JP5281569B2 - Apparatus and method for forming glass substrate with increased edge stability - Google Patents

Description

  The present invention relates generally to glass substrate forming apparatus, and more particularly to structural standards for apparatus based on glass flow.

  Glass display panels in the form of liquid crystal displays (LCDs) are used in a wide variety of applications ranging from personal digital assistants (PDAs) to computer monitors and television displays. These applications require a glass sheet or glass substrate having a clean defect-free surface and a certain thickness. The LCD comprises at least a few thin (eg less than 0.7 mm) glass sheets that are sealed together to form the skin. The growing market for glass display panels, particularly LCD display panels, has led to increased demand for glass substrates used in their manufacture.

One method of manufacturing glass for optical displays is by the overflow downdraw method. Patent Documents 1 and 2 (Dockerty), the entire contents of which are incorporated herein by reference, describe flowing molten glass over the upper edge or weir of a forming wedge generally called an isopipe. Including a fusion downdraw method is disclosed. The molten glass flows over both forming surfaces of the isopipe that converge, and these two individual streams reunite at the apex, or bottom edge, where the two forming surfaces converge, forming a glass ribbon. Therefore, the glass in contact with the molding surface is sealed inside the glass sheet, and nothing contacts the outer surface of the strip glass. A pulling roller is placed downstream of the bottom edge of the isopipe to capture the edge portion of the glass ribbon and adjust the speed of the glass strip leaving the isopipe and thus define the thickness of the finished glass sheet Have As the glass strip descending from the bottom edge of the isopipe passes through the pulling roller, the glass strip cools to form an elastic solid glass strip that is then cut into individual glass sheets or glass. A substrate is formed.
U.S. Pat. No. 3,338,696 US Pat. No. 3,682,609

  As the demand for display glass has increased, glass substrate manufacturers have faced the need for increased production. One measure is the installation of further traction equipment. However, this option requires significant capital investment. A more cost effective measure is an increase in glass flow for existing traction equipment. However, increasing the flow rate requires increasing the isopipe size (eg, isopipe width) in order to maintain a stable flow at the edge. The traction process itself consists of a delicate balance between many traction process conditions, and these traction process conditions can vary from one individual traction process to another. Therefore, it is often difficult to simply increase the glass flow rate. Furthermore, not only the demand for glass substrates has increased, but the size of displays has also steadily increased. This requires a larger substrate to maintain economies of scale. Thus, in addition to increasing the glass flow rate, larger (eg, wider) glass traction is required. What is needed is the ability to increase glass flow without exceeding the stability limits of the traction process, or the ability to install a large traction device by scaling up from a smaller, stable traction device. It is another structure given to existing traction equipment.

One embodiment of the present invention includes a glass sheet forming apparatus with a forming wedge that converges at the bottom edge of the wedge and has a vertical height L inches above the bottom edge. A pair of downwardly inclined molding surface portions, further comprising an edge guide body, the edge guide body extending along a vertical edge of the molding surface portion and having a web portion, The web portion is adjacent to the molding surface to block and thin the flow of G pounds / hour / inch glass flowing over the web portion, and G / L ³ is about 0.0017 pounds. / Hour / inch ⁴ (1 pound is 0.45 kg, 1 inch is 2.54 cm). G / L ³ is preferably greater than about 0.002 lb / hr / inch ⁴ (1 lb is 0.45 kg, 1 inch is 2.54 cm).

In another embodiment, a method for forming a glass substrate is disclosed, the method comprising flowing molten glass over a forming wedge, the forming wedge being converged at a bottom edge of the wedge. And a pair of downwardly inclined forming surface portions forming a glass traction line along the bottom edge, and between the traction line and a horizontal plane intersecting the top of the inclined forming surface portion. An edge guide having a vertical height of L inches and further having a web portion, the web portion, in order to interrupt and thin the glass flow of G pounds / hour / inch flowing over the web portion, Adjacent to the molding surface, G / L ³ is greater than about 0.0017 pounds / hour / inch ⁴ (1 pound is 0.45 kg, 1 inch is 2.54 cm).

  Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be described by those skilled in the art from the description or in the detailed description, claims and accompanying drawings below. It will be readily apparent by practicing the present invention.

  Both the foregoing general description and the following detailed description provide embodiments of the invention and are intended to provide an overview or framework for understanding the nature and features of the invention as claimed. It should be understood that The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. These drawings show various embodiments of the present invention, and together with the description, serve to explain the principle and operation of the present invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention shown in the attached drawings will be described. Throughout the drawings, the same or similar parts are denoted by the same reference numerals as much as possible.

  The design of molding wedges experienced in the past has been prone to repeated operations. Molding wedges were designed, manufactured and commissioned to evaluate their capabilities. For example, an unstable forming wedge that changes over time from edge to edge of a glass sheet pulled from the forming wedge requires modification of the structure and production of another forming wedge. It was. This process continued until the appropriate design characteristics were reached. Nevertheless, it has been found that the edge stability is sparse because the dimensions of the forming wedge change over time and various process variables such as, for example, temperature distribution and changes in glass flow. Glass molding requires a high temperature, invites a sag or creep of the forming wedge for a long time, and the molten glass tends to gradually dissolve the material that forms the forming wedge, typically zircon. As such, the molding wedge itself is exposed to unusually severe conditions. Thus, it has been found that the characteristics of certain forming wedges are sensitive to process conditions and induce changes in edge stability. This is especially true when an increase in the size of the forming wedge is required.

  One limitation of panel display size is the ability to form large sheets of clean glass that serve as a substrate for the display. Although the size (for example, width) of the first generation glass sheet was less than 1 meter, in the production of the current generation glass sheet, it is possible to form a clean glass sheet having a width of several meters.

  In order to achieve this size increase, the display glass manufacturer must increase the size and in particular the width of the forming wedge. In the past, this has usually evolved from the starting point of the previous generation of wedges. This molding wedge was used as a template for the next generation molding wedge following an increase in size from the previous generation.

  Nonetheless, changing the size was often unsuccessful, even for molding wedges that were formed based on the next generation design and that exhibit relatively good edge stability. For example, it is found that if only the size (width) of the forming wedge-shaped body is increased without increasing the size of the web portion of the edge guide body, an unstable edge flow or at least an edge flow sensitive to the process conditions is generated. It was. Thus, structural parameters (eg width, trough dimensions, etc.) are changed before a larger next generation molding wedge with a stable edge flow can be constructed and installed at the production site. It was necessary to produce several molding wedges. As will be appreciated, this random approach to the forming wedge is undesirable.

  Using the method of the present invention, it is not only possible to initially produce a molding wedge for overflow downdraw molding of a glass sheet with a stable edge flow, but also the first molding wedge This makes it easier to deploy the wedge-shaped bodies of different sizes, producing a stable edge flow, enlarged from

  An apparatus 10 for clean glass overflow downdraw according to the present invention is shown in FIG. As shown in FIGS. 1 and 2, the device 10 includes a forming wedge 12, which is an upwardly open groove 14 that is partitioned by walls 16 on both sides in the longitudinal direction. The upper end of this groove 14 terminates in an overflow weir or upper edge 18 that extends in the opposite longitudinal direction. These weirs or upper edges 18 are adjacent to the sheet forming surfaces on both outer sides of the forming wedge 12. As shown, the forming wedge 12 terminates in a pair of substantially vertical forming surface portions 20 adjacent to the top edge 18 and a substantially horizontal lower top or bottom edge 24 that forms a straight glass pull line. And a converging surface portion 22 inclined downward.

  The molten glass 26 is fed into the groove 14 using a feed passage 28 communicating with the groove 14. The feeding into the groove 14 may be performed from one side, but may be performed from both sides as necessary. A pair of current limiting dams 30 are provided above the upper edge 18 in the vicinity of each end of the groove 14 so as to get over the overflow weir 18 as two separate flows and form the molding surfaces 20 and 22 on both sides as bottom edges. Inducing the overflow of the free surface 32 of the molten glass 26 flowing down to 24, the two separated flows shown in phantom lines merge at the bottom edge 24 to form a strip glass 34 with a virgin surface. . Thereafter, the glass strip 34 is pulled by the pulling roller 35.

  A pair of edge guides or edge correction bodies 36 are provided at each longitudinal end of the wedge 12 for molding, and these edge guides are provided at the vertical edges of the respective longitudinal ends on each side of the wedge. Extending along. Accordingly, four edge guides 36 are provided at each corner of the forming wedge 12 for each forming wedge 12. The edge guides 36 are composed of two main parts, a protruding surface 38 intersecting the longitudinal surface of the wedge-shaped forming surface, and a convergent surface inclined with the protruding surface 38. A web portion or fillet portion 40 extending between and adjacent to (crossing) one of the portions 22.

  The web portion 40 intersects the protruding edge surface portion 38 along the intersection line 42 between the points A and B, and is inclined along the intersection line 44 between the points A and C. Crosses the surface 22. Accordingly, the intersecting line 44 extends diagonally downward from the point A to the point C that is inwardly separated from the protruding surface 38 along the bottom edge or top 24 of the forming wedge 12 by a distance d. However, in another embodiment, the point C may be above or below the horizontal plane. A bottom edge 46 of the web portion 40 extends from point B to point C. The bottom edge 46 may be a straight line or may not be a straight line.

  As described above, according to the present invention, the wedge-shaped body 12 includes the plurality of edge guide bodies 36. Specifically, one edge guide 36 is arranged at each vertical corner so that two edge guides 36 are arranged opposite each longitudinal end of the forming wedge-shaped body. A pair of edge guide bodies 36 are provided on each side of the wedge-shaped body.

  Molten glass flowing along the edges of the forming surface 22 to converge is interrupted by the web portion 40 along a diagonal intersection line 44 with the inclined forming surface 22. Both edge portions of the glass sheet flowing down are supported by the inclined molding surface first and then by the web portion 40 of the edge guide 36 so that they can be guided.

  The web portion 40 has a wetted length that is longer in the horizontal direction than the length obstructed by the forming surface 22 and effectively maximizes the width of the resulting glass ribbon that can be used. In addition, the web portion 40 widens or thins the glass flowing over it and reduces the thickness of both longitudinal edges of the molten glass stream before the molten glass stream leaves the bottom edge 46 of the web portion 40. .

  The linear width of the glass flowing over and in contact with the web portion 40 is the edge guide 36 along the bottom edge 24 inwardly of the ridge surface 38, as defined above. It is shown in FIG. The flow rate of this glass flow is shown in G pounds per hour of distance from the edge surface 38 to point C. Since there are generally four edge guides 36 and four web portions 40, G is schematically represented as an average value of the flow rate across all web portions 40.

  As described above, a glass substrate manufactured in a glass manufacturing system using the fusion method must have a certain thickness so as to be used in an apparatus such as a flat panel display. In order to ensure this, the inventors have studied and established a method for enhancing the function of the fusion method to produce such a glass substrate. In particular, the inventors have made it possible to influence the quality / characteristics of the glass substrate by managing the amount distribution of the molten glass 26 flowing on the forming apparatus 10. Accordingly, the subject of the present invention relates to the management of the flow rate of the molten glass 26 flowing over the forming apparatus 10.

It is known that an efficient fusion method results in a large area strip glass 34 having a constant thickness. It is also desirable that the width of the strip glass does not change during the pulling of the strip glass, that is, both edges of the strip glass remain stably. The ratio of the flow rate of the glass flowing over the top surface 52 of the web portion 40 (ie, along the distance d) to the cube L ³ of the height L of the forming surface 22 to converge, ie, G / L ³ is about 0.0017. More preferably about 0.002 lb / hr / inch ⁴ (1 lb is 0.45 kg) if kept above lb / hr / inch ⁴ (1 lb is 0.45 kg, 1 inch is 2.54 cm). The inventors have derived that edge stability can be obtained if 1 inch is maintained at 2.54 cm or more.

  The conditions outlined above are useful for establishing the stability of the edge (band glass width) in the fusion downdraw method, but do not affect the glass layer moving on the surface of the web. It should also be noted that the ability to keep the applied tension small is also beneficial. The force is an adhesive force that keeps the glass on the surface of the web and an applied force (gravity and pulling roller 35) that pulls the glass away from the edge guide (web portion). These forces can pull the glass sheet away from the edge guide and cause variations in sheet width. Therefore, it is desirable that the adhesive force is at least larger than the applied force and considerably larger than the applied force. Generally, the edge guide body is made of a heat-resistant metal such as platinum in order to withstand a high glass forming temperature (often exceeding 1000 ° C.). It has been found that the silicate glass used to make the display device is only slightly wetted with platinum, so that the glass is completely separated from the surface of the platinum. In addition, silicate glasses wet significantly with certain ceramic materials such as alumina or zircon. Therefore, it is effective to increase the adhesion by at least coating the noble metal (for example, platinum) web portion with at least a ceramic material such as alumina and / or zircon. Alternatively, the web portion may be an integral (eg monolithic) part of the forming wedge, in which case they are cast or machined as part of the forming wedge. In some cases, the web portion may be manufactured as an independent ceramic part and later attached to a forming wedge. The advantage of processing the web part as an integral or monolithic part of the forming wedge is that it avoids the use of expensive precious metals and can cause the glass wedge to converge and the forming surface to converge. It is to eliminate surface rupture. In some embodiments, the edge guide, in particular the web portion of the edge guide and / or the entire or part of the forming wedge, is incorporated herein by reference in its entirety, 2004 It can be made using any of the heat resistant materials as described in US Patent Application No. 60 / 640,686, filed December 30th. Specific examples of these materials include zircon, xenotime materials, xenotime and stabilized zircon materials, and xenotime and stabilized zircon materials, as defined and described in the above references. To which xenotime-like materials are added, or a mixture thereof.

Of course, it will be appreciated by those skilled in the art that any forming wedge with a stable edge flow (i.e., edge-to-edge width) will readily have the ability of a larger forming wedge according to the present invention. It will be obvious. That is, the future wedge-shaped body will be designed according to the following criteria. That means
G = G _ref (L / L _ref ) ³
Here, G is a flow rate that flows on the web portion of the molding wedge in the future, and L is the height of the molding surface on which the molding wedge in the future converges. G _ref and L _ref are the same parameters for current or existing molding wedges.

  It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention. Accordingly, the present invention is intended to cover modifications and variations of the present invention made within the scope of the appended claims and their equivalents.

The perspective view which made the cross section of a part of one embodiment of the present invention which shows the end of the device provided with the wedge-shaped object for forming for fusion drawing of beltlike glass 1 is an enlarged perspective view of the wedge-shaped body of FIG. 1 showing the edge guide and including the web portion of the edge guide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Molding device 12 Molding wedge 14 Groove 16 Wall 18 Overflow weir (upper edge)
20, 22 Molding surface portion 24 Bottom edge 26 Molten glass 28 Glass feed passage 30 Current limiting dam 32 Free surface of molten glass 34 Strip glass 35 Pulling roller 36 Edge guide body 38 Projection edge surface portion 40 Web portion 42, 44 Crossing Line 46 Bottom edge of web section

Claims (9)

A glass sheet forming apparatus,
A forming wedge (12), a pair of downwardly inclined forming surfaces (12) converging at the bottom edge (24) of the wedge and having a vertical height L inch above the bottom edge (24). 22) a molding wedge and an edge guide (36) extending along a vertical edge of said molding surface (22) and having a web (40), said web An edge guide adjacent to the molding surface (22) in order to block and thin the flow of G lb / hr / inch glass flowing over the web portion;
With
G / ^{L 3} 0.0017 lbs / hr / inch ⁴ (1 pound 0. 45 kg, 1 inch 2.54 cm) glass sheet forming apparatus characterized by greater than. G / ^{L 3} 0.002 lbs / hr / inch ⁴ (1 pound 0.45 kg, 1 inch 2.54 cm) glass sheet forming apparatus according to claim 1, wherein a greater than.   The apparatus of claim 1, wherein the surface of the web portion in contact with the glass stream is a ceramic material.   4. The apparatus of claim 3, wherein the web portion is in the form of a solid ceramic.   5. An apparatus according to claim 4, wherein said web portion is an integral part of said forming wedge.   4. The apparatus of claim 3, wherein the ceramic material is selected from the group consisting of zircon, alumina, xenotime materials, zenotime stabilized zircon materials, or combinations thereof.   4. An apparatus according to claim 3, wherein said web portion is made of a heat resistant material coated with ceramic. A method of forming a glass substrate,
Flowing molten glass over the forming wedge (12), the forming wedge (12) converging at the bottom edge of the wedge and the glass pull line (24) along the bottom edge; And a vertical height L inch between the traction line and a horizontal plane intersecting the top of the inclined molding surface portion. And an edge guide (36) with a web portion (40), said web portion being shaped to block and thin the G lb / hr / inch glass stream flowing over the web portion. A step adjacent to the surface portion (22) for use;
Having
G / L ³ is greater than 0.0017 lb / hr / inch ⁴ (1 lb is 0.45 kg, 1 inch is 2.54 cm). G / ^{L 3} 0.002 lbs / hr / inch ⁴ (1 pound 0.45 kg, 1 inch 2.54 cm) The method of claim 8, wherein greater than.

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