Patent Grant
7685692
Cross-reference is made to related, co-filed U.S. patent application Ser. No. 10/851,560 to Axtell et al., filed May 21, 2004, entitled “Nozzle Tip and Methods of Use,” issued on Feb. 3, 2009 as U.S. Pat. No. 7,485,191, U.S. patent application Ser. No. 10/851,451 to Axtell et al., filed May 21, 2004, entitled “Method of Making an Electronic Display,” now abandoned, co-filed U.S. patent application Ser. No. 10/851,492 to Weiner et al., filed May 21, 2004, entitled “Skiving Device And Methods Of Use”, issued on Apr. 4, 2006 as U.S. Pat. No. 7,024,153, U.S. patent application Ser. No. 10/851,590 to Weiner et al., filed May 21, 2004, entitled “METHOD OF MAKING AN ELECTRONIC DISPLAY”, issued on Jul. 17, 2007 as U.S. Pat. No. 7,245,346, and co-filed U.S. patent application Ser. No. 10/851,439 to Rankin et al., filed May 21, 2004, entitled “Method of Making an Electronic Display”, now abandoned.
A roller and methods for selectively removing material using the roller are presented.
Often in manufacturing processes, a material, or a portion of a material, needs to be removed before further processing steps can occur. Such material removal can be referred to as “skiving.” Various methods of skiving or material removal are known in manufacturing processes.
U.S. Pat. No. 6,678,496 discloses a mechanism for skiving fuser rollers using skive assemblies including elongated, thin, flexible members that scrape material from the fuser apparatus roller. An air plenum with a nozzle arrangement provides positive airflow to ensure that the fuser apparatus roller is fully stripped. The skiving assembly as described in this patent scrapes the material away, and any remaining material is removed by airflow from the nozzle.
It has been shown in U.S. Pat. Nos. 5,532,810; 5,589,925; and 6,029,039 that elongated skive fingers of limited flexibility mounted in particularly configured support bodies substantially prevent damaging flex of the skive fingers. In these skive mechanisms, the support bodies support a major portion of the skive fingers and pivot into engagement with the fuser roller to limit skive finger flexing when engaged by a material to be skived, typically from a roller. The skive fingers can be retractable to prevent damage by jammed materials.
U.S. Pat. No. 5,670,202 discloses a technique for selectively applying materials in a pattern by spraying and then collecting the excess materials using adjustable skive manifolds on each side of the spray pattern, which function to vacuum off the edges of the airless spray pattern. The system utilizes a robot manipulator, a masking tool assembly, and other hardware, to recover material sprayed and skived by the masking tool assembly.
U.S. Pat. No. 6,564,030 discloses a fuser station with a vented skive assembly for an image-forming machine. The image-forming machine has a photoconductor, a primary charger, an exposure machine, a toning station, a transfer charger, and a vented fuser station. The fuser station may include a pressure roller, a fuser roller, and a skive assembly. The skive assembly has rib sections forming one or more slots, which are configured to provide an airflow pattern to reduce condensation.
U.S. Pat. No. 6,136,141 discloses fabrication of lightweight semiconductor devices including removal of a substrate from a support member utilizing a beam of radiant energy. The substrate is skived from the support member without damage to the semiconductor device. This method can be implemented on a continuous, roll-to-roll basis wherein the substrate and support member each comprise an elongated web, and wherein the webs are continuously advanced through a plurality of deposition chambers and the skiving area.
U.S. Published Application No. 2003/0049059 discloses a method and structure for cleaning a roller in an imaging apparatus, including use of a cleaner assembly having a skive blade in contact with the roller. The skive blade can be selectively mounted on and removed from the cleaner assembly.
U.S. Pat. No. 6,469,757 discloses a technique for selectively removing a liquid crystalline material layer from a multi-layered substrate. The liquid crystalline material was coated and dried on the substrate, then a nozzle tip was used to remove the liquid crystalline material from the substrate, as it was moved on a rotating drum past the nozzle in a batch process. To remove all the desired material using this nozzle, multiple nozzle passes may be needed, prohibiting roll-to-roll processing. It has been found that harder materials, for example, cross-linked materials, cannot be skived with this process.
It would be advantageous to have a means of removing any amount of material, from a portion of a layer to more than one layer of material, in a batch or a roll-to-roll (continuous) manufacturing process. Further, a method and apparatus capable of removing materials of varying hardness, for example, solvents (including water), metal, gelatin, liquid crystal, polymers, ceramics and pulp, is desirable.
A process for skiving a substrate is described, wherein the substrate comprises a support and a layer, comprising providing the substrate to a skiving assembly comprising at least one roller having a surface; contacting the surface of at least one roller with the layer; and moving the skiving assembly in relation to the substrate to remove at least a portion of the layer and expose at least a portion of the support, wherein the exposed portion of the support is undamaged.
The process of skiving using the roller as described herein is suitable for skiving materials of all types, from soft coatings to hard materials such as metal, cross-linked polymers, or dried materials. The roller is capable of removing from a portion of a layer to more than one layer of material in a single pass. Skiving using the roller, or a device or apparatus including at least one roller, can be done in a batch or a roll-to-roll process. Single- or multiple-pass skiving can be done.
The invention can be understood with reference to the detailed description below and the accompanying figures, as follows:
The present invention provides methods and apparatuses useful for removing, displacing, or patterning materials in a layer by the use of a roller during a manufacturing process. The method and apparatus can be useful in manufacturing of various materials, including, for example, graphic arts, metal working, paper molding, food process, imaging and display materials, display devices, electronic devices, and other coated materials.
“Skiving” is the controlled removal of at least a portion of one or more layers. As used herein, skiving is done by a roller, alone or in combination with other material removal methods. The removal or patterning of the material can be by cutting or displacement.
“Substrate” as used herein is one or more layers, which can be the same or different composition. The substrate can be skived to remove material therefrom.
“Material” as used herein refers to the portion of the substrate that is removed, or intended to be removed, by skiving.
A roller can have two sides and a face. The roller can be made of a machinable material, a moldable material, or a combination thereof. For example, the roller can be metal, such as stainless steel; ceramic; glass; or a polymer. The roller can be acetal polyoxymethylene, polyethylene, or polypropylene. The roller, or a portion thereof, can be a combination of two or more materials. For example, the roller can be manufactured of one material, and a second material can be applied to the first material to form all or a portion of the roller face.
At least a portion of the roller face can be coated with a material suitable for increasing durabilty, reducing friction, preventing wear, or providing other desirable mechanical properties to the roller during use, wherein the roller interacts with a substrate to remove material from the substrate. For example, to increase wear and reduce friction of the roller face, fluoropolymers such as Teflon®, or acetal resins such as Delrin®, both from E. I. Dupont de Nemours and Company, Delaware, can be used.
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The roller can be configured so that the roller shape and configuration of the roller face minimizes contact area with the substrate. Reducing the contact surface area can reduce friction between the roller face and the substrate. The contact surface area between the roller face and the substrate can be large enough to create friction sufficient to rotate the roller about an axis during skiving. The roller can be configured to increase the cutting efficiency of the roller face. The roller can be configured to reduce or prevent material retention by the roller. The roller can be configured to provide minimal or no damage to the structure of the unskived portion of the substrate.
The width and diameter of the roller can vary depending on the application. The width “w” of the roller is a measurement of the roller from side to side across the widest portion of the roller face, as shown in
The roller can be part of a device 16, such as a skiving device, as shown in
The device 16 can be part of a skiving assembly 10 as shown in
The roller, housing, apparatus, or a combination thereof can include an indicia. The indicia can indicate, for example, the type of roller, or the location of the roller in an apparatus. The indicia can be in any form, for example, a line, color, dot, pictogram, lettering, numbers, or a combination thereof. The indicia can be an alignment means, such as a tab/slot interaction, groove, keyway, or other three-dimensional alignment feature.
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If a vacuum source, such as manifold 27, is used in assembly 10, the vacuum source and applied pressure can be common to all rollers. Separate vacuum sources can be used where one or more roller require a different level of vacuum for material removal. Different vacuum forces on at least two rollers can be achieved by various means, including, for example, use of separate vacuum sources, a metered manifold, or adjustments to the roller/vacuum configuration. Each roller can have a different vacuum force applied from at least one other roller.
Vacuum can be formed by any known means. For example, the vacuum can be generated by an air drawn suction system, for example, a turbine. The vacuum pressure can be controlled manually or automated. The vacuum pressure can range from 0 to 760 mm Hg. The force exerted by the vacuum on a roller face can range from 0 to an absolute value of 50 N/mm2. Methods of controlling vacuum pressure are known in the art, and can include use of a pressure regulator or valve. The vacuum can be connected to a reservoir for collection and disposal of material removed from the roller face. According to certain embodiments, the vacuum apparatus, reservoir, or any combination thereof, can be heated by a heating source, for example, electric heat, a water jacket, or a steam jacket, to aid in removal of material.
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The support 12 can be any material suitable for carrying the substrate 21 past the roller 15. For example, support 12 can be, but is not limited to, a web, conveyor belt, rotating table, translating table, rotating drum, or roll. The support material can be hard enough to provide support for the substrate, and provide resistance against the roller without causing damage to the substrate. The support 12 can be, for example, polymeric, metallic, ceramic, glass, fibrous, a composite material, or a combination thereof. According to various embodiments, the support 12 can be at least partially elastic, having some give under the pressure of the roller 15. For example, the support 12 can be polymeric, such as polyurethane, polyester, phenolic resin, or composite plastics.
The support can be movable relative to the assembly or device. The support and roller can be movable relative to one another. For example, the support can be moved relative to the assembly or device to compensate for side-to-side movement or slippage of the substrate. The support, device, or assembly can be translated to account for movement of the substrate. The support can be designed to minimize movement of the substrate. For example, the support can include a guide, track, groove, or other alignment mechanism to assist in keeping the substrate aligned with respect to one or more rollers. For example, the support can have a flanged edge to guide the substrate towards the assembly. According to certain embodiments, the support can be a flanged roller.
One or more roller in a device or apparatus can be positioned relative to the edge of the substrate so a material can be removed from a set location on the substrate. The roller can be positioned by attachment in the device or apparatus at a set location. For example, the roller can be attached to a manifold or alignment block at a desired distance from the edge of the substrate. The roller can be relocatably positioned in the device or apparatus, or permanently positioned. The positioning of the roller can be from a leading edge of the substrate, a side edge of the substrate, or both. The roller can be positionable within the device or apparatus, for example, by means of a linear slide actuator, spring, lever, or other adjustable mechanism. The device or apparatus can be positionable relative to the substrate to place a roller in a desired location. Any of the roller, device, or apparatus can be positioned manually, automatically, or a combination thereof. Positioning systems can include physical or optical guides to assist in locating the roller with respect to the substrate. The device or apparatus can be portable to assist in positioning.
The roller, device, assembly, or a combination thereof can be moved towards or away from the support to change the height of the roller in relation to the support. The positioning device can be a linear slide actuator, a linear motor, screw, wedge, pneumatics, hydraulics, or other mechanism capable of planar movement. The positioning device can be used to position one or more roller to maintain a uniform height with respect to the support. Each roller can have the same or a different positioning device as at least one other roller in an apparatus. The positioning device can move the roller, device, or apparatus about a pivot point, such that the movement of the roller, device, or apparatus is in an arc with respect to the substrate and support.
An application angle positioning mechanism can be used to move a device or assembly including one or more rollers around the support where the support is curved, such as a drum or roll. The position desirable for skiving can change depending upon the Tg of the material being skived, the density of the material, the configuration of the roller, drying or hardening rates of the material, vacuum speed, and other factors known to those skilled in the manufacturing arts.
One or more of the above positioning systems can be combined into a single system. The system can be manually controlled, automatically controlled, or a combination thereof. Indicia as described herein can be used on one or more of the support, substrate, roller, device, or assembly to aid in positioning of the roller relative to the support and substrate.
A device or assembly including one or more rollers can include a force mechanism to hold each roller against the substrate to be skived. For example, the device or assembly can include a spring, lever, block, weight, other force exerting mechanism, or a combination thereof to position and hold the roller in relation to the support or substrate. The force mechanism can be gravity. The pressure exerted by the roller face against the substrate can be from 0 to 55 Kilopascals. The force mechanism can apply a force to the roller to maintain a uniform pressure of the roller against the substrate. If more than one roller is present, uniform pressure can be maintained at each roller, or each roller can have a different applied pressure against the substrate. Each roller can be made to skive to the same or different depth than each other roller in the apparatus. The force mechanism can compensate for variability in support thickness, substrate thickness, or a combination thereof. The force mechanism can compensate for non-uniform movement of the support, substrate, or roller. The force mechanism can compensate for roller wear during operation.
The device or assembly can include a solvent dispenser for dispensing a solvent onto the substrate. The solvent dispenser can be a nozzle, opening, slit, spray head, or other known dispensing mechanism. The dispenser can be a separate assembly, or can be located anywhere on the apparatus or device. For example, the dispenser can be part of an alignment block, positioning system, or support for the device or apparatus. The amount of solvent administered can be controlled, for example, by a metering pump, valve, or like mechanism. The mechanism can be operated manually or automated with a timer, computer, automatic controller, other control device, or a combination thereof. The solvent can be capable of softening or removing a desired material from the substrate. Suitable solvents can include, for example, alcohol, acid, base, ammonia-based solvent, bleach-based solvent, water, distilled water, organic solvent, inorganic solvent, air, and surfactant. The solvent dispenser can provide a solvent stream having the same width as the skived area. The solvent dispenser can provide a solvent stream narrower or wider than the skived area as desired. The solvent dispenser can be movable with relation to the substrate, the roller, or both. With reference to the direction of material movement, the solvent dispenser can be located prior to the roller, after the roller, or adjacent the roller. According to certain embodiments, the solvent dispenser can be located before the roller a sufficient distance such that the solvent can soften the material to be skived before it reaches the roller. The solvent can be delivered at a flow rate sufficient to wet the material without causing movement of the material. A separate solvent dispenser can be associated with one or more rollers, wherein each solvent dispenser can have a different solvent or different solvent width. The solvent temperature can be raised or lowered.
One or more additional material removal mechanisms can be used in combination with the skiving device or apparatus. For example, a vacuum tip, doctor blade, skive finger(s), or skive nozzle tip can be used with the skiving device in any configuration. The removal mechanisms can be used to remove material from the substrate, or to clean the substrate prior to or after skiving with the roller.
In use, the face of the roller contacts the material to be removed from the substrate. The material can be displaced to either side of the roller on the substrate, can adhere to the roller and be stripped from the substrate, or a combination thereof. Where the material adheres to the roller, the material can adhere loosely or strongly, and can be removed by mechanical forces, such as gravity, a vacuum, a suction nozzle, a skive finger, a doctor blade, a brush, or a combination thereof. The roller can be designed to prevent adhesion of the material, for example, by forming the roller from, or coating at least a portion of the face and/or side of the roller with, a non-stick material, such as Teflon® or Delrin®, or by coating at least a portion of the face of the roller with a surfactant, lubricant, hydrophilic coating, or hydrophobic coating. To encourage adhesion, the roller can be constructed of a tacky material, for example, a polymer, or can be coated with an adhesive. To control adhesion, the roller, substrate, or both can be heated or chilled.
Two or more rollers can be joined by a common axis for use in a device or assembly. Each roller commonly joined can have the same or different profile. The rollers can be of one material, for example, a single mold can be used to form the rollers and axis. The axis of rotation for each roller can be an axle. The axis of rotation can include ball bearings or other materials suitable for enabling rotation of the roller about the axis. The axis of rotation can be at least partially enclosed, for example, by a housing. Each roller can independently be rotable about its axis. Each roller independently can be freely rotable, turning by friction between the roller surface and the substrate. Each roller independently can be motor-driven, such that the motor controls the speed of rotation of the roller, irrespective of the movement of the substrate. The speed at which the roller rotates about the axis can be the same as the speed of the substrate movement.
Where material is removed or displaced on the substrate, a chasm is formed. The profile of the chasm created by the roller can be determined by the profile of the roller face. The depth of the chasm is dependent upon the depth to which the roller is inserted into the substrate, or the distance between the support and the roller face.
The face of the roller can be designed to clean the chasm to ensure complete material removal to a desired depth in the desired path without damage to underlying materials. The roller can remove the material in a pattern. One or more additional methods of removing material can be used in combination with the roller. For example, a vacuum tip, doctor blade, skive finger(s), solvent applicator, skive nozzle tip, or the like can be used in line with the roller, adjacent the roller, or to remove material from a different section of the substrate than the roller.
The roller, device, and assembly allow for accurate removal of a material from a predetermined location on a substrate. Use of the roller, device, or assembly for a roll-to-roll or continuous process can provide improved accuracy of skiving in the web and cross-web directions, especially as compared to prior batch processes. Use of the device or apparatus can improve the repeatability of the skiving on a substrate because the one or more roller and the substrate can be held in continuous registration. The percentage of material removed can be greatly increased over the prior art processes, for example, that described in U.S. Pat. No. 6,469,757. In U.S. Pat. No. 6,469,757, the skive tip must make 10, 20, or more sequential passes over the same location in order to clean the substrate in the desired path, removing only 2-10% of the material with each pass. The roller can remove the material in one pass. For example, the roller can remove at least 90% of the material in a single pass, for example, at least 95%, or at least 98% of the material.
The roller can remove material of various viscosities and various hardnesses. For example, materials that are cross-linked, polymerized, chill-set, or otherwise hardened, as well as low-viscosity materials, can be removed, displaced, or patterned by the roller in a batch or roll-to-roll process. Skiving methods known previously in the art are not capable of removing hardened materials in a single pass.
Substrates skived with a roller and by the methods described herein can remain undamaged such that any desirable characteristics of the exposed substrate remain unchanged. For example, the exposed substrate can have little or no disturbance of the structure and topography of the unskived portions of the substrate. For example, little or no plowing of the substrate occurs using the roller as described herein. The edges of the chasm in the substrate can be substantially smooth and free of unwanted materials, having a standard deviation of width of the chasm of less than 5%, for example, less than 2%, from the width of the roller face in contact with the substrate. The exposed substrate can maintain other desirable characteristics, including but not limited to physical properties, electrical properties, or fluidic properties. For example, the substrate can exhibit the same electrical conductivity, smoothness, roughness, appearance, or other desired property both before and after skiving with the roller.
The roller and skiving assembly or device as described herein can be used to shape substrates for various applications. Skiving can be one of many steps in substrate preparation. Skiving can be used to form intricate patterns, such as in making intricate materials, including papers, building materials, or displays, and in forming plates for lithography, intaglio, engraving, or other printing processes. Skiving can be used for making precisely controlled cuts in finished substrates, for example, in separating, forming perforations, or other cutting operations. Skiving can also be used to prepare substrates for further steps by removing unwanted material from precise locations on the substrates. For example, in manufacturing liquid crystal displays, a substrate can be formed with a support, a conductive layer such as indium tin oxide, a liquid crystal layer, and a second conductive material. The second conductive material, or the second conductive material and the liquid crystal layer, can be skived in order to expose the liquid crystal layer or the first conductive material, respectively, to allow an electrically conductive path to the first conductive material to be created. The electrically conductive path is needed to create an electrical field to change the state of the liquid crystals, enabling use as a display. The liquid crystal layer can comprise more than one layer of liquid crystals. The liquid crystal material can be nematic, smectic, ferroelectric, cholesteric, or a combination thereof. Other types of imaging elements can be made using the rollers and methods described herein, including, for example, light emitting diodes, organic light emitting diodes, electrophoretic materials, electrochromic materials, reflective print materials, and bichromal materials.
Skiving can be done in the web direction, which is the direction of movement of the substrate, or in a cross-web direction, which is any direction not parallel the direction of movement of the substrate. According to various embodiments, skiving can be done in both a web direction and a cross-web direction simultaneously. Skiving can be controlled to form any desired shape in a substrate, for example, a linear or curved shape. Skiving can be performed in one or more phases of substrate preparation, with or without intermediate steps, such as coating. Other material removal systems can be used in combination with the skiving assembly.
In use, the roller described herein can be used in a device or apparatus in a batch or roll-to-roll manufacturing process. For example, a liquid crystal display can be made using the roller and according to the methods described herein. As shown in
As described herein, a roller can be made for skiving. A device or apparatus including one or more rollers can be positioned relative a substrate to remove at least a portion of the material from the substrate, forming a chasm in the substrate. The chasms can be created in the web or cross-web direction on the substrate, and can form a pattern.
Features of the invention as set forth herein are exemplified in the following examples.
Materials used herein to form rollers include the following:
ABS plastic from Curbell, Inc., Orchard Park, New York;
Viton #10320 and 40% Teflon filled Isoprene from Mosites Rubber Company, Inc., Fort Worth, Tex.;
Silicone having a low Durometer of 50 Shore A from Silicones, Inc, High Point, N.C., cast by Eastman Kodak Company, Rochester, N.Y.;
Silicone having a medium Durometer of 70 Shore A was Red Silicone #70-S-564 from West American Rubber Co., LLC, of Orange, Calif.;
Hard-Soft-Hard Silicone from Eastman Kodak Company; and
Rulon LD from Dixon Industries Corp., Water North Bennington, Vt.
Other materials used are described in the body of the relevant Example. Unless otherwise stated, materials were supplied by Eastman Kodak Company, Rochester, N.Y.
A variety of skiving rollers were prepared as described in Table 1. All the rollers had a smooth surface, an edge with an angle of from 75 to 90 degrees, a width of 3.175 mm, and a diameter of 19.05 mm. The rollers were tested to determine what roller materials were successful in removing a polymer dispersed liquid crystal emulsion coating from a substrate.
All examples were performed on a roll-to-roll coating machine, wherein a coating pack of gelatin was applied, chill-set, and dried. Skiving was performed in the chill-setting section of the machine. The parameters of the coating process are set forth in
The material to be skived was prepared as follows. A coating pack of a single layer gelatin system was applied to a substrate having a 250-Angstrom thick conductive layer of an Indium Tin Oxide (300 ohms per square) on a 120-micron polyethylene terephthalate substrate, using a slot hopper. The Indium Tin Oxide coated on the polyethylene terephthalate was from Bekaert Specialty Films, LLC, San Diego, Calif. The gelatin system was a 5 wt % gelatin material containing 8 wt % of MERCK BL118 droplets of cholesteric liquid crystal oil, available from E.M. Industries of Hawthorne, N.Y. U.S.A. The droplets had a volume mean diameter of 10 microns. The gelatin system was applied to the substrate at 38.43 ml/m2, and cooled to 20 degrees Celsius to chill-set the gelatin. As shown in Table 1, the material was skived by each roller at two different times. In one case, the material was skived in line with the coating, after chill-setting of the gelatin. In a second case, the material was prepared, chilled, and dried, and then skived off-line from the coating process.
All roller materials effectively removed the chilled gelatin system from the substrate, though some materials produced a better skive than others. The skive quality was determined by the width of the resulting skive, the height of the resulting skive edge, and the visual appearance along the edge of the skived material within the skived area. The edge height refers to any material build-up on top of the gelatin system material remaining after skiving. ABS Plastic achieved the best results, although all skives were at least acceptable in quality. As shown herein, a roller can be used to remove a material from a substrate.
A variety of skiving rollers having different materials and varying configurations, were tested. Delrin® from E. I. Dupont de Nemours and Company was used to prepare rollers with different configurations to examine the skiving effectiveness of the different roller configurations. In addition, two other materials, 316 stainless steel and Teflon® (from E. I. Dupont de Nemours and Company) were examined for comparison of roller material effectiveness with the same roller configuration. The results are shown in Table 2.
An aqueous coating solution was prepared containing 3 wt % gelatin, 8 wt % of droplets of dibutylsebacate having a diameter of ten microns, and 0.2 wt % of a coating surfactant. The solution was mixed with gelatin cross-linker bisvinylsulfonylmethane at 3 wt % relative to the total amount of gelatin immediately before coating. The solution was applied at 61.46 ml/m2 to a substrate having 125-micron thick polyethylene terephthalate of 5-inch width coated with an Indium Tin Oxide conductive layer of 300 ohms per square.
A second coating solution was prepared with 4 wt % gelatin and a mixture of pigments formulated to provide a neutral black density. The second coating solution was heated to 45° C., and the viscosity of the solution was 100 centipoises. The solution was continuously coated on the coated substrate at 10.76 ml/m2 on a photographic coating machine. The machine speed was set so that the solution temperature was reduced to 10° C. in a chill section of the machine such that the solution viscosity increased from a liquid state to a very high-viscosity gel state. Located in the chill section was a skiving apparatus having three identical rollers. A first roller was positioned to remove material located at the center of the substrate, and the two remaining rollers were positioned 2.5 cm on either side of the center roller. The wet material had a depth of approximately 100 microns. The material, once chill-set, was completely removed to a depth of 100 microns by the rollers to expose the ITO. A vacuum was applied to the rollers at a level of 20.32 cm of Hg. After passing through the chill box and skiving apparatus, the solution was chill-set hard enough to enable drying by warm air and passage over roller sets in a drying area of the photographic coating equipment. The dried coating had three continuous skives. The target skive width was 3.175 mm.
All roller shapes effectively removed the desired material from the substrate. The success of the skive quality was determined as described in Example 1. It was found that radiused rollers of Delrin® or Teflon® provided the best skive quality, although all rollers produced at least acceptable skives.
The radiused Delrin® roller of Example 2 was tested against other skiving methods for ability to remove hardened material from a substrate.
Preparation
An emulsion of cholesteric liquid crystal oil (BL118® from E. M. Merck, Inc. Hawthorne, N.Y., U.S.A.) was produced according to the methods disclosed in U.S. Pat. No. 6,556,262 to Stephenson et al. The resulting dispersion of liquid crystals had a volume mean diameter of 10 microns with low polydispersity.
Method 1 (Invention):
An aqueous coating solution was prepared containing 13.3 weight percent of liquid crystal emulsion prepared above, 5 weight percent gelatin, and about 0.2 weight percent of a coating surfactant. The coating solution was heated to 45° C., which reduced the viscosity of the emulsion to approximately 8 centipoises. A three percent by weight gelatin cross-linker bisvinylsulfonylmethane was added to the coating solution immediately before coating. A polyethylene terephthalate substrate with 125-micron thickness and 5-inch width having an Indium Tin Oxide conductive layer (“ITO”) of 300 ohms per square was continuously coated with the mixed heated emulsion at 61.5 cc/m2 on a photographic coating machine. The machine speed was set so that the emulsion temperature was reduced to 10° C. in the chill section of the machine so that the emulsion viscosity increased from a liquid state to a very high-viscosity gel state. Located in the chill section was a skiving apparatus having three rollers were spaced to remove material located at the center of the substrate and 2.5 cm on either side of the center roller. The wet material had a depth of approximately 100 microns, which was completely removed to expose the ITO. After passing through the chill box and skiving apparatus, the emulsion was chill-set hard enough to enable drying by warm air and passage over roller sets in a drying area of the photographic coating equipment. The dried coating had three continuous skives with target widths of 3.175 mm.
Method 2 (Comparison):
A sample was prepared in the same manner as Method 1, except the skiving apparatus was removed and no skive lines were made. The sample was subsequently skived after drying using the method of U.S. Pat. No. 6,469,757 to produce skives in the same relative locations as those produced by Method 1.
Method 3 (Comparison):
A sample was prepared in the same manner as Method 1, except the skiving apparatus was removed and no skive lines were made. Instead of using the gelatin cross-linker bisvinylsulfonylmethane, distilled water was added to the coating solution immediately before coating. The sample was subsequently skived after drying using the method of U.S. Pat. No. 6,469,757 to produce skives in the same relative locations as those produced by Methods 1 and 2.
Results are shown in Table 3. Widthwise repeatability is reported as the standard deviation of the location of the skive relative to the edge of the substrate. This is an indication of the variability of the repeatability of the skive location relative to the edge of the substrate. Skive width repeatability is reported as the standard deviation of the skive width over the length of 15 cm. This is an indication of the variability of the lengthwise accuracy of the skive width.
Method 1 resulted in a skive having excellent widthwise and skive width accuracy and repeatability, as well as an excellent physical appearance (cleanliness of skive). The comparison methods 2 and 3 exhibited poor widthwise and skive width accuracy and repeatability, as well as a poor physical appearance. Method 2 did not remove any of the material to be skived.
The invention has been described in detail with particular reference to certain embodiments thereof. Variations and modifications can be effected within the spirit and scope of the invention.
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