JPH04366142A - Gas barrier film and production thereof - Google Patents

Abstract

PURPOSE:To produce a gas barrier film useful in applications where gas barrier properties are required such as in retortable pouch packaging. CONSTITUTION:A gas barrier film is produced by forming a thin layer comprising at least 90wt.% component consisting of Si and Si oxide and 0.1-10wt.% at least one material selected from the group consisting of an alkali metal, an alkaline earth metal, and other basic material on at least one side of a plastic film.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas barrier film suitable for use as a packaging film for retort foods, etc., and a method for producing the same.

0002

2. Description of the Related Art Conventionally, gas barrier films manufactured by dry processes such as vapor deposition methods include aluminum vapor-deposited films. For example, a film made by depositing aluminum to a thickness of about 1000 angstroms on at least one side of a plastic film and then hard-coating and laminating the film is used as a food packaging film. However, the gas barrier properties of the thin film obtained by aluminum vapor deposition are 1 to 10 cc/m2.
・It is about 24 hours/ATM, which is not enough.

[0003] Furthermore, as a gas barrier film provided with a thin film of an inorganic oxide, there is a film in which SiO is vapor-deposited. For example, a plastic film in which SiO is deposited to a thickness of about 700 angstroms on at least one side is hard-coated and laminated to be used as a food packaging film. However, SiO is expensive due to its high material cost. Also, Si, SiO, S
In the vapor deposition method using a mixed material of iO2, an inorganic oxide thin film having a dense structure cannot be obtained due to scattering of the material, increase in the degree of vacuum, etc. Furthermore, the gas barrier property is 1 to 10cc.
/m2・24hr・atm, which is not sufficient.

0004

[Problems to be Solved by the Invention] As mentioned above, the gas barrier properties of conventional surface-deposited gas barrier films do not reach a fully satisfactory level, and the materials used for vapor deposition are expensive and have a dense structure. There were some difficulties, such as the inability to obtain a vapor-deposited thin film having . The present invention deals with material scattering,
The purpose of this invention is to provide a gas barrier film that does not substantially increase the degree of vacuum, uses relatively inexpensive materials, and has excellent gas barrier properties.

[0005]

[Means for Solving the Problems] To summarize, the present invention (
a) Si and/or oxide of Si, and (b) (
i) alkali metal, (ii) alkaline earth metal, (ii)
It consists of at least one substance selected from the group consisting of i) an alkali metal compound and (iv) a substance that is substantially basic, and (a) is 90% by weight or more and (b) is 0% by weight based on the entire thin film. The present invention relates to a gas barrier film characterized in that at least one surface of a plastic film is coated with an inorganic thin film of .1 to 10% by weight.

The present invention also provides a method for manufacturing a gas barrier film by coating at least one surface of a plastic film with an inorganic thin film using a dry process such as a vapor deposition method or a sputtering method. oxide, and (b)
(i) alkali metal, (ii) alkaline earth metal, (i)
ii) Comprised of at least one substance selected from the group consisting of an alkali metal compound and (iv) a substantially basic substance, where (a) is 90% by weight or more and (b) is 0.1 to 10% by weight. % of the composition of the gas barrier film.

[0007] The plastic film that can be used in the practice of the present invention is formed by extruding an organic polymer in the form of a solution or melt by a conventional method, and stretching the film in the longitudinal direction and/or the transverse direction if necessary. . Representative examples of organic polymers include polyester, polyethylene, nylon 6, polyamide, polyimide, and the like. The thickness of the film used can vary widely depending on the application, but is generally 5 to 100 μm.

The gas barrier film of the present invention is obtained by coating at least one surface of such a plastic film with an inorganic thin film having the above composition. The thickness of this thin film also varies depending on the application, but generally it is 5 to 5,000.
angstrom, preferably 100 to 2000 angstrom.

In the present invention, Si and/or Si
These oxides are used, but the two are usually used in combination. However, the mixing proportion of both can vary over a wide range (Si=0-100% by weight). Note that examples of Si oxides include SiO, SiO2, and mixtures thereof.

In the present invention, in addition to such Si-based substances, (i) alkali metals, (ii) alkaline earth metals, (
It is necessary to use at least one substance selected from the group consisting of iii) an alkali metal compound and (iv) a substantially basic substance. Examples of (i) include Na, K, etc.; examples of (ii) include Mg, Ca,
Examples of (iii) include sodium hydroxide,
Examples include sodium silicate, sodium orthosilicate, sodium metasilicate, and sodium tetraborate. Substantially basic substances in (iv) include basic aluminum chloride, Al2+n(OH)2nCl6, MgO
, BaO, etc.

In the present invention, in order to form the inorganic thin film on the plastic film, it is preferable to use a method (dry process) in a high vacuum chamber such as vapor deposition or sputtering. Vapor deposition methods include resistance heating, induction heating,
This is a method in which the material in a crucible is heated and evaporated using electron beam heating or the like, and is deposited as a thin film on a substrate (plastic film). At that time, the heating temperature and heating method differ depending on the material and purpose, and the most suitable one is selected. Alternatively, a reactive vapor deposition method may be used in which a reactive gas such as oxygen is introduced into a vacuum chamber to cause an oxidation reaction. Sputtering is a method in which a discharge gas (Ar, etc.) is introduced into a vacuum chamber, and a high-frequency voltage or DC voltage is applied between the target and the substrate (plastic film) to turn the discharge gas into plasma, which collides with the target and scatters the material. In this method, the film is deposited as a thin film on the substrate. It is also possible to use a reactive sputtering method in which a reactive gas such as oxygen is introduced to cause an oxidation reaction.

[0012] All of these various dry process methods are known per se. As described above, the present invention is characterized in that a material with a specific composition is used in the thin film forming method to form a thin film with a specific composition.

[0013] The material having such a specific composition is the above-mentioned (a)
) and (b) in a predetermined proportion, molded and sintered, and this is usually used as a material for the dry process. For such adjustment, means known per se can be used.

In the present invention, since a material with such a specific composition is used, scattering of the material can be prevented during thin film formation by a dry process, and an increase in the degree of vacuum can be suppressed, and a dense inorganic thin film can be formed on a plastic film. It can be made to form an adhesion to. The gas barrier property of the gas barrier film thus obtained is 1cc/m2・24hr・a
Shows excellent properties below tm.

Although the method of the present invention forms an inorganic thin film by a dry process as described above, it is preferable to use an evaporation method using an electron beam. Such a vapor deposition method can be carried out using a device known per se, and a schematic diagram of an example thereof is shown in FIG. 1 (however, the vacuum chamber is omitted). The degree of vacuum during vapor deposition is 5 x 10-3 torr or less, preferably 1 x 1
0-3 or less, and the temperature of the cooling drum is -20℃ to 10℃
°C, preferably -10 °C to 5 °C.

[0016] The present invention will be explained below by giving Examples along with Comparative Examples.

Comparative Example Ethyl silicate [Si(OC2H
5) A solution prepared by mixing 4] with absolute alcohol at a volume ratio of 1:1 was added to 100 g of powdered material.
cc was added, stirred, and molded, dried in the air at 150°C for 4 hours, and then sintered at 1300°C for 1 hour to prepare a vapor deposition material with a dense structure.

Using the vapor deposition material thus prepared, a thin film was deposited on one side of a polyester (polyethylene terephthalate) film using the electron beam vapor deposition apparatus shown in FIG. The thickness of the film was 12 μm, the film feeding speed was 70 m/min, and the power input to the electron beam was 35 kW. The slit width of the evaporation source was 100 mm, and the drum was cooled to -10°C. Inside the vacuum chamber 6×10-4Pa
After evacuation, a thin film of SiO (700 angstroms thick) was deposited on the film by electron beam evaporation. The oxygen permeability and other data of the gas barrier film thus obtained are shown in Table 1.

Example 1 Sodium silicate (Na2SiO3
) was mixed in an amount of 0.36% by weight with respect to water. 70cc of the solution was added to 200g of the powder material, stirred, molded, and foamed. After drying in the air at 150°C for 4 hours,
The vapor deposition material was prepared by sintering at 0° C. for 1 hour. This vapor deposition material had a porous structure.

Polyester (
Si on one side of polyethylene terephthalate (polyethylene terephthalate) film
A thin O film was deposited. At that time, the film thickness was 12μ
m, the film feeding speed during film formation was 80 m/min, and the input power of the electron beam was 38 kW. The slit width of the evaporation source was 100 mm, and the drum was cooled to -10°C. After the inside of the vacuum chamber was evacuated to 6×10 −4 Pa or less, electron beam evaporation was performed to deposit a thin SiO film (thickness: 700 angstroms) on the film. The oxygen permeability and other data of the gas barrier film thus obtained are shown in Table 1.

Example 2 0.5% by weight of NaOH was added to water in a powder material made by mixing Si and SiO2 powders in a ratio of 47:53% by weight.
70 cc of the mixed solution was added to 200 g of powder material, stirred, molded, and foamed, dried in the air at 150° C. for 4 hours, and then sintered at 1300° C. for 1 hour to prepare a vapor deposition material. This vapor deposition material had a porous structure.

Polyester (
Si on one side of polyethylene terephthalate (polyethylene terephthalate) film
A thin film of O was deposited. At that time, the film thickness was 12μ
m, the film feeding speed during film formation was 80 m/min, and the input power of the electron beam was 35 kW. The slit width of the evaporation source was 100 mm, and the drum was cooled to -10°C. After evacuating the inside of the vacuum chamber to 6×10 −4 Pa or less, electron beam evaporation was performed to deposit a thin film of SiO (thickness: 700 angstroms) on the film. The oxygen permeability and other data of the gas barrier film thus obtained are shown in Table 1.

[0023]

[0024]

As explained above, according to the present invention, a gas barrier film for packaging retort food, etc., which has gas barrier properties much better than conventional gas barrier films, is provided.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of an electron beam evaporation apparatus that can be used to carry out the method of the present invention.

[Explanation of symbols]

1. Roll of polyester film 2 Tensioner 3 Cooling drum 4 Shutter 5 Slit 6　Electron beam evaporation source 7 Take-up roll

Claims (2)

[Claims] Claim 1: (a) Si and/or an oxide of Si, and (b) a compound of (i) an alkali metal, (ii) an alkaline earth metal, (iii) an alkali metal, and (iv) a substantially basic base. An inorganic thin film is made of at least one substance selected from the group consisting of substances showing properties, and (a) is 90% by weight or more and (b) is 0.1 to 10% by weight based on the entire thin film. A gas barrier film characterized by being coated on at least one side. 2. In manufacturing a gas barrier film by coating at least one surface of a plastic film with an inorganic thin film by a dry process such as vapor deposition or sputtering, S is used as a material in the dry process.
oxide of i and/or Si, and (b) (i) an alkali metal, (ii) an alkaline earth metal, (iii)
It consists of at least one substance selected from the group consisting of an alkali metal compound and (iv) a substance showing substantially basicity, where (a) is 90% by weight or more, and (b) is 0.1 to 0.1% by weight.
A method for producing a gas barrier film, characterized in that a film having a composition of 10% by weight is used.