WO2025032460A1 - Composition d'adhésif - Google Patents

Composition d'adhésif Download PDF

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Publication number
WO2025032460A1
WO2025032460A1 PCT/IB2024/057508 IB2024057508W WO2025032460A1 WO 2025032460 A1 WO2025032460 A1 WO 2025032460A1 IB 2024057508 W IB2024057508 W IB 2024057508W WO 2025032460 A1 WO2025032460 A1 WO 2025032460A1
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WIPO (PCT)
Prior art keywords
adhesive
polyvinyl acetal
percent
monomers
acrylate
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PCT/IB2024/057508
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English (en)
Inventor
Hollis Z. BEAGI
Jason D. Clapper
Chun-Yi Ting
Hyunki Kim
Bradley J. JUST
Michael L. Steiner
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3M Innovative Properties Co
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3M Innovative Properties Co
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Application filed by 3M Innovative Properties Co filed Critical 3M Innovative Properties Co
Priority to CN202480051477.4A priority Critical patent/CN121666410A/zh
Publication of WO2025032460A1 publication Critical patent/WO2025032460A1/fr
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/30—Introducing nitrogen atoms or nitrogen-containing groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F261/00—Macromolecular compounds obtained by polymerising monomers on to polymers of oxygen-containing monomers as defined in group C08F16/00
    • C08F261/12—Macromolecular compounds obtained by polymerising monomers on to polymers of oxygen-containing monomers as defined in group C08F16/00 on to polymers of unsaturated acetals or ketals
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
    • C09J4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00

Definitions

  • the adhesive compositions and articles can be useful for bonding optical films in electronic display applications.
  • OCAs Optically clear adhesives
  • OCAs have diverse applications in consumer, industrial and automotive display technologies. These adhesives have become preferred bonding solutions for a number of reasons, including high adhesion and cohesion, protection, and enhanced performance of touchscreens as devices transitioned from resistive to capacitive touch technology. Desirable properties of OCAs can include optical clarity and high interfacial adhesion over a wide range of temperatures.
  • OLED organic light-emitting diode
  • Conventional organic light-emitting diode (OLED) displays have required use of a circular polarizer to prevent total internal reflectance from disrupting display quality.
  • Recent advancements in OLED display technology have enabled the reduction of total internal reflectance without the use of a circular polarizer, thus reducing or eliminating the need to include the polarizer in the OLED display assembly.
  • Elimination of the polarizer in an OLED display can provide various technical benefits, including an overall reduction in device thickness as well as increases in efficiency. Improvements in efficiency, in turn, can improve display brightness, extend battery life, or both.
  • New technical and material challenges may arise upon eliminating the polarizer from the display.
  • One of these challenges includes mechanical read-through of the components from the back of the display, such as the flexible printed circuit, the fingerprint sensor and texture from the cover panel. Where significant, these topological features can be visible to the viewer and are thus undesirable.
  • an adhesive and particularly an OCA, which is sufficiently stiff to resist deformation and prevent mechanical read-through of these backside components.
  • This adhesive must also be able to protect the display from a high impact event. Impact performance can be characterized by dropping a steel ball onto the display under precisely controlled conditions and checking for damage or loss of functionality.
  • an adhesive that provides good impact performance will also have a relatively low coefficient of restitution (COR).
  • COR is a fundamental property of kinetic energy absorption for a given material and can be correlated to ball drop performance.
  • adhesives that achieve the beneficial properties of both deformation resistance to prevent mechanical read-through of components from the backside of a polarizer-less display and a low COR for impact damping performance.
  • an adhesive comprises: a crosslinked network of polyvinyl acetal and acrylic copolymer obtained by reacting a functionalized polyvinyl acetal and acrylic monomers, the functionalized polyvinyl acetal comprised of a polyvinyl acetal backbone with pendent acrylate groups that are reactive with the acrylic monomers, wherein the functionalized polyvinyl acetal is present in a weight fraction of from 1 percent to 20 percent of the overall weight of the adhesive, and further wherein the acrylic copolymer is present in a weight fraction of from 60 percent to 99 percent of the overall weight of the adhesive.
  • a tape adhesive that comprises a layer of the adhesive.
  • a method of making an adhesive comprising: functionalizing polyvinyl acetal by reacting polyvinyl acetal with isocyanatoethyl (meth)acrylate and/or allyl isocyanate; and polymerizing acrylic monomers in the presence of the functionalized polyvinyl acetal to form a crosslinked network of polyvinyl acetal and acrylic copolymer.
  • FIGS. 1-3 are elevational side views of tape adhesives according to various exemplary embodiments.
  • alkyl refers to a monovalent group that is a radical of an alkane and includes straightchain, branched, cyclic, and bicyclic alkyl groups, and combinations thereof, including both unsubstituted and substituted alkyl groups. Unless otherwise indicated, the alkyl groups typically contain from 1 to 30 carbon atoms. In some embodiments, the alkyl groups contain 1 to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms. Cyclic groups can be monocyclic or polycyclic and typically have from 3 to 10 ring carbon atoms.
  • alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, isobutyl, t-butyl, isopropyl, n- octyl, n-heptyl, ethylhexyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and norbomyl.
  • curable refers to the joining of polymer chains together by covalent chemical bonds, usually via crosslinking molecules or groups, to form a network polymer. Therefore, in this disclosure the terms “cured” and “crosslinked” may be used interchangeably.
  • a cured or crosslinked polymer is generally characterized by insolubility but may be swellable in the presence of an appropriate solvent.
  • curable refers to a composition that can be cured.
  • glass transition temperature refers to a temperature at which an amorphous polymer changes from a hard/glassy state to a more pliable rubbery state, or vice versa, and can be determined by performing a Dynamic Mechanical Analysis (or “DMA”) temperature sweep at a given frequency. From this technique, the T g can be defined as the temperature at which the tan(5) peaks.
  • DMA Dynamic Mechanical Analysis
  • oligomer refers to a molecule that comprises at least two repeat units and that has a molecular weight less than its entanglement molecular weight; such a molecule, unlike a polymer, exhibits a significant change in properties upon the removal or addition of a single repeat unit.
  • the terms “preferred” and “preferably” refer to embodiments described herein that can afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.
  • the provided adhesives are generally based on a crosslinked network of polyvinyl acetal and acrylic copolymer obtained by reacting a functionalized polyvinyl acetal and an acrylic monomer.
  • the functionalized polyvinyl acetal can be reacted with a mixture of two or more different acrylic monomers.
  • Polyvinyl acetal is a useful class of polymers derived from the condensation reaction between polyvinyl alcohol and an aldehyde, typically formaldehyde.
  • the resulting material exhibits excellent chemical resistance, good mechanical properties, and exceptional thermal stability, making it applicable for different technical purposes.
  • Polyvinyl acetal is known for use in production of various engineering plastics. Its excellent thermal stability allows it to withstand high temperatures without significant degradation, making it suitable for applications where heat resistance is essential. Additionally, it exhibits good mechanical strength and dimensional stability, making it valuable in the production of components and parts for various industries, including automotive, electrical, and consumer goods.
  • the polyvinyl acetal can be prepared by saponifying polyvinyl acetate to prepare polyvinyl alcohol and then acetalizing the polyvinyl alcohol with an aldehyde in the presence of a catalyst.
  • the degree of saponification of the polyvinyl alcohol is not particularly limited, and is commonly within a range of 70 to 99.9 mol%.
  • the degree of saponification is preferably 70 to 99.9 mol%, more preferably 80 to 99.8 mol%.
  • the average degree of polymerization of the polyvinyl alcohol is also not particularly limited.
  • the polyvinyl alcohol used has a high average degree of polymerization for improved strength and toughness.
  • the lower limit of the average degree of polymerization of the polyvinyl alcohol is preferably 200 repeat units and the upper limit thereof is preferably 4,000 repeat units. With the average degree of polymerization of the polyvinyl alcohol falling within this range, the reaction upon acetalization of the polyvinyl alcohol is facilitated and the resulting polyvinyl acetal can exhibit high mechanical strength.
  • the lower limit of the average degree of polymerization of the polyvinyl alcohol is more preferably 300 repeat units and the upper limit thereof is more preferably 3,000 repeat units. The lower limit is more preferably 400 repeat units with the upper limit being preferably 2,000 repeat units.
  • the average degree of polymerization of the polyvinyl alcohol as used herein refers to a viscosity average degree of polymerization obtained based on JIS K6726: 1994.
  • the average degree of polymerization of the polyvinyl alcohol refers to an apparent viscosity average degree of polymerization of the whole polyvinyl alcohol resin mixture.
  • a solution containing the polyvinyl alcohol may be used.
  • An exemplary solvent used for the solution containing the polyvinyl alcohol is water.
  • the aldehyde is not particularly limited. Commonly, a Cl -CIO aldehyde is favorably used.
  • the Cl -CIO aldehyde is not particularly limited, and may be either a linear aldehyde or a branched aldehyde.
  • Examples thereof can include n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, 2- ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, formaldehyde, acetaldehyde, and benzaldehyde.
  • Aldehydes may be used alone or in combination of two or more thereof. Preferred among these are n-butyraldehyde, n-hexylaldehyde, and n- valeraldehyde, and more preferred is n-butyraldehyde.
  • the polyvinyl acetal is comprised of polyvinyl butyral (where the aldehyde is n-butyraldehyde, the polyvinyl acetal is referred to as polyvinyl butyral).
  • polyvinyl butyral allows appropriate adhesion force to glass, leading to better light resistance and weather resistance.
  • Two or more types of polyvinyl acetals may be optionally used in combination.
  • the polyvinyl acetal can be functionalized by reacting the polyvinyl acetal with isocyanatoethyl (meth)acrylate or allyl isocyanate in the presence of a suitable catalyst and an acrylic monomer.
  • This reaction provides a polyvinyl acetal backbone with pendent (meth)acrylate or allyl groups.
  • pendent functional groups are copolymerizable with any number of other acrylic monomers.
  • the isocyanatoethyl (meth)acrylate or allyl isocyanate can be present in any wt% based on the total weight of the polyvinyl acetal as appropriate to create the desired degree of functionality.
  • the isocyanatoethyl (meth)acrylate or allyl isocyanate can be present in an amount of from 0. 1 percent to 15 percent, from 0.3 percent to 13 percent, from 0.5 percent to 10 percent, or in some embodiments, less than, equal to, or greater than 0.1 percent, 0.3, 0.5, 1, 3, 6, 10, 13, or 15 percent by weight, relative to that of the polyvinyl acetal. If the degree of reactive functionalization of the polyvinyl acetal is too great, the adhesive may become highly crosslinked leading to a loss of adhesion performance. Contrarily, adhesive compositions in which the polyvinyl acetal is too low may decrease compatibility between the acrylic and PVA polymers which may create unwanted haze.
  • Additional hydroxyl reactive compounds that also contain co-polymerizable or crosslinkable functional groups may be used. Pendent crosslinkable functionality of a sufficient degree can enable the functionalized polyvinyl acetal to function as a crosslinking agent to form a crosslinked network even when reacted with acrylic monomers that are monofunctional.
  • the polyvinyl acetal can then be reacted with one or more acrylic monomers to form a crosslinked network comprised of the functionalized polyvinyl acetal and acrylic copolymer.
  • the acrylic copolymer is generally a random copolymer, but suitable copolymers can also include acrylic block copolymers and tapered block copolymers.
  • Useful acrylic monomers include both alkyl and polar monomers. Such polar monomers are inclusive of acid-functional monomers, hydroxy-functional monomers, nitrogen-containing monomers, and combinations thereof. Hydroxy-functional monomers include, for example,. 2-hydroxyethyl (meth)acrylate, and 2-hydroxy-propyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate.
  • polar monomers can help compatibilize the polyvinyl acetal (e .g . butyral) polymer with high glass transition temperature (high-T g ) and low glass transition temperature (low-T g ) alkyl (meth)acrylate monomers to produce an adhesive with relatively lower haze.
  • these polar monomers can have a glass transition temperature (T g ) greater than 0°C, while the T g can be less than that of the high-T g monofunctional alkyl (meth)acrylate monomer.
  • the adhesive is derived from precursors comprising from 40 wt% to 90 wt% of alkyl (meth)acrylate monomers having a homopolymer T g of less than 0°C.
  • the adhesive preferably displays at least one glass transition temperature (T g ) less than 10°C.
  • Acid-functional monomers include, but are not limited to, those selected from ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, ethylenically unsaturated phosphonic acids, and mixtures thereof.
  • examples of such compounds include those selected from acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, oleic acid, P-carboxyethyl (meth)acrylate, 2-sulfoethyl methacrylate, styrene sulfonic acid, 2- acrylamido-2 -methylpropanesulfonic acid, vinylphosphonic acid, and mixtures thereof.
  • the (meth)acrylate copolymer is substantially free of polymerized acid-functional monomers.
  • the term “substantially free” means that the (meth)acrylate polymer contains less than 1 weight percent, less than 0.5 weight percent, less than 0.2 weight percent, or less than 0.1 weight percent of these monomers.
  • the crosslinkable composition may be substantially free of acid-functional monomers in order to eliminate indium tin oxide (“ITO”) and metal trace corrosion that otherwise could damage touch sensors and their integrating circuits or connectors.
  • ITO indium tin oxide
  • Nitrogen-containing monomers include, but are not limited to, N-vinylpyrrolidone; N- vinylcaprolactam; acrylamide; mono- or di-N-alkyl substituted acrylamide such as N, N- dimethylacrylamide; t-butyl acrylamide; dimethylaminoethyl acrylamide; acryloylmorpholine, and N-octyl acrylamide.
  • the crosslinked network of polyvinyl acetal and acrylic copolymer comprises from 0 percent to 20 percent, 0.5 percent to 10 percent, from 1 percent to 5 percent, or in some embodiments equal to or greater than 0 percent, or less than, equal to, or greater than 0.1, 0.5, 1, 2, 3, 4, 5, 7, 10, 12, 15, or 20 percent polymerized units of nitrogen-containing monomers by weight, relative to the overall weight of the adhesive composition.
  • polar monomers include alkoxy-functional (meth)acrylate monomers.
  • alkoxy-functional (meth)acrylate monomers include alkoxy-functional (meth)acrylate monomers.
  • the crosslinked network of polyvinyl acetal and acrylic copolymer includes from 0.5 percent to 45 percent, from 1 percent to 30 percent, or in some embodiments, less than, equal to, or greater than 0.5, 1, 2, 3, 4, 5, 7, 10, 12, 15, 17, 20, 25, 30, 35, 40 and 45 percent polymerized units of alkoxy-functional (meth)acrylate monomers by weight, relative to the overall weight of the crosslinked network.
  • the crosslinked network comprises polymerized units of less than 20 percent, less than 15 percent, or less than 10 percent of alkoxyfunctional (meth)acrylate monomers by weight or is free of polymerized units of alkoxy-functional (meth)acrylate monomers.
  • butyral polymer displays a lower crosslinkable functionality, then higher amounts of polar monomer may be necessary to provide a compatibilized mixture. Conversely, when the polyvinyl acetal possesses a relatively higher degree of functionality, then less polar monomer may be needed for compatibilization.
  • the crosslinked network includes polymerized units of one or more polar monomers of 2-hydroxyethyl (meth)acrylate or N,N-dimethyl acrylamide.
  • the adhesive can include polymerized units of one or more of these monomers in an amount of from 5 percent to 55 percent, from 7 percent to 45 percent, from 10 percent to 35 percent, or in some embodiments, less than, equal to, or greater than 5 percent, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 percent relative to the overall weight of the adhesive composition.
  • the crosslinked network includes polymerized units of one or more low-Tg (meth)acrylate monomers, i.e., a (meth)acrylate monomer that, when reacted to form a homopolymer, has a T g no greater than 0°C.
  • the low-T g monomer has a homopolymer T g of from -80°C to -5°C, from -70°C to -10°C, or in some embodiments, less than, equal to, or greater than -80°C, -70, -60, -50, -40, -30, -20, -10, or 5°C.
  • the low-Tg monomer can, for example, have the formula:
  • R 1 is H or methyl and R 8 is an alkyl with 1 to 22 carbons or a heteroalkyl with 2 to 20 carbons and 1 to 6 heteroatoms selected from oxygen or sulfur.
  • the alkyl or heteroalkyl group can be linear, branched, cyclic, or a combination thereof.
  • low-T g monomers examples include but are not limited to ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-pentyl acrylate, isoamyl acrylate, n- hexyl acrylate, 2-methylbutyl acrylate, 2-ethylhexyl acrylate, 4-methyl-2-pentyl acrylate, n-octyl acrylate, 2-octyl acrylate, isooctyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate, isotridecyl acrylate, octadecyl acrylate, and dodecyl acrylate.
  • the crosslinked network comprises polymerized units of at least one low-T g monomer(s) having an alkyl group with 6 to 24 carbon atoms.
  • the low-T g monomer has an alkyl group with 7 or 8 carbon atoms.
  • Exemplary monomers include, but are not limited to, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-octyl (meth)acrylate, 2- octyl (meth)acrylate, isodecyl (meth)acrylate, and lauryl (meth)acrylate.
  • the monomer is an ester of (meth)acrylic acid with an alcohol derived from a renewable source, such as 2-octyl (meth)acrylate.
  • suitable monomers include branched long chain acrylates such as those described in U.S. Patent No. 8,137,807, hereby incorporated by reference.
  • Additional suitable alkyl monomers include secondary alkyl acrylates such as those described in U.S. Patent No. 9,102,774, hereby incorporated by reference.
  • the adhesive can comprise at least 20, 30, 40, 50, 60, 70 or 80 percent by weight of polymerized units of monofunctional alkyl (meth)acrylate low-T g monomer (i.e., having a homopolymer T g of less than 0°C), based on the total weight of the adhesive.
  • the adhesive typically comprises no greater than 60, 70, 80 or 90 percent by weight of polymerized units of monofunctional alkyl (meth)acrylate monomer having a T g of less than 0°C, based on the total weight of the adhesive composition.
  • the T g of the homopolymer of various monomers is known and is reported in various handbooks.
  • the T g of some illustrative monomers is also reported in International Patent Application No. WO 2016/094277 (Janoski et al.).
  • the polyvinyl acetal can be present in an amount of from 85.0 wt% to 99.9 wt%, from 87.0 wt% to 99.7 wt%, from 90.0 wt% to 99.5 wt%, or in some embodiments less than, equal to, or greater than 85.0 wt%, 87.0, 90.0, 91.0, 92.0, 94.0, 96.0, 97.0, 98.0, 99.0, 99.5, 99.7 or 99.9 wt% relative to the overall weight of the functionalized polyvinyl acetal.
  • the functionalized polyvinyl acetal can represent a weight fraction of from 1 percent to 20 percent, from 2 percent to 15 percent, from 3 percent to 12 percent, or in some embodiments, less than, equal to, or greater than 1 percent, 2, 3, 4, 5, 8, 10, 12, 15 or 20 percent.
  • the acrylic copolymer can be present in a weight fraction of from 60 percent to 99 percent, from 70 percent to 98 percent, from 80 percent to 97 percent, or in some embodiments, less than, equal to, or greaterthan 60 percent, 70, 80, 85, 90, 93, 95, 97, 98, or 99 percent, relative to the overall weight of the adhesive.
  • the functionalized polyvinyl acetal and acrylic monomers can be combined with any number of additional additives, including catalysts, crosslinkers, ultraviolet light absorbers, dyes and pigments.
  • two or more T g values can be detectable for respective phases or domains within the adhesive.
  • the lowest T g will typically be associated with the acrylic copolymer phase of the crosslinked network.
  • it is generally preferred to maintain a low T g in the acrylate phase typically at least -60°C and up to 10°C, up to 0°C, or up to -10°C.
  • the adhesive should have a relatively high storage modulus at 25°C for an adhesive material, which can be measured by performing a dynamic mechanical analysis (DMA) using a temperature sweep at a frequency of 1 Hz.
  • DMA dynamic mechanical analysis
  • a storage modulus greaterthan 200,000 pascals, greaterthan 400,000 pascals, greaterthan 600,000 pascals, greaterthan 800,000 pascals, or even greater than 1 megapascal at 25°C can be preferred.
  • additional heat from a heat-assisted lamination and/or autoclave process for instance, at temperatures exceeding 60°C, or even exceeding 65°C can be helpful.
  • the adhesive is considered optically transparent with low haze (less than 4%, 3%, or 2%).
  • FIGS. 1-3 show exemplary transfer adhesives incorporating the provided adhesive compositions.
  • a tape adhesive according to one exemplary embodiment is illustrated in FIG. 1 and hereafter denoted by the numeral 100.
  • the tape adhesive 100 is comprised of a primary layer 102 composed of a polyvinyl acetal-based adhesive composition as described herein and having opposed first and second major surfaces 104, 106.
  • the primary layer 102 provides mechanical resistance to deformation while preserving high impact performance.
  • FIG. 2 shows a tape adhesive assembly 150 representing a bonded assembly.
  • the assembly 150 includes the tape adhesive 100 comprised of the primary layer 102, whose characteristics are described above.
  • the assembly 150 further includes a pair of release substrates 152, 154 disposed on each of the respective opposing major surfaces 104, 106 of the primary layer 102.
  • the primary layer 102 directly contacts both of the release substrates 152, 154 thereby acting to adhesively couple these release substrates 152, 154 to each other.
  • Useful release substrates are known in the art, and can include for example liners constructed of silicone-coated polyester or silicone-coated paper.
  • FIG. 3 shows a tape adhesive 200 according to yet another embodiment, bearing similarities to the construction of tape adhesive 100 except a pair of secondary layers 252, 254 are interposed between a primary layer 202 and the release substrates 252, 254, as shown.
  • the secondary layers 210, 210’ can function as skin layers made from acrylic OCAs that contain a lower weight fraction of polyvinyl acetal relative to that of the primary layer 202.
  • one or both of the secondary layers 210, 210’ contain a zero or essentially zero amount of polyvinyl acetal.
  • a potential advantage of this embodiment is the retention of high room temperature tack, which can be beneficial for certain applications.
  • Another potential advantage is the possibility of introducing greater flowability at the surface, which can improve adhesive wetting of the substrate or topological features such as an inkstep, where present. Further advantages can include the possibility of isolating certain functionalities, such as UV blocking, to a particular layer.
  • Adhesives and adhesive layers described herein can be made using a batch or continuous process.
  • the adhesive includes a plurality of contiguous layers which cannot be delaminated.
  • Each of the layers includes a photopolymerized matrix of polymeric chains, and at least one of the outer layers is photopolymerized to a pressure-sensitive adhesive state. Details of this process are described, for example, in European Patent No. EP 0 305 161 (Zimmerman, et al.).
  • Uncured compositions can be coated on an unstructured or structured release liner using conventional coating techniques.
  • these compositions can be applied by methods such as roller coating, flow coating, dip coating, spin coating, spray coating knife coating, and die coating. Coating thicknesses may vary.
  • the composition may be of any desirable concentration for subsequent coating based on the desired viscosity.
  • the coated release liner may be brought in contact with a second backing prior to curing.
  • curing takes place by activating a photoinitiator.
  • photoinitiators include benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether; substituted acetophenones such as 2, 2-dimethoxy-2 -phenylacetophenone photoinitiator, available the trade name IRGACURE 651, available from Merck KGaA, Darmstadt, Germany or ESACURE KB-1 photoinitiator, available from LEHVOSS Group, Hamburg, Germany, and dimethylhydroxyacetophenone; substituted a-ketols such as 2-methyl-2-hydroxy propiophenone; aromatic sulfonyl chlorides such as 2-naphthalene-sulfonyl chloride; photoactive oximes such as 1- phenyl-l,2-propanedione-2-(O-ethoxy-carbonyl)oxime; mono- or bis-acrylphosphine oxides such as IRGANOX 819 from
  • Preferred photoinitiators are photoactive compounds that undergo a Norrish I cleavage to generate free radicals that can initiate by addition to the acrylic double bonds.
  • the photoinitiator can be added to the mixture to be coated after the polymer (e.g. syrup) has been formed, i.e., photoinitiator can be added.
  • Such polymerizable photoinitiators are described, for example, in U.S. Patent Nos. 5,902,836 and 5,506,279 (Gaddam et al.).
  • Photoinitiators can be present in an amount of from 0.1 to 5 percent by weight, based on the overall weight of the uncured composition. Relatively thick coatings can be achieved when the extinction coefficient of the photoinitiator is low.
  • Polymerization can be conducted in the absence of non-polymerizable organic solvents such as ethyl acetate, toluene and tetrahydrofuran, which are non-reactive with the functional groups of the monomers. Solvents influence the rate of incorporation of different monomers in the polymer chain and generally lead to lower molecular weights as the polymers gel or precipitate from solution. It can thus be beneficial for the crosslinked network composition can be free of non-polymerizable organic solvent.
  • solvents such as ethyl acetate, toluene and tetrahydrofuran
  • the uncured composition with the photoinitiator can be cured by irradiation with actinic radiation.
  • Actinic radiation can be, for instance, ultraviolet (UV) radiation having a UVA maximum at a wavelength range of 280 to 425 nanometers to polymerize the monomer components.
  • UV light sources are not particularly restricted.
  • Low light intensity sources, such as blacklights generally provide intensities ranging from 0. 1 or 0.5 mW/cm 2 (milliwatts per square centimeter) to 10 mW/cm 2 (as measured in accordance with procedures approved by the United States National Institute of Standards and Technology as, for example, with a UVIMAP UM 365 L-S radiometer manufactured by Electronic Instrumentation & Technology, Inc., in Sterling, VA).
  • High light intensity sources generally provide intensities greater than 10, 15, or 20 mW/cm 2 and up to 450 mW/cm 2 . High intensity light sources provide intensities up to 500, 600, 700, 800, 900 or 1000 mW/cm 2 .
  • UV light used to polymerize the monomer components can be provided by various light sources such as light emitting diodes (LEDs), blacklights, medium pressure mercury lamps, or any combination thereof.
  • UV exposure time for polymerization and curing generally varies depending on the intensity of the light source(s) used. For example, complete curing with a low intensity light course can be accomplished with an exposure time ranging from about 30 to 300 seconds; whereas complete curing with a high intensity light source can be accomplished with shorter exposure time ranging from about 5 to 20 seconds. Partial curing with a high intensity light source can typically be accomplished with exposure times of from 2 to 10 seconds, or from 2 to 5 seconds.
  • the uncured composition optionally contains one or more additives.
  • additives can include antioxidants, plasticizers, tackifiers, stabilizers, ultraviolet absorbers, lubricants, processing aids, antistatic agents, colorants, impact resistance aids, fillers, matting agents, flame retardants (e.g., zinc borate) and the like.
  • fillers or pigments include inorganic oxide materials such as zinc oxide, titanium dioxide, silica, carbon black, calcium carbonate, antimony trioxide, metal powders, mica, graphite, talc, ceramic microspheres, glass or polymeric beads or bubbles, fibers, starch and the like.
  • additives can represent from 0.1 percent to 15 percent, from 0.3 percent to 10 percent, from 0.5 percent to 5 percent, or in some embodiments less than, equal to, or greater than 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1, 2, 5, 7, or 10, 11, 12, 13, 14, or 15 percent of the weight of the uncured adhesive composition.
  • Table 1 lists components used in preparing the Examples and Comparatives described herein.
  • examples were coated between release-coated carrier liners (RF02N and RF22N, SKC Haas, Korea) and were cut to approximately 5 cm width by 10 cm length and their thickness was measured.
  • Each example was prepared for testing of the COR by removing a carrier layer and laminating the adhesive to a piece of 51 -micrometer (2-mil) polyethylene terephthalate (PET) and then autoclaving at 65 °C with 5 kg force for 5 minutes. The purpose of this step was to prevent adhesion to dynamic testing components of the test system.
  • the adhesive-PET construction was dwelled overnight in a controlled environment held at 23 ⁇ 2°C and 50 ⁇ 10% relative humidity, then laminated directly to the mounting plate of the test system. Accordingly, reported COR values were not a direct measurement of the adhesive in isolation, but rather a comparative measurement of an adhesive-PET laminate. Three replicates were tested and their average was reported.
  • a test coupon is prepared by removing a carrier liner and laminating the adhesive to 51 -micrometer (2-mil) PET, then to 0.7 millimeter LCD glass. Samples are allowed to dwell overnight in a controlled environment held at 23 ⁇ 2°C and 50 ⁇ 10% relative humidity prior to testing. The sample is then tested using a TA XT Plus Texture Analyzer with a 7 -mm rounded probe. The test coupon is placed on the base stage of the instrument with the PET side up, and the probe is applied to the PET surface of the test coupon with a force of 50 g for 60 seconds. The relative penetration depth in millimeters is measured as a function of time. The maximum penetration depth, referred to as the Average (Avg) Peak Positive (Pos) Distance from this test, is then recorded.
  • Avg Average
  • Pos Peak Positive
  • OCAs which resist mechanical deformation that leads to mechanical read-through of components from the backside of a polarizer-less display perform better in this test, with a lower penetration depth result. OCAs which allow more mechanical deformation will perform worse as evidenced by a higher penetration depth result. Note that for this test, performance trends with 1 h testing were found to closely match those that were observed with 60 second testing. Therefore, the faster test time was selected for reasonable timing of data gathering with multiple concepts and replicates. Twelve replicates were tested and their average was reported.
  • Haze measurements were made using a HunterLab (Reston, VA) UltrascanPro Spectrophotometer in transmission mode. One of the carrier liners was removed and the sample was laminated to a clear piece of 0.7 mm thick LCD glass (Swift Glass, Elmira Heights, New York). The remaining carrier liner was removed, and the sample was placed in the UltrascanPro Spectrophotometer to measure transmission and %Haze through the OCA/glass assembly.
  • PE1-PE3 were prepared according to the formulations listed in Table 3. Functionalized PVB (PVBO-IEM, PVB0.6-IEM, PVB6-IEM) and Acrylate monomers were charged in a vessel to provide a 2000 g mixture at the wt% ratios that are shown. Values of wt% are relative to the overall composition of the preparatory example. HDDA, 1819, and BL IB were then added. The vessel was sealed and mixed on ajar roller for 16 hours.
  • PE4-PE6 were prepared according to the formulations listed in Table 4. Functionalized PVB (PVB0.6-IEM), if present, and acrylate monomers were charged in a vessel to provide a 2000 g mixture at the wt% ratios that are shown. Note that PE5 and PE6 do not contain PVB. DI 173 was then added to the vessel. Values of wt% are relative to the overall composition of the preparatory example. The mixture was then irradiated with 365 nm UVLEDs with an intensity of 0.3 mW/cm 2 until the mixture (herein referred to as the pre-polymer) reached a viscosity of about 100-1500 cp as measured by a Brookfield viscometer. EB230 or HDDA, 1819, BL1B and KBM403 were then added. The vessel was sealed and mixed on ajar roller for 16 hours. Table 4.
  • Examples EX1-EX5 and Comparative CE1 were prepared according to Table 5, and consisted of single layer adhesives prepared by blending the preparatory adhesive compositions listed in Tables 2-3 to provide the overall compositions shown.
  • DMA test results including T g values and 25 °C shear storage modulus, and Impact and Deformation Resistance Test results, including average COR and average peak positive distance (50 g for 60 seconds), are also reported in Table 5.
  • Final composition wt% are relative to the overall weight of the adhesive composition unless otherwise indicated.
  • the examples were coated onto 51 -micrometer carrier release liners (RF02N/RF22N from SKC Haas) using a roll-to-roll coating method and subsequently polymerized and cured with a 3380 mJ dose of UVV light irradiation from a 405 -nm UVLED light source. All adhesive layers had a caliper (i.e., thickness) of approximately 150 micrometers.
  • Table 6 Reported in Table 6 are the overall compositions of Examples EX6-EX8 and Comparatives CE2-CE3, consisting of single layer adhesives. Table 6 also reports corresponding DMA test results (T g values and 25°C shear storage modulus), Impact and Deformation Resistance Test results, including average COR and average peak positive distance (50 g for 60 seconds), and Haze Test results. These examples were prepared by charging functionalized PVB (preparatory example PVBO-IEM, PVB0.6-IEM, or PVB6-IEM) and acrylate monomers into a vessel to provide a 100 g mixture at the wt% ratios that are shown. DI 173 was then added to the vessel. Values of wt% are relative to the overall composition of the example.
  • functionalized PVB preparatory example PVBO-IEM, PVB0.6-IEM, or PVB6-IEM
  • the mixture was then irradiated with 365nm UVLEDs with an intensity of 0.3 mW/cm 2 until the pre-polymer reached a viscosity of about 100- 1500 cp as measured by a Brookfield viscometer.
  • HDDA, 1819, BL1B, and KBM403 were then added.
  • the vessel was sealed and mixed on ajar roller for 16 hours.
  • the examples were coated onto 51 -micrometer carrier release liners (RF02N/RF22N from SKC Haas) using a roll-to-roll coating method, and subsequently polymerized and cured with 3380 mJ of UVV light from a 405-nm UVLED light source.
  • Adhesive layers had a caliper of approximately 150 micrometers.
  • Example EX9 is the overall composition of Example EX9, consisting of a single layer adhesive. Table 7 also reports corresponding 25°C shear storage modulus, Impact and Deformation Resistance Test results, including average COR and average peak positive distance (50 g for 60 seconds).
  • This example was prepared by charging functionalized PVB (preparatory example PVB9.1 -Allyl) and acrylate monomers into a vessel to provide a 100 g mixture at the wt% ratios that are shown. BL1B, OMNIPOL TP and BD1 were then added. The vessel was sealed and mixed on a jar roller for 16 hours.
  • the example was coated onto 51 -micrometer carrier release liners (RF02N/RF22N from SKC Haas) using a roll-to-roll coating method, and subsequently polymerized and cured with 2400 mJ of UVV light from a 405 -nm UVLED light source.
  • the adhesive had a caliper of approximately 150 micrometers. Table 7.
  • compositions of Examples EX10-EX22 and Comparative CE4 are reported in Table 8. These were multilayer adhesives prepared using the preparatory example compositions shown in Tables 3 and 4 with corresponding Impact and Deformation Resistance Test results also reported in Table 8. The adhesives were coated onto 51um carrier release liners (RF02N/RF22N from SKC) using a multilayer coating die according to the methods as described in European Patent No. EP 0 305 161 (Zimmerman, et al.), and subsequently polymerized and cured with 2480 mJ of UVV light from a 405 -nm UVLED light source.
  • Combined adhesive layers had a caliper of approximately 150 micrometers.
  • Layer numbers were defined as follows: “LI” is a layer disposed against the 1 st release liner; “L2” is a layer disposed between LI and L3; and “L3” is a layer disposed against the 2 nd release liner. Table 8.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Adhesives Or Adhesive Processes (AREA)

Abstract

L'invention concerne un adhésif qui comprend un réseau réticulé de poly(acétal de vinyle) et de copolymère acrylique obtenu par réaction d'un poly(acétal de vinyle) fonctionnalisé et de monomères acryliques. Le poly(acétal de vinyle) fonctionnalisé est présent dans une fraction en poids de 1 pour cent à 20 pour cent du poids total de l'adhésif et est composé d'un squelette de poly(acétal de vinyle) avec des groupes fonctionnels pendants réactifs avec les monomères acryliques. Le copolymère acrylique est présent dans une fraction en poids de 60 pour cent à 99 pour cent du poids total de l'adhésif. De manière avantageuse, l'adhésif peut fournir à la fois une résistance à la déformation pour empêcher une lecture mécanique de composants depuis la face arrière d'une unité d'affichage sans polariseur et un faible coefficient de restitution pour une performance d'amortissement des chocs.
PCT/IB2024/057508 2023-08-07 2024-08-02 Composition d'adhésif Pending WO2025032460A1 (fr)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0305161A2 (fr) 1987-08-28 1989-03-01 Minnesota Mining And Manufacturing Company Ruban adhésif, sensible à la pression, unifié
US5506279A (en) 1993-10-13 1996-04-09 Minnesota Mining And Manufacturing Company Acrylamido functional disubstituted acetyl aryl ketone photoinitiators
US5902836A (en) 1994-07-29 1999-05-11 Minnesota Mining And Manufacturing Company Acrylic syrup curable to a crosslinked viscoelastomeric material
US20070092733A1 (en) * 2005-10-26 2007-04-26 3M Innovative Properties Company Concurrently curable hybrid adhesive composition
US8137807B2 (en) 2010-03-26 2012-03-20 3M Innovative Properties Company Pressure-sensitive adhesives derived from 2-alkyl alkanols
US9102774B2 (en) 2010-12-21 2015-08-11 3M Innovative Properties Company Polymers derived from secondary alkyl (meth)acrylates
WO2016094277A1 (fr) 2014-12-08 2016-06-16 3M Innovative Properties Company Films acryliques de poly(acétal de vinyle) et composition
US20180304576A1 (en) * 2015-12-22 2018-10-25 3M Innovative Properties Company Acrylic films comprising a structured layer

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0305161A2 (fr) 1987-08-28 1989-03-01 Minnesota Mining And Manufacturing Company Ruban adhésif, sensible à la pression, unifié
US5506279A (en) 1993-10-13 1996-04-09 Minnesota Mining And Manufacturing Company Acrylamido functional disubstituted acetyl aryl ketone photoinitiators
US5902836A (en) 1994-07-29 1999-05-11 Minnesota Mining And Manufacturing Company Acrylic syrup curable to a crosslinked viscoelastomeric material
US20070092733A1 (en) * 2005-10-26 2007-04-26 3M Innovative Properties Company Concurrently curable hybrid adhesive composition
US8137807B2 (en) 2010-03-26 2012-03-20 3M Innovative Properties Company Pressure-sensitive adhesives derived from 2-alkyl alkanols
US9102774B2 (en) 2010-12-21 2015-08-11 3M Innovative Properties Company Polymers derived from secondary alkyl (meth)acrylates
WO2016094277A1 (fr) 2014-12-08 2016-06-16 3M Innovative Properties Company Films acryliques de poly(acétal de vinyle) et composition
US20180304576A1 (en) * 2015-12-22 2018-10-25 3M Innovative Properties Company Acrylic films comprising a structured layer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
SK6RSKI ET AL.: "Experimental Determination of the Coefficient of Restitution for Selected Modern Hybrid Composites", MATERIALS, vol. 14, no. 19, 2021, pages 5638

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