JPS61112126A - Liquid crystal display body - Google Patents

Abstract

PURPOSE:To simplify a process for production by forming first a metal on the surface of an insulating substrate which supports a liquid crystal layer, patterning the metal then forming a transparent conductive film thereon by using a chemical vapor deposition method and patterning the film to signal electrodes and picture element electrodes. CONSTITUTION:A tantalum film on the insulating substrate 4 is first formed to 2,000-3,000Angstrom film thickness by a sputtering method. The tantalum film is then patterned by a photolithography method, by which an island-shaped metallic electrode 1 is obtd. The transparent conductive film is formed in succession thereto by using the chemical vapor deposition method. The surface of the electrode 1 is thermally oxidized in this stage and therefore the insulating film of tantalum pentaoxide is formed between the transparent conductive film and the island-shaped metallic electrode of tantalum simultaneously with the formation of the transparent conductive film. The transparent conductive film is finally patterned by using the photolithographic method, by which the signal electrode 2 and picture element electrode 3 are obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a liquid crystal display that is composed of a liquid crystal layer and an insulating substrate that supports it and has a plurality of pixels. The present invention relates to a liquid crystal display having a mechanism in which a nonlinear resistance element is formed on the surface in contact with a liquid crystal layer, and the drive of the liquid crystal is controlled using the nonlinear resistance element.

[Conventional technology]

Conventionally known liquid crystal displays that have a mechanism for controlling the drive of liquid crystals using nonlinear resistance elements include a liquid crystal display using M technology (SXD 80 DI).
GKS'j, P, 200), liquid crystal display using varistor (8'OD engineering G1113T, 'P, 193),
A liquid crystal display using two amorphous silicon diodes connected in series or parallel with the rectifying direction reversed (TAPAN DI3PLAY '8!
P, 416°SID 84 D engineering GIC3T,? ,
324) etc. are known.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional liquid crystal display system that uses a nonlinear resistance element to control the driving of the liquid crystal has a complicated substrate manufacturing process for the insulating substrate that forms the nonlinear resistance element. There were drawbacks. More specifically, in the substrate manufacturing process of the insulating substrate, no matter which type of nonlinear resistance element is used, at least five patterning steps are required, including the formation and patterning of the pixel electrode. Further, in the substrate manufacturing process of the insulating substrate described above, the number of types of thin films that require independent steps to form is five or more, regardless of which type of nonlinear resistance element is used. In this way, the conventional method requires at least three patterning processes and at least three thin film formation processes, which not only has the problem of long and complicated processes, but also low manufacturing yields and high manufacturing costs. There was a problem.

The present invention solves these conventional problems,
The purpose is to provide a nonlinear resistive element type liquid crystal display that can be manufactured at high yield and at low cost using a simple manufacturing process.

[Means for solving problems]

The liquid crystal display of the present invention is composed of a liquid crystal layer and an insulating substrate supporting the liquid crystal layer and has a plurality of pixels. The metal is divided into a plurality of island-shaped metal electrodes, and the transparent conductive film is formed and patterned using a chemical vapor deposition method. Signal 1 that transmits the input drive signal! It is divided into a pole and a pixel electrode, and each of the island-shaped metal N poles is partially covered with a part of one signal electrode, and the other part is covered with a part of one pixel electrode. It is characterized by

[Effect]

The effects of the present invention are as follows. When forming a transparent conductive film using chemical vapor deposition, the insulating substrate on which the transparent conductive film is formed is inevitably exposed to high temperature and atmospheric gas, so it is necessary to use a method that has already been formed and patterned on the insulating substrate. The surface of the island metal electrode will be thermally oxidized. Therefore, after the transparent conductive film is formed, a three-layer structure of the island-shaped metal electrode, the thermally oxidized metal insulator, and the transparent conductive film is formed on the insulating substrate. This three-layer structure is similar to MIM structure, which is one of the conventionally used nonlinear resistance elements, and its resistance characteristics also have nonlinearity similar to those of M structure. However, the resistance characteristics of this three-layer structure have a so-called polarity difference phenomenon in which the amount of current flowing differs depending on the direction of voltage application, and this point differs from the resistance characteristics of conventional M process M. This phenomenon is attributable to the fact that in the present invention, one of the metals in the conventional M process M is replaced with the transparent film 4. However, if we follow the route of the drive signal input from the outside, we can see that the drive signal flows through the transparent conductive film of the signal electrode, the island-shaped metal electrode, and the transparent conductive film of the pixel electrode in this order. The polarity phenomenon described above is canceled out because the current flows through a circuit in which two of the currents are connected in series in opposite directions. Therefore, in the liquid crystal display of the present invention, a drive signal input from the outside is processed and applied to the liquid crystal in exactly the same way as in the case of a liquid crystal display using an M process.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing one pixel portion of a first embodiment of the present invention, in which an island-like metal electrode 1. It is composed of a signal electrode 2 and a pixel electrode 3.

In this embodiment, the area where the island metal electrode 1 and the signal electrode 2 intersect, that is, the area where the signal electrode 2 covers the island metal electrode 1 and the area where the island metal electrode 1 and the pixel electrode 3 intersect. , that is, the area of the portion of the pixel electrode 3 that covers the island-shaped metal electrode 1 is equal to each other. FIG. 2 is a diagram showing the α-α' cross section of FIG. 1, in which 1 to 5 correspond to those in the tIX1 diagram, and 4 is an insulating substrate. The manufacturing method of this example will be described as follows. First, a tantalum film is formed on the insulating substrate 4 using a sputtering method. The thickness of the tantalum film is 2000 to 3000X. Next, the tantalum film is patterned using photolithography to obtain the island-shaped metal side 1. Subsequently, a transparent conductive film is formed using chemical vapor deposition. In this step, the surface of the island metal electrode 1 is thermally oxidized, so
Simultaneously with the formation of the transparent conductive film, an insulating film of tantalum pentoxide is formed between the transparent conductive film and the tantalum island metal electrode. Finally, the transparent conductive film is patterned using photolithography to obtain the signal electrode 2 and the pixel electrode 5. Through the above steps, the structure shown in FIG. 1 is completed. FIG. 5 is a diagram showing an electrical equivalent circuit of the structure shown in FIG. handle. Figure 5 shows that if the electrical characteristics between A and 0 are
If the circuit constants between -B and B-0 all match, it shows that they are symmetrical. In this example, since the area of the intersection between the island metal electrode and the signal electrode is equal to the area of the intersection between the island metal electrode and the pixel electrode, the circuit constant between A and B and the area between B and 0 are actually the same. The circuit constants of are the same, therefore the electrical characteristics between A and 0 are symmetrical and there is no polarity difference. FIG. 4 is a graph showing the measured values of the voltage-current characteristics between the signal electrode and the pixel electrode of this example, where ■ is the voltage and h is the current, the horizontal axis is JV, and the vertical axis is log (Engine/V), and the measured characteristics are signal 1!
The solid line shows the characteristics measured with the polarity being positive and the pixel electrode negative, and the dotted line shows the characteristics measured with the polarity reversed. The measured characteristics shown in FIG. 4 show that the electrical characteristics between the signal electrode and the pixel electrode in this example are actually symmetrical and there is no polarity difference. On the other hand, FIG. 5 shows the part obtained by removing a part of the surface thermal oxide film of the island-shaped metal electrode of this example other than the part where it intersects with the signal m pole and the pixel electrode, that is, the island-shaped metal electrode. It is a graph showing the measured values of the voltage-current characteristics between the metal part of the metal electrode and the signal electrode or the pixel electrode, where the horizontal axis is JTl and the vertical axis is log (k/V), and the measured characteristics are as follows: The solid line shows the characteristics measured with the metal part of the island-like metal electrode being positive and the signal electrode or pixel electrode being negative, and the dotted line shows the characteristics measured with the polarity reversed. The measured characteristics shown in FIG. 5 show that the electrical characteristics between the metal part of the island-shaped metal electrode and the signal electrode or the pixel electrode of this example are asymmetrical and there is a polarity difference. Therefore, in order to obtain electrical characteristics that are symmetrical and have no polarity difference, it is necessary to construct a circuit in which two three-layer structures of an island-like metal electrode, a thermally oxidized metal insulator, and a film on a transparent 4 are connected in series in opposite directions. I understand that it is absolutely necessary to do so. By the way, the nonlinear resistance characteristics between the signal electrode and the pixel electrode quantitatively strongly depend on the conditions of the chemical vapor deposition method used to form the transparent conductive film and the material of the transparent conductive film. The conditions for the chemical vapor deposition method are as follows: (α) Preheating temperature of the insulating substrate: 480'C in an atmospheric pressure air atmosphere
~550℃ <b> Preheating time of insulating substrate...5 minutes ~ 15 minutes
Minutes (C) Temperature during chemical vapor deposition reaction...480℃~5
It has been experimentally confirmed that within a temperature range of 50° C., a strong nonlinear resistance element that is equivalent to or even stronger than the nonlinear resistance characteristics of the conventional M process M can be obtained. Regarding materials for transparent conductive films,
Experiments were conducted using tin oxide and tin oxide with a small amount of ammonium added, and both were shown to have good nonlinear resistance characteristics.

Next, FIG. 6 is a diagram showing one pixel portion of the second embodiment of the present invention, in which 1 to 5 correspond to those in FIG. 1, and 5 is an auxiliary metal electrode. be. FIG. 7 is a cross-sectional view taken along line 6-b' in FIG.
and 5 correspond to those in FIG. 4, respectively, and 4 is an insulating substrate. The manufacturing process, process conditions, and materials for each thin film in this example are completely the same as those in the first example, so detailed explanations will be omitted. This embodiment differs from the first embodiment in that the shape of the island metal electrode and the pixel electrode related thereto is different, and that an auxiliary metal electrode 5 is provided below the signal electrode 2. Two points.

Of these two points, the former is simply a pattern design problem and is not essential since the electrical equivalent circuit is exactly the same as that of the first embodiment. The essential difference is the presence of the latter auxiliary metal electrode 5. The purpose of the auxiliary J4 electrode 5 is to reduce the loss of the drive signal input from the outside due to the impedance of the signal electrode 2. Since the transparent conductive film that is the material of the signal electrode 2 generally has higher impedance than metal, loss of the drive signal cannot be avoided. Therefore, the drive signal loss is reduced by using an auxiliary metal electrode with low impedance integrally with the signal electrode. The auxiliary metal electrode 5 in this example is obtained by being formed and patterned simultaneously with the island-shaped metal electrode 1. Therefore, the process of providing the auxiliary metal electrode is not particularly added, so the manufacturing process of this embodiment is exactly the same as that of the first embodiment, and is not complicated in any way. In addition, in the method for forming the auxiliary metal electrode described above, an insulating film is inevitably formed between the eyebrows of the auxiliary metal electrode and the signal electrode, resulting in nonlinear resistance characteristics, but the contact area between the auxiliary metal electrode and the signal electrode is very large compared to the area where the island metal electrode and the signal electrode intersect or the area where the island metal electrode and the pixel electrode intersect. There's no problem with that.

〔Effect of the invention〕

As described above in detail in the Examples, according to the present invention, a metal is first formed and patterned on the surface of an insulating substrate that supports a liquid crystal layer, and then a transparent conductive film is formed using chemical vapor deposition. By using the process of forming and patterning into signal electrodes and pixel electrodes, two nonlinear resistance elements having a three-layer structure of a metal, a thermally oxidized insulating film on the surface of the metal, and a transparent conductive film are formed on an insulating substrate in opposite directions. By forming a series system, it has display characteristics that are the same as or better than those of conventional nonlinear resistance element type liquid crystal displays, and the thin film formation and patterning process can be performed at least three times, which was previously required. It is possible to provide a nonlinear resistive element type liquid crystal display that can be manufactured using a simple manufacturing process that requires fewer steps than the above. Therefore, if the present invention is applied to a liquid crystal display used in fields that require high display characteristics at low cost, such as image display and character display, the effect will be particularly great.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one pixel portion of a first embodiment of the present invention. FIG. 2 is a diagram showing the α-α' cross section of FIG. 1. FIG. 3 is a diagram showing an electrical equivalent circuit of the structure shown in FIG. 1 or FIG. 2. FIG. 4 is a diagram showing a graph of actually measured values of voltage-current characteristics between a signal electrode and a pixel electrode. FIG. 5 is a graph showing actual measured values of voltage-current characteristics between the metal part of the island-like metal electrode and the signal electrode or pixel electrode. FIG. 6 is a diagram showing one pixel portion of the second embodiment of the present invention. FIG. 7 is a diagram showing the bb' cross section of FIG. 6. 1...Insular metal electrode 2...Signal electrode 3...Pixel electrode 4...Absolute fjk substrate 5...Auxiliary metal electrode Up

Claims (7)

[Claims] (1) In a liquid crystal display having a plurality of pixels composed of a liquid crystal layer and an insulating substrate that supports it, the surface of the insulating substrate in contact with the liquid crystal layer is first formed and patterned with metal, and then It is composed of a transparent conductive film formed and patterned using a chemical vapor deposition method, and the metal is divided into a plurality of island-like metal electrodes having an island-like shape,
The transparent conductive film is divided into a signal electrode that transmits a drive signal input from the outside and a pixel electrode, and each of the island-shaped metal electrodes is partially covered with a part of one signal electrode, A liquid crystal display characterized in that the other part is covered with a part of one pixel electrode. (2) For each island-shaped metal electrode, the area of the portion of the signal electrode that covers the island-shaped metal electrode is equal to the area of the portion of the pixel electrode that covers the island-shaped metal electrode. The liquid crystal display according to item 1. (3) Below the signal electrode, there is provided an auxiliary metal electrode that is formed and patterned at the same time as the island-shaped metal electrode and is divided from the island-shaped metal electrode. The liquid crystal display according to item 2. (4) The liquid crystal according to claim 1, 2 or 3, wherein the metal first formed and patterned on the surface of the insulating substrate in contact with the liquid crystal layer is tantalum. Display body. (5) The liquid crystal display according to claim 1, 2, 3, or 4, wherein the transparent conductive film is made of tin oxide. (6) Claims 1 and 2, characterized in that the transparent conductive film is tin oxide added with a trace amount of antimony.
3. The liquid crystal display according to item 3, item 4, or item 4. (7) The conditions for forming a transparent conductive film by chemical vapor deposition are as follows: temperature is 450°C to 600°C in an air atmosphere at atmospheric pressure.
Claims 1, 2, 3, and 4 are characterized in that the insulating substrate on which the metal is formed and patterned is preheated at the temperature for 3 to 20 minutes immediately before the formation. 5. The liquid crystal display according to item 5 or 6.