JPH06320661A - Production of transparent conductive film - Google Patents

Abstract

PURPOSE:To provide a transparent conductive film having low resistance and high visible light transmissivity by forming the transparent conductive layer on a plastic substrate at the thermal deterioration temp. of the plastic substrate or lower and subsequently applying specific heat treatment to the conductive layer. CONSTITUTION:A transparent conductive layer is provided to a plastic substrate at the thermal deterioration temp. of the substrate or lower. The transparent conductive layer is formed from metal oxide such as Sn added In2O3, Sb added SnO2 or F added SnO2 by a vapor deposition method, a sputtering method, an ion plating method, a CVD method and a spray method. At this time, the transparent conductive layer is formed at the thermal deterioration temp. of the substrate or lower, for example, at temp. of 100 deg.C or lower. Thereafter, the plastic substrate having the transparent conductive layer provided thereto is heat-treated for 15min at temp. of 80 below 150 deg.C under vacuum of 1Torr or less. By this method, the transparent conductive film having low resistance and high transmissivity can be easily obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a transparent conductive film.

[0002]

2. Description of the Related Art In ₂ O ₃ , Z on a substrate
A transparent conductive thin film provided with a layer of a conductive material such as nO or SnO ₂ is widely used in the fields of liquid crystal displays, touch panels, sensors, transparent electrodes in solar cells and the like.

In the case of a liquid crystal display, for example, the transparent conductive thin film substrate is being replaced by a conventional glass substrate by a plastic substrate from the viewpoints of thinning, weight reduction and impact resistance improvement.

By the way, the quality of the transparent conductive thin film is determined by the specific resistance value of the film. For example, in a liquid crystal display, a transparent conductive thin film having a smaller specific resistance value is required with an increase in area and display density. It's starting to happen.
Similarly, in other applications, it is required to make the specific resistance value smaller. In the case of a glass substrate, crystallization of the film by heating (ITO film is 150
The above method was effective. However,
Since the plastic substrate has poor heat resistance, such heat treatment cannot be performed.

At present, a sputtering method is mainly used as a method for producing a transparent conductive thin film, but as a technique for reducing the resistance of a film by the sputtering method, quadrupole sputtering is performed, and further discharge by increasing the magnetic field of the cathode portion. Techniques such as lowering impedance and sputtering at low voltage have been developed. However, since the former uses a hot filament, there is a problem that the substrate is deteriorated due to its heat radiation, the surroundings of the cathode are complicated by providing a heat shield plate, and the operability is deteriorated.
In the latter case, it is effective to reduce the resistance to some extent,
It is not enough to obtain sufficiently low resistivity.

[0006] Further, when the above-mentioned method of reducing the resistance is performed, visible light transmittance can be obtained to some extent, but it is difficult to obtain high transmittance (85% or more) at present.

Therefore, it is an object of the present invention to provide a method for obtaining a transparent conductive film having low resistance and high visible light transmittance.

[0008]

Means for Solving the Problems The present inventors have found that when a transparent conductive layer is formed on a plastic substrate at a temperature not higher than its heat deterioration temperature and then subjected to a specific heat treatment, it is transparent with low resistance and high transmittance. The inventors have found that a conductive film can be obtained, and completed the present invention.

That is, according to the present invention, in a method for producing a transparent conductive film in which at least a transparent conductive layer is provided on a plastic substrate, after the transparent conductive layer is provided on the substrate at a temperature not higher than the heat deterioration temperature of the plastic substrate, 80 The present invention provides a method characterized by performing a heat treatment for 15 minutes or more at a temperature of less than 150 ° C and a vacuum degree of 1 Torr or less.

Examples of the plastic substrate used in the present invention include polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides,
Substrates made of polyvinyl chloride, polycarbonate, polystyrene, polypropylene, polyethylene and the like (including copolymers in addition to homopolymers) can be mentioned. Further, the substrate may be a laminated body containing two or more of these. The thickness of the substrate is
Although it depends on the application, it is usually 1.0 to 1000 μm.

As the transparent conductive layer, a conventional transparent conductive layer material such as a metal oxide can be used. Specifically, for example, Bi ₂ O ₃ , TiO ₂ , SnO ₂ , CdO,
ZnO, ZrO ₂ , CTO system (CdSnO ₃ , Cd ₂ S
nO ₄ , CdSnO ₄ ), In ₂ O ₃ , CdIn
₂ O ₄ , In ₂ TeO ₆ , WO series, MoO ₃ series, NiO
System, IrO system and the like. A complex (doped) phase in which one or more selected from Sn, Sb, W, Mo, F, As and Al is added to the above metal oxide is preferable. Among them, preferable ones are In ₂ O ₃ (ITO) containing Sn, SnO ₂ containing Sb,
For example, SnO ₂ with F added. As the transparent conductive layer, these layers can be used as a single layer or multiple layers. The layer thickness is
Although it depends on the material, for example, the ITO layer is 300 to 3
500 angstroms is preferable, and 3 is more preferable.
60 to 3100 angstroms. The sheet resistance of the transparent conductive layer is not particularly limited as long as it is 400Ω / □ or less.

Optionally, between the substrate and the ITO film,
For example, a SiO ₂ layer can be provided as the protective layer.

In the method of the present invention, the transparent conductive layer is first formed. As a film forming means, a known film forming method,
For example, vapor deposition method, sputtering method, ion plating method,
A CVD method, a spray method or the like can be used. At that time, film formation is performed at a temperature not higher than the heat deterioration temperature of the substrate, for example, a temperature not higher than 100 ° C. As other conditions, conventional film forming conditions can be used.

In the present invention, the transparent conductive film obtained as described above is heat-treated under specific conditions. That is,
Heat treatment is performed at a temperature of 80 to less than 150 ° C., preferably 100 to less than 150 ° C. and a vacuum of 1 torr or less, preferably 0.1 torr or less for 15 minutes or more, preferably 30 minutes or more. A higher heat treatment temperature is advantageous for lowering the resistance, but since the heat resistant temperature of the plastic substrate has an upper limit, it is effective to select the maximum possible temperature within the above range depending on the type of plastic. Such heat treatment can be performed in a commercially available simple vacuum oven. If the heat treatment temperature is too low, the resistivity decreases and the transmittance also decreases. Further, when the degree of vacuum exceeds 1 Torr, the progress of oxidation deteriorates the resistivity. The upper limit of time is not particularly limited, but it is usually 2 hours or less.

The above heat treatment reduces strain and impurities in the film, and thus increases the transmittance.

The transparent conductive film produced by the method of the present invention is used for photoelectric conversion such as solar cells and photosensors; for display devices such as liquid crystal, electroluminescence, electrochromic and EL; for buildings, automobiles, aircraft, Heat ray reflection applications for various windows such as furnace peep windows, variable light blocking applications for visible light,
It can be used in a wide range of fields such as anti-fogging and anti-icing applications; antistatic applications; touch switch applications; optical communication applications.

[0017]

The present invention will be described in more detail by the following examples. Examples 1 to 8 A substrate transport passage type (in-line type) DC planar type magnetron sputtering apparatus (U
The film was formed by sputtering by using LVAC). Using a powder sintered body of In ₂ O ₃ and SnO ₂ (weight ratio 90:10) as a target, an initial vacuum degree of 5 × 10 ⁻⁶ torr or less, gas type Ar + O ₂ (160 SCCM: 0.5 to 4.5 SCC)
M), gas pressure 4 × 10 ^-3 torr, target input power 3.
An ITO film having a film thickness of 1200 Å was formed under the conditions of 5 W / cm ² , leakage parallel magnetic flux density on the target of 1100 gauss (based on the conventional strong cathode magnetic field), and substrate transfer speed of 0.8 m / min.

The transparent conductive film thus obtained was heat-treated under the conditions shown in Table 1 using a commercially available vacuum oven (made by Yamato Scientific Co., Ltd.). The resistivity of the transparent conductive film after the heat treatment was measured with a Hall effect measuring device, and the transmittance was measured with a haze meter. The results are shown in Table 1. Comparative Examples 1 to 4 Transparent conductive films were produced in exactly the same manner as in Examples 1 to 4, but no heat treatment was performed after the film formation. Table 1 shows the resistivity and the transmittance of the transparent conductive film. Comparative Examples 5-8 Transparent conductive films were produced in exactly the same manner as in Examples 5-6. Then, heat treatment was performed under the conditions shown in Table 1.
Table 1 shows the resistivity and the transmittance of the transparent conductive film after the heat treatment.

[0019]

[Table 1]

[0020]

According to the present invention, a transparent conductive film having a low resistance and a high transmittance can be easily obtained. Therefore, the method of the present invention is industrially useful.

Claims (1)

[Claims] 1. A method for producing a transparent conductive film in which at least a transparent conductive layer is provided on a plastic substrate, the transparent conductive layer is provided on the substrate at a temperature not higher than the heat deterioration temperature of the plastic substrate, and then 80 to 150 ° C. A method characterized by performing a heat treatment for 15 minutes or more at a temperature of less than 1 torr and a vacuum degree of 1 Torr or less.