JPH07304127A - Gas barrier packaging material and production thereof - Google Patents

Abstract

PURPOSE:To obtain excellent gas barrier properties and transparency, in a gas barrier packaging material wherein a membrane of silicon oxide is formed on the single surface of a base material, by forming the membrane as a two- layered structure wherein a coarse film and a dense film are formed on the base material in this order. CONSTITUTION:A membrane 2 of silicon oxide is formed on the single surface of a plastic film 1 as a two-layered structure wherein a coarse film 21 and a dense layer 22 are formed in this order. The coarse layer 21 is composed of a columnar structure and easily formed by increasing the RF output of high frequency waves by a plasma CVD member and the dense layer 22 is easily formed by reducing the RF output of high frequencies. The dense membrane 22 may be continuously formed by altering the concn. of reactive gas, RF output or the film forming conditions such as a vacuum degree or the like immediately after the formation of the coarse film 21 or, after the coarse film 21 is formed, a base material 1 is taken out of an apparatus and the conditions of the apparatus, such as an electrode interval and/or film forming conditions are adjusted to form the dense film 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging material excellent in gas barrier property and a method for producing the same. More specifically, the present invention relates to a gas barrier packaging material in which a thin film of silicon oxide is formed on a substrate made of a plastic film or a three-dimensional container made of plastic.

[0002]

2. Description of the Related Art Conventionally, as a packaging material excellent in gas barrier properties such as water vapor barrier property and oxygen barrier property, a laminate containing a metal foil or a laminate containing a plastic film having a metal vapor deposition layer has been widely used. It is used and is molded into a bag-shaped container for use. Aluminum is generally used as the metal in terms of performance, cost, and workability.

However, the above-mentioned metal foil or metal vapor deposition layer has a drawback that it becomes opaque when it has a thickness that exhibits gas barrier properties, and the contents cannot be seen through when used as a packaging material. Further, the metal foil becomes a lump in the furnace when incinerated, and there is a problem in disposability. Further, the packaging material using metal has a drawback that it cannot be applied to a metal detector.

Various materials having a gas barrier property have been studied by overcoming the above-mentioned drawbacks of the metal foil and the metal vapor deposition layer. However, a plastic film formed with a silicon oxide thin film has a transparency, a gas barrier property, and a cost. Is excellent and has already been put to practical use.

As such a packaging material, for example, Japanese Patent Publication No. 51-48511 discloses that a thin film of silicon oxide is formed by a vacuum deposition method.

Further, as a means for forming a silicon oxide thin film,
A plasma CVD method using a material gas such as an organic siloxane or a mixed gas of silicon alkoxide and oxygen has been proposed and studied. The plasma CVD method is superior to the PVD method such as the vacuum evaporation method in that it has a high degree of freedom in film composition, can form a uniform thin film on a three-dimensional object, and can form a film at a low temperature.

[0007]

However, while repeating the experiment for forming a silicon oxide thin film by the plasma CVD method, the present inventors found that simply providing a silicon oxide thin film is sufficient as a gas barrier. We obtained the knowledge that there is a case that the sex is not obtained. It has been conventionally known that the composition and density of the silicon oxide film are changed by changing the film forming conditions such as the composition and absolute amount of the material gas, the vacuum degree of the reaction atmosphere, and the RF output. The inventors of the present invention discovered that the film can exhibit an excellent gas barrier property by making these combinations specific, and completed the present invention.

[0008]

Means for Solving the Problems That is, according to the present invention, when a thin film of silicon oxide is formed on a substrate by a plasma CVD method to obtain a gas barrier packaging material, the thin film is treated as a rough film or a dense film. It is characterized in that it is formed into a two-layer structure in which different films are formed in this order.

[0009]

The present invention exhibits excellent gas barrier properties by forming the silicon oxide thin film into the above specified two-layer structure.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the packaging material of the present invention, and FIG. 2 is an explanatory view of the manufacturing method of the present invention.

The packaging material of the present invention comprises a base material 1 and a silicon oxide thin film 2 formed on at least one surface of the base material 1.
The thin film 2 has a two-layer structure in which a rough film 21 and a dense film 22 are formed in this order on the base material 1.

As the substrate 1, a plastic film or sheet or a three-dimensional container made of plastic is applied.

The type of plastic is not particularly limited, but polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyamides and polycarbonates can be used. When a plastic film is used as a substrate, The use of a uniaxially or biaxially stretched film is preferable from the viewpoint of heat resistance, transparency and strength.

According to the present invention, the silicon oxide thin film 2 is formed on the substrate 1 by the plasma CVD method.

Although the plasma CVD method itself is a known technique, in the present invention, since the plastic base material 1 as described above is used as the base material 1, a plasma which can be formed at a low temperature from the viewpoint of heat resistance. The CDV method is suitable.

More specifically, for example, as shown in FIG. 2, a material monomer 3 such as an organic siloxane or silicon alkoxide is used as a carrier with an inert gas such as nitrogen or argon, and at the same time with oxygen as a reaction gas 4. The material gas (material monomer 3 and reaction gas 4) is introduced into the chamber 6 provided with a pair of flat plate-shaped electrodes 51 and 52 facing each other, and a high frequency (eg 13.56 MHz) power source is applied under reduced pressure. It is made into plasma and the silicon oxide 2 is reactively deposited on the base material 1 arranged between the electrodes 51 and 52.

In the present invention, as the material monomer 3 and the reaction gas 4 for forming the silicon oxide thin film 2, known materials can be used, but the material monomer 3 is easy to handle and can be used at room temperature. In terms of stability,
It is preferable to use an organic siloxane or a silicon alkoxide that is liquid at room temperature.

More specifically, as the organic siloxane, hexamethyldisiloxane, 1,1,3,3-tetramethyldisiloxane, octamethyltetrasiloxane, divinylhexamethyltrisiloxane, divinyltetramethyldisiloxane, trivinyl are used. Pentamethyltrisiloxane can be used.

As the silicon alkoxide, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethylmethoxysilane, ethyltrimethoxy are used. Silane can be used.

The material monomer 3 is usually introduced into the chamber 6 by using an inert gas such as nitrogen or argon as a carrier.

Further, it is preferable to use oxygen as the reaction gas 4 to react with the material monomer 3.

The inside of the chamber 6 is depressurized by a vacuum pump (not shown). Degree of vacuum (degree of vacuum) is 0.1
It is generally about 11 torr.

A pair of electrodes are arranged in the chamber 6. If the base material 1 is a film, the electrodes are a pair of flat plate-shaped electrodes 51, 52 arranged in parallel as shown in the figure.
It is preferable that Further, when the base material 1 is a three-dimensional container, it is preferable to change the illustrated electrode 52 to a rod-shaped electrode.

The power source applied between the electrodes 51 and 52 is
It is a high frequency RF power supply. The high frequency is not particularly limited, but may be a commonly used high frequency of 13.56 MHz.

The present invention is characterized in that, when forming the silicon oxide thin film 2, a two-layer structure is formed in the order of the rough film 21 and the dense film 22.

The rough film 21 has a columnar structure, and tends to be formed when the RF output of high frequency is increased.

On the contrary, the dense film 22 tends to be formed when the RF output of high frequency is reduced.

The order of forming the films 21 and 22 is important for the purpose of the present invention, and as will be apparent from the experimental results described later, this order provides excellent gas barrier properties.

In forming these films, immediately after forming the rough film 21, the film forming conditions such as the supply gas concentration, the RF output, and the degree of vacuum are changed to continuously form the dense film 22. Alternatively, after forming the rough film 21, the substrate 1 is taken out from the apparatus and the conditions of the apparatus (for example, the electrode interval) and / or the above-mentioned film forming conditions are adjusted to obtain the dense film 22. May be formed.

The thickness of these films is 10 for the film 21.
The processing conditions are preferably adjusted so that the film thickness is in the range of ˜300 nm and the film 22 is in the range of 10 to 200 nm.

The temperature of the reaction atmosphere can be adjusted by appropriate means, if necessary.

When it is necessary to control the temperature of the substrate 1, it can be adjusted by a heater H provided below the electrode 51. The preferable temperature range of the substrate 1 is
Considering the heat resistance of the substrate, it is 20 to 100 ° C.

<Example> Using a high frequency plasma CVD apparatus as shown in FIG. 2, a biaxially stretched polyethylene terephthalate film (25 μm) is used as a base material, hexamethyldisiloxane (HMDS) is used as a material gas, and a reaction gas is used. Using oxygen (O ₂ ) and argon (Ar) as a carrier gas, a film of silicon oxide having a one-layer or two-layer structure was formed on the substrate by variously changing the film-forming conditions as shown in Table 1 below. Formed. The electrode has a diameter of 120.
A circular parallel plate of mmφ was used.

[0034]

[Table 1]

The thickness of the thin film of the obtained packaging material, the adhesion strength between the thin film and the substrate, and the oxygen permeability of the packaging material were measured and evaluated. The results are shown in Table 2.

Here, the thickness of the thin film was measured by cutting the obtained packaging material and photographing its cross section with a transmission electron microscope. The adhesion strength between the thin film and the substrate was measured according to the peeling test using cellophane tape (JIS H8504), and the peeling degree of the film was evaluated. The oxygen permeability of the packaging material is OX-TRAN manufactured by Modern Controls.
10/50 equipment, 20 ℃, 100% RH
It was measured by the method (unit: cc / m ² · day).

The packaging materials obtained were all colorless and transparent.

[0038]

[Table 2]

As can be seen from the above results, according to the present invention,
Thin films (No. 1-5) formed in order of "rough film / dense film"
It can be seen that shows excellent gas barrier properties as compared with those formed only in one layer (No. 6, 7) and those formed in other orders (No. 8 to 10).

[0040]

As described above, according to the present invention, a thin film of silicon oxide formed on a substrate by the plasma CVD method,
By adopting a structure in which a rough film and a dense film are formed in the order of two layers, excellent gas barrier properties and high transparency can be given to the packaging material. Further, the present invention can be applied not only to flat films and sheets but also to molded products such as three-dimensional bottles and trays. And
The obtained packaging material does not require the use of aluminum foil and is therefore excellent in disposability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a packaging material of the present invention.

FIG. 2 is an explanatory view showing an embodiment of the manufacturing method of the present invention.

[Explanation of symbols]

 1 ... Substrate 2 ... Silicon oxide thin film 21 ... Silicon oxide rough film 21 22 ... Silicon oxide dense film 21 3 ... Material monomer 4 ... Reaction gas 51,52 ... Electrode 6 ... Chamber

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[Procedure amendment]

[Submission date] June 1, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

The chamber 6 is depressurized by a vacuum pump (not shown). Degree of vacuum (degree of vacuum) is 0.1
It is generally about 1 torr.

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Claims (6)

[Claims] 1. A gas barrier packaging material in which a thin film of silicon oxide is formed on at least one side of a substrate, wherein the thin film is formed on a substrate in the order of a rough film and a dense film. A gas barrier packaging material having a layered structure. 2. The gas barrier packaging material according to claim 1, wherein the rough film is a film having a columnar structure. 3. The gas barrier packaging material according to claim 1, wherein the substrate is a plastic film. 4. The gas barrier packaging material according to claim 1, wherein the substrate is a three-dimensional container made of plastic. 5. A method for producing a gas barrier packaging material in which a thin film of silicon oxide is formed on at least one surface of a base material, wherein a rough film of silicon oxide is formed on the base material by a plasma CVD method. A method for producing a gas barrier packaging material, characterized in that a dense film of silicon oxide is formed on the rough film by a plasma CVD method. 6. The method according to claim 5, wherein the material gas is a mixed gas of either an organic siloxane gas or a silicon alkoxide gas and oxygen.