Optical beam control member, light emitting device, surface light source device, and display device

Abstract

The present application relates to a light flux control member, a light emitting device, a surface light source device, and a display device. The light flux control member has an incident surface, a reflection surface, a ring-shaped groove including a first ring-shaped surface and a second ring-shaped surface, and an exit surface. The ring-shaped groove is configured not to intersect with a light path of light that is incident on the incident surface and is reflected by the reflection surface to reach the exit surface. The first ring-shaped surface is formed so as to be away from a central axis as it approaches from a back surface side toward a front surface side, and refracts light that is emitted from a center of a light emitting element and is incident on the incident surface to directly reach the first ring-shaped surface, toward the front surface. The second ring-shaped surface is formed so as to approach the central axis as it approaches from the back surface side toward the front surface side, and refracts light that is emitted from the center of the light emitting element and is incident on the incident surface to directly reach the second ring-shaped surface, toward the front surface side.

Description

TECHNICAL FIELD

[0001] The present application relates to a light flux control member that controls the light distribution of light emitted from a light emitting element. In addition, the present application relates to a light emitting device, a surface light source device, and a display device each having the light flux control member. BACKGROUND

[0002] In a transmissive image display device such as a liquid crystal display device, a direct type surface light source device is sometimes used as a backlight. In recent years, a direct type surface light source device having a plurality of light emitting elements as light sources has begun to be used.

[0003] For example, a direct type surface light source device has a substrate, a plurality of light emitting elements, a plurality of light flux control members, and a light diffusion member. The plurality of light emitting elements are arranged on the substrate in a matrix shape. The light flux control member that expands the light emitted from each light emitting element in the direction along the surface of the substrate is arranged above each light emitting element. The light emitted from the light flux control member is diffused by the light diffusion member and irradiates a surface light source device (for example, refer to Patent Literature 1) in a surface shape.

[0004] In Patent Literature 1, a surface light source device is described that has a housing, a substrate arranged inside the housing, a light emitting element arranged on the substrate, a light flux control member arranged on the substrate in a manner to cover the light emitting element, and controls the light distribution of light emitted from the light emitting element, and a light diffusion member that diffuses and transmits the light emitted from the light flux control member. The light flux control member has an incident surface that causes the light emitted from the light emitting element to be incident, a reflection surface formed on the opposite side of the incident surface that reflects the incident light to the side, an annular groove formed at a position further outside than the incident surface, and an exit surface that causes the light reflected by the reflection surface to exit.

[0005] The light emitted from the light emitting element is incident to the light flux control member from the incident surface. The light incident to the light flux control member is reflected to the side by the reflection surface. A part of the light reflected by the reflection surface is emitted to the outside of the light flux control member from the exit surface after passing through the annular groove. The other light of the light reflected by the reflection surface is emitted to the outside of the light flux control member from the exit surface without passing through the annular groove.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2015-197624 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] However, in the surface light source device described in Patent Document 1, since light is refracted toward the light-diffusing member by the annular groove, a part of the light emitted from the exit surface is emitted toward the light-diffusing member. Thus, in the surface light source device of Patent Document 1, sometimes a part of the light emitted from the light-emitting element is emitted toward the directly above of the light-beam control member, and thus the uniformity of the light on the light-diffusing member is easily affected by the distance between the light-beam control member and the light-diffusing member.

[0011] Therefore, an object of the present application is to provide a light-beam control member which is not affected by the distance between the light-beam control member and the light-diffusing member, and which can improve the uniformity of the light on the light-diffusing member.

[0012] In addition, an object of the present application is to provide a light-emitting device, a surface light source device, and a display device each having the light-beam control member.

[0013] Solution to the problem

[0014] To achieve the above object, a light-beam control member of the present application controls the light distribution of light emitted from a light-emitting element, and includes: an incident surface configured on a back surface side so as to intersect with a central axis of the light-beam control member, for causing the light emitted from the light-emitting element to be incident; a reflection surface configured on a front surface side so as to increase in height from the light-emitting element as it moves away from the central axis, for reflecting the light incident by the incident surface toward a lateral direction; an annular groove including a first annular surface and a second annular surface, the first annular surface being configured on the back surface side so as to surround the central axis at a position close to the central axis, further away from the central axis than the incident surface, the second annular surface being configured apart from the first annular surface, further away from the central axis than the first annular surface; and an exit surface configured further away from the central axis than the annular groove, so as to surround the central axis, for causing the light reflected by the reflection surface to be emitted, the annular groove being configured not to intersect with the optical path of light which is emitted from the light-emitting center of the light-emitting element, is incident by the incident surface, and is reflected by the reflection surface to reach the exit surface, in a cross section including the central axis, the first annular surface being an inclined surface which increases in height from the light-emitting element as it moves away from the central axis, and the first annular surface refracting the light emitted from the light-emitting center of the light-emitting element and incident by the incident surface directly to the first annular surface toward the front surface side, in the cross section including the central axis, the second annular surface being an inclined surface which increases in height from the light-emitting element as it approaches the central axis, and the second annular surface refracting the light emitted from the light-emitting element and directly reaching the second annular surface toward the front surface side.

[0015] The light emitting device of the present application has a light emitting element and the light flux control member of the present application, which is arranged so that the central axis coincides with the optical axis of the light emitting element.

[0016] The surface light source device of the present application has the light emitting device of the present application and a light diffusing member that diffuses and transmits light from the light emitting device.

[0017] The display device of the present application has the surface light source device of the present application and a display member that is irradiated with light emitted from the surface light source device.

[0018] Effects of the Invention

[0019] The light flux control member and the light emitting device of the present application are not affected by the distance between the light flux control member and the light diffusing member, and the uniformity of light on the light diffusing member can be improved. Therefore, the surface light source device and the display device of the present application can reduce luminance unevenness compared with conventional devices. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1A , Figure 1B is a diagram showing the structure of the surface light source device of Embodiment 1;

[0021] Figure 2A , Figure 2B is a cross-sectional view showing the structure of the surface light source device of Embodiment 1;

[0022] Figure 3 is a partially enlarged cross-sectional view of a part of Figure 2B ;

[0023] Figure 4 is a perspective view of the light flux control member of Embodiment 1 as viewed from the back side;

[0024] Figures 5A-5D is a diagram showing the structure of the light flux control member of Embodiment 1;

[0025] Figure 6 is a partially enlarged cross-sectional view of a part of Figure 5D ;

[0026] Figures 7A-7C is a diagram showing the structure of the light flux control member of Comparative Example 1;

[0027] Figures 8A-8C is a diagram showing the structure of the light flux control member of Comparative Example 2;

[0028] Figures 9A-9C is a diagram showing the simulation results of the light paths in the light flux control members of Comparative Example 1 and Comparative Example 2;

[0029] Figures 10A-10C is a graph showing a simulation result of an optical path in the light beam control member of Embodiment 1;

[0030] Figure 11 is a graph showing a simulation result of an illuminance distribution in a case where the light beam control members of Embodiment 1, Comparative Example 1, and Comparative Example 2 are used;

[0031] Figures 12A-12D is a partial enlarged sectional view of the light beam control member of Modification Examples 1 to 4; and

[0032] Figures 13A-13C is a graph showing a structure of the light beam control member of Embodiment 2.

[0033] Explanation of Reference Numerals

[0034] 100 surface light source device 100' display device 101 display member

[0035] 110 housing 111 bottom plate 112 substrate

[0036] 120 light diffusion member 130 light emitting device 131 light emitting element

[0037] 132, 232, 332, 532, 632, 732, 832, 932 light beam control member

[0038] 141, 941 incident surface 142 reflecting surface

[0039] 143, 243, 343, 543, 643, 743, 843 annular groove

[0040] 144 exit surface 145 back surface 146 flange

[0041] 151 first incident surface 152 second incident surface 153 recess

[0042] 155, 255, 355, 555, 655 first annular surface

[0043] 156, 256, 356, 556, 656 second annular surface

[0044] 157, 557, 657, 757, 857 third annular surface

[0045] 675a first individual annular surface 675b second individual annular surface

[0046] 775c third individual annular surface

[0047] CA central axis LA optical axis DETAILED DESCRIPTION

[0048] Next, embodiments of the present application will be described in detail with reference to the drawings. In the following description, as a representative example of the surface light source device of the present application, a surface light source device suitable for use as a backlight or the like of a liquid crystal display device will be described.

[0049] [Embodiment 1]

[0050] (Configuration of surface light source device and light emitting device)

[0051] Figure 1A Figure 1B Figure 2A Figure 2B Figure 3 is a sectional view of the A-A line shown in Figure 1A is a plan view of the surface light source device 100 of Embodiment 1, Figure 1B is a front view. Figure 2A is a sectional view of the A-A line shown in Figure 1B is a sectional view of the B-B line shown in Figure 2B is a sectional view of the B-B line shown in Figure 1A is a sectional view of the B-B line shown in Figure 3 is a partially enlarged sectional view of a portion of Figure 2B

[0052] As shown in Figure 1A Figure 1B Figure 2A Figure 2B Figure 3 Embodiment 1, the surface light source device 100 has a housing 110, a light diffusing member 120, and a plurality of light emitting devices 130. The plurality of light emitting devices 130 are arranged in a matrix on a bottom plate 111 of the housing 110. An inner surface of the bottom plate 111 functions as a diffusing reflection surface. In addition, as shown in Figure 1B Figure 1B the surface light source device 100 can also be used as a display device 100' by being combined with a display member 101 (indicated by a broken line in

[0053] The plurality of light emitting devices 130 are each fixed to a substrate 112. The plurality of substrates 112 are each fixed to a prescribed position on the bottom plate 111 of the housing 110. The plurality of light emitting devices 130 each have a light emitting element 131 and a light beam control member 132.

[0054] ​​​​​​​​​​The light emitting element 131 is a light source of the surface light source device 100, and is mounted on the substrate 112. The light emitting element 131 is, for example, a light emitting diode (LED) such as a white LED.

[0055] The light beam control member 132 is a diffusing lens for controlling the distribution of light emitted from the light emitting element 131, and is fixed to the substrate 112. The light beam control member 132 is disposed above the light emitting element 131 in such a manner that the central axis CA coincides with the optical axis LA of the light emitting element 131. Further, the incident surface 141, the reflecting surface 142, the annular groove 143, and the exit surface 144 of the light beam control member 132 described later are all rotationally symmetrical (circularly symmetrical), and their rotational axes coincide. The rotational axis of the incident surface 141, the reflecting surface 142, the annular groove 143, and the exit surface 144 is referred to as the "central axis CA of the light beam control member". In addition, the "optical axis LA of the light emitting element" refers to a light ray from the center of the three-dimensional exit light beam from the light emitting element 131. Between the substrate 112 on which the light emitting element 131 is mounted and the incident surface 141 of the light beam control member 132, a gap for releasing heat emitted from the light emitting element 131 to the outside is formed.

[0056] The light beam control member 132 is formed by integral molding. The material of the light beam control member 132 is not particularly limited as long as it is a material that allows light of a desired wavelength to pass therethrough. For example, the material of the light beam control member 132 is a light-transmissive resin such as polymethyl methacrylate (PMMA) or polycarbonate (PC), an epoxy resin (EP), or glass. Details of the light beam control member 132 will be described later.

[0057] The light diffusing member 120 is a plate-shaped member having light diffusing properties, diffuses and transmits the exit light from the light emitting device 130. In general, the light diffusing member 120 is almost the same size as the irradiated member such as a liquid crystal panel. For example, the light diffusing member 120 is formed of a light-transmissive resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), a styrene-methyl methacrylate copolymer resin (MS), or the like. In order to impart light diffusing properties, fine irregularities are formed on the surface of the light diffusing member 120, or light diffusing particles such as beads are dispersed in the interior of the light diffusing member 120.

[0058] In the surface light source device 100 of the present embodiment, the light emitted from each light emitting element 131 is expanded by each light beam control member 132 to irradiate a wide range of the light diffusion member 120. In addition, a part of the light emitted from the light emitting element 131 is reflected by the substrate 112 and reaches the light diffusion member 120. The light emitted from each light beam control member 132 is further diffused by the light diffusion member 120. As a result, the surface light source device 100 of the present embodiment can uniformly irradiate a planar irradiated member (for example, a liquid crystal panel).

[0059] (Configuration of light beam control member)

[0060] Figure 4 、 Figures 5A-5D and Figure 6 is a diagram showing the configuration of the light beam control member 132 of Embodiment 1. Figure 4 is a perspective view of the light beam control member 132 of Embodiment 1 as viewed from the back surface side. Figure 5A is a plan view of the light beam control member 132 of Embodiment 1, Figure 5B is a bottom view, Figure 5C is a side view, Figure 5D is Figure 5A is a cross-sectional view of the A-A line shown in Figure 6 is a partially enlarged cross-sectional view of Figure 5D

[0061] As shown in Figure 4 、 Figures 5A-5D and Figure 6 , the light beam control member 132 has an incident surface 141, a reflection surface 142, an annular groove 143, and an exit surface 144.

[0062] The incident surface 141 is an optical surface provided on the back surface (light emitting element 131) side of the light beam control member 132 for allowing the light emitted from the light emitting element 131 to be incident into the inside of the light beam control member 132. The incident surface 141 is disposed so as to intersect the central axis CA of the light beam control member 132, and refract the incident light toward the reflection surface 142. The shape of the incident surface 141 is not particularly limited as long as it is a shape capable of functioning as described above. The incident surface 141 can be an inner surface of a recessed portion 153 opened on the back surface side, or can be a flat surface. In the present embodiment, the incident surface 141 is an inner surface of a recessed portion 153 opened on the back surface side.

[0063] ​The incident surface 141 has a first incident surface 151 and a second incident surface 152. The first incident surface 151 is disposed on the bottom side of the recess 153 so as to intersect the central axis CA. The first incident surface 151 causes light having a small exit angle among the light emitted from the light emitting element 131 to be incident inside the light beam control member 132. The first incident surface 151 can be composed of one surface or can be composed of a plurality of surfaces. In the present embodiment, the first incident surface 151 is composed of one curved surface. In addition, the first incident surface 151 is rotationally symmetrical (circularly symmetrical) about the central axis CA. In a cross section including the central axis CA, the first incident surface 151 is formed so as to be closer to the opening edge portion of the recess 153 as it is farther from the central axis CA.

[0064] The second incident surface 152 is disposed on the opening portion side of the recess 153 so as to connect the outer edge portion of the first incident surface 151 and the opening edge portion of the recess 153. The second incident surface 152 causes light having a larger exit angle than the light incident by the first incident surface 151 to be incident inside the light beam control member 132. The second incident surface 152 is rotationally symmetrical (circularly symmetrical) about the central axis CA. In a cross section including the central axis CA, the second incident surface 152 is disposed so as to be parallel to the central axis CA.

[0065] The reflection surface 142 is an optical surface disposed on the side opposite to the incident surface 141 for reflecting light incident by the incident surface 141 to the side. The reflection surface 142 is a surface that is rotationally symmetrical (circularly symmetrical) about the central axis CA of the light beam control member 132. In addition, a generatrix from the central portion to the outer peripheral portion of this rotationally symmetrical surface is a curve that is concave with respect to the light emitting element 131, and the reflection surface 142 is a curved surface in a state in which this generatrix is rotated 360° about the central axis CA. That is, the reflection surface 142 has a curved surface of an aspherical shape in which the height from the light emitting element 131 increases as it is farther from the central axis CA. In addition, the outer peripheral portion of the reflection surface 142 is disposed and formed at a position that is closer to the front surface side than the portion of the reflection surface 142 that intersects the central axis CA. For example, the reflection surface 142 is a curved surface of an aspherical shape in which the height from the light emitting element 131 increases as it is closer to the outer peripheral portion from the central portion. The inclination angle of the reflection surface 142 with respect to the surface direction of the substrate 112 decreases as it is closer to the outer peripheral portion from the central portion.

[0066] The annular groove 143 is disposed further from the central axis CA than the incident surface 141 on the back surface side in a manner so as to surround the central axis CA. In the present embodiment, the annular groove 143 is disposed so as not to intersect the optical path of light that is emitted from the light emission center of the light emitting element 131, is incident on the incident surface 141, and reaches the exit surface 144 after being reflected by the reflection surface 142. In the present embodiment, the annular groove 143 is designed so that the light that is emitted from the light emission center of the light emitting element, is incident on the incident surface 141, and is reflected by the reflection surface 142 does not reach the first annular surface 155. The annular groove 143 has a first annular surface 155, a second annular surface 156, and a third annular surface 157. The shape of the annular groove 143 in a cross section including the central axis CA is not particularly limited as long as it is a shape that can function as described above. In the present embodiment, the shape of the annular groove 143 in a cross section including the central axis CA is a trapezoidal shape. That is, in the present embodiment, the first annular surface 155 and the second annular surface 156 correspond to the waist of the trapezoidal shape, and the third annular surface 157 corresponds to the upper base (lower base) of the trapezoidal shape.

[0067] In addition, the depth of the annular groove 143 can be the same or different in the circumferential direction about the central axis CA as a rotation axis. In the present embodiment, the depth of the annular groove 143 is the same in the circumferential direction about the central axis CA as a rotation axis. In addition, the width of the annular groove 143 can be the same or different in the circumferential direction about the central axis CA as a rotation axis. In the present embodiment, the width of the annular groove 143 is the same in the circumferential direction about the central axis CA as a rotation axis. That is, in the present embodiment, the annular groove 143 is rotationally symmetrical about the central axis CA. In addition, it is preferable that the bottom of the annular groove 143 be disposed at a position further toward the front surface side than the central portion of the reflection surface 142 (see the bidirectional arrow line shown in FIG. 1). Here, the bottom of the annular groove 143 refers to the "position in the annular groove 143 that is the deepest from the opening portion". Figure 6

[0068] ​The first annular surface 155 is disposed on the central axis CA side in a manner of surrounding the central axis CA. In a cross section including the central axis CA, the first annular surface 155 is an inclined surface whose height from the light emitting element 131 increases as it is farther from the central axis CA. The first annular surface 155 refracts light, which has been emitted from the light emitting center of the light emitting element 131 and has been incident by the incident surface 141, toward the front surface side. The inclination angle of the first annular surface 155 with respect to the central axis CA is an angle that does not totally reflect light incident by the second incident surface 152 and does not reflect light incident by the back surface toward the direction toward the central axis CA. The shape of the first annular surface 155 in the cross section including the central axis CA is not particularly limited. The shape of the first annular surface 155 in the cross section including the central axis CA is a straight line or a curved line. Examples of the curved line include an arc whose center of curvature is on the outer side of the first annular surface 155 and an arc whose center of curvature is on the inner side of the first annular surface 155, and the like. In the present embodiment, the shape of the first annular surface 155 in the cross section including the central axis CA is a straight line. That is, the first annular surface 155 can also be the shape of a side surface of an inverted circular truncated cone. Thereby, in a case where the light beam control member 132 is injection molded, the light beam control member 132 is easily released from a mold.

[0069] The second annular surface 156 is disposed in a manner of surrounding the central axis CA farther than the first annular surface 155 and spaced apart from the first annular surface 155. In a cross section including the central axis CA, the second annular surface 156 is an inclined surface whose height from the light emitting element 131 increases as it is closer to the central axis CA. The second annular surface 156 refracts light, which has been emitted from the light emitting element 131 and has directly reached the second annular surface 156, toward the front surface side. The shape of the second annular surface 156 in the cross section including the central axis CA is not particularly limited. The shape of the second annular surface 156 in the cross section including the central axis CA is a straight line or a curved line. Examples of the curved line include an arc whose center of curvature is on the outer side of the second annular surface 156 and an arc whose center of curvature is on the inner side of the second annular surface 156, and the like. In the present embodiment, the shape of the second annular surface 156 in the cross section including the central axis CA is a straight line. That is, the second annular surface 156 is the shape of a side surface of a circular truncated cone.

[0070] The third annular surface 157 connects the first annular surface 155 and the second annular surface 156. The shape of the third annular surface 157 is not particularly limited as long as it is a shape capable of functioning as described above. The third annular surface 157 can be one flat surface, a plurality of flat surfaces, or a curved surface. In the present embodiment, the third annular surface 157 is one flat surface. In addition, in a cross section including the central axis CA, the distance from the inner side end portion of the third annular surface 157 to the back surface 145 can be the same as or different from the distance from the outer side end portion of the third annular surface 157 to the back surface 145. In the present embodiment, the distance from the inner side end portion of the third annular surface 157 to the back surface 145 is the same as the distance from the outer side end portion of the third annular surface 157 to the back surface 145 in the cross section including the central axis CA. Preferably, the third annular surface 157 is disposed in such a manner that light emitted from the light emitting element 131 does not directly reach.

[0071] The exit surface 144 causes light reflected by the reflection surface 142 to exit to the outside of the light beam control member 132. The exit surface 144 is disposed in such a manner as to surround the central axis CA. The inner side end portion of the exit surface 144 is connected to the reflection surface 142, and the outer side end portion of the exit surface 144 is connected to the flange 146. In the present embodiment, the exit surface 144 is smoothly connected to the reflection surface 142.

[0072] The back surface 145 is disposed between the recessed portion 153 and the annular groove 143. In the present embodiment, the back surface 145 is a flat surface that is located on the back surface side of the light beam control member 132 and extends radially from the opening edge portion of the recessed portion 153.

[0073] Although not particularly illustrated, the light beam control member 132 has a plurality of leg portions. The plurality of leg portions are portions for positioning the light beam control member 132 with respect to the substrate 112. For example, three leg portions are disposed on the back surface 145.

[0074] (Simulation)

[0075] The light path of light in a light emitting device was simulated. In the present simulation, a light emitting device 130 having the light beam control member 132 of Embodiment 1, and light emitting devices having light beam control members 232, 332 of two comparative examples 1, 2 having different shapes of annular grooves were simulated. First, the structures of the light beam control members 232, 332 of the comparative examples 1, 2 will be described. Note that the light beam control member 132 of the present embodiment, the light beam control member 232 of the comparative example 1, and the light beam control member 332 of the comparative example 2 differ only in the structure of the annular groove, and thus the same reference numerals are assigned to the same structures and the descriptions thereof are omitted.

[0076] Figures 7A-7C is a view showing the structure of the light beam control member 232 of the comparative example 1.Figure 7A This is a perspective view of the beam control component 232 of Comparative Example 1, viewed from the rear side. Figure 7B It is a bottom view. Figure 7C yes Figure 7B The cross-sectional view of line AA shown. Figures 8A-8C This is a diagram showing the structure of the beam control component 332 in Comparative Example 2. Figure 8A This is a perspective view of the beam control component 332 of Comparative Example 2, viewed from the rear side. Figure 8B It is a bottom view. Figure 8C yes Figure 8B The cross-sectional view of line AA is shown. Furthermore... Figures 7A-7C and Figures 8A-8C The support legs are also omitted.

[0077] like Figures 7A-7C As shown, the beam control member 232 of Comparative Example 1 has an incident surface 141, a reflecting surface 142, an annular groove 243, and an exit surface 144. The annular groove 243 of the beam control member 232 of Comparative Example 1 has a first annular surface 255 and a second annular surface 256. That is, the annular groove 243 of the beam control member 232 of Comparative Example 1 does not have a third annular surface 157. In Comparative Example 1, the shape of the annular groove 243 in the cross-section including the central axis CA is triangular. In Comparative Example 1, in the cross-section including the central axis CA, the first annular surface 255 is arranged along the central axis CA. In Comparative Example 1, in the cross-section including the central axis CA, the second annular surface 256 is arranged such that it approaches the back side from the central axis CA side (central portion) towards the outer peripheral portion. In addition, in Comparative Example 1, the depth of the annular groove 243 is deeper than the depth of the annular groove 143 in Embodiment 1.

[0078] like Figures 8A-8C As shown, the beam control member 332 of Comparative Example 2 has an incident surface 141, a reflecting surface 142, an annular groove 343, and an exit surface 144. The annular groove 343 of the beam control member 332 of Comparative Example 2 has a first annular surface 355 and a second annular surface 356. That is, the annular groove 343 of the beam control member 332 of Comparative Example 2 does not have a third annular surface 157. In Comparative Example 2, the shape of the annular groove 343 in the cross-section including the central axis CA is triangular. In Comparative Example 2, in the cross-section including the central axis CA, the first annular surface 355 is arranged such that it approaches the front side as it moves from the central axis CA side (central portion) towards the outer peripheral portion. In the cross-section including the central axis CA, the second annular surface 356 is arranged such that it approaches the back side as it moves from the central axis CA side (central portion) towards the outer peripheral portion. In addition, in Comparative Example 2, the depth of the annular groove 243 is deeper than the depth of the annular groove 143 in Embodiment 1.

[0079] Next, the light paths in the beam control unit 132 of Embodiment 1, the beam control unit 232 of Comparative Example 1, and the beam control unit 332 of Comparative Example 2 will be described. Figure 9A , Figure 9B This is the light path in the beam control component 232 of Comparative Example 1. Figure 9C This is the light path in the beam control component 332 of Comparative Example 2.

[0080] like Figure 9A As shown, in the beam control member 232 of Comparative Example 1, a portion of the light emitted from the region outside the center of the light-emitting element 131 with a small exit angle is incident through the first incident surface 151 and refracted towards the reflecting surface 142. The light incident into the beam control member 232 is reflected laterally by the reflecting surface 142. Furthermore, a portion of the light reflected by the reflecting surface 142 (the light reflected from the region of the reflecting surface 142 that is closer to the exit surface 144) is emitted from the exit surface 144 towards the outside of the beam control member 232. Additionally, a portion of the light reflected by the reflecting surface 142 (the light reflected from the region of the reflecting surface 142 that is closer to the central axis CA) is emitted from the first annular surface 255 towards the outside of the beam control member 232. At this time, since the first annular surface 255 is parallel to the central axis CA, the light emitted from the first annular surface 255 is not refracted much. Furthermore, the light emitted from the first annular surface 255 is incident into the interior of the beam control member 232 through the second annular surface 256. At this time, since the second annular surface 256 is arranged such that it approaches the back side from the central portion towards the outer periphery, the light incident on the second annular surface 256 is refracted toward the front side. Thus, a portion of the light reflected by the reflecting surface 142 is refracted toward the front side by the first annular surface 255 and the second annular surface 256. Afterward, the light refracted toward the front side exits from the exit surface 144 toward the outside of the beam control member 232.

[0081] like Figure 9B As shown, a portion of the light emitted from the area outside the center of the light-emitting element with a large exit angle is incident on the back surface 145 and refracted towards the reflecting surface 142. A portion of the light refracted towards the reflecting surface 142 reaches the reflecting surface 142. A portion of the light reaching the reflecting surface 142 is internally reflected to the exit surface 144, then internally reflected again by the exit surface 144 and exited from the back surface 145. Another portion of the light reaching the reflecting surface 142 exits outward from the reflecting surface 142. A portion of the light incident from the back surface 145 is internally reflected by the first annular surface 255 and exits from the reflecting surface 142 towards the central axis CA.

[0082] like Figure 9CAs shown, in the beam control component 332 of Comparative Example 2, light with a large exit angle emitted from the center of the light-emitting element 131 enters the interior of the beam control component 332 from the second incident surface 152. The light incident on the beam control component 332 reaches the first annular surface 355. All the light reaching the first annular surface 355 is reflected internally (total internal reflection) towards the interior of the reflecting surface 142. The light after internal reflection reaches the reflecting surface 142. The light reaching the reflecting surface 142 is emitted externally from the reflecting surface 142.

[0083] Figure 10A As shown, in the beam control member 132 of this embodiment, light with a small exit angle emitted from the light-emitting center of the light-emitting element 131 enters the interior of the beam control member 132 through the first incident surface 151. The light entering the interior of the beam control member 132 is refracted toward the reflecting surface 142. The light reaching the reflecting surface 142 is reflected laterally. The light reflected by the reflecting surface 142 exits from the exit surface 144 in a direction orthogonal to the central axis CA or further toward the back side than in a direction orthogonal to the central axis CA.

[0084] like Figure 10B As shown, in the beam control member 132 of this embodiment, light with a large exit angle emitted from the light-emitting center of the light-emitting element 131 is incident on the interior of the beam control member 132 through the second incident surface 152. The light incident on the second incident surface 152 is emitted from the first annular surface 155 to the exterior of the beam control member 132. Furthermore, in Comparative Example 2, the light incident on the second incident surface 152 is totally internally reflected. At this time, since the first annular surface 155 is inclined relative to the central axis CA, the light emitted from the first annular surface 155 is refracted towards the front side. In addition, the light emitted from the first annular surface 155 is incident on the interior of the beam control member 132 through the second annular surface 156. At this time, since the second annular surface 156 is arranged such that it approaches the back side from the central portion towards the outer periphery, the light incident on the second annular surface 156 is hardly refracted. The light incident on the second annular surface 156 is emitted directly to the exterior.

[0085] like Figure 10C As shown, in the beam control member 132 of this embodiment, light with a larger emission angle emitted from the region other than the light-emitting center of the light-emitting element 131 is incident on the back surface 145 into the interior of the beam control member 132. The light incident on the back surface 145 is refracted toward the reflective surface 142. After being reflected by the reflective surface 142, the flange 146, and the interior of the second annular surface 156, the light incident on the back surface 145 is emitted from the reflective surface 142 toward the upper part of the beam control member 132.

[0086] Figure 11is a graph showing a simulation result of an illuminance distribution on the light-diffusing member 120 when the light beam control member of the present embodiment, the light beam control member of Comparative Example 1, and the light beam control member of Comparative Example 2 are used. Figure 11 The solid line indicates the illuminance when the light beam control member 132 of the present application is used, the long dashed line indicates the illuminance when the light beam control member 232 of Comparative Example 1 is used, and the short dashed line indicates the illuminance when the light beam control member 332 of Comparative Example 2 is used. Figure 11 The horizontal axis indicates the distance (mm) from the intersection of the optical axis LA and the diffusing plate, Figure 11 The vertical axis indicates the illuminance (lux).

[0087] As is apparent from Figure 11 , the luminance of the directly above portion of the light beam control member is, from high to low, the light beam control member 232 of Comparative Example 1, the light beam control member 332 of Comparative Example 2, and the light beam control member 132 of the present embodiment. In addition, as is apparent from

[0088] (EFFECTS)

[0089] As described above, in the light beam control member 132 of Embodiment 1, since the annular groove 143 is not formed in the optical path of the light reflected by the reflecting surface 142, the light reflected by the reflecting surface 142 is emitted toward a direction orthogonal to the central axis CA or a direction more toward the back surface side than the direction orthogonal to the central axis CA. Therefore, in the surface light source device 100 of the present embodiment, it is possible to improve the waveform of the illuminance distribution. In addition, by setting the shape of the annular groove 143 in the cross section including the central axis CA to a trapezoidal shape, the volume of the weight reduction increases, so it is also possible to reduce the manufacturing cost.

[0090] [MODIFIED EXAMPLES 1 TO 4 OF EMBODIMENT 1]

[0091] The surface light source devices of Modified Examples 1 to 4 of Embodiment 1 differ from the surface light source device 100 of Embodiment 1 only in the structure of the light beam control member. Therefore, only the light beam control members 532, 632, 732, 832 of Modified Examples 1 to 4 will be described.

[0092] Figures 12A-12D is a partial enlarged cross-sectional view of the light beam control members 532, 632, 732, 832 of Modified Examples 1 to 4. Figure 12A is a partial enlarged cross-sectional view of the light beam control member 532 of Modified Example 1, Figure 12B is a partial enlarged cross-sectional view of the light beam control member 632 of Modified Example 2, Figure 12C is a partial enlarged cross-sectional view of the light beam control member 732 of Modified Example 3,Figure 12D is a partial enlarged sectional view of the light beam control member 832 of Modification 4.

[0093] As shown in Figure 12A , the annular groove 543 in the light beam control member 532 of Modification 1 has a first annular face 555, a second annular face 556, and a third annular face 557. In this modification, the inclination angle of the first annular face 555 with respect to the central axis CA is smaller than the inclination angle of the second annular face 556 with respect to the central axis CA. In addition, in a sectional plane including the central axis CA, the length in the direction of the central axis CA of the upper side end portion of the first annular face 555 is longer than the length in the direction of the central axis CA of the upper side end portion of the second annular face 556. That is, the third annular face 557 in the light beam control member 532 of this modification is disposed in such a manner as to approach the back face 145 as it moves away from the central axis CA.

[0094] As shown in Figure 12B , the annular groove 643 in the light beam control member 632 of Modification 2 has a first annular face 655, a second annular face 656, and a third annular face 657. In this modification, the third annular face 657 has a first separate annular face 675a and a second separate annular face 675b. In a sectional plane including the central axis CA, the first separate annular face 675a and the second separate annular face 675b can be either straight lines or curved lines. In this embodiment, the first separate annular face 675a and the second separate annular face 675b are curved surfaces. The first separate annular face 675a is formed in such a manner as to approach the back face 145 as it moves from the center toward the outer peripheral portion. The second separate annular face 675b is formed in such a manner as to move away from the back face 145 as it moves from the center toward the outer peripheral portion.

[0095] As shown in Figure 12C , the annular groove 743 in the light beam control member 732 of Modification 3 has a first annular face 655, a second annular face 656, and a third annular face 757. In this modification, the third annular face 757 has a first separate annular face 675a, a second separate annular face 675b, and a third separate annular face 775c. The first separate annular face 675a and the second separate annular face 675b are the same as in Modification 2, so a description thereof is omitted. The third separate annular face 775c connects the first separate annular face 675a and the second separate annular face 675b. In this embodiment, the third separate annular face 775c is disposed in such a manner as to be parallel to the back face 145.

[0096] As shown in Figure 12D , the annular groove 843 in the light beam control member 832 of Modification 4 has a first annular face 655, a second annular face 656, and a third annular face 857. In this modification, the third annular face 857 is a curved surface that bulges toward the back face 145.

[0097] In Variations 1 to 4, in a cross section including the central axis CA, the first annular surface 555, 655 is an inclined surface whose height from the light emitting element 131 increases as it moves away from the central axis CA, and the first annular surface 555, 655 refracts light that has been emitted from the light emitting center of the light emitting element 131, has been incident on the incident surface 141, and has directly reached the first annular surface 555, 655, toward the front surface side. In addition, in a cross section including the central axis CA, the second annular surface 556, 656 is an inclined surface whose height from the light emitting element 131 increases as it moves closer to the central axis CA, and the second annular surface 556, 656 refracts light that has been emitted from the light emitting element 131 and has directly reached the second annular surface 556, 656, toward the front surface side.

[0098] [Embodiment 2]

[0099] Next, the structure of the light flux control member 932 of Embodiment 2 will be described. Figures 13A-13C is a view showing the structure of the light flux control member 932 of Embodiment 2. Figure 13A is a perspective view of the light flux control member 932 of Embodiment 2 as viewed from the incident surface 941 side, Figure 13B is a bottom view, Figure 13C is a cross-sectional view including the central axis CA.

[0100] As shown in Figures 13A-13C , the light flux control member 932 of Embodiment 2 has an incident surface 941, a reflection surface 142, an annular groove 143, and an exit surface 144. In this embodiment, the incident surface 941 is a flat surface.

[0101] Industrial Applicability

[0102] The light flux control member, the light emitting device, and the surface light source device of the present application can be applied to, for example, a backlight for a liquid crystal display device, general lighting, or the like.

Claims

1. A beam control component for controlling the light distribution of light emitted from a light-emitting element, comprising: An incident surface is arranged on the back side in such a way that it intersects with the central axis of the beam control component, for allowing light emitted from the light-emitting element to enter; A reflective surface is disposed on the front side such that its height from the light-emitting element increases as it moves away from the central axis, for the purpose of reflecting light incident from the incident surface to the side. An annular groove, the annular groove including a first annular surface, a second annular surface and a third annular surface connecting the first annular surface and the second annular surface, the first annular surface being farther away from the central axis than the incident surface and being disposed on the back side near the central axis in a manner surrounding the central axis, the second annular surface being farther away from the central axis than the first annular surface and being disposed spaced apart from the first annular surface; as well as The exit surface, located further away from the central axis than the annular groove, is configured to surround the central axis, allowing light reflected by the reflective surface to exit. The annular groove is configured so that it does not intersect with the light paths of all light emitted from the light-emitting center of the light-emitting element, incident on the incident surface, reflected by the reflecting surface, and reaching the exiting surface. In a cross-section including the central axis, the first annular surface is an inclined surface whose height from the light-emitting element increases with distance from the central axis, and the first annular surface refracts light emitted from the light-emitting center of the light-emitting element and incident on the incident surface directly onto the first annular surface toward the front side. In a cross-section including the central axis, the second annular surface is an inclined surface whose height from the light-emitting element increases as it approaches the central axis, and the second annular surface causes light emitted from the light-emitting element and directly reaching the second annular surface to refract towards the front side. The third annular surface is configured such that light emitted from the light-emitting element and not incident on the incident surface does not directly reach it.

2. The beam control component as claimed in claim 1, wherein, Light emitted from the light-emitting center of the light-emitting element, incident on the incident surface, reflected by the reflecting surface, and directly reaching the exiting surface, is emitted in a direction orthogonal to the central axis or further toward the back side than in a direction orthogonal to the central axis.

3. The beam control component as claimed in claim 1, wherein, The incident surface has: The first incident surface is the inner surface of a recess formed in a manner intersecting with the central axis; as well as The second incident surface is disposed between the opening edge of the first incident surface and the annular groove.

4. The beam control component as claimed in claim 1, wherein, The bottom of the annular groove is positioned further forward than the portion of the reflective surface that intersects the central axis.

5. The beam control component as claimed in claim 1, wherein, The annular groove is rotationally symmetrical about the central axis.

6. A light-emitting device, wherein, It has a light-emitting element and a beam control component as described in any one of claims 1 to 5. The beam control component is configured such that the central axis coincides with the optical axis of the light-emitting element.

7. A surface light source device, comprising: The light-emitting device according to claim 6; and A light-diffusing component that diffuses and transmits light from the light-emitting device.

8. A display device comprising: The surface light source device according to claim 7; and The display component is illuminated by light emitted from the surface light source device.

Images