JPH06177407A - Transparent conductive film - Google Patents

Abstract

PURPOSE:To provide a transparent conductive film of good humidity resistance having little change of characteristic with time. CONSTITUTION:A transparent conductive film is a zinc oxide transparent conductive film 2 wherein 0.4 to 4.5 atomic % Al and 0.05 to 2.0 atomic % fluorine are contained. A transparent conductive film 2a from another point of view of this invention is formed by laminating a zinc oxide upper side transparent conductive film 6 containing 0.4 to 4.5 atomic % Al and 0.05 to 2.0 atomic % fluorine on a surface of a lower side transparent conductive film 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive film used for photoelectric conversion elements such as solar cells, display elements, surface heating elements, antistatic films, touch panels, and more particularly, it has improved moisture resistance. The transparent conductive film.

[0002]

2. Description of the Related Art A transparent conductive film is indispensable when manufacturing photoelectric conversion elements such as solar cells, display elements, surface heating elements, antistatic films and touch panels. As a conventional transparent conductive film, an ITO film (tin-doped indium oxide film) is known. The ITO film has excellent transparency,
It has the advantage of low resistance.

However, the ITO film has a difficulty in economy because indium is expensive. Therefore, a zinc oxide-based transparent conductive film has been studied as a transparent conductive film that is less expensive than an ITO film. However, the zinc oxide-based transparent conductive film has a problem that the electrical properties such as the conductive properties are inferior.

[0004]

For this reason, JP-A-62-62
As shown in Japanese Patent Publication No. 154411, a zinc oxide-based transparent conductive film in which another element is added to zinc oxide to improve characteristics has also been developed. However, the present inventors have found that such a conventional zinc oxide-based transparent conductive film has poor moisture resistance and a large change over time in characteristics as compared with an ITO film.

As a result of earnest studies on the zinc oxide type transparent conductive film having excellent moisture resistance, the inventors of the present invention have found that the moisture resistance of the zinc oxide type transparent conductive film can be improved by adding a fluorine element in a specific range. The inventors have found that the properties are remarkably improved and have completed the present invention. Incidentally, JP-A-3-16
Japanese Patent Publication No. 954 describes that a zinc oxide-based sintered body contains a halogen element in order to reduce the resistance of the sintered body. Nothing is disclosed regarding the technical idea that the moisture resistance of the transparent conductive film is remarkably improved by containing Z in the zinc oxide type transparent conductive film in the range of a specific atomic%, and is not related to the present invention. is there.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transparent conductive film which is particularly excellent in moisture resistance and has little change in characteristics over time.

[0007]

In order to achieve the above object, the transparent conductive film of the present invention is a zinc oxide-based transparent conductive film, contains 0.4 to 4.5 atomic% of Al, and It is characterized in that it contains 0.05 to 2.0 atomic% of fluorine.
Moreover, the transparent conductive film which concerns on another viewpoint of this invention contains 0.4-4.5 atom% of Al and 0.05-2.0 atom of fluorine in the surface side of the lower layer side transparent conductive film. % Of the zinc oxide-based upper transparent conductive film is laminated. The lower transparent conductive film is not particularly limited, but is preferably a zinc oxide-based transparent conductive film.

[0008]

In the transparent conductive film of the present invention, Al is 0.4 to 4.
Contains 5 atomic% and contains 0.05 to 2.0 atomic% fluorine
The zinc oxide-based transparent conductive film contained is formed at least on the surface side. Inclusion of Al in the above range improves the conductivity and transparency of the zinc oxide-based transparent conductive film.
Further, by containing fluorine in the halogen element in a specific range in the zinc oxide-based transparent conductive film, the moisture resistance of the transparent conductive film is significantly improved, and the change with time can be effectively suppressed. When the fluorine content is lower than 0.05 atom% or higher than 2.0 atom%,
The effect of improving the moisture resistance cannot be expected effectively. Even if a halogen element other than fluorine is contained in the zinc oxide-based conductive film, the effect of improving the moisture resistance cannot be expected so much.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiments shown in the drawings. 1 is a cross-sectional view of a main part of a transparent conductive film according to the first aspect of the present invention, and FIG. 2 is a cross-sectional view of a main part of a transparent conductive film according to the second aspect of the present invention. The transparent conductive film 2 according to the first aspect of the present invention shown in FIG. 1 is composed of a single layer,
For example, it is formed by laminating on the surface of the transparent substrate 4. The transparent conductive film 2 is a zinc oxide-based transparent conductive film and is made of Al.
Is contained in an amount of 0.4 to 4.5 atomic% and fluorine is 0.05
.About.2.0 at%. The inclusion of Al is for lowering resistance and improving transparency, and by including Al in the above range, lowering resistance and improvement of transparency can be achieved. If the Al content is too high, the resistance tends to increase. On the other hand, if the amount is too small, there is no effect of lowering the resistance.

Further, by including fluorine in the halogen element in a specific range in the zinc oxide type transparent conductive film 2, the moisture resistance of the transparent conductive film is remarkably improved and the change with time is effectively suppressed. it can. The content of fluorine is
If it is lower than 0.05 atom% or higher than 2.0 atom%, it cannot be expected that the effect of improving the moisture resistance can be effectively obtained. Even if a halogen element other than fluorine is contained in the zinc oxide-based transparent conductive film 2, the effect of improving the moisture resistance cannot be expected so much.

The zinc oxide-based transparent conductive film 2 according to the present invention
Can be manufactured by, for example, a magnetron sputtering method, a CVD method, or the like. To form the transparent conductive film 2 by the sputtering method, first, a zinc oxide-based sintered body containing 0.5 to 6% by weight of aluminum oxide (Al ₂ O ₃ ) is prepared.

Such a zinc oxide sintered body can be manufactured by the following manufacturing method. That is, 0.5 to 6
After mixing the powder of aluminum oxide of 94 wt% and the powder of zinc oxide of 94-99.5 wt%, the mixture is molded by cold isostatic pressing or the like and then sintered at 900-1500 ° C.

Next, by using such a sintered body as a target, for example, by direct current (DC) or alternating current (RF) magnetron sputtering, the oxidation according to the present invention is carried out directly on the substrate 4 or through another functional thin film. A zinc-based transparent conductive film is formed. The sputtering conditions are not particularly limited, but in the case of DC sputtering, for example, the following conditions are used.

Sputtering gas: Argon / Fluorine Sputtering pressure: 1-10 × 10 ⁻³ Torr Argon flow rate: 10-40 SCCM Fluorine flow rate: 0.05-3 SCCM Sputtering current: 0.3-15 A Sputtering rate: 100 ~ 300 Å / min Sputtering time: 0.5-2 hours Substrate temperature: 200-300 ° C

The substrate 4 is not particularly limited, but for example, a glass substrate or a polymer substrate is used. The film thickness of the transparent conductive film of the present invention formed on the substrate is not particularly limited, but when it is used as a transparent conductive film of a solar cell, it is preferably about 20 to 30 nm. The application of the transparent conductive film 2 of the present invention is not limited to a photoelectric conversion element such as a solar cell, and is used for a display device such as a liquid crystal display device, a planar heating element, a heat ray reflection film, a visible light variable light shielding film, and an electromagnetic light shielding film. ,
It can be applied to various applications such as an antistatic film, a touch panel, and an optical communication member film, and is particularly suitable for applications requiring moisture resistance.

FIG. 2 shows a transparent conductive film 2a according to the second aspect of the present invention. The transparent conductive film 2a has a multilayer film structure laminated on the substrate 4, and includes a lower layer side transparent conductive film 8 and an upper layer side transparent conductive film 6. Lower transparent conductive film 8
Is not particularly limited and may be a transparent conductive film having poor moisture resistance.
The lower transparent conductive film 8 has, for example, Al of 0.4 to
It is made of a zinc oxide-based transparent conductive film or an ITO film containing 4.5 atomic%.

The upper transparent conductive film 6 has an Al content of 0.4 to 0.4.
It is composed of a zinc oxide-based transparent conductive film containing 4.5 atomic% and fluorine of 0.05 to 2.0 atomic%. Since this film has excellent moisture resistance, it is formed on the surface side of the transparent conductive film 2a. If this film is formed on the front surface side, the film structure of the transparent conductive film 2a may be a multilayer structure of two or more layers.

The thickness of the upper transparent conductive film 6 is not particularly limited, but is preferably 5 to 100 nm. If this film is too thin, the function as a moisture-resistant protective film is deteriorated, which is not preferable. Further, the interface between the upper layer side transparent conductive film 6 and the lower layer side transparent conductive film 8 does not necessarily have to be clear, and may be an interface where the fluorine concentration continuously changes in the film thickness direction.

Hereinafter, the present invention will be described with reference to more specific examples, but the present invention is not limited to these examples.

Example 1 A transparent substrate was prepared and the surface thereof was polished to an average surface roughness of 500 angstroms or less. The surface of the substrate was cleaned with acetone using an ultrasonic cleaner.

As shown in FIG. 2, the lower transparent conductive film 8 and the upper transparent conductive film 6 according to the embodiment of the present invention are formed on the surface of such a substrate by DC magnetron sputtering. The target to be used was prepared. The zinc oxide-based sintered body as a target contains 2% by weight of Al ₂ O ₃ and 98% by weight of ZnO.
Molded with CIP at a pressure of ² ton / cm ²
It can be obtained by firing at 200 ° C. for 3 hours.

First, the lower transparent conductive film 8 having a thickness of 150 nm was formed on the substrate 4 by the DC magnetron sputtering method using the zinc oxide type sintered body thus manufactured as a target. The sputtering conditions are shown below.

Sputtering gas: Argon / oxygen Sputtering pressure: 1 × 10 ⁻³ Torr Argon flow rate: 50 SCCM Oxygen flow rate: 0.2 SCCM Sputtering current: 0.05 A Sputtering rate: 80 Å /
Min Sputtering time: 1 hour Substrate temperature: 200 ° C

Subsequently, using the same target, fluorine was flowed in the atmosphere gas at 1 SCCM and the same DC sputtering was performed to form an upper transparent conductive film 6 having a thickness of 10 nm. Was deposited.

When the atomic analysis of the lower transparent conductive film 8 and the upper transparent conductive film 6 was performed using EPMA, the lower transparent conductive film 8 was a zinc oxide based film containing 1.5 atomic% of Al. It was confirmed that the upper transparent conductive film 6 was a zinc oxide-based film containing 1.5 atomic% of Al and 0.5 atomic% of fluorine.

The transparent conductive film 2a manufactured in this way
Table 1 shows the results of measuring changes in resistivity and changes in transmittance (at a wavelength of 550 nm) before and after 48 hours under conditions of 75 ° C. and 95% humidity. As shown in Table 1, the transparent conductive film 2a of this example was confirmed to be a film excellent in moisture resistance, with almost no increase in resistivity and decrease in transmittance before and after the moisture resistance test. .

[0027]

[Table 1]

Example 2 Except that the film thickness of the lower transparent conductive film was 200 nm, the flow rate of fluorine was 2 SCCM when the upper transparent conductive film was formed, and the substrate temperature during film formation was 250 ° C. A transparent conductive film was formed in the same manner as in Example 1. The fluorine content of the lower layer side transparent conductive film was 1 atomic%. The results of the moisture resistance test conducted in the same manner as in Example 1 are shown in Table 1.

As shown in Table 1, the transparent conductive film 2a of this example is a film excellent in moisture resistance, showing almost no increase in resistivity and decrease in transmittance before and after the moisture resistance test. confirmed.

Example 3 The content of aluminum contained in the lower transparent conductive film and the upper transparent conductive film was 3 atom%, and the content of fluorine contained in the upper transparent conductive film was 0.3 atom%. , The lower transparent conductive film has a thickness of 200 nm, the upper transparent conductive film has a thickness of 20 nm, the substrate temperature is 230 ° C., and R
A transparent conductive film was formed in the same manner as in Example 1 except that F magnetron sputtering was used. The results of the moisture resistance test conducted in the same manner as in Example 1 are shown in Table 1. Table 1
As shown in, the transparent conductive film 2a of this example was confirmed to be a film excellent in moisture resistance, with almost no increase in resistivity and decrease in transmittance before and after the moisture resistance test.

Example 4 The aluminum content in the lower transparent conductive film and the upper transparent conductive film was 3.5 atom%, and the fluorine content in the upper transparent conductive film was 1.5 atom. %, The thickness of the lower transparent conductive film was 300 nm, the thickness of the upper transparent conductive film was 20 nm, the substrate temperature was 350 ° C., and RF magnetron sputtering was used.
A transparent conductive film was formed in the same manner as in Example 1. Example 1
The results of the moisture resistance test conducted in the same manner as in Table 1 are shown in Table 1. As shown in Table 1, the transparent conductive film 2a of this example was confirmed to be a film excellent in moisture resistance, with almost no increase in resistivity and decrease in transmittance before and after the moisture resistance test. .

Example 5 The content of aluminum contained in the lower transparent conductive film and the upper transparent conductive film was 4 atom%, and the content of fluorine contained in the upper transparent conductive film was 0.1 atom%. , The lower transparent conductive film has a thickness of 300 nm, the upper transparent conductive film has a thickness of 30 nm, the substrate temperature is 580 ° C., and C
A transparent conductive film was formed in the same manner as in Example 1 except that the VD method was used. The results of the moisture resistance test conducted in the same manner as in Example 1 are shown in Table 1. As shown in Table 1, the transparent conductive film 2a of this example was confirmed to be a film excellent in moisture resistance, with almost no increase in resistivity and decrease in transmittance before and after the moisture resistance test. .

Comparative Example 1 A transparent conductive film composed of only a lower transparent conductive film was formed in the same manner as in Example 1 except that the upper transparent conductive film was not formed. The results of the moisture resistance test conducted in the same manner as in Example 1 are shown in Table 2. As shown in Table 2, in the transparent conductive film of the comparative example, after the moisture resistance test, the resistivity was increased and the transmittance was decreased, and the film was inferior in moisture resistance to Examples 1 to 5. Was confirmed.

[Table 2]

Comparative Example 2 A transparent conductive film consisting of only a lower transparent conductive film was formed in the same manner as in Example 2 except that the upper transparent conductive film was not formed. Table 2 shows the results of the moisture resistance test conducted in the same manner as in Example 2. As shown in Table 2, in the transparent conductive film of the comparative example, after the moisture resistance test, the resistivity was increased and the transmittance was decreased, and the film was inferior in moisture resistance to Examples 1 to 5. Was confirmed.

Comparative Example 3 A transparent conductive film consisting only of a lower transparent conductive film was formed in the same manner as in Example 3 except that the upper transparent conductive film was not formed. Table 2 shows the results of the moisture resistance test conducted in the same manner as in Example 3. As shown in Table 2, in the transparent conductive film of the comparative example, after the moisture resistance test, the resistivity was increased and the transmittance was decreased, and the film was inferior in moisture resistance to Examples 1 to 5. Was confirmed.

Comparative Example 4 A transparent conductive film composed of only a lower layer side transparent conductive film was formed in the same manner as in Example 4 except that the upper layer side transparent conductive film was not formed. Table 2 shows the results of the moisture resistance test conducted in the same manner as in Example 4. As shown in Table 2, in the transparent conductive film of the comparative example, after the moisture resistance test, the resistivity was increased and the transmittance was decreased, and the film was inferior in moisture resistance to Examples 1 to 5. Was confirmed.

Comparative Example 5 A transparent conductive film consisting only of a lower transparent conductive film was formed in the same manner as in Example 5 except that the upper transparent conductive film was not formed. Table 2 shows the results of the moisture resistance test conducted in the same manner as in Example 5. As shown in Table 2, in the transparent conductive film of the comparative example, after the moisture resistance test, the resistivity was increased and the transmittance was decreased, and the film was inferior in moisture resistance to Examples 1 to 5. Was confirmed.

Comparative Example 6 In the same manner as in Example 1 except that when forming the upper transparent conductive film, chlorine was flowed in place of fluorine to form an upper transparent conductive film containing 0.5 atom% of chlorine. To form a transparent conductive film. Table 3 shows the results of the moisture resistance test conducted in the same manner as in Example 1. As shown in Table 3, in the transparent conductive film of the comparative example, after the humidity resistance test, the resistivity was increased and the transmittance was decreased, and the film was inferior in moisture resistance to Examples 1 to 5. Was confirmed.

[Table 3]

Comparative Example 7 When forming the upper transparent conductive film, the fluorine-containing atomic% was
A transparent conductive film was formed in the same manner as in Example 1 except that was set to 3 atomic%. Table 3 shows the results of the moisture resistance test conducted in the same manner as in Example 1. As shown in Table 3, in the transparent conductive film of Comparative Example 7, the resistance and the transmittance were little changed before and after the humidity resistance test, but the resistivity was high and the transmittance was low. Then, it was confirmed that the transparent conductive film was not good.

[0040]

As described above, according to the present invention, the moisture resistance of the transparent conductive film is improved, the characteristics such as conductivity and transparency are less changed with time, and the durability is improved. It has an excellent effect. Therefore, the transparent conductive film of the present invention is suitable for use in a field where moisture resistance is particularly required.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a transparent conductive film according to a first aspect of the present invention.

FIG. 2 is a sectional view of an essential part of a transparent conductive film according to a second aspect of the present invention.

[Explanation of symbols]

 2, 2a ... Transparent conductive film 4 ... Substrate 6 ... Upper layer side transparent conductive film 8 ... Lower layer side transparent conductive film

Claims (3)

[Claims] 1. A zinc oxide-based transparent conductive film containing 0.4 to 4.5 atomic% of Al and 0.05 to 0.05 of fluorine.
A transparent conductive film containing 2.0 atom%. 2. The lower transparent conductive film contains 0.4 to 4.5 atomic% of Al and 0.05 to 0.05 of fluorine on the surface side.
A transparent conductive film, in which a zinc oxide-based upper transparent conductive film containing 2.0 atomic% is laminated. 3. The transparent conductive film according to claim 2, wherein the lower transparent conductive film is a zinc oxide-based transparent conductive film.