JP5493743B2 - Transparent barrier film - Google Patents

Description

  The present invention relates to a transparent barrier film that blocks oxygen and water vapor. In particular, the present invention relates to a transparent barrier film used in the packaging field of foods, daily necessities, pharmaceuticals, etc., or a transparent barrier film used in the field of members that need to block oxygen and water vapor in the 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. These alterations of contents occur when a gas such as oxygen or water vapor passes through the packaging material and reacts with the contents. Therefore, it is required to have a property (gas barrier property) that does not allow gas such as oxygen and water vapor to pass therethrough, and metal foils such as aluminum and aluminum vapor deposition films that are not affected by temperature, humidity, and the like have been used. In addition, gas barrier properties are also required for electronic members and the like whose durability deteriorates due to the ingress of oxygen or water vapor, even if they are 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, recently, as a packaging material that overcomes these drawbacks, a vapor deposition film on the basis of a transparent base film of an inorganic oxide such as magnesium oxide, calcium oxide, aluminum oxide, or silicon oxide has been put on the market. These vapor-deposited 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 properties that cannot be obtained with metal foil or the like. ing. Among metal oxide vapor deposited films, silicon oxide vapor deposited films have excellent gas barrier properties.

  In Patent Document 1, it is described that curling properties are suppressed by sequentially laminating a different composition of a barrier oxide deposition film such as a laminated configuration of an aluminum oxide deposition film and a silicon oxide deposition film. Cracks due to increased internal stress occur and there is a limit to improving barrier properties.

Japanese Patent Laid-Open No. 3-64449

  An object of the present invention is to provide a transparent barrier film having high barrier properties and capable of suppressing the occurrence of cracks.

The invention according to claim 1 is a transparent barrier film formed by laminating at least one barrier thin film on at least one surface of a transparent substrate.
The barrier thin film is formed by vacuum film formation while introducing an oxidation reactive gas, and the crack initiation start strain amount [%] of the barrier thin film is 2.5% or more and 3.3% or less. The
The oxidation reactive gas is composed of oxygen gas or carbon dioxide gas,
The barrier thin film is a silicon oxide film;
The conditions for the vacuum film formation are that the introduction amount of oxygen gas or carbon dioxide gas is 30 sccm or more and 1000 sccm or less, and the film formation pressure is 1.0 × 10 ⁻² Pa or more and 8.0 × 10 ⁻² Pa or less. A transparent barrier film characterized by the above.

  In the present invention, when the barrier thin film is vacuum-deposited on the transparent substrate, an oxidation reactive gas is introduced to promote the oxidation reaction, so that it has high barrier properties and can suppress the occurrence of cracks. A transparent barrier film is provided.

It is sectional drawing of an example of the transparent barrier film of this invention. It is explanatory drawing of the tensile testing machine used in order to measure the crack generation start distortion amount in this invention.

Hereinafter, the present invention will be described in more detail.
FIG. 1 is a cross-sectional view of an example of the transparent barrier film of the present invention. The transparent barrier film 10 of the present invention is formed by laminating at least one barrier thin film 104 on at least one surface of a transparent substrate 102, and the barrier thin film 104 is formed by vacuum film formation while introducing an oxidation reactive gas. The crack generation start strain amount [%] of the barrier thin film 104 is 2.5% or more and 3.3% or less.

  The barrier thin film 104 is preferably formed by vacuum film formation from the viewpoint of barrier performance and uniformity. Examples of the film forming means include known methods such as a vacuum evaporation method, a sputtering method, and a chemical vapor deposition method (CVD method), but the vacuum evaporation method is preferable because the film formation rate is high and the productivity is high. Among the vacuum evaporation methods, the electron beam heating method is particularly effective in that the film forming rate can be easily controlled by the irradiation area, the electron beam current, etc., and the temperature can be raised and lowered to the material in a short time. Various materials can be selected for forming the barrier thin film 104, and examples thereof include oxide compounds such as magnesium oxide, aluminum oxide, and silicon oxide. The barrier thin film 104 formed using these various materials is preferable in forming a transparent barrier film because it has a high transmittance in the visible light region and has properties of preventing transmission of oxygen and water vapor. In particular, a silicon oxide thin film is preferable because it has a higher barrier property and higher resistance to moisture than other oxide compounds. The thickness of the thin film can be selected depending on the application, but a film containing internal stress may curl the transparent substrate 102. The size of the curl varies depending on the thickness of the transparent substrate 102. However, assuming a film containing the same internal stress, the curl becomes large in a thin transparent substrate 102 such as 6 μm or 12 μm, and the thickness is 100 μm or more. The transparent base material 102 tends to be curled.

  A large curl has the disadvantage of being complicated in terms of handling, but generally a transparent barrier film is rarely used as a single unit and is often used by bonding it to other films, etc., which causes problems such as adhesion. If not, it can be used. However, it is considered that there is a high possibility that cracks will occur. When cracks occur, the barrier property is lowered, which is a problem.

  The transparent substrate 102 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, Examples of the resin film include, but are not limited to, polycarbonate, polyethersulfone, acrylic, and cellulose (such as triacetyl cellulose and diacetyl cellulose). In practice, it is desirable to select appropriately depending on the application and required physical properties, but 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 properties such as polyethylene naphthalate, polyimides, and polyethersulfone for packaging that protects extremely moisture-insensitive contents such as electronic members and optical members. Moreover, although the thickness of the transparent base material 102 is not limited, about 6 micrometers to 200 micrometers is easy to use according to a use.

  When producing the barrier thin film 104 by vacuum film formation, it is preferable to introduce an oxidation reactive gas. Suitable oxidation reactive gas includes at least one selected from oxygen gas, water vapor gas and carbon dioxide gas. By introducing oxygen, water vapor gas, and carbon dioxide as the oxidation reactive gas, the film stress changes and the elastic modulus can be lowered. Note that oxygen, water vapor gas, and carbon dioxide may be used alone or in combination.

  In the case of introducing oxygen, water vapor gas, and carbon dioxide, it is more preferable that these introducing means be installed on a locus where, for example, vapor deposition particles of silicon oxide adhere to the transparent substrate 102. As a gas introduction method, a known method such as a pipe method or a shower head method can be used.

When oxygen, water vapor gas, and carbon dioxide are introduced, the flow rate and the film forming pressure are preferably 30 sccm or more and 1000 sccm or less, and 1.0 × 10 ⁻² Pa or more and 8.0 × 10 ⁻² Pa or less, respectively. Even if the film expands in a high-temperature and high-humidity environment and the barrier thin film 104 is distorted by forming a film with the flow rate and pressure when introducing oxygen, water vapor gas, and carbon dioxide within the above ranges, cracks are not generated. A transparent barrier film that does not occur and can maintain the barrier can be obtained.

The crack initiation strain amount [%] in the present invention is measured as follows.
First, as shown in FIG. 2, a tensile testing machine 1 is prepared. The tensile testing machine 1 has a stage 3 fixed on a base 2 and a stage 4 movable on the base 2 in the horizontal direction. One end of the transparent barrier film 10 of the present invention is fixed to the stage 3 of the tensile tester 1. Further, the other end of the transparent barrier film 10 of the present invention is fixed to the stage 4 of the tensile tester 1. Note that the thickness of the transparent substrate 102 is preferably set to 12 μm, and the thickness of the barrier thin film 104 is preferably set to 25 nm. Next, the stage 4 is moved on the base 2 in the horizontal direction at a speed at which the following strain amount is 0.01% per second, and a tensile force is applied to the transparent barrier film 10 of the present invention. The state of the barrier thin film 104 is observed at a magnification of 100 times by the microscope observation means 5 installed above the barrier thin film 104. The measurement is terminated when crack fracture is observed in a direction perpendicular to the pulling direction by the stage 4. Strain amount of the transparent barrier film 10 at the end of measurement, that is, {(length after tension of the transparent barrier film 10−length before measurement of the transparent barrier film 10) / length before measurement of the transparent barrier film 10} X 100 (%) is defined as crack initiation strain amount [%] in the present invention.

  As a cause of the occurrence of cracks, it can be considered that the transparent barrier film 10 is stretched. This is because cracks are generated in the thin film due to a large strain applied to the barrier thin film 104 in a high temperature and high humidity or high temperature dry atmosphere. In addition, it is considered that cracks are also caused by laminating an anchor coat layer that is coated to increase the adhesion between the transparent substrate 102 and the barrier thin film 104 and an overcoat layer that is coated to protect the barrier thin film 104. It is done. In particular, in the case of coating, since various solvents are volatilized in a high-temperature oven by so-called wet coating, the shrinkage of the film and the stress of the coating layer are simultaneously applied, so the amount of strain is considered to increase.

  In particular, repeated lamination of a barrier thin film and a coating layer tends to generate half-surface cracks that can provide high barrier properties, and thus barrier performance tends to peak or deteriorate. For this reason, it is important to suppress the occurrence of cracks.

  The crack initiation strain amount [%] of the transparent barrier film is preferably 2.5% or more and 3.3% or less. When the crack initiation strain amount [%] is larger than 3.3%, an excessive oxidation state in which x of SiOx is 2 or more is obtained. In such a case, the barrier property does not appear at all, which is not preferable. On the other hand, when the crack initiation strain [%] is less than 2.5%, the crack resistance is weak and the film expands in a high-temperature and high-humidity environment and the barrier thin film is distorted. Since it deteriorates, it is not preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Using a 12 μm thick film of PET (polyethylene terephthalate, P60 manufactured by Toray Industries, Inc.) in a wind-up type vacuum deposition apparatus, the acceleration voltage of the electron gun is 40 kV, the beam current is 0.25 A, and silicon oxide material (SiO, Osaka Titanium Technologies) was heated, and a flow rate of oxygen 750 sccm was introduced at a pressure of 4.5 × 10 ⁻² (Pa). When evaporation started, the shutter was opened and the deposition rate was adjusted so that the silicon oxide film was 25 nm.

Under the same conditions as in Example 1, a flow rate of 60 sccm of water vapor instead of oxygen was introduced at a pressure of 2.0 × 10 ⁻² (Pa), and the film formation rate was adjusted so that the film thickness was 25 nm. The second embodiment is a reference example.

Under the same conditions as in Example 1, a flow rate of 500 sccm of carbon dioxide instead of oxygen was introduced at a pressure of 7.7 × 10 ⁻² (Pa), and the film formation rate was adjusted so that the film thickness was 25 nm.

[Comparative Example 1]
Under the same conditions as in Example 1, the deposition rate was adjusted so that the flow rate of oxygen was 0 sccm and the film thickness was 25 nm.

[Comparative Example 2]
Under the same conditions as in Example 1, the flow rate of oxygen was 1200 sccm, the pressure was 8.5 × 10 ⁻² (Pa), and the deposition rate was adjusted so that the film thickness was 25 nm.
[Comparative Example 3]
Under the same conditions as in Example 1, the flow rate of water vapor was 500 sccm, the pressure was 6.0 × 10 ⁻² (Pa), and the film formation rate was adjusted so that the film thickness was 25 nm.

Film evaluation method after film formation (1) Crack generation start strain amount: The obtained transparent barrier film was cut into a width of 5 mm and a length of 35 mm, and installed in the tensile tester 1 so as to have a length of 25 mm. This film was strained by pulling the film by stage 4. A strain amount of 0.01% per second was applied, and a strain amount [%] at the time of crack generation was obtained by observation with an optical microscope at a magnification of 100 times. In addition, as a result of observing the barrier thin film of the transparent barrier film, the measurement was terminated when crack fracture was observed in the direction perpendicular to the tensile direction by the stage 4.
(2) Water vapor transmission rate: Measured in a 40 ° C.-90% RH atmosphere using a modern control (MOCON PERMATRAN W3 / 33).
(3) Appearance: Transparency judgment by visual color check The above (1) to (3) were evaluated as comprehensive judgments. The results are shown in Table 1.

In Examples 1 to 3, the crack initiation strain was 2.5 to 3.3 [%], and the barrier property was also good. In Comparative Example 1, although the barrier property is good, the crack initiation strain is low, and since it is colored yellow, when it is laminated, the color becomes strong and there is a difficulty as a transparent barrier film. In Comparative Examples 2 and 3, the crack initiation strain amount is 3.3 [%] or more, and the barrier performance is deteriorated. This is considered to be because the barrier performance is deteriorated because the oxidation proceeds excessively and excess oxygen is taken into the film.
From the above, it is considered that Examples 1 to 3 are suitable as transparent barrier films in comprehensive judgment.

  The transparent barrier film of the present invention can maintain the barrier property without cracking even if the film expands in a high temperature and high humidity environment and the barrier thin film is distorted. It can be expected to be used in moisture-proof applications that require high durability.

DESCRIPTION OF SYMBOLS 1 ... Tensile tester 2 ... Base 3, 4 ... Stage 5 ... Microscope observation means 10 ... Transparent barrier film 102 ... Transparent base material 104 ... Barrier thin film

Claims (1)

In a transparent barrier film formed by laminating at least one barrier thin film on at least one side of a transparent substrate,
The barrier thin film is formed by vacuum film formation while introducing an oxidation reactive gas, and the crack initiation start strain amount [%] of the barrier thin film is 2.5% or more and 3.3% or less. The
The oxidation reactive gas is composed of oxygen gas or carbon dioxide gas,
The barrier thin film is a silicon oxide film;
The conditions for the vacuum film formation are that the introduction amount of oxygen gas or carbon dioxide gas is 30 sccm or more and 1000 sccm or less, and the film formation pressure is 1.0 × 10 ⁻² Pa or more and 8.0 × 10 ⁻² Pa or less. <br/> A transparent barrier film characterized by the above.

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