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
  • C03C23/00—Other surface treatment of glass not in the form of fibres or filaments
  • C03C23/0075—Cleaning of glass
• • 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
  • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
  • C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions

Definitions

• the present disclosure relates generally to reduction of electrostatic charge on glass substrates and more particularly to the reduction of electrostatic charge on glass substrates using metal halide treatment.
• Thin glass substrates are commonly utilized in flat panel display (FPD) devices such as liquid crystal display (LCD) and organic light emitting diode (OLED) displays.
• FPD flat panel display
• Substrates used in FPD devices generally have a functional A-side surface on which the thin- film transistors are fabricated and a non-functional backside or B-side surface which opposes the A-side surface.
• the B-side surface of the glass substrate may come into contact with conveyance and handling equipment of various materials, such as metals, ceramics, polymeric materials and the like.
• the interaction between the substrate and these materials often results in charging through the triboelectric effect or contact electrification.
• charge is transferred to the glass surface and can be accumulated on the substrate.
• the surface voltage of the glass substrate also changes.
• Electrostatic charging (ESC) of B-side surfaces of glass substrates used in FPD devices may degrade the performance of the glass substrate and/or damage the glass substrate.
• electrostatic charging of the B-side surface may cause gate damage to thin film transistor (TFT) devices deposited on the A-side surface of the glass substrate through dielectric breakdown or electric field induced charging.
• TFT thin film transistor
• charging of the B-side surface of the glass substrate may attract particles, such as dust or other particulate debris, which may damage the glass substrate or degrade the surface quality of the glass substrate.
• electrostatic charging of the glass substrate may decrease FPD device manufacturing yields thereby increasing the overall cost of the manufacturing process.
• Embodiments disclosed herein include a method for treating a glass substrate.
• the method includes applying a solution including a metal halide to a major surface of the glass substrate.
• the solution is applied at a concentration and time that reduces a voltage on the major surface of the glass substrate.
• FIG. 1 is a schematic view of an example fusion down draw glass making apparatus and process
• FIG. 2 is a perspective view of a glass sheet
• FIG. 3 is a chart showing percent voltage reduction of zinc chloride treated glass samples as compared to the measured surface voltage of an untreated control sample;
• FIG. 4 is a chart showing percent reduction in time for charge on zinc chloride treated glass samples to go to zero as compared to the time for charge on untreated glass samples to go to zero;
• FIG. 5 is a chart showing percent voltage reduction of aluminum chloride treated glass samples as compared to the measured surface voltage of an untreated control sample
• FIG. 6 is a chart showing percent reduction in time for charge on aluminum chloride treated glass samples to go to zero as compared to the time for charge on untreated glass samples to go to zero;
• FIG. 7 is a chart showing the correlation between the normalized intensity of zinc and chlorine ions on the surface of glass samples treated with zinc chloride.
• Ranges can be expressed herein as from“about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, for example by use of the antecedent“about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
• the term“voltage on a major surface of a glass substrate” refers to the measured voltage on a major surface (e g., 162 or 164 of FIG. 2) of a glass substrate as determined by the Surface Voltage Measurement Technique as described herein
• the glass manufacturing apparatus 10 can comprise a glass melting furnace 12 that can include a melting vessel 14.
• glass melting furnace 12 can optionally include one or more additional components such as heating elements (e.g., combustion burners or electrodes) that heat raw materials and convert the raw materials into molten glass.
• heating elements e.g., combustion burners or electrodes
• glass melting furnace 12 may include thermal management devices (e g., insulation components) that reduce heat lost from a vicinity of the melting vessel.
• glass melting furnace 12 may include electronic devices and/or electromechanical devices that facilitate melting of the raw materials into a glass melt.
• glass melting furnace 12 may include support structures (e.g., support chassis, support member, etc.) or other components.
• Glass melting vessel 14 is typically comprised of refractory material, such as a refractory ceramic material, for example a refractory ceramic material comprising alumina or zirconia. In some examples glass melting vessel 14 may be constructed from refractory ceramic bricks. Specific embodiments of glass melting vessel 14 will be described in more detail below.
• the glass melting furnace may be incorporated as a component of a glass manufacturing apparatus to fabricate a glass substrate, for example a glass ribbon of a continuous length.
• the glass melting furnace of the disclosure may be incorporated as a component of a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down-draw apparatus such as a fusion process, an up- draw apparatus, a press-rolling apparatus, a tube drawing apparatus or any other glass manufacturing apparatus that would benefit from the aspects disclosed herein.
• FIG. 1 schematically illustrates glass melting furnace 12 as a component of a fusion down-draw glass manufacturing apparatus 10 for fusion drawing a glass ribbon for subsequent processing into individual glass sheets.
• the glass manufacturing apparatus 10 can optionally include an upstream glass manufacturing apparatus 16 that is positioned upstream relative to glass melting vessel 14. In some examples, a portion of, or the entire upstream glass manufacturing apparatus 16, may be incorporated as part of the glass melting furnace 12
• the upstream glass manufacturing apparatus 16 can include a storage bin 18, a raw material delivery device 20 and a motor 22 connected to the raw material delivery device.
• Storage bin 18 may be configured to store a quantity of raw materials 24 that can be fed into melting vessel 14 of glass melting furnace 12, as indicated by arrow 26.
• Raw materials 24 typically comprise one or more glass forming metal oxides and one or more modifying agents.
• raw material delivery device 20 can be powered by motor 22 such that raw material delivery device 20 delivers a predetermined amount of raw materials 24 from the storage bin 18 to melting vessel 14.
• motor 22 can power raw material delivery device 20 to introduce raw materials 24 at a controlled rate based on a level of molten glass sensed downstream from melting vessel 14.
• Raw materials 24 within melting vessel 14 can thereafter be heated to form molten glass 28.
• Glass manufacturing apparatus 10 can also optionally include a downstream glass manufacturing apparatus 30 positioned downstream relative to glass melting furnace 12.
• a portion of downstream glass manufacturing apparatus 30 may be incorporated as part of glass melting furnace 12.
• first connecting conduit 32 discussed below, or other portions of the downstream glass manufacturing apparatus 30, may be incorporated as part of glass melting furnace 12.
• Elements of the downstream glass manufacturing apparatus, including first connecting conduit 32 may be formed from a precious metal. Suitable precious metals include platinum group metals selected from the group of metals consisting of platinum, iridium, rhodium, osmium, ruthenium and palladium, or alloys thereof.
• downstream components of the glass manufacturing apparatus may be formed from a platinum -rhodium alloy including from about 70 to about 90% by weight platinum and about 10% to about 30% by weight rhodium.
• platinum -rhodium alloy including from about 70 to about 90% by weight platinum and about 10% to about 30% by weight rhodium.
• suitable metals can include molybdenum, palladium, rhenium, tantalum, titanium, tungsten and alloys thereof.
• Downstream glass manufacturing apparatus 30 can include a first conditioning (i.e., processing) vessel, such as fining vessel 34, located downstream from melting vessel 14 and coupled to melting vessel 14 by way of the above-referenced first connecting conduit 32.
• a first conditioning (i.e., processing) vessel such as fining vessel 34
• molten glass 28 may be gravity fed from melting vessel 14 to fining vessel 34 by way of first connecting conduit 32.
• gravity may cause molten glass 28 to pass through an interior pathway of first connecting conduit 32 from melting vessel 14 to fining vessel 34.
• other conditioning vessels may be positioned downstream of melting vessel 14, for example between melting vessel 14 and fining vessel 34.
• a conditioning vessel may be employed between the melting vessel and the fining vessel wherein molten glass from a primary melting vessel is further heated to continue the melting process, or cooled to a temperature lower than the temperature of the molten glass in the melting vessel before entering the fining vessel.
• Bubbles may be removed from molten glass 28 within fining vessel 34 by various techniques.
• raw materials 24 may include multivalent compounds (i.e. fining agents) such as tin oxide that, when heated, undergo a chemical reduction reaction and release oxygen.
• fining agents include without limitation arsenic, antimony, iron and cerium.
• Fining vessel 34 is heated to a temperature greater than the melting vessel temperature, thereby heating the molten glass and the fining agent.
• Oxygen bubbles produced by the temperature-induced chemical reduction of the fining agent(s) rise through the molten glass within the fining vessel, wherein gases in the molten glass produced in the melting furnace can diffuse or coalesce into the oxygen bubbles produced by the fining agent.
• the enlarged gas bubbles can then rise to a free surface of the molten glass in the fining vessel and thereafter be vented out of the fining vessel.
• the oxygen bubbles can further induce mechanical mixing of the molten glass in the fining vessel.
• Downstream glass manufacturing apparatus 30 can further include another conditioning vessel such as a mixing vessel 36 for mixing the molten glass.
• Mixing vessel 36 may be located downstream from the fining vessel 34.
• Mixing vessel 36 can be used to provide a homogenous glass melt composition, thereby reducing cords of chemical or thermal inhomogeneity that may otherwise exist within the fined molten glass exiting the fining vessel.
• fining vessel 34 may be coupled to mixing vessel 36 by way of a second connecting conduit 38.
• molten glass 28 may be gravity fed from the fining vessel 34 to mixing vessel 36 by way of second connecting conduit 38. For instance, gravity may cause molten glass 28 to pass through an interior pathway of second connecting conduit 38 from fining vessel 34 to mixing vessel 36.
• mixing vessel 36 is shown downstream of fining vessel 34, mixing vessel 36 may be positioned upstream from fining vessel 34.
• downstream glass manufacturing apparatus 30 may include multiple mixing vessels, for example a mixing vessel upstream from fining vessel 34 and a mixing vessel downstream from fining vessel 34. These multiple mixing vessels may be of the same design, or they may be of different designs.
• Downstream glass manufacturing apparatus 30 can further include another conditioning vessel such as delivery vessel 40 that may be located downstream from mixing vessel 36.
• Delivery vessel 40 may condition molten glass 28 to be fed into a downstream forming device.
• delivery vessel 40 can act as an accumulator and/or flow controller to adjust and/or provide a consistent flow of molten glass 28 to forming body 42 by way of exit conduit 44.
• mixing vessel 36 may be coupled to delivery vessel 40 by way of third connecting conduit 46.
• molten glass 28 may be gravity fed from mixing vessel 36 to delivery vessel 40 by way of third connecting conduit 46.
• gravity may drive molten glass 28 through an interior pathway of third connecting conduit 46 from mixing vessel 36 to delivery vessel 40.
• Downstream glass manufacturing apparatus 30 can further include forming apparatus 48 comprising the above-referenced forming body 42 and inlet conduit 50.
• Exit conduit 44 can be positioned to deliver molten glass 28 from delivery vessel 40 to inlet conduit 50 of forming apparatus 48.
• exit conduit 44 may be nested within and spaced apart from an inner surface of inlet conduit 50, thereby providing a free surface of molten glass positioned between the outer surface of exit conduit 44 and the inner surface of inlet conduit 50.
• Forming body 42 in a fusion down draw glass making apparatus can comprise a trough 52 positioned in an upper surface of the forming body and converging forming surfaces 54 that converge in a draw direction along a bottom edge 56 of the forming body.
• Molten glass delivered to the forming body trough via delivery vessel 40, exit conduit 44 and inlet conduit 50 overflows side walls of the trough and descends along the converging forming surfaces 54 as separate flows of molten glass.
• the separate flows of molten glass join below and along bottom edge 56 to produce a single ribbon of glass 58 that is drawn in a draw or flow direction 60 from bottom edge 56 by applying tension to the glass ribbon, such as by gravity, edge rolls 72 and pulling rolls 82, to control the dimensions of the glass ribbon as the glass cools and a viscosity of the glass increases. Accordingly, glass ribbon 58 goes through a visco-elastic transition and acquires mechanical properties that give the glass ribbon 58 stable dimensional characteristics.
• Glass ribbon 58 may, in some embodiments, be separated into individual glass sheets 62 by a glass separation apparatus 100 in an elastic region of the glass ribbon A robot 64 may then transfer the individual glass sheets 62 to a conveyor system using gripping tool 65, whereupon the individual glass sheets may be further processed.
• FIG. 2 shows a perspective view of a glass sheet 62 having a first major surface 162, a second major surface 164 extending in a generally parallel direction to the first major surface (on the opposite side of the glass sheet 62 as the first major surface) and an edge surface 166 extending between the first major surface 162 and the second major surface 164 and extending in a generally perpendicular direction to the first and second major surfaces 162, 164.
• Further processing of glass sheets 62 may, for example, include grinding, polishing, and/or beveling of edge surfaces 166 and/or treating or washing at least one of first and second major surfaces 162, 164. Such glass sheets 62 may also be divided into smaller glass sheets 62. During such processing steps, electrostatic charge may build up on the first and/or second major surfaces 162, 164 of the glass sheets 62. Electrostatic charge may further build up in other downstream processing steps. Such electrostatic charge results in a voltage on the first and/or second major surfaces 162, 164 of the glass sheets 62.
• Embodiments disclosed herein include methods for treating glass sheets 62, such as a glass substrate, by applying a solution comprising a metal halide to at least one of first and second major surfaces 162, 164, wherein the solution is applied at a concentration and time that reduces a voltage on at least one of the first and second major surfaces 162, 164.
• the solution is an aqueous solution comprising the metal halide at a concentration of at least about 50 parts per million (PPM), such as at least about 100 PPM, and further such as at least about 200 PPM, and yet further such as at least about 500 PPM, including from about 50 PPM to about 5,000 PPM, such as from about 100 PPM to about 1,000 PPM.
• PPM parts per million
• the aqueous solution has a pH ranging from about 5 to about 9, such as a pH ranging from about 6 to about 8, and further such as a pH ranging from about 6.5 to about 7.5, including a pH of about 7.
• the solution can be applied to at least one of first or second major surfaces 162,
• the solution is applied to at least one of first or second major surfaces 162, 164 for a time ranging from about 5 seconds to about 5 minutes, such as from about 10 seconds to about 3 minutes, and further such as from about 30 seconds to about 2 minutes.
• the glass substrate has a temperature ranging from about 0°C to about 100°C, such as from about l0°C to about 60°C, and further such as from about 20°C to about 40°C during application of the solution to the major surface of the glass substrate.
• the solution may also have a temperature ranging from about 0°C to about l00°C, such as from about l0°C to about 60°C, and further such as from about 20°C to about 40°C during application of the solution to the major surface of the glass substrate.
• Embodiments disclosed herein include those in which the solution is applied at a concentration and time that reduces the voltage on at least one of first and second major surfaces 162, 164 by at least about 50%, such as by at least about 75%, and further such as by at least about 90%, including by about 50% to about 99%, such as by about 75% to about 99%, and further such as by about 90% to about 99%.
• Voltage on at least one of first and second major surfaces 162, 164 can be measured using the Surface Voltage Measurement Technique as described herein.
• Embodiments disclosed herein also include those in which the solution is applied at a concentration and time that changes a surface roughness on at least one of first and second major surfaces 162, 164 by less than about 20%, such as less than about 10%, and further such as less than about 5%, including by about 0% to about 20%, such as by about 0% to about 10%, and further by about 0% to about 5%.
• untreated Corning® Eagle XG® glass can be expected to have a surface roughness (Ra) of about 0.2 millimeters for a 2 x 2 micrometer (micron) scan size using atomic force microscopy (AFM).
• embodiments disclosed herein include those in which the solution is applied to Corning® Eagle XG® (or glass samples having a similar surface roughness) at a concentration and time that results in the surface roughness on at least one of first or second major surfaces 162, 164 to be from about 0.16 millimeters to about 0.24 millimeters, such as from about 0.18 millimeters to about 0.22 millimeters, and further such as from about 0.19 millimeters to about 0.21 millimeters.
• the metal halide comprises a metal chloride.
• the metal is selected from the group consisting of aluminum, zinc, magnesium, calcium, manganese, and barium.
• the metal is selected from the group consisting of aluminum, zinc, and magnesium.
• the metal comprises aluminum.
• the metal comprises zinc.
• the metal comprises magnesium.
• the metal halide is selected from the group consisting of aluminum chloride, zinc chloride, and magnesium chloride.
• the metal halide comprises aluminum chloride.
• the metal halide comprises zinc chloride.
• the metal halide comprises magnesium chloride.
• Embodiments disclosed herein may be used with a variety of glass compositions.
• Such compositions may, for example, include a glass composition, such as an alkali free glass composition, comprising 58-65 weight percent (wt%) S1O2, l4-20wt% AI2O3, 8-12wt% B2O3, l-3wt% MgO, 5-10wt% CaO, and 0.5-2wt% SrO.
• a glass composition such as an alkali free glass composition, comprising 58-65 weight percent (wt%) S1O2, l4-20wt% AI2O3, 8-12wt% B2O3, l-3wt% MgO, 5-10wt% CaO, and 0.5-2wt% SrO.
• compositions may also include a glass composition, such as an alkali free glass composition, comprising 58-65wt% S1O2, 16- 22wt% AI2O3, l-5wt% B2O3, l-4wt% MgO, 2-6wt% CaO, l-4wt% SrO, and 5-l0wt% BaO.
• a glass composition such as an alkali free glass composition, comprising 57-61wt% S1O2, l7-2lwt% AI2O3, 5-8wt% B2O3, l-5wt% MgO, 3- 9wt% CaO, 0-6wt% SrO, and 0-7wt% BaO.
• compositions may additionally include a glass composition, such as an alkali containing glass composition, comprising 55-72wt% S1O2, l2-24wt% AI2O3, l0-l8wt% Na 2 0, 0-l0wt% B2O3, 0-5wt% K 2 0, 0-5wt% MgO, and 0- 5wt% CaO, which, in certain embodiments, may also include l-5wt% K2O and l-5wt%
• a glass voltage measurement sensor tracks with the glass at a 10 millimeter distance during lift pin movement as it is raised off the vacuum chuck at about a 10 millimeter per second lift pin speed. The electric field from the charge on the glass is interpreted as voltage by the sensor. Ionization was used to remove charge on the glass before it is lowered on to the vacuum chuck. Six lift cycles were conducted per glass sample.
• Example 1 Treatment of glass with an aqueous solution of zinc chloride
• the washed Eagle XG® glass samples were then dipped into an aqueous solution containing zinc chloride at varying parts per million (PPM) levels: 50 PPM, 500 PPM, and 1000 PPM. Treatment time for each sample in the aqueous zinc chloride solution was for about three minutes. Following treatment, each sample was removed from the aqueous zinc chloride solution, washed with water for a period of about one minute, and dried with nitrogen. Each sample was then subjected to the Surface Voltage Measurement Technique described above.
• PPM parts per million
• FIG. 3 shows the percent voltage reduction of the zinc chloride treated glass samples at an 80 millimeter pin height (i.e., when the glass has been moved a distance of about 80 millimeters from the vacuum chuck) as compared to the measured surface voltage of an untreated control sample as measured by the Surface Voltage Measurement Technique.
• FIG. 4 shows the percent reduction in time for charge on the zinc chloride treated glass samples to go to zero as compared to the time for charge on untreated glass samples to go to zero as measured by the Surface Voltage Measurement Technique. As can be seen from FIG. 4, a greater than 40% reduction in charge dissipation time is observed when treated in a 1000 PPM aqueous zinc chloride solution.
• Example 2 Treatment of glass with an aqueous solution of aluminum chloride
• the procedure described above in Example 1 was followed, except that instead of dipping washed Eagle XG® glass into an aqueous solution containing zinc chloride, the washed Eagle XG® glass samples were dipped into an aqueous solution containing aluminum chloride at 50 PPM, 500 PPM, and 1000 PPM levels.
• FIG. 5 shows the percent voltage reduction of the aluminum chloride treated glass samples at an 80 millimeter pin height (i.e., when the glass has been moved a distance of about 80 millimeters from the vacuum chuck) as compared to the measured surface voltage of an untreated control sample as measured by the Surface Voltage Measurement Technique.
• FIG. 6 shows the percent reduction in time for charge on the aluminum chloride treated glass samples to go to zero as compared to the time for charge on untreated glass samples to go to zero as measured by the Surface Voltage Measurement Technique. As can be seen from FIG. 6, a 90% reduction in charge dissipation time is observed when treated in a 1000 PPM aqueous aluminum chloride solution.
• Treatment methods as disclosed herein can result in absorption of metal halide ion components on surfaces of glass substrates.
• Eagle XG® glass substrates are treated with zinc chloride, such as described herein in Example 1, a high degree of correlation between the intensity of zinc and chlorine ions on the surface of the glass substrates have been observed.
• FIG. 7 shows the correlation between the normalized intensity of zinc and chlorine ions on the surface of Eagle XG® glass substrates as measured by time of flight secondary ion mass spectrometry. As can be seen from FIG. 7, a high degree of correlation exists between the measured intensity of zinc and chlorine ions, suggesting that both are highly absorbed on the surface.
• the glass substrate may be washed.
• Such washing step if undertaken, may occur at any time subsequent to metal halide treatment.
• such washing step may be undertaken immediately following metal halide treatment.
• Such washing step may also be undertaken subsequent to a time interval following metal halide treatment, during which time interval other substrate processing steps may be undertaken.
• Such washing step may, for example, comprise applying an aqueous solution to the substrate.
• the aqueous solution may, for example, comprise at least one detergent.
• the substrates were subsequently washed with either water or an aqueous solution comprising about 4% Semiclean KG detergent.
• the concentration of chlorine was measured on the surface of the substrates using drop scan etch inductively coupled plasma mass spectroscopy. Inclusion of the detergent in the wash solution resulted in a surface with reduced chlorine concentration, which reduction in some cases was greater than 90%, as compared to wash solutions that did not contain the detergent.
• Embodiments disclosed herein can result in substantial surface voltage reduction of glass substrates, which can, in turn, enable reduced gate damage to TFT devices deposited on the A-side surface of the glass substrate, reduction of particles and debris on the B-side surface of the glass substrate, increase in FPD device manufacturing yields, and increase in service life of glass substrate handling and/or conveyance equipment. Such surface voltage reduction can be accomplished without substantial change to the surface roughness of the glass substrate.

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• Chemical & Material Sciences (AREA)
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• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Glass Compositions (AREA)
• Surface Treatment Of Glass (AREA)

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Citations (5)

• 2019
  • 2019-10-21 WO PCT/US2019/057182 patent/WO2020096756A1/en active Application Filing
  • 2019-11-06 TW TW108140181A patent/TW202023990A/zh unknown

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