Light guide plate and light emitting module

Abstract

To provide a light guide plate which enables an appearance of light emission to vary depending on a viewing angle and can express sparkle by increasing luminance locally, and to provide a light emitting module.SOLUTION: Each of light guide plates 12, 30, 40, 52 includes: a translucent base material 16 having translucency; multiple translucent protruding layers 18 each including a light emission surface 18B which is provided on a surface of the translucent base material 16 in a protruding manner and formed by a curved surface; and multiple light scattering layers 20 which are formed of a resin containing light scattering particles and are provided on a back surface of the translucent base material 16 so as to overlap with the multiple translucent protruding layers 18 with the translucent base material 16 sandwiched therebetween. Multiple types of translucent protruding layers 18 having different sizes and / or heights are provided in a mixed manner.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a light guide plate and a light emitting module using the light guide plate.

Background Art

[0002] In order to improve the texture of vehicle interiors such as automobiles, the adoption of products that combine decoration and indirect lighting has been increasing. For example, Patent Document 1 discloses that in a decorative sheet having a design by a decorative layer, the design property is improved by partially emitting light from the surface of the decorative sheet. The decorative sheet described in Patent Document 1 includes a high refractive index resin layer, a light diffusing layer provided on the back surface of the high refractive index resin layer, and a decorative layer provided on the surface of the high refractive index resin layer via a low refractive index resin layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] From the viewpoint of further improving the texture of vehicle interiors, interior parts capable of emitting crystal-like or glass-like light have been developed. However, the sparkle seen in real crystals or glass, that is, the effect of local strong light or the change in luminance depending on the viewing angle is insufficient, and further improvement in texture is required.

[0005] An object of embodiments of the present invention is to provide a light guide plate in which the appearance of light emission varies depending on the viewing angle and which can express sparkle by locally increasing the luminance, and a light emitting module using the same.

Means for Solving the Problems

[0006] The light guide plate according to an embodiment of the present invention includes: a translucent base material having translucency; a plurality of translucent convex layers made of a resin having translucency, provided convexly on either one of the front surface and the back surface of the translucent base material, and having a light emitting surface formed by a curved surface; and a plurality of light scattering layers made of a resin containing light scattering particles, provided on the other surface of the translucent base material facing the one surface so as to overlap with the plurality of translucent convex layers with the translucent base material interposed therebetween. The light guide plate is one in which a plurality of types of the translucent convex layers having different sizes and / or heights are mixed.

[0007] In the light guide plate according to one embodiment, the area ratio occupied by the curved surface in each light emitting surface of the plurality of translucent convex layers may be 80% or more.

[0008] In the light guide plate according to one embodiment, the overlapping amount of each of the plurality of translucent convex layers and the light scattering layer corresponding to the translucent convex layer may be 30% or more of the area of the light scattering layer as viewed from a direction perpendicular to the surface of the translucent base material.

[0009] The light guide plate according to one embodiment further includes a translucent resin layer having translucency provided on the one surface of the translucent base material, and the plurality of translucent convex layers may be provided on the one surface of the translucent base material via the translucent resin layer.

[0010] The light guide plate according to one embodiment further includes a plurality of coating resin layers having translucency for coating the plurality of light scattering layers, and the surface of each coating resin layer may be formed by a curved surface.

[0011] The light emitting module according to an embodiment of the present invention includes the light guide plate and a light source capable of injecting light into the side surface of the translucent base material.

[0012] In one embodiment, the light emitting module may further include a moving device for moving the light source along the side surface of the translucent base material.

Effects of the Invention

[0013] According to this embodiment, the light incident from the side surface of the light guide plate is scattered by the light scattering particles contained in the light scattering layer and enters the light-transmitting convex layer through the light-transmitting base material. The light incident on the light-transmitting convex layer is emitted to the outside through the light-emitting surface. At this time, since the light-emitting surface is formed by a curved surface, it is diffused by the lens effect, and the appearance of the light emission varies depending on the viewing angle. Further, as the light-transmitting convex layers for emitting light, a plurality of types having different sizes and / or heights are mixed, so that a portion with high luminance or a glitter can be locally expressed.

Brief Description of the Drawings

[0014]

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Figure 12

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this specification, the surface of the light guide plate refers to the surface (main design surface) that mainly comes into contact with a person's eyes during use (i.e., when used as a light emitting module) among the front and back surfaces of the light guide plate, and the back surface of the light guide plate refers to the surface on the opposite side of the surface. Also, the surface of the light-transmissive substrate refers to the surface facing in the same direction as the surface of the light guide plate among the front and back surfaces of the light-transmissive substrate, and the back surface of the light-transmissive substrate refers to the surface on the opposite side of the surface of the light-transmissive substrate.

[0016] (First Embodiment) As shown in FIGS. 1 and 2, the light emitting module 10 according to the first embodiment includes a light guide plate 12 and a light source 14.

[0017] The light guide plate 12 includes a light-transmissive substrate 16, a plurality of light-transmissive convex layers 18, and a plurality of light scattering layers 20. In this specification, the light guide plate is not limited to a plate-like shape in the ordinary sense, and is used to include those with a small thickness such as a sheet or a film.

[0018] The light-transmissive substrate 16 is a substrate forming the main body of the light guide plate 12 and has light-transmissivity. In this specification, light-transmissivity refers to light transmissibility, that is, the ability to transmit light, and is not limited to being colorless and transparent. As long as it can transmit light, it may be colored or translucent. In one embodiment, the light-transmissive substrate 16 is preferably colorless and transparent.

[0019] The material of the light-transmitting base material 16 is not particularly limited and may be a resin or glass. In one embodiment, examples of the light-transmitting base material 16 include polycarbonate resin (PC); polyester resins such as polyethylene terephthalate (PET); acrylic resins such as polymethyl methacrylate (PMMA); styrene resins such as polystyrene resin, acrylonitrile-styrene copolymer resin (AS resin), and acrylonitrile-butadiene-styrene copolymer (ABS); polyolefin resins such as polyethylene and polypropylene; or a resin sheet composed of a blend of two or more of these. As the light-transmitting base material 16, for example, a glass plate made of lead glass or soda-lime glass may also be used. Preferably, a resin sheet made of a thermoplastic resin is used as the light-transmitting base material 16.

[0020] The light-transmitting base material 16 serves as the main body of the light guide plate 12 and has the role of spreading the light incident from its side surface 16C over the entire area. That is, the light incident from the side surface 16C of the light-transmitting base material 16 is totally reflected at the front and back interfaces of the light-transmitting base material 16 and confined within the light-transmitting base material 16, and is transmitted laterally. Therefore, it is preferable that the light-transmitting base material 16 has a high refractive index. The refractive index (absolute refractive index) of the light-transmitting base material 16 is not particularly limited, but may be, for example, 1.40 to 1.70 or 1.50 to 1.60.

[0021] In this specification, the refractive index (absolute refractive index) is the refractive index of light with a wavelength of 589 nm (D line), and is measured, for example, at an environmental temperature of 25°C using an Abbe refractometer ("DR-M4" manufactured by Atago Co., Ltd.).

[0022] The thickness of the light-transmitting base material 16 is not particularly limited and may be, for example, 0.1 to 3.0 mm, 0.5 to 2.5 mm, or 1.0 to 2.0 mm.

[0023] The light-transmitting convex layer 18 is a resin layer made of a light-transmitting resin, which may be colorless and transparent or colored and transparent. Examples of the resin for forming the light-transmitting convex layer 18 include acrylic resins such as polymethyl methacrylate (PMMA) and urethane acrylate resins; styrene resins such as polystyrene resin, acrylonitrile-styrene copolymer resin (AS resin), and acrylonitrile-styrene-butadiene copolymer resin (ABS resin); polyolefin resins such as polyethylene and polypropylene; or blends of two or more of these. Preferably, the light-transmitting convex layer 18 does not contain light-scattering particles.

[0024] The refractive index (absolute refractive index) of the light-transmitting convex layer 18 is not particularly limited and may be higher than that of the light-transmitting base material 16, lower than that of the light-transmitting base material 16, or the same value. When the light-transmitting convex layer 18 is provided in contact with the light-transmitting base material 16, if the refractive index of the light-transmitting convex layer 18 is higher than the refractive index of the light-transmitting base material 16, the light extraction effect in the light-transmitting convex layer 18 can be enhanced. The refractive index of the light-transmitting convex layer 18 may be, for example, 1.35 to 1.65 or 1.40 to 1.55.

[0025] The light-transmitting convex layer 18 is provided convexly on either one of the front surface 16A or the back surface 16B of the light-transmitting base material 16. That is, the light-transmitting convex layer 18 is provided as a convex layer that partially covers the one surface. The "convex shape" of the light-transmitting convex layer 18 means that it bulges and rises with a curved surface with respect to the one surface (i.e., the reference surface on which the light-transmitting convex layer 18 is provided), and the height is not particularly limited as long as it is relatively raised with respect to the one surface. Preferably, the "convex shape" means a shape with a raised center. The light-transmitting convex layer 18 is provided dot-like on the one surface. Dot-like means that there are a plurality of dot-shaped (dot-like) light-transmitting convex layers 18. In this example, the light-transmitting convex layer 18 is provided in contact with the front surface 16A of the light-transmitting base material 16, that is, directly laminated on the front surface 16A.

[0026] The light-transmitting convex layer 18 may be distributed and arranged over the entire area on the one surface of the light-transmitting base material 16, or may be arranged locally. By dotting and arranging a plurality of dot-shaped light-transmitting convex layers 18 at predetermined positions on the one surface, a design composed of a pattern, figure, character, symbol, or a combination of two or more of these can be expressed by crystal-like light emission.

[0027] The light-transmitting convex layer 18 includes a light-emitting surface 18B that emits the light incident from its bottom surface 18A. Here, the light-emitting surface 18B is the surface of the light-transmitting convex layer 18 that protrudes convexly from the surface 16A of the light-transmitting base material 16 and is exposed to the outside, and is the surface that forms the interface between the light-transmitting convex layer 18 and air. The bottom surface 18A of the light-transmitting convex layer 18 is the surface with respect to the apex of the light-transmitting convex layer 18, and in this example, it is the surface in contact with the light-transmitting base material 16 (the interface between the light-transmitting convex layer 18 and the light-transmitting base material 16).

[0028] The light-emitting surfaces 18B of the plurality of light-transmitting convex layers 18 are formed by curved surfaces. Here, "formed by curved surfaces" includes not only the mode in which the light-emitting surface 18B is formed only by curved surfaces, but also the mode in which a plane is partially included. In order to enhance the effect that the light emitted from the light-emitting surface 18B diffuses and the appearance of the light emission varies depending on the viewing angle, the light-emitting surface 18B is preferably mainly formed by curved surfaces, and it is more preferable that the area ratio occupied by the curved surfaces in the light-emitting surface 18B is 80% or more. That is, in one embodiment, it is preferable that each light-emitting surface 18B has an area ratio of the curved surface of 80% or more and an area ratio of the plane of 20% or less. More preferably, as shown in FIGS. 1 and 2, the area ratio of the curved surface is 100%.

[0029] The light-emitting surfaces 18B of the plurality of light-transmitting convex layers 18 are formed by one or a plurality of curved surfaces.

[0030] For example, the light-emitting surface 18B of the light-transmitting convex layer 18 shown enlarged in FIG. 3 is formed by a single curved surface. The light-transmitting convex layer 18 in FIG. 3 has a plano-convex lens shape in which its bottom surface 18A, which is one surface thereof, is a plane and its light-emitting surface 18B, which is the other surface, is a curved convex surface.

[0031] The light-transmitting convex layer 18 having a light-emitting surface 18B formed of a single curved surface may be provided independently, but as shown in FIG. 4, a plurality of light-transmitting convex layers 18 may be formed connected to each other. When the distance between the light-scattering layers 20 is narrow and the light-transmitting convex layer 18 is formed larger than the light-scattering layer 20, a plurality of light-transmitting convex layers 18 may be formed connected in this way.

[0032] The light-emitting surface 18B of the light-transmitting convex layer 18 shown enlarged in FIG. 5 is formed by a plurality of curved surfaces. The light-transmitting convex layer 18 in FIG. 5 has a shape in which a smaller plano-convex lens-shaped convex portion is provided on a plano-convex lens-shaped convex portion. In this way, the light-transmitting convex layer 18 may have a shape in which a plurality of convex dots are stacked.

[0033] In one embodiment, the light-transmitting convex layer 18 preferably has a convex shape formed in a curved surface shape and rising from the periphery toward the center, and has a circular shape in plan view, that is, a circular bottom surface 18A. However, it is not limited to this, and it may be rectangular or triangular in plan view, and various shapes can be adopted. For example, the shape in plan view may have a complex shape formed by overlapping dots formed by inkjet printing.

[0034] The size of the light-transmitting convex layer 18 is not particularly limited. For example, the equivalent diameter of the circle of the bottom surface 18A may be 20 to 150 μm, or may be 30 to 100 μm. The equivalent diameter of the circle is the diameter of a perfect circle corresponding to the area of the bottom surface. Therefore, the area of the bottom surface 18A of the light-transmitting convex layer 18 is, for example, 300 to 18000 μm 2 or may be 700 to 8000 μm 2 or may be.

[0035] The height H (see FIG. 3) of the light-transmitting convex layer 18 is not particularly limited. For example, it may be 1 to 30 μm, or may be 3 to 15 μm. Here, the height H of the light-transmitting convex layer 18 is the distance from the bottom surface 18A to the apex of the light-transmitting convex layer 18.

[0036] The ratio of the height to the equivalent circle diameter of the light-transmitting convex layer 18 (height / equivalent circle diameter) is not particularly limited and may be 1 / 20 to 1 / 3, or may be 1 / 10 to 1 / 4.

[0037] The arrangement density of the light-transmitting convex layer 18 is not particularly limited. For example, in a design area that expresses a design consisting of crystal-like or glass-like light emission, the number of light-transmitting convex layers 18 per 1 cm 2 may be 800 to 15,000, may be 1,000 to 12,000, or may be 4,000 to 10,000.

[0038] The method for forming the light-transmitting convex layer 18 is not particularly limited, but it is preferable to form the light-transmitting convex layer 18 by printing such as inkjet printing. More preferably, the plurality of light-transmitting convex layers 18 are formed by printing (preferably inkjet printing) using a photocurable resin such as an ultraviolet curable resin.

[0039] When forming the light-transmitting convex layer 18 by inkjet printing, by adjusting the viscosity of the ink, it is possible to form the light-transmitting convex layer 18 having the light-emitting surface 18B formed of a curved surface as described above. For example, the higher the viscosity of the ink, the easier it is to form a convex lens-shaped light-transmitting convex layer 18 while maintaining a large contact angle of the droplets ejected onto the substrate surface. The viscosity of the ink in that case is not particularly limited and may be, for example, 13 to 20 mPa·s, or may be 15 to 18 mPa·s. Here, the viscosity is the measured value at 25°C measured by a cone-plate viscometer RE105H (manufactured by Toki Sangyo Co., Ltd.).

[0040] The light-scattering layer 20 is a resin layer made of a resin containing light-scattering particles. A plurality of light-scattering layers 20 are provided on the other surface of the light-transmitting substrate 16 facing the one surface. That is, a plurality of light-scattering layers 20 are provided as layers that partially cover the other surface. The light-scattering layers 20 are provided in a scattered manner on the other surface, similar to the light-transmitting convex layers 18 on the one surface side.

[0041] The light scattering layer 20 is partially in contact with the other surface. As a result, the light confined and transmitted in the light-transmitting base material 16 by total reflection is scattered by the light scattering particles. That is, the light is diffusely reflected and emitted at various angles, and light that travels at an angle close to perpendicular (less than the critical angle) to one surface facing the other surface is generated. Since such light does not undergo total reflection, it is radiated from the one surface, and thus light can be extracted from the light guide plate 12.

[0042] In this example, the light scattering layer 20 is provided in contact with the back surface 16B of the light-transmitting base material 16, that is, it is directly laminated on the back surface 16B. Therefore, the light traveling in the light-transmitting base material 16 is scattered by the light scattering particles of the light scattering layer 20 on the back surface 16B side. As a result, light that travels at an angle less than the critical angle with respect to the front surface 16A is generated, and at least a part of it enters the light-transmitting convex layer 18 provided on the front surface 16A side.

[0043] The shape of each light scattering layer 20 is not particularly limited. For example, it may be circular in plan view, that is, it may have a circular bottom surface, it may be rectangular or triangular in plan view, or it may even have a complex shape formed by overlapping dots formed by inkjet printing. Similar to the light-transmitting convex layer 18, the surface of the light scattering layer 20 may be formed by a curved surface, but it does not necessarily have to be formed by a curved surface. For example, it may have a flat cross-sectional shape with a constant thickness (height). Here, the bottom surface of the light scattering layer 20 is the surface in contact with the light-transmitting base material 16 (the interface between the light scattering layer 20 and the light-transmitting base material 16).

[0044] The size of the light scattering layer 20 is not particularly limited. For example, the equivalent diameter of the circle of the bottom surface may be 20 to 150 μm, or it may be 30 to 100 μm. The thickness (height) of the light scattering layer 20 is not particularly limited. For example, it may be 0.5 to 15 μm, or it may be 1 to 10 μm. The equivalent diameter of the circle means the diameter of a perfect circle corresponding to the area of the bottom surface.

[0045] The arrangement density of the light scattering layer 20 is not particularly limited. For example, in a design area expressing a design composed of crystal-like or glass-like light emission, 1 cm 2The number of the light-scattering layers 20 per hit may be 800 to 15,000, may be 1,000 to 12,000, or may be 4,000 to 10,000.

[0046] As the light-scattering particles included in the light-scattering layer 20, various fine particles having an effect of scattering light can be used. For example, titanium oxide, calcium carbonate, glass beads, aluminum powder, etc. can be mentioned, and any one of these or a combination of two or more thereof may be used. Among these, since titanium oxide has a high refractive index, it is excellent in the effect of improving luminance. Further, in the case of flaky titanium oxide, irregular reflection occurs on the reflection surface with light, so that the light emission with locally high luminance and the glittering light emission effect can be enhanced.

[0047] The refractive index of the light-scattering particles is not particularly limited, but is preferably higher than the refractive index of the matrix resin forming the light-scattering layer 20. For example, it may be 1.5 to 2.8, or may be 2.0 to 2.7.

[0048] The particle size of the light-scattering particles is not particularly limited. For example, the 50% volume particle size (D50) may be 100 to 4000 nm, or may be 200 to 800 nm.

[0049] The resin (matrix resin) forming the light-scattering layer 20 is not particularly limited. For example, acrylic resins such as polymethyl methacrylate (PMMA) and urethane acrylate resin; styrene resins such as polystyrene resin, acrylonitrile-styrene copolymer resin (AS resin), acrylonitrile-styrene-butadiene copolymer resin (ABS resin); polyolefin resins such as polyethylene and polypropylene; or a blend of two or more of these can be mentioned. As the matrix resin, it is preferable to use a resin having translucency, which may be colorless and transparent or colored and transparent.

[0050] The method for forming the light-scattering layer 20 is not particularly limited, and for example, the light-scattering layer 20 may be formed by printing such as inkjet printing. Preferably, the plurality of light-scattering layers 20 are formed by printing (preferably inkjet printing) using a photocurable resin such as an ultraviolet-curable resin. When the light-scattering layer 20 is formed by inkjet printing, the viscosity of the ink is not particularly limited, and may be, for example, 7 to 13 mPa·s or 10 to 13 mPa·s. Here, the viscosity is the measured value at 25°C measured by a cone-and-plate viscometer RE105H (manufactured by Toki Sangyo Co., Ltd.).

[0051] The plurality of light-scattering layers 20 are provided so as to overlap with each other with the translucent base material 16 interposed between the plurality of translucent convex layers 18. In this example, corresponding to each of the plurality of translucent convex layers 18 provided on the surface 16A of the translucent base material 16 (that is, in a one-to-one correspondence), a light-scattering layer 20 that overlaps with the translucent convex layer 18 is provided on the back surface 16B of the translucent base material 16. Thereby, the light scattered by the light-scattering layer 20 passes through the translucent base material 16 in its thickness direction and is incident into the translucent convex layer 18 from the bottom surface 18A of the translucent convex layer 18.

[0052] As shown enlarged in FIG. 3, the translucent convex layer 18 may be provided so as to overlap the entire corresponding light-scattering layer 20 via the translucent base material 16. That is, the overlapping amount of the translucent convex layer 18 and the light-scattering layer 20 corresponding to the translucent convex layer 18 may be 100% of the area of the light-scattering layer 20 as viewed from a direction perpendicular to the surface 16A of the translucent base material 16. However, it is not necessary to overlap entirely in this way, and the translucent convex layer 18 may overlap at least a part of the corresponding light-scattering layer 20.

[0053] FIG. 7 is a schematic cross-sectional view of an embodiment in which the light-transmitting convex layer 18 is provided with its position shifted so that a part of it overlaps with the corresponding light-scattering layer 20, and FIG. 8 is a schematic plan view thereof. By arranging them in this shifted manner, the change in the overlapping amount becomes large depending on the viewing angle from the surface side, and the glittering effect can be enhanced. The light-transmitting convex layer 18 may be provided so as to entirely overlap with the light-scattering layer 20, or may be provided so as to partially overlap with the light-scattering layer 20, and by mixing these, the glittering effect can be further enhanced.

[0054] The overlapping amount of each light-transmitting convex layer 18 of the plurality of light-transmitting convex layers 18 and the light-scattering layer 20 corresponding to the light-transmitting convex layer 18 is preferably 30% or more, more preferably 50% or more, and still more preferably 70% or more of the area of the light-scattering layer 20 as viewed from a direction perpendicular to the surface 16A of the light-transmitting substrate 16. Thereby, the light scattered by the light-scattering layer 20 can be effectively incident on the light-transmitting convex layer 18. Here, the overlapping amount between the light-transmitting convex layer 18 and the light-scattering layer 20 is the overlapping portion between the solid-line circle indicated by reference numeral 18 and the dotted-line circle indicated by reference numeral 20 in the example shown in FIG. 8. Therefore, it is preferable that this overlapping portion is 30% or more, 50% or more, or 70% or more with the area of the dotted-line circle indicated by reference numeral 20 being 100%.

[0055] The ratio of the size of the light-transmitting convex layer 18 to the light-scattering layer 20 is not particularly limited, but the bottom area of the light-transmitting convex layer 18 is preferably 40 to 200%, more preferably 70 to 150% of the bottom area of the light-scattering layer 20. The light-transmitting convex layer 18 may be larger than the light-scattering layer 20, and thus the light-transmitting convex layer 18 may protrude from the light-scattering layer 20 in plan view. Conversely, the light-scattering layer 20 may be larger than the light-transmitting convex layer 18, and thus the light-scattering layer 20 may protrude from the light-transmitting convex layer 18 in plan view. In the former case, the light scattered by the light-scattering layer 20 can be incident on the light-transmitting convex layer 18 over a wider range. In the latter case, the light emitted through the light-transmitting convex layer 18 and the light directly emitted from the light-transmitting substrate 16 without passing through the light-transmitting convex layer 18 are mixed, and the glittering state can be changed depending on the viewing angle.

[0056] In this embodiment, the plurality of translucent convex layers 18 are formed such that a plurality of types having different sizes (i.e., equivalent circle diameters) and / or heights are mixed. That is, as shown in FIG. 2, on the one surface (in this example, the surface 16A) of the translucent substrate 16, a plurality of types of translucent convex layers 18 having at least one of different sizes and heights are provided and are mixed. Therefore, an arrangement mode in which translucent convex layers having the same size and height are aligned in a plurality of rows over the entire one surface of the translucent substrate, or an arrangement mode in which translucent convex layers whose sizes gradually increase as the distance from the light source increases are aligned in a plurality of rows over the entire one surface of the translucent substrate, are not considered to be mixed and are not included in this embodiment. That is, the mixing of a plurality of types means that a plurality of types of translucent convex layers 18 having different sizes and / or heights are arranged in a mixed manner regardless of the distance from the light source, and it is not necessarily required to be arranged randomly. For example, even when a plurality of arrangement patterns composed of large and small mixed translucent convex layers 18 are repeatedly arranged, it is included in the concept of "mixing of a plurality of types".

[0057] As a mode of providing a plurality of types of translucent convex layers 18, for example, a mode of setting translucent convex layers 18 having a plurality of gradations according to the size and / or height and mixing and providing these translucent convex layers 18 having a plurality of gradations can be mentioned. As an example, when forming the translucent convex layer 18 by inkjet printing, a plurality of gradations may be set according to the number of droplets (ink particles) ejected from the nozzles (drop numbers). A plurality of droplets ejected from the nozzles either become one droplet in the air and land on the translucent substrate 16 or become integrated on the translucent substrate 16 to become one droplet, and a translucent convex layer 18 having a size and / or height corresponding to the number of ejected droplets is formed. At that time, there may be a variation in the spreading degree of the droplets due to the viscosity of the ink and the surface state of the translucent substrate 16, but including such cases having such a variation, a plurality of gradation translucent convex layers 18 having a size and / or height corresponding to the number of droplets are formed. Therefore, such translucent convex layers 18 having a plurality of gradations may be formed in a mixed manner. Note that the number of gradations is not particularly limited, and may be, for example, 3 to 20 or 5 to 15.

[0058] Since the light-scattering layer 20 is provided so as to correspond to the light-transmitting convex layer 18 and overlap with each other as described above, similar to the light-transmitting convex layer 18, a plurality of types of light-scattering layers 20 having different sizes and / or heights may be provided in a mixed manner. For this purpose, for example, there is an aspect in which a plurality of gradation light-scattering layers 20 are set according to the size and these plurality of gradation light-scattering layers 20 are provided in a mixed manner. As an example, when forming the light-scattering layer 20 by inkjet printing, a plurality of gradations may be set according to the number of droplets (ink particles) ejected from the nozzles (drop number). The number of gradations is not particularly limited, and may be, for example, 3 to 20, or may be 5 to 15.

[0059] In one embodiment, it is preferable to arrange the light-transmitting convex layer 18 and the light-scattering layer 20 such that the light-transmitting convex layer 18 and the light-scattering layer 20 are set to the same number of gradations, and each light-transmitting convex layer 18 of the plurality of light-transmitting convex layers 18 and the light-scattering layer 20 corresponding to the light-transmitting convex layer 18 have the same gradation.

[0060] As shown in FIGS. 1 and 2, the light-emitting module 10 according to the first embodiment includes a light guide plate 12 and a light source 14. The light source 14 can emit light onto the side surface (light-incident end face) 16C of the light-transmitting base material 16. As the light source 14, for example, a light-emitting diode (LED) can be used.

[0061] The light source 14 is provided at at least a part of the edge of the entire peripheral edge of the light guide plate 12, and is arranged so as to be able to irradiate light onto the side surface 16C of the light-transmitting base material 16 at the edge. For example, one light source 14 may be provided on one side of the light-transmitting base material 16 having a polygonal shape, or a plurality of light sources 14 may be arranged side by side along the one side. The light source 14 is attached to a part of the edge of the light guide plate 12 by a holder (not shown).

[0062] In one embodiment, the light-emitting module 10 includes a moving device 22 that moves the light source 14 along the side surface 16C of the light-transmitting base material 16. The moving device 22 is not particularly limited as long as it can move the light source 14, and can be configured using gears, belt drives, or the like.

[0063] The moving device 22 may be configured to move the light source 14 in the thickness direction of the light-transmitting base material 16 as indicated by the arrow X in FIG. 1. The moving device 22 may also be configured to move the light source 14 in the lateral direction along the one side of the light-transmitting base material 16 as indicated by the arrow Y in FIG. 2. Alternatively, the moving device 22 may be configured to move the light source 14 in an oblique direction with respect to the side surface 16C of the light-transmitting base material 16, that is, to move in the thickness direction X while moving in the lateral direction Y.

[0064] Note that although not shown, the light-emitting module 10 may be configured to include other components such as a frame in addition to electrical components such as wiring to the light source 14, a power source, and a control device.

[0065] In the first embodiment configured as described above, when light enters from the side surface 16C of the light-transmitting base material 16 forming the main body of the light guide plate 12, the light is confined within the light-transmitting base material 16 by total reflection and spreads within the light-transmitting base material 16. At this time, as shown in FIG. 6, the light is scattered by the light-scattering particles in the light-scattering layer 20, and light is generated that enters the light-transmitting convex layer 18 at an angle (less than the critical angle) close to perpendicular to the surface 16A of the light-transmitting base material 16. The light that has entered the light-transmitting convex layer 18 is emitted to the outside through the light-emitting surface 18B. At this time, since the light-emitting surface 18B is formed by a curved surface, the light is diffused by the lens effect, and an angular dependence is obtained in which the appearance of the light emission varies depending on the viewing angle. Further, as the light-transmitting convex layer 18 that emits light, a plurality of types having different sizes and / or heights are mixed, so that a portion with locally high luminance or a sparkle can be expressed. Therefore, it is possible to realize a crystal-like sparkle of light and the movement of light due to angular dependence similar to that of a real crystal, and to impart a high-class feeling.

[0066] In the first embodiment, by moving the light source 14 with the moving device 22, the emission direction can be changed. Therefore, it is possible to make the light move without changing the viewing angle, and in combination with changing the viewing angle, the movement of the light can be emphasized. Further, by moving the light source 14, it is also possible to realize an illumination effect as if the light is flowing.

[0067] In the first embodiment, due to light scattering in the light scattering layer 20 and light reflection in the light-transmitting convex layer 18, some light may be emitted from the back side of the light guide plate 12. That is, while the front side of the light guide plate 12 provided with the light-transmitting convex layer 18 is the main light-emitting surface, the back side of the light guide plate 12 provided with the light scattering layer 20 can be made into a secondary light-emitting surface with less light quantity than the main light-emitting surface. Therefore, the light guide plate 12 can also be used as a partition (partition) with light-emitting surfaces on both the front and back sides.

[0068] (Second Embodiment) FIG. 9 is an enlarged cross-sectional view of a main part showing a light guide plate 30 of a light-emitting module according to the second embodiment. The light guide plate 30 of the second embodiment is different from the light guide plate 12 of the first embodiment in that a light-transmitting resin layer 32 is provided as a protective layer on the one surface (in this example, the surface 16A) of the light-transmitting base material 16.

[0069] The light-transmitting resin layer 32 is a resin layer having light-transmitting property provided to protect the light-transmitting base material 16 which is a high refractive index layer. In this example, it is made of a resin having a refractive index lower than that of the light-transmitting base material 16. The refractive index (absolute refractive index) of the light-transmitting resin layer 32 is not particularly limited as long as it is lower than that of the light-transmitting base material 16, and may be, for example, 1.35 to 1.65, or 1.40 to 1.55.

[0070] The light-transmitting resin layer 32 may be colorless and transparent or colored and transparent. Examples of the resin for forming the light-transmitting resin layer 32 include acrylic resins such as polymethyl methacrylate (PMMA) and urethane acrylate resin; styrene resins such as polystyrene resin, acrylonitrile-styrene copolymer resin (AS resin), and acrylonitrile-styrene-butadiene copolymer resin (ABS resin); polyolefin resins such as polyethylene and polypropylene; or blends of two or more of these.

[0071] The thickness of the light-transmitting resin layer 32 is not particularly limited and may be, for example, 10 to 100 μm or 20 to 50 μm.

[0072] In the second embodiment, the light-transmitting resin layer 32 is provided in contact with the entire surface 16A of the light-transmitting base material 16. A plurality of light-transmitting convex layers 18 are provided in contact with the surface of the light-transmitting resin layer 32. That is, in the second embodiment, the plurality of light-transmitting convex layers 18 are provided via the light-transmitting resin layer 32 with respect to the one surface (surface 16A) of the light-transmitting base material 16. Therefore, in this case, the surface of the light-transmitting resin layer 32 is the reference surface for providing the light-transmitting convex layers 18.

[0073] The method for forming the light-transmitting resin layer 32 is not particularly limited, and examples include known coating methods such as spraying, dipping, spin coating, and bar coating, and printing methods such as inkjet printing and screen printing.

[0074] In the second embodiment, the translucent convex layer 18 is not directly provided on the translucent base material 16, but is provided via a translucent resin layer 32. The translucent resin layer 32 has a refractive index smaller than that of the translucent base material 16. However, since the light emitted to the outside through the translucent convex layer 18 is light that travels toward the surface 16A at an angle less than the critical angle scattered by the light scattering layer 20 on the back surface side, the decrease in luminance due to the provision of the translucent resin layer 32 is small. Further, when there is no translucent resin layer 32, if the surface 16A of the translucent base material 16 is scratched, there is a risk of light leakage from that portion. However, by providing the translucent resin layer 32 with a small refractive index, light leakage from that portion is less likely to occur even if it is scratched.

[0075] Regarding the second embodiment, the other configurations and effects are the same as those of the first embodiment, and the description thereof is omitted.

[0076] (Third Embodiment) FIG. 10 is an enlarged cross-sectional view of a main part showing a light guide plate 40 of a light-emitting module according to the third embodiment. The light guide plate 40 of the third embodiment differs from that of the second embodiment in the configuration of a translucent resin layer 42 as a protective layer provided on the surface 16A of the translucent base material 16.

[0077] In the third embodiment, as in the first embodiment, the translucent convex layer 18 is directly provided on the surface 16A of the translucent base material 16, and a translucent resin layer 42 is provided on the portion of the surface 16A other than the translucent convex layer 18. By directly providing the translucent convex layer 18 on the surface 16A of the translucent base material 16 in this way, it is possible to eliminate the possibility of a decrease in luminance due to the interposition of the translucent resin layer 32 as in the second embodiment. However, in terms of ease of manufacturing, the second embodiment is more preferable.

[0078] Regarding the third embodiment, the other configurations and effects are the same as those of the second embodiment, and the description thereof is omitted.

[0079] (Fourth Embodiment) FIG. 11 is a schematic cross-sectional view of a light-emitting module 50 according to the fourth embodiment. The light-emitting module 50 according to the fourth embodiment is different from the light-emitting module 10 according to the first embodiment in that the light guide plate 52 thereof includes a coating resin layer 54 that covers the light scattering layer 20.

[0080] The light guide plate 52 of the fourth embodiment has a light-transmitting base material 16, a plurality of light-transmitting convex layers 18, and a plurality of light scattering layers 20 similar to the light guide plate 12 of the first embodiment, and on top of that, a plurality of coating resin layers 54 that cover the plurality of light scattering layers 20 are provided.

[0081] The coating resin layer 54 is made of a resin having light-transmitting properties, and may be colorless and transparent or colored and transparent. The coating resin layer 54 is a resin layer that does not contain light-scattering particles. Examples of the resin for forming the coating resin layer 54 include the same resins as those of the light-transmitting convex layer 18, that is, the above-mentioned acrylic resin, styrene resin, polyolefin resin, or a blend of two or more of these.

[0082] The refractive index (absolute refractive index) of the coating resin layer 54 is not particularly limited, and may be higher than that of the light-transmitting base material 16, lower than that of the light-transmitting base material 16, or the same value. The refractive index of the coating resin layer 54 may be, for example, 1.35 to 1.65, or 1.40 to 1.55.

[0083] A plurality of coating resin layers 54 are provided so as to cover only each of the plurality of light scattering layers 20 provided on the other surface (back surface 16B) of the light-transmitting base material 16. However, the coating resin layer 54 is formed to have a portion that surrounds the periphery of each light scattering layer 20 and contacts the light-transmitting base material 16 so as to cover the entire surface of each light scattering layer 20. Since the coating resin layer 54 is formed larger than the light scattering layer 20 in this way, when the interval between the light scattering layers 20 is narrow as shown in FIG. 11, a plurality of coating resin layers 54 may be formed continuously.

[0084] As shown in Fig. 11, the surface 54A of the coating resin layer 54 is formed by a curved surface. The surface 54A of the coating resin layer 54 is the surface that forms the interface between the coating resin layer 54 and air. The surface 54A may be formed only by a curved surface, or may partially include a flat surface. Preferably, the surface 54A is mainly formed by a curved surface, and more preferably, the area ratio occupied by the curved surface in the surface 54A is 80% or more.

[0085] Similar to the light-transmitting convex layer 18, the surface 54A of the coating resin layer 54 is formed by one or more curved surfaces, and may be formed in a convex lens shape consisting of a single curved convex surface as shown in Fig. 11. The coating resin layers 54 having the surface 54A consisting of such a single curved convex surface may be provided independently, or a plurality of coating resin layers 54 may be formed by connecting them as described above. Further, similar to the light-transmitting convex layer 18 shown in Fig. 5, by providing convex portions in the shape of plano-convex lenses in two layers, the surface 54A having a plurality of curved surfaces may be obtained.

[0086] Preferably, the coating resin layer 54 is formed in a convex shape that is curved and higher from the periphery toward the center. In plan view, it is preferably circular, but is not limited thereto, and may be rectangular or triangular in plan view, and various shapes can be adopted.

[0087] The coating resin layer 54 can be formed, for example, by inkjet printing. By adjusting the viscosity of the ink, a coating resin layer 54 having the surface 54A formed by the above-described curved surface can be formed.

[0088] Since the coating resin layer 54 is provided so as to cover each light-scattering layer 20, similar to the light-scattering layer 20, a plurality of types of coating resin layers 54 having different sizes and / or heights may be mixed and provided. For this purpose, for example, a mode in which a plurality of gradations of coating resin layers 54 are set according to the size and these plurality of gradations of coating resin layers 54 are mixed and provided can be mentioned. As an example, when the coating resin layer 54 is formed by inkjet printing, a plurality of gradations may be set by the number (drop number) of droplets (ink particles) ejected from the nozzles.

[0089] According to the fourth embodiment, by providing a coating resin layer 54 that coats the light scattering layer 20 and forming its surface 54A as a curved surface, the light scattered by the light scattering layer 20 can be diffused by the lens effect in the coating resin layer 54. Therefore, a greater difference in luminance can be produced on the surface side of the light guide plate 52, and the range of design expression can be widened. Also, on the back side of the light guide plate 52, it is possible to emit shiny light. Therefore, for example, when the light guide plate 52 is used as a partition (partition), it is possible to obtain a design expression of light with a shiny effect on both its front and back surfaces.

[0090] Regarding the fourth embodiment, other configurations and operational effects are the same as those of the first embodiment, and the description thereof is omitted.

[0091] (Other Embodiments) An additional layer may be formed on the light guide plates 12, 30, 40, 52 in the above embodiments. For example, a resin layer with an extremely low refractive index may be provided on the back side of the light guide plates 12, 30, 40, 52, or a paint that forms a metal mirror surface may be applied to the back side to provide a mirror layer.

[0092] In the above embodiments, for each light scattering layer 20 provided on the back surface 16B side of the translucent base material 16, a translucent convex layer 18 having a light emitting surface 18B formed as a curved surface is provided on the surface 16A side. However, it is not necessary to form a curved translucent convex layer 18 corresponding to all the light scattering layers 20. For example, for some of the light scattering layers 20, a translucent resin layer having a flat cross-sectional shape of the light emitting surface that is not formed by a curved surface may be provided on the surface 16A side corresponding thereto. Alternatively, for some of the light scattering layers 20, it may not be necessary to provide a corresponding resin layer on the surface 16A side.

[0093] Each configuration in the above embodiments can be combined as appropriate. For example, in the light guide plate 52 of the fourth embodiment, the light-transmitting resin layer 32 of the second embodiment or the light-transmitting resin layer 42 of the third embodiment may be provided. Regarding the light-emitting convex layer 18 on the surface side, it is preferable that its light-emitting surface 18B is not covered with other resin layers.

Example

[0094] [Example 1] As the base material, "Technoloy (registered trademark) C003" manufactured by Sumika Chemical Sales Co., Ltd. was used (a rectangular sheet with a short side length of 180 mm and a long side length of 400 mm). The base material is a two-layer resin sheet in which a PMMA layer (thickness 0.03 mm, refractive index 1.49) corresponding to the light-transmitting resin layer 32 (protective layer) is laminated on the surface 16A of a polycarbonate layer (thickness 1.97 mm, refractive index 1.587) corresponding to the light-transmitting base material 16.

[0095] The formulations of the light-scattering layer ink and the light-emitting convex layer ink are as shown in Tables 1 and 2 below.

[0096]

Table 1

[0097]

Table 2

[0098] On the back surface of the above base material (the back surface 16B of the light-transmitting base material 16), after applying the light-scattering layer ink using a serial type inkjet printer, ultraviolet rays were immediately irradiated using an ultraviolet lamp to cure the ink, and a plurality of circular light-scattering layers 20 in plan view were formed. The viscosity of the ink (25 °C) was 12.2 mPa·s. The printing conditions were: head heating temperature: 35 °C, nozzle diameter: 20 μm, applied voltage: 21 V, pulse width: 15 μs, resolution: 300 dpi. The ultraviolet irradiation conditions were: lamp type: metal halide lamp, lamp output: 100 W, irradiation time: 0.5 s, irradiation times: 4 times, irradiation distance: 5 mm, integrated light amount: 200 mJ / cm 2It was set as follows.

[0099] At that time, as the plurality of types of light-scattering layers 20, the following 1st to 7th gradations were set according to the number of droplets ejected from the nozzle. · 1st gradation: 1 droplet, diameter 20 to 25 μm · 2nd gradation: 2 droplets, diameter 25 to 30 μm · 3rd gradation: 3 droplets, diameter 30 to 35 μm · 4th gradation: 4 droplets, diameter 40 to 50 μm · 5th gradation: 5 droplets, diameter 55 to 65 μm · 6th gradation: 6 droplets, diameter 70 to 80 μm · 7th gradation: 7 droplets, diameter 80 to 100 μm

[0100] Next, on the surface of the base material (the surface of the translucent resin layer 32), using a serial type inkjet printer, after applying the ink for the translucent convex layer, immediately irradiate with ultraviolet rays using an ultraviolet lamp to cure the ink and form a plurality of plano-convex lens-shaped translucent convex layers 18 in a circular shape in plan view. The translucent convex layers 18 were provided at the same positions as the light-scattering layers 20 so as to overlap with the light-scattering layers 20 with the base material interposed therebetween. The viscosity of the ink (at 25°C) was 15.0 mPa·s. The printing conditions were: head heating temperature: 35°C, nozzle diameter: 20 μm, applied voltage: 22 V, pulse width: 15 μs, resolution: 300 dpi. The ultraviolet irradiation conditions were: lamp type: metal halide lamp, lamp output: 160 W, irradiation time: 0.5 s, irradiation times: 8 times, irradiation distance: 40 mm, integrated light quantity: 640 mJ / cm 2 It was set as follows. The refractive index of the translucent convex layer 180 was 1.458.

[0101] At that time, as the plurality of types of translucent convex layers 18, the following 1st to 7th gradations were set according to the number of droplets ejected from the nozzle. · 1st gradation: 1 droplet, diameter 20 to 25 μm, height 1 to 2 μm · 2nd gradation: 2 droplets, diameter 25 to 30 μm, height 3 to 4 μm · 3rd gradation: 3 droplets, diameter 30 to 35 μm, height 5 to 6 μm · 4th gradation: 4 droplets, diameter 40 to 45 μm, height 7 to 8 μm ·5 - tone: 5 drops, diameter 45 - 50 μm, height 9 - 10 μm ·6 - tone: 6 drops, diameter 55 - 65 μm, height 11 - 13 μm ·7 - tone: 7 drops, diameter 70 - 90 μm, height 14 - 17 μm

[0102] After setting the light - transmitting convex layer 18 and the light - scattering layer 20 to the same number of tones in this way, the light - transmitting convex layers 18 among the plurality of light - transmitting convex layers 18 and the light - scattering layer 20 corresponding to the light - transmitting convex layer 18 are arranged so as to have the same tone. That is, for example, for the light - transmitting convex layer 18 of "3 - tone", the light - scattering layer 20 of "3 - tone" is provided at a position overlapping with it across the light - transmitting base material 16.

[0103] A part of the arrangement example of the plurality of types of light - transmitting convex layers 18 is shown in FIG. 12. In FIG. 12, one side of the grid is about 85 μm, and the arrangement pattern of the light - transmitting convex layer 18 in a square region with one side of about 0.85 mm is shown as a plan view of the light - transmitting convex layer 18 in FIG. 12(A), and the tone is indicated by numbers in FIG. 12(B). The arrangement example of the plurality of types of light - scattering layers 20 is the same as the arrangement example of the light - transmitting convex layer 18, with a one - to - one correspondence. Note that the blank grid means a 0 - tone part where the light - transmitting convex layer 18 is not provided.

[0104] The light - guide plate obtained as above corresponds to the light - guide plate 30 of the second embodiment shown in FIG. 9. When an LED is attached to the side surface on the short - side of the light - guide plate and the LED is lit to make light enter from the side surface, light is emitted from the light - transmitting convex layer 18 on the surface side, and there are locally high - luminance portions or glitters. Also, it had an angle - dependence in which the appearance of light emission differed depending on the viewing angle. Therefore, it was possible to realize the crystal - like glitter of light and the movement of light due to the angle - dependence, and a high - class design was obtained.

[0105] [Example 2] In the light guide plate obtained in Example 1, a plurality of coating resin layers 54 that respectively cover the plurality of light scattering layers 20 were provided. The coating resin layer 54 was formed by applying the ink for the light-transmitting convex layer of Example 1 to the surface of the light scattering layer 20 using a serial type inkjet printer, and then immediately irradiating ultraviolet rays using an ultraviolet lamp to cure the ink. The printing conditions, ultraviolet irradiation conditions, and gradation settings of the coating resin layer 54 were the same as those of the light-transmitting convex layer 18 in Example 1. The coating resin layer 54 had a convex lens-shaped surface that was circular in plan view and equivalent to the light-transmitting convex layer 18 on the surface side.

[0106] The light guide plate thus obtained has a configuration that combines the above-described fourth embodiment and second embodiment. When an LED was attached to the side surface on the short side of the light guide plate and the LED was lit to make light enter from the side surface, light was emitted from the light-transmitting convex layer 18 on the surface side, and there were locally high-brightness portions and glitters. Also, it had an angle dependence in which the appearance of light emission differed depending on the viewing angle. Compared with the light guide plate of Example 1, the difference in brightness by part was further emphasized, and it was excellent in the design effect on the surface side. Also, light emission with a glitter effect was observed on the back side. Therefore, a design expression of light with a glitter effect was obtained not only on the surface side but also on the back side of the light guide plate.

[0107] Note that various numerical ranges described in the specification can arbitrarily combine their upper limit values and lower limit values, and all of these combinations are described in the specification as preferred numerical ranges. Also, the description of the numerical range of "X to Y" means X or more and Y or less.

[0108] Although several embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Industrial Applicability

[0109] The uses of the light guide plate and the light emitting module according to this embodiment are not particularly limited. For example, they can be used for various vehicle interior parts such as automotive interior materials like instrument panels and inner door materials of automobiles, and the housings of various electrical products such as home appliances and communication devices.

Explanation of Reference Numerals

[0110] 10, 50... light emitting module, 12, 30, 40, 52... light guide plate, 14... light source, 16... light transmissive base material, 18... light transmissive convex layer, 20... light scattering layer, 32, 42... light transmissive resin layer, 54... coating resin layer

Claims

1. A light-transmissive base material having light-transmittance; A plurality of light-transmissive convex layers made of a resin having light-transmittance and not containing light-scattering particles, provided convexly on either the front surface or the back surface of the light-transmissive base material, and having a light-emitting surface formed by a curved surface; A plurality of light-scattering layers made of a resin containing light-scattering particles, provided on the other surface of the light-transmissive base material facing the one surface so as to overlap with the plurality of light-transmissive convex layers with the light-transmissive base material interposed therebetween; A light guide plate comprising: A light guide plate in which a plurality of types of the light-transmissive convex layers having different sizes and / or heights are mixed so that the luminance is locally increased.

2. In the light guide plate according to claim 1, the area ratio occupied by the curved surface in each light-emitting surface of the plurality of light-transmissive convex layers is 80% or more.

3. In the light guide plate according to claim 1 or 2, the overlapping amount of each light-transmissive convex layer of the plurality of light-transmissive convex layers and the light-scattering layer corresponding to the light-transmissive convex layer is 30% or more of the area of the light-scattering layer as viewed from a direction perpendicular to the surface of the light-transmissive base material.

4. Further comprising a light-transmissive resin layer having light-transmittance provided on the one surface of the light-transmissive base material, and the plurality of light-transmissive convex layers are provided on the one surface of the light-transmissive base material via the light-transmissive resin layer. The light guide plate according to any one of claims 1 to 3.

5. Further comprising a plurality of coating resin layers having light-transmittance for coating the plurality of light-scattering layers respectively, and the surface of each coating resin layer is formed by a curved surface. The light guide plate according to any one of claims 1 to 4.

6. A light-emitting module comprising the light guide plate according to any one of claims 1 to 5 and a light source capable of incident light on a side surface of the light-transmissive base material.

7. The light-emitting module according to claim 6, further comprising a moving device for moving the light source along the side surface of the light-transmissive base material.

Images