JPH04293088A - Driving method for active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To offer the driving method for the active matrix type liquid crystal display device which easily makes a gradational screen display at low cost. CONSTITUTION:Alternating voltages E1-E5 are applied to drain lines of an active matrix type liquid crystal panel. Those voltages E1, E2, E3, E4, and E5 are + or -V0 (V) in 1st and 2nd frames and + or -V0, + or -V1, + or -V2, + or -V3, and + or -V4 (V) in 3rd and 4th frames. The voltages applied to the drain lines are varied in amplitude in time series to display half-tones, so the gradational screen display can be made without using any drain driver for gradations.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an active matrix liquid crystal display device that displays a multi-gradation screen on an active matrix liquid crystal panel.

0002

2. Description of the Related Art Conventionally, when driving an active matrix liquid crystal display device, for example, in order to display a 5-gradation screen, five different voltage levels are applied from the drain driver to the drain line of the active matrix liquid crystal panel. It is necessary to select and supply two AC voltages.

FIG. 4 is a voltage waveform diagram showing a method of driving a conventional active matrix liquid crystal display device in five-gradation display. The drain driver supplies voltages E1 to E5 of the AC waveform shown in FIG. 4 to the drain line of the active matrix liquid crystal panel. This voltage E1, E2
, E3 , E4 , E5 are ±V0 , ±V1 , respectively
±V2, ±V3, ±V4 (V). For this reason, active matrix type liquid crystal panels have voltages of E1 to E.
5, it is possible to display a screen with 5 gradations. For example, by selecting an alternating voltage that corresponds one-to-one to five halftones and applying this alternating voltage to the liquid crystal, a halftone screen can be displayed. Therefore, the voltage ViLC applied to the liquid crystal is expressed by the following equation. However, i
is the gradation. ViLC =Vi-1...(
1)

0004

[Problems to be Solved by the Invention] However, in the above-mentioned conventional method for driving an active matrix type liquid crystal display device, when displaying a screen with multiple gradations, it is necessary to use the same number of voltages as the number of gradations to be displayed. level (for example, 3
It is necessary to use a drain driver that can output three voltage levels (for gray scales), and the number of voltage levels input to this drain driver must be the same as the number of gray scales to be displayed. As the number increases, the number of input lines input to the drain driver also increases. Therefore, in order to increase the number of gradations to be displayed, it is necessary to change the drain driver, which poses a problem in that it requires expense and time to develop a new multi-gradation drain driver.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a method for driving an active matrix liquid crystal display device that can easily display a multi-gradation screen at low cost. purpose.

[0006]

[Means for Solving the Problems] A method for driving an active matrix liquid crystal display device according to the present invention includes an active matrix liquid crystal panel having a plurality of gate lines and a plurality of drain lines, and scanning the gate lines. In a method of driving an active matrix liquid crystal display device having a gate driver to drive the drain line and a drain driver to alternately drive the drain line, an alternating voltage having an arbitrary voltage level selected at a predetermined period is applied to the drain line. It is characterized by

[0007]

According to the present invention, an alternating voltage having an arbitrary voltage level selected at a predetermined period is applied to the drain line of an active matrix liquid crystal panel. In this way, by changing the amplitude of the voltage applied to the drain line in time series, for example, a first gradation based on the first arbitrary voltage level and a second gradation based on the second arbitrary voltage level can be obtained. Second
It is possible to display intermediate tones between the gradation and the gradation on the liquid crystal panel. Therefore, without increasing the number of voltage levels,
Since the number of gradations can be increased, multi-gradation screen display can be easily performed at low cost using a conventional drain driver.

Further, in the present invention, a plurality of different alternating voltages can be applied to the drain line. In this case, the number of gray levels that can be displayed can be variously set depending on the combination of the arbitrary voltage levels.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a voltage waveform diagram showing a driving method for an active matrix liquid crystal display device according to a first embodiment of the present invention, and FIG. 2 is a wiring diagram showing an active matrix liquid crystal panel. Note that FIG. 1 shows a case of 5-gradation display.

As shown in FIG. 2, in the active matrix type liquid crystal panel, drain lines D1 to D3 and gate lines G1 to G3 are wired in a grid pattern, and the drain lines D1 to D3 and the gate lines G1 to G3 are connected to each other. The active elements 1 corresponding to the intersections have their drains connected to the drain lines D1 to D3, and their gates connected to the gate lines G1 to G3. Further, a liquid crystal 2 is connected to the source of each active element 1. The active element 1 is driven according to the gate voltage supplied to the gate lines G1 to G3 from a gate driver (not shown), and the AC voltage supplied to the drain lines D1 to D3 from a drain driver (not shown) is activated. It is applied to the liquid crystal 2 via the element 1.

Voltages E1 to E5 (alternating voltage) having an AC waveform shown in FIG. 1 are applied to the drain lines D1 to D3. These voltages E1, E2, E3, E4,
E5 is ±V0 for the first frame and second frame, respectively.
(V), and the third and fourth frames are ±V
0, ±V1, ±V2, ±V3, ±V4 (V)
It is.

For example, when displaying the first gradation (black) on a liquid crystal panel, voltage E1 is applied to drain lines D1 to D3.
Apply. Similarly, when displaying the second to fifth gradations on the liquid crystal panel, voltages E2 to E5 are applied to the drain lines D1 to D3.

In this case, the voltage ViL applied to the liquid crystal 2
C is represented by the following two formulas. However, i is a gradation. ViLC = (V0 2 +Vi-1 2 )/2
...(2) According to this embodiment, the drain line D1
By changing the amplitude of the voltages E1 to E5 applied to the voltages E1 to D3 in time series in the third and fourth frames with respect to the first and second frames, multi-gradation is achieved based on the above equation (2). can be displayed on the screen. Therefore, multi-gradation screen display can be easily performed at low cost using a conventional drain driver.

FIG. 3 is a voltage waveform diagram showing a method of driving an active matrix liquid crystal display device according to a second embodiment of the present invention.

In this embodiment, the drain lines D1 to D3 are supplied with voltages E1 to E of the AC waveform shown in FIG.
5 is applied. These voltages E1, E2, E3,
E4 and E5 have the first frame and second frame ±
V0, ±V0, ±V0, ±V3, ±V3 (V
), and the third and fourth frames are ±V0
, ±V1, ±V2, ±V3, ±V4 (V).

In this case, the voltage Vi applied to the liquid crystal 2
LC is represented by the following three formulas. However, i is a gray scale, and VK is a voltage level selected for the first frame. ViLC = (VK 2 +Vi-1 2 )/2
...(3) According to this embodiment, the drain line D1
By changing the amplitude of the voltages E1 to E5 applied to the voltages E1 to D3 in time series in the third and fourth frames with respect to the first and second frames, multi-gradation is achieved based on the above equation (3). can be displayed on the screen. Therefore, similarly to the first embodiment, multi-gradation screen display can be easily performed at low cost using the conventional drain driver.

Note that in each of the above embodiments, the voltage E1
Although the alternating period from E5 to E5 is set every two frames, the same effect can be obtained every frame or every gate line.

Furthermore, by arbitrarily setting the voltage level of each frame, the voltage ViLC applied to the liquid crystal can be set as many times as there are combinations of voltage levels. Therefore, the number of gradations that can be displayed is infinite.

[0019]

As explained above, according to the present invention, by applying an alternating voltage with an arbitrary voltage level selected at a predetermined period to the drain line of an active matrix liquid crystal panel, the amplitude of the voltage can be changed in a time series. Because it changes
Multi-gradation screen display can be easily performed at low cost using a conventional drain driver.

[Brief explanation of drawings]

FIG. 1 is a voltage waveform diagram showing a method of driving an active matrix liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a wiring diagram showing an active matrix liquid crystal panel.

FIG. 3 is a voltage waveform diagram showing a method of driving an active matrix liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a voltage waveform diagram showing a method of driving a conventional active matrix liquid crystal display device.

[Explanation of symbols]

1; Active element 2; Liquid crystal D1, D2, D3; Drain wire G1, G2, G3; Gate line

Claims (2)

[Claims] 1. An active matrix liquid crystal panel comprising: an active matrix liquid crystal panel having a plurality of gate lines and a plurality of drain lines; a gate driver that scans and drives the gate lines; and a drain driver that alternately drives the drain lines. 1. A method for driving an active matrix liquid crystal display device, comprising applying an alternating voltage of an arbitrary voltage level to the drain line at a predetermined period. 2. The method of driving an active matrix liquid crystal display device according to claim 1, wherein a plurality of said alternating voltages that are different from each other are applied to said drain line.