JP2932550B2 - Biaxially stretched plastic film for capacitor and capacitor using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a biaxially stretched plastic film suitably used for capacitor applications and a capacitor using the same.

2. Description of the Related Art It is widely known that a biaxially oriented film is used as a derivative of a capacitor. Also, plastic films are widely used for electrical insulation such as interlayer insulation of motors and transformers. When such a film is used for these purposes, it is preferable that fine projections (irregularities) are formed on the film surface by adding inert particles to the film, for example, so that the film can be easily handled and is suitable. Are known.

Polyolefin films and polyester films represented by polyethylene terephthalate have been widely used as films suitable for these purposes, and recently, films having excellent heat resistance such as polyphenylene sulfide films and polyetheretherketone films have been developed. It is also known to be used. Further, as a polyester film compatible with a capacitor derivative, there is known a film in which polyester contains substantially spherical silica particles originating from colloidal silica so that surface projections can be formed (for example, Japanese Patent Application Laid-Open No. 59-1984). No. 171623). In this film, fine projections are formed on the surface by the added silica particles, so that the coefficient of friction can be reduced and the handling property can be improved.

[Problems to be Solved by the Invention] However, the conventional biaxially stretched plastic film has the following disadvantages.

First, since the contained inactive particles are distributed almost randomly over the entire area in the thickness direction of the film, the height of the projections due to the contained particles on the film surface also varies at random. As a result, there is a point where a projection that is significantly higher than the other projections in the vicinity is present, and dielectric breakdown is likely to occur from this point as a starting point, so that dielectric breakdown of the capacitor and the insulating layer is likely to occur. However, there is a drawback that the dielectric breakdown voltage is lowered.

Secondly, the addition of inert particles reduces the breakdown voltage (BDV). For this reason, if the amount of the inert particles is reduced, sufficient slip properties cannot be obtained and the handling property is deteriorated. In addition, the film is damaged by slipping against a large frictional force, and the pinhole (insulation) is damaged. Defect) is increased, and the adverse effect is increased.

Thirdly, the addition of inert particles has the above-mentioned adverse effects, so that the types of inert particles used are significantly restricted. In other words, there is an inconvenience that even if there is a particle which gives a suitable surface morphology with respect to the required slipperiness and handleability, it may not be used because the electrical characteristics are deteriorated.

The present invention solves the above-mentioned drawbacks and has a surface having high-density projections, so that it has excellent slipperiness and handling properties, while maintaining the same breakdown voltage as that when no particles are added, and extremely uniform projections. An object of the present invention is to provide a biaxially stretched plastic film having a surface having a height and having a very high withstand voltage characteristic as a capacitor, and a capacitor using the same.

[Means for Solving the Problems] The present invention has the following configuration to achieve the above object. That is, a biaxially stretched film mainly composed of thermoplastic resin A containing inert particles is laminated on at least one surface layer of the biaxially stretched film mainly composed of thermoplastic resin B. A biaxially stretched plastic film, wherein the average particle size of the inert particles is 0.1 to 4 times the thickness of the biaxially stretched film of the thermoplastic resin A containing the inert particles, and the thermoplastic resin The content of the inert particles added to the resin A is 0.2
-10% by weight, and the thickness of the biaxially stretched film mainly containing at least one thermoplastic resin A is
0.00 as a ratio to the total thickness of the laminated film
1 to 0.2, and the thickness of the entire film is 0.3 or more and 25
The main features of the present invention are a biaxially stretched plastic film for a capacitor characterized by being not more than μm and a capacitor characterized by using the biaxially stretched plastic film for a capacitor as a dielectric.

Thermoplastic resin A and thermoplastic resin B in the present invention
Is not particularly limited as long as it is a thermoplastic resin that can be melt-extruded. For example, polyester, polyolefin, polyamide, polyphenylene sulfide,
Polyether ether ketone and the like can be mentioned. Among them, polyesters, among them, ethylene terephthalate, ethylene 2,6-naphthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate are mainly used. Polyester as a repeating unit,
Alternatively, a polyarylene sulfide having p-phenylene sulfide as a main repeating unit or a polyarylene ketone having p-phenylene ether ether ketone as a main repeating unit is preferable.

The thermoplastic resin A and the thermoplastic resin B may be the same or different, but as a combination, both the thermoplastic resin A and the thermoplastic resin B are polyester resins or both It is preferable to use an arylene sulfide-based resin or both polyarylene ketone-based resins from the viewpoints of interlayer adhesion, heat resistance, withstand voltage characteristics and the like of the laminated films.

Here, the polyester resin refers to a polymer in which a main repeating unit is constituted by an ester bond. Among these, the thermoplastic resin B is ethylene terephthalate, ethylene-2,6-naphthalate, ethylene α, β-
Polyesters containing bis (2-chlorophenoxy) ethane 4,4'-dicarboxylate as the main repeating unit are preferred. The thermoplastic resin A is also preferably selected from these polymer groups, but need not be the same as the thermoplastic resin B.

In addition, the polyarylene sulfide-based resin here refers to a polymer containing an arylene group in the main chain and having a main repeating unit formed by a sulfide bond. Among these, the thermoplastic resin B is preferably a polyarylene sulfide having poly-p-phenylene sulfide or poly-p-phenylene sulfide ketone as a main repeating unit. The thermoplastic resin A is also preferably selected from these polymer groups, but need not be the same as the thermoplastic resin B.

Further, the polyarylene ketone resin refers to a polymer having an arylene group in the main chain and a main repeating unit constituted by a ketone bond. Among them, the thermoplastic resin B is preferably a polyarylene ketone containing poly-p-phenylene ether ether ketone, poly-p-phenylene sulfide ketone, or poly-p-phenylene ether ketone as a main repeating unit. The thermoplastic resin A is also preferably selected from these polymer groups, but need not be the same as the thermoplastic resin B.

Further, when the thermoplastic resin constituting the present invention is crystalline, the coefficient of friction is further improved, which is very desirable. The crystallinity here indicates that it is not so-called amorphous, and quantitatively the cold crystallization temperature Tcc in the crystallization parameter is detected, and the crystallization parameter ΔTcg is 150 ° C or less. . In addition, as long as the present invention is not impaired, two or more thermoplastic resins are preferably used.
The polymer may be mixed at 30% by weight or less, or a polymer in which other components are preferably copolymerized at 30% by mole or less (more preferably at 15% by mole or less) may be used. Also, a combination of both is possible.

The shape of the inert particles in the thermoplastic resin A of the present invention is not particularly limited, but the particle diameter ratio (particle long diameter / short diameter) in the film is 1.0 to 1.3, particularly spherical particles. In this case, the height of the film surface protrusions is easily uniformized, and the dielectric breakdown voltage of the capacitor is further improved, which is desirable.

Further, the inert particles in the thermoplastic resin A of the present invention have better single-particle indices in the film of 0.7 or more, preferably 0.9 or more, so that the density of the projections can be further improved and the height can be made uniform. It is particularly desirable because it can be achieved.

The type of inert particles in the thermoplastic resin A of the present invention is not particularly limited, but in order to satisfy the above preferable particle characteristics, alumina silicate, silica in which primary particles are aggregated, internally precipitated particles, and the like are preferable. Absent. Preferable particles include silica particles having substantially a shape due to colloidal silica, particles made of a crosslinked polymer (eg, crosslinked polystyrene), and the like. Measured using 30M, heating rate 20
(° C / min) is 380 ° C or higher. In the case of shaped silica derived from colloidal silica, substantially spherical silica produced by an alkoxide method and having a low sodium content is particularly desirable.

However, according to the present invention, other particles which had a defect as particles to be added to a film for a capacitor, such as calcium carbonate, titanium dioxide, and alumina, have been appropriately controlled by appropriate control of film thickness and average particle size. It can be fully used.

The size of the inert particles is determined by the average particle size in a biaxially stretched laminated film (hereinafter, sometimes simply referred to as a laminated film) composed of the thermoplastic resin A and the inert particles. 0.1 to 4 times, preferably 0.5 to 4 times, and more preferably 1.1 to 3 times. Average particle size /
If the film thickness ratio is smaller than the above range, the height of the projections formed varies, the variation in the breakdown voltage in the capacitor configuration becomes large, and the projection density also becomes low, and the friction coefficient becomes poor, and conversely, If it is large, the coefficient of friction can be lowered to some extent, but the protrusion becomes too high and the dielectric breakdown voltage of the capacitor becomes poor, which is not preferable.

Further, the average particle size (diameter) of the inert particles in the film is 0.007 to 1.5 μm, preferably 0.02 to 1.5 μm.
A range of 0.7 μm is particularly preferable because it is easy to form a desired projection in terms of the dielectric breakdown voltage and the coefficient of friction.

Further, the weight average thickness of the laminated film is preferably 0.005 to 1.0 μm.

The content of the inert particles in the laminated film is 0.2 to the total weight of the resin composition constituting the laminated film.
It is in the range of ~ 10% by weight. If less than this range,
Since the density of the projections formed is low, the intended effect of reducing the friction coefficient cannot be obtained, and the effect of improving the handling properties during processing or the like becomes insufficient. Conversely, if it exceeds the above range,
The inert particles tend to agglomerate, and the agglomerated particles have more chances to form projections of non-uniform height, thereby increasing the variation in dielectric breakdown voltage. The content is preferably from 0.2 to
It is 5% by weight, more preferably 0.3 to 2% by weight.

The relationship between the amount of the inert particles added to the laminated film, the average particle size, and the thickness of the laminated film is as follows: the average particle size of the inert particles is φ (μm), and the thermoplastic resin A containing the inert particles The thickness of the biaxially stretched film is t (μm), and the content of the inert particles added to the thermoplastic resin A is c
(% By weight), it is preferable that these values satisfy the relationship of the following formula (1).

0.1 ≦ ct · φ ≦ 10 (1) More preferably, 0.1 ≦ ct / φ ≦ 5 (2) If this value is smaller than this range, wrinkles are likely to be formed as a capacitor, and if it is larger, meandering is likely to occur during running of the film.

That is, the laminated film layer of the thermoplastic resin A in the present invention contains inert particles having an average particle size near or larger than the film thickness. In other words, the ultra-thin laminated film contains fine inert particles having an average particle diameter near or greater than the film thickness.
Therefore, the inert particles can be distributed in the thickness direction of the entire biaxially oriented thermoplastic resin film substantially in a concentrated manner only on the laminated film layer. As a result, the particle density in the laminated film can be easily increased, and the density of projections on the film surface formed by the particles can be easily increased. In addition, by containing the inert particles in the laminated film, the position of the inert film is regulated in the thickness direction with respect to the entire biaxially oriented thermoplastic resin film. Since the diameter is in the above-described relationship, the height of the surface projections formed by the particles becomes extremely uniform.

The film mainly composed of the thermoplastic resin A and the inert particles as described above is laminated on the film mainly composed of the thermoplastic resin B to form a film for a capacitor.

The laminated film layer of thermoplastic resin A is made of thermoplastic resin B
Are laminated on both sides or one side of a film layer composed of In other words, although the laminated configuration is A / B / A or A / B, it is needless to say that A / B / C in which a C layer having a surface state different from A is provided on the opposite surface to A, or more. It may have a multilayer structure.

(Here, the types of thermoplastic resins A, B, and C may be the same or different. Further, at least one surface needs to be an A layer. Of these, preferred forms are A / B, A / B / A or A / B / A '(where A' is a resin composition based on the same thermoplastic resin as A and having a slightly different additive particle composition, etc.) Thermoplastic resin A biaxially stretched film containing the B composition as a main component (hereinafter sometimes simply referred to as a laminated film) is
Preferably, it does not substantially contain added inert particles. The inert particles added here are particles that are intentionally added for the purpose of improving the sliding of a film such as silica such as the thermoplastic resin A contains, and particles that precipitate when the polyester is polymerized. May be included. However, even in this case, it is not preferable to include particles having an average particle size of more than 2 μm.

When particles are added to the laminated film, those preferably used in the above-mentioned laminated film are preferable. At this time, it goes without saying that the type, size, and amount of particles added to the laminated film may be the same as or different from those added to the laminated film.

It is preferable that the resin composition containing thermoplastic resin A containing inert particles as a main component and the resin composition containing thermoplastic resin B as a main component as described above are laminated by co-extrusion. Here, the lamination by co-extrusion in the present invention means that a resin composition containing a thermoplastic resin A containing inert particles as a main component and a resin composition containing a thermoplastic resin B as a main component have different extrusion devices. And laminating them before discharging the laminated sheet from the die. This lamination may be performed in a die (for example, a manifold) for forming and discharging into a sheet shape. However, since the laminated film layer is extremely thin as described above,
It is preferable to carry out in a polymer tube before introduction into the base.
In particular, it is particularly preferable to form the laminated portion in the polymer tube in a rectangular shape, since the laminated portion can be uniformly laminated in the width direction. The molten polymer laminated at the rectangular laminated portion in the polymer tube is widened to a predetermined width in the sheet width direction by the manifold in the die, discharged from the die in a sheet shape, and then biaxially stretched. Therefore, even if the laminated film layer after biaxial orientation is extremely thin, in the rectangular laminated portion in the polymer tube, the inert particle-containing thermoplastic resin polymer is laminated with a considerable thickness, so that it can be easily formed. It can be laminated with high accuracy.

In the thus formed biaxially stretched plastic film (hereinafter sometimes simply referred to as a film) having a laminated structure, the thickness of the laminated film layer of one thermoplastic resin A relative to the total thickness of the dielectric material. Ratio 0.001-0.2
Range. Since this ratio is relative, the appropriate range of the absolute thickness of the laminated film layer of the thermoplastic resin A is also determined by the absolute thickness of the dielectric material. Considering the above, if the thickness of the laminated film layer of the thermoplastic resin A is smaller than the above range, the layer becomes too thin, and it becomes difficult to hold the inert particles in the layer at a high density, and the friction coefficient is increased. Is difficult to keep low. If the thickness is larger than the above range, it is necessary to increase the particle size of the inert particles as the thickness of the layer increases, from an appropriate relationship between the average particle size of the inert particles and the thickness of the layer. , Which causes the particle size to be too large,
Dielectric breakdown starting from the contained particles is likely to occur,
Variations in dielectric breakdown voltage are exacerbated.

The total thickness of the film of the present invention is 0.3 or more and 25
The effect of the present invention is great when it is not more than μm. Further, when the added inert particles are 0.02 to 1.0% by weight of the whole film, the effect of improving the withstand voltage characteristics is further increased, and it is very preferable.

In the film of the present invention, projections are formed on the film surface mainly by particles added to the laminated film, and the film has a surface roughness Ra (according to JIS R-0601) of 0.00.
A thickness of 5 to 0.1 μm is preferable from the viewpoint of the handling of the film and the withstand voltage characteristics of the capacitor. In particular,
When the linear density of the number of protrusions having a height of 100 nm or more is 5 / mm or less, the withstand voltage of a relatively large-capacity capacitor is improved, which is preferable. Here, the linear density of the number of protrusions is a stylus type surface roughness meter (cut-off value) over a film length of 30 mm.
0.08 μm, the tip radius of the stylus is 2 μm, the tip opening angle is 90 degrees), and is obtained from the roughness curve chart measured at the vertical magnification N while moving the stylus at a speed of 0.1 mm / sec. The number of protrusions per unit length is shown by dividing the number of protrusions having height by the measurement length. For example, the linear density of the number of protrusions having a height of 100 nm or more is the number of protrusions per unit length obtained by dividing the number of protrusions having a height of 100 nm or more by the measurement length. Here, the height of the protrusion is the height of the i-th protrusion, where Mi is the level of the crest of the i-th protrusion on the roughness curve chart, and Vi is the level of the bottom of the left side of the i-th protrusion. Pi is defined as Pi = (Mi−Vi) / N. However, the direction in which the stylus is moved is a direction orthogonal to the longitudinal direction of the film.

Further, the laminated film mainly composed of the thermoplastic resin A of the film of the present invention has a static friction coefficient of 0.4 to 1.5 and a dynamic friction coefficient of 0.3 to 0.8. It is preferable from the point of view.

Furthermore, in the film of the present invention, the particle concentration ratio of the inert particles on the surface layer on the side of the laminated film containing the inert particles is reduced.
It is preferably 0.1 or less. This surface particle concentration ratio indicates how the inert particles forming the film surface projections are covered with the thin film of the thermoplastic resin A on the film surface, as shown in the measurement method described later. The higher the degree of being substantially directly exposed to the surface, the higher the surface layer particle concentration ratio. The higher the degree of surface protrusions formed but covered with the thermoplastic resin A thin film, the lower the surface layer particle concentration ratio. Since the inactive particles forming the protrusions are covered with the thin film of the thermoplastic resin A, even when the inactive particles are densely distributed in the ultra-thin laminated film layer, the particles remain in the laminated film layer. The film is firmly held by the film layer, and thus the base film layer of the thermoplastic resin B, and the particles do not directly disturb the metal thin film or the metal foil. Is also advantageous. Such a surface particle concentration ratio can be easily achieved by performing lamination by coextrusion. By the way, it is also possible to coat a resin layer with a very thin thickness on the film similar to the present invention, i.e., a base film layer, and to contain inert particles in the resin layer, but also on the surface layer by the coating method. The particle concentration ratio becomes extremely high (that is, the degree of the particle being substantially directly exposed to the surface becomes extremely high), the surface is extremely brittle as compared with the film of the present invention, and the exposed tips of the projections have an influence on the metal thin film or metal foil. Is likely to exert an effect.

In the film of the present invention, the height of the surface projections formed by the inactive particles is not particularly limited. However, in order to obtain a desired effect such as improved slipperiness, the average height of the projections is set to the average particle size of the inactive particles. It is preferable to set the average particle size of the inert particles and the thickness of the laminated film layer mainly containing the thermoplastic resin A so as to be 0.3 times or more the diameter. Also,
In order to obtain uniform and high-density projections, the standard deviation of the particle size distribution of the inert particles themselves is preferably 0.5 or less.

 Next, the capacitor of the present invention will be described.

The capacitor of the present invention is a capacitor using the above-described biaxially stretched plastic film as a main dielectric.

The form of the capacitor of the present invention may be either a wound type or a laminated type. The internal electrodes may be any of known ones such as a metal foil and a metal thin film.

When a metal foil is used as the internal electrode of the capacitor of the present invention, at least one selected from an aluminum foil, a tin foil, and a copper foil is preferably used as a main internal electrode from the viewpoint of electrical characteristics and withstand voltage characteristics. The average thickness of the metal foil is preferably 2 μm or more and 15 μm or less from the viewpoint of handleability, electrical characteristics, and capacitor size.

When a metal thin film is used as the internal electrode of the capacitor of the present invention, it is preferable that at least one selected from an aluminum film, a zinc film, and a copper film formed by vacuum evaporation is used as a main internal electrode. Here, the metal thin film refers to a metal thin film having no self-supporting property formed by a vacuum evaporation method, a sputtering method, an ion plating method, plating, or the like.

In the capacitor of the present invention, a combination of a metal foil and a metal thin film as the internal electrode may be used.

 Next, a method for producing the film of the present invention will be described.

The method for incorporating the inert particles into the thermoplastic resin A may be any of after polymerization, during polymerization, and before polymerization, but a method of kneading the polymer with a vent-type twin-screw extruder is within the scope of the present invention. It is effective for obtaining a film in surface form. As a method of adjusting the content of the particles, a high-concentration master is prepared by the above method, and the content of the particles is reduced by diluting the master with a thermoplastic resin substantially containing no inert particles at the time of film formation. The adjusting method is effective to obtain a film having a surface morphology within the scope of the present invention. Further, the method of adjusting the melt viscosity of the high-concentration master polymer of the particles, the copolymerization component, and the like to keep the crystallization parameter ΔTcg in the range of 30 to 80 ° C. does not cause stretching breakage, and the film having the surface morphology in the range of the present invention is obtained. Effective to get.

Thus, the pellet A containing the thermoplastic resin A containing the inert particles as a main component is supplied to a known melt extruder, and is melted at a temperature equal to or higher than the melting point of the thermoplastic resin and equal to or lower than the decomposition point. The resin composition containing thermoplastic resin B as a main component not containing inert particles added thereto is supplied to the laminating apparatus as described above, extruded into a sheet form from a slit-shaped die, and cooled and solidified on a casting roll. At least make an unstretched film. That is, these thermoplastic resins are laminated by using two or three extruders, a merging block for two or three layers or a die. When using the merging block method, the laminated portion is rectangular as described above, and the ratio of the melt viscosities of both thermoplastic resins is kept in the range of 0.1 to 10 to stabilize the film having the surface morphology in the range of the present invention. Therefore, it is effective for industrial production without unevenness in the width direction.

Next, this multilayer unstretched film is biaxially stretched and biaxially oriented. The method of biaxial stretching may be any of simultaneous biaxial stretching and sequential biaxial stretching, but in the case of sequential biaxial stretching in which the film is stretched in the longitudinal direction and width direction in order to stabilize the film having the surface form within the scope of the present invention. Therefore, it is effective for industrial production without unevenness in the width direction. In the case of sequential biaxial stretching, the stretching in the longitudinal direction is divided into three stages, in particular, four or more stages.
Is carried out in a range of glass transition temperature Tg (° C.) to Tg + 50 (° C.) and at a stretching speed of 1000 to 50,000% / min. It is effective for obtaining a film having a form. The stretching temperature and speed in the width direction are the glass transition temperature Tg (° C.) to Tg + 50 (° C.) of the resin composition containing the thermoplastic resin B as a main component,
A range from 1000 to 20000% / min is preferred. Stretch ratio is 3
~ 10 times is preferred. Further, if necessary, the film can be further stretched in at least one of the longitudinal direction and the width direction. In any case, it is extremely effective to obtain a film of the present invention by providing an extremely thin layer containing inert particles and then stretching the film in an area stretching ratio (magnification in the longitudinal direction × magnification in the width direction) of 9 times or more. It is. Next, this stretched film is heat-treated. As the heat treatment conditions in this case, the melting point of the resin composition containing thermoplastic resin B as a main component is Tm (° C.) in any state of relaxation in the width direction, fine stretching, and constant length.
It is preferable to perform the heating for 0.5 to 60 seconds at a temperature in the range of Tm-100 (° C.) or lower and lower than Tm (° C.). Is desirable because it is easy to obtain

The feature of the production of the film of the present invention is that a biaxially stretched film is provided after a very thin layer containing inert particles is provided by using a high concentration particle polymer having a specific range of thermal characteristics prepared by a special method. In the film forming process, the film of the present invention has superior performance as compared with a method of uniaxially stretching the film and then applying a coating or the like and further stretching, or a laminated film made by coating a biaxially stretched film. In addition, the film of the present invention is excellent in cost.

Next, a method for manufacturing the capacitor of the present invention will be described.

When a metal foil is used as the internal electrode of the capacitor of the present invention, the metal foil and the biaxially stretched plastic film are alternately overlapped and wound by a method of sticking out a foil or a method of inserting a tab during winding. And so on,
A dielectric element and an electrode are alternately overlapped and wound so as to have a structure in which the electrode is drawn out to obtain a capacitor element or a capacitor mother element.

When a metal thin film is used as an internal electrode of the capacitor of the present invention, the above-described biaxially stretched plastic film is first metallized. At this time, the surface of the film to be metallized may be subjected to a corona treatment, a plasma treatment or the like to improve the adhesion between the metal thin film and the film.
It is a common method to provide a non-metallized portion (a so-called margin) by using a tape mask, an oil mask, a laser beam, or the like so as not to short-circuit the counter electrode during or after metallization. Thereafter, slitting may be performed in a narrow tape shape so that a margin portion comes to one end.

Next, a capacitor element is manufactured. When a wound capacitor is obtained, it is common practice to stack two metalized films that are slit into narrow tapes with a margin at one end, and then individually wind the individual elements. It is.
In the case of a multilayer capacitor, it is wound on a large-diameter drum or a flat plate to obtain a capacitor mother element.

When manufacturing a wound capacitor, it is common to press-mold the capacitor element obtained as described above. At this time, the film can be heated to a temperature of 100 ° C. or higher and lower than the melting point of the film. After that, the external electrode mounting process (using metal spraying, conductive resin, etc.), if necessary, a resin or oil impregnating process, if a lead type capacitor is used, the lead wire mounting process, and the exterior process, the capacitor of the present invention obtain.

In the case of a multilayer capacitor, a large diameter drum or a mother element wound on a flat plate is formed by applying pressure in the thickness direction of the film, for example, by tightening with a ring or the like, or by pressing with a parallel flat plate or the like. The temperature range at that time is from room temperature to the melting point of the film or lower. Before or after pressing, the mother element is cut in the longitudinal direction of the film so that the metal foil or metal thin film electrodes are opposed to each other with a margin, and an external electrode mounting process (metal spraying, conductive resin, etc.) is performed. The capacitor of the present invention can be obtained through an element cutting step, a resin or oil impregnating step if necessary, and a lead wire attaching step and an exterior step when a lead type capacitor is used.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows.

(1) Average particle size of particles The polymer is removed from the film by a plasma low-temperature incineration method (for example, PR-503 manufactured by Yamato Scientific Co., Ltd.) to expose the particles. Processing conditions are selected such that the polymer is ashed but the particles do not undergo damage. This is observed with a scanning electron microscope (SEM), and the image of the particles (shading of light generated by the particles) is linked to an image analyzer (for example, QTM900 manufactured by Cambridge Instrument). Is performed, and the number average diameter D is determined as the average particle diameter.

D = ΣDi / N Here, Di is the equivalent circle diameter of the particle, and N is the number.

(2) Content of Particles A solvent in which the polymer is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the polymer, and the ratio (% by weight) to the total weight of the particles is defined as the particle content. In some cases, the combined use of infrared spectroscopy is also effective.

(3) Glass transition point Tg, cold crystallization temperature Tcc, crystallization parameter ΔTcg, melting point Measured using a Perkin Elmer DSC (differential scanning calorimeter) type II. The measurement conditions for DSC are as follows.
That is, 10 mg of a sample is set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The quenched sample is heated at a rate of 10 ° C./min, and the glass transition point Tg is detected.
The temperature was further increased, and the crystallization exothermic peak temperature from the glassy state was defined as the cold crystallization temperature Tcc. The temperature was further raised, and the melting peak temperature was taken as the melting point. The difference between Tcc and Tg (Tcc-Tg) is defined as a crystallization parameter ΔTcg.

(4) Average height of surface protrusions, standard deviation The film is obtained by using a scanning electron microscope with two detectors [ESM-3200, manufactured by Elionix Co., Ltd.] and a cross-section measuring device [PMS-1, manufactured by Elionix Co., Ltd.]. Set the height of the flat surface to 0
The height measurement value of the projections when scanning is performed is sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.], and a film surface projection image is reconstructed on the image processing apparatus. next,
A circle-equivalent diameter is determined from the area of each projection obtained by binarizing the projection portion on the surface projection image, and this is defined as the average diameter of the projection. The highest value among the binarized individual projections is defined as the height of the projection, and this is determined for each individual projection. This measurement was repeated 500 times at different locations to determine the number of protrusions, and the average value of the heights of all the measured protrusions was defined as the average height. The standard deviation of the height distribution was determined based on the height data of each projection. The value obtained by dividing the obtained standard deviation by the average value of the heights was defined as a relative standard deviation. The magnification of the scanning electron microscope is 1000-80
Select a value between 00 times. In some cases, the height information obtained by using a high-precision optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40 to 200 times, use of a high-resolution camera is effective) is used as the above SEM. May be used instead of the value of.

(5) Surface particle concentration ratio Using a secondary ion mask spectrum (SIMS), the concentration ratio between the highest concentration element among the elements caused by the particles in the film and the carbon element of the polyester is defined as the particle concentration,
An analysis in the thickness direction is performed. The ratio of the particle concentration A at the outermost surface particle concentration (point at depth 0) measured by SIMS to the maximum concentration B obtained by continuing the analysis in the depth direction, A / B
Was defined as the surface particle concentration ratio. The measuring device and conditions are as follows.

Measurement device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measurement conditions Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement degree of vacuum: 6.0 × 10 ⁹ Torr E-GUN: 0.5KV-3.0A (6) Single particle index The cross section of the film is photograph-observed with a transmission electron microscope (TEM) to detect particles. When the observation magnification is set to about 100,000, one particle that cannot be further divided can be observed. When the total area occupied by the particles is A, and the area occupied by the aggregate in which two or more particles are agglomerated is B, (A
-B) / A is defined as a single particle index. The TEM conditions are as follows. One visual field area: 2 μm ² , measurement was performed at 500 visual fields at different locations.

-Apparatus: JEM-1200EX manufactured by JEOL-Observation magnification: 100,000 times-Section thickness: about 1000 angstroms (7) Particle size ratio In the measurement of (1) above, average value of major axis / average value of minor axis Is the ratio of

 That is, it is obtained by the following equation.

Major axis = ΣD1i / N Minor axis = ΣD2i / N D1i and D2i are the major axis (maximum diameter), minor axis (shortest axis) and N are the total number of the individual particles, respectively.

(8) Thickness of the thermoplastic resin A layer in the laminated film Using a secondary ion mass spectrometer (SIMS), the element resulting from the highest concentration of the particles in the film and the carbon element of the polymer The concentration ratio (M ⁺ / C ⁺ ) is defined as the particle concentration, and the analysis is performed in the depth (thickness) direction from the surface of the thermoplastic resin A layer. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration which once reached a maximum at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth [II] (where II>
I) was taken as the lamination thickness. The conditions are the same as in the measurement method (5).

In addition, when the particles most contained in the film are organic polymer particles, it is difficult to measure by SIMS. Therefore, XPS (X-ray photoelectron spectroscopy), IR
(Infrared spectroscopy) or a confocal microscope
The depth profile of the particle concentration may be measured, and the stacking depth may be obtained by the same method as described above.

Further, instead of the depth profile of the particle concentration described above, the lamination thickness of the thermoplastic resin A may be obtained by observing a cross section of a film or a thin film level measuring device.

(9) Static friction coefficient μs, dynamic friction coefficient μd According to ASTM-D-1894-B-63, the static friction coefficient and the dynamic friction coefficient of a film / film were measured using a slip tester.

(10) Dielectric breakdown strength of film 3 pieces of aluminum foil (5μm thick) on a brass plate
A film sample cut into a 10 cm square is placed on top of it, and an 8 mmφ brass electrode (50 g in weight) having a smooth finished surface is placed thereon. A DC voltage is applied between the brass plate and the brass electrode while increasing the voltage at 100 V / sec, and the voltage at the time of dielectric breakdown is recorded. Here, when a current of 10 mA or more flows between both electrodes, it is assumed that dielectric breakdown has occurred. After changing the sample and measuring at 20 points or more, the average value is calculated, divided by the film thickness to obtain the dielectric breakdown strength, and expressed in V / μm.

(11) Variation in capacitance of capacitors Measure the capacitance of 1000 capacitor elements manufactured under the same conditions, and calculate the relative standard deviation. Here, the relative standard deviation is a number obtained by dividing the standard deviation by an average value, and is expressed in%. The capacitance of the capacitor is measured with an LCR meter. The criteria for the determination are as follows.

…: Less than 2% relative standard deviation. Very little variation.

Δ: Relative standard deviation 2% or more and less than 10%;

×: Relative standard deviation 10% or more. Large variation.

(12) Dielectric breakdown voltage of capacitor and low-voltage breakdown failure rate DC voltage is applied between both electrodes of a capacitor or capacitor element while boosting it at 100 V / sec. I do. Here, when a current of 10 mA or more flows between both electrodes, it is assumed that dielectric breakdown has occurred. The values measured for 100 or more points are changed and the average is indicated by V. At this time, the frequency of the capacitor or the capacitor element in which the dielectric breakdown voltage did not reach the specified voltage is represented by% as the low-voltage breakdown defect rate. Here, the specified voltage is 50 V per 1 μm of the average thickness of the dielectric film.
And

(13) Element winding property Two films slit to a width of 15 mm are set on an automatic capacitor element winding machine (for a vapor deposition film), and the running state of the film when winding the element and the state of the completed wound body are observed. The judgment was based on the following criteria.

…: There is no meandering during running, and almost no winding deviation is observed on the end face of the wound body, and it is in perfect alignment. Also, no wrinkles are involved.

Δ: While running, there is no meandering that can be observed with the naked eye, but the wound body has a slightly unbalanced end face or slightly wrinkles inside the wound body within a practically acceptable range.

X: Large meandering was observed during running, which caused a winding deviation of 1 mm or more, which was not practical. Alternatively, wrinkles are almost involved over the entire length of the film.

[Examples] The present invention will be described based on examples.

Examples 1-6, Comparative Examples 1-5 Crosslinked polystyrene particles having different average particle sizes, an ethylene glycol slurry containing silica particles derived from colloidal silica was prepared, and the ethylene glycol slurry was heat-treated at 190 ° C for 1.5 hours. , After transesterification with dimethyl terephthalate, polycondensation, the particles 0.3 to 55
Polyethylene terephthalate (hereinafter referred to as PET)
Pellets). A thermoplastic resin A is prepared using the pellets, the content of the inert particles in the thermoplastic resin A is adjusted, and a PET substantially free of inert particles is produced by an ordinary method. Thermoplastic resin B (however, Example 4 and Comparative Example 1 contained the added particles in the same manner as described above). Each of these polymers was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours. The thermoplastic resin A is supplied to the extruder 1 and melted at 310 ° C., and the thermoplastic resin B is supplied to the extruder 2 at 280 ° C.
These polymers are merged and laminated in a merging block equipped with a rectangular laminating section, wrapped around a casting drum with a surface temperature of 30 ° C using an electrostatic application casting method, cooled and solidified, and formed into two layers or two surfaces. An unstretched film having a three-layer structure having a thermoplastic resin A layer was prepared. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the thermoplastic resin A layer. (However, Comparative Example 1 has a single layer B). This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. Stretching speed of this uniaxially stretched film using a stenter
Stretch 4.0 times in the width direction at 100 ° C at 2000% / min.
Heat treatment was performed at 200 ° C. for 5 seconds to obtain a biaxially oriented laminated film having a total thickness of 5 μm and a thermoplastic resin A layer thickness of 0.01 to 2 μm.

 A foil-wound capacitor was manufactured from these films.

First, the film is slit to 20mm width, and the aluminum foil (width 20mm, thickness 5μm) and film, aluminum foil, film, aluminum foil are stacked in order, and the electrodes are alternately protruded by 2mm and wound up. A capacitor element having a capacity of about 1.0 μF was obtained.

Next, the capacitor element was heated and pressed at 120 ° C. and a pressure of 30 Kg / cm ² for 5 minutes, and both sides were covered with metallikon, lead wire welding, and epoxy dip to obtain a foil-wound capacitor.

Separately, a vapor deposition capacitor was made from each film.

First, aluminum was vacuum-deposited on the above film so that the surface resistance was 2Ω. At this time, vapor deposition was carried out in a stripe shape having a margin portion running in the longitudinal direction (repeated 8.0 mm width of the vapor deposition portion and 1.0 mm width of the margin portion). Next, insert a blade in the center of each vapor deposition section and the center of each margin section, slit, and have a full width with a margin of 0.5 mm to the left or right
It was wound into a 4.5 mm tape.

One of each of the left margin and the right margin of the obtained reel was overlapped and wound to obtain a wound body. At that time, the two films were wound while being shifted so that the vapor deposition portion protruded 0.5 mm from the margin in the width direction. Remove the core material from this wound body, as it is, 150 ° C, 50 kg / cm ² temperature,
Pressed under pressure for 5 minutes. Metallicon was sprayed on both end surfaces to form external electrodes, and a DC voltage of 600 V was applied between both electrodes.
A voltage was applied by applying the voltage for 2 seconds, and a lead wire was welded to the metallikon to obtain a deposition capacitor having a capacitance of about 0.3 μF.

Table 1 shows the evaluation results of these films and capacitors.

Examples 7 to 9 and Comparative Examples 6 to 9 In an autoclave, 32.6 kg of sodium sulfide (250 mol, containing 40% by weight of water of crystallization), 100 g of sodium hydroxide,
36.1 kg (250 mol) of sodium benzoate and N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) 7
After 9.2 kg was charged and dehydrated at 205 ° C., 37.5 kg (255 mol) of 1.4 dichlorobenzene (abbreviated as p-DCB) and NM
P20.0Kg was added and reacted at 265 ° C. for 4 hours. The reaction product was washed with water and dried to obtain 21.1 kg (78% yield) of poly-p-phenylene sulfide consisting of 100 mol% of p-phenylene sulfide and having a melt viscosity of 3100 poise.

Silica particles derived from colloidal silica having different average particle diameters were added to the polyphenylene sulfide to obtain polyphenylene sulfide resin composition pellets. Using these pellets, a thermoplastic resin A was prepared, and the content of inert particles contained in the thermoplastic resin A was adjusted.

Example 1 using the above polyphenylene sulfide (no particles added, particles added only in Comparative Example 6) as thermoplastic resin B
Alternatively, it is supplied to the same laminated film manufacturing apparatus as in Comparative Example 1, melted at 310 ° C., cast on a metal drum whose surface is maintained at 25 ° C., cooled and solidified, and has three layers having thermoplastic resin A layers on both surfaces. An unstretched film having the structure was obtained. (However, Comparative Example 6 is a single layer of the B layer) This film was stretched 3.6 times at a film temperature of 100 ° C. and a stretching speed of 30,000% / min by a longitudinal stretching apparatus composed of rolls. ℃, stretching speed 1
The film is stretched 3.5 times at 000% / min and further heat-treated under tension at 270 ° C. for 10 seconds in a subsequent heat treatment chamber in the same tenter to obtain a total thickness of 5 μm and a thermoplastic resin A layer thickness of 0.01 to 2 μm. An axially stretched polyphenylene sulfide film was obtained.

From these films, the same method as in Example 1 (however,
The temperature at the time of pressing the capacitor element was 150 ° C., and the voltage treatment of the vapor deposition capacitor was performed at 400V. ) To produce a foil-wound capacitor and a vapor deposition capacitor.

Table 2 shows the evaluation results of these films and capacitors.

Examples 10 to 12, Comparative Examples 10 to 13 Polyether ether ketone (PEED 380, manufactured by ICI)
G) was added with silica particles derived from colloidal silica having different average particle diameters to obtain polyetheretherketone resin composition pellets. Using these pellets, a thermoplastic resin A was prepared, and the content of inert particles contained in the thermoplastic resin A was adjusted.

Using the above polyetheretherketone (no particles added, particles added only in Comparative Example 10) as thermoplastic resin B, supply to the same laminated film manufacturing apparatus as in Example 1 or Comparative Example 1 and melt at 400 ° C. Was cast on a metal drum kept at 80 ° C. and solidified by cooling to obtain an unstretched film having a three-layer structure having thermoplastic resin A layers on both surfaces. (However, Comparative Example 10 has a single layer of B layer) This film is stretched 3.0 times at a film temperature of 170 ° C. and a stretching speed of 5000% / min by a longitudinal stretching apparatus composed of rolls. ℃, stretching speed 100
It is stretched 3.0 times at 0% / min, and further heat-treated under tension at 300 ° C. for 10 seconds in a subsequent heat treatment chamber in the same tenter to obtain a total thickness of 5 μm and a thermoplastic resin A layer thickness of 0.01 to 2 μm. An axially stretched polyetheretherketone film was obtained.

From these films, the same method as in Example 1 (however,
The temperature at which the capacitor element was pressed was 180 ° C., and the voltage treatment of the vapor deposition capacitor was performed at 400V. ) To produce a foil-wound capacitor and a vapor deposition capacitor.

Table 2 shows the evaluation results of these films and capacitors.

[Effects of the Invention] As described above, the film of the present invention has high dielectric breakdown strength and excellent handling properties. And
When a capacitor is manufactured from this film, it is possible to achieve a high level of stability of the capacitance and a reduction in the low voltage breakdown failure rate without any change in the conventional capacitor manufacturing conditions, so that the capacitor manufacturing yield can be greatly improved. Not only that, the obtained capacitor has a high dielectric breakdown voltage and is extremely reliable.

(56) References JP-A-63-197643 (JP, A) JP-A-1-176556 (JP, A) JP-A-2-2144657 (JP, A) (58) Fields studied (Int .Cl. ⁶ , DB name) B32B 1/00-35/00 H01G 4/18 B29C 55/00-55/30 G11B 5/704

Claims (5)

(57) [Claims] 1. A thermoplastic resin A containing inert particles
A biaxially stretched plastic film for a capacitor laminated on at least one surface layer of the biaxially stretched film mainly containing thermoplastic resin B, wherein the inert film is The average particle size of the particles is 0.1 to 4 times the thickness of the biaxially stretched film of the thermoplastic resin A containing the inert particles, and the thermoplastic resin A
0.2 to 10% by weight of the inert particles added to
And the thickness of the biaxially stretched film containing at least one thermoplastic resin A as a main component is 0.001 to 0.2 as a ratio to the total thickness of the laminated film, and the entire film A biaxially stretched plastic film for capacitors, wherein the thickness of the film is 0.3 to 25 μm. 2. The method according to claim 1, wherein the thermoplastic resin A and the thermoplastic resin B are both polyester resins, polyarylene sulfide resins, or both polyarylene ketone resins. Biaxially stretched plastic film for capacitors. 3. The biaxially stretched plastic for a capacitor according to claim 1, wherein the film containing thermoplastic resin B as a main component is substantially free of added inert particles. Film. 4. An average particle diameter of the inert particles is φ (μm), and a thickness of the biaxially stretched film of the thermoplastic resin A containing the inert particles is t (μm). When the content of the inert particles added to is defined as c (% by weight),
The biaxially stretched plastic film for a capacitor according to any one of claims (1) to (3), wherein these values satisfy the relationship of the following formula (1). 0.1 ≦ ct / t ≦ 10 (1) 5. A capacitor using the biaxially stretched plastic film for a capacitor according to any one of claims (1) to (4) as a main derivative.