Field

[0001] The present disclosure relates generally to radiation curable adhesives having dark cure and/or shadow cure ability.

Brief Description of Related Technology

[0002] Highly integrated and sophisticated touch interface design is becoming increasingly important in vehicle displays, especially when it comes to enabling vehicle safety and user comfort with enhanced functionalities. Such displays are adhesively bonded in places. Liquid Optically Clear Adhesives (LOCA or LOC Adhesive) are preferred for use in displays as they cure to a clear state and allow light to pass through the cured adhesive. This provides both functional and aesthetic advantages over conventional adhesives that cure to an opaque state.

[0003] Vehicle displays continue to evolve with new designs presenting challenges to conventional adhesives. Some designs have adhesively bonded areas that are not exposed to radiation during the curing step (shadow areas). For these applications liquid optically clear adhesives are desired to cure in areas exposed to radiation as well as cure in the shadow areas not exposed to radiation (shadow cure). [0004] Some vehicle displays have clear plastic components that need to be bonded and/or require thick adhesive layer thicknesses. For these applications liquid optically clear adhesives are desired that can cure when exposed to only longer wavelength radiation that penetrates polymer materials and thick adhesive layer thicknesses.

[0005] Light Emitting Diodes (LEDs) have been developed that emit radiation in the longer UV wavelengths. Such LED lamps are more energy efficient and run cooler that traditional UV lamps. For these applications liquid optically clear adhesives are desired that can cure when exposed to LED lamps.

[0006] Vehicle displays are incorporating polymer materials such as poly(methyl methacrylate) (PMMA), polycarbonate (PC) and polyethylene terephthalate (PET). For these applications liquid optically clear adhesives are desired that can strongly bond to these materials and retain bond strength through a wide range of environmental conditions including temperatures up to 100°C and low temp at -40°C.

[0007] Vehicle displays are exposed to high temperature, high humidity and strong UV radiation. The displays and their components are expected to maintain clarity and not yellow during a lifetime of such exposure. For these applications liquid optically clear adhesives are desired that do not exhibit haze and yellowing, initially and after use.

[0008] Traditionally, silicone light and moisture dual curable LOCA resins have been used for vehicle displays. The silicone adhesive cures by exposure to UV radiation in exposed areas and by moisture cure in the shadow areas. Moisture cure in the shadow area relies on moisture permeation into that area, which can take a long time depending on moisture availability, moisture permeability and thickness of the adhesive. Silicone formulations typically require 2-3 days to reach full cure. Many customers desire faster shadow cure technology.

[0009] In this invention we describe a 2K dual UV and shadow hydrosilylation cure technology where the shadow hydrosilylation cure is achieved in a few minutes to a few hours at room temperature. The photo cure can also be achieved with longer wavelength LED irradiation. Under low intensity LED irradiation, some formulations showed delayed shadow cure after LED irradiation when only a photohydrosilation catalyst is used. This enables the use of formulations as a 1 K system with only the photolatent hydrosilylation catalyst without the need for thermal Pt catalyst.

Summary

[0010] In one embodiment the disclosure provides a two component (2K) liquid optically clear adhesive having both radiation cure and hydrosilylation cure mechanisms. In some embodiments hydrosilylation cure in the shadow areas can be achieved in a few minutes to a few hours at room temperature.

[0011 ] In one embodiment the two component (2K) liquid optically clear adhesive having both radiation cure and hydrosilylation cure mechanisms has both radiation induced hydrosilation and thermally induced hydrosilation mechanisms. [0012] In one embodiment the two component (2K) liquid optically clear adhesive having both radiation cure and hydrosilylation cure mechanisms can be cured using longer wavelength radiation from LED lamps.

[0013] In one embodiment the disclosure provides a one component (1 K) formulation with only a photohydrosilation catalyst. The one component (1 K) formulation has delayed cure in shadow areas after low intensity LED irradiation is used.

[0014] In one embodiment the one component (1 K) formulations can be used with only the photolatent hydrosilylation catalyst without any thermal Pt catalyst.

Detailed Description

[0015] The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0016] About or “approximately” as used herein in connection with a numerical value refer to the numerical value ± 10%, preferably ± 5% and more preferably ± 1% or less.

[0017] At least one, as used herein, means 1 or more, i.e. , 1 , 2, 3, 4, 5, 6, 7, 8, 9, or more. With reference to an ingredient, the indication refers to the type of ingredient and not to the absolute number of molecules. "At least one polymer" thus means, for example, at least one type of polymer, i.e., that one type of polymer or a mixture of several different polymers may be used.

[0018] The terms “comprising”, “comprises” and “comprised of” as used herein are synonymous with “including”, “includes”, “containing” or “contains”, and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.

[0019] When amounts, concentrations, dimensions and other parameters are expressed in the form of a range, a preferable range, an upper limit value, a lower limit value or preferable upper and limit values, it should be understood that any ranges obtainable by combining any upper limit or preferable value with any lower limit or preferable value are also specifically disclosed, irrespective of whether the obtained ranges are clearly mentioned in the context. [0020] Preferred and preferably are used frequently herein to refer to embodiments of the disclosure that may afford particular benefits, under certain circumstances. However, the recitation of one or more preferable or preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude those other embodiments from the scope of the disclosure.

[0021 ] The molecular weights given in the present text refer to number average molecular weights (Mn), unless otherwise stipulated. Molecular weight data can be obtained by gel permeation chromatography (GPC) calibrated against polystyrene standards in accordance with DIN 55672-1 :2007-08 at 35°C, unless otherwise stipulated. The weight average molecular weight M _w can be determined by GPC, as described for M _n . “Polydispersity index” refers to a measure of the distribution of molecular mass in a given polymer sample. The polydispersity index is calculated by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn).

[0022] As used herein a curable, one component (1 K) composition is a singular formulation that has sufficient commercial stability to be prepared, warehoused and shipped to an end user. The 1 K composition can be used without adding any additional components and will crosslink or cure when exposed to suitable conditions. As used herein a two component (2K) composition has two or more components. Each of the components is prepared, warehoused and shipped separately from the other components. The components are mixed immediately prior to use. Mixing of the components starts a cure reaction so commercial storage after mixing is not possible. [0023] As used herein, dark cure refers to curing of a photocurable composition that was exposed to photoradiation such as UV radiation before application to a substrate and cures on the substrate including in areas that are not exposed to subsequent photoradiation.

[0024] As used herein, shadow cure refers to curing of a composition without exposure of that composition to photo radiation such as UV radiation. Shadow cure is typically a result of curing brought about by mechanisms other than photoirradiation such as thermally induced curing or moisture induced curing. [0025] As used herein for each of the various embodiments, the following definitions apply:

[0026] Unless otherwise specifically defined, "acyl" refers to the general formula - C(O)alkyl.

[0027] Unless otherwise specifically defined, "acyloxy" refers to the general formula -O-acyl.

[0028] Unless otherwise specifically defined, "alcohol" refers to the general formula alkyl-OH.

[0029] Unless otherwise specifically defined, "alkenyl" or "lower alkenyl" refers to a linear, branched or cyclic carbon chain having from 1 to about 16 carbon atoms, and advantageously about 1 to about 6 carbon atoms, and at least one double bond between carbon atoms in the chain. Examples include, for example, ethylene, allene, butene, butadiene, hexene, hexadiene, 5, 5-dimethyl-1 -hexene and cyclohexene. Unless otherwise specifically limited an alkenyl group can be unsubstituted, singly substituted, or multiply substituted, with substituent groups in any possible position.

[0030] Unless otherwise specifically defined, "alkoxy" refers to the general formula -O-alkyl.

[0031] Unless otherwise specifically defined, "alkyl" refers to a linear, branched or cyclic alkyl group having from 1 to about 9 carbon atoms including, for example, methyl, ethyl, propyl, butyl, hexyl, octyl, isopropyl, isobutyl, tert-butyl, cyclopropyl, cyclohexyl, cyclooctyl, vinyl and allyl. Unless otherwise specifically defined, an alkyl group can be saturated or unsaturated and substituted or unsubstituted. Unless otherwise specifically limited, a cyclic alkyl group includes monocyclic, bicyclic and polycyclic rings, for example norbornyl, adamantyl and related terpenes.

[0032] Unless otherwise specifically defined, "alkylamino" refers to the general formula -(NH)-alkyl.

[0033] Unless otherwise specifically defined, "di-alkylamino" refers to the general formula -N-(alkyl).sub.2. Unless otherwise specifically limited di-alkylamino includes cyclic amine compounds such as piperidine and morpholine.

[0034] Unless otherwise specifically defined, "alkylmercapto" refers to the general formula -S-alkyl. [0035] Unless otherwise specifically defined, "alkynyl" or "lower alkynyl" refers to a linear, branched or cyclic carbon chain having from 1 to about 16 carbon atoms, and advantageously about 1 to about 6 carbon atoms, and at least one triple bond between carbon atoms in the chain. Examples include, for example, ethyne, butyne, and hexyne. Unless otherwise specifically limited an alkynyl group can be unsubstituted, singly substituted, or multiply substituted, with substituent groups in any possible position.

[0036] Unless otherwise specifically defined, an aromatic ring is an unsaturated ring structure having about 5 to about 6 ring members and including only carbon as ring atoms. Unless otherwise specifically defined, an aromatic ring can be substituted or unsubstituted.

[0037] Unless otherwise specifically defined, "aryl" refers to an aromatic ring system substituted or unsubstituted, that includes only carbon as ring atoms, for example phenyl, biphenyl or naphthyl.

[0038] Unless otherwise specifically defined, "aroyl" refers to the general formula --C(=O)-aryl.

[0039] Unless otherwise specifically defined, a carbocyclic ring is a ring structure having about 3 to about 8 ring members, substituted or unsubstituted, that includes only carbon as ring atoms, for example, benzene or cyclohexane.

[0040] Unless otherwise specifically defined, PDMS refers to polydimethylsiloxane.

[0041] Unless otherwise specifically defined, "halogen" refers to an atom selected from fluorine, chlorine, bromine and iodine.

[0042] Unless otherwise specifically defined, a heteroaromatic ring is an unsaturated ring structure having about 5 to about 8 ring members, substituted or unsubstituted, that has carbon atoms and one or more heteroatoms, including oxygen, nitrogen and/or sulfur, as ring atoms. Heteroaromatic rings (or groups) also include fused polycyclic systems in which one or more monocyclic aromatic ring or monocyclic heteroaromatic ring is fused to another heteroaromatic ring. Examples of heteroaromatic rings (or groups) include but are not limited to, furan, thiophene, pyrrole, oxazole, thiazole, isoxazole, pyrazole, imidazole, oxadiazole, triazole, tetrazole, pyridine, pyrimidine, pyrazine, purine, benzothiazole, benzimidazole, benzofuran, indole, quinoline, quinoxaline.

[0043] Unless otherwise specifically defined "heteroaryl" refers to an heteroaromatic ring.

[0044] Unless otherwise specifically defined, a heterocyclic ring is a saturated ring structure having about 3 to about 8 ring members, substituted or unsubstituted, that has carbon atoms and one or more heteroatoms, including oxygen, nitrogen and/or sulfur, as ring atoms. Examples of heterocyclic rings include but are not limited to oxetane, thietane, azetidine, diazetidine, tetrahydrofuran, thiolane, pyrrolidine, dioxolane, oxathiolane, imidazolidine, dioxane, piperidine, morpholine, piperazine, and their derivatives. Unless otherwise specifically limited a heterocyclic ring includes monocyclic, bicyclic and polycyclic rings, for example azaadamantyl and tropanyl.

[0045] Unless otherwise specifically defined, the term "phenacyl" refers to the general formula -phenyl-acyl.

[0046] Room temperature or r.t. refers a temperature of about 22 to 25°C.

[0047] Unless otherwise specifically defined, a spirocycle refers to a ring system wherein a single atom is the only common member of two rings. A spirocycle can comprise a saturated carbocyclic ring comprising about 3 to about 8 ring members, a heterocyclic ring comprising about 3 to about 8 ring atoms wherein up to about 3 ring atoms may be N, S, or O or a combination thereof.

[0048] Unless otherwise specifically limited the term substituted means substituted by at least one below described substituent group in any possible position or positions. Substituent groups for the above moieties useful in the disclosed compounds are those groups that do not significantly diminish the biological activity of the disclosed compound. Substituent groups that do not significantly diminish the biological activity of the disclosed compound include, for example, H, halogen, N3, NCS, CN, NO2, NX1X2, OX3, C(X4)s, OAc, O-acyl, O-aroyl, NH-acyl, NH-aroyl, NHCOalkyl, CHO, C(halogen)3, COOX4, SO3H, PO3H2, SO2NX1X2, CONX1X2, C(O)CF ₃ , alkyl, alcohol, alkoxy, alkylmercapto, alkylamino, di-alkylamino, sulfonamide or thioalkoxy wherein Xi and X2 each independently comprise H or alkyl, or Xi and X2 together comprise part of a heterocyclic ring having about 4 to about 7 ring members and optionally one additional heteroatom selected from 0, N or S, or Xi and X2 together comprise part of an imide ring having about 5 to about 6 members and X4 comprises H, alkyl, lower alkyl hydroxy, or alkyl-NX-iX2. Unless otherwise specifically limited, a substituent group may be in any possible position or any possible positions if multiply substituted.

[0049] The term “alkyl” is meant to mean straight or branched saturated hydrocarbon groups;

[0050] The term “substituted” means substituted with lower alkyl (C1-4), aryl, alkaryl, alkoxy( C 1-4), halo; additionally the term may also include a hetero atom such as O or N interrupting the C1-18 alkyl chain.

[0051] The terms “aromatic” or “aryl” means cyclic conjugated hydrocarbon structures (C 1-12) which may optionally be substituted as the term “substituted” is defined herein;

[0052] The terms “halogen,” “halo” or “hal” when used alone or as part of another group mean chlorine, fluorine, bromine or iodine;

[0053] The term “aliphatic” means saturated or unsaturated, straight, branched or cyclic hydrocarbon groups;

[0054] The term “oligomer” means a defined, small number of repeating monomer units such as 10 - 25,000 units, and desirably 10 - 100 units which have been polymerized to form a molecule, and is a subset of the term polymer. The term “polymer” means any polymerized product greater in chain length and molecular weight than the oligomer, i.e. greater than 25,000.

[0055] “One or more”, as used herein, relates to at least one and comprises 1 , 2, 3, 4, 5, 6, 7, 8, 9 or more of the referenced species. Similarly, “at least one” means one or more, i.e. 1 , 2, 3, 4, 5, 6, 7, 8, 9 or more. “At least one”, as used herein in relation to any component, refers to the number of chemically different molecules, i.e. to the number of different types of the referenced species, but not to the total number of molecules. For example, “at least one polyol” means that at least one type of molecule falling within the definition for a polyol is used but that also two or more different polyol types falling within this definition can be present but does not mean that only one type of said polyol is necessarily present. [0056] The disclosed compounds include any and all isomers and stereoisomers.

In general, unless otherwise explicitly stated the disclosed materials and processes may be alternately formulated to comprise, consist of, or consist essentially of, any appropriate components, moieties or steps herein disclosed. The disclosed materials and processes may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants, moieties, species and steps used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objective of the present disclosure.

[0057] The word “about” or “approximately” as used herein in connection with a numerical value refer to the numerical value ± 10%, preferably ± 5% and more preferably ± 1 % or less.

[0058] Unless explicitly indicated otherwise, all percentages that are cited in connection with the compositions described herein refer to weight percent (wt.%) with respect to final composition with all components, unless stated otherwise.

[0059] In one embodiment the curable liquid optically clear adhesive comprises a vinyl functional polyorganosiloxane; a SiH functional polydimethylsiloxane; a hydrosilation catalyst, an optional thermal hydrosilation catalyst and optional additives. The vinyl functional group on the polydimethylsiloxane can be pendent, in one terminal position, in both terminal positions or any combination. The SiH functional group on the polydimethylsiloxane can be pendent, in one terminal position, in both terminal positions or any combination.

[0060] In a 1 K variation the vinyl functional polyorganosiloxane; SiH functional polydimethylsiloxane; photohydrosilation catalyst, optional thermal hydrosilation catalyst and optional additives are all in the same part. In a 2K variation the vinyl functional polyorganosiloxane and photohydrosilation catalyst are in one part and the SiH functional polydimethylsiloxane is in a different part. The optional thermal hydrosilation catalyst and optional additives can be in either or both parts. vinyl functional polyorganosiloxane

[0061 ] The curable liquid optically clear adhesive comprises a vinyl functional polyorganosiloxane. The functional vinyl groups can be pendent, in one terminal position, in both terminal positions or any combination on the polyorganosiloxane molecule. Some vinyl functional polyorganosiloxanes have the formula H2C=CH[Si(B)2O]nSi(CH3)2CH=CH2, where n is the number of repeating monomer and is typically in the range of 0 to 500. Each B is independently selected from alkyl having 1 to 6 carbon atoms, for example CH3, vinyl (-CH=CH2), aryl, and fluoroalkyl.

[0062] Some examples of vinyl functional polyorganosiloxane include polymer VS50, VS100, VS200, VS500, VS1000, VS2000, VS5000, VS10,000 and VS200,000, all available from Evonik; GP977, GP907 and GP908, all available from Genesee polymers; DMS V35, DMS V05, DMS V52, DMS V25R, DMS V35R DMS V31 , DMS V22, DMS V51 , DMS V33, DMS V00, DMS V03,DMS Vm31 , DMS Vm35, DMS Vm41 , VDT-123, 127, 131 , 163, 431 , 731 , 954 and 5035 all available from Gelest.

SiH functional polydimethylsiloxane

[0063] The curable liquid optically clear adhesive comprises a SiH functional polydimethylsiloxane. Some SiH functional polydimethylsiloxanes can have the formula A(CH3)2SiO[Si(B)2O]nSi(CH3)2A; where n is the number of repeating monomer units and can be 1 to 500; A can be H or CH3; and each B is independently selected from H or CH3, with the proviso that the SiH functional polydimethylsiloxane contains at least one SiH moiety in the molecule. In some variations both A units are SiH. In some variations one or both A units are SiH and one or more B units are SiH. Typically, SiH functionality of about 2 at the terminal positions makes the polydimethylsiloxane act as a chain extender while SIH functionality greater than 2 including at a pendent position makes the polydimethylsiloxane act as a crosslinker. Examples include 100, 101 , 110, 120, 180, 190, 200 and 210 all available from Evonik; HMS 991 , 992, 993, 013, 031 , 053, 064, 071 , 082, 151 , 301 and 501 all available from Gelest. Other examples include Modifier 705 and 715 available from Evonik; GP535, GP678, GP499 and GP536 available from Genesee Polymers; DMS H03, H05, H11 , H21 , H25, H31 and H41 available from Gelest. photohydrosilation catalyst

[0064] The curable liquid optically clear adhesive comprises a photohydrosilation catalyst. Preferred photohydrosilation catalysts include platinum(ll) acetylacetonate (Pt(acac)2); Platinum hexafluroroacetylacetonate (Pt(HFAA)2); and combinations thereof. These catalysts are commercially available, typically as a mixture with another material for ease of handling and use. Other platinum catalysts such as [platinum(ll)(2- acetylcyclopentanoate)], [(platinum(ll)(2-acetylcyclohexanoate)], [platinum (ll)(benzoylacetonate)2 (Pt(ba)2)], [platinum(ll)(dibenzoylmethanate) (Pt(dbm)2)], [platinum(ll)2,4-pentanedionato(1 ,1 ,1-trifluoro-2,4-pentanedionate) (platinum(acac)(tfac))], [platinum (II) 1 ,1 ,1 ,5,5,5-hexafluro-2,4-pentanedionato(2,4- pentanedionate) (Pt(acac)(hfaa))], Platinum (ll)acetylacetonate sulfoxide complex can also be used. The synthesis of these catalysts is described in Eur. J. Inorg. Chem.

2005, 788-796; Chem. Mater. 1998, 10, 531-536; and Bull. Chem. Soc. Jpn., 1981 , 54, 1085-1095. thermal hydrosilation catalyst

[0065] The curable liquid optically clear adhesive can optionally comprise a thermal hydrosilation catalyst. Preferred thermal hydrosilation catalysts include Pt(0)1 ,3-divinyl-1 ,1 ,3,3-tetramethyldisiloxane complex, chloroplatinic acid, Wilkinson catalyst, Speier’s catalyst, Karstedt’s catalyst. These catalysts are commercially available, typically as a mixture with another material for ease of handling and use. When exposed to temperatures in a specific range the thermal catalyst will accelerate reaction of components in the adhesive composition. additives

[0066] The curable liquid optically clear adhesive can optionally comprise one or more additives, including plasticizer, diluent, adhesion promotor, catalyst, moisture scavenger, UV/light stabilizer, antioxidant, rheology modifier, colorant, filler and combinations thereof. [0067] The curable liquid optically clear adhesive can optionally comprise one or more plasticizers to adjust the elastic properties and to improve the processability of the composition. A plasticizer is understood to be a substance which reduces the viscosity of the composition and thus makes processing easier, and in addition improves flexibility and extensibility of the compositions.

[0068] The plasticizer is preferably selected from a fatty acid ester, a dicarboxylic acid ester (except cyclohexanedicarboxylic acid dialkyl ester), an ester of epoxidized fatty acids or fatty acids carrying OH groups, a fat, a glycolic acid ester, a benzoic acid ester, a phosphoric acid ester, a sulfonic acid ester, a trimellitic acid ester, an epoxidized plasticizer, a polyether plasticizer, a polystyrene, a hydrocarbon plasticizer and a chlorinated paraffin, and mixtures of two or more thereof. By the careful selection of one of these plasticizers or of a specific combination, further advantageous properties of the composition according to the invention, for example gelling properties of the polymers, low-temperature elasticity or low-temperature resistance or antistatic properties, can be achieved.

[0069] Among the polyether plasticizers, preferably end-capped polyethylene glycols are used, for example polyethylene or polypropylene glycol di-Ci-4-alkyl ethers, in particular the dimethyl or diethyl ethers of diethylene glycol or dipropylene glycol, and mixtures of two or more thereof. Also suitable as plasticizers are, for example, esters of abietic acid, butyric acid ester, acetic acid ester, propionic acid ester, thiobutyric acid ester, citric acid ester and esters based on nitrocellulose and polyvinyl acetate, as well as mixtures of two or more thereof. Also suitable are, for example, the asymmetrical esters of adipic acid monooctyl ester with 2-ethylhexanol (Edenol DOA, Cognis Deutschland GmbH, Dusseldorf). In addition, the pure or mixed ethers of monofunctional, linear or branched C4-16 alcohols or mixtures of two or more different ethers of such alcohols are suitable as plasticizers, for example dioctyl ether (available as Cetiol OE, Cognis Deutschland GmbH, Dusseldorf). Likewise suitable as plasticizers within the framework of the present invention are diurethanes, which can be produced e.g. by reaction of diols having OH end groups with monofunctional isocyanates, by selecting the stoichiometry so that substantially all free OH groups react fully. Any excess isocyanate can then be removed from the reaction mixture, e.g. by distillation. Another method for producing diurethanes consists in the reaction of monofunctional alcohols with diisocyanates, wherein as far as possible all NCO groups react fully. [0070] In principle, phthalic acid esters can also be used as plasticizers, but because of their toxicological potential these are not preferred.

[0071] The curable liquid optically clear adhesive can optionally comprise one or more diluents, either reactive or non-reactive. The reactive diluent preferably has at least one functional group which reacts with other components of the adhesive after application of the adhesive to a substrate. Examples of these groups are silyl groups, isocyanate groups, vinylically unsaturated groups and polyunsaturated systems. As reactive diluent, it is possible to use any compounds which are miscible with the composition according to the invention with a reduction of the viscosity and have at least one group that is reactive with the binder, individually or as a combination of several compounds. The viscosity of the reactive diluent is preferably less than 20,000 mPas, particularly preferably about 0.1 - 6000 mPas, most particularly preferably 1 - 1000 mPas (Brookfield RVT, 23°C, spindle 7, 10 rpm).

[0072] As reactive diluents it is possible to use, for example, polyalkylene glycols reacted with isocyanatosilanes (for example Synalox 100-50B, DOW), alkyltrimethoxysilane, alkyltriethoxysilane, such as methyltrimethoxysilane, methyltriethoxysilane and vinyltrimethoxysilane (XL 10, Wacker), phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, tetraethoxysilane, vinyldimethoxymethylsilane (XL12, Wacker), vinyltriethoxysilane (GF56, Wacker), vinyltriacetoxysilane (GF62, Wacker), isooctyltrimethoxysilane (IO Trimethoxy), isooctyltriethoxysilane (IO Triethoxy, Wacker), N-trimethoxysilylmethyl-O- methylcarbamate (XL63, Wacker), N-dimethoxy(methyl)silylmethyl-O-methylcarbamate (XL65, Wacker), hexadecyltrimethoxysilane, 3-octanoylthio-1 -propyltriethoxysilane and partial hydrolyzates of these compounds. Furthermore, the following polymers from Kaneka Corp, can also be used as reactive diluents: MS S203H, MS S303H, MS SAT 010 and MS SAX 350. Also suitable as reactive diluents are polymers which can be produced from an organic backbone by grafting with a vinylsilane or by reaction of polyol, polyisocyanate and alkoxysilane. [0073] Suitable as polyols for producing a reactive diluent are e.g., aliphatic alcohols include, for example, ethylene glycol, propylene glycol and higher glycols, as well as other polyfunctional alcohols. The polyols can additionally comprise other functional groups, such as e.g. esters, carbonates, amides. To produce a reactive diluent by reaction of polyol with polyisocyanate and alkoxysilane, the corresponding polyol component is reacted in each case with an at least difunctional isocyanate. Suitable as the at least difunctional isocyanate is in principle any isocyanate having at least two isocyanate groups, but within the framework of the present invention, compounds having two to four isocyanate groups, in particular two isocyanate groups, are generally preferred. Among the alkoxysilyl groups, the di- and trialkoxysilyl groups are preferred.

[0074] The polyisocyanates described above for producing polyurethanes are also suitable as polyisocyanates for producing a reactive diluent.

[0075] The diluent can also be a solvent. Suitable as solvents are aliphatic or aromatic hydrocarbons, halogenated hydrocarbons, alcohols, ketones, ethers, esters, ester alcohols, keto alcohols, keto ethers, keto esters and ether esters. Preferably, however, alcohols are used since alcohols can increase storage stability of the adhesive composition. C1-C10 alcohols are particularly preferred, particularly methanol, ethanol, isopropanol, isoamyl alcohol and hexanol.

[0076] The curable liquid optically clear adhesive can optionally comprise an adhesion promoter. Exemplary adhesion promoters are described in: Michel J. Owen, “Coupling agents: chemical bonding at interfaces”, in Adhesion Science and Engineering-2, Surfaces, Chemistry and Applications, M. Chaudhury and A. V. Pocius eds., Elsevier, New York, 2002, p. 403, incorporated by reference herein. Preferred adhesion promoters include organo-silanes which can link the silane-functional polymer to the surface such as amino silanes, epoxy silanes and silane containing olefins. Some exemplary aminosilane adhesion promoters include 3- aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl-3- aminopropyl)trimethoxysilane, 3-aminopropylmethyldiethoxysilane, 4-amino-3,3- dimethylbutyltrimethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, 1 - butanamino-4-(dimethoxymethylsilyl)-2,2-dimethyl, (N- cyclohexylaminomethyl)triethoxysilane, (N-cyclohexylaminomethyl)- methyldiethoxysilane, (N-phenylaminoethyl)trimethoxysilane, (N-phenylaminomethyl)- methyldimethoxysilane or gamma. -ureidopropyltrialkoxysilane. Particularly preferred amino silanes include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane. Some exemplary epoxy silane adhesion promoters include 3- glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane or beta-(3,4- epoxycyclohexyl)ethyltrimethoxysilane. Other silane adhesion promoters include mercaptosilanes. Some exemplary mercaptosilane adhesion promoters include 3- mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3- mercaptopropyltriethoxysilane. Some exemplary silane comprising olefin adhesion promoters include vinyltrialkoxysilane and allyltrialkoxysilane. The level of adhesion promoter employed can be from 0 to 4%, preferably 1 to 4% and more preferably 2 to 3% by weight based on the total weight of the high strength, moisture curable adhesive. [0077] The curable liquid optically clear adhesive can optionally comprise a moisture scavenger. Exemplary moisture scavengers include vinylsilanes such as 3- vinylpropyltriethoxysilane, oxime silanes such as methyl-O,O',O"-butan-2-one trioximosilane or O,O',O",O"'-butan-2-one tetraoximosilane (CAS no. 022984-54-9 and 034206-40-1 ); benzamidosilanes such as bis(N-methylbenzamido)methylethoxysilane (CAS no. 16230-35-6); carbamatosilanes such as carbamatomethyltrimethoxysilane; aminosilanes such as (3-aminopropyl)trimethoxysilane and combinations thereof. The use of methyl-, ethyl- or vinyltrimethoxysilane, tetramethyl- or tetraethylethoxysilane is also possible.

[0078] The curable liquid optically clear adhesive can optionally comprise a UV/light stabilizer. Exemplary light stabilizers include hindered amine light stabilizers (HALS) such as such as Tinuvin® 770 DF available from BASF, benzotriazoles such as Tinuvin® 328 available from BASF, benzophenones, benzoates, cyanoacrylates, acrylates, sterically hindered phenols, phosphorus and/or sulfur can also be added. Although the composition includes a photo (UV) cure mechanism, when used at customary amounts HALS were not seen to interfere with this photo cure mechanism. [0079] The curable liquid optically clear adhesive can optionally comprise a rheology modifier. Exemplary rheology modifiers include the Thixcin® materials available from Elementis Specialties and the Disparlon materials available from King Industries.

[0080] The curable liquid optically clear adhesive can optionally comprise a colorant. Exemplary coloring agents include carbon black, titanium dioxide, C.l. Pigment Blue 28, C.l. Pigment Yellow 53 and phthalocyanine blue BN. Fluorescing coloring agents can also be used to aid in inspection of the assembled component for presence of the adhesive.

[0081] The curable liquid optically clear adhesive can optionally comprise fillers. Exemplary fillers include lithopone, zirconium silicate, hydroxides, such as hydroxides of calcium, aluminum, magnesium, iron and the like, diatomaceous earth, carbonates, such as sodium, potassium, calcium, and magnesium carbonates, oxides, such as zinc, magnesium, chromic, cerium, zirconium and aluminum oxides, clay, nanosilica, silica that have been surface treated with a silane or silazane such as the AEROSIL products available from Evonik Industries, silica that have been surface treated with an acrylate or methacrylate such as AEROSIL R7200 or R711 available from Evonik Industries, precipitated silica, untreated fumed silica, graphite, synthetic fibers and mixtures thereof.

[0082] In one embodiment the one component (1 K) composition comprises: [0083] In one embodiment the two component (2K) composition comprises: [0084] Typically two component compositions will have catalyst(s) only in the one component that includes vinyl functional polysiloxane. All of the catalyst(s), vinyl functional polysiloxane and SiH containing materials should not be in one component to enhance stability and avoid premature curing of the adhesive composition.

[0085] The disclosed liquid optically clear adhesives can be prepared using the following general procedure. For the first part vinyl functional PDMS, UV catalyst and thermal hydrosilylation catalyst are mixed into one part under conditions to avoid exposure to UV radiation. For the second part SiH functional PDMS and optionally vinyl functional PDMS are taken. Each part is separately loaded into one barrel of a two component (2K) syringe. The loaded syringe should be stored in the absence of UV radiation. Black 2K syringes can be used to protect the composition parts from UV radiation. A longer static mixing nozzle with back pressure is used to ensure good mixing during dispensing. The formulation is used at a 1 : 1 ratio of the first part to the second part, although composition can also be designed to work at other ratios such as 2: 1 , 5: 1 or 10: 1 depending on molecular weights of the vinyl functional PDMS and SiH functional PDMS and by keeping the catalyst in only one reacting part.

[0086] In one embodiment the liquid optically clear adhesive can be applied to a first substrate in a variety of manners including extruding and as a bead. A second substrate is disposed adjacent the first substrate and into contact with the applied adhesive. The adhesive between the substrates is exposed to radiation, for example UV radiation, or heat or both radiation and heat in an amount sufficient to activate and/or cure the adhesive. Once activated, adhesive in shadow areas between the substrates will cure by hydrosilation.

[0087] In another embodiment useful with electronic assemblies such as displays and touch panel displays the typical process comprises the following steps align touch panels; apply LOCA adhesive to at least one of the touch panels; optionally vacuum degas before assembly (generally desirable for medium to large size panels); pre-cure with UV radiation; confirm/finalize touch panel alignment; fully cure with UV radiation. [0088] Liquid optically clear adhesives can have haze, color (b*) and % transparency values of less than or equal to 2 for each parameter, preferably less than or equal to 1 .5 for each parameter and more preferably less than or equal to 1 for each parameter.

[0089] In another embodiment the adhesive can be used as a potting material to seal electronic components where dark curing of the potting material is desirable.

Haze, color (b*) and % transparency values for a potting material are less of a concern and can be higher than for liquid optically clear adhesive use.

[0090] The following examples are included for purposes of illustration so that the disclosure may be more readily understood and are in no way intended to limit the scope of the disclosure unless otherwise specifically indicated.

EXAMPLES

[0091 ] The following components were utilized in the examples that follow. [0092] Samples were exposed to UV radiation using a Loctite Zeta 7216 bench top light cure system having a Hg vapor UV bulb in the UVA-UVC wavelength range or a Loctite 375nm LED flood system or a Loctite 405nm LED flood system Each system had an irradiation energy of about 3000 m J/cm ²

Measurement of Shore A hardness

[0093] The procedure is carried out in accordance with ASTM D2240.

Measurement of viscosity

[0094] Viscosity was tested using a Brookfield viscosimeter with a #27 spindle at 5 - 10 rpm and 25 °C.

Measurement of optical properties

[0095] The optical properties such as haze, color (b*) and % transparency were measured using Datacolor 650 spectrophotometer. The Datacolor 650 instrument was set up according to the manufacturer's instructions. The Datacolor procedure to measure haze uses ASTM D1003 Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics. Instrument - Datacolor 650 Transmission Spectrophotometer with Diffuse Illuminating Sphere and measuring angle of 8° to the plane of the sample being measured. Standard llluminant C2 Deg in specular included mode with 30 mm aperture in specular included mode. The CIE Lab result was collected in transmittance mode with the sample holder inside the sphere at the transmittance port. All spectra are compared to a 2 mm thick Gorilla Glass (Corning) standard.

[0096] Optical samples had a diameter of 1.5 inches with a thickness typically of 250 microns, unless otherwise noted. Sample thickness was controlled using spacer. To prepare samples two 250 micron spacers were placed toward the edge of a Gorilla glass (Corning) plate. 1 to 2 grams of the sample formulation was dispensed on the plate between the spacers and a second glass plate was placed carefully on the base glass plate containing spacer and the formulation so that no bubbles were formed. Two clamps were placed on either side close to the spacer. The sandwiched sample was then cured by exposure to UV radiation. After curing the sample was allowed maintained at room temperature for 24 hours before optical testing and data collection.

Example 1 - 2K curable composition with dual photo and thermal hydrosilation cure

1 Pt(acac)2 photohydrosilation catalyst is a premix of 115mg of Pt(acac)2 in 2.6g

1 ,3-dioxane.

2 Pt (0)1 , 3-d iviny 1-1 , 1 ,3,3-tetramethyldisiloxane complex thermal hydrosilation catalyst is a premix of Pt(0)1 ,3-divinyl-1 ,1 ,3,3-tetramethyldisiloxane complex solution in PDMS). A premix of the above catalyst (0.4g) in DMS V-22 (3g) was made.

[0097] Example 1 was made using both photo hydrosilylation catalyst Pt(acac)2 and thermal hydrosilylation catalyst Pt(0)1 ,3-divinyl-1, 1 ,3, 3, -tetramethyldisiloxane complex solution in PDMS. Typically, this would be a two-component system to achieve useful storage stability. For test purposes the components were mixed at the same time.

[0098] The formulation became a gel after UV irradiation with Loctite Zeta 7216 for 60 seconds. The initial gelling is coming from UV hydrosilylation only although thermal catalyst is used. The thermal hydrosilylation starts more slowly after this initial gelling as evidenced by increase in Shore hardness. The gel had a Shore 00 hardness of about 7. When stored at room temperature, there was increase in hardness to about 26 Shore 00 after 90 minutes and reaching a constant value of about 40 Shore 00 after 24 hours. The hardness increase after photocure was due to the thermal hydrosilylation reaction.

[0099] A sample of Example 1 was maintained at room temperature without exposure to a UV lamp, exemplifying a shadow cure. That sample became a gel in about 30 minutes

Example 2 - 1 K curable composition with only photo hydrosilation cure

[00100] The formulation of Example 1 was recreated without the thermal hydrosilylation catalyst. This formulation was irradiated with UV for about 60 seconds and a tack-free gel was obtained. This is evidence that Example 1 has both radiation hydrosilation and thermal hydrosilation cure mechanisms coming from both UV and thermal hydrosilylation catalysts.

Example 3 - 2K curable composition with dual photo and thermal hydrosilation cure [00101 ] A formulation was prepared using only 50ppm of the photohydrosilation catalyst and 25ppm of thermal hydrosilylation catalyst.

1 A premix of 115mg of Pt(acac)2 in 2.6g 1 ,3-dioxane was made

2 A premix of Pt(0)1 ,3-divinyl-1 ,1 ,3,3-tetramethyldisiloxane complex solution in

PDMS). A premix of the above catalyst (0.4g) in DMS V-22 (3g) was made

[00102] Typically, this would be a two-component system to achieve useful storage stability. For test purposes the components were mixed at the same time. [00103] The formulation was a gel after 60 sec UV irradiation with Loctite Zeta 7216 with a Shore 00 hardness of 1 . The Shore 00 hardness increased to 16 after 30 minutes at room temperature and to a constant value of 40 after 24 hours at room temperature.

Example 4 - 2K curable composition with dual photo and thermal hydrosilation cure

A solution of 30mg of Pt(acac)2 in 6.25g of g diethylene glycol diethyl ether was made.

2 A premix of Pt(0)1 ,3-divinyl-1 ,1 ,3,3-tetramethyldisiloxane complex solution in PDMS). A premix of the above catalyst (0.4g) in DMS V-22 (3g) was made

[00104] Typically, this would be a two-component system to achieve useful storage stability. For test purposes the components were mixed at the same time. [00105] The formulation was a gel after 60 sec UV irradiation with Loctite Zeta 7216 with a Shore 00 hardness of 1 . The Shore 00 hardness increased to 25 after 10 minutes at room temperature, to 33 after 90 minutes at room temperature and to a constant value of 38 after 24 hours at room temperature.

[00106] A sample of Example 4 was maintained at room temperature without exposure to a UV lamp, exemplifying a shadow cure. That sample became a gel after 4 hours.

[00107] Example 4 illustrates that the shadow cure by room temperature hydrosilylation can be slowed down by using additives having hetero atoms such as Tinuvin 292. This is believed due, at least in part, to interaction of the catalyst with the heteroatoms such as in thiols.

[00108] Formulation 4 shows that the shadow cure-only formula became a gel in about 4h at room temperature. This exemplifies one method of adjusting or tuning the composition open time for the shadow cure system using hetero atom containing additives.

Example 5 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation and extended shadow cure.

[00109] Curing feasibility of the disclosed liquid optically clear adhesives using LED lamps was investigated. A Loctite 375 nm LED flood unit was used for irradiation of formulations.

1 A solution of 30mg of Pt(acac)2 in 6.25g of g diethylene glycol diethyl ether was made.

[00110] Example 5, with no thermal hydrosilylation catalyst, was irradiated with 375nm radiation from a LED flood unit for 60 seconds. The material was a liquid after irradiation but became a gel after 15 minutes standing at r.t. The material had a Shore 00 hardness of 40 after 24 hours at room temperature. The delayed cure profile of Example 5 illustrates the feasibility of achieving shadow cure without the need for thermal hydrosilylation catalyst.

[00111 ] The formulation of example 5 can also be delay cured by irradiation with Loctite 405nm LED flood system for 60 seconds. The material was a liquid after irradiation but became a gel after 15 minutes standing at room temperature. The material had a Shore 00 hardness of 40 after 24 hours at room temperature. Example 6 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation and extended shadow cure.

[00112] Example 6 was made using lower amount of photohydrosilation catalyst (30ppm).

A solution of 30mg of Pt(acac)2 in 6.25g of g diethylene glycol diethyl ether was made.

[00113] Example 6, with no thermal hydrosilylation catalyst, was irradiated with 375nm radiation from a LED flood unit for 60 seconds. The material was a liquid after irradiation but became a gel after 30 minutes standing at room temperature. The material had a Shore 00 hardness of 30 after 24 hours at room temperature.

[00114] The formulation of example 6 can also be delay cured by irradiation with Loctite 405nm LED flood system for 60 seconds. The material was a liquid after irradiation but became a gel after 30 minutes standing at room temperature. The material had a Shore 00 hardness of 30 after 24 hours at room temperature.

[00115] Example 6 illustrates open time (time before gelling) can be tuned (in this Example increased) by adjusting (in this case decreasing) the photo hydrosilylation catalyst level.

Example 7 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation and extended shadow cure.

1 A solution of 46mg of Pt(acac)2 in 1 ,68g 1 ,3-dioxane was made. Used = 1 ,3mg of Pt(acac)2 catalyst, which is 47 mg of the solution, (about 50 ppm w.r.t Pt).

[00116] Example 7, with no thermal hydrosilylation catalyst and about 50ppm of photohydrosilation catalyst, was irradiated with 375nm radiation from a LED flood unit for 60 seconds. The material was a liquid after irradiation but became a gel after 10 minutes standing at room temperature. The Shore 00 hardness 30 minutes after LED irradiation is 32 and 35 after holding for 24 hours at room temperature.

[00117] The formulation of example 7 can also be delay cured by irradiation with Loctite 405nm LED flood system for 60 seconds. The material was a liquid after irradiation but became a gel after 15 minutes standing at room temperature.

Example 8 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation and extended shadow cure.

1 A solution of 30mg of Pt(acac)2 in 6.25g diethyleneglycol diethyl ether was made. Used = 0.7mg of Pt(acac)2 catalyst, which is 145 mg of the solution, (about 25 ppm w.r.t Pt). [00118] The Pt catalyst loading of Example 7 was decreased to about 25ppm in Example 8. Example 8 took longer (6 hours) to gel after irradiation with Loctite 375nm LED flood system for 60 seconds. The delayed gelling in this system could be coming from both decreased Pt catalyst and crosslinker level as compared to Example 7. The gelled material was too soft for a Shore 00 hardness measurement.

[00119] Example 8 also gelled after irradiation with 405nm Loctite LED flood system for 60 seconds and standing at room temperature for 6 hours.

Example 9 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation and extended shadow cure.

1 A solution of 46mg of Pt(acac)2 in 1 ,68g 1 ,3-dioxane was made. Used = 1 ,8mg of Pt(acac)2 catalyst, which is 65mg of the solution, (about 50 ppm w.r.t Pt).

[00120] Example 9 was prepared using an organic diallyl ether as one of the reacting components. Example 9 was a liquid after irradiation for 60 seconds with 375 nm Loctite LED flood system but gelled after 20 minutes standing at room temperature. [00121] Example 9 was a liquid after irradiation for 60 seconds with a 405nm Loctite LED flood system but gelled after 20 minutes standing at room temperature.

Optical aging results

[00122] Samples from some Examples were subjected to optical aging under heat (105°C), heat/humidity (85/85) and QUV conditions (ASTM G194 1 W/m ² , using QUV/se available from Q-Lab Corporation). After aging, the samples were tested using a Datacolor 650 spectrophotometer. The optical aging results are shown below.

[00123] Example 1 has good optical aging results after 1012 hours of aging under conditions as shown below. The haze, color and % transmittance were acceptable under the aging conditions indicating that this dual cure composition is suitable for liquid optically clear adhesive (LOCA) application.

[00124] Example 7 has good optical aging results after 1020 hours of aging under conditions as shown below. The color and % transmittance values were acceptable under the aging conditions indicating that this dual cure composition is suitable for liquid optically clear adhesive (LOCA) application. The haze value at 85°C/85% RH was high, however that value would be expected to decrease over time.

[00125] Example 8 has good optical aging results after 1020 hours of aging under conditions as shown below. The color and % transmittance values were acceptable under the aging conditions indicating that this dual cure composition is suitable for liquid optically clear adhesive (LOCA) application. The haze value at 85°C/85% RH was high, however that value would be expected to decrease over time.

[00126] Example 9 has good optical aging results after 820 hours of aging under conditions as shown below. The color and % transmittance values were acceptable under the aging conditions indicating that this dual cure composition is suitable for liquid optically clear adhesive (LOCA) application. The haze value at 85°C/85% RH was high, however that value would be expected to decrease over time.

Viscosity stability of photolatent 1 K formulation [00127] The presence of a delayed dark cure enables the use of hydrosilylation formulation as a 1 K formulation. All of the formulation components along with photohydrosilation catalyst can be prepared in one-part. That one-part formulation is warehoused, shipped, dispensed as needed and then irradiated to activate the photohydrosilation catalyst before the formulation is disposed onto a substrate. The activated formulation is dispensed onto a substrate. Curing occurs after assembling the components with activated adhesive dispensed thereon. To enable commercial use of a 1 K photolatent formulation, viscosity stability during storage of the 1 K system is crucial. Therefore, Examples 7 and 8 were stored in the dark as a 1 K formulation and the viscosity increase as a function of time was investigated. Table below shows that these formulations exhibit sufficient commercial stability to be used as a 1 K formulation.

Example 10 - UV preactivation of 2K hydrosilylation system

[00128] While Pt(acac)2 as a UV preactivated hydrosilylation catalyst gave good optical performance, tunable open time and good viscosity stability as a 1 K system, we investigated related other Pt catalysts. Platinum hexafl uroroacetylacetonate (Pt(HFAA)2) is also a commercially available catalyst. We developed two hydrosilylation formulations using this catalyst. [00129] Typically this would be a two component system to achieve useful storage stability. For test purposes the components were mixed at the same time.

[00130] Example 10 was a liquid after exposure to 405nm LED for 30 seconds and gelled in about 1 h upon standing at room temperature. The Shore 00 hardness for this formulation was 25 after 24h standing at room temperature.

[00131] The formulation that was not exposed to LED light became a gel in about 20h indicating that the latency of this catalyst was not as good as Pt(acac)2 and not good enough to use in a 1 K formulation. The Pt(HFAA)2 catalyst can be used as a 2K formulation with accelerated curing coming from UV exposure.

[00132] Example 10 prior to curing had an undesirable orange color due to the presence of Pt(HFAA)2 catalyst and would not be suitable for use as a liquid optically clear adhesive (LOCA) due to the color. Samples of Example 10 that were not exposed to UV radiation and gelled retained this undesirable orange color. Surprisingly, samples that were exposed to 405nm radiation from an LED lamp gelled to a colorless state and would be suitable for use as a liquid optically clear adhesive (LOCA). This shows that radiation curing not only makes the Pt(HFAA)2 catalyst formulation cure faster but also makes the Pt(HFAA)2 catalyst formulation cure to a desirable colorless state.

[00133] The samples were tested for optical properties at in the as cured state, e.g. no aging. Results of the optical property tests are shown below.

[00134] Example 10 showed good optical properties after 1000h of aging. Only the haze at 85°C/85% RH conditions was a higher, which is typical of silicone only adhesives. This result shows that UV preactivation can be used as a method to achieve good optical performance in a 2K system. Example 11 - 2K composition with no thermal hydrosilylation catalyst, LED irradiation and extended dark cure.

[00135] A 1 :1 2K formulation can be designed based where the Pt catalyst is only in the part that contains vinyl PDMS and not SiH functional silicone. This lessens premature gelling of the silicone formulation and provides commercially desirable stability.

A solution of 47.3mg of Pt(HFAA)2 in 0.64g of toluene was made (total = 0.68g).

[00136] The gel time would be very similar to the Example 10 1 K formulation.

Since the catalyst is with only one reacting component, stability is not an issue

Example 12 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation and extended dark cure.

1 A solution of 47.3mg of Pt(HFAA)2 in 0.64g of toluene was made (total = 0.68g). [00137] Example 12 was a liquid after irradiation for 30 seconds with 405 nm Loctite LED flood system but gelled after 60 minutes standing at room temperature. The Shore 00 hardness was 25 after 24 hours at room temperature.

[00138] The efficiency of UV preactivation using Pt(HFFA)2 catalyst was demonstrated using Example 12. After irradiating with 405nm LED for about 30 sec, this formulation became a gel in about 1 hour of standing at room temperature. The cured material was completely colorless. In contrast, samples of Example 12 (without LED radiation exposure) became a gel in about 5 hours of standing at room temperature, but the gelled material was visibly and undesirably colored. This result again showed the advantages of LED preactivation of hydrosilylation cure formulation containing Pt(HFFA)2 catalyst to obtain colorless cured material with faster cure time as compared to shadow cure-only formulation.

[00139] Samples of Examples 11 and 12, each using Pt(HFAA)2 catalyst, were tested for optical aging. The dark cure only formulation (without the UV radiation exposure) was highly colored and unusable as a liquid optically clear adhesive (LOCA). Surprisingly, the undesirable color imparted by the Pt(HFFA)2 catalyst was removed after 30 seconds LED irradiation as indicated by very low initial color of the 750u thick cured films as shown in the Table below.

[00140] Additional Examples comprising the Pt(HFFA)2 catalyst were tested for optical properties to confirm the unexpected and surprising loss of color after exposure to UV radiation.

Example 13 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation

1 Pt(HFFA)2 solution in EtOAc (a solution of 57mg of Pt catalyst in 0.87g of EtOAc) [00141] One set of samples from Example 13 were gelled by exposure to 405 nm radiation from a LED flood unit for 60 seconds. These samples were left at room temperature for 24 hours. Another set of samples from Example 13 was held at room temperature for 24 hours without exposure to UV radiation (dark cured). The samples were tested for optical properties at in the as cured state, e.g. no aging. Results of the optical property tests are shown below.

[00142] The shadow cured samples had a very high color and would not be usable as a liquid optically clear adhesive (LOCA). Surprisingly, the UV radiation cured samples had an acceptable color, as well as improved haze and transmittance.

Example 14 - 1 K composition with no thermal hydrosilylation catalyst, LED irradiation

Pt(HFFA)2 solution in EtOAc (a solution of 57mg of Pt catalyst in 0.87g of EtOAc)

[00143] One set of samples from Example 14 were gelled by exposure to 405 nm radiation from a LED flood unit for 60 seconds. These samples were left at room temperature for 24 hours. Another set of samples from Example 14 was held at room temperature for 24 hours without exposure to UV radiation. The samples were tested for optical properties in the as cured state, e.g. no aging. Results of the optical property tests are shown below.

[00144] The shadow cured samples had a very high color and would not be usable as a liquid optically clear adhesive (LOCA) due to that high color. Surprisingly, the UV radiation cured samples had an acceptable color, as well as improved haze and transmittance.

Example 15 - 1 K composition, LED irradiation

1 Pt(acac)2 solution in 1 ,3-dioxolane (a solution of 32mg of Pt catalyst in 1 g of 1 ,3- dioxalane)

[00145] One set of samples from Example 15 were gelled by exposure to 405 nm radiation from a LED flood unit for 60 seconds. These samples were left at room temperature for 24 hours. Another set of samples from Example 15 were gelled by holding them in a 60 °C oven for 4 hours without light exposure. The heated samples were subsequently held at room temperature for 24 hours without exposure to UV radiation. The samples were tested for optical properties in the as cured state, e.g. no aging. Results of the optical property tests are shown below.

[00146] The thermally cured samples had a high color and would not be usable as a liquid optically clear adhesive. Surprisingly, the UV radiation cured samples had a much lower and acceptable color.