WO2014021949A1 - Détection d'énergie de surface indicative du degré d'achèvement d'une polymérisation par réticulation - Google Patents

Détection d'énergie de surface indicative du degré d'achèvement d'une polymérisation par réticulation Download PDF

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Publication number
WO2014021949A1
WO2014021949A1 PCT/US2013/032393 US2013032393W WO2014021949A1 WO 2014021949 A1 WO2014021949 A1 WO 2014021949A1 US 2013032393 W US2013032393 W US 2013032393W WO 2014021949 A1 WO2014021949 A1 WO 2014021949A1
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WIPO (PCT)
Prior art keywords
liquid
substrate
polar
intersection
polar liquid
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PCT/US2013/032393
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English (en)
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Ed. S. RAMAKRISHNAN
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Unipixel Displays, Inc.
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Publication of WO2014021949A1 publication Critical patent/WO2014021949A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • C08J7/16—Chemical modification with polymerisable compounds
    • C08J7/18—Chemical modification with polymerisable compounds using wave energy or particle radiation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
    • C08J3/248—Measuring crosslinking reactions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/44—Resins; rubber; leather
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0092—Visco-elasticity, solidification, curing, cross-linking degree, vulcanisation or strength properties of semi-solid materials

Definitions

  • Polymer films may be used for a variety of applications in industries such as the electronics and automotive industries. These films and may be formed and/or have their properties refined during a polymerization process such as curing.
  • Polymer thin films may be used to protect a device or other commodity from damage, wear, or viewing by unauthorized parties.
  • the property requirements of these films may depend on the end use and may be affected by the polymerization process when molecules such as monomer molecules react to form polymer chains or networks BRIEF SUMMARY
  • a method for testing the degree of polymerization of cross- linked polymerized films comprises: coating at least one side of a substrate with a curable resin; drying the coated substrate, wherein drying at least partially solidifies the resin coating; and embossing at least one side of the substrate, wherein embossing is by using a master shim disposed on an embossing roller, wherein the master shim comprises a microstructural pattern, and wherein the embossing roller imprints the microstructural pattern into the ultraviolet-curable resin on the substrate.
  • the embodiment further comprises: at least partially curing the imprinted microstructural pattern using an ultraviolet source; and determining if a ratio of a polar component of a surface energy of the cured imprinted substrate to a dispersive component of the surface energy of the cured imprinted substrate is from 2:1– 3:1.
  • a system for testing the degree of polymerization of cross- linked polymerized films comprises: a coating station, where in the coating station coats a substrate with a curable resin coating; and a drying station, wherein the drying station at least partially solidifies the resin coating applied at the coating station.
  • the embodiment further comprises: an embossing station comprising an embossing roller and an ultraviolet source, wherein a master shim is disposed on the embossing roller, wherein the master shim comprises a microstructural pattern, wherein the embossing roller imprints the microstructural pattern in to the resin coating, and wherein the ultraviolet source at least partially cures the imprinted pattern; and a testing station, wherein the testing station measures a ratio of a polar component of a surface energy of the cured imprinted film to a dispersive component of the surface energy of the cured imprinted film and determines if the partial cure was sufficient, wherein the at least partial cure was sufficient if the measured ratio is between 1 :1– 10:1.
  • a method for testing the degree of polymerization of cross-linked polymerized films comprises: coating at least one side of a substrate with a curable resin coating; drying the coated substrate using a drying station, wherein the drying station at least partially solidifies the resin coating applied at the coating station; at least partially curing the substrate using an ultraviolet source; and determining if a ratio of a polar component of a surface energy of the cured substrate to a dispersive component of the surface.
  • FIGS. 1 A-1 D illustrate stages of a polymerization process.
  • FIGS. 2A-2C illustrate a plurality of contact angle measurements.
  • FIG. 3A is a flowchart of an embodiment of fabricating microstructurally-patterned master patterns.
  • FIG. 3C is an expanded view of a microstructure according to an embodiment of the disclosure.
  • FIG. 4 illustrates a system that may be used to emboss and test the surface energy of films according to embodiments of the disclosure.
  • FIG. 5 illustrates a cross-section of an embossed pattern manufactured by embodiments of the disclosure.
  • FIG. 6 is a flowchart of a method of fabricating embossed polymer thin films according to embodiments of the disclosure.
  • the completion of polymerization reactions may be determined on a periodic basis and constantly monitored in manufacturing operations in order to produce reliable and repeatable final product quality.
  • the monitoring method used should be simple, reliable, and cost-effective so that degree of cross-linking achieved in polymerization processes may be analyzed and controlled.
  • this testing may be conducted using sensitive chemical analysis techniques and/or surface analysis tools such as Fourier transform infrared spectroscopy (FTIR) where an infrared spectrum of absorption, emission, photoconductivity or other properties may be measured.
  • FTIR Fourier transform infrared spectroscopy
  • testing product at the end of a process may indicate overall product quality for the portion of the product that has already been produced, it does not allow for the in-line adjustment of process parameters during the product flow which may lead to excess scrap and/or machine damage, either or both of which may lead to increased cost, safety concerns, and environmental concerns.
  • in- line monitoring and adjusting the curing parameters may be even more crucial in reel-to- reel or roll-to-roll film processing where it may be impractical to interrupt the run to test product.
  • the product quality can be measured in a more rapid, more cost effective manner.
  • a cross-link or a cross-linking process or event may refer to the formation of covalent or ionic chemical bonds between monomers or oligomer chains.
  • the monomer or oligomer chains involved in the cross-linking process may be synthetic or natural and the chemical process of forming the cross-links may be initiated or catalyzed by any means.
  • the systems and methods disclosed herein may be for UV curable acrylate materials or e-beam acrylate materials and may be implemented for other types of polymerization reactions including conventional light curing, thermal polymerization, and other reactions without limitation. Additionally, the method of the present disclosure used to determine the degree of cross-linking polymerization may be employed as a quality control method in any industry involved in thermal, UV, Electron Beam, or any other form of cross-linking. The purpose of the testing described herein is to ensure that the curing process is producing a polymer thin film to a set of predetermined specifications. Curing as used herein refers to the process of drying, solidifying or fixing any coating or ink imprint previously applied to a substrate. Further, as used herein curing may include the act of applying radiation to change at least one physical or chemical property of a material. Further, curing may include to the process of chemical or physical changes in a fluid under irradiation.
  • Polymer films may be used in applications such as optical, display, environmental and mechanical applications.
  • thin polymer films may be used in applications such as Uni-Pixel’s Time Multiplexed Optical Shutter (TMOS), Finger Print Resistant (FPR) films, Privacy Films, as well as electronic devices, hard coatings and automotive coatings.
  • Photo-polymerization using ultraviolet (UV) may be used because these processes may take place rapidly, are solvent-free, may make it easier to emboss and form microstructures, and may require much less energy to manufacture than alternative methods.
  • Polymeric microstructures may also be employed for optical, electronic, display, MEMS, microfluidics and biomedical applications.
  • hexagonal shaped structures on acrylate materials have been used in polymer MEMS displays, and hot dog (elongated cellular or wire) shaped structures have been used in FPR applications.
  • the progress and endpoint of a plurality of monomer to polymer (long chain repeating units) conversion reactions may be monitored in order to achieve high quality materials, to meet product specification, and to optimize energy requirements for the reactions.
  • the functional properties of polymer materials such as wettability, scratch and abrasion resistance, hardness, weathering resistance, and chemical stability may depend on the degree of cross-linking. As such, the start, duration, and completion of the reaction may be monitored.
  • the surface properties may also be monitored. This monitoring may be performed not only to ensure that the product coming out of the process meets the predetermined quality parameters but also to ensure that subsequent products run in between the testing also conform to the desired properties.
  • a plurality of processing conditions may influence the different performance characteristics of the material and may affect the performance of the end product.
  • the optimization and control of the processing conditions of these materials are very important in high volume industrial processes.
  • the degree of cross-linking or curing of various polymers materials, including thermal or photo-curing polymers may effect of the properties of the end product, such as mechanical and stiction properties, among others.
  • the degree of conversion of monomer to polymer may depend on the light absorption characteristics and the amount of applied irradiation dose (joules/cm 2 ).
  • the wavelength of incident UV light, UV (lamp, LED) power, time of exposure, the chemical composition of the reactants, the type and amount of photo- initiators, and the process temperature are some of the factors that affect the conversion.
  • the photoinitiator used may comprise those from the alpha hydroxyketone family, phynylglyoxylate, benzyldimethyl-ketal, alpha aminoketone, mono acyl phosphine (MAPO), MAPO/alpha hydroxyketone, phosphine oxide, Bis Acyl Phosphine Oxide (BAPO), matallocene, iodonium salt.
  • the solvent used may comprise at least one of isobornyl acrylate, isodecyl acrylate, 2-phenoxyethyl acrylate, hexane diol diacrylate, tripropyleneglycol diacrylate, trimethyolpropane triacrylate, trimethyolpropane ethoxytriacrylate. These may be obtained from suppliers including Ciba, Lamberti, BASF, and Sigma-Aldrich. [0021] Contact angle measurements may be used to determine the degree of cross- linking of polymeric substrates by applying drops or micro-drops of different liquids of known surface tension to the surface of the cured polymer substrate.
  • the angle between the outline tangent of the drop at the contact location and the solid surface (the contact angle, ) is used as the tool to determine the cross-linking degree. From this data, the surface energy is computed and compared for different applied UV dosages. This same concept may also be applicable to surfaces with microstructures and materials cross-linked by thermal processing as well as other means. This measurement may be taken using a polar liquid, a non-polar liquid, or both may be used as discussed below to obtain a ratio to determine the degree of cross-linking polymerization.
  • polymer films and coatings may undergo several surface modifications when subjected to polymerization reactions, including a change in composition, surface roughness, and level of adhesion, among other changes.
  • these changes may be detected using sensitive chemical analysis techniques and surface analysis tools such as FTIR as discussed above.
  • FTIR surface analysis tools
  • the degree of conversion of monomer to polymer depends on the light absorption characteristics, and the amount of applied irradiation dose (joules/cm 2 ).
  • the wavelength of incident UV light, UV (lamp, LED) power, time of exposure, the chemical composition of the reactants, type and amount of photo-initiators and process temperature are some of the factors that affect the conversion.
  • Polymerization conditions may have a direct effect on the surface free energy of the substrates.
  • contact angle measurements are used herein to determine the degree of cross-linking of polymeric substrates instead of costlier, more time-consuming methods such as FTIR.
  • this may be achieved by applying drops or micro-drops of different (polar and non-polar) liquids of known surface tension to the surface of the cured polymer substrate.
  • the contact angle is used as the tool to determine the cross-linking degree. From this data, the surface energy is computed and compared for different applied UV dosages. This same concept may also be applicable to surfaces and materials cross-linked by thermal, e-beam, and other means.
  • the present disclosure relates to using the contact angles of a series of polar and non-polar liquids for distinguishing the polar and dispersive components of the total surface energy in order to calculate the degree of cross-linking.
  • Suitable liquids for this method include, but are not limited to, polar liquids such as water, ethanol, glycerol, formamide, ethylene glycol, and non-polar liquids such as di-iodomethane, diethyl ether, benzene, hexane, cyclohexane, hexadecane.
  • the contact angles and surface energy calculations are then directly correlated to the degree of cross-linking of the polymeric substrate by using a ratio of measurements (polar component: dispersive component) related to the surface energy.
  • FIGS. 1 A-1 D illustrate stages of a polymerization process.
  • monomers are joined together to form polymers chains.
  • a plurality of monomer structures 102 in FIG. 1 A are joined together in a reaction that may be caused by curing to form a plurality of oligomers 104 in FIG. 1 B.
  • Monomer structures 102 in FIG. 1 A due to their weak intermolecular forces, may be liquids or structurally weak molecular structures.
  • FIG. 2B may be joined together to form a plurality of polymers 106 in FIG. 1 C or a linear polymer structure.
  • the reactions may continue, resulting in a cross-linked polymer structure 108 as shown in FIG. 1 D.
  • FIG. 1 D In the cross-linked polymer structure 108, while the representation in FIG. 1 D is two-dimensional, a plurality of polymers such as shown by 106 in FIG. 1 C are linked together in a three dimensional structure that increases the intermolecular forces, which may be covalent bonds, within the polymer chains.
  • FIGS. 2A-2C illustrate a plurality of contact angle measurements.
  • a cross-section of a droplet 212 is shown on a substrate (surface) 214 in an environment 210 that may be referred to as a gaseous interface.
  • a contact angle 202a ( C ) is formed by the intersection of the solid/liquid interface ( SL ) 206a and the liquid/gas interface ( LG ) 204a. It may be alternately described as the angle between solid sample’s surface 214 and the tangent of the droplet’s 212 ovate shape at the edge of the droplet 212.
  • High contact angles as the one shown in FIG.
  • FIG. 2A may indicate a low solid surface energy or degree of chemical affinity which may also be referred to as a low degree of wetting.
  • FIG. 2C illustrates a cross-section of a droplet 212 is shown on a substrate (surface) 214 in an environment 210 that may be referred to as a gaseous interface.
  • a contact angle 202c ( C ) is formed by the intersection of the solid/liquid interface ( SL ) 206c and the liquid/gas interface ( LG ) 204c.
  • Low contact angles as the one shown in FIG. 2C, may indicate a high solid surface energy or chemical affinity, and a high or sometimes complete degree of wetting.
  • FIG. 2B illustrates contact angle of zero degrees which may be referred to as complete wetting, and it may occur when the droplet has turned into a flat puddle.
  • Goniometry involves the observation of a sessile drop of test liquid on a solid substrate, while tensiometry involves measuring the forces of interaction as a solid is contacted with a test liquid.
  • the contact angle may be assessed directly by measuring the angle formed between the solid and the tangent to the drop surface.
  • An instrument with high speed image capture capabilities shapes of drops in motion may be used to analyze and measure the drops.
  • a plurality of solid substrates exhibit a relatively flat portion for testing and can fit on the stage of the instrument.
  • substrates with regular curvature such as contact lenses or other curved structures, can also be tested. Testing can be done using very small quantities of liquid, and in some cases high temperature liquids such as polymer melts may also be tested using surface energy measurements as discussed herein.
  • Using the tensiometric method for measuring contact angles measures the forces that are present when a sample of solid is immersed in the contact with a test liquid. If the forces of interaction and geometry of the solid and surface tension of the liquid are known, then the contact angle may be calculated. At any point on an immersion graph, all points along the perimeter of the solid at that depth contribute to the force measurement recorded. Thus, the force used to calculate the contact angle at any given depth of immersion is already an averaged value. An averaged value can be calculated for the entire length of the sample or average any part of the immersion graph data to assay changes in contact angle along the length of the sample. This technique allows the user to analyze contact angles produced from wetting over an entire range of velocities from static to rapid wetting.
  • the methods disclosed herein may be implemented by either tensiometric or goniometric methods.
  • the primary focus of contact angle studies is assessing the wetting characteristics of solid/liquid interactions.
  • Contact angle is commonly used as the most direct measure of wetting.
  • Wetting ability of a liquid is a function of the surface energies of the solid-gas interface, the liquid-gas interface, and the solid-liquid interface.
  • the surface energy across an interface or the surface tension at the interface is a measure of the energy required to form a unit area of new surface at the interface.
  • the intermolecular bonds or cohesive forces between the molecules of a liquid cause surface tension.
  • the adhesive forces between the liquid and the second substance compete against the cohesive forces of the liquid.
  • Liquids with weak cohesive bonds and a strong attraction to another material tend to spread over the material. Liquids with strong cohesive bonds and weaker adhesive forces tend to bead-up or form a droplet when in contact with another material.
  • the ability of a substrate to anchor inks, coatings, adhesives or impurities like oils is directly related to its surface energy. If the substrate surface energy does not significantly exceed the surface tension of the fluid, wetting may be impeded and a poor bond may result.
  • plastics may be treated from about 36 dynes/cm 2 to about 40 dynes/cm 2 ; water-based inks may require from about 40 dynes/cm 2 to about 44 dynes/cm 2 .
  • the appropriate surface energies may be approximately 50 dynes/cm 2 or more.
  • FIG. 2A illustrates a polar liquid such as water
  • FIG. 2B illustrates a non-polar liquid, such as methylene iodide or formamide.
  • polar and dispersive non-polar liquids group at the surface.
  • the introduction of polar groups in an otherwise non-polar surface may produce a surface that is amphiphilic i.e. the surface combines both hydrophilic and hydrophobic properties.
  • the ratio of the polar components to the dispersive components may be used to control the degree of cross linking of polymeric substrates in mass production processes.
  • the migration of fingerprints oils also referred to as wetting or spreading may be further enhanced by modifying the surface energy of the substrate 214, since wetting of a surface may happen more readily over a surface having a higher surface energy than a surface having a lower surface energy.
  • the polar and dispersive components of the surface energy may be modified so their ratio follows within an optimal range for fingerprint resistance applications.
  • the ration of the polar component to the dispersive component may be 1 :1– 10:1.
  • the optimal range for the ratio between the polar component to the dispersive component may be between 2:1 and 3:1.
  • This ratio may be obtained by disposing a drop of more of a polar liquid and a drop or more of a non-polar liquid on the surface of a microstructure on at least one section of a thin polymer film and measuring the behavior of at least one polar and non-polar liquid on the surface to determine the ratio of the polar component to the dispersive component.
  • the measurements are taken across a sampling of the run of a product to determine the statistical properties and/or distribution of the degree of completion of cross-linking for that particular product run.
  • FIG. 3A is a flowchart of an embodiment of fabricating microstructurally-patterned master patterns which may also be referred to as shims or sleeves.
  • FIG. 3B is an illustration of a method of fabricating microstructurally-patterned master patterns which may also be referred to as shims or sleeves.
  • FIG. 3A depicts a process 300 of forming microstructures on substrates to form master shim/patterns for embossing substrates. Turning to both FIGS. 3A and 3B, the process 300 starts with substrate 316 preparation at block 302 in which a transparent substrate 316 is cleaned. The substrate 316 may be cleaned using water, web cleaner, or other known cleaners.
  • the photoresist may be prepared at block 304 when a photoresist material 318 is deposited on one side of the transparent substrate 316. It is appreciated that a photoresist may be referred to as either positive or negative.
  • the term“positive photoresist” describes what happens when the portion of the photoresist that is exposed to the curing source becomes soluble to the photoresist developer discussed below.
  • the negative photoresist is one where the portion exposed to the curing source becomes insoluble to the developer and the unexposed portion is instead dissolved during development.
  • the photoresist used to make the master shim may be selected depending upon the substrate, with a negative photoresist adhering to glass, Si, as well as metals such as gold (Au), copper (Cu), and aluminum (Al).
  • the thickness 320 of the layer of photoresist 318 is larger than the expected height of the microstructures.
  • the photoresist may be cured using UV light or heat.
  • a photomask 324 may be applied to the cured photoresist 322 with the desired pattern in a photomask application at block 308.
  • the photoresist 318 may be exposed and the photomask 324 removed.
  • the photoresist may be developed and a plurality of microstructures 326 may be formed on top of the substrate 316.
  • the photoresist is dissolved by a developer to form the master shim pattern.
  • the type of developer used, as well as which part of the photoresist dissolves, may depend whether the photoresist is positive or negative.
  • an aqueous developer may be used for a positive photoresist and an organic developer may be used for a negative photoresist.
  • the master shim may be coated with metal such as copper (Cu), nickel (Ni).
  • the cross-section of the process in the method in FIG. 3A shown in FIG. 3B represents a plurality of lines from a pattern that have a rectangular cross-sectional geometry.
  • the cross-sectional geometry may be rectangular, square, half-circle, triangular, trapezoidal, or a combination thereof.
  • the plurality of microstructures 326 may be used in the embossing system of FIG. 4 to manufacture polymer thin films with fingerprint resistant properties where the degree of cross-linking polymerization may be determined using the surface energy of the embossed/imprinted films.
  • the exterior surface of the substrate manufactured by this method may have a surface energy in the range from about 25 dynes/cm 2 to 35 dynes/cm 2 to enhance the spreading of the oils deposited by contact from fingers, palms, and the like.
  • the plurality of microstructures 326 of the pattern may have a height 328 from 1 micron to 50 microns and each line or feature of the microstructure may have a width 330 from 1 micron to 25 microns.
  • the microstructure pattern may be referred to as an inverted pattern because it is the master used to imprint a pattern or patterns on a substrate.
  • the height 328 is from about 3 microns to 10 microns.
  • the height 328 of the plurality of microstructures 326 may be optimized in accordance with the particular application in terms of the anticipated particular contaminant and the amount of the particular contaminant depending upon the type of application the embossed substrates in FIG. 4 will be used for.
  • a fingerprint pressed onto a smooth surface may leave a mark between 3 - 6 microns thick.
  • a suitable array of the plurality of microstructures 326 may be fabricated on a surface of the substrate 316 to provide a surface topology in the similar range of about 3 to 10 microns in the final product.
  • the plurality of microstructures 326 may reduce image distortion due to foreign marks or contaminant substance, such as oils form fingerprints, typically deposited onto the surface of a substrate 316 during normal handling.
  • the generally flat upper surface of the plurality of microstructures 326 is the distal end 332 of the microstructures 326 that a user is able to touch.
  • the plurality of microstructures 326 may be able to reduce light distortion caused by the foreign substance and the visibility of the same by braking up and redistributing the foreign mark substance deposited onto the upper surfaces of the plurality of microstructures 326 to other areas of the substrate 316. More specifically, the spaced apart relationship of the plurality of microstructures 326 created by the spacing (such as that discussed in FIG. 3C) provides a surface topography that breaks up the foreign marks and promotes the redistribution of the foreign mark via capillary action.
  • FIG. 3C is an expanded view of a microstructure according to an embodiment of the present disclosure.
  • FIG. 3C is an expanded view of the plurality of microstructures 326 in FIG. 3B.
  • the surface topography comprises the plurality of microstructures 326 surrounded by interstitial spacing 334 that are recessed areas, which may also be referred to as valleys or channels, between adjacent microstructures that accommodate the foreign mark substance that migrate contaminants to said areas of the final embossed product. This capillary action is discussed in detail below in FIG. 5.
  • a suitable density of the plurality of microstructures 326 on the surface of substrate 316 may be optimized depending upon factors such as the particular application and the normal viewing distance of the viewer to the surface of substrate 316.
  • the raised surface areas of the plurality of microstructures 326 may preferably be within a range from about 5% to about 45% of the total flat surface area of the substrate 316.
  • a low density of microstructures 326 in some cases less than 5 %, may tend to lose fingerprint resistant characteristics, particularly when the plurality of microstructures 326 are short. In that example, the plurality of microstructures 326 are so far apart that the capillary action between adjacent microstructural features of the plurality of microstructures 326 deteriorates and thus fingerprint resistance diminishes.
  • the density of the plurality of microstructures 326 on the surface of the substrate 316 may be optimized depending upon factors such as the particular application and the normal viewing distance of the viewer to the surface of substrate 316.
  • the raised surface areas of the plurality of microstructures 326 may preferably be within a range from about 5% to about 45% of the total flat surface area of substrate 316.
  • a density of microstructure 326 of less than 5 % may lose fingerprint resistant characteristics, particularly when microstructures 326 are short.
  • the plurality of microstructures 326 are so far apart that the capillary action between adjacent microstructures of the plurality of microstructures 326 deteriorates and thus fingerprint resistance diminishes.
  • the extent of randomization may impact in the resultant finger print resistance performance characteristics. Under optimally cured conditions, the finger print resistance depends on the relative distribution of the polar and dispersive components.
  • FIG. 4 illustrates a system that may be used to manufacture films according to embodiments of the present disclosure.
  • the manufacture of these films also comprises the testing component, since it is understood that a production run may only be considered to be complete once it is determined that the run produced saleable product or product suitable for further processing or another intended purpose.
  • the system 400 may be a roll-to-roll embossing system for manufacturing a substrate 402 that has a particular microstructure, for example, a finger-print resistant microstructure or other microstructure on at least one surface of the substrate 402.
  • the system 400 may be used to manufacture elongated sheets or rolls of micropatterned substrate or protective layers in an inline process.
  • An inline process means a substantially continuous process wherein a plurality of operations are performed in series where system components can be changed or adjusted as needed throughout the process.
  • a final product, intermediary product, components, and test samples for those products and combinations thereof may be manufactured.
  • the system 400 comprises a coating station 404, a drying station 406, and an embossing station 408.
  • the coating station 404 has a roll disposed on an unwind roller 408 of unpatterned substrate 402.
  • the unpatterned substrate may 402 be made of polyethylene terephthalate film (PET), polyethylene naphthalate (PEN), polymide, and polycarbonate, or other polymers or material suitable for the end application.
  • the substrate 402 may take the form of sheets or a series of flat sheets, in that case, a feeder would be used instead of the unwind roller 408.
  • the coating station 404 comprises a supply of resin 410 such as ultraviolet curable acrylate that is applied to the substrate 402.
  • the resin may comprise ultraviolet curable or e-beam curable acrylate resins, bearing one or several acrylate groups that are derived from chemical backbones such as polyol, polyester, polyurethane, polyether, epoxies and acrylics.
  • the substrate 402 may be cleaned (not pictured) prior to the application of the resin 410 by a water wash, web cleaner or other means.
  • the resin 410 may be applied at the coating station 404 in a bath as illustrated or, not pictured, as a spray, dip, brush, roll, or other application that provides a uniform distribution.
  • the resin may be applied to a thickness of at least 10nm and may be applied at a thickness greater than 10 microns depending upon the application.
  • the substrate 402 then passes through the drying station 412.
  • the drying station 412 may comprise one or a plurality of rollers 414 and more drying treatments including air drying, head application, curing, or other processes applied to fully or partially dry or solidify the resin 410 or to bond the resin 410 to the substrate 402. It is appreciated that a plurality of transfer rollers 416 may also be employed to move the substrate 402 through the system 400.
  • the embossing system 418 may comprise a curing station 420 such as an ultraviolet lamp, heat source, or other curing source and in some embodiments may comprise more than one such source of the same or different types.
  • the embossing system further comprises an embossing roller 422 on a master shim or sleeve that is manufactured as discussed in FIGS. 3A-3C above and disposed on the embossing roller 422.
  • the embossing roller 422 is brought into rolling contact with the resin 410 coating on the substrate 402, as the embossing roller 422 rolls over the substrate 402, a pattern, which may also be referred to as an inverted pattern, on the master shim or sleeve is impressed into the resin coating 410.
  • FIG. 5 illustrates a cross-section of an embossed pattern manufactured by embodiments of the disclosure.
  • FIG. 5 shows a cross-section of microstructural embossed pattern 502 that may have been formed, for example, by the master shim/pattern in FIG. 3C in the resin 410 coating the substrate 402.
  • the pattern forms troughs about the same size as the width 330 and depth 328 of the protrusions of the microstructural pattern 326.
  • the positive protrusions of the microstructural embossed pattern 502 may be about the width of the valley 334 of the pattern 326 in FIG. 3C, and about the size of the depth 328.
  • microstructures 502 The presence and proximity of adjacent microstructures 502 causes capillary redistribution of the foreign mark to recessed areas 332.
  • the redistribution of the marks substance by capillary action leaves relatively little foreign mark substance on the upper flat surfaces of microstructures 502 where the foreign mark was originally deposited. This redistribution permits the light to be transmitted from both the upper surfaces and recessed areas 332 to reach the operator viewing substrate 402 with less distortion.
  • the curing station 420 cures the imprinted pattern on the resin coating 410 which causes the pattern to at least partially solidify while preserving the pattern of microstructures impressed into the resin 410.
  • the substrate 402 may be molded, thermally formed, embossed, etched, or otherwise patterned using any number of polymer processing techniques to form the microstructure on a surface.
  • the substrate 402 may be wound after curing on a winding roll 424.
  • the winding roll 424 also allows for test pieces of the substrate 402 to be cut, for example, at the beginning and end of the substrate 402 to be tested at testing station 426 to determine the degree of completion of the cross-linking polymerization as discussed above.
  • Testing station 426 may comprise a testing unit or a plurality of testing units 428 that may employ methods, for example, such as goniometry and tensiometry. In that embodiment, a statistically valid number of samples may be pulled from each substrate roll, each shift, each lot number, or across a combination thereof.
  • testing station 428 wherein a polar liquid and a non-polar liquid are used on at least one sample, preferably a statistically valid number of samples, and the angles are compared as discussed above.
  • the testing station is used to determine the degree of completion of the cross-linking polymerization.
  • the optimal range for the ratio between the polar and the dispersive components may be between 2:1 and 3:1.
  • the wind roll 424 may instead be a receptacle for separated sheets and the system comprises a cutting station (not pictured), or a receptacle for fan-folded sheets or other forms of the substrate 402 after processing.
  • a cutting station not pictured
  • a receptacle for fan-folded sheets or other forms of the substrate 402 after processing can be applied to the side of the substrate 402 opposite where the pattern was imprinted.
  • the substrate can be cut not only for testing sections but also cut to size for a variety of applications in the electronics, automotive, and other industries.
  • FIG. 6 is a flowchart of a method of fabricating embossed polymer thin films according to embodiments of the disclosure.
  • This method 600 may be carried out, for example, by the system in FIG. 4.
  • the substrate may be cleaned.
  • the cleaning may occur at one or more cleaning stations that may comprise a room temperature or warm water bath, a web cleaner, a forced air clean, or combinations thereof.
  • the substrate as discussed above, may be in the form of a roll, continuous sheets, or other form that can be fed into a roll-to-roll handling system for curing and/or embossing.
  • the substrate is coated with resin on at least one side at block 604.
  • the substrate is coated in a bath where both sides may be coated, and in another embodiment, the substrate may be coated by spray, brush, roller, or other method where one or both sides are coated with resin.
  • the resin is at least partially dried to solidify it for embossing. The drying may occur through forced air, hot air, thermal curing, or ultraviolet curing, and the drying may only be performed to the point where the resin can be completely and uniformly embossed at block 608.
  • at least one master shim as discussed in FIGS. 3A-3C is disposed on at least one embossing roll.
  • the substrate is embossed by the microstructural pattern on the master shim, forming patterns comprising a plurality of lines between 1 micron to 100 microns and height between 10nm to 10 microns.
  • the embossed pattern is at least partially cured at block 610.
  • the term“partial cure” may refer to curing the pattern enough so that is solidifies and so that a sufficient degree of cross-linking polymerization occurs.
  • the degree of polymerization is determined at block 612. This determination is made by determining the ratio of a dispersive component of the substrate after block 610 to a polar component of the substrate. These components are measured as a function of surface energy as discussed above.
  • a plurality of test samples may be taken, or one sample may be taken from different period during run of product through the process. Each sample may be tested using both one or more polar liquids and one or more non- polar liquids to determine the polar and the dispersive components. In another embodiment, a plurality of samples may be used to determine the polar and the dispersive components, and an average of each may be taken in order to obtain the ratio. If the polar: dispersive ratio is determined to be, for example, between 2:1 to 4:1 , which may also be expressed as being between 2-4, the degree of cross-linking polymerization may be determined to be sufficient and the product may thereby be further processed including packaging and distribution. In an embodiment, the same station (not pictured) used to take samples from the production run of substrate may be used to cut and/or trim the substrate into the shape and size suitable for a particular application.
  • the method 600 proceeds without the embossing step and a flat, unembossed, film is cured at block 610 and tested at block 612. It is appreciated that, while the polar to dispersive component ratio range of 2-4 may be desirable for some applications, in other applications a degree of cross-linking polymerization may be indicated by the range of 1 :1 – 10:1 , 3:1 -7:1 , 4:1 -6:1 , or other ratio ranges may be appropriate, and can be measured by using the surface energy method discussed above. Applications such as those using water-based inks on polymer surfaces may require a higher polar component and lower dispersive component.
  • epoxy - acrylate polymers are prepared by photo- polymerization of epoxy - acrylate oligomers.
  • this photo acrylate material the effect of 365nm UV dosage is significant.
  • the measured polar component of the surface energy is seen to vary, indicating the polymerization (curing) of the material is incomplete.
  • the polar part stabilizes, indicating the reaction is complete.
  • the polar component starts to drop drastically, indicating the formation of a different phase or composition than that is of interest.
  • an UV dosage of 4000 ⁇ 250 mJ/cm 2 may result in a completely cured material, and could be implemented for scale up and volume production.
  • the ratio of the polar to the dispersive components of total surface energy determines the wetting / de-wetting (beading) characteristics.
  • the ratio between the polar and the dispersive components can be used to control the degree of cross linking of polymeric substrates in mass production processes, inline process, or other manufacturing scenarios as appropriate.
  • the measurements may be taken as follows: the substrate 402 of a first material having a surface with optimal fingerprint resistant characteristics exhibits a polar component of surface energy of 24.5 dynes/ cm 2 and a dispersive component of 10.5 dynes/ cm 2 . Thus, the ratio of polar to dispersive components is approximately 2.33.
  • a substrate 402 of a second material having a surface with optimal fingerprint resistant characteristics was obtained. The surface exhibits a polar component of surface energy of 26.1 dynes/cm 2 and a dispersive component of 8.5 dynes/cm 2 . Thus, the ratio of polar to dispersive components is approximately 3.06.
  • a ratio of 3.06 may indicate acceptable product depending upon the application.
  • substrate 402 of a third material having a surface with optimal fingerprint resistant characteristics was obtained. The surface exhibits a polar component of surface energy of 25.0 dynes/cm 2 and a dispersive component of 10.3 dynes/cm 2 . Thus, the ratio of polar to dispersive components is approximately 2.43.

Abstract

La présente invention concerne des systèmes et des procédés susceptibles d'être utilisés pour déterminer le degré de polymérisation par réticulation dans des polymères en film mince. Un polymère plat en film mince ou un motif gaufré peut être durci en utilisant un durcissement par ultraviolets ou par faisceau d'électrons et l'énergie de surface dudit polymère en film mince peut être utilisée pour déterminer si le degré de polymérisation par réticulation est suffisant pour l'application finale. Cette détermination peut être basée sur un rapport d'une composante polaire d'énergie de surface mesurée à l'aide d'un liquide polaire à une composante dispersive d'énergie de surface mesurée à l'aide d'un liquide non polaire. Le rapport peut indiquer une polymérisation suffisante, une polymérisation insuffisante ou une polymérisation excessive.
PCT/US2013/032393 2012-07-30 2013-03-15 Détection d'énergie de surface indicative du degré d'achèvement d'une polymérisation par réticulation WO2014021949A1 (fr)

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CN112437719A (zh) * 2018-07-20 2021-03-02 3M创新有限公司 分层构建对象的方法及用于执行此类方法的3d打印装置

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CN108107918A (zh) * 2018-01-11 2018-06-01 广州航海学院 控制液滴移动方向的装置与方法
CN108107918B (zh) * 2018-01-11 2023-11-17 广州航海学院 控制液滴移动方向的装置与方法
CN112437719A (zh) * 2018-07-20 2021-03-02 3M创新有限公司 分层构建对象的方法及用于执行此类方法的3d打印装置

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