JPH011217A - capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to capacitors.

For more details, please refer to the dielectric strength characteristics, life characteristics, high temperature
This relates to film capacitors with excellent value.

[Prior art and problems to be solved by the invention] Conventional film capacitors have been widely used, and polyester film capacitors in particular have superior physical, chemical and electrical properties compared to other film capacitors. It has been used since ancient times. In order to use polyester film for capacitors, it is necessary to satisfy several characteristics. For example, the product of capacitance and insulation resistance at room temperature and high transient conditions, that is, the property called "OR value" and withstand voltage properties should be good. Furthermore, it is necessary that the capacitor has a long life, that is, it must have excellent life characteristics. Furthermore, good lubricity properties are also essential during manufacturing processes such as roll winding, element winding, vapor deposition, and flattening.

In particular, if the film is thin and has poor slip properties, defects such as uneven end faces or curling will occur during roll winding and element assembly. Restricted air bubbles are generated between the two, causing various problems such as "shrinking" due to heat loss.

Conventionally, methods of adding various phosphorus compounds have been well known as a means of improving the electrical properties of polyester films for capacitors. However, although this method improves the electrical insulation resistance, it has the disadvantage that the sliding properties are significantly lowered, causing major problems during the manufacturing process. In order to improve the lubricity properties of a film, protrusions may be provided on the surface of the film by some method, and it is known that for this purpose, fine particles inert to the polyester may be present in the raw polyester.

There is one method for making these inert particles exist.

Seven of them are methods called precipitation methods, in which catalysts such as calcium and lithium compounds used in the transesterification reaction are precipitated as fine inert particles in the polyester production reaction system in the presence or absence of phosphorus compounds. . In this case, it goes without saying that calcium or lithium compounds may be added after the transesterification reaction to form fine inert particles, and the same method also applies to cases where the esterification reaction is performed. When attempting to improve lubricity using these precipitated inert fine particles, the diameter of the precipitated particles,
Since the particle violet changes easily, it becomes difficult to control lubricity. In addition, it generally has poor lubricity, and when recycled,
It also has the disadvantage that it no longer provides the original lubricity.

Another method, which is compared to the precipitation method, is the addition method, in which kaolin, silica, Merck, calcium carbonate, calcium phosphate, etc. are used as they are or after they are made into fine particles and then reacted with polyester.

It is added during molding, etc. These methods of adding inert inorganic particles to the Bolier stellate often result in the contamination of unnecessary coarse particles and the generation of coarse secondary particles due to aggregation. K to remove these coarse particles always requires a classification operation.

Further, since it is necessary to spread the powder and pulverize it as a pretreatment, the operation becomes complicated. Moreover, even if such an operation is performed, the contamination of coarse particles is still unavoidable. The presence of coarse particles or agglomerated secondary particles is particularly fatal for capacitor films, and adversely affects electrical properties such as withstand voltage characteristics and life characteristics.

However, this particle addition method has the advantage that the particle size and amount of fine particles can be controlled arbitrarily, and the reproducibility of the results is also better than that of the precipitation method, so these drawbacks can be overcome with the addition method. If so, its utility value is a dog.

[Means for solving problems]

In view of the above-mentioned circumstances, the inventors of the present invention have diligently studied a capacitor that has excellent electrical properties such as withstand voltage characteristics, life characteristics, and high-temperature "OR value", as well as excellent lubricity characteristics required in the capacitor manufacturing process. As a result, a polyester film containing a specific amount of silica particles manufactured by a specific manufacturing method and having a specific melting resistance of the film that satisfies a specific range is used as the body, and metal foil or a vapor-deposited metal thin film is used as the electrode layer. The present inventors discovered that a capacitor consisting of

That is, the gist of the present invention is that the dielectric is a polyester film;
In a capacitor whose electrode is made of metal foil or vapor-deposited metal thin film, the average particle size obtained by hydrolyzing and condensing alkoxysilane in the polyester film is 0.0/~3.0 μm, according to the following formula. Contains substantially amorphous monospherical silica particles fO0001~j wt% whose defined particle size distribution [B] is λ, 7 or less, and the specific resistance when melting the polyester film is OX/0 ”Ω
The present invention will be explained in more detail below.

Polyester in the present invention refers to terephthalic acid, λ, 6
- It refers to a polyester obtained using an aromatic dicarboxylic acid such as naphthalene dicarboxylic acid or its ester and ethylene glycol as the main starting materials, but it may contain other third components. In this case, dicarboxylic acid components include, for example, in-7talic acid, 7talic acid, 2,6-naphthalene dicarboxylic acid, terephthalic acid, adipic acid, cepacic acid, and oxycarboxylic acid components such as p-oxyethoxybenzoic acid. One type or two or more types can be used. Glycol components include diethylene glycol, glopylene glycol, butanediol, and hetei.
Preferably, it is a polyester having 7 chlorohexane dimetatool, neopentyl glyco.

The present invention is characterized by the particles contained in the polyester film used as the dielectric of the capacitor and the specific resistance of the film when it is melted. In other words, the process up to manufacturing a capacitor.

For example, in order to minimize troubles and defects during roll winding, vapor deposition, element winding, flattening, etc., it is necessary to improve the slipperiness of the dielectric polyester film. It is known that it is sufficient to make the surface of the film have fine irregularities. However, as mentioned above, the provision of such fine particles can sometimes significantly reduce the electrical properties. Who are the inventors? K, which satisfies both the W-shielding properties and the electrical properties, is obtained by hydrolyzing and condensing alkoxysilane as fine particles to be contained in the polyester film, and the average particle diameter obtained is o, ol to B, 0 μm, and the particle size distribution (2) 2. It has been found that it is sufficient to use amorphous and spherical silica particles that are extremely fine with a particle size of q or less and have a uniform particle size. Furthermore, improvement of the product of capacitance and insulation resistance, ie, the "au value", especially at high temperatures, can be achieved by increasing the melting resistivity of the polyester film to OX/0"Ω・α or more. The silica particles used in the present invention are obtained by a hydrolysis reaction and a condensation reaction using an amine catalyst using an alkoxysilane as a starting material.The alkoxysilane compound has the general formula (
Among the compounds represented by On &n++ O)a S 1, compounds such as tetramethoxysilane, tetraethoxine, tetrapropoxysilane, and tetramethoxysilane are preferably used. Ammonia, trimethylamine, an aqueous tetraethylammonia solution, urea, etc. can be used as the hydrolysis reaction and condensation reaction catalyst, and an ammonia aqueous solution is preferable.The method for synthesizing the silica particles is carried out, for example, as follows.

That is, a solution (At) in which tetramethoxysilane is dissolved in a methanol solvent is prepared separately, and a solution CB+ is prepared in which an ammonia aqueous solution is dissolved in a methanol solvent.

After storing both solutions at a predetermined temperature, for example, -0 to 30°C, add the solution fAt while vigorously stirring the solution (Bl).Next, after holding at the predetermined temperature for several hours, centrifugation,
After washing with alcohol as a solvent, the particles may be dispersed in ethylene glycol, or ethylene glycol may be added to a suspension of silica particles after the reaction is completed, followed by distillation to remove excess ammonia and alcoholic water. In any case, it is preferable that the silica particles of the present invention are finally prepared as an ethylene glycol slurry.

The silica particles of the present invention have many characteristics, representative of which include excellent particle size uniformity and spherical particle shape.

Particle size uniformity is indicated by particle size distribution, which was measured using an electron microscope. Particles approx. 1000 x 1J@: Ratio of particle sizes where the cumulative cancellation rate is IO and 90% (d+
@/a, ·) is used as a measure of particle size distribution.

The silica particles of the present invention have a value of d, / a,
7 or less, indicating that the particle size distribution is sharp. A uniform particle size distribution indicates a high presence of large particles, which is undesirable because large particles form large protrusions and cause a decrease in withstand voltage and capacity.

The particle shape was expressed using the following volume shape coefficient. Using the maximum diameter (d) of the particle in the projected plane and the particle volume (v), the volume shape factor was determined using the following formula.

COv]=v/aa The silica particles of the present invention have [Ov] in the range of 0.4t to π/6, indicating that they are close to a true sphere.

If the particle shape is close to a true sphere, the polyester film will have uneven properties in the width direction of the product (called bowing), and contrary to the above, uneven properties and anisotropy will become severe, which is undesirable. Capacitors made of films containing particles have been undesirable due to their poor withstand voltage characteristics and life characteristics.

The average particle size of the silica particles used in the present invention is 0.0/~J,
It is necessary that ρμm, preferably O,0S-
-co, opm, more preferably 001O~/jμm. If the average particle size is less than 0.0/μm, the sliding properties required in processes such as roll winding, element winding, and flattening will not be satisfactory, and the interaction between particles will increase, resulting in the formation of aggregates. It becomes like this. Such aggregates also become coarse protrusions on the surface of the film, resulting in poor withstand voltage and reduced life characteristics, which are undesirable. On the other hand, the average particle size is 380
If it exceeds m, the film surface will have good lubricity, but the film surface will become rough, the capacitance will decrease, the presence of coarse particles will increase, and voltage withstand voltage defects will be observed, which is an undesirable condition. Become.

The content of silica particles in polyester is O0θO/~j
It is necessary to be wt, preferably it is insufficient, and on the contrary! If it exceeds r wt%, the surface of the film will become rough;
This may result in a decrease in capacity, formation of aggregates, and poor withstand voltage.
This is undesirable because it may cause a decrease in life characteristics.

Since the silica particles of the present invention have an extremely sharp particle size distribution of 2.7 or less, they do not require special pulverization or classification operations, and also have extremely excellent slurry filterability.

Furthermore, as an important requirement of the present invention, the specific resistance (ρV) at the time of melting of the polyester film containing the silica particles
The goal is to make it 0x10''Ω・crrL or more.

When ρ7 becomes less than OX/0"Ω・α.

This is undesirable because the insulation resistance decreases, especially at high temperatures (715° C.).

In order to make ρV equal to or greater than P/OX/0"Ω"ll'm, for example, the ratio of the alkaline earth metal compound used as the transesterification catalyst to the phosphorus compound used as the thermal stability improver should be adjusted to the equal ratio (P/ Me) more than Heko, preferably /,
! This is achieved by making it more than r. As the alkaline earth metal compound, for example, calcium acetate, magnesium acetate, manganese acetate, etc. are preferably used, and as the phosphorus compound, phosphoric acid, phosphoric acid ester, etc. are preferably used.

In the present invention, the silica particles may be added to the polyester film before the polyester polycondensation starts, during the polycondensation, or after the polycondensation, but particularly preferably before the polycondensation or at the beginning of the polycondensation reaction. As the polycondensation reaction catalyst, one or more of antimony compounds, Go, Ti, Sn, and S1 compounds are usually used.

As detailed above, the present invention provides a film capacitor having a metal foil or a vapor-deposited metal thin film as an electrode layer, in which I!
! The present invention has great industrial significance as it dramatically improves the electrical properties such as life characteristics created by the f constant preparation method.

〔Example〕

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples unless the gist of the invention is exceeded. The various physical properties and characteristics of the present invention were measured by the following methods, and in the examples, parts and parts mean parts by weight and % by weight, respectively.

(1) The average particle size and particle size distribution of silica particles are photographed using an electron microscope and measured using a photographic method.

(2) Measurement of specific resistance when melted Polyester 1.22 was placed in a test tube with a drawer and -g5℃
After immersing it in an oil bath to melt it completely, remove the air bubbles by repeatedly applying vacuum and nitrogen gas. In this state, insert a stainless steel electrode and hold it for 70 minutes.
Apply 3 kV direct current. Read the current value immediately after application and calculate the specific resistance according to the linear formula.

ρ = 5ooo ×s-(Ω・CIrL)
1 In the formula, ρV is specific resistance (Ω・cm), and ■ is the current value (A).

A schematic diagram of the standard method is shown.

(3) Measuring the slipperiness of the film The slipperiness of the film is represented by the coefficient of dynamic friction, and its measurement is carried out by A.
The measurement was carried out using a method similar to STMD-/Z9DA, which was modified so that it could be measured using a tape-shaped sample. The measurement was carried out in an atmosphere with a temperature of 23° C. to 1° C. and a humidity of 50±5° C. The size of the sample used was 15% in width and 15% in length, and the tensile speed was 111A.

(4) Measurement of high temperature OR value The condenser was left in a constant temperature bath set at 723° C. for 7 hours and then measured.

The capacitance O was measured using General Radio Co., Ltd.'s [RLO DigiBridge] / KHz, 0. The electrical resistance was measured using a super megohmmeter made by Yokogawa Hewlett-Buckard Co., Ltd. after applying 10 OV of DC.
The measured value was read after a minute. The product of both is ORed [Ω・F
].

(5) Life characteristics A DC voltage of 11 CJOOV was applied across the electrodes of the capacitor, and an accelerated test was conducted in an atmosphere of 7°C.
It is expressed as the survival rate of the capacitor element which functions as a capacitor without shorting.

(6) Measurement of load resistance Using a 100kV DC withstand voltage tester, connect the electrode ends of the capacitor element with clips to the voltage application 'electrode and the ground electrode of the tester, respectively, and increase the voltage of the tester at a rate of 70,077 seconds to test the capacitor. I read the voltage when it broke down and caused a short circuit.

Example-/ (Synthesis of silica particles) Tetraethylsilane JO, 11f was dissolved in methanol at a temperature of 100° C. and maintained at a temperature of 0.degree. C. (Liquid A).

-10,000, add water/10f to methanol 9009 -ttS
Add aqueous ammonia solution and mix.

(Liquid B) was maintained at 0°C. Next, a stirring device was attached to Solution B, and Solution A was added while stirring.

Immediately after the addition, a 1m hydrolysis reaction occurred and the inside of the reaction system became cloudy. After adding solution A and stirring for an additional hour,
Add ethylene glycol 1032 and heat under reduced pressure to distill off excess water, methanol, and ammonia, and add io
% concentration of spherical silica particles was obtained. After drying the ethylene glycol slurry, the average particle size and particle size distribution (du/
6ao) was calculated. The average particle size was 1 dO, 7 g μm, the particle size distribution (d+s/a@o) was i, s, and the particles were spherical with extremely uniform particle sizes. The slurry was filtered using a filter having a Jμ cut and an e-filtration accuracy, and the filter's permeability was very good.

(Manufacture of polyester) 700 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0,000 parts of memanganese acetate tetrahydrate were placed in a reactor, heated, and methanol was distilled off to perform a transesterification reaction. The temperature was raised to 230°C over a period of time from the start, and the transesterification reaction was substantially completed.Then, the average particle size obtained above was 0.7! Added is part of the slurry containing micron silica particles, and further added 7 µm of ethyl acid.
Male 72-) 0.021 parts, antimony trioxide o, o
Part y was added and a polycondensation reaction was carried out for a period of time to obtain a polyethylene terephthalate resin.

(Manufacture of biaxially stretched film) The polyester resin obtained above was heated and dried at 110°C in a nitrogen atmosphere, then melted and extruded into a sheet using an extruder, and an amorphous sheet of 60 μm was created using an electrostatic cooling method. did. Next, this amorphous sheet was longitudinally stretched 3.7 times using a multi-stage longitudinal stretching machine, then laterally stretched 9.0 times using a stenter, and further stretched 20 times.
Heat setting was performed in a temperature range of 0° C. or higher to obtain a biaxially stretched film with a thickness of 5 μm. The melt specific resistance of the film is q, 5x
It was io・Ω・2.

(Creation of capacitor) Aluminum was vapor-deposited on the film thus obtained using a vacuum evaporation device. This vapor-deposited film was slit into 75 widths, and one slit tape with left and right undeposited ends (margins) different. A capacitor element was made by using an element winding machine to wind the material in layers.

Next, this capacitor element is pressed, heat treated, end-face sealed, and lead wires attached 9 in accordance with conventional methods, and the capacitance is o, i.
I made a μF capacitor.

Table 1 shows the properties of the capacitor and polyester film obtained as described above. Steps to create the capacitor, namely vapor deposition.

"Shrinking" and "wrinkling" during the element winding and flattening processes
``The results were satisfactory, with no defects such as uneven end surfaces.Also, the electrical characteristics of the capacitor were extremely good.

Example 3 The manufacturing method of silica particles was slightly changed in Example 1, and
A capacitor was obtained in exactly the same manner as in Example 1, except that silica particles having the average particle diameter shown in the table were prepared and used. The characteristics of the capacitor are shown in Table 1. All of the capacitors that met the requirements of the present invention had good and satisfactory electrical characteristics.

In Comparative Example/, Example/~3, the average particle size of silica contained in the polyester film was changed (Comparative Example/) or the glue of the phosphorus compound added at the polyester manufacturing stage was changed, and the specific resistance at the time of melting was changed. A capacitor was prepared by making the changes (comparative example C) as shown in Table 1. Characteristics of the capacitor 'Jk 1st
Shown in the table.

In the case of the comparative example in which the average particle diameter of the silica particles contained in the polyester film was smaller than the range of the present invention, "wrinkles" and "wrinkles" were observed in the stage up to the production of a capacitor element with a high coefficient of friction of the film. Many problems such as "uneven end surfaces" occurred, and at the same time, the electrical properties deteriorated due to the formation of aggregates, which was undesirable.

On the other hand, in Comparative Example 1, although there was no problem with lubricity, the specific resistance during melting exceeded the limit of the present invention and decreased.

In particular, the "OR value" at high temperatures decreased, which was an unfavorable condition.

Comparative Example J-j The addition of inert fine particles to polyester was changed to particles other than those of the present invention as listed in Table 1, and Example/
A capacitor was obtained in the same manner. The capacitor was made of polyester fill, had a large surface area, and had many large protrusions such as insects and insects, so its life characteristics and withstand voltage characteristics were unfavorable as compared to a capacitor of inferior quality.

〔Effect of the invention〕

According to the present invention described above, in particular, the ijt pressure relief characteristic,
A film capacitor with excellent life characteristics and high temperature ORJ is provided.

[Brief explanation of drawings]

Figure 1 shows an outline of the melt resistivity measurement device. Direct current high voltage generator and ammeter - Electrode (Stainless steel rod 3 directly connected to 57 Rubber stopper... Electrode ( 5) Teflon tube to prevent leakage from sources other than electrodes (made of stainless steel 9) 6. Teflon support for fixing the electrodes 7. e-fused PET Applicant: Diafoil Co., Ltd. Agent: Patent attorney For Hase - Others/Names

Claims (1)

[Claims] (1) In a capacitor in which the dielectric is a polyester film and the electrode is a metal foil or a vapor-deposited metal thin film, the average particle size obtained by hydrolyzing and condensing alkoxysilane in the polyester film is 0.01 to 3
．． 0μm, particle size distribution [B] defined by the following formula is 2.7
Substantially amorphous, spherical silica particles of less than 0.
001 to 5 wt%, and the specific resistance of the polyester film when melted is 2.0×10^■Ω·cm or more. [B] = (Particle size when the cumulative number of particles is 10%) / (Particle size when the cumulative number of particles is 90%)