JPH099180A - Driving method of liquid crystal display device - Google Patents

Abstract

(57) [Summary] [Object] To provide a driving method of a liquid crystal display device for displaying an image of a plurality of types of television signals such as an NTSC system and a wide system. [Structure] Aspect ratio of the image by the input video signal is converted, the image is displayed in the central part of the liquid crystal panel screen, and when performing black display at the upper and lower ends of the liquid crystal panel screen, it corresponds to the part that performs black display N out of many horizontal gate lines
For one horizontal gate line (L1 to Ln), one horizontal gate line L1 is selected and a black signal is written to the pixel in the row, and then the remaining horizontal gate lines (L2 to Ln) are selected at high speed or simultaneously. . [Effect] By writing a black signal in a short period of time, it is possible to give sufficient time to the video display portion, and even when displaying an aspect ratio-converted video signal without changing the aspect ratio of the original image, the display quality is The decrease can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a liquid crystal display device for displaying images of a plurality of types of television signals such as NTSC system and wide system.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display device for displaying an image based on a current television signal such as an NTSC system or a PAL system has 400 to 600 rows of pixels according to the number of scanning lines of the signal system. Or half that 2
A matrix type liquid crystal panel has been used which is composed of pixels of 00 to 300 rows, and is composed of pixels of 400 to 800 columns from its signal band.

In recent years, for example, wide-screen televisions have become widespread, and there has been an increasing demand for liquid crystal display devices capable of displaying wide-screen television signals. Under these circumstances, where the transition to the wide system is currently in progress, even in the liquid crystal display device that displays the current television signal, the wide system television signal,
That is, it is desired to be able to switch and display the video signal with the aspect ratio converted.

As a method of displaying an aspect ratio-converted video signal (for example, an image in the wide system) on a screen displaying an image in the NTSC system, the aspect ratio of the original image is correctly obtained and there is no loss of information. There is one in which a video signal is displayed in the center of a liquid crystal panel screen of the above-mentioned system, and black is displayed at both upper and lower ends of the screen. At this time, it is necessary to write the black signal within the period outside the image display.

Specifically, for example, when a 16: 9 wide type signal is displayed on a 4: 3 NTSC type liquid crystal panel, the image is vertically oriented as shown in FIG. 7A because of the difference in aspect ratio. It grows up to (double circle originally). Therefore, as shown in FIG. 7B, the video signal is vertically compressed to 3/4 and displayed without changing the aspect ratio of the original image, and the upper and lower ends of the screen are displayed in black.

[0006]

In the above liquid crystal display device, even when an image of the wide type is displayed on the screen of the image of the NTSC type, the rewriting frequency of the entire screen is constant at 60 Hz. There is a problem that the rewriting time of the video display portion is shortened according to the ratio of the video display portion to the screen, and the display quality is degraded. On the other hand, if the time required to display an image becomes long due to an increase in the number of driving lines of the liquid crystal panel in order to increase the image resolution, there is a problem that the time for writing the black signal becomes insufficient.

The present invention solves the above-mentioned conventional problems, and
Driving a liquid crystal display device capable of suppressing deterioration of display quality even when a video signal whose aspect ratio is converted is displayed on a liquid crystal panel displaying a TSC television signal without changing the aspect ratio of the original image. The purpose is to provide a method.

[0008]

Means and Actions for Solving the Problems The constitution of the present invention made to achieve the above object is as follows.

That is, the first aspect of the present invention is a driving method of a liquid crystal display device, comprising a liquid crystal panel sandwiching a liquid crystal between a pair of electrode substrates, and displaying an image of an input video signal. When the aspect ratio is converted and the image is displayed in the central portion of the liquid crystal panel screen, and when black display is performed at the upper and lower ends of the liquid crystal panel screen, among the many horizontal gate lines corresponding to the portion for performing the black display. A method for driving a liquid crystal display device is characterized in that at least two or more horizontal gate lines are selected at the same time and a black signal is written to each row pixel (all pixels arranged in one row).

A second aspect of the present invention is a method of driving a liquid crystal display device, which comprises a liquid crystal panel sandwiching liquid crystal between a pair of electrode substrates, and displays an image of an input video signal. When the aspect ratio is converted and the image is displayed in the central portion of the liquid crystal panel screen, and when black display is performed at the upper and lower ends of the liquid crystal panel screen, among the many horizontal gate lines corresponding to the portion for performing the black display. After selecting one horizontal gate line for any of a plurality of horizontal gate lines and writing a black signal to the pixels in the row (all pixels arranged in one row), the remaining horizontal gate lines are fast or simultaneously. A method of driving a liquid crystal display device is characterized by selecting.

According to the present invention, by writing the black signal to the non-image display portion in a shorter time, a sufficient time can be taken for the image display portion, and deterioration of display quality can be suppressed even for images having different aspect ratios. Images can be displayed.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples.

[Embodiment 1] In this embodiment, an embodiment of the first driving method of the present invention will be described.

The system configuration of the liquid crystal display device in this embodiment is shown in FIG. In the figure, 1 is a TV signal input terminal, 2 is a decoder for converting into RGB color signals, 3 is a line memory section, and 4 is a signal for driving liquid crystal which is sequentially switched to normal / inversion every predetermined period. The inversion control and signal amplification section 5 is a logic section that forms pulses for memory control, inversion control, and liquid crystal panel driving. Reference numeral 6 denotes a liquid crystal panel, of which 7 is a horizontal shift register (HSR) as horizontal scanning means, 8 is a vertical shift register (VSR) as vertical scanning means, and 9 is a pixel portion.

The NTSC signal input to the input terminal 1 is decoded by the decoder 2 and then the line memory 3
Is converted into a line-sequential scanning signal, and the entire screen of the liquid crystal panel 6 is rewritten at a cycle of 60 Hz.

FIG. 2 shows a part of the circuit configuration of the display section of the liquid crystal panel 6. In the figure, the same reference numerals as those in FIG.
Is a liquid crystal, 12 is a storage capacitor, 13 is a counter electrode, 14 is a video signal line, 15 is a vertical signal line, 16 is a horizontal gate line, 17
Is a signal line selection switch, and 18 is a signal input terminal of the liquid crystal panel.

Next, a method of driving the liquid crystal panel 6 will be described with reference to FIGS.

FIG. 3 shows driving signals for the liquid crystal panel 6, where HST is a start pulse for the horizontal shift register 7, HCK1 and HCK2 are two-phase clock pulses for the horizontal shift register 7, and VST is a vertical shift register 8. The start pulses for VCK1 and VCK2 are two-phase clock pulses for the vertical shift register 8. Among the vertical shift registers 8, VSR1 is a vertical shift register corresponding to the upper black display portion of the liquid crystal panel screen, and VSR2 is a vertical shift register corresponding to the lower black display portion of the liquid crystal panel screen.

FIG. 4 shows the circuit structure of the VSR1 portion. As shown in FIG. 4, the horizontal gate lines 16 connected to the VSR1 are grouped into m sets every n lines, and
Each set of horizontal gate lines 16 can be selected by the gate reset pulse of RS1 to GRSm. Although not shown, the circuit configuration of the VSR2 portion is also the same.

FIG. 5 shows the write timing in one vertical period in the present embodiment. The image is displayed in the center of the effective display period so that the image with the aspect ratio converted is displayed in the center of the screen of the liquid crystal panel. Assign a period,
The remaining periods before and after are set as the writing time of the upper and lower black display portions, respectively.

In the black signal writing period before the video display period, the gate reset pulse of the VSR1 portion causes
The black signal is transferred to the liquid crystal panel signal input terminal 18 in synchronization with the simultaneous selection of n of the horizontal gate lines 16 in this portion, and the black signal is simultaneously written to the row pixels of the nth row.
By performing this operation for m sets, a black signal can be written in each row pixel connected to the n × m horizontal gate lines corresponding to the upper black display portion.

In the video display period, the aspect ratio-converted video signal is transferred to the liquid crystal panel signal input terminal 18, and is sequentially selected and input by the vertical shift register 8.
At this time, the video signal is compressed, transferred, and displayed so that the aspect ratio of the original image is maintained at 1: 1.

In the black signal writing period after the video display period, the liquid crystal is synchronized with the simultaneous selection of n horizontal gate lines 16 in this portion by the gate reset pulse in the VSR2 portion. Panel signal input terminal 1
The black signal is transferred to 8, and the black signal is simultaneously written in the row pixels of the nth row. By performing this operation for m sets, a black signal can be written in each row pixel connected to the n × m horizontal gate lines corresponding to the lower black display portion.

As described above, in the present embodiment, the black signal is written over a plurality of row pixels at once, so that the writing of the black display portion can be completed in an extremely short period. Therefore, for example, even if the number of driving lines of the liquid crystal panel is increased in order to increase the image resolution, sufficient time can be allocated to the image display portion, and the display quality is not deteriorated even in the case of an image by a television signal such as a wide system. It can be displayed without inviting.

[Embodiment 2] In this embodiment, an embodiment of the second driving method of the present invention will be described.

In the first embodiment, among the horizontal gate lines 16 corresponding to the black display portion, n lines in the same group are collectively selected and the black signal is transferred to each row pixel. However, in the present embodiment, the black display is performed. Of the horizontal gate lines 16 corresponding to the portion, only one of n lines in the same group is first selected and the black signal is transferred to the row pixel, and then the remaining (n-1) lines are subjected to normal vertical scanning. The black signal is written in each row pixel by selecting at a higher speed or simultaneously.

In this embodiment, n lines (L1 to L) of the horizontal gate lines of the VSR1 and VSR2 (see FIG. 3) parts are used.
The timing when n) is selected is shown in FIG.

As shown in FIG. 6A, after the horizontal gate line L1 is selected and the black signal is written in the row pixels, black is not transferred to the video signal line 14 and the remaining (n-1) The horizontal gate lines L2 to Ln are selected at high speed. At this time, as can be seen from FIG. 2, charges are stored in the row pixels connected to one horizontal gate line L1, but the parasitic capacitance of the vertical signal line 15 and each row pixel connected to the vertical signal line 15 are stored. Because of capacitance division between them, the voltage applied to them changes. Therefore, when the number of horizontal gate lines corresponding to the row pixels which can be recognized as displaying black by this voltage is n, a set of n horizontal gate lines is taken as a set and a black signal is generated by the above drive signal. It writes in each line pixel. FIG.
As shown in (b), (n-1) lines may be selected at the same time.

If the above scanning is performed for m sets,
A black signal can be written to each row pixel connected to (n × m) horizontal gate lines corresponding to a black display portion in a short period.

In the present embodiment, the frequency of the clock pulse of the vertical shift registers (VSR1 and VSR2) corresponding to the black display portion need only be increased without modifying the circuit configuration of the vertical shift register 8.

[0031]

As described above, according to the present invention,
The writing of the black signal to the non-image display portion can be completed in a shorter time. Therefore, for example, even if the number of driving lines of the liquid crystal panel is increased to increase the resolution of the image, sufficient time can be allocated to the video display portion, and even a video with a different aspect ratio can be displayed without degrading the display quality. can do.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a system configuration of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a partial equivalent circuit diagram of a liquid crystal panel of a liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing drive signals to a liquid crystal panel of a liquid crystal display device according to an embodiment of the present invention.

FIG. 4 is a circuit diagram of a vertical shift register portion corresponding to an upper black display portion of a liquid crystal panel screen of a liquid crystal display device according to an embodiment of the present invention.

FIG. 5 is a diagram showing timings of video signals written in pixels of the liquid crystal display device according to the embodiment of the present invention.

FIG. 6 is a diagram showing a timing at which a horizontal gate line in a black display portion of a liquid crystal panel screen of a liquid crystal display device according to an embodiment of the present invention is selected.

FIG. 7 is a schematic diagram showing an example of a screen when an image is displayed on liquid crystal panels having different aspect ratios.

[Explanation of symbols]

 1 television signal input terminal 2 RGB color signal conversion decoder 3 line memory section 4 signal inversion control and amplification section 5 logic section for forming liquid crystal panel driving pulse 6 liquid crystal panel 7 horizontal shift register 8 vertical shift register 9 pixel section 10 thin film transistor 11 liquid crystal 12 storage capacitor 13 counter electrode 14 video signal line 15 vertical signal line 16 horizontal gate line 17 signal line selection switch 18 liquid crystal panel signal input terminal

Claims (2)

[Claims] 1. A driving method of a liquid crystal display device, comprising a liquid crystal panel sandwiching a liquid crystal between a pair of electrode substrates and displaying an image of an input video signal, wherein an aspect ratio of the image by the input video signal is converted,
When displaying the image in the central part of the liquid crystal panel screen and performing black display at the upper and lower end portions of the liquid crystal panel screen, at least two or more of a large number of horizontal gate lines corresponding to the portion for performing the black display are displayed. A method for driving a liquid crystal display device, comprising simultaneously selecting horizontal gate lines and writing a black signal to pixels in each row (all pixels arranged in one row). 2. A driving method of a liquid crystal display device, comprising a liquid crystal panel sandwiching a liquid crystal between a pair of electrode substrates, and displaying an image of an input video signal, wherein an aspect ratio of the image by the input video signal is converted,
When displaying the image at the center of the liquid crystal panel screen and performing black display at the upper and lower ends of the liquid crystal panel screen, among a large number of horizontal gate lines corresponding to the portion for performing the black display, an arbitrary plurality of horizontal gate lines Regarding the horizontal gate lines, one horizontal gate line is selected, a black signal is written to the pixels in the row (all pixels arranged in one row), and then the remaining horizontal gate lines are selected at high speed or simultaneously. Driving method for liquid crystal display device.