JPH05143019A - Matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate the difference in the brightness of display colors by a difference in the effective voltages impressed to liquid crystals and to obviate the generation of an unequal display in the joined part of divided screens by providing a matrix type liquid crystal display element, data drivers and scanning drivers which are respectively specific. CONSTITUTION:A memory 7 which can read the image data for one screen, a data driver 1 for the upper screen which outputs the image data displayed on the upper screen 2 of the liquid crystal display element (LCD), the data driver 3 for the lower screen which outputs the image data displayed on the lower screen 4 of the LCD, the scanning driver 5 for the upper screen which scans the upper screen and the scanning driver 6 for the lower screen which scans the lower screen are provided. The difference in the effective voltages applied to the liquid crystals on the picture elements nearest the joint part of the dividedly driven screens is entirely eliminated and the directions of the electric fields applied to the liquid crystals on the picture elements nearest the joint part of the screens divided in driving are made the same. The unequal display by the influence of the electric fields is, therefore, entirely eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix type liquid crystal display device in which a screen is divided into two and displayed.

[0002]

2. Description of the Related Art In recent years, the twisted nematic type (T
Applications of liquid crystal display devices (LCDs) centering on N-type) liquid crystals have been developed and used in large quantities in the fields of wristwatches and calculators. Further, a matrix type which is capable of arbitrary display of characters and figures is also beginning to be used. In order to expand the field of application of this matrix type LCD in which pixels are arranged in a matrix, it is necessary to increase the display capacity. However, conventional LC
Since the rise of the voltage-transmittance change characteristic of D is not so sharp, when the number of scans of the multiplex drive is increased to increase the display capacity, the effective voltage ratio applied to each of the selected pixel and the non-selected pixel becomes As a result, the transmissivity of the selected pixel also decreases, and crosstalk occurs in which the transmissivity of the non-selected pixel increases (in the case of normally black in which polarizing plates are arranged in parallel).

Further, when the number of scanning lines is increased, the duty ratio is increased, and the liquid crystal cannot hold the charges written during the selection time, so that the image quality is deteriorated. As one of means for significantly increasing the display capacity of this matrix type LCD, there is a matrix type liquid crystal driving method in which a screen is divided into two and displayed. This is a method in which the screen is divided into two by dividing all the data lines of the panel into upper and lower parts, and selection is performed in order from the top on each screen. As shown in FIG. 3, one of the most popular ones is
The data signal of the upper screen 2 is input from the upper screen data driver 11, and the lower screen data driver 13 inputs the lower screen 1
4 data signals are input, and scanning of the upper and lower screens is performed by the upper screen scanning driver 15 and the lower screen scanning driver 16 respectively.
There is a method to do. The selection signal is output from top to bottom for both the upper and lower screens.

There is also a method in which a data signal is input from the left and right and a scanning signal is input from the lower or upper.

[0005]

In the above-mentioned conventional matrix type liquid crystal display device, the selection signal is output only for the time obtained by dividing the data input time within one frame time by the total number of scanning lines, and one of the divided times is output. The first line is output to the second, and the second line is sequentially output to the second. Therefore, the time from the start time of the frame to the input of the selection signal gradually increases from the selection start line to the end line as shown in FIG.

The polarity of the voltage applied to the liquid crystal repeats positive and negative every frame. Due to these two causes, even when the same color is displayed on the entire screen, the effective voltage applied to the liquid crystal from the application of the selection signal to the input of the next selection signal is different for each scanning line, The scanning lines that select the pixel having the largest effective voltage difference to be applied are the selection start line and the selection end line.

FIG. 5 shows the waveform of the voltage applied to the liquid crystal on the pixel selected by the selection start line and the voltage applied to the pixel-shaped liquid crystal selected by the selection end line when the entire white display is performed on the normally white LCD. A waveform is shown, and since the selection last line and the selection start line are adjacent to each other in the center of the panel, the pixels having the largest effective voltage difference are adjacent to each other, and it is impossible to obtain a uniform display screen with a large display luminance difference.

Further, in the liquid crystal on the pixel selected by the selection end line, the electric field direction is maintained until the selection signal is applied even if it enters the next frame, but the selection start line enters the next frame. Since the selection signal is applied immediately, the liquid crystal on the pixel selected by the selection line is applied with an electric field in the opposite direction to the liquid crystal on the pixel selected by the selection end line. Because it is adjacent to the start line,
Electric field unevenness occurs between pixels, resulting in display unevenness.

An object of the present invention is to provide a method for obtaining a uniform screen without causing a difference in brightness of display colors and unevenness in brightness at the joints of the panel which is driven separately.

[0010]

A matrix type liquid crystal display device of a first invention is a matrix type liquid crystal display element in which a screen is divided into a first screen and a second screen for display, and an image signal is displayed as the first signal. A first and a second data driver for applying each of the second screens, and a first and a second scan driver for scanning and displaying the respective image signals from the joint portion of the first and the second screens. Have.

In the matrix type liquid crystal display device of the second invention, a matrix type liquid crystal display element in which a screen is divided into a first screen and a second screen for display, and an image signal is applied to each of the first and second screens. The first and second scan drivers include first and second scan drivers for scanning and displaying the respective image signals in the direction of the joint between one end and the other end of the first and second screens.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the first embodiment of the present invention.

In the first embodiment, a memory 7 capable of reading image data for one screen, an upper screen data driver 1 for outputting image data displayed on the upper screen 2 of the LCD, and a lower LCD screen. A lower screen data driver 3 that outputs image data displayed on the screen 4, an upper screen scan driver 5 that scans the upper screen, and a lower screen scan driver 3 that scans the lower screen are configured. ..

Next, the operation of the first embodiment will be described. After the image data sent serially is stored in the memory 7 for one screen, the data of the lowermost line of the upper screen is sent to the upper screen data driver 1, and the uppermost screen of the lower screen is sent to the lower screen data driver 3. Send line data. After transmitting one line of data to the upper and lower data drivers, a data signal is sent from the upper and lower data drivers 1 and 3 and a scanning signal is sent from the upper and lower screen scanning drivers 5 and 6 to the LCD upper and lower screens 2.
Applied to. At this time, the upper screen scanning driver 5 inputs the selection signal to the lowermost line of the upper surface, and the lower screen scanning driver 6 inputs the selection signal to the uppermost line of the lower screen. While the signals are being output to the LCD upper and lower screens 2 and 4, the upper screen data driver 1
Is sent to the lower screen data driver 3, and the lower screen data driver 3 is sent to the lower screen image data of the second line from the top.

After transmitting one line of image data, a data signal is applied to the LCD from the upper and lower data drivers 1 and 3, and at the same time, a selection signal is sent from the upper screen scan driver 5 to the second scan line from the bottom of the upper screen. However, a selection signal is applied from the lower screen scanning driver 6 to the second scanning line from the top of the lower screen, and a selection signal is applied from the lower screen scanning driver 6 to the second scanning line from the top of the lower screen. .. Similarly, in the upper screen, the selection is performed from the bottom to the top, and in the bottom screen, the selection is performed from the top to the bottom. When the scanning for one screen is completed, the same operation is repeated again.

FIG. 2 is a block diagram of the second embodiment of the present invention. In the second embodiment, the data of the bottom line of the lower screen 4 is sent to the upper screen data driver 3a first. When the upper and lower drivers 1a and 3a output data signals, the upper screen scanning driver 5a outputs a selection signal to the upper screen uppermost line and the lower screen scanning driver 6a outputs a selection signal to the lower screen lowermost line. While signals are being output to the LCD upper and lower screens 2 and 4, the upper screen data driver 1a receives the second image data from the top of the upper screen, and the lower screen data driver 3a receives the lower screen from below. The second image data is sent. Similarly, upper screen 2
Then, from the top to the bottom, and from the bottom screen 4 from the bottom to the top.

By using such a scanning method, there is no difference in the effective voltage applied to the liquid crystal on the pixel closest to the junction part of the screen which is divided and driven, so that there is no abrupt difference in the display brightness and the screen is reduced. The display is visually uniform.
Further, since the direction of the electric field applied to the liquid crystal on the pixel closest to the junction part of the screen which is divided and driven is the same, display unevenness due to the influence of the electric field can be eliminated.

In an LCD in which a data signal is input from the left and right direction and a scanning signal is input from the lower or upper direction,
Based on the same idea, there are a method of selecting from the center of the screen so as to spread to the left and right sides, and a method of selecting from the left and right sides of the screen toward the center.

[0019]

As described above, according to the present invention, since there is no difference in the effective voltage applied to the liquid crystal on the pixel closest to the junction of the divided two screens, there is no difference in the display brightness of the junction, A visually uniform screen is obtained.

Further, since the directions of the electric fields applied to the liquid crystal on the pixel closest to the junction coincide with each other, the electric field is not disturbed between the pixels and the display unevenness does not occur.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of an example of a conventional matrix type liquid crystal display device.

FIG. 4 is a timing chart showing a scanning signal of a conventional example.

FIG. 5 is a waveform diagram of a signal applied to a liquid crystal of a conventional example.

[Explanation of symbols]

 1 upper screen data driver 2 LCD upper screen 3,3a lower screen data driver 4 LCD lower screen 5,5a upper screen scan driver 6,6a lower screen scan driver 7 memory

Claims (2)

[Claims] 1. A matrix type liquid crystal display device in which a screen is divided into a first screen and a second screen, and first and second data for applying an image signal to each of the first and second screens. A matrix type liquid crystal display device, comprising: a driver; and first and second scanning drivers for scanning and displaying the image signals from the joint portion of the first and second screens. 2. A matrix type liquid crystal display element for displaying a screen divided into a first screen and a second screen, and a first and a second screen for applying an image signal to each of the first and second screens. A matrix type liquid crystal display device comprising: first and second scanning drivers for scanning and displaying the respective image signals in the direction of the joint from one end to the other end.