JP7459735B2 - Film manufacturing method and laminate manufacturing method - Google Patents

Description

The present invention relates to a method for producing a film in which pellets of tetrafluoroethylene polymer adjusted to a predetermined temperature are supplied to a kneading section and melt-extruded, and a method for producing a laminate having such a film as a layer.

Tetrafluoroethylene-based polymers such as polytetrafluoroethylene (PTFE) have a high melting temperature, making stable molding difficult. In particular, when forming into a film using the T-die method, the temperature unevenness of the tetrafluoroethylene polymer makes the melted state non-uniform, which tends to cause surging (discharge fluctuation) of the melt-kneaded product, reducing the accuracy of the film thickness. It's easy to do.
Patent Document 1 proposes a method of adding non-melting PTFE to a melting tetrafluoroethylene polymer to improve the non-uniformity of the melted state and improve the film thickness accuracy.

However, in the above method, since different types of polymers are mixed, fluctuations in the melt state occur due to uneven mixing, and as a result, the effect of improving shape stability such as film thickness accuracy is limited.
Furthermore, due to the presence of non-melting PTFE, spot-like unmelted portions called fish eyes are formed in the produced film, which tends to cause local thickness unevenness.

JP 2019-112563 A

The present inventors have intensively investigated a method for reducing the surging phenomenon of melt-kneaded products, film thickness fluctuations, and occurrence of fish eyes without mixing different types of polymers.
As a result, first of all, in the T-die method, the surging phenomenon of the melt-kneaded material and the film thickness fluctuation are caused by the non-uniformity of the melted state due to the temperature unevenness of the melt-kneaded material in the kneading section of the extrusion molding device. I found out the point. This temperature unevenness is thought to be caused by insufficient kneading in the kneading section, poor heat transfer due to molding of the heat insulating layer due to air entrainment, and the like.
If the rotational speed of the screw is increased or the screw is changed to a screw with strong shear stress in order to improve the uniformity of polymer mixing within the kneading section, the polymer will be heated more than necessary and its deterioration will likely occur.

The cause of fisheyes is the same as that described above: when temperature unevenness occurs in the molten kneaded product, the melt viscosity is low in the low temperature parts, making fisheyes more likely to occur. On the other hand, when a polymer is heated more than necessary, the deteriorated polymer becomes a nucleus, making fisheyes more likely to occur.
The present invention aims to provide a method for producing a film in which pellets of a tetrafluoroethylene polymer are heated in advance in a hopper to a predetermined temperature, thereby reducing temperature unevenness of the molten kneaded material in a kneading section, thereby suppressing the surging phenomenon of the molten kneaded material, improving the film thickness accuracy, and reducing the occurrence of fisheyes. Another object of the present invention is to provide a method for producing a laminate having such a film as a layer.

The present invention has the following aspects.
<1> A method for producing a film, comprising the steps of: preparing an extrusion molding apparatus having a kneading section and a hopper connected to the kneading section; and pellets of a tetrafluoroethylene-based polymer having a melting temperature X of 270 to 325°C; charging the pellets into the hopper; and discharging a molten mixture that has been melted and kneaded in the kneading section to produce a film, wherein the temperature of the pellets at a connection part of the hopper with the kneading section is adjusted to a range of X-200 to X-100°C, and then the pellets are supplied to the kneading section.
<2> The method for producing the above <1>, wherein the pellets have a diameter of 1.0 to 4.0 mm.
<3> The manufacturing method according to <1> or <2> above, wherein the hopper is a multi-stage hopper including a first stage and a second stage disposed closer to the kneading section than the first stage.
<4> The manufacturing method according to <3> above, wherein the pressure in the second stage is lower than the pressure in the first stage.
<5> The method according to <3> or <4> above, wherein a pressure in a step portion of the hopper closest to the kneading portion is 1000 Pa or less.
<6> The method according to any one of <1> to <5> above, wherein the extrusion molding apparatus includes a T-die connected to the kneading section on the axial side opposite to the hopper, and a static mixer provided between the kneading section and the T-die.
<7> The method according to any one of the above <1> to <6>, wherein the melting temperature of the tetrafluoroethylene polymer is 270 to 325° C.
<8> The method according to any one of <1> to <7> above, wherein the rate of change of melt viscosity of the tetrafluoroethylene polymer over time is from 50 to 150%.
<9> The method according to any one of <1> to <8> above, wherein the pellets have a metal content of 1 ppm or less.
<10> The method according to any one of the above <1> to <9>, wherein the film has a thickness of 1 to 1000 μm.
<11> The method according to any one of <1> to <10> above, wherein the film is a long film having a length in the short direction of 500 mm or more.
<12> The method according to any one of the above <1> to <11>, wherein the number of fisheyes in the film is 0.1 pcs/ ^m2 or less.
<13> A method for producing a laminate, comprising: superposing a film produced by any one of the production methods <1> to <12> above on a base layer; and heat-pressing the resulting laminate to obtain a laminate in which the film layer and the base layer are laminated in this order.

According to the present invention, a film having a uniform thickness in which the occurrence of fish eyes is prevented, particularly a thin long film, can be obtained, and a laminate suitable as a printed circuit board material can be obtained.

FIG. 1 is a schematic diagram showing one embodiment of an extrusion molding device used in the present invention.

The following terms have the following meanings.
The "rate of change in polymer melt viscosity over time" is the rate of change in melt viscosity after 1 hour relative to the initial melt viscosity, measured using a parallel plate viscometer (rheometer) while applying a shear stress of 0.1 rad/s to the polymer at 350° C., and is a value expressed in %.
The "melt viscosity of polymer" is a value measured in accordance with ASTM D 1238 using a flow tester and a 2Φ-8L die, with a polymer sample (2 g) that had been preheated at the measurement temperature for 5 minutes being held at the measurement temperature under a load of 0.7 MPa.
The "melting temperature (melting point) of a polymer" is the temperature corresponding to the maximum value of the melting peak of the polymer as measured by differential scanning calorimetry (DSC).
The "glass transition point of a polymer" is a value measured by analyzing a polymer using a dynamic mechanical analysis (DMA) method.

The method for producing a film of the present invention (method 1) uses, for example, an extrusion molding apparatus 1 shown in FIG. This is a method for producing a film from pellets.
FIG. 1 is a conceptual diagram showing one embodiment of an extrusion molding apparatus used in the present invention. In the following description, the right side in FIG. 1 (the front in the direction of transfer of the melt-kneaded material) will be referred to as the "tip" and the left side (the rear in the transfer direction) will be referred to as the "base end."
The extrusion molding apparatus 1 shown in FIG. 1 includes a hopper 2 and a kneading section 3 communicating with the hopper 2.

The kneading section 3 of this embodiment is composed of a single-shaft kneader having a cylinder 31 and one screw 32 rotatably provided within the cylinder 31 .
If a single-screw kneader is used, it is easy to prevent the F polymer from deteriorating when the pellets are melt-kneaded.
In this case, when the total length of the screw 32 is L (mm) and the diameter is D (mm), the effective length (L/D) expressed as the ratio of the total length L to the diameter D is preferably 25 to 50, more preferably 30 to 45. If the effective length is within the above range, sufficient shear stress can be applied to the F polymer while preventing deterioration of the F polymer, and temperature unevenness of the molten kneaded product can be easily reduced.

A gear box 33 and a motor 34 are arranged in this order on the base end side of the cylinder 31. A gear (not shown) is connected to the tip end of a rotating shaft 341 of the motor 34, and this gear meshes with a predetermined gear (not shown) in the gear box 33.
In the gear box 33, the rotational motion of the rotating shaft 341 is accelerated or decelerated and transmitted to the rotating shaft 331. The tip end of the rotating 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 to rotate the screw 32 at a predetermined rotation speed. As a result, the molten kneaded material is transported from the base end side (left side) to the tip end side (right side) in FIG.

Further, a heater 35 is provided on the outer circumference of the cylinder 31. The pellets (F polymer) supplied into the cylinder 31 are melted by heating by the heater 35, mixed (kneaded) by the rotation of the screw 32, and transferred toward the tip side. Thereby, the pellets are melted and kneaded, and the melted and kneaded product is extruded from the tip opening 311 of the cylinder 31.
A T-die 5 is arranged on the tip side of the cylinder 31 (on the side opposite to the hopper 2 in the axial direction of the kneading section 3). The melted and kneaded material extruded from the tip opening 311 of the cylinder 31 is discharged from the lower end opening (discharge port) of the T-die 5, and a film of F polymer (hereinafter also referred to as "main film") is produced (formed). be done. Although not shown, the T-die 5 is also provided with a heater.

In this embodiment, a static mixer 6 is provided between the cylinder 31 (kneading section 3) and the T-die 5. The static mixer 6 is an element that stirs the melt-kneaded material by dividing, converting, or reversing the flow path of the melt-kneaded material.
By installing such a static mixer 6, it is not necessary to apply unnecessary external force to the melt-kneaded product, so that deterioration of the melt-kneaded product can be suppressed and uniform kneading can be achieved.

A hopper 2 is arranged on the base end side of the cylinder 31. The hopper 2 of this embodiment is a two-stage type including a funnel-shaped first stage part 21 and a funnel-shaped second stage part 22 disposed closer to the kneading section 3 (cylinder 31) than the first stage part 21. It consists of a hopper.
A heater 211 and a pump P1 are connected to the first stage portion 21. Thereby, the pellets supplied into the first stage section 21 can be heated under reduced pressure.
The first step section 21 is connected to the second step section 22 via a connecting section 212.

A heater 221 and a pump P2 are connected to the second stage portion 22. Thereby, the pellets supplied into the second stage section 22 can be heated under reduced pressure.
The second stage portion 22 is connected to the cylinder 31 via a connecting portion 222 .
The inner surface (inner peripheral surface) of the hopper 2 (first step section 21 and second step section 22) is preferably coated with a resin film. That is, it is preferable that the inner surface of the hopper 2 is lined with resin. This can sufficiently prevent softened pellets from adhering to the inner surface of the hopper 2.
In addition, as a constituent material of the resin film, fluororesin such as polytetrafluoroethylene can be mentioned.

The pellets used in Method 1 may contain components other than the F polymer, but are preferably made of the F polymer. The content of F polymer in the powder is preferably 80% by mass or more, more preferably 100% by mass.
Components other than the F polymer include aromatic polyester, polyamideimide, thermoplastic polyimide, polyphenylene ether, and polyphenylene oxide.

The F polymer in the present invention is a polymer containing units based on tetrafluoroethylene (TFE) (TFE units).
The melt viscosity of the F polymer is preferably 1×10 ² to 1×10 ⁶ Pa·s at 380°C.
The rate of change in melt viscosity of the F polymer over time is preferably 50 to 150%, more preferably 75 to 125%. In this case, even if a melt-kneaded product remains in the kneading section 3 when the melt-kneaded product is kneaded for a long time, the change in the melt viscosity can be suppressed to a small level. As a result, the influence on variations in the thickness of the film is small.
The melting temperature of polymer F is preferably 270 to 325°C, more preferably 280 to 320°C.
The glass transition point of the F polymer is preferably 75 to 125°C, more preferably 80 to 100°C.

F polymer is preferably the polymer (PFA) that contains TFE unit and perfluoro(alkyl vinyl ether) (PAVE)-based unit (PAVE unit), or the polymer (FEP) that contains TFE unit and hexafluoropropylene-based unit, and more preferably PFA from the viewpoint that it is easier to have the physical properties of the above-mentioned preferred F polymer.
Preferably, PAVE _{is CF2} = _CFOCF3 , _CF2 = _CFOCF2CF3 or _CF2 = _CFOCF2CF2CF3 ( _PPVE ), more preferably _PPVE .

The F polymer may have a polar functional group. The polar functional group may be contained in a unit in the F polymer, or may be contained in a terminal group of the main chain of the F polymer. Examples of the latter polymer include an F polymer having a polar functional group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and an F polymer having a polar functional group obtained by subjecting an F polymer to plasma treatment or ionizing radiation treatment.
The polar functional group is preferably a hydroxyl group-containing group or a carbonyl group-containing group, and from the viewpoint of the dispersion stability of the present composition, a carbonyl group-containing group is more preferable.
The hydroxyl-containing group is preferably a group containing an alcoholic hydroxyl group, and is preferably --CF ₂ CH ₂ OH or --C(CF ₃ ) ₂ OH.
The carbonyl group-containing group is a group containing a carbonyl group (>C(O)), and is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH ₂ ), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) or a carbonate group (-OC(O)O-).

The F polymer contains a PAVE unit, preferably a tetrafluoroethylene polymer containing 1.5 to 5.0 mol% of PAVE units based on the total units, and contains a unit based on a monomer having a PAVE unit and a polar functional group, More preferred is a polymer (1) having a polar functional group, or a polymer (2) having no polar functional group, which contains a PAVE unit and contains 2.0 to 5.0 mol% of the PAVE unit based on the total units.
These F polymers tend to form microspherulites in the present film, and their adhesiveness tends to increase.

Polymer (1) contains 90 to 98 mol % of TFE units, 1.5 to 9.97 mol % of PAVE units, and 0.01 to 3 mol % of units based on monomers having polar functional groups, based on the total units. %, respectively.
Further, the monomer having a polar functional group is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (other name: himic anhydride; hereinafter also referred to as "NAH").
Specific examples of the polymer (1) include the polymers described in International Publication No. 2018/16644.

The content of PAVE units in the polymer (2) is preferably 2.1 mol% or more, more preferably 2.2 mol% or more, based on all units.
Polymer (2) consists only of TFE units and PAVE units, and contains 95.0 to 98.0 mol% of TFE units and 2.0 to 5.0 mol% of PAVE units based on the total units. preferable.
In addition, the polymer (2) does not have a polar functional group means that the number of polar functional groups that the polymer has is less than 500 per 1 × 10 ⁶ carbon atoms constituting the polymer main chain. do. The number of polar functional groups is preferably 100 or less, more preferably 50 or less. The lower limit of the number of polar functional groups is usually 0.
Polymer (2) may be produced using a polymerization initiator, chain transfer agent, etc. that does not produce a polar functional group as the terminal group of the polymer chain, or may be produced using a PFA-based polymer having a polar functional group (as a polymerization initiator). It may also be produced by subjecting a PFA-based polymer (such as a PFA-based polymer having a derived polar functional group to the terminal group of the main chain of the polymer) to a fluorination treatment. Examples of the fluorination treatment method include a method using fluorine gas (see Japanese Patent Application Publication No. 2019-194314, etc.).

The pellets of the present invention may contain polymers other than F polymer, inorganic fillers, thixotropic agents, antifoaming agents, silane coupling agents, dehydrating agents, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, brightening agents, colorants, conductive agents, release agents, surface treatment agents, viscosity regulators, and flame retardants.

Inorganic fillers include nitride fillers and inorganic oxide fillers, such as boron nitride fillers, beryllia (beryllium oxide), silica fillers, or metal oxides (cerium oxide, alumina, soda alumina, magnesium oxide, zinc oxide, Fillers such as titanium oxide are preferred.
The shape of the inorganic filler may be granular, fibrous, or plate-like.
The average particle diameter of the granular inorganic filler is preferably 0.01 to 1 μm.
The fibrous inorganic filler preferably has a fiber length of 1 to 10 μm and a fiber diameter of 0.01 to 1 μm.
When the present film contains an inorganic filler, the content thereof is preferably 1 or less relative to the content of the F polymer.

The inorganic filler may be surface-treated.
Examples of the surface treatment agent include polyhydric alcohols (trimethylolethane, pentaerythritol, propylene glycol, etc.), saturated fatty acids (stearic acid, lauric acid, etc.), esters thereof, alkanolamines, amines (trimethylamine, triethylamine, etc.), paraffin wax, silane coupling agents, silicones, polysiloxanes, and inorganic substances (oxides, hydroxides, hydrated oxides, or phosphates of aluminum, silicon, zirconium, tin, titanium, antimony, etc.).

Specific examples of inorganic fillers include silica fillers with an average particle size of 1 μm or less (such as the "Admafine" series manufactured by Admatechs), zinc oxide with an average particle size of 0.1 μm or less (such as the "FINEX" series manufactured by Sakai Chemical Industry Co., Ltd.), spherical fused silica (such as the SFP grade manufactured by Denka), rutile-type titanium oxide with an average particle size of 0.5 μm or less (such as the "Typec" series manufactured by Ishihara Sangyo Kaisha), and rutile-type titanium oxide with an average particle size of 0.1 μm or less (such as the "JMT" series manufactured by Teika Corporation).

The content of the F polymer in the pellets is 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. The content is 100% by mass. In this case, the present film having excellent electrical properties and adhesion to the substrate can be easily produced.
The shape of the pellets may be spherical or cylindrical, with cylindrical being preferred. The diameter of the pellets is preferably 1.0 to 4.0 mm, and more preferably 1.5 to 3.5 mm. Pellets with such a diameter can be heated (warmed) sufficiently to the inside when heated in the hopper 2 while preventing bridging (clogging) in the hopper 2.

In the film manufacturing method of the present invention (method 1), F polymer pellets are preheated in a hopper 2 and then supplied to a kneading section 3, where the melt-kneaded material is melted and kneaded in the kneading section 3. This film is manufactured by discharging from the die 5. At this time, the temperature of the pellets at the connection part 222 of the hopper 2 with the kneading part 3 is adjusted to a range of X-200 to X-100°C. Note that X is the melting temperature of the F polymer (the same applies hereinafter unless otherwise specified).
The temperature of the pellets at the connection section 222 of the hopper 2 with the kneading section 3 is preferably X-175 to X-125°C. The specific pellet temperature is preferably 70 to 225°C, more preferably 80 to 220°C, and even more preferably 105 to 195°C. In this case, bridging within the hopper 2 due to pellet softening is less likely to occur. Further, since the temperature unevenness of the melt-kneaded product in the kneading section 3 is sufficiently reduced, it is easy to obtain the present film having a uniform thickness and preventing the occurrence of fish eyes.

The pressure in the second stage 22 (the stage closest to the kneading section 3) is preferably lower than the pressure in the first stage 21, and is preferably 1000 Pa or less, and more preferably 100 Pa or less. This makes it possible to sufficiently remove air from within the pellets, preventing the formation of a heat insulating layer by air, and making it easy to prevent temperature unevenness from occurring in the molten kneaded material in the kneading section 3.
The metal content in the F polymer (pellet) is preferably 1 ppm or less, more preferably 0.75 ppm or less, and even more preferably 0.5 ppm or less. In this case, the decomposition of the F polymer caused by the metal acting as a catalyst and the increase in the local melt viscosity of the molten kneaded product caused by the metal acting as a thermal conductive agent are prevented, and the occurrence of fish eyes in the present film is easily suppressed.

The softened pellets are supplied to the kneading section 3.
The rotation speed of the screw 32 is preferably 10 to 50 ppm, more preferably 20 to 40 ppm.
The heating temperature by the heater 35 is preferably X+20 to X+60°C, more preferably X+30 to X+50°C.
If the pellets are melt-kneaded under the above conditions, a homogeneous melt-kneaded product with little temperature unevenness is likely to be formed. As a result, it is easier to obtain a film that has a uniform thickness and is free from fish eyes.

The melt-kneaded material is supplied to the T-die 5 via the static mixer 6, and is discharged from the T-die 5.
The melt-kneaded material discharged from the T-die 5 comes into contact with a plurality of cooling rolls (not shown), solidifies it, and forms a film.
The obtained long film is wound onto a take-up roll (not shown).
Moreover, the extrusion molding apparatus 1 may have a cutting machine as necessary.

The thickness of the film is preferably 1 to 1000 μm, more preferably 5 to 150 μm, and even more preferably 10 to 100 μm.
The shape of the present film may be elongated or leaf-like, and preferably elongated.
The length of the long film in the longitudinal direction is preferably 10 m or more, more preferably 100 m or more. The upper limit of the length in the longitudinal direction is usually 2000 m. Further, the length of the elongated sheet in the lateral direction is preferably 500 mm or more, and preferably 1000 mm or more. The upper limit of the length in the lateral direction is usually 3000 mm.

The number of fish eyes in this film is preferably 0.1 or less, more preferably less than 0.05 per m ² of film. The lower limit of the number of fish eyes is 0.
According to this method 1, a film is formed by uniformly melting and kneading the polymer without giving an excessive thermal history while highly suppressing the surging phenomenon. Therefore, it is possible to easily produce a wide and thin long film with few defects (fish eyes) and sufficient length in the lateral direction.

In the method for producing a laminate of the present invention (Method 2), the present film is superimposed on a base layer, and then heat-pressed to obtain a laminate in which a layer of the present film (hereinafter also referred to as a "polymer layer") and the base layer are laminated in this order.
The conditions for the hot pressing in Method 2 are preferably a temperature of 120 to 300° C., an atmospheric pressure of a vacuum of 20 kPa or less, and a pressing pressure of 0.2 to 10 MPa.

The substrate layer in Method 2 is preferably a metal substrate or a heat-resistant resin film, more preferably a metal foil, a metal steel plate or a heat-resistant resin film.
The ten-point average roughness of the surface of the metal foil is preferably 0.5 μm or less, more preferably less than 0.1 μm. The ten-point average roughness of the surface of the metal foil is preferably 0.01 μm or more. In this case, the polymer layer and the metal foil tend to adhere more firmly to each other.
For this reason, in a laminate having this film with high thickness accuracy or in a printed circuit board obtained by processing the same, electrical properties (low dielectric constant, low dielectric loss tangent, etc.) tend to be significantly exhibited.
Specifically, when the substrate layer in Method 2 is a metal foil, the dielectric loss tangent of the laminate at a frequency of 10 GHz is preferably 0.0020 or less, more preferably 0.0015 or less. The dielectric loss tangent is preferably 0.0001 or more.
Examples of materials for the metal substrate include iron, copper, nickel, titanium, aluminum, and alloys thereof (stainless steel, nickel 42 alloy, etc.).
The metal substrate is preferably a stainless steel plate, rolled copper foil, or electrolytic copper foil.

The surface of the metal substrate may be subjected to antirust treatment (formation of an oxide film such as chromate). Further, the surface of the metal substrate may be treated with a silane coupling agent. The treatment range at that time may be a part of the surface of the metal foil or the entire surface.
The thickness of the metal substrate is preferably 3 mm or less, more preferably 0.1 to 20 μm, and even more preferably 0.5 to 10 μm.

In addition, a carrier-attached metal foil containing two or more layers of metal foil may be used as the metal foil. Examples of carrier-attached metal foils include carrier-attached copper foils consisting of a carrier copper foil (thickness: 10 to 35 μm) and an ultra-thin copper foil (thickness: 2 to 5 μm) laminated on the carrier copper foil via a release layer. By using such a carrier-attached copper foil, it is possible to form a fine pattern by the MSAP (modified semi-additive) process. As the release layer, a metal layer containing nickel or chromium, or a multi-layer metal layer in which this metal layer is laminated, is preferable.
A specific example of the metal foil with a carrier is "FUTF-5DAF-2" manufactured by Fukuda Metal Foil & Powder Co., Ltd.

The heat-resistant resin film is a film containing one or more types of heat-resistant resins, and may be a single layer film or a multilayer film. Glass fibers, carbon fibers, or the like may be embedded in the heat-resistant resin film.
When the base layer is a heat-resistant resin film, it is preferable to laminate the film on both sides of the base layer. In this case, since the present film is laminated on both sides of the heat-resistant resin film layer, the coefficient of linear expansion of the laminate is significantly lowered and warpage is less likely to occur. Specifically, the absolute value of the coefficient of linear expansion of the laminate in this embodiment is preferably 1 to 25 ppm/°C.

Examples of the heat-resistant resin include polyimide, polyarylate, polysulfone, polyarylsulfone, aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystalline polyester, liquid crystalline polyesteramide, and fluororesin. Of these, polyimide (particularly, aromatic polyimide) or fluororesin (particularly, polytetrafluoroethylene (PTFE)) is preferred.
In the laminate which is a heat-resistant resin film having the present film on both sides, the thickness (total thickness) is preferably 25 μm or more, more preferably 50 μm or more, and is preferably 150 μm or less.
In such a configuration, the ratio of the total thickness of the two polymer layers to the thickness of the heat-resistant resin film is preferably 0.5 or more, more preferably 0.8 or more, and is preferably 5 or less.
In this case, the properties of the heat-resistant resin film (high yield strength, low plastic deformation property) and the properties of the polymer layer (low water absorbency) are exhibited in a well-balanced manner.

A preferred embodiment of the laminate according to method 2, in which the base layer is a heat-resistant resin film, is a three-layer film in which the heat-resistant resin film is a polyimide film having a thickness of 20 to 100 μm, and the heat-resistant resin film is laminated in direct contact with the present film, a polyimide film, and the present film in that order. In this embodiment, the thickness of the two present films is the same, and is preferably 15 to 50 μm. The ratio of the total thickness of the two present films to the thickness of the polyimide film is preferably 0.5 to 5. A laminate in this embodiment is most likely to exhibit the effects of the laminate described above.

The outermost surface of the laminate in the present invention (the surface of the polymer layer opposite to the base material) may be further surface-treated in order to further improve its linear expansion properties and adhesive properties.
Examples of surface treatment methods include annealing treatment, corona treatment, plasma treatment, ozone treatment, excimer treatment, and silane coupling treatment.
The conditions for the annealing treatment are preferably a temperature of 120 to 180° C., a pressure of 0.005 to 0.015 MPa, and a time of 30 to 120 minutes.
Examples of gases used for plasma processing include oxygen gas, nitrogen gas, rare gas (argon, etc.), hydrogen gas, ammonia gas, and vinyl acetate. These gases may be used alone or in combination of two or more.

On the outermost surface of the laminate of the present invention, another substrate may be further laminated.
Other substrates include a heat-resistant resin film, a prepreg which is a precursor of a fiber-reinforced resin plate, a laminate having a heat-resistant resin film layer, and a laminate having a prepreg layer.
Note that a prepreg is a sheet-like substrate in which a base material (tow, woven fabric, etc.) of reinforcing fibers (glass fiber, carbon fiber, etc.) is impregnated with a thermosetting resin or a thermoplastic resin.
The heat-resistant resin film may be the heat-resistant resin film described above.

Examples of the lamination method include a method of hot pressing the laminate and another substrate.
When the other substrate is a prepreg, the hot pressing conditions are preferably a temperature of 120 to 400° C., a vacuum atmosphere of 20 kPa or less, and a press pressure of 0.2 to 10 MPa.
The laminate of the present invention has a polymer layer with excellent electrical properties and is therefore suitable as a printed circuit board material. Specifically, the laminate of the present invention can be used in the production of printed circuit boards as a flexible metal-clad laminate or a rigid metal-clad laminate, and in particular can be suitably used as a flexible metal-clad laminate in the production of flexible printed circuit boards. .

A printed circuit board is obtained by etching the metal foil of a laminate (metal foil with polymer layer) in which the base material layer is metal foil to form a transmission circuit. Specifically, there are methods of etching metal foil to process it into a specified transmission circuit, and methods of processing metal foil into a specified transmission circuit using an electrolytic plating method (semi-additive method (SAP method), MSAP method, etc.). Printed circuit boards can be manufactured using this method.
A printed circuit board manufactured from a metal foil with a polymer layer has a transmission circuit formed from the metal foil and a polymer layer in this order. Specific examples of the structure of the printed circuit board include transmission circuit/polymer layer/prepreg layer and transmission circuit/polymer layer/prepreg layer/polymer layer/transmission circuit.
In manufacturing such a printed circuit board, an interlayer insulating film may be formed on the transmission circuit, a solder resist may be laminated on the transmission circuit, and a coverlay film may be laminated on the transmission circuit. This film may be used as a material for these interlayer insulating films, solder resists, and coverlay films.

A specific example of the printed circuit board is a multilayer printed circuit board in which printed circuit boards are multilayered.
A preferred embodiment of the multilayer printed circuit board is one in which the outermost layer of the multilayer printed circuit board is a polymer layer, and one or more metal foils or transmission circuits, a polymer layer, and a prepreg layer are laminated in this order. It will be done. Note that the number of the above configurations is preferably plural (two or more). Furthermore, a transmission circuit may be further disposed between the polymer layer and the prepreg layer.
The multilayer printed circuit board of this embodiment has particularly excellent heat-resistant processability due to the outermost polymer layer. Specifically, even at 288° C., interfacial swelling between the polymer layer and prepreg layer and interfacial peeling between the metal foil (transmission circuit) and the polymer layer are unlikely to occur. In particular, even when the metal foil forms the transmission circuit, the polymer layer is tightly adhered to the metal foil (transmission circuit), so warping is less likely to occur and it has excellent heat-resistant processability.

A preferred embodiment of the multilayer printed circuit board includes one or more embodiments in which the outermost layer of the multilayer printed circuit board is a prepreg layer, and one or more metal foils or transmission circuits, a polymer layer, and a prepreg layer are laminated in this order. It will be done. Note that the number of the above configurations is preferably plural (two or more). Furthermore, a transmission circuit may be further disposed between the polymer layer and the prepreg layer.
The multilayer printed circuit board of this embodiment has excellent heat-resistant processability even if it has a prepreg layer as the outermost layer. Specifically, even at 300° C., interfacial swelling between the polymer layer and prepreg layer and interfacial peeling between the metal foil (transmission circuit) and the polymer layer are unlikely to occur. In particular, even when the metal foil forms the transmission circuit, the polymer layer is tightly adhered to the metal foil (transmission circuit), so warping is less likely to occur and it has excellent heat-resistant processability.
In other words, according to the present invention, various configurations can be created in which the respective interfaces are firmly adhered to each other without performing various surface treatments, and interface blistering and interfacial peeling due to heating are suppressed, and in particular, blistering and peeling in the outermost layer are suppressed. A printed circuit board having the following properties can be easily obtained.

Although the method for producing a film and the method for producing a laminate according to the present invention have been described above, the present invention is not limited to the configurations of the embodiments described above.
For example, the method for manufacturing a film and the method for manufacturing a laminate of the present invention may each additionally include any other step in the configuration of the above embodiment, or may include any other step that produces the same effect. May be replaced.
Further, the hopper may be a one-stage hopper or a multi-stage hopper having three or more stages.
Further, the kneading section may be configured with a twin-screw kneader.
Furthermore, a round die may be used instead of the T die. A round die can be used to produce blown film.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.
1. Preparation of each component [Pellet]
- Pellet 1: Polymer containing TFE units, NAH units, and PPVE units in this order at 97.9 mol%, 0.1 mol%, and 2.0 mol%, and having polar functional groups (melting temperature: 300 ° C. Pellets (metal content: 0.1 ppm, diameter: 2.0 mm) (temporal change rate of melt viscosity: 130%)
- Pellet 2: Polymer containing TFE units and PPVE units at 97.5 mol% and 2.5 mol% in this order and having no polar functional groups (melting temperature: 300°C, rate of change in melt viscosity over time: 102%) (metal content: 0.1 ppm, diameter: 2.0 mm)
・Pellet 3: Polymer containing TFE units and PPVE units at 97.5 mol% and 2.5 mol% in this order and having no polar functional groups (melting temperature: 300°C, rate of change in melt viscosity over time: 160%) (metal content: 2 ppm, diameter: 2.0 mm)

[Extrusion molding equipment]
・Extrusion molding device 1: A device with a one-stage hopper and a static mixer in the neck portion ・Extrusion molding device 2: The device shown in Figure 1 In addition, in the extrusion molding devices 1 and 2, a kneading section and a static mixer and T-die have the same configuration and have the following specifications.
Diameter of cylinder tip opening (caliber): 75mm
Effective length (L/D): 32
T-die bottom opening length: 1600mm

2. Film production (Example 1)
Pellets 1 were charged into the hopper of the extrusion molding device 1, and the hopper was heated and kept warm so that the temperature of the pellets 1 at the connection part between the hopper and the kneading part was 140°C.
The heated pellets 1 were fed to the kneading section, and the molten and kneaded molten mixture was extruded from a T-die to produce a film 1 (width: 1200 mm, thickness: 50 μm). The heating temperatures of the kneading section and the T-die were set to 350° C., and the screw rotation speed was set to 40 rpm.
(Example 2)
Film 2 was produced in the same manner as in Example 1, except that pellet 1 was changed to pellet 2.
(Example 3)
Film 3 was produced in the same manner as in Example 1, except that pellet 3 was used instead of pellet 1.

(Example 4)
Pellets 1 were charged into the hopper of the extrusion molding device 2, and the hopper was heated and kept warm so that the temperature of the pellets 1 at the connection between the second stage of the hopper and the kneading section was 140° C. The pressure in the second stage was set to 100 Pa. After this, film 4 was produced in the same manner as in Example 1.
Example 5 (Comparative Example)
Except for omitting heating of the hopper, the film 5 was produced in the same manner as in Example 1. The temperature of the pellets 1 at the connection between the hopper and the kneading section was 50° C. due to heat from the kneading section.
Example 6 (Comparative Example)
A film 6 was produced in the same manner as in Example 1, except that the temperature of the pellets 1 at the junction between the hopper and the kneading section was set to 220°C.

3. Measurement and evaluation of pellets or films 3-1. Measurement of metal content in pellets Each pellet was analyzed for metal content by ICP-MS method. Note that the total of all detected metal species was defined as the metal content.
3-2. Measurement of the rate of change in melt viscosity of pellets over time Each pellet was sandwiched between parallel plates (φ20 mm) heated to 350°C, and with a shear stress of 0.1 rad/s applied, a parallel plate viscometer (Thermo Fisher Scientific The complex viscosity η ^* was continuously measured using a HAAKE MARS III (manufactured by Fick Inc.), and the rate of change in the melt viscosity after one hour with respect to the initial melt viscosity was calculated.

3-3. Film Thickness Measurement For each film, an online thickness meter (manufactured by Yokogawa Electric Corporation, "WEBFREX NV") was used to measure the thickness of the film by moving it in a direction perpendicular to the flow direction of the film in a traverse manner, with a pitch of 2 mm in the width direction, so that one scan could be made across the entire width while a length of 5 m was produced.
After a length of 500 m was produced, the average thickness (μm) for each scan was further averaged over the length of 500 m to obtain the "longitudinal thickness (μm)". The standard deviation of the average was obtained as the "longitudinal σ (μm)". When the longitudinal σ (μm) is large, it is suggested that discharge fluctuations (surging) occur due to temperature unevenness of the molten kneaded material.
After producing a length of 500 m, the thicknesses at the same position in the width direction of the film were averaged to obtain the "width direction thickness (μm)". The standard deviation of the average was obtained as the "width direction σ (μm)". When the width direction σ (μm) is large, it is suggested that the thickness is non-uniform due to the temperature unevenness of the molten kneaded material in the T-die.

3-4. Confirmation of fisheyes The number of fisheyes formed in each film was counted using a camera-based defect inspection machine. After producing a length of 500 m, the number of fisheyes having an area size of ¹ mm2 or more was divided by the area of the produced film to obtain the number of fisheyes formed per ^m2 .
These results are summarized in Table 1 below.

4. Production of Laminate A SUS304 stainless steel plate (width: 1 m, length: 1.2 m, thickness: 0.5 mm), a film 1 (width: 1 m, length: 1.2 m, thickness: 50 μm), and a PTFE film (width: 1 m, length: 1.2 m, "Nitoflon No. 920UL" manufactured by Nitto Denko Corporation) were stacked together and pressed under reduced pressure at 360° C. for 20 minutes to obtain a laminate 1 having the stainless steel plate, the film 1, and the PTFE film in this order.
Laminate 5 was obtained in the same manner as laminate 1, except that film 5 was used instead of film 1.

The laminate 1 or 5 was bent into a cylindrical shape with the PTFE film facing inward. Visual inspection of the cylindrical laminate after bending revealed that no wrinkles were present on the inner surface of the cylindrical laminate 1, but wrinkles were present on the inner surface of the cylindrical laminate 5.
The reason for this is believed to be that film 5 has greater thickness variation than film 1, and therefore stress is concentrated in the thin portions of film 5 during bending, making film 5 more likely to peel off.

The film obtained by the manufacturing method of the present invention has a uniform thickness and reduces the occurrence of fish eyes, making it suitable as a sleeve coating material for thermal transfer rubber rolls in copiers. In addition, the laminate obtained by the manufacturing method of the present invention is suitable as a fluororesin steel plate for printed circuit board materials, bearing applications that do not use lubricants, and building materials for snow sliding, etc.

DESCRIPTION OF SYMBOLS 1... Extrusion molding device, 2... Hopper, 21... First stage part, 211... Heater, 212... Connection part, P1... Pump, 22... Second stage part, 221... Heater, 222... Connection part, P2... Pump, 3... Kneading section, 31... Cylinder, 311... Tip opening, 32... Screw, 33... Gear box, 331... Rotating shaft, 34... Motor, 341... Rotating shaft, 35... Heater, 5... T-die, 6... Stationary Type mixer, L...full length, D...diameter

Claims (11)

An extrusion molding device having a kneading section and a hopper connected to the kneading section, and pellets of a tetrafluoroethylene polymer having a melting temperature When producing a film by discharging the melted and kneaded material melted and kneaded in the kneading section, the temperature of the pellets at the connection part of the hopper with the kneading section is adjusted to a range of X-200 to X-100 ° C. After that, supplying the pellets to the kneading section ,
The hopper is a multi-stage hopper including a first stage section and a second stage section disposed closer to the kneading section than the first stage section, and the hopper is a multi-stage hopper including a first stage section and a second stage section disposed closer to the kneading section than the first stage section. The pressure is 1000 Pa or less,
Film manufacturing method. The manufacturing method according to claim 1, wherein the pellets have a diameter of 1.0 to 4.0 mm. The method of claim 1 or 2 , wherein the pressure in the second stage is lower than the pressure in the first stage. The manufacturing method according to any one of claims 1 to 3, wherein the extrusion molding apparatus comprises a T-die connected to the kneading section on the axial side opposite to the hopper, and a static mixer provided between the kneading section and the T- die . The manufacturing method according to any one of claims 1 to 4 , wherein the tetrafluoroethylene polymer has a melting temperature of 270 to 325°C. The method according to any one of claims 1 to 5 , wherein the rate of change of melt viscosity of the tetrafluoroethylene-based polymer with time is 50 to 150%. The method according to any one of claims 1 to 6 , wherein the metal content in the pellets is 1 ppm or less. The manufacturing method according to any one of claims 1 to 7 , wherein the film has a thickness of 1 to 1000 μm. The manufacturing method according to any one of claims 1 to 8 , wherein the film is a long film and has a widthwise length of 500 mm or more. The method according to any one of claims 1 to 9 , wherein the number of fisheyes in the film is 0.1 fisheyes/ ^m2 or less. A method for producing a laminate, comprising: superposing a film produced by the production method according to any one of claims 1 to 10 on a base layer; and then heat-pressing the laminate to obtain a laminate in which the film layer and the base layer are laminated in this order.

Images