WO2025252453A1 - Cationic polymerized ultra-low loss hydrocarbon resin composition - Google Patents

Abstract

The present disclosure relates to a composition comprising: (a) a cationic polymerization initiator; and (b) an indene based or cyclopentadiene based resin; wherein the cationic polymerization initiator is selected from the group consisting of (i) an aromatic sulfonium salt-based cationic polymerization initiator; (ii) a phosphonium salt-based cationic polymerization initiator; (iii) a quaternary ammonium salt-based cationic polymerization initiator; (iv) an aluminum complex-based cationic polymerization initiator; (v) an aromatic iodonium salt-based cationic polymerization initiator; (vi) an aromatic diazonium salt-based cationic polymerization initiator; (vii) a pyridinium-based cationic polymerization initiator and (viii) a mixture thereof. Also described are varnishes and coatings formed from said composition.

Description

CATIONIC POLYMERIZED ULTRA-LOW LOSS HYDROCARBON RESIN COMPOSITION

FIELD

[0001] The present disclosure relates to cyclopentadiene and indene - based resin compositions comprising a cationic polymerization initiator, and to their uses in various applications, such as, in the production of a prepreg, a laminated board for printed wiring board, a molding material and an adhesive.

BACKGROUND

[0002] With the development of wireless network and satellite communications, electronic products are trending toward the need for higher speed, frequency and larger capacity for the transmission of voice, video and data. In addition, as these electronic products become thinner and smaller, electrical circuit boards tend to increase in complexity, density and multi-layer stratification. In order to maintain the high rate of transmission and signal integrity, printed circuit boards ("PCB") have a need for materials with a low dielectric constant (Dk) and low dielectric loss (sometimes also called loss factor or dissipation factor, Df) thereby resulting in lower signal loss.

[0003] Polymer insulating materials are usually used as substrate materials for PCB's. The laminate for the PCB is either made of the polymer insulating material alone or by blending the polymer insulating material with glass, fiber, nonwoven fabric, inorganic filler or the like. Epoxy resins have traditionally been employed due to their low cost and high heat and chemical resistant properties when cured. However, because of their relatively high dielectric constant and high dielectric loss tangent, it is difficult to achieve a suitable low dissipation factor at high frequency signals. Polyphenylene ether (PPO) resins have also been used in laminates due to their lower dielectric constants and dissipation properties, but the use of high frequency signals in new electronic fields require even lower dielectric loss constants and dissipation factors. Fluoro- resins, typically represented by polytetrafluoroethylene (PTFE), have low dielectric constants and dissipation factors, but they are thermoplastic resins and therefore undergo large expansion and shrinkage during molding and processing and are materials that are not easily handled.

[0004] Indene based or cyclopentadiene based resins (preferably with vinylbenzyl pending groups) are known. These types of resins provide improved properties compared to those described above. When these resins are cured thermally, they are initiated via radical mechanism which are formed by the vinylbenzyl (styrene) functional groups. However, it is known that indene and cyclopentadiene functional groups do not well react under radical polymerization (e.g., in combination with styrene functional groups they are not well incorporated into the crosslinked network). [0005] Accordingly, a need exists for the development of a composition comprising a resin and an initiator to support cationic polymerization which will improve the crosslinking network of the resultant polymer leading to the resultant polymer having improved thermomechanical properties.

SUMMARY

[0006] The present disclosure is generally directed to a resin composition comprising: a composition comprising: (a) a cationic polymerization initiator; and (b) an indene based or cyclopentadiene based resin; wherein the cationic polymerization initiator is selected from the group consisting of (i) an aromatic sulfonium salt-based cationic polymerization initiator; (ii) a phosphonium salt-based cationic polymerization initiator; (iii) a quaternary ammonium salt-based cationic polymerization initiator; (iv) an aluminum complex-based cationic polymerization initiator; (v) an aromatic iodonium salt-based cationic polymerization initiator; (vi) an aromatic diazonium salt-based cationic polymerization initiator; (vii) a pyridinium-based cationic polymerization initiator or a mixture thereof.

[0007] Other embodiments of the present disclosure include a method for preparing a varnish comprising providing the composition described above and optionally other components, and to methods of providing a coating comprising providing the varnish and curing.

[0008] In an alternative embodiment of the present disclosure is described a coating produced by the method described above and an article coated with said varnish.

DETAILED DESCRIPTION

[0009] The present disclosure is generally directed to a resin composition having a low dielectric constant (Dk), a low dielectric dissipation factor (Df) and excellent thermomechanical properties, such as high thermal stability, good processability, high Charpy impact strength, high peel strength, good moisture resistance and/or a high glass transition temperature (Tg).

[0010] The following terms shall have the following meanings:

[0011] The term "comprising" and derivatives thereof are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is disclosed herein. In order to avoid any doubt, all compositions claimed herein through use of the term "comprising" may include any additional additive, adjuvant, or compound, unless stated to the contrary. In contrast, the term, "consisting essentially of" if appearing herein, excludes from the scope of any succeeding recitation any other component, step or procedure, except those that are not essential to operability and the term "consisting of", if used, excludes any component, step or procedure not specifically delineated or listed. The term "or", unless stated otherwise, refers to the listed members individually as well as in any combination. [0012] The articles "a" and "an" are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical objects of the article. By way of example, "a crosslinker" means one crosslinker or more than one crosslinker. The phrases "in one embodiment", "according to one embodiment" and the like generally mean the particular feature, structure, or characteristic following the phrase is included in at least one embodiment of the present disclosure and may be included in more than one embodiment of the present disclosure. Importantly, such phrases do not necessarily refer to the same aspect. If the specification states a component or feature "may", "can", "could", or "might" be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0013] The term "about" as used herein can allow for a degree of variability in a value or range, for example, it may be within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range. [0014] Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but to also include all of the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range such as from 1 to 6, should be considered to have specifically disclosed sub-ranges, such as, from 1 to 3, from 2 to 4, from 3 to 6, etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0015] The terms "preferred" and "preferably" refer to embodiments that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the present disclosure.

[0016] The term "in the range" or "within a range" (and similar statements) includes the endpoints of the stated range.

[0017] Where substituent groups are specified by their conventional chemical formula, written from left to right, they equally encompass the chemically identical substituents that would result from writing the structure from right to left, for example, -CH2O- is equivalent to -OCH2-.

[0018] The term "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0019] The term "alkyl" refers to a linear or branched hydrocarbyl radical having 1 to 20 carbon atoms, and "substituted alkyl" refers to an alkyl further bearing one or more substituents selected from hydroxy, alkoxy, mercapto, cycloalkyl, heterocyclic, aryl, heteroaryl, aryloxy, halogen, trifluoromethyl, cyano, nitro, nitrone, amino, amido, C(O)H, acyl, oxyacyl, carboxyl, carbamate, sulfonyl, sulfonamide, and sulfuryl.

[0020] The term "lower alkyl" refers to a linear or branched hydrocarbyl radical having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms and "substituted lower alkyl" refers to a lower alkyl further bearing one or more substituents selected from hydroxy, alkoxy, mercapto, cycloalkyl, heterocyclic, aryl, heteroaryl, aryloxy, halogen, trifluoromethyl, cyano, nitro, nitrone, amino, amido, C(O)H, acyl, oxyacyl, carboxyl, carbamate, sulfonyl, sulfonamide, and sulfuryl.

[0021] The term "alkenyl" refers to a linear or branched hydrocarbyl radical having 2 to 20 carbon atoms and at least one carbon-carbon double bond.

[0022] The term "alkynyl" refers to a linear or branched hydrocarbyl radical having 2 to 20 carbon atoms and at least one carbon-carbon triple bond.

[0023] The terms "alkylcarbonyl", "alkenylcarbonyl" and "alkynylcarbonyl" refer to an alkyl group, alkenyl group or alkynyl group as defined above, which is bonded via the carbon atom of a carbonyl group (C=O) to the remainder of the molecule.

[0024] The term "cycloalkyl" refers to a divalent cyclic ring-containing group containing in the range of 3 to 8 carbon atoms, and "substituted cycloalkyl" refers to a cycloalkyl further bearing one or more substituents selected from hydroxy, alkoxy, mercapto, cycloalkyl, heterocyclic, aryl, heteroaryl, aryloxy, halogen, trifluoromethyl, cyano, nitro, nitrone, amino, amido, C(O)H, acyl, oxyacyl, carboxyl, carbamate, sulfonyl, sulfonamide, and sulfuryl.

[0025] The term "aryl" refers to a divalent aromatic group having 6 to 14 carbon atoms and "substituted aryl" refers to an aryl further bearing one or more substituents selected from hydroxy, alkoxy, mercapto, cycloalkyl, heterocyclic, aryl, heteroaryl, aryloxy, halogen, trifluoromethyl, cyano, nitro, nitrone, amino, amido, C(O)H, acyl, oxyacyl, carboxyl, carbamate, sulfonyl, sulfonamide, and sulfuryl.

[0026] The term "polyaryl" refers to a divalent moiety comprising a plurality (i.e., at least two, up to about 10) divalent aromatic groups (each having 6 to 14 carbon atoms), wherein said divalent aromatic groups are linked to one another directly, or via a 1-3 atom linker; and "substituted polyaryl" refers to polyaryl further bearing further bearing one or more substituents selected from hydroxy, alkoxy, mercapto, cycloalkyl, heterocyclic, aryl, heteroaryl, aryloxy, halogen, trifluoromethyl, cyano, nitro, nitrone, amino, amido, C(O)H, acyl, oxyacyl, carboxyl, carbamate, sulfonyl, sulfonamide, and sulfuryl. [0027] The term "heteroaryl¹ refers to a divalent aromatic group containing one or more heteroatoms (e.g., N, O, S, or the like) as part of the ring structure, and having in the range of 3 to 14 carbon atoms; and "substituted aryl" refers to arylene groups further bearing one or more substituents selected from hydroxy, alkoxy, mercapto, cycloalkyl, heterocyclic, aryl, heteroaryl, aryloxy, halogen, trifluoromethyl, cyano, nitro, nitrone, amino, amido, C(O)H, acyl, oxyacyl, carboxyl, carbamate, sulfonyl, sulfonamide, and sulfuryl.

[0028] The term "polyheteroaryl" refers to a divalent moiety comprising a plurality (i.e., at least two, up to about 10) heteroaryl groups (each containing at least one heteroatom, and in the range of 3 up to 14 carbon atoms), wherein the heteroarylene groups are linked to one another directly, or via a 1- 3 atom linker; and "substituted polyheteroarylene" refers to a polyheteroaryl further bearing one or more substituents selected from hydroxy, alkoxy, mercapto, cycloalkyl, heterocyclic, aryl, heteroaryl, aryloxy, halogen, trifluoromethyl, cyano, nitro, nitrone, amino, amido, C(O)H, acyl, oxyacyl, carboxyl, carbamate, sulfonyl, sulfonamide, and sulfuryl.

[0029] The terms "dielectric dissipation factor (Df)" and "loss tangent," as used herein, are synonymous and refer to the amount of energy dissipated (i.e., electrical loss) into an insulating material when a voltage is applied to the circuit. Df represents the loss of the signal in the circuit.

[0030] The terms "dielectric constant (Dk)" and "permittivity," as used herein, are synonymous and refer to a measurement of the relative capacitance of an insulating material to that of air or vacuum. The dielectric constant determines the speed of the electronic signal.

[0031] The term "peel strength" refers to the force required to separate the ultra-thin metal (e.g. copper) foil from a substrate to which it has been laminated.

[0032] The term glass transition temperature" or "T_g," as used herein, means the temperature at which the amorphous domains of a polymer take on the characteristic properties of the glass statebrittleness, stiffness, and rigidity. The term further means the temperature at which cured resins undergo a change from a glassy state to a softer more rubbery state.

[0033] According to one embodiment, the present disclosure is directed to a resin composition comprising: a composition comprising: (a) a cationic polymerization initiator; and (b) an indene based or cyclopentadiene based resin; wherein the cationic polymerization initiator is selected from the group consisting of (i) an aromatic sulfonium salt-based cationic polymerization initiator; (ii) a phosphonium salt-based cationic polymerization initiator; (iii) a quaternary ammonium salt-based cationic polymerization initiator; (iv) an aluminum complex-based cationic polymerization initiator; (v) an aromatic iodonium salt-based cationic polymerization initiator; (vi) an aromatic diazonium saltbased cationic polymerization initiator; (vii) a pyridinium- cationic polymerization initiator or (viii) a mixture thereof.

[0034] All the cationic polymerization initiators may be thermally activated or light activated. When used herein a light activated initiator may be ultra-violet (UV) or near infra-red (NIR) activated. When a cationic polymerization initiator is light activated a sensitizing agent or light sensitive dye may be present. In the case where the initiator is NIR activated, one or more of the following sensitization agents may be used. A sensitizing agent is capable of adsorbing light and either emitting at a different frequency, or converting the energy to heat to thermally activate a dye. Examples of NIR sensitizing agents suitable for use with the disclosure include, but are not limited to, cyanine dyes, squaraine dyes and immonium dyes. Suitable cyanine dyes include l,3,3-Trimethyl-2-[5-(l,3,3-trimethyl-l,3-dihydro- indol-2-ylidene)-penta-l,3-dienyl]-3H-indolium chloride, l,3,3-Trimethyl-2-[5-(l,3,3-trimethyl-l,3- dihydro-indol-2-ylidene)-penta-l,3-dienyl]-3H-indolium tetrafluoroborate, 2-[3-Chloro-5-[l,l- dimethyl-3-(3-methyl-butyl)-l,3-dihydro-benzo[e]indol-2-ylidene]-penta-l, 3-dienyl]- l,l-dimethyl-3- (3-methyl-butyl)-lH-benzo[e]indolium hexafluorophosphate, and 2-(2-[2-Chloro-3-[2-(3-ethyl-l,l- dimethyl-l,3-dihydro-benzo[e]indol-2-ylidene)-ethylidene]-cyclohex-l-enyl]-vinyl)-3-ethyl-l,l- dimethyl-lH-benzo[e]indolium 4-methylbenzenesulfonate. Examples of squaraine dyes include 1,3- Bis[4-(diethylamino)-2-hydroxyphenyl]-2,4-dihydroxy-cyclobutenediylium bis(inner salt), and 4-(2- Methyl-2-phenyl-lH-perimidin-3-ium-4(2H)-ylidene)-2-(2-methyl-2-phenyl-2,3-dihydro-lH- perimidin-4-yl)-3-oxocyclobut-l-enolate. Examples of immonium dyes include [4-[Bis-(4- dibutylamino-phenyl)-amino]-phenyl]-bis-(4-dibutylamino-phenyl)-ammonium hexafluorophosphate, and N,N,N',N'-Tetrakis-(p-di-n-butylaminophenyl)-p-benzochinon-bis- immonium hexafluoroantimonate.

[0035] The use of a cationic polymerization initiator in combination with the described resins part of the composition improves the toughness of the resultant post cured coating compared to a coating prepared with an alternative curing initiator. Without wishing to be bound by theory, when indene based or cyclopentadiene based resins are cured thermally they are initiated via a radical mechanism. It is believed that indene and cyclopentadiene functional groups do not well react under radical polymerization. The Applicant has found that indene and cyclopentadiene functional groups react very well under cationic polymerization. Hence, when such indene based or cyclopentadiene based resin systems are initiated by a cationic polymerization initiator, a different network is created compared to what would be formed by a radical initiated system. This network has more crosslinks leading to improved thermomechanical properties.

[0036] In some embodiments, the resin comprises a vinylbenzene group.

[0037] Vinylbenzene functional resins are a specific type of hydrocarbon resin which has improved reactivity compared to hydrocarbon resins that do not comprise a vinylbenzene group.

[0038] Examples of (i) the aromatic sulfonium salt-based thermal or light initiated cationic polymerization initiator include: hexafluoroantimonate salts such as (2-ethoxy-l-methyl-2- oxoethyl)methyl-2-naphthalenyisulfonium hexafluoroantimonate, 4-

(methoxycarbonyloxy)phenylbenzylmethylsulfonium hexafluoroantimonate, 4- acetoxyphenyldimethylsulfonium hexafluoroantimonate, 4-hydroxyphenylbenzylmethylsulfonium hexafluoroantimonate, 4-hydroxyphenyl(o-methyl benzyl)methylsulfonium hexafluoroantimonate, 4- hydroxyphenyl(a-naphthylmethyl)methylsulfonium hexafluoroantimonate, diphenyl-4- (phenylthio)phenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroantimonate, bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bishexafluoroantimonate, and bis[4- (diphenylsulfonio)phenyl]sulfide bishexafluoroantimonate; hexafluorophosphate salts such as (2- ethoxy-l-methyl-2-oxoethyl)methyl-2-naphthalenylsulfonium hexafluorophosphate, 4- acetoxyphenylbenzylmethylsulfonium hexafluorophosphate, 4-hydroxyphenyl(o- methylbenzyl)methylsulfonium hexafluorophosphate, 4-hydroxyphenyl(a- naphthylmethyl)methylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, bis[4-(di(4-(2- hydroxyethoxy))phenylsulfonio)phenyl]sulfide bishexafluorophosphate, and bis[4- (diphenylsulfonio)phenyl]sulfide bishexafluorophosphate; hexafluoroarsenate salts such as 4- hydroxyphenyl(o-methylbenzyl)methylsulfonium hexafluoroarsenate, and 4- hydroxyphenylbenzylmethylsulfonium hexafluoroarsenate; tetrafluoroborate salts such as (2-ethoxy- l-methyl-2-oxoethyl)methyl-2-naphthalenylsulfonium tetrafluoroborate, 4-hydroxyphenyl(o- methylbenzyl)methylsulfonium tetrafluoroborate, 4-hydroxyphenylbenzylmethylsulfonium tetrafluoroborate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, triphenylsulfonium tetrafluoroborate, bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bistetrafluoroborate, and bis[4-(diphenylsulfonio)phenyl]sulfide bistetrafluoroborate; trifluoromethanesulfonate salts such as 4-hydroxyphenyl(o-methylbenzyl)methylsulfonium trifluoromethanesulfonate, and 4- hydroxyphenylbenzylmethylsulfonium trifluoromethanesulfonate; trifluoromethanesulfonate salts such as diphenyl-4-(phenylthio)phenylsulfonium trifluoromethanesulfonate; bis(trifluoromethanesulfone)imide salts such as 4-hydroxyphenyl(a-naphthylmethyl)methylsulfonium bis(trifluoromethanesulfone)imide, and 4-hydroxyphenylbenzylmethylsulfonium bis(trifluoromethanesulfone)imide; tetrakis(pentafluorophenyl)borate salts such as (2-ethoxy-l- methyl-2-oxoethyl)methyl-2-naphthalenylsulfonium tetrakis(pentafluorophenyl)borate, 4-

(methoxycarbonyloxy)phenylbenzylmethylsulfonium tetrakis(pentafluorophenyl)borate, 4- hydroxyphenyl(o-methylbenzyl)methylsulfonium tetrakis(pentafluorophenyl)borate, 4- hydroxyphenyl(a-naphthylmethyl)methylsulfonium tetrakis(pentafluorophenyl)borate, 4- hydroxyphenyl benzyl methylsulfonium tetrakis(pentafluorophenyl)borate, diphenyl -4-

(phenylthio)phenylsulfonium tetrakis(pentafluorophenyl)borate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide tetrakis(pentafluorophenyl)borate, and bis[4-(diphenylsulfonio)phenyl]sulfide tetrakis(pentafluorophenyl)borate. [0039] Examples of (ii) the phosphonium salt-based thermal or light initiated cationic polymerization initiator include ethyltriphenylphosphonium hexafluoroantimonate, and tetrabutylphosphonium hexafluoroantimonate.

[0040] Examples of (iii) the quaternary ammonium salt-based thermal or light initiated cationic polymerization initiator include N,N-dimethyl-N-benzylanilinium hexafluoroantimonate, N,N-diethyl- N-benzylanilinium tetrafluoroborate, N,N-dimethyl-N-benzylpyridinium hexafluoroantimonate, N,N- diethyl-N-benzylpyridinium trifluoromethanesulfonic acid, N,N-dimethyl-N-(4- methoxybenzyl)pyridinium hexafluoroantimonate, N,N-diethyl-N-(4-methoxybenzyl)pyridinium hexafluoroantimonate, N,N-diethyl-N-(4-methoxybenzyl)toluidinium hexafluoroantimonate, and N,N- dimethyl-N-(4-methoxybenzyl)toluidinium hexafluoroantimonate.

[0041] Examples of (iv) the aluminum complex-based thermal or light initiated cationic polymerization initiator include aluminum carboxylates; aluminum alkoxide, aluminum chloride, aluminum (alkoxide) acetoacetic acid chelate, acetoacetonato aluminum, and ethylacetoacetato aluminum.

[0042] Examples of (v) the aromatic iodonium salt-based thermal or light initiated cationic polymerization initiator include phenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium trifluoromethanesulfonate, bis(dodecylphenyl)iodonium hexafluorophosphate, bis(dodecylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate, 4-methylphenyl-4-(l- methylethyl)phenyliodonium hexafluorophosphate, 4-methylphenyl-4-(l- methylethyl)phenyliodonium hexafluoroantimonate, 4-methylphenyl-4-(l- methylethyl)phenyliodonium tetrafluoroborate, 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate and 4-methylphenyl-4-(l-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate.

[0043] Examples of (vi) the aromatic diazonium salt-based thermal or light initiated cationic polymerization initiator include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate and phenyldiazonium tetrakis(pentafluorophenyl)borate.

[0044] Examples of (vii) the pyridinium-based thermal or light initiated cationic polymerization initiator include l-benzyl-2-cyanopyridinium hexafluorophosphate, l-benzyl-2-cyanopyridinium hexafluoroantimonate, l-benzyl-2-cyanopyridinium tetrafluoroborate, l-benzyl-2-cyanopyridinium tetrakis(pentafluorophenyl)borate, l-(naphthylmethyl)-2-cyanopyridinium hexafluorophosphate, 1- (naphthylmethyl)-2-cyanopyridinium hexafluoroantimonate, l-(naphthylmethyl)-2-cyanopyridiniurn tetrafluoroborate, and l-(naphthylmethyl)-2-cyanopyridiniurn tetrakis(pentafluorophenyl)borate.

[0045] These cationic polymerization initiators may be used alone, or as a mixture of two or more kinds thereof. In one preferable embodiment, the polymerization initiator is an aromatic iodonium salt-based thermal cationic polymerization initiator. In another embodiment, the aromatic iodonium salt-based thermal cationic polymerization initiator is diphenyliodonium hexafluorophosphate, di(4- methylphenyl)iodonium hexafluorophosphate, diaryliodonium hexafluoroantimonate, (4- methylphenyl)[4-(2-methylpropyl) phenyl] iodonium hexafluoroantimonate, (4-methylphenyl)[4-(2- methylpropyl)phenyl]iodonium hexafluorophosphate, (4-methylphenyl)[4-(2-methylpropyl) phenyl] iodonium tetrafluoroborate, 4-octyloxyphenyl phenyliodonium hexafluoroantimonate, 4-(2- hydroxytetradecyloxyphenyl)phenyliodonium hexafluoroantimonate, 4-isopropyl-4'- methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, or bis(t-butyl)-diphenyliodonium tetrakis(perfluoro-t-butoxy)aluminate.

[0046] In an embodiment, the resin may be a vinylbenzyl indene such as that described in WO2022207741A1, the contents of which are incorporated herein by reference. For example, a vinylbenzyl indene having a formula (1): where R¹, R² and R³ are each independently selected from a vinylbenzyl group, a hydrogen atom, a lower alkyl group, a thioalkoxy group having 1 to 5 carbon atoms, and an aryl group provided that at least one of R¹, R², and R³ is a vinylbenzyl group; and R⁴ is selected from a hydrogen atom, a halogen atom, a lower alkyl group, an alkoxy group having 1 to 5 carbon atoms, a thioalkoxy group having 1 to 5 carbon atoms, a thioaryloxy group, and an aryl group.

[0047] According to one embodiment, the vinylbenzyl indene having the formula (1) includes compounds where R¹, R² and R³ are independently selected from hydrogen and a vinylbenzyl group, provided that at least one of R¹, R² and R³ is a vinylbenzyl group and R⁴ is selected from a hydrogen atom, a halogen atom, and a lower alkyl group. In still another embodiment, the vinylbenzyl indene having the formula (1) includes compounds where R¹, R² and R³ are independently selected from hydrogen and a vinylbenzyl group provided that at least one of R¹, R² and R³ is a vinylbenzyl group and R⁴ is hydrogen. In yet another embodiment, the vinylbenzyl indene having the formula (1) includes compounds where R¹ and R² are a vinylbenzyl group and R³ is hydrogen or a vinylbenzyl group and R⁴ is hydrogen.

[0048] In yet another embodiment, the vinylbenzyl indene is selected from l,l,3-(2-vinylbenzyl)-lH- indene, l,l,2-(3-vinylbenzyl)-lH-indene, l,l,2-(4-vinylbenzyl)-lH-indene, l,l-(2-vinylbenzyl)-lH- indene, l,l-(3-vinylbenzyl)-lH-indene, l,l-(4-vinylbenzyl)-lH-indene, l,3-(2-vinylbenzyl)-lH-indene; l,3-(3-vinylbenzyl)-lH-indene; l,3-(4-vinylbenzyl)-lH-indene; l-(2-vinylbenzyl)-lH-indene; l-(3- vinylbenzyl)-lH-indene; l-(4-vinylbenzyl)-lH-indene; 3-(2-vinylbenzyl)-lH-indene; 3-(3-vinylbenzyl)- lH-indene; 3-(4-vinylbenzyl)-lH-indene and a mixture thereof.

[0049] In an embodiment, the resin is a compound having the following formula (3): wherein each R¹⁰ is independently selected from a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a thioalkoxy group having 1 to 5 carbon atoms, a thioaryloxy group having 6 to 14 carbon atoms, and an aryl group having 6 to 14 carbon atoms, and combinations thereof, and each R⁹ is independently selected from a hydrogen atom and a vinylbenzyl group, and combinations thereof, provided that at least one of R⁹ is a vinylbenzyl group: or a structure of the Formula (4):

- n, p and p', independently, can range from 0 to 50, preferably from 0 to 10,

- each R¹⁰ is independently selected from a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a thioalkoxy group having 1 to 5 carbon atoms, a thioaryloxy group having 6 to 14 carbon atoms, and an aryl group having 6 to 14 carbon atoms, and combinations thereof,

- each R^lla is independently selected from a hydrogen atom, a vinylbenzyl group, provided that at least one R¹¹ or one R^lla is a vinylbenzyl group,

R¹³ is selected from divalent groups of the Formula (5) or combinations thereof:

Wherein: Each Q. is independently selected from a hydrogen atom and a linear or branched C1-C6 alkyl group, or combinations thereof; and each R¹⁴ is independently selected from a hydrogen atom, a linear or branched C1-C6 alkyl group, a halogen atom, or combinations thereof.

[0050] In an embodiment, the resin is represented by the following general formula (6):

Wherein R¹⁸ is selected from the group consisting of a hydrogen atom, a halogen atom, a Ci.₅ alkyl group, a Ci.5 alkoxy group, and C1.5 thioalkoxy group. R¹⁹ represents a divalent organic group having 2 to 20 carbon atoms; R²⁰ represents a group selected from the group consisting of a vinylbenzyl group, a hydrogen atom, an alkyl group, alkoxy group, and thioalkoxy group each having 1 to 5 carbon atoms, which may be the same or different, and an aryl group; at least one R²⁰ is a vinylbenzyl group; and a, b, and c each represent an integer of 0 to 20.

[0051] In an embodiment, the resin is represented by the following general formula (7):

(A)X

X - (Z)_n - (B)Y ₍₇\

Wherein X is a cyclopentadiene, B is H, (Z)_n is a bond, m is 1 to 5 and A has the structure of formula (8): below.

Wherein R^d and R^b are independently selected from H, F, a Cl to CIO linear or cyclic, branched or straight chain aliphatic group; T is -CH₂ -, -phenyl, or -CH₂- -phenyl; Y is H, -CH₃- , -CH=CH₂- , -CH=CH- CH3 , or alkyne; T is 0 or an integer ranging from 1 to 20; u is 0 or 1; and z is an integer ranging from 1 to 5. In some embodiments, n is 1. In some embodiments, A is H. In some embodiments, y is 6. In some embodiments, y is 3.

[0052] In an embodiment, the composition may contain the cationic polymerization initiator in an amount of about 0.01%-10% by weight or about 0.01%-5% by weight or about 0.05%-2% by weight or about 0.05%-0.5% by weight, where the % by weight is based on the total weight of the resin.

[0053] In an embodiment, the composition further comprises a solvent. The amount of solvent is not limited, but typically is an amount sufficient to provide a concentration of solids in the solvent of at least about 30% by weight to no more than about 90% by weight solids, or between about 50%-85% by weight solids, or between about 55%-75% weight solids.

[0054] The solvent is not specifically limited. For example, it may be an organic solvent; for example, be a ketone, an aromatic hydrocarbon, an ester, an amide or an alcohol. More specifically, examples of organic solvents which may be used include, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, xylene, methoxyethyl acetate, ethoxyethyl acetate, butoxyethyl acetate, ethyl acetate, N-methylpyrrolidone formamide, N-methylformamide, N,N-dimethylacetamide, methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethylether, triethylene glycol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, and mixtures thereof. In preferred embodiments, the solvent is selected from the group consisting of toluene, xylene, cyclohexane, methyl ethyl ketone. Particularly preferred are toluene and/or xylene.

[0055] When a solvent is present in the composition, the activation temperature of the cationic polymerization initiator is preferably above the solvent evaporation temperature of the solvent, preferably about 5 °C or more above the solvent evaporation temperature, preferably about 10 °C or more above the solvent evaporation temperature. By providing an initiator with an activation temperature higher than the solvent evaporation temperature, it is possible to prepare a stable composition which does not initiate the cure during solvent evaporation. [0056] In another embodiment, the resin composition may optionally include an inorganic filler, organic filler or mixture thereof. Fillers contemplated for use in the practice of the present disclosure may be any of a variety of morphologies, e.g., angular, platelet, spherical, amorphous, sintered, fired, powder, flake, crystalline, ground, crushed, milled, and the like, or mixtures of any two or more thereof. Presently preferred particulate fillers contemplated for use herein are substantially spherical. [0057] Such fillers may optionally be thermally conductive. Both powder and flake forms of filler may be used in the resin compositions of the present disclosure. Fillers having a wide range of particle sizes can also be employed in the practice of the present disclosure. Particle sizes ranging from about 500 nm up to about 300 microns may be employed, with particle sizes of less than about 100 microns being preferred, and particle sizes in the range of about 5 up to about 75 microns being particularly preferred.

[0058] A wide variety of fillers can be employed in the practice of the present disclosure, e.g., soft fillers (e.g., uncalcined talc), naturally occurring minerals (e.g., aluminum nitride, boron nitride, silicon carbide, diamond, graphite, beryllium oxide, magnesia, silica, alumina, aluminum silicates, and the like), calcined naturally occurring minerals (e.g., enstatite), synthetic fused minerals (e.g., cordierite), treated fillers (e.g. silane-treated minerals), organic polymers (e.g., polytetrafluoroethylene), hollow spheres, microspheres, powdered polymeric materials, and the like.

[0059] Exemplary fillers include talc, mica, calcium carbonate, calcium sulfate, aluminum nitride, boron nitride, silicon carbide, diamond, graphite, beryllium oxide, magnesia, silica, alumina, TiO₂, aluminum silicate, aluminum-zirconium-silicate, cordierite, silane-treated mineral, polytetrafluoroethylene, polyphenylene sulfide, and the like.

[0060] Thermally conductive fillers contemplated for optional use in the practice of the present disclosure include, for example, aluminum nitride, boron nitride, silicon carbide, diamond, graphite, beryllium oxide, magnesia, silica, alumina, zirconium silicate, and the like. Preferably, the particle size of these fillers will be about 20 microns. If aluminum nitride is used as a filler, it is preferred that it is passivated via an adherent, conformal coating (e.g., silica, or the like).

[0061] When fillers are present, the resin composition may contain up to about 75% by weight, or up to about 50% by weight, or up to about 25% by weight, or up to about 10% by weight of the filler, where the % by weight is based on the total weight of the resin composition.

[0062] The resin composition of the present disclosure may optionally include one or more additives such as flexibilizers, anti-oxidants, dyes, pigments, surfactants, defoamers, silane coupling agents, dispersing agents, thixotropic agents, processing aids, flow modifiers, cure accelerators, strength enhancers, toughening agents, UV protectors (especially UV blocking dyes appropriate to enable Automatic-Optical Inspection (AOI) of Circuitry), flame retardants and the like, as well as mixtures of any two or more thereof.

[0063] Flexibilizers (also called plasticizers) contemplated for use in certain embodiments of the present disclosure include compounds that reduce the brittleness of the formulation, such as, for example, branched polyalkanes or polysiloxanes that lower the glass transition temperature of the compositions. Such plasticizers include, for example, polyethers, polyesters, polythiols, polysulfides, polybutadienes such as those sold under the Poly BD® and RICON® brand names. Plasticizers, when employed, are typically present in the range of about 0.5% by weight up to about 30% by weight of the resin composition.

[0064] Anti-oxidants contemplated for use in the practice of the present disclosure include hindered phenols (e.g., BHT (butylated hydroxytoluene), BHA (butylated hydroxyanisole), TBHQ. (tertiary-butyl hydroquinone), 2,2'-methylenebis(6-tertiarybutyl-p-cresol), and the like), hindered amines (e.g., diphenylamine, N,N'-bis(l,4-dimethylpentyl-p-phenylene diamine, N-(4- anilinophenyl)methacrylamide, 4,4'-bis(a,a-dimethylbenzyl)diphenylamine, and the like), phosphites, and the like. When used, the quantity of anti-oxidant typically falls in the range of about 100 up to 2000 ppm, relative to the weight of the resin composition.

[0065] Dyes contemplated for use in certain embodiments of the present disclosure include nigrosine, Orasol blue GN, phthalocyanines, fluorescent dyes (e.g., Fluoral green gold dye, and the like), and the like. When used, organic dyes in relatively low amounts (i.e., amounts less than about 0.2% by weight) provide contrast.

[0066] Pigments contemplated for use in certain embodiments of the present disclosure include any particulate material added solely for the purpose of imparting color to the formulation, e.g., carbon black, metal oxides (e.g., FejOa, titanium oxide), and the like. When present, pigments are typically present in the range of about 0.5% by weight up to about 5% by weight, relative to the weight of the resin composition.

[0067] Toughening agents contemplated for use in the practice of the disclosure are materials which impart enhanced impact resistance to various articles. Exemplary toughening agents include synthetic rubber containing compounds such as Hypro®(butadiene homo-polymers and butadiene-acrylonitrile copolymers with terminal functionality), Hypox® (high-viscosity adduct of the diglycidyl ether of bisphenol A (DGEBA) and a butadiene-acrylonitrile (CTBN) elastomer), and the like.

[0068] UV protectors contemplated for use in certain embodiments of the present disclosure include compounds which absorb incident ultraviolet (UV) radiation, thereby reducing the negative effects of such exposure on the resin or polymer system to which the protector has been added. Exemplary UV protectors include bis(l,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, silicon, powdered metallic compounds, hindered amines (known in the art as "HALS"), and the like.

[0069] Defoamers contemplated for use in certain embodiments of the present disclosure include materials which inhibit formation of foam or bubbles when a liquid solution is agitated or sheared during processing. Exemplary defoamers contemplated for use herein include n-butyl alcohol, sil iconcontaining anti-foam agents, and the like.

[0070] Exemplary silane coupling agents contemplated for use in the practice of the present disclosure include materials which form a bridge between inorganic surfaces and reactive polymeric components, including materials such as epoxy silanes, amino silanes, and the like.

[0071] Exemplary thixotropic agents contemplated for use in the practice of the present disclosure include materials which cause liquids to have the property of enhanced flow when shear is applied, including materials such as high surface area fillers (e.g., fumed silica) having particle sizes in the range about 2-3 microns, or even submicron size.

[0072] The resin composition of the present disclosure may be prepared by appropriately mixing the above components and also kneading or mixing, as needed, by a kneading means such as a 3 rolls mill, a ball mill, a bead mill or a sand mill, or a stirring means such as a high-speed rotary mixer, a super mixer or a planetary mixer.

[0073] In an aspect of the disclosure there is provided a method for preparing a varnish comprising providing the composition described above and at least one solvent and optionally other components as listed above.

[0074] In a further aspect there is provided a method for forming a coating comprising providing the varnish described above and curing.

[0075] In some embodiments, the curing may be a thermal curing step, a UV curing step or a near Infra-red curing step.

[0076] In a further aspect of the disclosure is a coating produced by the method described above.

[0077] In accordance with yet another aspect of the present disclosure, there are provided articles comprising a partially or fully cured layer of the above-described varnish on a substrate.

[0078] As readily recognized by those of skill in the art, a variety of substrates are suitable for use in the practice of the present disclosure, for example, polyesters, liquid crystalline polymers, polyamides (e.g., Aramids), polyimides, polyamide-imides, polyolefins, polyphenylene oxides, polyphenylene sulfides, polybenzoxazines, conductive materials (e.g., conductive metals), and the like, as well as combinations of any two or more thereof. When conductive metal substrates are employed, such materials as silver, nickel, gold, cobalt, copper, aluminum, alloys of such metals, and the like, are contemplated for use herein. [0079] In accordance with still another aspect of the present disclosure, there are provided methods of making the above-described articles (i.e., articles comprising the resin composition according to the present disclosure on a substrate), said methods comprising applying the resin composition to a substrate and, if an organic solvent is optionally employed to facilitate such application, removing substantially all organic solvent therefrom. The resin composition may be applied to the substrate by dipping, impregnating, spraying and the like.

[0080] In accordance with yet another aspect of the present disclosure, there are provided prepregs produced by impregnating a porous substrate with a resin composition according to the present disclosure, and, if an organic solvent is optionally employed to facilitate such impregnation, subjecting the resulting impregnated substrate to conditions suitable to remove substantially all of the organic solvent therefrom.

[0081] As readily recognized by those of skill in the art, a variety of porous substrates can be employed for the preparation of inventive prepregs. The porous substrate may be woven or nonwoven. The thickness of such substrate is not particularly limited, and may range, for example, from about 0.01 mm to 0.3 mm.

[0082] Examples of porous substrates can include, but are not limited to, woven glass, non-woven glass, woven aramid fibers, non-woven aramid fibers, woven liquid crystal polymer fibers, non-woven liquid crystal polymer fibers, woven synthetic polymer fibers, non-woven synthetic polymer fibers, randomly dispersed fiber reinforcements, expanded polytetrafluoroethylene (PTFE) structures and combinations of any two or more thereof. Specifically, materials contemplated for use as the porous substrate can include, but are not limited to, fiberglass, quartz, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, polyetherimide fiber, cyclic olefin copolymer fiber, polyalkylene fiber, liquid crystalline polymer, poly(p-phenylene-2,6-benzobisoxazole), copolymers of polytetrafluoroethylene and perfluoromethylvinyl ether (MFA) and combinations of any two or more thereof.

[0083] In accordance with still another aspect of the present disclosure, there are provided laminated sheets produced by layering and molding a prescribed number of sheets of the above-described prepreg.

[0084] Laminated sheets according to the present disclosure have many particularly beneficial properties, such as, for example, low dielectric constant, low dissipation factor, high thermal decomposition temperature, and the like. In a preferred embodiment, laminated sheets according to the present disclosure have a dielectric constant ^3.0 nominal and a dissipation factor ^0.002 at 10 GHz, and a glass transition temperature of at least 100°C or at least 150°C. [0085] In one aspect of the present disclosure, laminated sheets as described herein may optionally further comprise one or more conductive layers. Such optional conductive layers are selected from the group consisting of metal foils, metal plates, electrically conductive polymeric layers, and the like. In one embodiment, the metal may be copper, silver, nickel, gold, cobalt, aluminum and alloys of such metals, preferably copper.

[0086] In another embodiment, there is provided a method of forming a laminated sheet. The method includes contacting the porous substrate with a varnish bath comprising the resin composition of the present disclosure dissolved and intimately admixed in a solvent or a mixture of solvents. The contacting occurs under conditions such that the porous substrate is coated with the resin composition. Thereafter the coated porous substrate is passed through a heated zone at a temperature sufficient to cause the solvent to evaporate, but below the temperature at which the resin composition undergoes significant cure during the residence time in the heated zone to form a prepreg.

[0087] The porous substrate preferably has a residence time in the bath of from about 1 second to about 300 seconds, more preferably from about 1 second to about 120 seconds, and most preferably from about 1 second to about 30 seconds. The temperature of such bath is preferably from about 0°C to about 100°C, more preferably from about 10°C to about 40°C, and most preferably from about 15°C to about 30°C. The residence time of the coated porous substrate in the heated zone is from about 0.1 minute to about 15 minutes, more preferably from about 0.5 minute to about 10 minutes, and most preferably from about 1 minute to about 5 minutes.

[0088] The temperature of such zone is sufficient to cause any solvents remaining to volatilize away yet not so high as to result in a complete curing of the components during the residence time. Preferable temperatures of such zone are from about 80°C to about 250°C, more preferably from about 100°C to about 225°C, and most preferably from about 150°C to about 210°C. Preferably there is a means in the heated zone to remove the solvent, either by passing an inert gas through the oven, or drawing a slight vacuum on the oven. In many embodiments the coated substrate is exposed to zones of increasing temperature. The first zones are designed to cause the solvent to volatilize so it can be removed. The later zones are designed to result in partial cure of the resin composition (B- staging).

[0089] One or more sheets of prepreg are preferably processed into laminates optionally with one or more sheets of electrically-conductive material such as copper. In such further processing, one or more segments or parts of the coated porous substrate are brought in contact with one another and/or the conductive material. Thereafter, the contacted parts are exposed to elevated pressures and temperatures sufficient to cause the components to cure wherein the resin on adjacent parts react to form a continuous resin matrix between the porous substrates. Before being cured the parts may be cut and stacked or folded and stacked into a part of desired shape and thickness. The pressures used can be anywhere from about 1 psi to about 1000 psi with from about 10 psi to about 800 psi being preferred. The temperature used to cure the resin composition in the parts or laminates, depends upon the particular residence time, pressure used, and components used. Preferred temperatures which may be used are between about 100°C and about 250°C, more preferably between about 120°C and about 220°C, and most preferably between about 170°C and about 200°C. The residence times are preferably from about 10 minutes to about 120 minutes and more preferably from about 20 minutes to about 90 minutes.

[0090] In one embodiment, the process is a continuous process where the porous substrate is taken from the oven and appropriately arranged into the desired shape and thickness and pressed at very high temperatures for short times. In particular such high temperatures are from about 180°C to about 250°C, more preferably about 190°C to about 210 C, at times of about 1 minute to about 10 minutes and from about 2 minutes to about 5 minutes. Such high speed pressing allows for the more efficient utilization of processing equipment. In such embodiments the preferred reinforcing material is a glass web or woven cloth.

[0091] In some embodiments it is desirable to subject the laminate or final product to a post cure outside of the press. This step is designed to complete the curing reaction. The post cure is usually performed at from about 130°C to about 220°C for a time period of from about 20 minutes to about 200 minutes. This post cure step may be performed in a vacuum to remove any components which may volatilize.

[0092] Thus, in accordance with yet another embodiment of the present disclosure, there are provided methods of making a laminated sheet, said method comprising layering and molding a prescribed number of sheets of a prepreg according to the present disclosure.

[0093] In a further embodiment of the disclosure there are provided chips produced by coating a silicon wafer or a printed circuit board with a resin composition according to the present disclosure, and, if an organic solvent is optionally employed to facilitate such coating, subjecting the resulting coated wafer or printed circuit board to conditions suitable to remove substantially all of the organic solvent therefrom.

[0094] In accordance with a further embodiment of the present disclosure, there are provided printed wiring boards produced by forming conductive patterns on the surface of the above-described laminated sheet(s) or on the above-described chips. Forming the conductive patterns may can be carried out by, for example, forming a resist pattern on the surface of the laminated sheet(s) or chips, removing unnecessary portions of the sheet or the resin on the chip by etching, removing the resist pattern, forming the required through holes by drilling, again forming the resist pattern, plating to connect the through holes, and finally removing the resist pattern.

[0095] In accordance with a still further embodiment of the present disclosure, there are provided multilayer printed wiring boards produced by layering and molding a prescribed number of sheets of the above-described patterned laminate layers, bonded together with one or more layers of prepreg from which the printed wiring board layer was prepared.

[0096] In accordance with a still further embodiment of the present disclosure, there are provided methods of making printed wiring boards, said methods comprising forming conductive patterns on the surface of a laminated sheet or a chip according to the present disclosure.

[0097] In accordance with yet another embodiment of the present disclosure, there are provided multilayer printed wiring boards produced by layering and molding a prescribed number of sheets of the above-described prepreg, to obtain a printed wiring board for an inner layer, and layering the prepreg on the printed wiring board for an inner layer which forms conductive patterns on the surface. [0098] Accordingly, the prepreg and the printed wiring boards of the present disclosure may be usefully used as a component of a printed circuit board for a network for use in various electrical and electronic devices such as mobile communication devices that handle a high frequency signal of GHz or more, or the base station device thereof, and network-related electronic devices such as servers and routers, and large computers.

[0099] In some embodiments, the resin compositions of the present disclosure may have a dielectric dissipation factor (Df) that is flat over a wide frequency range, such that a component fabricated therefrom can operate efficiently at several different processing speeds. This is important because many state-of-the-art electronic devices can operate over a range of frequencies and it is therefore desired that the electronic components maintain proper function throughout this frequency range. In another embodiment, the resin compositions of the present disclosure may have a dielectric constant (Dk) at 10 GHz of less than about 3 or less than about 2.9 or less than about 2.8 and a dissipation factor (Df) at 10 GHz of less than about 0.0025 or less than about 0.002.

[0100] The present disclosure will now be further described with reference to the following nonlimiting examples.

EXAMPLES

[0101] The following components were used:

Tetrabutylammonium bromide (99+%). Supplier: Thermo Fisher Scientific, Belgium.

Vinylbenzyl chloride (mixture of o/m/p-isomers). Supplier: AK Scientific, Inc., USA. • Indene (90%, technical, stabilized). Supplier: Thermo Fisher Scientific, Belgium.

• 4,4'-Bis(chloromethyl)biphenyl (>95%). Supplier: Tokio Chemical Industry Co., LTD., Belgium.

• BLUESIL™ PI 2074 (lsopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate). Supplier: Elkem Silicones, France.

• S2617 (Bis(t-butyl)-diphenyliodonium tetrakis(perfluoro-t-butoxy)aluminate). Supplier: FEW Chemicals GmbH, Germany.

• SAN-AID SI-B5 ((4-acetoxyphenyl)dimethylsulfonium tetrakis(pentafluorophenyl)borate). Supplier: Sanshin Chemical Industry Co., LTD., Japan.

Thermogravimetric Analysis (TGA) was measured according to the standard set out in ISO 11358. Dynamic Mechanical Analysis (DMA) was measured according to the standard set out in ISO 6721. Gel Permeation Chromatography (GPC) was performed using standard methods known to the skilled person.

G' onset: The storage modulus G' is the measure of the samples' elastic behaviour. G' onset is the temperature at which cured resins undergo a change from a glassy state to a softer, more rubbery, state.

Td5: Td5 is the temperature when the weight loss of the sample reaches 5%.

Synthesis Example 1

[0102] 23.0 g (0.092 mol) 4,4'-bis(chloromethyl)biphenyl, 25.0 g (0.209 mol) indene, 3.4 g (0.010 mol) tetrabutylammonium bromide and 46.8 g (0.269 mol) vinylbenzyl chloride were dissolved in 500 mL toluene at an internal temperature of 50°C under continuous stirring in a 1.5 liters reaction flask equipped with a mechanical stirrer, cooling condenser and dropping funnel to prepare a homogenous solution. 140 mL (2.610 mol) of a 50% by weight solution of NaOH in water was added dropwise over 30 minutes. After the addition was complete the internal temperature was increased to 50°C by external heating. After 9 hours reaction time the mixture was diluted with water and the two layers separated. Toluene was removed by distillation to obtain 64.2 g (83 % yield) of Compound 1 as a yellow solid material. The product was identified from its 1H-NMR (lH-Nuclear Magnetic Resonance) spectrum and GPC measurement. GPC indicated a weight average molecular weight Mw = 1216 g/mol and a polydispersity of 2.1.

Application on a metal film [0103] The compounds referred in Table 1 below were dissolved at room temperature in toluene at a concentration of 40% by weight after which the cationic polymerization initiator was added to produce a homogenous resin composition varnish.

[0104] The homogenous resin compositions were casted on a metal plate and toluene was evaporated over night at ambient conditions. The pre-dried resin film was placed in an oven and cured stepwise under nitrogen using following cure cycle: 1 hour at 70°C, 1 hour at 90°C, 1 hour at 140°C, 2 hours at 200°C. The resulting plates with an approximate thickness of 0.8 mm were evaluated for the dielectric constant (Dk) and the dissipation factor (Df) on a Split Post Dielectric Resonator (SPDR) at a frequency of 5Ghz, for the storage modulus (G') onset on a Dynamic Mechanical Analyzer (DMA), and for the 5% weight loss temperature (T s) on a Thermal Gravimetric Analyzer (TGA). In the same manner plates with a thickness of 1.2 mm have been produced to evaluate the Charpy impact strength (ak) on a Charpy impact tester. Combined results are shown in Table 2 below.

[0105] Comparing the properties of the cured resin with (Example 1, 2, 3 and 4) and without cationic polymerization initiator (Comparative Example 1 and 2), it can be seen that curing the resin with cationic initiation instead of radical initiation leads to a significant increase in Charpy impact strength. The Charpy impact strength of the vinylbenzyl indene-based resin is increasing from 0.45 kJ/ m² (Comp. Ex.l) to 1.33 kJ/ m² (Ex.l), 0.78 kJ/ m² (Ex.3) and 1.02 kJ/ m² (Ex.4). The Charpy impact strength of Compound 1 is increasing from 1.53 kJ/ m² (Comp. Ex.2) to 3.65 kJ/ m² (Ex.2).

Table 1 ^a) A mixture of l,l,2-(various isomers of 2-, 3- and 4-vinylbenzyl)-lH-indene (83%) and l,l-(various isomers of

2-, 3- and 4-vinylbenzyl)-lH-indene (17%) ^b) Bluesil™ PI 2074 (Elkem Silicones) ^c> S2617 FEW Chemicals) ^d> SAN-AID SI-B5 (Sanshin Chemical Industry) Table 2 ^a) Charpy impact test (ISO 179-1/1FU/1O), at 25°C and 50% relative humidity ^b> SPDR (IEC 61189-2-721), at 5 GHz, 25°C and 50% relative humidity ^c) DMA (ISO 6721), ranges from 25°C to 400°C at a rate of 5 K/ min ^d) TGA (ISO 11358), ranges from 25°C to 800°C at a rate of 10K/ min under nitrogen

Claims

1. A composition comprising: (a) a cationic polymerization initiator; and (b) an indene based or cyclopentadiene based resin; wherein the cationic polymerization initiator is selected from the group consisting of (i) an aromatic sulfonium salt-based cationic polymerization initiator; (ii) a phosphonium salt-based cationic polymerization initiator; (iii) a quaternary ammonium salt-based cationic polymerization initiator; (iv) an aluminum complex-based cationic polymerization initiator; (v) an aromatic iodonium salt-based cationic polymerization initiator; (vi) an aromatic diazonium salt-based cationic polymerization initiator; (vii) a pyridinium-based cationic polymerization initiator and (viii) a mixture thereof.

2. The composition of claim 1, wherein the cationic polymerization initiator is thermally initiated or light initiated.

3. The composition of claim 1 or claim 1, wherein the resin comprises a vinylbenzene group.

4. The composition of any preceding claim, wherein the cationic polymerization initiator is selected from the group consisting of a diaryliodonium salt or an aromatic sulfonium salt.

5. The composition of any preceding claim, wherein the cationic polymerization initiator is present in an amount from about 0.01 wt.% to about 3 wt.%, preferably from about 0.05 wt.% to about 0.5 wt.%, based on the total weight of (b) the indene or cyclopentadiene based resin.

6. The composition of any preceding claim, wherein the composition further comprises a solvent.

7. The composition of claim 6, wherein the cationic polymerization initiator is thermally initiated at a defined activation temperature of the cationic polymerization initiator which is above a solvent evaporation temperature of the solvent, preferably about 5 °C or more above the solvent evaporation temperature, preferably about 10 °C or more above the solvent evaporation temperature.

8. A method for preparing a coating comprising providing the composition of any one of claims 1 to 7 and curing.

9. A coating produced by the method of claim 8.

10. An article coated with the coating of claim 9.

11. The article of claim 10, wherein the article is a copper clad laminate.