JP2551343B2 - Liquid crystal display - Google Patents

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 wide viewing angle.

[0002]

2. Description of the Related Art In a liquid crystal display device, a liquid crystal having a thickness of about 5 μm is sandwiched between two glass plates having X and Y electrodes, and the movement of liquid crystal molecules is controlled by a voltage applied to the XY electrodes, thereby displaying an image. This is a display method.

XY matrix driving of liquid crystal (time division driving)
For example, when the number of scanning lines increases as in a personal computer or a word processor, pixels to be displayed (selected pixels) and pixels not to be displayed (non-selected pixels)
, The difference between the effective voltages applied to the two is reduced. Therefore, there arises a problem that the contrast of the display image is lowered. An active matrix driving method using a thin film transistor has been studied as a method for realizing a high scanning line (large capacity) display by preventing the problem of the contrast reduction. However, when the thin film transistor is applied to a liquid crystal display device,
Although it is necessary to form a thin film transistor array with high yield and low cost, it is difficult. Therefore, an active matrix liquid crystal display device using a thin film two-terminal element having a simple structure has been researched and developed. On the other hand, when it is applied to a large-screen display device, a vehicle-mounted display device, or the like, it is desired that a display device that does not depend on a viewing angle be seen especially from all fields of view.
However, in the case of a liquid crystal display device, there is an inherent viewing angle dependency as shown in FIG. In particular, the viewing angle characteristics in the vertical direction are poor, and the viewing angle at which a contrast of 5: 1 or more can be ensured without causing gradation inversion is only 30 degrees, which has been a cause of hindering the expansion of applications of liquid crystal display devices. Therefore, the advent of a display device with high yield, low cost, and low viewing angle dependence is desired.

As a method for improving the viewing angle dependence, a method has been proposed in which a pixel is divided into two to three parts and different voltages are applied to the liquid crystal in each area (for example, T. Sunata).
et al International Disp
lay Research Conference p2
55 1991 or JP-A 2-12, JP-A 3-122621, and JP-A 2-310534). FIG. 6 shows a plan view of elements of a display device according to the method. Scan electrodes 61 and signal electrodes 66 are arranged in a matrix on a glass substrate, and thin film transistors 62 are provided at the intersections.
Is installed. The first pixel electrode is connected to the signal electrode 66 via the thin film transistor 62. This first
Of the voltage applied to the liquid crystal in the region corresponding to each pixel electrode by changing the size of the voltage applied to each pixel electrode. Change As a result, a voltage for halftone display is applied to the liquid crystal in the region on the first pixel electrode,
In the liquid crystal on the second pixel electrode, the signal voltage and the connection capacitance can be set so that a low voltage equal to or lower than the threshold voltage is applied. At this time, as the operation of the liquid crystal element, since the viewing angle characteristics of the liquid crystal element to which a printing voltage equal to or lower than the threshold voltage is applied are relatively good, the liquid crystal in the regions on the first pixel electrode and the second pixel electrode respectively The viewing angle characteristics corresponding to the voltage applied to the liquid crystal in the area (3) are obtained, and the characteristics as a whole are shown as a whole. As a result, a display element having relatively good viewing angle characteristics can be obtained even in a halftone display.

On the other hand, JP-A-4-77721 describes that a pixel is divided into a plurality of pixels, and at least one of the individual pixel electrodes has a non-linear two-terminal element between it and the thin film transistor. This is because the connection of the non-linear two-terminal element increases the voltage loss as compared with the pixel to which the non-linear two-terminal element is not connected. As a result, the individual pixels having different applied voltages are obtained and the viewing angle characteristics are improved. However, it is necessary to form the TFT and the thin film 2-terminal element at the same time, which requires a plurality of thin film transistors and the thin film 2-terminal element, resulting in an increase in the number of wirings and a complicated structure.

[0006]

However, a liquid crystal display device using a thin film two-terminal element and having good viewing angle characteristics needs to be manufactured at a low cost, which is the premise thereof. Therefore, such a pixel electrode structure is not increased. Must be formed. The present invention eliminates such an increase in the number of processes and reduces the thin film 2
An object of the present invention is to provide a liquid crystal display device having a simple structure and good viewing angle characteristics in the liquid crystal display device using the terminal element.

[0007]

According to the present invention, two opposing substrates, a liquid crystal layer sandwiched between the substrates, an electrode array formed on the inner surface of one substrate, and an electrode array formed on the substrate are provided. In a liquid crystal display element including a pixel electrode, a two-terminal element connecting the pixel electrode and the electrode array, and an electrode array formed on the inner surface of the other substrate, the pixel electrode includes a plurality of pixel electrodes. , Connect each pixel electrode 2
A liquid crystal display device comprising a terminal element.

[0008]

According to the present invention, as shown in the embodiment of FIG.
The thin film two-terminal element and the pixel electrode connecting element may basically have the same configuration. This means that the non-linear conductive material is shared by the thin film two-terminal element and the pixel electrode connecting element, which simplifies the process. At this time, as shown in FIG. 2, the first pixel electrode and the second pixel electrode are connected by the pixel electrode connecting element, but the potential difference between the respective pixel electrodes is as small as about several V and the pixel at this time is not small. The operation of the electrode connecting element includes a conductive operation and a capacitive operation, but the relatively capacitive operation is dominant and the second pixel electrode is low in voltage because of capacitance division compared to the first pixel electrode. Is applied. Therefore, even in the halftone display, a binary display having a good viewing angle characteristic is included, and the viewing angle characteristic can be improved. Therefore, it is possible to realize a liquid crystal display device having good viewing angle characteristics using a thin film two-terminal element having a simple structure.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a plan view (a) and a sectional view taken along line AA ′ of a thin film two-terminal element array substrate of a liquid crystal display device showing a first embodiment of the first invention. First, the transparent glass substrate 1
For example, Ta is sputter-deposited with a thickness of 1500 A on 0 to form the Y electrode and the pixel electrode connection element electrode 11 in an island shape. Subsequently, a non-linear conductive film 12 is formed by a 500A anodic oxidation method, and a Ta film, which is a counter electrode 13, is formed by 100A.
0A is formed and patterned in an island shape to complete the thin film two-terminal element 18 and the pixel electrode connecting element 19. Pixel electrode connection element 1
The capacitance of 9 is designed to be almost the same as the capacitance of the liquid crystal on the second pixel electrode here, but its size depends on the size of each pixel electrode and the like. Then, a transparent electrode of indium tin oxide is formed by 500 A sputtering to form the first pixel electrode 14 and the second pixel electrode 15 on the island at the same time. At this time, the areas of the first pixel electrode 14 and the second pixel electrode 15 differ depending on the display mode of the liquid crystal. In the normally black mode, the first pixel electrode 14 is set to be equal to or about twice as large as the second pixel electrode 15, and in the normally white mode, it is set to be approximately equal to about half. After this, alignment treatment was performed, the color filter substrates were bonded together, liquid crystal was injected and sealed, and then the glass substrate was cut, the drive circuit and the backlight were connected to complete the liquid crystal display device. The viewing angle characteristics of the obtained liquid crystal display device are shown in FIG. It can be seen that the viewing angle characteristics of the halftone display region are significantly improved as compared with the viewing angle characteristics of the liquid crystal display device having the structure formed by the conventional thin film two-terminal element shown in FIG. At this time, as the metal electrode, a metal such as TaN, A1 or the like, an alloy, or a laminated film is known in addition to Ta, but the present invention is effective in any case. Thin film 2
Although the element formed by anodic oxidation is used here as the terminal element, the present invention is also effective if an element formed by the CVD method or a bridge structure element is used. The present invention is also effective in a structure in which a third pixel electrode is formed and is further connected to the second pixel electrode and a new second pixel electrode connecting element.

[0010]

As described above, according to the present invention, the thin film two-terminal element has a simple structure as compared with the thin film transistor array structure used in the conventional liquid crystal display device having improved viewing angle characteristics shown in FIG. Is used. Further, since the element connecting the pixels can be formed at the same time as the thin film two terminal element, it can be formed in the same process as the liquid crystal display element using the thin film two terminal element shown in FIG. 4, and the structure is simplified. . Also, in the viewing angle characteristics shown in FIG. 3, in the liquid crystal display device using the conventional thin film two-terminal element shown in FIG. 5, the range in which the contrast 5: 1 can be maintained without causing grayscale inversion in the vertical direction is 30 degrees. Compared with the above, the present invention student also obtained an improved viewing angle characteristic up to 55 degrees in the vertical viewing angle. Therefore, a structure is provided that provides a liquid crystal display device with low cost and good viewing angle characteristics, and the effect of the present invention is remarkable.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of a thin film two-terminal element array of a liquid crystal display device showing an embodiment of the first invention.

FIG. 2 shows an equivalent circuit diagram of a liquid crystal display element of the present invention.

FIG. 3 shows vertical viewing angle characteristics of the liquid crystal display device of the present invention during 8-gradation display.

FIG. 4 shows a plan view and a cross-sectional view of a thin film two terminal element array of a conventional thin film two terminal element liquid crystal display device.

FIG. 5 is a diagram showing vertical viewing angle characteristics of a conventional liquid crystal display device during 8-gradation display.

FIG. 6 is a plan view of a thin film transistor array of a liquid crystal display device having improved viewing angle characteristics.

[Explanation of symbols]

 10, 40, 60 Glass substrate 11, 41 Y electrode 12, 42 Non-linear conductive material 13, 43 Counter electrode 14, 44, 64 First pixel electrode 15, 65 Second pixel electrode 16, 46 X electrode 17, 47 Liquid crystal 18, 48 Thin film 2-terminal element 19 Pixel electrode connection element 61 Scan electrode 66 Signal electrode

Claims (1)

(57) [Claims] 1. A pair of opposing substrates, a liquid crystal layer sandwiched between the substrates, an electrode array formed on the inner surface of one substrate, a pixel electrode formed on this substrate, and this pixel electrode. In a liquid crystal display element including a two-terminal element connected to the electrode array and an electrode array formed on the inner surface of the other substrate, the pixel electrode includes a plurality of pixel electrodes,
A liquid crystal display device comprising a two-terminal element for connecting each pixel electrode.