JP6150607B2 - Light emitting device - Google Patents

Description

  The present invention relates to a light-emitting device used in a display device such as a meter panel or a monitor panel mounted on a vehicle or the like, or an illumination device that emits or illuminates light outside or inside a vehicle.

Various vehicles are equipped with a display device for displaying data obtained from instruments such as a speedometer and a fuel gauge and various electronic devices. These display devices are provided with a display unit that displays various characters and graphics by printing, masking, and the like. In order to improve the visibility of such a display unit, particularly at night, the back of the display unit is provided. It is generally performed from the lighting.
In addition, as a decorative member disposed outside and inside a vehicle interior, an illumination device to which a light emitting function such as a ceiling illumination, a door illumination, and an emblem illumination is added is known. A portion disposed in such a display device or an illumination device and having a function of irradiating light is a light-emitting device that is an object of the present invention.

  As a light emitting device used for these display devices and illumination devices, a light guide body made of a light guide material and a light source such as an LED (light emitting diode) disposed in the vicinity of the light guide body are generally used. In order to make the light guide uniformly emit light, it is necessary to dispose a large number of LEDs (light sources) in the vicinity of the light guide. In this case, it is difficult not only to increase the cost due to an increase in the number of parts, but also to secure a light source space. In addition, since it becomes impossible to arrange other components near the light source, it is very difficult to design the board.

  As a configuration for solving the above problems, an illumination device described in Patent Document 1 has been proposed. The apparatus includes a first light guide that emits light in a planar shape with respect to the display panel, a second light guide that emits light to the first light guide, and the second light guide. An outer periphery that includes a light source that emits light to the light body, has a notch formed in the first light guide, and the second light guide closes in a non-contact manner along the inner surface of the notch The main body part which has a surface is disclosed, and this main body part is disclosing the illuminating device currently formed with the curve which has a predetermined curvature radius in the horizontal cross section with respect to the light emission surface of a 1st light guide.

JP 2011-238390 A

  Patent Document 1 shows a configuration that solves the above-described problem, but two light guides, a light guide for using a point light source as a line light source and a light guide using a line light source as a surface light source, are necessary. As a result, there remain problems such as an increase in the number of mounting steps accompanying the increase in cost and components, and the occurrence of assembly variations.

  In addition, a light-emitting device in which a light source is disposed directly under a light guide is known. In this case, a large number of light sources are necessary for uniform light emission. For example, the light-emitting device is applied to a speedometer for a vehicle. In such a light emitting device, it is difficult to achieve uniform light emission unless ten or more LEDs are arranged directly under the light guide. In such a configuration, the number of parts increases, the manufacturing cost increases, and other parts cannot be installed near the light source. Therefore, there are significant restrictions in designing the base.

  An object of the present invention is to provide a light-emitting device capable of uniform light emission even when the number of light source lamps is greatly reduced, and which can save space and cost without being restricted by the base design. That is.

  Here, the display device to which the light-emitting device of the present invention is applied may be any component that displays numerical values, images, and the like of various instruments and electronic devices provided for the vehicle. For example, a speedometer, a tachometer, Examples include various meters such as odometers, fuel gauges, water temperature gauges, shift lever panels, car navigation monitors, and panels that display the status of audio equipment. Moreover, as an illuminating device, the illumination components which light-emit and illuminate inside and outside the vehicle interior, such as an emblem illumination, a door illumination, a scuff illumination, a ceiling illumination, etc., are mentioned, for example.

The light-emitting device of the present invention includes a light guide and a light source that emits light toward the light guide, and the light guide has a substantially disk shape including a light-emitting surface that is a main surface and an outer peripheral surface. A main body having an outer shape, and a light incident portion that makes light incident on the main body toward a direction orthogonal to the light emitting surface, and the light incident portion extends from an incident surface that faces the light source. And a branch portion branched into two or more from the trunk portion and smoothly connected to the main body portion, and a cavity recessed from the light emitting surface toward the incident surface is formed between the branch portions. ing.
According to this configuration, the light incident on the incident surface of the light incident portion is guided in a plurality of directions by the branch portion, and the light that crosses the light emitting surface of the light guide and exits to the outside. Since the light is incident on the main body of the light guide so that it can be significantly reduced, the light can be guided substantially uniformly into the light guide even when the number of light sources is small, that is, the light emitting device can emit light uniformly. Is possible.

In the present invention, the light incident portion is formed in the vicinity of the outer peripheral surface of the light guide, and has two branch portions branched in opposite directions from the trunk portion. You may connect to the said main-body part in the direction which substantially follows the outer peripheral surface of the main-body part of a light body.
According to this configuration, the light incident portion is formed in the vicinity of the outer peripheral surface of the light guide, and the light incident portion branches to emit light in a direction along the outer peripheral surface, that is, a tangential direction of the outer peripheral surface of the light guide. Since it is designed to be incident, the incident light can be efficiently used while suppressing radiation to the outside. As a result, the number of light sources can be further reduced.

In the present invention, preferably, a main body portion of the light guide body is formed with a through hole adjacent to the light incident portion on the radially inner side of the light incident portion. The through hole preferably has substantially the same length as the light incident portion.
According to this configuration, since the through hole adjacent to the light entering part is formed in the main body part of the light guide, the light diffused in the main body part of the light guide is reflected by the through hole and emits light. Therefore, it is possible to improve the light use efficiency and reduce light unevenness due to darkening in the light incident portion. Furthermore, since a part of the incident light can be reflected by the inner surface on the radially outer side of the through hole, the light can be efficiently directed to the outer peripheral surface, so that the light use efficiency can be improved.

In the present invention, the trunk portion protrudes in the axial direction from the back surface of the main body portion, the incident surface is formed on the projecting end surface of the trunk portion, and the light source is disposed so as to face the incident surface, It is preferable to emit light toward the incident surface. Moreover, it is preferable that the incident surface of the said light entrance part is set substantially parallel to the said light emission surface.
According to this configuration, the light incident portion is formed on the light guide so as to protrude downward from the back surface side, and in particular, the incident surface is set substantially parallel to the light emitting surface, so that the light source is directly below the light guide. Therefore, as compared with the case where the light guide is disposed so as to face the outer peripheral surface, the base design is facilitated and the space is saved.

In the present invention, a plurality of reflection grooves arranged at intervals in the circumferential direction may be formed on the outer peripheral surface of the light guide. The reflection groove may have a U-shaped cross section and be formed so as to reach the back surface from the front surface, which is the light emitting surface of the light guide.
According to this configuration, by forming a plurality of reflection grooves, which are concave and convex shapes that refract and reflect light, at predetermined intervals in the circumferential direction on the outer peripheral surface of the light guide, from the light incident part to the main part of the light guide The incident light is guided around the outer peripheral surface of the disc-shaped light guide while being refracted and reflected by a reflection groove formed on the outer peripheral surface. As a result, the light incident on the light guide can make one round while reflecting off the outer surface of the disk-shaped light guide while suppressing the light emitted to the outside as much as possible. It becomes possible to uniformly emit light from the light guide. Furthermore, by forming a reflection groove having a U-shaped cross section on the outer peripheral surface of the light guide so as to reach the back surface from the light emitting surface of the light guide, the efficiency of use of light incident on the light guide Is further enhanced.

  In the present invention, the light incident on the incident surface of the light incident portion is guided in multiple directions by the branch portion, and the light that crosses the light emitting surface of the light guide and exits to the outside is greatly reduced. Since the light is incident on the main body of the light guide so as to be able to guide light evenly in the light guide even when the number of light sources is small, that is, the light emitting device can emit light uniformly. Become. When a through-hole adjacent to the light incident part is formed on the main body of the light guide in the radial direction, the light diffused in the main body of the light guide is reflected by the through-hole to emit light. Therefore, it is possible to improve the light use efficiency and reduce light unevenness due to darkening in the light incident portion.

It is a perspective view which shows the light-emitting device which concerns on one Embodiment of this invention. It is the top view which looked at the light-emitting device from the upper part. It is a top view which expands and shows the light-incidence part vicinity of a light guide in FIG. It is a side view which shows the light-incidence part vicinity of a light guide in the light-emitting device. It is the top view which looked at other embodiment which the light-incidence part of the light-emitting device of this invention protruded to the side from the upper direction. It is a front view of the embodiment. It is a side view of the embodiment. It is the top view which looked at other embodiment which made the light-incidence part of the light-emitting device of this invention into the shape of a quadrilateral from upper direction. It is a front view of the embodiment. It is a side view of the embodiment. It is a front view which shows another embodiment which branched the incident surface of the light-emitting device by this invention. It is the perspective view which showed the frame member of the light-emitting device by this invention. It is a characteristic view which shows the luminance distribution in the light emission surface of the light-emitting device of Example 1 by this invention. It is the top view which looked at the light-incidence part vicinity of the light-emitting device of Example 2 by this invention from the upper direction. It is the top view which looked at the light-incidence part vicinity of the light-emitting device of Examples 3-10 by this invention from upper direction. It is the top view which looked at the light-incidence part vicinity of the light-emitting device of a comparative example from upper direction. It is a side view which shows the light-incidence part vicinity of the light-emitting device of the comparative example. It is a front view which shows the simulation result of the optical path in Example 1 by this invention. It is a top view which shows the simulation result of the optical path in Example 1 by this invention. It is a front view which shows the simulation result of the optical path in Example 2 by this invention. It is a top view which shows the simulation result of the optical path in Example 2 by this invention. It is a front view which shows the simulation result of the optical path in a comparative example. It is a top view which shows the simulation result of the optical path in the comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the light emitting device 1 according to the first embodiment of the present invention, and FIG. 2 is a front view of the light emitting device 2 viewed from the light emitting surface 14 side.
A light emitting device 1 shown in FIG. 1 includes a light guide 10 and a light source 2, and one LED 2 is disposed as the light source 2. The light guide 10 is a disk-shaped molded body having a constant thickness, and a hollow portion 11 is provided at the center thereof. A reflection groove 16 for reflecting and refracting light in the direction of the cavity 11 is formed on the outer peripheral surface 13 of the light guide 10, and the surface of the light guide 10 is a light emitting surface 14. The back surface 15 of the light guide 10 is provided with a dot pattern for reflecting and refracting light toward the light emitting surface 14. Further, the light incident portion 12 is formed so as to protrude toward the back surface 15 side of the light guide 10 so as to be connected to the outer peripheral surface 13 of the light guide 10, and the LED 2 faces the light incident portion 12. Is arranged. As shown in FIG. 2, a through-hole 17 made of an arcuate or linear slit extending in the elongate circumferential direction is formed near the radially inner side of the light incident portion 12.

  The light emitting device 1 according to the present embodiment illuminates a display plate such as a panel for displaying each value in various display devices such as a speedometer, a tachometer, an odometer, a fuel meter, and a water temperature meter, Used to add an illumination effect. In this type of display device, the display plate and the light emitting device 1 are accommodated in an accommodation case having an accommodation recess. Further, a base is disposed between the light emitting device 1 and the housing case, and the LED 2 is mounted on the base.

(light source)
FIG. 3 is an enlarged front view showing the vicinity of the light incident portion 12 in FIG. FIG. 4 is a side view of the light-emitting device 1 as viewed from the vicinity of the light incident portion 12 from the side facing the outer peripheral surface 13. The LED 2 shown in FIG. 4 is disposed so that the light incident surface 12a of the light incident portion 12 of the light guide 10 and the light outgoing surface 2a of the LED 2 are parallel and have a clearance of about 0.7 mm. As the LED 2, NS2W123B, which is a white LED manufactured by Nichia Chemical, is used, but is not limited thereto, and may be an LED of another color such as blue or purple, or a full-color LED.

(Light guide)
The light guide 10 is formed by injection molding a transparent PMMA resin.
The light guide 10 is a substantially plate-shaped molded body having a thickness of 0.5 to 10.0 mm, more preferably 1.0 to 3.0 mm, and the planar shape thereof has an outer diameter of 50 to 200 mm. A hollow portion 11 having an inner diameter of 20 to 60 mm is formed in the center portion. In the present embodiment, since the light emitting device 1 is used as a display device such as a speedometer for a vehicle, the light emitting device 1 is formed in such a shape. It is not limited, and if it is a plate-shaped molded body having a predetermined thickness, the central cavity portion 11 may not be provided, and the outer shape is not circular, but is substantially circular, substantially elliptical, substantially fan-shaped, The shape may be any of a substantially polygonal shape, and a part of these shapes may be deformed according to the shape of the display unit.

  In the light guide 10, only one light incident portion 12 is formed so as to protrude downward from the back surface 15 side. The light incident part 12 is formed with an incident surface 12a substantially parallel to the back surface 15, and the LED 2 is disposed so as to face the incident surface 12a. The light emitted from the LED 2 is guided into the light guide 10 by irradiating the incident surface 12 a of the light incident portion 12.

  In the present embodiment, the light incident part 12 has only one place, but is not limited to this. The light incident part 12 is not limited to this. You may arrange more than a part. As described above, when the number of light entering portions is increased, the number of LEDs 2 is increased accordingly, which is disadvantageous in terms of cost and space saving. Further, the light entering portion 12 is incident on the main body portion 10a of the light guide 10. However, the light utilization efficiency is lowered, but the luminance of the light emitted from the entire light emitting surface 14 of the light guide 10 can be increased. Further, in the present embodiment, the light incident portion 12 is formed so as to protrude downward from the back surface 15 side of the light guide body 10, but not limited to this, from the light emitting surface 14 of the light guide body 10 upward. It may be formed so as to project, or may be formed so as to project sideways from the outer peripheral surface 13 of the light guide 10 as shown in FIGS.

  The light guide 10 may be formed by injection molding after kneading a scattering resin such as silicone resin particles at a ratio of 0.1% by weight, for example, using a transparent PMMA resin as a base material. In this case, the scattering resin is preferable because the light scattering property is increased and the light utilization efficiency is improved.

(Light receiving part)
As shown in FIG. 4, the light incident portion 12 has a trunk portion 22 that extends from a single incident surface 12 a toward the back surface 15 of the light guide 10, and is bifurcated from the trunk portion 22. Two branch portions 12b and 12c that are bent are formed. By these branch portions 12b and 12c, the light incident from the incident surface 12a travels in two directions. Each branch part 12b, 12c is designed so that it may become the same thickness as the plate | board thickness of the main-body part 10a of the light guide 10. FIG. The body 10a of the light guide 10 is smoothly connected to the body 10a while changing its direction from the vertical direction to the horizontal direction by approximately 90 ° while being curved. At this time, it is preferable that the curvature of the upper curved portion 12f of each branch portion 12b, 12c is 3 to 5, and the curvature of the lower curved portion 12e is 2 to 3. In addition, the first branch portion 12b and the second branch portion 12c are connected in directions opposite to each other and in the tangential direction of the main body portion 10a along the outer peripheral surface 13.

  The light incident part 12 is formed in a Y shape when viewed from the side as shown in FIG. 4, and a gap 12g is formed between the first branch part 12b and the second branch part 12c. Yes. By providing the gap 12g, the light can be reflected and refracted by the upper curved surface 12f, that is, the light can be guided in the light incident portion 12 while changing its direction. The radially inner end of the gap 12g is continuous with the through hole 17. In this way, the light incident portion 12 is bifurcated from the trunk portion 22 and is directed to the tangential direction of the outer peripheral surface 13 to be connected to the main body portion 10a of the light guide 10, so that light travels. The direction is not limited to one direction as in the clockwise direction or the counterclockwise direction as in the past, and the light is in both directions, so there is no need to complicate the optical design of the outer peripheral surface, and the disk can be efficiently The entire light guide 10 can be made to emit light.

  Further, as shown in FIG. 3, the light incident part 12 is formed so as to be continuous with a part of the outer peripheral surface 13 of the light guide 10, and the light is transmitted in the outer peripheral tangential direction of the disc-shaped light guide 10. Since the incident light is reflected and refracted by the outer peripheral surface 13, it becomes possible to guide the disc-shaped light guide 10 along the outer peripheral surface 13 one or more times. . Accordingly, light can be guided to the entire disc-shaped light guide 10 and emitted from the entire light emitting surface 14, and the entire disc-shaped light guide 10 can be formed by using only one LED 2 as the light source 2. Can be emitted with sufficient brightness as a function of the light-emitting device 1. From the simulation results to be described later, the light incident portion 12 is preferably formed in the vicinity of the outer peripheral surface 13 of the light guide 10, specifically, the outer periphery from the outer peripheral surface 13 (outer surface 12 d) of the light incident portion 12. The distance to the surface 13 is preferably in the range of 0 to 2.5 mm, more preferably in the range of 0 to 0.1 mm, 0 mm, that is, the outer surface 12 d and the outer surface 13 of the light incident portion 12. It has been found that it is more preferable that the film is formed to be flush with each other. When it exceeded 2.5 mm, it confirmed that the utilization efficiency of light fell.

  In the present embodiment, the light incident portion 12 is formed in a bifurcated shape so as to extend in two directions, ie, branch portions 12b and 12c. However, the present invention is not limited to this, and three branch portions are branched by three or more branches. You may form above. 8 to 10 show an embodiment in which the light incident part 12 is formed in a quadrangular shape so as to extend in four directions.

  Moreover, although the incident surface 12a was only one, it is good also as a structure which branches the incident surface side and arrange | positions two or more incident surfaces and LED2 of the number corresponding to it. FIG. 11 is an embodiment in which, in FIG. 4, the incident surface 12a is also branched into two corresponding to the two branch portions 12b and 12c that are branched, and the LEDs 2 are arranged facing the respective incident surfaces 12a. In this case, the luminance can be increased by increasing the number of the LEDs 2, but the light use efficiency is reduced because light does not escape from other light incident portions as compared with the case where a plurality of light incident portions are provided. This is preferable. Further, in this case, it is possible to produce an illumination effect by a plurality of colors or to add an indicator function by color change light emission by arranging the LEDs 2 having different colors.

(Prism shape of outer peripheral surface: cylinder shape)
It is preferable that a plurality of reflection grooves 16 that are concave and convex shapes that refract and reflect light are formed on the outer peripheral surface 13 of the light guide 10 at predetermined intervals in the circumferential direction. Since the connection direction from the light incident part 12 to the main body part 10a is designed so that the light L1 incident on the main body part 10a is directed in the tangential direction of the outer peripheral surface 13, the incident light L1 is The light is guided around the outer peripheral surface 13 of the disc-shaped light guide 10 while being refracted and reflected by the reflection grooves 16 formed on the outer peripheral surface 13. For this reason, the light use efficiency is improved, and even with a single light source, it is possible to realize uniform light emission with high luminance of the disc-shaped light guide 10.

  The reflection grooves 16 are formed on the outer peripheral surface 13 of the light guide 10 at equal intervals, and are formed to have the same groove shape and depth, and gradually increase the groove depth as the distance from the light source increases. Even so, the light guide 10 can emit light uniformly with a required luminance. This facilitates mold fabrication and reduces costs. This is designed so that the light incident portion 12 is formed close to the outer peripheral surface 13 and directed toward the tangential direction of the outer peripheral surface 13 when light enters the main body portion 10 a of the light guide 10. This is because the use efficiency of light is enhanced, and sufficient luminance and uniform light emission necessary for the light guide 10 can be obtained without changing the groove interval and groove depth of the reflection grooves 16. Here, it is of course possible to further increase the brightness and the uniform luminous intensity of the light guide 10 by gradually increasing the groove depth of the reflection groove 16 or gradually decreasing the groove interval. In this embodiment, the reflection groove 16 has a U shape that extends parallel to the axial direction of the light guide 10 and opens toward the outside in the radial direction.

(Back side prism processing: wrinkled dot shape)
In order to promote the emission of light from the light emitting surface 14 in FIG. 1, the dot pattern on the back surface 15 of the light guide 10 is applied by, for example, forming a minute dot group by laser processing. The diameter of each dot included in the dot group may be, for example, about 0.01 to 0.1 mm, preferably about 0.02 to 0.09 mm. Further, the dot density contained in the dot group is preferably about 0 to 30 pieces / mm ^2. In addition, these dot densities may or may not be formed uniformly. From the viewpoint of making the light emission from the light emitting surface 14 uniform, the processing density of the dot group is the light guide. The density may decrease continuously or stepwise from the outer peripheral surface 13 of the body 10 toward the cavity 11.

(Through hole)
As shown in FIG. 3, in the main body 10 a of the light guide 10, a through-hole 17 is formed at a position adjacent to the light incident portion 12 on the radially inner side. By providing a space between the light incident part 12 and the light emitting surface 14, a part of the incident light L1 can be reflected by the inner surface 17a on the radially outer side of the through-hole, so that the light can be efficiently reflected on the outer peripheral surface 13. Therefore, the light utilization efficiency can be increased. In order to sufficiently reflect the light incident from the light incident portion 12, it is preferable that the circumferential length of the through hole 17 is substantially the same as the circumferential length of the light incident portion 12. The light irradiated to the concave-convex shape (reflection groove 16) formed on the outer peripheral surface 13 is refracted and reflected, and transmits light over the entire circumference of the light guide 10, whereby the light emitting surface 14 of the light guide 10. It becomes possible to emit light substantially uniformly from the whole.
Further, the light L2 guided around the main body 10a of the light guide 10 and reflected around the inner surface 17b on the radially inner side of the through hole 17 is emitted from the light incident part 12 to the outside. Can be reduced. Thereby, generation | occurrence | production of the light nonuniformity which arises in the light-incident part 12 vicinity can be reduced.

  The width of the through-hole 17 is 0.2 to 3.0 mm, preferably 0.3 to 1.0 mm, depending on the moldability of the light guide 10 and the light emitting surface 14 of the light guide 10. It is preferable from the viewpoint of suppressing the occurrence of light unevenness. In addition, by forming the through hole 17 connected to the gap 12g, the gap 12g can be formed by injection molding in the entire region of the upper curved surface 12f of the branch portions 12b and 12c of the light incident portion 12, thereby increasing the light use efficiency. be able to.

(Frame member)
As shown in FIG. 12, in the light emitting device 1 according to the present invention, the LED 2 and the light guide 10 that are light sources are preferably accommodated in a frame member 30 in which an accommodation space is formed.
The frame member 30 is a case opened on one side so as to expose the light guide body 10 of the light emitting device 1, and has a disk-shaped bottom wall portion 31, and outer and inner peripheral standing wall portions 32, An accommodation recess 33 having substantially the same shape as the outer shape of the body 10 is formed. The light guide 10 is fixedly held by being fitted into the housing recess 33, and the positional relationship with the light source 2 is fixed. The frame member 30 is formed, for example, by injection molding a white resin of polycarbonate (PC). Furthermore, the light emitted from the back surface 15 and the outer peripheral surface 13 of the light guide 10 is reflected by the bottom wall portion 31 and the standing wall portion 32 of the housing recess 33 of the frame member and is incident on the light guide 10 again. It becomes possible. In other words, since light that is originally diffused to the outside and cannot be used can be reused, the utilization efficiency of light emitted from the light source can be increased.

Example 1
In the first embodiment, the light guide 10 of the light emitting device 1 shown in FIG. 2 is formed so that the outer diameter is 110 mm and the inner diameter of the hollow portion 11 in the central portion is 40 mm.
The general thickness t of the main body 10a of the light guide 10 is 1.5 mm, and the outer peripheral surface 13 is between 6 ° and 354 ° counterclockwise from the center of the light incident portion 12 shown in FIG. In other words, the reflection grooves 16 having a radius of curvature of 0.75 mm in steps of 3 ° are equally spaced in the circumferential direction in the outer peripheral region of the light guide 10 excluding the outer peripheral portion of the incident surface 12a and the branch portion 12b of the light incident portion 12. It is given in. The reflection groove 16 has a U-shape such that the groove depth is d = 0.5 mm and the cross-sectional shape is a semicircular shape having a curvature radius R = 0.75 mm. The outer peripheral surface 13 is vertically cut from the light emitting surface 14 to the back surface 15 of the ten main body portions 10a.

  The light incident surface 12a of the light incident portion 12 in FIG. 4 has a substantially square shape with a side W of about 3.4 mm, the curvature radius R1 of the lower curved surface 12e of the branch portions 12b and 12c is 2.5 mm, and the upper curved surface. The curvature radius R2 of 12f is formed to be 4.0 mm. The outer surface 12 d of the light incident portion 12 is continuously formed so as to be flush with the outer peripheral surface 13 of the light guide 10. Further, a through hole 17 is formed adjacent to the light incident part 12 on the side opposite to the outer surface 12 d of the light incident part 12. The width of the through hole 17 was 0.5 mm.

  The LED 2 is disposed so that the light incident surface 12a of the light incident portion 12 of the light guide 10 and the light outgoing surface 2a of the LED 2 are parallel and have a clearance of about 0.7 mm. As LED2, NS2W123B, which is a white LED manufactured by Nichia Chemical, was used.

FIG. 13 shows the luminance distribution measured with a two-dimensional color luminance meter (CA2000 manufactured by Konica Minolta) from the distance of 350 mm perpendicular to the light emitting surface 14 of the light emitting device 1 using the light emitting device 1 of Example 1. Is shown.
As a result, it can be confirmed that, as a light source, although only one LED 2 is used, the degree of uniformity is high and surface light emission with suppressed light unevenness can be realized. Although there is a region with low luminance near the light incident part 12, it is possible to reflect a part of the light that has passed through the light incident part 12 by the through hole 15 formed so as to be adjacent to the light incident part 12. Therefore, a decrease in luminance can be suppressed. In addition, since the light incident portion 12 is formed in the vicinity of the outer peripheral surface 13 of the light guide body 10, it is possible to easily shield the portion where the luminance is reduced by the frame member.

(Example 2)
The configuration of Example 2 of the present invention is shown in the front view of FIG. 14 in which the vicinity of the light incident portion 12 is viewed from the light emitting surface 14 side.
In the second embodiment, the through hole 17 provided next to the light incident portion 12 in the first embodiment is not provided. Since it is the same structure as Example 1 except not having the through-hole 17, description is abbreviate | omitted.

(Example 3)
The configuration of Example 3 of the present invention is shown in the front view of FIG. 15 in which the vicinity of the light incident portion 12 is viewed from the light emitting surface 14 side.
In Example 3, the outer surface 12 d of the light incident part 12 is formed away from the outer peripheral surface 13 of the light guide 10. The distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is formed to be 0.1 mm. Since the light incident portion 12 has the same configuration as that of the first embodiment except that the light incident portion 12 is formed apart from the outer peripheral surface 13 of the light guide 10, the description thereof is omitted.

Example 4
The configuration of the fourth embodiment of the present invention is such that the distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is 0.25 mm in the third embodiment of FIG. Since it is the same structure as Example 3 except having changed the distance L from the outer surface 12d of the light-incident part 12 to the outer peripheral surface 13, description is abbreviate | omitted.

(Example 5)
The configuration of the fifth embodiment of the present invention is such that the distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is 0.5 mm in the third embodiment of FIG. Since it is the same structure as Example 3 except having changed the distance L from the outer surface 12d of the light-incident part 12 to the outer peripheral surface 13, description is abbreviate | omitted.

(Example 6)
The configuration of the sixth embodiment of the present invention is such that the distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is 0.75 mm in the third embodiment of FIG. Since it is the same structure as Example 3 except having changed the distance L from the outer surface 12d of the light-incident part 12 to the outer peripheral surface 13, description is abbreviate | omitted.

(Example 7)
The configuration of the seventh embodiment of the present invention is such that the distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is 1 mm in the third embodiment of FIG. Since it is the same structure as Example 3 except having changed the distance L from the outer surface 12d of the light-incident part 12 to the outer peripheral surface 13, description is abbreviate | omitted.

(Example 8)
The configuration of the eighth embodiment of the present invention is such that the distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is 1.25 mm in the third embodiment of FIG. Since it is the same structure as Example 3 except having changed the distance L from the outer surface 12d of the light-incident part 12 to the outer peripheral surface 13, description is abbreviate | omitted.

Example 9
The configuration of the ninth embodiment of the present invention is such that the distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is 1.5 mm in the third embodiment of FIG. Since it is the same structure as Example 3 except having changed the distance L from the outer surface 12d of the light-incident part 12 to the outer peripheral surface 13, description is abbreviate | omitted.

(Example 10)
The configuration of the tenth embodiment of the present invention is such that the distance L from the outer surface 12d of the light incident portion 12 to the outer peripheral surface 13 is 2.5 mm in the third embodiment of FIG. Since it is the same structure as Example 3 except having changed the distance L from the outer surface 12d of the light-incident part 12 to the outer peripheral surface 13, description is abbreviate | omitted.

(Comparative example)
The structure of the comparative example of the light-emitting device 1 is shown in the front view which looked at the light-incident part 12 vicinity of FIG. 16 from the light emission surface 14 side, and the side view seen from the outer peripheral surface 13 of FIG.
In the comparative example, the through hole 17 and the gap 12g are not formed as compared with the first embodiment. Further, since the gap 12g is not formed in the light incident part 12 ′, it is not divided into two parts like the two branch portions 12b and 12c, and the upper curved surface exists only by the lower curved surface 12e ′. do not do. Since the configuration other than the light entrance 12 'is the same as that of the first embodiment, the description thereof is omitted.

For the configurations of Examples 1 to 10 and Comparative Example, using Lighttools made by Cybernet as calculation software, the light guide material is transparent PMMA, the LED is a white LED made by Nichia, NS2W123B, Table 1 and FIGS. 18 to 23 show the results of optical simulation under the condition that the clearance between the light incident surface of the light incident portion and the light exit surface of the LED is 0.7 mm.
The following results are the light utilization efficiency when the ratio of the light emitted from the light emitting surface 14 of the light guide 10 out of the light emitted from the LED 2 in FIG. It is a representation.

  18 and 19 show an optical path in the first embodiment. The light incident from the incident surface 12a of FIG. 18 is repeatedly reflected and refracted by the branch portions 12b and 12c, and is reflected by the radially inner surface 17a of the through hole 17 of FIG. 14 is emitted. 20 and 21 show an optical path in Example 2 that does not have the through hole 17. The light incident from the incident surface 12a of FIG. 20 is repeatedly reflected and refracted by the branch portions 12b and 12c, and is emitted from the light emitting surface 14 of the light guide 10.

22 and 23 show the simulation results of the comparative example. In the comparative example, since there is no gap in the light incident portion 12 ′ in FIG. 22, the light cannot be branched, and the light incident from the incident surface 12 a ′ is not reflected or refracted, and the light emitting surface of the light guide 10. Since all the light passes through 14 to the outside, the light cannot be guided into the light guide 10.
Comparing Examples 1 to 10, it can be seen from Table 1 that the light utilization efficiency increases as the distance L from the outer surface 12d to the outer peripheral surface 13 of the light incident portion 12 decreases. Comparing Example 1 and Example 2, it can be seen that the use efficiency of light is enhanced by forming the through hole 17 adjacent to the light incident part 12.

DESCRIPTION OF SYMBOLS 1 ... Light-emitting device 2 ... LED (light source)
DESCRIPTION OF SYMBOLS 10 ... Light guide 10a ... Main-body part 11 ... Cavity part 12 ... Incident part 12a ... Incident surface 12b, 12c ... Branch part 12d ... Outer surface 12e ... Lower curved surface 12f ... Upper curved surface 12g ... Gap 13 ... Outer peripheral surface DESCRIPTION OF SYMBOLS 14 ... Light-emitting surface 15 ... Back surface 16 ... Reflection groove | channel 17 ... Through-hole 17a ... Inner surface 17b on the radial direction outer side of a through-hole ... Inner surface 22 on the radial inner side of a through-hole ... Standing wall portion 33 ... accommodating recesses L1, L2 ... light

Claims (7)

A light guide, and a light source that emits light toward the light guide,
The light guide is a main body having a substantially disk-shaped outer shape including a light emitting surface consisting of a main surface and an outer peripheral surface;
A light incident part that enters light into the main body part in a direction orthogonal to the light emitting surface;
The light incident portion includes a trunk portion extending from an incident surface facing the light source, and branch portions branched into two or more from the trunk portion and smoothly connected to the main body portion. A gap that is recessed from the light emitting surface toward the incident surface is formed therebetween ,
A through-hole having a circular arc shape extending in the circumferential direction is formed in the main body portion of the light guide body, radially inward of the light incident portion and adjacent to the light incident portion.
A light emitting device having a main body portion of the light guide body having a circular shape, a substantially circular shape, or a substantially oval shape, and a hollow portion formed in a central portion .   The light incident portion is formed in the vicinity of the outer peripheral surface of the light guide and has two branch portions branched in opposite directions from the trunk portion, each branch portion being a main body of the light guide The light emitting device according to claim 1, wherein the light emitting device is connected to the main body portion in a direction substantially along the outer peripheral surface of the portion.   The light emitting device according to claim 1, wherein the through hole has substantially the same length as the light incident portion. The trunk portion projects from the back surface of the main body portion in the axial direction of the main body portion, the incident surface is formed on the projecting end surface of the trunk portion, and the light source is disposed so as to face the incident surface. is, the light emitting device according to any one of claims 1 to 3 for emitting light toward the incident surface. The light emitting device according to claim 4 , wherein an incident surface of the light incident portion is set substantially parallel to the light emitting surface. Wherein the outer peripheral surface of the light guide, the light-emitting device according to any one of claims 1 to 5, a plurality of circumferential reflective aligned spaced grooves. The light emitting device according to claim 6 , wherein the groove is formed so as to reach a back surface from a front surface that is a light emitting surface of the light guide, and the groove is formed in a U-shaped cross section.

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