Liquid crystal polymer film laminate, method for manufacturing liquid crystal polymer film laminate, and method for manufacturing liquid crystal polymer film

Abstract

The present invention provides a liquid crystal polymer film laminate comprising: a liquid crystal polymer film, and an aromatic polyetherketone film laminated on at least one side of the liquid crystal polymer film, wherein the shrinkage rate of the aromatic polyetherketone film is 13.5% or less when the aromatic polyetherketone film is heated to 300°C while being subjected to a tensile load using a thermomechanical analysis apparatus (TMA).

Description

Technical Field

[0001] This invention relates to a liquid crystal polymer film laminate, a method for manufacturing a liquid crystal polymer film laminate, and a method for manufacturing a liquid crystal polymer film. Background Technology

[0002] With the development of mobile communication technology, the speed and capacity of communication are advancing, and the frequency of communication is increasing. In 5G mobile communication systems, the 3.7GHz and 4.5GHz bands of the Sub-6 frequency band and the 28GHz band of the millimeter wave band are used. Furthermore, in 6G mobile communication systems, the frequency band in the range of 90GHz to 300GHz is being studied. For signals flowing in a circuit, the higher the frequency, the greater the transmission loss. Therefore, circuits and circuit materials with low transmission loss are required. As materials that can be used for such circuit materials, liquid crystal polymer films with reduced anisotropy and excellent smoothness are known (e.g., Patent Document 1).

[0003] Patent document 1 discloses the following method: liquid crystal polymer (LCP) and polyether ether ketone polymer (PEEK) are melt-blended separately, fed to a multi-manifold T-die and co-extruded to obtain a laminated film, the laminated film is stretched, and finally the PEEK film is peeled off, thereby manufacturing a stretched liquid crystal polymer film with adjusted surface roughness and planar orientation.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2024 / 004952 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the laminated film manufactured by co-extrusion as described in Patent Document 1, the adhesion between the liquid crystal polymer film and the PEEK film constituting the laminated film is low. In subsequent winding and conveying processes (hereinafter also referred to as follow-up processes), the liquid crystal polymer film and the PEEK film may peel off. Therefore, the technology described in Patent Document 1 may cause the following problems: deformation of the liquid crystal polymer film due to peeling from the PEEK film, and the inability to wind the laminated film into a roll.

[0009] The purpose of this invention is to provide a liquid crystal polymer film laminate in which the liquid crystal polymer film and the aromatic polyetherketone film have excellent adhesion, and can suppress the peeling of the liquid crystal polymer film and the aromatic polyetherketone film during the winding process and the conveying process (hereinafter also referred to as subsequent processes).

[0010] Solution for solving the problem

[0011] [1] Embodiment 1 of the present invention is a liquid crystal polymer film laminate comprising: a liquid crystal polymer film and an aromatic polyetherketone film laminated on at least one side of the liquid crystal polymer film, wherein the shrinkage rate of the aromatic polyetherketone film is 13.5% or less when the aromatic polyetherketone film is heated to 300°C while being subjected to a tensile load using a thermomechanical analysis apparatus (TMA).

[0012] [2] Embodiment 2 of the present invention is a liquid crystal polymer film laminate of Embodiment 1, wherein the linear expansion coefficient in the length direction of the liquid crystal polymer film is set as α. MD Let the coefficient of linear expansion in the width direction of the above-mentioned liquid crystal polymer film be α. TD When, the following equations (1) and (2) are satisfied.

[0013] 10ppm / ℃≤α TD ≤80ppm / ℃ (1)

[0014] |α MD -α TD |≤60ppm / ℃ (2)

[0015] [3] The third embodiment of the present invention is a liquid crystal polymer film laminate of embodiment 1 or 2, wherein the planar orientation degree of the liquid crystal polymer film calculated based on the pole determination by X-ray diffraction is -0.3 or more and 0.5 or less.

[0016] [4] Embodiment 4 of the present invention is a liquid crystal polymer film laminate of any one of Embodiments 1 to 3, wherein the surface roughness Ra of at least one side of the liquid crystal polymer film is 0.20 μm or less.

[0017] [5] Embodiment 5 of the present invention is a liquid crystal polymer film laminate of any one of Embodiments 1 to 4, wherein the slow axis orientation of the length direction of the aromatic polyetherketone film determined by phase difference measurement is 80° or more and 100° or less, or -100° or more and -80° or less.

[0018] [6] Embodiment 6 of the present invention is a liquid crystal polymer film laminate of any one of Embodiments 1 to 5, wherein the aromatic polyetherketone film is polyetheretherketone (PEEK).

[0019] [7] Embodiment 7 of the present invention is a method for manufacturing a liquid crystal polymer film laminate according to any one of Embodiments 1 to 6, comprising: a first step of extruding molten liquid crystal polymer and aromatic polyether ketone into a film by using an extruder to laminate a layer formed of aromatic polyether ketone on at least one side of a layer formed of liquid crystal polymer, thereby obtaining a laminate; a second step of stretching the laminate at least in the width direction; and a third step of performing a relaxation treatment on the laminate at a temperature of -150°C or higher and a relaxation rate of 4% or higher and 20% or lower, where the melting point of the aromatic polyether ketone is 150°C or higher.

[0020] [8] Embodiment 8 of the present invention is a method for manufacturing a liquid crystal polymer film, comprising: a step of obtaining a liquid crystal polymer film laminate by the method for manufacturing a liquid crystal polymer film laminate of Embodiment 7; and a fourth step of peeling off the aromatic polyetherketone film.

[0021] The effects of the invention

[0022] According to the liquid crystal polymer film laminate of the present invention, the liquid crystal polymer film and the aromatic polyetherketone film have excellent adhesion, and the separation of the liquid crystal polymer film and the aromatic polyetherketone film can be suppressed during the winding process and the conveying process (hereinafter also referred to as subsequent processes). Attached Figure Description

[0023] Figure 1 This diagram illustrates the stretching and relaxation processes used in laminates.

[0024] Figure 2 This is a diagram illustrating a method for determining the deformation of a test piece using a thermomechanical analysis apparatus (TMA).

[0025] Figure 3 This is a graph representing the measurement results of the PEEK thin film test piece in Example 2 using a thermomechanical analysis device.

[0026] Figure 4 This is a schematic diagram of the upper edge of a rotating circular knife used for evaluating interlayer adhesion of a liquid crystal polymer film laminate in an embodiment. Detailed Implementation

[0027] The liquid crystal polymer film stack of the present invention is composed of a liquid crystal polymer film and an aromatic polyetherketone film stacked on at least one side of the liquid crystal polymer film.

[0028] <Liquid Crystal Polymer Thin Film>

[0029] The liquid crystal polymer film used in the liquid crystal polymer laminate of the present invention is a film formed from a liquid crystal polymer. There is no particular limitation on the liquid crystal polymer, but a liquid crystal polyester exhibiting thermotropic liquid crystal properties 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. From the perspective of superior mechanical properties, electrical properties, and heat resistance, aromatic polyester-based liquid crystal polymers are preferred, 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 the liquid crystal polymer can be used alone, or two or more can be used in any combination and ratio. The content of the liquid crystal polymer relative to the total amount of the liquid crystal polymer film is preferably 50-100% by mass, more preferably 60-100% by mass, and even more preferably 70-100% by mass. Particularly preferred is that the liquid crystal polymer film is substantially formed solely of the liquid crystal polymer.

[0030] The synthesis of liquid crystal polymers 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 or acetylation can be performed according to conventional methods.

[0031] Within the scope that does not excessively impair the effects of the present invention, the liquid crystal polymer may include polymers such as fluororesins, polyolefins, polycyclic olefins, polyetherimides, and silicone-modified polyetherimides; release agents such as higher fatty acids with 10 to 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 may be included in the molten resin composition during the film-forming process of the liquid crystal polymer film. Furthermore, these polymers and additives may be used individually or in combination of two or more. The content of polymer and additives is not particularly limited. From the viewpoint of molding processability and thermal stability, it is preferably 0.01 to 50% by mass relative to the total amount of liquid crystal polymer film, more preferably 0.1 to 40% by mass, and even more preferably 0.5 to 30% by mass.

[0032] The coefficient of linear expansion along the length of the liquid crystal polymer film is set as α. MD The coefficient of linear expansion in the width direction of the liquid crystal polymer film is set as α. TD When the liquid crystal polymer film preferably satisfies the following formula (1) and the following formula (2), the liquid crystal polymer film is preferably satisfied.

[0033] 10ppm / ℃≤α TD ≤80ppm / ℃ (1)

[0034] |α MD -α TD |≤60ppm / ℃ (2)

[0035] As described below, the liquid crystal polymer film laminate of the present invention is manufactured by a method including stretching the laminate obtained by co-extruding a liquid crystal polymer and an aromatic polyetherketone using an extruder, at least along the width direction. Therefore, the liquid crystal polymer film is primarily subjected to stress from the laminated aromatic polyetherketone film, which tends to shrink along the width direction, resulting in residual strain. The liquid crystal polymer film satisfies the above formula (1), indicating that the residual strain in the width direction of the liquid crystal polymer film is small. By satisfying the above formula (1), deformation caused by the residual strain of the liquid crystal polymer film can be appropriately suppressed when heat treatment or hot pressing is performed on the liquid crystal polymer film laminate. Furthermore, when manufacturing an FPC by forming a metal layer on the liquid crystal polymer film obtained by peeling off the aromatic polyetherketone film, deformation caused by residual strain can also be appropriately suppressed.

[0036] linear expansion coefficient α TD As long as the above formula (1) is satisfied, it is preferable to have a temperature of 20 ppm / ℃ or higher and 80 ppm / ℃ or lower, more preferably 25 ppm / ℃ or higher and 80 ppm / ℃ or lower, even more preferably 30 ppm / ℃ or higher and 80 ppm / ℃ or lower, and particularly preferably 35 ppm / ℃ or higher and 80 ppm / ℃ or lower. In particular, by setting it to 35 ppm / ℃ or higher and 80 ppm / ℃ or lower, the liquid crystal polymer film can achieve excellent following of other components stacked on the liquid crystal polymer film. As a result, when other components (aromatic polyetherketone film, metal layer, etc.) are stacked on the liquid crystal polymer film and heat treatment or hot pressing is performed, deformation caused by residual strain can be appropriately suppressed, and the adhesion with other components can be improved.

[0037] The liquid crystal polymer film satisfies the above formula (2), indicating that the anisotropy of the liquid crystal polymer film is small. By satisfying the above formula (2), when heat treatment or hot pressing is performed on the liquid crystal polymer film laminate composed of aromatic polyetherketone film and liquid crystal polymer film, deformation caused by anisotropy can be appropriately suppressed. In addition, when forming a metal layer on the liquid crystal polymer film obtained by peeling off the aromatic polyetherketone film to manufacture FPC, deformation caused by anisotropy can also be appropriately suppressed.

[0038] linear expansion coefficient α MD With the coefficient of linear expansion α TD The absolute value of the difference |α MD -α TD |It is sufficient to satisfy the above formula (2), preferably 40ppm / ℃ or less, more preferably 20ppm / ℃ or less, and even more preferably 10ppm / ℃ or less. Preferably α TD and |α MD -α TD At least one of them is within the above range.

[0039] linear expansion coefficient α MD α TD The dimensional change rate can be determined by applying a tensile load to the liquid crystal polymer film obtained by peeling an aromatic polyetherketone film using a thermomechanical analysis (TMA) apparatus while simultaneously heating it. The dimensional change rate is not particularly limited and can be measured by mounting the liquid crystal polymer film on the fixture of the TMA apparatus, setting the tensile load to 10 mN, and heating it from 30°C to 150°C at a rate of 5°C / min. Let the length of the liquid crystal polymer film before heating be L. LCP Let the change in length be ΔL LCP Let the temperature change be ΔT LCP At that time, the coefficient of linear expansion α MD α TD Represented as ΔL LCP / L LCP / ΔT LCP [ppm / ℃]

[0040] The coefficient of linear expansion α of the liquid crystal polymer film MD α TD As described below, a method that adjusts to the above range can be exemplified by stretching a laminate obtained by co-extrusion of a liquid crystal polymer and an aromatic polyether ketone along its width direction and then performing a relaxation treatment.

[0041] The thickness of the liquid crystal polymer film is not particularly limited. From the viewpoint of the operability of the liquid crystal polymer film laminate and the dielectric properties of the liquid crystal polymer film after the aromatic polyetherketone film is peeled off, it is preferably 10 to 500 μm, more preferably 20 to 300 μm, even more preferably 30 to 250 μm, and particularly preferably 30 to 200 μm.

[0042] The melting point of the liquid crystal polymer constituting the liquid crystal polymer film is not particularly limited, but is preferably 250~380°C, more preferably 280~350°C.

[0043] The planar orientation degree of the liquid crystal polymer film, calculated based on pole determination using X-ray diffraction, is preferably -0.3 or higher and 0.5 or lower. Specifically, the planar orientation degree can be determined by the following method. First, in pole determination using X-ray diffraction, with the liquid crystal polymer film tilted at 45° (α=45° in the Schulz method), the diffraction intensity of plane 110 is measured while rotating along the in-plane direction (β direction) to create an X-ray diffraction intensity distribution. In this distribution, the length direction of the film is set to β=0°, and the integrated intensities at β=45~135°, 135°~225°, 225~315°, and 315~45° are calculated. The sum of the integrated intensities at β=45~135° and β=225°~315° is taken as the integrated intensity in the length direction. Furthermore, the sum of the integrated intensities at β=135~225° and β=315~45° is taken as the integrated intensity in the width direction. At this point, the orientation degree is represented by the following formula (3).

[0044] Surface orientation degree = (integral intensity in length direction - integral intensity in width direction) / (integral intensity in length direction + integral intensity in width direction) (3)

[0045] 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) of 10° to 40°. Regarding the diffraction intensity of the (110 plane) of the liquid crystal polymer oriented along the length direction, if the length direction of the film is set to β=0°, then β=90° and 270° reach their 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 calculated from the area represented by β on the horizontal axis and diffraction intensity on the vertical axis. If the value of the plane orientation degree 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.

[0046] The planar orientation degree is preferably -0.3 or higher and 0.5 or lower, more preferably -0.3 or higher and 0.3 or lower, and particularly preferably -0.2 or higher and 0.15 or lower. By keeping the planar orientation degree within the above range, the anisotropy of the mechanical properties, dielectric constant, and dielectric loss tangent of the liquid crystal polymer film can be reduced. As a method for adjusting the planar orientation degree to the above range, an example is the method described below of stretching a laminate obtained by co-extrusion of a liquid crystal polymer and an aromatic polyether ketone along the width direction.

[0047] The liquid crystal polymer film preferably has a surface roughness Ra of at least one side of 0.20 μm or less. The surface roughness Ra can be measured according to JIS B0601:1994. The surface roughness Ra can be measured along any direction of the surface of the liquid crystal polymer film, but preferably along the width direction (TD) or length direction (MD) of the liquid crystal polymer film. That is, the surface roughness Ra measured along the width direction (TD) or length direction (MD) of the liquid crystal polymer film is preferably 0.20 μm or less. It should be noted that the liquid crystal polymer film laminate of the present invention is manufactured by a method including the step of stretching the laminate obtained by co-extruding a liquid crystal polymer and an aromatic polyether ketone using an extruder, as described below, at least along the width direction. Figure 1 As shown, the width direction (TD) refers to the direction in which the laminate is stretched during the manufacturing process of the liquid crystal polymer film laminate, and the length direction (MD) refers to the direction in which the laminate is transported. Figure 1 This is a diagram used to illustrate the methods of stretching and relaxation treatments for laminates.

[0048] The surface roughness Ra is preferably 0.20 μm or less on at least one surface, and more preferably 0.20 μm or less on both sides of the liquid crystal polymer film. By setting the surface roughness Ra to 0.20 μm or less, when forming a metal layer on the liquid crystal polymer film to manufacture the FPC, transmission loss during high-frequency signal flow can be reduced.

[0049] As a method for adjusting the surface roughness Ra of the liquid crystal polymer film to the above-mentioned range, one example is the method described below of stretching a laminate obtained by co-extrusion of a liquid crystal polymer and an aromatic polyether ketone along the width direction at a temperature lower than the melting point of the aromatic polyether ketone.

[0050] <Aromatic polyetherketone film>

[0051] The aromatic polyetherketone film used in the liquid crystal polymer laminate of the present invention is formed of aromatic polyetherketone and is provided to prevent the liquid crystal polymer film from breaking during stretching. Furthermore, the aromatic polyetherketone film also functions as a protective film to prevent damage to the liquid crystal polymer film in subsequent processes (winding process, conveying process, etc.) of the liquid crystal polymer film laminate. From the viewpoint of good adhesion to the liquid crystal polymer film and its function as a protective film, the aromatic polyetherketone constituting the aromatic polyetherketone film preferably has a melting point higher than that of the liquid crystal polymer. Specific examples of aromatic polyetherketones include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and polyetheretherketoneketone (PEEKK). One of these polymers can be used alone or in combination of two or more. Among these, polyetheretherketone (PEEK) is preferred, because by using a film made of polyetheretherketone (PEEK), breakage can be prevented during the stretching process described later, and peeling of the liquid crystal polymer film laminate after stretching is suppressed, thus preventing damage to the liquid crystal polymer film. Furthermore, from the viewpoint of high heat resistance and the ability to be stretched at high temperatures, these films are preferably crystallized or stretched films.

[0052] The aromatic polyetherketone film only needs to be laminated on at least one side of the liquid crystal polymer film, preferably on both sides of the liquid crystal polymer film.

[0053] The thickness of the aromatic polyetherketone film is not particularly limited. From the viewpoint of the operability of the liquid crystal polymer film laminate and the suppression of deformation and peeling of the liquid crystal polymer film in subsequent processes (winding process, conveying process, etc.), it is preferably 5 to 100 μm, more preferably 5 to 50 μm, and particularly preferably 5 μm to 20 μm.

[0054] The aromatic polyetherketone (APE) film used in the liquid crystal polymer laminate of the present invention has the following characteristics: The APE film, when heated to 300°C while under a tensile load using a thermomechanical analysis (TMA) apparatus, exhibits a shrinkage rate of 13.5% or less. The liquid crystal polymer film laminate of the present invention is manufactured by a method including, as described below, stretching the laminate obtained by co-extruding a liquid crystal polymer and an APE using an extruder at least along its width direction. Therefore, the APE film constituting the liquid crystal polymer film laminate primarily generates stress that is expected to shrink along its width direction; if this stress is high, peeling from the liquid crystal polymer film is likely to occur. A shrinkage rate measured using a thermomechanical analysis apparatus of a specified value or less indicates that the residual strain of the APE film is small and the stress shrinking along its width direction is low.

[0055] Let the length of the aromatic polyetherketone film before heating be L. APK The shrinkage of the length of the aromatic polyetherketone film before and after heating is defined as ΔL. APK When the shrinkage rate is expressed as ΔL APK / L APK ×100 [%). The shrinkage rate is 13.5% or less, preferably 12.5% ​​or less, more preferably 11.0% or less, even more preferably 10.0% or less, and particularly preferably 9.0% or less. The lower limit of the shrinkage rate is not particularly limited, and is generally 0% or more. By keeping the shrinkage rate within the above range, it is possible to suppress the peeling from the liquid crystal polymer film caused by the residual strain of the aromatic polyetherketone film.

[0056] It should be noted that the shrinkage rate of the aromatic polyetherketone film can be determined simply by peeling the aromatic polyetherketone film off the liquid crystal polymer film and measuring the peeled aromatic polyetherketone film. The conditions for measuring the shrinkage rate are not particularly limited as long as a tensile load can be applied while heating to 300°C. Specifically, it is preferable to measure the shrinkage rate under the following conditions: preferably, the tensile load is set to 10 mN, and the temperature is increased from 30°C to 300°C at a rate of 10°C / min, thereby measuring the shrinkage rate.

[0057] The shrinkage rate only needs to be 13.5% or less in any direction of the aromatic polyetherketone film, preferably the maximum value among multiple directions is 13.5% or less. It is particularly preferred that the value measured along the width direction of the aromatic polyetherketone film is 13.5% or less. The reason for this is that during the manufacturing process of the liquid crystal polymer film laminate, the aromatic polyetherketone film mainly generates stress that is expected to shrink along the width direction, and the shrinkage rate measured along the width direction reaches its maximum. By ensuring that the shrinkage rate of the aromatic polyetherketone film measured along the width direction is 13.5% or less, the occurrence of peeling caused by residual strain of the aromatic polyetherketone film can be further suppressed.

[0058] As a method for adjusting the shrinkage rate of the aromatic polyetherketone film, which is determined by a thermomechanical analysis device, to 13.5% or less, one example is the method described below, which involves stretching a laminate obtained by co-extrusion of a liquid crystal polymer and aromatic polyetherketone along the width direction and then performing a relaxation treatment under specified conditions.

[0059] The aromatic polyetherketone film used in this invention preferably also possesses the following characteristics: Specifically, the slow axis orientation of the aromatic polyetherketone film, determined by phase difference measurement with its length direction set to 0°, is preferably 80° or higher and 100° or lower, or -100° or higher and -80° or lower. For the slow axis orientation, phase difference measurement can be performed on the aromatic polyetherketone film peeled from the liquid crystal polymer film with its length direction set to 0°, and the obtained data can be analyzed to determine the orientation. Specifically, it can be determined using the method described in the examples. The slow axis orientation is preferably 80° or higher and 100° or lower, or -100° or higher and -80° or lower, more preferably 85° or higher and 95° or lower, or -95° or higher and -85° or lower. A slow axis orientation within the above range indicates that the molecular chains constituting the aromatic polyetherketone film are mainly oriented along the width direction.

[0060] As a method for adjusting the slow axis orientation of the aromatic polyetherketone film to the above-mentioned range, one example is the method described below of stretching a laminate obtained by co-extrusion of a liquid crystal polymer and aromatic polyetherketone along the width direction.

[0061] <Method for manufacturing liquid crystal polymer thin film laminate>

[0062] The liquid crystal polymer film laminate of the present invention is manufactured by a method comprising the following steps: a first step, using an extruder to extrude molten liquid crystal polymer and aromatic polyetherketone in such a way that an aromatic polyetherketone layer is laminated on at least one side of a layer formed of liquid crystal polymer to obtain a laminate having a liquid crystal polymer film and an aromatic polyetherketone film laminated thereon; a second step, stretching the laminate at least in the width direction; and a third step, performing a relaxation treatment on the laminate at a temperature of -150°C or higher and a relaxation rate of 4% or higher and 20% or lower than that of the aromatic polyetherketone.

[0063] In the first step, a laminate of a layer formed of a liquid crystal polymer and a layer formed of an aromatic polyetherketone is manufactured by melt extrusion. Specifically, the liquid crystal polymer is melted using a first extruder, and the aromatic polyetherketone is melted using a second extruder. The polymers are extruded into a film (co-extrusion) such that the aromatic polyetherketone layer is laminated on at least one side of the liquid crystal polymer layer, thereby manufacturing the laminate.

[0064] The discharge rates of the liquid crystal polymer and the aromatic polyetherketone can be appropriately adjusted according to the thickness of the target liquid crystal polymer film and the aromatic polyetherketone film. From the viewpoint of operability and productivity during melt extrusion molding, the thickness of the layer formed by the liquid crystal polymer is preferably 20 to 1000 μm, more preferably 50 to 600 μm, further preferably 75 to 500 μm, and particularly preferably 100 to 400 μm. Furthermore, the thickness of the layer formed by the aromatic polyetherketone is preferably 10 to 200 μm, more preferably 15 to 100 μm, and particularly preferably 15 to 50 μm.

[0065] As a method for laminating a layer formed of aromatic polyetherketone (APE) onto at least one side of a layer formed of liquid crystal polymer, a multilayer extrusion film forming method using a T-die can be used. Specifically, examples include: a feed head method where molten liquid crystal polymer and APE supplied from two extruders are fed to a feed head and allowed to merge, then extruded in a film form from a T-die; and a manifold method where molten liquid crystal polymer and APE are separately fed to a T-die and extruded in overlapping film form. From the viewpoint of improving the smoothness of the liquid crystal polymer film constituting the resulting liquid crystal polymer film laminate, considering the differences in viscosity and flow characteristics of the liquid crystal polymer and APE during melting, the manifold method is preferred.

[0066] In the first step, an aromatic polyetherketone (APE) layer is deposited on at least one side of the liquid crystal polymer (LCP) layer, preferably on both sides of the LCP layer. By depositing APE layers on both sides of the LCP layer, the surface roughness Ra of both sides of the LCP film constituting the resulting LCP film laminate can be controlled within an appropriate range. Furthermore, by depositing APE layers on both sides of the LCP layer, breakage of the LCP layer can be more effectively suppressed during the stretching of the laminate in the second step.

[0067] In the second step, the laminate of the layer formed by the liquid crystal polymer and the layer formed by the aromatic polyetherketone is subjected to a stretching process, which involves stretching at least along the width direction (TD). As a method of stretching, such as... Figure 1As shown, a lateral stretching method using a tenter frame can be exemplified by clamping both ends of the laminate with a jig (not shown) and then heating and stretching it. By stretching the laminate along its width direction, the anisotropy of the liquid crystal polymer film constituting the resulting liquid crystal polymer film laminate can be reduced. Regarding the stretching ratio and stretching speed, they can be appropriately selected in a way that ensures the shape and physical properties of the liquid crystal polymer film obtained after stretching are within the desired range. The stretching ratio is preferably 2 to 5 times. The stretching speed is preferably 1 to 10000% / min, more preferably 50 to 5000% / min, and even more preferably 500 to 4000% / min. Furthermore, to adjust the planar orientation after stretching, additional stretching along the length direction (MD) can be performed as needed.

[0068] In the second step, the furnace temperature of the stretching apparatus (the furnace temperature of the stretching strip of the stretching apparatus) during the stretching of the laminate is preferably below the melting point of aromatic polyetherketone (APE) + 30°C, more preferably below the melting point of APE + 10°C, and even more preferably below the melting point of APE - 10°C. The furnace temperature of the stretching strip of the stretching apparatus is preferably above the melting point of APE - 130°C, more preferably above the melting point of APE - 110°C, and even more preferably above the melting point of APE - 90°C. In the second step, by setting the stretching ratio, stretching speed, and furnace temperature of the stretching apparatus within a specified range, the surface temperature of the laminate during stretching (reaching the stretching temperature) can be adjusted to be below the melting point of APE. By setting the reaching stretching temperature below the melting point of APE, the smoothness of the liquid crystal polymer film constituting the obtained liquid crystal polymer film laminate can be improved, and the surface roughness Ra of the liquid crystal polymer film can be controlled within an appropriate range. The stretching temperature can be any temperature lower than the melting point of aromatic polyetherketone, preferably 20-150°C lower than the melting point of aromatic polyetherketone, and more preferably 40-100°C lower than the melting point of aromatic polyetherketone.

[0069] It should be noted that, as Figure 1As shown, in the second step, it is preferable to preheat the laminate before stretching it. The furnace temperature of the stretching apparatus during preheating (the furnace temperature of the preheating zone of the stretching apparatus) is preferably below the melting point of aromatic polyetherketone (APE) + 40°C, more preferably below the melting point of APE + 20°C, and even more preferably below the melting point of APE. The furnace temperature of the preheating zone of the stretching apparatus is typically above the melting point of APE - 130°C. The preheating time, i.e., the time from when the laminate enters the preheating zone of the stretching apparatus until it passes through the preheating zone, can be adjusted appropriately according to the conveying speed of the laminate and is not particularly limited. For example, the preheating time of the laminate is preferably 3 to 40 seconds, more preferably 6 to 20 seconds. By preheating the laminate, it is easy to control the reaching stretching temperature of the laminate within an appropriate range.

[0070] In the third step, the laminate is subjected to relaxation treatment at a temperature above -150°C (the melting point of aromatic polyetherketone) and a relaxation rate of 4% to 20%. For example... Figure 1 As shown, relaxation treatment refers to the process of shrinking the stretched laminate along the stretching direction. For example, if the laminate is stretched along the width direction in the second step, it is then shrunk along the width direction in the third step. There is no particular limitation on the method for shrinking the laminate; for example, when stretching the laminate using a tenter frame's transverse stretching method, a method can be listed where the distance between the tenter frame's clamps is appropriately reduced downstream of the stretched laminate's conveying direction. By performing relaxation treatment on the stretched laminate under the above conditions, residual strain within the laminate caused by the stretching process can be reduced, and delamination between the liquid crystal polymer film and the aromatic polyetherketone film can be suppressed.

[0071] When the width of the laminate after the second process (after stretching) is defined as W, and the shrinkage of the width of the laminate before and after the relaxation treatment is defined as ΔW, the relaxation rate in the width direction of the laminate based on the relaxation treatment is expressed as ΔW / W×100 [%). The relaxation rate is 4% or more and 20% or less, preferably 4% or more and 16% or less, more preferably 8% or more and 16% or less, and particularly preferably 12% or more and 16% or less. If the relaxation rate is too small, the stress generated in the laminate due to stretching cannot be sufficiently reduced, and peeling of the liquid crystal polymer film from the aromatic polyetherketone film may occur in the obtained liquid crystal polymer film laminate. On the other hand, if the relaxation amount is too large, the tension of the aromatic polyetherketone film may be insufficient, resulting in relaxation in the width direction, shape damage, contact between the film and the furnace equipment, or the liquid crystal polymer film may not be able to be rolled into a roll in subsequent processes.

[0072] In the third step, the furnace temperature of the stretching apparatus during the relaxation process (the furnace temperature of the relaxation zone of the stretching apparatus) is at least 150°C below the melting point of aromatic polyetherketone (APE), preferably at least 120°C below the melting point of APE, more preferably at least 100°C below the melting point of APE, even more preferably at least 70°C below the melting point of APE, particularly preferably at least 50°C below the melting point of APE, and most preferably at least 30°C below the melting point of APE. The upper limit of the furnace temperature is typically below the melting point of APE. If the furnace temperature is too low, even with a specified relaxation rate, the stress generated within the laminate due to stretching cannot be sufficiently reduced, and peeling between the liquid crystal polymer film and the APE film may occur in the resulting liquid crystal polymer film laminate. Furthermore, if the furnace temperature is too low, the layer formed by the liquid crystal polymer may slightly solidify and shrink under conditions of high deformation resistance, potentially resulting in residual strain in the layer formed by the liquid crystal polymer due to the relaxation process. Therefore, in the obtained liquid crystal polymer film stack, the coefficient of linear expansion α in the width direction of the liquid crystal polymer film is... TD It is possible for the temperature to increase. On the other hand, if the temperature inside the furnace is too high, it may reach the melting point of the aromatic polyetherketone film and cause the aromatic polyetherketone film to melt.

[0073] As described above, the liquid crystal polymer film laminate of the present invention can be obtained. In the liquid crystal polymer film laminate thus obtained, the shrinkage rate of the aromatic polyetherketone film before and after heating to 300°C while applying a tensile load using a thermomechanical analysis apparatus (TMA) is 13.5% or less. Therefore, the residual strain of the aromatic polyetherketone film caused by the stretching treatment is sufficiently reduced, resulting in excellent adhesion between the liquid crystal polymer film and the aromatic polyetherketone film in the liquid crystal polymer film laminate of the present invention. Therefore, according to the present invention, deformation of the liquid crystal polymer film can be suppressed, and the liquid crystal polymer film laminate can be formed into a roll.

[0074] It should be noted that, as a subsequent process, the liquid crystal polymer film laminate obtained by the above method can be subjected to heat treatment or hot pressing. There are no particular limitations on the heat treatment method; for example, heating the rolled liquid crystal polymer film laminate in an oven at a temperature of 120~330°C can be cited. There are also no particular limitations on the hot pressing method; for example, pressing the laminate at high temperature using a hot press can be cited. By subjecting the liquid crystal polymer film laminate to heat treatment or hot pressing, the heat resistance of the liquid crystal polymer film can be improved. In this case, as an aromatic polyetherketone film, by using an aromatic polyetherketone film having a melting point higher than that of the liquid crystal polymer, heat treatment or hot pressing at higher temperatures is possible.

[0075] <Method for Manufacturing Liquid Crystal Polymer Thin Films>

[0076] A liquid crystal polymer film can be obtained by peeling an aromatic polyetherketone film from a liquid crystal polymer film laminate obtained using the above method. The liquid crystal polymer film thus obtained can be controlled by adjusting its coefficient of linear expansion α. MD α TD By controlling the surface alignment, anisotropy is reduced, and excellent surface smoothness is achieved by controlling the surface roughness Ra. Therefore, when manufacturing an FPC by forming a metal layer on the liquid crystal polymer film, deformation caused by anisotropy can be appropriately suppressed, and transmission loss during high-frequency signal flow can be reduced. Thus, the liquid crystal polymer film manufactured using the liquid crystal polymer film laminate of the present invention is suitable for circuit substrates such as FPCs.

[0077] Example

[0078] Next, specific examples will be given to illustrate the present invention, but the present invention is not limited thereto.

[0079] <Wide-direction shrinkage of PEEK films>

[0080] The PEEK film obtained by peeling off the obtained liquid crystal polymer film laminate is processed to prepare a rectangular test piece having a long side (19 mm in length) along the width direction (TD) and a short side (5 mm in length) along the length direction (MD). For example... Figure 2 As shown, in a thermomechanical analysis apparatus (Rigaku Electric Co., Ltd., model: TMA8310), the test specimen was mounted with a fixture spacing of 15 mm, applying a load along its long side, i.e., its width direction (TD). A tensile load of 10 mN was applied to the specimen while it was heated from 30°C to 300°C at a rate of 10°C / min. Figure 3 As shown, the shrinkage rate in the width direction (TD) of the PEEK film is calculated based on the amount of deformation (length shrinkage) of the test piece at the moment of reaching 300°C relative to the beginning of heating. Figure 2 This diagram illustrates a method for determining the deformation of a test piece using a thermomechanical analysis (TMA) apparatus. Figure 3 This is a graph representing the measurement results of the PEEK thin film test piece in Example 2 using a thermomechanical analysis device.

[0081] <Interlayer Fit Evaluation>

[0082] At both ends of the obtained liquid crystal polymer film laminate, slits were made using a rotating circular cutter (single-edged, upper blade thickness 0.5 mm, upper blade tip angle 65°) to expose the slit end faces. The length of the peel between the liquid crystal polymer film and the PEEK film was measured at the slit end faces and evaluated as follows. A shorter peel length indicates better adhesion (interlayer adhesion) between the liquid crystal polymer film and the PEEK film. Figure 4 A schematic diagram of the upper cutting edge of a rotary circular cutter used for interlayer adhesion evaluation.

[0083] A: Peeling length less than 1mm

[0084] B: Peeling length exceeding 1mm but less than 5mm

[0085] C: Peeling length exceeds 5mm

[0086] D: Frequent interlaminar dehiscence before incision formation prevents incision formation.

[0087] <Coefficient of linear expansion α of liquid crystal polymer film MD α TD >

[0088] A liquid crystal polymer film obtained by peeling a PEEK film from a liquid crystal polymer film laminate was processed to prepare a rectangular test piece having a long side (19 mm in length along the width direction (TD)) and a short side (5 mm in length along the length direction (MD). The test piece was mounted in a thermomechanical analysis apparatus (Rigaku Electric Co., Ltd., model: TMA8310) with a clamping distance of 15 mm, applying a load along the long side, i.e., the width direction (TD). A tensile load of 10 mN was applied to the test piece while heating it from 30°C to 150°C at a rate of 5°C / min. Based on the change in length of the test piece at the moment of reaching 150°C relative to the start of heating and the temperature change caused by heating, the coefficient of linear expansion α of the liquid crystal polymer film was calculated. TD Similarly, a rectangular liquid crystal polymer film test piece with a long side (19 mm in length) along the length direction (MD) and a short side (5 mm in length) along the width direction was prepared, and the linear expansion coefficient α of the liquid crystal polymer film was calculated by measuring the same parameters. MD .

[0089] <Surface alignment degree of liquid crystal polymer films>

[0090] A liquid crystal polymer film was prepared by peeling a PEEK film from a liquid crystal polymer film laminate. Using a sample-level multifunctional X-ray diffractometer (Rigaku Corporation, model: Ultima IV), with the diffraction angle (2θ) fixed at 20°, and under the following conditions: X-ray target: Cu, voltage: 40 kV, current: 40 mA, α angle = 45°, β angle = 0~360° (with the length direction of the film at 0° and the step angle at 5°), the poles of the liquid crystal polymer film were measured, and the X-ray diffraction intensity distribution was fabricated. Find the integral intensity of the distribution at β=45~135°, 135°~225°, 225~315°, and 315~45°. Take the sum of the integral intensity of β=45~135° and β=225°~315° as the integral intensity in the length direction, and take the sum of the integral intensity of β=135~225° and β=315~45° as the integral intensity in the width direction. Calculate the surface orientation degree based on the above equation (3).

[0091] <Surface roughness Ra of liquid crystal polymer film>

[0092] The surface roughness was measured using a contact surface roughness measuring instrument (SURFCOM 1400D-3DF, manufactured by Tosei Engineering Co., Ltd.). According to JIS B0601:1994, a stylus with a front-end radius of 2 μm was used, with a measuring length of 4 mm and a cutoff radius of λ. c Under the condition of 0.8 mm, the surface roughness Ra of the liquid crystal polymer film obtained by peeling off the PEEK film from the liquid crystal polymer film laminate is determined. For the front and back sides of the film, the surface roughness Ra is determined for the length direction (MD) and width direction (TD) of the film, respectively.

[0093] <Slow axis orientation of aromatic polyetherketone films>

[0094] A PEEK film, obtained by peeling off a liquid crystal polymer film laminate, was prepared. The PEEK film was positioned on the stage of a metal microscope (Olympus Corporation, model: BX51) with its length direction (MD) aligned with the 0° direction of the viewing area. Phase difference measurements (transmission measurement, measurement accuracy standard, measurement mode 3-wavelength measurement) were performed using a wide-range two-dimensional birefringence evaluation system (Photonic Lattice Inc., model: WPA-micro) to obtain image data including phase difference and slow axis orientation. A circular line with a diameter of at least half the minor axis of the measurement field of view, centered on the obtained image data and aligned with the center of the measurement field of view, was drawn. The slow axis orientation data on this line were analyzed to determine the slow axis orientation of the PEEK film.

[0095] <Melting points of liquid crystal polymers and PEEK>

[0096] Using a differential scanning calorimeter (PerkinElmer, model: DSC8500), the liquid crystal polymer film obtained from the peeling of the liquid crystal polymer film laminate was analyzed according to the differential scanning calorimetry method based on JIS K 7121. The melting point of the liquid crystal polymer film was determined by the endothermic peak temperature observed when the temperature was increased from 0°C at a rate of 10°C / min. Similarly, the melting point of the PEEK film obtained from the peeling of the liquid crystal polymer film laminate was determined by the same method, with the endothermic peak temperature observed when the temperature was increased from 0°C at a rate of 10°C / min. Measurements were performed on all examples and comparative examples, and the melting point of the liquid crystal polymer was 280°C, while the melting point of the PEEK was 340°C.

[0097] <Example 1>

[0098] A liquid crystal polymer (manufactured by Polyplastics Co., Ltd., LAPEROS A950RX) was fed into a twin-screw extruder (screw diameter 26 mm) and melt-blended at 300°C. Separately, a polyetheretherketone (PEEK) polymer (manufactured by Daicel-Evonik, VESTAKEEP 3300G), which is an aromatic polyetheretherketone, was fed into a single-screw extruder (screw diameter 40 mm) and melt-blended at 380°C. These molten polymers were then fed into a multi-manifold T-die and extruded by overlapping a PEEK layer on both sides of the liquid crystal polymer layer. After cooling, a laminate with a 175 μm liquid crystal polymer layer and two 30 μm PEEK layers on each side, totaling 235 μm, was produced.

[0099] The laminate prepared in this way was stretched 3.5 times along the width direction (TD) using a transverse stretching machine (furnace temperature 330°C) with a stretching zone length of 1.2 m and a conveying speed of 3 m / min (stretching speed 625% / min). Next, while holding the laminate in the tenter frame, the clamping gap of the tenter frame was linearly reduced at a relaxation speed of 40% / min at 330°C, resulting in a relaxation amount of 8%. The liquid crystal polymer film laminate was obtained as described above. The adhesion between the liquid crystal polymer film and the PEEK film was evaluated. Furthermore, the liquid crystal polymer film and the PEEK film were peeled off, and the above evaluation was performed on each film. The results are shown in Table 2.

[0100] <Examples 2-11, Comparative Examples 1-4>

[0101] The stretching ratio and stretching speed during the stretching of the laminate, as well as the furnace temperature, relaxation rate, and relaxation speed during the relaxation process, were changed to the values ​​shown in Table 1. Otherwise, the liquid crystal polymer film laminate was manufactured in the same manner as in Example 1, and the evaluation was performed in the same manner. The results are shown in Table 2.

[0102] [Table 1]

[0103]

[0104] [Table 2]

[0105]

[0106] As shown in Table 2, the interlayer adhesion of liquid crystal polymer film laminates with a shrinkage rate of less than 13.5% obtained by applying a tensile load to the aromatic polyetherketone (PEEK) film and heating it to 300°C using a thermomechanical analysis (TMA) apparatus is excellent. Furthermore, the anisotropy of the liquid crystal polymer film obtained by peeling off the PEEK film is reduced, and the smoothness is excellent.

[0107] On the other hand, in Comparative Examples 1-3, where the shrinkage rate of aromatic polyetherketone exceeded 13.5%, poor interlayer adhesion was observed. Furthermore, in Comparative Example 4, where relaxation treatment was performed under conditions exceeding 20%, insufficient film tension resulted in film relaxation, causing the film to come into contact with the furnace equipment, making it impossible to wind up using rollers.

Claims

1. A liquid crystal polymer thin film laminate, comprising: Liquid crystal polymer film, and An aromatic polyetherketone film laminated on at least one side of the liquid crystal polymer film. When the aromatic polyetherketone film is heated to 300°C while under tensile load using a thermomechanical analysis (TMA) device, the shrinkage rate of the aromatic polyetherketone film is less than 13.5%.

2. The liquid crystal polymer thin film laminate according to claim 1, wherein, The coefficient of linear expansion along the length of the liquid crystal polymer film is set as α. MD The coefficient of linear expansion in the width direction of the liquid crystal polymer film is set as α. TD When, the following equations (1) and (2) are satisfied; 10ppm / ℃≤α TD ≤80ppm / ℃ (1) |a MD -a TD |≤60ppm / ℃ (2).

3. The liquid crystal polymer film laminate according to claim 1 or 2, wherein, The planar orientation degree of the liquid crystal polymer film, calculated based on pole determination using X-ray diffraction, is greater than or equal to -0.3 and less than 0.

5.

4. The liquid crystal polymer thin film laminate according to any one of claims 1 to 3, wherein, The surface roughness Ra of at least one side of the liquid crystal polymer film is less than 0.20 μm.

5. The liquid crystal polymer thin film laminate according to any one of claims 1 to 4, wherein, The slow axis orientation of the aromatic polyetherketone film, determined by phase difference measurement, is either above 80° and below 100°, or above -100° and below -80°.

6. The liquid crystal polymer thin film laminate according to any one of claims 1 to 5, wherein, The aromatic polyetherketone film is polyetheretherketone (PEEK).

7. A method for manufacturing a liquid crystal polymer thin film laminate according to any one of claims 1 to 6, comprising: In the first step, molten liquid crystal polymer and aromatic polyether ketone are extruded into a film by using an extruder, in such a way that a layer formed of aromatic polyether ketone is stacked on at least one side of a layer formed of liquid crystal polymer, to obtain a laminate. In the second step, the laminate is stretched at least along its width; and In the third step, the laminate is subjected to a relaxation treatment at a temperature above -150°C where the melting point of the aromatic polyetherketone is above 4% and below 20%.

8. A method for manufacturing a liquid crystal polymer film, comprising: The process of obtaining a liquid crystal polymer thin film laminate by the manufacturing method of the liquid crystal polymer thin film laminate according to claim 7; and Step 4: Peeling off the aromatic polyetherketone film.

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