JPH0416982A - Liquid crystal driving device and liquid crystal panel driving method - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal panel without generating partail deterioration and with high reliability by providing a control means which controls the switching timing of a switching means, and a liquid crystal applying means which applies the output voltage of the switching means on the liquid crystal of the liquid crystal panel by inverting polarity at every prescribed period. CONSTITUTION:A voltage generating means 3 which generates a prescribed voltage value, and the switching means 4 which switches a video signal voltage and the output voltage of the voltage generating means are provided, and the AC-driving of liquid crystal is performed by applying a prescribed voltage on it in an area outside the display area of the liquid crystal panel 8. In other words, an image without generating the partial deterioration can be obtained by performing the AC-driving of the liquid crystal in the area outside the area where a video(data) is displayed even when video signals of plural specifications are inputted. In such a manner, it is possible to always display an appropriate image.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal drive device for displaying images on a liquid crystal display panel and a method for driving a liquid crystal display panel.

Conventional technology In recent years, as display devices have become larger, have higher definition, and higher brightness, liquid crystals have the characteristics of being small, lightweight, and low power consumption, and are being commercialized as color televisions and computer displays. etc., are attracting attention.

The operation of a standard twisted nematic mode liquid crystal is shown in FIG.

In FIG. 7, 71 is a deflection plate, 72 is a glass plate, and 73
is a transparent pole, and 74 is a liquid crystal molecule.

When the voltage applied between the two transparent electrodes 73 is off as shown in FIG. 7(a), the incident light is deflected by 90 degrees by the liquid crystal molecules, as shown in FIG. 7(b). When the liquid crystal molecules 74 are in the on state, the incident light is transmitted without being deflected by the liquid crystal molecules 74. Therefore, if the deflection directions of the two deflection plates 71 are orthogonal, light is transmitted in the off state and blocked in the on state.

Conversely, if the polarization directions of the two deflection plates 71 are parallel, light is blocked in the off state and transmitted in the on state. Through the above-described operations, an optical image corresponding to the video signal voltage is formed on the liquid crystal panel.

Hereinafter, a conventional liquid crystal driving device and liquid crystal driving method will be described with reference to the drawings.

FIG. 8 shows a block diagram of a conventional liquid crystal driving device. In FIG. 8, 1 is a first signal input terminal, 7 is a liquid crystal applying means that inverts the polarity of a signal voltage every predetermined period, for example, every field, and applies it to the liquid crystal, and 8 is a liquid crystal panel. The signal voltage manually input from the first signal input terminal 1 is applied at a predetermined period by the liquid crystal applying means 7 to the voltage value (hereinafter referred to as common voltage) applied between the two transparent electrodes 73 in FIG. The liquid crystal is constantly driven with alternating current, such as by reversing the polarity and applying a voltage of 0 or more to the liquid crystal of the liquid crystal panel 8, to prevent deterioration and extend the life of the liquid crystal.

FIG. 9 shows an explanatory diagram of a conventional liquid crystal panel driving method.
In FIG. 9, 91 is a common voltage. As shown in the figure, the liquid crystal is prevented from deteriorating by constantly AC driving the video signal voltage at a constant cycle with respect to the common voltage 91.
Efforts are being made to extend the lifespan.

Problems to be Solved by the Invention Generally, there are multiple standards for video signals for images displayed on a liquid crystal display, such as television signals and computer signals.

Therefore, in the above-mentioned liquid crystal display that displays both the television signal and the computer signal, as shown in Figure 2, for example, when displaying the television signal, all the pixels of the liquid crystal panel are used to display the computer signal. When displaying, only pixels in a certain area on the LCD panel are used to display the image.
In the remaining display area, it is possible to display a constant image in a single color, for example black or blue.

Now, let us consider a case where a computer is used as an input signal to display video (data), and an area other than the area where the video is displayed is displayed in a single color of black.

An effective voltage value of O volts, that is, a voltage value equal to the common voltage may be applied to the liquid crystal of a pixel that displays black. However, while the liquid crystal corresponding to the pixels in the video (data) display area is AC driven at a fixed period, for example, every field, the liquid crystal corresponding to the pixels in the black display area has an effective applied voltage value of 0. Because it is a volt, it is not driven by alternating current, and there is a difference in the degree of deterioration of the liquid crystal, especially when displaying only a certain area as a computer display for a long time, and then inputting a television signal to display the entire area. There is a problem that image quality deterioration occurs, such as the appearance of seams in the image.

In view of the above problems, the present invention provides a liquid crystal display that provides an appropriate display image regardless of the type of input signal and has high reliability without partial deterioration.

Means for Solving the Problems In order to solve the above problems, a liquid crystal driving device and a method for driving a liquid crystal panel according to the present invention include a voltage generating means for generating a predetermined voltage value, a video signal voltage and an output voltage of the voltage generating means. A switching means for switching is provided, and a predetermined voltage is also applied to the liquid crystal in an area outside the display area of the liquid crystal panel to drive the liquid crystal with alternating current.

Effect of the Invention With the above configuration, the present invention drives a predetermined voltage with alternating current to the liquid crystal in an area other than the area where images (data) are displayed. This makes it possible to realize images that are

EXAMPLE Hereinafter, a liquid crystal driving device and a method for driving a liquid crystal panel in an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a liquid crystal driving device in one embodiment of the present invention.

In FIG. 1, 1 is a first input signal terminal, 2 is a second input signal terminal, 3 is a voltage generating means for generating a predetermined voltage value, and 4 is an input signal from the second input signal terminal 2. a first switching means for switching the output signal of the voltage generating means 3; 5 a control means for controlling the switching timing of the first switching means 4; 6 a display displaying an input signal from a first input signal terminal l; A second switching means 7 selects the = side of the input signal from the second input signal terminal 2, and a second switching means 7 inverts the polarity of the output signal of the second switching means 6 at a fixed period, for example, every field. liquid crystal applying means,
8 is a liquid crystal panel.

Now, as shown in Figure 2, if the pixels in the entire display area are used to display a television signal, the pixels in a part of the area are used to display a computer signal, and the remaining area is to display black. Considering this, the display pixels of the television signal are N480 pixels and 640 pixels horizontally, while the display pixels of the computer signal are 400 pixels vertically and 600 pixels horizontally.

Figure 3 is a diagram showing an example of the characteristics of light transmittance with respect to the applied voltage of a liquid crystal.
The display voltage is set to 100 IRE.

However, ■o always satisfies the relationship of V, <Vo≦■2, and ■6 is a common voltage.

The operation of the liquid crystal driving device configured as described above will be explained below using FIGS. 1 to 3121.

First, a television signal is input from a first input signal terminal l, and a computer signal is input from a second input signal terminal 2. When displaying a television signal on the display device, the second switching means 6 is connected to the input signal terminal 1 side, and the liquid crystal applying means 7 applies a voltage to the liquid crystal of the liquid crystal panel 8 to display the signal.

When displaying a computer signal, the second switching means 6 is connected to the first switching means 4 side, and the pixel in the first row and first column from the upper left of the display section (hereinafter, the pixel in the m row and n column) is m
, n)) to (40640) and the display section from [41,1) to (480,640) are controlled by the control means 5 by controlling the first switching means 4.
■ in the third section from the voltage generating means 3. outputs the voltage to the second switching means 6. And from (41, 1) (
(11) (however, i
is the display interval from 41≦i≦440) to (i, 20) and from (+, 621) to (i.

640), the first switching means 4 is controlled by the control means 5, and the voltage generation means 3 is displayed as shown by ■ in FIG. and outputs the voltage to the second switching means (41
, 21) to (440, 600), the control means 5 controls the first switching means 4 to output the signal at the second input signal terminal 2 to the second switching means 6.

The signal voltage outputted to the second switching means 6 as described above is applied to the liquid crystal of the liquid crystal panel 8 by the liquid crystal applying means 7.

As described above, according to this embodiment, a predetermined voltage is applied even to pixels corresponding to areas other than the video (data) display area, and AC driving is performed, thereby achieving high core performance with no difference in the degree of deterioration. Display is possible, and by setting the predetermined voltage value applied to the non-display area to a voltage value smaller than IRE, an appropriate image can always be displayed.

FIG. 4 is an explanatory diagram of a method for driving a liquid crystal panel in an embodiment of the present invention.

The operation will be explained below using FIGS. 4 to 6.

As mentioned above, as shown in Figure 2, the pixels in the entire area of the display section are used to display television signals, the pixels in some areas are used to display computer signals, and the remaining area displays black. It shall be.

Figure 4 shows row j (1≦j≦40 and 4
41≦j≦480), the video signal voltage waveform during the -horizontal scanning period, (a) is when a television signal is input, and (b) is when a computer signal is input.

Figure 5 shows the video signal voltage waveform during the -horizontal scanning period in the row (41≦to≦440) in Figure 2, where (a) is when a television signal is input, and (b) is when a computer signal is input. be.

Moreover, FIG. 6 shows the video signal voltage waveform during one vertical scanning period in FIG. 2, and (a) shows when a television signal is input;
0:I) is when a computer signal is input.

As described above, in this embodiment, the video display w! Since a constant voltage is applied to the liquid crystal of the pixel corresponding to the area outside the area and AC drive is performed, there is no difference in deterioration within the display area, and the predetermined voltage value applied to the non-display area is the same as the applied voltage. By setting the value to a voltage value smaller than IRE, an appropriate image will always be displayed.

In this embodiment, the nine areas outside the video (data) display area are displayed in black, but for example, by applying the above-mentioned processing to the green and red signals in the case of blue display, A similar effect can be obtained.

Effects of the Invention As described above, according to the present invention, even when images of a plurality of standards are displayed in different areas on the same liquid crystal panel, proper display is possible without partial deterioration depending on the area.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a liquid crystal driving device according to an embodiment of the present invention, Fig. 2 is a diagram showing an example of displaying a television signal and a computer signal on a liquid crystal bubble, and Fig. 3 is a diagram showing applied voltage to the liquid crystal. FIG. 4 is a video signal voltage waveform diagram during the -horizontal scanning period of row j (1≦J≦40 and 441≦j≦480), and FIG.
440) - A video signal voltage waveform diagram during a horizontal scanning period, FIG. 6 is a video signal voltage waveform diagram during one vertical scanning period, and FIG. 7 is an explanatory diagram of the operation of a standard twisted nematic mode liquid crystal. The eighth session is a block diagram of a conventional liquid crystal driving device, and FIG. 9 is an explanatory diagram of a conventional liquid crystal panel driving method. 3... Voltage generating means, 4... First switching means, 5... Control means, 6...
Second switching means, 7...Liquid crystal applying means, 8
...LCD panel. Name of agent: Patent attorney Shigetaka Awano Haka 1 person 4-:f'
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Claims (5)

[Claims] (1) A voltage generating means for generating a predetermined voltage value, a switching means for switching between a video signal voltage and an output voltage of the voltage generating means, a control means for controlling switching timing of the switching means, and an output voltage of the switching means. 1. A liquid crystal driving device comprising: liquid crystal applying means for reversing the polarity and applying the voltage to the liquid crystal of a liquid crystal panel at predetermined intervals. (2) The liquid crystal drive device according to claim (1), wherein the control means controls a plurality of input signals of different standards to be displayed using a part or all of the display area. . (3) The liquid crystal driving device according to claim (1), wherein the predetermined voltage value is applied to the liquid crystal in an area other than an area where images or data are displayed. (4) In an active matrix type liquid crystal panel, when displaying an image using a part of the liquid crystal panel, a predetermined voltage value is applied to the liquid crystal in the area other than the display area with the polarity reversed at predetermined intervals. A method for driving a liquid crystal panel, characterized in that: (5) The method for driving a liquid crystal panel according to claim (5), wherein the liquid crystal panel displays an image in a normally black mode.