JPH02177310A - Electric insulating material and capacitor - Google Patents

Abstract

PURPOSE:To obtain an insulator whose dielectric property is stable by using a film-shaped substance consisting of mixture of at least one kind, which is selected between titanium oxide and titanic acid metallic salt, and resin, whose glass transition point is specified, for electric insulating material used for a capacitor, and further prescribing the thickness, flatness, etc., of the film-shaped substance. CONSTITUTION:One kind or two kinds of titanic acid metallic salts such as titanium oxide, barium titanate, lead titanate, etc., of rutile-type, anatase-type, or the like are mixed. Hereupon, the average grain diameter of these particles should be preferably 1mum or less and the particles above 30mum shall be within 30%. Next, they are mixed with resin whose glass transition point is 65 deg.C or more, for example, polyethylene telephthalate, polystyrene, aliphatic polyamide, etc., and this is made into film shape. At this time, the thick of this film-shaped substance as 0.1-30mum, the depth of the center line at the surface as 0.01-5.0mum, and the average sectional flatness of surface projections as 0.005-0.3, are prescribed, respectively. By doing it this way, an insulator having high permittivity, which is fit for practical use even if thin, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electrical insulating materials and capacitors.

[Prior Art] In order to increase the dielectric constant of an electrically insulating material, attempts have been made to incorporate particles of a high dielectric constant material into a polymer. For example, synthetic resin is mixed with barium titanate magnetic particles (Japanese Patent Laid-Open No. 52-6966), and single-layer or multi-layer thermoplastic polymer is mixed with a high dielectric material compound (Japanese Patent Laid-Open No. 58-149928). .58-85
514), and one in which a high dielectric material compound is mixed with polyester (Japanese Patent Application Laid-Open No. 58-185225).

As a result, it has been revealed that the relative dielectric constant increases with the content of high dielectric constant particles.

In addition, there are also products in which a mixture of these is applied to a support (Japanese Patent Application Laid-Open No. 61-59714.63-216323).
. Furthermore, regarding film capacitors using them, Japanese Patent Application Laid-Open No. 54-48064.60-170224.61-
59714 etc.

[Problem to be solved by the invention] However, adding more high-permittivity particles to obtain a higher dielectric constant for any polymer deteriorates the mechanical properties of the film-like material, making it difficult to form a thin film suitable for practical use. For example, when used as a dielectric film for a capacitor, the capacitor's external dimensions become large. There is also a method to obtain a thin film-like material by coating, but there is no method that focuses on the surface of the film.For example, when used as a dielectric for a capacitor, variations in the dielectric constant occur and the stability of the dielectric properties is affected. There was a drawback that it was expensive.

The purpose of the present invention is to solve the above-mentioned problems by providing an electrical insulator that is highly dielectric, can be put into practical use even if it is thin, and has stable dielectric properties by controlling the surface properties, and an electrical insulator using the same. The object of the present invention is to provide a capacitor with large capacity, small external dimensions, and excellent stable characteristics.

[Means for Solving the Problems] The present invention provides a film-like material comprising a mixture of at least one selected from titanium oxide and metal titanate and a resin having a glass transition point Tg of 65° C. or higher, The thickness of the film-like material is 0.1 to 30 μm, and the center line depth Rp of the surface is 0.01 to 5. Average cross-sectional flatness P of 0μm1 surface protrusion
The present invention relates to an electrically insulating material characterized in that the electrical insulating material is 0.005 to 0.3, and a capacitor formed using the electrically insulating material.

Here, resins with a glass transition point Tg of 65°C or higher include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polystyrene, polycarbonate, polysulfone, polyvinylidene fluoride, polyacrylate, polyphenylene sulfide, and polyether sulfone. Examples include, but are not limited to, polyetherimide, polyetheretherketone, aliphatic polyamide, aromatic polyamide, aromatic polyimide, or mixtures, copolymers, and mixtures thereof. Moreover, aromatic polyamide, aromatic polyimide, polycarbonate, and polyacrylonitrile are preferable, and aromatic polyamide is more preferable because of their particularly good affinity with particles. Tg
If the temperature is lower than 65°C, the heat resistance will be poor.

Furthermore, the titanium oxide of the present invention is a particle that includes, but is not limited to, rutile type, anatase type, etc., and is not limited to its shape.

Metal titanates are, for example, barium titanate, lead titanate, strontium titanate, or barium titanate in which part of the barium is replaced with another metal, or in which part of the titanium is replaced with another metal. what was given,
Specifically, (Bait--+ S r-) (T
1 (1-yl 3n, ) 03 (where 0<
x<1.0<y<1). In addition, there are synthesis methods such as hydrothermal synthesis and solid phase reaction synthesis, but the method is not limited to these, and the shape is not limited either.

The above-mentioned at least one particle selected from titanium oxide and metal titanate (hereinafter referred to as inorganic particles) exhibits high dielectric properties, has an average particle size of 10 μm or less, and has a particle size of 3
It is preferable that the proportion of 0 μm or more is within 30%,
More preferably, the average particle size is 1 μm or less, and the particle size is 30 μm.
The above is within 10%. If the average particle size is larger than 10 μm, it is not preferable because it becomes difficult to control the surface properties of a film-like material having a thickness that takes advantage of the effects of the present invention. Furthermore, two or more types of particles having different particle sizes may be used.

Furthermore, for the purpose of improving the mechanical properties of the film-like material, a coupling agent such as a silane type, titanate type, or aluminum type may be added to the mixture.

In addition, the average content of inorganic particles in the obtained film-like material was 3
It is preferable that it is at least % by volume. If it is less than 3% by volume, no clear difference in dielectric constant will appear between the resin and the resin not containing it, and the effect of the present invention will be insufficient.

The dielectric constant at this time is desirably 4 or more, preferably 8 or more, and more preferably 10 or more.

The thickness of the film-like material of the present invention is 0.1 to 30 μm, preferably 0.2 to 10 μm, and more preferably 0.5 to 5 μm.
It is m. The effect of thin water-sprinkling invention is greater, but 0.1
If it is thinner than μm, the electrical insulation is poor. Moreover, if the thickness is more than 30 μm, the effects of the present invention cannot be fully utilized, and for example, when used as a dielectric material for a capacitor, a product with small external dimensions cannot be obtained.

Further, the film-like material of the present invention has a center line depth Rp of 0.01 on the surface.
It is necessary that the thickness is 5.0 μm. If the thickness is less than 0.01 μm, the ease of handling the film-like material deteriorates, and the surface is damaged due to friction between the film-like materials, increasing insulation defects. This increases the failure rate of withstand voltage when used as a capacitor, for example. If it is larger than 5.0 μm, the stability of the dielectric properties of the same film-like material deteriorates, and, for example, when used in a capacitor, variations in capacitance increase. A more preferable range of Rp is 01 to 2.0 μm.

Furthermore, it is necessary that the average cross-sectional flatness P of the surface protrusions of the film-like material of the present invention is 0.005 to 0.3.

If it is less than 0.005, the protrusions will be too flat, making it difficult to handle the film-like materials, and the surface will be damaged due to friction between the film-like materials.
Insulation defects increase. This increases the failure rate of withstand voltage when used as a capacitor, for example.

If it is larger than 0.3, the protrusions will be too sharp and the protrusions will be scraped, resulting in poor stability of dielectric properties in the same film-like material and, for example, increased variation in capacitance when used in a capacitor. A more preferable range of the average cross-sectional flatness P is 0.05 to 0.15.

In addition, the film-like material of the present invention has a surface Ra (center line average roughness) of
is preferably 0.005 to 0850 μm, more preferably 0.005 to 0.850 μm. O1 to 0.3 μm.

Furthermore, Rz (10 point average roughness) of the surface of the film-like material of the present invention is preferably 0.05 to 5.0 m, more preferably 0.1 to 3.011 m. This case is particularly preferable because the above-mentioned effects are even more pronounced.

Next, the method for producing the film-like material of the present invention will be described, but the method is not limited thereto.

The resin and the inorganic particles may be mixed before, during, or after polymerization of the resin. For example, when mixing after polymerization, if the resin is commonly used for solution casting, there is a method of kneading inorganic particles dispersed in a solvent into the polymer stock solution.
For resins that are widely used for melt film formation, methods include direct blending with polymerized polymers using a twin-screw extruder or the like, but are not particularly limited thereto.

To obtain the film-like product of the present invention, there are two methods: a normal film-forming method for producing a single film-like product (hereinafter referred to as a film), and a method of coating a mixture of resin and inorganic particles on a support.

Ordinary film forming methods are broadly divided into solution film forming and melt film forming.

The former method includes a wet-dry method, a dry method, a wet method, etc., and the wet-dry method and dry method are preferable in order to obtain a film-like material with good surface properties. In the wet method, the stock solution is directly extruded from a die into a film-forming bath, or is first extruded onto a support such as a drum, and then introduced together with the support into a wet bath. This bath generally consists of an aqueous medium, and may contain an organic solvent, an inorganic salt, etc. in addition to water. By passing the polymer through a wet bath, salts, organic solvents, etc. contained in the polymer are extracted, and further stretching, drying, and heat treatment are performed.

In the dry-wet method, the stock solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and then the solvent is scattered from the thin film layer and the thin film is dried until it has self-supporting properties. After completing the first stage of the dry process, the film is peeled off from the support and introduced into the first stage of the wet process, where it is desalted and desalted in the same way as in the wet process described above.
Solvent removal etc. are performed, and further stretching, drying, and heat treatment are performed to form a film.

When a dry process is employed, the film is dried on a drum or an endless belt, and the self-supporting film is peeled off from the support and stretched.

Furthermore, drying, stretching, and heat treatment are performed to remove residual solvent.

Further, a typical example of the melt film forming method is a method for forming a polyester film. The mixture is continuously extruded from a T-die or the like, cast onto a cooled metal drum, and further stretched and heat treated to obtain a film-like product.

Known methods for coating the mixture of resin and inorganic particles on the support include, but are not limited to, gravure coaters, reverse roll coaters, rod coaters, and air doctor coaters. The support may be a film of polyester, polycarbonate, polypropylene, aromatic polyamide, etc., a metal layer provided thereon, or a single metal foil such as aluminum foil, but is not limited to these. .

In the method for forming a film-like material as described above, achieving the surface properties of the present invention can be achieved by adjusting the amount of particles added, particle size, stretching temperature, stretching ratio, or by adopting a rolling method. Become. In this rolling method, the desired surface properties can be obtained by changing the surface properties of the rolling rolls.

Next, the method for manufacturing the capacitor will be described.

When using a single film material without a support, a metal thin film is formed on the film material by a method such as vacuum evaporation, plating, sputtering, or ion blasting to form a metallized film that becomes a capacitor element. get. Examples of the metal at this time include aluminum, zinc, nickel, nickel-chromium alloy, etc. Among these, aluminum is preferable in terms of vapor deposition properties and characteristics.

In the case of a film-like product obtained by coating on a support, for example, a method of metallizing the support in the same manner as above and then applying the mixture, or a method of applying the mixture and then metallizing it in the same manner as above;
Alternatively, a metallized film that becomes a capacitor element is obtained by using a metal foil as a support.

Next, the metalized film as described above is wound or laminated to form the capacitor of the present invention. For example, if one side of the film is metallized, two layers are stacked and rolled or laminated, or if the film is metallized on both sides, it is wound or laminated with a non-metalized film to form a capacitor element. Apply an exterior and use it as a capacitor.

[Effects of the Invention] As described above, if the surface properties of the film-like material are within the scope of the present invention, the surface will not be scratched due to rubbing during processing, and the variation in dielectric constant of the same film-like material will be reduced. There are also few. Therefore, when used in a capacitor, for example, a capacitor with little variation in capacitance and a low failure rate withstand voltage can be obtained.

The film-like material of the present invention is also useful as a variable capacitor dielectric, a transformer insulator, an insulator for various motors, a coil insulator, a base for a flexible printed circuit board, and the like.

[Method for evaluating properties] (1) Glass transition point Tg Sample 1. Omg was added and the atmosphere was replaced with nitrogen. Next, the temperature was raised to 280° C. at a heating rate of 16° C./min, and this state was maintained for 5 minutes.

The sample is then quickly quenched in liquid nitrogen. The rapidly cooled sample is placed in a DSC-① mold which has been cooled down to room temperature, and the atmosphere is replaced with nitrogen again. Next, the temperature is raised at 16° C./min (2nd RtlN), and Tg is measured.

(2) Average particle size of particles An image of particles taken with an electron microscope or an optical microscope is sent to an image processing device [IBAS2000, manufactured by Carl Zeiss Co., Ltd.], and the particle parts are binarized to obtain individual The equivalent circle diameter is determined from the particle area and is taken as the average diameter of the particle. This measurement was repeated 500 times at different locations, and the average value of the average diameters of the measured particles was taken as the average particle diameter.

(3) Centerline average roughness Ra, centerline depth Rp, and 10-point average roughness Rz Measured using a high-precision thin film step measuring machine ET-10 manufactured by Koita Research Institute. The conditions were as follows, and the average value of 20 measurements was taken as the value.

Stylus tip radius = 0.5 μm Stylus load: 5 mg Measurement length: 1 mm Cutoff value + 0.08 mm The definitions of center line average roughness Ra, center line depth Rps, and 10 point average roughness Rz are, for example, given by Osamu Nara. The centerline depth Rp is the maximum value of the reference length extracted from the roughness curve. The distance from the peak of the mountain to the center line.

(4) Average cross-sectional flatness of surface protrusions P 2 detection method scanning electron microscope [ESM-3200, manufactured by Elionix Co., Ltd.] and cross-sectional measuring device [PMS-1, manufactured by Elionix Co., Ltd.] The height of the film The measured values were processed using an image processing device [I BAS2000, Carl Zeiss (
Co., Ltd.] to reconstruct the image of the film surface protrusions on an image processing device.

Next, the protrusion portion is binarized using this film surface protrusion image, and the equivalent circle diameter is determined from the area of each protrusion obtained, and this is taken as the average diameter of the protrusion. Furthermore, the highest value among the binarized individual protrusions is determined as the height of the protrusion, and this value is determined for each protrusion. Change this measurement location 5
00 times, the average value of the ratio of height and average diameter (height/average diameter) of the measured protrusions is calculated as the average cross-sectional flatness P
And so. The magnification of a scanning electron microscope is 1000-80
Select a value between 00 times.

(5) Dielectric constant Conforms to ASTM-D-150-68.

(6) Evaluation of capacitor withstand voltage failure rate 1000 capacitors were manufactured under the same conditions, the withstand voltage of each capacitor was measured, and the percentage of capacitors that did not reach the specified voltage was calculated and expressed in % as the withstand voltage failure rate. do. Note that the voltage was applied while increasing at a rate of 100 V/see, and the voltage at which the capacitor was destroyed and a current of 10 mA or more flowed was defined as the withstand voltage. Also, the specified voltage is 1 μm thick for the film thickness.
The voltage was set at 20V per m.

(7) Evaluation of variation in capacitance 1000 capacitors were manufactured under the same conditions, the capacitance of each capacitor was measured using an automatic capacitance bridge, and the variation (standard deviation) was expressed in %. did. The smaller this value is, the better the stability is.

(8) Capacitor characteristics Capacitor characteristics were evaluated as good (◯) if the withstand voltage failure rate and capacitance variation were both 10% or less.

[Example] The present invention will be described below with reference to Examples, but is not limited thereto. Tables 1 and 2 summarize the examples.

Example 1 (1) Production of film-like product NMP (N-
Barium titanate with an average particle size of 0.5 μm, which had been previously dispersed in NMP, was added to the methylpyrrolidone solution to give a polymer concentration of 9 wt % and 3000 poise to the final film polymer. A solution of This mixed solution was cast onto a stainless steel endless belt and dried with hot air at 150°C until it became self-supporting. The gel film that has achieved self-supporting properties is continuously peeled off from the belt, then introduced into a water tank to extract the solvent, and then dried in a stenter and subjected to heat treatment to form a film with a thickness of 465 μm. I got it. This film is referred to as a film-like material 1. The properties of the obtained film-like material 1 are as shown in Table 1, and it had a high dielectric constant.

(2) Aluminum was vacuum-deposited on the metallized film-like material 1 so that the surface resistance was 2Ω. At that time, the film was deposited in a stripe shape having a margin running in the longitudinal direction (width of the deposited part was 9.0 mm, and width of the margin part was 1.0 mm, repeated). Next, insert a blade into the center of the vapor deposition part and the center of each margin part to make a slit, and make a slit with a total width of 5.0 m with a margin of 0°5 mm on the left or right.
It was rolled up into a tape shape with a length of m.

(3) Manufacture of the wound body 1 each of the left margin and right margin of the obtained reel
The sheets were stacked one on top of the other and rolled up. At this time, the two films were wound with an offset so that the vapor-deposited portion protruded from the margin portion by 0.5 nm in the width direction.

(4) Manufacture of capacitors Remove the core material from this wound body and heat it at 180°C.
It was pressed for 5 minutes at a temperature and pressure of Ok g/Crn 2. Metallicon was thermally sprayed on both end faces of this to form external electrodes, and lead wires were connected to the metallicon to obtain a wound capacitor. This is called capacitor 1.

Table 2 shows the evaluation results of capacitance variations and withstand voltage defects of capacitor 1, and it was found that capacitor 1 had good capacitor characteristics.

Example 2 NMP (N-
Barium titanate with an average particle size of 0.05 μm dispersed in NMP was added to the methylpyrrolidone solution at a concentration of 40% by volume based on the final film polymer to give a polymer concentration of 5w.
It was made into a t% solution. This mixed solution was applied onto a 5 μm thick polyethylene terephthalate film (PET film) coated with aluminum and dried at 150° C. for 30 minutes. Furthermore, NMP was removed by heating at 100° C. for 24 hours in a vacuum dryer. This film-like material is referred to as film-like material 2. At this time, the thickness of the film-like material 2 on the PET film is 0. 3μ
m, and had the characteristics shown in Table 1. This was wound in the same manner as in Section (4) of Example 1 to obtain a wound capacitor. This is called capacitor 2. Table 2 shows the evaluation results of capacitance variations and withstand voltage defects of capacitor 2, and it was found that capacitor 2 had good capacitor characteristics.

Example 3 Titanium oxide having an average particle size of 5.0 μm dispersed in dichloromethane was added to a dichloromethane solution of polycarbonate in an amount of 25% by volume based on the final film polymer to obtain a mixed solution. This mixed solution was applied onto aluminum foil and cured at 150° C. for 30 minutes. This film-like material is referred to as a film-like material 3. The thickness of the film-like material at this time was 8.0 μm and had the characteristics shown in Table 1. A wound capacitor was obtained in the same manner as in Example 1 through a slitting process. This is called capacitor 3. Table 2 shows the capacitance variation and withstand voltage defect evaluation results of capacitor 3, and the capacitor characteristics were good.

Example 4 Barium titanate with a particle size of 11 μm was kneaded into polyphenylene sulfide using a twin-screw extruder several times in an amount of 5% by volume based on the final film polymer, and the mixture was transferred from a T-die onto a drum kept at 25°C. It was cast and solidified by cooling to obtain an unstretched film. Further, through stretching and heat treatment, a film having a thickness of 2.0 μm and having the characteristics shown in Table 1 was obtained (Membrane-like material 4). A wound capacitor was obtained through metallization, winding, and slitting steps in the same manner as in Example 1.

This will be referred to as capacitor 4. Table 2 shows the results of evaluating capacitance variations and withstand voltage defects of capacitor 4, and the capacitor characteristics were good.

Comparative Example 1 A film-like material 5 was obtained in the same manner as in Example 1 except that barium titanate having an average particle size of 15.0 μm was used instead of barium titanate having an average particle size of 0.5 μm. The thickness of this film-like material 5 is 2
．． 0 μm, and as shown in Table 1, Rp was large and the dielectric constant varied. Furthermore, a wound capacitor was obtained in the same manner as in Example 1. This capacitor 5
shall be.

Table 2 shows the evaluation results of capacitance variations and withstand voltage defects of this capacitor 5, and the capacitor characteristics were very poor.

Comparative Example 2 NMP (N-
Barium titanate with an average particle size of 0.1 μm dispersed in NMP was added to the methylpyrrolidone solution at a concentration of 40% by volume based on the final film polymer to give a polymer concentration of 1 w.
It was made into a solution of t96.

This mixed solution was applied to a polyethylene terephthalate film (PET film) with a thickness of 5 μm on which aluminum was deposited.
It was applied on top and dried at 150°C for 30 minutes. Furthermore, NMP was removed by heating at 100° C. for 24 hours in a vacuum dryer. This film-like material is referred to as a film-like material 6. The film-like material 6 had a thickness of 0.08 .mu.m, which was not sufficient, which caused problems such as conduction and poor handling, and it was also impossible to measure the dielectric constant.

Comparative Example 3 A film-like material 7 was obtained in the same manner as in Example 3 except that the titanium oxide having an average particle size of 5.0 μm was replaced with titanium oxide having an average particle size of 0.05 μm. The thickness of the film-like material at this time was 10 μm,
It had a small centerline depth and average cross-sectional flatness. Further, a wound capacitor was obtained in the same manner as in Example 1 through winding and slitting steps. This will be referred to as capacitor 7.

Table 2 shows the evaluation results of capacitance variations and defective withstand voltages of capacitor 7, and the defective rate of withstand voltages was very poor. This is thought to be because the surface was too smooth and many scratches occurred during processing into capacitors.

table

Claims (2)

[Claims] (1) A film-like material made of a mixture of at least one selected from titanium oxide and metal titanate and a resin having a glass transition point Tg of 65°C or higher, the film-like material having a thickness of 0.1 ~30 μm, and the center line depth Rp of the surface is 0.
01 to 5.0 μm, and the average cross-sectional flatness P of the surface projections is 0.0 μm.
Electrical insulating material characterized by having a ratio of 0.005 to 0.3 (2) A capacitor characterized by using the electrically insulating material according to claim (1).