Crosslinkable composition

Abstract

A crosslinkable composition comprising a (meth)acrylate polymer comprising an alkyl (meth)acrylate monomer, an acylphosphine oxide photoinitiator, and a crosslinking monomer comprising at least two end groups selected from the group consisting of allyl, methallyl, or combinations thereof. A method for preparing such a crosslinkable composition and an article comprising such a crosslinkable composition are disclosed.

Description

[Background technology]

[0001] In electronic devices, such as electronic display devices, pressure-sensitive adhesives ("PSA") are commonly used to bond a cover glass or lens to a display module underlying the electronic device, to bond touch sensors to the cover glass and display, or to bond lower components of the display to a housing. The pressure-sensitive adhesives used in these electronic devices may be optically clear adhesives ("OCA").

[0002] The presence of the OCA can improve the performance of the display device, for example, by increasing the brightness and contrast while also providing structural support to the assembly. In these applications (commonly referred to as electronics bonding or e-bonding), both the PSA and the OCA should have sufficiently high adhesive strength to adequately maintain good adhesion to the components not only when the electronic device is operating under normal conditions, but also when they are exposed to traumatic forces or extreme environmental conditions. Summary of the Invention

[0003] Disclosed herein is a multifunctional allylic crosslinker that can be used in UV-absorbing acrylic-based optically clear adhesives ("OCA"), such as those commonly used in electronic display devices. The disclosed crosslinker, when used in acrylic polymer systems, i.e., crosslinkable compositions, can desirably provide an efficient route that allows both the photopolymerization process to generate OCA and the latent curing mechanism to be utilized after OCA is incorporated into electronic display devices. This type of two-step curing process advantageously allows for the bifurcation of OCA material properties during different stages of electronic device integration and lifespan.

[0004] In one aspect, a crosslinkable composition is provided that includes a (meth)acrylate polymer that includes an alkyl (meth)acrylate monomer, an acylphosphine oxide photoinitiator, and a crosslinking monomer that includes at least two end groups selected from the group consisting of allyl, methallyl, or combinations thereof.

[0005] In another aspect, adhesives comprising the disclosed crosslinkable compositions are provided, as well as articles incorporating such adhesives.

[0006] As used herein, The term "and / or", such as in the expression "A and / or B", means A only, B only, or both A and B.

[0007] The term "crosslinkable composition" refers to a reaction mixture that can be crosslinked. In addition to the polymerizable components, the crosslinkable composition may include any other materials that can be included in the reaction mixture, such as, for example, free radical initiators, chain transfer agents, antioxidants, solvents, etc.

[0008] The term "hardenable" means that a solid material can be transformed into a more crosslinked solid by means of stimulus-induced crosslinking.

[0009] The term "gel fraction" as used herein refers to the mass fraction of network material resulting from the network-forming polymerization and / or crosslinking process.

[0010] The term "(meth)acryloyl" refers to a group of formula CH2=CR-(CO)-, where R is hydrogen (for an acryloyl group) or methyl (for a methacryloyl group).

[0011] The term "(meth)acrylate" refers to methacrylate and / or acrylate. Similarly, the term "(meth)acrylic acid" refers to methacrylic acid and / or acrylic acid, and the term "(meth)acrylamide" refers to methacrylamide and / or acrylamide. Similarly, the term "(meth)allyl group" refers to methallyl group and / or allyl group.

[0012] The term "polymer" means homopolymers, copolymers, terpolymers, and the like.

[0013] The term "polymerizable component" refers to a compound that can undergo polymerization (i.e., the compound has a polymerizable group). The polymerizable component typically has an ethylenically unsaturated group, such as a (meth)acryloyl-containing group or a vinyl group, that is the polymerizable group. A compound that has a polymerizable group can be referred to as a "monomer."

[0014] The term "pressure sensitive adhesive" or "PSA" is used in its conventional manner by the Pressure-Sensitive Tape Council, which is known to state that a pressure sensitive adhesive has properties including: (1) strong and permanent adhesion; (2) adhesion with no more than finger pressure; (3) sufficient holding ability to the substrate; and (4) sufficient cohesion to remove cleanly from the substrate. Materials found to perform well as PSAs include polymers designed and formulated to exhibit the necessary viscoelastic properties that provide the desired balance of tack, peel adhesion, and shear retention. PSAs are typically characterized as being tacky at room temperature (e.g., 20°C). Central to all PSAs is the desired balance of adhesive and cohesive strength, which is often achieved by optimizing the physical properties of the elastomer, such as glass transition temperature and modulus of elasticity. For example, the glass transition temperature (T g ) or if the modulus is too high and the Dahlquist rating scale for adhesion (3×10 at room temperature) 6 dyne / cm 2 and vibration frequency of 1 Hz), the material is no longer tacky and is not useful as a PSA material by itself.

[0015] The monomer, "T gThe term "glass transition temperature," which may be written interchangeably as "temperature", refers to the glass transition temperature of a homopolymer formed from a monomer. The glass transition temperature of a polymeric material is typically measured by Dynamic Mechanical Analysis ("DMA") at the maximum value of tan delta (δ).

[0016] The term "vinyl" refers to a polymerizable entity that has the group CH2=CH- but is not part of a (meth)acryloyl group.

[0017] As used herein, the term "comprising" and variations thereof do not have a limiting meaning when these terms appear in the specification and claims. Such terms are understood to imply the inclusion of a described step or element, or group of steps or elements, but not the exclusion of any other step or element, or group of steps or elements. "Consisting of" means to include and be limited to whatever follows the phrase "consisting of". Thus, the phrase "consisting of" indicates that the recited elements are necessary or mandatory, and that no other elements may be present. "Consisting essentially of" means to include any elements recited after the phrase, and is limited to other elements that do not interfere with or contribute to the action or function specified in this disclosure for those recited elements. Thus, the phrase "consisting essentially of" indicates that the recited elements are necessary or mandatory, but that other elements are optionally included and may or may not be present depending on whether they materially affect the action or function of the recited elements. Any element or combination of elements recited herein with open-ended language (e.g., "comprising" and its derivatives) shall be deemed to be further recited with closed-ended language (e.g., "consisting of" and its derivatives), as well as partially closed-ended language (e.g., "consisting essentially of" and its derivatives).

[0018] The words "preferred" and "preferably" refer to embodiments of the present disclosure that may provide certain benefits, under particular circumstances. However, other claims may also be preferred, under the same or other circumstances. Moreover, the recitation of one or more preferred claims does not imply that other claims are not useful, and is not intended to exclude other claims from the scope of the present disclosure.

[0019] In this application, terms such as "a," "an," and "the" are not intended to refer to only one entity, but include general categories of which a specific example may be used for illustration. The terms "a," "an," and "the" are used interchangeably with the term "at least one." The phrases "at least one of" and "including at least one of" following a list refer to any one of the items in the list, and any combination of two or more items in the list.

[0020] As used herein, the term "or" is generally utilized in its ordinary sense including "and / or" unless the content clearly dictates otherwise.

[0021] The term "and / or" means one or all of the listed elements or a combination of any two or more of the listed elements.

[0022] Additionally, all numbers herein are deemed to be modified by the term "about," and in certain embodiments, preferably, by the term "precisely." As used herein, in the context of a measured quantity, the term "about" refers to the variation in the measured quantity as would be expected by one of ordinary skill in the art making the measurement and exercising a level of care commensurate with the purpose of the measurement and the precision of the measuring device used. As used herein, a "up to" number (e.g., up to 50) is inclusive of that number (e.g., 50).

[0023] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range, as well as the endpoints thereof (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0024] The term "room temperature" refers to a temperature between 20°C and 25°C, or between 22°C and 25°C.

[0025] The terms "in the range" or "within a range" (and similar descriptions) include the endpoints of the stated range.

[0026] Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found in the group. It is anticipated that one or more members of a group may be included in or deleted from a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is deemed herein to include the modified group and thus implements the full recitation of all Markush groups used in the appended claims.

[0027] When a group occurs more than once in a formula described herein, each group is "independently selected," whether or not specifically stated. For example, when there is more than one R group in a formula, each R group is independently selected.

[0028] References throughout this specification to "one embodiment," "an embodiment," "certain embodiment," or "some embodiments" mean that the particular features, configurations, compositions, or characteristics described with respect to an embodiment are included in at least one embodiment of the present invention. Thus, the appearances of such phrases in various places throughout this specification are not necessarily referring to the same embodiment of the present invention. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

[0029] The above summary of the disclosure is not intended to describe each disclosed embodiment or every implementation of the disclosure. The following description more particularly illustrates exemplary embodiments. At several points throughout the disclosure, guidance is provided through lists of examples. These examples can be used in various combinations. In each instance, the recited items serve only as a representative group and should not be construed as an exclusive list. Thus, the scope of the disclosure should not be limited to the specific exemplary structures described herein, but extends to at least the structures described by the language of the claims, and equivalents of these structures. Any of the elements expressly recited herein as alternatives can be expressly included or excluded from the claims in any combination as desired. Although various theories and possible mechanisms may be discussed herein, in no event should such discussion be construed as limiting the claimed subject matter.

[0030] The features and advantages of the present disclosure will be further understood by considering the detailed description and the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Some advantages of using optically clear adhesives ("OCA") in optoelectronic devices may include, among others, improved light extraction efficiency between various optical components of a display, and reduced light scattering by mitigating refractive index mismatch at interfaces. As the topographical features of optoelectronic device structures evolve into more complex geometries, there is an increasing demand for the development of highly conformable OCAs that can accommodate these complex geometries and mitigate optical defects. However, once the OCA film is integrated into a display, the OCA material should also be mechanically robust during the device's lifetime to provide high mechanical stability and performance. One way to balance these potentially conflicting manufacturing requirements is through the use of a two-step UV curing process. Such a two-step process may allow for UV-process generation of OCA with significant viscous properties for compliance during the lamination step, followed by UV-driven increase in the crosslink density of the OCA after integration with the device.

[0032] In some applications, it may also be desirable for the OCA material to utilize a UV absorbing additive to protect any UV sensitive components under the OCA layer. For example, a hydroxyphenylbenzotriazole-based UV absorber (e.g., TINUVIN 928, available from BASF, Florham Park, New Jersey), which has high absorption at wavelengths below 380 nm, can be incorporated into the OCA to block UV light from reaching the photosensitive layer adjacent to the adhesive. However, this UV absorbing function may interfere with one or both of the UV-based processes used to 1) generate the OCA and 2) post-cure the OCA after lamination. The UV absorber in the OCA may not only block UV exposure from the end user's environment, but may also block a significant portion of the UV spectrum used during the manufacture of both the adhesive and the display device. Reduced access to post-lamination curing processes may not only limit the adhesive's ability to balance compliance with robust lifetime reliability, but may also limit the adhesive and mechanical performance properties of the OCA in general. Therefore, there is a need for technology development in the OCA material to incorporate a UV blocking function while retaining access to the photopolymerization and photocuring mechanisms.

[0033] The present disclosure provides UV absorbing, post-lamination curable OCA films produced using a scheme that utilizes a combination of a fast polymerizing acrylic monomer and a slower reacting crosslinker compound. This scheme allows for greater separation between the polymerization and crosslinking functions of the adhesive without the need for multi-wavelength light emitting devices, while allowing the achievement of both functions in the presence of UV absorber additives. Advantageously, the crosslinking reaction can be carried out at a later stage of conversion using a wavelength band of light similar to that used for the acrylic polymerization reaction.

[0034] crosslinkable composition In one aspect, a crosslinkable composition is provided that includes a (meth)acrylate polymer that includes an alkyl (meth)acrylate monomer, a phosphine oxide type photoinitiator, and a crosslinking monomer that includes at least two end groups selected from the group consisting of allyl, methallyl, or a combination thereof.

[0035] The crosslinkable composition of the present disclosure may be cured, for example, by exposure to actinic radiation. The gel fraction of the crosslinkable composition may be calculated both before and after curing as described in the Examples section below. In some preferred embodiments, the gel fraction of the crosslinkable composition before curing is 0.2-0.8, 0.3-0.75, or 0.4-0.7. In some preferred embodiments, the change in gel fraction of the crosslinkable composition after curing is greater than 0.03, greater than 0.04, greater than 0.05, or greater than 0.06.

[0036] (Meth)acrylate polymer (Meth)acrylate polymers can be prepared from polymerizable building blocks that include alkyl (meth)acrylate monomers using known polymerization methods.

[0037] Alkyl (meth)acrylate monomer Any suitable alkyl (meth)acrylate, or mixture of alkyl (meth)acrylates, can be used, provided that the final (meth)acrylate polymer has a sufficiently low glass transition temperature (e.g., 20° C. or less). Some alkyl (meth)acrylate monomers have low T g It can be classified as a monomer. The low T measured from the corresponding homopolymer g Monomers are often heated to a T below 20°C, below 10°C, below 0°C, or below -10°C. g has.

[0038] Suitable for low T gAlkyl (meth)acrylate monomers include, but are not limited to, non-tertiary alkyl acrylates, and can be alkyl methacrylates having a linear alkyl group having at least 4 carbon atoms. Specific examples of alkyl (meth)acrylates include, but are not limited to, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, sec-butyl acrylate, n-pentyl acrylate, 2-methylbutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2-octyl acrylate, isooctyl acrylate, isononyl acrylate, isoamyl acrylate, n-decyl acrylate, isodecyl acrylate, n-decyl methacrylate, lauryl acrylate, isotridecyl acrylate, n-octadecyl acrylate, isostearyl acrylate, n-dodecyl methacrylate, and combinations thereof. In some embodiments, the low T g The alkyl (meth)acrylate is selected from 2-ethylhexyl acrylate, isooctyl acrylate, n-butyl acrylate, 2-methylbutyl acrylate, 2-octyl acrylate, and combinations thereof. Other suitable monomers include branched long chain acrylates such as those described in U.S. Patent No. 8,137,807 (Clapper et al.). Additional suitable alkyl monomers include secondary alkyl acrylates such as those described in U.S. Patent No. 9,102,774 (Clapper et al.).

[0039] Other alkyl (meth)acrylates that may be included in the polymerizable component are those that have a high T based on the glass transition temperature of the corresponding homopolymer. g Classified as a monomer. High T g Monomers often have T values ​​greater than 30° C., greater than 40° C., or greater than 50° C. when homopolymerized. g(i.e., the homopolymer formed from the monomer has a T of greater than 30° C., greater than 40° C., or greater than 50° C. g Some suitable high T g Alkyl (meth)acrylate monomers include, for example, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl (meth)acrylate, cyclohexyl methacrylate, isobornyl (meth)acrylate, stearyl (meth)acrylate, and 3,3,5 trimethylcyclohexyl (meth)acrylate.

[0040] The amount of alkyl (meth)acrylate incorporated into the (meth)acrylate polymer can be any suitable amount up to 100 weight percent based on the total weight of the (meth)acrylic polymerizable component. This amount can be, for example, up to 99 weight percent, up to 95 weight percent, up to 90 weight percent, up to 85 weight percent, up to 80 weight percent, up to 75 weight percent, up to 70 weight percent, up to 65 weight percent, up to 60 weight percent, up to 55 weight percent, up to 50 weight percent, or up to 45 weight percent. The amount of alkyl (meth)acrylate is often at least 35 weight percent, at least 40 weight percent, at least 45 weight percent, or at least 50 weight percent.

[0041] Alkyl (meth)acrylate is high T g If a monomer is selected to be included, the amount of this monomer is often 40% by weight or less, based on the total weight of the polymerizable components. That is, the amount can range from 0 to 40 weight percent, based on the total weight of the polymerizable components. If a higher amount is used, the overall T of the (meth)acrylate polymer can be increased. g may be too high. High T gThe amount of alkyl (meth)acrylate monomer is often 35 weight percent or less, 25 weight percent or less, or 15 weight percent or less. g The amount of alkyl (meth)acrylate monomer is often at least 0.5 weight percent, at least 1 weight percent, at least 3 weight percent, at least 5 weight percent, or at least 10 weight percent. g If alkyl (meth)acrylate monomer is included, T below 20°C g To form a (meth)acrylate polymer having a sufficiently low T g An alkyl (meth)acrylate monomer is typically added.

[0042] Alkyl (meth)acrylate monomers typically have a T of -10°C or less when measured as homopolymers. g Low T g For example, the polymerizable component is often selected to include at least 40 weight percent, at least 45 weight percent, at least 50 weight percent, at least 55 weight percent, at least 60 weight percent, at least 65 weight percent, or at least 70 weight percent, and up to 95 weight percent, up to 90 weight percent, up to 85 weight percent, up to 80 weight percent, up to 75 weight percent, or up to 70 weight percent of a monomer having a T of −10° C. or less, when measured as a homopolymer. g With low T g The amount is based on the total weight of the polymerizable components.

[0043] T below -10°C when measured as a homopolymer g Suitable alkyl monomers having the formula include, but are not limited to, 2-ethylhexyl acrylate, isooctyl acrylate, N-butyl acrylate, 2-methylbutyl acrylate, 2-octyl acrylate, and combinations thereof.

[0044] In some embodiments, the (meth)acrylate polymer is substantially free of acidic monomers. When used herein to describe acidic 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. In some embodiments, the crosslinkable composition can be substantially free of acids to remove minor corrosion of indium tin oxide ("ITO") and metals, the presence of which can damage touch sensors and their integrated circuits or connectors.

[0045] The (meth)acrylate polymers typically have a glass transition temperature, as measured by dynamic mechanical analysis, of 15° C. or less. For example, the glass transition temperature can be 15° C. or less, 10° C. or less, 5° C. or less, 0° C. or less, or −5° C. or less. The glass transition temperature is often greater than −50° C., greater than −40° C., or greater than −30° C.

[0046] In some preferred embodiments, the alkyl (meth)acrylate monomer may be selected from the group consisting of 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hexyl acrylate, butyl acrylate, cyclohexyl acrylate, isobornyl (meth)acrylate, and combinations thereof.

[0047] Additional Monomers In some embodiments, the (meth)acrylate polymer may include a hydroxyl (meth)acrylate comonomer. Examples of suitable monomers include, but are not limited to, 2-hydroxyethyl (meth)acrylate, 2-hydroxy-propyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and the like. In some embodiments, the (meth)acrylate polymer includes from about 0 to about 40 parts by weight of a hydroxy-functional copolymerizable monomer, particularly from about 5 to about 35 parts, more particularly from about 10 to about 30 parts.

[0048] In some embodiments, (meth)acrylate polymers may include non-hydroxyl functional polar copolymerizable monomers. Examples of suitable non-hydroxyl functional polar copolymerizable monomers include, but are not limited to, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, ether functional monomers such as 2-ethoxyethyl (meth)acrylate, 2-ethoxyethoxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, nitrogen-containing monomers such as acrylamide, methacrylamide, N-alkyl-substituted and N,N-dialkyl-substituted acrylamide or methacrylamide, where the alkyl group has up to 3 carbons, and N-vinyl lactam. Examples of suitable substituted amide monomers include, but are not limited to, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-morpholino (meth)acrylate, N-vinylpyrrolidone, and N-vinylcaprolactam. In some embodiments, the (meth)acrylate polymer comprises from about 0 parts to about 20 parts by weight of a polar copolymerizable monomer, specifically from about 1 part to about 15 parts, more specifically from about 1 part to about 10 parts.

[0049] In some embodiments, the (meth)acrylate polymer may include a vinyl ester, specifically a C1-C10 vinyl ester. Examples of suitable commercially available vinyl esters include, but are not limited to, vinyl acetate and VEOVA 9 or VEOVA 10 (available from Momentive Specialty Chemicals, New Smyrna Beach, Florida). The vinyl ester is typically added to the monomer mixture in an amount of about 1 part to about 20 parts by weight, specifically about 1 part to about 15 parts, more specifically about 1 part to about 10 parts. Other monomers, such as styrene monomers, may also be used.

[0050] In some embodiments, the (meth)acrylate polymer may include a polar (meth)acrylate monomer. Examples of suitable polar (meth)acrylate monomers include, but are not limited to, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxylbutyl acrylate, tetrahydrofuryl acrylate, acrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, and acrylic acid. In some embodiments, the (meth)acrylate polymer includes from about 0 parts by weight to about 50 parts by weight of the polar (meth)acrylate monomer, specifically from about 5 parts to about 45 parts, more specifically from about 10 parts to about 40 parts.

[0051] In some embodiments, the (meth)acrylate polymer may include a monofunctional non-(meth)acrylate vinyl monomer. Examples of suitable monofunctional non-(meth)acrylate vinyl monomers include, but are not limited to, N-vinylpyrrolidone, N-vinylcarbazole, vinyl acetate, and vinyl ether. In some embodiments, the (meth)acrylate polymer includes from about 0 parts by weight to about 15 parts by weight of the monofunctional non-(meth)acrylate vinyl monomer, specifically from about 1 part to about 10 parts, more specifically from about 1 part to about 8 parts.

[0052] In some embodiments, the (meth)acrylate polymer may include a multifunctional (meth)acrylate monomer. Examples of useful multifunctional (meth)acrylate monomers include, but are not limited to, di(meth)acrylates, tri(meth)acrylates, and tetra(meth)acrylates, such as 1,6-hexanediol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, polybutadiene di(meth)acrylate, polyurethane di(meth)acrylate, and propoxylated glycerin tri(meth)acrylate, and mixtures thereof. When used, the multifunctional (meth)acrylate monomer is typically used in an amount of at least 0.01, 0.02, 0.03, 0.04, or 0.05 parts by weight, up to 1, 2, 3, 4, or 5 parts by weight, based on 100 parts by weight of total monomer content.

[0053] In some preferred embodiments, the (meth)acrylate polymer may comprise 0 wt % to 50 wt % (e.g., 10 wt % to 40 wt %) of a polar (meth)acrylate monomer selected from the group consisting of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxylbutyl acrylate, tetrahydrofuryl acrylate, acrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, acrylic acid, and combinations thereof, and 0 wt % to 10 wt % (e.g., 0 wt % to 5 wt %) of a monofunctional non-(meth)acrylate vinyl monomer selected from the group consisting of N-vinylpyrrolidone, N-vinylcarbazole, vinyl acetate, vinyl ether, and combinations thereof.

[0054] Polymerization method Polymerization methods include those activated thermally or by actinic radiation (e.g., actinic radiation in the visible and / or ultraviolet regions of the electromagnetic spectrum). A free radical initiator is typically combined with the polymerizable component. Other optional components, such as chain transfer agents, antioxidants, solvents, etc., may be included in the polymerizable composition.

[0055] A free radical initiator, which can be either a photoinitiator or a thermal initiator, is typically used to form the (meth)acrylate polymer. Multiple photoinitiators or multiple thermal initiators can be used. The amount of free radical initiator can affect the weight average molecular weight, with larger amounts typically producing lower molecular weight polymeric materials. The amount of free radical initiator is usually at least 0.001 weight percent, at least 0.005 weight percent, at least 0.01 weight percent, at least 0.05 weight percent, at least 0.1, at least 0.5 weight percent, or at least 1.0 weight percent, based on the total weight of the polymerizable components. This amount can be up to 5 weight percent, up to 4 weight percent, up to 3 weight percent, up to 2 weight percent, up to 1.5 weight percent, up to 1 weight percent, up to 0.5 weight percent, up to 0.3 weight percent, up to 0.2 weight percent, or up to 0.1 weight percent, based on the total weight of the polymerizable components.

[0056] Suitable thermal initiators include various azo compounds such as those commercially available under the trade name VAZO from Chemours Co. (Wilmington, DE, USA), e.g., VAZO 67, which is 2,2'-azobis(2-methylbutanenitrile), VAZO 64, which is 2,2'-azobis(isobutyronitrile), VAZO 52, which is 2,2'-azobis(2,4-dimethylpentanenitrile), and VAZO 88, which is 1,1'-azobis(cyclohexanecarbonitrile); benzoyl peroxide, cyclohexane peroxide, lauroyl peroxide, di-tert-amyl peroxide, tert-butyl peroxybenzoate, di-cumyl peroxide, and compounds commercially available under the trade name LUPERSOL (e.g., LUPERSOL, which is 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane) from Atofina Chemical, Inc. (Philadelphia, PA, USA). 101, and LUPERSOL 130, 2,5-dimethyl-2,5-di-(tert-butylperoxy)-3-hexyne; various hydroperoxides, such as tert-amyl hydroperoxide and tert-butyl hydroperoxide; and mixtures thereof.

[0057] In many embodiments, a photoinitiator is used to form the (meth)acrylate polymer. Some exemplary photoinitiators are benzoin ethers (e.g., benzoin methyl ether or benzoin isopropyl ether), or substituted benzoin ethers (e.g., anisoin methyl ether). Other exemplary photoinitiators are substituted acetophenones, such as 2,2-diethoxyacetophenone, or 2,2-dimethoxy-2-phenylacetophenone (commercially available under the trade name IRGACURE 651 from BASF Corp., Florham Park, NJ, USA, or under the trade name ESACURE KB-1 from Sartomer, Exton, PA, USA). Still other exemplary photoinitiators are substituted α-ketols, such as 2-methyl-2-hydroxypropiophenone, aromatic sulfonyl chlorides, such as 2-naphthalenesulfonyl chloride, and photoactive oximes, such as 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime. Other suitable photoinitiators include, for example, 1-hydroxycyclohexyl phenyl ketone (commercially available under the trade name IRGACURE 184), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (commercially available under the trade name IRGACURE 819), 1-[4-(2-1-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one (commercially available under the trade name IRGACURE 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (commercially available under the trade name IRGACURE 369), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (commercially available under the trade name IRGACURE 907), and other suitable photoinitiators available from IGM Resins USA Inc. (Charlotte, North Carolina). diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide available from Ciba Specialty Chemicals Corp., Tarrytown, NY, USA; and 2-hydroxy-2-methyl-1-phenylpropan-1-one (available under the trade name DAROCUR 1173 from Ciba Specialty Chemicals Corp., Tarrytown, NY, USA).

[0058] Sensitizers may also be used in certain embodiments to enhance the efficacy of the photoinitiator. Useful sensitizers can include, for example, isopropylthioxanthone (available under the trade name OMNIRAD ITX) and 4-diethyl-9H-thioxanthen-9-one (available under the trade name OMNIRAD DETX), as well as other thioxanthone-based sensitizers.

[0059] Chain transfer agents are often included in the polymerizable composition to control the molecular weight of the (meth)acrylate polymer. Suitable chain transfer agents include, but are not limited to, those selected from the group consisting of carbon tetrabromide, hexabromoethane, bromotrichloromethane, 2-mercaptoethanol, tert-dodecyl mercaptan, isooctyl thioglycoate, 3-mercapto-1,2-propanediol, cumene, pentaerythritol tetrakis(3-mercaptobutyrate) (available from Showa Denko K.K. under the trade name KARENZ MT PE1), 1,4-bis(3-mercaptobutyryloxy)butane (available from Showa Denko K.K. under the trade name KARENZ MT BD1), ethylene glycol bisthioglycolate, and mixtures thereof. Depending on the reactivity of the chain transfer agent selected, the amount of chain transfer agent often ranges from 0 weight percent to 5 weight percent based on the total weight of monomers in the polymerizable composition. In some embodiments, the amount of chain transfer agent is at least 0.05 weight percent, at least 0.1 weight percent, at least 0.2 weight percent, at least 0.3 weight percent, or at least 0.5 weight percent, and can be up to 5 weight percent, up to 4.5 weight percent, up to 4 weight percent, up to 3.5 weight percent, up to 3 weight percent, up to 2.5 weight percent, up to 2 weight percent, up to 1.5 weight percent, or up to 1 weight percent. The weight percent values ​​are based on the total weight of polymerizable components used to form the (meth)acrylate polymer.

[0060] The reaction of the polymerizable composition to form a (meth)acrylate polymer can occur in the presence or absence of an organic solvent. When an organic solvent is included in the polymerizable composition, the amount is often selected to provide a desired viscosity. Examples of suitable organic solvents include, but are not limited to, methanol, tetrahydrofuran, ethanol, isopropanol, pentane, hexane, heptane, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, toluene, xylene, and ethylene glycol alkyl ether. These organic solvents can be used alone or as a mixture thereof.

[0061] In some embodiments, the polymerization occurs in the presence of at least 10 weight percent of an organic solvent based on the total weight of the polymerizable composition. The amount can be, for example, at least 20 weight percent, at least 30 weight percent, at least 40 weight percent, and up to 70 weight percent, up to 60 weight percent, up to 50 weight percent. In other embodiments, the polymerization occurs with a small amount of organic solvent or without an organic solvent. That is, the polymerizable composition does not contain an organic solvent or contains a minimal amount of an organic solvent. If used, the organic solvent is often present in an amount of less than 10 weight percent, less than 5 weight percent, less than 4 weight percent, less than 3 weight percent, less than 2 weight percent, or less than 1 weight percent based on the total weight of the polymerizable composition.

[0062] The (meth)acrylate polymer can be formed from the polymerizable composition using any suitable method. Polymerization can occur in one or multiple steps. That is, all or a portion of the monomers and / or free radical initiator can be placed in a suitable reaction vessel and polymerized. For example, the polymerizable composition containing an organic solvent and a thermal initiator can be mixed and heated at an elevated temperature, such as in the range of 50°C to 100°C (e.g., 55°C to 70°C), for several hours.

[0063] In one possible method of making (meth)acrylate polymers, little or no organic solvent is included in the polymerization composition. Such free radical polymerization methods can be carried out in a continuous manner, for example, as described in U.S. Pat. Nos. 4,619,979 (Kotnour et al.) and 4,843,134 (Kotnour et al.). In an alternative method of making (meth)acrylate polymers, adiabatic processes can be used, for example, as described in U.S. Pat. Nos. 5,986,011 (Ellis et al.) and 5,637,646 (Ellis). In yet another method of making (meth)acrylate polymers, polymerization reaction can occur in a polymer package, for example, as described in U.S. Pat. No. 5,804,610 (Hamer et al.).

[0064] The resulting (meth)acrylate polymer may be uncrosslinked or crosslinked, depending on the composition of the polymerizable composition. In some embodiments, the (meth)acrylate polymer is crosslinked. In some embodiments, the monomer mixture may include a multifunctional crosslinker. For example, the mixture may include a thermal crosslinker that is activated during the drying step of preparing the solvent coated adhesive, and a crosslinker that copolymerizes during the polymerization step. Such thermal crosslinkers include, but are not limited to, multifunctional isocyanates, multifunctional aziridines, and epoxy compounds. Exemplary crosslinkers that may be polymerized include multifunctional acrylates, such as 1,6-hexanediol diacrylate, or multifunctional acrylates as known to those skilled in the art. In some embodiments, useful isocyanate crosslinkers include aromatic triisocyanates, available, for example, as DESMODUR N3300 (Bayer, Cologne, Germany). Ultraviolet or "UV" activated crosslinkers may also be used. Such UV crosslinkers can include non-copolymerizable photocrosslinkers such as benzophenones, and copolymerizable photocrosslinkers such as acrylated or methacrylated benzophenones such as 4-acryloxybenzophenone. Typically, the crosslinker, if present, is added to the monomer mixture in an amount of about 0.01 parts to about 5 parts, particularly about 0.01 parts to about 4 parts, more particularly about 0.01 parts to about 3 parts, by weight. Other crosslinking methods, such as the use of high T polymers such as polymethylmethacrylate macromers or polystyrene macromers, can be used. g Crosslinking may be used, such as by copolymerizing macromers, using ionic, acid-base, or physical crosslinking methods, etc. If included, macromers may be used in amounts of about 1 part to about 20 parts by weight of the total monomeric components.

[0065] Acylphosphine Oxide Photoinitiators The crosslinkable composition further comprises an acylphosphine oxide photoinitiator. Acylphosphine oxide photoinitiators useful in embodiments of the present disclosure can include, for example, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide ("TPO"), available from IGM Resins USA Inc. (Charlotte, North Carolina), and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide ("BAPO"), both available from IGM Resins USA Inc. (Charlotte, North Carolina).

[0066] In some embodiments, the acylphosphine oxide photoinitiator has the structure: [ka] (In the formula, R 1 is a light absorbing moiety (e.g., aromatic, substituted aromatic), and R 2 and R 3 are independently a light absorbing moiety and / or a solubilizing moiety (e.g., alkyl). The compound may include a mono-acylphosphine oxide (eg, TPO) represented by the following formula:

[0067] In some preferred embodiments, the acylphosphine oxide photoinitiator has the structure: [ka] (In the formula, R 1 is a light absorbing moiety (e.g., aromatic, substituted aromatic), and R 2 and R 3 are independently a light absorbing moiety and / or a solubilizing moiety (e.g., alkyl). Examples of suitable phosphine oxides include bis-acylphosphine oxides (eg, BAPO) represented by the following formula:

[0068] In a preferred embodiment, the crosslinkable composition comprises 0.05 pph to 5 pph (eg, 1 pph) of an acylphosphine oxide photoinitiator relative to the (meth)acrylate polymer mixture.

[0069] (Meth)allyl Crosslinking Monomer The crosslinkable composition further comprises a crosslinking monomer comprising at least two end groups selected from allyl, (meth)allyl, or a combination thereof. An allyl group has the structural formula H2C=CH-CH2-. It consists of a methylene bridge (-CH2-) bonded to a vinyl group (-CH=CH2). Similarly, a (meth)allyl group is a substituent having the structural formula H2C=C(CH3)-CH2-.

[0070] In some embodiments, the crosslinking monomer does not include a vinyl group, such as vinyl ether. Vinyl, also known as ethenyl, is the functional group -CH=CH2, i.e., an ethylene molecule (H2C=CH2) minus one hydrogen atom.

[0071] In one embodiment, the crosslinking monomer comprises two (meth)allyl groups and a (meth)acrylate group. Crosslinking monomers of this type are commercially available from Sartomer under the trade name "SR 523". In some embodiments, the crosslinking monomer does not comprise a (meth)acrylate group. The lower reactivity of (meth)allyl groups compared to (meth)acrylate groups may be modifiable to achieve an optimal amount of crosslinking, especially when the adhesive is cured by (e.g., UV) radiation.

[0072] The crosslinking monomer typically has the formula: [ka] (In the formula, R 1 is hydrogen or methyl, Z is a heteroatom or a polyvalent linking group, (x is in the range of 2 to 6) In some embodiments, y is 5 to 20. In some embodiments, x is 2 or 3.

[0073] In embodiments in which the crosslinking monomer comprises a polyvalent linking group, the linking group Z typically has a molecular weight of 1000 g / mole or less, and in some embodiments has a molecular weight of 500 g / mole or less, 400 g / mole or less, 300 g / mole or less, 200 g / mole or less, 100 g / mole or less, or 50 g / mole or less.

[0074] Various crosslinking monomers containing at least two allyl groups and / or (meth)allyl groups are commercially available. Representative species of commercially available crosslinking monomers are listed in Table A below. Although these species contain allyl groups, in many embodiments, the same species with (meth)allyl groups are available or can be synthesized. For example, (meth)allyl adipate can be prepared by the method described in U.S. Patent Publication No. 2017 / 0037282 (Lipscomb et al.). [Table 1-1] [Table 1-2] (Continuation of the above table)

[0075] Crosslinking monomers containing at least two allyl and / or (meth)allyl groups can also be synthesized according to various reaction schemes known in the art.

[0076] In one reaction scheme, an aryl or heteroaryl magnesium compound can be reacted with an allyl halide (e.g., bromine) as described in Krasovskiy, Straub, and Knochel; Angewandte Chemie-International Edition, 2006, vol. 45, p. 159-162. Suitable allyl halides include, for example, allyl chloride, allyl bromide, allyl iodide, 4-bromo-1-butene, 3-chloro-2-methylpropene, 3-bromo-2-methylpropene, 5-bromo-1-pentene, 6-bromo-1-hexene, 8-bromo-1-octene, 10-chloro-1-decene, and 11-chloro-1-undecene. Such a reaction scheme can be, for example, [ka] It is possible to produce diallylbenzene, which can be represented as follows:

[0077] In this embodiment, the polyvalent linking group Z is arylene.

[0078] The various reaction schemes for preparing the crosslinking monomers described herein utilize (meth)allyl alcohol as a starting material. Thus, the (meth)allyl group is the reaction product of allyl or (meth)allyl alcohol.

[0079] Various (meth)allyl alcohols can be used in such reaction schemes, including, for example, the allyl alcohols 2-methyl-2-propen-1-ol, 2-ethyl-2-propen-1-ol, 2-pentyl-2-propen-1-ol, 10-undecen-1-ol, 3-buten-1-ol, 3-methyl-3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 9-decen-1-ol, and 2-allyloxyethanol. In some embodiments, the crosslinking monomer is the reaction product of a (meth)allyl alcohol containing at least 8, 9, or 10 carbon atoms. Such alcohols typically contain a (meth)allyl group and an alkylene group containing at least 5, 6, 7, or 8 carbon atoms, typically no more than 20, no more than 18, or no more than 16 carbon atoms. In some embodiments, the (meth)allyl alcohol contains no more than 12 carbon atoms, and thus contains an alkylene group having no more than 9 carbon atoms. Thus, in various embodiments in which Z comprises an alkylene group, the alkylene group may contain at least 5, 6, 7, or 8 carbon atoms, and typically no more than 20, no more than 18, or no more than 16 carbon atoms.

[0080] Various alkoxylated allylic alcohols may also be used in such reaction schemes. Suitable alkoxylated allylic alcohols have the general formula: [ka] (In the formula, R 1 is hydrogen or methyl, A is a C2-C4 oxyalkylene group, in particular C2H4O-, optionally in combination with C3H6O-, and n is typically an average of 1 to 5. In this embodiment, Z comprises or consists of an oxyalkylene or polyoxyalkylene group. One representative compound is ethylene glycol diallyl ether shown in Table A.

[0081] In other embodiments, Z comprises an ether group (e.g., a single) and an alkylene group. The crosslinking monomer has the formula: [ka] (wherein y is in the range of 2 to 20; R 1 is hydrogen or methyl) In some embodiments, y is at least 5, 6, 7, or 8. Such crosslinking monomers can be prepared by reaction of allyl alcohol as previously described, or by reaction of thiols as described in Marvel and Cripps; Journal of Polymer Science, 1952, vol. 8, p. 313-320. One exemplary reaction scheme utilizing 10-undecen-1-ol to produce undecenyl ethers is shown below. [ka]

[0082] In other embodiments, Z is the reaction product of a multifunctional alcohol having 2 to 6 hydroxyl groups. In this embodiment, the crosslinking monomer is typically represented by the formula: [ka] (In the formula, L 2 is a linear or branched (C1-C 12 ) alkylene, x is in the range of 2 to 6, R 1 is hydrogen or methyl) In some embodiments, x is at least 2, such as in the case of butanediol (meth)allyl ether. In other embodiments, x is at least 3 and L 2is the residue of a polyfunctional alcohol such as glycerol, trimethylolpropane, trimethylolpropane ethoxylate, trimethylolpropane propoxylate, pentaerythritol, 1,2,4-butanetriol, 1,1,1-tris(hydroxymethyl)ethane, fructose, glucose, 1,3,5-tris(2-hydroxyethyl)isocyanurate, dipentaerythritol, and di(trimethylolpropane). Representative examples of such crosslinking monomers include, for example, trimethylolpropane diallyl ether and pentaerythritol allyl ether shown in Table A above.

[0083] In yet other embodiments, Z comprises or consists of an ester group. In some embodiments, the crosslinking monomer is typically a C1-C 20 In some embodiments, (C1-C 12 ) alkylene group. Such crosslinking monomers can be prepared by the reaction of (meth)allylic alcohols, as described above, with (meth)allylic acids, as described, for example, in Frostick et al., Journal of the American Chemical Society 1959, vol. 81, p. 3350-3352. When (meth)allylic acid is utilized as the starting material for generating the (meth)allylic group of the crosslinking monomer, the acid is one in which the double bond is (C1-C 20 ) is selected to be spaced from the acid group by an alkylene group. Representative acids include, for example, 3-butenoic acid, 4-pentenoic acid, 2,2-dimethyl-4-pentenoic acid, 5-hexenoic acid, 6-heptenoic acid, 9-decenoic acid, and 10-undecenoic acid. One exemplary reaction scheme is as follows: [ka]

[0084] In other embodiments, Z comprises two or more ester groups (e.g., a diester). In this embodiment, the crosslinking monomer typically has the formula: [ka] (In the formula, R 1 is hydrogen or methyl, L 3 (For example, C1~C 20 ) alkylene, arylene, or a combination thereof; (y ranges from 1 to 20) In some embodiments, y is at least 5, 6, 7, or 8.

[0085] Such crosslinking monomers are typically the residue of an aliphatic or aromatic dicarboxylic acid or diol. Representative examples of such crosslinking monomers include di(meth)allyl sebacate, di(meth)allyl adipate, di(meth)allyl terephthalate, di(meth)allyl isophthalate; the diallyl structures shown in Table A. Other examples include di(meth)allyl itaconate, di(meth)allyl maleate, di(meth)allyl fumarate, di(meth)allyl diglycolate, di(meth)allyl oxalate, di(meth)allyl succinate, and the following: [ka] An example of such an acid is 1,4-butanediol di(undecenylate), which is shown below.

[0086] In yet other embodiments, Z comprises or consists of an amide group. In some embodiments, the crosslinking monomer is typically (C1-C 20 ) bonded to an alkylene group, in some embodiments C1-C 12 The crosslinking monomer typically comprises a single amide group attached to an alkylene group. [ka] (In the formula, R 1 is hydrogen or methyl, R 5 is hydrogen, (C1-C6) alkyl, or aryl; (y ranges from 1 to 20) In some embodiments, y is at least 5, 6, 7, or 8.

[0087] Such crosslinking monomers can be prepared by the reaction of (meth)allylic acids with allylamines as described above, for example in Goldring, Hodder, Weiler; Tetrahedron Letters, 1998, vol. 39, #28 p. 4955-4958. Representative amines include, for example, allylamine, N-methylallylamine, diallylamine, triallylamine, tris(2-methallylamine), and N-allylcyclohexylamine. One exemplary reaction scheme is as follows: [ka] In yet another embodiment, the (meth)allylic acid described above can be reacted with a diamine. Conversely, the allylamine described above can be reacted with a dicarboxylic acid or tricarboxylic acid. In this embodiment, Z contains two or more (e.g., two or three) amide groups. In this embodiment, the crosslinking monomer is typically represented by the formula: [ka] (In the formula, R 1 is hydrogen or methyl, R 5 is hydrogen, (C1-C6) alkyl, or aryl; L 3 (For example, C1~C 20 ) alkylene, arylene, or a combination thereof, and y is in the range of 1 to 20. In some embodiments, y is at least 5, 6, 7, or 8.

[0088] One typical structure is as follows: [ka] The compound is N,N'-butanediyl-bis-undecenylamide, which is shown below.

[0089] In view of the various crosslinking monomers described herein, Z can be a heteroatom, such as nitrogen or oxygen, as well as a wide variety of polyvalent (e.g., di-, tri-) linking groups. Z can be, for example, (C1-C 20 Or C5~C 20 ) alkylenes, arylenes, oxyalkylenes (e.g., polyoxyalkylenes), esters (e.g., monoesters, diesters, residues of aliphatic and aromatic carboxylic acids), ethers (e.g., residues of polyfunctional alcohols), cyanurates, isocyanurates, amides, amine ureas, urethanes, carbonates, and (C1-C4 alkyl) silanes. In some embodiments, Z includes only one of such polyvalent linking groups. In other embodiments, Z includes two or more of the same class of polyvalent linking groups (e.g., diesters, triethers). In yet other embodiments, Z includes a polyvalent linking group of a different class, such as an ester, ether, carbonate, amide, urea, or urethane, and a polyvalent linking group of a different class, such as a (C1-C 20 or C1-C5) alkylene or arylene groups.

[0090] The concentration of the crosslinking monomer containing at least two (meth)allyl groups is typically from 0.05 pph to 5 pph (eg, 0.1 pph) relative to the (meth)acrylate polymer mixture.

[0091] In some preferred embodiments, the crosslinking monomer has the structure (I): [ka] (wherein Z represents a divalent linking group, and each R is independently -H or -CH3.) In some preferred embodiments, Z is linked to the allyl group of the multifunctional allyl-terminated monomer by at least one of an ester bond, an acetate bond, and an amide bond. In some preferred embodiments, Z is represented by the structure: [ka] It is represented by:

[0092] In some preferred embodiments, Z has the structure: [ka] It is represented by:

[0093] The crosslinkable composition may optionally include another crosslinking agent in addition to the crosslinking agent that includes at least two (meth)allyl groups. In some embodiments, the crosslinkable composition includes a multifunctional (meth)acrylate. Examples of useful multifunctional (meth)acrylates include, but are not limited to, di(meth)acrylates, tri(meth)acrylates, and tetra(meth)acrylates, such as 1,6-hexanediol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, polybutadiene di(meth)acrylate, polyurethane di(meth)acrylate, and propoxylated glycerin tri(meth)acrylate, and mixtures thereof.

[0094] Generally, the multifunctional (meth)acrylate is not part of the original monomer mixture, but is added subsequently after the formation of the (meth)acrylic polymer. If used, the multifunctional (meth)acrylate is typically used in an amount of at least 0.01, 0.02, 0.03, 0.04, or 0.05 parts by weight, up to 1, 2, 3, 4, or 5 parts by weight, based on 100 parts by weight of the total monomer content.

[0095] UV absorbers and antioxidants In some embodiments, additives such as ultraviolet light ("UV") absorbers (e.g., benzotriazoles, substituted triazines, oxazolinic acid amides, benzophenones, or derivatives thereof), UV stabilizers (e.g., hindered amines or derivatives thereof, imidazoles or derivatives thereof, phosphorus-based stabilizers, and sulfur ester-based stabilizers), and / or antioxidants (e.g., hindered phenolic compounds, phosphorus-based esters, or derivatives thereof) can be included in the crosslinkable composition. Exemplary antioxidants include those available from Ciba Specialty Chemicals Incorporated (Tarrytown, New York).

[0096] In some embodiments, the crosslinkable composition includes an ultraviolet light absorber, such as 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (available as TINUVIN 928 from BASF, Florham Park, New Jersey), at a concentration of at least 0.25, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 wt% of the crosslinkable composition. The concentration of the ultraviolet light absorber is typically 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, or 10 wt% or less. In some preferred embodiments, the concentration of the UV absorber ranges from 0.3 pph to 15 pph relative to the (meth)acrylate polymer.

[0097] In some embodiments, the inclusion of an ultraviolet absorber can reduce the transmittance at 380 nm and 385 nm (e.g., the transmittance of a 100 micron thick adhesive layer) to less than 20%, less than 15%, less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, or less than 2%. In some preferred embodiments, the UV absorber has a transmittance of less than 15% at 365 nm for a 0.1 mm thick coating. In some preferred embodiments, the UV absorber has a transmittance of more than 70% at 420 nm for a 0.1 mm thick coating.

[0098] Optional Additives As described below, various other optional components can be added to the crosslinkable composition and / or to the adhesive, such as adhesion promoters (e.g., (3-glycidyloxypropyl)trimethoxysilane or (3-glycidyloxypropyl)triethoxysilane), colorants (e.g., titania or carbon black), dyes, corrosion inhibitors (e.g., benzotriazole), antistatic agents, plasticizers, thickeners, thixotropic agents, processing aids, nanoparticles, fibers, and combinations thereof. Generally, the amount of each additive depends on the intended use of the resulting composition.

[0099] glue An adhesive composition is provided that includes the crosslinkable composition described above. In some embodiments, the adhesive composition is a pressure-sensitive adhesive. The (meth)acrylate polymer itself may have suitable adhesive properties to function as a pressure-sensitive adhesive. Alternatively, optional additives, such as tackifiers, may be combined with the crosslinkable composition to provide a composition with suitable adhesive properties. Useful tackifiers include, for example, rosin ester resins and terpene phenolic resins. The tackifier is often mixed in an amount equal to or less than the amount of (meth)acrylate-based polymeric material included in the core. The amount of optional tackifier is often in the range of 0 weight percent to 25 weight percent, 0 weight percent to 20 weight percent, 0 weight percent to 15 weight percent, 0 weight percent to 10 weight percent, or 0 weight percent to 5 weight percent based on the total weight of the polymerizable composition.

[0100] Optional antioxidants and / or stabilizers, such as hydroquinone monoethyl ether (p-methoxyphenol, MeHQ), and those available under the trade name IRGANOX 1010 (pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) from BASF Corp. (Florham Park, NJ, USA), can be added to enhance the temperature stability of the polymeric material. If used, antioxidants and / or stabilizers are typically added in the range of 0.01 weight percent to 1.0 weight percent based on the total weight of the polymerizable components used to form the (meth)acrylate polymer.

[0101] In some preferred embodiments, the adhesive composition is a pressure sensitive adhesive. In some preferred embodiments, the adhesive composition has a haze value of less than 5%, less than 2%, or less than 1% for a 0.1 mm thick coating.

[0102] Goods An article is provided that includes an adhesive composition and a substrate. Any suitable substrate can be used. In many embodiments, a layer of the adhesive composition is disposed adjacent to the substrate. The adhesive composition can be in direct contact with the substrate, or can be separated from the substrate by one of more layers, such as a primer layer.

[0103] Any suitable substrate can be used. In some articles, the substrate is flexible. Examples of flexible substrate materials include, but are not limited to, polymeric films, woven or nonwoven fabrics; metal foils, foams (e.g., polyacrylic, polyethylene, polyurethane), and combinations thereof (e.g., metallized polymeric films). Polymeric films include, for example, polypropylene (e.g., biaxially oriented), polyethylene (e.g., high density or low density), polyvinyl chloride, polyurethane (e.g., thermoplastic polyurethane), polyester (e.g., polyethylene terephthalate ("PET"), polyethylene naphthalate ("PEN"), and polylactic acid copolymers), polycarbonate, polyacrylate, polymethyl(meth)acrylate ("PMMA"), polyvinyl butyral, polyimide, polyamide, fluoropolymer, cellulose acetate, triacetyl cellulose (TAC), ethyl cellulose, and polycyclic olefin polymers ("COP"). Woven or nonwoven fabrics may include fibers or filaments of synthetic or natural materials, such as cellulose, cotton, nylon, rayon, glass, and ceramic.

[0104] In some embodiments, the article is or comprises an adhesive tape. Examples of such adhesive tapes include transfer tapes, single-sided adhesive tapes, double-sided tapes (i.e., a core substrate with an adhesive layer on each side of the substrate), or die-cut adhesive articles (e.g., the article has an adhesive layer adjacent to a release liner or between two release liners). Such adhesive tapes may include a wide variety of substrates for use as backings or release liners. Examples include woven and nonwoven materials, plastic films, metal foils, and the like.

[0105] Adhesive tapes are often prepared by coating adhesive compositions onto various flexible or non-flexible backing materials and / or release liners using conventional coating techniques to produce single-sided or double-sided tapes. For single-sided adhesive tapes, the adhesive composition can be coated onto a layer of backing material, and the side of the backing material opposite to where the adhesive is placed can be coated with a suitable release material (e.g., a release layer or release liner). Release materials are known and include, for example, silicone, polyethylene, polycarbamate, polyacrylic, and other materials. For double-sided adhesive tapes, a first adhesive composition is coated onto a layer of backing material, and a second layer of adhesive composition is placed on the opposite surface of the backing material. The second layer may comprise the adhesive composition described herein, or a different adhesive composition. For die-cut adhesive articles or transfer tapes, the adhesive composition is typically placed between two release liners.

[0106] The adhesive article can be part of another article. For example, the adhesive composition can bond two parts of an article together. In some such articles, the adhesive is disposed adjacent to a flexible and / or foldable substrate and is used within another flexible and / or foldable article, such as within a flexible and / or foldable electronic device.

[0107] In some embodiments, the article containing the adhesive composition is part of an electronic device.In such devices, the adhesive composition typically forms a layer between two substrates to bond the two substrates together.Examples of suitable substrates include materials such as polyacrylate, polymethylmethacrylate, polycarbonate, polyamide, polyimide, polyethylene terephthalate ("PET"), polyethylene naphthalate ("PEN"), polycyclic olefin polymer (COP), thermoplastic polyurethane, triacetyl cellulose ("TAC"), and metal foil.

[0108] A common application of adhesives in the electronics industry is in the manufacture of various displays, such as computer monitors, televisions, mobile phones, tablets, and small displays (in cars, appliances, wearables, electronics, etc.). The continued development of electronic displays is creating an increasing demand for adhesives, especially optically clear adhesives (OCAs), that serve as an assembly layer or gap-filling layer between the outer cover lens or sheet of an electronic display assembly (based on glass, polyethylene terephthalate ("PET"), polycarbonate ("PC"), polymethyl methacrylate ("PMMA"), polyimide, polyethylene naphthalate ("PEN"), cyclic olefin copolymers, etc.) and the underlying display module. The presence of an OCA can improve the performance of the display by increasing brightness and contrast while also providing structural support to the assembly. The adhesive compositions described herein can be formulated to be OCAs.

[0109] An article may be formed by placing an adhesive layer adjacent to a substrate. The adhesive composition may be coated onto a substrate (e.g., a backing or release liner) using conventional coating techniques. For example, the adhesive composition may be applied by methods such as roller coating, flow coating, dip coating, spin coating, spray coating, knife coating, and die coating. The coated adhesive composition may have any desired weight percent solids, but often ranges from 10 weight percent to 100 weight percent solids based on the total weight of the adhesive composition. The desired solids content may be achieved by further diluting the coating composition or by partial drying.

[0110] The adhesive composition disposed as a layer on a substrate or disposed as a layer between two release liners often has a thickness of up to 100 micrometers (i.e., microns or μm), up to 50 micrometers, up to 35 micrometers, or up to 25 micrometers. In some embodiments, the adhesive composition may have a total (average) thickness of the adhesive composition disposed on a substrate in a layer (e.g., in the form of a coating disposed between liners) of up to 500 micrometers, up to 400 micrometers, up to 300 micrometers, or up to 200 micrometers. In some embodiments, the adhesive composition may have a total (average) thickness of the adhesive composition disposed on a substrate in a layer (e.g., in the form of a coating disposed between liners) of at least 5 micrometers, at least 10 micrometers, or at least 15 micrometers. The desired thickness depends on the particular use of the adhesive layer.

[0111] The objects and advantages of the present disclosure are further illustrated by the following non-limiting examples, but the specific materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit the disclosure. EXAMPLES

[0112] Unless otherwise stated or readily apparent from the context, all parts, percentages, ratios, etc. in the examples, and the remainder of the specification, are by weight. [Table 2]

[0113] Test Method Gel fraction test The gel fraction of the adhesive film was characterized by gravimetric method. Circular samples of both the polymerized adhesive film and the polymerized and cured adhesive film (thickness: 0.1 mm, sample diameter: 25 mm) were loaded into a porous stainless steel container (McMaster-Carr, Elmhurst, Illinois; mesh size: 0.5 mm, width x length x height: 40 mm x 40 mm x 30 mm) with known mass. The mesh container and adhesive film were weighed and then immersed in a glass jar (diameter x height: 70 mm x 85 mm) containing a 1:1 v / v mixture of ethyl acetate / isopropanol (approximately 60 mL). After 24 hours, the metal container and remaining adhesive film were removed from the solvent jar and dried in a convection oven (DESPATCH, Minneapolis, MN) at 120°C for 3 hours to obtain the adhesive film after solvent incubation and drying. The mass of the adhesive film before and after solvent incubation was recorded after subtracting the mass of the empty cage from each value. Two gel fraction tests were performed for each sample and the gel fraction values ​​were averaged.

[0114] The gel fraction of each adhesive film was calculated as follows.

number

[0115] optical measurement Haze and transmittance measurements were performed using an ULTRASCANPRO Spectrophotometer (HunterLab, Reston, Virginia) in transmission mode. For the measurement samples, 0.1 mm thick coated adhesive layers between release coated carrier liners described in the following examples were cut to approximately 5 cm wide by 10 cm long. One of the carrier liners was removed and the sample was laminated to a clear piece of 1 mm thick LCD glass (Swift Glass, Elmira Heights, New York). The other liner was then removed and the sample was placed in the ULTRASCANPRO Spectrophotometer to measure the transmittance and color through the glass / OCA assembly. Haze and transmittance at specific wavelengths were recorded and listed in Table 3 below.

[0116] Working Example General Procedure The base polymer solution was prepared by partial UV polymerization in a clear jar of a monomer mixture of EHA / THFA / EHMA / HEA / AcM with a weight ratio of 55.8 / 14.6 / 8.3 / 17.7 / 3.6 and IRG 651 photoinitiator added at 0.15 pph per 100 parts of the monomer mixture. The output wavelength was 365 nm and 0.3 mW / cm. 2 The mixture was inerted by flowing nitrogen gas through the jar until a viscous solution of approximately 2,000 cP was achieved before irradiating the mixture with a light source having an intensity of 1.0 pph. After this first polymerization, the viscous solution was further mixed with TINUVIN 928 (1.8 pph) and additional photoinitiators and crosslinkers as shown in Table 2. This solution was coated between siliconized PET films (RF02N and RF22N, obtained from SKC Hass, Seoul, South Korea) with a coating thickness of 0.1 mm and irradiated with a 405 nm light source and approximately 200 mJ / cm2. 2The adhesive film was then further polymerized (i.e., second polymerization) using a power dose of approximately 3,000 mJ / cm of UVA using a Fusion UV Processor (Fusion UV Systems Inc., Gaithersburg, MD) equipped with a D bulb, as measured by a UVI Cure Power Puck 2 (EIT, Sterling, Virginia). 2 The samples were cured by exposing the adhesive film to a target dose of 100000000000000. [Table 3] [Table 4]

[0117] The entire disclosures of patents, patent documents, and publications cited herein are incorporated by reference in their entirety as if each were individually incorporated. To the extent that any conflict or inconsistency exists between the written specification and the disclosure of any document incorporated herein by reference, the written specification shall control. Various modifications and alterations to the present disclosure will become apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. It is to be understood that the present disclosure is not intended to be unduly limited by the exemplary embodiments and examples described herein, and that such examples and embodiments are presented only as examples within the scope of the present disclosure, which is intended to be limited only by the scope of the claims set forth herein as follows.

Claims

1. a (meth)acrylate polymer prepared from polymerizable components comprising alkyl (meth)acrylate monomers; an acylphosphine oxide photoinitiator; a crosslinking monomer comprising at least two end groups selected from the group consisting of allyl, methallyl, or a combination thereof; A crosslinkable composition comprising:

2. 2. The crosslinkable composition of claim 1, wherein the (meth)acrylate polymer has a glass transition temperature of 15[deg.] C. or less.

3. the polymerizable component 40 wt % to 100 wt % of the alkyl (meth)acrylate monomer; 0 wt % to 50 wt % of a polar (meth)acrylate monomer; 0 wt % to 15 wt % of a monofunctional non-(meth)acrylate vinyl monomer; The crosslinkable composition of claim 1 comprising:

4. 2. The crosslinkable composition of claim 1, wherein the alkyl (meth)acrylate monomer is selected from the group consisting of 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hexyl acrylate, butyl acrylate, cyclohexyl acrylate, isobornyl (meth)acrylate, and combinations thereof.

5. 4. The crosslinkable composition of claim 3, wherein the polar (meth)acrylate monomer is selected from the group consisting of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxylbutyl acrylate, tetrahydrofuryl acrylate, acrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, acrylic acid, and combinations thereof.

6. 4. The crosslinkable composition of claim 3, wherein the monofunctional non-(meth)acrylate vinyl monomer is selected from the group consisting of N-vinylpyrrolidone, N-vinylcarbazole, vinyl acetate, vinyl ethers, and combinations thereof.

7. The crosslinkable composition of claim 1 , wherein the (meth)acrylate polymer is substantially free of acidic monomers.

8. 10. The crosslinkable composition of claim 1, wherein the acylphosphine oxide photoinitiator comprises a bis-acylphosphine oxide.

9. 2. The crosslinkable composition of claim 1, comprising 0.05 pph to 5 pph of said acylphosphine oxide photoinitiator relative to said (meth)acrylate polymer.

10. 2. The crosslinkable composition of claim 1, comprising 0.05 pph to 5 pph of said crosslinking monomer relative to said (meth)acrylate polymer.

11. The crosslinking monomer has the structure: 【Chemistry 1】 (In the formula, Z represents a divalent linking group, and each R is independently —H or —CH ３ is) The crosslinkable composition of claim 1 , represented by:

12. Z is a group having the structure: 【Chemistry 2】 The crosslinkable composition of claim 11, represented by:

13. Z is a group having the structure: 【Transformation 3】 The crosslinkable composition of claim 11, represented by:

14. The crosslinkable composition of claim 1 further comprising a UV absorber.

15. 15. The crosslinkable composition of claim 14, comprising 0.3 pph to 15 pph of said UV absorber relative to said (meth)acrylate polymer.

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