Method for producing thermoplastic liquid crystal polymer film

Abstract

A method for producing a thermoplastic liquid crystal polymer film using a roll-up film-forming method in which a liquid crystal polymer that exhibits optical anisotropy when melted is melt-extruded from an annular mold into a tube shape, and the tube-shaped melt is cooled and expanded by supplying a gas into the internal space thereof, thereby forming a bubble, and the bubble is blown into the liquid crystal polymer to form a thermoplastic liquid crystal polymer film, and the thermoplastic liquid crystal polymer film is produced by the roll-up film-forming method. In the method for manufacturing the thermoplastic liquid crystal polymer film, the film bubbles are drawn while being folded into a sheet shape, and the film bubbles are heated by a heating mechanism arranged on the peripheral side of a film bubble forming area. The thermoplastic liquid crystal polymer film having a degree of molecular orientation SOR of 0.8-1.5 is produced by drawing the bubble while heating in a state in which the ratio (hf / ht) of the height (hf) from the outlet of the mold to the frost line of the bubble to the height (ht) from the outlet of the mold to the upper end of the heating means is 50-100%.

Description

Technical Field

[0001] This application claims the benefit of Japanese Patent Application No. 2022-161782, filed on October 6, 2022, the entirety of which is incorporated by reference as a part of this application.

[0002] The present invention relates to a method for producing a film composed of a thermoplastic polymer capable of forming an optically anisotropic molten phase (hereinafter referred to as a thermoplastic liquid crystal polymer) or a polymer composition containing the thermoplastic liquid crystal polymer. Background Art

[0003] In recent years, in the electronic and electrical fields, the demand for miniaturization and lightness of equipment has become increasingly strong, and insulating films with uniform thickness, excellent electrical properties, mechanical properties, etc. are required. However, for polyimide, polyethylene terephthalate, etc., which are raw materials for conventional insulating films, although films with uniform thickness can be obtained, not only are the electrical properties in the high-frequency region insufficient, but the electrical properties deteriorate due to high hygroscopicity, and large dimensional changes are problems, making it difficult to achieve a film that meets the above requirements.

[0004] In contrast, thermoplastic liquid crystal polymers are useful in the electronic and electrical fields because they show excellent electrical properties, low dimensional change rate, high heat resistance, chemical stability, etc. As a method for simply manufacturing a film composed of the thermoplastic liquid crystal polymer, a manufacturing method using inflation molding has been proposed. In inflation molding, air is blown into a thermoplastic resin extruded from a ring-shaped mold to form a film bubble, and the film bubble is pulled to form a film. At this time, the film is biaxially stretched due to the stretching in the pulling direction and the expansion of the film bubble in the radial direction, resulting in stretching in the circumferential direction. Thermoplastic liquid crystal polymer films have the characteristic of being easily anisotropically oriented molecules, but a method of isotropically controlling the degree of molecular orientation by biaxial stretching using inflation molding is being studied. For example, Patent Document 1 (Japanese Patent No. 4632558) describes a film blowing device, which is characterized in that it comprises: a bubble diameter measuring device for measuring the change in the lateral stretch ratio of the film bubble in the film blowing device; a molecular orientation measuring device for measuring the molecular orientation of the film; and a regulator for controlling the bubble diameter by adjusting the supply of air into the film bubble based on the measured lateral stretch ratio and molecular orientation of the film bubble.

[0005] Various studies have been conducted on methods for controlling the shape of film bubbles during inflation molding. For example, Patent Document 2 (Japanese Patent Laid-Open No. 5-286032) describes an inflation film molding device, characterized in that a mechanism for heating the surface of a film bubble from the periphery thereof is provided between the die head and a position where a molten resin film bubble extruded from the die head rapidly expands, in an inflation film molding device that extrude thermoplastic resin from a die head having an annular slit and expands the film bubble under internal pressure and then continuously winds the film bubble.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 4632558

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 5-286032 Summary of the invention

[0010] Problems to be solved by the invention

[0011] In recent years, the demand for thermoplastic liquid crystal polymer films has been increasing, and it is required to improve productivity. In order to improve the productivity of films formed by inflation molding, it is considered to increase the diameter of the mold and produce large-diameter films. However, when the diameter of the mold is only increased by the existing method, the cylindrical film bubble formed by the solidification of the molten film droops downward, and there is a problem that it is difficult to control the molecular orientation. As described in Patent Document 1, this problem is difficult to solve by only controlling the supply of air into the film bubble.

[0012] Patent Document 2 describes heating the bubble surface by a heating mechanism disposed between the die head and the position (neck) where the bubble expands rapidly, thereby alleviating melt fracture, thereby enabling low-temperature extrusion and high-speed traction, but the purpose of this technology is to improve the transparency of a film composed of polyethylene, etc., which melts at a relatively low temperature. Thermoplastic liquid crystal polymers reduce melt viscosity at an extremely low shear rate when melted, so the behavior of the melt forming the bubble is very different from that of polyethylene.

[0013] In view of the above situation, an object of the present invention is to provide a method for manufacturing a thermoplastic liquid crystal polymer film, which method can achieve a desired molecular orientation degree by biaxial stretching even when the productivity of the film bubble is improved by extruding the resin from a die with a large diameter when manufacturing the thermoplastic liquid crystal polymer film by the inflation film forming method.

[0014] Methods used to solve problems

[0015] The present invention may include the following aspects.

[0016] The first aspect is a method for producing a thermoplastic liquid crystal polymer film, which is a method for producing a thermoplastic liquid crystal polymer film using an inflation film method, wherein a liquid crystal polymer that exhibits optical anisotropy when melted (hereinafter referred to as a thermoplastic liquid crystal polymer) is melt-extruded from a ring-shaped die into a tubular shape, and a gas is supplied into the inner space of the tubular melt while cooling the tubular melt to expand the tubular melt, thereby forming a film bubble, and the film bubble is pulled while closing the film bubble into a sheet shape, wherein the method for producing a thermoplastic liquid crystal polymer film is characterized in that:

[0017] The film bubble is heated by a heating mechanism (e.g., a planar heating mechanism) disposed on the outer peripheral side of the film bubble forming region, thereby heating the film bubble while the ratio hf / ht of the height hf from the outlet of the mold to the frost line of the film bubble to the height ht from the outlet of the mold to the upper end of the heating mechanism is greater than 50% and less than 100%.

[0018] A thermoplastic liquid crystal polymer film having a molecular orientation ratio SOR of 0.8 to 1.5 is produced.

[0019] A second aspect may be a method in which, in the method for producing a TLCP film according to the first aspect, the temperature of each section is controlled using the heating mechanism divided into at least two sections in the height direction.

[0020] A third aspect may be a method in which, in the method for producing a TLCP film of the first or second aspect, the time from when the TLCP is extruded from the die to when it solidifies at the frost line is set to 3 seconds or more.

[0021] A fourth aspect may be a method in which, in the method for producing a TLCP film according to any one of the first to third aspects, the height of the frost line of the bubble is set to 0.4 m or more and 3.0 m or less.

[0022] A fifth aspect may be a method in which, in the method for producing a TLCP film according to any one of the first to fourth aspects, the bubble diameter of the frost line of the bubble is set to 300 mm or more.

[0023] The sixth method may be the following method: in the method for manufacturing a thermoplastic liquid crystal polymer film of any one of the first to fifth methods, a stack of two or more thermoplastic resin layers including a layer composed of the above-mentioned thermoplastic liquid crystal polymer is co-extruded from the above-mentioned mold to form a film bubble composed of the stack, and the film bubble is pulled to thereby manufacture a stacked film, and the above-mentioned thermoplastic liquid crystal polymer film is peeled off from the above-mentioned stacked film.

[0024] Effects of the Invention

[0025] According to the present invention, even when the productivity of the bubble is increased by extruding the resin from a die with a large diameter, it is possible to control the biaxial stretching by inflation molding and provide a TLCP film having a desired molecular orientation degree with high productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic side view showing an example of an inflation film production apparatus used in the method of the present invention.

[0027] Figure 2 It is shown Figure 1 Schematic cross-sectional view of the structure of the heating mechanism and the vicinity of the inflation film manufacturing apparatus shown. DETAILED DESCRIPTION

[0028] The method for producing a thermoplastic liquid crystal polymer film of the present invention is a method for producing a thermoplastic liquid crystal polymer film, which is a method for producing a thermoplastic liquid crystal polymer film using an inflation film forming method, in which a liquid crystal polymer (hereinafter referred to as a thermoplastic liquid crystal polymer) showing optical anisotropy when melted is melt-extruded from a ring-shaped die into a tubular shape, a gas is supplied into the inner space of the tubular melt while cooling the tubular melt to expand it, thereby forming a bubble, and the bubble is pulled while closing it into a sheet shape. The method for producing a thermoplastic liquid crystal polymer film is characterized in that the bubble is heated by a heating mechanism provided on the outer peripheral side of a bubble forming region, thereby pulling the bubble while heating in a state where the ratio hf / ht of the height hf from the outlet of the die to the frost line of the bubble to the height ht from the outlet of the die to the upper end of the heating mechanism is 50% or more and 100% or less, thereby producing a thermoplastic liquid crystal polymer film having a molecular orientation ratio SOR of 0.8 to 1.5.

[0029] The inventors conducted in-depth research to solve the above-mentioned problems and found that in the manufacturing devices of thermoplastic liquid crystal polymer films used in the past, it is impossible to form a film bubble with a shape similar to that of the previous manufacturing method by simply increasing the diameter of the mold, and the ratio of the frost line height to the bubble diameter becomes smaller, making it difficult to control the molecular orientation degree by biaxial stretching accompanied by blow molding. In addition, depending on the situation, the solidified film bubble sags and contacts the mold and the air ring, making film formation itself difficult. It is difficult to solve this problem by the previously used method of only keeping the film bubble warm or the method of locally heating the film bubble, thereby completing the present invention.

[0030] First, refer to Figure 1 , 2 The structure of the inflation film production apparatus 10 that can be used in the present invention will be described. It should be noted that each drawing is a schematic diagram, and the dimensional ratio of each part does not limit the dimensional ratio in the actual apparatus.

[0031] Figure 1 1 is a schematic side view showing the structure of a blown film manufacturing device 10 that can be used in the method of the present invention. The blown film manufacturing device 10 includes an extrusion mechanism (extruder) 1 for molten thermoplastic resin, and an annular mold 2 is provided at the extrusion port of the extrusion mechanism. Air is blown into the molten resin extruded from the mold 2 to form a film bubble 3. The solidified film bubble 3 is flattened by a guide plate 4 provided as required, passes through a clamping roller 5, is transported by one or more rollers R, and is wound by a winding mechanism 6. The blown film manufacturing device 10 of the present invention includes an air ring 7 for blowing air from the periphery to the film bubble 3 and a heating mechanism 8 for heating the film bubble 3 at a portion above the mold 2.

[0032] Figure 2 This is a schematic cross-sectional view for explaining the structure of the mold 2 and the vicinity of the inflation film manufacturing device 10. The molten thermoplastic liquid crystal polymer is extruded from the annular die lip (gap) 2a of the annular die 2, and during this period, air is blown in from the air blowing port 2b (ventilation mechanism) to form a cylindrical film bubble 3. From the die lip 2a (diameter D) to a certain height hc, the molten resin film forms a cylindrical portion 3a, and then expands due to the blown air, and is cooled while the radius is expanded in the expanded diameter portion 3b, solidifies at the height hf of the frost line F, and forms a cylindrical solid phase film in the straight cylinder portion 3c above it.

[0033] In the device of the present embodiment, an air ring 7 is provided at a height near the outlet of the mold 2. For air cooling, air is sprayed toward the base of the cylindrical portion 3a. A heating mechanism 8 is provided above the air ring 7. The heating mechanism 8 may be a single section. In the present embodiment, the heating mechanism 8 is divided into a first heating section I at the lower section and a second heating section II at the upper section, and the film bubble 3 is heated at different temperatures. For example, the first heating section I for heating the lower portion of the cylindrical portion 3a and the expanded diameter portion 3b is preferably heated at a temperature 20 to 60°C lower than the melting point Tm of the thermoplastic liquid crystal polymer, for example, 20 to 40°C lower than Tm, and the second heating section II for heating the upper portion of the expanded diameter portion 3b to the upper portion of the frost line is preferably heated at a temperature 40 to 100°C lower than the melting point Tm of the thermoplastic liquid crystal polymer, for example, about 60 to 100°C lower than Tm. Although not shown, the heating mechanism 8 may be divided into three or more sections, and the film bubble 3 may be heated while the heating temperature is lowered from the lower section to the upper section. The heating mechanism 8 forms the film bubble in such a manner that a part of the cylindrical portion 3a, the enlarged diameter portion 3b, and the straight portion 3c fall into the area surrounded by the heating mechanism 8, and the frost line height hf is preferably controlled to a height of 50 to 100%, preferably 60 to 95%, of the height ht from the outlet of the mold 2 to the upper end of the heating mechanism 8. Here, the frost line height hf refers to the length of the film bubble to the frost line F measured as the height from the outlet of the mold 2 to the frost line F. In addition, it is preferred that 90 to 99%, preferably 93 to 97%, of the film bubble 3 in the molten state from the outlet of the mold 2 to the frost line height hf in the height direction is formed between the lower end 8a and the upper end 8b of the heating mechanism 8. That is, the ratio hm / hf of the length hm of the portion heated in the height direction of the film bubble 3 in the molten state to the frost line height is preferably the above ratio.

[0034] In the device described above, the heating mechanism (heating device) 8 is not particularly limited as long as it is capable of heating the film bubble approximately equally from the periphery in each section. For example, it may be a structure in which a cast-in heater, a rubber heater with high heat resistance specifications, or other planar heating elements are arranged on the back of a heat sink (for example, a metal plate such as an iron plate) arranged in an axisymmetric cross-sectional shape such as a circle or a polygon relative to the pulling axis of the film bubble 3. Alternatively, it may be a structure in which a planar heating element is arranged on the inner surface side of a heat insulating member arranged in an axisymmetric cross-sectional shape, or a structure in which a heat reflecting plate is arranged on the back of an axisymmetric columnar heating element. In addition, the internal dimensions of the heating mechanism 8 may be changed around the upper portion 3a of the cylinder and around the expanded diameter portion 3b.

[0035] As described above, the present invention controls the shape of the film bubble 3 by pulling the film while heating the periphery of the film bubble in a molten state, so that the time until solidification at the frost line F is longer than that without heating. For example, according to the method of the present invention, the time until the molten resin extruded from the die 2 solidifies at the frost line F can be set to 3 seconds or more, and can be set to 10 seconds or more depending on the situation. The upper limit of this time can be about 15 seconds.

[0036] In the method of the present invention, even when a large diameter film bubble is formed, the molecular orientation of the film can be controlled to a desired level. According to the present invention, for example, the height hf of the frost line F of the film bubble 3 can be set to 0.4 m or more or 1.0 m or more. However, if the frost line height hf is too large, the device will be large-scale, so it is appropriate to set the frost line height hf to about 3.0 m or less.

[0037] In the method of the present invention, the bubble diameter at the frost line can be set to 300 mm or more, for example, 1000 mm or more, and in some cases 3000 mm. From the perspective of actual device design, it is appropriate to set the bubble diameter to 3000 mm or less.

[0038] In the above-described method, a single-layer film composed of a thermoplastic liquid crystal polymer can be manufactured, but a molten laminate composed of a thermoplastic liquid crystal polymer and other resins or a thermoplastic liquid crystal polymer with different melting points can also be co-extruded from a die 2, and the laminated film can be formed according to the above-mentioned method for manufacturing a thermoplastic liquid crystal polymer film, and then the thermoplastic liquid crystal polymer film can be peeled off. In this case, for example, both sides of the laminated film of a three-layer structure can be thermoplastic liquid crystal polymer films, and after film formation, the laminated film can be peeled off from the core film. In this way, the productivity of the thermoplastic liquid crystal polymer film can be further improved.

[0039] (Thermoplastic Liquid Crystal Polymer)

[0040] The thermoplastic liquid crystal polymer used in the manufacturing method of the present invention is formed of a liquid crystal polymer that can be melt-formed. The thermoplastic liquid crystal polymer is a polymer that can form an optically anisotropic melt phase. As long as it is a liquid crystal polymer that can be melt-formed, there is no particular limitation on its chemical composition, for example, thermoplastic liquid crystal polyester or thermoplastic liquid crystal polyester amide into which amide bonds are introduced.

[0041] The thermoplastic liquid crystal polymer may be a polymer in which an imide bond, a carbonate bond, a carbodiimide bond, or a bond derived from isocyanate such as an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide.

[0042] As specific examples of the thermoplastic liquid crystal polymer used in the present invention, there can be listed well-known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides derived from the compounds classified as (1) to (4) and their derivatives exemplified below. However, it is self-evident that there is an appropriate range for the combination of various raw material compounds in order to form a polymer capable of forming an optically anisotropic melt phase.

[0043] (1) Aromatic or aliphatic diols (see Table 1 for representative examples)

[0044]

[0045] (2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for representative examples)

[0046]

[0047] (3) Aromatic hydroxycarboxylic acid (see Table 3 for representative examples)

[0048]

[0049] (4) Aromatic diamine, aromatic hydroxylamine or aromatic aminocarboxylic acid (see Table 4 for representative examples)

[0050]

[0051] As representative examples of thermoplastic liquid crystal polymers obtained from these raw material compounds, copolymers having the structural units shown in Tables 5 and 6 can be cited.

[0052]

[0053]

[0054] Among these copolymers, polymers containing at least p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as repeating units are preferred, and particularly preferred are (i) copolymers containing repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid or (ii) copolymers containing repeating units of at least one aromatic hydroxycarboxylic acid, at least one aromatic diol and at least one aromatic dicarboxylic acid selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

[0055] For example, in the copolymer of (i), when the thermoplastic liquid crystal polymer contains at least repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the molar ratio (A) / (B) of the repeating unit (A) of p-hydroxybenzoic acid to the repeating unit (B) of 6-hydroxy-2-naphthoic acid in the thermoplastic liquid crystal polymer is preferably (A) / (B) = about 10 / 90 to about 90 / 10, more preferably (A) / (B) = about 15 / 85 to about 85 / 15, and further preferably (A) / (B) = about 20 / 80 to about 80 / 20.

[0056] In the case of the copolymer of (ii), at least one aromatic hydroxycarboxylic acid (C) selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, at least one aromatic diol (D) selected from the group consisting of 4,4'-dihydroxybiphenyl, hydroquinone, phenylhydroquinone and 4,4'-dihydroxydiphenyl ether, and at least one aromatic dicarboxylic acid (E) selected from the group consisting of terephthalic acid, isophthalic acid and 2,6-naphthalene dicarboxylic acid, are contained in the thermoplastic liquid crystal polymer in an amount of at least 1:1. The molar ratio of the complex units can be aromatic hydroxycarboxylic acid (C): the above-mentioned aromatic diol (D): the above-mentioned aromatic dicarboxylic acid (E) = about (30 to 80): about (35 to 10): about (35 to 10), more preferably (C): (D): (E) = about (35 to 75): about (32.5 to 12.5): about (32.5 to 12.5), and further preferably (C): (D): (E) = about (40 to 70): about (30 to 15): about (30 to 15).

[0057] In addition, the molar ratio of the repeating unit derived from 6-hydroxy-2-naphthoic acid in the aromatic hydroxycarboxylic acid (C) may be, for example, 85 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more. The molar ratio of the repeating unit derived from 2,6-naphthalenedicarboxylic acid in the aromatic dicarboxylic acid (E) may be, for example, 85 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more.

[0058] In addition, the aromatic diol (D) may be repeating units (D1) and (D2) derived from two different aromatic diols selected from the group consisting of hydroquinone, 4,4'-dihydroxybiphenyl, phenylhydroquinone and 4,4'-dihydroxydiphenyl ether. In this case, the molar ratio of the two aromatic diols may be (D1) / (D2)=23 / 77 to 77 / 23, more preferably 25 / 75 to 75 / 25, and even more preferably 30 / 70 to 70 / 30.

[0059] The molar ratio of the repeating structural unit derived from the aromatic diol to the repeating structural unit derived from the aromatic dicarboxylic acid is preferably (D) / (E) = 95 / 100 to 100 / 95. Outside this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

[0060] It should be noted that the molten phase capable of forming optical anisotropy in the present invention can be identified by, for example, placing a sample on a hot stage, heating it at elevated temperatures in a nitrogen atmosphere, and observing the transmitted light of the sample.

[0061] As a thermoplastic liquid crystal polymer, a thermoplastic liquid crystal polymer having a melting point (hereinafter referred to as Tm0) in the range of, for example, 200 to 360°C is preferred, a thermoplastic liquid crystal polymer having a melting point (hereinafter referred to as Tm0) in the range of 240 to 350°C is preferred, and a thermoplastic liquid crystal polymer having a Tm0 of 260 to 330°C is further preferred. It should be noted that the melting point can be obtained by observing the thermal behavior of a thermoplastic liquid crystal polymer sample using a differential scanning calorimeter. That is, the thermoplastic liquid crystal polymer sample is heated at a rate of 10°C / min to completely melt it, then the melt is cooled to 50°C at a rate of 10°C / min, and the position of the endothermic peak that appears after heating again at a rate of 10°C / min is used as the melting point of the thermoplastic liquid crystal polymer sample to obtain.

[0062] To the above-mentioned thermoplastic liquid crystal polymer, thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyetheretherketone, fluororesin, various additives, fillers, etc. may be added within the range not impairing the effects of the present invention.

[0063] (Thermoplastic Liquid Crystal Polymer Film)

[0064] When such a resin is extruded by inflation molding, a cylindrical sheet melt-extruded from an annular die can be stretched at a predetermined stretch ratio (equivalent to the stretch ratio in the MD direction) and inflation ratio (equivalent to the stretch ratio in the TD direction) to form a film.

[0065] Regarding the stretch ratio of such extrusion molding, the stretch ratio (or stretch ratio) in the MD direction may be, for example, about 1.0 to about 10, preferably about 1.2 to about 7, and more preferably about 1.3 to about 7. In addition, the stretch ratio (or blow-up ratio) in the TD direction may be, for example, about 1.5 to about 20, preferably about 2 to about 15, and more preferably about 2.5 to about 14. According to the method of the present invention, by forming the blown film while heating the periphery of the molten film bubble, it is possible to control the stretch ratio and blow-up ratio based on the desired stretch ratio and blow-up ratio.

[0066] By manufacturing a thermoplastic liquid crystal polymer film using the method of the present invention, the molecular orientation ratio SOR of the liquid crystal polymer film can be controlled in the range of 0.8 to 1.5. The molecular orientation ratio SOR is preferably 0.9 to 1.3, more preferably 1.0 to 1.2, and particularly preferably 1.0 to 1.1. Here, the molecular orientation ratio SOR (Segment Orientation Ratio) refers to an index providing the degree of molecular orientation of the segments constituting the molecule, and is a value that takes into account the thickness of the object.

[0067] In the measurement of molecular orientation, a liquid crystal polymer film is inserted into a microwave resonance waveguide in a microwave molecular orientation measuring machine in such a way that the film surface is perpendicular to the direction of travel of microwaves, and the electric field intensity (microwave transmission intensity) of microwaves passing through the film is measured. Then, based on the measured value, the m value (referred to as the refractive index) is calculated by the following formula.

[0068]

[0069] Here, Z o is the device constant, △z is the average thickness of the object, νmax is the vibration frequency that provides the maximum microwave transmission intensity when the microwave vibration frequency is changed, ν o The vibration frequency that provides the maximum microwave transmission intensity when the average thickness is zero (i.e. when there is no object).

[0070] Next, the value of m when the rotation angle of the object relative to the microwave vibration direction is 0°, that is, the microwave vibration direction coincides with the direction in which the molecules of the object are most oriented, that is, the direction that provides the minimum microwave transmission intensity, is set as m0, and the value of m when the rotation angle is 90° is set as m 90 , through m0 / m 90 The molecular orientation SOR was calculated.

[0071] If necessary, a known or customary heat treatment may be performed to adjust the melting point and / or thermal expansion coefficient of the thermoplastic liquid crystal polymer film. The heat treatment conditions may be appropriately set according to the purpose. For example, the melting point (Tm) of the thermoplastic liquid crystal polymer film may be increased by heating for several hours at a temperature of (Tm0-10)°C or higher (e.g., about (Tm0-10) to (Tm0+30)°C, preferably about (Tm0) to (Tm0+20)°C) relative to the melting point (Tm0) of the thermoplastic liquid crystal polymer.

[0072] The melting point (Tm) of the TLCP film may be, for example, 270 to 380° C., preferably 280 to 370° C. The melting point (Tm) of the TLCP film can be determined using a differential scanning calorimeter, similar to the melting point Tm0 of the TLCP.

[0073] The thickness of the TLCP film can be appropriately set depending on the application, and for example, in consideration of the material used for the insulating layer of the multilayer circuit board, it can be 10 to 500 μm, preferably 15 to 250 μm, and more preferably 25 to 180 μm.

[0074] Example

[0075] use Figure 2 The blown film manufacturing device shown in the figure, for thermoplastic liquid crystal polymers with different melting points, in the comparative example, the blown film is produced while performing one-stage temperature control or only keeping warm without heating, and in the embodiment, the blown film is produced while performing two-stage or three-stage temperature control. As a mold, a mold with a die lip diameter of 200 mm is used. The conditions of each embodiment and comparative example are shown below. In the table, hf / ht is the ratio of the frost line height hf to the height ht to the upper end of the heating mechanism 8, and hf / hm is the ratio of the frost line height hf to the length (height direction length) hm of the heating area of ​​the molten film bubble.

[0076]

[0077] According to the method of the present invention, in Examples 1 to 3 in which the blown film was produced while heating in a state where the ratio hf / ht of the height hf from the die outlet to the frost line to the height ht from the die outlet to the upper end of the heating mechanism was 50% or more and 100% or less, a film with a well-controlled molecular orientation and no wrinkles in appearance was obtained. On the other hand, in Comparative Example 1, the molten film bubble was surrounded by an insulating material and kept warm, but the frost line height hf was reduced, and the film bubble drooped and contacted the air ring, and the film failed to be pulled. In Comparative Example 2, the heated portion of the molten film bubble was short, the SOR was outside the expected value range, and wrinkles were formed in appearance, and a good film was not obtained.

[0078] Industrial Applicability

[0079] According to the present invention, when a thermoplastic liquid crystal polymer film is inflation-molded, even a large-diameter bubble has no wrinkles, and a film with controlled molecular orientation can be produced, thereby improving the productivity of thermoplastic liquid crystal polymer films used in applications such as insulating substrates of electronic devices.

[0080] As described above, the preferred embodiments of the present invention have been described, but those skilled in the art can easily conceive of various changes and modifications within an obvious range by referring to the present application specification. Therefore, such changes and modifications are interpreted as being within the scope of the invention defined by the claims.

[0081] Explanation of symbols

[0082] 1. Extrusion mechanism (extruder)

[0083] 2 Ring mold

[0084] 2a Die lip

[0085] 2b Blowing mouth

[0086] 3 membrane bubble

[0087] 4 Guide Plate

[0088] 5 Pinch Rollers

[0089] 6 Winding mechanism

[0090] 7 Wind Ring

[0091] 8Heating mechanism

Claims

1. A method for producing a thermoplastic liquid crystal polymer film, which is a method for producing a thermoplastic liquid crystal polymer film using an inflation film method, wherein a liquid crystal polymer that exhibits optical anisotropy when melted (hereinafter referred to as a thermoplastic liquid crystal polymer) is melt-extruded from a ring-shaped die into a tubular shape, a gas is supplied into the inner space of the tubular melt while cooling the tubular melt to expand the tubular melt, thereby forming a film bubble, and the film bubble is pulled while closing the film bubble into a sheet shape. The method for producing the thermoplastic liquid crystal polymer film is characterized in that: The bubble is heated by a heating mechanism disposed on the outer peripheral side of the bubble forming region, thereby pulling the bubble while heating it in a state where the ratio hf / ht of the height hf from the outlet of the mold to the frost line of the bubble to the height ht from the outlet of the mold to the upper end of the heating mechanism is greater than 50% and less than 100%, A thermoplastic liquid crystal polymer film having a molecular orientation ratio SOR of 0.8 to 1.5 is produced.

2. The method for producing a thermoplastic liquid crystal polymer film according to claim 1, wherein: The heating mechanism is divided into at least two sections in the height direction, and temperature control is performed in each section.

3. The method for producing a thermoplastic liquid crystal polymer film according to claim 1 or 2, wherein: The time from when the thermoplastic liquid crystal polymer is extruded from the die to when it is solidified at the frost line is set to 3 seconds or more.

4. The method for producing a thermoplastic liquid crystal polymer film according to claim 1 or 2, wherein: The height hf from the outlet of the die to the frost line of the bubble is set to be greater than or equal to 0.4 m and less than or equal to 3.0 m.

5. The method for producing a thermoplastic liquid crystal polymer film according to claim 1 or 2, wherein: The bubble diameter of the frost line of the film bubble is set to be 300 mm or more.

6. The method for producing a thermoplastic liquid crystal polymer film according to claim 1 or 2, wherein: A laminate of two or more thermoplastic resin layers including a layer composed of the thermoplastic liquid crystal polymer is coextruded from the die to form a bubble composed of the laminate, and the bubble is pulled to produce a laminate film, and the thermoplastic liquid crystal polymer film is peeled off from the laminate film.

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