JP2006259546A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of obtaining stability of adhesion of an LED mount substrate and an exterior member and suppressing lowering of light emission efficiency by decreasing a rise in temperature of an LED chip. <P>SOLUTION: The liquid crystal display device comprises a liquid crystal display panel 1, a back light which comprises a light guide plate and a light source body having a mount substrate having an LED unit mounted on one main surface and is arranged outside one substrate of the liquid crystal display panel, and the exterior member 10 including the liquid crystal display panel and back light, and is provided with an adhesive retention section 18 which adds to the depth of a heat-conductive adhesive 17 on one of surfaces of the mount substrate 8 and exterior member 10 which are bonded together. <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 an LED unit 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 and a light guide plate, and a small fluorescent tube called CCFL (cold cathode tube) is used as the light source. Further, the one main surface (light derivation surface) of the light guide plate is opposed to correspond to the display area of the liquid crystal display panel. On the other hand, a diffusion part for diffusing and reflecting light toward the light output surface side is mainly formed. 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.

  Meanwhile, as a new light source body, a backlight using a light emitting diode unit (LED unit) in which a light emitting diode (LED) chip having a feature of a point light source is accommodated has been developed. Backlights using this LED unit (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.

  Here, the biggest problem is that the light emission efficiency and life of the LED chip itself are reduced by the temperature rise of the LED unit and its surroundings due to the heat generated by the LED chip of the LED unit. Although the luminous efficiency of LED chips has been improved by 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 chip as a light source, this generated heat is stored in the LED unit and the mounting substrate on which the LED unit is mounted, and the LED chip itself and the surrounding temperature increase, resulting in a decrease in the luminous efficiency of the LED chip itself. Will be invited. 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 chip can cause damage to the LED unit and the wiring of the mounting board on which the LED unit is mounted. In addition, if the number of LED units mounted is increased in order to increase the brightness of the backlight, the amount of heat generated increases, so this heat generation cannot be ignored further.

As a conventional technique related to heat generated in an LED chip, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-281924, an LED generally has a disadvantage that its 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 LED unit is mounted on one main surface of the mounting substrate having metal wiring, the mounted light source body is accommodated in a predetermined portion of the housing container, and the heat insulating insulating resin layer In addition, there is known a lighting device having a heat dissipation structure in which a conductive adhesive is filled on the insulating resin layer for heat dissipation except for the light emitting surface of the LED unit.
JP2003-281924

  However, the LED backlight used in the liquid crystal display device and disposed on the back side of the liquid crystal display panel has fixed the light guide plate and the mounting substrate on which the LED unit is mounted to the casing of the liquid crystal display device. As a fixing method, a support protrusion is formed inside the housing in accordance with the shape of the backlight, and the support protrusion is used for fitting and fixing, or the backlight is attached with a double-sided adhesive tape. It was adhered to a predetermined part of the housing.

  However, in the contact portion between the back surface of the mounting substrate and the housing of the liquid crystal display device, the surface contact is insufficient due to the presence of fine irregularities on the surface, and the heat conduction is small due to the presence of an extremely small air layer. It has become. Also, in the case of fixing the double-sided pressure-sensitive adhesive tape, since the thermal conductivity of the double-sided pressure-sensitive adhesive tape is small, the heat conduction from the mounting substrate to the container becomes insufficient. As a result, heat is accumulated in the LED unit or its mounting substrate, and a problem arises in that the LED chip of the LED unit rises in temperature, resulting in a decrease in light emission efficiency and damage to the LED chip in a short time.

  In addition, a technique for suppressing the temperature rise of the LED chip by filling the surface of the mounting board on which the LED unit is mounted with thermal conductive resin has been disclosed, but heat radiation from the mounting board to the housing side is insufficient. Therefore, heat is stored in the insulating substrate.

  In addition, it is very difficult to fill a very narrow region with a resin paste to be a heat conductive resin, and it is difficult to supply an appropriate resin paste to this very narrow region.

  The present invention has been devised in view of the above-mentioned problems, and its purpose is to improve the adhesion structure between the mounting substrate on which the LED unit constituting the backlight is mounted and the exterior member of the liquid crystal display device, It is an object of the present invention to provide a liquid crystal display device capable of obtaining adhesion stability and suppressing a decrease in luminous efficiency by reducing a temperature rise of an LED chip.

The present invention includes a liquid crystal display panel in which liquid crystal is interposed between a pair of substrates having display electrodes and alignment films, a light guide plate, and a light source body having a mounting substrate on which an LED unit is mounted on one main surface. And a backlight disposed outside one substrate of the liquid crystal display panel; and a liquid crystal display device that houses the liquid crystal display panel and the backlight and includes an exterior member. The main surface and the exterior member are bonded and fixed via a thermally conductive adhesive, and the thickness of the thermally conductive adhesive adhesive is on any surface where the mounting substrate and the exterior member adhere to each other. It is characterized in that an adhesive staying portion for increasing the thickness is provided.

  The adhesive staying portion is constituted by a groove portion extending in the longitudinal direction of the mounting substrate.

  The adhesive staying portion is constituted by a groove portion that meanders in the longitudinal direction of the mounting substrate.

  The exterior member is characterized in that the adhesive surface is made of a heat sink metal plate.

In the present invention, a mounting substrate on which an LED unit, which is a light source body of a backlight, is bonded and fixed to an exterior member with a heat conductive adhesive. In addition, an adhesive retaining portion for locally increasing the thickness of the heat conductive adhesive agent is provided on the adhesive surface between the exterior member and the mounting substrate. That is, in order to provide an adhesive with a relatively large area and uniform thickness on this adhesive surface, for example, when adhesive is supplied to the exterior member and the mounting substrate is pressed and arranged, the adhesive stays on both adhesive surfaces. Since the groove portion to be the portion is formed, unnecessary adhesive can be retained in the adhesive retaining portion when pressed. Accordingly, as a result, the amount of the adhesive protruding around the mounting substrate can be reduced, and stable adhesion can be achieved by making the thickness of the adhesive at the contact portion between the exterior member and the mounting substrate uniform. For example, when another member is attached to the exterior member to which the mounting substrate is bonded, the protruding portion of the adhesive can be reduced, so that this separate member can be stably attached.

  In addition, since the adhesive itself is a heat conductive adhesive, even if the thickness of the adhesive in the adhesive stagnant portion is increased, even if the thickness of the adhesive is locally increased, the mounting substrate to the exterior member Thermal conductivity does not deteriorate. Rather, the contact area is increased due to the concave shape of the adhesive retaining portion, rather than the planar contact between the exterior member and the mounting substrate via the adhesive, and the heat dissipation action from the mounting substrate to the exterior member is increased. Thus, the heat generated in the LED unit can be efficiently radiated to the outside.

  Since the adhesive retaining part is composed of an adhesive retaining part groove extending in the longitudinal direction of the mounting substrate, the adhesive protruding from the lateral direction of the mounting substrate can be minimized.

  In addition, since the adhesive staying portion is constituted by a groove portion extending meandering in the longitudinal direction of the mounting substrate, the contact area between the adhesive and the mounting substrate or the exterior member can be increased, so that the heat dissipation efficiency is increased. In addition, by meandering in the longitudinal direction, the ratio of heat radiation from the mounting board to the exterior member can be made uniform in the mounting board.

  In addition, since the exterior surface of the exterior member is composed of a heat sink metal plate, in particular, heat from the LED unit that stores heat on the mounting substrate can be stably and efficiently radiated to the exterior member.

  As a result, the adhesion structure between the mounting substrate on which the LED unit constituting the backlight is mounted and the exterior member of the liquid crystal display device can be improved, adhesion stability can be obtained, and the temperature rise of the LED chip can be reduced to emit light. A liquid crystal display device capable of suppressing a decrease in efficiency is 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 a mounting substrate on which an LED light source is mounted, and Fig. 5 shows a perspective view of a heat conducting elastic sheet. 6 is a schematic plan view for explaining the LED light source, FIG. 7 is a diagram for explaining the mounting substrate, FIG. 8 is a schematic diagram showing an adhesion structure between the mounting substrate and the exterior member, and FIG. 9 is an adhesion region. It is a top view which shows the example of the groove part formed in this.

  The liquid crystal display device of the present invention is mainly composed of a liquid crystal display panel 1, an LED backlight, an upper member 6 of an exterior member of the liquid crystal display device, and a lower member 10 including a heat sink metal plate. The upper member 6 is an upper casing that mainly protects the liquid crystal display panel 1. The lower member 10 is a lower casing that mainly houses and protects the LED backlight, and has a heat sink function of releasing heat to the outside.

  As shown in FIG. 3, the liquid crystal display panel 1 includes a lower transparent substrate 11 that is the other substrate, an upper transparent substrate 12 that is one substrate, and a transparent portion 11 and 12 that are surrounded by a seal portion 14. A liquid crystal layer 13 surrounded by 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 11 is simply indicated by reference numeral 15, and the structure of the upper transparent substrate 12 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 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, in the outer peripheral region of the upper transparent substrate 12 which is a large-sized substrate, the display electrode and switching of the inner surface structure 16 of the upper transparent substrate 12 are provided. 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 lower transparent substrate side through conductive particles arranged at a distance 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 on the outer side of the lower transparent substrate 11 which is the other transparent substrate of the liquid crystal display panel 1.

  The LED backlight is mainly composed of a light guide plate 4 and a light source body disposed on the end face of the light guide plate 4. The light guide plate includes a lens sheet 2, a diffusion sheet 3, and a reflection sheet 5, and the light source body includes an LED unit 7, a mounting substrate 8, and a heat conduction elastic sheet 9.

Then, one main surface (surface from which light is emitted) of the light guide plate 4 of the backlight is disposed so as to face the display area of the liquid crystal display panel 1. The light guide plate 4 is made of a transparent resin substrate, and a light scattering member may be included 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. Further, the reflection sheet 5 may be formed on an end surface of the four end surfaces of the light guide plate 4 excluding an end surface on which the LED unit 7 is disposed.

  As shown in FIGS. 4 and 7, the mounting substrate 8 constituting the light source body includes an insulating substrate 80 made of glass cloth base epoxy resin or ceramic, and an LED unit 7 mounted on the main surface on the upper surface side. Composed. A metal wiring 81 for supplying a predetermined driving current to the LED unit 7 is formed on the mounting surface on which the LED unit 7 is mounted. A plurality of LED units 7 are mounted on the metal wiring 81 via the conductive member 89 at a predetermined interval. And since such LED unit 7 is mounted in the main surface of the upper side of the mounting substrate 8 as one side surface among four side surfaces, a light emission surface is a mounting substrate like FIG. 8 are aligned and mounted on one long side.

  As shown in the plan view of FIG. 6, the LED unit 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 voltage supply terminal 7c formed on a side 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. The container of the LED unit 7 has a back surface and four side surfaces opposed to the light emitting surface. In particular, a side surface mounted on one main surface of the mounting substrate 8 is referred to as a mounting surface. In FIG. 6, the voltage supply terminal 7 c is formed in an L shape extending over the mounting surface and the side surface adjacent to the mounting surface, and a part of the voltage supply terminal 7 c is formed on the two side surfaces. .

  Next, the mounting substrate 8 will be described with reference to FIG. The mounting substrate 8 is for mounting in which the LED unit 7 is mounted and fixed to an insulating substrate 80 such as a glass cloth base epoxy resin substrate or a ceramic substrate, and a main surface (LED mounting surface) on the upper surface side of the insulating substrate 80. The metal pattern 82a, the metal wiring 81 for supplying a predetermined driving current to the LED unit 7, and the first metal film pattern 82 that is spaced apart from the metal wiring 81 and surrounds the metal wiring 82 are formed. Further, a second metal pattern 83 for heat dissipation is formed on the main surface on the lower surface side of the insulating substrate 80 over substantially the entire surface of the insulating substrate 80. In FIG. 7, the metal pattern 82 a and the first metal pattern 82 that are fixed by mounting the LED unit 7 are integrally formed. Further, the metal pattern 82a and the first metal pattern 82 may be formed separately.

  Further, in the thickness direction of the insulating substrate 80, the first metal pattern 82a for mounting and the second metal pattern 83 for heat dissipation are used, and the first metal pattern 82 and the second metal pattern 83 for heat dissipation are used. A plurality of through holes 84 are formed to connect the two to each other.

  The first metal pattern 82a for mounting, the first metal pattern 82, the second metal pattern 83 for heat dissipation, and the through hole 84 are formed of, for example, a copper-based metal material. A copper plating layer 85 is coated on the metal base conductor film of the first metal pattern 82a, the first metal pattern 82, the second metal pattern 83 for heat dissipation, and the through hole 84 as necessary. A resin resist film 86 is covered in a region where the copper plating layer 85 is not formed or a portion where a short circuit is likely to occur between the metal patterns. The resist film 86 is preferably made of a resin using a white pigment or a white dye on the main surface of the insulating substrate 80 on the mounting side. If this resist film is white, the light leaked from the LED unit 7 can be efficiently supplied to the light guide plate 4.

  The LED unit 7 is supplied with a predetermined drive current from an external drive circuit via the metal wiring pattern 81.

  The LED unit 7 is mounted in close contact with the first metal pattern 82a for mounting via a heat conductive adhesive or a metal adhesive layer, and the terminal portion 7c of the LED unit 7 is connected to the metal wiring 81 with a conductive adhesive. Connected through. Thereby, the heat generated in the LED chip 7a of the LED unit 7 is transmitted well to the first metal pattern 82a and the metal wiring pattern 81 for mounting through the container 7b and the terminal portion 7c. It is transmitted to the substrate 80 side.

  Further, a through hole 84 for connecting the first metal pattern 82 (82 a) and the second metal pattern 83 is formed in the insulating substrate 80. Through this through hole 84, heat generated in the LED unit 7 can be transmitted from the main surface side on the upper surface side of the mounting substrate 8 on which the LED unit 7 is mounted to the main surface side on the lower surface side.

  The main surface of the mounting substrate 8 on which the LED unit 7 is mounted is perpendicular to the light emitting surface of the LED unit 7. Furthermore, since the light of the LED unit 7 is irradiated into the light guide plate 4 from the end face of the light guide plate 4, the light guide plate 4 of the backlight and the mounting substrate 8 are arranged in parallel in a plane. That is, as shown in FIG. 1, the lower surface side main surface of the mounting substrate 8 is arranged and fixed on the lower inner surface of the lower member 10 of the exterior member along with the light guide plate 4 as the adhesive surface.

  In FIG. 1, when the lower member 10 of the exterior member is formed of a metal member having excellent heat dissipation, the lower member 10 itself of the exterior member can be used as a heat sink metal plate. Further, when the lower member 10 of the exterior member is substantially made of a resin, in order to improve the thermal conductivity in the resin, in a predetermined position including a region where the mounting substrate 8 is arranged and fixed, When the metal material is contained in the resin material, or when the lower member 10 is resin-molded with resin, the heat sink metal plate is insert-molded to include a predetermined region including the area where the mounting substrate 8 is disposed and fixed. The position may expose the heat sink metal plate.

  Such a lower inner surface of the lower member 10 of the exterior member and the mounting substrate 8 are bonded via a heat conductive adhesive 17.

  If it does in this way, the 2nd metal pattern 83 for heat dissipation of mounting board 8 will contact heat conductive adhesive 17, and will constitute lower member 10 of an exterior member, or lower member 10 of an exterior member. The heat from the LED unit 7 can be transmitted to a large area to the heat sink metal plate substrate to be efficiently discharged to the outside air through the exterior member.

  At this time, even when there is a minute unevenness on the joint surface between the second metal pattern 83 for heat dissipation of the mounting substrate 8 and the exterior member, the thermal conductivity adhesive 17 is applied. By interposing, the adhesion is filled in the minute unevenness of the joint surface, and the efficiency of heat conduction can be improved.

  Here, as shown in FIG. 8, the mounting substrate 8 and the lower member 10 of the exterior member are formed with adhesive retaining portions 18 on either of the contact surfaces to which the heat conductive adhesive 17 is bonded. ing. Specifically, as shown in FIG. 9A, a wide groove 18a is formed in the adhesion region S indicated by a dotted line in the drawing, for example, in the adhesion region of the lower member 10 of the exterior member. The adhesive staying portion 18 defined by the groove 18a is formed along the longitudinal direction of the adhesive region S, and the end portion of the adhesive staying portion 18 extends in the longitudinal direction of the adhesive region. It is. The extended end portion stably adheres to the thickness of a predetermined adhesive retaining portion in which the adhesive thickness of the heat conductive adhesive 17 supplied to the adhesive region S is provided in advance, and the heat sink as the lower member 10 of the exterior member This is to prevent the peeling of the bonded portion due to the difference in thermal expansion and contraction between the metal plate and the mounting substrate 8, and it is necessary to change the thickness depending on the bonding length, but a bonding thickness of about 50 μm is preferable. Moreover, the thing overflowing from the adhesion | attachment area | region S is for staying in the extension end part of the groove part 18a.

  In this way, by providing the adhesive retaining portion 18, the adhesive 17 interposed between the lower member 10 of the exterior member and the mounting substrate 8 is applied to the adhesion surface of either member, and the exterior When the mounting substrate 8 is pressed against the lower member 10 of the member, the adhesive 17 spreads in the bonding region S in an attempt to be uniform. At this time, since the spread adhesive 17 stays in the adhesive staying portion 18, it is less likely that the useless adhesive 17 protrudes outside the adhesive region S. In addition, the thickness of the adhesive layer on the adhesive surface absorbs minute irregularities on the surface of the mounting board 8 and the lower member 10 of the exterior member, so that the entire thickness can be made substantially uniform, thereby increasing the adhesive strength. Can do.

  Further, the presence of the groove 18a can increase the contact area between the adhesive and, for example, the lower member 10 of the exterior member on which the groove 18a is formed, so that the heat dissipation action can be enhanced.

  In addition, as the shape of the groove part 18a in which the heat conductive adhesive 17 stays, for example, in addition to forming the groove part 18a having a relatively wide width in the longitudinal direction of the bonding region S, a plurality of groove parts 18b extending in the longitudinal direction are used. You may comprise, and may comprise further by the groove part 18c which meanders in the adhesion | attachment area | region.

  For example, in the plurality of groove portions 18b and the meandering groove portion 18c, the contact area between the adhesive in the bonding region and the lower member 10 of the exterior member can be further increased, so that the heat radiation effect can be further enhanced.

  Further, the heat conductive elastic sheet 9 is disposed on the main surface on the upper surface side of the mounting substrate 8. Specifically, as shown in FIG. 5, the heat conducting elastic sheet 9 has a storage opening 9 a formed so as to cover the LED unit 7 on the mounting substrate 8, and at the same time, between the LED units 7. A leg portion 9b is formed by contacting the upper surface mounting region of the mounting substrate 8. Note that the opening 9 is closed on the depth surface (back surface) of the storage opening 9 as shown in FIG. That is, the LED unit 7 covered with the heat conductive elastic sheet 9 is covered so as to surround four surfaces except the mounting surface and the light emitting surface. The LED unit 7 is covered so as to surround four surfaces excluding the mounting surface and the light emitting surface. Note that a liquid or sheet-like heat conducting member adhesive member is interposed between the first metal pattern 82 and the metal wiring pattern 81 for disposing the mounting substrate 8 so as to fill this gap. Good.

  The heat conducting elastic sheet 9 is disposed so that the LED unit 7 is accommodated in the opening 9 and the main surface on the upper surface side of the mounting substrate 8 is in contact with the leg 9b. Further, the upper surface of the heat conductive elastic sheet 9 is in contact with the inner surface of the upper member 6 of the exterior member, and as a result of integrating the upper member 6 and the lower member 10 constituting the exterior member, The conductive elastic sheet 9 is pressed against the mounting substrate 8 from the upper surface side. That is, the mounting substrate 8 is bonded and fixed to the lower member 10 of the exterior member, and is pressed and sandwiched by the upper member 6 of the exterior member. At the same time, when the upper member 6 has a wall surface extending to the lower side, or when the lower member 10 has a wall surface extending to the upper side, the end surface of the mounting substrate 8 and / or the heat conducting elastic sheet 9 is used. You may press and clamp toward the light-guide plate 4 from the back side.

  Note that the opening 9a of the heat conducting elastic sheet 9 shown in FIG. 5 is an opening opened on the lower side corresponding to the LED unit 7, but instead, only the light emitting part of the LED unit 7 is exposed. It does not matter if it has a window shape. When the mounting substrate 8 is arranged on such a heat conductive elastic sheet 9, the LED unit 7 mounted on the mounting substrate 8 may be press-fitted so as to be positioned in the opening 9a.

  Here, the thickness of the heat conductive elastic sheet 9 (the thickness of the leg portion 9b) is made slightly thicker than the distance between the mounting substrate 8 and the upper member 6 of the exterior member. This is because the heat conductive elastic sheet 9 can be pressed and fixed on the mounting substrate 8 when the exterior member is assembled. The height of the opening 9b is such that when the heat conductive elastic sheet 9 is pressed, an extreme load force is applied to the LED unit 7 and the mounting state of the LED unit 7 does not become unstable. The height on the mounting substrate 8 needs to be substantially the same. Therefore, even if the upper member 6 and the lower member 10 of the exterior member are mechanically integrated with, for example, a metal caulking or screwing structure, they are mounted on the upper surface of the mounting substrate 8 or on the mounting substrate 8. A heat conducting elastic sheet 9 can be disposed in close contact with the upper side surface of the LED unit 7.

  Here, it is important that the heat conductive elastic sheet 9 has elasticity. As described above, not only the pressing and clamping of the mounting substrate 8 is stably fixed, but also the warpage and the uneven shape of the mounting substrate 8 and the lower member 10 of the exterior member are absorbed, and the heat conductive elastic sheet 9 and the mounting substrate 8 are absorbed. The lower member 10 and the upper member 6 of the exterior member can be brought into close contact with each other and brought into surface contact with almost no air layer interposed therebetween. At the same time, by providing elasticity to the heat conducting elastic sheet 9, even if an external impact is applied to the liquid crystal display device, the impact can be absorbed by the heat dissipation sheet 9, and the impact is directly applied to the mounting substrate 8. Regardless of the situation, the mounting substrate 8 is not displaced and the insulating substrate itself is not damaged.

  Further, since the heat conductive elastic sheet 9 is provided with an opening 9a for accommodating the LED unit 7 and the leg 9b is in contact with the mounting surface of the mounting substrate 8, light other than the direction of the end face of the light guide plate 4 is shielded. It is possible to prevent light that is reflected from the surface and leaks to the outside, and to improve light use efficiency.

  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 unit 7 is turned on), heat is generated along with the light emission. The generated heat is transmitted from the LED unit 7 to the mounting substrate 8, and in the order of the mounting substrate 8 -the heat conductive elastic sheet 9 -the upper member 6 of the exterior member, and the mounting substrate 8 -the heat conductive adhesive 17 -the exterior. Heat can be radiated in the order of the lower member 10 of the member.

  Moreover, an air layer is formed between the mounting substrate 8 and the heat conductive elastic sheet 9, between the upper member 6 of the exterior member and the heat conductive elastic sheet 9, and between the container 7 b of the LED unit 7 and the heat conductive elastic sheet 9. By making the surface contact with almost no interposition, the surface contact is made between the mounting substrate 8 and the lower member 10 of the exterior member without interposing an air layer, thereby efficiently releasing heat to the outside. be able to.

  Therefore, the heat generated in the LED unit 7 is effectively radiated to the outside, and the LED unit 7 and the mounting substrate 8 are less likely to store heat, so that the temperature rise in the LED unit 7 and its surroundings can be effectively suppressed. it can.

  These actions are such 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 units are supplied to the mounting 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.

For the mounting substrate 8, metal patterns 82 and 83 arranged on both sides of the insulating substrate 80 with a thickness of 0.1 mm are made of copper foil with a thickness of 35 μm and plated with a diameter of 0.2 mm in the thickness direction of the insulating substrate 80. A through-hole 84 is provided. The through hole 84 was plated with 25 μm of Cu, and the outermost surface was plated with 25 μm of solder.
A heat sink metal plate was used as the lower member 10 of the exterior member. A rectangular plate made of aluminum and having a thickness of 2 mm was used, and the mounting substrate 8 was bonded and fixed to the heat sink metal plate via a heat conductive adhesive 17.

  Here, the thermal conductivity of each material used is 0.45 W / m · K for insulating substrate 80 made of glass epoxy, 403 W / m · K for Cu, 236 W / m · K for aluminum of the heat sink metal plate substrate, and heat conduction. The adhesive 17 is 0.92 W / m · K, and the heat conductive elastic sheet 9 is 5 W / m · K.

  Here, since the thermal conductivity of the insulating substrate 80 is very small compared to the metal material used for the metal wiring 81, each metal pattern 82, 83 and the heat sink metal plate, in order to improve the heat conduction to the heat sink metal plate substrate. Is effective to reduce the thickness of the insulating substrate 80 as much as possible. However, if the insulating substrate 80 is thinned, insulation cannot be secured due to minute hole defects on the surface, and further, the cost increases. As the insulating substrate 80, a generally used thin glass epoxy substrate was used in the examples.

  The second metal pattern 83 is formed so as to spread over the entire lower main surface of the LED mounting substrate 8 without increasing the number of steps simultaneously with the through-hole plating 84, and the thickness is increased to 35 μm to 60 μm. To do. As a result, the structure is such that heat is easily conducted and diffused also on the lower main surface of the mounting substrate 8.

  As the heat conductive adhesive, for example, a heat conductive adhesive SE4420 manufactured by Toray Dow Corning Silicone Co., Ltd. having a heat conductivity of 0.92 W / mK was used. In addition, as the heat conductive elastic sheet 9 that presses and contacts the LED unit 7 and the mounting substrate 8, a heat conductive elastic sheet N0.5509 having a thermal conductivity of 5 W / m · K was used.

  Further, as shown in FIG. 8, in order to stabilize the adhesive thickness of the adhesive layer of the heat conductive adhesive 17 between the mounting substrate 8 and the lower member 10 of the exterior member, the lower member 10 of the exterior member, for example, A bonding groove 18a having a depth smaller than the width of the mounting substrate 8 and having a depth of 50 μm is formed in the bonding area of the heat sink metal plate, and the thermally conductive adhesive 17 is applied to the bonding groove 18a by using a dispenser for quantitative discharge. The heat sink substrate as the lower substrate 10 and the mounting substrate 8 were bonded and fixed.

  In order to form the adhesive staying portion 18, a plurality of longitudinally extending projections (height 0.05 to 0 .0) supporting the bottom surface of the mounting substrate 8 on the heat sink substrate of the lower member 10 of the exterior member. (About 2 mm) may be provided.

  A 5.7-inch rectangular liquid crystal panel 1 is used as a liquid crystal display device, and five LED units 7 are mounted on a mounting substrate 8 as a light source body of a backlight, and each LED current flows through 250 mA. The temperature rise of the main surface on the upper surface side was measured. As a result, the temperature rise on the back surface of the lower member 10 (heat sink metal plate substrate) of the exterior member can be suppressed to 15 ° C. or less at 24 ° C. or less, which is about 2% compared to the room temperature luminous efficiency of the LED chip 7a. Only the luminous efficiency is reduced and bright display is possible. At the same time, heat conduction is improved by the heat conductive adhesive 17 between the mounting board 8 and the heat sink metal plate substrate of the lower member 10 which is the exterior member, and the bonded portion of the heat conductive adhesive 17 (bonding area excluding the groove). Thus, it is possible to obtain a stable adhesive layer that can be made uniform in thickness, to increase the adhesive strength, and to increase the contact area between the adhesive and the lower member 10 of the exterior member in the groove portion.

  Furthermore, by pressing and fixing the mounting substrate 8 and the LED unit 7 via the heat conducting elastic sheet 9, the heat generated by the LED unit 7 can be efficiently conducted and dissipated to the heat sink metal plate substrate and the housing. This reduces the heat storage of the LED mounting substrate and reduces the temperature rise of the LED light source, thereby suppressing a decrease in the luminous efficiency of the LED, preventing damage to the LED, and realizing a bright long-life liquid crystal display device. it can.

  In the above-described embodiment, the structure in which the adhesive staying portion is formed on the lower member of the exterior member is illustrated, but it may be formed on the surface side where the adhesive layer 17 of the mounting substrate 8 contacts. Absent.

It is sectional drawing of the liquid crystal display device of this invention. It is an external appearance perspective view of the liquid crystal display device of this invention. It is sectional drawing of the liquid crystal display panel of the liquid crystal display device of this invention. It is a light source body of the backlight used for the liquid crystal display device of this invention, and is a perspective view of the state which abbreviate | omitted the heat conductive elastic sheet. It is a perspective view of the heat conductive elastic sheet used for the light source body of the backlight used for the liquid crystal display device of this invention. It is the schematic of the partially see-through state explaining the LED unit used for this invention. It is a figure explaining the mounting board | substrate of this invention, (a) is an external appearance perspective view of an upper surface side, (b) is an external appearance perspective view of a back surface side, (c) is sectional drawing, (d) is a through hole. It is an expanded sectional view of a part. It is sectional drawing of the connection structure part of the mounting board | substrate of this invention. It is a figure explaining the adhesive agent retention | holding part in the adhesion | attachment area | region of this invention, (a) is the groove part formed in the longitudinal direction of the adhesion area | region, (b) is the some groove part formed in the longitudinal direction in the adhesion | attachment area | region, (c) FIG. 3 is a plan view of a meandering groove formed in the longitudinal direction of an adhesive region.

Explanation of symbols

8... Mounting board 7... LED unit 1... Liquid crystal display panel 4... Light guide plate 17. Retention part 18a-18b ... groove part 9 ... heat conduction elastic sheet

Claims (4)

A liquid crystal display panel in which liquid crystal is interposed between a pair of substrates having a display electrode and an alignment film;
A backlight comprising a light guide plate and a light source body having a mounting substrate on which an LED unit is mounted on one main surface, and disposed outside one substrate of the liquid crystal display panel; the liquid crystal display panel and the backlight; In a liquid crystal display device configured with an exterior member,
The other main surface of the mounting substrate and the exterior member are bonded and fixed via a heat conductive adhesive, and the thermal conductivity is provided on any surface where the mounting substrate and the exterior member adhere to each other. A liquid crystal display device comprising an adhesive retention portion for increasing the thickness of an adhesive contact agent. The liquid crystal display device according to claim 1, wherein the adhesive staying portion is configured by a groove portion extending in a longitudinal direction of the mounting substrate. 3. The liquid crystal display device according to claim 1, wherein the adhesive staying portion is constituted by a groove portion that meanders in the longitudinal direction of the mounting substrate. 4. The liquid crystal display device according to claim 1, wherein the outer surface of the exterior member is formed of a heat sink metal plate.

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