TW202444806A - Thermoplastic liquid crystal polymer film, laminate, and production method thereof - Google Patents

Abstract

A liquid crystal polymer film including a polymer capable of forming optically anisotropic melt phase, wherein at least one surface of the film has a skewness Ssk of -5 or more and 0 or less and an arithmetic mean roughness of 0.15 μm or more.

Description

Thermoplastic liquid crystal polymer film, laminate, and method for manufacturing the same

This application claims priority to Japanese Patent Application No. 2023-053939, filed on March 29, 2023, and is incorporated herein by reference in its entirety as a part of this application.

The present invention relates to 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), a laminate containing the thermoplastic liquid crystal polymer film, and a method for manufacturing the thermoplastic liquid crystal polymer film and the laminate.

In recent years, in the field of electronic materials, the use of flexible circuit substrates composed of a laminate of resin layers and metal layers has made progress. Thermoplastic liquid crystal polymer films are known as materials with excellent properties such as high heat resistance, low moisture absorption, and high frequency characteristics. In recent years, they have attracted attention as flexible circuit substrate materials for high-speed transmission.

Based on the requirements of miniaturization and high density, the circuit formation of flexible circuit substrates is progressing towards fine circuit patterning, and the semi-additive process (SAP process) is being explored as a technology that can perform fine circuit processing. For example, Patent Document 1 (WO2020/105289) describes: In the step of etching an electroless copper coating formed on the surface of a resin film as a substrate by the SAP method, in order to suppress the occurrence of embedding (difference) caused by the coating, a surface-treated copper foil and a resin film are heat-pressed to transfer the surface shape of the surface-treated copper foil to the surface of the resin film, and when the surface-treated copper foil is removed by etching, the skewness Ssk of the surface of the remaining resin film is set to less than -0.6 as measured in accordance with ISO25178. [Prior Technical Document] [Patent Document]

[Patent Document 1] International Publication No. 2020/105289

[The problem that the invention wants to solve]

Flexible circuit boards require good adhesion between the resin layer and the metal layer (conductor layer). On the other hand, in order to bring out the high-frequency characteristics of the thermoplastic liquid crystal polymer film, it is better to have a smooth interface between the resin layer and the metal layer.

In the technology of Patent Document 1, although a resin film is hot-pressed onto the treated surface of a surface-treated copper foil to transfer the surface shape of the treated surface to the surface of the resin film, and the surface-treated copper foil is removed by etching to set the surface skewness Ssk of the resin film to less than -0.6, it is difficult to provide a flat surface on the surface of the resin film by this method. In addition, in Patent Document 1, although a film made of a thermosetting resin is used, it is difficult to completely etch out copper that has penetrated deep into the valleys of the film surface for a thermoplastic liquid crystal polymer film with low hygroscopicity. Furthermore, when copper partially remains on the surface of the TLCP film, it becomes difficult to form a uniform metal layer in the subsequent plating process because it becomes a nucleus for crystal growth.

The purpose of the present invention is to provide a thermoplastic liquid crystal polymer film that can suppress transmission loss to a low level when forming a laminate with a metal layer and has good adhesion with the metal layer, 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 intensive studies to achieve the above-mentioned purpose, and have realized that by adjusting the conditions for roller-treating the surface of a thermoplastic liquid crystal polymer film, the film can be given a surface roughness with a deflection within a specified range, thereby achieving both adhesion to the conductive layer and maintenance of high-frequency characteristics, thereby completing the present invention.

That is, the present invention can be constituted by 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 in at least one surface, the skewness (skewness) Ssk is greater than -5 and less than 0 (preferably less than 0, more preferably less than -0.2), and the arithmetic mean roughness Sa of the surface is greater than 0.15μm. [Aspect 2] The thermoplastic liquid crystal polymer film as described in aspect 1, wherein the aforementioned surface is metal-free.

[Aspect 3] A thermoplastic liquid crystal polymer film as described in Aspect 1 or 2, wherein the arithmetic mean roughness Sa of the aforementioned surface is 0.50 μm or less (preferably 0.15 μm or more and 0.50 μm or less, for example 0.15 μm or more and 0.30 μm or more and 0.20 μm or less). [Aspect 4] A thermoplastic liquid crystal polymer film as described in any of Aspects 1 to 3, wherein the maximum peak height Sp of the aforementioned surface is 0.15 μm or more (preferably 0.5 μm or more) and 3.00 μm or less.

[Aspect 5] A thermoplastic liquid crystal polymer film as described in any of aspects 1 to 4, wherein the maximum valley depth Sv of the aforementioned surface is greater than 0.2μm and less than 3.5μm (preferably greater than 1.0μm and less than 3.0μm). [Aspect 6] A thermoplastic liquid crystal polymer film as described in any of aspects 1 to 5, wherein the maximum height Sz of the aforementioned surface is greater than 1.5μm and less than 5.0μm. [Aspect 7] A thermoplastic liquid crystal polymer film as described in any of aspects 1 to 6, wherein the melting point is greater than 315°C.

[Aspect 8] A laminate comprising a thermoplastic liquid crystal polymer film as described in any one of aspects 1 to 7, and a conductive layer laminated on the thermoplastic liquid crystal polymer film. [Aspect 9] A laminate as described in aspect 8, wherein a layer composed of at least one selected from the group consisting of a conductive ink, a metal film, and a circuit formed thereby is formed on the aforementioned surface of the thermoplastic liquid crystal polymer film as a conductive layer. [Aspect 10] A laminate as described in aspect 8 or 9, wherein a metal foil layer is formed as a conductive layer on the surface opposite to the aforementioned surface of the thermoplastic liquid crystal polymer film.

[Aspect 11] The laminate described in any of aspects 8 to 10 is a circuit substrate. [Aspect 12] A method for manufacturing a thermoplastic liquid crystal polymer film described in any of aspects 1 to 7, which comprises at least: a step of bringing a roughened surface roller into contact with at least one surface of the thermoplastic liquid crystal polymer film.

[Aspect 13] A method for manufacturing a laminate as described in any of aspects 8 to 11, which comprises at least: a step of bringing a roughened surface roller into contact with a surface of a thermoplastic liquid crystal polymer film of a laminate of a thermoplastic liquid crystal polymer film and a support. [Aspect 14] A method for manufacturing a laminate as described in aspect 13, wherein the support is a metal foil.

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

According to the thermoplastic liquid crystal polymer film of the present invention, a thermoplastic liquid crystal polymer film can be obtained which can suppress transmission loss to a low level when laminated with a conductor layer and has good adhesion with the conductor layer, and a laminate including such a thermoplastic liquid crystal polymer film has excellent circuit processability.

(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, its chemical composition is not particularly limited, but examples thereof include: thermoplastic liquid crystal polyester, or thermoplastic liquid crystal polyesteramide formed by introducing amide bonds therein, etc.

Furthermore, the thermoplastic liquid crystal polymer may also be a polymer obtained by further introducing an imide bond, a carbonate bond, a carbodiimide bond, a triisocyanate bond or the like, which is derived from isocyanate, 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, it goes without saying that the combination of various raw material compounds has an appropriate range in order to form a polymer that can form an optically anisotropic melt phase.

(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 hydroxylamine 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 these copolymers, copolymers containing at least p-hydroxybenzoic acid and/or 6-hydroxy-2-naphthoic acid as repeating units are preferred, and in particular (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 are preferred.

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

In the case of the copolymer of (i), from the viewpoint of adjusting the molecular weight, in addition to the repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, repeating units 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 thermoplastic liquid crystal polymer 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-naphthalene dicarboxylic acid is preferably a copolymer of at least one aromatic dicarboxylic acid (E) selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalene dicarboxylic acid. The molar ratio of the aromatic hydroxycarboxylic acid (C): the aromatic diol (D): the aromatic dicarboxylic acid (E) can be about (30-80): (35-10): (35-10), more preferably (C): (D): (E) = (35-75): (32.5-12.5): (32.5-12.5), and further 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. The molar ratio of the repeating unit 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.

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, more 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 deviates from this range, the degree of polymerization cannot be increased and the mechanical strength tends to decrease.

Furthermore, the optically anisotropic molten phase of the present invention can be identified by placing a sample on a high temperature stage, 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 is 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. In addition, the melting point of the thermoplastic liquid crystal polymer can be obtained by observing the thermal behavior of the thermoplastic liquid crystal polymer sample using a differential scanning calorimeter. That is, after the thermoplastic liquid crystal polymer sample is heated at a rate of 10°C/min to completely melt, the melt is cooled to 50°C at a rate of 10°C/min, and the temperature is again raised at a rate of 10°C/min. The position of the endothermic peak that appears can be recorded as the melting point of the thermoplastic liquid crystal polymer sample.

From the viewpoint 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/s at (Tm ₀ +20)°C, and preferably 50 to 100 Pa·s.

The thermoplastic liquid crystal polymer film may include thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyetheretherketone, fluororesin, and various additives within the scope that does not impair the effect of the present invention. In addition, fillers such as organic fillers and inorganic fillers may also be included as needed. Therefore, the thermoplastic liquid crystal polymer film of the present invention also includes a film composed of a thermoplastic liquid crystal polymer composition containing a thermoplastic liquid crystal polymer as a main component and 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, further preferably 95 wt % or more, further more preferably 98 wt % or more.

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

Furthermore, the thermoplastic liquid crystal polymer film can be stretched as needed after extrusion molding. The stretching method itself is well known, and either biaxial stretching or uniaxial stretching can be adopted. Biaxial stretching is preferred because it is easier to control the molecular orientation. Moreover, 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 a stretching treatment to control the orientation. For example, in extrusion molding by 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 MD direction and the TD direction to form a film. Alternatively, the molten sheet extruded from the T-die may be temporarily stretched in the MD direction and then stretched in the TD direction to form a film.

In addition, in the case of extrusion molding by 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.

Furthermore, the melting point and/or thermal expansion coefficient of the thermoplastic liquid crystal polymer film may be adjusted by a known or conventional heat treatment as required. The heat treatment conditions may be appropriately set according to the purpose. For example, the melting point ( _Tm ) of the thermoplastic liquid crystal polymer film may be increased by heating for several hours at a temperature of (Tm _{0 -10)°C or higher (e.g., (Tm 0 -10} )°C to (Tm ₀ +30)°C, preferably (Tm ₀ )°C to (Tm ₀ +20)°C) relative to the melting point (Tm 0 ) of the thermoplastic liquid crystal polymer. In addition, depending on the composition of the thermoplastic liquid crystal polymer film, the melting point may be increased by heating for a shorter time, for example, less than 1 hour. Furthermore, for example, the thermal expansion coefficient may be increased by heating at a temperature of (Tm ₀ -15)°C or higher and less than (Tm ₀ )°C relative to the melting point (Tm ₀ ) of the thermoplastic liquid crystal polymer for 5 to 60 seconds (eg, 10 to 30 seconds).

The melting point (Tm) of the thermoplastic liquid crystal polymer film may be, for example, above 315°C, preferably 315-380°C, more preferably 318-370°C, and even more preferably 320-360°C. In addition, the melting point (Tm) of the thermoplastic liquid crystal polymer film can be obtained by observing the thermal behavior of the thermoplastic liquid crystal polymer film sample using a differential scanning calorimeter. That is, the thermoplastic liquid crystal polymer film sample can be heated from room temperature (e.g., 25°C) at a rate of 10°C/min and completely melted at 400°C, then 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 again heated at a rate of 10°C/min is obtained as the melting point (Tm) of the thermoplastic liquid crystal polymer film.

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.

(Surface roughness of thermoplastic liquid crystal polymer film) In the present invention, the following parameters are used to adjust the surface roughness of the thermoplastic liquid crystal polymer film in order to improve the adhesion with the metal layer. These are all parameters specified in ISO25178 and can be measured by the method described in the following embodiment.

Skewness (skewness) Ssk The thermoplastic liquid crystal polymer film of the present invention has at least one surface with a skewness Ssk of -5 or more and 0 or less. Skewness is a parameter indicating the symmetry of the distribution of height relative to the reference surface. When Ssk is less than 0, there are more valleys. The skewness Ssk is preferably less than 0, and is further preferably less than -0.2. The skewness Ssk can be greater than -0.5 and less than 0, or greater than -5 and less than -2.

Arithmetic mean roughness Sa In addition, the thermoplastic liquid crystal polymer film of the present invention has an arithmetic mean roughness Sa of 0.15μm or more on the surface where the Ssk is -5 or more and 0 or less. When Sa is less than 0.15μm, it may be impossible to show good peeling strength by coating or evaporation. Furthermore, the arithmetic mean roughness Sa is preferably 0.50μm or less. The arithmetic mean roughness Sa may be 0.15μm or more and 0.30μm or more and 0.20μm or more and 0.50μm or less. If the Ssk of at least one surface of the thermoplastic liquid crystal polymer film is -5 or more and 0 or less and Sa is 0.15μm or more, peeling strength and transmission characteristics can be taken into account.

In addition to the skewness and arithmetic mean roughness, the following surface roughness parameters are also adjusted for better results. Maximum peak height Sp The maximum peak height Sp of the above surface is preferably 0.15μm or more and 3.0μm or less. The maximum peak height Sp is more preferably 0.5μm or more. The maximum peak height Sp can be 0.5μm or more and 1.0μm or less, or 2.0μm or more and 3.0μm or less.

Maximum valley depth Sv The maximum valley depth Sv of the above surface is preferably 0.2μm to 3.5μm. The maximum valley depth Sv is further preferably 1.0μm to 3.0μm, and even more preferably 1.5μm to 2.0μm.

Maximum height Sz The maximum height Sz of the above surface is preferably 1.5μm or more and 5.0μm or less. The maximum height Sz is more preferably 2.0μm or more. The maximum height Sz may be 2.0μm or more and 3.0μm or less, or 3.5μm or more and 5.0μm or less.

Peak Sku The peak Sku can be 1.0 to 40.0, preferably 1.5 to 30.0, and more preferably 2.5 to 20.0.

(Method for adjusting the surface roughness of thermoplastic liquid crystal polymer film) The surface roughness of the thermoplastic liquid crystal polymer film can be adjusted by any of the following methods or by a combination of these methods. (1) Adjustment of the peripheral speed of the heating roller relative to the film conveying speed When the film is conveyed along a heating roller (e.g., a metal roller), the peripheral speed of the heating roller relative to the film conveying speed can be changed to cause the film surface to be distorted and the surface roughness can be adjusted. The ratio of the peripheral speed of the heating roller to the film conveying speed is preferably 0.95 or more and 0.99 or less in terms of (film conveying speed/peripheral speed of the heating roller). (2) Shrinkage of the film on the heating roller If the film is transported along the convex heating roller, tension will be generated from both ends to the center of the film, so wrinkles can be formed in the film. At this time, the mountain parts on the film surface are pressed and flattened by the roller, so a surface with prominent valleys can be formed. In addition, if a thermoplastic liquid crystal polymer film with a negative thermal expansion coefficient in the TD direction is used, wrinkles can be generated efficiently. This process can be carried out while heating the film at a temperature of about Tm-110℃ to Tm-5℃ relative to the melting point Tm of the thermoplastic liquid crystal polymer film.

(3) Transfer of the rough surface of the surface roughening roller If the film is transported along the surface roughened heating roller, the rough surface of the heating roller will be transferred to the surface of the thermoplastic liquid crystal polymer film. In this case, if a metal roller with a linear pattern embossed is used as the heating roller, a surface consisting of a flat surface and valleys can be given to the thermoplastic liquid crystal polymer film. In this case, the preferred range of the surface roughness of the metal roller is an arithmetic mean roughness Ra of 0.2 to 3.0 μm, a maximum height roughness Rz of 0.4 to 20.0 μm, and a ten-point average roughness Rzjis of 0.3 to 20.0 μm as measured in accordance with JIS B 0601:2001. The temperature of the heating roller can be set to a temperature of about Tm-110℃ to Tm-5℃ relative to the melting point Tm of the thermoplastic liquid crystal polymer film.

(4) Pressing by a surface roughening roller When the film is sandwiched between two rollers and pressed while being transported, the rough surface of the roller can be transferred to the film surface by using a roughened surface on at least one roller to make the desired roughened surface. For this method, for example, a rubber roller with a surface treatment such as embossing or a metal roller with a surface roughened by sandblasting can be used. This process can be performed while heating the film at a temperature of about Tm-80℃ to Tm-5℃ relative to the melting point Tm of the thermoplastic liquid crystal polymer film. For example, the film can be heated by a metal heating roller while being pressed by a surface roughened rubber roller.

As a method for adjusting the surface roughness of a thermoplastic liquid crystal polymer film, a method is also known in which a metal foil having a predetermined surface roughness is laminated and pressed onto the thermoplastic liquid crystal polymer film and then the metal foil is removed by etching. However, in this case, metal residues may remain on the surface of the thermoplastic liquid crystal polymer film. In contrast, in the above method, metal residues will not remain on the surface of the thermoplastic liquid crystal polymer film, and a metal-free surface can be produced.

The surface roughness of the thermoplastic liquid crystal polymer film can be adjusted in the state of the thermoplastic liquid crystal polymer film alone (monomer), but it is also possible to adjust the surface roughness of the other side in the state where the support volume is laminated on one side of the thermoplastic liquid crystal polymer film. For example, a single-sided metal-coated laminate in which a metal foil is laminated on one side of the thermoplastic liquid crystal polymer film can be produced, and then the surface of the thermoplastic liquid crystal polymer film side can be roughened. Alternatively, in the step of hot pressing the metal foil and the thermoplastic liquid crystal polymer film, a roller with a roughened surface can be used as a roller on the side of the thermoplastic liquid crystal polymer film, and the single-sided metal-coated laminate and the surface roughening of the thermoplastic liquid crystal polymer film surface can be simultaneously performed.

When a metal foil is used as a support when adjusting the surface roughness of the thermoplastic liquid crystal polymer film in the present invention, a single-sided metal-clad laminate can be formed by a known method. The metal foil is not particularly limited, and aluminum or aluminum alloy foil, stainless steel foil, rolled copper foil, electrolytic copper foil, etc. can be used.

The thickness of the metal foil can be, for example, 1 to 100 μm, and a surface roughening treatment can also be used. The thermoplastic liquid crystal polymer film and the metal foil can be heat-pressed by using a pair of metal rolls, or a metal roll and a rubber roll, for example, while heating at a heating temperature in the range of (Tm-80)°C to (Tm)°C relative to the melting point (Tm) of the thermoplastic liquid crystal polymer film, and applying a pressure of about 1 to 15 kg/mm by a roll-to-roll method.

During the heat pressing, the laminated thermoplastic liquid crystal polymer film and the metal foil may be laminated in such a manner that a protective material such as a polyimide film contacts the outer side of the laminated thermoplastic liquid crystal polymer film and the metal foil, and then introduced into a pair of pressure rollers and heat pressed, and then separated from the single-sided metal-clad laminate before the heat treatment step. However, when the surface roughness of the thermoplastic liquid crystal polymer film is adjusted and heat pressed at the same time, the protective material is not provided on the thermoplastic liquid crystal polymer film side.

(Laminate) The laminate of the present invention (hereinafter sometimes referred to as a laminate) is a laminate comprising a thermoplastic liquid crystal polymer film, wherein the thermoplastic liquid crystal polymer film has a skewness Ssk of -5 to 0 on at least one surface and an arithmetic mean roughness Sa of 0.15 μm or more.

Here, if one side of the thermoplastic liquid crystal polymer film is set as the first side, the opposite side thereof is set as the second side, and the first side is set as the side showing the above-mentioned Ssk value and Sa value, the laminate may be formed by forming a metal layer (metal film) on the first side by evaporation, sputtering, chemical plating (electroless plating, electrolytic plating), etc. Alternatively, the laminate may be formed by applying circuit processing to such metal layers.

In the sputtering method or the evaporation method, a step is performed to bring metal parts into contact and connect the two parts by sputtering or evaporating metal. The sputtering method or the evaporation method is a well-known method in the field of electronic substrate manufacturing. Examples of metals used for sputtering or evaporation include copper, aluminum, gold, tin, chromium, etc.

In the electroless plating method, a step is performed in which a metal is deposited from a solution containing metal ions onto a thin film and then the two are connected. The electroless plating method is a well-known method in the field of manufacturing non-conductive materials (plastics, ceramics, etc.) plated products. Examples of metals include copper, nickel, cobalt, gold, tin, chromium, etc.

The metal layer formed by sputtering, evaporation, electroless plating and the like can be further thickened by electrolytic plating using the same or different metals.

The thickness of the metal layer can be appropriately set according to the purpose of the metal-clad laminate, for example, it can be selected from a wide range of 10nm to 100μm. When a metal foil is used as the metal layer, the thickness of the metal layer can be 1 to 100μm, preferably 5 to 50μm, and more preferably 8 to 35μm. In addition, when the metal layer is formed by sputtering, evaporation, electroless plating, or a combination of these and electrolytic plating, the thickness of the metal layer can be 10nm to 35μm, preferably 50nm to 12μm, and more preferably 100nm to 9μm.

The thermoplastic liquid crystal polymer film of the present invention is suitable for fine circuit processing by semi-additive method, but circuit formation by other methods does not constitute an obstacle, for example, it can also be formed by drawing the circuit using conductive ink. In particular, when the maximum valley depth Sv of the first surface is not less than 0.2μm and not more than 2.0μm, the adhesion of the conductive ink is also excellent.

The drawing of the pattern by the conductive ink can be performed by drawing with a marker, drawing with an inkjet, printing by screen printing, etc., and is not particularly limited. As the conductive ink, water-based or oil-based ink 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, In, etc. can be used. After drawing with the conductive ink, it is preferred to perform heat treatment in order to sinter the metal particles. Sintering can be performed at a temperature of about 180 to 450°C, but the heat treatment temperature is preferably set to a temperature lower than the melting point of the thermoplastic liquid crystal polymer film serving as the substrate.

Furthermore, the laminate of the present invention may be one in which a metal foil is pressed and bonded to the second surface by the above method. Alternatively, a metal layer may be formed on the second surface by sputtering, evaporation, chemical plating, etc. In this case, the surface roughness of the second surface may be adjusted to a skewness Ssk of not less than -5 and not more than 0 by the above method.

The multilayer body of the present invention can be effectively used as a component used in the electrical and electronic fields, office machinery and precision instrument fields, power semiconductor fields, etc., and can be effectively used as a circuit board material, for example.

The circuit substrate using the multilayer body of the present invention is ideal for use in high-frequency circuit substrates, automotive sensors, mobile circuit substrates, antennas, etc. [Example]

The present invention is described in more detail below by way of examples, but the present invention is not limited by the examples. In addition, in the following examples and comparative examples, various physical properties are measured by the following methods.

[Thickness] The thickness of various materials is measured using a digital indicator (made by Mitutoyo Co., Ltd.). The material to be measured is measured at intervals of 1 cm in the width direction, and the average value of 10 points randomly selected from the center and the ends is set as the thickness.

[Melting point] Using a differential scanning calorimeter (manufactured by Shimadzu Corporation), samples of a specified size were taken from the thermoplastic liquid crystal polymer film and placed in a sample container. The temperature was raised from room temperature at a rate of 10°C/min to completely melt at 400°C. The melt was then cooled to 50°C at a rate of 10°C/min. When the temperature was raised again at a rate of 10°C/min, the position of the endothermic peak that appeared was determined as the melting point (Tm) of the thermoplastic liquid crystal polymer film.

[Measurement of surface roughness] The surface roughness of the thermoplastic liquid crystal polymer film was measured according to ISO25178 using a white conjugate microscope (OPTELICS HYBRID(L)) manufactured by Lasertec Co., Ltd. to measure the arithmetic mean roughness Sa, maximum peak height Sp, maximum height Sz, skewness Ssk, and kurtosis Sku. The laser microscope was magnified 50 times, with an optical resolution of 0.05μm and a measurement range of 74.24μm×74.24μm (5512μm ² ). The measurement was performed at three locations, the center and both sides of a 30cm wide sample. The arithmetic mean of the values of Sa, Sz, Ssk, and Sku at the three locations was set as the value of Sa, Sz, Ssk, and Sku. In addition, in the white confocal microscope measurement, when the measurement surface of the measurement result is not a flat surface but a curved surface, the above surface properties are calculated after plane correction. In addition, the measurement environment for the white confocal microscope is set to a temperature of 23±2℃ and a humidity of 50%±5%.

<Determination of peel strength of copper layer/LCP film interface> A 5mm wide circuit was made from the copper vapor-deposited layer of the laminate, and the thermoplastic liquid crystal polymer film was fixed to a flat plate using double-sided adhesive tape. The strength when the copper foil was peeled off at a speed of 50mm/min was measured using the 90° method according to JIS C 5016. The results in the table are converted from the sample width.

<Measurement of transmission loss and impedance> After copper was evaporated on the sample, a copper foil layer was deposited to 12μm using a plating bath. Then, a microstrip line structure was formed. At this time, the circuit was made so that the characteristic impedance became 50Ω. For this circuit, the transmission loss and impedance were measured at 50GHz using a microwave network analyzer ("8722ES" made by Agilent Technologies) and a probe (ACP40-250) made by Cascade Microtech. In addition, the transmission loss was measured immediately after the circuit substrate was placed in an environment with a temperature of 23℃ and a humidity of 60%RH for 96 hours.

Example 1 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 single screw extruder, and then extruded through an inflation mold with a diameter of 40 mm and a slit spacing of 0.6 mm to obtain a thermoplastic liquid crystal polymer film with a thickness of 50 μm and a melting point of 320°C. Next, the heating temperature of the metal roller embossed to a surface roughness of Ra0.9μm, Rz6.7μm, and Rzjis4.9μm was set to 250°C, the speed ratio of the metal roller circumferential speed to the film transport speed was set to 0.98, and the thermoplastic liquid crystal polymer film was transported in a manner of embracing time (embracing time) of 30 seconds to shrink the film, thereby obtaining a film with controlled surface shape (surface roughness). In addition, in the surface roughness of the metal roller embossed, Ra is the arithmetic average roughness, Rz is the maximum height roughness, and Rzjis is the ten-point average roughness, which are values measured according to JIS B 0601:2001. In addition, the above-mentioned "embracing time" means the time that the thermoplastic liquid crystal polymer film contacts the surface of the metal roller during the step of transporting the film by contacting the surface of the metal roller.

Example 2 Except that the speed ratio of the metal roller circumferential speed to the film transport speed is set to 0.99 and the wrapping time is set to 10 seconds, a thermoplastic liquid crystal polymer film with controlled surface shape is obtained in the same manner as in Example 1.

Example 3 A thermoplastic liquid crystal polymer film having a thickness of 50 μm was obtained by the air-filled film forming method in the same manner as in Example 1. Meanwhile, the surface of a heat-resistant rubber roller was ground using 1200-grit rotary sandpaper to prepare a heat-resistant rubber roller having a roughened surface. The TLCP film and copper foil (JX Metal Co., Ltd.: JXEFL-BHM foil, thickness 12μm) were stacked, and the TLCP film was moved along the heat-resistant rubber roller at a speed of 3mm/min while being brought into contact with the heat-resistant rubber roller. The roughened surface of the heat-resistant rubber roller was transferred to the TLCP film surface while being introduced between the heat-resistant rubber roller and the heated metal roller for lamination and pressure bonding, thereby obtaining a single-sided copper-clad laminate. The temperature of the heated metal roller was set to 240°C, and the pressure applied to the TLCP film and the copper foil during lamination and pressure bonding was set to 40kg/ ^cm2 in terms of surface pressure.

Example 4 Except that the laminate of the thermoplastic liquid crystal polymer film and the metal foil is moved along the heat-resistant rubber roller at a speed of 1 mm/min, a single-sided copper-clad laminate is obtained in the same manner as in Example 3.

Comparative Example 1 The copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 80/20) was extruded from an extruder while exhausting air, and a film was formed using a T-die to obtain a thermoplastic liquid crystal polymer film with a thickness of 50 μm and a melting point of 320°C. The above-mentioned thermoplastic liquid crystal polymer film and copper foil (JX Metal Co., Ltd., JXEFL-BHM foil, 12μm) are laminated, and polyimide films (Kaneka Co., Ltd., "Apical" 50μm) are further arranged on the top and bottom as protective materials, and moved between a pair of heated metal rollers set at a surface temperature of 280℃ and a linear pressure of 4.2kg/mm. The laminate is then transported while being cooled, and the polyimide film is peeled off after cooling to obtain a single-sided copper-clad laminate composed of copper foil and a smooth liquid crystal polymer film.

Comparative Example 2 A thermoplastic liquid crystal polymer film with a thickness of 50 μm was obtained by the air inflation film forming method in the same manner as in Example 1. Afterwards, a glossy heat-resistant rubber roller and a heated metal roller set at a temperature of 240°C were prepared. The thermoplastic liquid crystal polymer film and a copper foil (JX Metal Co., Ltd.: JXEFL-BHM foil, thickness 12 μm) were overlapped, and the thermoplastic liquid crystal polymer film was brought into contact with the heat-resistant rubber roller and conveyed along the heat-resistant rubber roller at a speed of 2 mm/min. The glossy surface of the heat-resistant rubber roller was transferred to the surface of the thermoplastic liquid crystal polymer film while being introduced between the heat-resistant rubber roller and the heated metal roller for lamination and pressure bonding, thereby obtaining a single-sided copper-clad laminate. The pressure applied to the TLCP film and the copper foil during lamination was set to 40 kg/cm ² in terms of surface pressure.

Comparative Example 3 Similarly to Comparative Example 1, a single-sided copper-clad laminate was made from a thermoplastic liquid crystal polymer film extruded from a T-die and a copper foil. Afterwards, a solution of 30wt% potassium hydroxide, 40wt% monoethanolamine, and 30wt% water was prepared to a temperature of 90°C, and the solution was transported with an immersion time of 90 seconds to chemically etch the surface of the thermoplastic liquid crystal polymer film.

Comparative Example 4 A thermoplastic liquid crystal polymer film with a thickness of 50 μm was obtained by the same inflation film forming method as in Example 1. Next, the thermoplastic liquid crystal polymer film was pressed and bonded to a copper foil laminate in the same manner as in Comparative Example 1 to produce a single-sided copper-clad laminate. Thereafter, while the single-sided copper-clad laminate was transported at a transport speed of 1 m/min, a 1000 mesh polishing roller with a silicon carbide abrasive attached to resistant polyester was used to polish the side surface of the thermoplastic liquid crystal polymer film at a high speed of 2000 rpm.

Comparative Example 5 A thermoplastic liquid crystal polymer film with a thickness of 50 μm was obtained by the same inflation film forming method as in Example 1. Next, the inflation film-forming thermoplastic liquid crystal polymer film was pressed and bonded to a copper foil laminate in the same manner as in Comparative Example 1 to produce a single-sided copper-clad laminate. Afterwards, the surface of the thermoplastic liquid crystal polymer film was sandblasted using a wet sandblasting device. Polygonal alumina with an average particle size of 14 μm was used as an abrasive, and a mixture with water was prepared at a concentration of 15% by mass of the abrasive, and sprayed using a wide-width sandblasting gun. The spraying pressure was set to 0.25 MPa. While sandblasting is being performed under the above conditions, the single-sided copper-clad laminate attached to the flat plate is transported at a transport speed of 50mm/s to perform sandblasting on the thermoplastic liquid crystal polymer film surface.

The surface roughness of the thermoplastic liquid crystal polymer film of the embodiment and comparative example or the thermoplastic liquid crystal polymer film side surface of the single-sided copper-clad laminate prepared as described above was measured by the above method. The results are shown in Table 7. Next, a copper vapor-deposited layer was formed on the thermoplastic liquid crystal polymer film surface with adjusted surface roughness by the following method.

<Formation of copper vapor-deposited layer> Next, a copper vapor-deposited layer (thickness: 0.3 μm) was formed on the thermoplastic liquid crystal polymer film or the thermoplastic liquid crystal polymer film side of the single-sided copper-clad laminate by a roll-to-roll method using a vacuum vapor deposition device (Rock Giken Kogyo Co., Ltd., trade name: RVC-W-300).

More specifically, a TLCP film or a single-sided copper-clad laminate is placed on the side of a loader, and after the opening window is completely closed, a vacuum is applied, and at the same time, the temperature of the heating roller (the roller for metal evaporation of the TLCP film) is set to 100°C.

Next, the copper ingot was taken out and copper particles were added so that the total weight of copper was 450 g. The copper particles were washed with sodium persulfate water as a pretreatment and then washed with distilled water.

Next, after confirming that the vacuum degree in the evaporation chamber has reached 7×10 ^-3 Pa, the set temperature of the heating roller is set to 280°C. After that, the output of EMI (emission current value of the electron gun) is increased to melt the copper. In addition, at this time, the EMI output value is adjusted so that the evaporation speed becomes 2.7nm/s.

Next, after confirming that the temperature of the heating roller has reached the set temperature (280°C) and the vacuum in the evaporation chamber has become less than 5×10 ^-3 Pa, the copper evaporation treatment is carried out while the transport speed of the single-sided copper-clad laminate is set to 0.5m/min, forming a copper evaporation layer with a thickness of 0.3μm. After that, the copper is plated to a thickness of 12μm. The composition of the plating solution is 100g/L copper sulfate, 50g/L sulfuric acid, 30mg/L chlorine ion concentration, and a small amount of additives. The current density of the plating is set to 1A/dm ² , and the temperature is set to 10°C, and electrolytic plating is carried out until the specified thickness is reached.

The copper vapor-deposited layers formed by the embodiments and comparative examples were evaluated for peel strength and transmission characteristics using the above method. For peel strength, 0.7 kN/m or more was evaluated as good, and for transmission characteristics at 50 GHz, -8 dB/100 mm or less was evaluated as "good", and -8 dB/100 mm or more was evaluated as "poor". These results are shown in Table 7.

[Table 7] Surface roughness Evaluation of Evaporation Coating Ssk (μm) Sa (μm) Sp (μm) Sz (μm) Sv (μm) Sku Peel strength Transmission characteristics 50GHz Characteristics Embodiment 1 -1.36 0.23 0.62 2.50 1.88 2.68 0.7 good ○ Embodiment 2 -0.48 0.30 0.86 2.02 1.16 2.69 0.9 good ○ Embodiment 3 -0.22 0.47 2.35 4.60 2.25 3.06 0.8 good ○ Embodiment 4 -4.45 0.18 0.58 3.78 3.20 38.37 0.9 good ○ Comparison Example 1 0.27 0.09 1.04 1.50 0.46 4.53 0.4 good × Comparison Example 2 0.32 0.28 1.77 3.21 1.44 3.37 0.4 good × Comparison Example 3 1.20 0.10 1.66 2.10 0.44 10.02 0.8 bad × Comparison Example 4 0.42 0.12 1.45 1.92 0.47 5.04 1.2 bad × Comparison Example 5 0.45 0.63 3.43 4.54 1.02 4.69 1.6 bad ×

As shown in the table, the peeling strength and transmission characteristics of Examples 1 to 4, where the skewness Ssk and the arithmetic mean roughness Sa are within the scope of the present invention, show good results. In contrast, in Comparative Examples 1 and 2, since the interface between the thermoplastic liquid crystal polymer film and the metal layer is flat, although the transmission characteristics are good, the peeling strength is low; and in Comparative Examples 3, 4, and 5, which are subjected to surface roughening different from the scope of the present invention, although the peeling strength is high, the transmission characteristics are reduced. [Industrial Applicability]

The thermoplastic liquid crystal polymer film of the present invention is suitable for forming fine circuits by semi-additive method, and can take into account both peel strength and transmission characteristics. Therefore, it is highly applicable in applications such as flexible circuit substrates.

As described above, the ideal embodiment of the present invention is described. However, anyone with ordinary knowledge in the technical field to which the present invention belongs should be able to easily think of various changes and modifications within the obvious scope after 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 (14)

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 in at least one surface, the skewness (skewness) Ssk is greater than -5 and less than 0, and the arithmetic average roughness Sa of the surface is greater than 0.15μm. A thermoplastic liquid crystal polymer film as claimed in claim 1, wherein the surface is metal-free. A thermoplastic liquid crystal polymer film as claimed in claim 1 or 2, wherein the arithmetic mean roughness Sa of the surface is less than 0.5 μm. A thermoplastic liquid crystal polymer film as claimed in claim 1 or 2, wherein the maximum peak height Sp of the surface is greater than 0.15 μm and less than 3.00 μm. A thermoplastic liquid crystal polymer film as claimed in claim 1 or 2, wherein the maximum valley depth Sv of the surface is greater than 0.2 μm and less than 3.5 μm. A thermoplastic liquid crystal polymer film as claimed in claim 1 or 2, wherein the maximum height Sz of the surface is greater than 1.5 μm and less than 5.0 μm. The thermoplastic liquid crystal polymer film of claim 1 or 2, wherein the melting point is above 315°C. A laminate comprising the thermoplastic liquid crystal polymer film of claim 1 or 2, and a conductive layer laminated on the thermoplastic liquid crystal polymer film. A laminate as claimed in claim 8, wherein a conductive layer is formed on the surface of the thermoplastic liquid crystal polymer film and a layer consisting of at least one selected from the group consisting of conductive ink, metal film, and circuits formed thereby. A laminate as claimed in claim 9, wherein a metal foil layer is formed as a conductive layer on the surface opposite to the surface of the thermoplastic liquid crystal polymer film. The multilayer structure of claim 8 is a circuit substrate. A method for manufacturing a thermoplastic liquid crystal polymer film as claimed in claim 1 or 2, which comprises at least the step of bringing a roughened surface roller into contact with at least one surface of the thermoplastic liquid crystal polymer film. A method for manufacturing a laminate as claimed in claim 8, which comprises at least the step of bringing a roughened surface roller into contact with a surface of a thermoplastic liquid crystal polymer film of a laminate of a thermoplastic liquid crystal polymer film and a support. A method for manufacturing a laminate as claimed in claim 13, wherein the support is a metal foil.