WO2024166774A1

WO2024166774A1 - Method for lcp film production

Info

Publication number: WO2024166774A1
Application number: PCT/JP2024/003140
Authority: WO
Inventors: 奬野々下; 優亮升田
Original assignee: デンカ株式会社
Priority date: 2023-02-09
Filing date: 2024-01-31
Publication date: 2024-08-15

Abstract

The present invention provides a method for LCP film production, by which an LCP film having small absolute values of the coefficients of MD and TD linear expansion and having reduced anisotropy in the coefficients of MD and TD linear expansion can be easily produced in a manner not necessitating any special laminate film as in a conventional technique, the method being excellent in terms of production efficiency and versatility. This method for LCP film production at least includes: a step in which an extruded LCP film is prepared; and a step in which the extruded LCP film is subjected to an MD shrinkage treatment at a shrinkage ratio of 0.80-0.99 and to a TD stretch treatment, thereby obtaining an LCP film. In the stretch treatment, the extruded LCP film is subjected to the TD stretch treatment preferably at a stretch ratio of 1.20-2.50.

Description

Manufacturing method of LCP film

The present invention relates to a method for producing LCP films.

Conventionally, liquid crystal polymer (LCP) films manufactured by melt extrusion molding such as the inflation method or T-die method have been widely used in various fields. In particular, thermotropic liquid crystal polymers that exhibit liquid crystallinity in a molten or solution state can be extruded, and have excellent properties such as high gas barrier properties, high film strength, high heat resistance, high insulation, low water absorption, and low dielectric properties in the high frequency range, so their practical use in gas barrier film materials, electronic materials, electrical insulating materials, etc. is being considered. In addition, insulating materials for circuit boards using liquid crystal polymers have excellent high frequency properties and low dielectric properties, and have been attracting attention in recent years as insulating materials for circuit boards such as flexible printed circuit boards (FPCs), flexible printed circuit board laminates, and fiber-reinforced flexible laminates in the upcoming 5th generation mobile communication systems (5G) and millimeter wave radars.

However, it is known that in LCP films obtained by melt extrusion, the polymer chains are highly oriented in the flow direction of the film, i.e., the MD (Machine Direction; longitudinal direction), due to the high degree of liquid crystal orientation and relatively rigid molecular chains of the liquid crystal polymer, as well as due to shear stress caused by die and die swelling during melt extrusion. As a result, significant anisotropy occurs between the MD and TD (Transverse Direction; horizontal direction) in various physical properties such as film strength, thermal expansion coefficient, and dimensional accuracy, making it difficult to obtain a thermoplastic liquid crystal polymer film with high industrial utility.

In order to improve the anisotropy in the MD and TD directions, stretching the liquid crystal polymer film was once considered. However, because stretching is a technique that significantly stretches the entire liquid crystal polymer film in one or two axial directions, it is not possible to precisely adjust the orientation direction or degree of orientation. For this reason, currently, stretching of liquid crystal polymer films is mainly carried out to adjust the surface roughness and surface precision of the liquid crystal polymer film.

For example, Patent Document 1 discloses a method in which a laminate body is prepared in advance by sandwiching a liquid crystal polymer film between a pair of laminate films (a fluororesin porous film having a specific gravity of 1.3 or more and a breaking elongation rate in the stretching direction of 400% or more), and this laminate body is stretched uniaxially or biaxially under temperature conditions that soften the fluororesin porous film but do not substantially melt it, and soften or melt the liquid crystal polymer film.

Patent No. 3958629

However, the manufacturing technology described in the above-mentioned Patent Document 1 is premised on the use of a special laminate film, a fluororesin porous film, which has a high specific gravity and a high breaking elongation rate, and is therefore inherently poor in versatility. In fact, Patent Document 1 shows that when a PTFE skive film, which has a high specific gravity, or a polyimide film, which has a low breaking elongation rate, is used, the laminate film breaks during the stretching process, making it impossible to perform the desired stretching process.

In the above-mentioned Patent Document 1, a special laminate in which a liquid crystal polymer film is sandwiched between fluororesin porous films with a high specific gravity and high breaking elongation is subjected to a biaxial stretching process of 1.3 times in the MD direction and 3.9 times in the TD direction near the melting point of the liquid crystal polymer film, thereby obtaining an LCP film with low surface roughness and high surface precision. In other words, the manufacturing technology described in Patent Document 1 only adjusts the surface roughness and surface precision of the obtained stretched LCP film, and does not take into consideration any improvement of anisotropy such as the linear expansion coefficient in the MD and TD directions.

The present invention has been made in consideration of the above problems. The object of the present invention is to provide a method and the like for producing an LCP film that is excellent in productivity and versatility and can easily produce an LCP film that has small absolute values of linear expansion coefficients in the MD and TD directions and small anisotropy of the linear expansion coefficients in the MD and TD directions, without requiring a special laminate film such as that described in Patent Document 1.

As a result of extensive research into solving the above problems, the inventors discovered that the above problems could be solved by performing a biaxial expansion/contraction process (MD contraction-TD stretching process) in which the LCP extruded film is shrunk in the MD direction and stretched in the TD direction, thereby completing the present invention.

That is, the present invention provides various specific embodiments as shown below.
(1) A method for producing an LCP film, comprising at least the steps of preparing an LCP extruded film, and subjecting the LCP extruded film to a shrink treatment in the MD direction at a shrinkage ratio of 0.80 to 0.99 times and a stretching treatment in the TD direction to obtain an LCP film.

(2) The method for producing an LCP film described in (1) above, in which the stretching process is performed on the LCP extruded film at a stretch ratio of 1.20 to 2.50 in the TD direction.

(3) The method for producing an LCP film according to (1) or (2), in which the process for obtaining the LCP film has a linear expansion coefficient of -30.0 to 30.0 ppm/K in the TD direction and a linear expansion coefficient of -10.0 to 30.0 ppm/K in the MD direction.

(4) The method for producing an LCP film according to any one of (1) to (3), in which the process for obtaining the LCP film has a linear expansion coefficient of -20.0 to 5.0 ppm/K in the TD direction and a linear expansion coefficient of -10.0 to 10.0 ppm/K in the MD direction.

(5) The method for producing an LCP film according to any one of (1) to (4), in which the process for obtaining the LCP film has a linear expansion coefficient of -15.0 to 0.0 ppm/K in the TD direction and a linear expansion coefficient of -10.0 to 5.0 ppm/K in the MD direction.

(6) The method for producing an LCP film according to any one of (1) to (5), in which the LCP film is obtained in the step of obtaining the LCP film, and the LCP film has an orientation degree of 0.0 to 30.0%.

(7) The method for producing an LCP film according to any one of (1) to (6), wherein the extruded LCP film has a linear expansion coefficient of 5.0 to 60.0 ppm/K in the TD direction and a linear expansion coefficient of -30.0 to 5.0 ppm/K in the MD direction.

(8) The method for producing an LCP film according to any one of (1) to (7), in which a simultaneous biaxial stretching and shrinking machine is used in the process for obtaining the LCP film.

The present invention provides a method for producing an LCP film that is excellent in productivity and versatility and can easily produce an LCP film that has small absolute values of linear expansion coefficients in the MD and TD directions and small anisotropy of the linear expansion coefficients in the MD and TD directions without requiring a special laminate film.

FIG. 1 is a conceptual diagram showing a biaxial expansion/contraction process in the manufacturing method of an LCP film. FIG. 2 is a schematic diagram showing the MD shrinkage-TD stretching process of an LCP film using a simultaneous biaxial stretching shrinker. FIG. 3 is a conceptual diagram showing the principle of calculation of the degree of orientation based on the area ratio of the orientation peak.

Below, the embodiments of the present invention will be described in detail with reference to the drawings. Unless otherwise specified, the positional relationships, such as up, down, left, and right, are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to these. In other words, the present invention can be implemented with any modifications within the scope of the gist of the invention. In this specification, for example, the expression of a numerical range such as "1 to 100" includes both the lower limit "1" and the upper limit "100". The same applies to the expressions of other numerical ranges.

<Method of manufacturing LCP film>
1 is a conceptual diagram showing the biaxial expansion/contraction process (MD contraction-TD stretching process) in the manufacturing method of the LCP film 100 of this embodiment. The manufacturing method of the LCP film of this embodiment includes at least a process of preparing an LCP extruded film 10 (hereinafter also referred to as a preparation process S1), and a process of shrinking the LCP extruded film 10 in the MD direction at a shrinkage ratio of 0.80 to 0.99 and stretching it in the TD direction to obtain the LCP film 100 (hereinafter also referred to as a biaxial expansion/contraction process S2). Each process will be described in detail below.

(Preparation step S1)
In this preparation step S1, an LCP extruded film 10 containing a liquid crystal polymer (LCP) is prepared. As the LCP extruded film 10, a film known in the art can be used, and the type is not particularly limited. In the manufacturing method of this embodiment, the effect is more pronounced when a liquid crystal polymer film with high molecular orientation is used. As the liquid crystal polymer contained in the LCP extruded film 10, a film known in the art can be used, and the type is not particularly limited. The liquid crystal polymer is a polymer that forms an optically anisotropic molten phase, and a representative example is a thermotropic liquid crystal compound. The properties of the anisotropic molten phase can be confirmed by a known method such as a polarization inspection method using crossed polarizers. More specifically, the anisotropic molten phase can be confirmed by using a Leitz polarizing microscope and observing a sample placed on a Leitz hot stage at a magnification of 40 times under a nitrogen atmosphere.

Specific examples of liquid crystal polymers include liquid crystal polymers obtained by polycondensation of aromatic or aliphatic dihydroxy compounds, aromatic or aliphatic dicarboxylic acids, aromatic hydroxycarboxylic acids, aromatic diamines, aromatic hydroxyamines, aromatic aminocarboxylic acids, etc. Liquid crystal polymers include, but are not limited to, homopolymers of these, copolymers of these, modified products of these, polymer blends of these with thermoplastic resins other than liquid crystal polymers, and polymer alloys of these with thermoplastic resins other than liquid crystal polymers. From the viewpoint of obtaining an LCP extruded film 10 by extrusion molding, the liquid crystal polymer is preferably a thermoplastic liquid crystal polymer.

Specific examples of preferred liquid crystal polymers include aromatic polyamide resins obtained by polycondensation of monomers such as aromatic hydroxycarboxylic acids, aromatic diamines, and aromatic hydroxyamines; (all) aromatic polyester resins obtained by polycondensation of monomers such as aromatic diols, aromatic carboxylic acids, and aromatic hydroxycarboxylic acids; but are not limited to these. These can be used alone or in any combination and ratio of two or more. Thermoplastic liquid crystal polymers are generally classified into types I, II, and III from the viewpoint of heat distortion temperature (TDUL). The thermoplastic liquid crystal polymer used in this embodiment can be suitably used regardless of the type of thermoplastic liquid crystal polymer, and may be appropriately selected depending on the application. For example, in electronic circuit board applications requiring application to lead-free solder at about 260 to 290°C, a highly heat-resistant type I thermoplastic liquid crystal polymer with a TDUL of about 250 to 350°C and a relatively heat-resistant type II thermoplastic liquid crystal polymer with a TDUL of about 240 to 250°C are suitably used.

Among these, (fully) aromatic polyester resins that exhibit thermotropic liquid crystal-like properties and have a melting point of 250°C or higher, preferably 280°C to 380°C, are preferably used. As such (fully) aromatic polyester resins, for example, (fully) aromatic polyester resins that are synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids and that exhibit liquid crystallinity when melted are known. Representative examples include polycondensates of ethylene terephthalate and parahydroxybenzoic acid, polycondensates of phenol and phthalic acid and parahydroxybenzoic acid, and polycondensates of 2,6-hydroxynaphthoic acid and parahydroxybenzoic acid, but are not limited to these. The (fully) aromatic polyester resins can be used alone or in any combination and ratio of two or more. Depending on the required performance, a wholly aromatic polyester resin with a relatively high melting point or high heat distortion temperature and high heat resistance, or an aromatic polyester resin with a relatively low melting point or low heat distortion temperature and excellent moldability can be used.

A preferred embodiment is a (fully) aromatic polyester resin having a basic structure of 6-hydroxy-2-naphthoic acid and its derivatives (hereinafter, sometimes simply referred to as "monomer component A") and at least one monomer component (hereinafter, sometimes simply referred to as "monomer component B") selected from the group consisting of parahydroxybenzoic acid, terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate, and derivatives thereof. In the molten state, such (fully) aromatic polyester resins form an anisotropic molten phase in which the linear chains of molecules are regularly aligned, typically exhibiting thermotropic liquid crystal-like properties, and having excellent basic performance in terms of mechanical properties, electrical properties, high frequency properties, heat resistance, moisture absorption, etc.

Furthermore, the (all) aromatic polyester resin of the above-mentioned preferred embodiment can have any configuration as long as it has monomer component A and monomer component B as essential units. For example, it may have two or more types of monomer component A, or it may have three or more types of monomer component A. Furthermore, the (all) aromatic polyester resin of the above-mentioned preferred embodiment may contain another monomer component (hereinafter, simply referred to as "monomer component C") other than monomer component A and monomer component B. That is, the (all) aromatic polyester resin of the above-mentioned preferred embodiment may be a two-component or more polycondensate consisting of only monomer component A and monomer component B, or a three-component or more polycondensate consisting of monomer component A, monomer component B, and monomer component C. Examples of other monomer components include those other than the above-mentioned monomer component A and monomer component B, specifically aromatic or aliphatic dihydroxy compounds and derivatives thereof; aromatic or aliphatic dicarboxylic acids and derivatives thereof; aromatic hydroxycarboxylic acids and derivatives thereof; aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids and derivatives thereof; but are not particularly limited to these. The other monomer components can be used alone or in any combination and ratio of two or more.

In this specification, the term "derivative" refers to a monomer component having a modification group such as a halogen atom (e.g., fluorine atom, chlorine atom, bromine atom, iodine atom), an alkyl group having 1 to 5 carbon atoms (e.g., methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, etc.), an aryl group such as a phenyl group, a hydroxyl group, an alkoxy group having 1 to 5 carbon atoms (e.g., methoxy group, ethoxy group, etc.), a carbonyl group, -O-, -S-, -CH2-, etc., introduced into a part of the monomer component described above (hereinafter, this may be referred to as a "monomer component having a substituent"). Here, the "derivative" may be an ester-forming monomer such as an acylation product, ester derivative, or acid halide of the monomer components A and B which may have the above-mentioned modification group.

Particularly preferred embodiments include binary polycondensates of parahydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives; ternary or higher polycondensates of parahydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives and monomer component C; and polycondensates of parahydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives and terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol. ternary or higher polycondensates consisting of parahydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate, and their derivatives, and one or more monomer components C. These can be obtained as having a relatively low melting point compared to, for example, homopolymers of parahydroxybenzoic acid, and therefore, thermoplastic liquid crystal polymers using these have excellent moldability when thermocompressed to an adherend.

From the viewpoint of lowering the melting point of the (all) aromatic polyester resin, improving the moldability during thermocompression bonding of the LCP film 100 to an adherend, or obtaining high peel strength when the LCP film 100 is thermocompression bonded to a metal foil, the molar ratio of the monomer component A to the (all) aromatic polyester resin is preferably 10 mol% or more and 90 mol% or less, more preferably 30 mol% or more and 85 mol% or less, and even more preferably 50 mol% or more and 80 mol% or less. Similarly, the molar ratio of the monomer component B to the (all) aromatic polyester resin is preferably 10 mol% or more and 90 mol% or less, more preferably 15 mol% or more and 70 mol% or less, and even more preferably 20 mol% or more and 50 mol% or less. In addition, the molar ratio of the monomer component C that may be contained in the (all) aromatic polyester resin is preferably 10 mol% or less, more preferably 8 mol% or less, even more preferably 5 mol% or less, and particularly preferably 3 mol% or less.

The method for synthesizing the liquid crystal polymer is not particularly limited and may be any known method. Known polycondensation methods that form ester bonds using the above-mentioned monomer components, such as melt polymerization, melt acidolysis, and slurry polymerization, may be used. When applying these polymerization methods, an acylation or acetylation step may be carried out according to the usual method.

The LCP extruded film 10 may further contain an inorganic filler. By containing an inorganic filler, it becomes easier to obtain an LCP film 100 in which the anisotropy of the linear expansion coefficient in the MD direction, TD direction, and ZD direction (Z-axis direction; film thickness direction) is reduced. Such an LCP film 100 is particularly useful in rigid substrate applications requiring multi-layer lamination, for example.

The inorganic filler may be any inorganic filler known in the industry, and there is no particular limitation on the type. For example, kaolin, calcined kaolin, calcined clay, uncalcined clay, silica (e.g., natural silica, fused silica, amorphous silica, hollow silica, wet silica, synthetic silica, aerosil, etc.), aluminum compounds (e.g., boehmite, aluminum hydroxide, alumina, hydrotalcite, aluminum borate, aluminum nitride, etc.), magnesium compounds (e.g., magnesium aluminometasilicate, magnesium carbonate, magnesium oxide, magnesium hydroxide, etc.), calcium compounds (e.g., calcium carbonate, calcium hydroxide, calcium sulfate, calcium sulfite, calcium borate, etc.), molybdenum compounds (e.g., molybdenum oxide, zinc molybdate, etc.), talc (e.g., natural talc, calcined talc, etc.), mica, titanium oxide, zinc oxide, zirconium oxide, barium sulfate, zinc borate, barium metaborate, sodium borate, boron nitride, aggregated boron nitride, silicon nitride, carbon nitride, strontium titanate, barium titanate, stannates such as zinc stannate, etc., but are not particularly limited thereto. These can be used alone or in combination of two or more. Among these, silica is preferred from the viewpoint of dielectric properties, etc.

The inorganic filler used here may be one that has been subjected to a surface treatment known in the industry. The surface treatment can improve moisture resistance, adhesive strength, dispersibility, etc. Examples of surface treatment agents include, but are not limited to, silane coupling agents, titanate coupling agents, sulfonic acid esters, carboxylic acid esters, and phosphate esters.

From the viewpoint of reducing demands, etc., the median diameter (d50) of the inorganic filler is preferably 0.01 μm or more and 50 μm or less, more preferably 0.03 μm or more and 50 μm or less, and even more preferably 0.1 μm or more and 50 μm or less. In this specification, the median diameter (d50) of the inorganic filler means the value measured on a volume basis by the laser diffraction/scattering method using a laser diffraction/scattering type particle size distribution measuring device (LA-500 manufactured by Horiba, Ltd.).

The content of the inorganic filler is not particularly limited and can be set appropriately according to the required performance, taking into consideration the balance of the composition with other essential and optional components. From the viewpoints of kneadability and ease of handling during preparation, the effect of reducing the linear expansion coefficient, etc., the content of the inorganic filler is preferably 1% by mass or more and 45% by mass or less in total, more preferably 3% by mass or more and 40% by mass or less in total, and even more preferably 5% by mass or more and 35% by mass or less in total, calculated as solid content relative to the total amount of the LCP extruded film 10.

The LCP extrusion film 10 may contain resin components other than the above-mentioned thermoplastic resins (hereinafter, simply referred to as "other resin components"), such as thermosetting resins and elastomers, within the scope of not excessively impairing the effects of the present invention. In addition, the LCP extrusion film 10 may contain additives known in the art, such as release improvers such as higher fatty acids having 10 to 25 carbon atoms, higher fatty acid esters, higher fatty acid amides, higher fatty acid metal salts, polysiloxanes, and fluororesins; colorants such as dyes and pigments; organic fillers; antioxidants; heat stabilizers; light stabilizers; ultraviolet absorbers; flame retardants; antistatic agents; surfactants; rust inhibitors; defoamers; fluorescent agents, etc., within the scope of not excessively impairing the effects of the present invention. Each of these additives may be used alone or in combination of two or more. These additives may be included in the molten resin composition prepared when molding the LCP extrusion film 10. The content of these resin components and additives is not particularly limited, but from the viewpoints of moldability and thermal stability, it is preferably 0.01 to 10% by mass each, more preferably 0.1 to 7% by mass each, and even more preferably 0.5 to 5% by mass each, based on the total amount of the LCP extruded film 10.

As the above-mentioned LCP extrusion film 10, a melt extrusion film such as a T-die extrusion film or an inflation film is preferably used. The melt extrusion film can be obtained by extruding a resin composition containing the above-mentioned liquid crystal polymer and optional components such as inorganic fillers and other resin components to a predetermined thickness. The extrusion method can be applied to various known methods, and the type is not particularly limited. For example, the T-die method and the inflation method; for example, the multi-manifold coextrusion method and the feed block coextrusion method; and for example, the multi-layer coextrusion method such as the two-layer coextrusion method and the three-layer coextrusion method; can be applied in any combination. Among these, from the viewpoint of ease of control of the molecular orientation of the liquid crystal polymer on the film surface and inside the film, a preferred embodiment is a method in which the above-mentioned resin composition is extruded from a T-die by an extrusion molding method using a T-die (hereinafter, sometimes simply referred to as the "T-die extrusion method") to form a film, and then, as necessary, a cooling process, a pressing process, a pressurized heating process, etc. are performed to obtain a predetermined LCP extrusion film 10. Also preferably used as the LCP extruded film 10 is a liquid crystal polymer film layer that is the middle layer (core layer) of a three-layer coextruded film having a laminated structure in which a thermoplastic resin layer, a liquid crystal polymer film layer, and a thermoplastic resin layer are arranged in at least this order. In this case, a single liquid crystal polymer film layer (LCP extruded film 10) can be taken out by removing the thermoplastic resin layers of both outer layers of the three-layer coextruded film.

The thickness of the LCP extrusion film 10 can be set appropriately depending on the required performance, and is not particularly limited. Considering the ease of handling and productivity during extrusion molding, the thickness is preferably 15 μm or more and 300 μm or less, more preferably 18 μm or more and 250 μm or less, and even more preferably 20 μm or more and 200 μm or less.

The melting point (melting temperature) of the LCP extruded film 10 is not particularly limited, but from the viewpoint of the heat resistance and processability of the film, the melting point (melting temperature) is preferably 200 to 400°C, more preferably 250 to 360°C, more preferably 260 to 355°C, even more preferably 270 to 350°C, and particularly preferably 275 to 345°C. In this specification, the melting point of the LCP extruded film 10 means the melting peak temperature in differential scanning calorimetry (DSC) when the extruded film is heated (1st heating) at a temperature rise rate of 20°C/min in the temperature range of 30 to 400°C using a DSC8500 (manufactured by PerkinElmer) to see the value after eliminating the thermal history, and then cooled (1st cooling) at a temperature drop rate of 50°C/min, and then heated a second time (2nd heating) at a temperature rise rate of 20°C/min.

Here, the linear expansion coefficient (CTE, α2, 23-200°C) in the TD direction of the LCP extruded film 10 is not particularly limited, but is preferably 5.0-60.0 ppm/K, more preferably 5.0-55.0 ppm/K, and even more preferably 5.0-50.0 ppm/K. The linear expansion coefficient (CTE, α2, 23-200°C) in the MD direction of the LCP extruded film 10 is preferably -30.0-5.0 ppm/K, more preferably -25.5-5.0 ppm/K, and even more preferably -23.0-5.0 ppm/K. The LCP extruded film 10 to be subjected to the biaxial expansion/contraction process may be an unstretched film, a uniaxially stretched film, or a biaxially stretched film.

In this specification, the linear expansion coefficient is measured by the TMA method in accordance with JIS K7197, and the average linear expansion coefficient means the average value of the linear expansion coefficients between 23 and 200°C measured by the same method. The linear expansion coefficient measured here means the value when the target film, which is the measurement sample, is heated at a heating rate of 5°C/min (1st heating), cooled to the measurement environment temperature (23°C) (1st cooling), and then heated a second time at a heating rate of 5°C/min (2nd heating) in order to see the value after eliminating the thermal history. Other detailed measurement conditions are in accordance with the conditions described in the examples described later.

On the other hand, the dielectric properties of the LCP extruded film 10 can be appropriately set according to the desired performance, and are not particularly limited. From the viewpoint of obtaining higher dielectric properties, the relative dielectric constant _εr (36 GHz) is preferably 3.0 to 3.7, more preferably 3.0 to 3.5. Similarly, the dielectric loss tangent tanδ (36 GHz) is preferably 0.0010 to 0.0050, more preferably 0.0010 to 0.0045. In this specification, the relative dielectric constant _εr (36 GHz) and the dielectric loss tangent tanδ (36 GHz) refer to values at 36 GHz measured by a cavity resonator contact method in accordance with JIS K6471.

The LCP extruded film 10 can be used as is, but if necessary, a pressurized and heated process can be carried out to further reduce the molecular orientation (anisotropy) of the liquid crystal polymer or to further release the internal strain, thereby realizing an LCP film 100 with reduced anisotropy in the dimensional change rate or an LCP film 100 with a smaller absolute value for the dimensional change rate.

The pressurized heat treatment may be performed using a method known in the art, such as contact heat treatment or non-contact heat treatment, and the type is not particularly limited. For example, heat setting may be performed using known equipment such as a non-contact heater, oven, blower, heat roll, cooling roll, heat press, double belt heat press, etc. At this time, if necessary, a release film or porous film known in the art may be placed on the surface of the LCP extrusion film 10 and heat treatment may be performed. In addition, when performing this heat treatment, from the viewpoint of controlling the orientation, a heat compression molding method is preferably used in which a release film or porous film is placed on the front and back of the LCP extrusion film 10 and is thermocompressed while being sandwiched between a pair of endless belts of a double belt press, and then the release film or porous film is removed. The heat compression molding method may be performed by referring to, for example, JP 2010-221694 A. The processing temperature when the LCP extrusion film 10 using the above resin composition is thermocompressed between the pair of endless belts of a double belt press is preferably higher than the melting point of the liquid crystal polymer and lower than 70°C higher than the melting point in order to control the crystalline state of the LCP extrusion film 10, more preferably higher than +5°C higher than the melting point and lower than 60°C higher than the melting point, and even more preferably higher than +10°C higher than the melting point and lower than 50°C higher than the melting point. The thermocompression bonding conditions at this time can be appropriately set according to the desired performance and are not particularly limited, but are preferably performed under conditions of a surface pressure of 0.5 to 10 MPa and a heating temperature of 250 to 430°C, more preferably under conditions of a surface pressure of 0.6 to 8 MPa and a heating temperature of 260 to 400°C, and even more preferably under conditions of a surface pressure of 0.7 to 6 MPa and a heating temperature of 270 to 370°C. On the other hand, when a non-contact heater or oven is used, it is preferable to perform the thermocompression bonding under conditions of, for example, 200 to 320°C for 1 to 20 hours.

(Biaxial expansion/contraction process S2)
In the biaxial expansion/contraction step S2, the LCP extruded film 10, which is the object to be processed, is subjected to a shrinking treatment in the MD direction at a shrinkage ratio of 0.80 to 0.99 times and a stretching treatment in the TD direction. The LCP film 100 thus obtained after the biaxial expansion/contraction process (MD contraction-TD stretching process) is a uniaxially contracted film. As a stretched film, it is classified as a uniaxially stretched film (TD stretched film), and as a biaxially stretched film, it is classified as a uniaxially stretched film (MD shrinkage TD stretched film). do.

When shrinking the LCP extruded film 10 in the MD direction and stretching it in the TD direction, a known stretching machine or biaxial stretching shrinking machine (biaxial expansion and contraction machine) can be used. A known simultaneous biaxial expansion and contraction machine (shrink tenter machine) is described in JP 2022-051372 A, for example. Specifically, using a simultaneous biaxial stretching shrinking machine 20 shown in FIG. 2, the LCP extruded film 10 is fed out while being held between a number of

clips

21a, 22a of

endless loops

21, 22 arranged symmetrically on the left and right, and the LCP extruded film 10 is shrunk in the MD direction by reducing the spacing between the clips 21a and the spacing between the clips 22a. At the same time, since the spacing between the

endless loops

21, 22 gradually expands in the film transport direction, the LCP extruded film 10 held between the

endless loops

21, 22 is gradually pulled outward and stretched in the TD direction.

The processing temperature of the biaxial expansion and contraction step S2 is not particularly limited as long as it is equal to or higher than the glass transition point of the LCP extrusion film 10, but is preferably 70 to 180°C, and more preferably 90 to 180°C. After shrinkage in the MD direction and stretching in the TD direction, it is preferable to perform heat treatment (heat setting) at 100 to 240°C for 1 to 600 seconds. When performing heat setting, a method known in the industry, such as contact heat treatment or non-contact heat treatment, can be performed, and the type is not particularly limited. For example, heat setting can be performed using known equipment such as a non-contact heater, oven, blow device, heat roll, cooling roll, heat press machine, double belt heat press machine, etc. At this time, if necessary, a release film or porous film known in the industry can be placed on the surface of the LCP film 100 and heat pressure treatment can be performed. In the biaxial expansion and contraction step S2, the stretching treatment and the shrinking treatment can be performed sequentially, or the shrinking treatment and the stretching treatment can be performed sequentially by reversing the order, and the shrinking treatment and the stretching treatment can also be performed simultaneously.

The stretching ratio and shrinkage ratio of the LCP extruded film 10 in the biaxial expansion/contraction step S2 may be set according to the desired degree of anisotropy improvement, and are not particularly limited. From the viewpoint of alleviating the directional anisotropy of the LCP extruded film that is highly molecular oriented in the MD direction, the shrinkage ratio in the MD direction is preferably 0.80 to 0.99 times, more preferably 0.80 to 0.95 times, and even more preferably 0.80 to 0.93 times, based on the length in the MD direction before shrinkage. Similarly, from the viewpoint of alleviating the directional anisotropy of the LCP extruded film that is highly molecular oriented in the MD direction, the stretching ratio in the TD direction is preferably 1.20 to 2.50 times, more preferably 1.30 to 2.50 times, and even more preferably 1.40 to 2.50 times, based on the length in the TD direction before stretching. In addition, the stretching shrinkage ratio, which is expressed as the product of the shrinkage ratio in the MD direction and the stretching ratio in the TD direction (where m is the shrinkage ratio in the MD direction and n is the stretching shrinkage ratio expressed as m x n), is preferably 0.960 to 2.475, more preferably 1.040 to 2.375, even more preferably 1.120 to 2.325, and even more preferably 1.150 to 1.4950. According to this manufacturing method, even though the stretching shrinkage ratio in the biaxial expansion/contraction step S2 is relatively low, an LCP film 100 can be easily manufactured in which the absolute values of the linear expansion coefficients in the MD and TD directions are small and the anisotropy of the linear expansion coefficients in the MD and TD directions is small.

Furthermore, after the shrinkage and stretching process, the LCP film 100 can be cooled (or slowly cooled) as necessary. The LCP film 100 can be cooled, for example, by using a pair of cooling rolls, or by natural cooling. Then, after the biaxial expansion and shrinking process, the LCP film 100 can be taken up, for example, by a take-up roll and wound up in a roll on a take-up roll to form a rolled raw material.

In this embodiment, an example in which the LCP extruded film 10 is shrunk and stretched alone is shown, but the first and second film members may be arranged on the front and back sides of the LCP extruded film 10, respectively, and adhered to the front and back sides of the LCP extruded film 10, respectively, to form a laminated body having a first film member/LCP extruded film 10/second film member, and this laminated body may be subjected to a biaxial expansion and contraction process. The materials constituting the first and second film members are not particularly limited as long as they can adhere to the LCP extruded film 10 and have the strength not to break when subjected to the MD shrinkage-TD stretching process. For example, paper, woven fabric, nonwoven fabric, metal plate, alloy plate, metal foil, alloy foil, resin film, rubber sheet, foam sheet, laminates or impregnated bodies made of any combination of these, etc., can be used as the first and second film members. Among these, thermosetting resin films such as polyimide films; thermoplastic resin films having a higher melting point than the LCP extruded film 10; and metal foils such as aluminum foil and copper foil are preferred. The first and second membrane members may be made of the same or different materials.

The method for producing the laminate is not particularly limited, and known lamination methods can be applied. The first film member, the LCP extruded film 10, and the second film member are layered in this order, and the laminate can be obtained by laminating or thermocompressing the first film member using known equipment such as a press, a compression roll, a non-contact heater, an oven, a blowing device, a heat roll, a cooling roll, a heat press, or a double belt press. The processing conditions for lamination can be set appropriately depending on the material used, and are not particularly limited. For example, the lamination can be performed under conditions of a surface pressure of 0.3 to 10 MPa and a heating temperature of the LCP extruded film 10 or higher and melting point +70°C or lower, and preferably under conditions of a surface pressure of 0.6 to 8 MPa and a temperature of the LCP extruded film 10 or higher and 60°C higher than the melting point.

In order to achieve the desired peelability, various release agents may be placed between the LCP extruded film 10 of the pressure-bonded body and the first film member, or between the LCP extruded film 10 and the second film member. In addition, in order to achieve the desired adhesion, various primers, easy-to-use adhesives, etc. may be placed instead of release agents.

Then, after subjecting the LCP extrusion film 10 to MD shrinkage-TD stretching, the laminate is cooled as necessary, and then the first and second film members that are laminated to both surfaces of the laminate are peeled off (removed), thereby obtaining the LCP film 100 after MD shrinkage-TD stretching. The laminate can be cooled, for example, using a pair of cooling rolls, or it can be cooled naturally. The LCP film 100 after MD shrinkage-TD stretching can be made into a roll by, for example, taking it up with a take-up roll and winding it up in a roll on a take-up roll.

<LCP film>
The LCP film 100 obtained by the above-mentioned manufacturing method is an MD-shrunk/TD-stretched product of the LCP extruded film 10 (hereinafter, sometimes referred to as a biaxially stretched LCP film).

The thickness of the LCP film 100 can be set appropriately depending on the required performance, and is not particularly limited. Considering the ease of handling and productivity during extrusion molding, the thickness is preferably 15 μm or more and 300 μm or less, more preferably 18 μm or more and 250 μm or less, and even more preferably 20 μm or more and 200 μm or less.

The linear expansion coefficient (CTE, α2, 23-200°C) in the MD direction of the LCP film 100 can be set appropriately depending on the desired performance and is not particularly limited, but from the viewpoint of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate, and improving adhesion to the metal foil, it is preferably -10.0 to 30.0 ppm/K in the MD direction, more preferably -10.0 to 10.0 ppm/K, and even more preferably -10.0 to 5.0 ppm/K. According to the manufacturing method of this embodiment, an LCP film 100 with a linear expansion coefficient in the MD direction that has a negative value can be easily obtained.

The linear expansion coefficient (CTE, α2, 23-200°C) in the TD direction of the LCP film 100 can be set appropriately depending on the desired performance and is not particularly limited, but from the viewpoint of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate, and improving adhesion to the metal foil, it is preferably -30.0 to 30.0 ppm/K in the TD direction, more preferably -20.0 to 5.0 ppm/K, and even more preferably -15.0 to 0.0 ppm/K. According to the manufacturing method of this embodiment, an LCP film 100 with a linear expansion coefficient in the TD direction that has a negative value can be easily obtained.

The orientation of the LCP film 100 can be set appropriately depending on the desired performance and is not particularly limited, but from the standpoint of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate, and increasing adhesion to the metal foil, the degree of orientation is preferably 0.0 to 30.0%, more preferably 0.0 to 28.0%, even more preferably 0.0 to 26.0%, and particularly preferably 0.0 to 25.0%. The smaller this value, the more isotropic the physical properties are in the plane.

In this specification, the degree of orientation (%) of the LCP film 100 means a value calculated from the following formula based on the area ratio of the orientation peak in the diffraction intensity distribution curve obtained by performing X-ray diffraction measurement by a transmission method using an X-ray diffraction device. Generally, in the case of a measurement object with a low degree of orientation (%), a broad diffraction peak with a small peak intensity is observed in the X-ray diffraction measurement, so that a calculation method based on the half-width of the orientation peak cannot guarantee high measurement accuracy. Therefore, in this specification, the X-ray diffraction measurement is performed from one film surface side of the LCP film 100 using a calculation method based on the area ratio of the orientation peak, not the half-width of the orientation peak, and the degree of orientation (%) is calculated based on the area ratio of the obtained orientation peak. Specifically, as shown in FIG. 3 and Equation 1, the calculation method based on the area proportion of the orientation peak involves measuring the peak intensity (orientation component) by 2θ/θ scanning, and measuring the intensity in the azimuth direction from 0° to 360° by β scanning to obtain the intensity distribution in the azimuth direction (base intensity (isotropic component)). The orientation degree (%) is calculated as the percentage of the area occupied by the orientation component excluding the area of the base isotropic component to the total area (area of the orientation component + area of the isotropic component).

The dielectric properties of the LCP film 100 can be set appropriately according to the desired performance, and are not particularly limited. From the viewpoint of obtaining higher dielectric properties, the relative dielectric constant εr (36 GHz) is preferably 3.0 to 3.7, more preferably 3.0 to 3.5. Similarly, the dielectric loss tangent tanδ (36 GHz) is preferably 0.0010 to 0.0050, more preferably 0.0010 to 0.0045. In this specification, the relative dielectric constant εr (36 GHz) and the dielectric loss tangent tanδ (36 GHz) refer to the values at 36 GHz measured by the cavity resonator contact method in accordance with JIS K6471. Other detailed measurement conditions are in accordance with the conditions described in the examples described later.

As described above in detail, according to the manufacturing method of the LCP film 100 of this embodiment, it is possible to easily and stably manufacture the LCP film 100 having a small absolute value of the linear expansion coefficient in the MD direction and the TD direction and a small anisotropy of the linear expansion coefficient in the MD direction and the TD direction at a low cost without requiring a special laminate film as in the conventional technology. Therefore, the manufacturing method of the LCP film 100 of this embodiment has excellent industrial usefulness. In addition, the LCP film, which has excellent high-frequency characteristics and low dielectric properties, has been in the spotlight in recent years not only for applications such as electronic circuit boards, multilayer boards, high heat dissipation boards, flexible printed wiring boards, antenna boards, photoelectron hybrid boards, IC packages, etc., but also as an insulating material for circuit boards such as flexible printed wiring boards (FPCs), flexible printed wiring board laminates, and fiber-reinforced flexible laminates in the 5th generation mobile communication system (5G) and millimeter wave radar that will develop in the future. Therefore, the LCP film 100 obtained by applying the manufacturing method of the LCP film 100 of this embodiment has smaller absolute values of the linear expansion coefficient in the MD direction and TD direction, and has smaller in-plane anisotropy of the linear expansion coefficient compared to conventional technology, suppressing the occurrence of warping during manufacturing, and is adaptable to recent ultra-fine processing, making it widely usable as a material that is particularly useful in the relevant application.

The features of the present invention are explained in more detail below with reference to examples and comparative examples, but the present invention is not limited by these in any way. In other words, the materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Furthermore, the various manufacturing conditions and evaluation result values in the following examples are meant as preferred upper or lower limits in the implementation of the present invention, and the preferred numerical range may be a range defined by a combination of the above-mentioned upper or lower limits and the values of the following examples or the values of the examples themselves.

[Linear expansion coefficient]
The linear expansion coefficient (CTE, α2, 23 to 200° C.) in the MD and TD directions of each film was measured by the TMA method in accordance with JIS K7197.
Measuring equipment: TMA 4000SE (manufactured by NETZSCH)
Measurement method: Tensile mode Measurement conditions: Sample size 25 mm x 4 mm x thickness 50 μm
Chuck distance: 20mm
Temperature range: 23 to 200°C (2nd RUN)
Heating rate: 5°C/min
Atmosphere: Nitrogen (flow rate 50 ml/min)
Test load: 5gf
*The value from the 2nd run was used to see the value after eliminating the heat history.

[Orientation degree]
Using an X-ray diffraction device Smartlab (manufactured by Rigaku Corporation), X-ray diffraction measurements of the LCP film were performed from one film surface side by the transmission method, and the degree of orientation was measured. Here, a Cu sealed tube was used as the X-ray source, and X-ray diffraction measurements (2θ/θ scan, β scan) were performed by the parallel beam optical system and the transmission method, and it was confirmed that there was a peak top at 2θ = 19.5 ° in the 2θ/θ scan. Next, the intensity distribution in the azimuthal direction was obtained by measuring the intensity from 0 ° to 360 ° in the azimuthal direction for the diffraction peak at 2θ = 19.5 in the β scan. The degree of orientation was calculated from the above formula based on the area ratio of the orientation peak from the base intensity (isotropic component) and peak intensity (orientation component) of the obtained β profile.

(Reference Example 1)
A type II thermoplastic liquid crystal polymer (a copolymer having a monomer composition of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid, with a melt viscosity of 80 Pa·sec at a temperature of 300°C and a shear rate of 500 sec ^-1 ) was extruded from an extruder at 300°C by a T-die casting method to obtain an LCP extruded film (unstretched LCP film) of Reference Example 1 having a width of 400 mm, a thickness of 75 μm, and a melting point of 280°C.

Example 1
The LCP extruded film of Reference Example 1 was fed to a shrink tenter machine, and subjected to a shrink treatment of 0.90 times in the MD direction and a shrink/stretch treatment of 1.45 times in the TD direction at a temperature of 130°C, and then heat-set at 130°C for 30 seconds to obtain the LCP film of Example 1 (biaxially stretched LCP film).

Example 2
The LCP extruded film of Reference Example 1 was fed to a shrink tenter machine, and subjected to a shrink treatment of 0.86 times in the MD direction and a shrink/stretch treatment of 1.50 times in the TD direction at a temperature of 130°C, and then heat-set at 130°C for 30 seconds to obtain the LCP film of Example 2 (biaxially stretched LCP film).

Example 3
The LCP extruded film of Reference Example 1 was fed to a shrink tenter machine, and subjected to a shrink treatment of 0.85 times in the MD direction and a shrink/stretch treatment of 1.60 times in the TD direction at a temperature of 130°C, and then heat-set at 130°C for 30 seconds to obtain the LCP film of Example 3 (biaxially stretched LCP film).

(Comparative Example 1)
The LCP extruded film of Reference Example 1 was supplied to a uniaxial tenter stretching machine, stretched at a stretch ratio of 1.50 in the TD direction at a temperature of 130°C, and then heat-set at 130°C for 30 seconds to obtain an LCP film of Comparative Example 1 (TD-stretched LCP film).

(Comparative Example 2)
The LCP extruded film of Reference Example 1 was supplied to a uniaxial tenter stretching machine and was attempted to be stretched in the TD direction at a stretch ratio of 1.60 at a temperature of 130° C., but the LCP extruded film broke.

Table 1 shows the production conditions and the measurement results.

Example 4
The LCP extruded film of Reference Example 1 was fed to a shrink tenter machine, and subjected to a shrink treatment of 0.85 times in the MD direction and a shrink/stretch treatment of 1.70 times in the TD direction at a temperature of 130°C, and then heat-set at 130°C for 30 seconds to obtain the LCP film of Example 4 (biaxially stretched LCP film).

Example 5
The LCP extruded film of Reference Example 1 was fed to a shrink tenter machine, and subjected to a shrink treatment of 0.80 times in the MD direction and a shrink/stretch treatment of 1.90 times in the TD direction at a temperature of 130°C, and then heat-set at 130°C for 30 seconds to obtain the LCP film of Example 5 (biaxially stretched LCP film).

(Comparative Example 3)
The LCP extruded film of Reference Example 1 was supplied to a uniaxial tenter stretching machine and was attempted to be stretched in the TD direction at a stretch ratio of 1.70 at a temperature of 130° C., but the LCP extruded film broke.

(Comparative Example 4)
The LCP extruded film of Reference Example 1 was supplied to a uniaxial tenter stretching machine and was intended to be stretched in the TD direction at a stretch ratio of 1.80 at a temperature of 130° C., but the LCP extruded film broke.

As is clear from Table 1, by performing MD shrinkage and TD stretching, an LCP film with a small absolute value of the linear expansion coefficient in the MD and TD directions is obtained. Also, as is clear from Examples 1 to 5, by performing MD shrinkage and TD stretching, an LCP film with a negative linear expansion coefficient in the TD direction is obtained. On the other hand, it can be seen that the linear expansion coefficient and degree of orientation in the MD direction are still large when only uniaxial stretching (TD stretching) is performed as in Comparative Example 1. Also, when only uniaxial stretching (TD stretching) is performed as in Comparative Examples 2 to 4, there is a limit to the TD stretch ratio, and a comparison with the results of Examples 1 to 5 shows that performing MD shrinkage and TD stretching makes it possible to perform high-ratio processing, which was previously difficult.

The present invention provides a method for producing an LCP film that is excellent in productivity and versatility and can easily produce an LCP film with small absolute values of linear expansion coefficients in the MD and TD directions and small anisotropy of the linear expansion coefficients in the MD and TD directions without requiring a special laminate film as in conventional technology, and can be widely and effectively used in the field of LCP film materials.

Reference Signs List 100: LCP film 10: LCP extrusion film 11: LCP extrusion film after biaxial expansion and contraction 20: Simultaneous biaxial stretching and contraction machine 21: Endless loop 22: Endless loop 21a: Clip 22a: Clip

Claims

The method includes at least a step of preparing an LCP extruded film, and a step of subjecting the LCP extruded film to a shrinking treatment at a shrinkage ratio of 0.80 to 0.99 times in the MD direction and a stretching treatment in the TD direction to obtain an LCP film.
A method for manufacturing LCP films.
The method for producing an LCP film according to claim 1, wherein the stretching treatment is performed on the LCP extruded film at a stretch ratio of 1.20 times to 2.50 times in the TD direction.
2. The method for producing an LCP film according to claim 1, wherein the LCP film has a linear expansion coefficient of -30.0 to 30.0 ppm/K in the TD direction and a linear expansion coefficient of -10.0 to 30.0 ppm/K in the MD direction in the step of obtaining the LCP film.
2. The method for producing an LCP film according to claim 1, wherein the LCP film has a linear expansion coefficient of -20.0 to 5.0 ppm/K in the TD direction and a linear expansion coefficient of -10.0 to 10.0 ppm/K in the MD direction in the step of obtaining the LCP film.
2. The method for producing an LCP film according to claim 1, wherein the LCP film has a linear expansion coefficient of -15.0 to 0.0 ppm/K in the TD direction and a linear expansion coefficient of -10.0 to 5.0 ppm/K in the MD direction in the step of obtaining the LCP film.
The method for producing an LCP film according to claim 1, wherein in the step of obtaining the LCP film, the LCP film has an orientation degree of 0.0 to 30.0%.
The method for producing an LCP film according to claim 1, wherein the extruded LCP film has a linear expansion coefficient of 5.0 to 60.0 ppm/K in the TD direction and a linear expansion coefficient of −30.0 to 5.0 ppm/K in the MD direction.
The method for producing an LCP film according to claim 1 , wherein a simultaneous biaxial stretching shrinking machine is used in the step of obtaining the LCP film.