Lighting device and manufacturing method of light guide plate

Abstract

To provide a lighting device, etc. capable of suppressing light leakage from a plurality of prisms as much as possible.SOLUTION: A lighting device 1 includes: a light source 20; and a light guide plate 10 having an incidence surface 11, an emission surface 13, and a light extraction surface 15 where a plurality of prisms 16 for causing the emission surface 13 to emit light are formed. When a cross section when cutting the light guide plate 10 by a plane orthogonal to the light extraction surface 15 and parallel to an optical axis direction is viewed, a plurality of prisms 16 are formed on the light extraction surface 15, including a first surface 17a inclined upward along an optical axis direction of the light emitted by the light source 20, and a second surface 17b opposed to the first surface 17a and inclined upward along the optical axis direction. When a first angle of the first surface 17a with respect to the optical axis direction is represented as θ1 and a second angle in which the optical axis direction intersects with an extension direction along the second surface 17b is represented as θ2, formulas (1) and (2) are satisfied; (1) 5°≤θ1≤60° (2) θ2>90°.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an illumination device using a light guide plate and a method for manufacturing a light guide plate. [Background technology]

[0002] 2. Description of the Related Art Conventionally, an edge-light type lighting fixture is known as a light guide plate system using a light guide plate. The edge-light type lighting fixture includes a light guide plate and a light source disposed opposite an end surface of the light guide plate.

[0003] As an example of this type of lighting fixture, Patent Document 1 discloses a lighting fixture including a light-emitting module, and a light guide having an incident surface into which light is incident and an opposing surface for emitting the incident light from the exit surface, and in which a plurality of prisms are formed for emitting the light from the exit surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-136128 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a demand for further suppression of light leakage from the multiple prisms formed in the light guide plate.

[0006] The present disclosure has been made to solve such problems, and has an object to provide an illumination device and the like that can further suppress light leakage from multiple prisms. [Means for solving the problem]

[0007] One aspect of the lighting device according to the present disclosure includes a light source, and a light guide plate having an incident surface into which light emitted from the light source is incident, an exit surface from which the light incident from the incident surface exits, and a light extraction surface for emitting the light from the exit surface, and on which a plurality of prisms for emitting the light from the exit surface are formed, wherein, when a cross section of the light guide plate is cut along a plane perpendicular to the light extraction surface and parallel to the optical axis direction of the light source, the light extraction surface has a plurality of prisms formed thereon, the prisms having a first surface that slopes upward along the optical axis direction of the light emitted from the light source and a second surface that faces the first surface and slopes upward along the optical axis direction, the first surface is disposed closer to the light source than the second surface, and the following formulas (1) to (2) are established, where θ1 is a first angle of the first surface with respect to the optical axis direction and θ2 is a second angle at which the optical axis direction intersects with an extension direction along the second surface.

[0008] 5°≦θ1≦60° Formula (1)

[0009] θ2>90° Equation (2)

[0010] Moreover, one aspect of the method for manufacturing a light guide plate according to the present disclosure is a light guide plate having an incident surface into which light emitted from a light source is incident, an exit surface from which the light incident from the incident surface exits, and a light extraction surface for emitting light from the exit surface, wherein a plurality of prisms for emitting light from the exit surface are formed by laser processing the light extraction surface. Effect of the Invention

[0011] According to the present disclosure, light leakage from multiple prisms can be further suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an illumination device according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing the lighting device according to the embodiment taken along line AA in FIG. [Figure 3A]FIG. 3A is a diagram illustrating a configuration of a light guide plate and a light source in the lighting device according to the embodiment. [Figure 3B] FIG. 3B is a diagram showing another configuration of a light guide plate and a light source in the lighting device according to the embodiment. [Figure 4] FIG. 4 is a diagram showing light tracing in a light guide plate of the lighting device according to the embodiment. [Figure 5A] FIG. 5A is a diagram showing light distribution curves according to prism shapes. [Figure 5B] FIG. 5B is a diagram showing light distribution curves in a light guide plate using prisms in the embodiment and in a light guide plate using prisms inclined in the opposite direction to the prisms in the embodiment. [Figure 5C] FIG. 5C is a diagram showing an irradiation mode of light emitted from the exit surface of the light guide plate. [Figure 6] FIG. 6 is a diagram in which light is traced in a light guide plate of an illumination device according to a comparative example. [Figure 7] FIG. 7 is a cross-sectional view showing a lighting device according to a modified example of the embodiment. [Figure 8A] FIG. 8A is a diagram showing the light distribution of an illumination device when the size of a prism is uniform and when the size of the prism is changed. [Figure 8B] FIG. 8B is a diagram showing the light distribution of the lighting device when the coverage rate of the prism is changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described. Note that each of the embodiments described below shows a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims will be described as optional components.

[0014] In addition, each drawing is a schematic diagram and is not necessarily a precise illustration. In each drawing, the same reference numerals are used for substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0015] In addition, in the following embodiments, expressions such as "approximately parallel" or "rectangular" are used. For example, "approximately parallel" or "rectangular" does not only mean completely parallel or rectangular, but also means substantially parallel or rectangular, that is, includes an error of about a few percent. Furthermore, "approximately parallel" or "rectangular" means parallel or rectangular within a range in which the effects of the present disclosure can be achieved. The same applies to other expressions using "approximately" or "rectangular".

[0016] (Embodiment) <Configuration> First, the configuration of an illumination device 1 will be described with reference to FIGS.

[0017] FIG. 1 is a perspective view showing an illumination device 1 according to an embodiment. FIG. 2 is a cross-sectional view showing the illumination device 1 according to the embodiment along the line AA in FIG. 1. FIG. 3A is a diagram showing the configuration of a light guide plate 10 and a light source 20 in the illumination device 1 according to the embodiment. FIG. 3A (a) is a front view showing the illumination device 1 according to the embodiment, and FIG. 3A (b) is a cross-sectional view showing the illumination device 1 along the line IIIA-IIIA in FIG. 3A (a). FIG. 3B is a diagram showing another configuration of a light guide plate 10 and a light source 20 in the illumination device 1 according to the embodiment. FIG. 3B (a) is a front view showing the illumination device 1 according to the embodiment, and FIG. 3B (b) is a cross-sectional view showing the illumination device 1 along the line IIIB-IIIB in FIG. 3B (a). FIG. 4 is a diagram showing the tracing of light in the light guide plate 10 of the illumination device 1 according to the embodiment. In FIG. 4, light is shown by a dashed line.

[0018] As shown in FIG. 1, the lighting device 1 is a lighting fixture using a light guide plate 10, and is installed on construction materials such as a ceiling or a wall. The lighting device 1 can illuminate a space by irradiating light onto an irradiation surface of the construction material or the like. Construction materials are members that constitute a ceiling, a wall, a floor, or the like. For example, the lighting device 1 is installed on a wall or ceiling, and can illuminate a space by irradiating light onto an irradiation surface of the ceiling, a wall, a floor, or the like.

[0019] 2, the lighting device 1 is a lighting system using a light guide plate 10, and includes the light guide plate 10 and a light source 20. In the present embodiment, the lighting device 1 includes a housing 5, the light guide plate 10, the light source 20, and a power supply unit 30.

[0020] The light source 20 and the power supply unit 30 are contained in a housing 5, and the light guide plate 10 is fixed to the housing 5. In other words, the housing 5 is an outer casing member that forms the outer casing of the lighting device 1, and also serves as a housing that contains the light source 20 and the power supply unit 30 and holds the light guide plate 10. The housing 5 is a rigid body made of, for example, metal or resin.

[0021] 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.

[0022] 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 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.

[0023] The light guide plate 10 has an incident surface 11. The incident surface 11 is a light incident surface into which light emitted from a light source 20 is incident. Specifically, the incident surface 11 faces the light source 20.

[0024] The incident surface 11 is a side surface of the light guide plate 10. Since the light guide plate 10 is in a plate shape, the incident surface 11 is elongated. In this embodiment, the incident surface 11 is elongated and generally rectangular.

[0025] In the light guide plate 10, a light reflecting member or a light absorbing member may be provided on the back surface 12 facing away from the incident surface 11. In this embodiment, the incident surface 11 and the back surface 12 face each other in a direction perpendicular to the thickness direction of the light guide plate 10. That is, the back surface 12 is located on the opposite side to the incident surface 11. The incident surface 11 and the back surface 12 are each flat and approximately parallel. In addition, the incident surface 11 is not limited to a flat surface, and may include a concavely curved surface or a concavely recessed surface for each light emitting element of the light source 20 in order to efficiently input light from the light source 20 to the light guide plate 10. In addition, the back surface 12 is not limited to a flat surface. For example, the back surface 12 may be an inclined surface or an uneven surface.

[0026] The light guide plate 10 further has an exit surface 13 and a light extraction surface 15 facing away from the exit surface 13. The exit surface 13 and the light extraction surface 15 are surfaces that face each other when the light guide plate 10 is viewed from the front. The exit surface 13 and the light extraction surface 15 face each other in the thickness direction of the light guide plate 10. In this embodiment, the exit surface 13 and the light extraction surface 15 are each flat and substantially parallel to each other. Note that the light guide plate 10 has a substantially rectangular shape when viewed from the front, and therefore the exit surface 13 and the light extraction surface 15 are also substantially rectangular in shape.

[0027] The exit surface 13 is a light exit surface from which the light incident from the entrance surface 11 exits. Therefore, the exit surface 13 serves as a light-emitting surface that emits pseudo-light when the light guided within the light guide plate 10 exits to the outside.

[0028] Light extraction surface 15 is a light control surface that controls the light incident from incident surface 11 in order to emit the light from exit surface 13. In this embodiment, light extraction surface 15 has a light reflection structure for reflecting the light that is incident from incident surface 11 and guided to light guide plate 10 within light guide plate 10, toward exit surface 13.

[0029] On the light extraction surface 15, a plurality of concave or convex prisms 16 for emitting light from the exit surface 13 are formed as a light reflection structure. Fig. 2 illustrates a case where a plurality of concave prisms 16 are formed on the light extraction surface 15. The concave prisms 16 are recessed so as to slope upward along the optical axis direction of the light emitted by the light source 20. The optical axis direction is the direction from the entrance surface 11 toward the back surface 12.

[0030] The multiple prisms 16 are arranged in a matrix. Specifically, when the light guide plate 10 is viewed from a direction perpendicular to the light extraction surface 15 (front direction), the multiple prisms 16 are arranged along a first direction D1 from one of the entrance surface 11 and the back surface 12 to the other, and also along a second direction D2 substantially perpendicular to the first direction D1. In this embodiment, the first direction D1 is the optical axis direction of the light source 20. The multiple prisms 16 may be formed over the entire light extraction surface 15, or may be formed partially.

[0031] When viewed in a cross section of the light guide plate 10 cut along a plane perpendicular to the light extraction surface 15 and parallel to the optical axis direction, the cross-sectional shape of the multiple prisms 16 is substantially triangular. When viewed in this cross section, each of the multiple prisms 16 has a first surface 17a and a second surface 17b.

[0032] The first surface 17a is inclined upward along the optical axis direction of light emitted by the light source 20. Specifically, the first surface 17a is approximately half of the inner surface of the prism 16 on the light source 20 side and on the incident surface 11 side, and is a light reflecting surface that is inclined upward along the direction from the incident surface 11 to the back surface 12. The first surface 17a is disposed closer to the light source 20 than the second surface 17b.

[0033] The second surface 17b faces the first surface 17a and is inclined upward along the optical axis direction. Specifically, the second surface 17b is approximately half of the inner surface of the prism 16 on the side of the rear surface 12, and is inclined upward along the direction from the incident surface 11 toward the rear surface 12. Since the second surface 17b faces the first surface 17a, the second surface 17b is a light incident surface into which the light guided within the light guide plate 10 enters the first surface 17a and into which the light emitted from the first surface 17a re-enters.

[0034] Here, the following relationship exists in the prism 16. Specifically, when looking at a cross section of the light guide plate 10 cut along a plane that is perpendicular to the light extraction surface 15 and parallel to the optical axis direction, the following formulas (1) and (2) hold when a first angle of the first surface 17a with respect to the optical axis direction is θ1 and a second angle at which the optical axis direction intersects with the extension direction along the second surface 17b is θ2.

[0035] 5°≦θ1≦60° Formula (1)

[0036] θ2>90° Equation (2)

[0037] In addition, the second surface 17b has a first inclined surface 18a and a second inclined surface 18b.

[0038] Since the second surface 17b faces the first surface 17a, the first inclined surface 18a is also disposed to face the first surface 17a. The first inclined surface 18a is inclined upward along the optical axis direction. The tip of the first inclined surface 18a on the side of the exit surface 13 is connected to the first surface 17a.

[0039] Since the first inclined surface 18a is a part of the second surface 17b, the angle at which the extension direction along the first inclined surface 18a intersects with the light extraction surface 15 is the second angle θ2.

[0040] Since the second surface 17b faces the first surface 17a, the second inclined surface 18b is also disposed to face the first surface 17a. The second inclined surface 18b slopes downward along the optical axis direction. The second inclined surface 18b connects the first inclined surface 18a and the light extraction surface 15.

[0041] If a third angle at which the second inclined surface 18b intersects with the optical axis direction is θ3, the following formula (3) is established.

[0042] θ3≦90° Formula (3)

[0043] In this embodiment, the multiple prisms 16 are minute recesses processed into a predetermined shape. The multiple prisms 16 are microprisms of a micro-order size. The multiple prisms 16 can be formed by performing laser processing or cutting processing on the light extraction surface 15 of the flat light guide plate 10. When performing laser processing on the multiple prisms 16, the multiple prisms 16 can be formed by irradiating the light extraction surface 15 of the light guide plate 10 with a laser beam in an oblique direction or by cutting processing in an oblique direction. In addition, the light guide plate 10 having the multiple prisms 16 can also be produced by molding using a mold.

[0044] When the multiple prisms 16 are laser processed, the second inclined surface 18b may be rounded. Therefore, when viewed in a cross section of the light guide plate 10 cut along a plane perpendicular to the light extraction surface 15 and parallel to the optical axis direction, the second inclined surface 18b may be a flat surface or a curved surface.

[0045] In this embodiment, as shown in (a) of Fig. 3A, when the light guide plate 10 is viewed from the direction perpendicular to the light extraction surface 15 (when viewed from the front), the opening shape of the multiple prisms 16a1 is circular in a direction intersecting with the optical axis direction. In this case, the opening shape of the multiple prisms 16a1 is circular, so that the prisms are conical prisms. In the case of a conical prism, the first surface 17a and the first inclined surface 18a are curved surfaces.

[0046] Also, as shown in (a) of FIG. 3B, when the light guide plate 10 is viewed from a direction perpendicular to the light extraction surface 15 (when viewed from the front), the opening shape of the multiple prisms 16a2 may be elongated in a direction intersecting with the optical axis direction. In this case, the opening shape of the multiple prisms 16a2 is elongated, and thus becomes a long-groove prism. By forming the multiple prisms 16a2 in such a shape, it is possible to increase the amount of light emitted from the light guide plate 10 in the second direction D2 compared to the circular prism 16a1, and the light distribution of the lighting device 1 can be made wide. Specifically, the opening shape of the prism 16a2 may be a horizontally elongated racetrack shape when the light extraction surface 15 is viewed from the front. Also, the multiple prisms 16a2 may extend from an edge on one side of the light guide plate 10 to an edge on the other side. That is, the opening shape of the prism 16a2 may be a long-groove shape. The first surface 17a and the first inclined surface 18a have a flat surface.

[0047] In this embodiment, the prisms 16a1 and 16a2 are collectively referred to as the prism 16.

[0048] In the light guide plate 10 configured in this manner, light emitted from the light source 20 is incident on the incident surface 11, as shown in Figures 2 and 4. The light incident from the incident surface 11 is guided inside the light guide plate 10 and is incident on the light extraction surface 15. Specifically, a portion of the light incident from the light source 20 and guided to the light guide plate 10 is totally reflected at the interface between the first surface 17a of the multiple prisms 16 and the air layer. The light totally reflected at the first surface 17a travels towards the exit surface 13 and exits from the exit surface 13.

[0049] Furthermore, the light that is not reflected by the first surface 17a of the prism 16 and is emitted from the first surface 17a passes through the inside (air layer) of the prism 16 and enters the second surface 17b. A part of the light that is incident on the second surface 17b returns to the inside of the light guide plate 10, is guided inside the light guide plate 10, and is incident on the first surface 17a of the adjacent prism 16. In this way, even if the light is not totally reflected by the first surface 17a of the prism 16 or the second surface 17b, it can pass through multiple prisms 16 by re-entering the inside of the light guide plate 10. As a result, even if the light is emitted from the first surface 17a, it can have an opportunity to be reflected by the adjacent prism 16 by re-entering the inside of the light guide plate 10, and therefore it is possible to suppress a decrease in the light utilization efficiency.

[0050] In this case, by setting the first angle θ1 of the prism 16 to 45° to 50° or more, the light totally reflected by the first surface 17a tends to travel toward the rear surface 12 side rather than in a direction perpendicular to the exit surface 13 of the light guide plate 10. In other words, the proportion of light traveling toward the rear surface 12 side is greater than the proportion of light traveling toward the front direction of the exit surface 13 and toward the entrance surface 11 side.

[0051] In this way, the light incident on the light guide plate 10 from the light source 20 is reflected by the multiple prisms 16 and emitted from the exit surface 13, so that the exit surface 13 emits pseudo-light in a planar manner. At this time, the light reflected by the multiple prisms 16 is emitted to the outside of the light guide plate 10 with a predetermined light distribution.

[0052] 2, 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 incident surface 11 of the light guide plate 10.

[0053] The light source 20 is disposed opposite the incident surface 11 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 and the incident surface 11 of the light guide plate 10 face each other.

[0054] 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 incident surface 11 of the light guide plate 10.

[0055] The light source 20 has a substrate 21 and one or more light-emitting elements 22 mounted on the substrate 21. In the present embodiment, the light source 20 is an elongated LED module, and therefore the multiple light-emitting elements 22 are linearly mounted on one elongated substrate 21.

[0056] In this embodiment, the light source 20 is disposed 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 of the light emitting elements 22.

[0057] The substrate 21 is, for example, a wiring substrate on which wiring of a predetermined pattern is formed. As the substrate 21, a resin substrate, a ceramic substrate, a metal substrate with an insulating coating, or the like can be used.

[0058] The light emitting element 22 is an LED element made 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) arranged in the container, and a sealing member for sealing 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 energized 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. Note that, although an SMD type light emitting element is shown, this is not limiting. For example, the light emitting element 22 may include a COB (Chip On Board) type LED element in which an LED chip is directly mounted on a substrate.

[0059] The light source 20 emits light by power supplied from a power supply unit 30. The power supply unit 30 is configured, for example, by a circuit board on which a plurality of 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. In this embodiment, the power supply unit 30 is built into the lighting device 1, but is not limited to this. The power supply unit 30 may be a separate body that can be separated from the lighting device 1. The light source 20 may be configured to be dimming controlled and / or color toning controlled.

[0060] <Experimental Results> Next, experimental results of the lighting device 1 according to the present embodiment will be described with reference to FIG. 5A.

[0061] Fig. 5A is a diagram showing light distribution curves according to the prism shapes, which show light distribution curves using a light guide plate having a substantially isosceles triangular prism according to Comparative Example 1, a light guide plate having a substantially triangular irregular prism according to Comparative Example 2, and light guide plate 10 having prism 16 according to the present embodiment.

[0062] First, the light distribution curves of Comparative Examples 1 and 2 and this embodiment will be described.

[0063] As shown in FIG. 5A, in the light guide plate having the prism of a substantially isosceles triangle shape according to Comparative Example 1, as shown in the light distribution curve of Comparative Example 1, although the control light is emitted from the emission surface, it was found that leakage light occurs from the prism of the light extraction surface toward the light distribution surface side. In Comparative Example 1, the control light with respect to the total luminous flux was 60%. Therefore, in Comparative Example 1, as much as 40% of the light is emitted from the light extraction surface as leakage light. The beam angle of the control light in Comparative Example 1 was 50°.

[0064] In the light guide plate having the irregular prism of a substantially triangular shape according to Comparative Example 2, as shown in the light distribution curve of Comparative Example 2, the leakage light was suppressed compared to Comparative Example 1, but it was found that leakage light occurred from the prism of the light extraction surface toward the light distribution surface side. In Comparative Example 2, the control light with respect to the total luminous flux was 80%. Therefore, in Comparative Example 2, as much as 20% of the light was emitted from the light extraction surface as leakage light. The beam angle of the control light in Comparative Example 2 was 20°.

[0065] In the light guide plate 10 having the prism 16 according to the present embodiment, it was found that the leakage light was further suppressed compared to Comparative Examples 1 and 2, as shown in the light distribution curve of the present embodiment. In the present embodiment, the control light with respect to the total luminous flux was 89%. In the present embodiment, the leakage light from the light extraction surface 15 could be suppressed to 11%. The beam angle of the control light in the present embodiment was 10°.

[0066] Next, with reference to FIG. 5B, a light distribution curve in the case of using light guide plate 210 having prisms 216 inclined in the opposite direction to that of prisms 16 in this embodiment will be described.

[0067] FIG. 5B is a diagram showing light distribution curves of light guide plate 10 using prism 16 in this embodiment and light guide plate 210 using prism 216 that is inclined in the opposite direction to prism 16 in this embodiment.

[0068] As shown in FIG. 5B, in this embodiment, light (control light) is emitted in a direction perpendicular to emission surface 13, and the beam angle of the control light in this case is about 10°.

[0069] In contrast, in the light guide plate 210 using the prisms 216 inclined in the opposite direction, although a small amount of light is emitted from the exit surface 13, the light is emitted from the light extraction surface 215 toward the back surface 12. Therefore, even when the light guide plate 210 is used, it is possible to obtain control light with light distribution control. In the case of the light guide plate 210, since the light is emitted from the light extraction surface 215, the light may be emitted from the exit surface 13 of the light guide plate 210 by changing the direction of the light guide plate 210 or providing a reflector such as a mirror on the light extraction surface 215. Note that, as shown in FIG. 5B, the control light is emitted in two directions, so the light guide plate 10 of this embodiment is preferable.

[0070] Next, with reference to FIG. 5C, the light irradiation modes of a normal lighting device, a lighting device of Comparative Example 1, and a lighting device 1 using a light guide plate 10 having a prism 16 in which the first angle θ1 in this embodiment is adjusted will be described.

[0071] FIG. 5C is a diagram showing the irradiation mode of light emitted from the exit surface 13 of the light guide plate 10. FIG. 5C (a) illustrates the irradiation mode of light when a normal lighting device emits light. FIG. 5C (b) illustrates the irradiation mode of light when a lighting device using a light guide plate having a prism of Comparative Example 1 emits light. FIG. 5C (c) illustrates the irradiation mode of light when a lighting device 1 using a light guide plate 10 having a prism 16 in the present embodiment emits light when the first angle θ1 is about 30°. FIG. 5C (d) illustrates the irradiation mode of light when a lighting device 1 using a light guide plate 10 having a prism 16 in the present embodiment emits light when the first angle θ1 is about 20°. In FIG. 5C, the whiter the color, the higher the illuminance. The irradiation distance shown in FIG. 5C indicates the distance from the lighting device to the irradiation surface at which the luminous flux becomes 1lx when the luminous flux is 500lm.

[0072] In (a) of Fig. 5C, it is possible to illuminate a distance of about 0.9 (m) in the optical axis direction. Also, in (b) of Fig. 5C, it is possible to illuminate a distance of about 2 (m) in the optical axis direction. In contrast, in this embodiment, as shown in (c) of Fig. 5C, it is possible to illuminate a distance of about 2.5 (m) in the optical axis direction. Also, as shown in (d) of Fig. 5C, it is possible to illuminate a distance of about 3 (m) in the optical axis direction.

[0073] For this reason, it has been found that the light emitted from the exit surface 13 of the light guide plate can reach farther by making the first angle θ1 smaller. By adjusting the first angle θ1, the direction and range of the light emitted by the lighting device 1 can be adjusted.

[0074] <Method of Manufacturing Light Guide Plate 10> Next, a method for manufacturing the light guide plate 10 in this embodiment will be described.

[0075] In one example of the manufacturing method for the light guide plate 10, a laser processing device is used. The laser processing device has a laser light source, a galvanometer, a galvanometer mirror, and a lens. The laser light source irradiates a laser upon receiving a command from a controller. The galvanometer performs positioning for irradiating the laser onto the light extraction surface 15 of the light guide plate 10. The galvanometer also controls the attitude of the galvanometer mirror. The galvanometer mirror is a mirror that reflects the laser. The lens focuses the laser so that the focal point of the laser emitted by the laser light source is distributed on the light extraction surface 15 of the light guide plate 10.

[0076] At this time, the laser light source irradiates the laser in an oblique direction to the light extraction surface 15 of the light guide plate 10. Note that the galvanometer irradiates the laser light in an oblique direction to the light extraction surface 15 by controlling the attitude of the galvanometer mirror, but the laser light may be irradiated in an oblique direction to the light extraction surface 15 by adjusting the attitude of the light extraction surface 15 of the light guide plate 10.

[0077] The laser processing device scans the laser in any direction on the light extraction surface 15 of the light guide plate 10. As a result, a plurality of prisms 16 are formed on the light extraction surface 15 of the light guide plate 10.

[0078] As described above, in this embodiment, a plurality of prisms 16 may be formed on light extraction surface 15 of light guide plate 10 by cutting light extraction surface 15 of light guide plate 10 or by molding using a metal mold.

[0079] <Action and effect> Next, the effects of the illumination device 1 and the method for manufacturing the light guide plate 10 in this embodiment will be described. Here, the above-mentioned comparative example to the present disclosure will also be described.

[0080] FIG. 6 is a diagram in which light is traced in a light guide plate of an illumination device according to a comparative example.

[0081] As shown in FIG. 4 and FIG. 6, the illumination device of the comparative example has a different configuration of the light guide plate 110 from the light guide plate 10 of the illumination device 1 of the present embodiment. Specifically, the light guide plate 110 of the comparative example has a different prism shape from the light guide plate 10 of the present embodiment. The prism 116 in the light guide plate 110 of the comparative example is a recessed portion having a substantially isosceles triangle shape. Compared to the second surface 17b of the prism 16 of the present embodiment, the second surface 117b of the prism 116 of the comparative example is inclined downward along the optical axis direction. Therefore, the second angle θ2 at which the optical axis direction and the extension direction along the second surface 117b intersect in the comparative example is less than 90°.

[0082] In light guide plate 110 of the comparative example configured in this manner, a portion of the light incident from the light source and guided to light guide plate 110 is totally reflected at the interface between first surface 117a of multiple prisms 116 and the air layer. The light totally reflected at first surface 117a travels toward the exit surface and exits from the exit surface.

[0083] However, a portion of the light that is not reflected by first surface 117a of prism 116 and is emitted from first surface 117a passes through the inside of prism 116 and is emitted directly from light extraction surface 115 of light guide plate 110 to the outside of light guide plate 110. Moreover, the remaining light that is emitted from first surface 117a enters second surface 117b but is reflected by second surface 117b and is emitted from light extraction surface 115 of light guide plate 110 to the outside of light guide plate 110.

[0084] Therefore, in the light guide plate 110 of the comparative example, light leakage occurs from the light extraction surface 115, and the light utilization efficiency decreases.

[0085] However, the lighting device 1 according to the first technique of the present embodiment includes a light source 20, an incident surface 11 on which the light emitted by the light source 20 is incident, an exit surface 13 from which the light incident from the incident surface 11 exits, and a light extraction surface 15 for emitting the light from the exit surface 13, and a light guide plate 10 on which a plurality of prisms 16 for emitting the light from the exit surface 13 are formed. When a cross section of the light guide plate 10 is cut along a plane perpendicular to the light extraction surface 15 and parallel to the optical axis direction of the light source 20, a plurality of prisms 16 having a first surface 17a that slopes upward along the optical axis direction of the light emitted by the light source 20 and a second surface 17b that faces the first surface 17a and slopes upward along the optical axis direction are formed on the light extraction surface 15. The first surface 17a is disposed closer to the light source 20 than the second surface 17b. Then, if a first angle of first surface 17a with respect to the optical axis direction is θ1 and a second angle at which the optical axis direction intersects with the extension direction along second surface 17b is θ2, the following equations (1) and (2) are established.

[0086] 5°≦θ1≦60° Formula (1)

[0087] θ2>90° Equation (2)

[0088] According to this, by using light guide plate 10 having multiple prisms 16 set according to formulas (1) and (2), it is possible to return the light emitted from first surface 17a to the inside of light guide plate 10, so that the light emitted from first surface 17a is more likely to pass through multiple prisms 16. This makes it easier for the light to have multiple opportunities to be reflected by prisms 16, so that it is possible to suppress a decrease in the light utilization efficiency.

[0089] Therefore, according to the lighting device 1 of the present embodiment, the leakage of light from the plurality of prisms 16 can be further suppressed.

[0090] In particular, by changing the second angle θ2, the depth of the prism 16 can be adjusted. This ensures freedom in designing the multiple prisms 16. Furthermore, by increasing the depth of the prism 16, the light emitted from the first surface 17a can be more easily re-entered into the light guide plate 10, which is expected to improve the light utilization efficiency.

[0091] In addition, since the multiple prisms 16 are inclined obliquely with respect to the optical axis direction, the length of the multiple prisms 16 can be increased while ensuring the strength of the light guide plate 10, compared to, for example, a case in which the depth of the multiple prisms is increased in a direction perpendicular to the light extraction surface. The length of the prism 16 is the length from the opening surface of the prism 16 to the tip of the prism 16.

[0092] Furthermore, according to the present embodiment, since the decrease in light utilization efficiency can be suppressed, the lighting device 1 can emit more control light than the comparative example. Therefore, the lighting device 1 can control the light distribution in a desired direction.

[0093] Furthermore, in the manufacturing method of light guide plate 10 relating to technique 7 of this embodiment, in light guide plate 10 having incident surface 11 into which light emitted from light source 20 enters, exit surface 13 from which the light incident from incident surface 11 exits, and light extraction surface 15 for emitting light from exit surface 13, a plurality of prisms 16 for emitting light from exit surface 13 are formed on light extraction surface 15 by laser processing.

[0094] In this case as well, the same effects as those described above are achieved.

[0095] Moreover, the manufacturing method of the light guide plate 10 according to Technique 8 of the present embodiment is the manufacturing method of the light guide plate 10 described in Technique 7. In this case, the multiple prisms 16 are formed by irradiating the light extraction surface 15 with laser light in an oblique direction.

[0096] This makes it possible to form a plurality of prisms 16 inclined with respect to the light extraction surface 15 on the light extraction surface 15 as in this embodiment.

[0097] Moreover, the illumination device 1 according to Technology 2 of this embodiment is the illumination device 1 described in Technology 1. In this case, the second surface 17b has a first inclined surface 18a and a second inclined surface 18b. The angle at which the extension direction along the first inclined surface 18a intersects with the light extraction surface 15 is a second angle θ2. If the third angle at which the second inclined surface 18b intersects with the optical axis direction is θ3, the following formula (3) is established.

[0098] θ3≦90° Formula (3)

[0099] According to this, the formation of the second inclined surface 18b makes it possible to round off the corners of the boundary portion between the second surface 17b and the light extraction surface 15. This makes it possible to suppress damage to the corners of the boundary portion, thereby ensuring the strength of the light guide plate 10.

[0100] The illumination device 1 according to technique 3 of the present embodiment is the illumination device 1 according to technique 2. In this case, the first inclined surface 18a is inclined upward along the optical axis direction. The second inclined surface 18b connects the first inclined surface 18a and the light extraction surface 15 and is inclined downward along the optical axis direction.

[0101] According to this, the second inclined surface 18b can be formed by forming the multiple prisms 16 by laser processing on the light extraction surface 15. Even if the multiple prisms 16 are formed by laser processing, light leakage from the multiple prisms 16 can be suppressed.

[0102] Moreover, the illumination device 1 according to the fourth aspect of the present embodiment is the illumination device 1 according to any one of the first to third aspects. In this case, the opening shape of the plurality of prisms 16 is circular.

[0103] According to this, when the opening shape of prism 16 is circular, lighting device 1 can make the light distribution ratio of light traveling in a direction other than the incident surface 11 side approximately equal.

[0104] Moreover, the illumination device 1 according to technique 5 of the present embodiment is the illumination device 1 according to any one of techniques 1 to 3. In this case, the opening shape of the multiple prisms 16 is elongated in a direction intersecting with the optical axis direction.

[0105] According to this, when the opening shape of the prism 16 is elongated, not only can the light distribution ratio of the light traveling toward the back surface 12 side with respect to the front direction of the light guide plate 10 be increased, but also the light distribution ratio of the light traveling in the second direction D2 of the light guide plate 10 can be increased. This makes it possible to realize a wide light distribution.

[0106] <Modification> First, the configuration of an illumination device 1a according to this modification will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view showing an illumination device 1a according to the modification.

[0107] This modification differs from the embodiment in that the length of the prisms 16c of the light guide plate 10a in the lighting device 1a in the thickness direction of the light guide plate 10a gradually increases with increasing distance from the light source 20. In this modification, the same configurations and functions as those of the lighting device of the embodiment are denoted by the same reference numerals, and detailed descriptions of these configurations and functions will be omitted as appropriate.

[0108] The illumination device 1a according to the sixth aspect of the present modification is the illumination device 1a according to any one of the first to fifth aspects. In this case, the prisms 16c include two adjacent prisms, a first prism 16c1 and a second prism 16c2, arranged along the optical axis direction from the light source 20. In the thickness direction of the light guide plate 10, the length of the second prism 16c2 relative to the light extraction surface 15 is longer than the length of the first prism 16c1. That is, in this modification, the length of the prisms 16c relative to the light extraction surface 15 (the depth in the case of the concave prism 16c of this modification) gradually increases from the entrance surface 11 toward the back surface 12.

[0109] According to this, the light totally reflected by the first surface 17a of the prism 16c can proceed to the exit surface 13 without being incident (obstructed) on the first prism 16c1 closer to the entrance surface 11 adjacent to the second prism 16c2. Therefore, it is possible to suppress interference between two adjacent prisms 16c when the pitch between the multiple prisms 16c is reduced.

[0110] <Experimental Results> Next, with reference to Figs. 8A and 8B, the light distribution of the lighting devices 1 and 1a when the size of the prism 16c is changed and the light distribution of the lighting devices 1 and 1a when the coverage of the prism 16 is changed will be described.

[0111] FIG. 8A is a diagram showing the light distribution of the lighting device 1, 1a when the size of the prism 16 is uniform and when the size of the prism 16c is changed. In FIG. 8A, the solid line shows the case when the size of the prism 16 is uniform, and the dashed line shows the case when the size of the prism 16c is changed. FIG. 8B is a diagram showing the light distribution of the lighting device 1, 1a when the coverage of the prism 16 is changed. In FIG. 8B, the solid line shows the case when the coverage of the prism 16 is 1%, the dashed line shows the case when the coverage of the prism 16 is 10%, and the dashed line shows the case when the coverage of the prism 16 is 100%. In FIG. 8A and FIG. 8B, the horizontal axis shows the angle of the light emitted with respect to the vertical direction (the direction perpendicular to the light extraction surface 15), and the vertical axis shows the luminous intensity of the light emitted.

[0112] As shown in FIG. 8A , when the size of prism 16c is changed as in this modified example, the light extraction efficiency decreases compared to when the size of prism 16 is uniform, but it can be seen that the light distribution can be controlled in the direction from light source 20 toward the rear surface 12 of light guide plate 10.

[0113] As shown in FIG. 8B, it can be seen that the light extraction efficiency increases as the coverage rate of the prisms 16c on the light extraction surface 15 of the light guide plate 10 increases.

[0114] For this reason, by adjusting the size of the prisms 16c and the coverage of the prisms 16c on the light extraction surface 15, it is possible to adjust the light extraction efficiency and light distribution control so as to achieve a desired illumination mode.

[0115] (Other variations) Although the illumination device and the method for manufacturing a light guide plate according to the present disclosure have been described based on the embodiments, the present disclosure is not limited to the above-described embodiments.

[0116] For example, in the above embodiment, the connection portion between the first and second surfaces of the prism may be smoothly curved or bent so as to bend. Also, the connection portion between the first surface and the light extraction surface, the connection portion between the first inclined surface and the second inclined surface, and the connection portion between the second inclined surface and the light extraction surface may be smoothly curved or bent so as to bend.

[0117] In the above embodiment, the width of the opening of the prism along the optical axis direction may be set smaller than the length of the prism in the thickness direction of the light guide plate. In addition, in an arrangement of the prisms along the optical axis direction, the pitch between two adjacent prisms may be set smaller than the length of the prism.

[0118] In the above embodiment, a reflector or a light absorbing plate may be disposed on the rear surface. The reflector may be made of a resin material or a metal material. Specifically, the reflector may be a white resin sheet made of a resin material such as PBT (polybutylene terephthalate), or a metal plate made of a metal material such as aluminum, or a base material on which a metal film such as aluminum or a white resin is formed. The light absorbing material is disposed on the rear surface of the light guide plate. In the present embodiment, the light absorbing material may cover the entire rear surface. The light absorbing material may be, for example, a coating film made of a material that absorbs light. In this case, a coating material is applied to the rear surface of the light guide plate and solidified to form a light absorbing material made of a coating film in close contact with the rear surface. The light absorbing material may be a tape-shaped tape member. In this case, the light absorbing material may be attached to the rear surface of the light guide plate by an adhesive. The light absorbing material may be, for example, a base material made of a material having substantially the same refractive index as the light guide plate, to which an additive having a light absorbing function, such as carbon, has been added.

[0119] In the above modification, the length of the prism relative to the light extraction surface gradually increases with increasing distance from the light incidence surface, and the aperture area of ​​the prism gradually increases, but this is not limiting. For example, the length of the prism in the thickness direction of the light guide plate may be changed without changing the size of the aperture area of ​​the prism.

[0120] In the above embodiment, the second surface has the first inclined surface and the second inclined surface, but is not limited to this. In other words, the second surface may be composed of only the first inclined surface. Therefore, the second inclined surface is not an essential component of the second surface.

[0121] In the above embodiment, the length of the prisms relative to the light extraction surface in the thickness direction of the light guide plate may be gradually shortened as it gets farther away from the incident surface. In other words, the length of the prisms relative to the light extraction surface may be gradually shortened as it gets closer to the back surface from the incident surface. This makes it easier to control the light totally reflected by the first surface of the prism in a predetermined direction.

[0122] In the above embodiment, the light source is configured by an LED, but is not limited to this. For example, the light source may be configured by a solid-state light-emitting element other than an LED, such as a semiconductor laser or an organic EL (Electro Luminescence). In addition, existing lamps such as fluorescent lamps and high-intensity lamps may be used as the light source.

[0123] In the above-described embodiment, the light guide plate can be applied to any lighting device such as a pole light, a ceiling light, or the like.

[0124] In addition, in the above embodiment, the light guide plate is applied to a lighting device, but the present disclosure is not limited to this. The present disclosure can also be applied to a lighting system including a light guide plate.

[0125] Furthermore, the above modifications are considered to be included in the above embodiment.

[0126] In addition, the present disclosure 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 disclosure. [Explanation of symbols]

[0127] 1, 1a Lighting equipment 10, 10a, 210 light guide plate 11 Incidence plane 13 Exit surface 15, 215 Light extraction surface 16, 16a1, 16a2, 16c, 216 Prism 16c1 First prism 16c2 Second Prism 17a 1st page 17b Side 2 18a First Slope 18b 2nd slope 20 light source

Claims

1. A light source; a light guide plate having an incident surface into which light emitted from the light source is incident, an exit surface from which the light incident from the incident surface exits, and a light extraction surface for emitting the light from the exit surface, and on which a plurality of prisms for emitting the light from the exit surface are formed, When a cross section of the light guide plate is cut along a plane perpendicular to the light extraction surface and parallel to an optical axis direction of the light source, the light extraction surface has a plurality of prisms each having a first surface that slopes upward along the optical axis direction of light emitted from the light source and a second surface that faces the first surface and slopes upward along the optical axis direction, the first surface is disposed closer to the light source than the second surface, a first angle of the first surface with respect to the optical axis direction is θ1; When a second angle at which the optical axis direction intersects with the extension direction along the second surface is θ2, the following formulas (1) and (2) are established. 5°≦θ1≦60° Formula (1) θ2>90° Equation (2) Lighting equipment.

2. the second surface has a first inclined surface and a second inclined surface, an angle at which an extension direction along the first inclined surface intersects with the light extraction surface is the second angle θ2; When a third angle at which the second inclined surface intersects with the optical axis direction is θ3, the following formula (3) is established: θ3≦90° Formula (3) 10. The lighting device of claim 1.

3. The first inclined surface is inclined upward along the optical axis direction. The second inclined surface connects the first inclined surface and the light extraction surface, and is inclined downward along the optical axis direction.

3. The lighting device according to claim 2.

4. The opening shape of the plurality of prisms is circular.

3. The lighting device according to claim 1 or 2.

5. The opening shape of the plurality of prisms is elongated in a direction intersecting with the optical axis direction.

3. The lighting device according to claim 1 or 2.

6. The plurality of prisms include two adjacent first prisms and a second prism arranged along the optical axis direction from the light source, In a thickness direction of the light guide plate, a length of the second prism with respect to the light extraction surface is longer than a length of the first prism.

3. The lighting device according to claim 1 or 2.

7. In a light guide plate having an incident surface on which light emitted from a light source is incident, an exit surface from which the light incident from the incident surface exits, and a light extraction surface for emitting light from the exit surface, a plurality of prisms for emitting light from the exit surface are formed on the light extraction surface by laser processing. A method for manufacturing a light guide plate.

8. The plurality of prisms are formed by irradiating the light extraction surface with a laser beam in an oblique direction. The method for producing the light guide plate according to claim 7 .

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