JPH0764053A - Method for driving active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To make a driving voltage low and to reduce the influence of a data signal of other row electrode line to a holding electron by making a part of a fine scanning period in a selected period among the fine scanning periods constituted of further dividing one scanning period into plural periods a selected by level and making remaining fine scanning periods specified holding potential. CONSTITUTION:In a scanning signal, a part of the fine scanning period in the selected period among the fine scanning periods is made to be at the selected level, and remining fine scanning periods are made to be at the holding potential + or -Vc. Scanning signal waveforms applied to row electrodes X1, X2 are shown by figures X1, X2, and the period taking a selected/non-selected level being a real selected period is equal to the selected period with 1/10 duty. Further, a data signal waveform applied to a column electrode Y1 is shown by figure Y1, and the data signal is formed so that one scanning period is divided into plural parts similarly to the scanning signal, and only a part of fine scanning period is made to be at the selected/non-selected level, and remaining fine scanning periods are made to be at intermediate potential between the selected/non- selected level.

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 an active matrix type liquid crystal display device using a ferroelectric thin film element or a non-linear resistance element as an active element.

[0002]

2. Description of the Related Art Liquid crystal display panels are already in general use, and high precision display is achieved by an active matrix type liquid crystal display device using a ferroelectric thin film element or a non-linear resistance element as an active element. There are many active researches on techniques to achieve this.

The principle of operation of a device using a ferroelectric thin film device as an active device is to apply an electric field to a liquid crystal or the like by utilizing a memory function due to spontaneous polarization of a ferroelectric thin film, and also to have a non-linearity. The operation principle of the thin film element is that it has high resistance in a low voltage region and low resistance in a high voltage region.

As a common problem of the active matrix type liquid crystal display device using the ferroelectric thin film element or the non-linear resistance element as the active element as described above, the influence of distribution and fluctuation of individual element characteristics And the threshold voltage Vth of the element and the driving voltage are high. Further, a problem when the ferroelectric thin film element is used as the active element is that the ferroelectric property during the holding period is high. It is mentioned that the memory effect of the thin film is not sufficient.

As a method for solving these drawbacks, the following matrix driving method has been proposed.

As a driving method thereof, there are a selection phase and a holding phase, and the holding potential ± Vb is added to the scanning signal in the holding phase.
There is a bias that
No. 14), the above-mentioned holding potential ± Vb can be independently set according to the use situation (Japanese Patent Publication No. 5-1474), and by using these driving methods, high density can be achieved. Liquid crystal display panels have become possible with relatively easy means.

The above patent will be described in the case of a 5 × 6 dot matrix display as shown in FIG. In FIG. 5, white circles indicate ON display, black circles indicate OF.
F display is shown. For example, in the picture element (X1, Y1) on the row electrode X1 and the picture element (X2, Y1) on the row electrode X2 shown in FIG. 5, the picture element (X1, Y1) indicates ON and the picture element (X
2, Y1) indicates OFF display.

FIG. 6 shows the signal waveform of each row electrode X and each column electrode Y in the case of field inversion driving in which AC driving is performed for each field.

X1 and X2 represent scanning signal waveforms applied to the row electrodes X1 and X2, Y1 represents a data signal waveform applied to the column electrode Y1, and X1-Y1 and X2-Y1 represent potential differences between both electrodes. Is shown.

The characteristic of these driving methods is that the holding potential ± Vb is given during the holding period of the scanning signal. By providing the holding potential ± Vb during the holding period, the driving voltage is significantly lowered, and it becomes possible to compensate for the memory shortage of the ferroelectric thin film during the holding period.
It was greatly improved and made great strides toward practical application.

However, the use condition of the liquid crystal display panel is not always constant, and the display quality changes due to various factors such as temperature and viewing angle. Therefore, such a change is conventionally used. The driving method described above is not necessarily effective for a display panel using a non-linear resistance element.

Further, since the data signal is set to the selection level and the non-selection level, respectively, in the period synchronized with all the periods of one scanning period, the holding potential Vb greatly varies depending on the data signals of the other row electrodes. There was such a problem.

Therefore, in the case of the above driving method, the absolute value of the difference between the holding potential ± Vb and the data signal potential must be smaller than the threshold voltage Vth of the element, and the holding potential ± Vb is made too large. I couldn't.

As a method for solving these problems, the following matrix driving method has been proposed.

This driving method enables gradation display by controlling the fluctuation of the effective voltage. (Japanese Patent Application Laid-Open No. 58-181088) Similarly, assuming that the 5 × 6 dot matrix display as shown in FIG. 5 is used, the signal of each row electrode X and each column electrode Y in the case of field inversion drive in which AC drive is performed for each field. The waveform is shown in FIG. X1 and X2 represent scanning signal waveforms applied to the row electrodes X1 and X2, Y1 represents a data signal waveform applied to the column electrode Y1, and X1-Y1 and X2-Y1 represent potential differences between both electrodes.

A feature of this driving method is that a scanning signal is included in a fine scanning period obtained by further dividing one scanning period obtained by equally dividing all or part of each field period by the number of scanning lines into a plurality of periods. Has a part of the fine scanning period in the selection period as a selection level and the rest of the fine scanning period as a non-selection level, and the data signal is in a period synchronized with the fine scanning period in which the scanning signal takes the selection level of each row electrode. , The data signal is set to the non-selection level and the non-selection level oppositely to the selection level and the non-selection level, respectively, corresponding to ON and OFF of the pixel in the period synchronized with the remaining fine scanning period.

By using this driving method, the holding potential can be suppressed to be extremely small regardless of the display content of the other row electrodes, but the above-mentioned high driving voltage and holding voltage are maintained. Problems such as memory shortage of ferroelectric thin film during the period have not been solved.

[0018]

SUMMARY OF THE INVENTION The present invention is a subject of the conventional driving method as described above, that is, high driving voltage,
Problems such as insufficient memory of the ferroelectric thin film during the holding period that have not yet been solved, and that the holding potential is greatly affected by the data signals of other row electrodes. The purpose is to effectively solve problems.

[0019]

According to a method of driving an active matrix type liquid crystal display device of the present invention, a display element composed of a liquid crystal display element and a ferroelectric thin film element is provided with a row electrode for selectively driving the display element. A scanning signal having a selection period and a holding period in a field cycle is applied to the row electrodes of the matrix type liquid crystal display device connected to the column electrodes,
A data signal having a lighting potential and a non-lighting potential corresponding to display contents or a potential between them is applied to the column electrodes according to the selection period of the row electrodes to display display data on the liquid crystal display element. In a method of driving a matrix type liquid crystal display device such as writing, the scanning signal is formed by further dividing one scanning period in which all or part of each field period is equally divided by the number of scanning lines into a plurality of periods. Of the scanning period, a part of the fine scanning period within the selection period is set as a selection level, the remaining fine scanning period is set to the holding potential ± Vc, and the scanning period of the other row electrodes in the holding period corresponds to the scanning period. Similarly, each scanning period is also divided into a plurality of periods, a part of the fine scanning period is set to a non-selection level, and the remaining fine scanning period is set to the holding potential ± Vc. of In the period synchronized with the fine scanning period that takes the selection level, the selection level and the non-selection level are respectively taken corresponding to ON and OFF of the pixel, and the period synchronized with the remaining fine scanning period is the selection level of the data signal, The feature is that the intermediate potential of the non-selection level is used.

Further, the present invention is a method of driving an active matrix type liquid crystal display device, wherein the display element comprises a liquid crystal display element and a non-linear resistance element.

Further, according to the present invention, in the fine scanning period obtained by equally dividing each scanning period corresponding to the scanning period of each row electrode, the first half is selected, the non-selection level is set, and the second half is set to the holding potential ± Vc. A method of driving an active matrix type liquid crystal display device characterized by the above.

[0022]

The active matrix type liquid crystal display device using the ferroelectric thin film element or the non-linear resistance element as the active element in the present invention reduces the drive voltage by the means for solving the above-mentioned problems, and In addition, it is possible to reduce the influence of the data signal of the other row electrode line on the holding potential. Further, even when the ferroelectric thin film element is used as the active element, it is possible to sufficiently compensate for the memory shortage of the ferroelectric thin film.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of driving an active matrix type liquid crystal display device of the present invention will be described below with reference to the drawings.

FIG. 4 is a vertical sectional view of the liquid crystal display device according to the present invention.

As shown in the figure, the liquid crystal display device of the present invention has a liquid crystal 3 filled between the substrates 1 and 2.

On the surface of the substrate 1 facing the substrate 2,
A row electrode 4, an active element 5 made of a ferroelectric thin film or a non-linear resistance thin film, a pixel electrode 6, and a liquid crystal alignment film 7 are formed.

On the surface of the substrate 2 facing the substrate 1,
A column electrode 8 and a liquid crystal alignment film 7 are formed.

The substrate 1 and the substrate 2 are arranged to face each other via a spacer 9, and the liquid crystal 3 filled between them is sealed by a seal 10.

Polarizing plates 11 are attached to the other surfaces of the substrates 1 and 2, respectively.

Glass or polymer compounds are used for the substrates 1 and 2.

The row electrode 4 is formed of a conductive thin film such as aluminum, tantalum, titanium, molybdenum, copper, or ITO (indium tin oxide).

Here, FIG. 1 shows VQ characteristics of a typical ferroelectric thin film element.

The ferroelectric thin film 5 is made of a strong material such as polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-tetrafluoroethylene copolymer, or polyvinylidene cyanide-vinyl acetate copolymer. Dielectric polymer, barium titanate, PZT
(Pb (Zr, Ti) O3) or PLZT ((Pb,
Inorganic ferroelectrics such as La) O3) and other ferroelectric liquid crystal polymers are used.

The memory function of the ferroelectric thin film element is used as the operation principle of the one using the ferroelectric thin film element as the active element.

FIG. 2 shows the VI characteristic of a typical non-linear resistance element.

The non-linear resistance thin film 5 includes a varistor and MI.
An M element, a diode ring or the like is used.

The principle of operation of a device using a non-linear resistance element as an active element is as follows:
It uses a characteristic that exhibits low resistance in the high voltage region.

The pixel electrodes 6 and the column electrodes 8 are formed of a conductive thin film such as ITO.

The substrates 1 and 2 are the pixel electrodes 6 or the column electrodes 8 respectively.
Further, the liquid crystal alignment film 7 is applied to the upper surface of the liquid crystal, and after baking, a predetermined alignment treatment is performed.

After the spacer 9 is formed, the substrates 1 and 2 are faced to each other and attached to each other, and the periphery thereof is sealed with a seal 10 to inject and fill the liquid crystal 3.

After that, the polarizing plate 11 is attached to the back surfaces of the substrates 1 and 2, respectively.

The liquid crystal 3 used in the above liquid crystal display device.
May be any of twisted nematic type, super twisted nematic type, electric field control birefringence type, dynamic scattering type, polymer dispersion type, polymer network type, guest host type, etc. Ferroelectric liquid crystal or anti-ferroelectric liquid crystal can also be used.

Further, not only such a liquid crystal display device, but also a display device utilizing electroluminescence or electrochromic phenomenon, and other information processing devices other than the display device can be implemented. The configuration and the like are also arbitrary.

FIG. 3 shows an equivalent circuit diagram of a liquid crystal display device provided with a ferroelectric thin film element or a non-linear resistance element.

The above-mentioned liquid crystal display device is mounted with a driver for driving, and from there, by sequentially scanning each row electrode line for each field, the display data corresponding to the display contents of each picture element is sent to each column electrode for display. Done.

In this embodiment, the conventional example is also used.
It is assumed that the 5 × 6 dot matrix display as shown in FIG. In FIG. 5, white circles indicate ON display, and black circles indicate OFF display.

For example, picture elements (X1, Y1) on the scanning signal line X1 and picture elements (X2, Y on the scanning signal line X2 shown in FIG.
In 1), the picture element (X1, Y1) shows ON display, and the picture element (X2, Y1) shows OFF display.

FIG. 8 shows the signal waveform of each row electrode X and each column electrode Y in the case of field inversion driving in which AC driving is performed for each field.

First, the scanning signal has a selection level in a part of the fine scanning period within the selection period and a holding potential ± Vc in the remaining fine scanning period. The fine scanning period is one scanning period further divided into a plurality of periods, and the one scanning period is all or part of each field period equally divided by the number of scanning lines. Is.

Also, each scanning period corresponding to the scanning period of the other row electrode which is the holding period is similarly divided into a plurality of periods, and a part of the fine scanning periods is set to the non-selection level and the remaining fine scanning periods. The scanning period is set to the holding potential ± Vc.

Further, regarding the data signal, in the period in which the scanning signal is synchronized with the fine scanning period in which the selection level of each row electrode is taken, the data signal corresponds to ON / OFF of the pixel, and the selection level is The non-selection level is set, and an intermediate potential between the selection level and the non-selection level of the data signal is set in the period synchronized with the remaining fine scanning period.

Here, the method of dividing one scanning period into a plurality of can be selected by various methods such as various ratios, unequal intervals, and even intervals, but in the present embodiment, the scanning period of each row electrode is selected. Each corresponding scanning period is divided into two equal parts,
In the fine scanning period divided into two, the first half is selected and the non-selection level and the second half is the holding potential ± Vc, which will be described with reference to FIG.

X1 and X2 in FIG. 8 are row electrodes X1 and
The scanning signal waveform applied to X2 is shown, and the actual selection period, that is, the period during which the selection and non-selection levels are taken (the first half of the fine scanning period) is the same as the 1/10 duty selection period. ing.

Further, in Y1, the waveform of the data signal applied to the column electrode Y1 is shown, and one scanning period is divided into a plurality (in this case, half) like the scanning signal, and a part of the fine scanning period ( In this case, select only the first half fine scanning period),
For the non-selection level, the remaining fine scanning period is selected and the intermediate potential of the non-selection level is set. And X1-Y1 and X2-Y1 have shown the electric potential difference between both electrodes.

As can be seen from the above description and FIG. 8, the potential difference between the electrodes is always the holding potential ± Vc applied by the scanning signal during a part of the fine scanning period. The absolute value of the holding potential ± Vc may be Vth or less of the element, that is, the holding potential ± Vc can be more effectively given.

As a result, the driving voltage can be further lowered, and even when the ferroelectric thin film element is used as the active element, it is possible to compensate for the memory shortage of the ferroelectric thin film. It was

Further, since the period in which the data signal takes the selected / non-selected level is only a part of the fine scanning period, the influence of the data signal of the other row electrode line on the holding potential ± Vb can be reduced. As a result, the fluctuation of the holding potential ± Vb during the holding period can be suppressed to be extremely small.

In the above embodiment, the field inversion drive in which the write polarity is inverted for each field to perform the AC drive has been described, but the frame inversion drive can be performed in the same manner as in the above embodiment.

[0059]

As is clear from the above description, according to the driving method of the active matrix type liquid crystal display device of the present invention, a constant holding potential ± Vc is always maintained in a part of the fine scanning period regardless of the data signal. Since the voltage can be applied, the drive voltage can be further reduced, and the holding potential can be less affected by the data signal of another row electrode line.

Further, when the ferroelectric thin film element is used as the active element, it is possible to compensate for the memory shortage of the ferroelectric thin film.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the configuration of the present embodiment and is a diagram showing VQ characteristics of a typical ferroelectric thin film element.

FIG. 2 is a diagram for explaining the configuration of the present embodiment and is a diagram showing a VI characteristic of a typical nonlinear resistance element.

FIG. 3 is an equivalent circuit diagram of a liquid crystal display device provided with a ferroelectric thin film element or a non-linear resistance element for explaining the configuration of the present embodiment.

FIG. 4 is a vertical cross-sectional view of a liquid crystal display device for explaining the configuration of the present embodiment.

FIG. 5 is a schematic diagram of a 5 × 6 dot matrix liquid crystal display device for explaining the configuration of this embodiment or a conventional example.

FIG. 6 shows a drive waveform of a conventional example.

FIG. 7 shows drive waveforms of a conventional example.

FIG. 8 shows drive waveforms in this embodiment.

[Explanation of symbols]

1, substrate 2, substrate 3, liquid crystal 4, row electrode 5, ferroelectric thin film (or active element composed of nonlinear resistance thin film) 6, pixel electrode 7, liquid crystal alignment film 8, column electrode 9, spacer 10, seal 11, polarizing plate

Claims (3)

[Claims] 1. A row electrode of a matrix type liquid crystal display device, wherein a display element comprising a liquid crystal display element and a ferroelectric thin film element is connected to a row electrode and a column electrode for selectively driving the display element, A scanning signal having a selection period and a holding period is applied in a field cycle, and a lighting potential and a non-lighting potential corresponding to display contents, or a potential between them is applied to the column electrode depending on the selection period of the row electrode. In a method for driving a matrix type liquid crystal display device, in which display data is written to the liquid crystal display element by applying a data signal of Among the fine scanning periods formed by further dividing the divided one scanning period into a plurality of periods, a part of the fine scanning periods within the selection period is set as a selection level, and the remaining fine scanning periods are set to the holding potential ± Vc. Also, each scanning period corresponding to the scanning period of the other row electrodes in the holding period is similarly divided into a plurality of periods, and a part of the fine scanning periods is set as a non-selection level and the remaining fine scanning is performed. The period is set to the holding potential ± Vc, and the data signal is turned on and off in the pixel in the period synchronized with the fine scanning period in which the scanning signal takes the selection level of each row electrode.
An active matrix type liquid crystal having a selection level and a non-selection level corresponding to the FF, and a period synchronized with the remaining fine scanning period is set to an intermediate potential between the selection level and the non-selection level of the data signal. Driving method of display device. 2. The method for driving an active matrix type liquid crystal display device according to claim 1, wherein the display element comprises a liquid crystal display element and a non-linear resistance element. 3. A fine scanning period in which each scanning period corresponding to the scanning period of each row electrode is divided into two equal parts, the first half portion is selected, the non-selection level, and the second half portion is set to the holding potential ± Vc. The method for driving an active matrix type liquid crystal display device according to claim 1 or 2.