JPH02191640A - Method for treating surface of polyester film with plasma - Google Patents

Abstract

PURPOSE:To obtain a film excellent in adhesion of transparent electrically conductive films in a simple process without depositing low-molecular compounds by homogeneously subjecting the surface of a polyester film to plasma treatment with high-frequency discharge. CONSTITUTION:One or both surfaces of a saturated polyester film are subjected to plasma surface treatment with high-frequency discharge in an atmosphere under 0.01-5Pa pressure. In carrying out the surface treatment with the plasma, an inorganic gas is introduced into a vacuum vessel in an atmosphere under reduced pressure to apply a high-frequency voltage to the inner electrodes, carry out discharge and generate a plasma, which is then made to collide with the surfaces of the film, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for plasma treating the surface of a polyester film. More specifically, the present invention relates to a method for obtaining a highly transparent polyester film by preventing precipitation of low-molecular compounds from polyester onto the surface of the film during heating and exothermic conditions.

[Prior Art] Polyester film has excellent mechanical properties, dimensional stability, heat resistance, chemical stability, and good electrical properties, so it is used as electrical insulating materials, gold and silver threads, magnetic recording tapes, and drafting films. , has been applied to photographic film, etc., and recently it has been applied to electrical and
Transparent conductive films have been developed as electronic components.

Examples of the use of the transparent conductive film include electrodes of display elements, touch panels, photoelectric conversion elements, planar heating elements, electromagnetic shields, and the like.

To manufacture this transparent conductive film, a method utilizing vacuum such as a vacuum evaporation method, a sputtering method, an ion blating method, etc. is used, and a transparent conductive thin film is provided on at least one side of the polyester film.

Transparent conductive films manufactured by these methods have transparency,
It has properties such as conductivity, thinness, weight reduction, impact resistance, flexibility, large area, and workability, and is used for various purposes.
In applications that involve heating or generating heat, there is a problem in that low-molecular compounds precipitate from the polyester film, impairing transparency.

Examples of these include electrodes for display devices such as liquid crystals and electroluminescence, touch panels, and charge conversion elements such as solar cells, which are heated to high temperatures during the processing process; In planar heating elements such as cases, because heat is generated repeatedly, low-molecular compounds may precipitate from the polyester film, impairing its transparency.

Conventionally, as a countermeasure against this problem, a curable polymer layer by coating or a barrier layer such as a metal oxide by vapor deposition is formed on both or one side of the polyester film to prevent the precipitation of low-molecular compounds. A method of forming a transparent conductive film on one side has been used. However, this method requires additional processing steps such as coating and vapor deposition, resulting in high manufacturing costs.
There is also a problem with the adhesion between the polyester film and the barrier layer.

Furthermore, there is a method in which polyester resin is subjected to solid phase polymerization under special conditions to remove low molecular weight compounds, and then melt-extruded and stretched to form a film. However, this method has the drawback of high production costs due to the complexity of the polymerization process and long polymerization time.

[Problems to be Solved by the Invention] As described above, the conventional method for preventing the precipitation of low molecular weight compounds from polyester films has the problems of increasing processing steps;
There were problems with the adhesion between the polyester film and the barrier layer, high manufacturing costs, etc.

The present invention provides a treatment method that solves the above-mentioned problems and can continuously and easily treat the surface of a polyester film uniformly and prevent precipitation of low-molecular compounds.

[Means for Solving the Problems] The present inventors have developed various surface treatment methods for preventing the precipitation of low-molecular-weight compounds on polyester films, which have simple processing steps, good adhesion to transparent conductive films, etc., and low production costs. As a result of our investigation, we found that the conventional problems could be solved by a method in which the surface of a polyester film was treated with plasma using high-frequency discharge.

The present inventors investigated various surface treatment methods that have been reported in the past, and found that by introducing an active or inert gas into a vacuum container under a reduced pressure atmosphere and creating a plasma state by high-frequency discharge, the polyester film was When the surface was treated with plasma, the surface of the polyester film was cross-linked and sputter-etched by the plasma, so even when heated at 150℃ for 3 hours, there was no precipitation of low-molecular compounds, and the light transmittance decreased. It turns out that there are few
We have arrived at the present invention.

Hereinafter, the present invention will be explained in detail.

Polyester is a polymer having ester bonds in its molecular structure, and is broadly classified into saturated polyester and unsaturated polyester. Saturated polyester is a linear polyester and is thermoplastic, while unsaturated polyester is thermosetting and undergoes a crosslinking reaction to cure. The present invention targets films of the former saturated polyester, specifically films of polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene terephthalate, and the like.

In the surface treatment method of the present invention, in a polyester film,
Any of non-stretched film, -axially stretched film l2, and biaxially stretched film can be applied.

These polyester filters are made by melt extrusion, calendering, casting, etc.
In addition to the polyester, it may contain appropriate amounts of desired additives, such as pigments, fillers, lubricants, ultraviolet absorbers, and stabilizers, if necessary.

Furthermore, a composite film obtained by laminating films with different stretching processes may also be used.

In the present invention, the surface of the polyester film as described above is subjected to plasma surface treatment.

For plasma surface treatment, an inorganic gas is introduced in a vacuum container under a reduced pressure atmosphere, and a high-frequency voltage is applied to the internal electrodes to generate a discharge, resulting in plasma (ions, electrons, excited molecules, radicals, This is done by colliding ultraviolet light, etc.) onto the surface of a film, etc.

A suitable surface treatment device is one in which an inductively coupled electrode or a capacitively coupled electrode is provided in a vacuum container and connected to a high frequency power source via a matching box. This treatment may be carried out either batchwise or continuously.

In the present invention, the surface of the polyester film is subjected to plasma treatment under a reduced pressure atmosphere of 0.01 to 5 Pa. When the atmospheric pressure is lower than 0.01 Pa, the pressure tends to fluctuate due to the influence of degassing from the polyester film.
Moreover, when it exceeds 5 Pa, the discharge becomes unstable, which is not preferable.

The discharge power is generally within the range of 0.1 to 10 W/eJ. The processing time is approximately 1 to 600 seconds. As a high frequency power supply, it is usually several hundred kHz to several tons MIlz.
Use a frequency of . For example, "Practical" 2, 13.
Preferably, a 56 MHz power supply is used.

Various gases can be used as the atmospheric gas during plasma surface treatment, including argon, helium, oxygen,
Nitrogen, carbon dioxide gas, etc. are preferred.

"Example" Hereinafter, a detailed description will be given based on examples.

Example 1 Biaxially oriented polyethylene terephthalate (#100 manufactured by Diafoil ■) with a thickness of 100 μm was made into a predetermined size (10 emφ
) and subjected to plasma surface treatment using the apparatus shown in FIG. First, the same polyethylene terephthalate film 8 is placed on -L of the substrate support stand 7 in the vacuum container 1 of the apparatus shown in FIG. Then, a vacuum pump (not shown) connected to the exhaust pipe 2 pumps the inside of the device to 0.00.
1. After reducing the pressure to below Pa, open the gas introduction valve 3, introduce argon gas, and reduce the atmospheric pressure in the vacuum container 1 to 1.
1) Adjust to a and maintain the pressure inside the vacuum container 1 at this pressure.

Next, a high frequency voltage with a frequency of 1356 MHz is applied from the high frequency power supply 6 to the coil electrode 4 via the matching box 5, and one side surface of the polyethylene terephthalate is subjected to plasma surface treatment for 10 seconds using the discharge power IW/C. do.

Thereafter, the polyethylene terephthalate film on the substrate support 7 is turned over, and the gas introduction valve 9 is opened to introduce oxygen gas to the surface that has not been subjected to plasma surface treatment using the high-frequency ion blating method, and the atmospheric pressure is reduced to 0. 07P
a, the mixture 12 of indium oxide and tin oxide in the hearth J1 is evaporated by the electron gun 10, and the film thickness is about 3.
00 people obtained the transparent conductive film of Example 1.

Examples 2-8. Comparative Example 1 Approximately 300 people deposited a mixture of indium oxide and tin oxide 12 in the same manner as in Example 1 except that the plasma surface treatment conditions were set as shown in Table 1. A transparent conductive film was obtained.

Comparative Example 2 About 300 people deposited a mixture of indium oxide and tin oxide on a polyethylene terephthalate film, neither of which had plasma surfaces, using the high-frequency ion blating method in the same manner as in Example 1 to obtain a transparent conductive film. Ta.

In order to investigate the effect of preventing precipitation of low molecular weight compounds from the polyethylene terephthalate film surface after plasma surface treatment in the transparent conductive films of Examples 1 to 8 and Comparative Examples 1 to 2, each was heated at 150°C for 3 hours with hot air circulation. After heating in a thermostatic oven, use a haze meter (Suga Test Machine)
), the haze value was determined. (JIS K-8714
) Also, using a spectrophotometer (Hitachi ■), wavelength 20
Continuously measure light transmittance in the 0-900 nm region,
The light transmittance at a wavelength of 5500 cm was determined from the recording chart. The obtained results are also shown in Table 1.

7: 8; 9: 11: 12: 13: board support stand polyester film Gas introduction valve 10: Electron gun hearth Indium oxide and tin oxide mixture electron gun power supply

Claims (1)

[Claims] 0.01 on one or both sides of the saturated polyester film
A plasma surface treatment method for a polyester film, characterized in that the surface treatment is performed by high frequency discharge under an atmospheric pressure of ~5 Pa.