JP4587720B2 - Light source device and liquid crystal display device having the same - Google Patents

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. 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 in that the luminous efficiency decreases when the junction temperature increases. 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 has a light guide plate and an insulating substrate on which a light source body is mounted in a casing that also serves as a heat sink function of the liquid crystal display device. It was fixed. 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 light source device of the present invention includes an LED light source, one main surface on which the LED light source is mounted, the other main surface located on the opposite side of the one main surface, and between the one main surface and the other main surface. A mounting substrate having a side surface located; a light guide plate disposed on the one main surface side of the mounting substrate; a heat sink substrate disposed on the other main surface side of the mounting substrate; and the one main surface of the mounting substrate. A heat radiating sheet that contacts and covers the surface, the other main surface, the side surface, and the heat sink substrate.

  In the liquid crystal display device of the present invention, the insulating substrate on which the LED light source, which is a light emitting diode module, is mounted is in contact with the heat sink substrate and the front surface as one main surface, the back surface as the other main surface, and the lower surface perpendicular to both main surfaces. As described above, a rubber elastic heat conductive sheet having a high heat conductivity is used.

  As a result, of the heat generated by the LED light source, for example, heat released to the surface side of the insulating substrate is disposed between the light guide plate or the lower surface of the insulating substrate and the heat sink substrate through the heat dissipation sheet disposed on the surface side. Can escape through the heat dissipation sheet.

  Further, the heat transferred from the LED light source to the insulating substrate can be stably released from the lower surface of the insulating substrate to the heat sink substrate through the heat radiation sheet as well as the rear surface of the insulating substrate.

  That is, heat on the surface side of the insulating substrate and heat transferred to the insulating substrate can be efficiently released from the insulating substrate.

  In addition, a heat dissipation sheet between the insulating substrate and the heat sink substrate is pressed between the two substrates. That is, even if the surface state of the insulating substrate and the surface state of the heat sink substrate have minute unevenness, the heat dissipation sheet is pressed into the unevenness by pressing the heat dissipation sheet. Formation of an air layer that reduces the thermal conductivity with the heat sink substrate can be effectively suppressed. Thereby, it is possible to efficiently conduct heat from the insulating substrate to the heat sink substrate.

  In addition, the light guide plate needs to be fixed in accordance with 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. Further, 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 radiating sheet interposed between the insulating substrate and the housing (heat sink substrate) so as to be in pressure contact therewith. 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. That is, 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 light emission efficiency, and the LED light source can be prevented from being damaged. 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 radiating sheet having a U-shaped cross section. 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 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 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. Note that the substrate on the side where the wiring pattern is not formed, for example, the display electrode of the upper transparent substrate 12 is connected to the wiring pattern on the lower transparent substrate side via 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 an LED light source 7, which is an LED module, a light guide plate 4, a lens sheet 2, a diffusion sheet 3, a reflection sheet 5, an insulating substrate 8, a U-shaped heat radiation sheet 9, and a heat sink substrate. It consists of ten.

  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, and the cavity is filled with a translucent resin or a fluorescent resin so as to embed the LED chip 7a.

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

  Heat generated in the LED light source 7 is transmitted to the container 7 b, part of the heat is radiated around the container 7 b, and part of the heat 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 that the end surface of the light guide plate 4 and the light emitting surface of the LED light source 7 face each other. Furthermore, a heat radiation sheet 9 having a U-shaped cross section is installed so as to contact the surface of the insulating substrate 8 on which the LED light source 7 is mounted, the surface facing the surface, and the lower surface perpendicular to the surfaces. Has been. As shown in FIG. 5A, the heat radiating sheet 9 having a U-shaped cross section includes a first portion 9 a sandwiched between the other main surface (back surface) of the insulating substrate 8 and the heat sink substrate 10, and one of the insulating substrates 8. It consists of a second portion 9b sandwiched between the main surface (mounting surface) and the light guide plate 4, and a third portion 9c disposed between the lower surface of the insulating substrate 8 and the heat sink substrate 10. In other words, the first portion 9a, the second portion 9b, and the third portion 9c have a U-shaped cross-section that opens upward from the left and right sides of the drawing. An opening 9d is formed in the second portion 9b corresponding to the mounting position of the LED light source 7 mounted on the mounting surface of the insulating substrate 8.

  In the heat radiating sheet of FIG. 5A, since the second portion 9b of the heat radiating sheet 9 is present around the LED light source 7 and on the surface side of the insulating substrate 8, the heat released around the LED light source 7 The heat on the surface side of the insulating substrate 7 is transmitted to the second portion 9b of the heat radiating sheet 9, and can be released from the second portion 9b to the heat sink substrate 10 through the light guide plate 4 and the third portion 9c. Further, the heat transmitted from the LED light source 7 to the insulating substrate 8 is from the first portion 9a of the heat radiating sheet 9 on the back surface side of the insulating substrate 8, and the third portion of the heat radiating sheet 9 on the lower surface side of the insulating substrate 8. It is possible to escape from 9c to the heat sink substrate 10. In the case where the heat sink substrate 10 has a metal flat plate shape extending to the back surface of the light guide plate 4 and the lower surface of the insulating substrate 8 and uses a casing that acts as a heat sink on the lower side that houses the backlight and the heat sink substrate 10, The heat transmitted to the sheet 9 can be released from the third portion 9c of the heat radiating sheet 9 to the heat sink substrate 10 and from the first portion 9a to the housing.

  The opening 9d of the heat dissipation sheet 9 shown in FIG. 5 (a) is open on the upper side. However, when the insulating substrate 8 is disposed on such a heat dissipation sheet 9, the first portion 9a and the first portion 9d are arranged. The LED light source body 7 may be pressed into the opening 9d from the upper side between the two portions 9b.

  By using such a heat radiating sheet 9, the heat radiating sheet 9 comes into surface contact with two surfaces constituting the bent portion of the heat sink substrate 10 having an L-shaped cross section, for example.

  Here, the thickness of the first portion 9 a of the heat dissipation sheet 9 is set slightly thicker than the design value interval between the insulating substrate 8 and the heat sink substrate 10. By doing so, the first portion 9 a of the heat dissipation sheet 9 is securely pressed and sandwiched between the insulating substrate 8 and the heat sink substrate 10. Further, if the second part 9b of the heat dissipation sheet 9, that is, the part located between the insulating substrate 8 and the end face of the light guide plate 4 is set in the same manner, it is between the insulating substrate 8 and the end face of the light guide plate 4. With this, the pressure contact is surely held. Furthermore, the thickness of the third portion 9 c of the heat dissipation sheet 9 is also made slightly thicker than the distance between the lower surface of the insulating substrate 8 and the inner bottom surface of the heat sink substrate 10. By doing so, also in the height direction of the heat radiating sheet 9, the pressure contact is held between the lower surface of the insulating substrate 8 and the inner bottom surface of the heat sink substrate 10.

  Here, it is important that the heat dissipation sheet 9 has elasticity. This is because, as described above, the press-clamping is not only stable fixing of the insulating substrate 8, but also the fine uneven shapes on the surfaces of the insulating substrate 8 and the heat sink substrate 10 are absorbed, and the insulating substrate 8, the heat dissipation sheet 9, and the heat sink substrate 10 are absorbed. This is because the contact and the surface contact are surely made with almost no air layer interposed. At the same time, by providing elasticity to the heat radiating sheet 9 as described above, even if an external impact is applied to the liquid crystal display device, the impact can be absorbed by the heat radiating sheet 9 and the impact is not directly transmitted to the insulating substrate 8. This eliminates the occurrence of misalignment and the damage of the insulating substrate itself.

  In addition, in order to ensure the surface contact state between the heat dissipation sheet 9 and the heat sink substrate 10 having an L-shaped cross section, the corner ridgeline formed by the first portion 9a and the third portion 9c of the heat dissipation sheet 9 is provided. It is important to perform the removed C-face machining (including R-face machining). In this way, if the ridgeline at the corner is removed, even if an arc (R) occurs in the bent portion in the L-shaped processing (metal bending or metal pressing) of the heat sink substrate 10, the heat radiation sheet 9. And the heat sink substrate 10 are surely brought into close contact and in surface contact.

  5B to 5C show other examples of the heat dissipation sheet 9. For example, in the heat dissipation sheet 9 of FIG. 5B, the opening 9 d formed in the second portion 9 b corresponding to the LED light source 7 is an example of a window shape. In this case, since the second portion 9b of the heat dissipation sheet 9 is substantially present around the LED light source 7, the periphery of the LED light source 7, specifically, one main surface of the insulating substrate 8 is present. All the heat released to the side can be received by the heat dissipation sheet 9 and released to the heat sink substrate 10 and the light guide plate 4. In disposing the insulating substrate 8 on the heat dissipating sheet 9, the gap between the first portion 9a and the second portion 9b is widened from the upper side, and the insulating substrate 8 is disposed in this state. What is necessary is just to return the gap 9 in the expanded state to the initial state.

  For example, the heat dissipation sheet 9 in FIG. 5C further includes a fourth portion 9e on the upper surface side. The opening 9e through which the LED light source 7 is exposed forms an opening that bisects the second portion 9b in the height direction. In this case, since the four surfaces of the insulating substrate 8 are substantially covered with the heat radiating sheet 9, the heat conduction efficiency can be improved, and the upper surface of the heat radiating sheet 9 in the housing portion of the liquid crystal display device. It can also be clamped from the side. Moreover, since it is covered with the four surfaces of the insulating substrate 8 by the heat radiating sheet 9, it is excellent in impact resistance. In disposing the insulating substrate 8 on the heat dissipating sheet 9, the opening 9d formed in the second portion 9b is opened in the vertical direction, and the insulating substrate 8 is disposed in this state so that the heat dissipating sheet 9 is expanded. The opening 9e may be returned to the initial state, or the insulating substrate 8 may be press-fitted from the side surface side.

  In addition, by cutting at least the lower surface of the insulating substrate 8 on which the LED light source 7 is mounted, the unevenness of the lower surface can be almost eliminated, the heat radiation sheet 9 can be adhered, and the insulating substrate 8 is generated from the end surface. It is possible to prevent the generation of an air insulation layer between the insulating substrate 8 and the heat dissipation sheet 9 due to glass waste and resin waste, and adhere to the light emitting surface of the LED light source 7 of glass waste and resin waste generated from the end surface of the insulating substrate 8. Therefore, the light from the LED light source 7 can be utilized to the maximum while the heat conduction and heat dissipation can be efficiently performed. Further, the upper and lower surfaces of the insulating substrate 8 are polished and cut so as to be located at a predetermined dimension 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. In the central portion, an array of LED light sources 7 arranged in a straight line on the insulating substrate 8 can be easily arranged.

  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 insulating substrate 8, and the insulating substrate 8, the heat radiating sheet 9, and the heat sink substrate 10 are brought into surface contact with almost no air layer interposed therebetween. Thus, the heat sink substrate 10 is efficiently reached.

  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 radiation sheet 9 contacts the metal wiring of the insulating substrate 8, and further, the LED terminal portion 7c and The effect of heat dissipation is great when touched.

  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.

  A heat-dissipating sheet 9 is made of a U-shaped elastic sheet having a heat-dissipating characteristic (model number No. 5509 of Sumitomo 3M Limited), and heat sink substrate 10 is made of aluminum having a thickness of 2 mm. The 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 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 radiating sheet 9 to be radiated. 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 radiating sheet 9 is very small as compared with aluminum which is a heat sink substrate, in order to improve the heat conduction, the insulating substrate 8 and the heat radiating sheet 9 are made as thin as possible. The method to do 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 radiating 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 radiation sheet 9 is brought into close contact with the insulating substrate 8 and the heat sink substrate 10 to improve the heat conduction, and the heat generated by the LED light source 7 is efficiently radiated to the heat sink substrate 10. By reducing the heat storage of 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 the light emission efficiency, thereby realizing a long-life and bright liquid crystal display device.

  Further, the heat dissipation sheet 9 is formed in a U-shaped cross section, and is disposed on the front surface, the back surface, and the lower surface of the insulating substrate 8. Therefore, for example, the LED light source 7 and the insulating substrate 8 are sandwiched and fixed between the end face of the light guide plate 4 and the heat sink substrate 10 in the planar direction (left and right direction in the figure), and at the same time, the upper casing 6 and the heat sink substrate are fixed. When the insulating substrate 8 is sandwiched between a certain lower casing 10 from above and below, the insulating substrate 8 can be held in a very stable position, and even if an external impact is applied, the impact is prevented. The liquid crystal display device is highly reliable because it absorbs light and the LED light source 7 is unlikely to be displaced or damaged.

  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)-(c) are all the U-shaped thermal radiation sheet perspective views of the liquid crystal display device of this invention. 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 .... Heat dissipation sheet 10 .... Heat sink substrate

Claims (6)

An LED light source;
A mounting substrate having one main surface on which the LED light source is mounted, the other main surface located on the opposite side of the one main surface, and a side surface located between the one main surface and the other main surface;
A light guide plate disposed on the one main surface side of the mounting substrate;
A heat sink substrate disposed on the other main surface side of the mounting substrate;
A light source device comprising: a heat dissipation sheet that contacts and covers the one main surface, the other main surface, the side surface, and the heat sink substrate of the mounting substrate. The heat radiation to the sheet, a light source device of 請 Motomeko 1, wherein an opening to expose that have formed the LED light source. The heat dissipation sheet, the light source apparatus 請 Motomeko 1 wherein is nipped between the heat sink substrate and the other main surface of the mounting substrate. The heat dissipation sheet, the light source apparatus 請 Motomeko 1 wherein is nipped between the one main surface and the light guide plate of the mounting substrate. The heat sink substrate is extended toward the side from the other side main surface of the mounting substrate,
The heat dissipation sheet, the light source apparatus 請 Motomeko 1 wherein is nipped between the side surface of the mounting substrate by the the heat sink substrate. The light source device according to any one of claims 1 to 5,
A liquid crystal display device comprising the light source device and a liquid crystal display panel arranged to face the light source device.

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