EP2370348A2 - Fabrication of conductive nanostructures on a flexible substrate - Google Patents

Fabrication of conductive nanostructures on a flexible substrate

Info

Publication number
EP2370348A2
EP2370348A2 EP09836644A EP09836644A EP2370348A2 EP 2370348 A2 EP2370348 A2 EP 2370348A2 EP 09836644 A EP09836644 A EP 09836644A EP 09836644 A EP09836644 A EP 09836644A EP 2370348 A2 EP2370348 A2 EP 2370348A2
Authority
EP
European Patent Office
Prior art keywords
master
relief pattern
textured
support material
conductive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP09836644A
Other languages
German (de)
French (fr)
Other versions
EP2370348A4 (en
Inventor
Ding Wang
Jerome C. Porque
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Innovative Properties Co
Original Assignee
3M Innovative Properties Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3M Innovative Properties Co filed Critical 3M Innovative Properties Co
Publication of EP2370348A2 publication Critical patent/EP2370348A2/en
Publication of EP2370348A4 publication Critical patent/EP2370348A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/006—Nanostructures, e.g. using aluminium anodic oxidation templates [AAO]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
    • B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
    • B82B1/00—Nanostructures formed by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/003—3D structures, e.g. superposed patterned layers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/02—Electroplating of selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/02—Electroplating of selected surface areas
    • C25D5/028—Electroplating of selected surface areas one side electroplating, e.g. substrate conveyed in a bath with inhibited background plating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B2207/00—Coding scheme for general features or characteristics of optical elements and systems of subclass G02B, but not including elements and systems which would be classified in G02B6/00 and subgroups
    • G02B2207/101—Nanooptics
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state

Definitions

  • This application relates to a method for fabricating nanostructured and/or microstructured articles utilizing a continuous web-based process.
  • Microstructured and nanostructured devices can be used in articles such as flat panel displays, chemical sensors, and bioabsorption substrates.
  • Conventional methods for producing microstructured and nanostructured devices include molding a compliant material using a pressing or printing technology to reproduce a molded pattern, lithographic processes, and nanoimprint lithography.
  • Articles with microstructured and nanostructured topographies include a plurality of structures on a surface thereof (projections, depressions, grooves and the like) that are microscopic in at least two dimensions or having at least one dimension that measures less than a micron in the cases of a nanostructured topography. These topographies may be created in or on the article by any contacting technique, such as, for example, casting, coating or compressing.
  • these topographies may be made by at least one of: (1) casting on a tool with a microstructured or nanostructured pattern, (2) coating on a structured film with a microstructured or nanostructured pattern, or (3) passing the article through a nip roll to compress the article against a structured tool or textured master tool with a microstructured or nanostructured pattern.
  • United States Patent No. 6,375,870 discloses replicating a nanoscale pattern on the outer surface of a cylindrical roller.
  • the nanoscale pattern is transferred from the cylindrical roller onto a substrate surface.
  • Metal is coated into the depressions pattern formed on the substrate surface. Any material between the deposited metal is removed by either an etching or lift off to realize the final metal structure.
  • a portion of textured master tool having a relief pattern on a surface of the master tool is immersed into a coating bath containing an electrodepositable material.
  • the electrodepositable material is deposited onto the master tool by either an electrolytic or electrophoretic deposition process.
  • a support material can be applied to the surface of the master tool over top of the deposited layer. Removal of the resulting structure from the tool yields the flexible nanostructured material.
  • the relief pattern may be one of a microscale relief pattern or a nanoscale relief pattern.
  • the relief pattern on the master tool can include conductive regions and non- conductive regions, and the electrodepositable material is deposited on the conductive regions of the nanoscale relief pattern.
  • the master tool may be a cylindrical master drum, a master belt, a master sheet or a master tile.
  • a carrier film may be applied to the surface of the support material.
  • Fig. 1 is a schematic representation of an exemplary continuous nanostructured material according to an aspect of the invention.
  • Fig. 2 is a schematic representation of a fabrication system according to an aspect of the invention.
  • Fig. 3 is a flow diagram of an exemplary process for creating a continuous nanostructured material according to an aspect of the invention.
  • Fig. 4 is a scanning electron micrograph of the nanostructured material fabricated according to Example 1.
  • Fig. 5 shows a schematic cross-section of the durable master described in Example
  • Fig. 6A is an atomic force micrograph of the nanostructured material fabricated according to Example 2.
  • Fig. 6B is a scanning electron micrograph of the nanostructured material fabricated according to Example 1.
  • Fig. 7 is a schematic representation of an alternative fabrication system according to an aspect of the invention.
  • the disclosure provides a method of making a continuous flexible nanostructured or microstructured sheet having a replicated base structure made of a first material and a partial or complete surface made of second different material.
  • the second material may be either conductive or non-conductive.
  • the second material may be electrolytically or electrophoretically deposited.
  • Conductive materials can include metals, metal oxides, organic semiconductors or conductive polymers.
  • Non-conductive materials include non-conductive polymers and metal oxides.
  • the metal oxides can be any oxidized transition metal such as iron, aluminum, manganese, nickel, platinum, chromium, sliver, gold, copper, zinc and the like.
  • microstructure includes features that can be on the order of microns (from about 1 ⁇ m to about 1000 ⁇ m or even larger) and nanostructure include features that can be on the order of nanometers (from about 1 nm to about 1000 nm). This dimension is the average smallest dimension of the features in the array and can be the diameter, for example, if the features are cylindrical posts.
  • the microstructures or nanostructures may be in the form of an array on a substrate.
  • the array can be in the form of a regular array of structures, a random arrangement of structures, or a combination of different regular or random arrangements of structures.
  • the structured array can be formed directly in the substrate or can be formed as an added layer. While the terms nanostructure and nanofeature are used predominately in this disclosure, it should be understood that the method disclosed herein is extendible to the fabrication of microstructures or micro features.
  • Typical nanostructures can include post structures and ridge structures.
  • Exemplary post structures can have one dimension substantially perpendicular to the substrate referred to herein as the height, h, and two much smaller dimensions (x- and y- dimensions). The smaller of the x-dimension and y-dimension is herein referred to as the width of the nanostructure.
  • the cross-section (or base) of the posts can be circular where the x-dimensions and the y-dimensions are equal. When the cross-section is circular and does not vary along the z-direction the posts are cylinders. It is also possible that the x- and y-dimensions are equal but vary along the z-direction. In this case, the posts are conical.
  • the conical shape may be truncated parallel to or at an oblique angle to the base.
  • the cross-section of the base may be any closed plane figure including, but not limited to a circle, an ellipse, a polygon or any close curvilinear shape.
  • truncated cones, pyramids, and truncated pyramids are considered within the scope of possible post structures.
  • the posts can have a cross-section of a polygon such as a triangle, square, pentagon, etc. If the cross-section of the post structure is a polygon and it does not vary along its height, then the post can have the shape of a prism.
  • any shape of post is contemplated by this disclosure as long as the post has one long dimension and the cross-sectional area of the top of the post is approximately the same or less than the cross-sectional area of the base of the post.
  • An article having conductive microstructures on its surface or conductive nanostructures on its surface can be created by immersing a textured master tool having conductive regions and non-conductive regions into a bath of an electrodepositable material. Once a sufficient thickness of the electrodepositable material has been deposited, the master tool is removed from the bath and dried. A support material is applied to the master tool. When the support material is removed from the master tool the electro deposited material is also removed yielding the desired article.
  • the textured master tool can be in the form of a cylindrical master drum, a master belt, a master sheet or a master tile.
  • continuous material it is meant a material having a length (L) many times larger than its width (w).
  • continuous nanostructured material 100 can be many meters in length (i.e., including hundreds or thousands of meters in length), while the width can be from about 2.5 centimeters to about 2 meters.
  • the continuous nanostructured material 100 is made up of an array of nanostructures 105.
  • the nanostructures 105 include an electrodeposited surface layer 120 sitting atop a formed portion 130 on a carrier film or substrate layer 110.
  • the electrodeposited material may be conductive (e.g. a metal, organic semiconductors or conductive polymers) or nonconductive.
  • a metallic electrodeposited portion may be oxidized in a subsequent process to form a nonconductive metal oxide portion.
  • the nonconductive metal oxide portion can be made of CuO, Ag 2 O, CrO 2 or the like.
  • the nanostructured material 100 is prepared by an exemplary fabrication system and method as depicted in Figs. 2 and 3, respectively, and described in detail below.
  • the fabrication system 200 includes a master drum 210, having a relief pattern 212 formed thereon.
  • the relief pattern 212 is non-conductive and has low surface energy surfaces 214, 215.
  • the master drum is generally cylindrical in shape and may be made of an electrically conductive material (i.e. metal).
  • the relief pattern on the surface of the drum may be formed of non- conductive or dielectric material such as a non-conductive polymer, silicon dioxide, or a non-conductive carbon layer and is the negative image of the nanostructured material being produced.
  • the master drum is made of a material with good electrical conductivity such as aluminum or other metal.
  • the master may have an electrically conductive sleeve mounted on a non-conductive drum core (not shown).
  • an ITO (indium tin oxide) layer 216 may be coated at outer surface of master drum 210.
  • the ITO layer can also serve as a release layer between the master drum and the deposited material.
  • the master drum may be partially submerged into a coating bath 230.
  • the surface 211 of the master drum is connected to one electrode, such as cathode 242, of a DC power source 246. Inside the coating bath, the other electrode, such as an anode 244, is connected to the same DC power supply to form a complete electrical circuit.
  • the master drum rotates in a counter clockwise direction 219.
  • the coating bath contains an electro-depositable coating material in a carrier solution such as water.
  • the electro-depositable coating material may be a metallic plating solution or a dispersion of an electrically conductive oligomer or polymer.
  • Electrodeposited metals can include gold, silver, tin, copper, nickel, tungsten, vanadium and various metallic coatings.
  • plating chemistries such as High Speed Nickel FFP Solution and ACR 150 Gold Plating Solution are available from Technic, Inc., (Cranston, RI) and Copper Gleam ST-901 is available from Rohm & Haas, Inc., (Philadelphia, PA).
  • the electrodepositable coating material is deposited on to the surface 211 of the master drum in the openings in the relief pattern as the master drum sweeps through the coating bath.
  • the coating material does not deposit onto the surface 214 or sides 215 of the dielectric relief pattern 212 on the surface of the master drum 210.
  • the thickness of the coating will increase with the residence time of the portion of master drum in the coating bath 230. As the drum rotates, the deposited portion 213 will exit the coating bath.
  • the 250 will rinse any residual coating material from the master drum.
  • the cleaned portion of the coating drum may be dried by exposure to heat and/or blowing air.
  • a support material 260 is applied onto the surface of the master drum at a coating station 265.
  • the layer can be added, for example, by coating, lamination, deposition, printing, or any other techniques known to those skilled in the art.
  • Exemplary coating techniques to add the layer can include, for example, solution coating, dispersion coating, hot-melt coating, knife coating, and dip coating.
  • Lamination can include, for example, heat lamination, photochemical lamination, and also can include article modification of the substrate or the layer or both. Post-lamination annealing can be done, if desired, to enhance adhesion.
  • Vapor deposition techniques such as, for example, evaporative vapor deposition, sputtering, chemical vapor deposition, or plasma enhanced chemical vapor deposition are methods that can be used to add a layer to the substrate and are within the scope of this disclosure.
  • the support material may be a thermoplastic polymer that flows at elevated temperatures but not at lower temperatures such as room temperature.
  • thermoplastic polymers examples include acrylics; polyolefms; ethylene copolymers such as polyethylene acrylic acid; fluoropolymers such as polytetrafluoroethylene and polyvinylidene fluoride; polyvinylchloride; ionomers; ketones such as polyetheretherketone; polyamides; polycarbonates; polyesters; styrene block copolymers such as styrene-isoprene-styrene; styrene butadiene-styrene; styrene acrylonitrile; and others known to those skilled in the art.
  • thermosetting resins that can be cured using a catalyst, heat, or photoexposure depending upon its chemistry, such as, for example, acrylates, polydimethylsiloxanes, urethane acrylates and epoxies.
  • An example of thermosetting resins can be a photocrosslinkable system, such as a photocurable urethane acrylate, that forms a polymeric substrate with microfeatures upon curing.
  • the nanostructured material may be used as a wire grid polarizer, a microlens, a bio-detection chip, a micromirror array, a metamaterial (negative index material), an electromagnetic shielding materials, or touch screen components.
  • the biochip used for drug screening and bio-detection based on enhanced stimulated Raman effect is comprised of an array of sub-micron gold holes made on silicon chip.
  • Conventional methods of making biochips can be expensive because of processes used to make it and low yields. Making biochips by the inventive method disclosed herein can substantially lower the manufacturing cost at improved yields.
  • the support material can be selected for its optical clarity.
  • Optically clear support materials can include visibly transmissive thermoset polymers such as, for example, acrylic polymers, polycarbonates, polyesters (PET), polyester copolymers, polyethylene naphthalate polymers (PEN), urethane acrylates, epoxies, etc.
  • Optically transmissive thermoplastic materials can also be used to form microlens or micromirror arrays.
  • These materials can include, for example, polycarbonates, polymethylmethacrylates, polyolefms, polyethylene acrylic acids, polyvinyl chlorides, polyvinylfluorides, ionomers, ketones such as polyetheretherketone, polyamides, polyesters, polyester copolymers, polyethylene naphthalate polymers (PEN), styrene block copolymers and others known to those skilled in the art.
  • the support material coats the drum surface and fills in any area of the relief structure that was not coated with the electrodeposited material to produce the formed portion 130 of the nanostructured material 100.
  • the support material may be coated sufficiently thick such that the relief structure itself is over-coated with the support material.
  • the support material may form the substrate layer in addition to the formed portion 130 of the of the nanostructured material 100.
  • a separate substrate layer may be introduced after the support material has been applied to the master drum. If a separate substrate layer is used it can be any thin flexible material such as a polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyester film, polyimide film or a thin metal foil such as aluminum foil or copper foil.
  • PET polyethylene terephthalate
  • PEN polyethylene naphthalate
  • polyester film polyester film
  • polyimide film polyimide film
  • a thin metal foil such as aluminum foil or copper foil.
  • Fig. 2 shows the lamination of carrier film 110 to the support material layer 261 on the master drum by a nip roll 280 to form the substrate layer of the nanostructured material 100.
  • a curing station 270 is located adjacent to the nip roll 280 to cure the support material.
  • the curing station 270 may include a UV radiation source such as a UV light bulb (e.g. ELC-500 UV/Visible Curing Chamber available from Electro-Lite Corporation, Danbury, CT), a UV laser (e.g. an Innova Sabre FReD Laser available from Coherent, Inc., Santa Clara, CA), or a UV LED.
  • the curing station 270 may include an oven, an infrared lamp or other heat source. If the support material 260 is a thermoplastic polymer, no curing station is required.
  • the support material is to bind the electro-deposited portion to the substrate layer.
  • the adhesion of the support material 260 to the deposited portion should be much stronger than the adhesion of the deposited portion 213 to the surface 211 of the master drum 210. This enabled the removal of the nanostructured material 100 from the master drum 210 as the master drum rotates.
  • the fabrication system 500 includes a textured master belt 510, having a relief pattern 512 formed thereon.
  • the master belt is generally a band of material made of an electrically conductive material (i.e. metal) or having an electrically conductive layer between the relief pattern and a support substrate.
  • the relief pattern on the surface of the master belt may be formed of non-conductive or dielectric material such as a non-conductive polymer, silicon dioxide, or a non-conductive carbon layer and is the negative image of the nanostructured material being produced.
  • the master belt is made of a material with good electrical conductivity such as an aluminum foil or other metal foil.
  • the master belt may have an electrically conductive material coated onto a dielectric substrate.
  • an ITO (Indium Tin Oxide) layer may be coated on the outer surface of a strip of PEN or PET film or the belt may be made of a piece of metallized polyimide film (e.g. a copper clad polyimide film) which has been formed into a belt after the relief pattern has been formed.
  • the master belt drum may be mounted on a series of rollers 580, 581 such that a portion of the belt passes through a coating bath 530.
  • the surface 511 of the master belt may be electrically charged by connecting roller 581 to the cathode 542 of a DC power source 546 in the case where master belt is formed on a metallic foil and roller 581 is conductive.
  • an anode 544 is connected to the same DC power supply, to form a complete electrical circuit. If a metal clad dielectric film is used as the substrate for the master belt, the cathode is designed to contact the metallized surface of the belt.
  • the coating bath 530 contains an electrodepositable coating material 535 in a carrier solution such as water.
  • the electrodepositable coating material may be a metallic plating solution or a dispersion of an electrically conductive oligomer or polymer. Electrodeposited metals can include gold, silver, tin, copper, nickel, tungsten, vanadium and various metallic coatings.
  • the electrodepositable coating material is electrolytically deposited on to the surface 511 of the master belt in the openings in the relief pattern as the master belt sweeps through the coating bath.
  • the coating material does not deposit onto the surface 514 or sides 515 of the dielectric relief pattern 512 on the surface of the master belt 510.
  • the thickness of the coating will increase with the residence time of the master belt in the coating bath 530.
  • a nozzle or spray (not shown) will rinse any residual coating material from the master drum.
  • the cleaned portion of the coating drum may be dried by exposure to heat and/or blowing air.
  • a carrier film 110 may be supplied by another set of rollers 585.
  • a layer of support material 561 is applied onto the carrier film 110.
  • the layer of support material can be added, for example, by coating, lamination, deposition, printing, or any other techniques known to those skilled in the art.
  • Exemplary coating techniques to add the layer can include, for example, solution coating, dispersion coating, hot-melt coating, knife coating, and dip coating.
  • Lamination can include, for example, heat lamination, photochemical lamination, and also can include article modification of the substrate or the layer or both. Post-lamination annealing can be done, if desired, to enhance adhesion.
  • the support material may be a thermoplastic polymer that flow at elevated temperatures but not at lower temperatures such as room temperature or a thermosetting resin that can be cured using a catalyst, heat, or photoexposure depending upon its chemistry.
  • Fig. 7 illustrates a fabrication system that uses a photo-cured thermosetting resin chemistry.
  • the metal coated master belt and the support material are pressed together in a nip between rollers 580 and 585. Once the support material has filled in the relief pattern on the surface of the master belt it is cured by shining ultraviolet light 570 through the back side of the carrier film to cure the support material. The electro deposited portions 513 will be removed from the master belt when the carrier film and support material are separated from the master belt to form the nanostructured material 100.
  • a nanostructured material 100' having a sub-micron hole array structure was prepared utilizing the fabrication method previously described.
  • Figs. 3A-3G show a flow diagram of the fabrication method by which the nanostructured material 100' was formed. Preparing the master
  • a thin layer of a positive UV5 photoresist 306 (available from Rohm and Haas Electronic Materials, Marlborough, MA) was applied to a glass master 300 having a conductive ITO surface layer 304 with a thin chromium tie layer (not shown) between the glass layer 302 and the ITO layer 304 as shown in Fig. 3A.
  • the relief pattern 310 was made by interference lithography using a Innova Sabre FReD UV laser with an output of 270 mW (available from Company Coherent located at Santa Clara, CA) to pattern the photoresist layer 306 with an array of posts 314 (Fig. 3B).
  • the exposed areas were then removed using a developing solution to dissolve the undesired photoresist.
  • the diameter, D, of the nanostructures of the post is about 0.85 ⁇ m as shown in
  • the pitch, P, of the nanostructures was 1.7 ⁇ m.
  • This photo resist based structure was used as dielectric material based sub-micron structure mold.
  • a thin layer of gold 320 was electrodeposited onto the surface 311 of the ITO glass coated master 300 in the area 316 around posts 314 of the relief pattern 310.
  • the gold was electrodeposited using ACR 150 Gold Plating Solution available from Technic, Inc., Cranston, RI, with a current density of 1 amp per square foot, and a temperature of 48 0 C to yield a 0.2 ⁇ m gold layer.
  • a layer of a UV curable support material 330 was coated over the relief pattern 310.
  • the sample was placed in a vacuum chamber to prevent air entrapment in the area 316 around posts 314 of the relief pattern 310 between the deposited gold layer 320 and the support material 330.
  • the UV curable support material was prepared in a manner similar to that described in United States Patent No.
  • the nanostructured material 100' was removed from the glass master 300 and cleaned with methanol. As shown in Fig. 4, the resulting nanostructured material had a gold surface and an array of sub-micron holes that extended through the gold surface and into the support material layer.
  • a second replication master was made with a durable diamond-like carbon (DLC) relief structure on the surface of an ITO glass coated silicon master.
  • DLC diamond-like carbon
  • a 200 nm DLC film was vacuum coated onto the surface of the ITO glass followed by application of a thin layer (about 50 nm) diamond- like glass (DLG) as described in Untied States Patent Nos. 5,888,594; 6,015,597; and 6,696,157; herein incorporated by reference.
  • a layer of photo resist (UV5 photoresist 306, available from Rohm and Haas Electronic Materials, Marlborough, MA) is applied to the to the DLG surface.
  • the photo resist was patterned using interference lithography as generally described in United States Patent No. 7,085,450, herein incorporated by reference.
  • FIG. 5 shows a schematic cross-section of the silicon master 400 having an aluminum coated silicon base substrate 410 having a conductive ITO glass layer 420 disposed on the aluminum layer 412 and a DLC relief pattern 430 disposed on the ITO glass layer 420.
  • the ITO glass serves as a release coating to allow the easy removal of the electrodeposited material from the master drum.
  • the low- surface energy of the DLC and DLG also provided improved release characteristics for removing cured replicated material and the deposited material from the replication master.
  • a thin layer of gold was electrodeposited onto the surface 411 of the silicon master 400 in the holes 434 of the relief pattern 430.
  • the gold was electrodeposited using ACR 150 Gold Plating Solution available from Technic, Inc., Cranston, RI, with a current density of 1 amp per square foot, and a temperature of 48 0 C to yield a 0.2 micron gold layer.
  • a layer of a UV curable support material, described above, was coated over the relief pattern 430. The sample was placed in a vacuum chamber to ensure that there as no air trapped in the holes 434 of the relief pattern 430.
  • the thickness of support material applied was 200 ⁇ m.
  • a PEN carrier film was applied to the back side of supporting material prior to curing the support material.
  • the support material was cured subjecting the coated glass master to 350 nm UV radiation for 10 minutes in a nitrogen atmosphere.
  • the nanostructured material was removed from the silicon master and cleaned with methanol.
  • Fig. 6A shows an atomic force micrograph of the resulting nanostructured material having a gold surface and an array of sub-micron holes that extended through the gold surface and into the dielectric layer.
  • Fig. 6B shows a scanning electron micrograph of the resulting nanostructured material. Auger electron spectroscopy confirmed that the gold was only on the surface of the nanostructured material and that there was no gold in the hole area of the material. The period of the microstructure is 1.7 ⁇ m. The depth of the holes is about 0.6 ⁇ m.
  • Advantages of the disclosed method include providing reducing material scrap and producing a nanometer-scale pattern on a large flexible substrate surface for use in applications such as polarizing films for liquid crystal displays or electromagnet shielding for PDP displays.
  • This replication method does not require lift off or reactive ion etching of unwanted material thus simplifying manufacture and reducing the cost of the resultant film.
  • the electrodepositable material is deposited where it is needed, and thereby minimizing the waste of the material.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Nanotechnology (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biophysics (AREA)
  • Optics & Photonics (AREA)
  • Manufacturing & Machinery (AREA)
  • Laminated Bodies (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Manufacturing Of Printed Wiring (AREA)

Abstract

Provided is a method of fabricating a continuous nanostructured material having an electrodeposited surface layer. A conductive master drum having a relief pattern on its surface that exposes only a portion of the master drum surface is immersed into a plating bath. An electrodepositable material is coated onto the exposed surface of the drum. A support material is coated over the deposited layer and the relief structure. Removal from the drum yields the nanostructured material.

Description

FABRICATION OF CONDUCTIVE NANOSTRUCTURES ON A FLEXIBLE
SUBSTRATE
DESCRIPTION OF THE INVENTION
Field of the Invention This application relates to a method for fabricating nanostructured and/or microstructured articles utilizing a continuous web-based process.
Background of the Invention
Microstructured and nanostructured devices, for example, can be used in articles such as flat panel displays, chemical sensors, and bioabsorption substrates. Conventional methods for producing microstructured and nanostructured devices include molding a compliant material using a pressing or printing technology to reproduce a molded pattern, lithographic processes, and nanoimprint lithography.
Articles with microstructured and nanostructured topographies include a plurality of structures on a surface thereof (projections, depressions, grooves and the like) that are microscopic in at least two dimensions or having at least one dimension that measures less than a micron in the cases of a nanostructured topography. These topographies may be created in or on the article by any contacting technique, such as, for example, casting, coating or compressing. Typically, these topographies may be made by at least one of: (1) casting on a tool with a microstructured or nanostructured pattern, (2) coating on a structured film with a microstructured or nanostructured pattern, or (3) passing the article through a nip roll to compress the article against a structured tool or textured master tool with a microstructured or nanostructured pattern.
While molding technologies may be used in combination with the master replication tool to make a continuous roll of product, the resolution achieved with such procedure is generally limited to several microns and may not be capable of producing nanoscale features needed for some applications.
United States Patent No. 6,375,870 discloses replicating a nanoscale pattern on the outer surface of a cylindrical roller. The nanoscale pattern is transferred from the cylindrical roller onto a substrate surface. Metal is coated into the depressions pattern formed on the substrate surface. Any material between the deposited metal is removed by either an etching or lift off to realize the final metal structure. SUMMARY OF THE INVENTION
There is a need for a continuous flexible nanostructured or microstructured sheet having a replicated base structure having at least a partially conductive surface layer. Roll-to-roll manufacturing structured material saves manufacturing costs and improves production speeds.
In an exemplary method of making a nanostructured article, a portion of textured master tool having a relief pattern on a surface of the master tool is immersed into a coating bath containing an electrodepositable material. The electrodepositable material is deposited onto the master tool by either an electrolytic or electrophoretic deposition process. A support material can be applied to the surface of the master tool over top of the deposited layer. Removal of the resulting structure from the tool yields the flexible nanostructured material.
The relief pattern may be one of a microscale relief pattern or a nanoscale relief pattern. The relief pattern on the master tool can include conductive regions and non- conductive regions, and the electrodepositable material is deposited on the conductive regions of the nanoscale relief pattern.
The master tool may be a cylindrical master drum, a master belt, a master sheet or a master tile.
In an alternative embodiment of the inventive method, a carrier film may be applied to the surface of the support material.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic representation of an exemplary continuous nanostructured material according to an aspect of the invention.
Fig. 2 is a schematic representation of a fabrication system according to an aspect of the invention.
Fig. 3 is a flow diagram of an exemplary process for creating a continuous nanostructured material according to an aspect of the invention.
Fig. 4 is a scanning electron micrograph of the nanostructured material fabricated according to Example 1. Fig. 5 shows a schematic cross-section of the durable master described in Example
2. Fig. 6A is an atomic force micrograph of the nanostructured material fabricated according to Example 2.
Fig. 6B is a scanning electron micrograph of the nanostructured material fabricated according to Example 1. Fig. 7 is a schematic representation of an alternative fabrication system according to an aspect of the invention.
While the above-identified drawing figures set forth several embodiments of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope of the principals of this invention. The figures may not be drawn to scale. Like reference numbers have been used throughout the figures to denote like parts.
DETAILED DESCRIPTION The disclosure provides a method of making a continuous flexible nanostructured or microstructured sheet having a replicated base structure made of a first material and a partial or complete surface made of second different material. The second material may be either conductive or non-conductive. In an exemplary aspect of the invention, the second material may be electrolytically or electrophoretically deposited. Conductive materials can include metals, metal oxides, organic semiconductors or conductive polymers. Non-conductive materials include non-conductive polymers and metal oxides. The metal oxides can be any oxidized transition metal such as iron, aluminum, manganese, nickel, platinum, chromium, sliver, gold, copper, zinc and the like.
It is to be herein understood that the term "microstructure" includes features that can be on the order of microns (from about 1 μm to about 1000 μm or even larger) and nanostructure include features that can be on the order of nanometers (from about 1 nm to about 1000 nm). This dimension is the average smallest dimension of the features in the array and can be the diameter, for example, if the features are cylindrical posts.
The microstructures or nanostructures may be in the form of an array on a substrate. The array can be in the form of a regular array of structures, a random arrangement of structures, or a combination of different regular or random arrangements of structures. The structured array can be formed directly in the substrate or can be formed as an added layer. While the terms nanostructure and nanofeature are used predominately in this disclosure, it should be understood that the method disclosed herein is extendible to the fabrication of microstructures or micro features.
Typical nanostructures can include post structures and ridge structures. Exemplary post structures can have one dimension substantially perpendicular to the substrate referred to herein as the height, h, and two much smaller dimensions (x- and y- dimensions). The smaller of the x-dimension and y-dimension is herein referred to as the width of the nanostructure. For example, the cross-section (or base) of the posts can be circular where the x-dimensions and the y-dimensions are equal. When the cross-section is circular and does not vary along the z-direction the posts are cylinders. It is also possible that the x- and y-dimensions are equal but vary along the z-direction. In this case, the posts are conical. The conical shape may be truncated parallel to or at an oblique angle to the base. In fact, the cross-section of the base may be any closed plane figure including, but not limited to a circle, an ellipse, a polygon or any close curvilinear shape. Thus, truncated cones, pyramids, and truncated pyramids are considered within the scope of possible post structures. It is also contemplated, for example, that the posts can have a cross-section of a polygon such as a triangle, square, pentagon, etc. If the cross-section of the post structure is a polygon and it does not vary along its height, then the post can have the shape of a prism. In fact, any shape of post is contemplated by this disclosure as long as the post has one long dimension and the cross-sectional area of the top of the post is approximately the same or less than the cross-sectional area of the base of the post.
An article having conductive microstructures on its surface or conductive nanostructures on its surface can be created by immersing a textured master tool having conductive regions and non-conductive regions into a bath of an electrodepositable material. Once a sufficient thickness of the electrodepositable material has been deposited, the master tool is removed from the bath and dried. A support material is applied to the master tool. When the support material is removed from the master tool the electro deposited material is also removed yielding the desired article. The textured master tool can be in the form of a cylindrical master drum, a master belt, a master sheet or a master tile.
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. Referring to Fig. 1, a portion of an exemplary continuous nanostructured material 100 is depicted. By "continuous material" it is meant a material having a length (L) many times larger than its width (w). For example, continuous nanostructured material 100 can be many meters in length (i.e., including hundreds or thousands of meters in length), while the width can be from about 2.5 centimeters to about 2 meters.
The continuous nanostructured material 100 is made up of an array of nanostructures 105. The nanostructures 105 include an electrodeposited surface layer 120 sitting atop a formed portion 130 on a carrier film or substrate layer 110. The electrodeposited material may be conductive (e.g. a metal, organic semiconductors or conductive polymers) or nonconductive. Alternatively, a metallic electrodeposited portion may be oxidized in a subsequent process to form a nonconductive metal oxide portion. For example, the nonconductive metal oxide portion can be made of CuO, Ag2O, CrO2 or the like.
The nanostructured material 100 is prepared by an exemplary fabrication system and method as depicted in Figs. 2 and 3, respectively, and described in detail below.
An exemplary fabrication system 200 utilized to perform the continuous fabrication of an exemplary nanostructured article 100 having micron and submicron features is shown in Fig. 2. The fabrication system 200 includes a master drum 210, having a relief pattern 212 formed thereon. In an exemplary embodiment, the relief pattern 212 is non-conductive and has low surface energy surfaces 214, 215. The master drum is generally cylindrical in shape and may be made of an electrically conductive material (i.e. metal). The relief pattern on the surface of the drum may be formed of non- conductive or dielectric material such as a non-conductive polymer, silicon dioxide, or a non-conductive carbon layer and is the negative image of the nanostructured material being produced. For example, if the desired pattern on the final nanostructured material 100 is periodic dots, then the relief structure on the surface of the drum is periodical holes. In an exemplary embodiment, the master drum is made of a material with good electrical conductivity such as aluminum or other metal. Alternatively, the master may have an electrically conductive sleeve mounted on a non-conductive drum core (not shown). For example, an ITO (indium tin oxide) layer 216 may be coated at outer surface of master drum 210. In addition to providing a conductive surface to facilitate the electro-deposition of the coating material, the ITO layer can also serve as a release layer between the master drum and the deposited material. The master drum may be partially submerged into a coating bath 230. The surface 211 of the master drum is connected to one electrode, such as cathode 242, of a DC power source 246. Inside the coating bath, the other electrode, such as an anode 244, is connected to the same DC power supply to form a complete electrical circuit. In an exemplary embodiment, the master drum rotates in a counter clockwise direction 219. The coating bath contains an electro-depositable coating material in a carrier solution such as water. The electro-depositable coating material may be a metallic plating solution or a dispersion of an electrically conductive oligomer or polymer.
Electrodeposited metals can include gold, silver, tin, copper, nickel, tungsten, vanadium and various metallic coatings. For example, plating chemistries such as High Speed Nickel FFP Solution and ACR 150 Gold Plating Solution are available from Technic, Inc., (Cranston, RI) and Copper Gleam ST-901 is available from Rohm & Haas, Inc., (Philadelphia, PA).
The electrodepositable coating material is deposited on to the surface 211 of the master drum in the openings in the relief pattern as the master drum sweeps through the coating bath. The coating material does not deposit onto the surface 214 or sides 215 of the dielectric relief pattern 212 on the surface of the master drum 210. The thickness of the coating will increase with the residence time of the portion of master drum in the coating bath 230. As the drum rotates, the deposited portion 213 will exit the coating bath. A nozzle
250 will rinse any residual coating material from the master drum. The cleaned portion of the coating drum may be dried by exposure to heat and/or blowing air.
A support material 260 is applied onto the surface of the master drum at a coating station 265. The layer can be added, for example, by coating, lamination, deposition, printing, or any other techniques known to those skilled in the art. Exemplary coating techniques to add the layer can include, for example, solution coating, dispersion coating, hot-melt coating, knife coating, and dip coating. Lamination can include, for example, heat lamination, photochemical lamination, and also can include article modification of the substrate or the layer or both. Post-lamination annealing can be done, if desired, to enhance adhesion. Vapor deposition techniques such as, for example, evaporative vapor deposition, sputtering, chemical vapor deposition, or plasma enhanced chemical vapor deposition are methods that can be used to add a layer to the substrate and are within the scope of this disclosure. The support material may be a thermoplastic polymer that flows at elevated temperatures but not at lower temperatures such as room temperature. Examples of thermoplastic polymers that can be used include acrylics; polyolefms; ethylene copolymers such as polyethylene acrylic acid; fluoropolymers such as polytetrafluoroethylene and polyvinylidene fluoride; polyvinylchloride; ionomers; ketones such as polyetheretherketone; polyamides; polycarbonates; polyesters; styrene block copolymers such as styrene-isoprene-styrene; styrene butadiene-styrene; styrene acrylonitrile; and others known to those skilled in the art.
Other useful support materials for forming a flexible nanostructured material include thermosetting resins that can be cured using a catalyst, heat, or photoexposure depending upon its chemistry, such as, for example, acrylates, polydimethylsiloxanes, urethane acrylates and epoxies. An example of thermosetting resins can be a photocrosslinkable system, such as a photocurable urethane acrylate, that forms a polymeric substrate with microfeatures upon curing. By tailoring the shape of the nanostructures and the materials used, the nanostructured material may be used as a wire grid polarizer, a microlens, a bio-detection chip, a micromirror array, a metamaterial (negative index material), an electromagnetic shielding materials, or touch screen components. For example, the biochip used for drug screening and bio-detection based on enhanced stimulated Raman effect is comprised of an array of sub-micron gold holes made on silicon chip. Conventional methods of making biochips can be expensive because of processes used to make it and low yields. Making biochips by the inventive method disclosed herein can substantially lower the manufacturing cost at improved yields.
For some of these applications, the support material can be selected for its optical clarity. Optically clear support materials can include visibly transmissive thermoset polymers such as, for example, acrylic polymers, polycarbonates, polyesters (PET), polyester copolymers, polyethylene naphthalate polymers (PEN), urethane acrylates, epoxies, etc. Optically transmissive thermoplastic materials can also be used to form microlens or micromirror arrays. These materials can include, for example, polycarbonates, polymethylmethacrylates, polyolefms, polyethylene acrylic acids, polyvinyl chlorides, polyvinylfluorides, ionomers, ketones such as polyetheretherketone, polyamides, polyesters, polyester copolymers, polyethylene naphthalate polymers (PEN), styrene block copolymers and others known to those skilled in the art. The support material coats the drum surface and fills in any area of the relief structure that was not coated with the electrodeposited material to produce the formed portion 130 of the nanostructured material 100. The support material may be coated sufficiently thick such that the relief structure itself is over-coated with the support material. If the support material is sufficiently thick, it may form the substrate layer in addition to the formed portion 130 of the of the nanostructured material 100. Alternatively, a separate substrate layer may be introduced after the support material has been applied to the master drum. If a separate substrate layer is used it can be any thin flexible material such as a polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyester film, polyimide film or a thin metal foil such as aluminum foil or copper foil.
Fig. 2 shows the lamination of carrier film 110 to the support material layer 261 on the master drum by a nip roll 280 to form the substrate layer of the nanostructured material 100. In the case where the support material is a thermoset material, a curing station 270 is located adjacent to the nip roll 280 to cure the support material. If the support material 260 is a UV curable material, the curing station 270 may include a UV radiation source such as a UV light bulb (e.g. ELC-500 UV/Visible Curing Chamber available from Electro-Lite Corporation, Danbury, CT), a UV laser (e.g. an Innova Sabre FReD Laser available from Coherent, Inc., Santa Clara, CA), or a UV LED. If the support material 260 is a thermally curable material, the curing station 270 may include an oven, an infrared lamp or other heat source. If the support material 260 is a thermoplastic polymer, no curing station is required.
One function of the support material is to bind the electro-deposited portion to the substrate layer. The adhesion of the support material 260 to the deposited portion should be much stronger than the adhesion of the deposited portion 213 to the surface 211 of the master drum 210. This enabled the removal of the nanostructured material 100 from the master drum 210 as the master drum rotates.
An alternative fabrication system 500 utilized to perform the continuous fabrication of an exemplary nanostructured material 100 having micron and submicron features is shown in Fig. 7. The fabrication system 500 includes a textured master belt 510, having a relief pattern 512 formed thereon. The master belt is generally a band of material made of an electrically conductive material (i.e. metal) or having an electrically conductive layer between the relief pattern and a support substrate. The relief pattern on the surface of the master belt may be formed of non-conductive or dielectric material such as a non-conductive polymer, silicon dioxide, or a non-conductive carbon layer and is the negative image of the nanostructured material being produced. For example, if the desired pattern on the final nanostructured material 100 is periodic dots, then the relief structure on the surface of the master belt is periodical holes. In an exemplary embodiment, the master belt is made of a material with good electrical conductivity such as an aluminum foil or other metal foil. Alternatively, the master belt may have an electrically conductive material coated onto a dielectric substrate. For example, an ITO (Indium Tin Oxide) layer may be coated on the outer surface of a strip of PEN or PET film or the belt may be made of a piece of metallized polyimide film (e.g. a copper clad polyimide film) which has been formed into a belt after the relief pattern has been formed.
The master belt drum may be mounted on a series of rollers 580, 581 such that a portion of the belt passes through a coating bath 530. The surface 511 of the master belt may be electrically charged by connecting roller 581 to the cathode 542 of a DC power source 546 in the case where master belt is formed on a metallic foil and roller 581 is conductive. Inside the coating bath, an anode 544 is connected to the same DC power supply, to form a complete electrical circuit. If a metal clad dielectric film is used as the substrate for the master belt, the cathode is designed to contact the metallized surface of the belt.
The coating bath 530 contains an electrodepositable coating material 535 in a carrier solution such as water. The electrodepositable coating material may be a metallic plating solution or a dispersion of an electrically conductive oligomer or polymer. Electrodeposited metals can include gold, silver, tin, copper, nickel, tungsten, vanadium and various metallic coatings.
The electrodepositable coating material is electrolytically deposited on to the surface 511 of the master belt in the openings in the relief pattern as the master belt sweeps through the coating bath. Preferably, the coating material does not deposit onto the surface 514 or sides 515 of the dielectric relief pattern 512 on the surface of the master belt 510. The thickness of the coating will increase with the residence time of the master belt in the coating bath 530. As the drum rotates, the deposited portion 513 will exit the coating bath. A nozzle or spray (not shown) will rinse any residual coating material from the master drum. The cleaned portion of the coating drum may be dried by exposure to heat and/or blowing air.
A carrier film 110 may be supplied by another set of rollers 585. A layer of support material 561 is applied onto the carrier film 110. The layer of support material can be added, for example, by coating, lamination, deposition, printing, or any other techniques known to those skilled in the art. Exemplary coating techniques to add the layer can include, for example, solution coating, dispersion coating, hot-melt coating, knife coating, and dip coating. Lamination can include, for example, heat lamination, photochemical lamination, and also can include article modification of the substrate or the layer or both. Post-lamination annealing can be done, if desired, to enhance adhesion.
The support material may be a thermoplastic polymer that flow at elevated temperatures but not at lower temperatures such as room temperature or a thermosetting resin that can be cured using a catalyst, heat, or photoexposure depending upon its chemistry. Fig. 7 illustrates a fabrication system that uses a photo-cured thermosetting resin chemistry.
The metal coated master belt and the support material are pressed together in a nip between rollers 580 and 585. Once the support material has filled in the relief pattern on the surface of the master belt it is cured by shining ultraviolet light 570 through the back side of the carrier film to cure the support material. The electro deposited portions 513 will be removed from the master belt when the carrier film and support material are separated from the master belt to form the nanostructured material 100.
While the processes above described above depict continuous processes for fabricating conductive nanostructures on a flexible sheet, one skilled in the art would recognize that these structures may also be prepared by a batch process if a master tool in the form of a textured tile were used.
EXAMPLES
Example 1
A nanostructured material 100' having a sub-micron hole array structure was prepared utilizing the fabrication method previously described. Figs. 3A-3G show a flow diagram of the fabrication method by which the nanostructured material 100' was formed. Preparing the master
A thin layer of a positive UV5 photoresist 306 (available from Rohm and Haas Electronic Materials, Marlborough, MA) was applied to a glass master 300 having a conductive ITO surface layer 304 with a thin chromium tie layer (not shown) between the glass layer 302 and the ITO layer 304 as shown in Fig. 3A. The relief pattern 310 was made by interference lithography using a Innova Sabre FReD UV laser with an output of 270 mW (available from Company Coherent located at Santa Clara, CA) to pattern the photoresist layer 306 with an array of posts 314 (Fig. 3B). The exposed areas were then removed using a developing solution to dissolve the undesired photoresist. The diameter, D, of the nanostructures of the post is about 0.85 μm as shown in
Fig. 3B. The pitch, P, of the nanostructures was 1.7 μm. This photo resist based structure was used as dielectric material based sub-micron structure mold.
Creating the replicate
A thin layer of gold 320 was electrodeposited onto the surface 311 of the ITO glass coated master 300 in the area 316 around posts 314 of the relief pattern 310. The gold was electrodeposited using ACR 150 Gold Plating Solution available from Technic, Inc., Cranston, RI, with a current density of 1 amp per square foot, and a temperature of 480C to yield a 0.2 μm gold layer.
A layer of a UV curable support material 330 was coated over the relief pattern 310. The sample was placed in a vacuum chamber to prevent air entrapment in the area 316 around posts 314 of the relief pattern 310 between the deposited gold layer 320 and the support material 330. The UV curable support material was prepared in a manner similar to that described in United States Patent No. 7,074,463 (examples IA and IB, herein incorporated by reference) except that a mixture of 48 parts Sartomer 295 (Pentaerythritol tetraacrylate monomer, available from Sartomer Co., Exton, PA), 35 parts RDX-51027 (2,2',6,6'-Tetrabromobisphenol A diacrylate, available from Cytec Surface Specialties , Smyrna, GA) and 17 parts Sartomer 339 (Pentaerythritol tetraacrylate monomer, available from Sartomer Co., Exton, PA). The final SiO2 loading was 40% by wt. instead of 37.33%. The thickness of support material applied was 200 μm. A PEN carrier film 340 was applied to the back side of the support material 330 prior to curing the support material. The support material was cured by subjecting the coated glass master to 350 nm UV radiation 355 for 10 minutes in a nitrogen atmosphere.
The nanostructured material 100' was removed from the glass master 300 and cleaned with methanol. As shown in Fig. 4, the resulting nanostructured material had a gold surface and an array of sub-micron holes that extended through the gold surface and into the support material layer.
Example 2
A second replication master was made with a durable diamond-like carbon (DLC) relief structure on the surface of an ITO glass coated silicon master. A 200 nm DLC film was vacuum coated onto the surface of the ITO glass followed by application of a thin layer (about 50 nm) diamond- like glass (DLG) as described in Untied States Patent Nos. 5,888,594; 6,015,597; and 6,696,157; herein incorporated by reference. A layer of photo resist (UV5 photoresist 306, available from Rohm and Haas Electronic Materials, Marlborough, MA) is applied to the to the DLG surface. The photo resist was patterned using interference lithography as generally described in United States Patent No. 7,085,450, herein incorporated by reference. A 3-step reactive ion etching process utilizing perfluoropropane (CsF8), oxygen and argon gases was used to transfer the pattern from the photoresist into the DLC layer so that the surface of the ITO glass was exposed in selected areas. Fig. 5 shows a schematic cross-section of the silicon master 400 having an aluminum coated silicon base substrate 410 having a conductive ITO glass layer 420 disposed on the aluminum layer 412 and a DLC relief pattern 430 disposed on the ITO glass layer 420. Advantageously, the ITO glass serves as a release coating to allow the easy removal of the electrodeposited material from the master drum. Additionally, the low- surface energy of the DLC and DLG also provided improved release characteristics for removing cured replicated material and the deposited material from the replication master.
A thin layer of gold was electrodeposited onto the surface 411 of the silicon master 400 in the holes 434 of the relief pattern 430. The gold was electrodeposited using ACR 150 Gold Plating Solution available from Technic, Inc., Cranston, RI, with a current density of 1 amp per square foot, and a temperature of 480C to yield a 0.2 micron gold layer. A layer of a UV curable support material, described above, was coated over the relief pattern 430. The sample was placed in a vacuum chamber to ensure that there as no air trapped in the holes 434 of the relief pattern 430. The thickness of support material applied was 200 μm. A PEN carrier film was applied to the back side of supporting material prior to curing the support material.
The support material was cured subjecting the coated glass master to 350 nm UV radiation for 10 minutes in a nitrogen atmosphere.
The nanostructured material was removed from the silicon master and cleaned with methanol.
Fig. 6A shows an atomic force micrograph of the resulting nanostructured material having a gold surface and an array of sub-micron holes that extended through the gold surface and into the dielectric layer. Fig. 6B shows a scanning electron micrograph of the resulting nanostructured material. Auger electron spectroscopy confirmed that the gold was only on the surface of the nanostructured material and that there was no gold in the hole area of the material. The period of the microstructure is 1.7 μm. The depth of the holes is about 0.6 μm.
Advantages of the disclosed method include providing reducing material scrap and producing a nanometer-scale pattern on a large flexible substrate surface for use in applications such as polarizing films for liquid crystal displays or electromagnet shielding for PDP displays. This replication method does not require lift off or reactive ion etching of unwanted material thus simplifying manufacture and reducing the cost of the resultant film. The electrodepositable material is deposited where it is needed, and thereby minimizing the waste of the material. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

WHAT IS CLAIMED IS:
1. A method of making a surface structured article comprising: providing a textured master including a relief pattern formed on a surface of a conductive substrate, wherein the relief pattern is at least one of a microscale relief pattern and a nanoscale relief pattern; immersing a portion of the textured master into a coating bath comprising an electrodepositable material; depositing the electrodepositable material onto the textured master; contacting a support material to the textured master; and removing the electrodepositable material from the textured master when the support material is separated from the textured master.
2. The method of claim 1, wherein the relief pattern comprises conductive regions and nonconductive regions.
3. The method of claim 2, wherein the electodepositable material is deposited on the conductive regions of the relief pattern.
4. The method of claim 1 , wherein the textured master is a cylindrical master drum.
5. The method of claim 1 , wherein the textured master is a master belt.
6. The method of claim 1 , wherein the textured master is a master tile.
7. The method of claim 3, further comprising rinsing and drying a portion of the textured master having the electrodepositable material coated on the conductive regions.
8. The method in accordance with any of claims 1-7, further comprising applying a current between the coating bath and the textured master.
9. The method in accordance with any of claims 1-7, further comprising applying a carrier film to a surface of the support material.
10. The method in accordance with any of claims 1-7, wherein the support material is a thermoplastic polymer.
11. The method of claim 8, wherein thermoplastic polymer is one of a polyolefin polymer, an ethylene copolymers, a fluoropolymer, a polyketone, a polyamide, a polycarbonate, a polyester, a styrene block copolymers, and and styrene acrylonitrile polymer
12. The method in accordance with any of claims 1-7, wherein the support material is a thermosetting resin.
13. The method of claim 12, wherein curable resin is one of an acrylate, a polydimethylsiloxane, a urethane acrylate and an epoxy.
14. The method of claim 12, further comprising the step of curing the curable resin.
15. The method in accordance with any of claims 1-7, wherein the electrodepositable material is a conductive material.
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