JP2011222375A - Backlight for liquid crystal display - Google Patents

Abstract

In a liquid crystal display device having an edge type backlight, when a fast moving image is displayed, the moving image resolution is not sufficient, and thus motion blur occurs in the image.
In a liquid crystal display device having an edge-type backlight, in addition to the light emitting diode groups 1 disposed at the upper and lower portions in the longitudinal direction of the liquid crystal display panel 3, the liquid crystal display panel 3 is also provided at a substantially central portion in the lateral direction. By disposing the light emitting diode group 1, degradation of moving image resolution due to crosstalk is suppressed.
[Selection] Figure 1

Description

  The present invention relates to a liquid crystal display device provided with an edge-type LED backlight with improved moving image display performance.

As a backlight of a liquid crystal display device, many backlights using light emitting diodes (LEDs) that are superior in terms of power consumption as compared with cold cathode tube lamps (CCFL) are disclosed. In addition, among conventional liquid crystal display devices using LEDs as a backlight, in addition to the direct type in which a backlight is arranged behind the screen, a light guide provided at the back of the screen to realize a thinner liquid crystal display device. Many edge-type liquid crystal display devices in which a backlight is arranged on substantially the same plane as the light plate are also disclosed. For example, Patent Document 1 discloses a backlight arranged in the longitudinal direction of the display screen, and Patent Document 2 discloses a backlight arranged in the short direction.

JP 2009-199926 A JP 2001-92370 A

However, the display device described above has the following problems. In other words, in a liquid crystal display device having an edge-type backlight, in order to eliminate the afterimage feeling that occurs when displaying a scene with fast movement, the light source is not used as a constant light, but at the optimum phase according to the timing of the video writing signal. Adoption of backlight scanning for controlling the blinking of the backlight is in progress. In the liquid crystal display device in which the backlight is arranged adjacent to the longitudinal direction of the liquid crystal display panel as shown in FIG. 6, the light emitting diode group arranged in the upper part is turned on for a certain period and then turned off within one frame period. Similarly, the light emitting diode group disposed in the lower part is also turned on after being turned on for a certain period, and a phase difference is provided in the lighting of the upper and lower light emitting diode groups. However, when driven by such a backlight scan, leakage light from other backlights that are turned on also enters an area where a part of the backlight is to be extinguished to display black, and crosstalk occurs. In a liquid crystal display device having an edge-type backlight in which light sources are arranged at the upper and lower portions, the lighting phase difference between the upper and lower light sources is 180 degrees, so that the influence of crosstalk is large. In particular, when displaying a fast moving image, the moving image resolution of the image displayed in the central area of the screen is greatly degraded.

On the other hand, in the liquid crystal display device in which the backlight is disposed adjacent to the short side direction of the liquid crystal display panel as shown in FIG. 7, by driving by providing a plurality of light emitting diode groups having different lighting phase differences, Since the phase difference of the light source can be 180 degrees or less, the influence of crosstalk can be reduced. However, since it is necessary to arrange all the light emitting diode groups in a narrow width in the short direction of the panel, there is a problem that it is difficult to ensure sufficient luminance. In addition, in order to ensure sufficient luminance, placing a large number of light emitting diodes in a short width or increasing the luminance of individual light emitting diodes will lead to an increase in temperature, and the luminous efficiency of the light emitting diodes will deteriorate. However, there is also a problem of causing a decrease in luminance.

Therefore, in the present invention, in a liquid crystal display device having an edge-type backlight, in addition to the light emitting diode groups arranged at the upper and lower portions in the longitudinal direction of the liquid crystal display panel, light is emitted also at the substantially central portion in the short direction of the liquid crystal display panel. An object of the present invention is to provide a display device and a display device driving method in which degradation of moving image resolution due to crosstalk is suppressed by disposing a diode group.

In order to solve the above-described problems, a liquid crystal display device according to the present invention includes a liquid crystal display panel, a light guide plate disposed on a back surface of the liquid crystal display panel, and an upper edge in a longitudinal direction of the light guide plate. A first light emitting diode group disposed; a second light emitting diode group disposed adjacent to a lower edge in the longitudinal direction of the light guide plate; and a substantially central portion of a side of the light guide plate in the short direction. And a third light emitting diode group disposed adjacent to each other.

With the configuration described above, in the present invention, in the liquid crystal display device having an edge-type backlight, not only the first and second light emitting diode groups are disposed in the upper and lower portions in the longitudinal direction of the light guide plate, but also the short length of the light guide plate. By disposing the third light emitting diode group at the substantially central portion in the hand direction, the phase difference of lighting of the backlight can be reduced, so that degradation of moving image resolution due to crosstalk can be suppressed. Further, by limiting the group of light emitting diodes arranged in the short direction of the light guide plate to the substantially central portion of the liquid crystal display panel, luminance reduction due to temperature rise is prevented, and further economic efficiency is realized.

(A) Front view and (b) Side view showing the configuration of the liquid crystal display device according to Embodiment 1 of the present invention. 1 is a block diagram showing a configuration of a liquid crystal display device in Embodiment 1 of the present invention. Timing chart of writing video signal to pixel array and driving waveform of light emitting diode group in Embodiment 1 of the present invention The front view which shows the structure of the backlight part of the liquid crystal display device in Embodiment 2 of this invention. FIG. 9 is a block diagram showing a configuration of a liquid crystal display device according to Embodiment 3 of the present invention. Configuration diagram showing the configuration of a conventional liquid crystal display device Configuration diagram showing the configuration of a conventional liquid crystal display device

(Embodiment 1)
The present invention will be described with reference to FIGS. Note that the liquid crystal display device and the driving method of the liquid crystal display device described in this embodiment are just examples, and the present invention is not limited thereto.

First, each configuration of the display device of the present invention will be described in detail with reference to (a) front view and (b) side view of the display device of the present invention shown in FIG.

The liquid crystal display device of the present invention is adjacent to the liquid crystal display panel 3 for displaying the input video, the light guide plate 2 installed on the back surface of the liquid crystal display panel 3, the light guide plate 2, and the upper portion in the longitudinal direction. The first light emitting diode group 1a disposed in the same direction, the second light emitting diode group 1b disposed adjacent to the lower portion in the longitudinal direction, and disposed only adjacent to the substantially central portion of the side in the short direction. The third light emitting diode group 1c is configured. Note that the first to third light emitting diode groups 1 are simply referred to as the light emitting diode groups 1 when it is not necessary to distinguish them. Also, the upper and lower parts are distinguished from each other in that the side of the pixel array in which image writing to the liquid crystal display panel 3 starts is the upper part, the end side where writing is finished is the lower part, and the upper and lower parts of the light guide plate 2 are also in the liquid crystal display panel 3. Corresponding to

Light from the light emitting diode group 1 is guided by the light guide plate 2 and converted into surface light emission, and irradiates the screen 5 of the liquid crystal display panel 3. That is, the first light emitting diode group 1a illuminates a substantially upper part of the screen 5 of the liquid crystal display panel 3, the second light emitting diode group 1c illuminates a substantially lower part of the screen 5 of the liquid crystal display panel 3, and the third The light emitting diode group 1 b illuminates only the substantially central portion of the screen 5 of the liquid crystal display panel 3.

As described above, the screen 5 of the liquid crystal display panel 3 is conceptually divided into a substantially central portion in addition to a substantially upper portion and a substantially lower portion, but is not physically separated. In addition, the upper portion, the lower portion, and the substantially central portion of the screen 5 of the liquid crystal display panel 3 include a case where they overlap each other.

Next, a specific driving method of the display device having the above configuration will be described with reference to FIGS. Here, FIG. 2 is a block diagram showing a configuration of the liquid crystal display device according to the embodiment of the present invention.

As shown in FIG. 2, the liquid crystal display device according to the present embodiment includes a signal processing unit 6, a signal output unit 7, and a liquid crystal display panel 3, and further includes a duty / phase control unit 8. A light source driving unit 9, a current control unit 10, and an edge light source 11 are provided at the upper part, the middle part, and the lower part, respectively.

The signal processing unit 6 generates a panel vertical synchronizing signal and a writing video signal by performing scaling and necessary signal processing on the input video signal and the synchronizing signal. Then, the signal processing unit outputs these signals as digital signals to the signal output unit. The signal output unit converts the digital signal input from the signal processing unit 6 into, for example, LVDS (Low Voltage Differential Signal), and outputs the signal to the liquid crystal display panel 3. The signal processing unit 6 outputs the panel vertical synchronization signal and the write video signal to the liquid crystal display panel 3 via the signal output unit. The liquid crystal display panel 3 receives the panel vertical synchronization signal and the write video signal from the signal output unit. The liquid crystal display panel 3 is written with video based on these signals.

The signal processing unit 6 generates signals for controlling the upper, middle, and lower light emitting diodes 1 and outputs the signals to the upper, middle, and lower duty / phase control units 8, respectively. This control signal is synchronized with the panel vertical synchronization signal and has the same cycle as the panel vertical synchronization signal.

The duty / phase control unit 8 converts the signal generated by the signal processing unit into an arbitrary duty and phase signal and outputs the signal to the light source driving unit 9 and outputs a luminance signal to the current control unit 10. The light source driving unit 9 generates a light source driving waveform based on the duty and phase signal from the duty / phase control unit 8 and the current control signal from the current control unit 10 and drives the edge light source 11.

FIG. 3 is a timing chart of the writing of the video signal to the pixel array and the driving waveform of the light emitting diode group in the first embodiment of the present invention. The writing of the video to the pixel array by the writing video signal is sequentially performed from the upper part to the middle part and the lower part of the screen 5 of the liquid crystal display panel 3 in one frame period. On the other hand, the current control unit 10 controls to turn on and off the light emitting diode group 1 based on the signal from the duty / phase control unit 8 in association with the video writing timing with respect to the screen 5 of the liquid crystal display panel 3. The light emitting diode group 1 is controlled to be extinguished for a certain period during the period, and a phase difference is provided for lighting of the first, second, and third light emitting diode groups 1, respectively. Under such control, backlight scanning is performed, and the phase difference is reduced in lighting of the backlight, thereby suppressing the degradation of the moving image resolution.

In the present embodiment, the first light-emitting diode group 1a is turned off and the second light-emitting diode group 1a is turned off during a period in which video is written to the write pixel array substantially above the screen 5 of the liquid crystal display panel 3 by the write video signal. And the 3rd light emitting diode group 1 is lighted. Similarly, the third light emitting diode group 1c is extinguished during the period when the video is written to the writing pixel array in the substantially middle part of the screen 5 of the liquid crystal display panel 3 by the writing video signal, and the first and second light emitting diodes are turned off. The light emitting diode group 1 is turned on. Further, the second light emitting diode group 1b is turned off and the first and third light emitting elements are turned off during the period in which the video is written to the writing pixel array substantially below the screen of the liquid crystal display panel 3 by the writing video signal. The diode group 1 is turned on. As a result, the third light emitting diode group is turned on at least in a period after the first light emitting diode is turned off and before the second light emitting diode is turned on. As described above, during the period when the image is written on the screen 5 of the liquid crystal display panel 3, the backlight adjacent to the portion is turned off, and after the image writing is completed, the adjacent backlight is turned on. Thereby, the motion blur of a moving image can be reduced.

(Embodiment 2)
A liquid crystal display device according to this embodiment will be described with reference to FIG. In addition, about the structure which is not newly demonstrated below, it shall be the same as Embodiment 1. FIG.

FIG. 4 is a front view of the configuration of the backlight portion of the liquid crystal display device according to Embodiment 2 of the present invention. In order to irradiate the entire surface 8 of the screen of the liquid crystal display panel 3, the light guide plate 2, the first and second light emitting diode groups 1 disposed adjacent to the upper and lower portions in the longitudinal direction of the light guide plate 2, and the light guide plate 2 It is comprised from the 3rd light emitting diode group 1c arrange | positioned at the approximate center part of the right-and-left side of the transversal direction. In the light guide plate 2, the length ratio of the long side to the short side is B to C. Further, the light guide plate 2 is provided with grooves substantially parallel to the two long sides in FIG. 4A and three in FIG. 4B.

With this groove, the light guide plate 2 is divided into an upper portion of the light guide plate, a middle portion of the light guide plate, and a lower portion of the light guide plate, and the light irradiated to each of the light guide plates 2 is restricted from going back and forth. Therefore, the light from the first light emitting diode group 1a is guided at the upper part of the light guide plate and illuminates substantially the upper part of the liquid crystal display panel 3, and the light from the second light emitting diode group 1b is guided at the lower part of the light guide plate and is liquid crystal. The substantially lower part of the display panel 3 is illuminated, and the light from the third light emitting diode group 1 c is guided by the middle part of the light guide plate to illuminate the substantially middle part of the liquid crystal display panel 3. As shown in FIG. 4B, the light guide plate 2 that guides the light from the third light emitting diode 1c even when three grooves are provided and the light guide plate 2 is divided into four. (5) Combine (6) to make the middle part of the light guide plate. In FIG. 4B, which is the present embodiment, the third light emitting diode is divided into two parts, and a phase difference is provided for each lighting, thereby further reducing the lighting phase difference of each light emitting diode group. Therefore, it is possible to further suppress the degradation of the moving image resolution. In this embodiment, the case where the middle part of the light guide plate is not divided and the case where the light guide plate is divided into two parts are described. However, the present invention is not limited to this, and the number of divisions can be further increased. The video resolution can be improved.

In this embodiment, the light guide plate 2 is divided into the upper part of the light guide plate, the lower part of the light guide plate, and the middle part of the light guide plate by providing the grooves 4, but even if the groove 4 is not provided, for example, dots are formed in the light guide plate 2. By applying the pattern, light emitted from the first to third light emitting diode groups 1 is guided by the respective light guide plates 2, and when the upper, lower and middle portions of the screen 5 of the liquid crystal display panel 3 are irradiated, It has the effect of the invention. Moreover, even if it is other than a groove | channel, when the light-guide plate 2 is divided | segmented similarly to the above by all the processes which restrict | limit the light going back and forth to the adjacent part given to the opposing side surface between the light-guide plates 2 Has the effects of the present invention. Furthermore, although the case where the light guide plate 2 is integrated is illustrated above, even if the light is mutually separated and is restricted from traveling back and forth to the adjacent portion, It has the effect of the invention.

In this embodiment, the length of the side in the short direction of the middle part of the light guide plate (the light guide plate (2) in FIG. 4A and the light guide plates 5 and 6 in FIG. 4B) is integrated. However, the length is substantially the same as the length between both ends of the third light emitting diode group 1c, but is not limited thereto. However, when the area of the middle part of the light guide plate is 1 / A (A is 2 or more) with respect to the whole area of the light guide plate, the length between both ends of the third light emitting diode group 1c is the middle part of the light guide plate. Is preferably 1 / A or more and B / (A × C) or less with respect to the length of the side in the short direction. Since the middle part of the light guide plate is divided or separated by a boundary substantially parallel to the longitudinal direction of the whole light guide plate, the area ratio of the middle part of the light guide plate to the whole light guide plate is the ratio of the middle part of the light guide plate to the side in the short direction of the whole light guide plate. The length ratio of the sides in the short direction is substantially the same. The length between the both ends of the third light emitting diode group 1c is required to be at least the length of the side in the short direction of the middle portion of the light guide plate, so that the minimum 1 / A is defined. On the other hand, since it is sufficient to illuminate the substantially central portion of the screen 5 of the liquid crystal display panel 3 only by the light emission of the third light emitting diode group 1c, the maximum B / (A × C) (= 1 / A × B / C (the aspect ratio of the liquid crystal display panel 3 is B to C)).

For example, in FIG. 4A, the areas of the upper part (1) of the light guide plate, the middle part (2) of the light guide plate, and the lower part (3) of the light guide plate are substantially the same. One third of the total area. That is, the above A is 3. Since the current TV has an aspect ratio of approximately 16 to 9, the length between both ends of the third light-emitting diode group 1c is 1/3 or more of the length of the short side of the entire light guide plate. It is desirable that it is 16/27 or less.

Next, consider from the viewpoint of power consumption. Similarly to the above, when the area of the central portion of the light guide plate is 1 / A (A is 2 or more) with respect to the entire area of the light guide plate, the power consumption of the third light emitting diode group 1c is the first to It is desirable that it is C / (C + (A × B)) or more and 1 / A or less with respect to the power consumption of the entire three light emitting diodes. Since the length between both ends of the third light emitting diode group 1c is at least the length of the side in the short direction of the middle part of the light guide plate, it is the minimum C / (C + (A × B)) (= (C / A) / ((C / A) + B) (the aspect ratio of the liquid crystal display panel 3 is B to C)). On the other hand, since it is sufficient to illuminate the substantially central portion of the screen 5 of the liquid crystal display panel 3 by the light emission of the third light emitting diode group 1c alone, 1 / A which is the maximum area ratio is defined.

For example, in FIG. 4B, the areas of the light guide plates (4) to (7) are substantially the same, and the area of the middle portion of the light guide plate (integrated shape of the light guide plates (5) and (6)) is the same as that of the entire light guide plate. One half of the area. That is, the above A is 2. Since the current liquid crystal panel has an aspect ratio of 16: 9, the power consumption of the third light emitting diode 1c is 9/41 or more and 1/2 or less of the power consumption of the entire light emitting diode 1. Is desirable.

(Embodiment 3)
A liquid crystal display device according to this embodiment will be described with reference to FIG. In addition, about the structure which is not newly demonstrated below, it shall be the same as the above-mentioned embodiment.

FIG. 5 is a block diagram showing the configuration of the liquid crystal display device. The configuration of FIG. 5 is almost the same as that of FIG. 2 shown in the first embodiment, but the configuration of the video discrimination unit 12 is added to the signal processing unit 6. The video discriminating unit 12 discriminates the feature of the video, and when the video discriminating unit 12 determines that the feature amount of the video signal of the image is larger than a predetermined threshold, the current control unit 10 performs the third light emission. Control to decide to drive the diode 1c is performed.

Examples of the feature amount of the image determined by the video determination unit 12 include an image motion amount (referred to as a difference between input video signals of a plurality of frames) and an image parallax amount for displaying a 3D image. It is not limited to. Hereinafter, a case where the feature amount of the image determined by the video determination unit 12 is the amount of motion of the image will be described.

In general, the degradation of video resolution due to crosstalk is more noticeable when the projected image moves more intensely (the amount of motion of the image is larger), and the more the image is closer to a still image (the amount of motion of the image is smaller), It doesn't stand out. Therefore, when the feature amount of the image signal of the image determined by the image determination unit 12 is set as the amount of motion of the image, and it is determined that the determined amount of motion of the image is larger than a predetermined threshold value, the current control unit 10 decides to drive the third light emitting diode 1c. By such control, it is possible to suppress degradation of the moving image resolution due to crosstalk. On the other hand, when the amount of motion of the image is less than a predetermined threshold value set in advance, that is, when the image is close to a still image, only the first and second light emitting diode groups 1 are driven without driving the third light emitting diode 1c. To control. With this control, the burden on the third light emitting diode group 1c can be reduced.

Here, an example of a method for determining the amount of motion of an image by the video determination unit 12 will be described below. The video discriminating unit 12 calculates a difference between motion vectors of a frame memory that records one frame of input video input, a video output from the frame memory, and a currently input video for each region. And a summing means for summing up the difference of motion vectors calculated by the difference calculating means for one frame. The larger the motion vector value summed up by this summing means, the stronger the motion of the moving image (the larger the amount of motion), and the smaller the motion vector value, the closer to the still image (the smaller the amount of motion). Become.

Note that the method for determining the amount of motion is not limited to this, and it is possible to adopt a configuration such as a method for determining based on the frequency of the image, a density histogram, a frequency histogram, or the like.

The above control means is a control method according to the amount of movement of the entire image displayed in one frame, but other control methods will be described.

The screen 5 of the liquid crystal display panel 3 is conceptually divided into a plurality of regions, and the image discriminating unit 12 discriminates the feature amount of the image in one or a plurality of specific regions, and the video discriminating unit 12 When it is determined that the feature amount of the video signal of the image in the region is larger than the predetermined threshold, the current control unit 10 determines to drive the third light emitting diode group 1c.

In general, the degradation of moving image resolution due to crosstalk becomes more conspicuous as an image with intense movement appears in the center of the screen 5, and becomes less noticeable as the image moves with more movement, away from the center. Therefore, the central portion of the screen 5 is set as a specific region, and the video discriminating unit is set so as to discriminate the motion amount that is the feature amount of the image in the region. If it does so, the image | video discrimination | determination part 12 will discriminate | determine the motion amount of the image projected on the center part of the screen 5, and when it exceeds the preset threshold value, it will determine to drive the 3rd light emitting diode 1c. By such control, it is possible to suppress degradation of the moving image resolution due to crosstalk. On the other hand, when the amount of motion of the image is less than a predetermined threshold value set in advance, that is, when the image is close to a still image, only the first and second light emitting diode groups 1 are driven without driving the third light emitting diode 1c. To control. By performing such control, it is possible to reduce the burden by driving the third light emitting diode 1c only in the case of an image in which moving image blur is conspicuous.

In the present invention, in a liquid crystal display device having an edge type backlight, a third liquid crystal is disposed adjacent to only the substantially central portion of the side in the short direction of the light guide plate 2 disposed on the back surface of the liquid crystal display panel 3. By providing the light emitting diode group 1c, it is useful for a display device and a display device driving method in which deterioration of moving image resolution due to crosstalk is suppressed.

DESCRIPTION OF SYMBOLS 1 Light emitting diode 1a 1st light emitting diode 1b 2nd light emitting diode 1c 3rd light emitting diode 2 Light guide plate 3 Liquid crystal display panel 4 Groove 5 Screen 6 Signal processing part 7 Signal output part 8 Duty / phase control part 9 Light source drive part 10 current control unit 11 edge light source 12 image discriminating unit

Claims (15)

A liquid crystal display panel;
A light guide plate disposed on the back surface of the liquid crystal display panel;
A first light emitting diode group disposed adjacent to the upper edge in the longitudinal direction of the light guide plate;
A second group of light emitting diodes disposed adjacent to the lower edge of the light guide plate in the longitudinal direction;
A liquid crystal display device comprising: a third light emitting diode group disposed adjacent to substantially the central portion of the side in the short direction of the light guide plate. A liquid crystal display panel;
A light guide plate disposed on the back surface of the liquid crystal display panel;
A first light emitting diode group that is arranged adjacent to the upper edge in the longitudinal direction of the light guide plate and illuminates a substantially upper part of the screen of the liquid crystal display panel;
A second light emitting diode group disposed adjacent to the lower edge in the longitudinal direction of the light guide plate and illuminating a substantially lower part of the screen of the liquid crystal display panel;
A liquid crystal display device comprising a third group of light emitting diodes arranged adjacent to the lateral edge of the light guide plate and illuminating only the substantially central portion of the screen of the liquid crystal display panel. The liquid crystal display device includes a current control unit that controls a current to the light emitting diode group,
The current controller is
3. The liquid crystal according to claim 1, wherein a control is performed to turn off the light emitting diode group for a certain period in one frame period, and a phase difference is provided for lighting of the first, second and third light emitting diode groups. Display device. The liquid crystal display device includes a current control unit that controls a current to the light emitting diode group,
The current controller is
4. The liquid crystal display device according to claim 1, wherein control is performed to turn on the third light emitting diode group at least during a period after the first light emitting diode is turned off and before the second light emitting diode is turned on. The light guide plate is
An upper portion of a light guide plate that guides light of the first light emitting diode group;
A lower portion of a light guide plate that guides light of the second light emitting diode group;
5. The liquid crystal display device according to claim 1, further comprising a middle portion of a light guide plate that guides light of the third light emitting diode group. The light guide plate is
By the boundary substantially parallel to the longitudinal direction of the light guide plate,
The light guide plate is divided into an upper portion, a middle portion of the light guide plate, and a lower portion of the light guide plate, and light passes back and forth between adjacent portions of the side surfaces facing the middle portion of the light guide plate, the upper portion of the light guide plate, and the lower portion of the light guide plate. 6. The liquid crystal display device according to claim 5, wherein a process for limiting the above is performed. 6. The liquid crystal display according to claim 5, wherein the light guide plate is divided into an upper portion of the light guide plate, a middle portion of the light guide plate, and a lower portion of the light guide plate by a groove substantially parallel to a longitudinal direction of the light guide plate. apparatus. 6. The liquid crystal display according to claim 5, wherein the light guide plate is separated into the upper portion of the light guide plate, the middle portion of the light guide plate, and the lower portion of the light guide plate by substantially parallel sides in the longitudinal direction of the light guide plate. apparatus. The area of the middle part of the light guide plate is 1 / A (A is 2 or more) with respect to the whole area of the light guide plate, and the ratio of the length of the side of the light guide plate in the longitudinal direction to the short side is B to C. The power consumption of the third light emitting diode group is
9. The liquid crystal display device according to claim 5, wherein the total power consumption of the first to third light-emitting diodes is C / (C + (A × B)) or more and 1 / A or less. The area of the central portion of the light guide plate is 1 / A (A is 2 or more) with respect to the entire area of the light guide plate,
When the ratio of the length of the light guide plate in the lengthwise direction to the widthwise direction is B to C, the length between both ends of the third light emitting diode group is relative to the length of the light guide plate in the widthwise direction. 9. The liquid crystal display device according to claim 5, wherein the liquid crystal display device is 1 / A or more and B / (A × C) or less. A liquid crystal display panel;
A light guide plate disposed on the back surface of the liquid crystal display panel;
A first light emitting diode group disposed adjacent to the upper edge in the longitudinal direction of the light guide plate;
A second group of light emitting diodes disposed adjacent to the lower edge of the light guide plate in the longitudinal direction;
A liquid crystal display device comprising a third group of light emitting diodes arranged adjacent to the lateral edge of the light guide plate,
The light guide plate is divided into a light guide plate upper portion including a side in the upper longitudinal direction of the light guide plate, a light guide plate lower portion including the side in the lower longitudinal direction, and a middle portion of the light guide plate including the remainder, by a boundary substantially parallel to the longitudinal direction. Separated,
The length of the short method in the middle of the light guide plate and the length between both ends of the third light emitting diode group are as follows:
A liquid crystal display device characterized by being substantially the same. A signal processing unit for processing a video signal;
The liquid crystal display device including a current control unit for controlling a current to the light emitting diode group,
The signal processing unit has a video discriminating unit for discriminating characteristics of an image written on the liquid crystal display panel,
The current control unit determines to drive the third light emitting diode group when the video determination unit determines that the feature amount of the video signal of the image is larger than a predetermined threshold value. Item 5. A liquid crystal display device according to item 1 or 4. The liquid crystal display device including a signal processing unit that processes a video signal and a current control unit that controls a current to the light emitting diode group,
The signal processing unit includes a video discriminating unit that discriminates the characteristics of an image for each area written on the liquid crystal display panel,
When the video discriminating unit discriminates that the feature amount of the video signal of the image of one or more specific areas is larger than a predetermined threshold,
The liquid crystal display device according to claim 1, wherein the current control unit determines to drive the third light emitting diode group. 14. The liquid crystal display device according to claim 12, wherein the feature amount of the image is a motion amount of the image to be written. 14. The liquid crystal display device according to claim 12, wherein the feature amount of the image is a luminance of the image to be written.