JP4909095B2 - Dielectric antenna - Google Patents

Description

  The present invention relates to a dielectric elastomer molded body, and more particularly to a dielectric elastomer molded body used for a dielectric antenna of a high-frequency communication device in an environment where adhesion of rust prevention oil or the like is a concern.

  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 the communication device, when the relative dielectric constant of the antenna material incorporated in the communication device is increased, the frequency and size can be further reduced. The relative dielectric constant is a parameter indicating the degree of polarization inside the dielectric. Therefore, if an antenna material having a high relative dielectric constant can be used, high frequency can be increased, and therefore the circuit can be shortened and the communication device can be miniaturized.

Conventionally, ethylene-propylene rubber (hereinafter referred to as EPDM) -based materials are known as elastomer-based dielectric materials for antennas (see Patent Document 1).
When used as an antenna, it is punched or cut into a predetermined size from a large rubber sheet, which is an elastomeric dielectric material, or is used by using an antenna-sized die. At this time, the surface of the rubber sheet is used by bonding a copper foil serving as an electrode. Moreover, since the adhesive film for bonding uses an oil-resistant epoxy film or the like, the upper and lower surfaces of the antenna material are excellent in oil resistance.

However, the end face of the antenna material after processing is exposed. When the antenna is used in a housing case, this exposed end surface is protected from the external environment by the housing case, so that there is no problem. However, in a factory where the cutting oil or rust preventive oil is sprayed, when used as an RFID tag antenna directly attached to a container or pallet, the rust preventive oil on the exposed end face of the antenna material is used. There is a concern about the adhesion of etc. EPDM-based materials are inferior in oil resistance, and when oil adheres, there is a problem that the antenna material swells and its dimensions change drastically and the dielectric properties deteriorate.
JP 2006-1989

  The present invention has been made in order to cope with such problems, and is a dielectric elastomer molded body that is excellent in oil resistance and can be suitably used even in an environment where adhesion of rust prevention oil or the like is a concern. An object of the present invention is to provide a dielectric antenna using a body.

The dielectric elastomer molded body of the present invention is a dielectric elastomer molded body formed by molding a dielectric elastomer composition in which a dielectric ceramic powder is blended with an elastomer, and an oil-resistant protective film is formed on the exposed surface of the molded body. Is formed.
The protective film may be formed using at least one of thermosetting fluororubber, epoxy resin, ultraviolet-crosslinking epoxy resin, and urethane resin.
The elastomer is EPDM.

  The dielectric antenna of the present invention comprises a flat plate-shaped dielectric elastomer molded body, a resin layer formed on both upper and lower surfaces of the molded body, and an electrode provided on the molded body via one of the resin layers. A dielectric antenna is provided, wherein the protective film is formed on an end surface which is an exposed surface of the molded body.

The dielectric elastomer molded body of the present invention is a dielectric elastomer molded body formed by molding a dielectric elastomer composition in which a dielectric ceramic powder is blended with an elastomer, and an oil-resistant protective film is formed on the exposed surface of the molded body. Thus, excellent oil resistance can be exhibited even in an environment where adhesion of rust preventive oil or the like is a concern.
As a result, the dielectric antenna using the dielectric elastomer molded body of the present invention is excellent in oil resistance and can be suitably used even in the above environment.

A dielectric antenna using the dielectric elastomer molded body of the present invention will be described with reference to FIG. FIG. 1 is a perspective view of a dielectric antenna (patch antenna) using the dielectric elastomer molded body of the present invention.
As shown in FIG. 1, the dielectric antenna 1 has an electrode 3 as a radiating element formed at the center of the upper surface of a dielectric substrate 2 made of a dielectric elastomer molded body. 5 is attached. Examples of the method for forming the electrode 3 include metal plating treatment and adhesion of metal foil. Both end surfaces in the XY direction of the dielectric substrate 2 are covered with a protective film.
A ground conductor 4 is bonded to the lower surface of the dielectric substrate 2. The power supply pin 5 is electrically connected to an amplifier circuit, a transmission circuit, and the like (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 using a power supply line or the like extending from the electrode 3 without using the power supply pin 5.

The configuration of the dielectric substrate 2 will be described with reference to FIG. 2 is a partial cross-sectional view taken along line AA of FIG.
As shown in FIG. 2, the dielectric substrate 2 is a laminate of a resin layer 2a and a resin layer 2b for joining electrodes and the like, and a dielectric 2c that is a dielectric elastomer molded body. The dielectric 2c has a flat plate shape, and both upper and lower surfaces are covered with resin layers 2a and 2b, and both end surfaces, which are exposed surfaces, are covered with a protective film 6 to be shielded from the external environment. The electrode (see FIG. 1) is bonded to the dielectric 2c via the resin layer 2a, and the ground conductor 4 is bonded to the dielectric 2c via the resin layer 2b.

  The resin layers 2a and 2b can be formed by applying a liquid adhesive made of an epoxy resin, a urethane resin, or the like to the electrode 3, the dielectric 2c, and the ground conductor 4 and drying. Further, when molding the dielectric 2c, it is also possible to insert a copper foil and a resin layer into the mold and vulcanize and bond with the pressure during molding. By the resin layers made of these materials, the upper and lower surfaces of the dielectric 2c, which is a dielectric elastomer molded body, are protected and excellent in oil resistance. Moreover, by using an epoxy resin, even if a copper foil is attached as the electrode 3, it is excellent in adhesiveness, and warpage generated in the antenna member can be suppressed, which is advantageous in terms of cost.

The thickness of each resin layer is preferably about 1 to 200 μm. If the thickness of the resin layer is less than 1 μm, the resin layer cannot be locally present and the bonding area is reduced, which is not preferable. If it is larger than 200 μm, the dielectric properties (particularly the dielectric loss tangent) deteriorate, which is not preferable. A more practical range is 10-100 μm.
Each resin layer is preferably made of a resin having a positive dielectric constant relative dielectric constant.

  In the present invention, the protective film 6 is preferably a film formed using at least one selected from thermosetting fluororubber, epoxy resin, UV-crosslinking epoxy resin, and urethane resin.

  The thermosetting fluororubber used for forming a protective film in the present invention is a vinylidene fluoride-hexafluoropropylene binary copolymer (VDF-HFP) or a ternary copolymer obtained by adding tetrafluoroethylene thereto. It is preferable that it is a coalescence (VDF-HFP-TFE), so-called FKM. These thermosetting fluororubbers are thermally cured by polyamine vulcanization, polyol vulcanization, peroxide vulcanization or the like. Examples of commercially available products include FN-50 manufactured by Taihei Kasei Co., Ltd.

The epoxy resin used for forming the protective film in the present invention is a thermosetting resin having two or more epoxy groups in one molecule, and the epoxy group is formed by a curing agent such as amines, acid anhydrides, and catalysts. It cures by ring-opening reaction.
The epoxy resin used in the present invention includes various epoxy resins such as an epoxy novolac resin, an alicyclic epoxy resin, and a heterocyclic epoxy resin in addition to the most typical epoxy resin which is a condensation product of bisphenol A and epichlorohydrin. Can be used. Among these epoxy resins, it is preferable to use a bisphenol A type epoxy resin having excellent weather resistance and a large positive temperature coefficient of relative dielectric constant. As a commercial item, San-Yurek Co., Ltd. RS-900BK etc. are mentioned.

  In addition to the above epoxy resin, it is preferable to use an ultraviolet crosslinking epoxy resin that can be dried and cured in a short time after application by ultraviolet irradiation. As a commercial item, Daicel Chemical Industries, Ltd. Celoxide 2021P etc. are mentioned.

  The urethane resin used for forming the protective film in the present invention is a polyurethane resin in which a polyol (polyvalent hydroxyl group) and a polyisocyanate (polyvalent isocyanate group) are cross-linked, and is dried and cured after application by ultraviolet irradiation. It is preferably an ultraviolet crosslinking urethane resin that can be performed in a short time. Examples of commercially available products include NTX7296 manufactured by Sartomer Japan.

  The method of forming a protective film on each end face in the XY direction, which is an exposed portion of the dielectric elastomer molded body, is based on the above-mentioned thermosetting fluororubber, epoxy resin, UV-crosslinking epoxy resin, urethane resin, etc. Examples thereof include a method in which the resin coating composition to be formed is sprayed or brushed on the end face of the dielectric elastomer molded body and cured, and a method in which a liquid resin coating composition is impregnated with the dielectric elastomer molded body.

When there are exposed portions where the resin layer is not formed on the upper and lower surfaces of the dielectric elastomer molded body, oil resistance is imparted to the dielectric elastomer molded body by forming the protective film also on these exposed portions. Can do.
The thickness of the protective film is preferably 0.01 to 3 mm, and more preferably 0.1 to 2 mm.

The dielectric elastomer molded body of the present invention is formed by molding a predetermined dielectric elastomer composition.
The dielectric ceramic powder that can be blended in the dielectric elastomer composition is a metal titanate, at least one rare earth such as Nd, La, Ba, Sr, Ca, Mg, Co, Pd, Zn, Be, A ceramic powder containing one or more metal elements selected from Cd, Bi and the like is preferable. 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 dielectric ceramic powder is a Ti-Ba-Nd-Bi-based barium titanate-neodymium ceramic powder.

As the elastomer constituting the dielectric elastomer composition used in the present invention, a natural rubber elastomer and a synthetic rubber elastomer can be used.
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, a block polymer obtained by roughening natural rubber in the presence of a monomer in a nitrogen stream. These include natural rubber as a raw material and elastomers from synthetic cis-1,4-polyisoprene as a raw material.

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

  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 selected from natural rubber elastomers and / or synthetic nonpolar elastomers are used as the elastomer of the present invention, a dielectric elastomer having excellent electrical insulation can be obtained. It can be preferably used for applications requiring insulation. Examples of the synthetic non-polar elastomer include EPDM, ethylene propylene diene rubber, isobutylene rubber, isoprene rubber, and silicone rubber. In particular, EPDM and ethylene propylene diene rubber have a very low dielectric loss tangent, and therefore can be preferably used for electronic parts such as antennas and sensor applications.

  The dielectric elastomer composition used in the present invention includes (1) silane in order to improve the affinity and bondability of the interface between the elastomer and the ceramic powder and to improve the mechanical strength within a range not impeding the effects of the present invention. Coupling agents such as coupling agents, titanate coupling agents, zirconia aluminate coupling agents, etc. (2) Fine particle filling of talc, calcium pyrophosphate, etc. to improve the plating properties for electrode formation (3) Antioxidants to further improve thermal stability, (4) Light stabilizers such as ultraviolet absorbers to improve light resistance, and (5) Further improve flame retardancy. In order to color flame retardant aids such as halogen-based, phosphorus-based, inorganic hydroxide-based or expanded graphite, (6) impact resistance imparting agents to improve impact resistance, and (7) coloring Dyes, pigments, etc. A colorant, (8) a plasticizer in order to adjust the physical properties, the crosslinking agent such as sulfur or peroxides, can be incorporated respectively vulcanization accelerator for advancing (9) vulcanization.

  In addition, the dielectric elastomer composition used in the present invention includes glass fibers, alkali metal titanate fibers such as potassium titanate whiskers, titanium oxide fibers, magnesium borate whiskers and boric acid within a range not impairing the object of the present invention. Various organic or inorganic fillers such as metal borate fibers such as aluminum whiskers, metal silicate fibers such as zinc silicate whiskers and magnesium silicate whiskers, carbon fibers, alumina fibers, and aramid fibers can be used in combination.

  In the present invention, the method for producing the dielectric elastomer molded body is not particularly limited, and various mixed molding methods can be used. For example, the dielectric ceramic powder described above, various additives, vulcanizing agents and the like are blended into an elastomer to form a dielectric elastomer composition, which is kneaded with a Banbury mixer, a roller, a twin screw extruder, etc. Etc. are preferably used. Thereafter, a dielectric elastomer molded body can be obtained by injection molding, extrusion molding, heat compression molding or the like.

In each example and each comparative example, the dielectric antenna material is 600 parts by weight of dielectric ceramic powder (manufactured by Kyoritsu Materials Co., Ltd .: HF-120) with respect to 100 parts by weight of EPDM (manufactured by Mitsui Chemicals, Inc .: EPT-3095). A composition containing a part of the composition and an appropriate amount of other auxiliary agents was used.
As a dielectric antenna, a dielectric antenna 1 including an electrode 3, a dielectric substrate 2, and a ground conductor 4 shown in FIG. The dielectric substrate 2 is a laminate of a resin layer (epoxy film) 2a, a dielectric 2c that is an elastomer molded body, and a resin layer (epoxy film) 2b. The dielectric 2c is a resin layer on both upper and lower surfaces. 2a and 2b. A protective film 6 was formed on each end face in the XY direction, which is an exposed portion of the dielectric 2c, as follows.

Example 1
A fluororubber coating liquid (manufactured by Taihei Kasei Co., Ltd .: FN-50, with a curing agent) is applied to each end face in the XY direction, which is an exposed portion of the dielectric 2c, and dried at 150 ° C. for 0.5 hour to a thickness of 100 μm Thus, a dielectric antenna test piece was obtained in which the protective film 6 was formed and the exposed portion of the dielectric 2c was covered with the protective film 6. The paint was adjusted to an appropriate viscosity by using a diluent so that it could be easily applied to the edges. This test piece was used for the oil resistance test shown below, and the oil resistance was measured. The results are shown in Table 1.

Example 2
An epoxy resin coating liquid (San Yulec Co., Ltd .: RS-900BK, containing a curing agent) is applied to each end face in the XY direction, which is an exposed portion of the dielectric 2c, and dried at 100 ° C. for 0.5 hours to have a thickness of 100 μm. A protective film 6 was formed, and a dielectric antenna test piece in which the exposed portion of the dielectric 2c was covered with the protective film 6 was obtained. The paint was adjusted to an appropriate viscosity by using a diluent so that it could be easily applied to the edges. This test piece was used for the oil resistance test shown below, and the oil resistance was measured. The results are shown in Table 1.

Example 3
An ultraviolet curable epoxy resin coating liquid (manufactured by Daicel Chemical Industries, Ltd .: Celoxide 2021P, containing a polymerization initiator) is applied to each end face in the XY direction, which is an exposed portion of the dielectric 2c, and irradiated with ultraviolet rays to obtain a thickness. A protective film 6 having a thickness of 100 μm was formed, and a dielectric antenna test piece in which the exposed portion of the dielectric 2c was covered with the protective film 6 was obtained. The paint was adjusted to an appropriate viscosity by using a diluent so that it could be easily applied to the edges. This test piece was used for the oil resistance test shown below, and the oil resistance was measured. The results are shown in Table 1.

Example 4
An ultraviolet curable urethane resin coating liquid (Sartomer Japan, Inc .: NTX7296, with a polymerization initiator) is applied to each end face in the XY direction, which is an exposed portion of the dielectric 2c, and irradiated with ultraviolet rays to have a thickness of 100 μm. A protective film 6 was formed, and a dielectric antenna test piece in which the exposed portion of the dielectric 2c was covered with the protective film 6 was obtained. The paint was adjusted to an appropriate viscosity by using a diluent so that it could be easily applied to the edges. This test piece was used for the oil resistance test shown below, and the oil resistance was measured. The results are shown in Table 1.

<Oil resistance test>
A dielectric antenna test piece (elastomer unit size: 60 mm × 20 mm × t2 mm) was immersed in rust preventive oil (anti-last P2400) made by Japan Petroleum heated to 80 ° C. for 168 hours, and the appearance and dimensional change were measured. For dimensional change, the amount of change in the longitudinal direction (60 mm portion) was measured. If the appearance was not swollen and peeled off, and the dimensional change rate was within 5%, it was judged as “good”, and otherwise it was judged as “bad”.

Comparative Example 1
A dielectric antenna test piece was formed without forming a protective film on each end face in the XY direction, which is an exposed portion of the dielectric 2c of the dielectric antenna prepared in Example 1. The test piece was used for the oil resistance test and the oil resistance was measured. The results are shown in Table 1.

Comparative Example 2
A dielectric antenna test piece made of a single elastomer molded body was used for the oil resistance test without using a resin layer, and the oil resistance was measured. The results are shown in Table 1.

  Since the dielectric elastomer molded body of the present invention covers the exposed portion with a protective film, it can exhibit excellent oil resistance even in an environment where adhesion of rust preventive oil or the like is a concern.

It is a perspective view of the dielectric antenna (patch antenna) of this invention. FIG. 2 is a partial cross-sectional view taken along line AA in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric antenna 2 Dielectric substrate 2a, 2b Resin layer 2c Dielectric (dielectric elastomer molding)
3 Electrode 4 Grounding conductor 5 Feeding pin 6 Protective film

Claims (3)

A dielectric elastomer molded body flat plate shape, and a resin layer which is formed on both upper and lower surfaces of the molded article, Ri Na and a one was provided in the molded body through the electrodes of the resin layer, adhered oil A dielectric antenna used in an environment where
The dielectric elastomer molded body is formed by molding a dielectric elastomer composition in which a dielectric ceramic powder is blended with an elastomer that is ethylene propylene rubber or ethylene propylene diene rubber,
An oil-resistant protective film is formed on the end surface that is the exposed surface of the molded body,
The dielectric antenna is characterized in that the protective film is formed using at least one resin selected from thermosetting fluororubber, epoxy resin, ultraviolet crosslinking epoxy resin, and urethane resin .   The dielectric antenna according to claim 1, wherein the resin layer is made of an epoxy resin or a urethane resin.   The said protective film is formed by spray-applying or brushing and curing the resin coating composition made of the resin forming the protective film on the end face of the molded body. Item 3. The dielectric antenna according to Item 2.

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