Ultra-violet curable, pressure sensitive adhesives

Abstract

An ultra-violet (UV) curable, pressure sensitive adhesive (PSA) with high cohesive strength and high humidity resistance is described. The PSA has versatile cure profile and can be cured by conventional mercury bulbs or UV LED lamps and is particularly useful as a high-performance tape. In addition, the PSA is suitable for wide range of temperature processing, particularly from room temperature to 140⁰C. Articles of manufacture containing such adhesives are also described.

Description

ULTRA-VIOLET CURABLE, PRESSURE SENSITIVE ADHESIVESFIELD OF THE INVENTION

[0001] The present invention relates to an ultra-violet (UV) curable, pressure sensitive adhesive (PSA). The PSA has high cohesive strength, fast cure speed and high coating weight. The PSA also has a versatile cure profile and can be cured by conventional mercury bulb or UV LED lamp. The PSA is particularly useful as a high-performance tape. In addition, the PSA is suitable for low temperature processing, such as, for example, from about 25° C to about 140° C. The present invention also relates to articles of manufacture that include the PSA.BACKGROUND OF THE INVENTION

[0002] Pressure sensitive adhesives (PSAs) are aggressive, permanently tacky at room temperature, and adhere to surfaces by application of light finger pressure. PSA compositions are commonly applied to various substrates, such as paper, fabric, metal, and plastic films, which are then converted into many different products, such as pressure sensitive adhesive tapes and labels. These pressure sensitive adhesive products have a broad field of application in many industries, including the automobile industry for fastening or sealing, the pharmaceutical industry for bandages or transdermal drug delivery systems, and in the packaging industry for sealing, bonding, or labeling. PSAs can be formulated for application as a solution or a melt adhesive.

[0003] Hot melt pressure sensitive adhesives (HMPSAs) are compositions that combine the properties of hot melt adhesives with those of pressure sensitive adhesives. Hot melt adhesives are solid or semi-solid at room temperature and melt at elevated temperatures to coat on a substrate and regain their solid form on cooling. The combination of these properties provides compositions that melt at elevated temperatures and cool to form a permanently tacky solid coating that adheres on contact. A good workable HMPSA must exhibit high cohesive strength at room temperature, low shrinkage on substrates, retention of pressure sensitive properties during storage and use, and a relatively fluid viscosity at typical coating temperatures (e.g., between about 80° C and about 180° C). Although very low molecular weight polymers will yield hot melt adhesives with sufficient fluidity, the resultingadhesives lack cohesive strength. Very high molecular weight polymers give better cohesive strength but are too viscous at the common application temperatures to be easily coated on substrates. Accordingly, they must be blended with a high proportion of low molecular weight oils or resins to reduce the viscosity. The addition of low molecular weight oils or resins in turn detracts from the cohesive strength and heat resistance. To avoid these problems, polymers of moderate molecular weight have been made with various functional groups which undergo crosslinking reactions by heat or actinic radiation. In this manner, the cohesion of acrylic PSAs can be raised by means of sufficient crosslinking. Acrylic polymers with epoxy functional groups have been known. An example of such polymers is described in Japanese Patent Application No. 1186876. However, these polymers fail to crosslink under UV radiation and / or heat.

[0004] Japanese Patent Application No. 2008-208149 is directed to acrylic copolymers with non-polymerizable oxetane compounds as a polymerization medium and reactive diluent. Polymerization is achieved with heat and / or x-ray irradiation to form an adhesive for a flat panel display.

[0005] Japanese Patent Application Nos. 1994-0816 and 1996-060127 describe UV-curable acrylic polymers that require the addition of multifunctional polyol and other hydroxyfunctional groups for crosslinking the polymers.

[0006] Japanese Patent Application No. JP 2003147311 is directed to the use of photopolymerizable diacrylate. Due to the difunctional acrylate, it is less desirable for use in an adhesive because it becomes partially crosslinked before application onto substrates.

[0007] U.S. Patent Nos. 8,796,350 and 9,469,794 describe UV curable pressure sensitive adhesives that are coatable at temperatures of 80 - 180° C, which may be unsuitable for heatsensitive substrates and / or decrease the pot life of the adhesives.

[0008] There is therefore an ongoing demand and a continuing need in the art for UV-curable acrylic adhesives that are hot melt processable adhesives at a low temperature (such as, for example, from about room temperature to about 140° C) and curable with either conventional mercury UV lamps or UV LED lamps from about 365 nm to about 405 nm. In addition, alarge demand exists for improvements in fast cure rate and dark cure, for higher coating weights. The current invention addresses these needs by, e g., decreasing processability temperature and increasing bio-content.SUMMARY OF THE INVENTION

[0009] The present inventors have surprisingly found that UV-curable acrylic pressure sensitive adhesives that are hot melt processable adhesives at a low temperature may be prepared by including a silane co-catalyst (or a polymeric or oligomeric derivative thereof) in the composition. The addition of a silane co-catalyst (or its polymeric or oligomeric derivative) in the UV curable acrylic pressure sensitive adhesive offers multiple benefits.

[0010] First, the silane co-catalyst (or its polymeric or oligomeric derivative) improves the UV curing efficiency, especially for high coat weight adhesive films. Without wishing to be bound by theory, the inventors theorize that it helps transport super acid H+thereby enhancing the mobility of catalyst super acid inside the adhesive matrix after UV irradiation and during the dark cure process. It is known in the art that the presence of very small amounts of moisture or OH' from an alcohol will enhance the cationic curing efficiency due to increasing the mobility of H+. It is particular the case when alkoxy silane decomposes and generates alcohol and silanol (SiOH) functional groups in the presence of the super acid and moisture which is present either in the adhesive or from the air. The silanol functional group has a pKa of 5.0 to 14.0, which increases the mobility of H+, in comparison to moisture or alcohol with pKa of about 15 to 18.

[0011] A second benefit of the silane co-catalyst (or its polymeric or oligomeric derivative) is that it may act as an adhesion promoter for substrates such as metal, glass, plastics, ceramic, etc.

[0012] A third benefit of the silane co-catalyst (or its polymeric or oligomeric derivative) is that it acts as a moisture scavenger. It is well known that an excessive amount of moisture in the adhesive or air is detrimental to the cationic cure due the leveling-off effect of the water to the superacid. Under such condition, the adhesive may not cure well. Many alkoxysilanes are well known to act as moisture scavengers.

[0013] Yet another benefit of the presence of the silane co-catalyst (or its polymeric or oligomeric derivative) is to stabilize the adhesive before UV curing at elevated temperatures, especially above about 110° C. The improved thermal stability may be due to the combination effects that the silane co-catalyst (or its polymeric or oligomeric derivative) (i) reduces adhesive melt viscosity, (ii) removes the moisture and (iii) neutralizes any strong acid impurities acid from the cationic photoinitiator (pKa < 4.0). Typically, a UV cationic hotmelt adhesive is not thermally stable at elevated temperatures (such as, for example, above about 100° C) due to the strong acid residuals from either the acrylic monomers or acid impurities in the cationic photoinitiator, which initiates unwanted cationic crosslinking at temperatures above, for example, about 130° C.

[0014] In one aspect, the present invention relates to an ultra-violet (UV) curable acrylic pressure sensitive adhesive (PSA). The PSA exhibits high cohesive strength, fast cure speed and high coating weight for high performance tapes.

[0015] In one embodiment, the UV curable pressure sensitive adhesive comprises:(A) an acrylic polymer prepared from at least one acrylic monomer having a reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl SiR.3 (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen), benzophenone, or any combination of any of the foregoing;(B) a co-catalyst; and(C) a cationic photoinitiator.

[0016] In another embodiment, the UV curable pressure sensitive adhesive comprises:(A) about 80 wt. % to about 99.98 wt. % of an acrylic polymer having at least one terminal or pendant reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl SiIU (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino,enoxy, amino, amido, ester, H, or halogen), benzophenone, or any combination of any of the foregoing;(B) about 0.01 wt. % to about 10 wt. % of a cationic photoinitiator, a cationic and radical photoinitiator package, or a combination thereof; and(C) about 0.01 wt. % to about 10 wt. % of a silane co-catalyst; wherein the total weight of the ultra-violet curable pressure sensitive adhesive is 100 wt. %.

[0017] In one embodiment, the UV curable pressure sensitive adhesive has a viscosity of about 1,000 to about 100,000 cps at a coating temperature of, for example, between about 25° C and about 140° C.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a rheology comparison of the adhesives of Examples 6, 7 and 8.DETAILED DESCRIPTION OF THE INVENTION

[0019] All documents cited herein are incorporated in their entireties by reference.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present disclosure. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0021] As used herein, the term “alkyl” refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, containing no unsaturation, and which is attached to the rest of the molecule by a single bond. Examples include, but are not limited to, methyl, ethyl, 1 -propyl (n-propyl), 2-propyl (iPr), 1 -butyl, 2-methyl-l-propyl(i- Bu), 2-butyl (s-Bu), 2-dimethyl-2-propyl (t-Bu), 1 -pentyl (n-pentyl), 2-pentyl, 3 -pentyl, 2- methyl-2 -butyl, 3-methyl-2-butyl, 3 -methyl- 1 -butyl, 2-methyl-l -butyl, 1 -hexyl, 2-hexyl, 3-hexyl, 2-m ethyl -2-pentyl, 3-methyl-2-pentyl, 4-m ethyl -2-pentyl, 3 -methyl -3 -pentyl, 2- methyl-3 -pentyl, 2,3-dimethyl-2-butyl, 3,3-dimethyl-2-butyl, / / -heptyl, / -octyl, / / -nonyl, n- decyl, n-undecyl, / / -dodecyl, / / -tridecyl, / / -tetradecyl, / / -pentadecyl, / / -hexadecyl, n- heptadecyl, / / -octadecyl, / / -nonadecyl, and / / -icosyl. In some embodiments, the term alkyl refers to Ci-nalkyl (C1-12 hydrocarbons), for example to Ci-9alkyl (C1.9 hydrocarbons), or to Ci-ealkyl (Ci-6 hydrocarbons).

[0022] As used herein, the term “aryl” refers to an aromatic hydrocarbon of 6-20 carbon atoms derived by the removal of hydrogen from a carbon atom of a parent aromatic ring system. Typical aryl groups include, but are not limited to, 1 ring, or 2 or 3 rings fused together, derived from benzene, naphthalene, anthracene, biphenyl, and the like.

[0023] As used herein, the term “alkoxy” refers to a group having the formula -ORawherein Rais alkyl as defined above. Non-limiting examples of suitable C1-6 alkoxy include, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy and hexyloxy.

[0024] As used herein, the term aryloxy refers to group having the formula -ORbwherein Rbis aryl as defined above.

[0025] As used herein, the term acetoxy refers to the group -OC(O)CH3.

[0026] As used herein, the term “oximino” refers to the group -C(=N-OH)-RC, wherein Rcis hydrogen, alkyl or aryl as defined above.

[0027] As used herein, the term “enoxy” refers to -OC(CH3)=CH2.

[0028] As used herein, the term “amino” refers to -NRdRe, wherein Rdand Reare each, independently, hydrogen, alkyl or aryl as defined above.

[0029] As used herein, the term “amido” refers to the group -C(O)NRfRg, wherein Rfand Rgare each, independently, hydrogen, alkyl or aryl as defined above

[0030] As used herein, the term “ester” refers to a compound, which is formed by reaction between an acid and an alcohol with elimination of water. An ester can be represented by thegeneral formula RCOOR' (where R and R’ are, for example, each independently selected from alkyl and aryl).

[0031] As used in the specification and in the claims, the term "comprising" may include the embodiments "consisting of and "consisting essentially of." The terms "comprise(s)," "include(s)," "having," "has," "can," "contain(s)," and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients / steps and permit the presence of other ingredients / steps. However, such description should be construed as also describing compositions or processes as "consisting of and "consisting essentially of the enumerated ingredients / steps, which allows the presence of only the named ingredients / steps, along with any impurities that might result therefrom, and excludes other ingredients / steps.

[0032] Numerical values in the specification and claims of this application, particularly as they relate to polymers or polymer compositions, reflect average values for a composition that may contain individual polymers of different characteristics. Furthermore, unless indicated to the contrary, the numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0033] All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (for example, the range of "from 2 to 10" is inclusive of the endpoints, 2 and 10, and all the intermediate values). The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and / or values. As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about," may not be limited to the precise value specified, in some cases. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. The modifier "about" should also be considered asdisclosing the range defined by the absolute values of the two endpoints. For example, the expression "from about 2 to about 4" also discloses the range "from 2 to 4." The term "about" may refer to plus or minus 10% of the indicated number. For example, "about 10%" may indicate a range of 9% to 11%, and "about 1%" may mean from 0.9% to 1.1%. Other meanings of "about" may be apparent from the context, such as rounding off, so, for example "about 1" may also mean from 0.5 to 1.4.

[0034] As used herein, a polymer or an oligomer refers to a macromolecule that consists of monomer units equal or greater than about 2 monomer units. Polymer, copolymer and oligomer are used interchangeably herein.

[0035] As used herein, the terms “pressure sensitive adhesive” and “PSA,” are used interchangeably, and refer to a viscoelastic material which adheres instantaneously to most substrates with an application of slight pressure and remains permanently tacky.

[0036] As used in herein, the term, "essentially free" means that the composition has less than about 1% by weight, such as less than about 0.5 % by weight, less than about 0.4 % by weight, less than about 0.3 % by weight, less than about 0.2 % by weight, less than about 0.1 % by weight, or less than about 0.05 % by weight of a named component, and preferably, may not include more than trace amounts of the named component.

[0037] As used herein, the term, “no additional added component” means that the named component is purposefully not added, while trace amounts may be present.

[0038] In one embodiment, the present invention is directed to an ultra-violet (UV) curable pressure sensitive adhesive comprising:(A) an acrylic polymer having one or more reactive terminal or pendant functional groups bound to the acrylic polymer backbone (e.g., one or more reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl -SiRj (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen), benzophenone, and any combination of any of the foregoing;(B) a co-catalyst; and(C) a cationic photoinitiator.

[0039] The acrylic polymer (A) having one or more reactive terminal or pendant functional groups bound to the acrylic polymer backbone undergoes fast cationic crosslinking under the catalysis of a super acid generated by the decomposition of the cationic photoinitiator under UV irradiation. The initial fast crosslinking provides green strength to the adhesive, and a post-UV crosslinking (i.e., dark cure) that continues over a couple of minutes and up to a few days provides high cohesive strength and high adhesion performance over a wide range of application temperatures.

[0040] The acrylic polymer (A) may be prepared from:(i) about 0.01 wt. % to about 20 wt. % of a first monomer having a reactive functional group selected from a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl -SiRa (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen), benzophenone , or mixtures of any of the foregoing; and(ii) about 80 wt. % to about 99.99 wt. % of a second acrylic monomer comprising an acrylic or methacrylic acid derivative of the formula CH2=CH(RI)(COOR2), wherein Ri is H or CH3 and R2 is a linear, branched or cyclic C1-24 alkyl chain, or a linear, branched or cyclic Ci-24 alkyl -aryl chain containing the functionality of an ethoxy link, a hydroxy group, or mixtures of any of the foregoing; and optionally, (iii) about 0.1 wt. % to about 20 wt. % of a third monomer having a reactive silyl functional group -SiRs, wherein R is selected from the group consisting of (a) alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, halogen, or a combination thereof, and (b) a reactive benzophenone containing acrylic monomer.In one embodiment, the amount of the first monomer (i) is from about 0.01 to about 20 g per 100 g of the acrylic polymer. In one embodiment, the amount of the first monomer (i) is from about 0.1 to about 10 g per 100 g of the acrylic polymer.

[0041] In another embodiment, the acrylic polymer (A) is prepared from:(i) about 0.1 wt. % to about 10 wt. % of a first monomer having a reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, or mixtures of any of the foregoing(ii) (ii) about 70 wt. % to about 99.8 wt. % of a second acrylic monomer comprising an acrylic or methacrylic acid derivative of the formula CH2=CH(RI)(COOR2), wherein Ri is H or CH3 and R2 is selected from the group consisting of a C1-24 alkyl chain, an alkyl-aryl chain, and an alkyl-aryl derivative containing the functionality of an ethoxy link, a hydroxy group, or mixtures of any of the foregoing; and(iii) about 0.1 wt. % to about 20 wt. % of a third monomer having a reactive silyl functional group -S1R3, wherein R is selected from the group consisting of (a) alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, halogen, or a combination thereof, and (b) a reactive benzophenone containing acrylic monomer.

[0042] Suitable first monomers (i) of the polymer that is, e.g., capable of undergoing a UV- activated cationic crosslinking reaction and providing green strength to the adhesive, include, but are not limited to, vinyl or acrylic compounds containing cationic UV-reactive functional groups of the formula (1):whereinR1is O, S, C=O, or a linear, branched, or cyclic alkylene, oxyalkylene, or arylene,R2is a linear, branched, or cyclic alkyl, alkoxy, aryl, H, halogen, C=O, or is part of R1as a fused cycloaliphatic ring through a covalent bond connection,R3is (CH2)nwhere n is 0, 1 , 2 or 3;X is acrylate, methacrylate or comprises a -W-Y group,W is O, S, amide, carbonate, urethane, urea, siloxane, or a combination thereof, andY is -R4-C(R5)=CH2, where R4is a linear or branched C2-10 alkylene or C2-10 oxyalkylene, arylene or derivative thereof, and R5is H or CH3.

[0043] One suitable first monomer (i) is represented by the structural formula (1 A):

[0044] Another compound for use as the first monomer (i) is represented by the structural formula (IB):where R2= H or CH3,

[0045] Another compound for use as the first monomer (i) is represented by the structural formula ( 1 C):

[0046] Another compound for use as first monomer (i) is represented by the structural formula (ID):

[0047] Another compound for use as first monomer (i) is represented by the structural

[0048] Another compound for use as first monomer (i) is represented by the structural formula (IF):

[0049] Another compound for use as first monomer (i) is represented by the structural formula (1G):

[0050] Another vinyl or acrylic compound for use as first monomer (i) is represented by the structural formula (1H):where R6= H or CH3.

[0051] Another compound for use as first monomer (i) is represented by the structural formula (II):where R = H or CH3

[0052] In another embodiment, the first monomer (i) is a vinyl or acrylic compound capable of undergoing either a fast UV activated cationic crosslinking reaction or a slow post UV crosslinking reaction, and thus providing the adhesive with high performance adhesion strength. Exemplary monomers include, but are not limited to, glycidyl methacrylate (GMA), 4-hydroxybutylacrylate glycidyl ether (4-HBAGE), cycloaliphatic epoxide monomer Ml 00 and A400 (Daicel), TTA15 and TTA16 (Tetra), OXE-10 (Kowa), UVICURE S105 and S170, CD535 (Sartomer), 4-vinyl-l-cyclohexene-l,2-epoxide (DOW). Another example of a suitable monomer has the formula (2A):

[0053] The acrylic monomer (ii) comprises one monomer or a mixture of monomers from acrylic or methacrylic acid derivatives of the formula CH2=CH(R1)(COOR2), wherein R1is H or CH3 and R2is a Ci -24 alkyl, a C1-24 alkyl chain with aryl functionality, or an ethoxy link with a continuing repeating unit wherein the repeating unit can be interrupted or ended with an aryl derivative and can contain hydroxy groups, or R2 can directly be selected from an aryl derivative. Examples of the acrylic monomer (ii) include, but are not limited to, methyl acrylate, ethyl acrylate, ethyl methacrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, and n-octyl acrylate, n-nonyl acrylate, lauryl methacrylate, cyclohexyl acrylate, branched (meth)acrylic isomers, such as i-butyl acrylate, i-butyl methacrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, stearyl methacrylate, and isooctyl acrylate, benzyl acrylate, ethoxylated nonyl phenyl acrylate, 2-hydroxy-3 -phenoxypropyl acrylate, phenoxy ethyl acrylate, and mixtures of any of the foregoing. In one embodiment, an exemplary acrylic monomer (ii) is a monofunctional acrylate and does not include any di- or multi-acrylate monomers.

[0054] The choice and relative amount of the specific acrylic and vinyl monomers present in the acrylic polymers used in preparing the adhesives described herein depend upon the desired final properties and contemplated end uses of the adhesives. The choices of which acrylic and vinyl monomer or monomers and their relative amount in the final composition to achieve the desired properties are within the expertise of those of ordinary skill in the art.

[0055] In certain embodiments of any of the UV curable pressure sensitive adhesives described herein, the acrylic polymer has a Tg value less than about 10° C and a weight average molecular weight (Mw) from about 1,000 to about 3,000,000 g / mol. To achieve a high cohesive strength and high performance of the UV curable adhesive, higher molecular weight acrylic polymers are desirable. The preferred weight average molecular weight (Mw) of the acrylic polymers may be from about 50,000 to about 2,000,000 g / mol, such as from about 200,000 to about 1,000,000 g / mol. For a room temperature coatable UV curable pressure sensitive adhesive, the preferred weight average molecular weight (Mw) of the acrylic polymers is from about 5,000 to about 500,000 g / mol, such as from about 10,000 to about 100,000 g / mol.

[0056] For the polymerization process, the first monomer (i) and the acrylic monomer (ii) are converted by radical polymerization into acrylic polymers or copolymers. In the polymerization process, the monomers are chosen such that the resulting polymers can be used to prepare adhesives, especially such that the resulting polymers possess pressure sensitive adhesive properties in accordance with the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, N.Y. 1989). For these applications, the glass transition temperature of the resulting polymers will be below about 10° C, such as below about 0° C.

[0057] In one embodiment, the acrylic polymer is essentially free or is free of multi- (meth)acrylate, polyol or OH-functional groups and the polymer remains essentially linear after polymerization.

[0058] In one embodiment, the matrix of the UV curable pressure sensitive adhesive comprises: (A) an acrylic polymer having reactive pendant functional groups, selected from a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl SiFU (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen), benzophenone, or a mixture of any of the foregoing, bound to the acrylic polymer backbone. The reactive functional groups of the polymer undergo a UV crosslinking reaction in the presence of (B) the cationic photoinitiator or a cationic and radical photoinitiator package to form a crosslinked network having high cohesive strength over a wide range of application temperatures.

[0059] The UV curable pressure sensitive adhesive further comprises a cationic photoinitiator (B). The primary function of the cationic photoinitiator is to initiate a crosslinking reaction of the acrylic polymer (A) when irradiated by UV light. The mechanism of a cationic photoinitiator, when UV irradiated, forms an excited state which then breaks down to release a cation radical. This cation radical reacts with the solvent, moisture, or other hydrogen atom donors, and generates a protonic acid, which is the active species that initiates the crosslinking reaction of the acrylic polymer (A). The radical reactive functional groups such as (meth)acrylic C=C react with the cation radical decomposed from the cationic photoinitiator upon UV irradiation. Such a reaction hinders the formation of the superacid. Preferably, the adhesive compositions of the present invention are essentially free or are free of any radical reactive functional groups such as mono- or multi-(meth)acrylate to avoid competition and interference between radical cure and cationic cure during UV irradiation.

[0060] A number of cationic photoinitiators may be used to crosslink the acrylic polymer (A) of this invention, including, but not limited to, iodonium and sulfonium salts. These include, for example, diaryliodonium salts, triarylsulfonium salts, dialkylphenylsulfonium salts, dialkyl(hydroxydialkylphenyl)sulfonium salts and ferrocenium salts. The anions in theses salts generally possess low nucleophilic character and include SbFe , PFe , AsFe , BF4 ,B(CeFs)4 or Ga(C6Fs)4 , PFn(Rf)6-n . Specific examples include, for example, Omnicat 320 (Omnicat is a cationic, photoinitiator based on mixed triarylsulphonium hexaantimonate salts in 50% propylene carbonate) from IGM, SPEEDCURE 937, SPEEDCURE 938, SPEEDCURE 939 (SPEEDCURE is 4,6-trimethylbenzoyldiphenylphosphine oxide) from Sartomer, CPI-310B, CPI-200K, CPI-210S (CPI is a triarylsulfonium salt type photoinitiator) and IK-1 (from San-Apro). Particularly useful cationic photoinitiators for use in the present invention are soluble and LED reactive sulfonium salt photoinitiators having the structural formulae (6A) and (7A):2H5,C3H7, C12H25, OCH3, OC2H5, OC3H7, or OC12H25.

[0061] These cationic photoinitiators have a good solubility in the UV curable pressure sensitive adhesive of the present invention, promote efficient thick film UV curing, and exhibit thermal stability before cure, exhibit increased curing rates, and have a reduced dark cure time.

[0062] In a further embodiment, the cationic photoinitiator of the UV curable pressure sensitive adhesive has the following structure:where R is C3H7, C12H25, and W is S, SO, SO2 or CO.

[0063] A photosensitizer can be used in addition to a cationic photoinitiator to enhance crosslinking efficiency as a photoinitiator package, particularly when LED light sources in UVA range of from about 365 nm to about 405 nm, are used to cure the adhesive which contains conventional UVB and UVC cationic photoinitiators. Examples of photosensitizers include, but are not limited to, thioxanthen-9-one, 2-isopropylthioxanthone (ITX), 2- chlorothioxanthen-9-one, 2,4-diethyl-thioxanthen-9-one (DETX), l-chloro-4- propoxythi oxanthone (CPTX), anthraquinone, phenanthrenequinone, and camphorquinone.

[0064] The UV curable pressure sensitive adhesives described herein comprise a silane cocatalyst (C). The silane co-catalyst, or its polymeric or oligomeric derivatives, acts as a stabilizer to stabilize the adhesive at elevated temperature above, e.g., about 100° C, and at the same time it enhances the mobility of the super acidic proton in the curing adhesive matrix after UV irradiation. Another effect of the silane, or its polymeric or oligomeric derivatives, is to promote the adhesion to different substrates, such as, e.g., metal, glass, plastic, and ceramic. Yet another effect is that many of these silanes act as a moisture scavenger.

[0065] Any suitable silanes may be employed in the present invention, such as, for example, alkoxy and hydroxy functional silanes, and polymeric or oligomeric derivatives thereof. Examples of silanes that are useful in the present invention include, but are not limited to, Ci-C24 alkyltrialkoxysilane, (meth)acryl oxypropyl trialkoxysilane, chloropropylmethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrismethoxyethoxysilane, vinylbenzylpropylthmethoxysilane, aminopropyltrimethoxysilane, vinylthacetoxysilane, glycidoxypropyltrialkoxy silane, beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, mercaptopropylmethoxy silane, 3 -aminopropyltri ethoxy silane, aminomethyltrimethoxy silane, aminomethyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, and mixtures thereof, particularly preferably of silane is vinyltrialkoxysilane, C1-C24 alkyltrialkoxysilane, (meth)acryloxypropyl trialkoxysilane, glycidoxypropyltrialkoxysilane, (3,4- epoxycyclohexyl) ethyltrialkoxysilane, and oligomeric or polymeric derivatives thereof, or a mixture of any of the foregoing

[0066] Additional examples of silanes (and polymeric or oligomeric derivatives thereof) include polymeric or oligomeric VTMO (vinyltrimethoxysilane) and VTEO (vinyltriethoxy silane), commercially available from Evonik as Dynasylan 6490 and Dynasylan 6498. Other examples of functional polymeric and / or oligomeric adhesion promoters that are useful in the present invention include, but are not limited to, hydrolyzable PDMS polymer or oligomer, e.g., PDMS (poly dimethylsiloxane) that is endcapped with trialkoxylsilyl (meth)acrylates, dialkoxysilyl (meth)acrylates or methacrylates groups.

[0067] In one embodiment, the UV curable pressure sensitive adhesive comprises:(i) about 80 wt. % to about 99.98 wt. % of an acrylic polymer having at least one pendant reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl SiR? (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen), benzophenone, or mixtures thereof any of the foregoing;(ii) about 0.01 wt. % to about 10 wt. % of a cationic photoinitiator or a cationic and radical photoinitiator package; and(iii) about 0.01 wt. % to about 10 wt . % of a co-catalyst. wherein the total weight of the UV curable pressure sensitive adhesive is 100 wt. %.

[0068] Any of the UV curable pressure sensitive adhesives described herein optionally further comprises a reactive diluent. The reactive functional groups of both the polymer and the reactive diluent undergo a UV crosslinking reaction in the presence of (B) the cationic photoinitiator or a cationic and radical photoinitiator package to form a crosslinked network having high cohesive strength over a wide range of application temperatures. The reactive diluent of the UV curable pressure sensitive adhesive may be a polymer, oligomer or macromer comprising at least one terminal or pendant functional group selected from a cycloaliphatic epoxide, an oxirane, an oxetane, a vinyl ether, a cycloaliphatic epoxy silyl, or mixtures of any of the foregoing. The reactive diluent is essentially free, or free, of any mono- or multi-(meth)acrylates. The reactive diluent may have a weight average molecular weight from about 100 to about 500,000 g / mol. In addition, the reactive diluent may be an epoxy functionalized soybean oil, epoxy functionalized polybutadiene, epoxy-functional polyurethane, epoxy functionalized polysiloxane, epoxy functionalized polybutadiene, epoxy functionalized polyisobutylene, epoxy-difunctionalized bisphenol A epoxy resin, epoxydifunctionalized bisphenol F epoxy resin, epoxy functionalized polyacrylate, epoxy functionalized polyethylene glycol, epoxy functionalized polypropylene glycol, epoxy functionalized polyether or a mixture of any of the foregoing.

[0069] One primary function of the diluent is to reduce and control the viscosity of the adhesive so it can be coated at low temperature. Low adhesive viscosity and low coating temperature is always preferred for thermal stability of the adhesive, heat sensitive substrates, and LED cure and low energy consumption of coating process. However, non-reactive diluents typically compromise the cohesive strength of the adhesive. To achieve a high cohesive strength and high performance of the UV curable adhesive, normally a higher molecular weight and high viscosity acrylic polymers are used. The reactive diluent in the adhesive composition reduces the viscosity down to coatable range of about 1,000 to about 100,000cps between about 25 and about 120° C, and more importantly, does not deteriorate the cohesive strength of the adhesive after UV cure. The reactive diluent participates in the cationic crosslinking reaction and therefore increases crosslinking density to enhance the adhesive’s cohesive strength. The reactive diluent, however, must be balanced with a controlled amount of epoxy functionality between the acrylic polymer and the reactive diluent to avoid over-crosslinking leading to adhesive films with low peel, low tack, and poorwettability. Examples of commercially available reactive diluents include CELLOXIDE 2021P, CELLOXIDE 8000, CELLOXIDE 2081, EHPE 3150, EPOLEAD GT401, EPOLEAD PB Series, EPOFRIEND Series (from Daicel Corp ); UVICURE S128, UVICURE S150, UVICURE S160 (from Sartomer); EPON 828, EPON 862(from Hexicon Inc.); KF-8100, KF-8145, KF-12102, KEW-L2000, KET-L3000 (from Kolon Industries); and D.E.R. 335, 321, 324, 325, 326 liquid epoxy resins (from Olin Epoxy).; TTA20, TTA22, TTA26, TTA34, TTA60, TTA184, and TTA186 from Tetra. The reactive diluent can range from about 1 to about 50 wt. %, based on the total weight of the UV curable adhesive.

[0070] One particular embodiment of the reactive diluent is bio-based or made from a biosource. Bio-based or bio-sourced reactive diluents can be produced by reaction of renewable precursors, such as vegetable oils, saccharides, tannins cardanols, terpenes, rosins, and lignins. Examples of bio-based reactive diluent include vikoflex-7170 and epoxidized soybean oil. These diluents are compatible with the acrylic polymers described herein, and also slow the post-UV cure process with longer shadow cure and improve the wettability of the adhesive to substrates. Such wettability and bonding improvement enhance the adhesive strength over wide range of application temperatures, with a SAFT value of up to about 200° C.

[0071] Any of the UV curable pressure sensitive adhesives described herein may optionally further comprise a tackifier, a plasticizer, a thermal stabilizer, an antioxidant, a moisture scavenger, a desiccant, a solvent, or any combination of any of the foregoing.

[0072] Any of the UV curable pressure sensitive adhesives described herein may optionally further comprise a tackifier, e.g., from about 1 wt. % to about 50 wt. % of the adhesive, which are conventionally used in the preparation of PSAs. See e.g., "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, 1989). In general, it is possible to use any natural resins which are compatible with the corresponding acrylic polymers. Non-limiting examples include pinene resins, indene resins, rosins, terpene resins, terpene-phenolic resins, gum rosin, wood rosin, tail-oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, polymerized rosin; and their disproportionated, and esterified derivatives and salts, and combinations of any of the foregoing.

[0073] Other suitable tackifiers include, e.g., aliphatic and aromatic hydrocarbon resins, hydrogenated hydrocarbon resins, and functional hydrocarbon resins. Non-limiting examples include aliphatic and aromatic hydrocarbon resins, C5 resins, and C9 resins. Any desired combination of any of these resins may be used to adjust the properties of the resultant PSA in accordance with the desired final properties.

[0074] Specific examples of these tackifiers include, TECKROS R80H and R86 (from Teckrez Inc.); SYLV ALITE RE 85GB (from Kraton); FORAL 85-E (from Eastman); WINGTACK 95, CLEARTACK W85 (from Cray Valley); Kristalex 3085 (from Synthomer); and Lawter T90 (from Lawter). One preferred embodiment of the tackier is a liquid tackifier, which may further reduce the viscosity of the adhesive. Examples include polymerized C5 petroleum feed stream and polyterpenes such as, for example, WINGTACK 10 (from Cray Valley); ESCOREZ 2520 (from Exxon Mobil); and liquid rosin ester tackifier SYLVALITE 2038 (from Kraton).

[0075] Any of the UV curable pressure sensitive adhesives described herein may optionally further comprise a thermal stabilizer (e.g., a stabilizer to slow the tackifier oxidation and minimize color change due to changes in temperature), or an antioxidant. Examples of thermal stabilizers and antioxidants that may be used include high molecular weight hindered phenols and multifunctional phenols, such as sulfur and phosphorous containing phenols. Hindered phenols are well known to those skilled in the art and may be characterized as phenolic compounds which also contain sterically bulky radicals in close proximity to the phenolic hydroxyl group. Any known thermal stabilizer may be suitable. Preferred classes of thermal stabilizers include, but are not limited to, phenolic antioxidants, alkylated monophenols, alkylthiomethylphenols, hydroquinones, alkylated hydroquinones, tocopherols, hydroxylated thiodiphenyl ethers, alkylidenebisphenols, O-, N- and S-benzyl compounds, hydroxybenzylated malonates, aromatic hydroxybenzyl compounds, triazine compounds, aminic antioxidants, aryl amines, diaryl amines, polyaryl amines, acylaminophenols, oxamides, metal deactivators, phosphites, phosphonites, benzylphosphonates, ascorbic acid (vitamin C), hydroxylamines, nitrones, thiosynergists, benzofuranones, indolinones, and mixtures thereof. Examples of commercially available stabilizers include, for example, IRGANOX 1010, IRGANOX 1520, IRGANOX 1726,EVERNOX 1726, IRGANOX 565, IRGANOX 3114, EVERNOX 10 (IRGANOX AND EVERNOX are primary phenolic antioxidant stabilizers), IRGASTAB FS301 (IRGASTAB is a blend of oxidized bis(hydrogenated tallow alkyl) amines), TINUVIN 123, TINUVIN 292, TINUVIN 5100, TINUVIN 249, TINUVIN 770 (TINUVIN is a amine stabilizer based on an amino-ether functionality), BHT (butylated hydroxytoluene), and 4-MEHQ (4- m ethoxy phenol, from Sigma Aldrich).

[0076] Use of a thermal stabilizer is optional and, in some instances, may not preferred. When a thermal stabilizer is used, it may be present at a level of about 0.001 g to about 0.5 g by weight, based on the total 100 g by weight of the adhesive.

[0077] In a further embodiment of any of the UV curable pressure sensitive adhesives described herein, a desiccant may be used to improve the moisture barrier properties of the adhesive. Fillers with desiccant properties, referred to as desiccant fillers, suitable for use may include any that provide an appropriate moisture scavenging rate, capacity, and residual moisture level (the lowest level of moisture at which the desiccant can actively scavenge water) to meet the allowable moisture level for the specific electronic device. The desiccant fillers are capable of reacting with or adsorbing water and / or water vapor. A representative list of such desiccants can be found in, e.g., Dean, J. Lange's Handbook of Chemistry, 1999, McGraw Hill, Inc., New York, NY, pp. 11 .5. When a desiccant is used as a moisture scavenger, it may be present at a level of about 0.001 % to about 0.5 % by weight based on the total weight of the adhesive.

[0078] Any of the UV curable pressure sensitive adhesives described herein may also comprise additional additives, such as plasticizers and fillers, all of which are conventionally used in the preparation of PSAs. Any desired combination of these or other additives may be used to adjust the properties such as viscosity and rheology of the resultant adhesive in accordance with the desired final properties, as known to one of skill in the art.

[0079] In addition, one or more plasticizers or non-reactive diluents, such as low molecular weight acrylic polymers, phthalates, whale oil plasticizers, mineral oils, or plasticizer resins, may be added to the UV curable pressure sensitive adhesive, to adjust the viscosity, wettability, and rheology of the adhesive before and after cure.

[0080] The UV curable pressure sensitive adhesives described herein may be mostly 100% solid, or in either hot melt, warm melt or room temperature liquid form. The adhesives may have a Brookfield viscosity of from about 1,000 to about 1000,000 cps at the coating temperature, typically about 25 to about 140° C, such as a Brookfield viscosity of about 1,000 to about 100,000 cps at about 25° C to about 120° C. Such viscosity range allows the adhesive to be coat-able into films. The film thickness ranges from about 25 pm to about 250 pm, such as from about 50 pm to about 150 pm.

[0081] As known by those skilled in the art, the preparation of acrylic polymers can be performed in solution, as an emulsion, or bulk polymerization procedures using well-known free radical polymerization techniques in batch or continuous processes. The polymers and the uncured adhesives can then be formed into pure adhesives by removal of the solvent, coagulation of the latex, or melt-processing of the neat polymers.

[0082] Polymerization may be conducted in the presence of one or more organic solvents and / or in the presence of water. Suitable organic solvents or mixtures of solvents includes, for example, alkanes, such as hexane, heptane, octane, isooctane, and cyclohexane; aromatic hydrocarbons, such as benzene, toluene, and xylene; esters, such as ethyl, propyl, butyl and heptyl acetate; halogenated hydrocarbons, such as chlorobenzene; alkanols, such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; ethers, such as diethyl ether and dibutyl ether; ketones, such as acetone, methyl ethyl ketone; or mixtures of any of the foregoing.

[0083] In one embodiment of the process, the polymerization reaction proceeds in ethyl acetate solvent in the presence of the free radical initiator AIBN (2, 2'-azobis-(2 -methyl propionitrile), AMBN (2,2'-azobis(methylbutyronitrile), or Luperox® LP dilauroyl peroxide initiator.

[0084] In another embodiment of the process, the polymerization reaction proceeds in a binary solvent system of ethyl acetate and isopropanol in the presence of the free radical initiator AIBN, AMBN, or Luperox LP.

[0085] The acrylic polymers prepared for the UV curable pressure sensitive adhesive of the invention generally have an average molecular weight (Mw) of from about 1,000 to about 3,000,000 g / mol, such as between about 5,000 and about 500,000 g / mol. The molecular weight may be determined by gel permeation chromatography (GPC) or matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS).

[0086] To be formulated and used as a UV curable pressure sensitive adhesive of the present invention, the acrylic polymers are essentially free or are free of a solvent (e.g., an organic solvent). Any solvent being used in making the acrylic polymer and formatting the UV curable adhesive may be removed in a reaction tank or vacuum mixer before coating. However, the UV curable pressure sensitive adhesive can be also formulated to be a solvent borne or water borne adhesive and be used to make an adhesive film, then subsequently removing the solvent or water by drying the adhesive film.

[0087] The UV curable pressure sensitive adhesives according to any of the embodiments described herein are essentially free or are free of any radical reactive functional groups, to avoid competition and interference between radical cure and cationic cure during UV irradiation. The radical reactive functional groups, e.g., (meth)acrylic C=C, react with cation radical fragments decomposed from the cationic photoinitiator upon UV irradiation, can hinder the formation of the superacid. Such radical curable components are for example mono- or multi-(meth)acrylate.

[0088] In yet another aspect, the present invention relates to an article of manufacture comprising a UV curable, pressure sensitive adhesive according to any of the embodiments described herein. The article of manufacture may be, for example, a film form of a tape, a label, graphic, or a coating. Application of the UV curable pressure sensitive adhesive to the article of manufacture may be accomplished using any conventional means, such as roller, slot orifice, spray, curtain or extrusion coating. Non-limiting examples of substrates are films, tapes, sheets, panels, foam, and the like. These can be made of materials such as, e.g., paper, fabric, metal foil, glass, plastic (e.g., polyesters, polyethylene, polypropylene, biaxially oriented polypropylene (BOPP), and polyvinyl chloride), nonwoven fiber, metal, foil, glass, natural rubber, synthetic rubber, wood, plywood, and cement. If a coated substrateis used in the form of a self-wound roll, the back of the substrate is usually coated with a release coating to prevent the adhesive from adhering to the reverse side of the substrate. If a substrate is coated with the adhesive on both sides and rolled, a strippable paper or other protective means is laid over the adhesive on one side to prevent that adhesive from adhering to the adhesives on the other. In some embodiments, a second substrate may be applied directly to the adhesive.

[0089] In some articles with pressure sensitive adhesives, the adhesive is applied to a backing or substrate before crosslinking. The adhesive may typically be formulated to have a sufficient coatable viscosity in temperatures ranges of about 25 to about 180° C.

[0090] The UV curable, pressure sensitive adhesives of the present invention have a melted viscosity of about 1,000 to about 100,000 cps at application temperatures of about 25° C to about 140° C. The presence of a reactive diluent reduces the viscosity of the adhesive, allowing for lower application temperatures ranging from about 25° C to about 120° C. The lower application temperatures are particularly preferred for heat sensitive substates, including electronic devices.

[0091] A pressure sensitive adhesive film may be formed by applying the neat adhesive to a release liner, such as silicone coated paper or plastic film, and then after UV light irradiation, the adhesive may be removed from the release liner and used as a free film, to be laminated and transferred to a targeting substrate. The UV curable pressure sensitive adhesives described herein can be crosslinked in air by irradiation with UV light in the range from about 200 to about 500 nm, such as about 280 to about 400 nm, depending on the cationic photoinitiator present in the adhesive composition. Irradiation may be done immediately, such as while the adhesive film is freshly coated. A nitrogen blanket may also be used during the coating and curing process to exclude moisture.

[0092] The adhesive composition may be irradiated by UV light for a period of time sufficient to transform the low cohesive composition into a viscoelastic adhesive of higher modulus. The exact length of UV exposure or dosage is dependent upon the nature and intensity of the UV light, the amount of cationic photoinitiator, the acrylic polymer and the adhesive composition, the thickness of the adhesive film, environmental factors, such asrelative humidity and temperature, and the distance between the radiation source and the adhesive fdm. The dosage or the length of UV exposure may be controlled by the line speed. It may be appropriate to adapt the lamp output to the line speed or to shade off the line belt partly, to reduce its thermal load to heat sensitive substrate. The adhesive composition may also be irradiated by UV light at elevated temperatures from about 50° C to about 150° C, with heating sources from the UV lamp itself or added infrared lamp or oven. UV cure at high temperatures speeds up the curing rate and avoids humidity influence on the post-UV cure process.

[0093] Actinic light from any source may be used on the adhesive, provided the source furnishes an effective amount of UV radiation. Suitable sources of UV light include, e.g., carbon arcs, mercury -vapor arcs, fluorescent lamps with special ultraviolet light emitting phosphors, electronic flash lamps and lasers of specific wavelengths, UV LED, or combinations of any of the foregoing. Preferred lamps are the electrodeless microwave powered lamps from Fusion Systems, or commercially customary high or medium pressure mercury (H and / or D) lamps with an output of, for example, from about 80 W / cm to about 240 W / cm. A preferred UV light is a high intensity LED with a wavelength of about 365 nm, about 385 nm, about 395 nm, about 405 nm, or any combination thereof. The adhesive compositions described herein generally exhibit their maximum sensitivity to wavelengths in the ultraviolet range of about 280 nm to about 400 nm.

[0094] The adhesives described herein may be used to bond a first substrate to a second substrate. Suitable substrates include, but are not limited to, paper, plastic, glass, plastic- coated glass, wood, cement, metal, and foil. The adhesive may be applied by a variety of methods including, e.g., coating or spraying in an amount sufficient to cause the substrates to be bonded together to adhere. The adhesive coated substrate may be irradiated before or after bonding. Since the crosslinking reaction begins immediately upon UV irradiation, but may not be completed for several days, there is time immediately after irradiation, but before gelation for bonding to take place. Occasionally, the bond is made before UV irradiation for optimum wet out and adhesion.

[0095] The pressure sensitive adhesives described herein may advantageously be used in the manufacture of adhesive articles including, but not limited to, industrial tapes and transfer films. The tape may be a single or a double face tape, and the film may be a supported or unsupported free film. In one embodiment, the adhesive article comprises an adhesive as described herein coated on at least one major surface of a backing having a first and second major surface. Useful backing substrates include, but are not limited to, foam, metal, paper, fabric, and polymers such as, e.g., polypropylene, a polyamide, a polyester, polyethylene terephthalate, and mixtures of any of the foregoing. The adhesive may be present on one or both surfaces of the backing. When the adhesive is coated on both surfaces of the backing, the adhesive coatings can be the same or different.

[0096] In one embodiment, the present invention also relates to an UV curable pressure sensitive adhesive according to any of the embodiments described herein, wherein the adhesive has an application temperature between about 40° C and about 200° C and wherein the adhesive is stable such that the viscosity of the adhesive does not change more than about 15 % over about 24 hours.

[0097] In one embodiment, the present invention also relates to an UV curable, pressure sensitive adhesive according to any of the embodiments described herein, wherein the adhesive has a viscosity between about 5,000 cps and about 200,000 cps at an application temperature between about 25° C and about 140° C.

[0098] In one embodiment, the present invention also relates to an UV curable, pressure sensitive adhesive according to any of the embodiments described herein, wherein the adhesive is stable at a temperature of less than about 140° C for about 48 hours.

[0099] The following table provides additional exemplary parameters for any of the adhesives described herein.

[0100] The following examples are provided to describe the invention in further detail. These examples, which set forth a preferred mode presently contemplated for carrying out the invention, are intended to illustrate and not to limit the invention.EXAMPLES

[0101] Adhesives and their properties were tested according to the following test procedures or methods described below.

[0102] Viscosity

[0103] A Brookfield DV-I viscometer was used to measure viscosity. For testing, 11 g of sample was used with a No. 27 spindle at a speed setting from 2 to 4 rpm at a temperature from 110 to 140° C.

[0104] Preparation of Adhesive Coatings

[0105] A bench top Chemsultants® hot melt laminator coater was used to make the adhesive coatings. The adhesive was heated to 110 to 120° C and coated onto a 2 mil (51 pm) thick silicone-coated PET release liner. The adhesive on the PET liner was irradiated at certain line speeds to reach the necessary UV dosage. The UV light sources were either H- bulb (Fusion Systems) or a Heraeus 365 nm LED lamp. The film was then laminated and transferred to a polyethylene terephthalate substrate (MylarK, DuPont) and conditioned at 23° C and 50% relative humidity, unless otherwise specified.

[0106] UV Dosage

[0107] The UV dosage was measured and recorded using an EIT Power Puck II.

[0108] Shear Adhesion

[0109] Shear adhesion was measured according to Procedure A, PSTC-107, adapted as follows. All test samples of the acrylic polymers were UV irradiated according to the procedure described above. The shear adhesion was measured under a shear load of 1 kg on a ’A” x 1” area, applied after wetting out the test panel for 15 minutes. All testing was performed at 23° C and 50 % relative humidity. The time to failure was recorded.

[0110] Loop Tack

[0111] Loop tack was measured according to Test Method B, PSTC-16, adapted as follows. A loop tack tester was used for the measurement. All test samples of the acrylic polymers were UV-irradiated according to the procedure described above. The adhesive was coated on 2 mil PET fdm backing and the size of a specimen strip was 6” x 1”.

[0112] Peel Adhesion

[0113] Peel adhesion at 180° C between the substrate and the adherend test was measured according to Test method A, PSTC-101, adapted as follows. All test samples of the acrylic polymers were UV-irradiated according to the procedure described above. The peel strength was measured after wetting out a stainless-steel panel for 15 minutes.

[0114] Shear Adhesion Failure Temperature (SAFT)

[0115] Three samples, 1” x 3” in dimension, were cut from each cured sample in the machine coating direction. SAFT panels (mirrored steel) were cleaned with ethyl acetate. Samples were adhered to the steel panel overlapping up to an engraved line so that a square 1” x 1” of adhesive was in contact with the test panel. The test area was rubbed using a straight edged wooden applicator to ensure good contact between the panel and test sample. Samples were placed into the test oven at room temperature. The heating program was started, and 1 kg shear load applied when the temperature reached 40° C. The oven temperature was ramped at 0.5° C / minute up to 200° C and the shear adhesion failure temperature (SAFT) was recorded.Example 1 (Comparative Example)

[0116] A four-neck IL round-bottom polymerization flask was equipped with a thermometer connected to a temperature control device, a condenser, an overhead mechanical stirrer, two addition funnels, and nitrogen inlet / outlet. The set-up was purged with nitrogen gas for 15 minutes. A mixture of the following monomers was prepared: 2- ethylhexylacrylate (468.00 g), methyl acrylate (428.94 g), l-acrylomethyl-3,4-cyclohexene epoxide (3.06 g). To one of the funnels was charged 675.00 g of the monomer mixture. To another funnel was charged the initiator 2,2'-azobis-(2-methyl propionitrile) (AIBN, 3.60 g) and ethyl acetate (100 mL). To the polymerization flask was charged the remaining monomer mix (225.00 g), initiator AIBN (1.20 g), and ethyl acetate (750 mL). The mixture was heated to vigorous reflux and held for 15 minutes. Then, the monomer mixture in the funnel was added continuously over 2 hours at a constant rate. Simultaneously, the initiator solution in the funnel was added continuously over 3 hours at a constant rate. Upon complete addition of initiator solution, the mixture was stirred for an additional 3 hours at reflux. An acrylic polymer was obtained with a weight average molecular weight (Mw) of 227,000 g / mol and a poly dispersity index (PDI) of 6.5 by gel permeation chromatography (GPC). The polymerization solution was cooled to 60°C. TECKROS R86 (185.00g), Epon 828 (121.00), and Omnicat 320 (6.00g) were added and mixed thoroughly for 30 min. A UV curable pressure sensitive adhesive (PSA 1) was obtained having a viscosity (Brookfield) of 74,000 cps at 110° C.Example 2

[0117] A four-neck IL round-bottom polymerization flask was equipped with a thermometer connected to a temperature control device, a condenser, an overhead mechanical stirrer, two addition funnels, and nitrogen inlet / outlet. The set-up was purged with nitrogen gas for 15 minutes. A mixture of the following monomers was prepared: 2- ethyihexylacrylate (468.00 g), methyl acrylate (428.94 g), l-acrylomethyl-3,4-cyclohexene epoxide (3.06 g). To one of the funnels was charged 675.00 g of the monomer mixture. To another funnel was charged the initiator (AIBN, 3.60 g) and ethyl acetate (100 mL). To the polymerization flask was charged the remaining monomer mix (225.00 g), initiator AIBN (1.20 g), and ethyl acetate (750 mL). The mixture was heated to vigorous reflux and held for 15 min. Then, the monomer mixture in the funnel was added continuously over 2 hours at aconstant rate. Simultaneously, the initiator solution in the funnel was added continuously over 3 hours at a constant rate. Upon complete addition of initiator solution, the mixture was stirred for an additional 3 hours at reflux. An acrylic polymer was obtained with weight average molecular weight Mw of 227,000 g / mol and PDI of 6.5 by GPC. The polymerization solution was cooled to 60°C. TECKROS R86 (185.00g), Epon 828 (121.00g), Omnicat 320 (6.00g) and 1% vinyltrimethoxysilane (VTMO, 6.00g). were added and mixed thoroughly for 30 min. A UV curable pressure sensitive adhesive (PSA 2) was obtained having a viscosity (Brookfield) of 68,000 cps at 110° C.Example 3

[0118] The UV curable pressure sensitive adhesive of Examples 1 and 2 were separately coated onto 2 mil polyethyelene terephthalate (PET) film at 110 - 120° C into 50 gsm, and 100 gsm (grams per square meter) thickness and cured with a ultraviolet curing (UV-C) dosage of 2 mJ / cm2per gsm by a Fusion H bulb. Properties of the PSA were tested on stainless steel panels according to PSTC methods for the shear and SAFT. The resulting properties are shown in Table 1. As can be seen from Table 1, with the addition of VTMO (Example 2), the UV curable pressure sensitive showed lower melt viscosity and its viscosity changes over time at 110° C were less and thus more thermally stable for the hotmelt coating process. Furthermore, the cohesive strength and high temperature adhesion strength were dramatically improved.Table 1 - VTMO Effects on Film ThicknessExample 4

[0119] A four-neck IL round-bottom polymerization flask was equipped with a thermometer connected to a temperature control device, a condenser, an overhead mechanical stirrer, two addition funnels, and nitrogen inlet / outlet. The set-up was purged with nitrogen gas for 15 minutes. A mixture of the following monomers was prepared: 2- ethyihexylacrylate (500.00 g), methyl acrylate (396.85 g), l-acrylomethyl-3,4-cyclohexene epoxide (3.15 g). To one of the funnels was charged 675.00 g of the monomer mixture. To another funnel was charged the initiator (AIBN, 4.00 g) and ethyl acetate (100 mL). To the polymerization flask was charged the remaining monomer mix (225.00 g), initiator AIBN (0.80 g), and ethyl acetate (800 mL). The mixture was heated to vigorous reflux and held for 15 minutes. Then, the monomer mixture in the funnel was added continuously over 2 hours at a constant rate. Simultaneously, the initiator solution in the funnel was added continuously over 3 hours at a constant rate. Upon complete addition of initiator solution, the mixture was stirred for an additional 3 hours at reflux. An acrylic polymer was obtained with weight average molecular weight Mw of 206,000 g / mol and PDI of 6.8 by GPC. The polymerization solution was cooled to 60° C. TECKROS R86 (200.00 g), Epon 828 (120.00 g) were added and mixed thoroughly for 30 min. After ethyl acetate was removed by under vacuum at 60 to 120° C, and then Omnicat 320 (6.00 g) and VTMO (13.00 g) were added and mixed thoroughly for 30 minutes. A UV curable pressure sensitive adhesive was obtained having a viscosity (Brookfield) of 66,000 cps at 110° C. The PSA demonstrated an outstanding thermal stability at high temperatures, as shown in Table 2.Table 2 - Melt Viscosity ComparisonExample 5

[0120] The UV curable pressure sensitive adhesive of Example 4 was coated onto a 2 mil PET film at 110 to 120° C into 120 gsm thickness and cured with a UV-C dosage of 240ml / cm2by a Fusion H bulb. Some of the adhesive films were also aged in a humidity chamber at 35° C and 95% relative humidity right after being UV cured. Properties of the PSA were tested on stainless steel panels according to PSTC methods for the shear and SAFT. With the addition of VTMO (Example 4), the UV curable pressure sensitive showed good cohesive and adhesive strength, and high temperature adhesion strength, with all the failure modes being desirable adhesive failure. However, without VTMO, as in Example 1, all the failure modes for shear, SAFT, peel and tack were cohesive failure. The PSA film even after it was conditioned at a high humidity condition immediately after UV cure, maintained the PSA properties in comparison to Example 1 under the same humidity condition. The resulting PSA properties are shown in Table 3.Table 3 - Post Cure ComparisonExample 6

[0121] A 2 -liter reactor was equipped with an anchor agitator, a condenser and two automatic injection pumps. Injection pump 1 was charged with a monomer solution of methyl acrylate (87.6 g), 2-ethylhexyl acrylate (97.9 g), 3, 4-epoxy cyclohexylmethyl methacrylate (2.07 g), ethyl acetate (32.5 g). Injection pump 2 was charged with an initiator solution of AIBN (1.14 g) and ethyl acetate (60 g). The reactor was purged with nitrogen for 15 minutes. Then, methyl acrylate (29.2 g), 2-ethylhexyl acrylate (32.6 g), AIBN (0.16 g), 3, 4-epoxy cyclohexylmethyl methacrylate (0.69 g) and ethyl acetate (217.5 g) were added to the reactor. The reaction was heated to reflux and held for 15 minutes. Then, the monomersolution was added through injection pump 1 continuously over 3 hours at a constant rate. Simultaneously, the initiator solution was added through injection pump 2 continuously over 3 hours at a constant rate. After addition, the mixture was stirred for an extra 3 hours at reflux. Upon completion, the reaction solvent and any volatiles were removed under vacuum at reflux temperature. The resulting polymer was cool to room temperature under nitrogen. Photoinitiator Omnicat 320 (0.05 wt. %) was added and mixed for 30 minutes. The final product was coated on a 2-mil thick polyester film to give a l-mil thick dry adhesive, cured with 20 mJ / cm2of UV-C and then tested for pressure sensitive adhesive properties. See Table 4.Example 7

[0122] A 2 -liter reactor was equipped with an anchor agitator, a condenser and two automatic injection pumps. Injection pump 1 was charged with a monomer solution of methyl acrylate (87.6 g), 2-ethylhexyl acrylate (97.9 g), 3, 4-epoxy cyclohexylmethyl methacrylate (1.13 g), 3-methacryloxypropyltrimethoxysilane (0.94 g) and ethyl acetate (32.5 g). Injection pump 2 was charged with an initiator solution of AIBN (1.14 g) and ethyl acetate (60 g). The reactor was purged with nitrogen for 15 minutes. Then, methyl acrylate (29.2 g), 2-ethylhexyl acrylate (32.6 g), AIBN (0.16 g), 3, 4-epoxy cyclohexylmethyl methacrylate (0.38 g), 3-methacryloxypropyltrimethoxysilane (0.31 g) and ethyl acetate (217.5 g) were added to the reactor. The reaction was heated to reflux and held for 15 minutes. The monomer solution was then added through injection pump 1 continuously over 3 hours at a constant rate. Simultaneously, the initiator solution was added through injection pump 2 continuously over 3 hours at a constant rate. After addition, the mixture was stirred for an extra 3 hours at reflux. Upon completion, the reaction solvent and any volatiles were removed under vacuum at the reflux temperature. The resulting polymer was cool to room temperature under nitrogen. Photoinitiator Omnicat 320 (0.05 wt. %) was added and mixed for 30 minutes. The final product was coated on a 2-mil thick polyester film to give a 1-milthick dry adhesive, cured with 20 mJ / cm2of UVC and then tested for pressure sensitive adhesive properties. See Table 4.Example 8

[0123] Example 6 (80 g) was mixed with ethyl acetate (80 g) at room temperature until fully dissolved. Then, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (0.4 g) was added to the mixture and mixed at room temperature for 30 minutes. The final product was coated on a 2-mil thick polyester film to give a 1-mil thick dry adhesive, cured with 20 mJ / cm2of UV-C and then tested for pressure sensitive adhesive properties. Shear for the adhesives of Examples 6, 7 and 8 are shown in Table 4. A rheology comparison of the adhesives of Examples 6, 7 and 8 is shown in FIG. 1 .Table 4 - Shear Properties for the Adhesives of Examples 6, 7 and 8Example 9

[0124] A four-neck 1 L round-bottom polymerization flask was equipped with a thermometer connected to a temperature control device, a condenser, an overhead mechanical stirrer, two addition funnels, and nitrogen inlet / outlet. The set-up was purged with nitrogen gas for 15 minutes. A mixture of the following monomers was prepared: methyl acrylate (30 g), 2-ethylhexalacrylate (100 g), benzyl acrylate (20 g) and 1- acrylomethyl-3,4-cyclohexene epoxide (1.2 g). To one of the funnels was charged 112 g of the monomer mixture. To another funnel was charged the initiator (AIBN, 0.1 g) and ethyl acetate (45 m ). To the polymerization flask was charged the remaining monomer mix (38 g), initiator AIBN (0.2 g) and ethyl acetate (40 mL). The mixture was heated to vigorous reflux and held for 15 minutes. Then, the monomer mix in the funnel was added continuously for 2.5 hours at a constant rate. Simultaneously, the initiator solution in the funnel was added continuously over 3 hours at a constant rate. Upon complete addition of initiator solution, the mixture was stirred for an additional 2 hours at reflux. A short half-life initiator t-amyl peroxypivalate peroxide (0.75 g) and ethyl acetate (25 mL) were charged into the initiatorfunnel and then added into the polymerization flask over 1 hour to reduce residual monomers. After the ethyl acetate was removed by vacuum at 120° C, acrylic adhesive I was obtained with a weight average molecular weight Mw of 130,000 g / mol, a PDI of 3 by GPC and viscosity of 50,000 cps at 120° C by Brookfield.Example 10

[0125] A four-neck 1 L round-bottom polymerization flask was equipped with a thermometer connected to a temperature control device, a condenser, an overhead mechanical stirrer, two addition funnels, and nitrogen inlet / outlet. The set-up was purged with nitrogen gas for 15 minutes. A mixture of the following monomers was prepared: methyl acrylate (40 g), 2-ethylhexyl acrylate (100 g), 2-hydroxy -3- phenoxypropyl acrylate (10g) and l-acrylomethyl-3,4-cyclohexene epoxide (1.5 g). To one of the funnels was charged 112 g of the monomer mixture. To another funnel was charged the initiator (AIBN, 0.1 g) and ethyl acetate (45 mL). To the polymerization flask was charged the remaining monomer mix (38 g), initiator AIBN (0.6 g) and ethyl acetate (40 mL). The mixture was heated to vigorous reflux and held for 15 min. Then, the monomer mix in the funnel was added continuously for 3 hours at a constant rate. Simultaneously, the initiator solution in the funnel was added continuously over 3 hours at a constant rate. Upon complete addition of initiator solution, the mixture was stirred for an additional 2 hours at reflux. A short half-life initiator t-amyl peroxypivalate peroxide (0.75 g) and ethyl acetate (25 mL) were charged into the initiator funnel and then added into the polymerization flask over 1 hour to reduce residual monomers. After ethyl acetate was removed by vacuum at 120° C, acrylic adhesive II was obtained with a weight average molecular weight Mw of 130,000 g / mol and PDI of 3 by GPC and viscosity of 60,000 cps at 120°C by Brookfield.Example 11

[0126] The polymer made in Example 9 was formulated with 20% of an epoxy functionalized diluent Epon 828, 0.1% of 2-(3,4-epoxycyclohexyl) ethyltriethoxysilane, 0.1% of oligomeric 3-glycidyloxy-propyl-trimethoxysilane and 0.05% of Irganox 1726 (from BASF). In addition to that 0.5% Omnicat 320 and 0.75% isopropylthioxanthone were added. The resulting hotmelt adhesive had a viscosity of 35,000 cps at 110° C with an outstanding stability. The viscosity did not change over 72 h at 110° C. The adhesive was coated to 100gsm on a silicone paper and irradiated with 2000 mJ / cm2UV-A irradiation from a 365 nm LED. After laminating (transferring) with 50 pm PET foil, the adhesive was tested after 24 hours of conditioning time at room temperature and 50% relative humidity. The adhesive performance is Table 5. Peel values are given after 24 hours.Table 5 - Pressure Sensitive Properties of Example 11.

Claims

WHAT IS CLAIMED IS:

1. An ultra-violet curable, pressure sensitive adhesive comprising:(A) about 80 wt. % to about 99.98 wt. % of an acrylic polymer having at least one terminal or pendant reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl SiRa (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen) benzophenone, and any combination of any of the foregoing;(B) about 0.01 wt. % to about 10 wt. % of a cationic photoinitiator or a cationic and radical photoinitiator package; and(C) about 0.01 wt. % to about 10 wt. % of a co-catalyst and stabilizer.

2. The adhesive of claim 1, wherein the adhesive has viscosity of about 1,000 to about 100,000 cps at a coating temperature of between about 25° C and about 140° C.

3. The adhesive of claim 1, wherein the acrylic polymer (A) is prepared from:(i) about 0.01 wt. % to about 20 wt. % of a first monomer having a reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, a hydroxy group, silyl SiR (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen), benzophenone, or any combination of any of the foregoing; and(ii) about 80 wt. % to about 99.99 wt. % of a second acrylic monomer comprising an acrylic or methacrylic acid derivative of the formula CH2=CH(RI)(COOR2), wherein Ri is H or CH3 and R2 is selected from the group consisting of a C1-24 alkyl chain, an alkyl-aryl chain, and an alkyl-aryl derivative containing the functionality of an ethoxy link, a hydroxy group, or mixtures of any of the foregoing.

4. The adhesive of claim 1, wherein the acrylic polymer (A) is prepared from:(i) about 0.1 wt. % to about 10 wt. % of a first monomer having a reactive functional group selected from the group consisting of a cycloaliphatic epoxide, a vinyl ether, an oxirane, an oxetane, or mixtures of any of the foregoing;(ii) about 70 wt. % to about 99.8 wt. % of a second acrylic monomer comprising an acrylic or methacrylic acid derivative of the formula CH2=CH(RI)(COOR2), wherein Ri is H or CH3 and R2 is selected from the group consisting of a C1-24 alkyl chain, an alkyl-aryl chain, and an alkyl-aryl derivative containing the functionality of an ethoxy link, a hydroxy group, or mixtures of any of the foregoing; and(iii) about 0.1 wt. % to about 20 wt. % of a third monomer having a reactive silyl functional group -SiR wherein R is selected from the group consisting of (a) alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, halogen, or a combination thereof, and (b) a reactive benzophenone containing acrylic monomer.

5. The adhesive of any one of claims 2-4, wherein the acrylic polymer has (a) a Tg value less than about 10° C and (b) a weight average molecular weight (Mw) from about 1,000 to about 1,000,000 g / mol.

6. The adhesive of any one of claims 2-4, wherein (i) the first monomer is a cycloaliphatic epoxide having the formula:wherein:R1is O, S, C=O, a linear, branched, or cyclic alkylene, oxyalkylene, or arylene;R2is a linear, branched, or cyclic alkyl, alkoxy, aryl, H, halogen, C=O, or is part of R1as a fused cycloaliphatic ring through a covalent bond connection;R3is (CH2)n, where n is 0, 1, 2 or 3;X is acrylate or methacrylate, or comprises a -W-Y group;W is O, S, amide, carbonate, urethane, urea, siloxane, or a combination thereof; andY is -R4-C(R5)=CH2, where R4is a linear or branched C2-10 alkylene, C2-10 oxyalkylene, C=O, arylene or derivatives thereof, and R3is H or CH3.

7. The adhesive of claim 6, wherein the cycloaliphatic epoxide has the formula:or a mixture of any of the foregoing.

8. The adhesive of any one of claims 2-4, wherein the second acrylic monomer is methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, methyl acrylate, methyl methacrylate, t-octyl acrylamide, hydroxyethyl acrylate, acrylic acid, hydroxypropyl acrylate, hydroxylpropyl methacrylate, or a mixture of any of the foregoing.

9. The adhesive of claim 4, wherein the third monomer is 3- methacryloxypropyltrimethoxy silane, 3-[diethoxy(methyl)silyl]propyl methacrylate, benzophenone methacrylate, or a mixture of any of the foregoing.

10. The adhesive of claim 4, wherein the third monomer is 3- methacryloxypropyltrimethoxysilane, 3-[diethoxy(methyl)silyl]propyl methacrylate, or a mixture of any of the foregoing..

11. The adhesive of claim 1, wherein the cationic photoinitiator is a sulfonium salt or an iodonium salt.

12. The adhesive of claim 11, wherein the cationic photoinitiator has the structurewhere R is C3H7, C12H25, W is S, SO, SO2or CO.

13. The adhesive of claim 1, wherein the cationic photoinitiator is:where R1and R2are each, independently, H, CH3, C2H5, C3H7, C12H25, OCH3, OC2H5, OC3H7, or OC12H25.

14. The adhesive of claim 1, wherein the photoinitiator package is mixture of a cationic photoinitiator and a radical photosensitizer selected from the group consisting of thioxanthen-9-one, 2-isopropylthioxanthone, 2-chlorothioxanthen-9-one, 2,4-Diethyl- thioxanthen-9-one, l-chloro-4-propoxythi oxanthone, and any combination thereof.

15. The adhesive of claim 14, wherein the ratio of the cationic photoinitiator to the radical photosensitizer is about 0.1 to about 10.

16. The adhesive of claim 1, wherein the co-catalyst is a silane, or an oligomeric or polymeric derivative thereof.

17. The adhesive of claim 16, wherein the co-catalyst is an alkoxy functional silane, an epoxy functional silane, a (meth)acrylic functional silane, or an oligomeric, or polymeric derivative thereof, or a mixture of any of the foregoing.

18. The adhesive of claim 17, wherein the co-catalyst is vinyltri alkoxy silane, a C3-C24 alkyltrialkoxysilane, (meth)acryloxypropyl trialkoxysilane, glycidoxypropyltrialkoxy silane, (3, 4-epoxy cyclohexyl) ethyltrialkoxy silane, or an oligomeric or polymeric derivative thereof, or a mixture of any of the foregoing.

19. The adhesive of claim 18, wherein the co-catalyst is vinyltrimethoxysilane, vinyltriethoxysilane, glycydlepropyltrimethoxysilane, glycydlepropyltriethoxysilane, 2-(3,4- epoxy cyclohexyl) ethyltrimethoxy silane, 2-(3, 4-epoxy cyclohexyl) ethyltri ethoxy silane, or an oligomeric or polymeric derivative thereof, or a mixture of any of the foregoing.

20. The adhesive of claim 1, further comprising a reactive diluent of a polymer, oligomer or macromer comprising at least one terminal or pendant reactive functional group selected from the group consisting of a cycloaliphatic epoxide, an oxirane, an oxetane, a vinyl ether, a hydroxy group, silyl SiR.3 (wherein each R is, independently, alkyl, aryl, arylalkyl, alkoxy, aryloxy, acetoxy, oximino, enoxy, amino, amido, ester, H, or halogen), benzophenone, and any combination of any of the foregoing.

21. The adhesive of claim 20, wherein the reactive diluent has a weight average molecular weight of about 100 to about 500,000 g / mol.

22. The adhesive of claim 20, wherein the reactive diluent is an epoxy functionalized soybean oil, epoxy functionalized polybutadiene, epoxy-functional polyurethane, epoxy functionalized polysiloxane, epoxy functionalized polyisobutylene, epoxy-difunctionalized bisphenol A epoxy resin, epoxy-difunctionalized bisphenol F epoxy resin, epoxy functionalized polyacrylate, epoxy functionalized polyethylene glycol, epoxy functionalized polypropylene glycol, epoxy functionalized polyether, or a mixture of any of the foregoing.

23. The adhesive of claim 1, further comprising a tackifier, a thermal stabilizer, a moisture scavenger, or any combination thereof.

24. The adhesive of claim 1, wherein the adhesive is essentially free of an organic solvent.

25. An article of manufacture comprising the ultra-violet curable, pressure sensitive adhesive of any one of claims 1-24.

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