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This invention is directed to a thin glass substrate comprising a web portion extending beyond at least one of the edges of the glass substrate to facilitate handling and/or conveying and/or positioning the substrate.
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Thin glass substrates can be used in a variety of applications, including so-called “e-paper” and touch sensors. The glass for such substrates can be quite thin, typically less than about 0.3 mm. The processing of the substrates can be performed on an individual glass sheet basis, or most efficiently by conveying the substrate as a long glass ribbon wound on a roll. The method includes dispensing the ribbon from one roll, processing the dispensed portion, then winding the ribbon onto a take-up roll.
One drawback to a so-called “roll-to-roll” process is the fragility of the thin glass ribbon—mechanical contact of the ribbon during handling can lead to damage, including scratches, chipping and in the worst case, fracture. What is needed is a glass substrate, in either sheet or ribbon form, that can be safely handled without damaging the glass.
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A glass substrate is described that includes a coating material disposed thereon that extends from at least one edge of the substrate as a web portion that facilitates handing and/or conveying of the substrate without damage. The web portion of this handling coating is preferably flexible, and can be used to hold and/or convey and/or align the glass substrate for processing in a manufacturing step without the need to directly contact interior non-coated portions of the substrate. A method for holding, conveying and/or aligning the glass ribbon is also described.
In one embodiment, a glass substrate is described comprising first and second major surfaces and first and second edges, the first and second edges separated by a width W. The first and second edges are preferably substantially parallel with each other. The glass substrate includes a flexible coating disposed over at least a portion of the first and second major surfaces, and the coating comprises web portions extending from at least one of the first or second edge a distance of at least 1 mm.
The glass substrate may be in the form of a glass ribbon, or an individual glass sheet and preferably has a thickness equal to or less than 0.3 mm. The coating also comprises a web portion extending from the first edge of the glass substrate a distance of at least 1 mm and a web portion extending from the second edge a distance of at least 1 mm. The flexible coating may coat only a portion of either or both of the first and second major surfaces, or the flexible coating may extend across the entire width W of the glass substrate on either one or the other, or both of the major surfaces of the substrate.
The web portion extending from the at least one of the first or second edge of the glass substrate may comprise perforations for engaging with a sprocket or other toothed member. The toothed member may instead be a track that engages with the web portion.
A surface of the flexible coating that coats at least a portion of the first major surface of the glass substrate may include a non-planar shape complimentary to a non-planar shape of a surface of the flexible coating that coats at least a portion of the second major surface. For example, an upper portion of the coating on one side of a layer of glass may have a shape that is complimentary to the lower portion of the coating on another, adjacent layer of glass that aligns the glass layers, and preferably prevents the glass of one layer from contacting the glass of another adjacent layer.
The flexible coating may be adhered to the first and/or second major surfaces with an adhesive disposed between the coating and the glass substrate. The coating may further comprise strengthening members, such as fibers.
The web and non-web portions of the coating may include registration markings to aid in alignment or positioning of the glass substrate. In some embodiments, one or both of the first and second major surfaces of the glass substrate may include one or more layers of a laminating or deposited material. For example, the glass substrate may be coated with another material prior to the application of the web coating material. The other material may be a laminating material such as a barrier layer to prevent leaching of the glass. Additionally, after the application of the web and non-web portions of the handling coating, additional materials may be formed on the substrate, such as, for example, electrically functional materials that may comprise an electronic device (e.g. a semiconductor device). As used herein, an electrically functional device includes organic or inorganic semiconductor and/or conductor materials.
In another embodiment, a glass ribbon is described comprising first and second major surfaces and first and second edges and a polymer coating disposed over the first and second major surfaces and extending beyond the first and second edges a distance of at least 1 mm to form flexible web portions. The flexible web portions may comprise perforations that can be used to engage with teeth in a roller (sprocket) or a track. The flexible web portion(s) or non-web portions of the coating may comprise registration markings such as lines or symbols for aligning the glass ribbon.
In still another embodiment, a method of conveying a glass ribbon is disclosed comprising dispensing a length of a glass ribbon from a first spool, the glass ribbon comprising a coating including a web portion extending from an edge of the ribbon at least 1 mm, engaging the web portion with a feed apparatus to convey the ribbon, the feed apparatus comprising a roller or track for engaging with the web portion, and collecting the dispensed ribbon by winding the dispensed ribbon onto a take-up spool. The web portion may comprise perforations, for engaging with the feed apparatus. For example, the feed apparatus may comprise sprockets, wherein the teeth of the sprocket engage with the perforations to transport the glass ribbon. However, the feed apparatus is not limited to sprockets, but may further include rollers or tracks for engaging with the web portion. In another example, pinch rollers may be used to engage with the web and/or non-web portion of the handling coating.
In some embodiments, the coating may include registration indicia, and the method further comprises detecting the indicia and positioning the ribbon in response to the detected indicia. The detecting can be performed by any suitable machine vision system as is known in the art for performing such tasks. If the glass ribbon is to be used for the manufacturing of electronic devices, the method may further comprise depositing an electrically functional material on at least a portion of the dispensed length prior to the collecting. For example, the glass ribbon is rolled off a first spool, the desired components are deposited on ribbon, and then the ribbon is collected by rolling the ribbon onto a second spool. The web portions may be removed from the ribbon after the depositing, leaving the interior portions of the ribbon undamaged.
The invention will be understood more easily and other objects, characteristics, details and advantages thereof will become more clearly apparent in the course of the following explanatory description, which is given, without in any way implying a limitation, with reference to the attached Figures. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
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FIG. 1 a perspective view of a “roll-to-roll” process for conveying a glass ribbon.
FIG. 2A-2B are cross sectional views of a glass substrate (glass sheet or glass ribbon) comprising a coating that includes a web portion along an edge of the substrate.
FIGS. 3A-3B are cross sectional views of a glass substrate (glass sheet or glass ribbon) comprising a coatings that includes web portions along two edges of the substrate.
FIG. 4 depicts a cross sectional view of a glass substrate fully encapsulated by a coating that comprises two web portions along two edges of the substrate.
FIG. 5 is a cross sectional view of a stack (or roll) of glass sheets (or a rolled ribbon of glass) illustrating the formation of a gap between the layers that prevents contact between the glass layers.
FIG. 6 is a cross sectional view of a stack (or roll) of glass sheets (or a rolled ribbon of glass) illustrating complimentary features in the upper and lower surfaces of the coating that facilitate mating and alignment of the layers.
FIG. 7 is a top view of a portion of a glass substrate comprising a coating that includes web portions, wherein the web portions comprise perforations and indicia markings.
FIG. 8 is a side view showing sprockets being used to convey a glass substrate comprising a coating with web portions, wherein teeth of the sprocket engage with perforations in the web portions.
FIG. 9 is a cross sectional view of a glass substrate being conveyed by pinch rollers that engage web portions of the coating.
FIG. 10 is a side view of a glass ribbon being conveyed by tractor assemblies that engage with the web portions of a coating on the ribbon, including a payoff roll and a take up roll.
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In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.
While glass is known as a brittle material, inflexible and prone to scratching, chipping and fracture, in glass having a thin cross section can in fact be quite flexible. One need only consider the flexibility of hair-thin strands of optical fiber. Similarly, in thin sheets or ribbons, glass can be wound and un-wound from rolls, much like paper or plastic film. However, even though glass can be made flexible, it retains its brittle characteristic, and can be damaged by contact. For certain applications, particularly those for which visual defects can be distracting (e.g. display applications), even minor, seemingly cosmetic defects are unacceptable. For other applications requiring high mechanical strength, defects even less than 1 um can limit the mechanical reliability of the glass article. Thus, handling of the sheets in a manufacturing process, for example the depositing of thin film devices on the sheet, can become a source of loss and high cost.
Although glass can be processed on an individual sheet basis, a method contemplated herein, a more efficient method involves starting with a thin ribbon of glass wound on a roll as illustrated in FIG. 1. As glass ribbon 10 is un-wound from the roll 12, the un-wound or dispensed portion 14 can be processed, and then re-wound on a second “take-up” roll 16. In this context, the term “processed” can include any step subsequent to the formation of the glass, including but not limited to grinding, polishing, cleaning, or the deposition of additional layers and/or components (e.g. electrical/electronic components or portions thereof) on the glass. However, in some instances, the transport of the glass ribbon through the processing equipment can require precise positioning of the ribbon. For example, the formation of thin film devices (e.g. transistors, electroluminescent layers, etc.) on the glass substrate may require the ribbon to position, or index, between multiple stations or equipment placement, and require exacting registration from position to position. Performing this form of conveyance on a ribbon of glass less than 0.3 mm or less than 0.1 mm or less than 0.05 mm in thickness is difficult enough. Once the devices are formed, there is the problem of stacking or re-winding the ribbon for later use, perhaps in a subsequent manufacturing process, without damage to glass ribbon or the devices formed on one or both surfaces of the ribbon.