JP2828987B2 - Method for producing transparent conductive laminate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a transparent conductive laminate comprising a plastic substrate and a metal oxide thin film.

[Conventional technology]

Examples of the transparent conductive laminate include a substrate using glass or plastic as a base material, a transparent conductive layer provided thereon as a thin metal film type of gold, palladium, etc., indium oxide, tin oxide, titanium There are many known metal oxide thin film types such as oxides and multilayer thin film types such as titanium oxide / silver / titanium oxide.

Among these laminates, those formed by providing a metal oxide thin film on a plastic base material are excellent in lightness, workability, impact resistance, flexibility, etc., and also in transparency and conductivity. Because of its superiority, it is widely used in various industrial fields. Further, among such metal oxide thin film types, those containing the above thin film mainly containing indium oxide,
For example, a laminate composed of indium oxide alone or a mixed oxide obtained by adding a small amount of tin (hereinafter referred to as ITO) has particularly good transparency and conductivity, and has excellent etching characteristics, and has excellent electrode pattern. In recent years, it has attracted attention as the most practical one because it has a feature that it is easy to use.

Conventionally, a laminate comprising such a plastic base material and a metal oxide thin film mainly containing indium oxide such as ITO has been manufactured by a method of forming the thin film on the base material by a sputtering method. This is because, according to the sputtering method, advantages such as long-term production, little deviation in film composition, and easy widening are obtained.

[Problems to be solved by the invention]

However, the laminate manufactured by the above method has a problem that it is inferior in transparency and conductivity as compared with the case where the same metal oxide thin film is provided on a glass substrate by the same means as described above. I was The reason for this is that the glass substrate can be heated to a high temperature of about 300 ° C. during sputtering, and the properties of the oxide thin film formed by this heating are suitable for increasing the transparency and conductivity. On the other hand, the plastic base material cannot be heated to the above high temperature because of its heat resistance.

In view of the above circumstances, the present invention provides a method for forming a metal oxide thin film mainly containing indium oxide such as ITO on a plastic substrate by a sputtering method by performing a specific heat treatment after sputtering. Another object of the present invention is to provide a method capable of manufacturing a low-resistance and high-transparency laminate which cannot be achieved by the prior art and overcomes the problem of reduced conductivity.

[Means for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and as a result, after forming a metal oxide thin film mainly containing indium oxide by a sputtering method, heating under a non-oxidizing gas atmosphere or a vacuum atmosphere. When processed,
The inventor of the present invention has found that it is possible to greatly improve the transparency and conductivity of a laminate using a plastic substrate, and has completed the present invention.

That is, the present invention provides that a metal oxide thin film mainly containing indium oxide is formed on a plastic substrate by a sputtering method, and then heat-treated at 150 to 180 ° C. in a non-oxidizing gas atmosphere or a vacuum atmosphere. The present invention relates to a method for producing a transparent conductive laminate characterized by the following.

[Structure and operation of the invention]

The plastic substrate in the present invention is not particularly limited as long as it has good transparency and heat resistance, and is not particularly limited. Various plastics such as acryl, cellulose resin and fluorine resin can be widely used. The form of the substrate is usually a sheet or a film, but may be another molded product. In the case of a sheet or a film, the thickness of the substrate is generally about 25 to 200 μm.

Prior to providing a metal oxide thin film on such a plastic base material, dust removal by solvent cleaning, ultrasonic cleaning, etc.
After cleaning, if necessary, an undercoat layer may be formed or a surface treatment may be applied to improve the adhesion between the thin film and the substrate and the abrasion resistance. The formation and surface treatment of such an undercoat layer can be performed by a known method as disclosed in Japanese Patent Publication No. 57-39004.

In the present invention, first, a metal oxide thin film mainly containing indium oxide such as ITO is formed on the above-mentioned plastic base material by a sputtering method. The sputtering method itself can be performed according to a known method, and for example, a method such as direct current or high frequency bipolar sputtering, direct current or high frequency magnetron sputtering, or ion beam sputtering can be employed. Among them, the magnetron sputtering method is preferable because the plasma impact on the plastic substrate is small and high-speed film formation is possible.

As the target, use is made of indium metal or an alloy containing it as a main component and usually containing 10% by weight or less of other metal such as tin, or indium oxide or another metal such as tin oxide as a main component and containing it. A sintered body composed of a composite oxide containing an oxide in the same ratio as the above in terms of metal is used. In the former, a mixed gas of an inert gas such as an argon gas and an oxygen gas is introduced into a vacuum chamber to perform reactive sputtering, and in the latter, an inert gas such as an argon gas alone or a mixture thereof is used. What is necessary is just to introduce a mixture containing a small amount of oxygen gas into the vacuum chamber and perform sputtering.

The temperature of the plastic substrate during sputtering is determined according to the heat resistance of the substrate, but is generally 200 ° C or less,
Preferably, the temperature is in the range of 25 to 100 ° C. Film forming conditions cannot be determined unconditionally because they greatly vary depending on the sputtering method, target material, introduced gas atmosphere, and the like. In the magnetron sputtering method, for example, the degree of vacuum is 1 × 10 ⁻³ to 1 × 10 ⁻² Torr, and the discharge current is 1.
The film forming speed is preferably set to 300 to 600 ° / min at 5 to 3A.

The thickness of the metal oxide thin film mainly containing indium oxide formed as described above is usually appropriate in the range of 40 to 3,000 mm. The degree of oxidation and other film properties of the thin film differ greatly depending on the sputtering method, the target material, the introduced gas atmosphere, and the like, and the transparency and conductivity also differ accordingly. No matter how suitable the material is, a decrease in transparency and conductivity is inevitable as compared with a material using a glass substrate.

Therefore, in the present invention, after forming the thin film, heat treatment is performed in a non-oxidizing gas atmosphere or a vacuum atmosphere to greatly improve transparency and conductivity. By the way, in the past, attempts have been made to change the film properties by performing a heat treatment after the formation of the thin film. However, this heat treatment is performed in an oxidizing gas atmosphere, and mainly by increasing the degree of oxidation of the film. The aim was to increase transparency. However, as in the present invention, it has not been known at all that the transparency and conductivity of the film are greatly improved when heat-treated in a non-oxidizing gas atmosphere or a vacuum atmosphere. That is what the inventors have found for the first time. The reason that the transparency and conductivity are improved in this way is that
Although it is not clear at present, it is presumed that changes in film properties other than the degree of oxidation, such as densification and crystallization of the film, may occur.

The non-oxidizing gas atmosphere may be an inert gas atmosphere such as a nitrogen gas or an argon gas. Further, the degree of vacuum in the vacuum atmosphere is not particularly limited, but is preferably set to a high degree of vacuum of 1 × 10 ⁻⁵ Torr or less. The reason why it is preferable to use a high vacuum degree is as follows.

That is, as described above, the transparency and conductivity can be improved by the above-described heat treatment of the present invention, but the degree thereof varies considerably depending on the conditions at the time of spattering before the heat treatment, especially the amount of oxygen gas introduced. However, when this amount is set in an appropriate range, the highest transparency and conductivity can be obtained. Here, in the case where the above heat treatment is performed in a vacuum atmosphere, the appropriate range of the amount of oxygen gas introduced at the time of the sputtering can be wider when the degree of vacuum is higher than when the degree of vacuum is low.

For example, 1 × 10 ⁻¹ To
In the heat treatment at a low vacuum of about rr, the curve-1a in FIG.
As shown in the above, in order to obtain the highest conductivity of 100 to 150Ω / □, the amount of oxygen gas introduced during sputtering is limited.
It is desirable to set it in the range of 34 to 35.5 SCCM. In contrast, 1 × 10 ⁻⁵ Torr as in Example 2 described later.
According to the heat treatment at a high degree of vacuum, the curve-1c in FIG.
In order to obtain the same conductivity as described above, the oxygen gas introduction amount can be set to a wide range of 34 to 36.5 SCCM, as shown by.

As described above, if the heat treatment is performed in a high vacuum atmosphere of 1 × 10 ⁻⁵ Torr or more, high transparency and conductivity can be stably achieved without finely adjusting the amount of oxygen gas introduced during sputtering. It is very advantageous in this respect.

The temperature at the time of the heat treatment of the present invention is generally 150 to 180 ° C., preferably 160 to 180 ° C., whether in a non-oxidizing gas atmosphere or a vacuum atmosphere.
By performing a heat treatment at such a temperature for usually 2 to 8 hours, a desired low-resistance and high-transparency laminate can be obtained.

〔The invention's effect〕

As described above, according to the method of the present invention, a laminate having excellent transparency and conductivity composed of a plastic base material and a metal oxide thin film mainly containing indium oxide can be manufactured. In addition to a transparent electrode in a new display system such as a Tsusen display, it is possible to provide a transparent conductive laminate suitable for various uses such as antistatic of a transparent article and shielding of electromagnetic waves.

〔Example〕

Hereinafter, embodiments of the present invention will be described in more detail.

Example 1 A 75 μm-thick polyester film was placed in a vacuum chamber,
As a target, the main component is indium metal and tin is 10
With an alloy containing 4% by weight, and a degree of vacuum of 4 × 10 ^-3 Torr,
Argon gas introduction amount 130SCCM (standard cubic centimet
ers / minute), oxygen gas introduction amount 34.4SCCM, discharge current 1.5
A. Magnetron sputtering was performed at a film forming speed of 450Å / min.
IT ITO thin film was formed. Thereafter, a heat treatment was performed at 180 ° C. for 6 hours in a vacuum atmosphere of 1 × 10 ⁻¹ Torr to produce a transparent conductive laminate.

This laminate has a sheet resistance of 110Ω / □ and a wavelength of 550
The light transmittance of 87 nm was 87%, and the material had low resistance and high transparency.

Next, except that the oxygen gas introduction amount was changed, magnetron sputtering with a film thickness of 180 ° was performed under exactly the same conditions as described above, and then various transparent conductive laminates A obtained by performing the same heat treatment as described above. And various transparent conductive laminates B obtained in the same manner except that the heat treatment was omitted,
The relationship between the oxygen gas introduction amount, the sheet resistance, and the light transmittance at a wavelength of 550 nm was examined. The results were as shown in FIG. 1 and FIG.

FIG. 1 shows the relationship between the amount of oxygen gas introduced and the sheet resistance, and FIG. 2 shows the relationship between the amount of oxygen gas introduced and the light transmittance at a wavelength of 550 nm. In both figures, curves -1a and 2a indicate transparent conductive materials. Curves -1b and 2b are results of the transparent conductive laminate B as a result of the conductive laminate A.

As is clear from the above figures, the transparent conductive laminate A subjected to the specific heat treatment of the present invention and the transparent conductive laminate B not subjected to the heat treatment both have a reduced oxygen gas introduction amount during magnetron sputtering. Thus, the sheet resistance and the light transmittance greatly change. However, under a constant oxygen gas introduction amount, the transparent conductive laminate A of the present invention has a lower sheet resistance than the transparent conductive laminate B. It can be seen that it has a higher light transmittance.

In the transparent conductive laminate B, the lowest sheet resistance (330Ω / □) was obtained when the amount of oxygen gas introduced during magnetron sputtering was 36.4 SCCM, and the light transmittance was 8%.
Although a considerably high value of 5% was obtained, these values are the highest values of the transparent conductive laminate A of the present invention (the sheet resistance 110 Ω / sheet when the oxygen gas introduction amount was 34.4 SCCM of Example 1).
□ and light transmittance of 87%), and it is also clear that the method of the present invention enables the production of a low-resistance and high-transparency laminate which could not be achieved conventionally.

Example 2 The conditions for the heat treatment were 180 ° C. in a vacuum atmosphere of 1 × 10 ⁻⁵ Torr.
6 hours except that the transparent conductive laminate A of Example 1 was used.
In the same manner as in the above case, a transparent conductive laminate C was produced. With respect to the laminate C, the result of examining the relationship between the oxygen gas introduction amount during magnetron sputtering and the sheet resistance was as shown by the curve-1c in FIG.

As is clear from this curve, the oxygen gas introduction amount is 34 ~
A low sheet resistance of 100 to 150 Ω / □ was obtained in a wide range of 36.5 SCCM, and the laminate having such a low resistance value had a very good transparency of 85% or more.

Example 3 Magnetron sputtering with a film thickness of 180 ° was performed in the same manner as in Example 1 except that the amount of introduced oxygen gas was 34.4 SCCM, and a heat treatment was performed at 180 ° C. for 6 hours in an atmosphere of argon gas at 1 atm. A transparent conductive laminate was produced. This laminate had a sheet resistance of 130Ω / □ and a light transmittance of 87%.

Example 4 A transparent conductive laminate was produced in the same manner as in Example 3, except that heat treatment was performed at 180 ° C. for 6 hours under a nitrogen gas atmosphere of 1 atm instead of heat treatment under an argon gas atmosphere. . The sheet resistance of this laminate is 135Ω / □, and the light transmittance is 8
It was 6.5%.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing the relationship between the amount of oxygen gas introduced during sputtering and the sheet resistance with respect to the method of the present invention and a transparent conductive laminate manufactured by a method different from the present invention, and FIG. FIG. 4 is a characteristic diagram showing a relationship between an oxygen gas introduction amount and light transmittance at the time of sputtering for a conductive laminate.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-209809 (JP, A) JP-A-60-258460 (JP, A) JP-A-61-79647 (JP, A) 39090 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01B 13/00 503 H01B 5/14 C23C 14/08 C23C 14/58

Claims (3)

(57) [Claims] A metal oxide thin film mainly containing indium oxide is formed on a plastic substrate by a sputtering method, and then heat-treated at 150 to 180 ° C. in a non-oxidizing gas atmosphere or a vacuum atmosphere. Of producing a transparent conductive laminate. 2. The method for producing a transparent conductive laminate according to claim 1, wherein the heat treatment time is 2 to 8 hours. 3. The method for producing a transparent conductive laminate according to claim 1, wherein the degree of vacuum in the heat treatment in a vacuum atmosphere is a high degree of vacuum of 1 × 10 ⁻⁵ Torr or less.