JP2008087182A - Transparent gas barrier film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a transparent gas barrier film which is formed by providing a silicon oxide film on a transparent high-molecular film base material by using a vacuum vapor deposition method, not colored, transparent, has a gas barrier capacity and is equipped with the advantages of both aspects. <P>SOLUTION: The transparent gas barrier film is manufactured by evaporating a silicon oxide material under vacuum by a beam heating vapor deposition method to obtain silicon oxide particles 1, by introducing a reactive gas of steam and carbon dioxide in the vicinity of the silicon oxide material and providing the silicon oxide particles on one side or both sides of the transparent high-molecular film base material to form the silicon oxide film 1 on the transparent high-molecular film base material 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transparent gas barrier film that blocks oxygen and water vapor. In particular, the present invention relates to a transparent gas barrier film used in the packaging field of foods, daily necessities, pharmaceuticals, etc., or a transparent gas barrier film used in a member field that needs to block oxygen and water vapor in a non-packaging field.

  Conventionally, in the field of packaging of food, daily necessities and pharmaceuticals, it has been required to prevent the contents from being altered. In the alteration of the contents, gases such as oxygen and water vapor permeate the packaging material and react with the contents. Therefore, it is required to have a property (gas barrier performance) that does not allow gas such as oxygen and water vapor to pass through, and metal foils such as aluminum and aluminum vapor deposition films that are not affected by temperature, humidity, and the like have been used. However, packaging materials using metal foils such as aluminum and aluminum vapor deposition films are excellent in gas barrier performance, but not only can the contents not be seen through the packaging materials, but also nonflammable when discarded after use. There are drawbacks such as the fact that the metal detector cannot be used when inspecting the contents after packaging, etc. Similarly, gas barrier performance is required for an electronic member or the like whose durability deteriorates due to the ingress of oxygen or water vapor, even if it is not used for packaging. At the same time, when visible light transmission was required, there was a problem that metal foil and aluminum vapor deposition film could not cope.

  Therefore, as a packaging material that overcomes these drawbacks, a transparent gas barrier film in which an inorganic oxide such as magnesium oxide, calcium oxide, aluminum oxide, or silicon oxide is deposited on a transparent base film has recently been put on the market. . These transparent gas barrier films are known to have transparency and gas barrier properties such as oxygen and water vapor, and are suitable as packaging materials having both transparency and gas barrier performance that cannot be obtained with metal foil or the like. It is said that. Among transparent gas barrier films deposited with metal oxides, transparent gas barrier films deposited with silicon oxide have excellent gas barrier performance, but some coloration is inevitable. In particular, the vacuum deposition method has a high film formation speed, but in order to obtain gas barrier performance, there is a problem that sufficient gas barrier performance cannot be obtained without sacrificing transparency (Patent Documents 1 and 2).

The known literature is described below.
Japanese Patent Publication No. 51-48511 JP-A-6-136161

  A film obtained by vapor-depositing a silicon oxide film on a transparent polymer film substrate using a vacuum vapor deposition method, to obtain a transparent gas barrier film having both advantages of being transparent without being colored and having gas barrier performance. .

  In order to solve this problem, the present invention has a silicon oxide film formed by vapor deposition using at least carbon dioxide as a reactive gas on one surface or both surfaces of a transparent polymer film substrate. The transparent gas barrier film is characterized in that the degree of oxidation of SiOx of the composition is 1.8 or more and 2 or less, and the compressive stress of the silicon oxide film is 70 MPa or more and 200 MPa or less.

  The present invention is the above transparent gas barrier film, wherein the carbon concentration on the outermost surface of the silicon oxide film is 3 to 6 times the carbon concentration inside the silicon oxide film.

  The present invention provides silicon oxide particles by evaporating a silicon oxide material by a beam heating vapor deposition method under reduced pressure, and introducing a reactive gas of water vapor and carbon dioxide in the vicinity of the silicon oxide material, A method for producing a transparent gas barrier film, comprising forming a silicon oxide film on the transparent polymer film substrate by depositing particles on one or both surfaces of the transparent polymer film substrate.

  There is an effect that a transparent gas barrier film having a high barrier property against oxygen and water vapor can be obtained without impairing transparency. In addition, the film deposition rate is higher than other sputtering and chemical vapor deposition methods (CVD methods) by using the vacuum evaporation method, so the transparent gas barrier is excellent in the productivity of winding vacuum film formation for polymer films. Effect is obtained.

  Hereinafter, the present invention will be described in detail with reference to FIG. FIG. 1 shows a cross-sectional view of the transparent gas barrier film of the present invention. In the transparent gas barrier film, it is preferable from the viewpoint of gas barrier performance and uniformity that the silicon oxide film 1 is formed on the transparent polymer film substrate 2 by vacuum film formation. The film forming means can be formed by a known method such as a vacuum evaporation method, a sputtering method, a chemical vapor deposition method (CVD method), etc. Among the vacuum evaporation methods, silicon oxide by an electron beam, a laser beam or the like is used. The beam heating vapor deposition method of the material is particularly effective in that the film formation rate and the temperature increase / decrease of the silicon oxide material can be performed in a short time. Further, the transparent gas barrier film of the present invention can be used by further forming a polymer film on the silicon oxide film 1.

In the present invention, a silicon oxide material is evaporated by a beam heating vapor deposition method under reduced pressure, and vapor-deposited on a transparent polymer film substrate 2 to form a silicon oxide film 1. The silicon oxide film 1 has an amorphous structure whose composition is represented by SiOx, and when the degree of oxidation x is increased, the composition approaches SiO ₂ and the transparency increases. However, if x is increased too much and the silicon oxide film 1 has a composition of SiO ₂ , the gas barrier performance deteriorates. Therefore, the present invention achieves high transparency while maintaining sufficient gas barrier performance by producing the silicon oxide film 1 having internal compressive stress and compressive stress of 200 MPa or less and 70 MPa or more.

  The internal stress of the silicon oxide film 1 includes tensile stress and compressive stress. In the example in which the transparent polymer film substrate 2 is on the lower side and the silicon oxide film 1 is on the upper side, the tensile stress is normally exerted by a force that causes the silicon oxide film 1 to be inward as “∪”, and the compressive stress is “ A force to make the silicon oxide film 1 outward acts as shown by “∩”. That is, a force distorted in the direction in which the silicon oxide film 1 is compressed is always applied. That is, in the case of compressive stress, even if a defect that allows gas to permeate is included in part of the silicon oxide film 1, a force that closes the defect is applied internally, and gas barrier performance can be maintained.

  The thickness of the silicon oxide film 1 in the present invention is preferably in the range of 5 nm to 300 nm, and the value is appropriately selected. However, when the film thickness of the silicon oxide film 1 is 5 nm or less, the silicon oxide film 1 may not be formed on the entire surface of the transparent polymer film substrate 2 and may not function sufficiently as a barrier material. is there. In addition, when the film thickness is 300 nm or more, the silicon oxide film 1 cannot maintain flexibility, and the silicon oxide film 1 may be cracked due to external factors such as bending and pulling after the film formation. It is.

The polymer transparent plastic substrate used as the transparent polymer film substrate 2 is not particularly limited, and a known one can be used. For example, polyolefin (polyethylene, polypropylene, etc.), polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), polyamide (nylon-6, nylon-66, etc.), polystyrene, ethylene vinyl alcohol, polyvinyl chloride, polyimide, polyvinyl alcohol, Polycarbonate, polyethersulfone, acrylic, cellulose-based (triacetyl cellulose, diacetyl cellulose, etc.) and the like are exemplified, but not particularly limited. In addition, the use of a transparent plastic substrate is preferable because it is suitable for mass production by roll-to-roll. In practice, it is desirable to make appropriate selections depending on the application and required physical properties. This is not a limited example, but polyethylene terephthalate, polypropylene, nylon, etc. are easy to use for packaging medical supplies, drugs, foods, etc. In addition, it is desirable to use a base material having high gas barrier performance such as polyethylene naphthalate, polyimides, and polyethersulfone for packaging that protects extremely moisture-sensitive contents such as electronic members and optical members. Moreover, although the thickness of the transparent polymer film base material 2 is not limited, about 6 micrometers to 200 micrometers is easy to use according to a use. Further, the transparent polymer film substrate 2 may be a multilayer substrate in which another polymer film is formed on a polymer transparent plastic substrate.

  The silicon oxide film 1 containing internal stress may curl the transparent gas barrier film. The size of the curl varies depending on the film thickness of the transparent gas barrier film. However, when a film containing the same internal stress is assumed, the curl becomes large in a thin transparent gas barrier film such as 6, 12 μm, and the thickness is 100 μm or more. The transparent gas barrier film has a tendency to reduce curl. If the curl is large, there is a disadvantage that it becomes complicated in terms of handling, but since a transparent gas barrier film is rarely used alone, it is often used by sticking it to other films etc., so there is no problem with adhesion etc. Can be used.

  The compression stress of the silicon oxide film 1 is adjusted by using a reactive gas. In particular, by introducing water vapor and carbon dioxide, oxygen generated in the vapor phase during vapor deposition reacts with silicon in the silicon oxide film 1 to form the silicon oxide film 1. Thereby, the compressive stress increased, there was no coloring, and the film provided with the high gas barrier performance was able to be obtained. The position where water vapor and carbon dioxide are introduced as the reactive gas is preferably in the vicinity of the silicon oxide material, and the silicon oxide particles obtained by evaporating the silicon oxide material by the beam heating vapor deposition method are applied to the transparent polymer film substrate 2. It is more preferable to install on a sticking locus. As a method for introducing the reactive gas, a known method such as a pipe method or a shower head method can be used.

  The reason why a film having no gas coloring and high gas barrier performance was obtained is considered as follows. The film having high gas barrier performance had a compressive stress of 70 MPa or more. This compressive stress was observed by a force acting in the direction of expanding the silicon oxide film 1, thereby bending the transparent gas barrier film. It is considered that even if there is a defect that allows gas to pass through the silicon oxide film 1 due to this compressive stress, a high gas barrier performance can be obtained because the compressive stress acts to block the defect. In the film having high gas barrier performance, the carbon concentration on the outermost surface of the silicon oxide film 1 was three times or more higher than the carbon concentration in the film. The outermost surface of the silicon oxide film 1 becomes a SiOC component due to the high carbon concentration, and the stress on the outermost surface is reduced. On the other hand, since the compressive stress in the silicon oxide film 1 is still strong, the compressive stress is concentrated only in the inside, and it is considered that the compressive stress applied to the defect is larger and the action of closing is stronger. Regarding the relationship between the carbon concentration of the silicon oxide film 1 and the gas barrier performance, the effect began to appear when the carbon concentration on the outermost surface was twice as high as the carbon concentration inside the film, and the gas barrier performance was improved when the carbon concentration was approximately three times. The gas barrier performance of the silicon oxide film 1 was good at least when the carbon concentration was in the range of 3 to 6 times.

The compressive stress of the silicon oxide film 1 was increased by the reactive gas of carbon dioxide. At the same time, it is thought that Si and hydroxide are combined by the reactive gas of water vapor and react with the oxygen deficient part of SiOx to increase the degree of oxidation of SiOx. In the silicon oxide film 1, SiOx is generated by hydroxide or hydrogen bond.
In the composition where x exceeded 1.8, the film was not colored and had high transparency and good gas barrier performance. However, if the hardness of the film formed on the silicon oxide film 1 is too high, when the compressive stress is strong, the film may be broken and cause cracks, and the gas barrier performance may be deteriorated. Here, since the deposited film has a relatively low hardness, it is considered that even if the compressive stress is strong, cracks are not generated and the gas barrier performance is improved.

The method for measuring the compressive stress of the silicon oxide film 1 was the same as that for calculating the compressive stress σ using the well-known Stoney equation, and the silicon wafer was similarly formed on the silicon wafer, and the radius of curvature of the silicon wafer was measured with a laser. The method went in two ways. The transparent polymer film substrate 2 on which the silicon oxide film 1 was formed was formed into a strip shape having a length L of 40 mm and a width w of 3 mm. When the transparent polymer film base material 2 was a stretched film, the long side and the short side were all combined in the same stretching direction. One of these strip-shaped samples was fixed, and the displacement r of the other was measured. The Stoney formula of the strip-shaped transparent polymer film substrate 2 is shown in the following formula 1. Here, Es is the Young's modulus of the transparent polymer film substrate 2, [nu _s is Poisson's ratio of the transparent polymer film substrate 2, t _s is a transparent polymeric film substrate 2 having a thickness of, t _f is a silicon oxide film The thickness of 1 and R is the radius of curvature of the warp of the transparent polymer film substrate 2. The compressive stress σ was calculated from these relationships.

Here, R = r / L ² .

<Example 1>
In an electron beam heating vacuum deposition apparatus, a silicon oxide material was irradiated with an electron beam emitted from an electron gun inside an evaporation apparatus having an openable / closable shutter to evaporate the silicon oxide material. Then, by opening the shutter, evaporated silicon oxide particles were sprayed onto the transparent polymer film substrate 2 installed in the vacuum deposition apparatus to form a silicon oxide film 1. As the transparent polymer film substrate 2, a 25 μm thick film of PET (polyethylene terephthalate, T60 manufactured by Toray Industries, Inc.) was used. A silicon oxide material (SiO, manufactured by Canon Optron) was heated with an acceleration voltage of an electron beam emitted from an electron gun of an evaporation apparatus being 40 kV and an electron beam current being 0.25 A. Then, 1 sccm of water vapor and 3 sccm of carbon dioxide were introduced by pipe method on the locus where the evaporated particles of silicon oxide adhered to the transparent polymer film substrate 2. When the evaporation of the silicon oxide material begins, the shutter of the evaporation device is opened, and the film formation time is set so that a transparent gas barrier film in which the silicon oxide film 1 is laminated on the transparent polymer film substrate 2 is formed to a thickness of 250 nm. It was adjusted. The pressure was 0.043 Pa. At the same time, a silicon oxide film 1 was formed on a silicon wafer (diameter 76 mm).

<Example 2>
Under the same heating conditions for the transparent polymer film substrate 2 and the silicon oxide material as in Example 1, 3 sccm of water vapor and 5 sccm of carbon dioxide were introduced into the evaporator. The film formation time was adjusted so that a transparent gas barrier film in which the silicon oxide film 1 was laminated to 50 nm on the transparent polymer film substrate 2 was formed. The pressure was 0.043 Pa. At the same time, a silicon oxide film 1 was formed on a silicon wafer (diameter 76 mm).

<Example 3>
Under the same heating conditions of the transparent polymer film substrate 2 and silicon oxide material as in Example 1, the steam is 10 sccm and carbon dioxide in a pipe system on the locus where the evaporated particles of silicon oxide adhere to the transparent polymer film substrate 2. 2 sccm was introduced. When the evaporation of the silicon oxide material began, the shutter of the evaporation device was opened, and the film formation time was adjusted so that a transparent gas barrier film in which the silicon oxide film 1 was laminated to 50 nm was formed. The pressure was 0.049 Pa. At the same time, a silicon oxide film 1 was formed on a silicon wafer (diameter 76 mm).

<Comparative Example 1>
Under the same heating conditions of the transparent polymer film substrate 2 and the silicon oxide material as in Example 1, 3 sccm of water vapor was introduced into the evaporator, and the film was formed without carbon dioxide. The film formation time was adjusted so that the film thickness was 250 nm. The pressure was 0.031 Pa. At the same time, a silicon oxide film 1 was formed on a silicon wafer (diameter 76 mm).

<Comparative example 2>
In the same manner as in Example 1, the transparent polymer film substrate 2 and the silicon oxide material were heated, and 5 sccm of carbon dioxide was introduced into the evaporator without introducing water vapor into the evaporator, and the film was formed on the transparent polymer film substrate 2. Made a membrane. The film formation time was adjusted so that a transparent gas barrier film in which the silicon oxide film 1 was laminated to a thickness of 50 nm was formed. The pressure was 0.033 Pa. At the same time, a silicon oxide film 1 was formed on a silicon wafer (diameter 76 mm).

<Comparative Example 3>
Under the same heating conditions of the transparent polymer film substrate 2 and the silicon oxide material as those in Example 1, water vapor and carbon dioxide were not put in the evaporator, and a film was formed on the transparent polymer film substrate 2. The pressure was 0.028 Pa. The film formation time was adjusted so that a transparent gas barrier film in which the silicon oxide film 1 had a thickness of 50 nm was formed. At the same time, a silicon oxide film 1 was formed on a silicon wafer (diameter 76 mm).

  The evaluation methods of the transparent gas barrier film prepared in Examples and Comparative Examples and the silicon oxide film 1 of the silicon wafer are shown below.

○ Evaluation method for transparent gas barrier film
1) Light transmittance: The transmittance of light with a wavelength of 400 nm is measured using a spectrophotometer (Shimadzu Corporation UV-3100).
2) Water vapor transmission rate: Measured in a 40 ° C.-90% RH atmosphere using a modern control (MOCON PERMATRAN W3 / 33).
3) Element composition ratio: The element composition ratio of Si and O was measured by ESCA (ESCA-3200, manufactured by Shimadzu Corporation). The carbon component concentration in the silicon oxide film 1 is measured by etching the surface of the silicon oxide film 1 and etching (120 sec).
4) Compressive stress: The amount of warpage of the base material was measured with a micrometer, Es (Young's modulus of the base material): 4 GPa, ν _s (Poisson's ratio of the base material): 0.3, t _s The thickness and t _f are calculated by substituting the thickness of the silicon oxide film 1 obtained in 6).

○ Evaluation method of silicon oxide film 1 on a silicon wafer
5) Compressive stress of silicon oxide film: Measured by substituting the film thickness of silicon oxide film 1 obtained in 6) using a thin film stress measuring device (Tensor, FLX2320).
6) Thickness of silicon oxide film: Measured by X-ray reflection method (Rigaku, ATX-G)
Tables 1 and 2 show the evaluation results.

From Table 1, in Examples 1 to 3, the compressive stress of the silicon oxide film 1 was 200 MPa or less and 70 MPa or more, and the light transmittance of the transparent gas barrier film was 84% or more. The transparent gas barrier film had a sufficient gas barrier performance with a water vapor transmission rate of 1.3 g / m ² -day or less even when x of SiOx exceeded 1.8. On the other hand, in all of Comparative Examples 1 to 3, the water vapor permeability was large at 8 g / m ² -day or more, and the gas barrier performance of the transparent gas barrier film was insufficient. In Comparative Examples 2 and 3 in which the case where water vapor was not introduced was tested, the value of x representing the degree of oxidation of SiOx in the composition of the silicon oxide film 1 was less than 1.8 and the degree of oxidation was poor. The gas barrier performance of was poor. In Comparative Example 1 in which steam was introduced and carbon dioxide was not introduced, the value of the oxidation degree x was 1.8 or more, but the compressive stress of the silicon oxide film 1 was less than 70 MPa, and the compressive stress was not high. The gas barrier performance in this case was poor.

  In Comparative Example 1, the value of the oxidation degree x of SiOx in the composition of the silicon oxide film 1 was 1.8 or more. However, since the compressive stress is small and does not reach 70 MPa, it is considered that the gas barrier performance is deteriorated. In order to increase the compressive stress of the silicon oxide film 1, it was necessary to introduce carbon dioxide. Further, when the water vapor concentration was increased from Examples 1 to 3, the compressive stress decreased, but if the compressive stress was 70 MPa or more, the gas barrier performance was sufficient. In Comparative Example 2, the compressive stress of the silicon oxide film 1 was 200 MPa or more, but since the value of the oxidation degree x was less than 1.8, it is considered that the gas barrier performance was poor. In Comparative Example 3, the light transmittance of the transparent gas barrier film was low and yellowed. From Table 2, Examples 1 to 3 are particularly different from Comparative Examples 1 to 3 in that, in Examples 1 to 3, the carbon concentration on the outermost surface of the silicon oxide film 1 is 6% of the carbon concentration inside the silicon oxide film 1. It was less than twice and more than three times. The difference of three times or more between the carbon concentration on the outermost surface and the carbon concentration on the inner surface is a feature of the silicon oxide film 1 that gives good gas barrier performance.

  The ability to provide transparent gas barrier films that are highly productive, transparent and have high gas barrier performance, and can be widely used in the field of components that need to block oxygen and water vapor in the packaging and non-packaging fields of food, daily necessities, pharmaceuticals, etc. It is adaptable and can improve storage stability and durability while being transparent.

It is sectional drawing of the transparent gas barrier film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon oxide film 2 ... Transparent polymer film base material

Claims (3)

  A transparent polymer film base material has a silicon oxide film formed by vapor deposition using at least carbon dioxide as a reactive gas on one surface or both surfaces of the transparent polymer film substrate, and the oxidation degree x of SiOx in the composition of the silicon oxide film is 1.8. The transparent gas barrier film according to claim 1, which has a compressive stress of 70 MPa or more and 200 MPa or less.   2. The transparent gas barrier film according to claim 1, wherein the carbon concentration of the outermost surface of the silicon oxide film is 3 to 6 times the carbon concentration inside the silicon oxide film.   Silicon oxide particles are evaporated by a beam heating vapor deposition method under reduced pressure to obtain silicon oxide particles, and a reactive gas such as water vapor and carbon dioxide is introduced in the vicinity of the silicon oxide material to make the silicon oxide particles transparent A method for producing a transparent gas barrier film, characterized in that a silicon oxide film is formed on the transparent polymer film substrate by vapor deposition on one or both surfaces of the molecular film substrate.