JP2008066132A - Light-emitting device and display device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device in which uniformity of light from its light-emitting face is obtained while a heat radiating property of the light-emitting device is secured in the light-emitting device used as a backlight or the like of a liquid crystal display device. <P>SOLUTION: A light-emitting element, a substrate having the light-emitting element, a circuit element connected to the light-emitting element, and a substrate having the circuit element are equipped in the light-emitting device, in which the substrate having the light-emitting element is bent, and the end part of the substrate having the light-emitting element is electrically connected to the substrate having the circuit element to form the light-emitting device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting device using a light emitting element such as an LED and a display device using the light emitting device.

  In recent years, as a light source of a backlight used in a liquid crystal device, in addition to a conventionally used cold cathode fluorescent tube (hereinafter referred to as “CCFL”), a light-emitting diode (hereinafter referred to as “CCFL”) is used. Development of a method that partially uses “LED”) or a method that replaces all CCFLs with LEDs is underway. It has the characteristics that brightness adjustment is easy and that it is environmentally friendly because it does not contain mercury.

An example of a liquid crystal display device using an LED disclosed in Patent Document 1 is shown in FIG. FIG. 5A is a view from the rear side of the apparatus, and FIG. 5B is a view from the front side of the apparatus. On the front side of the printed circuit board 21, LEDs 22 are assembled over almost the entire surface. Further, the back surface of the printed circuit board 21 is provided with a brightness adjustment circuit 23 and a semiconductor chip 24 including a driver and a control circuit, and performs drive control of the LED 22. A heat sink 25 is installed on the back surface of the printed circuit board 21 so that heat emitted from the integrated circuits provided on the LED 22 and the back surface of the printed circuit board 21 is efficiently discharged. In order to improve heat conductivity by bringing the heat sink 25 and the printed circuit board 21 into close contact with each other, the heat sink 25 is provided with a recess 26 so that the integrated circuit provided on the back surface of the printed circuit board 21 can be accommodated in the recess 26. . In addition, a diffusion plate 27 for making light emitted from the LEDs 22 uniform is installed on the front side of the printed circuit board 21. In addition, a liquid crystal panel 29 is provided in front of the optical chamber 28 in which the heat sink 25, the printed circuit board 21 and the diffusion plate 27 are housed, and functions as a liquid crystal display device using light emitted from the LEDs 22.
In this liquid crystal display device, there is a problem that the temperature of the printed circuit board rises because an LED is mounted on the surface of one printed circuit board 21 and a semiconductor chip for LED drive control is mounted on the back surface.

An example of a lighting device using LEDs disclosed in Patent Document 2 is shown in FIG. Two of the LED mounting board 30 and the power circuit board 31 are built in, and the two are electrically connected by a cable 32. An LED 33 is assembled on the front side of the LED mounting substrate 30. Further, a heat radiating means 34 for releasing the heat generated by the LEDs 33 is bonded to the back surface of the LED mounting substrate 30, and is further discharged to the outside of the apparatus through the heat transfer means 35. In addition, the electrical connection between the LED mounting board 30 and the power circuit board 31 is such that wiring for supplying current to the LEDs 33 is taken out from the back surface of the LED mounting board 30 with a cable 32.
US Pat. No. 6,439,731 JP 2004-55800 A

However, in the lighting device in which the LED mounting board and the power circuit board as described in Patent Document 2 are configured as separate boards, heat dissipation can be ensured, but the LED mounting board and the power circuit are electrically connected. There were the following problems in connecting.
In Patent Document 2, a hole (through hole) for drawing a power supply line is provided in the LED mounting substrate. In this case, in order to provide the holes, an insulating material is selected as the substrate material of the LED-mounted circuit board. However, the insulating substrate generally has poor thermal conductivity and has reduced heat dissipation.
As another connection method, there is a method of arranging a connector on the LED mounting board and connecting it to the power circuit board. However, since there is a connector on the LED mounting board, the LED light around the connector is blocked. There was a problem of impairing the uniformity of light.
An object of the present invention is to provide a light emitting device capable of obtaining uniformity of light from a light emitting surface while ensuring heat dissipation.

  The present invention includes a light emitting element, a substrate having the light emitting element, a circuit element for controlling the light emitting element, and a substrate having the circuit element, and the substrate having the light emitting element is bent, In the light-emitting device, an end portion of the substrate is electrically connected to the substrate having the circuit element.

  The present invention includes a light emitting element, a circuit element for controlling the light emitting element, and a substrate having the light emitting element and the circuit element, wherein the substrate includes a region having the light emitting element and a region having the circuit element. It is the light-emitting device bent between.

In the present invention, it is preferable that the substrate having the light emitting element is supported by a support substrate.
In the present invention, the support substrate is preferably a metal.
The present invention preferably has a space between the substrate having the light emitting element and the substrate having the circuit element or between the region having the light emitting element and the region having the circuit element.
In the present invention, it is preferable that air flows in the space.
In the present invention, the substrate having the light emitting element is preferably a glass epoxy substrate.
In the present invention, the substrate having the light emitting element is preferably a multilayer glass epoxy substrate.
In the present invention, it is preferable that a portion of the substrate that is bent has a cut portion on a side of the substrate.
In the present invention, the light emitting element is preferably an LED.
In the present invention, it is preferable that the substrate or the region having the light emitting element is smaller than the substrate or the region having the circuit element.
In the present invention, it is preferable to combine a plurality of the light emitting devices.
The present invention is a display device including the light-emitting device and a non-self-luminous image display panel.

According to the present invention, it is possible to obtain uniformity of light from the light emitting surface while ensuring heat dissipation.
In addition, when the substrate on which the light emitting element is mounted is a foldable substrate, the connection with the substrate having a circuit element for driving the light emitting element is facilitated.

FIG. 1 is an overall schematic diagram of a liquid crystal display device 1 according to a first embodiment.
A plurality of backlight tiles 2 illuminate the liquid crystal panel 4 via the diffusion plate 3. One backlight tile 2 is equipped with a drive circuit element 5 for driving an LED mounted on the tile. In some cases, a temperature sensor (not shown) is mounted for measuring the ambient temperature, controlling the light emission luminance of the LED, and keeping the luminance constant.
The drive circuit element 5 is connected to a control circuit 7 installed on a control board 6 common to each backlight tile 2 via a cable 8. Note that the liquid crystal panel 4 can be replaced with another non-self-luminous image display panel, for example, a MEMS (microelectromechanical system) panel, a shutter panel using an electro-optic effect or an electrophoretic effect, or the like. .

FIG. 2 is an overall schematic diagram (FIG. 2A) and a cross-sectional schematic diagram (FIG. 2B) of the backlight tile 2 used in the first embodiment.
A plurality of LEDs are mounted and connected to the LEDs so as to cover the upper surface of the substrate 9 made of aluminum and having good thermal conductivity. It is preferable that the thin glass epoxy substrate 11 provided with the wiring pattern is bonded to the substrate 9 with a heat conductive adhesive (not shown).
The substrate 9 has both a role as a support substrate for supporting the thin glass epoxy substrate 11 and a role as a heat dissipation substrate for radiating heat generated from the LEDs 10 on the thin glass epoxy substrate. The material of the substrate 9 as the support substrate is preferably a metal, and more preferably a material having excellent heat conductivity such as aluminum. Since the thin glass epoxy substrate 11 is not bent by the substrate 9, the light from the LED 10 can be irradiated in a direction perpendicular to the thin glass epoxy substrate 11.
Moreover, you may affix the reflection sheet (not shown) for taking out light efficiently in places other than a mounting component on the surface at the side of LED10 mounting of the thin glass epoxy board | substrate 11. FIG.

A drive circuit mounting substrate 13 is disposed on the surface of the substrate 9 opposite to the side bonded to the thin glass epoxy substrate 11 via a plurality of spacers 12. With this spacer 12, a space can be provided between the thin glass epoxy substrate 11 and the drive circuit mounting substrate 13. This space efficiently dissipates heat.
Further, the size of the drive circuit mounting board 13 is not larger than the board 9. This is because when the backlight tile 2 described later is combined and used in a display device, the thin glass epoxy substrate 11 does not protrude into the area of the adjacent backlight tile 2, and a signal between the thin glass epoxy substrates 11 is displayed. This is to minimize interference.
A drive circuit element 14 is assembled on the drive circuit mounting board 13 to control the current supplied to the LED 10. Here, although LED was mentioned as an example as a light emitting element, the light emitting element etc. which irradiate fluorescent substance with organic EL and a laser may be sufficient.

The thin glass epoxy substrate 11 is made of a material in which a low elastic modulus thermosetting resin and an ultrathin glass cloth are combined, and is characterized by little dimensional stability and warp twist. The multilayer structure is a substrate that can be bent at 90 degrees or an acute angle in combination with a thickness of about 0.2 mm and low elasticity. In order to perform such bending, the thickness of the substrate is preferably 0.3 mm or less. Thus, by making the substrate on which the LED 10 is mounted much thinner than the thickness of the conventionally used substrate, the heat generated in the LED 10 can be transferred to the substrate 9 and the heat dissipation is improved. .
In order to improve the bendability, the thin glass epoxy substrate is preferably composed of a plurality of layers. Further, the material may be other than glass epoxy such as a polyimide-based flexible printed circuit board (FPC) or a glass epoxy board / FPC composite board (ADF board).

  Since the thin glass epoxy substrate 11 can be bent in this manner, for example, the LED 10 and the drive circuit element 14 can be connected without disposing the connector on the surface on which the LED 10 is mounted, so that the protrusion due to the connector is eliminated. A backlight with uniform optical characteristics can be obtained. This uniform optical characteristic is particularly useful in the case of a light emitting device used as a backlight of a liquid crystal display as in this embodiment, which has the effect of improving display quality.

For electrical connection between the LED 10 and the drive circuit element 14, at one end (not shown) of the substrate 9 or two opposing sides, a part of the end portion of the thin glass epoxy substrate 11 on which the plurality of LEDs 10 are mounted Alternatively, it is configured to be bent at 90 degrees along the side 9 </ b> A of the substrate 9 from a plurality of locations and connected to the connector 15 provided on the drive circuit mounting substrate 13. For this reason, it is not necessary to make a through-hole etc. in the board | substrate 9, and it can affix on the board | substrate 9 with favorable heat conductivity made from aluminum, and has improved heat dissipation.
In addition, the thin glass epoxy substrate 11 on which a plurality of LEDs 10 are mounted is directly wired to the drive circuit mounting substrate 13, thereby facilitating design and mounting, reducing the number of connectors on the thin glass epoxy substrate 11 side, and during production. The effect of reducing the number of assembly man-hours comes out.
The connector 15 and the drive circuit element 14 are electrically connected, and a drive current can be supplied to the plurality of LEDs 10. The drive circuit mounting board 13 has a single-layer or multi-layer wiring structure, and the drive circuit elements 14 can be mounted on one side or both sides of the drive circuit mounting board 13 depending on the number of drive circuit elements 14. Yes. A control connector 16 is mounted on the opposite side of the drive circuit mounting board 13 from the board 9 and is electrically connected to the control board 6 to input and output control signals for the entire liquid crystal display device 1. It is an interface.

  Further, the thin glass epoxy substrate 11 on which the LED 10 is mounted can be bent and turned to the drive circuit mounting substrate side, and the drive circuit element 14 can be mounted on the turned thin glass epoxy substrate 11. It is. That is, it is configured to bend between the area where the LED is mounted and the area where the circuit element is mounted. In this case, the region where the drive circuit element 14 is mounted is supported by bonding it to a support substrate (not shown) different from the drive circuit mounting substrate 13 and bonding the support substrate to the drive circuit mounting substrate 13. (FIG. 2 (c)). By adopting these configurations, effects such as a reduction in the number of connectors on the drive circuit mounting board 13 side and a reduction in assembly man-hours during production can be obtained as compared with the example shown above (FIGS. 2A and 2B). . Therefore, the failure rate can be reduced and the cost can be reduced.

A backlight as a liquid crystal display device requires white light with sufficient luminance, and when a driving current is supplied to the LED to emit light, a large amount of heat is generated in the LED and the driving circuit. When this large amount of heat stays in the backlight, the required white light cannot be obtained because the luminance and color tone change due to the temperature characteristics of the LED. Therefore, it is necessary to discharge heat sufficiently to obtain stable brightness and color tone. However, the LED mounting side of the backlight tile 2 has a liquid crystal panel with a diffusion plate in between, and this liquid crystal panel must be used in a dust-free environment, so that air cannot be allowed to flow through the internal space 17. . Therefore, heat radiation by air cooling on the LED mounting side of the backlight is generally not performed. In addition, since a large amount of heat is dissipated in the drive circuit element 14, the same problem of exhaust heat occurs.
In the present embodiment, there is a place where heat is dissipated by the air flow in the gap space 18 and the external space 19 on both surfaces of the drive circuit mounting substrate 13, so that efficient heat removal is possible. Natural convection may be used, or forced air cooling using a fan or the like may be used.

FIG. 3 shows a schematic diagram (FIG. 3A) and a cross-sectional schematic diagram (FIG. 3B) when a plurality of backlight tiles are combined.
In the large liquid crystal display device 1, a plurality of the backlight tiles 2 are used in combination. A part or a plurality of portions of the thin glass epoxy substrate 11 are bent for electrical connection. When one side of the backlight tile 2 that is bending the thin glass epoxy substrate 11 is aligned with one side of the other backlight tile 2, there is no gap, or a minute gap of about 1 mm considering the thermal expansion of the substrate 9. It arrange | positions at intervals and arrange | positions the edge | side of the other board | substrate 9 without leaving a gap. When arranging with a small gap, a tape-like reflective material is affixed to that part, or the reflective sheet where the thin glass epoxy substrate 11 is bent is designed to be slightly larger so that the gap is covered. Good. Thereby, the nonuniformity of the light emission as a backlight by the fall of the reflectance in the joint of each backlight tile can be suppressed.

FIG. 3C is a schematic view seen from the back when a plurality of backlight tiles 2 are combined. When the thin glass epoxy substrate 11 is bent and electrically connected at two opposite sides, the bent portion (A shown in FIG. 3C) is made the same place (B shown in FIG. 3C) on the opposite side. In addition, the air flow between the backlight tiles 2 (C shown in FIG. 3C) can be flowed unimpeded, and the heat dissipation efficiency is further increased. The air flow in these one backlight tile 2 or when a plurality of backlight tiles 2 are combined is naturally generated by convection due to heat generation in the LED 10 and the drive circuit element 14, but the backlight tile 2 If a small fan or the like is installed on the outer periphery (not shown), a further heat dissipation effect can be expected.
When one backlight tile 2 fails, the backlight tile 2 can be taken out and replaced. If the LED 10 is defective, the thin glass epoxy substrate 11 can be removed and the LED 10 can be replaced. Moreover, it becomes possible to replace the thin glass epoxy substrate 11 as a whole, shorten the repair time, and reduce the repair cost.

(Bendable board shape)
FIG. 4 shows a bent portion of the thin glass epoxy substrate 11 of the backlight tile.
4A is a top view of the thin glass epoxy substrate 11 before bending, and FIG. 4B is a sectional view after bending. In the first embodiment, the thin glass epoxy substrate 11 is bent at 90 degrees along the side 9A of the substrate 9 at the boundary line between the front surface portion 11A and the bent portion 11B of the thin glass epoxy substrate 11, and the leading end portion 11C is driven. The electrode (not shown) provided at the tip 11C is connected to the connector 15 on the drive circuit mounting board 13 by turning to the circuit mounting board 13 side.
A thin glass epoxy substrate 11 having a thickness of about 0.2 mm is used, but when it is bent, if it is bent at the side 9A of the substrate 9, a slack 11E is produced at the corner. If there is a slack 11E generated at this corner, an unnecessary protrusion may occur, and when the sides of the backlight tile 2 are combined, they cannot be combined as designed. Therefore, the portion where the thin glass epoxy substrate 11 is bent is as follows.
A cut portion 11D is slightly provided on the side of the thin glass epoxy substrate 11 along the side 9A of the substrate 9 inside the substrate 9 (FIG. 4 (c) top view, FIG. 4 (d) top view enlarged view). Bending is started from the innermost part 20 of 11D (FIG. 4 (e) a top view after bending, FIG. 4 (f) a sectional view after bending). With such a structure, there is no sagging during folding, and the backlight tiles can be adjacent as designed. The shape of the cut portion 11D may be a rectangle or the like in addition to the illustrated arc.

In the above description, the case where there are a plurality of backlight tiles 2 has been described, but it is not always necessary to divide the tiles into a plurality, and one may be used.
Moreover, the backlight tile 2 itself from which the liquid crystal panel 4 is removed can be used as an LED lighting device.
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

It is the schematic diagram which looked at the large sized liquid crystal display device of Embodiment 1 from the back surface. 3 is a schematic diagram of a backlight tile according to Embodiment 1. FIG. 2 is a schematic diagram in which a plurality of backlight tiles according to Embodiment 1 are combined. FIG. It is a schematic diagram which shows the bending state of the thin substrate of Embodiment 1. This is a conventional backlight device. It is a conventional lighting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Backlight tile 3 Diffusion plate 4 Liquid crystal panel 5 Drive circuit element 6 Control board 7 Control circuit 8 Cable 9 Board 10 LED
DESCRIPTION OF SYMBOLS 11 Thin glass epoxy board | substrate 12 Spacer 13 Drive circuit mounting board 14 Drive circuit element 15 Connector 16 Control connector 18 Gap space A B Thin glass epoxy board bending position C Air flow

Claims (13)

A light emitting element;
A substrate having the light emitting element;
A circuit element for controlling the light emitting element;
Comprising a substrate having the circuit element;
A light emitting device in which a substrate having the light emitting element is bent and an end portion of the substrate having the light emitting element is electrically connected to the substrate having the circuit element. A light emitting element;
A circuit element for controlling the light emitting element;
Comprising a substrate having the light emitting element and the circuit element;
The light emitting device, wherein the substrate is bent between a region having the light emitting element and a region having the circuit element.   The light emitting device according to claim 1, wherein the substrate having the light emitting element is supported by a support substrate.   The light emitting device according to claim 3, wherein the support substrate is made of metal.   2. A space is provided between the substrate having the light emitting element and the substrate having the circuit element or between the region having the light emitting element and the region having the circuit element. 5. The light emitting device according to any one of 4.   The light emitting device according to claim 5, wherein air flows in the space.   The light emitting device according to any one of claims 1 to 6, wherein the substrate having the light emitting element is a glass epoxy substrate.   The light emitting device according to claim 7, wherein the substrate having the light emitting element is a multilayer glass epoxy substrate.   9. The light-emitting device according to claim 1, wherein the bent portion of the substrate having the light-emitting element has a cut portion on a side of the substrate.   The light emitting device according to claim 1, wherein the light emitting element is an LED.   The light emitting device according to claim 1, wherein a substrate or a region having the light emitting element is smaller than a substrate or a region having the circuit element.   A light emitting device comprising a combination of a plurality of the light emitting devices according to claim 1.   A display device comprising the light-emitting device according to any one of claims 1 to 12 and a non-self-luminous image display panel.

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