Patent Application
20090274930
Certain example embodiments of this invention relate to the deposition of metal fluoride coatings onto substrates via combustion deposition. More particularly, certain example embodiments relate to the combustion deposition depositing of alkaline earth fluoride inclusive coatings from a metal inclusive organic precursor and a fluorinating reagent, or from a single-source precursor. In certain example embodiments, the fluorinating reagent may be an organic source or an inorganic source. In certain example embodiments, the alkaline earth fluoride inclusive coating may be a magnesium fluoride (e.g., MgF2 or other suitable stoichiometry) inclusive coating, although other Group 2 metals may be used in place of magnesium. In certain example embodiments, the alkaline earth fluoride inclusive coating may be an anti-reflective (AR) coating.
Combustion chemical vapor deposition (combustion CVD) is a relatively new technique for the growth of coatings. Combustion CVD is described, for example, in U.S. Pat. Nos. 5,652,021; 5,858,465; and 6,013,318, each of which is hereby incorporated herein by reference in its entirety.
Conventionally, in combustion CVD, precursors are dissolved in a flammable solvent and the solution is delivered to the burner where it is ignited to give a flame. Such precursors may be vapor or liquid and fed to a self-sustaining flame or used as the fuel source. A substrate is then passed under the flame to deposit a coating.
There are several advantages of combustion CVD over traditional pyrolytic deposition techniques (such as CVD, spray and sol-gel, etc.). One advantage is that the energy required for the deposition is provided by the flame. Another advantage is that combustion CVD techniques do not necessarily require volatile precursors. If a solution of the precursor can be atomized/nebulized sufficiently (e.g., to produce droplets and/or particles of sufficiently small size), the atomized solution will behave essentially as a gas and can be transferred to the flame without requiring an appreciable vapor pressure from the precursor of interest.
It will be appreciated that combustion deposition techniques may be used to deposit metal oxide coatings (e.g., single-layer anti-reflective coatings) on glass substrates, for example, to alter the optical and other properties of the glass substrates (e.g., to increase visible transmission). To this end, conventional combustion deposition techniques were used by the inventor of the instant application to deposit a single layer anti-reflective (SLAR) film of silicon oxide (e.g., SiO2 or other suitable stoichiometry) on a glass substrate. The attempt sought to achieve an increase in light transmission in the visible spectrum (e.g., wavelengths of from about 400-700 nm) over clear float glass with an application of the film on one or both sides of a glass substrate. In addition, increases in light transmission for wavelengths greater the 700 nm are also achievable and also may be desirable for certain product applications, such as, for example, photovoltaic solar cells. The clear float glass used in connection with the description herein is a low-iron glass known as “Extra Clear,” which has a visible transmission typically in the range of 90.3% to about 91.0%. Of course, the examples described herein are not limited to this particular type of glass, or any glass with this particular visible transmission.
The combustion deposition development work was performed using a conventional linear burner. As is conventional, the linear burner was fueled by a premixed combustion gas comprising propane and air. It is, of course, possible to use other combustion gases such as, for example, natural gas, butane, etc. The standard operating window for the linear burner involves air flow rates of between about 150 and 300 standard liters per minute (SLM), with air-to-propane ratios of about 15 to 25. Successful coatings require controlling the burner-to-lite distance to between about 5-50 mm when a linear burner is used.
Typical process conditions for successful films used a burner air flow of about 225 SLM, an air-to-propane ratio of about 19, a burner-to-lite distance of 35 mm, and a glass substrate velocity of about 50 mm/sec.
Particulate matter begins forming within the flame 18 and moves downward towards the surface 26 of the substrate 22 to be coated, resulting in film growth 120. As will be appreciated from
Using the above techniques, the inventor of the instant application was able to produce coatings that provided a transmission gain of 1.96% or 1.96 percentage points over the visible spectrum when coated on a single side of clear float glass. The transmission gain may be attributable in part to some combination of surface roughness increases and air incorporation in the film that yields a lower effective index of refraction.
Based in part on the successful deposition of metal oxide coatings on glass substrates, the inventor of the instant application realized that it would be advantageous to deposit alkaline earth fluorides including, for example, magnesium fluoride coatings (e.g., MgF2 or other suitable stoichiometry). Indeed, the deposition of magnesium fluoride coatings via combustion deposition would be advantageous, as magnesium fluoride is a prototypical material for single-layer anti-reflective (SLAR) coatings, owing to its low index of refraction. The index of refraction of bulk density (e.g., no or substantially no air incorporation) magnesium fluoride is nominally about 1.38. Magnesium fluoride (e.g., MgF2 or other suitable stoichiometry) is used for its inherent low refractive index and thus is used in anti-reflective coatings.
Thus, it will be appreciated that combustion deposition depositing alkaline earth fluorides including, for example, magnesium fluoride coatings, would be advantageous (e.g., in SLAR coatings).
At least one prior attempt has been used to generate alkaline earth fluoride nano-particles. In this attempt, Ca—, Sr—, and barium fluoride nano-particles were generated by flame spray pyrolysis of the corresponding metal organic precursor with hexafluorobenzene (see Grass, Robert N. and Wendelin J. Stark. “Flame synthesis of calcium-, strontium, barium fluoride nanoparticles and sodium chloride.” Chem. Commun., 2005, pp. 1767-69.). The metal organic precursors used were the 2-ethylhexanoate salts of the alkaline earth metal. These precursors were synthesized by dissolving Ca(OH)2, strontium acetate, or barium acetate in 2-ethylhexanoic acid. The nano-particles were collected on glass fiber filters placed above the flame. However, the possibility of depositing coatings (as opposed to generating bulk powders of nano-particles) does not appear to have been contemplated. Furthermore, the inventor of the instant application is not aware of any successful techniques for depositing alkaline earth metal fluoride coatings via combustion deposition.
Nevertheless, as noted above, the inventor of the instant application has recognized that the deposition of alkaline earth metal fluoride coatings via combustion deposition including, for example, the deposition of magnesium fluoride (e.g., MgF2 or other suitable stoichiometry), calcium fluoride (e.g., CaF2 or other suitable stoichiometry), strontium fluoride (e.g., SrF2 or other suitable stoichiometry), and barium fluoride (e.g., BaF2 or other suitable stoichiometry), would be advantageous. As such, it will be appreciated that there is a need in the art for viable atmospheric deposition routes to alkaline earth fluoride coatings, particularly magnesium fluoride (e.g., MgF2 or other suitable stoichiometry) inclusive coatings, using combustion deposition.
In certain example embodiments of this invention, a method of forming a coating on a glass substrate using combustion deposition is provided. A glass substrate having at least one surface to be coated is provided. An alkaline earth metal inclusive precursor and a fluorinating reagent to be combusted by a flame are introduced. At least a portion of the precursor and at least a portion of the reagent are combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate.
In certain example embodiments, a method of forming a coating on a glass substrate using combustion deposition is provided. A glass substrate having at least one surface to be coated is provided. A single-source precursor to be combusted by a flame is introduced. The single-source precursor is alkaline earth metal and fluorine inclusive. At least a portion of the precursor is combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate. The coating is a metal fluoride coating.
In certain example embodiments, a method of making a coated article including a combustion deposition deposited coating is provided. A glass substrate having at least one surface to be coated is provided. An alkaline earth metal inclusive precursor and a fluorinating reagent to be combusted by a flame are introduced. At least a portion of the precursor and at least a portion of the reagent are combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate.
In certain example embodiments, a method of making a coated article including a combustion deposition deposited coating is provided. A glass substrate having at least one surface to be coated is provided. A single-source precursor to be combusted by a flame is introduced. The single-source precursor is alkaline earth metal and fluorine inclusive. At least a portion of the precursor is combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate. The coating is a metal fluoride coating.
In certain example embodiments, a coated article is provided. The coated article comprises a substrate and a combustion deposition deposited alkaline earth metal fluoride coating supported by the substrate. The alkaline earth metal fluoride coating includes at least one of magnesium, calcium, strontium, and barium. The coating is a single-layer anti-reflective coating.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.
These and other features and advantages may be better and more completely understood by reference to the following detailed description of exemplary illustrative embodiments in conjunction with the drawings, of which:
a is a simplified view of an illustrative burner system used to carry out combustion deposition in accordance with an example embodiment;
b is a simplified view of another illustrative burner system used to carry out combustion deposition in accordance with an example embodiment;
a is an illustrative flowchart illustrating a process for depositing a metal fluoride coating on a glass substrate using combustion deposition in accordance with an example embodiment; and
b is an illustrative flowchart illustrating another process for depositing a metal fluoride coating on a glass substrate using combustion deposition in accordance with an example embodiment.
In certain example embodiments of this invention, a method of forming a coating on a glass substrate using combustion deposition is provided. A glass substrate having at least one surface to be coated is provided. An alkaline earth metal inclusive precursor and a fluorinating reagent to be combusted by a flame are introduced. At least a portion of the precursor and at least a portion of the reagent are combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate.
In certain example embodiments, a method of forming a coating on a glass substrate using combustion deposition is provided. A glass substrate having at least one surface to be coated is provided. A single-source precursor to be combusted by a flame is introduced. The single-source precursor is alkaline earth metal and fluorine inclusive. At least a portion of the precursor is combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate. The coating is a metal fluoride coating.
In certain example embodiments, a method of making a coated article including a combustion deposition deposited coating is provided. A glass substrate having at least one surface to be coated is provided. An alkaline earth metal inclusive precursor and a fluorinating reagent to be combusted by a flame are introduced. At least a portion of the precursor and at least a portion of the reagent are combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate.
In certain example embodiments, a method of making a coated article including a combustion deposition deposited coating is provided. A glass substrate having at least one surface to be coated is provided. A single-source precursor to be combusted by a flame is introduced. The single-source precursor is alkaline earth metal and fluorine inclusive. At least a portion of the precursor is combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate. The coating is a metal fluoride coating.
In certain example embodiments, a coated article is provided. The coated article comprises a substrate and a combustion deposition deposited alkaline earth metal fluoride coating supported by the substrate. The alkaline earth metal fluoride coating includes at least one of magnesium, calcium, strontium, and barium. The coating is a single-layer anti-reflective coating.
Certain example embodiments provide atmospheric deposition routes to alkaline earth fluoride coatings including, for example, magnesium fluoride (e.g., MgF2 or other suitable stoichiometry) inclusive coatings, using combustion deposition. In certain example embodiments, a metal inclusive precursor and a fluorinating reagent may be used in the combustion deposition coating of alkaline earth fluorides. The metal inclusive precursor may be a metal inclusive organic precursor including, for example:
It will be appreciated that any suitable stoichiometries of any of the above metal inclusive organic precursors may be used.
Suitable fluorinating reagents may be organic or inorganic fluorinating reagents. Suitable organic fluorinating reagents include, for example:
Organic based fluorinating agents may generate carbon dioxide and water in the combustion zone. By contrast, inorganic sources of fluorine may generate NOx and SOx emissions in the combustion zone. Such NOx and SOx emissions may combine with water produced from the combustion, thereby contributing to a corrosive environment. Thus, the use of an organic fluorinating agent may be advantageous in certain example implementations, in that its incorporation may help to provide for a less corrosive and more environmentally friendly environment.
In certain example embodiments, metal fluoride coatings may be formed from single-source precursors rather than using a metal inclusive precursor and a separate fluorinating reagent. Suitable single-source precursors include, for example, fluorinated acetoacetonates or Me(acacF)2 including, for example, tri- or hexafluoropentanedionates, as well as fluorinated metal alkoxides, alkanoates, and alkoxyalkoxides.
The forces behind these reactions are related to the affinity of Group 2 metals for fluorine and the corresponding lattice energy of forming the crystalline salt.
a is a simplified view of an illustrative burner system 200 used to carry out combustion deposition in accordance with an example embodiment.
As noted above, the metal organic precursor 204a and the fluorinating reagent 204b may be added to the combustion gas stream 102 using the same or different insertion mechanisms. For example, they may be added using a single insertion mechanism at substantially the same time in certain example embodiments when they are mixed together before insertion. In certain example embodiments when the metal organic precursor 204a and the fluorinating reagent 204b are not pre-mixed, they may be added to the combustion gas stream 102 at substantially the same time through the same or separate insertion mechanisms. When multiple insertion mechanisms 106 are implemented, they may be the same or different insertion system(s), and/or they may be provided at the same or different location(s).
b is a simplified view of another illustrative burner system 200′ used to carry out combustion deposition in accordance with an example embodiment. The burner system 200′ of
The precursor 204a and the reagent 204b in
While the coating 220 may be said to be “on” or “supported by” substrate 22 (directly or indirectly), other layer(s) may be provided therebetween. Thus, for example, the coating 220 may be considered “on” and “supported by” the substrate 22 even if other layer(s) are provided between growth 220a and substrate 22. Moreover, certain growths or layers of coating 220 may be removed in certain embodiments, while others may be added in other embodiments of this invention without departing from the overall spirit of certain embodiments of this invention.
a is an illustrative flowchart illustrating a process for depositing a metal fluoride coating on a glass substrate using combustion deposition in accordance with an example embodiment. In step S300, a substrate (e.g., a glass substrate) having at least one surface to be coated is provided. A fluorinating reagent and an optional carrier medium are selected and mixed together to form a reagent mixture in step S302. The reagent is selected so that at least a portion of the reagent forms the coating. The fluorinating reagent may be an organic fluorinating reagent or an inorganic fluorinating reagent. An alkaline earth metal inclusive precursor to be combusted using a burner is introduced in step S304. In step S306, at least a portion of the fluorinating reagent and/or reagent mixture, and at least a portion of the precursor are combusted, thereby forming a combusted material. The precursor and the fluorinating reagent and/or reagent mixture may be introduced by a number of means. For example, the precursor, fluorinating reagent, and/or reagent mixture may be introduced in a vapor state via a bubbler, as large particle droplets via an injector, and/or as small particle droplets via a nebulizer. Also, the precursor, fluorinating reagent, and/or reagent mixture may be injected into the combustion stream, for example. In step S308, the substrate is provided in an area so that the substrate is heated sufficiently to allow the combusted materials to produce growths, directly or indirectly, on the substrate when forming the coating. The combusted material may include at least some non-vaporized material (e.g., at least some particulate matter).
b is an illustrative flowchart illustrating another process for depositing a metal fluoride coating on a glass substrate using combustion deposition in accordance with an example embodiment. The process of
In certain example implementations of the processes of
Optionally, in one or more steps not shown, the opposing surface of the substrate also may be coated. Also optionally, the substrate may be wiped and/or washed, e.g., to remove excess particulate matter deposited thereon. A coating with a refractive index of 1.38 and low absorption is expected to provide a Tvis gain of greater than or equal to about 2.5% or 2.5% points, per side.
In certain example embodiments, magnesium fluoride (e.g., MgF2 or other suitable stoichiometry) coatings may be made via combustion deposition. However, in certain example implementations, other metal fluoride coatings may be made using combustion deposition where, for example, the metal is an alkaline earth metal (e.g., a Group 2 metal). Thus, in certain example implementations, coatings of Ca—, Sr—, and BaF2 (and suitable stoichiometries of the same) may be deposited via combustion deposition.
It will be appreciated that the metal inclusive organic precursors, fluorinating reagents, and/or single-source precursors identified above are provided by way of example. Any suitable stoichiometry similar to any of the precursors and/or reagents identified above may be used. Additionally, other metal fluorides may be deposited, other precursors may be used in connection with these and/or other metal fluoride depositions, the precursor delivery techniques may be altered, and/or other potential uses of such coatings may be possible.
Also, it will be appreciated that the techniques of the example embodiments described herein may be applied to a variety of products. That is, a variety of products potentially may use these and/or other AR films, depending in part on the level of transmission gain that is obtained. Such potential products include, for example, photovoltaic, green house, sports and roadway lighting, fireplace and oven doors, picture frame glass, etc. Non-AR products also may be produced.
The example embodiments described herein may be used in connection with other types of multiple layer AR coatings, as well. By way of example and without limitation, multiple reagents and/or precursors may be selected to provide coatings comprising multiple layers. The other layers may include the same and/or different materials
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
