Patent Application
20110236631
This application claims the benefit of European Application No. 09305911.1, filed on Sep. 29, 2009. The content of this document and the entire disclosure of publications, patents, and patent documents mentioned herein are incorporated by reference.
The present invention relates to a glass manufacturing system, a roll apparatus and a method for manufacturing a textured glass sheet by using one or more porous textured rolls under a vacuum.
Texturing of glass sheets has been of interest lately in several applications because textured glass sheets can help to improve or modify some characteristics of a product. For instance, in a photovoltaic application, a textured glass sheet is a potential lever to increase the efficiency and optical properties of photovoltaic devices. In a similar way, a textured glass sheet could help optimize light extraction from organic light emitting diode (OLED) lighting devices. The textured glass sheet can have anyone of a variety of textured patterns such as, for example, spherical portions, grooves, prismatic shapes or random shapes. However, when considering the texturing phase during the glass sheet forming process, some textured geometries become more difficult to achieve than other textured geometries. For instance, sub-millimeter textured shapes (<1 mm textured shapes) like prismatic shapes can be difficult to achieve because their edges need to be as sharp as possible in the glass sheet. A discussion is provided next to explain why it is difficult for conventional processes to successfully manufacture a textured glass sheet.
Referring to
In addition, this rolling process has some limitations in terms of shape and size of the textured patterns 102 relative to the thickness of the sheet 104. The driver to force the glass sheet 104 to replicate the textured pattern 102 is the pressure applied to the glass sheet 104 by the two rolls 106 and 108. To obtain the appropriate texturing, one has to find a compromise between the sufficient pressure to apply on the glass sheet 104 and the viscosity of the glass sheet 104. If the glass sheet 104 is too fluid, then the shear stress caused by the textured roll 106 is dissipated into a thin layer of the glass sheet 104 such that the texture patterns 102 are not fully replicated, especially for the deepest parts of the texture patterns 102. If the glass sheet 104 is too viscous, then the pressure becomes too small to impose the textured pattern 102 onto the glass sheet 104. This is a common problem since to prevent the glass sheet 104 from sticking to the rolls 106 and 108, the temperature of the rolls 106 and 108 needs to be maintained well below the temperature of the glass sheet 104. The temperature difference results in the glass sheet 104 having a very high viscosity at the interface with the textured roll 106 which limits the ability to form fine, accurate textured patterns 102.
Vacuum-assisted re-forming is another process that can be used to texture a glass sheet, but in this case, the suction which is applied on the glass sheet is created by using discrete orifices dispersed on a surface of a non-porous mold. The vacuum process allows the forming of large-scale shapes on the glass sheet, but it cannot form sub-millimeter texture patterns (<1 mm textured patterns) on the glass sheet. This limitation comes from the fact that the number of orifices within the non-porous mold needs to be limited, which makes it difficult if not impossible to apply a global suction on the whole surface of the glass sheet. In addition, to prevent the glass sheet from sticking to the non-porous mold (metal non-porous mold), the glass sheet needs to be kept at a relatively high viscosity. This limits the possibility to apply large deformations, which are required when forming sub-millimeter textured features into the glass sheet. Accordingly, it would be desirable to be able to manufacture a textured glass sheet which has one side with well-defined textured patterns (e.g., well-defined sub-millimeter textured patterns) and another side with a pristine surface.
A method and a roll apparatus are described in the independent claims of the present application. Advantageous embodiments are described in the dependent claims.
In one aspect, a method is described herein for manufacturing a textured glass sheet. The method includes the steps of: (a) delivering a glass ribbon to a porous textured roll having at least one orifice located therein and below an outer surface thereof, where the porous textured roll receives the glass ribbon on a portion of the outer surface while the glass ribbon is viscous; and (b) applying at least a partial vacuum to the at least one orifice within the porous textured roll to create a first pressure (P1) at an interface between a first side of the glass ribbon and the outer surface of the porous textured roll, where the first pressure is less than a second pressure (P2) on a second side of the glass ribbon such that the difference between the first pressure and the second pressure drives the first side of the glass ribbon towards the outer surface of the porous textured roll to at least substantially replicate a textured pattern on the outer surface of the porous textured roll to form the textured glass sheet.
In another aspect, a roll apparatus is described herein which textures a glass ribbon provided by a fusion forming apparatus. The roll apparatus includes: (i) a porous textured roll which has at least one orifice located therein and below an outer surface thereof, where the porous textured roll is positioned to receive the glass ribbon on a portion of the outer surface while the glass ribbon is viscous and moving in a substantially downward direction from the forming apparatus; and (ii) a vacuum pumping device adapted to apply at least a partial vacuum to the at least one orifice within the porous textured roll to create a first pressure at an interface between a first side of the glass ribbon and the outer surface of the porous textured roll, where the first pressure is less than a second pressure on a second side of the glass ribbon such that the difference between the first pressure and the second pressure drives the first side of the glass ribbon towards the outer surface of the porous textured roll to substantially replicate a textured pattern on the outer surface of the porous textured roll to form the textured glass sheet.
Additional aspects of the present solution will be set forth, in part, in the detailed description, figures and any claims which follow, and in part will be derived from the detailed description, or can be learned by practice of the present solution. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present solution as disclosed.
A more complete understanding of the present solution may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:
Referring to
The melting vessel 210 is where glass batch materials are introduced as shown by arrow 209 and melted to form molten glass 226. The fining vessel 215 (e.g., finer tube 215) has a high temperature processing area that receives the molten glass 226 (not shown at this point) via a refractory tube 213 from the melting vessel 210 and in which bubbles are removed from the molten glass 226. The fining vessel 215 is connected to the mixing vessel 220 (e.g., stir chamber 220) by a finer to stir chamber connecting tube 222. The mixing vessel 220 is connected to the delivery vessel 225 by a stir chamber to bowl connecting tube 227. The delivery vessel 225 delivers the molten glass 226 through a downcomer 229 to an inlet 232 and into the isopipe 212 (see
The glass ribbon 241 is subsequently rolled and textured by a porous textured roll 250 and then drawn downward by pulling rolls 264a and 264b (optional) which may be part of the roll assembly 202 to form the textured glass sheet 205 (see
Referring to
The closed controlled environment 230 if used would normally be located below the isopipe 212 (or any other forming apparatus) and would function to heat in a controlled manner the glass ribbon 241 and the subsequent textured glass sheet 205. The controlled environment 230 can have one or more devices 402 that control the heating of the glass ribbon 241 and the textured glass sheet 205 by using forced convection, or an array of heating elements etc. For example, the controlled environment 230 can be made by enclosing at least a section of the process including the porous textured roll 250 and using: (1) thermal insulation to limit cooling from outside the manufacturing process; and/or (2) active heating such as electric heating that is applied through heating elements, windings or heated tubes etc. If desired, the controlled environment 230 can have one or more devices 404 that provide an inert atmosphere around the porous textured roll 250 (e.g., graphite porous textured roll 250).
The roll apparatus 202 and specifically the porous textured roll 250 is located at a small distance below the isopipe 212 (or any other forming apparatus). The porous textured roll 250 has a textured outer surface 406 a portion of which receives the downward moving glass ribbon 241 so when the porous textured roll 250 rotates the glass ribbon 241 is textured to form the textured glass sheet 205. In this example, the porous textured roll 250 has one or more orifices 408 (eight shown) formed or bored therein and located below the outer surface 406. The roll apparatus 202 also includes a vacuum pumping device 410 that is adapted to apply at least a partial vacuum to the orifice(s) 408 within the porous textured roll 250 to create a first pressure P1 at an interface between a first side 242′ of the glass ribbon 241 and the outer surface 406 of the porous textured roll 250. The first pressure P1 (e.g., 0.8 atmosphere down to virtually 0 atmosphere) is less than a second pressure P2 (e.g., 1.0 atmosphere) on a second side 242″ of the glass ribbon 241. The difference between the first pressure P1 and the second pressure P2 is such that the first side 242′ of the glass ribbon 241 is driven towards the outer surface 406 of the porous textured roll 250 to substantially replicate a textured pattern 412 on the outer surface 406 of the porous textured roll 250 to form the textured glass sheet 205. For instance, the difference between the first pressure P1 and the second pressure P2 can be about 0.2-1.0 atmosphere.
The porous textured roll 250 should have a porosity that is small-fine enough to resist mechanical degradation to limit abrasion and wear of the roll material, that would degrade the precision of the textured patterns 412) to avoid undesirable micro-texturing on the glass ribbon 241, and to allow a significant reduced pressure P1. To accomplish this, the porous textured roll 250 can have for example a permeability in a range between 5 10−16 and 10−13 m2 and preferably between 10−15 and 5 10−13 m2. For example, the porous textured roll 250 can be made from graphite, metal alloys (that can be found in porous forms), or porous silicon carbide. An advantage of using a porous textured roll 250 made from graphite is that the glass ribbon 241 would be less prone to stick during the texturing phase when compared to a porous textured roll 250 made from a porous metal alloy or a porous silicon carbide. If the porous textured roll 250 is made from graphite then to prevent the problematical oxidation of the carbon it could be located within an inert atmosphere such as nitrogen or argon.
In one example, the porous textured roll 250 can be made from graphite which has an average pore size significantly smaller than the characteristic dimension of the textured pattern 412. For example, Carbone Lorraine 2191 graphite is one such graphite that can be used for some applications since it has an average grain size of about 15 μm, and a permeability of about 6.10−15 m2
As shown in
If desired, the roll apparatus 200 may include a pair of pulling rolls 264a and 264b located below the porous textured roll 250. In this example, the pulling rolls 264a and 264b extend across the width of the textured glass sheet 205 but have an undercut 265a and 265b formed therein so that the textured glass sheet 205 is contacted only near the two outer edges 266a and 266b. Thus, the pulling rolls 264a and 264b draw there between the first edge 266a and the opposing second edge 266b of the textured glass sheet 205. Alternatively, there could be four pulling rolls where two pulling rolls grab one outer edge 266a and the other two pulling rolls grab the other outer edge 266b. The pulling rolls 264a and 264b are shown located outside the controlled environment 230 but they could be located within the controlled environment 230. The pulling rolls 264a and 264b are connected to one or more suitable mechanical device(s) 416 (e.g., drive controllers, motors) that enable the rotational movements of the pulling rolls 264a and 264b. The pulling rolls 264a and 264b could be connected to one or more suitable mechanical device(s) 418 (e.g., air cylinder(s) 418) that apply a horizontal force between the pulling rolls 264a and 264b which enable the application of a horizontal force on the edges 266a and 266b of the textured glass sheet 205. For clarity, the brackets and supports used to support the pulling rolls 264a and 264b and the various mechanical devices 416 and 418 have not been shown.
The roll apparatus 202 includes a control device 420 which has one or more processors 422 and at least one memory 424 (storage 424) that includes processor-executable instructions where the one or more processors 422 are adapted to interface with the memory 424 and execute the processor-executable instructions to control the controlled environment 230, the vacuum pumping device 410, the temperature control system 415, and the various mechanical device(s) 414, 416 and 418. The one or more processors 422 and the at least one memory 424 can be implemented, at least partially, as software, firmware, hardware, or hard-coded logic.
The control device 402 interfaces with the controlled environment 230 to control the temperature of the glass ribbon 241 and if needed the inert atmosphere around the porous textured roll 250. The control device 402 also interfaces with the vacuum pumping device 410 to control the pressure of the vacuum drawn on the porous textured roll 250. Plus, the control device 420 interfaces with the temperature control system 415 to control the temperature of the porous textured roll 250. Moreover, the control device 420 interfaces with the mechanical device 414 and 416 to control the rotational speed, torque or combination speed and torque of the porous textured roll 250 and the pulling rolls 264a and 264b. In addition, the control device 420 interfaces with the mechanical device(s) 418 (e.g., air cylinder(s) 418) to open-close the pulling rolls 264a and 264b to apply a desired horizontal force to the textured glass sheet 205.
The control device 420 can be used to rotate the pulling rolls 264a and 264b at the same linear speed as the porous textured roll 250, or just slightly higher, to insure tensioning of the textured glass sheet 205. Alternatively, the control device 420 can control the pulling rolls 264a and 264b to rotate at a linear speed faster than the porous textured roll 250 to deliberately stretch and reduce the thickness of the textured glass sheet 205. In this case, the texture applied to the porous textured roll 250 would be designed to take into account the deformation of the texture that is rolled on the glass ribbon 241 during the further stretching caused by the pulling stage.
In any case, the textured glass sheet 205 after passing the pulling roll stage can be manipulated in various ways and in different directions (horizontal, inclined) using thermal devices and possibly mechanical (e.g. guidance) devices (not shown in
The individual textured glass sheets 205′ can be used in a wide-variety of devices including, for example, photovoltaic devices and organic light emitting diode (OLED) lighting devices. For instance, the textured glass sheet 205′ can improve the light trapping in photovoltaic devices through the addition of sub-millimeter prismatic patterns on a surface thereof. In particular, it has been evaluated that for such textured glass sheets 205′ used in photovoltaic devices, the conversion yield can be improved (e.g., for micrimorph silicon photovoltaic cells). Plus, the textured glass sheets 205′ can help with light management by optimizing light extraction from the OLED lighting devices.
In a small scale test, an experimental textured graphite piece and vacuum device where used to texture a soda lime glass sample.
From the foregoing, one skilled in the art will appreciate that the roll apparatus 202 can form and texture one surface of a glass ribbon 241 while the second surface of the glass sheet 205 is untouched during the process. The patterns that can be formed include a variety of shapes and sizes (e.g., spherical portions, grooves, prismatic shapes or random shapes) with a specifically high depth to width ratio and sharp edges, including sub-millimeter dimensions (e.g., sub-millimeter periods and/or sub-millimeter depths). The roll apparatus 202 textures the glass ribbon 241 at low viscosity on a porous textured roll 205 (e.g., textured graphite roll with micrometric porosity) onto which a partial vacuum is applied. Thus, the glass ribbon 241 is flattened against the porous textured roll 205 by the pressure difference existing between the reduced pressure (P1) residing at the interface with the porous textured roll 250 and the pressure (P2) on the opposite side of the glass ribbon 241 (equal to 1 atm. in normal conditions). The porous textured roll 250 is maintained at a temperature inducing the replication of its surface by the glass ribbon 241 and also to sufficiently cool it down such that further deformation is controlled. The roll apparatus 202 has several advantages some of which are as follows (for example):
The glass manufacturing system 200 that has been described herein used the fusion process and the isopipe 212 to provide the glass ribbon 241 to the roll apparatus 202. Alternatively, the glass manufacturing system 200 may use many different types of processes instead of the fusion process and many different types of forming apparatuses instead of the isopipe 212 to provide the glass ribbon 241 to the roll apparatus 202. For instance, the glass manufacturing system 200 may have a forming apparatus which includes a fishtail orifice with a slot orifice that delivers the glass ribbon 241 to the roll apparatus 202. Or, the glass manufacturing system 200 may have a forming apparatus which includes a downcomer tube with an inclined heated plate that delivers the glass ribbon 241 to the roll apparatus 202.
In addition, the roll apparatus 202 may include another porous textured roll in addition to the aforementioned porous textured roll 250. Like the first porous textured roll 250, the second porous textured roll would have one or more orifices formed or bored therein and located below an outer surface thereof. The second porous textured roll may be located below the first porous textured roll 250 and positioned to texture the second side 242″ of the textured glass sheet 205′. In particular, the vacuum pumping device 410 (or another vacuum pumping device) would apply at least a partial vacuum to the orifice(s) within the second porous textured roll to create a third pressure P3 at an interface between the second side 242″ of the glass ribbon 241 and the outer surface of the second porous textured roll. The third pressure P3 (e.g., 0.8 atmosphere down to virtually 0 atmosphere) is less than a fourth pressure P4 (e.g., 1.0 atmosphere) on the first side 242′ of the glass ribbon 241. The difference between the third pressure P3 and the fourth pressure P4 is such that the second side 242″ of the glass ribbon 241 is driven towards the outer surface of the second porous textured roll to substantially replicate a textured pattern on the outer surface of the second porous textured roll 250 to form a two sided textured glass sheet 205. Alternatively, the roll apparatus 202 may include a rolling roll (e.g., smooth rolling roll) which is positioned on the other side of the porous textured roll 250.
Although several embodiments of the present solution have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the solution is not limited to the disclosed embodiments, but is capable of numerous rearrangements, modifications and substitutions without departing from the solution as set forth and defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 09305911.1 | Sep 2009 | EP | regional |
