JPS6375732A - 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 disposed between two parallel support plates having surfaces facing each other, a pattern of row electrodes disposed on one surface and a pattern of row electrodes disposed on the other surface. a pattern of column electrodes provided therein, the row electrodes and the column electrodes intersecting each other to form a display element in the intersection area, and also a driving 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 row electrodes.

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 most commonly used to drive liquid crystal displays that are arranged as a matrix of pixels and do not use an active switch for each pixel. known as mode. The maximum number of rows Lag that can be driven with an acceptable contrast ratio by this mode is determined by the following equation.

V here. , , represents the rms voltage across the display element required to switch in the "on" state, and Voff represents the rms voltage at which the display cell is in the ``off'' state. Voh and V.

Since the squares are close to each other, a large number of 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 naturally does not 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 a selection voltage is present simultaneously across the center and center electrodes for a selection time t. Therefore, the voltage loss mentioned above can be reduced to a predetermined value.

SUMMARY OF THE INVENTION An object of the present invention is to provide a display device that can eliminate the above-mentioned drawbacks.

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 the column electrodes intersect with each other to form a display element in the intersecting area, and further includes a drive circuit that causes a data signal to be displayed to be present on the column electrodes, and a drive circuit that periodically scans the row electrodes. In a display device comprising a row scanning circuit, the row scanning circuit supplies a signal to both ends of each row electrode, in which first one end of the row electrode is connected to the row scanning circuit, and then the other end is connected to the row scanning circuit. A feature of the present invention is that the end of the line is connected to a row scanning circuit.

The present invention provides a method in which the selection voltage is first present at one end of a row electrode, preferably for approximately % of the selection time, and then the selection voltage is present at the other end of the row electrode for approximately the same period, and the display This is based on the recognition that voltage losses can be reduced in the rms drive matrix by making the information to be processed simultaneously present on the column electrodes as data voltages.

The selection of the ends of the row electrodes need not be done in close succession to each other. In particular, it is preferable that the row scanning circuit first supplies a selection signal to one end of all the row electrodes, and then supplies a selection signal to the other end.

The reason is that such measures are easier to achieve from the point of view of circuit technology.

The invention will be explained with reference to the drawings.

The display device shown in FIG. 1 includes two glass support plates 1 and 2.
will be established. This glass support plate 1 is provided with a pattern of strip-like 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 an optically different second state by appropriately driving the row and column electrodes 3 and 4.

FIG. 2 diagrammatically shows a matrix array of display elements 12 in such a device. These display elements 12 are arranged at the intersections of row electrodes 3 driven by row scanning circuits 13'', 13' and column electrodes 4 driven by a drive circuit 14.

According to the present invention, the row selection point is first determined by the first row scanning circuit 13''.
and then by the row scanning circuit 13b. The durations of these pulses are approximately equal. All the rows are first enabled sequentially by the row scanning circuit 13' while simultaneously supplying information via the drive circuit 14, and then all the rows are enabled by the row scanning circuit 13b. In order to mutually synchronize the row scanning circuit 13'' and the row scanning circuit 13b and make them follow each other in a timely manner, a synchronization line 15 and a driving line 16 are provided in the display device.

By configuring the display as described above, it is possible to obtain a higher multiplex ratio than in the case of normal bidirectional driving, when taking into account the voltage losses along the row electrodes 3. This will be explained below.

In FIG. 2, when the row electrodes 3 are driven in a single direction from, for example, the row scanning circuit 138, the voltage is
3' α. From v5 to row scanning circuit 13b.

(αo〉1). At points (a) and (b), voltage α is applied from both sides during period %tm for N rows. When individually driven with Vs, the following equation holds true.

... (2) When optimizing the above function under the boundary condition Vorr "Vthr (Vthr is the threshold voltage of the electro-optic effect), the voltage V.I between points (a) and Q) becomes too low. .

In order to find the position (b) where Van is minimum, the following equation holds true, assuming that α in (b) is linear, for example.

When addressing from the left side, α (b) = α. +(1-α.)p When addressing from the right side αCp)'= 1 +(αo+t)p Substituting these assumptions into the above equations (1) and (2), p = H as shown in the following equation. In this case, αV oh becomes minimum.

Due to the boundary condition V2off (a, b) = V2thr, also α. +1 can be obtained by the following equation when optimizing α'=□ using equation (2).

α. and when N is a predetermined value, V-/ that satisfies equation (4)
The combination of Vthr and vD/vthr can be determined. For each of these combinations, the relationship shown in the following equation can be calculated using equation (3).

v2゜. (1) = 'A) V''Lhr Figure 3 (broken line) shows the relationship v2゜, (p = each) 2Lhr changes in the liquid crystal display device when N = 128 and α = 1.10. It is shown as a function of vo/vLhr for one set of electrodes.As is clear from Fig. 3, Vn/Vt
When hr=0.74, the maximum value of v2°7 V'Lhr is approximately 1.9. The associated value of Vs/Vthr will be approximately 7.95. Therefore, in order to obtain satisfactory operation, it is necessary to select an electro-optic medium according to such a threshold slope S. In this case, is at least 1.1
It becomes 9. That is, according to the Aldo and Pleschko relation, this slope S corresponds to approximately 130 N+aa++. In addition, electricity with steep threshold voltage characteristics
Optical media are also suitable.

Drive the selection electrode from the left and right sides simultaneously (bidirectional drive)
Similar calculations can be performed when In this case, the following equation can be derived using the boundary condition V'orr(a+b)=V2thr.

N=128, α. - For an electrode system with a value of 1.10, the characteristics shown by the solid curve in FIG. 3 can be obtained. As is clear from this solid line curve, the above-mentioned ratio V2. , ,<p=each) 2thr is smaller than in the case of individual driving (inversion scanning). In this example, this ratio is approximately 1.14.

The slope of the electro-optic medium where is approximately 1.14 is approximately 215 Nma according to the Aldo and Pleschko relationship.
Corresponds to ll.

This requires an electro-optic medium for bidirectional or simultaneous drive, where N, aX is larger than the medium that can be used for the means according to the invention (reverse scanning), given the same electrode configuration.

To further illustrate the invention, 128 rows and 256
Table 1 shows comparative examples of electrode systems in which the value of α0 was variously changed for each row.

This table shows the relevant maximum ratio V. The N168 value corresponding to the relationship between I/Vthr and Aldo and Precico is shown.

These data consist of (see especially the * mark), for example, when NfiaM 268 media is bidirectionally driven
. = 1.15 can be driven with 1:128 multiplexing, and in the case of inversion scanning, 1:256 multiplexing is possible.

The present invention is not limited to the above-described examples, and various changes can be made without departing from the gist. For example, drive modes can be combined with variable data and selection voltages, as described in other patent applications filed on the same date by the same applicant.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a liquid crystal display device, FIG. 2 is a plan view of a liquid crystal display device in which pixels are arranged in a matrix and a part of its driving circuit, and FIG. 3 is a voltage ratio V2 at 172 points of a row electrode.゜n/
V2thr to Vo/Vthr for various drive modes
It is a characteristic diagram shown as a function of. 1.2... Glass support plate 3... Row electrode 4... Column electrode 6.7... Alignment layer 8... Liquid crystal material 9... Sealing edge 10... Polarizer
11...Analyzer 12...Display element 1
3", 13 b... Row scanning circuit 14... Drive circuit 15... Synchronization line 16... Drive line

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 pattern of row electrodes provided on the other surface. a pattern of column electrodes, the row electrodes and the column electrodes intersect with each other to form a display element in the intersecting area; the row electrodes also include a drive circuit for causing a data signal to be displayed to be present on the column electrodes; In a display device comprising a row scanning circuit that scans periodically, the row scanning circuit supplies a signal to both ends of each row electrode, and in this case, first, one end of the row electrode is connected to the row scanning circuit. 1. A display device, characterized in that the display device is connected to one another and then the other end is connected to a row scanning circuit. 2. According to claim 1, the row scanning circuit first supplies a signal to one end of all the row electrodes, and then supplies a signal to the other end of all the row electrodes. Display device as described. 3. The display device according to claim 1 or 2, wherein the signals present at both ends of the row electrodes have substantially the same duration width.