JP2000071378A - Breaking strain reinforced gas barrier film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of destruction in a glass membrane by applying compression residual strain to the glass membrane by setting the vapor deposition speed in a glass membrane forming process to a specific low speed range and increasing the breaking strain of the membrane by the quantity of the compression residual strain. SOLUTION: In producing a gas barrier film obtained by forming a glass membrane on a base material film by vapor deposition, the vapor deposition speed in a glass membrane forming process is set to a low speed range of 3-10 Å/sec to apply compression residual strain of 0.4-0.6% to the glass membrane and the breaking strain of the membrane is increased by the quantity of the compression residual strain. Otherwise, in producing the gas barrier film obtained by forming the glass membrane on the base material film by vapor deposition, a PET film is used as the base material film and the temp. of this film is raised to a high temp. of about 70-80 deg.C within a range not exceeding a glass transition point and the glass membrane is formed by vapor deposition and the heat shrinkage quantity of the base material film after membrane formation is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas barrier film in which a glass thin film is formed on a base film by vapor deposition, and a method for manufacturing the same. Related to a gas barrier film. Depending on the industry in which the gas barrier film is used, the range of the thickness of the glass thin film or the base material is limited, but in the present invention, the application is not particularly limited by the thickness.

[0002]

2. Description of the Related Art In recent years, glass thin film materials have been widely used throughout the industry. In particular, gas barrier films used as food packaging materials are functional films having a gas barrier function by coating a plastic film serving as a base material with a glass thin film, and these are already present in many places close to us.

[0003] Usually, gas barrier films are formed by vapor deposition or CV.
It is manufactured by forming a thin film having a gas barrier function on a substrate film by various film forming techniques such as D and sputtering.

[0004] However, in such a gas barrier film, when the thin film is broken or the like is broken, the gas barrier property is reduced or disappears. In addition, since such a gas barrier film needs to have flexibility, a plastic film having a thickness of several to several hundred mm is used as a base material. As described above, since the gas barrier film is thin and soft, it often poses a problem that the thin film is broken during the manufacturing process or even after the product is put on the market.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a glass thin film during a gas barrier film manufacturing process or after a product is put on the market. An object of the present invention is to provide a gas barrier film having improved productivity and quality reliability by preventing the occurrence of breakage. As a result, it is possible to expect a reduction in manufacturing cost, maintenance of gas barrier properties after shipment, and a significant extension of the expiration date of food and the like.

[0006]

Means for Solving the Problems In order to achieve the above object, a means provided by the present invention is to increase the breaking strain by applying a compressive residual strain to a glass thin film of a gas barrier film.

[0007] In the method for producing a gas barrier film having enhanced fracture strain according to the first aspect, in producing a gas barrier film in which a glass thin film is formed by vapor deposition on a base film, the vapor deposition rate in the process of forming the glass thin film is 3 to 10 °. / Sec, the glass thin film has a thickness of 0.4 to 0.6.
% Compressive residual strain (280 to 430 MPa in terms of stress), and the breaking strain of the thin film is increased by the compressive residual strain.

According to a second aspect of the present invention, there is provided a method for producing a gas barrier film comprising a glass thin film deposited and formed on a base film, wherein a PET film is used as the base film, and the temperature of the film is reduced. , About 70-80 which does not exceed the glass transition point
At a high temperature of ℃, a glass thin film is formed by vapor deposition, and the thermal shrinkage of the base film after film formation is increased to give a compressive residual strain of about 0.1% to the glass thin film, and the compressive residual strain of the thin film is reduced. It is characterized by increasing by the amount of strain.

According to a third aspect of the present invention, there is provided a method for producing a gas barrier film in which a glass thin film is formed by vapor deposition on a substrate film. The glass thin film is formed by vapor deposition by applying the tension described above.

[0010] A fourth aspect of the present invention is a gas barrier film having enhanced fracture strain, which is manufactured by the method according to any one of the first to third aspects.

The gas barrier film having enhanced fracture strain according to claim 5 is characterized in that a substrate film having a fracture strain larger than that of a glass thin film is used as a base film.

The phenomenon that the thin film is broken will be described. A functional film with a general two-layer structure consisting of a thin film / substrate film. When the breaking strain of the substrate film is greater than that of the thin film, the thin film / substrate system is formed into a thin film when pulled in one direction. The resulting crack will be described.

[0013] Both the thin film and the base film extend in the same manner up to the critical tensile strain of the thin film (hereinafter referred to as fracture strain). Occurs.

When the film is further stretched, if the adhesion between the film and the substrate remains, the film is pulled through the shear stress at the interface, and further cracks are generated in the film at substantially equal intervals. As a result, the thin film will have numerous cracks perpendicular to the tensile direction. (See Fig. 1)

Next, the case of a gas barrier film composed of a glass thin film / base film will be described. Typically,
Since the fracture strain of the glass thin film is smaller than that of the base film, as described above,
If the glass film is pulled in the direction beyond the breaking strain of the glass thin film, countless cracks perpendicular to the pulling direction occur only in the glass thin film (see FIG. 2). Thereby, the gas barrier property of the gas barrier film is significantly reduced as compared to before the glass thin film has cracks.

A case where a residual strain exists in a glass thin film will be described. There are two types of residual strain in glass thin films. One is the tensile residual strain, and the other is the compressive residual strain. The former is the residual strain when the base film is in a state where the base film is pulling in the direction that hinders the shrinkage during the growth process or post-treatment of the base film, and the latter is the case where the base film is likely to expand. Is the residual strain when the substrate is in a state of trying to compress it.

These residual strains can be seen as a phenomenon of curling of the film (see FIG. 3). The residual strain increases as the curl of the film becomes steeper (as the radius of curvature of the curl becomes smaller).

A film forming method for imparting compressive residual strain to a glass thin film will be described. Usually, a gas barrier film composed of a glass thin film / substrate is manufactured by a film forming method such as vapor deposition, CVD, or sputtering, but there is no limitation on the film forming method in the present invention. In addition, there are a winding type and a batch type as the film forming machine, but there is no limitation by the film forming machine.

There are mainly three possible causes of the residual strain of the thin film. The first is the tension of the base film during film formation, 2
The third is the temperature of the substrate during film formation, and the third is the film formation speed.

The tension of the base film during film formation is such that the above-mentioned compression residual strain is imparted to the thin film by intentionally distorting the base film within the yield point of the base film during film formation. Will be.

A method for giving a compressive residual strain to a glass thin film depending on the temperature of a substrate during film formation will be described. In the barrier film, generally, a plastic film such as PET or PE is used as a substrate. Since the plastic film and the thin film have different coefficients of thermal expansion, if the temperature during the film formation is different from the temperature after the film formation, residual strain exists in the thin film after the film formation. In particular, the larger the difference between the temperature after film formation and the temperature during film formation, the larger this residual strain. That is, by increasing the temperature of the base film during film formation, a larger residual compression strain remains in the thin film after film formation. (See Fig. 4)

A method for giving a compressive residual strain to a glass thin film by a film forming rate will be described. In a barrier film, generally, a thin film having a barrier function is made of SiO ₂
And ceramics such as MgO, all of which are formed by vacuum film formation, but there is not a small amount of residual gas in the vacuum chamber during the film formation.

The vapor-deposited particles that become thin-film materials that have jumped out into a vacuum by vapor deposition collide with the base material to form a film. At this time, since the film is formed while taking in the residual gas in the chamber, the slower the vapor deposition speed, the more the residual gas is taken in.

In the thin film incorporating the residual gas, the thin film expands as a result, and thus the compressive residual strain appears in the thin film. In other words, a slower deposition rate takes in more residual gas and produces a larger compressive residual strain. (See Figs. 5 and 6)

The gas barrier film composed of the thin film / substrate formed as described above has a compression residual strain in the thin film.

When the film having the compressive residual strain is pulled in one direction, the thin film has already been shrunk and must be pulled to a larger amount of strain before the breaking strain of the thin film is reached. Thus, the apparent fracture strain is greater than without compressive residual stress. The apparent fracture strain increases as the residual stress of compression increases. As a result, the gas barrier film composed of the thin film / substrate becomes a gas barrier film with enhanced fracture strain by imparting compressive residual strain to the thin film.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a gas barrier film having enhanced fracture toughness due to residual compressive strain and a method of manufacturing the same according to the present invention will be described in more detail with reference to the drawings.

<Example 1> 1. Sample Preparation As a sample, the relationship between the residual stress and the breaking strain of a gas barrier film formed by changing the deposition rate in the range of 3 to 150 ° / sec was examined. Base film thickness
Using a 12 mm PET film, one side of which is approximately 100 nm (10
The SiO _x thin film of (00) was formed by a batch type electron beam evaporation apparatus. (Sample: see Fig. 7, device: see Fig. 12)

The degree of vacuum during the vapor deposition is 2 × 10 ⁻³ Pa, and the film thickness is formed while monitoring the film thickness with a crystal oscillator type film thickness monitor. In the text, what is called a SiO _x thin film has a value of X almost equal to 2 by X-ray electron spectroscopy.
It is considered the same as O ₂ .

FIG. 8 shows the stress-strain curve of the PET film.
Shown in As can be seen from FIG. 8, the yield point of PET is about 2
%, And the stress at that time is 75 MPa. That is, it is necessary to keep the tension applied to the base film during film formation in a range where PET does not yield (less than 2% strain and less than 75MPa stress).

2. All samples residual strain measured fabricated, compressive strain remains in the SiO _X film is present, resulting in curling. (See FIG. 5) For each sample, a part of the sample was cut out into a 2 mm × 10 mm strip shape, and the radius of curvature of the curl was measured. (See FIG. 9) From the Young's modulus of the SiO _X layer and the warpage (curl) of the sample, S
iO of _X layer residual strain was estimated by the following equation.

[0032]

(Equation 1)

However, the above equation shows that 2 has different elasticity.
Based on equations describing the bending deformation of the layer material, obtained by assuming E _f d << E _s b.

FIG. 6 shows the result of the residual strain obtained by the calculation. As can be seen from this graph, the residual strain present in the SiO _x thin film increases as the deposition rate decreases.

By forming a film at a low deposition rate of 3 to 10 ° / sec, a compressive residual strain of 0.4 to 0.6% could be generated in the glass thin film.

3. Breaking strain measurement With respect to the sample formed at each deposition speed, a part of the sample was cut into a strip of 1 cm in the width direction and 10 cm in the winding direction, subjected to a tensile test under an optical microscope, and recorded on a VTR. The number of cracks is measured from the thin film destruction image. A schematic diagram is shown in FIG.

Each experimental condition is as follows. Field of view: 63 mm long x 82 mm wide (one screen of CRT monitor) Sample shape at the time of test: Approximately 47 mm (length) x 10 mm (width) strip type Pulling speed: 4.9 mm / sec

FIG. 11 shows the results. The horizontal axis shows the compressive residual strain existing in the SiO _X thin film, and the vertical axis shows the fracture strain of the SiO _X thin film. However, the breaking strain is a strain value at the time when the first crack occurs in the SiO _x thin film when the sample is pulled in one direction.

[0039] As can be seen from this graph, as the compressive residual strain present in the SiO _X film is large, greater fracture strain of SiO _X film. In addition, it can be seen that the fracture strain also increases linearly almost by the increase in the residual compression strain. (See Fig. 11)

From these results, it was found that the deposition speed was 3 to 10
By forming the film in the low speed range of Å / sec, a compressive residual strain of 0.4 to 0.6% was generated in the glass thin film, and the breaking strain could be increased by the amount corresponding to the compressive residual strain. (See Figures 6 and 11)

<Embodiment 2> 1. Sample Preparation Next, the relationship between residual strain and breaking strain was examined for a barrier film deposited by changing the temperature of the substrate during film formation in the range of 50 to 80 ° C.

The substrate is heated by a resistance heating heater generally used for a soldering iron or the like. Further, the temperature of the substrate during the vapor deposition is constantly measured by a radiation thermometer.

Incidentally, since the glass transition point of the PET film (biaxially stretched) used in this example is about 80 ° C., it is necessary to vapor-deposit at a temperature lower than that.

Also in this embodiment, the thickness of the base film is
Using a 12 mm PET film, one side of which is approximately 100 nm (10
The SiO _x thin film of (00Å) was formed by a batch type electron beam evaporation apparatus. The deposition speed was about 4 ° / sec, the degree of vacuum during the deposition was 2 × 10 ⁻³ Pa, and the film thickness was monitored by a crystal oscillator type film thickness monitor.

2. All samples residual strain measured fabricated, compressive strain remains in the SiO _X film is present, resulting in curling. In the same manner as in Example 1, the residual strain was measured from the radius of curvature of the curl.
FIG. 13 shows the results of the substrate temperature and residual strain.

As can be seen from FIG. 13, the higher the temperature during vapor deposition, the greater the residual strain present in the SiO _x thin film. This is due to the difference in thermal expansion coefficient between SiO _X and PET. In general, since the coefficient of thermal expansion of PET is larger than that of SiO ₂ , when the temperature of PET drops to room temperature after vapor deposition, the PET tends to shrink by a larger amount than SiO ₂ , resulting in compression residual strain in the SiO _X thin film. . This compressive residual strain increases as the temperature of the substrate during vapor deposition increases.

However, the compressive residual strain of the thin film which actually appears as a curl of the film also includes other factors such as the tension due to the substrate being deposited and the intrinsic strain of the thin film caused by the deposition speed and the degree of vacuum. Therefore, the compressive residual strain of the thin film due to the difference in the thermal expansion coefficient between the base material PET and SiO ₂ in this embodiment is a part of the entire compressive residual strain generated in the thin film and is not dominant. This can be understood from the fact that when the measurement points are linearly approximated in the graph of FIG. 13, a compression residual strain of about 0.59% exists at a position at 25 ° C. where the temperature after vapor deposition is the same as room temperature.

3. FIG. 17 shows the fracture strain measurement results. The horizontal axis shows the compressive residual strain existing in the SiO _X thin film, and the vertical axis shows the fracture strain of the SiO _X thin film.
As can be seen from this graph, as the compressive residual strain present in the SiO _X film is large, greater fracture strain of SiO _X film. In addition, it can be seen that the fracture strain also increases linearly almost by the increase in the residual compression strain. (Figure 17
This is as described in the first embodiment.

From these results, when the room temperature after vapor deposition was set at 25 ° C., by forming the PET film at a high temperature of 70 to 80 ° C. during vapor deposition, about 0.1% of the compression residual Strain was generated, and the breaking strain could be increased by the compression residual strain. (See Figures 13 and 17)

<Embodiment 3> Oxygen Permeability Measurement For only the sample formed at a deposition rate of 90 ° / sec, the tensile oxygen permeability was measured by a modified oxygen permeability measuring device (manufactured by MOCON) using a modified oxygen permeability measuring device. FIG. 14 shows a photograph and a schematic diagram of the apparatus. The compression set measured from the curl of this sample is 0.15%.

FIG. 15 shows the results of the tensile rate and the crack density.
FIG. 16 shows the results of the tensile rate and the oxygen permeability. Fig. 15
This shows that the fracture strain of this sample is about 1.07%. As can be seen from the comparison between the two graphs, it is clear that the oxygen transmission rate has deteriorated due to the occurrence of cracks.

[0052]

As described above, according to the present invention, the compressive residual stress of a thin film can be increased, and a fracture-strain-enhanced gas barrier film having an increased fracture strain can be produced. Thereby, for example, the productivity at the time of producing a functional film such as a gas barrier film is increased, and a significant reduction in production cost can be expected. Also,
Since gas barrier films are mainly used for packaging materials for foods, etc., it is expected that the expiration date (quality assurance period) can be greatly extended.

[0053]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing cracks generated in a thin film when a functional film composed of a thin film and a base material (destructive strain, base material> thin film) is pulled in one direction.

FIG. 2 is a photograph showing cracks generated in a thin film when a gas barrier film composed of a glass thin film / substrate (destructive strain: substrate> glass thin film) is pulled in one direction.

FIG. 3 is an explanatory view showing curling of a film due to residual strain (tensile, compressive).

FIG. 4 is an explanatory diagram showing curling of a film due to residual strain depending on the temperature of a substrate during film formation.

FIGS. 5A and 5B are a photograph and an explanatory diagram showing curling of a film due to residual strain depending on a film forming speed.

FIG. 6 is a graph showing a relationship between a film forming speed and a compression residual strain.

FIG. 7 is an explanatory diagram showing a configuration of a gas barrier film in an example of the present invention.

FIG. 8 is a graph showing the relationship between stress and strain of a PET film (single).

FIG. 9 is an explanatory view showing a state in which the radius of curvature of the curl of the gas barrier film is measured.

FIG. 10 is an explanatory diagram showing a state of analyzing an experimental sample (gas barrier film).

FIG. 11 is a graph showing experimental results (the relationship between compressive residual strain and fracture strain of a SiO _X thin film).

FIG. 12 is an explanatory view showing an apparatus for manufacturing a gas barrier film in an example of the present invention.

FIG. 13 is a graph showing the relationship between the temperature of a substrate during film formation and the residual compression strain.

FIG. 14 is an explanatory view showing an apparatus for measuring the oxygen permeability of a gas barrier film.

FIG. 15 is a graph showing measurement results (relationship between tensile rate and crack density).

FIG. 16 is a graph showing measurement results (relation between tensile rate and oxygen permeability).

FIG. 17 is a graph showing the relationship between residual compressive strain and fracture strain of a SiO _X thin film.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F100 AA20 AG00B AK01A AK42A BA02 EH662 EJ372 EJ422 GB23 JA03A JD02 JK20B JL02 JM02B YY00B 4K029 AA11 AA25 BA46 BC00 CA00 CA01 EA02 EA08

Claims (5)

[Claims] In producing a gas barrier film in which a glass thin film is formed by vapor deposition on a base film, the vapor deposition rate in the process of forming the glass thin film is set to a low range of 3 to 10 ° / sec. Giving a compressive residual strain of 0.4 to 0.6% (280 to 430 MPa in stress) to the thin film,
A method for producing a gas barrier film having enhanced strain-to-break, characterized by increasing the breaking strain of a thin film by an amount corresponding to the compression residual strain. 2. In the production of a gas barrier film in which a glass thin film is formed by vapor deposition on a substrate film, a PET film is used as the substrate film, and the temperature of the film is set to a value within a range not exceeding a glass transition point of about 70%. By raising the temperature to ~ 80 ° C, depositing a glass thin film by vapor deposition and increasing the amount of heat shrinkage of the base film after film formation, the glass thin film is reduced to about 0.
A method for producing a gas barrier film having enhanced fracture strain, characterized in that a compressive residual strain of 1% is given and the fracture strain of a thin film is increased by the amount of the residual compressive strain. 3. A method for producing a gas barrier film comprising a glass thin film formed on a base film by vapor deposition, by applying a tension within the elastic range (within the yield point) to the base film and forming the glass thin film by vapor deposition. A method for producing a gas barrier film having enhanced fracture strain. 4. A gas barrier film having an enhanced fracture strain, which is produced by the method according to claim 1. 5. The gas barrier film according to claim 4, wherein the substrate film has a breaking strain larger than that of the glass thin film.