JPH0112667B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing a transparent conductive film for use in transparent electrodes for liquid crystal devices, in which a conductive film mainly composed of indium oxide (hereinafter referred to as an ITO film) is added to a polymer. . Traditionally, transparent conductive films are mainly based on polyester films, and are used in transparent electrodes of electroluminescent displays and electrochromic displays, surface heating elements such as day frosters and transparent heaters, surface switches such as touch panels, and infrared reflective films. It is widely used in transparent flexible circuits, etc.
Recently, application to liquid crystal display elements is also being considered.

Transparent conductive films are advantageous in that they can be made thinner by using film-shaped electrodes, are easy to handle during the production process and can be processed by punching, and can be produced continuously from film-shaped element materials, which is cost-effective. It is attracting more attention than because it is advantageous.

Good transparency is one of the performance requirements for ordinary transparent conductive films. Furthermore, in order to use it as a transparent electrode for liquid crystals, thermal deformation and
It is necessary that poor conductivity and disconnection do not occur. Furthermore, it is absolutely necessary for a liquid crystal display element using a polarizing plate to have no optical anisotropy. For example, in the case of a uniaxially stretched polyester film that has optical anisotropy, the axis of optical anisotropy must strictly match the axis of the polarizing plate used in liquid crystal elements, resulting in very poor workability and yield. .

As a substrate film for a transparent conductive film that satisfies all of the above properties, we believe that polyether sulfone film is the most suitable film due to its excellent transparency, heat resistance, and lack of optical anisotropy.As a result, we conducted extensive research. Since a good transparent conductive film could be obtained, the method will be described below.

Generally, when forming a transparent conductive film on a plastic film, vapor deposition or sputtering methods are often used, but in the case of polyethersulfone, a transparent conductive film with good properties under the same conditions as other plastic substrates is used. A conductive film cannot be formed. This is because polyether sulfone differs from other plastics in the following points.

The moisture permeability of polyether sulfone film is ten times higher than that of polyester film, and in both vapor deposition and sputtering methods, a large amount of gas is generated from the film surface during work in a vacuum chamber, making it a good transparent conductor. A film cannot be formed. In addition, polyether sulfone contains a large amount of unreacted monomers, which deposit on the film surface when the film is heated during degassing or forming a conductive film, resulting in a decrease in the adhesion of the conductive film, etc. Cause. Furthermore, when producing with a continuous sputtering machine, the degree of vacuum decreases due to the released gas, making continuous production impossible.

We have found that gas released during thin film formation can be prevented by degassing the polyether sulfone film in advance. It has also been found that monomer precipitation can be prevented by undercoating one or both sides of the polyether sulfone film with an acrylic resin.

As for the above-mentioned degassing, a good transparent conductive film can be efficiently formed by performing it more completely.
However, on the other hand, these substances contained in the polyether sulfone film act as plasticizers in the film and impart flexibility to the film.
Therefore, if these are completely removed, the material becomes brittle and easily breaks or cracks when handled during processing. In order to avoid such poor processability, the film must have an elongation of 10% or more. However, if it exceeds 20%, a good transparent conductive film cannot be produced because of the gas released during the formation of the conductive film.

Figure 1 shows the relationship between the number of days of degassing treatment and elongation of polyether sulfone film, and Figure 2 shows the number of days of treatment and gauze abrasion resistance, which is a measure of adhesion. In FIG. 1, if the elongation is less than 10%, the film becomes brittle enough to crack when folded in two, which is not preferable. Therefore, elongation is required to be 10% or more. On the other hand, in Figure 2, when no undercoat is applied, the resistance change after gauze wear is 1.4.
However, if you apply an undercoat,
When degassing was carried out for one day or more, there was no noticeable change in resistance and the result was very good. As described above, by performing degassing treatment and further applying an undercoat so that the tensile elongation of the polyetherphone film is 10% or more, an industrially stable transparent conductive film with adhesion and flexibility can be obtained. be able to.

Both sides are coated with acrylic resin to a thickness of 5 μm.
Polyether sulfone film (100μ thickness 200mm
(width) was spread on an aluminum tube and treated in a dryer at 60°C for 8 days. As a result, the elongation at break of the film decreased from 60% to 10%, and the film was in a considerably degassed state. Using this film in a continuous vapor deposition device,
When ITO was deposited, even when the film was run at 1.0 m/min, the degree of vacuum did not exceed 1.0 x 10 ^-4 Torr, and deposition was possible in good conditions. When the ITO thus deposited was thermally oxidized at 180°C for 1 hour, an ITO film with good transparency and conductivity was obtained. Particularly good wear resistance, 100%
After rubbing 100 times with g/cm ² gauze, there was no noticeable change in resistance. When this transparent conductive film was bent, it did not crack or tear, and it maintained sufficient flexibility.
When a liquid crystal panel was produced using this transparent conductive film, it was possible to obtain a good plastic panel with good workability.

Example 2 Coated with acrylic resin to a thickness of 5μ,
The polyether sulfone film was placed in a vacuum dryer, vacuumed to 1×10 ⁻³ Torr, and heated with one iodine lamp for 36 hours. After that, the vacuum was broken and the elongation at break of the film was measured and was 10%.
It was hot. Next, quickly set the treated polyether sulfone film on the sputtering device,
The vacuum was pulled down to 1×10 ^-8 Torr, then Ar and O ₂
The reactive sputtering of ITO was carried out at 2×10 ^-3 Torr. The transparent conductive film obtained in this way has good transparency and resistance, and its abrasion resistance shows no change in resistance after 100 rubs with 100 g/cm ² gauze, and does not break even when bent. Flexibility was also good.

Comparative Example 1 Polyether sulfone film (100 μm thick) coated with acrylic resin on both sides to a thickness of 5 μm
When the film was wrapped around a 200 m aluminum tube and treated at 60°C for 10 days, and ITO was vapor-deposited using a continuous coater, the film broke during vapor deposition. In this case, the film elongation was 5%, which is thought to be because the polyether sulfone film had become brittle. When the film after vapor deposition was thermally oxidized to produce a transparent conductive film, the performance as a transparent conductive film was good, but when it was bent, it cracked and could not withstand subsequent processing.

Comparative example 2 Polyether sulfone film (100μ thickness)
It was wrapped around a 200 mm wide aluminum tube and treated in a dryer at 60°C for 8 days. A conductive film was formed on this film under the same conditions as in Example 1. In this case, when the wear resistance was examined, the change in resistance was 1.2 times, which was poor.

Comparative Example 3 Polyether sulfone film coated with acrylic resin on both sides to a thickness of 5 μm (100 μm thick)
was wrapped in a 200 m aluminum tube and treated in a dryer at 60°C for 5 days. In this case, the film elongation was 32%. A conductive film was formed on this film under the same conditions as in Example 1. In this case, the sheet resistance value of Example 1 was 300Ω/□, but 1000Ω/□
This resulted in high resistance. The scratch resistance was also poor.

For the above reasons, the tensile elongation is 10 to 20 after degassing.
%, a transparent conductive film with the best properties was obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the number of days of degassing treatment and the change in elongation of polyether sulfone film.
FIG. 2 is a diagram showing the relationship between the number of days of degassing treatment of a polyethersulfone film and gauze abrasion resistance, and the vertical axis is a diagram showing the rate of change in resistance before and after gauze abrasion.

Claims (1)

[Claims] 1 An undercoat layer is provided on one or both sides of a polyether sulfone film, degassed so that the tensile elongation of the undercoated polyether sulfone film becomes 10 to 20%, and further indium oxide is added on top of the undercoat layer. A method for producing a transparent conductive film, the method comprising forming a film containing as a main component.