JPS5875301A - Transmission line - Google Patents

Abstract

PURPOSE:To reduce a reduction of transmission loss, by forming a part of the transmission part with a dielectric material composed of crystalline polymer having the porous microstructure with high porosity and containing numbers of microknots which are connected to each other by microfibers. CONSTITUTION:A transmission line for transmission of the surge energy is formed with a rod-shaped central dielectric material 1 composed of crystalline polymer having the porous microstructure having high porosity and containing numbers of microknots which are connected to each other in a 3-dimensional way by micro-fibers. A sheet type crystalline polymer material having a porous microstructure is cut into a tape form and wound spirally around the outside of the dielectric material 1. Thus a dielectric layer 2 is formed. In addition, a protecting layer 3 of polyvinyl chloride is provided at the outside of the layer 2. The dielectric constant epsilon1 of the dielectric material 1 and the dielectric constants epsilon2-epsilonn of the layer 2 are set at epsilon1>epsilon2...>epsilonn-1 so that these constants reduce radially toward the outer side from the center and that the dielectric constant is increased to epsilonn>epsilonn-1 at the outermost circumference part. As a result, the effect of disturbance is avoided to reduce the transmission loss as well as to ensure a free control of the dielectric constant over a wide range. Thus a transmission line having a high speed of transmission and uniform quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission line (including an insulated line), a dielectric-filled and/or internal metal waveguide, and a combination structure thereof (hereinafter collectively referred to as a transmission line).

Millimeter waves, submillimeter waves, and waves in the optical domain are transmitted by a transmission line as any one of an in-dielectric mode, a surface wave mode, and a waveguide mode, or any combination thereof. and some (or all) of these transmission lines
A dielectric material is used as a transmission medium for the above-mentioned waves.

In other words, the dielectric material through which the wave energy in the transmission line is transmitted has conventionally been made of materials without pores or with extremely low porosity (generally referred to as a solid material in technical terms) such as polyethylene, polypropylene, and polytetrafluoroethylene. The material having a low dielectric constant for the cranoid portion is polyethylene, polypropylene, etc., which have closed cells foamed with a foaming agent.

However, the above-mentioned plastics that are foamed with a foaming agent have a large dielectric loss due to the foaming agent contained in the plastic, difficult to control the dielectric constant, and the foaming rate at the boundary of the dielectric tends to change. , it is difficult to reduce the diameter of foamed pores to a fraction of the wavelength or less, and it is difficult to mold the material. It was almost impossible to use it as an energy maintenance inspection part.

As a result of various studies in order to obtain a dielectric material for transmission lines that does not have the drawbacks of conventional materials as described above, the present inventors discovered a porous microstructure in which a large number of micronodules are three-dimensionally connected to each other by microfibers. A dielectric material made of a crystalline polymer having a low dielectric constant and tan δ has a small dielectric constant, and the dielectric constant can be easily and uniformly controlled, and after forming into a transmission line, the terminal etc. can be freely shaped into the desired shape and dielectric constant. It was discovered that it is extremely suitable as a dielectric material for transmission lines because it can be adjusted and has great flexibility, and based on this knowledge, the present invention was completed.

That is, the present invention provides at least a portion of the wave energy transmission portion in a dielectric material made of a crystalline polymer having a porous microstructure with high porosity in which a large number of micronodules are three-dimensionally bonded to each other by microfibers. This is a transmission line characterized by being formed of.

The dielectric used as at least a part of the wave energy transmission part used in the present invention is made of a crystalline polymer material, and its internal structure is composed of a large number of micronodules and a large number of microfibrils. These micronodules and microfibers are interconnected three-dimensionally, and a large number of intricate voids are formed between them, resulting in a porous fine structure with continuous pores as a whole.

Crystalline polymer materials used as dielectrics having such a porous microstructure are usually, for example, polytetrafluoroethylene (PTFE), a copolymer of PTFE and tetrafluoroethylene and hexafluoropropylene (F
EP) and/or with extractable inorganic additives, such as silicates, carbonates, metals, metal oxides, sodium chloride, ammonium chloride, or organic powders such as starch, and polyethylene, polypropylene Examples include olefin resins such as.

In order to process a crystalline polymer material as described above into a porous microstructure as described above, generally, the crystalline polymer material and a liquid lubricant (for example, a hydrocarbon oil such as solvent naphtha or white oil, (petroleum ether, etc.) or with extractable additives, and ram-extrudes the preform into any shape, e.g., sheet, rond, tube, etc., as required. The liquid lubricant is removed or not removed from the molded product, and this is stretched in an unsintered state (below the melting point temperature of the resin used) to create a porous three-dimensional structure. Obtain a fine structure. By heat-setting the internal strain of the stretched product thus obtained at a temperature higher than or slightly lower than the melting point temperature, a porous microstructure with good shape retention is produced.

In addition, when an additive is used, it is completely removed by extraction, dissolution, etc. after heat setting with or without stretching treatment.

Here, a method for producing the porous microstructured dielectric material from PTFE will be described in more detail, taking as an example.

First, PTFE fine powder (or PTFE dispersion condensate may be used) is coated with a liquid lubricant that can wet PTFE (hydrocarbons such as naphtha and white oil, aromatic hydrocarbons such as toluene and xylene, various alcohols, and surfactants). PTFE and liquid lubricant are added and mixed in a ratio of approximately 80:20, the resulting mixture is compressed and preformed, and the molded product is extruded using a ram extruder equipped with an orifice at the tip. tube, sheet,
Extrude into any cross-sectional shape such as a rod.

The PTFE mixture is subjected to an extremely large shear stress passing through this orifice, and the PTFE fine particles are stretched in the length direction and become intertwined, so that the extruded product has a certain degree of strength. In the case of a sheet-like molded product, it can be further rolled by calendering to increase its strength and density. Next, the extrudate containing the liquid lubricant is processed by means depending on the properties of the lubricant, generally by heating,
The liquid lubricant is removed by evaporation and a green PTFE molded article is obtained.

The microstructure of the unsintered PTFF molded product thus obtained is as follows:
Very fine spherical particles (diameter approx. 0
．． 1 micron) are subjected to shear force during extrusion and are rearranged and oriented in the extrusion direction (fibrillated P).
TFE). However, the shape of most PTFE microparticles is preserved even in extrudates and is essentially spherical. A void exists between these spherical fine particles and the oriented fibrils. The physical properties of unsintered PTFE molded products generally have a specific gravity of 1.45 to 1.
．． 8. Relative permittivity 1. , f, 71.9 (measurement frequency 10
GHz), tan δ 2×10 to 1×10 (measurement frequency 10 GHz), and porosity 18.2% to 32%.

The dielectric constant, tan δ, specific gravity, etc. of the above molded product are determined by the extrusion hole design of the extrusion molding die (mainly compression ratio: reauctton).
ratio). In addition, the above molded product is further added to the melting point of PTFE, which is 3.
The temperature can also be adjusted by heating to 27°C or higher, for example 350 to 380°C. Heat to a temperature of 327℃ or higher (
When fired), the fine particles and fibrils that make up the extruded product collapse and aggregate together, and the voids between the particles and fibrils disappear, and when completely fired, it becomes uniform and full with a specific gravity of 2.2 ( It becomes a body with no voids. However, the degree of firing was not performed until it was completely fired and the true specific gravity of PTFE was 2.2.

The specific gravity should rise to 1.9.

Next, the unsintered PTFE molded body obtained as described above was
According to the method described in 81, the unsintered state is stretched at least once in at least one axis direction to about 100 times. By changing the stretching ratio, the specific gravity, porosity, dielectric constant, etc. of the three-dimensional PTFE molded product can be changed over a very wide range. Therefore, by this change, it is possible to easily obtain a dielectric material for a transmission line in which the propagation state of wave energy is adjusted as desired. Next, this stretched product was melted at the melting point of PTFE (327°C).
) or above, preferably 340-380°C, especially 360°C
The sintering heat setting may be carried out at a temperature of 375° C. for about 1 to 15 minutes, or the fixing may be carried out at a temperature of about 250° C. or below the melting point. Further, the stretched molded body can be used as a dielectric material without being sintered or heat-set. The dielectric constant of porous PTFE can also be adjusted by appropriately changing the degree of sintering and/or heat setting of this stretched product. Characteristics of transmission line according to
This is an important process used to adjust performance.

The porous PTFE material made of PTFE used in the present invention thus obtained usually has a high porosity of around 60 to 90 cm, an average pore diameter of 0.01 to 50 μm, and an air permeability of 100 to 50 μm.
00 ct/min (1 psi for 2.54 cm long tube)
Approximate number under pressure), water leakage pressure O0l ~ 1.5 l/c
t/I, and the stretching ratio, density, and relative dielectric constant (εr)
, tan δ are as follows.

Stretching ratio 1210 Density (f/c4) 1.6 0.8 0.0
86r (at 10Hz) 1.71 1.
31 1.07 tan δ (at 106 Hz>
7X10-''3X10' lXl0-5Next, the transmission line of the present invention will be explained from the force δ with reference to the drawings.Figure 1 shows that the aforementioned large number of micronodules are three-dimensionally interconnected by microfibers. A cross section of a rod-shaped crystalline polymer having a bonded porous microstructure with high porosity and used as a transmission line.

FIG. 2 is a sectional view of another specific example of the transmission line of the present invention. In the example shown in FIG. 2, a sheet of the crystalline polymer material with the porous microstructure obtained by the above-described stretching method is cut into a tape shape on the outside of the center dielectric 1 similar to the transmission line shown in FIG. A second dielectric layer 2 is formed by spirally winding the second dielectric layer 2, and a protective layer 3 made of vinyl chloride is further provided on the outer side of the second dielectric layer 2. In addition, the second
The second dielectric layer 2 is made by forming the dielectric obtained by the above-described processing method into a cylindrical body with an inner diameter slightly thicker than the outer diameter of the center dielectric 1, covering the center dielectric 1, and then applying the cylindrical body as appropriate. It may also be made by heating it to shrink and bringing it into close contact with the center dielectric 1. 'FIG. 3 is a cross-sectional view of a generalized transmission line that is an expanded version of the transmission line of the type shown in FIG. In FIG. 3, the n-th layer from the center can be arbitrarily formed by the tape winding method and/or the cylindrical body insertion method described in connection with FIG. 2, and the dielectric constant of each dielectric layer (ε1;
ε2...εn) are normally arranged so that they decrease radially outward from the center,
61′〉ε2〉ε. -i ε. 〉εn−1. It is advantageous to increase the dielectric constant, which has been reduced in this manner, at the outermost periphery, since it is possible to prevent disturbances from entering. When the dielectric layer is integral, the dielectric constant can be made to have a gradient as described above by concentrating infrared rays or far infrared rays. Furthermore, in any case of Figures 1 to 3,
A metal layer can be provided on the outermost side. As the center dielectric 1, at least a part thereof is made of a crystalline polymer having a porous microstructure with a high porosity in which a large number of micronodules are interconnected by fine fibers, and the remaining part is For example, a mixture of tetrafluoroethylene resin powder and a liquid lubricant is molded by extrusion and/or rolling, and the liquid lubricant is removed from the molded product, or an unstretched product is obtained by incompletely firing the molded product. It may also be supplemented with PTFE moldings.

In the transmission line of the present invention as described above, the following various effects are achieved.

(1) Low transmission loss. (The tan δ of the dielectric material used in the present invention is small, and the expanded PTFE-t' with a density of 0.2 f /cfI is 1/10 or less of that of solid PTFE.

Another reason for the low loss is that the dielectric does not contain a foaming agent unlike other foamed plastics (e.g. polyethylene, polypropylene). (2) The dielectric constant is It can be freely controlled over a wide range and is uniform.

(3) Fast propagation speed.

(4) Can transmit electromagnetic waves with high energy density. .

(5) The shape and structure of the dielectric can be freely adjusted.

(6) The transmission line has great flexibility.

Hereinafter, the transmission line of the present invention will be explained in more detail with reference to Examples.

Example I From a mixture of PTFE powder and white oil,
1-18991 method: specific gravity 0.37 at 6x stretching rate
A rod of expanded porous PTFE with a dielectric constant of 1.3 and an outer diameter of 9 m was made. This rod was cut to a length of 1 m to form a transmission line, and a 100 GHz electromagnetic wave was sent in the longitudinal direction from the end face using a conical bone, and the attenuation at the other end was measured and was 0.2 dB/m. . This value is 2.7 dB/m lower than that of fully sintered solid PTFE, which was considered the best conventional dielectric line material, and this expanded porous PTFE rod itself can be put to practical use as a millimeter wave transmission line. It was something to be gained.

A porous PTFE tape (specific gravity 0.24) with a thickness of 0.2 ms and a width of 20 strips manufactured in the same manner as in Example 2 was spirally wound and bound with an outer diameter of 15 mm, and further electromagnetic wave absorbing tape was applied on top of the tape. The transmission line shown in FIG. 2 was then coated with vinyl chloride having a thickness of lsm for the purpose of reinforcement. When the millimeter wave transmission characteristics of this line (length 1 m) were measured, good results were obtained with an attenuation of 0.3 dB/m.

The dielectric material used in the transmission line of the present invention shown in the above specific example has fine pores, high porosity, continuous pores, and is plastically deformed when an appropriate pressure is applied. Compared to general dielectric materials such as tetrafluoroethylene, the volume change due to temperature changes is small, and the volume follows the properties (tension, contraction) of the material used to control the external shape. Since the dielectric constant changes, the temperature characteristic of the dielectric constant can be almost zero, providing a transmission line with good temperature characteristics, and furthermore, it can be used as a material for resonators and duplexers that require good temperature characteristics. - Also, since the dielectric material has fine pores as mentioned above, it can be used for all gases, water vapor, and liquids that wet the dielectric material, such as petroleum such as gasoline, kerosene, light oil, and heavy oil, ketones, alcohols, etc. Since it absorbs a lot of liquid, it is used in the main transmission part or cladding part of the transmission line, resonator duplexer, etc. so that those circuits come into contact with the gas and/or liquid. When installed, these contacting substances penetrate into the circuit, causing reflections of the transmitted energy, changes in the absorption propagation delay time, and changes in the amount of crosstalk, making them difficult to use as sensing elements or sensing lines for gases and/or liquids. can do. Moreover, expanded porous PTF
Since the E material is water repellent, it has the great advantage of being able to detect only the gas and/or liquid mentioned above even in places where water is present. When the protective layer 3 of the transmission line shown in FIG. 2 was removed and the central portion 10 cm was immersed in gasoline, the output became O after 30 seconds. Further, no change in output was observed even after immersion in water for 10 minutes. In the above embodiments, only dielectric lines and their connections have been described, but surface wave lines (including image lines and insulated lines) using the above materials, dielectric-incorporated metal waveguides, dielectric-filled metal waveguides, and The properties of those composites were also good. Further, although the cross-sectional shape of the material described above is only circular, it is clear that it is not limited to circular, but may be rectangular or any other arbitrary shape, and multi-core cables are also possible.

[Brief Description of the Drawings] Figures 1 and 2 are cross-sectional views of an example of the transmission line of the present invention, and Figure 3 is a generalized transmission line of the present invention.
It is a sectional view mainly for the purpose of explanation. In the figure, 1 indicates a center dielectric, 2 indicates a dielectric layer, and 3 indicates a protective layer. Applicant Junko Co., Ltd. Representative Patent Attorney Shun Yamamoto Figure 19 Figure 2 Figure 3

Claims (1)

[Claims] 1. At least a part of the wave energy transmission portion is made of a dielectric material made of a crystalline polymer having a porous microstructure with high porosity in which a large number of micronodules are interconnected by fine fibers. A transmission line characterized by forming a 2. In the transmission line as set forth in claim 1, the dielectric is formed into an integral rod shape, and the dielectric constant thereof continuously decreases radially outward from the central axis. The transmission line characterized by: 3. In the transmission line according to claim 1, the dielectric is composed of a plurality of coaxial dielectric layers having different dielectric constants, and the plurality of dielectric layers have different dielectric constants. The transmission line is arranged such that the rate decreases radially outward from the central axis. 4. In the transmission line as set forth in claim 1, the dielectric has a dielectric constant that decreases continuously or stepwise as it goes radially outward from the central axis, and increases at the outermost periphery. The transmission line is characterized in that: 5. In the transmission line according to claim 3, the plurality of dielectric layers include a rod-shaped center dielectric and a tape-shaped dielectric wound spirally around the center dielectric. The transmission line characterized in that it is comprised of: 6. In the transmission line according to claim 3, the plurality of dielectric layers are composed of a rod-shaped center dielectric and a cylindrical dielectric fitted around the outer periphery of the center dielectric. The transmission line characterized in that: 7. In the transmission line according to claim 3, the plurality of dielectric layers include a rod-shaped central dielectric, and a tape-shaped dielectric and a cylindrical dielectric surrounding the central dielectric. The transmission line is characterized in that: 8. The transmission line according to any one of claims 1 to 7, wherein the dielectric is made of a stretched continuous-porous tetrafluoroethylene resin molded body.