JP2010061837A - Transparent conductive base material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent conductive base material, having a transparent conductive film which reduces the use amount of indium being a rare source, and is concurrently provided with resistance value (conductivity), chemical resistance and durability. <P>SOLUTION: The transparent conductive base material includes at least three layers consisting of a first transparent film 1, a second transparent film 2, and a third transparent film 3 which are formed in this order from the layer closer to the base material on at least one surface of a base material 4. The first transparent conductive film and the third transparent conductive film are made of indium-tin oxide, and the second transparent conductive film contains zinc oxide as a principal component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a substrate having transparency and conductivity.

In a display device such as a liquid crystal display device and an input device such as a touch panel, a transparent conductive film is widely used because of the need for both transparency and conductivity.

Various materials including inorganic and organic materials have been studied as the transparent conductive film, but at present, tin-doped indium oxide (hereinafter referred to as ITO) is most widely used in terms of characteristics. However, there are problems in terms of supply stability of indium and reducibility, and other materials are actively studied for the purpose of replacing ITO or reducing the amount used. Among them, in particular, a transparent conductive film using zinc oxide has attracted attention (see Patent Document 1 and Patent Document 2).

However, the zinc oxide transparent conductive film has problems in terms of resistance value, durability, and chemical resistance. In particular, the chemical resistance is weak against an alkaline solution, and there arises a problem that the film peels off from the substrate.

JP-A-2-14959 JP-A-7-138745

In view of the above-mentioned problems of the background art, the present invention has been made to solve the problem of reducing the amount of indium used and also having the resistance value (conductivity), chemical resistance, and durability of the transparent conductive film. It is a thing.

This invention solved the said subject by setting it as the transparent conductive base material of the following structures.
On at least one surface of the base material, at least three layers of a first transparent conductive film, a second transparent conductive film, and a third transparent conductive film are formed in order from a layer close to the base material. A transparent conductive substrate, wherein the transparent conductive film and the third transparent conductive film are made of tin-doped indium oxide, and the second transparent conductive film is mainly composed of zinc oxide.
2. The transparent conductive substrate according to claim 1, wherein the first transparent conductive film and the third transparent conductive film have a thickness of 30 nm to 100 nm.
The transparent conductive substrate according to claim 1, wherein the second transparent conductive film is gallium-doped zinc oxide.
The transparent conductive substrate according to claim 1, wherein the second transparent conductive film is aluminum-doped zinc oxide.
The transparent conductive substrate according to claim 1, wherein the substrate is a flexible film substrate.
The transparent conductive substrate according to claim 1, further comprising a resin pattern on the third transparent conductive film.
The transparent conductive substrate according to claim 7, wherein the substrate is a color filter substrate, and the resin pattern is a photo spacer.

According to the present invention, the transparent conductive film mainly composed of zinc oxide is sandwiched between ITO, thereby reducing the amount of indium used and having excellent durability and chemical resistance. And was able to.

FIG. 1 shows one embodiment of the transparent conductive substrate of the present invention.
In the transparent conductive substrate of the present invention, the transparent conductive film on the substrate 1 includes at least three transparent conductive films, and the second transparent conductive film of the second layer mainly composed of zinc oxide on the substrate. 2 is sandwiched between a first transparent conductive film 1 of the first layer and a third transparent conductive film 3 of the third layer, each made of ITO.

The transparent substrate 1 may be any substrate as long as it has transparency, and various types of glass, plastic sheets and films can be used. Further, as long as the substrate has transparency, a functional layer other than the transparent conductive film may be provided. For example, in the case of a transparent conductive substrate for a liquid crystal display device, a color filter is formed. In the case of a sheet or film, a hard coat may be formed from the viewpoint of hardness.

Before forming the transparent conductive film, a surface treatment of the substrate may be performed to improve adhesion. At this time, examples of the surface treatment method include corona discharge treatment, glow discharge treatment, ion beam treatment, atmospheric pressure plasma treatment, and light irradiation treatment.

If it is necessary to further improve the adhesion strength, a primer layer may be provided before the formation of the transparent conductive film. As a material of the primer layer, for example, a metal such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, tungsten, zirconium, palladium, or an alloy composed of two or more of these metals, or These oxides, fluorides, sulfides, nitrides and the like can be mentioned. In particular, for example, a primer layer such as Si or SiOx using silicon is excellent as a primer layer of an oxide thin film. These primer layers are preferably formed by a dry coating method such as a sputtering method, a reactive sputtering method, a vapor deposition method, an ion plating method, or a chemical vapor deposition (CVD) method. The thickness of the primer layer may be determined according to the purpose, but is preferably in the range of about 1 to 20 nm.

The transparent conductive film can be formed by either a so-called dry method (vacuum film formation) or a wet method (coating), but at present, the dry method is common. Examples of the dry method include a sputtering method, a vapor deposition method, and a chemical vapor deposition (CVD) method. Among these, the sputtering method can form a dense film, and the most excellent film can be formed.

The first transparent conductive film 1 and the third transparent conductive film 3 are transparent conductive films made of ITO. ITO is indium oxide doped with tin. A target that is a material used for sputtering is generally a composite oxide target of indium oxide and tin oxide. Moreover, although it is not common, you may form a metal target by reactive sputtering. The content of tin oxide varies depending on the purpose, but about several to 10% by weight is widely used.

Moreover, in the transparent conductive film of this invention, it is preferable that the 1st transparent conductive film 1 and the 3rd transparent conductive film 3 which consist of ITO are crystallized. By crystallizing the second thin film layer which is an ITO layer, Sn and In which are dopants can efficiently form carriers by substitutional solid solution. Further, since defects are reduced by crystallization, the electrical conductivity of the transparent conductive film can be improved by increasing the mobility. Furthermore, it can be set as a transparent conductive film provided with high alkali resistance.

The film thickness of the first and third transparent conductive films is preferably in the range of 30 nm to 100 nm. When the first and third transparent conductive films made of ITO exceed 100 nm, the effects of chemical resistance and durability are saturated, and the amount of indium used can be sufficiently reduced. It becomes impossible. On the other hand, when the first thin film layer made of ITO is less than 30 nm, the ITO layer may be formed in an island shape due to the thin film thickness of the ITO layer. It may not be possible to obtain a transparent conductive film comprising Moreover, when it is less than 10 nm, it becomes difficult to obtain sufficient electrical conductivity.

As described above, the transparent conductive base material of the present invention has a structure in which the transparent conductive film mainly composed of zinc oxide, which is the second transparent conductive film, is sandwiched between ITO transparent conductive films. It becomes a transparent conductive base material with a reduced amount of use and improved chemical resistance and durability. In the present invention, since not only the front surface of the transparent conductive film but also the base material 1 is covered with the ITO transparent conductive film, elution of the zinc oxide transparent conductive film from the base material side, Can prevent the penetration of chemicals. For this reason, it is particularly suitable when the base material surface is covered with resin and chemicals are likely to penetrate from the base material surface side, or when durability is required using a flexible material such as a film as the base material. It is. In addition, since the first transparent conductive film and the third transparent conductive film are made of the same material, manufacturing is facilitated as described above.

The second transparent conductive film 2 is a transparent conductive film containing zinc oxide as a main component. Here, zinc oxide as a main component means that 70% or more of zinc oxide is contained by weight. The thin film mainly composed of zinc oxide includes one doped with metal or metal oxide. Aluminum, boron, scandium, gallium, silicon, yttrium, ytterbium, indium or gallium can be used as the metal in the metal or metal oxide to be doped. By including these metals or metal oxides, a first thin film layer having high electrical conductivity can be obtained. Especially, it can be set as the 2nd transparent conductive film provided with higher electrical conductivity by including at least one of aluminum or gallium in zinc oxide. In the case of forming a film by a sputtering method, a target that is a material to be used is generally a composite oxide of zinc oxide and aluminum oxide or zinc oxide and gallium oxide. In addition, the third element may be mixed slightly to improve the physical properties.

In the transparent conductive film of the present invention, the thickness of the second transparent conductive film made of zinc oxide is preferably 30 nm or more and 300 nm or less. When the film thickness of the second transparent conductive film is less than 30 nm, it may be impossible to obtain a transparent conductive film having sufficient electrical conductivity. Further, the deposition speed of zinc oxide is slower than the deposition speed of ITO, and the manufacturing cost may increase if the thickness of the second transparent conductive film exceeds 300 nm.

Moreover, in the transparent conductive film of the present invention, the specific resistance of the transparent conductive film forming surface is preferably in the range of 1 × 10 ⁻³ Ω · cm or less. By setting the specific resistance of the transparent conductive film forming surface within the above range, it can be suitably used as an electrode of a liquid crystal display. When the specific resistance of the transparent conductive film forming surface exceeds 1 × 10 ⁻³ Ω · cm, it cannot be made a transparent conductive film having sufficient electrical conductivity, and therefore when used as an electrode of a liquid crystal display In some cases, the loss of power consumption increases and a liquid crystal display with low power consumption cannot be obtained. On the other hand, the specific resistance of the transparent conductive film forming surface is preferably 1 × 10 ⁻⁴ Ω · cm or more. When the specific resistance of the transparent conductive film forming surface is to be less than 1 × 10 ⁻⁴ Ω · cm, it is necessary to increase the carrier concentration of the transparent conductive film, and at this time, the visible light transmittance of the transparent conductive film Is not preferable because of a tendency to decrease.

FIG. 2 shows an explanatory cross-sectional view of another embodiment of the transparent conductive substrate of the present invention. 2 is a color filter with a conductive film for the time being used for a liquid crystal display. The color filter 6 ′ with a transparent conductive film in FIG. 2 includes colored layers 14A, 14B, and 14C on a support substrate 11 ′. The colored layer has a structure in which a colored pigment is dispersed in a resin. The colored layer is for displaying a color on a liquid crystal display, and has, for example, three colors of red (R), green (G), and blue (B). A black matrix 13 is provided between the pixels on the glass substrate, and the pixels are separated by the black matrix. The black matrix is formed from a metal material such as chromium or a resin material in which a black pigment is dispersed.

The transparent conductive film 5 is provided on the colored layers 14A, 14B, and 14C. The transparent conductive film 5 includes a first transparent conductive film 1 made of ITO, a second transparent conductive film 2 containing zinc oxide as a main component, and a first transparent conductive film 3 made of ITO. It is configured. A photo spacer 15 is provided on the transparent conductive film 5 as necessary. The photo spacer 15 is a constant distance (gap) from the TFT substrate provided so as to face the color filter 1 ′, and a photosensitive resin material (photoresist) is used as a photo spacer forming material. The photo spacer is formed by photolithography. That is, a photo spacer is formed by a coating process of applying a photosensitive resin material on a transparent conductive film, an exposure process of performing pattern exposure on the applied resin material through a mask, and a developing process of removing unnecessary portions with a developer. Is formed. In the development step, an alkaline solution is used as a developer, but the transparent conductive film of the present invention has high chemical resistance and can suitably form a photo spacer on the transparent conductive film.

Further, in the color filter 6 ′ with a transparent conductive film of the present invention, an alignment control protrusion 16 is provided as necessary. The alignment control protrusion 16 is formed in the case of a color filter of a vertical alignment type (VA type) liquid crystal display. As the alignment control protrusion forming material, a photosensitive resin material is used, and the alignment control protrusion is formed by a photolithography method. That is, a coating process for applying a photosensitive resin material (photoresist) on the transparent conductive film, an exposure process for performing pattern exposure on the applied resin material through a mask, and a developing process for removing unnecessary portions with a developer. Thus, the alignment control protrusion is formed. In the development step, an alkaline solution is used as a developer. However, the transparent conductive film of the present invention has high chemical resistance, and the alignment control protrusions can be suitably formed on the transparent conductive film.

The substrate with a transparent conductive film having a transparent conductive film surface having high alkali resistance according to the present invention is a color filter having at least one of a photo spacer formed by a photolithography method and an alignment control protrusion formed by a photolithography method. It can be used suitably. For the same reason, it is suitable for a member that forms a resin pattern on a conductive film by a photolithography method.

The manufacturing method of the transparent conductive base material of this invention is demonstrated.

The transparent conductive film of the present invention is formed by a vacuum film forming method such as a vapor deposition method, a sputtering method, or an ion plating method. Especially, it is preferable that the transparent conductive film of this invention is formed by sputtering method. The sputtering method can form a film on a large-area substrate.

Especially, it is preferable that the transparent conductive film of this invention is formed by the magnetron sputtering method. By using the magnetron sputtering method as a method of forming the transparent conductive films 1 to 3, the film forming speed can be improved. In addition, since the electrons are captured in the vicinity of the target by the magnetic flux, the plasma density increases and the sputtering voltage can be reduced. This makes it possible to reduce the energy of particles that damage the formed transparent conductive film, such as oxygen negative ions and recoil sputtering gas, and the formed transparent conductive film has high conductivity and is a high-quality transparent conductive film. It can be.

Moreover, in this invention, it is preferable that the formation process of each transparent conductive film by magnetron sputtering method is 500 Gauss or more and 1500 Gauss or less. By setting the magnetic flux density to 500 Gauss or more and 1500 Gauss or less, a transparent conductive film having high electrical conductivity and good uniformity in film thickness can be obtained. When the magnetic flux density is less than 500 Gauss, the film thickness distribution of the formed transparent conductive film may not be uniform, and a transparent conductive film with insufficient electrical conductivity may be obtained. On the other hand, when the magnetic flux density exceeds 1500 Gauss, discharge is difficult to occur, and the utilization efficiency of the target may be reduced.

Hereinafter, description will be made using examples.

[Common conditions for Examples and Comparative Examples]
For the transparent substrate 1. A 100 mm square soda glass with a thickness of 2 mm was used. Surface treatment by glow discharge was performed in advance on the surface on which the transparent conductive film was formed. The film formation was performed by a magnetron sputtering method. Two types of targets can be attached to the film forming apparatus, and two types of materials were stacked while maintaining a vacuum state. A target of 10% by weight of tin oxide was used for the film formation of ITO, and a target of 5.7% by weight of gallium oxide was used for the film formation of the thin film layer mainly composed of zinc oxide (hereinafter referred to as ZnO: Ga).
(Although an experiment was conducted on an aluminum-doped (4 wt%) zinc oxide thin film, the results showed the same tendency as that of gallium-doped, so only the results of one example are added at the end)

The pressure (degree of vacuum) during film formation was 3 × 10 ⁻¹ Pa. Ar was 300 sccm as the sputtering gas, and O ₂ was used as the reaction gas. For the flow rate of O _2, the optimum value for decreasing the resistance value was examined in advance, and was set to 4 sccm for ITO and 0 sccm for ZnO: Ga. Is).

[Example 1]
The structure of the transparent conductive film was set to ITO (50) / ZnO: Ga (50) / ITO (50) from the transparent substrate side. The values in parentheses are the film thickness (nm) of each transparent conductive film. The same applies to the following examples.

[Example 2]
The configuration of the transparent conductive film was ITO (30) / ZnO: Ga (90) / ITO (30) from the transparent substrate side.

[Comparative Example 1]
The structure of the transparent conductive film was ITO (20) / ZnO: Ga (110) / ITO (20) from the transparent substrate side.

[Comparative Example 2]
The structure of the transparent conductive film was a single layer of ZnO: Ga (150) from the transparent substrate side.

[Comparative Example 3]
The structure of the transparent conductive film was made into two layers of ZnO: Ga (75) / ITO (75) from the transparent substrate side.

[Comparative Example 4]
The structure of the transparent conductive film was made into two layers of ITO (75) / ZnO: Ga (75) from the transparent base material side.

[Comparative Example 5]
The structure of the transparent conductive film was a single layer of / ITO (150) from the transparent substrate side.

[Evaluation]
The obtained sample was evaluated by the following method.

(1) Resistance value The initial resistance value was measured with a Loresta manufactured by Mitsubishi Chemical. The surface resistance (Ω / □) can be measured by bringing four electrodes into contact with the surface. This is one of the most common methods for evaluating the resistance value of transparent conductive films.

(2) Chemical resistance As an evaluation of chemical resistance, alkali resistance was examined. One drop of a 1.5% aqueous solution of NaOH was deposited on the transparent conductive film, allowed to stand for 30 minutes, and then wiped off to examine the change in resistance value. When the resistance change was within 10%, it was evaluated as ◯, when it exceeded 10% and within 15%, Δ, and when it exceeded 15%, it was marked as x.

(3) Durability After aging for 1 day in an environment of 60 ° C. and 95%, the durability of the transparent conductive substrate was judged from the change in resistance value. The resistance value change was investigated. When the resistance change was within 10%, it was evaluated as ◯, when it exceeded 10% and within 15%, Δ, and when it exceeded 15%, it was marked as x.

As already described, an experiment was also performed on aluminum doping, but the same result as that of gallium doping was obtained, so only an example will be described. For ITO (30) / ZnO: Al (90) / ITO (30), the resistance value is 50Ω / □, the chemical resistance ○, the durability ○, and the ITO film thickness standard ratio 0.4, confirming the effect. It was.

As a result of the examples and comparative examples, it was shown that the present invention can achieve the resistance value (conductivity), chemical resistance, and durability required for the transparent conductive film while reducing the amount of conventional ITO used.

It is a figure which shows the structural example of the transparent conductive base material of this invention. It is a figure which shows the structural example of the transparent conductive base material (color filter with a transparent conductive film) of this invention.

Explanation of symbols

1 ... Transparent conductive film 1 (ITO layer)
2 ... Transparent conductive film 2 (Zinc oxide layer)
3 ... Transparent conductive film 3 (ITO layer)
4 ... Transparent substrate 4 '... Transparent substrate (color filter)
5 ... Transparent conductive film 6 ... Transparent conductive substrate 6 '... Transparent conductive substrate (color filter with transparent conductive film)
DESCRIPTION OF SYMBOLS 11 ... Support base material 13 ... Black matrix 14A ... Colored layer 14B ... Colored layer 14C ... Colored layer 15 ... Photo spacer 16 ... Protrusion for orientation control

Claims (8)

  On at least one surface of the base material, at least three layers of a first transparent conductive film, a second transparent conductive film, and a third transparent conductive film are formed in order from a layer close to the base material. A transparent conductive substrate, wherein the transparent conductive film and the third transparent conductive film are made of tin-doped indium oxide, and the second transparent conductive film is mainly composed of zinc oxide.   2. The transparent conductive substrate according to claim 1, wherein the first transparent conductive film and the third transparent conductive film have a thickness of 30 nm to 100 nm.   The transparent conductive substrate according to claim 1, wherein the second transparent conductive film is gallium-doped zinc oxide.   The transparent conductive substrate according to claim 1, wherein the second transparent conductive film is aluminum-doped zinc oxide.   The transparent conductive substrate according to claim 1, wherein the substrate is a flexible film substrate.   The transparent conductive base material according to claim 1, wherein a surface treatment is applied to a surface of the base material on which the transparent conductive film is formed.   The transparent conductive base material according to claim 1, wherein the third transparent conductive film is provided with a resin pattern. The transparent conductive substrate according to claim 7, wherein the substrate is a color filter substrate, and the resin pattern is a photo spacer.

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