Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/006—Surface treatment of glass, not in the form of fibres or filaments, by coating with materials of composite character
  • C03C17/008—Surface treatment of glass, not in the form of fibres or filaments, by coating with materials of composite character comprising a mixture of materials covered by two or more of the groups C03C17/02, C03C17/06, C03C17/22 and C03C17/28
  • C03C17/009—Mixtures of organic and inorganic materials, e.g. ormosils and ormocers
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
  • C03C1/006—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce glass through wet route
  • C03C1/008—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce glass through wet route for the production of films or coatings
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2218/00—Methods for coating glass
  • C03C2218/10—Deposition methods
  • C03C2218/11—Deposition methods from solutions or suspensions
  • C03C2218/113—Deposition methods from solutions or suspensions by sol-gel processes

Definitions

• the present invention is directed to compositions and methods of creating and applying coatings to glass substrates for strengthening same.
• Glass is very sensitive to mechanical stress. Theoretically, regarding its structure, glass should have a very high strength. However in practice, devices fabricated from glass exhibit lower strength and higher failure rates than predicted due to mechanical imperfections, essentially surface defects. Thus, failure rates are determined at least in significant part by the quality of the glass at the surface and edges. Unfortunately, these types of defects contribute to reducing the useful lifetime of the glass.
• Possibilities for strengthening the glass after flaw creation include thermal tempering and chemical tempering.
• Chemical tempering requires an ion exchange involving generally alkaline elements over a penetration depth of about 10 ⁇ m, which strengthens the glass by induced compression at the surface.
• alkaline-free glass such as EAGLETM glass (from Corning Incorporated)
• thermal or chemical tempering does not assure the long term performance of the glass, and such processes can be expensive to implement.
• compositions and methods relating to the creation and application of coatings for strengthening glass substrates that already have surface flaws (or with non-defect free glass surfaces) include applying a thin film of a composition, made from a sol-gel precursor that is pre-hydrolyzed with an additive comprising at least water, to a glass substrate.
• Application of the composition may occur at ambient conditions, and the glass substrate with the composition coating layer is cured at moderately elevated temperatures .
• the moderately elevated temperatures used allow the potential for organic groups to still be present after thermal treatment.
• the coating might be bonded chemically to the glass substrate.
• coatings according to various embodiments of the present invention may be applied in any way known in the art, such as dip coating. Further, the coating methods may call for application of the composition to any portion of the glass substrate.
• a composition for a glass substrate coating may include a precursor and an additive, which contains an under-stoichiometric amount of water.
• the amount of water in the additive allows hydrolysis to occur when mixed with the precursor, and in some embodiments, the only water necessary for hydrolysis may be obtained from the humidity of ambient air.
• the precursor provides the foundation for the coating composition, and may contain Si, Ti, cross linkable moieties, or any combination thereof.
• the composition may be diluted with a solvent, such as water or alkanol, i.e., ethanol or isopropanol, to adjust the viscosity of the composition.
• water can be used as solvent as well, which may yield even better results than, for example, using ethanol to dilute poly(3-aminopropyl) silsesquioxane.
• additional coating compositions may be created through mixing a composition with another composition when necessary.
• the coatings in the present invention use an under stoichiometric amount of water, which yields a reaction product with a differently condensed molecular structure (as compared with the prior art) .
• the approach effectively hinders crack propagation when used to form/apply the coating.
• the conventional coating compositions are created in a stoichiometrical excess of water, there is very limited presence of water in the present invention, and such low-water containing compositions yield an improved, if not maximized, Weibull modulus and failure strength combination that has not previously been achieved with other coatings and processes.
• silsesquioxanes (1 mol of, for example, ⁇ - aminopropyl triethoxy silane or glycidoxypropyl trimethoxy silane pre-hydroIyzed with 1.5 mol of water) for strengthening
• cross-linkable silsesquioxanes allows for further cross-linking of the organic moieties, yielding a more dense network without precipitation, as is usually observed when working with an excess of water for hydrolysis.
• the hybrid organic-inorganic functionalities of the coating compositions cured around 200 degrees C not only reinforce the glass substrate but also have the potential to protect the surface from mechanical impacts .
• Fully pyrolyzed inorganic coatings yield a strength increase but no protection from mechanical impacts, which would be directly transmitted from the coating to the brittle substrate material.
• FIG. 1 is a graph depicting the change in Weibull parameter and failure strength of the strength distribution of coated specimens versus that of uncoated specimens using a number of types of sample substrates according to the prior art.
• FIG. 2 is a drawing illustrating a coating composition applied to one surface of a glass substrate.
• FIG. 3 is a drawing illustrating a coating layer covering most or all of the surfaces of a glass substrate.
• FIG. 4 is a graph depicting the Weibull modulus and the failure strength increase potential for a prior art coating and for a new coating composition according to one or more aspects of the present invention.
• FIG. 5 is a table listing the precursors, additive (s), solvents, dip coating withdrawal speeds, and curing temperatures for coating compositions according to one or more embodiments of the present invention.
• FIG. 6 is a table listing changes in Weibull modulus and failure strength for a number of coating compositions and processes used on Coming's EAGLETM glass substrates according to various aspects of the present invention.
• FIG. 7 is a table listing changes in Weibull modulus and failure strength for a number of coating compositions and processes used on Coming's EAGLETM glass substrates according to the prior art.
• the invention includes compositions and methods relating to the creation and application of coatings for strengthening of pre-damaged glass substrates.
• the present invention relates to compositions and methods for creation and application of coatings onto thin and ultra-thin glass , such as Corning Incorporated EAGLETM glass .
• FIG. 1 is a chart showing changes in the Weibull modulus and changes in the failure strength resulting from coating a number of (different) glass substrates. All five coating/substrate combinations of FIG. 1 are in accordance with the prior art. While there is always an increase in the strength of the coated glass specimens versus that of uncoated glass specimens, there is also a resultant decrease in the Weibull parameter due to the coating. Thus, there is a decrease in the overall strength distribution of the glass.
• the coatings used in the experiments from which the data of FIG. 1 was taken were applied from aqueous solutions. The water employed for hydrolysis of the precursor in the three coatings/substrates on the left of FIG. 1 was used in a stoichiometric excess process . Even in cases where the Weibull parameter of the glass specimens does not fall as a result of the coating process, the net increase in the Weibull modulus and the failure strength does not achieve satisfactory levels.
• a composition for a glass substrate coating may include a precursor and an additive, which contains an under-stoichiometric amount of water.
• the additive provides an amount of water for allowing hydrolysis to occur when mixed with the precursor.
• the only water necessary for hydrolysis may be obtained from the humidity of ambient air.
• the precursor provides the foundation for the coating composition and may contain Si, Ti, cross linkable moieties, or any combination thereof.
• a precursor is mixed with an additive.
• Many mixing methods known to those of skill in the art may be used.
• the composition may be mixed in a PE bottle with a cap by stirring the precursor and additives together. After mixing a precursor with the additive(s), an adequate amount of time is needed for the reaction to form a composition. Once the reaction is complete, the composition may be diluted with a solvent to adjust the viscosity of the composition.
• the solvent may comprise at least one of: an organic solvent containing one or more hydroxyl groups, ethanol, isopropanol, glycol, ethylene glycol, and water.
• a previously created composition may act as a precursor or an additive for the creation of additional coating compositions through mixing one composition with another composition.
• a glass substrate 100 is illustrated with a coating layer 112 in accordance with one or more embodiments of the present invention.
• the coating layer 112 is depicted on one surface of the glass substrate 100; however, the coating layer 112 may cover a greater amount of the glass substrate surface. For instance, referring to FIG. 3, the coating layer 112 covers some or all of the surfaces of the glass substrate 100. It is noted that the term "surface” as used herein has a definition broad enough to cover the major surfaces of the substrate and/or the edges thereof.
• the coating layer 112 may be applied with dip coating or any other method of application known in the art. Although the specific parameters of the dip coating process may vary depending on the composition of the solvent, the dilution characteristics, etc., one example of a withdrawal speed is between about 5 cm/minute to about 10 cm/minute.
• the glass substrate 100 with the applied coating layer 112 may be cured. Curing may occur with thermal curing, UV curing, local curing on the edges, or other curing conditions known to a person of skill in the art.
• the coating layer may end up with a thickness between about 5 nm and about 500 nm after thermal treatment.
• the moderately elevated curing temperature may be in the range of about 80 degrees Celsius to about 500 degrees Celsius. Process temperature, viscosity of the coating composition, and final coating thickness may be adjusted to coincide with the glass substrate type used.
• FIG. 4 is a graph depicting the Weibull modulus and the failure strength increase potential for a prior art coating and for a coating composition according to one or more aspects of the present invention.
• a composition for a glass substrate coating includes the precursor and an additive, where a ratio of water in the additive to the precursor is maintained at an under- stoichiometric amount . This is maintained by introducing or controlling the amount of water as a function of the number of alkoxy groups in the precursor.
• the precursor may contain between 1 and 4 alkoxy groups . It has been discovered that desirable strength results are obtained when the amount of water is controlled such that there is less than about 0.5 moles of water per mol of precursor per alkoxy group. Controlling the amount of water such that there is less than about 0.17 to about 0.5 moles of water per mol of precursor per alkoxy group is believed to be acceptable.
• contemplated ranges include: (i) less than about 0.33 to about 0.5 moles of water per mol of precursor per alkoxy group; and (ii) less than about 0.33 moles of water per mol of precursor per alkoxy group .
• the water is maintained at less than about 0.5 moles of water per mole of the precursor. If there are 2 alkoxy groups in the precursor, the water is maintained at less than about 1.0 moles of water per mole of the precursor. If there are 3 alkoxy groups in the precursor, the water is maintained at less than about 1.5 moles of water per mole of the precursor. On the other extreme, if there are 4 alkoxy groups in the precursor, the water is maintained at less than about 2.0 moles of water per mole of the precursor.
• FIG. 5 is a table listing the precursors, additive (s), solvents, withdrawal speeds, and curing temperatures for coating compositions according to one or more embodiments of the present invention. Details regarding these embodiments of the invention are provided below.
• a coating agent may be created via a reaction between a precursor and water.
• the precursor may be any aminosilane or any epoxysilane, - for example (3-aminopropyl) triethoxysilane
• the coating agent may be created via a reaction between a precursor and water plus a catalyst. Still further, the coating agent may be created via a reaction between a precursor and water plus a chelating agent, such as when titanium alkoxides are used.
• the coating agent may be created via a reaction between a precursor and water plus a catalyst and a chelating agent, such as when it is desirable to employ an in- situ combination of Si-alkoxides and/or Ti-alkoxides . It is noted that during the reaction of silane with water, in this stoichiometry 0.5 mol of water per mol alkoxy group, the reaction may be terminated before having reached an equilibrium, i.e., before the silsesquioxane has formed.
• the above-described coating agents may be produced on-site or obtained from a supplier, such as Sigma Aldrich, or any of the other suppliers.
• an acidic or basic catalyst may be required to complete the conversion of the precursor, i.e., the reaction of the precursor with water.
• the composition may be created with a precursor containing Si.
• precursors may comprise, (3-aminopropyl) triethoxysilane ("GAPS”), (3-glycidoxypropyl) trimethoxysilane (“GLYMO”), diethoxy (3-glycidoxypropyl) methylsilane, silsesquioxanes, poly(3-aminopropyl) silsesquioxane, poly (3-glycidoxypropyl) silsesquioxane, or a combination thereof.
• GAPS (3-aminopropyl) triethoxysilane
• GLYMO (3-glycidoxypropyl) trimethoxysilane
• diethoxy (3-glycidoxypropyl) methylsilane silsesquioxanes
• poly(3-aminopropyl) silsesquioxane poly (3-glycidoxypropyl) silsesquioxane
• these precursors may
• a composition for a glass substrate coating includes the precursor and an additive, where a ratio of water in the additive to the precursor is less than about 0.5 moles of water per mole alkoxy group in the precursor.
• the composition may comprise silsesquioxanes, which are obtained by adding 0.5 mol of water to 1 mol per alkoxy group, or to 1 mol of the precursor R' -Si (OR) 3 , as follows: n R'-Si(OR) 3 + 1.5 n H 2 O ⁇ - (R' -SiO x . 5 )n- + 3 n ROH. [0038] While stirring n moles of the amino silane precursor in a PE bottle with a cap, 1.5 n moles of distilled water are slowly added. Then, the bottle is closed to avoid further penetration of humidity into the solution.
• the composition may comprise SiO 2 , by taking 1 mol of the precursor containing Si
• TEOS tetraethyl orthosilicate
• additional additives may be used with water, such as at least a catalyst, for example, hydrogen chloride (“HCl”).
• HCl hydrogen chloride
• a composition may be created with a precursor containing Ti .
• precursors may comprise Ti alkoxides such as tetraisopropyl orthotitanate (“Ti(OPr) 4 "), titanium methacrylate triisopropoxide (“TiOPr-MA”), or a combination thereof.
• Ti(OPr) 4 tetraisopropyl orthotitanate
• TiOPr-MA titanium methacrylate triisopropoxide
• These precursors may be produced on-site or obtained from a supplier, such as Sigma Aldrich or ABCR Germany, or any of the other known suppliers.
• a composition may comprise precursor (s) of TiO 2 , by taking 1 mol of the precursor containing Ti (in this case Ti(OPr) 4 ) and chelating same with 1 mol of the additive ethyl acetoacetate ("AcAc") to prevent very fast hydrolysis.
• the small amount of water additive used for hydrolysis may be obtained from the humidity of the ambient air.
• Isopropanol may be used as a solvent to dilute the composition as necessary.
• the respective precursor may be diluted in isopropanol and applied by dip coating on the substrates. Thermal curing may be carried out at 200 deg C. Additionally or alternatively, UV curing may be performed.
• surfactants may be useful in increasing the wetting between the coating 112 (when in solution) and the surface of the substrate 100.
• FIG. 6 is a table listing changes in Weibull modulus and failure strength for a number of coating compositions and processes used on Coming's EAGLETM glass substrates according to various aspects of the present invention.
• the glass substrate specimens were indented to create reproducible strength limiting flaws on the surface that enable examination of the effectiveness of the coating, and that simulate production conditions where large size defects might be present .
• the references to Vickers 1 and Vickers 2 relate to two different batches of glass samples.
• the term "bare" in FIG. 7 refers to glass samples that were not indented and that come from the same batch as used for Vickers 1 samples .
• the specimens were aged for about 24 hours including a pyrolysis treatment at 500 degrees Celsius for about 5 hours.
• This treatment is intended for post indentation stress relaxation, and for rendering the surface more hydrophilic by bringing the OH groups to the glass/air interface thus improving adhesion.
• This process was carried out to assure the quality of the indented glass samples (taken as a reference) , but does not contribute to strengthening itself.
• Film deposition took place by dip coating with a withdrawal rate of 5 or 10 cm/minute, which was followed by drying (in air) and heat treatment.
• Coating thickness and curing temperatures should be carefully selected to increase, if not maximize, both the Weibull modulus and failure strength of the glass substrate.
• the most improved coating found during experimentation in accordance with various aspects of the present invention is the combination of poly (3-aminopropyl) silsesquioxane and poly(3- glycidoxypropyl) silsesquioxane, with a curing temperature at 200 degrees Celsius and a coating thickness of 66 nm.
• the Weibull modulus increased by 603% and the failure strength increased by 539%.
• the Weibull modulus increased significantly compared to that of the uncoated reference samples .
• the increase in failure strength was up to nine-fold relative to the failure strength of the uncoated specimen.
• the sample having a coating of 3700 nm thick was made to test an extreme, and resulted in a reduced Weibull modulus .
• FIG. 6 The results illustrated in FIG. 6 may be compared with the prior art coatings and processes (also used on Coming's EAGLETM glass substrates) shown in FIG. 7.
• EAS aminosilane and epoxysilane hydrolysed with stoichiometrical excess of water
• SiO 2 have been used in the prior art.
• Vickers 1 and "bare” refer to different substrates, each with the same glass type and thickness, but Vickers 1 includes an artificial defect, while “bare” does not include an artificial defect (only handling defects).

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• 2007
  • 2007-02-28 EP EP07734855A patent/EP2057101A1/de not_active Withdrawn
  • 2007-02-28 CN CN200780052523.9A patent/CN101641302B/zh not_active Expired - Fee Related
  • 2007-02-28 WO PCT/IB2007/001650 patent/WO2008104825A1/en not_active Ceased
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• 2008
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