JPS6377030A - Display device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a liquid crystal material provided between two parallel support plates having surfaces facing each other, a pattern of row electrodes provided on one surface, and a pattern of row electrodes provided on the other surface. The row electrodes and the column electrodes are intersected to form a display element in the intersection area, and the row electrodes are provided with a drive circuit for causing data signals to be displayed to be present on the column electrodes. The present invention relates to a display device including a row scanning circuit that periodically scans the row scanning circuit.

Display devices of this type are known and so-called rms
It normally operates in multiple drive states depending on the voltage according to the mode.

This drive mode is described in IEEE) Transactions on Ecretron Devices, Volume E D21, 197.
4, pp. 146-155, and is most commonly used to drive liquid crystal displays that are configured as a matrix of pixels and do not use active switches for each pixel. known as mode. The maximum number of rows NfiaX that can be driven with an acceptable contrast ratio in this mode is determined by the following equation.

V here. I represents the rms voltage across the display element required to switch in the "on" state, and Vorf represents the rms voltage at which the display cell is in the "off" state. Vort and V. Since the rrs are close to each other, multiple rows can be driven. In this case, it is necessary to make the threshold value of the transmission/voltage characteristics of the display element steep.

The rms voltage across the individual display elements will naturally track the selection and data voltages present. Due to the resistance of the electrodes, voltage losses occur such that the rms voltage across the display element is lower than the voltage required to switch.

This reduces the maximum number of rows to be multiplexed.

Known solutions for preventing the effects of eg voltage losses on the row electrodes are such that the selection voltage is present simultaneously across the row electrodes during the selection time t3.

Other inventions co-filed by the same applicant have proposed a display device with a different form of dual drive (so-called "inversion scan").

The object of the invention is to provide a display device of the above-mentioned type in which the problem of voltage drop due to the resistance of the drive electrodes can be solved by completely different means.

The present invention comprises a liquid crystal material provided between two parallel support plates having surfaces facing each other, a pattern of row electrodes provided on one surface, and a pattern of column electrodes provided on the other surface. The row electrodes and column electrodes intersect with each other to form a display element in the intersection area, and also include a drive circuit that causes data signals to be displayed to be present on the column electrodes, and a row electrode that periodically scans the row electrodes. A display device comprising a scanning circuit is characterized in that a voltage having a value depending on the column electrode to be driven by a drive circuit for a data signal to be displayed can be caused to exist on the column electrode.

In a related patent application filed simultaneously in the Netherlands, the present invention proposes a drive device with another different type of dual drive (so-called "reverse scanning").

The object of the invention is to provide a display device of the above-mentioned type in which the problem of voltage reduction due to the resistance of the drive electrodes is solved by completely different means.

The present invention comprises a liquid crystal material provided between two parallel support plates having surfaces facing each other, a pattern of row electrodes provided on one surface, and a pattern of column electrodes provided on the other surface. The row electrodes and column electrodes intersect to form a display element in the intersecting area, and are driven by a drive circuit for causing data signals to be displayed to exist in the column electrodes and a drive circuit for data signals to be displayed. The present invention is characterized in that a voltage having a value depending on the column electrode to be applied can be caused to exist on the column electrode.

The invention is based on the fact that the rms voltage across the display element can be effectively provided by shaping the column voltage values gradually or stepwise. As a result, it is possible to sufficiently prevent Nmax from decreasing due to voltage loss. Generally, supplying voltage per column is more complex and therefore more expensive, so it is preferred to supply groups of column electrodes with approximately the same level of voltage. In practice, the number of electrodes per group depends on the available integrated LCD drivers.

The manner in which the voltage changes across the various columns also depends on the drive mode. When driving a display device in a single direction,
In other words, if the associated row selection circuit supplies selection voltages to only one side of the liquid crystal matrix, the highest data voltages will be present in columns near the other side. In the case of bidirectional driving, the highest data voltage will be present in the central portion.

It is of course also possible to carry out the voltage compensation described above for the signal present at the selection electrode. Depending on the fact that the data signal exists in a single direction or in both directions, the value of the selection voltage increases from one side of the IJ sock to the other or from both sides towards the center.

The invention will be explained with reference to the drawings.

The display device shown in FIG. 1 includes two glass indicator plates 1 and 2.
will be established. This glass indicator plate 1 is provided with a pattern of strip-shaped row electrodes 3 made of, for example, indium tin oxide. Further, the glass support plate 2 is also provided with a pattern of strip-shaped column electrodes 4 made of, for example, indium tin oxide. These row electrodes 3
and the column electrodes 4, and these crossing points constitute display elements, and these display elements are arranged according to a matrix. Orientation layers 6 and 7 are provided on the surfaces of the glass support plates 1 and 2 provided with these electrodes.

A liquid crystal material 8 is interposed between the glass support plates 1 and 2.

The distance between the glass support plates is approximately 10 μm, and this distance is maintained by spacers, which are not shown in the drawings, that are regularly spaced and distributed on the surface of the glass support plates. A sealing edge 9 connects the glass support plates at their periphery.

In this example, each of the glass support plates 1 and 2 is further provided with a linear polarizer, namely a polarizer 10 and an analyzer 11, although this is not absolutely necessary. The display element can be switched from a first state to a second state different from light reflection by appropriately driving the row and column electrodes 3 and 4.

FIG. 2 shows the driving principle of such a display device. A large number of row electrodes 3 and a large number of column electrodes 4 constitute a matrix of display elements 12. Voltage pulses are supplied to the row electrodes 3 and column electrodes 4 from a row scanning circuit 13 and a drive circuit 14, which are synchronized with each other through a connecting conductor section 15, respectively.

According to the invention, the voltage level provided by the drive circuit 14 is made dependent on the column to be driven.

When the row electrode 3 is driven in a single direction, for example from the left side of FIG. 3, the row voltage decreases from, for example, αvS at point (a) to V at point (a) (α>1). These points (a), (b
) in N rows. h and V. 7. is the following formula % α〉1, and in order to derive a smaller number than the maximum number of lines to be plexed, the actual optical system slope 5 = Vo, , /voff is the number determined by The undisturbed liquid crystal effect influences the electrical resistance of the row electrodes and possible other side effects.

For various values of α, α=
The number of rows to be multiplexed in an optical system having the same contrast as when multiplexing N+a a x in the case of 1 is shown in Table 1 below.

Table 1 Figure 4 shows α=1, N=128 (S2), N=256
(S3) and for various optical systems with N = (S4), the ratios N N and V 'of f = V '' T H1 are derived from the following equations where V Tl111 is the threshold voltage of the optical effect. The maximum value of curve S2.33.34 is the selection ratio V according to the drive mode published by Aldo and Pleschko.

Corresponds to h/Voff. For an optical system with a threshold value S2 suitable for driving 256 rows, the selection ratio (see FIG. 4) is approximately 1,065. When such an optical system is used for a matrix of 128 rows, the fourth
As is clear from the figure, the ratios Vs/Voft and V. h/v
The area where otf is sufficient for driving, that is, the coordinates (i) and (
ii) The area between becomes larger. The selection ratio V that is relevant in this case. n/Vott will always be greater than or equal to 1.065.

Therefore, in this region in a matrix of 128 rows αsa, = Vs maX/Vs + mih then αV.

A voltage drop occurs from Vs to Vs.

The number of rows to be multiplexed for α and S is the data voltage vn(a) and V. For (c), symbols D+ and D, respectively.
2 is used, the following equation holds true.

Further, the following equation holds true for the related "On" voltage.

Equations (1) and (2) are made equal to each other, and X”Vs /D
, , Y=D, /D, the following equation can be obtained.

Similarly, the following equation is obtained from equations (3) and (4).

Since equations (5) and (6) are equal, the following equation is obtained.

For the selection ratio of Ll+ and also point (a), the following equation can be obtained.

When using equations (7) and (8), Vs / Va
Assuming (a) = r and v, +(b)·αVd(a), the maximum number of rows that can be used can be determined by the following equation.

This is shown in Table 2 below. As is clear from Table 2, the value of N is significantly larger than the value of N in Table 1.

Table 2 At point (1) located between points (a) and (b), the selection voltage becomes αi V−(1<α1<α), and the data voltage V.

(i) can be obtained from the following equation.

(α1Vs Dt)2+(N 1)(Va(i))
”=N ”V2Lhr' Therefore, the composite voltage V at point (i). , becomes higher than the combined voltage of points (a) and (b).

FIG. 5 details the drive circuitry in which these various variable data voltages may be present. For this purpose, the drive circuit 14 of FIG.
Sub drive circuit 14", 14b, --- connected to
14'i: split and supply the synchronization signal and data signal to the sub-drive circuits through connection lines 15 and 17, respectively. In order to be able to adjust the variable data voltage, each sub-drive circuit 14a, 14b, ---
14'' is connected via a connecting conductor 18 to variable resistors 19, which are arranged between two voltage conductors 20.21.The voltage of these conductors 20.21 causes the variable resistor 1 to
9 and the sub drive circuit 14”, 14b, ---
14'' to determine the voltage value of the auxiliary voltage at the output terminal 16 according to various reference levels.

When driving selected rows in a single direction, the voltage along these rows decreases in one direction, for example from left to right in FIG. Therefore, the compensation voltage due to the change in data voltage increases from the left side to the right side.

When bidirectional driving is performed simultaneously, the compensation voltage is approximately at its maximum at the center of the row electrode 3. In other words, it is highest at or near the sub-drive circuits 14&, 14b, --14''.

In the drive mode described in the above-mentioned co-filed Dutch patent application, the voltages mentioned decrease alternately from the left to the right. Lead wire 18 of variable resistor 19
An extra switch (not shown) is inserted in the sub-drive circuit 14a.

14b, ---14'' can be connected alternately to two different conductors of the variable resistor 19.

In the same manner as described for the data voltage, the selection voltage is also made variable so that voltage loss due to the resistance of the column electrodes 4 can be compensated for. For this purpose, the row scanning circuit 13 is connected to the drive circuit 1.
In the same manner as described in connection with No. 4, the sub-drive circuits are divided into sub-drive circuits, each connected to a different reference voltage. The compensation voltage due to this reference voltage can be increased in one direction for unidirectional driving of the column, and can be increased from both sides toward the center for bidirectional driving of the column.

The present invention is not limited to the above-mentioned examples, and various modifications can be made without changing the gist. For example, when the voltage loss across the row electrodes 3 can be ignored, only the row selection voltage can be compensated, for example when the number of columns is less than the number of rows. In this case as well, compensation can be performed per group of row electrodes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a liquid crystal display device, FIG. 2 is a plan view showing a display device in which pixels are arranged in a matrix together with part of its driving circuit, and FIG. 3 is a plan view of one row electrode. FIG. 4 shows the voltage V of various electro-optical systems. FIG. 5 is a characteristic diagram showing the ratio of l and VS. FIG. 5 is a connection layout diagram showing the configuration of the drive circuit. 1, 2...Glass support plate 3...Row electrode 4...
Column electrodes 6, 7...Alignment layer 8...Liquid crystal material 9...Sealing edge 10...Polarizer
11...Analyzer 12...Display element
13°, 13b... Row scanning circuit 14... Drive circuit
15... Synchronization line 16... Drive line Fl (1,1 m1rc:

Claims (1)

[Claims] 1. A liquid crystal material provided between two parallel support plates having surfaces facing each other, a pattern of row electrodes provided on one surface, and a column provided on the other surface. The row electrodes and the column electrodes are intersected to form a display element in the intersecting area, and the row electrodes are arranged in a periodic manner, and a driving circuit is provided to cause data signals to be displayed to be present on the column electrodes. A display device comprising a row scanning circuit that performs horizontal scanning, characterized in that a voltage having a value that depends on the column electrode to be driven by the drive circuit for the data signal to be displayed can be caused to exist in the column electrode. display device. 2. The display device according to claim 1, wherein the voltage value of the data signal to be displayed is substantially the same for each group of column electrodes. 3. comprising a row scanning circuit that periodically scans the row electrodes with a selection voltage, driving the row electrodes in a single direction from one side of the device;
Claim 1 characterized in that the value of the voltage associated with the data signal increases in the direction of the other side of the device.
The display device according to any one of Items 1 and 2. 4. A row scanning circuit is provided that periodically scans the row electrodes using a selection voltage, and the row electrodes are driven bidirectionally so that the voltage value related to the data signal in the column is approximately maximized from both sides toward the center. A display device according to any one of claims 1 and 2, characterized in that: 5. Any one of claims 1 to 4, characterized in that the data signal is supplied from one side of the device, and the value of the selection voltage increases toward the other side of the device. The display device described in . 6. Claims 1 to 4, characterized in that the data signal exists in both directions, and the value of the selection voltage in the row voltage is approximately maximum at approximately the center from both sides.
A display device described in any of the following paragraphs. 7. A liquid crystal material provided between two parallel support plates having surfaces facing each other, a pattern of row electrodes provided on one surface, and a pattern of column electrodes provided on the other surface. , these row electrodes and column electrodes are crossed to form a display element in the crossing area, and in addition, there is a drive circuit that scans the data signal to be displayed on the column electrodes, and a row scanning circuit that periodically scans the row electrodes. 1. A display device comprising a circuit, characterized in that a row scanning electrode of a selection pulse can cause a voltage of a value depending on the row electrode to be driven to exist on the row electrode. 8. The display device according to claim 7, wherein the voltage value of the selection pulse is approximately the same for each group of row electrodes. 9. Any one of claims 7 to 8, characterized in that the data signal is supplied from one side of the device, and the value of the selection voltage increases toward the other side of the device. The display device described in . 10. The data signal is present in both directions, and the value of the selection voltage in the row voltage is approximately maximum at approximately the center from both sides. Display device described in any of the sections.