JP2006064733A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display having an LED backlight capable of suppressing reduction of light emitting efficiency of an LED, preventing damage of the LED and performing bright liquid crystal display of a long life. <P>SOLUTION: The liquid crystal display is constituted of a liquid crystal panel 1, and the backlight provided with: a light guide plate 4; and a light source body disposed on an end face of the light guide plate 4. The light source body comprises: an insulating substrate 8; a plurality of light emitting diode modules 7 which are arranged and mounted on one principal surface of the insulating substrate 8 and has a light emitting diode 7a housed therein; a heat sink substrate 10 disposed on the other principal surface side of the insulating substrate 8; a first heat conductive elastic sheet 17 which is closely adhered to the one principal surface (front surface) of the insulating substrate 8 and has aperture parts formed for exposing the LED modules; and a thin plate-shaped second heat conductive elastic sheet 9 closely adhered to the other principal surface (rear surface) of the insulating substrate 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device including a liquid crystal display panel and a backlight, and more particularly to a liquid crystal display device using a light emitting diode (LED) as a light source body of a backlight.

  2. Description of the Related Art Conventionally, among transmissive and transflective liquid crystal display devices among liquid crystal display device display methods, a liquid crystal display panel and a backlight that supplies light transmitted to the liquid crystal display panel are arranged. In general, a 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 faces the main surface (front surface) on the liquid crystal display panel side so as to correspond to the display area of the liquid crystal display panel, and the main surface (back surface) on the opposite side of the main surface is exposed to light. A diffusion part that diffuses and reflects is formed on the side. The CCFL light source is disposed on the end face of the light guide plate, and the CCFL light incident from the end face of the light guide plate is transmitted into the light guide plate, diffused and reflected on the back side of the light guide plate, and directed from the light guide plate to the liquid crystal display panel. And is converted from a linear light source to a uniform planar light source and used as a light source for a liquid crystal display device.

  However, in this CCFL light source, 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, the use of an alternative light source is required by suppressing the use of harmful mercury. Further, in order to light the CCFL, a high-voltage high-frequency lighting circuit is required, and high-frequency noise is generated. Thus, there is a problem that not only a countermeasure against noise is separately required but also low-temperature lighting is difficult.

  On the other hand, as a new light source body, a backlight using a light emitting diode module (LED light source) containing a light emitting diode (LED) chip having a feature of a point light source as a light source has been developed. Backlights using this LED light source (LED backlights) are becoming widespread as backlights for liquid crystal display panels due to lower prices, improved luminous efficiency, and environmental regulations. At the same time, with the increase in brightness and size of liquid crystal display devices (increase in display area), there is an increasing demand for a plurality of LED light sources.

  Therefore, in order to obtain an LED backlight for use in high-brightness and large-sized liquid crystal display panels, the LED light source, which is a point light source, is converted into a planar light source that emits light uniformly (converted into uniform light on the light exit surface of the light guide plate) For example, it is necessary to control the material and structure of the diffusion part on the back surface of the light guide plate and to arrange the LED light source at an optimum position according to the directivity of the LED light source. is there.

  The biggest problem here is that the LED light source and its surrounding temperature rise due to the heat generated by the LED light source, thereby reducing the light emission efficiency and life of the LED chip of the LED light source. Although the LED light source has been improved in luminous efficiency due to recent improvements, the luminous efficiency is about 10% at present, and the remaining 90% is released as heat. That is, in a backlight using an LED as a light source, the generated heat is stored in an LED light source and an insulating substrate on which the LED light source is mounted, and as the LED light source and its surrounding temperature rise, the light emission efficiency of the LED itself decreases. It will be. Regarding the lifetime, for example, the estimated lifetime data (luminance half-life) of Nichia Top View LED (NSCW455) at forward current IF = 20 mA is about 12000 hours at an ambient temperature of 25 ° C. On the other hand, it is only about 5500 hours at 50 ° C., and it can be seen that the lifetime decreases as the ambient temperature of the LED increases. Furthermore, the heat generated in the LED may cause damage to the LED and the wiring of the insulating substrate 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 one side of the wiring board, which is a linear light source substrate having a power supply terminal, and covers the electrode of the insulating substrate disposed in the box-shaped metal case. 2. Description of the Related Art There is known a radiation device having a heat radiation structure in which a conductive adhesive is filled in a box-shaped metal case except for a light emitting element light emitting surface on a heat radiation insulating resin layer provided.
JP 2003-281924 A

  However, the LED backlight used in the liquid crystal display device and disposed on the back side of the liquid crystal display panel is fixed to the housing that also serves as the heat sink function of the liquid crystal display device with the light guide plate and the insulating substrate on which the light source body is mounted. Was. As a fixing method, a support protrusion or the like is formed inside the housing in accordance with the shape of the backlight, and the support protrusion is used for fixing, or the backlight is attached to the housing with a double-sided adhesive tape. It adhered to a predetermined site.

  Here, the insulating substrate is provided with a metal wiring such as copper on one main surface (mounting surface of the light source body) of a flexible substrate made of polyimide or polyester or a substrate made of glass epoxy, and an LED light source is mounted on the wiring, The other main surface of the insulating substrate (the back surface of the substrate) was brought into contact with the housing or the like.

  However, although the back surface of the insulating substrate and the housing of the liquid crystal display device are in surface contact, the surface contact is actually insufficient due to fine irregularities on the surface. When conducting heat conduction, an extremely small air layer due to unevenness is interposed. Also, in the case of adhesive fixing with a double-sided adhesive tape, since the thermal conductivity of the double-sided adhesive tape is small, heat conduction from the insulating substrate to the heat sink substrate is insufficient, and the LED light source or the insulating substrate stores heat, and the LED light source As the temperature rises, the luminous efficiency of the LED light source is lowered, and further, the light emitting diode chip is damaged in a short time.

  Moreover, although the technique which fills one main surface of the insulated substrate which mounted the LED light source with heat conductive resin and suppresses the temperature rise of LED light source is disclosed, the operation | work which fills heat conductive resin becomes complicated, and also Air often enters during the resin curing process, and heat conduction may be insufficient.

  The present invention has been devised in view of the above-mentioned problems, and an object thereof is a liquid crystal display device provided with an LED backlight, and an insulating substrate and a liquid crystal display device on which an LED light source is mounted with a simple and inexpensive structure. By improving the surface contact heat conduction with the housing or heat sink substrate, efficiently transferring the heat generated by the LED light source to the heat sink substrate, reducing the heat storage of the insulating substrate, and reducing the temperature rise of the LED light source, An object of the present invention is to provide a liquid crystal display device having a light-emitting diode element that can suppress a decrease in light emission efficiency of an LED light source, prevent damage to a light-emitting diode chip, can display a bright and long-lived liquid crystal display, and has excellent impact resistance. It is said.

The liquid crystal display device of the present invention includes a liquid crystal display panel in which a liquid crystal is interposed between a pair of substrates having a display electrode and an alignment film, and a display region is configured by a plurality of pixel regions;
A light guide plate disposed outside one substrate of the liquid crystal display panel and disposed so as to correspond to the display region, and a light source body disposed so that light is incident from an end surface of the light guide plate It consists of a backlight. The light source body includes an insulating substrate and a plurality of light emitting diode modules arranged and mounted on one main surface of the insulating substrate and accommodating a light emitting diode chip, and is disposed on the other main surface side of the insulating substrate. A heat sink substrate is disposed, and a first thermally conductive elastic sheet is disposed between the end surface of the light guide plate and one main surface of the insulating substrate, and a second heat conductive substrate is disposed between the other main surface of the insulating substrate and the heat sink substrate. A heat conductive elastic sheet was arranged respectively.

  The first thermally conductive elastic sheet is characterized in that an opening for exposing the light emitting diode module is formed.

  The thickness of the first heat conductive elastic sheet is thicker than the thickness of the light emitting diode module.

  Note that the above heat sink substrate may also be used as a part of the casing of the liquid crystal display device, or a heat sink substrate may be used separately from the casing.

  In the liquid crystal display device of the present invention, an elastic sheet having a large thermal conductivity is brought into close contact with the front surface which is one main surface and the back surface which is the other main surface of the insulating substrate on which the LED light source which is a light emitting diode module is mounted. Yes. Here, the heat conductive elastic sheet disposed between one main surface side of the insulating substrate, that is, the light guide plate is used as the first heat conductive elastic sheet, and the other main surface side of the insulating substrate, that is, the heat sink substrate. The heat conductive elastic sheet disposed between the two is the second heat conductive elastic sheet.

  Thereby, for example, heat released from the LED light source to the surface side of the insulating substrate can be radiated to the light guide plate through the first heat conductive elastic sheet disposed on the surface side of the insulating substrate. it can. Further, heat can be radiated to a member that contacts the end face of the first heat conductive elastic sheet, for example, a part of the housing (heat sink substrate).

  Of the heat generated by the LED light source, for example, heat transmitted from the light emitting diode module to the insulating substrate is transmitted to the surface side of the insulating substrate and can be radiated to the light guide plate as described above. Further, it is transmitted to the back side of the insulating substrate, and can be stably released to the heat sink substrate and the housing having the heat sink function through the second heat conductive elastic sheet.

  That is, heat on the front surface side of the insulating substrate and heat transferred to the back surface side of the insulating substrate can be efficiently released to other than the insulating substrate.

  Moreover, the 1st heat conductive elastic sheet arrange | positioned between an insulated substrate and a light-guide plate is press-contacted between both members. In addition, the second heat conductive elastic sheet disposed between the insulating substrate and the heat sink substrate is sandwiched between the two members. That is, even if the surface state of the insulating substrate, the end surface state of the conductor plate, and the surface state of the heat sink substrate are in a state where minute irregularities exist, this is caused by the pressure contact of the first and second heat conductive elastic sheets. A part of the heat conductive elastic sheet can be bitten into the irregularities, and the formation of an air layer between the insulating substrate and the light guide plate can be effectively suppressed to increase the heat conductivity. In addition, the thermal conductivity can be increased by effectively suppressing the formation of an air layer between the insulating substrate and the heat sink substrate. Thus, it is possible to efficiently conduct heat from the insulating substrate to the heat sink substrate.

  Moreover, since the opening which exposes the light emitting diode module mounted in the insulating substrate is formed in the 1st heat conductive sheet, the light from a light emitting diode module can be stably guide | induced to a conductor board. Moreover, since the thickness of the 1st heat conductive elastic sheet is thick compared with the thickness of the said light emitting diode module, the adhesiveness of a light-guide plate and a 1st heat conductive elastic sheet improves.

  In addition, the light guide plate needs to be fixed to match the display area of the liquid crystal panel. Specifically, fixing means for positioning the light guide plate and the insulating substrate at predetermined positions, for example, a plurality of support protrusions, are formed inside the casing of the liquid crystal display device. In addition, the inner wall of the housing and the light guide plate or the insulating substrate are bonded and fixed with a double-sided adhesive. In the present invention, the insulating substrate is positioned with the heat conductive elastic sheet interposed between the insulating substrate and the casing (heat sink substrate). For this reason, even if an external impact is received, the impact is not applied to the insulating substrate, so there is no damage to the insulating substrate or displacement of the insulating substrate from a predetermined position, and stable fixing with excellent impact resistance is possible. It becomes. In other words, by reducing the heat storage of the insulating substrate on which the LED light source is mounted and reducing the temperature rise of the LED light source, the LED light source can be prevented from lowering the luminous efficiency, and the LED light source can be prevented from being damaged, and the bright long-life liquid crystal display In addition, a liquid crystal display device having an LED backlight having excellent impact resistance can be provided.

  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 an insulating substrate on which an LED light source is mounted, and Fig. 5 shows a perspective view of a heat conducting elastic sheet. FIG. 6 is a schematic cross-sectional view illustrating an LED light source.

  The liquid crystal display device of the present invention is mainly composed of a liquid crystal display panel 1, an LED backlight, a housing 6 of the liquid crystal display device, and a heat sink substrate 10. In addition, the housing 6 in the figure is an upper housing that mainly protects the liquid crystal display panel 1, and the heat sink substrate 10 is a housing that mainly protects the LED backlight and has a heat sink function for releasing heat to the outside. It also serves as a heat sink substrate.

  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 side of the lower transparent substrate 11, and a display electrode and an alignment film are formed on the inner surface side of the upper transparent substrate 12. In FIG. 3, the structure on the inner surface side 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 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 the internal structure 15 of the lower transparent substrate 11 to control display for each pixel region.

  In addition, in one of the upper transparent substrate 12 and the lower transparent substrate 11, for example, a substrate having a large shape, for example, the outer peripheral region of the lower transparent substrate 11, display electrodes and switching among the inner surface structures 15 of the lower transparent substrate 11. 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. In addition, the substrate on the side where the wiring pattern is not formed, for example, the display electrode of the upper transparent substrate 12 is placed on the lower side through conductive fillers and connection bumps contained in the seal portion 14 disposed in the space between the substrates 11 and 12. It may be connected to the wiring pattern on the transparent substrate side.

  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 an LED light source 7, which is an LED module, a light guide plate 4, a lens sheet 2, a diffusion sheet 3, a reflective sheet 5, an insulating substrate 8, a first thermal conductive elastic sheet 17, 2 heat conductive elastic sheet 9 and heat sink substrate 10.

  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 insulating substrate 8 is made of a glass cloth base epoxy resin substrate or a ceramic substrate, and the LED light source 7 is mounted thereon. On the mounting surface of the LED light source 7, metal wiring for supplying a predetermined driving current to the LED light source 7 is formed. A plurality of LED light sources 7 are mounted on the metal wiring at a predetermined interval via a conductive member.

  As shown in the cross-sectional view of FIG. 6, the LED light source 7 includes an LED chip 7a having a light emitting portion made of a semiconductor material, an anode electrode, and a cathode electrode, and a container 7b made of a heat-resistant resin material or a ceramic material. Yes. A mortar-shaped cavity 7d is formed on the surface of the container 7b where light is emitted, and the LED chip 7a is disposed and accommodated at the bottom of the cavity 7d. The anode electrode and cathode electrode of the LED chip 7a are connected to a terminal portion 7c formed on the outer surface other than the light emitting surface of the container 7b. A reflective paint is applied to the inner wall surface of the mortar-shaped cavity 7d, and the cavity is filled with a translucent resin or a fluorescent resin so that the LED chip 7a is embedded.

  Next, a heat dissipation structure for heat generated from the LED light source 7 will be described.

  The heat generated in the LED chip 7 a is transmitted to the container 7 b, a part is radiated around the container 7 b, passes through the wiring conductor, is transmitted to the terminal portion 7 c, and a part is transmitted to the insulating substrate 8. The heat radiated around the container 7b is also transmitted to the insulating substrate 8 on the insulating substrate 8 side of the container 7b.

  First, the insulating substrate 8 on which the LED light source 7 is mounted is installed so as to face the end surface of the light guide plate 4 so that the light of the LED light source 7 is incident from the end surface of the light guide plate 4. Furthermore, the heat conductive elastic sheets 9 and 17 which contact the surface side of the insulating substrate 8 on which the LED light source 7 is mounted and the surface side facing the surface are installed. That is, the first heat conductive elastic sheet 17 is disposed on the mounting surface side of the insulating substrate 8, and the second heat conductive elastic sheet 9 is disposed on the back surface side of the insulating substrate 8.

  The second heat conductive elastic sheet 9 has a flat shape as shown in FIG. 5B and is sandwiched between the other main surface (back surface) of the insulating substrate 8 and the heat sink substrate 10. The first heat conductive elastic sheet 17 is formed with an opening 17 a corresponding to the mounting position of the LED light source 7 mounted on the mounting surface of the insulating substrate 8, and one main surface (mounting surface) of the insulating substrate 8. It is sandwiched between the light guide plate 4.

  The heat around the LED light source 7 and on the surface side of the insulating substrate 8 is transmitted to the light guide plate 4 and the heat sink substrate 10 and can be dissipated by the presence of the first heat conductive elastic sheet 17. Note that heat is radiated to the heat sink substrate 10 via the lower end face of the first heat conductive elastic sheet 17. Further, the heat on the back side of the insulating substrate 8 is transmitted to the heat sink substrate 10 and can be dissipated by the presence of the second heat conductive elastic sheet 9.

  Incidentally, the opening 17a of the first heat conducting elastic sheet 17 shown in FIG. 5A is provided with a window-like opening corresponding to the LED light source 7, but such first heat conducting elasticity is provided. When the insulating substrate 8 is disposed on the sheet 17, the LED light source 7 mounted on the insulating substrate 8 may be press-fitted while being positioned at the opening 17a.

  Here, it is important that the thickness of the first heat conductive elastic sheet 17 is slightly thicker than the design value interval between the insulating substrate 8 and the light guide plate 4, that is, the mounting height of the LED light source 7. The thickness of the second heat conductive elastic sheet 9 is made slightly thicker than the design value interval between the insulating substrate 8 and the heat sink substrate 10. By doing so, both the heat conductive elastic sheets 9 and 17 have elasticity, so that the insulating substrate 8 on which the LED light source 7 is mounted can be pressed and sandwiched between the light guide plate 4 and the heat sink substrate 10. Not only stable fixing, but also the surface state of the end face of the light guide plate 4, the surface state of the insulating substrate 8 and the surface state of the heat sink substrate 10, that is, the state where a fine uneven shape exists, fine unevenness is absorbed. As a result, fine irregularities on the surfaces of the insulating substrate 8 and the heat sink substrate 10 are absorbed. As a result, the light guide plate 4, the first heat conductive elastic sheet 17, the insulating substrate 8, the second heat conductive elastic sheet 9, and the heat sink substrate 10 are in close contact with each other with almost no air layer interposed therebetween. Surface contact. At the same time, by providing elasticity to the heat conductive elastic sheets 9 and 17, even if an external shock is applied to the liquid crystal display device, the shock can be absorbed by the heat conductive elastic sheets 9 and 17, Is not transmitted directly to the insulating substrate 8, so that there is no occurrence of displacement, the insulating substrate 8 itself is damaged, or the LED light source 7 is detached.

  FIG. 5A shows an example of the first heat conductive elastic sheet 17. In the 1st heat conductive elastic sheet 17, the opening part 17a which exposes the LED light source 7 corresponding to the LED light source 7 mounted in the insulated substrate 8 is an example which has comprised window shape. In this case, since the first portion 17b of the heat conductive elastic sheet 17 is substantially present around the LED light source 7, the periphery of the LED light source 7, specifically, one of the insulating substrates 8 is provided. All the heat released to the main surface side can be received by the heat conducting elastic sheet 17 and released to the light guide plate 4. Further, it is possible to escape from the lower surface side of the first heat conducting elastic sheet 17 to the heat sink substrate 10.

  FIG. 5B shows an example of the second heat conductive elastic sheet 9. The second heat conductive elastic sheet 9 is made of a thin plate-like elastic rubber material having good heat conductivity, and has a rectangular flat plate shape. The second heat conductive elastic sheet 9 is stable from the insulating substrate 8 to the heat sink substrate 10. Heat is dissipated.

  Further, at least the lower surface of the insulating substrate 8 on which the LED light source 7 is mounted is cut and polished, so that almost no irregularities on the lower surface can be eliminated and the heat sink substrate 10 can be adhered. At the same time, since glass waste and resin waste generated at the ridge line portion of the lower end surface of the insulating substrate 8 can be eliminated, generation of an air layer between the insulating substrate 8 and the heat conductive elastic sheets 9 and 17 can be prevented. . Further, the upper and lower surfaces of the insulating substrate 8 are cut and polished so as to be positioned at predetermined dimensions from the metal wiring on which the LED light source 7 is mounted, so that the thickness direction of the end surface of the light guide plate 4 on which the LED light source 7 is disposed is increased. The position of the LED light sources 7 arranged in a straight line at the center can be controlled.

  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. This heat is generated in the LED chip 7a and transmitted to the container 7b. Then, heat is radiated to the outer periphery of the container 7b, and at the same time, the heat is transmitted to the insulating substrate 8 via a contact portion (terminal portion 7c and the like) between the container 7b and the insulating substrate 8. The heat transferred from the LED light source 7 to the insulating substrate 8 is transferred from the insulating substrate 8 to the light guide plate 4 and the heat sink substrate 10 through the first and second heat conductive elastic sheets 17 and 9. In particular, the insulating substrate 8 and the first and second heats are in contact with the members sandwiching the first and second heat conducting elastic sheets 17 and 9 with almost no air layer interposed therebetween. The light guide plate 4 and the heat sink substrate 10 are efficiently reached via the conductive elastic sheets 17 and 9.

  The heat radiated to the outer periphery of the container 7b is transmitted to the light guide plate 4 side and the insulating substrate 8 side by the first heat conducting elastic sheet 17 arranged so as to surround the LED light source 7, and at least the LED light source The temperature around 7 does not become extremely high.

  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 insulating substrate 8 to store heat. it can.

  Since the heat of the LED light source 7 is transmitted most through the metal wiring formed on the insulating substrate 8 from the LED terminal portion 7c, the heat conductive elastic sheet 17 contacts the metal wiring of the insulating substrate 8, and further the terminal portion of the LED. When it comes into contact with 7c, the effect of heat dissipation is great.

  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 are supplied to the insulating substrate 8 in order to supply sufficient light to the enlarged light guide plate 4. The more the 7 is installed, the greater the effect.

  The heat conductive elastic sheets 9 and 17 are made of plate-like elastic sheets having heat dissipation characteristics (model number No. 5509 of Sumitomo 3M Limited), the heat sink substrate 10 is made of aluminum having a thickness of 2 mm, and the insulating substrate 8 The heat conductive elastic sheets 9 and 17 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 an insulating substrate made of glass epoxy, 5 W / m · K for a heat dissipation sheet, and 236 W / m · K for aluminum as a heat sink substrate.

  The heat generated by the LED light source 7 along with light emission is thermally conducted to the heat sink substrate 10 made of aluminum via the insulating substrate 8 and the heat conducting elastic sheets 9 and 17 and is radiated. Part of the heat passes through the heat conducting elastic sheet 17 and is also conducted and dissipated to the light guide plate 4. Moreover, the heat transmitted from the insulating substrate 8 to the heat sink substrate 10 is radiated from the three systems on the front surface side, the back surface side, and the lower surface side of the insulating substrate 8.

  Here, since the thermal conductivity of the insulating substrate 8 and the heat conductive elastic sheets 9 and 17 is very small as compared with aluminum as the heat sink substrate, in order to improve the heat conduction, the insulating substrate 8 and the heat conductive elastic sheet 9 are used. A method of reducing the thickness of the film as much as possible is effective. Further, the heat sink substrate 10 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, 16 LED light sources 7 are arrayed and mounted on the insulating substrate 8, and a current is supplied to each LED light source 7 at room temperature (25 ° C.). A current of 20 mA was passed, and the temperature around the LED light source 7 in the backlight was measured. As a result, it was found that the ambient temperature of the LED light source 7 can be suppressed to 36 ° C., and the estimated lifetime of the LED light source can be extended to about 8500 hours. In addition, the luminous efficiency of the LED light source showed a tendency to improve although it was very small.

  On the other hand, when the heat conductive elastic sheet was removed, it was found that the ambient temperature of the LED light source was 44 ° C., and the estimated life of the LED light source was only about 6600 hours.

  From the above experimental confirmation results, the heat conduction elastic sheets 9 and 17 are brought into close contact with the insulating 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. By reducing the heat storage of the LED light source 7 and the insulating 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 luminous efficiency, and a long-life and bright liquid crystal display device realizable.

  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, a lower casing that also serves as the heat sink substrate 10 may be a casing having the same side surface in the depth direction. Furthermore, the metal material of the heat sink substrate 10 is exposed on the back side of the liquid crystal display device by serving as the heat sink substrate 10 and the housing. In order to match the external appearance of the housing 6 on the upper surface side, the heat sink substrate 10 and the housing may be configured as separate members, or the resin may be molded only on the exposed surface of the sheet sink substrate 10. Absent.

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 insulated substrate which mounted the LED light source on the insulated substrate of the liquid crystal display device of this invention. (A) is a perspective view of the 1st heat conductive elastic sheet of the liquid crystal display device of this invention, (b) is a perspective view of a 2nd heat conductive elastic sheet. It is a schematic sectional drawing of the LED module (LED light source) used for this invention.

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 .... Frame 7 .... LED module ( LED light source)
8 ... Insulating substrate 9 ... Thermal conductive elastic sheet 10 ... Heat sink substrate 17 ... Thermal conductive elastic sheet

Claims (3)

A liquid crystal display panel in which a liquid crystal is interposed between a pair of substrates having a display electrode and an alignment film, and a display region is configured by a plurality of pixel regions;
A light guide plate disposed outside one substrate of the liquid crystal display panel and disposed so as to correspond to the display region, and a light source body disposed so that light is incident from an end surface of the light guide plate In a liquid crystal display device composed of a backlight,
The light source body includes an insulating substrate and a light emitting diode module which is mounted in plural on one main surface of the insulating substrate and accommodates a light emitting diode chip, and is disposed on the other main surface side of the insulating substrate. A first heat conductive elastic sheet between the end surface of the light guide plate and one main surface of the insulating substrate, and a second heat transfer between the other main surface of the insulating substrate and the heat sink substrate. A liquid crystal display device, characterized in that elastic sheets are respectively arranged.   The liquid crystal display device according to claim 1, wherein the first heat conductive elastic sheet has an opening for exposing the light emitting diode module.   The liquid crystal display device according to claim 1, wherein a thickness of the first heat conductive elastic sheet is larger than a thickness of the light emitting diode module.

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