JP2013047739A - Liquid-crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid-crystal display device provided with a backlight unit that uses light-emitting diodes arranged in a concentrated manner to illuminate an entire image-formation region, where heat from the light-emitting diodes is dissipated efficiently.SOLUTION: The liquid-crystal display device comprises: a liquid-crystal panel; a reflective sheet that is disposed on the rear-surface side of the liquid-crystal panel and curved such that the surface thereof that faces the liquid-crystal panel is concave; and a light-emitting-diode substrate 7 that has a light-emitting diode row where light-emitting diodes 13 are arranged in a longitudinal direction, and also has electrodes 21L, 21H connected to the light-emitting diodes 13. Within a circle 23 that is centered on one of the light-emitting diodes 13 and has a diameter equal to the separation between the one of the light-emitting diodes 13 and others of the light-emitting diodes 13 adjacent to the one of the light-emitting diodes 13, the surface area of the electrode 21H connected to the high-temperature-side electrode of the one of the light-emitting diodes 13 is larger than the surface area of the electrode 21L connected to the low-temperature-side electrode of the one of the light-emitting diodes 13.

Description

  The present invention relates to a liquid crystal display device.

  The following Patent Document 1 discloses a liquid crystal display device having a direct type backlight unit. In such a liquid crystal display device, a plurality of light emitting diodes (Light Emitting Diodes) are used as the light source of the backlight unit. The light emitting diodes are arranged in a grid pattern throughout the backlight unit.

JP 2007-286627 A

  In the liquid crystal display device described in Patent Document 1, since the light emitting diodes are arranged over the entire area of the backlight unit, the size of the substrate on which the large number of light emitting diodes are arranged should not cover the entire area of the backlight unit. Don't be. Therefore, not only the cost of preparing a large number of light emitting diodes, but also the material cost of the substrate on which the light emitting diodes are arranged increases.

  Therefore, the light emitting diodes are arranged along a specific direction in a part of the backlight unit, for example, the light emitting diodes are concentrated along the long side direction of the backlight unit near the center of the short side direction of the backlight unit. It can be considered that the light beam from the light emitting diode is reflected and diffused by an appropriate reflection sheet to irradiate the entire image forming region.

  FIG. 9 is an enlarged plan view showing a part of a state in which a plurality of light emitting diodes 13 are linearly arranged on the light emitting diode substrate 7. A lens 14 is disposed on the light emitting surface side of each light emitting diode 13 in order to diffuse light rays. In the figure, the portion located behind the lens 14 is indicated by a broken line. As shown in the figure, the light emitting diodes 13 are arranged in series in the longitudinal direction of the liquid crystal display device, that is, in the horizontal direction in this figure.

  Here, as shown in the figure, the electrodes 21 connected to the anode and the cathode of each light-emitting diode 13 spread in a plane and have a so-called solid pattern. This is because the heat from the light emitting diode 13 is diffused and dissipated by the electrode 21 having a high thermal conductivity. The upper limit of the maximum output and arrangement density of the light emitting diodes 13 is determined by the heat dissipation capability. In other words, the higher the heat dissipation performance, the more light emitting diodes 13 can be used with respect to the light emitting diode substrate 7 having the same area, or the arrangement density of the light emitting diodes 13 can be increased. Alternatively, if the output of the light emitting diode 13 is the same, the size of the light emitting diode substrate 7 can be reduced as the heat dissipation performance is higher.

  By the way, the heat generated by the light emitting diode 13 is transferred to the electrode 21 through the anode and the cathode. However, in the light emitting diode 13 that is generally used at present, the amount of heat transfer is not equal between the anode and the cathode. . In the example shown in FIG. 9, such circumstances are not taken into consideration at all, and the patterns of the electrode 21 on the side connected to the anode and the side connected to the cathode are equal. Of the anode and the cathode, if the heat generation amount is larger and the temperature is higher, the higher temperature side electrode is called, and the heat generation amount is smaller and the temperature relatively lower is called the low temperature side electrode. The maximum output and the arrangement density are determined by the heat dissipation performance on the high temperature side electrode side, which is a severe thermal condition, but in that case, there is a margin in the heat dissipation performance on the low temperature side electrode side. There is room for further improvement in heat dissipation performance. Note that most of the currently used light emitting diodes have a calorific value larger at the cathode than that at the anode. That is, the amount of heat transferred to the electrode 21 is larger on the cathode side and the temperature is higher.

  The present invention has been made in view of such circumstances, and in a liquid crystal display device including a backlight unit that irradiates the entire image forming region with concentrated light emitting diodes, heat generated from the light emitting diodes is efficiently dissipated. This is the issue.

Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.
(1) A liquid crystal panel, a reflective sheet that is arranged on the back side of the liquid crystal panel and is curved so that the surface facing the liquid crystal panel is concave, and a plurality of light emitting diodes are arranged along the longitudinal direction. A light emitting diode substrate having a light emitting diode array and an electrode connected to the light emitting diode, and centering on the one light emitting diode, from the light emitting diode to another light emitting diode adjacent to the light emitting diode A liquid crystal display device in which the area of the electrode connected to the high temperature side electrode of the light emitting diode is larger than the area of the electrode connected to the low temperature side electrode of the light emitting diode in a circle having a diameter of.
(2) In the liquid crystal display device according to (1), the low temperature side electrode is an anode of the light emitting diode, and the high temperature side electrode is a cathode of the light emitting diode.
(3) In (1) or (2), the electrode connected to the low temperature side electrode of the one light emitting diode and the electrode connected to the high temperature side electrode of the light emitting diode are partly Liquid crystal display devices that overlap each other in the short direction.
(4) In any one of (1) to (3), a boundary separating the electrode connected to the low temperature side electrode of the one light emitting diode and the electrode connected to the high temperature side electrode of the light emitting diode At least a portion of which is non-parallel to the short-side direction and is inclined toward the electrode connected to the low temperature side electrode with the light emitting diode as a starting point.

  According to the invention disclosed in the present application described above, in the liquid crystal display device including the backlight unit that irradiates the entire image forming region with the centrally arranged light emitting diodes, heat generated from the light emitting diodes can be efficiently dissipated. it can.

1 is an exploded perspective view of a liquid crystal display device according to a preferred embodiment of the present invention. It is a schematic sectional drawing of the liquid crystal display device by the II-II line | wire of FIG. It is a block diagram showing the structure of a liquid crystal display device. One of the pixels formed on the liquid crystal panel is shown by a circuit diagram. It is the figure which looked at the reflective sheet, light emitting diode board | substrate, and heat sink of the liquid crystal display device from the front side. FIG. 6 is a partially enlarged sectional view taken along line VI-VI in FIG. 5. It is the elements on larger scale of a light emitting diode board | substrate. It is the elements on larger scale of the light emitting diode board | substrate which concerns on the modification which has arrange | positioned a light emitting diode so that it may become 2 rows in a longitudinal direction. It is a top view which expands and shows a part of a mode that the some light emitting diode was linearly arranged on the light emitting diode board | substrate.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an exploded perspective view of a liquid crystal display device 1 according to the present embodiment. As shown in the figure, the liquid crystal display device 1 includes an upper frame 2, a liquid crystal panel 3, an intermediate frame 4, an optical sheet group 5, a reflective sheet 6, a light emitting diode substrate 7, a heat sink 8, and a lower frame 9 from the front side. Are arranged and assembled in this order. The optical sheet group 5, the reflection sheet 6, the light emitting diode substrate 7, and the heat radiating plate 8 constitute a backlight unit 10 that functions as a planar light source that illuminates the liquid crystal panel 3 from its back side. In the same figure, only the structural parts of the liquid crystal display device 1 are shown, and other components such as a control board and a speaker are not shown.

  FIG. 2 is a schematic sectional view of the liquid crystal display device 1 taken along line II-II in FIG. The figure shows a schematic cross section of the liquid crystal display device 1 after assembly. As shown in the figure, the liquid crystal display device 1 has a structure in which the liquid crystal panel 3 and the backlight unit 10 are accommodated in an outer frame composed of an upper frame 2 and a lower frame 9. And the intermediate frame 4 is provided between the liquid crystal panel 3 and the backlight unit 10, and the liquid crystal panel 3 and the backlight unit 10 are hold | maintained separately. In the figure, the left side is a side on which the user observes an image, and hereinafter referred to as a front side, and a surface facing the front side is referred to as a front surface. The opposite direction is referred to as the back side, and the surface facing the back side is referred to as the back side.

  The liquid crystal display device 1 shown in this embodiment is a television receiver. Therefore, the liquid crystal display device 1 includes a component for functioning as a television receiver, for example, the speaker 11 shown in FIG. In addition to the power supply, the control circuit of the liquid crystal panel 3 and the control circuit of the backlight unit 10, the control board 12 shown in the figure includes circuits such as a tuner for receiving television broadcasting. The liquid crystal display device 1 is not necessarily a television receiver, and may be a computer monitor, for example. In that case, parts for functioning as a television receiver may be omitted.

  The upper frame 2 and the lower frame 9 constitute a casing that accommodates the liquid crystal panel 3 and the backlight unit 10, and are preferably formed of a lightweight and highly rigid material, such as a steel plate, an aluminum alloy, a magnesium alloy, and the like. These metals, FRP, and various synthetic resins may be used. In particular, the lower frame 9 is preferably a material having high thermal conductivity in order to efficiently dissipate heat generated by light emission of the light emitting diode conducted from the light emitting diode substrate 7 through the heat dissipation plate 8, A steel plate is used. The material of the upper frame 2 may be the same as or different from that of the lower frame 9 and may be appropriately determined in consideration of factors such as the size, application, appearance, and weight of the liquid crystal display device 1. A buffer material 2 a is provided on the surface of the upper frame 2 facing the liquid crystal panel 3, and the liquid crystal panel 3 is shaken by vibrations or the like so as to alleviate an impact when contacting the upper frame 2. An appropriate rubber, resin, sponge or the like is used for the buffer material 2a. Of course, the support and buffer structure of the liquid crystal panel 3 shown here is an example.

  The intermediate frame 4 is a member that holds the liquid crystal panel 3 and the backlight unit 10 separately. On the front surface of the intermediate frame 4, a buffer material 4 a is provided to relieve shock when the liquid crystal panel 3 swings and contacts the intermediate frame 4. An appropriate rubber, resin, sponge or the like is used for the buffer material 4a. The structure of the intermediate frame 4 shown here is merely an example, and any structure may be used as long as it properly supports the liquid crystal panel 3 and the backlight unit 10, and may be omitted depending on circumstances. Good.

  The material of the intermediate frame 4 is also not particularly limited, but it is preferable to use a synthetic resin in terms of ease of molding and cost. In this embodiment, polycarbonate is used from the viewpoint of strength, but the present invention is not necessarily limited thereto. A reinforcing material may be mixed into the synthetic resin, such as FRP (Fiber Reinforced Plastic). Moreover, it is preferable that the intermediate frame 4 has a light-shielding property, and therefore it is preferable that the intermediate frame 4 be black or dark. As for the coloring of the intermediate frame 4, the material itself may be black or dark, or the surface of the intermediate frame 4 may be painted. In the present embodiment, the intermediate frame 4 is obtained by molding polycarbonate colored in black or dark color.

  The backlight unit 10 includes an optical sheet group 5, a reflection sheet 6, a light emitting diode substrate 7, and a heat radiating plate 8. In the present embodiment, the light emitting diode substrate 7 is an elongated substrate on which a plurality of light emitting diodes 13 are linearly mounted, and is provided so that the longitudinal direction of the light emitting diode substrate 7 is aligned with the longitudinal direction of the liquid crystal display device 1. Yes. The light emitting diode substrate 7 is attached to the heat sink 8. Here, the light-emitting diode 13 is a so-called light-emitting diode package in which a light-emitting diode chip is encapsulated with a sealing resin in this embodiment, and is mounted on the light-emitting diode substrate 7, but is not limited thereto. For example, a light emitting diode chip directly formed on the light emitting diode substrate 7 may be used. The lens 14 is an optical component for diffusing the light beam from the light emitting diode 13 and obtaining illumination with uniform brightness over the entire image forming region of the liquid crystal panel 3.

  In the present embodiment, the light emitting diode substrate 7 has a length in the longitudinal direction slightly shorter than the length in the corresponding direction of the liquid crystal panel 3, and is about 70 to 80% in the present embodiment. Further, the length in the short direction (in the plane of the light emitting diode substrate 7 and perpendicular to the long direction) is shorter than the length in the short direction of the liquid crystal panel 3, and is preferably half or less. In this embodiment, it is about 10 to 20%. The material of the light-emitting diode substrate 7 is not particularly limited as long as it is an insulating material, and is formed of an insulating material such as glass epoxy, paper phenol, paper epoxy, or a metal with an insulating coating. It's okay. Hereinafter, the term “longitudinal direction” in this specification refers to the longitudinal direction of the light emitting diode substrate, that is, the direction in which the light emitting diodes 13 are arranged. In the present embodiment, the longitudinal direction of the light emitting diode substrate 7 is the direction parallel to the long side of the liquid crystal panel, but instead, the direction parallel to the short side of the liquid crystal display device 1 may be the longitudinal direction. Further, the specific dimensions of the above-described light emitting diode substrate 7 are merely examples, and may be arbitrarily changed depending on the design of the liquid crystal display device 1.

  The reflection sheet 6 is a member for reflecting the light from the light emitting diode 13 and irradiating the back surface of the liquid crystal panel 3 evenly, and has a curved cross-sectional shape as shown in the figure. The light beam from the light emitting diode 13 is diffused in the vertical direction by the lens 14 provided on the front surface of the light emitting diode 13 and directly enters the optical sheet group 5 as indicated by an arrow 15 in the drawing, or is reflected by the reflecting sheet 6. The light is reflected and enters the optical sheet group 5. The reflective sheet 6 and the optical sheet group 5 have a size corresponding to the liquid crystal panel 3, so that the liquid crystal panel 3 is evenly illuminated from the back side.

  The reflection sheet 6 has a size corresponding to the liquid crystal panel 3 as described above, and has a curved shape that is concave when viewed from the front side. Further, a hole is provided at a position where the light emitting diode 13 is disposed so that the light emitting diode 13 is exposed to the front side of the reflection sheet 6. The material of the reflection sheet 6 is not particularly limited, but a white reflection sheet using a PET resin or the like may be used, or a specular reflection sheet or the like may be used. In this embodiment, it is a white reflective sheet. The optical sheet group 5 is a plurality of optical films including a diffusion sheet for diffusing the light incident from the light emitting diode 13 and a prism sheet for refracting the direction of the light rays toward the front side.

  The heat radiating plate 8 is a metal plate to which the light emitting diode substrate 7 is attached and which holds the reflective sheet 6. The heat sink 8 itself is fixed to the lower frame 9. The material of the heat sink 8 is preferably a material having high thermal conductivity, and various metals and alloys may be suitably used. In this embodiment, aluminum is used. The method for forming the heat sink 8 is not particularly limited, and any method such as pressing or cutting may be used. In this embodiment, the heat sink 8 is obtained by extrusion molding.

  FIG. 3 is a configuration diagram showing the configuration of the liquid crystal display device 1. Hereinafter, the function of each part of the liquid crystal display device 1 will be described with reference to FIG.

  The liquid crystal panel 3 has a rectangular shape, and the lengths in the left-right direction and the up-down direction are determined according to the use of the liquid crystal display device 1. Further, the liquid crystal panel 3 has a horizontally long shape (the length in the left-right direction is longer than the length in the up-down direction) or a vertically long shape (the length in the left-right direction is shorter than the length in the up-down direction). The lengths in the vertical direction may be equal. In the present embodiment, since the liquid crystal display device 1 is a television receiver, the liquid crystal panel 3 has a horizontally long shape.

  The liquid crystal panel 3 has a pair of transparent substrates. A plurality of video signal lines Y and a plurality of scanning signal lines X are formed on a TFT substrate which is one of the transparent substrates. The video signal line Y and the scanning signal line X are orthogonal to each other and are formed in a lattice shape. A region surrounded by two adjacent video signal lines Y and two adjacent scanning signal lines X is one pixel.

  FIG. 4 is a circuit diagram showing one of the pixels formed on the liquid crystal panel 3. A region surrounded by the video signal lines Yn and Yn + 1 and the scanning signal lines Xn and Xn + 1 shown in the drawing is one pixel. Here, it is assumed that the pixel of interest is driven by the video signal line Yn and the scanning signal line Xn. A TFT (Thin Film Transistor) 3a is provided on the TFT substrate side of each pixel. The TFT 3a is turned on by a scanning signal input from the scanning signal line Xn. The video signal line Yn applies a voltage (a signal representing the gradation value of each pixel) to the pixel electrode 3b of the pixel via the TFT 3a in the on state.

  On the other hand, a color filter is formed on the color filter substrate which is the other substrate of the transparent substrate, and a liquid crystal 3c is sealed between the TFT substrate and the color filter substrate. A common electrode 3d is formed so as to form a capacitor via the pixel electrode 3b and the liquid crystal 3c. The common electrode 3d is electrically connected to a common potential. Therefore, the electric field between the pixel electrode 3b and the common electrode 3d changes according to the voltage applied to the pixel electrode 3b, thereby changing the alignment state of the liquid crystal 3c, and the polarization state of the light beam transmitted through the liquid crystal panel 3 To control. And the polarizing filter is affixed on the back surface which is a surface on the opposite side to the display surface of the liquid crystal panel 3, and a display surface. Thereby, each pixel formed in the liquid crystal panel 3 functions as an element for controlling the light transmittance. An image is formed by controlling the light transmittance of each pixel according to the input image data. Therefore, in the liquid crystal panel 3, an area where pixels are formed is an image forming area.

  The common electrode 3d may be provided on either the TFT substrate or the color filter substrate. The arrangement of the common electrode 3d depends on the liquid crystal driving method. For example, in the case of an IPS (In Plane Switching) method, the common electrode 3d is provided on the TFT substrate. In the case of the VA (Vertical Alignment) method or the TN (Twisted Nematic) method, the common electrode is provided on the color filter substrate. In this embodiment, since the IPS method is used, the common electrode 3d is provided on the TFT substrate. The transparent substrate is glass in this embodiment, but other materials such as resin may be used.

  Returning to FIG. 3, video data received by a tuner or an antenna (not shown) and video data generated by another device such as a video playback device are input to the control device 16. The control device 16 may be a microcomputer provided with a CPU (Central Processing Unit) and a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The control device 16 performs various image processing such as color adjustment on the input video data, and generates a video signal indicating the gradation value of each pixel. The control device 16 outputs the generated video signal to the video line driving circuit 17b. Further, the control device 16 generates a timing signal for synchronizing the video line driving circuit 17b, the scanning line driving circuit 17a, and the backlight driving circuit 18 based on the input video data, and sends the timing signal to each driving circuit. Output. However, this embodiment does not particularly limit the form of the control device 16. For example, the control device 16 may be composed of a plurality of LSIs (Large Scale Integration) or may be a single unit. Further, the backlight drive circuit 18 and other circuits may not be synchronized.

  The backlight drive circuit 18 is a circuit that supplies necessary current to the plurality of light emitting diodes 13 that are light sources of the backlight unit 10. In the present embodiment, the control device 16 generates a signal for controlling the luminance of the light emitting diode 13 based on the input video data, and outputs the signal to the backlight drive circuit 18. Then, the backlight drive circuit 18 controls the amount of current flowing through the light emitting diode 13 according to the generated signal, and adjusts the luminance of the light emitting diode 13. The luminance of the light emitting diode 13 may be adjusted for each light emitting diode 13, or the plurality of light emitting diodes 13 may be divided into several groups and adjusted for each group. As a method for controlling the luminance of the light emitting diode 13, a PWM (Pulse Width Modulation) method in which the current amount is constant and the brightness is controlled in the light emission period may be used. Alternatively, the current amount may be constant so as to emit light with a constant light amount without controlling the luminance of the light emitting diode 13.

  The scanning line driving circuit 17a is connected to the scanning signal line X formed on the TFT substrate. The scanning line driving circuit 17a sequentially selects the scanning signal lines X according to the timing signal input from the control device 16, and applies a voltage to the selected scanning signal line X. When a voltage is applied to the scanning signal line X, the TFT connected to the scanning signal line X is turned on.

  The video line driving circuit 17b is connected to the video signal line Y formed on the TFT substrate. In accordance with the selection of the scanning signal line X by the scanning line driving circuit 17a, the video line driving circuit 17b responds to the video signal representing the gradation value of each pixel on each of the TFTs provided on the selected scanning signal line X. Apply the correct voltage.

  In this embodiment, both the control device 16 and the backlight drive circuit 18 shown in FIG. 3 are formed on the control board 12 in FIG. The liquid crystal panel drive circuit 17 including the scanning line drive circuit 17a and the video line drive circuit 17b constitutes the liquid crystal panel 3 on an FPC (Flexible Printed Circuits) electrically connected to the liquid crystal panel 3 (FIG. 3). (So-called SOG (System On Glass)). In addition, these arrangement | positioning is an example and it is arbitrary in which part each circuit is provided.

  FIG. 5 is a view of the reflection sheet 6, the light emitting diode substrate 7, and the heat dissipation plate 8 of the liquid crystal display device as viewed from the front side. In the figure, the portions where the light emitting diode substrate 7 and the heat radiating plate 8 are hidden by the reflection sheet 6 and are not visible are indicated by broken lines.

  On the periphery of the reflection sheet 6, an appropriate number of fixing portions 6 a protruding in a tongue shape are provided at appropriate intervals. This is for fixing the peripheral portion of the reflection sheet 6, and in this embodiment, holes are provided so as to be hooked and fixed to protrusions (not shown) provided on the intermediate frame 4. However, any structure may be used for fixing the peripheral edge portion of the reflection sheet 6.

  Further, a hole 6b for exposing the lens 14 to the front surface side of the reflection sheet 6 is provided in a central region in the short direction of the reflection sheet 6 according to the arrangement of the lenses 14, that is, the light emitting diodes. . In addition, the arrangement density of the light emitting diodes is high in the vicinity of the central portion in the longitudinal direction and is low in the vicinity of both end portions. That is, the interval between the adjacent light emitting diodes is larger in the peripheral portion of the image forming region than in the central portion of the image forming region. The positions of the lens 14 and the hole 6b shown in FIG. 5 correspond to the positions of the above-described light emitting diodes. In the figure, only one light emitting diode 13 and one hole 6b are represented as a representative.

  6 is a partially enlarged sectional view taken along line VI-VI in FIG. In FIG. 6, the lower frame 9 is shown at the same time. Further, the left side of the figure is the front side, and the right side is the back side. In the drawing, the light-emitting diode 13 mounted on the light-emitting diode substrate 7 and the lens 14 disposed on the front surface thereof are exposed to the front side of the reflective sheet 6 through the hole 6 b provided in the reflective sheet 6. The state of doing is shown. Further, the reflection sheet 6 is provided with a fixing hole 6 c, and is fixed to the heat radiating plate 8 in a region outside in the width direction of the light emitting diode substrate 7 by a fixing tool 19 penetrating the fixing hole 6 c. The size of the fixing hole 6 c is slightly larger than the cross section of the through portion of the fixing tool 19. This is to allow a relative change in dimensions due to a difference in linear expansion coefficient of each member in thermal expansion due to heat generation of the light emitting diode 13. Further, the front surfaces of the light emitting diode substrate 7 and the heat radiating plate 8 are substantially flush with each other, and on the front surface side, the reflection sheet 6 is held flat without being waved. The fixing tool 19 may be any type and is not particularly limited. In the present embodiment, a fixing pin having a snapping mechanism as illustrated is used, and the reflection sheet 6 can be fixed easily. The material of the fixture 19 is preferably the same as or similar to the reflective sheet 6 and made of white synthetic resin. Thereby, the luminance unevenness in the position where the fixing tool 19 is arranged is suppressed to the minimum.

  FIG. 7 is a partially enlarged view of the light emitting diode substrate 7. This figure shows the vicinity of the center of the light emitting diode substrate 7 shown in FIG. 5, and the lens is omitted for the sake of simplicity of explanation. As illustrated, the light emitting diodes 13 are arranged in the longitudinal direction to form a light emitting diode array. A solid pattern electrode 21 is formed between the anode and the cathode of the adjacent light emitting diodes 13, and the light emitting diodes 13 are connected in series. Here, in the figure, the light emitting diode 13 shown in the center is given a reference number, and the electrode 21L connected to the low temperature side electrode of the light emitting diode 13 is the electrode 21L, and the high temperature side of the light emitting diode 13 is also shown. The electrode 21 connected to the electrode is particularly shown as an electrode 21H. A boundary 22 where the electrode 21 is not formed is provided between the electrode 21L and the electrode 21H, and the both electrodes 21L and 21H are separated so as not to be short-circuited. In this example, the anode is a low temperature side electrode and the cathode is a high temperature side electrode.

  In the present embodiment, the boundary 22 is in the plane of the light emitting diode substrate 7 and is not parallel to the short direction (vertical direction in FIG. 7) that is orthogonal to the longitudinal direction, and starts from the light emitting diode 13. Inclined toward the electrode 21L connected to the low temperature side electrode.

  The reason why the boundary 22 has such an orientation will be described. Heat generated by the light emitting diode 13 is propagated to the electrodes 21L and 21H through the low temperature side electrode and the high temperature side electrode, and then dissipated by exchanging heat with the outside air. At this time, the heat transmitted from the low temperature side electrode and the high temperature side electrode to the electrodes 21L and 21H propagates and diffuses radially in the surfaces of the electrodes 21L and 21H. Therefore, the temperature distribution of the electrodes 21L and 21H is concentric with the low temperature side electrode and the high temperature side electrode as the center, and the temperature decreases as the distance from the low temperature side electrode and the high temperature side electrode increases. On the other hand, the magnitude of the heat flow rate generated by heat transfer from the electrodes 21L and 21H to the outside air is proportional to the temperature difference between the electrodes 21L and 21H and the outside air, as is well known. Therefore, if it is considered that the outside air temperature is substantially constant due to convection, the heat transfer from the electrodes 21L and 21H to the outside air increases as the area of the portion where the electrodes 21L and 21H become high temperature increases, and the heat radiation efficiency is improved. Become. That is, it is desirable that the electrodes 21L and 21H be close to the light-emitting diode 13 that is a heat source and have a shape that increases the area of the portion that becomes high temperature. As described above, the heat generation amount at the high temperature side electrode is larger than the heat generation amount at the low temperature side electrode of the light emitting diode 13. Therefore, in the vicinity of the light emitting diode 13 of interest, the electrode 21H has a higher temperature. Therefore, the shape of the electrode 21 is changed between the side connected to the low temperature side electrode and the side connected to the high temperature side electrode so that the area of the portion that becomes high temperature is increased because it is connected to the high temperature side electrode. If it is a simple shape, the heat radiation efficiency is improved as compared with a shape that is not so, that is, as shown in FIG. 9, in which the boundary 22 is parallel to the short direction. The shape of the boundary 22 shown in FIG. 7 is an example of the shape of the electrode 21 that improves the heat dissipation efficiency in this way. In this shape, the optimum inclination angle of the boundary 22 may be selected according to the difference in the amount of heat generated from the low temperature side electrode and the high temperature side electrode of the light emitting diode 13.

  The characteristics of the shape of the electrode 21 that improves the heat dissipation efficiency can be described by various expressions. One of such expressions is that the boundary 22 is not parallel to the lateral direction and is inclined toward the electrode 21 </ b> L connected to the low temperature side electrode starting from the light emitting diode 13. In addition, the following may be stated.

  That is, the area of the electrode connected to the low temperature side electrode of the light emitting diode in a circle centered on one light emitting diode and having a diameter from the light emitting diode to another light emitting diode adjacent to the light emitting diode Instead, it may be expressed that the area of the electrode connected to the high temperature side electrode of the light emitting diode is larger. This will be described with reference to FIG. Considering a circle 23 (shown by a broken line in the figure) centered on the light emitting diode 13 and having a distance to an adjacent light emitting diode as a diameter, it is included in the circle 23 and connected to the low temperature side electrode of the light emitting diode 13. The portion 24H (hatched in the figure) of the electrode 21H included in the circle 23 and connected to the high temperature side electrode of the light emitting diode 13 is larger than the area of the portion 24L (shown by hatching in the figure) of the electrode 21L. The area of (shown) is wider.

  Alternatively, the electrode 21 </ b> L and the electrode 21 </ b> H may be expressed as a part of which overlaps each other in the lateral direction. This will be described with reference to FIG. 7. In the illustrated example, a straight line 25 on the low temperature side electrode side of the light emitting diode 13 is considered as a straight line extending in a specific short direction (indicated by a one-dot chain line in the figure). The straight line 25 intersects both the electrode 21L and the electrode 21H.

  In addition, although the example of FIG. 7 shown as this embodiment satisfy | fills all the characteristics mentioned above simultaneously, it is not necessary to satisfy | fill all these characteristics, and any one should just be satisfy | filled.

  In the above description, the light emitting diodes 13 are linearly arranged in a row in the longitudinal direction. However, the present invention is not necessarily limited thereto, and the light emitting diodes 13 may be arranged in a plurality of rows in the longitudinal direction. .

  FIG. 8 is a partially enlarged view of a light emitting diode substrate 7 according to a modification in which the light emitting diodes 13 are arranged in two rows in the longitudinal direction as such an example. Also in this case, as in the previous example, the boundary 22 is at least partially non-parallel to the short direction, and is inclined from the light emitting diode 13 to the electrode 21L connected to the low temperature side electrode. . Further, in a circle 23 having a diameter at a distance from an adjacent light emitting diode with the light emitting diode 13 at the center, the light emitting diode is larger than the area of the portion 24L of the electrode 21L connected to the low temperature side electrode of the light emitting diode 13. The area of the portion 24H of the electrode 21H connected to the 13 high temperature side electrodes is larger. Furthermore, the electrode 21L and the electrode 21H partially overlap each other in the short direction, and the straight line 25 extending in the short direction intersects both the electrode 21L and the electrode 21H.

  The embodiments described above are specific examples given for the purpose of describing the present invention, and the present invention is not limited to these embodiments. For example, in the embodiment, a lens is provided on the front surface of the light emitting diode, but the lens is not necessarily required when light emitted from the light emitting diode element is sufficiently diffused. Further, in the embodiment, the liquid crystal display device is shown as having a configuration in which only one light emitting diode substrate is provided at the center in the short direction of the liquid crystal display device. It is good also as a structure arranged. Furthermore, the number and arrangement of the light emitting diodes shown in the embodiment, and the number, shape, and arrangement of other members are not limited to those shown in the embodiment, and should be optimized as needed.

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 2 Upper frame, 2a Buffer material, 3 Liquid crystal panel, 4 Intermediate frame, 4a Buffer material, 5 Optical sheet group, 6 Reflective sheet, 6a Fixing part, 6b Hole, 6c Fixing hole, 7 Light emitting diode substrate, 8 heat sink, 9 lower frame, 10 backlight unit, 11 speaker, 12 control board, 13 light emitting diode, 14 lens, 15 light beam, 16 control device, 17 liquid crystal panel drive circuit, 17a scanning line drive circuit, 17b video line drive Circuit, 18 backlight drive circuit, 19 fixture, 21, 21L, 21H electrode, 22 boundary, 23 circle, 24L, 24H part, 25 straight line.

Claims (4)

LCD panel,
A reflective sheet that is arranged on the back side of the liquid crystal panel and is curved so that the surface facing the liquid crystal panel is concave;
A light-emitting diode substrate having a light-emitting diode array in which a plurality of light-emitting diodes are arranged along the longitudinal direction, and an electrode connected to the light-emitting diode;
With
The area of the electrode connected to the low temperature side electrode of the light emitting diode in a circle centered on one light emitting diode and having a diameter from the light emitting diode to another light emitting diode adjacent to the light emitting diode A liquid crystal display device in which the area of the electrode connected to the high temperature side electrode of the light emitting diode is larger than that of the light emitting diode.   2. The liquid crystal display device according to claim 1, wherein the low temperature side electrode is an anode of the light emitting diode, and the high temperature side electrode is a cathode of the light emitting diode.   The electrode connected to the low temperature side electrode of the one light emitting diode and the electrode connected to the high temperature side electrode of the light emitting diode partially overlap each other in the lateral direction. Liquid crystal display device.   At least a part of a boundary separating the electrode connected to the low temperature side electrode of the one light emitting diode and the electrode connected to the high temperature side electrode of the light emitting diode is non-parallel to the short side direction, The liquid crystal display device according to claim 1, wherein the liquid crystal display device is inclined toward the electrode connected to the low temperature side electrode with a light emitting diode as a starting point.

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