WO2013153974A1 - Liquid crystal display device - Google Patents

Abstract

The purpose of the present invention is to provide a liquid crystal display device that can be manufactured at low cost while improving image quality. The liquid crystal display device comprises: a liquid crystal display panel; a backlight which periodically repeats turning on and off the light to emit the light onto said liquid crystal display panel; a backlight control unit for performing drive control for said backlight; and a panel control unit for scanning said liquid crystal display panel on the basis of an input video signal. Said panel control unit scans said liquid crystal display panel in a drive mode selected from among a first drive mode and a second drive mode. The scan time for one frame in said second drive mode is shorter than the scan time for one frame in said first drive mode, and said second drive mode satisfies the following formula: i) TFM = TSC + TBK, ii) 1/2 TFM ≥ TBK ≥ TBL ≥ TFM × 0.05 Where, TFM is the frame period, TSC is the scan time, TBK is the blanking time, and TBL is the backlight turn-on time.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device.

Conventionally, the occurrence of image blur (decrease in image quality) has been an important problem in liquid crystal display devices. Therefore, an active matrix type liquid crystal display device in which a backlight (light source) scans and emits light may be used in order to minimize deterioration in image quality. On the other hand, there is still a high demand for a low-cost liquid crystal display device, and a liquid crystal display device that is not an active matrix type (simple matrix type liquid crystal display device, for example, a liquid crystal display device having an edge-type backlight with one side incident light) is used. There are many things. Therefore, deterioration of image quality is still an important problem in a simple matrix type liquid crystal display device.

In a simple matrix type liquid crystal display device, the cause of the deterioration in image quality is that the backlight cannot be controlled in a time-sharing manner. That is, in a simple matrix type liquid crystal display device, liquid crystal drawing is performed while sequentially scanning from the upper part to the lower part of the liquid crystal display panel, for example, but a desired image is displayed due to the relationship with the response speed of the liquid crystal display panel. A predetermined amount of time is required until it is done. Accordingly, the entire screen of the liquid crystal display panel cannot be set as an optimum scanning region in one backlight period.

One method for solving the above problem is to drive the liquid crystal display panel at a higher frequency (for example, 240 Hz, 480 Hz, etc.) to increase the number of drawing per second and shorten the scanning time of the liquid crystal display panel. Can be considered. For example, the image display device of Patent Document 1 scans a display panel by selectively using a display panel having a plurality of pixels and two modes (a first drive mode and a second drive mode) having different scanning times. Drive control means for displaying an image corresponding to the input image signal on the display panel by performing control is provided. In the second drive mode, the scanning time is shorter than the scanning time in the first drive mode, and image quality is improved by inserting a black screen between successive frames.

Japanese Patent Publication “JP-A-2011-75668”

However, excessive shortening of the scanning time causes problems such as a decrease in luminance, an increase in the number of parts, and a need for high-performance parts, which increases the cost of the liquid crystal display device. The increase in the cost of the liquid crystal display device is contrary to the object of providing a low-cost liquid crystal display device by adopting a simple matrix type. Therefore, there is a certain limit to shortening the scanning time, and it is difficult to realize an improvement in image quality at low cost only by shortening the scanning time.

In view of the above-described problems, an object of the present invention is to provide a liquid crystal display device that can be manufactured at low cost while improving image quality.

In order to achieve the above object, a liquid crystal display device of the present invention performs a liquid crystal display panel, a backlight that periodically illuminates and extinguishes and irradiates the liquid crystal display panel with light, and performs drive control of the backlight. A backlight control unit, and a panel control unit that scans and drives the liquid crystal display panel based on an input video signal, and the panel control unit is selected from the first drive mode and the second drive mode. The liquid crystal display panel is scan-driven in a different drive mode, the scan time for one frame in the second drive mode is shorter than the scan time for one frame in the first drive mode, and The second drive mode satisfies the following expression. i) TFM = TSC + TBK, ii) 1/2 TFM ≧ TBK ≧ TBL ≧ TFM × 0.05, (TFM: frame period time, TSC: scanning time, TBK: blanking time, TBL: backlight lighting time).

According to the present invention, in the liquid crystal display device having the above configuration, the backlight control unit divides the liquid crystal display panel into a plurality of regions, and the second drive mode is selected as the drive mode of the liquid crystal display panel. In the liquid crystal display panel, it is preferable to perform drive control of the backlight based on the timing of scanning a predetermined area among the plurality of areas.

According to the present invention, in the liquid crystal display device having the above-described configuration, the backlight control unit causes any timing in the backlight lighting time and the timing to scan the predetermined area in the liquid crystal display panel to be the same. Further, it is desirable to perform drive control of the backlight.

In the liquid crystal display device having the above-described configuration, it is preferable that the backlight control unit performs drive control of the backlight based on a response speed of the liquid crystal display panel.

In the liquid crystal display device having the above-described configuration, it is preferable that the backlight control unit performs drive control of the backlight so that the backlight lighting time and the blanking time do not overlap.

In the liquid crystal display device having the above configuration according to the present invention, it is desirable that the predetermined area is an area to which a central portion of the screen of the liquid crystal display panel belongs.

In the liquid crystal display device having the above-described configuration, the present invention further includes a character information position detection circuit that detects presence / absence of character information displayed on the liquid crystal display panel and a display position of the character information, and the predetermined area includes: It is desirable that the number is determined based on the presence / absence of the character information and an area to which the display position of the character information belongs.

In the liquid crystal display device having the above-described configuration, it is preferable that the predetermined area is an area to which a central portion of the screen of the liquid crystal display panel belongs when the character information does not exist.

In the liquid crystal display device having the above-described configuration, it is preferable that when the character information is present, the predetermined region is a region to which the display position of the character information belongs.

According to the present invention, in the liquid crystal display device having the above-described configuration, the character information position detection circuit further detects a display timing of the character information, and there are a plurality of the character information, and each character information The predetermined area when the liquid crystal display panel is displayed in different areas at the same time is preferably an area to which a central portion of the screen of the liquid crystal display panel belongs.

According to the present invention, in the liquid crystal display device having the above-described configuration, the character information position detection circuit further detects a display timing of the character information, and there are a plurality of the character information, and each character information The predetermined area when being displayed in different areas at the same time on the liquid crystal display panel is an area to which the display position of the character information with the highest priority belongs among the plurality of character information displayed in each area. Is desirable.

According to the present invention, in the liquid crystal display device having the above-described configuration, the liquid crystal display panel can selectively display a two-dimensional image or a three-dimensional image, and one frame in the second driving mode in the two-dimensional image display mode. It is desirable that the scanning time for one minute and the scanning time for one frame in the 3D video display mode be the same time.

In the liquid crystal display device having the above-described configuration, the present invention preferably includes an FRC unit that generates an interpolated video for the video signal, converts the frequency of the video signal to an arbitrary frequency, and outputs the frequency.

According to the present invention, TFM (frame period time), TSC (scanning time), and TBK (blanking time) satisfy TFM = TSC + TBK, 1/2 TFM ≧ TBK ≧ TBL ≧ TFM × 0.05, respectively. Further, it is possible to effectively generate image blur in the entire area of the liquid crystal display panel without excessively shortening the scanning time in the second driving mode as compared with the scanning time in the first driving mode (in other words, without increasing the cost). Can be suppressed.

These are block diagrams which show the circuit structure of the liquid crystal display device which concerns on 1st Embodiment of this invention. These are the top views which showed the backlight of the liquid crystal display device by one Embodiment of this invention. These are figures which show the relationship between the scanning time by 1st drive mode in the liquid crystal display device of 1st Embodiment of this invention, frame period time, and backlight lighting time. These are figures which show the relationship between the scanning time by 2nd drive mode in the liquid crystal display device of 1st Embodiment of this invention, frame period time, and backlight lighting time. These are figures which show the response waveform (response speed) of a liquid crystal display panel. These are figures which show the relationship between the scanning time by the 1st drive mode in the liquid crystal display device of the 1st another example of 1st Embodiment of this invention, frame period time, and backlight lighting time. These are figures which show the relationship between the scanning time by 2nd drive mode in the liquid crystal display device of the 1st another example of 1st Embodiment of this invention, frame period time, and backlight lighting time. These are figures which show the relationship between the scanning time by the 1st drive mode, frame period time, and backlight lighting time in the liquid crystal display device of the 2nd another example of 1st Embodiment of this invention. These are figures which show the relationship between the scanning time by 2nd drive mode in the liquid crystal display device of 2nd another example of 1st Embodiment of this invention, frame period time, and backlight lighting time. FIG. 4 is a diagram comparing image blur generated by scanning drive in the first drive mode and image blur generated by scan drive in the second drive mode in the liquid crystal display device of the present embodiment. These are block diagrams which show the circuit structure of the liquid crystal display device which concerns on 2nd Embodiment of this invention. These are figures which show the relationship between the scanning time by 1st drive mode, frame period time, and backlight lighting time in the liquid crystal display device of 2nd Embodiment of this invention. These are figures which show the relationship between the scanning time by 2nd drive mode in the liquid crystal display device of 2nd Embodiment of this invention, frame period time, and backlight lighting time. These are block diagrams which show the circuit structure of the liquid crystal display device which concerns on 3rd Embodiment of this invention. These are figures which show the relationship between the response of the liquid crystal at the time of the scanning drive control by a 2nd drive mode, and lighting of a backlight in the liquid crystal display device of 3rd Embodiment of this invention.

[First embodiment]
Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below shows the liquid crystal display device of the present invention in order to embody the technical idea of the present invention, and is not intended to specify the present invention as this liquid crystal display device. In addition, the present invention can be equally applied to the liquid crystal display devices of other embodiments included in the scope of claims.

FIG. 1 is a block diagram showing a circuit configuration of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device according to the present embodiment is a simple matrix type (passive matrix type) liquid crystal display device, and as shown in FIG. 1, a liquid crystal display panel (display element) 30 and a back for supplying light to the liquid crystal display panel 30. And a light (illuminating device) 40.

The liquid crystal display panel (display element) 30 includes a simple matrix substrate (not shown) such as STN (Super Twisted Nematic) and DSTN (Double STN), and a counter substrate (not shown) facing the simple matrix substrate. It is comprised by bonding together with a sealing material (not shown). A liquid crystal (not shown) is injected into the gap between the two substrates. A polarizing film is attached to each of the light receiving surface side of the simple matrix substrate and the light emitting surface side of the counter substrate.

Further, on the simple matrix substrate, a plurality of source lines 31 as video signal lines and a plurality of gate lines (scanning lines) 32 as scanning signal lines are arranged in a lattice pattern, and the source lines 31 and the gate lines 32 are arranged. A pixel is selected by the combination.

Furthermore, a gate driver 34 is connected to the liquid crystal display panel 30 via a gate line 32 and a source driver 33 is connected via a source line 31. The gate driver 34 is supplied with a scanning drive signal based on a timing control signal output from a panel control unit 14 to be described later, and sequentially turns ON / OFF the gates of the liquid crystal display panel 30 from the top. The source driver 33 converts the received data (video signal) into a voltage value based on the timing control signal output from the panel control unit 14 and supplies a driving voltage to each pixel.

As described above, the liquid crystal display panel 30 applies the pulse voltage for turning on / off the liquid crystal display panel 30 to the gate line 32, so that data (video signal) is simultaneously applied to all the pixels in the horizontal row. Written. This operation is repeated a number of times corresponding to the number of vertical pixels to complete one frame of video. That is, the liquid crystal display panel 30 is scanned line-sequentially. Note that the data (voltage) written in the pixel is accumulated in the capacitance in the pixel, and the voltage is held until the next data is written.

The liquid crystal display panel 30 configured in this manner displays an image by using a change in transmittance due to the tilt of the liquid crystal. That is, video display based on the video signal is performed by modulating light (backlight light) supplied from the backlight 40.

The backlight 40 is a light source that periodically illuminates (starts lighting) and turns off (ends lighting) and irradiates the liquid crystal display panel 30 with light, and is disposed immediately below the liquid crystal display panel 30. In addition, the liquid crystal display device of this embodiment is an edge light (side light) including an LED (Light Emitting Diode) module disposed on one side of a light guide and a light guide that guides light from the LED module. It is good also as being comprised in a type | mold, and good also as being comprised in the direct light type | mold provided with the diffuser plate and the LED module arrange | positioned at the back side of this diffuser plate.

In order to obtain a low-cost liquid crystal display device, when the liquid crystal display device is an edge light type, either one of the upper, lower, left and right sides of the light guide plate is opposed to a light source unit composed of a plurality of LED modules. Light may be incident on or reflected from the light guide plate from one side. Thereby, the number of units of a light source unit can be made into one, and a number of parts can be reduced. Further, when the liquid crystal display device is a direct type, it is desirable to increase the number of LED modules driven by one LED circuit by combining a plurality of LED modules (more preferably all LED modules) into one system. . Thereby, the number of LED drive circuits can be reduced and the number of parts can be reduced.

Next, the edge-light type liquid crystal display device will be described with reference to FIG. 3, but it may be a direct-light type liquid crystal display device as described above, and the LED module 42 shown below includes the liquid crystal display panel 30. It is good also as being a light source which irradiates the liquid crystal display panel 30 from the back side. The LED module 42 is a module that emits light, and includes a mounting substrate 42a and an LED (light emitting diode) 42b as a light source mounted on the surface of the mounting substrate 42a.

The mounting substrate 42a is a plate-shaped and rectangular substrate, and a plurality of electrodes (not shown) are arranged on the mounting surface. And LED42b is attached on these electrodes.

The LED 42b emits light upon being supplied with a current by being mounted on an electrode (not shown) formed on the mounting surface of the mounting substrate 42a. The LEDs 42b are controlled to be turned on by pulse width modulation (PWM) control.

The light guide 41 is made of a transparent resin material such as acrylic or polycarbonate. The light guide 41 has a substantially rectangular shape when seen in a plan view.

As shown in FIG. 3, the LEDs 42 b (LED modules 42) are arranged on one or more sides of the light guide 41 in the upper, lower, left and right directions (in FIG. 3, they are arranged only on the left side of the light guide 41. ). Further, the LED 42 b (light source) is not disposed in a region corresponding to the display region of the liquid crystal display panel 30, but is disposed near an end serving as a non-display region of the liquid crystal display panel 30.

Thus, the backlight 40 according to the embodiment can perform light emission control by turning on the LED 42b that enters the light guide 41. The backlight control unit 15 described later controls driving of the LED 42b (see FIG. 3) based on a timing control signal output from the panel control unit 14.

The backlight 40 may further include a reflection sheet, a backlight chassis, a diffusion plate, a prism sheet, a lens sheet, and the like.

Next, video display will be described. As shown in FIG. 1, the liquid crystal display device according to the present embodiment includes a scaling unit 10, an image quality correction unit 11, an RGBγ / WB adjustment unit 12, and an FRC unit in addition to the above-described configuration (the liquid crystal display panel 30 and the backlight 40). 13, a panel control unit 14, a backlight control unit 15, a frame memory 16, and a dimming control circuit 20.

The scaling unit 10 changes the number of pixels of the video frame or the aspect ratio of the video frame indicated by the input video signal (input video signal) according to the resolution of the liquid crystal display panel 30. Here, the input video signal is not particularly limited. For example, a signal obtained by demodulating a video signal received as a broadcast wave, a video signal received via a communication network, a video signal stored in an internal storage device, and various recorders Or a video signal received from an external device such as a player or a tuner device, or a video signal obtained by performing various video processes on the video signal.

The image quality correction unit 11 changes the video contrast, color, and the like for the video signal output from the scaling unit 10 according to user settings and the like.

The RGB γ / WB adjustment unit 12 adjusts γ, WB (white balance) / CT (color temperature), etc., of the video signal output from the image quality correction unit 11.

The FRC unit 13 detects the motion vector of the video from the adjusted video signal output from the RGBγ / WB adjustment unit 12 and generates an interpolated video to arbitrarily set the frequency of the video signal (N times (N = natural number)). ) To convert the frequency to In the present embodiment, a video signal input at a frequency of 60 Hz is converted to a frequency of 120 Hz and output.

That is, if F1 (frame 1), F2 (frame 2), and F3 (frame 3) are included in the input video signal, the difference between the F1 image and the F2 image is large at a frequency of 60 Hz. Even if the F2 image is displayed to the user (viewer), the F1 image may remain as an afterimage in the eyes of the user (viewer). On the other hand, one interpolated image (for example, F1 ′ image) is generated between each image (for example, F1 image and F2 image) and inserted to obtain a frequency of 120 Hz. The afterimage feeling is reduced as compared with 60 Hz video.

The panel control unit 14 generates and outputs an instruction signal to the source driver 33 and the gate driver 34 based on the video signal output from the FRC unit 13. That is, the panel control unit 14 controls video signal writing driving for each pixel in the liquid crystal display panel 30.

As described above, the gate driver 34 is supplied with a scanning drive signal to the gate line 32 based on the timing control signal output from the panel control unit 14, and sequentially turns the gates of the liquid crystal display panel 30 on and off sequentially from the top. To do. In the present embodiment, the scan drive signal supplied from the gate driver 34 to the gate line 32 is the first scan drive signal Sd1 for performing the scan drive in the first drive mode or the scan drive in the second drive mode. There is a second scanning drive signal Sd2 for the purpose.

In this embodiment, as described above, the liquid crystal display panel 30 is driven at 120 Hz. The first drive mode is a normal drive mode when the liquid crystal display panel 30 is driven at 120 Hz. The scan time (from the start of scanning for one screen to the end of scanning for one screen) ( The scanning time for one frame is a normal scanning time when the liquid crystal display panel 30 is driven at 120 Hz. In contrast, in the second drive mode, the scan time (scan time for one frame) from the start of scan for one screen to the end of scan for one screen is the first drive mode ( This is a drive mode in which the liquid crystal display panel 30 is controlled so as to be shorter than a normal scanning time when the liquid crystal display panel 30 is driven at 120 Hz.

In this embodiment and the following embodiments, the user (viewer) can select via the menu screen whether scanning driving is performed in the first driving mode or scanning driving in the second driving mode. The gate driver 34 supplies a scanning drive signal corresponding to the selected drive mode to the gate line 32.

The backlight control unit 15 controls driving of the backlight 40 (lighting start timing and lighting end timing) based on the timing control signal output from the panel control unit 14. In addition to the timing control signal output from the panel control unit 14, the backlight control unit 15 receives the PWM signal from the dimming control circuit 20. The dimming control circuit 20 outputs a PWM signal corresponding to a luminance adjustment signal input from an operation unit (TV remote controller or the like) (not shown) to the backlight control unit 15. The backlight control unit 15 controls the luminance of the backlight 40 according to the PWM signal input from the dimming control circuit 20 as well as the driving of the backlight 40 as described above.

The frame memory 16 performs writing / reading of image data at a frame display cycle with respect to the liquid crystal display panel 30, writing image data of the current frame period, and reading of image data of one frame period before panel control. Is output to the unit 14.

Next, the first drive mode and the second drive mode described above will be described in detail with reference to FIGS. FIG. 3 is a diagram showing the relationship among the scanning time, frame period time, and backlight lighting time in the first drive mode in the liquid crystal display device of the present embodiment. FIG. 4 is a diagram showing the relationship among the scanning time, frame period time, and backlight lighting time in the second drive mode in the liquid crystal display device of this embodiment.

3A shows the relationship between the scanning time (TSC) and the frame period time (TFM), FIG. 3B shows the display frame of the liquid crystal display device, and FIG. 3C shows the scanning in the liquid crystal display panel. FIG. 3D shows the lighting timing of the backlight and the backlight lighting time (TBL). 4A shows the relationship among the scanning time (TSC), the frame period time (TFM), and the blanking time (TBK), and FIG. 4B shows the display frame of the liquid crystal display device. (C) shows the scanning position in the liquid crystal display panel, and FIG. 4 (d) shows the lighting timing of the backlight and the backlight lighting time (TBL).

In the first driving mode, the scanning driving shown in FIG. 3 is performed. In the first drive mode, the black image display time between consecutive frames is approximately 0 ms (TBK≈0 ms (milliseconds)). TBK can be rephrased as detection time, from the end of scanning of the video signal to the last pixel line in one TFM to the start of scanning of the video signal to the first pixel line in the next TFM. Is the time.

When the liquid crystal display panel 30 is driven at 120 Hz, TFM is about 8.3 ms, and TBK≈0 ms as described above. Therefore, in the first drive mode, 1 TFM and TSC are TFM≈ The relational expression of TSC≈8.3 ms is established. Further, since TBK≈0 ms, the relational expression TBL ≧ TBK (TBK≈0) is established between TBK and TBL.

On the other hand, in the second driving mode, the scanning driving shown in FIG. 4 is performed. Compared to the first drive mode, the second drive mode has a shorter scan time (the time from the start of scanning for one screen on the liquid crystal display panel 30 to the end of the scan for one screen). The black image is displayed between successive frames.

As described above, when the liquid crystal display panel 30 is driven at 120 Hz, TFM is about 8.3 ms, and in the second driving mode, TFM, TBK, and TSC have a relationship of TFM (TFM = 8.3 ms) = TSC + TBK. The formula holds.

Here, regarding the difference in image quality performance displayed on the liquid crystal display panel 30 between the first drive mode and the second drive mode, the central timing of the TBL in each drive mode and the upper part of the screen, the middle part of the screen, and the lower part of the screen A description will be given of what control is performed to further improve the image quality of the second drive mode, while explaining based on the relationship with the scanning timing. Note that the backlight control unit 15 performs drive control of the backlight 40 so as to optimize the image quality in a predetermined region of the liquid crystal display device 30 in both the first drive mode and the second drive mode. . The predetermined area is one area when the liquid crystal display panel 30 is divided into a plurality of areas. Although it is not particularly limited to which area the predetermined area is set, in the present embodiment, the liquid crystal display panel 30 is divided into three areas, and the predetermined area is set as the center of the screen of the liquid crystal display panel 30.

That is, in the present embodiment, in order to optimize the image quality of the central region in the entire screen of the liquid crystal display panel 30, the central portion of the screen is obtained in both the first drive mode and the second drive mode. It is assumed that the backlight 40 is turned off during scanning (in other words, the timing at which the backlight 40 is turned off from the lighting state and the scanning timing at the center of the screen are the same). The reason why the backlight 40 is turned off when scanning the center of the screen will be described later.

3 and 4, the broken line L1 indicates the central timing of TBL (for example, if TBL is Xms), the broken line L2 indicates the TBL end timing (backlight). 40 lighting end timing) and scanning timing in the center of the screen.

[Central timing of TBL by the first driving mode]
In the upper part of the screen, the central timing of TBL at F1 ′ is (TFM / 2−TBL / 2) ms after the scanning of F1 ′. In the central portion of the screen, the central timing of TBL in F1 ′ is (TFM−TBL / 2) ms after the scanning of F1. At the bottom of the screen, the central timing of TBL at F1 ′ is (TFM / 2−TBL / 2) ms after the scanning of F1.

[Central timing of TBL by the second driving mode]
In the upper part of the screen, the central timing of TBL at F1 ′ is (TFM / 2−TBK / 2−TBL / 2) ms after the scanning of F1 ′. In the central portion of the screen, the central timing of TBL in F1 ′ is (TFM−TBL / 2) ms after the scanning of F1. At the bottom of the screen, the center timing of TBL at F1 ′ is (TFM / 2−TBL / 2 + TBK / 2) ms after the scanning of F1.

In the first drive mode and the second drive mode, the center timing of TBL in F1 ′ is the desired image F1 displayed at the center and the bottom of the screen, while The image F1 ′, which is an image, is displayed. In such a situation, the image quality performance of the upper part of the screen, the central part of the screen, and the lower part of the screen in the first drive mode and the second drive mode will be described for comparison. Table 1 summarizes the relationship between the TBL center timing described above and the scanning timing at the upper part of the screen, the central part of the screen, and the lower part of the screen.

 

[Comparison of screen center]
In the central portion of the screen, the scanning of F1 has already been completed at the central timing of TBL in F1 ′. As described above, in both the first drive mode and the second drive mode, the backlight 40 is turned on so that the image quality in the central area of the entire screen of the liquid crystal display panel 30 is optimal. Control is being performed. Specifically, the time T1 from the scanning of F1 ′ at the center of the screen to the center timing of TBL at F1 ′ is (TFM-TBL / 2) in both the first driving mode and the second driving mode. ms, and there is no difference in image quality performance between the first drive mode and the second drive mode.

[Compare top of screen]
In the upper part of the screen, scanning of F1 ′ is already started at the center timing of TBL in F1 ′. Therefore, in order to suppress the image blur at the upper part of the screen, it is desirable to make the time T2 from the start of the scanning of F1 ′ at the upper part of the screen to the center timing of TBL at F1 ′ as short as possible. In the first drive mode, T2 is (TFM / 2−TBL / 2) ms, and in the second drive mode, T2 is (TFM / 2−TBK / 2−TBL / 2). Considering the improvement in image quality, it is desirable that TBK is as long as possible, and TBL is desirably as short as possible. Therefore, as long as the liquid crystal display panel 30 is scanned in the second drive mode for the purpose of improving the image quality, T2 is shorter in the second drive mode than in the first drive mode.

[Compare bottom of screen]
In the upper part of the screen, the scanning of F1 is completed at the central timing of TBL in F1 ′. This is the same as that at the center of the screen, but as described above, in this embodiment, the lighting control is performed so that the image quality of the area at the center of the screen is optimized. From time T3 to the central timing of TBL, it is desirable to make the time T3 as long as possible. In the first drive mode, T3 is (TFM / 2−TBL / 2) ms, and in the second drive mode, T3 is (TFM / 2−TBL / 2 + TBK / 2) ms. Here, at the bottom of the screen, in order to make the image quality in the second drive mode more optimal than the image quality in the second drive mode, the following expression TFM / 2−TBL / 2 (first drive mode) ≦ TFM / 2-TBL / 2 + TBK / 2 (second drive mode) may be used.

As described above, considering improvement in image quality, it is desirable that TBL be as short as possible. Therefore, the maximum value of T1 in the first drive mode is TFM / 2 when TBL is 0 ms (PWM = 0%). It is. Therefore, the following equation TFM / 2 (first driving mode) ≦ TFM / 2−TBL / 2 + TBK / 2 (second driving mode) may be satisfied. In the inequality, the TFM in the first drive mode and the TFM in the second drive mode are the same (TFM≈8.3 ms). Therefore, if TBL ≦ TBK is satisfied in the second drive mode, the second drive mode depends on the second drive mode. The image quality can be optimized more than the image quality in the first drive mode.

Next, a description will be given of conditions for further improving (optimizing) the image quality of the entire screen of the liquid crystal display panel 30 in the second drive mode. One method for improving the image quality is to shorten the scanning time (TSC) of the liquid crystal display panel 30 as described above. However, if the TSC is shortened, the luminance decreases and the TSC shortens. There is a problem that the number of parts increases due to time, and high-performance parts are required, resulting in an increase in cost. Therefore, it is not possible to provide a liquid crystal display device that realizes cost reduction and image quality improvement only by shortening the TSC of the liquid crystal display panel 30.

Therefore, the first matter to be considered in order to improve the image quality is the relationship between TFM and TBL. Image quality can be improved by shortening TBL. On the other hand, if the TBL is too short, the problem that the luminance decreases occurs. In consideration of the performance of the LED drive circuit, it is desirable that TFM and TBL satisfy the following formula: TBL ≧ TFM × 0.05 in order to perform stable lighting control.

The second matter to be considered in order to improve the image quality is the lighting start timing and lighting end timing (TBL start timing and end timing) of the backlight 40. Depending on the response speed of the liquid crystal display panel 30, a certain time is required for drawing one frame. When the lighting time of the backlight 40 is shortened to improve image quality, any position of the liquid crystal display panel 30 is set. Whether the viewer feels image blur greatly depends on whether or not the backlight 40 is turned on during scanning. In general, it is considered that the viewer's line of sight concentrates on the central area of the liquid crystal display panel 30. Therefore, it is desirable to turn on the backlight so that the central area of the liquid crystal display panel 30 is the optimum scanning area.

As described above, in FIGS. 3 and 4, the backlight 40 is turned off at the time of scanning the center of the screen (the timing of turning the backlight 40 from the on state to the off state is the same as the scanning timing of the center portion of the screen). However, it is not limited to this. Hereinafter, description will be made with reference to FIG. FIG. 5 is a diagram showing a response waveform (response speed) of the liquid crystal display panel. FIGS. 5A, 5B, and 5C show response waveforms of different liquid crystal display panels. The response waveform shown in FIG. 5A is steep at the rising edge of the response of the liquid crystal, and the response speed is fast. On the other hand, the rising waveform gradually increases as shown in FIGS. 5B and 5C. It is flat and the response speed is slow (conversely, in FIG. 5C, the waveform at the fall is the steepest).

As described above, considering improvement in the image quality of the entire screen of the liquid crystal display panel 30, T1 is desirably as short as possible, and T3 is desirably as long as possible. Accordingly, in the liquid crystal display panel having a fast response speed as shown in FIG. 5A, it is desirable to turn on the backlight at a relatively early stage in the TFM because the scanning of the upper part of the screen is completed early. Therefore, in the liquid crystal display panel that performs the response shown in FIG. 5A, it is desirable that the screen center scanning timing and the lighting end timing of the backlight 40 in TBL be the same as shown in FIGS.

On the other hand, in a liquid crystal display panel with a slow response speed as shown in FIG. 5 (c), since the scanning of the upper part of the screen is slow to finish, the backlight may be turned on at a relatively late stage in the TFM. desirable. Therefore, in the liquid crystal display panel that performs the response shown in FIG. 5C, it is desirable that the scanning timing at the center of the screen and the lighting start timing of the backlight 40 in TBL be the same. 6 and 7 show a first driving mode and a first driving mode in the liquid crystal display device according to the first other example of the present embodiment (when the response waveform of the liquid crystal display panel 30 is the response waveform shown in FIG. 5C). It is a figure which shows the relationship between the scanning time by 2 drive modes, frame period time, and backlight lighting time.

That is, it is desirable to control the lighting start timing and lighting end timing of the backlight 40 so that the screen center scanning timing and any timing in the TBL coincide with each other according to the response speed. Note that the response speed of the response waveform shown in FIG. 5B is a response speed just between the response speed of the response waveform shown in FIG. 5A and the response speed of the response waveform shown in FIG. 8 and 9 show a first driving mode and a first driving mode in the liquid crystal display device according to the second another example of the present embodiment (when the response waveform of the liquid crystal display panel 30 is the response waveform shown in FIG. 5B). It is a figure which shows the relationship between the scanning time by 2 drive modes, frame period time, and backlight lighting time. As shown in FIGS. 8 and 9, the lighting start timing and lighting end timing of the backlight 40 are controlled so that the screen center scanning timing and the center timing in the TBL coincide with each other.

The third matter to be considered in order to improve the image quality is the relationship between TFM and TBK. As described above, in the second drive mode, a black image is inserted to improve the image. In order to improve image quality, it is desirable to make TBK as long as possible and TSC as short as possible. As described above, since TFM = TBK + TSC, the longer the TBK is, the shorter the TSC is.

However, shortening the TSC requires that the response speed be extremely high, leading to enormous cost increases such as an increase in the number of parts and the need for high-performance parts as described above. Further, since the image blur occurs when the backlight 40 is turned on when the black image is inserted, it is desirable that the backlight 40 is turned off (not turned on) when the black image is inserted (during TBK). That is, it is desirable that the TBK is set to a long time so that the TBK and the TBL do not overlap.

As shown in FIG. 4, when the scanning timing at the center of the screen and the lighting end timing of the backlight 40 in TBL are the same, if the TBL exceeds (TFM-TBK) / 2, the lighting start of the backlight 40 is started. The timing is during the TBK of the previous frame, and the backlight 40 is lit during the TBK. Therefore, it is necessary to satisfy TBL ≦ (TFM−TBK) / 2. Further, as described above, TBK ≧ TBL. Therefore, it is desirable that TFM and TBK satisfy the following formula: TBK ≦ (TFM−TBK) / 2, that is, 1/3 TFM ≧ TBK, by combining the two formulas.

As shown in FIG. 7, when the screen center scanning timing and the lighting start timing of the backlight 40 in TBL are the same, if the TBL exceeds (TFM-TBK) / 2, the lighting of the backlight 40 ends. The timing is during the TBK of the current frame, and the backlight 40 is lit during the TBK. Therefore, it is necessary to satisfy TBL ≦ (TFM−TBK) / 2. Further, as described above, TBK ≧ TBL. Therefore, it is desirable that TFM and TBK satisfy the following formula: TBK ≦ (TFM−TBK) / 2, that is, 1/3 TFM ≧ TBK, by combining the two formulas.

As shown in FIG. 9, when the screen center scanning timing and the center timing in the TBL are the same, if the TBL exceeds TFM-TBK, the lighting start timing of the backlight 40 is in the TBK of the previous frame. Also, the lighting end timing is during the TBK of the current frame, and the backlight 40 is lit during the TBK. Therefore, it is necessary to satisfy TBL ≦ TFM-TBK. Further, as described above, TBK ≧ TBL. Therefore, it is desirable that TFM and TBK satisfy the following expression TBK ≦ TFM−TBK, that is, 1/2 TFM ≧ TBK by combining the two expressions.

That is, the relational expression (inequality) between TFM and TBK varies depending on the response waveform of the liquid crystal, and it is desirable that TFM and TBK satisfy the following expression 1 / 2TFM ≧ TBK, and more desirably, It is desirable to satisfy.

FIG. 10 is a diagram comparing the image blur generated by the scanning drive in the first drive mode and the image blur generated by the scan drive in the second drive mode in the liquid crystal display device of the present embodiment. FIG. 10 is a diagram comparing image blur when the TSC in the second drive mode is controlled to be ¾ of the TSC in the first drive mode. In FIG. 10, the vertical axis indicates the size (amount) of the image blur, and the horizontal axis indicates the screen position. As described above, in the present embodiment, in both the first drive mode and the second drive mode, the back of the liquid crystal display panel 30 so that the image quality in the central area of the entire screen of the liquid crystal display panel 30 is optimal. The lighting control of the light 40 is performed. Therefore, the image blur in the first drive mode and the second drive mode in the vicinity of the center of the screen is almost the same and small.

On the other hand, in the upper part and the lower part of the screen, the size of the image blur in the first drive mode is larger than the size of the image blur in the second drive mode. In the mode, the size of the image blur generated in the 3/4 length region (upper screen 3/4 or lower screen 3/4 in FIG. 10) of the liquid crystal display panel in the mode and the liquid crystal display panel in the second drive mode The size of the image blur generated at the vertical end (the upper part of the screen or the lower part of the screen in FIG. 10) is substantially the same.

Specifically, according to the present embodiment, the scanning time for one frame in the second driving mode is shorter than the scanning time for one frame in the first driving mode, and in the second driving mode, TFM, TSC , TBK, and TBL satisfy the following expressions, respectively, so that the image quality can be improved at a low cost over the entire area of the liquid crystal display panel. i) TFM = TSC + TBK, ii) 1/2 TFM ≧ TBK ≧ TBL ≧ TFM × 0.05.

Further, since the drive control of the backlight 40 is performed based on the timing of scanning the predetermined area in the liquid crystal display panel 30, the image quality in the predetermined area can be improved. Specifically, any timing in the lighting time of the backlight (for example, lighting start timing, lighting timing center timing, lighting end timing, etc.) and desired image quality improvement (would like to minimize image blur) By performing drive control of the backlight 40 so that the timing of scanning the region is the same, the image quality in the predetermined region can be improved.

Further, since the drive control of the backlight 40 is performed based on the response speed of the liquid crystal display panel 30, the image quality can be further improved in the entire area of the liquid crystal display panel including the predetermined area. Specifically, the timing at which the backlight 40 is turned on and the timing for scanning the predetermined area are determined in accordance with the response speed of the liquid crystal display panel 30, so that the characteristics of the liquid crystal display panel 30 can be determined. It is possible to perform control according to.

Also, since the drive control of the backlight 40 is performed so that TBL and TBK do not overlap, the image quality can be further improved over the entire liquid crystal display panel including the predetermined area.

Further, it is considered that the line of sight is usually concentrated at the center of the liquid crystal display panel 30 when the viewer views the video through the liquid crystal display panel 30. Therefore, by setting the predetermined area as the central portion of the liquid crystal display panel 30, it is possible to make it difficult for the viewer to feel image blur.

Further, the liquid crystal display device of this embodiment is a liquid crystal display device capable of displaying two-dimensional video and three-dimensional video, and the driving mode of the liquid crystal display panel 30 when displaying the two-dimensional video is the second driving mode. By making the scanning time when the three-dimensional video is displayed the same as the scanning time of the liquid crystal display panel 30 when displaying the three-dimensional video, software and hardware necessary for displaying the three-dimensional video can be used as they are. The liquid crystal display device of this embodiment can be manufactured without increasing the manufacturing cost.

In addition, since the FRC unit is included, for example, 60 Hz video is converted into 120 Hz video, interpolated video between frames is generated and inserted between the frames, so that a smooth playback video is provided to the viewer. Can do.

[Second Embodiment]
FIG. 11 is a block diagram showing a circuit configuration of a liquid crystal display device according to the second embodiment of the present invention. As shown in FIG. 11, the liquid crystal display device according to the present embodiment includes a scaling unit 10, an image quality, in addition to a liquid crystal display panel (display element) 40 and a backlight (illumination device) 40 that supplies light to the liquid crystal display panel 30. A correction unit 11, an RGBγ / WB adjustment unit 12, a panel control unit 14, a backlight control unit 15, a frame memory 16, and a dimming control circuit 20 are provided.

That is, the liquid crystal display device of the first embodiment is configured to include the FRC unit 13 in order to drive the liquid crystal display panel 30 at 120 Hz. However, the liquid crystal display device of the present embodiment drives the liquid crystal display panel 30 at 60 Hz. The FRC unit is not provided. In other configurations, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In this embodiment, as described above, the liquid crystal display panel 30 is driven at 60 Hz. Therefore, the difference in image between the frames in the input video signals F1, F2, and F3 is large, and the afterimage feeling is increased as compared with the first embodiment in which the liquid crystal display panel 30 is driven at 120 Hz.

In the present embodiment, the first drive mode is a normal drive mode when the liquid crystal display panel 30 is driven at 60 Hz, from the start of scanning for one screen until the end of scanning for one screen. The scanning time is a normal scanning time when the liquid crystal display panel 30 is driven at 60 Hz. On the other hand, the second drive mode is the first drive mode (the liquid crystal display panel 30 is driven at 60 Hz) from the start of the scan for one screen to the end of the scan for one screen. In this case, the drive mode is controlled so as to be shorter than the normal scanning time in this case.

Next, the first drive mode and the second drive mode described above will be described in detail with reference to FIGS. FIG. 12 is a diagram showing the relationship among the scanning time, the frame period time, and the backlight lighting time in the first drive mode in the liquid crystal display device of this embodiment. FIG. 13 is a diagram showing the relationship among the scanning time, frame period time, and backlight lighting time in the second drive mode in the liquid crystal display device of this embodiment.

12A shows the relationship between the scanning time (TSC) and the frame period time (TFM), FIG. 12B shows the display frame of the liquid crystal display device, and FIG. 12C shows the scanning in the liquid crystal display panel. The position is shown, and FIG. 12D shows the lighting timing of the backlight and the backlight lighting time (TBL). 13A shows the relationship among the scanning time (TSC), the frame period time (TFM), and the blanking time (TBK), and FIG. 13B shows the display frame of the liquid crystal display device. (C) shows the scanning position in the liquid crystal display panel, and FIG. 13 (d) shows the lighting timing of the backlight and the backlight lighting time (TBL).

In the first driving mode, scanning driving shown in FIG. 12 is performed. In the first drive mode, the black image display time between consecutive frames is approximately 0 ms (TBK≈0 ms (milliseconds)).

When the liquid crystal display panel 30 is driven at 60 Hz, the TFM is about 16.7 ms, and TBK≈0 ms as described above. , TFM≈TSC≈16.7 ms. In addition, the relational expression TBL ≧ TBK (TBK≈0) holds between TBK and TBL (see FIG. 8).

In contrast, in the second drive mode, the scanning drive shown in FIG. 13 is performed. In the second drive mode, drive control is performed so that the scanning time is shorter than in the first drive mode, and a black image is displayed between successive frames.

In the second drive mode of the present embodiment, the relational expressions of TFM, TSC, TBK, and TBL are the same as those in the second drive mode of the first embodiment. The same applies to controlling the lighting start timing and lighting end timing of the backlight 40 in accordance with the response speed of the liquid crystal display panel 30 so that the scanning timing at the center of the screen and any timing in the TBL coincide. is there.

According to this embodiment, the same effects as those of the first embodiment are obtained.

[Third embodiment]
FIG. 14 is a block diagram showing a circuit configuration of a liquid crystal display device according to the third embodiment of the present invention. As shown in FIG. 14, the liquid crystal display device according to the present embodiment includes a scaling unit 10, an image quality, in addition to a liquid crystal display panel (display element) 40 and a backlight (illumination device) 40 that supplies light to the liquid crystal display panel 30. A correction unit 11, an RGBγ / WB adjustment unit 12, a panel control unit 14, a backlight control unit 15, a frame memory 16, a character information position detection circuit 17, and a dimming control circuit 20 are provided.

In the first embodiment and the second embodiment, the drive control of the backlight 40 is performed so as to minimize the image blur at the center of the screen (in other words, the predetermined area is the center of the screen of the liquid crystal display panel 30). The drive control of the backlight 40 was performed.

By the way, when characters such as subtitles and telops are displayed in areas other than the center of the screen such as the upper and lower portions of the liquid crystal display panel 30, the viewer's line of sight is displayed from the center of the screen of the liquid crystal display panel 30. It is considered that the liquid crystal display panel 30 is concentrated on the end region (the upper part of the screen, the lower part of the screen, etc.). However, in the first embodiment and the second embodiment, the end region of the liquid crystal display panel 30 is not an optimal scanning region. In a non-optimal scanning area, image blur occurs.

Therefore, in this embodiment, it is detected in which area (position) of the display screen the character information is displayed, and image blur in the area where the character information is displayed (area where the display position of the character information belongs) is minimized. Thus, the drive control of the backlight is performed (in other words, the drive control of the backlight 40 is performed with the predetermined area in the first embodiment as the area to which the display position of the character information belongs).

A character information position detection circuit 17 is provided to detect in which area the character information is displayed. In this embodiment, the liquid crystal display panel 30 is controlled to be driven at 120 Hz, and the liquid crystal display panel 30 is driven at 60 Hz, although the character information position detection circuit 17 is added to the liquid crystal display device of the first embodiment. Control may be performed, and a configuration in which the character information position detection circuit 17 is added to the liquid crystal display device of the second embodiment may be employed.

The character information position detection circuit 17 detects the presence / absence of the character information shown together with the video displayed on the liquid crystal display panel 30, the timing at which the character information is displayed, and the display position. In this specification, the character information refers to a display object displayed together with a video such as a subtitle in a digital broadcast, a text super, a subtitle in a video recorded on a BD disc, a DVD disc or the like, an OSD display such as a menu screen. Say.

For example, subtitle data for digital broadcasting includes subtitle display position data (data indicating the position where subtitles are displayed) as well as character data (data indicating what character strings are displayed as subtitles). The information position detection circuit 17 can detect the presence / absence of a subtitle in digital broadcasting and the position where the subtitle is displayed. Furthermore, subtitles need to be displayed in a timely manner in accordance with the video, and at which timing in the video data, which character in the character data is to be displayed and in which position are determined by decoding the character data, the character information position The detection circuit 17 can detect the presence / absence of a caption of digital broadcasting, the display timing and the display position of the caption in advance.

Also, as another method for detecting the presence / absence of subtitles in digital broadcasting and the display timing and display position of subtitles, decoding subtitle data multiplexed in the transport stream can be mentioned. Thereby, the character information position detection circuit 17 can detect the presence / absence of a caption of digital broadcasting, the display timing and the display position of the caption in advance.

The character information position detection circuit 17 detects the presence of subtitles and the display timing and display position of the subtitles in advance, and outputs the detection signals to the panel control unit 14 and the backlight control unit 15. Based on the detection signal and the scanning drive signal input from the panel control signal 14, the backlight control unit 15 controls the drive of the backlight so that the image blur in the display area where the caption is displayed is minimized.

FIG. 15 is a diagram showing the relationship between the response of the liquid crystal and the lighting of the backlight during the scan drive control in the second drive mode in the liquid crystal display device of the third embodiment of the present invention. 15A shows the display frame of the liquid crystal display device, FIG. 15B shows the response of the liquid crystal display panel, and FIG. 15C shows the image blur in the first region in the liquid crystal display panel to the minimum. FIG. 15D shows the backlight on / off timing for minimizing the image blur in the second region in the liquid crystal display panel, and FIG. Indicates the timing of turning on and off the backlight for minimizing the image blur in the third region in the liquid crystal display panel.

The first area, the second area, and the third area correspond to the upper part of the screen of the liquid crystal display panel 30, the center part of the screen, and the lower part of the screen, respectively. The lighting start timing of the backlight 40 is one frame period time, after a certain time has elapsed since the scanning of the area where the image blur is to be minimized is completed, that is, sufficient time has elapsed since the image was displayed in that area. When Then, the lighting of the backlight 40 is ended before scanning of the next frame is started in an area where the image blur is to be minimized.

In the second drive mode of this embodiment, the relational expressions of TFM, TSC, TBK, and TBL are the same as those in the second drive mode in the first embodiment and the second embodiment. With respect to the lighting start timing and lighting end timing of the backlight 40, the scanning timing of the region where the image blur is to be minimized and any timing in the TBL are simultaneously set according to the response speed (response waveform) of the liquid crystal display panel 30. Control to be. FIG. 15 is a diagram showing the lighting start timing and lighting end timing of the backlight 40 when the response waveform of the liquid crystal display panel 30 is the response waveform shown in FIG. 5A, and it is desired to minimize image blur. Control is performed so that the scanning timing of the area and the timing of ending the lighting of the backlight 40 are the same.

Next, a description will be given of in which case the backlight lighting control for minimizing image blur in which region is performed. However, the following backlight lighting control standard is an example and is not limited to this. Different standards may be used as the backlight lighting control standard, and the user may arbitrarily set and change the backlight lighting control standard. . In this embodiment, the liquid crystal display panel 30 is divided into three regions (first region (upper screen portion), second region (center portion of the screen), and third region (vertical direction of the liquid crystal panel 30), Although the backlight lighting control is performed so that the image blur in any area is minimized by dividing it into the lower part of the screen)), the number of areas to be divided is not limited to three, The number of divisions (number of regions) may be used.

As described above, in a normal viewing state (for example, a state in which character information is not displayed on the video), it is considered that the viewer's line of sight is concentrated near the center of the liquid crystal display panel. Therefore, in the present embodiment, when determining whether to perform backlight lighting control so as to minimize the image blur in the first region to the third region, only the image blur in the first region is determined. When it is necessary to minimize the image blur of the third area, it is necessary to minimize only the image blur of the third area. Lighting control is performed, and in other cases, backlight lighting control is performed so as to minimize image blur in the second region.

Specifically, the first area is displayed when character information is displayed only at the top of the screen, the third area when character information is displayed only at the bottom of the screen, and the second area is displayed otherwise. The backlight is controlled so as to minimize the image blur. The conditions when the backlight lighting control is performed so as to minimize the image blur in the second area (other than the above) will be described in more detail. When character information is not displayed on the video, the character is displayed on the video. Information is displayed, but the display position is not only at the top or bottom of the screen (for example, when it is displayed at both the top and bottom of the screen or only at the center of the screen), video The presence or absence of character information or the display timing of character information or the display position of character information cannot be detected.

According to this embodiment, the same effects as those of the first embodiment are obtained. In addition, when the character information is displayed together with the video on the liquid crystal display panel 30, it is considered that the viewer's line of sight concentrates on the character information. Therefore, by determining the predetermined area based on the presence / absence of the character information displayed together with the video on the liquid crystal display panel 30 and the display position of the character information, it may be difficult for the viewer to feel image blur. it can.

That is, when there is no character information displayed together with the video on the liquid crystal display panel 30, the predetermined area is the central portion of the liquid crystal display panel 30 where the viewer's line of sight is considered to be concentrated.

On the other hand, when there is character information displayed together with video on the liquid crystal display panel 30 and the character information is displayed in one area on the liquid crystal display panel 30, the predetermined area belongs to the area to which the character information display position belongs. And Alternatively, when character information is displayed in a plurality of areas on the liquid crystal display panel 30, the predetermined area is determined based on the priority order of the character information displayed in each area. Specifically, the predetermined area is an area to which the display position of the character information with the highest priority belongs.

[Other]
In the third embodiment, when character information is displayed on the video, when there are two or more character information display positions such as the upper part of the screen and the lower part of the screen, the image blur at the center of the screen is minimized. However, when character information is displayed in a plurality of areas on a liquid crystal display panel divided into an arbitrary number of areas, the priority of the character information is determined and the highest priority is given. The backlight control may be performed so as to minimize image blur in an area where high character information is displayed.

For example, according to the third embodiment, when the caption is displayed on the video and the caption is displayed at the bottom of the screen, the backlight control is performed so as to minimize the image blur at the bottom of the screen. After that, when a breaking news telop is displayed at the top of the screen together with subtitles, backlight control is performed so as to minimize image blur in the center of the screen. On the other hand, according to this modification, by comparing “breaking news” and “subtitles” as attributes of text information, if it is determined that “breaking news” has higher priority (higher importance), the screen Backlight control is performed to minimize the image blur at the top.

Note that the viewer sets priority when character information is displayed in a plurality of areas, and performs backlight control so as to minimize image blur in the area where character information with high priority is displayed. It is good as well. If the priority of character information displayed in a plurality of areas is the same (character information with the same priority), backlight control may be performed so as to minimize image blur at the center of the screen. Good.

Further, the liquid crystal display device of the present invention may be capable of displaying a 3D image in addition to a 2D image. In particular, in a liquid crystal display device that employs a frame-sequential method (shutter method) as a 3D image display method, when displaying a 3D image, the left-eye image and the right-eye image are alternately scanned at high speed. The function to perform. Therefore, the control for shortening (shortening) the scanning time when displaying a three-dimensional image is applied to the control for shortening (shortening) the scanning time in the second drive mode in each of the above embodiments. (In other words, the scanning time for one frame in the 3D video display mode and the scanning time for one frame in the second drive mode in the 2D video display mode can be set to the same time). Software and hardware used in the video display mode can be used as they are. Thereby, an increase in cost can be suppressed.

The present invention can be used for a liquid crystal display device.

DESCRIPTION OF SYMBOLS 10 Scaling part 11 Image quality correction part 12 RGB (gamma) / WB adjustment part 13 FRC part 14 Panel control part 15 Backlight control part 16 Dimming restriction circuit 17 Character information position detection circuit 30 Liquid crystal display panel 33 Source driver 34 Gate driver 40 Backlight

Claims (13)

1. A liquid crystal display panel;
   A backlight that periodically illuminates and extinguishes light to irradiate the liquid crystal display panel; and
   A backlight control unit that performs drive control of the backlight;
   A panel controller that scans and drives the liquid crystal display panel based on an input video signal;
   With
   The panel control unit scans and drives the liquid crystal display panel in a drive mode selected from the first drive mode and the second drive mode.
   The scanning time for one frame in the second driving mode is shorter than the scanning time for one frame in the first driving mode, and the second driving mode satisfies the following expression: Liquid crystal display device.
   i) TFM = TSC + TBK
   ii) 1/2 TFM ≧ TBK ≧ TBL ≧ TFM × 0.05
   (TFM: frame period time, TSC: scanning time, TBK: blanking time, TBL: backlight lighting time)
2. The backlight control unit divides the liquid crystal display panel into a plurality of regions, and the plurality of regions in the liquid crystal display panel when the second drive mode is selected as the drive mode of the liquid crystal display panel. 2. The liquid crystal display device according to claim 1, wherein drive control of the backlight is performed based on a timing of scanning a predetermined region.
3. The backlight control unit performs drive control of the backlight such that any timing in the backlight lighting time and the timing of scanning the predetermined area in the liquid crystal display panel are simultaneous. The liquid crystal display device according to claim 2.
4. 4. The liquid crystal display device according to claim 2, wherein the backlight control unit performs drive control of the backlight based on a response speed of the liquid crystal display panel.
5. The backlight control unit performs drive control of the backlight so that the backlight lighting time and the blanking time do not overlap with each other. Liquid crystal display device.
6. 6. The liquid crystal display device according to claim 2, wherein the predetermined area is an area to which a central portion of the screen of the liquid crystal display panel belongs.
7. A character information position detection circuit for detecting presence / absence of character information displayed on the liquid crystal display panel and a display position of the character information;
   6. The liquid crystal display device according to claim 2, wherein the predetermined area is determined based on presence / absence of the character information and an area to which the display position of the character information belongs. .
8. 8. The liquid crystal display device according to claim 7, wherein when the character information does not exist, the predetermined area is an area to which a central portion of the screen of the liquid crystal display panel belongs.
9. 8. The liquid crystal display device according to claim 7, wherein when the character information exists, the predetermined area is an area to which a display position of the character information belongs.
10. The character information position detection circuit further detects the display timing of the character information, and there are a plurality of the character information, and each character information is simultaneously displayed on different areas on the liquid crystal display panel. 8. The liquid crystal display device according to claim 7, wherein the predetermined region at a certain time is a region to which a central portion of the screen of the liquid crystal display panel belongs.
11. The character information position detection circuit further detects the display timing of the character information, and there are a plurality of the character information, and each character information is simultaneously displayed on different areas on the liquid crystal display panel. 8. The liquid crystal display device according to claim 7, wherein the predetermined region at a certain time is a region to which a display position of character information having the highest priority belongs among the plurality of character information displayed in each region. .
12. The liquid crystal display panel can selectively display a 2D image or a 3D image, and the scanning time for one frame in the second driving mode in the 2D image display mode and one frame in the 3D image display mode. The liquid crystal display device according to any one of claims 1 to 11, wherein a scanning time of minutes is the same time.
13. The FRC unit according to any one of claims 1 to 12, further comprising: an FRC unit that generates an interpolated video for the video signal, converts the frequency of the video signal into an arbitrary frequency, and outputs the frequency. Liquid crystal display device.

Images