JPS62156623A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a homogeneous image by providing a memory where picture signals to be displayed on liquid crystal picture elements on a matrix of scanning lines and signal lines are stored and switching the scanning direction at intervals of a prescribed time to output corresponding picture signals from the memory to an output line. CONSTITUTION:A picture signal line driver 9 drives signal lines 8 in accordance with the signal from a memory 10 where one-field components of picture information are stored. A frequency divider 13 sends a control signal to forward and reverse drivers 11 and 12 alternately at intervals of one field period on a basis of a scanning signal to scan a picture from the top and the bottom alternately. The control signal from the frequency divider 13 is stored in the memory 10, and picture information in the memory is read out forward/reverse in accordance with a forward/reverse read signal and is outputted to the driver 9. Thus, picture signals are supplied to picture elements from the top or the bottom of the picture in accordance with forward or reverse scanning, and the black-and-white density distribution is reversed at every inversion of the scanning direction and is averaged to eliminate the density difference, and a homogeneous liquid crystal image is obtained.

Description

Detailed Description of the Invention (Hereinafter, blank) 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a liquid crystal display device in which a large number of liquid crystal display pixels are driven in a matrix manner.

[Prior Art] A simple matrix type liquid crystal display device (LC) is a simple matrix type liquid crystal display device (LC) in which scanning lines and signal lines are opposed to each other at right angles with a liquid crystal in between.
If D) is used for image display, sufficient contrast cannot be obtained. This is because the connection state between pixels is electrically similar to parallel connection of capacitive elements, so the influence of signals on other pixels is strong.

In order to overcome these drawbacks and obtain an even higher contrast image, a nonlinear element is connected between the scanning line and the signal line of each pixel to reduce the influence of the signal on other pixels. A so-called active matrix type LCD has been proposed.

Diodes, varistors, transistors, etc. are used as nonlinear elements, and due to their simple structure, ease of manufacture, and bulkiness, it is possible to use tie-outs connected in antiparallel. It is said to be useful.

FIG. 4 shows an example of an equivalent circuit of a conventional active matrix type LCD. In the diagram, 1 is a scanning line, 2 is a diode connected in antiparallel, and 8 is a signal line.

Reference numerals 3 and 7 denote a pair of electrodes that constitute a pixel facing each other with a liquid crystal 4 interposed between them, one (3) is connected to the scanning line 1 side via the diode 2, and the other (7) is connected to the signal Connect to line 8. A voltage equal to the difference between the scanning voltage and the signal voltage is applied to the matrix points (pixels).

[Problems to be solved by the invention] However, in the conventional LCD as described above,
There are the following problems. That is, first, the display density in the LCD configured as described above will be explained. Note that, for convenience, a case where the entire screen is displayed in black will be described.

FIGS. 2(8) and 2(B) show driving waveforms of the LCD.

Since the signal waveform is displayed entirely in black, it is a constant voltage, and on a normal screen, it is an arbitrary value between +ΔV and −ΔV. In the figure, the solid line is the scanning voltage, the dotted line A is the signal voltage, and the dotted line B is (scanning voltage - signal voltage), that is, a pair of electrodes 3.
7 shows the voltage applied between 7 and 7.

The display density of one pixel corresponds to the effective value for one frame of the voltage applied to a pair of electrodes constituting that pixel. On the other hand, since the effective value of the voltage applied to the pixel corresponds to the area of the shaded part in FIG. 2, different scanning lines i and j (i<
The difference in area of the shaded portion in j) corresponds to the density difference between pixels corresponding to the defining scan line. Therefore, the larger the difference between i and j (that is, the farther apart they are), the larger the difference in the effective value of the voltage applied to the pixel, and the density of the pixel corresponding to the last scanning line is the lowest. do. Furthermore, in the case of all white, the pixels on the first scanning line (the earliest scanning line) are the whitest, and the pixels on the last scanning line (the last scanning line) are grayish. For the same reason, the white part above the large black part of the screen becomes grayish (so-called crosstalk).

Therefore, the dependence of the display density on the screen on the scanning direction has a slope as shown in FIG. 3, and these phenomena are a serious drawback for the display device.

[Means for Solving the Problems] Therefore, the present invention eliminates the above-mentioned drawbacks in liquid crystal display devices, reduces density changes and cross strokes in the screen scanning direction, and provides a uniform image over the entire screen. The purpose of the present invention is to provide a liquid crystal display device that has liquid crystal display pixels on a matrix of a plurality of scanning lines and a plurality of signal lines, and a memory that stores image signals to be displayed on each pixel of the display device. , scanning means for scanning by switching the scanning direction of the scanning line every predetermined period, and image signal output means for outputting the image signal of the corresponding pixel from the memory to the signal line in accordance with the scanning of the scanning means.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of an active matrix type liquid crystal display device according to the present invention.

In FIG. 1, 1 is a scanning line, and 8 is a signal line. In this figure, a pair of pixel electrodes (3, 7) and a diode (2) at a matrix point as shown in FIG.
is omitted.

An image signal line driver 9 inputs an image signal from a memory 10 that stores image information for one field (one scanning cycle) and drives the signal line 8. 11 is in order
(Direction) A scanning driver that supplies a scanning signal to the signal line 8 in the forward direction (from the top to the bottom of the screen) when the control signal from the frequency divider 13 is input manually. Reference numeral 12 denotes a reverse (direction) scanning driver, which supplies a scanning signal to the signal line 8 in the reverse direction (from the bottom of the screen to the top) when the control signal from the frequency divider 13 is input manually. The frequency divider 13 is configured based on the scanning signal to alternately drive the forward scanning driver 11 and the reverse scanning driver 12 every one or more field periods or every plural frame periods (preferably every one field period). and outputs a control signal to both drivers 11 and 12.

The control signal from the dividing period 13 is input to the memory 10 as a forward read signal (control signal to the forward scan driver 11) and a reverse read signal (control signal to the reverse scan driver 12). When forward read signal is manually operated, memory 1
The image signal in memory 10 is read out in the forward direction and output to the image signal line driver 9, and when the backward read signal is manually operated, the image signal in the memory 10 is read out in the reverse direction and output to the image signal line driver 9.

Therefore, during forward scanning, image signals are supplied to pixels from above the screen, and during reverse scanning, image signals are supplied to pixels from below the screen. By doing this, the black or white density distribution in the top and bottom directions of the screen (see Figure 3) is reversed each time the scanning direction is reversed, and as a result, when observed with the naked eye, the density distribution in the top and bottom of the screen is the average and become uniform (that is, the density difference disappears).

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a liquid crystal display device having a uniform image over the entire screen.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a CD according to the present invention. Figure 2 is a diagram showing the driving waveform of the LCD, Figure 3 is a diagram showing the scanning direction dependence of the display density of the same LCD, and Figure 4 is a diagram showing the conventional active matrix method and LCD.
FIG. 2 is a diagram showing an example of an equivalent circuit. IO...Memory, 11...Forward scan driver, 12...Reverse scan driver, 13...Frequency divider. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1) A liquid crystal display having liquid crystal display pixels on a matrix of a plurality of scanning lines and a plurality of signal lines, a memory for storing an image signal to be displayed on each pixel of the display, and a scanning direction of the scanning line. A liquid crystal display characterized by comprising a scanning means that switches and scans at predetermined intervals, and an image signal output means that outputs an image signal of a corresponding pixel from the memory to the signal line in accordance with the scanning of the scanning means. Device.