JPH0339717A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To make gradation display of >=16 gradations even with a large-sized display screen without generating flickering and unequal displaying by making combination use of two systems; a dither system and data sampling system of displaying variable densities of picture elements with the combinations of partially black and white states by dividing one picture element to plural parts. CONSTITUTION:Each display picture element 1 is divided in to 4 pieces of parts 2. The displaying of 5 gradations shown respectively as 3 to 7 by the combinations of the flickering states of the respective parts (dots) 2 is possible. Since the frequency component of the driving voltage of this dither system does not increase, the increase in the unequal display is obviated and since the frequency component of the driving voltage does not lower, the generation of the flickering is obviated. However, the 5-gradation display is the upper limit by the mere quadrisection of each picture element by the dither system. The data sampling system is, therefore, combined with the dither system. The 16-gradation display free from the flickering and unequal display is attained with the liquid crystal device in this way.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention increases the number of display gradations to improve the OA of a liquid crystal display device.
The present invention relates to a liquid crystal display device which, when used for display in various types of equipment, can approach the case of cathode ray tubes, which have been widely used in the past, and can improve compatibility with existing software.

[Prior Art] Liquid crystal display devices, especially twisted nematic liquid crystal display devices, were initially used for applications that did not require gradation display. However, after the development of large-sized matrix-type devices capable of displaying high resolution, they began to be used in place of cathode ray tubes in applications where bulkiness was a problem, such as for fJ-band personal computers. It has become. Yin 1kjA
The tube can be displayed almost freely in terms of brightness, darkness, and color. Therefore, conventionally, OA systems that use a negative i-ray tube as a display terminal
Some software developed for such devices uses a fairly multi-level grayscale display. OA machine that uses a cathode ray tube as a display device)):
: When converting to a portable or laptop format and replacing the display device with a liquid crystal display device, it is desirable to be able to use the software that has already been stored as is. Machines have also come to be manufactured, but in this case, it is desired to be able to display completely freely in one color, bright and dark.

In response to the above-mentioned demand for multi-level display gradation of liquid crystal display devices, conventional gradation display systems for liquid crystal display devices include display screen (frame) r! Two methods are used: a data sampling method that extracts the data of III and makes a difference in the frequency with which it appears on the screen between each display pixel, and a pulse width modulation method that changes the pulse width of the driving pulse applied to the liquid crystal. Publication No. 54-16894). The former is used for personal computers, etc., but as the number of gradations increases, flickering occurs on the screen, and the limit is usually 4 to 8 gradations. On the other hand, the latter is used in pocket-type LCD television receivers, etc., but since the LCD driving frequency increases in proportion to the number of gradations, display unevenness occurs in large LCD devices with a large capacitive load. not being used.

[Problem M to be solved by the invention] As mentioned above, the conventional technology has a problem in terms of the number of display gradations.
It was strongly desired to withstand display of WrA or higher.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional technology and provide a liquid crystal display device that can display 16 or more gradations even on a large display screen without causing flickering or display unevenness. shall be.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a plurality of gradation display methods with less flicker 1 display unevenness are combined to perform multi-gradation display. Divide a pixel into multiple parts and display the pixel density by combining partial black and white states; R
We decided to use two methods together: the so-called dither method, which is popular in facsimiles, and the data sampling method described above.

[The action codeizer method divides one pixel into multiple dots; vlJL, and controls the gradation of one pixel by the combination of blinking.
No display unevenness or flickering occurs. For large-sized matrix type liquid crystal display devices, one pixel divided into four is suitable for practical use at present.

The data sampling method is theoretically capable of displaying a fairly large number of gradations using the 1G method, but in the frequency range that is practical with current technology, as the number of gradations increases, low frequency components will occur in the liquid crystal drive waveform. The flickering of the 1 display becomes noticeable. For normal humans, it is noticeable when the frequency is below 30Hz. In experiments conducted by the inventor, 4-gradation display causes almost no flickering, but 8-gradation display causes flickering, and 4-8 gradation display is the limit.

[Example] Hereinafter, the present invention will be explained in more detail with reference to the drawings.

As shown in FIG. 1(,), each display pixel 1 is divided into four parts 2. Figure 1 (b), (c), (d), (e) depending on the combination of blinking states of each part C dot) 2.
, (f), it is possible to display five gradations shown as 3, 4, 5, 6, and 7, respectively. The feature of this dither method is that the frequency component of the drive voltage does not increase, so display unevenness does not increase, and the frequency component of the drive voltage does not decrease, so no flicker occurs. However, if each pixel is divided into four parts using the dither method, the upper limit is five-gradation display.

In reality, display with 16 or more gradations is required, so a data sampling method is combined with the dither method as shown in Table 1 on the first page.

The number of minutes indicated by A/II of the data sampling method in Table 1 indicates that the display is performed A times while repeating the screen n times, and
The fraction C/D in the dither method means that C out of D dots are lit. As is clear from the table, by combining these, it is possible to display 16 or more gradations from white (0) to black (1).

In the case of 16-gradation display, depending on the properties of the liquid crystal, a combination that makes it easy to distinguish gradations can be selected from the table.

[Effects of the Invention] As described above, according to the present invention, a 16-gradation display with less flickering and display unevenness can be realized in a liquid crystal display device.

Therefore, it becomes easier to use the liquid crystal display device for displaying data on a laptop personal computer.

[Brief explanation of drawings]

FIG. 1 (,) is a diagram showing display pixels according to an embodiment of the present invention.
Figures (b), (c), Cd), (θ), (f
) is a diagram showing display gradations of pixels according to the present invention. 1...Display pixel, 2...Divided portion (ton 1~),
3. White display, 4...174 gradation display, 5...2
74 gradation display, 6...3/4 gradation display, 7...black display. Figure ■ (Q) (e) (1) 7-: l-

Claims (1)

[Claims] 1. Each display pixel of the liquid crystal display element is divided into four parts, and the number of display gradations for each display pixel determined by the combination of the lighting states of each divided part is further periodically displayed on the screen for each display pixel. A liquid crystal display device characterized in that the number of display gradations is increased by providing a difference in the frequency of repeated display.