JPH0622187B2 - Capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a capacitor using a biaxially oriented polyester film as a dielectric.

[Prior Art] A biaxially oriented film made of polyethylene terephthalate is used as a dielectric of a capacitor because it is excellent in mechanical properties, heat resistance, and electrical properties. When this film is used as a dielectric of a capacitor, a metal electrode foil having a thickness of 5 to 10 μm (mainly aluminum is used) and a film having a thickness of 4 to 30 μm are generally stacked and wound to form an element. In some cases (hereinafter referred to as a foil-wound capacitor element), there is a mode in which aluminum or zinc is directly vacuum-deposited on a film and wound around the element (hereinafter referred to as a vapor-deposited film capacitor element). Vapor-deposited film capacitor elements are especially prized for miniaturization of capacitors, but one of the important requirements required in the capacitor manufacturing process is that the elements have good winding and crushing properties. Is. That is, the film after vapor deposition is wound around a winding core (winding step), then extracted from the core and pressed to flatten the element (pressing step),
In order to be able to solder for attaching lead wires, a step of spraying metal particles on both end faces of the flattened element (metallikon step) must be performed. Further, some foil-wound capacitor elements also undergo a pressing process or a metallikon process, so that they are required to have good winding property and crushing property. Here, good winding property means that when the film is wound around the capacitor element with a winding machine, there is no meandering of the film or displacement of the end face, and good crushability means that the press is uniform. It is possible to make it flat without applying too much weight, and there is no gap for metal particles to enter the end face of the element after pressing in the metallikon process.

If the winding property is poor or the crushing property is poor and there is a void on the end face, the metallicon particles intrude to deteriorate the insulation resistance and the dielectric loss tangent, resulting in a defective product.

In order to improve the rollability and crushability, it is essential to improve the slipperiness of the film used as a dielectric material. Various particles are added and contained, or insoluble catalyst residues are formed in the polymer to provide projections on the film surface.

As described above, by adding inert inorganic fine particles to the polymer, forming insoluble catalyst residues, and forming many protrusions on the film surface, processability (for example, film rollability and crushability) is somewhat good. However,
On the other hand, the dielectric breakdown voltage is lowered, the dielectric breakdown abnormality rate is increased, and the performance as a capacitor element is lowered.
On the contrary, if the film surface is made smooth in order to increase the dielectric breakdown voltage and suppress the dielectric breakdown abnormality rate, the workability is deteriorated.

That is, the electrical insulating property of the inorganic fine particles added to the polymer in order to improve the processability such as winding property and crushability, or the catalyst residue particles formed in the polymer during the polymerization process is low, and The occurrence of insulation defects due to voids (voids) formed around the particles during the biaxially stretched film formation impedes compatibility between workability and electrical properties as a capacitor element.

Various studies have been conducted on methods for achieving these characteristics,
There are also many proposals.

Among them, for example, JP-A-52-78953 discloses an attempt to satisfy the above-mentioned characteristics by dispersing and containing two kinds of particles, large and small, in a polyester. Although this method is a relatively preferable method, it is not always satisfactory, and particularly in the case of a thin film having a thickness of 6 μm or less, the addition of large particles causes a deterioration in the electrical property of the capacitor element.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems while maintaining the advantages of using particles of two kinds, large and small, and having excellent workability, high dielectric breakdown voltage, and small dielectric defects. It is intended to provide a high quality condenser using a biaxially oriented polyester film for body.

[Structure / Effects of the Invention] According to the present invention, an object of the present invention is to provide a capacitor having a biaxially oriented polyester film having a thickness of 1.4 to 16 μm as a dielectric and having an average particle size in the polyester constituting the film. Inert particles (A) with a diameter of 0.01 to 1 μm
0.005% to 005% to 1% by weight of silicone resin particles (B) having an average particle size larger than that of particles (A) and 0.5 to 4 μm.
This is achieved by a capacitor characterized by containing 1% by weight.

Here, the silicone resin particles are particles of a resin whose composition of structural units is mainly composed of a trifunctional organopolysiloxane represented by the following formula.

(R · SiO 3/2) n (wherein R is a hydrocarbon group and n is a degree of polymerization) The polyester in the present invention includes terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid and the like. It is a thermoplastic polymer mainly composed of an aromatic dicarboxylic acid component and a glycol component such as ethylene glycol, diethylene glycol, tetramethylene glycol, neopentylene glycol and the like. The polyester is obtained by directly polycondensing an aromatic dicarboxylic acid and a glycol, or by subjecting an aromatic dicarboxylic acid dialkyl ester and a glycol to transesterification and then polycondensation, or a diglycol ester of an aromatic dicarboxylic acid. It can also be obtained by a method such as polycondensation. Typical examples of such polyesters include polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate. The polyester may be a non-copolymerized homopolymer, and up to 15 mol% of the dicarboxylic acid component is other aromatic dicarboxylic acid component or non-aromatic dicarboxylic acid component and / or 15% of the glycol component. It may be a copolyester in which a mol% or less is a diol component other than ethylene glycol. In addition, the polyester is 85% by weight or more
90% by weight or more) and 15% by weight or less (preferably 10% by weight or less) of other polymer may be used. Examples of other polymers that can be blended include polyamide, polyolefin, and other polyesters (including polycarbonate). Further, the polyester may contain additives such as a stabilizer, a colorant and an antioxidant, if necessary.

The polyester film in the present invention contains at least two kinds of particles having different average particle diameters. The first component is an inert particle (A) having an average particle size of 0.01 to 1 μm, and the second component is an inert particle (A) having an average particle size larger than 0.5 to 4 μm.
The silicone resin particles (B) are

The inert particles (A) are not particularly limited as long as they are inert and insoluble in the polymer and solid at room temperature, and may be externally added particles or internally generated particles. For example, it may be a metal salt of an acid or an inorganic substance. Preferred inert particles (A) include calcium carbonate, silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, etc.), alumina, SiO ₂
Silicates containing 30% by weight or more (eg, amorphous or crystalline clay minerals, alumina silicate compounds (including calcined products and hydrates), warm asbestos, zircon, fly ash, etc., Mg, Zn , Zr, and Ti oxides, Ca, and Ba sulfates, Li, Na, and Ca phosphates (including monohydrogen and dihydrogen salts), Li, Na, and K benzoates, Ca, Ba, Z
n, and Mn terephthalate, Mg, Ca, Ba, Zn, Cd, Pb, Sr,
Mn, Fe, Co, and Ni titanates, Ba, and Pb chromates, glasses (eg, glass powder, glass beads, etc.),
Examples are Ca, and Mg carbonates, fluorspar, and ZnS. Particularly preferred are silicic acid anhydride, hydrous silicic acid, aluminum oxide, aluminum silicate (including calcined products and hydrates), 1 lithium phosphate, 3 lithium phosphate, sodium phosphate, calcium phosphate, barium sulfate,
Examples include titanium oxide, lithium benzoate, double salts of these compounds (including hydrates), glass powder, clay (including kaolin, bentonite, clay, etc.), talc, diatomaceous earth, CaCO _{3 and the} like. Among such inert particles (A), inorganic fine particles, particularly externally added inorganic fine particles are preferable.

The main structural unit of the silicon resin particles (B) is R · Si.
It is composed of a trifunctional organopolysiloxane represented by O 3/2. The structural unit is (Wherein R is a hydrocarbon group), and it is preferable that this structural unit accounts for 80% by weight or more of all structural units. As is clear from the above structural unit, the silicon resin particles have a three-dimensional bond structure, and this structure has a structure of (R.SiO 3/2) n
When expressed as, the degree of polymerization n is preferably 100 or more. In the above formula, as the hydrocarbon group for R, methyl, ethyl, phenyl and the like can be preferably exemplified, and methyl is particularly preferable.
Examples of other components include difunctional organosiloxanes.

It is preferable that the silicone resin particles have a spherical shape,
The volume shape factor value is preferably 0.40 to π / 6, and more preferably 0.48 to π / 6. Furthermore, the sharper the particle size distribution is, the more preferable.

In the present invention, the inactive particles (A) as the first component have an average particle size of 0.01 to 1 μm, preferably an average particle size of 0.05 to 0.8 μm. On the other hand, the silicone resin particles (B) of the second component have an average particle size of inert particles.
It is larger than the average particle size of (A) and is 0.5 to 4 μm, but the average particle size is further 0.6 to 2 μm, especially 0.8 to 2.
It is preferably 0 μm. Further, the content of the inert particles (A) is 0.005 to 1.0% by weight, preferably 0.01 to 0.5% by weight, based on the polyester. On the other hand, the content of silicone resin particles (B) is 0.005 to polyester
It is 1% by weight, and more preferably 0.03 to 0.5% by weight.

If the content of the inert particles (A) or the silicone resin particles (B) is too small, the synergistic effect of using two kinds of particles, large and small, cannot be obtained, and the workability such as winding property and crushing property is deteriorated. Also,
Voids are formed on the end faces of the element after pressing, and metal particles penetrate into the voids in the metallikon process, which deteriorates the insulation resistance and dielectric loss tangent of the product, which is not preferable. On the other hand, when the content of the inert particles (A) is too large, the number of voids around or around the small particles in the polymer increases, and the dielectric breakdown voltage decreases. In addition, if the content of the silicon resin particles (B) is too large, the dielectric breakdown voltage and the dielectric breakdown abnormality rate also increase, which is not preferable. Furthermore, if the average particle size of the inert particles (A) is less than 0.01 μm, the effect of addition will not be exhibited,
The crushing property is deteriorated, while if it is larger than 1 μm, the electrical properties are deteriorated, which is not preferable. Furthermore, if the average particle size of the silicon resin particles (B) is less than 0.5 μm, the purpose of improving the slipperiness of the film by providing relatively large protrusions on the film surface cannot be achieved, and processing such as winding property is not achieved. On the other hand, if it is larger than 4 μm, the electrical properties are also deteriorated, which is not preferable.

In the present invention, the time of addition or formation of the inert particles (A) and the time of addition of the silicone resin particles (B) may be before polyester polymerization, during the polymerization reaction, or in the extruder when pelletizing after the polymerization. You may knead,
Further, it may be added at the time of melt extrusion into a sheet form and dispersed in an extruder and extruded, but it is preferable to add and contain it before polymerization.

As a method of incorporating the inert particles (A) and the silicone resin particles (B), any known method can be used.
For example, in the production of polyethylene terephthalate,
Add inactive particles (A) and silicone resin particles (B) together or separately to ethylene glycol, and then use ultrasonic vibration to uniformly disperse them before adding polyethylene terephthalate. Preferably.

The polyester film in the present invention is a biaxially oriented film. The film is preferably stretched in a biaxial direction (for example, a longitudinal direction and a transverse direction) at a draw ratio of 2 times or more. The stretch ratios in the biaxial direction may or may not be equal. Further, the film may be a single film or a laminated film.

This polyester film has, for example, a normal extrusion temperature,
That is, a polyester unstretched film having an intrinsic viscosity [η] of 0.35 to 1.0 melt-extruded at a temperature of not lower than the melting point (Tm) and not higher than (Tm + 70) ° C. is not less than the second-order transition point (Tg) of the polyester and not higher than (Tg + 70) ° C. 2.5 to 5.0 vertically or horizontally at temperature
Stretching at a draw ratio of 2 times, and then in a direction perpendicular to the stretching direction (or transverse direction if the stretching direction is a longitudinal direction)
Stretching is carried out at a stretching ratio of 2.5 to 5.0 times at a temperature of Tg to (Tg + 70) ° C. (The stretching may be such sequential biaxial stretching or simultaneous biaxial stretching. There is no particular limitation.) The biaxially oriented film thus obtained has a temperature of (Tg + 70) ° C. or higher and Tm or lower.
It is customary to heat set for 60 seconds.

The thus-obtained polyester film contains two kinds of particles having different average particle diameters inside thereof, and although relatively large protrusions and smaller protrusions are present on the surface,
The voids found in conventional films are characterized by the substantial absence of voids due to particularly large particles. It is speculated that this is because the silicone resin particles (B) have a high affinity for polyester. Furthermore, since the silicone resin particles (B) themselves have excellent electrical insulating properties, there is an advantage that even if the silicone resin particles (B) are added, the dielectric breakdown voltage is not lowered and the insulating defects are not increased.

The production of a capacitor using a polyester film can be performed by a conventionally known method.

The capacitor of the present invention uses the polyester film having the above-mentioned features and advantages as a dielectric, and is an excellent capacitor having excellent electrical properties and little variation in quality.

[Examples] Hereinafter, the present invention will be further described with reference to Examples. Various physical properties and characteristics in the present invention are measured and defined as follows.

(1) Average particle size Shimadzu CP-50 type Centrifugure particle size analyzer (Centri-fugal Particle Size
Analyzer) was used for the measurement. The particle size corresponding to 50 mass percent is read from the cumulative curve of the particles of each particle size and their abundance calculated based on the obtained stretched sedimentation curve, and this value is taken as the above average particle size. (See "Particle size measurement technology," published by Nikkan Kogyo Shimbun, 1975, pp. 242-247.) (2) Volumetric shape factor (f) 50 photographs of fine particles of silicon resin with a scanning electron microscope.
Luzex 50 image analysis and processing device
0 (manufactured by Nippon Regulator) was used to calculate the average value of the maximum diameters for each field of view, and the average value of 10 fields of view was calculated and designated as D.

Use the average particle size d of the particles obtained in (1) above to calculate the volume of the particles. And the shape factor f is calculated by the following equation.

f = V / D ^{3 In the} formula, V is the volume of the particle (μm ³ ), and D is the maximum diameter of the particle (μ
m).

(3) Intrinsic viscosity ([η]) Using O-chlorophenol as a solvent, the value was measured at 25 ° C, and the unit is 100 cc / g.

(4) Film surface roughness (Ra) This is a value defined by JIS-B0601 as the center line average roughness (Ra), and in the present invention, a stylus surface roughness meter (SURFCORDER SE of Kosaka Laboratory Ltd.) is used. -30 C). The measurement conditions are as follows.

(a) Stylus tip radius: 2 μm (b) Measuring pressure: 30 mg (c) Cutoff: 0.25 mm (d) Measuring length: 2.5 mm (e) Data compilation method The same sample was repeatedly measured 5 times, and the largest Value 1
Except for one, the 4th digit after the decimal point of the average value of the remaining 4 data is rounded off and displayed up to the 3rd digit after the decimal point.

(5) Dielectric breakdown voltage and abnormal dielectric breakdown rate Dielectric breakdown voltage is measured by the method specified in JIS-C-2318.
The average value of n = 100 is adopted, and the ratio (%) of those showing a value of 1/3 or less of this average value is taken as the dielectric breakdown abnormality rate.

(6) Heat shrinkage rate A film sample size of 350 mm x 350 mm is marked with a mark of 300 mm in the center in the vertical and horizontal directions.
The sample is placed in a tester industry hot air thermostat set at 150 ° C.
Ten sheets were hung under no tension, kept for 2 hours, then taken out, the distance between the reference points was measured again, and the heat shrinkage rate was calculated by the following formula, and represented by the average value of n = 10.

(7) Evaluation of vapor deposition processability Aluminum vapor deposition is 99.99% aluminum purity with respect to an original film with a film width of 500 mm and a winding length of 20,000 m, the vapor deposition source temperature is 1400 ° C, the distance between the vaporization surface and the film surface is 350 mm, and the incident angle is 40. Aluminum vapor deposition under the conditions of ゜, vacuum degree 5 × 10 ^-5 Torr, vapor deposition rate 300m / mm, vapor deposition tension 20Kg, vapor deposition pressure 100mμ, with regard to the vapor deposition workability of the original film. ◎, slightly wrinkled but does not reach vapor deposition spots or slit defects after vapor deposition ○, horizontal wrinkles or vertical wrinkles sometimes occur, and vapor spots or slit defects after vapor deposition are frequent. Happened to
Items that cannot be used are marked with x.

(8) Evaluation of the element end surface shape after unevenness and flattening of the element end surface A film of 4 to 12μ was vapor-deposited on aluminum and slit into a width of 20mm, wound on a core with an outer diameter of 3mm, winding tension 40g, winding speed 30cm. We made a device that wound a length of 4 m at / sec, and regarding the unevenness of the end faces of the device, mark the ones where all the end faces are perfectly aligned as ○, and some of them are slightly uneven, but the degree is also small. The ones that make no difference in practical use are marked with Δ, and those that cannot be used are marked with x.

When the element was flattened by a press, the shape of the element end face after flattening was evaluated as follows: ○ When the film layers were flattened in a straight line with no gaps, there were no gaps. If there is no problem, the mark is △, and if the crush is not uniform and there are gaps between the film layers, it cannot be used.

(9) Comprehensive evaluation Overall evaluation was performed on electrical characteristics such as crushability, winding workability, handling workability, vapor deposition processability, dielectric breakdown voltage, and dielectric breakdown abnormality rate. Those having inferior aspects but having no problems in practical use are evaluated as ○, those having practical problems are evaluated as Δ, and those that cannot withstand use are evaluated as ×.

Comparative Examples 1 to 7 Dimethyl terephthalate and ethylene glycol were used, manganese acetate was used as the transesterification catalyst, antimony trioxide was used as the polymerization catalyst, phosphorous acid was used as the stabilizer, and lubricants (added particles) shown in Table 1 were used. Transesterification and polycondensation to obtain an intrinsic viscosity ([η]) of 0.65
Of polyethylene terephthalate was obtained.

The above lubricant was added to ethylene glycol and added as a glycol dispersion obtained by ultrasonic dispersion treatment.

The polyethylene terephthalate pellets were
After drying for 3 hours, it is fed to the extruder hopper and melted at a temperature of 280-
Melt at 300 ℃, pass this molten polymer through a slit die with an opening of 1 mm, surface finish is about 0.3 S, surface temperature is 20 ℃
It was extruded on a rotary cooling drum of No. 1 to obtain an unstretched film of 80 μm.

The unstretched film thus obtained is preheated to 75 ° C., and further heated by a single IR heater having a surface temperature of 900 ° C. from 15 mm above between low speed and high speed rolls, and the lengthwise direction is increased to 3.6.
After being stretched twice, it was rapidly cooled, then fed to a stenter and stretched 3.7 times in the transverse direction at 105 ° C. The obtained biaxially stretched film was heat set at a temperature of 220 ° C. for 5 seconds to obtain a heat set biaxially oriented film having a thickness of 6 μm. A vapor deposition film capacitor was manufactured using this film.

The heat shrinkage of the above film at 150 ° C for 30 minutes was 1.5% in the longitudinal direction and 1.7% in the lateral direction.

Further characteristics are shown in Table 1.

Examples 1 to 4 Polyethylene terephthalate pellets were obtained in the same manner as in Comparative Examples 1 to 7 except that the lubricant (added particles) was changed to those shown in Table 2. The procedure of Comparative Examples 1 to 7 was repeated except that the pellets were used to obtain a heat-fixed biaxially oriented film having a thickness of 6 μm. Further, a vapor deposition film capacitor was manufactured using this film.

The characteristics of this film and condenser are shown in Table 2.

The films and capacitors obtained in these examples were of excellent quality.

The R of the silicon resin particles is methyl.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kinji Hasegawa Kinji Hasegawa 3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture, Teijin Ltd. Plastics Research Laboratory (56) Reference JP-A-52-78953 (JP, A) Japanese Patent Publication 52-48898 (JP, B2)

Claims (1)

[Claims] 1. A condenser comprising a biaxially oriented polyester film having a thickness of 1.4 to 16 .mu.m as a dielectric and having an average particle size of 0.01 to 1 .mu.m in the polyester constituting the film.
0.005 to 1% by weight of the inert particles (A) having a particle size of m, and 0.005 to 1% by weight of the silicone resin particles (B) having an average particle size larger than that of the particles (A) and 0.5 to 4 μm. Characteristic condenser.