Thermoplastic liquid crystal polymer film, and layered body and circuit board containing same

Abstract

Provided is a thermoplastic liquid crystal polymer film containing a polymer (hereinafter referred to as a thermoplastic liquid crystal polymer) which can form an optically anisotropic melt phase. In terms of surface roughness measured in accordance with ISO 25178, at least one surface of the film has an Spd of 1.3-2.5 / μm2. The coefficient of variation when Spd is measured at 10 points is not more than 0.20. The value of Str is not less than 0.40.

Description

Thermoplastic liquid crystal polymer film, laminate and circuit board including the same Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2023-166165, filed September 27, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a film made of a thermoplastic polymer capable of forming an optically anisotropic molten phase (hereinafter referred to as a thermoplastic liquid crystal polymer), a laminate including this thermoplastic liquid crystal polymer film (hereinafter also referred to simply as a "liquid crystal polymer film"), and a circuit board including the laminate.

[0003] In recent years, the use of flexible circuit boards consisting of a laminate of a resin layer and a metal layer has been increasing in the field of electronic materials. Thermoplastic liquid crystal polymer films are known as materials with excellent heat resistance, low moisture absorption, and high-frequency characteristics, and have attracted attention as electronic circuit materials for high-speed transmission. When using thermoplastic liquid crystal polymer films for electronic circuit board applications, a conductor layer is formed on one or both sides of the film by methods such as bonding or crimping metal foil, dry and / or wet plating of a metal layer, or coating with conductive ink, and then circuit processing is performed. In addition, when producing a laminate circuit board in which multiple circuits are stacked, thermoplastic liquid crystal polymer films may be bonded together.

[0004] However, films made from liquid crystal polymers (LCPs) have a problem of poor adhesion between insulating substrates and between insulating substrates and conductor layers due to the low adhesiveness caused by the molecular structure of the liquid crystal polymers. Treatments for improving the adhesiveness of liquid crystal polymer films have been studied, and Patent Document 1 considers a treatment for improving adhesion by imparting hydrophilic functional groups through plasma treatment or UV treatment.

[0005] International Publication No. 2014 / 109199

[0006] However, in the method of adding functional groups to the surface of a thermoplastic liquid crystal polymer film as described in Patent Document 1, although the adhesion strength increases after treatment, the effect does not last long, and bonding must be performed immediately after treatment, which is a problem in terms of quality. Also, in circuit design, adhesives such as epoxy resins are water-absorbent, so they have a high dielectric constant and are inferior in electrical properties to LCPs, so when used in combination with LCPs in circuit construction, the original performance of LCPs is not exhibited.

[0007] Therefore, a method for increasing adhesion by roughening the LCP surface through a molding process or the like can bond LCP films together, and the performance sustainability after the process is not an issue, making it a useful method for industrial applications. However, simply molding a liquid crystal polymer film may not always result in good adhesion. In particular, the appropriate roughness for achieving good adhesion in both the MD and TD directions for liquid crystal polymer films formed by melt extrusion molding has not been known until now.

[0008] The present invention aims to provide a liquid crystal polymer film having an optimum roughness for use in laminating a metal layer on the surface of a liquid crystal polymer film by wet plating or dry plating, bonding liquid crystal polymer films together, or bonding a liquid crystal polymer film to other materials using a low-dielectric adhesive.

[0009] That is, the present invention can be configured in the following aspects: [Aspect 1] 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), wherein the surface roughness Spd of at least one surface measured in accordance with ISO 25178 is 1.3 to 2.5 particles / μm. 2 (preferably 1.4 to 2.2 pieces / μm 2 , more preferably 1.5 to 2.0 pieces / μm 2A thermoplastic liquid crystal polymer film having a coefficient of variation of 0.20 or less (preferably 0.18 or less, more preferably 0.10 or less) in a 10-point evaluation of Spd, and a Str of 0.40 or more (preferably 0.45 or more, more preferably 0.50 or more). [Aspect 2] The thermoplastic liquid crystal polymer film of Aspect 1, wherein the surface roughness Rzjis measured in accordance with JIS B 0601:2001 is 2.5 μm or less (preferably 0.5 to 2.5 μm, more preferably 0.5 to 2.0 μm, and even more preferably 0.8 to 1.5 μm). [Aspect 3] The thermoplastic liquid crystal polymer film of Aspect 1 or Aspect 2, wherein the number average molecular weight (Mn) of the thermoplastic liquid crystal polymer is 55,000 or more (preferably 56,000 to 100,000, more preferably 60,000 to 80,000, and even more preferably 65,000 to 70,000). [Aspect 4] A laminate comprising the thermoplastic liquid crystal polymer film of any one of Aspects 1 to 3 and a metal layer laminated on at least one surface of the thermoplastic liquid crystal polymer film. [Aspect 5] The laminate of Aspect 4, wherein the adhesive strength between the metal layer and the insulating layer made of the thermoplastic liquid crystal polymer film is 0.70 N / mm or more (preferably 0.80 N / mm or more, more preferably 0.90 N / mm or more) with respect to peeling in the MD direction and / or TD direction of the thermoplastic liquid crystal polymer film. [Aspect 6] A circuit board comprising the laminate of Aspect 4 or 5. [Aspect 7] A laminate comprising a thermoplastic liquid crystal polymer film and a metal layer laminated on at least one surface of the thermoplastic liquid crystal polymer film, wherein the surface roughness Spd of the thermoplastic liquid crystal polymer film surface at the interface between the thermoplastic liquid crystal polymer film and the metal layer, as measured according to ISO 25178, is 1.3 to 2.5 particles / μm 2 (preferably 1.4 to 2.2 pieces / μm 2 , more preferably 1.5 to 2.0 pieces / μm 2A laminate in which the coefficient of variation of Spd in a 10-point evaluation is 0.20 or less (preferably 0.18 or less, more preferably 0.10 or less), and Str is 0.40 or more (preferably 0.45 or more, more preferably 0.50 or more). [Aspect 8] A laminate in which the thermoplastic liquid crystal polymer film contained in the laminate of Aspect 7 has a surface roughness Rzjis measured according to JIS B 0601:2001 of 2.5 μm or less. [Aspect 9] A laminate in which the thermoplastic liquid crystal polymer film contained in the laminate of Aspect 7 or Aspect 8 has a number average molecular weight (Mn) of 55,000 or more. [Aspect 10] A laminate in any one of Aspects 7 to 9, in which the adhesive strength between the metal layer and the insulating layer made of the thermoplastic liquid crystal polymer film is 0.70 N / mm or more with respect to peeling in the MD and TD directions of the thermoplastic liquid crystal polymer film. [Embodiment 11] A circuit board comprising the laminate of any one of embodiments 7 to 10.

[0010] It should be noted that any combination of at least two elements disclosed in the claims and / or the specification is included in the present invention, and in particular any combination of two or more of the claims described in the claims is included in the present invention.

[0011] According to the present invention, it is possible to provide a thermoplastic liquid crystal polymer film having excellent bonding properties with a metal layer or the like, and a laminate including the same.

[0012] The thermoplastic liquid crystal polymer film according to the present invention has a surface roughness Spd of 1.3 particles / μm on at least one surface as measured by ISO 25178. 2 2.5 pieces / μm or more 2 The following refers to a thermoplastic liquid crystal polymer film having a coefficient of variation of Spd in a 10-point evaluation of 0.20 or less and an Str of 0.40 or more.

[0013] (Thermoplastic liquid crystal polymer film) The thermoplastic liquid crystal polymer film of the present invention is formed from a melt-moldable liquid crystal polymer. This thermoplastic liquid crystal polymer is a polymer that can form an optically anisotropic molten phase, and its chemical structure is not particularly limited as long as it is a melt-moldable liquid crystal polymer, but examples thereof include thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides in which amide bonds are introduced therein.

[0014] The thermoplastic liquid crystal polymer may also be a polymer in which an isocyanate-derived bond such as an imide bond, a carbonate bond, a carbodiimide bond, or an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide.

[0015] Specific examples of the thermoplastic liquid crystal polymer used in the present invention include known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides derived from the compounds classified as (1) to (4) shown below and their derivatives. However, it goes without saying that there is an appropriate range for the combination of various raw material compounds in order to form a polymer that can form an optically anisotropic molten phase.

[0016] (1) Aromatic or aliphatic diol (see Table 1 for representative examples)

[0017] (2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for representative examples)

[0018] (3) Aromatic hydroxycarboxylic acids (see Table 3 for representative examples)

[0019] (4) Aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids (see Table 4 for representative examples)

[0020] Representative examples of thermoplastic liquid crystal polymers obtained from these raw material compounds include copolymers having structural units shown in Tables 5 and 6.

[0021]

[0022] Among these copolymers, copolymers containing at least p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as repeating units are preferred, and particularly preferred are (i) copolymers containing repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, or (ii) copolymers 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 dicarboxylic acid.

[0023] For example, in the copolymer (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 p-hydroxybenzoic acid in the repeating unit (A) to the 6-hydroxy-2-naphthoic acid in the repeating unit (B) in the thermoplastic liquid crystal polymer is preferably about (A) / (B) = 10 / 90 to 90 / 10, more preferably about (A) / (B) = 15 / 85 to 85 / 15, and even more preferably about (A) / (B) = 20 / 80 to 80 / 20.

[0024] In the case of the copolymer (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., it may contain repeating units composed of an aromatic diol or an aromatic dicarboxylic acid (for example, terephthalic acid).

[0025] In the case of the copolymer (ii), 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. The molar ratio of each repeating unit of the aromatic hydroxycarboxylic acid (C): the aromatic diol (D): the aromatic dicarboxylic acid (E) in the thermoplastic liquid crystal polymer may be about (30 to 80): (35 to 10): (35 to 10), more preferably about (C): (D): (E) = (35 to 75): (32.5 to 12.5): (32.5 to 12.5), and even more preferably about (C): (D): (E) = (40 to 70): (30 to 15): (30 to 15).

[0026] The molar ratio of repeating units 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. The molar ratio of repeating units derived from 2,6-naphthalenedicarboxylic acid in the aromatic dicarboxylic acid (E) may be, for example, 85 mol % or more, preferably 90 mol % or more, and more preferably 95 mol % or more.

[0027] Alternatively, 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 (D1) / (D2) may be 23 / 77 to 77 / 23, more preferably 25 / 75 to 75 / 25, and even more preferably 30 / 70 to 70 / 30.

[0028] Furthermore, the molar ratio of the repeating structural units derived from the aromatic diol to the repeating structural units derived from the aromatic dicarboxylic acid, (D) / (E), is preferably 95 / 100 to 100 / 95. If the ratio is outside this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

[0029] The ability to form an optically anisotropic molten phase in the present invention can be confirmed, for example, by placing a sample on a hot stage, heating it in a nitrogen atmosphere, and observing the light transmitted through the sample.

[0030] The melting point Tm0 of the thermoplastic liquid crystal polymer may be 260 to 360°C. The melting point Tm0 of the thermoplastic liquid crystal polymer can be obtained by observing the thermal behavior of a thermoplastic liquid crystal polymer sample using a differential scanning calorimeter. That is, a thermoplastic liquid crystal polymer sample is heated from room temperature (e.g., 25°C) at a rate of 10°C / min until it is completely melted at 400°C, and then the melt is cooled to 50°C at a rate of 10°C / min, and the temperature is raised again at a rate of 10°C / min. The position of the endothermic peak that appears when this is determined as the melting point (Tm0) of the thermoplastic liquid crystal polymer.

[0031] In addition, from the viewpoint of melt moldability, the thermoplastic liquid crystal polymer may have, for example, a melt viscosity of 30 to 120 Pa s at a shear rate of 1000 / sec at (Tm0 + 20) ° C., preferably 50 to 100 Pa s.

[0032] The thermal expansion coefficient of the thermoplastic liquid crystal polymer film may be 0 ppm / ° C. or more and 40 ppm / ° C. or less, or 5 ppm / ° C. or more and 30 ppm / ° C. or less. The thermal expansion coefficient is a value calculated using a thermomechanical analyzer (TMA) based on the change in length between 30° C. and 150° C. when a tensile load of 1 g is applied to both ends of a thermoplastic liquid crystal polymer film 5 mm wide and 20 mm long, the film is heated from room temperature to 200° C. at a rate of 5° C. / min, cooled to 30° C. at a rate of 20° C. / min, and then heated again at a rate of 5° C. / min.

[0033] The melting point (Tm) of the thermoplastic liquid crystal polymer film may be, for example, 270 to 380 ° C., preferably in the range of 280 to 370 ° C. The melting point (Tm) of the thermoplastic liquid crystal polymer film can be obtained by observing the thermal behavior of a thermoplastic liquid crystal polymer film sample using a differential scanning calorimeter. That is, a thermoplastic liquid crystal polymer film sample is heated from room temperature (e.g., 25 ° C.) at a rate of 10 ° C. / min until it is completely melted at 400 ° C., and then the melt is cooled to 50 ° C. at a rate of 10 ° C. / min. The position of the endothermic peak that appears when the temperature is raised again at a rate of 10 ° C. / min can be determined as the melting point (Tm) of the thermoplastic liquid crystal polymer film.

[0034] If necessary, known or conventional heat treatment may be performed to adjust the melting point and / or thermal expansion coefficient of the thermoplastic liquid crystal polymer film. Heat treatment conditions can be appropriately set depending on the purpose. For example, the melting point (Tm) of the thermoplastic liquid crystal polymer film may be raised by heating for several hours at (Tm-10)°C or higher (e.g., about (Tm-10) to (Tm+30)°C, preferably about (Tm) to (Tm+20)°C) relative to the melting point (Tm) of the thermoplastic liquid crystal polymer. Note that, depending on the components of the thermoplastic liquid crystal polymer, if the rate of melting point rise is rapid, the melting point (Tm) of the thermoplastic liquid crystal polymer film may be raised by heating at about (Tm-50) to (Tm)°C for 10 minutes to 1 hour.

[0035] Furthermore, the number average molecular weight (Mn) of the thermoplastic liquid crystal polymer in the thermoplastic liquid crystal polymer film may be 45,000 or more, preferably 55,000 or more, more preferably 56,000 or more, even more preferably 60,000 or more, and even more preferably 65,000 or more. Furthermore, the number average molecular weight (Mn) of the thermoplastic liquid crystal polymer may be 100,000 or less, preferably 80,000 or less, and more preferably 70,000 or less. Having the number average molecular weight (Mn) of the thermoplastic liquid crystal polymer within the above range results in superior flow characteristics when the thermoplastic liquid crystal polymer film is laminated in multiple layers. For example, the number average molecular weight of the thermoplastic liquid crystal polymer may be 56,000 to 100,000, 60,000 to 80,000, or 65,000 to 70,000. The number average molecular weight of the thermoplastic liquid crystal polymer can be adjusted, for example, by adjusting the polymerization conditions of the polymer and, if necessary, further performing solid-state polymerization by heat treatment or the like.

[0036] The thermoplastic liquid crystal polymer film may contain a thermoplastic polymer such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyether ether ketone, or fluororesin, as well as various additives, within the scope of the present invention. Furthermore, it may contain a filler such as an organic filler or an inorganic filler, as necessary. Therefore, the thermoplastic liquid crystal polymer film of the present invention also includes a film made of a thermoplastic liquid crystal polymer composition containing a thermoplastic liquid crystal polymer as a main component and one or more of these heterogeneous polymers, additives, fillers, etc.

[0037] The thermoplastic liquid crystal polymer film may contain 50% by weight or more of thermoplastic liquid crystal polymer, preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, and even more preferably 98% by weight or more.

[0038] The thermoplastic liquid crystal polymer film may be an extrusion film obtained by melt-extrusion molding the above-mentioned thermoplastic liquid crystal polymer or thermoplastic liquid crystal polymer film composition.At this time, any extrusion molding method can be used, but the well-known T-die film stretching method, laminate stretching method, inflation method, etc. are industrially advantageous.In particular, in the inflation method, stress is applied not only in the mechanical axis direction (hereinafter referred to as MD direction) of the thermoplastic liquid crystal polymer film, but also in the direction perpendicular thereto (hereinafter referred to as TD direction), and it can be uniformly stretched in the MD direction and the TD direction, so that a thermoplastic liquid crystal polymer film with controlled molecular orientation, dielectric properties, etc. can be obtained.

[0039] In addition, the thermoplastic liquid crystal polymer film may be stretched as needed after extrusion molding.The stretching method itself is known, and either biaxial stretching or uniaxial stretching may be adopted, but biaxial stretching is preferred because it is easier to control the molecular orientation degree.In addition, for stretching, known uniaxial stretching machines, simultaneous biaxial stretching machines, sequential biaxial stretching machines, etc. can be used.

[0040] In extrusion molding, a stretching process may be performed to control the orientation. For example, in extrusion molding using a T-die method, the molten sheet extruded from the T-die may be stretched not only in the MD direction of the thermoplastic liquid crystal polymer film but also in both the TD direction and the MD direction simultaneously to form a film, or the molten sheet extruded from the T-die may be stretched in the MD direction once and then in the TD direction to form a film.

[0041] In addition, in extrusion molding by the inflation method, a cylindrical sheet melt-extruded from a ring die may be stretched at a predetermined draw ratio (corresponding to the stretch ratio in the MD direction) and blow ratio (corresponding to the stretch ratio in the TD direction) to form a film.

[0042] The thickness of the thermoplastic liquid crystal polymer film can be appropriately set depending on the application. For example, when considering use as a material for the insulating layer of a multilayer circuit board, it may be 10 to 500 μm, preferably 15 to 250 μm, and more preferably 25 to 180 μm.

[0043] [Surface Properties of Thermoplastic Liquid Crystal Polymer Film] Spd: Peak Density of Peaks The thermoplastic liquid crystal polymer film of the present invention has a peak density of 1.3 peaks / μm on at least one surface. 2 2.5 pieces / μm or more 2 Spd is 1.4 particles / μm 2 2.2 pieces / μm or more 2 Preferably, the number is 1.5 / μm or less. 2 2.0 pieces / μm or more 2 It is more preferable that the coefficient of variation of Spd in a 10-point evaluation of the thermoplastic liquid crystal polymer film of the present invention is 0.20 or less. By adjusting the coefficient of variation within an appropriate range, the variation in the adhesive strength of the thermoplastic liquid crystal polymer film can be reduced, and the adhesive strength stability is excellent. The coefficient of variation of Spd in a 10-point evaluation is preferably 0.18 or less, more preferably 0.10 or less, and even more preferably 0.05 or less. The above Spd is an average value in a 10-point evaluation measured in accordance with ISO 25178 by the method described in the examples below.

[0044] Str: Aspect ratio of surface texture The thermoplastic liquid crystal polymer film of the present invention has an Str of 0.40 or more on at least one side. Str is preferably 0.45 or more, more preferably 0.50 or more. The closer Str is to the maximum value of 1, the more isotropic the surface texture becomes. By adjusting Spd and Str within an appropriate range, when a metal layer is formed on the surface of the thermoplastic liquid crystal polymer film, the adhesive strength can be increased and the anisotropy of the adhesive strength can be suppressed. Note that the Str is an average value in a 10-point evaluation measured in accordance with ISO 25178 using the method described in the Examples below.

[0045] Rzjis: Ten-point average roughness The thermoplastic liquid crystal polymer film of the present invention preferably has a ten-point average roughness Rzjis of 2.5 μm or less on at least one side. The upper limit of Rzjis is more preferably 2.0 μm, and even more preferably 1.5 μm. The lower limit of Rzjis may be 0.5 μm, and preferably 0.8 μm. The Rzjis is an average value in a 10-point evaluation measured in accordance with JIS B 0601:2001 by the method described in the Examples below.

[0046] [Method for adjusting the surface structure of a thermoplastic liquid crystal polymer film] The above surface structure can be produced by any method, but for example, as shown in the examples, it can be adjusted by preparing a stamper in which the surface of a metal sheet has been processed to the desired roughness, pressing this against a thermoplastic liquid crystal polymer film to transfer the surface roughness of the stamper to the surface of the thermoplastic liquid crystal polymer film, and then peeling the stamper from the thermoplastic liquid crystal polymer film.

[0047] The stamper can be produced by exposing a photosensitive resin applied to a glass substrate with an electron beam (EB) lithography device and etching it to form a desired uneven pattern on the surface of the glass substrate, electroforming a metal such as nickel onto the surface of the substrate, and then peeling it off to form a stamper with a transferred fine uneven pattern.If the uneven pattern is transferred to the surface of a thermoplastic liquid crystal polymer film using this, it is easier to design the surface structure of the thermoplastic liquid crystal polymer film than conventional surface roughening methods such as sandblasting and etching.

[0048] [Laminate] The laminate of the present invention may be a metal clad laminate including the above-mentioned thermoplastic liquid crystal polymer film and a metal layer laminated on at least one surface thereof.

[0049] In another embodiment, the laminate of the present invention is a laminate comprising a thermoplastic liquid crystal polymer film and a metal layer laminated on at least one surface of the thermoplastic liquid crystal polymer film, wherein the surface roughness Spd of the thermoplastic liquid crystal polymer film surface is 1.3 to 2.5 / μm as measured by ISO 25178 at the interface between the thermoplastic liquid crystal polymer film and the metal layer. 2 The coefficient of variation of Spd in a 10-point evaluation is 0.20 or less, and Str is 0.40 or more. The surface roughness of the interface is measured by the method described in the Examples below.

[0050] Here, one side of the thermoplastic liquid crystal polymer film is the first side and the opposite side is the second side, and if the first side is the side that exhibits the above-mentioned Spd value and Str value, the laminate may have a metal layer (metal coating) formed on the first side by a method such as chemical plating (electroless plating, electrolytic plating), vapor deposition, or sputtering.

[0051] Electroless plating is a process in which a metal is deposited on a film from a solution containing metal ions, forming a bond between the two. Electroless plating is a well-known method in the field of manufacturing plated products on non-conductive materials (such as plastics and ceramics). Metals that can be used include copper, nickel, cobalt, gold, tin, and chromium.

[0052] In the sputtering or vapor deposition method, a metal layer is formed on the surface of a thermoplastic liquid crystal polymer film by sputtering or vapor deposition of a metal. The sputtering or vapor deposition method is a well-known method in the field of electronic substrate manufacturing. Examples of metals for sputtering or vapor deposition include copper, aluminum, gold, tin, and chromium.

[0053] The metal layer formed by sputtering, vapor deposition, electroless plating or the like may be thickened by electrolytic plating using the same or a different metal.

[0054] In another embodiment, the laminate of the present invention may be one in which a metal foil is thermocompressed onto the first surface of the thermoplastic liquid crystal polymer film by a known method.The metal foil is not particularly limited, and may be, for example, a metal foil made of gold, silver, copper, iron, nickel, aluminum or an alloy metal thereof, etc., and from the viewpoints of conductivity, handling, cost, etc., copper foil or stainless steel foil is preferred.In addition, as the copper foil, rolled copper foil produced by a rolling method or electrolytic copper foil produced by an electrolytic method can be used.

[0055] The thickness of the metal layer can be appropriately set depending on the application of the metal clad laminate, and can be selected from a wide range of, for example, 10 nm to 100 μm. When a metal foil is used as the metal layer, the thickness of the metal layer may be 1 to 100 μm, preferably 5 to 50 μm, and more preferably 8 to 35 μm. When the metal layer is formed by sputtering, vapor deposition, electroless plating, or the like, or by a combination of these with electrolytic plating, the thickness of the metal layer may be 10 nm to 35 μm, preferably 50 nm to 12 μm, and more preferably 100 nm to 9 μm.

[0056] The thermoplastic liquid crystal polymer film of the present invention is suitable for fine circuit processing by a semi-additive method, but does not prevent circuit formation by other methods, and may have a circuit drawn thereon using, for example, conductive ink. In particular, when the maximum valley depth Sv of the first surface is 0.2 to 2.0 μm, the film has excellent adhesiveness to conductive ink.

[0057] The pattern can be drawn using a conductive ink by, for example, drawing lines with a marker, drawing lines with an inkjet printer, or printing by screen printing, and is not particularly limited. Examples of conductive inks that can be used include water-based or oil-based inks containing metal particles such as Au, Pt, Ag, Cu, Ni, Cr, Rh, Pd, Zn, Co, Mo, Ru, W, Os, Ir, Fe, Mn, Ge, Sn, Ga, and In. After drawing with the conductive ink, it is preferable to perform a heat treatment to sinter the metal particles. Sintering can be performed at a temperature of approximately 180 to 450°C, but the heat treatment temperature is preferably lower than the melting point of the thermoplastic liquid crystal polymer film used as the substrate.

[0058] The laminate may be a single-sided metal clad laminate in which a metal layer is laminated only on the first surface of the thermoplastic liquid crystal polymer film. Alternatively, the second surface may also be a double-sided metal clad laminate in which the Spd value and Str value are adjusted as described above and a metal layer is formed thereon. Alternatively, the laminate may have a metal foil thermocompression-bonded to the second surface by a known method.

[0059] In the laminate, the adhesive strength between the surface of the thermoplastic liquid crystal polymer film as an insulating layer with the adjusted Spd and Str values ​​and the metal layer formed thereon can be preferably 0.70 N / mm or more, more preferably 0.80 N / mm or more, and even more preferably 0.90 N / mm or more, against peeling in the MD and / or TD directions of the thermoplastic liquid crystal polymer film. The upper limit is not particularly limited, but may be 2.00 N / mm.

[0060] The above laminate preferably has a dimensional change rate of 0±0.30% or less, more preferably 0±0.25%, even more preferably 0±0.20%, and even more preferably 0±0.15% or less, when the metal layer is removed by etching and then annealed at 150°C for 30 minutes. The dimensional change rate is a value obtained by cutting the laminate into 250 mm square test pieces according to JIS C 6481, etching the metal layer, and then heating the resulting test pieces in an oven at 150°C for 30 minutes, and measuring the dimensional change rate of the sample. The distance between the rating points during measurement is 230 mm.

[0061] The laminate of the present invention can be effectively used as a part used in the fields of electricity and electronics, office equipment and precision equipment, power semiconductors, etc., for example, as a circuit board material.

[0062] A circuit board using the laminate of the present invention is suitable for use as a high frequency circuit board, an in-vehicle sensor, a mobile circuit board, an antenna, and the like.

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the preparation and evaluation were carried out by the following methods.

[0064] [Adjustment of the surface structure of thermoplastic liquid crystal polymer film] (Production of raw film) A thermoplastic liquid crystal polymer having a melting point of 280°C was polymerized using a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 73 / 27). By adjusting the conditions of the subsequent solid-state polymerization, thermoplastic liquid crystal polymers having different molecular weights as shown in Table 7 were prepared. Each of these thermoplastic liquid crystal polymers was melt-extruded, and a thermoplastic liquid crystal polymer film having a melting point of 280°C and a thickness of 50 μm was prepared by an inflation film-forming method.

[0065] (Fabrication of Stamper) Using a photolithography method with a photomask, a pattern consisting of a cylindrical fine concave-convex structure was formed on a glass substrate with a photosensitive resin using an EB lithography device, and a shape master was fabricated (see the following Examples and Comparative Examples for patterning conditions). Next, nickel electroforming was performed on the obtained shape master, forming a thin film of nickel metal approximately 0.3 mm thick on the shape master. The nickel thin film was then carefully peeled off from the shape master to obtain a thin stamper.

[0066] (Providing a textured structure to the surface of a thermoplastic liquid crystal polymer film) The above-mentioned thin stamper and the surface of the first side of the above-mentioned thermoplastic liquid crystal polymer film were aligned, and using a vacuum batch press (VH2-1600 manufactured by Kitagawa Seiki Co., Ltd.), they were heated and pressurized by a vacuum hot press (pressed for 5 minutes under conditions of 4 MPa and 260 ° C.), thereby transferring the pattern of the thin stamper to the surface of the first side of the thermoplastic liquid crystal polymer film. Then, the thin stamper was carefully peeled off from the thermoplastic liquid crystal polymer film, and a thermoplastic liquid crystal polymer film with a microstructure transferred to the surface of the first side was obtained.

[0067] [Production of Metal Clad Laminate] A metal layer (copper layer) was laminated by plating on the thermoplastic liquid crystal polymer film whose surface structure had been adjusted by the above-mentioned method, using the process described below.

[0068] (Electroless plating process) A 0.8 μm copper layer was formed on both surfaces (first and second surfaces) of the thermoplastic liquid crystal polymer film by the following process. Between each treatment, water rinsing was performed unless otherwise specified.

[0069] Step 1-1: Degreasing Treatment The thermoplastic liquid crystal polymer film was immersed in a treatment solution at 60°C for 5 minutes using a 40 ml / L concentration of Cleaner Securigant 902 (manufactured by Atotech Japan Co., Ltd.), a 3 ml / L concentration of Cleaner Additive 902 (manufactured by Atotech Japan Co., Ltd.), and a 20 g / L concentration of NaOH.

[0070] Step 1-2: Pre-dip treatment The thermoplastic liquid crystal polymer film was immersed in a treatment solution at 25°C for 1 minute using Pre-dip Neogant B (manufactured by Atotech Japan Co., Ltd.) at a concentration of 20 ml / L and 98% H2SO4 at a concentration of 1 ml / L, to obtain a plated object.

[0071] Step 1-3: Activator Treatment After step 1-2, the object to be plated was immersed for 5 minutes in a treatment solution at 40°C containing Activator Neogant 834 Concentrate (manufactured by Atotech Japan Co., Ltd.) at a concentration of 20 ml / L, boric acid at a concentration of 5 g / L, and NaOH at a concentration of 4 g / L, without rinsing with water, to allow palladium to be adsorbed onto the object to be plated.

[0072] Step 1-4: Reduction Treatment The object to be plated was immersed in a treatment solution containing Reducer Neogant WA (manufactured by Atotech Japan Co., Ltd.) at a concentration of 5 ml / L and boric acid at a concentration of 25 g / L at 25° C. for 3 minutes.

[0073] Step 1-5: Electroless copper plating An electroless copper-plated product was obtained by immersing the substrate in a plating solution containing 85 ml / L of Basic Printgant MV (manufactured by Atotech Japan Co., Ltd.), 45 ml / L of Copper Solution Printgant MV (manufactured by Atotech Japan Co., Ltd.), 8 ml / L of Starter Printgant MV (manufactured by Atotech Japan Co., Ltd.), 1.5 ml / L of Stabilizer Printgant MV Plus (manufactured by Atotech Japan Co., Ltd.), and 14 ml / L of Reducer Cu (manufactured by Atotech Japan Co., Ltd.) at 34°C for 15 minutes while stirring.

[0074] (Electrolytic Copper Plating Step) After electroless copper plating, a 12 μm copper layer was formed by the following steps, with water rinsing between each step.

[0075] Step 2-1: Degreasing Treatment Using Melplate PC-316 (manufactured by Meltex Inc.) with a concentration of 100 ml / L, the electroless copper plated product was immersed in a treatment solution at 45° C. for 3 minutes.

[0076] Step 2-2: Acid Activation Treatment The electroless copper plated product was immersed in a treatment solution of sulfuric acid with a concentration of 100 ml / L at 25° C. for 1 minute.

[0077] Step 2-3: Electrolytic copper plating treatment Using CuSO4.5H2O (copper sulfate II pentahydrate) at a concentration of 100 g / L, sulfuric acid at a concentration of 190 g / L, chloride ions (sodium chloride) at a concentration of 50 mg / L, Copper Gleam 125A (manufactured by DDP Specialty Products Japan Co., Ltd.) at a concentration of 5 ml / L, and Copper Gleam 125B (manufactured by DDP Specialty Products Japan Co., Ltd.) at a concentration of 5 ml / L, a copper plating solution was prepared at 2 A / dm 2 The electroless copper plated product was immersed in the solution for 40 minutes to obtain an electrolytic copper plated product.

[0078] Step 2-4: Antirust Treatment Using an antirust treatment solution AT7130 with a concentration of 25 ml / L and sulfuric acid with a concentration of 30 ml / L, the electrolytic copper plated product was immersed in the treatment solution at 25° C. for 10 seconds to obtain a double-sided copper clad laminate.

[0079] [Adhesion Strength Between Metal Layer and Thermoplastic Liquid Crystal Polymer Film] A peel test piece measuring 100 mm in length and 3 mm in width was cut from the double-sided copper-clad laminate obtained above. Next, the second surface of the peel test piece was fixed to a flat plate with double-sided adhesive tape, and the metal layer (copper layer) on the first surface was peeled at a speed of 50 mm / min according to JIS C 6471 using a digital force gauge (IMADA Co., Ltd., ZTS-5N) and an electric measuring stand with a slide table for 90° peel tests. The adhesive strength (peel strength) was measured by the 90° method at a speed of 50 mm / min in accordance with JIS C 6471. Data acquisition intervals were 0.1 seconds, and the average value (average value per second) for every 10 data points was calculated to create a graph showing the change in adhesive strength over time. The measurement length of the sample was 60 mm or more, and the minimum value of the average value for every 10 data points calculated from the peel strength graph in the central 40 mm range of the measurement length was taken as the adhesive strength. Two types of peel test specimens were prepared, one with the longitudinal direction in the MD direction of the thermoplastic liquid crystal polymer film, and the other with the longitudinal direction in the TD direction, and the adhesive strength of each sample was measured.

[0080] [Surface roughness of thermoplastic liquid crystal polymer film] Using a white light confocal microscope (manufactured by Lasertec Corporation, OPTELICS (registered trademark) HYBRID (L)), the first surface of the thermoplastic liquid crystal polymer film whose surface structure was adjusted by the above process was measured according to ISO 25178. The peak density (Spd) and the aspect ratio (Str) of the surface texture were measured according to ISO 25178, and the ten-point average roughness (Rzjis) was measured according to JIS B 0601:2001. Specifically, a 50x objective lens was used, with a resolution of 0.05 μm and a measurement range of 74.24 μm × 74.24 μm area (5512 μm 2 ) was used to measure a total of 10 locations from both ends to the center of a 30 cm wide sample. The peak density (Spd) and the aspect ratio (Str) of the surface texture at these 10 locations were measured, and the average value and coefficient of variation (standard deviation / average value) for Spd were calculated. In measurements using a white light confocal microscope, if the measurement surface was curved rather than flat, flatness correction was performed before calculating the average value of the surface roughness parameters. The measurement environment using the white light confocal microscope was a temperature of 23±2°C and a humidity of 50%±5%.

[0081] The surface roughness Rzjis of the thermoplastic liquid crystal polymer film was calculated by measuring the ten-point average roughness using a white light confocal microscope (OPTELICS (registered trademark) HYBRID (L) manufactured by Lasertec Corporation) in accordance with JIS B 0601: 2001. More specifically, a reference length was extracted from the roughness curve in the direction of the average line, and the difference between the average elevation of the fifth highest peak (convex vertex) and the average elevation of the fifth deepest valley (concave bottom) was expressed in μm.

[0082] [Surface roughness of metal clad laminate interface] The surface roughness of the interface between the liquid crystal polymer film and the metal layer in the metal clad laminate is measured using the film obtained by etching the copper foil from the double-sided copper clad laminate. Specifically, the copper foil of the double-sided copper clad laminate is removed by etching using ferric chloride aqueous solution, and then washed and dried to obtain a single liquid crystal polymer film. The surface roughness of the obtained liquid crystal polymer film is measured in the same manner as above.

[0083] [Lamination Flow of Metal Clad Laminate] The lamination flow of the metal clad laminate was evaluated as an index of heat resistance. One metal layer (copper layer) of the double-sided metal clad laminate prepared above was etched out with a ferric chloride aqueous solution, and then two of the laminates were stacked with the etched surfaces facing each other to produce an assembly. This assembly was heated in a vacuum press manufactured by Kitagawa Seiki Co., Ltd. from room temperature (25°C) to 250°C at a rate of 6°C / min and held for 15 minutes. Next, the assembly was heated to a temperature of melting point + 5°C at a rate of 6°C / min and held for 10 minutes under a surface pressure of 4 MPa for thermocompression bonding. Next, the assembly was cooled to 250°C at a rate of 7°C / min, and after reaching 250°C, it was rapidly cooled to 50°C. The vacuum was then released to obtain a multilayer laminate. The obtained multilayer laminate was visually observed for changes in the shape of the thermoplastic liquid crystal polymer film at the four corners of the multilayer laminate. If burrs from the metal layer due to the flow of the thermoplastic liquid crystal polymer were less than 5 mm, the evaluation was given an "A" rating, and if burrs of 5 mm or more but less than 10 mm were observed, the flow evaluation was given a "B" rating.

[0084] [Number average molecular weight of thermoplastic liquid crystal polymer] (Sample preparation) Sample preparation for GPC measurement was carried out as follows. 1. After freeze-pulverizing the pellets, they were shredded with an art knife and 0.6 mg was weighed into a screw tube. 2. 0.6 mL of pentafluorophenol (PFP, not distilled, purity 97%) was added to the screw tube containing the pellets and stirred for 6 hours while heating in a 60°C water bath. 3. 1.4 mL of chloroform (CF) was added. 4. The solution was passed through a 450 μm membrane filter and stored in a GPC vial. (Measurement conditions) The specific measurement conditions for GPC measurement are as follows. Apparatus: HLC-8420GPC (manufactured by Tosoh Corporation) Column: TSKgel Super HM-H × 2 + TSKgel H2000 (manufactured by Tosoh Corporation) Eluent: PFP / chloroform = 1 / 2 (wt / wt) Flow rate: 0.6 mL / min. Temperature: 40°C Molecular weight standard: polystyrene (manufactured by Tosoh Corporation)

[0085] In the examples, the surface roughness is adjusted using a raw film obtained by melt-extrusion molding a thermoplastic liquid crystal polymer, and therefore, in the above method, samples are prepared using pellets of the thermoplastic liquid crystal polymer. However, samples may be prepared using a thermoplastic liquid crystal polymer film instead of pellets, and the number average molecular weight may be measured.

[0086] [Example 1] The stamper patterning conditions were a convex pattern shape with a cylindrical height of 1.5 μm and a diameter of 0.5 μm, and the patterning was performed at equal intervals of 0.5 μm. A thermoplastic liquid crystal polymer having a number average molecular weight (Mn) of 66,000 was used, and a microstructured thermoplastic liquid crystal polymer film and a metal clad laminate were produced and evaluated using the above method.

[0087] [Example 2] The stamper patterning conditions were a convex pattern shape with a height of 1.5 μm and a diameter of 0.5 μm, with a regular interval of 0.5 μm in the MD direction and a random arrangement in the TD direction with a pitch of 0.5 to 2.0 μm. Using a thermoplastic liquid crystal polymer with a number average molecular weight (Mn) of 57,000, the production and evaluation of a microstructured thermoplastic liquid crystal polymer film and a metal clad laminate were carried out using the above method.

[0088] [Example 3] The stamper patterning conditions were a convex pattern shape with a cylindrical height of 1.5 μm and a diameter of 0.5 μm, and the patterning was performed at equal intervals of 0.5 μm. A thermoplastic liquid crystal polymer having a number average molecular weight (Mn) of 46,000 was used, and the production and evaluation of a microstructured thermoplastic liquid crystal polymer film and a metal clad laminate were carried out using the above method.

[0089] [Comparative Example 1] The stamper patterning conditions were a convex pattern shape with a cylindrical height of 1.5 μm and a diameter of 0.5 μm, and the number of patterns per 1 μm square was 1.5 to 3.0, randomly arranged. A thermoplastic liquid crystal polymer having a number average molecular weight (Mn) of 66,000 was used, and a microstructured thermoplastic liquid crystal polymer film and a metal clad laminate were produced and evaluated using the above method.

[0090] [Comparative Example 2] The stamper patterning conditions were a convex pattern shape with a cylindrical height of 2.3 μm and a diameter of 0.5 μm, and the number of patterns per 1 μm square was 1.5 to 3.0, randomly arranged. A thermoplastic liquid crystal polymer having a number average molecular weight (Mn) of 66,000 was used, and a microstructured thermoplastic liquid crystal polymer film and a metal clad laminate were produced and evaluated using the above method.

[0091] [Comparative Example 3] The stamper patterning conditions were a convex pattern shape with a cylindrical height of 1.5 μm and a diameter of 0.5 μm, and the number of patterns per 1 μm square was 1.5 to 3.0, randomly arranged. Using a thermoplastic liquid crystal polymer with a number average molecular weight (Mn) of 66,000, a microstructured thermoplastic liquid crystal polymer film and a metal clad laminate were produced and evaluated using the above method.

[0092] [Comparative Example 4] The stamper patterning conditions were a convex pattern shape with a height of 1.5 μm and a diameter of 0.5 μm, with a regular interval of 0.5 μm in the MD direction and a random arrangement in the TD direction with a pitch of 0.5 to 5.0 μm. Using a thermoplastic liquid crystal polymer with a number average molecular weight (Mn) of 66,000, the production and evaluation of a microstructured thermoplastic liquid crystal polymer film and a metal clad laminate were carried out using the above method.

[0093] The peak density (Spd), aspect ratio (Str), ten-point average roughness (Rzjis), and adhesion strength (minimum peel strength) of the copper layer of the metal clad laminate of the first surface of the microstructured thermoplastic liquid crystal polymer films produced in Examples 1 to 3 and Comparative Examples 1 to 4, and the evaluation results of lamination flow are shown in Table 7. Furthermore, the evaluation results of the surface roughness of the thermoplastic liquid crystal polymer film at the interface between the thermoplastic liquid crystal polymer film and the metal layer of the metal clad laminate produced in Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 8.

[0094]

[0095]

[0096] As shown in Table 7, the surface roughness measured by ISO 25178 is 1.3 particles / μm on at least one surface. 2 2.5 pieces / μm or more 2 In Examples 1 to 3, where the Str was 0.40 or more and the coefficient of variation of Spd in a 10-point evaluation was 0.20 or less, the adhesive strength of the thermoplastic liquid crystal polymer film in both the MD and TD directions in the metal-clad laminate was 0.70 N / mm or more. In contrast, in Comparative Examples 1 to 3, where the coefficient of variation of Spd was greater than 0.2, the adhesive strength of the thermoplastic liquid crystal polymer film in both the MD and TD directions was less than 0.70 N / mm. Although the coefficient of variation of Spd met the condition of 0.2 or less, Comparative Example 4, where Str was less than 0.1, had a large difference in adhesive strength between the MD and TD directions of the thermoplastic liquid crystal polymer film, and the adhesive strength in the MD direction was 0.70 mm / N or more, but the adhesive strength in the TD direction was less than 0.70 N / mm (0.54 N / mm). Furthermore, in Examples 1 and 2, where a thermoplastic liquid crystal polymer film having a number average molecular weight (Mn) of 55,000 or more was used, the flow during multilayer lamination was also good.

[0097] While the preferred embodiments of the present invention have been described above, those skilled in the art will readily recognize various changes and modifications within the scope of the present invention, which are obvious from the description of the present invention. Therefore, such changes and modifications are to be interpreted as falling within the scope of the invention as defined by the claims.

[0098] According to the present invention, a thermoplastic liquid crystal polymer film having excellent adhesion to other materials such as metal layers can be provided. A laminate including this film has excellent stability of the laminate structure during processing, and is therefore highly usable as a circuit board material.

Claims

1. 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), the surface roughness of which, as measured by ISO 25178, is 1.3 to 2.5 particles / μm on at least one surface. 2 A thermoplastic liquid crystal polymer film, in which the coefficient of variation of Spd in a 10-point evaluation is 0.20 or less and Str is 0.40 or more.

2. The thermoplastic liquid crystal polymer film according to claim 1, wherein the surface roughness Rzjis measured according to JIS B 0601:2001 is 2.5 μm or less.

3. A thermoplastic liquid crystal polymer film according to claim 1 or 2, wherein the number average molecular weight (Mn) of the thermoplastic liquid crystal polymer is 55,000 or more.

4. A laminate comprising the thermoplastic liquid crystal polymer film according to claim 1 or 2 and a metal layer laminated on at least one surface of the thermoplastic liquid crystal polymer film.

5. A laminate according to claim 4, wherein the adhesive strength between the metal layer and the insulating layer made of the thermoplastic liquid crystal polymer film is 0.70 N / mm or more against peeling in the MD and TD directions of the thermoplastic liquid crystal polymer film.

6. A circuit board comprising the laminate of claim 4.

7. A laminate comprising a thermoplastic liquid crystal polymer film and a metal layer laminated on at least one surface of the thermoplastic liquid crystal polymer film, wherein the surface roughness Spd of the thermoplastic liquid crystal polymer film surface is 1.3 to 2.5 particles / μm at the interface between the thermoplastic liquid crystal polymer film and the metal layer as measured by ISO25178. 2 , Spd has a coefficient of variation of 0.20 or less in a 10-point evaluation, and Str is 0.40 or more.

8. A laminate according to claim 7, wherein the thermoplastic liquid crystal polymer film contained therein has a surface roughness Rzjis of 2.5 μm or less as measured according to JIS B 0601:2001.

9. A laminate comprising the thermoplastic liquid crystal polymer film according to claim 7 or 8, wherein the thermoplastic liquid crystal polymer has a number average molecular weight (Mn) of 55,000 or more.

10. A laminate according to claim 7 or 8, wherein the adhesive strength between the metal layer and the insulating layer made of the thermoplastic liquid crystal polymer film is 0.70 N / mm or more against peeling in the MD and TD directions of the thermoplastic liquid crystal polymer film.

11. A circuit board comprising the laminate according to claim 7 or 8.

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