JPH08262466A - Transparent electrode plate - Google Patents

Abstract

PURPOSE: To provide a transparent electrode plate consisting of a thin film, high in conductivity and excellent in preservation stability. CONSTITUTION: The essential part of a transparent electrode plate consists of a glass substrate 1, a three-layered transparent electrode 2 consisting of the transparent conductive film 21, metallic thin film 22 and transparent conductive film 23 aligned with one another and laminated in the shape of an electrode and a moisture-proof transparent thin film 3 covering the electrode 2 uniformly and protecting the surface and side end face of the electrode. Meanwhile, the transparent conductive films 21 and 23 are formed with an indium oxide thin film contg. 10 atomic % zirconium oxide, and the moisture-proof transparent thin film 3 is formed with silicon oxide. The films 21, 22 and 23 are firmly integrated by the action of the thin film 3, the surface and side end face of the thin film 22 are protected from the sulfur compd. and moisture in the air, hence the thin film 22 is not deteriorated on ageing, and the preservation stability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent electrode plate used as a transparent electrode of a liquid crystal display, an input / output device or a display device such as a plasma display, and more particularly, it is a thin film having high conductivity and storage stability. The present invention relates to an improved transparent electrode plate.

[0002]

2. Description of the Related Art A transparent electrode plate having a transparent electrode for transmitting visible light on a transparent substrate such as glass or plastic film is used for display electrodes of various display devices such as liquid crystal displays and display screens of this display device. Widely used for input / output electrodes for direct input.

For example, a transparent electrode plate of a display device using liquid crystal has a glass substrate k as shown in FIG.
A color filter layer 1 which is provided at a pixel portion on the glass substrate k and colors the transmitted light of each pixel into red, green and blue, and a portion between the pixels on the glass substrate k (inter-pixel portion). A light-shielding film m that is provided on the entire surface of the color filter layer 1 and a transparent electrode g formed on the protective layer h. The alignment film f formed on the transparent electrode g constitutes the main part thereof. The transparent electrode g is formed by sputtering and is composed of a transparent conductive film that is etched into a predetermined pattern.

As the transparent conductive film, paying attention to its high conductivity, tin oxide is added to indium oxide.
TO thin film is widely used, its specific resistance is about 2.4 × 10 ⁻⁴ Ω · cm, and its area resistance is about 10 Ω in the case of a film thickness of 240 nm which is usually applied as a transparent electrode.
/ □.

In addition to this, a tin oxide thin film, a thin film formed by adding antimony oxide to this tin oxide (nesa film), a thin film formed by adding aluminum oxide to zinc oxide, and the like are known. However, these are all the above IT
Its conductivity is inferior to that of the O thin film, and its chemical resistance to acids and alkalis, water resistance and the like are insufficient, so that it is not widely used.

By the way, in recent years, in the display device and the input / output device, it is required to increase the pixel density to display a fine screen, and accordingly, the transparent electrode pattern is required to be made fine. , For example 100μ
It is required to form the terminal portion of the transparent electrode with a pitch of about m. Further, in a liquid crystal display device, a method in which a liquid crystal driving IC is directly connected to a substrate (CO
In G), there is a portion where the wiring is thin and has a width of 20 to 50 μm.

On the other hand, on the other hand, there is also a demand for a larger display screen. For such a large screen, the transparent electrode having the dense pattern as described above is formed, and moreover, a sufficient voltage can be applied to the liquid crystal. Therefore, it is necessary to apply a transparent conductive film having high conductivity of 5 Ω / □ or 3 Ω / □ or less as the transparent electrode.

Under such a background, in the 3rd ICVM held in Japan in 1982, a transparent conductive film having a three-layer structure formed by laminating an ITO thin film on the front and back surfaces of a silver thin film as a heat ray reflecting film is provided. Proposed. This transparent conductive film having a three-layer structure has a sheet resistivity of about 5 Ω / □, and its application to the transparent electrode was expected.

[0009]

However, in the above-mentioned transparent conductive coating film having a three-layer structure, the silver thin film is likely to combine with sulfur compounds and water in the air invading from the stacking interface or the like, and the surface thereof is subjected to sulfide or oxidation. However, there is a problem in that a liquid crystal display device is liable to generate display defects and the like.

The present invention has been made by paying attention to such a problem, and its object is to apply a transparent conductive coating film having a three-layer structure having excellent conductivity without deterioration with time and storage. It is to provide a transparent electrode plate having excellent stability.

[0011]

That is, the invention according to claim 1 is premised on a transparent electrode plate having a transparent electrode on a transparent substrate, and the transparent electrodes are aligned with each other on the transparent substrate to form an electrode shape. A metal thin film made of silver or a silver alloy and having a thickness of 2 to 20 nm, a transparent conductive film provided between the metal thin film and a transparent substrate, and a transparent conductive film provided on the metal thin film. And the surface and side end surface of the transparent electrode are covered with an electrically insulating moisture-proof transparent thin film.

In this transparent electrode plate, the surface and side end surface of the transparent electrode having a three-layer structure of transparent conductive film / metal thin film / transparent conductive film are covered with the electrically insulating moisture-proof transparent thin film. The three layers of transparent conductive film / metal thin film / transparent conductive film are firmly integrated, and both the surface and side end face of the metal thin film are protected from sulfur compounds and moisture in the air. Therefore, the deterioration of the metal thin film with time is prevented and the storage stability thereof is improved, so that it is possible to stably manufacture a liquid crystal display device or the like having no display defect due to a sulfur compound or moisture in the air.

If the thickness of the metal thin film is less than 2 nm, the conductivity of the transparent electrode will be low, and if it exceeds 20 nm, the light transmittance will be low. Not suitable for.

In such a technical means, the moisture-proof transparent thin film may be one that does not allow moisture in the air to pass therethrough, and for example, a thin film made of an organic material or an inorganic material can be applied. From the viewpoint of high moisture resistance, a thin film of a metal oxide such as silicon oxide, titanium oxide, zirconium oxide, cerium oxide, or tantalum oxide is preferable (provided that a metal oxide that is hard to form a solid solution with silver is preferable. ) Above all, a thin film containing silicon oxide as a base material is preferable from the viewpoints of processing suitability such as price and film forming speed. The invention according to claim 2 is based on such a technical reason.

That is, the invention according to claim 2 is premised on the transparent electrode plate according to the invention according to claim 1, wherein the moisture-proof transparent thin film is composed of an oxide film having silicon oxide as a base material. It is characterized by that.

The oxide film having silicon oxide as a base material preferably has a composition close to that of SiO ₂ from the viewpoint of light transmission characteristics.

As the transparent conductive film, a thin film containing indium oxide, zinc oxide or copper oxide as a main component and an additive for increasing the conductivity thereof can be applied.
In particular, in the case of a mixed oxide containing indium oxide as a main component and an oxide of an element having a small solid solution area with silver or an element having no solid solution area with silver as the above additive, a transparent conductive film and silver are used. Or, it can prevent a reaction with a metal thin film made of a silver alloy, and has excellent etching suitability when patterning into an electrode shape, and also has excellent adhesion to the metal thin film and the moisture-proof transparent thin film (particularly, the moisture-proof transparent film). When the thin film is made of silicon oxide as a base material, the adhesion to the moisture-proof transparent thin film is extremely excellent). The invention according to claim 3 is based on such a technical reason.

That is, the invention according to claim 3 is premised on the transparent electrode plate according to the invention according to claim 1 or 2, wherein the transparent conductive film is an element having a small solid solution region of silver with indium oxide or silver. It is characterized in that it is composed of a mixed oxide to which an oxide of an element having no solid solution region with is added.

In the invention according to claim 3, the element having a small solid solution area with silver or the element having no solid solution area with silver has an amount of solid solution with respect to silver of 5 atom% (atomic%) or less. An element, for example, a transition metal element such as Ti, Zr, or Ta; a lanthanide-based metal element such as Ce; Bi, Ge, S
Zr is preferable among the semimetals such as i.

By the way, the moisture-proof transparent thin film is composed of a metal oxide having a refractive index of 2 or more, such as titanium oxide, zirconium oxide, cerium oxide, and tantalum oxide. If the total exceeds 100 μm, the transmitted light transmitted through the transparent electrode may interfere and be colored. In order to prevent such coloring, the total thickness of the waterproof transparent thin film and the transparent conductive film is preferably 100 nm or less, and in order to obtain sufficient conductivity and moisture resistance, the total film thickness is 20 nm or more. Is desirable. The invention according to claim 4 is based on such a technical reason.

That is, the invention according to claim 4 is based on the transparent electrode plate according to any one of claims 1 to 3, wherein the moisture-proof transparent thin film has a refractive index of 2 or more, and , The total thickness of the moisture-proof transparent thin film and the transparent conductive film is 20.
˜100 nm.

In the inventions according to claims 1 to 4, the shape of the transparent electrode differs depending on the display device applied. For example, in a simple matrix drive type liquid crystal display device, it has a stripe shape connecting parts corresponding to pixels of a display screen.

Next, when the transparent conductive film contains indium oxide as the main component, the three-layer thin film of transparent conductive film / metal thin film / transparent conductive film can be patterned using nitric acid as an etching solution. That is, three layers of a transparent conductive film, a metal thin film made of silver or a silver alloy, and a transparent conductive film were formed on a transparent substrate, and an electrode-shaped resist film was formed on the transparent conductive film exposed on the surface. After that, by etching a portion exposed from the resist film with a nitric acid-based etching solution, the three-layer thin film can be patterned into an electrode shape aligned with each other. As the etching solution, nitric acid, nitric acid-based mixed acid obtained by adding other kinds of acids such as hydrochloric acid, sulfuric acid or acetic acid to nitric acid, or nitric acid with a slight amount of a surfactant added can be used.

Further, when the transparent conductive film contains indium oxide as a main component, it is desirable to form these transparent conductive films at a substrate temperature of 180 ° C. or lower or room temperature in order to secure the etching suitability. Then, after forming a thin film of silver or a silver alloy and the entire transparent conductive film at a substrate temperature of 180 ° C. or lower or room temperature, the entire three-layer thin film is etched and patterned with a nitric acid-based etching solution, and then 200 ° C. It is also possible to increase the conductivity of the entire three-layer thin film by performing the annealing treatment at the above temperature.

As the transparent substrate, for example, glass, plastic board, plastic film or the like can be used. When a plastic board or plastic film is used as a transparent substrate, a moisture-proof coating layer is formed on the surface of the plastic board or plastic film to prevent the moisture in the air from penetrating this substrate and damaging the metal thin film. It is desirable to form the transparent electrode after it is provided. A transparent substrate provided with a light scattering layer can also be used.

As the metal thin film made of silver or silver alloy, in addition to a thin film of silver alone, in order to prevent the diffusion of silver or increase its hardness, other elements may be added at a concentration below the solid solution limit of silver. The added alloy can be used. Examples of such additional elements include Mg, In, Al, Ti, Zr,
Ce or Si can be applied.

In forming the above-mentioned three-layer thin film on the transparent substrate, it is desirable to wash the surface of the transparent substrate before forming the film. Examples of the cleaning method include ion bombardment, reverse sputtering, ashing, ultraviolet cleaning, glow discharge treatment and the like.

[0028]

According to the transparent electrode plate of the present invention, the surface and side end surfaces of the transparent electrode having a three-layer structure of transparent conductive film / metal thin film / transparent conductive film are electrically insulating and moisture-proof. Since it is covered with a transparent thin film, the three layers of transparent conductive film / metal thin film / transparent conductive film are firmly integrated, and both the surface and side end face of the metal thin film are protected from sulfur compounds and water in the air. Be protected.

[0029]

Embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIG. 1, the transparent electrode plate according to this embodiment has a transparent conductive film 21 having a thickness of 40 nm and a glass substrate 1 having a thickness of 0.7 mm, each of which is positionally aligned and laminated in an electrode shape. And a transparent electrode 2 composed of a metal thin film 22 made of silver having a thickness of 14 nm and a transparent conductive film 23 having a thickness of 40 nm.
And an electrically insulating moisture-proof transparent thin film 3 having a thickness of 40 nm for uniformly covering the transparent electrode 2 to protect the surface and side end faces thereof, and the main part thereof is constituted. And 23 are both zirconium oxide (ZrO
₂ ) is composed of a thin film of indium oxide containing 10 atom%. The moisture-proof transparent thin film 3 is made of silicon oxide (SiO ₂ ). The electrode shape is set to a stripe pattern with a pitch of 210 μm, a width of 200 μm, and an interelectrode gap of 10 μm.

The transparent electrode plate is manufactured by the following method.

First, the surface of the glass substrate 1 was washed with an alkaline surfactant and water, then housed in a vacuum chamber and subjected to a plasma treatment called reverse sputtering for further washing.

Next, without removing the glass substrate 1 from the vacuum chamber, the glass substrate 1 was kept at room temperature,
The transparent conductive film 21 and the metal thin film 2 are formed by the sputtering method.
2 and the transparent conductive film 23 were sequentially formed.

Next, according to the well-known photolithography process,
The stripe-patterned resist film is formed on the transparent conductive film 23, and a 50% nitric acid solution is applied to apply the above-mentioned 3
The layer thin film was etched to form the above stripe pattern.

Next, the moisture-proof transparent thin film 3 was formed and subsequently annealed at 200 ° C. for 30 minutes to produce the transparent electrode plate. The sheet resistance of the transparent electrode of the transparent electrode plate thus obtained was about 2.8 Ω / □.

When this transparent electrode plate was left to stand in the air for one month and observed, no change in appearance was observed on the surface of the transparent electrode 2.

For comparison, when a silver thin film was formed on a glass substrate and left in the air for 1 month, the surface was discolored and many spots were observed.

[0038]

According to the inventions according to claims 1 to 4, the surface and the side end surface of the transparent electrode having a three-layer structure of transparent conductive film / metal thin film / transparent conductive film are made of an electrically insulating moisture-proof transparent thin film. Since it is covered, the three layers of transparent conductive film / metal thin film / transparent conductive film are firmly integrated, and both the surface and side end face of the metal thin film are protected from sulfur compounds and moisture in the air. .

Therefore, the deterioration of the metal thin film with time is prevented and its storage stability is improved, so that it is possible to stably manufacture a liquid crystal display device or the like having no display defect caused by a sulfur compound or moisture in the air. are doing.

[Brief description of drawings]

FIG. 1 is a sectional view of a transparent electrode plate according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a transparent electrode plate according to a conventional example applied to a display device.

[Explanation of symbols]

 1 Glass Substrate 2 Transparent Electrode 3 Moisture Proof Transparent Thin Film 21 Transparent Conductive Film 22 Metal Thin Film 23 Transparent Conductive Film

Claims (4)

[Claims] 1. A transparent electrode plate having a transparent electrode on a transparent substrate, wherein the transparent electrode is made of silver or a silver alloy having a thickness of 2 to 20 nm, which are laminated on the transparent substrate in an electrode shape in alignment with each other. It is composed of a metal thin film, a transparent conductive film provided between the metal thin film and a transparent substrate, and a transparent conductive film provided on the metal thin film, and the surface and side end surface of the transparent electrode are electrically conductive. A transparent electrode plate, which is covered with an insulating moisture-proof transparent thin film. 2. The transparent electrode plate according to claim 1, wherein the moisture-proof transparent thin film is composed of an oxide film having silicon oxide as a base material. 3. The transparent conductive film is composed of a mixed oxide in which an oxide of an element having a small solid solution area with silver or an oxide having no solid solution area with silver is added to indium oxide. The transparent electrode plate according to claim 1 or 2, wherein 4. The moisture-proof transparent thin film has a refractive index of 2 or more, and the total thickness of the moisture-proof transparent thin film and the transparent conductive film is 20 to 100 nm.
3. The transparent electrode plate according to any one of 3 above.