The present invention relates to optical elements comprising fluorochemical surface treatments. The invention further relates to articles such as retroreflective sheetings, pavement markings and beaded projection screens comprising a binder and the surface treated optical elements. The surface treatment comprises at least one fluoropolymer selected from a) fluoropolymers comprising a fluorinated hydrocarbon backbone and side chains comprising at least one of fluoroalkyl, fluoroether alkyl, fluoroalkoxy and mixtures thereof; and b) fluoropolymers comprising a hydrocarbon backbone and side chains comprising at least one of fluoroether alkyl, fluoroalkoxy and mixtures thereof.

The present invention relates to optical elements comprising fluorochemical surface treatments. The invention further relates to articles such as retroreflective sheetings, pavement markings and beaded projection screens comprising a binder and the surface treated optical elements. The surface treatment comprises at least one fluoropolymer selected from a) fluoropolymers comprising a fluorinated hydrocarbon backbone and side chains comprising at least one of fluoroalkyl, fluoroether alkyl, fluoroalkoxy and mixtures thereof; and b) fluoropolymers comprising a hydrocarbon backbone and side chains comprising at least one of fluoroether alkyl, fluoroalkoxy and mixtures thereof.
Beaded projection display screens, retroreflective sheeting used in the manufacture of roadway signs, and retroreflective paints typically include optical elements adhered through the use of a binder. In the case of beaded projection display materials, the optical elements are microscopic glass beads that act as lenses to collect projected light from the rear of the screen and focus it to relatively small spots, near the surfaces of the microspheres. The foci are approximately in the areas where the optical elements contact a front support layer. In other retroreflective materials, the optical elements act as lenses which focus the light onto a reflector (metal mirror of diffusely reflecting pigment) and once the light has been reflected off the reflector the microspheres again act as lenses to resend the light back toward the incoming light source. In order to contribute the desired retroreflective property, however, it is important that a layer of glass microspheres be present on the surface of the binder layer.
As discussed in U.S. Pat. No. 3,222,204, ordinary glass beads tend to sink into the uncured liquid binder layer. In instances wherein the individual beads are not entirely submerged, the optical properties of the bead can also be impaired by the binder wetting out the bead surface and spreading on the exposed bead surface. To address this problem, U.S. Pat. No. 3,222,204 teaches coating the glass beads with a thin surface coating of an oleophobic fluorocarbon-sizing agent. At column 5, lines 61-75, this reference states that, xe2x80x9cAqueous treating solutions of fluorocarbon chromium coordination complexes are preferred and are described in U.S. Pat. Nos. 2,662,835 (Dec. 15, 1953) and 2,809,990 (Oct. 15, 1957) and 2,934,450 (Apr. 26, 1960). The complex may be made by reacting chromyl chloride with a fluorocarbon monocarboxylic acid (having a highly fluorinated terminal chain or tail containing 4 to 10 carbon atoms) in an isopropanol vehicle that serves as both a solvent and reducing agent, the chromium to acid mole ratio being in the range of 2:1 to 5:1. The resultant green-colored isopropanol solution of the complex is diluted with water at the time of use. The fluorocarbon acid preferably has 6 to 8 fully fluorinated (perfluorinated) carbon atoms in the terminal fluorocarbon chain or tail.xe2x80x9d Specific working examples include chromium coordination complexes of perfluorooctanoic acid and N-ethyl-N-perfluorooctanesulfonyl glycine.
U.S. Pat. No. 4,713,295 teaches coating glass beads with a mixture of substances. The mixture comprises a first substance, which if used alone would tend to make the beads hydrophobic while leaving them oleophilic, and a second substance, which if used alone would tend to make the beads both hydrophobic and oleophobic. xe2x80x9cFor the best results, it is preferred to use a second substance which is an anionic fluorocarbon compound, and optimally, said second substance is a fluoro-alkyl-sulphonate, for example a fluoro-alkyl-sulphonate in which the alkyl has a long chain (C14 to C18).xe2x80x9d (See Column 4, lines 8-13). The exemplified hydrophobic and oleophobic substance is a potassium fluoroalkyl-sulphonate (for example FC129 from 3M). (See column 5, lines 50-52) FC129 is a potassium fluorooctyl sulphonyl-containing compound.
The present invention relates to optical elements having a surface treatment comprising at least one fluoropolymer selected from:
a) fluoropolymers comprising a fluorinated hydrocarbon backbone and side chains comprising at least one of fluoroalkyl, fluoroether alkyl, fluoroalkoxy and mixtures thereof; and
b) fluoropolymers comprising a hydrocarbon backbone and side chains comprising at least one of fluoroether alkyl, fluoroalkoxy and mixtures thereof.
The backbone of the fluoropolymer surface treatment is preferably free of oxygen atoms. The fluoropolymer is preferably perfluorinated. The surface treatment is substantially free of perfluoroalkyl side chains or end groups having 6 or more carbon atoms, and more preferably substantially free of perfluoroalkyl side chains or end groups having more than 4 carbon atoms.
In one aspect, the fluoropolymer is prepared from at least one fluorovinyl ether monomer and at least one comonomer having a polymerizable double bond. The fluorovinyl ether monomer is preferably selected from CF2xe2x95x90CFxe2x80x94Oxe2x80x94CF3 (PMVE), CF2xe2x95x90CFxe2x80x94Oxe2x80x94CF2CF2CF3 (PPVE), CF2xe2x95x90CFxe2x80x94Oxe2x80x94CF2CF(CF3)xe2x80x94Oxe2x80x94CF2CF2CF3 (PPVE-2) and mixtures thereof. For embodiments wherein PMVE is the sole fluorovinyl ether monomer, the fluoropolymer preferably comprises at least about 30 mole % of repeat units derived from PMVE. It is surmised, however, that lower concentrations of repeat units derived from PMVE would also be suitable provided that the fluoropolymer has a molecular weight of less than about 30,000 g/mole. For embodiments wherein PPVE is the sole fluorovinyl ether monomer, the fluoropolymer preferably comprises from about 10 to about 20 mole % of repeat units derived from PPVE. For embodiments wherein PPVE-2 is the sole fluorovinyl ether monomer, the fluoropolymer preferably comprises from about 1 to about 10 mole % of repeat units derived from PPVE-2. The comonomer is preferably tetrafluoroethylene (TFE) employed alone or in combination with vinylidene fluoride (VDF). The fluoropolymer preferably comprises about 10 to about 30 mole % of repeat units derived from TFE and about 50 to about 80 mole % of repeat units derived from VDF. Other suitable comonomers include alkyl (meth)acrylates, substituted alkyl (meth)acrylates, (meth)acrylic acid, (meth)acrylamides, alkenes, styrenes, vinyl halides, vinyl esters, and mixtures thereof.
In another aspect, the fluoropolymer is a homopolymer or copolymer prepared from at least one monomer selected from fluoroalkyl ether acrylate, fluoroalkoxy acrylate, and mixtures thereof. The copolymer further comprises repeat unit derived from at least one of alkyl (meth)acrylates, substituted alkyl (meth)acrylates, (meth)acrylic acid, (meth)acrylamides, fluorinated alkenes, styrenes, vinyl halides, malaic anhydride, vinyl esters, and mixtures thereof
The surface treatment may further comprise a second polymer blended therewith. The percent float in heptane of the surface treated optical elements is preferably at least about 90%. The fluoropolymer surface treatment is preferably present at an amount of less than about 300 ppm and more preferably at an amount of about 50 ppm or less.
In another aspect, the invention provides a method of coating optical elements comprising the steps of:
a) providing at least one surface treatment comprising:
i) fluoropolymers comprising a fluorinated hydrocarbon backbone and side chains comprising at least one of fluoroalkyl, fluoroether alkyl, fluoroalkoxy and mixtures thereof, and/or
ii) fluoropolymers comprising a hydrocarbon backbone and side chains comprising at least one of fluoroether alkyl, fluoroalkoxy and mixtures thereof;
b) coating optical elements with said composition; and
c) drying said composition.
The surface treatment is preferably an aqueous composition, yet may optionally comprise up to about 30 wt-% of a cosolvent, with respect to the total weight of the surface treatment solution.
In another aspect, the present invention relates to a pavement marking article comprising a liquid binder and a multitude of the surface treated optical elements.
In another aspect, the present invention relates to reflective sheeting articles comprising:
a) a top coat layer having an exposed surface;
b) a binder layer disposed on the exposed surface of the top coat layer;
c) a multitude of the surface treated optical elements disposed in the binder layer;
d) a space coat layer disposed on the binder layer; and
e) a reflective layer disposed on the space coat layer.
In another aspect, the present invention relates to a rear projection screen article comprising a transparent substrate and the surface treated optical elements embedded in an opaque binder matrix and wherein said optical elements are in contact with the transparent substrate.
In each of the articles, the optical elements are preferably embedded in the binder at a depth of about 40-70% of their diameters.
The present invention relates to optical elements such as glass beads coated with a fluorocarbon surface treatment. The terminology xe2x80x9coptical element(s)xe2x80x9d refers to a material having a particle size ranging from about 25 to 1000 microns and having a refractive index ranging from about 1.5 to about 2.3 and higher.
The optical elements have at least one dimension that is no larger than 2 millimeters and preferably no larger than 250 microns. The optical elements may be in the form of any shape such as granules, flakes and fibers. However, spheroidal glass elements, denoted as xe2x80x9cglass beadsxe2x80x9d, xe2x80x9cbeadsxe2x80x9d and xe2x80x9cmicrospheresxe2x80x9d hereinafter are preferred for materials such as retroreflective articles (e.g. retroreflective sheetings, pavement markings and beaded projection screens).
During the manufacture of retroreflective materials, optical elements are fixed in place by means of a liquid binder. Optical elements have a density or specific gravity several times that of the liquid binder, causing the optical elements to sink into the liquid binder layer, rather than float on the surface.
Preferred properties of optical elements will be described herein with respect to glass beads. Ordinary glass beads typically have a density of about 2.5 and a refractive index of about 1.5. xe2x80x9cHigh indexxe2x80x9d beads refers to beads having a density of about 3.5 and a refractive index of about 1.9, whereas xe2x80x9csuper high indexxe2x80x9d typically refers to beads having a density of about 5 and a refractive index of about 2.3 or higher. The diameter of the glass beads typically ranges from a few microns to approximately 2500 microns and is preferably from about 25 to 1000 microns.
In addition to having the desired particle size and refractive index, the glass beads are typically transparent. The term transparent means that when viewed under an optical microscope (e.g., at 100xc3x97) the microspheres have the property of transmitting rays of visible light so that bodies beneath the microspheres, such as bodies of the same nature as the microspheres can be clearly seen through the microspheres, when both are immersed in oil of approximately the same refractive index as the microspheres. The outline, periphery or edges of bodies beneath the microspheres are clearly discernible. Although the oil should have a refractive index approximating that of the microspheres, it should not be so close that the microspheres seem to disappear as would be the case for a perfect match.
The optical elements may comprise microspheres that are ceramic. In general, ceramic microsphere optical elements are comprised of metal oxides that are substantially colorless. Suitable metal oxides include Al2O3, SiO2, ThO2, SnO2, TiO2, Y2O3 and ZrO2 with the oxides of zirconium, silicon, and titanium being preferred. The ceramic microspheres can exhibit a range of properties, depending on the kind and amounts of the various metal oxides employed as well as the method of manufacture. Preferred, however, are dense microspheres having substantially no open porosity and having an average hardness greater than sand.
Additional information concerning the desired properties for various end-uses and methods of manufacture of microspheres (e.g. sol-gel process), can be found in U.S. Pat. Nos. 3,493,403; 3,709,706 and 4,564,556. Glass beads suitable for use as optical elements in the invention are also commercially available from Flex-O-Lite Corporation, Fenton, Mo. and Nippon Electric Glass, Osaka, Japan.
The optical elements of the invention are coated with a surface treatment that alters the floatation properties of the optical elements in the liquid binder. xe2x80x9cFloatxe2x80x9d and derivations thereof, described in the context of glass beads, refers to the beads assuming a position wherein slightly more than half of each bead is submerged. The liquid binder preferably contacts the embedded beads only up to 5xc2x0 to 30xc2x0 above their equators. The floatability of the glass beads can be affected to some extent by the particle size, particle size distribution, surface chemistry and chemical make-up of the particular glass beads as well as the chemical make-up, density, and viscosity of the binder. In general, however, only about 10% or less of the glass beads tend to float in heptane test liquid in the absence of an effective surface treatment.
The position that the glass beads attain relative to the undisturbed binder due to the surface treatment assists the anchoring of the beads in the ultimate dried or solidified binder coating. The glass beads are preferably embedded to about 40-70%, and more preferably to about 40-60% of their diameters. The beads are adequately exposed providing a sphere-lens having a large optical aperture relative to its size. During the drying or solidification of the binder, there is some shrinkage of the binder film. However, the beads remain bonded with the centers of the floated beads being approximately equidistant from the underlying back surface of the binder layer or the top surface of the base.
In addition to the improvement in floatation of the optical elements, it is also important that the surface treatment does not adversely affect the adhesion of the optical elements with the liquid binder. The adhesion can be evaluated in several ways and will be described herein with respect to a preferred optical element, glass beads. The initial adhesion can be subjectively determined by estimating the depth to which the embedded glass beads have sunk into the binder after curing. The glass beads are preferably embedded to a depth of about 40-70%, and more preferably to about 40-60% of their diameters. Another way of evaluating adhesion is accelerated aging evaluations. A piece of cured glass bead-embedded binder is conditioned in boiling water for 24 hours. After conditioning, the glass beads are preferably embedded to the same extent as prior to conditioning and the individual glass beads are difficult to remove with a dissection probe. Yet another way to evaluate the effect of the binder on adhesion is comparative tensile testing. A uniform mixture of binder and untreated glass beads at a ratio of about 1 to 3 is drawn down into a film having a thickness of about 0.4 mm. A second mixture of binder and surface treated glass beads employing the same ratio of ingredients and film thickness is prepared. After the samples are fully cured, the samples are conditioned for 24 hours in water at ambient temperature. Tensile testing is conducted with a 1xe2x80x3 (2.5 cm) wide sample employing a 2xe2x80x3 (5 cm) gap at a rate of 0.5 inches (1.3 cm)/minute. The stress at break of the sample comprising the surface treated beads is about the same as or preferably greater than the control sample, comprising untreated beads (xe2x89xa7about 90% of the standard deviation of the average value). Any one of the previously described methods is typically sufficient to determine whether the surface treatment adversely affects the adhesion of the glass beads to the binder. Preferably, however, all three of the evaluations are conducted.
The optical elements are coated with a fluoropolymer surface treatment. As used herein xe2x80x9csurface treatmentxe2x80x9d refers to a composition that causes at least about 80% of the optical elements to float in heptane or an aromatic solvent, such as toluene, as previously described. The surface treatment comprises at least one fluoropolymer comprising a partially or fully fluorinated hydrocarbon backbone and side chains comprising at least one of fluoroalkyl, fluoroether alkyl, fluoroalkoxy and mixtures thereof; and/or at least one fluoropolymer comprising a hydrocarbon backbone and side chains comprising at least one of fluoroether alkyl, fluoroalkoxy and mixtures thereof. Further, the side chains may optionally contain other heteroatoms.
Such fluoropolymer surface treatments preferably comprise a plurality fluoroalkyl, fluoroether alkyl side chains and/or fluoroalkoxy side chains. The fluoroether alkyl side chains and/or fluoroalkoxy side chains typically comprise 1 to 20 carbons atoms, more preferably 1 to 12 carbon atoms and most preferably 1 to 6 carbon atoms. The fluoroalkyl side chains preferably comprises 1 to 6 carbons atoms and more preferably 1 to 4 carbons atoms, particularly in the case of fluoroether-substituted alkyl (meth)acrylates. The presence of such side chains can be detected by means of x-ray photoelectron spectroscopy (XPS) or time of flight secondary ion mass spectrometry.
Preferred fluoropolymer surface treatments are substantially free of perfluoroalkyl side chains and end groups, having more than 4 carbon atoms. xe2x80x9cSubstantially freexe2x80x9d refers to less than about 1 wt-% of the fluoroalkyl segments containing more than 4 carbon atoms. Most preferably, only trace impurities of fluoroalkyl segments containing more than 4 carbon atoms are present.
Accordingly, the fluoropolymer comprises repeat units selected from xe2x80x94(CnH2n)xe2x80x94, xe2x80x94(CnF2n)xe2x80x94, xe2x80x94(CH(Z))xe2x80x94, xe2x80x94(CF(Z))xe2x80x94, xe2x80x94(CH2CH(Z))xe2x80x94 and combinations thereof, wherein n is an integer ranging from 1 to 20 and Z comprises a fluoroalkyl group, fluoroether alkyl, fluoroalkoxy, and mixtures thereof; with the proviso that wherein the backbone comprises xe2x80x94(CH2CH(Z))xe2x80x94 and Z comprises fluoroalkyl, the side chain comprises at least one fluoroether group.
The fluorinated alkyl groups of both the backbone segments as well as the side chains are preferably perfluorinated (i.e., all Cxe2x80x94H bonds replaced with Cxe2x80x94F bonds) with the exception of the fluoropolymers derived from perfluoroalkyl acrylate wherein the side chain is generally only partially fluorinated.
Fluoropolymers are generally prepared from fluorinated hydrocarbon monomers having a polymerizable double bond. Although many fluoropolymers have been prepared, the most common monomers include tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), and vinylidene fluoride (VDF), and selected copolymers of these olefins with ethylene, hexafluoropropylene (HFP) and perfluorovinyl ethers such as perfluoro(methyl vinyl ether) (PMVE), perfluoro(propyl vinyl ether) (PPVE) and higher homologs such as CF2xe2x95x90CFxe2x80x94Oxe2x80x94CF2CF(CF3)xe2x80x94Oxe2x80x94CF2CF2CF3 (xe2x80x9cPPVE-2xe2x80x9d).
Such monomers can be synthesized by known techniques, such as described in the Organofluorine Chemistry: Principles and Commercial Applications, Edited by R. E. Banks, B. E. Smart and J. C. Tatlow, Plenum Press, NY 1994. Further, many of such monomers are commercially available.
In the preparation of the fluoropolymers, such monomers are generally copolymerized with each other or with a non-fluorinated comonomer to produce a fluoropolymer having a glass transition temperature (Tg) of less than about 25xc2x0 C. Examples of suitable non-fluorinated comonomers include alkyl (meth)acrylates, substituted alkyl (meth)acrylates, (meth)acrylic acid, (meth)acrylamides, styrenes, vinyl halides, and vinyl esters.
The number of repeat units in the fluoropolymer combined with the molecular weight of optional end groups is sufficient to form a compound having a number average molecular weight (Mn) greater than about 5,000 g/mole. Preferably, the fluoropolymer has a Mn ranging from about 10,000 g/mole to about 30,000 g/mole. The Mn is typically less than about 500,000 g/mole, particularly in the case of fluoropolymers derived from fluorovinyl ether monomer(s). It is surprising that polymeric species that are many times larger in molecular weight than the previous preferred perfluorooctyl base compounds can effectively be employed as surface treatments without compromising bead flow properties or adhesion of the optical elements to the binder, particularly since such polymeric materials do not necessarily bear reactive functional groups A preferred fluoropolymer surface treatment is prepared from perfluorovinyl ether monomer (e.g. PMVE, PPVE, PPVE-2) in combination with a comonomer having a polymerizable double bond. Preferred comonomers include TFE as the sole comonomer or in combination with VDF.
In somewhat greater detail, perfluorovinyl ether monomers correspond to the general formula:
CF2xe2x95x90CF(OCnF2n)mORf
wherein n is an integer independently ranging from 1 to 6, the average value m ranges from 1 to 6, and Rf is a perfluoroalkyl groups having 1 to 6 carbon atoms. Rf can be a linear, branched, or cyclic perfluoroalkyl group. Examples of Rf groups include CF3xe2x80x94, CF3CF2xe2x80x94, CF3CF2CF2xe2x80x94 and CF3CF(CF3)xe2x80x94. Both n and m are preferably an integer of 1 to 3. Further, Rf is preferably a perfluoroalkyl group having 1 to 4 carbon atoms.
The Applicants have found that as the concentration (i.e. mole %) of repeat units derived from perfluorovinyl ether monomer in the fluoropolymer increases, the effective concentration to induce 100% float to optical elements decreases. The concentration of perfluorovinyl ether monomer derived repeat units in the fluoropolymer, as determined by nuclear magnetic resonance spectroscopy (NMR), is typically at least about 1 mole % of the fluoropolymer and preferably greater than about 3 mole %.
In general, the preferred molar concentration of repeat units derived from perfluorovinyl ether is related to the chain length of the side chain. Wherein m is 0 and Rf is CF3, as in the case of PMVE, generally a higher concentration of repeat units derived from perfluorovinyl ether are needed in the fluoropolymer to obtain 100% float of the beads. In such instances, the molar concentration of repeat units derived from perfluorovinyl ether is typically at least 30 mole %. At too high of a molar concentration of repeat units derived from perfluorovinyl ether, however, the fluoropolymer tends to become too compliant, which can result in agglomeration of the coated beads. Alternatively, for embodiments wherein n is 2 or greater (e.g. PPVE, PPVE-2), the concentration of repeat units derived from perfluorovinyl ether in the fluoropolymer, can be considerably lower. The Applicants have found that fluoropolymers having about 10 to about 20 mole % of repeat units derived from PPVE-2, for example, can advantageously be used at concentrations as low as 50 ppm.
The concentration of comonomer employed in the manufacture of the perfluorovinyl ether fluoropolymers is dependent on the choice of perfluorovinyl ether, as previously described, as well as the choice of comonomer(s). In general, however, preferred fluoropolymer surface treatments comprise 0 to about 80 mole % of repeat units derived from TFE and 0 to about 90% of repeat units derived from VDF. For instances wherein PMVE is employed as the sole perfluorovinyl ether monomer, the concentration of repeat units derived from TFE is more preferably about 40 to 60 mole %. Such fluoropolymers also tend to comprise small concentrations (e.g. less than 1 mole %) of a crosslinking agent such as bromotrifluoroethylene (BTFE). In the case of terpolymers having repeat units derived from TFE, VDF and PPVE-2, the preferred molar concentration of repeat units derived from TFE generally ranges from about 10 to about 30 mole %. Further, the concentration of repeat units derived from VDF preferably ranges from about 50 to about 80 mole %.
Particularly preferred perfluorovinyl ether fluoropolymers are substantially free of oxygen in the backbone and include the following general structures wherein x, y and z are each independently integers:
Since perfluorovinyl ether containing fluoropolymers tend to be relatively more expensive than many of the other fluoropolymers, it is advantageous to blend the perfluorovinyl ether fluoropolymer with one or more fluoropolymers that are substantially free of perfluorovinyl ether linkages. In such instances, the fluoropolymer blend preferably comprises the molar concentrations of perfluorovinyl ether linkages, as previously described. Preferred fluoropolymers for blending with the perfluorovinyl ether fluoropolymer include fluoroplastics (i.e. thermoplastic fluoropolymers) and fluoroelastomers such as homopolymers, copolymers and terpolymers comprised of TFE, HFP and VDF.
Another preferred class of fluoropolymer surface treatments for inducing float to the optical elements include homopolymers and copolymers of perfluoroether-substituted alkyl methacrylates and more preferably of perfluoroether-substituted alkyl acrylates. These are prepared by polymerization of monomers with general structure CH2xe2x95x90C(R)CO2-Q-Rf in which R is H or CH3, Q is an organic divalent linking group optionally comprising heteroatoms, unsaturations, and/or functional groups, and Rf is a perfluoroalkyl or perfluoroalkoxy group of 1 to 20 carbons substituted with one and preferably more than one ether oxygens, as described above. Preferred structures for Q are xe2x80x94(CH2)nxe2x80x94 where n=1-11 and preferably 1-2. A particularly preferred structure for Q is xe2x80x94CH2xe2x80x94. Preferred structures for Rfxe2x80x2 include xe2x80x94CnF2n(OCmF2m)pORfxe2x80x3 in which n=1-4, m=1-4, p=0-6 and preferably 1-4, and Rfxe2x80x3 is a perfluoroalkyl group having 1 to 6 carbon atoms. Rfxe2x80x3 can be a linear, branched, or cyclic perfluoroalkyl group. Examples of Rfxe2x80x2 groups include CF3xe2x80x94, C2F5xe2x80x94, and C3F7. Particularly preferred structures for Rfxe2x80x2 include C4F9OC2F4OCF2xe2x80x94, CF3O(C2F4O)2CF2xe2x80x94, and C3F7O(CF(CF3)CF2O)nCF(CF3)xe2x80x94 where n=0-3. The monomers are obtained by reaction of the corresponding alcohols with (meth)acryloyl chloride using standard synthetic techniques. Preferred fluorinated alcohols Rfxe2x80x2CH2OH for use in synthesis of these monomers are obtained by reduction, again using standard techniques, of derivatives of the corresponding carboxylic acid derivatives Rfxe2x80x2COX (where Xxe2x95x90F, OH, or OR where R=methyl or ethyl) using sodium borohydride or lithium aluminum hydride.
Fluorinated poly(meth)acrylates are generally prepared by free radical polymerization either neat or in solvent, using radical initiators well known to those skilled in the art. Other monomers which can be copolymerized with these fluorinated (meth)acrylate monomers include alkyl (meth)acrylates, substituted alkyl (meth)acrylates, (meth)acrylic acid, (meth)acrylamides, styrenes, vinyl halides, and vinyl esters.
Preferred substituted alkyl acrylate comonomers include:
I Rf*xe2x80x94(CH2)mCH2O2CCHxe2x95x90CH2, wherein m=0-25 and preferably 0-10, and Rf*xe2x95x90CnF2n+1 wherein n ranges from 1 to 12 and preferably from 1 to 4;
II CH2xe2x95x90CHCO2H;
III CH2xe2x95x90CHCO2(CH2)nCO2H, wherein n=1-10;
IV CH2xe2x95x90CHCO2(CH2)nCH2OH, wherein n=1-10; and
V CH2xe2x95x90CHCO2(CH2)nCH3, wherein n=1-10.
The fluoropolymer surface treatments described herein may further comprise polar constituents. Such polar groups or polar group containing radicals may be anionic, nonionic, cationic, or amphoteric. In general, the more commonly employed polar groups or polar group-containing organic radicals for aqueous delivery of the treatment solution include organic acids, particularly carboxylic acid, sulfonic acid and phosphonic acid; carboxylate salts, sulfonates, phosphonates, phosphate esters, ammonium salts, amines, amides, alkyl amides, alkyl aryl amides, imides, sulfonamides, hydroxymethyl, thiols, esters, silanes, and polyoxyalkylenes, as well as other organic radicals such as alkylene or arylene substituted with one or more of such polar groups.
The fluoropolymers described herein for use as surface treatment for optical elements are typically solids. The fluoropolymer(s) are combined with various solvents to form emulsion(s), solution(s) or dispersion(s). Dispersions of fluoropolymers can be prepared using conventional emulsion polymerization techniques, such as described in U.S. Pat. Nos. 4,418,186; 5,214,106; 5,639,838; 5,696,216 or Modern Fluoropolymers, Edited by John Scheirs, 1997 (particularly pp. 71-101 and 597-614) as well as assignees"" copending patent application Ser. No. 01/03195, filed Jan. 31, 2001.
The emulsion(s), solution(s), and dispersion(s) are then further diluted in order to deliver the desired concentration. It is assumed that negligible amounts of the diluted surface treatment are lost and substantially all of the surface treatment present in the emulsion, solution or dispersion is deposited on the optical elements. Hence, the concentration (ppm) based on the weight of the optical elements being coated with the emulsion, solution, or dispersion is approximately equal to the amount retained on the optical elements upon evaporation of the solvent. Although aqueous emulsions, solutions, and dispersions are preferred, up to about 50% of a cosolvent such as methanol, isopropanol, or methyl perfluorobutyl ether may be added. Preferably, the aqueous emulsions, solutions, and dispersions comprise less than about 30% cosolvent, more preferably less than about 10% cosolvent, and most preferably the aqueous emulsions, solutions, and dispersions are substantially free of cosolvent. The aqueous surface treatment is coated on the optical elements typically by combining the optical elements with the minimum volume of aqueous surface treatment to uniformly coat the optical elements and then drying the coated elements. Although aqueous delivery is preferred, the surface treatment could also be applied from 100% organic solvent as well as by other techniques such as vapor deposition.
Various fluoropolymer dispersions are commercially available from Dyneon, DuPont, Ausimont, as well as other suppliers.
The surface treatment comprises any one or any mixture thereof of the previously described fluoropolymers, with surface treatments comprising at least one perfluorovinyl ether polymer and or at least one perfluoroether acrylate being preferred.
The amount of fluoropolymer surface treatment employed for coating the optical elements typically ranges from about 5 ppm to about 1000 ppm with respect to the weight of the optical elements. A preferred fluoropolymer surface treatment is one that contributes the desired floatation at minimum concentrations. The amount of fluoropolymer surface treatment is usually about 600 ppm or less, preferably about 300 ppm or less, more preferably about 150 ppm, even more preferably about 100 ppm, and most preferably about 50 ppm or less. Typically, the overall coating thickness of the surface treatment of the present invention is greater than about 15 Angstroms, preferably, greater than about 20 Angstroms, and more preferably, greater than about 50 Angstroms. Thicker coatings can be obtained if desired, although it is preferred that the coating thickness be no greater than about 500 Angstroms, more preferably, no greater than about 300 Angstroms, and most preferably, no greater than about 150 Angstroms thick. Excessive concentrations of surface treatment can result in agglomeration of the optical elements. Such limits can be determined by routine experimentation and in some instances the agglomeration can be reduced by the use of flow control agents.
In addition to the fluoropolymer surface treatment of the invention, the optical elements may comprise one or more additional surface treatments such as adhesion promoters and flow control agents that reduce particle agglomeration. Various silanes such as 3-aminopropyltriethoxysilane are commonly employed as adhesion promoters, whereas methacrylato chromic chloride, commercially available from Zaclon Inc, Cleveland, Ohio under the trade designation xe2x80x9cVolanxe2x80x9d is a typical flow control agent.
The surface treated optical elements of the invention can be employed for producing a variety of reflective products or articles such as pavement markings, retroreflective sheeting, and beaded projection screens. Such products share the common feature of comprising a liquid binder layer and embedding a multitude of optical elements into the binder surface followed by solidifying the binder to retain the optical elements in place. In the pavement markings, retroreflective sheeting, and beaded projection screens of the invention, at least a portion of the optical elements will comprise the surface treated optical elements of the invention. Typically, the majority of, and preferably substantially all, the optical elements employed in the manufacture of the reflective products will comprise the surface treated optical elements of the invention.
Various known binder materials may be employed including various one and two-part curable binders, as well as thermoplastic binders wherein the binder attains a liquid state via heating until molten. Common binder materials include polyacrylates, methacrylates, polyolefins, polyurethanes, polyepoxide resins, phenolic resins, and polyesters. For reflective paints the binder may comprise reflective pigment. For reflective sheeting, however, the binder is typically transparent. Transparent binders are applied to a reflective base or may be applied to a release-coated support, from which after solidification of the binder, the beaded film is stripped and may subsequently be applied to a reflective base or be given a reflective coating or plating.
There are several types of retroreflective articles in which the surface treated optical elements may be used such as exposed lens (e.g. U.S. Pat. Nos. 2,326,634 and 2,354,018), embedded lens (e.g. U.S. Pat. No. 2,407,680), and encapsulated lens (e.g. U.S. Pat. No. 4,025,159) retroreflective sheeting. Retroreflective articles can be prepared by known methods including a method comprising the steps of: (i) forming a top coat on a release coated web (e.g. coating a solution of hydroxy-functional acrylic polyol and aliphatic polyfunctional isocyanate onto a release-coated paper web and then curing by conveying the coating through an oven at about 150xc2x0 C. for about 10 minutes); (ii) coating the exposed surface of the top coat with a liquid binder (e.g. coating a solution comprising an oil-free synthetic polyester resin and a butylated melamine resin); (iii) drying the binder to form an uncured tacky bead-bond layer; (iv) cascade-coating onto the bead-bond layer a plurality of glass microspheres forming a monolayer of embedded glass microspheres; (v) curing the bead-containing bead-bond layer to a non-tacky state (e.g. by heating to 150xc2x0 C.); forming a space coat layer over the bead-containing bead-bond layer (e.g. coating a 25% solids solution comprised of a polyvinylbutyral resin and a butylated melamine resin in a solvent and curing at 170xc2x0 C. for about 10 minutes); (vi) applying a reflective layer over the space coat layer (e.g. vapor deposition of aluminum metal at a thickness of about 100 nm); and stripping away the release-coated web. An adhesive layer is typically applied to the reflective layer (e.g. by coating a 0.025 mm thick layer of an aggressive acrylic pressure-sensitive adhesive onto a silicone-treated release liner and pressing the adhesive against the reflective layer).
The surface treated optical elements are also useful in pavement marking materials. The optical elements can be incorporated into coating compositions that generally comprise a film-forming material having a multiplicity of optical elements dispersed therein. The surface treated optical elements may also be used in drop-on applications for such purposes as highway lane striping in which the optical elements are simply dropped onto wet paint or hot thermoplastic and adhered thereto.
One typical pavement marking sheet is described in U.S. Pat. No. 4,248,932. This sheet material is a prefabricated strip adapted to be laid on and secured to pavement for such purposes as lane dividing lines and comprises a base sheet, such as a soft aluminum foil which is conformable to a roadway surface; a top layer (also called the support film or binder film) adhered to one surface of the base sheet and being very flexible and resistant to rupture; and a monolayer of surface treated optical elements such as transparent microsphere lens elements partially embedded in the top layer in a scattered or randomly separated manner. The pavement marking sheet construction may also include an adhesive (e.g., pressure sensitive, heat or solvent activated, or contact adhesive) on the bottom of the base sheet. The base sheet may be made of an elastomer such as acrylonitrile-butadiene polymer, polyurethane, or neoprene rubber. The top layer in which the surface treated microspheres are embedded is typically a polymer such as vinyl polymers, polyurethanes, epoxies, and polyesters. Alternatively, the surface treated microsphere lenses may be completely embedded in a layer of the pavement marking sheet.
Pavement marking sheets may be made by processes known in the art (see e.g. U.S. Pat. No. 4,248,932), one example comprising the steps of: (i) coating onto a base sheet of soft aluminum (50 micrometers thick) a mixture of resins (e.g., epoxy and acrylonitrile butadiene elastomer mixture), pigment (TiO2) and solvent (e.g., methyl ethyl ketone) to form the support film; (ii) dropping onto the wet surface of the support film ingredients a multiplicity of the surface treated optical elements of the invention; and curing the support film at 150xc2x0 C. for about 10 minutes. A layer of adhesive is then usually coated on the bottom of the base sheet.
Pigments or other coloring agents may be included in the top layer in an amount sufficient to color the sheet material for use as a traffic control marking. Titanium dioxide will typically be used for obtaining a white color; whereas, lead chromate will typically be used to provide a yellow color.
A rear projection screen is a sheet-like optical device having a relatively thin viewing layer that is placed at an image surface of an optical projection apparatus. Rear projection screen displays comprising glass microspheres embedded in an opaque matrix are known from U.S. Pat. No. 2,378,252, for example. Generally, the size of the microspheres is less than about 150 microns. For maximum brightness, the microspheres have an index of refraction of less than about 1.8 and preferably from about 1.45 to about 1.75. A plurality of the surface treated glass microspheres are attached to and are in intimate contact with a major surface of a transparent substrate. Alternatively, a diffusion layer can be formed by coating an optically inhomogeneous material as a separate layer onto the transparent substrate prior to application of the opaque binder and microspheres. Rear projection screens are prepared by i) providing a substrate (e.g. polyester, polycarbonate) having an opaque binder disposed thereon (e.g. acrylate loaded with carbon black to make it opaque); and ii) applying the surface treated glass microspheres under conditions effective to produce microspheres in optical contact with the substrate and embedded in the opaque matrix.
In some useful embodiments of the invention, a specular reflective means is provided by a layer of metal (e.g. aluminum) vapor-deposited on the surface treated microspheres. Another useful specular reflective means is a dielectric reflector which comprises one or more layers of a transparent material behind the microspheres, each layer having a refractive index of about 0.3 higher or lower than that of the adjacent layer or beads and each layer having an optical thickness corresponding to an odd numbered multiple of about xc2xc wavelength of light in the visible range. More detail on such dielectric reflectors is found in U.S. Pat. No. 3,700,305.
Objects and advantages of the invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in the examples, as well as other conditions and details, should not be construed to unduly limit the invention. All parts, percentages and ratios herein are by weight unless specified otherwise.
Test Methods
1. Heptane Float Testxe2x80x94A single layer of optical elements was spread on a clean inverted pint paint can lid. Heptane was slowly introduced with a syringe or dropper at the edge of the lid until it overflowed. The percentage of optical elements floating was estimated visually. In the absence of indicating otherwise, the beads were tested within 24 hours of being coated with the surface treatment.
2. Depth of Bead Embedment in Binderxe2x80x94A polyurethane liquid binder having the following components was prepared:
The binder was drawn down on a paper liner at thickness of 0.4 mm. Immediately thereafter, a plurality of the indicated glass beads were cascaded over the binder, maximizing the number of adhered beads per surface area of binder. The bead coated binder was then cured in an oven (100xc2x0 C. for 30 minutes was typically sufficient for the polyurethane binder). The bead-coated binder film was examined under a microscope. The sample passed when the optical elements were embedded to about 40-70% of their diameters.
3. Accelerated Aging Adhesionxe2x80x94A xc2xcxe2x80x3 (0.6 cm) by 1xe2x80x3 (2.5 cm) piece of cured bead-coated binder film, prepared for the Depth of Bead Embedment, was placed in a flask of boiling water for 24 hours. The aged sample was then inspected under a microscope to determine whether the optical elements remained embedded. The sample passed when the sample appeared approximately the same as the initial sample and the beads were difficult to remove with a dissection probe.
4. Coefficient of Retroreflection (RA), in cd/Lux/m2, was measured at an entrance angle of xe2x88x924.0 degrees and an observation angle of 0.2xc2x0 according to Procedure B of ASTM Standard E 809-94a. The photometer used for the measurements is described in U.S. Defensive Publication No. T987,003.
Optical Elements
Different types of reflective beads were employed to evaluate the effectiveness of the surface treatment of the invention. Type 1 reflective glass beads had an index of refraction of 2.3 and an average diameter of 71 microns. Type 2 reflective glass beads had an index of refraction of 2.3 and an average diameter of 56 microns. Both the Type 1 and Type 2 beads are representative of optical elements commonly used for reflective sheeting. The Type 1 and Type 2 glass beads had a density of about 4.6 and are composed of barium, titanium and zinc oxides as described in U.S. Pat. No. 3,493,403. Type 3 glass beads had an average diameter of 200 microns, an index of refraction of 1.75 and were prepared according to the teaching of U.S. Pat. No. 4,564,556.
Various fluoropolymers were evaluated to determine their efficacy for inducing float to optical elements. The following abbreviations are employed for the monomer components of the fluoropolymers.
VDF: vinylidene fluoride (CH2xe2x95x90CF2)
TFE: tetrafluoroethylene (CF2xe2x95x90CF2)
HFP: hexafluoropropylene (CF2xe2x95x90CFCF3)
PMVE: perfluoro(methyl vinyl ether) (CF2xe2x95x90CFxe2x80x94Oxe2x80x94CF3)
PPVE: perfluoro(propyl vinyl ether) (CF2xe2x95x90CFxe2x80x94Oxe2x80x94CF2CF2CF3)
PPVE-2: CF2xe2x95x90CFxe2x80x94Oxe2x80x94CF2CF(CF3)xe2x80x94Oxe2x80x94CF2CF2CF3
BTFE=bromotrifluoroethylene
Table 1, as follows, sets forth the molar concentrations of repeat units derived from the indicated monomer component for Fluoropolymers 1-3.
Synthesis of Fluoropolymer 1
A polymerization vessel with a total volume of 186.6 L, equipped with an impeller agitator system was charged with 105 L deionized water, 200 g 25% aqueous ammonia and 1780 g of a 30% ammonium perfluorooctanoate (APFO) solution in water. In three subsequent cycles, the vessel was degassed and subsequently charged with nitrogen to assure that all oxygen had been removed. The vessel was heated to 71xc2x0 C. and the agitation system set to 210 rpm. The vessel was charged with 19 g dichloromethane (CH2Cl2), 64 g bromotrifluoroethylene (BTFE), 7125 g PMVE and with 1927 g TFE to 16.0 bar absolute reaction pressure. The polymerization was initiated through the addition of 1763 g of a 20% solution of ammonium persulfate (APS) in water. As the reaction started, the reaction temperature of 71xc2x0 C. as well as the reaction pressure of 16.0 bar absolute was maintained by the feeding TFE, PMVE and BTFE into the gas phase. A feeding ratio of PMVE (kg)/TFE (kg) of 1.044 and BTFE (kg)/TFE (kg) of 0.015 was used. After feeding 24.29 kg TFE (353 min polymerization time), the monomer feed was interrupted and the monomer valves were closed. The reactor was vented and flushed with N2 in three cycles. The 158.3 kg polymer dispersion had a solids content of 31.0%. Latex particles having a diameter of 84 nm, as measured by dynamic light scattering, were obtained.
A small amount of this dispersion was worked up to raw gum by freeze coagulation overnight, and subsequent defrosting and washing with deionized water in three cycles. The raw gum was dried for 15 hours at 130xc2x0 C. under vacuum. The polymer had a Mooney viscosity, as measured according to ASTM D-1646, of ML 121xc2x0 C. (1+10) of 68.9 and a melt flow index (MFI), as measured according to ASTM D-1238, at 220xc2x0 C. with a 5 kg mass of 14.1 g/10 minutes. The polymer was evaluated by means of 19F-NMR, indicating a chemical composition of 64.3 mole % TFE, 35.1 mole % PMVE and 0.6 mole % BTFE.
Synthesis of Fluoropolymer 2
A polymerization vessel with a total volume of 7.2 l equipped with an impeller agitator system, was charged with 2000 g deionized water and 10 g 30% APFO solution. In three subsequent cycles, the vessel was degassed and subsequently charged with nitrogen to assure that all oxygen had been removed. The vessel was heated to 25xc2x0 C. and the agitation system set at 320 rpm. A pre-emulsion of PPVE-2 used for the precharge was prepared by emulsifying 100 g PPVE-2 and 10 g 30% APFO solution into 550 ml water with an Ultraturrax agitator at 24,000 rpm for 5 min. The pre-emulsion was further pressurized three times under high shear in a M-110EH Microfluidizer Processor (Microfluidizer Corporation) under 1500 bar pressure. The PPVE-2 pre-emulsion was charged into the reaction vessel. The vessel was further charged with 88.3 g VDF and 61.4 g TFE to a 9.0 bar absolute reaction pressure. A pre-emulsion of PPVE-2 for the continuous feed was prepared by emulsifying 675 g PPVE-2 and 10 g 30% APFO solution into 680 ml water. The polymerization was initiated by adding 417 mL of 0.1% aqueous KMnO4 solution. The amount of KMnO4 solution was continuously fed into the reaction vessel at such rate that the feed was completed within a polymerization time of 291 minutes. As the reaction started, the reaction temperature of 25xc2x0 C. as well as the reaction pressure of 9.0 bar absolute was maintained by feeding TFE and VDF into the gas phase with a feeding ratio of VDF (g)/TFE (g) of 1.92. The PPVE-2 (continuous feed) pre-emulsion was fed into the liquid phase with a feeding ratio of PPVE-2-pre-emulsion (g)/TFE (g) of 8.75. After feeding 156 g TFE, the monomer feed was interrupted and the monomer valves were closed. Within 10 minutes, the monomer gas phase was reacted down to a vessel pressure of 2.1 bar; then the reactor was vented and flushed with N2 in three cycles. A total of 4427 g of polymer dispersion was obtained having a solids content of 14.3%.
A small amount of this dispersion was worked up to raw gum by freeze coagulation overnight, subsequent defrosting and washing with deionized water in three cycles. The raw gum was dried for 15 hours at 130xc2x0 C. under vacuum. The polymer had a chemical composition of 23.1 mole % TFE, 69.3 mole % VDF and 4.6 mole % PPVE-2 as obtained by 1H/19F cross-integration NMR.
Synthesis of Fluoropolymer 3
A polymerization vessel with a total volume of 7.21, equipped with an impeller agitator system, was charged with 1500 g deionized water and 10 g 30% APFO solution. In three subsequent cycles, the vessel was degassed and subsequently charged with nitrogen to assure that all oxygen had been removed. The vessel was heated to 60xc2x0 C. and the agitation system set at 320 rpm. A pre-emulsion of PPVE-2 used for the precharge was prepared by emulsifying 100 g PPVE-2 and 10 g 30% APFO solution into 550 ml water with an Ultraturrax agitator at 24,000 rpm for 5 min. The pre-emulsion was further pressurized three times under high shear in a M-110EH Microfluidizer Processor (Microfluidizer Corporation) under 1500 bar pressure. The PPVE-2 pre-emulsion was charged into the reaction vessel. The vessel was further charged with 54.2 g VDF and 37.4 g TFE to a 6.0 bar absolute reaction pressure. A pre-emulsion of PPVE-2 for the continuous feed was prepared by emulsifying 675 g PPVE-2 and 10 g 30% APFO solution into 680 ml water. The polymerization was initiated by adding 3 g APS dissolved in a few milliliters water. As the reaction started, the reaction temperature of 60xc2x0 C. as well as the reaction pressure of 6.0 bar absolute was maintained by feeding TFE and VDF into the gas phase with a feeding ratio of VDF (g)/TFE (g) of 1.92. The PPVE-2 (continuous feed) pre-emulsion was fed into the liquid phase with a feeding ratio of PPVE-2-pre-emulsion (g)/TFE (g) of 8.75. After feeding 156 g TFE (24 minute reaction time), the monomer feed was interrupted and the monomer valves were closed. Within 10 min, the monomer gas phase was reacted down to a vessel pressure of 2.1 bar; then the reactor was vented and flushed with N2 in three cycles. 4055 g of polymer dispersion was obtained having a solids content of 24.9%.
A small amount of this dispersion was worked up to raw gum by freeze coagulation overnight, subsequent defrosting and washing with deionized water in three cycles. The raw gum is dried for 15 hours at 130xc2x0 C. under vacuum. The polymer had a chemical composition of 21.5 mole % TFE, 62.9 mole % VDF and 15.6 mole % PPVE-2 as obtained by 1H/19F cross-integration NMR.
Fluoropolymers 4-7
Fluoropolymers 4-7 are commercially available from Dyneon LLC, Oakdale, Minn. as latex dispersion polymers as set forth in Table II as follows:

Optical elements comprising a fluoropolymer surface treatment


A cooler for use in a computer or server is disclosed to include a holder frame, which has a plurality of wind holes and a rail extended along one long side of the flat elongated frame base thereof, and a fan module, which includes a rack with a sliding groove coupled to the holder frame and movable along the rail to one of a series of positions corresponding to the wind holes, a fan, and a locating frame holding the fan and insertable into the rack.

1. Field of the Invention
The present invention relates to a cooling apparatus for use in a personal computer, server, or industrial host computer and more particularly, to such a cooler that allows the user to adjust the position of the fan module conveniently after installation in the mainframe of a personal computer, server, or industrial host computer.
2. Description of the Related Art
Following fast development of high technology, lighter, thinner, shorter and smaller are becoming the key words for electronic instruments, including personal computers. Electronic instruments of new generation use sophisticated semiconductor chips or devices that release heat during operation. For example, an advanced personal computer uses a sophisticated CPU (Central Processing Unit) and GPU (Graphics Processing Unit) for processing any of a variety of data. These electronic devices release much heat during operation. The amount of heat energy released by these electronic devices during operation may be relatively increased subject to their operation speed. The working temperature of a CPU is normally at about 60˜95° C. In order to keep normal working of the CPU, GPU and other heat-releasing electronic devices in a computer or electronic apparatus, heat must be quickly carried away. Various coolers have been disclosed for use in computers and electronic apparatus to dissipate heat. FIG. 8 shows a prior art cooler used in a server's mainframe A. According to this design, the cooler comprises a frame bar A1 transversely mounted in side of the mainframe A, and a plurality of centrifugal type turbofans B installed in the frame bar A1. Each centrifugal type turbofan B has an exhaust hole B1 for output of a turbulent flow of air toward a specific electronic component part inside the mainframe A. This design of cooler is still not satisfactory in function. Because the centrifugal type turbofans B are affixed to the frame bar A1 at predetermined locations and because different models of electronic devices (CPU, chip, interface card or hard disk drive) have different arrangement and specifications, the exhaust hole B1 may be not accurately aimed at the respective heat source, thereby lowering the heat dissipation efficiency. Further, during operation of the centrifugal type turbofans B, produced currents of air may carry heat energy away from one electronic component part to other area inside the mainframe and heat energy may be accumulated in one corner inside the mainframe around other electronic component parts, causing the electronic apparatus unable to function normally. Further, because there are many component parts inside the mainframe A around the frame bar A1, it is difficult to mount/dismount the centrifugal type turbofans B with a hand tool, complicating the cleaning or repair work of the centrifugal type turbofans B.


A roll-to-roll reactor, which is assembled with an RTP (Rapid Thermal Process) compartment, a cooling compartment, and a series of modular heating sections, is provided. Its length is adjustable by adding or reducing numbers of the modular heating sections according to required reaction time and delivery speed of a continuous flexible workpiece. The reactor contains a reaction oven, assembled with a series of modular thermal control components, included inside a vacuum-tight reaction chamber. The oven temperature can be precisely controlled through combinations of heating elements, thermocouples and cooling tubing. The present reactor can be used for annealing and reaction of various precursor films on flexible substrates under vacuum and in inert or reactive gas ambient at temperatures ranging from room temperature to a thousand of Celsius degrees through a continuous roll-to-roll process.

Photovoltaic devices have recently been dramatically developed due to serious global warming and expectation of fossil fuel exhausting in the near future. The traditional photovoltaic devices, or solar cells, are based on silicon semiconductors such as single or multiple crystal silicon materials. However, these silicon materials are expensive, difficult for fabrication and in short supply in semiconductor industry. To overcome these problems, some substitutes such as thin film solar cells have been developed as the second generation of solar cells. At present, there are three main types of second generation thin film solar cells: amorphous silicon, CIGS and CdTe. In this thin film solar cell family, the CIGS solar cells possess the highest conversion efficiency that is as high as 20%, higher than 16% efficiency of the CdTe ones. In the periodic table of the elements, the elements of a CIGS absorber are located in Group IB-IIIA-VIA and the ones of CdTe absorber in Group IIB-VIA. These absorber materials all belong to multi-component p-type semiconductors. For such a semiconductor material, the distribution of different components, stoichiometry and crystal style may determine the quality of the materials.
Both of CIGS and CdTe solar cells contain a stack of absorber/buffer thin film layers to create an efficient photovoltaic heterojunction. A metal oxide window containing a highly resistive layer, which has a band gap to transmit the sunlight to the absorber/buffer interface, and a lowly resistive layer to minimize the resistive losses and provide electric contacts, is deposited onto the absorber/buffer surface. This kind of design significantly reduces the charge carrier recombination in the window layer and/or in the window/buffer interface because most of the charge carrier generation and separation are localized within the absorber layer. In general, CIGS solar cell is a typical case in Group IB-IIIA-VIA compound semiconductors comprising some of the Group IB (Cu, Ag, Au), Group IIIA (B, Al, Ga, In, Tl) and Group VIA (O, S, Se, Te, Po) elements of the periodic table, which are excellent absorber materials for thin film solar cells. In particular, compounds containing Cu, In, Ga, Se and S are generally referred to as CIGS(S), or Cu(In,Ga)(S,Se)2 or CuIn1-xGax (SySe1-y)n, where 0≦x≦1, 0≦y≦1 and n is approximately 2, and have already been applied in the solar cell structures that gave rise to conversion efficiencies approaching 20%. Here, Cu(In,Ga)(S,Se)2 means the whole family of compounds with Ga/(Ga+In) molar ratio varying from 0 to 1, and Se/(Se+S) molar ratio varying from 0 to 1. It should be noted that the molar ratios of Ga/(Ga+In) and Cu/(Ga+In) are very important factors to determine the compositions and the conversion efficiencies of the CIGS solar cells. In general, a good solar cell requires a ratio of Cu/(Ga+In) between 0.75 and 0.95, and Ga/(Ga+In) between 0.3 and 0.6. In comparison with CIGS, the composition of a CdTe solar cell is much simple. The content of Cd is usually close to 50% in the CdTe films. However, the Cd content may change after the deposition of a CdS layer and the subsequent annealing procedure. Close to the interface of the p-n-junction, for example, a CdSxTe1-x layer is formed with x usually not exceeding 0.06. However, x has a range changing from 0 to 1, which results in a compound from CdTe (x=0) to CdS (x=1).
Both CIGS and CdTe films has to be annealed to form a uniform stoichiometric compound. A CIGS film is usually annealed at a temperature between 350 and 600° C. in a typical two-stage fabrication procedure. For a CdTe solar cell, a CdS film may firstly be annealed in a superstrate configuration and a CdS/CdTe bilayer may be annealed in a substrate configuration. The importance of annealing is not only for the formation of a stoichiometric semiconductor material, but also for the determination of the crystal and boundary structures that may seriously affect the semiconductor properties. Therefore, the annealing should be well controlled in a carefully designed apparatus. For example, a CIGS film is usually going through a Rapid Thermal Processing (RTP) to approach a high temperature quickly at the beginning, followed by a reaction at the raised temperature in a super-pure inert, H2Se, H2S or Se atmosphere. After annealing, an n-type semiconductor buffer layer such as CdS, ZnS, or In2S3 should be deposited onto a CIGS semiconductor absorber. After then, transparent conductive oxide (TCO) materials, i.e., ZnO, SnO2, and ITO (indium-tin-oxide), should be deposited to form the solar cells.
The annealing process is sensitive to any impure species. For example, any residue oxygen or water inside a reactor may oxidize a CIGS absorber and destroy this semiconductor material. Therefore, an annealing reactor has to be totally isolated from the outside atmosphere. A vacuum apparatus should be helpful to clean the interior chambers at the beginning through some vacuum-inert gas cycles and remain a good sealing for the equipment during the reactions. However, most of high temperature reactors may not be designed as high vacuum apparatus. For these equipments, lots of inert gas has to be used to remain the annealing under a pure inert atmosphere. Especially for a roll-to-roll or reel-to-reel continuous process, more attention has to be paid to design a qualified reactor. Some high vacuum apparatus has recently been patented and assigned to SoloPower as a roll-to-roll reactor to anneal CIGS absorbers. For example, a few patent applications have been presented to provide methods and a high vacuum reactor to selenize and anneal CIGS absorbers in a roll-to-roll process, as shown in patent applications with publication numbers US2009/0183675A1, US2009/0148598A1 and US2010/0139557A1. With their designs, the reactor comprises a primary gap defined by a peripheral wall and an insert is placed within the gap to process the reaction of a continuously traveling workpiece. This insert processing gap is vacuum-tight and an inert or reactive gas can be introduced during the reaction under a certain temperature controlled by some heating elements surrounding the peripheral wall.
The main drawback for this reactor is that its integrated design requires a continuous piece of the peripheral wall. When the reaction needs time, the peripheral wall has to be designed very long or the travelling speed of the workpiece has to be very slow. The long peripheral wall may significantly increase the cost and the difficulty of fabrication, transportation and maintenance. In addition, the heating elements surrounding the body also significantly increase the temperature of the working environment. To solve these problems, the present invention provides a vacuum-tight reactor comprised with a series of modular sections. Moreover, the heating elements have been incorporated inside the reactor chamber that may be isolated with a vacuum chamber.

Assembled reactor for fabrications of thin film solar cell absorbers through roll-to-roll processes


Microfluidic devices for cell sorting or cell fractionation are disclosed. A microfluidic device can comprise one or more inlets, a first wall and a second wall, and two or more outlets. The first and second walls can be substantially planar to each other and the first wall having can have a plurality of ridges protruding from the first wall and defining a compression gap between the ridge and a surface of the second wall. The microfluidic device can also be a cell sorting device for sorting a plurality of cells based on one or more biophysical cellular properties including size, elasticity, viscosity, and/or viscoelasticity wherein the cells are subjected to one or more compressions due to the compression gap. Also disclosed are methods for cell sorting based on a variety of biophysical cellular properties.

In recent years, the links between disease states, cell function, and cell biophysical properties have been actively studied in a variety of pathologies, including cancer, malaria, and sickle cell anemia. Although determining biophysical properties of cells is currently employed in clinical care, particularly differences in cell density and size, utilizing new biophysical markers in conjunction with existing biochemical and biomolecular assays has the potential to greatly increase the sensitivity and specificity of detecting target cells.
Viscoelasticity is a biophysical property of cells that exhibits both elastic (reaction to deformation) and viscous (reaction to the rate of deformation) properties after undergoing stress and deformation. Viscoelasticity is a very important property of cells undergoing any dynamic process, such as the deformation of blood cells during circulatory flow. For example, changes in the ability of blood cells to deform and relax can result in severe complications. Whereas healthy leukocytes and erythrocytes deform when passing through capillaries and restore to their original shape after exit, highly viscous and stiffer leukemia cells, caused from altered cytoplasmic composition and enlarged nucleus, result in increased blood flow resistance. Variation in elasticity and viscosity of the red blood cells also affects the microcirculatory blood flow, which results in diminished ability to transport oxygen in sickle cells patients. Therefore, sorting and enriching cells by viscoelastic properties has tremendous clinical value.
Cell separation is also vital in several clinical diagnostic applications such as detection of cancer and infectious diseases. In hospitals and laboratories, cell separation is routinely carried out by centrifugation, size exclusion, and cell sorters based on fluorescent signals. The demand to obtain high-purity cell population at low cost spurred growing interest in exploring alternative cell separation methods based on microfluidics. For example, electric fields can be used to separate cells in microfluidic channels based on cell surface charge distribution. Magnetic fields can be used to separate cells with different surface proteins that bind magnetic particles in microfluidic channels. Also, acoustic fields can be used to separate cells of different sizes. In addition, research studies have shown that cell biomechanical properties including size and stiffness are biomarkers of diseases such as cancer and malaria. The changes in cell biomechanical properties are attributed to the transformation of cellular structures such as the cytoskeleton and nucleus. Therefore, cell biomechanical properties are phenotypes that could potentially be used for clinical diagnostics and therapies. Several recent studies have used hydrodynamic force and optical force to distinguish cell phenotypes based on cell mechanical properties.
Utilizing differences in cell biomechanical properties for disease detection would be greatly aided by means to sort cells biomechanically. Biomechanical properties are intrinsic to the cell and as such provide a label-free approach to enrichment without the need to discover and develop biomolecular reagents to aid detection. In addition, microfluidic platforms enable continuous sample processing, improve sensitivity, and utilize small sample volume. Recently, several microfluidic cell sorting approaches based on variations in cell biomechanical properties have been demonstrated. However, the ultimate purity of the separated cells is limited by the intrinsic variability and overlap of the biomechanical properties of different cell types, even if the average properties are substantially different. As a result, biomechanical approaches to cell enrichment are in general inferior to the best results achieved by cell sorting methods based on antibody binding of magnetic or fluorescent signals.

Microfluidic devices for cellular sorting


One example method of operation may include receiving a conference request from a moderator device, retrieving user profiles, included in the conference request, stored in a database, transmitting a conference access code to the user devices associated with the user profiles, retrieving and applying a moderator conference call agenda to a conference call at a conference call maturity time, and enacting one or more restrictions during the conference call based on the moderator conference call agenda.

Conventionally, when a person desires to setup a conference call at a later time, the ease of connecting to various different users via their computing/telephonic devices and ensuring a proper conference call format is usually not realized. A conference leader or moderator may have specific goals when conducting the conference. The goals may include having certain individuals on the conference bridge at a specific time, however, other goals may be desired as well which are not identified and are not translated to a single point of entry into the conference call by the invitees.

Conference call notification and setup configuration


A method for cartilage tissue engineering including fabricating a nanocomposite, injecting the nanocomposite into a defect site of cartilage, and forming a hydrogel in the defect site of the cartilage using a sol-gel transition responsive to increasing temperature of the nanocomposite from room temperature to 37° C. Fabricating a nanocomposite includes forming an activated copolymer by functionalizing a copolymer, forming a conjugated copolymer by grafting the activated copolymer to a polysaccharide, forming a protein-conjugated copolymer by crosslinking a protein with the conjugated copolymer, forming the nanocomposite by adding a plurality of nanoparticles to the protein-conjugated copolymer.

Articular cartilage is a flexible connective tissue in which chondrocytes are sparsely distributed into a highly organized extracellular matrix (ECM). The cartilage has low self-repair capacity which is attributed to the lack of chondrocyte mobility and the absence of progenitor cells and vascular networks in the ECM. Therefore, any cartilage damage which occurs because of injury, disease, trauma, or tumor continues to be one the most challenging clinical problems in orthopedics.
Various surgical procedures such as autograft and allograft have been used to treat cartilage damage, but each procedure has its own shortcomings. Autograft—the gold standard for cartilage repair suffers from donor site morbidity and restrained availability. On the other hand, allograft has some limitations including delayed vascular penetration and disease transmission. However, tissue engineering approaches are potential alternative methods for cartilage regeneration without limitations of surgical procedures.
Tissue engineering involves the use of a scaffold which acts as a template for tissue regeneration and provides a suitable environment for cellular growth. Among different scaffolds being developed for cartilage tissue engineering, hydrogels are of great interest due to their suitable properties that can mimic the physiochemical and biological properties of the hydrated ECM of cartilage. Nanostructured smart hydrogels with adjustable physicochemical properties have more structural similarity to natural ECM of cartilage and can up-regulate the interactions between cells and materials for faster tissue regeneration.
Therefore, there is a need for stable nanostructured hydrogels with tunable physicochemical properties for cartilage tissue engineering. Moreover, there is a need for tissue engineering scaffolds which may be stable for a longterm basis to support the growth of chondrocytes or other seeding cells.

Hydrogel for cartilage tissue regeneration


A butt welding apparatus, a butt welding method, and a product manufactured by the butt welding method involves two electrode rollers disposed on both the front and back sides of a thick sheet member and a thin sheet member whose end surfaces are butted. The electrode rollers bridge across the sheet members and are composed of small diameter portions on the side of the thick sheet member and large diameter portions on the side of the thin sheet member. The small diameter portions come into contact with and press the thick sheet member before the large diameter portions come into contact with the thin sheet member. Thus, the end surface of the thick sheet member swells and deforms toward the thin sheet member and reliably comes into contact with the end surface of the thin sheet member, and power is applied between the end surfaces, even if not polished.

1. Technical Field
The present invention relates to a butt welding apparatus for and a butt welding method of melting and jointing a butt portion where end surfaces of two welding sheet members are butted to each other with electric resistance heat generated by power applied between a pair of two electrode members, and to a butt welded product manufactured by the butt welding method.
2. Background Art
FIG. 21 shows a conventional butt welding apparatus. Two welding sheet members 101, 102 having the same thickness are set to the welding apparatus with end surfaces 101A, 102A butted to each other. Each of electrode rollers 103, 104 disposed on both the front and back surface sides of the sheet members 101, 102 has a thickness bridging across the sheet members 101, 102, and power is applied between the electrode rollers 103, 104 when the sheet members 101, 102 are welded. When the power is applied between the electrode rollers 103, 104 while they press both the sheet members 101, 102, the metal material of the sheet members 101, 102 is melted and a nugget 105 is formed in the sheet members 101, 102 at a central portion in the thickness thereof where an electric resistance is increased in the sheet members 101, 102 by the resistance heat of the power flowing in the thickness direction of both the sheet members 101, 102. Further, since the power also flows through a path passing through a butt portion 106 where the end surfaces 101A, 102A are butted to each other, the butt portion 106 is also melted at a central portion in the thickness thereof by the heat generated by the contact resistance of these end surfaces 101A, 102A. Thus, the nugget 105 is formed so as to bridge across both the sheet members 101, 102.
Then, when the electrode rollers 103, 104 move along the butt portion 106 while rolling or when the sheet members 101, 102 move with respect to the electrode rollers 103, 104 that are free to move at a definite position, the nugget 105, which can joint the sheet members 101, 102 with a large amount of strength, is formed over the entire length of the butt portion 106.
To form the nugget 105 bridging across both the sheet members 101, 102, an electrically conductive state must be secured by causing the end surface 101A of the sheet member 101 to be butted to come into contact with the end surface 102A of the sheet member 102. Thus, conventionally, both the end surfaces 101A, 102A are polished over the entire lengths thereof prior to butt welding so as to secure a contact state of the end surfaces 101A, 102A in the butt welding.
Therefore, conventionally, welding sheet members, for example, sheared in predetermined sizes by a shearing apparatus cannot be butt welded in a sheared state and must be subjected to finish processing to the end surfaces 101A, 102A prior to a welding operation, which increases a working cost and a working time.
An object of the present invention is to provide a butt welding apparatus and a butt welding method capable of eliminating processing such as polishing, and the like for finishing the end surfaces of two welding sheet members to be butted prior to butt welding, and to provide a butt welded product capable of being manufactured by the butt welding method.

This patent is subject to a terminal disclaimer.

Butt welding apparatus, butt welding method, and butt welded product


A lithographic apparatus comprising a control system, such as a motion control system, is presented. The control system includes an actuator for moving a moveable part, a feed-forward path from a setpoint input of the control system to the actuator, a feed-back loop, a feed-forward transfer function of the feed-forward path having a feed-forward transfer function part which is an inverse of a part of the actuator transfer function having a stable inverse, the actuator transfer function including a part having a stable inverse and a remainder potentially having an unstable inverse. The setpoint path includes a setpoint delay function, and the feed-forward transfer function further includes a second feed-forward transfer function part. A difference in delay between the setpoint delay function and the second feed-forward transfer function part is equal to a delay of the potentially unstable remainder of the actuator transfer function.

1. Field of the Invention
The present invention relates to a lithographic apparatus, a method for controlling a parameter of the lithographic apparatus, a control system and a method for dimensioning a transfer function in such a control system or lithographic apparatus.
2. Description of the Related Art
Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device may be used to generate a desired circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g. comprising one or more dies) on a substrate (silicon wafer) that has been coated with a layer of radiation-sensitive material (resist).
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the "scanning"—direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
Conventional control systems that control a position of a moveable part of an apparatus, often employ a control configuration that comprises a feed-forward and a feed-back controller. The feed-back, in a form of a feed-back loop, accounts for a high accuracy, a low steady state error and robustness against, for example, product variations and disturbances. The feed-forward accounts for a high speed of the control system and a fast response. Such control systems can be implemented in an analog form, such as, for example, analog electronics.
Alternatively, a part or all of the control system can be implemented in a numeric, i.e., a digital form. The numeric or digital parts can be implemented on a computer, controller or any other suitable numeric device. In an analog implementation a transfer function of the control system (or of parts thereof) can be expressed in the Laplace or s-domain, while in a numeric implementation such transfer function can be expressed in the z-domain.
The control system can be used for controlling any physical quantity, thus not only being limited to a control system for controlling a position of a movable part, however, can also be applied for e.g. a velocity, acceleration, a temperature, a slow, a light intensity, elimination, or any other physical quantity. In a lithographic apparatus, requirements on accuracy as well as on speed of the control system are generally strict. For this reason, a high performance control configuration comprising a feed-forward and a feed-back is frequently applied in a lithographic apparatus.
To obtain an optimal feed-forward, a transfer function of the feed-forward should comprise an inverse of a transfer function of the actuator, which is controlled by the control system. Hence, in the s-domain, if the actuator comprises an integrative transfer function, the feed-forward should comprise a differentiator, while in the z-domain if the actuator comprises a delay, the feed-forward should comprise a time lead thus compensating for the delay.
A problem that arises is that the inverse of the transfer function of the actuator is not always stable. In the s-domain, a pole in the transfer function of the actuator leads to a zero in the transfer function of the feed-forward and vice versa. Thus, if in the s-domain the transfer function of the actuator has a zero in the left half plane, this lead to a pole in the left half plane in the transfer function of the feed-forward. Thus, the transfer function of the feed-forward in the s-domain would be unstable. In a numeric implementation, in the z-domain, if the transfer function of the actuator has a zero which falls outside the unity circle in the z-domain, this will result in a pole outside the unity circle in the transfer function of the feed-forward. Thus, an unstable function of the feed-forward would result.
A known solution to avoid obtaining an unstable feed-forward transfer function in the numeric case, is to mirror the pole in the transfer function of the feed-forward which lies outside the unity circle, into the unity circle. Thus, if a pole in the feed-forward transfer function occurs as z=−4 than it is mirrored to z=−¼, thus being mirrored from outside the unity circle into the unity circle hence resulting in a stable transfer function in the feed-forward. A disadvantage of this solution, however, is that by using this mirroring operation, an inaccurate approximation of the feed-forward is created, since the operation, especially the phase performance of the feed-forward, has been changed. Thus, by this mirroring operation, a stable transfer function of the feed-forward is created but at the cost of a decrease in performance of the control system.
Whether or not a transfer function in the z-domain is unstable does not solely depend on the transfer function having a pole outside the unity circle. For example, ratios between a delay time of the actuator (and hence the position of the pole response zero) and a sample time of the numeric system (i.e., the time corresponding to a unity delay) may influence pole instability. Hence, in this application, when reference is made to an unstable pole, this is to be interpreted as also comprising a potentially unstable pole, thus a pole which could become unstable depending on the ratio between the position of the pole and the sample time.

Lithographic motion control system and method


Provided are techniques for a Data-Partitioned Secondary Index (DPSI) partition level join. While using a Data-Partitioned Secondary Index (DPSI) to perform a join of an outer table and an inner table, a different task from multiple tasks is assigned to each partition of the inner table. With each task, a join is performed of the outer table and the assigned partition of the inner table using the DPSI to generate results. The results from each different task are merged.

As technology advances, partitioned tablespaces are widely adopted as an effective way to manage larger volumes of data.
On a partitioned tablespace, there are two common types of secondary indexes that a user may create: 1) Non-Partitioned (Secondary) Index (NPI or NPSI, and also referred to as a global index by some Database Management Systems (DBMSs)) or 2) a Data-Partitioned Secondary Index (DPSI, also referred to as a local index by some DBMSs). NPI may be described as one massive index created that spans all partitions. DPSI may be described as a group of many smaller indexes, where one index is created for each partition. Comparing the two types of secondary indexes, DPSI allows the user to manage the index and data at the partition level. Therefore, DPSI provides better data availability and better utility performance.
DPSI was first introduced to improve data availability during utility maintenance. With conventional systems, in terms of query performance, a DPSI is generally not as effective as an NPI. As a result, users can not fully adopt DPSI to take advantage of its utility benefits. Typically, customers use NPIs to maintain query performance.
The following is an example Structured Query Language (SQL) statement:
SELECT *FROMCUSTOMER C,AREACODES AWHEREC.STATE = A.STATE
With the above SQL statement, there is a 2-table join between tables CUSTOMER and AREACODES, and the join predicate is CUSTOMER.STATE=AREACODES.STATE. For this example, a DPSI is created on AREACODES.STATE. For each probing value from the outer table (CUSTOMER.STATE), processing stripes through multiple partitions of the inner table (AREACODES.STATE) to find qualified rows. Then, the striping pattern is repeated for each next probing from the outer table. Because of this striping pattern, there is no sequential pattern detection, the benefit of index look-aside is decreased, and random Input/Output (I/O) is increased, which leads to more Central Processing Unit (CPU) getpage calls. Then, the query suffers from longer response time and CPU time.
This is a random I/O problem related to a standard nested loop join. Thus, customers keep the NPIs around in order to maintain optimal query performance for joins. This limits the adoption of DPSIs for customers with large partitioned tables.
However, there are potential solutions to avoid random I/O on the inner partitioned table by using other join methods such as Hash Join or Merge-Scan (Sort-Merge) Join. However, these join techniques may require significant resources given that they require a materialization of the inner table for joining very large tables. Thus, existing hash join or merge scan join may not scale due to insufficient resources or due to reprocessing the inner table to accommodate insufficient memory (as is common with hash join).
Some systems offer partition level join operations involving hash join that support bushy-tree join permutation logic or DBMSs that provide a comprehensive hash join implementation.

Data-partitioned secondary index (DPSI) partition level join

International Business Machines Corporation


A power control and indicator device for coupling to an acoustic string instrument preamp is provided. The device includes a light emitting diode having an anode terminal and a cathode terminal, a switch having a first terminal and a second terminal, the switch having a closed position that closes a circuit between the first and second terminal and an open position that opens the circuit between the first and second terminal, a battery connector having a positive terminal and a negative terminal, the battery connector adapted to couple to a battery, a preamp connector having a positive terminal and a negative terminal, whereby with a battery connected to the battery connector, wherein with the switch in the closed position, the light emitting diode is powered and illuminates and the battery connector is coupled to the preamp connector, the battery provides power to the preamp connector, and wherein with the switch in the open position, the light emitting diode is not powered and does not illuminate and the battery connector is not coupled to the preamp connector and the battery does not provide power to the preamp connector.

The invention is applicable to various string instruments. However, the disclosure will be directed primarily to acoustic guitars. It will be understood that the teachings of the invention are applicable to other string instruments.
Electric guitars are often amplified by means of a magnetic pickup built-in to the electric guitar. Typically one or more so-called magnetic pickups are used in electric guitars. The pick-up of the electric guitar may be connected to potentiometers for volume and tone and a two-conductor output jack. A guitar cable typically has a two-conductor male connector at each end of the cable. One connector plugs in to the guitar output connector and the other connector of the cable plugs in to an amplifier. The electric signal developed by the magnetic pick is coupled to the amplifier via the guitar cable. Traditionally, there is no electrical amplification of the signal from the magnetic pickup within the electric guitar.
In contrast, traditionally, the acoustic guitar did not include electrical amplification. However, amplification of the acoustic guitars is desirable for various reasons. For example, for performances it is often necessary to amply the sound level of an acoustic guitar. One manner of amplification utilizes a pickup on the acoustic guitar.
Due to the inherent difference in constructions between an electrical guitar and an acoustic guitar, a magnetic pickup is often not desirable in an acoustic guitar. Rather, a piezoelectric pickup is usually preferred. The piezoelectric pickup more accurately produces an electrical signal reflecting the tonality of the acoustic guitar.
However, the piezoelectric pickup produces a weaker signal in comparison to the magnetic pickup. To address this issue, a preamp is often located in the acoustic guitar between the piezoelectric pickup and the guitar output connector. Thus, the guitar cable coupled to the output connector of the acoustic guitar will receive a stronger signal than the signal output from the piezoelectric pickup. The preamp is powered by a battery, such as a typical 9 volt battery, also located in the acoustic guitar. This arrangement has been very successful in general.
Typically when the guitar cable is plugged in to the acoustic guitar and an amplifier, the preamp circuit is complete and the battery is under load. When the battery discharges to a level unable to power the preamp, the signal output from the piezoelectric pickup is effectively useless and the acoustic guitar will not be electrically amplified. During a performance, for example, it will become necessary for the performer to stop playing and change the battery. In many preamp systems, this requires the time consuming loosening or removing of some or all of the strings, in order to reach and replace the battery located within the acoustic guitar.
In preparation of a performance, the guitarist may setup the guitar, preamp and amplifier for the purpose of a sound check or the like. Once ready, the scheduled performance may not begin immediately or the player may take a break between songs. To conserve the battery of the preamp, or for some other reason, the performer or assistant may unplug the guitar cable from the acoustic guitar preamp in order to disconnect the battery from the circuit. However, if the volume at the amplifier or soundboard is not turned down first, unplugging the guitar cable is often met with a short but very load sound which may damage speakers and irritate the audience and others. Often, the amplifier may not be close to the player or under the player's control, contributing to the occasion of unplugging the cable without reducing the volume.
There is a need to improve the battery life of acoustic guitar preamps. In addition, there is a desire to minimize or avoid creating a loud sound when unplugging the guitar cable.

Power control and indicator for preamp of acoustic string instrument


A high fill factor spatial light modulator. The spatial light modulator includes a device layer coupled to a support base. The device layer includes a mirror plate and a coplanar flexible member. The spatial light modulator also includes a patterned spacer layer coupled to the mirror plate. In some embodiments, the spacer layer is fabricated from an aluminum layer. The method further includes a reflective layer coupled to the spacer layer.

This present invention relates generally to manufacturing objects. More particularly, the invention relates to a method and structure for fabricating a spatial light modulator with a high fill factor. Merely by way of example, the invention has been applied to the formation of a spatial light modulator having a torsion spring hinge and mirror plate positioned in the same plane with a uniform reflective layer covering the torsion spring hinge. The method and device can be applied to spatial light modulators as well as other devices, for example, micro-electromechanical sensors, detectors, and displays.
Spatial light modulators (SLMs) have numerous applications in the areas of optical information processing, projection displays, video and graphics monitors, televisions, and electrophotographic printing. Reflective SLMs are devices that modulate incident light in a spatial pattern to reflect an image corresponding to an electrical or optical input. The incident light may be modulated in phase, intensity, polarization, or deflection direction. A reflective SLM is typically comprised of an area or two-dimensional array of addressable picture elements (pixels) capable of reflecting incident light. A key parameter of SLMs, especially in display applications, is the portion of the optically active area to the pixel area (also measured as the fraction of the SLM's surface area that is reflective to the total surface area of the SLM, also called the "fill ratio" or "fill factor"). A high fill factor is desirable for some applications.
Some conventional SLMs utilize designs that include substantial non-reflective areas on their surfaces, reducing the SLMs reflective efficiency. Another problem that reduces reflective efficiency with some SLM designs, particularly in some top hanging mirror designs, is large exposed hinge surface areas. These exposed hinge surface areas result in scattering and diffraction due to the exposed hinge structure, which negatively impacts contrast ratio in display applications, among other parameters.
Other conventional SLMs require multiple layers including a separate layer for the mirrors, hinges, electrodes and/or control circuitry. Manufacturing such a multi-layer SLM requires the use of multi-layer thin film stacking and etching techniques and processes. Use of these techniques and processes may be expensive and produce lower than desired yields. For example, the use of these techniques sometimes involves extensive deposition and removal of sacrificial materials underneath the surface of the mirror plates. Multi-layer thin film deposition and stacking underneath the surface of the mirror plate typically results in rougher mirror surfaces, thereby reducing the reflective efficiency of the mirrors. Moreover, having the mirror and the hinge in a different layer or substrate results in translational displacement upon deflection of the mirror. With translational displacements, the mirrors in an array must be spaced to avoid mechanical interference among adjacent mirrors. Because the mirrors in the array cannot be located too closely to the other mirrors in the array, the SLM suffers from a lower than optimal optically active area or lower fill factor.
Thus, there is a need in the art for a spatial light modulator with improved reflective efficiency, SLM device long-term reliability, and simplified manufacturing processes.

Method and structure for high fill factor spatial light modulator with integrated spacer layer


A fuel injector for fuel-injection systems of internal combustion engines has a solenoid coil; a valve needle that is operatively connected to the solenoid coil and acted upon by a restoring spring in a closing direction, in order to actuate a valve-closure member which, together with a valve-seat surface formed at a valve-seat member, forms a sealing seat; and at least two spray-discharge orifices which are formed in the valve-seat member. The spray-discharge orifices are formed in the valve-seat member in such a way that they are shielded from mixture flows circulating in a combustion chamber of the internal combustion engine.

German Patent Application No. 198 04 463 describes a fuel-injection system for a mixture-compressing internal combustion engine having external ignition, which includes a fuel injector injecting fuel into a combustion chamber formed by a piston/cylinder construction, and which includes a spark plug projecting into the combustion chamber. The fuel injector is provided with at least one row of injection orifices distributed over the circumference of the fuel injector. By a selective injection of fuel via the injection orifices, a jet-controlled combustion method is implemented by a mixture cloud being formed using at least one jet.
What is disadvantageous about the fuel injector known from the aforementioned printed publication, in particular, is the deposit formation in the spray-discharge orifices. These deposits clog the orifices and cause an unacceptable reduction in the flow rate through the injector. This leads to malfunctions of the internal combustion engine.


Disclosed is a method and system that receives sensor information from each of a plurality of sensors. Each sensor in the plurality is associated with a vehicle. The sensor information includes location coordinates of each vehicle in the plurality. The sensor information associated with each vehicle in the plurality then is translated to parking statistics information. In one embodiment, the translation is based on an aggregate of sensor information corresponding to the plurality of vehicles. The system then communicates parking statistics information to the vehicle.

Parking space availability is a major problem in crowded areas, particularly urban areas. The importance of better parking systems in urban areas has been recognized recently as one of the most important avenues for betterment of urban infrastructure. One study estimated a loss of $78 billion in one year in the form of 4.2 billion lost hours and 2.9 billion gallons of wasted gasoline in the United States alone. Several projects recently have sought to address this issue through the design of mobile systems that collect traffic congestion information to improve route finding and trip planning. Unfortunately, a significant portion of traffic congestion and travel delays are experienced in downtown areas where it is not always possible to reroute a driver. In these densely populated urban areas, congestion and travel delays also are due to parking. In one study, researchers found in one small business district of Los Angeles that, over the course of a year, vehicles looking for parking created the equivalent of 38 trips around the world, burning 47,000 gallons of gasoline and producing 730 tons of carbon dioxide. Clearly, addressing the problems associated with parking in downtown areas would have significant societal impact, both economically and ecologically.
Prior attempts to solve this problem often have focused on monitoring the presence or absence of a vehicle over each parking spot using a dedicated sensor. These attempts typically rely on fixed sensors installed by municipalities in the ground or on parking meters. This results in a large fixed cost for installation and operation in order to cover parking spaces at a city-wide level (e.g., millions of dollars to cover a small percentage of the total number of parking spots).
As a result, there remains a need to better address problems associated with parking space availability.

Vehicular information systems and methods

RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY