WO2019000375A1

WO2019000375A1 - Surface modified inorganic nanoparticles and use thereof

Info

Publication number: WO2019000375A1
Application number: PCT/CN2017/091051
Authority: WO
Inventors: Puwei Liu; Nicolas BALL-JONES; Chunhua GU
Original assignee: Henkel Ag & Co. Kgaa; Henkel IP & Holding GmbH; Henkel (China) Co., Ltd.
Priority date: 2017-06-30
Filing date: 2017-06-30
Publication date: 2019-01-03
Also published as: TW201905058A

Abstract

Provided are surface modified inorganic nanoparticles and use thereof. In particular, provided are surface modified inorganic nanoparticles having a high refractive index of at least 1.50, and their use as fillers in adhesives, sealants and/or potting materials, especially in optical clear adhesives (OCAs), such as liquid optical clear adhesives (LOCAs).

Description

SURFACE MODIFIED INORGANIC NANOPARTICLES AND USE THEREOF

Technical field

The present invention relates to surface modified inorganic nanoparticles and use thereof. In particular, the invention relates tosurface modified inorganic nanoparticles having a high refractive index of at least 1.50, and their use as fillers in adhesives, sealants and/or potting materials, especially in optical clear adhesives (OCAs) , such as liquid optical clear adhesives (LOCAs) .

Background of the invention

Photo-curable optically clear adhesives (OCAs) and especially LOCAs are finding wide applications in optical bonding for optical electronic devices, such as optical displays. Optical bonding in display applications is used to bond optical elements such as display panels, glass plates, touch panels, diffusers, rigid compensators, heaters, and flexible films such as polarizers and retarders. Particularly, the use of such adhesives for bonding touch displays, for example, capacitive touch displays is of high interest.

The continuous development of new electronic display products, such as wearable display devices, image sensors, and light emitting diodes (LEDs) , increases the demands for optically clear adhesives. However, there are still some challenges for LOCAs, such as those used for bonding a substrate having a high refractive index. Such LOCAs are desired to have a high refractive index to match the optical property of the substrate and maintain its transparency.

Efforts have been made to develop such optically clear adhesives having a high refractive index. For example, US 8535576 B2 discloses a pressure-sensitive adhesive comprising a biphenyl monomer which has a high refractive index. The adhesives have a refractive index of at least 1.54, and sufficient conformability, tack and adhesion to form a bond to a substrate at room temperature.

However, there is still a need for optically clear adhesives, especially LOCAs which have a high refractivity, transparency and light stability.

Summary of the invention

In order to meet the requirements described above, the present invention provides surface modified inorganic nanoparticles, which can be used as fillers in OCAs (such as LOCAs) , wherein inorganic nanoparticles are surface modified with a surface modifier (also referred to as a “surface treating agent” or a “ (surface) modifier” ) comprising an organic compound. The organic compound has an intrinsic high refractive index value (RI) of at least 1.50. The organic compound used in this invention normally contains a functional group capable of forming covalent bond or ligand with the surfaces of the inorganic nanoparticles. In some embodiments, the organic compound has at least one group selected from hydroxyl group, carboxyl group, anhydride groups, isocyanate group and hydrolysable silane groups； and has at least one optionally substituted aryl or arylene moiety.

The present invention also provides a curable adhesive composition comprising surface modified inorganic particles according to the present invention and a curable resin component, and a cured product of the curable adhesive composition.

The present invention also provides use of the surface modified inorganic particles according to the present invention as fillers in adhesives, sealants and/or potting materials.

Detailed description of the invention

In the following passages the present invention is described in more detail. Each aspect so described may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

In the context of the present invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

As used herein, the singular forms “a” , “an” and “the” include both singular and plural referents unless the context clearly dictates otherwise.

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

The term “ (meth) acrylate” means acrylate and/or methacrylate.

The recitation of numerical end points includes all numbers and fractions subsumed within the respective ranges, as well as the recited end points.

All references cited in the present specification are hereby incorporated by reference in their entirety.

Unless otherwise defined, all terms used in the invention, including technical and scientific terms, have the meaning as commonly understood by one of the ordinary skill in the art to which this invention belongs to. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

As used herein, refractive index is defined herein as the absolute refractive index of a material (e.g., inorganic nanoparticle orcurable adhesive composition) which is understood to be the ratio of the speed of light in vacuum to the speed of the light in that material, with the light being sodium yellow light at a wavelength of about 583.9 nanometers (nm) . The refractive index can be measured using known methods and is generally measured using an Abbe Refractometer.

It will be appreciated that the phrase "optionally substituted"is used interchangeably with the phrase "substituted or unsubstituted. "In general, the term "substituted", whether preceded by the term "optionally"or not, means that a hydrogen radical of the designated moiety is replaced with the radical of a specified substituent. Unless otherwise indicated, an "optionally substituted"group may have a substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position.

The term "alkyl", used alone or as part of a larger moiety, refers to an optionally substituted straight or branched chain hydrocarbon group having 1-12, 1-10, 1-8, 1-6, 1-5, 1-4, 1-3, or 1-2 carbon atoms.

The term "alkenyl", used alone or as part of a larger moiety, refers to an optionally substituted straight or branched chain hydrocarbon group having at least one double bond and having 2-12, 2-10, 2-8, 2-6, 2-5, 2-4, or 2-3 carbon atoms.

The term "alkynyl", used alone or as part of a larger moiety, refers to an optionally substituted straight or branched chain hydrocarbon group having at least one triple bond and having 2-12, 2-10, 2-8, 2-6, 2-5, 2-4, or 2-3 carbon atoms.

The term “alkoxy” as used herein, refers to an alkyl group, as previously defined, attached to the principal carbon chain through an oxygen ( “alkoxy” ) atom.

The terms "aryl", used alone or as part of a larger moiety, e.g., "aralkyl", refer to an optionally substituted aromatic hydrocarbon moiety comprising one to three aromatic rings. Aryl groups include, without limitation, optionally substituted phenyl, naphthyl, or anthracenyl. The terms "aryl", as used herein, also include groups in which an aryl ring is fused to one or more cycloaliphatic rings to form an optionally substituted cyclic structure such as a tetrahydronaphthyl, indenyl, or indanyl ring.

The term "aralkyl"refers to an aryl group covalently attached to an alkyl group, either of which independently is optionally substituted. In at least one embodiment, the aralkyl group is C_6-10 aryl-C_1-6 alkyl, including, without limitation, benzyl, phenethyl, and naphthylmethyl.

The term "alkaryl"refers to an alkyl group covalently attached to an aryl group, either of which independently is optionally substituted. In at least one embodiment, the alkaryl group is C_1-6 alkyl-C_6-10 aryl.

The term "heteroaryl", used alone or as part of a larger moiety, e.g., "heteroaralkyl", or "heteroaralkoxy", refer to groups having 5 to 14 ring atoms； having 6, 10, or 14 πelectrons shared in a cyclic array； and having, in addition to carbon atoms, from one to five heteroatoms. A heteroaryl group may be mono-, bi-, tri-, or polycyclic. The term "heteroatom"refers to nitrogen, oxygen and/or sulfur, and includes any oxidized form of nitrogen or sulfur, and any quatenized form of a basic nitrogen. For example, a nitrogen atom of a heteroaryl may be a basic nitrogen atom and may also be optionally oxidized to the corresponding N-oxide. The term "heteroaryl", as used herein, also include groups in which a heteroaromatic ring is fused to one or more aryl, cycloaliphatic, or heterocycloaliphatic rings. Non-limiting examples of heteroaryl groups include thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl, purinyl, naphthyridinyl, pteridinyl, indolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl, benzthiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl. The term "heteroaralkyl"refers to an alkyl group substituted by a heteroaryl, wherein the alkyl and heteroaryl portions independently are optionally substituted.

The terms “alkylene” , “arylene” , "alkenylene", “aralkylene” , "alkarylene"or "heteroarylene", as used herein, represents a respective system as described herein, but has two points of attachment to the rest of the molecule.

In one aspect, the present invention provides surface modified inorganic nanoparticles, wherein inorganic nanoparticles are surface modified with a surface modifier comprising an organic compound having a refractive index of at least 1.50, and contains at least one functional group capable of forming covalent bond or ligand with the surfaces of the inorganic nanoparticles. According the present invention, the organic compound has at least one group selected from hydroxyl group, carboxyl group, anhydride group, isocyanate group and hydrolysable silane group, so as to interact with and modify the surfaces of the inorganic nanoparticles. The organic compound may also have an optionally substituted aryl or an optionally substituted arylene moiety.

In order to make inorganic nanoparticles compatible with the application conditions, inorganic nanoparticles are conventionally surface modified with an organic compound whose RI is not larger than 1.45, and is less than the RI of the inorganic nanoparticles. Since the density of the conventional surface modifier is usually much less than the density of the inorganic particles, the volume of the organic modifier is undesirably large, and thus the volume average density of the inorganic nanoparticles are drastically decreased after being modified, which will in turn decrease the RI value of the surface modified inorganic nanoparticles.

The inventors has surprisingly found that by employing organic compounds having high refractive index, such as at least 1.50, the surface modified inorganic nanoparticles and the cured products of adhesive composition containing the surface modified inorganic nanoparticles are provided with higher refractive index values than any current surface modified inorganic nanoparticles which are commercially available. In addition, such cured products of adhesive composition containing the surface modified inorganic nanoparticles exhibit high transparency, low haze, yellowness and light stability, and thus the surface modified inorganic nanoparticles are suitable to be used in optical adhesives such as LOCA as additives such as filler.

In some embodiments, the organic compound is selected from the group consisting of a cumylphenol derivative having at least one hydroxyl group, a phthalate derivative having at least one hydroxyl group, and combination thereof. The cumylphenol derivative having at least one hydroxyl group may be represented by Formula (1) ,

wherein R₁ is an optionally substituted alkylene group, an optionally substituted alkenylene group, an optionally substituted aralkylene group, an optionally substituted alkarylene group, an optionally substituted arylene group, an optionally substituted heteroarylene group, and an acyl group.

In one embodiment, R₁ is an optionally substituted C₁-C₆ alkylene group. In another embodiment, R₁ is a C₁-C₆ alkylene group substituted by one or two groups selected from ester groups, ether groups, acyl group, hydroxyl group, and carboxyl group. In yet another embodiment, R₁ is a C₁-C₆ alkylene group substituted by a hydroxyl group or carboxyl group. In one preferred embodiment, R₁ is selected from 1-hydroxyl propylene, 2-hydroxyl propylene, and 3-hydroxyl propylene. Preferred is 2-hydroxyl propylene. More preferably, the cumylphenol derivative having at least one hydroxyl group is 3- [4- (1-methyl-1-phenyl-ethyl) -phenoxy] -propane-1, 2-diol.

According to the present invention, the phthalate derivative is represented by Formula (2)

wherein R₂ is an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aralkyl group, an optionally substituted alkaryl group, an optionally substituted aryl group, an optionally substituted heteroaryl group and an optionally substituted ester group.

In one embodiment, R₂ is an optionally substituted C₁-C₆ alkyl group. In another embodiment, R₂is a C₁-C₆ alkyl group substituted by one or two groups selected from ester groups, ether groups, acyl group, hydroxyl group, and carboxyl group. In yet another embodiment, R₂is a C₁-C₆ alkyl group substituted by an ester group or an ether group. In one preferred embodiment, R₂is selected from the group consisting of (meth) acrylate group, fumate group, maleate group, urethane group, and more preferably is a (meth) acrylate group selected from methyl (meth) acrylate group, ethyl (meth) acrylate group, propyl (meth) acrylate group, butyl (meth) acrylate group, isobutyl (meth) acrylate group, 2-ethyl hexyl (meth) acrylate group, hydroxyethyl (meth) acrylate group, hydroxypropyl (meth) acrylate group, hydroxybutyl (meth) acrylate group, hydroxyhexyl (meth) acrylate group and hydroxyoctyl (meth) acrylate group. In particular, R₂ is methyl acrylate or methyl methacrylate group. In one preferred embodiment, the phthalate derivative is phthalic acid mono- (2-acryloyloxy-ethyl) ester.

In some embodiments, the organic compound may be a hydrolysable silane represented by Formula (3)

QSi (OX) ₃ (3)

wherein X each independently represents an optionally substituted alkyl； and Q represents an optionally substituted alkyl, an optionally substituted alkoxy, an optionally substituted aryl and/or a hydrolyzate/condensate obtained therefrom.

Here, the alkyl group may be linear, branched or cyclic. The linear or branched alkyl group may be, for example, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, a s-butyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group or an octyl group. A preferred linear or branched alkyl group is one having from 1 to 4 carbon atoms. The cycloalkyl group may be, for example, preferably a cyclohexyl group, a cycloheptyl group or a cyclooctyl group. The aryl group may be, for example, a phenyl group. In preferred embodiments, the organic group X represents C₁-C₄ alkyl and Q represents C₁-C₈ alkyl, phenyl, methoxy, or ethoxy, and/or a hydrolyzate/condensate obtained therefrom.

Suitable substituents may be, for example, a halogen atom (such as a chlorine atom, a bromine atom or a fluorine atom) , a (meth) acryloyl group, a mercapto group, and an alicyclic group.

Specific examples of hydrolysable silanes of formula (3) include, for example, methyl trimethoxysilane, methyl triethoxysilane, ethyl trimethoxysilane, ethyl triethoxysilane, n-propyl trimethoxysilane, n-propyl triethoxysilane, i-propyl trimethoxysilane, i-propyl triethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, 3, 3, 3-trifluoropropyl trimethoxysilane, 3, 3, 3-trifluoropropyl triethoxysilane, cyclohexyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyl trimethoxysilane, γ-mercaptopropyl triethoxysilane, phenyl trimethoxysilane, phenyl triethoxysilane, dimethyl dimethoxysilane, dimethyl diethoxysilane, diethyl dimethoxysilane, diethyl diethoxysilane, diphenyl dimethoxysilane, diphenyl diethoxysilane, methylphenyldimethoxysilane and dimethyl dipropoxysilane.

In one preferred embodiment, the hydrolysable silane comprises alkyltrialkoxysilane or a hydrolyzate/condensate obtained therefrom. Preferred is methyl trimethoxysilane, methyl triethoxysilane, ethyl trimethoxysilane, ethyl triethoxysilane, n-propyl trimethoxysilane, n-propyl triethoxysilane, and more preferred is n-propyl trimethoxysilane.

In addition to the organic compound having a refractive index of at least 1.50and having a functional group capable of forming covalent bond or ligand with the surfaces of the nanoparticles, the surface modifier according to the present invention may optionally further comprise other surface modifier (s) having a monocarboxylic acid end group, and also having a reactive group such as a (meth) acrylate end group.

In one embodiment, the other surface modifier is carboxyalkyl (meth) acrylate, preferably carboxy C₁-C₆ alkyl (meth) acrylate. Examples are carboxymethyl (meth) acrylate, carboxyethyl (meth) acrylate, carboxybutyl (meth) acrylate. Preferred is β-carboxyethyl (meth) acrylate.

In some embodiments, the organic compound is present in an amount from about 5％to about 40％by weight, preferably from about 10％to about 35％by weight, more preferably from about 12％to about 30％by weight, based on the total weight of the surface modified inorganic nanoparticles. With the content of the organic compound falling within the aforementioned ranges, the surface modified inorganic particles may exhibit high RI and high light stability while employing only small amount of the organic compound.

The surface modified inorganic nanoparticles according to the present invention may be used as fillers in adhesives (especially OCAs and LOCAs) , sealants and/or potting materials. Surface modified inorganic nanoparticles are present in the materials in an amount effective to enhance the durability and/or refractive index of the cured products of the adhesive compositions applied on articles or optical devices. The optical devices or optical articles include wearable display devices, image sensors and light emitting diodes (LEDs) . If used in a curable adhesive composition, the total amount of the surface modified inorganic nanoparticles can be present in an amount from 5％to 90％by weight, preferably from 7％to 85％by weight based on the total weight of the adhesive composition depending on actual needs.

The size of such particles is chosen to avoid significant visible light scattering. It may be desirable to employ a mixture of inorganic oxide particle types to optimize an optical or material property and to lower total composition cost. The surface modified nanoparticles can be oxide particles having a (e.g. unassociated) primary particle size or associated particle size of greater than 1 nm, 5 nm or 10 nm. The primary or associated particle size is generally less than 100 nm, 75 nm, or 50 nm. Typically the primary or associated particle size is less than 40 nm, 30 nm, or 20 nm. It is preferred that the nanoparticles are unassociated. Their measurements can be based on transmission electron microscopy (TEM) . Examples of nanoparticles can include but not limited to metal oxides such as, ZrO₂, TiO₂, Al₂O₃, Sb₂O₄ (or Sb₂O₃, Sb₂O₅) , CdO, CaO₂, Cu₂O, FeO, Fe₂O₃, PbO, MnO, MnO₃, SnO₂, ZnO, ZnS, ZnSe, ZnTe and mixtures thereof. Surface modified nanoparticles can be substantially fully condensed.

Fully condensed inorganic nanoparticles typically have a degree of crystallinity (measured as isolated metal oxide particles) greater than 55％, preferably greater than 60％, and more preferably greater than 70％. For example, the degree of crystallinity can range up to about 86％or greater. The degree of crystallinity can be determined by X-ray diffraction techniques. Condensed crystalline (e.g. zirconia) inorganic nanoparticles have a high refractive index whereas amorphous inorganic nanoparticles typically have a lower refractive index.

According to the present invention, ZrO₂, TiO₂ and Al₂O₃, nanoparticles are preferred, and can have a particle size from 5 to 50 nm, or from 5 to 15 nm, or from 8 nm to 12 nm. The inorganic nanoparticles can be present in a curable adhesive composition in an amount from 10％to 70％by weight, or from 30％to 60％by weight based on the total weight of the curable adhesive composition. ZrO₂nanoparticles for use in adhesive composition of the invention are available from Sakai Chemical under the trade designation “SZR” .

When used in curable compositions, such as adhesive composition, the surface modification of the inorganic nanoparticles may be dispersed in advance, and can be accomplished in a variety of ways. The dispersing process generally involves the mixture of an inorganic particle dispersion with surface modifier (s) . Optionally, a solvent, for example, toluene, methanol, 1-methoxy-2-propanol, ethanol, isopropanol, ethylene glycol, N, N-dimethylacetamide and 1-methyl-2-pyrrolidinone can be added in the dispersion. The solvent can enhance the solubility of the surface modified particles in the surface modifier. The mixed dispersion comprising the inorganic nanoparticles and surface modifier can be subsequently treated at room or an elevated temperature, with or without mixing.

In another aspect, the present application concerns a curable adhesive composition, comprising the surface modified inorganic nanoparticles according to the present invention and a curable resin. The curing mechanism of the adhesive composition may include, not limited to radiation curing, thermal curing, and combination thereof.

Preferably, the curable adhesive composition is a radiation curable, and contains a radiation curable resin. The backbone of the radiation-curable resins is not limited. The reactive functionalities on the resins will be those reactive to the initiators or catalysts formed by exposure to radiation and include, but are not limited to, epoxies, selected from glycidyl epoxy, aliphatic epoxy, and cycloaliphatic epoxy； oxetane； acrylate and methacrylate； itaconate； vinyl, propenyl, crotyl, allyl, and propargyl ether and thio-ethers of those groups； maleate, fumarate, and cinnamate esters； styrenic； acrylamide and methacrylamide； chalcone； epoxy-thiol； and thiol-alkene.

More suitable cationic polymerizable radiation-curable resins include epoxies, oxetanes, vinyl ethers, and propenyl ethers. Representative epoxy resins are glycidyl ethers and cycloaliphatic epoxies, which are commercially available from a number of sources known to those skilled in the art. Representative aromatic liquid glycidyl ethers include bisphenol F diglycidyl ether (sold under the trade name Epikote 862 from Resolution Performance Products) or bisphenol A diglycidyl ether (sold under the trade name Epikote 828 from Resolution Performance Products) . Representative solid glycidyl ethers include tetramethylbiphenyl diglycidyl ether (sold under the trade name RSS 1407) and resorcinol diglycidyl ether (sold under the trade name Erisys

available from CVC Specialty Chemicals, Inc. ) . Other aromatic glycidyl ethers are commercially available under the trade names Epon 1031, Epon 164, and SU-8 available from Resolution Performance Products. Representative cycloaliphatic epoxy resins include ERL 4221 and ERL 6128 available from Dow Chemical Co. A representative oxetane resin is OXT-121 available from Toagosei. Representative vinyl ether compounds include cyclohexanedimethyloldivinyl ether (Rapicure-CHVE) , tripropylene glycol divinyl ether (Rapicure-DPE-3) or dodecyl vinyl ether (Rapicure-DDVE) all available from International Specialty Products. Analogous vinyl ethers are also available from BASF. Suitable radically polymerizable radiation-curable resins include (meth) acrylates or thiol-ene based resins. In many cases, combinations of the curable resins can be utilized to tailor the properties of the sealant/adhesive material.

Representative (meth) acrylate resin includes but not limited to 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, menubutoxy ethylene glycol (meth) acrylate, 2-ethoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, benzyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, carboxymethyl diethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, 2, 2, 2, -trifluoroethyl (meth) acrylate, 2, 2, 3, 3, -tetrafuruo (meth) acrylate, 1 H, 1 H, 5H-octafluoropentyl (meth) acrylate, imide (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, n- butyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isononyl (meth) acrylate, isomyristyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, bicyclopentenyl (meth) acrylate, isodecyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, 2-(meth) acryloylacid, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2-(meth) acryloyloxyethyl 2-hydroxypropyl phthalate, glycidyl (meth) acrylate, 2-(meth) acryloyloxyethyl phosphate, 1, 4-butanediol di (meth) acrylate, 1, 3-butanediol di(meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate 1, 10-decanediol di (meth) acrylate, 2-n-butyl-2-ethyl -1, 3-propanediol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycidyl (meth) acrylate, ethylene glycol di (meth) acrylate, diethyleneglycol di (meth) acrylate, tetra-ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, ethylene oxide addition bisphenol A di (meth) acrylate, ethylene oxide addition bisphenol F di (meth) acrylate, cyclopentadienedistearate (meth) acrylate, 1, 3-butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide modified isocyanuric acid di(meth) acrylate, carbonate diol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, propylene oxide adduct of trimethylolpropane tri(meth) acrylate, dipentaerythritolpenta (meth) acrylate, dipentaerythritolhexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, propylene oxide addition glycerin tri (meth) acrylate, tris (meth) acryloyloxyethyl phosphate, and the like. Of these, the (meth) acrylate compounds having an aromatic ring or alicyclic ring are preferably used in the curable adhesive composition. Such resins are commercially available from Sartomer.

Additional suitable radiation-curable resins, and photoinitiators for those resins, will include those found in literature sources such as Fouassier, J-P., Photoinitiation, Photopolymerization and Photocuring Fundamentals and Applications 1995, Hanser/Gardner Publications, Inc., New York, N. Y.

The selection of a photoinitiating system for the inventive radiation curable adhesive composition is familiar to those skilled in the art of radiation curing. The photoinitiating system will comprise one or more photoinitiators and optionally one or more photosensitizers. The selection of an appropriate photoinitiator is highly dependent on the specific application in which the barrier sealant is to be used. A suitable photoinitiator is one that exhibits a light absorption spectrum that is distinct from that of the resins, fillers, and other additives in the radiation curable system.

In accordance with some embodiments of the present invention, the curable adhesive compositions described herein may further comprise one or more flow additives, adhesion promoters, rheology modifiers, toughening agents, fluxing agents, film flexibilizers, UV stabilizers, curing agents, diluent and the like, as well as mixtures of any two or more thereof, as long as the optical properties and other advantages achieved by the adhesive composition are not negatively influenced.

In yet another aspect, the present invention also relates to a cured product of the curable adhesive composition. Preferably, the cured product has a refractive index of at least 1.60 as defined above.

EXAMPLES

The present disclosure will be further described and illustrated in detail with reference to the following Examples. The Examples are intended to assist one skilled in the art to better understand and practice the present disclosure, however, are not intended to restrict the scope of the present disclosure.

Synthesis of 3- [4- (1-Methyl-1-phenyl-ethyl) -phenoxy] -propane-1, 2-diol (Modifier 1)

To a 250 mL flask was added 33.33 g of cumylphenol, 80 mL ethanol and 0.47 g potassium hydroxide. The mixture was heated to 80 ℃, and 10 mL of glycidol in 20 mL ethanol was added dropwise. After 4.5 hours the reaction mixture was concentrated in vacuo until no ethanol remained, at which point the reaction mixture was diluted with diisopropylether (100 mL) . Subsequently, 10 g potassium hydroxide dissolved in 100 mL water was added to the resultant reaction mixture. Then layer separation was observed. The aqueous layer was extracted five times with 40 ml diisopropylether each time. The organic layers were dried over sodium sulfate, followed by concentration in vacuo. The product (i.e., Modifier 1) was purified by column chromatography (ethyl acetate: hexanes, volume ratio being 90: 10) to afford 34.48 g of a clear viscous liquid in 80.3％by weight yield.

The resultant Modifier 1 was characterized by NMR: ¹H NMR (CDCl₃, 300 MHz) , δ(ppm) : 7.34-7.08 (7 H) , 6.85-6.76 (2H) , 4.15-4.04 (1H) , 4.04-3.96 (2H) , 3.96-3.68 (2H) , 1.69-1.62 (6 H) .

Preparation of surface modified nanoparticle dispersion 1 (SMND-1)

To a 250 mL flask was added 10 g toluene, 2.65 g Modifier 1, and 22.2 g methanol (with 30％by weight ZrO₂ dispersed in it, obtained from Sakai Chemical) . All solvents were removed in vacuo. The concentrated sample thus obtained was redispersed in 21.7 g toluene to afford surface modified ZrO₂ nanoparticle dispersion 1, with the organic content (i.e., Modifier 1) of the surface modified nanoparticle being 28.5％by weight.

Preparation of surface modified nanoparticle dispersion 2 (SMND-2)

To a 250 mL flask was added 7 g toluene, 0.63 g Modifier 1, 0.21 g β-carboxyethylacrylate, and 16.9 g methanol (with 30％ZrO₂ dispersed in it, obtained from Sakai Chemical) . All solvents were removed in vacuo. The concentrated sample was redispersed in 11.2 g toluene to afford surface modified ZrO₂nanoparticle dispersion 2, with the organic content (i.e., Modifier 1 and β-carboxyethylacrylate) of the surface modified nanoparticle being 14.2％by weight.

Preparation of surface modified nanoparticle dispersion 3 (SMND-3)

To a 250 mL flask was added 7 g toluene, 0.21 g Modifier 1, 0.06 g β-carboxyethylacrylate, and 8.55 g methanol (with 30％ZrO₂ dispersed in it, obtained from Sakai Chemical) . All solvent were removed in vacuo. The concentrated sample was redispersed in 11.8 g toluene to afford surface modified ZrO₂nanoparticle dispersion 3, with the organic content (i.e., Modifier 1 and β-carboxyethylacrylate) of the surface modified nanoparticle being 10％by weight.

Preparation of surface modified nanoparticle dispersion 4 (SMND-4)

SMND-4 were prepared in the same way as described above for SMND-1, except that 15.8 g toluene, 0.54 g modifier 2 (available from POLYGON company) , and 10.3 g methanol (with 30％ZrO₂ dispersed in it, obtained from Sakai Chemical) were used. The resultant surface modified ZrO₂ nanoparticles had an organic content (i.e., modifier 2) of the surface modified nanoparticle being 15 ％by weight.

Preparation of surface modified nanoparticle dispersion 5 (SMND-5)

SMND-5 were prepared in the same way as described above for SMND-1, except that 12.1 g toluene, 0.28 g Modifier 2 (available from POLYGON company) , and 8.3 g methanol (with 30％ZrO₂ dispersed in it, obtained from Sakai Chemical) were used. The resultant surface modified ZrO₂ nanoparticles had an organic content (i.e., Modifier 2) of the surface modified nanoparticle being 10 ％by weight.

Preparation of surface modified nanoparticle dispersion 6 (SMND-6)

SMND-6 were prepared in the same way as described above for SMND-2, except that acrylic acid was used instead of Modifier 1 and β-carboxyethylacrylate, and organic content (i.e., acrylic acid) of the surface modified nanoparticle is 20％.

Preparation of surface modified nanoparticle dispersion 7 (SMND-7)

SMND-7 were prepared in the same way as described above for SMND-2, except that hydroxyethyl methylacrylate was used instead of Modifier 1 and β-carboxyethylacrylate, and the organic content (i.e., hydroxyethyl methylacrylate) of the surface modified nanoparticle is 20％.

Preparation of surface modified nanoparticle dispersion 8 (SMND-8)

SMND-8 were prepared in the same way as described above for SMND-2, except that citric acid was used instead of Modifier 1 and β-carboxyethylacrylate, and the organic content (i.e., citric acid) of the surface modified nanoparticle is 20％.

RI test of curable adhesive compositions

Each surface modified nanoparticle dispersion prepared in SMND-1 to 5 and benzyl methacrylate (available from Aldrich Company) were mixed in a 100 ml round bottom flask. The weight parts of the surface modified nanoparticle dispersions were listed in Table 1. The total weight of the surface modified nanoparticle dispersion and benzyl methacrylate added up to 99.9 weight parts. Then 0.1 weight parts of Igracure 184 (available from BASF) was added into the flask. The solvent contained in the surface modified nanoparticle dispersion was removed at 40℃by using a rotatory evaporator. Then the mixture in the form of transparent paste was cured under UV irradiation (50mW/cm²) by a Loctite Zeta Conveyor 7415 for 1 minute.

The RI values of the cured products of adhesive composition were measured at room temperature by Metricon refractometer at 589 nm and recorded in Table 1.

It can be seen from Table 1 that the RI values of the surface modifiers used in the inventive examples are higher than conventional surface modifiers used in the art. In addition, with the same amount of surface modified nanoparticle dispersion (Examples 1 and 2 vs. Comparative example 1； Examples 3 and 4 vs. Comparative example 2； and Example 5 vs. Comparative example 3) , the cured products of inventive examples containing surface modified nanoparticles according to the present invention all possessed significantly higher RI values than the comparative examples. It should be noted that the increase by even 0.01 unit of the RI value of the cured product actually means a significant improvement for such material in the LOCA industry.

Preparation and optical properties of adhesive composition

Preparation of high RI formulations

All ingredients listed in Table 2 below were put into a 100 ml round bottom flask. The solvent contained in surface modified nanoparticle dispersion was removed at 40℃by using a rotatory evaporator to obtain a transparent paste.

Each of the paste compositions prepared as described above was dispensed between two pieces of 3 cm X5cm glass with a 300 μm gap. Then the compositions between glasses were cured under UV (50mW/cm²) by a Loctite Zeta Conveyor 7415for 1 minute.

The optical properties such as transmittance, haze, and yellow index were tested on a Datacolor 650 instrument available from Datacolor.

The adhesive compositions were tested in QUV accelerated weathering tester manufactured by Q-Lab Corporation, which reproduces the damage caused by sunlight, rain and dew. In a few days or weeks, the QUV accelerated weathering tester can reproduce the damage that occurs over months or years outdoors.

Table 2: Curable adhesive compositions (parts by weight) and test results of optical properties

¹Benchmark-1 is a surface modified ZrO₂ nanoparticle dispersion commercially available from Nippon Shokubai in the trade name of 153-A.

²Benchmark-2 is a surface modified ZrO₂ nanoparticle dispersion commercially available from Nippon Shokubai in the trade name of 158-A.

³Benchmark-3 is a surface modified ZrO₂ nanoparticle dispersion commercially available from Nippon Shokubai in the trade name of 159-A.

⁴Ethoxylated bisphenol A dimethacrylate is commercially available from Sartomer.

⁵Cyclohexane dimethanolmonoacrylate is commercially available from Aldrich.

It can be seen from Table 2 that by containing surface modified nanoparticles according to the present invention, the inventive adhesive compositions exhibited increased refractive indexes (RIs) than the compositions containing benchmark products of surface modified ZrO₂ nanoparticle dispersion. In addition, the inventive adhesive compositions showed comparable or better light stability including initial yellowness, haze and transparency compared to the comparative examples. Surprisingly, the inventive adhesive compositions achieved an excellent durability as demonstrated by the QUV accelerated weathering test. Therefore, the nanoparticles surface modified by the inventive modifier are suitable for the use in optical adhesive products, such as LOCA, and could increase the light stability and duration than those of the currently marked products.

Claims

Surface modified inorganic nanoparticles, wherein inorganic nanoparticles are surface modified with a surface modifier comprising, an organic compound having a refractive index of at least 1.50 and having at least one functional group selected from hydroxyl group, carboxyl group, anhydride group, isocyanate group and hydrolysable silane group.
The surface modified inorganic nanoparticles according to claim 1, wherein the organic compound further has an optionally substituted aryl or an optionally substituted arylene moiety.
The surface modified inorganic nanoparticles according to claim 1 or 2, wherein the organic compound is selected from the group consisting of cumylphenol derivative having at least one hydroxyl group, phthalate derivative having at least one hydroxyl group, and combination thereof.
The surface modified inorganic nanoparticles according to claim 3, wherein the cumylphenol derivative having at least one hydroxyl group is represented by Formula (1) :

wherein R₁ is an optionally substituted alkylene group, an optionally substituted alkenylene group, an optionally substituted aralkylene group, an optionally substituted alkarylene group, an optionally substituted arylene group, an optionally substituted heteroarylene group, and an acyl group, and preferably is an optionally substituted C₁-C₆alkylene group, and more preferably is a C₁-C₆ alkylene group substituted by one or two groups selected from ester groups, ether groups, acyl group, hydroxyl group, and carboxyl group.
The surface modified inorganic nanoparticles according to claim 3, wherein the phthalate derivative is represented by Formula (2) :

wherein R₂ is an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aralkyl group, an optionally substituted alkaryl group, an optionally substituted aryl group, an optionally substituted heteroaryl group and an optionally substituted ester group, and preferably is an optionally substituted C₁-C₆ alkyl group, and more preferably is a C₁-C₆ alkyl group substituted by one or more groups selected from ester groups, ether groups, acyl group, hydroxyl group, and carboxyl group.
The surface modified inorganic nanoparticles according to claim 1, wherein the organic compound is a hydrolysable silane represented by Formula (3) :

QSi (OX) ₃ (3)

wherein X each independently represents an optionally substituted alkyl； and Q represents an optionally substituted alkyl, an optionally substituted alkoxy, an optionally substituted aryl and/or a hydrolyzate/condensate obtained therefrom, and preferably selected from alkyltrialkoxysilanes and the hydrolyzates/condensates obtained therefrom.
The surface modified inorganic nanoparticles according to any of claims 1 to 6, wherein the organic compound is present in an amount from 5％to 40％by weight, preferably from 10％to 35％by weight, more preferably from 12％to 30％by weight, based on the total weight of the surface modified inorganic nanoparticles.
The surface modified inorganic nanoparticles according to any of claims 1 to 7, wherein the inorganic nanoparticles include metal oxides selected from the group consisting of ZrO₂, TiO₂, Al₂O₃, Sb₂O₄, Sb₂O₃, Sb₂O₅, CdO, CaO₂, Cu₂O, FeO, Fe₂O₃, PbO, MnO, MnO₃, SnO₂, ZnO, ZnS, ZnSe, ZnTe and mixtures thereof, and preferably include metal oxides selected from the group consisting of ZrO₂, TiO₂, Al₂O₃ and mixture thereof, and more preferably include ZrO₂.
A curable adhesive composition comprising the surface modified inorganic nanoparticles according to any of claims 1 to 8 and a curable resin component.
Use of the surface modified inorganic nanoparticles according to any of claims 1 to 8 as fillers in adhesives, sealants or potting materials.
A cured product of the curable adhesive composition according to claim 10.
The cured product according to claim 11, in which it has a refractive index of at least 1.60.