Liquid ejection hole orientation for web guide

A non-contact web guide includes a wall having a curved exterior surface and a hollow interior containing a pressurized liquid. A first row of liquid ejection holes is provided in proximity to the web guide entry position having axes that are inclined toward a downstream direction, and a second row of liquid ejection holes is provided in proximity to the web guide exit position having axes that are inclined toward an upstream direction. An intermediate array of liquid ejection holes is optionally provided. The pressurized liquid flows through the liquid ejection holes to force the web of media away from the bearing surface of the web guide. This configuration of liquid ejection holes provides the advantage that stable web guidance is achieved at low liquid flow rates.

FIELD OF THE INVENTION

This invention pertains to the field of web transport systems that include at least one web guide having a liquid bearing for non-contact guidance of the web, and more particularly to an arrangement of liquid ejection holes.

BACKGROUND OF THE INVENTION

Processing a web of media in a roll-to-roll fashion can be an advantageous and low-cost manufacturing approach for devices or other objects formed on the web of media. A number of manufacturing methods, such as etching, plating, developing, or rinsing include processing the media in a tank of liquid chemicals. Transporting the web of media through the liquid chemicals can provide technical challenges, especially if rollers are used to guide the web of media, as is conventionally done. An example of a process that includes web transport through liquid chemicals is roll-to-roll electroless plating.

Electroless plating, also known as chemical or auto-catalytic plating, is a 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 onto 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. Conventionally, electroless plating has typically been performed by immersing the item to be plated in a tank of plating solution. However, for high volume plating of features on both sides of a web of substrate material, it is preferable to perform the electroless plating in a roll-to-roll electroless plating system.

Touch screens are visual displays with areas that can 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 many common devices such as 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 electrolessly-plated metal layer.

Projected capacitive touch technology is a variant of capacitive touch 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 permits multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time.

WO 2013/063188 (Petcavich et al.) 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.

Patterns, especially fine line patterns that are plated using electroless plating systems, are often delicate and susceptible to being damaged as the web of substrate is transported along the web-transport path. For example, particulates can be located on the media support surface of a roller that contacts the web surface and cause scratches as the web of media passes. Therefore it is desirable to minimize contact between the web of media and hard surfaces where abrasion can occur.

WO 2009/044124 (Lymn), entitled “Web processing machine,” discloses a web transport system using submerged fluid bearings in which process liquid is directed through apertures to lift the web of media away from the bearing surface. In Lymn's preferred embodiment, it is contemplated that non-submerged upper web guides that are located above the liquid level can also use fluid bearings where air is used as the fluid. However, Lymn also contemplates using process liquid in place of air in a non-submerged upper web. U.S. Patent Application Publication No. 2013/0192757 (Lymn), also entitled “Web processing machine,” describes a configuration including drying guides over a processing tank. The guides have outlet slits through which air is blown to provide a bearing medium as well as a drying medium.

U.S. Pat. No. 3,065,098 (Brooks), entitled “Method for coating webs” provides air ejected through tubes to float a web along an undulating path. The holes are formed radially in the tube walls.

U.S. Pat. No. 3,186,326 (Schmidt), entitled “Fluid bearings for strip material” teaches ejecting processing liquid through holes in a tube for providing a fluid bearing for a web of media.

An objective for web guides that support the web of media using liquid bearings is to provide sufficient standoff (i.e., the distance between the web of media and the surface of the web guide) in order to reduce the likelihood of the web of media contacting the web guide surface. It is preferable to provide sufficient web standoff with a relatively low flow rate of ejected liquid in the liquid bearings. Furthermore, it is desirable to provide stable web transport without web flutter that can increase the chances of the web contacting the web guide surface. Finally, it is advantageous to control the ejection of liquid such that the ejected liquid is not wasted or cause contamination.

There remains a need for improved web transport systems using liquid bearings that can reduce the occurrence of scratches due to web contact with the web guide, while using a reduced amount of ejected liquid and providing improved flow control of the ejected liquid.

SUMMARY OF THE INVENTION

The present invention represents a web transport system for transporting a web of media along a web transport path in an in-track direction, the web of media having a width in a cross-track direction, includes:

at least one web guide for non-contact guidance of the web of media including:a wall having a curved exterior surface, wherein the web of media travels along the web transport path around a bearing portion of the curved exterior surface from a web guide entry position to a web guide exit position, thereby redirecting the web of media from an input travel direction to an output travel direction;a hollow interior containing a pressurized liquid;a first array of liquid ejection holes formed through the wall from the hollow interior to the curved exterior surface, the liquid ejection holes in the first array being distributed across the web guide in the cross-track direction in proximity to the web guide entry position, wherein the liquid ejection holes in the first array have axes that are non-perpendicular to the curved exterior surface and are inclined toward a downstream direction of the web transport path; anda second array of liquid ejection holes formed through the wall from the hollow interior to the curved exterior surface, the liquid ejection holes in the second array being distributed across the web guide in the cross-track direction in proximity to the web guide exit position, wherein the liquid ejection holes in the second array have axes that are non-perpendicular to the curved exterior surface and are inclined toward an upstream direction of the web transport path;

wherein the pressurized liquid flows through the liquid ejection holes to force the web of media away from the bearing surface of the web guide so that the web of media does not contact the web guide as it travels around the bearing portion of the curved exterior surface.

This invention has the advantage that it provides non-contact web guidance at a relatively low flow rate of ejected liquid through the holes of the web guide.

It has the additional advantage that it provides stable web transport without appreciable web flutter is provided.

It has the further advantage that it provides improved control of the ejection of liquid is provided such that the ejected liquid is not wasted and does not cause contamination.

DETAILED DESCRIPTION OF THE INVENTION

The 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. A web of 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. In some instances a fluid can flow in an opposite direction from the web advance direction. For clarification herein, upstream and downstream are meant to refer to the web motion unless otherwise noted.

As described herein, the example embodiments of the present invention describe a roll-to-roll electroless plating system for providing web transport without contacting the surface of the web with a hard surface such as a roller. 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. Furthermore, there are many other applications of liquid processing of a web of media in a roll-to-roll configuration in addition to electroless plating. There can also be applications of roll-to-roll web transport where a liquid bearing can be used for guiding a web of media without contact and where no liquid processing or tanks of processing liquids are used.

FIG. 1is a schematic side view of a flexographic printing system100that can be used for roll-to-roll printing of a catalytic ink on both sides of a substrate150for subsequent electroless plating. Substrate150is fed as a web of media from supply roll102to take-up roll104through flexographic printing system100. Substrate150has a first side151and a second side152. Within the context of the present disclosure, the term “web of media” is used interchangeably with the terms “substrate” or “web of substrate.”

The flexographic printing system100includes two print modules120and140that are configured to print on the first side151of substrate150, as well as two print modules110and130that are configured to print on the second side152of substrate150. The web of substrate150travels overall in roll-to-roll direction105(left to right in the example ofFIG. 1). However, various rollers106and107are used to locally change the direction of the web of substrate150as needed for adjusting web tension, providing a buffer, and reversing the substrate150for printing on an opposite side. In particular, note that in print module120roller107serves to reverse the local direction of the web of substrate150so that it is moving substantially in a right-to-left direction.

Each of the print modules110,120,130,140includes some similar components including a respective plate cylinder111,121,131,141, on which is mounted a respective flexographic printing plate112,122,132,142, respectively. Each flexographic printing plate112,122,132,142has raised features113defining an image pattern to be printed on the substrate150. Each print module110,120,130,140also includes a respective impression cylinder114,124,134,144that is configured to force a side of the substrate150into contact with the corresponding flexographic printing plate112,122,132,142. Impression cylinders124and144of print modules120and140(for printing on first side151of substrate150) rotate counter-clockwise in the view shown inFIG. 1, while impression cylinders114and134of print modules110and130(for printing on second side152of substrate150) rotate clockwise in this view.

Each print module110,120,130,140also includes a respective anilox roller115,125,135,145for providing ink to the corresponding flexographic printing plate112,122,132,142. 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 modules110,120,130,140also include respective UV curing stations116,126,136,146for curing the printed ink on substrate150.

FIG. 2is a schematic side view of a roll-to-roll electroless plating system200disclosed in commonly-assigned, co-pending U.S. patent application Ser. No. 14/571,328 entitled “Roll-to-roll electroless plating system with liquid flow bearing,” by S. Reuter et al., which is incorporated herein by reference. The roll-to-roll electroless plating system200includes a tank230of plating solution210. A web of media250is fed by a web advance system along a web-transport path in an in-track direction205from a supply roll202to a take-up roll204. The web of media250is a substrate upon which electroless plating is to be performed. A drive roller206is positioned upstream of the plating solution210and a drive roller207is positioned downstream of the plating solution210. Drive rollers206and207advance the web of media250from the supply roll202through the tank of plating solution210to the take-up roll204. Web-guiding rollers208are at least partially submerged in the plating solution210in the tank230and guide the web of media250along the web-transport path in the in-track direction205.

As the web of media250is advanced through the plating solution210in the tank230, a metallic plating substance such as copper, silver, gold, nickel or palladium is electrolessly plated from the plating solution210onto predetermined locations on one or both of a first surface251and a second surface252of the web of media250. As a result, the concentration of the metal or other components in the plating solution210in the tank230decreases and the plating solution210needs to be refreshed. To refresh the plating solution210, it is recirculated by a pump240, and replenished plating solution215from a reservoir220is added under the control of a controller242, which can include a valve (not shown). In the example shown inFIG. 2, plating solution210is moved from tank230to pump240through a drain pipe232and is returned from pump240to tank230through a return pipe234. In order to remove particulates from plating solution210, a filter236can be included, typically downstream of the pump240.

Particulates can be present in plating solution210due to contaminants that enter from outside of the tank230, or can be generated from hardware within tank230, or can result from spontaneous plating out of metal from the electroless plating solution210. Particulates that settle on the bottom of the tank230do not represent a significant problem. However, particulates that fall onto the web of media250and become trapped between web of media250and one of the drive rollers206,207or web-guiding rollers208can cause significant problems due to scratching of the delicate patterns formed on the web of media250. In some cases, a particulate can become embedded in a roller and cause scratches in successive portions of the web of media250that contact it.

A roll-to-roll liquid processing system300for processing a web of media250can have a plurality of processing tanks330,335,340,345, as shown schematically inFIG. 3. The web of media250is transported successively through the processing tanks330,335,340,345by web transport system301as it travels from the supply roll202to the take-up roll204. Each successive processing tank330,335,340,345can contain a different processing liquid305, or some or all of the processing tanks330,335,340,345can contain the same processing liquid305.

In an exemplary configuration, the roll-to-roll liquid processing system300is an electroless plating line for plating touch screen sensor films on catalytic ink patterns printed by flexographic printing system100ofFIG. 1. In this case, the processing tanks330,340can be plating tanks containing electroless plating solution, and the processing tanks335,345can be rinse tanks containing a rinsing liquid. For example, the processing liquid305in processing tank330can be a copper plating solution; the processing liquid305in processing tank335can be water for rinsing the web of media250; the processing liquid305in processing tank340can be a palladium plating solution; and the processing liquid305in processing tank345can be water for rinsing the web of media250.

The web of media250is transported along in-track direction205into each successive processing tank330,335,340,345where it is submerged in the associated processing liquid305, and then transported out of the processing tank330,335,340,345and into the next processing tank330,335,340,345, and finally to the take-up roll204. Web transport guides for each tank include both non-submerged web guides302and submerged web guides304.

U.S. patent application Ser. No. 14/812,078 to Hill et al., entitled “Web transport system including scavenger blade” and incorporated by reference herein in its entirety, teaches the use of a scavenger blade to remove at least some liquid that was ejected at the bearing surface of a non-submerged fluid bar or web guide from the surface of the web of media. Such scavenger blades can be useful in conjunction with the non-submerged web guides302ofFIG. 3.

Embodiments of the invention provide improved performance of web guides that support a web of media using liquid bearings. In particular, the disclosed liquid bearing configurations provide sufficient stand-off (i.e., the distance between the web of media250and the surface of the web guide) to reduce the likelihood of the web of media250contacting the web guide surface. The disclosed configurations have the advantage that they provide non-contact web guidance at a relatively low flow rate of ejected liquid in the liquid bearings. In addition, stable web transport without appreciable web flutter is provided. Furthermore, improved control of the ejection of liquid is provided such that the ejected liquid is not wasted and does not cause contamination.

FIG. 4is a perspective of a processing tank330including a reservoir of processing liquid310(e.g., a plating solution) that fills the processing tank330up to a liquid level311. A non-contact web guide320has a curved wall328with a curved exterior surface329. The curved exterior surface329has an arrangement of liquid ejection holes322within or near a bearing surface321portion. In the embodiment shown inFIG. 4, the arrangement of liquid ejection holes322includes a first array501, a second array502, and an optional intermediate array505that is disposed between the first array501and the second array502. In the illustrated arrangement, there are fewer liquid ejection holes322in the intermediate array505than there are in either the first array501or the second array502, although this is not required.

In the example ofFIG. 4, the first array501is a linear array including liquid ejection holes322distributed along a line to form a first row R1across the web guide320, and the second array502is a linear array including liquid ejection holes322distributed along a line to form a second row R2. Likewise, the intermediate array505is also a linear array including liquid ejection holes322distributed along a line to form an intermediate row Ri. In other embodiments, some or all of the arrays of liquid ejection holes322can be two-dimensional arrays including liquid ejection holes322distributed along a plurality of lines, or can include liquid ejection holes322arranged in other types of patterns such as hexagonal patterns.

Preferably, bearing surface321has a smooth cross-section. In the illustrated configuration, the curved exterior surface329of the web guide320has a circular cross-section so that the cross-section of the bearing surface321is a circular arc.

Web guide320is supported at its first end323by a first mount325, and at its second end324by a second mount326. Processing liquid310is forced through the liquid ejection holes322by a pump (not shown). Web guide320can have a hollow interior327(seeFIG. 6) that is in fluidic communication with the liquid ejection holes322. Processing liquid310can be supplied to the web guide320through appropriate plumbing (not shown) between the pump and the hollow interior327. In some configurations, the plumbing can be adjacent to or within one or both of the first mount325and the second mount326.

In the exemplary configuration ofFIG. 4, the liquid ejection holes322in the web guide320are above the liquid level311(although other portions of the web guide320may or may not be above liquid level311). In the terminology used herein, a web guide320is said to be “non-submerged” if at least some of the liquid ejection holes322through which processing liquid310is ejected are above liquid level311.

FIG. 5shows a shows a portion of a web transport system301in which a web of media250is guided in non-contact fashion along a web transport path500around and past the non-submerged web guide320ofFIG. 4. The web of media250travels in an in-track direction205and extends width-wise in a cross-track direction203from a first edge253to a second edge254to define a width W. The web guide320spans the width of the web of media250. The web of media250has a first surface251and an opposing second surface252, where the first surface251faces the bearing surface321of the web guide320. The bearing surface321is defined to be the portion of the exterior surface of the web guide320around which the web of media250is wrapped. As will be described in more detail below with reference toFIG. 7, the bearing surface321extends from a web guide entry position531to a web guide exit position532.

The first array501of liquid ejection holes322is located in proximity to the web guide entry position531, and the second array502of liquid ejection holes322is located in proximity to the web guide exit position532. The liquid ejection holes322in the first array501, the second array502, and the intermediate array505are distributed across the web guide320in the cross-track direction203. In the example shown inFIG. 5, the liquid ejection holes322of first array501are distributed as a linear array along a line spanning the web guide320in the cross-track direction203to form a first row R1. Similarly, the liquid ejection holes322of second array502are distributed as a linear array along a line spanning the web guide320in the cross-track direction203to form a second row R2. The optional intermediate array505includes additional liquid ejection holes322that are not located near either the web guide entry position531or the web guide exit position532. In the exemplary configuration ofFIG. 5, the liquid ejection holes322of the intermediate array505are distributed as a linear array along a line spanning the web guide320in the cross-track direction203. In other embodiments, the liquid ejection holes322of the intermediate array505can be arranged along a plurality of lines or in some other configuration.

As the web of media250approaches the web guide320it is traveling in an input travel direction510, and as the web of media250moves away from the web guide320it is traveling in an output travel direction511. The angle between the input travel direction510and the output travel direction511defines a wrap angle α. As pressurized processing liquid310is pumped through the liquid ejection holes322in the bearing surface321into a region between the first surface251of the web of media250and the bearing surface321of the web guide320, the web of media250is forced away from the web guide320. This permits guiding of the web of media250without scratching it by contact with the web guide320.

As shown schematically inFIG. 3, web guides in a web transport system301can have a variety of configurations. They can include non-submerged web guides302and submerged web guides304, and can have a variety of different wrap angles. It has been found that preferred configurations of liquid ejection holes322can depend on variables such as these, as well as other variables including web tension, web stiffness, orientation of the bearing surface, and characteristics of the ejected liquid. Several examples for non-submerged and submerged web guides having different wrap angles are described herein.

FIG. 6shows a cross-sectional view of an exemplary non-contact web guide320. In the illustrated configuration, the web guide320has a cylindrical shape with a circular cross-section. However, in other embodiments, the web guide320can have other shapes. The bearing surface321will preferably have a smoothly-varying profile, such as an arc of a circle or an ellipse. Other types of smoothly-varying profiles would include a curve corresponding to some other type of conic section or smoothly-varying function. Aside from the bearing surface321over which the web of media250rides, the other surfaces of the web guide320can have any shape (e.g., they can be flat surfaces).

The web of media250does not touch the bearing surface321, but is forced outward to a stand-off distance S with respect to the bearing surface321by the pressurized liquid (e.g., processing liquid310) that is pumped into the hollow interior327of web guide320and is ejected through liquid ejection holes521,522,523. The stand-off distance S is the gap between the web of media250and the bearing surface321. The stand-off distance S is preferably large enough to prevent against contact between the web of media250and the bearing surface321.

The web guide320ofFIG. 6has a wrap angle α of 90 degrees between the input travel direction510and the output travel direction511. With reference also toFIG. 5, processing liquid310that is pressurized within the hollow interior327of the web guide320is ejected through liquid ejection holes521of the first array501, liquid ejection holes522of the second array502, and liquid ejection holes523of the intermediate array505. Web guide320has a curved wall328having a wall thickness T with a curved exterior surface329. Liquid ejection holes521,522,523are formed through the curved wall328from the hollow interior327to the curved exterior surface329. All of the liquid ejection holes in this example have the same characteristic shape and size, but they have different orientations relative to the curved wall328. Although in general the hole diameter and the hole shape can vary from hole to hole and from array to array, in an exemplary configuration, the liquid ejection holes521,522,523are circular and have a diameter that is within 10% of a value which is referred to as the characteristic diameter D herein. It has been found to be advantageous if the ratio of the wall thickness T to the characteristic diameter D is between about 1.5 and 3.0. For example, in an embodiment where the wall thickness T was 3.0 mm, it was found that the best liquid bearing performance in terms of stand-off distance, total flow, and web stability was for a characteristic diameter D of about 1.5 mm (a ratio of 2.0). In other embodiments (not shown) the liquid ejection holes can have a non-circular shape, including shapes such as ovals or rectangular slots.

As shown inFIG. 6, axes524of the liquid ejection holes521in the first array501located in proximity to the web guide entry position531are not perpendicular to the curved exterior surface329of curved wall328, but rather are inclined toward a downstream direction of the web transport path500(i.e., the position of the axes524at the curved exterior surface329is father downstream than the position of the axes524at the hollow interior327) by a first inclination angle β1relative to a normal527to the curved exterior surface329. Similarly, axes525of the liquid ejection holes522in the second array502located in proximity to the web guide exit position532are not perpendicular to the curved exterior surface329of curved wall328. Rather, the axes525are inclined toward an upstream direction of the web transport path500(i.e., the position of the axes525at the curved exterior surface329is father upstream than the position of the axes525at the hollow interior327) by a second inclination angle β2relative to a normal528to the curved exterior surface329. In other words the direction that the processing liquid310is ejected through both the first array501and the second array502(FIG. 5) is into the region where the web of media250is wrapped around the bearing surface321(i.e., the portion of the curved exterior surface329between the web guide entry position531and the web guide exit position532). In the illustrated configuration, the liquid ejection holes523of the intermediate array505are oriented with their axes526coincident with the normal529to the curved exterior surface329(i.e., the axes526are perpendicular to the curved exterior surface329.) For a circular curved exterior surface329as in the configuration ofFIG. 6, this implies that the axis526of the liquid ejection holes523of the intermediate array505are oriented radially.

By tilting the axes524,525of the first array501and the second array502inward into the region where the web of media250is wrapped around the bearing surface321, it has been found that less liquid is required to be ejected from the intermediate array505. Consequently, if the liquid ejection holes523have the same diameter as the liquid ejection holes521,522, fewer liquid ejection holes523are required in the intermediate array505. More generically, a total cross-sectional area of the liquid ejection holes523in the intermediate array505can be less than a total cross-sectional area of the liquid ejection holes521in the first array501(row R1) and also less than a total cross-sectional area of the liquid ejection holes522in the second array502(row R2), where the total cross-sectional area of an array of liquid ejection holes is the sum of the cross-sectional areas for all of the liquid ejection holes in that array.

The hole configurations described herein, including the inclination of liquid ejection holes521of the first array501and the liquid ejection holes522of the second array502for ejecting liquid into the region where the web of media250is wrapped around the bearing surface321, enable the use of a lower flow rate of ejected liquid. Additionally, it has been found that such configurations provide the additional advantage that the web of media250moves with improved stability without appreciable vibration. As a result, the stand-off distance S between the web of media250and the bearing surface321can be maintained at a relatively small distance of between about 0.5 mm and 1.0 mm. It has been found that using the hole configurations described herein such a stand-off distance S can be maintained while using a cumulative flow rate of processing liquid310through the liquid ejection holes of less than 25 gallons/minute or even 20 gallons/minute for a 17 inch wide web guide. This flow rate is approximately 30% less than was found to be required for other hole configurations that were previously tested. In addition, by directing the ejected processing liquid310into the web wrap region, less ejected processing liquid310tends to be directed along the web of media250toward upstream or downstream processing tanks. This decreases the likelihood of processing liquid310leaving the corresponding processing tank and being wasted or contaminating the processing solution in a neighboring processing tank.

It has been found that that it is advantageous for the first inclination angle β1and the second inclination angle β2to have magnitudes that are between 15 degrees and 45 degrees. In the example shown inFIG. 6both β1and β2have magnitudes of approximately 30 degrees but are of opposite sign. Furthermore, in some embodiments the magnitude of the first inclination angle β1is substantially equal to the magnitude of the second inclination angle β2(i.e., equal to within about 5 degrees).

FIG. 7shows another view of the web guide320ofFIG. 6which more clearly indicates the circumferential location of the liquid ejection holes521of the first array501and the liquid ejection holes522of the second array502. Web guide320has a web guide entry position531, which is defined as the position at which the direction of the web of media250becomes tangent to the curved exterior surface329of curved wall328as the web of media250approaches the web guide320at the beginning of the bearing surface321. Similarly, web guide320has a web guide exit position532, which is defined as the position at which the direction of the web of media250becomes tangent to the curved exterior surface329of curved wall328as the web of media250moves away from the web guide320at the end of the bearing surface321.

In the exemplary configuration shown inFIG. 7, the liquid ejection holes521of the first array501(row R1) are located upstream of the web guide entry position531. In particular, a radial line533that passes through the center of liquid ejection hole521at the curved exterior surface329is at an angle θ1in an upstream direction with respect to a radial line535that intersects the web guide entry position531. Similarly, the liquid ejection holes522of the second array502(row R2) are located downstream of web guide exit position532. In particular, a radial line534that passes through the center of liquid ejection hole522at the curved exterior surface329is at an angle θ2in a downstream direction with respect to a radial line536that intersects the web guide exit position532.

In testing that was done for a web guide320having the configuration shown inFIGS. 6 and 7it was found that angles of θ1=θ2=7.5 degrees produced good results. More generally, magnitudes of angles θ1and θ2of about 15 degrees or less were found to be suitable. For a 2 inch diameter circular web guide, the circumference is 6.28 inches and an arc length corresponding to 7.5 degrees ( 1/48 of a full circle) is 0.13 inches. In general, for web guides having a bearing surface321with a radius of curvature r and a row position angle θ relative to the position of tangency, the circumferential distance L between the position of tangency at the web guide entry position531or the web guide exit position532is L=π r θ/180.

As described above, the first array501of liquid ejection holes521is located in proximity to the web guide entry position531, and the second array502of liquid ejection holes522is located “in proximity to” (i.e., “near to”) the web guide exit position532. In this context, relative to angular position the terms “in proximity to” or “near to” should be interpreted to mean within about 15 degrees, or relative to arc length they mean within a circumferential distance of about L=π r/12 (e.g., within about 0.26 inch for a 2 inch diameter circular web guide). This can include the first array501(row R1) being located exactly at the web guide entry position531, upstream of the web guide entry position531or downstream of the web guide entry position531. This can also include the second array502(row R2) being located exactly at the web guide exit position532, downstream of the web guide exit position532or upstream of the web guide exit position532.

FIG. 8shows a distribution plot of liquid ejection holes along the cross-track direction203as a function of angle around the curved exterior surface329for the web guide320example ofFIGS. 6 and 7. The web guide entry position531is defined to be the zero angle position and the web guide exit position532is at 90 degrees. The positions of the first edge253and second edge254of the web of media250(FIG. 5) are indicated by dashed lines for reference. First array501(Row R1) is located at −7.5 degrees (7.5 degrees upstream of web guide entry position531), and second array502(Row R2) is located at 97.5 degrees (7.5 degrees downstream of web guide exit position532). Intermediate array505is a linear array located at 45 degrees (i.e., midway between the web guide entry position531and the web guide exit position532).

In this exemplary configuration, the number of liquid ejection holes521in first array501(row R1) is the same as the number of liquid ejection holes522in second array502(row R2), and is about twice as many as the number of liquid ejection holes523in intermediate array505. A distance d1between the outermost liquid ejection hole521in first row R1and first edge253of web of media250is about the same as the distance d2between the outermost liquid ejection hole522in second row R2and first edge253of web of media250, and is about half as large as the distance dibetween the outermost liquid ejection hole523in intermediate array505and first edge253of web of media250. The uniform spacing or pitch p1between the liquid ejection holes521in first row R1is the same as the uniform pitch p2between the liquid ejection holes522in second row R2, and is about half as large as the uniform pitch pibetween the liquid ejection holes523in intermediate array505. The spacing Z between the two end-most liquid ejection holes522in the second row R2is preferably less than the width W of the web of media250. In this way, the processing liquid310is ejected at the web of media250rather than beyond the first and second edges253,254of the web of media250.

It has been found that the hole configuration described above with reference toFIGS. 5-8works well for a 90 degree wrap angle web guide320having the same orientation of the bearing surface321whether the web guide320is submerged or partially submerged in the processing liquid310or even positioned above liquid level311so that it is non-submerged. It has also been found that a similar hole configuration works well for a range of other wrap angles between about 45 degrees and 120 degrees. For example, a submerged web guide320has been designed and tested with a 109 degree wrap angle. In this case, the web guide entry position531is separated from the web guide exit position532by 109 degrees, and the intermediate array505is a linear array located at 54.5°, which is midway between the web guide entry position531and the web guide exit position532.

FIG. 9shows a hole configuration for another exemplary web guide320configuration having a 55 degree wrap angle with the bearing surface321at the upper left of the web guide as inFIG. 6. The primary difference relative to the hole configuration ofFIGS. 6-8is that there is no intermediate array505in the hole configuration ofFIG. 9. There is only the first array501(row R1) and the second array502(row R2). There are no additional liquid ejection holes523disposed along the web transport path500around the bearing surface321(FIG. 6) between the first row R1of liquid ejection holes and the second row R2of liquid ejection holes522. The web guide entry position531is defined to be at zero degrees, and the web guide exit position532is at 55 degrees. The 30 degree inclined liquid ejection holes521of first row R1are located 7.5 degrees upstream of the web guide entry position531, and the 30 degree oppositely inclined liquid ejection holes522of second row R2are located 7.5 degrees downstream of the web guide exit position532. In this case, it has been found that the intermediate array505of holes is not necessary due to the shorter circumferential distance between the first array501and the second array502.

FIG. 10shows a cross-sectional view of an exemplary submerged web guide320configuration having a 180 degree wrap angle with the center of the bearing surface321oriented toward the bottom. Input travel direction510is vertically downward and output travel direction511is vertically upward. The web guide entry position531is defined to be at zero degrees, and the web guide exit position532is at 180 degrees. In this example, the web guide entry position531is located at approximately the same height above the bottom of the web guide320as the web guide exit position532. The 30 degree inclined liquid ejection holes521of first row R1are located 7.5 degrees upstream of the web guide entry position531, and the 30 degree oppositely inclined liquid ejection holes522of second row R2are located 7.5 degrees downstream of the web guide exit position532. As in the example ofFIG. 9, there is no intermediate array505in the hole configuration ofFIG. 10. It has been found that the intermediate array505is not necessary in this case because gravity will pull the liquid downward toward the bottom of the web guide320in this configuration.FIG. 11shows the corresponding distribution of liquid ejection holes along the cross-track direction203as a function of angle.

FIG. 12shows a cross-sectional view of an exemplary non-submerged web guide320having a 180 degree wrap angle, with the web guide entry position531located near the bottom of the web guide320and the web guide exit position532located near the top of the web guide320. Due to gravity, it was found that ejected processing liquid310tended to pool near the web guide entry position531if the first array501has a similar number of holes as the second array502. With reference also toFIG. 13which illustrates a hole configuration corresponding toFIG. 12, this problem was addressed by adding a third row R3of liquid ejection holes522to the second row R2of liquid ejection holes522in second array502, while decreasing the number of liquid ejection holes521in the first array501, and also decreasing the number of liquid ejection holes523in the intermediate array505.

In the illustrated configuration, the liquid ejection holes522of third row R3are formed through the curved wall328from the hollow interior327to the curved exterior surface329and are distributed along a line spanning the web guide320in the cross-track direction203at a position upstream of the web guide exit position532. Both second row R2and third row R3are formed in proximity to the web guide exit position532with second row R2being located 7.5 degrees downstream and third row R3being located 7.5 degrees upstream of web guide exit position532. The pitch p3and number of liquid ejection holes522in third row R3are approximately equal to the pitch p2and the number of liquid ejection holes522in second row R2(e.g., equal to within 10%). In the hole configuration shown inFIG. 13, the positions of liquid ejection holes522in the cross-track direction203in third row R3are staggered relative to the positions of liquid ejection holes522in the second row R2. The first row R1of liquid ejection holes521is located at the web guide entry position531, and the total number of liquid ejection holes521in the first row R1is less than a total number of liquid ejection holes522in the second row R2.

In the example ofFIG. 13, the total number of liquid ejection holes522in the second array502(including rows R2and R3) is much larger than the number of liquid ejection holes521in first array501(row R1). In this case, the total number of liquid ejection holes522is more than five times greater than the number of liquid ejection holes521, and in other configurations (not shown) it can be as large as ten or twenty times greater.

Additionally, the spacing of liquid ejection holes521is non-uniform in first row R1in the example ofFIG. 13. The pitch p1bof liquid ejection holes521toward the center of web guide320in the cross-track direction203is greater than the pitch p1aof liquid ejection holes521toward the outer edges. Also, the distance d1between the outermost liquid ejection hole521in first array501and the first edge253of web of media250is greater than the distance d2between the outermost liquid ejection hole522in the second array502and first edge253of web of media250. In other configurations, the spacing of liquid ejection holes522in some or all of the second row R2, the third row R3or the intermediate array505can also be non-uniform.

With regard to the inclination of the various holes shown inFIG. 12, the 30 degree inclination of the first array501of liquid ejection holes521and the second array502of liquid ejection holes522is configured to eject processing liquid310into the region where the web of media250is wrapped around the bearing surface321. The liquid ejection holes523of the intermediate array505are oriented with their axes perpendicular to the curved exterior surface329as in the example ofFIG. 6.

In the exemplary web guide320described above with reference toFIGS. 12 and 13, more liquid ejection holes are provided near the web guide exit position532than near the web guide entry position531because of the tendency for the accumulation of ejected processing liquid310near the web guide entry position531due to gravitational effects. It is also contemplated that in analogous embodiments (not shown) where the web guide entry position531is near the top of the web guide320and the web guide exit position532is near the bottom of the web guide320, the number of liquid ejection holes521in the first array501can be greater than the number of liquid ejection holes522in the second array502, and the asymmetry of the distribution of liquid ejection holes in the first and second arrays501and502can be reversed relative to the distribution shown inFIG. 13.

FIG. 14shows a schematic side view of a roll-to-roll liquid processing system550having a web transport system551for guiding a web of media250between the supply roll202and the take-up roll204through a plurality of processing tanks, including processing tank560containing processing liquid555up to a liquid level561, and processing tank565containing processing liquid557up to a liquid level562. Web of media250is guided through processing tank560by a first arrangement of non-contact web guides including two non-submerged web guides552and one submerged web guide554. Subsequently web of media250is guided through processing tank565by a second arrangement of non-contact web guides including two non-submerged web guides552, three submerged web guides554and one partially-submerged web guide553. The various non-submerged web guides552, partially-submerged web guides553and submerged web guides554have a variety wrap angles and orientations of the respective bearing surfaces, and can eject different processing liquids through liquid ejection holes (not shown inFIG. 14). As described above with reference toFIGS. 6-13, configurations of liquid ejection holes for at least some of the non-contact web guides (both within a single processing tank560or565as well as from processing tank560to processing tank565) will generally be different.

As was described above with reference toFIGS. 4-6, a pump provides the pressurized liquid that is ejected through the liquid ejection holes. Each web guide can be independently pressurized by its own pump, but in some embodiments a single pump is used to pressurize two or more web guides. For simplicity, only one pump570is shown inFIG. 14. Pump570pumps liquid from the reservoir of processing liquid555in processing tank560through a distribution line572into the hollow interior327(FIG. 6) of the web guides. For simplicity,FIG. 14shows the pump570supplying processing liquid555to one non-submerged web guide552and one submerged web guide554. However, it will be desirable in many configurations for a single pump570to supply all of the web guides associated with the processing tank560.

Optionally a valve571is provided downstream of pump570for controlling the overall flow rate. After the processing liquid555is ejected through the liquid ejection holes, it is subsequently directed back into the reservoir of processing liquid555in the processing tank560. For submerged web guides554, the processing liquid555in the submerged web guide554is ejected directly back into the reservoir of processing liquid555. For a non-submerged web guide552, the ejected processing liquid555falls back as a stream or as droplets556into the reservoir of processing liquid555in processing tank560. Similarly for processing tank565, for a non-submerged web guide552, the ejected processing liquid557falls back as a stream or as droplets558into the reservoir of processing liquid557in processing tank565.

Submerged web guide554is positioned at a first height H1within processing tank560and non-submerged web guide552is positioned at a second height H2within processing tank560, where the second height H2is greater than first height H1. There will be a pressure drop in the processing liquid557in the distribution line572which will be proportional to the difference in heights. In order to prevent over-pressurizing a web guide that is positioned lower (leading to too much web stand-off) or under-pressurizing a web guide that is positioned higher (leading to too little web stand-off), restrictor(s)573can be provided to control the pressure provided to one or more of the web guides. In the illustrated configuration, a restrictor573is provided in the branch574of the distribution line572that leads to submerged web guide554. Restrictor573can include a fixed restriction, such as a reduction of the cross-section of a portion of a branch574, or it can include an adjustable restriction such as a valve for controlling flow rate and web stand-off independently for submerged web guide554and non-submerged web guide552. In any case, restrictor573provides a pressure drop in branch574to compensate for the pressure drop associated with the difference in heights H2−H1. In some configurations, restrictors573can also be used in the to compensate for other factors such as differences in hole patterns or differences in the required flow rates for different web guides552,554.

The examples described above describe web transport systems using liquid bearings that can be used in liquid processing systems such as an electroless plating system, where the processing liquid from a processing tank is used to provide a liquid bearing. More generally, web transport systems can use liquid bearings even in the absence of processing liquids and processing tanks, and such web transport systems can include non-contact web guides with liquid ejection hole configurations analogous to those described herein.

FIG. 15shows a high-level system diagram for an apparatus400having a touch screen410including a display device420and a touch sensor430that overlays at least a portion of a viewable area of display device420. Touch sensor430senses touch and conveys electrical signals (related to capacitance values for example) corresponding to the sensed touch to a controller480. Touch sensor430is an example of an article that can be printed on one or both sides by the flexographic printing system100and plated using an embodiment of roll-to-roll liquid processing system300where the web of media250is guided by non-contact web guides having liquid ejection hole configurations as described above.

FIG. 16shows a schematic side view of a touch sensor430. Transparent substrate440, for example polyethylene terephthalate, has a first conductive pattern450printed and plated on a first side441, and a second conductive pattern460printed and plated on a second side442. The length and width of the transparent substrate440, which is cut from the take-up roll104(FIG. 1), is not larger than the flexographic printing plates112,122,132,142of flexographic printing system100(FIG. 1), but it could be smaller than the flexographic printing plates112,122,132,142.

FIG. 17shows an example of a conductive pattern450that can be printed on first side441(FIG. 16) of substrate440(FIG. 16) using one or more print modules such as print modules120and140of flexographic printing system (FIG. 1), followed by plating using a roll-to-roll liquid processing system300or550(FIGS. 3 and 14). Conductive pattern450includes a grid452including grid columns455of intersecting fine lines451and453that are connected to an array of channel pads454. Interconnect lines456connect the channel pads454to the connector pads458that are connected to controller480(FIG. 15). Conductive pattern450can be printed by a single print module120in some embodiments. However, because the optimal print conditions for fine lines451and453(e.g., having line widths on the order of 4 to 8 microns) are typically different than for printing the wider channel pads454, connector pads458and interconnect lines456, it can be advantageous to use one print module120for printing the fine lines451and453and a second print module140for printing the wider features. Furthermore, for clean intersections of fine lines451and453, it can be further advantageous to print and cure one set of fine lines451using one print module120, and to print and cure the second set of fine lines453using a second print module140, and to print the wider features using a third print module (not shown inFIG. 1) configured similarly to print modules120and140.

FIG. 18shows an example of a conductive pattern460that can be printed on second side442(FIG. 16) of transparent substrate440(FIG. 16) using one or more print modules such as print modules110and130of flexographic printing system (FIG. 1), followed by plating using a roll-to-roll liquid processing system300or550(FIGS. 3 and 14). Conductive pattern460includes a grid462including grid rows465of intersecting fine lines461and463that are connected to an array of channel pads464. Interconnect lines466connect the channel pads464to the connector pads468that are connected to controller480(FIG. 15). In some embodiments, conductive pattern460can be printed by a single print module110. However, because the optimal print conditions for fine lines461and463(e.g., having line widths on the order of 4 to 8 microns) are typically different than for the wider channel pads464, connector pads468and interconnect lines466, it can be advantageous to use one print module110for printing the fine lines461and463and a second print module130for printing the wider features. Furthermore, for clean intersections of fine lines461and463, it can be further advantageous to print and cure one set of fine lines461using one print module110, and to print and cure the second set of fine lines463using a second print module130, and to print the wider features using a third print module (not shown inFIG. 1) configured similarly to print modules110and130.

Alternatively, in some embodiments conductive pattern450can be printed using one or more print modules configured like print modules110and130, and conductive pattern460can be printed using one or more print modules configured like print modules120and140ofFIG. 1followed by plating using a roll-to-roll liquid processing system.

With reference toFIGS. 15-18, in operation of touch screen410, controller480can sequentially electrically drive grid columns455via connector pads458and can sequentially sense electrical signals on grid rows465via connector pads468. In other embodiments, the driving and sensing roles of the grid columns455and the grid rows465can be reversed.

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