Glass articles having reduced thickness variation, methods of making the same, and apparatuses for making the same

Abstract

A glass article having a length equal to or greater than about 880 mm, a width orthogonal to the length and equal to or greater than about 680 mm, and a thickness T defined between a first major surface and a second major surface is described. The total thickness variation, TTV, across the width of the glass article is equal to or less than about 4 m. The maximum sliding interval range, MSIR, obtained by moving a predetermined interval in 5 mm increments across the width of the glass article is equal to or less than about 4 m. A method of making the glass article and apparatus therefor are also disclosed.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Serial No. 62 / 464,722, filed February 28, 2017. BACKGROUND TECHNICAL FIELD

[0004] The present disclosure relates generally to apparatuses for forming glass articles, such as glass sheets, and more particularly to apparatuses for forming glass articles that minimize thickness variation across the width of the glass article. BACKGROUND

[0006] Optical quality glass articles, such as glass sheets for use in various applications including light emitting panels or liquid crystal or other types of visual displays, are typically manufactured by drawing molten glass in the form of a ribbon. The ribbon can be separated into individual glass sheets or, in some cases, wound in longer lengths on suitable spools. Advances in display technology continue to increase the pixel density of display panels, thereby increasing the resolution of the display panels. As a result, the requirements for glass sheets incorporated into such panels are expected to increase. For example, it is desirable to further reduce the thickness variation limits that facilitate TFT deposition processes. To meet this challenge, it is necessary to maintain a precise temperature field across the ribbon as it is drawn from a forming body. SUMMARY

[0007] According to the present disclosure, a glass article is described comprising a length equal to or greater than about 880 millimeters, a width orthogonal to the length and equal to or greater than about 680 millimeters, a first major surface, a second major surface opposite the first major surface, a thickness T defined between the first major surface and the second major surface, wherein a total thickness variation across the width of the glass article TTV is equal to or less than about 4 μιη.

[0008] In some embodiments, the TTV is equal to or less than about 2 μιη. In further embodiments, the TTV is equal to or less than about 1 μιη. Still in further embodiments, the TTV is equal to or less than about 0.25 μιη. In various embodiments, the first major surface and the second major surface are unpolished.

[0009] In some embodiments, the average surface roughness Ra of the first major surface and the second major surface is equal to or less than about 0.25 nm.

[0010] In some embodiments, a maximum sliding interval range MSIR obtained by moving a predetermined interval in 5 millimeter increments across the width of the glass article is equal to or less than about 4 μιη.

[0011] In some embodiments, the predetermined interval is in a range from about 25 mm to about 750 mm, for example in a range from about 25 mm to about 100 mm, for example in a range from about 25 mm to about 75 mm.

[0012] In some embodiments, the width is equal to or greater than about 3100 mm. The length can be equal to or greater than about 3600 mm.

[0013] In some embodiments, the glass is a substantially alkali-free glass comprising, in mole percent:

[0014]

[0015] In some embodiments, the glass is a substantially alkali-free glass comprising, in mole percent:

[0016]

[0017] where 1.00 <∑[RO] / [Al203] < 1.25, [Al203] is the mole percent of Al203, and ∑[RO] is equal to the sum of the mole percent of MgO, CaO, SrO, and BaO.

[0018] In another embodiment, a glass article is described comprising: a length equal to or greater than about 880 millimeters, a width orthogonal to the length and equal to or greater than about 680 millimeters, a first major surface, a second major surface opposite the first major surface, a thickness T defined between the first major surface and the second major surface, wherein a maximum sliding interval range MSIR obtained by moving a sliding interval equal to or less than about 750 mm in 5 millimeter increments across the width of the glass article is equal to or less than about 8 μιη.

[0019] In some embodiments, the MSIR is equal to or less than about 6.5 μιη for a sliding interval equal to or less than about 400 mm.

[0020] In some embodiments, the MSIR is equal to or less than about 6 μιη for a sliding interval equal to or less than about 330 mm.

[0021] In other embodiments, the MSIR is equal to or less than about 4.5 μιη for a sliding interval equal to or less than about 150 mm.

[0022] In other embodiments, the MSIR is equal to or less than about 4 μιη for a sliding interval equal to or less than about 100 mm.

[0023] In various embodiments, the MSIR is equal to or less than about 2 μιη for a sliding interval equal to or less than about 25 mm.

[0024] In some embodiments, the first major surface and the second major surface are unpolished.

[0025] In various embodiments, the first major surface and the second major surface have an average surface roughness Ra equal to or less than about 0.25 nm.

[0026] In various embodiments, the width is equal to or greater than about 3100 mm. In some embodiments, the length is equal to or greater than about 3600 mm.

[0027] In another embodiment, a glass article is described comprising: a length equal to or greater than about 880 millimeters, a width orthogonal to the length and equal to or greater than about 680 millimeters, a first major surface, a second major surface opposite the first major surface, a thickness T defined between the first major surface and the second major surface, and a total thickness variation TTV across the width of the glass article equal to or less than about 4 μιη, a maximum sliding interval range MSIR obtained from moving a predetermined interval of 5 millimeter increments across the width of the glass article equal to or less than about 4 μιη.

[0028] In some embodiments, the TTV is equal to or less than about 2 μιη, for example equal to or less than about 1 μιη, for example equal to or less than about 0.25 μιη.

[0029] In some embodiments, the first major surface and the second major surface are unpolished. In some embodiments, the unpolished first major surface and the second major surface have an average surface roughness Ra equal to or less than about 0.25 nm.

[0030] In some embodiments, the predetermined interval is in the range of about 25 mm to about 750 mm.

[0031] In some embodiments, the predetermined interval is in the range of about 25 mm to about 100 mm, for example in the range of about 25 mm to about 75 mm.

[0032] In another embodiment, a glass disc blank is described comprising: a first major surface, a second major surface opposite the first major surface, a thickness T defined between the first major surface and the second major surface, and a total thickness variation TTV across the diameter of the glass disc blank equal to or less than about 2 μιη, for example equal to or less than about 1 μιη.

[0033] In some embodiments, a maximum sliding interval range MSIR obtained from moving a 25 mm interval of 5 millimeter increments across the diameter of the glass disc blank is equal to or less than about 2 μιη.

[0034] The average surface roughness Ra of one or both of the first and second major surfaces of the glass disc blank is equal to or less than about 0.50 nm, for example, equal to or less than about 0.25 nm.

[0035] In another embodiment, a method of making a glass article is described, the method comprising: drawing a glass ribbon from a forming body in a draw direction, the glass ribbon comprising opposing edge portions and a central portion located between each of the opposing edge portions, the glass ribbon comprising a viscous zone and an elastic zone; in a width direction of the glass ribbon orthogonal to the draw direction, forming a thickness perturbation in the viscous zone of the glass ribbon in the central portion, the thickness perturbation comprising a feature width equal to or less than about 225 mm, and a maximum slip interval range equal to or less than about 0.0025 mm according to a 100 mm slip interval moving in 5 mm increments across a width of the central portion in the elastic zone.

[0036] In some embodiments, the feature width is equal to or less than about 175 mm, and the maximum slip interval range is equal to or less than about 0.0020 mm.

[0037] In some embodiments, the feature width is equal to or less than about 125 mm, and the maximum slip interval range is equal to or less than about 0.0015 mm.

[0038] In some embodiments, the feature width is equal to or less than about 75 mm, and the maximum slip interval range is equal to or less than about 0.0006 mm.

[0039] In other embodiments, the feature width is equal to or less than about 65 mm, and the maximum slip interval range is equal to or less than about 0.0003 mm.

[0040] In various embodiments, the perturbation can be formed by cooling the glass ribbon, but in further embodiments, the perturbation can be formed by heating the glass ribbon, for example, with one or more laser beams impinging on the glass ribbon.

[0041] In some embodiments, the distance between the bottom edge of the forming body and the thickness maximum of the thickness perturbation is equal to or less than about 8.5 cm, while in other embodiments, the distance between the bottom edge of the forming body and the thickness maximum of the thickness perturbation can be equal to or less than about 3.6 cm.

[0042] In various embodiments, the total thickness variation of the central portion in the elastic zone in the width direction orthogonal to the draw direction is equal to or less than about 4 pm, for example, equal to or less than about 2 pm, for example equal to or less than about 1 pm.

[0043] In another embodiment, a method of making a glass article is disclosed, the method comprising: flowing molten glass into a trough of a forming body, the molten glass overflowing the trough and descending along opposing forming surfaces of the forming body as separate streams of molten glass that join below a bottom edge of the forming body, drawing a ribbon of the molten glass from the bottom edge in a draw direction, and cooling the ribbon with a cooling apparatus comprising a hot plate extending in a width direction of the glass ribbon that is orthogonal to the draw direction, the cooling apparatus further comprising a plurality of cooling tubes in the cooling apparatus, each cooling tube of the plurality of cooling tubes comprising a first tube having a closed end adjacent to the hot plate and a second tube extending into the first tube and having an open end spaced apart from the closed end of the first tube, the cooling comprising flowing a cooling fluid into the second tube of the plurality of cooling tubes, the cooling further comprising forming a plurality of thickness perturbations on the ribbon corresponding to a location of each cooling tube, each thickness perturbation comprising a feature width equal to or less than about 225 mm.

[0044] In some embodiments, the feature width is equal to or less than about 175 mm, for example equal to or less than about 125 mm, equal to or less than about 75 mm, or equal to or less than about 65 mm.

[0045] Each cooling tube of the plurality of cooling tubes can be in contact with the hot plate.

[0046] In another embodiment, an apparatus for making a glass ribbon is disclosed, the apparatus comprising a forming body comprising a trough configured to receive a stream of molten glass and converging forming surfaces that join along a bottom edge of the forming body from which a glass ribbon is drawn in a draw direction along a vertical draw plane; a cooling apparatus comprising a hot plate extending in a width direction of the stream of molten glass and a plurality of cooling tubes in the cooling apparatus, each cooling tube of the plurality of cooling tubes comprising a first tube having a closed end adjacent to the hot plate and a second tube extending into the first tube and having an open end adjacent to the closed end of the first tube.

[0047] In some embodiments, each first tube of the plurality of cooling tubes is in contact with the hot plate.

[0048] In some embodiments, a longitudinal axis of each first tube intersects the draw plane at a distance equal to or less than about 8.5 cm, for example equal to or less than about 3.6 cm, from the bottom edge.

[0049] In some embodiments, a distance between the draw plane and the hot plate is equal to or less than about 9 cm, for example equal to or less than about 1.5 cm.

[0050] In another embodiment, an apparatus for making a glass ribbon is described, the apparatus comprising a forming body comprising a trough configured to receive a flow of molten glass and converging forming surfaces joined along a bottom edge of the forming body from which the glass ribbon is drawn in a draw direction along a vertical draw plane; a cooling apparatus positioned below the bottom edge, the cooling apparatus comprising a metal plate extending in a widthwise direction of the flow of molten glass, the metal plate comprising a cooling tube and a plurality of channels formed in the metal plate, each channel of the plurality of channels comprising a closed distal end and an open proximal end, the cooling tube extending through the open proximal end such that an open distal end of the cooling tube is adjacent to but spaced apart from the distal end of the channel.

[0051] In some embodiments, the distance between the draw plane and the hot plate is equal to or less than about 10 cm, for example equal to or less than about 5 cm, for example equal to or less than about 3 cm. In some embodiments, the distance between the draw plane and the hot plate is equal to or less than about 1.5 cm based on the position of the cooling apparatus below the bottom edge of the forming body, although other distances are also contemplated.

[0052] Additional features and advantages of the disclosure are set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art who practice the disclosure, and which is further pointed out by the claims, or learned by practice of the methods described below, including the experiments described in the following detailed description.

[0053] It is to be understood that both the foregoing general description and the following detailed description present embodiments of the disclosure, and are intended to provide an overview or framework for understanding the nature and character of the disclosure as it is claimed. The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure and together with the description serve to explain the principles and operations of the disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is a perspective view of a glass article in the form of a glass sheet according to embodiments of the disclosure;

[0055] Figure 2 is an edge view of an exemplary glass sheet exhibiting thickness deviations and illustrating a measurement of total thickness variation (TTV);

[0056] Figure 3 is an edge view of an exemplary glass sheet exhibiting thickness deviations and illustrating a measurement of maximum sliding interval range (MSIR);

[0057] Figure 4is a perspective view of an HDD disk substrate according to embodiments of the disclosure;

[0058] Figure 5 is a schematic view of an exemplary glass manufacturing apparatus;

[0059] Figure 6 is Figure 5 is a schematic view of a portion of a glass manufacturing apparatus;

[0060] Figure 7 is Figure 6 is a close-up view of a portion of the apparatus of

[0061] Figure 8 is Figure 6 is a close-up view of a portion of the apparatus of

[0062] Figure 9A is a cross-sectional view of one embodiment of the slide gate shown in Figure 6

[0063] Figure 9B is a cross-sectional view of the slide gate embodiment shown in Figure 9 from an end view;

[0064] Figure 10 is a cross-sectional view of another embodiment of the slide gate from a top view;

[0065] Figure 11 is a partial cross-sectional view of another embodiment of the slide gate from a top view;

[0066] Figure 12 is a partial cross-sectional view of another embodiment of the slide gate from a top view;

[0067] Figure 13 is a partial cross-sectional view of another embodiment of the slide gate from a top view;

[0068] Figure 14 is a plot of the actual thickness of a ribbon drawn using the glass manufacturing apparatus of Figure 5 varies as a function of position across its width, as compared to the modeled thickness of a slide gate with active cooling, in the absence of active cooling of the slide gate;

[0069] Figure 15 is Figure 14 is a plot of the difference between the actual thickness difference and the modeled thickness difference of

[0070] Figure 16 is a plot of the actual thickness of a ribbon drawn using the glass manufacturing apparatus of Figure 5 ​A graph showing how the thickness of a strip drawn by glass manufacturing equipment varies with its position across its width, and... Figure 16 It also includes ΔT from both measured data and modeled data for a 25mm sliding interval. 最大 ;

[0071] Figure 17 yes Figure 16 The measured data and modeled data each pertain to ΔT for a 100mm sliding interval. 最大 The image;

[0072] Figure 18 This is a graph showing how the modeled thickness perturbation amplitude varies from the distance below the bottom edge (root) of the strip drawn from the exemplary forming body for three different sliding gate positions (distances from the strip).

[0073] Figure 19 It is aimed at Figure 18 The modeled thickness variation at the four sliding gate positions is shown in the figure, which illustrates how the width of the strip drawn from the exemplary forming body varies relative to the centerline of the strip.

[0074] Figure 20 It is aimed at Figure 18 A graph showing the modeled thickness variation at one of the four sliding gate positions, based on the distance in width of the strip drawn from the exemplary forming body relative to the centerline of the strip. Figure 20 A graph showing the temperature variation in relation to the thickness variation is also shown;

[0075] Figure 21 It is aimed at Figure 18 The diagram shows the thickness variation of another of the four sliding gate positions, modeled according to the distance in width of the strip drawn from the exemplary forming body relative to the centerline of the strip. Figure 21 A graph showing the temperature variation in relation to the thickness variation is also shown;

[0076] Figure 22 This is a graph showing how the modeled 100mm MSIR varies with the FWHM (feature width) based on the thickness perturbation of the strip drawn from the exemplary forming body. Detailed Implementation

[0077] Embodiments of this disclosure will now be described in detail, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used in the drawings to denote the same or similar parts. However, this disclosure may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein.

[0078] Herein, a range can be expressed as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that each endpoint is important and that the use of "about" with respect to any particular value should not be construed to eliminate any other particular value.

[0079] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and not intended to imply absolute orientation.

[0080] Unless specifically stated otherwise, any methods described herein are not to be construed as requiring their steps be performed in a specific order, or that they be performed in any order, or that they be performed at all. Accordingly, if a method claim does not actually recite a step to be performed in a specific order or that any order is required, or that any order is required, no order should be inferred from the mere fact that an order is presented in the claim. Similarly, unless specifically stated otherwise, or otherwise apparent from context, the order or orientation of steps and / or components within a claimed apparatus does not in itself amount to description of necessary sequence or order, nor do mere disclaimers of sequence or order amount to enabling disclosure as required above.

[0081] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects with two or more such components unless the context clearly indicates otherwise.

[0082] As described herein, total thickness variation (TTV) refers to the difference between the maximum thickness and the minimum thickness of a glass sheet over a defined interval, typically the entire width of the glass sheet.

[0083] As used herein, maximum sliding interval range (MSIR) refers to the difference between the maximum thickness and the minimum thickness of a glass substrate over a plurality of defined intervals. MSIR is obtained as the largest thickness difference in a plurality of maximum thickness differences obtained from a predetermined dimension of a glass sheet, moving a target interval by a predetermined length increment δ and n times over the predetermined dimension, each iteration of the target interval resulting in a maximum thickness difference ΔΤ 最大 Each target interval κ n includes a maximum thickness T 最大n and a minimum thickness T 最小n and the maximum thickness difference is defined as ΔΤ最大n = T 最大n -T 最小n The foregoing process results in n ΔT 最大n The largest thickness difference among the n ΔT 最大n is the maximum slide interval range MSIR. It should be noted that when interval κ becomes equal to interval υ, MSIR is equal to TTV.

[0084] As used herein, the full width at half maximum (FWHM) of a portion of a curve is the width of the portion measured between those points on the y-axis that are at half the maximum amplitude, which has the same meaning as characteristic width of the curve. FWHM can be used, for example, to describe the width of a bump on a curve or function.

[0085] As display resolution increases, the requirements for thickness uniformity of the glass substrates that make up the display panel also increase. A typical LCD display panel includes a backplane glass substrate on which a pattern of thin film transistors (TFTs) is deposited, for example by photolithography, that controls the polarization state of a liquid crystal material contained in the volume between the backplane substrate and a cover plate or sealing substrate sealed thereto, and which TFTs contribute to defining individual pixels of the display. Such thin film deposition processes rely on a flat substrate to accommodate the limited depth of focus of the photolithography process.

[0086] In other cases, annular glass disks can be used as platters for hard disk drives (HDDs). Because the read and / or write heads on the pickup arm travel only a few nanometers above the surface of the platter, the platter needs to be extremely flat. Multiple of these annular glass disks can be cut from a large glass sheet, and significant manufacturing cost savings can be realized if the major surfaces of the large glass sheet (or each annular disk cut from it) can be polished without requiring grinding and / or polishing of the major surfaces. Thus, a glass sheet that exhibits reduced thickness variation, and a method of manufacturing such a large glass sheet that is capable of producing extremely flat surfaces without post-shaping surface grinding and / or polishing would be beneficial.

[0087] Figure 1is a schematic illustration of a glass article, such as a glass sheet 10, which includes a first major surface 12, an opposing second major surface 14, and a thickness T defined between and normal to the first and second major surfaces 12 and 14. While the glass sheet 10 can be of any shape suitable for a particular application, for ease of description, hereinafter it will be assumed to comprise a rectangular shape bounded by a first pair of opposing edges 16a and 16b and a second pair of opposing edges 16c and 16d, with edges 16a, 16b being orthogonal to edges 16c and 16d, unless otherwise noted. Thus, the glass sheets described herein can comprise a width W and a length L orthogonal to the width W, with each of the width and length being parallel to a respective pair of opposing edges. While the orientation of the width and length can be chosen arbitrarily, for convenience, herein the width W will be denoted as the shorter of the two dimensions, and conversely, the length L will be denoted as the longer of the two dimensions. Thus, the width of the glass sheets described herein can be equal to or greater than about 680 mm, such as equal to or greater than about 1000 mm, equal to or greater than about 1300 mm, equal to or greater than about 1500 mm, equal to or greater than about 1870 mm, equal to or greater than about 2120 mm, equal to or greater than about 2300 mm, equal to or greater than about 2600 mm, or equal to or greater than about 3100 mm. The corresponding length can be equal to or greater than about 880 mm, equal to or greater than about 1200 mm, equal to or greater than about 1500 mm, equal to or greater than about 1800 mm, equal to or greater than about 2200 mm, equal to or greater than about 2320 mm, equal to or greater than about 2600 mm, or equal to or greater than about 3600 mm. For example, the dimensions of the glass sheets described herein can be denoted as W x L, which are equal to or greater than about 680 mm x 880 mm, equal to or greater than about 1000 mm x 1200 mm, equal to or greater than about 1300 mm x 1500 mm, equal to or greater than about 1500 mm x 1800 mm, equal to or greater than about 1870 x 2200 mm, equal to or greater than about 2120 mm x 2320 mm, equal to or greater than about 2300 mm x 2600 mm, equal to or greater than about 2600 mm x 3000 mm, or equal to or greater than about 3100 mm x 3600 mm.

[0088] The average roughness Ra of the first and / or second major surfaces can be equal to or less than about 0.5 nm, equal to or less than about 0.4 nm, equal to or less than about 0.3 nm, equal to or less than about 0.2 nm, equal to or less than about 0.1 nm, or in a range from about 0.1 nm to about 0.6 nm. In some embodiments, the surface roughness of the first major surface 12 and the second major surface 14 as just drawn can be equal to or less than about 0.25 nm. Surface roughness for as drawn means the surface roughness of the glass article as it is formed without surface treatment (e.g., surface grinding or polishing). Surface roughness is measured by coherent scanning interferometry, confocal microscopy, or other suitable method.

[0089] The thickness T can be equal to or less than 4 mm, equal to or less than about 3 mm, equal to or less than about 2 mm, equal to or less than about 1.5 mm, equal to or less than about 1 mm, equal to or less than about 0.7 mm, equal to or less than about 0.5 mm, or equal to or less than about 0.3 mm. For example, in some embodiments, the thickness T can be equal to or less than about 0.1 mm, such as in a range from about 0.05 mm to about 0.1 mm.

[0090] The glass articles described herein can exhibit a total thickness variation TTV equal to or less than about 4 μιη, for example, a TTV equal to or less than about 3 μιη, equal to or less than about 2 μιη, equal to or less than about 1 μιη, equal to or less than about 0.5 μιη, or equal to or less than about 0.25 μιη.

[0091] The glass articles described herein can exhibit a maximum slide interval range MSIR equal to or less than about 2 μιη for a slide interval κ equal to or less than about 25 mm and an increment δ of 5 mm, equal to or less than about 4 μιη for a slide interval κ equal to or less than about 100 mm and an increment δ of 5 mm, equal to or less than about 4.5 μιη for a slide interval κ equal to or less than about 150 mm and an increment δ of 5 mm, equal to or less than about 6 μιη for a slide interval κ equal to or less than about 330 mm and an increment δ of 5 mm, equal to or less than about 6.5 μιη for a slide interval κ equal to or less than about 400 mm and an increment δ of 5 mm, or equal to or less than about 8.5 μιη for a slide interval κ equal to or less than about 750 mm and an increment δ of 5 mm.

[0092] In some embodiments, the glass articles described herein can include two or more glass layers. For example, the individual glass sheets can be formed by a fusion process, and thus a fusion line 18 (see FIG. 1) can be visible from the edge of the glass article. Figure 2 、 3A fusion line represents the interface between glass layers that are fused together during the manufacturing process. In some embodiments, the at least two glass layers have the same chemical composition. However, in other embodiments, the layers may have different chemical compositions.

[0093] Now for reference Figure 4 In some embodiments, the glass article may be a glass disk, for example, a preform (“blank”) used as an HDD disk. As used herein, “disk blank” should be understood as a glass disk prior to the deposition of magnetic media onto its surface and the newly formed main surface. Figure 4 As shown, the disk blank 20 includes a first rigidly formed main surface 22, a second rigidly formed main surface 24, and a thickness T defined therebetween. The edges of the disk blank can be finished (e.g., by grinding and / or polishing). As used herein, the term rigidly formed means that the main surface has not been ground and / or polished, but in some embodiments, the main surface may be chemically treated, for example, during an ion exchange process. The diameter D of the disk blank 20 may be equal to or less than about 100 mm, for example, equal to or less than about 98 mm, for example, equal to or less than about 96 mm, but in other embodiments, the diameter of the disk blank may be greater than 100 mm. In some embodiments, the disk blank 20 may be an annular disk having a central notch 26 concentric with the outer periphery of the disk blank. The surface roughness Ra of the disk blank is equal to or less than about 0.5 nm, for example, equal to or less than about 0.25 nm. The TTV of the disk preform is equal to or less than about 4 μm, for example, equal to or less than about 3 μm, for example, equal to or less than about 2 μm, or equal to or less than about 1 μm. For a 25 mm interval moving in 5 mm increments on the main surface of the disk preform (e.g., on diameter D), the MSIR of the disk preform is equal to or less than about 2 μm. As described herein, the disk preform can be formed, for example, by cutting multiple disk preforms from a glass sheet.

[0094] In some embodiments, the glass articles described herein comprise alkali-free glasses with high annealing points and high Young's modulus, thereby enabling the glass to exhibit excellent dimensional stability (i.e., low compaction) during, for example, TFT manufacturing, thus reducing variability during the TFT process. Glass with high annealing points can help prevent panel deformation due to compaction (shrinkage) during hot processing and subsequent glass manufacturing. Additionally, some embodiments of this disclosure can have high etching rates, facilitating economical thinning of the backplane, and typically have high liquidus viscosity, thus reducing or eliminating the possibility of devitrification in the relatively cold formed body.

[0095] In some embodiments, the glass can comprise an annealing point greater than about 785 °C, 790 °C, 795 °C, or 800 °C. Without being bound by any particular theory, it is believed that such a high annealing point results in a low relaxation rate - and thus a relatively small amount of compaction.

[0096] In some embodiments, the exemplary glass can comprise a temperature at which the viscosity is about 35,000 poise (T 35k ) that is equal to or less than about 1340 °C, equal to or less than about 1335 °C, equal to or less than about 1330 °C, equal to or less than about 1325 °C, equal to or less than about 1320 °C, equal to or less than about 1315 °C, equal to or less than about 1310 °C, equal to or less than about 1300 °C, or equal to or less than about 1290 °C. In particular embodiments, the glass can comprise a temperature at which the viscosity is about 35,000 poise (T 35k ) that is equal to or less than about 1310 °C. In other embodiments, the exemplary glass can comprise a temperature at which the viscosity is about 35,000 poise (T 35k ) that is equal to or less than about 1340 °C, equal to or less than about 1335 °C, equal to or less than about 1330 °C, equal to or less than about 1325 °C, equal to or less than about 1320 °C, equal to or less than about 1315 °C, equal to or less than about 1310 °C, equal to or less than about 1300 °C, or equal to or less than about 1290 °C. In various embodiments, the glass can comprise a T 35k In the range from about 1275 °C to about 1340 °C, or in the range from about 1280 °C to about 1315 °C.

[0097] The liquidus temperature (T 液相线 ) of a glass refers to the temperature above which no crystalline phase can exist in equilibrium with the glass. In various embodiments, the glass used to form the glass sheet described herein can comprise a T 液相线 may be in the range from about 1180 °C to about 1290 °C, or in the range from about 1190 °C to about 1280 °C. In other embodiments, the viscosity corresponding to the liquidus temperature of the glass is greater than or equal to about 150,000 poise. In some embodiments, the viscosity corresponding to the liquidus temperature of the glass is greater than or equal to about 100,000 poise, greater than or equal to about 175,000 poise, greater than or equal to about 200,000 poise, greater than or equal to about 225,000 poise, or greater than or equal to about 250,000 poise.

[0098] In other embodiments, the exemplary glass can comprise a T 35k -T 液相线 > 0.25 T 35k - 225 °C. This ensures that the tendency for the glass in the molten state to devitrify on the forming body during the fusion process is minimized.

[0099] The glasses described herein can comprise a strain point equal to or greater than about 650 °C. The coefficient of linear thermal expansion (CTE) of various embodiments of the glasses can satisfy the following relationship over the temperature range of 0-300 °C: 28 x 10 -7 / °C≤ CTE≤ 34 x 10 -7 / °C.

[0100] In one or more embodiments, the glass is a substantially alkali-free glass comprising, in mole percent on an oxide basis:

[0101]

[0102] where Al2O3, MgO, CaO, SrO, BaO represent the mole percent of the respective oxide components. As used herein, "substantially alkali-free glass" is a glass having a total alkali concentration equal to or less than about 0.1 mole percent, where the total alkali concentration refers to the sum of the concentrations of Na2O, K2O, and Li2O.

[0103] In some embodiments, the glass can be a substantially alkali-free glass comprising, in mole percent on an oxide basis:

[0104]

[0105]

[0106] where 1.0≤ (MgO + CaO + SrO + BaO) / Al2O3< 2 and 0 < MgO / (MgO + Ca + SrO + BaO) < 0.5.

[0107] In certain embodiments, the glass can be a substantially alkali-free glass comprising, in mole percent on an oxide basis:

[0108]

[0109] where 1.0≤ (MgO + CaO + SrO + BaO) / Al2O3< 1.6 and 0.20 < MgO / (MgO + Ca + SrO + BaO) < 0.40.

[0110] In some embodiments, the glass can be a substantially alkali-free glass comprising, in mole percent on an oxide basis:

[0111]

[0112] wherein 1.00 < Σ[RO] / [AI2O3] < 1.25, where [AI2O3] is the mole percent of AI2O3 and Σ[RO] is equal to the sum of the mole percent of MgO, CaO, SrO, and BaO.

[0113] In other embodiments, the glass can be a substantially alkali-free glass comprising, in mole percent on an oxide basis:

[0114]

[0115] wherein Σ[RO] / [AI2O3] > 1.00, where [AI2O3] is the mole percent of AI2O3 and Σ[RO] is equal to the sum of the mole percent of MgO, CaO, SrO, and BaO.

[0116] Down-draw sheeting processes, and in particular fusion processes, can be used to produce the glass articles described herein. Without being bound by any particular theory of operation, it is believed that fusion processes can produce a certain glass substrate that does not require grinding and / or polishing of the major surfaces of the glass article prior to use in subsequent manufacturing processes. For example, existing glass substrate polishing can produce a glass substrate having an average surface roughness greater than about 0.5 nm (Ra) as measured by atomic force microscopy. Glass articles (e.g., glass sheets) produced by fusion processes can have an average surface roughness equal to or less than about 0.5 nm, such as equal to or less than about 0.25 nm, as measured by atomic force microscopy. Of course, the claims appended hereto are not limited to fusion processes, as the embodiments described herein can be applied to other forming processes, such as, but not limited to, slot draw, float, roll, and other sheet forming processes known to those skilled in the art.

[0117] Fusion processes are capable of forming very thin, very flat, very uniform sheets of glass having pristine surfaces relative to the alternative methods for forming glass sheets described previously. Slot draw can also form pristine surfaces, but the dimensional uniformity and surface quality of the glass slot drawn is generally inferior to that of the glass fusion drawn due to the changing orifice shape over time, the accumulation of volatile debris at the orifice-glass interface, and the difficulty of forming orifices to deliver glass that is completely flat. Float processes are capable of delivering very large uniform sheets of glass, but the surfaces are greatly compromised due to contact with the float bath on one side and exposure to condensation products from the float bath on the other side. This means that float glass must be polished prior to use in high performance display applications.

[0118] Despite the advantages of fusion forming of glass articles, new applications of glass sheets continue to challenge the limits of current manufacturing techniques. For example, the drive for increased resolution of visual display devices requires that the glass substrates on which electronic components, such as thin film transistors (TFTs), are deposited have more stringent specifications. Typically, these TFT components are deposited by photolithography, and the increased density of TFTs required to produce increased display resolution requires that the glass be extremely flat to accommodate the shallow depth of focus produced by the photoimaging equipment.

[0119] Other technologies can also require extremely flat glass sheets. For example, the demand for increased areal density of HDD platters has driven the HDD industry to adopt glass. In fact, glass platters have become extremely common for current HDDs, particularly for HDDs used in notebook computers, because glass platters have at least several advantages over aluminum platters. Glass platters can be made with a smoother surface than aluminum, accommodating the increased areal density and very small flying height of the read / write heads. Glass exhibits higher stiffness for a comparable material weight and is more robust for a comparable thickness, so glass platters can be made thinner than aluminum platters to accommodate the increased number of platters in a given device space. In addition, glass does not corrode as readily as aluminum and can be used without nickel plating prior to deposition of the magnetic media. The relatively low coefficient of thermal expansion of glass provides greater thermal stability than aluminum, reducing the amount of track movement and compensation required by the drive's servo mechanism, and facilitating newer recording technologies, such as heat-assisted magnetic recording. Also, the surface of a glass platter is harder than the surface of an aluminum platter, so it is less susceptible to damage from head crashes.

[0120] Manufacturing glass platters for HDDs typically relies on cutting a glass sheet into small pieces (e.g., squares) and then cutting the pieces into annular platters. However, because the read / write heads are only a few nanometers above the surface of the platter during operation of the disk drive, the platters need to be extremely flat and exhibit little variation in thickness. Therefore, platters that do not meet these requirements need to be lapped and / or polished to achieve the necessary flatness. However, lapping and / or polishing add steps and cost to the manufacturing process. In other manufacturing methods, a mass of molten glass is press-formed between two molds. However, the press-forming method is not capable of producing the necessary dimensional requirements, and as mentioned previously, the platter blank needs to be lapped and / or polished prior to subsequent processing.

[0121] In view of the above, the ability to manufacture flat glass sheets with minimal thickness variation can ensure meeting future product requirements. To this end, precise temperature control of the glass sheet is required as it is drawn from a forming body located in a forming chamber in the form of a ribbon during a fusion down-draw process and passes through a cooling chamber that includes various temperature control instruments to control shape and thickness, particularly in the transverse (width) direction that is orthogonal to the draw direction. In the past, such control equipment and methods included blowing a coolant (i.e., a gas, such as clean dry air) onto the ribbon as it is drawn from the forming body or over-flowing the glass over the forming body. Other methods included positioning cooling tubes behind a plate of high thermal conductivity material. Both methods are subject to spatter, which is the outward diffusion of gas from the surface upon which it impinges. In the first case, the gas jetted toward the molten glass itself spreads in all directions over the molten glass, limiting the proximity of one cooling tube to an adjacent cooling tube. Too close of a spacing of the cooling tubes results in interference between the spatter of one cooling tube and the spatter of an adjacent cooling tube. This interference can create a generally uncontrolled cooling zone between the impingement points of the gas streams. Additionally, the introduction of gas streams into the cooling and / or forming chamber can disturb the controlled environment within the chamber, causing unintended temperature fluctuations across the width of the ribbon. Such temperature fluctuations can result in thickness variations, shape variations, and residual stresses. Thus, the use of open-ended cooling tubes that discharge gas directly into the chamber must be spaced far enough apart so that the gas from one cooling tube does not interfere with an adjacent cooling tube, which limits the thickness control that can be achieved. Additionally, the use of liquid coolants is not possible since the coolant is directly impinging onto the molten glass. Since the heat capacity of a gas is generally much less than that of a liquid, the cooling capacity of such a gas direct impingement system is hindered. Finally, the side-by-side arrangement of cooling tubes that extend through the walls of the chamber into the forming and / or cooling chambers requires sealing many individual inlets into the chamber and maintaining such seals, since leakage between the cooling tubes and the chamber walls can result in the destruction of the environment within the chamber.

[0122] In the second case, positioning the cooling tubes behind a high thermal conductivity plate can avoid the direct impingement of the coolant onto the molten glass. However, such a system can still be subject to spatter, where the spatter generated by one cooling tube on the high thermal conductivity plate can still interfere with the spatter generated by an adjacent cooling tube, again creating a less controlled temperature inter-tube region on the high thermal conductivity plate. As in the first case, this thus limits the close spacing of the cooling tubes. Additionally, even if the cooling tubes are contained within a tank or vessel with a high thermal conductivity plate facing the ribbon, there is a risk of gas leaking from the vessel into the chamber.

[0123] Figure 5An exemplary fusion down-draw glass manufacturing apparatus 30 according to embodiments of the present disclosure is shown. In some embodiments, the glass manufacturing apparatus 30 can include a glass melting furnace 32, which can comprise a melting vessel 34. In addition to the melting vessel 34, the glass melting furnace 32 can optionally comprise one or more other components, such as heating elements (e.g., burners and / or electrodes) configured to heat the raw materials and convert the raw materials into a molten glass. For example, the melting vessel 34 can be an electrically-boosted melting vessel, in which energy is added to the raw materials by burners and by direct heating, in which an electric current is passed through the raw materials, thereby adding energy by Joule heating of the raw materials.

[0124] In further embodiments, the glass melting furnace 32 can comprise thermal management devices (e.g., insulating components) that reduce heat loss from the melting vessel. In further embodiments, the glass melting furnace 32 can comprise electronic and / or electromechanical devices that facilitate melting of the raw materials into a glass melt. Still further, the glass melting furnace 32 can include support structures (e.g., support pedestals, support members, etc.) or other components.

[0125] The glass melting vessel 34 is typically formed from a refractory material, such as a refractory ceramic material, such as a refractory ceramic material comprising alumina or zirconia, although the refractory ceramic material can comprise other refractory materials, such as yttrium (e.g., yttria, yttria-stabilized zirconia, yttrium phosphate), zircon (ZrSi04), or alumina-zirconia-silica, or even chromium oxides, used alternatively or in any combination. In some examples, the glass melting vessel 34 can be constructed from refractory ceramic bricks.

[0126] In some embodiments, the melting furnace 32 can be incorporated as a component of a glass manufacturing apparatus configured to manufacture glass articles, such as glass ribbon of indefinite length, although in further embodiments, the glass manufacturing apparatus can be configured to form other glass articles without limitation, such as glass rods, glass tubing, glass envelopes (e.g., glass envelopes for lighting devices, such as light bulbs), and glass lenses, although many other glass articles are contemplated. In some examples, the melting furnace can be incorporated as a component of a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down-draw apparatus (e.g., a fusion down-draw apparatus), an up-draw apparatus, a press apparatus, a roll apparatus, a tube draw apparatus, or any other glass manufacturing apparatus that can benefit from the present disclosure. By way of example, Figure 1 The glass melting furnace 32 is schematically illustrated as a component of a fusion down-draw glass manufacturing apparatus 30 for fusion drawing a glass ribbon for subsequent processing of the glass ribbon into individual glass sheets or winding the glass ribbon onto a spool.

[0127] The glass manufacturing apparatus 30, such as a fusion down-draw apparatus 30, can optionally include an upstream glass manufacturing apparatus 36 that is upstream of the glass melting vessel 34. In some examples, a portion or the entirety of the upstream glass manufacturing apparatus 36 can be incorporated as part of the glass melting furnace 32.

[0128] As Figure 1 As shown in the illustrated embodiment, the upstream glass manufacturing apparatus 36 can include a raw material storage bin 38, a raw material delivery device 40, and a motor 42 coupled to the raw material delivery device. The storage bin 38 can be configured to store an amount of raw material 44 that can be fed through one or more feed ports into the melting vessel 34 of the glass melting furnace 32, as indicated by arrow 46. The raw material 44 typically includes one or more glass-forming metal oxides and one or more modifiers. In some examples, the raw material delivery device 40 can be powered by the motor 42 such that the raw material delivery device 40 delivers a predetermined amount of raw material 44 from the storage bin 38 to the melting vessel 34. In further examples, the motor 42 can power the raw material delivery device 40 to add the raw material 44 at a controlled rate based on a molten glass level sensed downstream of the melting vessel 34 relative to a direction of flow of the molten glass. Thereafter, the raw material 44 within the melting vessel 34 can be heated to form the molten glass 48. Typically, in an initial melting step, the raw material is added to the melting vessel as particulates, such as particulates including various "sand." The raw material can also include scrap glass (i.e., cullet) from a previously performed melting and / or forming operation. A burner is typically used to initiate the melting process. In an electrically assisted melting process, once the electrical resistance of the raw material has been sufficiently reduced (e.g., when the raw material begins to liquefy), electrical assistance is initiated by establishing an electrical potential between electrodes in contact with the raw material to establish an electrical current through the raw material, at which point the raw material typically enters or is in a molten state.

[0129] The glass manufacturing apparatus 30 can also optionally include a downstream glass manufacturing apparatus 50 that is downstream of the glass melting furnace 32 relative to a direction of flow of the molten glass 48. In some examples, a portion of the downstream glass manufacturing apparatus 50 can be incorporated as part of the glass melting furnace 32. However, in some cases, the first connecting conduit 52 discussed below, or other portions of the downstream glass manufacturing apparatus 50, can be incorporated as part of the glass melting furnace 32. The elements of the downstream glass manufacturing apparatus, including the first connecting conduit 52, can be formed from a noble metal. Suitable noble metals include platinum group metals selected from the group consisting of platinum, iridium, rhodium, osmium, ruthenium, and palladium, or alloys thereof. For example, the downstream components of the glass manufacturing apparatus can be formed from a platinum-rhodium alloy that includes about 70 wt% to about 90 wt% platinum and about 10 wt% to about 30 wt% rhodium. However, other suitable metals can include molybdenum, rhenium, tantalum, titanium, tungsten, and alloys thereof.

[0130] Downstream glass manufacturing apparatus 50 can include a first conditioning (i.e., processing) vessel, such as a fining vessel 54, positioned downstream from melting vessel 34 and connected to melting vessel 34 by first connecting conduit 52, as described above. In some examples, molten glass 48 can be fed from melting vessel 34 to fining vessel 54 via first connecting conduit 52 by means of gravity. For example, gravity can drive molten glass 48 through an internal passageway of first connecting conduit 52 from melting vessel 34 to fining vessel 54. It should be appreciated, however, that other conditioning vessels can also be positioned downstream from melting vessel 34, such as between melting vessel 34 and fining vessel 54. In some embodiments, a conditioning vessel can be used between the melting vessel and the fining vessel, where the molten glass from the primary melting vessel is further heated in the secondary vessel to continue the melting process, or cooled to a lower temperature than the temperature of the molten glass in the primary melting vessel before entering the fining vessel.

[0131] In fining vessel 54, bubbles in molten glass 48 can be removed by various techniques. For example, raw materials 44 can include multivalent compounds (i.e., fining agents), such as tin oxides, which undergo a chemical reduction reaction and release oxygen gas when heated. Other suitable fining agents include, but are not limited to, arsenic, antimony, iron, and cerium, although, as previously described, the use of arsenic and antimony can be hindered in some applications due to environmental concerns. Fining vessel 54 is heated to a temperature higher than the temperature of melting vessel 34, thereby heating the fining agents. Oxygen bubbles produced by the chemical reduction reaction induced by the temperature of the one or more fining agents included in the melt rise through the molten glass within fining vessel, where the gases in the molten glass produced within the melting vessel can coalesce and or diffuse into the oxygen bubbles produced by the fining agents. The increased bubbles can then rise to the free surface of the molten glass in fining vessel and subsequently exit the fining vessel. As the oxygen bubbles rise through the molten glass, they can further induce mechanical mixing of the molten glass in the fining vessel.

[0132] Downstream glass manufacturing apparatus 50 can also include another conditioning vessel, such as mixing apparatus 56, for mixing molten glass flowing downstream from fining vessel 54. Mixing apparatus 56 can be used to provide a uniform glass melt composition, thereby reducing chemical or thermal inhomogeneities that can otherwise exist in the fined molten glass exiting the fining vessel. As shown, fining vessel 54 can be connected to mixing apparatus 56 by second connecting conduit 58. In some embodiments, molten glass 48 can be gravity fed from fining vessel 54 to mixing apparatus 56 via second connecting conduit 58. For example, gravity can drive molten glass 48 through an internal passageway of second connecting conduit 58 from fining vessel 54 to mixing apparatus 56. It should be noted that while mixing apparatus 56 is shown in the figures as being downstream of fining vessel 54 with respect to the direction of flow of molten glass, in other embodiments, mixing apparatus 56 can be located upstream of fining vessel 54. In some embodiments, downstream glass manufacturing apparatus 50 can include multiple mixing apparatuses, such as a mixing apparatus located upstream of fining vessel 54 and a mixing apparatus located downstream of fining vessel 54. These multiple mixing apparatuses can have the same design, or they can have different designs from one another. In some embodiments, one or more of the vessels and / or conduits can include static mixing vanes located therein to facilitate mixing and subsequent homogenization of the molten material.

[0133] Downstream glass manufacturing apparatus 50 can also include another conditioning vessel, such as delivery vessel 60, which can be located downstream of mixing apparatus 56. Delivery vessel 60 can condition molten glass 48 to be fed into a downstream forming device. For example, delivery vessel 60 can function as an accumulator and / or flow controller to regulate the flow of molten glass 48 and provide a constant flow of molten glass 48 to forming body 62 through outlet conduit 64. As shown, mixing apparatus 56 can be connected to delivery vessel 60 by third connecting conduit 66. In some examples, molten glass 48 can be gravity fed from mixing apparatus 56 to delivery vessel 60 via third connecting conduit 66. For example, gravity can drive molten glass 48 through an internal passageway of third connecting conduit 66 from mixing apparatus 56 to delivery vessel 60.

[0134] The downstream glass manufacturing apparatus 50 can also include a forming apparatus 68 comprising the above-described forming body 62 comprising an inlet conduit 70. The outlet conduit 64 can be positioned to deliver the molten glass 48 from the delivery vessel 60 to the inlet conduit 70 of the forming apparatus 68. The forming body 62 in a fusion down-draw glass manufacturing apparatus can include a trough 72 in the upper surface of the forming body and converging forming surfaces 74 (only one surface shown) that converge along the bottom edge (root) 76 of the forming body in the direction of draw. The molten glass delivered to the forming body trough via the delivery vessel 60, outlet conduit 64, and inlet conduit 70 overflows the trough walls and descends along the converging forming surfaces 74 as separate streams of molten glass. The separate streams of molten glass join along the root below the root to produce a single ribbon of molten glass 78 that is drawn in the direction of draw 80 along a draw plane 82 (see Figure 6 ) from the root 76 by applying tension to the glass ribbon [e.g., by means of gravity and various rollers, such as a pull roll 84 (see Figure 6 )] to control the glass ribbon dimensions as the molten glass cools and the viscosity of the material increases. Thus, the glass ribbon 78 undergoes a viscoelastic transition and acquires mechanical properties that give the glass ribbon 78 stable dimensional characteristics. In some embodiments, the glass ribbon 78 can be separated into individual glass sheets 10 in the elastic region of the glass ribbon using a glass separation apparatus (not shown), but in other embodiments, the glass ribbon can be wound onto a spool and stored for further processing. Additionally, thickened edge portions (known as beads) can be removed from the glass ribbon 78 either immediately or after the individual glass sheets 10 are separated from the glass ribbon 78.

[0135] Since the glass ribbon 78 and subsequent glass sheets 10 are formed by fusing two separate streams of molten glass, the glass sheets 10 contain an interface between the separate layers that is visible from the edges of the glass sheet. This interface can be visible as a line (fusion line) 18 along the edges of the glass sheet. Additionally, since the two layers of the glass sheet have a single source of molten glass, they have the same chemical composition. However, in other embodiments (not shown), multiple forming bodies can be used in which the stream of molten glass flowing from a first forming body onto the molten glass in the trough of a second forming body and the second forming body is positioned below the first forming body such that the ribbon drawn from the second forming body contains more than two layers. That is, the molten glass provided to the first forming body need not have the same chemical composition as the molten glass flowing to the second forming body. Thus, glass sheets containing more than two layers of glass and more than one fusion line (more than one interface) can be produced.

[0136] Reference is now made to Figures 6-8The forming body 62 is positioned in a forming chamber 90 to maintain a controlled environment around the forming body 62 and the glass ribbon drawn therefrom. For example, as shown in Figure 7 and 8 the forming chamber 90 can include a first inner forming chamber 92. The inner forming chamber 92 is further contained in and spaced apart from an outer forming chamber 94. Heating elements 96 can be positioned in the space between the inner and outer forming chambers for controlling the temperature of the molten glass 48, and thus the viscosity of the molten glass 48, so that the molten glass is at a suitable viscosity for forming. A lower cooling chamber 98 forms a channel around the glass ribbon 78 as the glass ribbon is drawn from the root 76 and helps establish a controlled environment for the glass ribbon as it transitions from a viscous liquid to an elastic solid having a fixed dimension. Accordingly, the forming apparatus 68 can further include cooling means 100, such as a pair of cooling doors 100 configured to extend parallel to the draw plane 82 in the width direction of the ribbon. The cooling doors 100 include a ribbon-facing panel 102 that also extends parallel to the draw plane 82 in the width direction of the ribbon. The ribbon-facing panel 102 can be formed of a high thermal conductivity material capable of withstanding the high temperatures (e.g., equal to or greater than 1100 °C) in the inner chamber 92. A suitable exemplary material is silicon carbide (SiC). The cooling doors 100 include a chamber 104 in which a plurality of cooling tubes 106 are positioned that are in fluid communication with a source of cooling gas (not shown). The cooling tubes 106 include open ends that are adjacent to and spaced apart from an inner surface of the ribbon-facing panel 102. Cooling gas 108 is directed into and flows from the cooling tubes to the inner surface of the ribbon-facing panel, thereby cooling the ribbon-facing panel. The cooled ribbon-facing panel 102 forms a heat sink adjacent to the glass ribbon 78 and helps cool the glass ribbon. The flow of cooling gas 105 to each cooling tube 106 can be individually controlled, and thus localized control of the temperature of the glass ribbon is possible. As shown in Figure 6 and 7 the ribbon-facing panel 102 is generally angled so that the end face is approximately parallel to the converging forming surface 74, thereby maximizing the effect of the cooling door on the glass overflowing the converging forming surface. The cooling doors 100 can be moved in a direction orthogonal to the draw plane 82, as indicated by arrow 110. It should be noted, however, that the ability to move the cooling doors in close proximity to the flow of molten glass is limited because the angled orientation of the end face increases the likelihood that molten glass that can drip from the forming body will contact and coat the outer surface of the ribbon-facing panel 102, thereby reducing the thermal conductivity of the ribbon-facing panel and thus affecting the temperature and viscosity control of the glass ribbon 78. Accordingly, the cooling doors 100 are generally positioned outside the direct vertical range of the forming surface.

[0137] The forming apparatus 68 also includes slide gates 112 located on opposite sides of the glass ribbon 78. In some embodiments, such as Figure 6 and 7 the slide gates 112 are located below the cooling doors 100. However, in other embodiments, such as Figure 8 the slide gates 112 can be located above the cooling doors 100. In other embodiments, the slide gates can be located both above and below the cooling doors. The slide gates 112 are movable in a direction orthogonal to the draw plane 82, as indicated by arrows 114.

[0138] Figure 9A and 9B respectively illustrate a cross-sectional top view and a side view of an exemplary slide gate 112. The slide gate 112 includes a top wall 120, a bottom wall 122, and a ribbon-facing faceplate (hot plate) 124. The slide gate 122 is positioned such that the hot plate 124 abuts the glass ribbon 78. The distance between the hot plate 124 and the major surface of the adjacent glass ribbon 78 is defined as "d". The hot plate 124 is formed of a high thermal conductivity material, such as SiC. The hot plate 124 can be angled, for example, at an angle generally that of the converging forming surface 74, or the hot plate 124 can be perpendicular and substantially parallel to the draw plane 82. The slide gate 112 can also include a back wall 126 connecting the top wall 120 and the bottom wall 122, and end walls 128, 130.

[0139] The slide gate 112 also includes a plurality of cooling tubes 132 located in the slide gate. Each cooling tube 132 of the plurality of cooling tubes includes an outer tube 134 and an inner tube 136. In some embodiments, the outer tube 134 and the inner tube 136 can include a circular shape in a cross-section orthogonal to the longitudinal axis of the cooling tube, but in further embodiments, either or both of the outer tube and the inner tube can have other cross-sectional shapes, such as a rectangular, oval, or any other suitable geometry. In some embodiments, the inner tube 136 can be concentric with the outer tube 134 about a central longitudinal axis of the cooling tube. Each outer tube 134 of the plurality of outer tubes includes a closed distal end 138 located proximate to an inner surface of the hot plate 124. In some embodiments, the distal end 138 is in contact with the hot plate 124. Each inner tube 136 of the plurality of inner tubes includes an open distal end 140 located proximate to the closed distal end 138 of the outer tube 134. Cooling fluid 142 supplied to the inner tube 136 exits through the open distal end 140 and impinges on the closed distal end 138 of the outer tube 134. The cooling fluid exiting the open distal end 140 then flows back through the space between the outer tube 134 and the inner tube 136, whereby the cooling fluid can be exhausted from the cooling tube, or chilled (e.g., in a heat exchanger (not shown)) and recirculated back to the cooling tube. The cooling fluid 142 can be a gas, such as an inert gas or even air, or a liquid, such as water.

[0140] Unlike cooling devices that direct cooling gas directly onto the ribbon, the internal cooling fluid flow circulating through cooling tubes 132 does not interact with the cooling fluid of adjacent cooling tubes, and thus cooling tubes 132 can be closely spaced together, as long as the size of the cooling tubes permits. Moreover, the flow rate of the cooling fluid through the cooling tubes can be increased to the highest cooling rate possible. In addition, by containing the cooling fluid entirely within the cooling tubes and simultaneously within the sliding gate, the flow of cooling fluid into the cooling chamber 98, which contains the ribbon, is prevented. In contrast, cooling gas from cooling tubes 106 that enters the cooling door 100 can leak into the cooling chamber and interfere with the thermal environment in the cooling chamber, causing uncontrolled temperature variations across the width of the glass ribbon 78 or along the length of the glass ribbon 78, which can result in residual stresses in the glass ribbon as it cools. In some embodiments, the cooling fluid 142 used in cooling tubes 132 can be a liquid, such as water, without the risk of injecting water into the cooling chamber. The use of a liquid, which has a higher heat capacity than a gas, can increase the cooling capacity of the cooling tubes.

[0141] In some embodiments, the sliding gate 112 can comprise a solid plate formed of a high-temperature resistant metal in which channels have been formed, such as by drilling holes in the metal plate. Each channel acts as an outer tube 134, with the walls of each channel defining the inner diameter of the "tube." An inner tube 136 can be positioned within each channel, with cooling fluid being injected into the channels in the manner described above. In some embodiments, the central longitudinal axis of each channel (e.g., outer tube) can be spaced apart from the central longitudinal axis of an adjacent channel by a distance of about 1 cm to about 1.5 cm.

[0142] The sliding gate 112 can have various shapes. For example, Figure 10 Another example sliding gate 112 is illustrated. In this example, the sliding gate 112 includes a center portion 214 and end portions 216a, 216b located near the ends of the center portion 214. The end portions 216a, 216b can have front edges that are parallel to the draw plane 82, or as in Figure 10 In embodiments of the sliding gate 112, the end portions 150 are recessed relative to the draw plane 82. In embodiments of the sliding gate 212, the end portions 216a, 216b are recessed relative to the draw plane 82. Figure 11 In embodiments of the sliding gate 112, the end portions 150 are angled relative to the draw plane 82 such that the front edges of the sliding gate at the end portions are tilted back in a direction away from the draw plane 82. In other embodiments, the sliding gate can comprise multiple separate components. For example, in embodiments of the sliding gate 212, the example sliding gate 212 comprises a center portion 214 containing the cooling tubes 132, and end portions 216a, 216b located near the ends of the center portion 214. The end portions 216a, 216b can have front edges that are parallel to the draw plane 82, or as in Figure 12 Figure 13 ​As shown, the end portions 216a, 216b can have angled leading edges that slope back in a direction away from the draw plane 82. The end portions 216a, 216b can be moved individually and separately so that the end portions and the center portion can be positioned at different distances from the glass ribbon 78.

[0143] Figure 14 FIG. 3 is a graph showing the effect of a single cooling tube pair on the thickness of a 3.3 mm thick molten glass ribbon located 105 mm from the lateral edge of the glass ribbon 78. The ribbon had a width of about 22 cm. The outer tube had a diameter of about 1.3 cm. The inner tube had a diameter of about 1 cm. The cooling tube had an internal air flow of 40 standard cubic feet per hour. The tube was located about 1.3 cm from the ribbon surface. Curve 300 represents the thickness in the absence of the cooling tube, while curve 302 represents the thickness in the presence of the cooling tube. Each curve shows a significant change in thickness in the vicinity of the cooling tube. Figure 15 Figure 14 FIG. 4 is a graph showing the difference between the curves of FIG. 3, where curve 304 represents the difference, and curve 306 represents a Gaussian fit to curve 304. The resulting thickness change is shown to be about 150 microns, or about 3.3% of the nominal 3.3 mm thickness. In addition, the full width at half maximum (FWHM) value of the Gaussian curve 306 is about 65 mm.

[0144] Figure 16 FIG. 3 is a graph showing the effect of a single cooling tube pair on the thickness of a 3.3 mm thick molten glass ribbon located 105 mm from the lateral edge of the glass ribbon 78. The ribbon had a width of about 22 cm. The outer tube had a diameter of about 1.3 cm. The inner tube had a diameter of about 1 cm. The cooling tube had an internal air flow of 40 standard cubic feet per hour. The tube was located about 1.3 cm from the ribbon surface. Curve 300 represents the thickness in the absence of the cooling tube, while curve 302 represents the thickness in the presence of the cooling tube. Each curve shows a significant change in thickness in the vicinity of the cooling tube. 最大 最大 As shown, the MSIR in the quality zone of the actual ribbon without the slide gates was about 0.0015 mm, while the MSIR of the modeled ribbon with the actively cooled slide gates present was about 0.0005 mm.

[0145] ​​Figure 17 is a graph showing ΔΤ 最大 as a function of position from the lateral edge of the ribbon. Lines 320 and 322 represent the boundaries of the quality region. Curve 324 represents the ΔΤ 最大 measured on the ribbon with no slide gate, while curve 326 represents modeled data for a slide gate with active cooling. These data show that the MSIR with no slide gate is about 0.00285 mm, while the MSIR with a slide gate with active cooling is about 0.00025 mm.

[0146] Figure 18 shows results of a study using a modeled 1.3 cm square "cold spot" positioned parallel to the flowing glass ribbon at various distances from the draw plane and perpendicular to the draw plane, as well as at various distances below the root 76 (plotted on the horizontal axis). The cold spot can be, for example, the end of a closed cooling tube 132, in this case having a square cross section. The vertical axis shows the magnitude of the thickness variation. In Figure 18 , curve 328 represents a distance of 1.3 cm between the cold spot (e.g., the end of a cooling tube) and the ribbon, curve 330 represents a distance d of 3.8 cm between the cold spot and the ribbon, curve 332 represents a distance of 6.4 cm between the cold spot and the ribbon, and curve 334 represents a distance of 8.9 cm between the cold spot and the ribbon. The data show that the smallest distance between the cold surface and the flowing surface of the ribbon, closer to the root line, produces the greatest thickness effect.

[0147] Figure 19 is shown for four different temperature (viscosity) perturbations at a location 3.6 cm below the root of the forming body, and using a modeled 1.3 cm square "cold spot" positioned parallel to the flowing glass ribbon and perpendicular to the draw plane and at various distances from the ribbon surface. When the cold spot is 1.3 cm from the glass surface (curve 336), the FWHM of the primary thickness perturbation is about 40 mm. Curve 338 represents the cold spot positioned 3.8 cm from the ribbon surface, curve 340 represents the cold spot positioned 6.4 cm from the ribbon surface, and curve 342 represents the cold spot positioned 8.9 cm from the ribbon surface. When the cold spot is positioned 8.9 cm from the glass surface, the FWHM is about 160 mm. As shown, in general, the FWHM and the distance of the cold spot to the glass surface will be linearly related.

[0148] Figure 20 and 21This illustrates how a change in the temperature field at the same location can cause... Figure 19 The thickness distribution variation observed (1.3cm and 8.9cm). Figure 20 Indicates from Figure 19 In the case of 1.3cm, and

[0149] Figure 21 Indicates from Figure 19 The case of 8.9 cm. In the two figures, curve Δthickness represents the curve of thickness variation, while curve Δtemperature represents the curve of temperature variation. The horizontal axis represents the distance from the centerline of the strip. The data shows that the magnitude of the thickness distribution variation is linearly correlated with the magnitude of the temperature variation at the glass surface, and the FWHM will be linearly identical in both cases. Due to mass conservation, the sum of the integral areas near the zero line should be zero in the case of thickness distribution. Additionally, the data shows the correlation between temperature variation at the glass surface and strip thickness variation.

[0150] Figure 22 Results from other modeling are shown, where the characteristic width (FWHM) of the thickness perturbation induced by a single control point varies from 65 mm to 220 mm. The data show that the ability to reduce MSIR (in this case, moving a 100 mm slip interval across the strip width in 5 mm increments) is a strong function of the FWHM at each control point distributed along the horizontal width of the glass strip. For example, the figure shows that to achieve an MSIR of 0.00025, a thickness perturbation with an FWHM of approximately 65 mm is required. As the FWHM increases, the MSIR also increases. Therefore, generally, for a 100 mm slip interval, to obtain an MSIR equal to or less than approximately 0.0024, for example, moving the interval in 5 mm increments, requires a thickness perturbation equal to or less than approximately 215 mm. For a 100 mm slip interval, to obtain an MSIR equal to or less than approximately 0.0020, for example, moving the interval in 5 mm increments requires a thickness perturbation equal to or less than approximately 165 mm. For a sliding gap of 100 mm, to obtain an MSIR equal to or less than approximately 0.0014, moving the gap in increments of 5 mm, for example, results in a thickness disturbance equal to or less than approximately 120 mm. For a sliding gap of 100 mm, to obtain an MSIR equal to or less than approximately 0.00055, moving the gap in increments of 5 mm, for example, results in a thickness disturbance equal to or less than approximately 60 mm. It should be noted that the manner in which the thickness disturbance is caused is different from... Figure 22 The result is irrelevant.

[0151] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Claims

1. An apparatus for manufacturing glass ribbons, comprising: A forming body includes a groove configured to receive a stream of molten glass and a converging forming surface joined along the bottom edge of the forming body, wherein a glass strip is drawn from the bottom edge of the forming body in a drawing direction along a vertical drawing plane. and A cooling device located below the bottom edge, the cooling device comprising a hot plate extending in the width direction of the molten glass flow and a plurality of cooling tubes located in the cooling device, each of the plurality of cooling tubes comprising a first tube and a second tube, the first tube having a closed end adjacent to the hot plate, and the second tube extending into the first tube and having an open end adjacent to the closed end of the first tube.

2. The device as claimed in claim 1, wherein, Each of the plurality of cooling pipes, first pipe, is in contact with the hot plate.

3. The device as claimed in claim 1, wherein, At a distance of 8.5 cm or less from the bottom edge, the longitudinal axis of each first tube intersects the drawing plane.

4. The device as described in claim 3, wherein, The distance between the intersection point and the bottom edge is equal to or less than 3.6 cm.

5. The device as described in claim 3, wherein, The distance between the drawn flat surface and the hot plate is equal to or less than 9 cm.

6. The device as claimed in claim 5, wherein, The distance between the drawn flat surface and the hot plate is equal to or less than 1.5 cm.

7. An apparatus for manufacturing glass ribbons, comprising: A forming body includes a groove configured to receive a stream of molten glass and a converging forming surface joined along the bottom edge of the forming body, wherein a glass strip is drawn from the bottom edge of the forming body in a drawing direction along a vertical drawing plane. and A cooling device located below a bottom edge, the cooling device comprising a metal plate extending in the width direction of a molten glass flow, the metal plate comprising a plurality of channels formed therein, each of the plurality of channels comprising a closed distal end and an open proximal end, a cooling tube extending through the open proximal end such that the open distal end of the cooling tube is adjacent to but spaced apart from the distal end of the channel.

8. The device as claimed in claim 7, wherein, The distance between the drawn flat surface and the hot plate is equal to or less than 1.5 cm.

9. A glass wafer preform manufactured by the apparatus according to any one of claims 1-8, comprising: A first main surface, a second main surface opposite to the first main surface, and a thickness T defined between the first main surface and the second main surface. Among them, the total thickness variation (TTV) along the diameter of the glass disc blank is equal to or less than 2 μm.

10. The glass wafer preform as described in claim 9, wherein, The diameter D is equal to or less than 100 mm.

11. The glass wafer preform as described in claim 9, wherein, The diameter D is greater than 100 mm.

12. The glass wafer blank as described in claim 9, wherein, The disc blank includes an annular disc having a central cutout concentric with the outer periphery of the disc blank.

13. The glass wafer preform as described in claim 9, wherein, The glass wafer blank is equal to or less than 1340 o The viscosity at temperature C is 35,000 poise.

14. The glass disc preform as described in claim 9, wherein, The annealing point of the glass wafer blank is greater than 785°C. o C.

15. The glass wafer blank as described in claim 9, wherein, TTV is equal to or less than 1 μm.

16. The glass wafer preform as described in claim 9, wherein, The maximum sliding interval range (MSIR) obtained by moving the sliding interval by 25 mm in 5 mm increments over the diameter of the glass disk blank is equal to or less than 2 μm.

17. The glass disc preform as described in claim 9, wherein, The average surface roughness Ra of one or both of the first and second primary surfaces is equal to or less than 0.50 nm.

18. The glass wafer blank as described in claim 17, wherein, Ra is equal to or less than 0.25 nm.

19. A method for manufacturing glass articles, the method comprising: A glass strip is drawn from a forming body in a drawing direction, the glass strip including opposing edge portions and a central portion located between the opposing edge portions, the glass strip including an adhesive region and an elastic region; as well as In the width direction of the glass ribbon orthogonal to the drawing direction, a thickness disturbance is formed in the central portion of the adhesive region of the glass ribbon, the thickness disturbance having a characteristic width equal to or less than 75 mm. The maximum sliding interval range obtained by moving 100 mm in 5 mm increments across the width of the central portion of the elastic zone is equal to or less than 0.0025 mm. The thickness disturbance is formed by cooling the glass strip using a cooling device, the cooling device including a hot plate extending in the width direction of the glass strip orthogonal to the drawing direction, the cooling device also including a plurality of cooling tubes located in the cooling device, each of the plurality of cooling tubes including a first tube and a second tube, the first tube having a closed end adjacent to the hot plate, the second tube extending into the first tube and having an open end spaced apart from the closed end of the first tube, the cooling including causing cooling fluid to flow into the second tube of the plurality of cooling tubes.

20. The method of claim 19, wherein, The maximum sliding interval range is equal to or less than 0.0020 mm.

21. The method of claim 20, wherein, The maximum sliding interval range is equal to or less than 0.0015 mm.

22. The method of claim 21, wherein, The maximum sliding interval range is equal to or less than 0.0006 mm.

23. The method of claim 22, wherein, The feature width is equal to or less than 65 mm, and the maximum sliding interval range is equal to or less than 0.0003 mm.

24. The method of claim 23, wherein, The disturbance is generated by cooling the glass strip.

25. The method of claim 23, wherein, The disturbance is generated by heating the glass strip.

26. The method of claim 19, wherein, The distance between the bottom edge of the formed body and the maximum thickness of the thickness disturbance is equal to or less than 8.5 cm.

27. The method of claim 26, wherein, The distance between the bottom edge of the formed body and the maximum thickness of the thickness disturbance is equal to or less than 3.6 cm.

28. The method of claim 19, wherein, In the width direction orthogonal to the drawing direction, the total thickness variation of the central portion in the elastic zone is equal to or less than 4 μm.

29. The method of claim 28, wherein, The total thickness variation is equal to or less than 2 μm.

30. The method of claim 29, wherein, The total thickness variation is equal to or less than 1 μm.

31. A method for manufacturing glass articles, the method comprising: Molten glass is allowed to flow into a groove in the forming body, the molten glass overflows through the groove, and flows down along the opposing forming surfaces of the forming body as separate molten glass streams, the separate molten glass streams combining below the bottom edge of the forming body; A strip of molten glass is drawn from the bottom edge in the drawing direction; as well as The strip is cooled using a cooling device comprising a hot plate extending in the width direction of the glass strip orthogonal to the drawing direction, and a plurality of cooling tubes located within the cooling device. Each of the plurality of cooling tubes comprises a first tube and a second tube, the first tube having a closed end adjacent to the hot plate, and the second tube extending into the first tube and having an open end spaced apart from the closed end of the first tube. The cooling includes: allowing cooling fluid to flow into the second tube of the plurality of cooling tubes. The cooling also includes: forming a plurality of thickness perturbations on the strip corresponding to the position of each cooling tube, each thickness perturbation having a characteristic width equal to or less than 225 mm.

32. The method of claim 31, wherein, The feature width is equal to or less than 175 mm.

33. The method of claim 32, wherein, The feature width is equal to or less than 125 mm.

34. The method of claim 33, wherein, The feature width is equal to or less than 75 mm.

35. The method of claim 34, wherein, The feature width is equal to or less than 65 mm.

36. The method of claim 31, wherein, Each of the plurality of cooling pipes is in contact with the hot plate.

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