JPH04280617A - Polypropylene film for double-side vapor deposition - Google Patents

Abstract

PURPOSE:To obtain a polypropylene film for double-side vapor deposition having less blocking, strong adhesive force between film and vapor-deposited metal and also having excellent uniformity in thickness of vapor-deposited film, having no exfoliation of vapor-deposited metal and generating no wrinkle. CONSTITUTION:The characteristic of the title polypropylene film for double-side vapor deposition is that surface roughness (Ra) of sides of the title film is 0.025 to 0.136mum, the friction coefficient of one surface (surface A) and other surface (surface B) is 0.75 or less) and also the ratio (O/C) of number of oxygen atoms/number of carbon atoms of the surface layer of the above-mentioned film and the ratio (N/C) of the number of nitrogen atoms/number of carbon atoms is in the range of O/C=0.15 to 0.34 on the surface A, and in the range of O/C=0.10 to 0.40 on the surface B.

Description

[Detailed description of the invention]

0001

[Industrial application field]

0002

2. Description of the Related Art Polypropylene films are widely used in capacitors because of their excellent electrical properties. In this application, vapor deposition on both sides of the polypropylene film has been considered for the purpose of improving productivity in the capacitor manufacturing process, but more recently, in order to improve capacitor performance, it has been There has been an increasing demand for a change in specifications from aluminum to zinc-based metals, which have better electrical properties.

That is, in aluminum, the capacitance decreases significantly with long-term charging, and there is a limit to increasing the potential frequency of the capacitor. On the other hand, zinc has the advantage that the decrease in capacitance is extremely small and can be used at high potential frequencies. On the other hand, zinc has the disadvantage of being inferior in moisture resistance and clearing properties compared to aluminum, so methods such as mixing different metals such as aluminum or reducing the thickness of the deposited film may be used in combination. many. In either case, in order to bring out the characteristics of zinc, it is necessary to increase the zinc ratio to 50% by weight or more.

[0004] As a polypropylene film for vapor deposition and a polypropylene film for easy adhesion, Japanese Patent Application Laid-Open No. 1-22314
Publication No. 4 or Japanese Patent Publication No. 61-9332 are known.

[0005]

[Problems to be Solved by the Invention] In the film obtained by the conventional method, that is, the method described in JP-A-1-223144, the adhesion between the film and the vapor-deposited metal is insufficient, and the thickness of the vapor-deposited film is insufficient. The drawback is that partial voids are likely to occur in the film, and the uniformity of the deposited film thickness is poor. In particular, zinc has weaker adhesion to the film than aluminum, so
When providing a vapor-deposited metal layer with a zinc ratio of 50% by weight or more, in the vapor-deposited film wound up in the final vapor deposition process,
Due to the blocking between the winding layers, the deposited metal peels off when it is unrolled in the next process such as narrow slits, making it unusable for practical use. This is remarkable in thin films, especially films with a thickness of 10 μm or less.

[0006] Furthermore, the film obtained in Japanese Patent Publication No. 61-9332 has the drawbacks that the films are blocked, causing film tearing, and wrinkles are observed during vapor deposition, making it impossible to obtain a satisfactory vapor-deposited film. .

[0007] The present invention solves these problems, reduces the occurrence of blocking, has strong adhesion between the film and the metal vapor deposition, has excellent uniformity in the thickness of the vapor deposited film, prevents the vapor deposited metal from peeling off, and eliminates wrinkles during vapor deposition. The purpose of the present invention is to provide a polypropylene film for double-sided vapor deposition without generation.

[0008]

[Means for Solving the Problems] The polypropylene film for double-sided deposition of the present invention has a surface roughness (Ra) of 0.025 to 0.136 μm and a friction coefficient of 0.75 or less between the A side and the B side. Yes, and the atomic composition ratio of the surface layer of side A of the film is: number of oxygen atoms/number of carbon atoms = 0.15 to 0.34, number of nitrogen atoms/number of carbon atoms = 0.005 to 0. .08, and the atomic composition ratio of the surface layer of the B-plane is in the range of number of oxygen atoms/number of carbon atoms = 0.10 to 0.40.

The polymer of the polypropylene film of the present invention may be a copolymer of propylene and other α-olefin polymers (for example, ethylene, butene, etc.) in addition to a homopolymer. It may be a blended product of combinations (for example, polyethylene, polybutene, etc.).

In the case of the present invention, a homopolymer is particularly preferred, and an isotactic degree of 97.0% or more is particularly preferred.

[0011] In the present invention, the atomic composition ratio of the surface layer on both sides or one side (side A) of the polypropylene film is number of oxygen atoms/number of carbon atoms (hereinafter abbreviated as O/C) = 0.
．． 15 to 0.34, more preferably O/C=0.20 to 0.30. For values smaller than this range,
The adhesion to the vapor-deposited metal is poor. Conversely, if the value is larger than this range, the film tends to block and wrinkles occur during vapor deposition. Next, number of nitrogen atoms/number of carbon atoms (abbreviated as N/C)=0.
It is necessary that N/C is in the range of 0.005 to 0.08, and more preferably in the range of N/C = 0.010 to 0.05. If the N/C value is smaller than this range, the adhesion to the deposited metal will be poor,
On the other hand, if the value is larger than this range, the film tends to block and wrinkles occur during vapor deposition.

The important point of the present invention is that the surface layer (usually an extremely thin layer of about 10 nm from the surface) on both sides or one side (A side) of the polypropylene film contains oxygen atoms and nitrogen atoms in the amount within the above range. It is held at the same time. In addition, if the surface layer only has oxygen atoms, or
On the other hand, if the film contains only nitrogen atoms, the deposited metal will peel off when the deposited film is wound up in the final double-sided deposition process and is unwound in the next process, making it impossible to put it into practical use. This tendency becomes particularly strong when the vapor-deposited metal is zinc.

In the present invention, it is particularly preferable that the atomic composition ratio on both sides of the film is within the above-mentioned range, but the atomic composition ratio on at least one side (side A) of the surface layer is within the above-mentioned range, and the atomic composition ratio on the other side of the film is within the above-mentioned range. O/C of surface (B side) is 0.1
If it is within the range of 0 to 0.40, the present invention is included.

[0014] If the O/C of the surface (B side) is less than 0.10, the adhesion to the deposited metal will be poor, and
．． When it exceeds 40, the film becomes sticky, difficult to slip and easy to block. Also, wrinkles are observed during vapor deposition.

The surface roughness (Ra) of the polypropylene film of the present invention must be in the range of 0.025 to 0.13 μm. If the surface roughness (Ra) is less than 0.025 μm, the anti-blocking property is insufficient for practical use. Moreover, if it exceeds 0.13 μm, the adhesion to the deposited metal will be poor, and the uniformity of the deposited film thickness will be poor, especially in the case of a zinc thin film.

[0016] Furthermore, the coefficient of friction between the A side and B side of the film of the present invention must be 0.75 or less. 0.75
If this value is exceeded, wrinkles will occur during vapor deposition, and the vapor-deposited metal will peel off when the vapor-deposited film wound up as a final product is unwound in the next process, making it difficult to put into practical use.

The lower limit of the friction coefficient is not particularly limited, but is approximately 0.4.

The thickness of the polypropylene film is not particularly limited, but is preferably 10 μm or less, more preferably 2 to 8 μm.

Various known additives such as heat stabilizers, antioxidants, charging voltage improvers, etc. can also be added to the polymer.

Next, an example of the method for manufacturing the polypropylene film for double-sided deposition of the present invention will be explained. However, it is not limited to the following manufacturing method.

[0021] Polypropylene resin is melted at a temperature of 220 to 280°C, extruded into a sheet through a T-die with slits, and cooled and solidified with a cooling roll at 30 to 96°C.
Stretched 3 to 7 times in the length direction at a temperature of 22 to 155°C,
Next, it is stretched 6 to 12 times in the width direction at a temperature of 150 to 167°C, and further heat treated at a temperature of 150 to 165°C. Next, both sides or one side (Side A) of the film is heated with a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide 0.5 to 50).
%) and set the temperature of the film to 30-100℃,
Preferably, while maintaining the temperature at 40 to 80°C, the processing power is 10 to 4
Corona discharge treatment is performed at 0 W/m2/min. One side (
When only side A) is treated, side B is subjected to corona discharge treatment in a mixed gas of nitrogen and oxygen (volume ratio of oxygen 1 to 30%) at the above temperature. By such a manufacturing method, a film having a specific atomic composition ratio can be produced. In addition, surface roughness Ra
This can be controlled by controlling the amounts of ethylene components, butene components, etc., by laminating ethylene/propylene block copolymers, or by roughening the surface by utilizing crystal modification of polypropylene.

The polypropylene film of the present invention is used for double-sided deposition. Although the metal to be vapor-deposited is not particularly limited, the film of the present invention is particularly suitable for vapor-depositing aluminum, zinc, copper, nickel, or silver, or alloys thereof. Specific examples of the alloy include aluminum/zinc, aluminum/copper, aluminum/nickel, and cadmium/bismuth/zinc. In the case of aluminum alloys, those having an aluminum content of 2 to 40% can be preferably used. The thickness of the vapor-deposited metal layer is not particularly limited, but is preferably 7 to 40 nm, more preferably 10 to 30 nm. In the case of the present invention, it is particularly preferable to deposit metals having a zinc ratio of 50% by weight or more.

The polypropylene film of the present invention is used for double-sided deposition, but it may also be used for single-sided deposition or without deposition.

[0024] The methods for measuring the characteristics and evaluating the effects are as follows.

(1) Surface roughness (Ra) According to JIS B0601-1976. The cutoff is 0.25 mm.

(2) Atomic composition ratio of film surface layer The film surface was measured using an ESCA spectrometer model ES200 manufactured by Kokusai Denki Co., Ltd. under the following conditions.

Excitation X-ray: Al Kα ray (14
86.6eV) X-ray output: 10kV, 20mA temperature
: 20℃ Kinetic energy correction : Neutral carbon (-CH2-)
The kinetic energy value of was adjusted to 1202.0 eV. From the obtained energy value, the area ratio of the C1s peak and the O1s peak is calculated as the ratio of the number of oxygen atoms/the number of carbon atoms (
O/C), and the ratio of the areas of the C1s peak and N1s peak to the ratio of the number of nitrogen atoms/the number of carbon atoms (N
/C).

(3) Coefficient of Friction The film was left in an atmosphere of 23° C. and 50% RH for 24 hours, and was measured according to ASTM D 1894, and expressed as a coefficient of dynamic friction. Note that this measurement was performed with the A side and the B side superimposed so that they were in contact with each other.

(4) Blocking resistance Samples measuring 3 cm wide x 10 cm long were stacked over a 4 cm x 3 cm area and heated for 50 minutes in an atmosphere of 40°C and 85% RH.
After being left for 24 hours under a load of 0 g, the force required for shear peeling (g/12 cm2) was measured using a tensile tester. Note that this measurement was performed with the A side and the B side superimposed so that they were in contact with each other.

(5) Metal vapor deposition adhesion index (adhesion strength) Aluminum is applied to both sides of the film to a thickness of 30 nm each using a double-sided vapor deposition machine.
The area where aluminum remained attached to the film was determined by image processing, and the remaining area was determined.
Adhesion index 75% or more
4
50% or more but less than 75%
325% or more but less than 50%
less than 225%

Judgment was made based on the criteria of 1. The higher the adhesion index, the better the adhesion.

(6) Uniformity of Deposited Film Thickness Turn on the fluorescent lamp below the deposited film and visually observe the deposited film from above. 1m wide and 20m long
Inspect ○: There is no unevenness in the thickness of the deposited film.

×: The thickness of the deposited film is uneven, and dark and light areas appear under transparent observation.

(7) Vapor-deposited metal blocking (vapor-deposited metal peeling) Vapor-deposition is performed on both sides using a double-sided vapor deposition machine, and the rolled product is heated to temperature 2.
The film was left in an atmosphere of 5°C and relative humidity of 65% RH, rewound at a speed of 200 m/min every day, and evaluated based on the number of days in which the peeling of the deposited metal due to blocking reached 30 mm in the width direction from both ends of the film. . The longer the number of days, the better the blocking resistance of the deposited metal.

[0034]

[Example] Example 1 Two extruders were prepared, and one extruder was used as the resin for layer A, with an isotactic degree of 97.6% and an intrinsic viscosity [η]=
2.0 polypropylene was extruded at 260°C, and from another extruder, a blend of 90% by weight of an ethylene/propylene random copolymer with an ethylene content of 1.2% by weight and 10% by weight of high-density polyethylene was used as the B layer resin. The ethylene/propylene block copolymer obtained by polymerization in a proportion of , 4.8 in the longitudinal direction at a temperature of 144°C
Stretch it twice as much, then stretch it in the width direction at a temperature of 168°C for 90 minutes.
．． The film was stretched 0 times and then heat-treated at 150° C. to obtain a film having a layer A thickness of 9.5 μm, a layer B thickness 0.5 μm, and a total thickness of 10 μm. Subsequently, both sides of the film were placed in a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 10%), and a corona discharge treatment was performed at a film temperature of 60° C. at a rate of 23 W/m 2 /min. Next, the film was subjected to mixed vapor deposition of zinc and aluminum on both sides of the sample using a double-sided vapor deposition machine so that the thickness of the vapor-deposited metal layer was 40 nm and the zinc ratio was 90% by weight, and the sample was wound up. The properties of the obtained film and the properties of the deposited film are shown in Tables 1 and 2. Example 2 The B side of the film produced in the same manner as in Example 1 was treated in air at a treatment intensity of 26 W/m2/min. It was carried out in exactly the same manner as in Example 1 except that the corona discharge treatment was performed. The results are shown in Tables 1 and 2.

Example 3 Isotactic degree 96.5%, intrinsic viscosity [η]=2.
0 polypropylene resin was melt-extruded at an extruder temperature of 260°C, cooled and solidified in a casting drum at 70°C, and then the sheet was stretched 5.0 times in the length direction at a temperature of 139°C, and then stretched in the width direction. The film was stretched 8.0 times at a temperature of 167°C and further heat-treated at a temperature of 160°C to obtain a biaxially stretched film having a thickness of 10 μm. Example 1 was then performed, except that both sides of the film were subjected to corona discharge treatment at a rate of 15 W/m2/min at a film temperature of 40°C in an atmosphere of a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 8%). It was carried out in the same manner. The results are shown in Tables 1 and 2.

Example 4 Example 3 except that the casting drum temperature was 96°C.
A film was formed in exactly the same manner as above, and the A side of the film was placed in a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 15%) and heated at a film temperature of 60°C at 26 W/.
Corona discharge treatment was performed at m2/min. Subsequently, a vapor-deposited film was obtained in exactly the same manner as in Example 1, except that the B side was subjected to a corona discharge treatment at 10 W/m2/min in air. The results are shown in Tables 1 and 2.

Comparative Example 1 A test was carried out in exactly the same manner as in Example 1, except that both surfaces of the biaxially stretched film obtained in Example 1 were subjected to corona discharge in air. The results are shown in Tables 1 and 2.

Comparative Example 2 Side A of the biaxially stretched film produced by the method of Example 3 was exposed to a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 6%).
Inside, a corona discharge treatment of 29 W/m2/min was performed at a film temperature of 70°C, and the B side was subjected to a corona discharge treatment of 20 W/m2 in air.
Example 1 was carried out in exactly the same manner as in Example 1, except that the corona discharge treatment was carried out at a rate of /min. The results are shown in Tables 1 and 2.

Comparative Example 3 Side A of the biaxially stretched film produced by the method of Example 3 was heated to 15 W/m2/m at a film temperature of 40° C. in a nitrogen atmosphere.
The B side was subjected to corona discharge treatment at 20W in the air.
The process was carried out in exactly the same manner as in Example 1, except that the corona discharge treatment was carried out at a rate of m2/min. The results are shown in Tables 1 and 2.

Comparative Example 4 Side A of the biaxially stretched film produced by the method of Example 3 was treated with a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 10%).
) at a film temperature of 60°C and a power output of 23W/m2/
A corona discharge treatment of min. Subsequently, the same procedure as in Example 1 was carried out except that side B was subjected to corona discharge treatment in air at 29 W/m2/min. Table 1 shows the results.
, 2.

Comparative Example 5 The corona discharge treatment strength of the B side of Comparative Example 4 was set to 10 W/m2/
It was carried out in exactly the same manner as in Example 3 except that the setting was set to min. The results are shown in Tables 1 and 2.

Comparative Example 6 Isotactic degree 96.5%, intrinsic viscosity [η]=2.
The polypropylene resin No. 10 was melt-extruded at an extrusion temperature of 260°C, cooled and solidified in a casting drum at 25°C, and then longitudinally stretched at a temperature of 155°C using a simultaneous biaxial stretching machine.
The film was stretched 8 times in width and 8 times in width to obtain a biaxially stretched film of 10 μm. Example 1 was followed, except that both sides of the film were subjected to corona discharge treatment at a rate of 20 W/m2/min at a film temperature of 40° C. in an atmosphere of a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 10%). It was carried out in exactly the same way. The results are shown in Tables 1 and 2.

Comparative Example 7 Two extruders were prepared, and one extruder produced a layer A resin with an isotactic degree of 97.6% and an intrinsic viscosity [η]=
2.10 polypropylene was extruded at 260°C, and from another extruder, the ethylene content was 0.8 as B layer resin.
An ethylene/propylene block copolymer obtained by polymerizing a blending ratio of 96% by weight of ethylene/propylene random copolymer and 4% by weight of high density polyethylene was melted at an extrusion temperature of 260°C to form a two-layer composite die. After that, it was cooled and solidified in a casting drum at 55°C, and then rolled in the longitudinal direction at a temperature of 144°C.
Stretched 8 times, then stretched 9.1 times in the width direction at a temperature of 167°C, and then heat treated at 152°C to form a film with A layer thickness of 9.6 μm, B layer thickness of 0.4 μm, and total thickness of 10 μm. Obtained. Example 1 was followed, except that both sides of the film were subjected to corona discharge treatment at a rate of 20 W/m2/min at a film temperature of 40°C in an atmosphere of a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 10%). It was carried out in exactly the same way. The results are shown in Tables 1 and 2.

Comparative Example 8 A test was carried out in exactly the same manner as in Example 1 except that the thickness of the composite layer (layer B) was 2.0 μm and the thickness of layer A was 8.0 μm. The results are shown in Tables 1 and 2.

[0045]

[Table 1]

[0046]

[Table 2]

From Tables 1 and 2, in Examples 1 to 4, the blocking shear force is small, the thickness of the deposited metal film is uniform, the adhesion is strong, the blocking of the metal deposition is small, and there are no wrinkles during deposition. It can be seen that it is something like this.

On the other hand, in Comparative Example 1, if the atomic composition ratios O/C and N/C of the surface layer on at least one side are not simultaneously maintained in specific amounts, the metal vapor deposition adhesive strength and metal vapor deposition blocking resistance will be poor.

As in Comparative Examples 2 and 3, O
If the value of /C is too high, blocking tends to occur, and wrinkles are observed during vapor deposition. On the other hand, if it is too low, the uniformity of the deposited film thickness and the blocking resistance of metal deposition will be poor.

As in Comparative Examples 4 and 5, O
If the value of /C is too high, blocking tends to occur and wrinkles may appear during vapor deposition. Furthermore, if the value of O/C is too low, the vapor deposition adhesion and uniformity of the vapor deposited film will be poor, and the blocking resistance of metal vapor deposition will be poor.

If the surface roughness of the film is too small as in Comparative Example 6, blocking will occur easily and the blocking resistance of metal vapor deposition will be poor.

[0052] Furthermore, when the coefficient of friction of the film is high as in Comparative Example 7, wrinkles are observed during vapor deposition and the blocking resistance of metal vapor deposition is also poor.

If the surface roughness of the film is too large as in Comparative Example 8, the uniformity of the deposited film thickness will be poor and the blocking resistance of metal vapor deposition will also be poor.

[0054]

Effect of the invention: The polypropylene film for double-sided deposition of the present invention has a surface roughness (Ra) of 0.025 to 0.
．． 136 μm, the coefficient of friction between the A side and the B side is 0.75 or less, and the atomic composition ratio of the surface layer of the A side of the film is: number of oxygen atoms/number of carbon atoms = 0.15 to 0.34. , the number of nitrogen atoms/the number of carbon atoms is in the range of 0.005 to 0.08, and the atomic composition ratio of the surface layer of the B-plane is the number of oxygen atoms/the number of carbon atoms.
The number of carbon atoms = 0.15 to 0.34, the number of nitrogen atoms/the number of carbon atoms = 0.005 to 0.08, or the atomic composition ratio of the surface layer of the B side is oxygen atoms. By setting the number of carbon atoms/the number of carbon atoms in the range of 0.10 to 0.40, the blocking shearing force is small, the thickness of the deposited metal film is uniform, the adhesion is strong, and the blocking of the metal deposition is small, and the deposition The result is an excellent product with no wrinkles caused by time.

Claims (2)

[Claims] Claim 1: The surface roughness (Ra) of both sides of the film is 0.025 to 0.136 μm, and the surface roughness (Ra) of one side of the film (A
The coefficient of friction between the surface (surface) and the other surface (surface B) is 0.75 or less, and the atomic composition ratio of the surface layer of surface A of the film is: Number of oxygen atoms/number of carbon atoms = 0.15 ~0.34, number of nitrogen atoms/number of carbon atoms = range of 0.005 to 0.08, and the atomic composition ratio of the surface layer of the B-plane is: number of oxygen atoms/number of carbon atoms = 0.10 A polypropylene film for double-sided deposition, characterized in that it has a value in the range of 0.40 to 0.40. 2. The atomic composition ratio of the surface layer of the B-plane is such that the number of oxygen atoms/the number of carbon atoms = 0.15 to 0.34, and the number of nitrogen atoms/the number of carbon atoms = 0.005 to 0.08. The polypropylene film for double-sided vapor deposition according to claim 1, wherein the polypropylene film is in the range of .