JP7515058B2 - Light guide plate and light guide plate system - Google Patents

Description

The present invention relates to a light guide plate and a light guide plate system using the light guide plate.

Conventionally, an edge-light type lighting device is known as a light guide plate system that uses a light guide plate. An edge-light type lighting device includes a light guide plate and a light source arranged opposite the end face of the light guide plate.

As an example of this type of lighting device, Patent Document 1 discloses a surface light source device that includes a plate-shaped light guide plate with multiple concave prisms formed on its main surface and a light source disposed opposite the end face of the light guide plate.

In such lighting devices, light emitted from the light source enters the end face of the light guide plate, is guided inside the light guide plate, is reflected by the prisms, and is emitted to the outside of the light guide plate from the main surface opposite the main surface on which the prisms are formed.

Japanese Patent Application Laid-Open No. 11-219609

In a light guide plate system using a light guide plate with a concave prism formed on the main surface, in order to suppress glare, the light distribution may be reduced by reducing the amount of light emitted in the direction perpendicular to the main surface of the light guide plate (front direction). In this case, for example, it is possible to reduce the control angle of the concave prism formed on the light guide plate and make the inclination angle of the inner surface of the concave prism gentle. In this way, it is possible to reduce the amount of light emitted in the direction perpendicular to the main surface of the light guide plate. In addition, by reducing the control angle of the concave prism, it is possible to increase the amount of light that travels toward the end face opposite the end face on the side where the light source is located, relative to the direction perpendicular to the main surface of the light guide plate. For example, if the light source is located above the light guide plate, it is possible to increase the amount of light that travels diagonally downward. Furthermore, in this case, by making the prism horizontally long, it is possible to increase the amount of light that is emitted in the left and right directions of the light guide plate, so that a wide light distribution can be realized.

However, in a light guide plate system using a light guide plate with a small prism control angle, if dust or other foreign matter adheres to the main surface of the light guide plate, if foreign matter gets mixed in the light guide plate, or if the main surface of the light guide plate is scratched, the foreign matter or scratches become noticeable, resulting in a decrease in the appearance quality of the light guide plate when light is emitted from the light guide plate.

The present invention has been made to solve these problems, and aims to provide a light guide plate and a light guide plate system that can suppress deterioration in the appearance quality of the light guide plate when light is emitted from the light guide plate, even if the control angle of the prism is reduced.

One aspect of the light guide plate according to the present invention is a light guide plate having a first end surface on which light emitted from a light source is incident, a first main surface from which the light incident from the first end surface exits, and a second main surface facing away from the first main surface, and further comprising a plurality of first concave prisms formed two-dimensionally on the second main surface, and one or more second concave prisms formed to overlap at least one of the plurality of first prisms, and the control angle of the second prism is larger than the control angle of the first prism.

One aspect of the light guide plate system according to the present invention includes the above-mentioned light guide plate and a light source that emits light to be incident on the first end surface of the light guide plate.

The present invention makes it possible to prevent deterioration in the appearance quality of the light guide plate when light is emitted from the light guide plate.

3A and 3B are diagrams illustrating a lighting state of the lighting device according to the first embodiment. 2 is an enlarged cross-sectional view of a main portion of the lighting device according to the first embodiment; FIG. 2A and 2B are diagrams illustrating configurations of a light guide plate and a light source in the lighting device according to the first embodiment. 2 is a partial cross-sectional view of the light guide plate according to the first embodiment. FIG. 5A to 5C are diagrams for explaining the optical effects of a first prism and a second prism in the light guide plate according to the first embodiment. FIG. 1 is a diagram showing a configuration of a lighting device according to a first comparative example. 11A and 11B are diagrams for explaining the optical action of a light guide plate in the lighting device of Comparative Example 1. 13A and 13B are diagrams for explaining the optical action of a light guide plate in the lighting device of Comparative Example 2. 5A to 5C are diagrams for explaining the optical action of a light guide plate in the lighting device according to the first embodiment. 13A and 13B are diagrams illustrating configurations of a light guide plate and a light source in an illumination device according to a first modification of the first embodiment. 10 is a partial cross-sectional view of a light guide plate according to a first modified example of the first embodiment. FIG. 13 is a diagram showing a configuration of a light guide plate and a light source in an illumination device according to a second modification of the first embodiment. FIG. 11 is a partial cross-sectional view of a light guide plate according to a second modification of the first embodiment. FIG. 13 is a diagram showing a configuration of a light guide plate and a light source in an illumination device according to a third modification of the first embodiment. FIG. 13 is a partial cross-sectional view of a light guide plate according to a third modified example of the first embodiment. FIG. 11A and 11B are diagrams illustrating configurations of a light guide plate and a light source in an illumination device according to a second embodiment. FIG. 11 is a partial cross-sectional view of a light guide plate according to a second embodiment. 13A and 13B are diagrams illustrating configurations of a light guide plate and a light source in an illumination device according to a third embodiment. FIG. 11 is a partial cross-sectional view of a light guide plate according to a third embodiment. 13A and 13B are diagrams illustrating the configuration of a light guide plate and a light source in a lighting device according to a fourth embodiment. FIG. 11 is a partial cross-sectional view of a light guide plate according to a fourth embodiment. FIG. 13 is a partial cross-sectional view of a light guide plate according to a modified example of the fourth embodiment. 13A and 13B are diagrams illustrating the configuration of a light guide plate and a light source in a lighting device according to a fifth embodiment. 13A and 13B are diagrams illustrating the configuration of a light guide plate and a light source in a lighting device according to a sixth embodiment. FIG. 11 is a partial cross-sectional view of a light guide plate according to a first modified example. FIG. 11 is a partial cross-sectional view of a light guide plate according to a second modified example. FIG. 11 is a partial cross-sectional view of a light guide plate according to a third modified example.

The following describes embodiments of the present invention. Note that each of the embodiments described below shows a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, arrangement positions of the components, and connection forms shown in the following embodiments are merely examples and are not intended to limit the present invention. Therefore, among the components in the following embodiments, components that are not described in the independent claims are described as optional components.

In addition, each figure is a schematic diagram and is not necessarily an exact illustration. In each figure, the same reference numerals are used for substantially the same configuration, and duplicate explanations may be omitted or simplified. In the following embodiments, expressions such as "approximately" also include manufacturing errors and dimensional tolerances.

(Embodiment 1)
First, a schematic configuration of a lighting device 1 according to embodiment 1 will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a diagram showing a lighting state of the lighting device 1 according to embodiment 1. Fig. 2 is an enlarged cross-sectional view of a main part of the lighting device 1. In Fig. 1 and Fig. 2, the vertical direction is defined as a first direction D1, and the left-right direction (horizontal direction) perpendicular to the vertical direction is defined as a second direction D2.

As shown in FIG. 1, the lighting device 1 is an outdoor light that emits illumination light to illuminate a passageway or the like, and is installed in an upright position on the ground. Specifically, the lighting device 1 is a pole light having a long rectangular prism shape, and comprises a long main body 2 and a light-emitting unit 3 provided on the top of the main body 2. The light-emitting unit 3 is provided, for example, at a position 30 cm to 90 cm above the ground. Note that the shape of the lighting device 1 need not be a rectangular prism, but may be a cylinder, etc.

The lighting device 1 according to this embodiment is a low pole light that irradiates illumination light downward from the light-emitting unit 3. By irradiating illumination light downward from the light-emitting unit 3 in this way, it is possible to prevent people passing by around the lighting device 1 from feeling dazzled, compared to when illumination light is irradiated in the front direction of the light-emitting unit 3 or upward from the light-emitting unit 2. The lighting device 1 irradiates illumination light to illuminate the feet of passersby, for example.

Furthermore, the lighting device 1 emits illumination light that spreads in the left-right direction of the light-emitting unit 3 (second direction D2 in FIG. 1). In other words, the light distribution of the lighting device 1 is a wide light distribution in which the illumination area spreads in the left-right direction of the lighting device 1. For example, by spreading the illumination light along the aisle direction, it is possible to brightly illuminate the front-rear direction along the aisle direction. Note that in FIG. 1, the illumination area of the illumination light of the lighting device 1 is indicated by dotted hatching.

The lighting device 1 is an example of a light guide plate system using a light guide plate, and includes a light guide plate 10 and a light source 20 as shown in FIG. 2. In this embodiment, the lighting device 1 includes a light emitting unit 3 including a light guide plate 10, a light source 20, a reflector 30, and a translucent panel 40. The light guide plate 10, the light source 20, the reflector 30, and the translucent panel 40 may be directly fixed to the main body 2, or may be indirectly fixed to the main body 2 via a holder or the like (not shown). The main body 2 is an outer casing member that forms the outer casing of the lighting device 1, and is a housing that stores and holds the light guide plate 10, the light source 20, the reflector 30, and the translucent panel 40. The main body 2 is a rigid body made of, for example, metal or resin.

Below, each component of the light-emitting section 3 in the lighting device 1 will be described in detail using Figs. 3 and 4 while referring to Figs. 1 and 2. Fig. 3 is a diagram showing the configuration of the light guide plate 10 and the light source 20 in the lighting device 1 according to the first embodiment. Fig. 4 is a partial cross-sectional view of the light guide plate 10. In Fig. 3, (a) shows a side view of the light guide plate 10 and the light source 20, and (b) shows a cross-sectional view taken along line IIIB-IIIB in (a). In Fig. 4, (a), (b), and (c) are cross-sectional views taken along lines IVA-IVA, IVB-IVB, and IVC-IVC in Fig. 3, respectively.

First, the light guide plate 10 will be described. The light guide plate 10 is an optical member having a function of guiding light. In this embodiment, the light guide plate 10 is a flat light guide having a rectangular shape in a plan view. The light guide plate 10 is a light-transmitting member having light-transmitting properties, and is made of a light-transmitting material. The light guide plate 10 is made of a light-transmitting resin material such as an acrylic resin such as PMMA (polymethyl methacrylate) resin or a polycarbonate resin. The light guide plate 10 may be made of a transparent resin material having a high transmittance so that the other side can be seen through. In this embodiment, the light guide plate 10 is made of a transparent plate made of an acrylic resin. The light guide plate 10 is not limited to a transparent resin plate made of a resin material, and may be a glass plate made of transparent glass.

As shown in FIG. 3, the light guide plate 10 has a first end face 10a and a second end face 10b facing away from the first end face 10a. The first end face 10a and the second end face 10b are side faces of the light guide plate 10. Since the light guide plate 10 is plate-shaped, each of the first end face 10a and the second end face 10b is elongated. In this embodiment, each of the first end face 10a and the second end face 10b is elongated and generally rectangular.

In this embodiment, the pair of first end faces 10a and second end faces 10b face each other in a direction perpendicular to the thickness direction of the light guide plate 10. That is, the second end face 10b is located on the opposite side to the first end face 10a. As an example, the first end face 10a and the second end face 10b are each flat and substantially parallel. Note that the first end face 10a is not limited to being flat, and may include a concavely curved surface or a concavely recessed surface for each light emitting element 22 of the light source 20 in order to efficiently allow light from the light source 20 to be incident on the light guide plate 10. The second end face 10b is also not limited to being flat. For example, the second end face 10b may be an inclined surface or an uneven surface.

The first end surface 10a is a light incident surface into which light emitted from the light source 20 is incident. Specifically, the first end surface 10a faces the light source 20. In other words, the first end surface 10a is the surface on the light source 20 side, and the second end surface 10b is the surface on the opposite side from the light source 20 side.

The light guide plate 10 further has a first main surface 10c and a second main surface 10d facing away from the first main surface 10c. The first main surface 10c and the second main surface 10d are surfaces that face each other when the light guide plate 10 is viewed from the front. In this embodiment, the first main surface 10c is a front surface that is the front side surface of the lighting device 1, and the second main surface 10d is a rear surface that is the rear side surface of the lighting device 1. The first main surface 10c and the second main surface 10d face each other in the thickness direction of the light guide plate 10. In this embodiment, the first main surface 10c and the second main surface 10d are each flat and substantially parallel. Note that the light guide plate 10 has a substantially rectangular shape when viewed from the front, and therefore the first main surface 10c and the second main surface 10d are substantially rectangular in shape.

The first main surface 10c is a light exit surface from which light incident from the first end surface 10a exits. Therefore, the first main surface 10c becomes a light emitting surface that emits light in a pseudo manner by emitting light guided within the light guide plate 10 to the outside. In this embodiment, the first main surface 10c is a light extraction surface for extracting light guided within the light guide plate 10.

The second main surface 10d is a light control surface that controls the light incident from the first end surface 10a. In this embodiment, the second main surface 10d has a light reflection structure for reflecting the light that is incident from the first end surface 10a and guided inside the light guide plate 10.

3 and 4, a plurality of concave first prisms 11 (first concave prisms) are formed on the second main surface 10d as a light reflection structure. The plurality of first prisms 11 are formed two-dimensionally. Specifically, when the light guide plate 10 is viewed from the direction perpendicular to the main surface of the second main surface 10d (front direction), the plurality of first prisms 11 are arranged along a first direction D1, which is a direction from one of the first end surface 10a and the second end surface 10b to the other, and along a second direction D2, which is approximately perpendicular to the first direction. In this embodiment, the first direction D1 is a vertical direction and is the optical axis direction of the light source 20. The second direction D2, which is perpendicular to the first direction D1, is a horizontal direction (left-right direction) and is perpendicular to the optical axis of the light source 20. The plurality of first prisms 11 may be formed over the entire second main surface 10d, or may be formed partially.

As shown in (b) and (c) of FIG. 3 and FIG. 4, a concave second prism 12 (second concave prism) is further formed on the second main surface 10d as a light reflecting structure. The second prism 12 is formed so as to overlap at least one of the multiple first prisms 11. In this embodiment, one second prism 12 is formed on one first prism 11. In this case, it is preferable that the center of one second prism 12 overlaps with the center of the first prism 11. Note that, although the second prism 12 is formed on all first prisms 11, this is not limited to the above.

In this way, the second prism 12 is an additional prism formed in addition to the first prism 11. In other words, the first prism 11 is a main prism that determines the main light distribution of the light emitted from the light guide plate 10, whereas the second prism 12 is a sub-prism that finely adjusts the light distribution of the light guide plate 10 generated by the first prism 11.

In addition, in this embodiment, when the second main surface 10d is viewed from the front, the second prism 12 is located inside the first prism 11. In other words, when the second main surface 10d is viewed from the front, the second prism 12 is contained within the first prism 11. Therefore, when the second main surface 10d is viewed from the front, the opening area of the second prism 12 is smaller than the opening area of the first prism 11.

For example, when the second main surface 10d is viewed from the front, the total opening area of the second prisms 12 in one first prism 11 is 1/10 or less of the opening area of the first prism 11. In this case, the total opening area of the second prisms 12 in one first prism 11 is preferably 1/50 or less of the opening area of the first prism 11, and more preferably 1/100 or less.

The first prism 11 is a reflecting prism and has a first reflecting surface 11a (first light control surface) that reflects the light traveling in the light guide plate 10 toward the first main surface 10c. Specifically, the first reflecting surface 11a is approximately half of the inner surface of the first prism 11 on the light source 20 side. In this embodiment, the angle θ1 between the first inner surface, which is the first reflecting surface 11a, of the inner surfaces of the first prism 11 and the second main surface 10d is the same as the angle θ1' between the second inner surface 11a' of the inner surface of the first prism 11 opposite the light source 20 side and the second main surface 10d, but is not limited to this. In other words, the angle θ1 and the angle θ1' may be different. In this case, in order to reduce the leakage light to the back side (second main surface 10d side) of the light guide plate 10 and increase the ratio of the control light to the front side (first main surface 10c side), it is preferable that the angle θ1' is greater than the angle θ1.

The second prism 12 is also a reflecting prism and has a second reflecting surface 12a (second light control surface) that reflects the light traveling inside the light guide plate 10 toward the first main surface 10c. Specifically, the second reflecting surface 12a is approximately half of the inner surface of the second prism 12 on the light source 20 side.

Each of the first prism 11 and the second prism 12 is a minute recess processed into a predetermined shape. The first prism 11 and the second prism 12 are microprisms of micro-order size. The first prism 11 and the second prism 12 can be formed by performing laser processing or cutting processing on the second main surface 10d of the flat light guide plate 10. In addition, the light guide plate 10 having the first prism 11 and the second prism 12 can also be produced by molding using a metal mold.

In this embodiment, the first prism 11 is a long groove having an elongated shape in the second direction D2 (the direction intersecting with the optical axis of the light source 20), which is the left-right direction. In other words, the first prism 11 is a long groove prism. By making the first prism 11, which is the main prism, into such a shape, it is possible to increase the amount of light emitted from the light guide plate 10 in the second direction D2 (the left-right direction of the light guide plate 10), and a wide light distribution can be realized. In other words, as shown in FIG. 1, the light distribution of the lighting device 1 can be made wide. Specifically, the opening shape of the first prism 11 is a horizontally elongated racetrack shape when the second main surface 10d is viewed from the front (i.e., when the second main surface 10d is viewed from the direction perpendicular to the main surface). Note that, when the second main surface 10d is viewed from the front, the opening shape of the second prism 12 is a circle. In this case, it is preferable that the diameter of the opening of the second prism 12 is smaller than the width of the opening of the first prism 11.

As shown in (b) and (c) of FIG. 4, the second prism 12 is formed so as to make the bottom of the first prism 11 even deeper. Specifically, the second prism 12 is formed so as to protrude in a protruding manner in the depth direction from the bottom of the first prism 11. Therefore, in the portion where the first prism 11 and the second prism 12 overlap, in a cross-sectional view of the light guide plate 10, the first reflecting surface 11a of the first prism 11 is formed on the second main surface 10d side, and the second reflecting surface 12a of the second prism 12 is formed in the depth direction continuous with the first reflecting surface 11a.

As shown in FIG. 4A, in the portion of the first prism 11 where the second prism 12 does not overlap, the cross-sectional shape of the first prism 11 cut along the first direction D1 is approximately triangular. Therefore, the first reflecting surface 11a of the first prism 11 is a plane inclined with respect to the second main surface 10d. In this embodiment, the cross-sectional shape of the first prism 11 cut along the first direction D1 is an isosceles triangle, with θ1=θ1'. Therefore, the inner half of the inner surface of the first prism 11 on the opposite side to the light source 20 side is also an inclined surface inclined at the same inclination angle as the first reflecting surface 11a. Note that in the present invention, it is not necessarily required that θ1=θ1'.

On the other hand, the second prism 12 formed on the first prism 11 has an approximately conical shape. That is, the second prism 12 is a conical prism. Therefore, the second reflecting surface 12a of the second prism 12 is a curved surface inclined with respect to the second main surface 10d. As shown in FIG. 4B, in this embodiment, the cross-sectional shape of the second prism 12 when cut along the first direction D1 is an approximately isosceles triangle with a curved apex angle. Therefore, the inner half of the inner surface of the second prism 12 on the opposite side to the light source 20 side is also an inclined surface inclined at the same inclination angle as the second reflecting surface 12a. The second prism 12 may have an approximately truncated cone shape.

As shown in FIG. 4B, the control angle θ2 of the second prism 12 is larger than the control angle θ1 of the first prism 11 (θ2>θ1). The control angle θ1 of the first prism 11 is the angle between the second main surface 10d and the first reflecting surface 11a in a cross section of the first prism 11 cut along the first direction D1. The control angle θ2 of the second prism 12 is the angle between the opening surface of the second prism 12 (a surface parallel to the second main surface 10d) and the second reflecting surface 12a in a cross section of the second prism 12 cut along the first direction D1.

In this embodiment, the control angle θ1 of the first prism 11 is made small to 45° or less, and the inclination angle of the first reflecting surface 11a is made gentle. This allows for a light distribution in which less light is emitted in the direction perpendicular to the main surface of the light guide plate 10 (front direction). Specifically, the control angle θ1 of the first prism 11 is preferably 10° or more and 40° or less. In this case, the control angle θ2 of the second prism 12 is larger than the control angle θ1 of the first prism 11, as described above. The control angle θ2 of the second prism 12 is not particularly limited as long as it is larger than the control angle θ1 of the first prism 11, but it is preferable that the control angle θ2 of the second prism 12 is larger than 40°. As an example, in this embodiment, the control angle θ1 of the first prism 11 is set to 20°, and the control angle θ2 of the second prism 12 is set to 60°.

In addition, since the control angle θ2 of the second prism 12 is different from the control angle θ1 of the first prism 11, the connection portion between the first reflecting surface 11a and the second reflecting surface 12a is bent.

In the light guide plate 10 configured in this manner, light incident on the light guide plate 10 from the light source 20 is reflected by the first prism 11 or the second prism 12 and is emitted to the outside of the light guide plate 10 from the first main surface 10c.

Specifically, as shown in FIG. 5A, a portion of the light incident from the light source 20 and guided through the light guide plate 10 is totally reflected at the interface between the first reflecting surface 11a of the first prism 11 and the air layer. At this time, since the control angle θ1 of the first prism 11 is 40° or less, the light totally reflected at the first reflecting surface 11a travels closer to the second end surface 10b than in the direction perpendicular to the first main surface 10c of the light guide plate 10 (the front direction). In other words, the proportion of light heading closer to the second end surface 10b can be made greater than the proportion of light heading closer to the front direction and the first end surface 10a.

In this embodiment, the light guide plate 10 is arranged so that the first main surface 10c is parallel to the first direction D1, which is the vertical direction, so that the light totally reflected by the first reflecting surface 11a travels downward from the front direction of the light guide plate 10. In other words, the light totally reflected by the first reflecting surface 11a travels diagonally downward (towards the ground).

As shown in FIG. 5B, another portion of the light incident from the light source 20 and guided through the light guide plate 10 is totally reflected at the interface between the second reflecting surface 12a of the second prism 12 and the air layer. At this time, since the control angle θ2 of the second prism 12 is larger than the control angle θ1 of the first prism 11 (for example, the control angle θ2 is larger than 40°), the light totally reflected by the second reflecting surface 12a travels closer to the first end surface 10a (closer to the light source 20) than the light reflected by the first reflecting surface 11a.

In this embodiment, the light guide plate 10 is arranged so that the first main surface 10c is parallel to the first direction D1, which is the vertical direction, so that the light totally reflected by the second reflecting surface 12a travels in the front direction of the light guide plate 10 or above the front direction of the light guide plate 10. In other words, the light totally reflected by the second reflecting surface 12a travels in the horizontal direction or diagonally upward (away from the ground).

In this way, the light incident on the light guide plate 10 from the light source 20 is reflected by the first prism 11 or the second prism 12 and enters the first main surface 10c, so that the first main surface 10c emits pseudo-light in a planar manner. At this time, the light reflected by the first prism 11 or the second prism 12 is emitted to the outside of the light guide plate 10 with a predetermined light distribution. In this embodiment, the first prism 11, which is the main prism that determines the light distribution of the light guide plate 10, is a long groove prism and the control angle θ1 of the first prism 11 is 40° or less, so that the light with a light distribution peak diagonally downward and a wide light distribution is emitted from the light guide plate 10.

Next, the light source 20 will be described. The light source 20 is a light-emitting device that emits light to be incident on the light guide plate 10. Specifically, the light source 20 emits light to be incident on the first end surface 10a of the light guide plate 10.

As shown in FIG. 3, the light source 20 is disposed opposite the first end surface 10a of the light guide plate 10. In other words, the light source 20 and the light guide plate 10 have an edge-light structure. Specifically, the light-emitting surface of the light source 20 faces the first end surface 10a of the light guide plate 10. In this embodiment, the light guide plate 10 is disposed so that the first end surface 10a is located on the upper side in the vertical direction, and therefore the light source 20 is disposed above the first end surface 10a.

In this embodiment, the light source 20 is an LED module composed of LEDs. The light source 20 emits, for example, white light. The white light emitted from the light source 20 enters the light guide plate 10 from the first end surface 10a of the light guide plate 10.

The light source 20 has a substrate 21 and one or more light-emitting elements 22 mounted on the substrate 21. In this embodiment, the light source 20 is an elongated LED module, so that the multiple light-emitting elements 22 are mounted in a linear row on one elongated substrate 21.

In this embodiment, the light source 20 is arranged so that the optical axis of the light source 20 is in the first direction D1. The optical axis of the light source 20 is the optical axis of each light-emitting element 22.

The substrate 21 is, for example, a wiring substrate on which wiring of a predetermined pattern is formed. The substrate 21 may be a resin substrate, a ceramic substrate, or a metal substrate with an insulating coating.

The light-emitting element 22 is an LED element composed of an LED. In this embodiment, the light-emitting element 22 is an individually packaged surface mount device (SMD) type LED element, and includes a container (package) made of resin or the like, an LED chip (bare chip) placed in the container, and a sealing member that seals the LED chip. Specifically, the light-emitting element 22 is an SMD type white LED element that emits white light. In this case, a blue LED chip that emits blue light when powered is used as the LED chip, and a silicone resin (phosphor-containing resin) containing a yellow phosphor such as YAG is used as the sealing member filled in the container.

The light source 20 emits light using power supplied from a power source. The power source is, for example, configured by a circuit board on which multiple circuit components are mounted, and receives commercial AC power, converts it into a predetermined power (for example, DC power), and supplies the power to the light source 20. This causes the light-emitting element 22 of the light source 20 to emit light. The power source may be built into the lighting device 1, or may be separate from the lighting device 1. The light source 20 may be configured to be dimmable and/or tonal controlled.

Next, the reflector 30 will be described. As shown in FIG. 2, the reflector 30 is disposed on the side of the light guide plate 10 on which the first prism 11 and the second prism 12 are formed. In other words, the reflector 30 is disposed on the second main surface 10d side of the light guide plate 10. Specifically, the reflector 30 is disposed so that the reflective surface of the reflector 30 faces the second main surface 10d. As a result, the light leaking out from the second main surface 10d out of the light guided through the light guide plate 10 can be reflected by the reflector 30 and returned to the light guide plate 10 to be emitted from the first main surface 10c, thereby improving the light extraction efficiency of the light guide plate 10.

The reflector 30 is formed, for example, from a resin material or a metal material. Specifically, the reflector 30 may be a white resin sheet made from a resin material such as PBT (polybutylene terephthalate), a metal plate made from a metal material such as aluminum, or a base material on which a metal film such as aluminum or a white resin is formed.

Next, the light-transmitting panel 40 will be described. As shown in FIG. 2, the light-transmitting panel 40 is disposed on the side of the light guide plate 10 on which the first prism 11 and the second prism 12 are not formed. That is, the light-transmitting panel 40 is disposed on the first main surface 10c side (light exit surface side) of the light guide plate 10. Specifically, the light-transmitting panel 40 is a front panel located forward in the light exit direction of the light guide plate 10. Therefore, the light-transmitting panel 40 covers the first main surface 10c of the light guide plate 10. By disposing the light-transmitting panel 40 in this manner, the light guide plate 10 can be protected more than when the light guide plate 10 is exposed as the outer shell of the lighting device 1.

Light emitted from the first main surface 10c of the light guide plate 10 enters the translucent panel 40, passes through the translucent panel 40, and is emitted to the outside of the translucent panel 40. Therefore, the outer surface of the translucent panel 40 becomes the light emitting surface of the light emitting unit 3. Specifically, the outer surface of the translucent panel 40 becomes the light emitting surface of the lighting device 1. In this embodiment, the translucent panel 40 is fitted into the opening of the main body 2.

The light-transmitting panel 40 is a light-transmitting member having light-transmitting properties. The light-transmitting panel 40 is preferably made of a transparent material having high light transmittance so as not to absorb the light emitted from the first main surface 10c of the light guide plate 10. Since the lighting device 1 is an outdoor lighting device, the light-transmitting panel 40 is preferably durable and water-resistant. As an example, the light-transmitting panel 40 is a flat transparent plate made of acrylic resin or glass material. Note that the light-transmitting panel 40 is not limited to a transparent plate, and may be a diffusion plate that scatters light.

Next, the effects of the lighting device 1 according to this embodiment will be described with reference to Figures 6 to 9, including how one aspect of the present invention was achieved.

Fig. 6 is a diagram showing the configuration of lighting device 1X of Comparative Example 1. Fig. 7 is a diagram for explaining the optical action of light guide plate 10X in lighting device 1X of Comparative Example 1 shown in Fig. 6. Fig. 8 is a diagram for explaining the optical action of light guide plate 10Y in lighting device 1Y of Comparative Example 2. Fig. 9 is a diagram for explaining the optical action of light guide plate 10 in lighting device 1 according to embodiment 1.

The lighting device 1X of Comparative Example 1 shown in FIG. 6 differs from the lighting device 1 shown in FIG. 3 in the configuration of the light guide plate 10X. Specifically, the light guide plate 10X shown in FIG. 6 does not have a second prism 12 formed therein, and the control angle θx of the prism 11X is larger (e.g., θx>40°) than the light guide plate 10 shown in FIG. 3. Specifically, the control angle θx of the prism 11X is 60°. Other than that, the configuration is the same as that of the lighting device 1 shown in FIG. 3.

Also, the lighting device 1Y of Comparative Example 2 shown in FIG. 8 is different from the lighting device 1X of Comparative Example 1 shown in FIG. 6 and FIG. 7 in the configuration of the light guide plate 10Y. Specifically, the light guide plate 10Y shown in FIG. 8 has a smaller control angle θy of the prism 11Y than the light guide plate 10X shown in FIG. 7 (for example, θy≦40°). Specifically, the control angle θy of the prism 11Y of the light guide plate 10Y in Comparative Example 2 is the same as the control angle θ1 of the first prism 11 of the light guide plate 10 in the above-mentioned embodiment 1. More specifically, the control angle θy of the prism 11Y of the light guide plate 10Y in Comparative Example 2 is 20°. The other configurations are the same as the lighting device 1X shown in FIG. 6 and FIG. 7.

As shown in FIG. 7, in the lighting device 1X of Comparative Example 1 shown in FIG. 6, the control angle θx of the prism 11X is greater than 40°. Therefore, in the lighting device 1X of Comparative Example 1, as shown in FIG. 7, the light incident from the light source 20 and entering the light guide plate 10X is reflected by the prism 11X and travels toward the front direction of the light guide plate 10X or above the front direction of the light guide plate 10X. In other words, in the lighting device 1X of Comparative Example 1, illumination light is irradiated toward the user's line of sight.

At this time, as shown in FIG. 7, if foreign matter 100 such as dust is attached to the first main surface 10c of the light guide plate 10X, the light emitted from the light guide plate 10X will be reflected by the foreign matter 100. However, since the lighting device 1X irradiates illumination light in the direction of the user's line of sight, the light reflected by the foreign matter 100 is drowned out by the illumination light irradiated from the lighting device 1X. As a result, the light reflected by the foreign matter 100 is not noticeable. In other words, in the lighting device 1X of Comparative Example 1, even if the foreign matter 100 is attached to the light guide plate 10X, the user is unlikely to notice the presence of the foreign matter 100.

In contrast, in the lighting device 1Y of Comparative Example 2 shown in FIG. 8, the control angle θy of the prism 11Y is 40° or less. Therefore, in the lighting device 1Y of Comparative Example 2, as shown in FIG. 8, the light that enters the light guide plate 10Y from the light source 20 is reflected by the prism 11Y and travels downward rather than in the front direction of the light guide plate 10Y. In other words, the lighting device 1Y of Comparative Example 2 has the advantage that glare can be suppressed because not much illumination light is irradiated in the direction of the user's line of sight.

However, in the lighting device 1Y of Comparative Example 2, as shown in FIG. 8, if a foreign object 100 is attached to the first main surface 10c of the light guide plate 10Y, the lighting device 1Y does not irradiate much illumination light toward the user's line of sight, and when the light emitted from the light guide plate 10Y is reflected by the foreign object 100, the reflected light by the foreign object 100 becomes noticeable. In other words, unlike the lighting device 1X of Comparative Example 1, the lighting device 1Y of Comparative Example 2 does not drown out the reflected light by the foreign object 100 with the illumination light irradiated from the lighting device 1Y, so the light reflected by the foreign object 100 becomes noticeable. As a result, in the lighting device 1Y of Comparative Example 2, if a foreign object 100 is attached to the light guide plate 10Y, the user is likely to notice the presence of the foreign object 100.

In addition, not only when foreign matter 100 adheres to the light guide plate 10Y, but also when foreign matter 100 adheres to an optical component that transmits or reflects the light emitted from the light guide plate 10Y (for example, a translucent panel arranged in front of the light guide plate 10Y or a reflector that reflects the light emitted from the light guide plate 10Y) or when foreign matter 100 gets mixed inside the light guide plate 10Y during the manufacturing process, if a light guide plate 10Y with a small control angle θy of the prism 11Y is used, the foreign matter 100 will be noticeable for the same reason as when foreign matter 100 adheres to the light guide plate 10Y. In addition, not only when the foreign object 100 is in close contact with the light guide plate 10Y or an optical component (closed foreign object), but also when the foreign object 100 is not in close contact with the light guide plate 10Y or an optical component (non-closed foreign object), if the foreign object 100 is present on the optical path of the light emitted from the light guide plate 10Y, the foreign object 100 will be noticeable for the same reason as above. In addition, not only when the foreign object 100 is in close contact with the light guide plate 10Y or an optical component, but also when the surface of the light guide plate 10Y is scratched, the scratch will be noticeable for the same reason as above.

In this way, in the lighting device 1Y using the light guide plate 10Y with the small control angle θy of the prism 11Y, glare can be suppressed by irradiating the illumination light diagonally downward. However, if foreign matter 100 such as dust adheres to the main surface of the light guide plate 10Y or the optical components, if foreign matter gets mixed inside the light guide plate 10Y, or if the main surface of the light guide plate 10 is scratched, the foreign matter 100 or the scratch becomes noticeable. As a result, the appearance quality of the light guide plate 10Y is reduced when light is emitted from the light guide plate 10Y.

After extensive research into these issues, the inventors of the present application came up with the idea that by overlapping a prism with a larger control angle on a main prism with a smaller control angle, it would be possible to make foreign matter and scratches less noticeable even if the control angle of the main prism was made smaller.

Specifically, in the light guide plate 10 according to this embodiment, one or more concave second prisms 12 are formed so as to overlap at least one of the multiple concave first prisms 11 formed two-dimensionally on the second main surface 10d, and further, the control angle θ2 of the second prism 12 is made larger than the control angle θ1 of the first prism 11.

With this configuration, as shown in FIG. 5(a), of the light emitted from the light source 20 and incident on the light guide plate 10 from the first end face 10a, the light reflected by the first prism 11 with a small control angle θ1 travels closer to the second end face 10b than in the front direction of the light guide plate 10. In this embodiment, the light reflected by the first prism 11 travels diagonally downward.

The second prism 12, which has a control angle θ2 larger than the control angle θ1 of the first prism 11, is formed to overlap the first prism 11. Therefore, as shown in FIG. 5B, of the light emitted from the light source 20 and incident on the light guide plate 10 from the first end face 10a, the light reflected by the second prism 12, which has a larger control angle θ2, travels closer to the first end face 10a (closer to the light source 20) than the light reflected by the first prism 11. For example, the light reflected by the second prism 12 travels in the front direction of the light guide plate 10 or upward from the front direction of the light guide plate 10.

9, even if a foreign object 100 is attached to the first main surface 10c of the light guide plate 10, the light reflected by the foreign object or scratches will not be noticeable when the light guide plate 10 is viewed from the front or diagonally above, due to the light reflected by the second prism 12. In addition, not only when the foreign object 100 is attached to the light guide plate 10, but also when a foreign object is attached to an optical component that transmits or reflects the light emitted from the light guide plate 10, a foreign object is mixed inside the light guide plate 10, or the main surface of the light guide plate 10 is scratched, the light reflected by the foreign object or scratches will not be noticeable when the light guide plate 10 is viewed from the front or diagonally above.

As described above, according to the light guide plate 10 of this embodiment, even if a foreign object is present on the light guide plate 10 or the light guide plate 10 is scratched, the user is unlikely to notice the presence of the foreign object or scratch. In other words, the foreign object or scratch is not noticeable due to the light distribution of the second prism 12, and the light distribution of the second prism 12 can provide a blinding effect to the user. As a result, it is possible to suppress a deterioration in the appearance quality of the light guide plate 10 when light is emitted from the light guide plate 10. Note that, similarly, for the lighting device 1 equipped with the light guide plate 10, it is possible to suppress a deterioration in the appearance quality of the light-emitting unit 3 of the lighting device 1 when it is turned on.

In addition, in the light guide plate 10 according to this embodiment, when the second main surface 10d is viewed from the front, the second prism 12 is located inside the first prism 11. In other words, when the second main surface 10d is viewed from the front, the second prism 12 is contained within the first prism 11.

As a result, the arrangement of the prism pattern when the light guide plate 10 is viewed from the front is dominated by the arrangement of the first prism 11, which is the main prism, so the second prism 12 does not disrupt the aesthetic appearance of the arrangement when viewed from the outside, improving the appearance of the light guide plate 10.

In the light guide plate 10 according to this embodiment, the first prism 11 is a long groove that is elongated in a direction intersecting the optical axis of the light source 20.

This configuration not only increases the light distribution ratio of light traveling toward the second end face 10b with respect to the front direction of the light guide plate 10 (in this embodiment, light traveling diagonally downward), but also increases the light distribution ratio of light traveling in the left-right direction of the light guide plate 10 (in this embodiment, light traveling in the second direction D2). This makes it possible to achieve a wide light distribution.

Furthermore, when the first prism 11 is a long groove, the opening shape of the second prism 12 is preferably circular when the second main surface 10d is viewed from the front. Specifically, the second prism 12 in this embodiment is approximately conical in shape.

This configuration allows the first prism 11 to effectively generate light distribution diagonally downward and in the left and right directions, so that even if the second prism 12 is superimposed on the first prism 11, it is possible to prevent the light distribution characteristics of the wide light distribution realized by the reflected light by the first prism 11 (light distribution by the first prism 11) from being disturbed.

In addition, in the light guide plate 10 according to this embodiment, the diameter of the opening of the second prism 12, which is a circular opening, is smaller than the width of the opening of the first prism 11, which is a long groove.

The light reflected by the second prism 12 (light distribution by the second prism 12) travels in a forward direction or diagonally upward, which has the effect of making dust and other foreign objects less visible, but if this effect is made too great, it can cause glare. Therefore, by making the diameter of the opening of the second prism 12 smaller than the width of the opening of the first prism 11, it is possible to suppress glare while still allowing the first prism 11 to generate light distribution diagonally downward and to the left and right, and to make foreign objects less noticeable using the second prism 12.

In addition, by making the diameter of the opening of the second prism 12 smaller than the width of the opening of the first prism 11, the first reflecting surface 11a of the first prism 11 is not covered by the second prism 12 and remains a flat surface, so that the wide light distribution component that propagates light in the left and right directions is less likely to be disturbed, and glare when the light guide plate 10 is viewed from an oblique direction can also be reduced.

In addition, in the light guide plate 10 according to this embodiment, when the second main surface 10d is viewed from the front, the total opening area of the second prisms 12 in one first prism 11 is preferably 1/10 or less of the opening area of the first prism 11.

With this configuration, even if the second prism 12 is overlapped on the first prism 11, the difference in coverage (difference in aperture) between the first prism 11 and the second prism 12 can be made large, so that the area of the first prism 11 (first reflecting surface 11a) can be sufficiently secured. As a result, glare can be suppressed within a range that does not disrupt the light distribution in the left and right directions generated by the first prism 11, while foreign objects and scratches can be effectively made less noticeable by the light distribution in the front direction or diagonally upward generated by the second prism 12.

In addition, in the light guide plate 10 according to this embodiment, the control angle θ1 of the first prism 11 is preferably 10° or more and 40° or less.

When the control angle θ1 of the first prism 11 exceeds 40°, the light distribution component traveling in the forward direction increases. On the other hand, when the control angle θ1 of the first prism 11 is smaller than 10°, the illumination area of the light emitted from the light guide plate 10 becomes too small.

Therefore, by setting the control angle θ1 of the first prism 11 to be greater than or equal to 10° and less than or equal to 40°, the reflected light by the first prism 11 (light distribution by the first prism 11) will be directed left and right and diagonally downward. And because the control angle θ2 of the second prism 12 is greater than the control angle θ1 of the first prism 11, the reflected light by the second prism 12 (light distribution by the second prism 12) will be directed relatively forward and diagonally upward. As a result, the first prism 11 can emit light over a wide range, and the second prism 12 can make foreign objects and scratches less noticeable.

In addition, in the light guide plate 10 according to this embodiment, in one first prism 11, the center of at least one second prism 12 overlaps with the center of the first prism 11.

With this configuration, the second prism 12 is located at the apex of the first prism 11, so that the light guided through the light guide plate 10 hits the second prism 12 and is reflected efficiently. As a result, the reflection efficiency of the second prism 12 is high. Furthermore, the directions in which the light reflected by each of the first prism 11 and the second prism 12 travel can be made symmetrical.

In addition, in this embodiment, the first prism 11 is a long groove and the second prism 12 is approximately conical in shape, but this is not limited to this.

For example, as in the lighting device 1A and light guide plate 10A shown in Figs. 10 and 11, not only the second prism 12 but also the first prism 11A may be substantially conical. However, the first prism 11A has a substantially truncated cone shape with the apex of the cone scraped off by the second prism 12. Fig. 10 is a diagram showing the configuration of the light guide plate 10A and the light source 20 in the lighting device 1A according to the first modification of the first embodiment, and Fig. 11 is a partial cross-sectional view of the light guide plate 10A. In Fig. 10, (a) shows a side view of the light guide plate 10A and the light source 20, and (b) shows a cross-sectional view taken along the line XB-XB in (a). In Fig. 11, (a) and (b) are cross-sectional views taken along the lines XIA-XIA and XIB-XIB in Fig. 10, respectively.

Alternatively, as in the lighting device 1B and light guide plate 10B shown in Figs. 12 and 13, not only the first prism 11 but also the second prism 12B may be long grooves. However, the length of the second prism 12B is preferably shorter than the length of the first prism 11. Fig. 12 is a diagram showing the configuration of the light guide plate 10B and the light source 20 in the lighting device 1B according to the second modification of the first embodiment, and Fig. 13 is a partial cross-sectional view of the light guide plate 10B. In Fig. 12, (a) shows a side view of the light guide plate 10B and the light source 20, and (b) shows a cross-sectional view taken along the line XIIB-XIIB in (a). In Fig. 13, (a) and (b) are cross-sectional views taken along the lines XIIIA-XIIIA and XIIIB-XIIIB in Fig. 12, respectively.

As shown in Figs. 10 to 13, the first prism and the second prism may have similar shapes. In this case, the same effect as the light guide plate 10 in the first embodiment is achieved. In other words, even if a foreign object is present on the light guide plate 10 or the light guide plate 10 is scratched, the foreign object or scratch can be made less noticeable.

However, as shown in Figures 3 and 4, it is better to make the first prism 11 a long groove and the second prism 12 an approximately conical shape. By doing so, even if the first prism 11 is overlapped with the second prism 12, the difference in coverage between the first prism 11 and the second prism 12 can be made large, so that the area of the first prism 11 (first reflecting surface 11a) can be easily secured. As a result, glare can be suppressed by the light distribution by the first prism 11, while foreign objects and scratches can be effectively made less noticeable by the light distribution by the second prism 12.

In addition, in this embodiment, the second prism 12 is located inside the first prism 11, and the second prism 12 is contained within the first prism 11, but this is not limited to the above.

For example, as in the lighting device 1C and light guide plate 10C shown in Figs. 14 and 15, the second prism 12C may protrude from the first prism 11 when the second main surface 10d is viewed from the front. Fig. 14 is a diagram showing the configuration of the light guide plate 10C and the light source 20 in the lighting device 1C according to the third modification of the first embodiment, and Fig. 15 is a partial cross-sectional view of the light guide plate 10C. In Fig. 14, (a) shows a side view of the light guide plate 10C and the light source 20, and (b) shows a cross-sectional view taken along the line XIVB-XIVB in (a). In Fig. 15, (a), (b), and (c) are cross-sectional views taken along the lines XVA-XVA, XVB-XVB, and XVC-XVC in Fig. 14, respectively.

In this modified example, the first prism 11 is a long groove, and the second prism 12C is generally conical. In this modified example, when the second main surface 10d is viewed from the front, the diameter of the opening of the second prism 12C is larger than the width of the opening of the first prism 11.

This modified example also has the same effect as the light guide plate 10 in the first embodiment. In other words, even if a foreign object is present on the light guide plate 10 or the light guide plate 10 is scratched, the foreign object or scratch can be made less noticeable.

Thus, the second prism 12C does not have to be included in the first prism 11, but it is better for the second prism 12C to be included in the first prism 11, as in the above-mentioned first embodiment. By doing so, the first reflecting surface 11a exists around the entire circumference of the first prism 11, so that even if the second prism 12C is overlapped on the first prism 11, it is possible to prevent the light distribution by the first prism 11 from being disturbed.

(Embodiment 2)
Next, an illumination device 1D according to the second embodiment will be described with reference to Figs. 16 and 17. Fig. 16 is a diagram showing the configuration of a light guide plate 10D and a light source 20 in the illumination device 1D according to the second embodiment. Fig. 17 is a partial cross-sectional view of the light guide plate 10D. In Fig. 16, (a) shows a side view of the light guide plate 10D and the light source 20, and (b) shows a cross-sectional view taken along line XVIB-XVIB in (a). In Fig. 17, (a), (b), and (c) are cross-sectional views taken along lines XVIIVA-XVIIA, XVIIB-XVIIB, and XVIIC-XVIIC in Fig. 16, respectively.

The lighting device 1D according to this embodiment is different from the lighting device 1 according to the above-mentioned embodiment 1 in the configuration of the light guide plate 10D. Specifically, in the light guide plate 10 in the above-mentioned embodiment 1, only one second prism 12 is formed in one first prism 11, but in the light guide plate 10D in this embodiment, multiple second prisms 12 are formed in one first prism 11.

Specifically, as shown in Figures 16 and 17, two second prisms 12 are formed in each first prism 11. The two second prisms 12 in each first prism 11 are the same size and shape, and are formed in symmetrical positions along the longitudinal direction of the first prism 11, which is a long groove.

In this way, in the light guide plate 10D according to this embodiment, similar to the light guide plate 10 according to the above-mentioned embodiment 1, second prisms 12 having a control angle θ2 larger than the control angle θ1 of the first prisms 11 are formed so as to overlap the first prisms 11 that are formed in a two-dimensional pattern on the second main surface 10d.

As a result, this embodiment also achieves the same effect as the light guide plate 10 in the first embodiment. In other words, even if a foreign object is present on the light guide plate 10D or the light guide plate 10D is scratched, the foreign object or scratch can be made less noticeable.

In this embodiment, multiple second prisms 12 are formed on one first prism 11.

This provides the following effects. To adjust the ratio of light distribution by the first prism 11 and the second prism 12, it is necessary to adjust the difference in coverage between the first prism 11 and the second prism 12. In this case, the difference in coverage can be adjusted by changing the size of the first prism 11 or the second prism 12. However, in this case, a separate means is required to perform processing to change the size of the first prism 11 or the second prism 12.

In contrast, by forming multiple second prisms 12 on one first prism 11 as in the present embodiment, the difference in coverage between the first prism 11 and the second prism 12 can be easily adjusted according to the number of second prisms 12. This makes it easy to adjust the ratio of light distribution by the first prism 11 and the ratio of light distribution by the second prism 12, so that a lighting device 1D having desired light distribution characteristics can be easily obtained. For example, it is possible to suppress glare while making foreign matter and scratches present on the light guide plate 10D less noticeable. Moreover, since only one means for processing the second prism 12 is required, the time required for prism design and prism processing can be shortened.

In this embodiment, two second prisms 12 are formed on one first prism 11, but this is not limited to the above. For example, three or more second prisms 12 may be formed on one first prism 11.

In addition, in this embodiment, the two second prisms 12 are arranged side by side along the longitudinal direction of the first prism 11, but this is not limited to this.

(Embodiment 3)
Next, an illumination device 1E according to the third embodiment will be described with reference to Figs. 18 and 19. Fig. 18 is a diagram showing the configuration of a light guide plate 10E and a light source 20 in the illumination device 1E according to the third embodiment. Fig. 19 is a partial cross-sectional view of the light guide plate 10E. In Fig. 18, (a) shows a side view of the light guide plate 10E and the light source 20, and (b) shows a cross-sectional view taken along line XVIIIB-XVIIIB in (a). In Fig. 19, (a), (b), (c), and (d) are cross-sectional views taken along lines XIXA-XIXA, XIXB-XIXB, XIXC-XIXC, and XIXD-XIXD in Fig. 18, respectively.

The lighting device 1E according to the present embodiment differs from the lighting device 1D according to the above-mentioned embodiment 2 in the configuration of the light guide plate 10E. Specifically, in the light guide plate 10D in the above-mentioned embodiment 2, one type of second prism 12 was formed in each first prism 11. In other words, multiple second prisms 12 were formed, but the control angle θ2 of each second prism 12 was the same. In contrast, in the light guide plate 10E in the present embodiment, there are multiple types of control angles for the multiple prisms added to one first prism 11.

Specifically, as shown in Figures 18 and 19, in addition to the first prism 11 and the second prism 12, the light guide plate 10E further has one or more concave third prisms 13 formed in one first prism 11 so as to overlap with each of the first prism 11 and the second prism 12. The control angle θ3 of this third prism 13 is different from each of the control angle θ1 of the first prism 11 and the control angle θ2 of the second prism 12. In this embodiment, the control angle θ3 of the third prism 13 is larger than the control angle θ1 of the first prism 11 and smaller than the control angle θ2 of the second prism 12 (θ1 < θ3 < θ2).

The third prism 13, like the second prism 12, is a sub-prism that adjusts the light distribution of the light guide plate 10E generated by the first prism 11, which is the main prism. When the second main surface 10d is viewed from the front, the third prism 13 is preferably located inside the first prism 11. In other words, the third prism 13 is preferably contained within the first prism 11. Therefore, when the second main surface 10d is viewed from the front, the opening area of the third prism 13 is smaller than the opening area of the first prism 11. The opening area of the third prism 13 is larger than the opening area of the second prism 12. As an example, the third prism 13 is approximately conical, like the second prism 12. Therefore, when the second main surface 10d is viewed from the front, the opening shape of the third prism 13 is circular.

Also, as shown in FIG. 19(c), in the portion where the first prism 11, the second prism 12, and the third prism 13 overlap, the first prism 11, the third prism 13, and the second prism 12 are formed in this order along the depth direction. In other words, the third prism 13 is formed so as to make the bottom of the first prism 11 even deeper, and the second prism 12 is formed so as to make the bottom of the third prism 13 even deeper. Specifically, the third prism 13 is formed so as to protrude in a protruding manner from the bottom of the first prism 11 in the depth direction, and the second prism 12 is formed so as to protrude in a protruding manner from the bottom of the first prism 11 in the depth direction.

Therefore, in the area where the first prism 11, the second prism 12, and the third prism 13 overlap, the first reflecting surface 11a of the first prism 11 is formed on the second main surface 10d side, the third reflecting surface 13a of the third prism 13 is formed contiguous with the first reflecting surface 11a in the depth direction, and the second reflecting surface 12a of the second prism 12 is formed contiguous with the third reflecting surface 13a in the depth direction.

As described above, in the light guide plate 10E according to this embodiment, similar to the light guide plate 10 according to the first embodiment, second prisms 12 having a control angle θ2 larger than the control angle θ1 of the first prisms 11 are formed so as to overlap the first prisms 11 that are formed in a two-dimensional pattern on the second main surface 10d.

As a result, this embodiment also achieves the same effect as the light guide plate 10 in the first embodiment. In other words, even if a foreign object is present on the light guide plate 10E or the light guide plate 10E is scratched, the foreign object or scratch can be made less noticeable.

Furthermore, the light guide plate 10E in this embodiment has one or more concave third prisms 13 formed in one first prism 11 so as to overlap with each of the first prism 11 and the second prism 12. In addition, the control angle θ3 of the third prism 13 is different from each of the control angle θ1 of the first prism 11 and the control angle θ2 of the second prism 12.

In this way, by stacking three types of reflecting prisms with different control angles, it is possible to emit light in more directions three-dimensionally without compromising the aesthetic appearance of the light guide plate compared to when only the first prism 11 is formed.

In the present embodiment, one third prism 13 is formed so as to overlap the first prism 11 and the second prism 12, but this is not limited to the above. For example, another sub-prism with a different control angle may be formed together with the third prism 13 so as to overlap the first prism 11 and the second prism 12.

In addition, in this embodiment, the third prism 13 is added to the first prism 11 and the second prism 12, but it is also possible to consider forming multiple types of second prisms 12 with different control angles θ2 (i.e., _θ21 , _θ22 , _θ23 , ...) for the first prism 11.

In addition, in this embodiment, a second prism 12 and a third prism 13 are added to the center of the first prism 11, and the number of second prisms 12 is three, compared to the light guide plate 10D in embodiment 2, but this is not limited to this. Only the central second prism 12 may be included among the three. In other words, a third prism 13 may be added to the light guide plate 10D in embodiment 1.

(Embodiment 4)
Next, an illumination device 1F according to embodiment 4 will be described with reference to Figs. 20 and 21. Fig. 20 is a diagram showing the configuration of a light guide plate 10F and a light source 20 in an illumination device 1F according to embodiment 4. Fig. 21 is a partial cross-sectional view of the light guide plate 10F. In Fig. 20, (a) shows a side view of the light guide plate 10F and the light source 20, and (b) shows a cross-sectional view taken along line XXB-XXB in (a).

The lighting device 1F according to this embodiment is different from the lighting device 1 according to the above-mentioned embodiment 1 in the configuration of the light guide plate 10F. Specifically, in the light guide plate 10 in the above-mentioned embodiment 1, no reflecting prisms are formed on the first main surface 10c, but in the light guide plate 10F in this embodiment, reflecting prisms are formed not only on the second main surface 10d but also on the first main surface 10c.

Specifically, as shown in Figures 20 and 21, the light guide plate 10F in this embodiment further has a fourth prism 14 formed on the first main surface 10c. The control angle θ4 of the fourth prism 14 is larger than the control angle θ1 of the first prism 11. In this embodiment, the control angle θ4 of the fourth prism 14 is the same as the control angle θ2 of the second prism 12 formed on the second main surface 10d. Therefore, the fourth reflecting surface 14a of the fourth prism 14 is the same as the second reflecting surface 12a of the second prism 12.

As described above, in the light guide plate 10F according to this embodiment, similar to the light guide plate 10 according to the first embodiment, second prisms 12 having a control angle θ2 larger than the control angle θ1 of the first prisms 11 are formed so as to overlap the first prisms 11 that are formed in a two-dimensional pattern on the second main surface 10d.

As a result, this embodiment also achieves the same effect as the light guide plate 10 in the first embodiment. In other words, even if a foreign object is present on the light guide plate 10F or the light guide plate 10F is scratched, the foreign object or scratch can be made less noticeable.

The light guide plate 10F according to this embodiment further has a fourth prism 14 formed on the first major surface 10c. In other words, reflecting prisms are formed on both the first major surface 10c and the second major surface 10d of the light guide plate 10F. The control angle θ4 of the fourth prism 14 is greater than the control angle θ1 of the first prism 11.

As a result, as shown in FIG. 21, foreign matter and scratches on the light guide plate 10F are less noticeable whether the light guide plate 10F is viewed from the first main surface 10c side or the second main surface 10d side.

In this embodiment, the control angle θ4 of the fourth prism 14 is the same as the control angle θ2 of the second prism 12, but the control angle θ4 of the fourth prism 14 and the control angle θ2 of the second prism 12 may be different. In addition, the shape and size of the fourth prism 14 are the same as the shape and size of the second prism 12, but are not limited to this.

In addition, in this embodiment, only one type of reflecting prism, the fourth prism 14, is formed on the first main surface 10c, but this is not limited to this. For example, multiple types of reflecting prisms with different control angles may be formed by stacking them on the first main surface 10c.

Specifically, as shown in FIG. 22, a fourth prism 14 and a fifth prism 15 may be formed on the first main surface 10c. In FIG. 22, the fifth prism 15 has a configuration similar to that of the first prism 11 formed on the second main surface 10d. Therefore, the control angle θ5 of the fifth prism 15 is the same as the control angle θ1 of the first prism 11. In other words, the inclination angle of the fifth reflecting surface 15a of the fifth prism 15 is the same as the inclination angle of the first reflecting surface 11a of the first prism 11. In addition, the shape and size of the fifth prism 15 are the same as the shape and size of the first prism 11.

In FIG. 22, the fourth prism 14 is formed so as to overlap the fifth prism 15. In other words, the first main surface 10c and the second main surface 10d of the light guide plate have the same light reflection structure in which two types of reflecting prisms with different control angles overlap. This makes it possible to make the light distribution on the first main surface 10c side and the second main surface 10d side the same, so that foreign objects and scratches on the light guide plate are similarly less noticeable when viewed from either the first main surface 10c side or the second main surface 10d side.

In FIG. 22, the light reflecting structure on the first main surface 10c side and the light reflecting structure on the second main surface 10d side are formed to be staggered when the light guide plate is viewed in cross section, but this is not limited to this. In other words, the light reflecting structure on the first main surface 10c side and the light reflecting structure on the second main surface 10d side are formed not to overlap when the light guide plate is viewed from the front, but this is not limited to this. For example, the light reflecting structure on the first main surface 10c side and the light reflecting structure on the second main surface 10d side may be formed to overlap when the light guide plate is viewed from the front.

(Embodiment 5)
Next, an illumination device 1G according to embodiment 5 will be described with reference to Fig. 23. Fig. 23 is a diagram showing the configuration of a light guide plate 10 and a light source 20G in an illumination device 1G according to embodiment 5. In Fig. 23, (a) shows a side view of the light guide plate 10 and the light source 20G, and (b) shows a cross-sectional view taken along line XXIIIB-XXIIIB in (a).

The lighting device 1G according to this embodiment differs from the lighting device 1 according to the above-mentioned embodiment 1 in the configuration of the light source 20G. Specifically, the light source 20 in the above-mentioned embodiment 1 was an SMD-type LED module using an SMD-type LED element as the light-emitting element 22, but the light source 20G in this embodiment is a COB (chip on board) type LED module in which the light-emitting element 22G itself is an LED chip (bare chip).

Specifically, as shown in FIG. 23, the light source 20G has a substrate 21, a light-emitting element 22G that is an LED chip directly mounted on the substrate 21, and a sealing member 23G that seals the light-emitting element 22G.

In this embodiment, a plurality of light-emitting elements 22G are mounted on the substrate 21. Specifically, the plurality of light-emitting elements 22G are mounted in a row along the longitudinal direction of the substrate 21. The plurality of light-emitting elements 22G are collectively sealed by a sealing member 23G. Therefore, the sealing member 23G is formed in a straight line along the longitudinal direction of the substrate 21.

The light source 20G emits white light. In this case, each of the multiple light-emitting elements 22G is, for example, a blue LED chip that emits blue light, and the sealing member 23G is a silicone resin (phosphor-containing resin) that contains a yellow phosphor such as YAG. As a result, when the light-emitting elements 22G emit light, white light is emitted from the sealing member 23G. In addition, in this embodiment, since the sealing member 23G is formed in a linear shape, continuous white light is emitted in a linear shape from the sealing member 23G. In other words, the light source 20G is a line light source that emits a line of white light.

The light source 20G thus configured is disposed opposite the first end surface 10a of the light guide plate 10. Specifically, the light source 20G is disposed so that the longitudinal direction of the light source 20G coincides with the longitudinal direction of the first end surface 10a. As a result, the light source 20G emits continuous light in an elongated shape along the longitudinal direction of the first end surface 10a.

As described above, the lighting device 1G according to this embodiment uses the same light guide plate 10 as the light guide plate 10 in the first embodiment.

As a result, this embodiment also achieves the same effect as the light guide plate 10 in the first embodiment. In other words, even if a foreign object is present on the light guide plate 10 or the light guide plate 10 is scratched, the foreign object or scratch can be made less noticeable.

Furthermore, the lighting device 1G in this embodiment uses a light source 20G that emits continuous light in an elongated shape along the longitudinal direction of the first end surface 10a of the light guide plate 10.

In this way, by making the light emitted from the light source 20G linear rather than dot-like, it is possible to prevent bright lines (vertical stripes) from appearing in the line of sight caused by the light reflected by the first prism 11 and the second prism 12. This makes it possible to improve the appearance quality of the light guide plate 10 when it is turned on.

(Embodiment 6)
Next, an illumination device 1H according to embodiment 6 will be described with reference to Fig. 24. Fig. 24 is a diagram showing the configurations of the light guide plate 10, the light source 20, and the light absorbing material 50 in the illumination device 1H according to embodiment 6. In Fig. 24, (a) shows a side view of the light guide plate 10, the light source 20, and the light absorbing material 50, and (b) shows a cross-sectional view taken along line XXIVB-XXIVB in (a).

The lighting device 1H according to this embodiment is configured to further include a light absorbing material 50 in addition to the lighting device 1 according to the first embodiment.

The light absorbing material 50 is formed on the second end surface 10b of the light guide plate 10. In this embodiment, the light absorbing material 50 covers the entire second end surface 10b. The light absorbing material 50 is optically in contact with the second end surface 10b. The light absorbing material 50 is, for example, a coating film made of a light absorbing material. In this case, the light absorbing material 50 made of a coating film in contact with the second end surface 10b can be formed by applying a coating material to the second end surface 10b of the light guide plate 10 and solidifying it. The light absorbing material 50 may be a tape-shaped tape member. In this case, the light absorbing material 50 can be attached to the second end surface 10b of the light guide plate 10 by an adhesive.

The light absorbing material 50 is, for example, a material (e.g., a resin material) having substantially the same refractive index as the light guide plate 10 as a base material to which an additive (e.g., a black additive) having a light absorbing function such as carbon has been added. Note that the refractive index of the base material of the light absorbing material 50 does not have to be the same as the refractive index of the light guide plate 10.

As described above, the lighting device 1H according to this embodiment also uses the same light guide plate 10 as the light guide plate 10 in the first embodiment.

As a result, this embodiment also achieves the same effect as the light guide plate 10 in the first embodiment. In other words, even if a foreign object is present on the light guide plate 10 or the light guide plate 10 is scratched, the foreign object or scratch can be made less noticeable.

Furthermore, in the lighting device 1H of this embodiment, a light absorbing material 50 is formed on the second end surface 10b of the light guide plate 10. In other words, the light absorbing material 50 is formed on the end surface opposite the light source 20 side.

This makes it possible to prevent the light from the light source 20 that enters the light guide plate 10 from the first end face 10a and reaches the second end face 10b from disrupting the light distribution of the light guide plate 10 or emitting dazzling light in the direction of the user's line of sight. This point will be explained below.

If the light absorbing material 50 is not formed on the second end face 10b of the light guide plate 10, a portion of the light that reaches the second end face 10b is totally reflected by the second end face 10b and returns to the first end face 10a side (light source 20 side) and is guided within the light guide plate 10. At this time, the light reflected by the second end face 10b may be reflected by the first prism 11 or the second prism 12, which may disrupt the light distribution of the light guide plate 10 or emit dazzling light in the direction of the user's line of sight.

In response to this, by forming a light absorbing material 50 on the second end surface 10b of the light guide plate 10, the light that reaches the second end surface 10b can be absorbed by the light absorbing material 50, and the light that reaches the second end surface 10b can be prevented from being reflected by the second end surface 10b and returning to the first end surface 10a side (light source 20 side). As a result, it is possible to prevent the light distribution of the light guide plate 10 from being disturbed and dazzling light from being emitted in the direction of the user's line of sight. For example, the first prism 11 can realize illumination light with a wide light distribution that is not dazzling.

(Modification)
Although the light guide plate and the light guide plate system according to the present invention have been described based on the first to sixth embodiments, the present invention is not limited to the first to sixth embodiments.

For example, in the above embodiments 1 to 6, the connection portion between the first reflecting surface 11a of the first prism 11 and the second reflecting surface 12a of the second prism 12 is bent in a folded manner, but this is not limited thereto. For example, as in the light guide plate 10I shown in FIG. 25, the connection portion between the first reflecting surface 11a of the first prism 11 and the second reflecting surface 12a of the second prism 12 may be smoothly bent.

Also, as in the light guide plate 10J shown in FIG. 26, the connection portion between the first reflecting surface 11a of the first prism 11 and the second reflecting surface 12a of the second prism 12 may be bent with an inflection point. For example, the connection portion between the first reflecting surface 11a and the second reflecting surface 12a may have a slightly raised shape.

Furthermore, as in the light guide plate 10K shown in FIG. 27, not only the connection portion between the first reflecting surface 11a of the first prism 11 and the second reflecting surface 12a of the second prism 12, but also the connection portion between the second main surface 10d and the first reflecting surface 11a of the first prism 11 may be bent with an inflection point. For example, the connection portion between the second main surface 10d and the first reflecting surface 11a may have a slightly raised shape.

In addition, in the above embodiments 1 to 6, the light source 20 is arranged so as to be located above the light guide plate, but this is not limited thereto. For example, the light source 20 may be arranged so as to be located below the light guide plate.

In addition, in the above embodiments 1 to 6, the light sources 20 and 20G are configured with LEDs, but this is not limited to this. For example, the light sources 20 and 20G may be configured with solid-state light-emitting elements other than LEDs, such as semiconductor lasers or organic EL (Electro Luminescence). Note that existing lamps such as fluorescent lamps and high-intensity lamps may also be used as the light source 20.

In addition, in the above embodiments 1 to 6, the light guide plates 10 to 10K are described as being used for pole lights, but this is not limited to this. For example, the light guide plates 10 to 10K can be applied to any lighting device other than pole lights, such as ceiling lights.

In addition, in the above embodiments 1 to 6, the light guide plates 10 to 10K are described as being applied to lighting devices, but this is not limiting. The present invention can also be applied to a light guide plate system that includes a light guide plate.

In addition, the present invention also includes forms obtained by applying various modifications to the above-described embodiments that would come to mind by a person skilled in the art, and forms realized by arbitrarily combining the components and functions of the above-described embodiments without departing from the spirit of the present invention.

1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1X, 1Y Illumination device (light guide plate system)
2 Main body 3 Light emitting section 10, 10A, 10B, 10C, 10D, 10E, 10F, 10I, 10J, 10K, 10X, 10Y Light guide plate 10a First end face 10b Second end face 10c First main surface 10d Second main surface 11, 11A First prism 12, 12B, 12C Second prism 13 Third prism 14 Fourth prism 20, 20G Light source 50 Light absorbing material

Claims (14)

A light guide plate having a first end surface to which light emitted from a light source is incident, a first main surface from which the light incident from the first end surface exits, and a second main surface facing away from the first main surface,
A plurality of first concave prisms are formed two-dimensionally on the second main surface;
and one or more concave second prisms formed to overlap at least one of the plurality of first prisms,
a control angle of the second prism is greater than a control angle of the first prism;
the first prism is a long groove having an elongated shape in a direction intersecting with an optical axis of the light source,
When the second main surface is viewed from the front, a total opening area of the second prisms in one of the first prisms is equal to or less than one tenth of an opening area of the first prism.
Light guide plate. When the second main surface is viewed from the front, the second prism is located inside the first prism.
The light guide plate according to claim 1 . When the second main surface is viewed from the front, the opening shape of the second prism is circular.
The light guide plate according to claim 1 . The diameter of the opening of the second prism is smaller than the width of the opening of the first prism.
The light guide plate according to claim 3 . The control angle of the first prism is greater than or equal to 10° and less than or equal to 40°.
The light guide plate according to any one of claims 1 to 4 . In one of the first prisms, a plurality of the second prisms are formed.
The light guide plate according to any one of claims 1 to 5 . A light guide plate having a first end surface to which light emitted from a light source is incident, a first main surface from which the light incident from the first end surface exits, and a second main surface facing away from the first main surface,
A plurality of first concave prisms are formed two-dimensionally on the second main surface;
and one or more concave second prisms formed to overlap at least one of the plurality of first prisms,
a control angle of the second prism is greater than a control angle of the first prism;
In one of the first prisms, a plurality of the second prisms are formed.
Light guide plate. Furthermore, one of the first prisms has one or more concave third prisms formed so as to overlap with each of the first prism and the second prism,
a control angle of the third prism is different from a control angle of the first prism and a control angle of the second prism;
The light guide plate according to any one of claims 1 to 7 . In one of the first prisms, a center of at least one of the second prisms overlaps with a center of the first prism.
The light guide plate according to any one of claims 1 to 8 . Further, a fourth prism is formed on the first main surface,
The control angle of the fourth prism is greater than the control angle of the first prism.
The light guide plate according to any one of claims 1 to 9 . A light guide plate having a first end surface to which light emitted from a light source is incident, a first main surface from which the light incident from the first end surface exits, and a second main surface facing away from the first main surface,
A plurality of first concave prisms are formed two-dimensionally on the second main surface;
and one or more concave second prisms formed to overlap at least one of the plurality of first prisms,
a control angle of the second prism is greater than a control angle of the first prism;
Further, a fourth prism is formed on the first main surface,
The control angle of the fourth prism is greater than the control angle of the first prism.
Light guide plate. Further, the light absorbing material is formed on a second end surface located opposite to the first end surface.
The light guide plate according to any one of claims 1 to 11. A light guide plate according to any one of claims 1 to 12,
a light source that emits light to be incident on the first end surface of the light guide plate,
Light guide plate system. The first end surface is elongated,
The light source is disposed opposite to the first end surface, and emits continuous light in an elongated shape along a longitudinal direction of the first end surface.
The light guide plate system according to claim 13.

Images