JPH0797539B2 - Polypropylene film for double-sided vapor deposition - Google Patents

Description

Detailed Description of the Invention

[0001]

[Industrial applications]

[0002]

2. Description of the Related Art Polypropylene films are widely used for capacitors because they have excellent electrical characteristics. In this application, vapor deposition on both surfaces of polypropylene film has been studied for the purpose of improving productivity in the manufacturing process of capacitors, but more recently, vapor deposition metal has been used to improve the performance of capacitors. There has been an increasing demand to change the specifications of the above aluminum to a zinc-based metal having more excellent electrical characteristics.

That is, aluminum has a large decrease in electrostatic capacitance with respect to long-term charging, and there is a limit to increase the frequency of potential of the capacitor. On the other hand, zinc has an advantage that the decrease in electrostatic capacity is extremely small and the frequency of high potential can be increased. On the other hand, zinc has the drawback of being inferior in moisture resistance and clearing property to aluminum, so that methods such as mixed vapor deposition of different metals such as aluminum and thin vapor deposition film can be used together. Many.
In any case, in order to bring out the characteristics of zinc, the zinc ratio must be 50% by weight or more.

A polypropylene film for vapor deposition and a polypropylene film for easy adhesion are disclosed in JP-A-1-22314.
No. 4, Japanese Patent Publication No. 61-9332, etc. are known.

[0005]

In the film obtained by the conventional method, that is, in the method described in JP-A-1-223144, the adhesion between the film and the vapor-deposited metal is insufficient and the vapor-deposited film thickness is low. However, there is a drawback that the partial deposition is likely to occur and the uniformity of the deposited film thickness is poor. In particular, zinc has a weaker adhesion to the film than aluminum,
When a vapor-deposited metal layer having a zinc ratio of 50% by weight or more is provided, in the vapor-deposited film wound in the vapor deposition final step,
Due to blocking between the winding layers, the vapor-deposited metal is peeled off when unwinding in the next step such as a narrow slit and cannot be put to practical use.
This is remarkable in a thin film, particularly a film having a heat of 10 μm or less.

Further, the film obtained in Japanese Patent Publication No. 61-9332 has the drawbacks that the film and the film are blocked to cause film breakage, and wrinkles are generated during vapor deposition, so that a satisfactory vapor deposited film cannot be obtained. .

The present invention solves the above problems, the occurrence of blocking is small, the adhesive force between the film and the metal vapor deposition is strong, the uniformity of the vapor deposition film thickness is excellent, the vapor deposition metal does not peel off, and wrinkles do not occur during vapor deposition. An object is to provide a polypropylene film for double-sided vapor deposition that does not occur.

[0008]

The polypropylene film for double-sided vapor deposition according to the present invention has a surface roughness (Ra) of 0.025 to 0.136 μm and a friction coefficient between the A side and the B side of 0.75 or less. And the atomic composition ratio of the surface layer on the A-side of the film is as follows: 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 In the range of 0.08, the atomic composition ratio of the surface layer of the B surface is in the range of the number of oxygen atoms / the number of carbon atoms = 0.10-0.40.

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

In the case of the present invention, a homopolymer is particularly preferable, and the isotacticity is particularly preferably 97.0% or more.

The atomic composition ratio of the surface layer on both sides or one side (A side) of the polypropylene film in the present invention is the number of oxygen atoms / the number of carbon atoms (hereinafter abbreviated as O / C) =
It is necessary to be in the range of 0.15 to 0.34,
More preferably, it is desirable that O / C is in the range of 0.20 to 0.30. If the value is smaller than this range, the adhesion to the vapor-deposited metal becomes poor. On the contrary, when the value is larger than this range, the film tends to be blocked, and wrinkles are generated during vapor deposition. Next, the number of nitrogen atoms / the number of carbon atoms (abbreviated as N / C)
= 0.005 to 0.08, more preferably N / C = 0.010 to 0.05. If the value of N / C is smaller than this range, the adhesion to the metal to be vapor-deposited will be inferior. On the contrary, if the value is larger than this range, the film will be easily blocked, and at the time of vapor deposition. Wrinkles occur.

An important point of the present invention is that the surface layer of both sides or one side (A side) of the polypropylene film (usually an ultrathin layer up to about 10 nm from the surface) has oxygen atoms and nitrogen atoms within the above range. That is to have at the same time. If the surface layer has only oxygen atoms, or
On the contrary, when it has only nitrogen atoms, the vapor-deposited film wound up in the final step of double-sided vapor deposition peels off the vapor-deposited metal when it is unwound in the next step, which makes it practically impossible. In particular, this tendency becomes stronger when the deposited metal is zinc.

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

If the O / C of the surface (B side) is less than 0.10, the adhesion to the vapor-deposited metal becomes poor, and if it exceeds 0.40, the film becomes sticky, and it is hard to slip and easily blocks. Become. In addition, 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. When the surface roughness (Ra) is less than 0.025 μm, the blocking resistance is impractical. On the other hand, when the thickness exceeds 0.13 μm, the adhesion to the vapor-deposited metal is poor, and especially the zinc thin film is inferior in the uniformity of the vapor-deposited film thickness.

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 it exceeds, wrinkles will occur during vapor deposition, and the vapor-deposited metal will peel off when the vapor-deposited film wound up in the final product is unwound in the next step, and it will be practically useless.

The lower limit of the friction coefficient is not particularly limited, but is about 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 a heat stabilizer, an antioxidant, and an electrostatic charge improver may be added to the polymer.

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

Polypropylene resin was melted at a temperature of 220 to 280 ° C., extruded into a sheet form from a slit T die, cooled and solidified by a cooling roll at 30 to 96 ° C., and then 1
Stretching at a temperature of 22 to 155 ° C. in the length direction 3 to 7 times,
Then, 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.
Then, on both sides or one side (A side) of the film, a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide 0.5 to 50
%), And the temperature of the film is 30 to 100 ° C.,
The processing power is preferably 10 to 4 while maintaining the temperature at 40 to 80 ° C.
Corona discharge treatment is performed at 0 W / m ² / min. When only one side (A side) is treated, the B side is subjected to corona discharge treatment at the above temperature in a mixed gas of nitrogen and oxygen (volume ratio of oxygen is 1 to 30%). By such a production method, a film having a specific atomic composition ratio can be produced. The surface roughness R
For a, a method of controlling by the amount of ethylene component, butene component, etc., a method of laminating ethylene / propylene block copolymer, a method of roughening the surface by utilizing the crystal modification of polypropylene, etc. can be used.

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

The polypropylene film of the present invention is used for vapor deposition on both sides, but it may be vapor-deposited on one side or may be used without vapor deposition.

The method of measuring the characteristic and the method of evaluating the effect 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 ESCA spectrometer ES manufactured by Kokusai Electric Co., Ltd.
The surface of the film was measured under the following conditions using Model 200.

Excited X-ray: Al Kα ray (1486.
6 eV) X-ray output: 10 kV, 20 mA Temperature: 20 ° C. Kinetic energy correction: The kinetic energy value of neutral carbon (—CH ₂ —) was adjusted to 1202.0 eV. From the obtained energy values, the ratio of the area of the peak of C _{1s and} the peak of O _1s was calculated by the ratio of the number of oxygen atoms / the number of carbon atoms (O /
C) and the ratio of the areas of the C _1s peak and the N _1s peak is the ratio of the number of nitrogen atoms / the number of carbon atoms (N /
The value is C).

(3) Coefficient of Friction A film left to stand in an atmosphere of 23 ° C. and 50% RH for 24 hours was measured according to ASTM D 1894 and shown as a dynamic friction coefficient. In addition, this measurement was carried out by overlapping so that the A surface and the B surface were in contact with each other.

(4) Blocking resistance A sample having a width of 3 cm and a length of 10 cm was piled up over a size of 4 cm × 3 cm and placed in an atmosphere of 40 ° C. and 85% RH for 50 minutes.
After standing for 24 hours under a load of 0 g, the force required for shear peeling (g / 12 cm ² ) was measured with a tensile tester. In addition, this measurement was carried out by overlapping so that the A surface and the B surface were in contact with each other.

(5) Adhesion index of metal vapor deposition (adhesive strength) With a double-sided vapor deposition machine, aluminum was applied to each side of the film to 3
It was vapor-deposited to 0 nm, peeled off with Nichiban Cellophane adhesive tape (registered trademark “Cellotape”), and the area where aluminum remained on the film was image-processed to find the remaining area. Adhesion index 75% or more 4 50% or more Less than 75% 3 25% or more and less than 50% 2 Less than 25% 1 The higher the adhesion index, the better the adhesion.

(6) Uniformity of evaporated film thickness The lower fluorescent lamp of the evaporated film is turned on, and visual observation is performed from the upper part of the evaporated film. Width 1m and length 20m
Inspect ○: There is no unevenness in the deposited film thickness.

X: There is unevenness in the vapor deposition film thickness, and a light and shade part is formed by transparent observation.

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

[0034]

EXAMPLES Example 1 Two extruders were prepared, and from one extruder, as the resin for the layer A, the isotacticity was 97.6% and the intrinsic viscosity [η] =
2.0 polypropylene was extruded at 260 ° C., and 90% by weight of an ethylene / propylene random copolymer having an ethylene content of 1.2% by weight and 10% by weight of high density polyethylene were used as a resin for the layer B from another extruder. The ethylene / propylene block copolymer obtained by polymerizing at a ratio is melted at an extrusion temperature of 250 ° C., introduced into a two-layer composite spinneret to form a two-layer laminated sheet, and then cooled and solidified by a casting drum at 55 ° C. 4.8 at a temperature of 144 ° C in the longitudinal direction
Double stretching, followed by 9.0-fold stretching in the width direction at a temperature of 168 ° C., and then heat treatment at 150 ° C. to obtain a film having an A layer thickness of 9.5 μm, a B layer thickness of 0.5 μm, and a total thickness of 10 μm. It was Then, the film was placed on both sides in a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 10%) and subjected to a corona discharge treatment of 23 W / m ² / min at a film temperature of 60 ° C. Then, the film was mixed and vapor-deposited with zinc and aluminum using a double-sided vapor deposition machine so that the vapor-deposited metal layer had a thickness of 40 nm and a zinc ratio of 90% by weight, and was wound up. The properties of the obtained film and the properties of the vapor-deposited film are shown in Tables 1 and 2. Example 2 The B side of the film formed in the same manner as in Example 1 was treated in air at a treatment strength of 26 W / m ² / min. Example 1 was carried out in 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 Isotacticity 96.5%, intrinsic viscosity [η] = 2.
0 polypropylene resin was melt-extruded at an extruder temperature of 260 ° C., cooled and solidified on 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 in the width direction. It 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. Subsequently, in both sides of the film, in a mixed gas atmosphere of nitrogen and carbon dioxide (volume ratio of carbon dioxide 8%), at a film temperature of 40 ° C., 15 W / m ² / min.
The same procedure as in Example 1 was carried out except that the corona discharge treatment was performed. The results are shown in Tables 1 and 2.

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

Comparative Example 1 The same procedure as in Example 1 was carried out except that both sides 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 A-side of the biaxially stretched film produced by the method of Example 3 was mixed with nitrogen and carbon dioxide (6% by volume of carbon dioxide).
Inside, a corona discharge treatment of 29 W / m ² / min was performed at a film temperature of 70 ° C., and the surface B was 20 W / m ^{2 in} air.
The same procedure as in Example 1 was carried out except that a corona discharge treatment of / min was performed. The results are shown in Tables 1 and 2.

Comparative Example 3 The biaxially stretched film formed by the method of Example 3 was coated on the surface A at a film temperature of 40 ° C. in a nitrogen atmosphere at 15 W / m ² / m.
20W in air after in-corona discharge treatment
The same procedure as in Example 1 was carried out except that the corona discharge treatment was carried out at m ² / min. The results are shown in Tables 1 and 2.

Comparative Example 4 A surface of the biaxially stretched film formed by the method of Example 3 was mixed with a mixed gas of nitrogen and carbon dioxide (volume ratio of carbon dioxide: 10).
%) And 23 W / m ² at a film temperature of 60 ° C.
/ Min of corona discharge treatment was applied. Then, the same procedure as in Example 1 was performed except that the surface B was subjected to corona discharge treatment in air at 29 W / m ² / min. The results are shown in Tables 1 and 2.

Comparative Example 5 The corona discharge treatment strength of the B side of Comparative Example 4 was set to 10 W / m ² /
The same procedure as in Example 3 was performed except that the time was set to min. The results are shown in Tables 1 and 2.

Comparative Example 6 Isotacticity 96.5%, intrinsic viscosity [η] = 2.
The polypropylene resin of No. 10 was melt extruded at an extrusion temperature of 260 ° C., cooled and solidified by a casting drum at 25 ° C., and then, a simultaneous biaxial stretching machine was used to make a longitudinal 6
10 times the biaxially stretched film. Subsequently, Example 1 was performed except that a corona discharge treatment of 20 W / m ² / min was performed 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%) on both surfaces of the film. Exactly the same as.
The results are shown in Tables 1 and 2.

Comparative Example 7 Two extruders were prepared. From one extruder, the resin for layer A had an isotacticity of 97.6% and an intrinsic viscosity [η] =
2.10 polypropylene was extruded at 260 ° C., and the ethylene content as a resin for layer B was 0.8 from another extruder.
An ethylene / propylene block copolymer obtained by polymerizing 96% by weight of an ethylene / propylene random copolymer of 4% by weight and 4% by weight of high density polyethylene was melted at an extrusion temperature of 260 ° C. to form a two-layer composite spinneret. 3. After being led to a two-layer laminated sheet, it is cooled and solidified by a casting drum at 55 ° C. and then at a temperature of 144 ° C. in the lengthwise direction.
The film was 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 obtain a film having an A layer thickness of 9.6 μm, a B layer thickness of 0.4 μm, and a total thickness of 10 μm. Obtained. Subsequently, Example 1 was performed except that a corona discharge treatment of 20 W / m ² / min was performed at a film temperature of 40 ° C. in an atmosphere of a mixed gas of carbon dioxide and carbon dioxide (volume ratio of carbon dioxide: 10%) on both surfaces of the film. It carried out exactly like the above. The results are shown in Tables 1 and 2.

Comparative Example 8 The procedure of Example 1 was repeated except that the thickness of the composite layer (layer B) was 2.0 μm and the thickness of the 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 shearing force was small, the vapor deposition metal film thickness was uniform, the adhesive force was strong, the metal vapor deposition blocking was small, and wrinkles did not occur during vapor deposition. It turns out that it is a thing.

On the other hand, in Comparative Example 1, unless the atomic composition ratios O / C and N / C of the surface layer on at least one side are simultaneously held, the metal vapor deposition adhesive strength and the metal vapor deposition blocking resistance are poor.

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

As in Comparative Examples 4 and 5, O on the film surface
If the value of / C is too high, blocking tends to occur, and wrinkles may occur during vapor deposition. On the other hand, if the value of O / C is too low, the vapor deposition adhesion and the uniformity of the vapor deposition film are poor, and the metal vapor deposition blocking resistance is also poor.

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

It is also understood that when the coefficient of friction of the film is high as in Comparative Example 7, wrinkles are generated during vapor deposition and the metal vapor deposition blocking resistance is poor.

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

[0054]

The polypropylene film for double-sided vapor deposition of the present invention has a surface roughness (Ra) of 0.025 to 0.025.
0.136 μm, the coefficient of friction between the A surface and the B surface is 0.75 or less, and the atomic composition ratio of the surface layer of the A surface of the film is: number of oxygen atoms / number of carbon atoms = 0.15-0 .34, the number of nitrogen atoms / the number of carbon atoms = 0.005 to 0.08, and the atomic composition ratio of the surface layer of the B-side is: the number of oxygen atoms / the number of carbon atoms = 0.15-0 .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 on the B-side is: the number of oxygen atoms / the number of carbon atoms = 0. By setting it in the range of 10 to 0.40, the blocking shearing force is small, the deposited metal film thickness is uniform, the adhesive force is strong, the metal deposition blocking is also small, and wrinkles do not occur during deposition, which is excellent. It became a thing.

Claims (2)

[Claims] 1. The surface roughness (Ra) of both surfaces of the film is 0.025 to 0.136 μm, and one surface (A) of the film is
The friction coefficient between the surface) and the other surface (the surface B) is 0.75 or less, and the atomic composition ratio of the surface layer of the surface A of the film is as follows: number of oxygen atoms / number of carbon atoms = 0.15 To 0.34, the number of nitrogen atoms / the number of carbon atoms = 0.005 to 0.08, and the atomic composition ratio of the surface layer of the B-side is: the number of oxygen atoms / the number of carbon atoms = 0.10 The polypropylene film for double-sided vapor deposition is in the range of .about.0.40. 2. The atomic composition ratio of the surface layer on the B side 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, characterized in that