JPH0512688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device using a nonlinear element that is a nonlinear resistance element.

The purpose of the present invention is to simplify the manufacturing process by making one side electrode of the nonlinear element common to the one side electrode of the liquid crystal.Another purpose of the present invention is to simplify the manufacturing process by making one side electrode of the nonlinear element common to the one side electrode of the liquid crystal. Another object of the present invention is to obtain a guest-host type liquid crystal display device, and another object is to utilize the aluminum electrode used for one side electrode of a nonlinear element and one side electrode of a liquid crystal as a reflection plate. Yet another purpose is to facilitate alignment of liquid crystals.

Liquid crystal display devices are characterized by low power consumption,
It is widely used due to its low operating voltage and high contrast. However, the demand for high-density display is increasing, and the original segment display based on static drive is now shifting to matrix display based on multiplex drive. The mainstream twisted nematic type is capable of achieving a drive duty ratio of about 1/16 using the electronic averaging drive method, and is now on the market as a commercial product. However, since viewing angle dependence is strong, a guest-host type high-density display with almost no viewing angle dependence is desired. However, since this type of device originally had a poor guest dichroic ratio, it was only possible to perform static drive or 1/2 multiplex drive to obtain sufficient contrast. The present invention eliminates the above-mentioned drawbacks and provides a high-density guest-host display device.

Furthermore, as shown in FIG. 1, in the conventional liquid crystal display device using nonlinearity, the patterning structure and alignment process are troublesome. For example, in 1, the Ta film formed on one side of the glass substrate and the surface were anodized.
It is Ta ₂ O ₅ . 2 was formed on Ta ₂ O ₅
NiCr and Au film, Ta−Ta ₂ O ₅ −TiCr
It has a three-layer nonlinear structure. 3 is a pixel electrode for driving the liquid crystal, which is a semi-transparent film made of the same material as 2 but with an extremely thin film thickness. 4 is a data electrode running in the vertical direction formed on the counter substrate, forming a matrix structure with the scanning electrode 1 running in the horizontal direction. The liquid crystal is placed between these two substrates, and each substrate has the function of arranging the liquid crystal by oblique evaporation treatment of SiO or the like. Therefore, the LCD is 90mm between both boards.
It is a twist nematic type that can be twisted many times.
FIG. 2 is a cross-sectional view of portions 5 and 5'. 2
1 is a substrate on the side where the scanning electrode, pixel electrode, and Ta ₂ O ₅ 23 are located, and 22 is the substrate on the side where the data electrode is located. 24 is twisted nematic liquid crystal, 2
5 is a pair of polarizing plates. As is clear from this example, the manufacturing process includes many steps, including patterned anodic oxidation in step 1, deposition and pattern formation in step 3, and deposit and pattern formation in step 3. In addition, since the liquid crystal drive electrode is semi-transparent, the contrast is reduced without sacrificing the advantages of the twisted nematic type. In addition, since the orientation process is an oblique evaporation process, when the display area becomes large,
It is difficult to form a film that is aligned in a constant direction over the entire area.

The present invention eliminates the above-mentioned drawbacks by changing the electrode material and display type, and provides a guest-host type display device with high density and high contrast.The present invention is described in detail below with reference to the drawings. .

FIG. 3 shows an embodiment of the present invention, and shows one pixel portion on the scanning electrode side. The counter electrode side is the same as that shown in FIG. Reference numeral 31 denotes a Ta first electrode and a scanning electrode, the surfaces of which are anodized. Reference numeral 32 denotes an electrode mainly composed of Al, which integrates the second electrode of the MIM and the pixel electrode.
Therefore, compared to the conventional embodiment, the number of deposits and patterning operations are reduced by one each, which can greatly contribute to cost reduction. Moreover, since the pixel electrode is mainly composed of Al, it also has the effect of acting as a reflecting plate. Furthermore, the work function of the Al electrode in the switching part of the nonlinear element at its interface with Ta ₂ O ₅ is almost equal to that of Ta, and the voltage-current characteristics of the nonlinear element are symmetrical regardless of the polarity of the electrodes at both ends, making it easy to drive. The liquid crystal can be driven almost completely with alternating current without making the waveform asymmetrical. Furthermore, the thickness of the Ta ₂ O ₅ film in the nonlinear element portion is several hundred Å, and alignment treatment by rubbing is impossible. In other words, almost all nonlinear elements are destroyed by rubbing.
Therefore, if the display area is several cm ² , the surface is made into a film with a homogeneous alignment effect by oblique evaporation treatment, and the guest host liquid crystal is a nematic type guest host in which a guest dye is added to a positive nematic liquid crystal. A liquid crystal display would suffice, but as the display area increases, it becomes difficult to use a homogeneous array processing method that aligns all directions. Therefore, the substrate side on which the nonlinear elements are located may be subjected to a homeotropic treatment that allows alignment by dipping and drying, and the liquid crystal may be a phase change type liquid crystal obtained by adding cholesteric liquid crystal and a guest to a nematic liquid crystal. Furthermore, the electrode surface can be roughened by using an Al electrode containing Si, or by etching the Al itself into stripes or grids with a pitch of several microns at a high density. FIG. 4 shows an embodiment of the present invention, in which the lower substrate is the substrate on the side with the nonlinear element shown in FIG. 3, and the upper substrate is shown at 22 in FIG. A is a case of a nematic type guest-host liquid crystal, b is a case where the lower substrate is vertically processed and a phase change type guest-host liquid crystal, and c is a case where the Al electrode surface is roughened in case a. It is clear that other combinations exist.

As described above, the liquid crystal display device of the present invention includes a liquid crystal sealed between a pair of opposing substrates, and a pixel electrode, a scanning electrode, and a structure between the pixel electrode and the scanning electrode on one of the substrates. A nonlinear element consisting of a first electrode, an insulating film, and a second electrode connected to is formed,
In a liquid crystal display device having a counter electrode on the other substrate, the first electrode and the scanning electrode are
formed of Ta, the insulating film is an oxide of Ta,
Since the second electrode and the pixel electrode are made of Al or Al containing Si, the following effects can be obtained.

(a) Since the work functions of Al and Ta ₂ O ₅ and those of Ta and Ta ₂ O ₅ are almost equal, the voltage-current characteristics of the nonlinear element are completely symmetrical with respect to zero voltage, and the display in AC drive is Flickering is completely eliminated, and zero point correction is not required in terms of the drive circuit, so it can be driven with a simple circuit configuration.

(b) Since the second metal of the pixel electrode and the nonlinear element are made of the same material, the patterning and deposition steps, which were required three times when conventionally different materials were used, are now completed in two steps.
This reduces the number of steps and improves yield.

(c) Since the pixel electrode is made of Al, a reflective type liquid crystal display device with excellent reflectance and high contrast can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a conventional embodiment. Figure 2 is the first
A cross-sectional view taken along line 5-5' in the figure. FIG. 3 is a plan view of one pixel section according to an embodiment of the present invention. Figures 4a, b, and c are cross-sectional views of embodiments of the present invention.

Claims (1)

[Claims] 1 A liquid crystal is sealed between a pair of opposing substrates, and on one of the substrates are a pixel electrode, a scanning electrode, and a first electrode-insulating film connected between the pixel electrode and the scanning electrode. - In a liquid crystal display device in which a nonlinear element consisting of a second electrode is formed and has a counter electrode on the other substrate, the first electrode and the scanning electrode are made of Ta, and the insulating film is made of Ta. 1. A liquid crystal display device, wherein the second electrode and the pixel electrode are formed of Al or Al containing Si.