JPH06136159A - Transparent conductive film and its production - Google Patents

Abstract

PURPOSE:To obtain a film excellent in water vapor barrier effect, gas barrier effect, alkali resistance, conductivity and transparency by successively forming a specified thin barrier film and a specified thin transparent conductive film on a transparent film base. CONSTITUTION:A thin transparent barrier film of a thickness of desirably 10-100nm made of a metal oxide based on silicon oxide or a metal nitrile based on silicon nitride (e.g. SiO1.5) is formed on a transparent base made of desirably a polyacrylate film, and a thin transparent conductive film of a thickness of desirably 10-400nm made of a metal oxide based on indium oxide (e.g. tin oxide (10%)/indium oxide mixture) is formed on the preceding film to form a thin transparent conductive film.

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 and a method for producing the same, and more particularly to a metal oxide mainly composed of silicon oxide or a metal nitride mainly composed of silicon nitride on a transparent film substrate. A transparent conductive thin film of a metal oxide mainly composed of indium oxide is formed on a transparent barrier thin film of an object, a water vapor barrier, a gas barrier,
The present invention relates to a transparent conductive film having good alkali resistance, conductivity and transparency, and a method for producing the same.

[0002]

2. Description of the Related Art With the rapid progress of electronics technology, there is an urgent need to improve the characteristics of transparent electrodes. In particular, application to liquid crystal display devices, photoelectric conversion devices for solar cells, and the like is progressing. The transparent electrodes used for these are generally formed on a glass substrate. Examples of those formed on a glass substrate include, for example, Nesa glass obtained by thin film processing of tin oxide, ITO glass formed of a thin film of a mixture of indium oxide and tin oxide (ITO), and conductive metal thin films such as gold and silver. Conductive glass and the like are known. However, glass used as a substrate has drawbacks such as weakness against impact, heavy, inflexible, and difficult to increase in area, and in order to compensate for those drawbacks, transparent conductivity using a plastic film as a substrate Films are also manufactured. The plastic film has advantages such as impact resistance, flexibility, light weight, easy increase in area, and good workability.
The transparent conductive film using a plastic film as a substrate is still used in liquid crystal display devices, touch panels, antistatic films, infrared reflective films and the like.

The conductive thin film currently used for the transparent conductive film is mainly an ITO thin film which is excellent in both conductivity and transparency and can be easily patterned. This transparent conductive thin film is used for electronic display. Widely used in the device field. As a method of forming the ITO thin film on a plastic film substrate, a vacuum deposition method, a sputtering method, an ion plating method, etc. are known, and among these, good adhesion to the film and film uniformity are obtained. The magnetron sputtering method is widely used because of its good quality, easy control of film quality, and good productivity.

[0004]

However, with a single plastic film substrate, it is not possible to obtain one which satisfies various properties such as gas barrier property, water vapor barrier property and solvent resistance. Therefore, a film base material is often subjected to undercoating or surface treatment to form a composite. A known method such as coating or sputtering may be used for compounding, but conventionally compounding by coating has been widely used. However, in the composite by coating, sufficient characteristics could not be obtained due to the limitation of the coating material.
Especially as a substrate for a liquid crystal display element, in its manufacturing process,
Although alkali resistance is required, problems such as peeling and cracking often occur when immersed in a sodium hydroxide aqueous solution having a concentration of about 5% for 5 to 10 minutes. The present invention satisfies various characteristics of gas barrier property, water vapor barrier property, conductivity and transparency by forming a specific transparent barrier thin film and a specific transparent conductive thin film on it on a plastic film substrate. In addition, it is an object of the present invention to obtain a transparent conductive film having excellent properties that have not been obtained up to now such that it is not attacked by an alkaline solution typified by an aqueous solution of sodium hydroxide.

[0005]

The present inventors have arrived at the present invention as a result of earnest studies in order to achieve the above-mentioned object in view of the above circumstances. That is, the first aspect of the present invention is
A transparent barrier thin film (B) of a metal oxide mainly composed of silicon oxide or a metal nitride mainly composed of silicon nitride is formed on a transparent film substrate (A), and indium oxide is further formed thereon. According to a second aspect of the present invention, a transparent conductive film characterized in that a transparent conductive thin film (C) of a metal oxide as a main component is formed on a transparent film substrate (A),
A transparent barrier thin film (B) of a metal oxide mainly composed of silicon oxide or a metal nitride mainly composed of silicon nitride is formed by a magnetron sputtering method, and a metal oxide mainly composed of indium oxide is further formed thereon. A transparent conductive thin film (C) is formed by a magnetron sputtering method.

As the transparent film substrate used in the present invention, the thickness formed of a plastic film is preferably about 20 to 200 μm, more preferably 75 to 1
About 25 μm, the light transmittance is preferably 85% or more,
A film having 90% or more and a good surface smoothness is more preferable. When the thickness of the substrate is in the range of 20 to 200 μm, the light transmittance is 85% or more, the surface smoothness is good, and a transparent film having a uniform film thickness is easily obtained. Further, when the light transmittance of the substrate is 85% or more, the transparency of the obtained transparent conductive film becomes good, the surface property of the thin film becomes good, and the fine workability such as etching is improved.

The plastic film is not limited to a film made of a single base material, and various undercoats and surface treatments may be applied for the purpose of improving adhesion strength, barrier property, solvent resistance and the like. The applied composite film may be used. A known method such as coating or sputtering can be used for forming the composite. Examples of the plastic include polyarylate (PA
R), polyethylene terephthalate (PET), polycarbonate (PC), polyether sulfone (PE
S), polysulfone, polyamide, cellulose triacetate (TAC) and the like, and these may be used alone or in combination of two or more kinds. Among these plastics, polyarylate, which has high transparency and excellent heat resistance, is preferable, and it is particularly preferable for use in the application of liquid crystal display devices.

The transparent barrier thin film of the metal oxide mainly composed of silicon oxide or the metal nitride mainly composed of silicon nitride in the present invention preferably has a thickness of about 10 to 100 nm, more preferably 20 to 60 nm. The oxygen permeability is preferably 5 cc / m ² / day or less, more preferably 1 cc / m ² / day or less, and the water vapor permeability is 5 g / m ²
/ day or less is preferable, and a barrier thin film of 1 g / m ² / day or less is more preferable. A metal nitride mainly composed of silicon oxide is a metal nitride mainly composed of silicon dioxide or a compound containing at least one metal oxide such as silicon monoxide or aluminum oxide. The metal nitride mainly composed of silicon nitride is silicon nitride or a compound containing silicon nitride as a main component and at least one kind of metal nitride such as aluminum nitride. . Specific examples thereof include SiO _x and SiAIN. Among the metal oxides mainly containing silicon oxide or the metal nitrides mainly containing silicon nitride, SiO
_x , especially the value of x is 1.3 to 1.8, preferably 1.5 to
1.8 is preferable because it exhibits excellent alkali resistance while maintaining the oxygen gas and water vapor barrier properties.

In the present invention, the transparent conductive thin film of metal oxide mainly composed of indium oxide has a thickness of 10 to 10.
It is preferably about 400 nm, more preferably 50 to 20.
0 nm, more preferably about 60 to 150 nm, the light transmittance is preferably 80% or more, more preferably 85% or more, and the sheet resistance is preferably 100Ω / □ or less, more preferably 50Ω / □ or less. It is a transparent conductive thin film having a uniform film thickness distribution. When the thickness of the transparent conductive thin film is within the range of about 10 to 400 nm, it is easy to set both the sheet resistance and the light transmittance to the target ranges. In addition, when the light transmittance of the transparent conductive thin film is about 80% or more, the transparency of the transparent conductive film can be improved. The metal oxide mainly composed of indium oxide includes indium oxide or a main component thereof, preferably 80%.
(Wt%, the same applies below) or more, more preferably 90 to 95
%, And preferably 20% or less, more preferably 5 to 10% of one or more other metal oxides such as tin oxide and cadmium oxide. Specific examples of this compound include ITO and CdIn. ₂ O _{4 and the} like. Among the metal oxides mainly composed of indium oxide, ITO is preferable, and tin is preferably 10% in terms of metal.
Hereafter, more preferably 5 to 10% from the viewpoint of lowering sheet resistance while maintaining high transparency.

Next, an example of the method for producing the transparent conductive film of the present invention will be described. The transparent conductive film of the present invention is produced by a known method such as a magnetron sputtering method. As a target used for film formation, in the case of a transparent barrier thin film, as described above, other metal oxides such as aluminum oxide mainly containing silicon oxide or metal nitrides such as aluminum nitride mainly containing silicon nitride are used. A mixed sintered body of the products is used. In particular, it is desirable to use a composite oxide sintered body of silicon dioxide and silicon monoxide. In the case of a transparent conductive thin film, indium oxide or a composite oxide sintered body containing this as a main component and another metal oxide such as tin oxide is used. Especially ITO
It is desirable to use a sintered body of (a mixture of indium oxide and tin oxide). As described above, the ratio of indium oxide to tin oxide of ITO is 10% tin in terms of metal.
The following are desirable:

As a gas composition during sputtering, an inert gas such as argon, or a gas containing an inert gas such as oxygen as a main component to which oxygen, hydrogen and the like are added is used. The total gas pressure is 1 × 10 ^{−3 to} 3 × 1 in the case of a transparent barrier thin film.
0 ^-3 Torr is preferred. When it is smaller than 1 × 10 ^-3 Torr, the discharge becomes unstable, and when it is larger than 3 × 10 ^-3 Torr, the gas barrier property is deteriorated. In the case of a transparent conductive thin film, 3 × 10 ^{−3 to} 9 × 10 ⁻³ Torr is preferable. 3 x 10
^When it is less than ^-3 Torr, the alkali resistance is deteriorated, and when it is more than 9 × 10 ^-3 Torr, the sheet resistance is deteriorated, which is not practical. As for the gas ratio, for example, in the case of an ITO thin film, it is desirable to control the oxygen partial pressure within the range of 0.5 to 5% of the total gas pressure. If it is less than 0.5% or exceeds 5%, the resistance increases. The power supply used is DC (direct current),
Either RF (high frequency) may be used, but in the case of a transparent barrier thin film, RF is preferable from the physical properties of the target, and in the case of a transparent conductive thin film, DC is preferable from the viewpoint of productivity.
Sputtering is performed by controlling the power input to the target while taking into account the above conditions. RF 0.5 to 5 W / for transparent barrier thin film
It is desirable to form a film with a power density of about cm ² , and more desirably 1.1 W / cm ² or more. 0.
Becomes smaller than 5W / cm ² is insufficient barrier property and is preferably as power density is large, it is difficult to increase than 5W / cm ² from the target cooling capacity problem. The thickness of the thin film is 10 to 100 nm as described above.
Is preferable, and more preferably 20 to 60 nm. In the case of a transparent conductive thin film, it is desirable to form a film with a DC of about 0.1 to ² W / cm ² , and more desirably 1.2 W / cm ² or less. If it is less than 0.1 W / cm ² , productivity is extremely poor, and if it is more than ² W / cm ² , alkali resistance becomes insufficient. As described above, the thickness of the thin film is preferably 10 to 400 nm, more preferably 50 to 200 nm, further preferably 60 to 150 nm.
Is.

[0012]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto. The physical properties were evaluated by the following methods. [Oxygen gas barrier property] US made by Modern Control Co. O
It was measured using X-TRAN100 and displayed in units of cc / m ² / day. [Water vapor barrier property] It was measured according to the moisture permeability test method (cup method) JIS-Z-0208 of the moisture-proof packaging material. [Sheet resistance] The sheet resistance was measured according to the four-probe resistivity measurement method. [Light transmittance] Wavelength 550n with air as reference
The transmittance including the film substrate in m was expressed as a percentage. [Alkali resistance] The sample was dipped in a 5% sodium hydroxide aqueous solution for 10 minutes to observe the change in appearance, especially the presence or absence of peeling, and at the same time, the change in sheet resistance before and after the treatment was examined. That is, the sheet resistance before treatment was taken as R _O and that after treatment was taken as R, and the values of R / R _O were compared.

Example 1 125 μm polyarylate transparent film as a substrate, SiO _1.5 as a target for a transparent barrier thin film, and IT with a tin oxide ratio of 10% as a transparent conductive thin film target.
O, as a sputtering gas, the transparent barrier thin film is argon only, the total gas pressure is 1.0 mTorr, and the gas flow rate is 10 sccm. For the transparent conductive thin film, argon is added with 1% oxygen, the total gas pressure is 7 mTorr, and the gas flow rate is 20 sccm. As a transparent barrier thin film, RF400W (2.35W / c)
m ² ), DC0.6A250V for transparent conductive thin film
(0.88 W / cm ² ) so that the magnetron sputtering device (HSM-72 manufactured by Shimadzu Corporation)
The film was formed by the 0 type. Transparent barrier thin film is 1.5
The transparent conductive thin film having a thickness of 30 nm and the transparent conductive thin film was processed for 3 minutes to obtain a transparent conductive film having a thickness of 100 nm. Table 1 shows the measurement results of physical properties. As is clear from Table 1, sheet resistance 74 Ω / □, light transmittance 79%, oxygen gas barrier property 0.5 cc / m ² / day, water vapor barrier property 0.
A transparent conductive film having a sufficient alkali resistance of 5 g / m ² / day was obtained.

Comparative Example 1 The substrate film and other conditions were the same as in Example 1, and the film-forming power of the transparent conductive thin film was DC 1.6 A 250 V (2.
The film was formed at a power of 35 W / cm ² ). The transparent barrier thin film was treated for 1.5 minutes to a thickness of 30 nm, and the transparent conductive thin film was treated for 1 minute to obtain a transparent conductive film having a thickness of 100 nm. As is clear from Table 1, when the film forming power of the transparent conductive thin film exceeds ² W / cm ² , the sheet resistance is 45 Ω / □, the light transmittance is 79%, and the oxygen gas barrier property is 0.5 g / m ² / day. Although a transparent conductive film was obtained, the alkali resistance was insufficient and the thin film was peeled off, making it impossible to assemble a liquid crystal cell.

Comparative Example 2 The substrate film and other conditions were the same as in Example 1, and the process pressure for forming the transparent conductive thin film was 1 × 10 ⁻³ Torr. The transparent barrier thin film is treated for 1.5 minutes,
The thickness of 30 nm, the transparent conductive thin film is processed for 3 minutes, and the thickness is 10
A transparent conductive film having a thickness of 0 nm was obtained. As is clear from Table 1, the process pressure for forming the transparent conductive thin film is 3 × 1.
A transparent conductive film having a sheet resistance of 45 Ω / □, a light transmittance of 79%, an oxygen gas barrier property of 0.5 cc / m ² / day, and a water vapor barrier property of 0.5 g / m ² / day when it is less than 0 ^-3 Torr. However, since the pressure of the film forming process of the transparent conductive thin film was low, peeling by alkali occurred as in Comparative Example 1, and the liquid crystal cell could not be assembled.

[0016]

[Table 1] * Alkali resistance test is 10% for 5 wt% NaOH aqueous solution.
Changes in appearance and sheet resistance (R / R _o ) after immersion for a minute
Was observed.

[0017]

EFFECT OF THE INVENTION The transparent conductive film of the present invention has sheet resistance and light transmittance equivalent to or higher than those of transparent conductive glass, and has excellent gas barrier properties and water vapor barrier properties. Furthermore, by controlling the film forming conditions of the thin film, it has sufficient alkali resistance when used as a liquid crystal cell substrate. Further, since the transparent film substrate is used, it has features such as impact resistance, light weight, flexibility, easiness of increasing the area, and good workability.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Matsumoto 7-1, 1-1 Gakuen Nishimachi, Nishi-ku, Kobe City, Hyogo Prefecture Building 737 205

Claims (8)

[Claims] 1. A transparent barrier thin film (B) of a metal oxide mainly composed of silicon oxide or a metal nitride mainly composed of silicon nitride is formed on a transparent film substrate (A), and further thereon. A transparent conductive film comprising a transparent conductive thin film (C) of a metal oxide containing indium oxide as a main component. 2. The transparent barrier thin film (B) has a thickness of 10
The transparent conductive film according to claim 1, which has a thickness of -100 nm. 3. The transparent conductive thin film (C) has a thickness of 10 to 4.
It is 00 nm, The transparent conductive film of Claim 1 or 2. 4. The transparent conductive film according to claim 1, wherein the transparent barrier thin film (B) has an oxygen permeability of 1 cc / m ² / day or less and a water vapor permeability of 1 g / m ² / day or less. 5. The transparent conductive thin film (C) having a sheet resistance value of 1
It is less than 00 Ω / □ and the light transmittance including the transparent film substrate (A) and the transparent barrier thin film (B) is 7
It is 5% or more, The transparent conductive film of Claims 1-4. 6. The transparent conductive film according to claim 1, wherein the transparent film substrate (A) is a polyarylate film. 7. A transparent barrier thin film (B) of a metal oxide mainly composed of silicon oxide or a metal nitride mainly composed of silicon nitride is formed on a transparent film substrate (A) by a magnetron sputtering method. And a transparent conductive thin film (C) of a metal oxide mainly composed of indium oxide formed thereon by a magnetron sputtering method. Deposition power density of 8. on the target, 0.5~5.0W / cm ² in the case of transparent barrier film, if the transparent conductive thin film in 0.1~2.0W / cm ² Yes, the film forming process pressure is 1 × 10 ^{-3 for} a transparent barrier thin film
~3 × 10 ^-3 Torr, in the case of the transparent conductive thin film 3 × 10 ^-3
The production method according to claim 7, which is -9 x 10 ^-3 Torr.