JP2002234958A - Polypropylene film for double-side vapor deposition and capaciter comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double-side vapor-deposition polypropylene film developing less blocking in a handling step such as storage or a vapor-deposition process, and a capasitor comprising the film. SOLUTION: This film is a polypropylene film having both sides subjected to corona discharge treatment, wherein the sum of the heat shrinkage factors in the longitudinal direction and the width direction of the film is <=5%, and an antioxidant contained in the film is a carbonyl group-free phenolic antioxidant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene film for double-sided vapor deposition and a capacitor using the same.

[0002]

2. Description of the Related Art Polypropylene films are widely used in electrical applications because of their excellent electrical properties. Above all, the demand for dielectric materials for capacitor applications has grown remarkably, and accordingly, improvement in productivity and economic efficiency in capacitor production has become an important issue. A polypropylene film used as a dielectric of a capacitor is subjected to metal deposition on one side of the film to function as an electrode of the capacitor, and is often used by winding two single-sided metallized films as a pair.
If metal deposition can be performed simultaneously on both sides of the film in this deposition process, one double-sided metallized film and one raw film can be used as a pair, and the efficiency of the deposition process is doubled. There is a growing demand for a high supply of polypropylene film for double-sided deposition.

In general, the surface of a polypropylene film on which metal deposition is performed is previously subjected to a treatment for increasing the surface tension, such as a corona discharge treatment, in order to facilitate the formation of a deposited metal layer. However, simply performing the corona discharge treatment on both surfaces of the film causes problems such as blocking between the films before vapor deposition and blocking between the metals after vapor deposition, and is not usable.
Therefore, proposals have been made for obtaining a polypropylene film for double-sided deposition that does not cause blocking.

For example, Japanese Patent Application Laid-Open No. 1-223144 discloses that an antioxidant having a melting point of 140 ° C. or less and a melting point of 170 ° C.
It contains the above antioxidant, has at least one surface roughness of 0.02 μm or more, and has a wet tension of 34 to 4 on both surfaces.
A polypropylene film for double-sided evaporation of 5 dyne / cm has been proposed. JP-A-3-83636 discloses an antioxidant having a melting point of 140 ° C. or less, a double-sided vapor deposition with a surface roughness of at least one side of 0.04 μm or more, and a wet tension of both sides of 36 to 44 dyne. Polypropylene films have been proposed. Japanese Patent Application Laid-Open No. Hei 4-216829 discloses that a polymer having a melt crystallization temperature higher than that of polypropylene by 0.5 to 10% by weight is blended with polypropylene having an isotacticity of 96.5% or more, and the wetting tension on both sides is reduced. 35-45 dyne / cm,
In addition, the surface roughness Ra of at least one side is 0.025 to 0.2.
It has been proposed that the thickness be 15 μm.

[0005]

However, in the polypropylene films proposed in JP-A-1-223144 and JP-A-3-83636, an antioxidant having a carbonyl group is contained in the film. Blocking between films may occur during handling processes such as storage, and if the heat shrinkage of the film is large, the film may be exposed to high temperatures. However, it was insufficient as a film for double-sided evaporation. Also, Japanese Patent Application Laid-Open No. Hei 4-21682
In the polypropylene film proposed in Japanese Patent Publication No. 9 as well, the formulation of the additive was not specified, and as in the former two, it was insufficient as a film for double-sided evaporation.

Accordingly, an object of the present invention is to improve the drawbacks of the prior art, and to provide a polypropylene film for double-sided vapor deposition and a capacitor using the same, which cause less occurrence of blocking in a handling process such as ordinary storage or a vapor deposition process. To provide.

[0007]

Means for Solving the Problems In order to achieve the above object, a polypropylene film for double-sided vapor deposition according to the present invention is a polypropylene film having both surfaces of a film subjected to a corona discharge treatment, and the film is heated in the longitudinal direction of the film. The sum of the shrinkage rate and the heat shrinkage rate in the width direction is 5% or less, and
The film is characterized in that the antioxidant contained in the film is only a phenolic antioxidant containing no carbonyl group.

The capacitor according to the present invention comprises at least a part of the capacitor using such a polypropylene film for double-sided evaporation.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with preferred embodiments. The polypropylene film according to the present invention, in order to provide a vapor-deposited metal layer on both surfaces of the film, it is necessary that both surfaces of the film have been subjected to corona discharge treatment, the wetting tension provided by the corona discharge treatment is too low. If a metal is not deposited, or if a metal is deposited, a metal layer effective as an electrode of a capacitor cannot be obtained, and if it is too high, blocking may be induced, which is not preferable. Preferably, the wetting tension on both sides of the film is 35 mN / m or more and 50 mN / m or less, and more preferably 36 mN / m or more and 45 mN / m or less.

The polypropylene film according to the present invention has a temperature of 120 ° C. according to JIS C-2330.
The sum of the heat shrinkage in the longitudinal direction and the heat shrinkage in the width direction after the heat treatment at the above temperature for 15 minutes needs to be 5% or less. If it exceeds 5%, thermal shrinkage of the film due to thermal stress at the time of the vapor deposition processing causes an increase in the shrinkage of the film, which may cause blocking between the metals after the vapor deposition. The sum of the heat shrinkage is preferably 4% or less, more preferably 3% or less.

Further, the antioxidant contained in the polypropylene film according to the present invention needs to be a phenolic antioxidant containing no carbonyl group, and it is particularly preferable to use only the phenolic antioxidant. Not only phenolic compounds but also antioxidants containing a carbonyl group may bind to other substance molecules due to the nature of the double bond possessed by the carbonyl group, resulting in blocking. is there. Examples of phenolic antioxidants containing no carbonyl group include 1,3,5 trimethyl-2,4,6-tris (3,5-di-tert-butyl-4hydroxybenzyl) benzene and 2,6.
-Di-tert-butyl-4-methylphenol, 2,
4-bis-[(n-octylcio) -6- (4-hydroxy-3,5-di-tertiarybutyranilino) -1,
3,5-triazine] and the like, and taking into account the handling properties and the fact that good electrical characteristics of the capacitor are achieved, 1,3,5 trimethyl-2,4,6-tris (3,5-triazine) is taken into consideration. Di-tert-butyl-4hydroxybenzyl) benzene is preferred.

If the content of the phenolic antioxidant containing no carbonyl group is too small, the original antioxidant effect is weakened. Preferably 0.02 wt.
% Or more and 2% by weight or less, more preferably 0.04w
It is not less than t% and not more than 1.5 wt%.

If the center line average roughness Ra of at least one surface of the polypropylene film according to the present invention is too small, the running property of the film may be impaired.
The thickness is preferably 4 μm or more, but if it is too large, the withstand voltage characteristics may be impaired. Therefore, it is more preferably 0.05 μm or more and 0.2 μm or less.

It is preferable that the polypropylene film according to the present invention contains polymethylpentene in an amount of 0.2 wt% or more and 5 wt% or less in order to impart an appropriate slip property to the film. If the amount is less than 0.2 wt%, the effect of imparting the slipperiness is small, and if it exceeds 5 wt%, the film may unwind. More preferably, 0.5 wt%
The range is at least 3 wt%.

The polymer constituting the polypropylene film according to the present invention is not particularly limited. In addition to a homopolymer of polypropylene, propylene and other α
-It may be a copolymer of olefins (eg, ethylene, butene, etc.), or a blend of polypropylene and another α-olefin polymer (eg, polyethylene, polybutene, etc.).

Further, the method for stretching the polypropylene film according to the present invention is not particularly limited, and a tenter method,
Although any film obtained by the inflation method or the like may be used, biaxial stretching by a tenter method is preferable because a film for a capacitor is required to be thin and has small thickness unevenness.

The structure and form of the capacitor made of the polypropylene film according to the present invention are not particularly limited, but the present invention is particularly suitable for a flat press type.

When the polypropylene film according to the present invention is used for a capacitor, the electrodes are not particularly limited. For example, even if it is a metal foil or a paper or a plastic film having both sides metallized, the present invention is not limited thereto. One side or both sides of such a polypropylene film may be directly metallized, but it is preferable to directly metallize the film. At this time, the type of metal used is zinc, tin, silver,
Examples thereof include simple substances such as chromium, aluminum, copper, and nickel, and mixtures or alloys of plural kinds, but are not particularly limited. Also, the vapor deposition pattern is not particularly limited, and may be a normal pattern or a special margin pattern provided for the purpose of improving the security of the capacitor. Further, the configuration of the margins is not particularly limited, and may be, for example, a tape type or an oil type.

The dielectric material to be wound together in a pair with the polypropylene film having both sides metal-deposited is not particularly limited. For example, the dielectric material may be paper or a plastic film of another material. It may be a polypropylene film.

Incidentally, the polypropylene film according to the present invention may be used without being subjected to single-sided vapor deposition or vapor deposition, in addition to double-sided vapor deposition.

Next, an example of a method for producing a polypropylene film according to the present invention will be described, but is not particularly limited. 1,3,5 trimethyl-2,4,6-tris (3,3
5-di-tert-butyl-4 hydroxybenzyl)
A polymer obtained by adding 0.5 wt% to 5 wt% of polymethylpentene to a polypropylene resin containing 0.1 to 1 wt% of benzene is supplied to an extruder at a temperature of 200 to 270 ° C., melted, and subjected to slitting. It is extruded into a sheet form from a die and cooled and solidified by a cooling roll at a temperature of 20 to 95 ° C. At this time, the higher the melt index of the polypropylene resin is, the smaller the heat shrinkage ratio is. In general, the higher the cooling roll temperature, the higher the surface roughness. Therefore, the cooling roll temperature may be appropriately selected.

Next, the film is stretched 3 to 7 times in the longitudinal direction by a stretching roll at 115 to 155 ° C. Also in this case, the magnitude of the surface roughness can be changed by selecting the stretching temperature. Next, the film is stretched 7 to 12 times in the width direction at a temperature of 155 to 175 ° C, and further subjected to a heat treatment at 140 to 165 ° C. Generally, the lower the stretching temperature or the heat treatment temperature, and the higher the stretching ratio, the greater the heat shrinkage. Therefore, these conditions may be appropriately selected.

After the corona discharge treatment is applied to both surfaces of the thus obtained polypropylene film, it is wound up by a winder.

Next, the measurement method and the evaluation method used in the present invention will be described. (1) Blocking peeling force A sample having a size of 10 cm in the longitudinal direction and 5 cm in the width direction was collected, and the two samples were overlapped so that a certain surface and an opposite surface were in contact with each other. 5cm x 5c
m) is sandwiched between two glass plates, and a weight is applied so that the load applied to the area becomes 1 kg. The sample thus set is heat-treated for 1 hour in a hot-air circulation oven heated to 90 ° C., and then allowed to cool at room temperature for 1 hour or more.
The two samples were peeled at an angle of 180 °, the peeling force was read with a spring, and the average value of n = 3 was determined.

(2) Metal blocking film The film was slit into a width of 620 mm and a length of 30,000 m, rolled up, and then the film was vapor-deposited with aluminum on one side to a film resistance of 3.5 Ω / □ by a vacuum vapor deposition machine for capacitors. Then, slits were made to a width of 30 mm and a length of 4800 m, and 120 reels were collected. At this time,
The number of reels in which metal peeling due to blocking was recognized was divided by the total number of reels (120 reels) and expressed as a percentage. In the present invention, those having 7% or less were accepted.

(3) Wetting tension Measured according to JIS K-6768 (1995).

(4) Center line average roughness (Ra) Measured according to JIS B-0601 (1982). However, the cutoff was 0.25 mm.

(5) Heat shrinkage rate According to JIS C-2330 (1995),
After measuring the heat shrinkage in each of the width directions, the sum of the heat shrinkage in the longitudinal direction and the heat shrinkage in the width direction was obtained.

(6) Melt index Measured according to ASTM D 1238 (230 ° C., 2.16 kg).

[0030]

Next, an embodiment of the present invention will be described. Example 1 1,3,5 trimethyl-2,4,6-tris (3,5-
Melt index 3.0 containing 0.5 wt% of (di-tert-butyl-4-hydroxybenzyl) benzene
A polymer obtained by adding 2.0 wt% of polymethylpentene to a polypropylene resin of g / 10 min is supplied to an extruder at 250 ° C., melted, extruded from a T-die into a sheet,
After cooling and solidifying with a cooling roll at a temperature of 85 ° C, 140 ° C
The film was stretched 5 times in the longitudinal direction at a temperature of, then stretched 10 times in the width direction at a temperature of 167 ° C, and then heat-treated at a temperature of 165 ° C. Thereafter, the film was subjected to a corona discharge treatment so that the wetting tension of each side of the film became 40 mN / m, and the film was wound by a winder.

At this time, the film thickness is 5 μm, the center line average roughness Ra on one surface is 0.04 μm, the center line average roughness on the opposite surface is 0.08 μm, and the heat shrinkage in the longitudinal direction is 2.8. %, The heat shrinkage in the width direction was 0.5%, and the blocking peeling force was 5 g.

Further, this film was slit at a speed of 450 m / min to a width of 620 mm and a length of 30,000 m and wound up. This film was vapor-deposited on one side of a film using a vacuum vapor deposition machine for a capacitor so as to have a film resistance of 3.5 Ω / □, and then slit into a width of 30 mm and a length of 4800 m to collect 120 reels. At this time, the metal blocking was 0.8%.

Example 2 A polypropylene film was obtained under the same conditions as in Example 1 except that a polypropylene resin having a melt index of 4.0 g / 10 min was used. The thickness of the film is 5 μm, the center line average roughness Ra on one side is 0.04 μm, the center line average roughness on the opposite side is 0.08 μm, the wetting tension on both sides of the film is 40 mN / m each, and the heating in the longitudinal direction. 1.9 shrinkage
%, The heat shrinkage in the width direction was 0.1%, and the blocking peeling force was 1 g.

This film was slit at a speed of 450 m / min at a width of 620 mm and a length of 30,000 m and wound up. This film was vapor-deposited on one side of a film using a vacuum vapor deposition machine for a capacitor so as to have a film resistance of 3.5 Ω / □, and then slit into a width of 30 mm and a length of 4800 m to collect 120 reels. At this time, the metal blocking was 0%.

Example 3 A polypropylene film was obtained under the same conditions as in Example 1 except that polymethylpentene was not added. The thickness of the film is 5 μm, and the center line average roughness Ra of one surface is 0.0
4 μm, the center line average roughness of the opposite surface is 0.07 μm, the wetting tension on each side of the film is 40 mN / m, the heat shrinkage in the longitudinal direction is 2.9%, the heat shrinkage in the width direction is 0.5%,
The blocking peel strength was 10 g.

This film was slit at a speed of 450 m / min at a speed of 450 m / min to a width of 620 mm and a length of 30,000 m. This film was vapor-deposited on one side of a film using a vacuum vapor deposition machine for a capacitor so as to have a film resistance of 3.5 Ω / □, and then slit into a width of 30 mm and a length of 4800 m to collect 120 reels. At this time, the metal blocking was 5.0%.

Example 4 A polypropylene film was obtained under the same conditions as in Example 1 except that the film was subjected to a corona treatment so that the wetting tension on both sides of the film became 52 mN / m and wound up with a winder.
The thickness of the film is 5 μm, and the center line average roughness R of one surface is
a is 0.04 μm, and the center line average roughness of the opposite surface is 0.08
μm, the wetting tension on each side of the film was 52 mN / m, the heat shrinkage in the longitudinal direction was 2.9%, the heat shrinkage in the width direction was 0.5%, and the blocking peeling force was 7 g.

Further, this film was slit at a speed of 450 m / min to a width of 620 mm and a length of 30,000 m and wound up. This film was vapor-deposited on one side of a film using a vacuum vapor deposition machine for a capacitor so as to have a film resistance of 3.5 Ω / □, and then slit into a width of 30 mm and a length of 4800 m to collect 120 reels. At this time, the metal blocking was 2.5%.

Example 5 A molten polymer extruded into a sheet from a T-die was heated at 35 ° C.
A polypropylene film was obtained under the same conditions as in Example 1 except that the film was cooled and solidified by a cooling roll having a temperature of. The thickness of the film is 5 μm, and the center line average roughness Ra of one surface is 0.02.
μm, the center line average roughness of the opposite surface is 0.02 μm, the wetting tension on each side of the film is 40 mN / m, the heat shrinkage in the longitudinal direction is 3.1%, the heat shrinkage in the width direction is 0.6%, The blocking peel strength was 7 g.

This film was slit at a speed of 450 m / min into a width of 620 mm and a length of 30,000 m and wound up. This film was vapor-deposited on one surface of a film with a vacuum vapor deposition machine for a capacitor so as to have a film resistance of 3.5 Ω / □, and then slit into a width of 30 mm and a length of 4,800 m, and 120 reels were collected. At this time, the metal blocking was 4.2%.

Example 6 5.0 wt% of polymethylpentene was added, and the molten polymer extruded into a sheet from a T-die was cooled and solidified by a cooling roll at a temperature of 95 ° C., and then longitudinally at a temperature of 140 ° C. A polypropylene film was obtained under the same conditions as in Example 1 except that the film was stretched 5.0 times, then stretched 10 times in the width direction at a temperature of 170 ° C, and then heat-treated at a temperature of 165 ° C. The thickness of the film is 5 μm, the center line average roughness Ra on one side is 0.07 μm, the center line average roughness on the opposite side is 0.14 μm, and the wetting tension on both sides of the film is 40 mN.
/ M, the heat shrinkage in the longitudinal direction was 2.9%, the heat shrinkage in the width direction was 0.5%, and the blocking peeling force was 0 g.

The film started to be slit at a speed of 450 m / min at a speed of 450 m / min at a width of 620 mm and a length of 30000 m. However, the film was wound at a speed of 400 m / min because of winding deviation due to meandering of the film. This film was treated with aluminum at 3.5 Ω /
□ Deposited on one side to obtain a film resistance of 30
It was slit to a length of 4800 m in mm and 120 reels were collected. At this time, the metal blocking was 0%.

COMPARATIVE EXAMPLE 1 Melt index 2.9 containing 0.1 wt% of tetrakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane
A polypropylene film was obtained under the same conditions as in Example 1 except that a g / 10 min polypropylene resin was used. The thickness of the film is 5 μm, and the center line average roughness Ra of one surface is
Is 0.04 μm and the center line average roughness of the opposite surface is 0.08 μm
m, the wetting tension on each side of the film was 40 mN / m, the heat shrinkage in the longitudinal direction was 2.9%, the heat shrinkage in the width direction was 0.5%, and the blocking peeling force was 30 g.

Further, this film was slit at a speed of 450 m / min to a width of 620 mm and a length of 30,000 m and wound up. This film was vapor-deposited on one side of a film using a vacuum vapor deposition machine for a capacitor so as to have a film resistance of 3.5 Ω / □, and then slit into a width of 30 mm and a length of 4800 m to collect 120 reels. At this time, the metal blocking was 50.0%.

Comparative Example 2 A polypropylene film was obtained under the same conditions as in Comparative Example 1 except that a polypropylene resin having a melt index of 4.0 g / 10 min was used. The thickness of the film is 5 μm, the center line average roughness Ra on one side is 0.04 μm, the center line average roughness on the opposite side is 0.08 μm, the wetting tension on both sides of the film is 40 mN / m, and the heating in the longitudinal direction. 1.9 shrinkage
%, The heat shrinkage in the width direction was 0.1%, and the blocking peeling force was 20 g.

Further, this film was slit at a speed of 450 m / min to a width of 620 mm and a length of 30,000 m and wound up. This film was vapor-deposited on one side of a film using a vacuum vapor deposition machine for a capacitor so as to have a film resistance of 3.5 Ω / □, and then slit into a width of 30 mm and a length of 4800 m to collect 120 reels. At this time, the metal blocking was 21.7%.

Comparative Example 3 Melt index 2.9 containing 0.5 wt% of tetrakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane
A polypropylene film was obtained under the same conditions as in Example 1 except that a g / 10 min polypropylene resin was used. The thickness of the film is 5 μm, and the center line average roughness Ra of one surface is Ra.
Is 0.04 μm and the center line average roughness of the opposite surface is 0.08 μm
m, the wetting tension on both sides of the film were 40 mN / m, the heat shrinkage in the longitudinal direction was 2.9%, the heat shrinkage in the width direction was 0.5%, and the blocking peeling force could not be measured because the films did not peel off. .

Further, the film was slit into a width of 620 mm and a length of 30,000 m. However, the film was broken by blocking and could not be slit.

[0049]

According to the present invention, it is possible to obtain a double-sided vapor-deposited polypropylene film with little occurrence of blocking in a handling process such as storage, a vapor deposition process, and a capacitor manufacturing process until the capacitor is completed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 14/20 C23C 14/20 A 5E082 H01G 4/18 (C08L 23/12 // (C08L 23/12 23 : 20) 23:20) B29K 23:00 B29K 23:00 B29L 7:00 B29L 7:00 31:34 31:34 H01G 4/24 321C F term (reference) 4F006 AA12 AA56 AB73 BA07 CA08 DA01 EA03 4F073 AA01 BA08 BB01 CA21 4F210 AA11 AA12 AB06 AB19 AF16 AG01 AH33 QA02 QA03 QC06 QG01 QG18 QW34 4J002 BB121 BB172 EJ026 EJ046 EU186 FD076 GQ00 4K029 AA11 AA25 BA03 BB04 BD00 FA05 5E082 AB05 EE04 PP37 EE08

Claims (9)

[Claims] 1. A polypropylene film having a corona discharge treatment applied to both surfaces of a film, wherein the sum of the heat shrinkage in the longitudinal direction and the heat shrinkage in the width direction of the film is 5% or less, and The polypropylene film for double-sided vapor deposition characterized in that the antioxidant contained in is a phenolic antioxidant containing no carbonyl group. 2. The polypropylene film for double-sided vapor deposition according to claim 1, wherein the film contains only a phenolic antioxidant containing no carbonyl group as an antioxidant in the film. 3. The wetting tension on both sides of the film is 35 m each.
N / m or more and 50 mN / m or less,
The polypropylene film for double-sided vapor deposition according to claim 1 or 2. 4. The phenolic antioxidant containing no carbonyl group is 1,3,5 trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene. The polypropylene film for double-sided vapor deposition according to any one of claims 1 to 3, characterized in that: 5. A film having a center line average roughness Ra of at least one side of at least 0.04 μm.
The polypropylene film for double-sided evaporation according to any one of claims 1 to 4. 6. The double-sided vapor deposition polypropylene according to claim 1, wherein the content of the phenolic antioxidant containing no carbonyl group is 0.02 wt% or more and 2 wt% or less. the film. 7. A film comprising 0.2 parts of polymethylpentene.
The polypropylene film for double-sided vapor deposition according to any one of claims 1 to 6, wherein the content of the polypropylene film is not less than 5.0 wt% and not more than 5.0 wt%. 8. A double-sided metallized polypropylene film, wherein a metal is vapor-deposited on both sides of the polypropylene film for double-sided vapor deposition according to claim 1. 9. A capacitor comprising at least a part of the polypropylene film for double-sided vapor deposition according to claim 1.