Polymer films, laminates and substrates for high-speed communication

Abstract

To provide: a polymer film to which a metal-containing layer is stuck to produce a laminate having excellent peel strength; and a laminate and a substrate for high-speed communication.SOLUTION: The polymer film of the present invention is a polymer film including a liquid crystal polymer, in which a difference between a melting start temperature and a melting end temperature in differential scanning calorimetry in a depth region up to 10 μm of the polymer film from one surface toward the other surface of the polymer film is 5.0 to 50°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to polymer films, laminates and substrates for high speed communications. [Background technology]

[0002] Fifth-generation (5G) mobile communication systems, considered the next-generation communication technology, will use higher frequencies and wider bandwidths than ever before. Therefore, film substrates for circuit boards used in 5G mobile communication systems must have low dielectric constants and low dielectric dissipation factors, and development using various materials is underway. Liquid crystal polymer (LCP) film is one such film substrate. Liquid crystal polymer (LCP) film has a lower dielectric constant and lower dielectric dissipation factor than films commonly used in fourth-generation (4G) mobile communication systems, such as polyimide film and glass epoxy film, and is therefore expected to be a film substrate for high-frequency circuit boards.

[0003] For example, Patent Document 1 describes a liquid crystal polymer film made of a thermoplastic polymer capable of forming an optically anisotropic molten phase, in which the rate of change in the relative dielectric constant before and after heating the film satisfies a specific relationship, as well as a laminate comprising a film layer made of the thermoplastic liquid crystal polymer film and a metal layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6640072 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have studied the liquid crystal polymer film described in Patent Document 1 and found that there is room for improvement in the peel strength of a laminate produced by laminating a liquid crystal polymer film and a metal-containing layer.

[0006] Therefore, an object of the present invention is to provide a polymer film having excellent peel strength for a laminate produced by laminating a metal-containing layer, and a laminate and a substrate for high-speed communication. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the inventors have found that, in differential scanning calorimetry analysis of the surface region of a polymer film, if the difference between the melting start temperature and the melting end temperature is within a specific range, the peel strength of a laminate produced by bonding a metal-containing layer is excellent, and have completed the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0008] [1] A polymer film comprising a liquid crystal polymer, A polymer film in which, in a differential scanning calorimetry analysis performed in a region from one surface of the polymer film to the other surface to a depth of 10 μm, the difference between the melting start temperature and the melting end temperature is 5.0 to 50°C. [2] The polymer film described in [1], wherein the area A1 of the melting peak in differential scanning calorimetry analysis in a depth region of 10 μm from one surface of the polymer film is smaller than the area A2 of the melting peak in differential scanning calorimetry analysis of the entire polymer film. [3] The polymer film according to [2], wherein the area A1 is 1.0 to 12.0 J / g, and the area A2 is 3.0 J / g or more. [4] The polymer film according to any one of [1] to [3], wherein the polymer film has a melting peak temperature of 290 to 340°C in a region up to a depth of 10 µm from one surface thereof in differential scanning calorimetry. [5] The polymer film according to any one of [1] to [4], wherein the thickness of the polymer film is more than 10 μm and not more than 250 μm. [6] The polymer film according to any one of [1] to [5], wherein the linear expansion coefficient in a first direction within the plane of the polymer film and the linear expansion coefficient in a second direction within the plane of the polymer film that is perpendicular to the first direction are both 0 to 40 ppm / °C. [7] The polymer film according to any one of [1] to [6], wherein the liquid crystal polymer contains a repeating unit derived from 6-hydroxy-2-naphthoic acid. [8] The polymer film according to any one of [1] to [6], wherein the liquid crystal polymer contains at least one repeating unit selected from the group consisting of a repeating unit derived from 6-hydroxy-2-naphthoic acid, a repeating unit derived from an aromatic diol compound, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid. [9] The polymer film according to any one of [1] to [8], further comprising a polyolefin.

[10] The polymer film according to [9], wherein the content of the polyolefin is 0.1 to 40% by mass based on the total mass of the polymer film.

[11] The polymer film according to [9] or

[10] , wherein the polyolefin forms a dispersed phase in the polymer film, and the dispersed phase has an average dispersed particle diameter of 0.01 to 10.0 μm.

[12] A laminate comprising the polymer film according to any one of [1] to

[11] and a metal-containing layer disposed on at least one surface of the polymer film.

[13] A substrate for high-speed communication, comprising the polymer film according to any one of [1] to

[11] . [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a polymer film that has excellent peel strength for a laminate produced by laminating a metal-containing layer, as well as a laminate and a substrate for high-speed communication that include the same. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing an example of a DSC curve obtained by differential scanning calorimetry of the surface region of a polymer film. [Figure 2] FIG. 1 is a diagram showing an example of a DSC curve obtained by differential scanning calorimetry of the entire polymer film. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.

[0012] In this specification, when a polymer film or laminate is long, the length direction means the longitudinal direction and MD (machine direction) of the polymer film or laminate, and the width direction means the direction perpendicular to the length direction within the plane of the polymer film or laminate (the short side direction and TD (transverse direction)). In this specification, for each component, a single substance corresponding to the component may be used, or two or more substances may be used. When two or more substances are used for each component, the content of the component refers to the total content of the two or more substances, unless otherwise specified. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit. In this specification, the dielectric loss tangent of a polymer film or a liquid crystal polymer contained in a polymer film measured under conditions of a temperature of 23° C. and a frequency of 28 GHz is also referred to as the "standard dielectric loss tangent."

[0013] [Polymer film] The polymer film of the present invention contains a liquid crystal polymer, and in a differential scanning calorimetry (DSC) analysis of a region extending from one surface of the polymer film to a depth of 10 μm (hereinafter also referred to as the "surface region") of the polymer film, the difference between the melting start temperature and the melting end temperature is 5.0 to 50° C. When a laminate is produced by laminating the polymer film of the present invention and a metal-containing layer, the peel strength between the polymer film and the metal-containing layer is excellent. Although the details of the reason for this are not clear, it is generally assumed as follows. When the polymer film is used as a circuit board, a metal-containing layer (metal foil or the like) is attached to at least one surface of the polymer film to form a laminate. When the liquid crystal polymer is melt-molded to obtain a polymer film, the molecules are oriented in the plane of the polymer film, and crystallization progresses. The crystallized liquid crystal polymer is brittle, so it is prone to cohesive failure at the interface with the metal-containing layer. If the metal-containing layer peels off from the polymer film due to cohesive failure, it will cause a loss of reliability for the wiring substrate. To address this issue, it is presumed that polymer films in which the difference between the melting start temperature and the melting end temperature in the surface region is within a specific range in differential scanning calorimetry analysis have low orientation and crystallinity of the liquid crystal polymer in the surface region, and therefore, when used as a laminate with a metal-containing layer, the occurrence of cohesive failure is suppressed.

[0014] [Differential scanning calorimetry] The polymer film of the present invention has a difference of 5.0 to 50°C between the melting start temperature and the melting end temperature measured by DSC in the surface region (region up to 10 μm deep in the polymer film) from one surface to the other surface of the polymer film. The difference between the melting start temperature and the melting end temperature is preferably 6.0°C or more, more preferably 8.0°C or more, and even more preferably 10°C or more, from the viewpoint of preventing the polymer film from becoming brittle and further improving adhesion to the metal-containing layer. The difference between the melting start temperature and the melting end temperature is preferably 40°C or less, more preferably 35°C or less, and even more preferably 30°C or less, from the viewpoint of reducing the crystallinity in the surface region of the polymer film and further improving adhesion to the metal-containing layer.

[0015] The difference between the melting start temperature and the melting end temperature can be adjusted, for example, by setting the heating temperature of one side of the polymer film to be equal to or higher than the melting point of the liquid crystal polymer in the post-heating treatment of the polymer film manufacturing method described below, and by heating the polymer film so that the temperature of one side is 30°C or more higher than the temperature of the other side.

[0016] The melting onset temperature (extrapolated melting onset temperature) means the temperature at which the liquid crystal polymer film starts to absorb heat, and is located on the low-temperature side of the melting peak temperature. Specifically, as described in JIS K7121:2012, it is the temperature at the intersection of a straight line extending the low-temperature side baseline to the high-temperature side and a tangent drawn at the point where the slope of the curve on the low-temperature side of the melting peak is maximum. The melting end temperature (extrapolated melting end temperature) means the temperature at which the liquid crystal polymer film ends its endothermic reaction, and is located on the higher temperature side of the melting peak temperature. Specifically, as described in JIS K7121:2012, it is the temperature at the intersection of a straight line extending the high temperature side baseline to the lower temperature side and a tangent drawn at the point where the slope of the curve on the high temperature side of the melting peak is maximum. The melting initiation temperature and melting end temperature are obtained by analyzing the DSC curve, and the difference between the melting initiation temperature and the melting end temperature is calculated by subtracting the melting initiation temperature from the melting end temperature. Here, the DSC curve is a curve showing the change in the amount of heat absorbed and released by a film, with the horizontal axis representing temperature and the vertical axis representing heat flow, and is measured using a differential scanning calorimeter in accordance with JIS K7122:2012 (heat flux differential scanning calorimetry). Detailed measurement conditions are as described in the Examples section. For example, when a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation) is used, the melting start temperature and melting end temperature can be determined using the accompanying analysis software (TA-60, manufactured by Shimadzu Corporation).

[0017] The melting peak temperature in differential scanning calorimetry in a region up to a depth of 10 μm from one surface of the polymer film is preferably 280 to 350°C, and from the viewpoint of better effects of the present invention, is preferably 290 to 340°C, more preferably 300 to 330°C, and even more preferably 310 to 320°C. The melting peak temperature in differential scanning calorimetry of the entire polymer film is preferably 270 to 360°C, more preferably 280 to 350°C, and even more preferably 290 to 340°C, in terms of better effects of the present invention.

[0018] The melting peak temperature is obtained by analyzing a DSC curve, and means the temperature at the peak of the portion of the DSC curve from when it leaves the baseline until when it returns to the baseline again. The DSC curve is measured by the above-mentioned method, and the details of the measurement method are as shown in the Examples section. For example, when a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation) is used, the melting peak temperature can be determined using the accompanying analysis software (TA-60, manufactured by Shimadzu Corporation).

[0019] It is preferable that the area A1 of the melting peak in differential scanning calorimetry analysis in a depth region of 10 μm from one surface of the polymer film is smaller than the area A2 of the melting peak in differential scanning calorimetry analysis of the entire polymer film (i.e., from one surface to the other surface of the polymer film) (area A2 - area A1 > 0). This results in a more excellent effect of the present invention. While the details of the reason for this are unclear, it is presumed to be due to the following reasons. The above areas A1 and A2 are related to the orientation of the liquid crystal polymer contained in the polymer film; when the area of ​​the melting peak is large, the orientation of the liquid crystal polymer tends to be high, and when the area of ​​the melting peak is small, the orientation of the liquid crystal polymer tends to be low. In other words, when the area A1 is smaller than the area A2, the liquid crystal polymer in the surface region has a lower orientation than the liquid crystal polymer contained in other regions of the polymer film, and it is presumed that cohesive failure is suppressed when the laminate is formed. The area A1 is preferably 1.0 to 17.0 J / g, and from the viewpoint of better effects of the present invention, is more preferably 1.0 to 12.0 J / g, more preferably 1.5 to 10.0 J / g, and even more preferably 2.0 to 5.0 J / g. The area A2 is preferably 3.0 J / g or more, more preferably 3.5 J / g or more, and even more preferably 4.0 J / g or more, in order to obtain a more excellent effect of the present invention. The upper limit of the area A2 is not particularly limited, but is usually 30 J / g or less.

[0020] The values ​​of area A1, area A2, and the difference between area A1 and area A2 can be adjusted, for example, by setting the heating temperature of one side of the polymer film to be equal to or higher than the melting point of the liquid crystal polymer in the post-heating treatment of the polymer film manufacturing method described below, and by heating the polymer film so that the temperature of one side is 30°C or more higher than the temperature of the other side.

[0021] Area A1 and area A2 are obtained by analyzing the DSC curve, and refer to the area enclosed by the DSC curve and a straight line connecting the point corresponding to the melting start temperature and the point corresponding to the melting end temperature on the DSC curve. The areas A1 and A2 will be described in detail below with reference to the drawings. Fig. 1 shows an example of a DSC curve measured for a surface region of a polymer film according to a method in accordance with JIS K 7122. Fig. 2 shows an example of a DSC curve measured for the entire polymer film according to a method in accordance with JIS K 7122. As shown in Figure 1, the area A1 is the melting peak temperature T P1 The melting temperature T is lower than S1 The point S1 on the DSC curve corresponding to the melting peak temperature T P1 The melting end temperature T E1 This is the area of ​​the region enclosed by the DSC curve and the line connecting the point E1 on the DSC curve corresponding to the value of As shown in Figure 2, the area A2 is the melting temperature T S2 The point S2 on the DSC curve corresponding to the melting end temperature T E2 This is the area of ​​the region enclosed by the DSC curve and the line connecting point E2 on the DSC curve corresponding to the value of

[0022] In measuring the areas A1 and A2, the DSC curve is measured by the method described above, and the details of the measurement method are as shown in the Examples section. For example, when a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation) is used, the areas A1 and A2 are determined by the attached analysis software (TA-60, manufactured by Shimadzu Corporation).

[0023] 〔component〕 The components contained in the polymer film will be described in detail below.

[0024] <Liquid Crystal Polymer> The liquid crystal polymer contained in the polymer film of the present invention is not particularly limited, and examples thereof include melt-formable liquid crystal polymers. The liquid crystal polymer is preferably a thermotropic liquid crystal polymer, which means a polymer that exhibits liquid crystallinity in a molten state when heated within a predetermined temperature range. The thermotropic liquid crystal polymer is not particularly limited in terms of its chemical composition as long as it is a liquid crystal polymer that can be melt-molded, and examples thereof include thermoplastic liquid crystal polyesters and thermoplastic polyester amides in which amide bonds are introduced into thermoplastic liquid crystal polyesters. As the liquid crystal polymer, for example, the thermoplastic liquid crystal polymer described in International Publication No. 2015 / 064437 and Japanese Patent Application Laid-Open No. 2019-116586 can be used.

[0025] More specific examples of the liquid crystal polymer include thermoplastic liquid crystal polyesters or thermoplastic liquid crystal polyester amides having repeating units derived from at least one selected from the group consisting of aromatic hydroxycarboxylic acids, aromatic or aliphatic diols, aromatic or aliphatic dicarboxylic acids, aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids.

[0026] Examples of aromatic hydroxycarboxylic acids include parahydroxybenzoic acid, metahydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-(4-hydroxyphenyl)benzoic acid. These compounds may have a substituent such as a halogen atom, a lower alkyl group, or a phenyl group. Among these, parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are preferred. The aromatic or aliphatic diol is preferably an aromatic diol, such as hydroquinone, 4,4'-dihydroxybiphenyl, 3,3'-dimethyl-1,1'-biphenyl-4,4'-diol, or acylated products thereof, with hydroquinone or 4,4'-dihydroxybiphenyl being preferred. The aromatic or aliphatic dicarboxylic acid is preferably an aromatic dicarboxylic acid, such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, with terephthalic acid being preferred. Examples of aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids include p-phenylenediamine, 4-aminophenol, and 4-aminobenzoic acid.

[0027] The liquid crystal polymer preferably has at least one repeating unit selected from the group consisting of repeating units represented by the following formulas (1) to (3). -O-Ar1-CO- (1) -CO-Ar2-CO- (2) -X-Ar3-Y- (3) In formula (1), Ar1 represents a phenylene group, a naphthylene group, or a biphenylylene group. In formula (2), Ar2 represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4). In formula (3), Ar3 represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), and X and Y each independently represent an oxygen atom or an imino group. -Ar4-Z-Ar5- (4) In formula (4), Ar4 and Ar5 each independently represent a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group. The phenylene group, naphthylene group and biphenylylene group may have a substituent selected from the group consisting of a halogen atom, an alkyl group and an aryl group.

[0028] In particular, the liquid crystal polymer preferably has at least one repeating unit selected from the group consisting of a repeating unit derived from an aromatic hydroxycarboxylic acid represented by the above formula (1), a repeating unit derived from an aromatic diol represented by the above formula (3) in which X and Y are both oxygen atoms, and a repeating unit derived from an aromatic dicarboxylic acid represented by the above formula (2). Furthermore, the liquid crystal polymer more preferably has at least a repeating unit derived from an aromatic hydroxycarboxylic acid, even more preferably has at least a repeating unit derived from parahydroxybenzoic acid, particularly preferably has at least one selected from the group consisting of a repeating unit derived from parahydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid, and most preferably has a repeating unit derived from parahydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid.

[0029] In another preferred embodiment, in terms of better effects of the present invention, the liquid crystal polymer preferably has at least one repeating unit selected from the group consisting of repeating units derived from 6-hydroxy-2-naphthoic acid, repeating units derived from aromatic diols, repeating units derived from terephthalic acid, and repeating units derived from 2,6-naphthalenedicarboxylic acid, and more preferably has all of repeating units derived from 6-hydroxy-2-naphthoic acid, repeating units derived from aromatic diols, repeating units derived from terephthalic acid, and repeating units derived from 2,6-naphthalenedicarboxylic acid.

[0030] When the liquid crystal polymer contains repeating units derived from aromatic hydroxycarboxylic acid, the composition ratio thereof is preferably 50 to 65 mol % based on the total repeating units of the liquid crystal polymer. It is also preferable that the liquid crystal polymer contains only repeating units derived from aromatic hydroxycarboxylic acid. When the liquid crystal polymer contains a repeating unit derived from an aromatic diol, the composition ratio thereof is preferably 17.5 to 25 mol % based on the total repeating units of the liquid crystal polymer. When the liquid crystal polymer contains a repeating unit derived from an aromatic dicarboxylic acid, the composition ratio thereof is preferably 11 to 23 mol % based on the total repeating units of the liquid crystal polymer. When the liquid crystal polymer contains a repeating unit derived from any one of aromatic diamine, aromatic hydroxyamine and aromatic aminocarboxylic acid, the composition ratio thereof is preferably 2 to 8 mol % based on the total repeating units of the liquid crystal polymer.

[0031] The method for synthesizing the liquid crystal polymer is not particularly limited, and the liquid crystal polymer can be synthesized by polymerizing the above-mentioned compound by a known method such as melt polymerization, solid phase polymerization, solution polymerization, or slurry polymerization. Commercially available liquid crystal polymers may be used, such as "LAPEROS" manufactured by Polyplastics Co., Ltd., "VECTRA" manufactured by Celanese Corporation, "UENO LCP" manufactured by Ueno Pharmaceutical Co., Ltd., "Sumikasuper LCP" manufactured by Sumitomo Chemical Co., Ltd., "ZYDAR" manufactured by ENEOS Corporation, and "Civelas" manufactured by Toray Industries, Inc. In addition, the liquid crystal polymer may form a chemical bond with an optional component such as a crosslinking agent or a compatible component (reactive compatibilizer) in the polymer film. This also applies to components other than the liquid crystal polymer.

[0032] In order to easily produce a polymer film having a low standard dielectric loss tangent (preferably 0.005 or less), the standard dielectric loss tangent of the liquid crystal polymer is preferably 0.005 or less, more preferably 0.003 or less, and even more preferably 0.002 or less. The lower limit is not particularly limited, and may be, for example, 0.0001 or more. When the polymer film contains two or more types of liquid crystal polymers, the "dielectric loss tangent of the liquid crystal polymer" means the mass average value of the dielectric loss tangent of the two or more types of liquid crystal polymers.

[0033] The standard dielectric loss tangent of the liquid crystal polymer contained in the polymer film can be measured by the following method. First, the polymer film is immersed in an organic solvent (e.g., pentafluorophenol) in an amount 1000 times by mass relative to the total mass of the polymer film, and then heated at 120°C for 12 hours to dissolve the organic solvent-soluble components, including the liquid crystal polymer, into the organic solvent. Next, the eluate containing the liquid crystal polymer is separated from the undissolved components by filtration. Next, acetone is added to the eluate as a poor solvent to precipitate the liquid crystal polymer, and the precipitate is separated by filtration. The obtained precipitate is filled into a PTFE (polytetrafluoroethylene) tube (outer diameter 2.5 mm, inner diameter 1.5 mm, length 10 mm), and the dielectric properties are measured using a cavity resonator (e.g., "CP-531" manufactured by Kanto Electronics Application Development Co., Ltd.) at a temperature of 23°C and a frequency of 28 GHz by the cavity resonator perturbation method. The influence of the voids in the PTFE tube is corrected using the Bruggeman equation and the void ratio, and the standard dielectric tangent of the liquid crystal polymer is obtained. The porosity (volume ratio of voids in the tube) is calculated as follows: The volume of the space inside the tube is determined from the inner diameter and length of the tube. Next, the tube is weighed before and after filling with the precipitate to determine the mass of the filled precipitate, and the volume of the filled precipitate is then determined from the obtained mass and the specific gravity of the precipitate. The volume of the precipitate thus obtained is divided by the volume of the space inside the tube determined above to calculate the filling rate, thereby calculating the porosity. When a commercially available liquid crystal polymer is used, the value of the dielectric loss tangent listed in the catalogue of the commercially available product may be used.

[0034] The liquid crystal polymer preferably has a melting point Tm of 250° C. or higher, more preferably 280° C. or higher, and even more preferably 310° C. or higher, in terms of better heat resistance. The upper limit of the melting point Tm of the liquid crystal polymer is not particularly limited, but is preferably 400° C. or lower, more preferably 380° C. or lower, in terms of superior moldability. The melting point Tm of the liquid crystal polymer can be determined by measuring the temperature at which an endothermic peak appears using a differential scanning calorimeter ("DSC-60A" manufactured by Shimadzu Corporation). When a commercially available liquid crystal polymer is used, the melting point Tm listed in the catalog value of the commercially available product may be used.

[0035] The number average molecular weight (Mn) of the liquid crystal polymer is not particularly limited, but is preferably from 10,000 to 600,000, and more preferably from 30,000 to 150,000. The number average molecular weight of the liquid crystal polymer is a value calculated using standard polystyrene by gel permeation chromatography (GPC). GPC measurement can be carried out using the following equipment and conditions. The measurement device used was a Tosoh Corporation "HLC (registered trademark)-8320GPC" and two Tosoh Corporation TSKgel (registered trademark) SuperHM-H columns (6.0 mm ID x 15 cm). The solvent (eluent) used to dissolve the liquid crystal polymer is not particularly limited, but examples include a mixed solution of pentafluorophenol / chloroform = 1 / 2 (mass ratio). Measurement conditions are a sample concentration of 0.03 mass%, a flow rate of 0.6 ml / min, a sample injection volume of 20 μL, and a measurement temperature of 40°C. Detection is performed using an RI (differential refractive index) detector. The calibration curve is created from eight samples of "Standard sample TSK standard, polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0036] The polymer film may contain one type of liquid crystal polymer alone, or may contain two or more types of liquid crystal polymers. The content of the liquid crystal polymer is preferably 40 to 99.9% by mass, more preferably 50 to 95% by mass, and even more preferably 60 to 90% by mass, based on the total mass of the polymer film. The contents of the liquid crystal polymer and components described below in the polymer film can be measured by known methods such as infrared spectroscopy and gas chromatography mass spectrometry.

[0037] <Optional ingredients> The polymer film may contain optional components other than the above polymers, such as polyolefins, compatible components, heat stabilizers, and additives described below.

[0038] (Polyolefin) The polymer film may comprise a polyolefin. In this specification, the term "polyolefin" refers to a polymer having repeating units derived from an olefin (polyolefin resin). The polymer film preferably contains a liquid crystal polymer and a polyolefin, and more preferably contains a liquid crystal polymer, a polyolefin, and a compatible component. By using a polyolefin together with a liquid crystal polymer, a polymer film having a dispersed phase formed by the polyolefin can be produced, the method for producing such a polymer film having a dispersed phase being described later.

[0039] The polyolefin may be linear or branched, and may have a cyclic structure, such as polycycloolefin. Examples of polyolefins include polyethylene, polypropylene (PP), polymethylpentene (TPX manufactured by Mitsui Chemicals, Inc., etc.), hydrogenated polybutadiene, cycloolefin polymer (COP, Zeonor manufactured by Nippon Zeon Co., Ltd., etc.), and cycloolefin copolymer (COC, Apel manufactured by Mitsui Chemicals, Inc., etc.). The polyethylene may be either high density polyethylene (HDPE) or low density polyethylene (LDPE), or may be linear low density polyethylene (LLDPE).

[0040] The polyolefin may be a copolymer of an olefin and a copolymerization component other than an olefin, such as an acrylate, methacrylate, styrene, and / or vinyl acetate-based monomer. An example of the polyolefin copolymer is styrene-ethylene / butylene-styrene copolymer (SEBS), which may be hydrogenated. However, in order to obtain a more excellent effect of the present invention, it is preferable that the copolymerization ratio of copolymerization components other than olefins is small, and it is more preferable that no copolymerization components are contained. For example, the content of the copolymerization components is preferably 0 to 40 mass %, more preferably 0 to 5 mass %, based on the total mass of the polyolefin. Furthermore, the polyolefin preferably does not substantially contain a reactive group, which will be described later, and the content of repeating units having a reactive group is preferably 0 to 3% by mass relative to the total mass of the polyolefin.

[0041] The polyolefin is preferably polyethylene, COP or COC, more preferably polyethylene, and even more preferably low-density polyethylene (LDPE).

[0042] The polyolefins may be used alone or in combination of two or more. When the polymer film contains polyolefin, its content is preferably 0.1% by mass or more, more preferably 5% by mass or more, relative to the total mass of the polymer film, in order to improve the surface properties of the polymer film. There is no particular upper limit, but in order to improve the smoothness of the polymer film, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, relative to the total mass of the polymer film. Furthermore, when the polyolefin content is 50% by mass or less, it is easy to sufficiently increase the heat distortion temperature and improve the solder heat resistance.

[0043] (compatible components) Examples of compatible components include polymers (non-reactive compatibilizers) having a portion that is highly compatible or has a high affinity with the liquid crystal polymer, and polymers (reactive compatibilizers) having a group reactive to the phenolic hydroxyl group or carboxyl group at the end of the liquid crystal polymer. The reactive group of the reactive compatibilizer is preferably an epoxy group or a maleic anhydride group. The compatible component is preferably a copolymer having a portion with high compatibility or affinity with the polyolefin. When the polymer film contains the polyolefin and the compatible component, the compatible component is preferably a reactive compatibilizer, which can finely disperse the polyolefin. The compatible component (particularly the reactive compatibilizer) may form a chemical bond with the component such as the liquid crystal polymer in the polymer film.

[0044] Examples of reactive compatibilizers include epoxy group-containing polyolefin copolymers, epoxy group-containing vinyl copolymers, maleic anhydride-containing polyolefin copolymers, maleic anhydride-containing vinyl copolymers, oxazoline group-containing polyolefin copolymers, oxazoline group-containing vinyl copolymers, and carboxyl group-containing olefin copolymers. Among these, epoxy group-containing polyolefin copolymers and maleic anhydride-grafted polyolefin copolymers are preferred.

[0045] Examples of epoxy group-containing polyolefin copolymers include ethylene / glycidyl methacrylate copolymer, ethylene / glycidyl methacrylate / vinyl acetate copolymer, ethylene / glycidyl methacrylate / methyl acrylate copolymer, polystyrene graft copolymer onto ethylene / glycidyl methacrylate copolymer (EGMA-g-PS), polymethyl methacrylate graft copolymer onto ethylene / glycidyl methacrylate copolymer (EGMA-g-PMMA), and acrylonitrile / styrene graft copolymer onto ethylene / glycidyl methacrylate copolymer (EGMA-g-AS). Commercially available epoxy group-containing polyolefin copolymers include, for example, Bondfast 2C and Bondfast E manufactured by Sumitomo Chemical Co., Ltd.; Lotadar manufactured by Arkema; ​​and Modiper A4100 and Modiper A4400 manufactured by NOF Corporation.

[0046] Examples of epoxy group-containing vinyl copolymers include glycidyl methacrylate grafted polystyrene (PS-g-GMA), glycidyl methacrylate grafted polymethyl methacrylate (PMMA-g-GMA), and glycidyl methacrylate grafted polyacrylonitrile (PAN-g-GMA).

[0047] Examples of maleic anhydride-containing polyolefin copolymers include copolymers of maleic anhydride and ethylene (E-MAH), maleic anhydride-grafted polypropylene (PP-g-MAH), maleic anhydride-grafted ethylene / propylene rubber (EPR-g-MAH), and maleic anhydride-grafted ethylene / propylene / diene rubber (EPDM-g-MAH). Commercially available maleic anhydride-containing polyolefin copolymers include, for example, the Orevac G series manufactured by Arkema, the FUSABOND E series manufactured by Dow Chemical Company, and Admer manufactured by Mitsui Chemicals.

[0048] Examples of maleic anhydride-containing vinyl copolymers include maleic anhydride-grafted polystyrene (PS-g-MAH), maleic anhydride-grafted styrene / butadiene / styrene copolymer (SBS-g-MAH), maleic anhydride-grafted styrene / ethylene / butene / styrene copolymer (SEBS-g-MAH), and styrene / maleic anhydride copolymer and acrylic ester / maleic anhydride copolymer. Commercially available maleic anhydride-containing vinyl copolymers include the Tuftec M series (SEBS-g-MAH) manufactured by Asahi Kasei Corporation.

[0049] Other compatible components include oxazoline-based compatibilizers (e.g., bisoxazoline-styrene-maleic anhydride copolymer, bisoxazoline-maleic anhydride-modified polyethylene, and bisoxazoline-maleic anhydride-modified polypropylene), elastomer-based compatibilizers (e.g., aromatic resins, petroleum resins), ethylene glycidyl methacrylate copolymer, ethylene maleic anhydride ethyl acrylate copolymer, ethylene glycidyl methacrylate-acrylonitrile styrene, acid-modified polyethylene wax, COOH-modified polyethylene graft polymer, COOH-modified polypropylene graft polymer, polyethylene-polyamide graft copolymer, polypropylene-polyamide graft copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene rubber, EVA-PVC graft copolymer, vinyl acetate-ethylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, hydrogenated styrene-isopropylene block copolymer, and amine-modified styrene-ethylene-butene-styrene copolymer.

[0050] An ionomer resin may also be used as a compatible component. Examples of such ionomer resins include ethylene-methacrylic acid copolymer ionomers, ethylene-acrylic acid copolymer ionomers, propylene-methacrylic acid copolymer ionomers, propylene-acrylic acid copolymer ionomers, butylene-acrylic acid copolymer ionomers, ethylene-vinylsulfonic acid copolymer ionomers, styrene-methacrylic acid copolymer ionomers, sulfonated polystyrene ionomers, fluorine-based ionomers, telechelic polybutadiene acrylic acid ionomers, sulfonated ethylene-propylene ionomers, and the like. Examples of ionomers include propylene-diene copolymer ionomers, hydrogenated polypentamer ionomers, polypentamer ionomers, poly(vinylpyridium salt) ionomers, poly(vinyltrimethylammonium salt) ionomers, poly(vinylbenzylphosphonium salt) ionomers, styrene-butadiene acrylic acid copolymer ionomers, polyurethane ionomers, sulfonated styrene-2-acrylamido-2-methylpropane sulfate ionomers, acid-amine ionomers, aliphatic ionenes, and aromatic ionenes.

[0051] When the polymer film contains a compatible component, the content thereof is preferably from 0.05 to 30% by mass, more preferably from 0.1 to 20% by mass, and even more preferably from 0.5 to 10% by mass, based on the total mass of the polymer film.

[0052] (heat stabilizer) The polymer film may contain a heat stabilizer for the purposes of preventing thermal oxidative deterioration during melt extrusion film formation and improving the flatness and smoothness of the polymer film surface. Examples of thermal stabilizers include phenol-based stabilizers and amine-based stabilizers that have a radical scavenging action; phosphite-based stabilizers and sulfur-based stabilizers that have a peroxide decomposition action; and hybrid stabilizers that have both a radical scavenging action and a peroxide decomposition action.

[0053] Examples of the phenol-based stabilizer include a hindered phenol-based stabilizer, a semi-hindered phenol-based stabilizer, and a less hindered phenol-based stabilizer. Commercially available hindered phenol stabilizers include, for example, Adekastab AO-20, AO-50, AO-60, and AO-330 manufactured by ADEKA Corporation; and Irganox 259, 1035, and 1098 manufactured by BASF. Commercially available semi-hindered phenol stabilizers include, for example, Adeka Stab AO-80 manufactured by ADEKA Corporation and Irganox 245 manufactured by BASF. Commercially available unhindered phenol stabilizers include, for example, Nocrac 300 manufactured by Ouchi Shinko Chemical Industry Co., Ltd., and Adeka Stab AO-30 and AO-40 manufactured by ADEKA Corporation. Commercially available phosphite stabilizers include, for example, Adeka Stab 2112, PEP-8, PEP-36, and HP-10 manufactured by ADEKA Corporation. An example of a commercially available hybrid stabilizer is Sumilizer GP manufactured by Sumitomo Chemical.

[0054] As the heat stabilizer, a hindered phenol-based stabilizer, a semi-hindered phenol-based stabilizer, or a phosphite-based stabilizer is preferred in terms of a more excellent heat stabilizing effect, and a hindered phenol-based stabilizer is more preferred, while a semi-hindered phenol-based stabilizer or a phosphite-based stabilizer is more preferred in terms of electrical properties.

[0055] The heat stabilizer may be used alone or in combination of two or more. When the polymer film contains a heat stabilizer, the content of the heat stabilizer is preferably 0.0001 to 10 mass %, more preferably 0.01 to 5 mass %, and even more preferably 0.1 to 2 mass %, based on the total mass of the polymer film.

[0056] (additives) The polymer film may contain additives other than the above components, such as plasticizers, lubricants, inorganic and organic particles, and UV absorbers.

[0057] Examples of the plasticizer include alkylphthalyl alkyl glycolate compounds, bisphenol compounds (bisphenol A, bisphenol F), alkylphthalyl alkyl glycolate compounds, phosphate ester compounds, carboxylate ester compounds, and polyhydric alcohols. The content of the plasticizer may be 0 to 5% by mass based on the total mass of the polymer film. Examples of lubricants include fatty acid esters and metal soaps (such as inorganic stearates). The content of the lubricant may be 0 to 5% by mass based on the total mass of the polymer film. The polymer film may contain inorganic particles and / or organic particles as a reinforcing material, a matting agent, or a material for improving the dielectric constant or dielectric loss tangent. Examples of inorganic particles include silica, titanium oxide, barium sulfate, talc, zirconia, alumina, silicon nitride, silicon carbide, calcium carbonate, silicates, glass beads, graphite, tungsten carbide, carbon black, clay, mica, carbon fiber, glass fiber, and metal powder. Examples of organic particles include crosslinked acrylic and crosslinked styrene. The content of inorganic and organic particles may be 0 to 50% by mass based on the total mass of the polymer film. Examples of UV absorbers include salicylate compounds, benzophenone compounds, benzotriazole compounds, substituted acrylonitrile compounds, and s-triazine compounds. The content of the UV absorber may be 0 to 5% by mass based on the total mass of the polymer film.

[0058] The polymer film may also contain a polymer component other than the liquid crystal polymer. Examples of the polymer component include thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, and polyester ether ketone.

[0059] <Physical properties of polymer film> (Thickness) The thickness of the polymer film is preferably more than 10 μm and not more than 1000 μm, more preferably from 15 to 500 μm, and even more preferably from 20 to 250 μm. The thickness of the polymer film is the arithmetic mean value of the thicknesses of the polymer film measured at 100 arbitrary different points on an image obtained by observing a cross section of the laminate along the thickness direction using a scanning electron microscope (SEM).

[0060] (Dielectric properties) The standard dielectric loss tangent of the polymer film is not particularly limited and is, for example, 0.0050 or less, preferably 0.0040 or less, more preferably 0.0030 or less, and even more preferably 0.0020 or less. The lower limit is not particularly limited and may be 0.0001 or more. The relative dielectric constant of the polymer film varies depending on the application, but is preferably 2.0 to 4.0, more preferably 2.5 to 3.5. The dielectric properties of the polymer film, including the standard dielectric loss tangent and the relative dielectric constant, can be measured by a cavity resonator perturbation method. A specific method for measuring the dielectric properties of the polymer film will be described in the Examples section below.

[0061] (dispersed phase) When the polymer film contains a polyolefin, the polyolefin preferably forms a dispersed phase in the polymer film. The dispersed phase refers to a phase containing a polyolefin dispersed in a polymer film. There are no limitations on the method for making the polyolefin exist as a dispersed phase in the polymer film. For example, the dispersed phase of the polyolefin can be formed by adjusting the contents of the liquid crystal polymer and polyolefin contained in the polymer film to be within the preferred content ranges described above.

[0062] The average dispersed diameter of the dispersed phase is preferably from 0.001 to 50.0 μm, more preferably from 0.005 to 20.0 μm, and even more preferably from 0.01 to 10.0 μm, in terms of superior smoothness.

[0063] The dispersed phase is also preferably flat, and the flat surface of the flat dispersed phase is preferably approximately parallel to the surface of the polymer film. In order to reduce the anisotropy of the polymer film, it is preferable that the flat surface of the flat dispersed phase is substantially circular when observed from a direction perpendicular to the surface of the polymer film. It is believed that when such a dispersed phase is dispersed in the polymer film, it can absorb dimensional changes that occur in the polymer film, thereby achieving better surface properties and smoothness. The average dispersed diameter and shape of the dispersed phase are determined from an image obtained by observing a cross section of the laminate in the thickness direction using a scanning electron microscope (SEM). A detailed method for measuring the average dispersed diameter of the dispersed phase will be described in the Examples section below.

[0064] (coefficient of linear expansion) The linear expansion coefficient in a first direction within the plane of the polymer film and the linear expansion coefficient in a second direction perpendicular to the first direction within the plane of the polymer film are both preferably 0 to 40 ppm / ° C., more preferably 5 to 30 ppm / ° C., and even more preferably 10 to 25 ppm / ° C. If the linear expansion coefficient of the polymer film is within the above range, the difference with the linear expansion coefficient of the copper foil (18 ppm / ° C.) is small, so that warping of the laminate containing the copper foil and the polymer film during production can be suppressed and adhesion between the copper foil and the polymer film can be improved. The linear expansion coefficient of the polymer film can be adjusted, for example, by the stretching conditions during film formation, the temperature conditions and heating time in post-heat treatment, etc. The method for measuring the linear expansion coefficient in the in-plane direction of the polymer film will be described in the Examples below.

[0065] The polymer film may have a single layer structure or a laminate structure in which multiple layers are laminated. Note that the "single layer structure" of a polymer film means that the polymer film is made of the same material throughout its entire thickness.

[0066] [Method for producing polymer film] The method for producing the polymer film is not particularly limited, but the polymer film is preferably formed using a composition containing at least a liquid crystal polymer and a non-liquid crystal compound, and more preferably formed using a composition containing at least a liquid crystal polymer having a reactive group at its end and a non-liquid crystal compound having a functional group that reacts with or interacts with the reactive group.

[0067] A preferred embodiment of the method for producing a polymer film includes, for example, a pelletizing step of kneading the above-mentioned components to obtain pellets, and a film-forming step of using the pellets to obtain a polymer film. Each step will be described below.

[0068] <Pelletizing process> (1) Raw material form The liquid crystal polymer used for film production can be in pellet, flake or powder form as is, but for the purpose of stabilizing the film production or uniformly dispersing additives (meaning components other than the liquid crystal polymer; the same applies below), it is preferable to use pellets obtained by kneading one or more raw materials (meaning at least one of the liquid crystal polymer and additives; the same applies below) using an extruder and pelletizing them. Hereinafter, polymer raw materials and mixtures containing polymers used in the production of polymer films will also be collectively referred to as resins.

[0069] (2) Drying or venting to replace drying Before pelletizing, it is preferable to dry the liquid crystal polymer and additives. Drying methods include circulating heated air with a low dew point and dehumidifying by vacuum drying. In particular, for resins that are easily oxidized, vacuum drying or drying using an inert gas is preferable.

[0070] (3) Raw material supply method The raw material supply method may be a method in which the raw materials are mixed in advance before being kneaded and pelletized and then supplied, a method in which the raw materials are supplied separately into the extruder so as to be in a constant ratio, or a combination of both methods.

[0071] (4) Extrusion atmosphere During melt extrusion, it is preferable to prevent thermal and oxidative degradation as much as possible within the scope that does not hinder uniform dispersion, and it is also effective to reduce the oxygen concentration by reducing the pressure using a vacuum pump or by injecting an inert gas. These methods may be carried out alone or in combination.

[0072] (5)Temperature The kneading temperature is preferably set to the thermal decomposition temperature of the liquid crystal polymer and the additives or lower, and is preferably set as low as possible within a range in which the load on the extruder and the deterioration of uniform kneading do not become a problem.

[0073] (6) Pressure The kneading pressure for the resin during pelletization is preferably 0.05 to 30 MPa. In the case of a resin that is prone to discoloration or gelation due to shear, it is preferable to apply an internal pressure of about 1 to 10 MPa to the extruder to fill the resin raw material inside the twin-screw extruder.

[0074] (7) Pelletizing method As a pelletizing method, a noodle-shaped material is generally extruded, solidified in water, and then cut. However, pelletization may also be performed by an underwater cutting method in which the material is melted in an extruder and then cut while being directly extruded from a nozzle into water, or a hot cutting method in which the material is cut while still hot.

[0075] (8) Pellet size Pellet size: cross-sectional area 1 to 300 mm 2 The length is preferably 1 to 30 mm, and the cross-sectional area is preferably 2 to 100 mm. 2 and the length is more preferably 1.5 to 10 mm.

[0076] (Dry) (1) Purpose of drying Before melt film formation, it is preferable to reduce the moisture and volatile content in the pellets, and drying the pellets is effective. If the pellets contain moisture or volatile content, not only will bubbles be mixed into the formed film or the appearance will be deteriorated due to a decrease in haze, but the physical properties may be deteriorated due to molecular chain scission of the liquid crystal polymer, or roll contamination may occur due to the generation of monomers or oligomers. Furthermore, depending on the type of liquid crystal polymer used, removal of dissolved oxygen by drying may be able to suppress the generation of oxidized crosslinked products during melt film formation.

[0077] (2) Drying method / heating method The drying method is generally a dehumidifying hot air dryer in terms of drying efficiency and economy, but is not particularly limited as long as the desired moisture content can be obtained. In addition, a more appropriate method can be selected in accordance with the physical properties of the liquid crystal polymer. Examples of heating methods include pressurized steam, heater heating, far-infrared radiation, microwave heating, and heat medium circulation heating.

[0078] <Film forming process> The film-forming process will be described below.

[0079] (1) Extrusion conditions ·Raw material drying In the step of melting and plasticizing the pellets in the extruder, it is preferable to reduce the moisture and volatile content as in the pelletizing step, and it is effective to dry the pellets.

[0080] ·Raw material supply method When multiple types of raw materials (pellets) are fed into the feed port of an extruder, they may be mixed together in advance (premix method), fed separately to the extruder at a constant ratio, or a combination of both methods may be used. To stabilize extrusion, it is common to minimize fluctuations in the temperature and bulk density of the raw materials fed through the feed port. From the standpoint of plasticization efficiency, the raw material temperature is preferably high enough to prevent adhesion and blocking at the feed port. For amorphous resins, the temperature is preferably in the range of {glass transition temperature (Tg) (°C) - 150°C} to {Tg (°C) - 1°C}, and for crystalline resins, the temperature is preferably in the range of {melting point (Tm) (°C) - 150°C} to {Tm (°C) - 1°C}, and the raw materials are heated or kept warm. From the standpoint of plasticization efficiency, the bulk density of the raw material is preferably at least 0.3 times that of the molten state, and more preferably at least 0.4 times. When the bulk density of the raw material is less than 0.3 times the density of the raw material in the molten state, it is also preferable to subject the raw material to processing such as compressing it into pseudo-pellets.

[0081] Extrusion atmosphere As in the pelletizing process, the atmosphere during melt extrusion must be such that heat and oxidative degradation are prevented as much as possible without interfering with uniform dispersion, and it is effective to inject an inert gas (such as nitrogen), reduce the oxygen concentration in the extruder using a vacuum hopper, or provide a vent port in the extruder and reduce the pressure using a vacuum pump. These methods of reducing pressure and injecting an inert gas may be carried out independently or in combination.

[0082] Rotation speed The rotation speed of the extruder is preferably 5 to 300 rpm, more preferably 10 to 200 rpm, and even more preferably 15 to 100 rpm. If the rotation speed is equal to or higher than the lower limit, the residence time is shortened, and it is possible to suppress a decrease in molecular weight due to thermal degradation and to suppress discoloration. If the rotation speed is equal to or lower than the upper limit, it is possible to suppress scission of molecular chains due to shear, and it is possible to suppress a decrease in molecular weight and an increase in crosslinked gel. It is preferable to select an appropriate condition for the rotation speed from the viewpoints of both uniform dispersion and thermal degradation due to an extended residence time.

[0083] ·temperature Barrel temperature (feed section temperature T1℃ 、 The compression zone temperature (T2°C) and metering zone temperature (T3°C) are generally determined using the following method. When pellets are melted and plasticized in an extruder at a target temperature (T°C), the metering zone temperature (T3) is set to T ± 20°C, taking into account the shear heat generated. T2 is set within the range of T3 ± 20°C, taking into account extrusion stability and the thermal decomposition of the resin. T1 is generally set between {T2 (°C) - 5°C} and {T2 (°C) - 150°C}, with the optimum value selected to ensure both friction between the resin and the barrel, which acts as the driving force (feed force) for feeding the resin, and preheating in the feed zone. In a typical extruder, the temperatures can be set by dividing the T1 to T3 zones into smaller zones. Setting the temperature so that the temperature changes between each zone are gradual allows for greater stability. In this case, T is preferably set below the thermal degradation temperature of the resin. If the shear heat generated by the extruder exceeds the thermal degradation temperature, it is common to actively cool and remove the shear heat. In order to achieve both improved dispersibility and thermal degradation, it is also effective to melt and mix the resin at a relatively high temperature in the first half of the extruder and then lower the resin temperature in the second half.

[0084] ·pressure The resin pressure inside the extruder is generally 1 to 50 MPa, and from the viewpoint of extrusion stability and melt uniformity, it is preferably 2 to 30 MPa, more preferably 3 to 20 MPa. If the pressure inside the extruder is 1 MPa or higher, the melt filling rate inside the extruder is sufficient, which can prevent the instability of the extrusion pressure and the generation of foreign matter due to the occurrence of stagnation. Furthermore, if the pressure inside the extruder is 50 MPa or lower, it can prevent excessive shear stress inside the extruder, which can prevent thermal decomposition due to an increase in resin temperature.

[0085] Residence time The residence time in the extruder (residence time during film formation) can be calculated from the volume of the extruder and the discharge volume of the polymer, as in the pelletization process. The residence time is preferably 10 seconds to 60 minutes, more preferably 15 seconds to 45 minutes, and even more preferably 30 seconds to 30 minutes. A residence time of 10 seconds or more ensures sufficient melt plasticization and dispersion of the additives. A residence time of 30 minutes or less is preferred in that resin deterioration and discoloration can be suppressed.

[0086] (filtration) ·Type, installation purpose, structure In order to prevent damage to the gear pump due to foreign matter contained in the raw material and to extend the life of the fine pore filter installed downstream of the extruder, a filtration device is generally installed at the outlet of the extruder. It is preferable to perform so-called breaker plate type filtration, in which a mesh filter material is combined with a strong reinforcing plate with a high opening ratio.

[0087] Mesh size, filtration area The mesh size is preferably 40 to 800 mesh, more preferably 60 to 700 mesh, and even more preferably 100 to 600 mesh. A mesh size of 40 mesh or larger can sufficiently prevent foreign matter from passing through the mesh. Furthermore, a mesh size of 800 mesh or smaller can suppress the increase in filtration pressure speed, reducing the frequency of mesh replacement. Furthermore, filter meshes are often stacked with multiple types of mesh sizes to maintain filtration accuracy and strength. Furthermore, a breaker plate can be used to reinforce the filter mesh, as this allows for a large filtration opening area and maintains the mesh strength. The opening ratio of the breaker plate used is often 30 to 80% in terms of filtration efficiency and strength. Screen changers with the same diameter as the extruder barrel are often used, but to increase the filtration area, tapered piping is used to allow for a larger filter mesh, or the flow path is branched and multiple breaker plates are used. The filtration area is for a flow rate of 0.05 to 5 g / cm per second. 2It is preferable to select the thickness as a guideline, and it is 0.1 to 3 g / cm 2 More preferably, 0.2 to 2 g / cm 2 is more preferred. When foreign matter is trapped in the filter, it becomes clogged, causing an increase in filtration pressure. When this happens, the extruder must be stopped and the filter replaced, but filters that allow replacement while extrusion is continuing can also be used. To counter the increase in filtration pressure caused by trapped foreign matter, filters that have the function of reducing filtration pressure by reversing the polymer flow path and washing away the foreign matter trapped in the filter can also be used.

[0088] (Thailand) Type, structure, material The molten resin, after being filtered to remove foreign matter and further having its temperature homogenized by a mixer, is continuously sent to a die. The die is not particularly limited as long as it is designed to minimize retention of the molten resin, and any of the commonly used types, such as a T-die, a fishtail die, and a hanger coat die, can be used. Of these, a hanger coat die is preferred in terms of thickness uniformity and minimal retention.

[0089] ·Multilayer film formation A single-layer film-forming apparatus, which requires low equipment costs, is generally used to produce films. Alternatively, a multilayer film-forming apparatus may be used to provide a functional layer, such as a surface protection layer, an adhesive layer, an easy-adhesion layer, and / or an antistatic layer, on the outer layer. Specific examples include a method of multi-layering using a multi-layer feed block and a method using a multi-manifold die. Generally, it is preferable to thinly laminate a functional layer on the surface layer, but the layer ratio is not particularly limited.

[0090] (cast) The film-forming process preferably includes a step of supplying a molten liquid crystal polymer from a supply means, and a step of depositing the molten liquid crystal polymer on a casting roll to form a film. The molten liquid crystal polymer may be cooled and solidified and wound up as a film, or may be passed between a pair of clamping surfaces and continuously clamped to form a film. In this case, there is no particular limitation on the means for supplying the molten liquid crystal polymer (melt). For example, as a specific means for supplying the melt, an extruder that melts the liquid crystal polymer and extrudes it into a film shape may be used, an extruder and a die may be used, or the liquid crystal polymer may be solidified into a film shape, and then melted by a heating means to form a melt and supplied to the film-forming process. When molten resin extruded into a sheet form from a die is clamped using an apparatus having a pair of clamping surfaces, not only can the surface shape of the clamping surfaces be transferred to the film, but the orientation can also be controlled by applying elongation deformation to a composition containing a liquid crystal polymer.

[0091] ·Film forming method and type Among the methods for forming a molten raw material into a film, passing the material between two rolls (e.g., a touch roll and a chill roll) is preferred because it allows for the application of a high clamping pressure and results in excellent film surface condition. In this specification, when there are multiple casting rolls for transporting the molten material, the casting roll closest to the most upstream liquid crystal polymer supply means (e.g., a die) is referred to as the chill roll. Other methods that can be used include clamping between metal belts or combining a roll with a metal belt. In some cases, in order to increase adhesion to the roll or metal belt, a combination of film-forming methods such as electrostatic application, air knife, air chamber, and vacuum nozzle methods can be used on a casting drum. Although it is preferable to obtain a multilayer film by nipping molten polymers extruded in multiple layers from a die, a multilayer film can also be obtained by introducing a single-layer film into the nipping section in the manner of melt lamination. In this case, by changing the difference in peripheral speed or the orientation axis direction in the nipping section, a film with a different gradient structure in the thickness direction can be obtained, and by repeating this process several times, a film with three or more layers can also be obtained. Furthermore, deformation may be imparted by periodically vibrating the touch roll in the TD direction during nipping.

[0092] Molten polymer temperature The discharge temperature (resin temperature at the outlet of the supply means) is preferably (Tm of the liquid crystal polymer - 10)°C to (Tm of the liquid crystal polymer + 40)°C in terms of improving the moldability of the liquid crystal polymer and suppressing deterioration. The melt viscosity is preferably 50 to 3500 Pa s. It is preferable that the cooling of the molten polymer in the air gap is as small as possible, and it is preferable to reduce the temperature drop due to cooling by increasing the film-forming speed, shortening the air gap, or other measures.

[0093] Touch roll temperature The temperature of the touch roll is preferably set to the Tg of the liquid crystal polymer or lower. If the temperature of the touch roll is set to the Tg of the liquid crystal polymer or lower, the molten polymer can be prevented from sticking to the roll, resulting in a good film appearance. For the same reason, the temperature of the chill roll is also preferably set to the Tg of the liquid crystal polymer or lower.

[0094] (Procedure for producing polymer film) Film production procedure In the film-forming step, it is preferable to perform film formation according to the following procedure in terms of the film-forming step and stabilization of quality. The molten polymer extruded from the die is allowed to land on a casting roll and formed into a film, which is then cooled and solidified and wound up as a film. When pressing a molten polymer, the molten polymer is passed between a first pressing surface and a second pressing surface set at a predetermined temperature, and then cooled and solidified, and wound up as a film.

[0095] <Stretching process, heat relaxation treatment, heat setting treatment> Furthermore, after the unstretched film is produced by the above method, it may be continuously or discontinuously stretched and / or heat-relaxed or heat-set. For example, the following steps (a) to (g) may be combined to carry out the respective steps. The order of longitudinal stretching and transverse stretching may be reversed, the longitudinal stretching and transverse stretching steps may be carried out in multiple stages, or the longitudinal stretching and transverse stretching steps may be combined with oblique stretching or simultaneous biaxial stretching. (a) Transverse stretching (b) Transverse stretching → heat relaxation treatment (c) Longitudinal stretching (d) Longitudinal stretching → heat relaxation treatment (e) Vertical (horizontal) stretching → Horizontal (vertical) stretching (f) Longitudinal (horizontal) stretching → transverse (longitudinal) stretching → heat relaxation treatment (g) Transverse stretching → heat relaxation → longitudinal stretching → heat relaxation

[0096] Longitudinal stretching Longitudinal stretching can be achieved by heating the film between two pairs of rolls while increasing the peripheral speed at the outlet side compared to the peripheral speed at the inlet side. To prevent film curling, it is preferable that the film temperature be the same on both sides. However, if the optical properties are to be controlled in the thickness direction, stretching can be performed at different temperatures on the front and back sides. The stretching temperature here is defined as the temperature on the lower side of the film surface. The longitudinal stretching process can be performed in one stage or multiple stages. The film is generally preheated by passing it through temperature-controlled heated rolls, but in some cases, the film can also be heated using a heater. To prevent the film from sticking to the rolls, ceramic rolls with improved adhesive properties can also be used.

[0097] ·Horizontal stretching The transverse stretching step can be performed by conventional transverse stretching. Conventional transverse stretching includes a stretching method in which both widthwise ends of the film are held with clips and the clips are widened while the film is heated in an oven using a tenter. For the transverse stretching step, methods described in, for example, Japanese Utility Model Laid-Open Publication Nos. 62-035817, 2001-138394, 10-249934, 6-270246, 4-030922, and 62-152721 can be used, and these methods are incorporated herein by reference.

[0098] The stretching ratio in the width direction of the film in the transverse stretching step (transverse stretching ratio) is preferably 1.2 to 6, more preferably 1.5 to 5, and even more preferably 2 to 4. When longitudinal stretching is performed, the transverse stretching ratio is preferably larger than the stretching ratio in the longitudinal stretching. The stretching temperature in the transverse stretching step can be controlled by blowing air of the desired temperature into the tenter. The film temperature may be the same on both sides or different on both sides for the same reasons as in longitudinal stretching. The stretching temperature used here is defined as the temperature on the lower side of the film surface. The transverse stretching step may be carried out in one stage or multiple stages. When transverse stretching is carried out in multiple stages, it may be carried out continuously or intermittently with a zone in between where no width expansion occurs. In addition to the usual transverse stretching in which clips are used to expand the width in the tenter, the following stretching method in which the film is gripped with clips and expanded in the same way can also be applied to such transverse stretching.

[0099] Diagonal stretching In the oblique stretching step, the clips are expanded in the transverse direction as in normal transverse stretching, but stretching in the oblique direction can be achieved by changing the conveying speed of the left and right clips. As the oblique stretching step, for example, the methods described in JP-A Nos. 2002-022944, 2002-086554, 2004-325561, 2008-23775, and 2008-110573 can be used.

[0100] ·Simultaneous biaxial stretching In simultaneous biaxial stretching, the clip is expanded in the transverse direction, and simultaneously stretched or contracted in the longitudinal direction, as in normal transverse stretching. For simultaneous biaxial stretching, for example, the methods described in Japanese Utility Model Application Laid-Open No. 55-093520, Japanese Patent Laid-Open No. 63-247021, Japanese Patent Laid-Open No. 6-210726, Japanese Patent Laid-Open No. 6-278204, Japanese Patent Laid-Open No. 2000-334832, Japanese Patent Laid-Open No. 2004-106434, Japanese Patent Laid-Open No. 2004-195712, Japanese Patent Laid-Open No. 2006-142595, Japanese Patent Laid-Open No. 2007-210306, Japanese Patent Laid-Open No. 2005-022087, Japanese Patent Laid-Open No. 2006-517608, and Japanese Patent Laid-Open No. 2007-210306 can be used.

[0101] Heat treatment to improve bowing (axis misalignment) During the transverse stretching process, the edges of the film are held by clips, so the deformation of the film due to the heat shrinkage stress generated during the heat treatment is greater in the center of the film and smaller at the edges, resulting in a distribution of properties in the width direction. If a straight line is drawn along the width direction on the surface of the film before the heat treatment process, the straight line on the surface of the film after the heat treatment process will be arched, with the center concave toward the downstream. This phenomenon, known as bowing, disrupts the isotropy and width direction uniformity of the film. As an improvement method, preheating can be performed before transverse stretching or heat setting can be performed after stretching to reduce the variation in orientation angle due to bowing. Either preheating or heat setting can be performed, but both are more preferable. These preheating and heat setting are preferably performed by holding the film with clips, that is, they are preferably performed consecutively with stretching.

[0102] Preheating is preferably carried out at a temperature about 1 to 50° C. higher than the stretching temperature, more preferably 2 to 40° C. higher, and even more preferably 3 to 30° C. higher. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During preheating, it is preferable to keep the width of the tenter approximately constant, where "approximately" refers to ±10% of the width of the unstretched film.

[0103] The heat setting is preferably carried out at a temperature 1 to 50° C. lower than the stretching temperature, more preferably 2 to 40° C. lower, and even more preferably 3 to 30° C. lower. It is particularly preferably carried out at a temperature lower than the stretching temperature and lower than the Tg of the liquid crystal polymer. The heat setting time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During heat setting, it is preferable to keep the tenter width almost constant. Here, "almost" refers to 0% (the same width as the tenter width after stretching) to -30% (reduced width by 30% from the tenter width after stretching). Other known methods include those described in JP-A-1-165423, JP-A-3-216326, JP-A-2002-018948, and JP-A-2002-137286.

[0104] Heat relaxation treatment After the stretching step, the film may be subjected to a heat-relaxing treatment in which the film is heated to shrink it. By performing the heat-relaxing treatment, the thermal shrinkage rate of the film during use can be reduced. The heat-relaxing treatment is preferably performed at least once after film formation, after longitudinal stretching, and after transverse stretching. The heat-relaxing treatment may be carried out online immediately after stretching, or may be carried out offline after winding up the film after stretching. The heat-relaxing temperature may be, for example, from the glass transition temperature Tg to the melting point Tm of the liquid crystal polymer. When oxidation degradation of the film is a concern, the heat-relaxing treatment may be carried out in an inert gas such as nitrogen gas, argon gas, or helium gas.

[0105] <Post-heat treatment> In terms of facilitating the production of the film according to the present invention, it is preferred that the unstretched film or the longitudinally stretched film produced by the above method be subjected to the transverse stretching and then subjected to a post-heat treatment.

[0106] In the post-heat treatment, it is preferable to perform the heat treatment while fixing the film so as not to shrink in the width direction, for example by holding both ends of the film in the width direction with jigs (clips), or without fixing the film. The width of the film after the post-heat treatment is preferably 85 to 105%, and more preferably 95 to 102%, of the width of the film before the post-heat treatment. The heating temperature in the post-heat treatment is preferably {Tm-200}°C or higher, more preferably {Tm-100}°C or higher, even more preferably {Tm-50}°C or higher, and particularly preferably {Tm}°C or higher, where Tm is the melting point of the liquid crystal polymer (°C). Alternatively, the heating temperature in the post-heat treatment is preferably 240°C or higher, more preferably 255°C or higher, and even more preferably 270°C or higher. The upper limit of the heating temperature in the post-heat treatment is preferably {Tm+70}°C or lower, more preferably {Tm+50}°C or lower, and even more preferably {Tm+30}°C or lower.

[0107] In particular, in the post-heating treatment, it is preferable to set the heating temperature of one side of the polymer film to a temperature higher than the melting point of the liquid crystal polymer (preferably {Tm}°C to {Tm+30°C}, more preferably {Tm}°C to {Tm+15}°C), and to heat the polymer film so that the heating temperature of one side is 30°C or more higher than the heating temperature of the other side. This reduces the orientation of the liquid crystal polymer near the surface (surface region) of one side of the polymer film, making it easier to adjust the difference between the melting start temperature and the melting end temperature in the surface region of the polymer film, and the difference between area A2 and area A1, etc., within the above ranges.

[0108] Examples of heating means used in the post-heating treatment include a hot air dryer, an infrared heater, pressurized steam, microwave heating, and a heat medium circulation heating method. The treatment time of the post-heating treatment can be appropriately adjusted depending on the type of liquid crystal polymer, the heating means, and the heating temperature. The treatment time is preferably 20 hours or less, more preferably 1 hour or less, and even more preferably 20 minutes or less.

[0109] <Surface treatment> It is preferable to perform a surface treatment on the film, since this can further improve the adhesion between the film and a metal-containing layer such as a copper foil or a copper plating layer. Examples of surface treatments include glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, and acid or alkali treatment. The glow discharge treatment here refers to 10 -3Low temperature plasma generated under low pressure gas of about 20 Torr may be used, but plasma treatment under atmospheric pressure is also preferred. The glow discharge treatment is carried out using a plasma-excitable gas, which is a gas that is excited into plasma under the above-mentioned conditions, and examples of such a gas include argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, fluorocarbons such as tetrafluoromethane, and mixtures thereof. It is also preferable to provide a primer layer on the film for adhesion to the metal-containing layer, which may be applied after the above-mentioned surface treatment or without any surface treatment. These surface treatment and priming steps can be incorporated into the final film-forming step, can be carried out independently, or can be carried out during the copper foil or copper plating layer application step.

[0110] To improve the mechanical properties, thermal dimensional stability, or winding appearance of the wound film, it is also useful to subject the film to aging treatment at a temperature equal to or lower than the Tg of the liquid crystal polymer. After the film-forming step, the film may be subjected to a step of squeezing the film with a heated roll and / or a step of stretching the film to further improve the smoothness of the film.

[0111] In the above-mentioned production method, the case where the film is a single layer has been described, but the film may have a laminated structure in which multiple layers are laminated.

[0112] The polymer film is preferably laminated with a metal-containing layer to be used for producing a laminate, which will be described later. The polymer film can also be used as a film substrate.

[0113] [Laminate] The laminate of the present invention comprises the polymer film and a metal-containing layer disposed on at least one surface of the polymer film. In the laminate, one metal-containing layer may be disposed on one side of the polymer film, or two metal-containing layers may be disposed on both sides of the polymer film. The metal-containing layer is not particularly limited as long as it is formed on the surface of the polymer film and contains a metal, and examples thereof include a metal layer that covers the entire surface of the polymer film and metal wiring formed on the surface of the polymer film.

[0114] Examples of materials constituting the metal-containing layer include metals used for electrical connection. Examples of such metals include copper, gold, silver, nickel, aluminum, and alloys containing any of these metals. Examples of alloys include copper-zinc alloys, copper-nickel alloys, and zinc-nickel alloys. Copper is preferred as a material for the metal-containing layer because of its excellent conductivity and processability. The metal-containing layer is preferably a copper layer or copper wiring made of copper or a copper alloy containing 95% by mass or more of copper. Examples of the copper layer include rolled copper foil produced by a rolling method and electrolytic copper foil produced by an electrolysis method. The metal-containing layer may be subjected to a chemical treatment such as acid washing. As will be described later, the metal-containing layer is prepared using, for example, a metal foil, and a wiring pattern is formed by a known processing method as needed.

[0115] The thickness of the metal-containing layer is not particularly limited and is appropriately selected depending on the application of the circuit board, but is preferably 4 to 100 μm, more preferably 10 to 35 μm, from the viewpoint of the electrical conductivity of the wiring and economic efficiency.

[0116] The metal-containing layer constituting the laminate preferably has a maximum height Rz of 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less, on the surface facing the polymer film, in order to reduce the transmission loss of the laminate when used as a communication circuit board. There is no particular lower limit, but a value of 0.1 μm or more is preferred. The maximum height Rz of the surface of the metal-containing layer is determined by measuring the maximum height Rz at any 10 points on the surface of the metal-containing layer that was peeled off from the laminate and faced the polymer film using a stylus roughness tester in accordance with JIS B 0601, and then calculating the arithmetic average of the obtained measurements. When a commercially available metal foil is used as the metal-containing layer, the value of the maximum height Rz listed in the catalogue value of the commercially available product may be used.

[0117] The peel strength between the polymer film and the metal-containing layer in the laminate is preferably 6.5 N / cm or more, more preferably 6.8 N / cm or more, and even more preferably 7.0 N / cm or more. The higher the peel strength, the better the adhesion between the polymer film and the metal-containing layer. The upper limit of the peel strength of the laminate is not particularly limited, and may be 7.5 N / cm or less. The method for measuring the peel strength of the laminate will be described in the Examples section below.

[0118] The laminate may optionally have layers other than the polymer film and the metal-containing layer, such as an adhesive layer, an anticorrosive layer, and a heat-resistant layer, which will be described later.

[0119] The method for producing the laminate is not particularly limited, and a laminate having a polymer film and a metal-containing layer can be produced, for example, by laminating a polymer film and a metal foil made of the above metal and then pressing them together under high-temperature conditions. When using a metal foil whose maximum surface height Rz is within the above-mentioned preferred range, the polymer film and the metal foil are laminated together so that the surface is in contact with the polymer film. The method and conditions for the pressure bonding treatment are not particularly limited and may be appropriately selected from known methods and conditions. The temperature condition for the pressure bonding treatment is preferably 90 to 310° C., and the pressure condition for the pressure bonding treatment is preferably 1 to 100 MPa.

[0120] In order to improve adhesion, the polymer film and the metal-containing layer may be laminated via an adhesive layer, i.e., the laminate may have an adhesive layer between the polymer film and the metal-containing layer. The adhesive layer is not particularly limited as long as it is a known adhesive layer used in the manufacture of wiring boards such as copper-clad laminates, and examples thereof include a cured product of an adhesive composition containing a known curable resin such as polyimide and epoxy resin. A laminate having an adhesive layer can be produced, for example, by applying an adhesive composition to at least one surface of a polymer film or at least one surface of a metal foil, drying and / or curing the applied film as necessary to form an adhesive layer, and then laminating the polymer film and the metal foil via the adhesive layer according to the method described above.

[0121] Applications of the laminates and polymer films include laminated circuit boards, flexible laminates, and wiring boards such as flexible printed circuit boards (FPCs). The laminates and polymer films are particularly preferably used as substrates for high-speed communication. [Example]

[0122] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below. Unless otherwise specified, "parts" and "%" are based on mass.

[0123] [raw materials] <Liquid Crystal Polymer> Liquid crystal polymer (LCP1): A polymer synthesized based on Example 1 of JP 2019-116586 A (melting point Tm: 320°C, dielectric tangent: 0.0007) Liquid crystal polymer (LCP2): Polyplastics Laperos C-950 (melting point: 310°C, dielectric tangent: 0.0017) LCP1 is composed of repeating units derived from 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, terephthalic acid, and 2,6-naphthalenedicarboxylic acid. LCP2 is a polymer represented by the following chemical formula: The dielectric loss tangent of each liquid crystal polymer was measured by the cavity resonator perturbation method using a cavity resonator (CP-531 manufactured by Kanto Electronics Application Development Co., Ltd.) according to the method described above.

[0124] [ka]

[0125] <Compatible components> Compound 1: Bondfast (registered trademark) E (ethylene and glycidyl methacrylate copolymer (E-GMA copolymer)) manufactured by Sumitomo Chemical Co., Ltd.

[0126] <Heat stabilizer> Heat stabilizer 1: BASF Irganox 1010 (hindered phenol-based heat stabilizer)

[0127] <Polyolefin> PE: Novatec LD (low-density polyethylene) manufactured by Japan Polyethylene Corporation

[0128] [Example 1] <Production of polymer films>

[0129] (Supply process) The components (liquid crystal polymer, polyolefin, compatible component, and heat stabilizer) shown in the table below were mixed in the proportions shown in the table and kneaded and pelletized using an extruder. The kneaded and pelletized resin was dried for 12 hours using a dehumidifying hot air dryer at 80°C with a dew point of -45°C to reduce the moisture content to 50 ppm or less. The pellets dried in this manner are also referred to as raw material A.

[0130] (Film forming process) The dried raw material A was fed into the cylinder of a twin-screw extruder with a screw diameter of 50 mm from the same feed port, heated and kneaded at 270 to 350 ° C, and extruded into a molten film-like liquid crystal polymer from a die with a die width of 750 mm and a slit spacing of 300 μm. The thickness unevenness of the extruded film-like liquid crystal polymer in the width direction was improved by fine-tuning the clearance of the die lip. In this way, a film with a thickness of 50 μm was obtained.

[0131] (lateral stretching process) The film produced in the film-forming process was stretched in the TD direction using a tenter at a stretching ratio of 3.2 times.

[0132] (Post-heat treatment) The obtained film was subjected to post-heat treatment. Specifically, the film was heated using a heater so that the temperature difference between one surface and the other surface was 30°C or more, and the temperature of one surface (the higher temperature) was adjusted to exceed the melting point (Tm) of the liquid crystal polymer. In the post-heating treatment, a film for measuring the film surface temperature was placed near the film to be heat-treated, and the film surface temperatures on the front and back of the film were measured using a thermocouple attached to the surface of the film surface temperature measurement film with polyimide tape. In this manner, polymer film 1 in Example 1 was produced.

[0133] <Production of laminate> (Formation of adhesive layer) 17.7 g of a polyimide resin solution ("PIAD-200" manufactured by Arakawa Chemical Industries, Ltd.), 0.27 g of N,N-diglycidyl-4-glycidyloxyaniline, and 1.97 g of toluene were mixed and stirred to obtain an adhesive varnish with a solids concentration of 28 mass %. The obtained adhesive varnish was applied using an applicator to one surface of Film 1. The applied film was dried at 85°C for 1 hour to provide an adhesive layer with a thickness of 0.8 μm, thereby producing Film 1 with an adhesive layer.

[0134] (Formation of a laminate with a copper layer) The obtained film 1 with adhesive layer and unroughened copper foil ("CF-T9DA-SV-18" manufactured by Fukuda Metal Foil & Powder Co., Ltd., thickness 18 μm) were laminated so that the adhesive layer of the film 1 with adhesive layer and the unroughened surface of the unroughened copper foil (maximum height Rz 0.85 μm) were in contact with each other, and then the laminate was pressed together for 1 hour using a heat press (Toyo Seiki Seisakusho Co., Ltd.) under conditions of 200°C and 4 MPa to produce a laminate 1 in which the film 1, adhesive layer and copper foil were laminated in that order.

[0135] [Examples 2 to 8] Polymer films and laminates of Examples 2 to 8 were produced in the same manner as in Example 1, except that the post-heat treatment conditions (at least one of the time and heating temperature) were changed as appropriate. In all of Examples 2 to 8, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film was 30°C or more.

[0136] [Example 9] A polymer film and a laminate of Example 9 were produced in the same manner as in Example 1, except that the type of liquid crystal polymer used in the supplying step was changed.

[0137] [Example 10] The polymer film and laminate of Example 10 were prepared in the same manner as in Example 1, except that the type of liquid crystal polymer used in the supplying process and the conditions of the post-heating treatment (at least one of the time and heating temperature) were appropriately changed. In Example 10, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film was 30° C. or more.

[0138] [Example 11] A polymer film and a laminate of Example 11 were produced in the same manner as in Example 1, except that the post-heat treatment conditions (at least one of the time and heating temperature) were appropriately changed. In Example 11, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film was 30° C. or more.

[0139] [Examples 12 to 14] Polymer films and laminates of Examples 12 to 14 were produced in the same manner as in Example 1, except that the film-forming rate was appropriately adjusted so that the thickness of the polymer film would be as shown in Table 1.

[0140] [Examples 15 to 18] Polymer films and laminates of Examples 15 to 18 were produced in the same manner as in Example 1, except that the conditions for the transverse stretching step were changed as appropriate.

[0141] [Examples 19 to 22] Polymer films and laminates of Examples 19 to 22 were produced in the same manner as in Example 1, except that the concentration of the polyolefin used in the supplying step was changed as shown in Table 1.

[0142] [Examples 23 to 24] Polymer films and laminates of Examples 23 and 24 were produced in the same manner as in Example 1, except that the extrusion conditions in the film-forming step were changed as appropriate.

[0143] [Comparative Example 1] A polymer film and a laminate of Comparative Example 1 were produced in the same manner as in Example 1, except that the conditions for the post-heat treatment were changed. In Comparative Example 1, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film ((one surface) - (other surface)) was 0°C or higher and less than 30°C.

[0144] Comparative Example 2 A polymer film and a laminate of Comparative Example 2 were produced in the same manner as in Example 1, except that the type of liquid crystal polymer used in the supplying step was changed as shown in Table 1 and the conditions for the post-heat treatment were changed. In Comparative Example 2, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film ((one surface) - (other surface)) was 0°C or higher and less than 30°C.

[0145] Comparative Example 3 A polymer film and a laminate of Comparative Example 3 were produced in the same manner as in Example 1, except that no polyolefin was used in the supplying step and the conditions for the post-heat treatment were changed. In Comparative Example 3, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film ((one surface) - (other surface)) was 0°C or more and less than 30°C.

[0146] Comparative Example 4 The polymer film and laminate of Comparative Example 4 were produced in the same manner as in Example 1, except that the type of liquid crystal polymer used in the supplying process was changed as shown in Table 1, no polyolefin was used in the supplying process, and the conditions for the post-heating treatment were changed. In Comparative Example 4, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film ((one surface) - (other surface)) was 0°C or more and less than 30°C.

[0147] Comparative Example 5 A polymer film and a laminate of Comparative Example 1 were produced in the same manner as in Example 1, except that the conditions for the post-heat treatment were changed. In Comparative Example 5, the post-treatment heating was carried out so that the temperature difference between one surface and the other surface of the film ((one surface) - (other surface)) was 0°C or higher and lower than 30°C.

[0148] [Measurement and Evaluation] The polymer films and laminates obtained by the above methods were subjected to the following measurements and evaluations.

[0149] <Average dispersion diameter> The dispersed phase of polyolefin in each polymer film of the Examples and Comparative Examples was observed using a scanning electron microscope (SEM), and the average dispersed particle diameter was determined by the following method. At 10 different locations on the sample, a cut surface parallel to the width direction of the polymer film and perpendicular to the polymer film surface, and a cut surface perpendicular to the width direction of the polymer film and perpendicular to the polymer film surface were observed, yielding a total of 20 observation images. Observations were performed at appropriate magnifications of 100 to 100,000 times, and images were taken so that the dispersion state of particles (dispersed phase formed by polyolefin) across the entire thickness of the polymer film could be confirmed. The periphery of each particle was traced for 200 randomly selected particles from each of the 20 images, and the particle diameter was determined by measuring the equivalent circle diameter of the particles from these traced images using an image analyzer. The average particle diameter measured from each captured image was defined as the average dispersed diameter of the dispersed phase.

[0150] <Differential scanning calorimetry> For each polymer film of the Examples and Comparative Examples, a DSC curve was measured using a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation) by increasing the temperature to 400°C at a rate of 10°C / min based on JIS K7122:2012 (heat flux differential scanning calorimetry). The DSC curves were analyzed using analytical software (TA-60, manufactured by Shimadzu Corporation) to determine the melting peak temperatures present between 200°C and 400°C, the difference between the melting start temperature and the melting end temperature, and the melting peak areas (areas A1 and A2 described above). Here, the measurements were carried out on both an extracted region (surface region) from one surface of the polymer film to a depth of 10 μm, and on the entire polymer film. In this example, the surface region was extracted by polishing one side of the polymer film with abrasive paper, leaving a thickness of 10 μm on the other side. However, the surface region may also be extracted by polishing one side of the polymer film with a slurry containing water and an abrasive at high pressure, leaving a thickness of 10 μm on the other side.

[0151] <Dielectric loss tangent> Using samples cut out so as to include the entire thickness of each polymer film of the Examples and Comparative Examples, the dielectric loss tangent in the 28 GHz frequency band was measured using a split cylinder resonator ("CR-728" manufactured by Kanto Electronics Application Development Co., Ltd.) and a network analyzer (Keysight N5230A) under an environment of a temperature of 23°C and a humidity of 65% RH.

[0152] <Linear expansion coefficient> The linear expansion coefficient in the in-plane direction of each polymer film in the Examples and Comparative Examples was measured using a thermal mechanical analyzer (TMA, manufactured by Shimadzu Corporation) in accordance with JIS K 7197. More specifically, a sample 5 mm wide and 14 mm long was cut from the center of the polymer film and removed. The center of the polymer film was measured at five locations in each of the MD and TD directions, and the arithmetic average value for each measurement direction was calculated.

[0153] <Peel strength> Each laminate of the Examples and Comparative Examples was cut into a 1 cm x 5 cm strip to prepare a sample. The peel strength (unit: kN / m) of the obtained sample was measured according to the method for measuring peel strength under normal conditions described in JIS C 6481. In the peel strength test, the copper foil was peeled from the sample at an angle of 90° to the sample at a peel rate of 50 mm / sec. Measurements were made at five points for each sample, and the arithmetic average value was calculated. The evaluation criteria were as follows: (Evaluation criteria) A:7.0N / cm or more B: 6.8N / cm or more and less than 7.0N / cm C: 6.5N / cm or more and less than 6.8N / cm D: Less than 6.5N / cm

[0154] [Table 1]

[0155] [Table 2]

[0156] From the results shown in the above table, it was confirmed that the liquid crystal polymer film of the present invention can solve the problems of the present invention. [Explanation of symbols]

[0157] A1,A2 area S1,S2,E1,E2 points TP1 Melting temperature T S1 ,T S2 Melting start temperature T E1 ,T E2 melting end temperature

Claims

1. A polymer film comprising a liquid crystal polymer, In a differential scanning calorimetry analysis in a region from one surface of the polymer film to the other surface to a depth of 10 μm of the polymer film, the difference between the melting start temperature and the melting end temperature is 5.0 to 50° C., A polymer film, wherein the linear expansion coefficient in a first direction within the plane of the polymer film and the linear expansion coefficient in a second direction within the plane of the polymer film that is perpendicular to the first direction are both 0 to 40 ppm / °C.

2. 2. The polymer film of claim 1, wherein the area A1 of the melting peak in differential scanning calorimetry analysis in a depth region of 10 μm from one surface of the polymer film is smaller than the area A2 of the melting peak in differential scanning calorimetry analysis of the entire polymer film.

3. 3. The polymer film according to claim 2, wherein the area A1 is 1.0 to 12.0 J / g and the area A2 is 3.0 J / g or more.

4. 4. The polymer film according to claim 1, wherein the polymer film has a melting peak temperature of 290 to 340° C. in a depth region of 10 μm from one surface thereof in differential scanning calorimetry.

5. The polymer film according to any one of claims 1 to 4, wherein the thickness of the polymer film is more than 10 µm and not more than 250 µm.

6. 6. The polymer film according to claim 1, wherein the liquid crystal polymer contains repeating units derived from 6-hydroxy-2-naphthoic acid.

7. The polymer film according to any one of claims 1 to 5, wherein the liquid crystal polymer comprises at least one repeating unit selected from the group consisting of a repeating unit derived from 6-hydroxy-2-naphthoic acid, a repeating unit derived from an aromatic diol compound, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid.

8. The polymer film of any one of claims 1 to 7, further comprising a polyolefin.

9. 9. The polymer film according to claim 8, wherein the content of the polyolefin is 0.1 to 40% by mass based on the total mass of the polymer film.

10. 10. The polymer film according to claim 8, wherein the polyolefin forms a dispersed phase in the polymer film, and the dispersed phase has an average dispersed diameter of 0.01 to 10.0 μm.

11. A laminate comprising the polymer film according to any one of claims 1 to 10 and a metal-containing layer disposed on at least one surface of the polymer film.

12. A substrate for high-speed communication, comprising the polymer film according to any one of claims 1 to 10.

Images