CN115335438A

CN115335438A - Fluororesin film and method for producing same

Info

Publication number: CN115335438A
Application number: CN202180023851.6A
Authority: CN
Inventors: 笠井涉
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2020-03-31
Filing date: 2021-03-26
Publication date: 2022-11-11
Also published as: WO2021200627A1; CN118438634A; JPWO2021200627A1; TW202146479A; KR20220162686A

Abstract

The present invention relates to a film comprising a tetrafluoroethylene polymer, having a thickness of 100 to 200 [ mu ] m and a haze value of 8% or less, wherein the thermal expansion and contraction rate after heating at 180 ℃ for 30 minutes is-1 to +1% in both the flow direction and the width direction.

Description

Fluororesin film and method for producing same

Technical Field

The present invention relates to a film of a tetrafluoroethylene polymer and a method for producing the same.

Background

In the progress of weight reduction and compactness of electronic equipment, as a measure against the restriction of the wiring amount and space in the equipment, a flexible printed circuit board (FPC) is widely used as a light and flexible wiring material. In recent years, with the increase in the speed of signal transmission of printed wiring boards, the increase in the frequency of signals has been advanced. With this, there is a strong demand for low dielectric characteristics (low dielectric constant and low dielectric loss tangent) of FPCs in the high frequency region. In order to meet such a demand, it has been proposed to replace conventional Polyimide (PI) and polyethylene terephthalate (PET) with a base film made of a Liquid Crystal Polymer (LCP) having low dielectric characteristics, syndiotactic Polystyrene (SPS), polyphenylene sulfide (PPS), or the like.

On the other hand, with the pursuit of improvement in design of electronic devices, there is an increasing chance of using FPCs in places that are accessible to human eyes, such as flexible devices such as flexible display panels and touch panels, and electronic devices used after semiconductor elements such as LEDs are reflow-soldered. In such electronic devices and the like, the FPC should have transparency.

The PI film is excellent in heat resistance but has a problem in transparency. The PET film has excellent transparency but low heat resistance, and when used for a flexible printed wiring board, the heat during reflow soldering causes problems such as warpage of the substrate and dimensional change. Tetrafluoroethylene polymers such as Polytetrafluoroethylene (PTFE) have high transparency and excellent physical properties such as chemical resistance, water and oil repellency, heat resistance, and electrical characteristics, and have a low dielectric constant and a low dielectric loss tangent even when compared with materials such as PI, LCP, SPS, and PPS, and therefore can be used as a substrate film for FPC which is transparent and has excellent reflow soldering resistance.

On the other hand, the tetrafluoroethylene polymer is not excellent in dimensional stability and is likely to be displaced in the circuit processing stage. Therefore, patent document 1 proposes a method of removing the strain by annealing (heat treatment) after film formation.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2019/203243

Disclosure of Invention

Technical problem to be solved by the invention

The tetrafluoroethylene polymer has crystallinity, and the crystal is easily grown in the cooling process of melt molding, so that the haze value of the obtained film is easily increased even if the light transmittance is high. Further, if the film is thickened, it is difficult to remove the strain even by heat treatment as in the method of patent document 1, and the dimensional stability is not good, and therefore, the flatness of the film may be impaired by the heat treatment.

The present inventors have conducted extensive studies and found a film which is excellent in dimensional stability, has a low haze value, has a high yield in forming a circuit, and can achieve both transparency and heat resistance.

The object of the present invention is to provide a film having the above characteristics and a method for producing the same.

Technical scheme for solving technical problem

The present invention has the following aspects.

[ 1] A film which is an extrusion-molded film comprising a tetrafluoroethylene polymer and has a thickness of 100 to 200 [ mu ] m, a haze value of 8% or less, and a thermal expansion/contraction ratio after heating at 180 ℃ for 30 minutes of-1 to +1% in both the flow direction and the width direction of the film.

<2> the film as <1>, wherein the tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer comprising a tetrafluoroethylene-based unit and a perfluoro (alkyl vinyl ether) -based unit.

<3> the film according to <1> or <2>, wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer containing a perfluoro (alkyl vinyl ether) -based unit and having a polar functional group, or a tetrafluoroethylene polymer containing a perfluoro (alkyl vinyl ether) -based unit in an amount of 2.0 to 5.0 mol% based on the total units and having no polar functional group.

<4> the film according to any one of <1> to <3>, wherein the tetrafluoroethylene polymer has a melting temperature of 260 to 320 ℃.

<5> A production method for producing the film according to any one of <1> to <4> by a T-die casting method, comprising the steps of discharging the tetrafluoroethylene polymer in a molten state from a die to perform extrusion molding, and further cooling the film by sandwiching the film between 2 rolls having a controlled temperature.

<6> the production process according to <5>, wherein the temperature of the 2 rolls controlled in temperature is 150 to 250 ℃ for one roll and 80 to 150 ℃ for the other roll.

<7> the production method of <5> or <6>, which comprises an extrusion molding apparatus comprising a kneading section and a hopper connected to the kneading section, wherein when a pellet of a tetrafluoroethylene polymer having a melting temperature of 260 to 320 ℃ is fed into the hopper and a molten kneaded product melted and kneaded in the kneading section is discharged from a T-die to produce a film, the method further comprises an operation of adjusting the temperature of the pellet in the section connected to the kneading section of the hopper to a range of (the melting temperature is-200 ℃ to (the melting temperature is-100) ° C, and then supplying the pellet to the kneading section.

<8> the production method according to any one of <5> to <7>, wherein the diameter of the pellet is 1.0 to 4.0mm.

<9> the manufacturing method according to any one of <5> to <8>, wherein the hopper is a multistage hopper including a 1 st stage part and a 2 nd stage part disposed closer to the kneading part side than the 1 st stage part.

<10> the production method according to any one of <5> to <9>, wherein a pressure in a segment of the hopper closest to the kneading section is 1000Pa or less.

<11> the production method according to any one of <5> to <10>, wherein the extrusion molding apparatus comprises a T-die connected to a side of the kneading section opposite to the hopper in an axial direction thereof, and a static mixer provided between the kneading section and the T-die.

<12> the production method according to any one of <5> to <11>, which further comprises an operation of discharging the tetrafluoroethylene-based polymer from a T-die in a molten state and heating the molten tetrafluoroethylene-based polymer in a non-contact heating section before the molten tetrafluoroethylene-based polymer comes into contact with the first cooling roll.

<13> the production process according to <12>, wherein a difference between the temperature of the tetrafluoroethylene polymer in the T-die and the temperature of the first cooling roll is 250 ℃ or less.

<14> the production process according to <12> or <13>, wherein an absolute value of a difference between a temperature of the tetrafluoroethylene-based polymer in the T-die and a temperature of the non-contact heating section is 70 ℃ or less.

<15> a laminate comprising a layer comprising the film of any one of <1> to <4> and a base material layer comprising a base material other than the film.

ADVANTAGEOUS EFFECTS OF INVENTION

The invention provides a film which has excellent dimensional stability, a low haze value, a high yield in forming a circuit, and both transparency and heat resistance. According to the present invention, a thick film of about 100 μm which is particularly preferable as a base material of an antenna substrate can be provided. The film of the present invention can be used as a colorless transparent and low-loss antenna substrate.

Drawings

Fig. 1 is a schematic diagram showing an embodiment of an apparatus for producing a film used in the method 1.

Fig. 2 is a schematic view showing an embodiment of an extrusion molding apparatus usable in the present invention.

Fig. 3 is a schematic diagram showing an embodiment of a film production apparatus used in the method 1.

Detailed Description

The following terms have the following meanings.

The "film thickness" is an average value of measured values obtained by measuring the film thickness at 10 points at equal distances in the width direction with a measuring head AA-026 (Φ 10mm, SR 7) on a contact thickness meter DG-525H (manufactured by Kumason Co., ltd.).

The "melting temperature of the polymer" is a temperature corresponding to the maximum value of a melting peak measured by a Differential Scanning Calorimetry (DSC) method.

"Unit" in a polymer refers to a radical formed by polymerization of a monomer based on the monomer 1 molecule. The unit may be a unit directly formed by polymerization, or a unit in which a part of the unit is converted into another structure by treating a polymer. Hereinafter, the unit based on the monomer a is also referred to simply as "monomer a unit".

"glass transition temperature of a polymer" means a value measured by analyzing a polymer by a dynamic viscoelasticity measurement (DMA) method.

The film of the present invention is an extrusion-molded film comprising a tetrafluoroethylene polymer (hereinafter also referred to as "F polymer"), and has a thickness of 100 to 200 μm and a haze value of 8% or less, and a thermal expansion and contraction rate after heating at 180 ℃ for 30 minutes of-1 to +1% in both the flow direction (hereinafter referred to as MD) and the width direction (hereinafter referred to as TD) of the film.

The film of the present invention may be a roll film in a wound state.

In addition, as the laminate of the present invention including a layer composed of the film of the present invention and a base material layer composed of a base material other than the film of the present invention, a laminate in which the film of the present invention and a metal foil are laminated is preferable. The laminate in which the film of the present invention and the metal foil are laminated is suitably used as a PFC, for example, as an antenna substrate which is colorless and transparent and has excellent electrical characteristics, if the metal foil is processed into a transmission circuit (including a through hole (via)) while being cut into a predetermined length.

The layer composed of the film of the present invention is hereinafter referred to as "F polymer layer", and the base layer composed of a base material other than the film of the present invention is hereinafter simply referred to as "base layer" unless otherwise noted.

In a general heat-fusible fluororesin film, a molding strain by a production method (a melt molding method by extrusion molding) remains. The film of the present invention has a small deformation in each direction, is sufficiently homogenized, has excellent dimensional stability, has a haze value of 8% or less even when the film has a thickness of 100 to 200 μm, and has excellent transparency by appropriately controlling the cooling conditions of the resin film during molding so that the thermal expansion and contraction rates in the MD and TD are both-1 to +1%.

Therefore, the laminate including the film layer is also considered to be excellent in thermal shock property, suppressed in deformation, and excellent in dimensional stability because the laminate is sufficiently uniform with little deformation. For example, the laminate of the present invention, which has a metal foil as a base material layer, has high thermal shock resistance when forming through holes or through holes when processed into a printed wiring board, and as a result, a printed wiring board that is less likely to cause disconnection can be easily obtained.

The thermal expansion and contraction rate of the film was measured as follows. First, a 12cm square test piece having 2 sides along MD and 2 sides along TD was cut out from the film. Then, a 10 cm-long mark was drawn on the surface of the obtained sample sheet along the MD and TD, respectively. Subsequently, the sample piece was placed in a 180 ℃ furnace and heated for 30 minutes, then taken out, naturally cooled to 25 ℃, and the length of the reticle was measured again.

The thermal expansion and contraction ratio is represented by the following formula: a value calculated by { (length of reticle before heating) - (length of reticle after heating) }/(length of reticle before heating) × 100. That is, the thermal expansion/contraction ratio is the rate (percentage) of change in the length of the reticle before and after heating. Negative values represent film elongation and positive values represent film shrinkage.

The thermal expansion and contraction rate of the film of the present invention is-1 to +1%, preferably-0.8 to +0.8%, and more preferably-0.5 to +0.5% in both MD and TD of the film. When the thermal expansion/contraction ratio is within the above range, wrinkles are less likely to occur due to deformation of the film even when the film is heated.

The F polymer of the present invention is a polymer comprising Tetrafluoroethylene (TFE) -based units (TFE units). The F polymer of the present invention has thermal fusion properties, and its melting temperature is preferably 260 to 320 ℃, more preferably 275 to 315 ℃, and even more preferably 290 to 310 ℃. In this case, the moldability of the F polymer and the mechanical strength of the film of the present invention are easily balanced.

The glass transition temperature of the F polymer is preferably from 75 to 125 ℃ and more preferably from 80 to 100 ℃.

The polymer F may, for example, be Polytetrafluoroethylene (PTFE) or a mixture containingA Polymer (PFA) of TFE units and perfluoro (alkyl vinyl ether) (PAVE) based units (PAVE units), a polymer (FEP) comprising Hexafluoropropylene (HFP) based units, preferably PFA. As PAVE, CF is preferred ₂ ＝CFOCF ₃ 、CF ₂ ＝CFOCF ₂ CF ₃ And CF ₂ ＝CFOCF ₂ CF ₂ CF ₃ (PPVE), more preferably PPVE.

The F polymer preferably has polar functional groups. The polar functional group may be included in the units in the F polymer, and may also be included in the terminal groups of the F polymer backbone. The latter form may, for example, be an F polymer having a polar functional group as an end group derived from a polymerization initiator, a chain transfer agent or the like, or an F polymer having a polar functional group obtained by subjecting an F polymer to plasma treatment or ionization treatment. The polar functional group is preferably a hydroxyl-containing group or a carbonyl-containing group.

As the hydroxyl group-containing group, a group containing an alcoholic hydroxyl group is preferable, and-CF is more preferable ₂ CH ₂ OH and-C (CF) ₃ ) ₂ OH。

The carbonyl-containing group being a group containing a carbonyl group: (>C (O)) as a carbonyl group-containing group, a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC (O) NH) are preferable ₂ ) Acid anhydride residues (-C (O) OC (O) -) imide residues (-C (O) NHC (O) -, etc.) or carbonate groups (-OC (O) O-), anhydride residues are more preferred.

In the case where the F polymer has a carbonyl group-containing group, the number of carbonyl groups-containing groups in the F polymer is 1X 10 ⁶ The number of carbon atoms in the main chain is preferably 10 to 5000, more preferably 100 to 3000, and still more preferably 800 to 1500. The number of carbonyl-containing groups in the F polymer can be determined by the composition of the polymer or by the method described in International publication No. 2020/145133.

The F polymer is preferably a polymer (1) having a polar functional group and containing TFE units and PAVE units, and a polymer (2) having a polar functional group and containing TFE units and PAVE units and containing 2.0 to 5.0 mol% of PAVE units relative to the total units.

These F polymers are likely to form fine spherulites in the molded article, and to improve adhesion to other components. As a result, a molded product having excellent surface smoothness, adhesiveness, and electrical characteristics can be easily obtained.

The polymer (1) is preferably a polymer containing a unit based on a monomer having a polar functional group, a unit based on TFE, a unit based on PAVE, and a unit based on a monomer having a polar functional group, and more preferably a polymer containing a unit based on a monomer having a polar functional group, each of which is 90 to 99 mol% of TFE, 0.5 to 9.97 mol% of PAVE, and 0.01 to 3 mol%, relative to the whole units. Further, as the monomer having a polar functional group, itaconic anhydride, citraconic anhydride, and 5-norbornene-2, 3-dicarboxylic anhydride (hereinafter, also referred to as "NAH") are preferable. Specific examples of the polymer (1) include polymers described in International publication No. 2018/16644.

The polymer (2) is preferably composed of only TFE units and PAVE units, and contains from 95.0 to 98.0 mol% of TFE units and from 2.0 to 5.0 mol% of PAVE units, relative to the total units. The content of PAVE units in the polymer (2) is preferably 2.1 to 5.0 mol%, more preferably 2.2 to 5.0 mol%, based on the total units.

The polymer (2) having no polar functional group means that the ratio is 1X 10 ⁶ The number of carbon atoms constituting the main chain of the polymer, and the number of polar functional groups contained in the polymer is less than 500. The number of the above-mentioned polar functional groups is preferably 100 or less, and more preferably less than 50. The lower limit of the number of the polar functional groups is usually 0.

The polymer (2) may be produced by using a polymerization initiator or a chain transfer agent which does not generate a polar functional group as an end group of a polymer chain, or may be produced by subjecting an F polymer having a polar functional group (e.g., an F polymer having a polar functional group derived from a polymerization initiator in an end group of a polymer chain) to a fluorination treatment. As a method for the fluorination treatment, a method using a fluorine gas may be mentioned (see, for example, japanese patent laid-open publication No. 2019-194314).

The film of the present invention may further contain other resins than the F polymer. The content of the F polymer contained in the film is preferably 80% by mass or more, and more preferably 100% by mass. Examples of the resin other than the F polymer include epoxy resin, polyimide resin, polyamic acid which is a precursor of polyimide, acrylic resin, phenol resin, liquid crystalline polyester resin, polyolefin resin, modified polyphenylene ether resin, polyfunctional cyanate ester resin, polyfunctional maleimide-cyanate ester resin, polyfunctional maleimide resin, vinyl ester resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, melamine-urea copolycondensation resin, styrene resin, polycarbonate resin, polyarylate resin, polysulfone, polyarylsulfone, aromatic polyamide resin, aromatic polyetheramide, polyphenylene sulfide, polyaryl ether ketone, polyamideimide, and polyphenylene ether.

The film of the present invention may further contain, for example, an inorganic filler, an organic filler, a thixotropy-imparting agent, an antifoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weather-resistant agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a colorant, a conductive agent, a mold release agent, a surface treatment agent, a viscosity modifier, a flame retardant, and the like.

As the inorganic filler, a silicon nitride filler, a beryllium oxide filler (beryllium oxide filler), a silicate filler (silica filler, wollastonite filler, talc filler), and a metal oxide (cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, etc.) filler are preferable. In addition, at least a part of the surface of the inorganic filler may be surface-treated. Examples of the surface treatment agent used for the surface treatment include polyhydric alcohols, saturated fatty acids, esters thereof, amines, paraffins, silane coupling agents, silicones and polysiloxanes.

The shape of the inorganic filler is preferably 1 kind of the shape selected from the group consisting of a granular shape, a needle shape (fibrous shape), a plate shape and the like. Specific examples of the shape include spherical, scaly, lamellar, foliated, almond-shaped, columnar, crowned, equiaxed, foliated, mica-shaped, massive, flat, wedge-shaped, rosette-shaped, mesh-shaped, and prismatic shapes.

The following describes a method for producing a film of the present invention. The film of the present invention is suitably produced by a T-die casting method (a melt extrusion method through a T-die) from the viewpoint of being able to adjust the deformation of the film.

The present inventors have found that the deformations in MD and TD of a film formed by the T-die casting method depend on the state (temperature, fluidity) of the F polymer in a molten state and cooling conditions, and are determined by the state of the molten F polymer discharged from the T-die before it is crystallized by a cooling roll. In other words, the present inventors have found that if the crystallization of the F polymer is controlled by appropriately setting the state of the F polymer and the cooling conditions, the thermal shrinkage (strain) in the MD and TD of the obtained film is limited to a predetermined range, and the crystal growth is suppressed, so that a low haze can be achieved even in a thick film of 100 to 200 μm.

The film production method of the present invention includes an operation of extruding and molding the F polymer in a molten state through a T-die, and cooling the film by sandwiching the film between 2 rolls controlled in temperature (method 1). Preferably, the temperature of the 2 rollers subjected to temperature control is 150-250 ℃ for one roller and 80-150 ℃ for the other roller. More preferably, 1 of the 2 temperature-controlled rolls is a metal roll controlled to have a temperature of 150 to 250 ℃, and the other 1 roll is a metal elastic roll controlled to have a temperature of 80 to 150 ℃.

Fig. 1 is a schematic diagram showing an embodiment of an apparatus for producing a film used in the present method 1. The manufacturing apparatus 10 shown in fig. 1 includes a T-die 20, a 1 st cooling roll (first cooling roll) 30 disposed vertically below the T-die 20, a chill roll 301, a 2 nd cooling roll 40 disposed in parallel with the 1 st cooling roll 30, a winding roll 50 for winding a film 1, and transfer rolls 61 and 62 disposed between the winding roll 50 and the 2 nd cooling roll 40.

The 1 st cooling roll 30 may further include an air knife 70, and preferably includes an air knife.

The polymer F is heated and melted in an extruder (not shown) connected to the T-die 20, and then supplied to the T-die 20. The molten polymer F is discharged from the lip 21 of the T-die 20 to the 1 st cooling roll 30. Then, the discharged molten F polymer is cooled while being nipped between the chill roll 301 and the 1 st chill roll 30 while being in contact with the 1 st chill roll 30. Subsequently, the F polymer passes through the 2 nd cooling roll 40 and is conveyed by the conveying rolls 61 and 62. Then, the F polymer is taken up as a film 1 by a take-up roll 50. As the 1 st cooling roll 30, a temperature-controllable metal roll is preferably used, and as the chill roll 301, a metal elastic roll is preferably used.

The metal elastic roller may be a roller whose surface is made of a metal material such as stainless steel, and an elastic material such as a fluid or rubber is filled between the metal material of the surface and the roller. The metal elastic roll is composed of, for example, a substantially cylindrical freely rotatable roll, a cylindrical metal thin film in contact with the film-like material disposed so as to cover the outer peripheral surface of the roll, and a fluid sealed between the roll and the metal thin film. The metal elastic roller is elastic by the fluid, and has a characteristic that the roller can be formed by pressing with low line pressure. The present invention exploits this characteristic to facilitate control of film cooling conditions.

The material of the mandrel may, for example, be stainless steel. The metallic thin film is made of stainless steel, and preferably has a thickness of 2 to 5mm. The metal film preferably has flexibility or pliability, and is preferably of a seamless construction without welded seams. The metal elastic roller provided with the metal thin film has excellent durability, and can be treated in the same manner as a normal mirror-surface roller when the metal thin film is made into a mirror surface. From the viewpoint of obtaining a film having excellent surface smoothness, it is more preferable that the surface of the metal elastic roller is a mirror surface roller. Examples of commercially available products of the metal elastic roll include a UF roll manufactured by Hitachi Takara Shuzo, and an SF roll manufactured by Qianye machinery Industrial Co., ltd.

The molten F polymer is preferably sandwiched and cooled between the chill roll 301, which is a metal elastic roll, and the 1 st chill roll 30, which is a metal roll, thereby rapidly cooling the film to suppress crystal growth and reduce haze, and reducing the accumulation of strain applied to the film sandwiched between the 1 st chill roll and the chill roll.

The temperature of the 1 st chill roll 30 is preferably 150 to 250 ℃ and the temperature of the chill roll 301 is preferably 80 to 150 ℃ from the viewpoint of being able to rapidly cool the film. The 1 st chill roll and the chill roll each preferably have a structure in which a heat medium passes through them, and more preferably have a structure in which a heat medium repeatedly passes through a double-type structure while reciprocating in the axial direction. The temperature of the cooling roll 1 and the temperature of the chill roll both represent the temperature of the heat medium.

When the chill roll is a metal elastic roll, a temperature range in which the characteristics of the metal elastic roll itself are not impaired is preferable.

In the method 1, it is preferable that an air knife 70 is further provided at a position immediately after the molten F polymer is nipped between the 1 st cooling roll 30 and the quenching roll 301. The air knife 70 has the following functions: the slit-shaped air flow is uniformly blown in a linear shape in the width direction of the 1 st cooling roll 30 by the slit nozzle on the line on which the molten state F polymer is in contact with the 1 st cooling roll 30, whereby the molten state F polymer is pressed against the 1 st cooling roll 30 while being cooled. Like the chill roll 301, the air knife 70 has the effect of increasing the cooling efficiency of the F polymer, suppressing the haze of the resulting film, and reducing the thermal expansion and contraction rate.

The temperature of the air blown out by the air knife is preferably 150 to 200 ℃, more preferably 170 to 200 ℃. When the temperature is 150 ℃ or higher, the thermal expansion/contraction ratio of the film is small, and when the temperature is 200 ℃ or lower, the haze tends to be weak.

The flow rate of the air blown by the air knife is preferably 10 to 20 m/sec.

The film production method of the present invention also includes a method of producing a film from pellets of an F polymer having a melting temperature of 260 to 320 ℃ in method 1 (method 2) using, for example, an extrusion molding apparatus 11 shown in fig. 2.

Fig. 2 is a schematic view showing an embodiment of an extrusion molding apparatus used in the method 2. In the following description, the right side (forward in the conveying direction of the molten kneaded material) in fig. 2 is referred to as the "front end" and the left side (rearward in the conveying direction) is referred to as the "base end".

The extrusion molding apparatus 11 shown in fig. 2 includes a hopper 2 and a kneading section 3 communicating with the hopper. The kneading section 3 of the present embodiment is composed of a single-screw kneader having a cylinder 31 and 1 screw 32 rotatably provided in the cylinder 31, and if the single-screw kneader is used, deterioration of the F polymer is easily prevented when the pellets are melt-kneaded.

In this case, when the overall length of the screw 32 is L (mm) and the diameter is D (mm), the effective length (L/D) represented by the ratio of the overall length L to the diameter D is preferably 30 to 45. When the effective length is within the above range, the F polymer can be imparted with a sufficient shear stress while preventing the deterioration of the F polymer, and the temperature unevenness of the melt-kneaded product can be easily reduced.

A gear box 33 and a motor 34 are disposed in this order on the base end side of the cylinder 31. A gear (not shown) is connected to a distal end portion of the rotating shaft 341 of the motor 34, and the gear meshes with a predetermined gear (not shown) in the gear case 33.

In gear box 33, the rotational motion of rotary shaft 341 is accelerated or decelerated and transmitted to rotary shaft 331. The tip of the rotary shaft 331 is connected to the base end side of the screw 32.

With this configuration, the rotation of the motor 34 is transmitted to the screw 32, and the screw 32 is rotated at a predetermined rotational speed. As a result, the melt-kneaded material is conveyed from the base end side (left side) to the tip end side (right side) in fig. 2.

Further, a heater 35 is provided on the outer periphery of the cylinder 31. The pellets (F polymer) fed into the cylinder 31 are mixed (kneaded) by the rotation of the screw 32 while being melted by the heating of the heater 35, and are conveyed toward the tip side. The pellets are thereby melted and kneaded, and the molten and kneaded product is extruded from the distal end opening 311 of the cylinder 31.

The T-die 5 is disposed on the front end side of the cylinder 31 (the side opposite to the hopper 2 in the axial direction of the kneading section 3). The molten kneaded material extruded from the front end opening 311 of the cylinder 31 is discharged from the lower end opening (discharge port) of the T-die 5, and then an F polymer film is produced as described in the present method 1. Here, the T-die 5 of fig. 2 can be understood as corresponding to the T-die 20 in fig. 1 (or fig. 3 described later). Although not shown, the T-die 5 may be provided with a heater.

In the present embodiment, a static mixer (static mixer) 6 is provided between the cylinder 31 (kneading section 3) and the T-die 5. The static mixer 6 is a member for stirring a molten kneaded product by dividing, switching, or inverting a flow path of the molten kneaded product.

By providing the static mixer 6, deterioration of the molten kneaded product can be suppressed without applying an additional external force to the molten kneaded product, and uniform kneading can be achieved.

The hopper 2 is disposed on the base end side of the cylinder 31. The hopper 2 of the present embodiment is composed of a 2-stage hopper including a 1 st funnel-shaped stage 21 and a 2 nd funnel-shaped stage 22 disposed closer to the kneading section 3 (cylinder 31) than the 1 st stage 21.

The heater 211 and the pump P1 are connected to the 1 st stage part 21. Thereby, the pellet supplied into the 1 st stage part 21 can be heated in a reduced pressure state.

The 1 st step portion 21 is connected to the 2 nd step portion 22 via a connection portion 212.

The heater 221 and the pump P2 are connected to the 2 nd stage 22. Thereby, the pellets supplied into the 2 nd stage part 22 can be heated in a reduced pressure state.

The 2 nd stage part 22 is connected to the cylinder 31 via a connection part 222.

The inner surface (inner circumferential surface) of the hopper 2 (the 1 st step 21 and the 2 nd step 22) is preferably coated with a resin film. That is, the inner surface of the hopper 2 is preferably lined with resin. This can sufficiently prevent the softened pellets from adhering to the inner surface of the hopper 2. The resin film may be made of a fluororesin such as PTFE.

The pellet used in the method 2 may further contain a component other than the F polymer, and the content of the F polymer is preferably 80 mass% or more, more preferably 100 mass%. Examples of the component other than the polymer F include the above-mentioned other resins and additives.

The shape of the pellets may be spherical or cylindrical, and preferably cylindrical. The diameter of the pellets is preferably 1.0 to 4.0mm. If the granular material is of such a diameter, it can be sufficiently heated (warmed) to the inside when heated in the hopper 2 while preventing bridging (clogging) in the hopper 2.

In this method 2, pellets of the F polymer are preheated in a hopper 2, supplied to a kneading section 3, and a molten kneaded product melted and kneaded in the kneading section 3 is discharged from a T-die 5 to produce a film. At this time, the temperature of the pellets in the connection 222 of the hopper 2 and the kneading section 3 was adjusted to the range of (X-200) to (X-100) DEG C. X is the melting temperature of the F polymer. The temperature of the pellets in the connection 222 of the hopper 2 to the kneading section 3 is preferably (X-175) to (X-125) DEG C. The pellet temperature is preferably 70 to 225 ℃ and more preferably 105 to 195 ℃. In this case, the bridging in the hopper 2 due to softening of the pellets is less likely to occur. In addition, since the temperature unevenness of the molten kneaded material in the kneading section 3 was sufficiently reduced, a film having a uniform thickness and preventing the generation of fish eyes (Japanese: 1250112451124831245012452124).

The pressure in the 2 nd step 22 (the step closest to the kneading section 3) is preferably lower than the pressure in the 1 st step 21, preferably 1000Pa or less, more preferably 100Pa or less, whereby air in the pellets can be sufficiently removed, formation of a heat insulating layer by air can be blocked, and the occurrence of temperature unevenness of the molten kneaded product in the kneading section 3 can be easily prevented.

The softened pellets are supplied to the kneading section 3. The rotation speed of the screw 32 is preferably 10 to 50ppm. The heating temperature of the heater 35 is more preferably (X + 30) to (X + 50) ° c.

When the pellets are melt-kneaded under the above conditions, a homogeneous melt-kneaded product with little temperature unevenness is easily formed. As a result, the film of the present invention is more easily obtained.

The molten and kneaded material is supplied to the T-die 5 through the static mixer 6 and discharged from the T-die 5. The molten kneaded material discharged from the T-die 5 is formed into a film as described in method 1, and then wound up by a winding roll.

The extrusion molding apparatus 11 may further include a cutter as needed.

With this method 2, a polymer can be uniformly melted and kneaded without excessive heat history while highly suppressing a surge phenomenon (japanese: 1254072\\12464. Therefore, a wide film having few defects (fish eyes) and a sufficient length in the short-side direction can be easily produced.

The number of fish eyes of the film of the present invention is preferably 1m per film ² The number of membranes was less than 0.05, and the lower limit of the number of fish eyes was 0.

The film production method of the present invention further includes a method (method 3) in which the F polymer is discharged from the T-die in a molten state in the method 1 or the method 2, and the molten F polymer is heated by a non-contact heating section before contacting with the first cooling roll.

Fig. 3 is a schematic view showing one embodiment of a film production apparatus used in the method 3. The manufacturing apparatus 101 shown in fig. 3 is the same as the manufacturing apparatus 10 of the present method 1 except that the manufacturing apparatus 10 further includes a pair of heaters (noncontact heating sections) 80 provided to face each other between the T-die 20 and the 1 st cooling roll 30.

The polymer F is heated and melted in an extruder (not shown) connected to the T-die 20, and then supplied to the T-die 20. The molten polymer F is discharged from the lip 21 of the T-die 20 to the 1 st cooling roll 30. Then, the discharged molten F polymer is heated so as not to contact the heaters 80 when passing between the pair of heaters 80, and is pressed against the 1 st cooling roller 30 by the quenching roller 301 while contacting the 1 st cooling roller 30, thereby being cooled. At this time, the air knife 70 provided in the direction perpendicular to the line connecting the 1 st chill roll 30 may uniformly blow a slit-shaped air flow in a linear shape in the width direction of the 1 st chill roll 30, thereby cooling and pressing the molten F polymer against the 1 st chill roll 30. Subsequently, the F polymer passes through the 2 nd cooling roll 40, is conveyed by the conveying rolls 61 and 62, and is wound up as the film 1 by the winding roll 50.

With the above configuration, the molten F polymer discharged from the T-die 20 can be maintained at a high temperature by heating the heater 80 even in the process of reaching the 1 st cooling roll 30. Therefore, the molten polymer F flowing down the 1 st chill roll 30 maintains high fluidity and is less likely to be stretched by its own weight or the tension of the 1 st chill roll 30. As a result, it is presumed that the occurrence of the drooping effect (orientation of the F polymer in MD and TD) in the film formation of the F polymer in a molten state (1250840\\ 124523164).

In particular, in the configuration shown in fig. 3, since the heater 80 heats the F polymer discharged from the T-die 20 from both sides in the thickness direction thereof, the uniformity of the temperature in the thickness direction is high, and the effect of suppressing the occurrence of the drooping effect is excellent. Further, from the viewpoint of further enhancing the effect of suppressing the occurrence of the head-hanging effect, it is preferable that the heater 80 is constituted so that the temperature in the width direction of the F polymer is also uniform. In this case, for example, the width of the heater 80 may be designed to be sufficiently larger than the length of the F polymer in the width direction.

The temperature of the F polymer in the T-die 20 is specified as X ¹ [℃]The temperature of the heater 80 is defined as Z ¹ [℃]The absolute value of the temperature difference (| X) ¹ －Z ¹ I) is preferably 70 ℃ or lower, more preferably 30 to 50 ℃. In this case, the temperature of the F polymer can be maintained sufficiently high until it reaches the 1 st cooling roll 30 while preventing the F polymer from being deteriorated. When the die temperature and the die lip temperature are different from each other, X ¹ Refers to the die temperature.

Further, the temperature of the 1 st cooling roll 30 is defined as Y ¹ [℃]Time, temperature difference (X) ¹ －Y ¹ ) Preferably 250 ℃ or lower, more preferably 200 ℃ or lower, and still more preferably 125 to 175 ℃. In this case, since the degree of cooling of the F polymer by the 1 st cooling roll 30 becomes more appropriate, the distortion in MD and TD is less likely to remain in the obtained film 1, and the distortion due to insufficient cooling can be appropriately prevented. Specifically, Y ¹ Preferably 150 to 250 ℃.

In addition, in the cooling by the 1 st cooling roll 30, the 1 st cooling roll 30 is preferably configured so that the temperatures in the MD and TD of the F polymer become uniform, from the viewpoint of further enhancing the effect of suppressing the occurrence of the droop effect.

Therefore, the 1 st cooling roller 30 preferably has a structure of a mechanism for passing the heat medium therethrough, and more preferably has a structure of a multiple mechanism in which the heat medium repeatedly passes while reciprocating in the axial direction. Temperature Y of No. 1 Cooling roll 30 ¹ Indicating the temperature of the thermal medium.

In the configuration shown in fig. 3, a pair of heaters 80 is arranged, but only one heater may be arranged. The non-contact heating section may be configured by an air blowing device that blows hot air instead of the heater 80.

In each of the methods 1 to 3, the thickness of the molten F polymer (thickness t in FIGS. 1 and 3) before contact with the 1 st chill roll 30 is preferably 100 to 200. Mu.m. In this case, the accuracy of heating by the heater 80 and cooling by the 1 st cooling roll 30 is improved, and the distortion in MD and TD is less likely to remain in the obtained film 1.

If the ratio (draw ratio) of the opening degree of the die lip 21 of the T-die 20 to the thickness of the finally obtained film 1 is large, the molecular chains of the polymer contained in the F polymer are strongly stretched, and the polymer molecules are easily oriented. As a result, the distortion remaining in the MD and TD of the film 1 tends to increase. Therefore, the stretching ratio is preferably 50 or less.

The circumferential speed of the 1 st cooling roll 30 (circumferential speed S in fig. 1 and 3) is more preferably 2 to 20 m/min from the viewpoint of further reducing the distortion remaining in the MD and TD of the film 1. The temperature of the 2 nd cooling roll 40 is more preferably 30 to 90 ℃.

The F polymer (film 1) after being released from the 1 st cooling roll 30 may be subjected to a surface treatment capable of introducing an adhesive functional group into the surface thereof. Examples of the surface treatment include a discharge treatment such as a corona discharge treatment or a plasma treatment, a plasma graft polymerization treatment, an electron beam irradiation treatment, a light irradiation treatment such as excimer UV light irradiation, an ITRO treatment using a flame, and a wet etching treatment using sodium metal.

By this surface treatment, a polar functional group such as a hydroxyl group, a carbonyl group, or a carboxyl group can be introduced into the surface of the film 1, and as a result, adhesiveness to other surfaces is further improved.

The laminate of the present invention (hereinafter also referred to as "the present laminate") will be described below.

The laminate is a laminate in which an F polymer layer (layer composed of the film of the present invention) and a base material layer are sequentially laminated. The laminate is preferably produced by laminating the film of the present invention and a film-like or sheet-like substrate other than the film of the present invention in a roll-to-roll manner, for example, by a method of laminating the films at a temperature of from the melting temperature of the F polymer to 400 ℃, or by a method of laminating the films and the substrate and then hot-pressing the laminated films at a temperature of from the melting temperature of the F polymer to 400 ℃.

The material of the base layer of the laminate may, for example, be a metal or a resin. Examples of the resin include a thermoplastic resin, a non-heat-fusible resin, an uncured product of a curable resin, and a cured product of a curable resin. Metals and heat-resistant resins are particularly preferred.

The substrate layer of the laminate is preferably a layer formed of a film-like or sheet-like substrate. As the film-shaped or sheet-shaped substrate, a metal foil and a heat-resistant resin film are preferable.

The base layer of the laminate may be a resin layer or a metal layer formed on the surface of the film of the present invention by coating, plating, or the like.

When the base layer of the laminate is a layer formed of a metal foil, the ten-point average roughness of the surface of the metal foil is preferably 0.01 μm or more and 0.5 μm or less. In this case, the film of the present invention and the metal foil are easily and firmly adhered to each other. Therefore, the laminate having the film of the present invention with high film thickness accuracy and the printed circuit board processed from the laminate can more easily exhibit remarkable electrical characteristics.

Specifically, when the base layer of the laminate is made of a metal foil, the dielectric loss tangent at a frequency of 10GHz of the F polymer layer of the laminate is preferably 0.0001 to 0.0020.

Examples of the material of the metal foil include iron, copper, nickel, titanium, aluminum, and alloys thereof (stainless steel, nickel 42 alloy, and the like). As the metal foil, rolled copper foil and electrolytic copper foil are preferable.

The surface of the metal foil may be subjected to rust-proofing treatment (formation of an oxide film such as chromate film). In addition, the surface of the metal foil may be treated with a silane coupling agent. The treatment range in this case may be a part of the surface of the metal foil or the entire surface.

The thickness of the metal foil is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm.

As the metal foil, a metal foil with a carrier including 2 or more layers of metal foil may be used. The metal foil with a carrier may, for example, be a copper foil with a carrier comprising a carrier copper foil (thickness: 10 to 35 μm) and an extra thin copper foil (thickness: 2 to 5 μm) laminated on the carrier copper foil via a release layer. If a copper foil with a carrier is used, a fine pattern can be formed by an MSAP (modified semi-additive) method. The release layer is preferably a metal layer containing nickel or chromium, or a multilayer metal layer obtained by laminating such metal layers.

As a specific example of the metal foil with a carrier, there may be mentioned FUTF-5DAF-2, a trade name of Futian Metal foil powder Industrial Co., ltd. (Futian Metal foil powder Ltd.).

The base layer of the laminate may be a metal layer formed by a vapor deposition method or a plating method. The metal layer may be formed, for example, as follows: a metal seed layer (japanese: 124711254012489, run) is formed on the surface of the film of the present invention by sputtering or electroless plating, and metal is grown from the seed layer by electroplating. The surface of the film of the present invention may be surface treated prior to formation of the seed layer. Examples of the method of surface treatment include annealing treatment, corona treatment, plasma treatment, ozone treatment, excimer treatment, and silane coupling agent treatment.

Examples of the metal to be plated by the electroless plating method include copper and nickel.

Examples of the metal in the seed layer include copper, nickel, chromium, a nickel-chromium alloy, and a titanium alloy.

The metal to be plated by the electroplating method may, for example, be copper.

When the base layer of the laminate is a layer of a heat-resistant resin film, the film contains 1 or more kinds of heat-resistant resins, and may be a single-layer film or a multilayer film. The heat-resistant resin film may contain glass fibers, carbon fibers, or the like.

When the substrate layer is a layer of a heat-resistant resin film, the laminate is preferably a laminate having a structure in which the film of the present invention is laminated on both surfaces of the substrate layer. In this case, since the film of the present invention is laminated on both surfaces of the heat-resistant resin film, the linear expansion coefficient of the laminate is remarkably reduced, and warpage is less likely to occur.

Examples of the heat-resistant resin include polyimide, polyarylate, polysulfone, polyarylsulfone, aramid, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystalline polyester, and liquid crystalline polyesteramide. Polyimides (particularly aromatic polyimides) are preferred.

The thickness (total thickness) of the laminate of the heat-resistant resin film having the film of the present invention on both sides is preferably 220 μm or more, more preferably 250 μm or more. The thickness is preferably 500 μm or less. In this configuration, the ratio of the total thickness of the 2F polymer layers to the thickness of the heat-resistant resin film is preferably 0.8 or more. The above ratio is preferably 5 or less.

In this case, the properties of the heat-resistant resin film (high yield strength, low plastic deformation) and the properties of the F polymer layer (low water absorption) can be exhibited in a well-balanced manner.

Specific examples of the laminate include a metal-clad laminate having a metal foil and an F polymer layer on at least one surface of the metal foil, and a multilayer film having a polyimide film and F polymer layers on both surfaces of the polyimide film.

As a preferred embodiment of the present laminate in which the base layer is a heat-resistant resin film, there may be mentioned a 3-layer film in which the heat-resistant resin film is a polyimide film having a thickness of 20 to 100 μm and the film of the present invention, the polyimide film, and the film of the present invention are laminated in direct contact in this order. In this embodiment, the thickness of the 2-layer film of the present invention is the same, and preferably 100 to 200. Mu.m. The ratio of the total thickness of the 2-layer film of the present invention to the thickness of the polyimide film is preferably 0.5 to 5. The laminate of this embodiment most easily exhibits the above effects of the laminate.

Here, in order to further improve the linear expansibility or adhesiveness, the outermost surface (the surface of the F polymer layer opposite to the base material layer) of the laminate may be subjected to a surface treatment.

Examples of the method of surface treatment include annealing treatment, corona treatment, plasma treatment, ozone treatment, excimer treatment, and silane coupling treatment.

The annealing treatment is preferably carried out at a temperature of 120 to 180 ℃ under a pressure of 0.005 to 0.015MPa for 30 to 120 minutes.

Examples of the gas used for the plasma treatment include oxygen, nitrogen, a rare gas (e.g., argon), hydrogen, ammonia, and vinyl acetate. These gases may be used in combination of 1 or 2 or more.

A transmission circuit was formed by etching a metal foil of the laminate (metal foil with an F polymer layer) in which the base layer was a metal foil, and a printed board was obtained. Specifically, the printed board can be manufactured by a method of processing a metal foil into a predetermined transmission circuit by etching or a method of processing a metal foil into a predetermined transmission circuit by an electroplating method (a semi-additive process (SAP method), an MSAP method, or the like).

The printed substrate made of the F polymer layer-bearing metal foil has a transmission circuit formed of the metal foil and an F polymer layer in this order. Specific examples of the structure of the printed board include: transmission circuit/F polymer layer/prepreg layer, transmission circuit/F polymer layer/prepreg layer/F polymer layer/transmission circuit.

In the production of the printed circuit board, an interlayer insulating film may be formed on the transmission circuit, or a cover film may be stacked on the transmission circuit. These interlayer insulating films and cover films may also be formed of the film of the present invention.

The film of the present invention, the method for producing the same, and the laminate of the present invention have been described above, but the present invention is not limited to the configuration of the above embodiment.

For example, the film of the present invention and the laminate of the present invention may be configured to have any other structure added to the above-described structure, or may be replaced with any structure that exhibits the same function.

In the manufacturing method of the present invention, other arbitrary steps may be added to the configuration of the above embodiment, or may be replaced with arbitrary steps that produce the same effect.

Examples

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. The details of each component are as follows.

[ F Polymer ]

F Polymer 1: polymer containing 98.0 mol% TFE unit, 0.1 mol% NAH unit and 1.9 mol% PPVE unit and having acid anhydride group (melting temperature: 300 ℃ C.)

F Polymer 2: f Polymer containing 98.0 mol% TFE units and 2.0 mol% PPVE units and having no polar functionality (melting temperature: 300 ℃ C.)

Polymer 1 to 1X 10 ⁶ The number of carbon atoms in the main chain is 1000, and the number of the F polymer 2 is 40.

[ pellets ]

Granule 1: pellets of F Polymer 1 (diameter: 2.2 mm)

[ measurement of haze value ]

The haze value of the film obtained in each example was measured by NDH5000 (manufactured by electrochromism industry corporation, japan) according to JIS K7136.

[ thermal expansion ratio ]

After a film having a size of 120mm × 120mm was cut out in accordance with JIS K7133. The film was left to stand in a 180 ℃ furnace and heated for 30 minutes, then naturally cooled to 25 ℃, and then the length of the reticle was measured again, and the expansion and contraction ratio was calculated according to the following formula.

Formula (II): { (reticle length before heating) - (reticle length after heating) }/(reticle length before heating) × 100

[ film appearance ]

The film was left to stand on a smooth glass surface, and the presence or absence of warpage (undulation) was confirmed, and evaluated according to the following criteria.

Good: no warpage (undulation) was confirmed.

X: warpage (undulation) was confirmed.

[ example 1]

After feeding the F polymer 1 into an extruder at 350 ℃, it was extruded from a T die 1600mm wide to a thickness of 125 μm. The T die temperature was 350 ℃ and the die lip temperature was 370 ℃. The extruded molten F polymer 1 was sandwiched between a chill roll 301 which was a metal elastic roll controlled at 90 ℃ and a 1 st chill roll 30 controlled at 200 ℃, and then a slit-shaped air flow of 200 ℃ was uniformly blown linearly in the width direction of the 1 st chill roll 30 at a wind speed of 15 m/sec toward the 1 st chill roll by an air knife (height 50 mm) provided in the direction perpendicular to the line connecting the 1 st chill roll, and the molten F polymer 1 was pressed against the 1 st chill roll 30. Subsequently, the steel sheet passes through the 2 nd cooling roll 40 at 90 ℃ and is wound by the winding rolls 61 and 62 heated to 90 ℃. The haze value of the obtained film (hereinafter referred to as PFA film 1) was 3%, the MD of the thermal expansion coefficient after heating at 180 ℃ for 30 minutes was 0.2%, and the TD was-0.3%.

A hopper was connected to the front of the kneading section of the extruder, and the F polymer 1 was charged as follows: the pellets 1 were charged into a hopper, and a reduced pressure treatment and a heating treatment of 100Pa or less were performed in the hopper, and the temperature of the F polymer in the connection portion was adjusted to 180 ℃. The molten F polymer 1 extruded from the T-die was subjected to a heat treatment at 320 ℃ by a non-contact heater before being brought into contact with the chill roll and the 1 st roll.

(2) Manufacture and evaluation of antenna substrate

On the PFA film 1, a nickel-chromium alloy layer was formed by sputtering a nickel-chromium alloy to a thickness of 10nm by roll-to-roll, and then, a copper layer was formed by sputtering copper on the nickel-chromium alloy layer to a thickness of 200 nm. Subsequently, the dry film resist was roll-laminated on the copper layer at 90 ℃, and then exposed and developed until the mesh width reached 6 μm.

The copper was electrolytically plated through copper sulfate so that the width of the mesh portion became 6 μm. Then, the dry film resist was peeled off, and the copper layer and the nichrome layer formed by sputtering were removed by etching, thereby obtaining an antenna substrate.

The resistance of the antenna substrate thus obtained was measured, and whether or not the antenna substrate was on was evaluated in terms of on (good)/off (x). In addition, the haze value after the mesh antenna of the antenna substrate was formed was measured by the above method.

The film production conditions and film properties, and the results of the antenna performance evaluation are shown in table 1.

[ example 2]

A film (PFA film 2) was produced in the same manner as in (1) of example 1, except that the F polymer 2 was used instead of the F polymer 1, and that air blowing by an air knife was not performed on the F polymer 2 in a molten state at the 1 st cooling roll. Using the obtained PFA film 2, an antenna substrate and an antenna were produced in the same manner as in (2) of example 1, and evaluated in the same manner. The film production conditions and film properties, and the results of the antenna performance evaluation are shown in table 1.

[ example 3]

A film (PFA film 3) was produced in the same manner as in (1) of example 1, except that the F polymer 1 was extruded from the T die to a thickness of 125 μm, the chill roll 301 was not used (i.e., the nip between the chill roll 301 and the 1 st chill roll 30 was not performed), and the film was taken up via the 1 st chill roll without performing air blowing by an air knife on the molten F polymer 1 at the 1 st chill roll. Using the obtained PFA film 3, an antenna substrate and an antenna were produced in the same manner as in (2) of example 1, and evaluated in the same manner.

The film production conditions and film characteristics of the obtained PFA film 3, and the results of performance evaluation as an antenna are shown in table 1. The adhesion of the PFA film 3 to the 1 st cooling roll was poor, and air entered between the film and the 1 st cooling roll was marked, and the appearance was poor.

TABLE 1

* Using metal resilient rollers

Possibility of industrial utilization

The film of the present invention is transparent and has excellent dimensional stability, and therefore, can be used as a coating material for an antenna. The film of the present invention can be easily processed into a metal laminate (with resin metal foil), and the obtained processed article can be applied to various fields such as wearable devices and medical devices, which place importance on design, including flexible device instruments such as flexible printed boards, antenna members, printed boards, sports equipment, and food industry products, which have transparency.

Description of the symbols

1, 8230,

films

10 and 101, 8230, a manufacturing device 20, 8230, a T die head 21, 8230, a die lip 30, a cooling roller 1, 301, 8230, a quenching roller 40, 8230, a cooling

roller

2, 50, 8230, a winding

roller

61, 62, 8230, a conveying roller 70, 8230, an air knife 80, 8230, a heater, T8230, thickness, S8230, a circumferential speed, 11, 8230, an extrusion forming device 2, 8230, a hopper 21, 8230, a section 1, 211, 8230and a heater, 212 \8230, connecting part P1 \8230, pump 22 \8230, segment 2 part 221 \8230, heater 222 \8230, connecting part P2 \8230, pump 3 \8230, mixing part 31 \8230, cylinder 311 \8230, front end opening part 32 \8230, screw 33 \8230, gear box 331 \8230, rotating shaft 34 \8230motor341 \8230, rotating shaft 35 \8230heater, 5 \8230, T die head 6 \8230, static mixer, L \8230, full length D \ 8230, diameter

Claims

1. A film which is an extrusion-molded film comprising a tetrafluoroethylene polymer and has a thickness of 100 to 200 μm, a haze value of 8% or less, and a thermal expansion/contraction ratio after heating at 180 ℃ for 30 minutes of-1 to +1% in both the flow direction and the width direction of the film.

2. The film according to claim 1, wherein the tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer comprising a tetrafluoroethylene-based unit and a perfluoro (alkyl vinyl ether) -based unit.

3. The film according to claim 1 or 2, wherein the tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer containing a perfluoro (alkyl vinyl ether) -based unit and having a polar functional group, or a tetrafluoroethylene-based polymer containing a perfluoro (alkyl vinyl ether) -based unit in an amount of 2.0 to 5.0 mol% based on the total units and having no polar functional group.

4. A film according to any one of claims 1 to 3 wherein the tetrafluoroethylene-based polymer has a melting temperature of 260 to 320 ℃.

5. A process for producing the film according to any one of claims 1 to 4 by a T-die casting method, which comprises discharging the tetrafluoroethylene polymer in a molten state from a die to extrude the polymer, and cooling the film by sandwiching the film between 2 rolls having controlled temperature.

6. The method of claim 5, wherein the temperature of the 2 controlled rolls is 150-250 ℃ one and 80-150 ℃ the other.

7. The production process according to claim 5 or 6, wherein the extrusion molding apparatus comprises a kneading section and a hopper connected to the kneading section, and when the tetrafluoroethylene polymer pellets having a melting temperature of 260 to 320 ℃ are fed into the hopper and a molten kneaded product melted and kneaded in the kneading section is discharged from a T-die to produce a film, the extrusion molding apparatus further comprises an operation of adjusting the temperature of the pellets in the connecting section of the hopper to the kneading section to a range of (the melting temperature is-200 ℃ to) - (the melting temperature is-100) ° C, and then supplying the pellets to the kneading section.

8. The production process according to any one of claims 5 to 7, wherein the pellet has a diameter of 1.0 to 4.0mm.

9. The manufacturing method according to any one of claims 5 to 8, wherein the hopper is a multistage hopper including a 1 st stage and a 2 nd stage disposed closer to the kneading section side than the 1 st stage.

10. The production method according to any one of claims 5 to 9, wherein the pressure in a section of the hopper closest to the kneading section is 1000Pa or less.

11. The production method according to any one of claims 5 to 10, wherein the extrusion molding apparatus comprises a T-die connected to the kneading section on the side opposite to the hopper in the axial direction, and a static mixer provided between the kneading section and the T-die.

12. The production process according to any one of claims 5 to 11, further comprising an operation of discharging the tetrafluoroethylene based polymer in a molten state from a T-die, and heating the tetrafluoroethylene based polymer in the molten state by a non-contact heating section before the tetrafluoroethylene based polymer comes into contact with a first cooling roll.

13. The production process according to claim 12, wherein the difference between the temperature of the tetrafluoroethylene-based polymer in the T-die and the temperature of the initial cooling roll is 250 ℃ or less.

14. The production process according to claim 12 or 13, wherein an absolute value of a difference between the temperature of the tetrafluoroethylene-based polymer in the T-die and the temperature of the non-contact heating section is 70 ℃ or less.

15. A laminate comprising a layer comprising the film according to any one of claims 1 to 4 and a base material layer comprising a base material other than the film.