JPH05262371A - Transparent gas barrier film - Google Patents

Abstract

PURPOSE:To improve the transparency, gas barrier property and retort property as well by coating a silicon oxynitride film on the surface of a transparent plastic film for the title film for food packaging. CONSTITUTION:A polyester film with a thickness of approximately 12mum is made to be a base material, and on the surface of one side, a silicon oxide nitride film with a thickness of approximate 1000Angstrom is vapor-deposited by the sputtering process. This film keeps an excellent gas barrier property even when being exposed under a high temperature and high humidity, and the permeability of which in a visible light area shows 80% or higher at a wavelength of 370-1100nm the same as a conventional single layer polyester film. Also, the values of (x) and (y) for the silicone oxide nitride Si0xNy shall be made to be (x)=0.6-0.8, (y)=0.7-0.9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent gas barrier film, and more specifically, a transparent gas barrier film having transparency and gas barrier properties used as a packaging material for foods, pharmaceuticals and the like and having retort resistance. Regarding

[0002]

2. Description of the Related Art Conventionally, as a packaging material for preventing alteration of contents such as foods and pharmaceuticals, polyvinylidene chloride-coated polyester film having a small gas permeability such as oxygen and water vapor, so-called gas barrier property, ethylene. Plastic films such as vinyl alcohol copolymer films are known.

Further, when a higher gas barrier property is required, an aluminum vapor deposition film is known in which a metal foil such as an aluminum foil is attached to the surface of a plastic film, or aluminum is vacuum vapor deposited.

[0004]

However, although plastic films such as polyvinylidene chloride coated polyester film and ethylene vinyl alcohol copolymer film have excellent transparency, their gas permeability, which should be small, is low in temperature and humidity. Is significantly susceptible to the influence of the above, that is, such a plastic film has temperature and humidity dependency on gas barrier property, and therefore the gas barrier property is remarkably lowered under high temperature and high humidity. Therefore, there is a problem that it cannot be used especially for retort products in the field of food packaging.

Further, a laminated film obtained by sticking a metal foil such as an aluminum foil or depositing a metal thin film such as an aluminum thin film on the surface of a plastic film is excellent in gas barrier property under high temperature and high humidity, but aluminum or the like. Since it is covered with the metal material, there is a problem that it is not transparent, the packaged contents cannot be seen, and it cannot be heated by a microwave oven.

An object of the present invention is to solve the above problems and provide a transparent gas barrier film having transparency and gas barrier property and having retort resistance.

[0007]

The transparent gas barrier film of the present invention is characterized in that the surface of a substrate made of a transparent plastic film is coated with a silicon oxynitride film.

[0008]

[Function] Since the silicon oxynitride film coated on the surface of the base material has little temperature and humidity dependency on the gas barrier property, the film coated with the silicon oxynitride film has high gas permeability even under high temperature and high humidity. small. Further, the silicon oxynitride film does not lose transparency unlike a metal material such as aluminum.

[0009]

EXAMPLES Specific examples of the present invention will be described below.

Example The transparent gas barrier film of this example has a thickness of 12 μm.
A polyester film of m was used as a base material, and a 1000 Å-thick silicon oxynitride film was deposited on the surface (one side) of the base material by a sputtering method.

Further, the deposition of silicon oxynitride by the sputtering method is performed by high frequency discharge using a magnetron cathode, the sputtering gas at the time of the sputtering discharge is argon (Ar) gas, and the targets are Si ₃ N ₄ and S.
iO ₂ mixed target (mixing ratio 80:20 atm
%, Shin-Etsu Chemical Co., Ltd., trade name NS target).

The permeability of oxygen and water vapor of the prepared coating film of the silicon oxynitride film was examined, and the oxygen permeability was 0.77 cc / m ² · day,
The water vapor permeability is 0.99 at 40 ° C and 90% RH.
It was g / m ² · day.

The produced coating film of the silicon oxynitride film was measured with a spectrometer Ubest-30 type (manufactured by JASCO Corporation) so that the wavelength in the visible light region was 200 nm to 1100 n.
The light transmittance was examined for each wavelength while changing to m. The result of the examination is shown as a curve A in FIG.

Conventional Example A commercially available polyvinylidene chloride coated polyester film has an oxygen permeability of ^{2 to} 8 cc / m ² · day and a water vapor permeability of ^{2 to} 10 g / m ² · da at 40 ° C. and 90% RH.
a y, oxygen permeability of the ethylene-vinyl alcohol copolymer film ^{1~3cc / m 2 · day, 30~100g} / m 2 · In steam moisture permeability 40 ° C. 90% RH
It is day.

Further, a commercially available polyester film having a thickness of 12 μm was measured with a spectroscope Ubest-30 type (manufactured by JASCO Corporation) so that the wavelength in the visible light range was 200 nm to 1100.
The light transmittance was examined for each wavelength while changing to nm. The examined result is shown as a curve B in FIG.

As described above, the film comprising the polyester film and the silicon oxynitride film of the present invention has an excellent gas barrier property even when exposed to high temperature and high humidity, and as is clear from FIG. Despite the fact that the surface of the base material is covered with a silicon oxynitride film, it has a transmittance in the visible light range of 370 to 110 as in the case of a conventional single-layer polyester film.
It had a transmittance of 80% or more at a wavelength of 0 nm, and was confirmed to have high transparency.

Further, in the above-mentioned embodiment, the formation of the coating of the silicon oxynitride film on the substrate made of the transparent plastic film is one side, but the present invention is not limited to this.
The coating of the silicon oxynitride film may be formed on both the front and back surfaces of the base material.

The composition of the silicon oxynitride (SiOxNy) film coated on the surface of the substrate is Si ₃ N ₄ and S which are targets used when the substrate is deposited by sputtering.
The x value and the y value in the silicon oxynitride (SiOxNy) film are not necessarily constant depending on the mixing ratio of iO ₂ , discharge, sputtering voltage, pressure, etc., but generally x = 0.6 to
The various conditions during sputtering may be adjusted so that 0.8 and y = 0.7 to 0.9.

[0019]

According to the present invention, since the silicon oxynitride film has little temperature or humidity dependency on the gas barrier property, the film obtained by coating the transparent plastic film surface with the silicon oxynitride film under high temperature and high humidity. However, the gas barrier property does not deteriorate, and it has excellent transparency unlike conventional films such as aluminum foil or other metal foil adhered or aluminum thin film or other metal thin film deposited, and it can be heated in a microwave oven etc. It has an effect that treatment can be performed.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the wavelength of light and the transmittance of a transparent gas barrier film of one example of the present invention and a conventional example.

Claims (1)

[Claims] 1. A transparent gas barrier film, characterized in that the surface of a substrate made of a transparent plastic film is coated with a silicon oxynitride film.