ROLL-TO-ROLL ELECTROLESS PLATING SYSTEM WITH LIQUID FLOW BEARING
A roll-to-roll electroless plating system includes a web advance system for advancing a web of media through a tank containing plating solution where a plating substance in the plating solution is plated onto predetermined locations on the web of media. The web advance system includes a web-guiding roller that is at least partially submerged within the plating solution in the tank. A roller mount is provided for supporting the web-guiding roller while allowing free rotation of the web-guiding roller. A pump is configured to cause plating solution to flow between a bearing surface on the web-guiding roller and a bearing surface on the roller mount.
This invention pertains to the field of roll-to-roll electroless plating, and more particularly to a bearing for a web-guiding roller within a plating solution.
BACKGROUND OF THE INVENTIONElectroless plating, also known as chemical or auto-catalytic plating, is a non-galvanic plating process that involves chemical reactions in an aqueous plating solution that occur without the use of external electrical power. Typically, the plating occurs as hydrogen is released by a reducing agent and oxidized, thus producing a negative charge on the surface of the part to be plated. The negative charge attracts metal ions out of the plating solution to adhere as a metalized layer on the surface. Using electroless plating to provide metallization in predetermined locations can be facilitated by first depositing a catalytic material in the predetermined locations. This can be done, for example by printing features using an ink containing a catalytic component.
Touch screens are visual displays with areas that may be configured to detect both the presence and location of a touch by, for example, a finger, a hand or a stylus. Touch screens can be found in televisions, computers, computer peripherals, mobile computing devices, automobiles, appliances and game consoles, as well as in other industrial, commercial and household applications. A capacitive touch screen includes a substantially transparent substrate which is provided with electrically conductive patterns that do not excessively impair the transparency—either because the conductors are made of a material, such as indium tin oxide, that is substantially transparent, or because the conductors are sufficiently narrow that the transparency is provided by the comparatively large open areas not containing conductors. For capacitive touch screens having metallic conductors, it is advantageous for the features to be highly conductive but also very narrow. Capacitive touch screen sensor films are an example of an article having very fine features with improved electrical conductivity resulting from an electroless plated metal layer.
Projected capacitive touch screen technology is a variant of capacitive touch screen technology. Projected capacitive touch screens are made up of a matrix of rows and columns of conductive material that form a grid. Voltage applied to this grid creates a uniform electrostatic field, which can be measured. When a conductive object, such as a finger, comes into contact, it distorts the local electrostatic field at that point. This is measurable as a change in capacitance. The capacitance can be measured at every intersection point on the grid. In this way, the system is able to accurately track touches. Projected capacitive touch screens can use either mutual capacitive sensors or self capacitive sensors. In mutual capacitive sensors, there is a capacitor at every intersection of each row and each column. A 16×14 array, for example, would have 224 independent capacitors. A voltage is applied to the rows or columns. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field which reduces the mutual capacitance. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location by measuring the voltage in the other axis. Mutual capacitance allows multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time.
International patent application WO2013/063188 by Petcavich et al., entitled “Method of manufacturing a capacitive touch sensor circuit using a roll-to-roll process to print a conductive microscopic patterns on a flexible dielectric substrate,” discloses a method of manufacturing a capacitive touch sensor using a roll-to-roll process to print a conductor pattern on a flexible transparent dielectric substrate. A first conductor pattern is printed on a first side of the dielectric substrate using a first flexographic printing plate and is then cured. A second conductor pattern is printed on a second side of the dielectric substrate using a second flexographic printing plate and is then cured. The ink used to print the patterns includes a catalyst that acts as seed layer during a subsequent electroless plating operation. The electrolessly plated material (e.g., copper) provides the low resistivity in the narrow lines of the grid needed for excellent performance of the capacitive touch sensor. Petcavich et al. indicate that the line width of the flexographically printed material can be 1 to 50 microns.
Flexography is a method of printing or pattern formation that is commonly used for high-volume printing runs. It is typically employed in a roll-to-roll format for printing on a variety of soft or easily deformed materials including, but not limited to, paper, paperboard stock, corrugated board, polymeric films, fabrics, metal foils, glass, glass-coated materials, flexible glass materials and laminates of multiple materials. Coarse surfaces and stretchable polymeric films are also economically printed using flexography.
Flexographic printing members are sometimes known as relief printing members, relief-containing printing plates, printing sleeves, or printing cylinders, and are provided with raised relief images onto which ink is applied for application to a printable material. While the raised relief images are inked, the recessed relief “floor” should remain free of ink.
Although flexographic printing has conventionally been used in the past for printing of images, more recent uses of flexographic printing have included functional printing of devices, such as touch screen sensor films, antennas, and other devices to be used in electronics or other industries. Such devices typically include electrically conductive patterns.
To improve the optical quality and reliability of the touch screen, it has been found to be preferable that the width of the grid lines be approximately 2 to 10 microns, and even more preferably to be 4 to 8 microns. In addition, in order to be compatible with the high-volume roll-to-roll manufacturing process, it is preferable for the roll of flexographically printed material to be electroless plated in a roll-to-roll electroless plating system. More conventionally, electroless plating is performed by immersing the item to be plated in a tank of plating solution. However, for high volume uniform plating of features on both sides of the web of substrate material, it is preferable to perform the electroless plating in a roll-to-roll electroless plating system.
Roll-to-roll electroless plating systems are commercially available from Chemcut Corporation, for example. With reference to prior art
An alternate configuration of a roll-to-roll electroless plating system is to have a tank of plating solution without a separate sump and pan. In this configuration, some of the web-guiding rollers can be at least partially submerged within the plating solution within the tank. Because there is no sump to catch drops of plating solution as in the roll-to-roll electroless plating system 10 of
There remains a need for a bearing configuration for a web-guiding roller submerged in a tank of electroless plating solution such that plating out onto the bearing surfaces is inhibited.
SUMMARY OF THE INVENTIONThe present invention represents a roll-to-roll electroless plating system, comprising:
a tank containing a plating solution;
a web advance system for advancing a web of media in an in-track direction along a web transport path from an input roll through the plating solution in the tank to a take-up roll, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media as it is advanced through the plating solution in the tank, and wherein the web advance system includes:
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- a web-guiding roller for guiding the web of media, the web-guiding roller being at least partially submerged within the plating solution in the tank; and
- a roller mount for supporting the web-guiding roller while allowing free rotation of the web-guiding roller, wherein the web-guiding roller and the roller mount include corresponding bearing surfaces; and
a pump configured to cause plating solution to flow between the bearing surface of the web-guiding roller and the bearing surface of the roller mount.
This invention has the advantage that pumping plating solution between the bearing surfaces reduces the amount of the plating material that plates out on the bearing surfaces.
It has the additional advantage that the web-guiding roller can be fully submerged within the plating solution without suffering from problems caused by the plating material that plates out on the bearing surfaces.
It has the further advantage that using the plating liquid as the lubricant for the bearing surfaces prevents the plating liquid from being contaminated as could occur if a different lubricant were used.
It is to be understood that the attached drawings are for purposes of illustrating the concepts of the invention and may not be to scale.
DETAILED DESCRIPTION OF THE INVENTIONThe present description will be directed in particular to elements forming part of, or cooperating more directly with, an apparatus in accordance with the present invention. It is to be understood that elements not specifically shown, labeled, or described can take various forms well known to those skilled in the art. In the following description and drawings, identical reference numerals have been used, where possible, to designate identical elements. It is to be understood that elements and components can be referred to in singular or plural form, as appropriate, without limiting the scope of the invention.
The invention is inclusive of combinations of the embodiments described herein. References to “a particular embodiment” and the like refer to features that are present in at least one embodiment of the invention. Separate references to “an embodiment” or “particular embodiments” or the like do not necessarily refer to the same embodiment or embodiments; however, such embodiments are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. It should be noted that, unless otherwise explicitly noted or required by context, the word “or” is used in this disclosure in a non-exclusive sense.
The example embodiments of the present invention are illustrated schematically and not to scale for the sake of clarity. One of ordinary skill in the art will be able to readily determine the specific size and interconnections of the elements of the example embodiments of the present invention.
References to upstream and downstream herein refer to direction of flow. Web media moves along a media path in a web advance direction from upstream to downstream. Similarly, fluids flow through a fluid line in a direction from upstream to downstream.
As described herein, the example embodiments of the present invention provide a roll-to-roll electroless plating system having a web-guiding roller with a bearing at least partially submerged in a plating solution, such that plating solution is forced past the bearing surfaces. In an exemplary configuration, the roll-to-roll electroless plating system is useful for metalizing printed features in sensor films incorporated into touch screens. However, many other applications are emerging for printing and electroless plating of functional devices that can be incorporated into other electronic, communications, industrial, household, packaging and product identification systems (such as RFID) in addition to touch screens. In addition, roll-to-roll electroless plating systems can be used to plate items for decorative purposes rather than electronic purposes and such applications are contemplated as well.
The flexographic printing system 100 includes two print modules 120 and 140 that are configured to print on the first side 151 of substrate 150, as well as two print modules 110 and 130 that are configured to print on the second side 152 of substrate 150. The web of substrate 150 travels overall in roll-to-roll direction 105 (left to right in the example of
Each of the print modules 110, 120, 130, 140 includes some similar components including a respective plate cylinder 111, 121, 131, 141, on which is mounted a respective flexographic printing plate 112, 122, 132, 142, respectively. Each flexographic printing plate 112, 122, 132, 142 has raised features 113 defining an image pattern to be printed on the substrate 150. Each print module 110, 120, 130, 140 also includes a respective impression cylinder 114, 124, 134, 144 that is configured to force a side of the substrate 150 into contact with the corresponding flexographic printing plate 112, 122, 132, 142. Impression cylinders 124 and 144 of print modules 120 and 140 (for printing on first side 151 of substrate 150) rotate counter-clockwise in the view shown in
Each print module 110, 120, 130, 140 also includes a respective anilox roller 115, 125, 135, 145 for providing ink to the corresponding flexographic printing plate 112, 122, 132, 142. As is well known in the printing industry, an anilox roller is a hard cylinder, usually constructed of a steel or aluminum core, having an outer surface containing millions of very fine dimples, known as cells. Ink is provided to the anilox roller by a tray or chambered reservoir (not shown). In some embodiments, some or all of the print modules 110, 120, 130, 140 also include respective UV curing stations 116, 126, 136, 146 for curing the printed ink on substrate 150.
As the web of media 250 is advanced through the plating solution 210 in the tank 230, a metallic plating substance such as copper, silver, gold, nickel or palladium is electrolessly plated from the plating solution 210 onto predetermined locations on one or both of a first surface 251 and a second surface 252 of the web of media 250. As a result, the concentration of the metal or other components in the plating solution 210 in the tank 230 decreases and the plating solution 210 needs to be refreshed. To refresh the plating solution 210, it is recirculated by pump 240, and replenished plating solution 215 from a reservoir 220 is added under the control of controller 242, which can include a valve (not shown). In the example shown in
Axial recess 272 is preferably cylindrical, and has a cylindrical recess surface 274 with a recess diameter D1. Hollow shaft 275 has an inner surface 277 and a cylindrical outer surface 276 with an outer shaft diameter D2. Recess diameter D1 is slightly greater than outer shaft diameter D2 so that there is clearance between the cylindrical outer surface 276 of hollow shaft 275 and the cylindrical recess surface 274 of axial recess 272. In an exemplary embodiment, the difference between the diameters is approximately D1−D2≈1.0 mm. The differences between the diameters is preferably in the range of about 0.5 mm≦D1−D2≦3.0 mm. Web-guiding roller 270 rotates freely around hollow shaft 275 with recess surface 274 of axial recess 272 being the bearing surface of the web-guiding roller 270, and with outer surface 276 of the hollow shaft 275 being the bearing surface of the roller mount 269.
Hollow shaft 275 can be a continuation of return pipe 234 or can be connected to return pipe 234. In the exemplary embodiment illustrated in
In the illustrated configuration, all of the plating solution 210 from the pump 240 is shown as passing through the return pipe 234 into the hollow shaft 275, and from there into the axial recess of the web-guiding roller 270. In other embodiments, the hollow shaft 275 can be a branch off the return pipe 234, and the return pipe 234 can also outlet into the tank 230 in order to return a portion of the plating solution 210 directly into the tank 230 similar to the configuration of
In the embodiment shown in
In the embodiments described above the hollow shaft 275, 295 carrying plating solution 210 extends into an axial recess 272 or a hollow cavity 292 in a web-guiding roller 270, 290.
The plating solution 210 is pumped into the hollow shaft 285 in plating solution flow direction. As with the embodiments described earlier, the plating solution 210 is then forced to flow between bearing surfaces on the web-guiding roller 280 and the roller mount 269 (i.e., hollow shaft 285), to provide a liquid bearing, thereby inhibiting plating on the bearing surfaces. In further detail, axial shaft 282 has a cylindrical outer surface 284 with an axial shaft diameter D3, and the hollow shaft 285 has a cylindrical inner surface 287 with an inner diameter D4, where D3 is slightly less than D4. The outer surface 284 of the axial shaft 282 is the bearing surface of the web-guiding roller 280, and the inner surface 287 of the hollow shaft 285 is the bearing surface of the roller mount 269. In an exemplary embodiment, the difference between the diameters is approximately D4−D3≈1.0 mm. The differences between the diameters is preferably in the range of about 0.5 mm≦D4−D3≦3.0 mm.
As described above with reference to
Recirculating lubricant past the bearing surfaces of an apparatus is known (for example, see U.S. Patent Application Publication 2013/0309340 to Day, entitled “Lubrication of bearing and roller shaft in pellet mill machines”). A significant difference in the present invention is that plating solution 210 is not an additional lubricant, but rather is a working fluid that the web-guiding roller 260, 270, 280 is submerged in to perform the electroless plating operation. Pumping a lubricant that is not the plating solution 210 past the bearing surfaces would contaminate the plating solution. Furthermore, the fact that the web-guiding roller 260, 270, 280 is submerged in an electroless plating solution 210 presents an additional problem due to the tendency for the plating solution 210 to plate out on the bearing surfaces. The inventors have discovered that pumping the plating solution 210 past the bearing surfaces mitigates this effect and substantially reduces the amount of material that is plated out on the bearing surface, while providing the necessary bearing lubrication.
Alternatively, in some embodiments conductive pattern 450 can be printed using one or more print modules configured like print modules 110 and 130, and conductive pattern 460 can be printed using one or more print modules configured like print modules 120 and 140 of
With reference to
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
PARTS LIST
- 10 roll-to-roll electroless plating system
- 20 pan
- 25 side wall
- 27 hole
- 30 sump
- 40 web-guiding roller
- 45 shaft
- 50 bearing
- 65 drop
- 70 pump
- 100 flexographic printing system
- 102 supply roll
- 104 take-up roll
- 105 roll-to-roll direction
- 106 roller
- 107 roller
- 110 print module
- 111 plate cylinder
- 112 flexographic printing plate
- 113 raised features
- 114 impression cylinder
- 115 anilox roller
- 116 UV curing station
- 120 print module
- 121 plate cylinder
- 122 flexographic printing plate
- 124 impression cylinder
- 125 anilox roller
- 126 UV curing station
- 130 print module
- 131 plate cylinder
- 132 flexographic printing plate
- 134 impression cylinder
- 135 anilox roller
- 136 UV curing station
- 140 print module
- 141 plate cylinder
- 142 flexographic printing plate
- 144 impression cylinder
- 145 anilox roller
- 146 UV curing station
- 150 substrate
- 151 first side
- 152 second side
- 200 roll-to-roll electroless plating system
- 202 supply roll
- 204 take-up roll
- 205 in-track direction
- 206 drive roller
- 208 web-guiding roller
- 210 plating solution
- 212 plating solution flow direction
- 215 replenished plating solution
- 220 reservoir
- 230 tank
- 232 drain pipe
- 234 return pipe
- 236 filter
- 240 pump
- 242 controller
- 250 web of media
- 251 first surface
- 252 second surface
- 260 web-guiding roller
- 262 shaft
- 264 support
- 267 shaft end
- 266 hole
- 268 bearing surfaces
- 269 roller mount
- 270 web-guiding roller
- 271 end
- 272 axial recess
- 273 radially outward direction
- 274 recess surface
- 275 hollow shaft
- 276 outer surface
- 277 inner surface
- 278 end wall
- 279 holes
- 280 web-guiding roller
- 281 end
- 282 axial shaft
- 284 outer surface
- 285 hollow shaft
- 287 inner surface
- 290 web-guiding roller
- 291a first end
- 291b second end
- 292 hollow cavity
- 294 cavity surface
- 295 hollow shaft
- 296 outer surface
- 400 apparatus
- 410 touch screen
- 420 display device
- 430 touch sensor
- 440 transparent substrate
- 441 first side
- 442 second side
- 450 conductive pattern
- 451 fine lines
- 452 grid
- 453 fine lines
- 454 channel pads
- 455 grid column
- 456 interconnect lines
- 458 connector pads
- 460 conductive pattern
- 461 fine lines
- 462 grid
- 463 fine lines
- 464 channel pads
- 465 grid row
- 466 interconnect lines
- 468 connector pads
- 480 controller
- D1 recess diameter
- D2 shaft diameter
- D3 shaft diameter
- D4 inner diameter
Claims
1. A roll-to-roll electroless plating system, comprising:
- a tank containing a plating solution;
- a web advance system for advancing a web of media in an in-track direction along a web transport path from an input roll through the plating solution in the tank to a take-up roll, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media as it is advanced through the plating solution in the tank, and wherein the web advance system includes: a web-guiding roller for guiding the web of media, the web-guiding roller being at least partially submerged within the plating solution in the tank; and a roller mount for supporting the web-guiding roller while allowing free rotation of the web-guiding roller, wherein the web-guiding roller and the roller mount include corresponding bearing surfaces; and
- a pump configured to cause plating solution to flow between the bearing surface of the web-guiding roller and the bearing surface of the roller mount.
2. The roll-to-roll electroless plating system of claim 1, wherein the web-guiding roller includes an axial recess in an end of the web-guiding roller, and the roller mount includes a non-rotating hollow shaft that is disposed within the axial recess of the web-guiding roller, and wherein the web-guiding roller rotates around the hollow shaft.
3. The roll-to-roll electroless plating system of claim 2, wherein the axial recess is cylindrical and has a cylindrical recess surface with a recess diameter, and the hollow shaft has an inner surface and a cylindrical outer surface with an outer shaft diameter, the recess diameter of the axial recess being greater than the outer shaft diameter of the hollow shaft, and wherein the cylindrical recess surface of the axial recess is the bearing surface of the web-guiding roller and the cylindrical outer surface of the hollow shaft is the bearing surface of the roller mount.
4. The roll-to-roll electroless plating system of claim 3, wherein the pump pumps plating solution through the hollow shaft and between the bearing surface of the web-guiding roller and the bearing surface of the roller mount.
5. The roll-to-roll electroless plating system of claim 4, wherein the hollow shaft includes a plurality of holes around the circumference of the hollow shaft which enable plating solution to pass radially outward from the inner surface to the outer surface of the hollow shaft.
6. The roll-to-roll electroless plating system of claim 4 wherein the pump draws plating solution from the tank.
7. The roll-to-roll electroless plating system of claim 4, wherein the pump draws plating solution from a reservoir to provide replenished plating solution.
8. The roll-to-roll electroless plating system of claim 1, wherein the web-guiding roller includes an axial shaft protruding from an end of the web-guiding roller, and the roller mount includes a non-rotating hollow shaft, the axial shaft of the web-guiding roller being disposed within the hollow shaft, and wherein the axial shaft of the web-guiding roller rotates within the hollow shaft.
9. The roll-to-roll electroless plating system of claim 8, wherein the axial shaft has a cylindrical outer surface with an axial shaft diameter, and the hollow shaft has a cylindrical inner surface with an inner diameter, the axial shaft diameter of the axial shaft being less than the inner diameter of the hollow shaft, and wherein the cylindrical outer surface of the axial shaft is the bearing surface of the web-guiding roller and the cylindrical inner surface of the hollow shaft is the bearing surface of the roller mount.
10. The roll-to-roll electroless plating system of claim 9, wherein the pump pumps plating solution through the hollow shaft so that it passes between the bearing surface of the web-guiding roller and the bearing surface of the roller mount.
11. The roll-to-roll electroless plating system of claim 10 wherein the pump draws plating solution from the tank.
12. The roll-to-roll electroless plating system of claim 9, wherein the pump draws plating solution from a reservoir to provide replenished plating solution.
13. The roll-to-roll electroless plating system of claim 1, wherein the web-guiding roller includes a hollow cavity that extends from an opening on a first end of the web-guiding roller to an opening on a second end of the web-guiding roller, and wherein the plating solution is pumped into the hollow cavity through one or both of the openings on the first and second ends of the web-guiding roller and the plating solution passes out of the hollow cavity by passing between the bearing surface of the web-guiding roller and the bearing surface of the roller mount.
14. The roll-to-roll electroless plating system of claim 13, wherein the roller mount includes a non-rotating hollow shaft that is disposed within the hollow cavity of the web-guiding roller, and wherein the web-guiding roller rotates around the hollow shaft.
15. The roll-to-roll electroless plating system of claim 14, wherein the hollow cavity includes a cylindrical portion within which the hollow shaft is disposed, the cylindrical portion having a cylindrical cavity surface with a cavity diameter, and the hollow shaft having a cylindrical outer surface with an outer shaft diameter, the cavity diameter being greater than the outer shaft diameter, and wherein the cylindrical cavity surface of the cylindrical portion of the hollow shaft is the bearing surface of the web-guiding roller and the cylindrical outer surface of the hollow shaft is the bearing surface of the roller mount.
16. The roll-to-roll electroless plating system of claim 1, further including a return pipe from the pump to the tank for recirculation of the plating solution.
17. The roll-to-roll electroless plating system of claim 1, further including a filter disposed downstream of the pump.
18. The roll-to-roll electroless plating system of claim 1, wherein the plating substance includes copper, silver, gold, nickel or palladium.
19. An article having features that were plated using the roll-to-roll electroless plating system of claim 1.
20. The article of claim 19, wherein at least some of the features have widths between 2 microns and 10 microns.
Type: Application
Filed: Dec 16, 2014
Publication Date: Jun 16, 2016
Inventors: Shawn A. Reuter (Rochester, NY), Gary P. Wainwright (Fairport, NY)
Application Number: 14/571,328