WO2020251868A1

WO2020251868A1 - Reduction of glass elecrostatic charging with wet chemistry

Info

Publication number: WO2020251868A1
Application number: PCT/US2020/036547
Authority: WO
Inventors: Gabriel Pierce Agnello; David Michael CABRERA; He JING; Aize LI; Sara Jean Sick
Original assignee: Corning Incorporated
Priority date: 2019-06-10
Filing date: 2020-06-08
Publication date: 2020-12-17
Also published as: TW202108536A

Abstract

Methods for treating glass substrates include applying a solution comprising a fluorine- containing acid and a non-fluorine-containing acid on a major surface of the substrate. Application of the solution can result in glass substrates having reduced electrostatic charge.

Description

REDUCTION OF GLASS ELECROSTATIC CHARGING WITH WET CHEMISTRY

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.

Provisional Application Serial No. 63/018,065, filed on April 30, 2020 and U.S. Provisional Application Serial No. 62/859,383, filed on June 10, 2019, the content of each are relied upon and incorporated herein by reference in their entirety.

Field

[0002] 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 wet chemistry.

Background

[0003] 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. 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. During manufacture of the FPD device, 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. As a result, charge is transferred to the glass surface and can be accumulated on the substrate. As charge accumulates on the surface of the glass substrate, the surface voltage of the glass substrate also changes.

[0004] 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. For example, 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. Moreover, 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. In either circumstance, electrostatic charging of the glass substrate may decrease FPD device manufacturing yields thereby increasing the overall cost of the manufacturing process.

[0005] Further, frictional contact between the glass substrate and handling and/or conveyance equipment may cause such equipment to wear, thereby reducing the service life of the equipment. Repair or replacement of worn equipment results in process down-time, decreasing manufacturing yields and increasing the overall costs of the FPD device manufacturing process.

[0006] Accordingly, a need exists for glass substrate processing methods that mitigate the generation of charge and decrease the friction between the glass substrates and equipment utilized in the manufacture of FPD devices.

SUMMARY

[0007] Embodiments disclosed herein include a method for treating a glass substrate. The method includes applying an aqueous solution including a fluorine-containing acid and a non fluorine-containing acid to a major surface of the glass substrate. Application of the solution results in at least one major surface of the glass substrate having an electrostatic charge reduction of at least about 50% as compared to a control glass sheet sample that has not been exposed to the solution.

[0008] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the disclosed embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0009] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the claimed embodiments. The accompanying drawings are included to provide further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. l is a schematic view of an example fusion down draw glass making apparatus and process;

[0011] FIG. 2 is a perspective view of a glass sheet;

[0012] FIG. 3 is a chart showing lift testing results following glass surface treatment with various chemistries; and

[0013] FIG. 4 is a chart showing etch rate, surface roughness, and biproduct amount following glass surface treatment with various chemistries.

DETAILED DESCRIPTION

[0014] Reference will now be made in detail to the present preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings.

Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0015] 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.

[0016] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0017] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0018] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to“a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0019] As used herein, the term“fluorine-containing acid” refers to an acid comprising at least one fluorine ion. Exemplary fluorine-containing acids include, but are not limited to, hydrofluoric acid (HF), ammonium fluoride (NFEF), and ammonium bifluoride (NH4HF2).

[0020] As used herein, the term“non-fluorine-containing acid” refers to an acid that does not comprise at least one fluorine ion. Exemplary non-fluorine-containing acids include, but are not limited to, hydrochloric acid (HC1), citric acid (CeHsCh), nitric acid (HNO3), phosphoric acid (H3PO4), sulfuric acid (H2SO4), and perchloric acid (HCIO4).

[0021] As used herein, the term“a ratio of total fluorine to free proton in the solution” refers to the ratio of the total amount of fluorine in the solution to the amount of hydrogen ions in the solution at equilibrium.

[0022] As used herein, the term“electrostatic charge” refers to the measured charge 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.

[0023] Shown in FIG. 1 is an exemplary glass manufacturing apparatus 10. In some examples, the glass manufacturing apparatus 10 can comprise a glass melting furnace 12 that can include a melting vessel 14. In addition to 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. In further examples, glass melting furnace 12 may include thermal

management devices (e.g., insulation components) that reduce heat lost from a vicinity of the melting vessel. In still further examples, glass melting furnace 12 may include electronic devices and/or electromechanical devices that facilitate melting of the raw materials into a glass melt. Still further, glass melting furnace 12 may include support structures (e.g., support chassis, support member, etc.) or other components. [0024] 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.

[0025] In some examples, the glass melting furnace may be incorporated as a component of a glass manufacturing apparatus to fabricate a glass sheet, for example a glass ribbon of a continuous length. In some examples, 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. By way of example, 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.

[0026] The glass manufacturing apparatus 10 (e.g., fusion down-draw 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

[0027] As shown in the illustrated example, 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. In some examples, 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. In further examples, 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.

[0028] Glass manufacturing apparatus 10 can also optionally include a downstream glass manufacturing apparatus 30 positioned downstream relative to glass melting furnace 12. In some examples, a portion of downstream glass manufacturing apparatus 30 may be incorporated as part of glass melting furnace 12. In some instances, 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. For example, 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. However, other suitable metals can include molybdenum, palladium, rhenium, tantalum, titanium, tungsten and alloys thereof.

[0029] 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. In some examples, molten glass 28 may be gravity fed from melting vessel 14 to fining vessel 34 by way of first connecting conduit 32. For instance, 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. It should be understood, however, that other conditioning vessels may be positioned downstream of melting vessel 14, for example between melting vessel 14 and fining vessel 34. In some embodiments, 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.

[0030] Bubbles may be removed from molten glass 28 within fining vessel 34 by various techniques. For example, 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. Other suitable 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.

[0031] 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. As shown, fining vessel 34 may be coupled to mixing vessel 36 by way of a second connecting conduit 38. In some examples, 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. It should be noted that while mixing vessel 36 is shown downstream of fining vessel 34, mixing vessel 36 may be positioned upstream from fining vessel 34. In some embodiments, 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.

[0032] 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. For instance, 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. As shown, mixing vessel 36 may be coupled to delivery vessel 40 by way of third connecting conduit 46. In some examples, molten glass 28 may be gravity fed from mixing vessel 36 to delivery vessel 40 by way of third connecting conduit 46. For instance, gravity may drive molten glass 28 through an interior pathway of third connecting conduit 46 from mixing vessel 36 to delivery vessel 40.

[0033] 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. For example, 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.

[0034] FIG. 2 shows a perspective view of a glass article, and, specifically, 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 162 (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.

[0035] Embodiments disclosed herein include methods for treating glass sheets, such as glass substrates, by applying a solution comprising a fluorine-containing acid and a non fluorine-containing acid to the glass sheets.

[0036] In certain exemplary embodiments, the fluorine-containing acid has a molarity of less than or equal to about 1 (less than or equal to about 1M), such as a molarity ranging from about 0.01 to about 1 (about 0.01M to about 1M), and the non-fluorine-containing acid has a molarity of greater than or equal to about 1 (greater than or equal to about 1M), such as a molarity ranging from about 1 to 12 (about 1M to about 12M).

[0037] In certain exemplary embodiments, the solution is an aqueous solution and the fluorine-containing acid has a molarity of less than or equal to about 1 (less than or equal to about 1M), such as a molarity ranging from about 0.01 to about 1 (about 0.01M to about 1M), and further such as from about 0.05 to about 0.5 (about 0.05M to about 0.5M), and the non fluorine-containing acid has a molarity of at least about 0.1 (greater than or equal to about 0.1M), such as a molarity ranging from about 0.1 to about 6 (about 0.1M to about 6M), and further such as from about 0.5 to about 3 (about 0.5M to about 3M).

[0038] In certain exemplary embodiments, the solution is an aqueous solution and the fluorine-containing acid has a molarity of less than or equal to about 0.1 (less than or equal to about 0.1M), such as a molarity ranging from about 0.01 to about 0.1 (about 0.01M to about 0.1M), and further such as from about 0.03 to about 0.07 (about 0.03M to about 0.07M), and the non-fluorine-containing acid has a molarity of at least about 1 (greater than or equal to about 1M), such as a molarity ranging from about 1 to about 12 (about 1M to about 12M), and further such as from about 1.5 to about 6 (about 1.5M to about 6M), and yet further such as from about 2 to about 4 (about 2M to about 4M).

[0039] In certain exemplary embodiments, the solution is an aqueous solution and the fluorine-containing acid comprises one or more acids selected from hydrofluoric acid (HF), ammonium fluoride (NH4F), or ammonium bifluoride (NH4HF2). In certain exemplary embodiments, the non-fluorine-containing acid comprises one or more acids selected from hydrochloric acid (HC1), citric acid (CeHsCb), nitric acid (HNO3), phosphoric acid (H3PO4), sulfuric acid (H2SO4), or perchloric acid (HCIO4).

[0040] In certain exemplary embodiments, the solution is an aqueous solution and the fluorine-containing acid comprises hydrofluoric acid (HF) and the non-fluorine-containing acid comprises hydrochloric acid (HC1). In certain exemplary embodiments, the hydrofluoric acid (HF) has a molarity of less than or equal to about 0.1 (less than or equal to about 0.1M), such as a molarity ranging from about 0.01 to about 0.1 (about 0.01M to about 0.1M), and further such as from about 0.03 to about 0.07 (about 0.03M to about 0.07M), and the hydrochloric acid (HC1) has a molarity of greater than or equal to about 1 (greater than or equal to about 1M), such as a molarity ranging from about 1 to about 12 (about 1M to about 12M), and further such as from about 1.5 to about 6 (about 1.5M to about 6M), and yet further such as from about 2 to about 4 (about 2M to about 4M).

[0041] In certain exemplary embodiments, the solution is an aqueous solution and the fluorine-containing acid comprises ammonium bifluoride (NH4HF2) and the non-fluorine- containing acid comprises citric acid (CeHsCb). In certain exemplary embodiments, the ammonium bifluoride (NH4HF2) has a molarity of less than or equal to about 0.105M, such as a molarity ranging from about 0.01M to about 0.105M, and the citric acid (CeHsCb) has a molarity of greater than or equal to about 0.1M, such as a molarity ranging from about 0.1M to about 1.8M. [0042] In certain exemplary embodiments, the solution is an aqueous solution and the fluorine-containing acid comprises ammonium bifluoride (NH4HF2) and the non-fluorine- containing acid comprises hydrochloric acid (HC1). In certain exemplary embodiments, the ammonium bifluoride (NH4HF2) has a molarity of less than or equal to about 0.92M, such as a molarity ranging from about 0.92M to about 0.05M, and the hydrochloric acid (HC1) has a molarity of greater than or equal to about 0.1M, such as a molarity ranging from about 0.1M to about 3M.

[0043] In certain exemplary embodiments, the solution is an aqueous solution and the fluorine-containing acid comprises hydrofluoric acid (HF) and the non-fluorine-containing acid comprises citric acid (CeHsCb). In certain exemplary embodiments, the hydrofluoric acid (HF) has a molarity of less than or equal to about 0.1M, such as a molarity ranging from about 0.01M to about 0.1M, and the citric acid (CeHsCb) has a molarity of greater than or equal to about 0.1M, such as a molarity ranging from about 0.1M to about 3M.

[0044] The solution can be applied to glass sheets, such as glass substrates, by any means known to those having ordinary skill in the art such as dipping, spraying, rolling, or brushing. The solution can be applied to one or both major surfaces of the glass sheets. In certain exemplary embodiments, the solution is applied to only one major surface (e.g., the B-side) of the glass sheets.

[0045] In certain exemplary embodiments, the solution is applied to glass sheets, such as glass substrates, for a time of less than about 2 minutes, such as a time ranging from about 20 seconds to about 100 seconds, and further such as a time ranging from about 40 second to about 80 seconds.

[0046] In certain exemplary embodiments, the solution is applied to glass sheets, such as glass substrates, at a solution temperature of at least about 30°C, such as from about 30°C to about 80°C, and further such as from about 35°C to about 70°C, and yet further such as from about 40°C to about 60°C.

[0047] 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, 14-20wt% AI2O3, 8-12wt% B2O3, l-3wt% MgO, 5-10wt% CaO, and 0.5-2wt% SrO. Such 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 5-10wt% BaO. Such compositions may further include a glass composition, such as an alkali free glass composition, comprising 57-61wt% S1O2, 17-21wt% AI2O3, 5-8wt% B2O3, l-5wt% MgO, 3- 9wt% CaO, 0-6wt% SrO, and 0-7wt% BaO. Such compositions may additionally include a glass composition, such as an alkali containing glass composition, comprising 55-72wt% Si0₂, 12-24wt% AI2O3, 10-18wt% Na₂0, 0-10wt% B₂0₃, 0-5wt% K₂0, 0-5wt% MgO, and 0- 5wt% CaO, which, in certain embodiments, may also include l-5wt% K₂0 and l-5wt%

MgO.

[0048] In certain exemplary embodiments, application of the solution to the glass sheets can result in at least one side of the glass sheets (e.g., the B-side) having a surface roughness (Ra) for a 10 x 10 micrometer (micron) scan size using atomic force microscopy (AFM) of from about 0.2 to about 0.8 nanometers, such as from about 0.25 to about 0.7 nanometers, and further such as from about 0.3 to about 0.6 nanometers.

[0049] In certain exemplary embodiments, the solution, when applied to the glass sheets, etched the glass at an etch rate of less than about 0.15 microns per minute, such as less than about 0.10 microns per minute, and further such as less than about 0.05 microns per minute, such as from about 0.01 microns per minute to about 0.15 microns per minute, and further such as from about 0.02 microns per minute to about 0.10 microns per minute.

[0050] In certain exemplary embodiments, application of the solution to the glass sheets can result in at least one side of the glass sheets (e.g., the B-side) having an electrostatic charge reduction. For example, application of the solution to the glass sheets can result in at least one side of the glass sheets (e.g., the B-side) having an electrostatic charge reduction of at least about 50%, such as at least about 55%, and further such as at least about 60%, and yet further such as at least about 65%, such as an electrostatic charge reduction of from about 50% to about 80%, including from about 55% to about 75%, as determined by the Surface Voltage Measurement Technique as described herein, as compared to a control glass sheet sample that has not been exposed to the solution.

[0051] In certain exemplary embodiments, application of the solution to the glass sheets can result in at least one side of the glass sheets (e.g., the B-side) having a change in surface composition. For example, application of the solution to glass compositions comprising Si0₂, and A1₂0,, B?0,, MgO, CaO, BaO, and/or SrO can result in the concentration ratio of at least one of Al₂0₃/Si0₂, B₂0₃/Si0₂, MgO/Si0₂, CaO/Si0₂, SrO/Si0₂, and/or BaO/Si0₂ on the surface of at least one side (e.g., the B-side) of the glass sheets being less than the concentration ratio of at least one of Al₂0₃/Si0₂, B₂0₃/Si0₂, MgO/Si0₂, CaO/Si0₂,

SrO/Si0₂, and/or BaO/Si0₂ on the surface of at least one side (e.g., the B-side) of the glass sheets where the solution has not been applied. [0052] Application of the solution to glass compositions comprising SiCh, and AI2O3,

B2O3, MgO, CaO, BaO, and/or SrO can result in the concentration ratio of at least one of AI2O3/S1O2, B2O₃/S1O2, MgO/SiCh, CaO/Si0₂, SrO/Si0₂, and/or BaO/Si0₂ on the surface of at least one side (e.g., the B-side) of the glass sheets being less than the concentration ratio of at least one of AI2O₃/S1O2, B2O₃/S1O2, MgO/SiCh, CaO/SiCh, SrO/SiCh, and/or BaO/SiCL on the surface of at least one side (e.g., the B-side) of the glass sheets that have been treated with a comparative aqueous solution comprising 0.35 molar (0.35M) NaF and 1 molar (1M) H3PO4.

[0053] Surface Voltage Measurement Technique

[0054] Voltage on a major surface of glass substrates was determined by the following Surface Voltage Measurement Technique. Four inch by four inch (10.2 centimeter x 10.2 centimeter) samples of treated and control (untreated) Corning® Lotus™ NXT glass were lowered on to and raised off of a vacuum chuck with rounded insulative Dupont™ Vespel® pins. The vacuum chuck was made of aluminum with an insulative anodized coating and had a square perimeter vacuum channel and a smaller square inner vacuum channel, an example of which is shown and described in WO2018/217624, the entire disclosure of which is incorporated herein by reference. The vacuum level achieved when the glass was in contact with the vacuum chuck was approximately -83 kiloPascal (kPa). Charge is generated on the glass when it is contacted and separated from the chuck. Charge is also generated by tribo- electrification when the glass is being pulled against the chuck, deforms near the vacuum channel edges, and rubs against the edges. 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. Three to six lift cycles were conducted per condition to which each glass sample was subjected.

[0055] Examples

[0056] Embodiments disclosed herein will be further described with reference to the following non-limiting examples.

[0057] Example 1 :

[0058] Samples of Corning® Lotus™ NXT glass were dipped in three different aqueous solutions comprising hydrofluoric acid (HF) and hydrochloric acid (HC1) each solution having, respectively, the following concentration of HF and HC1: about 0.01 molar HF and about 3 molar HC1 (about 0.01M HF and about 3M HC1), about 0.05 molar HF and about 3 molar HC1 (about 0.05M HF and about 3M HC1), and about 0.10 molar HF and about 3 molar HC1 (about 0.10M HF and about 3M HC1). Samples of Coming® Lotus™ NXT glass were also exposed to an aqueous solution comprising about 0.35 molar NaF and about 1 molar H3PO4 (about 0.35M NaF and about 1M H3PO4). Each sample was exposed to a respective solution for a time of about 80 seconds and a solution temperature of about 40°C. These samples were compared to an untreated control sample.

[0059] For each sample, glass surface electrostatic charging reduction was evaluated using a the above-referenced Surface Voltage Measurement Technique, with results shown in FIG. 3, wherein an average of three samples were tested for each condition with three lift cycles per sample. Compared to the untreated control sample, the sample treated with about 0.35 molar NaF and about 1 molar H3PO4 was observed to have an electrostatic charge reduction of about 30%. Compared to the untreated control sample, the sample treated with about 0.01 molar HF and about 3 molar HC1 was observed to have an electrostatic charge reduction of about 14%. Compared to the untreated control sample, the sample treated with about 0.05 molar HF and about 3 molar HC1 was observed to have an electrostatic charge reduction of about 50%. Compared to the untreated control sample, the sample treated with about 0.10 molar HF and about 3 molar HC1 was observed to have an electrostatic charge reduction of about 54%.

[0060] For each sample, glass surface roughness (Ra) was evaluated for a 10 ^c 10 micrometer (micron) scan size using atomic force microscopy (AFM) with results shown in FIG. 4. The sample treated with about 0.35 molar NaF and about 1 molar H3PO4 was observed to have a surface roughness (Ra) of about 0.564 nanometers. The sample treated with about 0.01 molar HF and about 3 molar HC1 was observed to have a surface roughness (Ra) of about 0.529 nanometers. The sample treated with about 0.05 molar HF and about 3 molar HC1 was observed to have a surface roughness (Ra) of about 0.580 nanometers. The sample treated with about 0.10 molar HF and about 3 molar HC1 was observed to have a surface roughness (Ra) of about 0.631 nanometers. By comparison, the untreated control sample had a surface roughness (Ra) of about 0.2 nanometers.

[0061] Etch rate also varied by sample, with results shown in FIG. 4. The sample treated with about 0.35 molar NaF and about 1 molar H3PO4 was observed to have an etch rate of about 0.19 microns per minute. The sample treated with about 0.01 molar HF and about 3 molar HC1 was observed to have an etch rate of about 0.02 microns per minute. The sample treated with about 0.05 molar HF and about 3 molar HC1 was observed to have an etch rate of about 0.05 microns per minute. The sample treated with about 0.10 molar HF and about 3 molar HC1 was observed to have an etch rate of about 0.11 microns per minute.

[0062] Surface composition also varied by sample. For example, certain samples treated with solutions comprising HF and HC1 were shown to have lower relative surface

concentrations of at least one of AI2O3, B2O3, MgO, CaO, BaO, and/or SrO and/or lower relative ratios of at least one of AhCb/SiC , B2O₃/S1O2, MgO/SiCE, CaO/SiCh, SrO/SiCh, and/or BaO/SiCE as compared to samples treated with 0.35 molar NaF and about 1 molar H3PO4 or the untreated control sample as measured by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS).

[0063] Example 2:

[0064] Samples of Corning® Lotus™ NXT glass having a major surface area of about 100 square millimeters and a thickness of about 0.4 millimeters were pre-washed in a 2% Parker 225x detergent bath at about 50°C for 10 about minutes. The samples were then dipped in aqueous solutions comprising a fluorine-containing acid and a non-fluorine containing acid as set forth in Table 1. Each sample was exposed to a respective solution for a time of about 80 seconds and a solution temperature of about 40°C. For each sample, glass surface electrostatic charging reduction (as compared to an untreated reference sample) was evaluated using a the above-referenced Surface Voltage Measurement Technique, with the results shown in Table 1. In addition, certain selected samples were evaluated for glass surface roughness (Ra) for a 10 x 10 micrometer (micron) scan size using atomic force microscopy (AFM), with the results shown in Table 1.

[0065] Table 1

[0066] Applicants have found that when a solution comprising one or more fluorine- containing acids, such as hydrofluoric acid (HF) and/or ammonium bifluoride (NH4HF2), and one or more non-fluorine-containing acids, such as hydrochloric acid (HC1) and/or citric acid (C6H8O7), is applied to a major surface of a glass substrate, at concentrations and/or amounts such that a ratio of total fluorine to free proton in the solution is within a specified range, improved electrostatic charge reduction of the major surface occurs as compared to a control glass sheet sample that has not been exposed to the solution. For example, when a solution comprising one or more fluorine-containing acids and one or more non-fluorine-containing acids is applied to a major surface of a glass substrate such that a ratio of total fluorine to free proton in the solution ranges from about 0.03 to about 0.1, application of the solution can result in the major surface having an electrostatic charge reduction of at least about 60%, such as from about 60% to about 80%, as compared to a control glass sheet sample that has not been exposed to the solution. In addition, when a solution comprising one or more fluorine-containing acids and one or more non-fluorine-containing acids is applied to a major surface of a glass substrate such that a ratio of total fluorine to free proton in the solution ranges from about 0.1 to about 10, application of the solution can result in the major surface having an electrostatic charge reduction of at least about 50%, such as from about 50% to about 80%, as compared to a control glass sheet sample that has not been exposed to the solution.

[0067] 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.

[0068] While the above embodiments have been described with reference to a fusion down draw process, it is to be understood that such embodiments are also applicable to other glass forming processes, such as float processes, slot draw processes, up-draw processes, tube drawing processes, and press-rolling processes.

[0069] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiment of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method for treating a glass substrate comprising:

applying an aqueous solution comprising a fluorine-containing acid and a non-fluorine-containing acid to a major surface of the glass substrate, wherein application of the solution results in at least one major surface of the glass substrate having an electrostatic charge reduction of at least about 50% as compared to a control glass sheet sample that has not been exposed to the solution.

2. The method of claim 1, wherein a ratio of total fluorine to free proton in the solution ranges from about 0.03 to about 0.1.

3. The method of claim 1, wherein a ratio of total fluorine to free proton in the solution ranges from about 0.1 to about 10.

4. The method of claim 1, wherein the fluorine-containing acid has a molarity of less than or equal to about 1 and the non-fluorine-containing acid has a molarity of greater than or equal to about 1.

5. The method of claim 1, wherein fluorine-containing acid has a molarity

ranging from about 0.01 to about 1 and the non-fluorine-containing acid has a molarity ranging from about 1 to about 12.

6. The method of claim 1, wherein the fluorine-containing acid comprises at least one of hydrofluoric acid (HF) or ammonium bifluoride (NH₄HF₂) and the non-fluorine-containing acid comprises at least one of hydrochloric acid (HC1) or citric acid (C6H8O7).

7. The method of claim 1, wherein the solution is applied for a time ranging from about 20 seconds to about 100 seconds.

8. The method of claim 1, wherein the solution is applied at a temperature ranging from about 30°C to about 80°C.

9. The method of claim 1, wherein application of the solution results in at least one major surface of the glass substrate having a surface roughness (Ra) of from about 0.2 to about 0.8 nanometers as measured by using atomic force microscopy (AFM)

10. The method of claim 2, wherein application of the solution results in at least one major surface of the glass substrate having an electrostatic charge reduction of at least about 60% as compared to a control glass sheet sample that has not been exposed to the solution.

11. The method of claim 1, wherein application of the solution results in at least one major surface of the glass substrate being etched at a rate of from about 0.01 microns per minute to about 0.15 microns per minute.

12. The method of claim 1, wherein the glass substrate comprises S1O2, and

AI₂O₃, B₂O₃, MgO, CaO, BaO, and/or SrO and application of the solution results in at least one major surface of the glass substrate having a surface composition wherein the surface concentration ratio of at least one of Al₂0₃/Si02, B2O3/S1O2, MgO/SiC , CaO/Si0₂, SrO/Si0₂, and/or

BaO/SiC is less than the surface concentration ratio of at least one of AI2O3/S1O2, B2O3/S1O2, MgO/SiC , CaO/Si0₂, SrO/Si0₂, and/or

BaO/SiC on the surface of the glass substrate where the solution has not been applied.

13. The method of claim 1, wherein the glass substrate comprises an alkali free glass composition comprising 58-65wt% S1O₂, 14-20wt% AI₂O₃, 8-12wt% B₂O₃, l-3wt% MgO, 5-10wt% CaO, and 0.5-2wt% SrO.

14. The method of claim 1, wherein the glass substrate comprises 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 5-10wt% BaO.

15. The method of claim 1, wherein the glass substrate comprises an alkali free glass composition comprising 57-6 lwt% S1O₂, 17-21wt% AI₂O₃, 5-8wt% B₂O₃, l-5wt% MgO, 3-9wt% CaO, 0-6wt% SrO, and 0-7wt% BaO.

16. The method of claim 1, wherein the glass substrate comprises a glass

composition comprising 55-72wt% S1O2, 12-24wt% AI2O3, 10-18wt% Na₂0, 0-10wt% B2O3, 0-5 wt% K2O, 0-5 wt% MgO, and 0-5 wt% CaO, 1- 5wt% K2O, and l-5wt% MgO.

17. A glass substrate treated by the method of claim 1.

18. An electronic device comprising the glass substrate of claim 17.