JP2006164911A - Dielectric antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric antenna showing a high specific dielectric constant in a range from low temperature to high temperature, having a low dielectric tangent. <P>SOLUTION: The dielectric antenna is composed of a molded body of high dielectric elastomer composition formed by combining high dielectric ceramic powder in an elastomer, and an electrode arranged on the molded body. The specific dielectric constant of the ceramic powder is 7 or higher at 1 GHz and 25°C, and the dielectric tangent thereof is 0.01 or lower. The electrode is formed by a copper foil on which a nickel or silver plating is applied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an elastomeric dielectric antenna having electrodes formed of plated copper foil, and more particularly to a dielectric antenna used in a high frequency band of 100 MHz or higher.

In recent years, with the remarkable spread of patch antennas used for mobile phones, cordless phones, RFID, etc., lens antennas such as radio telescopes and millimeter wave radars, and the remarkable development of satellite communication equipment, the frequency of communication signals has been increased and the frequency of communication equipment has increased. Further downsizing is desired.
In order to meet the demands for downsizing, there are those in which an antenna body is molded using a dielectric resin material having a small specific gravity and low dielectric loss and advantageous for high gain, and electrodes are formed on the molded body. is there. Such a dielectric antenna will be described with reference to FIG. FIG. 1 is a perspective view of a dielectric antenna (patch antenna). In the dielectric antenna 1, an electrode 3, which is a radiating element, is formed at the center of the upper surface of a dielectric substrate 2, and a feed pin 5 is attached to a predetermined portion of the electrode 3. Examples of the method for forming the electrode 3 include metal plating treatment and adhesion of metal foil.
A ground conductor 4 is formed on the lower surface of the dielectric substrate 2. The power supply pin 5 is electrically connected to an amplifier circuit, a transmission circuit, etc. (not shown), and a high frequency signal is supplied to the electrode 3 through the power supply pin 5. In addition, there is a structure in which a power supply line or the like extending from the electrode 3 is used without using the power supply pin 5.

  Conventionally, as a method of forming electrodes on resin-based antenna members by metal plating treatment, a styrenic polymer (SPS) having a syndiotactic structure is mixed with an inorganic filler and a rubber-like elastic material soluble in a solvent, and then etched. A composite dielectric material whose surface is roughened by treatment to improve plating properties is used as an antenna (see Patent Document 1), or a hard-plating resin and an easy-plating resin are used in combination. There are those using an easily plating resin as an antenna member (see Patent Document 2). Moreover, there exists what formed the electrode with the copper foil pattern (refer patent document 3).

However, in the case where a resin material is used as an antenna member such as a dielectric substrate, it is generally difficult to perform metal plating, and there is a problem that it is necessary to perform special ground treatment as in Patent Document 1 and Patent Document 2. . In addition, when the electrode is formed by plating, the adhesion to the antenna member is poor even after the base treatment, which may lead to deterioration of dielectric characteristics, which is not preferable. Further, when a copper foil is used for the electrode as in Patent Document 3, the electrode is easily oxidized, and therefore, there is a problem that the conductivity is lowered when the operating temperature is increased.
Japanese Patent Laid-Open No. 2001-143531 JP 2003-78322 A Japanese Patent Laid-Open No. 7-66620

  The present invention has been made to cope with such problems, and an object thereof is to provide a dielectric antenna that exhibits a high relative dielectric constant and has a low dielectric loss tangent over a wide temperature range from a low temperature to a high temperature. To do.

The dielectric antenna of the present invention is a dielectric antenna comprising a molded body of a high dielectric elastomer composition obtained by blending a high dielectric ceramic powder into an elastomer, and an electrode provided on the molded body, The high dielectric ceramic powder has a relative dielectric constant of 7 or more and a dielectric loss tangent of 0.01 or less at a frequency of 1 GHz and a temperature of 25 ° C., and the electrode is formed of a plated copper foil. And
Further, the plating process is nickel plating. The plating treatment is silver plating.

  The elastomer includes a nonpolar olefin unit as a structural unit. In particular, the elastomer is ethylene propylene rubber.

  The dielectric antenna is used in a frequency band of 100 MHz or more.

  The dielectric antenna of the present invention has a high ratio over a wide temperature range from a low temperature to a high temperature by forming an antenna electrode by adhering a plated copper foil to an elastomer molded body mixed with a dielectric ceramic powder. It exhibits a dielectric constant, has a low dielectric loss tangent, and is excellent in aging resistance.

  The dielectric antenna of the present invention can be obtained by using a molded body of a high dielectric elastomer composition in which a high dielectric ceramic powder is blended in an elastomer as an antenna body, and bonding a plated copper foil as an electrode thereto. .

  The plating material to be processed on the copper foil is not particularly limited as long as it can maintain conductivity that functions as an antenna, but gold (Au), platinum (Pt), silver (Ag), nickel (Ni), tin (Sn), etc. There is. Among them, Ni and Ag are preferable because of excellent oxidation resistance and conductivity. Ni is particularly preferred because of its low cost. The thickness of the plating is preferably from 0.1 to 5 μm, more preferably from 0.5 to 3 μm. If the plating thickness is less than 0.1 μm, the improvement in oxidation resistance is small, and if it is more than 5 μm, the plating thickness is not uniform or the required amount of plating material increases, which is not preferable.

The plating process includes an electroless plating method, an electroplating method, or a combination thereof. In particular, the electroless plating method is simple and preferable because the thickness of the plating layer becomes uniform.
The electroless plating method uses a plating solution obtained by dispersing nickel sulfate, phosphatizing agent, stabilizer, pH buffering agent, appearance modifier, dispersion aid, etc. in a reducing bath such as hypophosphite. And a plating layer is formed by immersing a metal plate in this plating solution. In electroless plating, the plating forming portion of the metal plate is degreased and pickled, and then plated.

For adhesion between the copper foil and the elastomer molded body, an epoxy or urethane adhesive film or a liquid adhesive can be used. The thickness of the adhesive layer is preferably about 1 to 100 μm. If the thickness of the adhesive layer is 1 μm or less, the adhesive layer cannot be locally present and the adhesive area is reduced, which is not preferable. If it is larger than 100 μm, the dielectric properties (particularly, dielectric loss tangent) deteriorate, which is not preferable. A more practical range is 20-50 μm.
Further, when molding the elastomer, it is also possible to insert a copper foil into the mold and vulcanize and bond with the pressure during molding.
As described above, by using the plated copper foil as the electrode of the elastomeric dielectric antenna, the adhesion is good and the oxidation resistance is excellent.

  The high dielectric ceramic powder that can be used in the present invention includes a metal titanate, at least one rare earth such as neodymium (Nd) and lanthanum (La), barium (Ba), strontium (Sr), calcium ( One or more metals selected from Ca), magnesium (Mg), cobalt (Co), palladium (Pd), zinc (Zn), beryllium (Be), cadmium (Cd), bismuth (Bi), etc. Ceramic powders containing elements are preferred. Rare earths such as Nd and La contribute to the improvement of the temperature characteristics that reduce the temperature change of the relative dielectric constant, and metal elements such as Ba and Sr increase the dielectric constant and reduce the dielectric loss tangent. Contribute. A preferable high dielectric ceramic powder is a Ti—Ba—Nd—Bi-based barium titanate-neodymium ceramic powder.

The particle diameter of the high dielectric constant and low dielectric loss tangent ceramic powder is preferably about 0.01 μm to 100 μm. When it is smaller than 0.01 μm, it is not preferable because it is difficult to handle such as scattering during weighing. If it is larger than 100 μm, it is not preferable because it may cause variations in dielectric properties in the molded body. A more practical range is about 0.1 μm to 20 μm.
In addition, the dielectric antenna of the present invention used in a high frequency region is required to have a high dielectric constant and a low dielectric loss tangent. A high dielectric constant having a relative dielectric constant of 7 or more and a dielectric loss tangent of 0.01 or less at a frequency of 1 GHz and a temperature of 25 ° C. It is preferable to use a porous elastomer composition as a material.
When the relative dielectric constant of the highly dielectric elastomer composition is smaller than 7, it is not preferable because the effect of shortening the wavelength propagating in the composite material is small and the product cannot be miniaturized. When the dielectric loss tangent is larger than 0.01, the loss in the composite material is increased, which is not preferable. This composite material is used in the high frequency band of 100MHz or higher.

Natural rubber elastomers and synthetic rubber elastomers can be used for the high dielectric elastomer composition that can be used in the present invention.
Natural rubber-based elastomers include natural rubber, chlorinated rubber, hydrochloric acid rubber, cyclized rubber, maleated rubber, hydrogenated rubber, and vinyl monomers such as methyl methacrylate, acrylonitrile, and methacrylic acid ester grafted onto the double bond of natural rubber. Examples thereof include a graft-modified rubber and a block copolymer obtained by coarsely kneading natural rubber in the presence of a monomer in a nitrogen stream. These include elastomers made from synthetic cis-1,4-polyisoprene as well as those made from natural rubber.

  Synthetic rubber elastomers include polyolefin elastomers such as isobutylene rubber, ethylene propylene rubber, ethylene propylene diene rubber, ethylene propylene terpolymer, chlorosulfonated polyethylene rubber, styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene- Styrene elastomers such as styrene copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), isoprene rubber, urethane rubber, epichlorohydrin rubber, silicone rubber, nylon 12, butyl rubber, butadiene rubber, polynorbornene rubber, acrylonitrile- Examples thereof include butadiene rubber.

  These elastomers can be used alone or in combination of two or more. Further, one or two thermoplastic resins can be blended and used within a range that does not impair the elasticity of the elastomer. When one or more kinds selected from natural rubber elastomers and / or synthetic nonpolar elastomers are used as the elastomer of the present invention, a highly dielectric elastomer having excellent electrical insulation can be obtained. In particular, it can be preferably used for applications requiring insulation. Examples of synthetic nonpolar elastomers include ethylene propylene rubber (hereinafter referred to as EPDM), ethylene propylene diene rubber, isobutylene rubber, isoprene rubber, silicone rubber, and the like. In particular, EPDM and ethylene propylene diene rubber have a very low dielectric loss tangent and can be preferably used as an antenna member.

The blending ratio of the high dielectric ceramic powder is such that the dielectric constant of the high dielectric elastomer composition can be maintained at 7 or more, the dielectric loss tangent can be maintained at 0.01 or less, and the moldability capable of forming the dielectric antenna of the present invention can be maintained. It is.
For example, 300 to 1000 parts by weight (phr) of high dielectric ceramic powder is blended with 100 parts by weight (phr) of elastomer.

  In addition to the above essential components, the high dielectric elastomer composition that can be used in the present invention (1) improves the affinity and bondability of the interface between the elastomer and the ceramic powder within the range that does not hinder the effects of the present invention, In order to improve the strength, coupling agents such as silane coupling agents, titanate coupling agents, zirconia aluminate coupling agents, etc. are used. (2) In order to improve plating properties for electrode formation, talc Particulate fillers such as calcium pyrophosphate, (3) antioxidants to further improve thermal stability, (4) light stabilizers such as UV absorbers to improve light resistance, (5 ) In order to further improve the flame retardancy, flame retardants such as halogen or phosphorus, and flame retardants such as antimony compounds, zinc borate, barium metaborate, zirconium oxide (6) Impact modifier for improving impact resistance, (7) Colorants such as dyes and pigments for coloring, (8) Plasticizer, sulfur for adjusting physical properties (9) A vulcanization accelerator for proceeding with vulcanization can be blended with each other.

  Further, the high dielectric elastomer composition that can be used in the present invention includes glass fiber, alkali metal titanate fibers such as potassium titanate whisker, titanium oxide fiber, magnesium borate whisker, and the like within the range not impairing the object of the present invention. Combined with various organic or inorganic fillers such as metal borate salts such as aluminum borate whisker, metal silicate fibers such as zinc silicate whisker and magnesium silicate whisker, carbon fiber, alumina fiber and aramid fiber it can.

  A method for producing the dielectric antenna of the present invention using the high dielectric elastomer composition as a material is not particularly limited, and various mixed molding methods can be used. For example, a method of kneading and manufacturing with a twin screw extruder is preferably used. Immediately, a molded product may be obtained by injection molding, extrusion molding, or the like, or a molding material such as a pellet, bar, or plate. In order to improve the adhesion between the antenna member and the adhesive layer, the surface of the antenna member is roughened by sandpaper, blasting, etc., or surface treatment such as solvent etching, UV etching, plasma etching, primer application, etc. You may give it.

Dielectric antenna having a dielectric constant and a dielectric loss tangent of a molded body (antenna member) of a high dielectric elastomer composition obtained in each of Examples and Comparative Examples, and a dielectric antenna in which an electrode is formed of a plated copper foil on the antenna member The antenna characteristics were measured by the following methods.
Test Method 1 (Cavity Resonator Method): Measurement of relative dielectric constant and dielectric loss tangent at 25 ° C. From a molded body (antenna member) obtained by heat compression molding of a high dielectric elastomer composition, 1.5 mm × 1.5 mm × 80 mm The sample was processed into a strip-shaped test piece, and the relative dielectric constant and dielectric loss tangent at 25 ° C. were measured at 1 GHz band by the cavity resonator method (July 1998, Electronic Monthly, pages 16 to 19).
Test method 2: Measurement of antenna characteristics Using the obtained patch antenna, the resonance frequency, VSWR (standing wave ratio), and the gain of each resonance frequency are compared with a reference antenna whose gain is known. It was measured. Here, in the case of (VSWR <2) and (gain> 2 dBi), the determination was ◯, and in the other cases, the determination was ×.
Test method 3: Measurement of changes in antenna characteristics The obtained patch antenna was aged at 100 ° C for 500 hours, and changes in antenna characteristics (resonance frequency, VSWR, gain) were measured.

Examples 1 to 3
EPDM is mixed with barium titanate / neodymium ceramic powder (manufactured by Kyoritsu Materials Co., Ltd .: HF-120 relative dielectric constant: 120), trace additives such as vulcanization accelerators and processing aids in the mixing ratios shown in Table 1, respectively. Then, a compact of 80 mm × 80 mm × 2 mm was obtained by heat compression molding. The vulcanization conditions are 170 ° C. × 30 minutes, and the contents of the vulcanization accelerator and processing aid are 1 part by weight (phr) of stearic acid (manufactured by Kao Corporation; LUNAC S-30), zinc oxide. (Made by Inoue Coal Industry; META-Z L-40) 5 parts by weight (phr), processing aid (made by Kao; Splendor R-100), 3 parts by weight (phr), vulcanization accelerator (Sumitomo Chemical) 2.5 parts by weight (phr) of Soxinol M) and 1.5 parts by weight (phr) of sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd .; Jinhua stamp fine powder sulfur) were blended.
The relative permittivity and dielectric loss tangent of the obtained molded body (antenna member) were measured by the above test method 1. The results are shown in Table 1.
Further, a nickel-plated copper foil was heated and pressure-bonded to both surfaces of the molded body with an epoxy adhesive film (40 μm) to form a 60 mm × 60 mm × 2 mm sheet. A patch antenna for 2450 MHz was fabricated using this antenna member. The feeding position and the antenna electrode shape of the radiation surface were selected according to the relative dielectric constant of the material, and unnecessary portions were removed by etching. Etching was performed using a ferric chloride solution by printing an electrode pattern resist.
Table 1 shows the types of electrodes of each antenna, the plating thickness, and the copper foil thickness. The characteristics of this antenna were measured by Test Method 2. The results are shown in Table 2. The change in the antenna characteristics was measured by Test Method 3. The results are also shown in Table 2.

Example 4 to Example 6
EPDM is mixed with strontium titanate-based ceramic powder (manufactured by Kyoritsu Materials Co., Ltd .: ST-NAS relative dielectric constant: 180), trace additives such as vulcanization accelerator and processing aid in the blending ratio shown in Table 1, respectively. A compact of 80 mm × 80 mm × 2 mm was obtained by heat compression molding. The vulcanization conditions were 170 ° C. × 30 minutes, and the contents of the vulcanization accelerator and processing aid were the same as in Example 1.
The relative permittivity and dielectric loss tangent of the obtained molded body (antenna member) were measured by the above test method 1. The results are shown in Table 1.
Further, a silver-plated copper foil was heated and pressure-bonded to both surfaces of the molded body with an epoxy adhesive film (40 μm) to form a 60 mm × 60 mm × 2 mm sheet. A patch antenna for 2450 MHz was fabricated using this antenna member. The feeding position and the antenna electrode shape of the radiation surface were selected according to the relative dielectric constant of the material, and unnecessary portions were removed by etching. Etching was performed using a ferric chloride solution by printing an electrode pattern resist.
Table 1 shows the types of electrodes of each antenna, the plating thickness, and the copper foil thickness. The characteristics of this antenna were measured by Test Method 2. The results are shown in Table 2. The change in the antenna characteristics was measured by Test Method 3. The results are also shown in Table 2.

  With respect to all the antennas of the first to sixth embodiments, the determination of the antenna characteristics is “good” both before and after aging, so that the antennas can be sufficiently used.

Comparative Examples 1 to 3
EPDM is mixed with barium titanate / neodymium ceramic powder (manufactured by Kyoritsu Materials Co., Ltd .: HF-120 relative dielectric constant: 120), vulcanization accelerators and processing aids, etc., in a mixture ratio shown in Table 3, respectively. Then, a compact of 80 mm × 80 mm × 2 mm was obtained by heat compression molding. The vulcanization conditions were 170 ° C. × 30 minutes, and the contents of the vulcanization accelerator and processing aid were the same as in Example 1.
The relative permittivity and dielectric loss tangent of the obtained molded body (antenna member) were measured by the above test method 1. The results are shown in Table 3.
Further, a copper foil that was not plated on both surfaces of the molded body was heated and pressure-bonded with an epoxy adhesive film (40 μm) to form a 60 mm × 60 mm × 2 mm sheet. A patch antenna for 2450 MHz was fabricated using this antenna member. The feeding position and the antenna electrode shape of the radiation surface were selected according to the relative dielectric constant of the material, and unnecessary portions were removed by etching. Etching was performed using a ferric chloride solution by printing an electrode pattern resist.
Table 3 shows the types of electrodes of each antenna, the plating thickness, and the copper foil thickness. The characteristics of this antenna were measured by Test Method 2. The results are shown in Table 4. The change in the antenna characteristics was measured by Test Method 3. The results are also shown in Table 4.

  The antennas before aging of Comparative Examples 1 to 3 are all judged as “good”, but after aging, (VSWR> 2) and (gain <2 dBi) are obtained, and the antenna characteristics are remarkably deteriorated.

  The dielectric antenna of the present invention shows a high dielectric constant over a wide temperature range by forming an antenna electrode by bonding a copper foil plated to an elastomer molded body mixed with a dielectric ceramic powder. In addition, since it has a low dielectric loss tangent and excellent aging resistance, it can be suitably used as an antenna for a high-frequency communication device.

It is a perspective view of a dielectric antenna (patch antenna).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric antenna 2 Dielectric board 3 Electrode 4 Grounding conductor 5 Feeding pin

Claims (6)

A dielectric antenna comprising a molded body of a high dielectric elastomer composition obtained by blending a high dielectric ceramic powder with an elastomer, and an electrode provided on the molded body,
The high dielectric ceramic powder has a relative dielectric constant of 7 or more and a dielectric loss tangent of 0.01 or less at a frequency of 1 GHz and a temperature of 25 ° C.
The dielectric antenna is characterized in that the electrode is formed of a plated copper foil.   The dielectric antenna according to claim 1, wherein the plating process is nickel plating.   The dielectric antenna according to claim 1, wherein the plating process is silver plating.   4. The dielectric antenna according to claim 1, wherein the elastomer includes a nonpolar olefin unit as a constituent unit.   5. The dielectric antenna according to claim 4, wherein the elastomer is ethylene propylene rubber.   The dielectric antenna according to any one of claims 1 to 5, wherein the dielectric antenna is used in a frequency band of 100 MHz or more.

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