JPH0331823A - Production of liquid crystal display device and electrode substrate - Google Patents

Abstract

PURPOSE:To obtain good display images by forming a counter electrode of a wiring electrode and transparent electrode, consisting the wiring electrode of a low resistance metal and providing these electrodes at the specified line width above the place between picture element electrodes or on the image element electrode. CONSTITUTION:The liquid crystal display device 1 is constituted by crimping a liquid crystal compsn. 51 between a 1st electrode substrate 11 and a 2nd electrode substrate 31. The electrode substrate 11 is formed of striped signal electrodes 35 formed on a transparent glass substrate 13, plural MIM elements 40 connected to the signal electrodes 35, the picture element electrodes 41 connected and installed to the MIM elements 40 and an oriented film 27 installed on these electrodes. The electrode substrate 31 is installed with the counter electrode 21 constituted of the wiring electrode 20a formed of tantalum, which is the low resistance metal similarly to the 1st metal 37 constituting the MIM elements 40, at a fine wire width of 10 micron and the counter electrode 21 constituted of the transparent electrode 20b on the substrate 13. Further, the oriented film 27 is installed on the counter electrode 21. The good display images are obtd. in this way.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention uses MIM (Meta
The present invention relates to a method for manufacturing a liquid crystal display device and an electrode substrate using an l-Insulator-Metal) element.

(Prior Art) In recent years, applications have expanded from relatively simple devices such as watches, calculators, and M1 devices to large-capacity information displays such as personal computers, word processors, terminal devices for office automation, and TV image displays. Liquid crystal display devices are used in In such large-capacity liquid crystal display devices, a matrix display multiplex driving method is generally adopted.

However, due to the essential characteristics of the liquid crystal itself, this method is insufficient in terms of contrast ratio between display areas (on pixels) and non-display areas (off pixels) even when it has about 200 scanning lines. Furthermore, when performing large-scale matrix driving with 500 or more scanning lines, the deterioration of contrast is fatal.

Developments to solve the drawbacks of this liquid crystal display device are actively being carried out in various places. One direction is to directly switch drive individual pixels. Thin film transistors are used as switching elements in this case. Various materials such as single crystal silicon, polycrystalline silicon, cadmium selenide, and tellurium have been proposed as semiconductors constituting thin film transistors, but amorphous silicon is currently being studied the most. However, in manufacturing this type of liquid crystal display device, several microfabrication steps are required, which may result in a complicated process and poor yield. As a result, product costs have increased, and manufacturing of large-scale liquid crystal display devices has become extremely difficult.

Another way to use a switching element array is to use nonlinear resistance elements.

A nonlinear resistance element basically has a two-terminal structure and is easier to manufacture than a three-terminal thin film transistor. Therefore, an improvement in product yield can be expected, and there is an advantage in cost reduction.

Nonlinear resistance elements are made of the same materials as thin film transistors, such as diode type junctions, varistor types using zinc oxide, and metal insulating layers with an insulator sandwiched between electrodes.
A metal (MIM) type and a type using a semiconductive layer (MSI) between metal electrodes have been developed.

Among these, the MIM type has one of the simplest structures,
At present, it can be said that this is the closest to practical application.

Generally, in manufacturing an electrode substrate having MIM, a tantalum (Ta) film is formed on a glass substrate by a thin film forming method such as sputtering or vacuum evaporation, and then the desired signal electrode and MIM are formed using photolithography technology. and a first metal. Next, the first metal is chemically converted by an anodic oxidation method using an aqueous citric acid solution or the like to form an insulator. Furthermore, a chromium (C'') film was used as the other electrode of the MIM.
By forming it by a thin film formation method and using it as the second metal,
The MIM element is completed. Furthermore, after this, a pixel electrode for image display may be connected to the second metal. Such a basic manufacturing technique is disclosed in Japanese Patent Application Laid-Open No. 55-61273, and improved techniques thereof are shown in Japanese Patent Application Laid-Open No. 58-178320, etc.

A liquid crystal display device was obtained by sandwiching a liquid crystal composition between the first electrode substrate thus formed and the second electrode substrate having a counter electrode formed in a stripe shape of a transparent conductor.

(Problems to be Solved by the Invention) However, as the display size of liquid crystal display devices progresses, there is a tendency for the wiring length of signal electrodes or counter electrodes to increase and for the wiring pitch to become extremely fine.

Under these circumstances, various liquid crystal display devices with low resistance on the signal electrode side have been developed, but the same problem has not been solved regarding the counter electrode.

As the wiring resistance of the counter electrode increases, the drive waveform becomes distorted or the order constant increases, which has an adverse effect on the displayed image of the liquid crystal display device.

This invention was made in view of the above circumstances,
It is an object of the present invention to provide a liquid crystal display device that can reduce wiring resistance without reducing light transmittance and provide a good display image. Another object of the present invention is to provide a method of manufacturing an electrode substrate, which can easily manufacture the electrode substrate of the above-mentioned liquid crystal display device, for example.

[Structure 1 of the Invention (Means for Solving the Problems) The liquid crystal display device of the present invention has a nonlinear display device comprising a plurality of pixel electrodes and a first metal-insulator-second metal electrically connected to each of the pixel electrodes. a first electrode substrate on which a resistive element is formed; a second electrode substrate having a counter electrode facing the pixel electrode of the first electrode substrate; a first electrode substrate and a second electrode substrate. A liquid crystal display device comprising a liquid crystal composition sandwiched between pixel electrodes, wherein the opposing electrode is composed of a wiring electrode and a transparent electrode, and the wiring electrode is made of a low resistance metal and is provided above between the pixel electrodes. Alternatively, it is characterized by being provided on the pixel electrode with a line width of 10 microns or less.

Further, the method for manufacturing an electrode substrate of the present invention includes a plurality of pixel electrodes in a first region on the substrate and a nonlinear resistance element made of a first metal-insulator-second metal electrically connected to each of the pixel electrodes. , a first step of forming a wiring electrode and a counter electrode made of a transparent electrode in a second region different from the first region of the substrate, and dividing the substrate into a first region and a second region, A second step of forming a first electrode substrate having a pixel electrode and a second electrode substrate having a counter electrode, wherein the first step is to form a first metal or a second electrode substrate. The feature is that at least one process selected from the process of forming a wiring electrode on the substrate at the same time as forming the second metal, and the process of forming a transparent electrode at the same time as forming the pixel electrode is performed, and then the other process is performed. That is.

(Function) Through various experiments, the present inventors have found that the resistance value required for the counter electrode is 1007, and that by realizing this, it is possible to obtain a liquid crystal display device that can obtain good display characteristics for the first time. I found out.

As a result of various studies to lower the resistance value of the counter electrode, there is a limit to the ability to lower the resistance by increasing the thickness of the counter electrode. That is, the counter electrode is I.

T, 0. (Indium Tin Oxide)
Although it depends on the density of the film, it is necessary to increase the film thickness in order to achieve a resistance value of F. Such a thick film 1. is applied to the counter electrode of a liquid crystal display device. T, 0. Providing such a display will result in a decrease in light transmittance, making it impossible to obtain a display with good contrast characteristics.

For this reason, we focused on forming the counter electrode from a 2Pli type material. That is, the counter electrode is made of a metal with a low resistance value, and 1. By forming a transparent electrode of T, 0°, etc., the resistance value can be sufficiently reduced. This low resistance metal is, for example, copper (C
u), tantalum (Ta), aluminum (Ari), titanium (T1
) or alloys selected from these metals.

However, since wiring electrodes formed of low-resistance metal do not transmit light, it is necessary to prevent the light transmittance of the liquid crystal display device from decreasing. For this reason, the inventors of the present invention have determined from various experiments whether the
Alternatively, it has been found that when provided inside the display area, the light transmittance can be set to a line width of 10 microns or less. If the line width of the wiring electrode is 10 microns or more, sufficient light transmittance for a liquid crystal display device will not be obtained. Further, in order to at least make the resistance value of the counter electrode 1007, it is preferable that the line width be 3 microns or more.

By the way, from the viewpoint of manufacturing, it is not preferable to form the counter electrode of a liquid crystal display device with two layers of a wiring electrode and a transparent electrode as described above.

The conventional manufacturing method of an electrode substrate equipped with a nonlinear resistance element is as follows:
A first electrode substrate having a plurality of nonlinear resistance elements and pixel electrodes is formed on one substrate, and a second electrode substrate having a counter electrode facing the pixel electrodes is formed on the other substrate. For example, a liquid crystal display device has been produced by sandwiching a liquid crystal composition between a pair of these substrates.

Therefore, in order to manufacture a liquid crystal display device having the above-described complicated structure, at least one photolithography process is required to form wiring electrodes.

As a result of various studies on manufacturing methods for electrode substrates equipped with nonlinear resistance elements, the inventors of the present invention discovered that the first electrode substrate and the second electrode substrate can be formed on the same substrate in the same manner. Furthermore, the pixel electrode of the first electrode substrate and the transparent electrode of the second electrode substrate are simultaneously formed using the same material, and the metal forming the wiring electrode of the first electrode substrate and the nonlinear resistance element of the second electrode substrate is formed. By simultaneously forming them using the same material, it is possible to prevent an increase in the number of photolithography steps due to a complicated structure. That is, this is because the first electrode substrate can be sufficiently formed within the manufacturing process of the second electrode substrate.

(Example) The details of this invention will be explained below with reference to the drawings. 1st
The figure shows a schematic cross-sectional view of one display part of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 shows a cross-sectional view taken along the line A-A- in FIG. It is something.

The liquid crystal display device (1) of this example has a first electrode substrate (1
1) and a second electrode substrate (31), and a liquid crystal composition (51) is sandwiched therebetween.

The first electrode substrate (11) is a transparent glass substrate (13)
A striped signal electrode (35) formed on the top and a plurality of MIM elements (4) connected to this signal electrode (35).
0), a pixel electrode (41) connected and installed to this MIM element (40), and an alignment film (2) installed on these electrodes.
7).

As shown in FIG. 2, this MIM element (40) consists of a first metal (37) made of tantalum (Ta) integrated with a signal electrode (35), and an insulator (38) from the glass substrate (13) side.
, and a second metal (39) made of titanium (Ti).

Next, the second electrode substrate (31) is a transparent glass substrate <1
3) Place the first metal (3) constituting the MIM element (40) on top.
Similarly to 7), the wiring electrode (20a) is made of tantalum (Ta), a low resistance metal, and has a fine line width of 10 microns, and the striped transparent electrode (20a) is covered with the wiring electrode (20a). 20b) constituted by a counter electrode (
21) is installed. As shown in FIG. 1, the wiring electrodes (20a) are formed in a stripe shape above between the opposing pixel electrodes (41), and are formed in the liquid crystal display device (
Since the display area 1) is installed to avoid the display area, the light transmittance of the liquid crystal display device is not reduced.

Here, the wiring electrode (20a) is placed above between the pixel electrodes (41), but it may be placed on the pixel electrode as long as the line width is 10 microns or less.

Further, an alignment film (27) is provided on this counter electrode (21) to constitute a second electrode substrate (31).

Such a first electrode substrate (11) and a second electrode substrate (
A liquid crystal display device (1) is constructed by sandwiching a liquid crystal composition (51) between the liquid crystal compositions (51) and (31).

Then, as shown in FIG. 3, the signal electrode (35) of the first electrode substrate (11) is connected to the signal electrode driving means (61), and the second
The counter electrode of the electrode substrate (31) is connected to the counter electrode drive means (7).
1) and is controlled by the control means (81), the liquid crystal display device (1) can be operated.

The signal electrode drive means (81) and the counter electrode drive means (7
1) is composed of a shift register circuit and a driver circuit, and sequentially applies information signals in synchronization with a timing signal from a control means.

As described above, in the liquid crystal display device (1) of this embodiment, the wiring electrode (20a) made of a low-resistance metal and forming a part of the counter electrode (21) is formed above between the opposing pixel electrodes (41). As a result, the transparent electrode (20b) has the same thickness as the conventional one. Even when formed using T, O, film, etc., the wiring resistance of the counter electrode (21) could be set to 10 Ω/hole without reducing the light transmittance.

Therefore, compared to conventional liquid crystal display devices, a much better display image was obtained without a decrease in the order constant.

Next, a method for manufacturing such a liquid crystal display device will be described in detail with reference to FIG.

First, as shown in FIG. 4(a), a transparent glass substrate (
13) A tantalum (Ta) film (
14) is formed with a film thickness of 3000 angstroms.

In the initial state of this sputtering, 10
By adding % of oxygen, tantalum (Ta) film (
The contact surface of 14) with the glass substrate (13) is an oxide layer of about 300 angstroms, thereby ensuring good adhesion.

Additionally, this oxide layer (not shown) is made of tantalum (Ta).
It also has the effect of preventing external light from being reflected on the surface of the film (14).

Next, after coating a resist on the tantalum (Ta) film (14), it is exposed and developed using a mask, and the signal electrode (3
5) and the first metal (
A plurality of resist patterns (15) for forming resist patterns (37)
a) on the first region of the glass substrate (13), and at the same time, a wiring electrode (20a) constituting the counter electrode (21).
) is actually formed on a second region of the same glass substrate (13).

Here, the first region is a region divided into 1/2 parts at the center of the glass substrate (13), and the second region is the remaining 1/2 region of the glass plate 13).

As shown in FIG. 4(b), the glass substrate (13)
is dry-etched in a plasma containing a mixture of CF4 and 02 at a ratio of 1:2 to obtain a desired electrode pattern.

Next, the surfaces of the signal electrode (35) and the first metal (37) are
．． An insulator (38) with a film thickness of 700 angstroms is formed on the surfaces of the transmission electrode 35) and the first metal (37) by anodizing in a citric acid aqueous solution containing 01 rn amount.

Next, as shown in FIG. 4(c), a titanium (Ti) film (not shown) with a thickness of 1500 angstroms is formed on the insulator (3g) 1 by sputtering. A resist was applied on this titanium (Ti) film, exposed and developed using a mask, and etched with a mixture of ammonia water, hydrogen peroxide, EDTA and water.
) titanium (T) only on the insulator (38) installed on the surface
j) Form a film to serve as the second metal (39), thus forming the signal electrode (35) and the N11M element (40).

Next, as shown in FIG. 4(d), 1.7. 0 membrane (17
) is formed on the entire surface by sputtering.

The pixel electrode (40) is connected to the second metal (39).
) and the transparent electrode connected to the wiring electrode (20a)? (i-pole (
20b), a plurality of resist patterns (tea) of a predetermined shape, (18b) are placed on a glass substrate (1
3) are installed in the first area and the second area.

Subsequently, an etching process is performed to remove the pixel electrode (41) connected to the second metal (39) of the MIM element (40) and the top of the wiring electrode (20a), as shown in FIG. 4(e). A striped transparent electrode (20b) is formed.

FIG. 5 shows a schematic perspective view of the glass substrate (13) in such a state, and a plurality of pixel electrodes (41) or counter electrodes (21) are formed on the same glass substrate (13).

Such a glass substrate (13) is cut into the first region and the second region, and the pixel electrode (41) is cut as shown in FIG. 4(f).
) and a counter electrode (21).
A second electrode substrate (31) is formed.

In order to form a liquid crystal display device (1) from the first electrode substrate (11) and second electrode substrate (31) obtained in this way, the following steps may be performed, for example.

MIM element (40) of the obtained first electrode substrate (11)
Opposite electrode (21) on forming surface and second electrode substrate (31)
The alignment direction of the liquid crystal composition (51) is regulated by applying, baking and rubbing an alignment film made of polyimide resin on the formation surface. The counter electrode (21) of the first electrode substrate (11) and the signal electrode (3) of the second electrode substrate (31)
5) are formed so as to overlap with the counter electrode (21) and the pixel electrode (41) with the liquid crystal composition (51) in between. In this way, the liquid crystal composition (51) is maintained at an interval of 5 to 20 μm so that the long axis direction of the molecules is twisted approximately 90° between the substrates (11) and (31).
51). And the first 7 hypopolar substrate (11)
and a polarizing plate (39) on the glass substrate (13) 1 (33) with the polarization axis twisted by about 90 degrees on the outside of the second electrode substrate (31).

(49) may be placed.

By forming the first electrode substrate (11) and the second electrode substrate (31) on the same substrate as described above, it is possible to reduce the manufacturing cost due to the y2 complexity of the configuration of the counter electrode (21). We were able to prevent an increase in the number of processes. Additionally, compared to conventional methods, the number of masks used in manufacturing could be significantly reduced.

Furthermore, the wiring electrode (20a) of the counter electrode (21) is MIM
Since the element (40) is made of a low-resistance metal, the wiring resistance of the counter electrode (21) is reduced and the waveform distortion of the signal during transmission is eliminated, making it possible to obtain a good display image. It could be used as a display device (1).

In this example, the first metal (37) of the MIM element (40)
At the same time as forming the wiring electrode (20a),
The present invention is not limited to this, and the wiring electrode (20a) may be formed at the same time as the second metal (39) is formed. Alternatively, after forming the picture 'll electrode (41), the second metal (39) may be formed to form the MIM element (40).

(Other Embodiments) In the embodiments described above, M constituting the liquid crystal display device (1)
The first metal (37) and the counter electrode (2) of the IM element (40)
Although the wiring electrode (20a) forming 1) was formed of the same metal in the same process, for example, the counter electrode (21) was constructed by installing the wiring electrode (20a) on a transparent electrode (20b). It's okay. Such a configuration can be easily obtained, for example, by manufacturing as follows.

FIG. 6 is a schematic process diagram showing a method for manufacturing a liquid crystal display device according to this embodiment, and the same parts as those in the first embodiment will be omitted and explained with reference to this process diagram.

First, as shown in FIG. 6(a), a transparent glass substrate (
13) A tantalum (Ta) film (
14) with a film thickness of 3000 angstroms, and further, after coating a resist on the tantalum (Ta) film (14), it was exposed and developed using a mask to form a signal electrode (35).
) and the first metal (37) constituting the MIM element (40)
A plurality of resist patterns (15a) are formed on a first region of a glass substrate (13). Here again, the first region is the center of the glass substrate (13)
The area is divided into two areas, and the second area is the glass substrate (
The remaining 1/2 area of 13) was used.

As shown in FIG. 6(b), a glass substrate (13)
is dry-etched in a plasma containing a mixture of CF4 and 02 at a ratio of 1:2 to form a signal electrode (
35) and the first metal (37) are obtained.

Then, the surfaces of the signal electrode (35) and the first metal (37) are anodized in a 0.01% by weight citric acid aqueous solution, and a 700 angstrom film is formed on the surfaces of the signal electrode (35) and the first metal (37). A thick insulator (38) is formed.

Next, as shown in FIG. 6(C), a plurality of pixel electrodes (41) are provided in the first region excluding the insulator 38), and a striped transparent electrode is provided in the second region. (20b) is formed. This is 1. T, 0. It can be formed by forming a film over the entire surface by sputtering and then etching it.

Then, as shown in FIG. 6(d), the pixel electrode (40) and the insulator (38) in the first region are connected, and the MIM
At the same time as forming the second metal (39) constituting the element (40), a striped wiring electrode (20a) is formed on the transparent electrode (20b) in the second region using the same material as the second metal (39). to form. This can also be formed by etching after forming titanium (Ti), which forms the second metal (39), over the entire surface of the first region and the second region.

By cutting such a glass substrate (13) into the first region and the second region in the same manner as in the first embodiment,
a first electrode substrate (11) including a pixel electrode (41);
A second electrode substrate (31) having a counter electrode (21) is formed.

The thus obtained first electrode substrate (11) and the second electrode substrate (11)
A liquid crystal display device (1) was prepared by sandwiching a liquid crystal composition (51) between the electrode substrates (31) in the same manner as in the first example.

As explained above, even if the configuration of the counter electrode becomes complicated,
By forming the first electrode substrate (11) and the second electrode substrate on the same substrate, the second electrode substrate (31) can be manufactured in the same number of steps as in the first embodiment. be able to. Conventionally, the first electrode substrate (11)
In contrast, in the manufacturing method of the liquid crystal display device of this embodiment, the first electrode substrate (11) and the second electrode substrate (11) are formed on the same substrate. By simultaneously forming the second electrode substrate, the number of masks can be significantly reduced.

Furthermore, in the liquid crystal display device (1) manufactured in this manner, the wiring resistance of the counter electrode (21) could be significantly reduced compared to the conventional device, and a good display image could be obtained.

Here, a case has been shown in which the method for manufacturing a 7M polarity substrate of the present invention is applied to a liquid crystal display device g, but it can also be applied to various other devices.

[Effects of the Invention] As described in detail above, the liquid crystal display device of the present invention has a configuration in which the counter electrode includes a transparent electrode and a wiring electrode formed of a low-resistance metal, and the wiring electrode is connected to the upper part between the pixel electrodes. Alternatively, by installing the line width on the pixel electrode with a line width of 10 microns or less, the wiring resistance can be suppressed without increasing the light transmittance of the liquid crystal display, thereby making it possible to obtain a good display image. We were able to. Therefore, the liquid crystal display device of the present invention is particularly suitable for a liquid crystal display device with a large display screen, and can fully exhibit its effects.

In addition, in the method for manufacturing a 7ti electrode substrate of the present invention, the same substrate
By forming the wiring electrode forming the counter electrode at the same time as forming the metal forming the nonlinear resistance element in step 1-, and forming the transparent electrode forming the counter electrode at the same time as forming the pixel electrode,
Even if the configuration of the counter electrode is complicated, it can be easily manufactured without increasing the number of manufacturing steps. Furthermore, by simultaneously forming the first electrode substrate and the second electrode substrate on the same substrate, the number of masks used in manufacturing can be significantly reduced compared to the conventional method.

As described above, the method for manufacturing an electrode substrate used in a liquid crystal display device of the present invention allows even a liquid crystal display device with a complicated structure to be easily manufactured without impairing productivity.

[Brief explanation of drawings]

FIG. 1 is a schematic front view of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the liquid crystal display device of FIG. 1 taken along line A-A″, and FIG. A schematic configuration diagram of the liquid crystal display device, FIG. 4 is a schematic process diagram of the liquid crystal display device of this example, and FIG.
FIG. 6 is a schematic perspective view of the glass substrate in e) and a schematic process diagram of a liquid crystal display device of another embodiment. (1)...Liquid crystal display device (11)...First electrode substrate (20a)...Wiring electrode (20b)...Transparent electrode (2L)...Counter electrode (31)...First No. 2 electrode substrate (40)...MIM, g-son (51)...liquid crystal composition

Claims (2)

[Claims] (1) A first electrode substrate on which a plurality of pixel electrodes and a nonlinear resistance element made of a first metal-insulator-second metal electrically connected to each of the pixel electrodes are formed; a second electrode comprising a counter electrode facing the pixel electrode of the electrode substrate;
In the liquid crystal display device comprising an electrode substrate and a liquid crystal composition sandwiched between the first electrode substrate and the second electrode substrate, the counter electrode is constituted by a wiring electrode and a transparent electrode; A liquid crystal display device characterized in that the wiring electrode is made of a low-resistance metal and is provided above between the pixel electrodes or on the pixel electrode with a line width of 10 microns or less. (2) a plurality of pixel electrodes in a first region on the substrate and a nonlinear resistance element made of a first metal-insulator-second metal electrically connected to each pixel electrode; a first step of forming a wiring electrode and a counter electrode made of a transparent electrode in a second region different from the pixel electrode; and dividing the substrate into the first region and the second region; A method for manufacturing an electrode substrate, comprising a second step of forming a first electrode substrate comprising a counter electrode, and a second electrode substrate comprising a counter electrode, the first step comprising: At least one step selected from a step of forming the wiring electrode on the substrate at the same time as forming the first metal or the second metal, and a step of forming the transparent electrode at the same time as forming the pixel electrode was performed. A method for manufacturing an electrode substrate, characterized in that the other step is performed afterwards.