JP2013047738A - Liquid crystal display device and television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of improving a radiation performance for an LED.SOLUTION: A plurality of LEDs 12 are disposed on a circuit board 11 and aligned in three lines in a second direction X. The circuit board 11 is provided with a plurality of connection plates 14A, 14B each located between two LEDs 12 adjacent to each other in the second direction X and electrically connecting the two LEDs 12. The connection plates 14B provided in a line L2 are larger than the connecting plates 14A provided in two lines L1, L3 respectively disposed in opposite sides of the line L2.

Description

  The present invention relates to a liquid crystal display device including a backlight unit using an LED as a light source and a television receiver including the same, and more particularly to a technique for improving heat dissipation performance for the LED.

  Conventionally, as shown in the following Patent Document 1, a direct type backlight unit using a plurality of LEDs arranged in a grid as a light source has been used.

JP 2007-305341 A

  The structure in which a plurality of LEDs are arranged in a grid pattern as in the conventional backlight unit has a problem that a large number of LEDs are required.

  In view of this, a structure in which LEDs are arranged only in the center of the backlight unit in the vertical direction or the horizontal direction and the light is spread in the vertical direction or the horizontal direction using a reflection sheet is being studied. However, in such a structure, since it is necessary to increase the arrangement density of the LEDs, the temperature of the LEDs tends to increase. In particular, when a plurality of LEDs are arranged in three or four rows at the center in the vertical direction or the horizontal direction, the temperature of the LEDs arranged in the central row sandwiched between the two rows on both sides tends to increase.

  An object of this invention is to provide the liquid crystal display device and television receiver which can improve the thermal radiation performance for LED.

  The liquid crystal display device according to the present invention includes a liquid crystal display panel and a backlight unit. The backlight unit is a circuit board on which a plurality of LEDs that are light sources are mounted, and is arranged to face the liquid crystal display panel. The backlight unit is one of a vertical direction and a horizontal direction of the liquid crystal display panel. A circuit board having a width in the direction smaller than that of the liquid crystal display panel is provided. Further, the backlight unit is two regions located on opposite sides of the circuit board in the first direction, and has a width in the first direction larger than the circuit board. An area where no light source is provided is provided. The plurality of LEDs are arranged in at least three rows in a second direction orthogonal to the first direction. On the circuit board, there are arranged a plurality of connection plates that are located between two LEDs adjacent in the second direction and electrically connect them. The plurality of connection plates arranged in a row between two rows on both sides of the at least three rows are larger than the plurality of connection plates arranged in the two rows on both sides. A television receiver according to the present invention includes the liquid crystal display device.

  According to the present invention, the heat of the LED can be released from the connection plate. In addition, the connection plate arranged in the row between the two rows on both sides is larger than the connection plate arranged in the two rows on both sides. Therefore, the heat of the LEDs arranged in the row between the two rows on both sides can be efficiently released.

  In one aspect of the present invention, the plurality of connection plates arranged in a row between the two rows on both sides are the plurality of connection plates arranged in the two rows on both sides in the width in the first direction. May be larger. According to this aspect, it is not necessary to lower the arrangement density of the LEDs arranged in the central row as compared with the arrangement density of the LEDs arranged in the two rows on both sides. As a result, it becomes easy to increase the luminance of the backlight unit.

  In this aspect, the plurality of connection plates arranged in a row between the two rows on both sides are the plurality of connection plates arranged in the two rows on both sides in the width in the second direction. May be equal. According to this structure, the LED arrangement density in each row is uniform.

  In another aspect of the invention, the positions of the plurality of LEDs in one of the two adjacent columns are offset in the second direction with respect to the positions of the plurality of LEDs in the other column. Also good. According to this aspect, the heat from the LED is easily dispersed.

  In still another aspect of the invention, the backlight unit may further include a reflection sheet for reflecting the light of the plurality of LEDs toward the liquid crystal display panel. The reflective sheet may have a concave shape that opens toward the liquid crystal display panel, and the circuit board may be positioned at the bottom of the reflective sheet. According to this aspect, it becomes easy to spread the heat of the LED over the entire liquid crystal display panel.

  In still another aspect of the present invention, the circuit board may have at least five rows as a row constituted by the plurality of LEDs and the plurality of connection plates. The plurality of connection plates arranged in the at least five rows may be increased according to the distance from the two rows on the both sides of the row in which the connection plates are arranged. According to this aspect, even in a structure having many rows, the heat of the LEDs arranged in the center row can be efficiently released.

  In still another aspect of the present invention, the plurality of connection plates are rectangular. According to this aspect, it becomes easy to ensure the area of the connection plate.

  In the circuit board, the temperature around the LED terminal is particularly high, and the heat spreads concentrically. In still another aspect of the invention, each of the plurality of connection plates includes an edge portion connected to the LED, and each of the plurality of connection plates is stretched in the first direction on the edge portion side. You may have a protrusion to take out. According to this aspect, it is possible to increase the radius of a circle that can be recalled on the connection plate with the terminal of the LED as the center. As a result, the heat of the LED can be released more efficiently.

1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention. It is a front view of the backlight unit with which the said liquid crystal display device is provided. It is a top view of the circuit board with which the said backlight unit is provided. It is a figure which shows roughly the temperature distribution in the C-C 'line | wire shown in FIG. It is a top view which shows the 2nd example of the circuit board based on this invention. It is a top view which shows the 3rd example of the circuit board based on this invention. It is a top view which shows the 4th example of the circuit board based on this invention. It is a top view which shows the 5th example of the circuit board based on this invention. It is a disassembled perspective view of the television receiver which concerns on one Embodiment of this invention. It is a front view which shows the member arrange | positioned back rather than the reflection sheet of the television receiver shown in FIG. It is a side view of the television receiver shown in FIG. It is the schematic which shows the longitudinal cross-section of the television receiver shown in FIG. The light intensity distribution (directional characteristic) of the point light source is shown. It is a figure which shows the measurement result of the intensity | strength of the light which came out of the lens, specifically the illumination intensity of a point light source.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to an embodiment of the present invention. FIG. 2 is a plan view of the backlight unit 10 included in the liquid crystal display device 1.

  In the following description, Y shown in FIG. 2 is the first direction in the claims, and X is the second direction orthogonal to the first direction. In the example described here, the first direction Y is the vertical direction of the liquid crystal display panel 20 described later, and the second direction X is the horizontal direction of the liquid crystal display panel 20. The first direction may be defined as the left-right direction of the liquid crystal display panel 20, and the second direction may be defined as the up-down direction of the liquid crystal display panel 20.

  As shown in FIG. 1, the liquid crystal display device 1 has a liquid crystal display panel 20. The liquid crystal display panel 20 has two glass substrates, and liquid crystal is sealed between them. A TFT (Thin Film Transistor), a source signal line, and a gate signal line are formed on one substrate (TFT substrate), and a color filter is formed on the other substrate. The gate signal line and the source signal line are drawn out of the liquid crystal display panel 20 and connected to the driver IC. A polarizing plate (not shown) is attached to each surface of the glass substrate. A backlight unit 10 for irradiating the liquid crystal display panel 20 with light is disposed on the back side of the liquid crystal display panel 20. A plurality of optical sheets 21 such as a diffusion sheet and a prism sheet are disposed between the liquid crystal display panel 20 and the backlight unit 10.

  The backlight unit 10 includes a circuit board 11 on which a plurality of LEDs (Light Emitting Diodes) 12 as light sources are mounted. As shown in FIG. 2, the circuit board 11 in this example is a board that is elongated in the second direction X, and is arranged at the center of the backlight unit 10 in the first direction Y. The width of the circuit board 11 in the first direction Y is smaller than the width of the liquid crystal display panel 20 in the first direction Y. The backlight unit 10 has areas A and B where no light source is provided. Regions A and B are regions on both sides of the circuit board 11, and are located on opposite sides of the circuit board 11 in the first direction Y. In this example, the area A is an area on the upper side of the circuit board 11, and the area B is an area on the lower side of the circuit board 11. The area A and the area B are larger than the circuit board 11 in the width in the first direction Y.

  As shown in FIG. 1, the backlight unit 10 has a reflection sheet 13 for reflecting the light of the LED 12 toward the liquid crystal display panel 20. The reflection sheet 13 is formed so as to avoid the positions of the plurality of LEDs 12 and is disposed on the circuit board 11. In this example, as shown in FIG. 2, holes are formed in the reflective sheet 13 at the positions of the respective LEDs 12, and the LEDs 12 are respectively disposed inside the holes. The reflective sheet 13 may be formed with a long and narrow hole in the second direction X, and a plurality of LEDs 12 may be disposed inside the hole.

  As shown in FIG. 1, the reflection sheet 13 has a concave shape that opens toward the liquid crystal display panel 20. The circuit board 11 is located at the bottom of the reflection sheet 13. With such a shape of the reflection sheet 13, the light of the plurality of LEDs 12 can be irradiated on the entire surface of the liquid crystal display panel 20. The reflection sheet 13 has a flat surface (hereinafter referred to as a bottom surface) 13e at the bottom (see FIG. 2). The circuit board 11 is disposed on the back side of the bottom surface 13e. A hole in which the plurality of LEDs 12 are arranged is formed in the bottom surface 13e.

  An upper part 13a (part belonging to the above-described area A) and a lower part 13b (part belonging to the above-described area B) of the reflection sheet 13 are spread on the liquid crystal display panel 20 while spreading from the bottom surface 13e in the first direction Y, respectively. It is approaching. In the example shown in FIG. 1, the upper portion 13 a and the lower portion 13 b are curved so as to approach the liquid crystal display panel 20. In this example, as shown in FIG. 2, the right side portion 13c and the left side portion 13d of the reflection sheet 13 also approach the liquid crystal display panel 20 while spreading from the bottom surface 13e. In this example, the right part 13c and the left part 13d are flat slopes. The shape of the reflection sheet 13 is not limited to this. For example, the upper portion 13a and the lower portion 13b may be slopes that are not curved.

  As shown in FIG. 1, a lens 15 is disposed on each LED 12 in this example. The pair of LEDs 12 and the lens 15 constitute one point light source S. The lens 15 is made of, for example, an acrylic resin. The lens 15 has a function of spreading the light of the LED 12 in the first direction Y. That is, the light irradiation angle is expanded in the vertical direction by the lens 15. Therefore, part of the light from the LED 12 is directed toward the upper part 13a and the lower part 13b of the reflection sheet 13, and is reflected toward the liquid crystal display panel 20 by the parts 13a and 13b. As a result, light is applied to a wide range of the liquid crystal display panel 20. As described above, the right portion 13 c and the left portion 13 d of the reflection sheet 13 are inclined toward the liquid crystal display panel 20. The light of the LED 12 toward the right portion 13c and the left portion 13d is reflected toward the liquid crystal display panel 20 by these portions 13c and 13d.

  As shown in FIG. 1, the liquid crystal display device 1 includes a back cabinet 31 that houses a reflection sheet 13 and a circuit board 11. The circuit board 11 is fixed to the back cabinet 31. In this example, a heat radiating plate 32 of a size corresponding to the circuit board 11 is disposed on the back surface of the circuit board 11, and the circuit board 11 is fixed to the back cabinet 31 through the heat radiating plate 32. That is, the circuit board 11 is fixed to the heat sink 32 and the heat sink 32 is fixed to the back cabinet 31. The heat of the circuit board 11 is released through connection plates 14A and 14B, which will be described later, and the heat dissipation plate 32.

  As described above, the circuit board 11 in this example is an elongated board in the second direction X. FIG. 3 is a plan view showing an example of the circuit board 11. In this figure, the lens 15 described above is omitted. The plurality of LEDs 12 are arranged in three rows in the second direction X on the circuit board 11. In this example, the plurality of LEDs 12 are arranged in the second direction X at equal intervals. The arrangement density of the LEDs 12 may change in the second direction X. For example, the interval between two adjacent LEDs 12 may be gradually enlarged as going to the right or left.

  A plurality of connection plates 14 </ b> A and 14 </ b> B are arranged on the circuit board 11. Each of the connection plates 14A and 14B is disposed between two adjacent LEDs 12 in the second direction X and electrically connects them. That is, each LED 12 is disposed across two connection plates 14A or 14B adjacent in the second direction X. One edge of each of the connection plates 14 </ b> A and 14 </ b> B is connected to the cathode of one LED 12 of the two LEDs 12, and the opposite edge is connected to the anode of the other LED 12. With this structure, the plurality of LEDs 12 are connected to each other through the connection plates 14A and 14B. Both the LED 12 and the connection plates 14 </ b> A and 14 </ b> B are disposed on the front surface 11 a of the circuit board 11 facing the liquid crystal display panel 20.

  The connection plates 14A and 14B are made of a metal foil such as copper. The connection plates 14A and 14B are formed so as to have a function of releasing the heat of the LED 12. In the LED, the temperature on the cathode side is generally higher than that on the anode side. Therefore, the connection plates 14A and 14B are used to lower the temperature particularly on the cathode side. In this example, as shown in FIG. 3, the connection plates 14 </ b> A and 14 </ b> B are rectangles larger than the LEDs 12 in plan view.

  Each of the connection plates 14A and 14B is formed in the same process as the process of forming a wiring pattern on a circuit board, for example. That is, the connection plates 14A and 14B are formed on the circuit board 11 by plating the metal foil and then partially removing the metal foil by etching. A metal foil formed separately from the circuit board 11 may be attached to the circuit board 11 as the connection plates 14A and 14B.

  As described above, the circuit board 11 in the example shown in FIG. 3 has a plurality of LEDs 12 arranged in three rows, and three rows L1 parallel to each other as a row constituted by the LEDs 12 and the connection plate 14A or 14B. , L2, L3. The three rows L1, L2, and L3 are arranged in the first direction Y. The columns L1 and L3 are two columns on both sides, that is, two columns on the end side, and the column L2 is a column between them (hereinafter referred to as a central column).

  When the circuit board 11 includes three or more rows, the temperature of the LEDs 12 arranged in the central row L2 tends to be high. Therefore, in the present embodiment, the plurality of connection plates 14B arranged in the row L2 are larger than the connection plates 14A arranged in the two rows L1 and L3 on both sides in the plan view of the circuit board 11. Specifically, the area of the connection plate 14B is larger than the area of the connection plate 14A. In this example, the width Wy2 in the first direction Y of the connection plate 14B is larger than the widths Wy1 and Wy3 in the first direction Y of the connection plate 14A. On the other hand, the width Wx2 in the second direction X of the connection plate 14B is equal to the widths Wx1 and Wx3 in the second direction X of the connection plate 14A. That is, the connection plate 14B has a shape obtained by extending the connection plate 14A in the first direction Y. Therefore, in the interval between two adjacent LEDs in the second direction X, the column L1, the column L2, and the column 3 are equal to each other.

  In the example shown in FIG. 3, the width Wy1 of the connection plate 14A in the row L1 is equal to the width Wy3 of the connection plate 14A in the row L3. However, the width Wy1 of the connection plate 14A in the row L1 and the width Wy3 of the connection plate 14A in the row L3 may be different.

  As shown in FIG. 3, the position of the LED 12 in one of the two adjacent columns is offset in the second direction X with respect to the position of the LED 12 in the other column. Such an arrangement can prevent heat from accumulating around the cathode of each LED 12. In this example, the position of the LED 12 in one row is offset from the position of the LED 12 in the other row by a distance that is half the interval of the LEDs 12. Therefore, the LEDs 12 in the row L2 are located on a straight line passing through the intermediate position between the two LEDs 12 arranged in the rows L1 and L3.

  FIG. 4 is a diagram schematically showing the temperature distribution along the line C-C ′ shown in FIG. 3. In the figure, solid lines T1, T2, and T3 individually indicate temperature distributions due to heat from the LEDs 12 in the row L1, the LEDs 12 in the row L2, and the LEDs 12 in the row L3. The alternate long and short dash line Tt indicates the temperature distribution due to heat from the LEDs 12 in all rows. The line C-C ′ is a line passing through the cathode side of the LED 12.

  As shown by solid lines T1, T2, and T3 in FIG. 4, in the temperature distribution due to heat from the LEDs 12 in each row, the temperatures are highest at the positions P1, P2, and P3 where the LEDs 12 are arranged, and the positions P1, P2, and P3 are the same. The temperature decreases according to the distance from P3. As described above, the width of the connection plate 14B is larger than the width of the connection plate 14A. Therefore, as indicated by a solid line T2, the temperature distribution caused by the heat from the LEDs 12 in the row L2 is generally lower than the temperature distribution caused by the heat from the LEDs 12 in the rows L1 and L3. For this reason, in the temperature distribution due to heat from the LEDs 12 in all the rows indicated by the alternate long and short dash line Tt, it is possible to suppress a particularly high temperature in the vicinity of the position P2 where the LEDs 12 in the row L2 are arranged.

  The number of rows formed by the LEDs 12 and the connection plates 14A and 14B is not limited to three, and the circuit board 11 may have more rows. For example, four rows may be formed on the circuit board 11. In this case, the width in the first direction Y of the connection plate 14B included in the two central rows is larger than the width in the first direction Y of the connection plate 14A included in the two rows on both sides. In this case, the widths in the first direction Y of the connection plates 14B included in the two central rows may be equal to each other. By doing so, the temperatures of the LEDs 12 included in the two central rows are likely to be uniform.

  FIG. 5 is a plan view showing a second example of the circuit board 11. In the following description, points different from the example shown in FIG. 3 will be mainly described, and the other points are the same as in the example of FIG.

  In the example of FIG. 5, the circuit board 11 has five rows L1, L2, L3, L4, and L5 as rows constituted by the LEDs 12 and the connection plates 14A, 14B, and 14C. In FIG. 5, columns L1 and L5 are two columns on both sides, that is, two columns on the end side, and columns L2, L3, and L4 are columns between them.

  The connection plates 14A, 14B, and 14C arranged in the five rows L1, L2, L3, L4, and L5 are increased according to the distance from the two rows L1 and L5 on both sides. That is, the connection plate 14B of the rows L2 and L4 is larger than the connection plate 14A of the rows L1 and L5, and the connection plate 14C of the center row L3 is further larger than the connection plate 14B of the rows L2 and L4. By doing so, it is possible to effectively suppress heat accumulation around the cathodes of the LEDs 12 in the center row L3.

  In this example, the widths Wy2 and Wy4 in the first direction Y of the connection plate 14B are larger than the widths Wy1 and Wy5 in the first direction Y of the connection plate 14A. Further, the width Wy3 in the first direction Y of the connection plate 14C in the center row L3 is larger than the widths Wy2 and Wy4 in the first direction Y of the connection plate 14B. On the other hand, the widths Wx2, Wx3, Wx4 in the second direction X of the connection plates 14B, C are equal to the widths Wx1, Wx5 in the second direction X of the connection plate 14A. That is, also in this example, the connection plates 14B and 14C have a shape obtained by expanding the connection plate 14A in the first direction. Similarly to FIG. 3, the position of the LED 12 in one of the two adjacent columns is offset in the second direction X by a distance that is half the distance between the LEDs 12 with respect to the position of the LED 12 in the other column. doing.

  FIG. 6 is a plan view showing a third example of the circuit board 11. In the following description, points different from the example shown in FIG. 3 will be mainly described, and the other points are the same as in the example of FIG.

  The heat of the LED 12 spreads concentrically from the terminals (ie, cathode and anode). As described above, the temperature on the cathode side is particularly high. Therefore, in the example of FIG. 6, the connection is made so that the radius of the maximum circle (two-dotted line T in FIG. 6) that can be assumed on the connection plate centered on the terminal of the LED 12 is larger than that of the rectangular connection plate. The shape of the board is devised.

  Specifically, the circuit board 11 of FIG. 6 includes a plurality of connection plates 114A and 114B arranged in the second direction X together with the plurality of LEDs 12. Each of the connection plates 114A and 114B has two edge portions 114b located on the opposite sides in the second direction. The cathode and anode of the LED 12 are connected to the edge 114b. Each connection plate 114A, 114B has a protrusion 114a that protrudes in the first direction Y in plan view on the edge 114b side. With such shapes of the connection plates 114A and 114B, it is possible to increase the radius of the maximum circle T that can be assumed on the connection plate with the terminal of the LED 12 as the center. In this example, the connection plates 114 </ b> A and 114 </ b> B have an edge 114 c along the second direction X. Two protrusions 114a are formed on the side opposite to the edge 114c. In this example, the protrusion 114a has a triangular shape in plan view.

  Also in this example, the position of the LED 12 in one of the two adjacent rows is offset in the second direction X by a distance that is half the distance of the LED 12 with respect to the position of the LED 12 in the other row. Yes. The protrusion 114a of the connection plate 114A or 114B in one row and the protrusion 114a of the connection plate 114A or 114B in the other row overlap in the second direction X. In other words, the protrusion 114a of the connection plate 114A or 114B in one row is fitted in a recess formed between the two protrusions 114a of the connection plate 114A or 114B in the other row. With such an arrangement, the expansion of the width of the circuit board 11 in the first direction Y can be suppressed.

  In the example of FIG. 6, the circuit board 11 has four rows L1, L2, L3, and L4 as rows constituted by a plurality of LEDs 12 and a plurality of connection plates 114A and 114B. The two rows L1 and L4 on both sides include a connection plate 114A, and the two rows L2 and L3 in the center include a connection plate 114B. The connection plate 114A and the connection plate 114B are arranged such that their protrusions 114a overlap in the second direction X. Further, the connection plate 114B in the row L2 and the connection plate 114B in the row L3 are arranged such that their edges 114c face each other in the first direction.

  In the example of FIG. 6 as well, as in the example of FIG. 3, the connection plates 114B arranged in the central two rows L2 and L3 have a larger area than the connection plates 114A arranged in the two rows L1 and L4 on both sides. Have. Specifically, the connection plate 114B is larger than the connection plate 114A in the width in the first direction Y. Further, regarding the width in the second direction X, the connection plate 114B is equal to the connection plate 114A. That is, the connection plate 114B has a shape obtained by extending the connection plate 114A in the first direction Y. Therefore, the maximum width WyB and the minimum width in the first direction Y of the connection plate 114B are larger than the maximum width WyA and the minimum width of the connection plate 114A, respectively. In this example, the connection plates 114A and 114B have a protrusion 114a on the edge 114b side. Therefore, the width in the first direction Y of each of the connection plates 114A and 114B is the maximum WyA and WyB at the two edge portions 114b to which the LEDs 12 are connected. Then, their width gradually decreases according to the distance from the edge portion 114b, and is minimum at the center in the second direction X.

  FIG. 7 is a plan view showing a fourth example of the circuit board 11. In the following description, points different from the example shown in FIG. 6 will be mainly described, and the other points are the same as in the example of FIG.

  The circuit board 11 in FIG. 7 includes a connection plate 214A and a connection plate 214B corresponding to the connection plates 114A and 114B, respectively. Each connection plate 214A, 214B has two edges 214b to which the LEDs 12 are connected. Each connection plate 214A, 214B has a protrusion 214a corresponding to the protrusion 114a described above on the edge 214b side. Therefore, also in this example, it is possible to increase the radius of the maximum circle that can be assumed on the connection plate with the terminal of the LED 12 as the center. The protrusion 214a in this example has a trapezoidal shape, and includes an edge 214d along the second direction X and an edge 214e extending obliquely from the edge 214d.

  Also in this example, the position of the LED 12 in one of the two adjacent rows is offset in the second direction X by a distance that is half the distance of the LED 12 with respect to the position of the LED 12 in the other row. Yes. The protrusion 214a of the connection plate 214A or 214B in one row and the protrusion 214a of the connection plate 214A or 214B in the other row overlap in the second direction X. That is, the protrusion 214a is positioned so as to fit into a recess between the two protrusions 214a of the connection plate 214A or 214B in the adjacent row.

  In the example of FIG. 7, the circuit board 11 has four rows L1, L2, L3, and L4. The two rows L1 and L4 on both sides include a connection plate 214A, and the center two rows L2 and L3 include a connection plate 214B. The connection plate 214A in the row L1 and the connection plate 214B in the row L2 are arranged such that their protrusions 214a overlap in the second direction X. Similarly, the connection plate 214B in the row L3 and the connection plate 214A in the row L4 are arranged such that their protrusions 214a overlap in the second direction X. The connection plate 214B in the row L2 and the connection plate 214B in the row L3 are arranged so that their edges 214c face each other.

  Also in the example of FIG. 7, the connection plate 214 </ b> B has a shape in which the connection plate 214 </ b> A is expanded in the first direction Y, similarly to the connection plate 114 </ b> B described above. Therefore, the maximum width and the minimum width in the first direction Y of the connection plate 214B are larger than the maximum width and the minimum width of the connection plate 214A, respectively. Further, in the width in the second direction X, the connection plate 214B is equal to the connection plate 214A.

  FIG. 8 is a plan view showing a fifth example of the circuit board 11. In the following description, points different from the example shown in FIG. 7 will be mainly described, and the other points are the same as in the example of FIG.

  The circuit board 11 in FIG. 8 has a plurality of connection plates 314A and 314B. Each connection plate 314A, 314B has two edge portions 314b, 314f to which the LED 12 is connected. The cathode of the LED 12 is connected to the edge 314b, and the anode of the LED 12 is connected to the edge 314f. Each of the connection plates 314A and 314B has a protrusion 314a corresponding to the protrusion 214a described above only on the edge 314b side. Therefore, in this example, it is possible to further increase the radius of the maximum circle that can be assumed on the connection plate with the cathode terminal of the LED 12 as the center. In addition, the protrusion 314a in this example is also trapezoidal in plan view, like the above-described protrusion 214a.

  Also in this example, the position of the LED 12 in one of the two adjacent rows is offset in the second direction X by a distance that is half the distance of the LED 12 with respect to the position of the LED 12 in the other row. Yes. The protrusion 314a of the connection plate 314A and the protrusion 314a of the connection plate 314B overlap in the second direction X.

  Also in the example of FIG. 8, the circuit board 11 has four rows L1, L2, L3, and L4. The two rows L1 and L4 on both sides include a connection plate 314A, and the center two rows L2 and L3 include a connection plate 314B. The connection plate 314A in the row L1 and the connection plate 314B in the row L2 are arranged such that their protrusions 314a overlap in the second direction X. Similarly, the connection plate 314B in the row L3 and the connection plate 314A in the row L4 are arranged such that their protrusions 314a overlap in the second direction X. The connection plate 314B in the row L2 and the connection plate 314B in the row L3 are arranged so that the edges 314c along the second direction X are close to each other.

  Also in the example of FIG. 8, as in the example of FIG. 3, the connection plates 314 </ b> B arranged in the central two rows L <b> 2 and L <b> 4 are larger than the connection plates 314 </ b> A arranged in the two rows L <b> 1 and L <b> 4 on both sides. It has an area. Specifically, the connection plate 314B has a shape obtained by extending the connection plate 314A in the first direction Y, and the connection plate 314B is larger than the connection plate 214A in the width in the first direction Y. Further, in the width in the second direction X, the connection plate 314B is equal to the connection plate 314A.

  As described above, in the liquid crystal display device 1, the plurality of connection plates 14A, 114A, 214A, and 314A arranged in two rows on both sides of the three or more rows are arranged in two rows on both sides. It is larger than the plurality of connection plates 14B, 14C, 114B, 214B, and 314B disposed in the. Therefore, the heat of the LEDs 12 arranged in the row between the two rows on both sides can be efficiently released. In particular, the connection plates 14A, 114A, 214A, and 314A are larger in width in the first direction Y than the connection plates 14B, 14C, 114B, 214B, and 314B. Therefore, it is not necessary to lower the arrangement density of the LEDs 12 arranged in the center row as compared with the arrangement density of the LEDs 12 arranged in the two rows on both sides. As a result, it becomes easy to increase the luminance of the backlight unit 10.

  In the above description, the first direction Y is the vertical direction of the backlight unit 10, and the second direction X is the horizontal direction of the backlight unit 10. However, the first direction may be defined as the left-right direction of the backlight unit 10, and the second direction may be defined as the up-down direction of the backlight unit 10. In this case, the circuit board 11 is a board that is elongated in the vertical direction, and is disposed at the center in the horizontal direction of the backlight unit 10.

  In the above description, in the second direction X, the plurality of connection plates 14A to 314B have the same width. However, the connection plates 14B, 14C, 114B, 214B, and 314B that constitute one or more rows in the center are the connection plates 14A, 114A, 214A, and 314A that constitute two rows on both sides in the width in the second direction X. May be larger. That is, in the center row, the arrangement density of the LEDs 21 may be lowered as compared with the two rows on both sides.

  In the liquid crystal display device 1, the regions A and B on both sides of the circuit board 11 are larger than the circuit board 11 in the width in the first direction Y. However, the connection plate described above is applied to a liquid crystal display device in which the areas A and B are smaller than the circuit board 11 in the width in the first direction Y, although the circuit board 11 is located in the center of the first direction Y. May be.

  A liquid crystal display device 1 can be incorporated to constitute a television receiver that receives television broadcast radio waves, displays video, and outputs sound. Hereinafter, an example of a television receiver will be described.

  FIG. 9 is an exploded perspective view of a television receiver according to an embodiment of the present invention. FIG. 10 is a front view showing members disposed behind the reflection sheet 13 of the television receiver shown in FIG. FIG. 11 is a side view of the television receiver shown in FIG. 12 is a schematic view showing a longitudinal section of the television receiver shown in FIG.

  The television receiver has a liquid crystal display panel 20 having a horizontally long screen. The aspect ratio of the screen of the television receiver (the ratio between the left and right dimensions and the vertical dimension) is 16: 9. The front side (the image display side) of the liquid crystal display panel 20 is supported by the front frame 41, and the rear side is supported by the mold frame 42. The television receiver has a backlight unit 10 that overlaps the liquid crystal display panel 20.

  The liquid crystal display panel 20, the front frame 41, the mold frame 42, and the backlight unit 10 are accommodated in a cabinet including a front cabinet 33 and a back cabinet 31. The front cabinet 33 is made of resin, and the back cabinet 31 is made of painted iron. The cabinets 31 and 33 are supported by a stand 53 including a pedestal 55 and legs 54. As shown in FIG. 11, switches 57 are arranged on the side surfaces of the cabinets 31 and 33.

  A cover 51 is attached to the rear of the lower portion of the back cabinet 31. A speaker 56 and a circuit board 52 are disposed inside the cover 51. The circuit board 52 includes a tuning circuit (tuner) for selecting radio waves of specific frequencies from radio waves of various frequencies.

  The backlight unit 10 has the reflection sheet 13 as described above. The reflection sheet 13 is arranged so that its concave surface faces the liquid crystal display panel 20. The part except the bottom 13e of the reflection sheet 13 is separated forward from the back cabinet 31 (see FIGS. 1 and 12). The upper portion 13a and the lower portion 13b are positioned so as to sandwich the plurality of LEDs 12. A circuit board 52 is disposed below the space between the reflection sheet 13 and the back cabinet 31 (see FIG. 12).

  The circuit board 11 is located on the opposite side of the liquid crystal display panel 20 with the reflective sheet 13 interposed therebetween, and overlaps the reflective sheet 13. The vertical width of the circuit board 11 is not more than half the vertical length of the liquid crystal display panel 20. As described above, the plurality of LEDs 12 (see FIG. 1) are arranged at the rear of the center of the liquid crystal display panel 20 and are mounted on the circuit board 11. The LEDs 12 are arranged in three rows in the left-right direction and are arranged in a staggered manner.

  The circuit board 11 is fixed to the back cabinet 31. For example, the circuit board 11 is directly fixed to the back cabinet 31. The circuit board 11 is fixed to the back cabinet 31 with screws, for example. Further, as in the example described here, the circuit board 11 may be fixed to the back cabinet 31 through the heat sink 32. For example, the circuit board 11 may be fixed to a metal heat sink 32 such as aluminum with screws, and the heat sink 32 may be fixed to the back cabinet 31.

  The circuit board 11 and the reflection sheet 13 are close to the back cabinet 31. Therefore, it is possible to reduce the thickness of the television receiver. That is, in the conventional backlight structure, the circuit board on which the LED is mounted is fixed to a back frame (not shown) of a liquid crystal display device made of iron or aluminum, and the power source that drives the LED outside the back frame In addition, a timing controller substrate for controlling the gate signal lines and drain signal lines of the liquid crystal display panel is disposed, and a back cabinet is disposed outside the substrate. Therefore, in addition to the distance between the optical sheet of the backlight and the LED, the distance between the back frame and the back cabinet is also required, and the liquid crystal display device is thick. In this embodiment, the circuit board 11 and the heat sink 32 are in contact, and the heat sink 32 and the back cabinet 31 are fixed with screws. Therefore, there is no unnecessary distance other than the distance Zd between the optical sheet 21 and the circuit board 11 (see FIG. 12), and the television receiver is thinned.

  Thinning of the television receiver is also realized by the arrangement of a circuit board 52 having a power circuit, a video circuit, a tuning circuit (tuner), and a timing circuit of the liquid crystal display panel 20. Specifically, since the upper portion 13 a and the lower portion 13 b of the reflection sheet 13 are curved away from the back cabinet 31, a wide space can be obtained between the reflection sheet 13 and the back cabinet 31. In addition, a circuit board 52 having a power circuit, a video circuit, a tuning circuit (tuner), and a timing circuit for the liquid crystal display panel 20 is stored compactly in a lower portion of the television receiver. As a result, there is no need to provide a space for storing a power supply circuit or the like between the circuit board 11 and the back cabinet 31.

  A printed wiring board can be used as the circuit board 11. As described above, the backlight unit 10 has the regions A and B where no light source is provided. The vertical widths of the regions A and B are larger than the vertical width of the circuit board 11. Therefore, as shown in FIG. 10, the vertical dimension YL of the circuit board 11 is １ ／ or less of the vertical dimension YH of the liquid crystal display panel 20.

  As described above, the lens 15 is disposed on each LED 12, and the pair of LEDs 12 and the lens 15 constitute one point light source S (see FIG. 1). The point light source S is mounted on the circuit board 11 and protrudes to the front side of the bottom portion 13e through a hole formed in the bottom portion 13e (see FIG. 2) of the reflection sheet 13. The plurality of point light sources S are arranged in at least three rows in the left-right direction of the screen. The overall vertical width of the plurality of point light sources S is less than or equal to half the vertical length of the liquid crystal display panel 20.

  The point light source S emits light not only in a direction perpendicular to the circuit board 11 but also in other directions. The light intensity of the point light source S is higher in the other direction than the direction perpendicular to the circuit board 11. The lens 15 further spreads the emitted light from the LED 12 in the viewing angle direction compared to the front direction. FIG. 13 shows such a light intensity distribution (directional characteristic) of the point light source S. FIG. 14 is a diagram showing the measurement result of the intensity of light exiting the lens 15, specifically the illuminance of the point light source S. Note that θ is an angle formed by a direction perpendicular to the circuit board 11 and a light emitting direction.

  One of the features of the television receiver described here is that although the vertical dimension YL of the circuit board 11 is as small as 1/3 or less of the vertical dimension YH of the liquid crystal display panel 20, the entire screen is It is bright and has high luminance uniformity throughout the screen.

  A conventional television receiver has a plurality of circuit boards on which a plurality of light emitting diodes are mounted, and the overall size of the plurality of circuit boards matches the size of the liquid crystal display panel. Further, the circuit board and the LEDs mounted on the circuit board are laid out so that the luminance does not change even in the area between the circuit boards. Specifically, a large number of LEDs are used so that the positions of the individual LEDs cannot be recognized optically, and the intervals between the LEDs are set small.

  In the example described here, the distance between the two lenses 15 that are located farthest in the vertical direction is 1/3 or less of the dimension YH of the liquid crystal display panel 20. The LED 12 and the lens 15 are set to dimensions that do not protrude outside the circuit board 11 in order to reduce costs.

  In this example, the distance Y between the dimension YL of the circuit board 11 or the upper edge of the lens 15 in the uppermost row and the lower edge of the lens 15 in the lowermost row is 1 of the dimension YH of the liquid crystal display panel 20. / 3 or less. Thereby, the number of LED12 reduces compared with the past, and cost can be reduced significantly. Further, since the lens 15 and the reflection sheet 13 are used, the liquid crystal display panel 20 that is bright and has a natural luminance distribution can be obtained even if the number of LEDs 12 is reduced.

  In the present embodiment, the entire width of the upper portion 13a and the lower portion 13b of the reflection sheet 13 is set so as to have a width obtained by removing the dimension YL of the circuit board 11 from the dimension YH of the liquid crystal display panel 20. Has been. If the sum of the width of the upper portion 13a and the width of the lower portion 13b is ½ or more of the dimension YH, the luminance distribution of the screen becomes smooth, and the number of LEDs 12 can be greatly reduced, thereby reducing the cost. can do. That is, the cost can be reduced by increasing the reflection region including the upper portion 13a and the lower portion 13b than the region where the point light source S is disposed.

  The light emitted from the LED 12 is spread by the lens 15. The light distribution characteristic of the LED 15 is such that the light intensity in the oblique direction is stronger than the straight front. Since the lens 15 is attached to each of the plurality of LEDs 12, in the space from the circuit board 11 to the optical sheet 21 (see FIG. 1), the intensity of the radiated light traveling in the vertical direction is greater than the radiated light traveling straight forward. ing. Part of the light emitted forward from the lens 15 passes through the optical sheet 21 and is displayed as an image through the liquid crystal display panel 20. The remainder of the light emitted forward is reflected by the optical sheet 21 and the reflection sheet 13 and is also emitted obliquely with respect to the front. Part of the light emitted obliquely in the vertical direction through the lens 15 passes through the outer peripheral portion of the liquid crystal display panel 20 through the optical sheet 21. Further, another part of the light emitted obliquely is reflected by the reflection sheet 13 and travels toward the optical sheet 21.

  As for the luminance performance of the television receiver described here, if the luminance measured at the front is 100%, the luminance at the outer peripheral portion is about 30%. The ratio between the central luminance of the liquid crystal display panel 20 and the average luminance is 1.65. However, since the upper part 13a and the lower part 13b of the reflection sheet 13 are gently curved, the luminance changes gently from the circuit board 11 in the vertical direction. Since there is no point at which the luminance changes abruptly in this way, a high-quality image can be provided. In other words, a smooth luminance distribution can be obtained even when the central luminance and the average luminance are 1.65 or more, which means that the number of LEDs 12 can be reduced and the width of the circuit board 11 can be reduced. In the structure that blocks light radiation to the front of the liquid crystal display panel 20, the center of the liquid crystal display panel 20 becomes dark. Therefore, the light emission characteristic of the point light source S including the individual LEDs 12 and the lens 15 has a predetermined output straight ahead.

  The back cabinet 31 constitutes the outermost surface of the television receiver. The circuit board 11 is fixed to the heat radiating plate 32 with screws, and the heat of the LED 12 is released from the connection plates 14A and 14B (see FIG. 3) and the heat radiating plate 32 of the circuit board 11. When the brightness of the television receiver is low, that is, when the amount of heat emitted from the LED 12 is small, the circuit board 11 may be directly fixed to the back cabinet 31 without using the heat radiating plate 32. In this case, the heat radiation of the LED 12 is performed only by the circuit board 11, but the temperature of the connection portion of the LED 12 can be suppressed by the heat radiation effect of the circuit board 11 itself and the connection plates 14 </ b> A and 14 </ b> B on the circuit board 11.

  Next, a manufacturing process of the television receiver will be described. A wall-mounted metal fitting 34 is attached to the inside of a back cabinet 31 formed by painting a member made of iron. The metal fitting 34 reinforces the strength of the back cabinet 31. A screw hole is formed in the metal fitting 34, and a screw fixed to the wall is caught in this screw hole. After attaching the metal fitting 34, the heat radiating plate 32 is fixed inside the back cabinet 31.

  Next, the circuit board 11 on which the LEDs 12 are mounted is attached to the heat sink 32. A lens 15 is capped on the LED 12 and fixed with an adhesive, for example. When there is a margin in the heat resistance of the connection portion of the LED 12, the circuit board 11 may be directly attached to the back cabinet 31. Here, in order for the surface of the circuit board 11 to easily reflect the light emitted from the LED 12, a white resist is applied on the circuit board 11. Next, the reflection sheet 13 is attached to the circuit board 11. An optical sheet 21 such as a diffusion sheet or a prism sheet having a thickness of 1.5 to 3 mm is disposed further in front of the reflection sheet 13.

  Next, the optical sheet 21 is fixed with a mold frame 42 divided into four parts made of a resin material. The liquid crystal display panel 20 is disposed in front of the optical sheet 21. A front frame 41 made of iron for preventing electromagnetic waves from the driver IC and fixing the liquid crystal display panel 20 is attached to the front side of the liquid crystal display panel 20.

  In order to finally complete the television receiver, a front cabinet 33 made of a resin material is attached to the surface of the front frame 41, and the control circuit, timing control circuit, and video circuit for the LED 12 are mounted under the cabinets 31 and 33. A power supply circuit for supplying power, a connection terminal with the outside, and the like are disposed, and a protective resin cover 51 is attached.

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 10 Backlight unit, 11 Circuit board, 12 LED, 13 Reflection sheet, 14A, 14B, 14C, 114A, 114B, 214A, 214B, 314A, 314B Connection board, 15 Lens, 20 Liquid crystal display panel, L1 , L2, L3, L4, L5 columns, Y first direction, X second direction.

Claims (9)

In a liquid crystal display device comprising a liquid crystal display panel and a backlight unit,
The backlight unit is
A circuit board on which a plurality of LEDs, which are light sources, is mounted, and is disposed so as to face the liquid crystal display panel. A circuit board smaller than the liquid crystal display panel;
Two regions located opposite to each other across the circuit board in the first direction, each having a width in the first direction larger than the circuit board and no light source provided; With
The plurality of LEDs are arranged in at least three rows in a second direction orthogonal to the first direction,
On the circuit board, a plurality of connection plates that are located between two LEDs adjacent in the second direction and electrically connect them are arranged,
The plurality of connection plates arranged in a row between two rows on both sides of the at least three rows are larger than the plurality of connection plates arranged in two rows on both sides,
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1.
The plurality of connection plates arranged in a row between the two rows on both sides are larger in width in the first direction than the plurality of connection plates arranged in the two rows on both sides.
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 2,
The plurality of connection plates arranged in a row between the two rows on both sides are equal to the plurality of connection plates arranged in the two rows on both sides in the width in the second direction.
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1 or 2,
The positions of the plurality of LEDs in one of the two adjacent columns are offset in the second direction with respect to the positions of the plurality of LEDs in the other column.
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1.
A reflection sheet for reflecting the light of the plurality of LEDs toward the liquid crystal display panel;
The reflection sheet is a concave shape that opens toward the liquid crystal display panel, and the circuit board is located at the bottom of the reflection sheet.
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1.
The circuit board has at least five rows as a row composed of the plurality of LEDs and the plurality of connection plates,
The plurality of connection plates arranged in the at least five rows increases in accordance with the distance from the two rows on both sides of the row in which the connection plates are arranged.
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1 or 2,
The plurality of connection plates are rectangular.
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1.
Each of the plurality of connection plates includes an edge connected to the LED;
Each of the plurality of connection plates has a protrusion projecting in the first direction on the edge side.
A liquid crystal display device characterized by the above.   A television receiver comprising the liquid crystal display device according to any one of claims 1 to 8, wherein the television receiver is configured to receive a radio wave of a television broadcast, display an image, and output a sound. .

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