Ulllted States Patent [19]
`Brennan et al.
`
`USOO5844523A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,844,523
`Dec. 1, 1998
`
`[54] ELECTRICAL AND ELECTROMAGNETIC
`APPARATUSES USING LAMINATED
`STRUCTURES HAVING THERMOPLASTIC
`ELASTOMERIC AND CONDUCTIVE
`LAYERS
`
`FOREIGN PATENT DOCUMENTS
`
`525:2 ............................. .. H01Q 1/42
`1050462A 4/1991 Switzerland .
`WO 95/32528 11/1995 WIPO ............................ .. H01Q 9/04
`
`[75] Inventors: Joan V. Brennan, Woodbury; Scott T.
`G' k l St'll
`t
`' T'
`th S.
`sllggfaild 15:12:13; allllngf Damn
`’
`’
`'
`[73] Assignee: Minnesota Mining and
`Manufacturing Company, St Paul,
`Minn
`
`21 A 1. N .: 609 092
`[
`1
`pp
`0
`’
`[22]
`Filed:
`Feb. 29, 1996
`
`6
`
`9
`
`OTHER PUBLICATIONS
`Brydson, J ., “Relation of Stucture to Chemical Properties,”
`Plastic Materials, 5th ed., p. 100 (Mid—County Press, Lon
`don’ 1989)
`_
`_
`_
`Brochure, CoWperthWa1t, 1., “Properties of Thermoplastic
`Ole?ns (TPOs) as Compared With Thermoplastic Elas
`tomers (TPEs) Based on Ethylene Propylene Rubbers,” pp.
`1—8 Montell Incorporated.
`’
`Brochure, CoWperthWait, J ., “Reactor—made TPOs: A NeW
`Class of Materials Creating NeW Market Opportunites,” pp.
`1—12 Montell Incorporated.
`H01 den, G.’ “Elestomers, SynthetiC_Styrene_Styrene_Buta_
`[51] Int. Cl. ..................................................... .. I-I01Q 1/38
`diene Ruber,”Elasmmers) Synthetic (Thermoplastic),vol_ 9,
`[52] U.S. Cl. ................................. .. 343/700 MS, 343/846,
`174/138 A; 174/153 A pp 15_37'
`[58] Field Of Search ........................... .. 343/700 MS, 846,
`Ivan, G‘, “Elastomeric polyole?n Processing,” pp‘ 94_3_966~
`343/767’ 770’ 174/138 A’_149 R’ 148’
`Legge, N., “Thermoplastic Elastomers—The Future,” Elas
`153 A’ 152 A’ H01Q 1/38
`tomerics, pp. 19—24, (Oct. 1985).
`_
`PoZar et al., “Design Considerations for LoW Sidelobe
`References Clted
`Micostrip Arrays,” IEEE Trans. on Antennas and Propaga
`
`[56]
`
`3,349,164 10/1967 Wyatt ...................................... .. 174/73
`
`(Listcontinlle01 0n neXt Page)
`
`.. 260/33.6
`9/1969
`3,470,127
`4/1975 Snell et a1. ........................... .. 117/22 P
`3,876,454
`4,173,019 10/1979 Williams ........................ .. 343/700 MS
`
`_
`_
`_
`Primary Exammer?oanganh T~ Le
`Attorney. Agent. or Flrm—H- Sanders GWIH, Jr
`
`4,363,842 12/1982 Nelson . . . . . . . . . .
`
`4,666,742
`
`5/1987 Takakura et a1
`
`. . . . .. 428/36
`
`427/229
`
`[57]
`
`ABSTRACT
`
`1133552: ' ' ' ' ' ' ' ' ' '
`
`' ' ' ' "
`
`Electromagnetic and electrical apparatuses use a laminate
`
`6/1989 Tsao et a1”
`4:843:400
`478877089 12/1989 Shibata et a1_
`4,914,445
`4/1990 Shoemaker
`4,937,585
`6/1990 Shoemaker
`4,963,891 10/1990 Aoyagi et a1.
`4,975,329 12/1990 B9016 et al- -
`
`/700 MS
`343/7O0 MS
`343/700 MS
`_ 343/700 Ms
`343/700
`428/461
`
`structure having a thermoplastic elastomer With. variable
`dielectric loss as a dielectric layer. A conductive layer
`laminated to the thermoplastic elastomer alloW use for
`applications such as printed circuit boards and slot antennas.
`Additional conductive and dielectric layers still alloW use as
`a printed circuit board as Well as other antenna structures.
`
`5,070,340 12/1991 Diaz . . . . . . . . . . . . . .
`
`. . . . . . .. 343/767
`
`some embodiments of the apparatuses disclosed exhibit
`
`343/700 MS
`6/1992 Niayes ‘1; a1‘ '
`231243713
`...... .. 343/828
`,363,114 11/1994 S oe'rna er
`382/156
`5,440,651
`8/1995 Martin ......... ..
`..... .. 343/866
`5,526,006
`6/1996 Akahane et al. ..
`5,621,571
`4/1997 Bantli et a1. ................... .. 343/700 MS
`
`many desired properties, such as ?exibility, conformability
`and Weatherab?ity~
`
`24 Claims, 7 Drawing Sheets
`
`152
`
`148 %l
`
`146
`
`150
`
`142
`
`1 of 20
`
`FITBIT EXHIBIT 1010
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`

`
`5,844,523
`Page 2
`
`OTHER PUBLICATIONS
`
`PoZar et a1., “Microstrip Antennas—The Analysis and
`Design of Microstrip Antennas and Arrays,” IEEE Antennas
`and Propagation, pp. 1—7 (reprint, NeW York, 1995).
`Rader et a1., “Introduction TPEs,” Modern Plastics Mid—0c
`tober Encyclopedia Issue, pp. 122—132, (Oct.).
`
`Schaubert et a1., “Effect of Microstrip Antenna Substrate
`Thickness and Perrnittivity: Comparison of Theories With
`Experiment,” IEEE Trans. on Antennas and Propagation,
`v01. 37, No. 6, pp. 677—682 (Jun. 1989).
`Carver, K. et a1., “Microstrip Antenna Technology,” IEEE
`Transactions on Antennas and Propagation, vo1. AP—29,
`No. 1, pp. 2—24 (Jan. 1981).
`
`2 of 20
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`Dec. 1,1998
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`5,844,523
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`\ 104
`104
`1 r/psml r-Z /
`\11O
`Fig.1b
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`104
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`l/////////////////A
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`140
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`K152
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`142
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`/////////////////A\ Y//////////////// /
`WW
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`1 46
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`148
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`F i .4 g
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`270
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`9° 7
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`\ \l \ —30.00
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`SWR
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`MARKER1
`905 MHz
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`1
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`0.9050 GHz
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`Fig.6
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`I I
`
`I
`I
`I
`162’ i
`I
`I I
`i I
`
`I
`I
`I
`I
`
`I I I
`Flg. 7a
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`160 \ 164
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`162
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`172
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`Dec. 1,1998
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`5,844,523
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`194
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`196
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`198
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`186
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`192
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`k
`200 \
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`180
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`192 200
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`194
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`196 198
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`184
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`
`1
`ELECTRICAL AND ELECTROMAGNETIC
`APPARATUSES USING LAMINATED
`STRUCTURES HAVING THERMOPLASTIC
`ELASTOMERIC AND CONDUCTIVE
`LAYERS
`
`FIELD OF THE INVENTION
`
`The present invention generally relates to patterned lami
`nated structures having at least one thermoplastic elasto
`meric layer. More speci?cally, the present invention relates
`to laminated electrical or electromagnetic structures, such as
`antennas or printed circuit boards, utilizing such laminated
`structures.
`
`BACKGROUND OF THE INVENTION
`Many substrate materials With particular electrical prop
`erties for the mounting of electronic devices are Well knoWn
`in the art, and are used Widely in many different types of
`electronic devices. For example, laminates serve predomi
`nantly as substrates for printed circuits and the like and are
`conventionally made up of resin-impregnated sheets Which
`are cut into leaves or panels and superimposed into layers.
`The layers are placed under heat and pressure and joined to
`form a solid unit. The resulting laminates can be covered on
`one or both sides by laminating With a metallic material, or
`can be provided With metal layers by Well-knoWn deposition
`methods.
`AWide range of polymeric materials are used as substrate
`or laminate elements in electronics applications, and a great
`deal of information regarding their properties is knoWn. See,
`for example, Relation of Structure to Electrical Properties
`article (need cite). These polymeric materials are electrical
`insulators, i.e. they may Withstand a potential difference
`betWeen different points of a given piece of material With the
`passage of only a small electric current and a loW dissipation
`energy. In certain applications the in?uence of a polymeric
`material on the capacitance of a condenser, knoWn as its
`dielectric constant, becomes particularly important. The
`dielectric constant of a material, er, is de?ned as the ratio of
`the condenser capacity, using the given material as a
`dielectric, to the capacity of the same condenser Without the
`dielectric.
`When a polymeric material is placed in an electric ?eld,
`its dielectric constant depends on both electronic polariZa
`tion effects Within its molecular structure and on dipole
`polariZation effects With neighboring molecules. Therefore,
`a symmetrical or non-polar molecule, Which experiences
`only electronic polariZation effects, Will have a loWer dielec
`tric constant than a polar molecule, Which is under the
`in?uence of both electronic and dipole polariZation effects.
`Since dipole polariZation involves movement of part or even
`the Whole of the molecule, the dielectric constant of polar
`molecules Will depend on the “internal viscosity”, i.e. the out
`of step motions of the dipoles, in the material.
`This internal viscosity also produces dielectric poWer
`losses at certain frequencies When the dielectric material is
`placed in an alternating electric ?eld. These losses are
`measured as the fraction of energy absorbed per cycle by the
`dielectric from the electric ?eld. The poWer factor and the
`dissipation factor arise by considering the delay betWeen the
`changes in the ?eld and the change in polariZation, Which in
`turn leads to a current in a condenser leading the voltage
`across it When a dielectric is present. The angle of lead is
`referred to as the phase angle 0, While the term 90-0 is
`knoWn as the loss angle, 6. The dissipation factor, or loss
`tangent, for a particular material is tan 6.
`
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`5,844,523
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`2
`An important ?rst step in the design of any electronic
`device Which Will absorb or transmit energy is the selection
`of an appropriate dielectric substrate material. There is no
`one ideal substrate, and the material selected depends on the
`properties required for the intended application. The most
`important properties of a particular material are its dielectric
`constant (6,) and loss tangent (tan 6) in the selected tem
`perature and frequency range over Which the device Will
`operate. Generally, a loW loss tangent suggests excellent
`energy transmittance, and such materials are useful in the
`design of electronic devices such as antennas. Conversely, a
`microWave or radar absorber may require a dielectric mate
`rial With a much higher loss tangent. LoW frequency, loW
`loss applications, such as tapered slot antennas, require a
`material With high dielectric constant, While patch antennas
`require a loW loss, loW dielectric constant material. The
`bandWidth and ef?ciency of the microstrip patch antenna
`may also increased by selecting a material With a loWer
`dielectric constant.
`HoWever, dielectric properties of a polymeric material are
`not the only consideration in designing a substrate for an
`electronic device. Processing considerations are also
`important, such as dimensional stability, resistance to
`temperature, humidity and aging, resistance to chemicals,
`tensile and structural strengths, ?exibility, machinability,
`impact resistance, strain relief, conformability, bondability
`and amenability to cladding.
`The dielectric properties of the substrate material, par
`ticularly loW loss tangent, are important in a microstrip
`antenna. The structure of the microstrip antenna, including
`its radiator and transmission line feed, is a Well knoWn (see,
`for example, Bahl et al., MicrostripAntennas, Artech House,
`1980; PoZar and Shaubert, eds., Microstrip Antennas-T he
`Analysis and Design of Microstrip Antennas and Anrays,
`IEEE Press 1995.). In its simplest form, the microstrip patch
`antenna (MPA) may be a shaped metal conductor fed at one
`of its edges by an integral microstrip transmission line. This
`shaped transmission line/radiator structure is typically sup
`ported a short distance above a ground plane by a dielectric
`sheet or layer having a thickness substantially less than
`one-fourth Wavelength at the intended operating frequency
`of the antenna (generally on the order of one-tenth Wave
`length or less). The resonance dimension of the shaped
`radiator patch is typically selected to be one-half
`Wavelength, thus providing a pair of radiating slots betWeen
`opposed edges (e.g. transverse to the feedline) and the
`underlying ground plane. The transverse or non-radiant
`dimension is typically selected, in part, as a function of the
`desired radiated poWer. If the non-resonant dimension is on
`the order of one Wavelength or more, multiple feed points
`may be provided by, for example, a corporate feed structure
`netWork. Microstrip patch antennas are described in numer
`ous patents and publications, such as, for example, US. Pat.
`No. 4,887,089 to Shibata, et al., US. Pat. No. 5,055,854 to
`Gustafsson, US. Pat. No. 4,963,891 to Aoyagi et al., US.
`Pat. No. 5,070,340 to DiaZ, and Tarot, et al., New Technology
`to Realize Printed Radiating Elements, MicroWave and
`Optical Technology Letters, vol. 9, no. 1, May 1995.
`In addition to the MPA, other types of microstrip antennas
`include microstrip traveling Wave antennas, Which consist of
`chain-shaped periodic conductors on a substrate backed by
`a ground plane. Microstrip slot antennas comprise a slot cut
`in the ground plane perpendicular to the strip conductor of
`a microstrip feed line.
`Desired antenna characteristics may be obtained With a
`single microstrip element as described above, but charac
`teristics such as high gain, beam scanning, or steering
`
`10 of 20
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`

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`5,844,523
`
`3
`capability may be obtained by combining discrete radiators
`into arrays. Microstrip antenna arrays are described in many
`references, including, for example, US. Pat. No. 4,173,019
`to Williams, and US. Pat. Nos. 4,914,445 and 4,937,585 to
`Shoemaker, and references cited therein.
`A Wide variety of materials are available for use as
`dielectrics for microstrip antennas (See, for example, Bahl,
`et al., Microstrip Antennas, pages 317—327 and references
`cited therein; Carver and Mnk, Microstrip Antenna
`Technology, IEEE Trans. Antennas Propaga, vol. AP-29, no.
`1, page 2—24, Jan. 1981.). Typical substrate materials may
`include polytetra?uoroethylene (PTFE), crystalline thermo
`plastics such as polystyrene, polyethylene and
`polypropylene, silicones, polyphenylene oxide (PPO),
`polyester, polyimides, mica, ?berglass, alumina and beryllia.
`FolloWing selection of a dielectric material for a particular
`application, conventional microstrip antenna structures may
`be conveniently formed by photochemical etching processes
`similar to those used in the manufacture of printed circuit
`boards. A microstrip antenna assembly is formed from a
`laminate, Which in its simplest form is a dielectric sheet
`material With a thin layer of conductive metal, such as
`copper, adhered to its opposed sides. One conductive layer
`of the laminate normally forms the ground plane, and
`conductive material may be removed from the opposed layer
`by chemical etching or similar processes to form the very
`thin microstrip radiator and interconnected transmission line
`structure as shaped conductive patches on the dielectric
`sheet. Examples of laminates for microstrip antennas are
`described in US. Pat. No. 4,914,445 to Shoemaker, US. Pat.
`No. 4,937,585 to Shoemaker and US. Pat. No. 4,833,005 to
`Klaar et al.
`As reported in US. Pat. No. 4,816,836 to LaleZari, an
`effective microstrip antenna laminate structure should be
`conformable and mountable to a curved surface. A micros
`trip antenna is often mounted on an external, curved surface
`of airplanes, missiles, artillery shells and the like, and
`mounting to a curved surface provides a loW pro?le and
`reduces turbulence. Generally, the mounting surface has a
`convex shape, and the antenna assembly is simply deformed
`and adhered directly on the curved surface. As the antenna
`is bent around a small radius curve, the outer convex surface
`is placed under substantial tension and must stretch, Which
`causes a non-?exible material to crack. The crack ultimately
`results in deformation and tearing of the copper antenna
`elements, Which pulls the antenna apart. This cracking is a
`particular problem With rigid, crystalline polymeric materi
`als and foams.
`The LaleZari reference describes an antenna With a multi
`layer PTFE and ?berglass substrate and a method for mount
`ing the antenna on a curved surface. The antenna structure
`described in this patent comprises a relatively thin dielectric
`substrate With antenna elements on a surface thereof, and a
`second relatively thick dielectric substrate. As shoWn in FIG.
`2 of the LaleZari patent, to adhere the antenna structure to the
`curved surface, the thick dielectric substrate material 41b
`must initially be adhered to the curved surface as a spacer.
`The thinner ?rst dielectric substrate 41a is then adhered to
`the spacer 41b. The method described in LaleZari illustrates
`that PTFE dielectric substrates lack the conformability
`required in many applications. In addition, the multi-layer
`structure is expensive and dif?cult to manufacture.
`Another desirable characteristic of an antenna dielectric
`material is Weatherability. As noted above, microstrip anten
`nas are typically mounted on external surfaces Which are
`exposed to severe Weather conditions, and antenna proper
`
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`4
`ties may be signi?cantly affected if the dielectric layer
`absorbs moisture or has poor thermal stability over its
`operating temperature range. Liquid Water has a very high
`dielectric constant, and moisture absorption by foamed
`dielectric substrate materials may signi?cantly alter antenna
`tune and ultimately result in substrate deformation. Conven
`tional foamed materials readily absorb moisture and have
`extremely poor impact resistance, Which limits their desir
`ability as antenna substrates or laminate layers.
`If Weatherability and toughness are a concern, it is Well
`knoWn in the art to select PTFE as a dielectric substrate
`material for antenna applications. The PTFE may also be
`reinforced With ceramics or glass ?bers, or formed into a
`cloth laminate. As noted above, these materials are not
`suf?ciently conformable for some applications. PTFE is also
`dif?cult to extrude, and is not compatible With many con
`ventional adhesives and antenna materials. In addition, a
`signi?cant disadvantage is PTFE’s high manufacturing cost.
`There is a need for a tunable dielectric substrate material
`Which may be manufactured inexpensively and easily in a
`Wide variety of laminate con?gurations Without sacri?ce of
`critical performance properties. At present no loW-cost
`dielectric substrate material is commercially available Which
`provides the desired combination of properties for electronic
`device design, such as variable er and tan 6, Weatherability
`and toughness, conformability, and processability.
`
`SUMMARY OF THE INVENTION
`
`The present invention describes electrical and electro
`magnetic apparatuses that use a ?exible polymeric substrate
`material laminated or printed With a conductive layer. In one
`embodiment, the polymeric substrate material is a loW
`dielectric loss thermoplastic elastomer substrate or laminate
`material having a loss tangent less than about 0.005. The loW
`loss thermoplastic elastomer of the invention comprises a
`thermoplastic polymeric component comprising polar or
`non-polar monomeric units, or mixtures thereof, and an
`elastomeric polymeric component comprising polar or non
`polar monomeric units, and speci?cally excluding mixtures
`thereof, such that the resultant loss tangent of the thermo
`plastic elastomer is less than about 0.003. The thermoplastic
`elastomers may be block copolymers, graft copolymers, or
`multi-phase dispersions, and multi-phase dispersions having
`an ole?nic thermoplastic component and an elastomeric
`component of an ethylene-propylene rubber are preferred. A
`thermoplastic elastomer With a thermoplastic component
`comprising crystalline polypropylene and an elastomeric
`component comprising ethylene-propylene-diene monomer
`(EPDM) are particularly preferred. The dielectric materials
`of the ?rst embodiment are particularly preferred for use in
`electronic devices such as microstrip antennas.
`The dielectric material may also be a high dielectric loss
`thermoplastic elastomer substrate or laminate material hav
`ing a loss tangent greater than about 0.005 and up to about
`0.200. The thermoplastic elastomer of this embodiment of
`the invention comprises a thermoplastic polymeric compo
`nent comprising polar or non-polar monomeric units, or
`mixtures thereof, and an elastomeric polymeric component
`comprising polar or non-polar monomeric units, or mixtures
`thereof, such that the resultant loss tangent of the thermo
`plastic elastomer is greater than about 0.005 and up to about
`0.200.
`The thermoplastic elastomer substrate material of the
`invention is compatible With a Wide variety of ?llers. A
`suf?cient amount of a ?ller may be added to the thermo
`plastic elastomer substrate material to provide a predeter
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`11 of 20
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`mined dielectric constant over a broad range of about 1 to
`about 50, preferably about 2 to about 35. Particularly good
`loW-loss dielectric performance has been observed When the
`?ller material is a doped or undoped “capacitor grade”
`ceramic, such as barium titanate or lead oxide. The vari
`ability of the dielectric constant of the thermoplastic elas
`tomer material alloWs optimiZation of electrical or electro
`magnetic properties of printed circuit boards or antennas.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`The present invention Will be more fully described With
`reference to the accompanying draWings Wherein like ref
`erence numerals identify corresponding components, and:
`FIGS. 1a and 1b shoW a perspective vieW and a side
`cross-sectional vieW of a printed circuit board of the present
`invention;
`FIGS. 2a and 2b shoW an exploded vieW and a side
`cross-sectional vieW of a probe-fed microstrip patch antenna
`of the present invention;
`FIGS. 3a and 3b shoW a side cross-sectional vieW and an
`exploded vieW of an aperture coupled microstrip patch
`antenna of the present invention;
`FIGS. 4 and 5 shoW co-polariZed E-plane and H-plane
`antenna radiation patterns at 905 MHZ for the aperture
`coupled microstrip antenna shoWn in FIG. 3;
`FIGS. 6 shoWs the bandWidth of the aperture coupled
`microstrip antenna shoWn in FIG. 3a;
`FIGS. 7a and 7b shoW a side cross-sectional vieW and an
`exploded vieW of a slot antenna of the present invention;
`FIG. 8 shoWs an exploded vieW of an electronic license
`plate of the present invention; and
`FIG. 9 shoWs an exploded vieW of an electronic sign of
`the present invention.
`
`DETAILED DESCRIPTION OF A PREFERRED
`EMBODIMENT
`
`The substrate material of the present invention is a
`polymeric material comprising a thermoplastic elastomer.
`“Thermoplastic elastomers”, as used herein, refers to a class
`of polymeric substances Which combine the processability
`(When molten) of thermoplastic materials With the functional
`performance and properties of conventional thermosetting
`rubbers (When in their non-molten state).
`The loW loss thermoplastic elastomers of the invention
`may comprise any thermoplastic polymeric component and
`any elastomeric polymeric component Which provides a
`predetermined dielectric constant and resultant loss tangent
`(tan 6) of less than about 0.005, preferably less than about
`0.003. The loW loss thermoplastic elastomer of the invention
`comprises a thermoplastic polymeric component comprising
`polar or non-polar monomeric units, or mixtures thereof, and
`an elastomeric polymeric component comprising polar or
`non-polar monomeric units, and speci?cally excluding mix
`tures thereof, such that the resultant loss tangent of the
`thermoplastic elastomer is less than about 0.005, preferably
`less than about 0.003.
`As explained in the Kirk-Othmer Encyclopedia of Chemi
`cal Technology, 4th ed., vol. 9 at 15, thermoplastic elas
`tomers are typically divided into tWo principal classes: (a)
`block or graft copolymers; and (b) multi-phase dispersions.
`In the block or graft thermoplastic elastomers, the hard
`and elastomeric phases are chemically bonded by block or
`graft polymeriZation, and have the structure A-B-A or (A-B)
`n, Where A is a hard or thermoplastic phase and B is a soft
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`or elastomeric phase. For the purpose of the present
`invention, A-B-A structures are preferred for their superior
`physical properties. In block/graft thermoplastic elastomers
`the hard polymer end segments form separate physical
`regions, referred to as domains, dispersed in a continuous
`elastomer phase. Most of the polymer molecules have hard
`segments Which act as physical crosslinks at room tempera
`ture and tie the elastomer chains together in a three dimen
`sional netWork. When the material is heated or dissolved in
`solvents, the domains lose their strength, and the polymer
`may ?oW. Upon cooling or solvent evaporation, the domains
`harden and the three dimensional netWork retains its physi
`cal integrity.
`In the loW loss embodiment of the present invention,
`thermoplastic polymeric component A may comprise any
`polar or non-polar monomeric unit, or mixtures thereof, and
`elastomeric polymeric component B may comprise any
`polar or non-polar monomeric unit, including mixtures and
`copolymers thereof, such that the bonded structure thereof
`has a resultant loss tangent of less than about 0.005, pref
`erably less than about 0.003.
`As noted in the above discussion, polymers With loW
`dielectric loss typically have non-polar or substantially
`non-polar substituents, and thermoplastic elastomers With
`thermoplastic and elastomeric polymeric components com
`prised of non-polar monomeric units are preferred for use in
`the present invention. The term “non-polar” as used herein
`refers to monomeric units that are free from dipoles or in
`Which the dipoles are substantially vectorially balanced. In
`these polymeric materials the dielectric properties are prin
`cipally a result of electronic polariZation effects.
`To provide a loW-loss dielectric material in the present
`invention the thermoplastic polymeric component A may be
`comprised of the folloWing polar or non-polar monomeric
`units, for example: styrene, ot-methylstyrene, ole?ns, halo
`genated ole?ns, sulfones, urethanes, esters, amides,
`carbonates, and imides, acrylonitrile, and co-polymers and
`mixtures thereof. Non-polar monomeric units such as, for
`example, styrene and ot-methylstyrene, and ole?ns such as
`propylene and ethylene, and copolymers and mixtures
`thereof, are preferred. The thermoplastic polymeric compo
`nent is preferably selected from polystyrene, poly(ot
`methylstyrene), and polyole?ns. Polyole?ns are preferred,
`and polypropylene and polyethylene, and copolymers of
`propylene and ethylene, are particularly preferred.
`The elastomeric polymeric component B in the loW-loss
`dielectric material of the invention may comprise any of the
`folloWing polar monomeric units, for example: esters,
`ethers, and copolymers and mixtures thereof. The elasto
`meric component B may comprise any of the folloWing
`non-polar monomeric units, for example: butadiene,
`isoprene, ole?ns such as ethylene-co-butylene, siloxanes,
`and isobutylene, and mixtures and copolymers thereof.
`Mixtures and copolymers of polar and non-polar monomeric
`units are not contemplated in the elastomeric component of
`the loW-loss thermoplastic elastomers of the invention.
`Non-polar monomeric units such as butadiene, isoprene
`ole?ns, siloxanes and mixtures and copolymers thereof are
`preferred, and the elastomeric component B is preferably
`selected from polybutadiene, polyisoprene, poly(ethylene
`co-butylene), poly(ethylene-co-propylene),
`polydimethylsiloxane, polyisobutylene, poly(ethylene-co
`butylene), and poly(ethylene-co-propylene).
`For example, styrenic block copolymeric thermoplastic
`elastomers Which may be useful in the present invention
`include linear and/or branched materials having a polybuta
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`diene or polyisoprene elastomeric segment available from
`Union Carbide Chemicals and Plastics Company, Inc.,
`Danbury, Conn., under the trade names Kraton D and
`Cari?ex, and from Philips Petroleum, Bartlesville, Okla.
`under the trade name Solprene. Linear styreneic block
`thermoplastic elastomers having a poly(ethylene-co
`butylene) (EB) and a poly(ethylene-co-propylene) (EP) elas
`tomeric segment Which may be useful in the present inven
`tion include EB/EP materials available from Union Carbide
`Chemicals and Plastics Company, Inc. under the trade name
`Kraton G, EB materials available from Union Carbide
`Chemicals and Plastics Company, Inc. under the trade name
`Elexar, polybutadiene or EB materials available from Great
`Lakes Terminal and Transport Corp. under the trade name
`Dyna?ex, EB materials available under the trade name
`Tekron from Teknor Apex, and EB materials With silicone
`oils available under the trade name C-Flex from Concept.
`Other useful copolymeriZed thermoplastic elastomers
`include materials available under the trade name Engage
`from DoW, Midland, Mich., and Exact from Exxon,
`Houston, Tex.
`The block/graft copolymer thermoplastic elastomers
`Which may be used in the present invention may be synthe
`siZed by any sequential polymeriZation and step groWth
`process as Well knoWn in the art. See, for example, Kirk
`Othmer Encyclopedia of Chemical Technology, 4th ed., vol.
`9 at 21—25; Handbook ofPolyole?ns. Vasilie, Seymour, eds.
`Decker, NY, 1993, pages 943—966.
`In the second general class of thermoplastic elastomers,
`multi-phase materials, at least one phase comprises a mate
`rial that is hard at room temperature, but becomes ?uid upon
`heating, and another phase comprises a softer material that
`is rubber-like at room temperature. The multi-phase ther
`moplastic elastomers typically consist of a thermoplastic
`polymeric component and more rubber-like elastomeric
`polymeric component. The tWo components normally form
`interdispersed multiphase systems, although in some cases a
`very ?nely dispersed “single phase” system is formed if the
`rubber-like phase is crosslinked during high shear mixing.
`This crosslinking procedure, referred to as “dynamic vulca
`nization” is described in, for example, US. Pat. No. 3,037,
`954 to Gessler.
`In the loW loss multi-phase structures of the present
`invention, the thermoplastic polymeric component prefer
`ably comprises any polar or non-polar monomeric unit
`normally regarded as a thermoplastic, and mixtures and
`co-polymers thereof. The elastomeric component preferably
`comprises any polar or non-polar monomeric unit normally
`regarded as elastomeric, speci?cally excluding mixtures
`thereof, such that the multi-phase dispersion has a resultant
`loss tangent of less than about 0.005, preferably less than
`about 0.003.
`The thermoplastic component of the loW-loss multi-phase
`thermoplastic elastomers of the invention may be comprised
`of the folloWing polar and non-polar monomeric units:
`ole?ns, such as propylene and ethylene, vinyls and mixtures
`and co-polymers thereof. For the purpose of the present
`invention, the thermoplastic polymeric component is pref
`erably selected from non-polar monomeric units, and
`polyole?ns, particularly polypropylene and polyethylene,
`and copolymers With ethylene and propylene monomeric
`units, are preferred. Isotactic polypropylene is particularly
`preferred for use as the thermoplastic polymeric component.
`The elastomeric polymeric component of the loW-loss
`multi-phase thermoplastic elastomers of the invention may
`be comprised of crosslinked or uncrosslinked polar rubbers
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`such as nitrile rubber, or crosslinked or uncrosslinked non
`polar rubbers such as butyl rubber, natural rubber, ethylene
`propylene rubber (EPR), ethylene-propylene diene rubber
`(EPDM) and silicone rubber. Crosslinked or uncrosslinked
`non-polar rubbers are preferred, and EPR and EPDM are
`particularly preferred. The elastomeric rubber component
`may be uncrosslinked (green), or may be partially or fully
`crosslinked using typical crosslinking agents (eg phenolics
`and peroxides) during mixing or as part of the dynamic
`vulcaniZation process.
`Examples of multi-phase thermoplastic elastomers having
`a crystalline polypropylene thermoplastic polymeric com
`ponent and EPR or EPDM elastomeric polymeric compo
`nent Which are preferred for use in the loW-loss dielectric
`materials of the present invention include blends available
`under the tradenames TPR from Advanced Elastomer
`Systems, Ren-Flex from Dexter, Polytrope from Schulman,
`Telcar from Teknor Apex, Ferro?ex from Ferro, WRD-7-507
`from Union Carbide Chemicals and Plastics Company, Inc.,
`and HiFax from Montell USA, Wilmington, Del., and the
`like. Dynamically vulcaniZed blends With a crystalline
`polypropylene t