TW202440747A - Thermoplastic liquid crystal polymer film, laminate, and production methods thereof - Google Patents

Abstract

A thermoplastic liquid crystal polymer film including a polymer capable of forming optically anisotropic melt phase, wherein at least one surface of the film shows pencil hardness within a range from 6B to H both in MD direction and TD direction, where the pencil hardness is standardized by JIS-K5600-5-4.

Description

Thermoplastic liquid crystal polymer film and laminate, and methods for producing the same

This application claims priority to Japanese Patent Application No. 2023-026541 filed in Japan on February 22, 2023, and the entirety of the application is incorporated herein by reference.

The present invention relates to a thermoplastic liquid crystal polymer film comprising a polymer capable of forming an optically anisotropic melt phase (hereinafter referred to as a thermoplastic liquid crystal polymer), a laminate having a conductive layer formed on at least one surface thereof, and methods for producing the same.

In recent years, in the field of electronic materials, the use of flexible circuit substrates including laminates of resin layers and metal layers has become increasingly widespread. Thermoplastic liquid crystal polymer films are known to be excellent materials with high heat resistance, low moisture absorption, high frequency characteristics, etc., and are attracting attention as electronic circuit materials for high-speed transmission. When thermoplastic liquid crystal polymer films are used for electronic circuit substrates, a conductor layer is formed on one or both sides of the film by bonding or pressing metal foils, dry and/or wet plating of metal layers, and coating of conductive inks, and circuit processing is performed. In addition, when making a multilayer circuit substrate with multiple circuits layered, thermoplastic liquid crystal polymer films are sometimes joined to each other.

In recent years, thermoplastic liquid crystal polymer films have been produced by extrusion molding methods including resins such as the T-die method or the inflation film method. However, during extrusion molding, a hard layer called a skin layer is formed on the surface of the film, which has a problem of reducing the adhesiveness when the thermoplastic liquid crystal polymer films are heat-pressed together. Therefore, various methods for improving the adhesiveness (press-bonding) of thermoplastic liquid crystal polymer films during press-bonding have been studied.

For example, Patent Document 1 (Japanese Patent Publication No. 2006-179609) describes a method for improving adhesion by performing chemical roughening treatment or plasma roughening treatment using an alkali mixed solution on at least one side of a thermoplastic liquid crystal polymer layer in a method for manufacturing a multilayer wiring substrate. In addition, Patent Document 2 (Japanese Patent Publication No. 2010-103269) describes a method for softening the surface of a thermoplastic liquid crystal polymer film by physical polishing or ultraviolet irradiation in a method for manufacturing a multilayer circuit substrate. [Prior Technical Document] [Patent Document]

Patent document 1: Japanese Patent Publication No. 2006-179609 Patent document 2: Japanese Patent Publication No. 2010-103269

[Problems to be solved by the invention]

However, the surface state of the thin film formed by plasma irradiation or ultraviolet irradiation changes over time, and also changes due to the chemical treatment used for etching the metal layer, so these steps need to be included in the steps of manufacturing the laminated circuit board. In addition, when the surface is made uneven by chemical treatment, there is a problem that the convex part of the surface that is flattened during lamination forms a new skin layer, and the adhesion of the interface is reduced. In addition, when the surface of the thin film is polished in order to physically remove the skin layer, the desired adhesion may not be obtained due to the change in the surface state caused by polishing.

When a thermoplastic liquid crystal polymer film or a metal-clad laminate having a metal foil bonded to a thermoplastic liquid crystal polymer film is press-bonded to another thermoplastic liquid crystal polymer film or metal foil, the bonding property can be improved by setting the temperature to a high level. However, in this case, the dimensional stability of the film is impaired, and there is a problem that the circuit has already been formed and the circuit has a deviation.

Therefore, the object of the present invention is to provide a thermoplastic liquid crystal polymer film that exhibits excellent adhesion to other thermoplastic liquid crystal polymer films or metal layers, a laminate containing such a thermoplastic liquid crystal polymer film, and a method for manufacturing the same. [Means for Solving the Problem]

The inventors of the present invention have made careful studies to achieve the above-mentioned purpose and have found that the compression-bonding property of the thermoplastic liquid crystal polymer film can be improved by rapidly heating the thermoplastic liquid crystal polymer film formed by extrusion molding to a prescribed temperature and maintaining the film at the highest temperature for a short time, and that the pencil hardness can be used as an indicator of the surface state of the thermoplastic liquid crystal polymer film with good compression-bonding property, thereby completing the present invention.

That is, the present invention can be constructed in the following aspects. [Aspect 1] A thermoplastic liquid crystal polymer film, which is a thermoplastic liquid crystal polymer film comprising a polymer that can form an optically anisotropic melt phase (hereinafter referred to as a thermoplastic liquid crystal polymer), wherein at least one surface of the film has a hardness in the range of 6B to H (preferably 4B to H, more preferably 2B to H) in both the MD direction and the TD direction using the pencil hardness test method specified in JIS-K5600-5-4. [Aspect 2] A thermoplastic liquid crystal polymer film as described in aspect 1, wherein the difference in hardness between the MD direction and the TD direction in the pencil hardness test method specified in JIS-K5600-5-4 of the aforementioned surface is 3 levels or less.

[Aspect 3] Thermoplastic liquid crystal polymer film as described in Aspect 1 or 2, wherein the aforementioned surface has a hardness of at least one of the hardness in the MD direction and the hardness in the TD direction of HB or less using the pencil hardness test method specified in JIS-K5600-5-4. [Aspect 4] Thermoplastic liquid crystal polymer film as described in any one of Aspects 1 to 3, wherein the melting point of the thermoplastic liquid crystal polymer film is 290°C or more.

[Aspect 5] The thermoplastic liquid crystal polymer film as described in any one of aspects 1 to 4, wherein the molecular orientation SOR is in the range of 0.95 to 1.10.

[Aspect 6] A laminated body, which is a laminated body of a thermoplastic liquid crystal polymer film as described in any one of aspects 1 to 5 and a conductive layer and/or other thermoplastic liquid crystal polymer films. [Aspect 7] A laminated body as described in aspect 6, wherein a layer composed of at least one selected from the group consisting of ink, metal film, metal foil and a circuit formed by these is formed on the aforementioned surface of the aforementioned thermoplastic liquid crystal polymer film as a conductive layer. [Aspect 8] A laminated body as described in aspect 6 or 7, which is a circuit substrate.

[Aspect 9] A method for producing a laminate, which comprises at least a step of heating a laminate of a thermoplastic liquid crystal polymer film containing a polymer capable of forming an optically anisotropic melt phase (hereinafter referred to as a thermoplastic liquid crystal polymer) and a support, raising the temperature to a maximum reaching temperature at 1.5 to 15°C/second, and maintaining the maximum reaching temperature for less than 60 seconds. [Aspect 10] A method for producing a laminate as described in aspect 9, wherein the maximum reaching temperature is greater than Tm and less than Tm+90°C relative to the melting point Tm of the thermoplastic polymer film. [Aspect 11] A method for producing a thermoplastic liquid crystal polymer film, which comprises a step of removing the support from the laminate obtained by the production method described in aspect 9 or 10. According to the above method, a thermoplastic liquid crystal polymer film as described in any one of the embodiments 1 to 5 can be manufactured.

Furthermore, any combination of at least two constituent elements disclosed in the patent application and/or the specification is included in the present invention. In particular, any combination of two or more claim items recorded in the patent application is included in the present invention. [Effect of the invention]

According to the present invention, a thermoplastic liquid crystal polymer film having excellent pressure-bonding properties, a laminate including the thermoplastic liquid crystal polymer film, and a simple method for manufacturing the same can be provided.

[Form used to implement the invention]

[Thermoplastic liquid crystal polymer film] Thermoplastic liquid crystal polymer film includes thermoplastic liquid crystal polymer. Thermoplastic liquid crystal polymer is composed of a melt-formable liquid crystal polymer (or a polymer that can form an optically anisotropic melt phase). As long as it is a melt-formable liquid crystal polymer, there is no particular limitation on its chemical composition. Examples include: thermoplastic liquid crystal polyester, or thermoplastic liquid crystal polyesteramide with amide bonds introduced therein. Thermoplastic liquid crystal polymer may also be a main chain type liquid crystal polymer having a rigid mesogen structure in the main chain of the polymer.

Furthermore, the thermoplastic liquid crystal polymer may be a polymer in which an imide bond, a carbonate bond, a carbodiimide bond, or a isocyanate bond or the like derived from isocyanate is further introduced into an aromatic polyester or an aromatic polyester amide.

As specific examples of the thermoplastic liquid crystal polymer used in the present invention, there can be cited well-known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyesteramides derived from the compounds classified into (1) to (4) and their derivatives as exemplified below. However, in order to form a polymer that can form an optically anisotropic melt phase, the combination of various raw material compounds is of course within an appropriate range.

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

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

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

(4) Aromatic diamine, aromatic hydroxyamine or aromatic aminocarboxylic acid (see Table 4 for representative examples) [Table 4]

As representative examples of thermoplastic liquid crystal polymers obtained from these raw material compounds, copolymers having the repeating units shown in Tables 5 and 6 can be cited.

[Table 5] [Table 6]

Among the copolymers, a copolymer containing at least p-hydroxybenzoic acid and/or 6-hydroxy-2-naphthoic acid as repeating units is preferred, and particularly preferred is (i) a copolymer containing repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, or (ii) a copolymer containing repeating units of at least one aromatic hydroxycarboxylic acid selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, at least one aromatic diol and/or aromatic hydroxyamine, and at least one aromatic carboxylic acid. The copolymers are main chain type thermoplastic liquid crystal polymers.

For example, in the copolymer of (i), when the thermoplastic liquid crystal polymer contains at least repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the molar ratio (A)/(B) of the repeating unit (A) of p-hydroxybenzoic acid to the repeating unit (B) of 6-hydroxy-2-naphthoic acid is preferably about (A)/(B)=10/90 to 90/10 in the thermoplastic liquid crystal polymer, more preferably (A)/(B)=15/85 to 85/15, and even more preferably (A)/(B)=20/80 to 80/20.

Furthermore, in the case of the copolymer of (i), in addition to the repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, from the viewpoint of adjusting the molecular weight, etc., a repeating unit composed of an aromatic diol or an aromatic dicarboxylic acid (e.g., terephthalic acid) may be contained.

In the case of the copolymer of (ii), the weight ratio of each of the thermoplastic liquid crystal polymers of at least one aromatic hydroxycarboxylic acid (C) selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, at least one aromatic diol (D) selected from the group consisting of 4,4'-dihydroxybiphenyl, hydroquinone, phenylhydroquinone, and 4,4'-dihydroxydiphenyl ether, and at least one aromatic dicarboxylic acid (E) selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid is 0.1% to 0.1%; The molar ratio of the complex units may be about (C): (D): (E): (35-10), more preferably (C): (D): (E) = (35-75): (32.5-12.5): (32.5-12.5), and even more preferably (C): (D): (E) = (40-70): (30-15): (30-15).

In addition, the molar ratio of the repeating unit derived from 6-hydroxy-2-naphthoic acid in the aromatic hydroxycarboxylic acid (C) may be, for example, 85 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more. In the aromatic dicarboxylic acid (E), the molar ratio of the repeating unit derived from 2,6-naphthalenedicarboxylic acid may be, for example, 85 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more.

Furthermore, the aromatic diol (D) may be repeating units (D1) and (D2) derived from two different aromatic diols selected from the group consisting of hydroquinone, 4,4'-dihydroxybiphenyl, phenylhydroquinone, and 4,4'-dihydroxydiphenyl ether. In this case, the molar ratio of the two aromatic diols may be (D1)/(D2)=23/77 to 77/23, preferably 25/75 to 75/25, and even more preferably 30/70 to 70/30.

The molar ratio of the repeating structural unit derived from the aromatic diol to the repeating structural unit derived from the aromatic dicarboxylic acid is preferably (D)/(E) = 95/100 to 100/95. If it is out of this range, the degree of polymerization will not increase and the mechanical strength tends to decrease.

Furthermore, the optically anisotropic molten phase mentioned in the present invention can be determined by, for example, placing a sample on a hot plate, heating it in a nitrogen environment, and observing the transmitted light of the sample.

The melting point (Tm ₀ ) of the thermoplastic liquid crystal polymer may be above 290°C, and may be, for example, preferably in the range of 300 to 380°C, more preferably in the range of 305 to 360°C, and even more preferably in the range of 310 to 350°C. Furthermore, the melting point of the thermoplastic liquid crystal polymer can be obtained by observing the thermal characteristics of the thermoplastic liquid crystal polymer sample using a differential scanning calorimeter. That is, the thermoplastic liquid crystal polymer sample is heated at a rate of 10°C/min, and after it is completely melted, the melt is cooled to 50°C at a rate of 10°C/min, and the position of the endothermic peak that appears after the temperature is again raised at a rate of 10°C/min is recorded as the melting point (Tm ₀ ) of the thermoplastic liquid crystal polymer sample.

In terms of melt moldability, the thermoplastic liquid crystal polymer may have a melt viscosity of, for example, 30 to 120 Pa·s at a shear rate of 1000/sec at (Tm ₀ +20)°C, and preferably 50 to 100 Pa·s.

The thermoplastic liquid crystal polymer film may also contain thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyetheretherketone, fluororesin, or various additives within the scope that does not impair the effect of the present invention. In addition, fillers such as organic fillers or inorganic fillers may also be included as needed. Therefore, the thermoplastic liquid crystal polymer film of the present invention contains a thermoplastic liquid crystal polymer as a main component, and also includes a film composed of a thermoplastic liquid crystal polymer composition containing any one or more of these heterogeneous polymers, additives, fillers, etc.

The thermoplastic liquid crystal polymer film may contain 50 wt % or more of the thermoplastic liquid crystal polymer, preferably 80 wt % or more, more preferably 90 wt % or more, more preferably 95 wt % or more, and even more preferably 98 wt % or more.

The thermoplastic liquid crystal polymer film can be a cast film of the above-mentioned thermoplastic liquid crystal polymer or thermoplastic liquid crystal polymer composition, or an extruded film formed by extruding the thermoplastic liquid crystal polymer or thermoplastic liquid crystal polymer composition. At this time, any extrusion molding method can be used, but the well-known T-type mold film stretching method, multilayer stretching method, inflation method, etc. are industrially advantageous. In particular, the inflation method not only applies stress to the mechanical axis direction of the thermoplastic liquid crystal polymer film (hereinafter referred to as MD direction), but also to the direction orthogonal to it (hereinafter referred to as TD direction). Because it can be uniformly extended in the MD direction and the TD direction, a thermoplastic liquid crystal polymer film with controlled molecular orientation, dielectric properties, etc. in the MD direction and the TD direction is obtained.

Furthermore, the thermoplastic liquid crystal polymer film can be stretched as needed after extrusion. The stretching method itself is well known, and either biaxial stretching or uniaxial stretching can be adopted, but biaxial stretching is preferred from the viewpoint of easier control of molecular orientation. Furthermore, the stretching can be performed using a well-known uniaxial stretching machine, a simultaneous biaxial stretching machine, a sequential biaxial stretching machine, etc.

Extrusion molding may be accompanied by stretching treatment in order to control the orientation. For example, in extrusion molding using the T-die method, the molten sheet extruded from the T-die can be stretched not only in the MD direction of the thermoplastic liquid crystal polymer film but also in both the TD direction to form a film. Alternatively, the molten sheet extruded from the T-die can be temporarily stretched in the MD direction and then stretched in the TD direction to form a film.

In addition, by extrusion molding using the inflation method, a cylindrical sheet melt-extruded from a ring die can be stretched at a specified stretch ratio (equivalent to the stretching ratio in the MD direction) and inflation ratio (equivalent to the stretching ratio in the TD direction) to form a film.

The biaxially stretched film using the T-die method or the inflation method can obtain a relatively isotropic molecular orientation in the film plane. For example, the thermoplastic liquid crystal polymer film can also be an orientation with a molecular orientation ratio (SOR) in the range of 0.95 to 1.10.

Furthermore, the "molecular orientation ratio SOR" mentioned here is an index of the degree of molecular orientation given to the chain segments of the constituent molecules. It is different from the conventional MOR (Molecular Orientation Ratio) and is a value that takes the thickness of the object into consideration. It is calculated as follows by the void resonance method.

First, using a known microwave molecular orientation measuring machine, a thermoplastic liquid crystal polymer film is inserted into the microwave resonance waveguide with the film facing perpendicular to the direction of microwave travel, and the electric field intensity of microwaves passing through the film (microwave transmission intensity) is measured.

Then, based on the measured value, the m value (referred to as the refractive index) is calculated by the following formula (1).

(Number 1) m = (Zo/△z)X[1-νmax/νo]…(1) (Here, Zo is the device constant, △z is the average thickness of the object, νmax is the frequency that gives the maximum microwave transmission intensity when the microwave frequency changes, and νo is the frequency that gives the maximum microwave transmission intensity when the average thickness is zero (that is, when there is no object).

Next, when the rotation angle of the object in the microwave vibration direction is 0°, that is, the microwave vibration direction and the direction of the best orientation of the molecules of the object (usually the long side direction of the extruded film), the m value that matches the direction that gives the minimum microwave transmission intensity is set as _m0 , and the m value when the rotation angle is 90° is set as _m90 , and the molecular orientation SOR is calculated by _m0 / _m90 .

The melting point (Tm) of the thermoplastic liquid crystal polymer film can be, for example, above 290°C, preferably 300-380°C, and more preferably 310-360°C. Furthermore, the melting point (Tm) of the thermoplastic liquid crystal polymer film can be obtained by observing the thermal characteristics of the thermoplastic liquid crystal polymer film sample using a differential scanning calorimeter. That is, the temperature is raised from room temperature (for example, 25°C) at a rate of 10°C/min, and after the thermoplastic liquid crystal polymer film sample is completely melted at 400°C, the melt is cooled to 50°C at a rate of 10°C/min, and the position of the endothermic peak that appears when the temperature is raised again at a rate of 10°C/min can be obtained as the melting point (Tm) of the thermoplastic liquid crystal polymer film. Furthermore, the short-time heat treatment used in the present invention hardly changes the domain structure or crystallinity of the thermoplastic liquid crystal polymer film, so the melting point of the film measured before the heat treatment is regarded as indicating the melting point of the film after the heat treatment.

The thickness of the thermoplastic liquid crystal polymer film can be appropriately set according to the application. For example, if the material is used as an insulating layer of a circuit substrate, the thickness can be 10 to 500 μm, preferably 15 to 250 μm, more preferably 20 to 200 μm, and even more preferably 25 to 150 μm.

[Heat treatment method of thermoplastic liquid crystal polymer film] In the present invention, the thermoplastic liquid crystal polymer film after film formation is heat treated to improve the adhesion between the film and the metal foil or other thermoplastic liquid crystal polymer film during press bonding. In order to maintain the shape stability of the film at high temperature, the heat treatment is preferably performed in a state where the film is laminated on a support. As a support, metal foils such as copper foil, stainless steel foil, and aluminum foil can be used. When bonding with a support, for example, the thermoplastic liquid crystal polymer film can be moved along a heated roller surface at a temperature lower than the above-mentioned melting point (for example, Tm-80 to Tm-5°C), and then a support (for example, a metal foil) can be temporarily bonded to one side at a low surface pressure (9kg/ ^cm2 to 40kg/ ^cm2 ) to form a laminate including the support and the thermoplastic liquid crystal polymer film.

Next, the thermoplastic liquid crystal polymer film can be heat-treated by heating the laminate. In the heat treatment, the film is preheated at a temperature lower than the melting point of the thermoplastic liquid crystal polymer film (e.g., Tm-80°C to Tm-30°C, e.g., 240 to 260°C) for a short time (e.g., less than 180 seconds, preferably 20 to 120 seconds), and then rapidly heated at an average heating rate of about 1.5 to 15°C/second, preferably 1.8 to 10°C/second, and more preferably 2 to 7°C/second to a maximum temperature (maximum temperature). Relative to the melting point Tm of the thermoplastic liquid crystal polymer film, the highest temperature reached at this time is above Tm and below Tm+90°C, preferably above Tm+20°C and below Tm+50°C, and may also be, for example, above Tm+30°C and below Tm+40°C. The holding time at the highest temperature reached is preferably set to be below 60 seconds, more preferably 2 to 40 seconds, and may also be, for example, 5 to 30 seconds.

The above heat treatment can be performed in a single-piece manner, using, for example, an infrared heat treatment device, etc., to perform non-contact heating, or can be performed in a roll-to-roll manner while conveying a laminate of the thermoplastic liquid crystal polymer film and the support.

The heat-treated laminate can be used directly as a single-sided metal-clad laminate, for example. Alternatively, the support can be peeled off or etched from the laminate and used as a thermoplastic liquid crystal polymer film monomer.

By the above heat treatment, the surface of the thermoplastic liquid crystal polymer film softens and the press-bonding property with the metal foil or the thermoplastic liquid crystal polymer film is improved. The film after the above heat treatment can be easily press-bonded with thermoplastic liquid crystal polymer films, which are difficult to press-bond, as long as the film is not subjected to the conventional treatments such as plasma irradiation, ultraviolet irradiation, surface grinding, etc.

[Pencil hardness of thermoplastic liquid crystal polymer film] The surface state of the thermoplastic liquid crystal polymer film after the above-mentioned heat treatment can be specified by the pencil hardness measured in accordance with JIS-K5600-5-4:1999. The thermoplastic liquid crystal polymer film of the present invention preferably has a pencil hardness in the range of 6B to H (that is, 6B < 5B < 4B < 3B < 2B < B < HB < F < H) on at least one surface in both the MD direction and the TD direction. Among them, 6B represents the softest and H represents the hardest pencil hardness. The pencil hardness can be 4B to H or 2B to H in both the MD direction and the TD direction. When the extruded thermoplastic liquid crystal polymer film is viewed in the MD direction, which is the winding direction, and the TD direction, which is orthogonal to it, at least one of the pencil hardnesses measured in the MD direction and the TD direction is preferably HB or less, and more preferably B or less. The difference in pencil hardness between the MD direction and the TD direction is preferably 3 levels or less (for example, when the pencil hardness of the MD direction and the TD direction is B, the other is any one of B, HB, F, and H, or any one of B, 2B, 3B, and 4B), and more preferably 2 levels or less.

[Laminate] The laminate of the present invention is a laminate comprising at least one layer of a thermoplastic liquid crystal polymer film subjected to the above-mentioned heat treatment. The laminate may also be a laminate having a metal layer formed on at least one surface as a conductive layer. The conductive layer may be a metal foil such as copper foil, copper alloy foil, stainless steel foil, aluminum foil, aluminum alloy foil, etc., which is pressed onto the surface of the thermoplastic liquid crystal polymer film. Alternatively, the metal layer may be formed on the surface by dry plating such as evaporation and sputtering, and/or wet plating. The conductive layer may also be a metal layer subjected to circuit processing. The conductive layer may be formed by using conductive ink containing metal particles to form a circuit pattern on the surface of the thermoplastic liquid crystal polymer film by drawing with a marker, drawing with an inkjet, or printing with screen printing.

The laminate may be a thermoplastic liquid crystal polymer film bonded together by compression. For example, the thermoplastic liquid crystal polymer film peeled off from the support body after the heat treatment may be bonded together by compression, or a single-sided metal-clad laminate and a thermoplastic liquid crystal polymer film, or single-sided metal-clad laminates may be bonded together on the thermoplastic liquid crystal polymer film surface.

In the case of the laminate of the present invention, the thermoplastic liquid crystal polymer film has excellent compression bonding properties, so the temperature during compression bonding can be Tm-40°C to Tm relative to the melting point Tm of the thermoplastic liquid crystal polymer film. The compression bonding temperature can be below Tm-5°C, or below Tm-10°C.

The above-mentioned laminate can be used as a circuit substrate material, especially as a laminate circuit substrate material. [Example]

[Preparation of Thermoplastic Liquid Crystal Polymer Film] [Reference Example 1] A copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 75/25) was heated and kneaded at 280-340°C using a uniaxial extruder, and then extruded from an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm, and a thermoplastic liquid crystal polymer film with a thickness of 50 μm was obtained by inflation (Reference Example 1). The melting point Tm of the thermoplastic liquid crystal polymer film of Reference Example 1 is 310°C. The melting point was obtained by observing the thermal properties of the film using a differential scanning calorimeter. That is, the film is heated at a rate of 10°C/min, and after it is completely melted at 400°C, the melt is cooled to 50°C at a rate of 10°C/min, and the position of the endothermic peak that appears after heating again at a rate of 10°C/min is taken as the melting point of the thermoplastic liquid crystal polymer film.

[Reference Example 2] The copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 80/20) was heated and kneaded at 280-340°C using a uniaxial extruder, and then extruded through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm, and a thermoplastic liquid crystal polymer film with a thickness of 50 μm was obtained by inflation (Reference Example 2). The melting point Tm of the thermoplastic liquid crystal polymer film of Reference Example 2 is 320°C.

[Reference Example 3] A copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 80/20) and 10 parts by weight of silicon dioxide particles were extruded by a uniaxial extruder and T-type molded film to obtain a thermoplastic liquid crystal polymer film with a thickness of 50 μm (Reference Example 3). The melting point Tm of the thermoplastic liquid crystal polymer film of Reference Example 3 is 320°C.

[Reference Example 4] The copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 73/27) was heated and kneaded at 280-340°C using a uniaxial extruder, and then extruded through an inflation die with a diameter of 40 mm and a slit spacing of 0.6 mm, and a thermoplastic liquid crystal polymer film with a thickness of 50 μm was obtained by inflation (Reference Example 4). The melting point Tm of the thermoplastic liquid crystal polymer film of Reference Example 4 is 280°C.

[Reference Example 5] The same procedure as Reference Example 4 was followed to obtain a thermoplastic liquid crystal polymer film with a thickness of 50 μm and a melting point of 280°C. The film was then subjected to a heat treatment to raise the melting point. During the heat treatment, the film surface temperature was fixed at 260°C for 4 hours, then fixed at 300°C for 6 hours, and the heat treatment was performed under two-stage temperature conditions. The melting point Tm of the thermoplastic liquid crystal polymer film obtained in Reference Example 5 was 335°C.

[Example 1] Next, the thermoplastic liquid crystal polymer film of Reference Example 1 and copper foil (JX Metal Co., Ltd.: JXEFL-BHM foil, thickness 12 μm) were laminated by a roll-to-roll method to obtain a laminate (single-sided copper-coated laminate) in which one side of the surface was the surface of the copper foil and the other side of the surface was the surface of the thermoplastic liquid crystal polymer film. First, the surface temperature of the heated metal roll was set to 280°C. Furthermore, the pressure applied to the TLCP film and the copper foil between the heat-resistant rubber roller and the heated metal roller was set to 40 kg/cm ² in terms of surface pressure. Under this condition, the TLCP film was moved along the heat-resistant rubber roller, and then the copper foil and the TLCP film were temporarily bonded.

The temporarily bonded laminate was subjected to heat treatment in an infrared heat treatment device (manufactured by Noritake Co., Limited, trade name: RtoR far infrared heating furnace) as a heat treatment means to produce the laminate of Example 1 (single-sided copper-clad laminate). The heat treatment was divided into a preheating zone, a heating zone, a maximum temperature zone, and a cooling zone, and the temperature measurement was set to the actual temperature of the sample. The preheating setting temperature was set to 250°C, and the actual temperature of the sample was adjusted to the heating rate shown in Table 7 by changing the temperature setting and zone width of the heating zone and the maximum temperature zone. The actual temperature is measured by connecting a thermocouple (φ0.2mm) and a 30m compensation wire (φ0.32mm) to the surface of the sample and transporting them with heat-resistant tape. The average heating rate from 250℃ to the maximum temperature (reaching the maximum temperature) is calculated from the actual temperature measurement results of the sample. The average heating rate, heating time, and maximum temperature holding time are shown in Table 7.

[Examples 2 to 5] Using the thermoplastic liquid crystal polymer film of Reference Example 2, the heat treatment conditions of the temporarily bonded laminate were changed as shown in Table 7. Otherwise, the laminates of Examples 2 to 5 (single-sided copper-clad laminates) were prepared in the same manner as in Example 1.

[Example 6] Using the thermoplastic liquid crystal polymer film of Reference Example 3, the heat treatment conditions of the temporarily bonded laminate were set to the conditions shown in Table 7. Other than that, the laminate of Example 6 (single-sided copper-clad laminate) was prepared in the same manner as Example 1.

[Comparative Example 1] In order to verify the difference from the thermoplastic liquid crystal polymer film that has not been heat-treated, the thermoplastic liquid crystal polymer film prepared in Reference Example 2 is used as Comparative Example 1.

[Comparative Example 2] Using the thermoplastic liquid crystal polymer film of Reference Example 1, the heat treatment conditions of the temporarily bonded laminate were set to the conditions shown in Table 7. Other than that, the laminate of Comparative Example 2 (single-sided copper-clad laminate) was prepared in the same manner as in Example 1.

[Comparative Example 3] Using the thermoplastic liquid crystal polymer film of Reference Example 4, the heat treatment conditions of the temporarily bonded laminate were set to the conditions shown in Table 7. Other than that, the laminate of Comparative Example 3 (single-sided copper-clad laminate) was prepared in the same manner as in Example 1.

[Comparative Examples 4-5] Using the thermoplastic liquid crystal polymer film of Reference Example 2, the heat treatment conditions of the temporarily bonded laminate were set to the conditions shown in Table 7. Except for this, the laminates of Comparative Examples 4 and 5 (single-sided copper-clad laminates) were prepared in the same manner as in Example 1.

[Comparative Example 6] Using the thermoplastic liquid crystal polymer film of Reference Example 5, the heat treatment conditions of the temporarily bonded laminate were set to the conditions shown in Table 7. Other than that, the laminate of Comparative Example 6 (single-sided copper-clad laminate) was prepared in the same manner as in Example 1.

[Determination of pencil hardness] When measuring the pencil hardness of the film surface of the single-sided copper-clad laminate obtained in Examples 1 to 6 and Comparative Examples 2 to 6, first, the copper foil is removed from each single-sided copper-clad laminate by etching to obtain a thermoplastic liquid crystal polymer film monomer. Then, the pencil hardness in the MD direction and the TD direction of the surface of the thermoplastic liquid crystal polymer film opposite to the surface on which the copper foil is etched is measured according to the pencil hardness test specified in JIS-K5600-5-4:1999. In addition, for Comparative Example 1, the pencil hardness in the MD direction and the TD direction of the surface of the thermoplastic liquid crystal polymer film is also measured according to the pencil hardness test specified in JIS-K5600-5-4:1999. During the measurement, a pencil hardness tester (MJ-PHT SATOTECH (registered trademark)) manufactured by Sato Shoji Co., Ltd. was used, and as the pencil for the test, a Mitsubishi pencil uni certified by the Japan Paint Inspection Association manufactured by Mitsubishi Pencil Co., Ltd. was used. Each thermoplastic liquid crystal polymer film sample was placed on a glass table, and the hardness of the hardest pencil that did not produce scratches caused by plastic deformation or cohesive fracture was recorded as the pencil hardness.

[Preparation of test laminate 1 (double-sided copper-clad laminate)] The surface temperature of the heated metal roller was set to 280°C. Furthermore, polyimide films (manufactured by KANEKA Co., Ltd., "APICAL" (registered trademark) 50μm) as protective materials were placed above and below between a pair of heated metal rollers to sandwich the laminated material. The surface of the thermoplastic liquid crystal polymer film side of the single-sided copper-clad laminate of Examples 1 to 6 and Comparative Examples 2 to 6 was overlapped with the roughened surface of a copper foil (JX EFL-BHM, 12 μm, manufactured by JX Metal Co., Ltd.) and laminated. The linear pressure was set to 4.2 kg/mm, and under this condition, the laminate sandwiched by the polyimide film was moved along a pair of heated metal rollers. The winding tension from the metal rollers was 10 N/mm2 or ^more , so that the copper foil and the thermoplastic liquid crystal polymer film surface were bonded to form a double-sided copper-clad laminate. Regarding the thermoplastic liquid crystal polymer film of Comparative Example 1, a copper foil was pressed onto one side under the same conditions as above to produce a single-sided copper-clad laminate.

[Preparation of test laminate 2] As test laminate 2, a laminate of two thermoplastic liquid crystal polymer films was prepared by heat pressing. Therefore, two samples were taken from the single-sided copper-clad laminates of Examples 1 to 6 and Comparative Examples 2 to 6, and the surfaces of the laminated thermoplastic liquid crystal polymer films were attached to each other. The laminate was heated and pressed by vacuum batch pressing (VH2-1600 manufactured by Kitagawa Seiki Co., Ltd.) (pressed for 15 minutes at 4 torr, 290°C, and 2.0 MPa) to heat press the liquid crystal polymer surfaces of the single-sided copper-clad laminates to each other. For the thermoplastic liquid crystal polymer film in Comparative Example 1, the same conditions as above were used to produce a laminate in which the liquid crystal polymer surfaces were heat-pressed together.

[Peel strength of copper foil/LCP interface] Using each prepared test laminate 1, 3 mm wide peeling test pieces were prepared in the MD direction and TD direction. Then, one side of the peeling test piece was fixed to a flat plate with double-sided adhesive tape, and the strength of the copper foil layer pressed during the preparation of the test laminate 1 was measured at a speed of 50 mm/min by the 90° method according to JIS-C5016. The measurement results were converted into units based on the sample width. These results are shown in Table 7.

[Peel strength of LCP/LCP interface] A 5 mm wide peeling test piece was made from each test laminate 2, and the copper foil on one side of the test piece was not etched and fixed to a flat plate with double-sided adhesive tape. According to JIS-C5016, the strength of the upper single-sided copper-coated laminate was measured by the 90° method when it was peeled off from the bonding interface between the thermoplastic liquid crystal polymer films at a speed of 50 mm/min. The measurement results were converted into units based on the sample width. These results are shown in Table 7.

[Table 7] Melting point(℃) Maximum heat treatment temperature (℃) Heating conditions from 250℃ to the maximum temperature Maximum temperature holding time (seconds) Pencil hardness Copper foil/LCP peeling strength (kN/m) LCP/LCP peeling strength (kN/m) Average heating rate (℃/second) Heating time (seconds) MD TD MD TD MD TD Embodiment 1 310 340 2.9 31 5 HB F 0.7 0.8 0.7 0.8 Embodiment 2 320 340 5.0 18 10 H HB 0.7 0.9 0.7 0.9 Embodiment 3 320 340 6.4 14 10 B HB 0.8 1.1 1.0 1.0 Embodiment 4 320 345 6.3 15 10 B B 1.0 1.0 1.0 1.0 Embodiment 5 320 340 2.4 38 30 B 2B 0.7 0.7 0.8 0.8 Embodiment 6 320 340 2.2 41 30 F F 0.6 0.7 0.7 0.8 Comparison Example 1 320 - - - - 4H 5H 0.2 0.3 0.3 0.4 Comparison Example 2 310 330 0.8 100 5 2H H 0.3 0.3 0.4 0.4 Comparison Example 3 280 295 0.8 56 10 H 2H 0.4 0.4 0.4 0.3 Comparison Example 4 320 340 0.7 129 10 2H 4H 0.3 0.3 0.4 0.4 Comparison Example 5 320 340 1.0 90 10 B 3H 0.4 0.4 0.4 0.3 Comparison Example 6 335 340 2.2 41 180 H 2H 0.9 0.8 0.5 0.6

In the heat treatment, the temperature of Examples 1 to 6 was rapidly raised to the highest temperature and the heat treatment was performed for a short time. The surface of the thermoplastic liquid crystal polymer (LCP) showed a pencil hardness of less than H in both the MD and TD directions. Whether it was pressed with a copper foil or pressed with each other, it showed good adhesion as indicated by a large peeling strength. Compared with the aforementioned comparative example 1 without heat treatment, the pencil hardness of the LCP surface was large, and the adhesion during pressing was insufficient whether it was relative to the copper foil or relative to the LCP. In Comparative Examples 2 to 5, the heating rate to the maximum temperature of the heat treatment is slow, and the heating time is long. The LCP surface is larger than H in either the MD direction, the TD direction, or both directions. Whether it is relative to the copper foil or the LCP, the adhesion during press-bonding is insufficient. In Comparative Example 6, the holding time at the maximum temperature is long, and the long-term heat treatment causes the film melting point to rise. Therefore, the LCP surface shows a pencil hardness (2H) larger than H in the TD direction. Although the copper foil with a rough surface has good adhesion during press-bonding, the adhesion when the LCPs are pressed together is insufficient. From the above results, it can be understood that for films made by extrusion molding of thermoplastic liquid crystal polymers, the compression properties of thermoplastic liquid crystal polymer films can be improved by heat treatment of rapid heating and short-term retention, and the condition below the pencil hardness H can be used as an indicator of compression properties. [Possibility of industrial use]

The thermoplastic liquid crystal polymer film of the present invention has excellent pressure-bonding properties with a metal layer or a thermoplastic liquid crystal polymer film, and can be effectively used as a circuit substrate material.

As described above, appropriate embodiments of the present invention are described. However, anyone with ordinary knowledge in the relevant technical field can easily make various changes and modifications within the self-evident scope by reading this specification. Therefore, such changes and modifications are interpreted as being within the scope of the invention defined by the scope of the patent application.

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Claims (11)

A thermoplastic liquid crystal polymer film, comprising a polymer that can form an optically anisotropic melt phase (hereinafter referred to as a thermoplastic liquid crystal polymer), wherein at least one surface of the film has a hardness in the range of 6B to H in both the MD direction and the TD direction using the pencil hardness measurement method specified in JIS-K5600-5-4. A thermoplastic liquid crystal polymer film as claimed in claim 1, wherein the hardness difference between the MD direction and the TD direction of the aforementioned surface in the pencil hardness measurement method specified in JIS-K5600-5-4 is less than 3 levels. As for the thermoplastic liquid crystal polymer film of claim 1 or 2, wherein the aforementioned surface has a hardness of at least one of the hardness in the MD direction and the TD direction being less than HB using the pencil hardness measurement method specified in JIS-K5600-5-4. The thermoplastic liquid crystal polymer film of claim 1 or 2, wherein the melting point of the thermoplastic liquid crystal polymer film is above 290°C. The thermoplastic liquid crystal polymer film of claim 1 or 2, wherein the molecular orientation SOR is in the range of 0.95 to 1.10. A laminate is a laminate of the thermoplastic liquid crystal polymer film of claim 1 or 2 and a conductive layer and/or other thermoplastic liquid crystal polymer films. A laminate as claimed in claim 6, wherein a layer composed of at least one selected from the group consisting of ink, metal film, metal foil and circuits formed thereby is formed as a conductive layer on the aforementioned surface of the aforementioned thermoplastic liquid crystal polymer film. The multilayer structure of claim 6 is a circuit substrate. A method for manufacturing a laminate comprises at least a step of heating a laminate of a thermoplastic liquid crystal polymer film and a support body, which comprises a polymer capable of forming an optically anisotropic molten phase (hereinafter referred to as a thermoplastic liquid crystal polymer), and heating the laminate to a maximum reaching temperature at a temperature of 1.5 to 15°C/second, and maintaining the temperature at the maximum reaching temperature for less than 60 seconds. A manufacturing method as claimed in claim 9, wherein the aforementioned maximum temperature reached is above Tm and below Tm+90°C relative to the melting point Tm of the thermoplastic polymer film. A method for producing a thermoplastic liquid crystal polymer film comprises a step of removing a support from a laminate obtained by the production method of claim 9 or 10.