Liquid crystal polymer film, metal-clad laminate and method for producing same, and circuit board and multilayer circuit board

Abstract

Provided is a liquid crystal polymer film which, when laminated with a metal sheet to form a metal-clad laminate, makes it possible to produce a metal-clad laminate that is excellent in appearance and has superior isotropy of mechanical properties. The liquid crystal polymer film has a ratio of tensile elongation in a machine direction MD to tensile elongation in a transverse direction TD (tensile elongation MD) / tensile elongation TD) of 0.5 to 1.0.

Description

Liquid crystal polymer film, metal-clad laminate and its manufacturing method, as well as circuit board and multilayer circuit board Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2024-091799, filed on June 5, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a liquid crystal polymer film, a metal-clad laminate and a method for producing the same, a circuit board, and a multilayer circuit board.

[0003] Polymers capable of forming an optically anisotropic molten phase (hereinafter referred to as "liquid crystal polymers") are widely used as engineering plastics due to their high strength and high heat resistance. In particular, liquid crystal polymer films have excellent low moisture absorption, heat resistance, chemical resistance, and electrical properties, and in recent years, metal-clad laminates with liquid crystal polymer films have been used as materials for flexible wiring boards, circuit boards for semiconductor packaging, and the like.

[0004] For example, Patent Document 1 discloses a method for manufacturing a liquid crystal polymer film comprising a thermoplastic liquid crystal polymer film and a thermoplastic liquid crystal polymer layer, and also discloses a method for manufacturing a high-frequency circuit board material by laminating copper foil onto such a liquid crystal polymer film.

[0005] Patent Document 2 describes a metal-clad laminate obtained by laminating an unheated liquid crystal polymer film with a metal material using a double belt press.

[0006] JP 2023-181136 A Taiwan Patent No. I796650 A

[0007] In recent years, the widespread use of high-performance compact electronic devices such as smartphones has led to an increase in the density of components and the miniaturization of electronic devices, creating a demand for thin, lightweight circuit boards that can be bent and shaped to fit the installation shape during wiring and circuit assembly.

[0008] Due to their mechanical and electrical properties, liquid crystal polymer films are more flexible than conventional polyimide films, exhibiting less rebound when bent, allowing for thinner and lighter substrates, and are characterized by excellent heat resistance and heat dissipation. On the other hand, liquid crystal polymer films also have the characteristic that the molecules are more likely to orient due to the rigid molecular structure of the liquid crystal polymer, and that these properties tend to become anisotropic in the in-plane direction due to the influence of molecular orientation. If the mechanical properties of liquid crystal polymer films in metal-clad laminates are anisotropic, problems such as twisting and tearing can occur when circuits incorporating the film are bent and processed. Patent Document 1 describes that liquid crystal polymers are prone to tearing due to their anisotropy, but does not specifically describe the isotropy of the mechanical properties of liquid crystal polymer films in metal-clad laminates obtained using liquid crystal polymer films.

[0009] Furthermore, liquid crystal polymer films are difficult to process into metal-clad laminates. When a thin liquid crystal polymer film is laminated to a metal sheet while being transported to form a metal-clad laminate, high temperatures are required to enhance adhesion. High tension during transport stretches the liquid crystal polymer film at a high temperature, resulting in wrinkles in the machine direction. On the other hand, weak tension can result in poor appearance, such as the formation of wavy wrinkles. As in Patent Document 2, when a liquid crystal polymer film that has not been heat-treated is laminated using a double belt press, wrinkles and other poor appearances tend to occur. Furthermore, when a liquid crystal polymer film is laminated to a metal sheet, high temperatures are required to ensure adhesion, which can lead to problems such as poor isotropy of mechanical properties due to changes in molecular orientation and domain structure.

[0010] An object of the present invention is to provide a liquid crystal polymer film that, when laminated with a metal sheet, results in a metal-clad laminate that has a good appearance and isotropic mechanical properties in both the MD and TD. Another object of the present invention is to provide a metal-clad laminate, a circuit board, a multilayer circuit board, and a method for producing a metal-clad laminate obtained using the liquid crystal polymer film.

[0011] That is, the present invention can be configured in the following aspects: [Aspect 1] Tensile elongation in the machine direction ＭＤ and transverse tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤ ) is 0.5 or more and 1.0 or less (preferably 0.6 or more and 0.9 or less). ＭＤ and transverse tensile modulus ＴＤ Ratio of (tensile modulus ＭＤ / Tensile modulus ＴＤ The liquid crystal polymer film according to aspect 1, wherein the tensile elongation in the machine direction is 1.2 or more and 2.0 or less (preferably 1.3 or more and 1.8 or less). ＭＤ and transverse tensile elongation ＴＤ The liquid crystal polymer film according to aspect 1 or 2, wherein the tensile modulus in the machine direction is 8.0% or more (preferably 8.0% or more and 25.0% or less). ＭＤ is 5000 MPa or more (preferably 5000 MPa or more and 15000 MPa or less, more preferably 7000 MPa or more and 14000 MPa or less), and the tensile modulus in the transverse direction is ＴＤ The liquid crystal polymer film according to any one of aspects 1 to 3, wherein the tensile elongation in the machine direction of the liquid crystal polymer film is 3,500 MPa or more (preferably 3,500 MPa or more and 11,000 MPa or less, more preferably 4,000 MPa or more and 10,000 MPa or less). [Aspect 5] The liquid crystal polymer film according to any one of aspects 1 to 4, which is in the form of a roll. [Aspect 6] The liquid crystal polymer film according to any one of aspects 1 to 5, which is for producing a metal-clad laminate by continuously laminating it with a metal sheet. [Aspect 7] A metal-clad laminate in which a metal sheet is laminated on a liquid crystal polymer film, wherein the tensile elongation in the machine direction of the liquid crystal polymer film is ＭＤ and transverse tensile elongation ＴＤ is 20.0% or more (preferably 25.0% or more and 50.0% or less, more preferably 28.0% or more and 45.0% or less), and the tensile elongation ＭＤ and tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤA metal-clad laminate in which the tensile modulus in the machine direction of the liquid crystal polymer film is 0.80 or more and 1.20 or less (preferably 0.90 or more and 1.15 or less). ＭＤ and transverse tensile modulus ＴＤ is 3000 MPa or more (preferably 3200 MPa or more), and the tensile modulus ＭＤ and tensile modulus ＴＤ Ratio of (tensile modulus ＭＤ / Tensile modulus ＴＤ ) is 0.80 or more and 1.50 or less (preferably 0.90 or more and 1.40 or less, more preferably 0.90 or more and 1.20 or less). [Aspect 9] The metal-clad laminate according to aspect 7 or 8, wherein the peel strength between the liquid crystal polymer film and the metal sheet is 0.50 N / mm or more (preferably 0.65 N / mm or more, more preferably 0.80 N / mm or more). [Aspect 10] A circuit board, in which a circuit pattern is formed on the metal sheet of the metal-clad laminate according to any one of aspects 7 to 9. [Aspect 11] A multilayer circuit board, comprising the circuit board according to aspect 10. [Aspect 12] A method for producing a metal-clad laminate, in which a metal sheet and the liquid crystal polymer film according to any one of aspects 1 to 5 are continuously laminated using a double belt press or a roll press.

[0012] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms "at least one," unless the content clearly dictates otherwise. As used herein, the terms "and / or," "at least one," and "one or more" include any and all combinations of the associated listed items.

[0013] It should be noted that any combination of at least two elements disclosed in the claims and / or the specification and / or the drawings is included in the present invention, and in particular any combination of two or more of the claims set forth in the claims is included in the present invention.

[0014] When the liquid crystal polymer film of the present invention is laminated with a metal sheet to form a metal-clad laminate, the metal-clad laminate has a good appearance and isotropic mechanical properties, and it is easy to produce such a metal-clad laminate.

[0015] 1 is a schematic diagram showing the configuration of a pretreatment device used in a manufacturing method according to an embodiment of the present invention. 2 is a schematic diagram showing the configuration of a double belt press device used in a manufacturing method according to an embodiment of the present invention. 3 is a schematic diagram showing the configuration of a continuous heat press device used in a manufacturing method according to an embodiment of the present invention.

[0016] <Liquid Crystal Polymer Film> The liquid crystal polymer film of the present invention is a film containing a liquid crystal polymer, and has a tensile elongation in the machine direction. ＭＤ and transverse tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤ ) is 0.5 or more and 1.0 or less. The machine direction of the liquid crystal polymer film is the longitudinal direction parallel to the direction in which the liquid crystal polymer is extruded to form a film and transported in the film-forming process of the liquid crystal polymer film, and may be abbreviated as MD. The transverse direction is the direction perpendicular to the MD in the plane of the liquid crystal polymer film, and may be abbreviated as TD. For example, when the liquid crystal polymer film is a roll-shaped product, the longitudinal direction of the roll-shaped product is the MD, and the width direction of the roll-shaped product is the TD. In one embodiment, when the liquid crystal polymer film is laminated with a metal sheet by roll-to-roll roll press or double belt press or the like to continuously produce a metal-clad laminate, the liquid crystal polymer film is transported in the MD and processed, such as being laminated with a metal sheet.

[0017] Liquid crystal polymer film has a tensile elongation in the transverse direction. ＴＤ is the tensile elongation in the machine direction ＭＤ The larger the elongation in the machine direction, the better. ＭＤ and transverse tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤ ) is preferably 0.6 or more and 0.9 or less.

[0018] Tensile elongation of liquid crystal polymer film ＭＤis preferably 5.0% or more and 30.0% or less, and more preferably 8.0% or more and 25.0% or less. ＴＤ In one embodiment, the tensile elongation of the liquid crystal polymer film is preferably 8.0% or more and 25.0% or less, and more preferably 10.0% or more and 20.0% or less. ＭＤ and tensile elongation ＴＤ Preferably, both are 8.0% or more, and more preferably, both are 8.0% or more and 25.0% or less.

[0019] The liquid crystal polymer film has a tensile modulus in the machine direction. ＭＤ is the transverse tensile modulus ＴＤ The larger the modulus of elasticity in the machine direction, the more preferable. ＭＤ and transverse tensile modulus ＴＤ Ratio of (tensile modulus ＭＤ / Tensile modulus ＴＤ ) is preferably 1.2 or more and 2.0 or less, and more preferably 1.3 or more and 1.8 or less.

[0020] Tensile modulus of liquid crystal polymer film ＭＤ The tensile modulus of the liquid crystal polymer film is preferably 5000 MPa or more and 15000 MPa or less, and more preferably 7000 MPa or more and 14000 MPa or less. ＴＤ is preferably 3500 MPa or more and 11000 MPa or less, and more preferably 4000 MPa or more and 10000 MPa or less.

[0021] In this specification, the tensile elongation and tensile modulus of a liquid crystal polymer film are values ​​measured by the following method. That is, a liquid crystal polymer film is cut into a length of 100 mm and a width of 10 mm, and two samples are prepared: one cut so that the MD is the sample length direction, and the other cut so that the TD is the sample length direction. A tensile test is performed on each sample at a chuck distance of 50 mm and a tensile speed of 10 mm / min, and the MD and TD tensile elongation and tensile modulus are calculated from the resulting stress-strain curve (SS curve). The sample thickness is measured with a micrometer at three points: the center and both ends of a 50 mm chuck distance. The average value of the three points is used as the sample thickness to calculate the cross-sectional area of ​​the sample. The tensile elongation is the tensile strain at break and is calculated as tensile elongation (%) = [(L - Lo) / Lo] x 100 (where Lo is the sample length before the test and L is the sample length at break). The tensile modulus is calculated from the slope of the line connecting the point where the stress is 11.8 N (1.2 kgf) and the point where the stress is 19.6 N (2.0 kgf). Specifically, it is a value measured by the method described in the Examples below.

[0022] Generally, in the process of producing a metal-clad laminate by thermocompression bonding a liquid crystal polymer film and a metal sheet using a double belt press or a roll press, the shear force applied to the heat-softened liquid crystal polymer film changes the molecular orientation of the liquid crystal polymer film. Furthermore, whether a double belt press or a roll press is used, the liquid crystal polymer film is stretched in both the MD and TD, and this stretching also changes the molecular orientation of the film. In particular, when a low-roughness metal sheet with excellent high-frequency characteristics is used as the metal sheet, higher temperatures and pressures are required for thermocompression bonding to improve adhesion, which results in more pronounced changes in the molecular orientation of the liquid crystal polymer film. In prior art, changes in the molecular orientation of the liquid crystal polymer film caused by the above-mentioned complex factors result in anisotropy in the mechanical properties of the resulting metal-clad laminate. In particular, when laminating a low-roughness metal sheet with excellent high-frequency characteristics and a liquid crystal polymer film, it has been difficult to control the mechanical properties isotropically while ensuring the peel strength of the resulting metal-clad laminate, even when the thermocompression bonding conditions are adjusted. This problem is particularly pronounced in the small, complex-shaped circuits that have been adopted in recent years. When the circuits are bent and installed or bent to be incorporated into a substrate, the anisotropy of the mechanical properties of the liquid crystal polymer film contained in the circuits can cause problems such as twisting of the circuits.

[0023] On the other hand, the liquid crystal polymer film of the present invention has a tensile elongation ＭＤ / Tensile elongation ＴＤ is controlled within the above range, and when such a liquid crystal polymer film is thermocompression bonded to a metal sheet to produce a metal-clad laminate, the molecular orientation can be easily controlled by adjusting the temperature and pressure during thermocompression bonding, and as a result, the mechanical properties (at least tensile elongation) of the resulting metal-clad laminate are excellent in isotropy. In particular, the liquid crystal polymer film of the present invention can be made isotropic in mechanical properties even when used with a low-roughness metal sheet that has excellent high-frequency characteristics.

[0024] The liquid crystal polymer film of the present invention contains a liquid crystal polymer, which is a polymer capable of forming an optically anisotropic melt phase. The liquid crystal polymer film may contain a thermoplastic liquid crystal polymer that can be melt-formed, or may be a thermoplastic liquid crystal polymer film, i.e., a thermoplastic liquid crystal polymer film. The chemical structure of the liquid crystal polymer is not particularly limited, but examples thereof include liquid crystal polyesters and liquid crystal polyesteramides in which amide bonds have been introduced therein.

[0025] The liquid crystal polymer may also be a polymer in which an isocyanate-derived bond such as an imide bond, a carbonate bond, a carbodiimide bond or an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide.

[0026] Specific examples of liquid crystal polymers include known liquid crystal polyesters and liquid crystal polyesteramides derived from compounds classified as (1) to (4) below and their derivatives. However, it goes without saying that there is an appropriate range for the combination of various raw material compounds in order to form a polymer capable of forming an optically anisotropic molten phase.

[0027] The ability to form an optically anisotropic molten phase as referred to in this specification can be confirmed, for example, by placing a sample on a hot stage, heating it in a nitrogen atmosphere, and observing the light transmitted through the sample.

[0028] (1) Aromatic or aliphatic diol (see Table 1 for representative examples)

[0029] (2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for representative examples)

[0030] (3) Aromatic hydroxycarboxylic acids (see Table 3 for representative examples)

[0031] (4) Aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids (see Table 4 for representative examples)

[0032] Representative examples of liquid crystal polymers obtained from these raw material compounds include copolymers having the repeating units shown in Tables 5 and 6.

[0033]

[0034]

[0035] Among these copolymers, copolymers containing at least p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as repeating units are preferred, and particularly preferred are (i) copolymers containing repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, or (ii) copolymers containing repeating units of at least one aromatic hydroxycarboxylic acid selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, at least one aromatic diol and / or aromatic hydroxyamine, and at least one aromatic dicarboxylic acid.

[0036] For example, in the copolymer (i), when the liquid crystal polymer contains at least repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the molar ratio (A) / (B) of the p-hydroxybenzoic acid in the repeating unit (A) to the 6-hydroxy-2-naphthoic acid in the repeating unit (B) in the liquid crystal polymer is preferably (A) / (B)=10 / 90 to 90 / 10, more preferably (A) / (B)=15 / 85 to 85 / 15, even more preferably (A) / (B)=30 / 70 to 90 / 10, even more preferably (A) / (B)=50 / 50 to 85 / 15, and particularly preferably (A) / (B)=70 / 30 to 85 / 15.

[0037] In the case of the copolymer (i), in addition to the repeating units derived from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, from the viewpoint of adjusting the molecular weight, etc., it may contain repeating units derived from an aromatic diol or an aromatic dicarboxylic acid (for example, terephthalic acid).

[0038] In the case of the copolymer (ii), at least one aromatic hydroxycarboxylic acid (C) selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, at least one aromatic diol (D) selected from the group consisting of 4,4'-dihydroxybiphenyl, hydroquinone, phenylhydroquinone, and 4,4'-dihydroxydiphenyl ether, and at least one aromatic diol (E) selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. The molar ratio of each repeating unit of the carboxylic acid (E) in the liquid crystal polymer may be the aromatic hydroxycarboxylic acid (C): the aromatic diol (D): the aromatic dicarboxylic acid (E) = (30 to 80): (35 to 10): (35 to 10), more preferably (C): (D): (E) = (35 to 75): (32.5 to 12.5): (32.5 to 12.5), and even more preferably (C): (D): (E) = (40 to 70): (30 to 15): (30 to 15).

[0039] The molar ratio of repeating units derived from 6-hydroxy-2-naphthoic acid in the aromatic hydroxycarboxylic acid (C) may be, for example, 85 mol % or more, preferably 90 mol % or more, and more preferably 95 mol % or more. The molar ratio of repeating units derived from 2,6-naphthalenedicarboxylic acid in the aromatic dicarboxylic acid (E) may be, for example, 85 mol % or more, preferably 90 mol % or more, and more preferably 95 mol % or more.

[0040] Alternatively, the aromatic diol (D) may be repeating units (D1) and (D2) derived from two different aromatic diols selected from the group consisting of hydroquinone, 4,4'-dihydroxybiphenyl, phenylhydroquinone, and 4,4'-dihydroxydiphenyl ether. In this case, the molar ratio of the two aromatic diols (D1) / (D2) may be 23 / 77 to 77 / 23, more preferably 25 / 75 to 75 / 25, and even more preferably 30 / 70 to 70 / 30.

[0041] Furthermore, the molar ratio of the repeating structural units derived from the aromatic diol to the repeating structural units derived from the aromatic dicarboxylic acid, (D) / (E), is preferably 95 / 100 to 100 / 95. If the ratio is outside this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

[0042] The melting point of the liquid crystal polymer is preferably 260°C or higher, more preferably 270°C or higher, and even more preferably 280°C or higher. The melting point of the liquid crystal polymer may be 380°C or lower, preferably 370°C or lower, more preferably 360°C or lower, even more preferably 350°C or lower, and even more preferably 340°C or lower. The melting point of the liquid crystal polymer can be obtained by observing the thermal behavior of the liquid crystal polymer using a differential scanning calorimeter. That is, the liquid crystal polymer is heated from room temperature (e.g., 25°C) at a rate of 10°C / min until it is completely melted at 400°C, and then the melt is cooled to 50°C at a rate of 10°C / min, and the position of the endothermic peak that appears when the temperature is raised again at a rate of 10°C / min can be determined as the melting point of the liquid crystal polymer.

[0043] Furthermore, from the viewpoint of melt moldability, the liquid crystal polymer may have, for example, a melt viscosity of 30 to 120 Pa·s at a shear rate of 1000 / s at its melting point + 20°C, and preferably a melt viscosity of 50 to 100 Pa·s.

[0044] As described above, the liquid crystal polymer film is a film containing the liquid crystal polymer. The liquid crystal polymer film may contain a thermoplastic polymer such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyether ether ketone, or fluororesin, and various additives, within a range that does not impair the effects of the present invention. Furthermore, it may contain a filler, if necessary. A liquid crystal polymer film containing such various additives and / or fillers can be obtained, for example, by forming a film from a resin composition containing a liquid crystal polymer and various additives and / or fillers using the method described below.

[0045] The liquid crystal polymer film may contain 50% by weight or more of liquid crystal polymer, preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, and even more preferably 98% by weight or more.

[0046] The shape of the liquid crystal polymer film is preferably a long product, or may be a roll, from the viewpoint of continuous processing when laminating with a metal sheet, etc. For example, when a metal-clad laminate is produced by continuously laminating a metal sheet on a roll-shaped liquid crystal polymer film by a method such as roll-to-roll roll press or double belt press, the liquid crystal polymer film is transported in the MD direction and continuously processed.

[0047] In one embodiment, the liquid crystal polymer film of the present invention is a liquid crystal polymer film for continuously laminating with a metal sheet to produce a metal-clad laminate, preferably a liquid crystal polymer film for continuously laminating with a metal sheet using a roll-to-roll double belt press or roll press to produce a metal-clad laminate, and the liquid crystal polymer film of the present invention is particularly suitable for continuously laminating with a metal sheet using a double belt press to produce a metal-clad laminate.

[0048] The melting point Tm of the liquid crystal polymer film is preferably 260°C or higher, more preferably 270°C or higher, and even more preferably 280°C or higher. The melting point of the liquid crystal polymer may be 380°C or lower, preferably 370°C or lower, more preferably 360°C or lower, even more preferably 350°C or lower, and even more preferably 340°C or lower. The melting point Tm of the liquid crystal polymer film can be obtained by observing the thermal behavior of the liquid crystal polymer film using a differential scanning calorimeter. That is, the liquid crystal polymer film is heated from room temperature (e.g., 25°C) at a rate of 10°C / min until it is completely melted at 400°C, and then the melt is cooled to 50°C at a rate of 10°C / min, and the position of the endothermic peak that appears when the temperature is raised again at a rate of 10°C / min can be determined as the melting point Tm of the liquid crystal polymer film.

[0049] Heat distortion temperature T of liquid crystal polymer filmｄｅｆ The heat distortion temperature T of the liquid crystal polymer film may be 150°C or higher, preferably 180°C or higher, more preferably 200°C or higher, and even more preferably 220°C or higher. ｄｅｆ The thermal distortion temperature of the liquid crystal polymer film may be 380°C or less, preferably 350°C or less, more preferably 320°C or less, even more preferably 300°C or less, and even more preferably 280°C or less. The heat distortion temperature of the liquid crystal polymer film can be measured by observing the thermal behavior of the film using a thermomechanical analyzer (TMA). Specifically, the liquid crystal polymer film is cut into a test piece having a width of 5 mm and a length of 20 mm, and the thermal expansion amount of the test piece in the longitudinal direction is measured under the conditions of a chuck distance of 15 mm, a tensile load of 0.01 N, and a heating rate of 10°C / min. The tangent line on the low-temperature side of the inflection point in the obtained thermal expansion variation curve is extended to the high-temperature side to draw a first straight line, and the tangent line on the high-temperature side of the inflection point is extended to the low-temperature side to draw a second straight line. A vertical line at the intersection of the two straight lines is drawn on the temperature axis of the abscissa, and this temperature is determined as the heat distortion temperature T of the liquid crystal polymer film. ｄｅｆ Let's say.

[0050] The liquid crystal polymer film preferably has a molecular orientation ratio (SOR) of 0.8 to 1.5, more preferably 0.85 to 1.25, and even more preferably about 0.90 to 1.20. Here, the molecular orientation ratio (SOR) is an index that indicates the degree of molecular orientation for the segments that make up the molecules, and is a value that takes into account the thickness of the object.

[0051] The molecular orientation ratio SOR can be obtained by the following measurement method. That is, in a microwave molecular orientation ratio measurement device, a sample of a liquid crystal polymer film is inserted into a microwave resonant waveguide so that the sample surface is perpendicular to the direction of microwave propagation, and the electric field strength (microwave transmission intensity) of the microwaves transmitted through the sample is measured. Then, based on this measurement value, the m value (referred to as refractive index) is calculated by the following formula: m = (Zo / Δz)X[1 - vmax / νo] where Zo is an apparatus constant, Δz is the average thickness of the object, vmax is the frequency that gives the maximum microwave transmission intensity when the microwave frequency is changed, and vo is the frequency that gives the maximum microwave transmission intensity when the average thickness is zero (i.e., when there is no object). Next, the m value when the rotation angle of the object with respect to the microwave vibration direction is 0°, that is, when the microwave vibration direction coincides with the direction in which the molecules of the object are most oriented and which gives the minimum microwave transmission intensity, is calculated as m ０ , the m value when the rotation angle is 90° is m ９０ The molecular orientation ratio SOR is m ０ / m ９０ It is calculated as follows.

[0052] The liquid crystal polymer film preferably has a MD thermal expansion coefficient of −30 ppm / K or more and +10 ppm / K or less, more preferably −28 ppm / K or more and +8 ppm / K or less, and a TD thermal expansion coefficient of −30 ppm / K or more and +20 ppm / K or less, more preferably −25 ppm / K or more and +16 ppm / K or less.

[0053] The thermal expansion coefficient is calculated using a thermomechanical analyzer (TMA) based on the change in length of a sample of a liquid crystal polymer film 5 mm wide and 20 mm long, when a tensile load of 1 g is applied to both ends of the sample, the sample is heated from room temperature (e.g., 25°C) to 200°C at a rate of 5°C / min, cooled to 30°C at a rate of 20°C / min, and then heated again at a rate of 5°C / min between 30°C and 150°C.

[0054] The thickness of the liquid crystal polymer film can be appropriately set depending on the application. For example, when considering use as a material for an insulating layer of a circuit board, the thickness may be 10 to 500 μm, preferably 15 to 250 μm, more preferably 20 to 200 μm, and even more preferably 25 to 150 μm.

[0055] <Method for producing a liquid crystal polymer film> Hereinafter, a method for producing a liquid crystal polymer film will be described. In the following description, the "liquid crystal polymer" may be, for example, a resin composition containing a liquid crystal polymer, the above-mentioned thermoplastic polymer, various additives, fillers, etc.

[0056] The liquid crystal polymer film may be an extrusion film obtained by extruding the above-mentioned liquid crystal polymer, or may be a cast film of the liquid crystal polymer. In the case of an extrusion film, any extrusion molding method can be used, but well-known T-die film stretching method, laminate stretching method, inflation method, etc. are industrially advantageous. In particular, in the inflation method, stress is applied not only in the machine direction MD of the liquid crystal polymer film but also in the transverse direction TD perpendicular to it, and uniform stretching can be achieved in MD and TD, thereby obtaining a liquid crystal polymer film with controlled molecular orientation, dielectric properties, etc. in MD and TD. In the case of a cast film, the direction in which a molten liquid crystal polymer or a composition such as a solution containing a liquid crystal polymer is transported while forming the film during the film formation process is the machine direction MD of the film.

[0057] In one embodiment, the liquid crystal polymer film may be stretched as needed after extrusion molding. The stretching method itself is known, and either biaxial stretching or uniaxial stretching may be used, but biaxial stretching is preferred because it is easier to control the degree of molecular orientation. For stretching, known uniaxial stretching machines, simultaneous biaxial stretching machines, sequential biaxial stretching machines, etc. may be used.

[0058] In extrusion molding, a stretching treatment may be performed to control the orientation. For example, in extrusion molding using a T-die method, the molten sheet extruded from the T-die may be stretched not only in the MD of the liquid crystal polymer film but also in both the MD and TD simultaneously to form a film, or the molten sheet extruded from the T-die may be stretched once in the MD and then in the TD to form a film.

[0059] In addition, in extrusion molding by the inflation method, a cylindrical sheet melt-extruded from a ring die may be stretched at a predetermined draw ratio (corresponding to the stretch ratio in MD) and blow ratio (corresponding to the stretch ratio in TD) to form a film.

[0060] A preferred method for producing a liquid crystal polymer film is to apply a pressure of 1.0 to 5.0 N / mm to a film containing a liquid crystal polymer in its machine direction MD. ２ (preferably 1.0 to 4.0 N / mm ２ a first step of supplying the film to a heating roll under a tension of 1.0 to 4.0 N / mm; a second step of contacting the film with the heating roll; and a second step of applying a tension of 1.0 to 4.0 N / mm to the film after the second step. ２ The method includes a third step of winding the film while applying a tension of 1000 to 15000 to obtain a liquid crystal polymer film, and the temperature of the heating roll is Tm-80°C to Tm-15°C (preferably Tm-75°C to Tm-15°C) when the melting point of the film containing the liquid crystal polymer is Tm. ＭＤ / Tensile elongation ＴＤ can be adjusted to 0.5 or more and 1.0 or less. Preferred forms of the liquid crystal polymer film produced by this production method include the above-mentioned liquid crystal polymer film forms. The "film containing a liquid crystal polymer" may be, for example, a film produced by forming a liquid crystal polymer (which may be a resin composition containing a liquid crystal polymer) by the above-mentioned method.

[0061] Hereinafter, an example of an embodiment of the first to third steps of the method for producing a liquid crystal polymer film will be shown with reference to FIG. 1. Hereinafter, the first to third steps may be referred to as "pretreatment." For the sake of explanation, the tensile elongation ＭＤ / Tensile elongation ＴＤThe liquid crystal polymer film (film containing liquid crystal polymer) before adjustment is called a "precursor film." ＭＤ / Tensile elongation ＴＤ The apparatus shown in Fig. 1 includes an unwinding roll 1, a take-up roll 2, heating rolls 3 to 7, and guide rolls 9 and 10. The precursor film 8 is unwound from the unwinding roll 1, and is introduced via the guide roll 9 to the rotating heating rolls 3 to 7. The precursor film 8 is brought into contact with the outer circumferential surface of each of the heating rolls 3 to 7. While being heated, the precursor film 8 is taken up by the take-up roll 2 via the guide roll 10, and the tensile elongation is adjusted. ＭＤ / Tensile elongation ＴＤ The liquid crystal polymer film 11 is obtained by adjusting the above.

[0062] Tensile elongation of the liquid crystal polymer film 11 ＭＤ / Tensile elongation ＴＤ From the viewpoint of adjusting the tension, the unwinding tension applied to the precursor membrane 8 during unwinding is set to 1.0 to 5.0 N / mm ２ The winding tension applied to the liquid crystal polymer film 11 during winding is preferably 1.0 to 4.0 N / mm. ２ Here, the unwinding tension is the tension applied to the precursor film between the unwinding roll and the heating roll with which the precursor film first comes into contact, and the take-up tension is the tension applied to the liquid crystal polymer film between the heating roll with which the liquid crystal polymer film last comes into contact and the take-up roll. In the case of the device configuration of Figure 1, the tension applied to the precursor film 8 between the unwinding roll 1 and the heating roll 3 is the unwinding tension, and the tension applied to the liquid crystal polymer film 11 between the heating roll 7 and the take-up roll 2 is the take-up tension.

[0063] The heating roll may be, for example, a nickel-plated or chrome-plated metal roll, or a coated metal roll coated with a thin layer of resin such as Teflon (registered trademark), silicone, or polyamide. The chrome-plated metal roll may be mirror-finished. The heating roll may have a surface roughened by a chemical or physical method to form a large number of recesses, and is preferably treated with a matte finish (unevenness treatment) from the viewpoint of controlling the slippage of the roll surface. The diameter of the heating roll is preferably 300 mm or more and 1000 mm or less, more preferably 500 mm or more and 700 mm or less.

[0064] The heating rolls 3 to 7 may be heated by, for example, a heating medium circulating inside them, and the film in contact with the heating rolls 3 to 7 is heated by the heat transmitted from the surface of each heating roll. ＭＤ / Tensile elongation ＴＤ From the viewpoint of control, the temperature of the heating roll is preferably in the range of from a temperature 80°C lower than the melting point Tm of the liquid crystal polymer film (precursor film) to a temperature 15°C lower than the melting point Tm (Tm-80°C to Tm-15°C), and more preferably in the range of from a temperature 75°C lower than the melting point Tm to a temperature 15°C lower than the melting point Tm (Tm-75°C to Tm-15°C).

[0065] It is preferable that a large number of recesses are formed on the outer peripheral surface of the heating rolls 3 to 7. Here, the recesses refer to recesses (concaves) formed on a substantially continuous flat surface (hereinafter referred to as the reference surface). The depth of the recesses, expressed as the maximum roughness (Rmax) according to JIS B 0601:1982, is preferably set so that this Rmax is in the range of 5 to 20 μm, more preferably in the range of 8 to 16 μm.

[0066] Tensile elongation of liquid crystal polymer film ＭＤ / Tensile elongation ＴＤ From the viewpoint of adjusting the above, the rotation speed of the heating roll is preferably 0.5 m / min or more and 10 m / min or less, more preferably 1 m / min or more and 5 m / min or less, converted into the linear velocity of the outer periphery thereof.

[0067] Although the device shown in FIG. 1 has five heating rolls, the number of heating rolls is not particularly limited. ＭＤ / Tensile elongation ＴＤ The number may be adjusted appropriately from the viewpoint of adjustment. For example, the number of heating rolls may be one or two or more. Furthermore, when a plurality of heating rolls are used, the respective heating rolls may have the same specifications or may have different specifications. For example, when a plurality of heating rolls are used, the respective heating rolls may be set to different temperatures to provide a temperature gradient, or a cooling roll set to a lower temperature may be provided.

[0068] <Metal-clad laminate> One embodiment of the present invention is a metal-clad laminate obtained by laminating the above-mentioned liquid crystal polymer film and a metal sheet. The metal-clad laminate may be a metal-clad laminate obtained by thermocompression bonding the above-mentioned liquid crystal polymer film and a metal sheet. As will be described later, known means such as a double belt press or a roll press can be used as a means for thermocompression bonding the liquid crystal polymer film and the metal sheet. Such a metal-clad laminate can be obtained by laminating the liquid crystal polymer film and the metal sheet with a tensile elongation of 100% or less before laminating the liquid crystal polymer film with the metal sheet. ＭＤ / Tensile elongation ＴＤ is in a specific range, and in the process of thermocompression bonding with the metal sheet, the molecular orientation of the film is controlled to be more isotropic, resulting in a metal-clad laminate with highly isotropic mechanical properties and excellent appearance.

[0069] Another embodiment of the present invention is a metal-clad laminate in which a metal sheet is laminated on a liquid crystal polymer film, wherein the liquid crystal polymer film has a tensile elongation in the machine direction of ＭＤ and transverse tensile elongation ＴＤ is 20.0% or more, and the tensile elongation ＭＤ and tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤ ) is 0.80 or more and 1.20 or less.

[0070] Tensile elongation in the machine direction of liquid crystal polymer film in metal-clad laminate ＭＤ and transverse tensile elongation ＴＤis preferably 25.0% or more, and more preferably 28.0% or more. ＭＤ and tensile elongation ＴＤ The tensile elongation of the liquid crystal polymer film in the metal-clad laminate is preferably 50.0% or less, more preferably 45.0% or less. ＭＤ and tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤ ) is preferably 0.90 or more and 1.15 or less.

[0071] The liquid crystal polymer film in the metal-clad laminate has a tensile modulus in the machine direction. ＭＤ and transverse tensile modulus ＴＤ is 3000 MPa or more, and the tensile modulus ＭＤ and tensile modulus ＴＤ Ratio of (tensile modulus ＭＤ / Tensile modulus ＴＤ The tensile modulus of elasticity in the machine direction of the liquid crystal polymer film in the metal-clad laminate is preferably 0.80 or more and 1.50 or less. ＭＤ and transverse tensile modulus ＴＤ The tensile modulus is preferably 3200 MPa or more. ＭＤ and tensile modulus ＴＤ The tensile modulus of elasticity of the liquid crystal polymer film in the metal-clad laminate is preferably 5000 MPa or less, more preferably 4300 MPa or less. ＭＤ and tensile modulus ＴＤ Ratio of (tensile modulus ＭＤ / Tensile modulus ＴＤ ) is preferably 0.90 or more and 1.40 or less, more preferably 0.90 or more and 1.20 or less.

[0072] The tensile elongation and tensile modulus of the liquid crystal polymer film in the metal-clad laminate are measured using a liquid crystal polymer film obtained by removing the metal sheet of the metal-clad laminate by etching.

[0073] In a preferred embodiment, the metal-clad laminate of the present invention has a peel strength between the liquid crystal polymer film and the metal sheet of 0.50 N / mm or more, preferably 0.65 N / mm or more, and more preferably 0.80 N / mm or more. Here, the peel strength is a value measured by the following method. That is, a 3 mm wide peel test piece is prepared using the metal-clad laminate. Next, the liquid crystal polymer film side of the peel test piece is fixed to a flat plate with double-sided adhesive tape, and the metal sheet is peeled at a rate of 50 mm / min using the 90° method in accordance with JIS C 5016, and the strength is measured.

[0074] The metal-clad laminate may be a double-sided metal-clad laminate in which metal sheets are laminated on both sides of a liquid crystal polymer film, or a single-sided metal-clad laminate in which a metal sheet is laminated on one side of a liquid crystal polymer film. In the case of a double-sided metal-clad laminate, the two metal sheets laminated on the liquid crystal polymer film may be the same or different. In the case of a single-sided metal-clad laminate, a separate metal layer may be provided on the side of the liquid crystal polymer film on which the metal sheet is not laminated. In this case, another metal sheet may be laminated on the side of the liquid crystal polymer film on which the metal sheet is not laminated, or the metal layer may be formed by vapor deposition or plating.

[0075] From the viewpoint of efficient shipping, the shape of the metal-clad laminate is preferably a long product, and may be a roll product.

[0076] (Metal Sheet) The metal sheet is not particularly limited and may be, for example, a sheet (for example, metal foil) formed of gold, silver, copper, iron, nickel, aluminum, or an alloy metal thereof, etc. Copper foil or stainless steel foil is preferred from the viewpoints of conductivity, handleability, cost, etc. In addition, as the copper foil, a rolled copper foil produced by a rolling method or an electrolytic copper foil produced by an electrolytic method can be used.

[0077] The thickness of the metal sheet can be appropriately set as needed, and may be, for example, 1 to 100 μm, preferably 5 to 50 μm, and more preferably 8 to 35 μm.

[0078] The metal sheet may be subjected to a surface treatment such as a roughening treatment. From the viewpoint of improving high-frequency characteristics, the roughened surface (such as a matte surface) of the metal sheet preferably has an arithmetic mean roughness Ra of 0.02 to 0.50 μm, more preferably 0.05 to 0.30 μm, and even more preferably 0.10 to 0.20 μm. The arithmetic mean roughness Ra is measured in accordance with JIS B 0601:2001.

[0079] From the viewpoint of improving high-frequency characteristics, the roughened surface of the metal sheet preferably has a ten-point average roughness Rzjis of 0.08 to 1.5 μm, more preferably 0.5 to 1.2 μm, and even more preferably 0.7 to 1.0 μm. The ten-point average roughness Rzjis is measured in accordance with JIS B 0601:2001.

[0080] The liquid crystal polymer film of the present invention can be laminated with a metal sheet having high-frequency characteristics to obtain a metal-clad laminate having excellent appearance and isotropic mechanical properties. For example, when laminated with a metal sheet having an arithmetic mean roughness Ra of 0.02 to 0.50 μm and a ten-point mean roughness Rzjis of 0.08 to 1.5 μm, it is possible to obtain a metal-clad laminate having excellent appearance and isotropic mechanical properties. Another feature of metal sheets having high-frequency characteristics is that they contain little or no magnetic material (e.g., nickel) among the alloy species on the surface. The liquid crystal polymer film of the present invention can be laminated with such a metal sheet to obtain a metal-clad laminate having excellent appearance and isotropic mechanical properties.

[0081] <Method for producing a metal-clad laminate> One embodiment of the present invention is a method for producing a metal-clad laminate, in which a metal sheet and the above-mentioned liquid crystal polymer film are continuously laminated using a double belt press or a roll press. Preferred forms of the liquid crystal polymer film and the metal sheet in this production method include the forms of the liquid crystal polymer film and the metal sheet described above.

[0082] In the method for manufacturing a metal-clad laminate, a single-sided metal-clad laminate may be manufactured by laminating a metal sheet on one side of a liquid crystal polymer film, or a double-sided metal-clad laminate may be manufactured by laminating metal sheets on both sides of a liquid crystal polymer film. Furthermore, multiple metal-clad laminates may be manufactured simultaneously. For example, a single metal-clad laminate may be manufactured by laminating a metal sheet on one or both sides of a single liquid crystal polymer film, or multiple metal-clad laminates may be manufactured by simultaneously laminating multiple metal sheets on one or both sides of multiple liquid crystal polymer films.

[0083] (Double Belt Press) In one embodiment of the method for producing a metal-clad laminate, it is preferable to laminate a metal sheet and a liquid crystal polymer film using a double belt press. In this case, a long liquid crystal polymer film and a metal sheet are supplied in the machine direction MD between a pair of endless belts provided in the double belt press, and the liquid crystal polymer film and the metal sheet are thermocompressed between the endless belts to form a metal-clad laminate. In this case, the liquid crystal polymer film and the metal sheet used in the double belt press may each be one sheet or multiple sheets. For example, a single-sided metal-clad laminate may be produced by using one liquid crystal polymer film and one metal sheet in the double belt press, or a double-sided metal-clad laminate may be produced by sandwiching the liquid crystal polymer film between two metal sheets.

[0084] One embodiment of a method for manufacturing a metal-clad laminate using a double belt press will be described in detail below with reference to Fig. 2. Fig. 2 shows the configuration of a double belt press for continuously manufacturing a double-sided metal-clad laminate in which metal sheets are laminated on both sides of a liquid crystal polymer film. The apparatus in Fig. 2 includes a double belt press 23, unwinding rolls 12-14 that respectively supply a liquid crystal polymer film 16 and two metal sheets 15 to the double belt press 23, and a take-up roll 21 that takes up the metal-clad laminate 22 discharged from the double belt press 23.

[0085] A long liquid crystal polymer film 16 is wound in a roll shape around the unwinding roll 13, and long metal sheets 15 are wound in a roll shape around each of the unwinding rolls 12 and 14. The metal sheets 15 unwound from the unwinding rolls 12 and 14 are superimposed on both sides of the liquid crystal polymer film 16 unwound from the unwinding roll 13 while being transported in the machine direction MD of the liquid crystal polymer film, and are continuously supplied to a double belt press 23 (between a pair of endless belts 19a and 19b described later), where they are thermocompression-bonded in a pressure unit 20 described later to form a metal-clad laminate 22, which is then discharged from the double belt press 23 and wound by a winding roll 21.

[0086] The double belt press 23 has a pair of entry pulleys 17a, 17b and a pair of exit pulleys 18a, 18b. An endless belt 19a is stretched between the entry pulley 17a and the exit pulley 18a, and an endless belt 19b is stretched between the entry pulley 17b and the exit pulley 18b. The endless belt 19a is configured to rotate when the pair of upper pulleys, the entry pulley 17a and the exit pulley 18a, rotate. Similarly, the endless belt 19b is configured to rotate when the pair of lower pulleys, the entry pulley 17b and the exit pulley 18b, rotate. The endless belts may be made of a metal material such as stainless steel, a copper alloy, or an aluminum alloy.

[0087] An upper pressure unit 20a is disposed between the entry pulley 17a and the exit pulley 18a, and the upper pressure unit 20a is in contact with the inner surface of the endless belt 19a. A lower pressure unit 20b is disposed between the entry pulley 17b and the exit pulley 18b, and the lower pressure unit 20b is in contact with the inner surface of the endless belt 19b. Each pressure unit 20a, 20b applies a predetermined pressure to a portion of the endless belt 19a, 19b located between the pressure units 20a, 20b and heats the portion. In the embodiment shown in FIG. 2, each pressure unit 20a, 20b includes a pressure chamber containing a pressurizing fluid such as pressurized oil and a heating element such as a heater. The heating element heats the pressurizing fluid contained in the pressure chamber, and therefore, the liquid crystal polymer film and metal sheet passing between the endless belts 19a, 19b are compressed in a heated state.

[0088] To facilitate adjustment of the temperature and time conditions during thermocompression bonding, the pressure unit may include multiple heating elements. By including multiple heating elements in the pressure unit, the set temperature and spacing of each heating element can be adjusted, making it easier to maintain the temperature and time conditions during thermocompression bonding within specific ranges. Furthermore, the bonding time can also be adjusted by, for example, adjusting the conveying speed of the liquid crystal polymer film and the metal sheet.

[0089] When the melting point of the liquid crystal polymer film is Tm, the compression temperature during lamination in the double belt press is preferably Tm+5° C. to Tm+35° C., and more preferably Tm+5° C. to Tm+30° C. The compression temperature is the temperature of the liquid crystal polymer film and the metal sheet during lamination, and can be measured, for example, by introducing a temperature sensor such as a thermocouple between the endless belts together with the liquid crystal polymer film and the metal sheet.

[0090] The pressure applied to the liquid crystal polymer film and the metal sheet in the double belt press is preferably 1 MPa or more and 6 MPa or less, more preferably 2 MPa or more and 5 MPa or less. The pressure may be constant or may be varied as the liquid crystal polymer film and the metal sheet pass through the endless belt. For example, the pressure during the pressing process can be varied by using a double belt press equipped with multiple pressure units.

[0091] The pressing time during lamination in a double belt press can be adjusted by the configuration of the double belt press device, but from the viewpoint of achieving good adhesion between the liquid crystal polymer film and the metal sheet and suppressing thermal degradation of the liquid crystal polymer film, it is preferably 15 seconds or more and 10 minutes or less, more preferably 15 seconds or more and 5 minutes or less, even more preferably 20 seconds or more and 3 minutes or less, and even more preferably 20 seconds or more and 2 minutes or less.

[0092] In terms of productivity, the conveying speed of the liquid crystal polymer film and the metal sheet in the double belt press is preferably 2 m / min or more and 5 m / min or less. The conveying speed can be adjusted by adjusting the rotation speed of the unwinding roll, winding rope, pulley, etc., and can also be adjusted by the device configuration of the double belt press.

[0093] For example, when producing a double-sided metal-clad laminate, a release film may be introduced between endless belts in a configuration of release film / metal sheet / liquid crystal polymer film / metal sheet / release film, thermocompression bonded to form a laminate, and then the release films on the outermost surfaces on both sides may be peeled off to obtain a double-sided metal-clad laminate in a configuration of metal sheet / liquid crystal polymer film / metal sheet. A polyimide film is preferred as the release film.

[0094] (Roll Press) In another embodiment of the method for producing a metal-clad laminate, it is preferable to laminate a metal sheet and a liquid crystal polymer film by roll pressing. In this case, a long liquid crystal polymer film and a metal sheet are supplied in the machine direction MD between a pair of heated rolls by roll-to-roll processing, and the liquid crystal polymer film and the metal sheet are thermocompression bonded between the heated rolls to form a metal-clad laminate. In this case, the liquid crystal polymer film and the metal sheet fed to the heated rolls may each be one sheet or multiple sheets. For example, a single-sided metal-clad laminate may be produced by feeding one liquid crystal polymer film and one metal sheet to the heated rolls, or a double-sided metal-clad laminate may be produced by sandwiching a liquid crystal polymer film between two metal sheets.

[0095] Hereinafter, one embodiment of a method for producing a metal-clad laminate by roll pressing will be specifically described with reference to Fig. 3. Fig. 3 is a schematic diagram of a continuous hot press device used in the production of a metal-clad laminate by roll-to-roll.

[0096] This continuous heat press device 33 is configured to produce a double-sided metal-clad laminate in which metal sheets are bonded to both sides of a liquid crystal polymer film, and as shown in Figure 3, the continuous heat press device 33 is equipped with an unwinding roll 25 on which a roll-shaped liquid crystal polymer film 27 is attached, unwinding rolls 24 and 26 on which a roll-shaped metal sheet 28 is attached, and a pair of heating rolls 29 that thermally press-bond the liquid crystal polymer film 27 and the metal sheet 28 together to form a metal-clad laminate 34.

[0097] Then, as shown in Figure 3, the liquid crystal polymer film 27 is sandwiched between two metal sheets 28 and transported in the machine direction MD, where it is supplied between a pair of heating rolls 29, and the liquid crystal polymer film 27 and the metal sheet 28 are thermocompression bonded to each other to laminate them, thereby obtaining a metal-clad laminate 34.

[0098] The temperature of the heating roll is preferably Tm-80°C to Tm-5°C, where Tm is the melting point of the liquid crystal polymer film.

[0099] The pressure of the heating roll is preferably 5 kg / mm ​​to 20 kg / mm ​​in linear pressure. The temperature and pressure of the heating roll may be appropriately adjusted depending on the conditions of both pressure and temperature, the stretched state of the liquid crystal polymer film, etc.

[0100] In a preferred embodiment, the liquid crystal polymer film and the metal sheet may be heat-treated after lamination. A continuous heat press device 33 shown in Fig. 3 includes a pair of nip rolls 30 for conveying the laminate obtained by laminating the liquid crystal polymer film and the metal sheet, a heat treatment means 32 for heat-treating the laminate, and a take-up roll 31 for winding up the heat-treated metal-clad laminate 34.

[0101] Examples of heat treatment methods that can be used include a hot air heat treatment furnace, a hot air circulation dryer, a heated roll, a ceramic heater, an IR (far infrared) heat treatment device, or a combination of these. From the viewpoint of preventing oxidation of the metal sheet surface, it is preferable to perform the heat treatment using heated nitrogen gas in an inert atmosphere with an oxygen concentration of 0.1% or less.

[0102] From the viewpoint of further improving the adhesive strength between the liquid crystal polymer film and the metal sheet, the heat treatment temperature is preferably set to a temperature higher than the melting point Tm of the liquid crystal polymer film by 1° C. to 30° C., and more preferably set to a temperature higher than Tm by 2° C. to 20° C. From the same viewpoint, the heat treatment time is preferably set to 5 seconds to 8 minutes, more preferably 8 seconds to 5 minutes, and even more preferably 8 seconds to 3 minutes.

[0103] In one embodiment, a single-sided metal-clad laminate may be produced by laminating a metal sheet on one side of a liquid crystal polymer film by roll pressing. In this case, for example, a pair of heat-resistant rubber roll and heated metal roll (preferably, both have a roll surface hardness of 80 degrees or more) is used as the heating roll. It is preferable that the heat-resistant rubber roll and the metal roll are arranged such that the heat-resistant rubber roll is arranged on the liquid crystal polymer film side and the metal roll is arranged on the metal sheet side.

[0104] The heat-resistant rubber roll may preferably have a roll surface hardness of 80 degrees or more, more preferably 80 to 95 degrees, as determined by a test using a type A spring hardness tester in accordance with JIS K 6301. Rubber having a hardness of 80 degrees or more can be obtained by adding a vulcanizing agent, an alkaline substance, or other vulcanization accelerator to synthetic rubber such as silicone rubber or fluorine-based rubber or natural rubber.

[0105] <Circuit Board> One embodiment of the present invention is a circuit board in which a circuit pattern is formed on the metal sheet of the above-mentioned metal-clad laminate. Such a circuit board can be manufactured by wiring and circuit processing the metal sheet of the metal-clad laminate. As a circuit processing method, a known method can be used, and for example, a circuit can be formed by etching the metal sheet on the liquid crystal polymer film using a subtractive method.

[0106] Furthermore, one embodiment of the present invention encompasses a method for manufacturing a circuit board, which includes a step of forming a circuit pattern on the metal sheet of the metal-clad laminate obtained by the above-described manufacturing method.

[0107] <Multilayer Circuit Board> One embodiment of the present invention is a multilayer circuit board including the circuit board described above. Such a multilayer circuit board may include a plurality of the circuit boards described above, and may also include other materials.

[0108] The circuit board of the present invention can be effectively used as a circuit board material for components used in the electrical and electronic fields, the office equipment and precision equipment fields, the power semiconductor fields, and the like, and is particularly suitable for applications requiring bending, such as high-frequency circuit boards, in-vehicle sensors, mobile circuit boards, and antennas.

[0109] As described above, a preferred embodiment of the present invention has been described, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention, and such additions, modifications, or deletions are also included within the scope of the present invention.

[0110] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, various physical properties were measured by the following methods.

[0111] <Melting Point (°C)> The melting point of the liquid crystal polymer and the melting point Tm of the liquid crystal polymer film were determined by using a differential scanning calorimeter (DSC manufactured by Shimadzu Corporation) to heat the prepared film at a rate of 10°C / min until it was completely melted at 400°C, then cooling the molten material to 50°C at a rate of 10°C / min, and heating it again at a rate of 10°C / min. The position of the endothermic peak that appeared when this was determined as the melting point Tm of the liquid crystal polymer film.

[0112] <Tensile elongation and tensile modulus of liquid crystal polymer film> The liquid crystal polymer films obtained in the examples and comparative examples were cut into samples with a length of 100 mm and a width of 10 mm. The sample thickness was measured with a micrometer at three points, the center and both ends, with a chuck distance of 50 mm, and the average value of the three points was taken as the film thickness of the sample. A tensile test was performed on these samples using a tensile tester (Tensilon universal testing machine: A&D Corporation, model number RTE-1210) with a chuck distance of 50 mm and a tensile speed of 10 mm / min.

[0113] The tensile elongation is the amount of tensile elongation when a film is stretched in a tensile test and breaks, and is calculated by the following formula: Tensile elongation (%) = [(L - Lo) / Lo] x 100, where Lo is the sample length before the test, and L is the sample length at break.

[0114] The tensile modulus was determined from the slope of the SS curve when the sample was stretched and plastically deformed in the tensile test. The slope was calculated as the slope of the line connecting the two points where the stress was 11.8 N and 19.6 N (1.2 kgf and 2.0 kgf).

[0115] The tensile elongation and tensile modulus of elasticity were measured for each of the samples cut out so that the MD was the sample length direction and the TD was the sample length direction, and the tensile elongation ＭＤ and elongation ＴＤ , and tensile modulus ＭＤ and tensile modulus ＴＤ The value of tensile elongation is obtained. ＭＤ / Tensile elongation ＴＤ , and tensile modulus ＭＤ / Tensile modulus ＴＤThe measurement was carried out five times in each of the MD and TD, and the tensile elongation and tensile modulus were calculated as the average values.

[0116] <Thermal expansion coefficient> The liquid crystal polymer films obtained in the examples and comparative examples were cut into a length of 20 mm and a width of 5 mm, and samples were prepared in which the MD was the length direction of the sample and the TD was the length direction of the sample. Using a thermomechanical analyzer (TMA), a tensile load of 1 g was applied to both ends of the sample, and the sample was heated from 25°C to 200°C at a rate of 5°C / min, cooled to 30°C at a rate of 20°C / min, and then heated again at a rate of 5°C / min. The thermal expansion coefficient was calculated based on the change in the length of the sample between 30°C and 150°C. Measurements were performed three times in each of the MD and TD, and the average values ​​were used.

[0117] <Tensile elongation and tensile modulus of liquid crystal polymer film in copper clad laminate> The copper foil laminated on the double-sided copper clad laminate obtained in Examples and Comparative Examples was removed by etching using copper chloride solution, washed and dried, and then a single liquid crystal polymer film was obtained. From the obtained liquid crystal polymer film, a sample to be measured was cut out, and the tensile elongation and tensile modulus were measured in the same manner as above. In the evaluation of the copper clad laminate, the tensile elongation measured as above was ＭＤ and tensile elongation ＴＤ are both 20% or more, and the tensile elongation ＭＤ / Tensile elongation ＴＤ When the ratio was 0.80 or more and 1.20 or less, the tensile elongation was judged to be isotropic and good (rating A), and otherwise it was judged to be bad (rating B). ＭＤ and tensile modulus ＴＤ are both 3000 MPa or more, and the tensile modulus ＭＤ / Tensile modulus ＴＤ When the modulus of elasticity was 0.80 or more and 1.50 or less, the tensile modulus was judged to be isotropic and good (rating A), and otherwise it was judged to be bad (rating B).

[0118] <Peel Strength> The double-sided copper-clad laminates obtained in the Examples and Comparative Examples were cut into a width of 3 mm and a length of 100 mm, and the copper foil on one side was peeled off to prepare a peel test specimen. Next, the liquid crystal polymer film surface from which the copper foil was peeled was fixed to a flat plate with double-sided adhesive tape. The copper foil laminated on one side of the liquid crystal polymer film was peeled off at a rate of 50 mm / min using the 90° method in accordance with JIS C 5016, and the peel strength was measured. Measurement results at 0.1-second intervals were converted to a 1-second average, and the minimum value was taken as the peel strength. Measurements were performed twice in the MD of the double-sided copper-clad laminate, and the smaller 1-second average value of the two measurements was used. The value obtained by converting the 1-second average peel strength value from the width of the peel test specimen was taken as the peel strength (N / mm).

[0119] <Evaluation of Appearance> A 10 m length of each of the double-sided copper-clad laminates obtained in the Examples and Comparative Examples was randomly taken out and visually inspected on both sides, with wrinkles of 5 μm or more in depth or scratches of 5 mm or more in length being considered as defects in appearance, with those with no defects being rated A and those with defects being rated B. The depth of the wrinkles was determined by measuring the depth of the surface from the average surface height using a white light interference microscope.

[0120] [Example 1] <Preparation of Liquid Crystal Polymer Film> A thermoplastic liquid crystal polyester having a melting point of 310°C, composed of 6-hydroxy-2-naphthoic acid units (23 mol%) and p-hydroxybenzoic acid units (77 mol%), was heated and kneaded using a single-screw extruder at 310 to 345°C, and then melt-extruded through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm at a discharge rate of 20 kg / h. An inflation film was formed under conditions of a transverse stretch ratio of 4.77 times and a longitudinal stretch ratio of 2.09 times to obtain a thermoplastic liquid crystal polyester film having a thickness of 50 μm. The melting point Tm of this film was 310°C.

[0121] The above film was pretreated using an apparatus equipped with five heating rolls as shown in FIG. 1 . Each of the five heating rolls 3 to 7 was a chrome-plated stainless steel roll with a diameter of 600 mm, with numerous recesses 12 μm deep formed on its surface. A heater was built into each of the heating rolls 3 to 7, and the surface temperature of the heating rolls 3 to 7 was maintained at 250°C. The film was unwound from unwinding roll 1, brought into contact with the outer circumferential surfaces of the rotating heating rolls 3 to 7, and conveyed at a conveying speed of 3.0 m / min while being heated. The film was then wound up by take-up roll 2 to obtain a liquid crystal polymer film. The unwinding tension applied to the film was adjusted to 3.1 N / mm by adjusting the amount of film unwound from unwinding roll 1 to heating roll 3 and the amount of film wound from heating roll 7 to take-up roll 2. ２ , winding tension 2.4 N / mm ２ The tensile elongation and tensile modulus of the obtained liquid crystal polymer film were measured, and the results are shown in Table 7.

[0122] Example 2 A thermoplastic liquid crystal polyester having a melting point of 310°C and composed of 6-hydroxy-2-naphthoic acid units (23 mol%) and p-hydroxybenzoic acid units (77 mol%) was heated and kneaded at 310 to 345°C using a single-screw extruder, and then melt-extruded at a discharge rate of 10 kg / h through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm. The resulting film was inflation-formed under conditions of a transverse stretch ratio of 4.77 times and a longitudinal stretch ratio of 2.09 times to obtain a thermoplastic liquid crystal polyester film having a thickness of 25 μm. The melting point Tm of this film was 310°C. This film was pretreated in the same manner as in Example 1, except that the conditions were changed as shown in Table 7, to obtain a liquid crystal polymer film. The tensile elongation and tensile modulus of the obtained liquid crystal polymer film were measured, and the results are shown in Table 7.

[0123] Example 3 A thermoplastic liquid crystal polyester having a melting point of 320°C and consisting of 6-hydroxy-2-naphthoic acid units (20 mol%) and p-hydroxybenzoic acid units (80 mol%) was heated and kneaded at 320 to 350°C using a single-screw extruder, and then melt-extruded at a discharge rate of 40 kg / h through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm. The resulting film was inflation-formed under conditions of a transverse stretch ratio of 4.77 times and a longitudinal stretch ratio of 2.09 times to obtain a thermoplastic liquid crystal polyester film having a thickness of 100 μm. The melting point Tm of this film was 320°C. This film was pretreated in the same manner as in Example 1, except that the conditions were changed as shown in Table 7, to obtain a liquid crystal polymer film. The tensile elongation and tensile modulus of the obtained liquid crystal polymer film were measured, and the results are shown in Table 7.

[0124] [Comparative Example 1] A thermoplastic liquid crystal polyester having a melting point of 310 ° C. and consisting of 6-hydroxy-2-naphthoic acid units (23 mol%) and p-hydroxybenzoic acid units (77 mol%) was heated and kneaded at 310 to 345 ° C. using a single-screw extruder, and then melt-extruded at a discharge rate of 20 kg / h through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm. A 50 μm thick thermoplastic liquid crystal polyester film was obtained by inflation film formation under conditions of a transverse stretching ratio of 4.77 times and a longitudinal stretching ratio of 2.09 times. The melting point Tm of this film was 310 ° C. The tensile elongation and tensile modulus of the obtained liquid crystal polymer film were measured, and the results are shown in Table 7.

[0125] [Comparative Example 2] A thermoplastic liquid crystal polyester having a melting point of 310°C and consisting of 6-hydroxy-2-naphthoic acid units (23 mol%) and p-hydroxybenzoic acid units (77 mol%) was heated and kneaded using a single-screw extruder at 310 to 345°C, and then melt-extruded at a discharge rate of 20 kg / h through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm. The extrusion was carried out by inflation film formation under conditions of a transverse stretching ratio of 4.77 times and a longitudinal stretching ratio of 2.09 times to obtain a thermoplastic liquid crystal polyester film having a thickness of 50 μm. The melting point Tm of this film was 310°C. The produced film was laminated to a metal sheet using a roll press device equipped with a pair of heated metal rolls, and then heat-treated at the melting point of the film + 30°C. The film was then peeled off from the metal sheet to obtain a liquid crystal polymer film. The tensile elongation and tensile modulus of the obtained liquid crystal polymer film were measured, and the results are shown in Table 7.

[0126] [Comparative Example 3] A thermoplastic liquid crystal polyester having a melting point of 310°C and composed of 6-hydroxy-2-naphthoic acid units (23 mol%) and p-hydroxybenzoic acid units (77 mol%) was heated and kneaded using a single-screw extruder at 310 to 345°C, and then melt-extruded through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm at a discharge rate of 20 kg / h. An inflation film was produced under conditions of a transverse stretching ratio of 4.77 times and a longitudinal stretching ratio of 2.09 times to obtain a thermoplastic liquid crystal polyester film having a thickness of 50 μm. The melting point Tm of this film was 310°C. This film was pretreated in the same manner as in Example 1, except that the conditions were changed as shown in Table 7, to obtain a liquid crystal polymer film. The tensile elongation and tensile modulus of the obtained liquid crystal polymer film were measured, and the results are shown in Table 7.

[0127] [Comparative Example 4] A thermoplastic liquid crystal polyester having a melting point of 320 ° C. consisting of 6-hydroxy-2-naphthoic acid units (20 mol%) and p-hydroxybenzoic acid units (80 mol%) was heated and kneaded at 320 to 350 ° C. using a single-screw extruder, and then extruded from an extruder with a die width of 600 mm. The molten extruded film was brought into contact with a cooling roll having a diameter of 45 cm at 250 ° C. and cooled slowly. It was then transferred to a cooling roll having a diameter of 45 cm cooled with water at 25 ° C. to obtain a thermoplastic liquid crystal polyester film having a thickness of 100 μm. The tensile elongation and tensile modulus of the obtained liquid crystal polymer film were measured and the results are shown in Table 7.

[0128]

[0129] <Preparation of Metal-Clad Laminate (Double-Sided Copper-Clad Laminate)> [Example 4] Using a double belt press (DBP), rolled copper foil ("JXEFL-BHM" foil manufactured by JX Nippon Oil & Gas Corporation, matte surface arithmetic mean roughness Ra of 0.18 μm, ten-point mean roughness Rzjis of 0.9 μm, thickness of 12 μm, width of 580 mm) was laminated on both sides of the 550 mm-wide liquid crystal polymer film prepared in Example 1 to prepare a double-sided copper-clad laminate. The laminate had a release film / rolled copper foil / liquid crystal polymer film / rolled copper foil / release film configuration, and was introduced into the double belt press with the matte surface of the rolled copper foil in contact with the liquid crystal polymer film, and an unwinding tension of 10 N / mm was applied. 2 The laminate was then thermocompressed at a pressure of 2.0 MPa, a temperature of 340°C, and a bonding time of 90 seconds to obtain a laminate. A polyimide film (Apical (registered trademark) manufactured by Kaneka Corporation, thickness 50 μm) was used as the release film. The release films on both outermost surfaces of the obtained laminate were peeled off to obtain a double-sided copper-clad laminate. The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0130] [Example 5] A double-sided copper-clad laminate was produced in the same manner as in Example 4, except that the liquid crystal polymer film produced in Example 2 was used as the liquid crystal polymer film. The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0131] [Example 6] The liquid crystal polymer film produced in Example 3 was used as the liquid crystal polymer film, and the lamination temperature was 350°C and the unwinding tension was 6.6 N / mm 2 A double-sided copper-clad laminate was produced in the same manner as in Example 4, except that the following was used: The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0132] [Example 7] Using a roll press (RP) device, rolled copper foil ("JXEFL-BHM" foil manufactured by JX Nippon Oil & Gas Corporation, arithmetic mean roughness Ra of the matte surface was 0.18 μm, ten-point mean roughness Rzjis was 0.9 μm, and thickness was 12 μm) was laminated on both sides of the liquid crystal polymer film produced in Example 2 to produce a double-sided copper-clad laminate. The rolled copper foil / liquid crystal polymer film / rolled copper foil configuration was introduced between heated rolls with the matte surface of the rolled copper foil in contact with the liquid crystal polymer film, and the unwinding tension was 10 N / mm. ２ The laminate was then thermocompressed at a linear pressure of 14.5 kg / mm, a temperature of 250°C, and a compression time of approximately 2 seconds to obtain a double-sided copper-clad laminate. The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0133] [Comparative Example 5] A double-sided copper-clad laminate was produced in the same manner as in Example 4, except that the liquid crystal polymer film produced in Comparative Example 1 was used as the liquid crystal polymer film. The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0134] [Comparative Example 6] A double-sided copper-clad laminate was produced in the same manner as in Example 4, except that the liquid crystal polymer film produced in Comparative Example 2 was used as the liquid crystal polymer film. The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0135] [Comparative Example 7] A double-sided copper-clad laminate was produced in the same manner as in Example 4, except that the liquid crystal polymer film produced in Comparative Example 3 was used as the liquid crystal polymer film. The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0136] Comparative Example 8 The liquid crystal polymer film produced in Comparative Example 4 was used as the liquid crystal polymer film, and the lamination temperature was 350° C. and the unwinding tension was 6.6 N / mm 2 A double-sided copper-clad laminate was produced in the same manner as in Example 4, except that the following was used: The peel strength, appearance, and isotropy of the obtained double-sided copper-clad laminate were evaluated. The results are shown in Table 8.

[0137]

[0138] The liquid crystal polymer films of Examples 1 to 3 had a tensile elongation ＭＤ / Tensile elongation ＴＤ Since the value of the tensile elongation was 0.5 or more and 1.0 or less, it was possible to manufacture metal-clad laminates with excellent appearance and isotropy, as shown in Examples 4 to 7. On the other hand, the liquid crystal polymer films of Comparative Examples 1, 2 and 4, which were not pretreated, had a tensile elongation of 0.5 or more and 1.0 or less. ＭＤ / Tensile elongation ＴＤ The tensile elongation of the liquid crystal polymer film of Comparative Example 3, which had a low temperature condition in the pretreatment, was poor. ＭＤ / Tensile elongation ＴＤ exceeded 1.0, and as shown in Comparative Example 7, the metal-clad laminate obtained by laminating this liquid crystal polymer film with a metal sheet was inferior in isotropy.

[0139] The liquid crystal polymer film of the present invention is useful for producing a metal-clad laminate. The metal-clad laminate obtained using such a liquid crystal polymer film can be used for parts used in, for example, the electrical and electronic fields, the office equipment and precision equipment fields, and the power semiconductor fields, and can be particularly effectively used as a circuit board material.

[0140] While the preferred embodiments of the present invention have been described above, those skilled in the art will readily recognize various changes and modifications within the scope of the present invention, which are obvious from the description of the present invention. Therefore, such changes and modifications are to be interpreted as falling within the scope of the invention as defined by the claims.

[0141] REFERENCE SIGNS LIST 1 Unwinding roll 2 Winding roll 3 to 7 Heating roll 8 Precursor film 9, 10 Guide roll 11 Liquid crystal polymer film 12, 14, 24, 26 Metal sheet unwinding roll 13, 25 Liquid crystal polymer film unwinding roll 15, 28 Metal sheet 16, 27 Liquid crystal polymer film 17a, 17b Entry pulley 18a, 18b Exit pulley 19a, 19b Endless belt 20 Pressurizing unit 21, 31 Winding roll 22, 34 Metal-clad laminate 23 Double belt press 29 Heating roll 30 Nip roll 32 Heat treatment means 33 Continuous heat press device

Claims

1. Tensile elongation in the machine direction ＭＤ and transverse tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤ ) is 0.5 or more and 1.0 or less.

2. Tensile modulus in the machine direction ＭＤ and transverse tensile modulus ＴＤ Ratio of (tensile modulus ＭＤ / Tensile modulus ＴＤ 2. The liquid crystal polymer film according to claim 1, wherein the σ is 1.2 or more and 2.0 or less.

3. Tensile elongation in the machine direction ＭＤ and transverse tensile elongation ＴＤ The liquid crystal polymer film according to claim 1, wherein the tensile strength is 8.0% or more.

4. Tensile modulus in machine direction ＭＤ is 5000 MPa or more, and the transverse tensile modulus ＴＤ The liquid crystal polymer film according to claim 1, wherein the modulus of elasticity is 3500 MPa or more.

5. The liquid crystal polymer film according to claim 1, which is in the form of a roll.

6. The liquid crystal polymer film according to any one of claims 1 to 5, for producing a metal-clad laminate by continuously laminating it with a metal sheet.

7. A metal-clad laminate in which a metal sheet is laminated on a liquid crystal polymer film, wherein the tensile elongation in the machine direction of the liquid crystal polymer film is ＭＤ and transverse tensile elongation ＴＤ is 20.0% or more, and the tensile elongation ＭＤ and tensile elongation ＴＤ Ratio of tensile elongation ＭＤ / Tensile elongation ＴＤ ) is 0.80 or more and 1.20 or less.

8. The tensile modulus of the liquid crystal polymer film in the machine direction ＭＤ and transverse tensile modulus ＴＤ is 3000 MPa or more, and the tensile modulus ＭＤ and tensile modulus ＴＤ Ratio of (tensile modulus ＭＤ / Tensile modulus ＴＤ 8. The metal-clad laminate according to claim 7, wherein the value of (a) is 0.80 or more and 1.50 or less.

9. The metal-clad laminate according to claim 7, wherein the peel strength between the liquid crystal polymer film and the metal sheet is 0.50 N / mm or more.

10. A circuit board, comprising a metal sheet of the metal-clad laminate according to any one of claims 7 to 9, on which a circuit pattern is formed.

11. A multilayer circuit board comprising the circuit board of claim 10.

12. A method for producing a metal-clad laminate, comprising continuously laminating a metal sheet and the liquid crystal polymer film according to any one of claims 1 to 5 using a double belt press or a roll press.

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