JP2022017153A - Luminous flux control member, light emitting device, surface light source device, display device, and luminance unevenness improving method for light-emitting device - Google Patents

Abstract

To provide a luminous flux control member capable of more properly distributing light from a plurality of light emitting elements while arranging a luminous flux control member on the plurality of light emitting elements and improving handling in mounting.SOLUTION: A luminous flux control member has: n incidence units on which light emitted from n light emitting elements is made incident; an emission unit which is arranged between the n incidence units, and concurrently guiding and emitting the light made incident on the n incidence units; and a plurality of legs. The plurality of incidence units have an incidence surface, and a reflection surface reflecting the light made incident on the incidence surface to a direction along a substrate. The emission unit has a first emission surface for emitting part of the light from the incidence units, and a second emission surface arranged opposite the first emission surface and emitting part of the light from the incidence units. The plurality of legs are arranged at positions meeting predetermined conditions, respectively.SELECTED DRAWING: Figure 4

Description

The present invention relates to a light flux control member that controls the distribution of light emitted from a light emitting element, a light emitting device having the light beam control member, a surface light source device having the light emitting device, a display device having the surface light source device, and the present invention. The present invention relates to a method for improving uneven brightness of a light emitting device.

In a transmissive image display device such as a liquid crystal display device, a direct type surface light source device having a plurality of light emitting elements as a light source has been used in recent years. In addition, a large number of light emitting elements may be arranged to irradiate light over a wide range.

Patent Document 1 discloses a luminous flux control member (microarray lens) suitable for being arranged on a large number of light emitting elements. In this microarray lens, a large number of lenses are connected by a support plate, and one microarray lens is arranged on a large number of light emitting elements (mini LEDs) arranged on a substrate. By doing so, it is not necessary to arrange individual lenses on the individual light emitting elements, the handling property at the time of mounting is improved, and the mounting becomes easy.

Chinese Patent Application Publication No. 110208984

Although the above-mentioned luminous flux control member (microarray lens) has good handleability at the time of mounting, the luminous flux control member may become thick when trying to distribute the light from the light emitting element as desired. be. As a result, the surface light source device may also become thick.

An object of the present invention is to arrange one luminous flux control member on a plurality of light emitting elements to improve the handling property at the time of mounting, and to more appropriately distribute the light from the plurality of light emitting elements. It is an object of the present invention to provide a luminous flux control member. Another object of the present invention is to provide a light emitting device, a surface light source device, and a display device having the above-mentioned luminous flux control member. Further, another object of the present invention is to provide a method for improving the luminance unevenness of the above-mentioned light emitting device.

The light beam control member of the present invention is a light beam control member for controlling the light distribution of the light emitted from the n light emitting elements arranged on the substrate, and is the light emitted from the n light emitting elements. An emission unit that is arranged between the n incident units in the direction along the substrate and emits the incident light by the n incident units while guiding the light incident on the n incident units. And a plurality of legs arranged on the back side of the light beam control member and supporting the light beam control member with respect to the substrate, and the n incident units are arranged on the back side of the light beam control member, respectively. The light emitted from the light emitting element is incident on the incident surface, and the light incident on the incident surface is arranged at a position facing the light emitting element with the incident surface on the front side of the light beam control member. It has a reflecting surface that reflects laterally away from the optical axis of the light emitting element, and the emitting unit is arranged on the front side of the light beam control member and reflects a part of the light from the incident unit. , A first emission surface for emitting another part and a part of the light emitted from the incident unit are reflected on the back side of the light beam control member so as to face the first emission surface, and the other part. The plurality of legs are arranged at positions satisfying the following condition 1 or condition 2, respectively.
[Condition 1]
When the light beam control member is viewed in a plan view, the center of gravity of the polygon formed by connecting the centers of the n incident units is ± (60) from the center of each of the n incident units. At least a part of the leg is arranged outside the first region, which is the region surrounded by the 2n straight lines when the two straight lines are drawn at an angle of / n) °.
[Condition 2]
Of the light emitting surface of the light emitting element, the light emitted from the light emitting center which is the intersection with the central axis of the incident unit, and of the light incident on the incident surface, directly reaches the reflecting surface from the incident surface and reaches the reflecting surface. Light that has been reflected by and then not reflected by another surface, directly reaches the reflecting surface from the incident surface, is sequentially reflected by the reflecting surface and the first emitting surface, and then is not reflected by the other surface. Inside a second region, which is a region in which light and light that reaches the first emission surface directly from the entrance surface and is reflected by the first emission surface but not reflected by other surfaces does not substantially reach. All of the legs are arranged in.

The light emitting device of the present invention has n light emitting elements arranged on a substrate and the above-mentioned luminous flux control member arranged on the n light emitting elements.
In the light emitting device, it is preferable that the plurality of legs are adhered to the substrate with an adhesive having a color having less optical absorption than black.

The surface light source device of the present invention has a plurality of the above-mentioned light emitting devices and a light diffusing plate that diffuses and transmits the light emitted from the plurality of light emitting devices.

The display device of the present invention includes the above-mentioned surface light source device and a display member irradiated with light emitted from the surface light source device.

The method for improving the luminance unevenness of the light emitting device of the present invention is the above-mentioned method for improving the luminance unevenness of the light emitting device, and is the method for improving the luminance unevenness of the luminous flux control member by using an adhesive having an optical absorption rate selected according to the luminance distribution. Secure multiple legs to the board.

According to the present invention, it is possible to more appropriately distribute the light from the plurality of light emitting elements while improving the handleability at the time of mounting by arranging one light flux control member on the plurality of light emitting elements. A luminous flux control member can be provided. Further, according to the present invention, it is possible to provide a light emitting device, a surface light source device, and a display device having the above-mentioned luminous flux control member.

1A and 1B are diagrams showing the configuration of a surface light source device according to an embodiment. 2A to 2C are views showing the configuration of the surface light source device according to the embodiment. FIG. 3 is a partially enlarged view of FIG. 2B. FIG. 4 is a perspective view showing the configuration of the luminous flux control member according to the embodiment. 5A to 5C are views showing the configuration of the luminous flux control member according to the embodiment. FIG. 6 is an optical path diagram of the light emitting device according to the embodiment. 7A to 7C are schematic views for explaining the condition 1. 8A to 8D are schematic views for explaining the condition 1. FIG. 9 is a schematic diagram for explaining condition 2. 10A to 10D are schematic views for explaining the condition 2. 11A and 11B are bottom views of the luminous flux control member according to the embodiment. 12A is a bottom view of the light flux control member according to the embodiment, and FIG. 12B is a bottom view of the light flux control member for comparison. 13A and 13B are diagrams showing the configuration of the luminous flux control member according to the modified example of the embodiment. FIG. 14A shows the illuminance distribution of the surface light source device using the comparative luminous flux control member having no legs, and FIG. 14B shows the illuminance distribution of the surface light source device using the comparative luminous flux control member shown in FIG. 12B. Is shown. 15A and 15B show the illuminance distribution of the surface light source device using the luminous flux control member according to the embodiment. FIG. 16 shows the illuminance distribution of the surface light source device using the luminous flux control member according to the embodiment. 17A to 17C are views showing the configuration of the light flux control member according to the modified example of the embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, as a typical example of the surface light source device according to the present invention, a surface light source device suitable for a backlight of a liquid crystal display device or the like will be described. This surface light source device can be used as a display device 100'by combining with a display member 102 (for example, a liquid crystal panel) irradiated with light from the surface light source device (see FIG. 1B).

(Structure of surface light source device and light emitting device)
1A and 1B are views showing the configuration of a surface light source device 100 according to an embodiment of the present invention. 1A is a plan view, and FIG. 1B is a front view. 2A is a cross-sectional view taken along the line AA shown in FIG. 1B, FIG. 2B is a cross-sectional view taken along the line BB shown in FIG. 1A, and FIG. 2C shows a light emitting element 220 and a luminous flux control member 300. It is a partially enlarged plan view which shows the positional relationship with. FIG. 3 is a partially enlarged cross-sectional view of a part of FIG. 2B.

As shown in FIGS. 1A to 3, the surface light source device 100 according to the present embodiment includes a housing 110, a plurality of light emitting devices 200, and a light diffusing plate 120. The plurality of light emitting devices 200 are arranged in a grid pattern (matrix shape) on the bottom plate 112 of the housing 110. The inner surface of the bottom plate 112 functions as a diffuse reflection surface. Further, the top plate 114 of the housing 110 is provided with an opening. The light diffusing plate 120 is arranged so as to close this opening, and functions as a light emitting surface. The size of the light emitting surface is not particularly limited, but is, for example, about 400 mm × about 700 mm.

As shown in FIG. 3, the light emitting device 200 is fixed on the substrate 210. The substrate 210 is fixed at a predetermined position on the bottom plate 112 of the housing 110. The light emitting device 200 has a plurality of light emitting elements 220 and a light flux control member 300 (see also FIG. 2C).

The light emitting element 220 is a light source of the surface light source device 100 and is mounted on the substrate 210. The light emitting element 220 is a light emitting diode (LED) such as a white light emitting diode. The type of the light emitting element 220 is not particularly limited, but a light emitting element 220 (for example, a COB type light emitting diode) that emits light from the top surface and side surfaces is suitable for the light emitting device 200 according to the embodiment of the present invention. Used for.

The size of the light emitting surface of the light emitting element 220 is not particularly limited, but it is preferably smaller from the viewpoint of appropriately distributing light and reducing color unevenness. Specifically, the size of the light emitting surface of the light emitting element 220 is preferably 0.1 mm to 0.6 mm, more preferably 0.1 mm to 0.3 mm.

The luminous flux control member 300 is an optical member that controls the light distribution of the light emitted from the light emitting element 220, and is fixed on the substrate 210. As will be described later, the luminous flux control member 300 has a plurality of incident units 310, and in the luminous flux control member 300, the central axis CA of each incident unit 310 (incident surface 311) is the optical axis LA of each light emitting element 220. It is arranged on a plurality of light emitting elements 220 so as to match. In the luminous flux control member 300 according to the present embodiment, the incident unit 310 (incident surface 311 and reflecting surface 312) of the luminous flux control member 300 is rotationally symmetric. The axis of rotation of the incident unit 310 is referred to as "incident unit 310, central axis CA of the incident surface 311 or the reflecting surface 312". Further, the "optical axis LA of the light emitting element 220" means a light ray at the center of a three-dimensional emitted light flux from the light emitting element 220. The “light emitting center of the light emitting element 220” means an intersection of the light emitting surface of the light emitting element 220 with the central axis CA of the incident unit 310.

The luminous flux control member 300 has a plurality of legs 330, and the heat generated from the light emitting element 220 is released to the outside between the substrate 210 on which the light emitting element 220 is mounted and the back surface of the luminous flux control member 300. A gap is formed (see FIG. 3). The plurality of legs 330 of the luminous flux control member 300 may be fixed to the substrate 210 by an adhesive.

The method of fixing the luminous flux control member 300 to the substrate 210 is not particularly limited. For example, the plurality of legs 330 of the luminous flux control member 300 may be fixed to the substrate 210 using black or a colored adhesive having less optical absorption than black. In this case, when the light emitting device 200 is viewed from above, it is preferable to fix the legs 330, which are arranged in a region that tends to be bright, to the substrate 210 using a black adhesive or a color adhesive having a large amount of optical absorption. .. On the other hand, when the light emitting device 200 is viewed from above, the legs 330 arranged in a region that tends to be a dark part are preferably fixed to the substrate 210 by using an adhesive having a color such as white that has little optical absorption. When a colorless and transparent adhesive is used, it is easily affected by the color of the adhered member such as the substrate, but by selectively using a colored adhesive, it is possible to realize a light emitting device with less uneven brightness. can. In this way, by fixing the plurality of legs 330 of the luminous flux control member 300 to the substrate 210 by using the adhesive having the optical absorption coefficient selected according to the luminance distribution, the luminance unevenness of the light emitting device 200 is re-elected. be able to.

The luminous flux control member 300 is integrally molded. The material of the luminous flux control member 300 is not particularly limited as long as it is a material capable of passing light of a desired wavelength. For example, the material of the luminous flux control member 300 is a light-transmitting resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), or epoxy resin (EP), or glass.

The surface light source device 100 according to the present embodiment has a main feature in the configuration of the luminous flux control member 300. Therefore, the luminous flux control member 300 will be described in detail separately.

The light diffusing plate 120 is a plate-shaped member having light diffusing properties, and transmits light emitted from the light emitting device 200 while diffusing it. Usually, the light diffusing plate 120 has almost the same size as a display member such as a liquid crystal panel. For example, the light diffusing plate 120 is formed of a light transmissive resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), and styrene / methyl methacrylate copolymer resin (MS). In order to impart light diffusivity, fine irregularities are formed on the surface of the light diffusing plate 120, or light diffusing elements such as beads are dispersed inside the light diffusing plate 120.

In the surface light source device 100 according to the present embodiment, the light emitted from each light emitting element 220 is spread by the luminous flux control member 300 so as to illuminate a wide range of the light diffusing plate 120. The light emitted from each luminous flux control member 300 is further diffused by the light diffusing plate 120. As a result, the surface light source device 100 according to the present embodiment can uniformly illuminate the surface-shaped display member 102 (for example, a liquid crystal panel). When a bright part or a dark part is generated on the light emitting surface (light diffusing plate 120), the color of the adhesive used in the adhesive is adjusted according to the position and degree of the bright part or the dark part. The degree of absorption and reflection may be adjusted to eliminate the occurrence of bright or dark areas.

As shown in FIGS. 2A and 2C, in the present embodiment, the plurality of light emitting elements 220 and the plurality of light emitting devices 200 are all arranged in a grid pattern and separated from each other. The distance L1 between the adjacent light emitting devices 200 may be smaller than half of the center-to-center distance L2 of the plurality of light emitting elements 220. Here, the "center-to-center distance L2 of the plurality of light-emitting elements 220" means the center-to-center distance of two light-emitting elements 220 belonging to different light-emitting devices 200. By doing so, the light is guided more widely by the luminous flux control member 300, and it is possible to prevent the space between the light emitting devices 200 from becoming dark.

It is also important that there is a gap between the adjacent light emitting devices 200 and that the light emitting devices 200 are arranged so as not to be in contact with each other. If the light emitting device 200 is not arranged with a gap, the light emitted from the end of the light flux control member 300 may be incident on or reflected at the end of the adjacent light flux control member 300, and the light diffuser plate may be used. There is a risk of adversely affecting the light emission quality above 120.

(Structure of luminous flux control member)
FIG. 4 is a perspective view of the luminous flux control member 300 according to the embodiment. 5A is a plan view of the light flux control member 300 according to the embodiment, FIG. 5B is a bottom view of the light flux control member 300, and FIG. 5C is a cross-sectional view taken along the line CC of FIG. 5A. FIG. 5C shows the luminous flux control member 300 in an enlarged manner as compared with FIGS. 5A and 5B. Hereinafter, the configuration of the luminous flux control member 300 will be described.

The luminous flux control member 300 is a luminous flux control member 300 for controlling the orientation of light emitted from n light emitting elements 220 arranged on the substrate 210, and is an n incident unit 310 and an emission unit 320. And has a plurality of legs 330. In the present embodiment, the luminous flux control member 300 has four incident units 310 in order to control the orientation of the light emitted from the four light emitting elements 220. The n (4) incident units 310 are arranged in a grid pattern corresponding to the arrangement of the light emitting elements 220. The emitting units 320 are arranged between n (4) incident units 310 in the direction along the substrate 210. The plurality of legs 330 are arranged on the back side of the luminous flux control member 300. In this embodiment, the luminous flux control member 300 has four legs 330 (see FIG. 5B).

Each of the plurality of incident units 310 incidents the light emitted from the light emitting element 220. The incident unit 310 has an incident surface 311 for incident light emitted from the light emitting element 220 and a reflecting surface 312 for reflecting the light incident on the incident surface 311 toward the emitting unit 320.

The incident surface 311 is an inner surface of a recess arranged on the back side of the luminous flux control member 300 and formed at a position facing the light emitting element 220. The incident surface 311 causes most of the light emitted from the light emitting element 220 to enter the inside of the luminous flux control member 300 while controlling the traveling direction thereof. The incident surface 311 intersects the optical axis LA of the light emitting element 220 and is rotationally symmetric (circular symmetry) with respect to the optical axis LA. The shape of the incident surface 311 is not particularly limited, and the light incident on the incident surface 311 is set so as to be directed toward the reflecting surface 312 and the first emitting surface 321. In the present embodiment, the recess constituting the incident surface 311 has a shape in which a small deep recess is arranged in the center of a large shallow recess (see FIG. 3). The small recess in the center has a shape in which the distance from the substrate 210 gradually decreases as the distance from the optical axis LA of the light emitting element 220 increases. A part of the incident surface 311 formed by the small recesses is the light emitting element 220 so that the light emitted from the light emitting element 220 at a small angle with respect to the optical axis LA is directed to a region other than the central portion of the reflecting surface 312. Control the light from. The large recesses located around the small recesses have a shape such that the distance from the substrate 210 is substantially constant for a while even if the light emitting element 220 is separated from the optical axis LA, and then gradually shortens. A part of the incident surface 311 formed by the large recess controls the light from the light emitting element 220 so that the light emitted from the light emitting element 220 at a large angle with respect to the optical axis LA is directed to the first emission surface 321. do.

The reflecting surface 312 is arranged on the front side of the light flux control member 300 at a position facing the light emitting element 220 with the incident surface 311 interposed therebetween, and laterally so as to separate the light incident on the incident surface 311 from the optical axis LA of the light emitting element 220. Reflect in the direction. Here, the lateral direction does not mean the outer edge direction of the luminous flux control member 300, but means all the radial directions (directions perpendicular to the optical axis LA) about the optical axis LA. Therefore, the reflecting surface 312 also reflects the light incident on the incident surface 311 toward the central portion of the luminous flux control member 300 (see FIG. 6). By doing so, the reflective surface 312 suppresses the light incident on the incident surface 311 from escaping upward to prevent a bright portion from being generated directly above the light emitting element 220, and the light between the light emitting elements 220. It also prevents dark areas from being generated between the light emitting elements 220.

The shape of the reflecting surface 312 is not particularly limited as long as the light incident from the incident surface 311 can be reflected laterally. The reflecting surface 312 is configured to be rotationally symmetric (circularly symmetric) with respect to the optical axis LA of the light emitting element 220, and to face the front side (away from the substrate 210) as the distance from the optical axis LA of the light emitting element 220 increases. It may have been done. The generatrix from the central portion to the outer peripheral portion of the rotational symmetry is a curved line or a straight line inclined with respect to the optical axis of the light emitting element 220. In the present embodiment, this generatrix is a curve whose angle with respect to the optical axis LA increases as the distance from the optical axis LA of the light emitting element 220 increases. The reflective surface 312 is a concave surface in a state where the generatrix is rotated by 360 ° with the central axis CA of the incident surface 311 as the rotation axis.

The reflective surface 312 may have a plurality of ridges arranged so as to connect a central portion thereof and an outer edge thereof. Each ridge has a first inclined surface, a second inclined surface arranged in pairs with the first inclined surface, and a ridge line which is a boundary line between the first inclined surface and the second inclined surface. The plurality of ridges are arranged so that a valley is formed between two ridges adjacent to each other. Since the reflecting surface 312 has such ridges, it is possible to further suppress the light incident on the incident surface 311 from being reflected more and the light from passing upward.

In the present embodiment, the incident surface 311 and the reflecting surface 312 have a part of the light emitted from the light emitting center of the light emitting element 220 incident on the incident surface 311 and reflected by the reflecting surface 312, and then the emitting unit 320. It is configured to reach the second exit surface 322.

When viewed in a plan view, the area of the opening edge of the recess constituting the reflecting surface 312 is preferably 0.5 to 2.0 times the area of the opening edge of the recess constituting the incident surface 311. , 0.5 times to 1.5 times, more preferably 0.5 times to 1.3 times, and particularly preferably 0.5 times to 1.3 times. As described above, the size of the reflecting surface 312 with respect to the incident surface 311 is smaller than that of the conventional total internal reflection lens. This is because, in the present embodiment, the light emitted from the light emitting center of the light emitting element 220 and incident on the incident surface 311 is designed to reach not only the reflecting surface 312 but also the first emitting surface 321. caused by.

The emission unit 320 emits light incident on each incident unit 310 while guiding the light. In the present embodiment, assuming that the four incident units 310 are arranged at each vertex of the virtual rectangle (square), the luminous flux control member 300 has each side at a position corresponding to the four sides of the virtual rectangle. It has four emission units 320 arranged along the above, and one emission unit 320 arranged so as to be surrounded by a virtual rectangle. Each emission unit 320 is arranged on the front side of the light flux control member 300, and on the first emission surface 321 that reflects a part of the light from the incident unit 310 and emits the other part, and on the back side of the light flux control member 300. It has a second emission surface 322 that is arranged to face the first emission surface 321 and reflects a part of the light from the incident unit 310 to emit the other part.

The emission unit 320 preferably has an emission promotion unit for promoting the emission of light traveling between the first emission surface 321 and the second emission surface 322. It is preferable that the emission promotion unit is arranged on at least one of the first emission surface 321 and the second emission surface 322. In the present embodiment, the emission promoting unit is formed on the first emission surface 321 and the second emission surface 322, and the distance between the first emission surface 321 and the second emission surface 322 is such that the distance from the incident unit 310 increases. It's getting smaller. With such a configuration, the light guided from the incident unit 310 is more likely to be emitted from the first emitting surface 321 as the distance from the incident unit 310 increases.

The shapes of the first exit surface 321 and the second exit surface 322 are not particularly limited. In the present embodiment, the four first exit surfaces 321 arranged at positions corresponding to the four sides of the virtual rectangle have a curvature in the direction along the side of the virtual rectangle and are perpendicular to the sides. It is a concave surface having no curvature in the direction (see FIG. 4). Further, the four second exit surfaces 322 arranged at positions corresponding to the four sides of the virtual rectangle are concave surfaces composed of two inclined planes that face toward the front side as the distance from the incident unit 310 increases. On the other hand, the first emission surface 321 arranged so as to be surrounded by the virtual rectangle is a concave surface formed by a part of the upper bottom and the side surface of the truncated cone arranged upside down, and the second emission surface 322. Is a plane (see FIGS. 5A, 5C).

The configuration of the emission promoting unit is not particularly limited as long as the above functions can be exhibited. For example, the emission promotion unit is at least one selected from the group consisting of a concave surface, a rough surface, a Fresnel surface, a groove, and a through hole, which are arranged on at least one of the first emission surface 321 and the second emission surface 322. It may be the above.

When the emission promoting portion is a concave surface formed on the first emission surface 321 or the second emission surface 322, the distance between the first emission surface 321 and the second emission surface 322 becomes smaller as the distance from the incident unit 310 increases. Light traveling between the emission surface 321 and the second emission surface 322 is likely to be emitted from the first emission surface 321 and the second emission surface 322. When the emission promoting portion is a rough surface formed on the second emission surface 322, the light traveling between the first emission surface 321 and the second emission surface 322 is diffusely reflected on the rough surface instead of specular reflection. 1 It becomes easy to emit light from the exit surface 321. When the emission promoting portion is a rough surface formed on the first emission surface 321, the light traveling between the first emission surface 321 and the second emission surface 322 is diffused and transmitted on the rough surface instead of specular reflection. It is easy to emit light from the first emission surface 321. When the emission promoting portion is a Fresnel surface or a groove formed on the second emission surface 322, the light traveling between the first emission surface 321 and the second emission surface 322 is on the Fresnel surface or the surface constituting the groove. Since the light is reflected toward the first emission surface 321 so that the incident angle on the first emission surface 321 becomes smaller, it becomes easier to emit light from the first emission surface 321. When the emission promoting portion is a Fresnel surface or a groove formed on the first emission surface 321, the light traveling between the first emission surface 321 and the second emission surface 322 constitutes the Fresnel surface or the surface constituting the Fresnel surface. Since it is emitted at the first emission surface 321 it is likely to be emitted from the first emission surface 321. When the emission promoting portion is a through hole opened in the first emission surface 321 and the second emission surface 322, the light traveling between the first emission surface 321 and the second emission surface 322 is formed on the surface constituting the through hole. Since it is emitted, it is likely to be emitted from the first emission surface 321.

FIG. 6 is an optical path diagram of the light emitting device 200 in the cross section shown by the line CC of FIG. 5A. Here, the optical path of the light emitted from the light emitting center of one light emitting element 220 is shown. As shown in FIG. 6, the light emitted from the light emitting element 220 is incident on the luminous flux control member 300 at the incident surface 311. A part of the light incident on the incident surface 311 is directly directed to the emitting unit 320, and the other part is reflected by the reflecting surface 312 and directed to the emitting unit 320. The light that has reached the emission unit 320 is repeatedly reflected between the first emission surface 321 and the second emission surface 322, and is guided through the emission unit 320. At this time, a part of the light that has reached the first emission surface 321 is emitted from the first emission surface 321 without being reflected, and a part of the light that has reached the second emission surface 322 is not reflected and is second. It is emitted from the emission surface 322.

In this way, the light that has reached the emission unit 320 travels between the first emission surface 321 and the second emission surface 322 of the emission unit 320, and is gradually emitted from the first emission surface 321 and the second emission surface 322. To. Here, the emission unit 320 has an emission promotion unit in which the distance between the first emission surface 321 and the second emission surface 322 becomes smaller as the distance from the incident unit 310 increases. As a result, the farther away from the incident unit 310, the easier it is for light traveling between the first emission surface 321 and the second emission surface 322 to be emitted from the first emission surface 321 and the second emission surface 322.

The plurality of legs 330 are arranged on the back side of the luminous flux control member 300 and support the luminous flux control member 300 with respect to the substrate 210. The number and shape of the legs 330 are not particularly limited as long as the luminous flux control member 300 can be stably supported. In the present embodiment, the luminous flux control member 300 has four cylindrical legs 330.

In the light flux control member 300 according to the present embodiment, the plurality of legs 330 are arranged at positions satisfying the following condition 1 or condition 2, respectively, from the viewpoint of reducing the influence on the light distribution characteristics of the light flux control member 300. ing. The luminous flux control member 300 shown in FIG. 5B satisfies the condition 1.
[Condition 1]
When the light beam control member 300 is viewed in a plan view, each of the n incident units 310 with respect to the polygonal center of gravity CP formed by connecting the centers (central axes CA) of the n incident units 310. At least a part of the leg 330 is placed outside the first region, which is the region surrounded by the 2n straight lines when two straight lines are drawn at an angle of ± (60 / n) ° from the center of. There is.
[Condition 2]
Of the light emitting surface of the light emitting element 220, the light emitted from the light emitting center which is the intersection with the central axis CA of the incident unit 310, and among the light incident on the incident surface 311, directly reaches the reflecting surface 312 from the incident surface 311 and reaches the reflecting surface 312. Light that has been reflected by 312 but not reflected by other surfaces, directly reaches the reflecting surface 312 from the incident surface 311 and is sequentially reflected by the reflecting surface 312 and the first exit surface 321 and then reflected by other surfaces. In the second region, which is a region in which no light and light that reaches the first emission surface 321 directly from the incident surface 311 and is reflected by the first emission surface 321 but not reflected by the other surface does not substantially reach. Inside, all of the legs 330 are located.

First, condition 1 will be described with reference to the drawings. Condition 1 stipulates that the leg 330 is not arranged between the incident unit 310 and the central portion of the luminous flux control member 300. This is because if the leg 330 is arranged between the incident unit 310 and the central portion of the light flux control member 300, a dark portion is likely to occur in a region located directly above the central portion of the light flux control member 300 in the light diffusing plate 120.

First, a polygon formed by connecting the centers (central axes CA) of the n incident units 310 in a plan view of the luminous flux control member 300 and its center of gravity CP are defined. In the case of the luminous flux control member 300 according to the present embodiment, a quadrangle (square) is formed as shown by a broken line in FIG. 7A.

Next, from the center of each of the n incident units 310 (the apex of the polygon) to the center CP of the polygon at + (60 / n) ° and − (60 / n) ° angles. Draw two straight lines. In this embodiment, since n = 4, as shown in FIG. 7B, ± 15 ° from the center of each of the four incident units 310 (the apex of the quadrangle) to the center CP of the quadrangle. Draw two straight lines so that they are at an angle. Each straight line is extended from the center of the incident unit 310 until it intersects with another straight line.

Then, the area surrounded by the drawn 2n straight lines is set as the first area. Each leg 330 is arranged on the back side of the luminous flux control member 300 so that at least a part thereof is located outside the first region. In the present embodiment, as shown in FIG. 7C, in the area on the back side of the light flux control member 300, the area other than the first area and the incident surface 311, that is, the area where the hatching is attached, the leg 330 is formed. At least part is placed. Further, for each leg 330, the ratio of the portion existing outside the first region is preferably 30% or more, more preferably 50% or more, and particularly preferably 100%.

For example, as shown in FIG. 8A, for all legs 330, the luminous flux control member 300 satisfies condition 1 when the entire leg 330 is located outside the first region. Further, as shown in FIG. 8B, the luminous flux control member 300 satisfies the condition 1 even when a part of the legs 330 is located outside the first region for all the legs 330. In the luminous flux control member 300 shown in FIG. 5B, for the two legs 330, the entire leg 330 is located outside the first region, and for the two legs 330, a part of the leg 330 is located. It is located outside the first region and satisfies condition 1. On the other hand, as shown in FIGS. 8C and 8D, when the entire leg 330 is located inside the first region for at least one leg 330, the luminous flux control member 300 does not satisfy the condition 1.

Next, the condition 2 will be described with reference to the drawings. Condition 2 stipulates that the leg 330 is arranged in a region existing around the incident unit 310 on the back side of the luminous flux control member 300 and where the light incident on the incident surface 311 does not substantially reach. This is because if the legs 330 are arranged in a region where the light incident on the incident surface 311 does not substantially reach, the influence on the light distribution characteristics of the luminous flux control member 300 is reduced.

As shown in FIG. 6, a part of the light emitted from the light emitting center of the light emitting element 220 and incident on the incident surface 311 is not reflected by the reflecting surface 312 but is reflected on the first emitted surface 321 of the emitting unit 320. Head directly. Further, the other part of the light emitted from the light emitting center of the light emitting element 220 and incident on the incident surface 311 is reflected by the reflecting surface 312 and directed to the second emitting surface 322 of the emitting unit 320. Further, the other part of the light emitted from the light emitting center of the light emitting element 220 and incident on the incident surface 311 is sequentially reflected by the reflecting surface 312 and the first emitting surface 321 of the emitting unit 320, and is second of the emitting unit 320. It faces the exit surface 322. Light directed from the reflecting surface 312 or the first emitting surface 321 toward the second emitting surface 322 reaches the second emitting surface 322 at a certain distance from the incident surface 311. Therefore, as indicated by reference numeral A in FIG. 6, the light incident on the incident surface 311 does not substantially reach the back side of the light flux control member 300, more specifically, around the incident surface 311. Area exists. Here, it is assumed that all the light emitted from the light emitting center of the light emitting element 220 passes through the incident surface 311 and all the light reaching the reflecting surface 312 is totally reflected by the reflecting surface 312. Further, it is assumed that the light arriving from the distant incident unit 310 through the emitting unit 320 is not considered. In the present embodiment, as shown in FIG. 9, the entire leg 330 may be arranged in a second region, that is, a region with hatching, on the back surface of the luminous flux control member 300. ..

For example, as shown in FIGS. 10A to 10C, the luminous flux control member 300 satisfies the condition 2 when the entire leg 330 is located inside the second region for all the legs 330. In the example shown in FIG. 10C, the condition 1 may not be satisfied, but the condition 2 is satisfied. On the other hand, as shown in FIG. 10D, for at least one leg 330, when at least a part of the leg 330 is located outside the second region, the luminous flux control member 300 does not satisfy the condition 2.

FIG. 11A is a bottom view of the luminous flux control member 300 according to the embodiment satisfying the above condition 1 (same as FIG. 5B). FIG. 11B is a bottom view of the luminous flux control member 300 according to a modified example of the embodiment satisfying the above conditions 1 and 2. FIG. 12A is a bottom view of the luminous flux control member 300 according to a modified example of the embodiment satisfying the above condition 2. FIG. 12B is a bottom view of a light flux control member for comparison that does not satisfy any of the above conditions 1 and 2. The luminous flux control members shown in these figures have the same configuration except for the thickness and position of the legs 330.

Although the plurality of legs 330 are arranged so as to project from the back surface of the luminous flux control member 300,
A recess 331 (groove) may be formed on the back surface around each leg 330 so as to surround the leg 330. That is, the luminous flux control member 300 may have a recess 331 that surrounds the base end portion of the leg 330. FIG. 13A is a bottom view of the luminous flux control member 300 according to a modified example of the embodiment having such a recess 331. FIG. 13B is a partially enlarged cross-sectional view of the periphery of the leg 330. By providing the recess 331 so as to surround the leg 330 in this way, when the leg 330 of the light flux control member 300 is fixed to the substrate 210 by using an adhesive, the adhesive to the light distribution characteristics of the light flux control member 300 can be obtained. The impact can be reduced. It should be noted that this effect can also be obtained when the plurality of legs 330 do not satisfy the above conditions 1 and 2.

The shape of the recess 331 is not particularly limited, but is preferably set according to the luminance distribution of the light emitting device 200. For example, the cross-sectional shape of the recess 331 along the thickness direction of the luminous flux control member 300 is a triangle or a rectangle. The position of the recess 331 is also not particularly limited as long as it surrounds the base end portion of the leg 330, but is preferably close to the base end portion of the leg 330. Further, it is preferable that the side surface of the leg 330 and the inner surface of the recess 331 are continuous. For example, the plurality of legs 330 are fixed to the substrate 210 by pouring an adhesive into the recess 331 having a shape set according to the brightness distribution of the light emitting device 200.

The outer edge of the front side of the luminous flux control member 300 may be chamfered such as R chamfered or C chamfered (inclined surface). By chamfering the outer edge of the front side of the luminous flux control member 300, it becomes possible to irradiate more light to the region located between the light emitting devices 200 in the light diffusing plate 120, and the region between the light emitting devices 200 becomes dark. You can prevent that.

(Simulation of illuminance distribution)
Here, in order to show the influence of the position of the leg 330 on the light distribution characteristic of the light flux control member 300, the simulation result of the illuminance distribution of the surface light source device 100 having the light flux control member 300 is shown. Here, the illuminance distribution on the light diffusing plate 120 when only the four light emitting elements 220 included in one light emitting device 200 are turned on in the surface light source device 100 is shown.

FIG. 14A shows the illuminance distribution when the luminous flux control member having no leg 330 is used for comparison. This luminous flux control member has the same configuration as the luminous flux control member 300 shown in FIGS. 4 and 5A to 5C, except that the leg 330 is not provided. In FIG. 14A, the lower graph shows the lateral illuminance distribution between the upper two light emitting elements 220 and the lower two light emitting elements 220, and the right graph shows the right two light emitting elements. The illuminance distribution in the vertical direction passing through the emission center of 220 is shown (the same applies to the subsequent simulation results).

From the result of FIG. 14A, by appropriately configuring the incident unit 310 and the emitting unit 320 like the luminous flux control member 300 according to the present embodiment, the light emitted from each light emitting element 220 is appropriately expanded and determined. It can be seen that the area of is illuminated almost uniformly.

FIG. 14B shows an illuminance distribution when a light flux control member in which a plurality of legs 330 are arranged at positions that do not satisfy any of the above conditions 1 and 2 shown in FIG. 12B is used. This luminous flux control member has the same configuration as the luminous flux control member 300 shown in FIGS. 4 and 5A to 5C, except that the thickness and position of the plurality of legs 330 are different.

From the result of FIG. 14B, if the plurality of legs 330 are arranged at positions that do not satisfy any of the above conditions 1 and 2, the original light distribution characteristics of the light flux control member cannot be exhibited, and the center of the light flux control member cannot be exhibited. It can be seen that a dark part is generated directly above.

FIG. 15A shows the illuminance distribution when the luminous flux control member 300 according to the present embodiment in which the plurality of legs 330 are arranged at the positions satisfying the above condition 1 shown in FIG. 11A (FIG. 5B) is used. FIG. 15B shows the illuminance distribution when the luminous flux control member 300 according to the modified example of the present embodiment in which the plurality of legs 330 are arranged at the positions satisfying the above conditions 1 and 2 shown in FIG. 11B is used. .. FIG. 16 shows the illuminance distribution when the luminous flux control member 300 according to the modification of the present embodiment in which the plurality of legs 330 are arranged at the positions satisfying the above condition 2 shown in FIG. 12A is used. These luminous flux control members have the same configuration as the luminous flux control member 300 shown in FIGS. 4 and 5A to 5C, except that the thickness and position of the plurality of legs 330 are different.

From the results of FIGS. 15A to 16, it can be seen that when the plurality of legs 330 are arranged at positions satisfying the above condition 1 or condition 2, the original light distribution characteristics of the luminous flux control member can be maintained even if the plurality of legs 330 are provided.

From these results, it can be seen that the luminous flux control member 300 according to the present embodiment spreads the light emitted from each light emitting element 220 and illuminates the region corresponding to each light emitting element 220 substantially uniformly.

(effect)
According to the light flux control member 300 of the present embodiment, even when the distance between the substrate 210 and the light diffusing plate 120 is narrow, it is appropriate while suppressing excessive spread of the light from the plurality of light emitting elements 220. It can be expanded within the range. Therefore, the present invention is effective for local dimming. Further, according to the present invention, since the light from the plurality of light emitting elements 220 can be controlled by one luminous flux control member 300, the light flux control member 300 can be easily mounted.

(Modification example)
Although the luminous flux control member 300 having the four incident units 310 arranged on the four light emitting elements 220 has been described above, the luminous flux control member according to the present invention is not limited to this. The luminous flux control member according to the present invention is not particularly limited as long as it is used for a plurality of light emitting elements 220.

17A and 17B are a plan view and a bottom view of a light flux control member 400 having six incident units 310 arranged on the six light emitting elements 220. Like the luminous flux control member 300, the luminous flux control member 400 has an number of incident units 310 corresponding to the number of light emitting elements 220, an emission unit 320, and a plurality of legs 330, respectively. The plurality of legs 330 are arranged at positions satisfying the above condition 1 or condition 2. As shown in FIG. 17C, in the example shown in FIG. 17B, the plurality of legs 330 are arranged at positions satisfying the above condition 1.

The luminous flux control member, the light emitting device, and the surface light source device according to the present invention can be applied to, for example, a backlight of a liquid crystal display device, general lighting, and the like.

100 surface light source device 100'display device 102 display member 110 housing 112 bottom plate 114 top plate 120 light diffuser plate 200 light emitting device 210 board 220 light emitting element 300, 400 light flux control member 310 incident unit 311 incident surface 312 reflective surface 320 emission unit 321 1st emission surface 322 2nd emission surface 330 Leg 331 Recessed area A Area where light does not reach CA Central axis CP n Square center LA Optical axis

Claims (9)

A luminous flux control member for controlling the light distribution of light emitted from n light emitting elements arranged on a substrate.
N incident units for incident light emitted from the n light emitting elements, and n incident units.
An emission unit that is arranged between the n incident units in a direction along the substrate and emits light incidented by the n incident units while guiding the light.
A plurality of legs arranged on the back side of the luminous flux control member and supporting the luminous flux control member with respect to the substrate,
Have,
The n incident units are arranged on the back side of the luminous flux control member, respectively, and have an incident surface on which light emitted from the light emitting element is incident.
A reflective surface arranged on the front side of the luminous flux control member at a position facing the light emitting element with the incident surface interposed therebetween, and reflecting light incident on the incident surface laterally so as to be away from the optical axis of the light emitting element. When,
Have,
The emission unit is
A first emission surface, which is arranged on the front side of the luminous flux control member, reflects a part of the light from the incident unit, and emits the other part.
A second emission surface, which is arranged on the back side of the luminous flux control member so as to face the first emission surface, reflects a part of the light from the incident unit, and emits the other part.
Have,
The plurality of legs are arranged at positions satisfying the following condition 1 or condition 2, respectively.
Luminous flux control member.
[Condition 1]
When the light beam control member is viewed in a plan view, the center of gravity of the polygon formed by connecting the centers of the n incident units is ± (60) from the center of each of the n incident units. At least a part of the leg is arranged outside the first region, which is the region surrounded by the 2n straight lines when the two straight lines are drawn at an angle of / n) °.
[Condition 2]
Of the light emitting surface of the light emitting element, the light emitted from the light emitting center which is the intersection with the central axis of the incident unit, and of the light incident on the incident surface, directly reaches the reflecting surface from the incident surface and reaches the reflecting surface. Light that has been reflected by and not reflected by other surfaces, directly reaches the reflecting surface from the incident surface, is sequentially reflected by the reflecting surface and the first emitting surface, and then is not reflected by other surfaces. Inside a second region, which is a region in which light and light that reaches the first emission surface directly from the entrance surface and is reflected by the first emission surface but not reflected by other surfaces does not substantially reach. All of the legs are arranged in. The luminous flux control member according to claim 1, wherein the luminous flux control member has four incidental units arranged at positions corresponding to each vertex of a rectangle when viewed in a plan view. The luminous flux control member according to claim 1 or 2, wherein the plurality of legs are respectively arranged at positions satisfying the condition 1. The luminous flux control member according to claim 1 or 2, wherein the plurality of legs are respectively arranged at positions satisfying the condition 2. The luminous flux control member according to any one of claims 1 to 4, further comprising a plurality of recesses each arranged so as to surround the base ends of the plurality of legs. N light emitting elements arranged on the substrate and
The luminous flux control member according to any one of claims 1 to 5, which is arranged on the n light emitting elements.
A light emitting device. A plurality of light emitting devices according to claim 6,
A light diffusing plate that diffuses and transmits light emitted from the plurality of light emitting devices,
A surface light source device. The surface light source device according to claim 7 and
A display member that is irradiated with light emitted from the surface light source device, and
Has a display device. The method for improving luminance unevenness of a light emitting device according to claim 6.
The plurality of legs of the luminous flux control member are fixed to the substrate by using an adhesive having an optical absorption rate selected according to the luminance distribution.
How to improve the uneven brightness of the light emitting device.

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