OPTICAL WAVELENGTH CONVERSION COMPOSITE MATERIAL, RELATED MANUFACTURING METHOD AND RELATED OPTICAL WAVELENGTH CONVERSION COMPOSITE STRUCTURE

Abstract

An optical wavelength conversion composite material is provided and includes a first wavelength conversion material and an inorganic covering layer. The first wavelength conversion material is selected from the group consisting of a first quantum dot, a first phosphor, and a combination thereof. The inorganic covering layer covers the first wavelength conversion material, and the inorganic covering layer includes SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4−z, wherein x is from 0.1 to 0.4, y is from 0.5 to 0.8, and z is from 0.01 to 3.99. The optical wavelength conversion composite material has improved luminous efficiency and is stable. Besides, a related manufacturing method and a related optical wavelength conversion composite structure are provided.

Claims

1. An optical wavelength conversion composite material comprising: a first wavelength conversion material selected from the group consisting of a first quantum dot, a first phosphor, and a combination thereof; and an inorganic covering layer covering the first wavelength conversion material, and the inorganic covering layer comprising SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4−z, wherein x is from 0.1 to 0.4, y is from 0.5 to 0.8, and z is from 0.01 to 3.99.

2. The optical wavelength conversion composite material of claim 1, further comprising a silicone polymer layer covering the inorganic covering layer, the silicone polymer layer comprising a second wavelength conversion material dispersed evenly, the second wavelength conversion material being selected from the group consisting of a second quantum dot, a second phosphor, and a combination thereof, and the second wavelength conversion material being identical to or different from the first wavelength conversion composite material.

3. The optical wavelength conversion composite material of claim 2, wherein the silicone polymer layer is made of polysiloxane or polysilazane.

4. The optical wavelength conversion composite material of claim 2, wherein the first quantum dot or the second quantum dot is an all-inorganic perovskite quantum dot selected from the group consisting of CsPbCl.sub.3 exhibiting blue emission, CsPbBr.sub.3 exhibiting green emission, CsPbI.sub.3exhibiting red emission, and combinations thereof.

5. The optical wavelength conversion composite material of claim 2, wherein the first phosphor or the second phosphor is a fluoride phosphor selected from the group consisting of fluosilicate (K.sub.2SiF.sub.6:Mn.sup.4+, KSF), fluotitanate (K.sub.2TiF.sub.6:Mn.sup.4+, KTF), fluogermanate (K.sub.2GeF.sub.6:Mn.sup.4+, KGF), and combinations thereof.

6. The optical wavelength conversion composite material of claim 1, wherein the first quantum dot or the second quantum dot is an all-inorganic perovskite quantum dot selected from the group consisting of CsPbCl.sub.3 exhibiting blue emission, CsPbBr.sub.3 exhibiting green emission, CsPbI.sub.3 exhibiting red emission, and combinations thereof.

7. The optical wavelength conversion composite material of claim 1, wherein the first phosphor or the second phosphor is a fluoride phosphor selected from the group consisting of fluosilicate (K.sub.2SiF.sub.6:Mn.sup.4+, KSF), fluotitanate (K.sub.2TiF.sub.6:Mn.sup.4+, KTF), fluogermanate (K.sub.2GeF.sub.6:Mn.sup.4+, KGF), and combinations thereof.

8. A manufacturing method of an optical wavelength conversion composite material comprising: a mixing step comprising: mixing a first wavelength conversion material and an inorganic oxide to form a light emitting composite mixture, wherein the inorganic oxide comprises SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4−z, and x is from 0.1 to 0.4, y is from 0.5 to 0.8, z is from 0.01 to 3.99; and a miniaturization step comprising: micronizing the light emitting composite mixture by spray drying method to obtain the optical wavelength conversion composite material.

9. The manufacturing method of claim 8, further comprising: a silane treatment step comprising: mixing the light emitting composite mixture, a polysilane compound and a second wavelength conversion material, so as to generate a silane treated light emitting composite mixture.

10. The manufacturing method of claim 8, wherein a precursor of the inorganic oxide is selected from the group consisting of tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), 3-Aminopropyltriethoxysilane (APTES), titanium isopropoxide (TTIP), tetrabutyl orthotitanate (TBOT), and combinations thereof.

11. An optical wavelength conversion composite structure comprising: a first base plate; an optical wavelength conversion composite material layer disposed on the first base plate, the optical wavelength conversion composite material layer comprising an optical wavelength conversion composite material, the optical wavelength conversion composite material comprising: a first wavelength conversion material selected from the group consisting of a first quantum dot, a first phosphor, and a combination thereof; and an inorganic covering layer covering the first wavelength conversion material, and the inorganic covering layer comprising SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4−z, wherein x is from 0.1 to 0.4, y is from 0.5 to 0.8, and z is from 0.01 to 3.99; and a second base plate disposed on the optical wavelength conversion composite material layer, so that the optical wavelength conversion composite material layer is clamped by the first base plate and the second base plate.

12. The optical wavelength conversion composite structure of claim 11, wherein the optical wavelength conversion composite material further comprises a silicone polymer layer covering the inorganic covering layer, the silicone polymer layer comprises a second wavelength conversion material dispersed evenly, the second wavelength conversion material is selected from the group consisting of a second quantum dot, a second phosphor, and a combination thereof, and the second wavelength conversion material is identical to or different from the first wavelength conversion composite material.

13. The optical wavelength conversion composite structure of claim 12, wherein the silicone polymer layer is made of polysiloxane or polysilazane.

14. The optical wavelength conversion composite structure of claim 12, wherein the first quantum dot or the second quantum dot is an all-inorganic perovskite quantum dot selected from the group consisting of CsPbCl.sub.3 exhibiting blue emission, CsPbBr.sub.3 exhibiting green emission, CsPbI.sub.3 exhibiting red emission, and combinations thereof.

15. The optical wavelength conversion composite structure of claim 12, wherein the first phosphor or the second phosphor is a fluoride phosphor selected from the group consisting of fluosilicate (K.sub.2SiF.sub.6:Mn.sup.4+, KSF), fluotitanate (K.sub.2TiF.sub.6:Mn.sup.4+, KTF), fluogermanate (K.sub.2GeF.sub.6:Mn.sup.4+, KGF), and combinations thereof.

16. The optical wavelength conversion composite structure of claim 11, wherein the first quantum dot or the second quantum dot is an all-inorganic perovskite quantum dot selected from the group consisting of CsPbCl.sub.3 exhibiting blue emission, CsPbBr.sub.3 exhibiting green emission, CsPbI.sub.3 exhibiting red emission, and combinations thereof.

17. The optical wavelength conversion composite structure of claim 11, wherein the first phosphor or the second phosphor is a fluoride phosphor selected from the group consisting of fluosilicate (K.sub.2SiF.sub.6:Mn.sup.4+, KSF), fluotitanate (K.sub.2TiF.sub.6:Mn.sup.4+, KTF), fluogermanate (K.sub.2GeF.sub.6:Mn.sup.4+, KGF), and combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a diagram of an optical wavelength conversion composite material according to an embodiment of the present invention.

[0024] FIG. 2 is a diagram of an optical wavelength conversion composite material according to another embodiment of the present invention.

[0025] FIG. 3 is a flow chart of a manufacturing method of an optical wavelength conversion composite material according to an embodiment of the present invention.

[0026] FIG. 4 is a flow chart of a manufacturing method of an optical wavelength conversion composite material according to another embodiment of the present invention.

[0027] FIG. 5 is a diagram of an optical wavelength conversion composite structure according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0028] In order to illustrate technical specifications and features as well as achieved purposes and effects of the present invention, relevant embodiments and figures are described as follows. The drawings and descriptions will be regarded as illustrative in nature and not as restrictive. Also, the term “or” is intended to include any one or a combination of more than one of the associated listed items.

[0029] Please refer to FIG. 1. FIG. 1 is a diagram of an optical wavelength conversion composite material P according to an embodiment of the present invention. As shown in FIG. 1, the optical wavelength conversion composite material P includes a first wavelength conversion material 11 and an inorganic covering layer 12 covering the first wavelength conversion material 11.

[0030] Please refer to FIG. 2. FIG. 2 is a diagram of an optical wavelength conversion composite material P′ according to another embodiment of the present invention. As shown in FIG. 2, the optical wavelength conversion composite material P′ includes the first wavelength conversion material 11 and the inorganic covering layer 12 covering the first wavelength conversion material 11, and the optical wavelength conversion composite material P′ further includes a silicone polymer layer 13 covering the inorganic covering layer 12. The silicone polymer layer 13 includes at least one second wavelength conversion material 14 dispersed evenly, and the second wavelength conversion material 14 can be identical to or different from the first wavelength conversion composite material 11.

[0031] Specifically, the first wavelength conversion composite material 11 is selected from the group consisting of a first quantum dot, a first phosphor, and a combination thereof, and the second wavelength conversion composite material 14 is selected from the group consisting of a second quantum dot, a second phosphor, and a combination thereof. By using multiples quantum dots and/or phosphors with different emission wavelengths, emission spectrum of a light emitting device and color gamut of a display device can be improved effectively. Also, color purity and color authenticity of the display device can be improved effectively, and the NTSC color space can be greatly improved.

[0032] More specifically, the first quantum dot or the second quantum dot can be selected from the group consisting of a group II-VI quantum dot, a group III-V quantum dot, and a perovskite quantum dot, and the first quantum dot or the second quantum dot can be a red quantum dot, a green quantum dot or a blue quantum dot.

[0033] For example, the group II-VI quantum dot can be selected from the group consisting of a CdSe quantum dot, a CdS quantum dot, a CdTe quantum dot, a ZnSe quantum dot, a ZnS quantum dot, a ZnTe quantum dot, a CdZnS quantum dot, a CdZnSe quantum dot, a CdZnSe quantum dot, a ZnSeS quantum dot, a ZnSeTe quantum dot, a ZnTeS quantum dot, a CdSeS quantum dot, a CdSeTe quantum dot, a CdTeS quantum dot, a CdZnSeS quantum dot, a CdZnSeTe quantum dot, and CdZnSTe quantum dot.

[0034] For example, the group III-V quantum dot can be selected from the group consisting of an InP quantum dot, an InAs quantum dot, a GaP quantum dot, a GaAs quantum dot, a GaSb quantum dot, an AlN quantum dot, an AlP quantum dot, an InAsP quantum dot, an InNP quantum dot, an InNSb quantum dot, a GaAlNP quantum dot, and an InAlNP quantum dot.

[0035] Preferably, each of the first quantum dot and the second quantum dot can be the perovskite quantum dot, wherein the perovskite quantum dot is selected from the group consisting of a CH.sub.3NH.sub.3PbI.sub.3 quantum dot, a CH.sub.3NH.sub.3PbCl.sub.3 quantum dot, a CH.sub.3NH.sub.3PbBr.sub.3 quantum dot, a CH.sub.3NH.sub.3PbI.sub.2Cl quantum dot, a CH.sub.3NH.sub.3PbICl.sub.2 quantum dot, a CH.sub.3NH.sub.3PbI.sub.2Br quantum dot, a CH.sub.3NH.sub.3PbIBr.sub.2 quantum dot, a CH.sub.3NH.sub.3PbIClBr quantum dot, a CsPbI.sub.3 quantum dot, a CsPbCl.sub.3 quantum dot, a CsPbBr.sub.3 quantum dot, a CsPbI.sub.2Cl quantum dot, a CsPbICl.sub.2 quantum dot, a CsPbI.sub.2Br quantum dot, a CsPbIBr.sub.2 quantum dot and a CsPbIClBr quantum dot. Preferably, each of the first quantum dot and the second quantum dot can be selected from the group consisting of CsPbCl.sub.3 exhibiting blue emission, CsPbBr.sub.3 exhibiting green emission, and CsPbI.sub.3 exhibiting red emission

[0036] In detail, each of the first phosphor and the second phosphor can be selected from the group consisting of LuYAG, GaYAG, YAG, silicate (such as Ba.sub.2SiO.sub.4:Eu.sup.2+, Sr.sub.2SiO.sub.4:Eu.sup.2+, (Mg, Ca, Sr, Ba).sub.3Si.sub.2O.sub.7:Eu.sup.2+, Ca.sub.8Mg (SiO.sub.4).sub.4Cl.sub.2:Eu.sup.2+ (CS), (Mg, Ca, Sr, Ba).sub.2SiO.sub.4:Eu.sup.2+, SLA, KSF, SILION, sulfide (such as SrS:Eu.sup.2+, SrGa.sub.2S.sub.4:Eu.sup.2+, ZnS:Cu.sup.+, ZnS:Ag.sup.+, Y.sub.2O.sub.2S:Eu.sup.2+, La.sub.2O.sub.2S:Eu.sup.2+, Gd.sub.2O.sub.2S:Eu.sup.2+, SrGa.sub.2S.sub.4:Ce.sup.3+, ZnS:Mn.sup.2+, SrS:Eu.sup.2+, CaS:Eu.sup.2+, (Sr.sub.1−xCa.sub.x) S:Eu.sup.2+), nitride (such as (Ca, Mg, Y) Si.sub.wAl.sub.xO.sub.yN.sub.z:Ce.sup.2+, Ca.sub.2Si.sub.5N.sub.8:Eu.sup.2+, (Ca, Mg, Y) Si.sub.wAl.sub.xO.sub.yN.sub.z:Eu.sup.2+, (Sr, Ca, Ba) Si.sub.xO.sub.yN.sub.z:Eu.sup.2+), and fluoride (such as fluosilicate (K.sub.2SiF.sub.6:Mn.sup.4+;KSF), fluotitanate (K.sub.2TiF.sub.6:Mn.sup.4+;KTF), fluogermanate (K.sub.2GeF.sub.6:Mn.sup.4+;KGF)).

[0037] Preferably, each of the first phosphor and the second phosphor can be a fluoride phosphor and selected from the group consisting of fluosilicate (K.sub.2SiF.sub.6:Mn.sup.4+;KSF), fluotitanate (K.sub.2TiF.sub.6:Mn.sup.4+;KTF), fluogermanate (K.sub.2GeF.sub.6:Mn.sup.4+;KGF).

[0038] For example, the first wavelength conversion material and the second wavelength conversion material of the optical wavelength conversion composite material P′ can be fluosilicate (KSF) and CsPbBr.sub.3 exhibiting green emission, respectively.

[0039] The inorganic covering layer 12 includes SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4−z, wherein x is from 0.1 to 0.4, y is from 0.5 to 0.8, and z is from 0.01 to 3.99. Specifically, the inorganic covering layer 12 is made of a mixture of SiO.sub.2 and TiO.sub.2. Preferably, Si.sub.xTi.sub.yO.sub.4−z can be Si.sub.0.1Ti.sub.0.5O.sub.3.95. More preferably, Si.sub.xTi.sub.yO.sub.4−z can be Si.sub.0.2Ti.sub.0.6O.sub.3.95.

[0040] Besides, the silicone polymer layer 13 is made of polysiloxane and/or polysilazane.

[0041] Furthermore, polysiloxane and/or polysilazane are used to provide a source of silicon to form the inorganic covering layer 12 made of silicon oxide, silicon nitride or silicon oxynitride to cover the second wavelength conversion material. Preferably, a weight ratio of polysiloxane and/or polysilazane to the second wavelength conversion material is from 10:1 to 1000:1, so as to obtain the inorganic covering layer 12 with a thickness between about 10 nm to 10 μm. Preferably, a molecular weight of polysiloxane or a molecular weight of polysilazane can be from about 500 to 5,000 g/mol. Preferably, a particle diameter of the optical wavelength conversion composite material is from 50 nanometers (nm) to 5 micrometers (μm).

[0042] However, the above-mentioned example is only one of the feasible embodiments and is not intended to limit the present invention.

[0043] Please refer to FIG. 3. FIG. 3 is a flow chart of a manufacturing method of the optical wavelength conversion composite material according to an embodiment of the present invention. As shown in FIG. 3, the manufacturing method includes a mixing step S102 and a miniaturization step S104. Specifically, the mixing step S102 includes mixing a first wavelength conversion material and an inorganic oxide to form a light emitting composite mixture, wherein the inorganic oxide includes SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4, and x is from 0.1 to 0.4, y is from 0.5 to 0.8, z is from 0.01 to 3.99. The miniaturization step S104 includes micronizing the light emitting composite mixture by spray drying method to obtain the optical wavelength conversion composite material.

[0044] Specifically, in this embodiment, a precursor of the inorganic oxide is selected from the group consisting of tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), 3-Aminopropyltriethoxysilane (APTES), titanium isopropoxide (TTIP), tetrabutyl orthotitanate (TBOT), and combinations thereof. Preferably, the precursor of the inorganic oxide can be a mixture of TMOS and TTIP for manufacturing the inorganic covering layer made of Si.sub.xTi.sub.yO.sub.4−z, which has a higher synthesis rate than a mixture of TEOS and TMOS.

[0045] In detail, a weight ratio of the first wavelength conversion material to the whole optical wavelength conversion composite material is not limited. Preferably, the weight ratio of the of the first wavelength conversion material to the whole optical wavelength conversion composite material can be from 0.01 to 10 wt %, which has better aggregation characteristics and better luminescence. Furthermore, an average particle diameter of the first wavelength conversion material is not limited. Preferably, the average particle diameter of the first wavelength conversion material can be from 1 nm to 50 nm, or less, which maintains a better crystal structure.

[0046] Optionally, a solvent may be further added as a medium for dispersing the first wavelength conversion material. For example, the solvent can be ester (such as methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate), or ketone (such as y-butyrolactone, N-methyl-2-pyrrolidone, acetone, dimethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl cyclohexanone), or ether (such as diethyl ether, methyl tert-butyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, 4-methyldioxolane, tetrahydrofuran, methyltetrahydrofuran, anisole, phenylethyl ether), or alcohol (such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol, methoxypropanol, diacetone alcohol, cyclohexanol, 2-fluoroethanol, 2, 2, 2-trifluoroethanol, 2, 2, 3, 3-tetrafluoro-l-propanol), or glycol ether (such as Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, triethylene glycol dimethyl ether), or organic solvent with amide group (such as N, N-dimethylformamide, acetamide, N, N-dimethylacetamide), or organic solvent with nitrile group (such as acetonitrile, isobutyronitrile, propionitrile, methoxyacetonitrile), or organic solvent with carbonate group (such as ethylene carbonate, propylene carbonate), or organic solvent with halogenated hydrocarbon group (such as dichloromethane, chloroform), or organic solvent with hydrocarbyl group (such as n-pentane, cyclohexane, n-hexane, benzene, toluene, xylene), or dimethyl sulfoxide.

[0047] In the miniaturization step S104, the spray drying method is configured to remove liquid from the dispersion with a carrier gas selected from air, inert gas (such as argon) or nitrogen at an inlet temperature ranging from 150° C. to 500° C., so as to form optical wavelength conversion composite microspheres whose first wavelength conversion material is covered by the inorganic oxide, by curing.

[0048] Preferably, the carrier gas for spray drying can be nitrogen, wherein a pressure can be from 0.30 MPa to 0.50 MPa, and a nozzle speed can be from 500 ml/hour to 3000 ml/hour, or from 1000 ml/hour to 2000 ml/hour, or about 1760 ml/hour.

[0049] Preferably, an average particle diameter of the optical wavelength conversion composite microspheres whose first wavelength conversion material is covered by the inorganic oxide, manufactured by the spray drying method is from 10 nm to 30 μm. It depends on a ratio of solution formulation and setting conditions of the spray drying method.

[0050] Please refer to FIG. 4. FIG. 4 is a flow chart of a manufacturing method of an optical wavelength conversion composite material according to another embodiment of the present invention. As shown in FIG. 4, the manufacturing method includes a mixing step S202, a silane treatment step S204, and a miniaturization step S206. Specifically, the mixing step S202 includes mixing a first wavelength conversion material and an inorganic oxide to form a light emitting composite mixture, wherein the inorganic oxide includes SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4−z, and x is from 0.1 to 0.4, y is from 0.5 to 0.8, z is from 0.01 to 3.99. The silane treatment step S204 includes mixing the light emitting composite mixture, a polysilane compound and a second wavelength conversion material, so as to generate a silane treated light emitting composite mixture. The miniaturization step S206 includes micronizing the silane treated light emitting composite mixture by spray drying method to obtain the optical wavelength conversion composite material.

[0051] The mixing step S202 and the miniaturization step S206 of this embodiment are the same as the mixing step 5102 and the miniaturization step S104 of the embodiment of FIG. 3. Detailed description is omitted herein for simplicity.

[0052] Different from the embodiment of FIG. 3, the silane treatment step S204 is used to generate the silane treated light emitting composite mixture by mixing the light emitting composite mixture, the polysilane compound and the second wavelength conversion material.

[0053] Specifically, in this embodiment, a precursor of the inorganic oxide is selected from the group consisting of tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), 3-Aminopropyltriethoxysilane (APTES), titanium isopropoxide (TTIP), tetrabutyl orthotitanate (TBOT), and combinations thereof. Preferably, the precursor of the inorganic oxide can be a mixture of TMOS and TTIP for manufacturing the inorganic covering layer made of Si.sub.xTi.sub.yO.sub.4−z, which has a higher synthesis rate than a mixture of TEOS and TMOS.

[0054] Please refer to FIG. 5. FIG. 5 is a diagram of an optical wavelength conversion composite structure according to an embodiment of the present invention. As shown in FIG. 5, the optical wavelength conversion composite structure includes a first base plate 21, an optical wavelength conversion composite material layer 22 and a second base plate 23. The optical wavelength conversion composite material layer 22 is disposed on the first base plate 21. The second base plate 23 is disposed on the optical wavelength conversion composite material layer 22, so that the optical wavelength conversion composite material layer 22 is located between and clamped by the first base plate 21 and the second base plate 23.

[0055] Preferably, each of the first base plate 21 and the second base plate 23 can be a flexible substrate or a glass substrate. The flexible substrate can be a substrate made of polyethylene terephthalate (PET), polyethylene dicarboxylate (PEN), or polyether sulfite resin (PES resin). Preferably, the first base plate 21 and the second base plate 23 can be a substrate made of polyethylene terephthalate (PET).

[0056] The optical wavelength conversion composite material layer 22 includes an optical wavelength conversion composite material. The optical wavelength conversion composite material of this embodiment is the same as the optical wavelength conversion composite material of any one of the aforementioned embodiments. Detailed description is omitted herein for simplicity.

[0057] In detail, a manufacturing method of the optical wavelength conversion composite structure includes mixing and stirring the optical wavelength conversion composite material, dispersion medium and photoinitiator into a solution; coating the solution between the first base plate and the second base plate; pressing the first base plate and the second base plate by rollers to obtain a laminated substrate with a fixed thickness; and curing the laminated substrate with ultraviolet light to obtain optical wavelength conversion composite structure.

[0058] In summary, since the inorganic covering layer of the present invention includes SiO.sub.2, TiO.sub.2 and Si.sub.xTi.sub.yO.sub.4−z, wherein x is from 0.1 to 0.4, y is from 0.5 to 0.8, and z is from 0.01 to 3.99, the optical wavelength conversion composite material of the present invention has improved luminescence characteristics and color saturation.

[0059] Besides, the related manufacturing methods of the present application are easy and safe, and the miniaturization step can increase uniformity of the optical wavelength conversion composite material.

[0060] Furthermore, the optical wavelength conversion composite material of the present application has improved luminous efficiency.

[0061] Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.