JPH03279926A - Driving method for electrooptic device - Google Patents

Abstract

PURPOSE:To adjust respective picture elements finely and stably by controlling the resistance of a nonlinear resistance element by using a couple of row electrodes, providing the nonlinear resistance element with a high switch function, and writing data by column electrodes. CONSTITUTION:In the electrooptic device wherein plural nonlinear resistance elements 44a and 44b are provided for each picture element electrode and connected to two different row electrodes 41a and 41b, the resistance values of the nonlinear resistance elements 44a and 44b are controlled while row electrodes are selected, couple by couple, in line sequence, thereby enabling the nonlinear resistance elements 44a and 44b to operate as complete switches. Then data is applied to the column electrodes 42 and then written and held. Consequently, a high-level display such as a gradational display can stably and securely be made even on a panel which uses the nonlinear resistance elements.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving an electro-optical device having a pixel electrode and a nonlinear resistance element for each pixel arranged along a driving electrode.

[Summary of the invention]

This invention drives an electro-optical device in which each pixel electrode and a plurality of nonlinear resistance elements provided for each pixel electrode are connected to two adjacent driving electrodes with each pixel electrode sandwiched between them. By applying a waveform to this pair of drive electrodes and controlling the resistance value of the nonlinear resistance element, data writing is stabilized against variations in the characteristics of the nonlinear resistance element and changes over time. The present invention provides a driving method for an electro-optical device that enables operation in such a way that the retention of data input to one pixel is not affected by data input manually to other pixels. be.

[Conventional technology]

As a thin, lightweight, low power consumption display panel,
Liquid crystal display panels have excellent characteristics and are currently widely used in laptops, book-type personal computers, and the like. Among these, active matrix display panels are attracting attention as a method that can increase the amount of displayed information and improve image quality. As an active element, a three-terminal element using an m-film transistor, etc.
There are two-terminal elements such as nonlinear resistance elements such as M, and PN junction thin film diodes.

Among these, three-terminal devices have the drawbacks of complicated processes, low yields, and high costs because they require a large number of films to be formed.

Additionally, diodes have problems such as low breakdown voltage and vulnerability to static electricity. On the other hand, nonlinear resistance elements have a simple structure and can have high breakdown voltages, so they are advantageous for application to large-area display panels at low cost.

FIG. 3(a) is an X-Y matrix panel circuit diagram of a conventional electro-optical device using a nonlinear resistance element, and FIG.
Generally, about 100 to 1000 column electrodes 1 and 32 are formed on each of the substrate B and the counter substrate A. The XY intersection has a pixel electrode 342 and a nonlinear resistance layer 341, and the row electrode 31
A nonlinear resistance element 34 connected to is provided. An electro-optic material (liquid crystal) 33 is held between the substrates A and B.

Driving this type of display panel is as follows.
That is, a large number of row electrodes 31 in FIG. 3 are selected line-by-line from the top one by one, and data is written by the column electrodes 32 within the selected period. FIG. 2 shows the conventional voltage averaging method. This shows the waveform. That is, when the waveform shown in FIG. 2 fat is applied to one of the rows tli31 and the waveform shown in FIG. (a) shown in al.
The waveform shown by the solid line in FIG. 2 [C1] is applied to the waveform shown in FIG.

At this time, a voltage as shown by the broken line is applied to both ends of the nonlinear resistance element 34, and therefore, the effective voltage applied to the liquid crystal is the average of the areas surrounded by diagonal lines.

At this time, in order to display with sufficient contrast, the effective voltage applied to the liquid crystal at the selected point must be higher than the saturation voltage of the liquid crystal, and the effective voltage applied to the liquid crystal at non-selected points must be the threshold voltage of the liquid crystal. It is necessary that it be lower than . In a nonlinear resistance element, the effective voltage applied to the liquid crystal can be controlled by changing the resistance value of the element during each of the writing period and the holding period. That is, at the selection point, a higher voltage is applied to the nonlinear resistance element 34 during the selection period, thereby lowering the resistance of the element and making it easier for the pixel electrode 342 to be charged. Furthermore, at the non-selected point, the voltage applied to the nonlinear resistance element 34 is kept low during the selection period, preventing the resistance of the element from becoming low and making it difficult for the pixel electrode 342 to be charged. Then, during the holding period, a low voltage is applied to the nonlinear resistance element 34 at both the selected point and the non-selected point, thereby increasing the resistance of the element and increasing the ability to hold the charged charge.

In this way, high contrast can be obtained even when the number of dots is increased. In addition, in order to obtain sufficient drive margin when displaying on this type of display panel, the capacitance C of the liquid crystal section in each pixel must be
It is also important to set a large ratio between +c and the capacitance CNL of the nonlinear resistance element section.

[Problem to be solved by the invention]

In this way, display panels using non-linear resistance elements can have a large display capacity, but when trying to display gradation in addition to simple selection and non-selection, it is necessary to use a display panel that uses non-linear resistance elements compared to a three-terminal element. Difficult things happen. This is due to the nonlinear Since a weak current can flow in the resistive element even during the holding period, the influence of data on other pixels is added little by little through the column electrodes. Therefore,
Depending on the display pattern, the effective voltage value applied to the liquid crystal deviates from a predetermined value. In addition, the resistance value of the element is the charging capacity of the electric charge,
This has a significant impact on the retention ability, so if the element characteristics vary within the panel plane or shift due to changes over time, this will directly affect the effective voltage value applied to the liquid crystal. Therefore, when the effective voltage value applied to the liquid crystal must be precisely controlled, such as in gradation display, a difference in contrast appears, and this difference becomes larger as the panel size becomes larger and the number of dots increases. There was a problem.

Therefore, an object of the present invention is to provide a driving method for an electro-optical device that allows more advanced display such as gradation display to be performed more stably and reliably even on a panel using non-linear resistance elements. .

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention has the following features:
(A plurality of nonlinear resistance elements 44a and 44b are provided for each pixel electrode 442 as shown in bl, and each
In the electro-optical device connected to the row electrodes 41a and 41b of the book, the resistances of the nonlinear resistance elements 44a and 44b are controlled while selecting the row electrodes 41a and 41b line-sequentially one pair at a time, so that the nonlinear resistance elements 44a and 44b are completely In addition, by adding data to the column electrode 42, data is written and held. If the electrode connected to the pixel electrode via a nonlinear resistance element is a column electrode, the effects of the present invention will not change if writing and holding are performed from the row electrode to the pixel electrodes arranged in the column direction.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1st
The figures are driving waveform diagrams for explaining the present invention in detail.
l is the waveform applied to the second row electrode 41b, FIG.
(dl, tel, (fl indicates the waveform applied to the column electrode 8i42. In FIG. 1 fal, the row electrode 41
The potential of a is kept at Va during the holding period and rises to Va+Vop during the selection period. In FIG. 1Cb), the row electrode 41b has a potential of vb during the retention period and vbV' during the selection period.
It becomes the potential of OP. Therefore, the pair of nonlinear resistance elements 44
Both ends of a and 44b (shown in FIG. 4(a)).

The voltage applied between ) is Va-Vb during the holding period and Vop+V'op+Va-Vb during the selection period.

At this time, in order for the nonlinear resistance element to work effectively as a switch, 1Va-Vbl must be small and I■op+V'
It is important that op+Va-Vb 1 is large, and when performing gradation display on a normal panel, the resistance of the nonlinear resistance element is lXl0''Ω or more during the holding period and lXl0''Ω or more during the selection period.
It is desirable to set it to 0”Ω or less, and
Since the pair of nonlinear resistance elements 44a and 44b are arranged very close to each other, their characteristics can be considered to be almost the same, and the potential of the pixel electrode 442 is (Va+V
b)/2, during the selection period (Va+Vb+Vop-V'o
p)/2 respectively.

The information to be displayed is determined by the potential difference between the pixel electrode 442 and the column electrode 42, and the adjustment is performed using the column electrode 42.

Therefore, it is desirable that the reference potential of the pixel electrode 442 be stable during the selection period and the holding period, so Vop-V'ap
It is important that l is small.

From the above, the row electrode applied waveform should ideally be V
It is desirable that a=Vb and Vop=V'op. (
Below, Va=Vb, Vop=V'.

Consider it as p. ) Figure 3 fcl, (di, tel, (fl) shows the waveform applied to the column electrode for each pattern of data to be written to all pixels lined up along one column electrode,
Figure 3 (C) shows that when all pixels are selected, Figure 3 +d
+ indicates that all pixels are unselected; tel in Figure 3 indicates that one pixel is selected and all remaining pixels are unselected; ffl in Figure 3 indicates that one pixel is unselected and all remaining pixels shows the case of selection.

Here, Vc= (Va+Vb+Vop-v'op)
/ 2 = V a, the voltage applied to the electro-optic material 43 when the nonlinear resistance element becomes low resistance during the selection period is V when the pixel is selected. H, V if not selected
, 1. Also, data is inverted every - period when the electro-optic material 43 is a liquid crystal, etc.
This is to prevent deterioration of characteristics due to bias. In this way, in order for the charge charged in the pixel electrode 442 during the selection period to be sufficiently retained during the retention period,
In the meantime, the nonlinear resistance elements 44a and 44b have high resistance (IX
8 rows of electrodes 42 that must be kept at IO”Ω or higher
Since the potential of can change within the range of ±(Volt VOFF), the nonlinear resistance element 44a on one side has a potential of Va−(V
±(VON VO
FF ) voltage is applied.

V on the liquid crystal display panel. Since N VOFF is only about the same level (about IV) as the difference between the saturation voltage of the liquid crystal and the threshold voltage, the nonlinear resistance element can operate as a sufficiently high resistance element. Therefore, the charge stored in the selection period is not easily discharged during the retention period, no matter how the potential of the column electrode 42 changes, and the effective voltage applied to the electro-optic material 43 is Mostly determined by data.

And this means that the operation of this panel is less dependent on the characteristics of the nonlinear resistive element.

This is because a nonlinear resistance element only needs to be able to inject and hold charge, so if Vop is set sufficiently large, it will be able to function satisfactorily as a switch even if the characteristics of the element vary or change over time. be.

〔Effect of the invention〕

As explained above, the driving method of the present invention uses a pair of row electrodes to control the resistance of a nonlinear resistance element, gives the nonlinear resistance element a high switching function, and then writes data using a column electrode. Since this is a driving method, it is possible to stably perform fine adjustments for each pixel, making it suitable for gradation display. In fact, ±
Even if there is a variation of about 20%, the effective voltage applied to the liquid crystal layer can be adjusted to ± the desired value for any display pattern.
It has been confirmed that it can be set within 0.1v.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram illustrating an embodiment of the method for driving an electro-optical device of the present invention. Figure 1 shows the waveforms applied to the row or column electrodes when all pixels are selected; Figure 1 tdl shows the waveforms applied to the column or row electrodes when all pixels A diagram showing the waveform applied to the column or row electrode when non-selected, Figure 1 t
el is a diagram showing the waveform applied to the column or row electrode when one specific pixel is selected and all remaining pixels are non-selected,
Figure 1ffl is a diagram showing the waveform applied to the column or row electrode when one particular pixel is not selected and all remaining pixels are selected, and Figure 2 is the drive waveform of the conventional voltage averaging method. Figure 2 (al is a diagram showing the applied waveform to the row or column electrode, Figure 2 (bl is the column or row electrode) is a diagram showing the applied waveform, Figure 2 fcl is the waveform at the intersection Figure shown, 3rd
(al is an X-Y matrix panel circuit diagram of a conventional electro-optical device, FIG. 3 (bl is a sectional view showing the structure of a conventional electro-optical device, and FIG. 4 ia+ is an X-Y matrix panel circuit diagram of the electro-optical device of the present invention. Y matrix panel circuit diagram (in Fig. 4) is a sectional view showing the structure of the electro-optical device of the present invention. 41b --- Row electrodes 32, 4
2... Column electrodes 33, 43... Electro-optic material (liquid crystal) 34, 44a
, 44b...nonlinear resistance elements 342, 442...
- Pixel electrodes 341.441a, 441b... - on nonlinear resistance element

Claims (3)

[Claims] (1) Two opposing substrates and a material having an electro-optic effect sandwiched between the substrates, a large number of row electrode groups formed on one substrate and a large number of column electrode groups formed on the other substrate, at least one of them. It consists of a pixel electrode group arranged in a matrix on a substrate, and a plurality of nonlinear resistance elements provided for each electrode of the pixel electrode group, and each pixel electrode is An electro-optical device connected to a second row or column electrode via a second nonlinear resistance element is connected to the first row or column electrode using the first and second row or column electrodes. and a second nonlinear resistance element to write and hold data from column or row electrodes to pixel electrodes arranged in the row or column direction. How to drive the device. (2) The method of driving an electro-optical device according to claim 1, wherein the potential difference between the first and second row or column electrodes is large during a data write period and small during a data retention period. (3) Driving the electro-optical device according to claim 1 or 2, wherein the average potential between the first and second row or column electrodes is always kept constant or close to a constant value. Method.