| Method for manufacturing optical glasses and coloured glasses at low temperatures -> Monitor Keywords |
|
|
  Method for manufacturing optical glasses and coloured glasses at low temperaturesUSPTO Application #: 20060240968Title: Method for manufacturing optical glasses and coloured glasses at low temperatures Abstract: The invention relates to a method for manufacturing optical glasses and coloured glasses with the aid of a fluid phase sintering process from a basic material encompassing at least SiO2 powder as well as additives for reducing the temperature of the fluid phase sintering and/or melting process encompassing the following steps: the starting materials are dissolved in any sequence in a fluid medium to produce a solution as far as is possible and a suspension to the extent that they are not dispersed in solution; a greenbody is produced from the dissolved and dispersed starting materials; the greenbody is dried the dried greenbody is fluid-phase sintered at temperatures below 1200° C., in particular in the temperature range from 600° C. to 1200° C. (end of abstract) Agent: Baker & Daniels LLP 111 E. Wayne Street - Fort Wayne, IN, US Inventors: Jochen Freund, Monika Gierke, Uwe Kolberg, Ruediger Hentschel, Rolf Clasen USPTO Applicaton #: 20060240968 - Class: 501058000 (USPTO) Related Patent Categories: Compositions: Ceramic, Ceramic Compositions, Glass Compositions, Compositions Containing Glass Other Than Those Wherein Glass Is A Bonding Agent, Or Glass Batch Forming Compositions, Silica Containing, 40 Percent - 90 Percent By Weight Silica, And Halogen Or Nitrogen, Fluorine, The Patent Description & Claims data below is from USPTO Patent Application 20060240968. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The invention concerns a method for manufacturing optical glasses and/or coloured glasses using a sintering or melting process. A sintering process is defined as a process involving a viscosity of 0>1.times.10.sup.8 dPa s and a melting process is defined as a process involving a viscosity of 0<1.times.10.sup.2 dPa s. In particular cases this method can be used to manufacture multi-component glasses, particularly coloured glass which is tinted by means of MX semiconductor doping, with M being defined as either Cd alone or Cd+Zn and X being defined as S, Se or Te. [0002] Essentially two methods for manufacturing glasses by means of a sintering process are known by those conversant with current state of the art technology: [0003] the sol-gel process and [0004] a method employing powder technology. [0005] One method that can be employed to produce glass by means of a sol-gel process is described in U.S. Pat. No. 4,432,956. However, this patent only describes the production of silica glass manufactured at temperatures of 1300-1500.degree. C. [0006] In order to include further components in glass synthesis one can avail oneself of methods such as those described in patents DE 4129409 A1, EP 0233732 A1 and U.S. Pat. No. 5,091,115. All these methods are based on silicon alkoxides such as tetraethyl orthosilicate (TEOS) and other soluble compounds that as a rule are processed using alcoholic solvents. A base material for SiO.sub.2 can be, for example tetraethyl orthosilicate and the base materials for adding further glass components, such as B.sub.2O.sub.3, Al.sub.2O.sub.3, Na.sub.2O or P.sub.2O.sub.5, can be boric acid trimethyl ester, aluminium triisopropylate, sodium methylate, zinc-2,4-pentanedionat, tributyl phosphate, or other alkoxides. Some of these raw materials are toxic so the sol-gel method is disadvantageous in terms of environmental aspects due to the raw materials employed and to date have only been used for coated glasses. A further disadvantage of the sol-gel method is that the process is costly due to the expense of the raw materials, requires a considerable amount of time and cannot be employed for large components due to the high level of shrinkage in drying and cracking. [0007] A manufacturing process by means of which a CdSSe-doped coloured glass can be produced using a sol-gel process is described in JP 02221130 A. However, this method employs the same silica alkoxide as its raw material as that described in U.S. Pat. No. 4,432,956, so that it has the same disadvantages as all sol-gel methods, particularly in terms of the environment. [0008] Another method for producing glass using a sintering process is a method employing powder technology. The patent EP 0196140 B1 describes a method employing powder technology. The method disclosed in EP 0196140 B1 employs a nanoscale Si0.sub.2 powder such as Aerosil OX-50 (DEGUSSA AG) as a base material. In comparison with the sol-gel method this method has the advantage in the preferred case that no alcoholic raw materials or solvents have to be used and water can be employed as the dispersion medium. This results in less environmental contamination, the prevention of unpleasant smelling vapours, the elimination of fire danger and more cost-effective production. [0009] The production of glass in accordance with EP 0196140 B1 is based on the fact that a glass powder suspension is produced and that this suspension is further processed into a greenbody. The greenbody can be condensed to form transparent, dimensionally stable glass following drying. This has the advantage that the intermediate glass product can be produced at room temperature and retains its shape and form during firing. [0010] However, EP 0196140 B1 only describes the production of silica glass that is sintered at temperatures between approximately 1300 and 1500.degree. C. These temperatures are too high for employing MX as the doping material since a large proportion of the doping material is sublimated or oxidised at these temperatures. Another disadvantage is that the high temperatures make the process exceptionally energy consuming. [0011] Further methods that employ nanoscale SiO.sub.2 powder and other components in addition to SiO.sub.2 are described in the patents JP 62167233 A, JP 60171228 A, JP 62100428 A and JP 03159924 A. [0012] However, in accordance with JP 62167233 A, JP 60171228 A, JP 62100428 A and JP 03159924 A, the nanoscale SiO2 is only utilised as an additional component to the alkoxide silicates such as for instance TEOS. These raw materials and the use of alcoholic solvents also result in environmental contamination from the production of these glasses. Moreover, in order to manufacture glasses in accordance with JP 62167233 A, JP 60171228 A, JP 62100428 A and JP 03159924 A, temperatures have to be employed which are between 1200 and 2000.degree. C. [0013] U.S. Pat. No. 5,122,178 and JP 60016830 A disclose manufacturing processes for CdS, CdSe and CdTe doped glasses. The methods in both these patents are based, however, on the glass being melted. In U.S. Pat. No. 5,122,178, as in the normal manufacturing process for these glasses, the doping agent is added during the melting process. The sole differences with respect to the established manufacturing process are the modified processing temperatures and process stages. However, relatively high processing temperatures of 1300.degree. C. are still required for melting the glass. The patent JP 60016830 A is based on a two-phase process. Initially a colourless base glass is melted and doped by adding powdered CdS after the grinding process and then finally sintered. The drawbacks to the process described in JP 60016830 A are the time-consuming and costly multi-stage processing and the fact that it is not possible to produce the shape of the final product at the greenbody production stage when using the manufacturing method pursuant to JP 60016830. This means that the shape of the end product is achieved in JP 60016830 A by means of sintering a powder blank. Shaping during the sintering process is particularly difficult, however, when bodies of a complex shape are to be manufactured. [0014] It is therefore the aim of the invention to make known a production method for optical glasses that overcomes the disadvantages of current state-of-the-art technology and in particular, makes it possible to manufacture coloured glasses using MX doping substances. The method is environmentally friendly, cost-effective and energy-efficient and presents no fire hazard. [0015] In accordance with the invention, this aim is fulfilled by a method in accordance with Claim 1. [0016] The inventors have recognised the fact that the method in accordance with the invention is conducted in a viscosity range that corresponds neither with that of the classic sintering process with its viscosity of 0>1.times.10.sup.5 dPa s nor with that of the classic melting process with its viscosity of 0<1.times.10.sup.2 dPa s, but in a viscosity range between these. Therefore, the process in accordance with the invention is termed fluid phase sintering or high viscosity melting. The advantage over the sintering process is that with the process in accordance with the invention, the grain boundary between the components and therefore also the concentration gradients are reduced not only by the diffusion process, but also by plastic flow processes. This results in the process in accordance with the invention being clearly more effective than the classic sintering process. In order to fully maintain the external shape, a ceramic aid is used for stabilisation purposes. In comparison with a pure melting process, it is the substantially lower temperature that constitutes the advantage. [0017] In accordance with the method specified in the invention, a powdery SiO2 or SiO.sub.2 suspension encompassing a greenbody and that can be sintered is produced by means of a method employing powder technology. Further additives are used in addition to the powdery SiO.sub.2 to reduce the temperature of the sintering process in comparison with that found in current state-of-the-art processes and to match the properties of the glass to the doping agent, with no alcoholic solvents being required. [0018] The raw material is SiO.sub.2 powder with a primary particle size between 8 nm and 800 nm, preferably 20-100 nm or a SiO.sub.2 suspension. The raw materials used as additives are boric acid, zinc oxide, potassium carbonate, potassium hydroxide solution and other compounds that have network-modifying properties. However, the additives can also be any other kind of carbonate, alkaline solutions and bases, such as for instance a caustic soda solution or potassium hydrogen fluoride. It is irrelevant whether the raw materials are added individually or in suspension or whether two or more of these raw materials are introduced into the process as previously semi-processed physical or chemical multi-component mixing phases. Moreover, the dispersion aids such as ammonium fluoride, other alkaline solutions and acids, such as for instance sulphuric acid or phosphoric acid, can be added. As these chemicals are also available in standardised, analytically pure form, it is possible to produce highly refined optical glasses with the aid of the method in accordance with the invention, with the degree of purity of the glasses being subject to the impurities in the additional glass components. [0019] The production of a glass in accordance with the invention described here encompasses the production of a greenbody from the base materials including Si02 powder or SiO.sub.2 suspension and the additives, such as for instance dispersion aids, and from sintering or melting the glass from these greenbodies. [0020] The greenbodies are produced by means of dispersion and dissolution of the base materials in any sequence in water, or optionally also in an alcoholic solvent. [0021] In order to attain coloured glass, the MX doping substance, such as for instance CdS, CdSe, CdTe, but also mixed crystals such as CdS/CdSe, is dispersed or dissolved together with the base materials. Instead of using CdS, CdSe or CdTe it is also possible to employ in-situ production of doping substances from the elements, such as Cd+Te.fwdarw.+CdTe, or from other materials, for instance CdO, Na.sub.2SeO.sub.3 and reduction gases. Other dyes such as for instance copper indium diselenide (CuInSe.sup.2) or transition metals such as for instance CoO are also possible. [0022] Dissolving and dispersing the base materials and any dopants that may be used for producing a greenbody is undertaken advantageously in such a way that this results in a suspension that can be poured or spread. In a preferred embodiment the suspension is poured into a mould. After the suspension has hardened at room temperature or at temperatures below 100.degree. C. the greenbody is dried at room temperature or at temperatures not exceeding 400.degree. C. The dried greenbody in then sintered or melted at temperatures between 600-1200.degree. C., preferably between 700-1100.degree. C., subject to the glass composition. [0023] Optionally, the greenbodies can be ground again or ground again, then dispersed and dried in order to improve the homogeneity and quality of the resultant glass. [0024] The glasses can contain common purifiers in their customary quantities. Purifiers are deemed to be those components that release or vaporise gases within the temperature range determined by the method as a result of redox reactions. Preference is given to purifiers that in addition to having a purifying effect have a positive effect upon coloration as a consequence of the intervention in the redox process. Redox additives are for instance As.sub.2O.sub.3, Sb.sub.2O.sub.3, AS.sub.2S.sub.3 and Sb.sub.2S.sub.3. [0025] It has proven particularly advantageous for the schliere quality if the maximum proportion of F is 2 wt. %. [0026] The invention is described in an exemplary manner with reference to the embodiments and the FIGURE. Continue reading... Full patent description for Method for manufacturing optical glasses and coloured glasses at low temperatures Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method for manufacturing optical glasses and coloured glasses at low temperatures patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Method for manufacturing optical glasses and coloured glasses at low temperatures or other areas of interest. ### Previous Patent Application: Alkali resistant glass compositions Next Patent Application: Composition for grey silica-sodium calcic glass for producing glazing Industry Class: Compositions: ceramic ### FreshPatents.com Support Thank you for viewing the Method for manufacturing optical glasses and coloured glasses at low temperatures patent info. IP-related news and info Results in 0.90054 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf |
||
