Fusion-molded glass articles exhibiting minimal optical distortion and related methods

Abstract

Glass articles exhibiting low optical distortion and related methods are described. Glass articles can be fabricated by applying laser power to a ribbon of glass-forming material based on at least one of a thickness profile measurement or an optical distortion map of the ribbon. The laser power is configured to mitigate localized topographic variations on the ribbon, providing a glass material that exhibits low vertical and horizontal optical distortion values, even at high measurement angles and relatively high thicknesses. For example, in embodiments, a glass article may have a thickness of 0.05 mm or more and 6.0 mm or less, while exhibiting maximum vertical and optical distortion values ​​of less than 16 millidiopters and 60 millidiopters, respectively, when measured at tilt angles of 60° or more and cross viewing angles of 20° or more.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims the benefit of priority from U.S. Provisional Application No. 63 / 530,174, filed on 1 August 2023, and U.S. Provisional Application No. 63 / 471,895, filed on 8 June 2023, the contents of which are relied upon and incorporated herein by reference in their entirety.

[0002] This disclosure relates to glass articles, and more specifically to glass articles exhibiting relatively low optical distortion compared to glass articles manufactured by certain existing manufacturing methods, and to methods for forming them. [Background technology]

[0003] Many applications benefit from glass articles that exhibit relatively low optical distortion. Automotive glass is one example of such an application. With increasing vehicle connectivity, more active components (e.g., advanced driver assistance systems (ADAS), sensors, cameras, etc.) are being incorporated into vehicles. For example, a particular vehicle may employ an imaging system to detect one or more aspects of the vehicle's operating environment in order to provide feedback to vehicle components. Certain applications may benefit particularly from imaging systems with high resolution. Such higher resolution can be made possible through advances in imaging components (e.g., detector arrays). As a result, vehicle manufacturers may adopt higher resolution imaging systems in their vehicles. Such systems may be located behind the vehicle's glass components (e.g., windshield or other glazing, separate protective windows), and any optical distortion caused by such glass components can directly affect the ability to fully realize the benefits of the high-resolution system.

[0004] Glass manufacturing methods are known to introduce variations in thickness into the resulting articles. Such variations in thickness are directional in that they can generally be oriented in the direction in which the molten glass is stretched during the manufacturing process. Float manufacturing methods can result in glass articles having variations in thickness along the direction in which the glass advances. Downdraw methods can result in vertically oriented draw lines such that the thickness of the glass article varies in a direction perpendicular to the downdraw direction (e.g., represented by gravity). Downdraw methods generally exhibit smaller amplitude variations in thickness than those associated with float methods, but such variations in thickness can still be problematic in terms of optical distortion for certain applications because they represent regions of localized curvature. Such regions of localized curvature generally impart unintended optical power to the glass article, which can result in various existing glass articles having unacceptably high levels of optical distortion due to localized lensing effects from the curvature.

[0005] Therefore, there is a need for glass articles that exhibit minimal optical distortion and for methods of manufacturing them. [Overview of the Initiative]

[0006] This disclosure describes how, when softened glass is allowed to solidify into a glass article in a down-draw process, optical distortion can be minimized by applying energy to the softened glass during the formation of various glass articles in areas where high optical distortion is likely to occur. The energy may be applied in the form of a laser having a relatively limited heat-affected zone (e.g., less than 100 mm) to mitigate (or even eliminate) localized high curvature areas in the glass article. The laser may be controlled based on detected (or estimated) high thickness gradient or curvature areas, or, as described herein, based on direct measurement of optical distortion rather than a specific thickness target. The energy is applied to the glass with the aim of mitigating localized curvature and / or thickness variations rather than achieving a specific target thickness, in order to provide a glass article exhibiting relatively low optical distortion compared to one produced using a particular existing process. As described herein, the articles described herein can exhibit relatively low levels of vertical optical distortion ("VOD") and horizontal optical distortion ("HOD") when measured using commercially available strain gauges such as the SCREENSCAN-Faultfinder® supplied by ISRA VISION AG. In embodiments suitable for automotive applications, for example, the glass articles described herein can exhibit a combined HOD and VOD value of 80 millidiopters or less, or even 50 millidiopters or less, or even 20 millidiopters or less, when measured at a tilt angle of 60° and a cross-viewing angle of 20°. This is below what can be achieved by certain existing methods (e.g., float-molded soda lime silicate glass), particularly at relatively high thicknesses (e.g., 2.0 mm or more, 3.0 mm or more, 3.5 mm or more).

[0007] Embodiment (1) of the present disclosure relates to a glass article comprising a first main surface, a second main surface disposed on the opposite side of the first main surface, a thickness measured between the first main surface and the second main surface in a direction perpendicular to the first main surface and the second main surface, and a plurality of draw lines extending in a first direction, wherein the thickness is 0.05 mm or more and 6.0 mm or less, the glass article exhibits a maximum vertical optical distortion (VOD) of 16 millidiopters or less when the vertical direction is parallel to the first direction and the glass article is oriented at an inclination angle of 60° with respect to the vertical direction, and the glass article exhibits a maximum horizontal optical distortion (HOD) of 60 millidiopters or less when the horizontal direction is perpendicular to the vertical direction and the glass article is oriented at a cross viewing angle of 20° with respect to the horizontal direction.

[0008] Aspect (2) of the present disclosure relates to the glass article described in Aspect (1), wherein the sum of VOD and HOD is 20 millidiopters or less.

[0009] Aspect (3) of the present disclosure relates to the glass article described in Aspect (1) or (2), wherein 6 millidiopters ≤ VOD ≤ 10 millidiopters.

[0010] Aspect (4) of this disclosure relates to a glass article according to any one of aspects (1) to (3), wherein 6 millidiopters ≤ HOD ≤ 10 millidiopters.

[0011] Aspect (5) of the present disclosure relates to a glass article according to any one of aspects (1) to (4), wherein the glass article includes a horizontally measured length, the length being 500 mm or more, and the thickness along a horizontal line having a profile length of at least 50% of the length, is in a range of 0.05% or more of the average thickness along the line and 5.0% or less of the average thickness along the line.

[0012] Aspect (6) of this disclosure relates to the glass article described in Aspect (5), wherein the length is 2000 mm or more.

[0013] Aspect (7) of the present disclosure relates to a glass article according to aspect (5) or (6), wherein a 500 mm segment of the line includes a range of predicted optical distortion values ​​of 2.0 millidiopters or less, calculated as 0.5 times the second derivative of the thickness profile along the line.

[0014] Aspect (8) of the present disclosure relates to the glass article described in Aspect (7), wherein the maximum magnitude of the predicted optical distortion (in millidiopters) is less than 80% of the average thickness (in millimeters).

[0015] Aspect (9) of this disclosure relates to a glass article according to any one of aspects (6) to (8), wherein the range of predicted optical distortion is less than 150% of the average thickness (in mm).

[0016] Aspect (10) of the present disclosure relates to a glass article according to any one of aspects (6) to (9), wherein the predicted optical distortion value is less than 0.5 millidiopters over most of the 500 mm segment.

[0017] Aspect (11) of this disclosure relates to a glass article according to any one of aspects (1) to (10), wherein the average thickness is 2.0 mm or more.

[0018] Aspect (12) of this disclosure relates to the glass article described in Aspect (11), wherein the average thickness is 3.0 mm or more and 4.0 mm or less.

[0019] Aspect (13) of the present disclosure relates to a glass article according to any one of aspects (1) to (12), wherein the glass article comprises a borosilicate glass composition.

[0020] Aspects (14) of the present disclosure include a first major surface, a second major surface disposed on the opposite side of the first major surface, and a thickness measured in a direction perpendicular to the first major surface and the second major surface. The thickness includes an average value of 0.05 mm or more and 4.0 mm or less. Along a line extending in a first direction between the edges of the glass article, the thickness includes a range of 0.05% or more and 5.0% or less of the average value of the thickness along the line. A 500 mm segment of the line includes a range of predicted optical distortion values that are 2.0 millidiopters or less, calculated as 0.5 times the second derivative of the thickness profile along the line. The present disclosure relates to a glass article.

[0021] Aspects (15) of the present disclosure relate to the glass article according to aspects (14), wherein the average value is 2.0 mm or more.

[0022] Aspects (16) of the present disclosure relate to the glass article according to aspects (15), wherein the average value of the thickness is 3.0 mm or more and 4.0 mm or less.

[0023] Aspects (17) of the present disclosure relate to the glass article according to aspects (15) or (16), wherein the maximum magnitude of the predicted optical distortion value (in millidiopters) is less than 80% of the average value (in mm).

[0024] Aspects (18) of the present disclosure relate to the glass article according to any one of aspects (15) to (17), wherein the range of the predicted optical distortion value is less than 150% of the average value (in mm).

[0025] Aspects (19) of the present disclosure relate to the glass article according to any one of aspects (15) to (18), wherein the predicted optical distortion value is less than 0.5 millidiopter over most of the 500 mm segment.

[0026] Aspects (20) of the present disclosure relate to the glass article according to any one of aspects (15) to (19), wherein the glass article includes a length measured in the first direction, and the length is 1000 mm or more.

[0027] Aspect (21) of the present disclosure relates to the glass article described in aspect (20), wherein the glass article exhibits a maximum vertical optical distortion (VOD) of 16 millidiopters or less when the vertical direction is perpendicular to a first direction and the glass article is oriented at an inclination angle of 60° with respect to the vertical direction, and the glass article exhibits a maximum horizontal optical distortion (HOD) of 25 millidiopters or less when the horizontal direction is perpendicular to the vertical direction and the glass article is oriented at a cross viewing angle of 20° with respect to the horizontal direction.

[0028] Aspect (22) of the present disclosure relates to the glass article described in aspect (21), wherein the sum of VOD and HOD is 20 millidiopters or less.

[0029] Aspect (23) of the present disclosure relates to the glass article described in aspect (21) or (22), wherein 6 millidiopters ≤ VOD ≤ 10 millidiopters.

[0030] Aspect (24) of this disclosure relates to a glass article according to any one of aspects (21) to (23), wherein 6 millidiopters ≤ HOD ≤ 10 millidiopters.

[0031] Aspect (25) of the present disclosure relates to a glass article according to any one of aspects (15) to (24), wherein the glass article comprises a borosilicate glass composition.

[0032] Aspect (26) of the present disclosure relates to a method for manufacturing a glass article, the method comprising: measuring a thickness profile along the width of an initial ribbon of a glass-forming material; generating a smoothed thickness profile and generating a target thickness profile by removing high-spatial-frequency thickness variations from the thickness profile in order to offset the smoothed thickness profile, wherein the target thickness profile includes a non-constant thickness; and applying a laser output to the glass-forming material based on the difference between the measured thickness profile and the target thickness profile when the glass-forming material is in a viscous state, wherein the laser output varies along the width as the glass-forming material advances in a direction perpendicular to the direction in which the width is measured.

[0033] Aspect (27) of the present disclosure relates to the method of aspect (26), wherein the target thickness profile is greater than 20 μm and extends over a 500 mm segment.

[0034] Aspect (28) of the present disclosure relates to the method of aspect (26) or (27), wherein applying laser power involves changing the power supplied to the CO2 laser in proportion to the magnitude of the difference between the measured profile and the target thickness profile.

[0035] Aspect (29) of the present disclosure relates to a method according to any one of aspects (26) to (28), wherein the smoothed thickness profile is shifted downward by at least the maximum difference between the smoothed thickness profile and the measured thickness profile.

[0036] Aspect (30) of the present disclosure relates to the method according to aspect (29), wherein the laser power is applied to at least 80% of the width of the ribbon after the glass forming material.

[0037] Aspect (31) of this disclosure relates to the method of aspect (29), wherein the target thickness profile deviates by more than 10 μm from the nominal target value of the ribbon thickness.

[0038] Aspect (32) of this disclosure relates to the method according to aspect (30) or (31), wherein the nominal target value is 3.0 mm or more.

[0039] Aspect (33) of the present disclosure further comprises periodically measuring the nominal thickness profile of the ribbon, wherein the nominal thickness profile represents the thickness profile produced by the glass forming apparatus without the ribbon being modified by laser energy, and the amount of laser power applied to the ribbon varies based on the nominal thickness profile, relating to a method according to any one of aspects (26) to (30).

[0040] Aspect (34) of the present disclosure relates to the method of aspect (30), wherein applying laser power includes automatically calculating a vector of laser power values ​​using a model predictive control framework based on a nominal thickness profile.

[0041] Aspect (35) of the present disclosure relates to a method for manufacturing a glass article, the method comprising: measuring an optical strain map along the width of an initial ribbon of a glass-forming material using an optical strain gauge; and applying a laser output to the glass-forming material based on the difference between the optical strain value of the optical strain map and a target optical strain value, wherein the laser output varies along the width as the glass-forming material advances in a direction perpendicular to the direction in which the width is measured.

[0042] Aspect (36) of this disclosure relates to the method of aspect (35), wherein the target optical distortion value is 0 millidiopters.

[0043] Aspect (37) of the present disclosure relates to the method according to aspect (35) or (36), wherein the optical distortion map comprises at least one of a vertical optical distortion map and a horizontal optical distortion map.

[0044] Aspect (38) of the present disclosure relates to the method of aspect (37), wherein the optical distortion map includes a combination of a vertical optical distortion map and a horizontal optical distortion map.

[0045] Aspect (39) of the present disclosure further comprises periodically measuring a nominal optical strain map of a ribbon, the nominal optical strain map representing the optical strain map produced by a glass forming apparatus without the ribbon being modified by laser energy, and the amount of laser power applied to the ribbon varies based on the nominal optical strain map, relating to the method according to aspect (35) or (36).

[0046] Aspect (40) of the present disclosure relates to the method of aspect (39), wherein applying a laser output includes automatically calculating a vector of laser output values ​​using a model predictive control framework based on a nominal optical strain map.

[0047] Aspect (41) of the present disclosure relates to a method according to any one of aspects (35) to (40), wherein applying a laser output includes periodically calculating a vector of laser output values, so that the laser output mitigates localized peaks in an optical distortion map.

[0048] Additional features and advantages are described in the following detailed description, some of which will be readily apparent to those skilled in the art from that description, or will be recognized by carrying out the embodiments described herein, including the following detailed description, claims, and accompanying drawings.

[0049] It should be understood that both the above summary and the detailed description below are merely illustrative and intended to provide an overview or framework for understanding the nature and features of the claims. The accompanying drawings are included to provide further understanding and are incorporated herein and constitute part of it. The drawings illustrate one or more embodiments and, together with their descriptions, serve to illustrate the principles and operations of various embodiments. [Brief explanation of the drawing]

[0050] [Figure 1A]This is a side view of a vehicle in an external environment illustrating a sensing system on the roof of the vehicle and another system on the front portion of the vehicle, according to one or more embodiments of the present disclosure. [Figure 1B] Figure 1A schematically illustrates one of the vehicle sensing systems depicted in one or more embodiments of the present disclosure. [Figure 2A] Figure 1 schematically depicts a side view of the windshield of a vehicle shown in Figure 1 relative to an imaging system according to one or more embodiments of the present disclosure. [Figure 2B] Figure 2A schematically depicts a top view of the windshield of an imaging system according to one or more embodiments of the present disclosure. [Figure 3] A schematic description of a glass manufacturing apparatus according to one or more embodiments of the present disclosure is provided. [Figure 4] Figure 3 illustrates a schematic perspective cross-sectional view of a glass manufacturing apparatus along line 2-2, according to one or more embodiments of the present disclosure. [Figure 5] A thickness sensor that senses the thickness of the first portion of a ribbon of glass-forming material after the first portion has been separated from the second portion of the ribbon, according to one or more embodiments of the present disclosure, is schematically described. [Figure 6A] This is a flowchart illustrating a method for producing a glass article exhibiting low optical distortion according to one or more embodiments of the present disclosure. [Figure 6B] This is a flowchart illustrating a method for producing a glass article exhibiting low optical distortion according to one or more embodiments of the present disclosure. [Figure 7] This is a plot of exemplary examples of measured and target thickness profiles for carrying out the method described in Figure 6A according to one or more embodiments of the present disclosure. [Figure 8A] This is a plot of a 600 mm segment of the thickness profile of a glass article formed by the method described in Figure 6A, according to one or more embodiments of the present disclosure, and the associated predicted optical distortion profile. [Figure 8B]This is a plot of a 600 mm segment of the thickness profile of another glass article formed via the method described in Figure 6A, according to one or more embodiments of the present disclosure, and the associated predicted optical distortion profile. [Figure 9A] This is an optical distortion map of a glass article formed by the method described with respect to Figure 6A, according to one or more embodiments of the present disclosure. [Figure 9B] This is an optical distortion map of a glass article formed by the method described with respect to Figure 6A, according to one or more embodiments of the present disclosure. [Figure 10] A perspective view of a glass substrate according to one or more embodiments of the present disclosure is shown. [Modes for carrying out the invention]

[0051] Hereinafter, embodiments of glass articles exhibiting ultra-low optical distortion and related methods are referred to in detail. Wherever possible, the same reference numerals are used throughout the drawings to refer to the same or similar parts. The glass articles described herein can generally be characterized as having a main surface exhibiting minimally localized variations in thickness and curvature, and thus the glass articles have segments with relatively low levels of predictive optical distortion, which include a thickness profile measured along a line extending perpendicular to the draw line within the glass article and approximated as 0.5 times the second derivative of the thickness profile along the line. The glass articles described herein can exhibit a maximum predictive optical distortion value, which represents the optical distortion value (absolute value in millidiopters) at normal incidence, less than 20% of the average thickness (in mm) of the glass article measured along the line. Glass articles having a maximum thickness of 6.0 mm with such segments are considered to be formable via the methods described herein, and such glass articles exhibit a maximum predictive optical distortion value of 0.9 millidiopters or less when the thickness profile is measured over a 500 mm line between the ends of the article. Such low levels of maximum optical distortion make the glass articles according to this disclosure suitable for a variety of distortion-sensitive applications, such as protective windows for various sensors, automotive glazing, and other applications. Such low optical distortion values ​​cannot be obtained using certain existing molding methods (e.g., float molding) without additional processing steps such as polishing or etching. It should be noted that the glass articles described herein may exhibit such desirable properties without necessarily having a uniform thickness. Thickness variations over relatively large distances (e.g., 300 mm or more) can occur without necessarily preventing the glass articles from having the desirable optical performance described herein. Generally speaking, thickness variations with relatively large spatial frequencies are eliminated via the methods described herein to avoid localized lensing effects that can be amplified under various viewing conditions.

[0052] In some embodiments, the glass articles described herein can be formed using a down-draw process in which laser energy is applied to the glass-forming material in a viscous state in a spatially variable manner, based on regions where the glass is determined to be likely to exhibit a relatively high level of optical distortion. The laser energy is applied to reduce the viscosity of certain regions of the glass-forming material so as to reduce local surface perturbations within the glass-forming material (e.g., regions of relatively high thickness gradients, regions of relatively high surface curvature). Care is taken in the application of laser energy to avoid introducing features into the glass that would cause excessive levels of optical distortion. For example, in embodiments, a maximum variation in laser output over a specific linear distance (e.g., 50 mm) in a direction parallel to the variation in glass thickness is applied to prevent regions of high gradient and curvature.

[0053] Unless otherwise expressly stated, no method described herein is intended to be construed as requiring its steps to be performed in a specific order. Therefore, if a claim for a method does not actually list the order in which its steps are followed, or if it is not otherwise specifically stated in the claims or description that the steps should be limited to a specific order, no order is ever intended to be inferred. This also applies to any possible implicit grounds for interpretation, including logical matters relating to the arrangement of steps or operational flows, obvious meanings arising from grammatical structure or punctuation, and the number or type of embodiments described in the specification.

[0054] As used herein, the term "and / or" means, when used in a list of two or more items, that any one of the listed items may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B, and / or C, the composition may contain A only, B only, C only, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0055] Those skilled in the art, and those who create or use the Disclosure, will likely conceive of modifications to the Disclosure. Therefore, it should be understood that the embodiments shown in the drawings and described above are for illustrative purposes only and are not intended to limit the scope of the Disclosure, and are defined by the following claims, to be interpreted in accordance with the principles of patent law, including the doctrine of equivalents.

[0056] In this text, relational terms such as first and second, upper and lower are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. "Comprises," "comprising," or any other variation is intended to encompass non-exclusive inclusions such that a process, method, article, or apparatus comprising a list of elements may include other elements that are neither explicitly listed nor inherent in such a process, method, article, or apparatus, rather than containing only those elements. An element beginning with "comprises...a" does not, to a lesser extent, exclude the presence of additional identical elements in a process, method, article, or apparatus comprising that element.

[0057] Where used herein, the term “approximately” means that quantities, sizes, formulations, parameters, and other quantities and characteristics are not and do not need to be exact, and may be approximate and / or greater or less, as desired, to reflect tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art. Where the term “approximately” is used when describing values ​​or endpoints of a range, this disclosure should be understood to include the specific values ​​or endpoints being referenced. Whether or not the numerical values ​​or endpoints of a range in the specification cite “approximately,” the numerical values ​​or endpoints of a range are intended to include two embodiments: those modified by “approximately” and those not modified by “approximately.” Furthermore, it will be understood that each endpoint of a range is important either in relation to the other endpoints or independently of the other endpoints.

[0058] The term "formed from" can mean one or more of the following: include, essentially come from, or consist of. For example, a component formed from a particular material may include, essentially come from, or consist of a particular material.

[0059] Furthermore, as used herein, the terms “article,” “glass article,” “ceramic article,” “glass ceramic,” “glass element,” “glass ceramic article,” and “multiple glass ceramic articles” may be used interchangeably and, in their broadest sense, include any object made entirely or partially from glass and / or glass ceramic material.

[0060] The term "displaced" is used herein to refer to a layer or sublayer that is coated, deposited, formed, or otherwise provided on a surface. The term "displaced" may include layers / sublayers provided in direct contact with adjacent layers / sublayers, or layers / sublayers separated by intervening materials that may or may not form a layer.

[0061] As used herein, the term “draw line” is defined as a continuous strip of positive or negative perpendicular optical strain when measured using a commercially available strain gauge, such as the SCREENSCAN-Faultfinder® supplied by ISRA VISIION AG. Such draw lines arise from stresses in the glass-forming material during molding and can generally be characterized as variations in the thickness of the glass article in a direction perpendicular to the direction of progression of the molten glass material during fabrication.

[0062] As used herein, the term “vertical optical distortion” or “VOD” is an index that measures the degree to which an image transmitted through a glass article is distorted by the article in the vertical direction (the vertical direction is defined as the direction of gravity). “Horizontal optical distortion” or “HOD” is an index that measures the degree to which an article distorts an image transmitted through a glass article in a direction perpendicular to the vertical direction (for example, parallel to the ground on which the vehicle is positioned). Unless otherwise stated herein, the measured optical distortion values ​​are generated by reflecting moiré illumination from the article and measuring the illumination with a commercially available optical distortion gauge. Unless otherwise stated herein, the optical distortion measurements provided herein are for flat glass articles (flat sheets). Optical distortion measurements herein are reported for glass articles in their as-formed state, without the main surface being subjected to etching or polishing.

[0063] Referring here to Figure 1, the vehicle 5 includes a body 10 and, optionally, one or more sensor systems 12 disposed on the body 10. The one or more sensor systems 12 can be disposed on or anywhere within the vehicle 5. For example, the one or more sensor systems 12 can be disposed on the roof 14 and / or the front portion 16 of the vehicle 5. Referring here to Figure 1B, in an embodiment, the one or more sensor systems 12 include an electromagnetic emission emitter and sensor 18 disposed within an enclosure 20. A particular sensor system depicted in Figure 1B represents, for example, a light detection and ranging ("LiDAR") system. Other sensing systems may employ components other than the electromagnetic emission emitter and sensor 18 depicted (e.g., a camera, an infrared photodetector, or other suitable sensing system). In the depicted example, the electromagnetic emission emitter and sensor 18 emit electromagnetic radiation 22 having a wavelength or a range of wavelengths. The emitted radiation 22 exits the enclosure 20 through the window 24 and, in some situations, is reflected from objects in the external environment 26 of the vehicle 5, returning to the electromagnetic radiation emitter and sensor 18 as reflected radiation 28. The reflected radiation 28 again passes through the window 24 to reach the electromagnetic radiation emitter and sensor 18. The window 24 generally functions as a protective cover for the components inside the enclosure 20. Because the window 24 is in the path of the emitted radiation 22 and / or reflected radiation 28, any optical distortion present within the window can adversely affect the imaging performance of the sensor system 12. Therefore, the glass articles described herein may be particularly well suited for use as the window 24.

[0064] Referring again to Figure 1A, the vehicle 5 further includes automotive glazing 50, i.e., windows, disposed within openings in the main body 10. In embodiments, the automotive glazing 50 may form at least one of the side lights, windshield, rear window, window, and sunroof within the vehicle 5. In some embodiments, the automotive glazing 50 may form internal partitions (not shown) inside the vehicle 5 or may be disposed on the external surface of the vehicle 5 and may form, for example, an engine block cover, headlight cover, taillight cover, door panel cover, or pillar cover. As used herein, a vehicle includes automobiles (examples of which are shown in Figure 1A), railway vehicles, locomotives, boats, ships, and airplanes, helicopters, drones, spacecraft, etc. Furthermore, although this disclosure is framed in relation to vehicles, the glass articles described herein may be used in a wide variety of applications (e.g., as cover glass in home appliance applications, in the fabrication of optical elements, in display components).

[0065] Referring here to Figure 2A, a side view of an automotive glazing 50 according to an exemplary embodiment is shown. In the exemplary embodiment, the automotive glazing 50 is a laminated glass article comprising a first glass substrate 52, an intermediate layer 54, and a second glass substrate 56. Embodiments of glass articles described herein are not limited to laminated articles and may include integral glass substrates. The first glass substrate 52 may generally face the external environment 26 when the automotive glazing 50 is installed in a vehicle 5, and the second glass substrate 56 may face the interior of the vehicle 5. The intermediate layer 54 may include a suitable polymer material (e.g., polyvinyl butyral) for bonding the first glass substrate 52 and the second glass substrate 56 to each other. In the embodiment, the first glass substrate 52 differs from the second glass substrate 56 in at least one of its thickness and composition to provide improved impact and acoustic performance. In the embodiment, for example, the first glass substrate 52 includes a first thickness of at least 2.0 mm (e.g., 3.0 mm, at least 3.5 mm, at least 3.8 mm, at least 4.0 mm, at least 5.0 mm), and the second glass substrate 56 includes a second thickness of less than 2.0 mm (e.g., 0.0 mm or more and 1.5 mm or less, 0.7 mm or more and 1.1 mm or less). Examples of glass that may be used in the first glass substrate 52 or the second glass substrate 56 may include borosilicate glass compositions, aluminosilicate glass compositions, alkali aluminosilicate glass compositions, alkali aluminoborosilicate glass compositions, and other suitable glass compositions.

[0066] In the embodiment, one or both of the first glass substrate 52 and the second glass substrate 56 are used in U.S. Provisional Patent Application No. 63 / 123863, filed December 10, 2020, titled "Fusion Formable Borosilicate Glass Composition and Articles Formed Therefrom", U.S. Provisional Patent Application No. 63 / 183271, filed May 3, 2021, titled "Fusion Formable Borosilicate Glass Composition and Articles Formed Therefrom", U.S. Provisional Patent Application No. 63 / 183292, filed May 3, 2021, titled "Glass with Unique Fracture Behavior for Vehicle Windshield", and U.S. Patent Application No. 17 / 363266, filed June 30, 2021, titled "glass with Unique Fracture Behavior for Vehicle The invention particularly benefits from including one of the fused-moldable borosilicate glass compositions described in International Patent Application PCT / US2021 / 061966, filed on December 6, 2021, titled "Glass with Unique Fracture Behavior for Vehicle Windshield," and U.S. Provisional Patent Application 63 / 341,603, filed on May 13, 2022, titled "Glass with Unique Fracture Behavior for Vehicle Windshield," the contents of each of these are incorporated herein by reference in their entirety. In embodiments, such borosilicate glass compositions include, with respect to component oxides, SiO2, B2O3, Al2O3, one or more alkali metal oxides, and one or more divalent cation oxides selected from the group consisting of MgO, CaO, SrO, BaO, and ZnO. In the embodiment, the borosilicate glass composition includes, for example, a total amount of 11 mol% or more and 16 mol% or less of B2O3, 2 mol% or more and 6 mol% or less of Al2O3, and 7.0 mol% or more of Na2O, K2O, MgO, and CaO.The oxide-based molar percentage concentrations of SiO2, B2O3, one or more alkali metal oxides, Al2O3, and one or more alkaline earth metal oxides satisfy the following relationship: (R2O + R'O) ≥ Al and 0.80 < (1 - [(2R2O + 2R'O) / (SiO2 + 2Al2O3 + 2B2O3)]) < 0.93, where R2O is the sum of the concentrations of one or more alkali metal oxides and R'O is the sum of the concentrations of one or more alkaline earth metal oxides. Such glass may exhibit unique fracture behavior in which ring cracks form around the contact area between the glass and the impactor and radial crack propagation is prevented. Such fused glass may also exhibit superior chemical durability, scratch resistance, mechanical strength, and optical performance compared to other glass used in automotive glazing applications (e.g., both in terms of optical transmission and optical distortion).

[0067] In the embodiment, one or both of the first glass substrate 52 and the second glass substrate 56 are formed by a preferred down-draw process as described herein. Such a process generally results in variations in thickness extending in a particular direction (so that a region of constant thickness in the glass article extends parallel to the draw direction). These variations in thickness are known as draw lines, and each draw line generally represents a contour of constant thickness extending in the draw direction. In the automotive industry, it is common to orient such draw lines perpendicularly (for example, in a direction perpendicular to the ground 70 as depicted in Figure 1A, represented by the vertical axis 60), so that the eyes of the vehicle occupants tend not to move across the draw lines while driving, and thus tend to amplify the optical distortion caused by it.

[0068] One trend in the automotive industry, which tends to amplify the optical distortion effect of draw lines, is that certain windshields are mounted at a relatively high angle with respect to the vertical axis 60. In particular, in battery electric vehicles, where aerodynamics are becoming increasingly important from the standpoint of efficiency due to increased weight, automotive glazing 50 may be mounted at a relatively high rake angle α with respect to the vertical axis 60. Such a large inclination of automotive glazing 50 can reduce drag. In embodiments, the rake angle α is 60° or greater (e.g., 65° or greater, or even 70° or greater). Such a high rake angle increases the HOD and VOD caused by the automotive glazing 50, thereby making the overall optical distortion performance of the article more significant. Optical distortion measurements taken at “inclination angle” with respect to the vertical, as described herein, refer to the rake angle α depicted in Figure 2A.

[0069] Figure 2A also depicts an image sensor 58 disposed on the inside of the automotive glazing 50. The image sensor 58 may facilitate the detection of at least one aspect of the external environment 26 and provide feedback to at least one other component of the vehicle 5. For example, the image sensor 58 may be a camera configured as a component of ADAS to capture images and identify objects in the external environment 26 and their movement paths. Another trend in the automotive industry is the use of higher resolution detection components in the image sensor 58 (e.g., in terms of pixels per field of view). Such higher resolution components may make the image sensor 58 more sensitive to vertical optical distortion caused by the glazing 50.

[0070] In addition, as shown in Figure 2B, the image sensor 58 may be used with a relatively high field of view β in the horizontal direction (for example, extending perpendicular to the vertical axis 60 and parallel to the ground 70). Fields of view of ±20° (e.g., β=40°), or even ±25° (e.g., β=50°), or even larger may be used to facilitate the image sensor 58 capturing a relatively large portion of the external environment 26 in each image. Thus, the optical distortion imparted to light incident on the automotive glazing 50 at angles up to β / 2 is relevant to various applications. Such horizontal incidence angles on the automotive glazing 50 generally amplify the optical effect of thickness variations extending horizontally (perpendicular to the draw line in automotive glazing applications). The optical distortion measurements described herein are taken at the “cross-view angle” relative to the horizontal direction and refer to the angle β / 2 depicted in Figure 2B.

[0071] Considering the above, the increasing utilization of high-resolution sensors in vehicles generally reduces the acceptable level of optical distortion that can be introduced by the automotive glazing 50. Furthermore, if the automotive glazing 50 is mounted at a relatively high inclination with respect to the vertical, horizontal and vertical optical distortions are amplified. The use of wide-field sensors also increases the importance of reducing the vertical optical distortion introduced by the automotive glazing 50. Given that the overall level of optical distortion introduced by the automotive glazing 50 is proportional to the optical distortion introduced by each of the first glass substrates 52 and the second glass substrate 56, controlling variations in the thickness of each of the first glass substrates 52 and the second glass substrate 56 is important to provide the desired level of optical performance. Furthermore, the optical distortion introduced by each of the first glass substrate 52 and the second glass substrate 56 can generally be considered as a combination of two factors: (a) inherent local thickness variations due to the sheet formation process, and (b) optical distortion introduced during the bending process of the first glass substrate 52 and the second glass substrate 56 (described as flat, but each of the first glass substrate 52 and the second glass substrate 56 can be bent about at least one axis of curvature via any known process such as gravity bending or press bending, so that in some embodiments the first glass substrate 52 and the second glass substrate 56 are bent about two different axes of curvature such that the first glass substrate 52 and the second glass substrate 56 are convexly curved). The forming process described herein beneficially reduces the local curvature resulting from the forming process, thereby lowering the overall level of optical distortion that can be achieved. The glass articles described herein may exhibit a maximum (99.9%) VOD value of less than 16 millidiopters (preferably 7 millidiopters or more and 12 millidiopters or less, or more preferably 6 millidiopters or more and 10 millidiopters or less, or even more preferably 6 millidiopters or more and 9 millidiopters or less).The glass articles described herein can also exhibit a maximum (99.9%) HOD value of 60 millidiopters or less (preferably 6 millidiopters or more and 50 millidiopters or less, or more preferably 6 millidiopters or more and 12 millidiopters or less, or even more preferably 6 millidiopters or more and 10 millidiopters or less, or even more preferably 6 millidiopters or more and 9 millidiopters or less) when measured at a 60° tilt angle and a 20° cross viewing angle. Such values ​​are much lower than those associated with existing glass used in automotive applications. The relatively low levels of both horizontal and vertical optical distortion exhibited by the glass articles described herein (therefore, in some embodiments, the sum of the HOD and VOD values ​​is 80 millidiopters or less, or even more preferably 50 millidiopters or less, or even more preferably 20 millidiopters or less) beneficially facilitate the use of high-resolution sensing systems at wide viewing angles.

[0072] Referring here to Figure 3, an exemplary embodiment of the glass manufacturing apparatus 100 is shown. The glass manufacturing apparatus 100 can be used to form a sheet of glass material exhibiting a relatively low amount of optical distortion, as described herein. The glass sheet formed via the glass manufacturing apparatus 100 can be used to form various glass articles, such as the first glass substrate 52 or the second glass substrate 56 described herein, and other glass articles.

[0073] In the described embodiment, the glass manufacturing apparatus 100 comprises a glass melting and feeding apparatus 102 and a molding apparatus 101 having a molding vessel 140 designed to produce ribbons of glass-forming material 103 from a large amount of molten material 121. In some embodiments, the ribbons of glass-forming material 103 may have a central portion 152 positioned between opposing edge portions (e.g., edge beads) formed along a first outer edge 153 and a second outer edge 155 of the ribbons of glass-forming material 103, and the thickness of the edge portions may be greater than the thickness of the central portion. In addition, in some embodiments, the separated glass ribbons 104 may be separated from the ribbons of glass-forming material 103 along a separation path 151 by a glass separator 149 (e.g., a scribe, score wheel, diamond tip, laser, etc.).

[0074] In some embodiments, the glass melting and feeding apparatus 102 may include a melting vessel 105 oriented to receive batch material 107 from a storage bin 109. The batch material 107 can be introduced by a batch feeding device 111 actuated by a motor 113. In some embodiments, an optional controller 115 can be operated to activate the motor 113 and introduce a desired amount of batch material 107 into the melting vessel 105, as indicated by an arrow 117. The melting vessel 105 can heat the batch material 107 to provide molten material 121. In some embodiments, a melting probe 119 may be employed to measure the level of molten material 121 in a standpipe 123 and to transmit the measured information to the controller 115 via a communication line 125.

[0075] In addition, in some embodiments, the glass melting and feeding device 102 may include a first adjustment station comprising a clarification vessel 127 located downstream of the melting vessel 105 and coupled to the melting vessel 105 by a first connecting conduit 129. In some embodiments, the molten material 121 can be supplied by gravity from the melting vessel 105 to the clarification vessel 127 by the first connecting conduit 129. For example, in some embodiments, gravity can deliver the molten material 121 from the melting vessel 105 to the clarification vessel 127 through the internal path of the first connecting conduit 129. In addition, in some embodiments, bubbles can be removed from the molten material 121 in the clarification vessel 127 by various techniques.

[0076] In some embodiments, the glass melting and feeding apparatus 102 may further include a second adjustment station comprising a mixing chamber 131 which may be located downstream of the clarification vessel 127. The mixing chamber 131 is employed to provide a homogeneous composition of the molten material 121, thereby reducing or eliminating any heterogeneity that may otherwise exist in the molten material 121 as it exits the clarification vessel 127. As shown, the clarification vessel 127 may be coupled to the mixing chamber 131 by a second connecting conduit 135. In some embodiments, the molten material 121 may be gravity-fed from the clarification vessel 127 to the mixing chamber 131 by the second connecting conduit 135. For example, in some embodiments, gravity may feed the molten material 121 from the clarification vessel 127 to the mixing chamber 131 through an internal path of the second connecting conduit 135.

[0077] In addition, in some embodiments, the glass melting and feeding apparatus 102 may include a third adjustment station comprising a feeding chamber 133 which may be located downstream of the mixing chamber 131. In some embodiments, the feeding chamber 133 may be adjusted so that the molten material 121 is supplied to the inlet conduit 141. For example, the feeding chamber 133 may function as an accumulator and / or flow controller for adjusting and providing a consistent flow of the molten material 121 to the inlet conduit 141. As shown, the mixing chamber 131 may be coupled to the feeding chamber 133 by a third connecting conduit 137. In some embodiments, the molten material 121 may be gravity-fed from the mixing chamber 131 to the feeding chamber 133 by the third connecting conduit 137. For example, in some embodiments, gravity may feed the molten material 121 from the mixing chamber 131 to the feeding chamber 133 through the internal path of the third connecting conduit 137. As further illustrated, in some embodiments, the supply pipe 139 can be positioned to supply the molten material 121 to the inlet conduit 141 of the molding apparatus 101, for example, the molding container 140.

[0078] The molding apparatus 101 may comprise various embodiments of a molding vessel according to the features of the present disclosure, for example, a molding vessel with a wedge for fusion drawing a glass ribbon, a molding vessel with slots for slot drawing a glass ribbon, or a molding vessel with press rolls for press rolling a glass ribbon from the molding vessel. In some embodiments, the molding apparatus 101 may comprise, for example, a sheet redraw having the molding apparatus 101 as part of a redraw process. For example, a glass ribbon 104 which may have thickness may be heated and redrawed to achieve a thinner glass ribbon 104 with a smaller thickness. Exemplarily, a molding vessel 140 shown and disclosed below may be provided for fusion drawing a molten material 121 from a bottom edge defined as the route 145 of a molding wedge 209 to produce a ribbon of glass-forming material 103. For example, in some embodiments, the molten material 121 may be fed into the molding vessel 140 from an inlet conduit 141. Next, the molten material 121 can be partially formed into a ribbon of glass-forming material 103 based on the structure of the molding vessel 140. For example, as shown, the molten material 121 can be drawn from the bottom edge (e.g., root 145) of the molding vessel 140 along a draw path extending in the direction of travel 154 of the glass manufacturing apparatus 100. In some embodiments, edge directors 163, 164 can direct the molten material 121 away from the molding vessel 140 and partially define the width "W" of the ribbon of glass-forming material 103. In some embodiments, the width "W" of the ribbon of glass-forming material 103 extends between the first outer edge 153 and the second outer edge 155 of the ribbon of glass-forming material 103.

[0079] In some embodiments, the width "W" of the ribbon of the glass-forming material 103, extending between the first outer edge 153 and the second outer edge 155 of the ribbon of the glass-forming material 103, can be about 20 millimeters (mm) or more, for example, about 50 mm or more, for example, about 100 mm or more, for example, about 500 mm or more, for example, about 1000 mm or more, for example, about 2000 mm or more, for example, about 3000 mm or more, for example, about 4000 mm or more, but other widths less than the widths listed above or other widths greater than the widths listed above may be provided in further embodiments. For example, in some embodiments, the width "W" of the ribbon of the glass forming material 103 is in the range of approximately 20 mm to approximately 4000 mm, for example, in the range of approximately 50 mm to approximately 4000 mm, for example, in the range of approximately 100 mm to approximately 4000 mm, for example, in the range of approximately 500 mm to approximately 4000 mm, for example, in the range of approximately 1000 mm to approximately 4000 mm, for example, in the range of approximately 2000 mm to approximately 4000 mm, for example, in the range of approximately 3000 mm to approximately 4000 mm. This includes the ranges, for example, the range from approximately 20 mm to approximately 3000 mm, for example, the range from approximately 50 mm to approximately 3000 mm, for example, the range from approximately 100 mm to approximately 3000 mm, for example, the range from approximately 500 mm to approximately 3000 mm, for example, the range from approximately 1000 mm to approximately 3000 mm, for example, the range from approximately 2000 mm to approximately 3000 mm, for example, the range from approximately 2000 mm to approximately 2500 mm, and all ranges and partial ranges in between.

[0080] Figure 4 shows a cross-sectional perspective view of the molding apparatus 101 (e.g., molding vessel 140) along line 2-2 in Figure 3. In some embodiments, the molding vessel 140 may include a trough 201 oriented to receive molten material 121 from an inlet conduit 141. For illustrative purposes, the cross-hatching of the molten material 121 is removed from Figure 2 for clarity. The molding vessel 140 may further include a molding wedge 209 having a pair of downwardly inclined converging surface portions 207, 208 extending between the opposing ends 210, 211 (see Figure 3) of the molding wedge 209. The pair of downwardly inclined converging surface portions 207, 208 of the molding wedge 209 may converge along the direction of travel 154 and intersect along the route 145 of the molding vessel 140. Route 145 defines the bottom of the forming wedge 209, where downward-sloping converging surface portions 207 and 208 intersect to form a point. The draw plane 213 of the glassmaking apparatus 100 can extend along the direction of travel 154 and through route 145. In some embodiments, a ribbon of glass-forming material 103 can be drawn along the draw plane 213 in the direction of travel 154. As shown, the draw plane 213 can bisect the forming wedge 209 through route 145, but in some embodiments, the draw plane 213 can extend in other orientations relative to route 145. In some embodiments, a method for producing a glass ribbon may include moving a ribbon of glass-forming material 103 along a travel path 221 in the direction of travel 154, where the travel path 221 may be coplanar with the draw plane 213.

[0081] In addition, in some embodiments, the molten material 121 can flow into and along the trough 201 of the molding vessel 140 in direction 156. The molten material 121 can then overflow from the trough 201 by flowing over the corresponding weirs 203, 204 and simultaneously flowing downward on the outer surfaces 205, 206 of the corresponding weirs 203, 204. For example, a method for producing a glass ribbon may include flowing a first flow 241 of glass-forming material over a first weir 203 of a molding wedge 209 and flowing a second flow 243 of glass-forming material over a second weir 204 of the molding wedge 209. The first flow 241 and the second flow 243 of glass-forming material can flow along the downward-sloping converging surface portions 207, 208 of the molding wedge 209 and be drawn out of the root 145 of the molding vessel 140. In some embodiments, a method for manufacturing a glass ribbon may include fusing a first flow 241 and a second flow 243 of the glass-forming material to form a fused ribbon 245. For example, the first flow 241 and the second flow 243 may converge and fuse at a route 145. In some embodiments, the fused ribbon 245 may be drawn from the route 145 in a draw plane 213 along the direction of travel 154. In some embodiments, a ribbon of the glass-forming material 103 may include a first flow 241 and a second flow 243 of the glass-forming material upstream of the route 145 with respect to the direction of travel 154, and may comprise a fused ribbon 245 drawn from the route 145 downstream of the forming wedge 209 with respect to the direction of travel 154, before fusing. A ribbon of the glass-forming material 103 may include at least one state of the material based on the vertical location of the ribbon of the glass-forming material 103. For example, in one location, the ribbon of the glass-forming material 103 may include the viscous molten material 121, while in another location, the ribbon of the glass-forming material 103 may include an amorphous solid in a glassy state (e.g., a glass ribbon).

[0082] The ribbon of the glass-forming material 103 comprises a first main surface 215 and a second main surface 216 that face in opposite directions and define the thickness "T" (e.g., average thickness) of the ribbon of the glass-forming material 103 along an axis that is normal to one or both of the first main surface 215 or the second main surface 216. In some embodiments, the thickness "T" of the ribbon of the glass-forming material 103 can be about 6 millimeters (mm) or less, 5 millimeters or less, 4 millimeters or less, 3 mm or less, about 2 millimeters (mm) or less, about 1 millimeter or less, about 0.5 millimeters or less, for example, about 300 micrometers (μm) or less, about 200 micrometers or less, or about 100 micrometers or less, although other thicknesses may be provided in further embodiments. For example, in some embodiments, the thickness "T" of the ribbon of the glass-forming material 103 can be in the range of about 20 micrometers to about 6 mm. As described herein, one aspect of the present disclosure is that the ribbon of the glass-forming material 103 may have a relatively high thickness, such as 2.0 mm or more, 3.0 mm or more, or even 3.5 mm or more, in some embodiments, while also exhibiting a relatively low level of optical distortion. Such thickness may facilitate the formation of a glass sheet for use as a first glass substrate 52 for automotive glazing 50 (see Figure 2A). In addition, the ribbon of the glass-forming material 103 may include a variety of compositions, such as borosilicate glass, aluminoborosilicate glass, alkali-containing glass, or alkali-free glass, alkali aluminosilicate glass, alkaline earth aluminosilicate glass, soda-lime glass, etc.

[0083] In some embodiments, a glass separator 149 (see Figure 3) can separate the glass ribbon 104 along a separation path 151 from the ribbon of glass-forming material 103 to provide multiple separated glass ribbons 104 (i.e., multiple glass sheets). According to other embodiments, longer portions of the glass ribbon 104 can be coiled on a storage roll. The separated glass ribbons can then be processed for desired applications, such as automotive applications or display applications. For example, the separated glass ribbons can be used in automotive applications (e.g., as one of the first glass substrate 52 and the second glass substrate 56, as a window 24 (see Figure 2B), or as a cover glass for an internal display), consumer electronics (e.g., as a cover glass or protective cover), and in a wide range of display applications, including liquid crystal displays (LCDs), electrophoretic displays (EPDs), organic light-emitting diode displays (OLEDs), plasma display panels (PDPs), touch sensors, photocells, and other electronic displays.

[0084] Figure 5 illustrates a schematic diagram of the molding vessel 140. In some embodiments, the glass manufacturing apparatus 100 may be equipped with a thickness sensor 301 capable of measuring the thickness of the ribbon of the glass-forming material 103 (e.g., thickness "T" as illustrated in Figure 4). For example, the thickness may be measured between a first main surface 215 and a second main surface 216 of the ribbon of the glass-forming material 103 (e.g., perpendicular to the width "W" of the ribbon of the glass-forming material 103 extending between a first outer edge 153 and a second outer edge 155 as illustrated in Figure 3). In some embodiments, the thickness sensor 301 may sense the thickness of the ribbon of the glass-forming material 103 at the bottom of the molding vessel 140, for example, downstream from the route 145 of the molding vessel 140 with respect to the direction of travel 154 (e.g., upstream of the separator 149 as depicted in Figure 3), when the ribbon of the glass-forming material is traveling in the direction of travel 154. In the embodiments described, the thickness of the ribbon of the glass-forming material 103 can be sensed after the first ribbon portion 401 has been separated from the second ribbon portion 403. For example, in some embodiments, a method for manufacturing a glass ribbon may include separating the first ribbon portion 401 of the ribbon of the glass-forming material 103 from the second ribbon portion 403 of the ribbon of the glass-forming material 103 before sensing the thickness of the first ribbon portion 401. As the ribbon of the glass-forming material 103 moves in the direction of travel 154, the first ribbon portion 401 can be separated from the second ribbon portion 403, for example, by a glass separator 149 in Figure 3. In some embodiments, the first ribbon portion 401 can be transported to a remote location after separation, for example, a location where the first ribbon portion 401 can be inspected and its thickness measured. In some embodiments, the thickness sensor 301 may comprise a laser-based thickness measuring device.

[0085] In some embodiments, although not depicted in Figure 3, the thickness sensor 301 can sense the thickness of the ribbon of the glass-forming material 103 at one or more locations, such as a first location 303, a second location 305, a third location 307, and a fourth location 309. While this specification refers to the first location 303, the second location 305, the third location 307, and the fourth location 309, it should be understood that the thickness sensor 301 can sense the thickness at any number of locations across the width of the ribbon of the glass-forming material 103 (for example, the thickness sensor 301 can perform thickness measurements at intervals of 5 mm, 2 mm, 1 mm, or even smaller intervals across the entire width). In some embodiments, a method for manufacturing a glass ribbon may include sensing the thickness of the ribbon of the glass-forming material 103 at multiple locations on the ribbon of the glass-forming material 103 (e.g., a first location 303, a second location 305, a third location 307, a fourth location 309, etc.). Sensing the thickness of the ribbon of the glass-forming material 103 can occur at multiple spaced locations along a first axis 313 that may be substantially perpendicular to the direction of travel 154. For example, the first axis 313 may extend along a direction that may be substantially parallel to the first main surface 215 and / or second main surface 216 of the ribbon of the glass-forming material 103 (e.g., between the first outer edge 153 and the second outer edge 155). In some embodiments, the distance separating the first location 303 from the first outer edge 153 may be less than the distance separating the second location 305, the third location 307, and / or the fourth location 309 from the first outer edge 153. In some embodiments, the distance separating the fourth location 309 from the second outer edge 155 may be less than the distance separating the first location 303, the second location 305, and / or the third location 307 from the second outer edge 155. In some embodiments, the second location 305 and the third location 307 may be located between the first location 303 and the fourth location 309.

[0086] The glass manufacturing apparatus 100 is not limited to sensing the thickness of the ribbon of glass-forming material 103 along a single axis, for example, a first axis 313. Rather, in some embodiments, the thickness sensor 301 and / or additional thickness sensors may sense the thickness of the ribbon of glass-forming material 103 along one or more axes that can be angled with respect to the first axis 313, for example, along a second axis 315 that may be substantially perpendicular to the first axis 313 and substantially parallel to the direction of travel 154. The second axis 315 may intersect with the second location 305. In some embodiments, the thickness sensor 301 and / or additional thickness sensors may sense the thickness of the ribbon of glass-forming material 103 along one or more axes that may be substantially parallel to the first axis 313 and / or the second axis 315.

[0087] In some embodiments, the thickness sensor 301 can generate a thickness profile 321 corresponding to the thickness sensed by the thickness sensor 301 at multiple locations, for example, a first location 303, a second location 305, a third location 307, and a fourth location 309. The thickness sensor 301 can sense the thickness of the ribbon of the glass-forming material 103 periodically and / or continuously. For example, in some embodiments, the thickness sensor 301 can sense the thickness continuously at multiple locations (e.g., without interruption or gaps) so that the thickness sensor 301 can generate an updated thickness profile 321 corresponding to the real-time thickness of the ribbon of the glass-forming material 103. The real-time thickness of the ribbon of the glass-forming material 103 can represent the thickness at the moment the ribbon of the glass-forming material 103 is measured, thereby allowing the thickness of the ribbon of the glass-forming material 103 to be immediately transmitted to a device (e.g., a control device 325) for processing. In some embodiments, the thickness sensor 301 can periodically sense the thickness at multiple locations, for example, by sensing the thickness of a ribbon of the glass forming material 103, then waiting for a predetermined period without sensing the thickness, and then sensing the thickness again. Thus, the thickness sensor 301 can generate an updated thickness profile 321 that cannot correspond to real-time thickness at multiple locations. In some embodiments, the thickness sensor 301 can sense the thickness at static locations relative to the molding vessel 140. For example, in some embodiments, the thickness sensor 301 can sense the thickness at multiple locations 303, 305, 307, or 309, and the multiple locations 303, 305, 307, or 309 may be located at a static and unchanging distance from the first axis 313 and therefore from the route 145.

[0088] In some embodiments, the glass manufacturing apparatus 100 may include a control device 325 that can be coupled to a thickness sensor 301. The control device 325 may include, for example, a computer, a computer-like device, a programmable logic controller, and the like. In some embodiments, the control device 325 may be configured to cause changes in the thickness of the ribbon of glass-forming material 103 based on the thickness sensed by the thickness sensor 301 (e.g., programmed, coded, designed, and / or created). For example, the thickness sensor 301 may communicate with the control device 325 via a communication line 327 (e.g., wired, wireless, etc.). A thickness profile 321 may be transmitted from the thickness sensor 301 to the control device 325 via the communication line 327. In some embodiments, a target thickness profile 331 may be transmitted to the control device 325. The target thickness profile 331 may include an operating range for the target thickness of the ribbon of glass-forming material 103. For example, the target thickness profile 331 may include a first target thickness at a first location 303, a second target thickness at a second location 305, a third target thickness at a third location 307, and a fourth target thickness at a fourth location 309.

[0089] In some embodiments, the glass manufacturing apparatus 100 may include a laser device 335 that emits a laser beam to increase the temperature and decrease the viscosity of a portion of the ribbon of glass-forming material 103 that is in a viscous state, thereby changing the thickness of the portion of the ribbon of glass-forming material 103 irradiated by the laser beam, as well as the heat-affected zone around the laser beam. In some embodiments, the laser device 335 may include a laser generator 337. The laser generator 337 can generate and emit a laser beam. In some embodiments, the laser generator 337 may include a high-intensity infrared laser generator, such as a carbon dioxide (CO2) laser generator. The laser generator 337 can generate a laser beam with a wavelength and power sufficient to increase the temperature and decrease the viscosity of the portion of the ribbon of glass-forming material 103 irradiated by the laser beam. In some embodiments, the laser apparatus 335 may include a beam directionor 339 to control the direction in which the laser beam from the laser generator 337 is oriented. The beam directionor 339 may include a reflective surface, such as a mirror. The beam direction device 339 can be coupled to a moving device that can move the beam direction device 339, for example, by rotating the beam direction device 339 and / or translating the beam direction device 339.

[0090] The beam direction device 339 can receive a laser beam from the laser generator 337 and direct the laser beam toward a ribbon of glass-forming material 103 (for example, by reflection when the beam direction device 339 is equipped with mirrors). In embodiments, the beam direction device can scan the laser beam in a continuous (e.g., linear) pattern across the ribbon of glass-forming material 103. For example, in some embodiments, the beam direction device 339 can direct the laser beam toward one or more of the first location 303, the second location 305, the third location 307, and / or the fourth location 309. In some embodiments, the beam direction device 339 can direct a first laser beam 351 toward the first location 303, and the first laser beam 351 can irradiate the ribbon of glass-forming material 103 at a location below the root 145 of the molding vessel 140. In some embodiments, the beam direction device 339 can direct a second laser beam 353 toward a second location 305, so that the second laser beam 353 can irradiate a ribbon of glass-forming material 103 at a location below the root 145 of the molding vessel 140. In some embodiments, the beam direction device 339 can direct a third laser beam 355 toward a third location 307, so that the third laser beam 355 can irradiate a ribbon of glass-forming material 103 at a location below the root 145 of the molding vessel 140. In some embodiments, the beam direction device 339 can direct a fourth laser beam 357 toward a fourth location 309, so that the fourth laser beam 357 can irradiate a ribbon of glass-forming material 103 at a location below the root 145 of the molding vessel 140. In this embodiment, the first laser beam 351, the second laser beam 353, the third laser beam 355, and the fourth laser beam 357 represent a single laser beam at different points in time as the laser beam is scanned across the ribbon via the beam directionation device 339.In some embodiments, the beam directing device 339 can be moved based on control commands that may be provided to the laser device 335 from a control device 325, which may instruct the beam directing device 339 to direct one or more of the laser beams 351, 353, 355, or 357 to a specific location.

[0091] In some embodiments, the control device 325 can compare the thickness profile 321 with a target thickness profile 331 to determine whether the corresponding thickness at one of locations 303, 305, 307, or 309 exceeds the target thickness of the target thickness profile 331. For example, the control device 325 can receive a thickness profile 321 that may include the thickness of the glass-forming material 103 ribbon at a first location 303, a second location 305, a third location 307, and a fourth location 309, as measured by a thickness sensor 301. For example, the control device 325 can compare the thicknesses at locations 303, 305, 307, and / or 309 with the target thicknesses of the target thickness profile 331, for example, at locations 303, 305, 307, and / or 309, respectively. In some embodiments, a method for manufacturing a glass ribbon may include identifying a location among several locations 303, 305, 307, and / or 309 where the corresponding thickness at that location exceeds a target thickness (e.g., a target thickness profile 331). The control device 325 can determine the thickness difference between the thickness measured at one of locations 303, 305, 307, or 309 and the target thickness at that location 303, 305, 307, or 309. In addition, as illustrated with reference to Figure 5, the control device 325 can determine the appropriate laser power of the laser beams 351, 353, 355, and 357 to cause a decrease in viscosity at that location and achieve the target thickness at that location.

[0092] The control device 325 can transmit commands to the laser device 335, including appropriate laser power and location. In some embodiments, the method for manufacturing a glass ribbon may include directing laser beams 351, 353, 355, and 357 toward a ribbon of glass-forming material 103 to reduce the viscosity at a location and achieve a target thickness at that location. For example, in some embodiments, the measured thickness of the ribbon of glass-forming material 103 at a first location 303 may exceed a target thickness at the first location 303. The control device 325 can determine the difference between the measured thickness at the first location 303 and the target thickness and correlate the rate of thickness change with the laser power. In some embodiments, the rate of thickness change and the laser power may be provided to the control device 325 and may be based on the actually observed effect of thickness change based on a specific laser power. In some embodiments, the rate of thickness change and the laser power provided to the control device 325 may be based on a mathematical model. In some embodiments, the model may be updated with the actually observed effect based on different laser powers. The control device 325 can cause the laser generator 337 to direct the first laser beam 351 toward the first location 303 at the laser output. In response, the viscosity at the first location 303 may decrease, which can reduce the thickness at the first location 303 until the target thickness at the first location 303 is achieved.

[0093] Following separation, the method for manufacturing the glass ribbon may include sensing the thickness at multiple locations on the first ribbon portion 401. For example, a thickness sensor 301 may sense the thickness of the first ribbon portion 401 at a first location 411, a second location 413, a third location 415, and a fourth location 417 of the first ribbon portion 401. In further embodiments, the thickness may be sensed at five or more locations, although in even further embodiments, the thickness may be sensed at fewer than four locations. In some embodiments, sensing the thickness of the ribbon of the glass-forming material 103 may occur on the first ribbon portion 401 of the ribbon of the glass-forming material 103 after separating the first ribbon portion 401 from the second ribbon portion 403 of the ribbon of the glass-forming material 103. In some embodiments, the thickness of the first ribbon portion 401 can be detected immediately after separation of the first ribbon portion 401 from the second ribbon portion 403, thus reducing the time delay between the separation of the first ribbon portion 401 and the detection of its thickness. In some embodiments, the time delay may be longer, for example, if the thickness of the first ribbon portion 401 is detected not immediately after separation, but rather after a certain period of time has elapsed following the separation. For example, the time delay may arise from transporting the first ribbon portion 401 from the location where it is separated to a remote location where it can be inspected and its thickness measured.

[0094] In some embodiments, the positions of the first location 411, second location 413, third location 415, and / or fourth location 417 relative to the first outer edge 153 and second outer edge 155 of the first ribbon portion 401 can correspond to the positions of the first location 303, second location 305, third location 307, and / or fourth location 309 relative to the first outer edge 153 and second outer edge 155 of the second ribbon portion 403, respectively. For example, the first location 411 can be located at a first distance from the first outer edge 153 of the first ribbon portion 401, and the first location 303 can be located at a first distance from the first outer edge 153 of the second ribbon portion 403. In some embodiments, the fourth location 417 can be separated by a second distance from the second outer edge 155 of the first ribbon portion 401, and the fourth location 309 can be separated by a second distance from the second outer edge 155 of the second ribbon portion 403. In some embodiments, the distances separating a plurality of locations 411, 413, 415, or 417 of the first ribbon portion 401 can coincide with the distances separating a plurality of locations 303, 305, 307, or 309 of the second ribbon portion 403. Therefore, the thickness of the first ribbon portion 401 at multiple locations 411, 413, 415, or 417 can be altered by irradiating the second ribbon portion 403 at multiple locations 303, 305, 307, or 309 with laser beams 351, 353, 355, or 357, and / or by irradiating the first flow 241 flowing over the first weir 203 and / or the second flow 243 flowing over the second weir 204 with laser beams 361, 363, 365, or 367.

[0095] In some embodiments, a method for manufacturing a glass ribbon may include identifying a first location among a plurality of locations 411, 413, 415, or 417 where the corresponding thickness at the first location 303 exceeds a target thickness. A thickness sensor 301 can sense the thickness of a plurality of locations 411, 413, 415, or 417 of the first ribbon portion 401 and generate a thickness profile 321. In some embodiments, a control device 325 can compare the measured thickness of the thickness profile 321 with a target thickness profile 331 to determine whether any of the measured thicknesses at locations 411, 413, 415, or 417 exceeds the target thickness. In addition, in some embodiments, the control device 325 can calculate a time delay between the separation of the first ribbon portion 401 (e.g., from a second ribbon portion 403) and the sensing of the thickness. For example, a period of time may elapse between separating the first ribbon portion 401 and sensing its thickness with the thickness sensor 301 at locations 411, 413, 415, or 417, and this period may, in part, include the time required to transport the first ribbon portion 401 to a remote location. While the above example illustrates controlling the laser output using a thickness profile measurement, it is also conceivable that optical distortion could be measured instead of, or in addition to, the thickness profile, and that the laser output could be controlled using such an optical distortion measurement.

[0096] Referring here to Figure 6A, a flowchart of Method 600 for producing a glass sheet having a desired thickness profile is shown according to an exemplary embodiment. Method 600 may be carried out via a glass manufacturing apparatus 100 described herein with respect to Figures 3 to 5 to form a glass sheet having desirable optical properties for various applications. The description of Method 600 will be aided by referring to the various components depicted in Figures 3 to 5. Method 600 may be formed after a batch material 107 has been melted and fed into a molding vessel 140 to form a ribbon of glass-forming material 103. In block 602, the thickness profile 321 of the ribbon of glass-forming material 103 is measured. For example, in an embodiment, a thickness sensor 301 may measure the thickness of the first ribbon portion 401 at a first location 411, a second location 413, a third location 415, and a fourth location 417 in order to generate the thickness profile 321. In the embodiment, the thickness profile 321 may typically include at least one measurement per 5 mm increment in the width W direction to ensure accuracy. Although only four locations detected by the thickness sensor 301 are depicted in Figure 5, it should be understood that typically at least 100 (e.g., at least 200, at least 300, at least 400, at least 500, at least 1000) thickness measurements may be obtained to generate the thickness profile 321.

[0097] In block 604, the thickness profile 321 is smoothed to remove high spatial frequency thickness variations within it. In the measurement state, the thickness profile 321 may contain measurement noise that is not physically present in the ribbon of the glass-forming material 103. Such a smoothing operation removes such noise to produce a smoothed thickness profile that actually represents the ribbon. In embodiments, such artifacts can be removed, for example, by calculating a moving window average over relatively small width intervals (e.g., 50 mm or less, 30 mm or less, 20 mm or less, or 10 mm or less). For example, a control device 325 can calculate such a moving average and generate a smoothed thickness profile (e.g., by executing instructions related to a suitable control algorithm stored in its internal memory). Such a smoothing operation can also be performed in the spatial frequency domain using a suitable Fourier filter (e.g., a low-pass filter).

[0098] In the embodiment, smoothing the thickness profile 321 is intended not to remove internal high-frequency thickness variations that are thought to actually exist in the ribbon of the glass-forming material 103 (not related to measurement signal noise) and are below the spatial resolution of the laser. Such high-frequency thickness variations (e.g., draw lines) are desired to be mitigated in order to improve the optical distortion performance of the glass article. Referring to Figure 7, plot 700 is shown, which includes an example of an exemplary smoothed thickness profile 702. The smoothed thickness profile 702 is an example of the thickness profile 321 described herein, smoothed with a 10 mm moving average. The smoothed thickness profile 702 includes localized thickness variations that generally form localized convexities 704 and localized concavenesses 706. The localized convexities 704 and localized concavenesses 706 generally result from deviations of the first principal surface 215 and the second principal surface 216 (see Figure 4) from a perfect planar shape. The localized protrusions 704 and localized recesses 706 are draw lines formed from the stretching of the ribbon of the glass-forming material 103. Such draw lines are considered to be the source of optical distortion.

[0099] When taking a smoothed thickness profile 702 and calculating its slope and curvature, the approximate radius of curvature of the ribbon can be calculated from the smoothed thickness profile 702 as follows:

number

[0100] Taking the above into consideration, a further smoothing operation is performed on the smoothed thickness profile 702 to generate a target thickness profile 331 that successfully reduces local convexity 704 and local concaveness 706 and effectively reduces observable optical distortion. Such a smoothing operation reduces localized areas where the curvature of the glass-forming material 103 ribbon exceeds a predetermined threshold. It has been found that utilizing a moving average over a relatively wide window (e.g., approximately 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 300 mm, 400 mm, or 500 mm) helps to illuminate such areas of localized curvature by smoothing the measured thickness profile 321. In embodiments, other smoothing functions can be used instead of a moving average (e.g., a Fourier filter, where the second derivative of the measured thickness profile 321 is averaged and then integrated to provide the target thickness profile). Such processing may be performed to generate a zero-phase-shifted target thickness profile (not depicted). Because the zero-phase-shifted target profile still contains variations in thickness over considerable distances or at small magnitudes, the radius of curvature is limited to avoid visible levels of optical distortion.

[0101] Referring again to Figure 6A, in block 606, the zero-phase-shifted profile is offset to generate the target thickness profile 331. Figure 7 depicts the target thickness profile 708, generated based on the aforementioned zero-phase-shifted target profile, obtained from the smoothed thickness profile 702. To generate the target thickness profile 708, the zero-phase-shifted target thickness profile can be offset by a fixed thickness amount. Such an offset is necessary so that the smoothed thickness profile 702 may include portions below (or less than) the zero-phase-shifted target profile. As described herein, the application of laser energy heats the glass and reduces its viscosity so as to locally reduce the thickness of the target region. Therefore, if a purely smoothed and thus zero-phase-shifted target thickness profile is used as the target, the laser energy will not be applied to a particular region (about half), and significant curvature will still be observed in the glass article (mainly as local depressions 706). Therefore, in the embodiment, the zero-phase-shifted target thickness profile is offset over the entire width W such that the target thickness profile 708 is less than or equal to the smoothed thickness profile 702 (for example, the zero-phase-shifted target thickness profile can be offset by at least the maximum amount by which the smoothed thickness profile 702 is less than the zero-phase-shifted target thickness profile). In this way, the laser energy can be applied (if necessary) over the entire width W to correct localized curvature regions over the entire width and reduce the maximum optical distortion exhibited by the glass article. The laser energy can be applied to any preferred portion of the ribbon of the glass-forming material 103 where improved optical distortion performance is desired.

[0102] In block 608, the laser power is applied to the ribbon of the glass-forming material 103 based on the difference between the thickness profile 321 and the target thickness profile 331. For example, at locations 303, 305, 307, and 309, the control device 325 may calculate the difference 710 between the smoothed thickness profile 702 (see Figure 7) and the target thickness profile 708, and determine the required laser power based on the magnitude of the difference. The required laser power may be determined based on a predictive model of the resulting thickness change, as described herein. In embodiments, the difference between the thickness profiles is multiplied by an output scaling factor, which can be between 1 W / μm and 10 W / μm, to determine the laser power applied to that particular location using a CO2 laser source. Such an output scaling factor depends on the type of laser used. In embodiments, the output scaling factor may be determined based on the composition of the ribbon of the glass-forming material 103 and other laser operating parameters (e.g., beam size, incident angle, cross-sectional beam profile, etc., when incident on the glass).

[0103] In block 610, the optical strain performance is measured and downstream processing is performed. For example, after the laser energy is applied to the ribbon of the glass-forming material 103 according to the output profile determined in block 608, another ribbon section may be cut, and the optical strain performance can be measured using a commercially available optical strain gauge. If the desired optical strain performance is met, downstream processing (e.g., one or more of cleaning, edge finishing, strengthening via ion exchange or heat treatment, application of coating, and / or surface treatment) is performed. If it is determined that the target thickness profile has not been achieved, method 600 can be reconfigured and used to generate a different target thickness profile for controlling the laser energy.

[0104] In the embodiment, the thickness profile 321 of the ribbon of glass-forming material 103 may have some time dependence inherent to the operation of the glass forming apparatus 100 (apart from the laser). Such fluctuations in the baseline thickness profile may change the laser power profile required to obtain a thickness profile with attributes associated with low optical distortion. Therefore, in the embodiment, in order to properly control the laser apparatus 335, method 600 takes such time fluctuations into account by continuously updating the target thickness profile of method 600 from iteration to iteration (or after a predetermined number of iterations or after a predetermined period) (regardless of any particular optical distortion performance achieved in preceding iterations). As shown in Figure 6A, for example, after the initial glass article is formed (during the initial iteration of method 600), method 600 may return to step 602. The thickness sensor 301 measures the thickness profile 321 periodically or irregularly without any laser energy being applied to the ribbon of glass-forming material 103 to obtain the nominal thickness profile y nom This can generate a thickness profile which can fluctuate unpredictably over time due to variations in the glass manufacturing apparatus 100. In addition, the thickness profile 321 can be measured by the laser energy applied to the ribbon of the glass forming material 103 (i.e., the laser profile determined in the previous control iteration) to generate a thickness profile for feedback control.

[0105] The target thickness profile can then be updated via the execution of blocks 604, 606, and 608 as described herein. The thickness profile y(k+1) measured at time k+1 (where k is an integer representing the time sampling increment) can be modeled as a linear matrix equation as follows: y(k+1)=G*U(k)+y nom (2) In the formula, G is a sensitivity matrix (G is a constant and can be updated from time to time by in-situ system identification) that correlates the change in laser power with the change in the thickness of the ribbon of the glass-forming material 103, and U(k) is a vector of the magnitude of the laser power applied to the ribbon in the preceding iteration. nom It has been observed that this exhibits substantial time drift, which necessitates persistent time-dependent laser-based feedback control.

[0106] In Equation 2, the value of vector U(k) is determined via blocks 604, 606, and 608 of Method 600, as follows: The measured thickness, or a low-pass filtered version of the measured thickness, or a high-pass filtered version of the measured thickness, or a band-pass filtered version of the measured thickness can provide a target thickness profile. The type of filtering depends on which thickness variation is sufficiently persistent so as to be compensated. The smoothing operation in block 604 is a low-pass filtering of the thickness profile 321 at time k, which, after offset, is used as the target thickness profile 331. Taking the difference between the target thickness profile 331 and the measured thickness profile 321 yields the high-frequency component of the measured thickness profile 321, which can significantly contribute to the optical distortion performance. While the low-frequency component of y(k) was highly variable in one type of application, the high-frequency component has been observed to be sufficiently persistent to facilitate effective control of the laser. Therefore, if the low-frequency filtering operation performed by smoothing is represented as filter F(), the control model is: y(k+1)-F(y(k+1))=G*U(k)+y nom -F(y nom )(3) It can be expressed as follows. In equation (3), the 1-F() operation performed is a high-pass filtering operation.

[0107] An important consideration is the type of filtering to be selected for operation F(). Under steady-state conditions, when applied repeatedly, the linear high-pass filter 1 - F() will eventually reduce the signal to zero. However, spline filtering has no such undesirable steady-state behavior and is thus a suitable filtering approach. In an embodiment, such a spline filter can be represented by a function g(x) that represents an approximation of the measured thickness profile y. Numerical techniques can be used to obtain a function g(x) that minimizes the following

Number

[0108] Considering the above, the final control model for the laser output vector U(k) is y f (k + 1)=G(k)*U(k)+β f , (5) where f represents the high-pass filtering operation of 1 - F(), and β f represents y after high-pass filtering nom . Equation 5 is in a form that can be used as a model within the standard model predictive control framework. This attempts to minimize the weighted difference between the predicted thickness profile and the thickness profile target, which is the subject of the constraints, at each time step.

[0109] With respect to Figure 6A, the preceding approach described herein relies on controlling the laser output as a function of time using thickness profile measurement. That is, the thickness profile is used as a proxy for the ultimate objective of fabricating glass articles with minimal levels of optical distortion. In embodiments, optical distortion can be measured directly on the ribbon of the glass-forming material 103, and these measurements can be used to control the operation of the laser apparatus 335. Such an alternative framework is represented by method 612, depicted in Figure 6B. When fabricating glass articles based on the objective defined by the optical distortion target (e.g., zero optical distortion), directly measuring the optical distortion of the ribbon is more beneficial than control methods based on thickness profiles for several reasons. Firstly, direct measurement of optical distortion is considered to enable more accurate and efficient control of the laser apparatus 335. Such efficient control of the laser apparatus 335 can improve the lifespan of the various optical components in the system and reduce the overall cost of operation. Also, compared to methods based on measured thickness profiles, directly measuring optical distortion is considered to result in faster adjustments with higher precision and higher yields.

[0110] In block 614, the optical strain of the ribbon of the glass-forming material 103 can be measured. For example, in addition to (or instead of) the thickness sensor 301, the glass manufacturing apparatus 100 may include an optical strain gauge, such as the SCREENSCAN-Faultfinder® supplied by ISRA VISION AG, configured to detect an optical strain map of the ribbon of the glass-forming material 103 either before or after separation. In embodiments, the first ribbon portion 401 can be measured for optical strain using a commercially available optical strain gauge. Optical strain can be measured in any orientation (defined by the rake and cross viewing angles described herein). In embodiments, for example, optical strain can be measured at tilt angles or pitches of 60°, 65°, 70°, or larger (see rake angle α depicted in Figure 2A), and yaw angles with respect to the horizontal of 20°, 25°, 30°, 35°, or larger (see cross viewing angle β depicted in Figure 2B). In embodiments, only the vertical optical strain map is used to control the laser apparatus 335. In one embodiment, only the horizontal optical distortion map is used to control the laser device 335. In another embodiment, the laser device 335 can be controlled using a combination of the vertical optical distortion map and the horizontal optical distortion map (for example, the vertical optical distortion map and the horizontal optical distortion map can be added to each other).

[0111] In block 616, the control device 325 controls the laser apparatus 335 based on the difference between the measured optical strain and the optical strain target to apply the laser output to the ribbon of the glass-forming material 314. In embodiments, the optical strain target is 0 millidiopters, but embodiments in which the optical strain target is non-constant and non-zero at at least one location are also contemplated and within the scope of the disclosure. In embodiments, the laser apparatus 335 is controlled based on the optical strain measurement using a model predictive control framework or other methods common in the field of automatic feedback control. As described herein, optical strain can be thought of as a localized lens effect caused by variations on the surface of the ribbon from a perfectly flat shape. The optical power of such a localized lens effect can be approximated using a thin lens model as follows:

number

number

[0112] G from G od Considering the formulation, the control model implemented by the control device 325 to control the operation of the laser beam 335 based on the optical distortion map can be similar to that described herein with respect to Figure 6A. In fact, a preferred control objective can be formulated in the standard model predictive control form, and the model is currently OD(k+1)=G od *Laser power (k) + OD 公称 (8) In the formula, the laser output (k) is the magnitude vector of the laser output applied to the ribbon in the preceding iteration, OD 公称 This is the vector of the nominal optical strain measurement of the ribbon without correction by laser power. The laser power (k) is G od *Laser power (k) + OD 公称 It is possible to determine that the value approximates a suitable target optical distortion level. When the target optical distortion level is zero, this approach aims to directly measure and minimize the optical distortion. In embodiments, the laser power (k) can be automatically determined by the control device 325 based on direct optical distortion measurement of the ribbon using a suitable model predictive control method. [Examples]

[0113] Embodiments of this disclosure may be further understood by considering the following embodiments.

[0114] Referring here to Figure 8A, plot 800 is shown, which includes a segment of the thickness profile measured in a first exemplary glass ribbon section. The glass ribbon was formed using method 600 as described herein. The molten glass was a fusion-moldable borosilicate glass composition having the composition shown in Table 1 below. The glass ribbon was formed using a nominal target thickness of 3.8 mm. Plot 800 includes the thickness profile segment 802 of the ribbon and the predicted optical distortion profile 804 of the thickness profile segment 802 (which is 600 mm long in the width direction perpendicular to the draw line) before the ribbon was separated. The thickness profile segment 802 was measured using a colorimetric interferometer. Thickness measurements were taken at 5 mm intervals (in the width direction) to produce the shown thickness profile segment 802. The measured thickness profile was smoothed using a 20 mm moving average to smooth out noise present in the data due to the movement of the ribbon during measurement. The thickness profile of the separated ribbon portion may not require such correction in other examples. The smoothed measurements are represented in the thickness profile segment 802 provided in Figure 8A. To generate the predicted optical distortion profile 804, the quadratic polynomial was fitted to the thickness profile segment 802 using a least-squares curve fitting algorithm. All data points within 10 mm of each data point were used in generating the quadratic polynomial (a total of 5 points were used when sampling the thickness profile 802 to generate the quadratic polynomial). The coefficients of the quadratic term were then used as an approximation of the second derivative of the thickness profile segment 802. This approximation of the second derivative was used to calculate P(x) according to Equation 7 herein, which represents the predicted optical distortion profile 804 depicted in Figure 8A. [Table 1]

[0115] As shown in Figure 8A, the thickness profile segment 802 is substantially flat over the represented 600 mm segment and exhibits a total thickness range of less than 12 μm over the 600 mm segment. The thickness range was approximately 0.316% of the nominal target over the entire 600 mm segment. Such thickness variation represents the transient target thickness profile used to achieve the preferred optical performance results described herein. As demonstrated by the predicted optical distortion profile 804, the predicted optical distortion (calculated using Equation 7 above, assuming n = 1.5) had a range of approximately 1.2 millidiopters (maximum-minimum over the entire segment). Therefore, as a percentage of the target thickness in mm units, the range of optical distortion in millidiopters was less than 33% (approximately 31.5%). The maximum magnitude of the predicted optical distortion was approximately 0.6 millidiopters (approximately 15.8% of the target thickness in mm units). A low maximum magnitude of 2% of the target minimum thickness is considered achievable via the methods described herein. In fact, the predicted optical distortion was only slightly above 0.4 millidiopters over approximately 60 mm (10%) of the 600 mm segment. For comparison, similar measurements were performed on a 600 mm segment of another ribbon that had not been modified with the laser beam described herein. This ribbon segment had a maximum predicted optical distortion amplitude of approximately 1.6 millidiopters, or approximately 42.1% of the target thickness in millidiopter units. The predicted optical distortion ranged from approximately 3.1 millidiopters across the 600 mm segment. Moreover, the majority (over 50%) of the 600 mm segment had predicted optical distortion values ​​exceeding 0.5 millidiopters. These results demonstrate the ability of the method described herein to reduce optical distortion by more than twofold. Due to the relatively small overall variation of 0.316% of the thickness across the expressed segments, the range of percentages of optical distortion considered in this paragraph relative to the target thickness is also generally applicable to the average thickness.

[0116] Referring here to Figure 8B, plot 806 is shown, which includes a segment of the thickness profile measured for a second exemplary glass ribbon section. The glass ribbon was formed using method 600 as described herein. The second embodiment was formed from the same composition as the first embodiment and using a nominal target thickness of 0.522 mm. Plot 806 includes the thickness profile segment 808 of the ribbon (which is 600 mm long in the width direction perpendicular to the draw line) and the predicted optical distortion profile 810 of the thickness profile segment 808 before the ribbon was separated. The thickness profile segment 808 and the predicted optical distortion profile 810 were produced using the same techniques as described herein with respect to the first exemplary glass ribbon section. As shown in Figure 8B, the thickness profile segment 808 is substantially flat over the represented 600 mm segment and exhibits a total thickness range of less than 2.7 μm over the 600 mm segment. The thickness range was approximately 4.95% of the nominal target over the entire 600 mm segment. Such variations in thickness represent the transient target thickness profile used to achieve the preferred optical performance results described herein. As demonstrated by the predicted optical distortion profile 810, the predicted optical distortion (calculated using Equation 7 above, assuming n = 1.5) had a range of approximately 0.65 millidiopters (maximum-minimum across the entire segment). Therefore, as a percentage of the target thickness in millimeters, the range of optical distortion in millidiopters was less than 150% (approximately 124%). The maximum magnitude of the predicted optical distortion was approximately 0.425 millidiopters (approximately 80% of the target thickness in millimeters). In fact, the predicted optical distortion was only slightly above 0.4 millidiopters over less than 10% of the total length of the segment. For comparison, similar measurements were performed on a 600 mm segment of another ribbon that was not modified with the laser beam described herein (having the same target thickness). This ribbon segment had a maximum predicted optical distortion amplitude of approximately 0.85 millidiopters, or approximately 162% of the target thickness in millidiopters. The predicted optical distortion ranged from approximately 1.3 millidiopters across the 600 mm segment.Furthermore, the much higher portion of the 600mm segment exhibited predicted optical distortion values ​​exceeding 0.4 millidiopters. The predicted optical distortion profiles depicted in Figures 8A and 8B demonstrate, as expected, that the entire range and maximum values ​​of predicted optical distortion generally decrease with decreasing thickness. Glass ribbons molded to a thickness of less than 3.8mm are expected to exhibit a range of predicted optical distortion values ​​of less than 1.2 millidiopters. The magnitude of the maximum predicted optical distortion value is expected to show a similar trend.

[0117] The fusion molding process is expected to exhibit better thickness uniformity along with a reduced target thickness for the glass ribbon. Therefore, the degree of optical distortion reduction provided by the methods described herein is expected to decrease with decreasing target thickness. However, the application of laser energy via the methods described herein generally reduces the maximum optical distortion exhibited by the glass article compared to an equivalent glass article not modified by laser energy by the methods described herein. In embodiments, the glass articles according to this disclosure may include a thickness of 0.05 mm or more and 6.0 mm or less (e.g., 0.05 mm or more and 4.0 mm or less). Furthermore, along a line extending between the edges of the glass article in a first direction (e.g., perpendicular to the draw line) and having a length of at least 50% of the length of the glass article in the first direction, the thickness may include a range of 0.05% or more and 5.0% or less of the average thickness along the line (e.g., 0.01% or more, 0.2% or more, and 0.1% or less of the average). In such embodiments, the 500 mm segment of the line is calculated as 0.5 times the second derivative of the thickness profile along the line and includes a range of predicted optical distortion values ​​of 2.0 millidiopters or less. In some embodiments, the maximum magnitude of the predicted optical distortion value (in millidiopters) can be less than 85% of the average value (in mm), and the maximum magnitude can be 20% or less of the average value (in mm). In some embodiments, the range of predicted optical distortion values ​​is less than 150% of the average value (in mm), or less than 100% of the average value, or even less than 50% of the average value, or even less than 33% of the average value (for example, in embodiments where the average is 3.8 mm or more). Along the line, the predicted optical distortion value can be less than 0.5 millidiopters over most of the 500 mm segment, even when the thickness is 2.0 mm or more, or even more, 3.0 mm or more and 4.0 mm or less. Such a range of thickness and distortion can be observed even when the line length is 1000 mm or more (when the article length is 2000 mm or more). The “predicted optical distortion” value used herein is not directly measured, but rather calculated from the measured thickness profile.

[0118] Vertical and horizontal optical distortion measurements were performed on glass articles formed from ribbons having a structure equivalent to that shown in Figure 8 above (e.g., target thickness of 3.8 mm). Vertical and horizontal optical distortion measurements were performed with the vertical direction being the direction in which the draw line of the glass article extends (parallel to the draw direction). Measurements were performed using glass articles with relatively large angles relative to the vertical (greater than 60°) (to simulate the rake angle α depicted in Figure 2A) and relatively large cross-view angles greater than 20° (to simulate the large field of view β depicted in Figure 2B). Without laser treatment, the maximum horizontal distortion (99.9%) was approximately 84.0 millidiopters, while the maximum vertical distortion (99.9%) was 25.3 millidiopters. With laser treatment, the maximum horizontal distortion (99.9%) was approximately 58.8 millidiopters, while the maximum vertical distortion (99.9%) was 15.3 millidiopters. Therefore, the performance of Method 600 was such that the maximum vertical optical distortion could be reduced by almost 50%, and the horizontal optical distortion could also be reduced. In fact, the sum of the maximum vertical and maximum horizontal optical distortion was less than 80 millidiopters for the example using laser processing. Considering that the measured distortion increases with increasing angle of incidence, the processed example is thought to exhibit a maximum vertical optical distortion of less than 15.3 millidiopters at an angle of 60° relative to the vertical, and less than 58.8 millidiopters when measured at a cross viewing angle of 20° relative to the horizontal.

[0119] Figures 9A and 9B are optical strain maps of a second exemplary glass article formed by the method described herein. The second example had the same composition and target thickness as the first exemplary glass ribbon described herein with respect to Figure 8A. The vertical and horizontal optical strain maps were measured using commercially available optical strain gauges. Measurements were made at a rake angle of 60° with respect to the vertical and a cross-view angle of 20° with respect to the horizontal. Figure 9A is the vertical optical strain map, and Figure 9B is the horizontal optical strain map. As shown in Figure 9A, the vertical optical strain value was less than 10 millidiopters over more than one-third of the surface area of ​​the glass article. As shown in Figure 9A, the horizontal optical strain value was less than 10 millidiopters over more than 50% of the surface area of ​​the glass article. The maximum measured optical strain values ​​are provided in Tables 1 and 2. [Table 2] [Table 3]

[0120] As shown, the maximum values ​​(both absolute and 99.9%) of both the horizontal and vertical optical distortion maps are less than 10 millidiopters. In fact, the sum of the 99.9% maximum horizontal optical distortion value and the 99.9% maximum vertical optical distortion value is less than 16.5 millidiopters. Such consistently low optical distortion values ​​across the article demonstrate that the method described herein is effective in providing an article with superior optical distortion performance, thereby facilitating the use of high-resolution sensing technology in relatively high fields of view. In aspects, the glass article described herein is considered to have a thickness of 0.05 mm or more and 4.0 mm or less, and can exhibit 99.9% maximum vertical and optical distortion values ​​of less than 10 millidiopters in the zone excluding the periphery of the article near the edge. Such low optical distortion values ​​at high thicknesses (e.g., 3.0 mm or more and 4.0 mm or less) can facilitate the placement of high-resolution sensors behind glass articles formed via the method described herein (e.g., as a component of a windshield, as a separate sensor window). Therefore, articles formed by the methods described herein can facilitate improved operation of ADAS systems and other sensors located within the vehicle cabin and provide design flexibility.

[0121] Referring here to Figure 10, details of various structures and compositions of the glass substrate 900 formed by the method described herein are provided. The glass substrate 900 may correspond to window 24 as described herein with respect to Figures 1A to 2B, or to one of the first glass substrate 52 and the second glass substrate 56. In embodiments, the glass substrate 900 has a thickness t that is substantially constant over the width and length of the glass substrate 900, but with some variation, as described herein. The thickness t is defined as the distance in the first direction (y-direction) between the first main surface 902 and the second main surface 904. In various embodiments, the thickness varies from the nominal target and includes draw lines that extend substantially parallel to each other in the draw direction (corresponding to the direction of travel 154 depicted in Figure 3). Such draw lines may include contours in which the thickness extends substantially constant in the draw direction (thus the thickness t varies significantly in the direction perpendicular to the draw direction). Such draw lines are observable to those skilled in the art using known techniques. The nominal target of the glass substrate 900 may be any of the values ​​described herein with respect to the first glass substrate 52 and the second glass substrate 56, or the ribbon of the glass forming material 103.

[0122] As shown in Figure 10, the glass substrate 900 includes a width W defined as a first maximum dimension of one of the first main surface 902 or the second main surface 904 perpendicular to the thickness t, and a length L defined as a second maximum dimension of one of the first main surface 902 or the second main surface 904 perpendicular to both the thickness and the width. The width W is measured in a second direction (x-direction) extending perpendicular to the first direction, and the length L is measured in a third direction (z-direction) extending perpendicular to the first and second directions. In embodiments, the glass substrate 900 can be cut (e.g., from a ribbon of glass-forming material 103) such that the draw line extends in one of the second and third directions. For example, in embodiments, the draw line may extend in the second direction (parallel to W), and therefore the thickness t varies along the third direction (parallel to length L) as a result of the draw line. Unless otherwise specified herein, perpendicular optical distortion (VOD) measurements are performed in a direction parallel to the direction in which the draw line extends.

[0123] In embodiments, both L and W can be 100 mm or more (e.g., 200 mm or more, 300 mm or more, 500 mm or more, 1000 mm or more) and 5000 mm or less. The substrate 900 can exhibit a thickness profile such as the thickness profile 802 described herein with respect to Figure 8, where the thickness profile is obtained perpendicular to the draw line, and the draw line extends in the width direction (therefore, the thickness profile is in the length direction perpendicular to the draw line). In embodiments, such a thickness profile may include segments with a length of at least 500 mm, where the thickness t has a range (maximum-minimum) of less than 1% of the average thickness t across the segment. In embodiments, the length L is 2000 mm or more, and such a thickness profile may include segments with a length of 1000 mm, where the thickness has a range of 0.05% or more and 0.8% or less of the average (e.g., 0.2% or more and 0.8% or less). Such uniformity of thickness may be present while the glass article exhibits the preferred optical distortion attributes described herein. Such properties enable desirable performance in a variety of applications, including protective sensor covers, automotive glazing, mobile consumer electronics, and display applications.

[0124] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.

Claims

1. Glass articles, The first main surface and A second main surface is disposed on the opposite side of the first main surface, Between the first main surface and the second main surface, the thickness measured in a direction perpendicular to the first main surface and the second main surface, It comprises a plurality of draw lines extending in a first direction, The aforementioned thickness is 0.05 mm or more and 6.0 mm or less. The glass article exhibits a maximum vertical optical distortion (VOD) of 16 millidiopters or less when its vertical direction is parallel to the first direction and it is oriented at an inclination angle of 60° with respect to the vertical direction. The glass article is a glass article whose horizontal direction is perpendicular to the vertical direction, and which exhibits a maximum horizontal optical distortion (HOD) of 60 millidiopters or less when the glass article is oriented at a cross viewing angle of 20° with respect to the horizontal direction.

2. The glass article according to claim 1, wherein the sum of the VOD and the HOD is 20 millidiopters or less.

3. The glass article according to claim 1 or 2, wherein 6 millidiopters ≤ VOD ≤ 10 millidiopters.

4. A glass article according to any one of claims 1 to 3, wherein 6 millidiopters ≤ HOD ≤ 10 millidiopters.

5. The glass article includes the length measured in the horizontal direction, The aforementioned length is 500 mm or more, A glass article according to any one of claims 1 to 4, wherein the thickness along the horizontal line having a profile length of at least 50% of the aforementioned length is in a range of 0.05% or more and 5.0% or less of the average value of the thickness along the line.

6. The glass article according to claim 5, wherein the aforementioned length is 2000 mm or more.

7. The glass article according to claim 5 or 6, wherein the 500 mm segment of the line includes a range of predicted optical distortion values ​​of 2.0 millidiopters or less, calculated as 0.5 times the second derivative of the thickness profile along the line.

8. The glass article according to claim 7, wherein the maximum magnitude of the predicted optical distortion value (in millidiopters) is less than 80% of the average thickness (in millimeters).

9. The glass article according to any one of claims 6 to 8, wherein the range of the predicted optical distortion value is less than 150% of the average thickness (in mm).

10. The glass article according to any one of claims 6 to 9, wherein the predicted optical distortion value is less than 0.5 millidiopters over most of the 500 mm segment.

11. The glass article according to any one of claims 1 to 10, wherein the average value of the aforementioned thickness is 2.0 mm or more.

12. The glass article according to claim 11, wherein the average value of the thickness is 3.0 mm or more and 4.0 mm or less.

13. The glass article according to any one of claims 1 to 12, wherein the glass article comprises a borosilicate glass composition.

14. Glass articles, The first main surface and A second main surface is disposed on the opposite side of the first main surface, The first main surface and the second main surface are provided with a thickness measured in a direction perpendicular to the first main surface and the second main surface, The aforementioned thickness includes an average value of 0.05 mm or more and 4.0 mm or less, Along a line extending in a first direction between the edges of the glass article, the thickness includes a range where the average thickness along the line is 0.05% or more and 5.0% or less of the average thickness, A glass article wherein the 500 mm segment of the line includes a range of predicted optical distortion values ​​of 2.0 millidiopters or less, calculated as 0.5 times the second derivative of the thickness profile along the line.

15. The glass article according to claim 14, wherein the average value is 2.0 mm or more.

16. The glass article according to claim 15, wherein the average value of the thickness is 3.0 mm or more and 4.0 mm or less.

17. The glass article according to claim 15 or 16, wherein the maximum magnitude of the predicted optical distortion value (in millidiopters) is less than 80% of the average value (in millimeters).

18. The glass article according to any one of claims 15 to 17, wherein the range of the predicted optical distortion value is less than 150% of the average value (in mm).

19. The glass article according to any one of claims 15 to 18, wherein the predicted optical distortion value is less than 0.5 millidiopters over most of the 500 mm segment.

20. The glass article according to any one of claims 15 to 19, wherein the glass article includes a length measured in the first direction, and the length is 1,000 mm or more.

21. The glass article exhibits a maximum vertical optical distortion (VOD) of 16 millidiopters or less when its vertical direction is perpendicular to the first direction and it is oriented at an inclination angle of 60° with respect to the vertical direction. The glass article according to claim 20, wherein the horizontal direction is perpendicular to the vertical direction, and when the glass article is oriented at a cross viewing angle of 20° with respect to the horizontal direction, it exhibits a maximum horizontal optical distortion (HOD) of 25 millidiopters or less.

22. The glass article according to claim 21, wherein the sum of the VOD and the HOD is 20 millidiopters or less.

23. The glass article according to claim 21 or 22, wherein 6 millidiopters ≤ VOD ≤ 10 millidiopters.

24. A glass article according to any one of claims 21 to 23, wherein 6 millidiopters ≤ HOD ≤ 10 millidiopters.

25. The glass article according to any one of claims 14 to 24, wherein the glass article comprises a borosilicate glass composition.

26. A method for manufacturing glass articles, Measuring the thickness profile along the width of the initial ribbon of the glass-forming material, A target thickness profile is generated by generating a smoothed thickness profile and removing high-spatial-frequency thickness variations from the thickness profile in order to offset the smoothed thickness profile, wherein the generated target thickness profile includes a non-constant thickness. A method comprising applying a laser output to the glass-forming material, based on the difference between the measured thickness profile and the target thickness profile, when the glass-forming material is in a viscous state, wherein the laser output varies along the width as the glass-forming material advances in a direction perpendicular to the direction in which the width is measured.

27. The method according to claim 26, wherein the target thickness profile includes a range exceeding 20 μm across a 500 mm segment.

28. Applying the aforementioned laser output is proportional to the magnitude of the difference between the measured profile and the target thickness profile, CO 2 The method according to claim 26 or 27, comprising changing the output supplied to the laser.

29. The method according to any one of claims 26 to 28, wherein the smoothed thickness profile is shifted downward by at least the maximum difference between the smoothed thickness profile and the measured thickness profile.

30. The method according to claim 29, wherein the laser output is applied to at least 80% of the width of the ribbon after the glass-forming material.

31. The method according to claim 29, wherein the target thickness profile deviates by more than 10 μm from the nominal target value of the ribbon thickness.

32. The method according to claim 30 or 31, wherein the nominal target value is 3.0 mm or more.

33. The method according to any one of claims 26 to 30, further comprising periodically measuring the nominal thickness profile of the ribbon, wherein the nominal thickness profile represents the thickness profile produced by the glass forming apparatus without the ribbon being modified by laser energy, and the amount of laser power applied to the ribbon varies based on the nominal thickness profile.

34. The method according to claim 30, wherein applying the laser output includes automatically calculating a vector of laser output values ​​using a model predictive control framework based on the nominal thickness profile.

35. A method for manufacturing glass articles, Using an optical strain gauge, measure the optical strain map along the width of the initial ribbon of the glass-forming material, A method comprising applying a laser output to the glass-forming material based on the difference between the optical distortion value of the optical distortion map and a target optical distortion value, wherein the laser output varies along the width as the glass-forming material advances in a direction perpendicular to the direction in which the width is measured.

36. The method according to claim 35, wherein the target optical distortion value is 0 millidiopters.

37. The method according to claim 35 or 36, wherein the optical distortion map includes at least one of a vertical optical distortion map and a horizontal optical distortion map.

38. The method according to claim 37, wherein the optical distortion map includes a combination of the vertical optical distortion map and the horizontal optical distortion map.

39. The method according to claim 35 or 36, further comprising periodically measuring a nominal optical distortion map of the ribbon, wherein the nominal optical distortion map represents an optical distortion map generated by a glass forming apparatus without the ribbon being corrected by laser energy, and the amount of laser power applied to the ribbon varies based on the nominal optical distortion map.

40. The method according to claim 39, wherein applying the laser output includes automatically calculating a vector of laser output values ​​using a model predictive control framework based on the nominal optical distortion map.

41. The method according to any one of claims 35 to 40, wherein the application of the laser output includes periodically calculating a vector of laser output values, so that the laser output mitigates localized peaks in the optical distortion map.

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