JP2913779B2 - Biaxially stretched film for capacitors - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a biaxially stretched film for a capacitor. More specifically, the present invention relates to a biaxially stretched film for a capacitor suitable for a capacitor or the like.

[Conventional technology] Inert particles are added to a film to form fine irregularities on the film surface to give the film an appropriate slipperiness and to improve the handling properties (slipperiness, running stability, etc.) of the film. It is known.

Further, as an effective means for obtaining an ultra-thin film, after forming a laminated film with a support film, if necessary, after processing such as evaporation, slit, etc., the ultra-thin film or evaporated ultra-thin film etc. The method obtained by peeling from the support film is known in JP-A-60-163419, JP-A-60-195918 and the like.

[Problems to be Solved by the Invention] With the recent miniaturization of electronic devices and the like, the demand for ultra-thin films has been increasing in the field of films. However, in the application of film capacitors, which require a very thin film, the processing process is complicated, so that excellent slipperiness is required, and the added inert particles fall off, the film is damaged, It is necessary to minimize adverse effects such as an increase in insulation defects and a decrease in withstand voltage due to voids and the like generated around the particles, which has made it difficult to realize a microminiature capacitor using an ultrathin film.

In addition, after forming a laminated film with a support film for efficiently obtaining an ultra-thin film, in order to utilize in various fields by making full use of a method of obtaining an ultra-thin film by peeling from the support film. It is required that the handleability of the laminated film with the support film and the handleability of the ultra-thin film after peeling are both compatible.However, in order to satisfy the handleability of the laminated film with the support film, Insufficient lubricity causes problems such as wrinkling of the film in the process of handling the ultra-thin film. In this case, the effect of eliminating the air trapped on the film surface becomes insufficient, so that meandering is not likely to occur during film running. Problem has occurred of.

The present invention solves the above-mentioned problems, and by adding carefully selected inert particles to the film, it is possible to achieve both the handleability and practical characteristics of the film even when the film is extremely thin, and in particular, the film is used as a support film. In the case of forming a film with the film, the handleability of the film with the support film, the handleability of the film after peeling, and the practical properties such as electrical properties, even when the film is extremely thin, It is an object of the present invention to provide a biaxially stretched film for a capacitor that can be compatible with both.

[Means for Solving the Problems] The present invention has the following configuration to solve the above problems. That is, (1) a biaxially stretched film comprising the crystalline thermoplastic resin composition (A), wherein the resin composition (A) has the following (1)
Biaxially stretched film for capacitors characterized by adding inert particles so as to satisfy formulas (5) to (5) 0.3 ≦ t / φ ≦ 2.0 (1) 0.1 ≦ ct · t / φ ≦ 10 ... (2) 1.5 ≧ S _c ≧ 1.0 (3) 0.5 ≧ s / φ (4) x ≧ 0.9 (5) where φ: average particle size of inert particles (μm) t: The thickness (μm) of the biaxially stretched film made of the resin composition (A) c: the amount of inert particles added by weight (%) S _c : the sphericity of the inert particles s: the standard deviation of the particle size of the inert particles (Μm) x: Monodispersity index of inert particles (2) The biaxially stretched film for a capacitor according to the above (1), wherein the support film comprising the resin composition (B) is laminated in a peelable state. (3) The resin composition (A) is a resin composition containing polyethylene terephthalate as a main component, and the biaxially stretched film for a capacitor comprising the resin composition (A). The thickness of Lum is
(1) or (2) above having a size of 0.2 μm or more and 1.0 μm or less.
6. The biaxially stretched film for a capacitor according to 4.

(4) The resin composition (A) is a resin composition containing polyethylene naphthalate as a main component, and the biaxially stretched film made of the resin composition (A) has a thickness of 0.2 μm or more.
The biaxially stretched film for a capacitor according to the above (1) or (2), which has a thickness of 1.0 μm or less.

(5) The resin composition (A) is a resin composition containing polyphenylene sulfide as a main component, and the biaxially stretched film made of the resin composition (A) has a thickness of 0.2 μm or more.
The biaxially stretched film for a capacitor according to the above (1) or (2), which has a thickness of 1.0 μm or less.

In the present invention, the resin composition (A) contains 70% by weight of a crystalline thermoplastic resin (hereinafter, may be referred to as resin A).
The resin composition contains at least 85% by weight or more.
If it is less than 30% by weight, preferably less than 15% by weight, various additives such as a stabilizer, an antiadhesive, and inert particles may be contained. Here, the crystallinity is generally referred to as crystallinity in which an endothermic peak is observed at a temperature lower than the melting point when the temperature is lowered from a molten state by differential thermal analysis.

Examples of the resin A in the present invention include polyester, polyolefin, polyamide, polyphenylene sulfide, polyether ether ketone, and the like. Among these, polyesters, among them, ethylene terephthalate, ethylene-2,6-naphthalate, ethylene α , Β-bis (2-chlorophenoxy) ethane-4,4'-
Polyester having dicarboxylate as a main repeating unit, polyphenylene sulfide or polyarylene sulfide having p-phenylene sulfide as a main repeating unit, or polyarylene ketone having p-phenylene ether ether ketone as a main repeating unit is preferred.

In the present invention, polyethylene terephthalate is a polymer having an ethylene terephthalate unit as a main repeating unit. In the present invention, polyethylene naphthalate is a polymer having an ethylene naphthalate unit as a main repeating unit. Furthermore, in the present invention, polyphenylene sulfide is a polymer having a phenylene sulfide unit as a main repeating unit. Here, the term "as the main repeating unit" means that the repeating unit is at least 70 mol%, preferably at least 85 mol%, more preferably at least 95 mol%.
It is a polymer containing at least mol% and other copolymerizable components such as polyethylene terephthalate, glycol components other than ethylene glycol in the case of polyesters such as polyethylene naphthalate, terephthalic acid or 2,2
Dicarboxylic acid groups other than 6-dicarboxynaphthalate and α, β-bis (2-chlorophenoxy) ethane-4,4-dicarboxylate, or a small amount of trifunctional components, and m-phenylene in the case of polyphenylene sulfide There is no problem that a sulfide unit, a sulfone group, a ketone group, a substituted phenylene group, or a small amount of a trifunctional component is copolymerized.

The intrinsic viscosity of polyethylene terephthalate is 0.
It is preferable to use one having 65 or more in view of the pinhole resistance of the obtained film.

As polyphenylene sulfide, the amount of xylene extracted is
The effect is particularly large when the polyphenylene sulfide film is 1.5% by weight or less. Here, the xylene extraction amount refers to the ratio of the weight of the extract when the film is extracted with xylene for 36 hours to the weight of the film before extraction by a Soxhlet extractor immersed in an oil bath heated to 200 ° C. .

The biaxially stretched film for a capacitor of the present invention is a film obtained by melt-extruding, biaxially stretching, and thermally fixing the resin composition (A) containing the above-mentioned resin A to which inert particles are added as a main component. The thickness of the film is 0.2 μm or more and 1.0 μm
When the following conditions are satisfied, the effect of the present invention is great.

The inert particles used in the film of the present invention must be selected and added so as to satisfy the following requirements.

0.3 ≦ t / φ ≦ 2.0 (1) 0.1 ≦ c · t / φ ≦ 10 (2) 1.5 ≧ S _c ≧ 1.0 (3) 0.5 ≧ s / φ (4) x ≧ 0.9 (5) where: φ: average particle size of inactive particles (μm) t: thickness of biaxially stretched film composed of resin composition (A) (μm) c: weight addition amount of inert particles (% ) S _c : sphericity of inert particles s: standard deviation (μm) of particle size of inert particles x: monodispersity index of inert particles Hereinafter, the significance of these formulas will be described in order.

Equation (1) shows the relationship between the average particle size (μm) of the inert particles and the thickness (μm) of the biaxially stretched film made of the resin composition (A). In the present invention, the film thickness means a weight average thickness. The expression (1) is more preferably in the range of 0.5 ≦ t / φ ≦ 1.5 (6), and still more preferably in the range of 0.5 ≦ t / φ ≦ 1.1 (7). As described above, by adding inert particles having a relatively large particle diameter to the film thickness, all the inert particles are located substantially at the center in the film thickness direction. In combination with the shape characteristics described above, it is possible to greatly reduce coarse projections which become insulation defects when a capacitor is formed. In addition, since each projection itself is a relatively high projection, the handleability with the support film can be satisfied. However, if the value of t / is less than 0.3, the film is liable to break, and the particles are liable to fall off, resulting in insulation defects.

Equation (2) shows the amount of inert particles added in relation to equation (1). More preferably, it is in the range of 0.1 ≦ ct · φ ≦ 2.0 (8). This relational expression is satisfied, that is, the addition amount is small when the film thickness is large with respect to the average particle size of the inert particles, and the addition amount is large when the film thickness is small with respect to the average particle size of the inert particles. As a result, the density and height of protrusions formed on the film surface can be controlled, and all required properties such as the handling properties of ultra-thin films, the handling properties with a support film, and the electrical properties of ultra-thin films are satisfied. be able to.

Equation (3) shows the sphericity of the inert particles. More preferably, it is in the range of 1.3 ≧ S _c ≧ 1.0 (9). By using such truly spherical inert particles, the shape of the protrusions formed on the film becomes uniform, and the inert particles having a relatively large particle size with respect to the film thickness as in the above formula (1) can be obtained. Even if it is added, it is possible to suppress an increase in insulation defects due to damage of the film or loss of particles due to friction between the films or the metal and the film.

Equation (4) shows the variation in the particle size of the inert particles. By using such particles having a uniform particle size, the effect of regulating the position of the particles in the film thickness direction shown in the above formula (1) is fully exhibited, and a preferable surface morphology having a uniform projection height is obtained. Obtained for the first time.

Equation (5) shows the monodispersion index of the inert particles. By dispersing the inert particles well in this manner, the effect of using spherical particles having a uniform size as shown in the above formulas (3) and (4) is fully exhibited.

As the inert particles used in the present invention that satisfy the above relational expression, silica particles derived from colloidal silica and particles such as a crosslinked polymer are preferably used. These particles have good affinity with the polymer and are unlikely to form voids around the particles during stretching, so that a film having a high withstand voltage can be obtained as a film for a capacitor. This is a very important point in ultra-thin films. As a method of adding these inert particles, either a method of adding at the time of polymerization of the resin A or a method of melting or kneading after polymerization may be used. Further, it may contain inert particles such as a catalyst residue precipitated during polymerization. However, it is not preferable that one or more of these precipitated particles have a particle size exceeding three times the film thickness t per cm ^{2 of the} film. Further, fine inert particles having an average particle diameter of 0.3 μm or less and 0.3 times or less of the film thickness t can be added.In this case, the amount of the fine inert particles added is 1.0. Wt% or less, more preferably 0.3%
% By weight or less.

In the biaxially stretched film for a capacitor of the present invention, it is preferable that a peelable support film is laminated. As the thickness of the support film, the biaxially stretched film for a capacitor of the present invention comprising the resin composition (A) to be laminated (hereinafter referred to as film A when distinguished from the support film)
(May be referred to as). The support film is also a crystalline thermoplastic resin composition, and is preferably biaxially stretched and thermally fixed.

Here, "peelable" means that the peeling force between the biaxially stretched film for a capacitor (film A) of the present invention and the support film is 10 g / cm or less. When the peeling force is 5 g / cm or less, more preferably 3 g / cm or less, when the biaxially stretched film for a capacitor of the present invention is extremely thin, it is preferably not substantially damaged, and is preferably 0.3 g / cm. cm or more,
It is preferable in that a trouble of peeling when processing with a support film or the like is prevented.

As a material of such a support film, a resin composition containing a resin (hereinafter referred to as resin B) whose difference ΔSP from the solubility parameter of resin A in the solubility parameter SP value is 0.5 or more as a main component ( Resin composition (B)) is preferred from the viewpoint of releasability.

It is preferable that the film A and the support film be laminated by co-extrusion in order to facilitate the production. in this case,
The melting point Tmb of the resin B is the difference ΔTm from the melting point Tma of the resin A is 100.
C. or lower, more preferably 50 ° C. or lower. In addition, the melt viscosity ratio is preferably 0.25 or more and 4.0 or less from the viewpoint of adjusting the flow at the merged portion of the molten polymer during coextrusion and reducing the thickness unevenness of the biaxially stretched film composed of the resin composition (A). . Here, the conditions for measuring the melt viscosity are measured at the higher of + 30 ° C. of Tmb or Tma, and the shear rate is set to 200 sec ⁻¹ .

In the present invention, the following examples can be shown as preferable combinations of the resin A and the resin B.

When the resin A is polyethylene terephthalate,
As the resin B, polyolefin and polyarylene sulfide are preferable. As the polyolefin, ethylene copolymerized polypropylene obtained by copolymerizing an ethylene component with 1 to 6 mol% is preferable. As the polyarylene sulfide, polyphenylene sulfide is preferable. Here, the polyphenylene sulfide is the same as that shown for the resin A. Among these, polyphenylene sulfide is most preferable from the viewpoint of handleability of the laminated film.

When the resin A is polyethylene naphthalate, examples of the resin B are the same as those when the resin A is polyethylene terephthalate.

When the resin A is polyphenylene sulfide, the resin B
It is preferable to use a polyester having a melting temperature of 260 ° C. or higher, such as polyethylene terephthalate and polyethylene naphthalate. Of these, polyethylene terephthalate is preferred from the viewpoint of easy production of a laminated film. Here, polyethylene terephthalate or polyethylene naphthalate is the same as that shown as resin A.

The resin composition (B) is obtained by adding the resin B as exemplified here to 70%.
It is a resin composition containing at least 85% by weight, preferably at least 85% by weight. If it is less than 30% by weight, preferably less than 15% by weight, various additives such as a stabilizer, an antiadhesive, and inert particles may be contained. Particularly, in order to enhance the releasability between the biaxially stretched film made of the resin composition (A) and the support film made of the resin composition (B), the resin B
It is preferable that a substance incompatible with water is added as a release agent.

Although the resin composition (B) may contain inert particles, the addition of the inert particles having an average particle size exceeding the thickness t of the biaxially stretched film made of the resin composition (A) may be carried out by adding a resin. The biaxially stretched film comprising the composition (A) may be damaged, which is not preferable.

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

The film of the present invention can be produced by a conventional ordinary film forming method.However, since the film is extremely thin, it is formed with a support film as described above, and in some cases, a process such as vapor deposition is performed. The method in which the film is peeled at the time of use is superior in terms of productivity and maintaining characteristics of the film.

In the present invention, as described above, the biaxially stretched film for a capacitor of the present invention and the biaxially stretched film for a capacitor of the present invention provided with a support film are laminated by co-extrusion (hereinafter, may be referred to as a laminated film). It is preferable from the viewpoint of thickness and surface control. In lamination by co-extrusion, the resin composition (A) to be the film A and the resin composition (B) to be the support film are supplied to separate melt extruders, and are provided between the melt extruder and a die outlet (so-called lip). Are preferably combined and laminated in the polymer flow path. That is, the resin composition (A) and the resin composition (B) which were supplied to separate melt extruders and heated and melted to the melting points of the individual compositions or higher were provided between the extruder and the die outlet. Two or three layers are laminated in a molten state by a merging device and extruded from a slit-shaped die outlet. The molten laminate is cooled below the glass transition temperature of the resin composition (A) and the resin composition (B) on a rotary cooling drum to obtain a substantially amorphous laminated sheet. As the melt extrusion device, a known device can be applied, but an extruder is simple and preferable. Depending on the configuration of the laminated film, the merging apparatus has two layers (resin composition (A) / resin composition (B)) or three layers (resin composition (A) / resin composition (B) / resin composition (A)). ) Has a function of laminating in a molten state.

Next, the laminated sheet in an amorphous state is formed into a resin composition (B).
At a temperature lower than the glass transition temperature of the resin composition (A), preferably at a temperature lower than the glass transition temperature of the resin composition (A) by 25 ° C., and biaxially oriented, and at a temperature lower than the melting point of the resin composition (A). After the heat treatment, the biaxially stretched film for a capacitor with a support film of the present invention is obtained. The biaxial stretching magnification is preferably 10 times or more in terms of area magnification (longitudinal magnification × lateral magnification), and the stretching magnification ratio (longitudinal magnification / lateral magnification) is preferably 0.5 or more and 2.0 or less. If necessary, it is possible to perform a limited shrinkage (relaxation) at a temperature lower than the heat treatment temperature in the range of 0 to 20% in each of the vertical and horizontal directions.

The biaxially stretched film for a capacitor of the present invention is suitably used for a metallized film capacitor. At this time, the method of manufacturing the capacitor is not particularly limited. When a support film is provided, the step of peeling the biaxially stretched film for a capacitor of the present invention from the support film layer is not particularly limited. Hereinafter, a method for manufacturing a capacitor when the film of the present invention is used for a capacitor will be exemplified, but it goes without saying that the present invention is not limited thereto.

Representative capacitors include metallized film capacitors and foil-wound capacitors. A foil-wound capacitor is made by winding and laminating a film and a metal foil alternately, and a metallized film capacitor is obtained by forming a metal thin film typified by a vapor-deposited film on the film and obtaining a metalized film. , To manufacture capacitors.

Since it is easy to obtain an ultra-thin film that is advantageous for miniaturization of the capacitor, the film of the present invention is preferably a metallized film capacitor that can be miniaturized as a type of capacitor. There are the following methods for manufacturing a metallized film capacitor.

First, a biaxially stretched film for a capacitor of the present invention (hereinafter, sometimes simply referred to as a film) is made of aluminum,
A metal thin film is formed by depositing a metal such as zinc, copper, or nickel by a method such as vapor deposition or sputtering.
At this time, the film may be masked with a tape, oil, or the like, and a non-evaporated portion running in the longitudinal direction of the film, that is, a so-called margin may be provided. Alternatively, a margin can be provided by metallizing the entire surface of the film and then removing the deposited film using a laser beam, discharge, or the like. Thereafter, a slit is formed in a tape shape on which a non-deposition portion runs left or right.
At this time, the film can be slit so that the left or right end is a non-deposited portion, or a so-called inner margin type in which the non-deposited portion runs slightly inside the left or right end of the film. . Next, the obtained two tape-shaped metallized films having left and right margins are wound one upon another so that the non-margin ends slightly protrude outward. There is also a method of forming a vapor-deposited film on both sides and winding a double-sided metallized film and a non-metallized film in which margins are formed at different ends on both sides. To obtain a wound capacitor, use a small shaft with a diameter of about several millimeters.To obtain a multilayer capacitor, use a wheel with a diameter of about tens of centimeters or a flat shaft with a length of about tens of centimeters. It is common to wind up. The obtained wound body is heated and / or before or after being removed from the winding shaft.
Alternatively, a capacitor element or a capacitor mother element is obtained by pressing and molding. It can also be preformed during winding with a heating press roller or the like. In this case, it is also preferable to improve the adhesion between the metallized films by a method such as electric discharge treatment, coating, or formation of an easily adhesive layer on the metallized surface and / or the non-metallized surface of the metallized film. The obtained capacitor element or capacitor mother element is provided with an external electrode electrically connected to a metal thin film on a film serving as an internal electrode by a method such as metal spraying or application of a conductive resin.
The capacitor mother element is thereafter cut into individual elements so as to have an optimum capacity, thereby forming a capacitor element. After that, if necessary, heat treatment process, impregnation process of resin or wax by immersion under vacuum or long time, lead wire mounting process, resin molding, resin coating, film and sheet pasting etc. Becomes

Further, when the resin A is polyphenylene sulfide, since the film has high heat resistance, it can be used as a so-called chip capacitor having no lead wire. In this case, the exterior is preferably as simple as possible in terms of miniaturization of the capacitor, and it is preferable to apply a high heat-resistant resin such as polyimide or epoxy to the cut surface of the element, or to attach a high heat-resistant film such as a polyimide film. It is. In addition, at any stage after the film winding until becoming a capacitor, preferably after the external electrode is provided
Heat treatment at a temperature of 200 ° C. or more and 265 ° C. or less for 1 hour or more is preferable because the characteristics of the capacitor are stabilized.

As means for obtaining higher production efficiency, a wide film is wound so that a plurality of elements are obtained in the width direction of the film, or a plurality of tapes are slit in the width direction by slitting the wide film just before winding. There is also a method of winding the metallized film in one winding axis. Also in this case, any of a method of laminating two or more single-sided metallized films and a method of laminating a double-sided metallized film and a non-metallized film can be employed. Furthermore, there is a method of winding a single-sided metallized film in which a margin position is alternately moved for each winding turn. The shape of the winding shaft includes a columnar shape and a flat shape as described above. These methods are particularly effective when obtaining a multilayer capacitor. In these methods, a method in which a margin is provided by a laser beam or the like before or during winding of a metallized film deposited on the entire surface of the film is preferably used due to the problem of margin positional accuracy at the time of winding. As the margin, an inner margin type margin is preferably used so that adjacent capacitor elements do not adversely affect each other. The thus obtained wound body having a plurality of capacitor element precursors in the width direction is molded by heating and / or pressing before or after being removed from the winding axis, and cut in the width direction. To obtain a capacitor element or a capacitor mother element. The flat winding shaft is advantageous in that a parallel flat plate press that can be pressed with high accuracy without removing the wound body from the winding shaft can be performed. Also, if a method of preforming during winding with a heating press roller or the like is adopted, the film will not be separated even if the winding body is removed from the winding shaft, so that a parallel plate press can be performed. Further, when the division in the width direction is performed by cutting after winding, the cut surface on which the external electrode is to be provided is relatively smooth, and the electrical and mechanical connection between the external electrode and the internal electrode (metal thin film) is performed. Therefore, it is preferable to take measures for strengthening the contact of the external electrode with the internal electrode by a physical or chemical method on the cut surface before winding or after cutting.
Examples of such a technique include a method in which a cut portion (voids, dents, etc.) is provided in a film before winding along a line to be cut so that the cut surface is eventually made uneven. There are a method of forming irregularities by a method such as plasma etching and sand blasting, and a method of chemically bonding easily by a discharge treatment. The capacitor element or the capacitor mother element obtained in this way is converted into a capacitor through the same steps as described above.

When the film of the present invention is provided with a support film in the above-described capacitor manufacturing process, the step of peeling the film A from the support film layer may be any step, or the peeled film A may be once wound before moving to the next step. In this case, the film A may be wound while inserting a slip sheet between the film layers in order to avoid damage to the film A. This method is particularly effective when used in a portion where the film may be deformed, such as after forming a margin by vapor deposition or laser.

As a step of peeling the film A from the support film layer, first, the film A is peeled from the support film layer to obtain a single film A, and then a method of manufacturing a capacitor is performed by a conventional method. There is an advantage that the capacitor manufacturing process can be used as it is. In addition, a method of manufacturing a capacitor after performing only evaporation in a laminated film state and obtaining a metalized film A by peeling after evaporation is performed in a state in which a film is deposited with a support layer. Can be minimized. Also, the conventional process can be used as it is for the capacitor manufacturing process. However, from the viewpoint of the productivity of the capacitor, handling of the film A after peeling becomes more difficult as the film thickness becomes thinner. In particular, when there is a step of slitting into a narrow width before winding, a method of slitting before peeling is preferably used in order to improve slit accuracy. When a margin is formed by a laser beam, a method of forming a margin before peeling is preferably used from the viewpoint of suppressing damage to the film due to laser. Regardless of the method used to manufacture the capacitor, the method of peeling immediately before or simultaneously with the winding is most preferable since there is almost no step of handling the ultrathin film after peeling alone.

[Effect] Even when the biaxially stretched film for a capacitor of the present invention is extremely thin, if it is used for a film capacitor in which the demand for extremely thin film is strong, excellent sliding properties can be obtained. It has sufficient handling properties and has sufficient practicality with almost no adverse effects such as dropout of added inert particles, damage to the film, increase in insulation defects due to voids generated around the particles, reduction in withstand voltage, etc. It became possible to make it into a film. In addition, after forming a laminated film with a support film for efficiently obtaining an ultra-thin film, it is utilized in various fields by making full use of a method of obtaining an ultra-thin film by peeling off the support film. Therefore, even with the support film, the handleability of the laminated film and the handleability of the ultra-thin film after peeling can be compatible, so that the practical value of such a method is sufficiently exhibited. Can be.

[Evaluation Method of Characteristics] Hereinafter, an evaluation method of each characteristic in the present invention will be described.

(1) Average particle size of inert particles φ The thermoplastic resin is removed from the film surface by a plasma low-temperature incineration method to expose particles near the surface. At this time,
Select the conditions under which the particles will not be damaged. This is observed with a scanning electron microscope (SEM), and the image of the particles is processed with an image analyzer. Change the observation point and the number of particles is 5,00
The following numerical processing is performed on 0 or more pieces, and the number average diameter φ obtained thereby is defined as the average particle diameter.

φ = Σφ _i / N where φ _i is the equivalent circle diameter of the particles and N is the number of particles.

(2) The standard deviation s of the particle size of the inert particles and the relative standard deviation s / φ of the particle size are calculated from the individual particle size φ _i , the average particle size φ, and the number N of the particles measured by the above method (1). Is the standard deviation s calculated by

The particle diameter relative standard deviation s / φ is a value obtained by dividing the standard deviation s of the particle diameter by the average particle diameter φ.

(3) Sphericity of inert particles In the measurement of (1), the sphericity was represented by the ratio of (average major axis) / (average minor axis) of the individual particles. That is, it is obtained by the following equation.

Major axis = Σφ _1i / N Minor axis = Σφ _2i / N φ _1i , φ _2i are the major axis (maximum diameter) of each particle,
The short diameter (shortest diameter), N is the number of particles.

(4) Monodispersity index of inert particles A cross section of the film is photographed with a transmission electron microscope (TEM) to detect the 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 aggregated is B,
Let (AB) / A be the monodispersity index. The TEM conditions are as follows, and 500 visual fields are measured by changing the measurement place of one visual field area of 2 μm ² .

Apparatus: JEM-1200EX manufactured by JEOL Observation magnification: 100000 times Film section thickness: about 1000 angstrom (5) Resin solubility parameter (SP value) It was determined by the method of Fedors. This method is described in detail in, for example, "Science Polymer for Engineers (Kodansha), Ch. 3, Section 4".

(6) Peeling force of the laminated film When the width of the laminated film is W (cm), the tension applied to the surface film when the surface film layer is continuously peeled at a peel angle of 180 degrees and at a speed of 200 mm / min. Is measured with a tensiometer. When the tension at this time was defined as T (g), the peeling force (g / cm) was determined by the formula of T / W.

(7) Film handling The two films slit to a width of 15 mm are set on an automatic capacitor element winding machine (for a vapor-deposited 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 surface of the wound body, and the wound body is aligned neatly. Also, no wrinkles are involved.

Δ: While running, there is no meandering that can be observed with the naked eye, but in the wound body, winding deviation is slightly observed on the end face or wrinkles are slightly entangled within a range where there is no practical problem.

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

(8) Dielectric breakdown voltage (withstand voltage) and withstand voltage failure rate of capacitor The DC voltage is applied between both electrodes of the capacitor or capacitor element while boosting it at 100 V / sec. Breakdown voltage. 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 whose insulation breakdown voltage did not reach the specified voltage is indicated as% withstanding voltage failure rate. Here, the specified voltage was 25 V per 1 μm of the average thickness of the dielectric film.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited thereto.

Example 1 and Comparative Example 1 (1) Production of Film A polyethylene terephthalate resin composition (hereinafter referred to as PET) containing 0.5% by weight of spherical silica particles having a diameter of 500 μm and having an intrinsic viscosity of 0.7, 300 ° C., and a shear rate of 200 sec. ^-1
Polyphenylene sulfide resin composition obtained by adding 0.5% of petroleum resin to polyphenylene sulfide having a lower melt viscosity of 4000 poise (hereinafter, referred to as PPS) is supplied to a separate extruder, and a double-tube type is provided in a molten state at the upper part of the die. Guide the center layer to PPS with the laminating device, then discharge from the T-die die provided and quench with the cooling rotary drum to obtain a substantially amorphous PET / PPS / PET three-layer laminated sheet Was.

Next, the laminated sheet was run in contact with a plurality of heating rolls having a surface temperature of 90 ° C., and stretched 3.7 times in the longitudinal direction between cooling rolls provided next to the heating roll group and having different peripheral speeds of 30 ° C. This uniaxially stretched sheet is stretched 3.5 times at 100 ° C. in a direction perpendicular to the longitudinal direction using a tenter, and then heat-treated at 215 ° C. for 10 seconds to form a 0.5 μm thick PPS support film laminated on a 3.0 μm thick PPS support film. A surface layer film of the present invention was obtained. The peel strength of this laminated film was 0.9 g / cm, which was within an appropriate range.

Next, using a continuous peeling and winding machine, winding up while peeling the support film from the laminated film obtained here.
An ultra-thin 5 μm PET film was obtained. Table 1 shows the properties of the film and the particles added to the film.

(2) Production of Capacitor The laminated film obtained in (1) was vapor-deposited to a thickness of 3Ω with aluminum as the surface resistance using a continuous winding vacuum vapor deposition machine. At this time, vapor deposition was performed in a stripe shape having a margin portion running in the longitudinal direction (the vapor deposition portion width was 8.0 mm and the margin portion width was 1.0 mm). Next, insert a blade in the center of each vapor deposition section and the center of each margin section, slit it, and set it to 0 or left or right.
The resultant was wound into a tape having a width of 4.5 mm having a margin of 5 mm and wound to obtain a laminated metallized film.

The metallized film was wound up while peeling the support film from the laminated metallized film using a continuous peeling winder from the laminated metallized film.

The left and right margins of the metallized film obtained in this way are superposed on each other to form a 600 mm
After winding 1000 turns on a drum having a diameter, the obtained wound body together with the drum as a winding shaft was placed in a hot air oven at 180 ° C. and heat-treated for 1 hour. Thereafter, metallicon was sprayed on both end surfaces of the wound body to form external electrodes, and the wound body was cut at two opposite locations to obtain a semicircular capacitor mother element. This capacitor mother element was cut to a length of 1.0 μF to obtain a capacitor element, and a lead wire was welded to a metallikon portion to obtain a multilayer capacitor. Table 1 shows the evaluation results of this capacitor.

Next, the kinds of inert particles to be added were variously changed, and a laminated film, a PET film, and a capacitor were produced in the same manner as described above. Table 1 shows these characteristics and evaluation results.

Example 2 and Comparative Example 2 300% by weight of spherical silica particles having a diameter of 1000 μm
C., a polyphenylene sulfide resin composition having a melt viscosity of 4000 poise under a shear rate of 200 sec ^-1 (hereinafter, referred to as PPS), and a polyethylene terephthalate resin composition having an intrinsic viscosity of 0.7 to which 0.5% of petroleum resin is added (hereinafter, PET) Using the same film forming apparatus as used in Example 1 except that the heat treatment temperature was set to 245 ° C., and the film was formed under the same film forming conditions and laminated on a PET support film having a thickness of 3 μm. A 0.7 μm PPS film was obtained. The peeling force of this laminated film was within an appropriate range of 2 g / cm. Table 2 shows the properties of the particles added to the film and the evaluation results of the film.

A capacitor was manufactured from this laminated film in the same manner as in Example 1. Table 2 shows the evaluation results of this capacitor.

Further, the kinds of inert particles to be added were variously changed, and a laminated film, a PPS film, and a capacitor were produced in the same manner as described above. Table 2 shows these characteristics and evaluation results.

Example 3 and Comparative Example 3 A polyethylene naphthalate resin composition containing 0.5 wt% of spherical crosslinked polystyrene particles having a diameter of 500 μm and having an intrinsic viscosity of 0.61 (hereinafter referred to as PEN), and 300 ° C. to which 0.5% of a petroleum resin was added, Melt viscosity under shear rate 200sec ^-1 is 4000
Poise polyphenylene sulfide resin composition (hereinafter, referred to as
PPS) was used in Example 1, and the film was formed under the same film forming conditions except that the heat treatment temperature was set to 230 ° C., and laminated on a PPS support film having a thickness of 3 μm. A 0.5 μm thick PEN film was obtained. The peeling force of this laminated film was within an appropriate range of 1.7 g / cm. Table 3 shows the characteristics of the particles added to the film and the evaluation results of the film.

A capacitor was manufactured from this laminated film in the same manner as in Example 1. Table 3 shows the evaluation results of this capacitor.

Further, the kinds of inert particles to be added were variously changed, and a laminated film, a PEN film, and a capacitor were produced in the same manner as described above. Table 2 shows these characteristics and evaluation results.

As described above, when the film of the present invention is a laminated film, the handleability of the laminated film is achieved, and the film alone achieves both the handleability and the electrical characteristics of a capacitor.

Comparative Example 4 In the same manner as in No. 5 of Example 1, the amount of particles added was 4.0 w
A film formed by the above method was used as Comparative Example 4 except that the content was set to t%. The single dispersion index was evaluated to be 0.8,
The withstand voltage was 65 V, and the withstand voltage failure rate was 12.6%, which was unsatisfactory.

Continuation of the front page (51) Int.Cl. ⁶ identification code FI B29K 67:00 B29L 7:00 C08L 67:00 81:02 (58) Field surveyed (Int.Cl. ⁶ , DB name) C08J 5/00 -5/02 C08J 5/12-5/22 B29C 55/12 H01G 4/18

Claims (5)

(57) [Claims] 1. A biaxially stretched film comprising a crystalline thermoplastic resin composition (A), wherein said resin composition (A) contains inert particles so as to satisfy the following formulas (1) to (5). A biaxially stretched film for a capacitor, characterized by being added. 0.3 ≦ t / φ ≦ 2.0 (1) 0.1 ≦ c · t / φ ≦ 10 (2) 1.5 ≧ S _c ≧ 1.0 (3) 0.5 ≧ s / φ (4) x ≧ 0.9 (5) where: φ: average particle size of inactive particles (μm) t: thickness of biaxially stretched film composed of resin composition (A) (μm) c: weight addition amount of inert particles (% ) S _c : sphericity of inert particles s: standard deviation of particle size of inert particles (μm) x: monodispersity index of inert particles 2. The biaxially stretched film for a capacitor according to claim 1, wherein the support film comprising the resin composition (B) is laminated in a releasable state. 3. The resin composition (A) is a resin composition containing polyethylene terephthalate as a main component, and the biaxially stretched film made of the resin composition (A) has a thickness of 0.2 μm.
The biaxially stretched film for capacitors according to claim 1 or 2, wherein the thickness is at least 1.0 µm. 4. The resin composition (A) is a resin composition containing polyethylene naphthalate as a main component, and the biaxially stretched film made of the resin composition (A) has a thickness of 0.2 μm or more and 1.0 μm or less. The biaxially stretched film for a capacitor according to claim (1) or (2). 5. The resin composition (A) is a resin composition containing polyphenylene sulfide as a main component, and the biaxially stretched film comprising the resin composition (A) has a thickness of 0.2 μm or more and 1.0 μm or less. The biaxially stretched film for a capacitor according to claim 1 or 2.