JP2011071815A - Thermoplastic liquid crystal polymer film for transmission line and transmission line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission line which can reduce a transmission loss even in a high frequency band. <P>SOLUTION: The transmission line includes: at least one conductor; and at least one insulator where the insulator is formed of a thermoplastic liquid crystal polymer film, and in the thermoplastic liquid crystal polymer film, a ratio of a dielectric loss tangent (D<SB>TD</SB>/D<SB>MD</SB>) of a mechanical axis direction (abbreviated as an MD direction hereafter) of the film and a direction perpendicular to it (abbreviated as a TD direction hereafter) in a frequency of ≥1 GHz is ≤1.02, and the TD direction of the thermoplastic liquid crystal polymer film and the longitudinal direction of the transmission line are arranged approximately in the same directions. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmission line that can reduce transmission loss even in a high-frequency band, and a thermoplastic liquid crystal polymer film that can be usefully used for such a transmission line.

  In recent years, the information processing field such as a PC and the communication device field such as a mobile phone have been remarkably developed, and the frequency used for such electronics and communication devices has shifted to the gigahertz range. However, it is generally known that the transmission loss of the transmission line increases in such a high frequency band.

  Therefore, in order to reduce the loss during transmission in the high frequency region and improve the information processing speed, that is, the propagation speed, there is a demand for an electrically insulating substrate material having excellent dielectric characteristics. However, since the intrinsic characteristics of the wiring material have already been determined depending on the material, it has been difficult to control the dielectric constant and dielectric loss at the material stage.

  In order to control such properties at the material stage, for example, many porous materials have been reported in which air having a low dielectric constant of 1 is included in the material to make it porous so that the dielectric properties of the material are controlled. Porous materials are classified according to their structure. For example, there are a sponge structure in which small pores are uniformly dispersed, and a void structure in which a space surrounded by upper and lower film layers and an internal structure is a pore.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-154273) discloses a porous body made of a polyimide-based resin dry gel, having an apparent density of 800 kg / m ³ or less and an average pore diameter of 1 μm or less. .

  This document describes that a porous body having continuous micropores can be produced by performing a supercritical drying process, and the porous body obtained in the examples has a high porosity and is a bulk of polyimide resin. It has been reported that the relative permittivity can be reduced as compared with the above.

JP 2000-154273 A (claims, paragraph number [0037])

  However, in the porous body described in Patent Document 1, since bubbles exist, the strength is insufficient. For example, in a transmission line that may be bent repeatedly, bubbles are only broken. Therefore, the strength required for the transmission line cannot be satisfied. Furthermore, if the bubble distribution is non-uniform, the capacitance in the wiring varies depending on the bubble distribution.

  Moreover, when carrying and carrying, temperature and a moisture environment change according to the environment of a carrying destination. In such a case, moisture may be generated in the voids in the porous body. And since the dielectric constant and dielectric loss as an insulator material will become large with the water | moisture content, such a porous body cannot maintain the stability as an insulator material. Therefore, the porous body lacks stability as an electronic device, and it is difficult to satisfy the demands required for making a consumer electronic device.

  Furthermore, in harsh environment usage situations such as outdoor installation and on-vehicle use, the temperature tends to be high and / or high, and the porous body may not be able to withstand use under such harsh conditions.

Accordingly, an object of the present invention is to provide a transmission line that is advantageous in terms of strength, has a low dielectric loss tangent even when used at high frequencies, and can suppress transmission loss.
Another object of the present invention is to provide a transmission line excellent in both dielectric constant and dielectric characteristics.

Still another object of the present invention is to provide a transmission line that exhibits excellent dielectric characteristics even when the temperature and moisture environment fluctuate, or even under high temperature and / or high humidity conditions.
Another object of the present invention is to provide a thermoplastic liquid crystal polymer film that can be suitably used for such an excellent transmission line.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have (1) conventionally recognized that it is difficult to change the dielectric characteristics at the material stage, but (2) rigid In the liquid crystal polymer film composed of rod-like molecular chains, the polarization in the width direction is smaller than the polarization in the longitudinal direction in each of the longitudinal direction and the width direction of each rod-like molecule, (3) It has been found that the directionality of the rod-like molecules can suppress the resistance (dielectric loss) due to thermal vibration of the constituent molecules of the dielectric, and as a result, the dielectric loss tangent can be controlled by the direction of the film.

  And (4) If such a liquid crystal film is used in a transmission line, it is advantageous in terms of dielectric properties, and can be used advantageously in terms of strength and low hygroscopicity. (5) By aligning the longitudinal direction of the rod-like molecules with the mechanical axis direction of the thermoplastic liquid crystal polymer film (hereinafter abbreviated as MD direction), the dielectric loss tangent in the MD direction and the direction orthogonal to the MD direction (hereinafter referred to as TD direction) A predetermined relationship occurs in the dielectric loss tangent of (abbreviated)), and it has been found that the transmission loss of the transmission line can be improved by using the dielectric characteristics generated from the direction of the film. It came to do.

That is, the present invention is a transmission line including at least one conductor and at least one insulator,
The insulator is formed of a thermoplastic liquid crystal polymer film, and the thermoplastic liquid crystal polymer film has a dielectric loss tangent ratio (D _TD / D _MD ) at a frequency of 1 GHz or more in the TD direction to the MD direction of the film of 1.02. Is:
In the transmission line, a TD direction of the thermoplastic liquid crystal polymer film and a longitudinal direction of the transmission line are arranged in substantially the same direction.

The thermoplastic liquid crystal polymer film used in the transmission line may have a predetermined relationship depending not only on the dielectric loss tangent but also on the dielectric constant. For example, the thermoplastic liquid crystal polymer film has a TD with respect to the MD direction of the film. The dielectric constant ratio (P _TD / P _MD ) at a frequency of 1 GHz or more in the direction may be less than 1.0.

Furthermore, the thermoplastic liquid crystal polymer film has a ratio of the breaking strength in the MD direction to the breaking strength in the TD direction (R _MD / R _TD ) of about 1 to 3 from the viewpoint of satisfying practical strength characteristics. May be.

  Such thermoplastic liquid crystal polymer films often have a degree of molecular orientation SOR of about 1.02 to 1.20. In addition, since the thermoplastic liquid crystal polymer film has low hygroscopicity, for example, the equilibrium moisture content of the thermoplastic liquid crystal polymer film may be 1.5% or less.

  From the viewpoint of effectively using the thermoplastic liquid crystal polymer film having the specific dielectric property, the ratio of the length in the longitudinal direction to the width direction of the transmission line is preferably, for example, twice or more.

  The present invention includes a thermoplastic liquid crystal polymer film used as an insulator in such a transmission line.

  In the transmission line of the present invention, the dielectric loss tangent of the thermoplastic liquid crystal polymer film used as an insulator is different between the TD direction and the MD direction of the film, and this property is used to reduce loss during transmission in the high frequency region. be able to. Furthermore, since a thermoplastic liquid crystal polymer film having a solid inside is used as the insulator, it is possible to achieve both excellent transmission characteristics and strength.

  Further, in the transmission line of the present invention, the relative permittivity of the thermoplastic liquid crystal polymer film has a specific relationship in the MD direction and the TD direction of the film. The signal transmission speed can also be improved. Furthermore, the breaking strength ratio of the thermoplastic liquid crystal polymer film also has a specific relationship in the MD direction and TD direction of the film, so that it has excellent transmission characteristics and has no practical problem with respect to the strength of the film. Is possible.

  Furthermore, the transmission line of the present invention is derived from the thermoplastic liquid crystal polymer film and has excellent low moisture absorption, heat resistance, and chemical resistance, and can improve the dielectric properties as compared with the conventional thermoplastic liquid crystal polymer film. The transmission loss and the transmission speed can be improved.

  Therefore, the transmission line of the present invention can be suitably used as, for example, an elongated transmission line in which the ratio of the longitudinal direction to the width direction of the transmission line exceeds twice, and the thermoplastic liquid crystal polymer film obtained by the present invention Is a material suitable as an insulating substrate material for transmission lines.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are merely for illustration and description and should not be used to define the scope of the present invention. The scope of the invention is defined by the appended claims.
(A) is a schematic sectional drawing which shows the transmission line which concerns on one Embodiment of this invention, (b) is the schematic perspective view. (A) is a schematic sectional drawing which shows the transmission line which concerns on one Embodiment of this invention, (b) is the schematic perspective view. (A) is a schematic sectional drawing which shows the transmission line which concerns on one Embodiment of this invention, (b) is the schematic perspective view. (A) is a schematic sectional drawing which shows the transmission line which concerns on one Embodiment of this invention, (b) is the schematic perspective view. (A) is a schematic sectional drawing which shows the transmission line which concerns on one Embodiment of this invention, (b) is the schematic perspective view. (A) is a schematic sectional drawing for demonstrating the process of producing the transmission line of the Example of this invention, (b) is a schematic sectional drawing which shows the transmission line produced by this process, (c) FIG. 3 is a schematic perspective view of a transmission line.

  The transmission line of the present invention includes at least one conductor and at least one insulator, and the insulator is formed of a thermoplastic liquid crystal polymer film.

(Thermoplastic liquid crystal polymer film)
The thermoplastic liquid crystal polymer film is formed from a liquid crystalline polymer that can be melt-molded. The thermoplastic liquid crystal polymer is not particularly limited as long as it has a chemical structure as long as it is a liquid crystalline polymer that can be melt-molded. , Thermoplastic liquid crystal polyester, or thermoplastic liquid crystal polyester amide having an amide bond introduced therein.

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

  Specific examples of the thermoplastic liquid crystal polymer used in the present invention include known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides derived from the compounds (1) to (4) listed below and derivatives thereof. Can be mentioned. However, it goes without saying that there is an appropriate range of combinations of various raw material compounds in order to form a polymer capable of forming an optically anisotropic melt phase.

(1) Aromatic or aliphatic dihydroxy compounds (see Table 1 for typical examples)

(2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for typical examples)

(3) Aromatic hydroxycarboxylic acids (see Table 3 for typical examples)

(4) Aromatic diamine, aromatic hydroxyamine or aromatic aminocarboxylic acid (see Table 4 for typical examples)

  Representative examples of the liquid crystal polymer obtained from these raw material compounds include copolymers having the structural units shown in Tables 5 and 6.

  Of these copolymers, a polymer containing at least p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as a repeating unit is preferable, and in particular, (i) p-hydroxybenzoic acid and 6-hydroxyoxy- A polymer containing a repeating unit with 2-naphthoic acid, (ii) at least one aromatic hydroxycarboxylic acid selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and 4,4 ′ A repeating unit of at least one aromatic diol selected from the group consisting of dihydroxybiphenyl and hydroquinone and at least one aromatic dicarboxylic acid selected from the group consisting of terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid Polymers containing are preferred.

  For example, in the polymer (i), when the thermoplastic liquid crystal polymer contains at least repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the repeating unit (A) of p-hydroxybenzoic acid is used. And the molar ratio (A) / (B) of the repeating unit (B) to 6-hydroxy-2-naphthoic acid is (A) / (B) = about 10/90 to 90/10 in the liquid crystal polymer. Desirably, it is desirable that (A) / (B) = about 50/50 to 85/15, and more preferably (A) / (B) = 60/40 to 80/20. It may be a degree.

  In the case of the polymer (ii), at least one aromatic hydroxycarboxylic acid (C) selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and 4,4′-dihydroxy At least one aromatic diol (D) selected from the group consisting of biphenyl and hydroquinone, and at least one aromatic dicarboxylic acid (E) selected from the group consisting of terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid. The molar ratio of each repeating unit in the liquid crystal polymer is about aromatic hydroxycarboxylic acid (C): aromatic diol (D): aromatic dicarboxylic acid (E) = about 30-80: 35-10: 35-10. More preferably, (C) :( D) :( E) = 35 to 75: 32.5 to 12.5: 3 May be about .5～12.5, more preferably, (C) :( D) :( E) = 40~70: it may be about 30 to 15: 30-15.

  Moreover, it is preferable that the molar ratio of the repeating structural unit derived from aromatic dicarboxylic acid and the repeating structural unit derived from aromatic diol is (D) / (E) = 95 / 100-100 / 95. Outside this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

  The optical anisotropy at the time of melting referred to in the present invention can be recognized by, for example, placing a sample on a hot stage, heating and heating in a nitrogen atmosphere, and observing the transmitted light of the sample.

  The thermoplastic liquid crystal polymer preferably has a melting point (hereinafter referred to as Mp) in the range of 260 to 360 ° C, more preferably Mp of 270 to 350 ° C. Mp is determined by measuring the temperature at which the main endothermic peak appears with a differential scanning calorimeter (Shimadzu Corporation DSC).

  The thermoplastic liquid crystal polymer may contain a thermoplastic polymer such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyester ether ketone, and fluororesin within a range not impairing the effects of the present invention. It may be added.

  The thermoplastic liquid crystal polymer film used in the present invention is obtained by extrusion molding of a thermoplastic liquid crystal polymer. Any extrusion molding method can be applied as long as the direction of the rigid rod-like molecules of the thermoplastic liquid crystal polymer can be controlled, but the known T-die method, laminate stretching method, inflation method and the like are industrially advantageous. In particular, in the inflation method and the laminate stretching method, stress is applied not only in the mechanical axis direction of the film (hereinafter abbreviated as MD direction) but also in the direction orthogonal to this (hereinafter abbreviated as TD direction). A film with controlled dielectric properties in the TD direction is obtained.

  In extrusion molding, it is preferable to involve a stretching process in order to control the orientation. For example, in extrusion molding by the T-die method, the melt sheet extruded from the T-die is used in the machine axis direction of the film (hereinafter referred to as MD direction). (Not abbreviated), and may be simultaneously stretched in both directions perpendicular to this (hereinafter abbreviated as TD direction), or the melt sheet extruded from the T-die is once stretched in the MD direction. You may extend | stretch in TD direction.

  In addition, in the extrusion molding by the inflation method, a predetermined draw ratio (corresponding to a stretching ratio in the MD direction) and a blow ratio (corresponding to a stretching ratio in the TD direction) with respect to a cylindrical sheet melt-extruded from a ring die. May be stretched.

  The stretch ratio of such extrusion molding may be, for example, about 1.0 to 10, preferably about 1.2 to 7, more preferably about 1. as the stretch ratio (or draw ratio) in the MD direction. It may be about 3-7. Further, the draw ratio (or blow ratio) in the TD direction may be, for example, about 1.5 to 20, preferably about 2 to 15, and more preferably about 2.5 to 14.

  And ratio (TD direction / MD direction) of each draw ratio of MD direction and TD direction may be 2.6 or less, for example, about 0.4-2.5 may be sufficient.

Further, the die shear rate that the thermoplastic polymer undergoes in the die region during melt extrusion from the die (sometimes simply referred to as shear rate) is 200 seconds ⁻¹ or more (for example, about 200 to 5000 sec ^-1), preferably be selected from about 210 to 4000 sec ^-1.

  Further, if necessary, the extruded raw sheet is subjected to a known or conventional heat treatment (for example, a melting point (Mp) or higher of the liquid crystal polymer (for example, about Mp to Mp + 30 ° C., preferably about Mp + 10 to Mp + 20 ° C.). ) To adjust the melting point and thermal expansion coefficient of the thermoplastic liquid crystal polymer film.

  The thermoplastic liquid crystal polymer film may be stretched as necessary after extrusion. The stretching method itself is known, and either biaxial stretching or uniaxial stretching may be adopted, but biaxial stretching is preferred because it is easier to control the degree of molecular orientation. For stretching, a known uniaxial stretching machine, simultaneous biaxial stretching machine, sequential biaxial stretching machine or the like can be used.

(Thermoplastic liquid crystal polymer film)
In the thermoplastic liquid crystal polymer film of the present invention thus obtained, the dielectric loss tangent thereof is highly controlled according to the MD direction and TD direction of the film, and 1 GHz or more in the MD direction and TD direction of the film (for example, 10 GHz), preferably a ratio of dielectric loss at a frequency of 1 to 300 GHz (D _TD / D _MD ) is 1.02 or less. Preferably, the dielectric loss tangent ratio (D _TD / D _MD ) may be about 0.50 to 1.01, more preferably about 0.55 to 1.00.

Further, the ratio of dielectric constant (permittivity) at a frequency of 1 GHz or more in the MD direction and the TD direction of the thermoplastic liquid crystal polymer film (P _TD / P _MD ) may be less than 1.0, preferably 0.8. It may be about 0.99, more preferably about 0.85 to 0.97.

  More specifically, the dielectric loss tangent in the TD direction at 1 GHz of the thermoplastic liquid crystal polymer film is 0.0021 or less (for example, about 0.0001 to 0.0021), preferably about 0.0010 to 0.0020. May be. By having such a dielectric loss tangent, it is possible to reduce power consumption and noise.

The relative dielectric constant in the TD direction of the thermoplastic liquid crystal polymer film varies depending on the thickness of the film. For example, the relative dielectric constant in the TD direction of the thermoplastic liquid crystal polymer film at 10 GHz is 3.25 or less (for example, 1.8 to 3.23), preferably about 2.5 to 3.20. In general, the dielectric constant can be calculated by multiplying the relative dielectric constant by a vacuum dielectric constant (= 8.855 × 10 ⁻¹² (F / m)).

  In a film having such dielectric characteristics, as a result of controlling the orientation of rigid rod-like molecules, SOR (Segment Orientation Ratio) indicating the degree of molecular orientation is, for example, SOR ≦ 1.20 (for example, 1.02 to 1.02). It may be about 1.20), preferably 1.05 to 1.19, and more preferably 1.07 to 1.19. Here, the molecular orientation SOR refers to an index that gives the degree of molecular orientation, and is a value that takes into account the thickness of an object, unlike conventional MOR (Molecular Orientation Ratio). The SOR of the thermoplastic liquid crystal polymer film used in the present invention needs to improve the dielectric properties in the MD direction and consider the good balance of mechanical and thermal properties between the MD and TD directions, SOR shows the value measured by the method described in the Example mentioned later.

The thermoplastic liquid crystal polymer film used in the present invention exhibits a strength that can withstand actual use. For example, the ratio of the breaking strength in the MD direction to the breaking strength in the TD direction (R _MD / R _TD ) is 1 About 3 may be sufficient, Preferably it is about 1.1-2.8, More preferably, about 1.2-2.5 may be sufficient. In addition, the breaking strength here is a value measured by the method described in the Example mentioned later.

  Further, the thermoplastic liquid crystal polymer film used in the present invention has low hygroscopicity, and its equilibrium moisture content is, for example, 1.5% or less (for example, 0.01 to 1.4%), preferably 1.3%. Hereinafter, it may be 1.0% or less. In addition, the equilibrium moisture content here is a value measured by the method described in the Example mentioned later.

  The thermoplastic liquid crystal polymer film used in the present invention may have any thickness, and includes a plate or sheet having a thickness of 5 mm or less. However, when it is used for a high-frequency transmission line, the transmission loss decreases as the thickness increases, so it is necessary to increase the thickness as much as possible. However, when a thermoplastic liquid crystal polymer film is used alone as the electrical insulating layer, the film thickness is preferably in the range of 10 to 500 μm, and more preferably in the range of 15 to 200 μm. When the thickness of the film is too thin, the rigidity and strength of the film are reduced. Therefore, a method of obtaining an arbitrary thickness by laminating films having a film thickness in the range of 10 to 200 μm may be used.

(Transmission line)
The transmission line of the present invention includes at least one conductor and at least one insulator, and the form thereof is not particularly limited as long as the thermoplastic liquid crystal polymer film is used as an insulator, and various kinds of materials extending in the longitudinal direction. A transmission line such as a coaxial line, a strip line, a microstrip line, a coplanar line, a parallel line, or the like can be used.

  In any transmission line, the thermoplastic liquid crystal polymer film used as an insulator is disposed in the transmission line so that the TD direction and the longitudinal direction of the transmission line are substantially in the same direction. Note that the TD direction and the longitudinal direction being substantially the same direction means that the angle formed between the TD direction and the longitudinal direction is in the range of −10 ° to + 10 ° (preferably in the range of −5 ° to + 5 °). It means that there is.

  Transmission lines generally have different lengths in the longitudinal direction and the width direction. From the viewpoint of effectively using the dielectric properties of the liquid crystal polymer film used in the present invention, for example, the lengths of the transmission line in the longitudinal direction and the width direction are used. The ratio may be 2 times or more, preferably 3 times or more, and more preferably 5 times or more. Note that the ratio of the length in the longitudinal direction to the width direction of the transmission line is often 20 times or less from a practical viewpoint.

  For example, FIGS. 1 to 5 show schematic cross-sectional views and schematic perspective views of various transmission lines. First, as shown in FIG. 1, in the case of the coaxial line 10 extending in the longitudinal direction, the basic structure is a linear inner conductor 13 having a substantially circular axial cross section and an insulation concentrically disposed on the outer periphery thereof. A body 12 and an outer conductor 14 arranged concentrically on the outer periphery of the insulator. Here, the TD direction of the liquid crystal polymer film constituting the insulator 12 is oriented in the same direction as the longitudinal direction (X direction) of the coaxial line 10.

  As shown in FIG. 2, in the case of the strip line 20, the basic structure includes an insulator 22 having a substantially rectangular axial cross section, and a strip-shaped center as a signal line disposed inside the insulator 22. It comprises a conductor 23 and planar ground conductors 24 and 24 disposed on both sides of the insulator 22. Here, the TD direction of the liquid crystal polymer film constituting the insulator 22 is oriented in the same direction as the longitudinal direction (X direction) of the strip line 20.

  Further, as shown in FIG. 3, in the case of the microstrip line 30, the basic structure includes an insulator 32 having a substantially rectangular axial section, a center conductor 33 as a signal line disposed on the upper surface thereof, It is comprised with the planar grounding conductor 34 arrange | positioned in the lower surface. Here, the TD direction of the liquid crystal polymer film constituting the insulator 32 is oriented in the same direction as the longitudinal direction (X direction) of the microstrip line 30.

  Further, as shown in FIG. 4, in the case of the coplanar line 40, the basic structure is that an insulator 42 having a substantially rectangular axial section, a strip-shaped central conductor 43 disposed on the upper surface thereof, and both sides thereof. The planar ground conductors 44 and 44 are arranged in parallel to the central conductor 43 with a gap having a constant width. Here, the TD direction of the liquid crystal polymer film constituting the insulator 42 is oriented in the same direction as the longitudinal direction (X direction) of the coplanar line 40.

  Further, as shown in FIG. 5, in the case of the parallel line 50, the basic structure is composed of an insulator 52 having a substantially rectangular axial cross section and a plurality of conductors 53, 53 disposed on the upper surface thereof. Yes. Here, the TD direction of the liquid crystal polymer film constituting the insulator 52 is oriented in the same direction as the longitudinal direction (X direction) of the parallel line 50.

  Although not shown, the transmission line of the present invention has, for example, a jacket for covering the basic structure of the transmission line, a terminal for connecting to the signal line, etc. in addition to the basic structure described above. May be.

  The conductor (or conductor) is formed on one surface of the thermoplastic liquid crystal polymer film, and constitutes a signal line or a ground plane line having a predetermined pattern. Formation of such a conductor is performed by a known or conventional method, and a sputtering method, a plating method, or the like may be used. Further, for example, after a conductor sheet is attached to the thermoplastic liquid crystal polymer film by a known or conventional method such as thermocompression bonding, a signal line having a predetermined pattern is obtained through photosensitive resist processing, exposure, and etching. Alternatively, a ground plane line may be formed on one surface of the thermoplastic liquid crystal polymer film.

  In addition, as a conductor, the metal used for an electrical connection is suitable, and gold | metal | money, silver, nickel, aluminum etc. can be mentioned besides copper. As the copper foil, any one produced by a rolling method, an electrolysis method or the like can be used, but one produced by an electrolysis method having a large surface roughness is preferable. The metal foil may be subjected to chemical treatment such as acid cleaning that is usually applied to the copper foil. Of these metals, copper is preferably used.

  The thickness of the conductor (or conductor) can be appropriately set according to the type of the transmission line and the role inside the transmission line, but may be in the range of 1 to 100 μm, for example, Within the range of 5-50 micrometers is preferable, and the inside of the range of 10-35 micrometers is more preferable.

  Since the transmission line of the present invention has such excellent dielectric characteristics, it can be effectively used as various electric transmission lines such as a coaxial cable and a strip line. It can be suitably used as a transmission line that requires high performance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this Example. In the following examples and comparative examples, various physical properties were measured by the following methods.

[Melting point]
The film was obtained by observing the thermal behavior of the film using a differential scanning calorimeter. In other words, the sample film was heated at a rate of 20 ° C./min to be completely melted, and then the melt was rapidly cooled to 50 ° C. at a rate of 50 ° C./min, and again raised at a rate of 20 ° C./min The position of the endothermic peak that appeared when the film was recorded as the melting point of the film.

[Film thickness]
The film thickness was measured using a digital thickness meter (manufactured by Mitutoyo Corporation) at a 1 cm interval in the TD direction, and the average value of 10 points arbitrarily selected from the center and the edge was taken as the film thickness. .

[Mechanical properties measurement]
The film breaking strength was measured using a mechanical property measuring apparatus (ORIENTEC RTE-1210) according to ASTM D882. The definition of the breaking strength ratio is MD breaking strength / TD breaking strength.

[Equilibrium moisture percentage]
In accordance with JIS L1013, after the sample was completely dried in an atmosphere of 120 ° C., it was adjusted at a temperature of 20 ° C. and a relative humidity of 65% RH for 72 hours, and the moisture content contained in the sample with respect to the mass of the sample in the completely dried state Was calculated and expressed as a percentage (%).

[Dielectric properties]
The dielectric constant was measured by a resonance perturbation method at a frequency of 10 GHz. A 1 GHz cavity resonator (Kanto Electronics Co., Ltd.) was connected to a network analyzer (Agilent Technology “E8362B”), and a minute material (width: 2.7 mm × length: 45 mm) was connected to the cavity resonator. The dielectric constant and dielectric loss of the material were measured from the change in the resonance frequency before and after the insertion for 96 hours in an environment of temperature 20 ° C. and humidity 65% RH.

Definition of dielectric constant ratio (P _TD / P _MD ): dielectric constant in TD direction / dielectric constant in MD direction, and definition of dielectric loss tangent ratio (D _TD / D _MD ): dielectric tangent in TD direction / MD direction Is the dielectric loss tangent of

[Molecular orientation (SOR)]
In a microwave molecular orientation measuring machine, a liquid crystal polymer film is inserted into a microwave resonant waveguide so that the film surface is perpendicular to the traveling direction of the microwave, and the electric field strength of the microwave transmitted through the film (Microwave transmission intensity) is measured.

And based on this measured value, m value (it calls a refractive index) is computed by following Formula.
m = (Zo / Δz) X [1-νmax / νo]

  Where Zo is a device constant, Δz is the average thickness of the object, νmax is the frequency that gives the maximum microwave transmission intensity when the microwave frequency is changed, and νo is zero when the average thickness is zero (that is, the object is Is the frequency that gives the maximum microwave transmission intensity.

Next, when the rotation angle of the object with respect to the vibration direction of the microwave is 0 °, that is, the vibration direction of the microwave and the direction in which the molecules of the object are best oriented, the minimum microwave transmission intensity is given. m ₀ to m value when the direction meets the rotation angle of the m value at 90 ° as _{m 90,} orientation ratio SOR is calculated by m ₀ / m _90.

[Characteristic impedance]
Using a characteristic impedance measuring instrument (manufactured by Agilent Technologies, 86100C / 54754A), measurement was performed at a frequency of 10 GHz.

[Transmission loss]
Using a vector network analyzer (manufactured by Agilent Technologies, HP8753D), transmission loss was measured in a frequency range of 3 to 10 GHz under an environment of a temperature of 20 ° C. and a humidity of 65% RH.

Example 1
(1) Production of thermoplastic liquid crystal polymer film A thermoplastic liquid crystal polymer having a melting point of 280 ° C. is a single copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 73/27). Heat-kneaded with a shaft extruder, melt-extruded from an annular inflation die having a die diameter of 33.5 mm and a die slit interval of 950 μm at a die shear rate of 500 sec ⁻¹ , a longitudinal draw ratio (Dr) of 2.9, and transverse stretch A film having a melting point of 280 ° C., a film thickness of 100 μm, an SOR of 1.07, an equilibrium moisture content of 0.04%, and a dielectric loss tangent ratio (D _TD / D _MD ) of 1.00 was obtained under the condition of the ratio (Bl) 6.2.

(2) Production of Strip Line Using the thermoplastic liquid crystal polymer film 1 obtained in (1) and the central conductor 3 having a width of 100 μm and a thickness of 12 μm, a strip line having a length of 150 mm and a width of 0.1 mm is formed as follows. It was produced by the method described in 1. The wiring width was designed so that the characteristic impedance (Z0) was 50 ± 2Ω from the thickness and dielectric constant of the insulating layer.

  Specifically, first, as shown in FIG. 6A, the two thermoplastic liquid crystal polymer films 1 and 1 are aligned so that the TD direction of each film is the longitudinal direction of the strip line. The central conductor (conductor as a signal line) 3 is sandwiched between the thermoplastic liquid crystal polymer films 1 and 1 so that the longitudinal direction of the central conductor 3 coincides with the longitudinal direction of the strip line, and these thermoplastics The planar ground conductors 4 and 4 as ground planes were disposed outside the liquid crystal polymer films 1 and 1 to produce an assembly.

  Next, this assembly was placed between the metal plates 5 and 5 of the hot press apparatus and thermocompression bonded under the conditions of a surface temperature of the metal plate of 260 degrees and a surface pressure of 4 MPa, and a strip line shown in FIG. The strip line includes a linear insulator 2 having a substantially rectangular cross section, a strip-shaped central conductor 3 as a signal line disposed inside the insulator 2, and both sides of the insulator 2. The planar ground conductors 4 and 4 are arranged. Here, as shown to (c), the TD direction of the liquid crystal polymer film which comprises the insulator 2 is orient | assigned to the longitudinal direction (X direction) of a stripline.

(Example 2)
A strip line was produced in the same manner as in Example 1 except that the thermoplastic liquid crystal polymer film was formed of the following film. That is, the same thermoplastic liquid crystal polymer as in Example 1 was heat-kneaded with a single-screw extruder, melt-extruded at a die shear rate of 450 seconds ⁻¹ from an annular inflation die having a die diameter of 33.5 mm and a die slit interval of 900 μm, Under the conditions of a longitudinal stretch ratio (Dr) of 7.9 and a lateral stretch ratio (Bl) of 4.7, melting point 280 ° C., film thickness 100 μm, SOR 1.12, equilibrium moisture content 0.04%, dielectric loss tangent ratio (D _TD / _DMD ) 0.91 film was obtained.

(Example 3)
A strip line was produced in the same manner as in Example 1 except that the thermoplastic liquid crystal polymer film was formed of the following film. That is, the same thermoplastic liquid crystal polymer as in Example 1 was heat-kneaded with a single screw extruder, melt-extruded at a die shear rate of 500 sec- ¹ from an annular inflation die having a die diameter of 33.5 mm and a die slit interval of 900 μm, Under the conditions of a longitudinal stretch ratio (Dr) of 5.2 and a lateral stretch ratio (Bl) of 3.3, melting point 280 ° C., film thickness 100 μm, SOR 1.18, equilibrium moisture content 0.04%, dielectric loss tangent ratio (D _TD / _DMD ) 0.77 was obtained.

(Comparative Example 1)
A strip line was produced in the same manner as in Example 1 except that the thermoplastic liquid crystal polymer film was formed of the following film. That is, the same thermoplastic liquid crystal polymer as in Example 1 was heat-kneaded with a single screw extruder, melt-extruded at a die shear rate of 700 sec- ¹ from an annular inflation die having a die diameter of 33.5 mm and a die slit interval of 700 μm, Under the conditions of a longitudinal stretch ratio (Dr) of 2.2 and a lateral stretch ratio (Bl) of 6.2, melting point 280 ° C., film thickness 100 μm, SOR 1.01, equilibrium moisture content 0.04%, dielectric loss tangent ratio (D _(TD / _DMD ) 1.03 film was obtained.

  The physical properties of the obtained film and the physical properties of the strip line are shown in Table 7 and Table 8, respectively.

  As shown in Table 7, the thermoplastic liquid crystal polymer films of Examples 1 to 3 have a dielectric loss tangent in the TD direction lower than the dielectric loss tangent in the MD direction. It can be made lower than the relative dielectric constant in the MD direction.

  As described above, in the thermoplastic liquid crystal polymer film, anisotropy occurs in terms of dielectric properties, but the breaking strength in each direction is in a practically no problem range between the MD direction and the TD direction. The ratio of occurrence is within 3 times. Further, since the equilibrium moisture content is also a low value, the hygroscopicity is low.

  Furthermore, as shown in Table 8, it is possible to suppress the transmission loss to a low value for the transmission line obtained by utilizing the dielectric loss tangent characteristic of such a liquid crystal polymer film. In addition, since the transmission speed can be calculated by dividing the speed of light in vacuum by the square root of the dielectric constant of the dielectric, it can be seen that the speed can be improved as the dielectric constant of the liquid crystal polymer film is reduced. .

  On the other hand, the thermoplastic liquid crystal polymer film of Comparative Example 1 has a higher dielectric loss tangent in the TD direction than a dielectric loss tangent in the MD direction. As a result, the transmission line using this liquid crystal polymer film has a low transmission loss. It cannot be suppressed. Also, with respect to the relative permittivity, the relative permittivity in the TD direction is about the same as the relative permittivity in the MD direction. Therefore, even if the TD direction of the film coincides with the longitudinal direction of the transmission line, the transmission speed is improved. It is not possible.

  The transmission line of the present invention can be used as a transmission line material for electrical and electronic products, and is particularly excellent in strength, low moisture absorption, and chemical resistance, so that it can be used in portable applications such as mobile phones and computers. It can be effectively used as a transmission line for use in electrical / electronic products or as a transmission line for use in electrical / electronic products for outdoor use.

  As described above, the preferred embodiments of the present invention have been described. However, various additions, modifications, or deletions are possible without departing from the spirit of the present invention, and such modifications are also included in the scope of the present invention. It is.

DESCRIPTION OF SYMBOLS 1 ... Thermoplastic liquid crystal polymer film 2, 12, 22, 32, 42, 52 ... Insulator 3, 23, 33, 43 ... Center conductor 4, 24, 34, 44 ... Planar ground conductor 5 ... Metal plate 10 ... Coaxial Line 13 ... Inner conductor 14 ... Outer conductor 20 ... Strip line 30 ... Micro strip line 40 ... Coplanar line 50 ... Parallel line 53 ... Conductor

Claims (7)

A transmission line comprising at least one conductor and at least one insulator,
The insulator is formed of a thermoplastic liquid crystal polymer film, and the thermoplastic liquid crystal polymer film has a mechanical axis direction of the film (hereinafter abbreviated as MD direction) and a direction orthogonal to the direction (hereinafter abbreviated as TD direction). The dielectric loss tangent ratio (D _TD / D _MD ) at a frequency of 1 GHz or higher is 1.02 or lower;
A transmission line in which a TD direction of the thermoplastic liquid crystal polymer film and a longitudinal direction of the transmission line are arranged in substantially the same direction. The transmission line according to claim 1, wherein a ratio (P _TD / P _MD ) of dielectric constant at a frequency of 1 GHz or more of the thermoplastic liquid crystal polymer film is less than 1.0. The transmission line according to claim 1 or 2, wherein a ratio (R _MD / R _TD ) between the breaking strength in the MD direction and the breaking strength in the TD direction of the thermoplastic liquid crystal polymer film is 1 to 3.   The transmission line according to any one of claims 1 to 3, wherein the thermoplastic liquid crystal polymer film has a molecular orientation SOR of 1.02 to 1.20.   The equilibrium moisture content of the thermoplastic liquid crystal polymer film according to any one of claims 1 to 4 is 1.5% or less.   The transmission line according to any one of claims 1 to 5, wherein a ratio of the length in the longitudinal direction to the width direction of the transmission line is twice or more.   The transmission line as described in any one of Claims 1-6 WHEREIN: The thermoplastic liquid crystal polymer film used as an insulator.

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