TW202408783A - Stretched liquid crystal polymer film, laminate, circuit substrate, and method for manufacturing liquid crystal polymer film - Google Patents

Abstract

A liquid crystal polymer film is provided, which is a liquid crystal polymer film composed of a liquid crystal polymer, in which the surface roughness Ra of at least one side measured by a laser microscope is 0.5 μm or less.

Description

Stretched liquid crystal polymer film, laminate, circuit substrate, and method for manufacturing liquid crystal polymer film

The present invention relates to a stretched liquid crystal polymer film, a laminate, a circuit substrate, and a method for manufacturing the liquid crystal polymer film.

With the advancement of mobile communication technology, the frequency used in communication is also moving towards high frequency as communication speed and capacity increase. In the fifth generation mobile communication system, the 3.7GHz band and 4.5GHz band of the Sub6 band and the 28GHz band of the millimeter wave band are used, and in the sixth generation mobile communication system, the frequency band in the range of 90GHz~300GHz has been reviewed. The higher the frequency of the signal flowing in the circuit, the greater the transmission loss will be, so circuits and circuit materials with less transmission loss are required.

Since devices used in mobile communications such as smartphones are required to be smaller and lighter, flexible printed circuit boards (FPCs) that are lightweight and can be bent freely are used. FPC is composed of conductors such as copper wires that can communicate signals and insulating materials that hold them, and uses a lightweight and flexible polymer film as the insulating material. In addition to the heat resistance required for continuous use in high-temperature environments, the polymer film is also required to have low dielectric constant and loss tangent in order to suppress transmission loss when high-frequency signals flow (for example, Non-Patent Document 1).

As polymer films with low dielectric constant and low loss tangent used in FPC, there are polyimide films and liquid crystal polymer films. However, although polyimide films are excellent in heat resistance and flexibility, they suffer from water absorption. The rate is high, and the dimensional change rate for moisture absorption is also high, so the connection reliability in circuits with fine pitch patterns is low. Therefore, current efforts are being made to develop FPC using a liquid crystal polymer film that has excellent heat resistance, low water absorption, and a small dimensional change rate.

Liquid crystal polymers have the property of easily aligning molecules in the direction of their flow. The melt extrusion method, a general method for producing films, melts the polymer and extrudes it from a T-shaped die to form a film. Therefore, the liquid crystal polymer of the film produced by this method will be extruded in the length direction of the film. Molecular alignment. Therefore, in the film produced by this method, the film physical properties (strength, linear expansion coefficient, etc.) are greatly different in the longitudinal direction of the film and the direction perpendicular thereto, resulting in a state in which the so-called anisotropy is large. On the other hand, FPC is manufactured by laminating a copper foil on a polymer film, or applying copper plating to a polymer film to stack a metal layer, and then etching or the like to form a wiring pattern or the like. At this time, if the expansion rates (linear expansion coefficients) of the polymer film and the metal layer are different, the insulating film and the metal layer may peel off due to temperature changes, or the FPC may warp, etc., thereby creating holes in the FPC. After processing, defects such as hole position deviation will occur. Therefore, if a liquid crystal polymer film with large anisotropy is used as the insulating material of FPC, the linear expansion coefficient will be greatly different depending on the direction, and the above-mentioned disadvantages will easily occur.

As a method of reducing the anisotropy of polymer films such as polyethylene terephthalate (PET) films, a film that is perpendicular to the molecular alignment is used, for example, above the glass transition temperature of the polymer film and below the melting point. A method of stretching a film in one direction. However, the tensile strength of the liquid crystal polymer film extruded from the T-shaped die is significantly low, especially in the direction perpendicular to the molecular alignment. Therefore, at a temperature below the melting point of the liquid crystal polymer, the tensile strength in the direction perpendicular to the molecular alignment is It will easily break when stretched in the vertical direction.

Therefore, methods have been proposed, such as heating and pressurizing a liquid crystal polymer film extruded from a T-die between a pair of endless belts of a double-belt press (for example, Patent Document 1); or, extruding a liquid crystal polymer film into a cylindrical shape from an inflation die and blowing hot air into the film to expand it before the film is cooled and fixed (for example, Patent Document 2); heating and laminating porous polytetrafluoroethylene (PTFE) films on both sides of the liquid crystal polymer film extruded from a T-die, and stretching the liquid crystal polymer film in a direction perpendicular to the longitudinal direction at a temperature above the melting point of the liquid crystal polymer film (for example, Patent Document 3), etc.

In addition, the signal flowing through the conductor will flow through the surface of the conductor due to the skin effect. The higher the frequency, the more it becomes. For example, the skin depth δ of a signal flowing in a conductor becomes as shown in the following formula (1) (for example, if the magnetic permeability of the conductor is μ, the electrical conductivity is σ, and the signal frequency of the flowing conductor is f Patent document 2). In addition, when copper is used as a conductor, μ is set to 5.90×10 ⁷ (H/m), and σ=1.26×10 ^-6 (S/m), and the skin depth of f from 1 GHz to 300 GHz is obtained. When δ, it will become as shown in Figure 1. At 3.7GHz in the Sub6 frequency band used in the fifth generation mobile communication system, the skin depth δ is about 1.1μm, but at 28GHz in the millimeter wave band, the skin depth δ is about 0.4μm. Therefore, the greater the depth of the concave and convex on the surface of the conductor, and the shorter the interval between the concavities and convexes, even if the conductor is of the same length, the signal flow distance will become longer, thus increasing the transmission loss. Therefore, the conductor surface is required to be highly smooth, and the conductor surface of FPC used in the millimeter wave frequency band (approximately 30~300GHz) that will be used in future mobile communication systems requires a surface roughness Ra of less than 0.5 μm.

Furthermore, the smoothness of the conductor surface will also affect the smoothness of the polymer film surface on which the conductor is layered. In particular, when a metal layer is formed on the surface of a polymer film by evaporation, electroplating, or electroless plating to form an FPC, the polymer film is required to have the same degree of smoothness as the conductor. As a method for improving the smoothness of a polymer film, for example, when a metal layer is formed on the surface of a polymer film by electroless plating, in order to reduce the surface roughness of the polymer film surface and improve the adhesion with the metal layer, a method can be cited. However, this method requires that the contact time with the mixture of alkaline aqueous solution and pentanol be prolonged when the surface roughness of the polymer film is large, resulting in undesirable conditions such as reduced production efficiency and reduced strength of the film. Therefore, it is desired to have a liquid crystal polymer film with a small surface roughness even without such treatment. [Prior art literature] [Non-patent literature]

Non-patent document 1: Yukio Matsushita et al., "Substrate materials for high-speed transmission", Journal of the Electronic Equipment Installation Society, Vol. 4, No. 7, page 551, 2001 Non-patent document 2: Nakata Omiya et al., Fukuda Technical Report (October 2021) [Patent Document]

Patent document 1: Japanese Patent No. 6930046 Patent document 2: Japanese Patent No. 6656231 Patent document 3: Japanese Patent No. 3958629

[The problem that the invention wants to solve]

In the conventional method of extruding a liquid crystal polymer film into a cylindrical shape from a blow die and blowing hot air into the film before the film is cooled and fixed, although the anisotropy of the liquid crystal polymer can be eliminated, the uneven film thickness or the unevenness of the film surface will also increase due to the uneven temperature of the film during expansion. In addition, in the method of heating a porous polytetrafluoroethylene (PTFE) film on both sides of the liquid crystal polymer film extruded from a T-die and laminating them at the same time, and stretching the liquid crystal polymer film in a direction perpendicular to the longitudinal direction at a temperature above the melting point of the liquid crystal polymer, it is difficult to control the thickness of the film because the film is stretched at a temperature above the melting point of the liquid crystal polymer, and the unevenness of the surface of the porous PTFE will be transferred to the liquid crystal polymer film, so the smoothness is poor. Patent document 3 discloses a liquid crystal polymer film with a surface roughness Ra of less than 0.1μm, but it is measured by a contact-type surface roughness meter. The contact-type surface roughness meter makes the probe contact the surface of the film, tracks the surface and simultaneously detects the changes (displacement) in the up and down directions of the probe. Since the minimum diameter of the front end of the probe is about 2μm, it is impossible to measure the roughness of the unevenness of the interval smaller than this. Therefore, the contact-type surface roughness meter is not sufficient to evaluate the smoothness of the polymer film surface. When the liquid crystal polymer film described in Patent document 3 is used in FPC, there is a concern that the transmission loss of high-frequency signals will increase.

The purpose of the present invention is to provide a liquid crystal polymer film with high smoothness, which, when used as an insulating material of an FPC, can provide an FPC with less transmission loss when a high-frequency signal is circulated, especially when a metal layer is formed on the surface by evaporation, electroplating, or electroless plating. [Means for solving the problem]

As a result of careful examination of liquid crystal polymer films that have low transmission loss when high-frequency signals flow and have high smoothness, the inventors found that by appropriately controlling the surface roughness measured by a laser microscope , a liquid crystal polymer film with excellent smoothness that can even reflect fine unevenness on the surface of the film can be obtained, and the present invention has been completed.

[1] That is, according to the first aspect of the present invention, there is provided a stretched liquid crystal polymer film, which is a stretched liquid crystal polymer film composed of a liquid crystal polymer, wherein at least one unit measured by a laser microscope is The surface roughness Ra of the surface is 0.5 μm or less.

[2] According to a second aspect of the present invention, a stretched liquid crystal polymer film is provided, which is a stretched liquid crystal polymer film composed of a liquid crystal polymer, wherein at least one side is measured by a laser microscope. The greater of the surface roughness Ra (MD) in the longitudinal direction of the film and the surface roughness Ra (TD) in the width direction of the film is less than 0.7 μm, and the difference between the aforementioned Ra (MD) and the aforementioned Ra (TD) The absolute value is less than 0.15μm.

[3] According to the third aspect of the present invention, a stretched liquid crystal polymer film as in the first or second aspect is provided, wherein in the polar point measurement using X-ray diffraction, when the film is tilted at 45° (α=45° in the Schulz method), the film is rotated in the in-plane direction (β direction) and the diffraction intensity of the 110-plane is measured, and the longitudinal direction of the film is set to β=0°, and β=45~135°, 135°~22 5°, 225~315°, 315~45°, the sum of the integrated strength of β=45~135° and the integrated strength of β=225°~315° is set as the integrated strength in the length direction, and the sum of the integrated strength of β=135~225° and the integrated strength of β=315~45° is set as the integrated strength in the width direction, the plane orientation degree shown in the following formula (2) is greater than -0.5 and less than 0.5; Plane orientation degree = (integrated strength in the length direction - integrated strength in the width direction) / (integrated strength in the length direction + integrated strength in the width direction)   (2).

[4] According to the fourth aspect of the present invention, a method for manufacturing a stretched liquid crystal polymer film is provided, which has: On at least one side of an unstretched liquid crystal polymer film made of a liquid crystal polymer, a support film made of a support polymer and with a surface roughness Ra of 1.5 μm or less as measured by a laser microscope is bonded. The first step to obtain the laminated film; The second step of stretching the aforementioned laminated film in at least the width direction; and, The third step is to peel off the stretched support film.

[5] According to the fifth aspect of the present invention, a method for manufacturing a stretched liquid crystal polymer film is provided, which has: The molten liquid crystal polymer and support polymer are extruded using an extruder to form a film in such a manner that a layer composed of the support polymer is laminated on at least one side of the layer composed of the liquid crystal polymer. The first step of obtaining the laminated film; The second step of stretching the aforementioned laminated film in at least the width direction; and, The third step is to peel off the stretched layer composed of the aforementioned support polymer.

[6] According to the sixth aspect of the present invention, a method for manufacturing a stretched liquid crystal polymer film as in the fourth aspect is provided, wherein the first step comprises: before bonding the support film to the unstretched liquid crystal polymer film, applying surface treatment to the bonding surface of the unstretched liquid crystal polymer film and the bonding surface of the support film.

[7] According to the seventh aspect of the present invention, a method for manufacturing a stretched liquid crystal polymer film as in the sixth aspect is provided, wherein the surface treatment is selected from the group consisting of plasma treatment, corona treatment, and chemical treatment.

[8] According to the eighth aspect of the present invention, a method for manufacturing a stretched liquid crystal polymer film as in any one of aspects 4 to 7 is provided, wherein the aforementioned second step comprises: stretching at a temperature lower than the melting point of the aforementioned liquid crystal polymer.

[9] According to the 9th aspect of the present invention, a method for manufacturing a stretched liquid crystal polymer film as in any one of the 4th or 6th to 8th aspects is provided, wherein in the aforementioned second step, the stretching load calculated by multiplying the tensile stress of the aforementioned supporting film at the temperature during stretching by the cross-sectional area of the aforementioned supporting film is greater than the tensile load calculated by multiplying the tensile stress of the aforementioned unstretched liquid crystal polymer film at the temperature during stretching by the cross-sectional area of the aforementioned unstretched liquid crystal polymer film.

[10] According to the tenth aspect of the present invention, a method for manufacturing a stretched liquid crystal polymer film of the fifth aspect is provided, wherein in the second step, the stretching load calculated by multiplying the tensile stress of the layer composed of the aforementioned supporting polymer at the temperature during stretching by the cross-sectional area of the layer composed of the aforementioned supporting polymer is greater than the tensile load calculated by multiplying the tensile stress of the layer composed of the aforementioned liquid crystal polymer at the temperature during stretching by the cross-sectional area of the layer composed of the aforementioned liquid crystal polymer.

[11] According to the 11th aspect of the present invention, a method for producing a stretched liquid crystal polymer film as in any one of the 4th to 10th aspects is provided, wherein the supporting polymer is an aromatic polyether ketone or a polyester.

[12] According to the twelfth aspect of the present invention, a method for producing a stretched liquid crystal polymer film as in the eleventh aspect is provided, wherein the aforementioned polyester is at least one polymer selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate.

[13] According to a thirteenth aspect of the present invention, there is provided a laminate including a film layer including the stretched liquid crystal polymer film of any one of the first to third aspects, and a metal layer.

[14] According to the 14th aspect of the present invention, a circuit substrate is provided, which has a multilayer body as in the 13th aspect. [Effect of the invention]

The surface roughness Ra of at least one side of the stretched liquid crystal polymer film of the present invention measured by a laser microscope is 0.5 μm or less when used as an insulating material for FPC and when high-frequency signals are passed through. The transmission loss is reduced, and high-speed and large-capacity communication can be achieved.

＜Liquid crystal polymer film＞

The stretched liquid crystal polymer film of the present invention is a film composed of liquid crystal polymer. The liquid crystal polymer is not particularly limited, but a liquid crystal polyester that exhibits thermotropic liquid crystal properties and has a melting point of 250°C or higher, preferably 280°C to 380°C, is preferred. Examples of such a liquid crystal polyester include aromatic polyesters that exhibit liquid crystallinity when melted and are synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids. Specific examples include the condensation polymer of ethylene terephthalate and p-hydroxybenzoic acid, the condensation polymer of phenol and phthalic acid and p-hydroxybenzoic acid, and the condensation polymer of 2,6-hydroxynaphthoic acid and p-hydroxybenzoic acid. Condensation polymers, etc. In particular, from the viewpoint of excellent mechanical properties, electrical properties, heat resistance, etc., 6-hydroxy-2-naphthoic acid and its derivatives are used as the basic structure, and have at least one selected from the group consisting of p-hydroxybenzoic acid, terephthalic acid, Isophthalic acid, 6-naphthalene dicarboxylic acid, 4,4'-bisphenol, bisphenol A, hydroquinone, 4,4-dihydroxybisphenol, ethylene terephthalate and their derivatives A group of at least one aromatic polyester-based liquid crystal polymer as a monomer component is preferred. In addition, the liquid crystal polyester system may be used individually by 1 type, or 2 or more types may be used in arbitrary combinations and ratios.

The liquid crystal polyester can be synthesized by a known method and is not particularly limited. For example, melt polymerization, melt acidolysis, slurry polymerization, etc. can be applied. When these polymerization methods are applied, conventional methods can also be followed for acylation or acetylation.

The liquid crystal polymer may also include polymers such as fluororesins, polyolefins, polycyclic olefins, or higher fatty acids, higher fatty acid esters, and higher Release improvers for fatty acid amide and higher fatty acid metal salts, colorants for dyes, pigments, carbon black, etc., organic fillers, inorganic fillers, hollow particles, antioxidants, thermal stabilizers, light stabilizers, and ultraviolet absorbers Additives such as agents, flame retardants, lubricants, anti-charging agents, surfactants, anti-rust agents, foaming agents, defoaming agents, fluorescent agents, etc. These polymers or additives may be included in the molten resin composition during film formation of the liquid crystal polymer film. Moreover, each of these polymers or additives may be used individually by 1 type, or 2 or more types may be used in arbitrary combinations and ratios. The content of the polymer or additive is not particularly limited. From the viewpoint of molding processability, thermal stability, etc., it is preferably 0.01 to 50 mass %, more preferably 0.1 to 40 mass %, based on the total amount of the liquid crystal polymer film. More preferably, it is 0.5~30 mass %. These polymers, additives, etc. may be added to the liquid crystal polymer in advance, or may be added to the liquid crystal polymer when the stretched liquid crystal polymer film described below is formed.

The stretched liquid crystal polymer film of the present invention has a surface roughness Ra of one or both sides measured by a laser microscope of 0.5 μm or less. The surface roughness Ra referred to in the present invention specifically refers to the arithmetic mean roughness of the film surface measured by a non-contact method based on the confocal principle that the amount of reflected light becomes maximum when the focus is converged (focused).

Figure 2(a) is a comparison of the unevenness measured by a contact-type surface roughness meter and a laser microscope. Figure 2(b) is a comparison of the unevenness measured by a contact-type surface roughness meter and a laser microscope. A picture of the concave and convex sizes of tiny intervals.

As shown in Figure 2(a), regarding the concave and convex (concave part) of the interval (W ₁ ) that the probe (N) of the contact-type surface roughness meter can enter, the size (depth) of the concave and convex measured by the contact-type surface roughness meter (D ₁ -N) and the size (D ₁ -L) of the concave and convex measured by the laser microscope (L) are roughly the same size. Therefore, it is believed that when the surface (S ₁ ) of the measurement object mainly has concave and convex of this interval, the surface roughness values measured by each method will not have a large difference.

However, as shown in Figure 2(b), when there are irregularities with very small intervals ( _{W2) on the surface (S2 )} of the measurement object, the width of the contact surface roughness measuring instrument is larger than the width of the irregularities. , and cannot enter the interior of the concavity. Therefore, the contact type surface roughness measuring device will cause the measured unevenness at small intervals to be smaller than the actual value (D ₂ -N) or be ignored, so that the surface roughness value will be smaller than the actual value. On the other hand, measurement using a laser microscope can measure the exact size of the bumps (D ₂ -L) because the laser can also penetrate into the concavities and convexes at minute intervals. Therefore, compared with the conventional contact-type surface roughness measurement, surface roughness measurement using a laser microscope enables accurate surface roughness evaluation that reflects the uneven shape of finer intervals. In particular, since high-frequency signals can also produce such finely spaced irregularities, in order to reduce the transmission loss of high-frequency signals when using liquid crystal polymer films for FPC, the measured values of the liquid crystal polymer films measured by a laser microscope are controlled. Surface roughness is extremely important.

The surface roughness Ra of at least one side of the stretched liquid crystal polymer film of the present invention measured by a laser microscope is below 0.5μm. When the film is bonded to a conductor to manufacture a laminate, the interface between the film and the conductor becomes smooth and the transmission loss when a high-frequency signal is circulated is suppressed, so that the communication speed and capacity of the laminate can be achieved. Moreover, the surface roughness Ra can be measured along any direction of the surface of the stretched liquid crystal polymer film. That is, as long as the surface roughness Ra measured along any direction is below 0.5μm, it is better to have the average of the surface roughness Ra measured multiple times along any direction be below 0.5μm. Furthermore, it is preferred that the surface roughness Ra measured along the length direction (MD) or the width direction (TD) of the film is less than 0.5 μm, and it is more preferred that both the surface roughness Ra (MD) measured along the length direction and the surface roughness Ra (TD) measured along the width direction are less than 0.5 μm. In particular, it is preferred that the average of the surface roughness Ra (MD) measured multiple times along the length direction is less than 0.5 μm, and the average of the surface roughness Ra (TD) measured multiple times along the width direction is less than 0.5 μm. Furthermore, when conductors are bonded to both sides of the stretched liquid crystal polymer film, it is preferred that the surface roughness Ra of both sides of the stretched liquid crystal polymer film measured by a laser microscope is less than 0.5 μm from the viewpoint of suppressing the transmission loss of the two conductors. The surface roughness Ra of the stretched liquid crystal polymer film is preferably below 0.4μm in any direction and on any surface, and particularly preferably below 0.2μm. As long as Ra is below 0.2μm, the accumulation depth of the 90GHz signal tested by the 6th generation mobile communication system when flowing on the copper surface will be lower than 0.22μm, thereby reducing transmission loss.

In addition, the stretched liquid crystal polymer film of the present invention can suppress the transmission loss of high-frequency signals as described above by having the larger of the surface roughness Ra(MD) in the longitudinal direction and the surface roughness Ra(TD) in the width direction on at least one side being less than 0.7 μm, and the absolute value of the difference between the surface roughness Ra(MD) and the surface roughness Ra(TD) being less than 0.15 μm. In addition, by the circuit substrate manufacturing method described below, when manufacturing a circuit substrate using the stretched liquid crystal polymer film of the present invention, since the conductor formed on the film in the non-wiring portion can be removed with a small amount of etching, and the influence of etching on the wiring portion can be reduced, a circuit substrate forming a precision circuit can be manufactured. In such a stretched liquid crystal polymer film, the larger of the surface roughness Ra (MD) and the surface roughness (TD) is less than 0.7 μm, preferably less than 0.5 μm, more preferably less than 0.4 μm, and more preferably less than 0.2 μm. In addition, the absolute value of the difference between the surface roughness Ra (MD) and the surface roughness Ra (TD) is less than 0.15 μm, preferably less than 0.1 μm, and more preferably less than 0.05 μm. Moreover, the surface roughness Ra (MD) and the surface roughness Ra (TD) can satisfy the above relationship as long as the values obtained by measuring at least once on one side of the stretched liquid crystal polymer film meet the above relationship, but it is preferred that the average of the surface roughness Ra (MD) and the average of the surface roughness Ra (TD) obtained by measuring multiple times satisfy the above relationship. In addition, regarding both sides of the stretched liquid crystal polymer film, it is preferred that the surface roughness Ra (MD) and the surface roughness Ra (TD) satisfy the above relationship.

The anisotropy of the molecular orientation of the stretched liquid crystal polymer film is preferably within a specified range as specified below. First, in the extreme point measurement using X-ray diffraction, the stretched liquid crystal polymer film is tilted at 45° (α=45° in the Schulz method) and rotated in the in-plane direction (β direction). Simultaneously measure the diffraction intensity of 110 surfaces to produce an X-ray diffraction intensity distribution map. In this distribution diagram, set the length direction of the film to β=0°, find the integrated intensity of β=45~135°, 135°~225°, 225~315°, and 315~45°, and set β=45 The sum of the integrated intensity at ~135° and the integrated intensity at β=225°~315° is set as the integrated intensity in the length direction. Furthermore, the sum of the integrated intensity at β=135~225° and the integrated intensity at β=315~45° is the integrated intensity in the width direction. At this time, the plane alignment degree represented by the following formula (3) is preferably -0.5 or more and 0.5 or less. The plane alignment degree is preferably -0.3 or more and 0.3 or less, more preferably -0.2 or more and 0.2 or less. Surface alignment = (Integrated intensity in the length direction - Integrated intensity in the width direction) / (Integrated intensity in the length direction + Integrated intensity in the width direction) (3)

The diffraction intensity of the 110 plane refers to the diffraction intensity of the crystallographic plane (110 plane) of the liquid crystal polymer. For example, the diffraction intensity of the 110-plane liquid crystal polymer obtained by condensation polymerization of 2,6-hydroxynaphthoic acid and p-hydroxybenzoic acid at a molar ratio of 73 to 27 means that the diffraction angle (2θ) is at 10° When measuring X-ray diffraction in the range of ~40°, the maximum diffraction intensity observed at 2θ=20°. The diffraction intensity of the (110 plane) of the liquid crystal polymer aligned in the length direction is set to β=0° in the length direction of the film. Since β=90° and 270° will become the largest, β=45 The sum of the integrated intensity of ~135° and the integrated intensity of β=225°~315° is set as the integrated intensity in the length direction. The sum of the integrated intensity of β=135~225° and the integrated intensity of β=315~45° is set as is the integrated intensity in the width direction. The integrated intensity is calculated using the area when β is represented as the horizontal axis and the diffraction intensity is represented as the vertical axis. If the value shown in the above formula (3) is a positive value, it means that the molecular chain is aligned in the length direction, and if it is a negative value, it means that the molecular chain is aligned in the width direction.

Since the anisotropy of the linear expansion coefficient of the stretched liquid crystal polymer film of the present invention can be reduced by having the value of the plane alignment degree represented by the above formula (3) between -0.5 and -0.5, the stretched liquid crystal polymerization When a physical film and copper are laminated to form an FPC, deformation caused by differences in linear expansion coefficients can be suppressed. In particular, this effect becomes more remarkable when the stretched liquid crystal polymer film is subjected to heat treatment (described later). The value of the plane alignment degree is preferably -0.2~0.2. If it is within this range, the linear expansion coefficient of the stretched liquid crystal polymer film can be made to be about 10~30ppm in both the length direction and width direction of the film, and by The value of the plane alignment degree is set to -0.1~0.1, and the linear expansion coefficient will be a value close to the copper branch line expansion coefficient of 18ppm.

＜Production method of stretched liquid crystal polymer film＞ The method for producing the stretched liquid crystal polymer film of the present invention will be described below. The stretched liquid crystal polymer film of the present invention is formed by laminating supporting polymer films on both sides of the unstretched liquid crystal polymer film so as to adhere closely to each other (the first step). After stretching the laminated film ( Step 2), peeling off the supporting polymer film (Step 3).

The unstretched liquid crystal polymer film used in the first step can be manufactured by a known method. For example, the liquid crystal polymer can be formed into a film by using a T-die melt extrusion film-making method (T-die melt extrusion) to form an unstretched liquid crystal polymer film. Specifically, the unstretched liquid crystal polymer film can be obtained by melt-kneading the liquid crystal polymer with an extruder, extruding the molten resin through a T-die, and solidifying it on a metal roller. The cylinder temperature of the extruder is preferably 230~360℃, and more preferably 280~350℃. The slit spacing of the T-die can be appropriately set according to the type and composition of the liquid crystal polymer used, the performance of the target film, etc. There is no particular limit to the slit spacing of the T-type die, but 0.1~1.5mm is preferred, and 0.1~1.0mm is more preferred.

The thickness of the unstretched liquid crystal polymer film obtained by the above method is not particularly limited. From the perspective of operability or productivity during T-die melt extrusion molding, 10 to 500 μm is preferred, 20 to 300 μm is more preferred, and 30 to 250 μm is even more preferred.

The supported polymer film is a film that is layered on the unstretched liquid crystal polymer film to prevent the film from breaking when the unstretched liquid crystal polymer film is stretched. As supporting polymers constituting the supported polymer film, aromatic polyether ketones or polyesters can be cited. Specific examples of aromatic polyether ketones include polyether ketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ether ketone ketone (PEEKK), etc. Specific examples of polyesters include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), etc. These polymers can be used alone or in combination of two or more. Among them, polyether ether ketone (PEEK), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT) are preferred. Furthermore, in terms of high heat resistance and the ability to be stretched at high temperatures, the films are preferably crystallized or stretched films.

The surface roughness Ra of the supporting polymer film measured by a laser microscope is preferably 1.5 μm or less, more preferably 1.0 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less. By making the surface roughness of the supporting polymer film within the above range, the surface roughness Ra of the obtained stretched liquid crystal polymer film measured by a laser microscope can be controlled to be less than 0.5 μm.

In the case of laminating unstretched liquid crystal polymer and supported polymer films, the supported polymer film can be laminated on only one side of the unstretched liquid crystal polymer film or on both sides. However, from the viewpoint of being able to control the surface roughness Ra of both sides of the obtained stretched liquid crystal polymer film to be below 0.5 μm, and from the viewpoint of reducing undesirable conditions such as breakage of the stretched liquid crystal polymer film when the laminated film formed by laminating the unstretched liquid crystal polymer film and the supported polymer film is stretched in the width direction (TD) in the second step described later, lamination on both sides is preferred.

The method of laminating the unstretched liquid crystal polymer film and the supporting polymer film is not particularly limited, but the thermal lamination method is preferable from the viewpoint that no adhesive or the like is required. The thermal lamination method uses a pair of heated rollers to heat the laminated film of the unstretched liquid crystal polymer film and the support polymer film, and press the unstretched liquid crystal polymer film and the support polymer film simultaneously. The conditions of the thermal deposition method can be appropriately selected according to the physical properties of the liquid crystal polymer and the supporting polymer. It is not particularly limited, but it is preferable to perform heating and pressure bonding at a temperature near the melting point of the liquid crystal polymer and at a temperature near the melting point of the supporting polymer.

In the case where it is difficult to adhere the unstretched liquid crystal polymer film and the support film only by thermal lamination, the unstretched liquid crystal polymer film and the support polymer film must be bonded together before laminating them. It is preferable that the surface in contact with the supporting polymer film (laminated surface) and the surface of the supporting polymer film in contact with the unstretched liquid crystal polymer film (laminated surface) be subjected to surface treatment respectively. Examples of surface treatment methods include plasma treatment in which electric energy is supplied to the surface to create a gas in a plasma state, corona treatment in which the surface is activated by electric discharge, and activation by irradiating the surface with ultraviolet rays or electron beams. methods, methods of activating the surface in contact with flame, chemical treatment of surface oxidation using potassium dichromate, etc., primer treatment of applying primer, etc. By performing such surface treatment before laminating the unstretched liquid crystal polymer film and the support polymer film, the adhesion between the unstretched liquid crystal polymer film and the support polymer film can be improved. The surface treatment method can be appropriately selected according to the physical properties of the liquid crystal polymer and the support polymer, so as to improve the adhesion between the unstretched liquid crystal polymer film and the support polymer film and reduce the obtained stretched liquid crystal polymerization. From the perspective of damage to the physical film, plasma treatment, corona treatment, and chemical treatment are better, especially plasma treatment.

Furthermore, as a method of improving the adhesion between the unstretched liquid crystal polymer film and the support polymer film, another method is to provide an easy-adhesion film made of a polyester resin material on the surface of the support polymer film. layer methods, etc.

Next, as a second step, the laminated film in which the unstretched liquid crystal polymer film and the supporting polymer film are laminated is stretched in the width direction (TD). By stretching the laminated film in the width direction, the anisotropy of the obtained stretched liquid crystal polymer film can be reduced. The method of stretching the laminated film is not particularly limited, but a tenter transverse stretching method is preferred, in which both ends of the laminated film are held with a clip and heated and stretched. Regarding the stretching ratio and stretching speed, the support film is appropriately selected so that the stretched shape and physical properties of the film composed of the liquid crystal polymer can be within a desired range. The stretching ratio is preferably 1.5 to 10 times, and more preferably 2 to 5 times. The stretching speed is preferably 1~5000%/min, and more preferably 50~2500%/min. In addition, in order to adjust the degree of plane alignment after stretching, stretching in the longitudinal direction (MD) may be added as necessary.

The temperature when stretching the laminated film is preferably in the range of 50 to 350°C, preferably less than the melting point of the liquid crystal polymer, and even more preferably 30 to 200°C lower than the melting point of the liquid crystal polymer. It is best to make the temperature 80~200℃ lower than the melting point of the liquid crystal polymer. By setting the temperature when stretching the laminated film to a temperature that is less than the melting point of the liquid crystal polymer, the smoothness of the obtained stretched liquid crystal polymer film can be improved, and it can also be produced without uneven thickness or streaks and with excellent film forming properties. . Furthermore, it is preferable to set the temperature when stretching the laminated film to be higher than the glass transition temperature of the liquid crystal polymer because the unstretched liquid crystal polymer film becomes easier to stretch.

Furthermore, during stretching of the laminated film, the total of the tensile loads applied to the two supporting polymer films laminated on both sides of the unstretched liquid crystal polymer film is such that the unstretched liquid crystal polymer film becomes The method above the additional tensile load is better. Here, the tensile load refers to the load added to the film when the film is stretched, and the tensile stress on the film multiplied by the cross-sectional area of the film.

By creating a method in which the total tensile load added to the two supporting polymer films during stretching of the laminated film becomes greater than the tensile load added to the unstretched liquid crystal polymer film, even if the liquid crystal polymerization is not fully completed, The temperature of the melting point of the liquid crystal polymer can still be stretched without breaking the unstretched liquid crystal polymer film. The reason for this is not clear, but it is thought to be due to the fact that the support polymer film, which has a higher tensile load than the unstretched liquid crystal polymer film, is in close contact with the unstretched liquid crystal polymer film and is added to the liquid crystal polymer film. The tensile load is dispersed, thereby suppressing stress concentration on parts that are prone to fracture.

In addition, in order to achieve a method in which the total tensile load added to the two supporting polymer films becomes greater than the tensile load added to the unstretched liquid crystal polymer film, the unstretched liquid crystal polymer film can be appropriately selected. This is achieved by the ratio of the thickness to the thickness of the supporting polymer film, the material and surface roughness of the supporting polymer film, as well as the temperature and stretching speed during stretching. For example, the material supporting the polymer film can be selected in accordance with the temperature during stretching, which is determined by the type of liquid crystal polymer.

In addition, when using a laminated film in which a support polymer film is laminated on only a single surface of an unstretched liquid crystal polymer film, the stretching load added to one support polymer film becomes the load applied to the unstretched liquid crystal. The laminated film can be stretched using a method above the tensile load of the polymer film.

From the viewpoint of being able to well adjust the relationship between the tensile load applied to the supporting polymer film and the tensile load applied to the unstretched liquid crystal polymer film, the thickness ratio of the supporting polymer film to the unstretched liquid crystal polymer film is In terms of the ratio of "the thickness of one support polymer film/the thickness of the unstretched liquid crystal polymer film", it is preferably 0.01 to 10.0, more preferably 0.1 to 1.0, and more preferably 0.2 to 0.8. .

Finally, as a third step, the stretched liquid crystal polymer film can be obtained by peeling off the supporting polymer film of the stretched laminated film.

In the third step, after the supporting polymer film is peeled off, the stretched liquid crystal polymer film may be heat treated in a range from -50°C of its melting point to its melting point. In this way, the heat resistance of the liquid crystal polymer film may be improved and the linear expansion coefficient may be reduced.

In addition, in the first step of the above method, a laminated film is obtained by laminating a film composed of a liquid crystal polymer and a film composed of a support polymer, but the method of obtaining the laminated film is not particularly limited thereto. . For example, a first extruder can be used to melt the liquid crystal polymer, and a second extruder can be used to melt the support polymer, and a layer composed of the liquid crystal polymer can be polymerized by the support on one or both sides of the layer. A laminated film is formed by extruding individual polymers into a film shape (co-extrusion).

As a method of laminating a layer composed of a support polymer on one or both sides of a layer composed of a liquid crystal polymer, a method of forming a multilayer extruded film from a T-shaped die can be used. Specifically, for example, molten liquid crystal polymer and support polymer supplied from two extruders are supplied to a feed-block and merged, and then extruded from a T-shaped die into a film shape. Feeding port method; multi-manifold method (multi-manifold method), which supplies the melted liquid crystal polymer and support polymer to a T-shaped mold respectively, and repeatedly extrudes them into a film shape. From the viewpoint of improving the smoothness of the obtained stretched liquid crystal polymer film, it is better to apply the multi-manifold method, taking into account the difference in viscosity or flow characteristics of the liquid crystal polymer and the support polymer when melted.

In the first step, when the liquid crystal polymer and the support polymer are separately extruded into a film shape to form a laminated film, in the second step, the tensile load added to the layer composed of the support polymer will It is preferable to stretch the laminated film in a manner that exceeds the tensile load added to the layer composed of the liquid crystal polymer.

＜Laminated body＞ The laminated body of the present invention includes the above-mentioned film layer composed of a stretched liquid crystal polymer film, and a metal layer. Examples of the metal material constituting the metal layer include gold, silver, copper, iron, nickel, aluminum, and alloy metals thereof. Copper is preferably used.

The laminated body can be produced by a known method as long as the smoothness and anisotropy of the stretched liquid crystal polymer film can be maintained. For example, a laminate may be produced by evaporating a metal layer on the surface of a stretched liquid crystal polymer film, or a metal layer may be formed on the surface of a stretched liquid crystal polymer film by electroless plating or electroplating. In addition, the stretched liquid crystal polymer film and the metal foil can also be bonded together by using a roll-to-roll method or a continuous isostatic pressing method (double-belt method), such as copper foil, and Hot pressing is performed continuously to produce a laminated body. Furthermore, the laminated body can also be manufactured using surface-activated bonding in which the surfaces of the stretched liquid crystal polymer film and metal foil are activated by removing oxides or stains by sputter etching or the like, and The stretched liquid crystal polymer film and the metal foil are brought into contact and rolled together.

<Circuit board> The circuit board of the present invention has: the above-mentioned insulator (or dielectric) and conductor layer composed of stretched liquid crystal polymer film. The shape of the circuit board is not particularly limited, and it can be used as various high-frequency circuit boards by known means. The circuit board can also carry semiconductor components such as IC chips.

The circuit pattern can be formed on the conductor layer of the circuit substrate by known processing methods. Examples of metal materials constituting the conductor layer include gold, silver, copper, iron, nickel, aluminum, and alloy metals thereof. Furthermore, a circuit pattern may be formed on the metal layer of the above-mentioned laminated body by a known method.

As a method for manufacturing a circuit board having a circuit pattern formed thereon, there can be specifically exemplified a conventionally known method such as a modified semi-additive process (MSAP process), a semi-additive process (SAP process), or a subtractive process. For example, in the case of the SAP process, electroless copper plating is applied to an insulator formed of a stretched liquid crystal polymer film as a conductor layer, a non-wiring portion on the conductor layer is used as a mask, copper plating is applied to the unmasked portion to form an additional conductor layer, the mask is removed, and the conductor layer hidden by the mask is removed by etching, thereby manufacturing a circuit board. In addition, in the case of the MSAP process, a circuit board can be manufactured by laminating an extremely thin copper foil instead of electroless copper plating in the SAP process.

The manufacturing method of the circuit substrate such as the above-mentioned MSAP method and SAP method has the step of forming a circuit by removing the conductor of the non-wiring part of the conductor layer stacked on the film by etching. Since the conductor of the non-wiring part is not removed and remains on the film, it will become the cause of the circuit short circuit, so it is necessary to completely remove the conductor of the non-wiring part. Here, when using a film with a large surface roughness, the electroless copper plated copper layer (conductor layer) will enter the deep concave part of the film surface and become difficult to remove by etching. If an attempt is made to completely remove the conductor of the non-wiring part at a very deep part of the film and the etching is strengthened, there will be a problem that even the conductor of the wiring part will be etched. Furthermore, when the difference in surface roughness between the length direction (MD) and the width direction (TD) is large, in order to completely remove the conductor, it is necessary to perform etching in conjunction with the surface with the larger surface roughness. However, when etching is strengthened in conjunction with the surface with the larger surface roughness, there is a problem that the conductor of the wiring part in the direction with the smaller surface roughness is excessively etched, and the roughness of the wiring becomes uneven in MD and TD. Therefore, when a thin film with a large surface roughness or a large difference in surface roughness between MD and TD is used to manufacture a circuit substrate, the conductor of the wiring part is etched, and a problem that a precision circuit cannot be formed. In contrast, the surface roughness Ra of the stretched liquid crystal polymer film of the present invention measured by a laser microscope is controlled, so when a conductor layer is formed on the surface of the stretched liquid crystal polymer film and removed during the manufacture of a circuit substrate, it is not easy for the conductor to remain on the surface of the film. Therefore, according to the stretched liquid crystal polymer film of the present invention, since the conductor of the non-wiring portion formed on the film can be removed with a small amount of etching, and the influence of etching on the wiring portion is reduced, a circuit substrate with a precise circuit can be manufactured.

The circuit substrate of the present invention can be used in various transmission lines, such as coaxial lines, strip lines, microstrip lines, coplanar lines, parallel lines, etc., due to its property of low transmission loss when flowing high-frequency signals. road. Furthermore, the circuit board of the present invention can be used in an antenna and an antenna device in which the antenna and the transmission line are integrated.

Antennas include waveguide slot antennas, horn antennas, lens antennas, printed antennas, tri-plate antennas, microstrip antennas, patch antennas, etc., which utilize millimeter waves or microwaves. When the circuit substrate of the present invention is used as an antenna, it is preferred that the circuit substrate be a multi-layer circuit substrate.

The circuit substrate of the present invention can also be used as a sensor such as a vehicle-mounted radar having semiconductor components. [Example]

Next, the present invention is specifically described with reference to the embodiments, but the present invention is not limited thereto.

＜Film Formability＞ The produced stretched liquid crystal polymer film was visually evaluated for thickness unevenness, streaks, etc. The films obtained in Examples 10 to 14 were evaluated. ◎: No uneven thickness or streaks, good. ○: Although there is no thickness unevenness, slight streaks are observed. △: Uneven thickness or streaks are found. ×: Uneven thickness or large breakage.

<Melting point of film> Using a differential scanning calorimeter (manufactured by Perkin Elmer, model: DSC8500), the endothermic peak temperature observed when the temperature of the prepared stretched liquid crystal polymer film was raised from 0°C at 10°C/min was taken as the melting point.

＜Surface roughness of film (laser type)＞ Using a laser microscope equipped with a white interferometer (manufactured by Keyence Co., Ltd., model: VK-X3000), the surface roughness Ra of the support polymer film and the stretched liquid crystal polymer film was determined. By measuring the roughness curve in the visual field range of 1052 × 1404 μm, under the conditions of a measurement reference length of 0.25mm, an evaluation length of 1mm, a cutoff value λc of 0.25mm, (no cutoff value λs), and calculating the arithmetic average roughness degree to obtain the surface roughness Ra. Furthermore, the surface roughness Ra is obtained by calculating the individual longitudinal direction (MD) and width direction (TD) of the film for the front and back sides of the film.

＜Surface roughness of film (contact type)＞ Use a contact surface roughness measuring instrument (manufactured by Tosei Engineering Co., Ltd., model: (SURFCOM 1400D-3DF)) with a probe with a tip radius of 2 μm. According to JIS B0601:1994, the measurement length is 4 mm and the cutoff value λc is The surface roughness Ra of the stretched liquid crystal polymer film was determined at 0.8 mm. Hereinafter, in order to distinguish the surface roughness Ra determined by the laser type, the surface roughness determined by the contact type is described as Ra'. The surface roughness Ra' is calculated from the longitudinal direction (MD) and the width direction (TD) of the film on the front and back sides of the film respectively. The films obtained in Examples 10 to 14, Comparative Example 4, and Reference Example 1 were evaluated. .

<Surface orientation of film> For the stretched liquid crystal polymer film, a sample horizontal multi-purpose X-ray diffraction device (Rigaku Co., Ltd., model: Ultima IV) was used to fix the diffraction angle (2θ) at 20°, and the X-ray target: Cu, voltage: 40kV, current: 40mA, α angle = 45°, β angle = 0~360° (the length direction of the film was set to 0°, and the step angle was 5°) was used to perform pole measurement and produce the X-ray diffraction intensity distribution. The integrated intensity of β=45~135°, 135°~225°, 225~315°, and 315~45° of the distribution is obtained. The sum of the integrated intensity of β=45~135° and β=225°~315° is set as the integrated intensity in the length direction, and the sum of the integrated intensity of β=135~225° and β=315~45° is set as the integrated intensity in the width direction. The plane orientation is obtained from the following formula (4). The thin films obtained in Examples 1~14, Comparative Example 4, and Reference Example 1 are evaluated. Planar orientation = (integrated intensity in the length direction - integrated intensity in the width direction) / (integrated intensity in the length direction + integrated intensity in the width direction) (4)

＜Comparison of tensile load of films＞ Cut the unstretched liquid crystal polymer film sample into a sample with a width direction (TD) of 120mm and a length direction (MD) of 25mm. The sample is stretched in a tensile testing machine so that the direction becomes TD. (Tensilon A-500 manufactured by ORIENTEC Co., Ltd.) was set with a distance between the chucks of 20 mm, and the tensile test was conducted at the specified tensile temperature and tensile speed in each example and comparative example. From the results of the tensile test, an SS curve was obtained with the tensile stress at an elongation of 0mm~60mm (distance between chucks 20mm~80mm, 1~4 times) as the vertical axis and the elongation as the horizontal axis. The tensile stress of the unstretched liquid crystal polymer film is multiplied by the cross-sectional area of the unstretched liquid crystal polymer film, and the vertical axis of the SS curve of the unstretched liquid crystal polymer film is converted into tensile load. The support polymer film was similarly subjected to a tensile test to obtain an SS curve and convert it into a tensile load. For individual SS curves, compare the tensile load values of the unstretched liquid crystal polymer film and the supported polymer film under the same elongation in the range of elongation from 0mm to 60mm, and evaluate as follows. Furthermore, regarding Example 14 in which a laminated film is produced by co-extrusion of a liquid crystal polymer and a support polymer, a support polymer layer peeled off from the laminated film before stretching is used instead of the support polymer film. Similarly, Conduct a tensile test and evaluate the tensile load. ○: The entire range of elongation from 0mm to 60mm, The tensile load of the supporting polymer film or supporting polymer layer ≧ the tensile load of the unstretched liquid crystal polymer film ×: In the range of extension 0mm~60mm, There are cases where the tensile load of the supporting polymer film or the supporting polymer layer is less than the tensile load of the unstretched liquid crystal polymer film.

<Linear expansion coefficient of film> A stretched liquid crystal polymer film (5 mm in width) (15 mm between chucks) was placed in a thermomechanical analyzer (manufactured by Rigaku Electric Co., Ltd., model number: TMA8310), a load of 10 mN was applied, and the dimensional change was measured while heating from 30°C to 150°C at 5°C/min.

＜Etching removal performance＞ It is assumed that a circuit substrate is manufactured by the SAP method, and the etching removal performance of the metal layer formed on the stretched liquid crystal polymer film is evaluated according to the following procedure. First, the stretched liquid crystal polymer films tested in Examples 1 to 14 and Comparative Examples 3 and 4 were subjected to degreasing treatment, Pd-based catalyst imparting treatment, and activation treatment using a known electroless plating method. The surface of the thin film was electrolessly plated with copper to form a metal layer with a thickness of 1 μm to obtain a laminate. Next, an etching bath consisting of 35% hydrogen peroxide 4.5% by volume, 98% sulfuric acid 5% by volume, and 30 g/L of copper sulfate pentahydrate was prepared, and the laminated body was immersed in 30° C. to perform 1 μm etching. Use an optical microscope (500x) to confirm whether there is any residual copper on the surface of the stretched liquid crystal polymer film to evaluate the etching removal performance. The results are shown in Table 3. In addition, in Table 3, the larger one of the surface roughness Ra of MD and the surface roughness Ra of TD is shown as the maximum value. ◎: No residual copper on the surface of both sides ○: There is no copper residue on the surface of one side, but there is copper residue on the surface of the other side. ×: Copper remains on both sides.

<Example 1> Made of liquid crystal polymer (Polyplastics Co., Ltd.), LAPEROS A950RX ) is supplied to a twin-screw extruder (screw diameter 32mm), extruded from the T-shaped die at the front end of the extruder (lip length 350mm, lip gap approximately 1mm, die temperature 300°C) into a film shape, and then cooled to obtain Unstretched liquid crystal polymer film with a thickness of 75μm.

Secondly, for both sides of the unstretched liquid crystal polymer film and the polyether ether ketone (PEEK) film as the supporting polymer film (made by Victrex, APTIV Film 1000-025G, thickness 25 μm, surface roughness Ra= 0.14 μm (MD) , 0.12μm (TD)) single surface is subjected to direct atmospheric pressure plasma treatment at a power of 1.5kW and a conveying speed of 1.0m/min in a gas environment containing oxygen. Then, the individual plasma treated surfaces are stacked, using the first roller heated to 305°C and the second roller heated to 120°C, under the conditions of nip pressure 0.2MPa and conveying speed 0.5m/min, without stretching. The two sides of the stretched liquid crystal polymer film are thermocompressed and bonded to the PEEK film. After thermocompression bonding, the unstretched liquid crystal polymer film and the PEEK film are closely adhered.

From the laminated film produced in this way, a sample having a width direction (TD) of 150 mm and a length direction (MD) of 150 mm was cut out. The sample was installed in a tensile testing machine (50 mm between chucks) with the tensile direction TD. After preheating at 100°C for 5 minutes in a constant temperature bath, it was tested at a tensile speed of 2500%/min. Stretch to 3 times (distance between chucks 150mm). Thereafter, the PEEK film was peeled off to obtain a stretched liquid crystal polymer film with a thickness of 25 μm, and the melting point, surface roughness Ra, plane alignment, and etching removal performance were evaluated. The results are shown in Table 1 and Table 3.

Regarding the above-mentioned unstretched liquid crystal polymer film and PEEK film, as a tensile load comparison, after preheating at 100°C for 5 minutes (stretching temperature 100°C), the stretching speed was 2500%/min, and the SS curve was measured. When the tensile load of the unstretched liquid crystal polymer film and the tensile load of the PEEK film are compared by the above method, as shown in Figure 3, the tensile load of the PEEK film is higher than the tensile load of the liquid crystal polymer film. Figure 3 is a graph comparing the tensile load of the unstretched liquid crystal polymer film and the tensile load of the PEEK film in Example 1.

<Examples 2~6> Except that the supporting polymer film, stretching temperature, and stretching speed were changed to those described in Table 1, the same operation was performed as in Example 1 to obtain a liquid crystal polymer stretched film and evaluated in the same manner. The results are shown in Table 1 and Table 3.

<Example 7> The same conditions as in Example 1 were used except that a biaxially stretched PBT film (Boblet, manufactured by Kojin Film & Chemical Co., Ltd., thickness 25 μm) was used as the supporting polymer film, and the temperature of the first roller during thermocompression bonding was set to 200°C. A liquid crystal polymer stretched film was obtained in the same manner and evaluated in the same manner. The results are shown in Table 1 and Table 3.

<Example 8> In addition to replacing the PEEK film with a biaxially stretched PET film with an easy-adhesive layer (Toyobo, A4300, thickness 38 μm), no plasma treatment was performed on the surface of the unstretched liquid crystal polymer and the biaxially stretched PET film. The liquid crystal polymer stretched film was obtained in the same manner as in Example 7 except that the first roll temperature was 200° C. and thermocompression bonding was performed. The liquid crystal polymer stretched film was obtained and evaluated in the same manner. After thermocompression bonding, the unstretched liquid crystal polymer film and the biaxially stretched PET film are closely adhered. Evaluation results of stretched liquid crystal polymer films are shown in Table 1 and Table 3.

<Example 9> In addition to the single side of the unstretched liquid crystal polymer film and the polyether ether ketone (PEEK) film as the supporting polymer film (made by Victrex, APTIV Film 1000-025G, thickness 50 μm, surface roughness Ra=0.14 μm (MD) , 0.12μm (TD)) single surface, direct atmospheric pressure plasma treatment is carried out in a gas environment containing oxygen, with a power of 1.5kW and a conveying speed of 1.0m/min. Then, the individual plasma treated surfaces were stacked, and the first roller heated to 305°C and the second roller heated to 120°C were used to draw the undrawn parts under the conditions of nip pressure 0.2MPa and conveying speed 0.5m/min. The same operation was performed as in Example 3, except that one side (surface) of the stretched liquid crystal polymer film was thermocompression-bonded to the PEEK film to produce a two-layer laminated film of an unstretched liquid crystal polymer film and a support polymer film. A stretched liquid crystal polymer film was obtained and evaluated in the same manner. The results are shown in Table 1 and Table 3.

<Example 10> Using the same method as in Example 1, a laminated film in which PEEK films were thermocompression-bonded on both sides of an unstretched liquid crystal polymer film was produced.

The laminated film thus prepared was stretched 3 times in the width direction (TD) at a conveying speed of 15 m/min (stretching speed 2500%/min, reaching stretching temperature 170°C) using a transverse stretching machine of tentering mode (furnace temperature 320°C), and the PEEK film was peeled off to obtain a stretched liquid crystal polymer film with a thickness of 25 μm. The reaching temperature of stretching refers to the temperature of the laminated film at the end of stretching. The film's film-forming properties, melting point, surface roughness Ra and Ra', surface orientation, and linear expansion coefficient were evaluated. In addition, the film was heat treated at 250°C for 24 hours, and the linear expansion coefficient was evaluated. Furthermore, for the unstretched liquid crystal polymer film and PEEK film used in this embodiment, the stretching load at the stretching temperature and stretching speed in this embodiment was measured and evaluated. The results are shown in Table 1 and Table 3.

<Examples 11~12> In addition to setting the conveying speed to 5m/min (stretch speed 833%/min, reaching stretching temperature 240°C) and 1m/min (stretching speed 167%/min, reaching stretching temperature 290°C), the other systems A stretched liquid crystal polymer film was obtained in the same manner as in Example 10. The film's film forming properties, melting point, surface roughness Ra and Ra', plane alignment, linear expansion coefficient, tensile load, and etching removal performance were evaluated. The results are shown in Table 1 and Table 3.

<Example 13> It was obtained in the same manner as in Example 11 except that a polyetheretherketone (PEEK) film (manufactured by Shin-Etsu Polymer, thickness 25 μm) with surface roughness Ra of 0.96 μm (MD) and 1.04 μm (TD) was used. Stretched liquid crystal polymer film with a thickness of 25μm. The film's film forming properties, melting point, surface roughness Ra and Ra', plane alignment, linear expansion coefficient, tensile load, and etching removal performance were evaluated. The results are shown in Table 1 and Table 3.

<Example 14> A liquid crystal polymer (LAPEROS A950RX manufactured by Polyplastics Co., Ltd.) was supplied to a double-screw extruder (screw diameter 32 mm) and melt-kneaded at 300°C. In addition, a polyetheretherketone (PEEK) polymer (VESTAKEEP 3300G manufactured by Daicel Evonik) was supplied to a single-screw extruder (screw diameter 40 mm) as a supporting polymer and melt-kneaded at 380°C. By supplying the molten polymers to a multi-manifold T-die, a layer composed of a supporting polymer is superimposed and extruded on both sides of a layer composed of a liquid crystal polymer, and then cooled to produce a layered film with a liquid crystal polymer layer of 75μm and supporting polymer layers of 25μm on both sides, for a total of 125μm.

The laminated film thus prepared was stretched 3 times in the width direction (TD) using a transverse stretching machine of the tentering method (furnace temperature 320°C) at a conveying speed of 5m/min (stretching speed 833%/min, reaching a stretching temperature of 240°C), and the PEEK film was peeled off to obtain a stretched liquid crystal polymer film with a thickness of 25μm. The film forming properties, surface roughness Ra and Ra', plane orientation, linear expansion coefficient, tensile load, and etching removal performance of the film were evaluated. The results are shown in Tables 1 and 3.

<Comparative Example 1> The same operation as Example 1 was performed to obtain an unstretched liquid crystal polymer film. A sample with a width direction (TD) of 150 mm and a length direction (MD) of 150 mm was cut from the film. Sample B was installed in a stretching tester (50 mm between chucks) in a way that the stretching direction was TD. After preheating at 150°C for 5 minutes in a constant temperature chamber, it was stretched to 3 times at a stretching speed of 2500%/min. However, the liquid crystal polymer film was broken, and the surface roughness Ra and plane orientation of the film could not be evaluated. The results are shown in Table 2.

＜Comparative example 2＞ An unstretched liquid crystal polymer film was obtained in the same manner as in Example 1. A porous polytetrafluoroethylene (PTFE) film with a thickness of 100 μm and a specific gravity of 1.9 was laminated on both sides of the unstretched liquid crystal polymer film, using a first roll heated to 305°C and a second roll heated to 120°C. The porous PTFE film was thermocompressed on both sides of the unstretched liquid crystal polymer film at a nip roller pressure of 0.2MPa and a conveying speed of 0.5m/min. From the laminated film produced in this way, a sample having a size of 150 mm in the width direction (TD) and 150 mm in the length direction (MD) was cut out. Install the sample in a tensile testing machine (50mm between chucks) with the tensile direction TD, preheat at 150°C for 5 minutes in a constant temperature bath, and then stretch at a speed of 2500%/min. to stretch to 3 times. As a result, although the porous PTFE film layer of the laminated film could be stretched, the liquid crystal polymer film layer was broken, and the surface roughness and plane alignment of the film could not be evaluated. The results are shown in Table 2.

For the above-mentioned unstretched liquid crystal polymer film and porous PTFE film, as a tensile load comparison, after preheating at 150°C for 5 minutes, they were stretched at a stretching speed of 2500%/min and the SS curve was measured. Next, when the tensile load of the unstretched liquid crystal polymer film and the tensile load of the porous PTFE film were compared using the above method, as shown in FIG4, the tensile load of the porous PTFE film was lower than the tensile load of the liquid crystal polymer film. FIG4 is a graph comparing the tensile load of the unstretched liquid crystal polymer film and the tensile load of the porous PTFE film in Comparative Example 2.

<Comparative Example 3> Except for changing the stretching temperature and stretching speed to those shown in Table 2, the same operation as in Comparative Example 2 was performed to stretch a film formed by laminating porous polytetrafluoroethylene (PTFE) films on both sides of an unstretched liquid crystal polymer film. Although the liquid crystal polymer film layer was not broken to obtain a stretched liquid crystal polymer film, the film had a large thickness unevenness and a surface roughness Ra greater than 0.5μm. The evaluation results of the melting point, surface roughness Ra and Ra', and the stretching load are shown in Table 2. In addition, the evaluation results of the etching removal performance are shown in Table 3.

＜Comparative Example 4＞ A stretched liquid crystal polymer film with a thickness of 25 μm was obtained in the same manner as in Example 11, except that a polyetheretherketone (PEEK) film with a surface roughness Ra exceeding 1.5 μm (manufactured by Shin-Etsu Polymer, thickness 25 μm) was used. . The surface roughness Ra of the film is higher than 0.5 μm. The evaluation results of the melting point, surface roughness Ra and Ra', plane alignment, linear expansion coefficient, and tensile load are shown in Table 2. In addition, the evaluation results of the etching removal performance are shown in Table 3.

<Reference Example 1> The melting point, surface roughness, and plane orientation of the unstretched liquid crystal polymer film with a thickness of 75 μm produced in Example 1 were measured. In addition, the film was heat treated at 250°C for 24 hours, and the linear expansion coefficient was evaluated. The results are shown in Table 2. In addition, the evaluation results of the etching removal performance are shown in Table 3.

As shown in Table 1, a film composed of a supporting polymer film having a surface roughness Ra of less than 1.5 μm is bonded to a film composed of a liquid crystal polymer to form a laminated film, and the film is stretched and then the supporting polymer film is peeled off to obtain the stretched liquid crystal polymer films of Examples 1 to 13, and a stretched liquid crystal polymer film of Example 14 is formed by overlapping and extruding a liquid crystal polymer and a supporting polymer through a T-die to form a laminated film, and the supporting polymer layer is stretched and then peeled off to obtain the stretched liquid crystal polymer film. Both have a surface roughness Ra of less than 0.5 μm and have good smoothness. In addition, the larger value of the surface roughness Ra(MD) in the longitudinal direction and the surface roughness Ra(TD) in the width direction of the stretched liquid crystal polymer film of Examples 1 to 14 is less than 0.7 μm, and the difference between the surface roughness Ra(MD) and the surface roughness Ra(TD) is less than 0.15 μm, and has good smoothness. In addition, as shown in Table 3, in Examples 1 to 14, there is no copper residue on the surface of at least one side of the stretched liquid crystal polymer film after etching of the laminate, and the etching removal performance is excellent.

Specifically, when comparing Examples 1 to 4 in which the stretching speed is set at 2500%/min and the stretching temperature is changed from 100°C to 250°C, the surface roughness Ra of the stretched liquid crystal film obtained at the stretching temperature of 100°C is the smallest 0.11 to 0.15 μm, but the plane orientation is as high as 0.25. The higher the stretching temperature, the larger the surface roughness Ra becomes, but the plane orientation becomes smaller. At the stretching temperature of 250°C, the surface roughness Ra becomes 0.21 to 0.3 μm, and the plane orientation becomes 0.1. Moreover, compared with Example 2 in which the stretching temperature is 150°C and the stretching speed is 2500%/min, Example 5 in which the stretching temperature is set at 150°C and the stretching speed is made as low as 50%/min, although the surface roughness Ra does not change significantly, the plane orientation becomes smaller. Furthermore, although the surface roughness Ra of Example 6 in which the stretching temperature was set to 280°C, the melting point of the liquid crystal polymer, increased to 0.26-0.32 μm, the plane orientation decreased to 0.01. It is believed that the lower the stretching temperature, the harder the film will be, the more stable the shape of the film after stretching, and the smaller the surface roughness Ra will be, but since the molecular motion is reduced, the molecular orientation (MD) before stretching is not easy to change, and the plane orientation increases.

In addition, even when a polymer other than PEEK is used as the support polymer (Examples 7 and 8), a stretched liquid crystal film can be obtained, and by using a support polymer film provided with an easy-adhesion layer, even if no electrolysis is performed, a stretched liquid crystal film can be obtained. A stretched liquid crystal film can also be obtained by surface treatment such as slurry treatment (Example 8). Furthermore, when only one side was made into a supporting polymer film (Example 9), the surface roughness Ra of the side where the supporting polymer was not laminated was large, but the surface roughness of the side where the supporting polymer was laminated was larger. Stretch laminated film with Ra of 0.5μm or less.

Even in the case of stretching using a tenter-type transverse stretching machine (Examples 10 to 12), the lower the stretching temperature and the higher the stretching speed, the smaller the surface roughness Ra and the smaller the plane alignment. get taller. In addition, the film forming properties of the film are also better as the stretching temperature is lower and the stretching speed is higher. It was found that the surface roughness Ra' of these films measured by a contact surface roughness meter was in the range of 0.09~0.15 μm. There was no difference between the surface roughness Ra measured by a laser microscope and the stretching temperature. , correlation of stretching speed. It is believed that it is difficult for a contact surface roughness meter to measure the correct surface roughness.

Even when a co-extruded film of a liquid crystal polymer and a supporting polymer (PEEK) is used, a stretched polymer film (Example 14) can be obtained. The surface roughness Ra of the stretched liquid crystal polymer film and the laminated film of the supporting polymer film (Example 13) stretched under the same conditions is almost the same.

On the other hand, as shown in Comparative Example 1 in Table 2, when a film composed only of an unstretched liquid crystal polymer was stretched, the film was broken and the surface roughness or plane alignment could not be evaluated.

As shown in Comparative Example 2, when the total tensile load of the supporting film is lower than the tensile load of the unstretched liquid crystal polymer film, the liquid crystal polymer film may be fractured during stretching.

As shown in Comparative Example 3, a stretched liquid crystal polymer film obtained by stretching a laminated film tightly adhered to a porous PTFE film at a temperature higher than the melting point of the liquid crystal polymer has a thickness measured with a contact surface roughness meter. Although the surface roughness Ra' is less than 0.5 μm, the surface roughness Ra measured by a laser microscope exceeds 0.5 μm. Furthermore, as shown in Comparative Example 4, even when a polyetheretherketone (PEEK) film is used as the supporting polymer film, a laminated film in which a polyetheretherketone film with a surface roughness Ra exceeding 1.5 μm is stretched and closely adhered At this time, the surface roughness Ra measured by a laser microscope still exceeds 0.5 μm.

Furthermore, as shown in Table 3, the surface roughness Ra exceeds 0.5 μm, and the larger value of the surface roughness Ra (MD) in the longitudinal direction and the surface roughness Ra (TD) in the width direction is 0.7 μm or more. In Comparative Examples 3 and 4, copper remained on both sides of the stretched liquid crystal polymer film after etching the laminate, and the etching removal performance was poor.

As shown in Reference Example 1, although the surface roughness Ra of the unstretched liquid crystal polymer film is less than 0.5 μm, the plane alignment degree is as high as 0.71. The linear expansion coefficient is -21.7 ppm in the length direction (MD) and -21.7 ppm in the width direction. (TD) became 80.3 ppm, and the anisotropy of the linear expansion coefficient became large.

[Figure 1] Figure 1 is a diagram showing the relationship between the frequency of the signal flowing on the surface of the copper foil and the skin depth of the circulating signal. [Figure 2] Figure 2(a) is a comparison of the unevenness measured by a contact type surface roughness meter and a laser microscope. Figure 2(b) is a comparison of the size measured by a contact type surface roughness meter. A diagram showing the size of bumps and convexes at minute intervals measured by a laser microscope. [Fig. 3] Fig. 3 is a graph comparing the tensile load of the unstretched liquid crystal polymer film and the tensile load of the PEEK film in Example 1 of the embodiment of the present invention. [Fig. 4] Fig. 4 is a graph comparing the tensile load of the unstretched liquid crystal polymer film and the tensile load of the porous PTFE film in Comparative Example 2.

Claims (14)

A stretched liquid crystal polymer film is a stretched liquid crystal polymer film composed of a liquid crystal polymer, in which the surface roughness Ra of at least one side measured by a laser microscope is 0.5 μm or less. A stretched liquid crystal polymer film, which is a stretched liquid crystal polymer film composed of liquid crystal polymer, wherein the larger of the surface roughness Ra(MD) in the length direction and the surface roughness Ra(TD) in the width direction of the film measured by a laser microscope for at least one side is less than 0.7μm, and the absolute value of the difference between the aforementioned Ra(MD) and the aforementioned Ra(TD) is less than 0.15μm. The stretched liquid crystal polymer film of claim 1 or 2, wherein in the polar measurement using X-ray diffraction, the film is tilted to 45° (α=45° in the Schultz method). When rotating in the in-plane direction (β direction) and measuring the diffraction intensity of the 110 plane, set the length direction of the film to β=0° and find β=45~135°, 135°~225°, 225~315°, For the integrated intensity of 315~45°, let the sum of the integrated intensity of β=45~135° and the integrated intensity of β=225°~315° be the integrated intensity in the length direction, and set the integrated intensity of β=135~225°. When the sum of the integrated intensity with β=315~45° is taken as the integrated intensity in the width direction, the plane alignment degree shown in the following formula (1) is -0.5 or more and 0.5 or less; Surface alignment = (Integrated intensity in the length direction - Integrated intensity in the width direction) / (Integrated intensity in the length direction + Integrated intensity in the width direction) (1). A method for manufacturing a stretched liquid crystal polymer film comprises: A first step of laminating a supporting film composed of a supporting polymer and having a surface roughness Ra of 1.5 μm or less measured by a laser microscope on at least one side of an unstretched liquid crystal polymer film composed of a liquid crystal polymer to obtain a laminated film; A second step of stretching the laminated film at least in the width direction; and, A third step of peeling off the stretched supporting film. A method for manufacturing a stretched liquid crystal polymer film, which has: The molten liquid crystal polymer and support polymer are extruded using an extruder to form a film in such a manner that a layer composed of the support polymer is laminated on at least one side of the layer composed of the liquid crystal polymer. The first step of obtaining the laminated film; The second step of stretching the aforementioned laminated film in at least the width direction; and, The third step is to peel off the stretched layer composed of the aforementioned support polymer. A method for manufacturing a stretched liquid crystal polymer film as claimed in claim 4, wherein the aforementioned step 1 comprises: before laminating the aforementioned support film to the aforementioned unstretched liquid crystal polymer film, applying surface treatment to the laminating surface of the aforementioned unstretched liquid crystal polymer film and the laminating surface of the aforementioned support film. The manufacturing method of stretched liquid crystal polymer film as claimed in claim 6, wherein The aforementioned surface treatment is one selected from the group consisting of plasma treatment, corona treatment, and chemical treatment. The method for manufacturing a stretched liquid crystal polymer film according to any one of claims 4 to 7, wherein The aforementioned second step includes: stretching at a temperature lower than the melting point of the aforementioned liquid crystal polymer. The method for manufacturing a stretched liquid crystal polymer film according to any one of claims 4 or 6 to 7, wherein In the aforementioned second step, the tensile load calculated by multiplying the tensile stress of the aforementioned support film at the temperature at the time of stretching by the cross-sectional area of the aforementioned support film is calculated by multiplying the tensile stress at the temperature at the time of stretching. The tensile stress of the unstretched liquid crystal polymer film is equal to or more than the tensile load calculated by multiplying the cross-sectional area of the unstretched liquid crystal polymer film. The manufacturing method of stretched liquid crystal polymer film as claimed in claim 5, wherein In the aforementioned second step, the tensile load is calculated by multiplying the tensile stress of the layer composed of the aforementioned support polymer at the temperature during stretching by the cross-sectional area of the layer composed of the aforementioned support polymer. It is equal to or more than the tensile load calculated by multiplying the tensile stress of the layer composed of the liquid crystal polymer at the temperature during stretching by the cross-sectional area of the layer composed of the liquid crystal polymer. The method for manufacturing a stretched liquid crystal polymer film according to claim 4 or 5, wherein the supporting polymer is aromatic polyetherketone or polyester. A method for producing a stretched liquid crystal polymer film as claimed in claim 11, wherein the aforementioned polyester is at least one polymer selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. A laminate comprising: a film layer comprising a stretched liquid crystal polymer film as described in any one of claims 1 to 3, and a metal layer. A circuit board provided with the laminate according to claim 13.

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