JP2009044099A - Led light source, method of manufacturing led light source, surface light-source device and video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: an LED light source which can be easily manufactured while improving the connection reliability of an LED substrate; a surface light-source device provided with the LED light source; and a video display device. <P>SOLUTION: An LED backlight 2 loaded on the video display device of this invention includes: interdigital LED substrates 21a and 21b which are mutually the same; and a plurality of LEDs 25 are nonlinearly arranged on the respective LED substrates 21a and 21b. When the LED substrate 21a is rotated, the LED substrate 21b is achieved and a plane without a gap is formed by the LED substrate 21a and the LED substrate 21b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an LED light source in which a light emitting element is a light emitting diode (LED), a manufacturing method thereof, a surface light source device including a plurality of the LED light sources, and an image display device including the surface light source device as a backlight light source.

  An image display device including a transmissive liquid crystal display element is widely used for applications such as a monitor for a television or a PC (personal computer). The transmissive liquid crystal display element has a structure in which a liquid crystal layer is sandwiched between two glass plates, and a large number of pixels are formed in a matrix on the glass plate. In order to display an image by such an image display device, first, transistor switches existing in each pixel are driven in accordance with an image signal input from the outside. Thus, the driving changes the alignment direction of the liquid crystal molecules, and the light transmittance of each pixel changes. In this state, when backlight light is emitted from the backlight source disposed on the back side of the liquid crystal display element to the liquid crystal display element, it is possible to display an image according to the input video signal.

  Conventionally, CCFLs (cold cathode fluorescent lamps) have been mainly used as a backlight light source for video display devices. However, in recent years, backlight light sources using light emitting diodes (LEDs) have begun to spread.

  There are two types of LED backlight light irradiation methods: a side edge method and a direct method. The side edge method is a method in which an LED is arranged on the side surface of the screen of the video display device and light is incident on the light guide plate. On the other hand, the direct method is a method in which LEDs are arranged in a matrix (two-dimensional) form immediately below the screen to directly use the emitted light. Since the direct method is easier to increase the luminance than the side edge method, an LED backlight of a direct method is mainly used in a video display device using a large liquid crystal display element.

Such a direct-type LED backlight is configured by a large number of LEDs, which are light sources, arranged in a matrix on the back surface of a liquid crystal panel (matrix-type LED backlight). In a matrix type LED backlight, a printed circuit board having an area substantially the same as the screen size is required as a wiring board (LED board) on which LEDs are mounted. That is, the shape of the LED substrate (printed substrate) in the matrix type LED backlight is a rectangle substantially equal to the screen size. However, when such a matrix type LED backlight is to be applied to a large image display device, the area of the LED substrate needs to be increased in accordance with the screen size. For example, in the liquid crystal television 0.49 m ^2, 57-inch wide type in screen size 42 inch wide liquid crystal television, the printed circuit board of 0.88 m ² things area becomes each required.

  Here, since the price of the printed circuit board is generally proportional to the area, when the matrix type LED backlight is applied to a large-screen liquid crystal display element, the member price becomes very expensive.

  Therefore, Patent Documents 1 and 2 propose an array type LED backlight in which LEDs are arranged in a straight line (array) rather than a matrix type LED backlight in which LEDs are arranged in a matrix (two dimensions). . FIG. 16 is a plan view showing an array type LED backlight.

  In the array type LED backlight 200 of FIG. 16, a plurality of LED substrates 221 are arranged on a chassis 223. FIG. 16 illustrates an array type LED backlight 200 applied to a video display device having a 42-inch wide screen (horizontal 930 mm × vertical 523 mm). Here, in general, the LED substrate 221 has maximum horizontal and vertical outer dimensions at the time of manufacture, that is, a standard size. The standard length varies depending on the material of the LED substrate 221 and the manufacturing apparatus, but is, for example, 510 mm in length and 340 mm in width. For this reason, when any one of the vertical and horizontal dimensions of the LED substrate 221 exceeds the standard size, the LED substrate 221 is manufactured by dividing it into several parts. In order to exceed this standard in the case of FIG. 16, the LED substrate 221 is divided into two in the horizontal direction, and two LED substrates 221 are arranged in the horizontal direction, two in the vertical direction and ten in the vertical direction. On each LED substrate 221, eight LEDs 225 are arranged side by side on the same axis (in a straight line). That is, the array type LED backlight 200 of FIG. 16 uses a total of 160 LEDs 225 for the entire screen. In FIG. 16, the interval between adjacent LEDs 225 is 60 mm, and the LEDs 225 are arranged in a hexagonal lattice as a whole.

  As described above, in the case of a matrix type LED backlight, an LED substrate substantially equal to the screen size (screen area) is required. On the other hand, in the array type LED backlight 200 as shown in FIG. 16, a plurality of LED substrates 221 are arranged with a space (gap) therebetween. For this reason, in the array type LED backlight 200, the total area of all 20 LED substrates is smaller than the screen size. In FIG. 16, since the area of the chassis 223 is substantially equal to the screen size, it can be seen that the total area of the LED substrates is considerably narrower than the screen size.

Thus, in the array type LED backlight 200, the area of the LED substrate 221 is smaller than that of the matrix type LED backlight. Therefore, when the array-type LED backlight 200 is applied to a large-screen video display device, it can be manufactured at a lower cost than when a matrix-type LED backlight is applied. That is, it is possible to reduce the cost of the LED substrate, and hence the cost of the LED backlight. Moreover, if the number of LED boards 21 is increased / decreased according to a screen size, it will become possible to apply the LED board 21 to various screen sizes.
JP 07-226537 A (published August 22, 1995) JP 2006-53340 A (published February 23, 2006) JP 2005-258403 A (published September 22, 2005)

  However, in the array type LED backlight 200 of FIG. 16, there is a problem that an electrical connection failure tends to occur on the LED substrate 221 and the manufacturing process becomes complicated.

  Specifically, as described above, in the array type LED backlight 200, the area of the LED substrate 221 is smaller than that of the matrix type LED backlight. However, in the array type LED backlight 200, the number of LED substrates 221 constituting one array type LED backlight 200 increases. In order to drive the LED 225 mounted on the LED board 221, it is necessary to electrically connect the LED board 221 to a driver board provided outside. For this reason, as the number of LED substrates 221 increases, the number of connection members (connection locations) necessary for driving the LED 225 also increases. Specifically, electrical connection between the LED boards 221 divided in the horizontal direction and electrical connection between one of the LED boards 221 and an external driver board are required. That is, 10 harnesses 222a for connecting the two divided LED boards 221, and 10 harnesses 222b for connecting one LED board 221 to an external driver board, a total of 20 harnesses 222a. -222b is required. Furthermore, it is necessary to install the connector 226 to which the harnesses 222a and 222b are connected to each LED board 221.

  However, when the number of connecting members such as the harnesses 222a and 222b and the connector 226 increases in this way, there arises a problem that problems due to poor connection are likely to occur. In addition, the workability at the time of assembling the LED substrate 221 is remarkably deteriorated, and the manufacturing process becomes very complicated. Note that, as described above, the matrix type LED backlight cannot be manufactured at low cost because the area of the LED substrate becomes large and the member price becomes very expensive.

  Therefore, the present invention has been made in view of the above-mentioned problems, and the purpose thereof is an LED light source, a surface light source device, which can be manufactured easily and inexpensively while improving the connection reliability of the LED substrate, And providing an image display device.

In order to solve the above problems, an LED light source of the present invention is an LED light source that includes three or more light emitting diodes on a wiring board, and current is supplied from the wiring board to the light emitting diodes.
The light emitting diode is non-linearly arranged on the wiring board,
The outer shape of the wiring board is a non-rectangular shape, and when the wiring board is rotated or translated, the wiring board before and after the movement can form a flat surface without a gap. It is said.

  The LED light source of the present invention is mounted on a surface light source device such as an LED backlight.

  A conventional matrix LED backlight is configured by using one or a small number of LED light sources in which a plurality of LEDs are arranged in a matrix on a rectangular wiring board. For this reason, the number of necessary wiring boards is small. However, since a wiring board having the same area as the screen size is required, the area of the wiring board becomes large (wide). For this reason, the manufacturing cost of an LED light source becomes high.

  On the other hand, the conventional array type LED backlight is configured by using a large number of LED light sources in which a plurality of LEDs are linearly arranged on a rectangular wiring board. In the case of the array type, the area of the entire wiring board is smaller (narrower) than that of the matrix type, but much more wiring boards are required than the matrix type. As a result, to each wiring board, for external connection (connection between multiple LED light sources (connection between each wiring board) or connection between LED light source and external circuit (connection between wiring board and external circuit)) The number of connection points increases. For this reason, poor connection is likely to occur, and the manufacturing process becomes complicated.

  On the other hand, in the LED light source of the present invention, the LEDs are arranged non-linearly on a wiring board having a non-rectangular outer shape. That is, the LED light source of the present invention can be applied to an array type LED backlight in which LEDs are linearly arranged on a wiring board, even if the LED light source is applied to a matrix type LED backlight using a rectangular wiring board. It is not an LED light source.

  That is, unlike the LED light source of the conventional matrix type LED backlight, since the wiring board is non-rectangular in the LED light source of the present invention, the area of the wiring board does not increase even when applied to the LED backlight. In addition, unlike the LED light source of the conventional array-type LED backlight, the LED light source of the present invention is arranged in a non-linear manner on the wiring board, so external connection (between a plurality of LED light sources or LED The number of connection points for the light source and the external circuit can be reduced. Therefore, it is possible to reduce the occurrence of problems due to poor connection and simplify the connection work.

  Further, according to the above configuration, when the wiring board is moved, a plane without a gap is formed between the wiring boards before and after the movement when rotated or translated. In other words, the wiring boards before and after the movement are in close contact with each other to form a plane. For example, when considering two boards constituting the LED light source, the two wiring boards can be spread in a two-dimensional plane without any gaps. For this reason, even when a plurality of wiring boards are formed from a single board sheet (flat plate) during the manufacture of the LED light source, the loss of the board sheet is reduced. Therefore, an LED light source can be manufactured at low cost.

  Thus, according to said structure, the LED light source which can be manufactured simply and cheaply can be comprised, improving connection reliability.

  In the LED light source of the present invention, the wiring board may have a comb-like outer shape.

  According to said structure, since the external shape of a wiring board is a comb-tooth type | mold, if a wiring board is rotated and moved and it overlaps, a plane without a clearance gap will be formed. Therefore, an LED light source can be manufactured at low cost.

  In the LED light source of the present invention, the outer shape of the wiring board may be a zigzag shape.

  According to said structure, since the external shape of a wiring board is a zigzag shape, if a wiring board is moved in parallel, a plane without a clearance gap will be formed. Therefore, an LED light source can be manufactured at low cost.

  In the LED light source of the present invention, it is preferable that the plane without the gap is a rectangle. Thereby, even if a plurality of wiring boards are formed from one board sheet (flat plate), the loss of the board sheet is particularly reduced. Therefore, the LED light source can be manufactured at a lower cost.

  In the LED light source of the present invention, it is preferable that the wiring board is made of a glass epoxy board, and the thickness of the wiring board is 0.8 mm or less.

  According to said structure, a wiring board is comprised from a glass epoxy board | substrate with a thickness of 0.8 mm or less. Thereby, the heat which LED emits can be easily transmitted to the back surface of a wiring board. Therefore, an LED light source with high heat dissipation can be configured.

  In the LED light source of the present invention, the LEDs are preferably arranged in a hexagonal lattice shape. According to said structure, since LED is arrange | positioned on the wiring board at the hexagonal lattice form, uniform light irradiation is attained.

In order to solve the above problems, a manufacturing method of an LED light source of the present invention is a manufacturing method of any of the above LED light sources,
Including a dividing step of dividing a single substrate sheet to form a plurality of wiring boards constituting the LED light source;
The dividing step is characterized in that a plurality of wiring boards are assigned to a board sheet so as to form a plane without a gap, and after mounting LEDs on each wiring board, the board is divided into individual wiring boards.

  According to the above method, one substrate sheet is divided by the dividing step to form a wiring substrate for a certain LED light source. That is, in the dividing step, a plurality of wiring boards are allocated on the board sheet so as to form a plane without gaps. Thereby, the loss of a board | substrate sheet at the time of forming a some wiring board from one board | substrate sheet | seat can be reduced. Further, in the dividing step, the LED is mounted on each wiring board assigned to the board sheet, and then divided into individual wiring boards. Thereby, it is not necessary to mount LED for every wiring board, and LED can be mounted collectively. For this reason, mounting processing costs can be reduced. Therefore, an LED light source with high connection reliability can be manufactured easily and inexpensively.

  In the LED light source manufacturing method of the present invention, it is preferable that the dividing step further includes a step of forming a perforation for dividing the substrate sheet into individual wiring boards.

  According to the above method, before the substrate sheet is divided into the individual wiring substrates, the perforation for division is formed on the substrate sheet. Thereby, even a wiring board having a complicated shape can be reliably formed.

  The surface light source device of the present invention is characterized by comprising a plurality of any one of the LED light sources.

  According to said structure, even if it is a surface light source device of a large area, a connection light reliability is high, and the surface light source device which can be manufactured simply and cheaply is realizable. In addition, it is preferable that the same LED light source is mounted in a surface emitting device. Thereby, the surface light source device which can be manufactured more simply and cheaply is realizable.

  In order to solve the above-described problems, the video display device of the present invention is characterized in that any one of the surface light source devices is provided as a backlight of a liquid crystal display element that displays video.

  According to the above configuration, since the surface light source device of the present invention is provided as a backlight, even a large-screen video display device has a high connection reliability and can be manufactured easily and inexpensively. An apparatus can be realized.

  In the video display device of the present invention, it is preferable that a luminance control unit that performs area active luminance control is provided for the surface light source device and the liquid crystal display element.

  According to the above configuration, since the brightness control unit that performs area active brightness control is provided, it is possible to improve contrast and reduce power consumption.

  The LED light source, the surface light source device, and the image display device according to the present invention move when the light emitting diode is non-linearly arranged, the outer shape is non-rectangular, and the wiring board is rotated or translated. The front and rear wiring boards are provided with a wiring board having a shape capable of forming a flat surface without a gap. Therefore, it is possible to construct an LED light source that can be manufactured easily and inexpensively while improving connection reliability.

  Hereinafter, the present invention will be described with reference to FIGS. The video display device of the present invention is equipped with a surface light emitting device including a plurality of LED light sources in which a plurality of LEDs are arranged on an LED substrate as a backlight light source. Hereinafter, as an example of the present invention, a video display device having a screen size of 930 mm wide × 523 mm long (corresponding to a 42-inch wide type) will be described. The screen size is not limited to this. In the following description, the horizontal direction and the vertical direction are appropriately used in accordance with the screen size.

[Embodiment 1]
First, the configuration and basic operation of the video display device of this embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a schematic configuration of the video display device 1 of the present embodiment. As shown in FIG. 2, the video display device 1 includes an LED backlight 2, a video circuit 11, a liquid crystal panel 12, a power supply circuit 13, and a video signal input terminal 14.

  The LED backlight 2 irradiates the liquid crystal panel 12 with backlight light from the back side of the liquid crystal panel 12. A specific configuration of the LED backlight 2 will be described later. The LED backlight 2 can provide a very high response speed, and accordingly, the backlight brightness can be appropriately changed almost instantaneously (several micro to several hundred microseconds or less) in accordance with the change of the image to be displayed. It becomes possible.

  The video circuit 11 is a circuit that processes a video signal input from the outside. In the present embodiment, the video circuit 11 includes a video signal processing unit 15 and an area active luminance control unit 16. The video signal processing unit 15 performs signal conversion processing for displaying an externally input video signal on the liquid crystal panel 12. On the other hand, the area active luminance control unit 16 performs area active luminance control by dividing the light emitting surface of the LED backlight 2 and the display area of the liquid crystal panel 12 into a plurality of control areas, respectively. The area active luminance control unit 16 will be described later.

  The liquid crystal panel 12 is a transmissive liquid crystal display element for displaying an image processed by the video circuit 11. The liquid crystal panel 12 has a structure in which a liquid crystal layer is sandwiched between two glass plates, and a large number of pixels are formed in a matrix on the glass plate. In the present embodiment, there are horizontal 1920 × vertical 1080 = approximately 2.70 million pixels.

  The power supply circuit 13 is connected to an external AC power supply, converts the voltage of the AC power supply into a predetermined DC voltage, and supplies power to each of the LED backlight 2, the video circuit 11, and the liquid crystal panel 12. The video signal input terminal 14 receives a video signal from the outside via an antenna and outputs the video signal to the video circuit 11.

  In such a video display device 1, a video signal input from the outside to the video signal input terminal 14 is converted into a signal format suitable for display on the liquid crystal panel 12 by the video signal processing unit 15 in the video circuit 11. The Then, the converted video signal is sent to the liquid crystal panel 12. Thereby, in the liquid crystal panel 12, the transistor switch which exists in each pixel drives according to a video signal. As a result, the alignment direction of the liquid crystal molecules changes, and the light transmittance of each pixel changes. In this state, the liquid crystal panel 12 is irradiated with backlight from the LED backlight 2 arranged on the back side of the liquid crystal display element, so that an image can be displayed according to the input video signal. . In the video display device 1 of the present embodiment, a still image of one frame composed of information of “horizontal 1920 × vertical 1080 × RGB × 8” bits is updated at a rate of 60 frames per second, and a moving image is displayed on the liquid crystal panel 12. It is carried out.

  Here, the LED backlight 2 which is a characteristic part of the video display device 1 will be described in detail with reference to FIGS. 1 and 3. FIG. 1 is a plan view of the LED backlight 2.

  The LED backlight 2 is a surface light source device including a plurality of LED light sources as light emitting elements. Specifically, the LED backlight 2 includes a plurality of LED substrates 21 in which a plurality of LEDs 25 are arranged in a non-linear manner on a metal chassis 23. In the present embodiment, one LED backlight 2 is composed of four LED substrates 21a and 21b, which are identical to each other, and a total of eight LED substrates 21a and 21b. Note that each of the LED boards 21a and 21b including the plurality of LEDs 25 corresponds to an LED light source. In FIG. 1, for convenience of explanation, the LED substrate 21 is distinguished as an LED substrate 21 a and an LED substrate 21 b having different arrangement directions (arrangement shapes). Hereinafter, when the LED substrates 21a and 21b are not distinguished from each other, the LED substrate 21 may be simply described.

  In the present embodiment, the LED substrate 21 has a comb-shaped outer shape (comb shape). In the present embodiment, the LED substrate 21 has five comb teeth parallel to each other in the vertical direction, and each comb-teeth protruding portion 24a of the LED substrate 21 has a lateral direction (the length direction of the comb teeth). Four LEDs 25 are mounted at equal intervals on the same axis. That is, 20 (25 horizontal x 5 vertical) LEDs 25 are mounted on each LED board 21 at equal intervals. Accordingly, the LED backlight 2 includes a total of 160 (8 × 20) LEDs 25.

  Although the arrangement | positioning shape of LED25 is not specifically limited, As this embodiment, it is preferable that LED25 is arrange | positioned at 60 mm space | interval at the hexagonal lattice form. That is, the LED 25 is arranged at the apex of a virtual regular hexagon formed around a certain LED 25. Note that the LEDs 25 are arranged in a hexagonal lattice pattern regardless of the LED substrates 21 or the entire LED backlight 2. Thereby, the LED backlight 2 can irradiate the liquid crystal panel 12 with uniform backlight light.

  When the LEDs 25 are arranged in a hexagonal lattice, the number of LEDs 25 that are closest to a certain LED 25 is six. On the other hand, in the square lattice arrangement, the number of the closest LEDs to a certain LED is only four in the vertical and horizontal directions. In this case, even if all LEDs are lit at the same luminous intensity, the distance between adjacent LEDs is close in the vertical and horizontal directions, and the relatively distant 45 ° direction is dark, and the LED backlight as a whole is vertically and horizontally latticed. Brightness unevenness is easily perceived. On the other hand, in the hexagonal lattice shape, the number of closest LEDs is large, and the difference in the interval between adjacent LEDs is small, so that the luminance unevenness is less noticeable than in the case of the square lattice arrangement.

  The LEDs 25 mounted on the LED boards 21a and 21b are connected in series with each other by wiring patterns (not shown) formed on the LED boards 21a and 21b.

  External connection connectors 26 are mounted on both ends of each LED substrate 21. Each LED substrate 21 is fixed to the chassis 23 by screws 29 arranged in the vicinity of each connector 26. The LED backlight 2 includes an LED driver mounted on a driver board (drive circuit board) (not shown). The LED backlight 2 supplies current to the LEDs 25 connected in series, and the LEDs 25 are controlled by constant current or PWM (pulse width modulation). To drive. The LED board 21a and the LED board 21b that are adjacent to each other in the vertical direction are electrically connected to each other by a harness 22a connected to the connectors 26 and 26 adjacent to each other. That is, the harness 22a is a connection member for connecting the adjacent LED board 21a and LED board 21b. Further, the connector 26 and the driver board to which the harness 22a in each LED board 21a is not connected are electrically connected to each other by the harness 22b. That is, the harness 22b is a connection member for external connection. As a result, the four units composed of the LED substrates 21a and 21b arranged in the vertical direction are independently driven.

  Here, the feature of the LED backlight 2 is the shape of the LED substrate 21. That is, when attention is paid to one LED substrate 21, the outer shape thereof is a non-rectangular shape, and when the LED substrate 21 is moved, the LED substrate 21 before and after the movement has a shape that can form a flat surface without a gap. ing. For example, in the present embodiment, the LED substrate 21 has a comb-shaped outer shape (comb shape). Specifically, each LED board 21 has five protrusions (comb teeth) 24a parallel to each other, and each protrusion 24a shares a comb root part. Each protrusion 24a extends in the horizontal direction and is spaced apart from each other in the vertical direction. Thus, the LED substrate 21 has a comb-teeth shape and a non-rectangular shape.

  Furthermore, the LED substrate 21a and the LED substrate 21b are the same as each other, and when the LED substrate 21a is rotated by 180 °, the LED substrate 21b is obtained. Here, the width (X) of the protruding portion 24a and the width (Y) of the depressed portion 24b corresponding to the separation distance of the protruding portion 24a are substantially equal to each other. For this reason, when the LED board 21a is moved in parallel toward the adjacent LED board 21b, the comb-shaped protrusions 24a of the LED board 21a correspond to the comb-shaped depressions 24b of the LED board 21b without gaps. Thereby, the plane (here rectangular) without a gap is formed by the LED substrate 21a and the LED substrate 21b before and after the movement. As will be described later, these widths (X and Y) are slightly different from each other by the dividing perforations of the LED substrates 21a and 21b. For this reason, strictly speaking, a slight gap is formed between the LED board 21a and the LED board 21b on a flat surface without a gap, but substantially no gap is formed (closely). Can be considered. That is, the “gap” does not include a gap formed by the perforation for division when the LED substrate 21 is manufactured.

  Thus, in the LED backlight 2, the LEDs 25 are non-linearly arranged on the LED substrate 21 whose outer shape is non-rectangular. Therefore, the LED backlight 2 is different from a matrix type LED backlight in which a rectangular LED substrate is used and an array type LED backlight in which LEDs are linearly arranged on the LED substrate.

  That is, in the LED backlight 2, since the LED substrate 21 is non-rectangular, the area of the LED substrate 21 does not increase as in the case of a matrix LED backlight. In addition, the LED 25 is not linearly arranged on each LED board 21 as in the array type LED backlight. For this reason, the electrical connection location between the LED board 21a and the LED board 21b or between the LED board 21 and the external driver board can be reduced. That is, the number of harnesses 22a and harnesses 22b can be greatly reduced. Specifically, in the present embodiment, there are four harnesses 22a and harnesses 22b. On the other hand, in FIG. 16 (array type LED backlight) described above, there are ten harnesses 222a corresponding to the harness 22a and ten harnesses 222b corresponding to the harness 22b.

  Furthermore, in the present embodiment, the number of connectors 26 to which the harness 22a and the harness 22b are connected can be greatly reduced. Specifically, in this embodiment, the LED backlight 2 is composed of eight LED boards 21, and the total number of connectors 26 provided on each LED board 21 is sixteen. On the other hand, in FIG. 16, the LED backlight 200 is composed of 20 LED boards 221, and the total number of connectors 226 provided on each LED board 21 is 40.

  Thus, by reducing the number of harnesses 22a and 22b and connectors 26, the occurrence of problems due to poor connection can be reduced, and the connection work can be simplified.

  Moreover, when each LED board 21 is moved, planes without gaps are formed by the LED boards 21 before and after the movement. For this reason, as will be described later, a plurality of LED substrates 21 can be efficiently manufactured from one rectangular substrate sheet. In the case of FIG. 1, if the LED substrate 21 a and the LED substrate 21 b are combined, a rectangular shape is obtained, so that the loss of the substrate sheet is particularly small. Therefore, an LED light source can be manufactured at low cost.

  The LED backlight 2 in FIG. 1 has a heat dissipation structure for releasing heat generated by the LED 25 to the outside. FIG. 3 is a diagram for explaining this heat dissipation structure, and shows a longitudinal section of a broken line portion Z of the LED backlight 2 of FIG. As shown in FIG. 3, in the LED backlight 2, a heat dissipation sheet 27 is sandwiched between the chassis 23 and the LED substrate 21. A screw 29 for fixing the LED substrate 21 to the chassis 23 passes through the LED substrate 21, the heat dissipation sheet 27, and the chassis 23.

  The heat dissipating sheet 27 dissipates heat generated by the LED 25. For example, a silicone rubber sheet or a silicone gel sheet (Surcon (registered trademark) of Fuji Polymer Industries Co., Ltd.) is suitable. The heat generated by the LED 25 during the operation of the LED backlight 2 is transmitted from the land 21c formed on the surface of the LED substrate 21 through the through-through hole 28 to the land 21d on the back surface, the heat dissipation sheet 27, and the chassis 23 in this order. It is dissipated from the chassis 23 into the air.

  In the present embodiment, the LED substrate 21a is a glass epoxy substrate. The glass epoxy substrate (FR-4) is a material that has a lower thermal conductivity than a metal or the like and hardly transfers heat. However, the value of thermal resistance varies depending on the cross-sectional shape through which heat is transmitted even with the same thermal conductivity. In particular, in the case of a flat plate shape, the thermal resistance value in the vertical direction is significantly lower than in the horizontal direction. For this reason, the heat | fever which LED25 emits is transmitted to the thickness direction of LED board 21a, and can escape to the chassis 23 efficiently.

  Although the thickness of LED board 21a is not specifically limited, In this embodiment, it is below half (0.8 mm or less) of a standard glass epoxy board (FR-4 (1.6 mm)). Is preferred. In the present embodiment, a glass epoxy substrate having a thickness of 0.6 mm is used as the LED substrate 21, but a sufficient heat dissipation effect is obtained even at this thickness. Thus, a sufficient heat dissipation effect can be obtained while using an inexpensive glass epoxy substrate as the LED substrate 21. Moreover, in the present embodiment, since the heat radiation sheet 27 is provided between the LED substrate 21 and the chassis 23, the heat radiation effect can be further enhanced.

  In addition, although the upper limit of the thickness at the time of comprising the LED board 21 from a glass epoxy board | substrate is preferable to be 0.8 mm, it is so preferable that a minimum is thin. The reason why the upper limit of the thickness is 0.8 mm is as follows. That is, in the LED backlight 2 of the present embodiment, the heat generated by the LED 25 is released to the chassis 23 via the LED board 21a and the heat dissipation sheet 27 on which the LED 25 is mounted. In such a heat dissipation system, the temperature of the LED 25 (LED chip) can be expressed by the following equation (1).

_{T jc -T air = (R jc} -B + R B + R B-air) · P LED ······ (1)
However,
T _jc : LED25 (LED chip) temperature [° C.]
T _air : ambient air temperature [° C.]
R _jc-B : Thermal resistance [K / W] between LED 25 (LED chip) and LED substrate 21
R _B : Thermal resistance [K / W] of the LED substrate 21,
R _B-air : LED board 21-(via chassis 23)-Thermal resistance of ambient air [K / W]
P _LED : Input power to the _LED 25 (= heat generated per unit time) [W]
It is.

In the present embodiment, it has been confirmed by experiments that R _jc-B is about 10 K / W and R _B-air is about 50 K / W. Further, since the LED backlight 2 is sealed inside the video display device 1, T _air may rise to about 60 ° C. Therefore, in order to prevent T _jc from exceeding 130 ° C., which is the absolute maximum rating, when the input power P _LED = 1.0 [W] to the _LED 25, the following formula (2) R _B ≦ (130 −60) /1.0− (10 + 50) = 10 [K / W] (2)
It is necessary to satisfy.

On the other hand, when the thermal resistance value of the glass epoxy substrate (FR-4) at the thickness L = 1.6 [mm] in the configuration similar to the present embodiment was measured, R _B = 13.1 [K / W]. In this case, since the above equation (2) is not satisfied, T _jc may exceed the absolute maximum rating.

Here, the heat transfer path in the LED board 21 may be a path that passes through the lands 21c and 21d and the through hole 28 and a path that passes through the LED board 21 itself. It is considered that the thermal resistance by any of these paths is substantially proportional to the thickness L of the LED substrate 21. Thus, the thermal resistance _{R B} of the LED substrate 21 is the synthetic resistance, when considered proportional to the thickness L of the LED substrate 21, satisfies the above expression (2), to fit within the rating of the chip temperature of LED25 For example, the thickness L of the LED substrate 21 may be 1.2 mm or less. Actually, it is preferable to secure a margin in consideration of heat wrap-around from other components, and therefore, the upper limit value of the thickness L of the LED substrate 21 is preferably 0.8 mm.

  As the LED substrate 21, a metal base substrate such as aluminum can be applied. The metal base substrate is normally used as a high heat dissipation substrate suitable for mounting the high output LED 25. However, it is more expensive than a glass epoxy substrate.

  However, a glass epoxy substrate having a thickness of 1.6 mm is standard and has the lowest price, and the price per unit area (unit price per square meter) tends to increase as the thickness is reduced. On the other hand, a metal base substrate such as aluminum is far superior in heat dissipation than a glass epoxy substrate, but the unit price of the square meter is 5 to 10 times.

  As described above, in the conventional matrix type LED backlight, an LED substrate (wiring board) having an area substantially the same as the screen size is required, and the substrate price is originally higher than that of the array type LED backlight. There is a tendency. For this reason, it is possible to employ an expensive metal base substrate in the array type LED backlight. However, in the matrix type LED backlight, in order to reduce the substrate price as much as possible, it is not only changed to a glass epoxy substrate having a low thermal conductivity, but also the unit price of 1.6 mm is the cheapest. An LED board (wiring board) must be used. In this case, since the heat dissipation of the LED substrate is deteriorated, the light output of the LED cannot be increased, and sufficient luminance cannot be obtained.

  On the other hand, in the LED backlight 2 of the present embodiment, the area of the necessary LED substrate can be suppressed to 0.19 to 0.5 times that of the matrix type LED backlight as described later, and the substrate price can be reduced. . For this reason, it becomes possible to employ a thin glass epoxy substrate having a high unit price per square meter as the substrate area is reduced. That is, in this embodiment, a glass epoxy substrate having a thickness of 0.8 mm or less can be applied as the LED substrate 21 to ensure heat dissipation.

  In order to secure heat dissipation, it is advantageous to use the LED substrate 21 that is as thin as possible. However, if the LED substrate 21 is extremely thin, the unit price of the LED substrate 21 is further increased, which may exceed the cost reduction effect of the configuration of the LED backlight 2 of the present embodiment. For this reason, in order to ensure that the cost reduction effect is not exceeded, in this embodiment, the thickness of the LED substrate 21 is set to 0.6 mm.

  Here, as described above, the video display device 1 of the present embodiment includes the area active luminance control unit 16, and the area active luminance with respect to the light emitting surface of the LED backlight 2 and the display area of the liquid crystal panel 12. Control is possible. The area active luminance control unit 16 controls the light emitting surface of the LED backlight 2 and the display area of the liquid crystal panel 12 by dividing them into several control areas. Thereby, it is possible to improve contrast and reduce power consumption. Here, the procedure of area active luminance control will be described below with reference to FIGS. FIG. 4 is a diagram illustrating an example of a control area in area active luminance control. FIG. 5 is a graph comparing changes in backlight luminance depending on the presence / absence of area active luminance control. FIG. 5A shows a case where area active luminance control is not performed, and FIG. 5B shows area active luminance control. It shows the case of doing.

  As shown in FIG. 4, it is assumed that the LED backlight 2 and the liquid crystal panel 12 are divided into control areas composed of 16 pixels of 2 vertical pixels × 8 horizontal pixels for brightness control. In this case, when a video signal is input, a pixel having the maximum luminance is detected in one control area. The brightness level of the LED backlight corresponding to the control area is increased by increasing the brightness level of a part of the pixel in the control area while increasing the brightness level of the pixel within the range where the pixel exhibits the maximum brightness. Lower. Thereby, the luminance of the output image becomes the same as that of the original image signal. Such control is performed in real time for each frame of the video signal, and the luminance of the LED backlight is appropriately changed according to the video signal.

More specifically, when the area active luminance control is not performed as shown in FIG. 5A, the LED backlight is always lit at the maximum luminance (L _BLmax ) of 100%. In other words, the LED backlight is uniformly lit and displayed on the screen.

On the other hand, when area active luminance control is performed as shown in FIG. 5B, a part of the control area within a range not exceeding 100% (maximum luminance) in the aperture ratio graph of each pixel in the upper stage. Increase the luminance level in the liquid crystal panel. Here, the hatched portion in the graph is the increase in the luminance level of the pixel. Next, as in the graph of the luminance distribution of the LED backlight in the middle stage, in the region where the luminance level of this pixel is increased, the luminance level of the LED backlight is lowered accordingly. Thereby, as shown in the graph, the luminance of the LED backlight has a distribution from the maximum luminance (L _BLmax ) to the minimum luminance (L _BL ). By multiplying each graph of the aperture ratio of each pixel and the luminance distribution of the LED backlight, a graph of the luminance distribution of the actual liquid crystal panel in the lower stage is obtained. As shown in this graph, the luminance distribution of the liquid crystal panel (that is, the luminance of the output image) is the same as when area active luminance control is not performed. That is, if area active luminance control is performed, the luminance of the LED backlight can be reduced without changing the luminance of the output image. For this reason, if area active control is performed, the power consumption of the video display apparatus 1 can be significantly reduced.

  Moreover, when area active brightness control is not performed, the LED backlight is always lit all the time, so when displaying images with a mixture of bright and dark areas on the screen, the contrast decreases due to leakage light. Was. On the other hand, when performing area active brightness control, the brightness level of the backlight can be controlled to be higher in the bright screen area, and the brightness level of the backlight can be set lower in the dark screen area. be able to.

  Such area active luminance control can also be performed with a backlight using a conventional CCFL. However, since the CCFL which is a light source has a long and narrow shape, the control area cannot be divided finely, and the effect is limited. On the other hand, since the LED is a point light source, the control area can be divided relatively finely. Moreover, the LED has an advantage that finer brightness control is easier than the CCFL. Therefore, by adopting the LED backlight 2 in the video display device 1, it is possible to further enhance the effects of reducing power consumption and improving contrast by area active luminance control. Further, in actual area active luminance control, more complex luminance control is required near the boundary between adjacent control areas than the contents described above. A detailed control procedure of area active luminance control is disclosed in Patent Document 3, for example.

  In the area active luminance control, as the number of control areas of the LED backlight 2 and the liquid crystal panel 12 increases, the power consumption reduction and the contrast improvement effect can be enhanced. However, on the other hand, there is a trade-off that if the number of control areas is increased too much, the calculation at the time of control becomes complicated and the scale of the drive circuit becomes large. Therefore, in order to reduce the cost, it is required to increase the effect of area active luminance control as much as possible without increasing the number of control areas (that is, without making the area of the control area too small).

  When the luminance of the pixels existing in one control area greatly fluctuates and the difference between the minimum value and the maximum value increases, there is less room for changing the luminance of the backlight. Therefore, in order to perform effective area active luminance control, it is desirable that the variation in luminance of each pixel in the control area is as small as possible.

  When such area active luminance control is performed, the shape of the control area is not particularly limited, but the control area is preferably close to a square. Thereby, the effect by area active luminance control can be heightened more.

  Here, a case where the area of the control area is the same and the shape is a square is compared with a case where the shape is an elongated rectangle. 6 and 7 are diagrams illustrating control areas of pixels having the same area. 6 shows a square control area of 4 horizontal pixels × 4 vertical pixels = 16 pixels, and FIG. 7 shows a rectangular control area of 16 horizontal pixels × 1 vertical pixel = 16 pixels. Comparing these control areas, when the pixel pitch is P and the average value of the distance between any two pixels in the control area is calculated, it is 2.14P in FIG. 6 and 5.67P in FIG. In a normal video signal, it is considered that the closer the distance between two pixels, the greater the correlation between the luminances of those pixels. Therefore, in the case of the square in FIG. 6, the luminance correlation in the control area is higher and the luminance variation is smaller than in the case of the rectangle in FIG. Therefore, when considering the control area of the same area, the shape of the control area is preferably a shape close to a square rather than a rectangular shape (array shape) that is elongated in either the vertical or horizontal direction.

  In the case of the array type LED backlight 200 as shown in FIG. 16, the LED substrate 221 has an elongated rectangular shape as shown in FIG. That is, the LEDs 225 are linearly arranged on each LED board 221 in accordance with the shape of the LED board 221 and connected to the same driver board. That is, since the rows of LEDs 225 are arranged in a single row (on the same axis), the control area at the time of area active luminance control is an elongated rectangle. Therefore, the effect of area active luminance control is reduced as compared with the case where the control area has a shape close to a square.

  On the other hand, in this embodiment, the LED 25 is non-linearly arranged on the LED substrate 21. For this reason, it is easy to make the control area of each LED board 21 close to a square. Specifically, in the present embodiment, the control area is a rectangle as shown in FIG. 4, and has a shape close to the square of FIG. 6 as compared with the array type LED backlight. Therefore, the effect of area active luminance control can be enhanced.

  In addition, when performing area active brightness control in the conventional matrix type LED backlight, it is possible to make the shape of the control area close to a square as in the LED backlight 2 of the present embodiment. However, in the case of a matrix LED backlight, an LED substrate having the same area as the screen size is required.

  Therefore, it is assumed that the number of LEDs and the LED substrate of the matrix type LED backlight are reduced to be closer to the array type LED backlight. For example, by reducing the number of LEDs of a matrix LED backlight in which m horizontal x n vertical (m and n are integers greater than or equal to 2) LEDs are arranged, the horizontal 1 x vertical n (or horizontal m It is assumed that it is close to an array type backlight device in which LEDs of 1 × vertical) are arranged. Thus, when the matrix type is brought closer to the array type, the area of the LED substrate can be reduced. However, in the case of the array type, the required number of LED substrates is considerably increased compared to the matrix type. For this reason, the connection location of LED boards increases compared with the case of a matrix type.

  As described above, in the matrix type, although there are few connection portions between the LED substrates, the area of the LED substrate is widened. On the other hand, in the array type, although the area of the LED substrate is smaller than that of the matrix type, the number of connection portions between the LED substrates increases. That is, there is a technical problem with both matrix type and array type LED backlights.

  In contrast, in the LED backlight 2 of the present embodiment, as described above, the LEDs 25 are non-linearly arranged on the non-rectangular LED substrates 21a and 21b. Thereby, the connection location of LED board 21a * 21 can also be reduced, reducing the area of an LED board. That is, the technical problems of the matrix type and the array type can be solved all at once. Furthermore, it is possible to enhance the effect of area active luminance control by keeping the shape of the control area at the time of area active luminance control close to a square. Accordingly, the LED backlight 2 is not simply an intermediate configuration between the matrix type and the array type, but has a structure based on a new technical concept that has not been conventionally available.

  In the present embodiment, the area active brightness control unit 16 is provided, but a configuration in which the area active brightness control unit 16 is not provided may be employed. However, it is preferable to provide the area active luminance control unit 16 because an effect of improving contrast and reducing power consumption can be obtained.

  Next, a method for manufacturing the LED backlight 2 will be described. FIG. 8 is a flowchart showing a manufacturing process of the LED backlight 2. FIG. 9 is a plan view showing a substrate sheet for forming the LED substrate 21. As described below, a plurality of LED substrates 21 are formed by dividing one substrate sheet.

  First, in step 1 (S 1), a circuit pattern and a resist are formed on the substrate sheet 30. Specifically, first, as illustrated in FIG. 9, the LED substrate 21 a and the LED substrate 21 b are allocated on the rectangular substrate sheet 30. That is, a large number of LED boards 21 a and 21 b having the same shape are taken on one board sheet 30 (multiple picks). In FIG. 9, four LED boards 21 are allocated from one board sheet 30. The LED substrate 21 is allocated so that a plane without a gap is formed by the plurality of LED substrates 21. Here, the LED substrate 21a and the LED substrate 21b have the same comb-teeth shape, and the LED substrate 21b is obtained by rotating the LED substrate 21a by 180 degrees. For this reason, as shown in FIG. 9, when the LED substrate 21a and the LED substrate 21b are combined, a plane without a gap is formed.

  Thus, circuit pattern formation (formation of the land in which LED25 is mounted, the wiring which connects LED25, etc.) and resist formation are performed with respect to the board | substrate sheet | seat 30 to which LED board 21 was allocated. Pattern formation can be performed by an etching method or the like in the same procedure as that for manufacturing a normal printed wiring board. The land on which the LED is mounted is electrically connected to the pattern of the land 21d formed on the back surface of the LED substrate 21 through a through-through hole 28 (see FIG. 3) provided in the immediate vicinity.

  In addition, the board | substrate sheet | seat 30 is a copper clad laminated board with which copper foil was affixed on the glass epoxy board | substrate (FR-4). The sizes of the substrate sheet 30 and the substrate 30 in FIG. 9 are 330 mm in length, 500 mm in width, and 0.6 mm in thickness.

  Next, in step 2 (S2), after the pattern is formed, a gap between the LED board 21a and the LED board 21 is cut, and a perforation 31 for dividing the board sheet 30 into the individual LED boards 21a and 21b is formed. To do. Then, the LED 25 and the connector 26 are mounted on the assigned LED substrate 21 by reflow soldering on the substrate sheet 30 on which the perforations 31 are formed (mounting process). For example, components such as the LED 25 and the connector 26 are mounted in accordance with the land to which cream solder is applied, and heated in a reflow furnace to melt the cream solder. Thereby, the electrode of each component and the land of LED board 21 are electrically connected mutually. In this way, since the components such as the LED 25 are mounted without cutting the perforation 31, the components can be mounted together.

  Next, in step 3 (S3), the substrate sheet 30 after the mounting process is cut along the perforations 31. In this cutting, a portion where the perforations 31 are connected is cut using a jig such as a Thomson blade. Thereby, the piece LED board 21 is divided | segmented from the board | substrate sheet | seat 30 (division | segmentation process).

  Next, in step 4 (S4), as shown in FIG. 3, after attaching the heat dissipation sheet 27 to the back surface of each LED board 21, the LED board 21 is fixed to the chassis 23 with screws 29 in step 5 (S5). To do. Finally, the connector 26 of each LED board 21 is connected. Thereby, manufacture of LED backlight 2 is completed.

  As described above, in this method, a plurality of LED boards 21 are allocated on the board sheet 30, and after the LEDs 25 are mounted on the LED boards 21, they are divided into individual LED boards 21 a and 21 b. Thereby, it is not necessary to mount LED25 for every LED board 21, and LED25 can be mounted collectively. For this reason, mounting processing costs can be reduced. Therefore, the LED light source and the LED backlight 2 with high connection reliability can be manufactured easily and inexpensively. Further, before the substrate sheet 30 is divided into the individual LED substrates 21, a perforation 31 for division is formed on the substrate sheet 30. Thereby, even if it is the LED substrate 21 of complicated shape like a comb-tooth shape, it can form reliably.

  Further, in this method, when the LED substrate 21a and the LED substrate 21b are combined, a flat surface without a gap is formed. Therefore, in the case of manufacturing a plurality of LED substrates from a large substrate sheet, the number of LED substrates that can be taken out from one substrate sheet can be increased. In the above example, four LED boards 21 can be arranged for one board sheet 30. Therefore, the price of the LED substrate can be reduced.

  As described above, in the present embodiment, the number of LED substrates necessary for one LED backlight is eight, so that two substrate sheets 30 can cover one LED backlight 2. it can. On the other hand, in the case of the conventional matrix type LED backlight, the LED substrate becomes a simple rectangle. In other words, since an LED substrate having the same area as the screen size is required, the number of LED substrates that can be arranged on one substrate sheet is two, and the number of substrates necessary per one LED backlight (eight LED substrates). The number of sheets is four. Further, when an array type LED backlight is used in order to reduce the board price, the LED board is rectangular (array shape), so the number of LED boards that can be arranged on one board sheet is 30, one The required number of substrate sheets per LED backlight (20 LED substrates) is estimated to be 0.67.

  Here, assuming that the price of the LED substrate is proportional to the area, the member price of the comb-shaped LED substrate of the present embodiment is approximately the same as that of the array-shaped LED substrate (in the case of the array-type LED backlight device). When the rectangular LED substrate is used 3 times, it is about 0.5 times that of the matrix type LED backlight device. By adopting the comb-shaped LED substrate, although it does not reach the array-shaped LED substrate, the cost becomes lower than when a rectangular LED substrate is used. However, in the present embodiment, the number of connection points (the number of harnesses 22a and 22b and the number of connectors 26) can be greatly reduced as compared with the array type LED backlight. Therefore, it can be manufactured more easily and cheaply than in the case of an array type LED backlight.

[Embodiment 2]
Next, another embodiment will be described based on FIGS. 10 and 11. In addition, about the same concept as 1st Embodiment, the same symbol is attached | subjected and description is abbreviate | omitted. FIG. 10 is a plan view showing the overall configuration of the LED backlight 4 of the second embodiment.

  As shown in FIG. 10, in this embodiment, the shape of the LED substrate 41 is different from that of the first embodiment. That is, in this embodiment, a wedge-shaped (zigzag-shaped) LED substrate 41 is applied instead of the comb-shaped LED substrate 21 of the first embodiment. Other than that, it is basically the same as the LED backlight 2 of the first embodiment. That is, the LED backlight 4 includes an LED board 41, harnesses 42a and 42b, a chassis 44, a heat dissipation sheet and a driver board (not shown), and the like.

  The LED backlight 4 is composed of ten wedge-shaped LED substrates 41 that are identical to each other, and each LED substrate 41 is arranged in a vertical direction of 5 × 2 in the horizontal direction. A plurality of LEDs 45 are mounted on each LED substrate 41 at equal intervals, and are connected in series by a wiring pattern on the LED substrate 41. Two connectors 46 are mounted on both ends of the LED substrate 41. The LED boards 41 adjacent in the horizontal direction are electrically connected by a harness 42a, and the one LED board 41 and the driver board arranged in the horizontal direction are electrically connected by a harness 42b. Harnesses 42 a and 42 b are each connected to a connector 46. An LED driver is mounted on the driver board, and a current can be passed through the LEDs 45 on the LED boards 41 connected in series to be driven by constant current or PWM (pulse width modulation).

  In the present embodiment, the LED substrate 41 has a zigzag outer shape as shown in FIG. That is, it can be said that the LED substrate 41 has a sawtooth shape or a shape having a predetermined angle and alternately bent and extended. In addition, the LED substrates 41 are arranged to face each other so as to mesh with each other. In addition, LEDs 45 are mounted on each peak and valley of the LED substrate 41, and 16 LEDs 45 are mounted on each LED substrate 41. Similar to the first embodiment, the LEDs 45 are arranged in a hexagonal lattice pattern at intervals of 60 mm, and there are 160 LEDs 45 in total.

  Thus, each LED substrate 41 has a zigzag shape and a non-rectangular shape. In addition, when the plurality of LED substrates 41 are translated and the outer shapes are combined, a plane without a gap is formed, and the two-dimensional plane can be spread without gaps.

  As a result, the total of the harnesses 42a connecting the adjacent LED boards 41 and the harnesses 42b connecting the LED boards 41 and the external driver boards becomes ten. This is significantly reduced from 20 in the case of the array type LED backlight 200 of FIG. Also, the number of connectors 46 is reduced. As described above, in the present embodiment, similarly to the first embodiment, by reducing the number of the harnesses 42a and 42b and the connectors 46, the wiring connection work can be simplified, and the occurrence of problems due to poor connection can be reduced. it can.

  Moreover, when manufacturing LED board | substrates from a large-sized board sheet | seat and manufacturing many surfaces, the number of LED boards which can be taken out from one board | substrate sheet | seat can be increased, and the price of an LED board | substrate can be reduced.

  Further, also in this embodiment, the LED substrate 41 has a shape that is relatively closer to a square than the array-shaped substrate, so that the control area shape at the time of area active luminance control can be made closer to a square. Therefore, more effective area active luminance control can be performed, power consumption of the video display device can be reduced, and contrast can be improved.

  The LED backlight 4 of the present embodiment can be manufactured in the same manner as in the first embodiment. The difference from the first embodiment is only the shape of the LED substrate 41, and the other methods are the same. FIG. 11 is a plan view showing the shape of the substrate sheet before the individual division in the manufacturing process of the LED backlight 4 of FIG.

  As shown in FIG. 11, in manufacturing the LED backlight 4, a large number of LED substrates 41 having the same zigzag shape are arranged on a single substrate sheet 50. The outer shapes of the LED substrates 41 adjacent to each other are separated by perforations 51. Other manufacturing and assembling procedures are the same as those in the first embodiment, and are therefore omitted.

  In the present embodiment, as shown in FIG. 11, 13 LED substrates 41 can be arranged on one substrate sheet 50 (500 mm × 330 mm) having the same size as that of the first embodiment (FIG. 9). Accordingly, the number of substrate sheets required for one LED backlight (10 LED substrates) is 0.77.

  Assuming that the price of the LED substrate 41 is proportional to the area, the member price of the zigzag LED substrate 41 is about 1.2 times that of an array-shaped LED substrate (array-type LED backlight device), and a comb-tooth shape. This is about 0.38 times that of the LED substrate 21 and about 0.19 times that of the rectangular LED substrate (matrix LED backlight device). Therefore, by adopting the zigzag LED substrate 41, the price of the member is more than the rectangular LED substrate or the comb-shaped LED substrate 21 of the first embodiment, although it does not reach the array-shaped LED substrate. Can be made cheaper. However, also in the present embodiment, the number of connection points (the number of harnesses 42a and 42b and the number of connectors 46) can be greatly reduced as compared with the array type LED backlight. Therefore, it can be manufactured more easily and cheaply than in the case of an array type LED backlight.

  In the first embodiment, the comb-shaped LED substrate 21 is used. In the second embodiment, the zigzag LED substrate 41 is used. However, other shapes such as those shown in FIGS. it can. 12 to 15 are plan views showing other shapes of the LED substrate. As shown in each figure, a V-shaped LED board 61 as shown in FIG. 12, an N-shaped (Z-shaped) LED board 71 as shown in FIG. 13, a corrugated LED board 81 as shown in FIG. The LED substrate 91 having a spiral shape (saddle shape) such as 15 may be used. Note that the LED substrates 61 and 71 in FIGS. 12 and 13 are obtained by cutting out a part of the zigzag LED substrate 41 in FIG. 10 (Embodiment 2). Further, it can be said that the LED substrate 81 of FIG. 14 is configured by configuring the zigzag LED substrate 41 of FIG. 10 with a curve. Moreover, it can be said that the LED substrate 91 of FIG. 15 is a modification of the comb-shaped LED substrate 21 of FIG. 1 (Embodiment 1). On these LED substrates 61, 71, 81, 91, LEDs 65, 75, 85, 95 are non-linearly arranged, as in the first and second embodiments. Moreover, when each LED board 61,71,81,91 is combined, the plane without a clearance gap will be formed. Therefore, similarly to the first and second embodiments, a plurality of LED substrates 61, 71, 81, 91 can be manufactured from a single substrate sheet 60, 70, 80, 90, respectively. Therefore, the price of the LED substrate can be reduced.

  In addition, this invention can also be expressed as follows.

  The LED light source of the present invention includes a plurality of LEDs arranged at a predetermined interval, a wiring board that supplies current to the plurality of LEDs, and a connection member for electrically connecting the wiring board and an external circuit. The external shape of the wiring board may be a non-linear shape and a non-rectangular shape, and a shape that can be spread on a two-dimensional flat surface without a gap. According to this, the outer shape of the wiring board, which is a constituent element of the LED light source, is a non-linear shape and a non-rectangular shape, and can be spread in a two-dimensional plane without any gaps, thereby reducing the board area. In addition, the member price can be reduced and the area active luminance control effect can be enhanced because it is easy to make the shape of the control area close to a square at the time of area active luminance control.

  The LED light source of the present invention may have a configuration in which the outer shape of the wiring board is a comb-tooth shape. According to this, since the outer shape of the wiring board is a comb-teeth shape, the area at the time of manufacturing can be reduced by rotating the two wiring boards by rotating 180 degrees and arranging them, thereby reducing the member price. Can be reduced.

  In the LED light source of the present invention, the outer shape of the wiring board may be a zigzag type (wedge type). According to this, since the outer shape of the wiring board is a zigzag type, it is possible to reduce the area at the time of manufacturing by arranging a plurality of wiring boards at close intervals, and to reduce the member price. .

  The LED light source of the present invention may be configured such that a large number of the wiring boards are manufactured on a rectangular wiring board sheet, and are divided into pieces after the LEDs are mounted. According to this, since a large number of wiring boards are manufactured on a rectangular wiring board sheet and are divided into individual pieces after the LEDs are mounted, the LEDs are mounted on each wiring board. There is no need to do it. That is, mounting processing costs can be reduced by mounting LEDs in a lump.

  In the LED light source of the present invention, the outer shape of the wiring board may be formed by dividing perforations provided in advance on the wiring board sheet. According to this, since the outer shape of the wiring board is formed by dividing the perforations provided in advance on the wiring board sheet, the outer shape of a relatively complicated shape such as a comb tooth shape or a zigzag shape can be easily formed. be able to. Moreover, since LED etc. can be mounted in the connected state before dividing a perforation, the workability | operativity at the time of mounting can be improved.

  In the LED light source of the present invention, the wiring board may be a glass epoxy board, and the board thickness may be 0.8 mm or less. According to this, since the wiring board is a glass epoxy board and the board thickness is 0.8 mm or less, the heat generated by the LED can be easily transmitted to the heat dissipation member on the back surface of the wiring board. That is, an LED light source with high heat dissipation can be configured with an inexpensive configuration.

  The surface light source device of the present invention may have a configuration in which any one of the LED light sources described above is mounted. According to this, since the surface light source device is configured by mounting a plurality of any of the above LED light sources, a large area surface light source device can be realized at low cost.

  The image display device of the present invention may be configured to use the surface light source device as a backlight of a liquid crystal display element and display an image on the liquid crystal display element. According to this, since the surface light source device is used as a backlight of the liquid crystal display element to display an image, the contrast is improved by area active luminance control and the power consumption is reduced, and the cost is reduced by reducing the material price. It is possible to achieve both.

  The video display device of the present invention may be configured to perform area active luminance control by dividing the display area of the liquid crystal display element and the light emitting surface of the surface light source device into a plurality of areas, respectively. According to this, since the area active luminance control is performed by dividing the display area of the liquid crystal display element and the light emitting surface of the surface light source device into a plurality of areas, respectively, the contrast of the video display device is improved and the power consumption is reduced. be able to.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  As described above, since the LED light source of the present invention can be manufactured easily and inexpensively while improving connection reliability, it can be used for applications such as liquid crystal televisions and liquid crystal monitors for personal computers (PCs). Can do.

It is a top view which shows the whole structure of the LED backlight of this invention. It is a block diagram which shows schematic structure of the video display apparatus of this invention. It is sectional drawing which shows the thermal radiation structure in the LED backlight of FIG. FIG. 3 is a diagram illustrating a control area that is a control unit of an area active luminance control unit in the video display device of FIG. 2. 3 is a conceptual diagram comparing a video signal and backlight luminance depending on whether or not luminance control is performed by an area active luminance control unit in the video display device of FIG. It is a top view which shows the control area of a shape different from the control area of FIG. It is a top view which shows the control area in the video display apparatus using the conventional array type LED backlight. It is a flowchart which shows the manufacturing process of the LED backlight of FIG. It is a top view which shows the shape of the board | substrate sheet | seat before the piece division | segmentation in the manufacturing process of FIG. It is a top view which shows the whole structure of another LED backlight in this invention. It is a top view which shows the shape of the board | substrate sheet | seat before the piece division | segmentation in the manufacturing process of the LED backlight of FIG. It is a top view which shows another form of the LED board in this invention. It is a top view which shows another form of the LED board in this invention. It is a top view which shows another form of the LED board in this invention. It is a top view which shows another form of the LED board in this invention. It is a top view which shows the conventional array type LED backlight.

Explanation of symbols

1 Video display device 2, 4 LED backlight (surface light source device)
11 Video Circuit 12 Liquid Crystal Panel (Liquid Crystal Display Element)
16 area active brightness controller (brightness controller)
21a, 21b LED board (wiring board)
22a, 22b Harness 25 LED
26 Connector (connection part)
41 LED board (wiring board)
42 Harness 45 LED (LED light source)
46 Connector (connection part)
60, 70, 80, 90 Board sheet 61, 71, 81, 91 LED board 65, 75, 85, 95 LED

  The present invention relates to an LED light source in which a light emitting element is a light emitting diode (LED), a manufacturing method thereof, a surface light source device including a plurality of the LED light sources, and an image display device including the surface light source device as a backlight light source.

  An image display device including a transmissive liquid crystal display element is widely used for applications such as a monitor for a television or a PC (personal computer). The transmissive liquid crystal display element has a structure in which a liquid crystal layer is sandwiched between two glass plates, and a large number of pixels are formed in a matrix on the glass plate. In order to display an image by such an image display device, first, transistor switches existing in each pixel are driven in accordance with an image signal input from the outside. Thus, the driving changes the alignment direction of the liquid crystal molecules, and the light transmittance of each pixel changes. In this state, when backlight light is emitted from the backlight source disposed on the back side of the liquid crystal display element to the liquid crystal display element, it is possible to display an image according to the input video signal.

  Conventionally, CCFLs (cold cathode fluorescent lamps) have been mainly used as a backlight light source for video display devices. However, in recent years, backlight light sources using light emitting diodes (LEDs) have begun to spread.

  There are two types of LED backlight light irradiation methods: a side edge method and a direct method. The side edge method is a method in which an LED is arranged on the side surface of the screen of the video display device and light is incident on the light guide plate. On the other hand, the direct method is a method in which LEDs are arranged in a matrix (two-dimensional) form immediately below the screen to directly use the emitted light. Since the direct method is easier to increase the luminance than the side edge method, an LED backlight of a direct method is mainly used in a video display device using a large liquid crystal display element.

Such a direct-type LED backlight is configured by a large number of LEDs, which are light sources, arranged in a matrix on the back surface of a liquid crystal panel (matrix-type LED backlight). In a matrix type LED backlight, a printed circuit board having an area substantially the same as the screen size is required as a wiring board (LED board) on which LEDs are mounted. That is, the shape of the LED substrate (printed substrate) in the matrix type LED backlight is a rectangle substantially equal to the screen size. However, when such a matrix type LED backlight is to be applied to a large image display device, the area of the LED substrate needs to be increased in accordance with the screen size. For example, in the liquid crystal television 0.49 m ^2, 57-inch wide type in screen size 42 inch wide liquid crystal television, the printed circuit board of 0.88 m ² things area becomes each required.

  Here, since the price of the printed circuit board is generally proportional to the area, when the matrix type LED backlight is applied to a large-screen liquid crystal display element, the member price becomes very expensive.

  Therefore, Patent Documents 1 and 2 propose an array type LED backlight in which LEDs are arranged in a straight line (array) rather than a matrix type LED backlight in which LEDs are arranged in a matrix (two dimensions). . FIG. 16 is a plan view showing an array type LED backlight.

  In the array type LED backlight 200 of FIG. 16, a plurality of LED substrates 221 are arranged on a chassis 223. FIG. 16 illustrates an array type LED backlight 200 applied to a video display device having a 42-inch wide screen (horizontal 930 mm × vertical 523 mm). Here, in general, the LED substrate 221 has maximum horizontal and vertical outer dimensions at the time of manufacture, that is, a standard size. The standard length varies depending on the material of the LED substrate 221 and the manufacturing apparatus, but is, for example, 510 mm in length and 340 mm in width. For this reason, when any one of the vertical and horizontal dimensions of the LED substrate 221 exceeds the standard size, the LED substrate 221 is manufactured by dividing it into several parts. In order to exceed this standard in the case of FIG. 16, the LED substrate 221 is divided into two in the horizontal direction, and two LED substrates 221 are arranged in the horizontal direction, two in the vertical direction and ten in the vertical direction. On each LED substrate 221, eight LEDs 225 are arranged side by side on the same axis (in a straight line). That is, the array type LED backlight 200 of FIG. 16 uses a total of 160 LEDs 225 for the entire screen. In FIG. 16, the interval between adjacent LEDs 225 is 60 mm, and the LEDs 225 are arranged in a hexagonal lattice as a whole.

As described above, in the case of a matrix type LED backlight, an LED substrate substantially equal to the screen size (screen area) is required. On the other hand, in the array type LED backlight 200 as shown in FIG. 16, a plurality of LED substrates 221 are arranged with a space (gap) therebetween. For this reason, in the array-type LED backlight 200, the total area of all 20 LED substrates 221 is smaller than the screen size. In FIG. 16, since the area of the chassis 223 is substantially equal to the screen size, it can be seen that the total area of the LED substrate 221 is considerably narrower than the screen size.

Thus, in the array type LED backlight 200, the total area of the LED substrate 221 is smaller than that of the matrix type LED backlight. Therefore, when the array-type LED backlight 200 is applied to a large-screen video display device, it can be manufactured at a lower cost than when a matrix-type LED backlight is applied. That is, the cost of the LED substrate 221 and the cost of the LED backlight can be reduced. Further, if increasing or decreasing the number of LED substrates 2 21 according to the screen size, the LED substrate 2 21 can be applied to various screen sizes.
JP 07-226537 A (published August 22, 1995) JP 2006-53340 A (published February 23, 2006) JP 2005-258403 A (published September 22, 2005)

  However, in the array type LED backlight 200 of FIG. 16, there is a problem that an electrical connection failure tends to occur on the LED substrate 221 and the manufacturing process becomes complicated.

Specifically, as described above, the array type LED backlight 200 has a smaller total area of the LED substrate 221 than the matrix type LED backlight. However, in the array type LED backlight 200, the number of LED substrates 221 constituting one array type LED backlight 200 increases. In order to drive the LED 225 mounted on the LED board 221, it is necessary to electrically connect the LED board 221 to a driver board provided outside. For this reason, as the number of LED substrates 221 increases, the number of connection members (connection locations) necessary for driving the LED 225 also increases. Specifically, electrical connection between the LED boards 221 divided in the horizontal direction and electrical connection between one of the LED boards 221 and an external driver board are required. That is, 10 harnesses 222a for connecting the two divided LED boards 221, and 10 harnesses 222b for connecting one LED board 221 to an external driver board, a total of 20 harnesses 222a. -222b is required. Furthermore, it is necessary to install the connector 226 to which the harnesses 222a and 222b are connected to each LED board 221.

  However, when the number of connecting members such as the harnesses 222a and 222b and the connector 226 increases in this way, there arises a problem that problems due to poor connection are likely to occur. In addition, the workability at the time of assembling the LED substrate 221 is remarkably deteriorated, and the manufacturing process becomes very complicated. Note that, as described above, the matrix type LED backlight cannot be manufactured at low cost because the area of the LED substrate becomes large and the member price becomes very expensive.

  Therefore, the present invention has been made in view of the above-mentioned problems, and the purpose thereof is an LED light source, a surface light source device, which can be manufactured easily and inexpensively while improving the connection reliability of the LED substrate, And providing an image display device.

In order to solve the above problems, an LED light source of the present invention is an LED light source that includes three or more light-emitting diodes on a wiring board, and current is supplied from the wiring board to the light- emitting diodes. It is characterized by being arranged non-linearly on the wiring board .

Moreover, the LED light source of the present invention is characterized in that the outer shape of the wiring board is non-rectangular.

Further, in the LED light source of the present invention, the outer shape of the wiring board is such that when the wiring board is rotated or translated, the wiring board before and after the movement can form a plane without a gap. It is a feature.

  The LED light source of the present invention is mounted on a surface light source device such as an LED backlight.

  A conventional matrix LED backlight is configured by using one or a small number of LED light sources in which a plurality of LEDs are arranged in a matrix on a rectangular wiring board. For this reason, the number of necessary wiring boards is small. However, since a wiring board having the same area as the screen size is required, the area of the wiring board becomes large (wide). For this reason, the manufacturing cost of an LED light source becomes high.

  On the other hand, the conventional array type LED backlight is configured by using a large number of LED light sources in which a plurality of LEDs are linearly arranged on a rectangular wiring board. In the case of the array type, the area of the entire wiring board is smaller (narrower) than that of the matrix type, but much more wiring boards are required than the matrix type. As a result, to each wiring board, for external connection (connection between multiple LED light sources (connection between each wiring board) or connection between LED light source and external circuit (connection between wiring board and external circuit)) The number of connection points increases. For this reason, poor connection is likely to occur, and the manufacturing process becomes complicated.

  On the other hand, in the LED light source of the present invention, the LEDs are arranged non-linearly on a wiring board having a non-rectangular outer shape. That is, the LED light source of the present invention can be applied to an array type LED backlight in which LEDs are linearly arranged on a wiring board, even if the LED light source is applied to a matrix type LED backlight using a rectangular wiring board. It is not an LED light source.

  That is, unlike the LED light source of the conventional matrix type LED backlight, since the wiring board is non-rectangular in the LED light source of the present invention, the area of the wiring board does not increase even when applied to the LED backlight. In addition, unlike the LED light source of the conventional array-type LED backlight, the LED light source of the present invention is arranged in a non-linear manner on the wiring board, so external connection (between a plurality of LED light sources or LED The number of connection points for the light source and the external circuit can be reduced. Therefore, it is possible to reduce the occurrence of problems due to poor connection and simplify the connection work.

  Further, according to the above configuration, when the wiring board is moved, a plane without a gap is formed between the wiring boards before and after the movement when rotated or translated. In other words, the wiring boards before and after the movement are in close contact with each other to form a plane. For example, when two substrates constituting the LED light source are considered, the two wiring substrates can be spread in a two-dimensional plane without any gap. For this reason, even when a plurality of wiring boards are formed from a single board sheet (flat plate) during the manufacture of the LED light source, the loss of the board sheet is reduced. Therefore, an LED light source can be manufactured at low cost.

  Thus, according to said structure, the LED light source which can be manufactured simply and cheaply can be comprised, improving connection reliability.

  In the LED light source of the present invention, the wiring board may have a comb-like outer shape.

  According to said structure, since the external shape of a wiring board is a comb-tooth type | mold, if a wiring board is rotated and moved and it overlaps, a plane without a clearance gap will be formed. Therefore, an LED light source can be manufactured at low cost.

  In the LED light source of the present invention, the outer shape of the wiring board may be a zigzag shape.

  According to said structure, since the external shape of a wiring board is a zigzag shape, if a wiring board is moved in parallel, a plane without a clearance gap will be formed. Therefore, an LED light source can be manufactured at low cost.

  In the LED light source of the present invention, it is preferable that the plane without the gap is a rectangle. Thereby, even if a plurality of wiring boards are formed from one board sheet (flat plate), the loss of the board sheet is particularly reduced. Therefore, the LED light source can be manufactured at a lower cost.

  In the LED light source of the present invention, it is preferable that the wiring board is made of a glass epoxy board, and the thickness of the wiring board is 0.8 mm or less.

  According to said structure, a wiring board is comprised from a glass epoxy board | substrate with a thickness of 0.8 mm or less. Thereby, the heat which LED emits can be easily transmitted to the back surface of a wiring board. Therefore, an LED light source with high heat dissipation can be configured.

  In the LED light source of the present invention, the LEDs are preferably arranged in a hexagonal lattice shape. According to said structure, since LED is arrange | positioned on the wiring board at the hexagonal lattice form, uniform light irradiation is attained.

In order to solve the above-described problems, the LED light source manufacturing method of the present invention is a method of manufacturing an LED light source that includes three or more light emitting diodes on a wiring board, and current is supplied from the wiring board to the light emitting diodes. And a step of mounting the light emitting diode non-linearly on the wiring board.

Moreover, the manufacturing method of the LED light source of this invention includes the division | segmentation process which divides | segments one board sheet | seat and forms multiple wiring boards which comprise an LED light source, and the said division | segmentation process includes a plurality of wiring boards on a board | substrate sheet | seat. Is assigned so as to form a plane without a gap, and after mounting the LED on each wiring board, it is divided into individual wiring boards.

  According to the above method, one substrate sheet is divided by the dividing step to form a wiring substrate for a certain LED light source. That is, in the dividing step, a plurality of wiring boards are allocated on the board sheet so as to form a plane without gaps. Thereby, the loss of a board | substrate sheet at the time of forming a some wiring board from one board | substrate sheet | seat can be reduced. Further, in the dividing step, the LED is mounted on each wiring board assigned to the board sheet, and then divided into individual wiring boards. Thereby, it is not necessary to mount LED for every wiring board, and LED can be mounted collectively. For this reason, mounting processing costs can be reduced. Therefore, an LED light source with high connection reliability can be manufactured easily and inexpensively.

  In the LED light source manufacturing method of the present invention, it is preferable that the dividing step further includes a step of forming a perforation for dividing the substrate sheet into individual wiring boards.

  According to the above method, before the substrate sheet is divided into the individual wiring substrates, the perforation for division is formed on the substrate sheet. Thereby, even a wiring board having a complicated shape can be reliably formed.

In the manufacturing method of the LED light source of this invention, it is preferable that the external shape of each said wiring board is non-rectangular shape.

The surface light source device of the present invention is characterized by comprising a plurality of any one of the LED light sources. That is, the surface light source device of the present invention is a surface light source device including a plurality of LED light sources, and the LED light source includes three or more light emitting diodes on a wiring board, and current is supplied from the wiring board to the light emitting diodes. The light emitting diode is characterized by being non-linearly arranged on the wiring board.

In the surface light source device of the present invention, the wiring board preferably has a non-rectangular outer shape.

In the surface light source device of the present invention, it is preferable that the outer shape of the wiring board has such a shape that the wiring board before and after the movement can form a flat surface without a gap when the wiring board is rotated or translated. .

  According to said structure, even if it is a surface light source device of a large area, a connection light reliability is high, and the surface light source device which can be manufactured simply and cheaply is realizable. In addition, it is preferable that the same LED light source is mounted in a surface emitting device. Thereby, the surface light source device which can be manufactured more simply and cheaply is realizable.

  In order to solve the above-described problems, the video display device of the present invention is characterized in that any one of the surface light source devices is provided as a backlight of a liquid crystal display element that displays video.

  According to the above configuration, since the surface light source device of the present invention is provided as a backlight, even a large-screen video display device has a high connection reliability and can be manufactured easily and inexpensively. An apparatus can be realized.

  In the video display device of the present invention, it is preferable that a luminance control unit that performs area active luminance control is provided for the surface light source device and the liquid crystal display element.

  According to the above configuration, since the brightness control unit that performs area active brightness control is provided, it is possible to improve contrast and reduce power consumption.

  The LED light source, the surface light source device, and the image display device according to the present invention move when the light emitting diode is non-linearly arranged, the outer shape is non-rectangular, and the wiring board is rotated or translated. The front and rear wiring boards are provided with a wiring board having a shape capable of forming a flat surface without a gap. Therefore, it is possible to construct an LED light source that can be manufactured easily and inexpensively while improving connection reliability.

Hereinafter, the present invention will be described with reference to FIGS. 1-16. The video display device of the present invention is equipped with a surface light emitting device including a plurality of LED light sources in which a plurality of LEDs are arranged on an LED substrate as a backlight light source. Hereinafter, as an example of the present invention, a video display device having a screen size of 930 mm wide × 523 mm long (corresponding to a 42-inch wide type) will be described. The screen size is not limited to this. In the following description, the horizontal direction and the vertical direction are appropriately used in accordance with the screen size.

[Embodiment 1]
First, the configuration and basic operation of the video display device of this embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a schematic configuration of the video display device 1 of the present embodiment. As shown in FIG. 2, the video display device 1 includes an LED backlight 2, a video circuit 11, a liquid crystal panel 12, a power supply circuit 13, and a video signal input terminal 14.

  The LED backlight 2 irradiates the liquid crystal panel 12 with backlight light from the back side of the liquid crystal panel 12. A specific configuration of the LED backlight 2 will be described later. The LED backlight 2 can provide a very high response speed, and accordingly, the backlight brightness can be appropriately changed almost instantaneously (several micro to several hundred microseconds or less) in accordance with the change of the image to be displayed. It becomes possible.

  The video circuit 11 is a circuit that processes a video signal input from the outside. In the present embodiment, the video circuit 11 includes a video signal processing unit 15 and an area active luminance control unit 16. The video signal processing unit 15 performs signal conversion processing for displaying an externally input video signal on the liquid crystal panel 12. On the other hand, the area active luminance control unit 16 performs area active luminance control by dividing the light emitting surface of the LED backlight 2 and the display area of the liquid crystal panel 12 into a plurality of control areas, respectively. The area active luminance control unit 16 will be described later.

  The liquid crystal panel 12 is a transmissive liquid crystal display element for displaying an image processed by the video circuit 11. The liquid crystal panel 12 has a structure in which a liquid crystal layer is sandwiched between two glass plates, and a large number of pixels are formed in a matrix on the glass plate. In the present embodiment, there are horizontal 1920 × vertical 1080 = approximately 2.70 million pixels.

  The power supply circuit 13 is connected to an external AC power supply, converts the voltage of the AC power supply into a predetermined DC voltage, and supplies power to each of the LED backlight 2, the video circuit 11, and the liquid crystal panel 12. The video signal input terminal 14 receives a video signal from the outside via an antenna and outputs the video signal to the video circuit 11.

  In such a video display device 1, a video signal input from the outside to the video signal input terminal 14 is converted into a signal format suitable for display on the liquid crystal panel 12 by the video signal processing unit 15 in the video circuit 11. The Then, the converted video signal is sent to the liquid crystal panel 12. Thereby, in the liquid crystal panel 12, the transistor switch which exists in each pixel drives according to a video signal. As a result, the alignment direction of the liquid crystal molecules changes, and the light transmittance of each pixel changes. In this state, the liquid crystal panel 12 is irradiated with backlight from the LED backlight 2 arranged on the back side of the liquid crystal display element, so that an image can be displayed according to the input video signal. . In the video display device 1 of the present embodiment, a still image of one frame composed of information of “horizontal 1920 × vertical 1080 × RGB × 8” bits is updated at a rate of 60 frames per second, and a moving image is displayed on the liquid crystal panel 12. It is carried out.

  Here, the LED backlight 2 which is a characteristic part of the video display device 1 will be described in detail with reference to FIGS. 1 and 3. FIG. 1 is a plan view of the LED backlight 2.

  The LED backlight 2 is a surface light source device including a plurality of LED light sources as light emitting elements. Specifically, the LED backlight 2 includes a plurality of LED substrates 21 in which a plurality of LEDs 25 are arranged in a non-linear manner on a metal chassis 23. In the present embodiment, one LED backlight 2 is composed of four LED substrates 21a and 21b, which are identical to each other, and a total of eight LED substrates 21a and 21b. Note that each of the LED boards 21a and 21b including the plurality of LEDs 25 corresponds to an LED light source. In FIG. 1, for convenience of explanation, the LED substrate 21 is distinguished as an LED substrate 21 a and an LED substrate 21 b having different arrangement directions (arrangement shapes). Hereinafter, when the LED substrates 21a and 21b are not distinguished from each other, the LED substrate 21 may be simply described.

  In the present embodiment, the LED substrate 21 has a comb-shaped outer shape (comb shape). In the present embodiment, the LED substrate 21 has five comb teeth parallel to each other in the vertical direction, and each comb-teeth protruding portion 24a of the LED substrate 21 has a lateral direction (the length direction of the comb teeth). Four LEDs 25 are mounted at equal intervals on the same axis. That is, 20 (25 horizontal x 5 vertical) LEDs 25 are mounted on each LED board 21 at equal intervals. Accordingly, the LED backlight 2 includes a total of 160 (8 × 20) LEDs 25.

  Although the arrangement | positioning shape of LED25 is not specifically limited, As this embodiment, it is preferable that LED25 is arrange | positioned at 60 mm space | interval at the hexagonal lattice form. That is, the LED 25 is arranged at the apex of a virtual regular hexagon formed around a certain LED 25. Note that the LEDs 25 are arranged in a hexagonal lattice pattern regardless of the LED substrates 21 or the entire LED backlight 2. Thereby, the LED backlight 2 can irradiate the liquid crystal panel 12 with uniform backlight light.

  When the LEDs 25 are arranged in a hexagonal lattice, the number of LEDs 25 that are closest to a certain LED 25 is six. On the other hand, in the square lattice arrangement, the number of the closest LEDs to a certain LED is only four in the vertical and horizontal directions. In this case, even if all the LEDs are lit at the same luminous intensity, the vertical and horizontal directions in which the adjacent LEDs are close to each other are bright and the relatively distant 45 ° direction is dark, and the entire LED backlight is vertically and horizontally latticed. Brightness unevenness is easily perceived. On the other hand, in the hexagonal lattice shape, the number of closest LEDs is large, and the difference in the interval between adjacent LEDs is small, so that the luminance unevenness is less noticeable than in the case of the square lattice arrangement.

  The LEDs 25 mounted on the LED boards 21a and 21b are connected in series with each other by wiring patterns (not shown) formed on the LED boards 21a and 21b.

  External connection connectors 26 are mounted on both ends of each LED substrate 21. Each LED substrate 21 is fixed to the chassis 23 by screws 29 arranged in the vicinity of each connector 26. The LED backlight 2 includes an LED driver mounted on a driver board (drive circuit board) (not shown). The LED backlight 2 supplies current to the LEDs 25 connected in series, and the LEDs 25 are driven by constant current or PWM (pulse width modulation). Drive. The LED board 21a and the LED board 21b that are adjacent to each other in the vertical direction are electrically connected to each other by a harness 22a connected to the connectors 26 and 26 adjacent to each other. That is, the harness 22a is a connection member for connecting the adjacent LED board 21a and LED board 21b. Further, the connector 26 and the driver board to which the harness 22a in each LED board 21a is not connected are electrically connected to each other by the harness 22b. That is, the harness 22b is a connection member for external connection. As a result, the four units composed of the LED substrates 21a and 21b arranged in the vertical direction are independently driven.

  Here, the feature of the LED backlight 2 is the shape of the LED substrate 21. That is, when attention is paid to one LED substrate 21, the outer shape thereof is a non-rectangular shape, and when the LED substrate 21 is moved, the LED substrate 21 before and after the movement has a shape that can form a flat surface without a gap. ing. For example, in the present embodiment, the LED substrate 21 has a comb-shaped outer shape (comb shape). Specifically, each LED board 21 has five protrusions (comb teeth) 24a parallel to each other, and each protrusion 24a shares a comb root part. Each protrusion 24a extends in the horizontal direction and is spaced apart from each other in the vertical direction. Thus, the LED substrate 21 has a comb-teeth shape and a non-rectangular shape.

  Furthermore, the LED substrate 21a and the LED substrate 21b are the same as each other, and when the LED substrate 21a is rotated by 180 °, the LED substrate 21b is obtained. Here, the width (X) of the protruding portion 24a and the width (Y) of the depressed portion 24b corresponding to the separation distance of the protruding portion 24a are substantially equal to each other. For this reason, when the LED board 21a is moved in parallel toward the adjacent LED board 21b, the comb-shaped protrusions 24a of the LED board 21a correspond to the comb-shaped depressions 24b of the LED board 21b without gaps. Thereby, the plane (here rectangular) without a gap is formed by the LED substrate 21a and the LED substrate 21b before and after the movement. As will be described later, these widths (X and Y) are slightly different from each other by the dividing perforations of the LED substrates 21a and 21b. For this reason, strictly speaking, a slight gap is formed between the LED board 21a and the LED board 21b on a flat surface without a gap, but substantially no gap is formed (closely). Can be considered. That is, the “gap” does not include a gap formed by the perforation for division when the LED substrate 21 is manufactured.

  Thus, in the LED backlight 2, the LEDs 25 are non-linearly arranged on the LED substrate 21 whose outer shape is non-rectangular. Therefore, the LED backlight 2 is different from a matrix type LED backlight in which a rectangular LED substrate is used and an array type LED backlight in which LEDs are linearly arranged on the LED substrate.

  That is, in the LED backlight 2, since the LED substrate 21 is non-rectangular, the area of the LED substrate 21 does not increase as in the case of a matrix LED backlight. In addition, the LED 25 is not linearly arranged on each LED board 21 as in the array type LED backlight. For this reason, the electrical connection location between the LED board 21a and the LED board 21b or between the LED board 21 and the external driver board can be reduced. That is, the number of harnesses 22a and harnesses 22b can be greatly reduced. Specifically, in the present embodiment, there are four harnesses 22a and harnesses 22b. On the other hand, in FIG. 16 (array type LED backlight) described above, there are ten harnesses 222a corresponding to the harness 22a and ten harnesses 222b corresponding to the harness 22b.

Furthermore, in the present embodiment, the number of connectors 26 to which the harness 22a and the harness 22b are connected can be greatly reduced. Specifically, in this embodiment, the LED backlight 2 is composed of eight LED boards 21, and the total number of connectors 26 provided on each LED board 21 is sixteen. In contrast, LED backlight 200 in Figure 16 is constituted from twenty LED substrate 221, total connector 226 provided on the LED substrate 2 21 is 40.

  Thus, by reducing the number of harnesses 22a and 22b and connectors 26, the occurrence of problems due to poor connection can be reduced, and the connection work can be simplified.

  Moreover, when each LED board 21 is moved, planes without gaps are formed by the LED boards 21 before and after the movement. For this reason, as will be described later, a plurality of LED substrates 21 can be efficiently manufactured from one rectangular substrate sheet. In the case of FIG. 1, if the LED substrate 21 a and the LED substrate 21 b are combined, a rectangular shape is obtained, so that the loss of the substrate sheet is particularly small. Therefore, an LED light source can be manufactured at low cost.

  The LED backlight 2 in FIG. 1 has a heat dissipation structure for releasing heat generated by the LED 25 to the outside. FIG. 3 is a diagram for explaining this heat dissipation structure, and shows a longitudinal section of a broken line portion Z of the LED backlight 2 of FIG. As shown in FIG. 3, in the LED backlight 2, a heat dissipation sheet 27 is sandwiched between the chassis 23 and the LED substrate 21. A screw 29 for fixing the LED substrate 21 to the chassis 23 passes through the LED substrate 21, the heat dissipation sheet 27, and the chassis 23.

  The heat dissipating sheet 27 dissipates heat generated by the LED 25. For example, a silicone rubber sheet or a silicone gel sheet (Surcon (registered trademark) of Fuji Polymer Industries Co., Ltd.) is suitable. The heat generated by the LED 25 during the operation of the LED backlight 2 is transmitted from the land 21c formed on the surface of the LED substrate 21 through the through-through hole 28 to the land 21d on the back surface, the heat dissipation sheet 27, and the chassis 23 in this order. It is dissipated from the chassis 23 into the air.

  In the present embodiment, the LED substrate 21a is a glass epoxy substrate. The glass epoxy substrate (FR-4) is a material that has a lower thermal conductivity than a metal or the like and hardly transfers heat. However, the value of thermal resistance varies depending on the cross-sectional shape through which heat is transmitted even with the same thermal conductivity. In particular, in the case of a flat plate shape, the thermal resistance value in the vertical direction is significantly lower than in the horizontal direction. For this reason, the heat | fever which LED25 emits is transmitted to the thickness direction of LED board 21a, and can escape to the chassis 23 efficiently.

  Although the thickness of LED board 21a is not specifically limited, In this embodiment, it is below half (0.8 mm or less) of a standard glass epoxy board (FR-4 (1.6 mm)). Is preferred. In the present embodiment, a glass epoxy substrate having a thickness of 0.6 mm is used as the LED substrate 21, but a sufficient heat dissipation effect is obtained even at this thickness. Thus, a sufficient heat dissipation effect can be obtained while using an inexpensive glass epoxy substrate as the LED substrate 21. Moreover, in the present embodiment, since the heat radiation sheet 27 is provided between the LED substrate 21 and the chassis 23, the heat radiation effect can be further enhanced.

  In addition, although the upper limit of the thickness at the time of comprising the LED board 21 from a glass epoxy board | substrate is preferable to be 0.8 mm, it is so preferable that a minimum is thin. The reason why the upper limit of the thickness is 0.8 mm is as follows. That is, in the LED backlight 2 of the present embodiment, the heat generated by the LED 25 is released to the chassis 23 via the LED board 21a and the heat dissipation sheet 27 on which the LED 25 is mounted. In such a heat dissipation system, the temperature of the LED 25 (LED chip) can be expressed by the following equation (1).

_{T jc -T air = (R jc} -B + R B + R B-air) · P LED ······ (1)
However,
T _jc : LED25 (LED chip) temperature [° C.]
T _air : ambient air temperature [° C.]
R _jc-B : Thermal resistance [K / W] between LED 25 (LED chip) and LED substrate 21
R _B : Thermal resistance [K / W] of the LED substrate 21,
R _B-air : LED board 21-(via chassis 23)-Thermal resistance of ambient air [K / W]
P _LED : Input power to the _LED 25 (= heat generated per unit time) [W]
It is.

In the present embodiment, it has been confirmed by experiments that R _jc-B is about 10 K / W and R _B-air is about 50 K / W. Further, since the LED backlight 2 is sealed inside the video display device 1, T _air may rise to about 60 ° C. Therefore, in order to prevent T _jc from exceeding 130 ° C., which is the absolute maximum rating, when the input power P _LED = 1.0 [W] to the _LED 25, the following formula (2) R _B ≦ (130 −60) /1.0− (10 + 50) = 10 [K / W] (2)
It is necessary to satisfy.

On the other hand, when the thermal resistance value of the glass epoxy substrate (FR-4) at the thickness L = 1.6 [mm] in the configuration similar to the present embodiment was measured, R _B = 13.1 [K / W]. In this case, since the above equation (2) is not satisfied, T _jc may exceed the absolute maximum rating.

Here, the heat transfer path in the LED board 21 may be a path that passes through the lands 21c and 21d and the through hole 28 and a path that passes through the LED board 21 itself. It is considered that the thermal resistance by any of these paths is substantially proportional to the thickness L of the LED substrate 21. Thus, the thermal resistance _{R B} of the LED substrate 21 is the synthetic resistance, when considered proportional to the thickness L of the LED substrate 21, satisfies the above expression (2), to fit within the rating of the chip temperature of LED25 For example, the thickness L of the LED substrate 21 may be 1.2 mm or less. Actually, it is preferable to secure a margin in consideration of heat wrap-around from other components, and therefore, the upper limit value of the thickness L of the LED substrate 21 is preferably 0.8 mm.

  As the LED substrate 21, a metal base substrate such as aluminum can be applied. The metal base substrate is normally used as a high heat dissipation substrate suitable for mounting the high output LED 25. However, it is more expensive than a glass epoxy substrate.

  However, a glass epoxy substrate having a thickness of 1.6 mm is standard and has the lowest price, and the price per unit area (unit price per square meter) tends to increase as the thickness is reduced. On the other hand, a metal base substrate such as aluminum is far superior in heat dissipation than a glass epoxy substrate, but the unit price of the square meter is 5 to 10 times.

  As described above, in the conventional matrix type LED backlight, an LED substrate (wiring board) having an area substantially the same as the screen size is required, and the substrate price is originally higher than that of the array type LED backlight. There is a tendency. For this reason, it is possible to employ an expensive metal base substrate in the array type LED backlight. However, in the matrix type LED backlight, in order to reduce the substrate price as much as possible, it is not only changed to a glass epoxy substrate having a low thermal conductivity, but also the unit price of 1.6 mm is the cheapest. An LED board (wiring board) must be used. In this case, since the heat dissipation of the LED substrate is deteriorated, the light output of the LED cannot be increased, and sufficient luminance cannot be obtained.

  On the other hand, in the LED backlight 2 of the present embodiment, the area of the necessary LED substrate can be suppressed to 0.19 to 0.5 times that of the matrix type LED backlight as described later, and the substrate price can be reduced. . For this reason, it becomes possible to employ a thin glass epoxy substrate having a high unit price per square meter as the substrate area is reduced. That is, in this embodiment, a glass epoxy substrate having a thickness of 0.8 mm or less can be applied as the LED substrate 21 to ensure heat dissipation.

  In order to secure heat dissipation, it is advantageous to use the LED substrate 21 that is as thin as possible. However, if the LED substrate 21 is extremely thin, the unit price of the LED substrate 21 is further increased, which may exceed the cost reduction effect of the configuration of the LED backlight 2 of the present embodiment. For this reason, in order to ensure that the cost reduction effect is not exceeded, in this embodiment, the thickness of the LED substrate 21 is set to 0.6 mm.

  Here, as described above, the video display device 1 of the present embodiment includes the area active luminance control unit 16, and the area active luminance with respect to the light emitting surface of the LED backlight 2 and the display area of the liquid crystal panel 12. Control is possible. The area active luminance control unit 16 controls the light emitting surface of the LED backlight 2 and the display area of the liquid crystal panel 12 by dividing them into several control areas. Thereby, it is possible to improve contrast and reduce power consumption. Here, the procedure of area active luminance control will be described below with reference to FIGS. FIG. 4 is a diagram illustrating an example of a control area in area active luminance control. FIG. 5 is a graph comparing changes in backlight luminance depending on the presence / absence of area active luminance control. FIG. 5A shows a case where area active luminance control is not performed, and FIG. 5B shows area active luminance control. It shows the case of doing.

  As shown in FIG. 4, it is assumed that the LED backlight 2 and the liquid crystal panel 12 are divided into control areas composed of 16 pixels of 2 vertical pixels × 8 horizontal pixels for brightness control. In this case, when a video signal is input, a pixel having the maximum luminance is detected in one control area. The brightness level of the LED backlight corresponding to the control area is increased by increasing the brightness level of a part of the pixel in the control area while increasing the brightness level of the pixel within the range where the pixel exhibits the maximum brightness. Lower. Thereby, the luminance of the output image becomes the same as that of the original image signal. Such control is performed in real time for each frame of the video signal, and the luminance of the LED backlight is appropriately changed according to the video signal.

More specifically, when the area active luminance control is not performed as shown in FIG. 5A, the LED backlight is always lit at the maximum luminance (L _BLmax ) of 100%. In other words, the LED backlight is uniformly lit and displayed on the screen.

On the other hand, when area active luminance control is performed as shown in FIG. 5B, a part of the control area within a range not exceeding 100% (maximum luminance) in the aperture ratio graph of each pixel in the upper stage. Increase the luminance level in the liquid crystal panel. Here, the hatched portion in the graph is the increase in the luminance level of the pixel. Next, as in the graph of the luminance distribution of the LED backlight in the middle stage, in the region where the luminance level of this pixel is increased, the luminance level of the LED backlight is lowered accordingly. Thereby, as shown in the graph, the luminance of the LED backlight has a distribution from the maximum luminance (L _BLmax ) to the minimum luminance (L _BL ). By multiplying each graph of the aperture ratio of each pixel and the luminance distribution of the LED backlight, a graph of the luminance distribution of the actual liquid crystal panel in the lower stage is obtained. As shown in this graph, the luminance distribution of the liquid crystal panel (that is, the luminance of the output image) is the same as when area active luminance control is not performed. That is, if area active luminance control is performed, the luminance of the LED backlight can be reduced without changing the luminance of the output image. For this reason, if area active control is performed, the power consumption of the video display apparatus 1 can be significantly reduced.

  Moreover, when area active brightness control is not performed, the LED backlight is always lit all the time, so when displaying images with a mixture of bright and dark areas on the screen, the contrast decreases due to leakage light. Was. On the other hand, when performing area active brightness control, the brightness level of the backlight can be controlled to be higher in the bright screen area, and the brightness level of the backlight can be set lower in the dark screen area. be able to.

  Such area active luminance control can also be performed with a backlight using a conventional CCFL. However, since the CCFL which is a light source has a long and narrow shape, the control area cannot be divided finely, and the effect is limited. On the other hand, since the LED is a point light source, the control area can be divided relatively finely. Moreover, the LED has an advantage that finer brightness control is easier than the CCFL. Therefore, by adopting the LED backlight 2 in the video display device 1, it is possible to further enhance the effects of reducing power consumption and improving contrast by area active luminance control. Further, in actual area active luminance control, more complex luminance control is required near the boundary between adjacent control areas than the contents described above. A detailed control procedure of area active luminance control is disclosed in Patent Document 3, for example.

  In the area active luminance control, as the number of control areas of the LED backlight 2 and the liquid crystal panel 12 increases, the power consumption reduction and the contrast improvement effect can be enhanced. However, on the other hand, there is a trade-off that if the number of control areas is increased too much, the calculation at the time of control becomes complicated and the scale of the drive circuit becomes large. Therefore, in order to reduce the cost, it is required to increase the effect of area active luminance control as much as possible without increasing the number of control areas (that is, without making the area of the control area too small).

  When the luminance of the pixels existing in one control area greatly fluctuates and the difference between the minimum value and the maximum value increases, there is less room for changing the luminance of the backlight. Therefore, in order to perform effective area active luminance control, it is desirable that the variation in luminance of each pixel in the control area is as small as possible.

  When such area active luminance control is performed, the shape of the control area is not particularly limited, but the control area is preferably close to a square. Thereby, the effect by area active luminance control can be heightened more.

  Here, a case where the area of the control area is the same and the shape is a square is compared with a case where the shape is an elongated rectangle. 6 and 7 are diagrams illustrating control areas of pixels having the same area. 6 shows a square control area of 4 horizontal pixels × 4 vertical pixels = 16 pixels, and FIG. 7 shows a rectangular control area of 16 horizontal pixels × 1 vertical pixel = 16 pixels. Comparing these control areas, when the pixel pitch is P and the average value of the distance between any two pixels in the control area is calculated, it is 2.14P in FIG. 6 and 5.67P in FIG. In a normal video signal, it is considered that the closer the distance between two pixels, the greater the correlation between the luminances of those pixels. Therefore, in the case of the square in FIG. 6, the luminance correlation in the control area is higher and the luminance variation is smaller than in the case of the rectangle in FIG. Therefore, when considering the control area of the same area, the shape of the control area is preferably a shape close to a square rather than a rectangular shape (array shape) that is elongated in either the vertical or horizontal direction.

  In the case of the array type LED backlight 200 as shown in FIG. 16, the LED substrate 221 has an elongated rectangular shape as shown in FIG. That is, the LEDs 225 are linearly arranged on each LED board 221 in accordance with the shape of the LED board 221 and connected to the same driver board. That is, since the rows of LEDs 225 are arranged in a single row (on the same axis), the control area at the time of area active luminance control is an elongated rectangle. Therefore, the effect of area active luminance control is reduced as compared with the case where the control area has a shape close to a square.

  On the other hand, in this embodiment, the LED 25 is non-linearly arranged on the LED substrate 21. For this reason, it is easy to make the control area of each LED board 21 close to a square. Specifically, in the present embodiment, the control area is a rectangle as shown in FIG. 4, and has a shape close to the square of FIG. 6 as compared with the array type LED backlight. Therefore, the effect of area active luminance control can be enhanced.

  In addition, when performing area active brightness control in the conventional matrix type LED backlight, it is possible to make the shape of the control area close to a square as in the LED backlight 2 of the present embodiment. However, in the case of a matrix LED backlight, an LED substrate having the same area as the screen size is required.

  Therefore, it is assumed that the number of LEDs and the LED substrate of the matrix type LED backlight are reduced to be closer to the array type LED backlight. For example, by reducing the number of LEDs of a matrix LED backlight in which m horizontal x n vertical (m and n are integers greater than or equal to 2) LEDs are arranged, the horizontal 1 x vertical n (or horizontal m It is assumed that it is close to an array type backlight device in which LEDs of 1 × vertical) are arranged. Thus, when the matrix type is brought closer to the array type, the area of the LED substrate can be reduced. However, in the case of the array type, the required number of LED substrates is considerably increased compared to the matrix type. For this reason, the connection location of LED boards increases compared with the case of a matrix type.

  As described above, in the matrix type, although there are few connection portions between the LED substrates, the area of the LED substrate is widened. On the other hand, in the array type, although the area of the LED substrate is smaller than that of the matrix type, the number of connection portions between the LED substrates increases. That is, there is a technical problem with both matrix type and array type LED backlights.

  In contrast, in the LED backlight 2 of the present embodiment, as described above, the LEDs 25 are non-linearly arranged on the non-rectangular LED substrates 21a and 21b. Thereby, the connection location of LED board 21a * 21 can also be reduced, reducing the area of an LED board. That is, the technical problems of the matrix type and the array type can be solved all at once. Furthermore, it is possible to enhance the effect of area active luminance control by keeping the shape of the control area at the time of area active luminance control close to a square. Accordingly, the LED backlight 2 is not simply an intermediate configuration between the matrix type and the array type, but has a structure based on a new technical concept that has not been conventionally available.

  In the present embodiment, the area active brightness control unit 16 is provided, but a configuration in which the area active brightness control unit 16 is not provided may be employed. However, it is preferable to provide the area active luminance control unit 16 because an effect of improving contrast and reducing power consumption can be obtained.

  Next, a method for manufacturing the LED backlight 2 will be described. FIG. 8 is a flowchart showing a manufacturing process of the LED backlight 2. FIG. 9 is a plan view showing a substrate sheet for forming the LED substrate 21. As described below, a plurality of LED substrates 21 are formed by dividing one substrate sheet.

  First, in step 1 (S 1), a circuit pattern and a resist are formed on the substrate sheet 30. Specifically, first, as illustrated in FIG. 9, the LED substrate 21 a and the LED substrate 21 b are allocated on the rectangular substrate sheet 30. That is, a large number of LED boards 21 a and 21 b having the same shape are taken on one board sheet 30 (multiple picks). In FIG. 9, four LED boards 21 are allocated from one board sheet 30. The LED substrate 21 is allocated so that a plane without a gap is formed by the plurality of LED substrates 21. Here, the LED substrate 21a and the LED substrate 21b have the same comb-teeth shape, and the LED substrate 21b is obtained by rotating the LED substrate 21a by 180 degrees. For this reason, as shown in FIG. 9, when the LED substrate 21a and the LED substrate 21b are combined, a plane without a gap is formed.

  Thus, circuit pattern formation (formation of the land in which LED25 is mounted, the wiring which connects LED25, etc.) and resist formation are performed with respect to the board | substrate sheet | seat 30 to which LED board 21 was allocated. Pattern formation can be performed by an etching method or the like in the same procedure as that for manufacturing a normal printed wiring board. The land on which the LED is mounted is electrically connected to the pattern of the land 21d formed on the back surface of the LED substrate 21 through a through-through hole 28 (see FIG. 3) provided in the immediate vicinity.

  In addition, the board | substrate sheet | seat 30 is a copper clad laminated board with which copper foil was affixed on the glass epoxy board | substrate (FR-4). The sizes of the substrate sheet 30 and the substrate 30 in FIG. 9 are 330 mm in length, 500 mm in width, and 0.6 mm in thickness.

  Next, in step 2 (S2), after the pattern is formed, a gap between the LED board 21a and the LED board 21 is cut, and a perforation 31 for dividing the board sheet 30 into the individual LED boards 21a and 21b is formed. To do. Then, the LED 25 and the connector 26 are mounted on the assigned LED substrate 21 by reflow soldering on the substrate sheet 30 on which the perforations 31 are formed (mounting process). For example, components such as the LED 25 and the connector 26 are mounted in accordance with the land to which cream solder is applied, and heated in a reflow furnace to melt the cream solder. Thereby, the electrode of each component and the land of LED board 21 are electrically connected mutually. In this way, since the components such as the LED 25 are mounted without cutting the perforation 31, the components can be mounted together.

  Next, in step 3 (S3), the substrate sheet 30 after the mounting process is cut along the perforations 31. In this cutting, a portion where the perforations 31 are connected is cut using a jig such as a Thomson blade. Thereby, the piece LED board 21 is divided | segmented from the board | substrate sheet | seat 30 (division | segmentation process).

  Next, in step 4 (S4), as shown in FIG. 3, after attaching the heat dissipation sheet 27 to the back surface of each LED board 21, the LED board 21 is fixed to the chassis 23 with screws 29 in step 5 (S5). To do. Finally, the connector 26 of each LED board 21 is connected. Thereby, manufacture of LED backlight 2 is completed.

  As described above, in this method, a plurality of LED boards 21 are allocated on the board sheet 30, and after the LEDs 25 are mounted on the LED boards 21, they are divided into individual LED boards 21 a and 21 b. Thereby, it is not necessary to mount LED25 for every LED board 21, and LED25 can be mounted collectively. For this reason, mounting processing costs can be reduced. Therefore, the LED light source and the LED backlight 2 with high connection reliability can be manufactured easily and inexpensively. Further, before the substrate sheet 30 is divided into the individual LED substrates 21, a perforation 31 for division is formed on the substrate sheet 30. Thereby, even if it is the LED substrate 21 of complicated shape like a comb-tooth shape, it can form reliably.

  Further, in this method, when the LED substrate 21a and the LED substrate 21b are combined, a flat surface without a gap is formed. Therefore, in the case of manufacturing a plurality of LED substrates from a large substrate sheet, the number of LED substrates that can be taken out from one substrate sheet can be increased. In the above example, four LED boards 21 can be arranged for one board sheet 30. Therefore, the price of the LED substrate can be reduced.

  As described above, in the present embodiment, the number of LED substrates necessary for one LED backlight is eight, so that two substrate sheets 30 can cover one LED backlight 2. it can. On the other hand, in the case of the conventional matrix type LED backlight, the LED substrate becomes a simple rectangle. In other words, since an LED substrate having the same area as the screen size is required, the number of LED substrates that can be arranged on one substrate sheet is two, and the number of substrates necessary per one LED backlight (eight LED substrates). The number of sheets is four. Further, when an array type LED backlight is used in order to reduce the board price, the LED board is rectangular (array shape), so the number of LED boards that can be arranged on one board sheet is 30, one The required number of substrate sheets per LED backlight (20 LED substrates) is estimated to be 0.67.

  Here, assuming that the price of the LED substrate is proportional to the area, the member price of the comb-shaped LED substrate of the present embodiment is approximately the same as that of the array-shaped LED substrate (in the case of the array-type LED backlight device). When the rectangular LED substrate is used 3 times, it is about 0.5 times that of the matrix type LED backlight device. By adopting the comb-shaped LED substrate, although it does not reach the array-shaped LED substrate, the cost becomes lower than when a rectangular LED substrate is used. However, in the present embodiment, the number of connection points (the number of harnesses 22a and 22b and the number of connectors 26) can be greatly reduced as compared with the array type LED backlight. Therefore, it can be manufactured more easily and cheaply than in the case of an array type LED backlight.

[Embodiment 2]
Next, another embodiment will be described based on FIGS. 10 and 11. In addition, about the same concept as 1st Embodiment, the same symbol is attached | subjected and description is abbreviate | omitted. FIG. 10 is a plan view showing the overall configuration of the LED backlight 4 of the second embodiment.

  As shown in FIG. 10, in this embodiment, the shape of the LED substrate 41 is different from that of the first embodiment. That is, in this embodiment, a wedge-shaped (zigzag-shaped) LED substrate 41 is applied instead of the comb-shaped LED substrate 21 of the first embodiment. Other than that, it is basically the same as the LED backlight 2 of the first embodiment. That is, the LED backlight 4 includes an LED board 41, harnesses 42a and 42b, a chassis 44, a heat dissipation sheet and a driver board (not shown), and the like.

  The LED backlight 4 is composed of ten wedge-shaped LED substrates 41 that are identical to each other, and each LED substrate 41 is arranged in a vertical direction of 5 × 2 in the horizontal direction. A plurality of LEDs 45 are mounted on each LED substrate 41 at equal intervals, and are connected in series by a wiring pattern on the LED substrate 41. Two connectors 46 are mounted on both ends of the LED substrate 41. The LED boards 41 adjacent in the horizontal direction are electrically connected by a harness 42a, and the one LED board 41 and the driver board arranged in the horizontal direction are electrically connected by a harness 42b. Harnesses 42 a and 42 b are each connected to a connector 46. An LED driver is mounted on the driver board, and a current can be passed through the LEDs 45 on the LED boards 41 connected in series to be driven by constant current or PWM (pulse width modulation).

  In the present embodiment, the LED substrate 41 has a zigzag outer shape as shown in FIG. That is, it can be said that the LED substrate 41 has a sawtooth shape or a shape having a predetermined angle and alternately bent and extended. In addition, the LED substrates 41 are arranged to face each other so as to mesh with each other. In addition, LEDs 45 are mounted on each peak and valley of the LED substrate 41, and 16 LEDs 45 are mounted on each LED substrate 41. Similar to the first embodiment, the LEDs 45 are arranged in a hexagonal lattice pattern at intervals of 60 mm, and there are 160 LEDs 45 in total.

  Thus, each LED substrate 41 has a zigzag shape and a non-rectangular shape. In addition, when the plurality of LED substrates 41 are translated and the outer shapes are combined, a plane without a gap is formed, and the two-dimensional plane can be spread without gaps.

  As a result, the total of the harnesses 42a connecting the adjacent LED boards 41 and the harnesses 42b connecting the LED boards 41 and the external driver boards becomes ten. This is significantly reduced from 20 in the case of the array type LED backlight 200 of FIG. Also, the number of connectors 46 is reduced. As described above, in the present embodiment, similarly to the first embodiment, by reducing the number of the harnesses 42a and 42b and the connectors 46, the wiring connection work can be simplified, and the occurrence of problems due to poor connection can be reduced. it can.

  Moreover, when manufacturing LED board | substrates from a large-sized board sheet | seat and manufacturing many surfaces, the number of LED boards which can be taken out from one board | substrate sheet | seat can be increased, and the price of an LED board | substrate can be reduced.

  Further, also in this embodiment, the LED substrate 41 has a shape that is relatively closer to a square than the array-shaped substrate, so that the control area shape at the time of area active luminance control can be made closer to a square. Therefore, more effective area active luminance control can be performed, power consumption of the video display device can be reduced, and contrast can be improved.

  The LED backlight 4 of the present embodiment can be manufactured in the same manner as in the first embodiment. The difference from the first embodiment is only the shape of the LED substrate 41, and the other methods are the same. FIG. 11 is a plan view showing the shape of the substrate sheet before the individual division in the manufacturing process of the LED backlight 4 of FIG.

  As shown in FIG. 11, in manufacturing the LED backlight 4, a large number of LED substrates 41 having the same zigzag shape are arranged on a single substrate sheet 50. The outer shapes of the LED substrates 41 adjacent to each other are separated by perforations 51. Other manufacturing and assembling procedures are the same as those in the first embodiment, and are therefore omitted.

  In the present embodiment, as shown in FIG. 11, 13 LED substrates 41 can be arranged on one substrate sheet 50 (500 mm × 330 mm) having the same size as that of the first embodiment (FIG. 9). Accordingly, the number of substrate sheets required for one LED backlight (10 LED substrates) is 0.77.

  Assuming that the price of the LED substrate 41 is proportional to the area, the member price of the zigzag LED substrate 41 is about 1.2 times that of an array-shaped LED substrate (array-type LED backlight device), and a comb-tooth shape. This is about 0.38 times that of the LED substrate 21 and about 0.19 times that of the rectangular LED substrate (matrix LED backlight device). Therefore, by adopting the zigzag LED substrate 41, the price of the member is more than the rectangular LED substrate or the comb-shaped LED substrate 21 of the first embodiment, although it does not reach the array-shaped LED substrate. Can be made cheaper. However, also in the present embodiment, the number of connection points (the number of harnesses 42a and 42b and the number of connectors 46) can be greatly reduced as compared with the array type LED backlight. Therefore, it can be manufactured more easily and cheaply than in the case of an array type LED backlight.

  In the first embodiment, the comb-shaped LED substrate 21 is used. In the second embodiment, the zigzag LED substrate 41 is used. However, other shapes such as those shown in FIGS. it can. 12 to 15 are plan views showing other shapes of the LED substrate. As shown in each figure, a V-shaped LED board 61 as shown in FIG. 12, an N-shaped (Z-shaped) LED board 71 as shown in FIG. 13, a corrugated LED board 81 as shown in FIG. The LED substrate 91 having a spiral shape (saddle shape) such as 15 may be used. Note that the LED substrates 61 and 71 in FIGS. 12 and 13 are obtained by cutting out a part of the zigzag LED substrate 41 in FIG. 10 (Embodiment 2). Further, it can be said that the LED substrate 81 of FIG. 14 is configured by configuring the zigzag LED substrate 41 of FIG. 10 with a curve. Moreover, it can be said that the LED substrate 91 of FIG. 15 is a modification of the comb-shaped LED substrate 21 of FIG. 1 (Embodiment 1). On these LED substrates 61, 71, 81, 91, LEDs 65, 75, 85, 95 are non-linearly arranged, as in the first and second embodiments. Moreover, when each LED board 61,71,81,91 is combined, the plane without a clearance gap will be formed. Therefore, similarly to the first and second embodiments, a plurality of LED substrates 61, 71, 81, 91 can be manufactured from a single substrate sheet 60, 70, 80, 90, respectively. Therefore, the price of the LED substrate can be reduced.

  In addition, this invention can also be expressed as follows.

The LED light source of the present invention is an LED light source that includes three or more light emitting diodes on a wiring board, and supplies current to the light emitting diodes from the wiring board. The light emitting diodes are non-linear on the wiring board. The outer shape of the wiring board is non-rectangular, and when the wiring board is rotated or translated, the wiring board before and after the movement can form a flat surface without a gap. The configuration may be a shape.

  The LED light source of the present invention includes a plurality of LEDs arranged at a predetermined interval, a wiring board that supplies current to the plurality of LEDs, and a connection member for electrically connecting the wiring board and an external circuit. The external shape of the wiring board may be a non-linear shape and a non-rectangular shape, and a shape that can be spread on a two-dimensional flat surface without a gap. According to this, the outer shape of the wiring board, which is a constituent element of the LED light source, is a non-linear shape and a non-rectangular shape, and can be spread in a two-dimensional plane without any gaps, thereby reducing the board area. In addition, the member price can be reduced and the area active luminance control effect can be enhanced because it is easy to make the shape of the control area close to a square at the time of area active luminance control.

  The LED light source of the present invention may have a configuration in which the outer shape of the wiring board is a comb-tooth shape. According to this, since the outer shape of the wiring board is a comb-teeth shape, the area at the time of manufacturing can be reduced by rotating the two wiring boards by rotating 180 degrees and arranging them, thereby reducing the member price. Can be reduced.

  In the LED light source of the present invention, the outer shape of the wiring board may be a zigzag type (wedge type). According to this, since the outer shape of the wiring board is a zigzag type, it is possible to reduce the area at the time of manufacturing by arranging a plurality of wiring boards at close intervals, and to reduce the member price. .

  The LED light source of the present invention may be configured such that a large number of the wiring boards are manufactured on a rectangular wiring board sheet, and are divided into pieces after the LEDs are mounted. According to this, since a large number of wiring boards are manufactured on a rectangular wiring board sheet and are divided into individual pieces after the LEDs are mounted, the LEDs are mounted on each wiring board. There is no need to do it. That is, mounting processing costs can be reduced by mounting LEDs in a lump.

  In the LED light source of the present invention, the outer shape of the wiring board may be formed by dividing perforations provided in advance on the wiring board sheet. According to this, since the outer shape of the wiring board is formed by dividing the perforations provided in advance on the wiring board sheet, the outer shape of a relatively complicated shape such as a comb tooth shape or a zigzag shape can be easily formed. be able to. Moreover, since LED etc. can be mounted in the connected state before dividing a perforation, the workability | operativity at the time of mounting can be improved.

  In the LED light source of the present invention, the wiring board may be a glass epoxy board, and the board thickness may be 0.8 mm or less. According to this, since the wiring board is a glass epoxy board and the board thickness is 0.8 mm or less, the heat generated by the LED can be easily transmitted to the heat dissipation member on the back surface of the wiring board. That is, an LED light source with high heat dissipation can be configured with an inexpensive configuration.

  The surface light source device of the present invention may have a configuration in which any one of the LED light sources described above is mounted. According to this, since the surface light source device is configured by mounting a plurality of any of the above LED light sources, a large area surface light source device can be realized at low cost.

  The image display device of the present invention may be configured to use the surface light source device as a backlight of a liquid crystal display element and display an image on the liquid crystal display element. According to this, since the surface light source device is used as a backlight of the liquid crystal display element to display an image, the contrast is improved by area active luminance control and the power consumption is reduced, and the cost is reduced by reducing the material price. It is possible to achieve both.

  The video display device of the present invention may be configured to perform area active luminance control by dividing the display area of the liquid crystal display element and the light emitting surface of the surface light source device into a plurality of areas, respectively. According to this, since the area active luminance control is performed by dividing the display area of the liquid crystal display element and the light emitting surface of the surface light source device into a plurality of areas, respectively, the contrast of the video display device is improved and the power consumption is reduced. be able to.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  As described above, since the LED light source of the present invention can be manufactured easily and inexpensively while improving connection reliability, it can be used for applications such as liquid crystal televisions and liquid crystal monitors for personal computers (PCs). Can do.

It is a top view which shows the whole structure of the LED backlight of this invention. It is a block diagram which shows schematic structure of the video display apparatus of this invention. It is sectional drawing which shows the thermal radiation structure in the LED backlight of FIG. FIG. 3 is a diagram illustrating a control area that is a control unit of an area active luminance control unit in the video display device of FIG. 2. 3 is a conceptual diagram comparing a video signal and backlight luminance depending on whether or not luminance control is performed by an area active luminance control unit in the video display device of FIG. It is a top view which shows the control area of a shape different from the control area of FIG. It is a top view which shows the control area in the video display apparatus using the conventional array type LED backlight. It is a flowchart which shows the manufacturing process of the LED backlight of FIG. It is a top view which shows the shape of the board | substrate sheet | seat before the piece division | segmentation in the manufacturing process of FIG. It is a top view which shows the whole structure of another LED backlight in this invention. It is a top view which shows the shape of the board | substrate sheet | seat before the piece division | segmentation in the manufacturing process of the LED backlight of FIG. It is a top view which shows another form of the LED board in this invention. It is a top view which shows another form of the LED board in this invention. It is a top view which shows another form of the LED board in this invention. It is a top view which shows another form of the LED board in this invention. It is a top view which shows the conventional array type LED backlight.

Explanation of symbols

1 Video display device 2, 4 LED backlight (surface light source device)
11 Video Circuit 12 Liquid Crystal Panel (Liquid Crystal Display Element)
16 area active brightness controller (brightness controller)
21a, 21b LED board (wiring board)
22a, 22b Harness 25 LED
26 Connector (connection part)
41 LED board (wiring board)
42 Harness 45 LED (LED light source)
46 Connector (connection part)
60, 70, 80, 90 Board sheet 61, 71, 81, 91 LED board 65, 75, 85, 95 LED

Claims (11)

An LED light source comprising three or more light emitting diodes on a wiring board, wherein current is supplied from the wiring board to the light emitting diodes,
The light emitting diode is non-linearly arranged on the wiring board,
The outer shape of the wiring board is a non-rectangular shape, and when the wiring board is rotated or translated, the wiring board before and after the movement can form a flat surface without a gap. LED light source.   2. The LED light source according to claim 1, wherein an outer shape of the wiring board is comb-shaped.   2. The LED light source according to claim 1, wherein an outer shape of the wiring board is a zigzag shape.   The LED light source according to claim 1, wherein the flat surface without a gap is a rectangle. The wiring board is made of a glass epoxy board,
The thickness of the said wiring board is 0.8 mm or less, The LED light source of any one of Claims 1-4 characterized by the above-mentioned.   The LED light source according to claim 1, wherein the light emitting diodes are arranged in a hexagonal lattice shape. It is a manufacturing method of the LED light source of any one of Claims 1-6,
Including a dividing step of dividing a single substrate sheet to form a plurality of wiring boards constituting the LED light source;
In the dividing step, a plurality of wiring boards are allocated to a board sheet so as to form a plane without gaps, and after mounting LEDs on each wiring board, the board is divided into individual wiring boards. Production method.   The method of manufacturing an LED light source according to claim 7, wherein the dividing step further includes a step of forming a perforation for dividing the substrate sheet into individual wiring boards.   A surface light source device comprising a plurality of the LED light sources according to claim 1.   An image display device comprising the surface light source device according to claim 9 as a backlight for irradiating a liquid crystal display element for displaying an image.   The video display device according to claim 10, further comprising: a luminance control unit that performs area active luminance control on the surface light source device and the liquid crystal display element.

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