JP2012009147A - Led backlight device and display device with led backlight device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED backlight device which can prevent collapse of a white balance while minimizing decrease in luminance.SOLUTION: The backlight device comprises: a plurality of white LEDs (first white LEDs 10A); a plurality of hue correction LEDs (second white LEDs 10B); and a light control unit 8 which controls relationship between the degree of light control of the white LEDs and the degree of light control of the hue correction LEDs depending on the integrated data of secular change correlated with change in hue of the white LEDs caused by secular change.

Description

  The present invention relates to an LED backlight device using a plurality of LEDs (Light Emitting Diodes) as a light source and a display device including the LED backlight device.

  A display device (for example, a transmissive liquid crystal display device) including a display panel and a backlight device that illuminates the display panel from the back surface of the display panel is a display device having a relatively large screen size such as a television receiver. In this case, a configuration using a backlight device using a fluorescent tube such as CCFL (Cold Cathode Fluorescent Lamp) or EEFL (External Electrode Fluorescent Lamp) as a light source is common.

  However, in recent years, since the price of white LEDs has been reduced and the luminous efficiency has been improved, from the viewpoint of environmental problems and the like, a display device that uses an LED that consumes less power than a fluorescent tube as the light source of the backlight device, that is, A display device equipped with an LED backlight device is in the spotlight. Further, even in display devices having a relatively large screen size, the adoption of LED backlight devices is progressing.

Japanese Patent No. 4422190

  For example, in the case of a television receiver, it is not so rare to be used for a long period of 10 years or more. In such long-term use, deterioration due to aging can be a problem.

  In a backlight device using a fluorescent tube as a light source, the luminance deteriorates due to secular change, but the hue hardly changes. Therefore, the white balance was not lost due to secular change.

  On the other hand, in an LED backlight device using an LED as a light source, luminance deterioration and hue change occur due to aging of the LED itself. In the case of a white LED, the hue change due to secular change is most severely degraded by green, followed by severe degradation of red. In general white LEDs, in terms of chromaticity values of x and y, after about 30000 hours, x deteriorates by about 0.01 to 0.02, and y deteriorates by about 0.02 to 0.04. The white balance is lost due to deterioration. Of course, some LEDs have a small hue change due to aging, but such LEDs are expensive and are not in a situation where they can be used for general consumer equipment such as a television receiver.

  Therefore, in a display device (see, for example, Patent Document 1) that includes an LED backlight device and can change the hue by correcting the signal value of the input video signal, match the expected decrease in chromaticity x, y due to secular change. Thus, it is conceivable to perform the correction that decreases the blue component signal value of the input video signal as the usage time increases, thereby suppressing white balance collapse due to secular change. A schematic configuration of a display device capable of realizing such a method is shown in FIG. Note that a plurality of white LEDs are arranged in a line in the light source section in FIG.

  However, in such a method, in addition to the LED itself decreasing in luminance with aging, the blue component signal value of the input video signal is decreased as the usage time increases, so that the luminance decrease is further increased. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an LED backlight device and a display device including the LED backlight device that can suppress the collapse of white balance due to secular change while minimizing a decrease in luminance. .

  In order to achieve the above object, an LED backlight device according to the present invention comprises a plurality of white LEDs and a plurality of white LEDs and hue correction LEDs having different emission colors, and correlates with a hue change of the white LEDs due to secular change. A configuration (first configuration) is provided that includes a dimming control unit that controls the relationship between the dimming degree of the white LED and the dimming degree of the hue correction LED according to accumulated aging data. In this specification, when two types of LEDs emit white light from each other and their color temperatures are different from each other, it is defined that the emission colors of the two types of LEDs are different from each other.

  In the LED backlight device of the first configuration, the hue correction LED may be an LED, a yellow LED, a green LED, or a yellow-green LED that emits yellowish white light having a color temperature lower than that of the white. A certain configuration (second configuration) may be adopted.

  In the LED backlight device having the first or second configuration, the dimming control unit reduces a difference between the dimming degree of the white LED and the dimming degree of the hue correction LED as the secular change proceeds. As such, a configuration (third configuration) may be employed in which the relationship between the dimming degree of the white LED and the dimming degree of the hue correction LED is controlled.

  In the LED backlight device having the third configuration, the hue correction LED may have a configuration (fourth configuration) having higher luminance than the white LED.

  In the LED backlight device having the first or second configuration, a plurality of the white LEDs are not located near the hue correction LED and a neighboring white LED located near the hue correction LED. It is classified as a neighboring white LED, and the dimming control unit reduces the difference between the dimming degree of the non-neighboring white LED and the dimming degree of the hue correction LED as the secular change proceeds, and the non-neighboring white LED The configuration (fifth configuration) is configured to control the relationship between the dimming degree of the white LED and the dimming degree of the hue correction LED so that the difference between the dimming degree of the white LED and the dimming degree of the neighboring LED becomes large. Good.

  In order to achieve the above object, a display device according to the present invention includes a display panel and the LED backlight device having any one of the first to fifth configurations that illuminates the display panel from the back surface of the display panel. The configuration.

  According to the present invention, the LED backlight device includes a plurality of white LEDs and a plurality of hue correction LEDs having different emission colors from the white LEDs, and the accumulated secular change data correlated with the hue change of the white LEDs due to aging. Accordingly, a dimming control unit that controls the relationship between the dimming degree of the white LED and the dimming degree of the hue correction LED is provided. According to such a configuration, the hue can be corrected without reducing the blue component signal value of the input video signal as the usage time increases, and therefore, the cause of the decrease in the luminance of the LED is only the luminance deterioration due to secular change. Therefore, it is possible to suppress the collapse of white balance due to secular change while minimizing the decrease in luminance.

It is a figure which shows schematic structure of the display apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the example of a waveform of the light control signal in 1st Embodiment of this invention. It is a figure which shows schematic structure of the display apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the example of a waveform of the light control signal in 2nd Embodiment of this invention. It is a figure which shows the outline | summary of the modification of the display apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the outline | summary of the other modification of the display apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows schematic structure of the display apparatus which implements correction | amendment which reduces the blue component signal value of an input video signal with the increase in use time.

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

<First Embodiment>
FIG. 1 shows a schematic configuration of a display device according to the first embodiment of the present invention. The display device according to the first embodiment of the present invention shown in FIG. 1 includes a video processing unit 1, a liquid crystal display control unit 2, a signal driver 3, a scanning driver 4, a liquid crystal display panel 5, and an LED backlight device. 6 is a liquid crystal display device. The LED backlight device 6 is an edge-type backlight device including an aging accumulation unit 7, a dimming control unit 8, an LED driver 9, a light source unit 10, and a light guide plate 11.

  The video processing unit 1 performs various processing on video signals generated inside the liquid crystal display device (for example, video signals generated by a tuner unit (not shown)) and video signals input from the outside of the liquid crystal display device. After the above processing is performed, the data is output to the liquid crystal display control unit 2. The liquid crystal display control unit 2 controls the signal driver 3 and the scanning driver 4 according to the video signal output from the video processing unit 1. The signal driver 3 supplies data to signal lines (not shown) of the liquid crystal display panel 5 according to the control of the liquid crystal display control unit 2, and the scanning driver 4 operates according to the control of the liquid crystal display control unit 2. Data is supplied to scanning lines (not shown). Thereby, the liquid crystal display panel 5 is driven.

  The light source unit 10 of the LED backlight device 6 includes a plurality of first white LEDs 10A and second white LEDs 10B. The second white LED 10B emits white light with a higher brightness than the first white LED 10A, that is, the brightness when the supply current is the same, higher than that of the first white LED 10A, lower in color temperature than the first white LED 10A, and yellowish. To do. In the present embodiment, the first white LED 10A and the second white LED 10B are periodically arranged in the order of the first white LED 10A, the first white LED 10A, and the second white LED 10B.

  The aging accumulation unit 7 has a built-in timer, measures the accumulated lighting time of the LED backlight device 6, and uses the measured accumulated lighting time of the LED backlight device 6 as aging accumulated data. Output to.

  The dimming control unit 8 sets the on-duty value of the dimming signal for the first white LED, which is a PWM (Pulse Width Modulation) signal, based on the dimming setting value, and from the dimming setting value and the secular change integration unit 7 The on-duty value of the dimming signal for the second white LED, which is a PWM signal, is set based on the transmitted aging integration data, and the dimming signal for the first white LED and the dimming signal for the second white LED are generated. To do.

  Since the second white LED 10B has higher brightness than the first white LED 10A, the on-duty value of the second white LED dimming signal is set smaller than the on-duty value of the first white LED dimming signal. Further, as the secular change progresses, that is, as the integrated lighting time of the LED backlight device 6 increases, the on-duty value of the first white LED dimming signal and the on-duty value of the second white LED dimming signal So that the difference between is small. Thereby, as the secular change progresses, the yellowish white light emitted from the second white LED 10B becomes stronger and the green and red deterioration of the first white LED 10A due to the secular change is compensated. Can be prevented from collapsing. In addition, from the viewpoint of suppressing illumination unevenness of the LED backlight device 6, the first white LED 10A and the second white LED 10B have substantially the same brightness when the integrated lighting time of the LED backlight device 6 is zero. It is desirable to set the on-duty value of the dimming signal for two white LEDs.

  Here, the example of a waveform of the light control signal for 1st white LED and the light control signal for 2nd white LED is shown in FIG. FIG. 2A shows an example of a waveform when the dimming setting value is a value of 50% dimming and the integrated lighting time of the LED backlight device 6 is zero. FIG. 2B shows an example of a waveform when the dimming set value is 80% dimming and the integrated lighting time of the LED backlight device 6 is zero. FIG. 2C shows an example of a waveform when the dimming setting value is a value of 50% dimming and the integrated lighting time of the LED backlight device 6 is 30000 hours. FIG. 2D shows a waveform example in the case where the dimming setting value is 80% dimming value and the lighting integrated time of the LED backlight device 6 is 30000 hours.

  The LED driver 9 is an M channel output drive circuit. Each channel of the LED driver 9 is connected with N first white LEDs 10A or N second white LEDs 10B. The LED driver 9 outputs the first PWM current generated according to the first white LED dimming signal to the channel to which the first white LED 10A is connected, and generates the first PWM current according to the second white LED dimming signal. 2PWM current is output to the channel to which the second white LED 10B is connected.

  With the configuration as described above, the hue can be corrected without decreasing the blue component signal value of the input video signal as the usage time increases, and therefore, the cause of the decrease in the luminance of the LED is only the luminance deterioration due to secular change. Therefore, it is possible to suppress the collapse of white balance due to secular change while minimizing the decrease in luminance.

Second Embodiment
FIG. 3 shows a schematic configuration of a display device according to the second embodiment of the present invention. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. The display device according to the second embodiment of the present invention shown in FIG. 3 removes the LED backlight device 6 from the display device according to the first embodiment of the present invention shown in FIG. 1, and instead uses the LED backlight device 6 ′. Is provided. The LED backlight device 6 ′ is an edge type backlight device including an aging accumulation unit 7, a dimming control unit 8 ′, an LED driver 9 ′, a light source unit 10 ′, and a light guide plate 11.

  The light source unit 10 ′ of the LED backlight device 6 ′ includes a plurality of white LEDs 10 </ b> C and yellow LEDs 10 </ b> D. In this embodiment, the white LEDs 10C are arranged in a line, the yellow LEDs 10D are arranged in a line in the same arrangement direction as the arrangement direction of the white LEDs 10C, and further in the arrangement direction, the white LED 10C, the white LED 10C, the yellow LED 10D, and the white LED 10C in this order. White LED 10C and yellow LED 10D are periodically arranged.

  The secular change integrating unit 7 has a built-in timer, measures the integrated lighting time of the LED backlight device 6 ', and performs dimming control using the measured integrated lighting time of the LED backlight device 6' as aging integrated data. Output to unit 8 '.

  The dimming control unit 8 ′ sets the on-duty value of the white LED dimming signal, which is a PWM signal, based on the dimming setting value, and the aging change integration sent from the dimming setting value and aging integration unit 7. Based on the data, the on-duty value of the dimming signal for yellow LED, which is a PWM signal, and the on-duty value of the dimming signal for white LED near the yellow LED (hereinafter abbreviated as “dimming signal for near white LED”) are set. The white LED dimming signal, the yellow LED dimming signal, and the nearby white LED dimming signal are generated.

  When the lighting integration time of the LED backlight device 6 'is zero, there is no need to correct the hue, so the on-duty value of the yellow LED dimming signal is set to zero. Further, as the secular change progresses, that is, as the lighting integrated time of the LED backlight device 6 ′ increases, the difference between the on-duty value of the white LED dimming signal and the on-duty value of the yellow LED dimming signal To be smaller. Thereby, as the secular change progresses, the yellow light emitted from the yellow LED 10D becomes stronger and compensates for the deterioration of the green and red of the white LED 10C due to the secular change, so that the collapse of the white balance can be suppressed. . Further, from the viewpoint of suppressing illumination unevenness of the LED backlight device 6 ′, the on-duty value of the near white LED dimming signal is decreased according to the increase of the on-duty value of the yellow LED dimming signal. Note that the total luminance of one yellow LED 10D surrounded by a dotted line in FIG. 3 and two white LEDs 10D in the vicinity thereof is substantially the same as the luminance of two white LEDs 10D not surrounded by a dotted line. It is desirable to set the on-duty value of the dimming signal for the nearby white LED.

  Here, FIG. 4 shows waveform examples of the white LED dimming signal, the yellow LED dimming signal, and the near white LED dimming signal. FIG. 4A shows an example of a waveform when the dimming setting value is a value of 50% dimming and the integrated lighting time of the LED backlight device 6 'is zero. FIG. 4B shows an example of a waveform when the dimming setting value is 80% dimming and the integrated lighting time of the LED backlight device 6 'is zero. FIG. 4C shows an example of a waveform when the dimming setting value is a value of 50% dimming, and the lighting integrated time of the LED backlight device 6 'is 30000 hours. FIG. 4D shows an example of a waveform when the dimming setting value is 80% dimming and the LED backlight device 6 ′ has an integrated lighting time of 30000 hours.

  The LED driver 9 'is an M channel output drive circuit. N white LEDs 10C or N yellow LEDs 10D are connected to each channel of the LED driver 9 '. The LED driver 9 ′ outputs the first PWM current generated according to the white LED dimming signal to the channel to which the white LED 10C not surrounded by the dotted line in FIG. 3 is connected, and according to the yellow LED dimming signal. The second PWM current generated in this way is output to the channel to which the yellow LED 10D is connected, and the third PWM current generated according to the nearby white LED dimming signal is connected to the white LED 10C surrounded by the dotted line in FIG. Output to the current channel.

  With the configuration as described above, the hue can be corrected without decreasing the blue component signal value of the input video signal as the usage time increases, and therefore, the cause of the decrease in the luminance of the LED is only the luminance deterioration due to secular change. Therefore, it is possible to suppress the collapse of white balance due to secular change while minimizing the decrease in luminance.

<Others>
As mentioned above, although embodiment which concerns on this invention was described, the range of this invention is not limited to this, A various change can be added and implemented in the range which does not deviate from the main point of invention. Some examples of changes are shown below.

  In the first and second embodiments described above, the light source unit is a single unit, but the light source unit may be composed of a plurality of units. FIG. 5 shows an example of such a configuration (an example in which the number of units of the light source unit is changed from 1 to 4 in the display device according to the first embodiment of the present invention). In FIG. 5, only the light source unit 10 and the light guide plate 11 are illustrated.

  Further, in the display device according to the first embodiment of the present invention, even if the second white LED 10B that emits yellowish white light is replaced with a yellow LED, a green LED, or a yellow-green LED, the luminance reduction is minimized. It is possible to suppress the collapse of the white balance due to secular change while limiting to the limit. However, when the green LED is used, the most severe green degradation among the hue changes due to the secular change of the first white LED 10A can be compensated, but the next most severe red degradation cannot be compensated.

  Similarly, in the display device according to the second embodiment of the present invention, the yellow LED has a color temperature lower than that of the white LED 10C and other white LED, green LED, or yellow-green LED that emits yellowish white light. Even if it is replaced with, white balance collapse due to secular change can be suppressed while minimizing luminance reduction. However, when the green LED is used, the most severe green degradation among the hue changes due to the secular change of the white LED 10C can be compensated, but the next severe red degradation cannot be compensated.

  Further, although the edge type backlight device is used in the first embodiment and the second embodiment described above, a configuration using a direct type backlight device may be used instead. FIG. 6 shows an example of such a configuration (an example in which the edge type backlight device is modified into a direct type backlight device in the display device according to the first embodiment of the present invention). In FIG. 6, only the light source part of the direct type backlight device is illustrated.

  In the first embodiment and the second embodiment described above, the lighting integrated time of the LED backlight device is used as the aging integrated data, but other parameters may be used as the aging integrated data. For example, the correlation with LED hue change due to secular change is weaker than the integrated lighting time of the LED backlight device, but the elapsed time from factory shipment is measured using the clock function, and the measured elapsed time May be integrated with aging.

  Further, in the first embodiment and the second embodiment described above, the backlight device includes the aging accumulation unit, but instead, the aging accumulation unit may be provided outside the backlight device.

  Moreover, it is needless to say that the arrangement of the LEDs shown in the drawings is merely an example, and other arrangements may be adopted.

DESCRIPTION OF SYMBOLS 1 Image processing part 2 Liquid crystal display control part 3 Signal driver 4 Scan driver 5 Liquid crystal display panel 6, 6 'LED backlight apparatus 7 Aging accumulation part 8, 8' Dimming control part 9, 9 'LED driver 10, 10' Light source unit 10A First white LED
10B Second white LED
10C white LED
10D yellow LED
11 Light guide plate

Claims (6)

A plurality of white LEDs and a plurality of hue correction LEDs having different emission colors from the white LEDs,
A dimming control unit that controls the relationship between the dimming degree of the white LED and the dimming degree of the hue correction LED according to the aging integrated data correlated with the hue change of the white LED due to aging. A featured LED backlight device.   2. The LED backlight device according to claim 1, wherein the hue correction LED is an LED, a yellow LED, a green LED, or a yellow-green LED that emits yellowish white light having a color temperature lower than that of the white color. The dimming control unit is
Control the relationship between the dimming degree of the white LED and the dimming degree of the hue correction LED so that the difference between the dimming degree of the white LED and the dimming degree of the hue correction LED decreases as the aging progresses. The LED backlight device according to claim 1, wherein:   The LED backlight device according to claim 3, wherein the hue correction LED has higher luminance than the white LED. A plurality of the white LEDs are classified into a neighboring white LED located in the vicinity of the hue correction LED and a non-neighboring white LED not located in the vicinity of the hue correction LED,
The dimming control unit is
As the secular change progresses, the difference between the dimming degree of the non-neighboring white LED and the dimming degree of the hue correction LED decreases, and the difference between the dimming degree of the non-neighboring white LED and the dimming degree of the neighboring LED increases. The LED backlight device according to claim 1, wherein the LED backlight device controls the relationship between the dimming degree of the white LED and the dimming degree of the hue correction LED.   A display device comprising: a display panel; and the LED backlight device according to claim 1 that illuminates the display panel from a back surface of the display panel.

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