JP5602828B2 - Solar reflector having protective coating and method of manufacturing the same - Google Patents

Description

  This application claims the benefit of US Provisional Application No. 61 / 164,047, filed Mar. 27, 2009 and entitled “ALKALI BARRIER LAYER”. Application 61 / 164,047 is hereby incorporated by reference in its entirety.

  This application is based on Abhinav Handari, Harry Buhay, William R., et al. Siskos, and James P. US patent application Ser. No. 12 / 709,045, filed Feb. 19, 2010 under the name of Thiel and entitled “SOLAR REFECTING MIRROR HAVING A PROTECTIVE COATING AND METHOD OF MAKING SAME”; Based on the subject matter of US patent application Ser. No. 12 / 709,091, filed on 19 February 2010 in the name of Thiel and entitled “A SOLAR REFINGING MIRROR AND METHOD OF MAKING SAME”, This application claims the benefit of US patent application Ser. No. 12 / 709,045 and US patent application Ser. No. 12 / 709,091. Application 12 / 709,045 and US patent application 12 / 709,091 are hereby incorporated by reference in their entirety.

  The present invention relates to a solar reflector such as a parabolic shaped solar reflector glass mirror having a protective coating such as an alkali barrier layer, and a method of manufacturing the same, and more particularly, for example, sodium ions on the concave surface of the mirror. It is related with the alkali barrier layer on the concave surface of a mirror for preventing precipitation of alkali ions, such as. Preferred alkali barrier layers of the present invention have scratch resistance and chemical resistance to prevent abrasion of the concave surface of the mirror.

  Currently, for example, and not limited to this description, to improve the efficiency of solar mirrors such as parabolic shaped mirrors used to reflect solar rays to devices located at the focal point of the parabolic mirror, etc. There is interest in increasing the efficiency of solar heat collectors. This device is generally of the type known in the art for converting solar energy into another form of available energy, for example electrical energy. In another embodiment of the prior art, the parabolic mirror is a primary mirror that is positioned to a secondary mirror that is positioned relative to the focal point of the primary mirror to reflect sunlight into the conversion device. And reflect sunlight.

  In general, a parabolic shaped mirror includes a parabolic shaped substrate, which has a reflective surface, such as a silver coating, on the convex surface of the shaped substrate. Preferred materials for this molded substrate include a high yield when a flat glass sheet is formed into a parabolic sheet or a parabolic substrate, a low production cost of the flat glass sheet, and a molded glass substrate. Soda lime silica glass because of its high yield and low cost when applying solar reflective coatings on its surface.

  Soda lime silica glass is an acceptable material for substrates for solar reflectors, but there are limitations to the use of this glass. More specifically, in the forming process, the flat glass sheet is heated to a temperature exceeding 649 ° C. (hereinafter referred to as F) (1200 ° F.) and formed into a parabolic shape. During heating and molding of the glass sheet, alkali ions such as sodium ions in the glass sheet are diffused or eluted from the glass sheet to the outside. Further, when the parabolic shaped glass substrate is exposed to solar energy, for example, exposure to the environment over a long period of time, additional sodium ions are eluted from the glass substrate. As will be appreciated by those skilled in the art, the elution or dissipation of sodium ions from the glass is an expected situation, and the process is slow at low temperatures. However, heating of the glass and / or long-term environmental exposure of the glass to solar energy accelerates the elution or dissipation of sodium ions from the glass and increases the amount of sodium ions eluted from the glass. Sodium ions eluted from the glass react with moisture in the atmosphere and change from sodium ions to sodium compounds such as sodium hydroxide and sodium carbonate. The sodium compound may etch the surface of the glass and may be deposited as a precipitate on the surface of the glass. This sodium compound deposit reduces the visible light transmission through the glass, for example in the case of a parabolic shaped glass substrate, and transmits solar energy to the reflective coating on the convex surface of the shaped glass substrate. Reducing the rate of transmission of solar energy reflected from the reflective coating and passing through the shaped glass substrate toward the concave surface of the shaped glass substrate.

  Moreover, as will be appreciated by those skilled in the art, the surface of the shaped glass substrate is a specular surface, and solar energy is incident on the concave surface of the glass substrate as parallel rays. Parallel rays are reflected from the concave surface and reflected as convergent rays from the reflective coating. The sodium compound precipitate on the concave glass surface changes the specular surface to a non-specular or scattering surface, so that the light reflected from the precipitate and passing through the precipitate is focused on the primary mirror. Oriented away from In this specification, the term “specular reflection surface” means a light reflection surface when a light ray incident on the reflection surface has an incident angle equal to the reflection angle. As used herein, the term “non-specular or scattering surface” means a reflective surface when light rays incident on the reflective surface have an incident angle different from the reflective angle.

  Another limitation of glass is that care must be taken to avoid scratching the glass surface. Scratches on the glass surface can still turn the specular surface into a non-specular or scattering surface. As will be appreciated by those skilled in the art, when a reflective concave surface changes from a specular reflective surface to a non-specular reflective surface or a scattering surface, the percentage of reflected sunlight that is incident on the focal point of the parabolic shaped mirror is: Lowers and reduces the efficiency of the solar reflector.

  Current techniques for removing and / or eliminating sodium compound deposits from the concave surface of a parabolic mirror include cleaning the surface and / or the mirror in a sealed chamber containing an inert gas. Encapsulating a concave surface to prevent sodium ions from forming precipitates. Current techniques for removing scratches include buffing the surface of the glass sheet with scratches. All of these techniques for maintaining the surface of the solar mirror as a specular surface are very expensive.

  For example, U.S. Patent No. 4,238,276, U.S. Patent No. 5,270,615, U.S. Patent No. 5,830,252, and U.S. Patent No. 6,027,766, U.S. Patent Application No. 08/597343. , And U.S. Patent Application Publication No. 2007 / 0275253A1, etc. are known in the art. One of the limitations of currently available alkali barrier layers and / or scratch-resistant layers is that they are effective for use on flat or molded surfaces of glass substrates, for example, parabolic mirrors. It is not effective for use on flat surfaces that are later shaped into curved surfaces such as concave surfaces. In the prior art, recognition or description of this problem to be solved when a substrate coated with a barrier layer and / or a scratch resistant layer is molded from a flat coated substrate to a parabolic molded coated substrate. But there are few, if any. More particularly, in the prior art, cracks in the coating and / or buckling of the coating as the coated glass profile changes from a glass piece having a flat surface to a shaped glass substrate having a concave surface. There are few, if any, descriptions of how to solve the problem. As will be understood by the present application, when the barrier coating is stressed, the coating cracks, the sodium ions are exposed to the atmosphere, forming precipitates of sodium compounds on the surface of the glass substrate, and / or Or, when the barrier coating and / or scratch resistant coating buckles, this surface changes from a specular reflective surface to a non-specular reflective surface or scattering surface.

  As will now be understood by those skilled in the art, having scratch-resistant properties prevents the concave surfaces of the primary and secondary mirrors from changing from specular to non-specular or scattering surfaces. It is advantageous to provide an alkaline barrier coating or layer, for example a sodium ion barrier coating.

  The present invention is a solar reflector having a curved reflecting surface, and in particular, a transparent substrate having a convex surface and an opposite concave surface, a reflective coating covering the convex surface, and an alkali barrier layer covering the concave surface. It is related with the solar reflector provided. This reflective coating reflects selected wavelengths of the electromagnetic spectrum.

  Furthermore, the present invention is a method of manufacturing a solar reflector having a curved reflecting surface, in particular, providing a flat transparent sheet, which is molded to form a convex surface and an opposite concave surface and focal area. The present invention relates to a production method by forming a molded transparent substrate having a surface, applying a reflective coating over the convex surface of the substrate, and forming an alkali barrier layer over the concave surface of the substrate.

  Furthermore, the invention relates to an alkaline barrier coating comprising inter alia oxides consisting of silicon and aluminum.

  The present invention further relates to a solar reflector having a curved reflective surface. The mirror includes, among other things, a plurality of transparent shaped segments, and holding the segments together, having a convex surface and an opposite concave surface, covering a focal area and one of these surfaces of the shaped substrate. A fixed installation that forms a shaped transparent substrate with a reflective coating, which reflects visible and infrared waves of the electromagnetic spectrum in the direction of the focal area of the shaped transparent substrate.

  Furthermore, the present invention relates to a method for manufacturing a shaped solar reflector. This method includes, among other things, forming two or more flat transparent segments to form two or more molded transparent segments (each of which is part of a molded glass transparent substrate (1 / (molded Including all segments of the transparent substrate)), and fixing the molded transparent segments together to form a molded transparent substrate (this molded transparent substrate comprises, inter alia, a convex surface and an opposite concave surface having a focal zone) ), Forming a reflective coating over at least one of the surfaces of the transparent substrate.

1 is an elevational plan view of an array of prior art solar thermal integrators. FIG.

1 is an isometric view of a prior art solar heat accumulator. FIG. It is an enlarged view of the sunlight which injects into the concave surface of the solar-heat-integrator of FIG.

It is a figure similar to the figure of FIG. 2 which shows the solar mirror of this invention.

1 is an isometric view of a glass piece having a coating of the present invention. FIG. The coating of FIG. 4 has been partially removed for clarity.

FIG. 5 is a side elevational view of the vacuum forming die with the glass piece of FIG. 4 attached to the open end of the vacuum forming die. It is sectional drawing of the vacuum forming method in which the shaping | molding glass substrate of this invention is located inside a vacuum forming die.

It is an elevational top view of the molded glass substrate of the present invention showing a pattern of circumferential compressive strain at the outer periphery of the molded glass substrate.

FIG. 7 is a view taken along line 7-7 of FIG. 6, showing in particular the transition strain line of the shaped glass substrate.

FIG. 8 is a view taken along line 8-8 of FIG. 7 showing the outer peripheral tensile strain and radial tensile strain of the molded glass substrate.

FIG. 5 is an isometric view of one segment of the glass piece illustrated in FIG. 4. FIG. 9B is an isometric view of the segment illustrated in FIG. 9A after a glass piece has been formed into a shaped glass substrate. The coating has peaks and valleys. FIG. 9B is a view similar to the view of FIG. 9B showing one segment of a shaped glass substrate made in accordance with the teachings of the present invention. The coating has a reduced number of peaks and valleys, a reduced mountain height and a shallow valley depth.

FIG. 5 is a view similar to the view of FIG. 4 showing another embodiment of the present invention for making the shaped solar mirror of the present invention, including cutting the coated glass into multiple segments.

FIG. 11 is an isometric top view of a glass sheet press working apparatus that can be used in the practice of the present invention to form a plurality of segments cut from the coated glass of FIG.

It is a top view of the shaping | molding solar mirror of this invention produced by joining shaping | molding glass segments.

It is a figure similar to FIG. 3 which shows the shaping | molding solar mirror of this invention produced with the shape | molded glass segment.

It is a figure similar to FIG. 4 which shows the coating shield which covers a circular glass piece.

It is an elevation surface top view of a shaped glass substrate at a position between a transition strain line and the bottom of the shaped glass substrate. This figure shows cracks in the peripheral and radial tension zones of the shaped glass substrate. The shaded lines of the coating are not shown for clarity.

FIG. 5 is a cross-sectional side view of multiple sections of the flat glass piece of FIG. 4 having the barrier coating and / or scratch resistant coating of the present invention on both surfaces of the glass piece. A plurality of the flat glass pieces of FIG. 4 having the barrier coating and / or scratch resistant coating of the present invention on both surfaces of the glass pieces, and optionally having a reflective surface covering one side of the glass piece. It is a section side view of a section. A plurality of flat glass pieces of FIG. 4 having the barrier coating and / or scratch resistant coating of the present invention on one surface of the glass piece, and optionally having a reflective surface covering one side of the glass piece. It is a section side view of a section. A plurality of the flat glass pieces of FIG. 4 having the barrier coating and / or scratch resistant coating of the present invention on both surfaces of the glass pieces, and optionally having a reflective surface covering one side of the glass piece. It is a section side view of a section.

1 is a side view of one section of a photovoltaic cell having a barrier layer of the present invention. FIG.

  In the following description, terms relating to space or direction such as “inward”, “outward”, “left”, “right”, “up”, “down”, “horizontal”, “vertical”, etc. It relates to the present invention shown in the drawings. However, it is to be understood that the present invention can take a variety of alternative orientations and therefore such terms should not be considered limiting. Moreover, as used in the specification and claims, all numbers representing dimensions, physical features, etc. should be understood as being modified in all instances by the term “about”. Accordingly, unless indicated otherwise, the numerical values set forth in the following specification and claims can vary depending on the desired properties sought to be obtained by the present invention. At least, and not as an attempt to limit the application of the doctrine of claims, each numerical parameter is interpreted at least in light of the reported significant digits and by the application of conventional rounding techniques. Should be. Moreover, all ranges disclosed herein are to be understood to encompass any subranges subsumed therein. For example, a range stated as “1 to 10” is any sub-range between (and including) the minimum value 1 and the maximum value 10, ie, for example, 1 to 6.7, or 3.2 It should be considered to include any sub-range that starts with a minimum value of 1 and ends with a maximum value of 10 or less, such as 8.1, or 5.5 to 10. Further, in this specification, the expression “applied over” or “provided over” means applied over or provided over, but not necessarily on the surface. It is not in contact. For example, a material “applied over” a substrate or substrate surface excludes the presence of one or more materials of the same or different composition located between the material being deposited and the substrate or substrate surface. Not what you want.

  Before discussing a plurality of non-limiting examples of the present invention, the invention is not limited in its application to the details of the specific non-limiting examples shown and discussed herein, because It should be understood that the invention is because other embodiments are possible. Furthermore, the terminology used herein to discuss the present invention is for purposes of illustration and not limitation. Moreover, unless otherwise indicated, in the following description, like numerals refer to like elements.

  The barrier coating or barrier layer of the present invention is a silicon / aluminum oxide coating discussed in detail below. This silicon / aluminum oxide coating of the present invention is also suitable for chemical damage such as mechanical damage such as scratches, and chemical corrosion such as with materials having a pH in the range of 7-14, especially 9-14. Provides protection against damage. The following description of the barrier properties of this coating of the present invention also applies to the scratch resistance properties of the coating of the present invention unless otherwise indicated. In this regard, at coating thicknesses less than 50 nanometers (hereinafter also referred to as “nm”), the silicon / aluminum oxide coating of the present invention loses resistance to mechanical and chemical damage.

  For the sake of clarity, the terms “alkali barrier layer or alkali barrier coating” and “sodium ion barrier layer or sodium ion barrier coating” are used on the surface that this layer or coating is applied over or on. A layer or coating that acts as a barrier to prevent or limit the formation of alkaline or sodium precipitates, and optionally has resistance to prevent or limit mechanical and / or chemical damage to this surface Means. A “protective layer or coating” has a resistance that prevents or limits mechanical and / or chemical damage to the surface covered or on which this layer or coating is covered and / or By means of a layer or coating capable of limiting the formation of alkali or sodium precipitates on the surface.

  Covers or above the substrate surface, which is a barrier to alkali ions (eg, a compound that prevents sodium ions from reacting with moisture in the atmosphere and so that sodium ions are deposited on the glass surface as described above, for example. A non-inventive method that utilizes a magnetron sputtering vacuum deposition (hereinafter also referred to as “MSVD”) coating process to apply a coating or layer (which prevents conversion to sodium compounds such as sodium hydroxide and sodium carbonate). Limited examples are discussed. As will be appreciated, the present invention is not limited to this coating process, which involves applying a barrier film or layer of alkali ions, such as sodium ions, on or over the glass surface. It can be any coating process that covers or coats.

  The following description is directed to non-limiting examples of applying an alkali ion barrier coating or an alkali ion barrier layer. Unless indicated otherwise, this description also applies to the scratch-resistant coating or scratch-resistant layer.

  As will be appreciated, the glass substrate or piece of glass is not a limitation of the present invention, and the glass can be a glass of any composition. The glass can be transparent glass or colored glass and / or the glass can be annealed glass, heat tempered glass, or tempered glass. The glass piece or glass substrate can have any shape, thickness, and size. Non-limiting examples of the present invention are presented as examples relating to solar reflectors. However, the present invention is not limited to solar reflectors, but is a transparent material for industrial and home windows, glass shower doors, aerial aircraft, spacecraft, landcraft, and underwater aircraft, coated bottles, thin film light Implementation is possible in the production of coated glass for electromotive applications, electrothermal glass for anti-fog commercial refrigerators, and glass for furniture applications.

  In the following description, the shaped solar reflector is referred to as a parabolic shaped reflector, but the invention is not limited thereto, and unless otherwise indicated, for example, but not limited to the invention, It can be implemented with any mirror having a curved reflective surface and a focal point or focal area, such as a surface shaped mirror and a spherical shaped mirror. “Focus” and “focal zone” are defined as positions where more than 80% of the sunlight is reflected from this mirror focus. The size and position of the “focal zone” is not a limitation of the present invention, and in one non-limiting embodiment of the present invention, the focal zone is one fifth (1/5) of the reflective area of the mirror. Is less than.

  FIG. 1 shows an array 18 of a prior art shaped solar heat collector 20 (see FIG. 2) for converting solar energy into electrical energy. The present invention is not limited to the manner of joining the solar heat collector 20 in this array 18, and any technique known in the art can be used to join the solar heat collector 20 to the array 18. is there. Further, the present invention is not limited to the number of solar heat collectors 20 in this array 18; for example, the present invention may be implemented in one solar heat collector 20 as well as two, three, five, It can also be implemented in an array of combinations of 10, 20, more than 50, and any number of solar thermal integrators. Furthermore, the present invention provides that the array 18 of solar heat collectors 20 is mounted in a fixed position in any conventional manner, or that the array 18 of solar heat collectors 20 is solar heat accumulation for solar energy in any conventional manner. It is expected to be mounted to follow the solar path to maximize the exposure of the vessel. Each solar heat collector 20 may have the same or different design for directing solar energy to a particular area where solar energy is converted into alternative energy sources, such as electrical energy or heat.

  Referring to FIG. 2, each solar heat collector 20 collects solar energy on a device 26 for converting solar energy into electrical energy, for example, a parabolic shaped mirror 22 (herein “primary” A shaped reflecting mirror such as a mirror. The paraboloid shaped mirror 22 includes a paraboloid shaped glass substrate 28. The glass substrate 28 preferably has a total iron content of less than 0.020 weight percent and in the visible range, such as 350 to 770 nanometers ("nm") of the electromagnetic spectrum, and from above 770 nm of the electromagnetic spectrum. It has a 90% transmission in the infrared (“IR”) region, such as 2150 nm, and a low absorbance, such as less than 2% in the visible and IR ranges. Glasses having the aforementioned optical properties are disclosed in US patent application Ser. No. 12 / 275,264, filed Nov. 21, 2008, and US Pat. No. 5,030,594, which is incorporated by reference in its entirety. As incorporated herein by reference. PPG Industries, Inc. Sells glass with the above properties under the trademarks STARPHIRE and SOLARPHIRE PV. The molded glass substrate 28 has a concave surface 30 and an opposite convex surface 32. The shape of the outer peripheral portion of the molded glass substrate 28 is set so as to form the side portion 33. As shown in FIG. 1, the sides 33 of adjacent solar heat collectors 20 are in contact with each other to maximize the convergence of a given area due to the reflective surface. A reflective coating, reflective layer, or reflective film 34 (shown clearly in FIG. 2) lies over and preferably over the convex surface 32 of the shaped glass substrate 28. The reflective film 34 can be a metal, such as, but not limited to, silver, aluminum, nickel, stainless steel, or gold. Usually, the reflective film 34 is silver.

  With continued reference to FIG. 2, parallel solar energy rays represented by light rays 36 are incident on the concave surface 30. A portion 37 of the light beam 36 is reflected from the concave surface 30 to the conversion device 26, a portion 38 passes through the concave surface 30, passes through the shaped glass substrate 28, and reflects as a reflected light beam 43 (see FIG. 2A). From the surface 42, passes through the shaped glass substrate 28 and returns to the conversion device 26. These solar energy rays are shown in FIG. 2 as two rays 36 instead of innumerable parallel solar energy rays incident on the concave surface 30 for clarity and simplicity. Furthermore, as will be appreciated by those skilled in the art, there is a reflection of sunlight between the concave surface 30 and the convex surface 32 of the shaped glass substrate 28. However, detailed descriptions of the transmission, absorption, and reflection of solar energy rays incident on and through the transparent substrate are well known in the art and will not require further description. .

  In the embodiment illustrated in FIGS. 1 and 2, the conversion device 26 includes a shaped secondary mirror 44 positioned with respect to the focal point of the parabolic shaped mirror or primary mirror 22, and the focal area of the primary mirror 44. With an optical rod or light bar 46 (shown clearly in FIG. 2). A multi-junction solar cell 48 is positioned at the end 50 of the light bar 46. With this configuration, the reflected rays 37 and 43 (see FIG. 2A) are incident on the secondary mirror 44, which reflects the rays 37 and 43 to the end 52 of the light bar 46 (as clearly shown in FIG. 2). To show). Light rays 37 and 43 pass through the light bar 46, exit the end 50 of the light bar 46, and enter a solar cell 48 for converting solar energy into electrical energy. One skilled in the art will appreciate that the solar cell 48 can be positioned at the focal point of the primary mirror 22 and the secondary mirror 44 can be omitted.

  The present invention is not limited to the shape of the secondary mirror 44. More specifically, the secondary mirror in carrying out the present invention preferably has a flat reflective surface. In the practice of the present invention, the secondary mirror was a flat piece of flat glass having a solar reflective coating surface such as a silver coated surface. However, the present invention can also be implemented using a shaped secondary mirror having a concave and convex surface and a reflective coating on at least one surface, such as a convex surface.

  Referring to FIG. 1, a cover 60 (partially shown in the upper left corner of FIG. 1) is supported over the array of solar thermal integrators and the concave shape of the parabolic shaped mirror 22 of the solar thermal integrator 20. Prevents dust and water from adhering to the surface 30. As is known in the art, the cover 60 is transparent to the visible and IR wavelength ranges of the electromagnetic scale. Optionally, the molded glass substrate 28 of the primary mirror 22 has a notch 64 (shown clearly in FIG. 2) at the bottom of the glass molded substrate 28 to provide access to the light bars 46 and solar cells 48.

  As described above in the section entitled “Background Art”, one limitation of currently available solar thermal integrators is the use of soda-lime-silica glass substrates for primary mirror 22 and secondary mirror 44. This glass substrate is usually cut from a continuous glass ribbon made by a float glass process such as the glass manufacturing process disclosed in, for example, US Pat. No. 3,333,936 and US Pat. No. 4,402,722. Cut glass pieces. The patents are hereby incorporated herein by reference in their entirety. As is well known in the art, soda lime silica glass contains sodium ions. For example, the molded glass substrate 28 is heated by long-term environmental exposure to sunlight 36 or the like impinging on the primary mirror 22, and the sodium ions are formed into the molded glass by heating the glass to form the parabolic molded substrate 28. Energy that diffuses or elutes out of the substrate 28 is applied. Sodium ions eluted from the shaped glass substrate 28 at the surfaces 30 and 32 react with moisture in the atmosphere and convert the sodium ions into sodium compounds such as sodium hydroxide and sodium carbonate. These sodium compounds are deposited as precipitates on the surface of the molded glass substrate 28. The precipitate of the sodium compound on the concave surface 30 of the molded glass substrate 28 reduces the visible light transmittance of the molded glass substrate 28, and the concave surface 30 portion having the precipitate of the sodium compound becomes a non-specular reflection surface or scattering surface. So that the reflected rays 37 and 43 are oriented away from the focal point of the primary mirror 22 or away from the secondary mirror 44. Since the convex surface has a reflective coating 34 and a protective plastic coating or protective plastic layer 53 (shown only in FIG. 2) covering the reflective coating, on the convex surface 32 of the primary mirror 22 there is no deposit of sodium compounds. Even if it exists, it is minimized. As is known in the art, the protective coating 53 protects the reflective coating 34 from the environment, and in the practice of the present invention, the protective coating 53 is free of sodium ions located on the convex surface 32 of the glass substrate 28. Limiting the formation of sodium precipitates upon reaction with the environment. Although the protective coating 53 for the reflective coating 34 prevents the formation of sodium compound precipitates, the present invention contemplates the practice of the present invention on the convex surface 32 of the glass substrate 28. As will now be understood, the secondary mirror 44 made from soda-lime-silica glass is oriented so that the reflected light from the primary mirror 22 is separated from the optical rod 46 by precipitation of sodium compounds on the secondary mirror. It may have the same disadvantages as the primary mirror 22 except that.

  Referring to FIG. 3, in one non-limiting embodiment of the present invention, the concave surface 30 of the shaped glass substrate 28 of the primary mirror 22 has a sodium barrier coating or sodium barrier layer or sodium barrier film 66.

  Referring to FIG. 4, a sodium barrier coating 66 is applied over and preferably on the surface 68 of the circular shaped flat glass piece 70. The surface 68 of the glass piece 70 is designated to be the concave surface 30 of the shaped glass substrate 28. In the practice of the present invention, the barrier layer 66 preferably transmits more than 90% of the visible spectrum and IR spectrum of electromagnetic waves, more preferably more than 95%, and most preferably 100%. The barrier layer 66 is preferably capable of withstanding temperatures above the glass forming or bending temperature, such as temperatures above 660 ° C. (1220 ° F.) for soda lime silica glass. Furthermore, the barrier layer 66 preferably prevents alkali ions such as sodium ions from moving through cracks in the barrier coating 66 when the glass piece 70 is formed, and the light rays 37 and To the extent that 43 does not deviate significantly from the focus of the parabolic shaped mirror 22, no cracks and / or buckling occurs. A description of cracks in the barrier coating 66 and buckling of the barrier coating 66 is provided in further detail below.

  In one non-limiting example of the present invention, the circular flat glass piece 70 had a diameter of 45.72 cm (18 inches) and a thickness of 2.1 mm (0.083 inches). An 800 Å thick barrier coating 66 of 85 atomic percent silicon and 15 atomic percent aluminum oxide is designated by the MSVD coating process (designated to be the concave surface 30 of the shaped glass substrate 28). 68 was deposited. The surface 72 of the coating glass piece designated to be the convex surface 32 of the molded glass substrate 28 was placed on the open end 74 of the vacuum mold 76 (see FIG. 5A). Glass piece 70 and mold 76 were heated in a furnace (not shown) to heat the glass piece to 660 ° C. (1220 ° F.). This coated glass piece 70 and vacuum mold 76 were uniformly heated in any conventional manner. After the coated glass piece 70 and the vacuum mold 76 are heated to 660 ° C. (1220 ° F.), air is exhausted from the interior 78 of the mold 76 through the holes 77 spaced apart from each other, and the interior of the vacuum mold 76 is heated. The molded glass substrate 28 having the coating 66 was produced by pressing the glass piece 70 (see FIG. 5B). This heated molded glass substrate was cooled in a controllable manner to anneal the molded glass substrate. As will be appreciated, the present invention heats the glass piece 70 and the vacuum mold 76 separately, and then places the glass piece 70 on the open end 74 of the vacuum mold 76, as described above. Expect to mold 70. Processes and equipment for heating glass, for forming glass in a vacuum mold, and for annealing glass and coated glass are well known in the art and do not require detailed description. Let's go.

  During the molding process, the flat glass piece 70 (see FIG. 4) is urged or drawn into the interior 78 of the vacuum mold 76 so that the central portion 79 of the flat glass piece 70 is stretched. The As a result of this stretching, the thickness of the bottom area 80 of the shaped glass substrate 28 (see FIG. 5B) (corresponding to the central portion 79 of the glass piece 70 in FIG. 4 and the hole 64 in FIG. 3) is 80% of the thickness of the central portion 79 (see FIG. 4), and the thickness of the peripheral edge 81 (see FIG. 5B) of the molded glass substrate 28 is equal to the peripheral edge 82 (see FIG. 4) of the flat glass piece 70. The thickness is 105%. As will be appreciated, the peripheral edge 81 of the molded glass substrate 28 is greatly distorted and has optical distortion. In the practice of the present invention, although not limiting, the segment 83 (see FIG. 5B) of the shaped glass substrate 28 is excised to remove the heavily distorted and optically distorted portion of the glass, The side portions 33 of the adjacent shaped solar mirrors 20 were positioned so as to contact each other as shown in the array 18 (see FIG. 1). In this practice of the present invention, a section of about 2 inches is cut from the peripheral edge 84 in the direction of the bottom 80 of the molded glass substrate 28 (see FIG. 5B), without limiting the invention. did. A further portion of the peripheral edge of the molded glass substrate was removed to form a side 33 (see FIG. 3) of the molded glass substrate. A notch or hole 64 (see FIG. 3) was cut into the bottom area 80 (see FIG. 5B) of the shaped glass substrate 28. Thereafter, a reflective coating such as a silver layer 34 is applied so as to cover the convex surface 32 of the molded glass substrate 28 (see FIG. 3), and a protective film 53 (see FIG. 2) is applied on the reflective coating 34. did.

  As will be appreciated, the present invention is not limited to this process of cutting holes 64 in the bottom region 80 (see FIG. 5B) of the shaped glass substrate 28 and cutting the peripheral edge 24 of the shaped glass substrate, or reflecting The cutting process and / or coating technique known in the art is not limited to this coating process in which the coating 34 and the protective coating 53 covering the convex surface 32 of the molded glass substrate 28 are applied, in the practice of the present invention. It is possible to use.

  At temperatures in the range of 649-704 ° C. (1200-1300 ° F.), the glass piece 70 is heat softened or viscous, while the barriers of the present invention such as, for example, aluminum and silicon oxides. The coating 66 is a material that is difficult to dissolve and remains dimensionally stable at temperatures in the range of 649-704 ° C. (1200-1300 ° F.). As used herein, the expression “dimensionally stable” means that the physical dimension of the coating during and / or after heating of the glass piece is greater than ± 5%, preferably greater than ± 2%. It means no change. When the flat glass piece 70 is formed on the molded glass substrate 28, the distortion patterns illustrated in FIGS. 6 to 8 are generated in the molded glass substrate 28. Referring to FIGS. 6-8, if necessary, a radial tensile strain indicated by numeral 90 is present at the bottom portion of the shaped glass substrate (see FIG. 8) and circumferential compression indicated by numeral 92 is provided. Distortion exists in the outer peripheral portion 84 of the molded glass substrate 28. The barrier coating 66 is subjected to these stresses by being adhered to the concave surface of the glass substrate. As the distance from the outer periphery 84 of the molded glass substrate 28 increases in the direction of the bottom section 80 of the molded glass substrate 28 (see FIG. 7), the radial tensile strain 90 remains substantially the same, and the circumference The directional compression distortion 92 is designated as a “transition line” and is reduced to a position to which the numeral 94 is assigned in FIG. In this position, circumferential tensile strain (see FIG. 8) assigned the number 102 begins to occur in the glass, and radial tensile strain 90 (see FIG. 8) is present in the glass. . Formed glass substrate 28 in question, such as formed glass substrate 28 made from flat glass piece 70 having a diameter of 18 inches (45.72 cm) and a thickness of 0.083 inches (2.1 mm). , The transition line 94 corresponds to a position on the flat glass piece 70 that is about 3 inches (7.62 cm) from the center of the flat glass piece 70, ie, the center of the central portion 79. In the upper position. As the distance from the transition line 94 in the direction of the bottom region 80 of the shaped glass substrate 28 increases, the shaped glass substrate increases in circumferential tensile strain assigned the number 102 and has a radial tensile strain 90 ( (See FIG. 8).

  As will be appreciated by those skilled in the art, these strains in the shaped glass substrate 28 can be measured in any conventional manner. In this implementation of the invention, these distortions of the shaped glass piece 28 at issue were calculated using the ANSYS finite element computer program.

  The sodium barrier coating 66 (see FIG. 7) in the circumferential compression zone 103 of the molded glass substrate 28, ie, the zone between the outer periphery 84 of the molded glass substrate 28 and the transition line 94, is resistant to compressive strain in the glass. And vertical radial buckling was observed. At the location of the transition line 94, the barrier coating 66 was found to have an area consisting of a plurality of radial cracks. In the circumferential tension zone 104 of the molded glass substrate 28, ie, the zone between the transition line 94 and the bottom zone 80 of the molded glass substrate 28 (see FIG. 7), the barrier coating 66 has small random cracks or cracks. It was found to have

  As described above, these maximum compressive stresses are located at the peripheral edge portion 81 of the molded glass substrate 28 (see FIGS. 5B and 7), and the maximum buckling of the barrier coating 66 occurs at the peripheral edge portion 81. Is expected. Furthermore, it has been observed that a very small amount of sunlight that impinges on the peripheral edge portion 81 of the initially molded glass substrate 28 is directed to the focal point or focal area of the molded glass substrate 28. In view of the foregoing, initially extending from the peripheral edge 84 of the molded glass substrate 28 by a distance corresponding to 10-15% of the distance from the peripheral edge 84 to the center of the bottom area 80 of the initially formed glass substrate. The peripheral edge portion 81 of the glass substrate 28 to be molded was removed. In one non-limiting embodiment of the present invention, for a molded glass substrate 28 molded from a flat glass piece 70 having a diameter of 18 inches (45.72 cm), from the peripheral edge 84 to the bottom 80 of the molded glass substrate ( An approximately 2 inch (5.08 cm) section was cut in the direction of (see FIG. 5B) to remove the heavily strained and optically distorted glass portion. A further portion of the peripheral edge of the molded glass substrate was removed to form a side 33 (see FIG. 3) of the molded glass substrate.

  Next, the observed and / or expected defects caused by cracks and / or cracks in the barrier coating 66 and the observed and / or expected defects caused by buckling of the barrier coating will be described. Cracks or cracks extending through the thickness of the barrier coating 66 provide a passage for atmospheric moisture and sodium ions eluting from the glass, whereby the moisture and sodium ions interact to interact with the sodium compound. And this deposit may deposit on the surface 108 of the barrier coating 66 (see FIG. 7) and / or between the barrier coating 66 and the concave surface 30 of the shaped glass substrate 28. Expected to be. Sodium compounds on the surface 108 of the barrier coating 66 may change the specular surface of the barrier coating 66 into a non-specular or scattering surface, and the sodium compound between the barrier coating 66 and the convex surface 30 The deposit may cause the barrier coating 66 to peel off.

  Buckling defects can change the surface 108 of the barrier coating 66 from a specular reflective surface to a non-specular reflective surface or a scattering surface, and in severe cases, can cause additional cracks in the barrier coating. There is. Next, the barrier coating 66 will be described, but this description also applies to the scratch resistance characteristics of the barrier coating (described above) unless otherwise indicated.

  Referring to FIGS. 9A-9C, the barrier coating 66 (FIG. 9A) on the segment 110 of the glass piece 70 that is expected to be located within the area of circumferential compression 103 (see FIG. 7), if desired. ) Has a certain length between the side parts 112 and 113 and a certain width between the side parts 116 and 117. After the glass piece 70 is formed on the molded glass substrate 28, the segment 110 of the flat glass piece 70 corresponds to the segment 118 of the molded glass substrate 28. The convex surface 32 of the segment 118 of the shaped glass substrate 28 has a length between the sides 112 and 113 of the segment 118, which is the side 112 of the segment 110 of the flat glass piece 70. And the convex surface 32 of the segment 118 of the shaped glass substrate 28 has a width that is between the sides 116 and 117 of the segment 118, which is the width of the segment 118. Less than the width of the segment 110 of the flat glass piece 70 between the sides 116 and 117. The concave surface 30 of the segment 110 of the shaped glass substrate 28 has a length that lies between the sides 112 and 113 of the segment 118, which is the same as the side 112 of the segment 110 of the flat glass piece 70. The concave surface 30 of the segment 118 of the shaped glass substrate 28 has a width that lies between the sides 116 and 117 of the segment 118, which is on the side of the segment 118. It is smaller than the width of the flat glass piece 70 between the portions 116 and 117.

  The difference in increase between the length of the convex surface 32 and the length of the concave surface 30 between the sides 112 and 113 of the segment 118 is small. The difference in reduction between the width of the concave surface 30 between the sides 116 and 117 of the segment 118 is greater than the difference between the length of the concave surface of the segment 118 and the length of the convex surface. By way of example and not limitation, the measured expansion between the sides 112 and 113 of the segment 110 and between the sides 112 and 113 of the segment 118 is concave side. And 2-6% on both the convex side. The shrinkage between the side portions 116 and 118 of the segment 110 on the outer periphery of the molded glass substrate 28 and between the side portions 116 and 118 of the segment 118 is 14%, and the concave side 30 is 14%. The convex side 32 had a shrinkage rate of 13%. In the bottom part 80 of the molded glass substrate 28, the elongation percentages on the convex side and the concave side were 5% and 4%, respectively.

  On the other hand, the length and width of the barrier coating 66 remain the same and are generally referred to as strain, the concave and convex surfaces of the shaped glass substrate 28 when compared to the corresponding width of the flat glass piece 70. Buckling due to the reduction of the width. More particularly, the glass is viscous during the molding process, and the buckling of the barrier coating 66 causes the contour profile of the concave surface 30 of the molded glass substrate 28 to be wrinkled, such as a corrugated surface (see FIG. 9B). By changing to a surface having 120, the width of the surface 72 of the flat glass piece 70 is reduced. These folds 120 change the surface 108 of the barrier coating 66 and the concave surface 30 of the shaped glass substrate 28 from the specular surface of FIG. 9A to the non-specular or scattering surface of FIG. 9B. In the first instance (FIG. 9B), the thickness of the barrier coating 66 is increased, for example, the barrier coating is increased to a thickness of 160 nanometers (“nm”), while the width of the flat glass piece is increased. If the amount of shrinkage remains the same, the number of ridges 120 and the height of the ridges 120 increase, and the proportion of reflected sun rays 37 and 43 (see FIGS. 2 and 2A) scattered increases. In the second example (FIG. 9C), the thickness of the barrier coating 66 increases, for example, the barrier coating 66 increases to a thickness of 60 nm, while the amount of shrinkage of the flat glass piece 70 remains the same. And the number of ridges 120 and the height of the ridges in the second example (FIG. 9C) are less than the number of ridges 120 and the height of the ridges 120 in the first example (see FIG. 9B) and are scattered. The ratio of the reflected sun rays 37 and 43 (see FIGS. 2 and 2A) is reduced. As described above, the area 103 of circumferential compression (see FIG. 7) shrinks and thus decreases as the distance from the outer periphery 84 of the shaped glass substrate 28 increases (see FIGS. 6-8). The shrinkage ratio in the circumferential width of the concave surface 30 of the molded glass substrate 28 decreases as the distance from the outer peripheral portion 84 of the molded glass substrate 28 increases, and the thickness of the barrier coating 66 becomes smaller than that of the flange 12. It can be increased without increasing the number and width of ridges 120 (see FIGS. 9B and 9C).

  In one non-limiting embodiment of the present invention, the thickness of the barrier coating 66 is selected to have sodium barrier properties and minimize buckling. More specifically, the minimum thickness of the barrier coating 66 prevents the sodium ions from reacting with atmospheric moisture to convert the sodium ions into sodium compound precipitates and minimizes buckling. Selected to suppress. As will be appreciated by those skilled in the art, the phenomenon of sodium ions moving out of the glass is the dissipation process, and in the present invention, the parameter of interest is the amount of sodium ions present in the glass. . The emission rate, for example, the size of alkali ions such as sodium ions, and the energy that drives the sodium ions to the surface of the shaped glass substrate 28 is relevant to this description because the use of the sun is a long-term use such as 30 years. It is not considered to be.

  Based on the foregoing, the amount of alkali ions or sodium ions in the glass is a function of the glass composition and the thickness of the glass piece, for example, as the thickness of the glass piece 70 or the shaped glass substrate 28 increases, The number of sodium ions increases and the thickness and / or density of the barrier coating preferably increases. For soda lime silica glass, the sodium concentration is approximately 14 weight percent. In one non-limiting embodiment of the present invention, the parabolic shaped mirror 22 is made from a glass substrate having a thickness of 2.1 mm (0.083 inches). In this non-limiting embodiment of the invention, the barrier coating is an oxide MSVD coating consisting of 85 atomic percent silicon and 15 atomic percent aluminum. The minimum coating thickness to prevent sodium ions from reacting with moisture in the environment and converting them into sodium compound precipitates is 40 nm. As will be appreciated, any thickness above this minimum thickness prevents sodium ions from reacting with moisture in the environment, but as the thickness of the barrier coating 66 increases, the severity of buckling increases. Rises. In this practice of the invention, the barrier coating 66 (see FIG. 7) in the circumferential tension zone 104 is preferably in the range of 40-100 nm, more preferably in the range of 60-100 nm, most preferably. Is in the range of 60-80 nm. The same coating composition with a coating thickness in the range 40-100 nm forms a protective coating against mechanical and chemical erosion and / or damage.

  As described above, the flat glass piece 70 is formed using the vacuum mold 76 (see FIGS. 5A and 5B). After the flat glass piece 70 is formed, the formed glass substrate is removed from the mold 76 and annealed when the glass is dimensionally stabilized. In the context of the present invention, a glass is considered dimensionally stable if the shaped glass can support its own weight without changing its shape. For the glasses disclosed in US patent application Ser. No. 12 / 275,264 filed Nov. 21, 2008 and US Pat. No. 5,030,594, the glass is 566 ° C. (1050 ° F.). Dimensionally stable at temperatures of The annealing process reduces the inherent stress in the barrier coating 66 and the molded glass substrate 28 to minimize residual stress, thereby causing the barrier coating and the molded glass substrate 28 to crush the substrate 28 or break the barrier coating. So that it can be cut without The rate of annealing equipment and the rate at which the flat glass substrate 28 is annealed is not a limitation of the present invention; any equipment, method, and ratio for annealing known in the art can be used in the practice of the present invention. It is possible to use. Annealing of coated and uncoated glass objects is well known in the art and will not require further explanation.

  The present invention is not limited to this thickness of the glass piece 70, and the glass piece can be of any thickness. In a preferred implementation of the present invention, the glass piece 70 is preferably thin so as to form a lightweight British glass substrate 28. Although thin glass is preferred, the glass thickness should be sufficient to have structural stability. As used herein, the term “structural stability” refers to parabolic molding of glass from a flat glass piece 70 (see FIG. 4) using a vacuum or press mold with minimal glass breakage. This means that it must be processed into a mirror 22 (see 3). In this practice of the invention, the glass thickness is preferably in the range of 1.9 to 3.2 mm (0.075 to 0.126 inches), more preferably 2.0 to 2.8 mm (0 0.078 to 0.110 inch), most preferably 2.1 to 2.3 mm (0.083 to 0.091 inch).

  In this preferred practice of the invention, the barrier coating 66 is an oxide consisting of 15 atomic percent aluminum and 85 atomic percent silicon. The increase in atomic percent of aluminum makes the coating harder. A harder coating reduces buckling but is prone to cracking. These cracks in the coating can result in atmospheric moisture reacting with sodium ions and adding sodium ions to the sodium compound. For oxide barrier coatings comprised of aluminum and silicon, the coating preferably comprises 30-100 atomic percent silicon and 0-70 atomic percent aluminum, more preferably 50-95 atomic percent silicon and 5-50 atomic percent. Including atomic percent aluminum, including, for example, 30 to less than 100 atomic percent silicon and greater than 0 to 70 atomic percent aluminum, most preferably 60 to 90 atomic percent silicon and 10 to 40 atomic percent aluminum. As will be appreciated, the present invention is not limited to oxide barrier coatings or films of aluminum and silicon, and any sodium barrier film of the type known in the art may be used to implement the present invention. Can be used. Types of barrier coatings that can be used in the practice of the present invention include, but are not limited to, the coatings or films disclosed in US Patent Application No. 2007 / 0275253A1. This document is incorporated herein by reference in its entirety.

  As will be appreciated by those skilled in the art of MSVD coating, the deposition parameters can be varied to reduce the intrinsic stress in the coated barrier film. However, as described above, the barrier film and the molded glass substrate are annealed simultaneously to minimize residual stresses so that the molded glass substrate 28 can be cut without crushing the substrate 28. Therefore, the reduction of the intrinsic stress in the barrier coating during the deposition of the coating is arbitrary and does not limit the present invention.

  The present invention contemplates reducing distortion in the shaped glass substrate 28 by reducing the time to form the glass piece 70 (see FIG. 4) into the shaped glass substrate 28 (see FIG. 5B). As will be appreciated, as the temperature of the glass piece 70 increases, the viscosity of the glass decreases and the width of the buckling of the barrier coating 66 increases by having time for the coating to fully buckle, e.g., glass The glass has time to flow in the plane of the coating, such as has time to flow between the ridges of the barrier coating 60 or 120 (see FIG. 9C). Furthermore, the buckling width of the barrier coating 66 is increased by having the coating 66 fully buckle by increasing the molding time, ie, the time required to pull the glass piece 70 into the cavity of the mold 76. Increasing, the glass has time to flow between the ridges of the barrier coating 66 (see FIG. 4) or 120 (see FIG. 9C).

In this implementation of the invention, the glass piece 70 during molding is preferably 1.00 × 10 ^7.8 poise to 5.36 × 10 ⁹ poise when the glass piece is drawn into the sink mold 76. Has a viscosity in the range. In this viscosity range, the minimum buckling of the barrier coating 66 occurred when the molding time was 3 seconds, and the maximum buckling of the barrier coating 66 occurred when the molding time was 25 seconds. Based on the foregoing, for glasses with a viscosity range of 1.00 × 10 ^7.8 poise to 5.36 × 10 ⁹ poise, the minimum buckling of the barrier coating 66 is greater than 0 to 5 seconds, preferably 3 seconds. And the maximum buckling of the barrier coating 66 is expected to be 25 seconds or more.

As will be appreciated by those skilled in the art, the temperature versus viscosity curve of glass depends on the glass composition. Under the registered trademark of STARPHIRE, PPG Industries, Inc. The type of soda-lime-silica glass sold by the company is in the range of 1.00 × 10 ^7.8 poise to 5.36 × 10 ⁹ poise at a temperature in the range of 649-704 ° C. (1200-1300 ° F.) It has been found to have a viscosity of In this practice of the invention, the STARPHIRE glass piece 70 was heated in a furnace set at 704 ° C. (1300 ° F.) to heat the glass piece 70 to the expected temperature of 660 ° C. (1220 ° F.). . The glass has a viscosity of 2.60 × 10 ⁹ poise, and the minimum buckling of the barrier coating 66 occurs when the molding time is 3 seconds, and the maximum buckling of the barrier coating 66 is 25 seconds of molding time. It occurred when

  As will now be understood by those skilled in the art, the strain pattern on the convex side of the shaped glass piece 28 is similar to the strain pattern on the concave side of the shaped glass piece 28.

  Referring to FIGS. 10 to 13, as necessary, the present invention cuts a plurality of segments from a flat glass sheet, forms these segments, and joins the formed segments together to form a molded glass substrate 28. It is contemplated to reduce distortion in the shaped glass substrate 28 by forming a shaped glass substrate similar in shape to (see FIG. 3). In one non-limiting example of the present invention, the surface 124 of the flat glass sheet 126 is coated with a barrier coating 66 (see FIG. 10). The surface 124 of the glass sheet 126 is expected to be the concave surface 128 of the molded glass substrate 130 (see FIGS. 12 and 13). Four flat segments 132-135 are cut from the glass sheet 126. Each of the flat segments 132-135 includes a rounded corner 136 that joins the side portions 138 and 140 and a flat end 142 that joins the side portions 144 and 146, and the side portion 138 is a side portion at the corner 148. 144 is joined to the side 146 at the corner 149.

  Each of the segments 132-135 is formed by forming the segments 132-135 as described below to form a quarter of the molded glass substrate 130 (see FIGS. 12 and 13), which will be described below. In such a manner, the molded segments 132 to 135 are joined to form a molded glass substrate 130 similar to the molded glass substrate 28 (see FIG. 3).

  The present invention is not limited to the manner in which the segments 132-135 are cut from the glass sheet 126, and any cutting or scratching technique known in the art can be utilized in the practice of the invention. The edges of the segments 132-135 can be seamed as is known in the art for safety. Each of the flat segments 132-135 is, for example, but not limited to, a rigid having a molded surface as disclosed in US Pat. No. 7,240,519 and US Pat. No. 7,437,892. Press processes known in the art, such as press bending using a lower mold having an upper mold and a flexible support surface, a rigid upper mold and a lower ring mold having a molding surface, and a vacuum upper mold having a molding surface It is molded in any conventional manner using either the method or the press working equipment. The patent is hereby incorporated herein by reference in its entirety.

In the preferred practice of the invention, the segments 132-135 are molded using an upper vacuum mold having a molding surface. Referring to FIG. 11, one of the segments 132-135, such as segment 132, is heated to a viscosity in the range of 1.00 × 10 ^7.8 poise to 5.36 × 10 ⁹ poise, and the lower support member 157 On the curved surface 156. The upper vacuum shaping mold 158 having the molding surface and the support member 157 are moved relative to each other, for example, the upper mold 158 is moved in the direction of the lower front support member 157 to bring the segment 132 into contact with the molding surface 159. . A vacuum is drawn from the molding surface 159 of the upper mold 158 to mold the segment 132. This process is repeated to mold the remaining three segments 133-135 to form four molded segments 160-163. Optionally, these four segments can be molded simultaneously by providing a mold having four molding areas.

  A reflective coating 34 and a protective coating 53 (see FIG. 2) are applied to the convex surfaces of the molded segments 160-163.

  In the preferred practice of the invention, the barrier coating 66 is applied to the surface 124 of the flat glass sheet 126 before the segments 132-135 are cut from the glass sheet 126. However, the present invention contemplates applying a barrier coating 66 to the flat segments 132-135 or molded segments 160-163. In this implementation of the present invention, the reflective coating 34 and protective coating 54 are applied to the convex surfaces of the molded segments 160-163, although the present invention is directed to the surface of the glass sheet 126 opposite the glass sheet surface 124. It is anticipated that a reflective coating 34 and a protective coating 53 will be applied. As will be appreciated, if the reflective coating 34 and protective coating 54 are applied before the segments 132-135 are formed, the reflective coating 34 and protective coating 54 form the glass segments 132-135. Must withstand the temperature to be. Optionally, the protective coating 54 may be applied after the segments are molded.

  The present invention is not limited to this number of segments 132-135 that are joined to make a shaped glass substrate 130, and the shaped glass substrate 130 can be two, three, four, five, or more. It can be formed by joining segments. As will now be appreciated, the greater the number of molded segments that are joined to form the molded glass substrate 130, the greater the reduction in distortion in the molded glass substrate 28 or 130.

  Referring to FIGS. 12 and 13, the shaped glass segments 160-163 are joined together in any conventional manner. In one non-limiting embodiment of the invention, the segments 160-163 are positioned together to form a shaped glass substrate 130, and a pair of rings 166 and 168 (shown only in FIG. 12) are adhesives. To the reflective coating 34. In another non-limiting embodiment of the invention, the rings 166 and 168 are joined to the convex surface 32 of the shaped glass substrate. Thereafter, the convex surfaces of the joined molded segments 160-163 and the rings 166 and 168 are covered in any conventional manner by the reflective coating 34 and the protective coating 53. In yet another non-limiting embodiment of the present invention, the sides of the molded segments are joined together by an adhesive such that the adhesive is adjacent in the molded segment as shown in FIG. The side portions 140 of the mating ones are joined together, and the side portions 138 of the neighboring ones in the molded segment are joined together. As shown in FIGS. 10 and 13, the rounded corner 136 forms a notch 64 of the molded substrate 130.

  The present invention is not limited to the manner in which these dimensions of the flat segments 132-135 are derived. For example, and without limiting the present invention, these dimensions of the flat segment can be determined from the computer program and by creating a molded parabolic substrate, cutting the molded substrate into the desired number of segments, It can be derived from measuring the sides.

  As will now be appreciated, the use of the techniques described above reduces strain in the glass and reduces the buckling and breakage of the barrier coating 66, but as long as strain remains in the glass, the barrier coating 66 is Has some buckling and cracking. In view of the foregoing, the present invention provides multiple selections of flat glass pieces 70 designated to be concave surfaces 30 of the shaped glass substrate 28 (see FIG. 3) and the shaped glass substrate 126 (see FIG. 13). By providing a plurality of barrier coatings 66 of different thicknesses covering the surface portion, it is anticipated that breakage and buckling of the barrier coating 66 will be further reduced. In the following description, embodiments of the present invention are implemented on a flat glass piece 70 to form a shaped glass substrate 28 formed from the flat glass piece 70. However, unless otherwise indicated, this description also applies to the installation of the barrier coating 66 on the glass segments 132-135 or on the shaped glass segments 160-163.

  In a first non-limiting embodiment of the present invention, the barrier coating 66 applies a surface 68 (see FIG. 4) of a flat glass piece 70 that is designated to be the concave surface 30 of the shaped glass substrate 28. It has a certain covering thickness (hereinafter referred to as “coating technology first”). In a second non-limiting example of the present invention, the change in circumferential strain on the concave surface 30 of the shaped glass substrate 28 is, for example, from the outer periphery 150 (see FIG. 4) of the circular closed birth glass piece 70. By applying or depositing a barrier coating or barrier layer 66 having a varying thickness, such as a thickness that increases as the distance increases in the direction of the central portion 79 of the flat glass piece 70 (hereinafter referred to as Is called “Coating Technology No. 2”). In a third non-limiting example, the change in circumferential strain on the concave surface 30 of the shaped glass substrate 28 is the first from the outer periphery 170 of the flat glass piece 70 to the expected position of the transition line 94. Having a constant thickness (see FIG. 7) and a second constant thickness from the transition line 94 to the central portion 79 of the flat glass piece 70, this second thickness of the barrier coating being It is compensated by applying or depositing a barrier layer 66 that is thicker than the first thickness (hereinafter referred to as “coating technique third”).

  The change in coating thickness to make the shaped glass substrate 28 (see FIGS. 3 and 5B) is the circumference when the central portion 79 of the flat glass piece 70 is coated, for example using the shield 170. Masking multiple areas of the flat piece 70 to obtain a thin coating, such as covering the surface of a glass piece 70 (see FIG. 14) that is expected to be located in the directional compression zone 103 (see FIG. 7) Can be realized.

  The first coating technique is performed to form the segments 160-163 by coating the surface 124 of this sheet before or after cutting the contours of the segments 132-136 into the flat glass sheet 126. The coating technique second is that the segments 160-136 are covered by the segments 160 by coating the segments after the segments 132-136 have been contoured into the flat glass sheet 126 by a cutting line or after the segments 132-136 have been removed from the glass sheet. Implemented to form ~ 163. The thickness of the coating 66 for the coating technique second increases as the distance from the flat end 142 (see FIG. 10) increases in the direction of the rounded corner 136. The third coating technique involves segment 160-136 by coating segment 132-136 after it has been contoured into the flat glass sheet 126 by a cutting line or after segments 132-136 have been removed from the glass sheet. Implemented to form ~ 163. The coating 66 for the coating technique 3 has a first constant thickness from the sides 144 and 146 of the flat segments 132-136 to the expected position of the transition line 94 (see FIG. 7) and the transition line 94 to the segment. Applied to segments 132-135 having a second constant thickness over the rounded ends 136 of 132-136.

  The barrier coating 66 for the coating technique first has a constant thickness in the range of 40-100 nm, or in the range of 80-100 nm. In one non-limiting example of the present invention, the barrier coating 66 comprised an oxide consisting of 85 atomic percent silicon and 15 atomic percent aluminum. A barrier coating 66 having a thickness of 80 nm was deposited on the surface 72 of the flat piece glass 70 by MSVD. This glass was of the type disclosed in US patent application Ser. No. 12 / 275,264 filed Nov. 21, 2008 or US Pat. No. 5,030,594. Flat glass piece 70 has a diameter of 45.1 cm (17.75 inches), a total iron content of less than 0.020 weight percent, 90% transmission in the visible and IR ranges of the electromagnetic spectrum, and visible It was a circular piece of glass with an absorbance of less than 2% in the range and IR range. The flat glass piece 70 was molded in a vacuum mold to form the shaped glass substrate 28, for example, for a bending time of less than 25 seconds. After cooling the molded glass substrate, the outer periphery of the molded glass substrate 28 was molded as described above in order to form the side 33 and the central hole 28 (see FIG. 3) in the molded glass substrate 28. A reflective silver coating 34 was applied over the convex surface 32 of the molded glass substrate 28 to form a parabolic shaped mirror 22.

  The second coating technique is, for example, a barrier coating 66, but is not limited to the present invention, but from the thickness of 40 nm at the outer periphery 172 of the flat glass piece 70, the central portion of the flat glass piece 70. A barrier coating 66 is formed that increases in thickness as the distance from the outer periphery of the flat glass piece 70 toward the central portion 79 increases, such as increasing to a thickness of 80 nm at 79. In this embodiment, the thickness of the barrier coating 66 increases as the circumferential strain in the glass increases, the percent width shrinkage of the concave surface 30 of the shaped glass substrate 28 decreases, and buckling decreases. . Beyond the transition line 94 in the direction of the central portion 80 of the shaped glass substrate 28, the thickness of the barrier coating 66 increases as the circumferential tension increases. Referring to FIG. 15, a cross-section of the shaped glass substrate 28 in the circumferential tension zone 104 is shown, which is located between the transition line 94 and the central zone 80 (FIGS. 7 and 9). 15). The barrier coating 66 has a crack 174, but the barrier coating 66 is sufficiently thick so that the crack 154 does not extend to the surface 108 of the barrier coating 66, for example 80 nm.

  The barrier coating 66 for the third coating technique includes a first constant thickness from the outer periphery 172 of the flat glass piece 70 to the expected position of the transition line 94 of the molded glass substrate 28, and the flat glass piece from the transition line 94. The first constant thickness of the barrier coating 66 is less than the second thickness of the barrier coating 66. In one non-limiting embodiment of the present invention, the first constant thickness of the barrier coating 66 is in the range of 40-60 nm, more preferably in the range of 40-50 nm, and the second constant thickness. The thickness is in the range of more than 60 to 100 nm, more preferably in the range of more than 60 to 80 nm. With this configuration, buckling of the barrier coating 66 is minimized in the circumferential compression zone 103, and the thickness of the barrier coating 66 is circular so that the crack 174 does not extend to the surface 108 of the barrier coating 66. The circumferential tension zone 104 is sufficiently thick. Further, this configuration results in a relatively thin barrier coating 66 between the peripheral edge 84 and the transition line 94, i.e., in the thick glass area, reducing the buckling of the barrier coating 66 and reducing the barrier. The thickness of the coat 66 is relatively thick between the transition line 94 and the bottom area 80 of the shaped glass substrate 28, i.e. in the area of relatively thin glass, in which position the buckling is a circumferential compression area. There is a concern about cracks 174, not as severe as in 103. As will be appreciated, the present invention is not limited to this coating thickness change in the area of the transition line 94, and the coating thickness change may be a gradual change or a step change. .

  As will now be appreciated, in the instance where the secondary mirror 44 comprises a molded substrate, techniques to prevent buckling of the barrier coating 66 can be implemented to create the molded secondary mirror. is there.

Other embodiments of the present invention include, but are not limited to:
1. A barrier layer 66 and / or scratch resistant coating covering the surface 68 of the flat glass piece 70 designated to be the concave surface 30 of the shaped glass substrate 28 and a flat glass designated to be the convex surface. A barrier layer 66 (see FIG. 16) covering the surface 72 of the piece 70 is applied, and the flat glass sheet 70 is formed so as to match the formed glass substrate 28. Thereafter, a reflective layer 34 and optionally a protective coating 53 is applied over the barrier layer 66 on the convex surface 32 of the shaped glass substrate 28.
2. A barrier layer 66 and / or scratch resistant coating covering the surface 68 of the flat glass piece 70 designated to be the concave surface 30 of the shaped glass substrate 28, and a convex surface of the flat glass piece 70. A barrier layer 66 covering the surface 72 of the specified flat glass piece 70 is applied, a reflective coating layer 34 is applied over the barrier layer 66 on the surface 72 (see FIG. 17), and then the flat glass sheet 70 is applied. Molded into a molded glass substrate 28.
3. A flat glass piece 70 is formed into a parabolic shaped glass substrate 28, a barrier layer 66 and / or a scratch resistant coating covering the concave surface 30, and a convex surface 32 of the parabolic shaped glass substrate 28. A reflective coating 34 is applied (see FIG. 18).
4). A flat glass piece 70 is formed into a parabolic shaped glass substrate 28, a barrier layer 66 covering the convex surface 32, a barrier layer and / or a scratch resistant coating covering the concave surface 30 of the molded glass substrate 28, and And a reflective coating 34 is applied over the convex surface 32 or over the barrier surface 66 on the convex surface 32 (see FIG. 19).

  As will be appreciated, the reflective layer 34 and / or the barrier layer 66 and / or the scratch resistant coating is applied to the flat glass piece 70, and the coated flat glass is non- When heated and molded in one limited implementation, the reflective layer 34 and barrier layer 66 and / or the scratch resistant coating may have a high molding temperature, such as greater than 649 ° C. (1200 ° F.). Must be able to withstand Reflective coatings capable of withstanding high temperatures are known in the art, see for example US Pat. No. 7,329,433. The patent is hereby incorporated herein by reference in its entirety. The patent discloses an undercoat deposited on the reflective layer to protect the reflective layer during high temperature processing.

  In a preferred implementation of the present invention, the barrier layer 66 is applied using MSVD equipment. As will be appreciated by those skilled in the art, the cathode for the MSVD coating must be conductive. To form a conductive silicon cathode, aluminum, such as greater than 5 weight percent, is added to the silicon. However, the present invention is not limited to MSVD placement of the barrier layer, and any known coating process for applying the barrier layer can be utilized in the practice of the present invention. Furthermore, the present invention is not limited to having a homogeneous barrier layer, and the present invention contemplates barrier layers having oxides of various compositions consisting of silicon and aluminum. For example, in one non-limiting embodiment of the present invention, an oxide first barrier layer comprising 60 atomic weight percent aluminum and 40 atomic weight silicon is applied to the surface of the glass and 85 atomic weight percent. A second barrier layer of oxide consisting of aluminum and 15 atomic weight percent silicon is applied over the first barrier layer.

  As will now be appreciated, the barrier layer 66 of the present invention can be used to prevent sodium ions from damaging the conductive layer of the photovoltaic device. More particularly, and referring to FIG. 20, a photovoltaic device 184 having a conductive coating 186 overlying the barrier layer 66 of the present invention is shown. The barrier layer 66 is applied to the surface 188 of the glass sheet 190. The barrier layer 66 prevents sodium ions from forming precipitates of sodium compounds that erode and damage the conductive coating 186 of the photovoltaic cell 184.

  As discussed in detail above, the oxide barrier layer of silicon and aluminum provides mechanical damage to the glass surface in addition to forming a barrier to prevent sodium ions from moving out of the glass. And a protective layer on the glass to prevent chemical damage.

  Those skilled in the art will readily appreciate that these non-limiting examples of the present invention can be modified without departing from the concepts disclosed in the foregoing description. Accordingly, these specific, non-limiting examples of the invention described in detail herein are exemplary only and do not limit the scope of the invention. The scope of the invention should be given the full scope of the appended claims and any equivalents thereof.

Claims (4)

A solar reflector having a curved reflective surface,
It has a convex surface and an opposite concave surface, and a transparent soda-lime-silica molded glass base plate having a focal zone,
A reflective coating that covers the convex surface and reflects selected wavelengths of the electromagnetic spectrum; and a sodium ion barrier layer of silicon and aluminum oxide coating that covers the concave surface;
The molded glass substrate has a strain pattern having a radial tensile strain in a bottom area of the molded glass substrate and a circumferential compressive strain in an outer peripheral portion of the molded glass substrate, and the outer peripheral portion of the molded glass substrate. As the distance from the surface increases in the direction of the bottom section of the molded glass substrate , the circumferential compressive strain is a position where there is a circumferential tensile strain and the radial tensile strain in the molded glass substrate . As the distance from the transition line toward the bottom area of the shaped glass substrate increases as it shrinks to the area designated as the “transition line”, the circumferential tension strain increases,
The solar reflector, wherein the barrier layer increases in thickness as the distance from the outer periphery of the molded glass substrate toward the bottom area of the molded glass substrate increases. The solar mirror of claim 1, wherein the barrier layer has a thickness range of 40 to 100 nanometers. A solar reflector having a curved reflective surface,
Having a convex surface and an opposite concave surface, and a transparent soda-lime-silica shaped glass board,
A reflective coating that covers the convex surface and reflects a selected wavelength of the electromagnetic spectrum; and a sodium ion alkali barrier layer of silicon and aluminum oxide coating that covers the concave surface;
The molded glass substrate has a strain pattern having a radial tensile strain in a bottom area of the molded glass substrate and a circumferential compressive strain in an outer peripheral portion of the molded glass substrate, and the outer peripheral portion of the molded glass substrate. As the distance from the surface increases in the direction of the bottom section of the molded glass substrate , the circumferential compressive strain is a position where there is a circumferential tensile strain and the radial tensile strain in the molded glass substrate . As the distance from the transition line toward the bottom area of the shaped glass substrate increases as it shrinks to the area designated as the “transition line”, the circumferential tension strain increases,
The barrier layer has a first constant thickness from the outer periphery of the molded glass substrate to the transition line of the molded glass substrate, and from the transition line of the molded glass substrate to the bottom area of the molded glass substrate. A second constant thickness, wherein the first constant thickness is different from the second constant thickness. 4. The first constant thickness of the barrier layer is in the range of 40 to 60 nanometers, and the second constant thickness is in the range of greater than 60 to 100 nanometers. Solar mirror.

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