and light scattering particles 5, and it is preferable that the light scattering particles 5 are not aggregated in the light-transmitting resin 4 and are monodispersed (i.e., the particles are dispersed as monodispersed as possible). In other words, the light scattering layers 2a and 2b have a light-transmitting resin 4 and light scattering particles 5 that are dispersed in the light-transmitting resin 4 without agglomeration and that Rayleigh scatter the incident visible light to generate Rayleigh scattered light. The non-aggregated light scattering particles 5 may include not only a state in which the particles are present alone, but also a state in which a small number of particles (e.g., less than 10 particles) that cannot be said to be aggregated are in contact with each other. It is preferable that all of the light scattering particles 5 in the light scattering layer are dispersed without agglomeration, but it is acceptable that 10% or less of all the light scattering particles 5 are aggregated. If the amount of aggregated light scattering particles is 10% or less, the color of the Rayleigh scattered light is hardly hindered and the desired color can be expressed.

The incident light 7 guided through the light scattering layers 2a and 2b is reflected and guided at the light exit surface 103 and the back surface 102. The incident light 7 is guided, for example, by total reflection.

The light scattering layers 2a and 2b emit Rayleigh scattered light as scattered light 8 scattered by the light scattering particles 5. It is desirable that the surfaces (upper and lower surfaces in FIG. 1) of the conductive heat transfer layers 1a and 1b, the light scattering layers 2a and 2b, and the translucent resin layer 3 each have high smoothness. For example, it is preferable that the surface roughness Ra of the surfaces (upper and lower surfaces in FIG. 1) of the conductive heat transfer layers 1a and 1b, the light scattering layers 2a and 2b, and the translucent resin layer 3 each have a surface roughness Ra of 1 μm or less. It is more preferable that the surface roughness Ra is 0.5 μm or less. It is even more preferable that the surface roughness Ra is 0.1 μm or less. This is because, when fine scratches or fine irregularities occur on the surfaces of the conductive heat transfer layers 1a, 1b, the light scattering layers 2a, 2b, and the translucent resin layer 3, the amount of light that leaks out from the light exit surface 103 of the light guided within the light scatterer 10 increases slightly.

The light exit surface 103 is the surface facing the observer. In this case, the scattered light 8 exiting from the back surface 102 is lost. In the lighting device 20, in order to utilize the scattered light 8 exiting from the back surface 102, a reflective layer 11 that reflects light is disposed on the back surface 102 side of the light scatterer 10. The reflective layer 11 is, for example, a white reflector. The reflective layer 11 may be a reflector other than a white reflector, such as a colored reflector such as blue or yellow.

In the lighting device 20, incident light 7 emitted from the light source 6 is reflected at the internal interface of the light scattering layers 2a and 2b and travels in the X direction, which is the light guide direction. Light scattering particles 5 are dispersed in the light scattering layers 2a and 2b (usually uniformly dispersed so as not to aggregate), and when the incident light 7 hits the light scattering particles 5, scattered light 8 is generated. The scattered light 8 includes Rayleigh scattered light.

In this embodiment, the lighting device 20 is configured to receive incident light 7 from the side of the light scattering body 10 (edge incidence method), so the light guide distance is the distance from the light incidence surface 101 of the light scattering layers 2a, 2b to the opposite side of the light incidence surface 101.

By increasing the light guide distance as in the lighting device 20, the frequency with which the incident light 7 comes into contact with the light scattering particles 5 increases, and scattered light 8 is generated efficiently. Therefore, the light scattering body 10 according to the present embodiment can reduce the filler concentration required to generate the same amount of scattered light 8 compared to a conventional light scattering body of the same size.

When the concentration of the light scattering particles 5 in the light scattering layers 2a and 2b is high, the distance between the particles becomes closer, so that the particles are more likely to aggregate. When the size of the particle aggregates becomes equal to or larger than the wavelength of light, Mie scattering in the scattered light 8 increases. In that case, the color of the Rayleigh scattered light is hindered, and the desired color cannot be expressed. In addition, when the thickness of the light scattering layers 2a and 2b is increased to increase the light guide distance, the entire lighting device becomes large. In the lighting device 20 of this embodiment, the concentration of the light scattering particles 5 is appropriately adjusted so that the scattered light 8, which is the efficiently emitted Rayleigh scattered light, can be emitted to the lower surface of the light scatterer 10 while suppressing Mie scattering in the light scattering layers 2a and 2b, and the incident light 7 is made incident from the side of the light scatterer 10. As a result, the observer can observe the efficiently generated Rayleigh scattered light with suppressed Mie scattering from the light exit surface 103.

In addition, conductive heat transfer jigs 9a and 9b (first conductive heat transfer jig, second conductive heat transfer jig) are installed at the X-direction ends of the light scatterer 10 in this embodiment, and the conductive heat transfer jigs 9a and 9b are attached in a manner that sandwiches the upper and lower surfaces of the light scatterer 10. Furthermore, the conductive heat transfer jigs 9a and 9b are connected to either one or both of the grounding member and the heat dissipation member outside the lighting device 20. In FIG. 2, the length in the Y direction of the conductive heat transfer jigs 9a and 9b is the same as the length in the Y direction of the light scatterer 10, but may be different. In addition, the conductive heat transfer jigs 9a and 9b may only be in contact with a part of the conductive heat transfer layers 1a and 1b.

The lighting device 20 is installed, for example, on the ceiling of a building. In this case, the lighting device 20 is installed on the ceiling so that the light emitting surface 103 faces the ground. An observer can observe the light emitted from the light emitting surface 103 by looking toward the ceiling. The lighting device 20 may also be installed in other positions on the building, such as on a wall.

The conductive heat transfer layers 1a and 1b are preferably made of a material that transmits visible light. The conductive heat transfer layers 1a and 1b are preferably made of a material that contains either or both of a metal or an inorganic material. The conductive heat transfer layers 1a and 1b may also be made of a composite material that contains either or both of a metal or an inorganic material with an organic polymer as a base material. The conductive heat transfer layers 1a and 1b can be formed of one or a combination of two or more of Au (gold), Ag (silver), Cu (copper), Pd (palladium), Pb (lead), and Pt (platinum). The inorganic material that constitutes the conductive heat transfer layers 1a and 1b is an inorganic oxide. The conductive and heat-transfer layers 1a and 1b may be made of an inorganic material such as one _or a combination of two or more of _SnO2 (tin dioxide), ITO (indium-doped tin dioxide), PTO (phosphorus-doped tin oxide), ATO (antimony-doped tin oxide), _Sb2O5 (antimony pentoxide), ZnO (zinc oxide) _{, In2O3} (indium oxide), etc.

When the conductive heat transfer layers 1a and 1b are made of a composite material containing an organic polymer and either or both of a metal or an inorganic material, the proportion of the metal or inorganic material is preferably 20 wt% or more and 90 wt% or less. Furthermore, the proportion of the metal or inorganic material is more preferably 40 wt% or more and 80 wt% or less. Furthermore, the proportion of the metal or inorganic material is even more preferably 50 wt% or more and 70 wt% or less.

The conductive heat transfer layers 1a and 1b may be formed as thin films by sputtering on the surfaces of the light scattering layers 2a and 2b (the upper surface of the light scattering layer 2a and the lower surface of the light scattering layer 2b in FIG. 1). The conductive heat transfer layers 1a and 1b may also be formed by methods other than sputtering, such as vacuum deposition, CVD (chemical vapor deposition), spray pyrolysis, etc.

The conductive heat transfer layers 1a and 1b may be formed by vapor deposition of a thin metal film such as aluminum nitride, alumina, or an indium compound, which has a light transmittance of 80% or more in the visible light range.

When the conductive heat transfer layers 1a and 1b are made of an inorganic oxide, the thickness of each of the conductive heat transfer layers 1a and 1b is preferably 0.1 μm or more and 100 μm or less. When the conductive heat transfer layers 1a and 1b are made of a metal, the thickness of each of the conductive heat transfer layers 1a and 1b is preferably 1 nm or more and 100 nm or less.

The thermal conductivity of the conductive heat transfer layers 1a and 1b is preferably 0.4 W/m·K or more and 300 W/m·K or less. The thermal conductivity of the conductive heat transfer layers 1a and 1b is more preferably 10 W/m·K or more and 200 W/m·K or less. The thermal conductivity of the conductive heat transfer layers 1a and 1b is even more preferably 50 W/m·K or more and 100 W/m·K or less. This is because a material with a thermal conductivity of more than 100 W/m·K has a low transmittance of light in the visible light range, and the Rayleigh scattered light, which is the scattered light 8 scattered by the light scattering layers 2a and 2b, is less likely to transmit.

When the conductive heat transfer layers 1a and 1b are made of a composite material containing an organic polymer and either or both of a metal or an inorganic material, and particles of a metal or an inorganic material are used, the particle diameter is preferably 1 nm or more and 500 nm or less. Furthermore, the particle diameter is more preferably 10 nm or more and 100 nm or less.

The light-transmitting resin 4 of the light-scattering layers 2a and 2b may be made of one or two or more of the following materials: thermoplastic polymers, thermosetting resins, or photopolymerizable resins, acrylic polymers, olefin polymers, vinyl polymers, cellulose polymers, amide polymers, fluorine polymers, urethane polymers, silicone polymers, imide polymers, etc.

The thickness of each of the light scattering layers 2a and 2b is preferably 1 μm or more and 100 μm or less. Furthermore, the thickness of each of the light scattering layers 2a and 2b is more preferably 5 μm or more and 50 μm or less. Furthermore, the thickness of each of the light scattering layers 2a and 2b is more preferably 10 μm or more and 30 μm or less.

The proportion of the light scattering particles 5 in the light scattering layers 2a and 2b is preferably 1 wt% or more and 50 wt% or less. The proportion of the light scattering particles 5 in the light scattering layers 2a and 2b is more preferably 5 wt% or more and 30 wt% or less. Furthermore, the proportion of the light scattering particles 5 in the light scattering layers 2a and 2b is even more preferably 10 wt% or more and 20 wt% or less.

The light exit surface 103 emits the scattered light 8 scattered by the light scattering particles 5. It is desirable that the light exit surface 103 and the back surface 102 have high smoothness. This is because if the light exit surface 103 and the back surface 102 have fine scratches or fine irregularities, the light guided through the light scatterer 10 will leak out slightly from the light exit surface 103. Specifically, it is preferable that the surface roughness Ra of the back surface 102 and the light exit surface 103 is 500 nm or less. It is more preferable that the surface roughness Ra of the back surface 102 and the light exit surface 103 is 200 nm or less. It is more preferable that the surface roughness Ra of the back surface 102 and the light exit surface 103 is 100 nm or less.

<<Variation 1>>
3 is a cross-sectional view showing a light scattering body 10a and a lighting device 20a according to a first modified example of the embodiment. In FIG. 3, the same reference numerals as those shown in FIG. 1 are used for the same or corresponding components as those shown in FIG. 1. The light scattering body 10a and the lighting device 20a according to the first modified example are different from the light scattering body 10 and the lighting device 20 shown in FIG. 1 in that they do not include a light scattering layer 2a. That is, as shown in FIG. 3, the light scattering body 10a according to the first modified example has a light-transmitting resin layer 3, a light scattering layer 2b formed on the surface of the light-transmitting resin layer 3 (the lower surface in FIG. 3), a conductive heat transfer layer 1b formed on the surface of the light-scattering layer 2b (the lower surface in FIG. 3), and a conductive heat transfer layer 1a formed on the surface of the light-transmitting resin layer 3 (the upper surface in FIG. 3). Other than the above, the light scattering body 10a and the lighting device 20a according to the first modified example are the same as the light scattering body 10 and the lighting device 20 shown in FIG. 1.

<<Variation 2>>
4 is a cross-sectional view showing a light scattering body 10b and a lighting device 20b according to a second modified embodiment of the embodiment. In FIG. 4, the same or corresponding components as those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG. 1. The light scattering body 10b and the lighting device 20b according to the second modified embodiment are different from the light scattering body 10 and the lighting device 20 shown in FIG. 1 in that they do not include the light scattering layer 2a and the conductive heat transfer layer 1a. That is, as shown in FIG. 4, the light scattering body 10b according to the second modified embodiment has a translucent resin layer 3, a light scattering layer 2b formed on the surface of the translucent resin layer 3 (the lower surface in FIG. 4), and a conductive heat transfer layer 1b formed on the surface of the light scattering layer 2b (the lower surface in FIG. 4). Other than the above, the light scattering body 10b and the lighting device 20b according to the second modified embodiment are the same as the light scattering body 10 and the lighting device 20 shown in FIG. 1.

<<Variation 3>>
5 is a cross-sectional view that shows a light scattering body 10c and a lighting device 20c according to a third modified example of the embodiment. FIG. 5 is a cross-sectional view that shows a light scattering body 10c and a lighting device 20c according to a third modified example of the embodiment. In FIG. 5, the same reference numerals as those in FIG. 1 are used for the same or corresponding configurations as those in FIG. 1. The light scattering body 10c and the lighting device 20c according to the third modified example are different from the light scattering body 10 and the lighting device 20 shown in FIG. 1 in that they do not include a light scattering layer 2b. That is, as shown in FIG. 5, the light scattering body 10c according to the third modified example has a translucent resin layer 3, a light scattering layer 2a formed on the surface of the translucent resin layer 3 (upper surface in FIG. 5), a conductive heat transfer layer 1a formed on the surface of the light scattering layer 2a (lower surface in FIG. 5), and a conductive heat transfer layer 1b formed on the surface of the translucent resin layer 3 (lower surface in FIG. 3). Other than the above, light scattering body 10c and lighting device 20c according to modification example 3 are the same as light scattering body 10 and lighting device 20 shown in FIG.

<<Variation 4>>
6 is a cross-sectional view showing a light scattering body 10d and a lighting device 20d according to a fourth modified embodiment of the embodiment. In FIG. 6, the same reference numerals as those shown in FIG. 1 are used for the same or corresponding components as those shown in FIG. 1. The light scattering body 10d and the lighting device 20d according to the fourth modified embodiment are different from the light scattering body 10 and the lighting device 20 shown in FIG. 1 in that they do not include the light scattering layer 2b and the conductive heat transfer layer 1a. That is, as shown in FIG. 6, the light scattering body 10d according to the fourth modified embodiment has a translucent resin layer 3, a light scattering layer 2a formed on the surface of the translucent resin layer 3 (upper surface in FIG. 6), and a conductive heat transfer layer 1b formed on the surface of the translucent resin layer 3 (lower surface in FIG. 6). Other than the above, the light scattering body 10d and the lighting device 20d according to the fourth modified embodiment are the same as the light scattering body 10 and the lighting device 20 shown in FIG. 1.

Performance evaluation
Below, performance evaluation experiments of Examples E1 to E4 of this embodiment and Comparative Example C1 will be described. However, Examples E1 to E4 are merely specific examples of this embodiment and do not limit the scope of the present disclosure.

Example E1
The light scatterer of Example E1, which is a light scatterer for performance evaluation, is manufactured by the following procedure: The structure of the light scatterer of Example E1 corresponds to that shown in FIG.
First, a thermosetting resin to which light-scattering particles 5 have been added at a concentration of 30 wt % relative to the coating solids content is applied to both sides (i.e., the front and back sides) of an acrylic plate so as to have a total film thickness of 10 μm, and then heated and cured to form light-scattering layers 2 a and 2 b.
Next, a coating material made by adding antimony pentoxide to an ultraviolet (UV) curing resin so that the content is 50 wt % of the coating solids is applied to the surfaces of the light scattering layers 2a and 2b to a total film thickness of 10 μm, and the applied material is cured with a UV irradiation device to form the conductive heat transfer layers 1a and 1b.

Example E2
The light scatterer of Example E2, which is a light scatterer for performance evaluation, is manufactured by the following procedure: The structure of the light scatterer of Example E2 corresponds to that shown in FIG.
First, a thermosetting resin containing light scattering particles 5 added at a concentration of 30 wt % relative to the coating solid content is applied to one side of an acrylic plate to a film thickness of 10 μm, and then heated and cured to form a light scattering layer 2b.
Next, a coating material made by adding diantimony pentoxide to a UV-curable resin so that the content is 50 wt % of the coating solids is applied onto the light-scattering layer 2b to a film thickness of 10 μm, and the applied material is cured using a UV irradiation device to form the conductive heat transfer layer 1b.

Example E3
The light scatterer of Example E3, which is a light scatterer for performance evaluation, is manufactured by the following procedure: The structure of the light scatterer of Example E3 corresponds to that shown in FIG.
First, a thermosetting resin to which light-scattering particles 5 have been added at a concentration of 30 wt % relative to the coating solids content is applied to both sides (i.e., the front and back sides) of an acrylic plate so as to have a total film thickness of 10 μm, and then heated and cured to form light-scattering layers 2 a and 2 b.
Next, a coating material made by adding diantimony pentoxide to a UV-curable resin so that the content is 50 wt % of the coating solid content is applied onto the light-scattering layer 2b to a total film thickness of 10 μm, and the applied material is cured using a UV irradiation device to form the conductive heat transfer layer 1b.

Example E4
The light scatterer of Example E4, which is a light scatterer for performance evaluation, is manufactured by the following procedure: The structure of the light scatterer of Example E4 corresponds to that shown in FIG.
First, a thermosetting resin to which light-scattering particles 5 have been added at a concentration of 30 wt % relative to the coating solids content is applied to both sides (i.e., the front and back sides) of an acrylic plate so as to have a total film thickness of 10 μm, and then heated and cured to form light-scattering layers 2 a and 2 b.
Next, gold is evaporated to a thickness of 100 nm onto each of the two surfaces of the light scattering layers 2a and 2b, thereby forming the electrically conductive and heat transfer layers 1a and 1b.

Comparative Example C1
The light scatterer of Comparative Example C1, which is a light scatterer for performance evaluation, is manufactured by the following procedure.
A thermosetting resin to which light scattering particles 5 have been added at a concentration of 30 wt % relative to the coating solid content is applied to one side of an acrylic plate to a film thickness of 10 μm, and then heated and cured to form a light scattering layer 2b.

<evaluation>
Using the light scatterers manufactured in this manner, an evaluation device having the structure shown in Fig. 7 was manufactured. Fig. 7 shows how incident light is incident from two sides of the light scatterers when evaluating the light scatterers of Examples E1, E2, E3, E4, and Comparative Example C1. Fig. 8 shows the evaluation results of the light scatterers of Examples E1, E2, E3, E4, and Comparative Example C1 in a table. In the table, a "double circle" indicates very good, a "single circle" indicates good, and an "x" indicates poor.

As can be seen from the table in Figure 8, Example E1, which is a light scatterer including a conductive heat transfer layer according to the present disclosure, is excellent in terms of the surface resistivity [Ω/□] of the front and back surfaces, the total light transmittance [%], and heat dissipation. In the heat dissipation column, a "double circle" indicates very good.

On the other hand, in the case of Example E2, which has a light scattering layer on one side and a conductive heat transfer layer on the other side, heat dissipation occurs only on one side, but the heat dissipation performance is a "single circle", i.e., good.

In addition, in the case of Example E3, which has light scattering layers on both sides and a conductive heat transfer layer on one side, the heat dissipation is slightly better than in Example E2, i.e., a "single circle mark," but the heat dissipation is insufficient compared to Example E1.

Furthermore, in the case of Example E4, in which a thin film of gold was vapor-deposited on the outermost surface, the heat dissipation was marked with a "single circle," i.e., good, but the surface resistivity [Ω/□] was above the required specifications, and the total light transmittance [%] was slightly reduced.

In comparative example C1, the heat dissipation is poor, marked with an "X", because there is no conductive heat transfer layer. It is believed that a conductive heat transfer layer is essential to improve the heat dissipation of the light scatterer.

Effects of the embodiment
As described above, according to the light-scattering body 10, 10a to 10d of the present embodiment, the heat generated by the scattering of light can be efficiently released by the heat dissipation action of the electrically conductive heat-transfer layers 1a, 1b or the electrically conductive heat-transfer layer 1b. This makes it possible to reduce deterioration due to heat and also to make the device more compact.

As described above, in the light-scattering bodies 10, 10a to 10d according to the present embodiment, the electroconductive heat transfer layers 1a, 1b or the electroconductive heat transfer layer 1b are electrically conductive, so that the electrostatic charge is removed, and dust and dirt are less likely to be attracted. This makes it possible to prevent the emission color from becoming whitish, which is a deterioration in the color tone that is specific to Rayleigh scattering.

1a, 1b: conductive heat transfer layer (first conductive heat transfer layer, second conductive heat transfer layer), 2a, 2b: light scattering layer (first light scattering layer, second light scattering layer), 3: translucent resin layer, 4: translucent resin, 5: light scattering particles, 6: light source, 7: incident light, 8: scattered light, 9a, 9b: conductive heat transfer tool, 10, 10a, 10b, 10c, 10d: light scattering body, 11: reflector, 20, 20a, 20b, 20c, 20d: lighting device, 101: light incident surface (side surface), 102: rear surface, 103: light exit surface (front surface), 61: base, 62: LED element.

Claims (9)

a light-transmitting resin layer having a plate shape with a side surface and a surface, the light-transmitting resin layer guiding visible light incident from the side surface in a light-guiding direction along the surface;
a first light scattering layer having a plate shape with a first surface in contact with the surface and a second surface opposite to the first surface, the first light scattering layer including a light-transmitting resin and light scattering particles dispersed without agglomeration within the light-transmitting resin, the light scattering particles scattering the visible light incident from the surface through the first surface to generate Rayleigh scattered light;
a first electrically conductive and heat transfer layer having a plate shape and including a third surface in contact with the second surface of the first light scattering layer and a fourth surface opposite to the third surface, the first electrically conductive and heat transfer layer being made of an inorganic oxide that transmits visible light, and emitting the Rayleigh scattered light incident from the second surface through the third surface from the fourth surface;
an electrically conductive and heat-transferring tool in contact with an end portion of the fourth surface of the first electrically conductive and heat-transfer layer;
A light scattering body comprising: 2. The light-scattering body according to claim 1, further comprising a second light-scattering layer in contact with the surface opposite to the surface of the light-transmitting resin layer, the second light-scattering layer comprising a light-transmitting resin and light-scattering particles that generate Rayleigh scattered light. 3. The light-scattering body according to claim 2, further comprising a second electrically conductive and heat-conductive layer in contact with a surface of the second light-scattering layer. 2. _The light-scattering body according to claim 1, wherein the inorganic oxide includes any one of _SnO2 , ITO, PTO, ATO, _Sb2O5 , ZnO, and _In2O3 , or a combination of two or _more thereof. 2. The light-scattering body according to claim 1, wherein the first electrically conductive and heat-transfer layer has a thickness of 0.1 μm or more and 100 μm or less. 6. The light-scattering body according to claim 1, wherein the thermal conductivity of the first electrically conductive and heat-transfer layer is equal to or greater than 0.4 W/m·K and less than 400 W/m·K. 6. The light-scattering body according to claim 1, wherein the first light-scattering layer has a thickness of 1 μm or more and 100 μm or less. 6. The light-scattering body according to claim 1, wherein the light-scattering particles in the first light-scattering layer are present in an amount of 1 wt % or more and 50 wt % or less. The light scattering body according to any one of claims 1 to 5,
a light source that emits the visible light incident from at least one of a side surface of the light-transmitting resin layer and the side surface of the first light scattering layer;
a reflector disposed on one side of the light-transmitting resin layer or the first light-scattering layer.

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