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A photomask assembly is described having a frame for supporting a transparent pellicle above a photomask substrate, defining a closed pellicle space overlaying the substrate. The frame is formed of a porous material configured to allow the pellicle space to be purged with an inert gas within a reasonable processing time period, thereby removing any harmful chemicals that might be present. The frame preferably is made by a method that includes preparing a gel by a sol-gel process, drying the gel, and partially densifying the dry gel. The resulting frame has a gas permeability to oxygen or nitrogen higher than about 10 ml.mm/cm.sup.2.min.MPa, an average pore size between 0.001 micrometer and 10 micrometers, and a coefficient of thermal expansion between 0.01 ppm/.degree. C. and 10 ppm/.degree. C.
An encapsulant is described for an optoelectronic device or optical component, which provides a coefficient of thermal expansion of less than 50 ppm/.degree. C., with a variation of less than .+-.30%, and further provides an optical transmittance of at least 20% at a wavelength in the range of 400 to 900 nm, at an encapsulant thickness of about 1 mm. The encapsulant includes a filler consisting essentially of glass particles having diameters smaller than 500 .mu.m, being essentially free of titania and lead oxide, and having a refractive index in the range of 1.48 to 1.60, with a variance of less than about 0.001. A method for making the encapsulant also is described, the method including steps of (1) processing the glass to form particles having diameters between 1 and 500 .mu.m, (2) preparing an epoxy resin composition having at a cured stage a refractive index close to that of the glass filler particles, (3) mixing the epoxy resin composition with the filler particles to form a filled epoxy resin composition, (4) encapsulating an optoelectronic device with the filled epoxy resin composition, and (5) curing the filled epoxy resin composition. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A process for forming a siloxane oligomer from a mixture comprising at least one alkoxysilane, at least one phase transfer catalyst having a specified structure, and water is described. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A process including forming a siloxane oligomer from a mixture including at least one alkoxysilane, at least one phase transfer catalyst, and water, and adding at least one latent curing catalyst to the siloxane oligomer to form a coating composition is described. Also described is a process for producing a rapidly cured abrasion resistant coating, including providing a coating composition including a siloxane oligomer and thermal latent curing catalyst, applying the coating composition to an article, and curing the coating composition for less than about 10 minutes to form a coating that has a Bayer ratio of abrasion resistance of at least about 2.0. A coating composition including at least one siloxane oligomer, at least one phase transfer catalyst, and at least one latent curing catalyst is also described. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
An encapsulant is described for an optoelectronic device or optical component, which provides a coefficient of thermal expansion of less than 50 ppm/.degree. C., with a variation of less than .+-.30% and further provides an optical transmittance of at least 20% at a wavelength in the range of 400 to 900 nm, at an encapsulant thickness of about 1 mm. The encapsulant includes a filler consisting essentially of glass particles having diameters smaller than 500 .mu.m, being essentially free of titania and lead oxide, and having a refractive index in the range of 1.48 to 1.60, with a variance of less than about 0.001. A method for making the encapsulant also is described, the method including steps of (1) processing the glass to form particles having diameters between 1 and 500 .mu.m, (2) preparing an epoxy resin composition having at a cured stage a refractive index close to that of the glass filler particles, (3) mixing the epoxy resin composition with the filler particles to form a filled epoxy resin composition, (4) encapsulating an optoelectronic device with the filled epoxy resin composition, and (5) curing the filled epoxy resin composition. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
An encapsulant for use with opto-electronic devices and optical components incorporates a filler made from a glass that has been processed into particle form and heated to a predetermined temperature for a predetermined time, along with an epoxy having an index of refraction matched to that of the glass and heated to a predetermined temperature for a predetermined time, to prevent settling of the filler particles after mixing the filler particles with the epoxy, and thereby obtaining uniform dispersion of the particles within the epoxy. The encapsulant provides for high light transmittance, and its coefficient of thermal expansion can be varied by varying the amount of filler without substantially altering the optical properties of the encapsulant. The coefficient of thermal expansion variation within the encapsulant preferably is less than 30%, due to uniform dispersion of the filler particles within the epoxy. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A method suited for producing thin fused glass articles includes, in preferred aspects, preparing a dry gel having edges configured to reduce or eliminate warping of the gel during densification of the gel. Preferred aspects include partially densifying the gel, machining the gel into a suitable shape, and fully sintering the gel. The gel preferably is a hybrid incorporating silicon alkoxide and fumed silica particles, and it preferably is machined to have chamfered edges. The method is easier and more cost-effective than those previously known, and it allows for production of high-quality articles for use in, for example, photomask systems as pellicles. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A photomask assembly is described having a frame for supporting a transparent pellicle above a photomask substrate, defining a closed pellicle space overlaying the substrate. The frame is formed of a porous material configured to allow the pellicle space to be purged with an inert gas within a reasonable processing time period, thereby removing any harmful chemicals that might be present. The frame preferably is made by a method that includes preparing a gel by a sol-gel process, drying the gel, and partially densifying the dry gel. The resulting frame has a gas permeability to oxygen or nitrogen higher than about 10 ml.mm/cm.sup.2.min.MPa, an average pore size between 0.001 micrometer and 10 micrometers, and a coefficient of thermal expansion between 0.01 ppm/.degree. C. and 10 ppm/.degree. C. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Electrical connectors incorporate a composite coating of molybdenum disulfide and a metal, preferably tin, for one or both of the contact surfaces of the electrical connector. The coating provides for a low coefficient of friction, low contact resistance, and good electrical conductivity, as well as good mechanical properties. The coating also reduces the insertion force of the electrical connectors, thereby increasing the number of possible terminal pairs and/or reducing terminal bending and breakage for a manually mated connector. The coating can be deposited on copper, tin-plated copper, tin alloy-plated copper or other metallic substrates, using any of the several physical vapor deposition methods. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
This invention resides in an apparatus and related method for rapidly curing thin film sol-gel coatings, particularly substrates, whether rigid or flexible, without deforming the substrate. The curing is achieved using IR heating lamps and dry or humid hot gas flow. This curing densities the sol-gel coating and provides desired optical and mechanical properties. The use of IR lamps and hot-gas nozzles, either singularly or in combination, produces a rapid cure by effectively heating the thin film coating layer. In this manner, a sufficiently high temperature can be attained in the film layer, to densify the sol-gel coating, but for a sufficiently short time duration to avoid melting or otherwise deforming the substrate. The sol-gel coatings can be cured two to three orders of magnitude faster than with conventional oven curing, leading to significant cost reductions and manufacturing efficiency. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
An encapsulant for use with opto-electronic devices and optical components incorporates a filler made from a glass that has been processed into particle form and heated to a predetermined temperature for a predetermined time, along with an epoxy having an idex of refraction matched to that of the glass and heated to a predetermined temperature for a predetermined time, to prevent settling of the filler particles after mixing the filler particles with the epoxy, and thereby obtaining uniform dispersion of the particles within the epoxy. The encapsulant provides for high light transmittance, and its coefficient of thermal expansion can be varied by varying the amount of filler without substantially altering the optical properties of the encapsulant. The coefficient of thermal expansion variation within the encapsulant preferably is less than 30%, due to uniform dispersion of the filler particles within the epoxy. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A new method is disclosed for producing thin plates by sintering a thin gel plate (e.g. silica) made using a sol-gel process, which substantially eliminates warpage of the plate during the sintering step. Sintering a sol-gel based silica plate in a dense glass typically causes significant shrinkage, and this can cause the plate to curl, especially around its edges. This phenomenon is referred to as warpage. In the method of the invention, the sintering step is performed while the gel plate is mounted on a support surface, separated by a thin layer of refractory powder. At the high sintering temperature, the powder partially fuses and sticks to both the gel plate and the support surface, which prevents non-uniform stresses in the gel plate from warping the plate. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A sol-gel process for producing dry porous gel monoliths, e.g., silica glass monoliths, in which the successive process steps of gelling, aging and drying all occur within a mold formed of a selected porous material, e.g., graphite. The mold is inert to the gel solution and it has sufficient strength to withstand the temperatures and pressures encountered during the process. The mold and gel thereby can remain within a sealed autoclave during these process steps, and mechanical handling of the mold and the gel are minimized. This substantially enhances the process' efficiency. Alternatively, the mold can have a non-porous inner skin to enhance ease of cleaning of the mold, and of removal of the gel. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A process is described for applying a thin-film, hydrophobic, oil-repellant, stain-resistant, optical coating to a transparent substrate. The coating is applied using a treatment solution that incorporates an organosilane in a solvent of water, alcohol, and ethylene glycol or glycerol, and an acid catalyst, with the organosilane having a preferred concentration in the range of 0.05 to 50 mmole per liter. The treatment solution preferably is prepared in a two-step procedure, in which the organosilane is first reacted in concentrated form and then diluted. After the treatment solution has been applied to the transparent substrate, e.g., by dip coating, the coated substrate is dried, preferably by flash-drying at room temperature and then heating it to a prescribed elevated temperature, in a prescribed humidity. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Disclosed is a sol-gel process for making high-density monolithic alpha-alumina articles. Cracking problems caused by shrinkage of the gel during the drying and firing stages are minimized by controlling the temperature and humidity during the drying process and by using molds formed of prescribed polymeric materials, preliminarily coated with a silicone release agent. The proess of the invention provides porous alpha-alumina articles having a controlled microstructure and a controlled pore size distribution, which are beneficial features when the material is used in practical applications, e.g., as substrates for gas sensors. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
An improved partial reflector is disclosed in which the reflector is configured to provide selected levels of reflectance, transmittance and efficiency that are substantially uniform over the visible wavelength range of 400 to 70 nanometers. This result is achieved using a special three-layer coating that includes a metal layer sandwiched between two metal oxide dielectric layers having relatively high refractive indices >2.0. Advantageously, the three layers all incorporated the same metal, preferably niobium. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A sol-gel process for producing dry porous gel monoliths, e.g., silica glass monoliths, in which the successive process steps of gelling, aging and drying all occur within a mold formed of a porous material, e.g. graphite. The mold is inert to the gel solution and it has sufficient strength to withstand the temperatures and pressures encountered during the process, yet it has sufficient porosity to facilitate the escape of liquid from the gel thereby can remain within a sealed autoclave during these process steps, and mechanical handling of the hold and the gel are minimized. This substantially enhances the process’ efficiency. Alternatively, the mold can have a non-porous inner skin.
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An improved apparatus, and related method of operation, is described for rapidly drying large monoliths of glass, ceramic and/or composite material, under subcritical conditions, while minimizing the risk of cracking the monolith during the drying process. The apparatus incorporates a pressure chamber for carrying the monolith to be dried, with no significant limitation on the size of the monolith relative to the size of the chamber. The monolith is initially immersed in a suitable drying solvent, and the temperature of the pressure chamber is raised to a predetermined value below the solvents critical temperature, which raises the pressure to a predetermined value, likewise below the solvents critical pressure. At a selected time during the drying process the pressure chamber is connected to a diffusion chamber, to draw away and condense solvent vapor. This drawing away of solvent vapor continues until the monolith is dry, at which time the pressure chamber is purged with an inert gas and then depressurized in a controlled manner. The apparatus thereby is configured to dry the monolith at an even lower subcritical pressure than previous apparatus of this kind, leading to increased safety and reduced operating expenses. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A coated transparency, and method for making it, is disclosed, the transparency having a multi-layer antireflection coating that provides high transmittance with low specular reflectance, yet that also provides reduced visibility of surface defects. The coating includes alternating layers of polymerized silicon dioxide and polymerized titanium dioxide on a transparent substrate, with at least one of the layers incorporating discrete particles having a refractive index different from that of surrounding polymer. This provides the coating with a diffuse reflectance that is comparable to, or larger than, its specular reflectance, yet that still is negligible when compared to the coatings transmittance. The diffuse reflectance creates a loss of contrast for any reflected image or glare, thus masking any surface defects and proving a comfortable visual appearance. The successive layers of the antireflective coating are deposited on the substrate by applying separate solutions of an alkoxide, an alcohol, and water, and by curing the layer at an elevated temperature before the next succeeding layer is applied. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
An improved apparatus, and related method of operation, is described for rapidly drying large monoliths of glass, ceramic and/or composite material, under subcritical conditions, while minimizing the risk of cracking the monolith during the drying process. The apparatus incorporate a pressure chamger for carrying the monolith to be dried, with no significant limitation on the size of the monolith relative to the size of the chamber. The monolith is initially immersed in a suitable drying solvent, and the temperature of the pressure chamber is raised to a predetermined value below the solvents critical temperature, which raises the pressure to a predetermined value, likewise below the solvents critical pressure. At a selected time during the drying process the pressure chamber is connected to a diffusion chamber, to draw away and condense solvent vapor. This drawing away of solvent vapor continues until the monolith is dry, at which time the pressure chamber is purged with an inert gas and then depressurized in a controlled manner. The apparatus thereby is configured to dry the monolith at an even lower subcritical pressure than previous apparatus of this kind, leading to increased safety and reduced operating expenses. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A sol-gel process is disclosed for depositing multi-layer antireflection coatings on plastic substrates. One or more polymerized, titanium-containing solutions are provided by mixing titanium alkoxide, an alcohol, and water, and one more polymerized, silicon-containing solutions are provided by mixing a silicon alkoxide, an alcohol, and water. These solutions are applied to the plastic substrate in an alternating fashion, to produce a succession of uniform layers of polymerized titanium dioxide and polymerized silicon dioxide. Each layer is individually cured before the next layer is applied. The resulting coating of multiple polymerized layers provides very low reflectance over the entire visible wavelength range, yet with excellent mechanical strength and durability. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A process is disclosed for drying sol-gel derived porous wet bodies without inducing cracks therein. The wet gel preferably is immersed in a liquid solvent before being placed inside a drying chamber capable of withstanding relatively high pressures and temperatures. After the wet gel is loaded, the chamber is sealed from the outside environment, and then is heated from outside the chamber in a controlled manner until a prescribed subcritical pressure is reached. The final temperature and pressure are always lower than the critical temperature and pressure of the drying solvent. The solvent vapor is then evacuated from the chamber in a controlled fashion to decrease the pressure until ambient pressure is reached, while preferably maintaining the temperature inside the chamber at the prescribed level. Thereafter, the inside of the chamber is purged with an inert gas for a prescribed time period, after which the chamber is cooled to ambient temperature and the dry crack-free porous gel is removed. The resulting dry gels are crack-free and monolithic. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A process and apparatus are described for rapidly drying a wet, porous gel monolith of glass or ceramic, at subcritical temperatures without inducing any cracking of the gel. The wet gel is immersed in a liquid solvent in a chamber, and the liquid solvent is then heated and expelled from the chamber. Further heating, with or without the presence of a flowing inert gas, fully dries the wet gel. When an inert gas is used, the gas is delivered to the chamber with a controlled solvent partial vapor pressure, to correspondingly control the driving force for drying the gel. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
An improved sol-gel process for fabricating large, crack-free gel monoliths (e.g. of silica) is described in which a specially-tailored gel microstructure is provided by adjusting the relative concentrations of an alcohol diluent (e.g. ethanol) and/or one or more catalysts (e.g. HCI and HF). Controlled variations in the gels average pore radius, bulk density, rupture modulus, and elastic modulus over a wide range can be tailored in this fashion. This enables the process to be optimized for the particular application involved. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A sol-gel process for forming a germania-doped silica glass rod that is suitable for use as a perform in the manufacture of high numerical aperture optical fibers. The sol is produced by mixing together prescribed quantities of alkoxides including tetraethyl orthosilicate and tetraethyl orthogermanate, deionized water, ethanol and a precipitation catalyst such as hydrofluoric acid. Premature precipitation of germania is avoided by adding ethanol and deionized water to an alkoxide solution at a controlled, drop-wise rate and by then similarly adding the catalyst at a controlled, drop-wise rate. After drying the resulting gel, sintering is performed by chlorinating the dry gel to remove residual hydroxyl groups, then oxygenating the chlorinated gel to remove the chlorine, and finally heating the oxygenated gel in helium to a temperature of about 1300 C. Chlorinating and oxygenating the gel for extended time durations, and maintaining the gel above 1200 C for less than 30 minutes, ensures that the final glass rod will not bubble when subsequently raised in temperature to 1800 deg. C during the final fiber draw step. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
A process and apparatus are described for rapidly drying a wet, porous gel monolith of glass or ceramic, at subcritical temperatures without inducing any cracking of the gel. The wet gel is immersed in a liquid solvent in a chamber, and the liquid solvent is then heated and expelled from the chamber. Further heating, with or without the presence of a flowing inert glass, fully dries the wet gel. When a inert gas is used, the gas is delivered to the chamber with a controlled solvent partial vapor pressure, to correspondingly control the driving force of drying the gel. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
An improved sol-gel process is disclosed for fabricating large monoliths of silica or ceramic material, which are substantially free of cracks. Following formation of the gel, but before the gel is dried, the gel is subjected to a hydrothermal aging treatment, in which it is heated in an autoclave to a temperature of between 100? and 300? C, for a time duration of at least about one hour. This hydrothermal aging treatment causes silica (or ceramic) particles to migrate and fill small pores in the porous gel matrix, such that the average pore size increases and capillary forces encountered in the subsequent drying step are reduced to a point where cracking of the gel is substantially eliminated. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |