JPH0234328A - Gas barrier laminated film - Google Patents

Abstract

PURPOSE:To obtain a transparent film having high-degree gas barrier properties without increasing film thickness by forming the thin-film layer of an silicon oxide, silicon binding energy of which differs in the thickness direction of the layer and which has large silicon binding energy in a section near a plastic film, onto one surface of the plastic film. CONSTITUTION:The thin-film layer of an silicon oxide is shaped onto one surface of a plastic film having a polar group through either of a vacuum deposition method, a sputtering method or an ion plating method. The silicon binding energy of the thin-film layer of the silicon oxide differs in the thickness direction of the layer, and large silicon binding energy is acquired in a section near the plastic film. Consequently, a plastic surface and the thin-film layer are bonded firmly, and gas moleculaes are difficult to be substantially passed, thus displaying excellent gas barrier properties. Accordingly, a laminated film having high-degree gas barrier properties can be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a laminated plastic film with excellent gas barrier properties, and more particularly, to a laminated plastic film having excellent gas barrier properties against water vapor and oxygen, and various types of plastic films that exhibit transparency. The present invention relates to a laminated plastic film suitable for packaging materials.

[Conventional technology]

Plastic films and molded products used as packaging materials for foods, medicines, chemicals, etc. are made of gas barrier materials that do not allow gases such as water vapor or oxygen to permeate, in order to prevent the contents of the package from deteriorating. There is. In packaging that requires a high degree of gas barrier property, materials in which metal foil such as aluminum is laminated or metal such as aluminum is vapor-deposited are used.

In addition, films made of polyvinylidene chloride-based resins such as polyvinylidene chloride and copolymers containing vinylidene chloride as a main component and other monomers copolymerizable therewith, such as vinyl chloride, methyl acrylate, methyl methacrylate, acrylonitrile, etc. Vinylidene chloride resin-coated films obtained by coating these vinylidene chloride resins with films made of polypropylene, polyester, polyamide, etc. are known as packaging materials with gas barrier properties.

Furthermore, polyvinyl alcohol and polyvinyl alcohol resins such as ethylene-vinyl alcohol copolymer films are also materials with excellent oxygen barrier properties. However, polyvinyl alcohol resins have poor water vapor barrier properties and deteriorate oxygen barrier properties under high humidity, so when used as packaging materials, water vapor barrier resin films such as polypropylene, polyester, and polyester are used.
It is used as a laminated film laminated to a polyvinyl alcohol resin film.

It has been proposed to provide gas barrier properties to a plastic film with excellent mechanical strength by vapor-depositing an oxide film. For example, silicon oxide is vapor-deposited on biaxially oriented nylon film, biaxially oriented polyester film, etc. (Japanese Patent Publication No. 12953/1983), and magnesium oxide is vapor-deposited on polyethylene terephthalate film, biaxially oriented polypropylene film, etc. film (
JP-A No. 60-27532).

[Problem to be solved by the invention]

However, although conventional packaging materials using metal foil or metal vapor-deposited films have excellent gas barrier properties against water vapor and oxygen, they are always opaque because they are laminated with metal.
Since the contents cannot be seen from the outside, its use as a packaging material is extremely narrowly limited.

In contrast, conventional vinylidene chloride-based resin films and polyvinyl alcohol-based laminated films can be made transparent, but do not have sufficient gas barrier properties against water vapor and oxygen, and are suitable for packaging materials that require a high degree of gas barrier property. When used, the thickness of the film must be increased, and increasing the thickness of the film conversely impairs transparency and flexibility, making it unsuitable for packaging materials that require a high degree of gas barrier property. .

Furthermore, packaging materials in which gas barrier properties are provided by depositing an oxide film on a plastic film also do not have sufficient gas barrier properties against water vapor and oxygen.

This invention was made based on the above background, and its purpose is to provide a gas barrier plastic film that has high gas barrier properties without increasing the thickness of the film and can also be made transparent. It is to be.

[Means to solve the problem]

The present inventors have conducted various tests and studies to solve the above-mentioned problems, and have found that the object of the present invention can be achieved by forming a silicon oxide thin film layer with high silicon bond energy on the plastic film surface at the bonding part. We have found that this invention is effective and have completed this invention.

That is, the gas barrier laminated film of the present invention is a laminated film in which a thin film layer of silicon oxide is formed on one side of a plastic film, and the bond energy of silicon in the silicon oxide of the thin film layer is distributed in the thickness direction of the layer. different,
It is characterized by having a large silicon bonding energy in the vicinity of the plastic film.

In a preferred embodiment of the invention, the silicon oxide thin film layer can be formed by either vacuum evaporation, sputtering, or ion plating.

In a preferred embodiment of this invention, a plastic film can be further laminated on the thin film layer surface.

In a preferred embodiment of the invention, the plastic film is made of a plastic having polar groups.

This invention will be explained in more detail below.

In the gas barrier liquid layer film according to the present invention, the thin film layer of silicon oxide formed on one side of the plastic film exhibits large silicon bond energy in the vicinity thereof where it is bonded to the plastic film.

As will be explained later, this is because the silicon oxide thin film layer has a silicon bond energy that is smaller or the same in the vicinity of the plastic film as compared to the silicon bond energy in the center or surface layer of the thin film layer that is not bonded to the plastic film. This is because gas barrier properties are not sufficiently improved.

In this specification, "silicon bond energy of silicon oxide" refers to X-ray photoelectron spectroscopy (ESCA).

Electron 5pectroscopy For
Refers to the binding energy of 5i2p measured by Chemical Analysfs).

Using X-ray photoelectron spectroscopy, the 5i2p silicon bond energy in the thickness direction of the silicon oxide thin film layer can be measured while etching the exposed thin film layer with argon ions or the like.

For example, the silicon bond energy in the vicinity of the plastic film is 0.0.
It is desirable that the voltage is greater than 3 eV, preferably greater than 0.5 eV.

The formation of this thin film layer means that -
This can be carried out by depositing a silicon oxide thin film layer using a vapor deposition raw material such as silicon oxide, silicon dioxide, or a mixture thereof, using either a vacuum vapor deposition method, a sputtering method, or an ion bleaching method. .

The present invention is not limited to the method for forming the thin film layer described above, and various methods can be applied. For example, by using a vapor deposition raw material such as silicon, silicon oxide, silicon dioxide, or a mixture thereof, oxygen gas is evaporated. A reactive vapor deposition method performed while being supplied can also be employed.

The thickness of the silicon oxide thin film layer formed on the plastic film is 3 to 700 nm, preferably 5 to 500 nm.
It is na+. This is because if the thickness of the thin film layer is less than 5 nm, the gas barrier property is insufficient, if it is less than 311 nm, this tendency becomes significant, and if it exceeds 500 nm, the film may warp or cracks may occur in the thin film layer. This is because flexibility is impaired due to peeling, and this tendency becomes significant when the thickness exceeds 700 nm.

The silicon oxide thin film layer can contain additives as needed, and if it is 10% by weight or less, it will not contain impurities such as calcium, magnesium, or their oxides. There are no negative effects.

The plastic film used in this invention is
It is a plastic that can be laminated and bonded to the silicon oxide thin film layer and the plastic film in a manner that increases the silicon bond energy in the vicinity, and any material can be selected as long as it satisfies this requirement. . Specifically, such plastics include plastics having polar groups, such as polyvinyl alcohol and polyvinyl alcohol resins such as ethylene-vinyl alcohol copolymer films.

The dimensions, shape, etc. of this plastic film are selected as appropriate. Further, this film may be either unstretched or -axially or biaxially stretched.

The thickness of the plastic film on which the silicon oxide thin layer is formed is 5 to 400 μm, preferably 10 to 200 μm.
It is μm.

In a preferred embodiment of the present invention, a plastic film is laminated on one side of the silicon oxide thin film layer, and a plastic film of the same or different type can be further laminated on the other side.

Lamination methods include laminating a plastic film on the silicon oxide thin film layer; or forming a plastic coating on the silicon oxide thin film layer.

The plastic film used for lamination is not particularly limited, but the moisture permeability measured at a temperature of 40°C and a relative humidity of 9026 is 50% according to ASTM F372.
It is preferable to have a characteristic of g/rrf・24 hr or less, and the thickness can be selected within the range of 5 to 400 μm.

Suitable types of plastic for laminating plastic films include olefin resins such as polyethylene and ethylene copolymers, polypropylene and propylene copolymers, and polyvinyl chloride such as polyvinyl chloride and its copolymers. Polyvinylidene chloride resins such as polyvinylidene chloride and its copolymers, polyester resins such as polyethylene terephthalate, fluororesins such as polytetrafluoroethylene, and other resins such as polyvinylidene chloride resins on these resin films. There are coated films etc. These resin films may be unstretched or -axially or biaxially stretched.

When bonding plastic membranes, use urethane adhesive,
Known methods such as dry lamination and extrusion lamination using acrylic adhesives, polyester adhesives, etc. can be employed.

On the other hand, when forming a plastic film by coating, a coating agent is used. At this time, suitable coating agents include:
A solution or dispersion of polyvinylidene chloride resin such as polyvinylidene chloride and its copolymer, polyester resin such as polyethylene terephthalate, fluororesin such as polytetrafluoroethylene, etc. in tetrahydrofuran is preferable.

When forming a plastic film by coating, an anchor coating agent can be used to increase the adhesive strength between the coating film and the thin film layer. Suitable anchor coating agents include adhesion promoters such as isocyanate-based, polyethyleneimine-based, and organic titanium-based adhesives, and adhesives such as polyurethane-based and polyester-based adhesives.

In this invention, in addition to the silicon oxide thin film layer formed on the plastic film surface, the above-mentioned plastic film, etc., the silicon oxide thin film layer formed on the surface of the thin film layer, the plastic film surface, or the plastic film surface, and also on both surfaces, depending on the usage mode. and a substance that improves the heat sealing properties of the film.
Can be coated or laminated.

Examples of substances that improve heat-sealability include low-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, and ionomer.

[For production]

In the present invention having the above structure, the silicon bond energy is large in the vicinity of the joint between the plastic film and the silicon oxide thin film layer. This means that there is a strong bond between the plastic surface and the thin film layer, and the network of atoms at the tightly bonded joint effectively allows gas molecules such as water and oxygen molecules to pass through. It is believed that it exhibits excellent gas barrier properties. Note that this explanation is for better understanding of the present invention, and does not limit the scope of the present invention.

〔Effect of the invention〕

As demonstrated in the Examples below, the present invention has the following effects.

The gas barrier multilayer plastic film according to claims 1 and 2 has extremely high gas barrier properties without increasing the thickness of the film, and can also exhibit excellent transparency. It is also flexible, strong and economical.

Therefore, it can be used as a packaging material for foods, medicines, chemicals, etc., and can also be applied to packaging that requires high gas barrier properties.It can be used for a wide range of applications, and its industrial value is extremely high. It's large.

In the gas barrier laminated plastic film according to the third aspect, since the plastic film is further laminated, the water vapor permeability can be further reduced and even more excellent gas barrier properties can be exhibited.

In the gas barrier laminated plastic film according to claim 4, since a plastic having a polar group such as the hydroxyl group of a polyvinyl alcohol film is used, a silicon oxide thin film layer is formed on this film by a vacuum evaporation method or the like. When this is done, the polar groups of the plastic film and silicon oxide interact with each other in the initial stage of formation, resulting in larger silicon binding energy in the vicinity, making it possible to obtain a film that exhibits excellent gas barrier properties.

〔Example〕

This invention will be specifically explained below based on Examples and in comparison with Comparative Examples, but this invention is not limited to the following Examples unless it exceeds the gist thereof.

In the following examples, the silicon bond energy (Si2p) of the silicon oxide thin film layer, the moisture permeability, oxygen permeability, and transparency of the obtained laminated film were measured or determined by the following h method. Further, the thickness of the transparent thin film layer of silicon oxide was measured using a quartz crystal film thickness meter.

Using a silicon bond energy X-ray photoelectron spectrometer (manufactured by Shimabara Seisakusho, ESCA850 type, X-ray source MgKα), the silicon oxide thin film layer was etched with Ar ions at 3-minute intervals and then 5i2p
We measured the change in the binding energy in the thickness direction.

In accordance with ASTM F-372, under the conditions of a temperature of 40°C and a relative humidity of 90%, (i) in the case of a transparent plastic film in which only a thin film layer of silicon oxide is formed on one side of the plastic film, silicon The measurement was performed with the oxide thin film layer placed on the high humidity (90% RH) side and the plastic film placed on the bone dry side. In addition, (ii) in the case of a transparent plastic film in which another plastic film other than the above film is further formed on the surface of the silicon oxide thin film layer, the surface of this plastic film is kept at high humidity (90% R
Measurements were made with the plastic film placed on the absolutely dry side on the H) side.

Oxygen permeability oxygen permeability measuring device (manufactured by Modern Control Co., Ltd., 0X-
TRAN100 type), temperature 30℃, relative humidity 8
The measurement was performed under the condition of 0%.

Transparency was evaluated with the naked eye, and those showing good transparency were marked with a ◎.

Example 1 Polyvinyl alcohol film with saponification degree of 99.9% (
5 on the surface of the stretching ratio 3 x 3 times, biaxial stretching, thickness 12μ)
Silicon monoxide (Sin) with a purity of 99.9% is heated and evaporated using an electron beam heating method under a vacuum of
A transparent thin film layer of silicon oxide of n was formed to obtain a gas barrier laminate film.

Regarding the gas barrier laminate film, the silicon (Si2p) bond energy of the silicon oxide thin film layer, the moisture permeability and oxygen permeability of the laminate film were measured using the methods described above, and the transparency was visually evaluated.

The results of the measurements are shown in FIG. 1 and Table 1.

Example 2 In the example described in [Example], a polyvinyl alcohol film with a degree of saponification of 99.9% was converted into an ethylene-vinyl alcohol copolymer film (ethylene content 32 mol%, stretching ratio 3 x 3 times, biaxial stretching). A transparent thin film layer of silicon oxide was formed on one side of the ethylene-vinyl alcohol copolymer film in the same manner as in the same example except that the film had a thickness of 12 μm).

Regarding the obtained gas barrier laminated film, Example 1
An evaluation test was conducted for the same items as in . The results are shown in FIG. 2 and Table 1.

Comparative Example 1 In the example described in Example 1, a polyvinyl alcohol film with a degree of saponification of 99.9% was replaced with a polyethylene terephthalate film (ethylene content 32 mol%, stretching ratio 3).
A transparent thin film layer of silicon oxide was formed on one side of a polyethylene terephthalate film in the same manner as in the same example except that the film was stretched by 3 times x, biaxially stretched, and 12 μm in thickness.

The obtained laminated film was subjected to the same evaluation tests as in Example 1.

The results are shown in FIG. 3 and Table 1.

Comparative Example 2 Same as the example described in Example 1 except that the polyvinyl alcohol film with a degree of saponification of 99.9% was replaced with a polypropylene film (stretching ratio 3 x 10 times, two-wheel stretching, thickness 20μ). A transparent thin film layer of silicon oxide was formed on one side of the polypropylene film.

The obtained laminated film was subjected to the same evaluation tests as in Example 1.

The results are shown in FIG. 4 and Table 1.

Example 3 A polypropylene film (
Stretching ratio 3x10 times, biaxial stretching, thickness 20μm, moisture permeability 8g/rr?・24hr, hereafter this film is rOPP
J) with a 2μ thick urethane adhesive layer (Takeda Pharmaceutical Co., Ltd., Takelac A-606 and Takenate A-1).
A gas barrier transparent laminated plastic film was obtained by laminating the two-component adhesive (a two-component adhesive prepared by mixing 0 and 0 in a ratio of 9=1).

Regarding the gas barrier transparent laminated film, the moisture permeability and oxygen permeability of the laminated film were measured by the method described above, and the transparency was evaluated with the naked eye.

The results of the measurements are shown in Table 2.

Example 4 Using the gas barrier laminated film obtained in Example 3,
On the polyvinyl alcohol film side of this film,
A 40 μm thick ethylene-vinyl acetate copolymer film was used as the heat seal layer, and a 2 μm thick urethane adhesive layer (manufactured by Takeda Pharmaceutical Co., Ltd., using Takelac A-606 and Takenate A-10 in a ratio of 9:1). A transparent laminated plastic film with gas barrier properties was obtained by laminating the two-component adhesive (two-component adhesive mixed in the same proportions) to obtain a gas barrier transparent laminated plastic film.

Regarding the gas barrier transparent laminated film, the moisture permeability and oxygen permeability of the laminated film were measured by the method described above, and the transparency was evaluated with the naked eye.

The results of the measurements are shown in Table 2.

Example 5 In the example described in Example 1, the gas barrier transparent laminate film obtained in Example 2 was used in place of the gas barrier transparent laminate film obtained in Example 1 used in the same example. A gas barrier transparent laminated plastic film having OPP adhesively laminated thereon was obtained in the same manner as in the same example.

Regarding the obtained gas barrier laminated film, Example 3
An evaluation test was conducted for the same items as in .

The results are shown in Table 2.

Example 6 In the example described in Example 3, the OPP film laminated on the silicon oxide vapor deposition surface was replaced with a nylon 6 film (stretching ratio 3x3, two-wheel stretching, thickness 15μ, moisture permeability 150g).
/rr? A gas barrier transparent laminated plastic film was obtained in the same manner as in the same example, except that the reaction time was changed to 24 hours.

Regarding the obtained gas barrier laminated film, Example 3
An evaluation test was conducted for the same items as in .

The result! It is shown in Table J2.

Comparative Example 3 The same type of oPP as used in Example 3 was applied to the silicon oxide vapor-deposited surface of the laminated film obtained in Comparative Example 1 to a thickness of 2
Transparent laminate is laminated through a urethane adhesive layer (manufactured by Takeda Pharmaceutical Co., Ltd., a two-component adhesive consisting of Takelac A-606 and Takenate A-10 mixed at a ratio of 9:1). A plastic film was obtained.

Regarding the laminated film, the moisture permeability and oxygen permeability of the laminated film were measured by the method described above, and the transparency was evaluated with the naked eye.

The results of the measurements are shown in Table 2.

Comparative Example 4 A transparent laminated plastic film was obtained in the same manner as in Comparative Example 3, except that the silicon oxide-deposited plastic film was replaced with the laminated film obtained in Comparative Example 2.

The obtained laminated film was subjected to the same evaluation tests as in Example 3.

The results are shown in Table 2.

Evaluation of the results of Examples and Comparative Examples The following can be seen from the results shown in Tables 1 and 2.

(i) As shown in FIGS. 1 and 2, in the silicon oxide thin film layer formed on the plastic film, the joint part (nearby part) with the plastic film
When the silicon bond energy is large (Examples 1 and 2), both the water vapor permeability and the oxygen permeability are small, and the laminated film according to the present invention exhibits excellent gas barrier properties.

Furthermore, when another plastic film is laminated on the thin film layer, the moisture permeability is further reduced, and the layer exhibits excellent gas barrier properties (Examples 3.4.5 and 6).

Note that even when a substance that improves heat sealability was laminated, no change in gas barrier properties was observed (Example 4).

(1■) As shown in Figures 3 and 4,
In the silicon oxide thin film layer formed on the plastic film, when the silicon bond energy at the joint (nearby area) with the plastic film is the same as the silicon bond energy at the center and surface layers (Comparative Examples 1 and 2) , did not show good moisture and oxygen permeability.

Furthermore, even if another plastic film is laminated, the moisture permeability and oxygen permeability are not sufficiently improved (Comparative Example 3).
and 4).

(fil) The laminated film according to the present invention exhibits excellent gas barrier properties and also has good transparency.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the change in silicon bond energy in the thickness direction of the thin film layer in the laminated film obtained in Example 1 according to the present invention, and FIG. A line diagram showing changes in silicon bond energy in the thickness direction of a thin film layer in a laminated film. FIG. 3 is a diagram showing changes in silicon bond energy in the thickness direction of a thin film layer in a laminated film obtained in Comparative Example 1 FIG. 4 is a diagram showing the change in silicon bond energy in the thickness direction of the thin film layer in the laminated film obtained in Comparative Example 2.

Claims (1)

[Claims] 1. A laminated film in which a thin film layer of silicon oxide is formed on one side of a plastic film, wherein the silicon bond energy of the thin film layer of silicon oxide differs in the thickness direction of the layer, and the plastic film A gas barrier laminate film characterized by having large silicon bond energy in the vicinity. 2. The gas barrier laminate film according to claim 1, wherein the silicon oxide thin film layer is formed by any one of a vacuum evaporation method, a sputtering method, or an ion plating method. 3. The gas barrier multilayer film according to claim 1 or 2, further comprising a plastic film laminated on the thin film layer surface. 4. The gas barrier laminate film according to claim 1, 2 or 3, wherein the plastic film is made of a plastic having a polar group.