JP2008166304A - Backlight device and liquid crystal display device - Google Patents

Abstract

A backlight device and a liquid crystal display device capable of improving productivity by easily fixing a wiring board on which an LED is mounted and an array base, and capable of uniformly and efficiently dissipating heat generated from the LED. To provide.
A light source array 7 of a backlight device 10 is provided with a resin wiring board 22 on which a plurality of LEDs 21 are mounted, a metal array base 16 holding the wiring board 22, and a gap between them. The adhesive material 23 is made of a heat conductor and an insulator. The heat generated from the LED 21 is dissipated by being transmitted from the thermal via 52 of the wiring board 22 to the array base 16 and the back chassis 8 via the adhesive material 23. Since the wiring board 22 and the array base 16 are closely fixed with the adhesive material 23, heat from the LEDs 21 can be uniformly transmitted to the array base 16 while maintaining insulation, and the wiring board 22 is fixed with screws or the like. Installation is also easier than in the case.
[Selection] Figure 5

Description

  The present invention relates to a backlight device using a light emitting diode (LED) as a light source and a transmissive liquid crystal display device equipped with the backlight device.

  2. Description of the Related Art Conventionally, in a transmissive LCD (Liquid Crystal Display) mounted on an electronic device such as a liquid crystal television or a PC (Personal Computer), a backlight is disposed on the back side of the LCD, and the backlight uses the LCD. The image is displayed by illuminating the back of the camera. Conventionally, CCFL (Cold Cathode Fluorescent Lighting) has been used as the light source of the backlight, but in recent years, LEDs have been promising as a light source that replaces the CCFL. By using an LED, high efficiency and a high color gamut can be achieved, and since no mercury is used unlike CCFL, adverse effects on the environment can be lost.

  However, the LED consumes more power than the CCFL, and the amount of heat generation is increased accordingly, so that heat dissipation measures are important. As a backlight device that takes measures against heat dissipation of heat generated from the LED, for example, the one described in Patent Document 1 below can be cited. In this backlight device, a plurality of wiring boards on which a plurality of LEDs are mounted are held by a long heat radiation plate (array base), and a plurality of array bases are arranged and fixed on the back panel. Since the wiring board and the array base are made of a metal such as aluminum, the heat generated from the LEDs is transferred from the wiring board to the array base, and further, air around the back panel and the array base is provided by heat pipes provided on the array base. Heat is dissipated by being transmitted to.

Although not described in Patent Document 1, in the conventional backlight device, a heat conductive sheet having elasticity and adhesion is provided between the wiring board and the array base, and the heat of the LED is transferred to the array base. Some are evenly transmitted.
Japanese Patent Laying-Open No. 2005-352427 (FIG. 7 etc.)

  However, in the backlight device described in Patent Document 1, since the wiring substrate is made of aluminum, the wiring substrate itself is expensive. Further, since the wiring board and the array base are fixed with screws, the number of man-hours and the number of parts are increased.

  Furthermore, when a heat conductive sheet is sandwiched between the wiring board and the array base, the heat conductive sheet itself is expensive. Therefore, when combined with an aluminum wiring board, it is further disadvantageous in terms of cost. Moreover, since a heat conductive sheet has elasticity and adhesiveness, it is necessary to apply a predetermined pressure to the heat conductive sheet and to manage it by crushed to some extent. In this case, the heat conduction sheet is crushed near the part where the wiring board is tightened with screws, and heat can be transferred efficiently because it is in close contact with the wiring board and the array base. The difference in the amount of crushing leads to uneven heat conduction. Furthermore, since it is not easy to attach such a heat conductive sheet to the array base, it takes time and effort.

  In view of the circumstances as described above, an object of the present invention is to easily fix a wiring board on which an LED is mounted and an array base to improve productivity, and to uniformly and efficiently dissipate heat generated from the LED. An object of the present invention is to provide a backlight device and a liquid crystal display device that can be used.

  Another object of the present invention is to provide a backlight device and a liquid crystal display device with high heat dissipation efficiency and reliability with an inexpensive configuration.

  In order to solve the above problems, a backlight device according to a main aspect of the present invention includes a housing, a plurality of light emitting diodes, and a plurality of wirings having a heat transfer path for conducting heat generated from each of the light emitting diodes. A board, a metal holding member that is fixed to the housing and holds each wiring board, and is provided between each wiring board and the holding member, and from the heat transfer path of each wiring board An adhesive capable of conducting the conducted heat to the holding member.

  Here, the heat transfer path may be a through-hole for heat dissipation such as a thermal via, or may be a wiring board itself formed of a heat conductor such as metal. As the adhesive material, for example, an acrylic or rubber material is used. With this configuration, the wiring board and the holding member are uniformly fixed over the entire surface of both via the adhesive material. Therefore, the heat generated from the light emitting diode can be uniformly transmitted from the wiring board to the holding member through the adhesive material, and can be efficiently and uniformly dissipated in the air in contact with the holding member or through the housing. Can be reduced. Moreover, compared with the case where a wiring board and a holding member are fixed with other components, such as a screw, the man-hour and number of components at the time of manufacture can be reduced, and productivity can be improved.

  In the backlight device, the wiring board is made of resin, the heat transfer path is a thermal via that penetrates the wiring board from the light emitting diode side to the holding member side, and the adhesive material is an insulator. May be.

  Thereby, the cost of the wiring board can be reduced by using a resin of the wiring board as compared with other materials such as metal. In addition, by providing thermal vias, heat can be uniformly and efficiently transferred from the light emitting diode to the holding member, and by using an adhesive as an insulator, insulation between the thermal via and the holding member, which are conductors, is provided. can do. That is, a backlight device with high heat dissipation efficiency and reliability can be provided with an inexpensive configuration.

  The backlight device may further include a locking member for locking the wiring board to the holding member.

  Here, the locking member is, for example, a screw, a pin, a hook, or a spring. Thereby, it is possible to reinforce the holding force of the wiring board by the adhesive material and prevent the wiring board from dropping from the holding member. In addition, since this latching member is provided only for prevention of dropout, it is not necessary to tighten and press the wiring board to the holding member side. Therefore, it is sufficient that this locking member is provided only at one place, and an increase in man-hours and costs due to the provision of this locking member can be minimized.

  A liquid crystal display device according to another aspect of the present invention includes a casing, a plurality of light emitting diodes, a plurality of wiring boards each having a heat transfer path for conducting heat generated from each of the light emitting diodes, and the casing. The metal holding member that is fixed to the wiring board and holds the wiring boards, and is provided between the wiring boards and the holding members, and the heat conducted from the heat transfer paths of the wiring boards is And a liquid crystal panel capable of displaying an image by changing a transmittance of light emitted from the light emitting diode unit.

  In the liquid crystal display device, the wiring board is made of resin, the heat transfer path is a thermal via that penetrates the wiring board from the light emitting diode side to the holding member side, and the adhesive material is an insulator. May be.

  As described above, according to the present invention, the wiring board and the array base can be easily fixed to improve productivity, and heat generated from the light emitting diode can be uniformly and efficiently radiated. In addition, a liquid crystal display device can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic exploded perspective view of a liquid crystal display device having a backlight device according to an embodiment of the present invention, and FIG. 2 is a partial sectional view in the Z direction of the liquid crystal display device of FIG. FIG. 3 is a partially cutaway plan view showing the configuration of the backlight device of the liquid crystal display device shown in FIGS. 1 and 2.

  This liquid crystal display device is used for a display panel of a television receiver having a large display screen of, for example, 40 inches or more, and is a transmission type that displays an image by illuminating the liquid crystal panel from the back side with a backlight device. Liquid crystal display device.

As shown in both figures, the liquid crystal display device 100 sandwiches the liquid crystal panel 2, the middle frame 3, the optical sheet laminate 4, the diffusion plate 5, the reflection plate 6, and the light source array 7 between the front chassis 1 and the back chassis 8. It is comprised by holding in. The front chassis 1, the middle frame 3, and the back chassis 8 are made of metal such as aluminum. These may be made of resin, but since the liquid crystal panel 2 of the liquid crystal display device 100 is large, considering the strength and the difference in coefficient of thermal expansion, metallicity is preferable.
The optical sheet laminate 4, the diffusion plate 5, the reflection plate 6, the light source array 7, and the back chassis 8 form a backlight device 10 and supply display light from the back side of the liquid crystal panel 2.

  As shown in FIG. 2, the outer peripheral edge of the liquid crystal panel 2 is supported between the lower surface of the front chassis 1 and the upper surface 3 a of the middle frame 3 via, for example, a spacer 11 and a guide member 12. Although not described in detail, the liquid crystal panel 2 encloses a liquid crystal between the first glass substrate and the second glass substrate and applies a voltage to the liquid crystal to change the direction of the liquid crystal molecules to thereby transmit the light transmittance. To change. A striped transparent electrode, an insulating film, and an alignment film are formed on the inner surface of the first glass substrate, and light, three primary colors of red, green, and blue (RGB) are formed on the inner surface of the second glass substrate. The color filter, the overcoat layer, the striped transparent electrode, and the alignment film are formed. A polarizing film and a retardation film are bonded to the surfaces of both glass substrates.

  In the liquid crystal panel 2, an alignment film made of polyimide is arranged in the horizontal direction (both X and Y directions) with the liquid crystal molecules as an interface, and the polarizing film and the retardation film have achromatic wavelength characteristics and are white. The image is displayed in color by achieving full color using a color filter. In addition, the liquid crystal panel 2 is not limited to such a configuration, and a liquid crystal panel having various existing configurations can be applied.

  As shown in FIGS. 1 and 2, a rectangular opening 41 is formed in the upper surface 3 a of the middle frame 3, and a rectangular opening 42 is also formed in the lower surface 3 b of the middle frame 3. The area of the opening 42 is formed larger than the area of the opening 41.

  The optical sheet laminate 4 and the diffusion plate 5 are supported so as to be sandwiched between the lower surface 3b of the middle frame 3 and the bracket member 15 attached to the back chassis 8 in a state where the optical sheet laminate 4 and the diffusion plate 5 are laminated. For example, a spacer 11 is interposed between the middle frame 3 and the optical sheet laminate 4. Further, between the bracket member 15 and the diffusing plate 5, an edge portion 6c of the reflecting plate 6 to be described later is inserted.

  Although details are omitted for the optical sheet laminate 4, for example, a polarization conversion sheet for decomposing display light emitted from the light source array 7 side and supplied to the liquid crystal panel 2 into orthogonal polarization components, or a phase difference between light waves. A plurality of retardation films (films) for compensating for wide-angle viewing angle and preventing coloring, and a plurality of optical functions such as a diffusion sheet and a prism sheet for diffusing display light to achieve uniform brightness An optical function sheet is laminated.

  The diffusion plate 5 reflects a part of the display light incident from one main surface side (the light source array 7 side) to the light source array 7 side, and transmits a part of the display light to be refracted and reflected inside. By making it diffuse, it is made to enter into the optical sheet laminated body 4 in a uniform state from the other main surface side over the entire surface.

  By the way, in the liquid crystal display device 100, when an observer observes a peripheral part from the center of the liquid crystal panel 2 from an oblique angle (for example, 45 degrees), it is necessary to prevent the peripheral image from becoming dark. . The necessity increases as the display screen becomes larger as in the liquid crystal display device 100 of the present embodiment. Therefore, the middle frame 3 is provided with a step portion 13 so that the inner surface connecting the opening 41 of the upper surface 3a and the opening 42 of the lower surface 3b expands toward the back along the observation angle of the observer. Therefore, no matter what angle the observer observes the liquid crystal panel 2, the illumination light of the backlight device 10 is obtained so that the image can be observed.

  The step portion 13 includes a plane portion 13a substantially parallel to the main surface of the liquid crystal panel 2, a side surface portion 13b connecting the plane portion 13a and the opening 41 of the upper surface 3a, and an opening 42 of the plane portion 13a and the lower surface 3b. It is comprised by the side part 13c which connects. However, when light emitted from the backlight device 10 via the diffuser plate 5 and the optical sheet laminate 4 is reflected on the flat surface portion 13a, the reflected light strikes the optical sheet laminate 4 to cause halation (middle frame 3). Frame-like reflection along the shape) may occur.

  For example, as shown in FIG. 2, when the observer observes the peripheral portion of the liquid crystal panel 2 at the observation angle a, since the observation is from a direction perpendicular to the main surface of the liquid crystal panel 2, as described above. Such halation cannot be visually recognized by the observer, but when the observer observes the peripheral portion of the liquid crystal panel 2 from an oblique angle as in the observation angle b, the halation is visually recognized by the observer. Such halation will cause an unnatural image to appear, degrading the quality of the liquid crystal display device 100.

  Therefore, in the present embodiment, the matte black tape 14 is affixed to the flat surface portion 13a. As a result, the light incident on the stepped portion 13 side from the optical sheet laminate 4 is absorbed by the black tape 14 and does not strike the optical sheet laminate 4, thereby providing a high-quality liquid crystal display device 100 without halation. be able to.

  Instead of applying the black tape 14, the stepped portion 13 or the tapered portion 63 of the middle frame 3 may be painted black. When the middle frame 3 is made of aluminum as in the present embodiment, it is preferable to perform black alumite processing. Further, in the present embodiment, the middle frame 3 is made of metal (made of aluminum) in consideration of the influence of the strength and the difference in thermal expansion coefficient when the liquid crystal display device 100 is enlarged, but these influences are solved. If possible, the middle frame 3 itself may be formed of black resin.

  As shown in FIG. 3, the light source array 7 has a long shape extending in the horizontal direction (X direction in the figure), and a plurality of rows are arranged on the bottom surface of the back chassis 8 at predetermined intervals along the Y direction in the figure. Are lined up. In the present embodiment, 12 rows of light source arrays 7 are provided, but the number is not limited to this number. 3 shows a state in which the middle frame 3, the optical sheet laminate 4, and the diffusion plate 5 are excluded from the backlight device 10.

  As shown in FIGS. 2 and 3, each light source array 7 includes a metal array base 16 and a plurality of light source devices 20 arranged in the recess 16 a of the array base 16. The number of light source devices 20 arranged in one array base 16 is four, for example, but is not limited to this number. The light source array 20 is fixed to the bottom surface of the back chassis 8 by screwing the light source device 20 with the array base 16 and the back chassis 8, for example.

  Each light source device 20 includes a wiring board 22, a plurality of LED units 25 mounted on the wiring board 22, an input connector 18, and an output connector 19. As a material for the wiring board 22, for example, a resin such as a glass epoxy resin is used instead of a metal such as aluminum for cost reduction.

  4 is an enlarged view of a portion of the backlight device 10 surrounded by a broken line A in FIG. As shown in FIG. 3 and FIG. 3, each LED unit 25 is configured such that a plurality of LEDs 21 are close to each other in a non-linear shape (cross shape) as a unit, and one light source device 20 includes a plurality of LED units 25. Provided. Each LED 21 of each LED unit 25 is provided so as to protrude from the surface of the wiring board 22 in the Z direction. Specifically, for example, one LED unit 25 is formed by arranging a red LED 21a and a blue LED 21b each provided in the X direction and two green LEDs 21c and 21d provided in the Y direction in a cross shape. Composed. However, the left end and right end LED units 25 are arranged not in a cross shape in the XY direction but in an oblique direction, and the left and right LED units 25 are symmetrically arranged. The LED units 25 are arranged, for example, 6 units at a predetermined interval (for example, 60 mm) in the longitudinal direction (X direction) on the wiring board 22 of one light source device 20. Accordingly, in the backlight device 10 of the present embodiment, 6 × 4 × 12 = 288 units of LED units 25 are provided, and 4 × 288 = 1152 LEDs 21 are provided. Note that the numbers and arrangement intervals of the LED units 25 and the LEDs 21 are not limited to those described or illustrated above, and can be appropriately changed depending on the size of the liquid crystal panel 2, the light emission capability of the LEDs 21, and the like.

  FIG. 5 is a cross-sectional view taken along the line AA ′ of the backlight device 10 shown in FIG. As shown in the figure, each LED 21 includes a light-emitting element (not shown) and a light-emitting element holding base 27 that holds the light-emitting element inside, a resin holder 24 that is connected to the light-emitting element, and a resin holder 24 that is connected to the light-emitting element. Lead wire 26 drawn out from. Each LED 21 is a so-called side emission type LED having directivity for emitting the main component of the emitted light in the outer peripheral direction of the light emitting element.

  The wiring board 22 of each light source device 20 is made of a resin material such as glass epoxy resin (FR4). By making the wiring board 22 made of resin, the cost can be reduced as compared with the case where it is made of metal such as aluminum as in the prior art. Each wiring board 22 is formed with a wiring pattern for connecting the LEDs 21 of the respective colors of the LED units 25 in series, lands (not shown) for connecting the terminals of the LEDs 21, and the like. In addition, a solder pad 28 made of a metal such as copper is formed on the wiring board 22 in order to solder the light emitting element holding base 27 and the lead wire 26 of each LED 21. The solder pad 28 electrically connects the light emitting element and the lead wire of the LED 21 to the wiring pattern on the wiring board 22.

  The wiring board 22 is provided with a thermal via 52 that penetrates the wiring board 22 in the Z direction from a solder pad 28 soldered to the light emitting element holding base 27 of each LED 21. The thermal via 52 is provided with a metal plating layer 53 such as copper or silver. The metal plating layer 53 is also formed over the lower surface of the wiring board 22. With this thermal via 52, even when the wiring board 22 is made of a resin having low thermal conductivity, the heat generated from each LED is conducted to the array base 16 and radiated through the back chassis 8 or the surrounding air. Is possible.

  A plate-like adhesive material 23 is provided between the wiring board 22 and the array base 16. The adhesive material 23 is made of a material having high thermal conductivity based on, for example, an acrylic or rubber adhesive material, and both surfaces thereof are adhesive. By pressing the wiring board 22 to the array base 16 side through the adhesive material 23 with a specified load, the both are closely fixed over the entire surface. Thereby, the heat generated from the LEDs 21 can be uniformly conducted to the array base 16 uniformly and can be efficiently radiated, and the temperature difference between the LEDs 21 can be reduced. In addition, compared with the conventional case where the wiring board 22 and the array base 16 are fixed with other parts such as screws via a heat conductive sheet or the like, the mounting becomes much easier, and the number of man-hours at the time of manufacture is increased. And the number of parts can be reduced and productivity can be improved. Moreover, since this heat conductive sheet itself is expensive, the cost can be further reduced by using the adhesive material 23 instead.

  The adhesive material 23 is made of an insulating material. As described above, the thermal via 52 has the metal plating layer 53, and the metal plating layer 53 functions not only as a heat conductor but also as a conductor. However, by using the adhesive material 23 as an insulator, the thermal via 52 (LED 21) and the array base 16 can be reliably insulated and the reliability can be improved.

  As described above, by fixing the wiring board 22 and the array base 16 with the heat conductor and the insulating adhesive material 23, the heat of the LED 21 is uniformly and efficiently reduced while reducing the manufacturing cost, man-hours, and labor. The backlight device 10 that can dissipate heat well can be provided.

  As shown in FIG. 4, each wiring board 22 is arrayed via an adhesive material 23 at a substantially central portion in the longitudinal direction (X direction) and one end side in the short direction (Y direction) of each wiring board 22. One screw 32 for locking to the base 16 is provided. Thereby, the holding force of the wiring board 22 by the adhesive material 23 can be reinforced, and the wiring board 22 can be prevented from dropping from the array base 16 by any chance. The purpose of the screw 32 is only to prevent the wiring board 22 from falling off, and the purpose of the screw 32 is different from that of a fixing screw for uniform heat conduction from the wiring board 22 to the array base 16 as in the prior art. Therefore, the screw 32 does not need to be tightly pressed by pressing the wiring board 22 toward the array base 16 side, and only one place is sufficient. Therefore, an increase in man-hours and costs due to the provision of the screws 32 can be minimized.

As shown in FIGS. 2 and 5, a white solder resist 61 is applied to the surface of each wiring board 22. The white solder resist 61 includes a highly light reflective material that reflects light efficiently. Examples of the highly light-reflective material include inorganic materials such as fine titanium oxide (TiO ₂ ) and barium titanate (BaTiO ₃ ), and organic materials such as fine, high-quality acrylic having numerous holes for light scattering and polycarbonate. A material etc. are used suitably.

  Conventional wiring boards are generally coated with a solder resist such as green, yellow, and black. However, as described above, the diameter d2 of each opening 6d provided in the reflecting plate 6 is formed to be slightly larger than the diameter d1 of each LED 21, so that the solder resist of the wiring board is made green or yellow and In the case of black or the like, if light enters the clearance 71 between each LED 21 and each opening 6d, the light is absorbed by the solder resist portion, and as a result, the light from the LED 21 is lost. It will be.

  Therefore, in this embodiment, by applying a white solder resist 61 containing a highly light-reflective material to the wiring board 22, the light emitted from the LED 21 and reflected from the diffusion plate 5 to the reflection plate 6 side or the reflection plate 6 is used. Even if the light reflected and reflected again from the diffusion plate 5 to the reflection plate 6 side enters the clearance 71 between the LED 21 and the opening 6d, the white solder resist 61 reflects the light to the diffusion plate 5 side. I have to. Thereby, luminance unevenness due to light loss can be minimized.

  As shown in FIGS. 3 and 4, an input connector 18 is mounted on each wiring board 22 at one end in the short direction (Y direction) and at one end in the long direction (X direction). In addition, an output connector 19 is mounted on the other end.

  In addition, as described above, each light source array 7 is formed by arranging the wiring boards 22 in the same direction on each array base 16 in each light source device 20. Further, among the light source arrays 7, the first row, the third row, the fifth row,... The light source devices 20 are arranged so that one side portion on which the output connector 19 is mounted faces downward. On the other hand, in the light source array 7 in the second row, the fourth row, the sixth row,..., The even row of the twelfth row, each wiring board 22 has an input connector 18 and an output connector 19 respectively. Each light source device 20 is arranged so that the mounted one side portion faces upward.

  That is, each light source array 7 is provided so that one light source device 20 and another light source device 20 adjacent to the light source device 20 in the Y direction are inverted by 180 degrees on the XY plane. Accordingly, the input connector 18 of one light source device 20 and the output connector of another light source device 20 adjacent thereto in the Y direction face each other, and the output connector 19 of one light source device 20 and the other light source device 20 The input connector 18 is opposed to the input connector 18. Thereby, the shortest wiring can be performed between the light source devices 20 in different rows.

  Further, as shown in FIG. 4, the two green LEDs 21c (G1) and 21d (G2) of each light source device 20 are different in chromaticity from each other, and the average chromaticity of the two becomes a predetermined chromaticity. Has been. That is, as long as the average chromaticity becomes a predetermined chromaticity, green LEDs having any chromaticity can be combined. By comprising in this way, the dispersion | variation in especially large green LED can be absorbed among each color LED.

  The green LEDs 21c and 21d (G1 and G2) are arranged in a zigzag shape along the X direction. That is, in each LED unit 25, the green LEDs 21c and 21d are alternately switched as the vertical position goes in the X direction.

  As described above, in the backlight device 10, each light source device 20 adjacent in the Y direction is arranged by being inverted 180 degrees, and therefore, the green LEDs 21 c and 21 d having different chromaticities are temporarily arranged along the X direction. When arranged in a straight line, the green LEDs 21c and 21d (G1 and G2) having the same chromaticity are close to each other between the light source devices 20 adjacent in the Y direction, thereby causing uneven color and uneven brightness. It will occur. However, by arranging the green LEDs 21c and 21d in a zigzag manner as in the present embodiment, the distances between G1 and G2 are uniformly arranged between the light source devices 20 adjacent in the Y direction. Therefore, occurrence of uneven color and uneven brightness can be suppressed.

  The green LEDs 21c and 21d may have different luminance as well as chromaticity. In this case, green LEDs having any luminance can be combined as long as the average luminance of the green LEDs 21c and 21d becomes a predetermined luminance.

  In addition to the green LEDs 21c and 21d, a plurality of red LEDs 21a or blue LEDs 21b are mounted on the LED unit 25, and the average chromaticity (or average chromaticity) of the plurality of red LEDs 21a or blue LEDs 21b is a predetermined chromaticity ( (Or brightness).

  As shown in FIGS. 2 to 5, a reflector 6 is provided above each light source array 7 (in the Z direction) so as to cover all the light source arrays 7. The reflecting plate 6 is formed by bonding a reflecting material made of foaming PET (Polyethylene terephthalate) containing a fluorescent material on the surface of an aluminum plate or a stainless steel plate, for example. Of the light emitted from each LED unit 25 of the light source device 20, the light reflected by the diffusion plate 5 is reflected by the reflection plate 6 and enters the diffusion plate 5 again. By repeatedly reflecting the emitted light from the LEDs 21 of each color between the diffuser plate 5 and the reflector plate 6, the reflectance and color mixing properties are improved by the principle of increased reflection.

  As shown in FIG. 2, the reflecting plate 6 includes a flat portion 6a, an edge portion 6c formed on the periphery of the reflecting plate 6 substantially in parallel with the flat portion 6a, and between the flat portion 6a and the edge portion 6c ( And an inclined portion 6b formed from the diffusion plate 5 side to the light source device 20 side around the flat surface portion 6a. The flat surface portion 6a is provided with a plurality (1152) of circular openings 6d according to the number and shape of each LED of each LED unit 25, and the reflecting plate 6 allows each LED 21 to pass through the opening 6d. In this manner, the flat portion 6a is provided on the upper surface of the array base 16 of each light source array 7 so as to be fixed by, for example, adhesion.

  As shown in FIG. 4, each opening 6 d is formed so that its diameter d <b> 2 (and outer peripheral length) is slightly larger than the diameter d <b> 1 (and outer peripheral length) in the XY plane of each resin holder of each LED 21. As a result, a clearance 71 is formed between each LED 21 and each opening 6d. Therefore, by absorbing the dimensional tolerance of each LED 21 and variations such as mounting accuracy when each LED 21 is mounted on each wiring board 22, The reflector 6 can be easily assembled. Further, as described above, only one reflector 6 is provided so as to cover all the light source devices 20 and is provided with a flexible material such as aluminum. Although it may be considered that the position is displaced between the respective openings 6d and the respective LEDs 21, the reflector 71 can be easily assembled by the clearance 71 in response to the bending. The width c of the clearance 71 on the XY plane is, for example, about 1 mm to 2 mm, but is not limited to this.

  Further, as described above, the reflection plate 6 is held by inserting the edge portion 6 c between the diffusion plate 5 and the bracket member 15 provided in the back chassis 8. Further, the reflecting plate 6 is also held by an optical stud 17 described later.

  As shown in FIGS. 2 to 4, a plurality of optical studs 17 are provided between the diffusion plate 5 and the reflection plate 6. As shown in FIG. 2, the optical stud 17 is composed of a protrusion 17a, a base portion 17c, and a shaft portion 17b that connects them, for example, a fitting hole (see FIG. 2) provided in the recess 8b of the back chassis 8 and the reflection plate 6. (Not shown) is penetrated by the shaft portion 17b, and the concave portion 8b and the reflection plate 6 are fixed so as to sandwich the projection portion 17a and the base portion 17c. The optical stud 17 is integrally formed of a milky white synthetic resin material having light guiding properties, mechanical rigidity, and a certain degree of elasticity, such as polycarbonate resin. By providing the optical stud 17, the bottom surface of the diffusion plate 5 is held so as to abut against the tip of the projection 17 a of the optical stud 17, and the distance and parallelism between the diffusion plate 5 and the reflection plate 6 are maintained. Further, the occurrence of uneven color due to the deflection of the diffusion plate 5 and the reflection plate 6 is prevented.

  As shown in FIG. 3, a plurality of optical studs 17 are provided over the entire surface of the backlight device 10. For example, three or four optical studs 17 are provided at predetermined intervals in the Y direction every time the LED units 25 for three rows are provided, and at the central portion of the backlight device 10, predetermined intervals are provided in the Y direction. Five are provided, and a total of 27 backlight devices 10 are provided. Of course, this number can be changed as appropriate. Further, as shown in FIGS. 3 and 4, the optical stud 17 is provided at a position that is substantially the same distance from the four LED units 25 adjacent to each other. If the optical stud 17 is provided at an intermediate position between two LED units 25 adjacent in the X direction or the Y direction, the optical stud 17 prevents the color mixture of the emitted lights between the two LED units 25. Color unevenness or luminance unevenness due to any of red, blue, and green colors occurs. However, in the present embodiment, by providing the optical stud 17 at substantially the center of the four LED units 25 as described above, it is possible to provide a high-quality liquid crystal display device that suppresses the occurrence of color unevenness and luminance unevenness. Can do.

  As described above, the reflection plate 6 is provided so that the LED 21 penetrates the opening 6d and is exposed on the surface of the reflection plate 6. However, when provided in this way, the reflection plate 6 is provided on each wiring substrate 22. Since the input connector 18 and the output connector 19 interfere with the reflecting plate 6, the reflecting plate 6 penetrates the input connector 18 and the output connector 19 and is exposed to the surface of the reflecting plate 6. An opening (not shown) must also be provided. However, when the light emitted from the LED 21 hits the opening, the input connector 18 and the output connector 19, the light is lost without being reflected toward the diffusion plate 5, and as a result, the luminance of the backlight device 10 is reduced. This causes a decrease, and local brightness unevenness occurs.

  Therefore, in the present embodiment, as shown in FIG. 3, the reflective sheet 31 is attached to the reflective plate 6 so as to cover the exposed input connector 18 and output connector 19. The reflective sheet 31 is made of a reflective material such as foamable PET, as with the reflective plate 6. As a result, even when it is necessary to provide openings for the input connector 18 and the output connector 19 in the reflecting plate 6, it is possible to provide a backlight device 10 with high luminance and low luminance unevenness without loss of light. it can.

  In addition to the connector, a screw for fixing the light source device 20 to the back chassis 8 is also provided on the wiring board 22, and the reflection plate 6 has an opening through which this screw can be exposed. Must also be provided. This also causes the problem of light loss. Therefore, a reflection sheet (not shown) that covers the screws may be provided on the reflection plate 6 in the same manner as the reflection sheet 31.

  Instead of providing the reflection sheet 31, a highly reflective material may be used for the input connector 18, the output connector 19, and the screws themselves. Further, instead of providing the reflection sheet 31, the gaps between the input connector 18 and the output connector 19 and the opening are made as small as possible so that the input connector 18 and the output connector 19 and their wirings interfere with the reflection plate 6. In this case, a flap (cut) is attached to the reflector 6 so that the flap portion is floated to prevent interference while light is reflected on the flap portion to prevent light loss. I do not care.

  By the way, when the LED unit 25 is employed as the light source of the backlight device 10 as in the present embodiment, if the LED unit 25 is continuously turned on, the temperature of the back chassis 8 of the light source device 20 and the like with time elapses. The temperature rises by about 30 ° C. with respect to room temperature. Along with this, the temperature of the liquid crystal panel 2 also rises, for example, by about 20 ° C. with respect to room temperature via the front chassis 1, the middle frame 3, and the like. As a result, a temperature difference is generated between the peripheral portion of the liquid crystal panel 2 held by the front chassis 1 and the middle frame 3 and the central portion of the liquid crystal panel 2 away from the peripheral portion. As a result, a stress is generated in the glass substrate in which the liquid crystal is sealed, the refractive index of the glass substrate changes, and a phenomenon in which the polarization characteristics change occurs. In particular, on a black screen, the polarization characteristic changes in the direction in which it appears white, which results in uneven brightness.

  Therefore, in the present embodiment, as shown in FIG. 3, for example, isosceles triangular black sheets 51 are attached to the four corners of the flat portion 6 a of the reflecting plate 6 to reduce the reflectance at the four corners of the reflecting plate 6, Improves brightness unevenness. The shape of the black sheet 51 is not limited to an isosceles triangle shape, and may be another shape such as an L shape. Further, the black sheets 51 may be provided at the four corners of the inclined portion 6b instead of the four corners of the flat surface portion 6a of the reflecting plate 6. Further, instead of applying the black tape 51, a black coating or black printing process may be performed. That is, a process for reducing the reflectivity at the four corners of the reflecting plate 6 may be performed.

  Next, the drive circuit of the liquid crystal display device 100 will be briefly described. FIG. 6 is a block diagram showing the drive circuit.

  As shown in the figure, the liquid crystal display device 100 is provided with respect to the liquid crystal panel 2 for displaying an image, the backlight device 10 disposed on the back side of the liquid crystal panel 2, the backlight device 10 and the liquid crystal panel 2. A control unit 40 for performing various controls and a memory 36 accessible by the control unit 40 are provided. The control unit 40 includes a video signal detection circuit 39 that detects a video signal, a backlight lighting control circuit 35 that controls lighting of the backlight device 10, and a liquid crystal panel control circuit 34 that controls driving of the liquid crystal panel 2. ing.

  The liquid crystal panel 2 has a source driver 37 and a gate driver 38 for sending drive signals to the liquid crystal panel 2. Further, as described above, the liquid crystal panel 2 is provided with color filters of three primary colors (RGB) (not shown), and one pixel is composed of three sub-pixels corresponding to RGB. The configuration of the color filter may be a configuration of four or more primary colors including colors other than RGB, for example, colors such as emerald or cyan.

  The video signal detected by the video signal detection circuit 39 is supplied to the source driver 37 and the gate driver 38 by the liquid crystal panel control circuit 34 via the memory 36 at a predetermined timing, and the liquid crystal panel 2 is driven by the control of both drivers. The video is displayed. On the other hand, the backlight lighting control circuit 35 generates a backlight lighting signal and drives each LED 21 of each light source device 20 of the backlight device 10.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

  In the embodiment described above, the adhesive material 23 provided between the wiring board 22 and the array base 16 itself is an adhesive body and an insulator, but is an insulating plate-like non-adhesive body having elasticity. An adhesive material may be applied to both sides of the body material.

  In the above-described embodiment, the screw 32 is provided as a locking member for preventing the wiring board 22 from falling off the array base 16. However, for example, a pin, a hook, a spring, or the like may be used in addition to the screw. I do not care. In other words, any device may be used as long as the purpose of preventing dropout can be achieved. Further, when the adhesive performance of the adhesive material 23 is high, a locking member such as the screw 32 may not be provided.

  In the above-described embodiment, the wiring board 22 is made of resin, but may be made of resin such as aluminum. Alternatively, a substrate having a structure in which a resin substrate and a metal substrate are multilayered may be used. In this case, a thermal via is provided in the resin substrate portion, and the adhesive material 23 may be provided between the resin substrate and the metal substrate or between the metal substrate and the array base 16.

  In the above-described embodiment, a heat pipe, a heat sink, a cooling fan, or the like may be provided on the array base 16 to further increase the heat dissipation efficiency.

1 is a schematic exploded perspective view of a liquid crystal display device having a backlight device according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view in the Z direction of the liquid crystal display device of FIG. 1. It is a partially cutaway top view which shows the structure of the backlight apparatus which concerns on one Embodiment of this invention. FIG. 4 is an enlarged view of a portion surrounded by a broken line A in FIG. 3 of the backlight device according to the embodiment of the present invention. It is AA 'sectional drawing of the backlight apparatus shown in FIG. It is the block diagram which showed the drive circuit of the liquid crystal display device in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Front chassis 2 ... Liquid crystal panel 3 ... Middle frame 4 ... Optical sheet laminated body 5 ... Diffusing plate 6 ... Reflecting plate 7 ... Light source array 8 ... Back chassis 10 ... Backlight apparatus 16 ... Array base 17 ... Optical stud 20 ... Light source Device 21 ... LED
DESCRIPTION OF SYMBOLS 22 ... Wiring board 23 ... Adhesive material 24 ... Resin holder 25 ... LED unit 26 ... Lead wire 27 ... Light emitting element holding stand 28 ... Solder pad 32 ... Screw 52 ... Thermal via 53 ... Metal plating layer 61 ... White solder resist 100 ... Liquid crystal Display device

Claims (5)

A housing,
A plurality of wiring boards having a plurality of light emitting diodes and a heat transfer path for conducting heat generated from each of the light emitting diodes;
A metal holding member that is fixed to the housing and holds each wiring board;
A backlight comprising: an adhesive provided between each of the wiring boards and the holding member and capable of conducting heat conducted from the heat transfer path of each of the wiring boards to the holding member. apparatus. The backlight device according to claim 1,
The wiring board is made of resin,
The heat transfer path is a thermal via that penetrates the wiring board from the light emitting diode side to the holding member side,
The said adhesive material is an insulator. The backlight apparatus characterized by the above-mentioned. The backlight device according to claim 2,
The backlight device further comprising a locking member for locking the wiring board to the holding member. A housing, a plurality of light emitting diodes and a plurality of wiring boards each having a heat transfer path for conducting heat generated from each of the light emitting diodes, and a metal fixed to the housing and holding each wiring board A backlight having a metal holding member and an adhesive material provided between the wiring boards and the holding member and capable of conducting heat conducted from the heat transfer path of the wiring boards to the holding member. Equipment,
A liquid crystal display device comprising: a liquid crystal panel capable of displaying an image by changing a transmittance of light emitted from the light emitting diode unit. The liquid crystal display device according to claim 4,
The wiring board is made of resin,
The heat transfer path is a thermal via that penetrates the wiring board from the light emitting diode side to the holding member side,
The liquid crystal display device, wherein the adhesive material is an insulator.

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