Liquid crystal display method and liquid crystal display device improving motion picture display grade

• US 6,937,224 B1
• Filed: 06/15/2000
• Issued: 08/30/2005
• Est. Priority Date: 06/15/1999
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Miyachi, Koichi
• Primary Examiner(s): Nguyen, Jimmy H.
• Application Number:
  US09/595,363
• Time in Patent Office: 1,902 Days
• Field of Search: 345/87, 345 98-100, 345102-104, 345/204, 345/214
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0297 Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A source driver outputs a data signal and a reset (black) signal alternately to a source line. Four-hundred and eighty gate lines are divided into three groups each comprising 160 lines, and connected to gate drivers. A display control section outputs a discriminant signal, a scan start signal and a clock signal to the gate drivers, where the nth gate line is selected with the data signal outputted by the source driver, and where the (n+160)th gate line is selected with the reset signal outputted. Further, n is shifted sequentially. By writing the reset signal during the latter ⅓ of one frame like this, light leakage of pixels that are changed over from white display to black display is eliminated. Also, blurs of edge portions of a motion picture are reduced. Thus, display grade for motion pictures is enhanced with a minimum improvement.

Claims

1. A liquid crystal display device having:

a display panel in which are formed at least a plurality of column lines arranged in parallel to one another, a plurality of row lines arranged in parallel to one another in a direction in which the row lines intersect the column lines, and pixels provided corresponding to intersecting points of the column lines and the row lines;

a column line driver for supplying a data signal to the column lines; and

a row line driver for supplying a select signal to the row lines, wherein the liquid crystal display device comprises;

a display control section for supplying an image signal and a control signal to the column line driver, while supplying a control signal to the row driver, thereby controlling image display operation to the display panel;

black display signal generating means for generating a black display signal for displaying a black image at the pixels; and

a selector switch provided in the column line driver for switchedly selecting alternately between a data signal based on an image signal derived from the display control section and a black display signal derived from the black display signal generating means, wherein

the display control section selectively outputs a control signal for a first display mode or a control signal for a second display mode, such that in the first display mode, the control signal for making the row lines sequentially selected is supplied to the row line driver, where the select signal is supplied to the nth (n;

a positive integer) row line while the data signal is selected by the selector switch, and where the select signal is supplied to at least one of the row lines other than the nth row line while the black display signal is selected by the selector switch, and

such that in the second display mode, only the data signal is selected by the selector switch and a black display signal supply operation is not performed.

2. The liquid crystal display device according to claim 1, wherein

the row lines are divided into L (where L is a positive integer) blocks on an m-line (m:

a positive integer) basis; and

the row line driver comprises L partial row line drivers for supplying a select signal to row lines of each block.

3. The liquid crystal display device according to claim 1, wherein

the control signal from the display control section to the column line driver includes a switching control signal for controlling switching operation performed by the selector switch;

and

the switching control signal makes the select time of the data signal longer than the select time of the black signal display.

4. The liquid crystal display device according to claim 1, wherein

the control signal from the display control section to the column line driver includes a switching control signal for controlling the switching operation performed by the selector switch;

and

the switching control signal makes the select time of the data signal and the select time of the black display signal equal to each other.

5. The liquid crystal display device according to claim 1, wherein

the control signal from the display control section to the row line driver includes a discriminant signal for discriminating whether it is a black display signal supply period during which the black signal is supplied;

and

based on the discriminant signal, the row line drive supplies the select signal to the (n+m)th to (n+m+k−

1)th row lines (m, k;

a positive integer) during the black display signal supply period.

6. The liquid crystal display device according to claim 5, wherein

the control signal from the display control section to the row line driver includes a scan start signal, and

wherein the row line driver comprises:

a shift register having a plurality of latch circuits; and

scan start signal supplying means for supplying the scan start signal to the first latch circuit of the shift register during a data signal supply period, and also supplying the scan start signal to continuous k latch circuits starting from the mth latch circuit of the shift register during a black display signal supply period.

7. The liquid crystal display device according to claim 6, wherein

the scan start signal supplying means is enabled to change the latch circuit number “

m” and

the number of latch circuits “

k”

for the black display signal supply period.

8. The liquid crystal display device according to claim 7, further comprising:

supply control means for controlling the operation of the scan start signal supplying means, and

the supply control means outputs a control signal for setting the latch circuit number “

m”

to the scan start signal supplying means based on a scan-start-position designating signal from external.

9. The liquid crystal display device according to claim 1, further comprising:

a signal-use reference power supply for setting a voltage of a data signal supplied from the column line driver, wherein

the voltage of the signal-use reference power supply is changeable between the first display mode and the second display mode.

10. The liquid crystal display device according to claim 1, further comprising:

motion picture/still picture discriminating means for monitoring data of the same position on a screen based on an image signal derived from the display control section, thereby discriminating whether a picture based on the image signal is a motion picture or a still picture, and

outputting a command signal representing a result of the discrimination to the display control section, wherein,

the display control section selectively outputs the control signal for the first display mode or the control signal for the second display mode in response to the command signal.

11. The liquid crystal display device according to claim 1, further comprising:

a backlight for illuminating the display panel from its rear side; and

backlight adjusting means for switching brightness of the backlight between the first display mode and the second display mode according to the command signal.

12. The liquid crystal display device according to claim 1, wherein

the black display signal generating means is a black display signal use power supply, and

the voltage of the black display signal use power supply is changeable.