JPH02129905A - Capacitor - Google Patents

Abstract

PURPOSE:To realize good deposition processability and high breakdown voltage by using as a dielectric a biaxial oriented polypropylene film having a specified isotactic degree, crystal size, peak temperature of fusion, peak temperature of crystallization of component extracted using n-heptane, and degree of face orientation. CONSTITUTION:As for a dielectric is used a biaxial oriented polypropylene film of which an isotactic degree is at least 98.0%, a crystal size at most 13.5nm, a peak temperature of fusion at least 165 deg.C, a peak temperature of crystallization of component extracted using n-heptane of 135 deg.C, 85 deg.C or above, and a degree of face orientation 12.0X10<-3> or above. A breakdown voltage is thereby improved resulting in reduction of deposition processing loss.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a capacitor using a biaxially oriented polypropylene film as a dielectric.

(Prior Art) Capacitors using a polypropylene film as a dielectric layer are commonly used because of their small dielectric loss tangent and excellent electrical properties such as dielectric strength.

[Problem to be solved by the invention]

However, since such conventional polypropylene films are subjected to heat during vapor deposition processing, thin polypropylene films are susceptible to wrinkles during processing, resulting in a large amount of processing loss.

Moreover, it does not necessarily have high insulation properties and does not fully enjoy the excellent electrical properties unique to polypropylene. For example, there are materials such as those disclosed in Japanese Patent Publication No. 14564/1983, which have a high isotactic pentad fraction and a small content in boiling@n-heptane, but the dielectric strength voltage is not necessarily satisfactory. Although JP-A-61-110906 is a film with high crystallinity, it does not satisfy vapor deposition processability.
The dielectric strength is also not necessarily sufficient.

In view of these problems, the present invention aims to provide a capacitor with excellent vapor deposition processability, high breakdown voltage, and long life.

[Means to solve the problem]

The present invention provides a capacitor having a metal vapor deposited layer on at least one surface of the dielectric, in which the dielectric has an isotactic degree of 98.0% or more, a crystal size of 13.5 nm or less, a melting peak temperature of 165° C. or more, and 135 The crystallization peak temperature of the component extracted with n-heptane at °C is 85 °C or higher,
It is characterized by using a biaxially stretched polypropylene film with a degree of plane orientation of 12°0 x 10' or more.

In the present invention, isotactic degree (r1.IJ
) refers to the weight percentage of the residue after extraction with n-heptane at 135°C for 12 hours, and is the weight percentage of the polypropylene film used in the present invention.

(2) is 98% or more, preferably 98.5% or more.

With regular Monte catalysts, lowering the polymerization temperature is the way to maintain high stereoregularity, and using a catalyst system with high activity makes it easy to produce polypropylene with high stereoregularity. .

- For example, using titanium trichloride, bisdiethylaluminum sulfate and phosphorus trichloride described in Japanese Patent Publication No. 43-21741 in a molar ratio of 2:1:0.1, Polymerized polypropylene exhibits extremely high stereoregularity.

In this way, when the melting peak temperature is 165°C or higher, 1.
Highly crystalline polypropylene with I of 98% or more, preferably 98.5% or more can be produced by selecting the polymerization temperature and catalyst.

1. If I is less than 98.0%, the proportion of amorphous parts in the film will be high, which will not only reduce the dielectric strength but also reduce the crystallinity and cause wrinkles to be introduced due to thermal deformation during vapor deposition. Processing losses tend to increase. In addition, 1. The upper limit of I is not particularly limited, but is usually about 99.6%.

The crystal size of the polypropylene film used in the present invention as determined by wide-angle X-ray scattering is 13.5 nm or less, preferably 13.0 nm or less. If it exceeds 13°5nm,
The segment density of the amorphous portion in the film decreases and the length of the molecular chains decreases, leading to a decrease in life span, that is, a decrease in dielectric strength voltage at a constant applied voltage, resulting in a shortened life span. The lower limit of the crystal size is not particularly limited, but is usually 11.0 nm.
That's about it.

In the present invention, the melting peak temperature (hereinafter abbreviated as rTmJ) refers to the temperature of melting in a differential scanning calorimeter (DSC), and the Tm of the polypropylene film used in the present invention is 165°C or higher, preferably 167°C. Stay above ℃. If the temperature is less than 165° C., the crystallinity decreases, leading to the generation of wrinkles and defects on the metal surface due to thermal deformation. T
The upper limit of m is not particularly limited, but is usually about 172°C.

The crystallization peak temperature (hereinafter referred to as "Tm
(abbreviated as cJ) is 85°C or higher, preferably 85°C or higher.
The temperature is 89°C or higher. The upper limit of TmC is not particularly limited, but is usually 95°C.

The polypropylene constituting the film does not necessarily have to be a polypropylene homopolymer, but may contain other species such as polyethylene or poly(4-methylpentene) in a small amount, preferably 5% by weight or less, as long as it does not impair the purpose and effect of the present invention. Polyolefins may also be mixed. When TmC decreases, the dielectric strength decreases significantly.

The degree of plane orientation of the polypropylene film used in the present invention is 12.0X10-3 or more, preferably 14X10
'That's it. If the degree of plane orientation is less than 12.0 x 10-3, the Young's modulus decreases, that is, the film becomes stiff, the tensile strength at high temperatures during vapor deposition decreases, and the film is likely to be thermally deformed, resulting in poor winding. The disadvantage is that wrinkles tend to form in the transverse direction perpendicular to the length direction during removal. The upper limit of the degree of plane orientation is not particularly limited, but is usually 16.0×10
It is about -3.

The surface roughness of the biaxially stretched polypropylene film of the present invention is not particularly limited, but the roughness (Ra> is 0.1
It is desirable that the roughness is less than μm, and the smaller the roughness, the more remarkable the effects of the present invention will be.

That is, the smaller the roughness, the denser the presence of fine crystals, the higher the crystallinity, and the greater the rigidity of the film, suppressing thermal deformation during vapor deposition and significantly reducing the occurrence of wrinkles.

In particular, the effect is more remarkable in very thin films with a film thickness of about 2 to 12 μm.

The structure of the film is not limited to a single film, but may be a composite film.

In a capacitor using a metal-deposited film, aluminum (Al
), zinc (Zn), and alloys thereof, but the present invention is not limited thereto, and any known metal may be used.

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

1,I obtained by polymerization in solvent-free liquefied propylene using an ultra-highly activated catalyst and a rapid treatment has a value of 98.5 to 99.
A 5% polypropylene resin was supplied to an extruder heated to 230 to 285°C and discharged from a slit-shaped mouthpiece.
The film is cooled and solidified by contacting with a chill roll having a surface temperature of 20 to 95°C to obtain an unstretched film having a thickness of 350 to 800 μm.

In order to increase the degree of plane orientation, the higher the crystallization of the film, the better the value, so slow cooling with a chill roll is preferable. However, in this case, care must be taken because the film surface tends to become rough due to the production of zero products.

When making a two-wheel stretched film, the above unstretched film is
4.0 in the length direction after heating at a temperature of 25-155℃
Stretch by ~5.8 times.

In addition, in order to increase the degree of plane orientation, it is preferable to stretch at a low temperature and a high magnification, but since it promotes uneven thickness, the heating temperature is 14
The temperature is preferably 0 to 152°C, and the stretching ratio is preferably 4.8 to 5.5 times.

Preferably 4°75-5 at 140-152°C
．． 1.05-1 at a temperature of 145-154℃ after 0 times stretching
．． 1x re-stretching.

The TfflC of the component extracted with n-heptane at 135°C depends on the raw material, but in order to increase the TmC, slow cooling is preferable when cooling the molten polymer. Depending on the stretching conditions in the length direction, it is preferable to perform re-stretching as described above.

Next, the film is sent to a tenter type stretching device,
The film is stretched 7 to 12 times in the perpendicular direction (transverse direction).The stretching temperature at this time is 140 to 165°C.

After stretching, heat treatment is performed at a temperature of 140 to 163° C. with relaxation of 10% or less. Heat treatment at high temperature is preferable to increase Tm, but since the crystal size increases,
Temperatures between 155°C and 155°C are preferred.

Then, if necessary, one or both surfaces of the film are subjected to surface activation treatment (any known discharge treatment such as corona discharge treatment), and the film is wound up. The film formed as described above was coated with AI and Zn in a vacuum.
A metal such as the following is vapor-deposited so as to have a film resistance of 2 to 6 Ω/portion to form an electrode, and two layers of this are wound together to form a capacitor element with the required capacity.

Note that the dielectric may be the above film alone, or may be a laminate with other films or paper. The capacitor of the present invention may be either a dry type or an oil-impregnated type.

Note that the characteristic values of this invention are measured by the following measuring method.

(1) Aistatic degree (1, I) A. Take a sample of weight W (g) from the film and place it in a thimble filter paper.

B, thimble with sample in extractor and n-heptane 80
ml and perform extraction at 135°C for 12 hours.

After the C0 extraction, remove the thimble and dry it in a vacuum dryer for 5 hours. Measure the weight of the sample, and calculate the value as W' (Q).
shall be.

According to the 01st equation, 1. Find I (%).

1. I (%) = (W' /W)
mA, 5can 5peed 1°/mnS7'i
me C0n5t 2sec, FS8000cps
, slit system DS SS 1°R80.3mm, nickel filter was used, and after measurement under the above conditions, it was calculated using the following formula, and the measured value of the (110) plane was calculated as the crystal size of the film (n
m).

Crystal size = K·λ/(β·COSθ) and Nizier error constant, here, K=1.

λ: 0.15418 β: Half width θ: Beak angle (3) Melting peak temperature (Tm) Melting temperature obtained under the following measurement conditions using a DSC-II type scanning differential calorimeter manufactured by PERKIN ELMER. The peak temperature at 100°C was defined as the melting peak temperature (Tm>).

Sample amount: 5 mg Range: 5 mcal/sec Heating rate: 20°C/min Sensitivity: 10 mV (4) Crystallization peak temperature of extracted components (Tmc>1, extract obtained by measurement of I was evaporated to dryness) After cooling, the peak temperature during cooling was defined as the crystallization peak temperature (TmC>) using the scanning differential calorimeter.

Sample amount: 5 mg Range: 5 mcal/sec Heating rate: 20°C/min Sensitivity: IOMV Melting temperature, holding time: 280°C, 5 minutes (5) Degree of plane orientation Using an Atsube refractometer, both sides of the film was mounted with methyl salicylate, and the refractive index in the length direction, lateral direction, and thickness direction was measured and calculated using the following formula.

Degree of plane orientation - (η8 + ηy) / 2 - η7 where ηX: refractive index in the length direction ηy = refractive index in the lateral direction η2: refractive index in the thickness direction (6) Vapor deposition processing loss rate Width 530 mm, length 20000 m A film having a thickness of 8 μm is vapor-deposited with A1 metal under a vacuum of 3×10 −4 orr at a film resistance of 2.50/mouth at a rate of 300 m/min to a width of 100 mm including a margin of 3 mm. Steamer Shun 100mm
The product was wound up at a speed of 350 m/min while being cut into widths, and the loss rate (%) of the product due to folding and wrinkles was determined using the following formula.

Here, the number of vapor-deposited products to be inspected was 500.

(7) Dielectric breakdown voltage 8 μm thick and membrane resistance 2.50/mouth A1 @ observed width 1
A capacitor element with a capacitance of 10 μF is manufactured using a device winding machine using a film of 00 mm (including a margin width of 3 mm), and the ends are fused by metallization. 115℃
Heat treated for 5 hours and attached terminals to form a capacitor.

This capacitor was charged with alternating current from 600 V for 1 minute, and the applied voltage was increased by 50 V to determine its breakdown voltage.

The breakdown voltage is the average value of 20 capacitors.

(8) Destruction rate (%) of sheet V- A film with a thickness of 8 μm was sampled in a size of 150 mm x 150 mm, and an anode of 50 mmφ was
Brass electrode, cathode made of 8 μm A1 foil wrapped in three layers of 3 mm thick silicone rubber, a film placed between the anode and cathode, and 1 kV AC current applied. The time from when electricity was applied until destruction was determined, and the percentage of destruction within 60 seconds was determined using the following formula. However, the total number of measurements was 50.

Destruction rate (%) of sheet V- [Example] Hereinafter, embodiments of the present invention will be described based on Examples.

Example 1 1. Polypropylene resin with I of 99.3% was heated at 250°C
The mixture was fed to an extruder heated to 40°C, discharged from a slit-shaped mouthpiece, cooled and solidified by contacting a chill roll at 85°C, and
An unstretched sheet of 40 μm was obtained. Heat this sheet to 145℃
After stretching 4.75 times in the longitudinal direction at a temperature of Heat treatment was performed at a temperature of 145° C. with 5.0% relaxation to form a film of 8 μm. 10W・min/m2 on one side of this film
corona discharge treatment was applied. This film is 530mm
2.5Ω under vacuum of 3X10'Torr after slit width
A metal of A1 was deposited on the corona discharge treated surface using a film resistor of /.

After slitting the film to have a film width of 100 mm including a margin width of 3 mm, a capacitor element of 10 μF was made using an element winding machine, and a metallicon was heat-treated at 115° C. for 5 hours by a conventional method and a lead wire was attached. Using this capacitor, an alternating current voltage of 600 V was applied for 1 minute, and the voltage was increased in steps of 50 V until breakdown occurred. The results are shown in Table 1.1. I is 98% or more, crystal size is 13.5 nm or less, Tm is 165°C or more,
TmC of extracted components is 85℃ or higher, degree of plane orientation 12.0X1
0' or more, that is, the capacitor of Example 1, it can be seen that the withstand voltage is clearly improved compared to Comparative Examples 1 to 4 described later.

On the other hand, it is clear that the rate of processing loss during vapor deposition has improved, with no wrinkles occurring in the product.

Example 2 Using a polypropylene resin with 98.3% of 1.7,
The other conditions were the same as in Example 1.

As shown in Table 1, it can be seen that, like Example 1, the dielectric strength and processability of vapor deposition are excellent.

Comparative Example 1 1. Using a polypropylene resin with I of 97.5%,
An unstretched sheet was obtained under the same conditions as in Example 1 except that the chill roll temperature was 88°C. This sheet was stretched 5.0 times in the longitudinal direction at a temperature of 150°C, then 10.0 times in the perpendicular direction at a temperature of 158°C, and then heat treated at a temperature of 150°C while relaxing by 5.0%. A film of 8 μm was obtained. The subsequent steps are the same as in Example 1. As is clear from the results in Table 1, the obtained film has low crystallinity, large crystal size, low degree of plane orientation, poor dielectric strength, large thermal deformation during vapor deposition, and wrinkles. The loss rate increases due to

Comparative Example 2 The same conditions as in Example 1 were used except that a polypropylene resin containing 1.1 and 97.5% I was used.

Although the degree of plane orientation increases and the loss rate due to wL contamination tends to improve, the dielectric strength is insufficient.

Comparative Example 3 1. Using a polypropylene resin with I of 98.3%,
The other conditions were the same as in Comparative Example 1.

1. Due to the effect of increasing I, the dielectric strength tends to improve, but the crystal size is large and the life characteristics under a constant applied voltage are still insufficient.

Comparative Example 4 A test was carried out under the same conditions as in Comparative Example 1 using a polypropylene resin containing 99.3% of 1.I.

The degree of plane orientation is low, and the loss rate due to wrinkles is high.

〔Effect of the invention〕

As mentioned above, the capacitor of this invention has I.

■ is 98% or more, crystal size is 13.5 nm or less, Tm
Since the dielectric layer is a biaxially oriented polypropylene film with a temperature of 165°C or higher, a TmC of extracted components of 85°C or higher, and a plane orientation of 12X10' or higher, the breakdown voltage is improved compared to conventional products, and the vapor deposition process loss is reduced. It's getting smaller.

Therefore, it is expected that the lifespan in accelerated tests will be improved by about 20%, and the withstand voltage can be significantly increased.

Claims (1)

[Claims] (1) In a capacitor having a metal vapor deposited layer on at least one surface of a dielectric, the dielectric has an isotactic degree of 98.0% or more, a crystal size of 13.5 nm or less, a melting peak temperature of 165°C or more, and a temperature of 135°C. A capacitor characterized by using a biaxially stretched polypropylene film having a crystallization peak temperature of components extracted with n-heptane of 85° C. or higher and a plane orientation of 12.0×10^-^3 or higher.