JP2007095555A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device having a superior heat radiation efficiency while suppressing increase in thickness dimension and capable of securing freedom in selection of light emitting diodes. <P>SOLUTION: The light emitting device comprises a light source 7 consisting of a light emitting diode, a light guide plate 4 having a light receiving face 43a to introduce the light from this light source 7 and an irradiation surface 41 to surface emit by the light introduced from this light receiving face 43a, and a circuit board 6 to supply power to the light source 7. The circuit board 6 is arranged so that its board surface may extend in the extension direction of the irradiation surface 41, and a light source holder (structure) 8 which supports the light source 7 on the circuit board 6 so that its light emitting face 76 may be opposed to the light receiving face 43a and connects the light source 7 and the circuit board 6 electrically and thermally is provided between the light source 7 and the circuit board 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting device that illuminates a light receiving display panel made up of, for example, a liquid crystal panel, and more particularly to a light emitting device that uses a light source made up of a light emitting diode as a light source.

This type of light source device is called a backlight device that illuminates the light receiving display panel from the back or a front light device that illuminates the light receiving display panel from the surface, and various devices have been proposed. For example, those described in Patent Documents 1 and 2 below are known as examples of the backlight device. The backlight device described in Patent Document 1 includes a light guide plate extending along a liquid crystal panel, a plurality of light sources arranged to face each other along a side end surface (light receiving surface) of the light guide plate, and the plurality of light sources. A circuit board for supporting and supplying power. As a light source, a top-view type light-emitting diode is used in which the light-emitting surface faces the direction perpendicular to the surface of the mounted object when mounted on an object to be mounted (mounted) such as a circuit board. The circuit board on which the light-emitting diode is mounted is arranged in a direction perpendicular to the extending direction of the light guide plate and is arranged along the side end surface of the light guide plate, so that the top view type light emission The light emitting surface of the diode is configured to face the side end surface of the light guide plate.
On the other hand, similarly to the backlight device described in Patent Document 2, a light guide plate extending along the liquid crystal panel, and a plurality of light sources arranged to face each other along a side end surface (light receiving surface) of the light guide plate, Although the circuit board which supports these several light sources and supplies electric power is provided, the type of light source and the direction of a circuit board differ from patent document 1. FIG. That is, as a light source, a side-view type light-emitting diode whose light-emitting surface faces the extending direction of the surface of the mounting object when mounted on a mounting object such as a circuit board is adopted. The circuit board on which the diode is mounted has a configuration in which the light emitting surface of the side view type light emitting diode is opposed to the side end surface of the light guide plate by arranging the substrate surface in parallel with the extending direction of the light guide plate. It has become.
JP 2002-90735 A JP 2005-190942 A

By the way, in a light-emitting device using a light-emitting diode as a light source, it is necessary to suppress heat generation of the light-emitting diode itself in order to secure the light emission intensity, and in many cases, a heat dissipation pattern is formed on a circuit board. In other words, the heat dissipation of the light emitting diode is radiated through the circuit board by increasing the contact area with the circuit board. For this reason, considering heat dissipation, it is necessary to make the circuit board large to some extent, but in the case of the backlight device described in Patent Document 1, the circuit board extends in a direction perpendicular to the extending direction of the light guide plate. Because of the existing configuration, when the circuit board is made large, there is a problem that the thickness dimension of the device increases.
On the other hand, in the case of the backlight device described in Patent Document 2, since the circuit board is configured to extend in parallel with the extending direction of the light guide plate, the thickness dimension can be suppressed even if the circuit board is large. Since the type of light emitting diode is used, there is a problem in that the degree of freedom of product selection is reduced and the cost is increased. In other words, the side view type light emitting diodes are less in number than the top view type, and it is not possible to select a suitable type (dimensions, characteristics, etc.) from commercially available products (decrease in product selection flexibility), There was a case where it became a custom-made product and the cost was increased.
Accordingly, the main object of the present invention is to provide a light-emitting device that has good heat dissipation efficiency while suppressing an increase in the thickness dimension, and that can ensure a degree of freedom in selecting a light-emitting diode.

  In order to achieve the above object, the present invention provides a light guide plate having a light source composed of a light emitting diode, a light receiving surface for introducing light from the light source, and an irradiation surface for emitting light from the light introduced from the light receiving surface, A circuit board that supplies power to a light source, the circuit board is disposed such that a surface of the circuit board extends in an extending direction of the irradiation surface, and the light source emits light between the light source and the circuit board. A structure is provided which is supported on the circuit board such that a surface thereof faces the light receiving surface and electrically and thermally connects the light source and the circuit board.

  In the invention, it is preferable that the circuit board supports at least the light guide plate.

  In addition, the present invention is characterized in that it has a support body that supports at least the circuit board and the light guide plate, and the support body and the circuit board are in contact with each other through a heat conductor.

  Further, the invention is characterized in that the circuit board extends to a position where it overlaps at least a part of the light guide plate in the thickness direction.

  In the invention, it is preferable that the circuit board has a bent portion.

  Further, the invention is characterized in that no wiring pattern is located at the bent portion.

  Further, the invention is characterized in that a light reflecting layer is provided at least in a region facing the light guide plate on the circuit board.

  Further, the invention is characterized in that the light source comprises a surface mount type light emitting diode having a conducting portion electrically connected to the structure on the side opposite to the light emitting surface.

  According to the present invention, it is possible to provide a light-emitting device that can achieve the initial purpose, has good heat dissipation efficiency while suppressing an increase in thickness, and can secure a degree of freedom in selecting a light-emitting diode.

  Embodiments will be described below with reference to the drawings, taking as an example a display device to which a light source device according to the present invention is applied. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a perspective view of a display device according to the present embodiment, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. FIG.

  The display device according to the present embodiment includes a frame 1, a display panel 2, an optical film 3, a light guide plate 4, a reflection film 5, a circuit board 6, a light source 7, a light source holder (structure) 8, A support 9 and a heat conductive sheet (heat conductor) 10 are provided.

  The frame 1 is made of a light-shielding synthetic resin, and supports the positioning of the display panel 2 and the optical film 3, and stores each component from the optical film 3 to the heat conductive sheet 10 in combination with the support 9. The housing (housing | casing) to comprise is comprised.

  The display panel 2 is composed of, for example, a TFT (thin film transistor) type liquid crystal display panel, and displays predetermined information as the light source 7 is turned on.

  The optical film 3 is, for example, arranged on the light guide plate 4 on the back side of the display panel 2 so that the two prisms for increasing brightness in which the prism rows having a triangular cross section are formed at regular intervals are orthogonal to each other. Has been.

  The light guide plate 4 includes, for example, a transparent resin (for example, acrylic resin) having a good light transmittance, an irradiation surface 41, an opposing surface 42 facing the irradiation surface, and four connecting the opposing surface 42 and the irradiation surface 41. It is formed on a rectangular plate having a side end face 43 and is disposed on the back side of the display panel 2 with the optical film 3 interposed therebetween.

  The irradiation surface 41 is a flat surface extending along the panel surface (back surface side) of the display panel 2, and the facing surface 42 is a flat surface extending in parallel with the irradiation surface 41. Of the four side end surfaces 43, a predetermined (one in this case) side end surface 43 is formed as a light receiving surface 43 a that faces the light source 7 and takes light from the light source 7 into the light guide plate 4. The irradiation surface 41 emits light with the light taken from the light receiving surface 43a.

  The reflective film 5 is made of, for example, a white synthetic resin film, and is disposed so as to be in close contact with the opposite surface 42 on the back side of the light guide plate 4, and reflects the light in the light guide plate 4 to the irradiation surface side.

  The circuit board 6 includes, for example, a metal substrate 61 such as aluminum, an insulating layer 62 provided on the substrate 61, a wiring pattern 63 provided on the insulating layer 62, and a part of the wiring pattern 63. It is made of a metal substrate having an insulating coating 64 that exposes and is located on the back surface side of the reflective film 5 so that the substrate surface extends in the extending direction of the irradiation surface. The wiring pattern 63 forms at least a power feeding path to the light source 7.

  The light source 7 is composed of a so-called top-view type surface-mounted light-emitting diode chip in which the light-emitting surface (described later) faces the light-receiving surface 43a of the light guide plate 4 and the side opposite to the light-emitting surface is a conductive portion (described later). A plurality are arranged. Each of these light sources 7 includes a housing 72 made of an insulating synthetic resin material having a recess 71 opened on one surface, a semiconductor light emitting element (bare chip) 73 disposed in the recess 71 of the housing 72, and the semiconductor light emission. Wiring members 74 and 75 made of a metal material serving as a power common path to the element 73 are provided. The light emitting surface 76 is disposed opposite to the light receiving surface 43 a of the light guide plate 4 with the release side of the recess 71 as a light emitting surface 76. Is done. Further, the wiring members 74 and 75 have one end thereof exposed to the recess 71 and mounted with the semiconductor light emitting element 73, or wire bonded to the semiconductor light emitting element 73, and the other end via the side wall surface of the housing 72. The bottom wall surface, that is, the wall surface on the side opposite to the light emitting surface 76, and conductive portions 77 and 78 exposed to the outside of the housing 72 are formed. The recess 71 is sealed with a light-transmitting resin such as an epoxy resin or a silicone resin.

  The light source holder 8 is located between the light source 7 and the circuit board 6, supports the light source 7 on the circuit board 6 so that the light emitting surface 76 faces the light receiving surface 43 a, and supports the light source 7 and the circuit board 6. It consists of a structure that is electrically and thermally connected, and is provided for each light source 7.

  The light source holder 8 is composed of a main body portion 81 made of an insulating synthetic resin such as ceramic, heat-resistant polymer or ABS, and a pair of conductive members 82 and 83 made of a conductive material held by the main body portion 81. When the light emitting surface 76 of the light source 7 and the light receiving surface 43a of the light guide plate 4 are opposed to each other, the light emitting surface 76 of the light source 7 also functions as a spacer for setting the light emitting surface 76 at an appropriate position with respect to the light receiving surface 43a of the light guide plate 4.

  The main body 81 is formed in a substantially rectangular parallelepiped shape, and has a light source mounting surface 84 facing the bottom wall surface of the light source 7 (housing 72) and the conducting portions 77 and 78, and a substrate mounting surface 85 facing the circuit board 6. The conductive members 82 and 83 have first ends exposed at the light source mounting surface 84 to form first connection portions 86 and 87 soldered to the conductive portions 77 and 78 of the light source 7, and the other end sides thereof. Forms second connection portions 88 and 89 that are exposed on the substrate mounting surface 85 and soldered to the wiring pattern 63 of the circuit board 6 (the second connection portion 88 overlaps the second connection portion 89). The lead line is indicated by a dotted line in the figure).

  Since the main body 81 is soldered as described above (for example, soldering by reflow means), the first connecting portions 86 and 87 are in close contact with the conducting portions 77 and 78 of the light source 7, and the second connecting portion. Naturally, 88 and 89 are in close contact with the wiring pattern 63 of the circuit board 6, but part of the light source mounting surface 84 is on the bottom wall surface of the light source 7 (housing 72) and part of the substrate mounting surface 85 is on the circuit board. 6 (insulating coating 64) respectively, and contact surface CF is formed. Since the contact surface CF with the circuit board 6 overlaps with the connection portion 89, a lead line is indicated by a dotted line in the figure.

  The support 9 is formed by bending an end portion of a plate material made of a metal material into a substantially L shape to form a bent portion 91, and by combining with the frame 1 as described above, the heat conductive sheet 10 is formed from the optical film 3. A housing that accommodates each of the constituent elements is formed, and functions as a back cover or chassis that supports these constituent elements from the back side.

  The heat conductive sheet 10 is made of a pressure sensitive adhesive sheet based on a material having good heat conduction efficiency, for example, a silicone elastomer or an acrylic elastomer.

  In the display device configured as described above, the light source 7 is held on the circuit board 6 via the light source holder 8, and the light emitting surface 76 faces the light receiving surface 43 a of the light guide plate 4. The power supply to the light source 7 is performed through the wiring pattern 63 of the circuit board 6 → the conductive members 82 and 83 of the light source holder 8 → the wiring members 74 and 75 of the light source 7, while the heat generated from the light source 7 supplies these powers. In addition to the path (the wiring members 74 and 75 of the light source 7 → the conductive members 82 and 83 of the light source holder 8 → the wiring pattern 63 of the circuit board 6), the contact surfaces CF (the bottom wall surface of the light source 7 and the light source of the light source holder 8 The contact surface CF with the mounting surface and the contact surface CF between the substrate mounting surface of the light source holder 8 and the circuit substrate 6), and then guided to the support 9 through the heat conductive sheet 10 and externally. The heat is introduced into the atmosphere or by a heat sink (not shown) to dissipate heat, and the contact surface CF may be eliminated if the heat dissipation effect can be sufficiently obtained with only the power supply path. Although it is effective to increase the area, the area of the power supply path may be limited to the minimum necessary area if the heat radiation effect can be sufficiently obtained with only the contact surface CF. In addition to the surface CF, a dedicated heat radiation path may be provided using various conductive materials and heat transfer materials.

  As described above, this embodiment has a light guide 7 having a light source 7, a light receiving surface 43 a for introducing light from the light source 7, and an irradiation surface 41 for surface emitting with light introduced from the light receiving surface 43 a. An optical plate 4 and a circuit board 6 for supplying power to the light source 7 are provided. The circuit board 6 is arranged so that the board surface extends in the extending direction of the irradiation surface 41, and the light source 7 and the circuit board 6 In the meantime, the light source 7 is supported on the circuit board 6 so that the light emitting surface 76 faces the light receiving surface 43a, and the light source holder (structure) 8 electrically and thermally connects the light source 7 and the circuit board 6. By providing the above, it is possible to improve heat dissipation efficiency while suppressing an increase in the thickness dimension, and to secure a degree of freedom in selecting the light emitting diode.

  That is, by arranging the circuit board 6 so that the board surface extends in the extending direction of the irradiation surface 41, an increase in the thickness dimension can be suppressed even if the size of the circuit board 6 is increased in order to improve the heat radiation efficiency. Since the light source 7 is mounted on the circuit board 6 via the light source holder (structure) 8 that electrically and thermally connects the light source 7 and the circuit board 6, a top view type light emitting diode can be used. , Can increase the freedom of product selection. The extending direction of the circuit board 6 does not necessarily have to be parallel to the extending direction of the irradiation surface 41, and may have a slight crossing angle with respect to the extending direction of the irradiation surface 41.

  Moreover, in this embodiment, it has the support body 9 which supports the circuit board 6 and the light-guide plate 4, and improves heat dissipation efficiency by making this support body 9 and the circuit board 6 contacted via the heat conductor 10. FIG. be able to.

  In the present embodiment, the circuit board 6 is extended so as to overlap the light guide plate 4 in the thickness direction, so that the area of the circuit board 6 can be increased correspondingly, thereby improving the heat dissipation efficiency. In the present embodiment, the circuit board 6 is set to a size that covers substantially the entire surface of the light guide plate 4, but it is desirable to extend at least a part of the light guide plate 4 in the thickness direction.

  In the present embodiment, the light source 7 includes a surface-mount type light emitting diode having conductive portions 77 and 78 that are electrically connected to the light source holder 8 on the side opposite to the light emitting surface 76, thereby realizing a compact configuration.

  FIG. 4 is a cross-sectional view showing a second embodiment of the present invention, and FIG. 5 is an enlarged cross-sectional view of the main part showing the vicinity of the light source in FIG.

  In the present embodiment, a function is added as a support to the circuit board 6 having a metal substrate 61 as a base material, and the support 9 functioning as a back cover or chassis adopted in the first embodiment is abolished. In other words, the circuit board 6 is provided with a function as a back cover or a chassis, and the other parts are the same as those in the first embodiment.

  That is, the circuit board 6 according to the present embodiment extends in the extending direction of the irradiation surface 41 so as to cover substantially the entire surface of the light source holder 8, the light source 7, and the light guide plate 4, and the circuit board on which the light source holder 8 and the light source 7 are mounted. 6 and the light guide plate 4 supporting the optical film 3 are supported from the back side. The display panel 2 and the frame 1 may be supported by the circuit board 6 as long as the circuit board 6 on which at least the light source holder 8 and the light source 7 are mounted and the light guide plate 4 are held.

  Moreover, the edge part of the circuit board 6 is bend | folded by substantially L shape, and forms the bending part 610, thereby improving the intensity | strength as a support body. Note that the wiring pattern 6 is routed so that the wiring pattern 63 is not located at the bent portion 610 and the base portion (bent portion) of the bent portion 610 (the wiring pattern 63 is provided avoiding the bent portion 610 and the bent portion). As a result, the insulating layer 62, the insulating film 64, and the wiring pattern 63 are prevented from being destroyed, and the power supply reliability is ensured.

  In the present embodiment, for example, a white light reflecting layer 620 is provided on the circuit board 6 at least in a region facing the light guide plate 4, thereby improving the illumination efficiency.

  Although not shown in the above embodiments, for example, the light source holder 8 is provided in a longitudinal shape (for example, a rectangular parallelepiped) extending along the light receiving surface 43 a of the light guide plate 4, and a plurality of light sources 7 are provided in the longitudinal light source holder 8. The light source 7 and the circuit board 6 may be electrically and thermally connected while being held together.

  The substrate 61 (base material) of the circuit board 6 is not limited to a metal, and may be, for example, a glass epoxy material or a flexible FPC (flexible printed circuit).

  The connection between the light source holder 8 and the light source 7 or the circuit board 6 is not limited to soldering, but may be insertion connection between terminals, plug-in connection with a connector device interposed, caulking, welding, or the like.

1 is a perspective view showing a display device according to a first embodiment of the present invention. AA sectional drawing of FIG. FIG. 3 is an essential part cross-sectional view showing an enlarged vicinity of a light source in FIG. 2. Sectional drawing which shows the 2nd Embodiment of this invention. FIG. 5 is an essential part cross-sectional view showing an enlarged vicinity of a light source in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame 2 Display panel 3 Optical film 4 Light guide plate 5 Reflective film 6 Circuit board 7 Light source 8 Light source holder (structure)
9 Support 10 Thermal conductive sheet (thermal conductor)
41 Irradiation surface 42 Opposing surface 43 Side end surface 43 Light receiving surface 61 Substrate 62 Insulating layer 63 Wiring pattern 64 Insulating coating 71 Recessed portion 72 Housing 73 Semiconductor light emitting device (bare chip)
74, 75 Wiring member 76 Light emitting surface 77, 78 Conducting portion 81 Main body portion 82, 83 A pair of conductive members 84 Light source mounting surface 85 Substrate mounting surface 86, 87 First connecting portion 88, 89 Second connecting portion CF contact surface 91,610 bent portion 620 light reflection layer

Claims (8)

A light source comprising a light emitting diode;
A light guide plate having a light receiving surface for introducing light from the light source and an irradiation surface for emitting light by light introduced from the light receiving surface;
A circuit board for supplying power to the light source,
The circuit board is arranged such that the board surface extends in the extending direction of the irradiation surface,
Between the light source and the circuit board, the light source is supported on the circuit board such that a light emitting surface thereof faces the light receiving surface, and the light source and the circuit board are electrically and thermally connected. A light-emitting device including a structure. The light emitting device according to claim 1, wherein the circuit board supports at least the light guide plate. The light-emitting device according to claim 1, further comprising a support body that supports at least the circuit board and the light guide plate, wherein the support body and the circuit board are in contact with each other through a heat conductor. The light emitting device according to claim 1, wherein the circuit board extends to a position overlapping at least a part of the light guide plate in the thickness direction. The light emitting device according to claim 2, wherein the circuit board has a bent portion. 6. The light emitting device according to claim 5, wherein a wiring pattern is not located at the bent portion. The light emitting device according to claim 2, wherein a light reflecting layer is provided at least in a region facing the light guide plate on the circuit board. The light-emitting device according to claim 1, wherein the light source includes a surface-mounting type light-emitting diode having a conduction portion that is electrically connected to the structure on a side opposite to the light-emitting surface.

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