JP2013131444A - Planar lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar lighting device capable of reducing light leakage from vicinity of an incident surface of a light guide plate and achieving higher luminance of illumination light.SOLUTION: A planar lighting device is provided with an FPC 31 having a mounting surface 31a mounted with an LED 11 of which at least a portion of a front side part than the part where the LED 11 is mounted is superposed on a light guide plate and, moreover, a white-color cover-lay film 32a functioning as a light reflection member is arranged on the mounting surface 31a, and since a region of the mounting surface 31a where the light reflection member is arranged includes a first region 51 extending frontward from a position corresponding to the central part of an emission surface 12 of the LED 11, the light incident into a part covering a gap of the FPC is reflected to make it incident into the light guide plate 12, and thereby, higher luminance of illumination light can be achieved, even if there is a gap between the emission surface 12 of the LED 11 and the incident surface of the light guide plate.

Description

  The present invention relates to a sidelight type planar illumination device including a light guide plate that arranges a light source on a light incident end face and emits planar illumination light from an emission part.

  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 side end surface of a light guide plate is a small portable such as a mobile phone. Widely adopted mainly in the field of information equipment. In recent years, in order to cope with further thinning of a small portable information device, an inclined portion whose thickness gradually decreases as the distance from a side end surface (hereinafter also referred to as a light incident surface) on which an LED is disposed is an incident surface and an output portion. A light guide plate formed between the two is used. By using such a light guide plate, the emission part of the light guide plate can be made thin regardless of the thickness of the LED.

  In this type of planar illumination device, the LED is usually disposed opposite to the light incident surface of the light guide plate in a state of being mounted on a strip-shaped circuit board, and at this time, the front portion of the circuit board is placed on the light guide plate. It is positioned and fixed with respect to the light guide plate by being closely fixed to a portion near the light incident surface (including the inclined surface of the inclined portion).

Conventionally, in such a planar lighting device, when the light emitted from the LED and incident on the light guide plate is reflected by the inclined surface, it is absorbed by the circuit board that is closely fixed to the inclined surface, and In a state where the circuit board is closely fixed to the inclined surface of the light guide plate, the light emitting surface of the LED cannot face the light incident surface of the light guide plate in parallel, so that part of the light emitted from the light emitting surface of the LED is guided. There has been a problem that the luminance of the illumination light is reduced by leaking outside without entering the light incident surface of the light plate.
Therefore, the present applicant has previously proposed the following planar illumination device in order to solve the above problems and improve the luminance of illumination light (see Patent Document 1).

  FIG. 5 is a cross-sectional view schematically showing the overall configuration of the planar illumination device shown as an example in Patent Document 1. As shown in FIG. In the planar lighting device 100 shown in FIG. 5, the light guide plate 121 is formed continuously from the light incident portion 126 and the light incident portion 126 forward from the light incident surface 122, and the thickness increases toward the front. A slope part 127 that gradually decreases and an emission part 128 that is formed in front of the slope part 127 and guides the light from the LED 111 guided through the slope part 127 are emitted from the emission surface 125. A pedestal 129 for fixing and arranging the FPC 131 in a region excluding the front portion of the LED 111 in the inclined surface 127a of the inclined portion 127 formed near the light incident surface 122 of the light guide plate 121 has a main plane 129a. The light guide plate 121 is formed so as to be substantially orthogonal to the light incident surface 122.

In the planar lighting device 100, with this configuration, the light emitting surface 112 of the LED 111 faces the light incident surface 122 of the light guide plate 121 substantially in parallel with the FPC 131 fixed to the pedestal 129. It is possible to efficiently enter the light into the light guide plate 121 without generating leakage light. As described above, the planar lighting device 100 solves the above-described problem and achieves high brightness of the illumination light.
Furthermore, in the state lighting device 100, in a state where the FPC 131 is fixed to the pedestal 129, a gap is formed between the inclined surface 127a of the front portion of the LED 111 and the surface 131a on the side facing the inclined surface 127a of the FPC 131. Further, the light that enters the light guide plate 121 and is reflected by the inclined surface 127a is suppressed from being absorbed by the FPC 131, and the effect of increasing the luminance of the illumination light is also achieved.

JP 2011-96523 A

As described above, the planar illumination device 100 shown in FIG. 5 has the above-described effects in terms of increasing the luminance of the illumination light, but there is room for improvement as follows from the viewpoint of further improvement. .
That is, in a general arrangement mode of the LED 111, as shown in FIG. 5, the clearance between the light emitting surface 112 of the LED 111 and the light incident surface 122 of the light guide plate 121 is used as a clearance for dealing with thermal deformation or the like of the light guide plate 121. In addition, a constant gap g (usually about 0.2 mm) is provided. For this reason, in the conventional planar illumination device 100, a part of the light emitted from the LED 111 does not enter the light incident surface 122 of the light guide plate 121 but enters the part of the FPC 131 that covers the gap g. Thus, leakage light that is not used as illumination light is transmitted through the FPC 131 or absorbed by the FPC 131. Therefore, it is desirable to reduce such leakage light in order to achieve higher brightness of the illumination light.

  In particular, as the demand for thinning the light guide plate increases in recent years, the height of the light incident surface 122 of the light guide plate 121 can be further increased even when the light emitting plate 128 is thinned by providing the light guide plate 121 with the inclined portion 127 (see FIG. It has become necessary to make the thickness of the light incident portion 126 equal to or slightly smaller than the height of the LED 111 from the mounting plane 131a of the FPC 131. In this case, since the light leaking upward of the LED 111 increases, reducing the light leaking from the portion covering the gap g of the FPC 131 becomes a more important issue.

  The present invention has been made in view of the above problems, and provides a planar illumination device capable of reducing leakage light from the vicinity of a light incident surface of a light guide plate and achieving high brightness of illumination light. Objective.

  The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each section does not limit the technical scope of the present invention, and some of the components of each section are replaced, deleted, or further, while referring to the best mode for carrying out the invention. Those to which the above components are added can also be included in the technical scope of the present invention.

(1) A point light source having a light emitting surface for emitting light toward the front, a circuit board having a mounting surface on which the point light source is mounted, a light incident surface on which the point light source is disposed, and the light incident And a light guide plate having an emission surface for emitting light incident from the light surface in a planar shape, wherein the circuit board is at least one of a front portion of the portion on which the point light source is mounted. And a light reflecting member is disposed on the mounting surface, and a region of the mounting surface on which the light reflecting member is disposed is a light emitting surface of the point light source. A planar illumination device comprising a first region extending forward from a position corresponding to the central portion (claim 1).

  According to the planar illumination device described in this section, the light reflecting member is disposed on the mounting surface of the circuit board on which the point light source is mounted, and the area on the mounting surface where the light reflecting member is disposed is dotted. Even if a gap exists between the light emitting surface of the point light source and the light incident surface of the light guide plate by including the first region extending forward from the position corresponding to the central portion of the light emitting surface of the light source, the circuit At least part of the light incident on the portion of the substrate that covers the gap is reflected by the light reflecting member disposed in the first region and is incident on the light incident surface of the light guide plate. Light that is transmitted through the circuit board through the covered portion or absorbed by the circuit board can be reduced, and high luminance of the illumination light can be achieved.

(2) In the planar illumination device according to item (1), a region where the light reflecting member is disposed on the mounting surface of the circuit board is rearward from a position corresponding to a central portion of the light emitting surface of the point light source. A planar illumination device comprising a second region having a portion extending to the surface (Claim 2).

  According to the planar illumination device described in this section, in the region where the light reflecting member is disposed on the mounting surface of the circuit board, the first portion having a portion extending backward from the position corresponding to the central portion of the light emitting surface of the point light source. 2 is included, the light reflecting member is also disposed on the portion of the mounting surface of the circuit board corresponding to the bottom surface of the point light source (the surface facing the mounting surface when mounted on the circuit board). Thus, since at least a part of the leaked light from the bottom surface of the point light source is reflected by the light reflecting member and enters the light incident surface of the light guide plate, it is possible to achieve higher brightness of the illumination light. .

(3) The planar illumination device according to (1) or (2), wherein the light reflecting member is composed of a coverlay film that covers a mounting surface of the circuit board. (Claim 3).
According to the planar illumination device described in this section, the light reflecting member disposed on the mounting surface of the circuit board is easily and highly accurately formed corresponding to the first region and the second region of the mounting surface. can do.

(4) In the planar illumination device according to item (2), the light reflecting member includes a coverlay film that covers a mounting surface of the circuit board, and the point light source is a light incident surface of the light guide plate. A pair of terminals disposed at both ends in a direction along the longitudinal direction of the light source, and the light reflecting member disposed in the second region is formed on the coverlay film and the pair of point light sources. A planar illumination device characterized in that a pair of openings are formed so as to expose a pair of electrode pads corresponding to the terminals, thereby being provided between the pair of openings.

  According to the planar illumination device described in this section, the light reflecting member disposed on the mounting surface of the circuit board is easily and highly accurately formed corresponding to the first region and the second region of the mounting surface. can do. In particular, positioning when mounting the point light source on the circuit board is based on a pair of openings provided on the coverlay film so that a pair of electrode pads corresponding to the pair of terminals of the point light source are exposed. Since the second region is provided between the pair of openings, the light reflecting member can be arranged with high accuracy with respect to the light emitting surface and the bottom surface of the point light source. .

(5) In the planar illumination device according to item (4), the second region has a portion extending forward from a position corresponding to the central portion of the light emitting surface of the point light source, The area lighting device includes a portion that spreads out toward the front and widens toward the front (Claim 5).

  According to the planar illumination device described in this section, the light reflecting member that spreads in a divergent shape toward the front is disposed on the front portion of the light emitting surface of the point light source on the mounting surface of the circuit board. It is possible to efficiently reflect the light that is emitted from the light source and travels forward with a predetermined spread angle, thereby further increasing the brightness of the illumination light.

(6) In the planar illumination device according to any one of (1) to (5), the light guide plate includes an inclined portion whose thickness gradually decreases from the light incident surface side toward the front. And a pedestal having a receiving surface on which the circuit board is arranged is formed in an area excluding a front portion of the point light source on the inclined surface side of the inclined part, and the receiving surface of the pedestal includes the light incident surface A first surface formed on the surface side, and a second surface formed in front of the first surface and inclined from the first surface side toward the front side toward the inclined portion side. A surface illumination device characterized in that (claim 6).

  In the state where the circuit board is fixed to the pedestal by forming the pedestal having the receiving surface on which the circuit board is arranged in the area excluding the front portion of the point light source, Since a gap is formed between the inclined surface of the front portion of the light source and the circuit board, the light reaching the inclined surface after entering the light guide plate is suppressed from being directly absorbed by the circuit board, and the point light source In addition to the effect that the light emitted from the light can be efficiently guided through the inclined portion, the following effects are further achieved.

  That is, in the planar lighting device described in this section, the receiving surface of the pedestal is formed on the first surface formed on the light incident surface side and on the front side of the first surface, and forward from the first surface side. A point-like light source in a state where the positional relationship between the light-emitting surface of the point-like light source and the light-incident surface of the light guide plate is stably maintained. The distance between the emission surface of the front part of the circuit board and the front end side of the circuit board fixed to the receiving surface of the pedestal is narrowed. In the planar lighting device described in this section, even when there is some leakage light from the inclined surface of the inclined portion, the leakage light travels to the exit surface side. It is possible to effectively prevent the reflection or absorption by the portion covering the surface and improve the uniformity of the luminance of the illumination light.

  In the planar lighting device described in this section, preferably, a light absorbing member or a light reflecting member is disposed on a portion of the mounting surface of the circuit board that covers at least the inclined surface of the inclined portion. Further, the uniformity of the luminance of the illumination light can be further improved.

(7) The planar illumination device according to (6), wherein the first surface of the pedestal is formed substantially perpendicular to the light incident surface. Item 7).

  According to the planar illumination device described in this section, in a state where the circuit board is fixed to the receiving surface of the pedestal, the light emitting surface of the point light source faces substantially parallel to the light incident surface of the light guide plate, thereby Light emitted from the light emitting surface of the light source can be efficiently incident on the light guide plate, and high brightness of the illumination light can be achieved.

(8) In the planar illumination device according to (6) or (7), the inclination angle of the second surface of the pedestal is smaller than the inclination angle of the inclined surface of the inclined portion. Lighting device (Claim 8).

  According to the planar illumination device described in this section, the area of the surface of the second surface is compared with the case where the inclination angle of the second surface of the pedestal is greater than or equal to the inclination angle of the inclined surface of the inclined portion. Since it can be widely used, the fixing area of the circuit board is increased, and the long-term stability of fixing to the light guide plate of the circuit board is improved.

  Further, in the configuration of the planar lighting device described in this section, the circuit board is configured by a flexible printed circuit board (FPC), and the FPC is defined as a boundary between the first surface and the second surface of the receiving surface of the base. In the case of arranging in a bent state, the reaction force due to the bending is reduced, which is a particularly advantageous configuration from the viewpoint of long-term stability of fixing to the light guide plate of the circuit board.

  According to the present invention, with the above configuration, a point light source having a light emitting surface that emits light forward, a circuit board having a mounting surface on which the point light source is mounted, and the point light source are arranged. A light guide plate having a light incident surface and a light guide plate having a light exit surface that emits light incident from the light incident surface in a planar manner, and reduces leakage light from the vicinity of the light incident surface of the light guide plate Thus, it is possible to achieve high brightness of the illumination light.

It is sectional drawing which shows typically the principal part of the planar illuminating device in 1st Embodiment of this invention. It is a partial expansion perspective view which shows the principal part of the light-guide plate which is a component of the planar illuminating device shown in FIG. (A) is the top view which looked at FPC which is a component of the planar illuminating device shown in FIG. 1 from the white coverlay film side, (b) and (c) are the elements on larger scale of (a). It is. (A) is the top view which looked at FPC which is a component of the planar illuminating device shown in FIG. 1 from the base film side, (b) is a light-guide plate which is a component of the same planar illuminating device. It is a principal part top view. It is sectional drawing which shows an example of the conventional planar illuminating device.

  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, the shape, size, and the like of each component are exaggerated as appropriate in order to facilitate understanding of the present invention.

  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 an FPC as a circuit board on which the LED 11 is mounted. (Flexible Printed Circuit Board) 31.

  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, the LED 11 has a surface (hereinafter also referred to as a bottom surface) 13 mounted on the FPC 31 and the light emitting surface 12 substantially orthogonal to each other. In the present embodiment, the three LEDs 11 are disposed along the light incident surface 22 with a predetermined distance from each other with the light emitting surface 12 facing a light incident surface 22 described later of the light guide plate 21 ( (See FIG. 2). Further, a gap g (for example, about 0.2 mm) is provided as a clearance for dealing with thermal deformation of the light guide plate 21 between the light emitting surface 12 of the LED 11 and the light incident surface 22 of the light guide plate 21. ing.

  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 surface 22 that is an end surface on the side where the LEDs 11 are disposed, a counter end surface 23 that is an end surface facing the light incident surface 22, and one of the light incident surfaces 22 that is substantially orthogonal to the light incident surface 22. It has a reflecting surface 24 that is a main plane and an exit surface 25 that is the other main plane that faces the reflecting surface 24 in parallel.

  In the present invention, the direction in which the light incident surface 22 faces the opposing end surface 23 (therefore, the direction in which the light emitting surface 12 of the LED 11 faces and also the light guiding direction) is “front”, and the reflecting surface 24 is the outgoing surface 25. The direction to face is defined as “upward”, and the direction (longitudinal direction of the light incident surface 22) orthogonal to the front-rear direction and the vertical direction (if necessary, “right” and “left” are defined forward. It is also called the left-right direction. Unless otherwise specified, “length”, “thickness (thickness)”, and “width” refer to dimensions in the front-rear direction, the up-down direction, and the left-right direction, respectively.

  In addition, as shown in FIG. 2, the light guide plate 21 includes a flat portion 26 formed forward from the light incident surface 22 and an inclined portion 27 formed continuously from the flat portion 26 and gradually decreasing in thickness toward the front. And an emission part 28 that is formed in front of the inclined part 27 and emits light from the LED 11 guided through the inclined part 27 from the emission surface 25.

  The flat portion 26 has a constant thickness in the forward direction, and is formed so that an upper surface 26 a that is a surface on the emission surface 25 side is substantially orthogonal to the light incident surface 22. 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 reflecting surface 24 side toward the front side, on the emitting surface 25 side along the longitudinal direction of the light incident surface 22.

  The emitting portion 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 reflecting surface 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 in a planar shape from the emitting surface 25.

  Note that a reflective sheet 51 is disposed on the reflective surface 24 side of the light guide plate 21 in order to return light leaking from the reflective surface 24 to the light guide plate 21 again. Although not shown, the planar illumination device 10 typically emits from the exit surface 25 to the exit surface 25 side of the exit portion 28, as in the conventional planar illumination device 100 shown in FIG. A diffusion sheet (152 in the example of FIG. 5) and a pair of prism sheets (153 and 154 in the example of FIG. 5) for controlling the directivity of the light are sequentially stacked. Moreover, the planar illumination device 10 may include a frame (141 in the example of FIG. 5) that houses each component, similarly to the conventional planar illumination device 100 shown in FIG.

  In the planar lighting device 10, the light guide plate 21 further includes a plurality of pedestals 29 (four in the present embodiment) formed on the inclined surface 27 a side of the inclined portion 27 and spaced from each other, and the light incident surface 22. It has a plurality of claw portions 30 (four in this embodiment) formed so as to protrude rearward from each other.

  The four pedestals 29 are for fixedly placing (mounting) the FPC 31. In the vicinity of the inclined surface 27a and the inclined surface 27a of the emission surface 25, the four pedestals 29 are arranged in front of the three LEDs 11 (shown by broken lines in FIG. 2). Are formed apart from each other so that they do not exist. The upper surface of each pedestal 29 functions as a receiving surface on which the FPC 31 is mounted, and is formed in front of the first surface 29a and the first surface 29a formed on the light incident surface 22 side. And a second surface 29b inclined toward the inclined portion 27 from the side toward the front. Further, the pedestal 29 is formed such that its top view shape becomes narrower toward the front at the front tip side.

Here, the thickness of each pedestal 29 is constant in the forward direction from the light incident surface 22 to the boundary with the second surface 29b, and the first surface constituting the upper surface of each pedestal 29 therebetween is provided. The surface 29 a is formed so as to be substantially orthogonal to the light incident surface 22. Further, the first surface 29a is formed substantially flush with the upper surface 26a of the flat portion 26. In other words, the first surface 29a of each pedestal 20 excludes the flat portion 26 from the front portion of the LED 11. The shape is extended forward.
The second surface 29b of each pedestal 29 is formed so as to be inclined more gently than the inclined surface 27a of the inclined portion 27, and the inclination angle of the second surface 29b of the pedestal 29 with respect to the emission surface 25 is The inclination angle of the inclined surface 27 a of the inclined portion 27 is smaller than the inclination angle with respect to the emission surface 25.

  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 surface 22 where the LEDs 11 face each other. The claw portion 30 is formed so that the upper surface 30 a thereof is substantially flush with the upper surface 26 a of the flat portion 26 and the first surface 29 a of the pedestal 29.

  In the case where the FPC 31 is partially joined to a part of the upper surface 26a of the flat portion 26, the first and second surfaces 29a and 29b of the pedestal 29, and the upper surface 30a of the claw portion 30, that portion Alternatively, a concave portion in which an adhesive (for example, a double-sided tape) is disposed may be provided on the surface portion to be joined.

  Next, the FPC 31 is laminated so as to cover the surface of the base film 32a, the conductive circuit 32b formed on one surface of the base film 32a, and the surface of the base film 32a on which the conductive circuit 32b is formed. It is comprised from the white coverlay film 32c stuck. Further, as shown in FIG. 3A, the FPC 31 is formed in a strip shape when viewed from above, and the width (the dimensions of the long sides 31b and 31c) is the same as the dimension in the longitudinal direction of the light incident surface 22 of the light guide plate 21. It is formed substantially the same.

  In the present invention, in the FPC 31, the surface of the base film 32a on which the conductive circuit 32b is formed is referred to as the mounting surface 31a of the FPC 31 including the conductive circuit 32b formed on the surface.

  In the planar illumination device 10, the LED 11 has a pair of terminals (not shown) arranged at both ends in the direction along the longitudinal direction of the light incident surface 22 of the light guide plate 21, and the conductive circuit 32 b of the FPC 31. Includes a pair of electrode pads 42 corresponding to the pair of terminals of the LED 11. The white coverlay film 32c is formed with a pair of substantially rectangular openings 41 so that the pair of electrode pads 42 of each LED 11 is exposed.

  Here, the white coverlay film 32c includes a white reflective layer over the entire surface, and the white coverlay film 32c itself functions as a light reflecting member. For example, the white reflective layer is formed by applying a white paint on the surface of the film substrate constituting the white coverlay film 32c on the side opposite to the surface to be attached to the mounting surface 31a. May be. Alternatively, the white coverlay film 32c may be configured of a film base material that has been whitened by, for example, dispersing a white pigment, and the film base material itself may form a white reflective layer.

  The FPC 31 forms the necessary opening 41 (for example, by punching) on the white coverlay film 32c previously provided with the white reflective layer over the entire surface, and then the white coverlay film 32c is mounted on the mounting surface. It sticks to 31a. Each LED 11 is mounted on the mounting surface 31a by joining corresponding terminals to a pair of electrode pads 42 exposed from the corresponding pair of openings 41 by soldering or the like. At this time, the three LEDs 11 are arranged along the long side 31c on the rear side of the FPC 31 in a state where the light emitting surface 12 is substantially orthogonal to the mounting surface 31a and substantially parallel to the long sides 31b and 31c. Has been implemented.

  Further, in the FPC 31, at least a part of the front part of the part where the LED 11 is mounted is on the light guide plate 21 (specifically, the upper surface 26a of the flat part 26 and the first and second surfaces 29a and 29b of the pedestal 29). Therefore, the dimension of the short side of the FPC 31 is long enough to have a part necessary for the fixed arrangement ahead of the part where the LED 11 is mounted.

Here, in the example shown in FIG. 3, the positions corresponding to the both end sides of the mounting surface 31 a are present in the opening 41 of the white coverlay film 32 c with respect to the left and right ends of the light emitting surface 12 of the LED 11. In addition, there is a portion that is not covered with the white coverlay film 32c until the outline of the opening 41 is reached immediately before the position corresponding to the both end sides of the mounting surface 31a.
However, among the positions corresponding to the light emitting surface 12 of the LED 11 on the mounting surface 31a, the portion between the pair of openings 41, in other words, the position corresponding to the central portion in the left-right direction of the light emitting surface 12 of the LED 11, There is a white coverlay film 32c that covers a region extending forward from the position.

  Thus, in the FPC 31, as shown in FIG. 3B, the white coverlay film 32c has a portion extending forward from the position corresponding to the central portion of the light emitting surface 12 of the LED 11 in the left-right direction. The structure which has arrange | positioned the light reflection member is implement | achieved in the 1st area | region 51 extended ahead from the position corresponding to the center part of the left-right direction of the light emission surface 12 of LED11 of the mounting surface 31a.

  In addition, although this invention is not limited by the length of the 1st area | region 51 extended ahead from the position corresponding to the light emission surface 12 of LED11, Preferably, the 1st area | region 51 is the light emission surface of LED11. 12 and the light entrance surface 22 of the light guide plate 21 have the same length as the gap g, and more preferably have a length equal to or greater than the gap g (FIG. 4B). As an example of the first region 51, the case where it has the same length as the gap g is shown).

  Of course, in the FPC 31, the light reflecting member is configured by the white coverlay film 32c, and the FPC 31 has a length that allows a portion to be disposed and fixed on the light guide plate 21 in the front portion of the LED 11. Therefore, regardless of whether the definition of the length of the first region 51 is longer or shorter than the gap g, the first region 51 is always provided with a light reflecting member that covers it. It has become.

  Moreover, in FPC31, a strip | belt-shaped part is formed between a pair of opening parts 41 of the white coverlay film 32c. Therefore, in the FPC 31, the presence of this band-like portion on the white coverlay film 32c corresponds to the center portion of the mounting surface 31a of the FPC 31 in the left-right direction of the light emitting surface 12 of the LED 11, as shown in FIG. A configuration in which a light reflecting member is arranged in a second region 55 including a portion (hereinafter also simply referred to as a front portion) 52 and a portion (hereinafter also simply referred to as a rear portion) 53 that extends forward from a position where the light reflection is performed is realized. Has been.

  Here, in the FPC 31, the opening 41 is formed so as to form an R portion in which the four corners of the rectangle that forms the outline are rounded. Therefore, the front end side of the band-shaped portion formed between the pair of openings 41 of the white coverlay film 32c spreads toward the front in accordance with the shape of the R portions 43 of the pair of openings 41 facing each other. It has a shape that spreads out. Therefore, in the FPC 31, a configuration in which the light reflecting member is arranged in the front portion 52 of the second region 55 including the portion that spreads toward the front by the front end side of the band-like portion of the white coverlay film 32c is realized. ing.

As shown in FIG. 4, in the FPC 31 on which the LED 11 is mounted, the light emitting surface 12 of the LED 11 faces a predetermined position (between adjacent claw portions 30, 30) on the light incident surface 22 of the light guide plate 21. And the light incident surface 22 of the light guide plate 21 are bonded and fixed on the light guide plate 21 while being aligned so that a predetermined gap g is provided.

At this time, the first and second surfaces 29a and 29b of the pedestal 29, the upper surface 26a of the flat portion 26, and the upper surface 30a of the claw portion 30 (the hatched portion in FIG. 4B) are the white coverlay film 32c of the FPC 31. It becomes a joint surface (contact surface). 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 is not a part of the upper surface 26a of the light incident part 26, the first and second surfaces 29a and 29b of the pedestal 29, and the entire upper surface 30a of the claw part 30. You may make it join.

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

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

  The planar lighting device 10 includes the white coverlay film 32c (light reflecting member) of the FPC 31 that has a portion disposed in the first region 51 of the mounting surface 31a. At least a part of the light incident on the portion covering the gap g between the light guide plate 21 and the light incident surface 22 is reflected by the portion disposed in the first region 51 of the cover lay film 32 c and is reflected on the light guide plate 21. Since the light is incident on the light incident surface 22, it is possible to reduce the light transmitted through the FPC 31 through the portion covering the gap g of the FPC 31 or absorbed by the FPC 31, thereby achieving high brightness of the illumination light.

  In general, in the LED 11, the LED chip (die) is housed in a position corresponding to the center of the light emitting surface 12 of the lamp house, and the emitted light from the LED 11 has a relatively high directivity from the center of the light emitting surface 12. Is emitted forward. Therefore, in the planar lighting device 10, the coverlay film 32 c is disposed in the first region 51 that extends forward from the position corresponding to the central portion of the light emitting surface 12 of the LED 11 on the mounting surface 31 a of the FPC 31. The presence of the portion is an advantageous configuration for achieving a high brightness of the illumination light by causing most of the light incident on the portion covering the gap g of the FPC 31 to enter the light reflecting member.

  In general, the lamp house of the LED 11 is made of a white resin. In addition to the light emitted from the light emitting surface 12, the LED 11 includes a certain amount of light leaked from the lamp house. However, in the planar illumination device 10, the white coverlay film 32 c has a portion disposed in the rear portion 53 of the second region 55 of the mounting surface 31 a of the FPC 31, and therefore, the LED 11 of the mounting surface 31 a of the FPC 31. The light reflecting member is also disposed on the portion corresponding to the bottom surface 13 (the surface facing the mounting surface 31a when mounted on the FPC 31), and at least a part of the leaked light from the bottom surface of the LED 11 is caused by the light reflecting member. Since the light is reflected and enters the light incident surface of the light guide plate 32, it is possible to achieve higher luminance of the illumination light.

  Furthermore, in the planar lighting device 10, the white coverlay film 32c has a portion disposed in the front portion 52 of the second region 55 of the mounting surface 31a of the FPC 11, and the front portion 52 is directed forward. Since it has a shape that spreads in a divergent shape, it efficiently reflects the portion of the light emitted from the LED 11 that travels forward with a certain spread angle, and achieves higher brightness of the illumination light. It becomes possible.

  Here, in the planar lighting device according to the present invention, as long as the light reflecting member disposed on the circuit board includes a portion disposed in the first region 51 of the mounting surface 31a, the white coverlay film 32c is not necessarily included. It may not be constituted by, and may be constituted by any appropriate means.

However, like the planar lighting device 10, the light reflecting member is configured by the white coverlay film 32c after, for example, forming an FPC having a normal coverlay film (without a white reflective layer). Compared with the configuration in which the light reflecting member is arranged by applying white printing on the surface of the coverlay film, the following advantages are obtained.

  That is, after forming an opening for exposing the electrode pad to the normal coverlay film, the coverlay film is laminated and pasted on the mounting surface of the base film, and then the surface of the coverlay film is white. When printing is performed, the printing range is determined from a range including the entire pair of openings (and the LED mounting range) in consideration of the printing positioning accuracy, and a margin of a certain dimension (usually about 0.4 mm) is provided. It is common to take and set. Therefore, in this method, it is actually difficult to perform white printing on the first region 51 extending forward from a position corresponding to the central portion of the light emitting surface 12 of the LED 11. The same applies to the second region 55 having a portion 53 extending rearward from a position corresponding to the central portion of the light emitting surface 12 of the LED 11.

  On the other hand, the FPC 31 in the planar illumination device 10 mounts the white coverlay film 32c after forming a necessary opening 41 with respect to the white coverlay film 32c previously provided with a white reflective layer over the entire surface. Since the FPC 31 is attached to the surface 31a, the light reflecting members arranged in the first region 51 and the second region 55 of the mounting surface 31a are attached to the white coverlay film 32c. It will be incorporated at the same time.

  Moreover, in the FPC 31, the positioning in the left-right direction when the LED 11 is mounted on the mounting surface 31a is based on the opposite sides of the pair of openings 42 of the white coverlay film 32c (sides that define the width e of the belt-like portion). As a result, the band-shaped portion is always the central portion of the light emitting surface 12 of the LED 11 in the left-right direction regardless of the positioning accuracy of the sticking to the mounting surface 31a of the white coverlay film 32c. It is arranged with high accuracy at a position corresponding to.

  In the FPC 31, the light reflecting member made of the white coverlay film 32 c includes a first region 51 extending forward from a position corresponding to the central portion in the left-right direction of the light emitting surface 12 of the LED 11, and the light emitting surface 12 of the LED 11. This means that the second region 55 having a portion 53 extending rearward from a position corresponding to the central portion in the left-right direction is always arranged with high accuracy along the left-right direction.

  In addition, in the FPC 31, a portion disposed in the first region 51 of the white coverlay film 32c and a portion disposed in the rear portion 53 of the second region 55 are continuously formed by the band-shaped portion. Therefore, even when the LED 11 is mounted on the mounting surface 31a, even if the position in the front-rear direction is shifted, the white coverlay film 32c has the first extending forward from the position of the light-emitting surface 12 shifted in the front-rear direction. There is always a portion arranged in the rear portion 53 of the first region 51 and the second region 55.

This is because, in the FPC 31, even if the mounting position of the LED 11 is shifted in the front-rear direction, the light reflecting member made of the white coverlay film 32c is from the position corresponding to the central portion of the light emitting surface 12 of the LED 11 in the left-right direction. With respect to the first region 51 extending forward and the rear portion 53 of the second region 55 extending rearward from the position corresponding to the central portion of the light emitting surface 12 of the LED 11 in the left-right direction, always along the front-rear direction. It means that it is arranged with high accuracy.

  As described above, in the planar illumination device 10, the light reflecting member disposed on the FPC 31 is configured from the white coverlay film 32 c, thereby being disposed in the first region 51 and the second region 55 of the mounting surface 31 a. The light reflecting member can be easily formed. Furthermore, by configuring the light reflecting member arranged in the FPC 31 from the white coverlay film 32c, it becomes possible to arrange the light reflecting member with respect to the first region 51 and the second region 55 with high accuracy. As a result, the luminance of the illumination light can be stabilized at a high level without causing variations among apparatuses.

  Here, in the planar illumination device 10, the conventional planar illumination device shown in FIG. 5 will be described with respect to the effects of the pedestal 29 having the inclined portion 27 and the first and second surfaces 29 a and 29 b provided on the light guide plate 21. It will be as follows if compared with 100.

  In the state lighting device 100 shown in FIG. 5, in a state where the FPC 131 is fixed to the pedestal 129, the light emitting surface 112 of the LED 111 faces substantially parallel to the light incident surface 122 of the light guide plate 121. It is possible to efficiently enter the light into the light guide plate 121 without generating leakage light, and it is possible to achieve higher brightness of the illumination light.

  Furthermore, in the state lighting device 100, in a state where the FPC 131 is fixed to the pedestal 129, a gap is formed between the inclined surface 127a of the front portion of the LED 111 and the surface 131a on the side facing the inclined surface 127a of the FPC 131. Further, the light that enters the light guide plate 121 and is reflected by the inclined surface 127a is suppressed from being absorbed by the FPC 131, and the effect of increasing the luminance of the illumination light is also achieved.

  Here, in the planar illumination device 100, some light is emitted as leakage light from the inclined surface 127a of the inclined portion 127, and the leakage light travels toward the emission surface 125, whereby the uniformity of the illumination light. May be damaged. Therefore, in the planar lighting device 100, the light absorbing member 132 is disposed on the FPC 131 so as to cover at least a part of the inclined surface 127a of the light guide plate 121 and the vicinity of the inclined surface 127a of the emission surface 125. Even if some light leaks from the inclined portion 127, the light absorbing member 132 absorbs the leaked light to improve the uniformity of the illumination light.

  Although this configuration has a certain effect in improving the uniformity of illumination light, there is room for improvement in the following points. That is, in the example of the planar lighting device 100, since the FPC 131 is fixed to the pedestal 29a having the upper surface 122a perpendicular to the light incident surface 122, the inclined surface 127a of the inclined portion 127 and the FPC 131 are positioned in front of the LED 111. The distance increases toward the front, and the front side of the inclined surface 127a is opened by the height D from the emission surface 125 of the pedestal 29 on the tip side of the pedestal 29 (the boundary portion with the emission surface 125). It is the composition which is.

  As a result, even if the light absorbing member 132 is disposed on the FPC 131, the leakage light from the inclined surface 127a of the inclined portion 127 proceeds to the emission surface 125 side without being absorbed by the light absorbing member 132, and the luminance is uniform. In some cases, it becomes noise light that impairs performance.

  On the other hand, in the planar lighting device 10 according to the present embodiment, the receiving surface on which the FPC 31 of the pedestal 29 is mounted includes the first surface 29a formed on the light incident surface 22 side of the light guide plate 21, and the first surface 29a. The second surface 29b is formed in front of the first surface 29a and is inclined from the first surface 29a side toward the front side toward the inclined portion 27 side. With this configuration, in the planar illumination device 10, the gap between the emission surface 25 in the front portion of the LED 11 and the front end side of the FPC 31 fixed to the receiving surfaces 29 a and 29 b of the pedestal 29 is narrowed. Even if there is some leakage light from the inclined surface 27a, the leakage light travels toward the emission surface 25 side, and is reflected by the white coverlay film 32c disposed on the portion covering the inclined surface 27a of the FPC 31. Therefore, it is possible to effectively prevent and improve the uniformity of the luminance of the illumination light.

  In addition, in FIG. 1 (and FIG. 2), the opening which has slight height d from the output surface 25 exists in the front end side (boundary part of the 2nd surface 29b and the output surface 25) of the base 29. FIG. This height d is at least smaller than the height from the emission surface 25 to the first surface 29a of the pedestal 29 (corresponding to the height D shown in FIG. 5). However, the planar illumination device 10 may be one in which the pedestal 29 is formed so that the height d becomes zero, thereby improving the uniformity of the luminance of the illumination light. .

  Further, in the planar illumination device 10, the FPC 31 is provided with a light reflecting member made of a white coverlay film 32 c on a portion covering the inclined surface 27 a and the vicinity of the inclined surface 27 a of the emission surface 25. At least a part of the light reflected from the white coverlay film 32c out of the light leaked from the surface 27a is incident on the light guide plate 21 again and can be used as illumination light. Therefore, in the planar lighting device 10, the configuration in which the second surface 29b is provided on the receiving surface on which the FPC 31 of the pedestal 29 is mounted also contributes to higher illumination light.

  However, as described above, in the circuit board according to the present invention, it is sufficient that the light reflecting member is disposed at least in the first region 51. Further, in a preferred embodiment, the first region 51 and the second region are provided. 55, and in a more preferred embodiment, the light reflecting member only needs to be disposed in the first region 51 and the front region 52 and the rear region 53 of the second region 55. Therefore, the inclined surface 27a of the FPC 31 In addition, the light reflecting member may be arranged in a part or all of the portion covering the vicinity of the inclined surface 27a of the emission surface 25.

In this case, for example, the white coverlay film 32c of the FPC 31 is positioned rearward from the position corresponding to the light incident surface 22 when being placed on the light guide plate 21 (the portion on which the LED 11 is mounted) 34 (FIG. 4A). As a configuration provided with a white reflective layer only in the reference), the front portion (the upper surface 26a of the flat portion 26 and the first and second surfaces 29a and 29b of the base 29 from the position corresponding to the light incident surface 22 is provided. The portion including the portion to be disposed 33 (see FIG. 4A) may be configured as a normal coverlay film that does not include a white reflective layer.
In this configuration, the progress of the leaked light from the inclined surface 27a toward the emission surface 25 side is mainly prevented by absorption by the portion covering the inclined surface 27a of the FPC 31, thereby making the luminance uniformity of the illumination light uniform. Will improve.

  Furthermore, preferably, in order to more effectively absorb the leak light from the inclined surface 27a of the inclined portion 27 by the portion covering the inclined surface 27a of the FPC 31, at least a part of the portion 33 located in front of the coverlay film 32c. The light absorbing member (for example, black paint) may be preferably disposed all over.

  In the case where a light absorbing member is applied to the front portion 33 of the cover lay film 32c, the cover lay film 32c is provided with a white reflective layer on the front portion 33 as well. The member may be disposed so as to overlap the white reflective layer. Moreover, a light absorption member is not limited to a black coating material, For example, the film which has a diffusibility may be arrange | positioned as a light absorption member.

  Further, in the planar lighting device 10, the first surface 29 a of the pedestal 29 is formed substantially perpendicular to the light incident surface 22 of the light guide plate 21 together with the upper surface 26 a of the flat portion 26 and the upper surface 30 a of the claw portion 30. Therefore, in a state where the FPC 31 is fixed on the light guide plate 21, the light emitting surface 12 of the LED 11 faces substantially parallel to the light incident surface 22 of the light guide plate 21. Conventionally, it is possible to efficiently enter the light emitted from the light source 12 into the light guide plate 21 without causing leakage light, and to achieve high brightness of the illumination light. While maintaining the level equivalent to that of the planar illumination device 100, the above-described luminance uniformity can be further improved.

  In addition, in the planar illumination device 10, as in the conventional planar illumination device 100, in a state where the FPC 31 is fixed on the light guide plate 21, the inclined surface 27 a of the front portion of the LED 11 and the coverlay film 32 c of the FPC 31 Since a gap is formed between the surface and the surface, the light that enters the light guide plate 21 and is reflected by the inclined surface 27a is suppressed from being absorbed by the FPC 31, and the brightness of the illumination light is increased. This effect is obtained particularly when the white coverlay film 32c of the FPC 31 is configured not to include the white reflective layer in the front portion 33 from the position corresponding to the light incident surface 22. This is advantageous in achieving high brightness.

  In the planar lighting device 10, the first surface 29 a formed on the light incident surface 22 side of the light guide plate 21 and the first surface 29 a are formed on the receiving surface of the pedestal 29, and the first surface 29 a is formed. Since the second surface 29b is inclined from the surface 29a side toward the front toward the inclined portion 27 side, the FPC 31 is at a corresponding folding position f at the boundary between the first surface 29a and the second surface 29b. The second surface 29b is bent along the inclination of the first surface 29a, and is fixed on the first and second surfaces 29a, 29b of the pedestal 29.

  Therefore, in order to reduce the reaction force of the bending and improve the long-term stability of fixing the FPC 31 to the light guide plate 21, the second surface 29b of the pedestal 29 is gently set with respect to the first surface 29a. It is preferable to configure so as to be inclined (in other words, the inclination angle of the second surface 29b with respect to the emission surface 25 is reduced).

  As a result, the reaction force of the bending of the FPC 31 at the bending position f is reduced, and the area of the second surface 29b can be increased, so that the fixing area of the FPC 31 is increased and the FPC 31 is fixed to the light guide plate 21. Improves long-term stability. In the planar illumination device 10, the configuration in which the inclination angle of the second surface 29 b of the pedestal 29 (relative to the emission surface 25) is smaller than the inclination angle of the inclined surface 27 a of the inclined portion 27 is from this point of view. This is advantageous compared to the case where the inclination angle of the second surface 29b (relative to the emission surface 25) is equal to or greater than the inclination angle of the inclined surface 27a of the inclined portion 27.

  However, in the planar illumination device 10, the second surface 29 b of the pedestal 29 is necessary when considering the characteristics of the FPC 31, the specifications of the emission surface 25, and / or the appropriate length of the first surface 29 a, etc. The inclination angle may be equal to or greater than the inclination angle of the inclined surface 27a of the inclined portion 27.

  In the planar lighting device 10 configured as described above, the configuration in which the pedestal 29 is provided with the first surface 29a and the second surface 29b as described above is, for example, without providing the pedestal 29. Compared with the configuration in which the flat portion 26 in front of the LED 11 is extended forward and the FPC 31 is disposed and fixed on the upper surface 26a of the flat portion 26 and the inclined surface 26a of the inclined portion 27, the formation position of the inclined portion 27 is changed. As a result of shifting to the front, it is advantageous in that the uniformity of luminance is further improved while maintaining the narrow frame of the planar illumination device without narrowing the effective emission area of the emission surface 25.

  Furthermore, the light emitted from the emission surface 12 of 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 the planar lighting device 10, the configuration in which the pedestal 29 is formed so that the width becomes narrower toward the front on the front tip side in a top view is wider as the distance from the adjacent pedestal 29 goes forward. The area of the first surface 29a and the second surface 29b of the pedestal 29 is increased as much as possible without hindering the light guided through the inclined portion 27, and the adhesive strength between the FPC 31 and the light guide plate 21 is increased. This is advantageous in that it can be 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-described embodiment, the pedestal 29 is formed so that the tip thereof has a length that extends to the vicinity of the inclined surface 27a of the emission surface 25. In the planar illumination device according to the present invention, The front tip portion does not necessarily extend to the emission surface 25, and takes into consideration the design conditions such as the length of the first surface 29a, the inclination angle of the second surface 29b, and the height d on the tip side as described above. In addition, the length of the pedestal 29 may be configured to be the same as or shorter than the length of the inclined surface 27a.

  Moreover, in the said embodiment, although the gradient of the inclined surface 27a of the inclined part 27 is illustrated as constant, the gradient of the inclined surface 27a of the inclined part 27 changes continuously toward the front in the light guide direction. There may be. In the planar lighting device according to the present invention, the presence of the flat portion 26 and the claw portion 30 is not essential from the viewpoint of optical functions, and the flat portion 26 and the claw portion 30 may be omitted. It ’s good.

  Further, in the above embodiment, the FPC 31 according to the present invention includes the inclined portion 27 whose thickness gradually decreases from the light incident surface 22 side toward the front, the first surface 29a and the second surface on which the FPC 31 is fixedly disposed. Although the structure applied with respect to the light-guide plate 21 provided with the base 29 which has 29b is illustrated, the planar illumination device which concerns on this invention is not provided with the inclination part in the light-incidence surface side (typical) The circuit board (for example, FPC31) according to the present invention is fixedly disposed on the light emitting surface side or the reflective surface side near the light incident surface. It may be a thing.

Alternatively, the planar illumination device according to the present invention has an inclined portion 127 whose thickness gradually decreases from the light incident surface 122 side toward the front and the light incident surface 122 as in the planar illumination device 100 shown in FIG. A light guide plate 121 having a pedestal 129 having only a substantially vertical upper surface 129a is provided, and the upper surface 129a of the pedestal (and the upper surface 126a of the flat portion 126 and the upper surface 130a of the claw portion 130, if any) is provided. The circuit board (for example, FPC 31) according to the present invention may be fixedly arranged.

10: planar illumination device, 11: point light source (LED), 12: light emitting surface, 21: light guide plate, 22: light incident surface, 25: light exit surface, 27: inclined portion, 27a: inclined surface, 29: pedestal , 29a: first surface, 29b: second surface, 31: circuit board (FPC), 32c: light reflecting member (white coverlay film), 51: first region, 55: second region

Claims (8)

  From a point light source having a light emitting surface that emits light toward the front, a circuit board having a mounting surface on which the point light source is mounted, a light incident surface on which the point light source is disposed, and the light incident surface In a planar lighting device comprising a light guide plate having an exit surface that emits light that has been incident into a planar shape, the circuit board has at least a part of a front portion of the portion on which the point light source is mounted. The light reflecting member is disposed on the mounting surface, and the region where the light reflecting member is disposed on the mounting surface is located at the center of the light emitting surface of the point light source. A planar illumination device comprising a first region extending forward from a corresponding position.   The region where the light reflecting member is disposed on the mounting surface of the circuit board includes a second region having a portion extending rearward from a position corresponding to the central portion of the light emitting surface of the point light source. The planar illumination device according to claim 1.   The planar lighting device according to claim 1, wherein the light reflecting member is formed of a coverlay film that covers a mounting surface of the circuit board.   The light reflecting member includes a coverlay film that covers a mounting surface of the circuit board, and the point light source includes a pair of terminals disposed at both ends in a direction along the longitudinal direction of the light incident surface of the light guide plate. The light reflecting member disposed in the second region has a pair of openings so that a pair of electrode pads corresponding to the pair of terminals of the point light source is exposed on the coverlay film. The planar illumination device according to claim 2, wherein the planar illumination device is provided between the pair of openings by forming a portion.   The second region has a portion extending forward from a position corresponding to the central portion of the light emitting surface of the point light source, and the portion extending forward includes a portion that widens toward the front. The planar illumination device according to claim 4.   The light guide plate has an inclined portion whose thickness gradually decreases from the light incident surface side toward the front, and on the inclined surface side of the inclined portion, in a region excluding the front portion of the point light source, A pedestal having a receiving surface on which the circuit board is disposed is formed, and the receiving surface of the pedestal is formed on a first surface formed on the light incident surface side and in front of the first surface, The planar illumination device according to any one of claims 1 to 5, further comprising a second surface inclined forward from the first surface side toward the inclined portion side.   The planar illumination device according to claim 6, wherein the first surface of the pedestal is formed substantially perpendicular to the light incident surface.   The planar illumination device according to claim 6 or 7, wherein an inclination angle of the second surface of the pedestal is smaller than an inclination angle of the inclined surface of the inclined portion.

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