JPH03166527A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To allow sharp picture element display free from unequalness by adding resistors in electrically series to sintered body varistor elements and setting the resistance values of the resistors smaller the further the liquid crystal picture element electrodes part from the voltage supply terminal of a line electrode and thereby uniformizing the supply voltages to the respective liquid crystal picture elements along the line electrode. CONSTITUTION:The line electrode 11 and the liquid crystal picture element electrodes 12-1 to 12-n are connected by the sintered body varistor elements 13 and the resistors 18-1 to 18-n. The sectional areas S1 to Sn of the resistors 18-1 to 18-n are set larger the further from a power source 20 to uniformize the supply voltage to the respective liquid crystal picture elements along the line electrode 11. Namely, the resistance values of the resistors 18-1 to 18-n are set smaller the further the liquid crystal picture element electrodes 12-1 to 12-n part from the power source 20 of the line electrode 11 to decrease the influence of the voltage drop the further from the power source 20, by which the supply voltages to the respective liquid crystal picture elements along the line electrode 11 are uniformized. The sharp image display free from the unequalness is executed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a two-terminal element type liquid crystal display device (LCD) using a sintered varistor element as a nonlinear element.

[Prior Art] At present, image display devices for, for example, liquid crystal televisions are broadly classified into simple matrix type and active matrix type.

In the simple matrix method, a plurality of liquid crystal pixels are arranged in a matrix and connected between two sets of band-shaped electrode groups (row electrode group and column electrode group) arranged at right angles. During this time, a predetermined voltage is applied by a drive circuit to operate the liquid crystal pixels. This method has the advantage of being able to realize a system at a low cost due to its simple structure, but because crosstalk occurs in each LCD pixel, the contrast of the image is low, and it cannot be used for displaying images on LCD TVs. there were.

On the other hand, in the active matrix method, a switch is provided for each liquid crystal pixel to maintain the voltage, and even if the liquid crystal display device is time-divisionally driven, the liquid crystal pixel can maintain the voltage at the time of selection. It is possible to increase the display capacity,
It has good image quality characteristics such as contrast, and can be used to display images on a liquid crystal television. However, the active matrix method has the disadvantage that the structure is complicated and the manufacturing cost is high.

For example, in a TFT type switch that uses a film-like field effect transistor as a switch, it is difficult to increase the product yield because five or more photomasks are used in the manufacturing process to stack five or more thin films.

Due to the above-mentioned circumstances, there is a desire to realize a liquid crystal display device that has good characteristics related to image quality such as contrast, has a simple structure, and is low in cost. Two-terminal element type liquid crystal display devices using varistor elements are attracting attention.

A two-terminal element type liquid crystal display device is an improvement on the simple matrix method, and as shown in FIG.
The sintered varistor element 3 and the liquid crystal pixel 4 are electrically connected in series between the sintered varistor element 3 and the liquid crystal pixel 4. It takes advantage of its characteristics. That is, in time-division driving using the simple matrix method, as shown in FIG. 8, the ratio γ of the voltage V90 at which the liquid crystal pixel is turned on (light transmittance is 90%) and the voltage V10 at which the liquid crystal pixel is turned off (light transmittance is 10%) is γ. (=V90/
V10= (V10+AV)/V10)
Therefore, the maximum number of scanning lines Nmax that is allowed without causing crosstalk between each liquid crystal pixel is Nmax=(
(r2+1)/72-1))2, and the smaller the value of γ, the larger the number of scanning lines, which is advantageous for liquid crystal television display. On the other hand, in the case of the two-terminal element type, the voltage exceeding the threshold voltage vv is applied to the liquid crystal pixel 3 by the sintered varistor element 4, and when the sintered varistor element is not provided. The operating voltage of the liquid crystal pixel (Figure 9 (a)
)) is increased by its threshold voltage vv by providing a sintered varistor element (see FIG. 9(b)). As a result of ζ, the value of γ is improved from V 90 / V 10 to (VV + V 90) / (VV + V 10), and by decreasing the γ value, the maximum number of scanning lines NmaX can be increased, and high quality liquid crystal display can be achieved. It can come true.

2 to 5 show conventional two-terminal element type liquid crystal display devices.

As shown in the figure, a row electrode 11 and a pixel electrode 12 are provided on a lower glass substrate 10 at a predetermined distance d, and these row electrodes 11 and pixel electrodes 12 are connected by a sintered ZnO varistor element 13. It has been done. Then, attach the upper part of these to the liquid crystal 14.
Further, column electrodes 15, color filters 16, and an upper glass substrate 17 are provided.

As shown in detail in FIG. 5, the sintered varistor element l3 is
Varistor grains 13a in which ZnO is coated with Mn and Co oxides
is sintered with a glass frit 13b, and a threshold voltage of about 3 V can be obtained for each varistor grain with a grain size of about 5 μm. Therefore, the distance d between the row electrode 1l and the pixel electrode 12
If varistor grains 13a are set to 25 μm, the row electrode 11 and the pixel electrode l2 are connected through substantially five varistor grains 13a in series existing within this interval d, and between these electrodes IL12 there are five varistor grains A threshold voltage of 5V is obtained.
As shown in FIG. 2, a large number of pixel electrodes 12 are provided for each row electrode 11 at a constant interval d, and the row electrodes 11 and pixel electrodes 12 are connected to each sintered varistor element 13 at a constant distance d. It is connected with a threshold voltage VV. In addition, in the figure, 1, 2
...(n-1), a subscript of n is attached.

[Problems to be Solved by the Invention] The two-terminal element type can realize a liquid crystal display device with a simple structure and low cost and good image quality. A voltage was supplied to the sintered varistor element 13 with a constant threshold voltage V■.

Therefore, with the recent trend of increasing the screen size of liquid crystal display devices, there is a problem that unevenness occurs on the display screen. This is because as the display screen becomes larger, the row electrodes 11 also become longer, so the voltage drop due to the resistance of the row electrode l1 cannot be ignored, and the voltage of the row electrodes 11 to which the voltage is supplied from the power source 20 increases. Pixel electrode 12-1 near the supply end
This is because there is a large difference in the voltage supplied to the pixel electrode 12-n and the far pixel electrode 12-n. For example, if the row electrodes 11 are made of indium oxide (ITO) or chromium (Cr) and the line length is 30I? m, line width 0. 3Ω/2mm
When formed at the mouth, the line resistance is 4.5KΩ.If the number of pixels connected to this row electrode is 1000, and the current value flowing per pixel is IX10-8A, then the voltage drop due to the line resistance alone is , a difference of 4.5 V occurs in the voltage supplied between the pixel electrode 12-1 near the voltage supply end and the pixel electrode 12-n far from the voltage supply end. Under these conditions, the power supply 20 is set to 30 V, and the sintered varistor element 13 is
When calculating the threshold voltage of 25V, the voltage at the position of the row electrode 11 near the power supply 20 is 30V due to the voltage drop due to the threshold voltage, line resistance, voltage consumption in each pixel, etc. The voltage at the farthest point from the power supply 20 is 2
The voltage supplied to the pixel electrode 12-1 closest to the voltage supply source is 5V, but the voltage supplied to the pixel electrode 12-n furthest from the voltage supply source is 0.5V, which is noticeable in the displayed image. This results in unevenness.

The present invention has been developed in view of the above-mentioned conventional circumstances, and aims to stabilize the voltage supplied to each liquid crystal pixel from the side close to the voltage supply source of the row electrode to the side far from the voltage supply source, thereby realizing clear image display without unevenness. The purpose of the present invention is to provide a liquid crystal display device.

[Means for Solving the Problems] A liquid crystal display device according to the present invention is a liquid crystal display device in which a sintered varistor element and a liquid crystal pixel are electrically connected in series between a row electrode and a column electrode. , a resistor is electrically added in series with the sintered varistor element connecting the row electrode and the liquid crystal pixel electrode, and the resistance value of the resistor is determined when the liquid crystal pixel electrode is connected to the voltage supply terminal of the row electrode. The feature is that the supply voltage to each liquid crystal pixel along the row electrode is made uniform by setting the voltage to be smaller as the distance from the row electrode increases.

[Function] In the liquid crystal display device of the present invention, a resistor is electrically added in series with the sintered varistor element, and the resistance value of this resistor decreases as the distance from the voltage supply end of the row electrode increases. By setting this, the influence of the voltage drop of the row electrode decreases as the distance from the voltage supply end increases, and a generally uniform voltage is supplied to each pixel connected to the row electrode from the side closer to the voltage supply source to the side farther from the voltage supply source.

[Example] The liquid crystal display device according to the present invention will be specifically explained based on an example. Note that the same parts as in the conventional example described above are given the same reference numerals, and redundant explanations will be omitted.

FIG. 1 is a plan view showing a liquid crystal display device according to an embodiment of the present invention.

As shown in the figure, the row electrode 11 and the liquid crystal pixel electrode 12-1-1
The resistors 18-1 to 18-n are connected to the sintered varistor element 13 which is electrically connected in series with the resistors 18-1 to 18-n. These resistors 18-1 to 18-n have the same length, but their cross-sectional areas S1 to Sn are set to increase as they move away from the power source 20, so that the resistors 18-1 to 18-n have the same length. The supply voltage is equalized. That is, the resistance values of the resistors 18-1 to 18-n are the same as those of the liquid crystal pixel electrodes!
2-1 to 12-n are set smaller as the distance from the power source 20 of the row electrode 11 decreases to reduce the effect of voltage drop as the distance from the power source 20 increases, and as a whole, the supply voltage to each liquid crystal pixel along the row electrode 11 is reduced. have been made uniform. Note that the resistors l8-1 to 1B-n are formed of, for example, titanium nitride, indium oxide (ITO), tantalum oxide, or the like.

In this embodiment, the resistor 1
On the contrary, the resistance values of 8-1 to 18-n are decreased, and the voltage supplied to each pixel electrode in the longitudinal direction of the row electrode 11 is generally made uniform. Therefore, even in a large-sized liquid crystal display device in which the row electrodes 11 are long, the voltage supplied to each pixel can be made uniform, and an even and clear image can be displayed.

In addition to changing the cross-sectional area as described above, methods for changing the resistance value of a resistor include changing the length of the resistor or changing the material of the resistor itself. You can also let them do it. Further, in the above embodiment, a sintered varistor element made of Zno was shown, but a sintered varistor element made of other known materials such as SiC may also be used. In addition, the connection relationship between the resistor and the sintered varistor element is reversed from the above embodiment, and the sintered varistor element is connected to the row electrode, while the resistor is connected to the pixel electrode, and these sintered varistor elements are connected to the pixel electrode. The varistor element and the resistor may be connected.

[Effect] According to the liquid crystal display device of the present invention, a resistor is electrically added in series with the sintered varistor element, and the resistance value of the resistor increases as the distance from the voltage supply end of the row electrode increases. Because it is set to a small value, the effect of the voltage drop on the row electrode decreases as it moves away from the voltage supply end, and it is possible to connect the row electrode from the side close to the voltage supply source to the side far from the voltage supply source without making delicate adjustments to the varistor characteristics. A uniform voltage can be supplied to each pixel. Therefore, even if the screen of the liquid crystal display device is made larger, it is possible to display an even and clear image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional liquid crystal display device, FIG. 3 is a plan view of a conventional liquid crystal display device, and FIG. 4 is a block diagram of a conventional liquid crystal display device. IV-I in Figure 3
V arrow sectional view, Figure 5 is an enlarged view of the main part in Figure 4, Figure 6
The figure shows a schematic configuration diagram of a two-terminal element type liquid crystal display device, Figure 7 shows voltage-current characteristics of a sintered varistor element, Figure 8 shows operating characteristics of a liquid crystal pixel, and Figures 9 (a) and (b). ) is an operational characteristic diagram of a liquid crystal pixel explaining the action of a sintered body varistor element. 11 is a row electrode, 12 and 12-1 to 12-n are pixel electrodes, 13 is a sintered varistor element, 14 is a liquid crystal, 15 is a column electrode, and 18-1-1.8-n is a resistor.

Claims (1)

[Claims] A sintered varistor that connects a row electrode and a liquid crystal pixel electrode in a liquid crystal display device in which a sintered varistor element and a liquid crystal pixel are electrically connected in series between a row electrode and a column electrode. A resistor is electrically added in series with the element, and the resistance value of the resistor is set to decrease as the liquid crystal pixel electrode moves away from the voltage supply end of the row electrode, and is applied to each liquid crystal pixel along the row electrode. A liquid crystal display device characterized in that supply voltage is made uniform.