JPS61290421A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To form an ITO film having superior chemical resistance on a film substrate by depositing the lower oxide of indium on the substrate by sputtering to form a transparent, electrically conductive film and by irradiating ultraviolet rays to crystallize the film. CONSTITUTION:The lower oxide of indium (InXOY, 0<y/x<1.5) is deposited on a film substrate by sputtering in an oxygen atmosphere having low concn. at <=40 deg.C to form an ITO film having >=300OMEGA/square sheet resistivity, 85-90% transmissivity and 300-400Angstrom thickness. The ITO film is then crystallized by irradiating ultraviolet rays. A transparent, electrically conductive film having superior chemical resistance can be easily formed on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing a liquid crystal display element using a plastic film or a plastic substrate as a substrate for forming pattern display electrodes.

[Background of the invention]

Conventionally, a liquid crystal display element has been constructed by interposing a liquid crystal between two upper and lower glass substrates each having a counter electrode formed on their inner surfaces, and sealing the peripheral portion with a sealing material.

In recent years, plastic liquid crystal display elements using plastic film substrates instead of glass substrates have been developed, for example, in Japanese Patent Laid-Open No. 5
It has been proposed in Publication No. 3-68099 and the like.

A liquid crystal display element using this type of plastic film substrate is used to form electrodes on the plastic film substrate because the film substrate has low heat resistance.
, B (electron beam) vapor deposition method, resistance heating vapor deposition method, or sputtering method is used. In particular, since the sputtering method uses little radiant heat, it is possible to form a transparent and conductive thin film on a film substrate at a low temperature. When forming this type of thin film on a film substrate using a low temperature sputtering method,
There are roughly two types of methods. One of them is In!
A method of forming a transparent conductive film (hereinafter referred to as ITO film) on a film substrate by sputtering in an Ar (argon) atmosphere using a metal oxide sonic target such as O, ITO, etc.

Another method is engineering. There is a method in which a -8n alloy is sputtered in a mixed atmosphere of A and A2 (oxygen), and metal oxide is generated during sputtering and deposited on a film substrate to form an ITO film.

The ITO film thus formed is etched in a post-process to form desired pattern display electrodes.

An electrode terminal and a translucent electrode such as a lead electrode for electrically connecting the two are formed.

However, the ITO film formed by the second son method mentioned above is not completely crystallized, but when it is conventionally formed on a glass substrate, it can be crystallized by firing at a high temperature of about 400 to 500 degrees Celsius. However, in the case of a film substrate on which an ITO film is formed, it is impossible to perform high-temperature firing at about 400°C, except for special polyimide films, so the ITO film may not be exposed to acid. It dissolves easily in both alkali and alkali, and has chemical resistance such as crystallization and fcI
Very low compared to TO film. In other words, the problem when using a plastic substrate is that it is extremely difficult to crystallize the ITO film by heating.

To improve this kind of problem, the
As proposed in Publication No. 41241.

A method has been proposed in which the ITO film is crystallized by raising the film substrate temperature to about 170°C. However, even in this method, since the film substrate is made of an organic material, the heating temperature is approximately 17
Even 0°C is a sufficiently high temperature, and in extreme cases, the film substrate itself becomes thick (deformed, shrinks, or depending on the material, it exceeds its melting point, causing the problem that it cannot function as an electrode substrate). Ta.

[Purpose of the invention]

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to form an ITO film that is crystallized on a film substrate without impairing its function as an electrode substrate. Another object of the present invention is to provide a method for manufacturing a liquid crystal display element in which an eI To film with excellent chemical resistance can be formed on a film substrate. It's about doing.

[Summary of the invention]

In order to achieve such an object, the present invention forms an amorphous ITO film on a film substrate by a low-temperature sputtering method, and then crystallizes the ITO film by irradiating it with ultraviolet rays. .

[Embodiments of the invention]

<Comparative example> Indium oxide (!nt Os) containing 10 wt% tin oxide (Sn02) as a sputtering target
), sputtering is performed in an (argon) atmosphere while ensuring that the temperature of the substrate does not exceed 40°C. During sputtering, sufficient oxygen (oxygen) is added from the outside to ensure that the sheet resistance of the ITO film formed on the substrate is at least 300 Ω/hole or less, and the transmittance is 85 to 90%.
(ITO film only) is formed. The film thickness at this time is 30
0 to 400. For the substrate formed by the above method, 1) no treatment, (2) heating at 170°C for 24 hours, (3)
) UV light irradiation at 40°C for 20 minutes (365 nm,
30 mw), and using an HC1 aqueous solution,
Check out the acid resistance. The results are shown in Table 1 (HCl W is HC
l...1. H, O-@-・5゜HNO3・・・・0
．． (Use one with a mixing ratio of 0.08%).

Table 1 Acid resistance was evaluated by the time it took for the resistance value to reach infinity.
In the experiment in this comparative example, no change in acid resistance was observed in the ultraviolet irradiation treatment performed under condition (3).

The reason why the acid resistance of the untreated crystal is low is that the formed mITO film is not crystallized. It is thought that in treatment (2), crystallization of the ITO film occurred in the heated portion, resulting in the same acid resistance.

<Example> Compared to the sputtering conditions described as a comparative example, the concentration of oxygen in the atmosphere is lowered, and conditions are determined so that the formed ITO film has a low oxide content. Other conditions were the same as in the comparative example.

In this specification, the low oxide of indium means the following:
It refers to something expressed by a general formula.

Inx0Y(0(Y/X<1.5) The general formula of indium oxide is In2O3, and the ratio of indium and oxygen is less than 2=3 in the general formula In10g.
Indicates a case where the amount of indium is larger or a case where the amount of oxygen is smaller. The characteristics of the formed ITO film were a resistance value of 60 to 70 Ω/hole and a transmittance of 40 to 50%.

Processing similar to that shown in the comparative example tl), (2),
Table 2 shows the results of (3) and the same evaluation.

Table 2 Unlike the case of the comparative example, the ITO film irradiated with UV light showed the same tendency as that of the heat-treated film, and the acid resistance was improved. By irradiating UV light, it is possible to lower the resistance of NESA without increasing the temperature of the substrate, and further improve acid resistance.There are still unknown points about the conditions such as the irradiation intensity of QUV light for 9 hours. However, the same effect can be obtained in a shorter time by heating to the heat-resistant temperature of the substrate film.

Also.

Regarding NESA, even if it is formed by sputtering and MOFB (electron beam) evaporation, the effect is rFfJ or the like. Furthermore, there is no difference depending on the target (metal or oxide) used during sputtering. [Effects of the Invention] As explained above, according to the present invention, a transparent conductive film is formed on a substrate by low-temperature sputtering, and after t By irradiating the substrate with ultraviolet rays, it is possible to crystallize the substrate without deforming it, resulting in a poorly transparent conductive film, as well as improve its chemical resistance, making it possible to realize liquid crystal display elements with high quality and reliability. Effects can be obtained.

Claims (1)

[Claims] In a method of manufacturing a liquid crystal display element, a liquid crystal is interposed between two upper and lower substrates made of plastic having electrodes made of a transparent conductive film adhered to the inner surfaces thereof, and the peripheral portions are sealed with a sealing material. is a low oxide of indium (I_n_xO_Y, 0<Y/X<1.5) on the substrate.
After forming by sputtering, irradiating with ultraviolet rays,
A method for manufacturing a liquid crystal display element, comprising crystallizing the transparent conductive film.