Liquid crystal polyester resin composition, liquid crystal polyester film, metal laminated film, and circuit board

Abstract

purpose of the present invention is to provide a liquid crystal polyester resin composition, a liquid crystal polyester-based film, a metal laminated film, and a circuit board which are excellent in mechanical properties, electrical properties, and heat resistance, while suppressing the occurrence of slack and wrinkles in a film during extrusion molding such as a blow extrusion molding method, and which are capable of forming a stable film. A liquid crystal polyester-based resin composition containing a thermoplastic liquid crystal polyester (A) and an amorphous copolyester (B), characterized in that the amorphous copolyester (B) has a glass transition temperature of

Description

[Technical Field]

[0001] This invention relates to a liquid crystal polyester resin composition with a thermoplastic liquid crystal polyester as the main component, which can form an optically anisotropic molten phase. Additionally, it relates to a liquid crystal polyester film using the resin composition and a metal laminate and circuit board using the film. [Previous Technology]

[0002] In recent years, the requirements for miniaturization and lightweighting of equipment have increased in the field of electronics and electrical engineering, necessitating an insulating film with excellent electrical and mechanical properties. However, current raw materials for insulating films, such as polyimide and polyethylene terephthalate, have the following problems: insufficient electrical performance at high frequencies, and high hygroscopicity leading to deterioration of electrical performance and large dimensional changes, making it difficult to achieve a film that meets the above requirements.

[0003] Thermoplastic liquid crystal polyester has attracted much attention as a material for flexible printed circuit (FPC) substrates due to its excellent heat resistance, rigidity and other mechanical properties, reagent resistance, dimensional accuracy, excellent electrical properties at high frequencies (GHz band) (low dielectric constant, low dielectric loss tangent) and low transmission loss in circuits.

[0004] Thermoplastic liquid crystal polyester can be formed into films by various extrusion molding methods. However, as a film formed by T-die extrusion molding, due to the property that the molecules of thermoplastic liquid crystal polyester with rigid molecular structure tend to orient along the flow direction in the molten state, the orientation of the molecular chains in the stretching direction (MD direction) and the direction orthogonal to it (TD direction) shows anisotropy, making it difficult to obtain thermoplastic liquid crystal polyester films with isotropic molecular chain orientation.

[0005] In contrast, blow molding can stretch the molten thermoplastic liquid crystal polyester extruded from the annular die along both the MD and TD directions. Therefore, by appropriately adjusting the blow ratio and controlling the orientation of the molecular chains, it is easy to obtain an isotropic thermoplastic liquid crystal polyester film.

[0006] However, the melt viscosity of thermoplastic liquid crystal polyester is highly dependent on shear stress and temperature. It has the characteristic that even a slight increase in shear stress and temperature will lead to a significant decrease in melt viscosity. Therefore, when thermoplastic liquid crystal polyester is melt-extruded by blow extrusion molding, there is a problem that the melt viscosity may decrease sharply due to the increase in shear stress and temperature generated in the die head, making it difficult to maintain the shape of the bubbles and thus difficult to form a stable film.

[0007] Patent Document 1 is an invention relating to a polymer alloy composed of a thermoplastic polymer (thermoplastic liquid crystal polymer) and an amorphous polymer that can form an optically anisotropic molten phase. It describes that by combining a polyarylate resin with the thermoplastic liquid crystal polymer, the film-forming stability in the blow molding process can be improved. Specifically, it prevents horizontal swaying of bubbles extruded from the annular die, reduces the displacement, and maintains a stable film formation.

[0008] Patent Document 2 relates to an invention of a liquid crystal polymer composition containing a liquid crystal polymer and a polyaryl ester resin, wherein it is described that by combining the liquid crystal polymer with the polyaryl ester resin, the melt tension is increased, resulting in excellent film-forming properties of extrusion molding.

[0009] [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2000-290512 [Patent Document 2] Japanese Patent Application Publication No. 2020-193261 [Summary of the Invention]

[0010] However, thermoplastic liquid crystal polyester has a high tensile elastic modulus and a low elongation at break, resulting in high rigidity. After being formed into a film by blow molding, the film is prone to wrinkles and loosening, making it difficult to obtain a smooth film.

[0011] For example, in blow molding, molten resin is extruded into bubbles through an annular slit. Air or inert gas is blown into the inside of the bubbles composed of molten resin, thereby causing the bubbles to expand and stretch along the MD and TD directions. The expanded and stretched bubbles come into contact with a pair of stabilizing plates that are inclined towards each other in the downstream direction of the MD direction. At the same time, they are slowly folded into flat shapes and guided towards the pinch rollers. The bubbles are folded into planar shapes by a pair of pinch rollers. In the process of bringing cylindrical bubbles into contact with stabilizing plates and folding them into flat shapes by pinch rollers, the straight-line distance from the position where the bubble is in direct contact with the stabilizing plate to the pinch rollers is different in geometry between the bubbles located at the center of the stabilizing plate and the bubbles located at both ends of the stabilizing plate. Therefore, when the rigidity of the resin is high, the film cannot be deformed when it is clamped into a planar shape between the pinch rollers, resulting in relaxation or wrinkles (longitudinal wrinkles) in the MD direction of the film.

[0012] Therefore, when forming a film of thermoplastic liquid crystal polyester by blow molding, it is effective to control the resin temperature of the bubbles when they are folded into a planar shape between the pinch rollers to be near the softening point where the film is easily deformed, thereby suppressing the formation of relaxation and longitudinal wrinkles on the film. On the other hand, if the resin temperature of the bubbles is controlled to be near the softening point before the pinch roller position, a new problem arises, namely, the bubbles near the softening point have insufficient sliding properties, and the friction between the bubbles and the stabilizing plate causes crescent-shaped wrinkles (transverse wrinkles) to be generated in the TD direction of the bubbles, making it difficult to form a smooth film.

[0013] The present invention was made in view of the following problems. The object of the present invention is to provide a liquid crystal polyester resin composition that suppresses the relaxation and wrinkle formation of the film in extrusion molding such as blow molding and can form a stable film with excellent mechanical properties, electrical properties and heat resistance.

[0014] The inventors have conducted in-depth research on resin compositions that can stably form films while maintaining the mechanical, electrical, and heat resistance properties of thermoplastic liquid crystal polyesters and suppressing film relaxation and wrinkle formation. As a result, they discovered that by incorporating an amorphous copolyester with a glass transition temperature of 80 to 200°C into thermoplastic liquid crystal polyesters, film relaxation and wrinkle formation can be suppressed in extrusion molding processes such as blow molding and film extrusion, and film can be stably formed, thus completing the present invention.

[0015] According to the present invention, the following are provided: (1) a liquid crystal polyester resin composition, characterized in that it comprises a thermoplastic liquid crystal polyester (A) and an amorphous copolyester (B), wherein the glass transition temperature of the amorphous copolyester (B) is above 80°C and below 200°C, and the mixing ratio of the thermoplastic liquid crystal polyester (A) to the amorphous copolyester is (A):(B) = 50~99.5% by weight: 0.5~50% by weight; (2) the liquid crystal polyester resin composition according to (1), characterized in that the thermoplastic liquid crystal polyester (A) comprises at least one constituent unit selected from the group consisting of a constituent unit from p-hydroxybenzoic acid and a constituent unit from 6-hydroxy-2-naphthoic acid; (3) the liquid crystal polyester resin composition according to (1), characterized in that the amorphous copolyester (B) comprises a constituent unit from a terephthalic acid monomer and a constituent unit from 1,4-cyclohexanediethanol. (4) The liquid crystal polyester resin composition according to (1), characterized in that the amorphous copolyester (B) comprises constituent units from terephthalic acid monomers, constituent units from 1,4-cyclohexanediethanol, and constituent units from 2,2,4,4-tetramethyl-1,3-cyclobutanediol; (5) The liquid crystal polyester resin composition according to (1), characterized in that the thermoplastic liquid crystal polyester (A) has a melting point of 250°C or higher; (6) The liquid crystal polyester resin composition according to (1), characterized in that the resin composition is used for blow molding; (7) A liquid crystal polyester film, characterized in that it is formed from the resin composition of any one of (1) to (6); (8) A metal laminate film, characterized in that a metal layer is laminated on one or both sides of the liquid crystal polyester film of (7); (9) A circuit board having at least one conductor layer and the liquid crystal polyester film of (7). [Effects of the Invention]

[0016] The liquid crystal polyester resin composition of the present invention, by comprising an amorphous copolyester with a glass transition temperature of 80-200°C, reduces the dependence of the melt viscosity of the resin composition on temperature and shear stress. Therefore, during film formation in extrusion molding such as blow molding, horizontal sloshing of bubbles extruded from the die can be suppressed, and pores in the bubbles can be suppressed, resulting in stable film formation. Furthermore, the sliding properties of the resin composition near its softening point can be improved. Therefore, during extrusion molding such as blow molding, wrinkles caused by friction with a stabilizing plate can be suppressed, resulting in a smooth film without relaxation or wrinkles. Moreover, film processing properties can be improved, while maintaining the excellent mechanical, electrical, and heat resistance properties of thermoplastic liquid crystal polyesters. Thus, liquid crystal polyester films formed from the liquid crystal polyester resin composition of the present invention, and metal laminates obtained by laminating liquid crystal polyester films with metal layers, possess excellent mechanical, electrical, and reflow solderability, making them suitable for applications such as laminates for circuit boards suitable for high-speed communication applications.

Implementation Method

[0017] Hereinafter, the present invention will be described in detail. It should be noted that the present invention is not limited to the following forms, and various forms can be adopted within the scope of achieving the effects of the present invention.

[0018] [Liquid Crystal Polyester Resin Composition] The liquid crystal polyester resin composition of the present invention comprises a resin composition including a thermoplastic liquid crystal polyester (A) and an amorphous copolyester (B). By blending with an amorphous copolyester (B) having a glass transition temperature of 80°C or higher and 200°C or lower, a smooth film can be stably formed in extrusion molding such as blow molding. The reason for this has not yet been determined, but it is speculated that: since the dependence of the melt viscosity of the resin composition on temperature and shear stress is reduced, the horizontal sloshing of bubbles extruded from the die and the opening of bubbles can be suppressed in extrusion molding such as blow molding, thereby stably forming a film. In addition, it is speculated that: by blending with an amorphous copolyester (B) having a glass transition temperature of 80°C or higher and 200°C or lower, the sliding property of the resin composition near the softening point is improved. Therefore, in extrusion molding such as blow molding, friction with the stabilizing plate can be reduced, and a smooth film without relaxation and wrinkles can be obtained.

[0019] [Thermoplastic Liquid Crystal Polyester (A)] The thermoplastic liquid crystal polyester (A) used in this invention is a liquid crystal polyester exhibiting melt anisotropy (a polyester capable of forming an optically anisotropic molten phase). The melt anisotropy property can be confirmed by the conventional polarization inspection method using orthogonal polarizers. Specifically, melt anisotropy can be confirmed by melting a sample placed in a melting point apparatus (LINKAM, etc.) using a polarizing microscope (Olympus Corporation, etc.) and observing it at 150x magnification under a nitrogen atmosphere. A liquid crystal resin exhibiting optical anisotropy during melting is optically anisotropic and transmits light after being inserted between orthogonal polarizers. When the sample is optically anisotropic, it will transmit polarized light even in, for example, a molten still liquid state.

[0020] As a thermoplastic liquid crystal polyester (A), as long as it is a liquid crystal polyester that can be melt-formed, its chemical composition is not particularly limited. Examples include thermoplastic liquid crystal polyesters having repeating units selected from at least one of the groups consisting of aromatic hydroxycarboxylic acids, aromatic or aliphatic diols, aromatic or aliphatic dicarboxylic acids, aromatic diamines, aromatic hydroxyamines and aromatic aminocarboxylic acids.

[0021] Examples of aromatic hydroxycarboxylic acids include: p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-(4-hydroxyphenyl)benzoic acid. These compounds may have substituents such as halogen atoms, lower alkyl groups, and phenyl groups. P-hydroxybenzoic acid or 6-hydroxy-2-naphthoic acid is preferred. As an aromatic or aliphatic diol, an aromatic diol is preferred. Examples of aromatic diols include: hydroquinone, 4,4'-dihydroxybiphenyl, 3,3'-dimethyl-1,1'-biphenyl-4,4'-diol, and their acetylated compounds, preferably hydroquinone or 4,4'-dihydroxybiphenyl. As an aromatic or aliphatic dicarboxylic acid, an aromatic dicarboxylic acid is preferred. Examples of aromatic dicarboxylic acids include: terephthalic acid, isophthalic acid, and 2,6-naphthoic acid, preferably terephthalic acid. Examples of aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids include p-phenylenediamine, 4-aminophenol, and 4-aminobenzoic acid.

[0022] The thermoplastic liquid crystal polyester (A) preferably has at least one of the repeating units selected from the group consisting of formulas (1) to (3) below. In formula (1), Ar1 represents phenylene, naphthylene, or biphenylene. In formula (2), Ar2 represents phenylene, naphthylene, biphenylene, or a group represented by formula (4) below. In formula (3), Ar3 represents phenylene, naphthylene, biphenylene, or a group represented by formula (4) below, and X and Y independently represent an oxygen atom or an imino group, respectively. In formula (4), Ar4 and Ar5 independently represent phenylene or naphthylene, respectively, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonylurea group, or an alkylene group. The phenylene, naphthylene, and biphenylene described above may have substituents selected from the group consisting of halogen atoms, alkyl groups, and aryl groups.

[0023] The thermoplastic liquid crystal polyester (A) preferably has at least one of the following groups: repeating units of an aromatic hydroxycarboxylic acid represented by formula (1) above, repeating units of an aromatic diol represented by formula (3) above, where X and Y are both oxygen atoms, and repeating units of an aromatic dicarboxylic acid represented by formula (2) above.

[0024] In addition, as a thermoplastic liquid crystal polyester (A), it is preferable to have a constituent unit from an aromatic hydroxycarboxylic acid, more preferably to have at least one selected from the group consisting of a constituent unit from p-hydroxybenzoic acid and a constituent unit from 6-hydroxy-2-naphthoic acid, and even more preferably to have a constituent unit from p-hydroxybenzoic acid and a constituent unit from 6-hydroxy-2-naphthoic acid.

[0025] In other preferred embodiments, the thermoplastic liquid crystal polyester (A) is more preferably having at least one selected from the group consisting of a constituent unit from 6-hydroxy-2-naphthoic acid, a constituent unit from an aromatic diol, a constituent unit from terephthalic acid, and a constituent unit from 2,6-naphthoic acid, and even more preferably having all of the constituent units from 6-hydroxy-2-naphthoic acid, a constituent unit from an aromatic diol, a constituent unit from terephthalic acid, and a constituent unit from 2,6-naphthoic acid.

[0026] The synthesis method of the thermoplastic liquid crystal polyester (A) is not particularly limited, and it can be synthesized by polymerizing the above-mentioned compound using known methods such as melt polymerization, solid-state polymerization, solution polymerization, and slurry polymerization. Commercially available products can also be used as the thermoplastic liquid crystal polyester (A). Examples of commercially available thermoplastic liquid crystal polyesters include: LAPEROS manufactured by POLYPLASTICS, Vectra manufactured by Celanese, UENO LCP manufactured by Ueno Pharmaceuticals, SUMIKASUPER LCP manufactured by Sumitomo Chemical, Xydar manufactured by ENEOS, and Siveras manufactured by Toray Industries. It should be noted that the thermoplastic liquid crystal polyester (A) can form chemical bonds with optional crosslinking agents or compatibility components (reactive compatibility agents).

[0027] The preferred melting point of the thermoplastic liquid crystal polyester (A) is 250°C or higher. When the melting point is below 250°C, the reflow solderability is poor, thus limiting processing methods for applications such as printed circuit boards. The melting point of the thermoplastic liquid crystal polyester (A) is not particularly limited, but from the viewpoint of heat resistance and molding processability, it is preferably below 400°C, more preferably below 350°C, even more preferably below 330°C, and particularly preferably below 300°C. The lower limit of the melting point is preferably above 260°C, and even more preferably above 270°C. It should be noted that the melting point of the thermoplastic liquid crystal polyester (A) is determined by heating the sample at a rate of 10°C / min using a differential scanning calorimeter (DSC) until it is completely melted, then cooling the melt to 30°C at a rate of 10°C / min, and then heating it again at a rate of 10°C / min. The position of the endothermic peak that appears after this process is taken as the melting point.

[0028] [Amorphous Copolyester (B)] The amorphous copolyester (B) used in this invention is a condensation polymer of polycarboxylic acids and polyols, which does not have a distinct endothermic peak in thermal analysis measurements using differential scanning calorimetry (DSC). For example, in thermal analysis measurements using DSC, it only exhibits a step-like endothermic change, is solid at room temperature, and undergoes thermoplasticization at temperatures above the glass transition temperature.

[0029] The amorphous copolyester (B) preferably comprises a constituent unit derived from a terephthalic acid monomer and a constituent unit derived from 1,4-cyclohexanediethanol. The terephthalic acid monomer is terephthalic acid or a derivative thereof. Examples of terephthalic acid derivatives include, for example, halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, and mixtures thereof. Examples of terephthalic acid derivatives include, for example, dialkyl esters and diaryl esters of terephthalic acid, and specific examples include, for example, dimethyl terephthalate (DMT) and diethyl terephthalate.

[0030] The amorphous copolyester (B) may also contain constituent units from other monomers. In one embodiment, it further contains constituent units from dicarboxylic acids (other dicarboxylic acids) other than terephthalic acid monomers. Examples of other dicarboxylic acids include cyclohexanedicarboxylic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, stilbenedicarboxylic acid, etc. Examples of cyclohexanedicarboxylic acids include 1,3- and / or 1,4-cyclohexanedicarboxylic acid, etc. When the amorphous copolyester (B) contains constituent units from other dicarboxylic acids, the proportion of constituent units from terephthalic acid monomers relative to the total amount of dicarboxylic acids (the total amount of constituent units from terephthalic acid monomers and constituent units from other dicarboxylic acids) is preferably 40 mol% or more, more preferably 40 mol% to 90 mol%, and even more preferably 50 mol% to 85 mol%.

[0031] The amorphous copolyester (B) may further comprise constituent units of diols other than 1,4-cyclohexanediethanol (other diols). Examples of other diols include, for example, aliphatic or alicyclic diols (preferably having 2 to 20 carbon atoms). Examples of other diols include, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, neopentanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, etc. In one embodiment, the amorphous copolyester (B) further comprises constituent units of 2,2,4,4-tetramethyl-1,3-cyclobutanediol. When the amorphous copolyester (B) includes a constituent unit from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD), the proportion of the constituent unit from 1,4-cyclohexanediethanol (CHDM) relative to the total of the constituent units from TMCD and CHDM is preferably 10 mol% to 90 mol%, more preferably 20 mol% to 85 mol%, and even more preferably 30 mol% to 80 mol%. Furthermore, the proportion of the constituent unit from TMCD relative to the total of the constituent units from TMCD and CHDM is more preferably 10 mol% to 90 mol%, more preferably 15 mol% to 80 mol%, and even more preferably 20 mol% to 70 mol%.

[0032] The glass transition temperature (Tg) of the amorphous copolyester (B) is 80°C or higher and 200°C or lower, more preferably 85°C or higher and 180°C or lower, more preferably 90°C or higher and 160°C or lower, even more preferably 95°C or higher and 150°C or lower, and particularly preferably 100°C or higher and 140°C or lower. It should be noted that the glass transition temperature can be determined by existing known methods, for example, it can be obtained by differential scanning calorimetry based on JISK-7121:2012. Furthermore, if the glass transition temperature is a manufacturer-published value, the manufacturer's published value can be used.

[0033] The liquid crystal polyester resin composition of the present invention comprises the above-mentioned thermoplastic liquid crystal polyester (A) and amorphous copolyester (B) in a ratio of (A):(B) = 50~99.5 wt%: 0.5~50 wt%. More preferably, (A):(B) = 70~99 wt%: 1~30 wt%, more preferably, (A):(B) = 80~98.5 wt%: 1.5~20 wt%, even more preferably, (A):(B) = 85~98 wt%: 2~15 wt%, and most preferably, (A):(B) = 90~97.5 wt%: 2.5~10 wt%. When the amount of amorphous copolyester (B) is less than the above range, it lacks the effect of reducing the dependence of the melt viscosity of the liquid crystal polyester resin composition on temperature and shear stress. In addition, it lacks the effect of improving the sliding properties of the resin composition near the softening point. Therefore, it is difficult to obtain a smooth film by blow molding. When the amount of amorphous copolyester (B) exceeds the above range, the heat resistance and mechanical properties of the liquid crystal polyester film formed from the liquid crystal polyester resin composition may decrease.

[0034] The liquid crystal polyester resin composition of the present invention may include other resin components besides the above-mentioned thermoplastic liquid crystal polyester (A) and amorphous copolyester (B) without impairing the effects of the present invention. Examples of other resin components include: polyarylates, polyphenylene sulfides, polyphenylene ethers, polyetheretherketones, polyetherimides, cycloolefin polymers, polyamides, polyamide-imides, polyamides, epoxy-containing olefin copolymers, styrene resins, copolyester elastomers, and other thermoplastic resins. Furthermore, the liquid crystal polyester resin composition of the present invention may include additives such as compatibilizers, lubricants, antioxidants, and fillers. It should be noted that when the liquid crystal polyester resin composition of the present invention includes other components, it is preferable to include a total amount of thermoplastic liquid crystal polyester (A) and amorphous copolyester (B) as the main component. Wherein, the main component refers to the component constituting the resin composition in a proportion of 50% by weight or more, more preferably 60% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more.

[0035] [Manufacturing Method of Liquid Crystal Polyester Film] In this invention, a film formed from the above-described resin composition and a method for manufacturing the film are also provided. The liquid crystal polyester film of this invention can be obtained by blending the above-described thermoplastic liquid crystal polyester (A) and amorphous copolyester (B) into a film using a known method. It should be noted that, as the resin composition of this invention, when the proportion of amorphous copolyester (B) is reduced, in order to provide a stable compounding state, it is preferable to pre-melt-blend and granulate before film formation.

[0036] As equipment for melt mixing, there are no particular limitations, and examples include various known extruders such as batch mixers, kneaders, co-kneaders, Banbury mixers, roller mills, single-screw or twin-screw extruders, etc. Among these, single-screw extruders and twin-screw extruders are preferred from the perspective of superior mixing capacity and productivity.

[0037] In the resin composition of the present invention, by incorporating an amorphous copolyester (B), the rapid decrease or change in the melt viscosity of the resin composition due to temperature and shear stress can be suppressed, thereby improving the film-forming processability of the film formed by blow molding. Furthermore, by blending with the amorphous copolyester (B), the sliding properties of the resin composition near its softening point are improved. In extrusion molding methods such as blow molding, wrinkles caused by friction with a stabilizing plate can be suppressed, resulting in a smooth film without relaxation or wrinkles.

[0038] As a blow extrusion molding process, for example, the following method can be used: the above-mentioned resin composition is fed to a melt extruder equipped with a die having an annular slit; the molten resin composition is extruded from the annular slit of the extruder from above or below in a bubble-like manner; air or inert gas is blown into the inside of the bubbles formed by the molten resin composition, thereby causing the bubbles to expand and stretch in a direction perpendicular to the flow direction (MD direction) (TD direction), thereby obtaining a film. The barrel temperature of the melt extruder is typically 260~400°C, preferably 280~380°C. The spacing of the annular slits is typically 0.1~5 mm, preferably 0.2~2 mm. The diameter of the annular slits is typically 20~1000 mm, preferably 25~600 mm.

[0039] In blow molding, the blow-up ratio is preferably 1.5 or more, more preferably 2.0 or more, even more preferably 4.0 or more, and especially preferably 4.5 or more. The upper limit of the blow-up ratio is not particularly limited; for example, the blow-up ratio is 10 or less. Furthermore, the draw ratio is preferably 1.5 or more and 20 or less, more preferably 1.5 or more and 10 or less. Here, the blow-up ratio is the stretch ratio in the TD direction, and the draw ratio is the stretch ratio in the MD direction. When the blow-up ratio and draw ratio are within the above ranges, the anisotropy of the tensile modulus of elasticity and tensile strength of the obtained film (the difference between the MD and TD directions) can be improved. However, in blow molding of liquid crystal polyester resin compositions, increasing the blow-up ratio to improve the anisotropy of the film tends to result in unstable bubble shapes formed by the molten resin composition, thus easily leading to bubble vibration and opening. In contrast, the resin composition of the present invention, by incorporating an amorphous copolyester (B), can reduce the sharp decrease or change in the melt viscosity of the resin composition caused by temperature and shear stress, etc. Therefore, even if the blow-up ratio is 4.0 or higher, it can suppress the formation of openings on bubbles, improve the anisotropy of the film, and stably form the film.

[0040] The thickness of the liquid crystal polyester film of the present invention is not particularly limited. For example, it is 0.5 μm or more and 1000 μm or less. Considering the operability and productivity during melt extrusion, it is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 300 μm or less, and even more preferably 20 μm or more and 200 μm or less.

[0041] The tensile strength of the liquid crystal polyester film of the present invention in both the flow direction (MD direction) and width direction (TD direction) is preferably 180 MPa or more. More preferably, the tensile strength is 200 MPa or more, and even more preferably 220 MPa or more. The upper limit of the tensile strength is not particularly limited; for example, it is preferably 500 MPa or less, more preferably 400 MPa or less, and even more preferably 350 MPa or less. If the tensile strength is within the above range, the operability is excellent when processing it into a laminate suitable for circuit boards used in high-speed communication applications, and defects and cracking at the film ends can be suppressed.

[0042] The liquid crystal polyester film of the present invention preferably has low anisotropy in both the flow direction (MD direction) and the width direction (TD direction). Specifically, the tensile strength F(TD) in the width direction of the film relative to the tensile strength F(MD) in the flow direction (i.e., F(TD) / F(MD)) is preferably 0.5 or more and 1.5 or less, more preferably 0.75 or more and 1.25 or less, even more preferably 0.85 or more and 1.15 or less, and particularly preferably 0.90 or more and 1.10 or less. If the tensile strength F(TD) in the width direction of the film relative to the tensile strength F(MD) in the flow direction is within the above range, the anisotropy of the mechanical and electrical properties of the film is small, making it suitable for applications such as laminates for circuit boards suitable for high-speed communication applications.

[0043] The dielectric loss tangent of the liquid crystal polyester film of the present invention is preferably 0.0025 or less, more preferably 0.0024 or less, even more preferably 0.0022 or less, and particularly preferably 0.0020 or less. Furthermore, the relative permittivity of the liquid crystal polyester film of the present invention is preferably 2.0 to 4.0. The relative permittivity is even more preferably 2.5 to 3.9, more preferably 2.6 to 3.8, and even more preferably 2.8 to 3.8. The dielectric properties, including the standard dielectric loss tangent and the relative permittivity, can be measured by the cavity resonator perturbation method.

[0044] The liquid crystal polyester film of the present invention can improve the dimensional stability of the film by further applying heat treatment to mitigate the orientation of the molecular chains. The heat treatment can be performed using existing known methods, such as contact heat treatment, non-contact heat treatment, etc., and the type is not particularly limited.

[0045] [Metal Laminate] The liquid crystal polyester film of the present invention can also be laminated with a metal layer to form a metal laminate. When laminating the metal layer, in order to improve the adhesion, corona discharge treatment, ultraviolet irradiation treatment or plasma treatment can be applied to the surface of the laminated metal layer of the liquid crystal polyester film.

[0046] As a method for laminating a metal layer on the liquid crystal polyester film of the present invention, examples include: (1) a method of bonding the liquid crystal polyester film to a metal foil by heating and pressing; (2) a method of bonding the liquid crystal polyester film and the metal foil by an adhesive; and (3) a method of forming a metal layer on the liquid crystal polyester film by vapor deposition. Among these, the lamination method (1) is a method of pressing the liquid crystal polyester film to the metal foil near the flow initiation temperature of the liquid crystal polyester film using a press or heated roller, which is easy to implement and therefore recommended. As an adhesive used in the lamination method (2), examples include: hot melt adhesives and polyurethane adhesives. Among these, ethylene copolymers containing epoxy groups are preferably used as adhesives. As a lamination method (3), examples include: ion beam sputtering, high-frequency sputtering, DC magnetron sputtering, and glow discharge. Among these, high-frequency sputtering is preferred.

[0047] Examples of metals used for the metal layer include gold, silver, copper, copper alloys, nickel, nickel alloys, aluminum, aluminum alloys, iron, and iron alloys. Copper is preferred for leadframe and circuit board applications, while aluminum is preferred for capacitor applications. Examples of structures for the resulting metal laminate include a two-layer structure of a liquid crystal polyester film and a metal layer, a three-layer structure formed by laminating metal layers on both sides of a liquid crystal polyester film, and a five-layer structure formed by alternately laminating liquid crystal polyester films and metal layers. It should be noted that, in order to achieve high-intensity display, the laminate can be heat-treated as needed. The thickness of the metal layer is not particularly limited; for example, it is preferably 1.5 to 1000 μm, more preferably 2 to 500 μm, even more preferably 5 to 150 μm, and particularly preferably 7 to 100 μm. Thinner layers within this range have poor mechanical strength, while thicker layers within this range have poor operability and processability.

[0048] The circuit board of the present invention includes at least one conductor layer and at least one insulating (or dielectric) layer. Its form is not particularly limited as long as the liquid crystal polyester film of the present invention is used as the insulating (or dielectric), and it can be used in various high-frequency circuit boards in a known or conventional manner. Additionally, the circuit board can be a circuit board (or semiconductor element mounting substrate) on which semiconductor elements (e.g., IC chips) are mounted.

[0049] The conductor layer of the circuit board used in the present invention is formed, for example, at least of a conductive metal, and a circuit pattern is formed on the conductor layer using a known circuit processing method. As the conductor forming the conductor layer, various conductive metals can be used, such as gold, silver, copper, iron, nickel, aluminum, or alloy metals thereof. Furthermore, the circuit pattern can be formed on the metal layer portion of the aforementioned metal laminate. Example

[0050] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is limited to the following examples.

[0051] The following substances were used as the resins in the examples and comparative examples. (Thermoplastic Liquid Crystal Polyester) ･LCP(1): A thermoplastic liquid crystal polyester composed of units derived from p-hydroxybenzoic acid and units derived from 6-hydroxy-2-naphthoic acid (LAPEROS A950RX manufactured by POLYPLASTICS AG, melting point: 280℃, softening point: 266℃) ･LCP(2): A thermoplastic liquid crystal polyester composed of units derived from p-hydroxybenzoic acid, units derived from 6-hydroxy-2-naphthoic acid, and units derived from terephthalic acid (LAPEROS C950RX manufactured by POLYPLASTICS AG, melting point: 320℃, softening point: 303℃) (Amorphous Polymer) ･Amorphous Polymer(1): An amorphous copolyester containing units derived from terephthalic acid, units derived from 1,4-cyclohexanediol, and units derived from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (Eastman) Amorphous polymer (2): Amorphous copolyester containing units from terephthalic acid, 1,4-cyclohexanediethanol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TraitanTX1001, Tg: 108℃, manufactured by Eastman Chemical Company). Amorphous polymer (3): Amorphous copolyester containing units from terephthalic acid, 1,4-cyclohexanediethanol and ethylene glycol (PETGGN001, Tg: 90℃, manufactured by Eastman Chemical Company). Amorphous polymer (4): Amorphous copolyester containing units from terephthalic acid, 1,4-cyclohexanediethanol and ethylene glycol (PCTGDN011, Tg: 90℃, manufactured by Eastman Chemical Company). • Amorphous polymer (5): Contains building blocks derived from terephthalic acid, derived from 1,Amorphous copolyesters of 4-cyclohexanediethanol and isophthalic acid (PCTAAN004, Eastman Chemical, Tg: 90℃) • Amorphous polymer (6): Polyarylate resin (U-polymer U-100, Unigene Corporation, Tg: 193℃) • Amorphous polymer (7): Polyurethane resin (Ultrason S3010, BASF, Tg: 187℃) • Amorphous polymer (8): Polyurethane resin (Udel P-1700NT11, Solvay, Tg: 185℃) • Amorphous polymer (9): Polymer alloy of polyetherimide resin and polyethylene terephthalate resin (ULTEMDU319, SABIC, Tg: 185℃) • Amorphous polymer (10): Polycarbonate resin (SABIC LEXANXHT3143T, Tg: 175℃) • Amorphous polymer (11): Polymer alloy of polyphenylene ether resin and polystyrene resin (SABIC NORYLEFN4230S, Tg: 175℃) • Amorphous polymer (12): Polymethyl methacrylate resin (Mitsubishi Chemical ACRYPET VH001, Tg: 100℃) (Additive) • Polyester elastomer: Block copolymer of polybutylene terephthalate and polybutanediol (PBT / PTMG) According to JIS K7196 (1991), prepare a sample 5 mm wide, 5 mm long and 0.05 mm thick, and use a thermochemical mechanical analysis apparatus (SII) The instrument, manufactured by NanoTechnology (model: TMA / SS7100), was used as the measuring apparatus. Five sheets were stacked under nitrogen atmosphere, with a heating rate of 5°C / min, and a temperature range of 30°C to 350°C. A load of 50 gf was applied, and a transparent quartz pin (tip diameter ϕ0.5 mm) was inserted into the resulting sample to determine the softening point. The glass transition temperature was obtained from the manufacturer's catalog value.

[0052] (1) Manufacturing of molded articles in injection molding: The thermoplastic liquid crystal polyester resin composition was premixed according to the proportions recorded in Table 1, and then extruded using an injection molding machine (Toyo Seiki Manufacturing Co., Ltd. Hand Truder M-1) at a barrel temperature of 300°C to obtain strip-shaped test pieces (82 mm long, 10 mm wide, and 4 mm thick). The obtained strip-shaped test pieces were visually inspected for the presence or absence of foaming and their appearance. The evaluation results are shown in Table 1.

[0053]

[0054] Regarding the basic evaluation results of the injection-molded articles, in the resin composition of Reference Example 7, which contains polycarbonate resin as an amorphous polymer, foaming occurred during injection molding, resulting in yellowing and poor appearance of the obtained injection-molded articles. Furthermore, in the resin composition of Reference Example 8, which contains a polymer alloy of polyphenylene ether resin and polystyrene resin as an amorphous polymer, and in the resin composition of Reference Example 9, which contains polymethyl methacrylate resin as an amorphous polymer, foaming occurred during injection molding. In the evaluation of injection molding, no problems were observed with the processability and appearance of the resin compositions of Reference Examples 1 to 6.

[0055] (2) A film was manufactured by blow extrusion molding. The thermoplastic liquid crystal polyester resin composition was premixed according to the proportions recorded in Table 2, heated and mixed by a single screw extruder, and melt-extruded into bubbles from a ring blow molding die (diameter 25 mm) at a spray rate of 3 kg / h. The bubbles were stretched under the conditions of draw ratio = 2 and blow-up ratio = 5, and a liquid crystal polyester film with a thickness of 50 μm was obtained by blow extrusion molding. The resin temperature of the bubbles during film formation was controlled such that the softening point between the contact position with the stabilizing plate and the pinch roller reached -40°C or higher. The film-forming properties and physical properties of the film obtained by the following evaluation method are shown in Table 2.

[0056] (Film-forming properties: Bubble stability) When a film is formed by blow molding, the horizontal swaying of the bubble tip at the point where the molten bubble has completed expansion is visually evaluated according to the following standards: ○: The bubble hardly moves; ○△: The bubble sways slightly and repeatedly along the TD direction, unstable; △: The bubble sways significantly and repeatedly along the TD direction, unstable. (Film-forming properties: Bubble porosity) When a film is formed by blow molding, the appearance of the bubbles composed of molten resin extruded from the die is visually evaluated according to the following standards: ○: No pores on the bubble; ○△: Small pores are sparsely produced on the bubble; △: Many small pores are produced on the bubble (venting from inside the bubble affects the bubble shape); ×: A large number of pores are produced on the bubble, making continuous film formation impossible. (Film-forming properties: Film wrinkles) The relaxation and wrinkles (transverse wrinkles) in the TD direction of the obtained film are visually evaluated according to the following standards. ○: No looseness or wrinkles are seen on the membrane; ○△: Blurry wrinkles are visible on the membrane; △: Multiple blurry wrinkles are visible on the membrane, and looseness is also visible; △×: Multiple blurry wrinkles and clear wrinkles are visible on the membrane, and looseness is also visible; ×: Multiple clear wrinkles are visible on the membrane, and looseness is also visible.

[0057] (Physical Property: Tensile Strength) According to ASTM D882, using an autograph AGS-500NX (manufactured by Shimadzu Corporation), at a tensile speed of 12.5 mm / min, with the fixture distance set to 125 mm, a 190 mm × 15 mm sample was measured. The measurement temperature was 23°C. It should be noted that both the flow direction (MD direction) and width direction (TD direction) of the membrane were measured. (Physical Property: Relative Permittivity, Dielectric Loss Tangent) Using a cavity resonator (10 GHz resonator manufactured by AET Corporation) and a network analyzer (MS46122B manufactured by Anritsu Corporation), at an environment of 23°C and 65% RH, the relative permittivity and dielectric loss tangent were measured at a frequency of 10 GHz. It should be noted that both the flow direction (MD direction) and width direction (TD direction) of the membrane were measured.

[0058]

[0059] As shown in Table 2, in the liquid crystal polyester films of Examples 1 to 12, which contain amorphous copolyesters with glass transition temperatures of 80 to 200°C, the following results were observed: the opening of bubbles extruded from the die and horizontal sloshing could be suppressed, the film could be formed stably, and a smooth film without relaxation and wrinkles was obtained. Furthermore, in the liquid crystal polyester films of Examples 1 to 12, the following results were observed: film processing properties were improved, and the excellent mechanical and electrical properties of thermoplastic liquid crystal polyesters were maintained.

[0060] On the other hand, in the liquid crystal polyester film of Comparative Example 1, which contained polyarylate as an amorphous polymer, although it showed some effect in terms of bubble stability and bubble opening, it resulted in film relaxation and transverse wrinkles, and a smooth film was not obtained. This result shows that using an amorphous copolyester with a glass transition temperature of 80~200°C is crucial for improving the sliding properties of bubbles near the softening point.

[0061] The resin compositions of Comparative Examples 2 to 4, which use a polymer alloy comprising polyurethane resin, polyetherimide resin, and polyethylene terephthalate resin as an amorphous polymer, showed some effect in terms of bubble stability and bubble opening, but resulted in the formation of many relaxations and transverse wrinkles in the film, yielding films that were difficult to evaluate in terms of physical properties. Furthermore, in Reference Example 10, where the film was formed solely from thermoplastic liquid crystal polyester, many openings were formed on the bubbles, making continuous film formation impossible, and no film was obtained. Industrial Applicability

[0062] As described above, the liquid crystal polyester film obtained by the present invention exhibits excellent mechanical properties, electrical properties, dimensional stability, and heat resistance, and is used for electrical insulation applications in motors and transformers, as well as for forming film applications in flexible solar cells. It can also be used in acoustic fields such as surface protective films and vibrating plates. The metal laminate film of the present invention can also be used in circuit boards, capacitors, electromagnetic shielding materials, etc. The circuit board of the present invention can be used for various transmission lines and antennas (e.g., microwave or millimeter-wave antennas), and can also be used in antenna devices in which antennas and transmission lines are integrated.

Claims

1. A liquid crystal polyester resin composition, characterized in that it comprises a thermoplastic liquid crystal polyester (A) and an amorphous copolyester (B), wherein the glass transition temperature of the amorphous copolyester (B) is above 80°C and below 200°C, and the mixing ratio of the thermoplastic liquid crystal polyester (A) to the amorphous copolyester is (A):(B) = 50~99.5% by weight: 0.5~50% by weight.

2. The liquid crystal polyester resin composition as claimed in claim 1, characterized in that the thermoplastic liquid crystal polyester (A) comprises at least one of the constituent units of p-hydroxybenzoic acid and constituent units of 6-hydroxy-2-naphthoic acid.

3. The liquid crystal polyester resin composition as claimed in claim 1, characterized in that the amorphous copolyester (B) comprises constituent units derived from terephthalic acid monomers and constituent units derived from 1,4-cyclohexanediethanol.

4. The liquid crystal polyester resin composition as claimed in claim 1, characterized in that the amorphous copolyester (B) comprises constituent units from terephthalic acid monomers, constituent units from 1,4-cyclohexanediethanol and constituent units from 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

5. The liquid crystal polyester resin composition as claimed in claim 1, characterized in that the thermoplastic liquid crystal polyester (A) has a melting point of 250°C or higher.

6. The liquid crystal polyester resin composition as claimed in claim 1, characterized in that the resin composition is used for blow molding.

7. A liquid crystal polyester film, characterized in that it is formed from any one of claims 1 to 6.

8. A metal laminate film, characterized in that a metal layer is laminated on one or both sides of the liquid crystal polyester film described in claim 7.

9. A circuit board having at least one conductor layer and the liquid crystal polyester film of claim 7.