Illuminating device and manufacturing method of light guide plate

Abstract

The invention provides a lighting device and a method for manufacturing a light guide plate. An illumination device (1) is provided with a light source (20), and a light guide plate (10) having an incident surface (11), an exit surface (13), and a light extraction surface (15), and having formed therein a plurality of prisms (16) for emitting light from the exit surface (13). When a cross section when the light guide plate is cut with a plane orthogonal to the light extraction surface and parallel to the optical axis direction is observed, a plurality of prisms having a first surface (17a) and a second surface (17b) are formed on the light extraction surface, the first surface being inclined upward in the optical axis direction of the light emitted by the light source, and the second surface facing the first surface being inclined upward in the optical axis direction. If a first angle of the first surface with respect to the optical axis direction is theta1, and a second angle where the optical axis direction intersects the extension direction along the second surface is theta2, the following formulae (1)-(2) satisfy: 5 DEG < = theta1 < = 60 DEG (1) theta2gt; and 90 DEG formula (2).

Description

Technical Field

[0001] This disclosure relates to lighting devices using light guide plates and methods for manufacturing light guide plates. Background Technology

[0002] Previously, edge-lit lighting fixtures were known as light guide plate systems using light guide plates. Edge-lit lighting fixtures include a light guide plate and a light source arranged opposite to the end face of the light guide plate.

[0003] As such a lighting device, for example, Patent Document 1 discloses a lighting device comprising: a light-emitting module; and a light guide having an incident surface for light incidence and an opposing surface for causing incident light to exit from an emission surface, and having formed a plurality of prisms for causing light to exit from the emission surface.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-136128 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, there is a need to further suppress light leakage from the multiple prisms formed on the light guide plate.

[0009] This disclosure was made to solve such a problem, with the aim of providing an illumination device, etc., that can further suppress light leakage from multiple prisms.

[0010] Methods used to solve problems

[0011] A technical solution of the lighting device disclosed herein includes: a light source; and a light guide plate having an incident surface for light emitted from the light source, an exit surface for light emitted from the incident surface, and a light extraction surface for light to be emitted from the exit surface. A plurality of prisms for light to be emitted from the exit surface are formed. When observing the cross section of the light guide plate when cut by a plane orthogonal to the light extraction surface and parallel to the optical axis of the light source, a plurality of prisms having a first surface and a second surface are formed on the light extraction surface. The first surface is inclined upward along the optical axis of the light emitted from the light source, and the second surface is opposite to the first surface and is inclined upward along the optical axis. The first surface is positioned closer to the light source side than the second surface. When the first angle of the first surface relative to the optical axis is θ1, and the second angle of the intersection of the optical axis and the extension direction along the second surface is θ2, the following equations (1) to (2) hold.

[0012] 5°≤θ1≤60° Equation (1)

[0013] θ2>90° Formula (2)

[0014] Furthermore, in one technical solution of the manufacturing method of the light guide plate disclosed herein, in a light guide plate having an incident surface on which light emitted from a light source is incident, an exit surface on which light emitted from the incident surface is exited, and a light extraction surface for causing light to exit from the exit surface, a plurality of prisms for causing light to exit from the exit surface are formed on the light extraction surface by laser processing.

[0015] Invention Effects

[0016] According to this disclosure, it is possible to further suppress light leakage from multiple prisms. Attached Figure Description

[0017] Figure 1 This is a perspective view showing the lighting device according to the relevant implementation method.

[0018] Figure 2 It means Figure 1 A cross-sectional view of the lighting device according to the relevant implementation method on line A-A.

[0019] Figure 3A This is a diagram showing the structure of the light guide plate and the light source in the lighting device according to the relevant implementation method.

[0020] Figure 3B This is a diagram showing the structure of other light guide plates and light sources in the lighting device according to the relevant embodiments.

[0021] Figure 4 This is a diagram showing the tracing of light in the light guide plate of the lighting device according to an embodiment.

[0022] Figure 5A It is a diagram showing the light distribution curve corresponding to the shape of the prism.

[0023] Figure 5B This is a diagram showing the light guide plate using the prism of the embodiment and the light distribution curve in the light guide plate using a prism tilted in the opposite direction to the prism of this embodiment.

[0024] Figure 5C This is a diagram showing the illumination pattern of light emitted from the light guide plate's emission surface.

[0025] Figure 6 This is a diagram showing the light tracing in the light guide plate of the lighting device for the comparative example.

[0026] Figure 7 This is a cross-sectional view of a lighting device showing a variation of the embodiment.

[0027] Figure 8AThis is a diagram showing the light distribution of an illumination device when the prism size is uniform and when the prism size is changed.

[0028] Figure 8B This is a diagram showing the light distribution of an illumination device when the coverage of the prism is changed. Detailed Implementation

[0029] The embodiments of this disclosure will now be described. Furthermore, the embodiments described below represent specific examples of this disclosure. Therefore, the numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, and connection methods shown in the following embodiments are examples and are not intended to limit this disclosure. Therefore, any constituent elements in the constituent elements of the following embodiments that are not described in the independent claims will be described as arbitrary constituent elements.

[0030] Furthermore, the figures are schematic diagrams and not necessarily rigorous representations. In some figures, substantially identical structures are given the same labels, and repeated explanations are omitted or simplified.

[0031] Furthermore, in the following embodiments, terms such as "generally parallel" or "rectangular" are used. For example, "generally parallel" or "rectangular" not only means completely parallel or rectangular, but also means substantially parallel or rectangular, i.e., including an error of about a few percentage points. Moreover, "generally parallel" or "rectangular" means parallel or rectangular within the range that achieves the effects of this disclosure. The same applies to other uses of "generally" or "rectangular".

[0032] (Implementation Method)

[0033] <Structure>

[0034] First, refer to Figures 1-4 The structure of lighting device 1 will be described.

[0035] Figure 1 This is a perspective view showing the lighting device 1 according to the relevant implementation method. Figure 2 It means Figure 1 A cross-sectional view of the lighting device 1 according to the relevant embodiment on line A-A. Figure 3A This is a diagram showing the structure of the light guide plate 10 and the light source 20 in the lighting device 1 according to the relevant embodiment. Figure 3A (a) is a front view showing the lighting device 1 according to the embodiment. Figure 3A (b) means Figure 3A (a) Cross-sectional view of the lighting device 1 on line IIIA-IIIA. Figure 3B This is a diagram showing the structure of the other light guide plates 10 and light sources 20 in the lighting device 1 according to the relevant embodiment. Figure 3B(a) is a front view showing the lighting device 1 according to the embodiment. Figure 3B (b) means Figure 3B (a) Cross-sectional view of the lighting device 1 on line IIIB-IIIB. Figure 4 This is a diagram illustrating the tracing of light in the light guide plate 10 of the lighting device 1 according to the relevant embodiment. Figure 4 In the image, a single-dot dash is used to represent light.

[0036] like Figure 1 As shown, the lighting device 1 is a lighting fixture that uses the light guide plate 10, such as a building material installed on a ceiling, wall, etc. The lighting device 1 illuminates a space by illuminating the surface of the building material, etc. The building material is a component that constitutes a ceiling, wall, floor, etc. For example, the lighting device 1 is installed on the wall and ceiling, etc., and illuminates the space by illuminating the surface of the ceiling, wall, floor, etc.

[0037] like Figure 2 As shown, 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 this embodiment, the lighting device 1 includes a housing 5, a light guide plate 10, a light source 20, and a power supply unit 30.

[0038] The light source 20 and the power supply unit 30 are housed in the housing 5, and the light guide plate 10 is fixed to the housing 5. That is, the housing 5 is the outer part that forms the outline of the lighting device 1, and is the shell that houses the light source 20 and the power supply unit 30 or holds the light guide plate 10. The housing 5 is, for example, a rigid body made of metal or resin.

[0039] The light guide plate 10 is an optical component that guides light. In this embodiment, the light guide plate 10 is a flat plate with a rectangular shape in planar view.

[0040] The light guide plate 10 is a light-transmitting component and is made of a light-transmitting material. The light guide plate 10 is made of a light-transmitting resin material, such as acrylic resin or polycarbonate resin. Furthermore, the light guide plate 10 is preferably made of a transparent resin material with a high transmittance, sufficient to allow transmission and visibility from the opposite side. In this embodiment, the light guide plate 10 is made of a transparent plate formed of acrylic resin. However, the light guide plate 10 is not limited to a transparent resin plate made of resin material; it can also be a glass plate made of transparent glass.

[0041] The light guide plate 10 has an incident surface 11. The incident surface 11 is the light incident surface on which the light emitted by the light source 20 is incident. Specifically, the incident surface 11 is opposite to the light source 20.

[0042] The incident surface 11 is the side surface of the light guide plate 10. Since the light guide plate 10 is plate-shaped, the incident surface 11 is elongated. In this embodiment, the incident surface 11 is an elongated, approximately rectangular shape.

[0043] Additionally, in the light guide plate 10, a light reflecting component or a light absorbing component may be provided on the back surface 12, which faces away from the incident surface 11. In this embodiment, the incident surface 11 and the back surface 12 are opposite each other in a direction orthogonal to the thickness direction of the light guide plate 10. That is, the back surface 12 is located on the side opposite to the incident surface 11. The incident surface 11 and the back surface 12 are both planes and are substantially parallel. Furthermore, the incident surface 11 is not limited to a plane, and may include a concave curved surface or a concave recessed surface for each light-emitting element of the light source 20 in order to efficiently incident light from the light source 20 onto the light guide plate 10. In addition, the back surface 12 is not limited to a plane. For example, the back surface 12 may also be an inclined surface or a convex-concave surface.

[0044] The light guide plate 10 also has an emission surface 13 and a light extraction surface 15 facing away from the emission surface 13. The emission surface 13 and the light extraction surface 15 are opposing surfaces when the light guide plate 10 is viewed from the front. Furthermore, the emission surface 13 and the light extraction surface 15 are opposing each other in the thickness direction of the light guide plate 10. In this embodiment, the emission surface 13 and the light extraction surface 15 are both planes and are substantially parallel. In addition, since the shape of the light guide plate 10 when viewed from the front is substantially rectangular, the shapes of the emission surface 13 and the light extraction surface 15 are also substantially rectangular.

[0045] The emission surface 13 is a light emission surface from which light incident from the incident surface 11 is emitted. Therefore, the emission surface 13 is a light-emitting surface that emits light by simulating light emitted from the light guided within the light guide plate 10.

[0046] The light extraction surface 15 is a light control surface that controls the light incident from the incident surface 11 so that the light can be emitted from the emission surface 13. In this embodiment, the light extraction surface 15 has a light reflection structure for reflecting the light incident from the incident surface 11 and guided by the light guide plate 10 in the light guide plate 10 toward the emission surface 13.

[0047] On the light extraction surface 15, multiple concave or convex prisms 16 are formed as a light reflection structure to allow light to exit from the emission surface 13. Figure 2 The example shown illustrates a case where multiple concave prisms 16 are formed on the light extraction surface 15. The concave prisms 16 are recessed in a manner that slopes upwards along the optical axis direction of the light emitted from the light source 20. The optical axis direction is from the incident surface 11 towards the back surface 12.

[0048] Multiple prisms 16 are arranged in a matrix. Specifically, when the light guide plate 10 is viewed from the direction perpendicular to the light extraction surface 15 (front direction), multiple prisms 16 are arranged along a first direction D1 from one side of the incident surface 11 and the back surface 12 toward the other, and multiple prisms are arranged along a second direction D2 that is approximately orthogonal to the first direction D1. In this embodiment, the first direction D1 is the optical axis direction of the light source 20. Furthermore, while the multiple prisms 16 are formed over the entire light extraction surface 15, they can also be formed locally.

[0049] When observing the cross-section of the light guide plate 10 cut by a plane orthogonal to the light extraction surface 15 and parallel to the optical axis, the cross-sectional shape of the plurality of prisms 16 is approximately triangular. In this cross-section, the plurality of prisms 16 each have a first surface 17a and a second surface 17b.

[0050] The first surface 17a is inclined upwards along the optical axis of the 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 the incident surface 11 side, and is a light-reflecting surface that is inclined upwards along the direction from the incident surface 11 toward the back surface 12. The first surface 17a is positioned closer to the light source 20 side than the second surface 17b.

[0051] The second surface 17b is opposite to the first surface 17a and is inclined upwards along the optical axis. Specifically, the second surface 17b is approximately half of the inner surface of the back surface 12 of the prism 16, and is inclined upwards along the direction from the incident surface 11 toward the back surface 12. Since the second surface 17b is opposite to the first surface 17a, the second surface 17b is the light incident surface where light guided within the light guide plate 10 is incident on the first surface 17a and light emitted from the first surface 17a is re-incident.

[0052] Here, the following relationship exists in prism 16. Specifically, when observing the cross section of light guide plate 10 cut by a plane orthogonal to light extraction surface 15 and parallel to the optical axis direction, if we set the first angle of the first surface 17a relative to the optical axis direction as θ1, and the second angle of the optical axis direction intersecting the extension direction along the second surface 17b as θ2, then the following equations (1) to (2) hold.

[0053] 5°≤θ1≤60° Equation (1)

[0054] θ2>90° Formula (2)

[0055] Furthermore, the second surface 17b has a first inclined surface 18a and a second inclined surface 18b.

[0056] Since the second surface 17b is opposite to the first surface 17a, the first inclined surface 18a is also configured to be opposite to the first surface 17a. The first inclined surface 18a is inclined upward along the optical axis. The front end of the first inclined surface 18a on the emission surface 13 side is connected to the first surface 17a.

[0057] Since the first inclined plane 18a is part of the second plane 17b, the angle at which the first inclined plane 18a intersects the light extraction plane 15 along its extension direction is the second angle θ2.

[0058] Since the second surface 17b is opposite to the first surface 17a, the second inclined surface 18b is also configured to be opposite to the first surface 17a. The second inclined surface 18b slopes downward along the optical axis. The second inclined surface 18b connects the first inclined surface 18a to the light extraction surface 15.

[0059] If we define the third angle at which the second inclined plane 18b intersects the optical axis as θ3, then the following equation (3) holds true.

[0060] θ3≤90° Equation (3)

[0061] In this embodiment, the plurality of prisms 16 are fine recesses processed into a predetermined shape. The plurality of prisms 16 are microprisms with a micrometer-scale size. The plurality of prisms 16 can be formed by laser processing or cutting the light extraction surface 15 of the light guide plate 10 of the flat plate. When laser processing the plurality of prisms 16, the plurality of prisms 16 can be formed by irradiating the light extraction surface 15 of the light guide plate 10 with a laser in an oblique direction or by cutting it in an oblique direction. In addition, the light guide plate 10 having the plurality of prisms 16 can also be manufactured by die casting using a metal mold.

[0062] Furthermore, when multiple prisms 16 are laser-processed, an R-shaped portion can also be formed on the second inclined surface 18b. Therefore, when observing the cross-section of the light guide plate 10 cut by a plane orthogonal to the light extraction surface 15 and parallel to the optical axis, the second inclined surface 18b can be either a plane or a curved surface.

[0063] In this embodiment, such as Figure 3A As shown in (a), when the light guide plate 10 is viewed from a direction perpendicular to the light extraction surface 15 (viewed from the front), the opening shapes of the plurality of prisms 16a1 are circular in the direction intersecting the optical axis. In this case, since the opening shapes of the plurality of prisms 16a1 are circular, it is a conical prism. In the case of a conical prism, the first surface 17a and the first inclined surface 18a are curved surfaces.

[0064] In addition, such as Figure 3BAs shown in (a), when the light guide plate 10 is viewed from the direction perpendicular to the light extraction surface 15 (viewed from the front), the opening shape of the plurality of prisms 16a2 is elongated in the direction intersecting the optical axis. In this case, since the opening shape of the plurality of prisms 16a2 is elongated, it is a long slot prism. By making the plurality of prisms 16a2 in this shape, compared with the circular prism 16a1, more light can be emitted from the light guide plate 10 along the second direction D2, and the light distribution of the illumination device 1 can be made into a wide light distribution. Specifically, the opening shape of the prisms 16a2 can also be a horizontally elongated race track shape when viewed from the front of the light extraction surface 15. In addition, the plurality of prisms 16a2 can also extend from one end edge of the light guide plate 10 to the other end edge. That is, the opening shape of the prisms 16a2 can also be a long slot shape. In addition, the first surface 17a and the first inclined surface 18a have flat surfaces.

[0065] In this embodiment, prisms 16a1 and 16a2 are collectively referred to as prism 16.

[0066] In the light guide plate 10 constructed in this way, such as Figure 2 and Figure 4 As shown, light emitted from light source 20 is incident on incident surface 11. The light incident from incident surface 11 is guided within light guide plate 10 and incident on light extraction surface 15. Specifically, a portion of the light incident from light source 20 and guided by light guide plate 10 undergoes total internal reflection at the interface between the first surface 17a of the plurality of prisms 16 and the air layer. The light totally reflected at the first surface 17a is directed towards and exits from the exit surface 13.

[0067] Furthermore, light that is not reflected by the first surface 17a of prism 16 and exits from the first surface 17a passes through the interior of prism 16 (air layer) and enters the second surface 17b. A portion of the light entering the second surface 17b returns to the interior of the light guide plate 10, where it is guided and enters the first surface 17a of the adjacent prism 16. In this way, even light that is not totally reflected by the first surface 17a of prism 16 or by the second surface 17b can pass through multiple prisms 16 by re-entering the interior of the light guide plate 10. Thus, even light exiting from the first surface 17a has the opportunity to be reflected by the adjacent prisms 16 by re-entering the interior of the light guide plate 10, thereby suppressing the decrease in light utilization efficiency.

[0068] At this time, by setting the first angle θ1 of the prism 16 to 45° to 50° or more, the light that is totally reflected at the first surface 17a travels more easily toward the back surface 12 than in the direction perpendicular to the emission surface 13 of the light guide plate 10. That is, the proportion of light toward the back surface 12 increases compared to the light toward the front direction of the emission surface 13 and the light toward the incident surface 11.

[0069] In this way, the light incident from the light source 20 onto the light guide plate 10 is reflected by multiple prisms 16 and emitted from the emission surface 13, thereby simulating light emission from the emission surface 13 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 prescribed light distribution.

[0070] like Figure 2 As shown, the light source 20 is a light-emitting device that emits light incident on the light guide plate 10. Specifically, the light source 20 emits light incident on the incident surface 11 of the light guide plate 10.

[0071] The light source 20 and the incident surface 11 of the light guide plate 10 are arranged opposite each other. That is, the light source 20 and the light guide plate 10 form an edge-light configuration. Specifically, the emitting surface of the light source 20 faces the incident surface 11 of the light guide plate 10.

[0072] In this embodiment, the light source 20 is an LED module composed of LEDs. The light source 20 emits white light, for example. The white light emitted from the light source 20 enters the light guide plate 10 from the incident surface 11.

[0073] The light source 20 has a substrate 21 and one or more light-emitting elements 22 mounted on the substrate 21. In this embodiment, since the light source 20 is a strip-shaped LED module, multiple light-emitting elements 22 are mounted in a straight line on a strip-shaped substrate 21.

[0074] In this embodiment, the light source 20 is configured such that its optical axis is in the first direction D1. Furthermore, the optical axis of the light source 20 is the same as the optical axis of each light-emitting element 22.

[0075] The substrate 21 is, for example, a wiring substrate with a prescribed pattern of wiring formed thereon. As the substrate 21, a resin substrate, a ceramic substrate, or a metal substrate with an insulating coating can be used.

[0076] The light-emitting element 22 is an LED element composed of LEDs. In this embodiment, the light-emitting element 22 is a surface-mount device (SMD) type LED element that is encapsulated, comprising a container (encapsulation) made of resin or the like, an LED chip (bare chip) disposed within the container, and a sealing member for sealing the LED chip. Specifically, the light-emitting element 22 is a white LED element of the SMD type 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 into the container. In addition, an SMD type light-emitting element has been shown, but it is not limited to this. For example, the light-emitting element 22 may also be a COB (Chip On Board) type LED element in which the LED chip is directly mounted on a substrate.

[0077] The light source 20 emits light by power supplied from the power supply unit 30. The power supply unit 30, for example, is a circuit board on which multiple circuit components are mounted, accepts commercial alternating current (AC) power and converts it into a specified power (e.g., DC power), which is then supplied to the light source 20. As a result, the light-emitting element 22 of the light source 20 emits light. In this embodiment, the power supply unit 30 is built into the lighting device 1, but it is not limited to this. The power supply unit 30 may also be a separate component that can be detached from the lighting device 1. Furthermore, the light source 20 may also be configured to be dimmed and / or color-controlled.

[0078] <Experimental Results>

[0079] Next, refer to Figure 5A The experimental results of the lighting device 1 of this embodiment will be explained.

[0080] Figure 5A This is a graph showing the light distribution curves corresponding to the shape of the prism. Figure 5A The diagram shows the light distribution curves of a light guide plate using a prism with a generally isosceles triangular shape as in Comparative Example 1, a light guide plate using an irregularly shaped prism with a generally triangular shape as in Comparative Example 2, and a light guide plate 10 using a prism 16 related to this embodiment.

[0081] First, the light distribution curves of Comparative Examples 1 and 2 and this embodiment will be explained.

[0082] like Figure 5AAs shown, in the light guide plate having a prism with a roughly isosceles triangular shape similar to that of Comparative Example 1, as indicated by the light distribution curve of Comparative Example 1, it can be seen that although the control light is emitted from the emission surface, light leakage occurs from the prism at the light extraction surface towards the light distribution surface. In Comparative Example 1, the proportion of control light to the total beam is 60%. Therefore, in Comparative Example 1, up to 40% of the light is emitted from the light extraction surface as leakage. Furthermore, the beam angle of the control light in Comparative Example 1 is 50°.

[0083] In the light guide plate with the approximately triangular-shaped irregular prism of Comparative Example 2, as shown in the light distribution curve of Comparative Example 2, it can be seen that although light leakage is suppressed compared to Comparative Example 1, light leakage occurs from the prism at the light extraction surface toward the light distribution surface. In Comparative Example 2, the proportion of control light to the total beam is 80%. Therefore, in Comparative Example 2, up to 20% of the light is emitted from the light extraction surface as leakage. Furthermore, the beam angle of the control light in Comparative Example 2 is 20°.

[0084] In the light guide plate 10 with the prism 16 of this embodiment, as shown in the light distribution curve of this embodiment, light leakage is further suppressed compared to Comparative Examples 1 and 2. In this embodiment, the proportion of control light to the total beam is 89%. In this embodiment, light leakage from the light extraction surface 15 can be suppressed to 11%. In addition, the beam angle of the control light in this embodiment is 10°.

[0085] Next, refer to Figure 5B This describes the light distribution curves of this embodiment and the case where a light guide plate 210 with a prism 216 tilted in the opposite direction to the prism 16 of this embodiment is used.

[0086] Figure 5B This is a graph showing the light distribution curves of the light guide plate 10 using the prism 16 of this embodiment and the light guide plate 210 using the prism 216 which is tilted in the opposite direction to the prism 16 of this embodiment.

[0087] like Figure 5B As shown, in this embodiment, the light (control light) is emitted in a direction orthogonal to the emission surface 13, and the beam angle of the control light in this case is about 10°.

[0088] In contrast, in the light guide plate 210 using a prism 216 tilted in the opposite direction, although light is slightly emitted from the emission surface 13, it is emitted from the light extraction surface 215 towards the back surface 12. Therefore, even when using the light guide plate 210, controllable light that can be controlled by light distribution can be obtained. With the light guide plate 210, since light is emitted from the light extraction surface 215, light can also be emitted from the emission surface 13 of the light guide plate 210 by changing the orientation of the light guide plate 210 or by providing a reflector such as a mirror on the light extraction surface 215. Furthermore, as... Figure 5B As shown, since the light is controlled to be emitted in two directions, the light guide plate 10 of this embodiment is more preferably preferred.

[0089] Next, refer to Figure 5C The illumination methods of a conventional lighting device, the lighting device of Comparative Example 1, and the lighting device 1 using a light guide plate 10 with a prism 16 having an adjusted first angle θ1 as described in this embodiment will be explained.

[0090] Figure 5C This diagram illustrates the illumination pattern of light emitted from the emission surface 13 of the light guide plate 10. Figure 5C (a) illustrates the way light is emitted when a typical lighting device emits light. Figure 5C (b) illustrates the illumination method when light is emitted from an illumination device using a light guide plate with a prism of Comparative Example 1. Figure 5C (c) illustrates the illumination method when the light is emitted from the illumination device 1 of the light guide plate 10 of the prism 16 having a first angle θ1 of about 30° in this embodiment. Figure 5C Example (d) illustrates the light illumination method when light is emitted from the illumination device 1 using a light guide plate 10 with a prism 16 having a first angle θ1 of approximately 20° as described in this embodiment. Additionally, in Figure 5C In this context, the whiter the color, the higher the illuminance. Figure 5C The illumination distance indicated in the figure represents the distance from the lighting device to the irradiated surface that is 1 lx when the luminous flux is 500 lm.

[0091] exist Figure 5C In (a), a distance of approximately 0.9 (m) is illuminated along the optical axis. Furthermore, in Figure 5C In (b), an illumination distance of approximately 2 (m) is provided along the optical axis. In contrast, in this embodiment, as... Figure 5C As shown in (c), the light was illuminated over a distance of approximately 2.5 (m) along the optical axis. Furthermore, Figure 5C As shown in (d), the light was illuminated over a distance of approximately 3 (m) along the optical axis.

[0092] Therefore, it can be seen that if the first angle θ1 is made smaller, the light emitted from the light guide plate's emission surface 13 will reach a farther distance. By adjusting the first angle θ1, the direction and range of the light irradiated by the lighting device 1 can be adjusted.

[0093] <Manufacturing Method of Light Guide Plate 10>

[0094] Next, the manufacturing method of the light guide plate 10 of this embodiment will be described.

[0095] In the manufacturing method of the light guide plate 10, a laser processing apparatus is used as an example. The laser processing apparatus includes a laser source, a galvanometer, a galvanometer mirror, and a lens. The laser source irradiates the light by receiving instructions from a controller. The galvanometer positions itself to irradiate the light extraction surface 15 of the light guide plate 10 with the laser. Furthermore, the galvanometer controls the posture 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 from the laser source is distributed on the light extraction surface 15 of the light guide plate 10.

[0096] At this time, the laser source irradiates the light extraction surface 15 of the light guide plate 10 at an angle. In addition, the galvanometer irradiates the light extraction surface 15 at an angle by controlling the posture of the galvanometer mirror, but it can also irradiate the light extraction surface 15 at an angle by adjusting the posture of the light extraction surface 15 of the light guide plate 10.

[0097] The laser processing apparatus scans the light extraction surface 15 of the light guide plate 10 in a free direction with a laser beam. As a result, a plurality of prisms 16 are formed on the light extraction surface 15 of the light guide plate 10.

[0098] In addition, as described above, in this embodiment, multiple prisms 16 can also be formed on the light extraction surface 15 of the light guide plate 10 by machining the light extraction surface 15 or by molding using a metal mold.

[0099] <Effects>

[0100] Next, the effects of the manufacturing method of the lighting device 1 and the light guide plate 10 in this embodiment will be explained. Here, the comparative examples described above will also be included in the explanation.

[0101] Figure 6 This is a diagram showing the light tracing in the light guide plate of the lighting device for the comparative example.

[0102] like Figure 4 and Figure 6 As shown, the structure of the light guide plate 110 in the comparative example lighting device differs from that of the light guide plate 10 in the lighting device 1 of this embodiment. Specifically, the prism shape of the comparative example light guide plate 110 differs from that of the light guide plate 10 of this embodiment. The prism 116 of the comparative example light guide plate 110 is a concave portion of approximately isosceles triangular shape. Compared to the second surface 17b of the prism 16 of this embodiment, the second surface 117b of the comparative example prism 116 is inclined downward along the optical axis direction. Therefore, the second angle θ2 intersecting the optical axis direction of the comparative example with the extension direction along the second surface 117b is less than 90°.

[0103] In the comparative example light guide plate 110 configured in this way, a portion of the light incident from the light source and guided by the light guide plate 110 undergoes total internal reflection at the interface between the first surface 117a of the plurality of prisms 116 and the air layer. The light totally reflected at the first surface 117a is directed toward the emission surface and emitted from the emission surface.

[0104] However, a portion of the light emitted from the first surface 117a of the prism 116, which is not reflected, passes through the interior of the prism 116 and exits unchanged from the light extraction surface 115 of the light guide plate 110 to the outside of the light guide plate 110. Furthermore, the remaining light emitted from the first surface 117a is incident on the second surface 117b, but is reflected there and exits from the light extraction surface 115 of the light guide plate 110 to the outside of the light guide plate 110.

[0105] 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.

[0106] However, the lighting device 1 of the present embodiment has a light source 20 and a light guide plate 10. The light guide plate 10 has an incident surface 11 on which light emitted from the light source 20 is incident, an exit surface 13 on which light emitted from the incident surface 11 is emitted, and a light extraction surface 15 for emitting light from the exit surface 13. It also has a plurality of prisms 16 for emitting light from the exit surface 13. Furthermore, when observing a cross-section of the light guide plate 10 cut by a plane orthogonal to the light extraction surface 15 and parallel to the optical axis of the light source 20, a plurality of prisms 16 are formed on the light extraction surface 15. Each prism 16 has a first surface 17a that is inclined upwards along the optical axis of the light emitted from the light source 20, and a second surface 17b that is opposite to the first surface 17a and also inclined upwards along the optical axis. Furthermore, the first surface 17a is positioned closer to the light source 20 than the second surface 17b. Furthermore, if we set the first angle of the first surface 17a relative to the optical axis direction as θ1, and set the second angle of the optical axis direction intersecting the extension direction along the second surface 17b as θ2, then the following equations (1) to (2) hold true.

[0107] 5°≤θ1≤60° Equation (1)

[0108] θ2>90° Formula (2)

[0109] Therefore, if a light guide plate 10 with multiple prisms 16 configured according to formulas (1) and (2) is used, the light emitted from the first surface 17a can be returned to the interior of the light guide plate 10, so the light emitted from the first surface 17a can easily pass through the multiple prisms 16. As a result, the light can also easily have multiple opportunities to be reflected by the prisms 16, so the decrease in light utilization efficiency can be suppressed.

[0110] Therefore, the lighting device 1 according to this embodiment can further suppress light leakage from the plurality of prisms 16.

[0111] In particular, the depth of the prism 16 can be adjusted by changing the second angle θ2. Therefore, the design freedom of multiple prisms 16 can be ensured. Furthermore, if the depth of the prism 16 is made deeper, the light emitted from the first surface 17a can be more easily re-intruded into the light guide plate 10, so it is expected that the light utilization efficiency can be improved.

[0112] Furthermore, since the multiple prisms 16 are tilted obliquely relative to the optical axis, for example, compared to making the depth of the multiple prisms deeper in a direction orthogonal to the light extraction surface, it is possible to make the length of the multiple prisms 16 longer while ensuring the strength of the light guide plate 10. The length of the prism 16 is the length from the opening face of the prism 16 to the front end of the prism 16.

[0113] Furthermore, according to this embodiment, since the decrease in light utilization efficiency can be suppressed, the lighting device 1 is better able to emit control light compared to the comparative example. Therefore, in the lighting device 1, the light distribution can be controlled to the desired direction.

[0114] Furthermore, in the manufacturing method of the light guide plate 10 of the present embodiment 7, in the light guide plate 10 having an incident surface 11 on which light emitted from the light source 20 is incident, an emission surface 13 on which light emitted from the incident surface 11 is emitted, and a light extraction surface 15 for emitting light from the emission surface 13, a plurality of prisms 16 for emitting light from the emission surface 13 are formed by laser processing for the light extraction surface 15.

[0115] In this case, it also has the same effect as described above.

[0116] Furthermore, the manufacturing method of the light guide plate 10 in Technology 8 of this embodiment is the same as the manufacturing method of the light guide plate 10 described in Technology 7. In this case, a plurality of prisms 16 are formed by irradiating the light extraction surface 15 with laser light in an oblique direction.

[0117] Thus, as in this embodiment, a plurality of prisms 16 inclined relative to the light extraction surface 15 can be formed on the light extraction surface 15.

[0118] Furthermore, the lighting device 1 of Technology 2 of this embodiment is the lighting 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. In addition, the angle at which the light extraction surface 15 intersects along the extension direction of the first inclined surface 18a is the second angle θ2. And, if the third angle at which the second inclined surface 18b intersects with the optical axis direction is θ3, then the following equation (3) holds.

[0119] θ3≤90° Equation (3)

[0120] Therefore, by forming the second inclined surface 18b, the angle between the second surface 17b and the boundary portion of the light extraction surface 15 can be obtained. Thus, damage to the angle of the boundary portion can be suppressed, thereby ensuring the strength of the light guide plate 10.

[0121] Furthermore, the lighting device 1 of Technology 3 in this embodiment is the same lighting device 1 described in Technology 2. In this case, the first inclined surface 18a rises and tilts along the optical axis. And the second inclined surface 18b connects the first inclined surface 18a to the light extraction surface 15 and descends and tilts along the optical axis.

[0122] Therefore, by forming multiple prisms 16 on the light extraction surface 15 using laser processing, the second inclined surface 18b can be formed. Even if multiple prisms 16 are formed by laser processing, light leakage from the multiple prisms 16 can be suppressed.

[0123] Furthermore, the lighting device 1 of technique 4 in this embodiment is the lighting device 1 described in any one of techniques 1 to 3. In this case, the opening shape of the plurality of prisms 16 is circular.

[0124] Therefore, when the opening shape of the prism 16 is circular, the illumination device 1 can make the light distribution ratio of light traveling in directions other than the incident surface 11 side approximately equal.

[0125] Furthermore, the illumination device 1 of technique 5 of this embodiment is the illumination device 1 described in any one of techniques 1 to 3. In this case, the opening shape of the plurality of prisms 16 is elongated in the direction intersecting the optical axis.

[0126] Therefore, when the opening shape of the prism 16 is elongated, not only can the light distribution ratio of light traveling towards the back surface 12 relative to the front direction of the light guide plate 10 be increased, but the light distribution ratio of light traveling in the second direction D2 of the light guide plate 10 can also be increased. Thus, a wide light distribution can be achieved.

[0127] <Variation Example>

[0128] First, refer to Figure 7 The structure of the lighting device 1a in this modified example will be described. Figure 7 This is a cross-sectional view showing the lighting device 1a of a modified example.

[0129] In this variation, the difference from the embodiment is that, in the thickness direction of the light guide plate 10a, the length of the prism 16c of the light guide plate 10a in the lighting device 1a gradually increases with distance from the light source 20. In this variation, the same reference numerals are assigned to the same structures and functions as in the lighting device of the embodiment, and detailed descriptions related to these structures and functions are appropriately omitted.

[0130] The illumination device 1a of the present modification 6 is the illumination device 1 described in any of modifications 1 to 5. In this case, the plurality of prisms 16c includes two adjacent first prisms 16c1 and second prisms 16c2 arranged from the light source 20 along the optical axis. Furthermore, 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 plurality of prisms 16c relative to the light extraction surface 15 (in this modification, the depth of the concave prism 16c) gradually increases as it approaches the back surface 12 from the incident surface 11.

[0131] Therefore, the light totally reflected by the first surface 17a of prism 16c can be directed towards the exit surface 13 without being obstructed by the first prism 16c1, which is adjacent to the second prism 16c2 and closer to the incident surface 11. Thus, interference between two adjacent prisms 16c can be suppressed when the spacing between the plurality of prisms 16c is set to be small.

[0132] <Experimental Results>

[0133] Next, refer to Figure 8A and Figure 8B The light distribution of illumination devices 1 and 1a when the size of prism 16c is changed, and the light distribution of illumination devices 1 and 1a when the coverage of prism 16 is changed, will be explained.

[0134] Figure 8A This diagram illustrates the light distribution of illumination devices 1 and 1a when prism 16 is of uniform size and when the size of prism 16c is changed. Figure 8A In the diagram, the case where the size of prism 16 is uniform is represented by a solid line, and the case where the size of prism 16c is changed is represented by a dashed line. Figure 8B This is a diagram showing the light distribution of illumination devices 1 and 1a when the coverage of prism 16 is changed. Figure 8B In the diagram, a solid line represents the coverage of prism 16 at 1%, a dashed line represents the coverage at 10%, and a single-dotted line represents the coverage at 100%. Figure 8A and Figure 8B In the diagram, the horizontal axis represents the angle of the emitted light relative to the vertical direction (the direction orthogonal to the light extraction surface 15), and the vertical axis represents the luminous intensity of the emitted light.

[0135] like Figure 8AAs shown, when the size of prism 16c is changed as in this modified example, although the light extraction efficiency decreases compared to the case where the size of prism 16 is uniform, the light distribution can be controlled to be directed from the light source 20 toward the back side of the guide plate 10 towards the surface 12.

[0136] like Figure 8B As shown, the greater the coverage of the prism 16c on the light extraction surface 15 of the light guide plate 10, the greater the light extraction efficiency.

[0137] Therefore, by adjusting the size of the prism 16c and the coverage of the prism 16c on the light extraction surface 15, the light extraction efficiency and light distribution control can be adjusted to achieve the desired lighting method.

[0138] (Other variations)

[0139] The above describes the manufacturing method of the lighting device and light guide plate of this disclosure based on the embodiments, but this disclosure is not limited to the above embodiments.

[0140] For example, in the above embodiment, the connection between the first and second surfaces of the prism can be either smoothly bent or bent in a folded manner. Furthermore, the connection between the first surface and the light extraction surface, the connection between the first and second inclined surfaces, and the connection between the second inclined surface and the light extraction surface can also be either smoothly bent or bent in a folded manner.

[0141] Furthermore, in the above embodiments, the width of the prism's opening face along the optical axis can be set to be smaller than the length of the prism in the thickness direction of the light guide plate. Additionally, in an arrangement of multiple prisms along the optical axis, the spacing between two adjacent prisms can be set to be smaller than the length of the prism.

[0142] Furthermore, in the above embodiments, a reflector or light-absorbing plate may be disposed on the back surface. The reflector may be formed of resin or metal. Specifically, the reflector may be a white resin sheet made of resin material such as PBT (polybutylene terephthalate), a metal plate made of metal material such as aluminum, or a structure in which a metal film such as aluminum or white resin is formed on a substrate. The light-absorbing element is disposed on the back surface of the light guide plate. In this embodiment, the light-absorbing element may also cover the entire back surface. The light-absorbing element may, for example, be a coating film made of a light-absorbing material. In this case, a light-absorbing element composed of a coating film closely adhering to the back surface is formed by coating the back surface of the light guide plate with a coating material and curing it. Alternatively, the light-absorbing element may be a strip-shaped component. In this case, the light-absorbing element may also be attached to the back surface of the light guide plate by an adhesive. The light-absorbing element may, for example, be a structure in which a material having substantially the same refractive index as the light guide plate is used as the base material, and an additive with light-absorbing function, such as carbon, is added to the base material.

[0143] Furthermore, in the above-described modified examples, the length of the prism relative to the light extraction surface gradually increases with distance from the incident surface, and the opening area of ​​the prism gradually increases, but this is not a limitation. For example, the length of the prism in the thickness direction of the light guide plate can be changed without changing the size of the prism's opening area.

[0144] Furthermore, in the above embodiment, the second surface has a first inclined surface and a second inclined surface, but it is not limited to this. That is, the second surface may also be composed of only the first inclined surface. Therefore, the second inclined surface is not a necessary component of the second surface.

[0145] Furthermore, in the above embodiment, the lengths of the plurality of prisms relative to the light extraction surface in the thickness direction of the light guide plate can gradually decrease as they move away from the incident surface. That is, the lengths of the plurality of prisms relative to the light extraction surface can gradually decrease as they approach the back surface from the incident surface. As a result, it is easy to control the light totally reflected by the first surface of the prism to a predetermined direction.

[0146] Furthermore, while the light source in the above embodiment is composed of an LED, it is not limited to this. For example, the light source may also be composed of a solid-state light-emitting element other than an LED, such as a semiconductor laser or an organic EL (Electro Luminescence). Alternatively, existing lamps such as fluorescent lamps and high-brightness lamps may also be used as the light source.

[0147] Furthermore, in the above embodiments, the light guide plate can also be applied to any lighting device such as column lights and ceiling lights.

[0148] Furthermore, while the above embodiments describe the application of a light guide plate to a lighting device, the invention is not limited thereto. This disclosure can also be applied to lighting systems equipped with light guide plates.

[0149] Furthermore, it is assumed that the above-described variations are included in the above-described embodiments.

[0150] In addition, this disclosure also includes forms obtained by applying various modifications to the above embodiments as conceived by those skilled in the art, and forms achieved by arbitrarily combining the constituent elements and functions of the above embodiments without departing from the spirit of this disclosure.

[0151] Label Explanation

[0152] 1. 1a lighting device

[0153] 10, 10a, 210 light guide plates

[0154] 11. Incident surface

[0155] 13. Injection surface

[0156] 15, 215 light extraction surface

[0157] 16, 16a1, 16a2, 16c, 216 prisms

[0158] 16c1 First Prism

[0159] 16c2 second prism

[0160] Page 1 of 17a

[0161] Page 2 of 17b

[0162] 18a 1st slope

[0163] 18b Second inclined plane

[0164] 20 light sources

Claims

1. A lighting device, wherein: have: Light source; and The light guide plate has an incident surface for incident light emitted by the light source, an exit surface for exiting light incident from the incident surface, and a light extraction surface for exiting light from the exit surface, and is formed with a plurality of prisms for exiting light from the exit surface. When observing a cross section of the light guide plate cut by a plane perpendicular to the light extraction surface and parallel to the optical axis direction of the light source, a plurality of prisms having a first surface and a second surface are formed on the light extraction surface, the first surface is inclined upward along the optical axis direction of the light emitted by the light source, and the second surface is opposite to the first surface and inclined upward along the optical axis direction. The first surface is arranged closer to the light source than the second surface. When the first angle of the first surface relative to the optical axis direction is θ1, and the second angle of intersection of the optical axis direction and the extension direction along the second surface is θ2, the following equations (1) and (2) hold: 5°≤θ1≤60° Formula (1) θ2>90°Equation (2).

2. The lighting device according to claim 1, wherein: The second surface has a first inclined surface and a second inclined surface, The angle at which the extension direction of the first inclined surface intersects the light extraction surface is the second angle θ2. When the third angle at which the second inclined surface intersects the optical axis direction is θ3, the following formula (3) holds true: θ3≤90°Formula (3).

3. The lighting device according to claim 2, wherein: 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.

4. The lighting device according to claim 1 or 2, wherein: The openings of the plurality of prisms are circular.

5. The lighting device according to claim 1 or 2, wherein: The openings of the plurality of prisms are elongated in a direction intersecting the optical axis direction.

6. The lighting device according to claim 1 or 2, wherein: The plurality of prisms include two adjacent first prisms and a second prism arranged along the optical axis direction from the light source, In the thickness direction of the light guide plate, the length of the second prism relative to the light extraction surface is longer than the length of the first prism.

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

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

Images