JP2011096523A - Spread illuminating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spread illuminating apparatus having high brightness, in which a point light source can be positioned and fixed to a light incident end face side of a light guide plate having an inclined face with high precision. <P>SOLUTION: The spread illuminating apparatus 10 includes an LED 11, a light guide plate 21, and an FPC 31 mounted with the LED 11. The light guide plate 21 includes: the light incident end face 22 on which the LED 11 is arranged; a light-emitting portion 28 to planarly emit light from the LED 11 incident from the light incident end face 22; and an inclined portion 27 of which the thickness gradually decreases as going toward the side of the light-emitting portion 28 and which is formed between the light incident end face 22 and the light-emitting portion 28. In the inclined portion 27, a plurality of pedestals 29 to fix the FPC 31 are dispersed and formed in regions excluding front portions of the LEDs 11. The upper face 29a of the pedestal 29 is formed so as to be orthogonal to the light incident end face 22 of the light guide plate 21. Moreover, on a mounting plane 31a of the FPC 31 arranged at the pedestal 29, a light absorption member 32 is formed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sidelight type planar illumination device including a light guide plate that arranges a light source on an incident light end surface and emits planar illumination light from an emission part, and more specifically, the thickness increases as the distance from the incident light end surface increases. The present invention relates to a planar illumination device including a light guide plate in which an inclined portion gradually decreasing is formed closer to a light incident end surface.

  As a lighting means for a liquid crystal display panel, a side-light type planar lighting device (backlight) in which small and excellent environmentally friendly LEDs are arranged along the light incident end face of a light guide plate is a small-sized mobile phone or the like. Widely adopted mainly in the field of portable information devices. In recent years, in order to cope with further thinning of small portable information devices, a light guide plate is used in which an inclined portion whose thickness gradually decreases as it moves away from the light incident end surface is formed between the light incident end surface and the light emitting portion. (For example, refer to Patent Document 1).

JP 2007-287550 A

  By forming the inclined portion (inclined surface) closer to the light incident end face of the light guide plate as described above, the emission portion of the light guide plate can be made thin regardless of the thickness of the LED. However, when the inclined portion is provided near the light incident end face of the light guide plate, the following problems have occurred. That is, the LED is usually disposed opposite to the light incident end face of the light guide plate in a state of being mounted on a strip-shaped circuit board. Then, the LED is positioned and fixed with respect to the light guide plate by tightly fixing a portion of the circuit board in front of the portion where the LED is mounted to a portion near the light incident end face of the light emission plate. As shown in FIG. 4A, when the inclined portion is not formed near the light incident end surface 103a of the light guide plate 103, in a state where the circuit board 102 is closely fixed to the emission plane 103b of the light guide plate 103, The light emitting surface 101a of the LED 101 faces the light incident end surface 103a of the light guide plate 103 in parallel.

  However, as shown in FIG. 4B, when the inclined surface 113 b is formed near the light incident end surface 113 a of the light guide plate 113, the circuit board 102 is closely fixed to the inclined surface 113 b of the light guide plate 113. In the state, the light emitting surface 101a of the LED 101 cannot face the light incident end surface 113a of the light guide plate 113 in parallel. This is because the light incident end surface 113a and the inclined surface 113b of the light guide plate 113 are not orthogonal to each other. For this reason, a part of the light emitted from the light emitting surface 101a of the LED 101 (shown by a broken line with an arrow in the figure) leaks outside without entering the light incident end surface 113a of the light guide plate 113, and the light exiting portion of the light guide plate There has been a problem that the luminance of the illumination light emitted from the light source decreases.

  Even when the circuit board 102 is fixedly fixed to either the portion near the light incident end face 103a (FIG. 4A) or the inclined surface 113b (FIG. 4B) of the exit plane 103b, the exit plane 103b. When the light incident on the portion near the light incident end face 103a or the inclined surface 113b is reflected, it is absorbed by the circuit board 102, and this also causes a problem that the luminance of the illumination light decreases.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a thin sidelight type planar illumination device having excellent luminance of illumination light.

Therefore, in order to solve the above-described problem, the planar illumination device according to the present invention is characterized by a point light source mounted on a printed circuit board, a light incident end surface on which the point light source is disposed, and the light incident A light guide plate having an emission part that emits light from the point light source incident from the end face in a planar shape,
In the light guide plate, an inclined portion whose thickness gradually decreases toward the emitting portion side is formed between the light incident end face and the emitting portion, and the dotted surface has the point-like shape on the inclined surface. A pedestal for arranging the printed circuit board is formed in a region excluding the front portion of the light source.

  According to this invention, the base for arrange | positioning a printed circuit board is formed in the area | region except the front part of a point light source among the inclined surfaces of the inclined part formed in the light-incidence end surface side of a light-guide plate. For this reason, when the printed circuit board is fixed to the pedestal, a gap is formed between the inclined surface of the front portion of the point light source and the printed circuit board. As a result, light absorption by the printed circuit board, which has occurred in the prior art, is suppressed, and high brightness of the illumination light can be achieved.

  In a preferred embodiment of the present invention, the point light source is formed such that a surface mounted on the printed circuit board is substantially orthogonal to the light emitting surface, and the pedestal is substantially orthogonal to the light incident end surface. The printed circuit board is mounted on the plane of the pedestal.

  According to this invention, the point light source is mounted on the printed circuit board so that the light emitting surface of the point light source is substantially orthogonal to the mounting plane of the printed circuit board. The light guide plate is formed so that the plane of the base of the light guide plate is substantially orthogonal to the light incident end surface of the light guide plate. For this reason, in a state where the printed circuit board is disposed and fixed on the plane of the pedestal, the light emitting surface of the point light source faces substantially parallel to the light incident end surface of the light guide plate. Thereby, the light radiate | emitted from the light emission surface of a point light source can be efficiently entered in a light-guide plate, and the high brightness | luminance of illumination light can be achieved.

  In another preferred embodiment of the present invention, a light absorbing member is formed on a surface of the printed circuit board facing the light guide plate.

  According to this invention, even if some light leaks from the inclined surface by forming the light absorbing member on the printed circuit board that covers the inclined surface of the inclined portion, the light absorbing member absorbs the leaked light. Can do. Thereby, the uniformity of illumination light can be further improved.

It is sectional drawing which shows typically the whole structure of the planar illuminating device which concerns on embodiment of this invention. It is a partial expansion perspective view which shows the principal part of the light-guide plate which comprises the same planar illumination apparatus. (A) is a top view of FPC which comprises a same-surface lighting apparatus, (b) is a principal part top view of the light-guide plate which comprises a same-surface lighting apparatus. It is a figure for demonstrating the problem of the planar illumination device of a prior art, (a) is a case where the inclination part is not formed in the light-guide plate, (b) is an inclination part formed in the light-guide plate. Is the case.

  Hereinafter, a planar illumination device 10 according to an embodiment of the present invention will be described with reference to the drawings. In each of the drawings shown below, in order to facilitate understanding of the present invention, the shape and the like of each component are exaggerated as appropriate, and there are portions that do not match each other's dimensional relationships.

  As shown in FIG. 1, the planar illumination device 10 includes an LED 11 as a point light source, a light guide plate 21 for emitting light emitted from the LED 11 in a planar shape, and a printed circuit board on which the LED 11 is mounted. An FPC (Flexible Printed Circuit Board) 31 and a frame 41 for housing each component are provided.

  In the present embodiment, the LED 11 is a pseudo-white LED composed of a blue LED and a yellow phosphor, and is a so-called side view type LED that is formed in a rectangular parallelepiped shape as a whole and has a light emitting surface 12 on one side surface. That is, in the LED 11, the surface (mounting surface) 13 mounted on the FPC 31 and the light emitting surface 12 are substantially orthogonal. In the present embodiment, the three LEDs 11 are arranged along the light incident end surface 22 with a predetermined distance from each other with the light emitting surface 12 facing a light incident end surface 22 described later of the light guide plate 21 ( (See FIG. 2).

  Next, the light guide plate 21 is formed in a rectangular shape in a top view using a transparent material (in this embodiment, polycarbonate resin). The light guide plate 21 has, on its outer surface, a light incident end surface 22 that is an end surface on the side where the LED 11 is disposed, a facing end surface 23 that is an end surface facing the light incident end surface 22, and one of the light incident end surfaces 22 that is substantially orthogonal to the light incident end surface 22. It has a reflection plane 24 that is a main plane and an emission plane 25 that is the other main plane that faces the reflection plane 24 in parallel. The light incident end surface 22 is formed such that the dimension in the short direction (thickness direction) is equal to or slightly larger than the dimension in the same direction of the light emitting surface 12 of the LED 11. In the present invention, the direction in which the light incident end face 22 faces the opposite end face 23 (also the light guide direction) is defined as “front”.

  In addition, as shown in FIG. 2, the light guide plate 21 has a light incident portion 26 formed forward from the light incident end surface 22, and an inclination that is formed continuously from the light incident portion 26 and gradually decreases in thickness toward the front. A light emitting portion 28 that emits light from the emission plane 25 from the LED 11 that is formed in front of the inclined portion 27 and guides the inclined portion 27, and is formed discretely on the emission plane 25 side of the inclined portion 27. The pedestal 29 (four in this embodiment) and the claw portions 30 (four in the present embodiment) formed discretely so as to protrude rearward from the light incident end face 22 are configured.

  The light incident portion 26 has a constant thickness in the forward direction, and is formed such that an upper surface 26 a that is a surface on the emission plane 25 side is substantially orthogonal to the light incident end surface 22. The light incident portion 26 is not essential in the present invention, and may be omitted from the viewpoint of the optical function.

  The inclined portion 27 is configured by providing an inclined surface 27 a that is inclined with a certain gradient so as to approach the reflection plane 24 side toward the front side on the emission plane 25 side along the longitudinal direction of the light incident end surface 22. In the present embodiment, the inclined portion 27 is an abbreviation of the maximum thickness of the inclined portion (corresponding to the thickness of the light incident portion 26 or the dimension of the light incident end face 22 in the short direction). It is formed to be 1.78 times. Note that the length of the inclined portion is the length of the forward direction component parallel to the reflection plane 24 of the inclined surface 27a (that is, the length in the forward direction when the inclined surface 27a is projected onto the reflection plane 24).

  The emission part 28 is formed in a rectangular flat plate shape having a constant thickness, and an optical path changing pattern composed of, for example, a plurality of dots is formed on the reflection plane 24 side. By forming the optical path changing pattern, the traveling direction of the light guided through the emitting portion 28 can be changed, and the light can be emitted from the emitting plane 25. A reflection sheet 51 is disposed on the reflection plane 24 side of the emitting portion 28 in order to return light leaking from the reflection plane 24 to the light guide plate 21 again. A diffusion sheet 52 and a pair of prism sheets 53 and 54 are sequentially stacked on the emission plane 25 side of the emission unit 28 in order to control the directivity of light emitted from the emission plane 25. .

  The four pedestals 29 are for fixing and mounting (mounting) the FPC 31. In the vicinity of the inclined surface 27a and the inclined surface 27a of the emission plane 25, the four pedestals 29 are arranged in front of the three LEDs 11 (shown by broken lines in FIG. 2). Are separated from each other so that they do not exist, and each is formed in a flat plate shape. Each pedestal 29 has a flat upper surface 29 a that is substantially flush with the upper surface 26 a of the light incident portion 26. Further, the pedestal 29 is formed such that its top view shape becomes narrower toward the front at the front tip side.

  The claw portion 30 is for fixing and arranging the FPC 31 similarly to the pedestal 29, and is formed in a rectangular parallelepiped shape extending rearward from both sides of the area of the light incident end face 22 where the LEDs 11 face each other. The claw portion 30 is formed such that the upper surface 30a, which is the surface on the exit plane 25 side, is substantially flush with the upper surface 26a of the light incident portion 26 and the upper surface 29a of the pedestal 29. When the FPC 31 is partially bonded to the upper surface 26a of the light incident portion 26, the upper surface 29a of the pedestal 29, and a part of the upper surface 30a of the claw portion 30 and bonded to the partially bonded surface portion. You may make it provide the recessed part which arrange | positions an agent (double-sided tape).

  Next, as shown in FIG. 3A, the FPC 31 is formed in a strip shape, and the length of the long side is substantially the same as the length of the light incident end face 22 of the light guide plate 21 in the longitudinal direction. In addition, on the mounting plane 31a, which is one plane of the FPC 31, three LEDs 11 extend along the rear long side 31b with the light emitting surface 12 substantially orthogonal to the mounting plane 31a and substantially parallel to the long side. Has been implemented.

  The FPC 31 on which the LED 11 is mounted is positioned on the light guide plate 21 while aligning so that the light emitting surface 12 of the LED 11 faces a predetermined position (between adjacent claw portions 30 and 30) of the light incident end surface 22 of the light guide plate 21. Bonded and fixed. At this time, the upper surfaces 29a, 26a, and 30a of the pedestal 29, the light incident portion 26, and the claw portion 30 become joint surfaces (contact surfaces) with the mounting plane 31a of the FPC 31 (hatching in FIG. 3B described later). Part is equivalent). Thus, the LED 11 is positioned and fixed with respect to the light guide plate 21 by fixing the FPC 31 on the light guide plate 21. As described above, the FPC 31 may be joined not to the entire upper surface 26a of the light incident portion 26, the upper surface 29a of the pedestal 29, and the entire upper surface 30a of the claw portion 30 but to a part of them.

  Further, the FPC 31 absorbs leakage light from the light guide plate 21 (inclined portion 27) on the long side 31c side (front side of the LED 11) on the front side of the mounting plane (surface facing the light guide plate) 31a. A light absorbing member (black paint) 32 is applied. The light absorbing member 32 has a long side 31c on the front side of the FPC 31 so that at least a part of the inclined surface 27a and a portion near the inclined surface 27a of the emission plane 25 are covered with the FPC 31 fixed on the light guide plate 21. It is formed in a strip shape along the line (in FIG. 3 (a), the light absorbing member 32 is applied to the portion subjected to the hatching process by the broken line). The planar shape and size of the light absorbing member 32 are not particularly limited, but the length in the front direction is larger than the maximum thickness of the inclined portion and straddles the boundary between the inclined surface 27a and the emission plane 25. It is preferable that it is formed.

  Next, in this embodiment, the frame 41 is formed in a frame shape using a white resin, and integrally stores components such as the LED 11 and the light guide plate 21.

  By constructing the planar illumination device 10 as described above, the light emitted from the LED 11 is guided to the emission part 28 via the light incident part 26 and the inclined part 27 of the light guide plate 21, and the emission plane 25 of the emission part 28. It can be emitted as planar light from the side.

  Next, operations and effects unique to the planar lighting device 10 according to the embodiment of the present invention will be described.

  In the planar illumination device 10, a pedestal 29 for fixing and arranging the FPC 31 is formed in a region excluding the front portion of the LED 11 in the inclined surface 27 a of the inclined portion 27 formed near the light incident end surface 22 of the light guide plate 21. ing. For this reason, in a state where the FPC 31 is fixed to the pedestal 29, a gap is formed between the inclined surface 27a of the front portion of the LED 11 and the mounting plane 31a of the FPC 31, and the light guided in the light guide plate 21 is FPC 31 (light absorption). Absorption by the member 32) is suppressed. As a result, light absorption by the printed circuit board, which has occurred in the prior art, is suppressed, and high brightness of the illumination light can be achieved.

  Note that the light emitted from the LED 11 travels in a divergent shape toward the front in the light guide plate 21 as shown as part A in FIG. Therefore, in this embodiment, the pedestal 29 is formed so that the width becomes narrower toward the front on the front tip side in a top view, so that the interval between the adjacent pedestals 29 becomes wider toward the front. Yes. Thereby, the area of the upper surface 29a of the pedestal 29 is increased as much as possible, and the adhesive strength between the FPC 31 and the light guide plate 21 is improved.

  In the planar illumination device 10, the LED 11 is mounted on the FPC 31 so that the light emitting surface 12 of the LED 11 is substantially orthogonal to the mounting plane 31 a of the FPC 31. The light guide plate 21 is formed with a pedestal 29 for fixing and arranging the FPC 31 so that a main plane 29 a thereof is substantially orthogonal to the light incident end face 22 of the light guide plate 21. For this reason, in a state where the FPC 31 is disposed and fixed on the main plane 29 a of the pedestal 29, the light emitting surface 12 of the LED 11 faces the light incident end surface 22 of the light guide plate 21 substantially in parallel. Thereby, the light emitted from the light emitting surface 12 of the LED 11 can be efficiently incident without causing leakage light in the light guide plate 21, and further increase in luminance of the illumination light can be achieved. .

  In the planar illumination device 10, the light absorbing member 32 is disposed so as to cover at least a part of the inclined surface 27 a of the light guide plate 21 and a portion near the inclined surface 27 a of the emission plane 25. Thereby, even if some light leaks from the inclined portion 27, the leaked light can be absorbed by the light absorbing member 32. Thereby, the uniformity of illumination light can be further improved.

  The preferred embodiments of the present invention have been described above. However, the embodiments are not limited to the above, and various modifications and combinations can be made without departing from the gist of the present invention.

  For example, in the above embodiment, the pedestal 29 is formed in such a size that the tip thereof extends to the vicinity of the inclined surface 27a of the emission plane 25, but is not limited thereto. The front tip portion of the pedestal 29 does not necessarily extend to the emission plane 25, and the pedestal 29 may be formed only on the inclined surface 27a.

  Moreover, in the said embodiment, although the light absorption member formed in FPC31 was arrange | positioned at the output plane 25 side of the light-guide plate 21, it is not limited to this. When priority is given to the uniformity of the illumination light, it is preferable to provide a light absorbing member. However, for example, when priority is given to the luminance of the illumination light, a light reflecting member may be provided instead of the light absorbing member. Good. Moreover, when providing a light absorption member, it is not necessary to use what was formed in FPC31, for example, you may use what was formed in the film which has a diffusivity.

  Moreover, in the said embodiment, although the inclination of the inclined surface 27a of the inclination part 27 was made constant, it is not limited to this. For example, the gradient of the inclined surface 27a of the inclined portion 27 may be continuously changed toward the front in the light guide direction.

10 Planar illumination device 11 LED
12 Light emitting surface 21 Light guide plate 22 Light incident end surface 23 Opposite end surface 24 Reflective plane 25 Output plane 26 Light incident portion 27 Inclined portion 27a Inclined surface 28 Outlet portion 29 Base 29a Upper surface 30 Claw portion 31 FPC
32 Light Absorbing Member 41 Frame 51 Reflective Sheet 52 Diffusion Sheets 53 and 54 Prism Sheet

Claims (3)

A point light source mounted on a printed circuit board;
A light incident plate on which the point light source is disposed, and a light guide plate having an emission part that emits light from the point light source incident from the light incident end surface in a plane,
In the light guide plate, an inclined portion is formed between the light incident end face and the emitting portion, the thickness of which gradually decreases toward the emitting portion side,
The planar illumination device in which the base for arrange | positioning the said printed circuit board is formed in the area | region except the front part of the said point light source on the inclined surface of the said inclination part. The light source is formed such that a surface mounted on the printed circuit board is substantially orthogonal to the light emitting surface,
The pedestal has a plane substantially orthogonal to the light incident end face;
The planar illumination device according to claim 1, wherein the printed circuit board is mounted on the plane of the pedestal. The planar illumination device according to claim 1, wherein a light absorbing member is formed on a surface of the printed circuit board facing the light guide plate.

Images