JP2006216244A - Led backlight and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED backlight and a liquid crystal display device enabled to realize reduction of size and thickness thereof by restraining temperature increase by effectively radiating heat generated at an LED light source, and by preventing the lowering of brightness by restraining lowering of light emission efficiency. <P>SOLUTION: The LED back light is composed of a square-shaped light guide plate 24 having a main face as a light-emitting face 24a, and a face almost perpendicularly crossing the light-emitting face 24a as an incident-side end face 24c; a plurality of LED light sources 23 arranged so that a light-emitting face 23a faces the incident-side end face 24c along the incident side end face 24c of the light guide plate 24; and frames 31, 33 supporting the light guide plate 24 and the LED light sources 23. The plurality of light sources 23 are mounted on a wiring plate 25 having a thickness same as that of the light guide plate 24 so as to form an array-shape, and heat radiation bodies 26, 28 are arranged on both faces of the wiring plate 25, and the heat radiation bodies 26, 28 are made to directly contact the frames 31, 33. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an LED backlight and a liquid crystal display device.

  As is well known, liquid crystal display devices have features such as light weight, thinness, and low power consumption, so OA devices, information terminal devices, personal computers (PCs), television receivers (TVs), car navigation systems, and other portable devices. Widely used as display devices in various fields such as equipment. Since the liquid crystal (LC) used in such a liquid crystal display device does not emit light by itself, an illumination device is required for display, and a light emitting diode (LED) is used as a light source as one of the illumination devices. There was something that was there. In such a liquid crystal display device, a backlight system is adopted in which an illuminating device is disposed on the back surface of a liquid crystal display element (LCD) and light is emitted from the back side so that display is performed with transmitted light.

  And in such a liquid crystal display device, when the device is downsized, how to dissipate heat generated by the LED becomes a problem. In order to deal with such generated heat, there is a configuration in which an LED is brought into direct contact with a chassis of a liquid crystal display device (see, for example, Patent Document 1).

However, although it is possible to make the device thinner in this way, the arrangement of the LED light sources can be reduced by further downsizing the liquid crystal display device or increasing the number of arrayed LED light sources. When the interval is reduced, the generated heat can not be sufficiently dissipated, the temperature of the LED light source itself increases, the luminous efficiency decreases, and the luminance decreases, resulting in the required performance as an LED backlight. Cannot be obtained. Further, when the temperature rises further, there is a possibility that problems such as the inability to operate the LED light source normally occur.
JP 2004-186004 A

  The present invention has been made in view of the above situation, and its purpose is to efficiently dissipate the heat generated by the LED light source to suppress a temperature rise, suppress a decrease in luminous efficiency, and reduce a luminance. An object of the present invention is to provide an LED backlight and a liquid crystal display device that can realize a reduction in size and thickness of the device by preventing it.

The LED backlight of the present invention is
A rectangular light guide plate having one main surface as a light exit surface and a surface substantially orthogonal to the light exit surface as an incident surface, and a light emitting surface disposed along the incident surface of the light guide plate so as to face the incident surface An LED backlight comprising a plurality of LED light sources and a frame that supports the light guide plate and the LED light source, wherein the plurality of LED light sources are mounted in an array on the wiring board, A heat radiator is provided on both surfaces of the wiring board, and the heat radiator is in direct contact with the frame.

The liquid crystal display device of the present invention is
A transmissive rectangular liquid crystal display element and a plurality of LED light sources mounted on a wiring board so as to form an array along the light incident surface of a rectangular light guide plate disposed on the back surface of the liquid crystal display element A liquid crystal display device comprising an LED backlight having a frame that integrates the liquid crystal display element and the LED backlight, wherein the wiring board has a heat radiator on both sides thereof, and the heat radiator is the frame. It is characterized by being in direct contact with.

  As is clear from the above description, according to the present invention, the heat generated by the LED light source can be efficiently dissipated, the temperature rise is suppressed, the decrease in luminous efficiency is suppressed, and the decrease in luminance can be prevented, There is an effect that the apparatus can be reduced in size and thickness.

  An embodiment of the present invention will be described below with reference to FIGS. 1 is a cross-sectional view showing an outline of a liquid crystal display device, FIG. 2 is an exploded perspective view showing a configuration of an LED backlight, FIG. 3 is a cross-sectional view of an arrayed LED light source, and FIG. It is a top view of the LED light source.

  1 to 4, reference numeral 20 denotes a substantially rectangular flat liquid crystal display device used for a car navigation system or the like, which is formed with a liquid crystal layer, a thin film transistor (TFT) substrate, a polarizing plate, a counter substrate, etc. (not shown). A transmissive liquid crystal display element 21 having a square shape and an illuminating device (LED backlight) 22 having the same rectangular shape provided on the back side thereof are provided. Further, the LED backlight 22 includes a plurality of, for example, 10 to 20 LED light sources 23 formed by sealing white LED chips with a resin such as an epoxy resin, and, for example, polycarbonate, acrylic, and the like. The light guide plate 24 is a substantially rectangular flat plate having a predetermined thickness and made of a translucent resin.

  The 10 to 20 LED light sources 23 are, for example, rectangular shapes made of a glass epoxy substrate having a width substantially the same as the thickness of the light guide plate 24 and a length substantially the same as the length of the long side of the light guide plate 24. Is mounted by fixing a light emitting back surface 23b on the back surface of the light emitting surface 23a at a predetermined position on the wiring board 25, and each LED light source 23 is connected in series, An array of light sources is formed.

  In addition, the wiring board 25 on which the LED light source 23 is mounted has a back surface which is the back surface of the mounting surface, a material having the same outer shape as the wiring board 25 and having a predetermined thickness and good thermal conductivity, such as aluminum or copper, A first heat radiator 26 made of a metal material such as silver or an alloy thereof or a ceramic material such as aluminum nitride is fixed. Further, a second heat radiating body 28 in which a rectangular through hole 27 through which each LED light source 23 passes is formed on the mounting surface of the wiring board 25 can be manufactured between the side surfaces of each LED light source 23. It is fixed so as to enclose with a minimum gap in such a range. The second radiator 28 is made of a material having good thermal conductivity similar to that of the first radiator 26, and has the same outer shape.

  On the other hand, the substantially rectangular flat light guide plate 24 is provided with an optical sheet 29 such as a diffusion sheet on the exit surface 24a, a reflection sheet 30 on the back surface 24b on the back side of the exit surface 24a, and an incident side end surface 24c. On the side end surfaces of the other three sides excluding one long side, the sea and 30a, 30b, 30c extending from the reflection sheet 30 are arranged. Each of the sheets 29 and 30 has, for example, a substantially U-shaped shape formed of a metal material such as stainless steel and a first inner frame 31 having a substantially U-shaped cross section. It is attached to the light guide plate 24 by being fitted into the side end surface portions of the other three sides. Reference numeral 32 denotes a back plate made of a metal material.

  The LED light source 23 formed in an array has a cross section in which the back surface and the four side surfaces of the first radiator 26 and the four side surfaces of the second radiator 28 are formed of a metal material such as stainless steel, for example. The shape is substantially U-shaped, and is held so as to be in direct contact with the inner bottom surface and the inner side surface of the second inner frame 33 having partially closed walls 33a at both ends. The LED light source 23 held by the second inner frame 33 has the second inner frame 33 at the incident side end face 24c portion of the light guide plate 24 and a predetermined gap between the light emitting surface 23a and the incident side end face 24c. The light guide plate 24 is attached along the long side of the incident side end face 24c by being fitted so as to be provided.

  As described above, the LED backlight 22 configured by integrating the LED light source 23 and the light guide plate 24 by the first inner frame 31 and the second inner frame 33 causes each LED light source 23 to emit light. The light is emitted from the light emitting surface 23a and enters the light guide plate 24 from the incident side end surface 24c. In the light guide plate 24, the incident light propagates through the transparent light guide plate 24 to the emitted light, and the light reaching the end surface other than the back surface 24b and the incident side end surface 24c is reflected by the reflection sheet 30 and the sheets 30a, 30b, The light is reflected by 30c, reaches the emission surface 24a, and is emitted to the liquid crystal display element 21 through the optical sheet 29.

  In addition, the heat generated in each LED light source 23 due to light emission is transmitted to the first heat radiator 26 and the second heat radiator 28 via the wiring board 25, and is further in direct contact with both the heat radiators 26 and 28. The light is transmitted to the second inner frame 33 and further from the second inner frame 33 to the first inner frame 31 and efficiently dissipated out of the LED backlight 22. Thereby, the temperature rise of each LED light source 23 can be suppressed, each LED light source 23 can be made into predetermined temperature, a brightness fall can be prevented, and it can be operated normally.

  Furthermore, the LED backlight 22 configured as described above is provided so as to be in direct contact with the first inner frame 31 and the second inner frame 33 and surrounds the outer peripheral portion, for example, a metal material such as stainless steel. The liquid crystal display device 20 is configured by being assembled on the back side of the rectangular liquid crystal display element 21 by the outer frame 35 having a substantially L-shaped cross section formed by the above. Then, the LED backlight 22 is caused to emit light, and light is emitted from the emission surface 24a through the optical sheet 29 toward the back side of the liquid crystal display element 21, so that the content displayed on the liquid crystal display element 21 is Visible to.

  In addition, the heat generated by each LED light source 23 due to light emission is transmitted to the first inner frame 31 and the second inner frame 33 through the first radiator 26 and the second radiator 28, and further to these. It is transmitted to the outer frame 35 that is in direct contact and is efficiently dissipated out of the liquid crystal display device 20. Thereby, similarly, the temperature rise of each LED light source 23 can be suppressed, each LED light source 23 can be made into predetermined temperature, a brightness fall can be prevented, and it can be operated normally. Furthermore, since there are no inclusions between the liquid crystal display element 21 and the LED backlight 22, the liquid crystal display device 20 can be reduced in size and thickness.

  In addition, about the wiring board 25, it is not restricted to an above-mentioned epoxy board | substrate, The more improved thermal radiation characteristic can be acquired by comprising with insulating materials, such as aluminum nitride with more favorable heat conductivity.

It is sectional drawing which shows the outline of the liquid crystal display device concerning one Embodiment of this invention. It is a disassembled perspective view which shows the structure of the LED backlight concerning one Embodiment of this invention. It is sectional drawing of the array-shaped LED light source in the LED backlight concerning one Embodiment of this invention. It is a top view of the array-like LED light source in the LED backlight concerning one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Liquid crystal display element 22 ... LED backlight 23 ... LED light source 23a ... Light emission surface 24 ... Light guide plate 24a ... Outgoing surface 24c ... Incident side end surface 25 ... Wiring board 26 ... 1st heat radiator 27 ... Through-hole 28 ... 2nd Of radiator 31 ... first inner frame 33 ... second inner frame 35 ... outer frame

Claims (6)

  A rectangular light guide plate having one main surface as a light exit surface and a surface substantially orthogonal to the light exit surface as an incident surface, and a light emitting surface disposed along the incident surface of the light guide plate so as to face the incident surface An LED backlight comprising a plurality of LED light sources and a frame that supports the light guide plate and the LED light source, wherein the plurality of LED light sources are mounted in an array on the wiring board, An LED backlight, wherein a radiator is provided on both sides of the wiring board, and the radiator is in direct contact with the frame.   The LED backlight according to claim 1, wherein the heat dissipating body provided on both surfaces of the wiring board is formed to have the same width as the wiring board.   The LED backlight according to claim 1, wherein the wiring board is formed of an insulating material having thermal conductivity.   The LED backlight according to claim 1, wherein the heat radiating body provided on a surface of the wiring board on which the LED light source is mounted has a through hole of the LED light source.   2. The LED backlight according to claim 1, wherein four surfaces of the heat dissipating body provided on the surface of the wiring board on which the LED light source is mounted are in direct contact with the frame.   A transmissive rectangular liquid crystal display element and a plurality of LED light sources mounted on a wiring board so as to form an array along the light incident surface of a rectangular light guide plate disposed on the back surface of the liquid crystal display element A liquid crystal display device comprising an LED backlight having a frame that integrates the liquid crystal display element and the LED backlight, wherein the wiring board has a heat radiator on both sides thereof, and the heat radiator is the frame. A liquid crystal display device which is in direct contact with the liquid crystal display device.

Images