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 that, when laminated with a metal sheet to form a metal-clad laminate, makes it possible to produce a metal-clad laminate in which the coefficient of thermal expansion at or below the Tg of the post-lamination liquid crystal polymer film and the coefficient of thermal expansion at or above the Tg of the post-lamination liquid crystal polymer film are equal. The liquid crystal polymer film is a film containing a liquid crystal polymer and has a melting point of 270°C or higher, and the coefficients of thermal expansion (CTE1MD, CTE1TD) from 30°C to the glass transition temperature (Tg) of the film in the machine direction and the transverse direction and the coefficients of thermal expansion (CTE2MD, CTETD) from Tg to 200°C are such that CTE1MD>CTE2MD, CTE1TD>CTE2TD, CTE1MD≤0 ppm / °C, and CTE1TD≤5.0 ppm / °C.

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. 2024-108949, filed on July 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] In recent years, rapid advances in electronics technology, such as the increasing demand for intelligent automobiles and data servers due to the spread of AI, have led to demand for faster, higher-density, and lower-power ICs. In this environment, there is also a demand for improved performance in the semiconductor packages used to connect IC chips. Semiconductor packages play a vital role in connecting ICs to external components, and are required to have mechanical, thermal, and electrical properties. Specifically, semiconductor packages are required to protect ICs from external impacts, block moisture, provide heat resistance, heat dissipation, and long-term reliability.

[0004] Generally, glass epoxy resin substrates (FR-4) are used in semiconductor packages. Patent Document 1 examines a method for improving heat resistance by changing the epoxy resin composition used in FR-4 to increase the glass transition temperature (Tg) of the resin. However, because the base material is an epoxy resin, the heat resistance of the material is insufficient. In order to improve the high-temperature reliability of semiconductor packages, it is necessary not only to increase the glass transition temperature of the resin, but also to lower the thermal expansion coefficient of the package substrate. In FR-4, the thermal expansion coefficient increases rapidly above the Tg of the epoxy resin used, so the inclusion of glass cloth suppresses the increase in the thermal expansion coefficient above the Tg.

[0005] However, Patent Document 2 describes that in recent years, there has been a demand for substrates that do not use glass cloth or the like, from the viewpoint of environmental impacts such as recycling.

[0006] On the other hand, 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, films containing liquid crystal polymers (hereinafter referred to as "liquid crystal polymer films") have excellent low moisture absorption, heat resistance, chemical resistance, and electrical properties, and therefore, in recent years, metal-clad laminates including liquid crystal polymer films have been used as materials for flexible wiring boards, circuit boards for semiconductor packaging, semiconductor package substrates, etc.

[0007] Liquid crystal polymer film is superior to FR-4 in various properties such as heat resistance, heat dissipation, water absorption, and dielectric constant, and is expected to be a substitute for FR-4. In addition, as the range of applications expands, there is a demand for semiconductor packages that can withstand use at higher temperatures than ever before, and in light of the need for highly heat-resistant resin substrates, liquid crystal polymer film is ideal.

[0008] Patent No. 7416118 International Publication No. 2024 / 003066

[0009] However, although liquid crystal polymer films have high heat resistance, their thermal expansion coefficients are difficult to control due to the tendency of the liquid crystal polymer to undergo molecular orientation. Furthermore, even if the average thermal expansion coefficient from room temperature to high temperatures can be controlled, there is a problem that the thermal expansion coefficient increases rapidly above the Tg, similar to that of epoxy resins. In particular, since metal-clad laminates are used as various substrate materials, considering the manufacturing processes of various substrates, they are required to exhibit thermal expansion behavior that is as constant as possible regardless of the temperature range, without significant changes in the thermal expansion coefficient around the Tg. A common method for processing liquid crystal polymer films into metal-clad laminates is a continuous process using a roll-to-roll method, such as thermocompression bonding using a roll press or double belt press. However, there is a problem in that the molecular orientation of the liquid crystal polymer film is likely to change during thermocompression bonding, resulting in differences in the thermal expansion coefficient around the Tg.

[0010] Therefore, one of the objects of the present invention is to provide a liquid crystal polymer film and a method for manufacturing the same that can produce a metal-clad laminate in which, when laminated with a metal sheet, the thermal expansion coefficient below the Tg of the liquid crystal polymer film after lamination is equivalent to the thermal expansion coefficient above the Tg.

[0011] Another object of the present invention is to provide a method for manufacturing a metal-clad laminate using the liquid crystal polymer film, a metal-clad laminate having a liquid crystal polymer film whose thermal expansion coefficient below Tg is equivalent to that above Tg, and to provide a circuit board and a multilayer circuit board.

[0012] That is, the present invention can be configured in the following aspects: [Aspect 1] A film containing a liquid crystal polymer, having a melting point of 270°C or higher, and a coefficient of thermal expansion (CTE) of 30°C to the glass transition temperature (Tg) of the film in the machine direction and the transverse direction. ＭＤ , CTE1 ＴＤ ) and the coefficient of thermal expansion from Tg to 200 ° C (CTE2 ＭＤ , CTE2 ＴＤ ) and satisfy the following formulas (1) to (4): ＭＤ >CTE2 ＭＤ (1) CTE1 ＴＤ >CTE2 ＴＤ (2) CTE1 ＭＤ ≦0ppm / ℃ (3) CTE1 ＴＤ ≦5.0 ppm / ° C. (4) [Aspect 2] CTE1 ＭＤ and CTE2 ＭＤ Difference from (CTE1 ＭＤ -CTE2 ＭＤ ), and CTE1 ＴＤ and CTE2 ＴＤ Difference from (CTE1 ＴＤ -CTE2 ＴＤ ) are each 1.0 to 20.0 ppm / °C (preferably 2.0 to 19.0 ppm / °C, more preferably 3.0 to 18.5 ppm / °C). ＭＤ and CTE2 ＭＤThe liquid crystal polymer film according to aspect 1 or 2, wherein CTE1 is from −30.0 to 0 ppm / ° C. (preferably from −28.0 to −1.0 ppm / ° C., more preferably from −25.0 to −3.0 ppm / ° C.). ＴＤ and CTE2 ＴＤ The liquid crystal polymer film according to any one of Aspects 1 to 3, wherein CTE1 is from −20.0 to 5.0 ppm / ° C. (preferably from −19.0 to 3.0 ppm / ° C., more preferably from −15.0 to 0 ppm / ° C.). ＭＤ and CTE1 ＴＤ The absolute value of the difference between ＭＤ -CTE1 ＴＤ |), and CTE2 ＭＤ and CTE2 ＴＤ The absolute value of the difference between ＭＤ -CTE2 ＴＤ The liquid crystal polymer film according to any one of Aspects 1 to 4, wherein the values ​​of |) are 0 to 20.0 ppm / °C (preferably 1.0 to 18.0 ppm / °C, more preferably 2.0 to 13.0 ppm / °C). Aspect 6: The liquid crystal polymer film according to any one of Aspects 1 to 5, which is in the form of a roll. Aspect 7: The liquid crystal polymer film according to any one of Aspects 1 to 6, which is for producing a metal-clad laminate by continuously laminating it with a metal sheet. Aspect 8: A film containing a liquid crystal polymer is laminated to a sheet of metal by a strain of 1.0 to 5.0 N / mm in the machine direction. 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 conveying the film in contact with a plurality of heating rolls; and ２and a third step of winding the film under a tension of 1000 .mu.m to obtain a liquid crystal polymer film, wherein the rotational speed of the second or subsequent heating rolls in the second step is equal to or greater than the rotational speed of the immediately preceding heating roll, and the rotational speed of the final heating roll is greater than the rotational speed of the initial heating roll. [Aspect 9] 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 coefficient of thermal expansion (CTE) of 1000 .mu.m to 3000 .mu.m in the machine direction and the transverse direction. ＭＤ , CTE1 ＴＤ ) and the coefficient of thermal expansion from Tg to 200 ° C (CTE2 ＭＤ , CTE2 ＴＤ ) and satisfy the following formulas (5) and (6): -8.0 ppm / °C≦CTE1 ＭＤ -CTE2 ＭＤ ≦8.0ppm / ℃ (5) -8.0ppm / ℃≦CTE1 ＴＤ -CTE2 ＴＤ ≦8.0 ppm / ° C. (6) [Aspect 10] CTE1 of the liquid crystal polymer film ＭＤ and CTE1 ＴＤ The absolute value of the difference between ＭＤ -CTE1 ＴＤ |), and CTE2 ＭＤ and CTE2 ＴＤ The absolute value of the difference between ＭＤ -CTE2 ＴＤ |) are 0 to 10.0 ppm / °C (preferably 0 to 5.0 ppm / °C, more preferably 0 to 3.0 ppm / °C). [Aspect 11] A circuit board, in which a circuit pattern is formed on the metal sheet of the metal-clad laminate of aspect 9 or 10. [Aspect 12] A multilayer circuit board, comprising the circuit board of aspect 11. [Aspect 13] A method for producing a metal-clad laminate, in which a metal sheet and the liquid crystal polymer film of any one of aspects 1 to 6 are continuously laminated using a double belt press or a roll press.

[0013] 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.

[0014] 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.

[0015] When the liquid crystal polymer film of the present invention is laminated with a metal sheet to form a metal-clad laminate, it is easy to produce a metal-clad laminate in which the thermal expansion coefficient below the Tg of the liquid crystal polymer film after lamination is equivalent to the thermal expansion coefficient above the Tg.

[0016] 1 is a schematic diagram showing the configuration of a film pretreatment device used in a production 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 production 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 production method according to an embodiment of the present invention, and 4 is a schematic diagram showing the configuration of a film pretreatment device used in a production method according to an embodiment of the present invention.

[0017] <Liquid Crystal Polymer Film> The liquid crystal polymer film of the present invention is a film containing a liquid crystal polymer, and has a melting point of 270°C or higher and a coefficient of thermal expansion (CTE) from 30°C to the glass transition temperature (Tg) of the film in the machine direction and the transverse direction. ＭＤ , CTE1 ＴＤ ) and the coefficient of thermal expansion from Tg to 200 ° C (CTE2 ＭＤ , CTE2 ＴＤ ) satisfy the following formulas (1) to (4): CTE1 ＭＤ >CTE2 ＭＤ (1) CTE1 ＴＤ >CTE2 ＴＤ (2) CTE1 ＭＤ ≦0ppm / ℃ (3) CTE1 ＴＤ ≦5.0ppm / ℃ (4)

[0018] 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 during the film-forming process of the liquid crystal polymer film, and is sometimes abbreviated as MD. The transverse direction is the direction perpendicular to the MD in the plane of the liquid crystal polymer film, and is sometimes abbreviated as TD. For example, when the liquid crystal polymer film is a roll, the longitudinal direction of the roll is the MD, and the width direction of the roll is the TD. In one embodiment, when a liquid crystal polymer film is laminated with a metal sheet or the like using a roll-to-roll double belt press or roll press to continuously produce a metal-clad laminate, the liquid crystal polymer film is transported in the MD and processed, such as by laminating with a metal sheet.

[0019] The liquid crystal polymer film has a CTE of 1 ＭＤ and CTE2 ＭＤ Difference from (CTE1 ＭＤ -CTE2 ＭＤ ), and / or CTE1 ＴＤ and CTE2 ＴＤ Difference from (CTE1 ＴＤ -CTE2 ＴＤ ) is preferably 1.0 to 20.0 ppm / °C, more preferably 2.0 to 19.0 ppm / °C, and even more preferably 3.0 to 18.5 ppm / °C. ＭＤ -CTE2 ＭＤ and CTE1 ＴＤ -CTE2 ＴＤ It is preferable that all of the above satisfy the above ranges.

[0020] The liquid crystal polymer film has a CTE of 1 ＭＤ and CTE2 ＭＤ is preferably −30.0 to 0 ppm / ° C., more preferably −28.0 to −1.0 ppm / ° C., and further preferably −25.0 to −3.0 ppm / ° C. In addition, the CTE1 ＭＤis preferably −30.0 to 0 ppm / °C, more preferably −20.0 to −3.0 ppm / °C, and further preferably −15.0 to −5.0 ppm / °C. ＭＤ is preferably −30.0 to 0 ppm / ° C., more preferably −29.0 to −1.0 ppm / ° C., and even more preferably −28.0 to −10.0 ppm / ° C.

[0021] The liquid crystal polymer film has a CTE of 1 ＴＤ and CTE2 ＴＤ is preferably −20.0 to 5.0 ppm / ° C., more preferably −19.0 to 3.0 ppm / ° C., and further preferably −15.0 to 0 ppm / ° C. ＴＤ is preferably −20.0 to 5.0 ppm / °C, more preferably −10.0 to 4.5 ppm / °C, and further preferably −8.0 to 4.0 ppm / °C. ＴＤ is preferably −20.0 to 5.0 ppm / ° C., more preferably −19.0 to 0 ppm / ° C., and even more preferably −15.0 to −3.0 ppm / ° C.

[0022] The liquid crystal polymer film has a CTE of 1 ＭＤ and CTE1 ＴＤ The absolute value of the difference between ＭＤ -CTE1 ＴＤ |), and / or CTE2 ＭＤ and CTE2 ＴＤ The absolute value of the difference between ＭＤ -CTE2 ＴＤ |) is preferably 0 to 20.0 ppm / °C, more preferably 1.0 to 18.0 ppm / °C, and even more preferably 2.0 to 13.0 ppm / °C. ＭＤ -CTE1 ＴＤ | and | CTE2 ＭＤ -CTE2 ＴＤ It is preferable that both of | satisfy the above ranges.

[0023] In this specification, the thermal expansion coefficient of the liquid crystal polymer film is a value measured by the following method. That is, a liquid crystal polymer film is cut into a width of 5 mm and a length of 20 mm, and a sample cut so that the MD is the length direction of the sample and a sample cut so that the TD is the length direction of the sample are prepared. Using a thermomechanical analyzer (TMA), a tensile load of 1 g is applied to both ends of the sample, and the sample is 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 heated again at a rate of 5 ° C. / min. The thermal expansion coefficient between 30 ° C. and the glass transition temperature (Tg) of the liquid crystal polymer film and the thermal expansion coefficient between Tg and 200 ° C. are calculated. The thermal expansion coefficient means a value expressed as the rate of change in the length of the sample in a predetermined temperature range as a rate of change per unit temperature. These thermal expansion coefficients are measured in the MD and TD, and the thermal expansion coefficients of the MD and TD from 30 ° C. to Tg are respectively CTE1 ＭＤ and CTE1 ＴＤ , and the thermal expansion coefficients of MD and TD from Tg to 200 ° C are CTE2 ＭＤ and CTE2 ＴＤ It is calculated as follows.

[0024] In this specification, the glass transition temperature Tg of the liquid crystal polymer film can be measured using a dynamic mechanical analyzer (DMA). Specifically, a sample cut out from the liquid crystal polymer film with a width of 10 mm in TD and a length of 40 mm in MD is heated from 25°C to 220°C under conditions of a sine wave of 10 Hz and a heating rate of 3°C / min, and the peak temperature of tanδ, which is the ratio of the storage modulus to the loss modulus (loss modulus / storage modulus), is calculated as the glass transition temperature Tg.

[0025] Generally, in the process of producing a metal-clad laminate by thermocompression bonding a liquid crystal polymer film and a metal sheet using a roll-to-roll double belt press or roll press, the liquid crystal polymer film is softened by heat and shear force is applied to the film, causing molecular motion within the film and changing the molecular orientation of the liquid crystal polymer film. Furthermore, whether double belt press or roll press is used, the liquid crystal polymer film is stretched in both MD and TD, and this stretching also changes the molecular orientation of the film. Here, the molecular orientation of the liquid crystal polymer film affects its thermal expansion behavior. That is, the temperature and pressure conditions during thermocompression bonding affect the thermal expansion behavior of the liquid crystal polymer film in the resulting metal-clad laminate. Because metal-clad laminates are used as various substrate materials, considering the manufacturing processes for various substrates, advanced control of the thermal expansion behavior of metal-clad laminates is required. In particular, the degree of molecular motion changes significantly across the Tg of the liquid crystal polymer film, which is prone to differences in the thermal expansion coefficient before and after the Tg. Therefore, it is required that the thermal expansion behavior be as consistent as possible regardless of the temperature range.

[0026] Conventionally, the molecular orientation of liquid crystal polymer films has been controlled by adjusting the shear force, etc., when laminating with a metal sheet, but when considering the adhesiveness with the metal sheet, there are limitations to the thermocompression bonding conditions, and there is a limit to adjusting the molecular orientation based on those conditions alone. In particular, when it is desired to improve the adhesiveness with the metal sheet to be laminated, thermocompression bonding conditions with higher temperatures and pressures are required, which further promotes molecular motion due to heat in the liquid crystal polymer film, making it difficult to control the molecular orientation, that is, the thermal expansion behavior.

[0027] In the present invention, it has been found that the control of molecular orientation during thermocompression bonding is greatly influenced by the initial orientation state of the liquid crystal polymer film before being subjected to thermocompression bonding.The liquid crystal polymer film of the present invention is controlled so that the thermal expansion coefficients before and after Tg in each direction of MD and TD have a specific relationship, and if the liquid crystal polymer film has such a specific thermal expansion behavior, when it is thermocompressed with a metal sheet to produce a metal-clad laminate, it is easy to control the molecular orientation by adjusting the temperature and pressure during thermocompression bonding.As a result, in the obtained metal-clad laminate, the difference in the thermal expansion coefficients before and after Tg of the liquid crystal polymer film is small, and it is possible to adjust the thermal expansion behavior to be as constant as possible regardless of the temperature range.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] (1) Aromatic or aliphatic diol (see Table 1 for representative examples)

[0033] (2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for representative examples)

[0034] (3) Aromatic hydroxycarboxylic acids (see Table 3 for representative examples)

[0035] (4) Aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids (see Table 4 for representative examples)

[0036] Representative examples of liquid crystal polymers obtained from these raw material compounds include copolymers having the repeating units shown in Tables 5 and 6.

[0037]

[0038]

[0039] 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.

[0040] 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.

[0041] 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).

[0042] 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).

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 a roll-to-roll double belt press or roll press, the liquid crystal polymer film is transported in the MD direction and continuously processed.

[0051] 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.

[0052] The melting point Tm of the liquid crystal polymer film is 270°C or higher. The melting point Tm of the liquid crystal polymer film is preferably 280°C or higher, more preferably 290°C or higher, and even more preferably 300°C or higher. The melting point Tm of the liquid crystal polymer film 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 completely melted at 400°C, and then cooled to 50°C at a rate of 10°C / min. The melting point Tm of the liquid crystal polymer film can be determined by the position of the endothermic peak that appears when the temperature is raised again at a rate of 10°C / min.

[0053] The glass transition temperature Tg of the liquid crystal polymer film may be 80° C. or higher, preferably 90° C. or higher, and more preferably 100° C. or higher. The glass transition temperature Tg of the liquid crystal polymer film may be 150° C. or lower, preferably 140° C. or lower, more preferably 130° C. or lower, and even more preferably 120° C. or lower.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] <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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] In one embodiment of the present invention, a film containing a liquid crystal polymer is subjected to a mechanical stress of 1.0 to 5.0 N / mm ２a 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 for producing a liquid crystal polymer film includes a third step of winding the film while applying a tension of 1000 kJ / cm to obtain a liquid crystal polymer film. By adjusting the conditions in this production method, it is possible to adjust the thermal expansion coefficient of the obtained liquid crystal polymer film.

[0063] In the above-mentioned manufacturing method, the number of heating rolls is not particularly limited, and may be appropriately adjusted from the viewpoint of adjusting the thermal expansion coefficient. For example, the number of heating rolls may be one or two or more. The thermal expansion coefficient (CTE) of the liquid crystal polymer film in each of the MD and TD directions around Tg is ＭＤ , CTE1 ＴＤ , CTE2 ＭＤ , CTE2 ＴＤ ) to have a specific relationship, it is preferable to use a plurality of heating rolls.

[0064] In the above embodiment, the film containing the liquid crystal polymer is subjected to a mechanical stress of 1.0 to 5.0 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 conveying the film in contact with a plurality of heating rolls; and ２ and a third step of winding the film under a tension of 1000 MPa to obtain a liquid crystal polymer film, wherein the rotation speed of the second or subsequent heating rolls in the second step is equal to or greater than the rotation speed of the heating roll that contacts the film immediately before, and the rotation speed of the last heating roll that contacts the film is greater than the rotation speed of the first heating roll that contacts the film. ＭＤ , CTE1 ＴＤ , CTE2 ＭＤ , CTE2 ＴＤ) can be adjusted to have a specific relationship. A preferred form of the liquid crystal polymer film produced by this production method is the form of the liquid crystal polymer film described above. One embodiment of the present invention is the above production method, wherein the liquid crystal polymer film obtained has a CTE of ＭＤ >CTE2 ＭＤ , CTE1 ＴＤ >CTE2 ＴＤ , CTE1 ＭＤ ≦0 ppm / °C, and CTE1 ＴＤ ≦5.0 ppm / ° C. The “film containing a liquid crystal polymer” may be, for example, a film formed by the above-mentioned method from a liquid crystal polymer (which may be a resin composition containing a liquid crystal polymer).

[0065] An example of an embodiment of steps 1 to 3 of the manufacturing method of the present invention is shown below with reference to FIG. 1 . Hereinafter, steps 1 to 3 are sometimes referred to as "film pretreatment." For the sake of explanation, the liquid crystal polymer film (a film containing a liquid crystal polymer) before its thermal expansion coefficient is adjusted is sometimes referred to as the "precursor film" to distinguish it from the liquid crystal polymer film after its thermal expansion coefficient has been adjusted by film pretreatment. The apparatus shown in FIG. 1 includes an unwinding roll 1, a take-up roll 2, heating rolls 3 and 4, rotational speed adjusting heating rolls 5 to 7, and guide rolls 9 and 10. Precursor film 8 is unwound from unwinding roll 1 and introduced via guide roll 9 between heating rolls 3 and 4 and rotational speed adjusting heating rolls 5 to 7. The precursor film 8 is brought into contact with the outer peripheral surfaces of the heating rolls. While heated, the precursor film 8 is wound around take-up roll 2 via guide roll 10, yielding a liquid crystal polymer film 11 with an adjusted thermal expansion coefficient.

[0066] In order to adjust the thermal expansion coefficient of the liquid crystal polymer film 11, the unwinding tension applied to the precursor film 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 1.0 to 4.0 N / mm ２Here, 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 rotation speed adjusting heating roll 7 and the take-up roll 2 is the take-up tension.

[0067] From the viewpoint of adjusting the thermal expansion coefficient of the liquid crystal polymer film 11, the rotational speeds of the heating rolls 4 to 7 that contact the liquid crystal polymer film 11 after the heating rolls 3 to 7 are equal to or greater than the rotational speeds of the heating rolls 3 to 6 that contact the film immediately before, and the rotational speed of the heating roll 7 that contacts the film last is greater than the rotational speed of the heating roll 3 that contacts the film first. By adjusting the rotational speed of the heating rolls while heating the liquid crystal polymer film in contact with the heating rolls and fine-tuning the stress on the liquid crystal polymer film, the molecular orientation in the liquid crystal polymer film can be adjusted, thereby enabling control of the thermal expansion coefficient. For example, the rotational speed of the heating roll 4 may be adjusted to be the same as the rotational speed of the heating roll 3, and the rotational speeds of the rotational speed-adjusting heating rolls 5 to 7 may be adjusted to be equal to or greater downstream. Furthermore, the ratio of the rotational speed of the heating roll 3 that contacts the film first to the rotational speed of the rotational speed-adjusting heating roll 7 that contacts the film last may be 1.01 or greater, preferably 1.02 or greater, and more preferably 1.03 or greater.

[0068] 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.

[0069] The heating rolls 3 to 7 may be heated, for example, by a heating medium circulating therein, 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. From the viewpoint of controlling the thermal expansion coefficient of the liquid crystal polymer film, the temperature of the heating rolls is preferably in the range from a temperature 75°C lower than the melting point Tm of the liquid crystal polymer film to a temperature 15°C lower than the melting point Tm (Tm-75°C to Tm-15°C).

[0070] 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 B0601:1982, is preferably set so that this Rmax is in the range of 5 to 20 μm, and more preferably in the range of 8 to 16 μm.

[0071] From the viewpoint of adjusting the thermal expansion coefficient of the liquid crystal polymer film, the rotation speed of the heating rolls, converted into the linear velocity of the outer periphery thereof, is preferably 0.5 m / min to 10 m / min, more preferably 1 m / min to 5 m / min, The rotation speed of the heating rolls may be controlled for some of the heating rolls or may be controlled for each heating roll.

[0072] Although the apparatus shown in FIG. 1 has five heating rolls, the number of heating rolls is not particularly limited as long as multiple heating rolls are installed, and the number may be adjusted appropriately from the viewpoint of adjusting the thermal expansion coefficient. For example, the number of heating rolls may be two or more, or may be three or more. Furthermore, each heating roll may have the same specifications or may have different specifications. For example, each heating roll may be set to a different temperature to provide a temperature gradient, or a cooling roll set to a lower temperature may be provided.

[0073] <Metal-clad laminate> One embodiment of the present invention is a metal-clad laminate formed by laminating the above-mentioned liquid crystal polymer film and a metal sheet. The metal-clad laminate may be a metal-clad laminate formed by thermocompression bonding the above-mentioned liquid crystal polymer film and a metal sheet. As described below, known means such as a double belt press or a roll press can be used to thermocompress the liquid crystal polymer film and the metal sheet. In the present invention, the thermal expansion coefficients of the liquid crystal polymer film before lamination with the metal sheet have a specific relationship around Tg in the MD and TD directions, respectively. This makes it easy to control the molecular orientation associated with the stretching of the liquid crystal polymer film that occurs when thermocompression bonding with the metal sheet. This makes it possible to produce a metal-clad laminate including a liquid crystal polymer film whose thermal expansion coefficient below Tg is equivalent to that above Tg. It is also possible to suppress appearance defects such as warping.

[0074] 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 coefficient of thermal expansion (CTE) of the liquid crystal polymer film in the machine direction and the transverse direction is 30° C. to the glass transition temperature (Tg). ＭＤ , CTE1 ＴＤ ) and the coefficient of thermal expansion from Tg to 200 ° C (CTE2 ＭＤ , CTE2 ＴＤ ) satisfy the following formulas (5) and (6): -8.0 ppm / °C≦CTE1 ＭＤ -CTE2 ＭＤ ≦8.0ppm / ℃ (5) -8.0ppm / ℃≦CTE1 ＴＤ -CTE2 ＴＤ ≦8.0ppm / ℃ (6)

[0075] CTE1 of liquid crystal polymer film in metal-clad laminate ＭＤ and CTE2 ＭＤ Difference from (CTE1 ＭＤ -CTE2 ＭＤ ) is preferably −5.0 to 5.0 ppm / ° C., more preferably −3.0 to 3.0 ppm / ° C.

[0076] CTE1 of liquid crystal polymer film in metal-clad laminate ＴＤ and CTE2 ＴＤ Difference from (CTE1 ＴＤ -CTE2 ＴＤ ) is preferably −5.0 to 5.0 ppm / ° C., more preferably −3.0 to 3.0 ppm / ° C.

[0077] CTE1 of the liquid crystal polymer film in the metal-clad laminate ＭＤ and CTE1 ＴＤ The absolute value of the difference between ＭＤ -CTE1 ＴＤ |), and / or CTE2 ＭＤ and CTE2 ＴＤ The absolute value of the difference between ＭＤ -CTE2 ＴＤ |) is preferably 0 to 10.0 ppm / °C, more preferably 0 to 5.0 ppm / °C, and even more preferably 0 to 3.0 ppm / °C. ＭＤ -CTE1 ＴＤ | and | CTE2 ＭＤ -CTE2 ＴＤ It is preferable that both of | satisfy the above ranges.

[0078] Coefficient of thermal expansion (CTE) of liquid crystal polymer film in metal-clad laminate ＭＤ , CTE1 ＴＤ , CTE2 ＭＤ , CTE2 ＴＤ From the viewpoint of suppressing appearance defects such as warpage, each of the above is preferably 5.0 to 30.0 ppm / °C, more preferably 10.0 to 27.0 ppm / °C, and even more preferably 15.0 to 25.0 ppm / °C.

[0079] The thermal expansion coefficient of the liquid crystal polymer film in the metal-clad laminate is measured using the liquid crystal polymer film obtained by removing the metal sheet of the metal-clad laminate by etching.

[0080] 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.

[0081] From the viewpoint of efficient shipping, the shape of the metal-clad laminate is preferably a long product, and may be a roll product.

[0082] (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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 thermal expansion properties and appearance. 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, a metal-clad laminate having excellent thermal expansion properties and appearance can be obtained. 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 thermal expansion properties and appearance.

[0087] <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.

[0088] 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.

[0089] (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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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. The thermocompression bonding time can also be adjusted by, for example, adjusting the conveying speed of the liquid crystal polymer film and the metal sheet.

[0095] 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+40°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.

[0096] 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.

[0097] 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.

[0098] From the viewpoint 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 roll, pulley, etc., and can also be adjusted by the device configuration of the double belt press.

[0099] 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.

[0100] (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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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 40° C., and more preferably set to a temperature higher than Tm by 2° C. to 30° 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.

[0109] 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.

[0110] 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.

[0111] <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.

[0112] 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.

[0113] <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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] <Thermal expansion coefficient of liquid crystal polymer film> The liquid crystal polymer films obtained in the examples and comparative examples were cut into a width of 5 mm and a length of 20 mm, and samples were prepared by cutting out samples so that the MD was the length direction of the sample and samples so that 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, then cooled to 30 ° C. at a rate of 20 ° C. / min, and heated again at a rate of 5 ° C. / min. Based on the change in the length of the sample between 30 ° C. and the glass transition temperature (Tg) of the liquid crystal polymer film and from Tg to 200 ° C., each thermal expansion coefficient CTE1 ＭＤ and CTE1 ＴＤ , and CTE2 ＭＤ and CTE2 ＴＤ The measurement was carried out three times in each of the MD and TD, and the average value was used.

[0118] <Glass Transition Temperature> The glass transition temperature Tg of the liquid crystal polymer film was measured using a dynamic viscoelasticity measuring device (Rheology Corp.'s "DVE V4 FT Rheospectr"). A sample cut from the liquid crystal polymer film with a width of 10 mm in the TD and a length of 40 mm in the MD was heated from 25°C to 220°C under conditions of a sine wave of 10 Hz and a heating rate of 3°C / min. The peak temperature of tan δ, which is the ratio of the storage modulus to the loss modulus (loss modulus / storage modulus) that appears during heating, was taken as the glass transition temperature Tg.

[0119] <Melting Point of Liquid Crystal Polymer Film> The melting point Tm of the liquid crystal polymer film was measured using a differential scanning calorimeter (DSC manufactured by Shimadzu Corporation). The liquid crystal polymer film was heated from room temperature (e.g., 25°C) at a rate of 10°C / min until it was completely melted at 400°C, and then cooled to 50°C at a rate of 10°C / min. The melt was then heated again at a rate of 10°C / min. The position of the endothermic peak that appeared when the temperature was increased again was taken as the melting point Tm of the liquid crystal polymer film.

[0120] <Thermal expansion coefficient of the liquid crystal polymer film in the copper clad laminate> The copper foil laminated on the copper clad laminate obtained in Examples and Comparative Examples was removed by etching using copper chloride solution, washed and dried, and then obtained a single liquid crystal polymer film. From the obtained liquid crystal polymer film, a sample to be measured was cut out, and the thermal expansion coefficient was measured in the same manner as above.

[0121] <Evaluation of Warpage of Copper-Clad Laminate> The copper-clad laminates obtained in the Examples and Comparative Examples were randomly cut to 300 mm in MD and 250 mm in TD, and held in an oven at 150°C to evaluate the warpage of the copper-clad laminate. The copper-clad laminate sample was placed on a horizontal table, and the height of the part of the four corners of the sample that was furthest from the table was measured with a scale, and this was taken as the warpage. Those with a warpage of less than 5 mm were rated as A, and those with a warpage of 5 mm or more were rated as B.

[0122] <Preparation of Liquid Crystal Polymer Film> [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 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 0.25 mm. The extrusion was carried out by inflation film formation 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., and the glass transition temperature Tg was 110 ° C.

[0123] The above film was pretreated using an apparatus equipped with five heating rolls as shown in FIG. 1 . The five heating rolls 3 and 4 and the rotation speed adjusting heating rolls 5 to 7 were each chrome-plated stainless steel rolls with a diameter of 600 mm, each with numerous 12 μm-deep recesses formed on the surface. Furthermore, 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 −70°C, the melting point of the liquid crystal polymer film. 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 2.0 m / min while being heated. Then, the film was taken 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 rotational speed ratios of the rotational speed adjusting heating rolls 5 to 7 to the rotational speed of the heating roll 3 were adjusted to 1.00, 1.05, and 1.09, respectively. The thermal expansion coefficients of the obtained liquid crystal polymer films were measured, and the results are shown in Table 7.

[0124] Example 2 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 320-350°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 0.25 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 320°C, and the glass transition temperature (Tg) was 110°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 thermal expansion coefficient of the obtained liquid crystal polymer film was measured, and the results are shown in Table 7.

[0125] Example 3 A thermoplastic liquid crystal polyester having a melting point of 280°C and consisting of 6-hydroxy-2-naphthoic acid units (27 mol%) and p-hydroxybenzoic acid units (73 mol%) was heated and kneaded using a single-screw extruder at 280 to 340°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 0.5 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 50 μm thick thermoplastic liquid crystal polyester film. The melting point (Tm) of this film was 280°C, and the glass transition temperature (Tg) was 110°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 thermal expansion coefficient of the obtained liquid crystal polymer film was measured, and the results are shown in Table 7.

[0126] Example 4 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 340°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 0.5 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 50 μm. The melting point (Tm) of this film was 310°C, and the glass transition temperature (Tg) was 110°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 thermal expansion coefficient of the obtained liquid crystal polymer film was measured, and the results are shown in Table 7.

[0127] Example 5 A thermoplastic liquid crystal polyester having a melting point of 309°C and composed of 6-hydroxy-2-naphthoic acid units (60 mol%), 2,6-naphthalenedicarboxylic acid units (20 mol%), hydroquinone units (15 mol%), and 4,4'-dihydroxybiphenyl units (5 mol%) was heated and kneaded using a single-screw extruder at 310-330°C, and then melt-extruded through an inflation die with a diameter of 40 mm and a slit spacing of 0.25 mm at a discharge rate of 20 kg / h. An inflation film was produced 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, and the glass transition temperature (Tg) was 140°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 thermal expansion coefficient of the obtained liquid crystal polymer film was measured, and the results are shown in Table 7.

[0128] Example 6 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 340°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 1 mm. 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 100 μm. The melting point Tm of this film was 310°C, and the glass transition temperature Tg was 110°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 thermal expansion coefficient of the obtained liquid crystal polymer film was measured, and the results are shown in Table 7.

[0129] [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 340 ° 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 45 cm diameter slow-cooling roll at 250 ° C. and slowly cooled. It was then transferred to a 45 cm diameter cooling roll cooled with 25 ° C. water to obtain a 25 μm thick thermoplastic liquid crystal polyester film. The melting point Tm of this film was 310 ° C. and the glass transition temperature Tg was 110 ° C. The thermal expansion coefficient of the obtained film was measured and the results are shown in Table 7.

[0130] [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 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 0.2 mm. A 25 μm thick thermoplastic liquid crystal polyester film was obtained by inflation film formation under conditions of a transverse stretch ratio of 4.4 times and a longitudinal stretch ratio of 2.0 times. The melting point (Tm) of this film was 310 ° C., and the glass transition temperature (Tg) was 110 ° C. The thermal expansion coefficient of the obtained film was measured, and the results are shown in Table 7.

[0131] [Comparative Example 3] 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 pulverized using a freeze pulverizer and dissolved in pentafluorophenol (PFP) heated to 60°C at a weight concentration of 2.0% while stirring to prepare a solution containing a liquid crystal polymer. The solution was then cast onto a 600 mm square glass plate and dried to obtain a liquid crystal polymer film having a thickness of 12.5 μm. The melting point (Tm) of this film was 310°C, and the glass transition temperature (Tg) was 110°C. The thermal expansion coefficient of the obtained film was measured, and the results are shown in Table 7.

[0132]

[0133] <Preparation of Metal-Clad Laminate (Single-Sided Copper-Clad Laminate)> [Example 7] Using a double belt press (DBP), rolled copper foil ("JXEFL-BHM" 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 one side of the 550 mm wide liquid crystal polymer film prepared in Example 1 to prepare a single-sided copper-clad laminate. The laminate had a release film / rolled copper foil / liquid crystal polymer film / 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 the unwinding tension was 10 N / mm ２ A laminate was obtained by thermocompression bonding under conditions of a pressure of 2.0 MPa, a temperature of the liquid crystal polymer film's melting point + 30°C, and a bonding time of 90 seconds. 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 prepare a single-sided copper-clad laminate. The measurement results of the thermal expansion coefficient of the liquid crystal polymer film and the evaluation results of the warpage of the single-sided copper-clad laminate for the obtained single-sided copper-clad laminate are shown in Table 8.

[0134] [Examples 8 to 11] Single-sided copper-clad laminates were produced in the same manner as in Example 7, except that the liquid crystal polymer film was changed to the liquid crystal polymer film shown in Table 8. For the obtained single-sided copper-clad laminates, the measurement results of the thermal expansion coefficient of the liquid crystal polymer film and the evaluation results of the warpage of the single-sided copper-clad laminates are shown in Table 8.

[0135] [Example 12] Using a roll press (RP) device, rolled copper foil ("JXEFL-BHM" 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 one side of the liquid crystal polymer film produced in Example 6 to produce a single-sided copper-clad laminate. The rolled copper foil / liquid crystal polymer film / release film configuration was introduced between heated rolls with the matte surface of the rolled copper foil in contact with the liquid crystal polymer film, and an applied tension of 10 N / mm was applied. 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, after which the release film was peeled off. The release film used was a polyimide film ("Apical" (registered trademark) manufactured by Kaneka Corporation, thickness 50 μm). Annealing was then performed at 340°C for 30 seconds using a heat treatment machine to produce a single-sided copper-clad laminate. The results of measuring the thermal expansion coefficient of the liquid crystal polymer film and the evaluation results of the warpage of the single-sided copper-clad laminate are shown in Table 8.

[0136] [Example 13] Using a vacuum batch press (VP; manufactured by Kitagawa Seiki Co., Ltd., "VH2-2325"), rolled copper foil (manufactured by JX Nippon Oil & Gas Corporation, "JXEFL-BHM", matte surface arithmetic mean roughness Ra of 0.18 μm, ten-point mean roughness Rzjis of 0.9 μm, thickness of 12 μm) was laminated on one side of the liquid crystal polymer film produced in Example 6 to produce a single-sided copper-clad laminate. Specifically, at a vacuum degree of 100 Pa and 300 ° C., the upper and lower surfaces of the laminate of the liquid crystal polymer film and the rolled copper foil were pressed at a pressure of 2 MPa for 30 minutes to produce a single-sided copper-clad laminate. For the obtained single-sided copper-clad laminate, the measurement results of the thermal expansion coefficient of the liquid crystal polymer film and the evaluation results of the warpage of the single-sided copper-clad laminate are shown in Table 8.

[0137] [Comparative Example 4] Using a double belt press (DBP), rolled copper foil ("JXEFL-BHM" 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, 580 mm width) was laminated on one side of the 550 mm wide thermoplastic liquid crystal polymer film produced in Comparative Example 1 to produce a single-sided copper-clad laminate. The laminate had a release film / rolled copper foil / liquid crystal polymer film / 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 the unwinding tension was 10 N / mm ２ A laminate was obtained by thermocompression bonding under conditions of a pressure of 2.0 MPa, a temperature of the liquid crystal polymer film's melting point + 30°C, and a compression bonding time of 90 seconds. 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 prepare a single-sided copper-clad laminate. The measurement results of the thermal expansion coefficient of the liquid crystal polymer film and the evaluation results of the warpage of the single-sided copper-clad laminate for the obtained single-sided copper-clad laminate are shown in Table 8.

[0138] [Comparative Example 5] A single-sided copper-clad laminate was produced in the same manner as in Comparative Example 4, except that the liquid crystal polymer film was changed to the liquid crystal polymer film produced in Comparative Example 2. For the obtained single-sided copper-clad laminate, the measurement results of the thermal expansion coefficient of the liquid crystal polymer film and the evaluation results of the warpage of the single-sided copper-clad laminate are shown in Table 8.

[0139] [Comparative Example 6] Using a vacuum batch press (VP; manufactured by Kitagawa Seiki Co., Ltd., "VH2-2325"), rolled copper foil (manufactured by JX Nippon Oil & Gas Corporation, "JXEFL-BHM", matte surface arithmetic mean roughness Ra of 0.18 μm, ten-point mean roughness Rzjis of 0.9 μm, thickness of 12 μm) was laminated on one side of the liquid crystal polymer film produced in Comparative Example 3 to produce a single-sided copper-clad laminate. Specifically, at a vacuum degree of 100 Pa and 300 ° C., the upper and lower surfaces of the laminate of the liquid crystal polymer film and the rolled copper foil were pressed at a pressure of 2 MPa for 30 minutes to produce a single-sided copper-clad laminate. For the obtained single-sided copper-clad laminate, the measurement results of the thermal expansion coefficient of the liquid crystal polymer film and the evaluation results of the warpage of the single-sided copper-clad laminate are shown in Table 8.

[0140]

[0141] The liquid crystal polymer films of Examples 1 to 6 have a specific relationship in which the thermal expansion coefficients before and after Tg in MD and TD satisfy the above formulas (1) to (4). Therefore, as shown in Examples 7 to 13, the difference in the thermal expansion coefficients before and after Tg was small, and it was possible to manufacture metal-clad laminates without warping.

[0142] On the other hand, the liquid crystal polymer film of Comparative Example 1 did not satisfy the above formulas (1), (2), and (4), the liquid crystal polymer film of Comparative Example 2 did not satisfy the above formula (4), and the liquid crystal polymer film of Comparative Example 3 did not satisfy the above formulas (1) to (4). Since the thermal expansion coefficients of all of them were not controlled, as shown in Comparative Examples 4 to 6, the difference in the thermal expansion coefficients before and after the Tg of the liquid crystal polymer film in the resulting metal-clad laminate was large, and the warping was significant, resulting in poor appearance.

[0143] 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.

[0144] 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.

[0145] 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. A film containing a liquid crystal polymer, having a melting point of 270°C or higher, and a coefficient of thermal expansion (CTE) of 30°C to the glass transition temperature (Tg) of the film in the machine direction and the transverse direction. ＭＤ , CTE1 ＴＤ ) and the coefficient of thermal expansion from Tg to 200 ° C (CTE2 ＭＤ , CTE2 ＴＤ ) and satisfy the following formulas (1) to (4): ＭＤ >CTE2 ＭＤ (1) CTE1 ＴＤ >CTE2 ＴＤ (2) CTE1 ＭＤ ≦0ppm / ℃ (3) CTE1 ＴＤ ≦5.0ppm / ℃ (4) 2. CTE1 ＭＤ and CTE2 ＭＤ Difference from (CTE1 ＭＤ -CTE2 ＭＤ ), and CTE1 ＴＤ and CTE2 ＴＤ Difference from (CTE1 ＴＤ -CTE2 ＴＤ 2. The liquid crystal polymer film according to claim 1, wherein each of the above is 1.0 to 20.0 ppm / °C.

3. CTE1 ＭＤ and CTE2 ＭＤ 2. The liquid crystal polymer film according to claim 1, wherein each of the values ​​is in the range of −30.0 to 0 ppm / ° C.

4. CTE1 ＴＤ and CTE2 ＴＤ 2. The liquid crystal polymer film according to claim 1, wherein each of the values ​​is in the range of −20.0 to 5.0 ppm / ° C.

5. CTE1 ＭＤ and CTE1 ＴＤ The absolute value of the difference between ＭＤ -CTE1 ＴＤ |), and CTE2 ＭＤ and CTE2 ＴＤ The absolute value of the difference between ＭＤ -CTE2 ＴＤ 2. The liquid crystal polymer film according to claim 1, wherein |) is 0 to 20.0 ppm / °C.

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

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

8. A film containing a liquid crystal polymer is subjected to a force of 1.0 to 5.0 N / mm in the machine direction. 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 conveying the film in contact with a plurality of heating rolls; and ２ and a third step of winding the film under tension to obtain a liquid crystal polymer film, wherein the rotation speed of the second or subsequent heating rolls in the second step is equal to or greater than the rotation speed of the heating roll that was brought into contact immediately before it, and the rotation speed of the last heating roll that was brought into contact is greater than the rotation speed of the first heating roll that was brought into contact.

9. A metal-clad laminate in which a metal sheet is laminated on a liquid crystal polymer film, wherein the coefficient of thermal expansion (CTE) of the liquid crystal polymer film in the machine direction and the transverse direction is less than 30°C from the glass transition temperature (Tg). ＭＤ , CTE1 ＴＤ ) and the coefficient of thermal expansion from Tg to 200 ° C (CTE2 ＭＤ , CTE2 ＴＤ ) and satisfy the following formulas (5) and (6): -8.0 ppm / °C≦CTE1 ＭＤ -CTE2 ＭＤ ≦8.0ppm / ℃ (5) -8.0ppm / ℃≦CTE1 ＴＤ -CTE2 ＴＤ ≦8.0ppm / ℃ (6) 10. CTE1 of the liquid crystal polymer film ＭＤ and CTE1 ＴＤ The absolute value of the difference between ＭＤ -CTE1 ＴＤ |), and CTE2 ＭＤ and CTE2 ＴＤ The absolute value of the difference between ＭＤ -CTE2 ＴＤ The metal-clad laminate according to claim 9, wherein |) is 0 to 10.0 ppm / °C.

11. A circuit board, comprising a metal sheet of the metal-clad laminate according to claim 9 or 10, on which a circuit pattern is formed.

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

13. 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 6 using a double belt press or a roll press.

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