JP5172128B2 - Backlight device, display device, and driving method of backlight device - Google Patents

Description

  The present invention relates to a direct type backlight device for a non-self-luminous image display panel such as a liquid crystal display panel, and more particularly to a backlight device using LEDs and a liquid crystal display device using the same.

  In recent years, as a light source of a backlight used in a liquid crystal device, in addition to a conventionally used cold cathode fluorescent tube (hereinafter referred to as “CCFL”), a light-emitting diode (hereinafter referred to as “CCFL”) is used. Development of a method that partially uses “LED”) or a method that replaces all CCFLs with LEDs is underway. In particular, the method of obtaining the three primary colors of red, green, and blue using only LEDs is characterized by a wide color reproducibility region (NTSC ratio) as compared with a method using a conventional CCFL tube. This is because the half-width of the emission spectrum of the LED is narrow, and RGB colors close to pure colors can be obtained. Furthermore, since the brightness can be adjusted by the amount of current for each color, the color balance can be changed. Moreover, since it does not contain mercury, it has the feature of being excellent in environmental resistance.

  An example of a backlight device using LEDs disclosed in Patent Document 1 is shown in FIG. FIG. 13A is a view from the back side of the apparatus, and FIG. 13B is a view from the front side of the apparatus. On the front side of the printed circuit board 30, LEDs 31 are assembled over almost the entire surface. Further, the back surface of the printed circuit board 30 is provided with a brightness adjustment circuit 32 and a semiconductor chip 33 including a driver and a control circuit, and performs drive control of the LED 31. A heat sink 34 is installed on the back surface of the printed circuit board 30 to efficiently discharge the heat emitted from the LEDs 31 and the brightness adjusting circuit 32 and the semiconductor chip 33 provided on the back surface of the printed circuit board. In order to improve heat conductivity by bringing the heat sink 34 and the printed circuit board 30 into close contact with each other, the heat sink 34 is provided with a recess 35, and the brightness adjustment circuit 32 and the semiconductor chip 33 provided on the back surface of the printed circuit board 30 are accommodated in the recess 35. It can be done. In addition, a diffusion plate 36 for making the light emitted from the LEDs 31 uniform is installed on the front side of the printed circuit board 30. In addition, a liquid crystal panel 38 is provided in front of the optical chamber 37 in which the heat sink 34, the printed circuit board 30, and the diffusion plate 36 are housed, and the liquid crystal display device uses the LED 31 as a backlight as a whole.

  Patent Document 2 discloses an LED backlight that stabilizes the luminance and chromaticity of an LED using a red, green, and blue LED and a set of optical sensors that detect three colors of red, green, and blue. doing. Here, in addition to the LED and the optical sensor, the LED lighting device can store the color and lumen output values set by the user in the memory array, and these values are stored in the memory according to the user selection. It can be read.

  Patent Document 3 discloses a backlight device in which one light sensor is driven in a time-sharing manner to stabilize the luminance and chromaticity of each color of red, green, and blue LEDs.

  Patent Document 4 discloses a light guide plate-use backlight device, using four RGB light sources installed at the upper and lower ends of the display area and four color sensors arranged at the left and right ends, It is said that uniform chromaticity and brightness can be obtained. Here, the four light sources and the four sensor outputs do not correspond one-to-one, and the feedback control is performed by comparing the sensor outputs with the common correlation data memory and the light source reference light emission amount memory, and performing matrix calculation. It is carried out.

Patent Document 5 discloses a device for storing the driving voltage of each color LED in an applied voltage storage register and driving each color LED with an independent driving voltage in order to reduce current consumption and absorb variations in LED characteristics. doing. The LED driving device includes an R (red) applied voltage storage register, a G (green) applied voltage storage register, a B (blue) applied voltage storage register, an R duty ratio storage register, a G duty ratio storage register, and a B A duty ratio storage register. According to this configuration and method, an independent minimum driving voltage is applied to each color LED based on the voltage value stored in the applied voltage storage means, so the same driving voltage is applied to each color LED. It is said that the current consumption can be reduced compared to the case of doing so.
US Pat. No. 6,439,731 JP-T-2004-525516 JP 2002-533870 A JP 2004-286971 A JP 2004-31460 A

  Recently, it has been proposed to apply an LED backlight to a large liquid crystal display device. In that case, when the substrate on which the LEDs are installed is simply enlarged, there arises a problem that nonuniformity in brightness (luminance) or color (chromaticity) due to temperature nonuniformity in the substrate becomes remarkable. Although a certain amount of correction can be performed with respect to a change in temperature in the substrate with a configuration using an optical sensor, it is difficult to eliminate nonuniformity in overall luminance or chromaticity. In addition, by dividing the substrate, it is easy to repair when a part of the substrate fails. Therefore, it is conceivable to use a backlight on which a plurality of substrates on which LEDs are installed are mounted.

  However, when the LED backlight is composed of a plurality of substrates, there is a problem that it is difficult to adjust the luminance or chromaticity of each substrate to be the same. If this adjustment is insufficient, the luminance or chromaticity varies depending on the display area, particularly in a liquid crystal backlight. For this reason, when a substrate breaks down and is repaired or replaced, it is necessary to make adjustments so that uniform light emission is performed with the adjacent substrate.

  The present invention automatically adjusts the luminance or chromaticity of each substrate to a predetermined value and obtains uniform light emission, a display device using the backlight device, and driving of the backlight device It aims to provide a method.

  It is another object of the present invention to provide a method for adjusting a substrate constituting such a backlight device.

The present invention is a backlight device including a plurality of substrates including a plurality of light emitting elements, optical sensors, and memory means, and a driving circuit for driving the light emitting elements, wherein the plurality of substrates are arranged in a vertical and horizontal direction. A plurality of the light sensors are disposed, and the light sensors are disposed at substantially the center of the surface of each substrate on which the light emitting elements are disposed, and the light of the light emitting elements in each substrate and the light emitting elements in the adjacent substrate emit light. and detecting the light was, the and the light emitting element in said memory means of each substrate is the light corresponding information stored in the output value of the sensor at conditions that emits light of a predetermined luminance or chromaticity, the light sensor Is standardized based on the information stored in the corresponding memory means, and the drive circuit is configured so that the output of the standardized photosensor matches the set value of luminance or chromaticity of the backlight device. A control circuit for generating a control signal for the control circuit, the performs feedback control based on the control signal in each substrate, the driving circuit to drive the light emitting element under control of the control circuit This is a featured backlight device.

  The present invention is preferably a backlight device characterized in that each substrate is provided with a drive circuit for driving a light emitting element of each substrate.

  The present invention is preferably a backlight device in which the control circuit is installed outside the substrate.

  The present invention is preferably a backlight device in which the control circuit generates a time-division control signal for each of the substrates.

  The present invention is preferably a backlight device characterized in that the control circuit includes a plurality of control circuits, and each control circuit is installed in each substrate.

  The present invention is preferably a backlight device in which the light emitting element includes a blue light emitting element, a green light emitting element, and a red light emitting element.

  The present invention is preferably a backlight device in which at least one of the light emitting elements of each color includes an LED.

  Preferably, the light sensor includes a light sensor that detects blue light, a light sensor that detects green light, and a light sensor that detects red light.

  The present invention is preferably a backlight device in which the light sensor detects light of each color of the light emitting element by driving the light emitting element in a time division manner.

  According to the present invention, the memory means stores information corresponding to an output value of the photosensor under a condition that the light emitting element in the substrate emits light of a predetermined color temperature. An apparatus is preferred.

  According to the present invention, the memory means stores information corresponding to an output value of the photosensor under a condition in which each color light emitting element in the substrate emits light having a predetermined luminance. A light device is preferred.

  The present invention is preferably a backlight device characterized in that the memory means stores information corresponding to variations in luminance or chromaticity of the light emitting elements in the substrate within the substrate.

  The present invention is preferably a backlight device characterized in that the light emitting element is composed of a light emitting element group.

  The present invention is preferably a backlight device in which the light emitting element group includes the light emitting elements connected in series.

  According to the present invention, the memory means stores information corresponding to a driving condition of the light emitting element under a condition in which each of the light emitting elements emits light of a predetermined luminance or chromaticity. An apparatus is preferred.

  In the present invention, the memory means stores a first memory in which information corresponding to an output value of the photosensor in a condition in which the light emitting element in the substrate emits light having a predetermined luminance or chromaticity is stored; It is preferable that the backlight device includes a second memory in which information corresponding to the in-substrate variation of the light emitting elements in the substrate is stored.

  The present invention is preferably a backlight device in which the light emitting element and the optical sensor are installed on the front surface of the substrate, and the memory means is installed on the back surface of the substrate.

  The present invention is preferably a backlight device in which the memory means is incorporated in an integrated circuit element integrated with the drive circuit.

  The present invention is preferably a backlight device in which the memory means is a writable memory or a rewritable memory.

  The present invention is a display device comprising the backlight device and a non-self-luminous image display panel that displays an image by controlling a transmission state of light from the backlight device.

The present invention relates to a driving method of a backlight device including a plurality of light emitting elements, a plurality of substrates provided with photosensors and memory means, a drive circuit, and a control circuit, wherein the plurality of substrates are arranged in a vertical and horizontal direction. A plurality of the light sensors are arranged, and the photosensors are arranged at substantially the center of the surface of each substrate on which the light emitting elements are arranged, and the light emitting elements provided on the substrate have a predetermined luminance in the memory means. Alternatively, information corresponding to an output value of the photosensor in a condition of emitting light of chromaticity is stored, the step of driving the light emitting element by the drive circuit, and the photosensor is a light emitting element in each substrate the detecting light-emitting element is emitted in the light and the adjacent substrate, the control circuit, and normalized using the information output stored in said memory means of said light sensor, said drive circuit The step of the output of standardized light sensor generates a control signal such that the set brightness or chromaticity is transmitted to the drive circuit performs a feedback control based on the control signal in said each substrate for And a method of driving the backlight device.

  According to the present invention, in a backlight device including a plurality of substrates, information corresponding to the output value of the optical sensor under the condition that the light emitting element in the substrate emits light of a predetermined luminance or chromaticity is stored in advance in the memory in the substrate. Remember me. By using this information, the output value of the optical sensor is standardized. By automatically controlling the light-emitting elements in each board so that the output value of the standardized light sensor matches the set value of brightness or chromaticity, the brightness or chromaticity of each board is automatically set to a predetermined value. Adjusted to Therefore, since this substrate is not affected by variations in the optical sensor, it becomes a backlight device that can obtain uniform light emission only by combining this substrate without adjustment. Accordingly, when a substrate fails, a backlight having a plurality of substrates that emits light of uniform brightness or chromaticity even after the substrate is replaced by simply replacing the substrate having a memory storing such information. It can be a device.

In addition , according to the present invention, a display device having excellent display quality can be provided by combining the backlight device having excellent uniformity with a non-light-emitting image display panel.

Further, according to the present invention, it is possible to provide a driving method of the backlight device having excellent uniformity.

(Embodiment 1)
FIG. 1 is a schematic view of the liquid crystal display device 1 of Embodiment 1 as viewed from the back side. A plurality of LED chips 4 (which will be described later because they are hidden in FIG. 1) are assembled on the front side of the plurality of tiles 12, and the light emitted from the LED chips 4 is made uniform by the diffusion plate 22, The liquid crystal panel 23 arranged on the outside is illuminated so that an image can be displayed. The number of tiles 12 arranged in the vertical and horizontal directions can be freely determined according to the screen size of the liquid crystal television. In this embodiment, the ratio of the length of the tile 12 to the width is 9: 8, and four pieces are arranged vertically and eight pieces are arranged horizontally, so that it is suitable for a screen having an aspect ratio of HDTV of 9:16. It is arranged. In the backlight device using the waveguide plate of Patent Document 3, the backlight region is not essentially divided, and it is difficult to make the display region corresponding to the sensor 4 or more. In the embodiment, any number of tiles can be used, which is suitable for a large backlight device. The liquid crystal panel 23 may be replaced with a non-self-luminous image display panel other than the liquid crystal panel, such as a MEMS (micro electro mechanical system) panel or a shutter panel using an electro-optic effect or an electrophoretic effect. it can.

  In order to connect a plurality of tiles 12, connectors 13 are arranged on two opposite sides of the four sides of the tiles 12, and the connectors 13 are connected by cables 16. In this way, each tile 12 is connected to the control board 24.

  A microcomputer 11 is mounted on the control board 24, and the microcomputer 11 functions as a control circuit that transmits a signal serving as a reference for LED driving to the integrated circuit element 10 of each tile 12.

  The surface of each tile 12 is shown in FIG. The material of the base substrate 12A of the tile 12 is glass epoxy (glass epoxy), and multilayer wiring is possible. An optical sensor 2 composed of three photodiodes that detect red, green, and blue is disposed at the center of the surface. A plurality of red LED chips, green LED chips, and blue LED chips (collectively referred to as LED chips 4) are die-bonded in the surrounding LED arrangement region 3. Since the light sensor 2 is arranged in the center of the tile 12 in this way, the light sensor 2 is not greatly affected by the light from the adjacent tiles. Therefore, the feedback is closed between the light sensor 2 inside the tile and the LED chip 4. Control can be performed.

  On the back surface of the tile 12, the integrated circuit element 10 is mounted as shown in FIG. The integrated circuit element 10 is connected to the outside through a connector 13 and a cable 16. Moreover, the heat sink 14 is installed except for the portion where the integrated circuit element 10 is disposed.

  As shown in FIG. 3, which is a cross-sectional view of the tile 12, gold is provided between electrode pads (not shown) of the plurality of LED chips 4 and wiring pads (not shown) in the tile 12 on the surface of the base substrate 12 </ b> A. The wire 5 is wire-bonded and electrically connected. The LED chip 4 and the gold wire 5 are protected by a transparent sealing resin 15 such as silicone or epoxy. A heat sink 14 is mounted on the back surface of the base substrate 12A on which the LED chip 4 is mounted. The heat radiating plate 14 is in contact with the chassis 20 constituting a part of the display device (unit) so that better heat dissipation than the chassis 20 can be obtained. The integrated circuit element 10 is mounted on the back surface of the base substrate 12A at a location that does not contact the heat sink 14. A connector 13 is disposed on the opposite side of the back surface of the base substrate 12A.

  FIG. 4 is an enlarged cross-sectional view of the vicinity of the portion where the LED chip 4 is die-bonded on the base substrate 12A. A through hole 17 is provided under the region where the LED chip 4 is assembled (die-bonded), and the wiring 18 where the LED chip 4 is die-bonded passes through the through-hole 17 and the wiring 18 on the back surface of the base substrate 12A. It is connected. Since the wiring 18 is made of a metal having high thermal conductivity such as copper and has a structure in contact with the heat radiating plate 14, the heat radiation effect of the LED chip 4 is enhanced.

  In this embodiment, since glass epoxy is used as the material of the base substrate 12A, multilayer wiring is possible, and wiring restrictions within the tile 12 are eliminated, so that the degree of freedom of LED chip wiring can be ensured. Since complicated wiring becomes possible, it becomes easy to mount the integrated circuit element 10 on the tile 12.

  Note that some or all of the blue, green, and red LEDs used in the present embodiment, for example, red LEDs, may absorb red light from blue LEDs and blue LEDs to emit red fluorescence. Further, the green LED may emit green fluorescence by absorbing light from the blue LED and the blue LED. Moreover, you may use LED which emits an ultraviolet-ray, and the fluorescent substance which emits blue, green, and red.

  In this embodiment, an example in which red, green, and blue LEDs are used as light emitting elements and the chromaticity and luminance are uniformed is described. However, for example, white LEDs may be used as the light emitting elements. . In that case, since control is not performed regarding chromaticity, only control regarding luminance is performed. As the white LED, a normal red LED and a yellow phosphor may be used, but a blue LED and a green and red phosphor as described above, or an ultraviolet LED and a blue / green / red phosphor. Those using can be suitably used.

(Circuit Configuration and Operation of Backlight Device in Embodiment 1)
FIG. 5A shows a schematic diagram of a circuit configuration. In the tile 12, an optical sensor 2, an LED chip 4, and an integrated circuit element 10 (consisting of an A / D converter 10A, a rewritable ROM 10B, and an LED drive circuit 10C) are mounted. The photosensor 2 is a set of photosensors including a photodiode with a red filter, a photodiode with a green filter, and a photodiode with a blue filter, and emits light of each color of the red, green, and blue LED chips 4 in each tile 12. The analog signal corresponding to the amount of light is digitized by the A / D converter 10A.

  The rewritable ROM 10B stores the output value of the optical sensor 2 (hereinafter referred to as “optical sensor reference value”) obtained when the LED chip 4 emits light with predetermined chromaticity and luminance (for the storage method). Will be described later).

  The backlight device operates as follows. When the LED chip 4 in each tile 12 constituting the backlight device is driven, the photosensor 2 receives the chromaticity and luminance in each tile, and the output value of the photosensor 2 and the rewritable ROM 10B are stored. The optical sensor reference value is sent to the microcomputer 11 outside the tile 12.

  The microcomputer 11 is commonly used for each tile 12. The microcomputer 11 compares the output of the optical sensor 2 with the optical sensor reference value stored in the rewritable ROM 10B, and standardizes the output value of the optical sensor 2. Standardization can be performed by, for example, calculating the ratio by dividing the output of the optical sensor 2 by the optical sensor reference value. The microcomputer 11 generates a control signal so that the output of the standardized optical sensor thus obtained approaches a set value (chromaticity and luminance set by a person viewing the liquid crystal display device), and the LED in the integrated circuit element 10 This is sent to the drive circuit 10C.

  Based on this control signal, the LED drive circuit 10C controls the pulse width of the drive current of PWM (Pulse Width Modulation) that is output to the LED chip 4. The PWM output in the present embodiment has a constant current value, but it is also possible to change the luminance or chromaticity by changing the current value. Further, instead of the PWM drive output, an analog output (a current value for obtaining a required light emission amount) may be used.

  The microcomputer 11 mounted in the control board 24 sends control signals to the plurality of tiles 12 in a time division manner. This is because the adjustment of the chromaticity and luminance of the backlight is mainly intended for correction with respect to temperature changes or changes with time, and it is not necessary to send control signals continuously.

  By performing such an operation, feedback control is performed to set the output value of the optical sensor 2 to a set value. Since this feedback operation is performed so that the standardized light sensor output of each tile is constant, the chromaticity and brightness itself of the light emitting element of each tile may vary from tile to tile. For example, in the tile arranged in the center of the backlight device, the light of the light emitting element is suppressed so that the standardized photosensor output is constant because much light from the adjacent tile enters the photosensor. In this way, the backlight device operates as a whole with uniform brightness.

  In the above operation, white light that is a constant set value is steadily emitted as a backlight device, but a feedback operation can also be performed when the set value fluctuates. For example, it is possible to adjust based on a video signal for liquid crystal display. While the set value of the standardized light sensor output for obtaining white light is normally red: green: blue = 1: 1: 1, the set value as a whole when the display image is dark is, for example, red: green. : Blue can be reduced to 0.2: 0.2: 0.2. Alternatively, an operation for adjusting not only luminance but also chromaticity can be performed. For example, when the image displayed by the tile 12 in the liquid crystal display device is a blue image (for example, the sea), the standardized light sensor output of each color is, for example, red: green: blue = 0.1: 0.2: 1. An operation such as 0 is possible.

  Further, as shown in FIG. 2B, a plurality of integrated circuit elements 10 are mounted on the tile 12, but it is not necessary that all of them are the same integrated circuit element. For example, one integrated circuit element 10 is provided. May comprise the A / D converter 10A, the rewritable ROM 10B, and the LED drive circuit 10C, and the remaining integrated circuit element 10 may comprise the LED drive circuit 10C.

  FIG. 5B is a schematic diagram showing a signal flow in another configuration. In the tile 12, an optical sensor 2, an LED chip 4, and an integrated circuit element 10Z (consisting of an A / D converter 10A, a rewritable ROM 10B, an LED control circuit 10D, and an LED drive circuit 10C) are mounted.

  The optical sensor 2 senses the light emission amount of each color of the red, green, and blue LED chips 4 in each tile 12, and an analog signal corresponding to the light amount is digitized by the A / D converter 10A.

  The rewritable ROM 10B stores an optical sensor reference value that is an output value of the optical sensor 2 obtained when the LED chip 4 emits light with a predetermined chromaticity and luminance. The photosensor reference value and the output value of the photosensor 2 are sent to the LED control circuit 10D inside the tile 12, and the LED drive circuit 10C drives the LED chip 4 in accordance with a control signal generated therefrom.

  The microcomputer 11 is commonly used for each tile 12. Here, the microcomputer 11 simply generates a setting signal that has the chromaticity and brightness set by the person viewing the liquid crystal display device, and sends it to the LED control circuit 10D in the integrated circuit element 10Z.

  The LED control circuit 10D sends a control signal to the LED drive circuit 10C such that the standardized photosensor output, which is the ratio of the signal obtained by the photosensor 2 and the photosensor reference value, matches the value based on this setting signal. The LED drive circuit 10C controls the pulse width of the drive current of PWM (Pulse Width Modulation, pulse width modulation) output to the LED chip 4 based on the control signal.

  It should be noted that there is a question whether feedback control can be performed only within a tile even though the optical sensor 2 captures light of an adjacent tile. For example, when the brightness of an adjacent tile actually decreases, feedback control that compensates for this causes the brightness of the light emitting elements in the tile to increase above a predetermined value, resulting in a loss of brightness. The disadvantage of increased uniformity occurs. The same applies to chromaticity. And in the structure which does not block the light between tiles like this Embodiment, the light of the tile which adjoins the light which the optical sensor 2 receives may be more than the light from an own tile. However, when feedback control is performed for all tiles in the display device, the brightness and chromaticity of adjacent tiles are kept stable, so even if feedback control closed within such tiles is performed, Since fluctuations in chromaticity and luminance in each tile can be mainly corrected, feedback control that does not cause nonuniformity in the entire backlight device can be performed.

(Method for Adjusting Optical Sensor Reference Value for Each Tile in Embodiment 1)
Setting of the optical sensor reference value necessary for obtaining the standardized optical sensor output and storage in the rewritable ROM 10B are performed as follows.

  The tile 12 is placed in the tile adjusting device 40 shown in FIG. The tile adjusting device 40 includes an external light sensor 42 that receives light emitted from the plurality of LED chips 4 of each tile 12. Further, the tile adjusting device 40 includes a diffusion plate 45 that diffuses light emitted from the LED chip 4 of the tile 12. The diffusion plate 45 is made of the same material as that of the diffusion plate 22 used in the liquid crystal display device 1 and is installed so that the distance between the tile 12 and the diffusion plate 45 is the same as the distance between the tile 12 and the diffusion plate 22. Yes. The same external light sensor 42 as that of the optical sensor 2 is used, but another external sensor may be used.

  The optical sensor 2 detects the light reflected by the diffusion plate 22, while the external optical sensor 42 detects the light transmitted through the diffusion plate 45. For this reason, the outputs of the optical sensor 2 and the external optical sensor 42 do not match. Therefore, in the state in which the LED chip 4 is caused to emit light, the light sensor 2 and the external light sensor 42 are simultaneously detected, and the correlation coefficient between the outputs is obtained in advance. In order to eliminate the background offset, the outputs of the optical sensor 2 and the external optical sensor 42 may be obtained even when the LED chip 4 is turned off, and the correlation coefficient may be corrected using this.

  The distance between the external light sensor 42 and the tile 12 is preferably longer than the diagonal length of the tile 12, and more preferably longer than twice the diagonal length of the tile 12.

  The external control circuit 44 reads the value corresponding to the predetermined chromaticity and luminance set in the external memory 43 and the detection value of the external light sensor 42 (step 1A), and the detection value of the external light sensor 42 is read from the external memory. A control signal is sent to the LED drive circuit 10C (see FIG. 5A) in the integrated circuit element 10 so that the set value is 43, and the LED drive circuit 10C drives all the LED chips 4 (step 1B). . The output of the optical sensor 2 at that time is input to the external control circuit 44 (step 2A), and an operation for obtaining a value (optical sensor reference value) multiplied by the correlation coefficient is performed (step 2B). Then, this optical sensor reference value is stored in the rewritable ROM 10B (see FIG. 5A) in the integrated circuit element 10 (step 3).

  The predetermined chromaticity and luminance may be a value at one point when the luminance is high and the predetermined color temperature (for example, 9000 K), and when the luminance is high, the luminance is low (for example, 1/5 when the luminance is high). ), When the color temperature is high (for example, 12000 K), or when the color temperature is low (for example, 5000 K), a plurality of points such as four points may be used. Instead of driving the red, green and blue LED chips simultaneously, the external control circuit 44 first reads a predetermined luminance (low luminance, medium luminance, high luminance) from the external memory 43 for the red LED, and the external light sensor 42. The red LED is driven by sending a control signal to the LED drive circuit 10C so that the detected value becomes a predetermined luminance (step 1 for R), and the external control circuit 44 reads the output of the light sensor 2 at that time The value (the optical sensor reference value) multiplied by the correlation coefficient is calculated (step 2 for R), and the optical sensor reference value is stored in the rewritable ROM 10B in the integrated circuit element 10 (step 3 for R). The same operation may be performed for the green and blue LEDs. Such a relatively small number of optical sensor reference values may be stored, and the optical sensor reference values of other conditions may be obtained by complementation by calculation. A large number of optical sensor reference values (for example, 256 points) may be stored.

  A tile adjustment device 40 having an external light sensor 42 (or substantially the same tile adjustment device configured to perform the same adjustment as this adjustment device) is commonly used for adjustment of each tile 12, and By storing the optical sensor reference value in the rewritable ROM 10 </ b> B of each tile 12, it becomes a backlight device with excellent uniformity without adjusting by simply combining the tiles 12. Further, for example, when one tile 12 fails in the backlight device, it is possible to perform uniform light emission with adjacent tiles without requiring adjustment after installation only by replacing the tile 12, so that repair is possible. Becomes easier.

(Embodiment 2)
Another problem is that it is difficult to adjust the brightness or chromaticity uniformity within the tile. For example, when the driving voltage and the duty ratio are stored for each LED in order to correct the luminance variation of each LED as in Patent Document 5, the conditions such as the LED temperature change even if the luminance uniformity is obtained in the initial stage. And the emission intensity of each LED changes. When a plurality of color LEDs are used, the uniformity of chromaticity is also lost.

  The second embodiment uses not only the setting of chromaticity and brightness for each tile, but also means for obtaining light uniformity within the surface of each tile substrate, and also performs feedback control by an optical sensor to control temperature changes. On the other hand, it is stabilized.

  The effect of improving the light uniformity can also be obtained by arranging a large number of tiles in a small size, but the number of parts such as optical sensors increases and the cost increases. The form may have higher industrial applicability.

  A schematic configuration diagram of the tile 50 is shown in FIG. 7A which is a front view and FIG. 7B which is a back view. On the surface, LED groups 51R, 52R, 53R and 54R in which red LEDs (R in the figure) are connected in series, LED groups 51G, 52G, 53G and 54G in which green LEDs (G in the figure) are connected in series, LED groups 51B, 52B, 53B and 54B, and an optical sensor 55, in which blue LEDs (B in the figure) are connected in series, are mounted. In this way, by arranging the LEDs in the LED group in series, a proportionality coefficient that is one correction value may be set for each LED group. In addition, it is also possible to individually set a correction value for each LED without being connected in series and to drive each LED individually.

  The LED groups 51 </ b> R to 54 </ b> B mounted on the front surface of the tile 50 are connected to the integrated circuit element 57 mounted on the back surface through the through hole 58, and the photosensor 55 is mounted on the back surface through the through hole 59. It is connected to the integrated circuit element 56.

  The backlight device in the second embodiment operates as follows. In each of the tiles 50 constituting the backlight device, the LED groups 51R to 54B are turned on. The light of the LED in the tile and in the adjacent tile is reflected by the diffusion plate 22 (the same as that shown in FIG. 1) and detected by the light sensor 55. The optical signal of the optical sensor 55 is sent to the A / D converter 56A in the integrated circuit element 56, and is tiled through the connector 13 together with the optical sensor reference value stored in the rewritable ROM 56B in the integrated circuit element 56. It is sent to 50 microcomputers 11 (same as those shown in FIG. 1).

  A control signal generated from the microcomputer 11 so that the standardized optical sensor output of the optical sensor 55 becomes constant is sent to the correction circuit 57B in the integrated circuit element 57. The correction circuit 57B corrects the control signal with reference to data (described later) in the rewritable ROM 57A storing the correction value, and sends it to the LED drive circuit 57C. The LED drive circuit 57C drives, for example, the LED group 51R based on the corrected control signal. The same applies to the other LED groups 51G and 51B. Here, the LED groups 51R, 51G, and 51B are regarded as one set and driven by the LED drive circuit 57C. For example, the LED groups 51R, 52R, 53R, and 54R are regarded as a set and A drive circuit may be provided, and all LED groups in the tile 50 may be driven by one LED drive circuit. Further, the LEDs in the LED group may be connected in parallel without being connected in series, or may be connected in combination with series and parallel, or may be driven independently by connecting a drive circuit for each LED instead of the LED group.

  As described above, the control signal is corrected and driven for each LED group, and feedback control is performed so that the standardized light sensor output becomes a predetermined value, so that it can be driven as a uniform backlight device even in the tile plane. .

  The optical sensor 55 may be composed of only one photodiode that does not use a filter. In this case, in order to detect the light emission of the red LED, the light emission of the green LED, and the light emission of the blue LED, for example, during the operation of the backlight device, for example, only the red LED is turned on and the other color LEDs are turned off. The light sensor 55 detects light emission of the red LED within that time. Information on chromaticity and luminance is obtained by detecting the LEDs of other colors in the same manner. This detection method has the advantage that it is not affected by filter deterioration or the like.

(Adjustment method of light sensor reference value and LED group correction coefficient for each tile in embodiment 2)
In the second embodiment, in addition to setting the optical sensor reference value as a whole as shown in the first embodiment, each LED group 51R to 54B has a predetermined luminance in order to reduce the in-plane distribution in the tile 50. Alternatively, information corresponding to driving conditions in the condition of emitting light of chromaticity (hereinafter referred to as “LED group correction coefficient”) is set. This setting is performed as follows.

  The tile 50 is placed in the tile adjusting device 70 shown in FIG. The tile adjustment device 70 includes a diffusion plate 71 that diffuses light emitted from the LED groups 51R to 54B of the tile 50, and an area sensor 72 that detects an in-plane distribution of chromaticity and luminance of the diffusion plate 71 as an image. The diffusion plate 71 is made of the same material as that of the diffusion plate 22 used in the liquid crystal display device 1 and is installed so that the distance between the tile 50 and the diffusion plate 71 is the same as the distance between the tile 50 and the diffusion plate 22. Yes.

  The external control circuit 74 issues a control signal to the integrated circuit element 57 (step 4A), and the LED drive circuit 57C lights the LED groups 51R to 54B to illuminate the diffusion plate 71, and the chromaticity and luminance of the diffusion plate 71 are set in the area. Detection is performed by the sensor 72, and a ratio (intra-substrate variation) to the average value is detected by the external control circuit 74 (step 4B). For example, when the color of the diffusion plate 71 near the LED groups 51R, 51G, and 51B is reddish, a rewritable ROM 57A corresponding to a correction coefficient that is a proportional coefficient that reduces the drive output of the red LED group 51R. (See step 5 for chromaticity). Further, for example, when the brightness of the diffusion plate 71 in the portion close to the LED groups 51R, 51G, and 51B is darker than the other portions, the rewrite corresponding to the correction coefficient that increases the drive output of the LED groups 51R, 51G, and 51B is performed. Write to possible ROM 57A (Step 5 for luminance).

  Next, the optical sensor reference value is stored in the memory as follows.

  The external control circuit 74 reads the value corresponding to the predetermined chromaticity and luminance set in the external memory 73 and the detection value of the area sensor 72 (step 1A), and the detection value of the area sensor 72 is set in the external memory 73. In addition, a control signal is sent to the correction circuit 57B (see FIG. 7B) of the integrated circuit element 57 so that the value corresponds to the predetermined chromaticity and luminance, and the LED drive circuit 57C causes all the LED groups 51R to 54B. Is driven (step 1B). Here, the area sensor 72 functions as a simple optical sensor by averaging the output of the area sensor 72 as an image for each of red, green, and blue colors.

  The output of the optical sensor 55 at that time is input to the external control circuit 74 (step 2A), and the optical sensor reference value is calculated (step 2B). Since there is the diffusion plate 71, the output of the optical sensor 55 almost corresponds to the output actually incorporated in the liquid crystal display device 1. If there is a deviation, the deviation is calculated and the above averaging is performed. The optical sensor reference value that is the output of the optical sensor 55 under the condition that the detected value becomes the predetermined chromaticity and luminance is calculated.

  Then, this optical sensor reference value is stored in the rewritable ROM 56B (see FIG. 7B) in the integrated circuit element 56 (step 3). Steps 1 to 3 may be performed for each color as described above.

  In this way, adjustment is simplified by setting the LED group correction coefficient first and then setting the photosensor reference value later. Note that the LED group correction coefficient may be set after the optical sensor reference value is set first, but the optical sensor reference value may be shifted at that time. In that case, the optical sensor reference value may be set again.

  The distance between the area sensor 72 and the diffusion plate 71 is preferably longer than the diagonal length of the tile 50, and more preferably longer than twice the diagonal length of the tile 50.

  In this way, the optical sensor reference value and the LED group correction coefficient for each tile 50 are stored in the rewritable ROMs 56B and 57A of each tile 50, and the backlight device is driven based on this, so that the inter-tile and A backlight device having uniform chromaticity and brightness inside the tile can be obtained.

  In this embodiment, the LED group correction coefficient is set for each LED group. However, in order to obtain more uniform light emission, driving is performed for each individual LED, and the correction coefficient is set for each individual LED. Is desirable. This corresponds to the case where the number of LEDs in the LED group is one.

(Embodiment 3)
In the third embodiment, the integrated circuit element 87 is arranged on the surface of the tile 80. Also, the arrangement and the LED groups are different.

  FIG. 9 is a cross-sectional view of the tile 80 according to the third embodiment. The integrated circuit element 87 is disposed on the surface of the base substrate 80A, and the highly reflective member 21 is provided so as to cover it. The high reflection member 21 functions to reflect light emitted from the LED chip 4 constituting each LED group in the lateral direction upward and to reflect light returned from the diffusion plate 22 (not shown) to the substrate again. Have. Further, the connector 13 and the cable 16 that connect the tiles 80 are also covered with the highly reflective member 21.

  The chassis 20 is in direct contact with the back surface of the tile 80, thereby improving heat dissipation.

  FIG. 10 is a partially enlarged sectional view of FIG. A through hole 17 is provided under the region where the LED chip 4 is assembled (die-bonded), and is connected to the multilayer wiring 18 on the back surface of the base substrate 80A. Further, a through hole 17 is also provided immediately below where the integrated circuit element 87 is assembled (die-bonded), and is connected to the multilayer wiring 18 on the back surface of the tile 80. The multilayer wiring 18 and the chassis 20 are in contact with each other. Thereby, the heat generated from the LED chip 4 and the integrated circuit element 87 can be guided to the through hole 17 and the multilayer wiring 18 to be radiated from the chassis 20 to the outside.

  A structural schematic diagram of the tile 80 is shown in FIG. On the surface, LED groups 81R, 82R, 83R and 84R in which red LEDs are connected in series, LED groups 81G, 82G, 83G and 84G in which green LEDs are connected in series, and LED groups 81B and 82B in which blue LEDs are connected in series 83B and 84B and the optical sensor 85 are mounted. The LED groups 81R, 81G, and 81B, which are combinations of red, green, and blue LED groups, are arranged in a quarter region of the tile 80, and are arranged symmetrically in the vertical and horizontal directions as viewed from the optical sensor 85. It has become.

  The backlight device using this tile operates as follows. By driving each LED group, the optical signal obtained by the optical sensor 85 is sent to the A / D converter 86A in the integrated circuit element 86, and stored in the rewritable ROM 86B in the integrated circuit element 86. Together with the reference value, it is sent to the microcomputer 11 (not shown) outside the tile 80 via the connector 13. The microcomputer 11 generates a control signal corresponding to a predetermined luminance and chromaticity, and the control signal is sent to the correction circuit 87B in the integrated circuit element 87 mounted on the surface of the tile 80. The correction circuit 87B refers to the data in the rewritable ROM 87A storing the LED group correction coefficient, corrects the control signal, and sends the corrected control signal to the LED drive circuit 87C. The LED drive circuit 87C drives, for example, the LED group 81R based on the corrected control signal. The same applies to the other LED groups 81G and 81B. Thus, feedback control is performed in which the luminance and chromaticity are made constant in the tile and the in-plane variation is corrected. Similar control is performed on adjacent tiles, so that the backlight device operates with uniform brightness and chromaticity.

(Adjustment method of light sensor reference value and LED group correction coefficient for each tile in Embodiment 3)
In the third embodiment, the entire optical sensor reference value shown in the first embodiment is set, and the in-plane distribution in the tile 80 is reduced without using an area sensor as in the second embodiment. Therefore, an LED group correction coefficient is set for each of the LED groups 81R to 84B. This setting is performed as follows.

  The tile 80 and the diffusion plate 91 are placed in the tile adjusting device 90 shown in FIG. 12, and the lid 90A is closed to make it a dark place. The diffusion plate 91 is supported by rails 91A. An external light sensor 92 is installed on the upper surface of the tile adjusting device 90.

  The external control circuit 94 issues control signals for lighting the red LED groups 81R, 82R, 83R, 84R to the LED drive circuits 87C (see FIG. 11) in the four integrated circuit elements 87, respectively (Step 4A for R). Thereby, the diffusion plate 91 is illuminated, the external control circuit 94 reads the chromaticity and luminance of the diffusion plate 91 from the external light sensor 92, and the external control circuit 94 detects a ratio (intra-substrate variation) to the average value (about R). In step 4B), the LED group correction coefficient, which is a proportional coefficient for making the drive output so that the output of the external light sensor 92 in that case is the same, is written in the writable ROM 87A in the four integrated circuit elements 87 (see FIG. 11). ) Respectively (step 5 for R).

  The same correction coefficient input operation is performed for the green LED groups 81G to 84G and further for the blue LED groups 81B to 84B.

  After the above operation, the external control circuit 94 reads the set value of the external memory 93 and the output value of the external light sensor 92 (Step 1A for R), and the output value of the external light sensor 92 is set to the set value of the external memory 93. Thus, the external control circuit 94 controls the lighting of the red LED groups 81R to 84R (step 1B for R), and the external control circuit 94 obtains the output value of the light sensor 85 and calculates the light sensor reference value. (Step 2 for R), the optical sensor reference value is written to the rewritable ROM 86B (see FIG. 11) in the integrated circuit element 86 (Step 3 for R). This operation is repeated for each color LED. In this case, in order to calculate the optical sensor reference value, a correlation between the output of the optical sensor 85 in the tile adjusting device 90 and the output of the optical sensor 85 when actually mounted on the liquid crystal device is previously obtained.

  By performing the above adjustment by inserting the diffusion plate 91, a value close to the output value of the optical sensor 85 when incorporated in the liquid crystal display device can be obtained, and the above calculation can be omitted depending on the conditions (the coefficient is 1). However, it is possible to perform the above adjustment even when the diffusion plate 91 is removed.

(Other possible embodiments)
In the above embodiment, one tile is composed of one base substrate and other components. However, any tile may be used as long as it can be handled as one unit. Therefore, one tile may be one in which, for example, another substrate is attached to the back surface of the substrate, and an integrated circuit or the like is disposed there.

  In addition, for example, when considering one tile having a configuration in which four tiles in the above embodiment are combined in the vertical and horizontal directions, four in total, there are four sets of optical sensors that are not arranged in the center. In particular, this embodiment is not different from the above embodiment.

  Moreover, in the above embodiment, the temperature sensor is not used. However, the wavelength of the LED chip, particularly the red LED chip, varies depending on the temperature, and the luminance considering the visual sensitivity may not be constant if the light intensity is simply constant. In order to correct this point, a temperature sensor may be used to correct the LED drive output based on the detected value.

  In the above embodiments, a rewritable ROM is used as a memory. However, a once writable ROM, a flash memory, a battery-backed RAM, or the like may be used.

Moreover, in the above embodiment, although the case where an optical sensor is used in all the tiles is described, the optical sensor may be mounted on only some tiles.
The invention according to the present embodiment is a method for adjusting a backlight device including a plurality of substrates each including a light emitting element, an optical sensor, and a memory means, wherein the light emitting element is driven for each of the substrates, and the light emitting element The first step of detecting the amount of emitted light by an external light sensor substantially common to the respective substrates, and the second step of calculating a reference value of the expected optical sensor output from the output of the optical sensor at that time And a third step of storing a reference value of the optical sensor output in the memory means.
According to the above invention, it is possible to provide a method for adjusting a substrate that can be incorporated into a backlight device as it is.
In the invention according to this embodiment, the light emitting element includes a plurality of light emitting elements having different light emission colors, and the light emitting element of one color is driven for each of the substrates, and light emission of the light emitting element of the one color is performed. A first step of detecting a quantity by a substantially common external light sensor; a second step of calculating a reference value of an optical sensor output expected from the output of the optical sensor at that time; and the optical sensor output Preferably, the backlight device adjustment method is characterized in that a series of steps including a third step of storing the reference value in the memory means is performed for the light emitting elements of the respective colors.
In the invention according to the present embodiment, the fourth step of driving the light emitting element and detecting information on the variation in the substrate of the brightness or chromaticity in the substrate by the external light sensor, and the substrate of the light emitting element Preferably, the backlight device adjustment method includes a fifth step of storing information on internal variation in the memory means.
In the invention according to the reference of the present invention, the backlight device adjustment method is preferably characterized in that the light emitting element is a light emitting element group.
In the invention according to this embodiment, after performing the fourth step and the fifth step, the first step, the second step, and the third step are performed. It is preferable that this adjustment method.
In the invention according to the present embodiment, the backlight device adjustment method is preferably characterized in that the external light sensor is an external light sensor that detects luminance or chromaticity as an image.
The invention according to this embodiment is preferably a method for adjusting a backlight device, wherein at least the third step is performed by installing a diffusion plate between the substrate and the external light sensor. .

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

It is the schematic diagram which looked at the liquid crystal display device of Embodiment 1 from the back surface. 3 is a schematic diagram of tiles in the backlight device of Embodiment 1. FIG. 3 is a cross-sectional view of a tile in the backlight device of Embodiment 1. FIG. 3 is an enlarged cross-sectional view of a tile in the backlight device according to Embodiment 1. FIG. FIG. 3 is a schematic diagram showing a signal flow in the first embodiment. 3 is a tile adjustment device in the backlight device according to the first embodiment. FIG. 6 is a front and back view of tiles in the backlight device of the second embodiment. 6 is a tile adjustment device in the backlight device according to the second embodiment. FIG. 10 is a cross-sectional view of a tile in the backlight device according to the third embodiment. 6 is an enlarged cross-sectional view of a tile in the backlight device of Embodiment 3. FIG. 6 is a schematic surface view of a tile in a backlight device according to Embodiment 3. FIG. 6 is a tile adjustment device in the backlight device according to the third embodiment. This is a liquid crystal display device using a conventional backlight device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Photosensor 3 LED arrangement | positioning area | region 4 LED chip 5 Gold wire 10, 10Z Integrated circuit element 10A A / D converter 10B Rewritable ROM
10C LED drive circuit 10D LED control circuit 11 Microcomputer 12 Tile 12A Base substrate 13 Connector 14 Heat sink 15 Transparent sealing resin 16 Cable 17 Through hole 18 Wiring 20 Chassis 21 High reflection member 22 Diffusion plate 23 Liquid crystal panel 24 Control board

Claims (22)

A backlight device comprising a plurality of light emitting elements, a plurality of substrates provided with optical sensors and memory means, and a drive circuit for driving the light emitting elements,
The plurality of substrates are arranged in the vertical and horizontal directions, respectively.
The optical sensor is disposed at substantially the center of the surface of each substrate on which the light emitting element is disposed, and detects light emitted from the light emitting element in each substrate and light emitted from the light emitting element in the adjacent substrate,
In the memory means of each substrate, information corresponding to an output value of the photosensor in a condition in which the light emitting element emits light having a predetermined luminance or chromaticity is stored .
The output of the photosensor is standardized based on the information stored in the corresponding memory means, so that the output of the standardized photosensor matches the set value of luminance or chromaticity of the backlight device. A control circuit for generating a control signal for the drive circuit;
The control circuit performs feedback control based on the control signal in each substrate,
The backlight device , wherein the drive circuit drives the light emitting element under the control of the control circuit .   The backlight device according to claim 1, wherein each substrate includes a drive circuit that drives a light emitting element of each substrate. Wherein the control circuit, a backlight device according to claim 1 or 2, characterized in that it is installed outside the substrate. 4. The backlight device according to claim 3 , wherein the control circuit generates a time-division control signal for each of the substrates. Wherein the control circuit comprises a plurality of control circuits, backlight device, wherein the first term any of claims 1 to 4, each control circuit is characterized in that it is installed in said each substrate. The light emitting element, a blue light emitting device, backlight device according to claim 1, characterized in that it comprises a green light emitting element and the red light emitting element in any one of 5. The backlight device according to claim 6 , wherein at least one of the light emitting elements of each color includes an LED. The said optical sensor is equipped with the optical sensor which detects blue light, the optical sensor which detects green light, and the optical sensor which detects red light, The any one of Claim 1 to 7 characterized by the above-mentioned. Backlight device. It said photosensor is a backlight device according to any one of claims 1 to 7, characterized in that to detect the respective colors of light of the light emitting element, respectively by driving by time division the light emitting element. Wherein the memory means, of claims 1 to 9, characterized in that the information light emitting element in the substrate corresponds to the output value of the light sensor in the condition that emits light of a predetermined color temperature is stored The backlight device according to any one of the above. Wherein the memory means, the claim 6, characterized in that the information of each color of light emitting elements in the substrate corresponds to the output value of the light sensor in each condition to emit light of a predetermined luminance is stored 9 The backlight device according to any one of the above. Wherein the memory means, according to any one of claims 1 to 11, characterized in that the information corresponding to the substrate variations in luminance or chromaticity of the light emitting element in the substrate is stored back Light equipment. The backlight device according to claim 12 , wherein the light emitting elements are made of a light emitting element group. The backlight device according to claim 13 , wherein the light emitting element group includes the light emitting elements connected in series. Wherein the memory means, from claim 12, characterized in that the information each of the light emitting element corresponding to the driving condition of the light emitting element in conditions which emits light of a predetermined luminance or chromaticity is stored 14 The backlight device according to any one of the above. Said memory means
A first memory in which information corresponding to an output value of the photosensor in a condition in which the light emitting element in the substrate emits light having a predetermined luminance or chromaticity is stored;
16. The backlight device according to claim 12, further comprising: a second memory in which information corresponding to in-substrate variation of the light emitting elements in the substrate is stored. Said light emitting element and the light sensor is placed on the surface of the substrate, a back light device according to any one of claims 1 to 16, characterized in that said memory means on the rear surface of the substrate is provided . The backlight device according to any one of claims 1 to 17, wherein the memory means is incorporated in the drive circuit and the integrated integrated circuit device. The backlight device according to any one of claims 1 to 18, characterized in that said memory means is a writable memory or rewritable memory. The backlight device according to any one of claims 1 to 19 ,
A display device comprising a non-self-luminous image display panel that displays an image by controlling a transmission state of light from the backlight device. 21. The display device according to claim 20 , wherein in the backlight device, the number of substrates arranged in the horizontal direction is larger than the number of substrates arranged in the vertical direction. A driving method of a backlight device including a plurality of light emitting elements, a plurality of substrates provided with optical sensors and memory means, a driving circuit, and a control circuit,
The plurality of substrates are arranged in the vertical and horizontal directions, respectively.
The optical sensor is disposed at substantially the center of the surface of the substrate on which the light emitting element is disposed;
The memory means stores information corresponding to the output value of the photosensor under the condition that the light emitting element provided on the substrate emits light of a predetermined luminance or chromaticity,
The drive circuit driving the light emitting element;
The optical sensor detecting light emitted from the light emitting elements in each of the substrates and light emitted from the light emitting elements in the adjacent substrates;
The control circuit standardizes the output of the photosensor using information stored in the memory means, so that the output of the standardized photosensor with respect to the drive circuit has a set luminance or chromaticity. the driving method of the backlight device is transmitted to the drive circuit generates a Do control signal, and having the steps of: performing a feedback control based on the control signal in said each substrate.

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