Biaxially-oriented polyarylene sulfide film

Abstract

To provide a polyarylene sulfide film having excellent transparency.SOLUTION: A biaxially-oriented polyarylene sulfide film is primarily composed of polyarylene sulfide (PAS), and has a crystal size of 90Å or less, obtained by applying the Scherrer equation to a half peak width of the (200) diffraction peak of polyarylene sulfide crystal determined by X-ray diffraction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to biaxially oriented polyarylene sulfide films. [Background technology]

[0002] In recent years, glass has been under consideration as a circuit board material that requires transparency. However, glass substrates have drawbacks such as being easily broken, being heavy, and being difficult to make thin. In addition, glass substrates do not have sufficient flexibility for use in car windshields or in parts that come into contact with curved surfaces indoors and outdoors.

[0003] Polyarylene sulfides possess excellent heat resistance, flame retardancy, rigidity, chemical resistance, electrical insulation, and low moisture absorption, making them particularly suitable for use in electrical and electronic devices, mechanical components, and automotive parts. The trend toward higher speeds and larger capacities in the electrical and electronic component fields has led to a demand for materials with low transmission loss. Polyarylene sulfide films, such as polyphenylene sulfide (PPS), are being increasingly used as circuit materials, taking advantage of their low transmission loss and low moisture absorption. However, PPS films have low transparency, as measured by haze. Therefore, when used as transparent circuit boards, for example, PPS films can easily impair visibility due to their transparency. Therefore, improved transparency is needed at film thicknesses suitable for circuit boards.

[0004] To date, a technique for improving the transparency and slipperiness of PPS films has been disclosed in which PPS films are subjected to a rubbing treatment (Patent Document 1). Also, a technique for improving the transparency and slipperiness by incorporating zinc oxide particles with controlled particle size and dispersibility has been disclosed (Patent Document 2). On the other hand, a technology has been disclosed that controls the crystal size of a sheet using polyphenylene sulfide to increase its thermal and mechanical properties (Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-67748 [Patent Document 2] Japanese Patent Application Publication No. 5-320380 [Patent Document 3] Japanese Patent Application Publication No. 7-205373 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the techniques described in Patent Documents 1 and 2, although disclosing techniques for improving transparency at a thickness of 25 μm, have the problem that they are insufficient to improve transparency as indicated by haze at a thickness of 30 μm or more, which is required for films for circuit boards. Also, the technique described in Patent Document 2 has the problem that transparency is insufficient when applied to film applications.

[0007] Furthermore, the technology described in Patent Document 3 is a technology for controlling the crystal size of a sheet in which glass fiber material is impregnated with PPS, but it has the problem that it is unable to control the crystal size of the orientation-controlled molecular chains in a film that has been biaxially oriented by stretching.

[0008] An object of the present invention is to solve the above-mentioned problems, that is, to provide a biaxially oriented polyarylene sulfide film having excellent transparency. [Means for solving the problem]

[0009] As a result of investigations to solve the above problems, the inventors have found that transparency can be improved by reducing the crystal size in a biaxially oriented polyarylene sulfide film, and provide a biaxially oriented polyarylene sulfide film that has high transparency even when it is thick. A preferred embodiment of the present invention is as follows. (1) A biaxially oriented polyarylene sulfide film whose main component is polyarylene sulfide (PAS) and whose crystal size is 90 Å or less, as calculated by applying the Schller formula to the half-width of the (200) diffraction peak of the polyarylene sulfide crystals obtained by X-ray diffraction. (2) The biaxially oriented polyarylene sulfide film according to (1), having a thickness of 30 μm or more. (3) A biaxially oriented polyarylene sulfide film according to either (1) or (2), in which the gloss of at least one film surface is 200% or higher. (4) The biaxially oriented polyarylene sulfide film according to any one of (1) to (3), wherein at least one of the film surfaces has a glossiness of 200% or more. (5) The biaxially oriented polyarylene sulfide film according to any one of (1) to (4), which has a haze of 10% or less. (6) A biaxially oriented polyarylene sulfide film according to any one of (1) to (5), having two or more layers whose main constituent is polyarylene sulfide, at least one of the outermost layers having a layer (layer A) whose main constituent is polyarylene sulfide and which contains at least one other thermoplastic resin different from polyarylene sulfide. (7) A biaxially oriented polyarylene sulfide film according to any one of (1) to (6), wherein the layer A contains a dispersion incompatible with the polyarylene sulfide, and the thickness ratio of the layer A to the total thickness of the film is 0.1% or more and 10% or less. (8) A transparent circuit substrate using the biaxially oriented polyarylene sulfide film according to any one of (1) to (7). (9) A transparent antenna substrate using the biaxially oriented polyarylene sulfide film according to any one of (1) to (7). (10) An insulating film made using the biaxially oriented polyarylene sulfide film according to any one of (1) to (7). (11) A metal film laminated film having a metal film on at least one side of the biaxially oriented polyarylene sulfide film according to (1) to (7). (12) A film capacitor using the metal laminated film according to (11). (13) A power control unit having the film capacitor according to (12). (14) An electric vehicle having the power control unit according to (13). (15) An electric aircraft having the power control unit described in (13). [Effects of the Invention]

[0010] The polyarylene sulfide film of the present invention has excellent transparency and surface quality, and therefore, by taking advantage of these properties, can be suitably used as an insulating film for various parts that require transparency, such as automotive components, battery components, display components, industrial packaging materials, decorative materials, electric and electronic materials, and electric insulating materials, including transparent circuit boards, transparent antenna boards, high-frequency transparent circuit boards, high-frequency transparent antenna boards, and capacitor materials that require surface quality. DETAILED DESCRIPTION OF THE INVENTION

[0011] The biaxially oriented polyarylene sulfide film of the present invention is made of a resin composition containing a polyarylene sulfide (hereinafter referred to as PAS) resin as a main constituent component.

[0012] In the present invention, "having a PAS resin as the main constituent" means that the PAS resin is contained in an amount of 50% by mass or more. Preferably, the PAS resin is contained in an amount of 60% by mass or more, and more preferably, the PAS resin is contained in an amount of 70% by mass or more. If the PAS resin content is less than 50% by mass, the heat resistance, dimensional stability, and mechanical properties that are characteristic of PAS films may be impaired.

[0013] The PAS resin used in the present invention is a homopolymer or copolymer having a repeating unit of -(Ar-S)-, where Ar includes units represented by the following formulas (A) to (K).

[0014] [ka]

[0015] (R1 and R2 are substituents selected from hydrogen, alkyl groups, alkoxy groups, and halogen groups, and R1 and R2 may be the same or different.) As the repeating unit, of the above formulas, a p-arylene sulfide unit is preferred, and representative examples thereof include polyphenylene sulfide, polysulfone, polyether sulfone, polyphenylene sulfide sulfone, and polyphenylene sulfide ketone. From the viewpoints of film properties and economic efficiency, a particularly preferred p-arylene sulfide unit is the p-phenylene sulfide unit.

[0016] The polyarylene sulfide resin used in the present invention preferably comprises p-arylene sulfide units represented by the following structural formula as the main structural unit, accounting for 97 mol % or more of all repeating units. More preferably, it is 98 mol % or more. By making this main component 97 mol % or more, the crystallinity and glass transition temperature are increased, and excellent heat resistance, electrical properties, and chemical resistance can be achieved.

[0017] [ka]

[0018] Furthermore, units containing copolymerizable sulfide bonds may be contained in less than 3 mol% of the repeating units. Examples of such repeating units include trifunctional units, ether units, sulfone units, ketone units, meta-bond units, aryl units having a substituent such as an alkyl group, biphenyl units, terphenylene units, vinylene units, and carbonate units, and one or more of these may be present together. In this case, the structural units may be in the form of either random copolymerization or block copolymerization.

[0019] Polyarylene sulfide resins can be synthesized by known methods, and in the case of polyphenylene sulfide, the synthesis method can be exemplified by Reference Example 1 described below, although it is not limited thereto.

[0020] The PAS resin composition constituting the biaxially oriented polyarylene sulfide film of the present invention may contain various additives such as antioxidants, heat stabilizers, antistatic agents, and antiblocking agents, within the range that does not impair the effects of the present invention.

[0021] The biaxially oriented polyarylene sulfide film of the present invention must have a crystal size of 90 Å or less, obtained by applying the Schller formula to the half-width of the (200) diffraction peak of polyarylene sulfide crystals determined by X-ray diffraction. The crystal size is preferably 80 Å or less, and more preferably 30 Å to 70 Å. A crystal size of 90 Å or less suppresses light scattering due to crystals, making it possible to obtain a biaxially stretched polyarylene sulfide film with low haze and high transparency even when the film is thick. On the other hand, by making the crystal size equal to or greater than the aforementioned size, heat resistance can be improved.

[0022] The crystal size referred to in the present invention is determined by X-ray diffraction, and specifically means the apparent crystal size obtained by measuring a diffraction pattern by a reflection method and applying the Schller formula to the half-width of the (200) diffraction peak of the polyarylene sulfide crystal.

[0023] The method for controlling the crystal size of a biaxially stretched polyarylene sulfide film is not particularly limited. For example, in the manufacturing process of a biaxially stretched polyarylene sulfide film, a preferred method is to stretch the film in the biaxial direction, then stretch it in the longitudinal direction and / or the width direction by 1.01 to 1.80 times at a temperature of (the melting point of the polyarylene sulfide resin - 10°C) or more (the melting point of the polyarylene sulfide resin + 10°C), and then heat-treat it at the same temperature, followed by a high-temperature stretching step. By performing the stretching at a temperature near the melting point of the polyarylene sulfide resin, the crystals partially melt and deform, thereby reducing the crystal size.

[0024] The biaxially oriented polyarylene sulfide film of the present invention must be a biaxially oriented film. By making the polyarylene sulfide film into a biaxially oriented film, it is possible to improve the mechanical strength and flatness and reduce thickness unevenness, and when the film is used as an automobile component, a battery component, various parts of electric and electronic materials, and industrial packaging material, biaxial orientation treatment is necessary from the viewpoint of improving the film properties.

[0025] Here, the polyarylene sulfide film of the present invention is a biaxially oriented film means that the average value of a parameter (Q value) indicating the sharpness of the resonance of the polyarylene sulfide film measured ten times using a molecular orientation meter (MOA-6015, manufactured by Oji Scientific Instruments) is 4300 or more.

[0026] Examples of methods for biaxial orientation treatment include sequential biaxial stretching (a stretching method that combines stretching in one direction at a time, such as a method in which stretching in the longitudinal direction is performed followed by stretching in the width direction), simultaneous biaxial stretching (a method in which stretching in the longitudinal direction and the width direction is performed simultaneously), or a combination of these, as exemplified in the manufacturing method described below.

[0027] The thickness of the biaxially oriented polyarylene sulfide film of the present invention is not particularly limited, but from the viewpoint of film formability, the film thickness is preferably 1 μm or more. The biaxially oriented polyarylene sulfide of the present invention is preferably adjusted appropriately depending on the application, but for circuit substrates, the thickness is preferably 30 μm or more, more preferably 50 μm or more. The upper limit is not particularly specified, but from the viewpoint of film formability, the thickness is preferably 200 μm or less.

[0028] The thickness referred to in the present invention refers to a value measured by observing the cross section of the film with a scanning electron microscope.

[0029] There are no particular limitations on the method for achieving such a thickness in the biaxially oriented polyarylene sulfide film, but it can be achieved, for example, by adjusting the amount of resin extruded from the extruder, the film-forming speed, and the stretching ratio during the film production process.

[0030] The biaxially oriented polyarylene sulfide film of the present invention preferably has a gloss of 140% or more on at least one film surface. A gloss within the above range indicates minimal surface irregularities that optically diffusely reflect light, and minimal scratches or foreign matter on the film surface. Therefore, when a metal layer is formed by vapor deposition, sputtering, plating, or other methods for use in circuits or capacitors, it is possible to obtain circuits with excellent transmission characteristics and capacitors that are less susceptible to insulation defects due to scratches, etc., due to minimal surface irregularities. If the gloss is less than 140%, the film may have poor transparency when used as a circuit material, or may have many surface scratches and defects, resulting in poor quality. While there is no upper limit to the gloss, it is preferably 240% or less from the viewpoint of film formability. The gloss is more preferably 160% or more, even more preferably 180% or more, and most preferably 200% or more. The gloss can be measured by the method described below. A preferred embodiment of the method for achieving a gloss level within the above-mentioned preferred range is to control the surface irregularities without forming voids by adjusting the lamination structure and stretching conditions of the production method described below. If particles and / or dispersions are not blended, voids will not be formed, but the surface runnability may be poor, scratches and defects may occur on the surface, and the surface gloss may not be high, resulting in poor surface quality.

[0031] The haze of the biaxially oriented polyarylene sulfide film of the present invention is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. By setting the haze of the biaxially oriented polyarylene sulfide film within the above range, light diffusion within the film is suppressed, allowing light to be transmitted and utilized efficiently, making it possible to detect defects and align products during the production process using the film, and enabling use as an optical film. If the haze of the polyarylene sulfide film is greater than 10%, defect detectability will be insufficient, which may cause problems in the optical applications described above.

[0032] The haze referred to in the present invention is a value measured in accordance with JIS-K7136 (2000).

[0033] A preferred method for adjusting the haze to the above range is to adjust the crystal size, obtained by applying the Schller formula to the half-width of the (200) diffraction peak of polyarylene sulfide crystals determined by X-ray diffraction, to 90 Å or less.

[0034] The biaxially oriented polyarylene sulfide film of the present invention preferably has two or more layers primarily composed of a PAS-based resin, with at least one outermost layer (layer A) primarily composed of a PAS-based resin and containing at least one other thermoplastic resin (X) different from the PAS-based resin. By constructing two or more layers, it is possible to control the surface irregularities primarily using the outermost layer, thereby improving surface runnability and suppressing surface scratches. This allows for a combination of multiple properties, including transparency, color, runnability, and the prevention of insulation defects due to surface quality. Examples of lamination structures include multilayer structures such as A / B, A / B / A, A / B / A / B, and A / B / A / B / A, where layer B is primarily composed of a PAS-based resin. From the standpoint of chemical resistance and other factors, the biaxially oriented polyarylene sulfide film of the present invention preferably has the outermost layer primarily composed of a PAS-based resin. For the same reason, it is also preferable for the film to have no coating layer.

[0035] In the present invention, a three-layer structure of A / B / A is more preferred from the viewpoints of transparency, color tone, surface quality, and running properties.

[0036] To achieve this structure, two types of resin raw materials, one containing a PAS-based resin as the main component and the other containing a PAS-based resin as the main component but also containing a thermoplastic resin different from the PAS-based resin, are supplied to separate melt extrusion devices in the film manufacturing process, and are heated to above the melting point of each resin to melt them.Then, in a confluence device installed between the melt extrusion device and the nozzle outlet, the layers containing a PAS-based resin as the main component and a PAS-based resin as the main component but also containing a thermoplastic resin different from the PAS-based resin are merged in the thickness direction, and the unstretched sheet extruded from the slit-shaped nozzle outlet is stretched biaxially to obtain the film.

[0037] In the biaxially oriented polyarylene sulfide film of the present invention, it is preferable that another thermoplastic resin (X) different from the PAS resin is incompatible with the PAS resin and is contained as a dispersion in the PAS resin in Layer A. By having a dispersion incompatible with the PAS resin in Layer A, which is mainly composed of a PAS resin, it is possible to form and control surface irregularities, and to obtain a film excellent in transparency, runnability, and quality.

[0038] In the present invention, the expression "the thermoplastic resin (X) is incompatible with the PAS resin and is contained as a dispersion in the PAS resin" means that the PAS resin and the thermoplastic resin (X) form a sea-island structure, with the PAS resin constituting the sea component and the thermoplastic resin (X) constituting the island component.

[0039] When the PAS resin is polyphenylene sulfide, examples of the thermoplastic resin (X) that is incompatible with the PAS resin include polysulfone, polyphenylsulfone, polyethersulfone, polyetherimide, nylon 6, and nylon 46. In particular, polysulfone, polyphenylsulfone, and polyethersulfone are preferred from the viewpoint of transparency because they have good dispersibility in polyphenylene sulfide and do not form voids at the interface during stretching during film formation, and polyethersulfone is more preferred because it allows the size of the dispersed particles to be reduced.

[0040] The shape of the dispersion is not particularly limited. The shape can be confirmed by observing the cross section of the film with a transmission electron microscope (TEM) or a scanning electron microscope (SEM), and examples of shapes include circular, elliptical, spindle-shaped, and irregular.

[0041] In the biaxially oriented polyarylene sulfide film of the present invention, when the sum of the PAS resin content WI of Layer A and the content WII of the thermoplastic resin (X) different from the PAS resin is taken as 100 parts by mass, the content WII of the thermoplastic resin (X) is preferably 0.01 parts by mass or more and 3.0 parts by mass or less. To achieve both runnability and transparency, the content WII of the thermoplastic resin (X) is more preferably 0.1 parts by mass or more and 1.0 parts by mass or less, and even more preferably 0.2 parts by mass or more and 0.5 parts by mass or less. By setting the content WII of the thermoplastic resin (X) to the aforementioned upper limit or less, deterioration of transparency due to refractive index differences between the resins can be suppressed. Furthermore, by setting the content WII of the thermoplastic resin (X) to the aforementioned lower limit or more, deterioration of runnability of the film and deterioration of surface quality due to scratches can be suppressed.

[0042] In the biaxially oriented polyarylene sulfide film of the present invention, the thickness ratio of the A layer is preferably 0.1% to 10% of the total film thickness. By setting the thickness ratio of the A layer within the above range, it is possible to easily form dense surface irregularities and also to reduce the amount of dispersion in the entire film, which is preferable because it improves transparency, color tone, and surface quality. By setting the thickness ratio of the A layer to be equal to or greater than the above-mentioned lower limit, the formation of surface irregularities is reduced and the surface becomes smooth, which prevents increased friction during transport and deterioration of runnability and surface quality. Furthermore, by setting the thickness ratio of the A layer to be equal to or less than the above-mentioned upper limit, the surface irregularities are formed densely, resulting in excellent transparency. The thickness ratio of the A layer is more preferably 0.5% to 5.0%, more preferably 1.0% to 3.0%.

[0043] In the present invention, the thickness ratio of Layer A can be determined by measuring the lamination thickness of Layer A and the thickness of the entire film from a scanning electron microscope (SEM) image of the cut surface of the film and calculating the ratio. When there are multiple Layer A layers, the total thickness of the layers is taken as the thickness of Layer A and the ratio to the entire film thickness is calculated.

[0044] The thickness ratio of layer A can be controlled by adjusting the discharge rate ratio of the extruders that supply the resins of layers A and B in the film manufacturing process to the lamination ratio.

[0045] The biaxially oriented polyarylene sulfide film of the present invention has excellent transparency and color tone, as well as excellent running properties and quality of the film surface, and can therefore be suitably used as an automotive component, a battery component, an electric / electronic material, an electric insulating material, in particular as various parts and industrial packaging materials that require transparency, such as a protective material for the lower plate of a flexible printed circuit board, and as an insulating film, transparent circuit board, transparent antenna substrate, including capacitor materials that require surface quality.

[0046] Furthermore, the biaxially oriented polyarylene sulfide film of the present invention may be coated on one or both sides with various coating agents in-line or off-line for the purpose of improving weather resistance and adhesiveness, surface protection, etc.

[0047] A conductive film is formed on the biaxially oriented polyarylene sulfide film thus obtained to produce a circuit board. When used as a transparent circuit, the conductive film is preferably a transparent or translucent conductor, such as a metal film such as Ag, a metal oxide film such as ITO (indium tin oxide), or a resin film containing conductive particles. Forming a mesh of thin conductor wires as the conductive film is also effective for improving transparency.

[0048] The conductor may be formed by any known method, such as sputtering or paste printing, but is not limited thereto. The circuit board may be patterned by any known method, such as photolithographic etching or screen printing. Furthermore, through holes may be formed in the circuit board by drilling, laser, melt-through, or the like, as needed, to obtain the circuit board.

[0049] A circuit board using the biaxially oriented polyarylene sulfide film of the present invention is useful as a transparent antenna substrate because of its excellent transparency and color tone.

[0050] The method for producing the biaxially oriented polyarylene sulfide film of the present invention will be described using an example of a film production method in which polyphenylene sulfide resin (hereinafter sometimes abbreviated as PPS resin) is used as the polyarylene sulfide-based resin, but the present invention is not limited to this example.

[0051] Sodium sulfide and p-dichlorobenzene are combined and reacted under high temperature and pressure in an amide-based polar solvent such as N-methyl-2-pyrrolidone (NMP). Copolymerization components such as m-dichlorobenzene and trihalobenzene can also be added as needed. Caustic potassium or alkali metal carboxylates are added as polymerization modifiers, and the polymerization reaction is carried out at 230-290°C. After polymerization, the polymer is cooled, and the polymer is made into a water slurry and filtered through a filter to obtain wet granular polymer. An amide-based polar solvent is added to the granular polymer, which is then stirred and washed at 30-100°C. It is then washed several times with ion-exchanged water at 30-80°C, washed several times with an aqueous solution of a metal salt such as calcium acetate, and dried to obtain polyphenylene sulfide polymer powder.

[0052] In the present invention, when washing the polymer powder, the obtained polymer powder is washed in an NMP solvent at a temperature of 100 to 200°C for 6 to 24 hours, and then washed several times with pure water at 30 to 80°C to obtain a washed polymer powder. This polymer powder is fed into a vented extruder and melt-extruded into a strand shape, cooled with water at a temperature of 25°C, and then cut into chips to form PPS chips.

[0053] A masterbatch is prepared by mixing the polymer powder and / or polymer powder (washed) obtained above as a polyarylene sulfide resin with inorganic particles and / or other thermoplastic resin (X) in any desired ratio. The concentration of inorganic particles and / or other thermoplastic resin (X) in the masterbatch is preferably 1% by mass to 25% by mass, more preferably 5% by mass to 10% by mass. If it is more than 25% by mass, dispersibility may deteriorate and the dispersed particle size may increase. If it is less than 1% by mass, it may be diluted and the amount of masterbatch used may increase, which may be undesirable from a cost perspective. In the present invention, a method for preparing a masterbatch using a device that applies shear stress, such as a twin-screw extruder, is preferred. In this case, kneading is preferably carried out in the kneading section so that the resin temperature ranges from (PAS resin melting point + 5°C) to (PAS resin melting point + 80°C), more preferably from (PAS resin melting point + 10°C) to (PAS resin melting point + 80°C), and even more preferably from (PAS resin melting point + 15°C) to (PAS resin melting point + 70°C). The screw rotation speed is preferably in the range of 100 rpm to 1500 rpm. The dispersion diameter of the dispersed phase can be controlled by setting the resin temperature and screw rotation speed within the preferred ranges.

[0054] If necessary, PPS chips that have been dried under reduced pressure at 180°C for 3 hours are mixed with the masterbatch in a predetermined ratio, and in the case of a single layer, the mixture is fed into a full-flight single-screw extruder with the melting section set to 300°C to 350°C, passed through a filter, and then extruded from a T-die nozzle.The mixture is then brought into close contact with a cooling drum with a surface temperature of 20°C to 70°C while applying a static charge, and rapidly cooled and solidified to obtain an unstretched film in a substantially unoriented state.

[0055] To create a laminated film with two or more layers, the PPS chips and chips made by mixing PPS chips and masterbatch in a specified ratio are fed into separate single-screw extruders and heated to above the melting point of each resin. The melted raw materials are then fed into a confluence device installed between the melt extrusion device and the die outlet, where they are laminated in a molten state into two layers (a layer primarily made of PPS) / (a layer primarily made of PPS and containing at least one other thermoplastic resin different from PPS) or three layers (a layer primarily made of PPS and containing at least one other thermoplastic resin different from PPS) / (a layer primarily made of PPS) / (a layer primarily made of PPS and containing at least one other thermoplastic resin different from PPS) at an arbitrary layering ratio (e.g., 0.3:24.4:0.3 or 0.3:24.7), and extruded from the slit-shaped die outlet. This sheet is placed in close contact with a cooling drum having a surface temperature of 20° C. to 70° C. and cooled to solidify, to obtain a substantially unoriented two-layer laminated unstretched film or a three-layer laminated unstretched film.

[0056] Furthermore, the desired thickness can be obtained by adjusting the amount of resin extruded from the extruder, the film-forming speed and the stretching ratio.

[0057] The unstretched film obtained above is then biaxially stretched. As the stretching method, a sequential biaxial stretching method (a stretching method in which stretching in one direction is performed, such as a method in which stretching in the longitudinal direction is performed after stretching in the width direction), a simultaneous biaxial stretching method (a method in which stretching in the longitudinal direction and the width direction is performed simultaneously), or a combination thereof can be used. Here, the sequential biaxial stretching method in which stretching in the longitudinal direction is performed first and then in the width direction is illustrated.

[0058] The unstretched film is heated by a group of heating rolls and stretched in the machine direction (MD) by 2.0 to 4.5 times, more preferably 2.8 to 4.2 times, in one or more stages (MD stretching). The stretching temperature is preferably Tg to Tcc, more preferably (Tg + 5°C) to (Tcc - 10°C). The film is then cooled by a group of cooling rolls at 20 to 50°C.

[0059] As a method of stretching in the width direction (TD direction) following MD stretching, for example, a method using a tenter is common. Both ends of the film are held with clips and introduced into the tenter, where it is stretched in the width direction (TD stretching). The stretching temperature is preferably Tg to Tcc, more preferably in the range of (Tg + 5°C) to (Tcc - 10°C). From the viewpoint of the flatness of the film, the stretching ratio is preferably 3.0 to 5.0 times, and more preferably 3.0 to 4.5 times.

[0060] Next, the film is preferably stretched 1.01 to 1.80 times in the longitudinal and / or transverse directions at a temperature between (the melting point of the polyarylene sulfide resin -10°C) and (the melting point of the polyarylene sulfide resin +10°C), followed by heat treatment at the same temperature, followed by a high-temperature stretching step. A more preferred temperature is between (the melting point of the polyarylene sulfide resin) and (the melting point of the polyarylene sulfide resin +5°C), and a more preferred stretching ratio is 1.3 to 1.5 times in the transverse direction. This step allows the crystals to partially melt and deform, thereby controlling the crystal size to the desired size and reducing haze. Furthermore, by applying stretching in a temperature range where the resin fluidity is high, this step allows stretching without forming fine voids at the interfaces of the particles and / or dispersions formed by MD stretching and TD stretching, thereby suppressing surface unevenness due to voids, thereby smoothing the surface unevenness and increasing the surface gloss. If the stretching ratio is less than 1.01 times, sufficient effect cannot be obtained, and if it is more than 1.8 times, tearing may occur during stretching. In addition, relaxation treatment may be performed in the longitudinal and / or transverse directions during the heat treatment.

[0061] Next, the film is cooled to room temperature, if necessary while being subjected to a relaxation treatment in the longitudinal and / or transverse directions, and then wound up to obtain a biaxially oriented polyarylene sulfide film. Next, a metal film laminated film formed using the biaxially oriented polyarylene sulfide film of the present invention, a film capacitor formed using the same, and methods for producing them will be described.

[0062] The metal film laminated film of the present invention has a metal film on at least one side of the biaxially oriented polyarylene sulfide film of the present invention. This metal film laminated film can be obtained by providing a metal film on at least one side of the biaxially oriented polyarylene sulfide film of the present invention described above.

[0063] In the present invention, the method for providing a metal film is not particularly limited, but a preferred method is to provide a metal film, such as a vapor-deposited film of aluminum or an aluminum-zinc alloy, on at least one side of the biaxially oriented polyarylene sulfide film to serve as an internal electrode of the film capacitor. In this case, other metal components, such as nickel, copper, gold, silver, or chromium, can also be vapor-deposited simultaneously with or sequentially with the aluminum. A protective layer, such as oil, can also be provided on the vapor-deposited film. When the surface roughness of the biaxially oriented polyarylene sulfide film differs between the front and back sides, it is preferable to provide a metal film on the smoother surface to form a metal film-laminated film from the viewpoint of improving voltage resistance.

[0064] In the present invention, if necessary, after forming the metal film, the metal film laminated film can be annealed or heat-treated at a specific temperature. Furthermore, for insulation or other purposes, at least one side of the metal film laminated film can be coated with a resin such as polyphenylene oxide.

[0065] The film capacitor of the present invention is formed using the metal film laminated film of the present invention, that is, the film capacitor of the present invention has the metal film laminated film of the present invention.

[0066] For example, the film capacitor of the present invention can be obtained by laminating or winding the metal film laminated film of the present invention by various methods. A preferred example of a method for producing a wound type film capacitor is as follows.

[0067] Aluminum is vapor-deposited under reduced pressure on one side of a biaxially oriented polyarylene sulfide film. This is done in stripes with longitudinal margins. Next, a blade is used to slit the center of each vapor-deposited area and the center of each margin on the surface, creating a tape-like take-up reel with a margin on one side of the surface. Two tape-like take-up reels with left and right margins are stacked and wound together so that the vapor-deposited area extends beyond the margin in the width direction, producing a wound body.

[0068] When vapor deposition is performed on both sides, one side is vapor deposited in stripes with a margin running in the longitudinal direction, and the other side is vapor deposited in stripes so that the longitudinal margin is located in the center of the vapor deposition area on the back side. Next, a blade is cut into the center of the margin on each side to create a tape-like take-up reel with a margin on one side on each side (for example, if there is a margin on the right side of the front side, there will be a margin on the left side on the back side). One resulting reel and one unvaporized laminated film are overlapped and wound together so that the metallized film extends beyond the laminated film in the width direction, to obtain a wound body.

[0069] One example of a method for obtaining the film capacitor of the present invention from the metal layer laminated film of the present invention is to remove the core material from the wound body prepared as described above, press the body, spray metallikon on both end surfaces to form external electrodes, and weld lead wires to the metallikon to form a wound film capacitor. Film capacitors have a wide range of applications, including power control units for electric vehicles (e.g., electric vehicles, hybrid vehicles, and fuel cell vehicles) and electric aircraft (e.g., drones), railroad vehicles, solar and wind power generation, and general home appliances. The film capacitor of the present invention can also be suitably used for these applications. The polypropylene film of the present invention can also be used in a variety of applications, such as packaging film, release film, processing film, sanitary products, agricultural products, construction products, and medical products, and is particularly suitable for applications involving a heating process in film processing.

[0070] The power control unit, electric vehicle, and electric aircraft of the present invention will be described below. The power control unit of the present invention includes the film capacitor of the present invention. The power control unit is a system that manages power in electric vehicles, electric aircraft, and the like that have mechanisms driven by electricity. By incorporating the film capacitor of the present invention into the power control unit, it is possible to reduce the size of the power control unit itself, improve its heat resistance, and increase its efficiency, resulting in improved fuel efficiency.

[0071] The electric vehicle of the present invention has the power control unit of the present invention. Here, the electric vehicle refers to a vehicle having a mechanism driven by electric power, such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle. As described above, the power control unit of the present invention can be made compact and has excellent heat resistance and efficiency, so that including the power control unit of the present invention in an electric vehicle leads to improved fuel efficiency, etc.

[0072] The electric aircraft of the present invention includes the power control unit of the present invention. Here, the electric aircraft refers to an aircraft with an electrically powered mechanism, such as a manned electric aircraft or a drone. As described above, the power control unit of the present invention can be made compact and has excellent heat resistance and efficiency, so that including the power control unit of the present invention in an electric aircraft can lead to improved fuel efficiency, etc.

[0073] [Method of measuring characteristics] (1) Crystal size The crystal size was measured by rotating the sample in-plane to eliminate the orientation effect of the sample, and the diffraction pattern was measured by the reflection method. The X-ray generator, X-ray source, goniometer, slit system, 2θ scanning speed, chart speed, and measurement sample were used in the same way as for determining the crystallinity.

[0074] The apparent crystallite size (ACS) was calculated from the half-width of the PPS(200) diffraction peak using the Scheller formula.

[0075] ACS(Å)=kλ / (βcosθ) β={B 2 -(B′) 2} 1 / 2 where k = Scheller constant (k = 1) λ=X-ray wavelength (λ=1.5418Å) 2θ=Bragg angle (°) β = corrected half-width (radian) B = measured half-width (radian) B' = half-width (radian) of the standard sample for correction (single crystal silicon). (2) Glossiness In accordance with JIS K-7105 (1981), the film surface was measured at an incident angle of 60° and an acceptance angle of 60° using a digital variable angle glossmeter UGV-5D manufactured by Suga Test Instruments Co., Ltd. The average value of data from five points was taken as the gloss (%). Measurements were performed on both sides of the film, and the value of the surface that achieved the highest gloss is shown in the table.

[0076] (3) Overall film thickness, thickness of layer A, and thickness ratio of layer A After embedding the film in epoxy resin, the film cross section was cut using a microtome parallel to the longitudinal direction and perpendicular to the film surface without crushing the film in the thickness direction. The cut film cross section was then fixed to the specimen stage of a scanning electron microscope under conditions that would prevent thermal deterioration of the material. Cross-sectional ion milling was performed using a Hitachi High-Technologies Corporation IM4000PLUS ion milling system, followed by platinum deposition. The resulting film cross section was then observed and images were obtained using a JEOL Ltd. JSM-6700F field emission scanning electron microscope at an accelerating voltage of 3.0 kV and a working distance of 8.0 mm.

[0077] The thickness of Layer A was observed at a magnification of 5000x, and from the analysis of the obtained image, the thickness of Layer A of the film was measured at five random points, and the average value was taken as the thickness of Layer A. If there was more than one Layer A, the thickness of each Layer A was measured, and the total of all Layer A thicknesses was taken as the thickness of Layer A.

[0078] Additionally, the overall thickness of the film was observed at a magnification of 3000x, and an image was taken that allowed the entire thickness of the film to be observed. The overall thickness of the film was measured from the image obtained through observation. If the entire thickness of the film could not be seen at the above magnification, images were taken at several points in the thickness direction and the images were stitched together to confirm the overall image. A total of five randomly selected locations were used as samples for thickness measurement, and the average of the measurements for the five samples was taken as the overall film thickness for that sample.

[0079] The ratio of the thickness of layer A to the total film thickness determined by the above method was determined and used as the thickness ratio of layer A.

[0080] (4) Hayes The haze of the entire film was measured using the following device. Equipment: Turbidity meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) Light source: White LED5V3W (rated) Photodetector: Si photodiode with V(λ) filter Measurement luminous flux: φ14mm (incidence aperture φ25mm) Optical conditions: Compliant with JIS-K7136 (2000) (5) Runnability Using a friction tester manufactured by Toyo Tester Kogyo, the initial resistance value was measured in accordance with ASTM-D1894 (1999) when one side of the film was placed in contact with the back side and rubbed against the other in the MD direction. The maximum value was taken as the static friction coefficient μs. However, if the initial resistance value was too large and exceeded the upper limit of the measurement value (5.0), it was deemed unmeasurable. Samples were cut into rectangular shapes measuring 80 mm wide and 200 mm long, and five sets (10 pieces) were cut out. Five measurements were taken and the average value was calculated. The runnability was evaluated based on the static friction coefficients calculated using the following criteria: D was determined as poor runnability. A:μs=0.50 or less (good running performance) B: μs=0.50 or more, 0.60 or less (normal running performance) C: μs = over 0.60 and below 0.70 (slightly poor running performance) D: μs = over 0.70 (poor running performance) (6) Heat resistance A strip-shaped sample measuring 200 mm in length and 10 mm in width was cut out in the longitudinal direction of the film. The breaking elongation was measured at 25°C and 65% RH using a tensile tester according to the method specified in ASTM-D882-97. The initial tensile chuck distance was 100 mm, and the tensile speed was 300 m / min. The measurement was performed 20 times using different samples, and the average breaking elongation (X) was calculated. A strip-shaped sample measuring 200 mm in length and 10 mm in width in the longitudinal direction of the film was placed in a gear oven and left in an atmosphere at 200°C, then naturally cooled. This sample underwent a tensile test 20 times under the same conditions as above, and the average breaking elongation (Y) was calculated. The elongation retention was calculated from the average breaking elongations (X) and (Y) obtained using the following formula: Elongation retention rate (%)=(Y / X)×100 The treatment time in the gear oven until the elongation retention rate reached 50% or less was defined as the time until the elongation at break was reduced by half. Heat resistance was evaluated according to the following criteria. A and B are acceptable. A: The elongation half-life is 120 hours or more. B: The elongation half-life is 80 hours or more and less than 120 hours. C: The elongation half-life is less than 80 hours. (7) Evaluation of insulation properties The film was cut into a 25 cm x 25 cm square and conditioned for 24 hours at 23°C and 65% RH. The breakdown voltage (kV) per unit thickness was measured using an AC breakdown tester (Kasuga Electric Co., Ltd., AC 30 kV) at a frequency of 60 Hz and a voltage ramp rate of 1000 V / sec according to JIS C2151 (2006). The thickness (μm) of the area surrounding the hole where breakdown occurred was then measured. The resulting breakdown voltage was then divided by the thickness (μm) to calculate the breakdown voltage per unit thickness (V / μm). Ten measurements were performed, and the average value was used as the breakdown voltage per unit thickness (V / μm). The insulation properties were evaluated based on the resulting breakdown voltage values ​​according to the following criteria.

[0081] AA: Breakdown voltage is 270V / μm or more A: Breakdown voltage is 240V / μm or more B: Breakdown voltage is 210V / μm or more C: Breakdown voltage is 180V / μm or more D: Breakdown voltage is less than 180V / μm [Example]

[0082] (Reference Example 1) Manufacturing method of PPS resin (granules) A 1-liter autoclave equipped with a process stirrer was charged with 1.00 mol of 47% sodium hydrosulfide, 1.03 mol of 96% sodium hydroxide, 1.65 mol of N-methyl-2-pyrrolidone (NMP), 0.45 mol of sodium acetate, and 150 g of ion-exchanged water. The mixture was gradually heated to 225°C over approximately 3 hours while stirring at 240 rpm and passing nitrogen through at atmospheric pressure. After distilling off 211 g of water and 4 g of NMP, the reaction vessel was cooled to 160°C.

[0083] Next, 1.00 mol of p-dichlorobenzene (p-DCB) and 1.31 mol of NMP were added. The reaction vessel was then sealed under nitrogen gas. While stirring at 240 rpm, the temperature was increased from 200°C to 235°C at a rate of 0.6°C / min. After reaching 235°C, the reaction was continued at 235°C for 95 minutes. The temperature was then increased to 270°C at a rate of 0.8°C / min and maintained at that temperature for 100 minutes. After reaching 270°C, 1 mol of water was injected into the system over 15 minutes. After 100 minutes at 270°C, the mixture was cooled to 200°C at a rate of 1.0°C / min and then rapidly cooled to near room temperature. The contents were removed, diluted with 0.4 L of NMP, and stirred at 85°C for 30 minutes. The solvent and solids were then filtered through an 80-mesh sieve. Following the post-treatment step, 0.5 L of NMP was added to the resulting solid, which was stirred at 85°C for 30 minutes and then filtered. The resulting solid was washed three times with 0.9 L of warm water and filtered. The resulting particles were then washed twice with 1 L of warm water and filtered to obtain polymer particles. These were then dried with hot air at 80°C and then dried under reduced pressure at 120°C to obtain polyphenylene sulfide (PPS) resin granules (PPS granules) with a melting point of 280°C and a mass-average molecular weight of 70,000.

[0084] (Reference Example 2) Manufacturing method of PPS pellets (PPS-1) The PPS resin (granules) prepared in Reference Example 1 was fed into a vented co-rotating twin-screw kneading extruder heated to 320°C, melt-extruded and discharged in the form of strands, which were then cooled with water at 25°C and immediately cut to prepare PPS pellets (PPS-1).

[0085] (Reference Example 3) Preparation of master pellets (MB-1) from PPS granules and thermoplastic resin A co-rotating, vented twin-screw kneading extruder equipped with one kneading paddle kneading section was heated to 320°C, and 90 parts by mass of the PPS granules obtained in Reference Example 1 and 10 parts by mass of polyethersulfone (PESU: Solvay Advanced Polymers, Inc., Veradel 3600) were fed into the feed port. The mixture was melt-kneaded at a screw rotation speed of 200 rpm, discharged in the form of a strand, cooled with water at 25°C, and immediately cut to produce master pellets (MB-1) containing 10 parts by mass of PESU.

[0086] Example 1 The PPS pellets (PPS-1) prepared in Reference Example 2 and the PPS master pellets (MB-1) prepared in Reference Example 3 were mixed uniformly in the ratio shown in Table 1, dried under reduced pressure at 180°C for 3 hours, and then fed into a single-screw extruder whose melting section had been heated to 315°C.

[0087] The molten polymer was then passed through a sintered stainless steel metal filter (20 μm cut) and melt-extruded through a T-die nozzle set at 310°C. The extrusion was then performed by applying a static charge to a casting drum at a surface temperature of 25°C, followed by solidification by contact cooling, yielding a 950 μm thick unstretched film. The unstretched film was then stretched 3.6 times in the longitudinal direction at a temperature of 105°C using a longitudinal stretching machine consisting of a group of heated rolls, utilizing the difference in the peripheral speed of the rolls. The film was then held at both ends with clips and introduced into a tenter, where it was stretched 3.6 times in the width direction at a temperature of 100°C. This was followed by a post-high-temperature stretching step in which the film was stretched 1.4 times in the width direction at 285°C, heat-treated at 285°C, then subjected to a 2% relaxation treatment. After cooling to room temperature, the film edges were removed to yield a 50 μm thick polyarylene sulfide film. The physical properties and characteristics of the resulting film are shown in Table 1.

[0088] Example 2 The PPS pellets (PPS-1) produced in Reference Example 2 and the PPS master pellets (MB-1) produced in Reference Example 3 were used to prepare the raw materials for layers A and B, with the compositions and ratios shown in Table 1. Each raw material was vacuum-dried separately at 180°C for 3 hours and then fed separately into two single-screw extruders heated to 315°C. The molten material was then introduced into a lamination device above the die to form a three-layer structure (A / B / A) with the lamination ratio shown in Table 1. The extrusion was then extruded through a T-die die and rapidly solidified by applying a static charge to a casting drum at a surface temperature of 25°C, yielding an unstretched film with a thickness of 950 μm. The unstretched film was then stretched 3.6 times in the longitudinal direction at 105°C using a longitudinal stretching machine consisting of a group of heated rolls, utilizing the difference in peripheral speed between the rolls. The film was then held at both ends by clips and introduced into a tenter, where it was stretched 3.6 times in the transverse direction at 100°C. Subsequently, in the post-high-temperature stretching step, the film was stretched in the width direction at the temperature and ratio shown in Table 1, and then heat-treated at the same temperature, followed by a 2% relaxation treatment. After cooling to room temperature, the film edges were removed to obtain a polyarylene sulfide film with a thickness of 50 μm. The physical properties and characteristics of the obtained film are shown in Table 1.

[0089] Example 3 A biaxially oriented polyarylene sulfide film having a thickness of 50 μm was obtained in the same manner as in Example 2, except that the thickness of the unstretched film was 800 μm and the composition, ratio, and stretching conditions were as shown in Table 1.

[0090] (Examples 4 to 5) A biaxially oriented polyarylene sulfide film having a thickness of 50 μm was obtained in the same manner as in Example 2, except that the thickness of the unstretched film was 950 μm and the composition, ratio, and stretching conditions were as shown in Table 1.

[0091] Example 6 A biaxially oriented polyarylene sulfide film having a thickness of 100 μm was obtained in the same manner as in Example 2, except that the thickness of the unstretched film was 1900 μm and the composition, ratio, and stretching conditions were as shown in Table 1.

[0092] Example 7 A biaxially oriented polyarylene sulfide film having a thickness of 50 μm was obtained in the same manner as in Example 2, except that the thickness of the unstretched film was 950 μm, the composition, ratio, and post-high-temperature stretching conditions were as shown in Table 1, and no heat treatment was performed.

[0093] (Examples 8 to 9) A biaxially oriented polyarylene sulfide film having a thickness of 50 μm was obtained in the same manner as in Example 2, except that the lamination ratio shown in Table 1 was used. (Examples 10 to 11) A biaxially oriented polyarylene sulfide film having a thickness of 50 μm was obtained in the same manner as in Example 2, except that the composition of Layer A was set to the ratio shown in Table 1.

[0094] (Comparative Example 1) A polyarylene sulfide film was obtained in the same manner as in Example 1, except that PPS pellets 1 and the master batch were mixed to obtain the composition and ratio shown in Table 1, and stretched under the conditions shown in Table 1.

[0095] (Comparative Example 2) A polyarylene sulfide film was obtained in the same manner as in Example 2, except that PPS pellets 1 and the master batch were mixed to have the composition and ratio shown in Table 1 and stretched under the conditions shown in Table 1.

[0096] [Table 1]

[0097] [Table 2] [Industrial Applicability]

[0098] The polyarylene sulfide film of the present invention has excellent transparency and can be suitably used as a transparent circuit board or a transparent antenna board.

Claims

1. A biaxially oriented polyarylene sulfide film having polyarylene sulfide (PAS) as a main constituent component, wherein the crystal size obtained by applying Scherrer's equation to the half-value width of the (200) diffraction peak of the polyarylene sulfide crystal determined by X-ray diffraction method is 90 Å or less.

2. The biaxially oriented polyarylene sulfide film according to Claim 1, having a thickness of 30 μm or more.

3. The biaxially oriented polyarylene sulfide film according to Claim 1 or 2, wherein the glossiness of at least one film surface is 140% or more.

4. The biaxially oriented polyarylene sulfide film according to Claim 3, wherein the glossiness of at least one film surface is 200% or more.

5. The biaxially oriented polyarylene sulfide film according to Claim 1 or 2, having a haze of 10% or less.

6. The biaxially oriented polyarylene sulfide film according to Claim 1 or 2, having two or more layers containing a layer having polyarylene sulfide as a main constituent component, and at least one outermost layer having a layer (layer A) containing at least one or more other thermoplastic resins different from polyarylene sulfide as a main component.

7. The biaxially oriented polyarylene sulfide film according to Claim 6, wherein the layer A contains a dispersion incompatible with polyarylene sulfide, and the thickness ratio of the layer A is 0.1% or more and 10% or less with respect to the total film thickness.

8. The biaxially oriented polyarylene sulfide film according to Claim 1 or 2, used for a transparent circuit base material.

9. The biaxially oriented polyarylene sulfide film according to Claim 1 or 2, used for a transparent antenna base material.

10. An insulating film using the biaxially oriented polyarylene sulfide film according to Claim 1 or 2.

11. A metal film laminated film having a metal film on at least one side of the biaxially oriented polyarylene sulfide film according to Claim 1 or 2.

12. A film capacitor using the metal film laminated film according to Claim 11.

13. A power control unit having the film capacitor according to Claim 12.

14. An electric vehicle having the power control unit according to Claim 13.

15. An electric aircraft having the power control unit according to Claim 13.