Patent Application
20130126576
The disclosure relates generally to the trimming of a flexible brittle substrate and more particularly to trimming the edge of a flexible brittle substrate for use in a continuous or a roll-to-roll process.
Flexible brittle substrates, such as substrates used in the manufacture of display devices, are normally processed in sheet form. Such processing can include, for example, the deposition of thin film electronics onto the substrate. Sheet form handling slows processing, since sheets must be individually transported, fixtured, processed and removed. While continuous processing of flexible brittle substrates in ribbon form promises to speed manufacturing, it brings with it new problems. For example, if a ribbon breaks, processing machinery is typically shut down, cleaned of debris and manually re-threaded with the ribbon, resulting in a loss of valuable time and raw materials. Further, the leading edge of the flexible brittle substrate where the break occurred is likely not in a condition to be immediately re-threaded after the break and would require further finishing.
Continuous processing of thin glass ribbon is a relatively new field. For example, the glass ribbon may have a thickness in a range from about 50 microns to about 200 microns. In other embodiments, the thickness is in a range of about 50 microns to about 300 microns. In processes typical to flat panel displays, silicon wafers, and other brittle materials, the product is typically handled in sheet form. The benefit for a thin glass substrate is that the flexibility afforded by the thin ribbon allows it to be used in processes utilizing rolls of the material. Although manufacturing processes for thin, flexible ribbon products are continuous, it is necessary to transport them in discrete form, typically on spools. One desirable feature for a continuous manufacturing line is the ability to slit the ribbon or web to dispose of edge anomalies. Embodiments described herein allow for the in-body initiation of a cut for thread up as well as the diversion of the quality portion of a ribbon of brittle material to downstream processing.
Accordingly, an apparatus for trimming a moving glass ribbon is disclosed comprising a quality portion and an edge portion adjacent to the quality portion, the apparatus comprising a support body for supporting the moving glass ribbon, the support body comprising an upper surface defining a plurality of orifices for emitting a gas. The emitted gas produces a gas layer between the upper surface of the support body and the glass ribbon that supports, or levitates, the glass ribbon over the upper surface, thereby preventing contact between the upper surface and the glass ribbon. The support body may comprise an arcuate upper surface, or in some embodiments only a portion of the upper surface may be arcuate.
The apparatus may further comprise a cutting device configured to separate the edge portion from the quality portion of the moving glass ribbon, the quality portion traveling along a first path after the separation. The first path may, for example, lead to further processing steps. The cutting device may comprise a first scoring device, a laser and a fluid nozzle configured to emit a cooling fluid. The first scoring device may, for example, comprise a roller including an abrasive material deposited on a surface thereof. Preferably, the abrasive material is deposited as a curved (e.g. helical) line on the surface of the roller. However, in some embodiments the abrasive material may be deposited on the surface of the roller in other configurations, such as in lines parallel with a rotational axis of the roller.
The apparatus may be further provided with a bypass apparatus configured to guide the edge portion that has been separated from the quality portion along a second path that is different from the first path, the edge portion remaining connected to the moving glass ribbon. That is, the edge portion, after being separated from the quality portion by the cutting device, comprises a free end removed from the quality portion of the glass ribbon, while another, opposite end of the edge portion remains attached to the glass ribbon. Relative movement between the separated edge portion and the quality portion may cause contact between the newly-formed edges thereof. This contact can damage the edge of the quality portion. Thus the free end of the glass ribbon follows a separate path from the quality portion it was separated from, and may be discarded, or collected for future use as cullet. In spite of the thinness of the glass ribbon in a direction perpendicular to the major surfaces of the glass ribbon, the “thickness” of the glass ribbon in a width-wise direction (perpendicular to a longitudinal axis of the glass ribbon) is the same as the width (a 10 cm wide glass ribbon has an edge-to-edge thickness of 10 cm), which makes in-plane bending of the ribbon, or portions thereof difficult if not impossible without fracturing the ribbon. However, the thinness of the ribbon (thickness or perpendicular distance between the major surfaces of the glass ribbon) allows the glass ribbon, or portions thereof, to be flexed or bent relatively easily in a direction out of the plane of the glass ribbon. Consequently, the second path taken by the edge portion is preferably a path that takes the edge portion out of the plane represented by the quality portion. As an example, if the first path followed by the quality portion is in a horizontal direction, the edge portion is redirected along a path that includes a direction above or below the plane of the quality portion (the edge portion is directed upward or downward, wherein the upward or downward second path is preferably an arcuate path having a bend radius insufficient to cause fracture of the edge portion).
The apparatus may further include a cross scoring device arranged to form a cross score in the quality portion in a direction perpendicular to a direction of travel of the quality portion as the quality portions travels along the first path, and a breaking apparatus configured to produce a tensile stress across the score. After the edge portions are separated from the quality portion of the glass ribbon and are being directed along a second path separate path from the first path of the quality portion, a scored is produced across at least a portion of a width of the quality portion. In one embodiment the cross scoring device comprises a swing arm, a motor coupled to a first end of the swing arm and a scoring element coupled to a second end of the swing arm, and wherein when the motor is activated the swing arm moves the scoring element through an arc perpendicular to the direction of travel. The scoring element contacts the glass ribbon at or near the top dead center of the arc and produces the cross score.
To provide for a relatively smooth, perpendicular leading free end to the moving quality portion, the apparatus preferably also includes a breaking apparatus for extending the cross score and removing a leading end of the quality portion. The breaking apparatus may comprise, for example, a plurality of bending rollers, each bending roller of the plurality of bending rollers having a longitudinal rotational axis, and wherein each of the longitudinal rotational axes is parallel with longitudinal rotational axes of the other bending rollers and perpendicular to the direction of travel of the quality portion. The longitudinal rotational axes of the bending rollers are preferably parallel with the cross score.
The apparatus may further comprise a platform for supporting the quality portion along the first path, the platform positioned downstream of the support body relative to the direction of travel of the moving glass ribbon (e.g. the quality portion) and comprising a plurality of orifices for emitting a gas that supports the glass ribbon. The platform may be movable. For example, the platform may be movable in an up or down direction, in a lateral, side direction or both such that the platform can be cleared from a position that interferes with movement or set up of the glass ribbon.
The apparatus may further be provided with a taping apparatus for applying a tape to an edge of the quality portion. The tape may rolled over and pressed to portions of the quality portion after the edge portions are separated so that the newly-formed edges of the quality portion are afforded mechanical protected. The tape may also provide a handling surface for further handling of the quality portion, and provide for winding of the quality portion on a spool without direct contact between the exposed glass surfaces of the quality portion when wound on the spool.
In another embodiment, a method for trimming a moving glass ribbon is described comprising a quality portion and an edge portion, the method comprising the steps of: supplying the moving glass ribbon to a trimming apparatus, the moving glass ribbon moving through the trimming apparatus along a first path; supporting the moving glass ribbon over a support body having an upper surface defining a plurality of orifices from which a gas is emitted that levitates the glass ribbon over the upper surface. The upper surface preferably comprises an arcuate portion. The moving glass ribbon may, in come cases, be supplied from a glass forming apparatus. The glass forming apparatus may be a fusion draw apparatus, a slot draw apparatus or a redraw apparatus. In other embodiments, the glass ribbon may be supplied from a supply spool.
Once the glass ribbon is supported by the support body, a crack is then formed in the moving glass ribbon, the crack propagating through a thickness of the moving glass ribbon in a direction opposite a direction of travel of the moving glass ribbon to separate the edge portion from the moving glass ribbon. The crack is spaced a predetermined distance from an edge of the moving glass ribbon. For example, the crack may be spaced at least about 2 cm from the nearest edge of the glass ribbon. However, the distance the crack may be spaced from the nearest edge depends on such factors as the width of the glass ribbon and the size of the bead contained by the edge portion. The edge portion is then diverted along a second path different from the first path as the crack propagates along a length of the glass ribbon, and wherein the edge portion remains attached to the glass ribbon as the as the edge portion is diverted. Preferably, the edge portion is not adjacent to the central quality region of the glass ribbon over substantially the entire length of the edge portion
Forming the crack may include forming a score spaced apart from the edge, intersecting the score with a laser beam to heat a region of the glass ribbon, contacting the heated region of the glass region with a cooling fluid that causes a crack to propagate and wherein the propagating crack does not intersect a leading edge of the glass ribbon.
The method may further comprise removing the leading edge by fracturing the glass ribbon, wherein the fracture intersects the propagating crack, thereby releasing a portion of the edge portion from the glass ribbon.
The method may further comprise forming a cross score in the glass ribbon that is perpendicular to the direction of travel of the moving glass ribbon.
The method may further comprise bending the glass ribbon to extend the cross score through the thickness of the moving glass ribbon.
In some embodiments the method may include applying an edge tape to a quality portion of the glass ribbon.
Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims.
The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment, and together with the description serve to explain principles and operation of the various embodiments.
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.
By their nature brittle materials are incapable of absorbing significant energy without damage, and most particularly fracture. However, if the brittle material is sufficiently thin, and a bending radius is sufficiently large, thin webs or ribbons of brittle material can be rolled, which provides the opportunity to process the ribbon in a so-called roll-to-roll process. In a typical roll-to-roll process, the material on one roll, the source roll, may be unwound, optionally passed through appropriate processing equipment, then rewound onto a take-up roll. Indeed, the roll-to-roll concept can be expanded to a manufacturing process for the material itself, wherein a production apparatus produces the ribbon of material in a continuous process, and the resulting ribbon is wound onto a receiving roll that becomes the source roll for subsequent processes. Alternatively, the ribbon may be further processed intermediate between the ribbon production and the receiving or take up roll. For the purposes of further discussion, this latter concept will be termed a manufacture-to-roll process, and more generically, processes that involve spooling of thin brittle webs or ribbons onto a roll will be termed roll processes.
One brittle material of particular interest is glass, such as glass suitable for use in display devices or other electronic devices. Such roll processes as described above can significantly increase the technical and economic advantages of glass substrates for uses such as flexible displays. For example, glass substrates are hermetic, and can provide protection for sensitive electronic and/or photonic devices that are susceptible to damage from exposure to oxygen and moisture, e.g. organic light emitting diodes, without the need for barrier layers deposited on the substrate. Thus, the ability to process glass substrates in ribbon form is an attractive alternative to piecemeal processing where individual glass sheets are handled one at a time. However, the processing of a ribbon of brittle material such as glass is complicated by not only the brittle nature of the material but artifacts of the initial manufacturing process.
Thin glass ribbons of high quality can be produced by several methods. For example, in a fusion process, a molten glass forming material is supplied to an open channel in a forming body. The molten glass forming material overflows the channel and flows over converging exterior forming surfaces of the forming body as separate flows. These separate flows rejoin at the base of the forming body where the forming surfaces converge to form a ribbon that descends from the bottom of the forming body. As the ribbon descends, the flow off the forming body and surface tension effects, among others, work to narrow the ribbon, resulting in thickened edges called beads. Other processes include the slot draw process, where the molten glass forming material is drawn from a slot at the bottom of a forming vessel, and the redraw process where a relatively thick glass plate is reheated to a softening temperature of the material. In the redraw process, the melted material pulls away from the original glass plate and thins as it flows downward from the plate. While the preceding exemplary processes illustrate different approaches to producing a thin ribbon of glass, they have in common the drawing of a viscous stream of material resulting in thickened regions or beads. Eventually these beads must be removed, either to facilitate roll processing itself, or to accommodate downstream processing or final product design.
Another challenge to roll processing of brittle materials, such as a glass ribbon, is the interruption caused if the ribbon breaks. That is, a fracture of the ribbon as the ribbon is moving likely results in a need to halt the process. For example, the take up spool may need to be replaced with a new spool, and at a minimum, the ribbon may require re-threading through the apparatus performing the processing. Moreover, the unpredictable break path more likely than not results in an irregular, if not jagged, free end that is more desirably “squared off” prior to restarting the process. Thus, finishing the free end may be necessary. This, and the preceding challenge being the case, it is desirable to perform such functions as trimming the beads and/or finishing the free end of the glass ribbon in-line as the process progresses.
Unlike the processing of a non-brittle web or ribbon of material, such as plastic film, where material removal can be initiated by simply starting a slit in the material as it travels below a blade, initiating bead removal on a ribbon of brittle material such as glass poses unique difficulties. Although bead removal is most easily initiated from an exposed edge of the ribbon, such as from the free or leading end of the ribbon, this is not always possible. For example, in the instance were the ribbon fails while traveling (in-process failure) the leading end of the ribbon will likely require finishing and re-threading. And, while the slit for bead removal can be initiated in-body (away from an edge) at any point along the ribbon, this leaves the ribbon and the removed bead attached downstream of the cutting process. It is possible to cross cut the beaded area and divert the new leading edges into a cullet chute for disposal, but the force of cutting the thickened bead may affect the quality of the slit upstream in the process. Consequently, it is desirable to cross cut the thin quality area of the glass ribbon and transport this leading edge onward to the next step of the process while diverting the beads. Accordingly, methods and apparatuses that can initiate in-body cutting of a glass ribbon are presented herein. Although the present description is written in the context of flexible glass ribbons, it is understood that these methods and apparatuses can be applied to other flexible brittle and such materials are included in the term flexible glass ribbon.
As used herein the term “edge” will refer to an outermost lateral position on the glass ribbon along a length of the ribbon, whereas “edge portion” will refer to a longitudinal strip of glass material along a length of the glass ribbon. The edge portion includes the bead referred to above. Thus, a ribbon of glass comprises two edge portions extending along a length of the glass ribbon, each edge portion having a predetermined width less than one half the width of the glass ribbon such that the edge portions bound an interior or central region of the glass ribbon referred to as the quality portion. It is the quality portion of the glass ribbon that may be provided to purchasers and should be protected from damaging contact.
Referring to
In the embodiment of
As best seen in
As noted above and in reference to
In operation, first scribing device 22 produces an initial flaw in the moving glass ribbon, wherein the initial flaw is preferably formed in the edge portion of the ribbon. Subsequently, this flaw is intersected by laser beam 42 originating from laser source 24 that heats a narrow path or region (represented by dashed line 44) of the glass ribbon that intersects the flaw. Laser source 24 is selected so that a wavelength of laser beam 42 produced by the laser source is absorbed by the glass ribbon. For example, a CO2 laser source is suitable for heating the glass ribbon when the glass ribbon is an aluminoborosilicate glass. Other glass compositions may require a laser source emitting at a different wavelength.
As best shown in the embodiment of
Abrasive material 48 may comprise, for example, an abrasive grit that is adhered to the surface of the roller and which abrasive grit extends above the surface of the roller. The one or more lines of abrasive material positioned on the surface of roller 46 produce a wide flaw region within the edge portion of the glass ribbon that reduces the precision alignment needed for the impinging laser beam. That is, as the glass ribbon 12 traverses apparatus 10, the glass ribbon may exhibit some side-to-side movement. If a single flaw was to be introduced, such as with a pointed scribe, precise positioning of the ribbon would be required to ensure laser beam 42 intersected the flaw. By introducing a region of flaws that extends in a width-wise direction across a portion of the glass ribbon width, the need for precise positioning of the laser beam in respect of the flaw or flaws is mitigated.
Next, the narrow heated region 44 of the glass ribbon produced by laser beam 42 is contacted with cooling fluid 50 issuing from fluid nozzle 26. The cooling fluid may be a liquid (e.g. water), a gas (e.g. air) or a mixture thereof. For example, cooling fluid 50 may be an air-water mist. The thermal stress induced into the glass ribbon along heated region 44 of the glass ribbon when quenched with the cooling fluid causes a crack 52 form at the initial flaw. Crack 52 propagates through the thickness of the glass ribbon and longitudinally along the glass ribbon substantially parallel with edge 54 of the ribbon, as illustrated in
By employing a pair of cutting devices 20, separation between both edge portions of the glass ribbon and the quality portion of the glass ribbon can be induced (as used herein separation should be construed to mean a crack that extends through the entire thickness of the glass ribbon). Advantageously, this separation can be induced without the need to originate the separation from an edge of the glass ribbon. Rather, the separation can be induced from an interior of the glass ribbon, spaced apart from an edge (i.e. in-body separation). In other words, a slit is formed in the body of the glass ribbon.
Returning to
As best seen with the aid of
To ensure a cut that is substantially perpendicular to the direction of motion of the glass ribbon (and substantially perpendicular to an edge of the glass ribbon), cross scoring device 30 may be used in conjunction with a breaking apparatus that produces a tensile stress in the glass ribbon by bending the glass ribbon perpendicular to the edges 54 of the glass ribbon. In one embodiment, best seen in
Removal of the edge portions from the glass ribbon may include spacing the edge portions apart from the remaining quality portion of the glass ribbon. Spacing the edge portions apart from the quality portion means more than simply separating an edge portion from the quality portion, but rather entails placing enough distance between the edge portion and the quality portion so as to prevent contact between the separated edge portion and the quality portion. This is, a length of the edge portion may be separated from the quality portion but may still be immediately adjacent to the quality region such that movement of the overall glass ribbon may cause the edge portion to contact or rub against the quality portion. Such contact can result in damage to the newly-formed edges of the quality portion that can in turn serve as the flaw source for subsequent undesirable, and indeed, unanticipated, breakage of the quality portion. It should be noted that although an edge portion is separated from the quality portion, during nominal operating conditions of apparatus 10 the edge portion is still attached to the quality portion at one end of the edge portion, a situation that will become clearer further below.
Accordingly, apparatus 10 further comprises a bypass mechanism 18 that redirects edge portions 55 of the glass ribbon so the edge portions are not adjacent to quality portion 70 of the glass ribbon over substantially the entire length of the edge portion. That is, while quality portion 70 positioned between edge portions 55 continues along a first path 72, edge portions 55 follow along a second path 74 different from the first path, while still being connected to the quality portion. One embodiment of a bypass mechanism is shown in
While the embodiment of apparatus 10 depicted in
In accordance with
After processing, the quality portion of the glass ribbon is wound onto take-up spool 36. As best shown in
Operation of apparatus 10 will now be described with the aid of
As free end 98 of glass ribbon 12 enters apparatus 10, the glass ribbon passes over support body 16, where gas exiting the plurality of orifices in the upper surface of the support body levitates the glass ribbon over the upper surface of the support body at a predetermined fly height. Free end 98 of the glass ribbon passes under first scribing device 22 and first scribing device 22 is lowered so that abrasive material 48 disposed on roller 46 forms a plurality of flaws on the edge portions 55 of the glass ribbon.
Referring now to
As glass ribbon continues to move forward through apparatus 10, platform 28 can be lowered, allowing free end 98 of the glass ribbon to fall downward and be received into a chopping mechanism (not shown) that removes glass from the free end of the ribbon and which waste glass may be collected in waste receptacle 100 (see
Next, because the chopping device can produce a rather ragged leading end, a square free end of the quality portion is formed. Turning to
In another embodiment, the glass ribbon may be supplied directly to apparatus 10 from a glass ribbon drawing apparatus rather than a supply spool. An exemplary fusion downdraw apparatus comprises a forming body having a channel formed in an upper surface thereof. The channel is supplied with a molten glass from a glass melting apparatus, wherein the molten glass overflows the channel and flows over converging forming surfaces as separate streams of molten glass. The separate streams join where the converging forming surfaces meet to form a glass ribbon that is drawn downward by gravity and pulling rollers positioned below the forming body. As the glass ribbon descends it transforms from a viscous liquid to a solid elastic material. The glass ribbon descending from the forming body may be supplied to apparatus 10 in a continuous process.
A slot draw process differs from a fusion downdraw process in that the molten glass is delivered to a reservoir comprising a slot in a lower surface thereof, wherein the molten glass descends through the slot as a glass ribbon that is pulled downward by gravity and pulling rolls.
In a redraw process, an edge of a glass sheet is reheated in a furnace, wherein the reheated glass edge exceeds the softening point of the glass and descends from the glass sheet. The descending glass is pulled downward by gravity and pulling rolls that thin the glass into a thin glass ribbon.
As each of the fusion, slot and redraw processes are well known, no further description is required or provided.
It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and their equivalents.
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 61/561,484 filed on Nov. 18, 2011 the content of which is relied upon and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61561484 | Nov 2011 | US |
