JP2017228383A - Planar light unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar light unit which prevents misalignment between an LED and a light guide plate when the LED and the light guide plate are stored in a case even if a transparent resin is disposed between the LED and an incidence plane of the light guide plate for adhesion.SOLUTION: A planar light unit 10 includes: a light guide plate 11; an elastomer 14; an LED 12; and a case 15. The elastomer 14 is disposed between an incidence plane 11a of the light guide plate 11 and the LED 12. At that time, screws 17, 18 are inserted into screw holes 15a, 15b formed on a side wall 15c of the case 15 and press the light guide plate 11 on a side surface 11b to fix the light guide plate 11 to the case 15.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a planar light unit that illuminates a liquid crystal panel or the like from the back. More specifically, a transparent flexible resin is disposed between a light source and an incident surface of a light guide plate to improve the incident efficiency on the light guide plate. The present invention relates to a side edge type planar light unit.

  2. Description of the Related Art A side edge type planar light unit including a light guide plate that emits light incident from one side surface (incident surface) from one main surface (exit surface) is known. In this planar light unit, the light source and the light guide plate may be brought into close contact with each other so as to suppress reflection at the interface as much as possible to improve the light emission efficiency. For example, FIG. 1 of Patent Document 1 describes a planar light unit that includes a light source, a light guide plate, and an intermediate layer that closely contacts the light source and the light guide plate.

  Further, in a side edge type planar light unit, a light source, a light guide plate, and the like are housed in a frame-like case, and a side surface of the light guide plate is pushed by an elastic member, and these are fixed to the case. For example, in FIG. 1 of Patent Document 2, an elastic holding portion provided between a side surface opposite to a side surface serving as a light receiving portion of a light guide plate and an inner wall surface of a frame body facing the side surface is provided with a light guide plate. Describes a planar light unit that is fixed to a frame while being closely attached to a light source.

Japanese Patent Laying-Open No. 2007-103101 (FIG. 1) JP 2006-318830 A (FIG. 1)

  However, if a transparent resin is interposed between the LED serving as the light source and the light incident surface of the light guide plate, when the LED and the light guide plate are housed in the case, the position of the LED is shifted relative to the light guide plate. Is likely to occur. This misalignment not only lowers the light emission efficiency but also causes uneven brightness on the exit surface.

  Therefore, the present invention has been made in view of the above problems, and when the LED and the light guide plate are housed in the case even if a transparent resin is interposed between the LED and the incident surface of the light guide plate for adhesion. An object of the present invention is to provide a planar light unit in which no positional deviation occurs between the LED and the light guide plate.

  The planar light unit of the present invention includes a case that houses a light guide plate, a transparent elastic resin, and an LED, and the transparent elastic resin is disposed between the incident surface of the light guide plate and the LED. The case has a screw hole on one side wall, and the side surface of the light guide plate facing the incident surface of the light guide plate is pressed by a screw inserted from the screw hole, and is fixed to the case. It is characterized by that.

  The light guide plate may include support portions disposed at both ends of the incident surface and in contact with the case.

  The light guide plate may have a reflection curved surface having a curved cross section at an incident portion provided between the incident surface and the incident surface.

  The screw and the central axis of the LED may coincide.

  In the planar light unit of the present invention, a light guide plate equipped with an LED and a transparent flexible resin is inserted into a case, and then the light guide plate is fixed to the case with a screw. As a result, in the planar light unit of the present invention, even when a transparent elastic resin is interposed between the LED and the light guide plate, a positional shift occurs between the LED and the light guide plate when the LED and the light guide plate are accommodated in the case. do not do.

It is a disassembled perspective view of the planar light unit shown as embodiment of this invention. It is a top view of the planar light unit shown in FIG. It is sectional drawing of the planar light unit shown in FIG. It is sectional drawing of the planar light unit shown in FIG.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted. The scale and the like of the drawings are changed as appropriate for explanation. The invention specific matters shown in the scope of claims are described in ().

  FIG. 1 is an exploded perspective view of a planar light unit 10 shown as an embodiment of the present invention. The light guide plate 11 is a flat plate with one side processed, and is formed between the incident surface 11a, the exit surface 11c serving as the main surface, and the entrance surface 11a and the exit surface 11c, and has a curved cross section. The reflection curved surface 11g and the support portions 11d and 11e arranged at both ends of the incident surface 11a are observed. A plurality of LEDs 12 are mounted on the substrate 13, and the LEDs 12 are in close contact with the elastomer 14 (transparent flexible resin). The elastomer 14 is in close contact with the incident surface 11a.

  The reflection sheet 16 includes a bottom portion and a portion bent vertically from the bottom portion. The bottom portion is in contact with the bottom surface 11f of the light guide plate 11 (see FIG. 3, another main surface facing the light exit surface 11c) via an air layer, and the bent portion is guided through a double-sided tape (not shown). 11 is in contact with side surfaces other than the incident surface 11a. The case 15 is a box having a bottom portion 15g and side walls 15c, 15d, 15e, and 15f and having an open top, and houses the light guide plate 11 to which the LED 12, the substrate 13, the elastomer 14, and the reflection sheet 16 are attached. . At this time, screws 17 and 18 are inserted into screw holes 15a and 15b formed in one side wall 15c of the case 15. The screws 17 and 18 push the side surface 11 b (see FIG. 2, the side surface facing the incident surface 11 a) of the light guide plate 11 through the reflection sheet 16. As a result, the support portions 11 d and 11 e press the side wall 15 d of the case 15, and the LED 12, the substrate 13, the elastomer 14, and the light guide plate 11 (including the reflection sheet 16) are fixed to the case 15.

FIG. 2 is a plan view of the planar light unit 10. FIG. 2 is simplified with respect to FIG. 1 by changing the number of LEDs 12 and the scale of members for explanation. Further, the bottom 15g (see FIG. 1) of the case 15 is not shown. When the planar light unit 10 is viewed from above, the light guide plate 11, the LED 12, the substrate 13, the elastomer 14, the case 15, the reflection sheet 16 and the screws 17 and 18 are observed. Moreover, in FIG. 2, the output surface 11c, the support parts 11d and 11e, and the reflective curved surface 11g contained in the light guide plate 11 are observed. The LED 12, the substrate 13, and the elastomer 14 are disposed in a space surrounded by the support portions 11 d and 11 e and the incident surface 11 a of the light guide plate 11 and the side wall 15 d of the case 15. The case 15 houses the light guide plate 11, the LED 12, the substrate 13, the elastomer 14 and the reflection sheet 16. The reflection sheet 16 surrounds three side surfaces of the light guide plate 11 other than the incident surface 11a. The screws 17 and 18 are attached to the side wall 15c of the case 15 and press the light guide plate 11 against the side wall 15d.

  FIG. 3 is a cross-sectional view illustrating only a cross section of the planar light unit 10 along the line AA ′ in FIG. 2. As shown in FIG. 3, the light guide plate 11 is provided with an incident portion 19 between the incident surface 11a and the exit surface 11c. The incident part 19 has an incident surface 11a and reflection curved surfaces 11g and 11h. The elastomer 14 is in close contact with the incident surface 11a. Similarly, the light exit surface 12 a of the LED 12 is in close contact with the elastomer 14. The LED 12 is mounted on the substrate 13, and the substrate 13 is in contact with the side wall 15 d of the case 15. The light guide plate 11 has a bottom surface 11f. The bottom surface 11f is formed with dots (not shown) for changing the traveling direction of the light propagating through the light guide plate 11 and emitting the light from the emission surface 11c. Further, the bottom surface 11f is laminated on the bottom of the reflection sheet 16 through an air layer.

  4 is a cross-sectional view of the planar light unit 10 and the screw 18 taken along the line BB ′ of FIG. As shown in FIG. 4, the support portion 11 e is pressed against the side wall 15 d of the case 15.

  The light guide plate 11 has a thickness of 2.0 to 3.0 mm and is made of polycarbonate, acrylic, or the like, and dots (not shown) whose diameter is changed depending on the location are formed on the bottom surface 11f so that the luminance on the exit surface 11c is uniform. Has been. This dot is a recess formed by laser processing and has a diameter of 50 to 500 μm. The LED 12 is a package product in which an LED die is mounted on a submount substrate serving as an interposer, and the periphery of the LED die is sealed with a resin. The substrate 13 is an FPC (flexible printed circuit) based on polyimide. The electrode of the LED 12 is connected to the electrode formed on the substrate 13.

  The elastomer 14 is made of a highly flexible silicone resin, and compressively deforms to optically and mechanically connect the light exit surface 12a and the incident surface 11a of the LED 12, and heat due to shape errors and temperature characteristics of the light guide plate 11 and the like. Absorbs expansion deformation. For example, the elastomer 14 may have a Young's modulus of about 0.1 to 1 mp. If the Young's modulus is this value, a pressure of about 10 Mp may be generated on the LED 12 due to thermal expansion or the like. However, since the LED 12 does not break down to about 100 Mp, there is no problem if the pressure is about 10 Mp. The elastomer 14 preferably has the same refractive index as that of the light guide plate 11, that is, the refractive index thereof is 1.4 to 1.6.

  Case 15 is made of aluminum. The light guide plate 11 and the substrate 13 are accommodated in the case 15 and then pressed against the case 15 with screws 17 and 18. At this time, most of the pressing force of the screws 17 and 18 is received by the support portions 11d and 11e. On the other hand, only a part of the pressing force is applied to the LED 12, the substrate 13 and the elastomer 14 due to the deformation of the elastomer 14. The reflection sheet 16 is made of white PET and has a thickness of 200 μm. A double-sided tape (not shown) has adhesive layers on both sides of a transparent PET sheet and has a thickness of 100 μm. On the exit surface 11c of the light guide plate 11, a diffusion sheet and a prism sheet (not shown) are laminated.

  The LED die included in the LED 12 emits blue light. A part of the blue light enters the elastomer 14 from the exit surface 12a of the LED 12, and then enters the light guide plate 11 from the elastomer 14 through the entrance surface 11a. The remaining part of the blue light emitted from the LED die is wavelength-converted by the phosphor contained in the sealing resin. This wavelength-converted light also enters the light guide plate 11. The light that has entered the light guide plate 11 propagates in the light guide plate 11 while being repeatedly reflected between the upper and lower main surfaces (the emission surface 11c and the bottom surface 11f). The traveling direction of this light is changed by the dots formed on the bottom surface 11 f, and the light is emitted from the light emitting surface 11 c to the outside of the light guide plate 11.

As is well known, when light enters a medium having a refractive index n1 from a medium having a refractive index n1,
R = | n1-n2 | / (n1 + n2)
(R is reflectivity, hereinafter referred to as Fresnel loss). In the planar light unit 10, since the refractive indexes of the light guide plate 11 and the elastomer 14 are both about 1.5, Fresnel loss hardly occurs. As a result, in the planar light unit 10, since the Fresnel loss is significantly reduced, the light emission efficiency is improved.

  In the planar light unit 10, when the light guide plate 11 on which the LED 12 is mounted, the elastomer 14, and the reflective sheet 16 are housed in the case 15, these are aligned, and then the light guide plate 11 is moved. The screws 17 and 18 are pressed to fix them to the case 15. At this time, the screws 17 and 18 push the elastomer 14 and the LED 12 linearly through the light guide plate 11, so that the positional deviation between the LED 12 and the light guide plate 11 does not occur. That is, the center axes of the screw 17, the light guide plate 11, and the LED 12 in FIG. As a result, when the planar light unit 10 accommodates the LED 12 and the light guide plate 11 in the case 15, even if the elastomer 14 is interposed between the LED 12 and the light guide plate 11, the positional deviation between the LED 12 and the light guide plate 11 does not occur. Does not occur.

  As described above, the support portions 11d and 11e prevent the LED 12 from being pressed more than necessary. However, the support portion is not necessarily required and can be omitted. At this time, the substrate 13 and the light guide plate 11 are fixed by the repulsive force of the elastomer 14 when the screws 17 and 18 are tightened. The planar light unit 10 was provided with reflection curved surfaces 11g and 11h in the input unit 19. The reflection curved surface 11 a causes the light traveling at a small incident angle upward (or downward) in FIG. 3 at the incident portion 19 to be totally reflected by the reflection curved surface 11 g (or the reflection curved surface 11 h) and tries to leak out from the light guide plate 11. It reduces light and improves luminous efficiency. When this loss can be ignored, the reflection curved surfaces 11g and 11h can be omitted.

10 ... A planar light unit,
11 ... light guide plate,
11a: Incident surface,
11b ... side,
11c: emitting surface,
11d, 11e ... support part,
11f ... the bottom surface,
11g, 11h ... reflective curved surface,
12 ... LED,
12a ... light-emitting surface,
13 ... substrate,
14 ... Elastomer (transparent flexible resin),
15 ... Case,
15a, 15b ... screw holes,
15c to f ... sidewalls,
15g ... bottom,
16 ... reflective sheet,
17, 18 ... screws,
19: Incident part.

Claims (4)

In a planar light unit comprising a light guide plate, a transparent elastic resin, and a case for housing the LED, wherein the transparent elastic resin is disposed between the incident surface of the light guide plate and the LED,
The case has a screw hole on one side wall;
The planar light unit, wherein the light guide plate is fixed to the case by pressing a side surface facing the incident surface of the light guide plate by a screw inserted from the screw hole.   The planar light unit according to claim 1, wherein the light guide plate includes support portions disposed at both ends of the incident surface and in contact with the case.   The planar light unit according to claim 1, wherein the light guide plate has a reflection curved surface having a curved cross section in an incident portion provided between the incident surface and the incident surface.   The planar light unit according to any one of claims 1 to 3, wherein a central axis of the screw and the LED coincide with each other.