JPS6338423B2 - - Google Patents

Description

[Detailed Description of the Invention] Conventionally, as a method for producing an indium oxide transparent conductive film, indium oxide is evaporated by electron beam heating at a temperature that promotes oxidation, that is, 200°C.
Although a method of vacuum evaporation on a substrate heated to above ℃ is known, the indium oxide transparent conductive film obtained by this method is thermally unstable and cannot be used, for example, as a transparent electrode for a liquid crystal display. In this case, the transmittance of the film after undergoing various heat treatments during the process of assembling it into a liquid crystal cell is approximately 2% lower than that of the film before the heat treatment.
It was observed that the resistivity had the disadvantage of increasing by a factor of 2 to 3.

The present invention eliminates the drawbacks of such an indium oxide transparent conductive film, and provides an indium oxide transparent conductive film that has good thermal stability and retains its initial high transmittance and low specific resistance even after the heat treatment. This method provides a manufacturing method in which indium or indium oxide is heated and evaporated under vacuum, and then heated or not heated.
The method is characterized in that after being deposited on a substrate heated to 100°C or less, the deposited film is heated to 300°C or more in the air or an oxidizing atmosphere.

Next, examples of the present invention will be described in detail.

In the present invention, indium oxide refers to In ₂ O, InO,
In ₂ O ₃ alone or combined _with SnO _{2 -} SnO ₂
(ITO), but for example, usually In ₂ O ₃
ITO containing 5 to 10% SnO ₂ as a dopant is used as an evaporation source, and is evaporated onto the surface of an arbitrary substrate such as synthetic resin, glass, or porcelain under vacuum by heating with an electron beam or the like. In this case, the process is carried out in an atmosphere with an oxygen partial pressure of 0 to 5 × 10 ^-4 Torr, in which case the substrate is not heated or at a temperature that does not promote oxidation, i.e.
Keep the temperature below 100℃. Deposition rate is 1-5 Å/sec
Then, electron beam evaporation is performed on the unheated substrate. The thickness of the resulting deposited film is generally 200 to 500 Å. Next, the vapor deposited film obtained in this way is taken out and heated in an electric furnace in the air or in an oxygen atmosphere, and the vapor deposited film is heated to 300°C or higher, usually around 500°C.
The process is completed by heating for 30 minutes to 2 hours.

In the above method, the visible light transmittance of the deposited film (thickness: 400 Å) when deposited on an unheated substrate is 30.
~40%, and the sheet resistance is extremely large at over 10KΩ/sq.
When heated to ℃, the visible light transmittance of the deposited film including the glass substrate increases to 84% (at 550 nm), and the sheet resistance becomes extremely small, approximately 120Ω/sq or less, resulting in good transparency and conductivity. Obtained as a film with properties. (See FIGS. 1 and 2) The inventor conducted a reheat treatment test in which the thus obtained vapor deposited film was reheated, and obtained the results shown in FIG. 3. That is, the high transmittance (at 550 nm) and small sheet resistance shown in FIGS. 1 and 2 before the reheat treatment are almost unchanged as shown in curve A and curve B, respectively, as shown in FIG. It maintained both good characteristics. When using soda lime glass as a substrate, heating up to 550°C is preferred. For comparison,
When a similar reheat treatment test was conducted on a deposited film obtained by performing vacuum evaporation using the same electron beam heating as above with the substrate heated to 200°C or higher, the curve
As shown in curve A' and curve B', it was found that the transmittance and sheet resistance, especially the sheet resistance, were significantly deteriorated by the heat received by the reheat treatment. Note that the initial vapor deposition of this method may be performed using resistance heating using a Mo basket using indium as a raw material, or it may also be possible to create a film without introducing any oxygen into a vacuum and then perform the heat treatment described above. I can do it.

As is clear from the above, according to the present invention, when indium oxide is vacuum-deposited on a substrate, the indium oxide is deposited on the substrate without heating it or at a temperature that does not promote oxidation during deposition, that is, 100°C or less. Since the deposited film was heat-treated to a temperature of approximately 300°C or higher, it has the effect of providing a deposited film with good thermal stability.

[Brief explanation of the drawing]

Figures 1 and 2 are characteristic curves of transmittance and sheet resistance of the indium oxide vapor deposited film in this method treatment,
FIG. 3 shows a comparison diagram with a conventional method showing the effects of the present invention. A... Transmittance characteristics of the film obtained by this method, B... Sheet resistance characteristics of the film obtained by this method, A'... Transmittance characteristics of the film obtained by the conventional method, B'... Sheet resistance characteristics of the film obtained by the conventional method.

Claims (1)

[Claims] 1. After heating and evaporating indium or indium oxide in a vacuum, depositing it on a substrate that is not heated or heated to 100°C or less, and then heating the deposited film to 300°C or more in the air or an oxidizing atmosphere. Characteristic manufacturing method for indium oxide transparent conductive film.