Liquid crystal polymer film stretching 3-layer film, stretching 3-layer film, and stretching liquid crystal polymer film, and methods of making the same

Abstract

The present application relates to a 3-layer film for stretching a liquid crystal polymer film, a stretched 3-layer film, and a stretched liquid crystal polymer film, and a method for manufacturing the same. A 3-layer film for stretching a liquid crystal polymer film is provided, which comprises a liquid crystal polymer film, and a pair of support films laminated on both surfaces of the liquid crystal polymer film, wherein the total value of the yield load of the pair of support films is greater than the yield load of the liquid crystal polymer film at any temperature within a range of a temperature T1 or higher and a temperature T2 or lower, the temperature T1 is the glass transition temperature of a liquid crystal polymer constituting the liquid crystal polymer film, and the temperature T2 is the lower of either the melting point of the liquid crystal polymer or the melting point of a polymer constituting the support film minus 20°C.

Description

Technical Field

[0001] This invention relates to a three-layer film for stretching liquid crystal polymer films, stretching a three-layer film, stretching a liquid crystal polymer film, and methods for manufacturing the same. Background Technology

[0002] Liquid crystal polymer (LCP) films are known for their excellent heat resistance, low water absorption, and small dimensional change rate, making them suitable for use in flexible printed circuit boards (PCBs) in 5G mobile communication systems, among other applications. However, LCPs exhibit a tendency for molecular orientation along their flow direction. In melt extrusion, a common method for film manufacturing, the polymer is melted and extruded through a die to form a film. Therefore, the LCPs in films manufactured by this method exhibit molecular orientation along the length of the film, resulting in anisotropy in properties such as dielectric constant and coefficient of linear expansion depending on the film's orientation. This makes them unsuitable for use in flexible printed circuit boards. Typically, stretching the film in a direction perpendicular to its molecular orientation at temperatures below its melting point eliminates this anisotropy. However, LCP films extruded from a die exhibit significantly low tensile strength, particularly in the direction perpendicular to the molecular orientation. Consequently, they are prone to breakage when stretched in this direction at temperatures below the melting point of the LCP. As a manufacturing method to reduce the anisotropy of such liquid crystal polymer films, a known method is to stretch a laminate formed by stacking thermoplastic resin films on a liquid crystal polymer film above the melting point of the liquid crystal polymer, cool the laminate, and then peel off the thermoplastic resin films to manufacture the liquid crystal polymer film (e.g., Patent Document 1). Another known method is to form a co-extruded film consisting of three layers, with the intermediate layer being a liquid crystal polymer layer, and then peel off the two outer layers from the intermediate layer and stretch it to manufacture the film (e.g., Patent Document 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 3659721

[0006] Patent Document 2: International Publication No. 2022 / 124308 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, as in the method of Patent Document 1, there is a concern that the surface smoothness of the film may be impaired due to melting when stretching is performed in the molten state. In the method of Patent Document 2, although the liquid crystal polymer is stretched at a temperature below its melting point, the stretching ratio is less than 2 times, and the resulting liquid crystal polymer film cannot eliminate the anisotropy of physical properties.

[0009] The object of the present invention is to provide: a three-layer film for stretching liquid crystal polymer films that can be manufactured by stretching at a temperature below the melting point, thereby reducing anisotropy of the liquid crystal polymer film, and a method for manufacturing a three-layer film for stretching liquid crystal polymer films.

[0010] Solution for solving the problem

[0011] The inventors conducted in-depth research on the manufacture of liquid crystal polymer films with reduced anisotropy, and found that the above-mentioned problem could be achieved by stacking a three-layer film for stretching a liquid crystal polymer film, which has a yield load within a specified range in a temperature range above T1 (the glass transition temperature of the liquid crystal polymer) and below T2 (the melting point of the liquid crystal polymer and the melting point of the polymer constituting the support film at -20°C). Thus, the present invention was completed.

[0012] [1] That is, according to the first aspect of the present invention, a three-layer film for stretching a liquid crystal polymer film is provided, comprising: a liquid crystal polymer film, and a pair of support films stacked on both sides of the liquid crystal polymer film, wherein at any temperature in the range of temperature T1 above and temperature T2 below, the total value of the yield load of the pair of support films is greater than the yield load of the liquid crystal polymer film, wherein the aforementioned temperature T1 is the glass transition temperature of the liquid crystal polymer constituting the liquid crystal polymer film, and the aforementioned temperature T2 is either the melting point of the liquid crystal polymer or the melting point of the polymer constituting the support film at -20°C, which is lower than either temperature.

[0013] [2] According to a second aspect of the present invention, a three-layer film for stretching the liquid crystal polymer film of aspect 1 is provided, wherein, at any temperature within the range of the aforementioned temperature T1 above and the aforementioned temperature T2 below, the total value of the maximum point load of a pair of the aforementioned support films is greater than the maximum point load of the aforementioned liquid crystal polymer film.

[0014] [3] According to embodiment 3 of the present invention, a three-layer film for stretching liquid crystal polymer film according to embodiment 1 or 2 is provided, wherein, at any temperature within the range of the aforementioned temperature T1 above and the aforementioned temperature T2 below, the elongation at break of at least one of the aforementioned support films is 200% or more.

[0015] [4] According to embodiment 4 of the present invention, a three-layer film for stretching a liquid crystal polymer film according to any one of embodiments 1 to 3 is provided, wherein the aforementioned three-layer film for stretching a liquid crystal polymer film is wound around a cylinder with an outer diameter of 84.2 mm in a manner that the surface of the aforementioned support film is in contact with the cylinder, and the cylinder is deformed at a winding angle of 90° or more, and then the aforementioned three-layer film for stretching a liquid crystal polymer film is wound around the cylinder in a manner that the surface of the aforementioned support film is in contact with the cylinder, and the cylinder is deformed at a winding angle of 90° or more, and there is no peeling between the aforementioned liquid crystal polymer film and the aforementioned support film.

[0016] [5] According to embodiment 5 of the present invention, a three-layer film for stretching a liquid crystal polymer film according to any one of embodiments 1 to 3 is provided, wherein the aforementioned support film is composed of a crystalline resin.

[0017] [6] According to embodiment 6 of the present invention, a three-layer film for stretching a liquid crystal polymer film according to any one of embodiments 1 to 5 is provided, wherein the aforementioned support film is composed of aromatic polyetherketone or polyester.

[0018] [7] According to embodiment 7 of the present invention, a three-layer film for stretching a liquid crystal polymer film according to any one of embodiments 1 to 6 is provided, wherein the thickness of the aforementioned support film is 5 to 300 μm.

[0019] [8] According to Embodiment 8 of the present invention, a method for manufacturing a three-layer film for stretching a liquid crystal polymer film is provided, which is the method for manufacturing a three-layer film for stretching a liquid crystal polymer film according to any one of Embodiments 1 to 7.

[0020] The manufacturing method includes the following steps: stacking a pair of the aforementioned support films on both sides of the aforementioned liquid crystal polymer film using a pressure lamination method or a thermal lamination method.

[0021] [9] According to embodiment 9 of the present invention, a method for manufacturing a three-layer film for stretching a liquid crystal polymer film is provided, which is the method for manufacturing a three-layer film for stretching a liquid crystal polymer film described in embodiment 8, wherein, before the process of stacking the liquid crystal polymer film and the support film, the following process is provided: a process of performing surface treatment on both sides of the liquid crystal polymer film and the surface of the support film that is bonded to the liquid crystal polymer film.

[0022]

[10] According to embodiment 10 of the present invention, a method for manufacturing a three-layer film for stretching a liquid crystal polymer film is provided, which is the method for manufacturing a three-layer film for stretching a liquid crystal polymer film described in embodiment 9, wherein the aforementioned surface treatment is any one of plasma treatment, corona treatment, or chemical conversion treatment.

[0023]

[11] According to Embodiment 11 of the present invention, a method for manufacturing a three-layer film for stretching a liquid crystal polymer film is provided, which is the method for manufacturing a three-layer film for stretching a liquid crystal polymer film according to any one of Embodiments 1 to 7, wherein the manufacturing method manufactures the aforementioned three-layer film for stretching a liquid crystal polymer film by melt extrusion.

[0024]

[12] According to embodiment 12 of the present invention, a method for manufacturing a stretched 3-layer film is provided, comprising the following steps: stretching the 3-layer film for stretching the liquid crystal polymer film as described in any one of embodiments 1 to 7 by at least 2.0 to 5.0 times along the TD direction in a temperature range above the glass transition temperature of the liquid crystal polymer and below the melting point of the liquid crystal polymer.

[0025]

[13] According to embodiment 13 of the present invention, a method for manufacturing a stretched three-layer film is provided, which is the method for manufacturing a stretched three-layer film described in embodiment 12, wherein, after the step of stretching the aforementioned liquid crystal polymer film with a stretched three-layer film, the method further comprises the following step: performing heat treatment in a temperature range above the glass transition temperature of the aforementioned liquid crystal polymer and below the melting point of the aforementioned liquid crystal polymer.

[0026]

[14] According to embodiment 14 of the present invention, a method for manufacturing a stretched liquid crystal polymer film is provided, comprising the step of peeling the aforementioned support film from a stretched three-layer film manufactured by the method for manufacturing a stretched three-layer film as described in embodiment 12 or 13.

[0027]

[15] According to embodiment 15 of the present invention, a method for manufacturing a stretched liquid crystal polymer film is provided, comprising the following steps: a step of peeling the aforementioned support film from a stretched three-layer liquid crystal polymer film manufactured by the method for manufacturing a stretched three-layer film according to embodiment 12; and a step of performing heat treatment in a temperature range above the glass transition temperature of the aforementioned liquid crystal polymer and below the melting point of the aforementioned liquid crystal polymer.

[0028]

[16] According to embodiment 16 of the present invention, a stretched three-layer film is obtained by stretching a liquid crystal polymer film stretched by a three-layer film stretching method according to any one of embodiments 1 to 7.

[0029] Regarding the fracture loads measured in two directions on the stretched liquid crystal polymer film obtained by peeling off the aforementioned support film, the ratio of the larger fracture load to the smaller fracture load is 6 or less.

[0030]

[17] According to embodiment 17 of the present invention, a stretched liquid crystal polymer film is provided, which is a stretched liquid crystal polymer film manufactured by the manufacturing method of stretched liquid crystal polymer film described in embodiment 14 or 15.

[0031] Regarding the fracture loads measured in two directions for the aforementioned stretched liquid crystal polymer film, the ratio of the larger fracture load to the smaller fracture load is 6 or less.

[0032]

[18] According to embodiment 18 of the present invention, a stretched liquid crystal polymer film is provided, which is the stretched liquid crystal polymer film described in embodiment 17, wherein the melting point of the stretched liquid crystal polymer film is above the melting point of the liquid crystal polymer film before stretching.

[0033] The effects of the invention

[0034] The three-layer film for stretching liquid crystal polymer films according to the present invention can be used to manufacture stretched liquid crystal polymer films with reduced anisotropy. Attached Figure Description

[0035] Figure 1 The schematic diagram illustrating the evaluation method of the adhesion force between the liquid crystal polymer film and the support film of the three-layer film for stretching the liquid crystal polymer film in the embodiment is a cross-sectional view of the three-layer film for stretching the liquid crystal polymer film and a 3-inch core.

[0036] Figure 2 A graph showing the results of the viscoelasticity test of the liquid crystal polymer film used in Example 1.

[0037] Figure 3 A graph showing the SS curves of the liquid crystal polymer film and the support film used in Example 4, obtained from a tensile test.

[0038] Figure 4 A graph showing the SS curves of the liquid crystal polymer film and the support film used in Comparative Example 4, obtained from the tensile test.

[0039] Explanation of reference numerals in the attached figures

[0040] 10…Three-layer film for stretching liquid crystal polymer films

[0041] 11, 12...end

[0042] 21, 22… Supporting film

[0043] 30…Liquid Crystal Polymer Film

[0044] 50…3-inch core

[0045] 51…Central Axis Detailed Implementation

[0046] <Three-layer film for stretching liquid crystal polymer films>

[0047] The three-layer film for stretching liquid crystal polymer films of the present invention comprises a liquid crystal polymer film and a pair of support films stacked on both sides of the liquid crystal polymer film. The three-layer film for stretching liquid crystal polymer films of the present invention is used to manufacture stretched liquid crystal polymer films by stretching the film and then peeling off the support films from the liquid crystal polymer film.

[0048] <Liquid Crystal Polymer Thin Film>

[0049] The liquid crystal polymer film used in this embodiment is a film formed from a liquid crystal polymer. There are no particular limitations on the liquid crystal polymer, but a thermotropic liquid crystal polyester is preferred. Examples of such liquid crystal polyesters include aromatic polyesters synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids, which exhibit liquid crystal properties when melted. Specifically, examples include condensation polymers of polyethylene terephthalate and p-hydroxybenzoic acid, condensation polymers of phenol and phthalic acid with p-hydroxybenzoic acid, and condensation polymers of hydroxynaphthoic acid and p-hydroxybenzoic acid. Particularly from the viewpoint of superior mechanical properties, electrical properties, and heat resistance, aromatic polyester-based liquid crystal polymers with 6-hydroxy-2-naphthoic acid and its derivatives as the basic structure, and having at least one monomer component selected from the group consisting of p-hydroxybenzoic acid, terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenyl, bisphenol A, hydroquinone, 4,4-dihydroxybiphenyl, polyethylene terephthalate, and their derivatives. It should be noted that liquid crystal polyesters can be used alone, or in any combination and ratio of two or more types.

[0050] The synthesis of liquid crystal polyesters can be carried out using well-known methods without particular limitations, such as melt polymerization, melt acid hydrolysis, and slurry polymerization. When using these polymerization methods, acylation and even acetylation can be performed according to conventional methods.

[0051] The liquid crystal polymer may also include, without excessively impairing the effects of the present invention, polymers such as fluororesins, polyolefins, polycyclic olefins, polyetherimides, and organosilicon-modified polyetherimides; release agents such as higher fatty acids with 10-25 carbon atoms, higher fatty acid esters, higher fatty acid amides, and higher fatty acid metal salts; chain extenders such as aliphatic carbodiimides, alicyclic carbodiimides, and aromatic carbodiimides; colorants such as dyes, pigments, and carbon black; organic fillers; inorganic fillers; hollow particles; antioxidants; heat stabilizers; light stabilizers; ultraviolet absorbers; flame retardants; lubricants; antistatic agents; surfactants; rust inhibitors; foaming agents; defoamers; and fluorescent agents. These polymers and additives can be included in the molten resin composition during the liquid crystal polymer film forming process. Furthermore, these polymers and additives can be used individually or in combination of two or more. The content of polymers and additives is not particularly limited, but from the viewpoint of processability and thermal stability, it is preferably 0.01 to 50% by mass, more preferably 0.1 to 40% by mass, and even more preferably 0.5 to 30% by mass relative to the total amount of the liquid crystal polymer film. These polymers and additives may be added to the liquid crystal polymer in advance, or they may be added to the liquid crystal polymer when forming the stretched liquid crystal polymer film described later.

[0052] Liquid crystal polymer films can be manufactured using known methods. For example, a liquid crystal polymer film can be formed by forming a film using a T-die melt extrusion method. Specifically, a liquid crystal polymer film can be obtained by melt-mixing the liquid crystal polymer in an extruder, extruding the molten resin through a T-die, and curing it on a metal roller. In the case of curing on a metal roller, contact molding based on a rubber roller or a metal roller can also be used. The temperature of the extruder barrel is preferably 230–360°C, more preferably 280–350°C. The slit spacing of the T-die can be appropriately set according to the type and composition of the liquid crystal polymer used, the properties of the target film, etc. The slit spacing of the T-die is not particularly limited, but is preferably 0.1–1.5 mm, more preferably 0.3–1.0 mm.

[0053] The thickness of the liquid crystal polymer film obtained by the above method is not particularly limited. From the viewpoint of operability and productivity during T-die melt extrusion molding, it is preferred to be 10-500 μm, more preferably 20-300 μm, and even more preferably 30-250 μm.

[0054] The melting point of the liquid crystal polymer constituting the liquid crystal polymer film is preferably 250–380°C, more preferably 280–350°C. Furthermore, the glass transition temperature of the liquid crystal polymer constituting the liquid crystal polymer film is preferably 90–150°C, more preferably 100–120°C.

[0055] <Supporting Thin Film>

[0056] The support film is a polymer film laminated on a liquid crystal polymer film to prevent the liquid crystal polymer film from breaking when stretched. As the support polymer constituting the support film, a crystalline resin is preferably used, such as aromatic polyetherketone (PEK) or polyester. Specific examples of aromatic polyetherketones include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and polyetheretherketoneketone (PEEKK). Specific examples of polyesters include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT). These polymers can be used alone or in combination of two or more. Furthermore, in terms of high heat resistance and the ability to be stretched at high temperatures, these films are preferably crystalline or stretched films. As described later, the polymer used as the support film is preferably selected based on characteristics that satisfy the yield load and maximum point load characteristics compared to the liquid crystal polymer, as well as the specified elongation at break characteristics.

[0057] The thickness of the supporting film is preferably 5 to 300 μm, more preferably 15 to 100 μm.

[0058] The supporting film used in this invention has the following characteristic: At any temperature within the range of T1 above and T2 below, the total yield load of a pair of supporting films becomes greater than the yield load of the liquid crystal polymer film. Here, T1 is the glass transition temperature of the liquid crystal polymer, and T2 is either the melting point of the liquid crystal polymer or a temperature 20°C lower than the melting point of the polymer constituting the supporting film (a temperature 20°C lower than the melting point of the polymer constituting the supporting film). Therefore, as described later, the three-layer film for stretching the liquid crystal polymer film of this invention can be stretched at a temperature below the melting point of the liquid crystal polymer film and at a stretching ratio of more than twice, thereby producing a stretched liquid crystal polymer film with low anisotropy.

[0059] It is generally believed that when stretching a laminate of a liquid crystal polymer film and a supporting film at temperatures below the melting point of the liquid crystal polymer, stress concentration occurs in the liquid crystal polymer film, leading to fracture. In tensile tests on liquid crystal polymer films, the SS curve obtained by setting the horizontal axis to elongation and the vertical axis to load shows a decreasing shape as the elongation increases and the load decreases (see reference). Figure 3This is believed to be due to the thinning effect caused by stretching, resulting in sections with low strength. Furthermore, it is argued that tensile stress concentrates in these sections, making them even more susceptible to stretching, thus failing to eliminate the thickness unevenness of the liquid crystal polymer film and leading to breakage from the thinned sections. To avoid this problem, in the existing liquid crystal polymer film manufacturing technology shown in Patent Document 1, the liquid crystal polymer is typically stretched at a temperature above its melting point, while the liquid crystal polymer is in a molten state.

[0060] In contrast, the three-layer film for stretching liquid crystal polymer films of the present invention satisfies the above-mentioned condition by satisfying the relationship between the yield load of the support film and the yield load of the liquid crystal polymer, thereby allowing stretching at a temperature below the melting point of the liquid crystal polymer and a stretching ratio of more than twice. In the present invention, the reason why the liquid crystal polymer film can be stretched at a temperature below its melting point by satisfying the above-mentioned relationship between the yield load of the liquid crystal polymer film and the support film is not clear, but it is considered as follows. Here, we consider the case where temperature T2 is the melting point of the liquid crystal polymer, that is, the melting point of the liquid crystal polymer is lower than the melting point of the polymer constituting the support film by -20°C. First, the three-layer film for stretching liquid crystal polymer films of the present invention is heated within a temperature range (e.g., 150–280°C) above the glass transition temperature of the liquid crystal polymer and below its melting point, thereby causing the elastic modulus of the liquid crystal polymer to be lower than 1000 MPa, resulting in a soft portion in the liquid crystal polymer film. In this invention, support films are disposed on both sides of the liquid crystal polymer film. Within a temperature range above the glass transition temperature and below the melting point of the liquid crystal polymer, the total yield load of the pair of support films is higher than the yield load of the liquid crystal polymer film. Therefore, the tensile load applied when stretching the liquid crystal polymer film using three layers of film is supported by the support films. Thus, even if a portion of the liquid crystal polymer film is stretched and becomes thinner, the concentration of tensile stress in the portion with reduced load can be suppressed. Furthermore, the support films are closely bonded to the liquid crystal polymer film, so that as the support films are stretched, the tensile force is applied equally to the liquid crystal polymer film through the interface with the liquid crystal polymer film. Based on the above, it is believed that the liquid crystal film can be stretched without breaking. It should be noted that the same reasoning applies when temperature T2 is 20°C below the melting point of the polymer constituting the support films, i.e., when the temperature 20°C below the melting point of the polymer constituting the support films is lower than the melting point of the liquid crystal polymer.

[0061] Furthermore, the SS curve obtained by tensile testing of the supporting film used in this invention exhibits an upward shape where stress increases with increasing elongation (see reference). Figure 3The load tends to increase with stretching. Therefore, when stretching a three-layer film for liquid crystal polymer film stretching, the load on the thinner portion of the support film increases, and the tensile stress applied to the support film preferentially acts on the thicker portion (the unstretched portion) of the support film, resulting in the support film being stretched uniformly as a whole. Therefore, in the three-layer film for liquid crystal polymer film stretching of the present invention, by tightly bonding the support film to both sides of the liquid crystal polymer film, when stretching the three-layer film for liquid crystal polymer film stretching, the liquid crystal polymer film is stretched uniformly as the support film is stretched uniformly, thus enabling the obtained stretched liquid crystal polymer film to have a uniform thickness.

[0062] It should be noted that, preferably, the total yield load of the pair of support films over the entire temperature range above T1 and below T2 is greater than the yield load of the liquid crystal polymer film. When T2 is the melting point of the liquid crystal polymer, i.e., when the melting point of the liquid crystal polymer is -20°C lower than the melting point of the polymer constituting the support film, for example, it is preferable that the total yield load of the pair of support films over the entire temperature range of 150 to 280°C is greater than the yield load of the liquid crystal polymer film. Furthermore, when T2 is the melting point of the polymer constituting the support film -20°C, i.e., when the melting point of the polymer constituting the support film is -20°C lower than the melting point of the liquid crystal polymer, for example, it is preferable that the total yield load of the pair of support films over the entire temperature range of 150 to 260°C is greater than the yield load of the liquid crystal polymer film. However, the above relationship may not necessarily be satisfied over the entire temperature range above T1 and below T2. For example, when stretching a three-layer film for stretching a liquid crystal polymer film at a temperature above T1 and below T2, the yield load of the liquid crystal polymer film and the supporting film measured at that specific temperature can satisfy the above relationship.

[0063] Furthermore, the support film used in this invention preferably has the following characteristic: Preferably, at any temperature within the range of temperature T1 above and temperature T2 below, the total value of the maximum point load of a pair of support films becomes greater than the maximum point load of the liquid crystal polymer film. Therefore, as described later, the three-layer film for stretching the liquid crystal polymer film of this invention can be stretched at a temperature below the melting point of the liquid crystal polymer film, thereby enabling the manufacture of a stretched liquid crystal polymer film with low anisotropy.

[0064] Furthermore, the supporting film used in this invention preferably has an elongation at break of 200% or more within a temperature range of T1 above and T2 below. It should be noted that at least one of the two supporting films stacked on the liquid crystal polymer film needs to have an elongation at break of 200% or more. Therefore, as described later, the three-layer film for stretching the liquid crystal polymer film of this invention can be stretched at a temperature below the melting point of the liquid crystal polymer film, thereby producing a stretched liquid crystal polymer film with low anisotropy.

[0065] The yield load, maximum point load, and elongation at break of the supporting membrane can be determined as follows: A tensile test is performed on the supporting membrane to obtain the SS curve with the longitudinal axis set as stress and the transverse axis as elongation. The values ​​can be determined from the obtained SS curve.

[0066] <Method for manufacturing three-layer films for stretching liquid crystal polymer films>

[0067] The three-layer film for stretching liquid crystal polymer film of the present invention can be manufactured by laminating the liquid crystal polymer film with the first support film and the second support film according to the pressure lamination method or the hot lamination method.

[0068] In the hot lamination process, the liquid crystal polymer film and the support film are heated using a pair of heated rollers while being pressed together. The conditions in the hot lamination process can be appropriately selected based on the physical properties of the liquid crystal polymer and the support polymer. There are no particular limitations, but it is preferable to perform heating and pressing at a temperature near the melting point of both the liquid crystal polymer and the support polymer.

[0069] In the pressure lamination method, surface treatments such as plasma treatment are applied to the bonding surfaces of the liquid crystal polymer and the supporting polymer to improve adhesion. Following this, the films are rolled to bond the liquid crystal polymer film and the supporting film. The conditions in the pressure lamination method can be appropriately selected based on the physical properties of the liquid crystal polymer and the supporting polymer.

[0070] In a method for manufacturing a three-layer film for stretching a liquid crystal polymer film, before the step of laminating the liquid crystal polymer film with the first and second support films, it is preferable to perform surface treatment on the surface of the liquid crystal polymer film that contacts the support film (adhesion surface) and the surface of the support film that contacts the liquid crystal polymer film (adhesion surface). Examples of surface treatment methods include: plasma treatment by irradiating the surface with a gas that forms a plasma state by providing electrical energy; corona treatment by activating the surface through discharge; activation by irradiating the surface with ultraviolet light or an electron beam; activation by contacting the surface with a flame; chemical conversion treatment by oxidizing the surface with potassium dichromate or the like; and pretreatment agent treatment by applying a pretreatment agent. By performing this surface treatment before bonding the liquid crystal polymer film and the support film, the adhesion between the liquid crystal polymer film and the support film can be improved. The surface treatment method can be appropriately selected based on the physical properties of the liquid crystal polymer and the support polymer. From the viewpoint of improving the adhesion between the liquid crystal polymer film and the support film and reducing the damage to the stretched liquid crystal polymer film obtained by stretching the liquid crystal polymer film into a three-layer film, plasma treatment, corona treatment, and chemical conversion treatment are preferred, with plasma treatment being particularly preferred.

[0071] As described above, a three-layer film for stretching liquid crystal polymer films according to the present invention can be obtained.

[0072] It should be noted that in the above method, a three-layer film for stretching a liquid crystal polymer film is obtained by stacking a film formed of a liquid crystal polymer and a film formed of a supporting polymer. However, the method for obtaining a three-layer film for stretching a liquid crystal polymer film is not particularly limited to this. For example, a three-layer film for stretching a liquid crystal polymer film can be formed by melt extrusion, in which the liquid crystal polymer is melted in a first extruder and the supporting polymer is melted in a second extruder, and the polymers are extruded into a film by stacking the supporting polymer layer on one or both sides of the liquid crystal polymer layer. It should be noted that the same polymer constituting the supporting film can be used as the supporting polymer.

[0073] As a method for laminating a layer of supporting polymer onto one or both sides of a layer formed of liquid crystal polymer, a multilayer extrusion film forming method from a T-die can be used. Specifically, examples include: a feedhead method where molten liquid crystal polymer and supporting polymer supplied from two extruders are fed to a feedhead and merged, then extruded into a film shape from a T-die; and a multi-Manifold method where molten liquid crystal polymer and supporting polymer are separately fed to a T-die, overlapped into a film shape, and extruded. From the viewpoint of improving the smoothness of the obtained stretched liquid crystal polymer film, considering the differences in viscosity and flow characteristics of the liquid crystal polymer and supporting polymer during melting, the multi-Manifold method is preferred.

[0074] <Methods for manufacturing stretched three-layer films and stretched liquid crystal polymer films>

[0075] The stretched three-layer film and stretched liquid crystal polymer film of the present invention can be manufactured according to the following methods.

[0076] First, the liquid crystal polymer film obtained by the above method is stretched into a three-layer film along the width direction (TD direction) to obtain a stretched three-layer film. Stretching the laminated film along the width direction reduces the anisotropy of the resulting stretched liquid crystal polymer film. The method for stretching the laminated film is not particularly limited, but a tenter frame transverse stretching method using a clamp to hold both ends of the laminated film and then heating and stretching is preferred. The stretching ratio and stretching speed are appropriately selected to stretch the supporting film and ensure that the stretched shape and physical properties of the liquid crystal polymer film are within the desired range. The stretching ratio is preferably 2 to 5 times. The stretching speed is preferably 1 to 5000% / min, more preferably 50 to 2500% / min. Furthermore, to adjust the planar alignment after stretching, additional stretching along the length direction (MD direction) may be performed as needed.

[0077] The temperature at which the liquid crystal polymer film is stretched using a three-layer film is preferably set to a temperature above T1 and below T2. When T2 is the melting point of the liquid crystal polymer (i.e., the melting point of the liquid crystal polymer is -20°C below the melting point of the polymer constituting the support film), the stretching temperature is preferably above the glass transition temperature of the liquid crystal polymer film and below its melting point. Specifically, it is preferably set in the range of 150–280°C, and more preferably in the range of 170–250°C. By setting the temperature during the stretching of the laminated film below the melting point of the liquid crystal polymer, the smoothness of the resulting stretched liquid crystal polymer film can be improved. Furthermore, it results in uniform thickness, no streaks, and excellent film-forming properties. Moreover, by setting the temperature during the stretching of the laminated film above the glass transition temperature of the liquid crystal polymer, the liquid crystal polymer film becomes easier to stretch, which is therefore more preferable. In this invention, as described above, at any temperature in the range above the glass transition temperature and below the melting point of the liquid crystal polymer, the total yield load of a pair of supporting films becomes greater than the yield load of the liquid crystal polymer film, thereby allowing the three-layer film for stretching the liquid crystal polymer film to be stretched at a temperature below the melting point of the liquid crystal polymer.

[0078] Furthermore, when temperature T2 is the melting point of the polymer constituting the support film minus 20°C, that is, when the melting point of the polymer constituting the support film minus 20°C is lower than the melting point of the liquid crystal polymer, it is preferable to make the temperature during stretching above the glass transition temperature of the liquid crystal polymer film and below the melting point of the polymer constituting the support film minus 20°C. Specifically, it is preferably set to a range of 150 to 260°C, and more preferably to a range of 150 to 230°C.

[0079] Next, the stretched three-layer film is preferably heat-treated at a temperature above the glass transition temperature and below the melting point of the liquid crystal polymer film. The heat treatment time is preferably 1 to 100 hours, more preferably 3 to 48 hours. By performing heat treatment, the heat resistance of the stretched liquid crystal polymer film can be improved, and the coefficient of linear expansion can be reduced.

[0080] It should be noted that the melting point of the liquid crystal polymer constituting the liquid crystal polymer film in the three-layer film for stretching after stretching and heat treatment is preferably above the melting point of the liquid crystal polymer constituting the liquid crystal polymer film before stretching.

[0081] Finally, the support films laminated on both sides of the liquid crystal polymer film are peeled off, thereby obtaining a stretched liquid crystal polymer film. The anisotropy of the stretched liquid crystal polymer film thus manufactured is effectively reduced. In particular, the anisotropy of molecular orientation and the anisotropy of mechanical properties are effectively reduced.

[0082] It should be noted that in the above method, the support film is peeled off after heat treatment, but there is no particular limitation on the order of heat treatment and support film peeling. Heat treatment can be performed after the support film is peeled off.

[0083] The support film for the stretched three-layer film can also be peeled off before the stretched liquid crystal polymer film is used. The support film can serve, for example, as a protective film to prevent scratches during transportation.

[0084] The anisotropy of molecular orientation of the stretched liquid crystal polymer film was determined as follows. First, in the pole determination based on X-ray diffraction, the stretched liquid crystal polymer film was rotated in the in-plane direction (β direction) with a tilt of 45° (α = 45° in the Schulz method), and the diffraction intensity of the 110 plane was measured to create an X-ray diffraction intensity curve. In this curve, the length direction of the film was set to β = 0°, and the integrated intensities of β = 45–135°, 135°–225°, 225–315°, and 315–45° were calculated. The sum of the integrated intensities at β = 45–135° and β = 225°–315° was taken as the integrated intensity in the length direction. In addition, the sum of the integrated intensities at β = 135–225° and β = 315–45° was taken as the integrated intensity in the width direction. At this time, the planar orientation degree of the molecular orientation of the stretched liquid crystal polymer film was expressed by the following equation (1). The planar orientation degree shown in formula (1) below is preferably -0.5 or more and 0.5 or less, more preferably -0.3 or more and 0.3 or less, and even more preferably -0.2 or more and 0.2 or less. According to the present invention, a three-layer film for stretching liquid crystal polymer film can be manufactured with a planar orientation degree controlled within the above-mentioned range.

[0085] Planar orientation degree = (Integral intensity in the length direction - Integral intensity in the width direction) / (Integral intensity in the length direction + Integral intensity in the width direction) (1)

[0086] The diffraction intensity of the 110 plane refers to the diffraction intensity of the crystal plane (110 plane) of the liquid crystal polymer. For example, the diffraction intensity of the 110 plane in a liquid crystal polymer obtained by polycondensation of 2,6-hydroxynaphthenic acid and p-hydroxybenzoic acid at a molar ratio of 73:27 refers to the maximum diffraction intensity observed at 2θ = 20° when X-ray diffraction is measured in the range of diffraction angle (2θ) from 10° to 40°. The diffraction intensity of the (110 plane) of a liquid crystal polymer oriented along the length direction is defined as follows: when the length direction of the film is set to β = 0°, β = 90° and 270° are the maximum. Therefore, the sum of the integral intensity of β = 45–135° and the integral intensity of β = 225°–315° is taken as the integral intensity in the length direction, and the sum of the integral intensity of β = 135–225° and the integral intensity of β = 315–45° is taken as the integral intensity in the width direction. The integral intensity is obtained by representing the area where β is the horizontal axis and the diffraction intensity is the vertical axis. If the value shown in equation (2) above is positive, it indicates that the molecular chain is oriented along the length direction; if it is negative, it indicates that it is oriented along the width direction.

[0087] The anisotropy of the mechanical properties of the stretched liquid crystal polymer film is determined as follows. First, a tensile test is performed along the TD direction of the stretched liquid crystal polymer film using a tensile testing machine. Based on the SS curve obtained from the tensile test results, the breaking load in the TD direction is determined. Next, a tensile test is also performed along the MD direction of the stretched liquid crystal polymer film, and the breaking load in the MD direction is determined based on the SS curve. The anisotropy of the mechanical properties of the stretched liquid crystal polymer film is expressed as the ratio of the breaking load in the MD direction to the breaking load in the TD direction. The breaking load ratio is preferably 6 or less, more preferably 3 or less. The lower limit of the breaking load ratio is not particularly limited, and is generally 1 or more. According to the present invention, a three-layer film for stretching liquid crystal polymer films can be manufactured with a breaking load ratio controlled within the above-mentioned range.

[0088] It should be noted that the direction for measuring the fracture load in the anisotropy evaluation of stretched liquid crystal polymer films is not particularly limited to the TD and MD directions. For example, for stretched liquid crystal polymer films, tensile tests can be performed in two different directions to determine the fracture load, and the ratio of the larger fracture load to the smaller fracture load should be within the aforementioned range. In this case, it is preferable that the ratio of the fracture loads measured along two directions intersecting at right angles on the surface of the stretched liquid crystal polymer film is within the aforementioned range.

[0089] Example

[0090] Next, specific examples will be given to illustrate the present invention, but the present invention is not limited to these examples.

[0091] <Comparison of Yield Loads (Upper Yield Points) between Liquid Crystal Polymer Films and Supported Films>

[0092] Samples with a width direction (TD) of 120 mm and a length direction (MD) of 25 mm were cut from the liquid crystal polymer film. Tensile tests were conducted in a tensile testing machine (Orientec TENSILON A-500) with the tensile direction of the sample as TD, the chuck spacing set to 20 mm, and the tensile temperature and speed specified in each example and comparative example. The tensile stress (SS) curve was obtained from the tensile test results, with tensile stress as the vertical axis and elongation as the horizontal axis. The yield load (upper yield point) of the liquid crystal polymer film was determined from the SS curve. Tensile tests were also performed on the support films in the same manner, and the yield load was determined. The measured values ​​of the yield loads of each film are shown in Table 1. Then, the total yield load of the two support films (which can be obtained by calculating the yield load of one support film and doubling it) was compared with the yield load of the liquid crystal polymer film for evaluation. It should be noted that for Examples 4 and 9, which produced a three-layer film for stretching a liquid crystal polymer film by co-extrusion, the support film constituting the three-layer film for stretching the liquid crystal polymer film was peeled off from the liquid crystal polymer film as a sample, and the yield load was determined for the obtained sample. The evaluation results of each example and comparative example are shown in Table 2.

[0093] 〇: The total yield load of the two supporting films > the yield load of the liquid crystal polymer film.

[0094] ×: The total yield load of the two supporting films is less than or equal to the yield load of the liquid crystal polymer film.

[0095] <Comparison of maximum point loads between liquid crystal polymer films and support films>

[0096] Based on the SS curve obtained from the tensile tests conducted on the liquid crystal polymer film using the method described above, at the specified tensile temperatures and speeds in each embodiment and comparative example, the maximum point load of the liquid crystal polymer film was determined. Similarly, the maximum point load of the support film was determined. The measured values ​​of the maximum point load of each film are shown in Table 1. Then, the total value of the maximum point load of the two support films (which can be obtained by doubling the maximum point load of one support film) was compared with the maximum point load of the liquid crystal polymer film, and the evaluation was performed as follows. The evaluation results for each embodiment and comparative example are shown in Table 2.

[0097] 〇: The total maximum point load of the two supporting films > the maximum point load of the liquid crystal polymer film.

[0098] ×: The total maximum point load of the two supporting films is less than or equal to the maximum point load of the liquid crystal polymer film.

[0099] <Elongation at break of the supporting film>

[0100] The elongation at break of the supporting film was determined and evaluated from the SS curve of the supporting film obtained by the above method. The measured values ​​of the elongation at break of each film are shown in Table 1.

[0101] [Table 1]

[0102]

[0103] <Adhesion force between liquid crystal polymer film and supporting film>

[0104] The obtained liquid crystal polymer film was stretched and wound with three layers of film onto a 3-inch core (a plastic cylinder) with an outer diameter of 84.2 mm to deform it. The presence or absence of delamination between the liquid crystal polymer film and the support film was visually confirmed, thereby evaluating the adhesion between the liquid crystal polymer film and the support film. Specifically, as... Figure 1 As shown, a three-layer liquid crystal polymer film 10 is wound around a 3-inch core 50 with the surface of a support film 21 in contact with the core 50. When observing the cross-section of the 3-inch core 50, the angle θ (hereinafter referred to as the winding angle) between the two ends 11, 12 of the three-layer liquid crystal polymer film 10 and the central axis 51 of the 3-inch core 50 is 90° or more. The winding angle θ only needs to be 90° or more, but is typically 160° or less. After maintaining the state where the entire surface of the support film 21 is in close contact with the 3-inch core 50 for 5 seconds, the three-layer liquid crystal polymer film 10 is peeled off from the 3-inch core 50. Next, with another support film 22 in contact with the 3-inch core 50, the three-layer liquid crystal polymer film 10 is flipped and wound around the 3-inch core 50 again. This time, the winding angle θ is also 90° or more. After maintaining this state for 5 seconds, the three-layer liquid crystal polymer film 10 is peeled off from the 3-inch core 50. Next, it was confirmed whether there was any peeling between the liquid crystal polymer film 30 of the three-layer film 10 for stretching the liquid crystal polymer film and the support films 21 and 22. Figure 1 The schematic diagram illustrating the evaluation method of the adhesion force between the liquid crystal polymer film and the support film of the three-layer film for stretching the liquid crystal polymer film in the embodiment is a cross-sectional view of the three-layer film for stretching the liquid crystal polymer film and a 3-inch core.

[0105] 〇: No peeling occurred between the liquid crystal polymer film and the support film, and the adhesion was excellent.

[0106] ×: Delamination occurs between the liquid crystal polymer film and the support film, indicating insufficient adhesion.

[0107] <Peelability of the Supporting Film>

[0108] For the heat-treated stretched three-layer films of Examples 1, 2, 4-11, the support films stacked on both sides of the stretched liquid crystal polymer film were peeled off to visually confirm the surface condition of the stretched liquid crystal polymer film. The peelability of the support films was evaluated based on the presence or absence of support film residue on the surface of the stretched liquid crystal polymer film. The same evaluation was performed on the stretched three-layer film of Example 3, which was not heat-treated.

[0109] 〇: No residue of the support film, and excellent peelability of the support film.

[0110] ×: Residues of the supporting film are present, and the peelability of the supporting film is insufficient.

[0111] <Stretchability of 3-layer films for stretching liquid crystal polymer films>

[0112] Visually evaluate the thickness unevenness, streaks, etc. of the stretched liquid crystal polymer film made of three-layer film for stretching liquid crystal polymer film.

[0113] 〇: No uneven thickness or streaks, indicating good quality.

[0114] △: Uneven thickness and stripes are visible.

[0115] ×: Uneven thickness, large cracks.

[0116] <Surface orientation degree of stretched liquid crystal polymer films>

[0117] For stretched liquid crystal polymer films, a sample horizontal multi-object X-ray diffraction apparatus (Rigaku Corporation, model: Ultima IV) was used. The diffraction angle (2θ) was fixed at 20°. The poles were measured under the following conditions: X-ray target: Cu, voltage: 40kV, current: 40mA, α angle = 45°, β angle = 0~360° (the length direction of the film was set to 0°, and the step angle was 5°). X-ray diffraction intensity curves were prepared. The integral intensities of the curves β = 45~135°, 135°~225°, 225~315°, and 315~45° were calculated. The sum of the integral intensities of β = 45~135° and β = 225°~315° was taken as the integral intensity in the length direction, and the sum of the integral intensities of β = 135~225° and β = 315~45° was taken as the integral intensity in the width direction. The surface orientation degree was calculated by the following equation (2).

[0118] Planar orientation degree = (Integral intensity in the length direction - Integral intensity in the width direction) / (Integral intensity in the length direction + Integral intensity in the width direction) (2)

[0119] <Tear strength ratio of stretched liquid crystal polymer films>

[0120] Samples with a width direction (TD) of 120 mm and a length direction (MD) of 25 mm were cut from a stretched liquid crystal polymer film made of three layers of film. These samples were placed on a tensile testing machine with the stretching direction TD and subjected to tensile tests. The breaking load on TD was determined based on the SS curve obtained from the tensile test results. Next, the stretched liquid crystal polymer film samples were placed on the tensile testing machine with the stretching direction MD and subjected to tensile tests. The breaking load on MD was determined based on the SS curve obtained from the tensile test results. Finally, the ratio of the breaking load on MD to the breaking load on TD was calculated.

[0121] <Melting point of stretched liquid crystal polymer film>

[0122] Using a differential scanning calorimeter (PerkinElmer Co., Ltd., model: DSC8500), the endothermic peak temperature observed when the liquid crystal polymer film prepared in Example 1 before stretching was heated from 0°C at a rate of 10°C / min was taken as the melting point of the liquid crystal polymer film before stretching. Additionally, the endothermic peak temperature observed when the stretched liquid crystal polymer film prepared in each example was heated from 0°C at a rate of 10°C / min was taken as the melting point of the stretched liquid crystal polymer film. The melting point of the liquid crystal polymer film before stretching was 280°C. The melting point of the stretched liquid crystal polymer film was determined for Examples 1-4 and 6.

[0123] <Glass transition temperature of liquid crystal polymer films>

[0124] Using a viscoelasticity measuring apparatus (DMA7100, manufactured by Hitachi, Ltd.), the peak temperature of the loss tangent tanδ of the liquid crystal polymer film before stretching, measured by increasing the temperature from 30°C to 5°C / min, was taken as the glass transition temperature of the liquid crystal polymer film (refer to...). Figure 2 The glass transition temperature of the liquid crystal polymer films used in the examples and comparative examples before stretching was 100–105°C. Figure 2 A graph showing the results of the viscoelasticity test of the liquid crystal polymer film used in Example 1.

[0125] <Example 1>

[0126] The liquid crystal polymer (manufactured by Polyplastics Co., Ltd., LAPEROS A950RX) was fed into a twin-screw extruder (screw diameter 32 mm) and extruded into a thin film from the T-die at the front of the extruder (lip length 350 mm, lip gap approximately 1 mm, die temperature 300 °C). After cooling, a liquid crystal polymer (LCP) film with a thickness of 75 μm was obtained.

[0127] Next, on both sides of the liquid crystal polymer film and one side of the supporting polyetheretherketone (PEEK) film (Victrex, APTIV Film 1000-025G, 25 μm thickness, surface roughness Ra = 0.14 μm (MD), 0.12 μm (TD), melting point 343 °C), direct atmospheric pressure plasma treatment was performed in an oxygen-containing atmosphere at a power of 1.5 kW and a conveying speed of 1.0 m / min. Then, the plasma-treated surfaces were overlapped, and the PEEK film was hot-pressed onto both sides of the liquid crystal polymer film using a first roller heated to 305 °C and a second roller heated to 120 °C, under a roll gap pressure of 0.2 MPa and a conveying speed of 0.5 m / min. The hot-pressed liquid crystal polymer film and PEEK film were then tightly bonded. Thus, a three-layer film for stretching liquid crystal polymer film was obtained.

[0128] The prepared liquid crystal polymer film for stretching, consisting of three layers, was stretched three times in the width direction (TD) at a conveying speed of 15 m / min (stretching speed 2500% / min, reaching stretching temperature 250°C) in a transverse stretching machine (furnace temperature 320°C) to obtain a stretched three-layer film. The stretching temperature refers to the temperature of the laminated film at the end of stretching. Subsequently, the stretched three-layer film was heat-treated in an oven at 260°C for 3 hours to peel off the PEEK film, obtaining a stretched liquid crystal polymer film with a thickness of 25 μm. The peelability of the support film and the stretchability of the three-layer liquid crystal polymer film for stretching were evaluated. Furthermore, the planar orientation, tensile breaking load ratio, and melting point of this stretched liquid crystal polymer film were evaluated. The results are shown in Table 2.

[0129] <Examples 2, 4, 6-8>

[0130] Similar to Example 1, a three-layer film for stretching liquid crystal polymer film was obtained. Next, the furnace temperature during stretching, stretching speed, stretching ratio, and heat treatment temperature were changed to the values ​​recorded in Table 1. Otherwise, a stretched liquid crystal polymer film was obtained in the same manner as in Example 1, and the evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

[0131] <Example 3>

[0132] No heat treatment was performed; otherwise, the stretched liquid crystal polymer film was obtained in the same manner as in Example 2 and evaluated. The results are shown in Table 2.

[0133] <Example 5>

[0134] A liquid crystal polymer (manufactured by Polyplastics Co., Ltd., LAPEROS A950RX) was fed into a twin-screw extruder and melt-blended at 300°C. Separately, a polyetheretherketone (PEEK) polymer (manufactured by Polyplastics-Evonik Corporation, 3300G, melting point 342°C) serving as the support polymer was fed into a single-screw extruder and melt-blended at 380°C. These molten polymers were fed into a Multi-Manifold T-die, and layers formed of the support polymer were overlapped on both sides of the liquid crystal polymer layer and extruded (co-extruded). After cooling, a three-layer film for stretching a liquid crystal polymer film was produced, consisting of a 75 μm liquid crystal polymer layer, two 25 μm support polymer layers on each side, and a total thickness of 125 μm. Using the obtained three-layer film for stretching, a stretched liquid crystal polymer film was obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0135] <Example 9>

[0136] The thickness of the liquid crystal polymer film was changed to 200 μm, and the thickness of the polyether ether ketone film used as the support film was changed to 50 μm. Otherwise, the three-layer film for stretching the liquid crystal polymer film and the stretched liquid crystal polymer film were obtained in the same manner as in Example 1, and the evaluation was carried out in the same manner.

[0137] <Example 10>

[0138] Unstretched polybutylene terephthalate (M-PBT) (manufactured by Mitsubishi Engineering-Plastics Corporation, Novaduran 5026, melting point 220°C) was used as the supporting polymer. Apart from this, a three-layer film for stretching the liquid crystal polymer film was prepared in the same manner as in Example 5, consisting of a 75 μm liquid crystal polymer layer, two 25 μm supporting polymer layers on each side, and a total thickness of 125 μm. The obtained three-layer film for stretching the liquid crystal polymer film was stretched and heat-treated under the conditions described in Table 2. After the supporting film was peeled off, it was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0139] <Example 11>

[0140] The thickness of the liquid crystal polymer film was changed to the thickness described in Table 2. A biaxially stretched PBT film (BO-PBT) (manufactured by KOHJIN Film & Chemicals Co., Ltd., Boblet, thickness 25 μm, melting point 220°C) was used as the support film. Otherwise, a three-layer film for stretching the liquid crystal polymer film was obtained in the same manner as in Example 1. Using the obtained three-layer film for stretching the liquid crystal polymer film, stretching and heat treatment were performed under the conditions described in Table 2. After the support film was peeled off, the evaluation was performed in the same manner as in Example 1.

[0141] <Comparative Example 1>

[0142] For the liquid crystal polymer film prepared in Example 1 before the support film is stacked, the planar orientation and tensile fracture load ratio were evaluated. The results are shown in Table 2.

[0143] <Comparative Example 2>

[0144] A 75 μm thick liquid crystal polymer film was used as the liquid crystal polymer film, and a porous PTFE film (50 μm thick) was used as the support film. Otherwise, three layers of films were obtained, similar to Example 1. The yield load and maximum point load of the liquid crystal polymer film and the support film were compared. The results showed that the total yield load of the two support films at 150°C, 200°C, and 250°C was lower than the yield load of the liquid crystal polymer film at the same temperature. Furthermore, the total maximum point load of the two support films at 150°C, 200°C, and 250°C was lower than the maximum point load of the liquid crystal polymer film at the same temperature. Stretching of this three-layer film at a stretching temperature of 250°C, a stretching speed of 2500% / min, and a stretching ratio of 3 times resulted in cracks in the liquid crystal polymer film, making it impossible to stretch the three-layer film.

[0145] <Comparative Example 3>

[0146] Similar to Example 1, the liquid crystal polymer was extruded into a film using a twin-screw extruder to obtain a liquid crystal polymer film with a thickness of 200 μm. Then, unstretched polybutylene terephthalate (manufactured by Toyo Kobe Co., Ltd., Esheet, thickness 50 μm) was used as a support film, and otherwise, similar to Example 1, a three-layer film was obtained consisting of the liquid crystal polymer film and a pair of support films. The yield load and maximum point load of the liquid crystal polymer film and the support films were compared. The results showed that the total yield load of the two support films at 150°C and 200°C was lower than the yield load of the liquid crystal polymer film at the same temperature. Furthermore, the total maximum point load of the two support films at 150°C and 200°C was lower than the maximum point load of the liquid crystal polymer film at the same temperature. This three-layer film was stretched at a stretching temperature of 250°C, a stretching speed of 2500% / min, and a stretching ratio of 3 times. As a result, cracks formed in the liquid crystal polymer film, making it impossible to stretch the three-layer film.

[0147] <Comparative Example 4>

[0148] Unstretched polybutylene terephthalate (manufactured by Toyo Steel Sheet Co., Ltd., E sheet, 35 μm thickness) was used as the support film. Otherwise, similar to Example 1, a three-layer film consisting of a liquid crystal polymer film and a pair of support films was obtained. A comparison of the yield load and maximum point load of the liquid crystal polymer film and the support films showed that the total yield load of the two support films at 150°C and 200°C was lower than the yield load of the liquid crystal polymer film at the same temperature. Stretching of this three-layer film at a stretching temperature of 200°C, a stretching speed of 2500% / min, and a stretching ratio of 3 times resulted in cracks in the liquid crystal polymer film, making it impossible to stretch the three-layer film.

[0149] <Comparative Example 5>

[0150] Using polymethylpentene (PMP) (50 μm thick) as the support film, a three-layer film consisting of a liquid crystal polymer film and a pair of support films was obtained, similar to Example 1. The yield load and maximum point load of the liquid crystal polymer film and the support films were compared. The results showed that the total yield load of the two support films at 150°C and 200°C was lower than the yield load of the liquid crystal polymer film at the same temperature. Furthermore, the total maximum point load of the two support films at 150°C and 200°C was lower than the maximum point load of the liquid crystal polymer film at the same temperature. Stretching of this three-layer film at a stretching temperature of 200°C, a stretching speed of 2500% / min, and a stretching ratio of 3 times resulted in cracks in the liquid crystal polymer film, making it impossible to stretch the three-layer film.

[0151] <Reference Example 1>

[0152] A three-layer liquid crystal polymer film for stretching was obtained in the same manner as in Example 1, with an elongation of 1.5 times. The heat treatment temperature was changed to 250°C. Otherwise, the stretched liquid crystal polymer film was obtained in the same manner as in Example 1. The results are shown in Table 2.

[0153] <Reference Example 2>

[0154] No surface treatment was performed on the liquid crystal polymer film and the support film. Otherwise, a three-layer film for stretching the liquid crystal polymer film was obtained in the same manner as in Example 1. Using the obtained three-layer film for stretching the liquid crystal polymer film, stretching was performed under the conditions described in Table 2. As a result, cracks were generated in the liquid crystal polymer film, and the three-layer film could not be stretched. The results are shown in Table 2.

[0155] [Table 2]

[0156]

[0157] Figure 3 A graph showing the SS curves of the liquid crystal polymer film and the support film used in Example 4, obtained from a tensile test. Figure 3 In the figure, the horizontal axis represents the elongation (mm) during the tensile test, and the vertical axis represents the load (N) applied to the film during the tensile test. The tensile test was performed as follows: Samples of liquid crystal polymer film (LCP) and support film (PEEK) (25 mm in the TD direction and 25 mm in the MD direction) were placed in a tensile testing machine (20 mm between chucks) with the stretching direction TD. After preheating at 150°C for 5 minutes in a constant temperature bath, the film was stretched to 3 times its original length (60 mm between chucks) at a stretching speed of 2500% / min. It should be noted that... Figure 3 In this context, the SS curve of the supporting film is constructed from twice the load measured in the tensile test of the supporting film (the load of the supporting film's 2-tensor). For example... Figure 3 As shown, in the three-layer film for stretching the liquid crystal polymer film of Example 4, the total yield load of the support film at 150°C is higher than the yield load of the liquid crystal polymer film. Similarly, in the three-layer film for stretching the liquid crystal polymer film obtained in Example 1, the total yield load of the support film at 250°C is higher than the yield load of the liquid crystal polymer film. Similarly, in the three-layer films for stretching the liquid crystal polymer film obtained in Examples 2 and 3, the total yield load of the support film at 275°C is higher than the yield load of the liquid crystal polymer film. Therefore, in the three-layer films for stretching the liquid crystal polymer film using polyetheretherketone (PEEK) film as the support film, the total yield load of the support film across the entire temperature range of 150–275°C is higher than the yield load of the liquid crystal polymer film.

[0158] In Examples 1 to 11, by using a three-layer film for stretching a liquid crystal polymer film in a specified temperature range, the total yield load of the supporting film is higher than that of the liquid crystal polymer film. Thus, the liquid crystal polymer film can be stretched at a temperature below the melting point of the liquid crystal polymer and at a stretching ratio of more than twice. This results in a stretched liquid crystal polymer film with a small facet orientation and a low breaking load ratio, and an effective reduction in anisotropy.

[0159] Figure 4 A graph showing the SS curves of the liquid crystal polymer film and the support film used in Comparative Example 4, obtained from the tensile test. Figure 4 In the figure, the horizontal axis represents the elongation (mm) during the tensile test, and the vertical axis represents the load (N) applied to the film during the tensile test. The tensile test was performed as follows: Samples of liquid crystal polymer film (LCP) and support film (PBT) (25mm length in the TD direction and 25mm length in the MD direction) were placed in a tensile testing machine (20mm between chucks) with the stretching direction TD. After preheating at 150°C for 5 minutes in a constant temperature bath, the film was stretched to 3 times its original length (60mm between chucks) at a stretching speed of 2500% / min. It should be noted that... Figure 4 In this context, the SS curve of the supporting film is constructed from twice the load measured in the tensile test of the supporting film (the load of the supporting film's 2-tensor). For example... Figure 4 As shown, in Comparative Example 4, the total yield load of the supporting film at 150°C was lower than the yield load of the liquid crystal polymer film. Therefore, in Comparative Example 4, cracks were generated in the liquid crystal polymer film when the three-layer film was stretched.

Claims

1. A three-layer film for stretching liquid crystal polymer films, comprising: Liquid crystal polymer film, and A pair of support films stacked on both sides of the liquid crystal polymer film. At any temperature above T1 and below T2, the total yield load of the pair of supporting films is greater than the yield load of the liquid crystal polymer film. The temperature T1 is the glass transition temperature of the liquid crystal polymer constituting the liquid crystal polymer film. The temperature T2 is the lower of the melting point of the liquid crystal polymer and the melting point of the polymer constituting the supporting film at -20°C.

2. The three-layer film for stretching liquid crystal polymer films according to claim 1, wherein, At any temperature within the range of above temperature T1 and below temperature T2, the total value of the maximum point loads of a pair of supporting films is greater than the maximum point load of the liquid crystal polymer film.

3. The three-layer film for stretching liquid crystal polymer films according to claim 1 or 2, wherein, At any temperature within the range of above temperature T1 and below temperature T2, at least one of the pair of supporting films has an elongation at break of 200% or more.

4. The three-layer film for stretching liquid crystal polymer films according to claim 1 or 2, wherein, The liquid crystal polymer film stretching three-layer film is wound around a cylinder with an outer diameter of 84.2 mm in contact with the surface of one of the supporting films, and deformed by a winding angle of 90° or more. Then, the liquid crystal polymer film stretching three-layer film is wound around the cylinder in contact with the surface of the other supporting film, and deformed by a winding angle of 90° or more, without peeling between the liquid crystal polymer film and the supporting film.

5. The three-layer film for stretching liquid crystal polymer films according to claim 1 or 2, wherein, The supporting film is made of crystalline resin.

6. The three-layer film for stretching liquid crystal polymer films according to claim 1 or 2, wherein, The supporting film is made of aromatic polyetherketone or polyester.

7. The three-layer film for stretching liquid crystal polymer films according to claim 1 or 2, wherein, The thickness of the supporting film is 5–300 μm.

8. A method for manufacturing a three-layer film for stretching a liquid crystal polymer film, as described in claim 1 or 2, wherein the manufacturing method comprises the following steps: A pair of the support films are stacked on both sides of the liquid crystal polymer film using either pressure lamination or thermal lamination.

9. The method for manufacturing a three-layer film for stretching a liquid crystal polymer film according to claim 8, wherein, Before the process of laminating the liquid crystal polymer film and the support film, The process includes the following steps: performing surface treatment on both sides of the liquid crystal polymer film and the side of the support film that is bonded to the liquid crystal polymer film.

10. The method for manufacturing a three-layer film for stretching a liquid crystal polymer film according to claim 9, wherein, The surface treatment is any one of plasma treatment, corona treatment, or chemical conversion treatment.

11. A method for manufacturing a three-layer film for stretching a liquid crystal polymer film, wherein the method for manufacturing a three-layer film for stretching a liquid crystal polymer film as described in claim 1 or 2 is... The manufacturing method uses melt extrusion to produce a three-layer film for stretching the liquid crystal polymer film.

12. A method for manufacturing a stretched three-layer film, comprising the following steps: stretching the three-layer film for stretching the liquid crystal polymer film according to claim 1 or 2 at least 2.0 to 5.0 times along the TD direction within a temperature range above the glass transition temperature of the liquid crystal polymer and below the melting point of the liquid crystal polymer.

13. The method for manufacturing a stretched three-layer film according to claim 12, wherein, After the process of stretching the liquid crystal polymer film using a three-layer film stretching method, the process further includes performing heat treatment within a temperature range above the glass transition temperature of the liquid crystal polymer and below the melting point of the liquid crystal polymer.

14. A method for manufacturing a stretched liquid crystal polymer film, comprising the step of peeling a support film from a stretched three-layer film manufactured by the method for manufacturing a stretched three-layer film according to claim 12.

15. A method for manufacturing a stretched liquid crystal polymer film, comprising the steps of: peeling a support film from a stretched three-layer film manufactured by the method for manufacturing a stretched three-layer film according to claim 12; and performing heat treatment in a temperature range above the glass transition temperature of the liquid crystal polymer and below the melting point of the liquid crystal polymer.

16. A stretched three-layer film, which is obtained by stretching a three-layer film for stretching a liquid crystal polymer film according to claim 1 or 2 by stretching it 2.0 to 5.0 times along the TD direction at a temperature above T1 and below the temperature T2. Regarding the fracture loads measured in two directions on the stretched liquid crystal polymer film obtained by peeling off the support film, the ratio of the larger fracture load to the smaller fracture load is 6 or less.

17. A stretched liquid crystal polymer film, which is a stretched liquid crystal polymer film manufactured by the manufacturing method of the stretched liquid crystal polymer film according to claim 14. Regarding the fracture loads measured in two directions for the stretched liquid crystal polymer film, the ratio of the larger fracture load to the smaller fracture load is 6 or less.

18. The stretched liquid crystal polymer film according to claim 17, wherein, The melting point of the stretched liquid crystal polymer film is above the melting point of the liquid crystal polymer film before stretching.

Images