JP2944668B2 - Manufacturing method of transparent conductive film - Google Patents

Description

The present invention relates to a method for producing a transparent conductive film based on a polyethylene terephthalate film.

[Conventional technology]

In general, thin films that are transparent in the visible light region and have conductivity are used for transparent electrodes in new displays such as liquid crystal displays and electroluminescence displays, as well as for preventing static electricity and blocking electromagnetic waves in transparent articles. Have been.

Conventionally, as such a transparent conductive thin film, a so-called conductive glass in which an indium oxide thin film is formed on glass is well known, but since the base material is glass, flexibility and workability are poor. However, it may not be preferable depending on the use.

For this reason, in recent years, in addition to flexibility and workability, a transparent conductive thin film based on a synthetic resin has been used due to advantages such as excellent impact resistance and light weight. Polyethylene terephthalate film is particularly preferably used as a base film because of its excellent heat resistance and strength.

[Problems to be solved by the invention]

However, a transparent conductive film based on a polyethylene terephthalate film has poor scratch resistance, and has drawbacks such as an increase in electric resistance due to scratches during use and breakage during use.

When this kind of conductive film is used as a transparent electrode, for example, it is patterned so as to have a predetermined shape. In that case, since a lot of acids and alkalis are used, polyethylene terephthalate as a base material is used. The film is hydrolyzed by the above reagent, and the surface is easily roughened. For this reason, when the adhesion between the substrate film and the conductive thin film is poor, the transparency of the film is lost after the patterning process or thereafter,
The conductive thin film is partially or entirely peeled off, resulting in an increase in electric resistance and an adverse effect such as difficulty in use as a transparent electrode.

The present invention, in view of the above-mentioned problems of the conventional transparent conductive film, has excellent adhesiveness between the substrate and the conductive thin film made of polyethylene terephthalate film and very good chemical resistance, particularly having alkali resistance, It is an object of the present invention to provide a method for producing a transparent conductive film having improved abrasion resistance and also having high transparency desired for such a film.

[Means for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and as a result, prior to forming a transparent conductive thin film on a polyethylene terephthalate film, the surface of the film was previously subjected to a specific etching treatment. By forming the above-mentioned thin film on the treated surface, and further forming a derivative thin film of a specific thickness on this thin film, excellent adhesion between the above-mentioned film and the conductive thin film is obtained, and good chemical resistance, in particular, The inventors have found that a transparent conductive film having alkalinity, excellent scratch resistance, and high transparency can be obtained, thereby completing the present invention.

That is, according to the present invention, 1 × 10 ^-3 to 1 × 10 ^-1 containing at least 50% of argon gas is provided on the surface of a polyethylene terephthalate film (hereinafter referred to as a PBT film).
In an atmosphere of Torr, to then subjected to high frequency sputter etching treatment in the discharge process amount in the range of 0.1～30W · sec / cm ^2, to form a transparent conductive thin film, then the refractive index of the thin film on the thin film The present invention relates to a method for producing a transparent conductive film, characterized in that a transparent dielectric thin film having a refractive index of 1.3 to 1.6 and a thickness of 100 to 2,000 mm is formed.

[Structure and operation of the invention]

The PET film used as a base material in the present invention is widely used as a base film for various uses as described above, having excellent heat resistance, strength, and even surface smoothness, and is easily available as a commercial product. It is possible. The thickness is not particularly limited, but generally is 2
It is preferable to use one having a thickness of about 300 μm.

Further, in the present invention, in addition to the PET film alone, the surface side on which a transparent conductive thin film is to be formed is made of polyethylene terephthalate, that is, a composite film having polyethylene terephthalate as a surface layer, such as the PET film. A laminated film with another resin film or the like can also be used.

In the present invention, the surface of the PET film is first subjected to a high frequency sputtering process. The first feature of this process is to provide an atmosphere containing at least 50%, preferably 80% or more of argon gas. . In other words, by using such an atmosphere mainly composed of argon gas, the adhesion between the PET film and the conductive thin film can be improved, and a transparent conductive film having excellent chemical resistance, particularly excellent alkali resistance, can be obtained. However, the above effects cannot be obtained in an atmosphere mainly composed of an inert gas such as nitrogen gas or helium gas as in the case of argon gas.

Note that as long as the argon gas occupies at least 50%, the remaining gas composition may be a gas used in ordinary sputtering processing, such as nitrogen gas, helium gas, neon gas, hydrogen gas, or air. Further, water vapor may be contained in the atmospheric gas.

A second feature is that the atmospheric pressure composed of the gas composition is set in a range of 1 × 10 ⁻³ to 1 × 10 ⁻¹ Torr. This is because glow discharge tends to be unstable at a vacuum higher than the above range, whereas at a vacuum lower than the above range, the effect of improving alkali resistance based on the improvement in adhesion between the base film and the conductive thin film is not sufficiently exhibited. .

Further, as a third feature, the discharge processing amount represented by the product of the high-frequency output (W / cm ² ) per electrode unit area and the discharge processing time is set in the range of 0.1 to 30 W · sec / cm ^2. This is very important. This is because if it is smaller than the above range, a sufficient processing effect cannot be obtained, and if it is larger than the above range, the film is deformed or colored.

As described above, in the present invention, the surface of the PET film is subjected to the specific high-frequency sputter etching treatment having the first to third characteristics as described above, and the treatment itself is performed according to a known method. In this case, the high-frequency power supply is practically an industrial allocated frequency.
It is convenient to use 13.56MHz.

In the present invention, after performing the above-described high-frequency sputter etching treatment, a transparent conductive thin film is formed on the treated surface. This shape may be taken out to the atmosphere once after the above-mentioned processing, and then returned to the same atmospheric pressure as the above-mentioned processing again, or may be performed while the atmospheric pressure during the above-mentioned processing is substantially maintained, that is, 1 × 10 ^It may be performed continuously without breaking the vacuum degree of ^-3 to 1 × 10 ^-1 Torr, and in each case, an improvement effect such as alkali resistance can be obtained. However, the latter, that is, the method performed while maintaining the atmospheric pressure is more preferable because a more preferable result is obtained.

The atmosphere gas composition when forming the conductive thin film is as follows:
It is not always necessary to be the same as that at the time of the high frequency sputtering processing, and it may be appropriately changed according to the conductive thin film forming method to be adopted.

As a method for forming the conductive thin film, any of conventionally known techniques such as a vacuum deposition method, a sputtering method, and an ion plating method can be adopted. Also, the thin film material to be used is not particularly limited, and for example, indium oxide containing tin oxide, tin oxide containing antimony, and the like are preferably used. The thickness of the conductive thin film is generally about 100 to 2,000 mm.

In the present invention, after forming a transparent conductive thin film as described above, a transparent dielectric thin film is further formed on this thin film. The formation of the dielectric thin film mainly improves the scratch resistance and also improves the transparency. From this viewpoint, the material of the dielectric thin film preferably has a refractive index of 1.3 to 1.6, which is smaller than the refractive index of the transparent conductive thin film, for example, SiO ₂ (refractive index 1.46), CaF ₂ (refractive index).
1.4), MgF ₂ (refractive index 1.38), Na ₃ AlF ₆ (refractive index 1.35),
ThF ₄ (refractive index 1.5) and the like are preferable, and among them, SiO ₂ is most preferable. Note that these materials are not limited to one kind, and two or more kinds may be used in combination.

The thickness of the dielectric thin film is 100 to 2,000 mm, preferably 200
A good range is ~ 1,000Å. If it is less than 100 mm, a continuous film will not be formed, so that an effect of improving scratch resistance and transparency cannot be expected. Also, if it is too thick, the conductivity and transparency of the film surface may be reduced, or cracks may occur,
Not preferred.

As a method of forming the dielectric thin film, for example, there are a vacuum deposition method, a sputtering method, an ion plating method, a coating method, and the like, and an appropriate method can be adopted according to the type of the material and the required film thickness. .

〔The invention's effect〕

As described above, in the present invention, a transparent conductive thin film is formed by subjecting a surface of a PET film to a specific high-frequency sputtering process, and a dielectric thin film having a specific thickness is further formed thereon. By doing so, it is possible to provide a transparent conductive film having good chemical resistance, particularly alkali resistance, excellent scratch resistance, high transparency, and satisfactory conductivity. .

〔Example〕

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

Example 1 The surface of a PET film having a thickness of 75 μm was made of 80% argon gas.
In an atmosphere of 4 × 10 ⁻³ Torr composed of
High-frequency sputter etching treatment was performed at a discharge treatment amount of 3 W · sec / cm ² . Then, on this treated surface, in the same atmospheric gas without breaking the above-mentioned degree of vacuum, by a reactive sputtering method using an indium-tin alloy, a composite oxide of indium oxide and tin oxide having a thickness of 400 mm was formed. A transparent conductive thin film (hereinafter, referred to as an ITO thin film) was formed.

Next, SiO ₂ was vacuum-deposited on the ITO thin film at a degree of vacuum of 1-2 × 10 ⁻⁴ Torr by an electron beam heating method.
Transparent dielectric thin film made of SiO ₂ having a thickness of about 400 Å (or less, S
iO ₂ thin film) to obtain a transparent conductive film of the present invention.

Examples 2 and 3 The thickness of the SiO ₂ thin film was set to 200Å (Example 2) and 1,000, respectively.
透明 A transparent conductive film was produced in exactly the same manner as in Example 1, except that the film was changed to (Example 3).

Comparative Example 1 A transparent conductive film was produced in the same manner as in Example 1 except that the thickness of the SiO ₂ thin film was changed to 50 °.

Comparative Example 2 A transparent conductive film was produced in the same manner as in Example 1, except that the atmosphere gas at the time of the high-frequency sputter etching treatment was changed to 80% of nitrogen gas and 20% of oxygen gas.

Comparative Example 3 Atmospheric pressure during high-frequency sputter etching treatment was 3 ×
A transparent conductive film was produced in the same manner as in Example 1 except that the film was changed to 10 ^-1 Torr.

Comparative Example 4 Discharge treatment amount during high-frequency sputter etching treatment was 0.05
A transparent conductive film was produced in the same manner as in Example 1 except that the film thickness was changed to W · sec / cm ² .

Comparative Example 5 A transparent conductive film was produced in the same manner as in Example 1, except that both the high-frequency sputter etching treatment and the formation of the SiO ₂ thin film were omitted.

Comparative Example 6 Except for omitting only the high-frequency sputter etching treatment,
A transparent conductive film was produced in the same manner as in Example 1.

Comparative Example 7 A transparent conductive film was produced in the same manner as in Example 1 except that the formation of the SiO ₂ thin film was omitted.

Next, the film resistance, transmittance, alkali resistance and scratch resistance of each of the transparent conductive films of the above Examples and Comparative Examples were measured and evaluated in the following manner.

<Film resistance> Using the four-terminal method, the surface electric resistance (Ω /
□) was measured.

<Transmittance> The visible light transmittance at a light wavelength of 550 nm was measured using a spectrophotometer UV-240 manufactured by Shimadzu Corporation.

<Alkali resistance> The transparent conductive film is cut into strips with a width of 1 cm, immersed in a 5% by weight aqueous KOH solution (20 ° C) for 20 minutes, and then the film resistance (Ra) is measured, and the initial film resistance (Ro) is measured. The change rate (Ra / Ro) with respect to was determined, and the alkali resistance was evaluated.

<Scratch resistance> Haydon surface property measuring instrument TYPE-HEIDON14 manufactured by Shinto Kagaku
Scratches: Gauze (Basic Pharmacopoeia Type I),
Load: 100 g / cm ² , Scratch speed: 30 cm / min, Scratch frequency: 10
Under the condition of 0 times (50 round trips), the film resistance (Rs) is measured after rubbing the thin film surface, and the initial film resistance (Ro)
The rate of change (Rs / Ro) with respect to was determined, and the scratch resistance was evaluated.

As is clear from the results in the above table, according to the method of the present invention, the conductivity according to the thickness of the SiO ₂ thin film, which is excellent in any of the properties of transparency, chemical resistance, particularly alkali resistance, and scratch resistance. It can be seen that transparent conductive films having various film resistances applicable as conductive films can be obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahide Toyooka 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nichidenki Kogyo Co., Ltd. (72) Inventor Masaaki Kawaguchi 1-1-1, Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Electric Industry Co., Ltd. (56) References JP-A-59-56313 (JP, A) JP-A-62-263610 (JP, A) JP-A-61-279004 (JP, A)

Claims (1)

(57) [Claims] 1. A polyethylene terephthalate film having a surface of 1 × 10 ^-3 containing at least 50% of argon gas.
After performing high-frequency sputter etching treatment in an atmosphere of ~ 1 × 10 ^-1 Torr at a discharge treatment amount in the range of 0.1 to 30 W · sec / cm ² , a transparent conductive thin film is formed. Forming a transparent dielectric thin film having a refractive index of 1.3 to 1.6 and a thickness of 100 to 2,000 mm, which is smaller than the refractive index of the thin film.