JPH11175037A - Liquid crystal display - Google Patents

Abstract

(57) [Problem] To reduce cost and reduce unnecessary radiation by reducing the driving frequency of a signal electrode driving circuit without causing a problem in image quality, a problem in increasing the capacity of an image memory, and complicating signal processing. Provided is a liquid crystal display device having a matrix electrode configuration capable of realizing a reduction and an improvement in image quality by extending a scanning time per display line. SOLUTION: A scan electrode driving circuit 2 for simultaneously scanning a plurality of scan electrodes X1, X2,..., Each of which is separated from each other by less than half of the total number thereof, A plurality of signal electrodes Y1, Y2,... And Y'1, Y'2,... Corresponding to each independently, and a plurality of signal electrodes Y1, Y2,.
, And signal electrode driving circuits 3 and 4 for driving the electrodes in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a matrix electrode structure, and more particularly to a reduction in cost and unnecessary radiation by reducing a driving frequency of a signal electrode driving circuit, and a reduction in scanning time per display line. The present invention relates to an image in which image quality is improved by decompression.

[0002]

2. Description of the Related Art In a liquid crystal display device having a matrix electrode configuration in which a plurality of scanning electrodes and signal electrodes are crossed and pixels are formed at intersections thereof, generally, scanning electrodes are sequentially selected one by one by line-sequential scanning. In synchronization with this, all the signal electrodes are sequentially driven with a video signal representing an image to be displayed on a pixel (display line) on the scanning electrode (or the phase of this video signal is changed by a sample and hold circuit). (They are driven together at the same time).

In recent years, in a liquid crystal display device having a matrix electrode configuration, the number of pixels has been increased due to an increase in the area of a display screen and an increase in the density of pixels (the number of signal electrodes and the number of scanning electrodes).
As a result, the following problems have arisen.

(A) As is well known, the period of one vertical scan of the entire screen (one field period) is kept shorter than a certain time in order to prevent human eyes from flickering on the screen. It is necessary to. Therefore, as the number of pixels increases, the frequency of the video signal supplied to the circuit for driving the signal electrode must be increased accordingly.
As a result, it is necessary to use a signal electrode driving circuit having a high driving frequency, which leads to an increase in cost of the device and an increase in unnecessary radiation from the signal electrode driving circuit.

(B) In addition, since it is necessary to keep one field period shorter than a certain length, the scanning time per one display line must be shortened in accordance with the increase in the number of scanning electrodes (ie, one time). The time for operating the liquid crystal on each display line must be shortened), which causes deterioration in image quality.

Therefore, there has been proposed a liquid crystal display device in which odd-numbered and even-numbered signal electrodes are driven by separate signal electrode drive circuits. According to this liquid crystal display device, the number of signal electrodes that must be driven by each signal electrode drive circuit is reduced by half, compared to the case where all signal electrodes are driven by one signal electrode drive circuit. Therefore, since the signal electrode drive circuit having a low drive frequency can be used, the problem (a) is solved.

However, in this liquid crystal display device, the scanning time per display line cannot be shortened.
The above problem (b) is not solved at all. Therefore, there has been proposed a liquid crystal display device in which a display screen is divided into upper and lower parts and an image is displayed in parallel on an upper screen and a lower screen.

FIG. 3 shows the driving principle of such a liquid crystal display device, in which the scanning electrodes X1 to Xm of the upper half screen of the display screen of one liquid crystal panel are sequentially scanned and the scanning electrodes of the lower half screen are simultaneously scanned. A scan electrode driving circuit 21 for sequentially scanning X (m + 1) to X2m;
m and X (m + 1) to X2m independently correspond to two signal electrodes Y1, Y2,... and Y′1, Y′2,.
, And two signal electrode driving circuits 22 and 23 for driving the signal electrodes Y1, Y2,... And Y′1, Y′2,.

According to this liquid crystal display device, the scanning electrode drive circuit 21 scans two display lines simultaneously, so that
The scanning time per display line can be doubled (that is, the time for operating the liquid crystal on each display line is doubled) while maintaining the field period at a predetermined short time. Therefore, the problem (b) is solved. Further, when the scanning time per display line is doubled in this manner, the video signal supplied to the signal electrode drive circuits 22 and 23 is one half that in the case where the scanning time is not extended. The one with the frequency will suffice. Therefore, the problem (a) is also solved.

[0010]

However, in the liquid crystal display device shown in FIG. 3, since the upper half scanning electrode and the lower half scanning electrode are simultaneously scanned, two scanning electrodes which are simultaneously scanned are used. Are m separated from each other, which is ２ of the total number of scanning electrodes 2 m. That is, in one field period, first, the uppermost scanning electrode X1 of the upper half screen and the uppermost scanning electrode X (m +
1) are simultaneously scanned, and finally, the lowermost scan electrode Xm of the upper half screen and the lowermost scan electrode X2 of the lower half screen
and m are scanned simultaneously.

Therefore, near the center of the screen (the boundary between the two divided screens), the scan timing of the upper half scan electrodes and the scan timing of the lower half scan electrodes are shifted by about one field period. As a result, when displaying a fast-moving moving image, there is a new problem in image quality that the image shift (step) near the center of the screen becomes noticeable.

Further, since the video signals representing the images to be displayed on the display lines which are far apart from each other must be simultaneously supplied to the signal electrode driving circuits 22 and 23,
In order to supply a video signal to the signal electrode driving circuits 22 and 23, a large-capacity image memory such as a frame memory is required as an image memory for temporarily storing the video signal, and a signal processing for supplying the video signal is performed. However, there has been a problem that is complicated.

The present invention has been made in view of the above points, and does not cause a problem as in the liquid crystal display device shown in FIG. 3 and lowers the cost and reduces unnecessary radiation by reducing the driving frequency of the signal electrode driving circuit. Another object of the present invention is to provide a liquid crystal display device having a matrix electrode configuration capable of realizing an improvement in image quality by extending the scanning time per display line.

[0014]

According to the liquid crystal display device having a matrix electrode structure according to the present invention, the number of scanning electrodes is two times the number of scanning electrodes.
A scan electrode driving circuit that simultaneously scans a plurality of scan electrodes that are separated from each other by less than one-one, a plurality of signal electrodes independently corresponding to each of the plurality of scan electrodes, and a plurality of these system electrodes And a signal electrode drive circuit for driving the signal electrodes in parallel.

In this liquid crystal display device, a plurality of scanning electrodes that are separated from each other by less than half of the total number thereof are simultaneously scanned by the scanning electrode drive circuit, and the plurality of scanning electrodes are scanned. A plurality of independently provided signal electrodes are driven in parallel by a signal electrode drive circuit.

As described above, without separating the display screen into upper and lower parts, the parts separated from each other by less than half the total number of the scanning electrodes are simultaneously scanned, so that the liquid crystal display device of FIG. Divided the screen into two as shown
Unlike the case where the scanning electrodes that are apart from each other are scanned simultaneously, there is no large shift in the scanning timing of the scanning electrodes near the center of the screen. Therefore, there is no problem in image quality as in the liquid crystal display device of FIG.

Since it is sufficient to simultaneously supply video signals representing images to be displayed on display lines closer to each other than in the liquid crystal display device of FIG. 3 to each signal electrode drive circuit, the liquid crystal display device of FIG. In this case, a smaller capacity of the image memory is required as compared with the above, and the signal processing for supplying the video signal to the signal electrode drive circuit can be simplified.

Also, in this liquid crystal display device, as in the liquid crystal display device of FIG. 3, as described below, the drive frequency of the signal electrode drive circuit is reduced to reduce cost and unnecessary radiation, And the image quality can be improved by extending the scanning time.

That is, since the scan electrode driving circuit scans a plurality of display lines at the same time, the scan time per display line is reduced by the number of scan electrodes simultaneously scanned while maintaining one field cycle at a predetermined short time. (That is, the time for operating the liquid crystal on each display line is extended according to this number). Therefore, it is possible to improve the image quality by extending the scanning time per display line.

Further, when the scanning time per display line is extended in this manner, the video signal supplied to each signal electrode drive circuit needs to have a lower frequency as compared with the case where the scanning time is not extended. Become like Therefore, since it is sufficient to use a low driving frequency as the signal electrode driving circuit, it is possible to reduce the cost and reduce unnecessary radiation by reducing the driving frequency of the signal electrode driving circuit.

As an example, it is more preferable that a plurality of adjacent scanning electrodes be simultaneously scanned by a scanning electrode driving circuit. By doing so, for example, the image memory can be constituted only by the number of line memories corresponding to the number of scanning electrodes scanned at the same time, so that a smaller capacity of the image memory is sufficient and the signal electrode driving circuit The signal processing for supplying the video signal to the video signal can be further simplified.

[0022]

FIG. 1 shows an example of a circuit configuration of a liquid crystal display device according to the present invention. This liquid crystal display device has a liquid crystal panel 1 of an active matrix drive system. Since the driving method itself is well known, a detailed description is omitted, but the scanning electrodes X1 and X1 are provided on a substrate (not shown).
X2,... And signal electrodes (there are two systems of Y1, Y2,... And Y′1, Y′2,. A transistor (TF) as a switching element is provided at each intersection with the electrode.
T) 17 are connected to this transistor 17.
Pixels are formed by the liquid crystal 18 existing at the intersection of the liquid crystal layer sealed between the substrate and the transparent electrode (not shown).

The liquid crystal panel 1 has scanning electrodes X1, X
2,... Are selected as a set of two adjacent ones and sequentially scanned (ie, two adjacent scanning electrodes are simultaneously scanned).
A scan electrode drive circuit 2 is provided.

The liquid crystal panel 1 has signal electrodes Y1, Y
, And two different signal electrodes Y′1, Y′2,... For the odd-numbered scan electrodes X1, X3,..., The signal electrodes Y1, Y2,
The transistor 17 is connected to the intersection with
With respect to the even-numbered scan electrodes X2, X4,...
Is connected.

As a result, signal electrodes Y1, Y2 and Y2 are respectively applied to odd-numbered and even-numbered scan electrodes of two adjacent scan electrodes which are simultaneously scanned by the scan electrode drive circuit 2.
.., The signal electrodes Y′1, Y′2,.

The liquid crystal panel 1 is provided with two signal electrode driving circuits 3 and 4, the signal electrode driving circuit 3 drives the signal electrodes Y1, Y2,... , Y′2,... Are driven.

Further, the liquid crystal display device is provided with an image memory 5 composed of four line memories 6 to 9 (each having a capacity capable of writing a video signal for one horizontal scanning period). The video signal input to this liquid crystal display device is
The video signal processing circuit 10 performs well-known signal processing such as gain adjustment (contrast adjustment), luminance adjustment, gamma correction, and AC conversion (for example, inversion of the polarity for each frame), and then performs digital conversion by the A / D converter 11. The data is written into one of the line memories 6 to 9 of the image memory 4 via the changeover switch 12.

The digital video signals read from the line memories 6 and 8 are supplied to the D / D
The analog signal is converted by the A-converter 15 and supplied to the signal electrode drive circuit 3. On the other hand, the digital video signal read from the line memories 7 and 9 is supplied to the changeover switch 1
The analog signal is converted by the D / A converter 16 through the analog signal 4 and supplied to the signal electrode drive circuit 4. The operation of each unit of the liquid crystal display device is controlled by a system controller (not shown).

Next, an example of the operation of the portion subsequent to the changeover switch 12 of the liquid crystal display device will be described with reference to the timing chart of FIG. A predetermined frequency f output from an imaging device (not shown) or the like and input to the liquid crystal display device.
2A shown in FIG. 2A (where,... Indicate signals for one horizontal period (1H) of this video signal).
Is subjected to the signal processing by the video signal processing circuit 10 and the A / D
When the digital signal is converted by the converter 11, the changeover switch 12 is operated to switch the digital video signal to the image memory 4 for one horizontal period as shown in FIGS.
Are sequentially and repeatedly written to the line memories 6 to 9.

From time T1 when the writing of the digital video signals for the first two horizontal periods into the line memories 6 and 7 is completed, the following reading is performed in parallel with the writing. That is, at the time T1, as shown in FIGS. 2F and 2G, the reading of the signal from the line memories 6 and 7 is started at the half frequency of the frequency f. Then, by operating the changeover switches 13 and 14, the read signals are analog-converted by the D / A converters 15 and 16 and supplied to the signal electrode driving circuits 3 and 4. This reading ends at time T2, which is two horizontal periods after time T1.

As a result, as shown in FIGS.
From 1 to time T2, signals of frequency f / 2 are simultaneously supplied to the signal electrode drive circuits 3 and 4, respectively.
The signal electrode drive circuit 3 uses this signal to generate the signal electrode Y
, Y2,..., And the signal electrode drive circuit 4 drives the signal electrodes Y′1, Y′2,. That is, signal electrodes Y1, Y2,... Corresponding to odd-numbered scan electrodes of two adjacent scan electrodes scanned simultaneously by scan electrode drive circuit 2, and even-numbered scan electrodes of these two scan electrodes. Signal electrodes Y'1, Y'2 corresponding to the scanning electrodes
Are driven in parallel by the signal electrode drive circuits 3 and 4.

The scan electrode driving circuit 2 scans the scan electrodes X1 and X2 for two horizontal periods from time T1 to time T2.
And scan simultaneously. As a result, an image based on the signal is displayed on each pixel on the scan electrodes X1 and X2.

At time T2, writing of signals for the next two horizontal periods into the line memories 8 and 9 is completed (FIGS. 2D and 2E). Then, at time T2, FIG.
As in I, reading of signals from the line memories 8 and 9 at the frequency f / 2 is started. Then, by operating the changeover switches 13 and 14, the signals read from the line memories 8 and 9 are respectively transferred to the D / A converter 1.
The signals are converted into analog signals at 5 and 16 and supplied to the signal electrode driving circuits 3 and 4. This reading ends at time T3, which is two horizontal periods after time T2.

As a result, as shown in FIGS.
From time 2 to time T3, a signal of frequency f / 2 is simultaneously supplied to the signal electrode drive circuits 3 and 4, respectively.
The signal electrode drive circuit 3 uses this signal to generate the signal electrode Y
, Y2,..., And the signal electrode driving circuit 4 drives the signal electrodes Y1, Y2,.

Scan electrode drive circuit 2 scans scan electrodes X3 and X4 for two horizontal periods from time T2 to time T3.
And scan simultaneously. Thereby, an image based on the signal is displayed on each pixel on the scanning electrodes X3 and X4.

At time T3, the writing of the signals for the next two horizontal periods into the line memories 6 and 7 is completed (FIGS. 2B and 2C). Therefore, at time T3, reading of signals from the line memories 6 and 7 at the frequency f / 2 is started. And, by the same operation as already described,
An image based on the signal is displayed on each pixel on the scan electrodes X5 and X6 over two horizontal periods from time T3. Hereinafter, similarly, every two horizontal periods, two consecutive
An image based on the video signal for the horizontal period is displayed on each pixel of two adjacent scanning electrodes.

As described above, in this liquid crystal display device, since the scan electrode drive circuit 2 simultaneously scans two display lines, one field cycle is maintained at a predetermined length (for example, 1/60 second by the NTSC system). The scanning time per display line can be doubled (that is, the time for operating the liquid crystal on each display line can be doubled) while keeping the same. Therefore, it is possible to improve the image quality by extending the scanning time per display line.

Further, since the video signal of the frequency f is reduced to half the frequency and supplied to the signal electrode drive circuits 3 and 4, the video signal of the frequency f is used as the signal electrode drive circuits 3 and 4. It is sufficient to use one having a lower driving frequency as compared with the case of supplying. Therefore, cost reduction and reduction of unnecessary radiation can be realized by reducing the driving frequency of the signal electrode driving circuit.

Moreover, in this liquid crystal display device, two adjacent
Since the scanning electrodes are simultaneously scanned, the screen is divided into two as in the liquid crystal display device shown in FIG. 3 and the scanning electrodes separated by a half of the total number are simultaneously scanned. Unlike the above, there is no large shift in the scan timing of the scan electrodes near the center of the screen. Therefore, there is no problem in image quality that a step of an image is conspicuous near the center of the screen as in the liquid crystal display device of FIG.

Since two adjacent scanning electrodes are simultaneously scanned, a small-capacity image memory consisting of only four line memories is provided, and the signal electrode driving circuits 3 and 4 are provided with a video memory. The signal processing for supplying the signal is simplified as described above with reference to FIG.

In the above example, an image memory consisting of four line memories is provided. However, the image memory is not limited to such a configuration. Of the written video signals, a video signal corresponding to each scanning electrode (two adjacent scanning electrodes in the example of FIG. 1) which scans at the same time is used for this scanning. An appropriate configuration may be used as long as it can be simultaneously read out at a frequency (half frequency in the example of FIG. 1) reduced according to the number of electrodes.

In the above example, two adjacent scanning electrodes are simultaneously scanned. However, the present invention is not limited to this, and three adjacent scanning electrodes may be simultaneously scanned,
Alternatively, two or three or more scanning electrodes that are not adjacent to each other (however, from the viewpoint of reducing the size of the image memory, it is preferable that the scanning electrodes are not so many apart from each other) are simultaneously scanned. Is also good. And at the same time 3
When scanning more than one scan electrode, a corresponding signal electrode may be independently provided for each of the scan electrodes, and the signal electrodes may be driven in parallel.

In the above example, the present invention is applied to the liquid crystal display device having the liquid crystal panel of the active matrix drive system. However, the liquid crystal display device having the liquid crystal panel of the passive matrix drive system, the structure of the matrix electrode, and the like. The present invention may be applied to a liquid crystal display device having a liquid crystal panel having a segment electrode configuration of an electrically equivalent dynamic drive system.

The present invention is not limited to the above embodiment,
It goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0045]

As described above, according to the liquid crystal display device according to the present invention, there is a problem in the image quality that the step of the image is conspicuous near the center of the screen as in the conventional liquid crystal display device, and the size of the image memory is large. The cost reduction and unnecessary radiation reduction by reducing the driving frequency of the signal electrode driving circuit and the improvement of the image quality by extending the scanning time per display line are achieved without causing the problem of increasing the capacity and complicating the signal processing. Can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a circuit configuration of a liquid crystal display device according to the present invention.

FIG. 2 is a timing chart showing an example of the operation of the liquid crystal display device of FIG.

FIG. 3 is a diagram illustrating an example of a circuit configuration of a conventional liquid crystal display device.

[Explanation of symbols]

1 liquid crystal panel, 2 scan electrode drive circuit, 3, 4
Signal electrode drive circuit, 5 image memory, 6-9 line memory, 10 video signal processing circuit, 11 A / D converter, 12, 13, 14 changeover switch, 1
5, 16 D / A converter, 17 transistors,
18 liquid crystal, X1, X2 scanning electrodes, Y1, Y2
..., Y'1, Y'2, ... signal electrodes

Claims (2)

[Claims] 1. A liquid crystal display device having a matrix electrode configuration, comprising: a scanning electrode driving circuit for simultaneously scanning a plurality of scanning electrodes separated from each other by less than half of the total number of the scanning electrodes; A liquid crystal display device comprising: a plurality of signal electrodes independently corresponding to each of the scan electrodes; and a signal electrode drive circuit that drives the plurality of signal electrodes in parallel. 2. The liquid crystal display device according to claim 1, wherein said scan electrode drive circuit scans a plurality of adjacent scan electrodes simultaneously.