JPH02170406A - Polypropylene film for vapor deposition for capacitor - Google Patents

Abstract

PURPOSE:To obtain a film for a capacitor excellent in vapor deposition processability, containing less deposits and minimizing the sliding friction with a cooling roll, by a method wherein the static coefficient of friction between a Cr-plated metallic sheet and a non-vapor-deposited surface after metallic vapor deposition on one surface of a polypropylene film as well as the content of an additive are specified. CONSTITUTION:The title film is made of a PP resin comprising II (isotactic index) exceeding 96% with specific additive added thereto. The state of separation on a cooling roll depends upon the additive. The melting point of the additive shall not exceed 130 deg.C while the content thereof shall be selected not to exceed 4000wt.ppm. As for the additive, tetrakis [methylene-3(3,5-di-tertiary- butyl-4-hydroxyphenyl) propionate)methane, etc., are applicable. Finally, Al or the like is evaporated on one surface of the film and then the coefficient of friction between non-evaporated surface and a Cr-plated metallic sheet at 80 deg.C is selected not to exceed 0.8 to minimize the sliding friction with the cooling roll.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polypropylene film for vapor deposition for capacitors.

[Conventional technology]

Polypropylene film is widely used as an industrial material due to its excellent properties. Recently, with changes in market demands and various improvements, applications in which metals are vapor-deposited on polypropylene films are rapidly increasing. Among these, for capacitors, there has been a remarkable shift towards vapor deposition because it can be made smaller and has self-healing properties compared to conventional ones that are wound with metal foil. For this reason, in addition to the conventional method, good vapor deposition processability is now required.

However, polypropylene film is not suitable for vapor deposition processing because it is weaker and has poorer dimensional stability against heat than polyester film or polyimide film. For this reason, the actual situation is that processing conditions such as tension and cooling temperature are finely adjusted during vapor deposition processing.

At this time, if the appropriate conditions are not met, various deposition defects such as heat loss, wrinkles, uneven density, etc. will occur, leading to a decrease in processing yield.

[Problem to be solved by the invention]

In other words, the key point in the vapor deposition process of polypropylene film is how to bring the polypropylene film into close contact with the cooling roll facing the vapor deposition source without distortion.
This is because it has a cooling effect on the entire surface.

However, even if the tension conditions are optimized, sufficient adhesion cannot be obtained due to poor slippage between the polypropylene film and the cooling roll, and precipitates from the polypropylene film accumulate on the cooling roll, significantly reducing the cooling effect. There were drawbacks.

In view of these problems, the present invention aims to provide a polypropylene film that has good sliding properties with a cooling roll, has few precipitates, and has excellent vapor deposition processability.

[Means to solve the problem]

The polypropylene film for vapor deposition for capacitors of the present invention has an 80% bond between the non-evaporated surface and the chrome-plated metal plate after metal vapor deposition is performed on one side of the polypropylene film.
The content of additives with a static friction coefficient of 0°C or lower and a melting point of 130°C or lower is 4000 ppm by weight
It is characterized by the following:

If this coefficient of static friction exceeds 0.8, the film will not slide on the cooling roll, will not fit even when tension is applied, and the film will partially lift off the cooling roll, easily causing wrinkles and uneven shading, making it unsuitable. It is. It is preferably 0.7 or less, more preferably 0.6 or less.

In addition, the state of precipitates on the cooling roll is influenced by the additives in the polypropylene film, and in the case of capacitors, if the content of additives with a melting point of 130°C or less exceeds 4000 ppm by weight, the cooling effect of the precipitates will be affected. The film is unsuitable because it significantly reduces the amount of heat it receives during vapor deposition and causes defects such as heat loss. Preferably 30
00 ppm by weight or less, more preferably 2000 ppm or less
It is less than ppm by weight.

Here, examples of additives having a melting point of 130°C or lower include tetrakis[methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate comethane, 2,2'-methylene-bis( 4-Methyl-6-tertiary petityl phenol, η-octadecyl-3
-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, 2. Examples include 2-thio[diethyl-bis-3(3'-5-di-tert-butyl-4-hydroxyphenyl)propionate].

F-10 in the longitudinal direction of the polypropylene film of the present invention
A value of 0 is not particularly limited, but it is 10 kg/
It is more preferable that it is more than mm2.

The method for producing the polypropylene film of the present invention is not particularly limited, and may be any ordinary stretching method, preferably biaxial stretching, but -axial stretching may also be used. Of course, the inflation method or the tenter method may also be used.

Furthermore, in addition to the homopolymer, the polymer used in the polypropylene film of the present invention includes propylene and other α-
It may be a copolymer of olefins (eg, ethylene, butene, etc.) or a blend of polypropylene and other α-olefin polymers (eg, polyethylene, polybutene, etc.).

Next, an example of the method for producing the polypropylene film of the present invention will be explained. However, the manufacturing method is not limited to the following.

A polypropylene resin with II (isotactic index) of 96% or more to which tetrakis[methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate comethane was added] was heated at 190 to 280°C.
The material is melted at a temperature of 1, extruded into a sheet through a T-die with slits, and cooled and solidified with a chill roll at 30 to 95°C.

Next, it is stretched 3 to 7 times in the length direction at a temperature of 120 to 160 °C, and then 5 to 7 times in 11 directions at a temperature of 145 to 165 °C.
It is stretched 12 times and further heat-treated at a temperature of 150 to 165°C. After that, the wetting tension on the surface to be vapor-deposited is 35 to 47
It is subjected to surface treatment such as corona discharge treatment so that it has a dyn e / cm, and then wound up with a winder.

Here, the coefficient of friction with the metal plate at a high temperature, for example 80° C., is related to the properties of the polypropylene film as follows. The smaller the surface roughness of the surface in contact with the metal plate, the higher the wetting tension of the surface in contact with the metal plate, and the greater the amount of the low melting point additive, the larger the friction coefficient becomes.

Incidentally, when depositing the polypropylene film of the present invention, the metal to be deposited is not limited, but aluminum (AI), zinc (Zn), or a mixture or alloy thereof is suitable.

Moreover, the vapor deposition surface may be one side or both sides.

Next, the measurement method and evaluation method used in the present invention will be explained.

(1) Static friction coefficient between non-evaporated surface and metal plate at 80°C A rectangular film sample measuring toomm in the length direction and 75mm in the width direction is taken. Next, AI is deposited to a thickness of 20 to 40 nm on the surface intended for metal deposition. Next, the vapor-deposited film is set so that the non-vapor-deposited surface is in contact with a metal hot plate plated with chromium (Cr). A load of 200g was placed on this sample at a distance of 65mm in the length direction and 63m in the width direction.
Place it so that it covers a rectangular area of
The temperature was raised to
Calculate using the following formula.

Static friction coefficient = maximum static resistance value / 200 In the above formula, 200 in the denominator is the load (g).

Further, the number of measurements is 3, and the average value is calculated.

(2) Quantitative amount of additive Cut the film into small pieces of 5 mm x 5 mm or less, and 8 g
Collect. Next, this sample was extracted with 50ml of chloroform at 65°C for 90 minutes, and the liquid was filtered with suction.
Further, suction filtration is carried out while washing with chloroform, and then the chloroform is recovered, and the extract is dried. Next, this extract is diluted with methanol to a volume of 100 ml. Collect 2 ml of this liquid and use a liquid chromatograph (Shimabara High Performance Liquid Chromatograph LC4A type manufactured by Shimabara Manufacturing Co., Ltd.).
The concentration (mg
/ml). From the concentration determined in this way, the content rate is determined by the following formula.

In the above formula, 100 in the molecule is the volume (ml) of the methanol solution.
, 8000 in the denominator is the weight it (mg) of the sample.

〔Example〕

Next, an explanation will be given based on examples of the present invention.

Example 1 A 97% propylene homopolymer with 500 ppm of tetrakis[methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate comethane added was fed to an extruder at 260°C, It was extruded through a T-die with slits, cooled and solidified with a chill roll at 80°C, then stretched 4.5 times in the length direction at a temperature of 135°C, and then stretched 8 times in the width direction at a temperature of 160°C. ,
Further, heat treatment was performed at a temperature of 160°C. Then, on one side of the film, a wet tension of 39 dyne/cm
It was subjected to corona discharge treatment so that The film thickness at this time was 8 μm.

Next, the Nikono film was slit to a width of 630 mm and a length of 25,000 m, and the vapor deposition processability was evaluated.

The vapor deposition process was performed using a ULVAC 630 mm width, Al specification vapor deposition machine, with an A1 film thickness of 25 nm and a conveyance speed of 250 m/min.
The test was carried out under the following conditions: unwinding force of 4 kg, winding tension of 4 kg, and cooling roll refrigerant temperature of -15°C, and the vapor deposition processability was determined based on the following criteria.

(1) Uneven density of deposited film ◎: No unevenness in density at all.

01 Although there are some uneven shading, it can be used for practical purposes.

×2 There are uneven shading on the entire surface, making it unusable.

(2) Loss of heat ◎・None at all.

○: There is heat loss, but it is minor and can be used for practical purposes.

×: Severe heat loss, impractical.

(3) The film after wrinkle deposition was divided into six 100mm widths in the width direction and five 5000m lengths in the length direction, and a total of 30 reels were judged pass/fail, and the number of defective reels was judged as follows. .

◎: Number of defective reels: 1 or less ○: Number of defective reels: 2 to 4 ×: Number of defective reels: 5 or more The results are shown in Table 1.

Example 2 Same as Example 1 except that the amount of tetrakis[methylene-3(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate comethane added was 3500 ppm. The results are shown in Table 1.

Example 3 Tetrakis[methylene-3(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate instead of comethane, 1,3.5trimethyl-2,4,6-
Tris(3,5-ditershacou-butyl-4-hydroxybenzyl)benzene (melting point 244°C) at 500°C
Same as Example 1 except that 0 ppm was added. Results first
Shown in the table.

Example 4 1.3.5 trimethyl-2,4,6-)lis(3,5-
di-tershaku-butyl-4-hydroxybenzyl)
Same as Example 1 except that the amount of benzene added was 2000 ppm. The results are shown in Table 1.

Comparative Example 1 Same as Example 1 except that the amount of tetrakis[methylene-3(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate comethane added was 5000 ppm. The results are shown in Table 1.

Comparative Example 2 Same as Example 2 except that the temperature of the chill roll was 30° C. and the material was cooled and solidified. The results are shown in Table 1.

Comparative Example 3 Wetting tension was 43 d on both sides of polypropylene film.
Same as Example 1 except that corona discharge treatment was performed so that yne/cm. The results are shown in Table 1.

Comparative Example 4 Tetrakis[methylene-3(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate The amount of comethane added was 6000 ppm, and the wetting tension was 35
Same as Example 1 except that dyne/cm was used. The results are shown in Table 1.

〔Effect of the invention〕

The polypropylene film of the present invention is less likely to suffer from the three defects of uneven density, heat loss, and wrinkles during vapor deposition processing, and a vapor-deposited film capacitor can be obtained with a high processing yield.

Claims (1)

[Claims] (1) The coefficient of static friction at 80°C between the non-evaporated surface after metal vapor deposition on one side of the polypropylene film and the chrome plated metal plate is 0.8 or less, and the melting point is 130°C or less The content of additives is 4000 p by weight.
1. A polypropylene film for vapor deposition for capacitors, characterized in that the film is pm or less.