JP2015042487A - Transparent barrier film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of evaluating a transparent barrier film having an inorganic thin-film layer and a transparent barrier film determined by the evaluation method to be preferable.SOLUTION: A transparent barrier film has an inorganic thin-film layer on at least one side of a plastic film, and the inorganic thin layer has a maximum value of the S parameter of 0.51 or smaller, determined by the positron annihilation method for the inorganic layer.

Description

  The present invention relates to a transparent barrier film used as a packaging material that requires airtightness such as foods, pharmaceuticals, and electronic parts having excellent gas barrier properties, or a gas barrier material.

As a film having an excellent gas barrier property, a film obtained by laminating aluminum on a plastic film or a film coated with vinylidene chloride or an ethylene vinyl alcohol copolymer is known. In addition, as a material using an inorganic thin film, a material in which a silicon oxide, an aluminum oxide thin film, or the like is laminated is known (for example, see Patent Document 1).
These transparent barrier films using inorganic thin films have been evaluated by measuring the amount of oxygen permeation and the amount of water vapor permeation.
The gas that permeates through the transparent barrier film using the inorganic thin film passes through the free volume (holes) of the substrate film, and permeates through a defect portion such as a crack in the inorganic thin film or a hole in the inorganic thin film layer.
Defects such as cracks in the inorganic layer may be generated when handling the transparent barrier film, or may be generated by protrusions or dust on the plastic film serving as the substrate.
On the other hand, the pores in the inorganic thin film layer are caused by the properties of the substance itself and the film forming conditions.
In considering the improvement of the barrier, even if only the permeation amount is evaluated, the countermeasure cannot be taken well.
In addition, a method for improving the barrier performance by laminating an organic layer and an inorganic layer is known, but a film having many voids in the inorganic layer has no effect by laminating.

As a method for measuring the free volume of a polymer film, there is known a positron annihilation lifetime measurement method in which evaluation is made based on the time until a positron implanted in a target film disappears in a vacancy. (For example, see Non-Patent Document 1)
The positron annihilation method is also used as a method for evaluating defects in inorganic materials. As an evaluation method using positron annihilation, there is a Doppler broadening evaluation method for evaluating the energy distribution of γ rays generated at the time of positron annihilation, in addition to the method of measuring lifetime. (For example, see Non-Patent Document 2)

Patent No. 2700019

Evaluation of free volume of polymer by positron annihilation and gas diffusion measurement EBARA Nuclear Power Technology Database Data No. 110014 Evaluation of advanced semiconductor materials with positrons Ueda Suzuki Ohira Ishibashi Applied Physics Vol. 74 No. 9 (2005)

  The present invention provides a transparent barrier film having an inorganic thin film layer having excellent barrier properties.

  That is, the present invention is characterized in that the maximum value of the inorganic thin film layer of the S parameter obtained by the positron annihilation method for a transparent barrier film having an inorganic thin film layer on at least one side of the plastic film is 0.51 or less. It is a barrier film.

  In this case, it is preferable that the maximum value of the inorganic thin film layer of the S parameter obtained by the positron annihilation method of the transparent barrier film is 0.505 or less.

  In this case, it is preferable that the inorganic layer is mainly made of alumina and silica.

  According to the present invention, a high-performance barrier film can be obtained, and can be used as a packaging material that requires airtightness such as an electronic component or a gas barrier material. Furthermore, a better barrier film can be obtained by alternately stacking organic layers and inorganic layers.

γ-ray energy distribution Conceptual diagram of low-speed positron beam equipment S parameter measurement example obtained by positron annihilation method Measurement results of transparent barrier film described in Examples

1: Energy Distribution 2: S Parameter area 3: positron source ⁽²² Na)
4: Moderator 5: Filter 6: Positron beam 7: Accelerator 8: Helmholtz coil 9: Sample 10: γ-ray 11: Detector 12: Eigenvalue of plastic film

  The transparent barrier film of the present invention is characterized in that the maximum value of the S parameter inorganic thin film layer determined by the positron annihilation method is 0.51 or less.

The positron annihilation method referred to in the present invention is a method for evaluating the energy distribution of γ-rays generated when the positrons implanted in the object disappear. There is also an explanation in Non-Patent Document 2 mentioned above.
A conceptual diagram of the energy distribution of γ rays obtained by the positron annihilation method is shown in FIG. The energy of γ-rays generated when electrons annihilate with electrons varies depending on the motion state of the electrons, and has an energy distribution ((1) in the conceptual diagram 1) that spreads around 511 keV.
In the present invention, attention is paid to the fact that the γ-rays are broadened by the collision of positrons with electrons in different orbits of atoms around the positron due to the size of the holes.
In the present invention, a value obtained by dividing the count number of the region of 511 ± 0.76 keV (region (2) in the conceptual diagram 1) centered on 511 keV by the total count number is defined as the S parameter obtained by the positron annihilation method.
In this application, when the S parameter in each layer in the depth direction from the surface of the inorganic layer to the plastic is obtained by sequentially changing the energy of the positrons injected from the surface of the inorganic layer, the maximum value in the inorganic layer is used for the evaluation of the thin film. ing.

The configuration of the apparatus will be described below as an example of the apparatus used in the present invention.
FIG. 2 shows an example in which sodium 22 is used as the positron source (3). High energy positrons are generated by β decay of the sodium 22 nucleus. The speed of the obtained positron is reduced by a moderator, and the positron beam (6) is taken out by removing the high-speed positron by a filter (5) using an electromagnetic field so that the speed is kept within a certain range.
The positron beam is accelerated to a desired speed by the accelerator (7), the implantation energy is adjusted, and the sample is implanted into the sample [9]. A Helmholtz coil (8) prevents beam divergence and stabilizes the orbit.
The injected positron forms a positron in the sample and decays with a certain lifetime. The energy of the γ-ray generated when it collapses is measured by the semiconductor detector (11).
The measured gamma rays are counted by energy. In the examples, the S parameter value obtained by the positron annihilation method was measured using the apparatus shown in FIG.

In a transparent barrier film having an inorganic thin film layer on at least one side of a plastic film, for example, the S parameter takes a form as shown in FIG. FIG. 3 is a plot of the positron energy on the horizontal axis and the S parameter obtained on the vertical axis. As the positron energy increases from 0 keV, the inorganic thin film layer inside, the interface with the film, and the plastic inside as the positron energy increases from 0 keV. The S parameter values at different positions in the depth direction are shown.
Since the S parameter is affected by the surface layer and the interface, the S parameter of the inorganic thin film layer and the plastic film is evaluated as follows. The S parameter where the positron has sufficiently entered the positron shows the eigenvalue (12) of the plastic film.
The S parameter in the present invention refers to the maximum value of the S parameter obtained in the inorganic thin film layer. As a specific determination method, the plastic characteristic eigenvalue is directed to the surface, and increases as the positron energy decreases. In this case, the maximum value is indicated, and when it reaches a minimum value after descending at the interface with the inorganic thin film layer, and shows a maximum value after rising, it indicates the maximum value after the minimum value has passed.

  The S-parameters determined by the positron annihilation method can be used to evaluate the size of the vacancies in the inorganic thin film layer itself. Even if there is a decrease, the barrier property of the inorganic thin film itself can be evaluated.

In the case of a defect such as a crack in the inorganic thin film layer, when an organic layer is laminated on the inorganic thin film layer, and further laminated with an inorganic layer, the inorganic defect is transmitted through the organic layer and passes through the second inorganic layer defect. Without an organic layer, gas permeation is greatly reduced because it must pass through a long distance connecting defects, not in the film thickness direction.
When the maximum value of the inorganic thin film layer of the S parameter determined by the positron annihilation method is 0.51 or less, the inorganic thin film layer has small vacancies and can be improved by lamination. Furthermore, if it is 0.505 or less, a film having low cracking, oxygen permeation amount, and water vapor permeation amount can be obtained.

  The plastic film as used in the present invention is a film obtained by melt-extrusion of an organic polymer and stretching, cooling, and heat setting in the longitudinal direction and / or the width direction as necessary. Polyethylene, polypropylene, polyethylene terephthalate, polyethylene-2,6-naphthalate, nylon 6, nylon 4, nylon 66, nylon 12, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamide, polyamideimide, polyimide , Polyetherimide, polysulfone, polyphenylene sulfide, polyphenylene oxide and the like. These organic polymers may be copolymerized or blended with a small amount of other organic polymers.

Furthermore, known additives such as ultraviolet absorbers, antistatic agents, plasticizers, lubricants, colorants and the like may be added to the organic polymer, and the transparency thereof is not particularly limited. When used as a transparent gas barrier film, those having a transmittance of 50% or more are preferred.
The plastic film of the present invention may be subjected to corona discharge treatment, glow discharge treatment and other surface roughening treatment prior to laminating the thin film layer, as long as the object of the present invention is not impaired. Further, known anchor coating treatment, printing, and decoration may be applied.

  The plastic film in the present invention preferably has a thickness in the range of 1 μm to 300 μm, more preferably in the range of 5 μm to 100 μm.

  The inorganic thin film layer referred to in the present invention includes, as materials, metals such as Al, Si, Ti, Zn, Zr, Mg, Sn, Cu, and Fe, and oxides, nitrides, fluorides, sulfides, and the like of these metals. Specifically, SiOx (x = 1.0 to 2.0), alumina, magnesia, zinc sulfide, titania, zirconia, cerium oxide, or a mixture thereof is exemplified. The inorganic thin film layer may be a single layer or a laminate of two or more layers.

In the case of a composite oxide layer prepared by vapor-depositing aluminum oxide and silicon oxide, the mass ratio of aluminum oxide contained in the inorganic compound thin film is not particularly limited, but aluminum oxide and silicon oxide contained in the inorganic compound thin film ( The ratio of aluminum oxide is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 40% by mass or more with respect to 100% by mass of the total of (magnesium oxide). The proportion of aluminum oxide is preferably 65% by mass or less, more preferably 55% or less, and particularly preferably 50% or less.
If the ratio of aluminum oxide exceeds mass%, the flexibility tends to be poor, so that cracking due to handling is likely to occur, and stable barrier properties may be difficult to obtain. On the other hand, if the ratio of aluminum oxide is less than 10% by mass, the barrier property is not good.

  The film thickness of the inorganic compound thin film is not particularly limited, but is preferably 5 to 500 nm, more preferably 8 nm to 100 nm. When the film thickness of the inorganic compound thin film is less than 5 nm, satisfactory gas barrier properties can be obtained. On the other hand, even if the thickness exceeds 500 nm, the corresponding effect of improving the gas barrier property cannot be obtained, which is disadvantageous in terms of bending resistance and manufacturing cost.

  As a method for forming the inorganic thin film layer, a known method, for example, chemical vapor deposition such as physical vapor deposition (PVD) such as vacuum vapor deposition, sputtering, ion plating, or plasma chemical vapor deposition (PECVD) is used. Laws are adopted.

In the vacuum deposition method, the deposition material is a metal such as aluminum, silicon, titanium, magnesium, zirconium, cerium, or zinc, SiOx (x = 1.0 to 2.0), alumina, magnesia, zinc sulfide, titania, Compounds such as zirconia and mixtures thereof are used. As the heating method, resistance heating, induction heating, electron beam heating or the like is employed. Moreover, you may employ | adopt the reactive vapor deposition method which introduce | transduced oxygen etc. as a reactive gas, or used means, such as ozone addition and ion assist.
The pores of the inorganic layer can be controlled by the composition of the inorganic layer, the surface state of the substrate film, and the production conditions.
The following conditions are preferable for an inorganic layer formed by an aluminum oxide-silicon oxide vapor deposition method.
The temperature of the plastic film during vapor deposition is preferably 15 to 30 ° C, and more preferably 20 to 25 ° C.
The pressure at the time of vapor deposition is preferably 10 ⁻⁵ to 10 ⁻³ Pa, and preferably 10 ⁻⁵ to 2 × 10 −4 Pa.
Furthermore, it is important to apply a humidification treatment to the prepared inorganic thin film layer. The humidification treatment is preferably performed in an atmosphere of 40 to 60 ° C. and a humidity of 60 RH% for 5 to 10 days.
The temperature of the plastic film during vapor deposition is preferably 15 to 30 ° C, and more preferably 20 to 25 ° C.
The pressure at the time of vapor deposition is preferably 10 ⁻⁵ to 10 ⁻³ Pa, and more preferably 10 ⁻⁵ to 2 × 10 ⁻⁴ Pa.
Furthermore, it is important to apply a humidification treatment to the prepared inorganic thin film layer. The humidification treatment is preferably performed in an atmosphere of 40 to 60 ° C. and a humidity of 60 RH% for 5 to 10 days.

  In the present invention, a particularly preferable inorganic thin film layer is preferably a composite oxide layer prepared by vapor deposition of aluminum oxide and silicon oxide or a composite oxide layer prepared by vapor deposition of aluminum oxide and magnesium oxide.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.
The film properties obtained in each example were measured and evaluated by the following methods.

1) Measurement of S parameter by positron annihilation method Sodium 22 is used as a positron source. The positrons that have passed through the moderator (tungsten) are decelerated by the electromagnetic field, the high-speed positrons are distributed, and an electric field is applied by the accelerator to accelerate to the required speed (eV). The positron beam is irradiated to the transparent barrier film set to about 10 mm.
The measured γ-rays are counted by energy with a rumanium semiconductor detector, and the value obtained by dividing the count number in the region of 511 ± 0.76 keV by the total count over the entire energy distribution centering on 511 keV of γ-rays is taken as the S parameter. did. After a certain period of time, the acceleration voltage is increased and the next depth is measured.

2) Composition and film thickness of inorganic compound thin film The film thickness composition of the inorganic compound was measured with a calibration curve prepared in advance using a fluorescent X-ray analyzer ("ZSX100e" manufactured by Rigaku Corporation). The conditions for the excitation X-ray tube were 50 kV and 70 mA.
The calibration curve was obtained by the following procedure.
A case of an inorganic thin film made of aluminum oxide and silicon oxide will be described as an example.
Several kinds of films having an inorganic compound thin film composed of aluminum oxide and silicon oxide are prepared, and the amounts of adhesion of aluminum oxide and silicon oxide are determined by inductively coupled plasma emission method (ICP method).
Next, each film for which the adhesion amount was determined was analyzed with a fluorescent X-ray analyzer (“ZSX100e” manufactured by Rigaku Corporation, excitation X-ray tube conditions: 50 kv, 70 mA). Fluorescent X-ray intensity is obtained.
A calibration curve is created by obtaining the relationship between the fluorescent X-ray intensity and the adhesion amount obtained by ICP.
Since the adhesion amount obtained by ICP is basically weight, it was converted as follows in order to make it a film thickness composition.
The film thickness was calculated on the assumption that the density of the inorganic oxide thin film was 80% of the bulk density, and that the volume was maintained even when aluminum oxide and silicon oxide were mixed.
The content ratio wa (mass%) in the aluminum oxide film and the content ws (mass%) in the silicon oxide film are the adhesion amount per unit area of aluminum oxide Ma (g / cm ² ), When the adhesion amount per unit area is Ms (g / cm ² ), the following formulas (1) and (2) are obtained, respectively.
wa = 100 × [Ma / (Ma + Ms)] (1)
ws = 100−wa (2)
That is, the adhesion amount per unit area of aluminum oxide is Ma (g / cm ² ), the bulk density thereof is ρa (3.97 g / cm ³ ), and the adhesion amount of silicon oxide per unit area is Ms (g / g cm ² ), and the bulk density is ρs (2.65 g / cm ³ ), the film thickness t (nm) is obtained by the following formula (3).
t = ((Ma / (ρa × 0.8) + Ms / (ρs × 0.8)) × 10 ⁷ Formula (3)

The film thickness value measured by fluorescent X-ray was close to the film thickness actually measured by TEM.
The same applies to the case of an inorganic thin film made of aluminum oxide and magnesium oxide, but the bulk density of magnesium oxide is ρm of 3.65 g / cm ³ .

3) Measurement of oxygen permeability and water vapor permeability As for oxygen permeability, an oxygen permeability measuring device (manufactured by OXTRAN 2/21 MOCOM) is prepared according to JIS K7126-2 A method, temperature 23 ° C, humidity 65% RH Measured under the atmosphere of
The water vapor permeability was measured according to JIS K7129 B method using a water vapor permeability measuring device (manufactured by PERMATRAN-W 3/31 MOCOM) in an atmosphere of a temperature of 40 ° C. and a humidity of 90% RH.

Example 1
As an evaporation source, particulate Al ₂ O ₃ (aluminum oxide, purity 99.5%) and SiO ₂ (silicon oxide, purity 99.9%) having a size of about 3 to 5 mm are used. An aluminum oxide / silicon oxide thin film was formed by simultaneously depositing aluminum oxide and silicon oxide on the non-coated surface side of a 50 μm thick PET film (Toyobo Co., Ltd .: E4100).
As the vapor deposition material, a circular crucible having a diameter of 40 mm was divided into two by a carbon plate, and granular aluminum oxide and granular silicon oxide were added to each without mixing. The PET film was placed on a support plate.
Using a single electron gun as a heating source, each of Al ₂ O ₃ and SiO ₂ is heated by irradiating an electron beam in a time-sharing manner, and the PET film surface is heated and vaporized to mix aluminum oxide and granular silicon oxide. Vapor deposited.
At that time, the emission current of the electron gun was 205 mA, the acceleration voltage was 6 kV, the aluminum oxide charged in the crucible was equivalent to 160 mA × 6 kV, and the silicon oxide alumina was equivalent to 45 mA × 6 kV.
The vacuum pressure during the deposition was 1.1 × 10 ⁻⁴ Pa, and the temperature of the film support was 23 ° C.
The thickness of the inorganic thin film layer was vapor-deposited with a target of 60 nm using a crystal oscillator type film thickness meter.
The prepared deposited film was left in an atmosphere of 40 ° C. and 60% RH for 7 days.
The S parameter, film thickness, composition, oxygen permeability, and water vapor permeability of the obtained deposited film were measured. The results are shown in Table 1. FIG. 4 shows changes in the thickness direction from the surface of the inorganic thin film layer of the S parameter vapor deposition film to the PET film.

(Example 2)
A transparent barrier film was prepared in the same manner as in Example 1 except that 45 mA was added to silica and 180 mA was added to alumina, and each item was measured.

Example 3
A transparent barrier film was prepared in the same manner as in Example 1 except that 40 mA was added to silica and 175 mA equivalent to alumina, and each item was measured.

Example 4
A transparent barrier film was prepared in the same manner as in Example 1, except that 35 mA was added to silica and 190 mA was added to alumina, and each item was measured.

(Comparative Example 1)
A transparent barrier film was prepared in the same manner as in Example 1 except that 45 mA equivalent was added only to silica, and each item was measured.

(Comparative Example 2)
A transparent barrier film was prepared in the same manner as in Example 1 except that only 190 mA was added to alumina, and each item was measured.

  According to the present invention, the quality of the transparent barrier film can be determined. Moreover, the transparent barrier film judged as good by evaluation of this invention can exhibit the outstanding barrier property, and can provide the film useful for protecting what deteriorates with oxygen and water vapor | steam.

Claims (3)

  A transparent barrier film having a maximum value in an inorganic thin film of S parameter obtained by positron annihilation with respect to a transparent barrier film having an inorganic thin film layer on at least one surface of a plastic film is 0.51 or less.   2. The transparent barrier film according to claim 1, wherein the S parameter is 0.505 or less.   4. The transparent barrier film according to claim 2, wherein the inorganic layer is mainly composed of alumina and silica.