Thermoplastic liquid crystal polymer molded body, metal-clad laminate, and circuit board

Abstract

In order to increase the total light transmittance while maintaining a high haze value of the thermoplastic liquid crystal polymer, a thermoplastic liquid crystal polymer molded body is produced with a haze value of 99% or more, a coefficient of thermal expansion of 16 to 27 ppm / °C, and a correlation between the absorption coefficient (ε) and the thickness (x) satisfying ε ≤ 0.21x<supgt;‑0.55< / supgt>. The thermoplastic liquid crystal polymer may be a polyester containing repeating units derived from a substance selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid; 6-hydroxy-2-naphthoic acid, terephthalic acid, and p-aminophenol; p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and terephthalic acid; 6-hydroxy-2-naphthoic acid, terephthalic acid, p-aminophenol, isophthalic acid, hydroquinone, and naphthalenedicarboxylic acid; and p-hydroxybenzoic acid, terephthalic acid, and 4,4'-dihydroxybiphenyl.

Description

[0001] Related Applications

[0002] This application claims the benefit of Japanese Patent Application No. 2020-105862, filed on June 19, 2020, the entirety of which is hereby incorporated by reference as a part of this application. Technical Field

[0003] The present invention relates to a thermoplastic liquid crystal polymer molded body having high total light transmittance and ultra-high haze value, and a metal-clad laminate and a circuit board using the molded body as a substrate. Background Art

[0004] Thermoplastic liquid crystal polymer molded articles have low dielectric properties (low dielectric constant and low dielectric loss tangent) due to the properties of thermoplastic liquid crystal polymers, and therefore have attracted attention in applications where dielectric properties are important.

[0005] For example, in recent years, as the transmission signals of printed wiring boards have become faster, the high frequencies of signals have continued to develop. Along with this, substrates used for printed wiring boards are required to have excellent low dielectric properties in the high frequency region. In response to such requirements, thermoplastic liquid crystal polymer films with low dielectric properties have attracted attention as substrate films for printed wiring boards, replacing conventional polyimide (PI) and polyethylene terephthalate films.

[0006] In addition, thermoplastic liquid crystal polymers have high light diffusion properties (high haze value) due to a collection of structures called microdomains. Therefore, the above-mentioned thermoplastic liquid crystal polymer molded products are also expected to be used in electronic / optical materials such as displays, lighting fixtures, polarizer protection, and anti-glare purposes.

[0007] However, thermoplastic liquid crystal polymer molded articles have low transparency and are therefore mostly treated as internal components that are invisible to the human eye in devices, which has the problem of limiting the degree of freedom and designability of device design.

[0008] In addition, as the demand for high-layer circuit substrates that can accommodate multiple circuit wirings increases, technology is needed to suppress the deviation of interlayer connection circuit wirings when connecting each layer. However, due to its low transparency, the thermoplastic liquid crystal polymer film has little information required for the alignment of the interlayer connection circuit wirings, which causes the problem of poor interlayer connection.

[0009] For example, Patent Document 1 (Japanese Patent Gazette No. 2005-178056) discloses a molding processing method, in which, during or after molding of a liquid crystalline polyester resin, the temperature is maintained at a temperature above -20°C from its melting temperature for more than 10 seconds, thereby obtaining a transparent molded body with a haze value of less than 40%.

[0010] Techniques for imparting light diffusivity while maintaining a certain degree of film transparency have also been studied. For example, Patent Document 2 (Japanese Patent Publication No. 2007-293316) describes a light diffusing film having a support layer composed of crystalline polyester and 2 to 40 parts by weight of an incompatible light diffusing agent mixed in the crystalline polyester.

[0011] On the other hand, Patent Document 3 (International Publication No. 2011 / 118449) discloses a thermoplastic liquid crystal polymer film having improved light reflectivity and having 8 to 40 crystal domains per 10 μm in the thickness direction of the film.

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent Application Publication No. 2005-178056

[0015] Patent Document 2: Japanese Patent Application Publication No. 2007-293316

[0016] Patent Document 3: International Publication No. 2011 / 118449 Summary of the invention

[0017] Problems to be solved by the invention

[0018] However, in Patent Document 1, although the transparency of the film is improved, the haze value is reduced, and there is a problem of reduced light diffusion. For example, when the film is used as a circuit substrate material, in order to ensure the freedom of design and convenience during processing, it is preferred that the film has a certain degree of transparency. However, when the circuit substrate is assembled in the final product, in order to maintain the concealment of the circuit design, it is preferred that the film has a certain degree of light diffusion.

[0019] In Patent Document 2, light diffusivity is exhibited by filling particles that are incompatible with the base material, based on the use of backlight units of liquid crystal displays, etc. However, in the case of manufacturing a high-layer circuit substrate using such a layer mixed with heterogeneous materials, there is the following problem: uneven removal of stains generated in the hole-opening process (for example, laser or drill) during conductive processing for interlayer connection is prone to occur, resulting in poor plating on the subsequent hole wall surface. Therefore, the management of inorganic particles and insulating resin materials with different appropriate processing characteristics becomes complicated, and from the perspective of cost increase, it is also industrially disadvantageous compared with the present invention.

[0020] In Patent Document 3, light reflectivity can be improved by stacking a large number of crystal domains in the thickness direction. However, in this case, the light transmittance of the film is impaired.

[0021] Therefore, an object of the present invention is to provide a thermoplastic liquid crystal polymer molded article having a high total light transmittance and an ultra-high haze value, and a metal-clad laminate and a circuit board using the molded article.

[0022] Methods used to solve problems

[0023] Generally, liquid crystalline polyester resins are composed of a collection of structures called microdomains (a kind of high-order structure). Since there are sometimes gaps and defects between microdomains and the optical anisotropy between microdomains is not continuous, light is strongly reflected at the interface between microdomains. It is believed that due to such a structure, it is difficult to make liquid crystalline polyester resins transparent.

[0024] The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object and have found that the light transmittance can be increased while maintaining an ultra-high haze by controlling the size of microdomains and the interface between microdomains.

[0025] Furthermore, it was found that the thermoplastic liquid crystal polymer molded product having a controlled high-order structure has a strong adhesive strength to an adherend and is excellent in heat resistance when used in a multilayer structure.

[0026] That is, the present invention provides the following preferred embodiments.

[0027] The first configuration of the present invention is a thermoplastic liquid crystal polymer molded body having a haze value of 99% or more, a thermal expansion coefficient of 16 to 27 ppm / °C, and a correlation between an absorption coefficient (ε) and a thickness (x) satisfying ε≤0.21x -0.55 .

[0028] In the above-mentioned thermoplastic liquid crystal polymer molded body, the above-mentioned thermoplastic liquid crystal polymer can be selected from a group consisting of polyesters containing repeating units derived from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid; polyesters containing repeating units derived from 6-hydroxy-2-naphthoic acid, terephthalic acid and p-aminophenol; polyesters containing repeating units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and terephthalic acid; polyesters containing repeating units derived from 6-hydroxy-2-naphthoic acid, terephthalic acid, p-aminophenol, isophthalic acid, hydroquinone and naphthalene dicarboxylic acid; and polyesters containing repeating units derived from p-hydroxybenzoic acid, terephthalic acid and 4,4'-dihydroxybiphenyl.

[0029] The thermoplastic liquid crystal polymer molded article may have a film-like shape.

[0030] A second configuration of the present invention is a laminated body which is a metal-clad laminated body comprising the above-mentioned thermoplastic liquid crystal polymer molded body in a film form and a metal layer bonded to at least one surface (one surface or both surfaces) of the above-mentioned molded body.

[0031] A third configuration of the present invention is a circuit board including the metal-clad laminate described above, wherein the at least one metal layer has a circuit pattern.

[0032] The circuit board may be a laminated circuit board including at least one layer of the metal-clad laminate.

[0033] It should be noted that any combination of at least two constituent elements disclosed in the claims and / or the specification is included in the present invention. In particular, any combination of two or more of the claims described in the claims is also included in the present invention.

[0034] Effects of the Invention

[0035] The thermoplastic liquid crystal polymer molded body of the present invention has high total light transmittance and ultra-high haze value at the same time, and has a specific thermal expansion coefficient, therefore, for example, when the multilayer of the electronic circuit substrate is stacked, the alignment of the circuit wiring between the layers can be made easy and the positional deviation of the circuit wiring can be suppressed by the high total light transmittance, and the functions such as the concealment of the wiring or the element in the device and the interference of light can be added by the high haze value, and it is extremely useful as an insulator material. In addition, the degree of freedom and design of the device design increase, and it can be expected to be applied to electronic / optical materials such as displays, optical sensors, anti-glare films, lighting fixtures, polaroid protective films. In addition, by the control of the micro-domain size, the adhesion to the adherend is high and the heat resistance is also excellent, so it is extremely useful as an insulator material of an electronic circuit substrate, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic cross-sectional view for explaining the manufacturing process of the formed body, the metal-clad laminate, and the circuit board according to one embodiment of the present invention.

[0037] Figure 2 It is a graph showing the correlation between the film thickness and the absorption coefficient of the films of Examples and Comparative Examples. DETAILED DESCRIPTION

[0038] The molded article of the present invention is a molded article composed of a liquid crystal polymer (hereinafter referred to as a thermoplastic liquid crystal polymer) showing optical anisotropy when melted, which shows an extremely high haze value of 99% or more, and the correlation between the absorption coefficient (ε) and the thickness (x) satisfies ε≤0.21x -0.55 .

[0039] The shape of the molded body is not particularly limited, and may be, for example, a molded body having a film-like shape (i.e., a thermoplastic liquid crystal polymer film). Furthermore, a laminated body (metal-clad laminated body) having a metal layer laminated on at least one surface (one surface or both surfaces) of the molded body, and a circuit substrate having a conductor circuit formed on at least one surface of the molded body are also included in the present invention.

[0040] (Thermoplastic Liquid Crystal Polymer)

[0041] The thermoplastic liquid crystal polymer used in the present invention is a polymer that can form an optically anisotropic melt phase. Examples of the thermoplastic liquid crystal polymer include thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides into which amide bonds are introduced.

[0042] The thermoplastic liquid crystal polymer may be a polymer in which an imide bond, a carbonate bond, a carbodiimide bond, or a bond derived from isocyanate such as an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide.

[0043] As specific examples of the thermoplastic liquid crystal polymer used in the present invention, there can be listed known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides derived from the compounds classified as (1) to (4) and their derivatives listed below. However, it is self-evident that there is an appropriate range for the combination of various raw material compounds in order to form a polymer capable of forming an optically anisotropic melt phase.

[0044] (1) Aromatic or aliphatic diols (see Table 1 for representative examples)

[0045] [Table 1]

[0046]

[0047] (2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for representative examples)

[0048] [Table 2]

[0049]

[0050] (3) Aromatic hydroxycarboxylic acid (see Table 3 for representative examples)

[0051] [Table 3]

[0052]

[0053] (4) Aromatic diamine, aromatic hydroxylamine or aromatic aminocarboxylic acid (see Table 4 for representative examples)

[0054] [Table 4]

[0055]

[0056] As representative examples of thermoplastic liquid crystal polymers obtained from these raw material compounds, copolymers having the structural units shown in Tables 5 and 6 can be cited.

[0057] [Table 5]

[0058]

[0059] [Table 6]

[0060]

[0061] Among these copolymers, polymers 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 and at least one aromatic diol and / or an aromatic hydroxyamine and at least one aromatic dicarboxylic acid are preferred.

[0062] When the thermoplastic liquid crystal polymer is a copolymer containing repeating units of p-hydroxybenzoic acid (A) and 6-hydroxy-2-naphthoic acid (B), the molar ratio (A) / (B) is preferably (A) / (B) = 10 / 90 to 90 / 10, more preferably 50 / 50 to 90 / 10, further preferably 75 / 25 to 90 / 10, further preferably 75 / 25 to 85 / 15, and particularly preferably 77 / 23 to 80 / 20.

[0063] For example, in the copolymer of (i), when the thermoplastic liquid crystal polymer contains at least repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the molar ratio (A) / (B) of the repeating unit (A) of p-hydroxybenzoic acid to the repeating unit (B) of 6-hydroxy-2-naphthoic acid in the thermoplastic liquid crystal polymer is preferably (A) / (B) = about 10 / 90 to about 90 / 10, more preferably (A) / (B) = about 15 / 85 to about 85 / 15, and further preferably (A) / (B) = about 20 / 80 to about 80 / 20.

[0064] In the case of the copolymer of (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-naphthalene dicarboxylic acid are contained in each repeating unit of the thermoplastic liquid crystal polymer. The molar ratio of the aromatic hydroxycarboxylic acid (C): the above-mentioned aromatic diol (D): the above-mentioned aromatic dicarboxylic acid (E) can be about (30-80): about (35-10): about (35-10), more preferably it can be (C): (D): (E) = about (35-75): about (32.5-12.5): about (32.5-12.5), and further preferably it can be (C): (D): (E) = about (40-70): about (30-15): about (30-15).

[0065] 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.

[0066] In addition, 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.

[0067] The molar ratio of the repeating structural unit derived from the aromatic diol (D) to the repeating structural unit derived from the aromatic dicarboxylic acid (E) is preferably (D) / (E) = 95 / 100 to 100 / 95. If it is out of this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

[0068] Among the thermoplastic liquid crystal polymers described above, as the thermoplastic liquid crystal polymer constituting the molded body of the present invention, it is particularly preferred to use a substance selected from the group consisting of a polyester containing repeating units derived from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid; a polyester containing repeating units derived from 6-hydroxy-2-naphthoic acid, terephthalic acid and p-aminophenol; a polyester containing repeating units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and terephthalic acid; a polyester containing repeating units derived from 6-hydroxy-2-naphthoic acid, terephthalic acid, p-aminophenol, isophthalic acid, hydroquinone and naphthalene dicarboxylic acid; and a polyester containing repeating units derived from p-hydroxybenzoic acid, terephthalic acid and 4,4'-dihydroxybiphenyl.

[0069] It should be noted that the molten phase capable of forming optical anisotropy in the present invention can be identified by, for example, placing a sample on a hot stage, heating it at elevated temperatures in a nitrogen atmosphere, and observing the transmitted light of the sample.

[0070] As a thermoplastic liquid crystal polymer, it is preferred that the melting point (hereinafter referred to as Tm0) is, for example, in the range of 200 to 360°C, more preferably in the range of 240 to 350°C, further preferably Tm0 is 260 to 330°C, and more preferably Tm0 is 290 to 330°C. It should be noted that the melting point 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 and completely melted, 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, and the position of the endothermic peak that appears after the temperature is raised is obtained as the melting point of the thermoplastic liquid crystal polymer sample.

[0071] To the above-mentioned thermoplastic liquid crystal polymer, thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyetheretherketone, fluororesin, various additives, fillers, etc. may be added within the range not impairing the effects of the present invention.

[0072] It is also a preferred embodiment that the thermoplastic liquid crystal polymer used in the present invention does not contain additives, fillers, etc. By not containing heterogeneous materials, it is difficult to produce uneven removal of stains generated in the hole-opening process (for example, laser or drill) during the conductive processing for interlayer connection, and it is difficult to cause poor plating on the subsequent hole wall surface. Therefore, the thermoplastic liquid crystal polymer molded body used in the present invention is preferably a thermoplastic liquid crystal polymer film that does not contain additives, fillers, etc.

[0073] (formed body)

[0074] The shape of the molded body of the present invention is not limited, and the above-mentioned thermoplastic liquid crystal polymer can be processed into any shape according to the purpose, for example, it can have a film-like shape. The film-like thermoplastic liquid crystal polymer, the so-called thermoplastic liquid crystal polymer film, is obtained by, for example, extruding the melt-kneaded product of the above-mentioned thermoplastic liquid crystal polymer. As an extrusion molding method, any method can be used, and the known T-die method, inflation method, etc. are industrially advantageous. In particular, for 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 orthogonal to the mechanical axis direction (hereinafter referred to as TD direction), and it can be stretched uniformly in the MD direction and the TD direction. Therefore, a thermoplastic liquid crystal polymer film having controlled molecular orientation, dielectric properties, etc. in the MD direction and the TD direction can be obtained.

[0075] For example, in extrusion molding using the T-die method, the molten sheet extruded from the T-die can be stretched not only in the MD direction of the thermoplastic liquid crystal polymer film, but also simultaneously in the MD direction and TD directions to form a film; or the molten sheet extruded from the T-die can be first stretched in the MD direction and then stretched in the TD direction to form a film.

[0076] In the extrusion molding by the inflation method, a cylindrical sheet melt-extruded from a ring die may be stretched at a predetermined stretch ratio (equivalent to the stretch ratio in the MD direction) and inflation ratio (equivalent to the stretch ratio in the TD direction) to form a film.

[0077] Regarding the stretching ratio of such extrusion molding, the stretching ratio (or stretch ratio) in the MD direction may be, for example, about 1.0 to about 10, preferably about 1.2 to about 7, and more preferably about 1.3 to about 7. In addition, the stretching ratio (or blow-up ratio) in the TD direction may be, for example, about 1.5 to about 20, preferably about 2 to about 15, and more preferably about 2.5 to about 14.

[0078] In addition, the melting point and / or thermal expansion coefficient of the thermoplastic liquid crystal polymer film can be adjusted by performing known or customary heat treatment as needed. The heat treatment conditions can be appropriately set according to the purpose. For example, the melting point (Tm) of the thermoplastic liquid crystal polymer film can be increased by heating for several hours at a temperature above (Tm0-10)°C (e.g., about (Tm0-10)°C to about (Tm0+30)°C, preferably about (Tm0)°C to (Tm0+20)°C) relative to the melting point (Tm0) of the thermoplastic liquid crystal polymer.

[0079] The melting point (Tm) of the thermoplastic liquid crystal polymer film may be, for example, 270 to 380° C., preferably 280 to 370° C., and more preferably 290 to 360° C. It should be noted that 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 position of the endothermic peak that appears when the thermoplastic liquid crystal polymer film sample is heated at a rate of 10° C. / min can be obtained as the melting point (Tm) of the thermoplastic liquid crystal polymer film.

[0080] The thickness of the thermoplastic liquid crystal polymer film can be appropriately set according to the application. For example, if the material used for the insulating layer of a multilayer circuit substrate is considered, it can be 10 to 500 μm, preferably 15 to 250 μm, more preferably 25 to 180 μm, for example 25 to 100 μm.

[0081] For the thermoplastic liquid crystal polymer molded article of the present invention, the thermal expansion coefficient in the plane direction of the molded article is adjusted to 16 to 27 ppm / °C, preferably 17 ppm / °C or more, more preferably 18 ppm / °C or more. In addition, it is preferably 25 ppm / °C or less, more preferably 23 ppm / °C or less, and further preferably 20 ppm / °C or less. The thermal expansion coefficient can be measured, for example, by the TMA method.

[0082] The above-mentioned thermoplastic liquid crystal polymer generally shows a high haze value, but in the present invention, the total light transmittance is improved compared with the existing products while maintaining the high haze value. That is, the thermoplastic liquid crystal polymer molded product (for example, a thermoplastic liquid crystal polymer film) of the present invention shows a haze value of 99% or more, and the correlation between the absorption coefficient (ε) and the thickness (x) satisfies ε≤0.21x -0.55 .

[0083] The above optical properties can be imparted to the molded body by, for example, first processing the thermoplastic liquid crystal polymer into a predetermined shape and then performing a predetermined heat treatment. The heat treatment is preferably performed at a temperature higher than the melting point Tm of the molded body (thermoplastic liquid crystal polymer film), for example, preferably at a temperature 20°C higher than the melting point Tm, for example, at a temperature 20 to 40°C higher than the melting point Tm. The heat treatment time is preferably at least 1 second, more preferably 4 seconds or more. On the other hand, if the heat treatment time is too long, degradation of the thermoplastic liquid crystal polymer occurs, so the heat treatment time is preferably 500 seconds or less, more preferably 400 seconds or less.

[0084] As the reason why the heat treatment can impart the desired optical properties, on the one hand, since the thermoplastic liquid crystal polymer film has a multi-domain structure itself and does not change, the haze value of more than 99% is maintained, and on the other hand, it is believed that the transparency is improved by the growth of the domain size caused by the heat treatment, the reduction of defects caused by the relaxation of the strain during the molding process, etc. It should be noted that in the case of the thermoplastic liquid crystal polymer film, the heat treatment can be performed after the metal layer is formed on one side or both sides. After the heat treatment, it can be used as the metal-clad laminated plate described below, or the metal layer can be peeled off and used for other purposes.

[0085] (Metal-clad laminate)

[0086] The laminate of the present invention is a laminate having the above-mentioned thermoplastic liquid crystal polymer molded body (e.g., a thermoplastic liquid crystal polymer film) and a metal layer laminated on at least one surface thereof (so-called metal-clad laminate). For example, the laminate may be a single-sided or double-sided metal-clad laminate having a metal layer laminated on one or both surfaces of a thermoplastic liquid crystal polymer film.

[0087] The metal layer can be appropriately determined according to the purpose, and preferably copper, nickel, cobalt, aluminum, gold, tin, chromium, etc. The thickness of the metal layer can be 0.01 to 200 μm, preferably 0.1 to 100 μm, more preferably 1 to 80 μm, and particularly preferably 2 to 50 μm.

[0088] The method of laminating the metal layer is not particularly limited. For example, a metal foil (e.g., copper foil) may be pressed onto the thermoplastic liquid crystal polymer film in a roll-to-roll manner using a roll press, or a double belt press, a vacuum hot press, etc. Alternatively, a metal layer may be vacuum-deposited onto the surface of the thermoplastic liquid crystal polymer film, and the metal layer may be formed on the deposited layer by electrolytic plating.

[0089] (Circuit board)

[0090] The circuit substrate as one embodiment of the present invention is formed using a metal-clad laminate having the thermoplastic liquid crystal polymer molded body of the present invention as a substrate. In the circuit substrate, a circuit is formed on a metal layer on one side or both sides. The circuit can be formed by a known subtractive method, an additive method, a semi-additive method, etc. The thickness of the circuit (metal layer) can be, for example, 10 to 14 μm, preferably 11 to 13 μm. The circuit substrate can be composed of the above-mentioned metal-clad laminate, or it can be a laminated circuit substrate on which other layers are further laminated.

[0091] It should be noted that the circuit substrate can also be formed with through holes, etc., as required by various known or conventional manufacturing methods. In this case, a through-hole plating layer can be formed on the circuit substrate, and the thickness of the circuit (metal layer) in the state of the through-hole plating layer can be, for example, 20 to 40 μm, preferably 25 to 35 μm.

[0092] (Method for producing thermoplastic liquid crystal polymer molded article)

[0093] Below, refer to Figure 1 An example of a manufacturing process of a molded body, a metal-clad laminate, and a circuit board according to an embodiment of the present invention is described. Figure 1 These are schematic cross-sectional views for explanation purposes, and the thickness ratio of the raw material, the lateral width, etc. do not reflect actual dimensions.

[0094] A. Preparation process

[0095] First, a thermoplastic liquid crystal polymer film 1 and a metal foil 2 forming a metal layer are prepared.

[0096] B. Lamination process

[0097] Next, the TLCP film 1 and the metal foil 2 are bonded together by thermocompression bonding to form a laminate precursor 3 .

[0098] C. Heat treatment process

[0099] Next, the laminate precursor 3 is heat-treated at a temperature higher than the melting point of the thermoplastic liquid crystal polymer film 1 (for example, 20°C or higher than the melting point) in an inert atmosphere such as preferably nitrogen, thereby improving the total light transmittance of the thermoplastic liquid crystal polymer film 1, and producing a metal-clad laminate 30 as a laminate of the present invention, which is a laminate of the film-like thermoplastic liquid crystal polymer molded body 10 of the present invention and the metal foil 2. In addition, when the heat treatment is continuously performed, the load and tension for stabilizing the laminate during the continuous heat treatment may be set according to the thickness and width of the laminate precursor, but from the viewpoint of dimensional stability, the heat treatment is preferably performed in a state where the laminate precursor 3 is left horizontally without applying a load or tension.

[0100] D. Circuit Processing

[0101] Next, the metal foil 2 is subjected to circuit processing to form a circuit board 40 having a circuit pattern 20 .

[0102] As the conditions for each of the above steps, the conditions described above can be applied. It should be noted that the metal foil 2 can be removed from the metal-clad laminate 30 after the heat treatment step by etching or the like, and the obtained film-like thermoplastic liquid crystal polymer molded body 10 can be used for other purposes. Figure 1In the embodiment, the metal foil 2 is pressed onto one side of the TLCP film 1, but the metal foil 2 may be pressed onto both sides.

[0103] In the above-mentioned B. lamination step, the metal foil 2 can be appropriately determined according to the purpose, and examples thereof include metal foils of copper, nickel, cobalt, aluminum, gold, tin, chromium, etc., and copper foil and aluminum foil are preferably used, and copper foil is more preferably used.

[0104] In the above C. heat treatment step, the heat treatment temperature is preferably the melting point Tm of the thermoplastic liquid crystal polymer film 1, which is 10°C or higher, more preferably Tm+15°C or higher, and further preferably Tm+20°C or higher. In addition, it is preferably Tm+40°C or lower, more preferably Tm+35°C or lower, and further preferably Tm+30°C or lower. The heat treatment time is preferably 1 second or longer, more preferably 2 seconds or longer, further preferably 3 seconds or longer, and further preferably 4 seconds or longer. In addition, it is preferably 500 seconds or shorter, more preferably 400 seconds or shorter, further preferably 350 seconds or shorter, and further preferably 300 seconds or shorter.

[0105] Example

[0106] The present invention is specifically described below by way of examples, but the present invention is not limited to these examples.

[0107] In addition, each evaluation method of the thermoplastic liquid crystal polymer film used in the following Examples and Comparative Examples is shown below.

[0108] (1)Film thickness

[0109] The film thickness was measured at 1 cm intervals in the TD direction of the obtained film using a digital thickness meter (manufactured by Mitutoyo Co., Ltd.), and the average value of 10 points was taken as the film thickness.

[0110] (2) Total light transmittance

[0111] The total light transmittance was measured using HAZEMETER HM-150 (manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K7136.

[0112] (3) Haze

[0113] The haze was measured using HAZEMETER HM-150 (manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K7136.

[0114] (4) Absorption coefficient

[0115] The absorption coefficient (ε) is calculated in the form of ε=-logR / x from the measured total light transmittance (R: 100R in percentage) and the thickness (x) of the film according to the Lambert-Beer equation.

[0116] (5) Coefficient of thermal expansion (CTE) of the film

[0117] Using a thermomechanical analyzer (TMA), the temperature was raised from 25°C to 200°C at a rate of 5°C / min, then cooled to 30°C at a rate of 20°C / min, and then raised again at a rate of 5°C / min, and the measurement was performed between 30°C and 150°C. The film was measured in both the TD and MD directions, and the average value was taken as the thermal expansion coefficient of the film.

[0118] (6) Dimensional change rate of copper-clad laminate

[0119] The measurement was performed in accordance with IPC-TM-6502.2.4. The heating conditions were 150° C.×30 minutes, and the dimensional change rate (%) of the sample before and after heating was measured.

[0120] (7) Adhesion strength of copper-clad laminates

[0121] According to JIS C5016-1994, the peel strength of the copper foil was measured using a tensile tester (digital force gauge FGP-2 manufactured by Nidec Shinpo Co., Ltd.) while peeling the copper foil of the copper-clad laminate in a 90° direction at a speed of 50 mm per minute. The obtained value was taken as the adhesive strength.

[0122] (8) Solder heat resistance

[0123] Solder heat resistance was measured by investigating the time the film surface maintained its original shape in a molten solder bath maintained at a predetermined temperature. That is, the laminate was placed in a 300°C solder bath for 60 seconds, and the morphological changes such as swelling and deformation on the film surface were visually observed. In Table 7, samples with no swelling or deformation for 60 seconds were evaluated as "good", and samples with swelling or deformation were evaluated as "bad".

[0124] (9) Visibility

[0125] The sample was placed on a paper printed with a stripe pattern with a width of 0.1 mm and a circle and square pattern of different sizes (diameter / side 0.5 to 5 mm), and the size that could be recognized was observed. The table shows the minimum size of the pattern that could be recognized.

[0126] [Reference example]

[0127] The raw material of the thermoplastic liquid crystal polymer molded body is a copolymer of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid. The thermoplastic liquid crystal polymer with a melting point of 310°C is heated and kneaded by a single screw extruder, and extruded from a circular die of a blowing device with a die diameter of 33.5 mm and a die slit interval of 500 μm to form a thermoplastic liquid crystal polymer film with an average film thickness of 25 to 100 μm. The melting point of the film with a thickness of 25 μm is 310°C, the total light transmittance is 26.8%, the haze value is 99.6%, and the absorption coefficient is 0.053 / μm.

[0128] The obtained 25 to 100 μm thick thermoplastic liquid crystal polymer film and “JXEFL-BHM” manufactured by JX Metal Co., Ltd. as copper foil were laminated at a temperature of 300° C. and a pressure of 4.0 MPa for 5 minutes to produce a copper-clad laminate.

[0129] [Examples 1 to 5]

[0130] The copper-clad laminate obtained in Reference Example was placed horizontally in a hot air dryer in a nitrogen atmosphere at 330° C. and subjected to heat treatment for the time shown in Table 7. Then, the copper foil was removed using a ferric chloride solution to obtain a thermoplastic liquid crystal polymer film.

[0131] [Example 6]

[0132] The same type of copper foil was laminated on both sides of a 50 μm thick thermoplastic liquid crystal polymer film obtained in the same manner as in the reference example under the same conditions to produce a double-sided copper-clad laminate. After being horizontally placed in a hot air dryer at a nitrogen atmosphere of 330° C. for 4 seconds, the copper foil was removed using a ferric chloride solution to obtain a thermoplastic liquid crystal polymer film.

[0133] [Comparative Examples 1 to 4]

[0134] A copper-clad laminate was prepared by laminating a film of 25 to 100 μm thick "Vecstar" (registered trademark) CTQ manufactured by Kuraray Co., Ltd. and a copper foil "JXEFL-BHM" manufactured by JX Metal Co., Ltd. at a temperature of 300°C and a pressure of 4.0 MPa for 5 minutes. Then, the copper foil was removed using a ferric chloride solution to obtain a thermoplastic liquid crystal polymer film.

[0135] [Comparative Example 5]

[0136] The copper-clad laminate obtained in Reference Example was heat-treated at the temperature and time shown in Table 7. Then, the copper foil was removed using a ferric chloride solution to obtain a thermoplastic liquid crystal polymer film.

[0137]

[0138] [Comparative Examples 6 and 7]

[0139] Separately from the samples shown in Table 7, as Comparative Examples 6 and 7, the metal-clad laminated plates obtained by laminating copper foil on the thermoplastic liquid crystal polymer film with a thickness of 25 μm obtained in the reference example were horizontally placed in a hot air dryer in a nitrogen atmosphere at 330° C., heat-treated for 600 seconds in Comparative Example 6 and for 1800 seconds in Comparative Example 7, and measured for physical properties of the films after removing the copper foil using a ferric chloride solution. The results showed that the total light transmittance was lower than that of Example 2, and the films of Comparative Examples 6 and 7 were discolored to yellow compared to the films obtained in Examples 1 to 5. In addition, the thermal expansion coefficient of the films could not be controlled within the specified range.

[0140] exist Figure 2 Graphs are shown in which the vertical axis represents the absorption coefficient and the horizontal axis represents the thickness of the thermoplastic liquid crystal polymer film for Examples 1-6 and Comparative Examples 1-5. The diamond-shaped examples and the square-shaped comparative examples represent ε=0.21x -0.55 The curve is distributed as the boundary.

[0141] As shown in Table 7, the thermoplastic liquid crystal polymer molded body shown in the examples that have undergone the heat treatment process has a low extinction coefficient, and has a high light transmittance and improved transmissive visibility compared to the comparative examples of the same thickness, and it can be seen that such a laminate controlled to a specific high-order structure has a high adhesive strength and excellent heat resistance. On the other hand, in Comparative Examples 1-5 in which the metal-clad laminate is not subjected to heat treatment or the heat treatment temperature is low, although the haze value shows a high value, the light transmittance is low and the visibility is poor compared to the examples of the same thickness.

[0142] In addition, in Comparative Examples 4 and 5, the thermal expansion coefficient of the film could not be controlled within the prescribed range.

[0143] Industrial Applicability

[0144] The thermoplastic liquid crystal polymer molded article of the present invention has both high total light transmittance and ultra-high haze value, and therefore, in addition to conventional uses such as multilayer circuit boards, insulators for electronic circuit boards, reinforcing plates for flexible circuit boards, and cover films for circuit surfaces, it can also be expected to be used as diffusion plates for displays, lighting fixtures, etc., which require freedom in device design and design. In addition, by controlling the microdomain size, the adhesion to the adherend is high, and the heat resistance is also excellent, so it is extremely useful as an insulator material for electronic circuit boards, etc.

[0145] As described above, the preferred embodiments of the present invention have been described. However, it will be apparent to those skilled in the art that various additions, changes, or deletions may be made without departing from the gist of the present invention, and such contents are also included in the scope of the present invention.

[0146] Explanation of symbols

[0147] 1 Thermoplastic Liquid Crystal Polymer Film

[0148] 2 metal foil

[0149] 3. Layered Precursors

[0150] 10 Film-like thermoplastic liquid crystal polymer molded article

[0151] 20 Circuit Pattern

[0152] 30 Metal-clad laminate

[0153] 40 Circuit board

Claims

1. A thermoplastic liquid crystal polymer molded product having a haze value of 99% or more, The thermal expansion coefficient is 16-27ppm / ℃. The correlation between the absorption coefficient (ε) and the thickness (x) satisfies ε≤0.21×x -0.55 , The thermoplastic liquid crystal polymer molded product is obtained by processing a thermoplastic liquid crystal polymer containing repeating units derived from p-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid in a molar ratio of 75 / 25 to 80 / 20 into a predetermined shape and then heat-treating it for 4 seconds or more and 400 seconds or less at a temperature 20 to 40° C. higher than the melting point after processing.

2. The thermoplastic liquid crystal polymer molded article according to claim 1, which is in the form of a film. 3 . A metal-clad laminate comprising the film-like thermoplastic liquid crystal polymer molded body according to claim 2 and a metal layer laminated on at least one surface of the film-like molded body. 4 . A circuit substrate comprising the metal-clad laminate according to claim 3 , wherein at least one of the metal layers has a circuit pattern. 5 . A laminated circuit board comprising at least one layer of the metal-clad laminate according to claim 3 .

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