JP2006154136A - Liquid crystal display device and display body using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has an LED backlight bringing about a bright and long-life liquid crystal display by suppressing lowering of luminous efficiency of an LED light source and preventing damage to the LED light source. <P>SOLUTION: The liquid crystal display device is constructed with a liquid crystal display panel 1, and the backlight equipped with a light guide plate 4, and a light source body arranged on an end face of the light guide plate 4. The light source body is constructed with: a lengthy mounted substrate 8; heat dissipating sheets 9 each of which has a U-shaped cross section, a plurality of which are aligned and mounted on one principal surface of the mounted substrate 8, and which cover the LED light source 7, and at least three faces out of the one principal surface (the front face), the other principal surface (the rear face), and the lengthy upper and lower faces forming right angles with both principal surfaces of the mounted substrate 8; and a heat sink substrate 10 disposed on the outside faces of the heat dissipating sheets 9. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using a backlight as an LED light source.

  Conventionally, among transmissive and transflective liquid crystal display devices among liquid crystal display device display methods, a liquid crystal display panel and a backlight for supplying light transmitted to the liquid crystal display panel are disposed outside the liquid crystal display panel. Configured.

  In general, the backlight includes a light source body and a light guide plate, and a small fluorescent tube called CCFL (cold cathode tube) is used as the light source body. The light guide plate is made of a transparent resin, and is disposed at a position facing the display region of the liquid crystal display panel. In addition, a diffusion layer and a lens sheet are attached to the front surface side main surface (main surface on the liquid crystal display panel side) of the light guide plate. Further, a diffusion portion that diffuses and reflects light toward the front surface side is formed on the back surface main surface side.

  The CCFL, which is a light source body, is arranged so that light is incident on the end face of the light guide plate, and the light incident from the end face of the light guide plate is transmitted into the light guide plate and diffused / reflected on the back side of the light guide plate. Then, the light is emitted from the main surface side of the light guide plate toward the liquid crystal display panel. That is, the backlight is converted from a line light source called CCFL into a uniform planar light source and used as a light source of a liquid crystal display device.

  However, in this CCFL light source body, Hg (mercury) is sealed in a discharge tube, and ultraviolet rays emitted from mercury excited by discharge strike the phosphor on the CCFL tube wall and convert it into visible light. For this reason, in consideration of the environment, harmful mercury is used, and suppression of its use and an alternative light source body are required.

  Further, in order to light the CCFL, a high-voltage high-frequency lighting circuit is necessary, and high-frequency noise is generated. Therefore, not only a countermeasure against noise is separately required, but there is a problem that it is difficult to light at low temperature.

  On the other hand, it is already known to use a light emitting diode chip (LED chip) which is a point light source as a new light source. Specifically, in order to facilitate the handling of the light emitting diode chip, the light emitting diode chip has been used by being housed in a container having an opening on the light emitting surface. That is, a light emitting diode module in which a light emitting diode chip is accommodated in the container is used. When using these light emitting diode modules as a light source body of a backlight, for example, an electrode pad and a wiring pattern are formed on one main surface of a long mounting substrate, and a plurality of light emitting die auto modules are arrayed on this electrode pad. (LED light source body).

  The LED light source body has an end surface of the light guide plate and one main surface of the mounting substrate through the light emitting diode module so that light emitted from each light emitting diode module enters the light guide plate from the end surface of the light guide plate. It was arranged to face each other.

Backlights using this LED light source (LED backlights) are becoming popular as backlights for liquid crystal display panels due to lower prices, improved luminous efficiency, and environmental regulations. At the same time, the demand for constructing a plurality of LED light source bodies is increasing as the brightness of liquid crystal display devices increases and the size (display area increases).

  The biggest problem here is that the LED light source body and its ambient temperature rise due to the heat generated by the light emitting diode chip itself, and the light emission efficiency and life of the LED chip are reduced. Although the luminous efficiency of the LED light source body has been improved by recent improvements, the luminous efficiency is about 10% of the supplied energy, and the remaining 90% is released as heat. That is, in a backlight using an LED as a light source body, the generated heat is stored in a container or a mounting substrate constituting the LED light source body, and the luminous efficiency of the LED chip itself increases as the LED light source body and its surrounding temperature rise. It will cause a decline. Regarding the lifetime, for example, the estimated lifetime data (luminance half-life) of the top view type LED at a forward current IF = 20 mA is about 12000 hours at an ambient temperature of 25 ° C., but about 5500 at 50 ° C. It has only been time and it has been found that the lifetime decreases with increasing ambient temperature of the LED.

  Furthermore, the heat generated by the LED chip may cause damage to the LED chip itself or the wiring pattern of the mounting board on which the LED is mounted. In addition, if the number of LEDs mounted is increased to increase the brightness of the backlight, the amount of heat generation increases, so this heat generation cannot be ignored further.

As a conventional technique related to heat generated in an LED, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-281924, a light emitting diode generally has a disadvantage that the luminous efficiency decreases when the junction temperature rises. When the junction temperature increases by 1 ° C., the luminous efficiency may decrease by about 1%. In order to suppress the temperature rise of the light emitting diode, the light emitting diode is mounted on a flexible substrate having a power supply terminal, and the light emitting diode is accommodated and fixed together with the flexible substrate through a double-sided adhesive tape in a box-shaped metal case. There is known a lighting device in which the inside of a box-shaped metal case is filled with a resin adhesive except for the light emitting surface. The opening of the box-shaped metal case was fitted and fixed to the end face of the light guide plate.
JP 2003-281924 A

  However, in the above-described lighting device, the flexible substrate is bonded to the metal case via the double-sided adhesive tape. As for the bonding surface, the surface of the metal case and the bonding surface of the flexible substrate are not sufficiently in surface contact due to fine unevenness, and an air layer with extremely small heat conduction is interposed. In addition, even when fixing double-sided adhesive tape, the thermal conductivity of the double-sided adhesive tape is small, so the heat conduction from the flexible substrate to the metal case is insufficient, and heat is stored around the light-emitting diode, the light-emitting diode, and the flexible substrate. End up. As a result, the problem that the light emission efficiency of the light emitting diode is reduced and the light emitting diode chip is damaged in a short time due to the temperature rise of the light emitting diode itself cannot be sufficiently solved.

  In addition, the process of filling the resin paste in a very narrow metal case becomes very difficult, and the resin paste is hardened, often containing air bubbles inside and being hardened. It will impede conduction.

  Furthermore, even if the light emitting surface of the light emitting diode is arranged so as to be in close contact with the end face of the light guide plate, the light incident from the light guide plate is diffused and reflected by the light guide plate because the light emitting diode is a point light source. Even if the light is returned to the end face where the light emitting diode is disposed again, the light cannot be effectively returned to the light guide plate, and as a result, light loss occurs.

  The present invention has been devised in view of the above-mentioned problems, and the purpose thereof is to mount the LED light source body by efficiently conducting and radiating the generated heat of the LED light source body to the metal case and the housing. The present invention provides a liquid crystal display device having an LED light source body that can suppress a decrease in light emission efficiency of the LED light source body by reducing the heat storage of the mounting substrate and reducing the temperature rise of the LED light source body.

The liquid crystal display device of the present invention includes a liquid crystal display panel having a display region composed of a plurality of pixel regions with a liquid crystal interposed between a pair of substrates having a display electrode and an alignment film,
A light guide plate disposed outside one substrate of the liquid crystal display panel and disposed at a position corresponding to the display region, and a backlight including a light source body disposed on an end surface of the light guide plate In a liquid crystal display device,
The light source body includes an elongate mounting substrate, a light emitting diode module that is arranged in plural on one main surface of the mounting substrate and accommodates a light emitting diode chip, both main surfaces of the mounting substrate, and both the main surfaces A heat dissipation sheet having a U-shaped cross section that covers three of the end surfaces in the longitudinal direction that form a right angle, and the mounting in the U-shaped heat dissipation sheet so that the light emitting surface of the light emitting diode module is exposed. A substrate is arranged.

  In addition, a notch portion where the light emitting surface of the light emitting diode module is exposed is formed on one surface of the heat radiating sheet having a U-shaped cross section.

  Further, the heat radiation sheet having a U-shaped cross section is covered with a metal case having a heat sink function.

  The liquid crystal display panel and the backlight are housed in a housing, and the metal case is formed integrally or in close contact with the housing.

  The metal case is bonded to a housing via a heat conductive adhesive or a heat conductive adhesive.

  A display body including at least the liquid crystal display device described above, a driving unit that supplies a predetermined signal to the display electrode, and a predetermined circuit that supplies the driving unit.

  In the liquid crystal display device of the present invention, the long mounting substrate on which the LED light source body is mounted has three surfaces among the four longitudinal surfaces of the mounting substrate (a pair of main surfaces and a pair of longitudinal end surfaces). It is covered with a heat-dissipating sheet having a U-shaped cross section. Therefore, the heat generated in the light-emitting diode chip is efficiently conducted and dissipated through the light-emitting diode module and the mounting board to the metal case, casing, and the outside, so that the heat around the LED light source body and the mounting board Thus, the heat storage stored in can be reduced, and the temperature rise of the light emitting diode module or the light emitting diode chip can be effectively suppressed. Accordingly, it is possible to provide a liquid crystal display device having an LED backlight that can suppress a decrease in light emission efficiency, prevent damage to the LED light source itself due to heat, and perform bright and long-life liquid crystal display.

  In addition, since the cutout portion where the light emitting surface of the light emitting diode module is exposed is formed on one surface of the heat radiation sheet having a U-shaped cross section, the light emitted from the light emitting diode module can be reliably supplied to the light guide plate. .

  Further, the U-shaped heat radiating sheet is covered with a metal case having a heat sink function, and the heat transmitted to the U-shaped heat radiating sheet can be efficiently conducted to the metal case. In addition, an external impact can be blocked by this metal case, and further reduced by a heat radiating sheet, resulting in a liquid crystal display device having excellent impact resistance.

  The liquid crystal display panel and the backlight are housed in a housing, and the metal case is formed integrally or in close contact with the housing, so that heat is reliably transmitted from the metal case to the housing. be able to. Specifically, since the adhesion to the housing is bonded via a heat conductive adhesive or a heat conductive adhesive, heat conduction efficiency can be greatly increased.

  Since the display body includes at least the liquid crystal display device described above, a driving unit that applies a predetermined signal to the display electrode, and a predetermined circuit that supplies the driving unit, the display body can also display a very bright liquid crystal display. Become.

  Hereinafter, the liquid crystal display device of the present invention will be described in detail with reference to the drawings.

1 is a schematic cross-sectional view of a liquid crystal display device of the present invention, FIG. 2 is a perspective view of an external appearance seen from the display surface of the liquid crystal display device, FIG. 3 is a schematic cross-sectional structure of a liquid crystal display panel, and FIG. Fig. 5 shows a perspective view of a mounting board on which an LED light source body is mounted, Fig. 5 shows an example of a heat dissipation sheet in a perspective view, and Fig. 6 shows an example of a metal case having a heat sink function in a perspective view.

  The liquid crystal display device of the present invention is mainly composed of a liquid crystal display panel 1, an LED backlight, a casing 6 of the liquid crystal display device, and a metal case 10 (referred to as a heat sink substrate) having a heat sink function. The housing 6 shown in the figure is mainly composed of an upper housing that protects the liquid crystal display panel 1 and a lower housing that is disposed behind the backlight, and the heat sink substrate 10 mainly holds and protects the light source body of the LED backlight. In addition, it also serves as a heat sink function for releasing heat to the outside. In FIG. 2, the heat sink substrate 10 is disposed so that a part of the heat sink substrate 10 is exposed from one side surface of the housing 6 so that heat can be directly released from the heat sink substrate 10 to the outside of the periphery of the housing 6. .

  The liquid crystal display panel 1 is surrounded by a seal portion 14 between a lower transparent substrate 11 which is the other substrate shown in FIG. 3, an upper transparent substrate 12 which is one substrate, and both transparent substrates 11 and 12. A liquid crystal layer 13 is disposed. Further, for example, a display electrode and an alignment film are formed on the inner surface of the lower transparent substrate 11, and a display electrode and an alignment film are also formed on the inner surface of the upper transparent substrate 12. In FIG. 3, the structure on the inner surface of the lower transparent substrate is simply indicated by reference numeral 15, and the structure of the upper transparent substrate is simply indicated by reference numeral 16.

  The display electrodes constituting the internal structure 15 of the lower transparent substrate 11 and the display electrodes constituting the internal structure 16 of the upper transparent substrate 12 form display pixel regions arranged in a matrix so as to face each other. .

  One pixel constituting each display pixel area is a translucent liquid crystal display device in which, for example, in a transmissive liquid crystal display device, the display electrodes are all formed of transparent electrodes and serve as a light transmissive portion that can transmit the light of the backlight. In the display device, a light reflecting portion, part of which is made of a reflective metal film, and a light transmitting portion, which is partly capable of transmitting light from the backlight, are provided side by side. That is, in this transflective liquid crystal display device, external light incident from the display surface side is reflected by the light reflecting portion of the pixel area and returned to the display surface side, and the backlight light is transmitted. The light is given to the display surface side. As a result, when the external light is strong, the display is performed in the reflective mode, and when the external light is weak, the display is performed in the transmissive mode.

  Further, although not shown in the drawing, a polarizing plate, a retardation plate, and, if necessary, a scattering plate are arranged on the outer surface of the lower transparent substrate 11 and the outer surface of the upper transparent substrate 12.

  In order to achieve color display, a color filter corresponding to each pixel region of either the internal structure 15 of the lower transparent substrate 11 or the internal structure 16 of the upper transparent substrate 12 may be formed.

  Further, depending on the display driving method, switching means may be formed in each pixel region of either the internal structure 15 of the lower transparent substrate 11 or the internal structure 16 of the upper transparent substrate 12, and display may be controlled for each pixel region. It may be.

  Further, any one of the upper transparent substrate 12 and the lower transparent substrate 11, for example, a substrate having a large shape, for example, an outer peripheral region of the upper transparent substrate 12, includes display electrodes and switching among the inner surface structures 15 of the upper transparent substrate 12. A wiring pattern connected to the element may be provided and an input terminal connected to a driving circuit for supplying a predetermined signal and a predetermined voltage to the wiring pattern or an external driving circuit may be provided. Note that the substrate on the side where the wiring pattern is not formed, for example, the display electrode of the lower transparent substrate 11 is connected to the wiring pattern on the upper transparent substrate 12 side through a conductive filler disposed in the space between the substrates 11 and 12. It doesn't matter.

  Examples of the lower transparent substrate 11 and the upper transparent substrate 12 include glass and translucent plastic. The display electrodes constituting the internal structures 15 and 16 are made of, for example, ITO or tin oxide which is a transparent conductive material, and the reflective metal film constituting the reflecting portion is made of aluminum or titanium. . The alignment film is made of a rubbed polyimide resin. In addition, when forming color filters, dyes or pigments are added to the resin to form red, green, and blue color filters for each pixel area, and between the filters and around the pixel area for light shielding purposes. A black resin may be used.

  The lower transparent substrate 11 and the upper transparent substrate 12 are bonded and pressure-bonded via the seal portion 14, and a liquid crystal material made of nematic liquid crystal or the like is injected from a part of the opening of the seal portion 14. Seal the inlet. At the time of bonding, both display electrodes arranged on the transparent substrates 11 and 12 are made to be orthogonal to each other, and the intersection of the display electrodes becomes each pixel region, and this pixel region is aggregated to become a display region.

  In this way, the liquid crystal display panel 1 is configured. An LED backlight is disposed outside the lower substrate 11 which is the other transparent substrate of the liquid crystal display panel 1.

  As shown in FIG. 1, the LED backlight includes a light emitting diode module (hereinafter referred to as an LED light source) 7 having a container accommodating a light emitting diode chip, a light guide plate 4, a lens sheet 2, a diffusion sheet 3, a reflective sheet 5, and a mounting. A heat sink substrate 10 is disposed on the outer surface of the heat radiating sheet 9. The light source body referred to in the present invention includes an LED light source 7, a mounting substrate 8, and a heat radiating sheet 9 having a U-shaped cross section, and includes a heat sink substrate 10 as necessary.

  Then, one main surface (surface from which light is emitted) of the light guide plate 4 is disposed so as to face the display area of the liquid crystal display panel 1.

  The light guide plate 4 constituting the LED backlight is made of a transparent resin substrate, and a light scattering member may be contained in the resin component. On the other main surface of the light guide plate 4, a reflection sheet 5 for diffusing and reflecting light is disposed. The reflection sheet 5 is for radiating light propagating through the light guide plate 4 to one main surface side. Instead of the reflection sheet 5, a groove for diffusing and reflecting directly may be formed on the other main surface, or a coating film having a diffusing and reflecting function may be formed on the other main surface. The reflection sheet 5 may also be formed on three end surfaces of the four end surfaces of the light guide plate 4 except for the end surface on which the LED light source 7 is disposed.

  The mounting substrate 8 is made of a long glass cloth base epoxy resin substrate or a ceramic substrate, on which the LED module (LED light source) 7 is mounted. A metal wiring pattern for supplying a predetermined driving current to the LED light source 7 is formed on the mounting surface of the LED light source 7. Then, a plurality of LED light sources 7 are arrayed and mounted on the metal wiring pattern at a predetermined interval via a conductive member.

  Next, the heat dissipation structure will be described with reference to FIG.

First, the mounting substrate 8 on which the LED light source 7 is mounted is installed so that the end surface of the light guide plate 4 and the light emitting surface of the LED light source 7 face each other. Further, a heat radiation sheet 9 having a U-shaped cross section is provided so as to contact the lower surface of the mounting substrate 8 on which the LED light source 7 is mounted, the back surface facing the surface, and the end surface perpendicular to the surface. is set up. Here, as shown in FIGS. 5A and 5B, the heat radiation sheet 9 is formed with an opening which is a notch 91 that exposes the LED light source 7. That is, the heat-dissipating sheet 9 having a U-shaped cross section has a long opening formed on only one surface on which the mounting substrate 8 on which the LED light source 7 is mounted is formed, and is constituted by the other three surfaces.

  Further, as shown in FIG. 5C, the heat radiation sheet 9 has a U-shaped cross section that contacts the surface of the mounting substrate 8 facing the surface on which the LED light source 7 is mounted and the upper and lower surfaces perpendicular to the surface. It may be. In this case, an opening used when the mounting substrate 8 is inserted into the heat radiating sheet 9 having a U-shaped cross section serves as a notch that exposes the light emitting surface of the LED light source 7.

  As shown in FIG. 6, the outer surface of the heat-dissipating sheet 9 having a U-shaped cross section is covered with a heat sink substrate 10 made of metal. The heat sink sheet 9 having a U-shaped cross section and the heat sink substrate 10 are in close contact with each other at the contact surface. The heat sink substrate 10 is provided with a notch 101 in which the light emitting surface of the LED light source 7 is exposed in FIG.

  In FIG. 6, the heat sink substrate 10 is formed by metal processing so as to have a U-shaped cross section. However, the heat sink substrate 10 may have a structure surrounding the heat-dissipating sheet 9 having a U-shaped cross section, for example, a cross-sectional shape. Absent.

  Here, since the heat radiating sheet 9 presses and holds the mounting substrate 8 and the heat sink substrate 10, it is preferable that the external dimension of the heat radiating sheet 9 is slightly larger than the internal dimension of the heat sink substrate 10.

  Further, since the heat dissipation sheet 9 is elastic, the fine uneven shapes on the surfaces of the mounting substrate 8 and the heat sink substrate 10 are absorbed, and the mounting substrate 8 and the heat dissipation sheet 9 Are in close contact with each other with almost no air layer interposed, and are brought into surface contact.

  In addition, the heat sink substrate 10 that contacts the outer surface of the heat dissipation sheet 9 may have a curved surface (R) at the inner corner portion during metal bending or metal pressing, and this curved surface is the elastic characteristic of the heat dissipation sheet 9. Absorb. Further, if the elastic properties cannot be absorbed, the outer corner portion of the heat radiation sheet 9 that contacts the inner curved portion can be chamfered to escape from the curved surface R, and the heat radiation sheet 9 and the heat sink substrate 10 It is surely brought into close contact and surface contact.

  Further, by cutting the end surface in the longitudinal direction of the mounting substrate 8 that is perpendicular to the one main surface on which the LED light source 7 is mounted, that is, the upper and lower surfaces, the unevenness of the cut surface can be almost eliminated, and the heat dissipation sheet 9 is adhered. In addition, it is possible to prevent generation of an air heat insulating layer between the mounting substrate 8 and the heat dissipation sheet 9 due to glass waste and resin waste generated from the end face of the mounting substrate 8.

  The heat sink substrate 10 is preferably in contact with or fixed to the housing 6 disposed on the back of the backlight. Particularly, a heat conductive adhesive (for example, a heat conductive adhesive SE4420 manufactured by Toray Dow Corning Silicone Co., Ltd.). Alternatively, when an adhesive (for example, heat conductive adhesive tape No. 8805 manufactured by Sumitomo 3M Co., Ltd.) is used for fixing, the heat of the heat sink substrate 10 is easily transmitted to the housing 6. Further, when the heat sink substrate 10 and the housing 6 are integrally molded or integrated using metal or the like, the heat of the heat sink substrate 10 is directly transmitted to the housing 6.

  Here, in order to improve the visibility of display information on the liquid crystal display panel 1, when the backlight of the liquid crystal display device is driven (the LED light source 7 is turned on), heat is generated along with the light emission. The generated heat is transmitted from the LED light source 7 to the mounting substrate 8, and the mounting substrate 8, the heat radiating sheet 9, and the heat sink substrate 10 are in surface contact with almost no air layer interposed therebetween. Then, the heat sink substrate 10 is efficiently reached and further transmitted to the housing 6.

  Therefore, the heat generated in the LED light source 7 is effectively radiated to the outside, and it is difficult for the LED light source 7 and the mounting substrate 8 to store heat, so that the temperature rise of the LED light source 7 and its surroundings can be effectively suppressed. it can.

  Since the heat of the LED light source 7 is transmitted most through the metal wiring formed on the mounting substrate 8 from the terminal portion formed on the container constituting the light emitting diode module, the heat radiation sheet 9 contacts the electrode portion of the mounting substrate 8; Furthermore, the heat dissipation effect is great when it comes into contact with the terminal portion, and the heat dissipation effect is further increased by arranging the heat sink substrate 10 with high thermal conductivity to be in close contact with the outer surface of the heat dissipation sheet 9 around the LED light source 7. It became bigger.

  These effects are that the display area of the liquid crystal display panel 1 is enlarged, the shape of the light guide plate 4 is enlarged, and a large number of LED light sources 7 are provided on the mounting substrate 8 in order to supply sufficient light to the light guide plate 4. The more you install, the greater the effect.

  In addition, the heat sink substrate 10 is disposed on the outer surface of the heat dissipation sheet 9 and the heat sink substrate 10 is disposed on the light emitting surface side of the LED light source 7 so as to be in close contact with the end surface of the light guide plate 4. Will improve. Specifically, after the light from the LED light source 7 is incident on the light guide plate 4, the light that is not emitted from the light guide plate 4 to the liquid crystal display panel 1 side but returns to the end surface side of the LED light source 7 of the light guide plate 4. is there. At this time, since the metal heat sink substrate 10 is arranged on the end face, the light can be reflected and returned to the light guide plate 4, and the loss of light can be reduced. If the heat sink substrate 10 is not present on the incident end face of the conductor plate 4 and the heat radiating sheet 9 is disposed on the end face of the light guide plate 4, the heat radiating sheet 9 of gray to black emits such light. It will be absorbed and light will be lost.

  An elastic sheet having a U-shaped cross section having heat dissipation characteristics (model number No. 5509 manufactured by Sumitomo 3M Co., Ltd.) is used for the heat dissipation sheet 9, aluminum having a thickness of 0.5 mm for the heat sink substrate 10, and a thickness of 0. 5 mm of aluminum was used, and the mounting substrate 8, the heat dissipation sheet 9, and the heat sink substrate 10 were fixed so as to be in surface contact.

  Here, the thermal conductivity of each material used is 0.45 W / m · K for the mounting substrate made of glass epoxy, 5 W / m · K for the heat dissipating sheet 9, 236 W / m for the heat sink substrate 10 and aluminum as the housing 6. -K.

  The heat generated along with light emission from the LED light source 7 is conducted through the mounting substrate 8 and the heat radiating sheet 9 to the heat sink substrate 10 made of aluminum and the housing 6 to be radiated. Moreover, the heat transmitted from the mounting substrate 8 to the heat sink substrate 10 is radiated from the three systems of the front surface side, the back surface side, and the lower surface side of the mounting substrate 8.

  Here, since the thermal conductivity of the mounting substrate 8 and the heat radiating sheet 9 is very small compared to the heat sink substrate 10 and the aluminum that is the housing 6, the mounting substrate 8 and the heat radiating sheet 9 are used to improve the heat conduction. A method of reducing the thickness of the film as much as possible is effective. Further, the heat sink substrate 10 and the housing 6 may be magnesium or iron. By the way, the thermal conductivity of magnesium is 157 W / m · K, the thermal conductivity of iron is 83.5 W / m · K, and if the heat dissipation is poor, increase the plate thickness or provide heat dissipation fins. Good.

  Then, using the liquid crystal display panel 1 having a size of 4.7 inches as the size of the display area, 18 LED light sources 7 are arranged and mounted on the mounting substrate 8, and a current is supplied to each LED light source 7 in a normal temperature (25 ° C.) state. The ambient temperature of the LED light source 7 in the backlight was measured at a current of 20 mA. As a result, it was found that the ambient temperature of the LED light source 7 can be suppressed to 34 ° C., and the estimated lifetime of the LED light source body can be extended to about 9000 hours. Moreover, about the luminous efficiency of the LED light source body, although it was very small, the improvement tendency was seen.

  On the other hand, when the heat radiating sheet 9 was removed, it was found that the ambient temperature of the LED light source 7 was 45 ° C., and the estimated lifetime of the LED light source body was only about 6400 hours.

  From the above experimental confirmation results, the heat dissipation sheet 9 is brought into close contact with the mounting substrate 8 and the heat sink substrate 10 to improve heat conduction, and the heat generated by the LED light source 7 is efficiently dissipated to the heat sink substrate 10 and the housing 6. By reducing the heat storage of the LED light source 7 and the mounting substrate 8 and reducing the temperature rise of the LED light source 7 and its surroundings, it is possible to suppress a decrease in the lifetime of the LED light source 7 and a decrease in light emission efficiency, and a long-life and bright liquid crystal display realizable.

  Further, since the heat radiation sheet 9 is arranged in a U-shaped cross section around the mounting substrate 8 and is sandwiched inside the heat sink substrate 10, the mounting substrate 8 can be held in a predetermined position very stably, Even if an impact is applied from the outside of the housing 6, the impact can be blocked by the heat sink substrate 10 of the light source body and can be absorbed by the heat radiating sheet 9 having a U-shaped cross section. The liquid crystal display device is highly reliable without being displaced or broken.

  In addition, although the light guide plate 4 of FIG. 1 has the thickness of the opposing end surface thinner than the thickness of the end surface on the side where the LED light source 7 is disposed, it may be a flat plate member having the same thickness on both end surfaces. Similarly, the lower casing 6 may be a casing having the same side surface in the depth direction.

  The heat sink substrate 10 and the housing 6 may be configured as separate members, or the resin may be molded only on the exposed surface of the sheet sink substrate 10.

It is a schematic sectional drawing of the liquid crystal display device of this invention. It is the surface perspective view seen from the display surface side of the liquid crystal display device of this invention. It is a cross-section figure of the liquid crystal display panel of the liquid crystal display device of this invention. It is a perspective view of the mounting substrate which mounted the LED light source of the liquid crystal display device of this invention. (A)-(c) is a perspective view of the heat-radiation sheet of the cross-sectional U shape used for the liquid crystal display device of this invention, respectively. (A)-(c) is a heat sink board | substrate perspective view used for the liquid crystal display device of this invention, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .... Liquid crystal display panel 2 .... Lens sheet 3 .... Diffusion sheet 4 .... Light guide plate 5 .... Reflection sheet 6 .... Case 7 ... LED module (LED light source)
8 .... Mounting board 9 .... Heat dissipation sheet 10 .... Heat sink board

Claims (6)

A liquid crystal display panel having a display region composed of a plurality of pixel regions with a liquid crystal interposed between a pair of substrates having a display electrode and an alignment film;
A light guide plate disposed outside one substrate of the liquid crystal display panel and positioned so as to correspond to the display area, and a backlight including a light source body positioned on an end surface of the light guide plate In liquid crystal display devices,
The light source body includes an elongate mounting substrate, a light emitting diode module that is arranged in plural on one main surface of the mounting substrate and accommodates a light emitting diode chip, both main surfaces of the mounting substrate, and both the main surfaces A heat dissipation sheet having a U-shaped cross section that covers three of the end surfaces in the longitudinal direction that form a right angle, and the mounting in the U-shaped heat dissipation sheet so that the light emitting surface of the light emitting diode module is exposed. A liquid crystal display device comprising a substrate. The liquid crystal display device according to claim 1, wherein a notch portion in which a light emitting surface of the light emitting diode module is exposed is formed on one surface of a heat radiating sheet having a U-shaped cross section. The liquid crystal display device according to claim 1, wherein the U-shaped heat radiation sheet is covered with a metal case having a heat sink function. 4. The liquid crystal display according to claim 3, wherein the liquid crystal display panel and the backlight are housed in a casing, and the metal case is formed integrally or in close contact with the casing. apparatus. 5. The liquid crystal display device according to claim 4, wherein the metal case is bonded to the housing via a heat conductive adhesive or a heat conductive adhesive. A display body comprising at least the liquid crystal display device according to claim 1, a driving unit that supplies a predetermined signal to the display electrode, and a predetermined circuit that supplies the driving unit.

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