JP2000273620A - Formation of transparent electrically conductive thin film-coated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously form a high performance electrically conductive thin film on a plastic film in such a manner that damage to a base material is suppressed by vaor-depositing electrically conductive metallic oxide via high frequency plasma of discharge frequency in a specified range in an oxygen atmosphere. SOLUTION: The discharge frequency is controlled to the range of 14 to 100 MHz. A vapor depositing material 6 held in a crucible 7 set to the lower part of a vacuum chamber 1 in which the degree of vacuum is controlled to <=1×10-5 Torr is evaporated by an electron beam irradiated from an electron gun 8, the evaporated particles 11 pass through the inside of the region of oxygen plasma introduced from a gas introducing port 10 into the space between a plastic film 2 and the crucible 7 to form a transparent electrically conductive thin film on the plastic film 2. Continuous film formation is executed to the surface of the plastic film unwound from the roll state. As to the base material, forced heating is not executed so that it can correspond to all plastics regardless of the stocks. As the base material, pglyolefine, polyester, polyamide or the like is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a low-resistance transparent conductive thin film coating film used as a transparent electrode for a liquid crystal display or a solar cell, an electromagnetic wave shielding film and the like.

[0002]

2. Description of the Related Art Conventionally, in order to form a transparent conductive thin film, a forming method in which a conductive material is deposited by resistance heating or using an electron beam has been often used. The vapor deposition method has a higher film formation rate and higher productivity than a sputtering method, a vapor phase chemical deposition (CVD) method, or the like. An oxide such as tin oxide or ITO (tin oxide added indium oxide) is mainly used for the conductive thin film. Among the vapor deposition methods, a plasma-assisted vapor deposition method using plasma during vapor deposition is effective.

[0003] This vapor deposition method has the effect of increasing the activity of evaporated particles through plasma and improving adhesion, crystallinity and reactivity.

In order to improve the effect of the above-described plasma-assisted deposition method, it is necessary to increase the density of plasma. In the conventional plasma-assisted deposition method, high-frequency plasma is mainly used due to its simplicity. The high-frequency plasma is characterized in that it can be generated even under a high vacuum of about 1 × 10 **-4 Torr and has low thermal damage to the substrate.

Conventionally, 13.56 MHz has been mainly used for high frequency plasma. In this case, a high discharge output is required to improve the plasma density, but there is a limit in practical use.

Therefore, recently, a vapor deposition method using a high-density plasma by a plasma gun including a cathode made of lanthanum borohydride as an assist, as represented by Japanese Patent Application Laid-Open No. 9-71858, has been reported. By this vapor deposition method, a high-performance transparent conductive thin film can be formed. However, conventional 1
Since the plasma density is one to two orders of magnitude higher than that of 3.56 MHz plasma, thermal damage to the substrate is large, and its use is difficult for a substrate having low heat resistance such as a plastic film.

[0007] In recent years, the range of use of transparent conductive thin films has been widened, and the needs for substrates to be formed in response have been diversified. Therefore, film formation on any substrate is desired. Further, the adhesion to the thin film is impaired due to damage to the base material.

In addition, since a high-density plasma beam is controlled by a magnetic field, a relatively complicated control system is required, and it is difficult to incorporate it into an existing device or the like, and it lacks simplicity.

[0009]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for continuously forming a high-performance transparent conductive thin film made of a conductive metal oxide on a plastic film to reduce damage to a substrate. An object of the present invention is to provide a method for forming a high-performance transparent conductive thin film that is suppressed as much as possible.

[0010]

According to the first aspect of the present invention, a transparent conductive metal oxide is deposited on a substrate by high-frequency plasma deposition in an oxygen atmosphere. A method for forming a thin film, wherein the discharge frequency is in the range of 14 MHz to 100 MHz.

According to a second aspect of the present invention, there is provided a method for forming a transparent conductive thin film covering film, wherein the substrate is a plastic film unwound from a roll.

According to a third aspect of the present invention, there is provided a method for forming a transparent conductive thin film-coated film, wherein a plastic film as a substrate is not forcibly heated.

By increasing the discharge frequency from 13.56 MHz conventionally used, the probability of collision between plasma active species (electrons, ions, radicals, etc.) and the deposited particles is increased, and a high active state is created, and high performance is achieved. A transparent conductive thin film can be formed at a high speed. Further, by using high-frequency plasma, the vapor deposition apparatus can be simplified and thermal damage to the base material can be suppressed.

The reason for setting the upper limit to 100 MHz is that
At frequencies higher than MHz, the circuit configuration of the discharge device becomes complicated, and the simplicity of the device is lost.

The productivity can be improved by forming a continuous film on the plastic film unwound from the roll state.

Further, the substrate is not forcibly heated so as to be applicable to any plastic film regardless of the material.

As the base material used in the present invention, for example, polyolefin (polyethylene, polypropylene, etc.),
Polyester (polyethylene terephthalate, etc.), polyamide (nylon 66, etc.) thickness 10 to 200 μm
A plastic film having a high degree of transparency does not depart from the object of the present invention.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

The present invention is carried out by using a take-up type vacuum evaporation apparatus as shown in FIG. 1. This apparatus comprises an unwinder 3 for feeding a plastic film 2 into a vacuum chamber 1, a winder 4, and A cooling can 5, a crucible 7 for holding a conductive metal oxide 6 as a vapor deposition material, an electron gun 8 for irradiating the vapor deposition material with an electron beam, and a plasma for generating a plasma between the plastic film 2 and the crucible 7. Discharge coil 9, inlet 10 for introducing oxygen
It is composed of

In the method of forming a transparent conductive thin film coating film of the present invention, which is carried out by using the above-mentioned roll-up type vacuum evaporation apparatus, first, the film is installed in the lower portion of the vacuum chamber 1 having a degree of vacuum of 1 × 10 **-5 torr or less. The vapor deposition material 6 held in the crucible 7 is evaporated by an electron beam emitted from an electron gun 8, and the evaporated particles 11 evaporate between the plastic film 2 and the crucible 7.
A transparent conductive thin film is formed on the plastic film 2 by passing through the plasma region of oxygen introduced from zero.

At this time, the oxygen partial pressure is 3 × 10 **-4 to
rr.

The plastic film 2 is supplied from the unwinder 3 along the cooling can 5 and supplied onto the discharge coil 9, where a transparent conductive thin film of oxide is formed. The formed plastic film 2 is taken up along a cooling can 5 by a take-up machine 4.

[0023]

EXAMPLE In this example, an ITO thin film was formed on a plastic film by the apparatus shown in FIG. 13.56 MHz, 27.12 as a discharge frequency to the discharge coil 9
MHz and 40.68 MHz were applied to generate plasma. ITO particles were used as a deposition material. At this time, no forced heating was applied to the plastic film.

In the following embodiment, the discharge frequency is 27.12.
13.56 MHZ for MHz and 40.68 MHz
The purpose of the present invention was to investigate whether the evaporating particles can be more efficiently activated with respect to the discharge output than z, and whether the specific resistance and the adhesion to the substrate can be improved.

The adhesion to the substrate was evaluated by a tape peel test. This makes the cellophane tape adhere to the film-forming substrate,
The tape is peeled off vertically from the surface of the base material at a stretch, and the state of peeling of the film is examined.

IT formed on plastic film
The dependence of the specific resistance of the O thin film on the discharge output was examined.
FIG. 2 shows that the discharge frequency is 13.56 MHz, 27.12 M
3 shows the specific resistance of the ITO thin film in the case of Hz and 40.68 MHz in the range of the discharge output from 200 W to 400 W.

FIG. 2 shows that the specific resistance of the ITO thin film formed at the discharge frequencies of 27.12 MHz and 40.68 MHz is lower by one to two orders of magnitude than that of the ITO thin film formed at the discharge frequency of 13.56 MHz. Was. From this result, by setting the discharge frequency to 14 MHz or more, the conventional 1
It was found that a transparent conductive thin film having lower resistance than 3.56 MHz could be formed.

The adhesion between the ITO thin film and the substrate is smaller than that of the ITO thin film formed at the discharge frequencies of 27.12 MHz and 40.68 MHz. The improvement of the property was shown.

[0029]

As described above, according to the method for forming a transparent conductive thin film-coated film of the present invention, a conductive metal oxide via a high-frequency plasma having a discharge frequency of 14 MHz to 100 MHz in an oxygen atmosphere. By vapor deposition, it is possible to form a high-performance transparent conductive thin film-coated film having better adhesion to a substrate than conventional plasma having a discharge frequency of 13.56 MHz.

Further, since the transparent conductive thin film-coated film can be formed on a plastic film which is unwound from a roll state and is not forcibly heated, continuous film formation with high productivity can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a winding type high frequency plasma assisted vapor deposition apparatus for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the discharge output and the specific resistance of an ITO thin film according to the embodiment of the present invention

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber 2 ... Plastic film 3 ... Unwinder 4 ... Winding machine 5 ... Cooling can 6 ... Conductive metal oxide material 7 ... Crucible 8 ... Electron gun 9 ... Discharge coil 10 ... Oxygen inlet 11 ... Evaporated particles

Claims (3)

[Claims] 1. A method for forming a transparent conductive thin film on a substrate by vapor deposition of a conductive metal oxide through high frequency plasma in an oxygen atmosphere, wherein a discharge frequency is in a range of 14 MHz to 100 MHz. A method for forming a transparent conductive thin film-coated film, characterized in that: 2. A method according to claim 1, wherein the substrate is a plastic film unwound from a roll. 3. A method for forming a transparent conductive thin film-coated film, wherein the plastic film as a substrate according to claim 1 or 2 is not forcibly heated.