Patent Application
20120255672
1. Field
The present specification generally relates to the manufacture of glass substrates and, more specifically, to methods and apparatuses for applying a handling tab to an edge of a glass substrate.
2. Technical Background
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 roller. The method includes dispensing the ribbon from one roller, processing the dispensed portion, and then winding the ribbon onto a take-up roller.
One drawback to a so-called “roller-to-roller” 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 are alternative methods and apparatuses as for applying handling tabs to edges of a glass substrates, in either sheet or ribbon form, such that the glass substrates can be handled without damage to the glass.
The embodiments described herein relate to methods of applying a handling tab to a glass substrate to mitigate damage to the glass substrate during handling. The handling tab also maintains the integrity of the glass substrate in the event that the glass substrate is fractured from edge to edge during conveyance (i.e., the handling tab holds the broken substrate together). Also disclosed are apparatuses for folding an adhesive tape ribbon onto a glass substrate to form a handling tab which may be used to mitigate damage to the glass substrate during handling.
According to one embodiment, a method for forming a glass substrate with a handling tab to mitigate damage to the glass substrate during handling is disclosed. The handling tab may include conveying a glass substrate in a conveyance direction. The glass substrate has a first major surface opposed to a second major surface. The first major surface and the second major surface extending between a first lateral edge and a second lateral edge. An adhesive tape ribbon may be positioned adjacent to the first lateral edge of the glass substrate such that an adhesive surface of the adhesive tape ribbon is spaced apart from the first lateral edge of the glass substrate and the adhesive surface is substantially perpendicular to the first surface and the second surface. The adhesive tape ribbon may be folded such that at least a portion of the glass substrate is positioned between the adhesive surface of a first portion of the adhesive tape ribbon and the adhesive surface of a second portion of the adhesive tape ribbon, and the adhesive surface of a third portion of the adhesive tape ribbon disposed between the first portion and the second portion is spaced apart from the first lateral edge of the glass substrate. The third portion of the adhesive tape ribbon may form a handling tab extending beyond the first lateral edge of the glass substrate.
In another embodiment, a method for forming a glass substrate with a handling tab to mitigate damage to the glass substrate during handling is disclosed. In this embodiment, the method may include conveying the glass substrate in a conveyance direction. An adhesive tape ribbon may be positioned adjacent to a lateral edge of the glass substrate such that an adhesive surface of the adhesive tape ribbon is spaced apart from a lateral edge of the glass substrate and the adhesive surface is substantially perpendicular to a first major surface of the glass substrate. Thereafter, the adhesive tape ribbon and the glass substrate may be directed through a folding plow such that, after exiting the folding plow, at least a portion of the glass substrate is positioned between the adhesive surface of a first portion of the adhesive tape ribbon and the adhesive surface of a second portion of the adhesive tape ribbon, and a third portion of the adhesive tape ribbon disposed between the first portion and the second portion forms a handling tab extending beyond the edge of the glass substrate. The glass substrate may then be directed between a first pair of pinch rollers such that the first pair of pinch rollers laminate the first portion of the adhesive tape ribbon against the first major surface of the glass substrate and laminate the second portion of the adhesive tape ribbon against a second major surface of the glass substrate.
In yet another embodiment, an apparatus for folding an adhesive tape ribbon into a handling tab on an edge of a glass substrate to mitigate damage to the glass substrate during handling is disclosed. The apparatus may include an upstream end and a downstream end with a glass conveyance pathway extending in a conveyance direction from the upstream end to the downstream end. The apparatus may also include an unwinding spindle having a spindle axis of rotation that is substantially perpendicular to the glass conveyance direction, the unwinding spindle supporting a wound adhesive tape ribbon. The apparatus may also include a folding plow for folding the adhesive tape ribbon onto the glass substrate drawn on the glass conveyance pathway. The folding plow may include a first wedge and a second wedge positioned such that the glass conveyance pathway is disposed between a contact surface of the first wedge and a contact surface of the second wedge. The apparatus may further comprise a first pair of pinch rollers for laminating the adhesive tape ribbon to the glass substrate drawn on the glass conveyance pathway. The first pair of pinch rollers may be positioned downstream of the folding plow and include a first pinch roller and a second pinch roller positioned such that the glass conveyance pathway is disposed between the first pinch roller and the second pinch roller, the first pinch roller and the second pinch roller having axes of rotation substantially perpendicular to the glass conveyance direction.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.
Reference will now be made in detail to embodiments of methods and apparatuses for forming a handling tab on an edge of a glass substrate such that the glass substrates can be handled without damage.
While glass is known as a brittle material, inflexible and prone to scratching, chipping, and fracture, 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 spools, 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 μm 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 substrates can be processed on an individual sheet basis, a more efficient method involves starting with a glass substrate of significant length which is wound on a spool. The glass substrate (in this case a “continuous” glass substrate) can be unwound from the spool, processed, and then re-wound on a second spool. In this context, the term “processed” can include any step subsequent to the formation of the glass, including but not limited to segmenting, 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 and require exacting registration from station to station. Performing this form of conveyance on a glass substrate less than 0.3 mm or less than 0.1 mm or even 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 the glass ribbon or the devices formed on one or both surfaces of the ribbon. The aforementioned difficulties can be mitigated by forming a handling tab on an edge or edges of the glass substrate.
Referring to
The handling tab 174 is formed from an adhesive tape ribbon 160, such as the adhesive tape ribbon illustrated in
The adhesive tape ribbon 160 generally has an adhesive surface 168 which includes an adhesive suitable for bonding the adhesive tape ribbon 160 to a glass substrate. In some embodiments, the adhesive tape ribbon 160 may be formed with perforations 170 which extend along the axial length of the adhesive tape ribbon 160. The perforations 170 facilitate folding the adhesive tape ribbon on a predetermined fold line (i.e., a fold line defined by the perforations 170). In some embodiments, the perforations 170 are centered between the edges of the adhesive tape ribbon 160 and generally extend along the entire axial length of the adhesive tape ribbon. However, it should be understood that the perforations 170 may be formed at other locations between the edges of the adhesive tape ribbon 160 depending on the specific requirements of the application.
The adhesive tape ribbon 160 can optionally include other features. For example, in the embodiment of the adhesive tape ribbon 160 depicted in
In some embodiments, the adhesive tape ribbon can include a strengthening member to provide increased strength to the ribbon. For example, a preformed tape may include glass or polymer fibers (e.g., Kevlar® fibers) which provide additional strength to the coating material.
In one embodiment, the adhesive tape ribbon is Kapton® tape with an acrylic adhesive with a total thickness preferably in the range between about 50 μm and 100 μm (e.g., 63.5 microns). The Kapton® tape facilitates processing of the glass substrate at temperatures as high as 300° C.
Referring again to
Referring now to
The folding operation proceeds until the adhesive surface 168 of the first portion 162 of the adhesive tape ribbon 160 contacts and is adhesively bonded to the first major surface 192 of the glass substrate 190 and the second portion 164 of the adhesive tape ribbon 160 contacts and is adhesively bonded to the second major surface 194 of the glass substrate 190, as shown in
In one embodiment, after the handling tab 172 is formed on the glass substrate 190, the first portion 162 of the adhesive tape ribbon 160 is laminated against the first major surface 192 of the glass substrate and the second portion 164 is laminated against the second major surface 194 of the glass substrate 190. The laminating process is performed by pressing the adhesive tape ribbon 160 against the major surfaces of the glass substrate 190, such as with a roller or similar device, in order to remove any creases or air bubbles formed between the adhesive tape ribbon 160 and the glass substrate 190 and to firmly bond the adhesive of the adhesive tape ribbon 160 to the major surfaces of the glass substrate 190. In one embodiment, the first portion 162 of the adhesive tape ribbon 160 and the second portion 164 of the adhesive tape ribbon 160 are simultaneously laminated with a pair of opposed pinch rollers, as will be described in more detail herein. As noted hereinabove, the glass substrate 190 may be brittle and subject to damage. Accordingly, the rollers used to laminate the adhesive tape ribbon 160 to the glass substrate 190 may be coated with a compliant material such that the contact surfaces of the rollers are compliant and the glass substrate is cushioned between the pinch rollers.
In another embodiment, after the handling tab 172 is formed on the glass substrate 190, the handling tab 172 is compressed to laminate the handling tab 172. The handling tab 172 may be compressed between a pair of opposed pinch rollers which remove any creases or air bubbles formed in the handling tab 172 and force the adhesive surfaces of the adhesive tape ribbon 160 together.
Referring now to
The folding apparatus 100 generally comprises an unwinding spindle 104, a folding plow 116, and a first pair of pinch rollers 112. In the embodiment of the folding apparatus 100 shown in
Still referring to
In the embodiment of the folding apparatus 100 depicted in
While
Referring now to
Referring to
In general, the spacing between the first contact surface 124 and the second contact surface 126 at the outlet end of the folding plow 116 is slightly larger than the sum of the thickness of the glass substrate and twice the thickness of the tape such that the glass substrate with the tape adhered to its first and second major surfaces can pass between the first wedge 128 and the second wedge 130 without binding.
Referring again to
In the embodiments described herein, the contact surfaces of the first pinch roller 112a and the second pinch roller 112b are coated with a layer of compliant material 122, such as rubber or another, similar material, to prevent the first pinch roller 112a and/or the second pinch roller 112b from damaging the surface of the glass substrate 190. For example, in one embodiment, the compliant surface 122 may have a durometer of 25 on the shore A scale (as measured according to ASTM standard D2240) such that the compliant material is firm enough to laminate the adhesive tape ribbon onto the surfaces of the glass substrate 190 and resilient enough to avoid damaging the glass substrate.
Referring again to
The folding apparatus 100 has heretofore been described as comprising a folding plow 116, a first pair of pinch rollers 112 and, optionally, a second pair of pinch rollers 114 in order to fold an adhesive tape ribbon to one edge 196 of a glass substrate 190 thereby forming a handling tab 176. However, it should be understood that an additional folding plow and one or more additional pairs of pinch rollers may be incorporated in the apparatus in order to fold an adhesive tape ribbon on to the opposing edge 198 of the glass substrate 190. Accordingly, it should be understood that the folding apparatus 100 may be utilized to form a handling tab on both edges of a glass substrate.
Referring again to
Referring now to FIGS. 7 and 9A-9C, the folding apparatus 100 may be used to form a handling tab 172 which extends beyond an edge 196 of the glass substrate 190. The glass substrate 190 is first conveyed in a conveyance direction 136 into an upstream end 132 of the folding apparatus 100 and conveyed on a glass conveyance pathway through the folding apparatus 100. As the glass substrate 190 is conveyed through the folding apparatus 100, an adhesive tape ribbon 160 is unwound from the unwinding spindle 104 and drawn in the conveyance direction 136. As the adhesive tape ribbon 160 is drawn in the conveyance direction 136, the adhesive tape ribbon 160 is positioned adjacent to a lateral edge 196 of the glass substrate 190 such that an adhesive surface 168 of the adhesive tape ribbon 160 faces and is spaced apart from the lateral edge 196 of the glass substrate 190 and the adhesive tape ribbon 160 is substantially perpendicular to the first major surface 192 of the glass substrate 190.
Thereafter, the adhesive tape ribbon 160 and the glass substrate 190 are directed through the folding plow 116. The folding plow 116 folds the adhesive tape ribbon 160 onto the glass substrate 190 such that, after the adhesive tape ribbon 160 and the glass substrate 190 exit the folding plow 116, at least a portion of the glass substrate 190 is positioned between the adhesive surface of a first portion of the adhesive tape ribbon 160 and the adhesive surface of a second portion of the adhesive tape ribbon 160, and a third portion of the adhesive tape ribbon 160 disposed between the first portion and the second portion forms a handling tab 172 extending beyond the edge 196 of the glass substrate 190, as described above.
Specifically, referring to
After the first portion 162 and the second portion 164 are folded onto the glass substrate 190, the glass substrate 190 with the applied adhesive tape ribbon 160 is directed through the first pair of pinch rollers 112. In the embodiments described herein, the first pinch roller 112a and the second pinch roller 112b are positioned relative to the glass substrate such that both the glass substrate 190 and the first portion 162 and the second portion 164 of the adhesive tape ribbon 160 are impinged between the compliant surfaces 122 of the pinch rollers. However, in other embodiments, the first pinch roller 112a and the second pinch roller 112b may be sized and configures such that the handling tab 174 is also impinged between the pinch rollers. As the glass substrate 190 passes through the first pair of pinch rollers 112, the first portion 162 and the second portion 164 of the adhesive tape ribbon 160 are laminated on to the first major surface 192 and the second major surface 194 of the glass substrate 190, respectively, while any air pockets and/or creases in the adhesive tape ribbon are pressed out by contact with the pinch rollers. Moreover, the compliant surface 122 of the pinch rollers 112a, 112b prevents the glass substrate 190 from being damaged as it passes through the pinch rollers.
In some embodiments, the handling tab 174 formed during the folding operation may be passed between a second set of pinch rollers 114 to laminate the adhesive surfaces of the handling table 174 to one another as well as to remove any creases and/or air pockets which may have formed in the handling tab 174 during the folding process. As shown in
Referring now to
The delivery vessel 225 supplies the molten glass 226 through a downcomer 230 into the FDM 241. The FDM 241 comprises an inlet 232, a forming vessel 235, and a pull roller assembly 240. As shown in
As the continuous glass substrate 190 exits the pull roll assembly 240, the molten glass solidifies. In one embodiment, after the molten glass solidifies and cools, the glass ribbon may be directed into a cutting device, such as a laser cutting device 250, which removes edge beads 252 formed on the glass substrate 190 during the formation process by laser separation. However, it should be understood that this step is optional and that in other embodiments (not shown) the edge beads 252 may be left in place on the glass substrate 190.
The glass substrate 190 is then directed into the folding apparatus where an adhesive tape ribbon may be applied to an edge 196 or edges 196, 198 of the glass substrate (with our without edge beads 252) as described hereinabove. Upon exiting the folding apparatus, handling tabs 174 may be formed on the lateral edges of the glass substrate to facilitate handling the glass substrate during downstream processing operations.
Accordingly, it should now be understood that a method for forming a handling tab on the edge of a glass substrate may include the initial step of forming the glass substrate by heating a batch of glass precursor materials to form molten glass and drawing the molten glass into a glass substrate with a fusion draw machine. Thereafter, an adhesive tape ribbon may be applied to an edge or edges of the glass substrate to form a handling tab according to the methods described herein. In one exemplary embodiment, the adhesive tape ribbon may be formed on an edge or edges of the glass substrate utilizing the folding apparatus depicted in
Further, while
It should now be understood that the methods and apparatuses described herein may be utilized to fold an adhesive tape ribbon on to an edge of a glass substrate to form a handling tab. The handling tab facilitates handling the glass substrate during downstream processing operations without contacting the quality areas (i.e., the central portions of the glass substrate between the lateral edges) of the glass substrate which could create flaws or other defects resulting in the glass substrate being discarded. More specifically, the adhesive tape ribbon holds the glass substrate together even when the glass substrate completely separates between the lateral edges thereby eliminating the need to “re-thread” the glass substrate during production processing after a break occurs. This mitigates production stoppages and maximizes production efficiencies. Moreover, formation of the handling tab from an adhesive tape ribbon facilitates maintaining the continuity of the glass substrate even when the glass substrate fractures. The handling tab also facilitates stacking or rolling a glass substrate such that the quality surfaces of adjacent substrates do not contact one another and cause damage. More specifically, as the glass substrates are wound or stacked, the portions of the adhesive tape ribbon on the surfaces create a buffer between adjacent surfaces with the glass substrates in either a roll or stack.
As described herein, the handling tab is formed by folding a single piece of adhesive tape ribbon onto a glass substrate, as opposed to separate pieces of adhesive tape ribbon being applied individually to the first and second major surfaces of the glass substrate and joined to form the handling tab. Accordingly, because only a single piece of adhesive tape ribbon is utilized, it is not necessary to precisely register a first piece of adhesive tape ribbon with a second piece of adhesive tape ribbon or to trim the handling tab to ensure that no exposed areas of adhesive are present following formation of the handling tab. Exposed areas of adhesive may cause the glass substrate to stick to itself or to pieces of processing equipment causing the glass substrate to fracture. Moreover, exposed areas of adhesive could attract debris which could potentially damage the glass substrate. Accordingly, use of a single piece of adhesive ribbon mitigates such risks.
It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.
