WO2019159080A1

WO2019159080A1 - Impact resistant adhesive

Info

Publication number: WO2019159080A1
Application number: PCT/IB2019/051170
Authority: WO
Inventors: Adam O. Moughton; Zhicheng TIAN; Dong-Wei Zhu; Samuel J. CARPENTER; Zhong Chen; John W. McAllister; Jennifer J. Sahlin; Sharon Wang; Shujun J. WANG; Hengxi YANG
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2018-02-19
Filing date: 2019-02-13
Publication date: 2019-08-22
Anticipated expiration: 2020-08-19

Abstract

A pressure sensitive adhesive composition includes a (co)polymer derived from polymerization of monomers comprising (i) one or more (meth)acrylic acid ester monomers; (ii) one or more acid functional ethylenically unsaturated monomers; and (iii) one or more non-acid functional, ethylenically unsaturated polar monomers. The (co)polymer comprises (i) derived units in an amount of between 80 and 96 wt. %, (ii) derived units in an amount of between 1 and 12 wt. %, and (iii) derived units in an amount of between 0.1 and 10 wt. %, each based the total weight of the (co)polymer.

Description

IMPACT RESISTANT ADHESIVE

Background

Various pressure sensitive adhesive (PSA) compositions are described in, for example, U.S. Pat. App. Ser. 15/124,471, and U.S. Pat. App. Pub. 2014/0044915.

Summary of the Invention

In some embodiments, a pressure sensitive adhesive composition is provided. The pressure sensitive adhesive composition includes a (co)polymer derived from

polymerization of monomers comprising (i) one or more (meth)acrylic acid ester monomers; (ii) one or more acid functional ethylenically unsaturated monomers; and (iii) one or more non-acid functional, ethylenically unsaturated polar monomers. The (copolymer comprises (i) derived units in an amount of between 80 and 96 wt. %, (ii) derived units in an amount of between 1 and 12 wt. %, and (iii) derived units in an amount of between 0.1 and 10 wt. %, each based the total weight of the (co)polymer.

Also described are articles such as laminating tapes and protective films as well as methods of bonding substrates with the pressure sensitive adhesive and laminating tape.

Detailed Description

In electronic devices, particularly mobile electronic devices (e.g., handheld or wearable electronic devices), PSAs are typically used to bond the cover glass (or lens) to the frame of the device (so called optically clear adhesives, or OCAs), bond the touch sensor to the cover glass and the display, or bond the lower components of the display to the housing. For these applications (commonly referred to as electronics bonding, or e- bonding), PSAs and OCAs should have sufficiently high strength of adhesive force to properly maintain good adhesion to those components, not only when the mobile electronic devices are operating under normal conditions, but also when they are deformed by external forces or subjected to traumatic forces (e.g., dropping of the mobile electronic device onto a hard surface). Regarding deformation, the components of the electronic devices may be deformed, for example, when users sit in chairs while the electronic devices are in their pockets or press down the electronic device with their hips. Under such conditions, the pressure sensitive adhesives should have a strength of adhesion sufficient to maintain the adhesion to, for example, the cover glass (sometimes referred to as anti- lifting properties). Regarding traumatic forces, the pressure sensitive adhesives should have sufficient impact proof reliability, or drop/impact resistance, such that the pressure sensitive adhesive maintains adhesion of the components even when large instantaneous impacts are applied to the portable electronic devices when dropped.

Adhesives which can dissipate energies and resist delamination forces associated with high strain and high strain rate events such as that experienced during a device drop, have gained increasing significance for the electronic device industry. The ability to produce pressure sensitive adhesives that resist de-bonding (via interfacial or cohesive failure modes) during these high impact and dynamic deformations has become a highly desired property, inclusive of traditional performance metrics such as good peel, shear and creep adhesion, amongst others, and thus has become a commercially attractive performance criterion for continued product differentiation within this competitive and fast paced market space.

To achieve an adhesive to resist the de-bonding forces involved during high impacts and to dissipate stresses, it is useful to quantify the peak force and total energy per unit area that an adhesive can absorb during tensile and shear impact tests, which can be measured with suitable instrumentation and reliable testing protocols. For example, certain known adhesives for such e-bonding applications can provide adequate impact/drop resistance (>500 mJ total energy absorbed during tensile impact) and high temperature adhesion (180° peel >0.5 N/mm at 85 °C and 300 mm/min), and yet cannot be made thinner than S0-1S0 μm ) due to requiring several different layers to enable the combination of these properties within one adhesive transfer tape (ATT) construction. Given the electronics industry's trend towards device simplification (i.e. combining layers and/or layer functions) and reducing bonding area and overall device thickness, (and moreover demanding enhanced flexibility), there exists a growing need for thinner pressure sensitive adhesive tapes (e.g., <50 μm ), which have good tensile impact resistance (e.g., >200 mJ/35 μm ) and high temperature adhesion (e.g., 180° peel >0.5 N/mm at 85 °C and 300 mm/min, and >10,000 mins shear at 70 °C).

Pressure sensitive adhesive materials have heretofore achieved this balance of dichotomous properties within a foam tape construction with one or more layers. Due to the ability of a foam to be compressed and yet recover elastically, it is able to dissipate a large amount of stress while still resisting debonding forces at the interfaces. However, such tape constructions typically have a thickness of more than SO μτη, and more typically 150 μτη or more, making their utility within the demanding device form factors of future devices (i.e. thin, flexible, wearable, shock resistant), particularly challenging.

Surprisingly however, it has been discovered that certain PSA compositions containing hydrogen bonding donors and acceptors (bonding through so called non- covalent interactions), have good impact resistance and can be achieved within a thin e- bonding PSA. Moreover, this performance can be optimized while maintaining excellent high temperature adhesion, which are very often competing properties to obtain within a thin, single layer PSA. More specifically, it has been discovered that certain acrylic PSA formulations provide a unique combination of excellent high impact resistance

(tensile/shear modes), or drop resistance properties, excellent bond making ability (i.e. good tack, instant bond formation) and high temperature adhesion/de-bonding resistance (peel/shear/creep mode). These performance criteria are highly desirable for applications within e-bonding and industrial market segments. Moreover, these certain acrylic PSA formulations are highly suitable for thin e-bonding applications due to their low thickness capabilities (<50 /mi), corrosion resistance, and durability (i.e. the ability to resist cavitation during heat ageing of an adhesive-component laminate).

As used herein:

the term "(co)polymer" refers to homo- and copolymers

the term "(meth)acrylic acid" refers to acrylic acid or methacrylic acid;

the term "(meth)acrylate" refers to acrylate or methacrylate;

As used herein, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended embodiments, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

As used herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).

Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

In some embodiments, the PSA compositions of the present disclosure may include one or more (copolymers derived from polymerization of at least (i) one or more

(meth)acrylic acid ester monomers; (ii) one or more acid functional ethylenically unsaturated monomers; and (iii) one or more non-acid functional, ethylenically

unsaturated polar monomers.

In some embodiments, suitable (meth)acrylic acid ester monomers may include a alkyl ester component, having from 1-20, 1-18, 2-15, or 4-12 carbon atoms, derived from the ester product of alkyl alcohols (e.g. 1-butanol) and acrylic acid. In some

embodiments, the (meth)acrylic acid ester monomers may include any one of, or combinations of: 2-ethylhexyl acrylate, 2-ethylhexyl (meth)acrylate, methyl acrylate, methyl (meth)acrylate, ethyl acrylate, iso-propyl acrylate, n-butyl acrylate, ferf-butyl acrylate, wo-octyl acrylate, 2-octadecyl acrylate, lauryl acrylate, citronel acrylate, iso- bornyl acrylate, n-hexyl acrylate, /so-stearyl acrylate, 10-undecenyl acrylate, cyclohexyl acrylate, phenyl ether acrylate.

In some embodiments, the (copolymers of the present disclosure may include (meth)acrylic acid ester monomer derived units in an amount of between 80 and 96 wt. %, between 85 and 95 wt. %, or between 87 and 95 wt. %, based on the total weight of the (copolymer.

In some embodiments, suitable acid functional ethylenically unsaturated monomers may include (meth)acrylic acid monomers. In some embodiments, the (meth)acrylic acid monomers may include acrylic acid monomers (AA). In some embodiments, suitable (meth)acrylic acid monomers may include acidic functional monomers, where the Lewis or Bronsted acidic functional group may be an acid per se, such as a carboxylic acid, or a salt thereof such as an alkali metal carboxylate, or a less acidic monomer such as an alcohol. Useful acidic functional monomers include those selected from ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, ethylenically unsaturated phosphonic acids, and mixtures thereof. Examples of such compounds include those selected from acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, vinyl-phosphonic acid, maleic acid, oleic acid, β-carboxyethyl acrylate, 2-sulfoethyl methacrylate, styrene sulfonic acid, 2-acrylamido-2- methylpropanesulfonic acid, 2-acrylamido-tert-butylsulfonic acid, hydroxylethyl acrylate, hydroxylethyl(meth)acrylate, 4-vinyl phenol, 4-vinyl phenol boronic acid, and mixtures thereof.

In some embodiments, the (copolymers of the present disclosure may include (meth)acrylic acid monomer derived units in an amount of between 1 and 12 wt. %, between 4 and 11 wt. %, or between 5 and 10 wt. %, based on the total weight of the (copolymer.

In some embodiments, suitable non-acid functional, ethylenically unsaturated polar monomers may include nitrogen containing non-acid functional, ethylenically unsaturated polar monomers. In some embodiments, the nitrogen containing non-acid functional, ethylenically unsaturated polar monomers may include any one of, or combination of N- vinyl pyrollidone, NiN-dimethyl acrylamide, N-vinyl lactam, or acrylamide. In some embodiments, suitable ethylenically unsaturated polar monomers may include a Lewis or Bronsted basic functional monomer (i.e. electron donating or proton accepting, respectively), where the basic group can be an amide group per se, such as an acrylamide, or nitrogen containing monomer such as an amine, urethane, urea, ureido-pyrimidinone, carbamate, or quaternary or metal salts thereof. Such useful polar monomers include those selected from ethylenically unsaturated amides, amines, ureas or the like. Examples of such compounds include those selected from acrylamide, methacrylamide, N, N '-dimethyl acrylamide, N, N^* -diethyl acrylamide, N-vinyl formamide, 4-acryloylmorpholine, N-tert- butyl acrylamide, N-hydroxyethyl acrylamide, N-vinyl pyrollidone, N-vinyl caprolactam, N-[tris-(hydroxylmethyl)methyl]-acrylamide, N-wo-propyl acrylamide, N-vinyl carbazole, N-vinyl formamide, 4-vinyl pyridine, 2-vinyl-pyridine, ureidoethyl (meth)acrylate, hexylcarbamoyloxy)isopropyl acrylate, hydroxypropylcarbamate acrylate,

(phenylcarbamoyloxy)isopropyl acrylate, l-methyl-3-(4-vinylbenzyl)imidazolium chloride, l-hexyl-3-(4-vinylbenzyl)imidazolium chloride and l-dodecyl-3-(4- vinylbenzyl)imidazolium chloride, l-methyl-3-(4-vinylbenzyl)imidazolium

litWumbis((trifluoromethyl)sulfonyl)-amide, 1 -hexyl-3 -(4-vinylbenzyl)imidazolium lithiumbis((trifluoromethyl)sulfonyl)-amide and 1 -dodecyl-3 -(4-vinylbenzyl)imidazolium lithiumbis((trifluoromethyl)sulfonyl)-amide, 2-ureido-4-[lH]-pyrimidinone acrylate.

In some embodiments, the (copolymers of the present disclosure may include non- acid functional, ethylenically unsaturated polar monomer derived units in an amount of between 0.05 and 10 wt. %, 0.1 and 10 wt. %, between 0.1 and 4 wt. %, or between 0.2 and 3 wt. %, based on the total weight of the (copolymer.

Regarding the above-described PSA compositions, it was discovered that certain combinations of unequal proportions of acidic and basic monomers provide the best impact resistance, while also maintaining good adhesion. Surprisingly, and counter to conventional wisdom, examples containing equal or near equal amounts of either monomer (e.g. 5 and 5, 5 and 3, 6 and 4, as wt. % combinations) provided relatively inferior impact resistance. Additionally, it was discovered that adding large amounts of both types of monomers (e.g., in excess of a total value of 10 wt. %) did not lead to enhanced impact resistance. It was found that low amounts of basic monomers (e.g., < 2 wt%) having a higher pKa value (i.e. higher basicity) such as a pka > 6, e.g. acrylamide, in combination with > 5 wt% of acidic monomers (e.g. acrylic acid, pka = 4.5) within the copolymer, had higher impact resistance and maintained excellent adhesion. In this regard, in some embodiments, the (copolymers of the present disclosure may have (i) a total amount of (a) acid functional ethylenically unsaturated monomer derived units and (b) non-acid functional, ethylenically unsaturated polar monomer derived units of less than 15 wt. %, less than 10 wt. %, or less than 9 wt. %, based on the total weight of the

(copolymer; and (ii) a wt. % ratio (expressed as decimal) of (a) to (b) of greater than 1.67, greater than 2.0, greater than 2.5, greater than 3.0, greater than 3.5, greater than 4.0, or greater than 4.5; or less than 0.6, less than 0.5, less than 0.4, less than 0.2 or less than 0.1.

In some embodiments, the above-described (copolymers may include one or more additional monomers or additives that may join in the polymerization reaction. For example, multifunctional monomers such as 1,6-hexanediol diacrylate (HDD A) may be employed to achieve a desirable molecular weight, molecular weight distribution, or degree of branching of the (copolymer. As an additional example, one or more chain transfer agents such as wo-octyl thioglycolate (IOTG) may employed to achieve a desirable molecular weight, molecular weight distribution, or degree of branching of the (copolymer. In some embodiments, the above-described (copolymers may have a number averaged molecular weight (Mn) of at least 50,000, at least 100,000, at least 200,000, or at least 300,000 g/mol; or between 50,000 and 850,000, between 100,000 and 750,000, or between 250,000 and 650,000 g/mol. In some embodiments, the above-described

(copolymers may have a weight averaged molecular weight (Mw,) of at least 400,000, at least 800,000, or at least 1,000,000 g/mol; or between 400,000 and 3,500,000, between 500,000 and 3,000,000, or between 700,000 and 2,500,000 g/mol.

In some embodiments, the above-described (copolymers may have a molecular weight distribution (MWD orMw/Mn or D ) of at least 1.5, at least, 1.75, or at least 2; or between 1 and 4, between 1.2 and 6, or between 1.4 and 10.

For the purposes of the present application, molecular weights (Mw,, Mn) and molecular weight distributions (MWD orMw/Mn or £>) aredetermined by size exclusion chromatography (SEC) as follows: samples are to be analyzed by SEC fitted with triple detection (multi angle light scattering/viscometry/refractive index) using tetrahydrafuran (THF) as eluent in order to measure the (copolymers absolute or standard-less molecular weight. The samples are also run vs. poly(styrene) (PS) standards on the same column to compare against other internal SEC molecular weight determinations utilizing PS standards. The SEC instrument utilized is an Agilent 1260 LC, utilizing a waters Styragel HR 5E, 300 x 7.8 mm inner diameter at °40 C and a flow rate of 1.0 mL/min. The detectors are as follows: a Wyatt Dawn Heleos-II 18 angle light scattering detector, a Wyatt ViscoStar Π viscometer detector and a Wyatt Optilab T-rEX differential refractive index (DRI) detector.

In some embodiments, the above-described (copolymers may be crosslinked to improve durability or cohesion properties of the (copolymers. Generally, any suitable crosslinking agent may be used. Exemplary crosslinking agents include covalent cross- linkers such as bisamides, epoxies, melamines, multi-functional amines and aziridines or acrylates; and non-covalent or ionic crosslinking agents such as metal oxides and organo- metallic chelating agents (e.g., aluminum acetylacetonate). The amount of crosslinking agent included depends on well-understood factors such as the desired degree of cross- linking and the relative effectiveness of the cross-linking agent in the particular system, as measured by well-known tests such as shear adhesion. Crosslinking of the (copolymer using chemical crosslinking agents may be initiated using any conventional technique, such as thermal or radiation initiation.

In some embodiments, in addition to the above-described (copolymers, the pressure sensitive adhesive compositions of the present disclosure may include one or more additives such as (e.g. inorganic oxide) fillers such as (e.g. fumed) silica and glass bubbles, tackifiers, adhesion promoters, plasticizers, (e.g. chemical) foaming or blowing agents, thixotropic agents, ultraviolet stabilizers, antioxidants, antistatic agents, colorants, nanoparticles, micro-particles, impact resistance aids, flame retardants (e.g. zinc borate), and the like.

In some embodiments, the pressure sensitive adhesive composition may include tackifiers or plasticizers to adjust the adhesion or wet out. In such embodiments, the total amount of tackifier or plasticizer of the adhesive composition is typically no greater than 50, 40, 30, 20, 15, 10, or 5 wt. % tackifier or plasticizer, based on the total weight of the pressure sensitive adhesive composition. In other embodiments, the pressure sensitive adhesive composition may include little or no tackifiers or plasticizers. In such embodiments, the adhesive composition may include no greater than 4, 3, 2, 1, 0.5, 0.1, or 0.05 wt. % of tackifer or plasticizer, based on the total weight of the pressure sensitive adhesive composition.

In some embodiments, it may desirable to achieve a transparent pressure sensitive adhesive composition. In such embodiments, the composition may be free of fillers that can detract from the transparency of the pressure sensitive adhesive composition (e.g., fillers having a particle size greater than 100 nm). In such embodiments, the amount of filler of the pressure sensitive adhesive composition is no greater than 10, 9, 8, 7, 6, 5, 4, 3, or 2 wt. %, based on the total weight of the pressure sensitive adhesive composition. However, in other embodiments, the pressure sensitive adhesive composition may include higher amounts of inorganic oxide filler such as fumed silica or titania.

In some embodiments, the pressure sensitive adhesive compositions may include colorants such as pigments or dyes such as titania or carbon black. Such pigments or dyes can be present in the pressure sensitive adhesive compositions in an amount of up to 20 wt. %, based on the total weight of the pressure sensitive adhesive compositions.

In some embodiments, the pressure sensitive adhesive compositions may include one or more corrosion inhibitors. Suitable corrosion inhibitors include benzotriazole. In some embodiments, the pressure sensitive adhesive compositions may include one or more adhesion promoters, such as, for example (3-glycidyloxypropyl)trimethoxysilane.

In some embodiments, the pressure sensitive adhesive compositions of the present disclosure may include the above-described (copolymers dissolved in a non-aqueous organic solvent such as ethyl acetate. In some embodiments, the organic solvent may range from about 2 wt. % to 98 wt. % or 20 to 80 wt. %, based on the total weight of the PSA composition. For purposes of the present application, non-aqueous refers to a liquid medium that includes less than 3, 2, or 1 wt. % water, based on the total weight of the liquid medium.

In some embodiments, the pressure sensitive adhesive composition may be in the form of a foam (e.g., in the form of a polymer matrix having a density that is less than the density of the (copolymer itself). Foaming, or density reduction, may be achieved in a number of ways including through creation of gas-filled voids in the matrix (e.g., by means of a blowing agent), inclusion of polymeric microspheres, or inclusion of non- polymeric microspheres. In some embodiments, the polymeric microspheres may include expandable polymeric microspheres that include a polymer shell and a core material in the form of a fluid that expands upon heating. In some embodiments, the pre-expanded polymeric microspheres may be added to achieve density reduction. It is understood that foaming in a pressure sensitive adhesive composition may improve its impact resistance and conformability.

In some embodiments, an adhesive tape can be formed by coating the pressure sensitive adhesive compositions on a backing or release liner using conventional coating techniques. For example, these compositions can be applied by methods such as roller coating, flow coating, dip coating, spin coating, spray coating, knife coating, and die coating. The composition may be of any desirable concentration for subsequent coating, but may be between 10 and 100 wt. % or between 20 and 60 wt. % (copolymer, based on the total weight of the pressure sensitive adhesive composition (including solvent). The desired concentration may be achieved by further dilution of the coating composition, or by partial drying.

In some embodiments, the thickness of the pressure sensitive adhesive layer may be no greater than 400, 300, 200, or 100 microns; or may be between 10 and 400, between 15 and 300, or between 20 and 200. The pressure sensitive adhesive composition can be coated in a single layer or multiple layers.

In some embodiments, the pressure sensitive adhesive compositions may be coated upon a variety of flexible and inflexible backing materials using conventional coating techniques to produce a single coated or double coated pressure sensitive adhesive tape. The tape may further comprise a release material or release liner. For example, in the case of a single-sided tape, the side of the backing surface opposite that where the adhesive is disposed is typically coated with a suitable release material. Release materials are known and include materials such as, for example, silicone, polyethylene, polycarbamate, polyacrylics, and the like. For double-sided tapes, a second layer of adhesive is disposed on the opposing surface of the backing surface. The second layer may also comprise the pressure sensitive adhesive compositions as described herein or a different adhesive composition. Flexible substrates are defined herein as any material which is

conventionally utilized as a tape backing or may be of any other flexible material.

Examples include, but are not limited to polymeric films, woven or nonwoven fabrics; metal foils, foams (e.g., polyacrylic, polyethylene, polyurethane, and combinations thereof (e.g. metalized polymeric film). Polymeric film includes for example polypropylene (e.g. biaxially oriented), polyethylene (e.g. high density or low density), polyvinyl chloride, polyurethane, polyester (polyethylene terephthalate), polycarbonate,

polymethylmethacrylate (PMMA), polyvinylbutyral, polyimide, polyamide,

fluoropolymer, cellulose acetate, cellulose triacetate, and ethyl cellulose. The woven or nonwoven fabric may comprise fibers or filaments of synthetic or natural materials such as cellulose (e.g. tissue), cotton, nylon, rayon, glass, ceramic materials, and the like.

A substrate may be bonded by the pressure sensitive adhesive or adhesive tape described herein. The substrate may comprise the same materials as just described for the backing.

One method of bonding comprises providing a first substrate and contacting a surface of the first substrate with the pressure sensitive adhesive composition (e.g.

adhesive tape or protective film). In some embodiments, the opposing surface of the pressure sensitive adhesive may be temporarily covered by a release liner.

In other embodiments, the method further comprises contacting the opposing surface of the pressure sensitive adhesive to a second substrate. The first and second substrate may be comprised of various materials as previously described such as metal, an inorganic material, an organic polymeric material, or a combination thereof.

In some methods of bonding, the substrate, pressure sensitive adhesive, or combination thereof may be heated to reduce the storage modulus (G') and thereby increase the (e.g. peel) adhesion. The substrate and/or pressure sensitive adhesive may be heated to a temperature up to 30, or 35, or 40, or 45, or 50, or 55, or 60, or 65 or 70 °C. In some embodiments, the substrate(s) together with the adhesive bonded to the substrate(s) by means of the initial peel adhesion at ambient temperature (e.g. 25 °C) is heated in an oven to the desired temperature. In other embodiments, the substrate and/or pressures sensitive adhesive is heated by means of a hot air gun.

In some methods of bonding, the pressure sensitive adhesive can be transfer laminated to another surface (e.g. metal foil, glass or plastic film) in a short timescale at ambient temperature (e.g. 25 °C) without further heat treatment.

The pressure sensitive adhesive compositions described herein may also be disposed on a transparent film for use as a removable or permanent surface protection film. In some embodiments, the pressure sensitive adhesive compositions and transparent film may have a transmission of visible light of at least 90 percent.

The pressure sensitive adhesive, adhesive tapes, and protective films described herein are suitable for use in the areas of electronics, appliances, automotive, and general industrial products. In some embodiments, the pressure sensitive adhesive and adhesive tapes can be utilized in (e.g. illuminated) displays that can be incorporated into household appliances, automobiles, computers (e.g. tablets), and various hand-held devices (e.g. phones, tablets, wearables).

In some embodiments, the physical and adhesive properties of the pressure sensitive adhesive compositions and adhesive tapes described herein are particularly suitable for bonding internal components or external components of an illuminated display devices such as liquid crystal displays ("LCDs") and inorganic or organic light emitting diode ("LEDs") displays such as in cell phones (including smart phones), wearable (e.g. wrist) devices, car navigation systems, global positioning systems, depth finders, computer monitors, notebook and tablet computer displays.

In some embodiments, the pressure sensitive adhesive compositions or adhesive tapes may exhibit an impact resistance (which can, generally, be considered a measure of the composition or tapes ability to absorb impact energy under various deformation modes at relevant rates and temperatures) of at least 400, at least 300, or at least 200 mJ/35 μιη. For the purposes of the present application, impact resistance is determined in accordance with the methods described in the Examples.

In some embodiments, the pressure sensitive adhesive compositions or adhesive tapes may exhibit desirable high temperature adhesion properties. For example, in some embodiments, the pressure sensitive adhesive compositions or adhesive tapes may exhibit a 180 degree peel adhesion at 85 °C at 300 mm/min (which can, generally, be considered a measure of the composition or tapes ability to resist debonding from a substrate through adhesive/inter-facial or cohesive/internal failure modes) of at least 0.6, at least 0.S, or at least 0.4 N/mm with an adhesive thickness of 35 fan on a backing that does not yield under high stain and/or elevated temperature. For purposes of the present application, 180 degree peel is as determined in accordance with the methods described in the Examples. As an additional example, in some embodiments, the pressure sensitive adhesive compositions or adhesive tapes may exhibit shear parameters of at least 10,000, at least 8,000, or at least 5,000 mins of shear for a 35 /mi adhesive under a load of 1 Kg at elevated temperatures (e.g. 70 °C). For purposes of the present application, shear parameters are as determined in accordance with the methods described in the Examples.

In some embodiments, the pressure sensitive adhesive compositions or adhesive tapes may exhibit properties that accommodate achieving minimal overall thickness of the adhesive (e.g., in the form of a coating place between liners) or an adhesive transfer tape. In this regard, in some embodiments, the pressure sensitive adhesive compositions, which may have the above-described performance parameters, may be disposed on a substrate in a layer of average thickness of less than 50 micrometers, less than 35 micrometers, or less than 25 micrometers. In some embodiments, such layers may have a density of at-least 0.6 g/cm³, at least, 0.8 g/cm³, or at least 1.0 g/cm³.

In some embodiments, the pressure sensitive adhesive compositions or adhesive tapes may exhibit a level of adhesion to glass or stainless steel. For example, the room temperature 180° peel values can be about 0.2, 0.3, 0.4 or 0.5 N/mm at a 300 mm/min peel rate after a 72 hour dwell time at 25 °C (as further described in the test method in the examples). In other embodiments, the 180° peel values of the pressure sensitive adhesive or laminating tape (e.g. heat bondable) can be higher, for example at least 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or 1.2 N/mm.

In some embodiments, the pressure sensitive adhesive or laminating tape may exhibit the same higher level of adhesion to glass or stainless steel after exposure to elevated temperatures and humidity, such as after a 72 hour dwell time at 65°C and 90% relative humidity. In some embodiments, the increase in adhesion is no greater than 300%, 250%, 200%, 150%, 100%, 90%, 80%, or 70% (as determine by subtracting the 72 hour room temperature value from the aged peel value, dividing by the 72 hr room temperature value and multiplying by 100%).

In some embodiments, the pressure sensitive adhesive composition has a storage modulus G' as can be measured by Dynamic Mechanical Analysis or Rheology (as further described in the examples) of less than 1, 0.8, 0.6, 0.4, 0.2 or 0.1 MPa at 25°C and a frequency of 1 Hertz. The storage modulus typically decreases with increasing

temperature. In some embodiments, the pressure sensitive adhesive composition has a storage modulus G' of less than 0.4 or 0.2 at 35°C and a frequency of 1 Hertz. In some embodiments, the pressure sensitive adhesive composition has a storage modulus G' of less than 0.3 or 0.1 at 45°C and a frequency of 1 Hertz. In some embodiments, the pressure sensitive adhesive composition has a storage modulus G' of less than 0.3 or 0.1 at 55°C and a frequency of 1 Hertz. In some embodiments, the pressure sensitive adhesive composition has a storage modulus G' of less than 0.3 or 0.1 at 65°C and a frequency of 1 Hertz. The pressure sensitive adhesive has a storage modulus G' of less than 0.3 at frequency of 1 Hertz at a temperature less than 70, or 65, or 60, or 55, or 50, or 45 °C.

The pressure sensitive adhesive compositions of the present disclosure may have a glass transition temperature of less 5 °C as can be measured by differential scanning calorimetry (DSC). In some embodiments, the glass transition temperature may be less than 0 °C or -5°C. In some embodiments, the glass transition temperature may be less than -10 °C, -20 °C, -30 °C, or -40 °C.

In some embodiments, the (copolymers of the present disclosure may be polymerized through any known polymerization methods including thermally activated and photoinitiated activation. In some embodiments, the (copolymers may be made by solution free radical polymerization. In some embodiments, the raw materials (e.g., monomers, multi-functional acrylate, chain transfer agent, and solvent, as needed) may be combined in the appropriate ratios at room temperature to target the desired final copolymer composition at a solids concentration of between 30 and 100%. The reaction mixture may be purged with an inert gas. The reaction mixture may then be heated to between 40-120 °C to obtain a suitable initiation rate by selecting appropriate

temperatures to suit various thermal initiators. In some embodiments, the reaction temperature and pressure may be monitored throughout the polymerization to manage any resultant exotherm via a reaction heating/cooling jacket.

Listing of Embodiments

1. A pressure sensitive adhesive composition comprising:

a (co)polymer derived from polymerization of monomers comprising

(i) one or more (meth)acrylic acid ester monomers;

(ii) one or more acid functional ethylenically unsaturated monomers; and

(iii) one or more non-acid functional, ethylenically unsaturated polar monomers;

wherein the (copolymer comprises (i) derived units in an amount of between 80 and 96 wt. %, (ii) derived units in an amount of between 1 and 12 wt. %, and (iii) derived units in an amount of between 0.1 and 10 wt. %, each based the total weight of the (copolymer.

2. The pressure sensitive adhesive composition of embodiment 1, wherein the wt. % ratio of (ii) derived units to (iii) derived units in the (co)polymer is greater than 1.67.

3. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the (co)polymer comprises (ii) and (iii) derived units, collectively, in an amount of less than 10 wt. %, based the total weight of the (co)polymer

4. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the (co)polymer comprises (i) derived units in an amount of between 87 and 95 wt. %, based the total weight of the (co)polymer. 5. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the (co)polymer comprises (ii) derived units in an amount of between 5 and 10 wt. %, based the total weight of the (co)polymer. 6. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the (co)polymer comprises (iii) derived units in an amount of between 0.2 and 3 wt. %

7. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the acid functional ethylenically unsaturated monomers comprise acrylic acid.

8. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the non-acid functional, ethylenically unsaturated polar monomers comprise nitrogen.

9. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the non-acid functional, ethylenically unsaturated polar monomers comprise acrylamide

10. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the non-acid functional, ethylenically unsaturated polar monomer has a pka > 6. 11. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the acid functional ethylenically unsaturated monomer has a pka < 5.

12. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the pressure sensitive adhesive composition exhibits an impact resistance of at least 200 mJ with a coating thickness at 35 μπι or higher 13. The pressure sensitive adhesive composition of any one of the previous embodiments,

wherein the pressure sensitive adhesive composition exhibits a 180-degree peel adhesion at 23 °C at 300 mm/min of at least 0.5 N/mm at a coating thickness of 35 μπι or higher

14. The pressure sensitive adhesive composition of any one of embodiments 1-13, wherein the pressure sensitive adhesive composition is in the form of a foam.

15. The pressure sensitive adhesive composition of embodiment 14, wherein the foam comprises expandable polymeric microspheres.

16. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the (co)polymer comprises (iii) derived units in an amount of between 5 and 10 wt. %, based the total weight of the (co)polymer.

17. The pressure sensitive adhesive composition of any one of the previous embodiments, wherein the (co)polymer comprises (ii) derived units in an amount of between 0.2 and 3 wt. % 18. The pressure sensitive adhesive composition of any one of the previous embodiments,

wherein the pressure sensitive adhesive composition exhibits a shear at 70 °C of at least 10,000 min at a coating thickness of 35 μπι or higher.

19. A laminating tape comprising

a substrate; and

a layer of a pressure sensitive adhesive composition according to any one of embodiments 1-18 disposed on a major surface of the substrate.

20. The laminating tape of embodiment 19, wherein the substrate is a backing or a release liner. 21. The laminating tape of any one of embodiments 19-20, wherein the pressure sensitive adhesive composition is disposed on both major surfaces of the substrate.

22. A protective film comprising

a film; and

a layer of a pressure sensitive adhesive composition according to any one of embodiments 1-18 disposed on a major surface of the film.

23. The protective film of embodiment 22, wherein the film and pressure sensitive adhesive composition have transparency of at least 90%.

24. A method of bonding comprising

providing a first substrate,

contacting a surface of the first substrate with the pressure sensitive adhesive composition of any one of embodiments 1-18.

25. The method of embodiment 24, further comprising contacting an opposing surface of the pressure sensitive adhesive to a second substrate.

26. The method of any one of embodiments 24-25, wherein the first and second substrate are comprised of a metal, an inorganic material, an organic polymeric material, or a combination thereof.

27. An illuminated display device comprising a component bonded with the pressure sensitive adhesive composition of any one of embodiments 1-18.

28. An article comprising

a substrate; and

a layer comprising the pressure sensitive adhesive composition of any one of embodiments 1-18 disposed on a major surface of the substrate, wherein the pressure sensitive adhesive composition has a density of at-least 0.6 g/cm³. Examples

Objects and advantages of this disclosure are further illustrated by the following comparative and illustrative examples. Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Corp., Saint Louis, MO, or may be synthesized by conventional methods. The following abbreviations are used herein: mL = milliliter, min = minutes, hr = hours, g = grams, μπι = micrometers (10^"6 m), °C = degrees Celsius. SAMPLE PREPARATION

Table 1. Materials list

Polymerization Procedure A (Glass Bottles/Launder-o-meter):

The raw materials (monomers, initiator and solvent) for Examples 1, 4-9, 12-14, 16, and 20-27 and Comparative Examples CE1-CE7 and CE10 were combined at room temperature in the appropriate ratios (provided in Table 2) at a solids concentration of 50% in 4 oz. glass bottles in ethyl acetate. The crosslinker was l,l'-isophthaloyl-bis(2- methylaziridine) (CAS No. 7652-64-4), provided as a 5% solution in toluene. The reaction mixtures were degassed by bubbling nitrogen through the solutions for 5 minutes and the headspace was purged with nitrogen for 5 seconds. The bottles were quickly sealed under slight positive pressure and the screw top lid was secured with electrical tape and a thick elastic band. The bottles were placed inside protective metal cages and put into the launder-o-meter at 70 °C. The bottles were removed after 20 hr of continuous mixing and heating and were quenched to room temperature with cold water upon completion.

Polymerization Procedure B (Buchi Reactor):

The raw materials (monomers, multi-functional acrylate, chain transfer agent and solvent) for Examples 2, 3, 10, 11, 15, and 17-19 and Comparative Examples CE8 and CE9 were combined in the appropriate ratios (provided in Table 2) at room temperature at a solids concentration of 50% in ethyl acetate and poured into a 1L Buchi reactor (Buchi AG, Uster, Switzerland). The crosslinker was l,l'-isophthaloyl-bis(2-methylaziridine) (CAS No. 7652-64-4), provided as a 5% solution in toluene. The reaction mixture was purged with nitrogen multiple times to de-gas the solution. The reaction mixture was heated to 70-80 °C and thermal free radical initiator was charged at several stages during the polymerization utilizing a de-gassed charge bomb. The reaction temperature and pressure were carefully monitored throughout the polymerization to manage any resultant exotherm via a reaction heating/cooling j acket.

Preparation of Adhesive Test Samples

Unless otherwise reported, the illustrative and comparative pressure sensitive adhesive (PSA) adhesive transfer tapes (ATT) examples were made as follows.

Polymer solutions prepared as described above at 50% solids were diluted to 30% solids with ethyl acetate. Various additives were mixed into the solution in the amounts listed in Table 2 using high shear mixing equipment just prior to coating. Additives included a bisamide crosslinking agent, a polar surface adhesion promoter (GPTS), and carbon black dispersion.

Final polymer solutions were coated onto a 75 um release liner (RFK-12N, available from SKC Films, Covington, GA, US), tight side using a notch bar coater set to a total gap of 175 um (to achieve a nominal dried adhesive thickness of 35 um ± 3 um). The hand-spreads were allowed to dry for 2 minutes at room temperature before drying and cross-linking in a batch oven at 80 °C for 15 minutes. Once removed and cooled to room temperature, the hand-spread was covered with a secondary release liner (RFK-02N, SKC Films, Covington, GA, US) easy side for protection during storage.

I ··«·

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S

TEST METHODS

180° Peel Adhesion to Stainless Steel (at 23 and 85 °C

The peel adhesion to stainless steel (SS) was measured for PSA ATTs at an angle of 180° following test method E of ASTM D333004(2010)/D3330M, "Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape" (liner side) with modifications as described below.

Annealed, 18 gauge, 304 stainless steel test panels (2" x 6" or 3" x 9", available from Chem Instruments, US) were used as test substrates. Panels showing any scratches in the testing area were routinely dis-guarded. When not in use, the panel test surface was protected and stored at a controlled temperature and humidity (CTH) at 23 °C and 50% RH. PSA ATTs were laminated to one side plasma treated, 2 mil Biaxially Oriented Polyethylene Terephthalate (PET) film for use as a backing material. Samples and substrates (SS panels, PET) were conditioned in a controlled temperature and humidity room for a period of no less than 24 hours prior to testing. Test panels were cleaned with Methyl Ethyl Ketone (MEK) solvent before and after testing. A 4.5 lb roller was used to laminate the PET tapes to the panels (4 x 3 sec roll downs).

Peel testing was done using a Universal Testing Instrument (INSTRON, US) in a CTH room equipped with an environmental chamber. Peel tests were conducted at a rate of 300 mm/min (cross-head speed) and temperature of 23 or 85 °C, with a total peel extension of 80 mm. Each sample was peeled at least three times from the same SS substrate and averages of all three measurements are reported in Table 5.

Tensile Impact Resistance

To evaluate the tensile impact resistance in a dynamic event, such as a drop, a modification of ISO 9653 : 1998, "Test method for shear impact strength of adhesive bonds" was used. The PSA ATTs were cut to a predetermined geometry and laminated between two circular coupons. Table 3 provides detailed test parameters. The coupon- adhesive stacks were allowed to dwell for 48 hrs at CTH conditions prior to being tested. At least 5 replicates were made and tested for each example and comparative example. The stacks were tested using a CEAST 9340 (INSTRON, US) drop tower (0.3-450 J energy delivery) with a drop height of 115 mm and a drop weight of 3 Kg. The total energy absorbed and the peak force are reported for each adhesive tested in this configuration. The impact energy delivered to the sample was calculated from the mass and height of the drop and results are listed in Table S.

Table 3. Tensile impact test parameters

Shear Impact Resistance

The shear impact test is a destructive test to measure an adhesive material's impact resistance in a shear mode of deformation during a dynamic event such as drop. The PSA ATTs were cut to a predetermined geometry and laminated between two coupons of a specified material type and geometry. Table 4 provides detailed test parameters. The ATT coupon stacks were allowed to dwell 48 hr at CTH conditions prior to being tested, and at least 5 replicates were made and tested for each example. The stacks were tested using an CEAST 9050 pendulum impact tester (INSTRON, US). The total energy absorbed and the peak force are reported in Table 5. Table 4. Shear impact test parameters

Glass Transition Temperature

The glass transition temperature, T_g, or peak tan(5) was measured for each adhesive sample (8 mm diameter discs, 1 mm thick) using dynamic mechanical thermal analysis (DMA) with a stress controlled oscillatory shear DHR-3 rheometer (TA

Instruments, US) fitted with a 8 mm parallel plate stainless steel geometry. The analysis was performed within the linear viscoelastic region for each adhesive sample (< 5% strain) at a frequency of 1 Hz and with a heating rate of 3 °C/min from -30 °C to + 160

°C.Results are recorded in Table 5.

Shear Adhesion to Stainless Steel at 70 °C

Results are summarized in Table 5. Shear adhesion testing was conducted as per ASTM D3654-02, "Standard Test Methods for Shear Adhesion of Pressure-Sensitive Tapes." Adhesive transfer tape (ATT) samples were laminated to one side plasma treated 2 mil PET film for use as a backing material, l x l" area of adhesive was tested on stainless steel panels with a 1 Kg weight. Stainless steel test panels were used and were cleaned with methyl ethyl ketone (MEK) solvent before and after testing. A 4.5 lb roller was used to laminate the PET tapes to the panels (4 x 1 sec roll downs). Samples for shear testing were placed in a shear stand within a heated oven at 70 °C. Samples were tested for a maximum of 10,000 minutes.

RESULTS

Results from impact testing and adhesion strength are summarized in Table 5.

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Various modifications and alterations to this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure. It should be understood that this disclosure is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the disclosure intended to be limited only by the claims set forth herein as follows. All references cited this disclosure are herein incorporated by reference in their entirety.

Claims

What is claimed is:

1. A pressure sensitive adhesive composition comprising:

a (co)polymer derived from polymerization of monomers comprising

(i) one or more (meth)acrylic acid ester monomers;

(ii) one or more acid functional ethylenically unsaturated monomers; and

2. The pressure sensitive adhesive composition of claim 1, wherein the wt. % ratio of (ii) derived units to (iii) derived units in the (co)polymer is greater than 1.67.

3. The pressure sensitive adhesive composition of claim 1, wherein the (copolymer comprises (ii) and (iii) derived units, collectively, in an amount of less than 10 wt. %, based the total weight of the (co)polymer

4. The pressure sensitive adhesive composition of claim 3, wherein the (copolymer comprises (i) derived units in an amount of between 87 and 95 wt. %, based the total weight of the (copolymer.

5. The pressure sensitive adhesive composition of claim 3, wherein the (copolymer comprises (ii) derived units in an amount of between 5 and 10 wt. %, based the total weight of the (copolymer.

6. The pressure sensitive adhesive composition of claim 3, wherein the (copolymer comprises (iii) derived units in an amount of between 0.2 and 3 wt. %

7. The pressure sensitive adhesive composition of claim 1, wherein the acid functional ethylenically unsaturated monomers comprise acrylic acid.

8. The pressure sensitive adhesive composition of claim 1, wherein the non-acid functional, ethylenically unsaturated polar monomers comprise nitrogen.

9. The pressure sensitive adhesive composition of claim 1, wherein the non-acid functional, ethylenically unsaturated polar monomers comprise acrylamide

10. The pressure sensitive adhesive composition of claim 1, wherein the non-acid functional, ethylenically unsaturated polar monomer has a pka≥ 6.

11. The pressure sensitive adhesive composition of claim 1, wherein the acid functional ethylenically unsaturated monomer has a pka≤ 5.

12. The pressure sensitive adhesive composition of claim 1, wherein the pressure sensitive adhesive composition exhibits an impact resistance of at least 200 mJ at a coating thickness of 35 μιη or higher.

13. The pressure sensitive adhesive composition of claim 1,

wherein the pressure sensitive adhesive composition exhibits a 180-degree peel adhesion at 23 °C at 300 mm/min of at least 0.5 N/mm at a coating thickness of 35 fan or higher.

14. The pressure sensitive adhesive composition of claim 1, wherein the pressure sensitive adhesive composition is in the form of a foam.

15. The pressure sensitive adhesive composition of claim 14, wherein the foam comprises expandable polymeric microspheres.

16. The pressure sensitive adhesive composition of claim 3, wherein the (co)polymer comprises (iii) derived units in an amount of between 5 and 10 wt. %, based the total weight of the (copolymer.

17. The pressure sensitive adhesive composition of claim 3, wherein the (copolymer comprises (ii) derived units in an amount of between 0.2 and 3 wt. %.

18. The pressure sensitive adhesive composition of claim 3, wherein the pressure sensitive adhesive composition exhibits a shear at 70 °C of at least 10,000 min at a coating thickness of 35 μτα or higher.

19. A laminating tape comprising

a substrate; and

a layer of a pressure sensitive adhesive composition according to claim 1 disposed on a major surface of the substrate.

20. The laminating tape of claim 19, wherein the substrate is a backing or a release liner.

21. The laminating tape of claim 19, wherein the pressure sensitive adhesive composition is disposed on both major surfaces of the substrate.

22. A protective film comprising

a film; and

a layer of a pressure sensitive adhesive composition according to claim 1 disposed on a major surface of the film.

23. The protective film of claim 22, wherein the film and pressure sensitive adhesive composition have transparency of at least 90%.

24. A method of bonding comprising

providing a first substrate,

contacting a surface of the first substrate with the pressure sensitive adhesive composition of claim 1.

25. The method of claim 24, further comprising contacting an opposing surface of the pressure sensitive adhesive to a second substrate.

26. The method of claim 24, wherein the first and second substrate are comprised of a metal, an inorganic material, an organic polymeric material, or a combination thereof.

27. An illuminated display device comprising a component bonded with the pressure sensitive adhesive composition of claim 1.

28. An article comprising

a substrate; and

a layer comprising the pressure sensitive adhesive composition of claim 1 disposed on a major surface of the substrate, wherein the pressure sensitive adhesive composition has a density of at-least 0.6 g/cm³.