WO2003077363A1

WO2003077363A1 - Antenna cover

Info

Publication number: WO2003077363A1
Application number: PCT/JP2003/002895
Authority: WO
Inventors: Katsusada Tokuhira; Yasuhiko Sawada; Hiroyuki Yoshimoto; Shunji Kasai; Shinichi Yano; Sigehito Sagisaka
Original assignee: Daikin Industries, Ltd.
Priority date: 2002-03-13
Filing date: 2003-03-12
Publication date: 2003-09-18
Also published as: JPWO2003077363A1

Abstract

An antenna cover prepared from a polytetrafluoroethylene based resin sheet, wherein the polytetrafluoroethylene based resin exhibits a dilelctric loss tangent as measured by a porcedure and under conditions specified in the specification of 2.0 X 10-4 or less, preferably 1.50 X 10-4 or less. The polytetrafluoroethylene based resin preferably has a standard specific gravity of 2.192 or more. The polytetrafluoroethylene based resin has excellent electric characteristics, and thus the antenna cover exhibits a low dielctric loss even in a high frequency region.

Description

Akira Itoda Antenna cover Technical field

The present invention relates to an antenna cover. More specifically, it relates to an antenna cover of an antenna used for a mobile phone base station and the like. Background art

Mobile phone base station antennas are installed on the roofs of high-rise buildings such as condominiums in urban areas.The antenna elements are formed by etching copper foil on both sides of a low dielectric loss resin substrate. .

Currently, this mobile phone is transitioning from the second generation to the third generation. On 2nd generation mobile phones :! The frequency range is 2 to 4 GHz, the third generation uses 2 to 4 GHz, and the fourth generation uses 5 to 8 GHz.The higher the frequency, the higher the dielectric loss tangent of the insulator (hereafter referred to as tan (5 ) dielectric loss (power loss) is increased by. Furthermore, because the resin substrate of the antenna elements hundreds watts of power is applied, tan 5 is approximately 1.5 low dielectric loss of X 1 0- ⁴ following levels It is necessary to use materials, and to reduce this dielectric loss, the impedance must be adjusted to the input and output, and a low dielectric constant is also required.

Conventionally, as the resin substrate material, a cyanate resin is used in terms of moldability, adhesiveness, and price. The electrical properties, tan <5 is about 1 0 ^3, life is said to be 1 five years.

When bonding copper foil to both surfaces of a sinate resin substrate, the surface treatment of the substrate, the use of a non-fluorine resin adhesive, or a combination of these Law. However, these methods have complicated processes and poor production efficiency, and can provide initial bond strength, but have a large change in temperature and bond strength at high temperatures, and range from a maximum of 80 ° C to a minimum of zero. When used for outdoor antenna elements with large temperature changes, peeling occurs.When non-fluorine resin adhesive is used, peeling occurs due to exposure to wind, rain, and direct sunlight, and dielectric loss occurs. Problems.

By the way, since the antenna is installed outdoors, it is exposed to rain, snow, dust and the like. In particular, if water adheres to the antenna, there is a problem that transmission loss due to water occurs and diffusion of electromagnetic waves occurs.

Therefore, antennas used outdoors are protected by antenna covers. Similarly, the antenna cover is required to have excellent electric characteristics such as low dielectric constant and low ta η δ.

An object of the present invention is to solve the above-mentioned problems, and to provide an antenna cover having excellent electric characteristics such as low dielectric constant and low t an. Disclosure of the invention

That is, the present invention relates to an antenna cover comprising a polytetrafluoroethylene-based resin sheet, wherein the polytetrafluoroethylene-based resin has a dielectric loss tangent calculated by the following condition (1): 2.0 X 1 The present invention relates to an antenna cover which is a polytetrafluoroethylene resin of 0 to ⁴ or less.

Condition 1 )

(Sheet preparation conditions)

Polytetrafluoroethylene resin powder is compression-molded into a cylindrical shape. A 0.5 mm-thick sheet cut out of the cylinder is heated and baked at 38 ° C. for 5 minutes in a hot-air circulation type electric furnace. Then, it is allowed to cool to room temperature at a cooling rate of 60 ° CZ time to prepare a sample sheet. (Dielectric loss tangent measurement method)

One L 2

Using a network analyzer, measure the change in the resonance frequency and Q value of the sample sheet with a cavity resonator at 22 to 25 ° C, and calculate the dielectric loss tangent at 12 GHz according to the following equation. .

ta η δ = (1 / Qu) X {1 + (W no λ ^)}-(Ρ ο / ω ν)

XtanX = (L / 2M) YcosY

X x

0 —k r

Y ^ M k ₀ ² -k / ko = — c

3.8317

k =

D / 2

Q .. = i—-/ 20)

Q =

1 F-

P = P + P + P

The symbols in the formula are as follows.

D: Cavity resonator diameter (mm)

M: One side length of cavity resonator (mm)

L: Sample length (mm)

c: Speed of light (mZ s)

I d: Attenuation (dB)

F. ： Resonant frequency (H z)

F _x : Upper frequency (Hz) at which the attenuation from the resonance point is 3 dB

F ₂ : Lower frequency (Hz) at which the attenuation from the resonance point is 3 dB

ε. : Dielectric constant of vacuum (H / m)

ε _r : dielectric constant of sample

o: Magnetic permeability of vacuum (HZm)

R s: Effective surface resistance (Ω) taking into account the surface roughness of the conductor cavity

J 0:-0.40 2 7 5 9

J! : 3. 8 3 1 7 1

The dielectric loss tangent is preferably 1. It 5 0 X 1 0- ⁴ below.

The standard specific gravity of the polytetrafluoroethylene resin is preferably 2.192 or more.

The specific gravity of the sheet is preferably 2.192 or more. The sheet is preferably unfired or has a crystal conversion of 90% or less.

The terminal group of the polytetrafluoroethylene resin is preferably fluorinated.

It is preferable that a metal foil is adhered to the sheet by heat fusion. After the surface treatment of the sheet, it is preferable to heat-bond the sheet.

The sheet and the metal foil are each formed of at least one resin adhesive selected from the group consisting of an epoxy resin, a phenol resin, and a silane resin; and Z or a hydroxyl group, a carboxylic acid group, a carboxylate, a carboxyester group. It is preferable that the adhesive be applied via a fluorine-containing ethylenic polymer having at least one functional group selected from the group consisting of epoxy group and epoxy group. Preferably, the sheet and the metal foil are adhered via a resin adhesive after the sheet is subjected to a surface treatment.

The surface treatment includes (a) discharge treatment in an inert gas atmosphere containing an organic compound having a functional group, (mouth) excimer laser irradiation, (c) plasma treatment, or (ii) chemical treatment using metallic sodium. It is preferable that the etching process be performed.

Further, the present invention has a dielectric loss tangent at 1 2 GH z measured in (A) above condition (1) is at 1. 5 X 1 0- ⁴ or less, Ru der standard specific gravity of 2.1 9 2 or more poly tetrafluoropropoxy O b ethylene-based resin powder, and Roh or (B) 3 8 0 melt viscosity at ° C is less than 1 0 ⁶ Boise polytetramethylene full O Roe Chile emission resin powder composition comprising 1 0% by weight or more The present invention relates to an antenna cover in which a metal foil is adhered to at least one surface of a sheet made of an object.

Preferably, the composition comprises a cyanate resin.

The terminal group of the polytetrafluoroethylene resin is preferably fluorinated. The metal foil is preferably a stainless steel foil or an aluminum foil. The sheet and the metal foil are each formed of at least one resin adhesive selected from the group consisting of an epoxy resin, a phenol resin, and a silicate resin, and z or a hydroxyl group, a hydroxyl group, a carboxylate, and a carboxy ester. It is preferable that the adhesive be applied via a fluorine-containing ethylenic polymer having at least one functional group selected from the group consisting of a group and an epoxy group. It is preferable that the sheet is formed and then obtained by bonding a metal foil. It is preferable that the sheet and the metal foil are adhered and then formed by heat treatment.

The present invention comprises a sheet using a polytetrafluoroethylene resin

-About. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing an example of an antenna cover according to the present invention. (A) is a perspective view, and (b) is a cross-sectional view taken along line AA.

FIG. 2 is a diagram showing an example of the antenna cover of the present invention. (A) is a perspective view, and (b) is a cross-sectional view taken along line BB.

FIG. 3 is a diagram showing an example of the antenna cover of the present invention. (A) is a perspective view, and (b) is a cross-sectional view taken along line C-C.

FIG. 4 is a diagram showing an example of the antenna cover of the present invention. This is an example in which the antenna element and the reflector are directly coated. BEST MODE FOR CARRYING OUT THE INVENTION

The polytetrafluoroethylene resin (hereinafter referred to as a PTFE resin) used in the present invention is a homopolymer of tetrafluoroethylene (TFE) or tetrafluoroethylene 99.9 to 99.9. 9.9 9 9 9 mol% and the formula ( I):

CX ₂ = CY (CF ₂ ) _n Z (I)

(Wherein, X, Y and z are the same or different and are all hydrogen atoms or fluorine atoms, n is an integer of 1 to 5).

II):

CF ₂ = CF-OR _f ¹ (II)

Wherein Rf ¹ is a perfluoroalkyl group having 1 to 3 carbon atoms, wherein at least one monomer selected from the group consisting of perfluoro (alkyl biether) A modified polytetrafluoroethylene having a modification amount of 0.1% by weight or less as a copolymer with 0.1 mol% is preferred.

Examples of the fluorofluorin represented by the above formula (I) include, for example, verfluoroolefin such as hexafluoropropylene (hereinafter abbreviated as HFP); and fluorofluorin such as perfluorobutylethylene. And so on. Of these, HFP is preferred because of its excellent electrical properties. The perfluoro (alkyl vinyl ether) represented by the formula (II) includes perfluoro (methyl vinyl ether) (hereinafter abbreviated as PMVE), perfluoro (ethyl vinyl ether) (hereinafter abbreviated as PEVE), Perfluoro (propyl vinyl ether) (hereinafter abbreviated as PP VE). Of these, PMVE is preferred because of its excellent electrical properties.

Examples of the shape of the PTFE resin used in the present invention include molding powders, fine powders, and aqueous dispersions.

The fine powder is obtained by emulsion-dispersion polymerization using a polymerization initiator in the presence of an emulsifier, particularly a fluorinated emulsifier. In emulsion polymerization, in order to reduce the molecular weight of the obtained polymer, the amount of the polymerization initiator must be reduced. Increasing, adding a chain transfer agent, adding a modified monomer, etc. are adopted.

Examples of the polymerization initiator include ammonium persulfate (APS) and disuccinic acid peroxide (DSP), and examples of the chain transfer agent include hydrocarbons such as hydrogen, methane, and ethane.

The method of emulsion polymerization is not particularly limited, and a known method may be used.

Further, by forming the colloid-secondary particles obtained by the emulsion polymerization method into a core-shell structure, moldability, particularly paste extrudability, can be improved. As the core-shell structure, for example, a core composed of a homopolymer of PTFE and a shell composed of a modified PTFE is preferred in terms of good paste extrusion moldability.

The molding powder is obtained by suspension polymerization using a polymerization initiator in the presence of a dispersant.

Examples of the polymerization initiator include persulfates and sulfites, and for example, ammonium persulfate and the like.

The suspension polymerization method is not particularly limited, and a known method may be used.

As the aqueous dispersion, the aqueous dispersion obtained by the emulsion polymerization can be used as it is, but a surfactant is added in order to increase the concentration of the fluoropolymer and improve the stability. And then concentrated to a polymer solids concentration of 40 to 70% by weight using a layer separation concentration method or a membrane separation concentration method, and then purified water, ammonia water and polyoxyethylene alkyl ether. It is preferable to add a tellurium-based surfactant and dilute the solution to 30 to 65% by weight.

R-O-A-H

(Wherein, R is a linear or branched alkyl group having 5 to 18 carbon atoms, preferably 10 to 16 carbon atoms, and A is 5 to 20 oxyethylene groups and Which is a polyoxyalkylene chain having 0 to 6 pyrene groups). Examples of the alkyl group R include decyl, lauryl, tridecyl, cetyl, stearyl and the like, and may be linear or branched. In particular, R is an alkyl group having 10 to 16 carbon atoms and polyoxyalkylene chain, because of its excellent surface activity, water solubility, and availability. A polyoxyalkylene alkyl ether surfactant comprising from 15 to 15 oxyethylene groups and 0 to 3 oxypropylene groups is preferred. As a raw material for producing this surfactant, a natural or synthetic higher alcohol may be used, but it is preferable that it does not contain any alkylphenols.

The addition amount of the polyoxyalkylene alkyl ether-based surfactant is preferably 3 to 20 parts per 100 parts by weight of the PTFE-based resin (hereinafter, referred to as “parts”).

For dilution, pure water, a water-soluble solvent, or various types of hydrocarbon-based surfactants not containing alkylphenol may be appropriately added, and a fluorine-based surfactant or a silicon-based surfactant may be used as a repelling agent. The viscosity may be adjusted by adding an activator, or by using a thickener, a rheology control agent, or a salt containing various water-soluble electrolytes.

The standard specific gravity of the PTFE-based resin is preferably at least 2.192. More preferably, it is at least 2.200. The upper limit is 2.300, preferably 2.280. PTFE resin with a standard specific gravity of 2.300 is completely crystallized and does not actually exist. That is, the PTFE-based resin used in the present invention preferably has a high degree of crystallinity. If the standard specific gravity is smaller than 2.192, the crystallinity tends to be low, and the t an <5 of the sheet tends to be high, or the formability tends to be poor. On the other hand, if the standard specific gravity is high, there is a problem in that the mechanical strength decreases. The standard specific gravity was measured at a temperature of 25 ° C. In this method, the density of the sample (ps) is determined from the difference between the weight of the sample in air (W1) and the weight of the sample in water (W2).

W, X p _w

Ps =

w ₁ -w ₂ p _s : Sample density (gZcm ³ ) '

p _w : Water density (g / cm ³ )

W: Sample weight in air (g)

W ₂ : Sample weight in water (g)

The molecular weight of the PTFE resin satisfying the standard specific gravity is considered to be 5,000,000 or less, and in the present invention, such a low molecular weight PTFE resin is preferably used.

Further, it is preferable to stabilize the terminal unstable group by subjecting the PTFE-based resin to a fluorination treatment by contacting the PTFE resin with a fluorine radical source. When the terminal labile group is fluorinated, not only thermal stability but also processing characteristics and high-frequency characteristics such as t an <5 are improved. Furthermore, the high-frequency and mechanical properties of the antenna cover obtained therefrom are also improved.

The reaction temperature of the fluorination treatment is preferably from 100 to 250 ° C, more preferably from 110 to 200 ° C. If the reaction temperature is lower than 100 ° C, the reaction rate tends to be slow. If the reaction temperature exceeds 250 ° C, the PTFE resins tend to fuse or decompose and volatilize.

As a fluorine radical source, in addition to fluorine gas, halogenated fluorides such as C 1 F, C 1 F ₃ Br F ₃ and IF ₃ ; rare gases such as Xe F ₂ , Xe F ₄ and Kr F ₂ Compounds that are gaseous at the above-mentioned reaction temperature, such as nitrogen-containing fluorine compounds such as NF ₃ and NF ₂ . Among them, fluorine gas is most preferable in terms of handling properties and price. Perform fluorination treatment using fluorine gas In this case, the PTFE resin is brought into contact with fluorine gas at 110 to 250 ° C for 1 to 10 hours. Preferably, the reaction temperature is 180 to 230 ° C. The reaction time is preferably 2 to 5 hours. The reaction pressure may be about 0.1 to 1 MPa, preferably atmospheric pressure. The fluorine gas may be pure fluorine gas, or may be diluted with an inert gas such as a nitrogen gas, an argon gas or a helium gas to a concentration of 5 to 25% by volume, preferably 7 to 20% by volume. The addition amount of the fluorine radical source varies depending on the reaction temperature, reaction time, type of the fluorine radical source, etc., but is preferably 0.01 to 1 part in terms of fluorine atoms, based on 100 parts of the PTFE-based resin. . More preferably, it is 0.1 to 0.5 part. When the addition amount of the fluorine radical source is less than 0.01 part, the fluorination of the raw material PTFE tends to be insufficient. Also, if the amount of the fluorine radical source exceeds 1 part, the effect of fluorination does not improve and tends to be uneconomical.

As a reaction apparatus used for the fluorination treatment, any apparatus that can sufficiently perform solid-at-a-time contact can be used without any problem. Specific examples include a fluidized bed type and a tray type solid-batch contact reactor.

PTFE resin used in the present invention, 1 t an, at 2 GHz [delta] is 2. 0 X 1 0- ⁴ indicates less, and preferably 1. is 5 X 1 0- ⁴ below. When tan 3 exceeds 2. OX 1 0 one ^4, the dielectric loss of the antenna cover (power loss) is increased.

In the method of measuring t an (5) in the present invention, a sample is prepared and measured under the following condition (1).

Condition 1)

(Sheet preparation conditions)

Polytetrafluoroethylene is compression molded into a cylindrical shape. A 0.5 mm-thick sheet cut from this cylinder was heated at 380 ° C for 5 minutes in a hot air circulation type electric furnace. Heat and bake. Then, let it cool to room temperature at a cooling rate of 60 ° C / hr.

Make a pull sheet.

However, if the PTFE resin is an aqueous dispersion, heat it at 80 ° C for 2 hours to evaporate water to form a powder before compression molding, and then perform sheet molding. Two

(T an δ measurement method)

Using a network analyzer (Hewlett-Packard, HP 8510C), measure the change in the resonance frequency and Q value of the film produced above with a cavity resonator at 22 to 25 ° C and 12 GHz Is calculated according to the following formula. The following formula is a formula developed by Yoshio Kobayashi and Junya Sato of the Faculty of Engineering of Saitama University (Kio Kobayashi, Junya Sato “Microphone opening of dielectric flat material” Wave complex permittivity measurement ”, IEICE Technical Report, MW87-7, May 1987. However, when a sample is introduced into a 12 GHz cavity resonator, the resonance frequency changes depending on the sample, and the The value of the resonance frequency is about 11.74 GHz for a 500-meter thick PTFE sample, where tan (5 is used for the unsampled resonance frequency.

tan (5 = (1 / Qu) X {1 + (W ₂ / W _x ))-(P c / ω \ Ν _x )

XtanX = (L / 2M) YcosY

L

Y = M-Jk ₀ ² -k _r ² ^k 0 =

c _r 3.8317

k =

'· D / 2

Q _r

Q „=

1 one io ( ^1/20)

^ F -F

1 2

1 2 huff 9 / sin W ₁ = -xs _r χε ₀ χ∑χπχτσ x μ ₀ xj ^ XJ x 1+

P = P i + P 2 + P 3

r, x- / r ₀ 2

Where the symbols in the equation are as follows.

D: Cavity resonator diameter (mm)

M: One side length of cavity resonator (mm)

L: Sample length (mm)

c: Speed of light (mZ s)

I d: Attenuation (dB)

F 0: resonance frequency (H z)

F! : Upper frequency (Hz) where the attenuation from the resonance point is 3 dB F ₂ : Lower frequency (Hz) at which the attenuation from the resonance point is 3 dB

ε. : Dielectric constant of vacuum (H / m)

ε _r : dielectric constant of sample

0: Permeability of vacuum (H / m)

Rs: Effective surface resistance (Ω) considering the surface roughness of the conductor cavity

J _Q : — 0.402759

J _x : 3.83171

The PTFE-based resin sheet used for the antenna cover of the present invention includes not only a sheet having a thickness of 200 m or more, but also a film having a thickness of less than 200 m.

As the antenna cover of the present invention, an antenna cover in which a sheet made of PTFE-based resin is located away from the antenna element or the reflector, or an antenna in which a sheet made of PTFE-based resin is directly coated on the antenna element and the reflector It refers to a cover.

When the sheet made of the PTFE-based resin is an antenna cover located away from the antenna element or the reflector, the three-dimensional shape is not particularly limited, such as a cylindrical shape, a polygonal shape, and a conical shape.

The thickness of the antenna cover is not particularly limited, but is preferably 1 to 6 mm. If it is smaller than 1 mm, mechanical strength tends to be insufficient.

In the case of an antenna cover in which the antenna element and the reflection plate are directly coated with a sheet made of PTFE-based resin, the thickness of the antenna cover is preferably 5 to 50 / m. If the film thickness is less than, the water repellency tends to decrease. If the film thickness exceeds 50 m, cracks are generated, water seeps, and the water repellency tends to decrease.

The antenna cover of the present invention comprises the PTFE-based resin sheet, The weight is preferably at least 2.192. More preferably, it is at least 2.200. The upper limit is 2.300, preferably 2.280. If the specific gravity is less than 2.192, the crystallinity will be low, t an <5 will be high, and the formability will be poor. On the other hand, if the standard specific gravity is high, there is a problem in that the mechanical strength decreases.

In order to obtain a sheet having a specific gravity of 2.192 or more, the sheet preferably contains 20% by weight or more, and more preferably 70% by weight or more of the PTFE-based resin having a standard specific gravity of 2.192 or more.

Further, the present invention is prepared by (A) The condition (1), measured 12 GHz to definitive t an, [delta] is 1. is a 5 X 10- ⁴ or less, the standard specific gravity 2. is the 192 or more Boritetora Fluoroethylene-based resin powder, and / or (Β) 38 O: Melt viscosity at 38 O: is less than 10 ⁶ % by volume. More particularly, the present invention relates to an antenna cover having a metal foil adhered to one side.

The polytetramethylene full O b ethylene resin powder (A), the condition (1) in work made, t an, S is the measured 12 GHz 1. is a 5X 10 ⁴ or less, preferably, 1. 0 X 10- ⁴ It is as follows. Outside this range, dielectric loss tends to increase.

Further, polytetramethylene full O b ethylene resin powder (B) is contact Keru melt viscosity 380 ° C is 10 ⁶ Boise less, preferably 10 ⁵ Boise below. If the melt viscosity exceeds 10 ⁶ boise, the dielectric loss tends to increase during fabrication under slow cooling conditions.

Here, the slow cooling condition may be such that, for example, the cooling rate after firing is lower than 60 ° C./hour.

The polytetrafluoroethylene-based resin powder (A) and / or the polytetrafluoroethylene-based resin powder (B) is 10% by weight of the sheet. More preferably, it is preferable to contain more than 30% by weight. If the content of the polytetrafluoroethylene resin powder is less than 10% by weight, the effect of reducing the dielectric loss tends to be hardly obtained.

The composition, in terms of low dielectric loss tangent at slow cooling molding preferably comprises a melt viscosity 1 0 ⁶ Boise following PTFE resin, in view further of low loss, end groups are fluorinated It is preferable to include a polytetrafluoroethylene resin.

The present invention also relates to an antenna cover using a sheet made of a PTFE resin.

Since the PTFE-based resin used in the present invention cannot be melt-processed, it is molded by a molding method such as a press molding method, an extrusion method such as sheet or tube (pipe) extrusion, or a compression molding method.

The obtained molded product is usually subsequently fired. The firing temperature is suitably from 360 to 400 ° C.

In addition, the above-mentioned baking may not be performed, and the baking may be partially performed to a crystal conversion ratio of 90% or less. Unsintered and semi-sintered with a crystal conversion ratio of 90% or less tend to reduce dielectric loss.

Thereafter, a sheet-like molded body made of a PTFE-based resin is obtained by pressing, paste extrusion, skiving, or the like. Then, the antenna cover of the present invention can be obtained by forming the obtained flat molded body into a three-dimensional shape by hot pressing or tube extrusion.

In the case of an antenna cover in which the antenna element and the reflector are directly coated with a sheet made of a PTFE-based resin, the antenna element and the antenna reflector are spray-coated with a water-soluble dispersion to obtain a 3 to 20 After drying for a minute, baking is preferably performed. An appropriate firing temperature is 360 to 400 ° C. The antenna cover used in the present invention thus obtained has excellent electrical characteristics in the microwave region (3 to 30 GHz), particularly in the high frequency region. 10_ ⁴ or less, preferably 1. 5 0 X 1 0 one ⁴ below. t an, <5 is more than 2. 0 X 1 0- ^4, there is a tendency that the dielectric loss increases.

Antenna covers and their peripheral devices are required to keep transmission loss low. Then, the transmission loss is obtained by the following equation.

Transmission loss-conductor loss + dielectric loss (ad)

Where the dielectric loss (ad) is

Dielectric loss (cud) =

27.3X (Frequency) Z. (Speed of light) ΧΛ (Dielectric constant) X t an (Represented by 5. The dielectric loss is proportional to t an δ. To reduce the transmission loss of the antenna, t It can be seen that the effect of reducing an δ is great.

Therefore, since ta eta [delta] of the antenna cover of the present invention: 1. is reduced to 50 X 1 0 one ⁴ or less, it is possible to significantly reduce the transmission loss. Further, since the antenna cover of the present invention is made of a fluororesin, it repels moisture such as rain and snow. As a result, the center frequency of the transmitting and receiving antennas is less likely to shift due to moisture, and stable receiving and transmitting performance can be obtained.

In the antenna cover of the present invention, it is preferable that a metal foil is adhered to at least one surface of the sheet from the viewpoint of fixing.

As the metal foil, stainless steel foil, aluminum foil and the like are preferable from the viewpoint of corrosion prevention. The thickness of the metal foil is not particularly limited, but is preferably 0.05 to 1.0 Omm.

From the viewpoint of adhesive strength, it is preferable that the metal foil be bonded to the sheet surface by heat fusion after the surface treatment of the sheet or without the surface treatment. Further, from the viewpoint of adhesive strength, the metal foil may have at least one selected from the group consisting of an epoxy resin, a phenol resin, and a cyanate resin on the sheet surface after or without surface treatment of the sheet. Fluorinated ethylenic polymer having at least one functional group selected from the group consisting of a resin binder, and z or a hydroxyl group, a hydroxyl group, a carboxylate, a carboxylester group, and an epoxy group. It is preferable that they are adhered through a gap.

The three types of adhesives composed of the epoxy resin, the phenolic resin, and the skeleton resin and the fluorine-containing ethylenic polymer having a functional group may be used alone, but two or more types may be used, and two or more layers may be used. May be used as an adhesive layer. For example, a two-layer adhesive layer composed of a fluorine-containing ethylenic polymer layer having a functional group and an epoxy resin layer may be used.

As the bonding method, one layer of a resin adhesive, one layer of a fluorinated ethylene polymer having a functional group, or two layers of a resin adhesive and a fluorinated ethylene polymer having a functional group are used. It means that it is adhered through.

Among these, the point of easy adhesion and the strength of adhesion to metal, not only the initial adhesive strength but also the post-processing with heat treatment is possible because the adhesive strength does not decrease even under severe temperature changes or high temperatures. Since the fluorocarbon resin has a main chain, it has excellent weather resistance, has a long outdoor life, and is unlikely to cause dielectric loss.Hydroxy group, carboxyl group, carboxylate, carboxylate group and epoxy group Preferred is a fluorine-containing ethylenic polymer having at least one functional group selected from the group consisting of:

The functional group-containing fluoroethylenic polymer includes: (a) a functional group having at least one type of functional group selected from the group consisting of a hydroxyl group, a hydroxyl group, a carboxylate, a hydroxyl group, and an epoxy group; And (b) a fluorine-containing ethylenic monomer having no functional group. It is preferably a copolymer with at least one of the monomers.

The content of the component (a) is preferably 0.05 to 30 mol%. The type, shape, purpose, application, required adhesive strength, adhesive form, and adhesive method of the substrate to be bonded are described. Although it is appropriately selected depending on the difference between them, it is more preferably 0. 05 to 20 mol%, particularly preferably 0.1 to 10 mol%. When the content is less than 0.05 mol%, it is difficult to obtain sufficient adhesion to other base materials, and peeling due to chemical permeation or temperature change is caused. On the other hand, if the content exceeds 30 mol%, the heat resistance is reduced, and peeling, coloring, foaming, and elution are likely to occur due to poor adhesion, coloring and foaming at the time of processing at high temperatures, and decomposition during use at high temperatures.

As the functional group-containing fluorine-containing ethylenic polymer (a),

CX ^ CX ¹ -R _f ² -Y (1)

(Where X and X ¹ are the same or different and are each a hydrogen atom or a fluorine atom, Y is — CH ₂ OH, monoCOOH, carboxylate, carboxyester group or epoxy group, and A divalent fluorinated alkylene group having 1 to 40 carbon atoms, a divalent fluorinated oxyalkylene group having 1 to 40 carbon atoms, a fluorinated alkylene group containing a 1 to 40 carbon ether group, or 1 to 40 carbon atoms Represents a fluorine-containing oxyalkylene group containing 40 ether groups)

And at least one monomer represented by More specifically, CF ₂ = CF-R _f ³ _CH ₂ 〇H (2)

Wherein ^ is a divalent fluorine-containing alkylene group or a OR _{_f} ^⁴ (R _f ⁴ is a divalent fluorine-containing alkylene group or an ether having a carbon number of 1 to 40 1 to 40 carbon atoms from 1 to 40 carbon atoms A divalent fluorine-containing alkylene group containing a bond)],

CF ₂ = CFCF ₂ -OR _f ⁵ -CH ₂ OH (3)

[In the formula, one R _f ⁵ is a divalent fluorinated alkylene group having 1 to 39 carbon atoms or Represents a divalent fluorinated alkylene group having an ether bond having 1 to 39 carbon atoms],

CH ₂ = CFCF ₂ -R _f ⁶ -CH ₂ OH (4)

[Wherein one R _f ⁶ is a divalent fluorine-containing alkylene group having 1 to 39 carbon atoms, or an 〇_R _{_f} ^⁷ (R _f ⁷ is a divalent fluorine-containing alkylene group having 1 to 39 carbon atoms, or Or a divalent alkylene group containing an ether bond having 1 to 39 carbon atoms)], or

CH ₂ = CH- _f ⁸ -CH ₂ OH (5)

[Wherein, ^ represents a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms],

CX ^ CX ¹ — R _f ⁹ — COOY ¹ (6)

(X and X ¹ are the same or different and are each a hydrogen atom or a fluorine atom, Y ¹ is a hydrogen atom, NH ₄ or a metal atom selected from the group consisting of I, II, III, IVa and VIII, and R _f ⁹ is a carbon atom. Represents a divalent fluorinated alkylene group having 1 to 40 carbon atoms, a divalent fluorinated oxyalkylene group having 1 to 40 carbon atoms, or a divalent fluorinated alkylene group having 1 to 40 carbon atoms having an ether bond. At least one kind of monomer represented by the formula: More specifically, one COOY ¹ is preferably —COOH, one COONH ₄ , one COONa, -COOK, one COOL i, _COOZn, one COOAl, one COOMg, one COOCa, and the like.

Examples of the fluorine-containing ethylenic monomer having no functional group (b) include tetrafluoroethylene or tetrafluoroethylene of 85 to 99.7 mol%.

CF ₂ = CF-R _f ¹⁰ (7)

(Where R _f ^1Q is CF ₃ or OR ¹¹ (R ¹ is a perfluoroalkyl group having 1 to 5 carbon atoms)) And a mixed monomer of 0.3 to 15 mol%. When an epoxy resin is used, it is preferable that the sheet is subjected to a surface treatment such as a sodium etching, a plasma treatment, an excimer laser treatment, and a discharge treatment, and then the epoxy resin is applied.

The coating amounts of the fluorine-containing ethylenic polymer having a functional group and the adhesive are not particularly limited, but are preferably 0.004 to 0.04 g Zcm ² . If it is less than 0.004 g / cm ² , the adhesive strength tends to be insufficient. If it exceeds 0.04 g Z cm ² , the transmission loss tends to increase. Further, an adhesive in a film form may be applied to the sheet in advance. At this time, the thickness of the film is preferably in the range of 0.2 to 0.2 mm. If it is smaller than 0.02 mm, the adhesive strength tends to be insufficient. If it exceeds 0.2 mm, transmission loss tends to increase.

The form of the adhesive is not limited to a film, but may be used as a powder or a dispersion.

In addition, the surface treatment may be performed in the following manner from the viewpoint of adhesive strength: (a) discharge treatment in an inert gas atmosphere containing an organic compound having a functional group, (mouth) excimer laser irradiation, (8) plasma treatment, or ( 2) Chemical etching using metallic sodium is preferred.

The antenna cover of the present invention can be bonded to an antenna, a metal reflector, or the like with the adhesive.

An example of the antenna cover of the present invention is shown in FIGS.

In FIG. 1, a metal reflector 2 to which an antenna 3 is bonded is bonded to an antenna cover 1 via an adhesive 4. The entire metal reflector is protected by the antenna cover of the present invention. When a metal foil is bonded to the sheet, the sheet may be formed and then the metal foil may be bonded, or the sheet and the metal foil may be bonded and then heat-treated. In FIG. 2, the three sides surrounding the antenna 3 and the upper part are protected by the antenna cover 1. The other side is a metal reflector 2 to which the antenna 3 is joined. The antenna cover 1 and the metal reflector 2 are adhered by an adhesive 4.

In FIG. 3, the hemispherical metal reflector 2 to which the antenna 3 is joined and the conical antenna cover 1 are adhered by an adhesive 4.

In FIG. 4, the antenna 3 and the hemispherical metal reflector 2 joined to the antenna 3 are coated with the antenna cover 1.

Next, the present invention will be described more specifically based on examples, but the present invention is not limited thereto.

The physical properties measured in the examples of the present invention were measured by the following methods.

(Standard specific gravity)

It is measured by a water displacement method using a sample prepared according to ASTM D4895-89.

W _{1 –} W ₂ p _s : Sample density (gZcm ³ )

p _w : Water density (g / cm ³ )

W _x : Sample weight in air (g)

W ₂ : Sample weight in water (g)

(Dielectric constant and dissipation factor)

(Sheet preparation conditions)

The raw material containing polytetrafluoroethylene finer is compression molded into a cylindrical shape. A sheet with a thickness of 0.5 mm cut from this cylinder is circulated with hot air. Bake at 38 O for 5 minutes in an electric furnace. Then, it is allowed to cool to room temperature at a cooling rate of 60 ° C / hour to produce a sample sheet.

If the PTFE resin is an aqueous dispurgeon, it must be heated at 8 before compression molding to evaporate the water and form a powder. (t an (5 measurement methods)

Using a network analyzer (Hewlett-Packard Co., HP 8510C), the change in the resonance frequency and the Q value of the sheet prepared above was measured at 22 to 25 ° C with a cavity resonator, and measured at 12 GHz. tan (5 is calculated according to the following equation.

tan (5 = (1 / Qu) X {1+ (Ψ ₂ / Ψ ₁ ))-(Ρ ο / ω \ ν ₁ )

XtanX = (L / 2M) YcosY

Y = M k ₀ ² -k _r ² ^k 0 =

c

= 2rF _n k = 3.8317

D / 2

Q _r

Q "., = Ϊ́_ιο ^{(_ίίί / 20)}

Q =

F '-F jrr 1 _r 2 2 T 2 r 2 Sin '

Wi = —xs _r xe _ri xL rx X Un XJi XJn 1+

¹ 8 ^{7 υ υ}丄^υ [2Χ χ ₀ xJi χ JQ

P = P + P + P 3

1 (-cosX ヽ D then sin2Y \

= — X xR5x— χ χπχ 1 x

¹ 2 sinY 2 2Y

Where the symbols in the equation are as follows.

D: Cavity resonator diameter (mm)

M: One side length of cavity resonator (mm)

L: Sample length (mm)

c: Speed of light (mZ s)

Id: Attenuation (dB)

F 0: resonance frequency (H z)

F! : Upper frequency (H z) where attenuation from resonance point is 3 dB F ₂ : Lower frequency (H z) where attenuation from resonance point is 3 dB ε 0: Dielectric constant of vacuum (H / m)

ε _r : dielectric constant of sample

H. ： Vacuum permeability (HZm)

R s: Effective surface resistance (Ω) considering surface roughness of conductor cavity

J. : -0. 40 2 7 5 9

J! : 3. 8 3 1 7 1 Example 1

Dielectric constant at a standard specific gravity. 2. 216, 12 GHz is 2.12, the condition (1) is t an, (5 measured at 1. 1 0 X 1 0 one ⁴ of the PTFE fine powder one (TFE / HFP = 99 9970/0. 0030 (molar ratio), chain transfer agent: ethane) is compression-molded into a cylindrical shape by a compression molding machine, heated and baked in a hot-air circulation electric furnace at 380 ^ for 60 minutes, and the cooling rate is 1 ° C Then, the sheet was gradually cooled to 270 ° C./hour, and then a 2 mm-thick sheet was cut out from the cylinder cooled to room temperature to obtain an antenna cover (2 mm in thickness). was measured, 1. a IX 1 0 one ^4, specific gravity, 2. was 24.

Example 2

17% by weight of Isopar G (manufactured by Etsuso Chemical Co., Ltd.) as an extrusion aid was mixed with the same PTFE fine powder as in Example 1. The extruder was used to form a pipe with an outer diameter of 120 mm and an inner diameter of 116 mm. The pipe was flattened by a flat press at room temperature and dried at 100 ° C. for 10 minutes. Then, the extruder was heated at 250 ° C. for 10 minutes in a dryer to remove the extrusion aid, and a film having a thickness of 1.7 mm was obtained. The resulting film was pressed with a hot plate press at 360 ° C. at a pressure of 50 kgZcm ³ for 10 minutes. Then, it was gradually cooled to 270 ° C at a cooling rate of 1 ° C / hour and allowed to cool to room temperature to obtain an antenna cover (1.7 mm thick). tan (5 was measured, 0.5 is a ⁵ X 10- 5, specific gravity, 2. was 26.

Example 3

Standard specific gravity of 2.1 7, the condition (1) as measured by the tan <5 is 1. 9 X 1 0- ⁴ of the PTFE fine powder (Daikin Industries, Ltd., TFE homopolymer, trade name: Polyflon F 104), and the melt viscosity (380 ° C, 7 kg load, nozzle diameter 10 mm Φ) is 350,000 Voids PTFE Fine Powder I (manufactured by Daikin Industries, Ltd., TFE polymer, trade name: Lubron L-1 2) ) Were mixed in a room temperature air at a weight ratio of 8: 2, and compression-molded into a cylindrical shape by a compression molding machine. The molded product was fired and heated in a hot air circulation type electric furnace at 380 for 60 minutes, gradually cooled to 270 ° C. at a cooling rate of 1 ° C.Z, and allowed to cool to room temperature. A sheet (film) having a thickness of 2 mm was cut out from the cylinder. An antenna cover (2 mm thick) was obtained from the obtained film in the same manner as in Example 1. Measurement of the t an, [delta], is 1. 4X 10- ^4, specific gravity, 2. was 22.

Example 4

Standard specific gravity of 2. is 25, the condition (1) was measured at a t an δ is 1. 4Χ 10- ⁴ of the PTFE fine powder (Daikin Industries, Ltd., TF Ε-based polymer, trade name: LeBron L- 2 ) Was placed in an electric furnace and brought into contact with a fluorine radical source (fluorine gas) at 200 ° C under atmospheric pressure for 5 hours to obtain a fluorinated PTFE fine powder. A PTFE fine powder having a standard specific gravity of 2.17 (manufactured by Daikin Industries, Ltd., TFE homopolymer, trade name: BORIFLON F104) and the fluorinated PTFE fine powder in a weight ratio of 9: 1, They were mixed in room temperature air and compression-molded into a cylindrical shape using a compression molding machine. The molded product was heated and fired at 380 ° C. for 60 minutes in a hot-air circulation electric furnace, gradually cooled to 270 ° C. at a cooling rate of lZ hours, and allowed to cool to room temperature. A 1.5 mm-thick sheet (film) was cut out from the cylinder, and an antenna cover (1.5 mm in thickness) was obtained in the same manner as in Example 1. tan (5 were measured, 1. a 3 X 10_ ^4, specific gravity, 2. was 25. Example 5

An antenna cover (thickness 1) was prepared in the same manner as in Example 1 except that PTFE fine powder 1 (standardized specific gravity: 2.17, TFE homopolymer, manufactured by Daikin Industries, Ltd., trade name: Polyflon F104) was used. .5mm). Measurement of the ta eta [delta], 1. a 6 X 10_ ^4, specific gravity, 2.19 Met.

Example 6

Aqueous dispurgeon (manufactured by Daikin Industries, Ltd., trade name: D-2, solid content standard specific gravity: 2.22) was heated at 80 ° C to evaporate water to form a padder, and the conditions (1 ) in was 1. 7 X 10- ⁴ was measured tan <5. This aqueous dispurgeon is spray-coated on an antenna reflector, dried for 30 minutes, baked at 38 O for 30 minutes, gradually cooled to 27 at a cooling rate of 1 ° C / min, and allowed to cool to room temperature. An antenna reflector with an antenna cover (20 m thick) was obtained. When the ta η δ of the sheet was measured, it was 1.0 × 10-4, and the specific gravity was 2.26. However, since the antenna cover was difficult to peel off, the powder was used as a substitute for t an δ of a sheet produced by the following method. The powder obtained by evaporating the water is compression-molded into a cylindrical shape, a sheet having a thickness of 0.5 mm is cut out, and then calcined at 380 ° C for 5 minutes. The sheet was slowly cooled down to, and allowed to cool to room temperature to prepare a sheet. Industrial applicability

According to the present invention, by using it ta eta [delta] in 12GHz measured at specific conditions 2. 0 X 10- ⁴ or less is PTFE-based resin, it is possible to obtain an antenna cover excellent low dielectric loss . Also, since it repels water, stable antenna reception / transmission performance can be obtained.

Claims

Scope of word blue 1

1. An antenna cover made of a polytetrafluoroethylene resin sheet, wherein the polytetrafluoroethylene resin has a dielectric tangent calculated according to the following condition (1): 0 X 10 0—Polytetrafluorene of ⁴ or less

Two

Antenna cover made of styrene resin.

Condition 1)

(Sheet preparation conditions)

The polytetrafluoroethylene resin powder is compression-molded into a cylindrical shape. A 0.5 mm thick sheet cut from this cylinder is heated and fired at 380 ° C for 5 minutes in a hot air circulation type electric furnace. Then, let it cool to room temperature at a cooling rate of 60 ° C / hour to prepare a sample sheet.

(Dielectric loss tangent measurement method)

Using a network analyzer, change the resonance frequency and Q value of the sample sheet with a cavity resonator at 22 to 25 ° C, and calculate the dielectric loss tangent at 12 GHz according to the following equation.

t an δ = (1 / Qu) X {1 + (W ₂ / W _x )} one (P c / ωΨ,)

XtanX = (L / 2M) YcosY

L

Y = M k ₀ ² -k _r ² k 0 m = 2rdF

, 3.8317

k =

'· D / 2

Q

Q u „= i-i lo (-, ²⁰ )

Q = ^

L F-

P C = P 1 + P 2 + P 3

D. Then sinX \ (f, x2, ⁴ _{τ 2}

Pt = — xRsx ~ xLx rx 1- X Jr

2 2 ²ノ

Symbols in the formula are those of the following _t

D: Cavity resonator diameter (mm)

M: One side length of cavity resonator (mm)

L: Sample length (mm)

c: Speed of light (m / s)

I d: Attenuation (dB)

F 0: resonance frequency (H z) F _x : Upper frequency (Hz) at which the attenuation from the resonance point is 3 dB

ε. : Dielectric constant of vacuum (H / m)

ε _r : dielectric constant of sample

0: Magnetic permeability of vacuum (H / m)

：ー 0.402759

J! : 3.83171

2. The dielectric loss tangent, 1. claims is 50 X 10 one ⁴ below first Kouki

3. The antenna of claim 1, wherein the polytetrafluoroethylene resin has a standard specific gravity of 2.192 or more.

4. The antenna cover according to claim 1, wherein the specific gravity of the sheet is 2.192 or more.

5. The antenna cover according to claim 1, wherein the sheet is unfired or has a crystal conversion ratio of 90% or less.

6. The antenna cover according to claim 1, wherein a terminal group of the polytetrafluoroethylene resin is fluorinated.

7. The claim 1 wherein a metal foil is bonded to the sheet by heat fusion.

8. The antenna cover according to claim 7, wherein the sheet is subjected to a surface treatment and then heat-sealed.

9. The sheet and the metal foil are each formed of at least one resin adhesive selected from the group consisting of an epoxy resin, a phenol resin and a cyanate resin, and z or a hydroxyl group, a hydroxyl group, a carboxylate, At least one selected from the group consisting of a carboxyl ester group and an epoxy group 2. The antenna cover according to claim 1, wherein the antenna cover is bonded via a fluorine-containing ethylenic polymer having a kind of functional group.

10. The method according to claim 9, wherein the sheet is surface-treated and then bonded.

11. The surface treatment may be performed by (a) discharge treatment in an inert gas atmosphere containing an organic compound having a functional group, (mouth) excimer laser irradiation, (8) plasma treatment, or (2) metal sodium. 9. The antenna cover according to claim 8, which is a chemical etching process used.

12. The surface treatment may be performed by (a) discharge treatment in an inert gas atmosphere containing an organic compound having a functional group, (mouth) excimer laser irradiation, (8) plasma treatment, or (2) metal sodium. The antenna cover according to claim 10, wherein the antenna cover is a chemical etching process used.

13. (A) The dielectric loss tangent at 12 GHz measured under the condition (1) is 1.

5 X 1 is 0 _ ⁴ below, poly standard specific gravity of 2.1 at 9 more polytetra Furuoroechiren resin powder, and / or (B) the melt viscosity at 3 8 0 ° C is less than 1 0 ⁶ Boys An antenna cover in which a metal foil is adhered to at least one surface of a sheet made of a composition containing 10% by weight or more of a tetrafluoroethylene resin powder.

14. The antenna cover according to claim 13, wherein the composition contains a cyanate resin.

15. The antenna cover according to claim 13, wherein a terminal group of said polytetrafluoroethylene resin is fluorinated.

16. The antenna cover according to claim 13, wherein said metal foil is a stainless steel foil or an aluminum foil.

17. the sheet and the metal foil are at least one resin adhesive selected from the group consisting of an epoxy resin, a phenol resin, and a cyanate resin; and And z or a hydroxyl group, a carboxyl group, a carboxylate, a carboxyl ester group, and a fluorine-containing ethylenic polymer having at least one functional group selected from the group consisting of an epoxy group. An antenna cover according to item 13.

18. The antenna cover according to claim 1, wherein the antenna cover is obtained by bonding a metal foil after forming the sheet.

19. The antenna cover according to claim 13, which is obtained by forming the sheet and bonding a metal foil thereto.

20. The antenna cover according to claim 1, wherein the antenna cover is obtained by bonding the sheet and a metal foil and then performing a heat treatment.

21. The antenna cover according to claim 13, which is obtained by bonding the sheet and a metal foil and then performing a heat treatment.

22. Antenna cover made of sheet using polytetrafluoroethylene resin.