Fluorine-free polysiloxane hard coating

Abstract

The present invention relates to a layered structure comprising a substrate layer (A) and a polysiloxane based outer coating layer (B), characterized in that none of the coating layer(s) of the layered structure comprises fluorine atoms, a method for preparing said layered structure, the use of said layered structure for flexible electronics applications, including displays, optical lens, transparent boards, and automotive industries especially as a lightweight alternative to glass and the use of said layered structure for flexible electronics applications.

Description

[0001] Fluorine-free polysiloxane hard coating

[0002] The present invention relates to a layered structure comprising a substrate layer (A) and a polysiloxane based outer coating layer (B), characterized in that none of the coating layer(s) of the layered structure comprises fluorine atoms, a method for preparing said layered structure, the use of said layered structure for flexible electronics applications, including displays, optical lens, transparent boards, and automotive industries especially as a lightweight alternative to glass and the use of said layered structure for flexible electronics applications.

[0003] Technical background

[0004] Transparent plastics have been widely used as a core material in optical and transparent display industries. In particular, transparent plastics such as PET (polyethylene terephthalate), PI (polyimide), PC (polycarbonate) or PMMA (polymethyl methacrylate) have been applied in flexible electronics applications, including displays, optical lens, transparent boards, and automotive industries as a lightweight alternative to glass owing to the properties of high light transmittance and suitable refractive index. However, these plastics have the disadvantage of low abrasion resistance, because they have lower surface hardness than glass.

[0005] For increasing abrasion resistance and photopatternability hard coating films have been suggested, which are flexible and bendable. Suitable flexible hard coatings are for instance polysiloxane based flexible hard coatings as e.g. disclosed in WO 2023 / 198747, WO 2023 / 198743 and WO 2023 / 198746, in which at least one layer comprises fluorinated components for improving the mechanical properties, especially the abrasion properties of the hard coatings.

[0006] Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals used in numerous industrial sectors with many daily consumer applications. They have been detected all over the globe, including at remote locations distant from their original production site, due to their sorption to aerosol particles found in the atmosphere. There are likely to be very harmful for humans and nature, including marine environments. They are linked to cardiovascular diseases, damaged the unborn child, inflammation and immunosuppression, and suspected to damage fertility, breast milk, diabetes.

[0007] Strong resistance to degradation and they are known as forever chemicals. For example, there are found in drinking water at very high levels. Due to national and international regulations, where the production and uses of PFAS is likely to be severely controlled and banned, this is an urgent need to shift from the fluorine-based chemicals to safer and greener alternatives. Thus, there is a need in the art for flexible coatings, which show a good balance of properties in regard of mechanical properties, such as high scratch resistance and hardness and low abrasion, and optical properties, such as a low haze and high light transmittance, which are free of per- and polyfluoroalkyl substances (PFAS).

[0008] In the present invention a polysiloxane based coating is suggested which shows a good balance of mechanical and optical properties. Said coating comprises at least one polysiloxane based coating layer, characterized in that none of the coating layer(s) comprises fluorine atoms.

[0009] Summary of the invention

[0010] The present invention relates to a layered structure comprising

[0011] (A) a substrate layer; and

[0012] (B) an outer coating layer coated on at least one surface of the substrate layer (A), wherein the outer coating layer (B) comprises a first siloxane polymer (B-1 ); wherein the first siloxane polymer (B-1 ) comprises monomer units selected from at least two different silane monomers, wherein at least one, such as one to five, preferably one to four, more preferably one or two first silane monomers independently have the general structure according to formula (I)

[0013] R1aSi(OR2)4-a (I), wherein R1is independently selected from substituted or non-substituted linear, branched or cyclic Ci to C20 alkyl groups and substituted or non-substituted C& to C20 aryl groups, whereby the substituents are selected from linear, branched or cyclic Ci to C20 alkyl groups, which optionally include heteroatoms selected from Si, O and / or N;

[0014] R2is independently selected from linear, branched or cyclic Ci to C20 alkyl groups; and a is a number selected from 1 to 3, preferably 1 or 2; and at least one, such as one to five, preferably one to four, more preferably one or two second silane monomers, which independently include an active group capable of achieving cross-linking to adjacent siloxane polymer chains; characterized in that none of the coating layer(s) of the layered structure comprises fluorine atoms. Further, the present invention relates to a method for producing a layered structure as described above or below comprising the following steps:

[0015] • Preparing a composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) comprising the steps of: a) Admixing the at least two different silane monomers in a first solvent to form a mixture; b) Subjecting the mixture to an at least partial hydrolysis of the monomers in the presence of a catalyst, whereby the hydrolysed monomers are at least partially polymerized and cross-linked to obtain the first siloxane polymer (B-1 ); c) Optionally mixing the first siloxane polymer (B-1 ) with a second siloxane polymer (B-2); d) Optionally changing the first solvent to a second solvent; e) Optionally subjecting the composition comprising the first siloxane polymer (B- 1 ) and optionally a second siloxane polymer (B-2) to further crosslinking by hydrosilylation, thermal or radiation initiation or radical polymerization;

[0016] • Providing a substrate (A);

[0017] • Depositing the composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) onto at least one surface of substrate (A) to form the outer coating layer (B);

[0018] • Curing the composition of the outer coating layer (B).

[0019] Thereby, in one embodiment the composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) is deposited onto at least one surface of substrate (A) to form the outer coating layer (B) in adherent contact with the at least one surface of the substrate (A).

[0020] In another embodiment the process further comprises the following steps:

[0021] • Providing a composition comprising a siloxane polymer (C-1 )

[0022] • Depositing the composition comprising a siloxane polymer (C-1 ) onto at least one surface of the substrate (A) to form an inner coating layer (C) in adherent contact with the at least one surface of the substrate (A); • Cross-linking the siloxane polymer chains of the inner coating layer (C) as to obtain a first coating layer (C) comprising a cross-linked siloxane polymer in adherent contact with the at least one surface of the substrate (A);

[0023] • Depositing the composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) onto at least one outer surface of inner coating layer (C) to form the outer coating layer (B);

[0024] • Curing the composition of the outer coating layer (B).

[0025] It is preferred that none of the composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) and the optional composition comprising a siloxane polymer (C-1 ) comprises a component which comprises fluorine atoms.

[0026] Still further, the present invention relates to the use of the layered structure as described above or below for flexible electronics applications, including displays, optical lens, transparent boards, and automotive industries especially as a lightweight alternative to glass.

[0027] Additionally, the present invention relates to the use of the outer coating layer (B) in the layered structure as described above or below in a fluorine-free hard coating.

[0028] Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.

[0029] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually free combinable unless otherwise explicitly stated.

[0030] Description of the invention

[0031] The present technology provides for layered structures wherein a substrate layer (A) is provided with at least one layer comprising siloxane polymers. The layered structures of the present invention are characterized in that none of the coating layer(s) of the layered structure comprises fluorine atoms.

[0032] This means that after coating no fluorine containing compound are detectable in the one or more coating layers, preferably that none of the components of the one or more coating layers include fluorine atoms after coating. Said components of the one or more coating layers, which do not include fluorine atoms, preferably include siloxane polymers, catalysts, additives and solvents. In the case that a fluorine-comprising components such as a fluorine comprising solvent, catalyst and / or additive, is used in the composition of a coating layer, the fluorine containing components are removed by solvent exchange, in which the solvent is preferably exchanged to a solvent, which does not comprise fluorine atoms, before coating.

[0033] It is preferred that the layered structure is “bendable” in the sense that it is capable of being bent about a mandrel, having a radius of curvature, without breaking.

[0034] The properties of bendability can be tested using a test involving infolding or outfolding of the layered structure about a mandrel as described in WO 2019 / 193258.

[0035] Substrate layer (A)

[0036] The substrate layer (A) can be any kind of substrates such as glass, quartz, silicon, silicon nitride, polymers, metals and plastics or mixtures thereof. Furthermore, the substrate layer (A) can also include number of different surfaces such as different oxides, doped oxides, semimetals and the like or mixture thereof.

[0037] Suitable polymers are e.g. thermoplastic polymers, such as polyolefins, polyesters, polyamides, polyimides, polycarbonates, acrylic polymers, such as poly(methylmethacrylate), and Custom Design polymers.

[0038] Especially preferred polymers are polymethylmethacrylate (PMMA), polyethyleneterephtalate (PET) and colorless polyimide (CPI).

[0039] The substrate layer (A) can be the outmost layer of a device or an internal layer of a single stack. The substrate layer (A) can be coated on one or both sides.

[0040] The substrate layer (A) preferably has a thickness of 10 to 5000 pm, more preferably 20 to 4000 pm. The substrate layer (A) can be flexible, bendable or both, such that it is capable of being bent about a mandrel having a first minimum radius of curvature without breaking. A layered structure of the present kind is in particular capable of being bent about a mandrel having a second minimum radius of curvature without breaking, said first minimum radius being smaller or equal to the second minimum radius of curvature.

[0041] The at least one surface of the substrate layer (A) can be modified before depositing the first composition onto at least one surface of the substrate to form a first coating layer (B).

[0042] The at least one surface of the substrate layer (A) can be modified physically or chemically.

[0043] Suitable physical modifications are plasma treatment or corona treatment or similar treatments.

[0044] Suitable chemical modifications could be a chemical cleaning process for cleaning the at least one surface of the substrate layer (A).

[0045] By means of physical or chemical modification the at least one surface is preferably activated to promote adhesion between the substrate layer (A) and the first coating layer (B).

[0046] In one embodiment an optional coating composition is deposited onto the at least one surface of the substrate layer (A) as such that an optional additional coating layer is formed onto the at least one surface of the substrate layer (A). Said optional additional coating layer is then on one side in adherent contact with the at least one surface of the substrate layer (A) and on the other side in adherent contact with the first coating layer (B).

[0047] “Adherent contact” in this regard means that there is no further coating layer or adhesive layer between the at least one surface of the substrate layer (A) and the optional additional coating layer and the optional additional coating layer and the first coating layer (B).

[0048] Said optional additional coating layer is usually applied in specific cases such as promoting the adhesion between the substrate layer (A) and the first coating layer (B), wetting of the first coating layer (B), promoting the optical performance of the layered structure or promoting the mechanical performance of the layered structure.

[0049] Said optional additional coating layer, if present, does not comprise fluorine atoms. It is, however, preferred that no optional additional coating layer is applied between the substrate layer and the first coating layer (B).

[0050] Outer coating layer (B)

[0051] The outer coating layer (B) is coated on at least one surface of the substrate layer (A). This means that the outer coating layer (B) can be coated directly on at least one surface of the substrate layer (A), so that the outer coating layer (B) is in adherent contact with at least one surface of the substrate layer (A), or that the one or more additional inner coating layers (C) are sandwiched between the at least one surface of the substrate layer (A) and the outer coating layer (B), so that the outer coating layer (B) is not in adherent contact with the at least one surface of the substrate layer (A).

[0052] In one embodiment, the layered structure is a layered structure with a monolayer coating. In said embodiment the coating layer (B) is coated on at least one surface of the substrate layer (A) so that the outer coating layer (B) is in adherent contact with at least one surface of the substrate layer (A). The coating thereby consists of the outer coating layer (B) as single coating layer. “Adherent contact” in this regard means that there is no further coating layer or adhesive layer between the at least one surface of substrate layer (A) and the outer coating layer (B).

[0053] In another embodiment, the layered structure is a layered structure with a multilayer coating, which comprises one or more inner coating layer(s) (C) as discussed above. In said embodiment, the outer coating layer (B) is coated on the outer surface of an inner coating layer (C) so that the outer coating layer (B) is in adherent contact with the outer surface of an inner coating layer (C). Thus, the outer coating layer (B) usually is an outer layer of the multi-layer coating with adherent contact with the outer surface of an inner coating layer (C) as such that the inner coating layer (C) is sandwiched between the substrate layer (A) and the outer coating layer (B). “Adherent contact” in this regard means that there is no further coating layer or adhesive layer between the outer surface of the inner coating layer (C) and the outer coating layer (B).

[0054] Outer coating layer means that there is no further coating layer coated onto the outer surface of the outer coating layer (B). The outer coating layer (B) preferably has a thickness of 5 nm to 60 pm, preferably of 7 nm to 50 pm, more preferably 10 nm to 30 pm.

[0055] In a mono-layered structure the outer coating layer (B) usually has a thickness of 1000 nm to 60 pm, preferably of 3 pm to 50 pm, more preferably 5 pm to 30 pm.

[0056] In a multi-layered structure the outer coating layer (B) usually has a thickness of 5 nm to 5 pm, preferably of 7 nm to 1 pm, more preferably 10 nm to 200 nm.

[0057] The outer coating layer (B) comprises one or more, such as one, two, three or four, preferably one to three, more preferably one or two, most preferably two first siloxane polymer(s) (B-1 ). In the case that the outer coating layer (B) comprises more than one first siloxane polymers (B-1 ) said siloxane polymers differ in at least one property. Said at least one property can be e.g. differences in the silane monomers and / or differences in the molecular weight.

[0058] The first siloxane polymer(s) (B-1 ) can comprise monomer units selected from at least two, such as from 2 to 10, preferably from 2 to 6, more preferably from 2 to 4, still more preferably 2 or 3 different silane monomers. “Different” in this connection means that the silane monomers differ in at least one chemical moiety.

[0059] It is preferred that the first siloxane polymer(s) (B-1 ) comprise at least one, such as one to five, preferably one to four, more preferably one or two first silane monomers independently have the general structure according to formula (I)

[0060] R1aSi(OR2)4-a (I), wherein

[0061] R1is independently selected from substituted or non-substituted linear, branched or cyclic Ci to C20 alkyl groups and substituted or non-substituted C& to C20 aryl groups, whereby the substituents are selected from linear, branched or cyclic Ci to C20 alkyl groups, which optionally include heteroatoms selected from Si, O and / or N;

[0062] R2is independently selected from linear, branched or cyclic Ci to C20 alkyl groups; and a is a number selected from 1 to 3, preferably 1 or 2.

[0063] None of R1and R2in formula (I) comprises fluorine atoms. It is preferred that the at least one first silane monomers according to formula (I) does not include an active group capable of achieving cross-linking to adjacent siloxane polymer chains.

[0064] The at least one first silane monomers according to formula (I) are present in the first siloxane polymers (B-1 ) in a molar amount of 5 to 99 mol%, preferably of 7 to 98 mol%, still more preferably of 9 to 95 mol%.

[0065] In one embodiment it is preferable to have the at least one first silane monomers according to formula (I) are present in the first siloxane polymers (B-1 ) in a molar amount of 75 to 99 mol%, preferably of 80 to 98 mol%, still more preferably of 85 to 95 mol%.

[0066] In another embodiment, it is preferable to have the at least one first silane monomers according to formula (I) are present in the first siloxane polymers (B-1 ) in a molar amount of 5 to 25 mol%, preferably of 7 to 20 mol%, still more preferably of 9 to 15 mol%.

[0067] In one preferred embodiment the at least one first silane monomer comprises at least one silane monomer with one Si-atom according to formula (II).

[0068] R3aSi(OR4)4-a (II), wherein R3is independently selected from substituted or non-substituted linear, branched or cyclic Ci to C20 alkyl groups and substituted or non-substituted C& to C20 aryl groups, whereby the substituents are selected from linear, branched or cyclic Ci to C20 alkyl groups, which optionally include heteroatoms selected from O and / or N;

[0069] R4is independently selected from linear, branched or cyclic Ci to C20 alkyl groups, preferably linear or branched Ci to C20 alkyl groups, more preferably linear or branched Ci to C10 alkyl groups, still more preferably linear or branched Ci to C& alkyl groups, most preferably methyl or ethyl groups; and a is a number selected from 1 to 3, preferably 1 or 2.

[0070] None of R3and R4in formula (II) comprises fluorine atoms. It is preferred that the at least one silane monomers according to formula (II) does not include an active group capable of achieving cross-linking to adjacent siloxane polymer chains.

[0071] Especially preferred are di- or trialkoxysilanes according to formula (II).

[0072] Particularly suitable silane monomers are selected from the group of methyltriethoxysilane (MTEOS), methyltrimethoxysilane (MTMS), dimethyldiethoxysilane (DMDEOS), dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPDMS), 5- (Bicycloheptenyl)triethoxysilane (BCHTEOS), phenylmethyldimethoxysilane (PMDMS), methoxytrimethylsilane (MeOTMS), propyl trimethoxysilane (Propyl-TMS), hexyl trimethoxysilane (Hexyl-TMS), octyl trimethoxysilane (Octyl-TMS), n- hexyltriethoxysilane, 3-chloropropylmethyldimethoxysilane (3-CPMDMEOS), 3- chloropropyltrimethoxysilane (3-CPMTEOS), 3-chloropropylmethyldiethoxysilane, 3- CPTEOS = 3_chloropropyltriethoxysilane (3-CPTEOS), 11 -chloroundecyltriethoxysilane, Bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane (BHEAPTEOS), 2-hydroxy-4(3- triethoxysilyl)propoxy diphenyl ketone (HDKPTEOS), 2- [methoxy(polyethyleneoxy)propyl]trimethoxysilane (9-12 PE-units), 2- [methoxy(polyethyleneoxy)propyl]trimethoxysilane (6-9 PE-units), 1 -(Phenylpropyl)-4-[3- (triethoxysilyl)propyl]-1 H-1 ,2 ,3-triazole, 1 ,3-Diphenyltetraethoxydisiloxane or mixtures thereof.

[0073] The at least one silane monomers according to formula (II) can be present in the siloxane polymer in a molar amount of 0 to 50 mol%, preferably of 0 to 45 mol%, still more preferably of 0 to 40 mol%.

[0074] In one embodiment it is preferable to have the at least one silane monomers according to formula (II) present in the siloxane polymer in a molar amount of 5 to 50 mol%, preferably of 10 to 45 mol%, still more preferably of 20 to 40 mol%.

[0075] In another embodiment the siloxane polymer does not comprise a silane monomers according to formula (II). In another preferred embodiment the at least one first silane monomer comprises a bisilane.

[0076] Suitable bi-silanes are preferably represented by formula (III) (R5)3Si-Z-Si(R6)3, (III) wherein

[0077] R5and R6are independently selected from hydrogen and a group consisting of linear or branched alkyl, cycloalkyl, alkenyl, alkynyl, alkoxy and aryl having 1 to 6 rings, and wherein the group is substituted or unsubstitued; and

[0078] Z is a linking group selected from bivalent unsubstituted or substituted aliphatic and aromatic groups, such as alkylene, arylene, -O-alkylene-O-; -O-arylene-O-; alkylene-O- alkylene, arylene-O-arylene; alkylene-Z1C(=O)Z2-alkylene, arylene-Z1C(=O)Z2-arylene and -O-alkylene-Z1C(=O)Z2-alkylene-O-; -O-arylene-Z1C(=O)Z2-arylene-O-, wherein Z1and Z2are each selected from a direct bond or -O-.

[0079] None of R5, R6and Z in formula (III) comprises fluorine atoms.

[0080] It is preferred that the bi-silane according to formula (III) does not include an active group capable of achieving cross-linking to adjacent siloxane polymer chains.

[0081] In the bivalent “alkylene” groups and other similar aliphatic groups, the alkyl residue (or residue derived from an alkyl moiety) stands for 1 to 10, preferably 1 to 8, or 1 to 6 or even 1 to 4, most preferably 1 or 2 carbon atoms, examples include ethylene and methylene and propylene, especially ethylene and methylene.

[0082] “Arylene” stands for an aromatic bivalent group containing typically 1 to 3 aromatic rings, and 6 to 18 carbon atoms. Such groups are exemplified by phenylene (e.g. 1 ,4- phenylene and 1 ,3-phenylene groups) and biphenylene groups as well as naphthylene or anthracenylene groups.

[0083] The alkylene and arylene groups can optionally be substituted with 1 to 5 substituents selected from hydroxy, halo, vinyl, epoxy and allyl groups as well as alkyl, aryl and aralkyl groups. The halo group thereby does not include fluorine atoms.

[0084] Preferred alkoxy groups contain 1 to 4 carbon atoms. Examples are methoxy and ethoxy. The term “phenyl” includes substituted phenyls such as phenyltrialkoxy, in particular phenyltrimethoxy or phenyltriethoxy. The phenyl as well as other aromatic or alicyclic groups can be coupled directly to a silicon atom, or they can be coupled to a silicon atom via a methylene or ethylene bridge.

[0085] Exemplary bi-silanes include 1 ,2-Bis(triethoxysilyl)ethane (BTESE), 1 ,2- Bis(trimethoxysilyl)ethane (BTMSE), 1 ,2-Bis(methyldiethoxysilyl)ethane (Me-BTESE), 1 ,2-Bis(methyldimethoxysilyl)ethane (Me-BTMSE), and mixtures thereof.

[0086] It is preferable to have the bi-silane present in the siloxane polymer in a molar amount of 5 to 75 mol%, preferably of 7 to 70 mol%, still more preferably of 9 to 65 mol%.

[0087] It is further preferred that the first siloxane polymer(s) (B-1 ) additionally comprises at least one, such as one to five, preferably one to four, more preferably one or two second silane monomers independently include an active group capable of achieving crosslinking to adjacent siloxane polymer chains, and wherein the first siloxane polymer(s) (B- 1 ) is crosslinked to adjacent siloxane polymer chains by means of said an active groups. The at least one second silane monomer(s) does not comprise fluorine atoms.

[0088] The active group capable of achieving cross-linking to adjacent siloxane polymer chains in the at least one second silane monomer is preferably selected from epoxy, alicyclic epoxy groups (e.g. glycidyl), vinyl, allyl, acrylate, methacrylate, silane, silanol, and primary hydroxy, carbinol, and anhydrate groups, and combinations thereof.

[0089] Thereby, the epoxy, alicyclic epoxy groups (e.g. glycidyl), vinyl, allyl, acrylate, methacrylate, silanol, hydroxyl, cabinol and anhydrate groups are capable of achieving cross-linking to adjacent siloxane polymer chains upon a thermal, radiation or photo initiation, preferably in the presence of a suitable initiator such as a thermal, radiation or photo initiator.

[0090] Suitable thermal, radiation or photo initiators are preferably radical initiators, which can be selected from tert-amyl peroxybenzoate, 4,4-azobis(4-cyanovaleric acid), 1 ,1 azobis(cyclohexanecarbonitrile), benzoyl peroxide, 2,2-bis(tert-butylperoxy)butane, 1 ,1 - bis(tert-butylperoxy)cyclohexane, 2,2'-azobisisobutyronitrile (AIBN), 2,5-bis(tert- butylperoxy)-Z,S-dimethylhexane, 2,5-bis(tert-Butylperoxy)- 2,5 -dimethyl-3 -hexyne, bis(1 -(tert-butylperoxy)- 1 -methylethyl)benzene, 1 ,1 -bis(tert-butylperoxy)-3,3,5- trimethylcyclohexane, tert-butyl hydroperoxide, tert-butyl peracetate, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxy isopropyl carbonate, bumene hydroperoxide, byclohexanone peroxide, bicumyl peroxide, lauroyl peroxide, 2,4- pentanedione peroxide, peracetic acid, potassium persulfate, 2-lsopropylthioxanthone or 2-Hydroxy-4'- (2-hydroxyethoxy)-2-methylpropiophenone or 2-Benzyl-2-(dimethylamino)-1 -(4- morpholinophenyl)butan-1 -one, or cationic initiators, such as sulfonium hexafluoroantimonate.

[0091] The silane group is capable of achieving cross-linking to a carbon-carbon double bond, such as a vinyl or allyl group) of an adjacent siloxane polymer chains upon hydrosilylation, preferably in the presence of a suitable catalyst, such as a platinum (Pt) - based catalyst such as the Speier catalyst (H2PtCle.H2O), Karstedt’s catalyst (Pt(O)-1 ,3- divinyl-1 ,1 ,3,3-tetramethyldisiloxane complex solution) or a rhodium (Rh)-based catalyst such as Tris(triphenylphosphine)rhodium (I) chloride.

[0092] None of the initiators or the catalysts preferably comprise fluorine atoms.

[0093] Suitable silane monomers are preferably represented by formula (IV) R7aSiW4-a(IV) wherein

[0094] R7is selected from hydrogen and a group comprising linear and branched alkyl, cycloalkyl, alkenyl, alkynyl, (alk)acrylate, epoxy, allyl, vinyl and alkoxy and aryl having 1 to 6 rings, and wherein the group is substituted or unsubstituted;

[0095] W is an active group capable of achieving cross-linking to adjacent siloxane polymer chains or a hydrocarbon residue; and a is an integer 1 to 3.

[0096] Neither R7nor X in formula (IV) comprises fluorine atoms.

[0097] The hydrolysable group is in particular an alkoxy group (cf. formula V).

[0098] The alkoxy groups of R7and / or the active group capable of achieving cross-linking to adjacent siloxane polymer chains W can be identical or different and preferably selected from the group of radicals having the formula

[0099] -O-R8(V) wherein R8stands for a linear or branched alkyl group having 1 to 10, preferably 1 to 6 carbon atoms, and optionally exhibiting one or two substituents selected from the group of halogen, hydroxyl, vinyl, epoxy and allyl.

[0100] R8does not comprise fluorine atoms.

[0101] Especially preferred are di-, tri- or tetraalkoxysilanes comprising alkoxy groups according to formula (V).

[0102] Particularly suitable silane monomers are selected from the group of 3- (Trimethoxysilyl)propylmethacrylate (MEMO), 3-(Triethoxysilyl)propylmethacrylate, 5 (3- Glycidoxypropyl)triethoxysilane, (3-Glycidoxypropyl)trimethoxysilane (GPTMS), allyltrimethoxysilane (allylTMS), allyltriethoxysilane (allylTEOS), vinyltrimethoxysilane, vinyltriethoxysilane, (3-Glycidopropyl)dimethoxymethylsilane (Me-GPTMS), methacryloxypropylmethyldimethoxysilane (Me-MEMO), 2-(3,4-

[0103] Epoxycyclohexyl)ethyltriethoxysilane (ECHETEOS), 1 ,3-Divinyltetraethoxydisiloxane, 3- (triethoxysilyl)propylsuccin inc anhydride or mixtures thereof.

[0104] Preferred are silane monomers are selected from the group of 3- (Trimethoxysilyl)propylmethacrylate (MEMO) and (3-Glycidoxypropyl)trimethoxysilane (GPTMS).

[0105] The at least one second silane monomers can present in the first siloxane polymer (B-1 ) in a molar amount of 1 to 95 mol%, preferably of 2 to 93 mol%, still more preferably of 5 to 91 mol%.

[0106] In one embodiment it is preferable to have the at least one second silane monomers are present in the first siloxane polymer (B-1 ) in a molar amount of 1 to 25 mol%, preferably of 2 to 20 mol%, still more preferably of 5 to 15 mol%.

[0107] In another embodiment it is preferable to have the at least one second silane monomers are present in the first siloxane polymer (B-1 ) in a molar amount of 75 to 95 mol%, preferably of 80 to 93 mol%, still more preferably of 85 to 91 mol%. It is preferred that the molar amounts of the at least one first silane monomers and the at least one second silane monomers make up 100 mol% of the first siloxane polymer (B- 1 ).

[0108] It is especially preferred that the at least two silane monomers are selected from mixture of two or more of the group of 1 ,2-Bis(triethoxysilyl)ethane (BTESE), phenylmethyldimethoxysilane (PMDMS), 3-(Trimethoxysilyl)propylmethacrylate (MEMO) and (3-Glycidoxypropyl)trimethoxysilane (GPTMS).

[0109] In one preferred embodiment the first siloxane polymer (B-1 ) comprises, preferably consists of (3-Glycidoxypropyl)trimethoxysilane (GPTMS), 1 ,2-Bis(triethoxysilyl)ethane (BTESE) and phenylmethyldimethoxysilane (PMDMS).

[0110] In another preferred embodiment the first siloxane polymer (B-1 ) comprises, preferably consists of (3-Glycidoxypropyl)trimethoxysilane (GPTMS), 3- (Trimethoxysilyl)propylmethacrylate (MEMO) and 1 ,2-Bis(triethoxysilyl)ethane (BTESE).

[0111] In yet another preferred embodiment the first siloxane polymer (B-1 ) is a functionalized siloxane polymer, preferably a functionalized polydimethylsiloxane, such as a vinyl- functionalized, an epoxy-functionalized siloxane polymer, silanol-functionalized siloxane polymer, carbinol-functionalized siloxane polymer, hydroxyl functionalized siloxane polymer and / or acryloxypropyl-functionalized siloxane polymer, preferably a vinyl- functionalized polydimethylsiloxane and / or an epoxy-functionalized polydimethylsiloxane.

[0112] The first siloxane polymer (B-1 ) usually has a molecular weight in range of about 300 to 100000 g / mol, preferably from 300 to 80000 g / mol.

[0113] In one embodiment the first siloxane polymer (B-1 ) usually has a molecular weight in range of about 300 to 10000 g / mol.

[0114] It is preferred that the outer coating composition (B) further comprises a second siloxane polymer (B-2).

[0115] Said second siloxane polymer (B-2) preferably comprises functional groups, which are capable of at least partially crosslinking with the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers of the first siloxane polymer (B-1 ).

[0116] Suitable functional groups which are capable of at least partially crosslinking with the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers of the first siloxane polymer (B-1 ) are preferably allyl, vinyl, alkoxy, hydroxy, thiol, amino, isocyanate, ester, epoxy, (meth)acryl or combinations thereof.

[0117] Said second siloxane polymer (B-2) is preferably a polydimethylsiloxane elastomer, which comprises functional groups, which are capable of at least partially crosslinking with the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers of the first siloxane polymer (B-1 ).

[0118] Commercially available examples for polydimethylsiloxane elastomer, which comprises such functional groups are e.g. BYK-3701 , BYK-3710 and BYK-3720, commercially available from BYK Chemie GmbH.

[0119] Another example for the second siloxane polymer (B-2) are e.g. a homopolymer of tetraethoxysilane (TEOS), which can be end-capped with chlorotrimethylsilane.

[0120] The weight ratio of the first siloxane polymer (B-1 ) to the second siloxane polymer (B-2) in the outer coating layer (B) is preferably in the range of from 99.0 : 1 .0 to 85.0 : 15.0, more preferably from 97.5 : 2.5 to 87.5 : 12.5, still more preferably from 95.0 : 5.0 to 90.0 : 10.0.

[0121] It is preferred that the composition comprising at least one first siloxane polymer (B-1 ) comprises functional groups which are suitable for curing, especially UV curing. Such functional groups can be either silane monomers of the at least one first siloxane polymer (B-1 ) and / or the second siloxane polymer (B-2) comprising functional groups or compounds comprising functional groups which are added to the composition separately.

[0122] Suitable functional groups are preferably allyl, vinyl, alkoxy, hydroxy, thiol, amino, isocyanate, ester, epoxy, (meth)acryl or combinations thereof. As discussed above, these functional groups in one embodiment can be present as modification of the at least one first siloxane polymer (B-1 ), such as a vinyl- functionalized and / or an epoxy-functionalized siloxane polymer, preferably a vinyl- functionalized polydimethylsiloxane and / or an epoxy-functionalized polydimethylsiloxane.

[0123] Exemplary epoxy-functional group containing monomers include (3- glycidoxypropyl)trimethoxysilane, 1 -(2-(Trimethoxysilyl)ethyl)cyclohexane-3,4-epoxide, (3-glycidoxypropyl)triethoxysilane, (3- glycidoxypropyl)tripropoxysilane, 3- glycidoxypropyltri(2-methoxyethoxy)silane, 2,3-epoxypropyltriethoxysilane, 3,4- epoxybutyltriethoxysilane, 4,5- epoxypentyltriethoxysilane, 5,6- epoxyhexyltriethoxysilane, 5,6- epoxyhexyltrimethoxysilane, 2-(3,4- epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 4- (trimethoxysilyl)butane- 1 ,2-epoxide 1 ,3-Bis(glycidoxypropyl)-tetramethyldisiloxane, T ris(glycidoxypropyldimethylsiloxy)phenyl silane, .

[0124] Further examples of functionalized compounds are acrylate and metacrylate compounds, such as tetraethylene glycol diacrylate, trimethylo Ipropane triacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate and combinations thereof. Such compounds can be used as part of the silane compositions.

[0125] It is preferred that none of the epoxy-functional group containing monomers and the functionalized compounds comprise fluorine atoms.

[0126] The composition comprising at least one first siloxane polymer (B-1 ) is preferably formed by a method comprising the steps of

[0127] • Admixing the at least two different silane monomers, preferably as described above or below, in a first solvent to form a mixture;

[0128] • Subjecting the mixture to an at least partial hydrolysis of the monomers in the presence of a catalyst, whereby the hydrolysed monomers are at least partially polymerized and cross-linked to obtain the first siloxane polymer (B-1 );

[0129] • Optionally mixing the first siloxane polymer (B-1 ) with the second siloxane polymer (B-2); Optionally changing the first solvent to a second solvent;

[0130] Optionally subjecting the mixture to further crosslinking by hydrosilylation, thermal or radiation initiation.

[0131] In the case that the composition comprises more than one first siloxane polymer (B-1 ) the above steps are repeated for each one of the first siloxane polymer (B-1 ).

[0132] It is preferred that the composition does not comprise a component which comprises fluorine atoms.

[0133] The first solvent is preferably selected from the group of acetone, tetrahydrofuran (THF), toluene, 1 -propanol, 2-propanol, methanol, ethanol, water (H2O), cyclopentanone, acetonitrile, propylene glycol propyl ether, methyl-tert-butylether (MTBE), propylene glycol monomethylether acetate (PGMEA), methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethylether (PGME) and propylene glycol propyl ether (PnP). It is preferred that the first solvent does not include fluorine atoms.

[0134] The at least two different silane monomers can be admixed in the first solvent at any suitable temperature for solving the silane monomers. Usually, room temperature suffices.

[0135] In the next method step the mixture is subjected to an at least partial hydrolysis in the presence of a catalyst.

[0136] Suitable catalysts are acidic catalysts, basic catalysts or other catalysts.

[0137] Acidic catalysts are preferably selected from nitric acid (HNO3), sulfuric acid (H2SO4), formic acid (HCOOH), hydrochloric acid (HCI), sulfonic acid, hydrogen fluoride (HF), acetic acid (CH3COOH), trifluoromethanesulfonic acid or p-toluene sulfonic acid. Especially preferred acidic catalysts are nitric acid (HNO3), formic acid (HCOOH) and hydrochloric acid (HCI).

[0138] Basic catalysts are preferably selected from triethylamine (TEA), ammonium hydroxide (NH4OH), tetraethylammonium hydroxide (TEAH), tetramethylammonium hydroxide (TMEA), 1 ,4-diazabicyclo[2.2.2]octane, imidazole and diethylenetriamine. Other catalysts are preferably selected from 2,2,3,3,4,4,5,5-octafluoropentylacrylate, polyethylene glycol) 200, polyethylene glycol) 300 and n-butylated melamine formaldehyde resin.

[0139] Preferably the catalyst does not comprise fluorine atoms.

[0140] The hydrolysis step is preferably performed at a temperature of from 20 to 80°C for 1 to 24 hours, such as at room temperature overnight.

[0141] During the hydrolysis step the silane monomers are at least partially hydrolysed. Said at least partially hydrolysed silane monomers then are at least partially polymerized, preferably by condensation polymerization and crosslinked to form a siloxane polymer. Said polysiloxane usually has a relatively low molecular weight in range of about 300 to 2000 g / mol.

[0142] According to a preferable embodiment the subjecting the mixture to an at least partial hydrolysis includes refluxing. A typical refluxing time is 2 h.

[0143] The first solvent can be changed to a second solvent in an optional further method step after the hydrolysis step. The optional solvent change is advantageous, since it assists the removal of water and alcohols formed during hydrolysis of the silane monomers. In addition, it improves the properties of the final siloxane polymer solution when used as coating layer(s) on the substrate. Further, by means of the optional solvent exchange components of the composition comprising fluorine atoms, if present, can be removed. The second solvent is preferably selected from the group of propylene glycol methyl ether (PGME), propylene glycol methyl ether acetate (PGMEA), 1 -ethanol, 2-ethanol (IPA), acrylonitrile diacetone alcohol (DAA), propylene glycol n-propyl ether (PnP), methyl isobutyl ketone, methyl ethyl ketone, 2-butanol, 1 -butanol, tert-butanol, pentanol, ethanol, ethylene glycol, 2-propanol or mixtures thereof.

[0144] The second solvent does not comprise fluorine atoms.

[0145] It is preferred that the first siloxane polymer (B-1 ) and the second siloxane polymer (B-2) are mixed during the change for the first solvent to the second solvent.

[0146] Thereby, the second siloxane polymer (B-2) is preferably mixed with the second solvent. The first solvent is then changed to the mixture of the second siloxane polymer (B-2) and the second solvent. Alternatively, the first siloxane polymer (B-1 ) and the second siloxane polymer (B-2) are mixed before or after the solvent change.

[0147] The mixture comprising the first siloxane polymer (B-1 ) and optionally the second siloxane polymer (B-2) can be further subjected to a crosslinking step after the hydrolysis step. Thereby, the siloxane polymer is preferably at least partially crosslinked by hydrosilylation, thermal or radiation initiation or radical polymerization.

[0148] In the present context, the term “partially crosslinked” means that the polymer is capable of further crosslinking at conditions conducive to cross-linking. In practice, the polymer still contains at least some reactive, crosslinking groups after the first polymerisation step. The further crosslinking, which typically takes place after deposition of the partially crosslinked composition on a substrate, will be described below. It is preferred that the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the first siloxane polymer (B-1 ) are at least partially crosslinked to the functional groups, which are capable of at least partially crosslinking with the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers, of the second siloxane polymer (B-2).

[0149] The first siloxane polymer (B-1 ) and optionally the second siloxane polymer (B-2) is / are preferably at least partially crosslinked by hydrosilylation thermal, radiation or photo initiation using catalysts as described above.

[0150] Thereby, thermal crosslinking is preferably conducted at temperatures in the range of about 30 to 200 °C.

[0151] Typically cross-linking is carried out at refluxing conditions of the solvent.

[0152] Upon crosslinking preferably a covalent bond is formed between the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers and the functional groups, which are capable of at least partially crosslinking with the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers.

[0153] To improve resolution of the material when applied to photolithography, the siloxane polymer(s) can be optionally partially cross-linked during polymerization, in particular during or immediately after condensation polymerization. Various methods can be used for achieving cross-linking. For example, cross-linking method where two chains are joined via reactive groups not affecting any of the active groups intended for the UV photolithography can be employed. To mention an example, hydrosilylation for example using a proton on one chain reacting with a double bond on another chain will achieve cross-linking of desired kind. Another example is cross-linking through double bonds or epoxy groups.

[0154] Different active groups are preferably used for cross-linking and for photolithography. Thus, the cross-linking of the siloxane polymer can be achieved with an active group having double bonds or epoxy groups or both, such as epoxy, vinyl or allyl or methacrylate group using radical initiators and photoacid generators.

[0155] Epoxy groups can be employed for UV-lithography and vice-versa. The proportion of active groups required for cross-linking is generally smaller than for UV lithography, e.g. about 0.1 to 10 mol%, based on the monomers, for cross-linking and about 5 to 50 mol%, based on the monomers, for UV lithography.

[0156] The amount of the initiator added to the reaction mixture / solution is generally about 0.1 to 10 wt%, preferably about 0.5 to 5 wt%, calculated from the total weight of the siloxane polymer.

[0157] As a result of the partial cross-linking, the molecular weight will typically be 2- to 1 fl- folded. Thus, from a molecular weight in the range of about 300 to 2000 g / mol, the crosslinking will increase it above 3000, preferably to 4000 to 20000 g / mol.

[0158] Optionally, resulting free Si-OH groups present in backbone of the siloxane polymer can be protected by an end-capping. For end capping, the free Si-OH groups are reacted with silanes such as methyldichlorofluorosilane (C^FSiCHs, methylfluorodimethoxysilane ((MeO^SiFCHs), 3-chloropropyltrimethoxysilane (CI(CH2)3Si(OMe)3), ethyltrimethoxysilane (ETMS), chlorodimethyl octadecylsilane, trichloro-octadecylsilane, n-decylmethyldichlorosilane or trimethylchlorosilane (CISiMes) in presence of a catalyst such as triethylaluminium (TEA) or imidazole. The amount of catalyst varies from 1 .5 to 2 wt% of total solid. The reaction time varies from 40 to 45 min. - l -

[0159] The silanes and catalysts do not comprise fluorine atoms.

[0160] Other additives typically introduced into the composition comprising the at least one first siloxane polymer (B-1 ) include chemicals that can further modify the final surface properties of coated and cured film or improve wettability / adhesion properties of the outer coating layer (B) to the substrate layer (A) or an optional inner coating layer (C) or improve coating drying and packing behavior during deposition and drying to reach good visual quality. In addition, the additives can contribute also to improve the mechanical and optical properties of the coatings.

[0161] These additives can be surfactants, defoamers, antifouling agents, wetting agents etc. Examples of such additives include: BYK-301 , BYK-306, BYK-307, BYK-308, BYK-333, BYK-051 , BYK-036, BYK-028, BYK-057A, BYK-011 , BYK-055, BYK-036, BYK-067A, BYK-088, BYK-302, BYK-310, BYK-322, BYK-323, BYK-331 , BYK-333, BYK-341 , BYK- 345, BYK-348, BYK-370, BYK-377, BYK-378, BYK-381 , BYK-390, BYK-3700, BYK- 3720.

[0162] The additives preferably do not comprise fluorine atoms.

[0163] The additives are preferably present in an amount of 0.01 -5 wt% by weight, more preferably 0.1 to 1 wt% of the total weight of the solids.

[0164] Before further condensation the excess of water is preferably removed from the material and at this stage it is possible to make a solvent exchange to another synthesis solvent if desired. This other synthesis solvent may function as the final or one of the final processing solvents of the siloxane polymer. The residual water and alcohols and other by-products may be removed after the further condensation step is finalized. Additional processing solvent(s) may be added during the formulation step to form the final processing solvent combination. Additives such as thermal initiators, radiation sensitive initiators, sensitizers, surfactants and other additives may be added prior to final filtration of the siloxane polymer(s). After the formulation of the composition, the polymer(s) are ready for processing in, for example, roll-to-roll film deposition or in a lithographic process.

[0165] By adjusting the hydrolysis and condensation conditions it is possible to control the concentration / content of the group capable of being deprotonated (e.g. an OH-group) and any residual leaving groups from the silane precursors (e.g. alkoxy groups) of the siloxane polymer composition and also to control the final molecular weight of the siloxane polymer(s). This greatly affects dissolution of the siloxane polymer material into the aqueous based developer solution. Furthermore, the molecular weight of the polymer(s) also greatly effects on the dissolution properties of the siloxane polymer(s) into developer solutions.

[0166] Thus, for example, it has been found that when the final siloxane polymer(s) have a high content of hydroxyl groups remaining and a low content of alkoxy (e.g. ethoxy) groups, the final siloxane polymer(s) can be dissolved into an alkaline-water developer solution (egg. tetra methyl ammonium hydroxide; TMAH, or potassium hydroxide; KOH).

[0167] On the other hand, if the remaining alkoxy-group content of the final siloxane polymer(s) is high and it contains hardly any OH-groups, the final siloxane polymer(s) has a very low solubility in an alkaline-water developer of the above kind. The OH-groups or other functional groups, such as amino (NH2), thiol (SH), carboxyl, phenol or similar that result in solubility to the alkaline developer systems, can be attached directly to the silicon atoms of the siloxane polymer backbone or optionally attached to organic functionalities attached into the siloxane polymer backbone to further facilitate and control the alkaline developer solubility.

[0168] As mentioned above the method for preparing the first siloxane polymer (B-1 ) is repeated for each one of the first siloxane polymer (B-1 ).

[0169] The first siloxane polymer (B-1 ) and the optional second siloxane polymer (B-2) can be diluted using a proper solvent or solvent combination to give a solid content which in film deposition will yield the pre-selected film thickness.

[0170] The solvent or solvent combination does not comprise fluorine atoms.

[0171] Usually, a further amount of an initiator molecule compound is added to the siloxane composition after synthesis. The initiator, which can be optionally similar to the one added during polymerization, is used for creating a species that can initiate the polymerization of the “active” functional group in the UV curing step. Thus, in case of an epoxy group, cationic or anionic initiators can be used. In case of a group with double bonds as “active” functional group in the synthesized material, radical initiators can be employed. Also, thermal initiators (working according to the radical, cationic or anionic mechanism) can be used to facilitate the crosslinking of the “active” functional groups. The choice of a proper combination of the photoinitiators and sensitizers also depends on the used exposure source (wavelength). Furthermore the selection of the used sensitizer depends on the selected initiator type.

[0172] The concentration of the thermal, radiation or photo initiator and sensitizers in the composition is generally about 0.1 to 10 %, preferably about 0.5 to 5 %, calculated from the mass of the siloxane polymer.

[0173] The composition comprising the first siloxane polymer (B-1 ) is deposited onto the least one surface of the substrate to form the outer coating layer (B) or on the outer surface of an optional inner surface layer (C).

[0174] Suitable deposition methods include spin-on, clip, spray, ink-jet, roll-to-roll, gravure, reverse gravure, bar coating, slot, flexo-graphic, curtain, screen printing coating methods, extrusion coating, dip coating, flow coating or slit coating.

[0175] The deposited composition forms the outer coating layer (B) on at least one surface of the substrate layer (A) or on the outer surface of an optional inner surface layer (C). Typically, after deposition, or during the deposition step, the solvent is evaporated and the outer coating layer (B) dried, preferably by thermal drying or optionally by vacuum and / or thermal drying combined. This step is also referred to as pre-curing.

[0176] In a second, subsequent step the outer coating layer (B) is cured to final hardness by thermal curing at elevated temperature or by using UV exposure followed by thermal curing at elevated temperature.

[0177] In one embodiment, the pre-curing and the final curing steps are combined by carrying out heating by using an increasing heating gradient. In addition to the thermal cure only process, the curing can be performed in three steps, the process comprising thermal pre-cure and UV-cure followed by final thermal cure. It is also possible to apply a two steps curing process where thermal pre-cure is followed by UV-cure. In such a case no final thermal cure is preferably applied after UV-cure). According to a particular embodiment the method further includes developing the deposited film. In one embodiment, developing comprises exposing (full area or selective exposure using photomask or reticule or laser direct imaging) the deposited first siloxane polymer composition to UV light. The step of developing is typically carried out after any pre-curing step and before a final curing step.

[0178] Thus, in one embodiment the method comprises the steps of pre-curing or drying the outer coating layer (B) deposited on at least one surface of the substrate layer (A) or the outer surface of an inner coating layer (C); optionally exposing the thus obtained outer coating layer (B); optionally developing the thus obtained outer coating layer (B); and curing the outer coating layer (B).

[0179] The outer coating layer (B) preferably shows a good balance of properties such as good optical properties, such as a low refractive index, good mechanical protection and weathering stability, such as good abrasion resistance, easy-to-clean properties, and good chemical stability, without need of fluorine containing components.

[0180] The outer coating layer (B) therefore qualifies as fluorine-free hard coating layer.

[0181] Optional inner coating laver(s) (C)

[0182] The layered structure can comprise one or more, such as one to three, preferably one or two, further coating layer(s) (C).

[0183] Said optional further layer(s), if present, is / are situated between the substrate layer (A) and the outer coating layer (B). Said optional further coating layer(s) therefore are named optional inner coating layer(s) (C).

[0184] The at least one inner coating layer(s) (C), if present, is preferably coated on at least one surface of the substrate layer (A) so that the innermost surface of the coating layer(s) (B), if present, is in adherent contact with at least one surface of the substrate layer (A).

[0185] The outer coating layer (B) is preferably coated on the outermost surface of the at least one coating layer(s) (C), if present, so that the innermost surface of the outer coating layer (B) is in adherent contact with outermost surface of the inner coating layer(s) (B), if present. “ Adherent contact” in this regard means that there is no further coating layer or adhesive layer between the at least one surface of the substrate layer (A) and the first coating layer (B).

[0186] In one embodiment, the layered structure comprises one inner coating layer (C).

[0187] In said embodiment, the single inner coating layer (C) is preferably sandwiched between the surface layer (A) and the outer coating layer (B) in the configuration (A) -(C)-(B).

[0188] The inner surface of the single inner coating layer (C) preferably is in adherent contact with at least one surface of the substrate layer (A).

[0189] The outer surface of the single inner coating layer (C) preferably is in adherent contact with inner surface of the outer surface layer (B).

[0190] In another embodiment, the layered structure comprises two or more inner coating layers (C).

[0191] In said embodiment, the two or more inner coating layers (C) are preferably sandwiched between the surface layer (A) and the outer coating layer (B) in the configuration (A)- (C)x-(B), whereby x denotes the number of inner coating layers (C).

[0192] The inner surface of the innermost coating layer (C)i preferably is in adherent contact with at least one surface of the substrate layer (A).

[0193] The outer surface of the outermost coating layer (C)opreferably is in adherent contact with inner surface of the outer surface layer (B).

[0194] In the following the optional inner coating layer(s) (C) are further defined. These definitions preferably independently apply to each optional inner coating layer (C).

[0195] The inner coating layer (C) preferably comprises a siloxane polymer (C-1 ).

[0196] The siloxane polymer (C-1 ) preferably comprises an active group capable of achieving cross-linking to adjacent siloxane polymer chains, and wherein the adjacent siloxane polymer chains are crosslinked by means of said an active groups

[0197] Active groups are preferably epoxy, alicyclic epoxy groups (e.g. glycidyl), vinyl, allyl, acrylate, methacrylate and silane groups and combinations thereof.

[0198] Thereby, the epoxy, alicyclic epoxy groups (e.g. glycidyl), vinyl, allyl, acrylate, methacrylate groups are capable of achieving cross-linking to adjacent siloxane polymer chains upon a thermal, radiation or photo initiation, preferably in the presence of a suitable initiator such as a thermal, radiation or photo initiator.

[0199] Suitable thermal, radiation or photo initiators are preferably radical initiators, which can be selected from tert-amyl peroxybenzoate, 4,4-azobis(4-cyanovaleric acid), 1 ,1 '- azobis(cyclohexanecarbonitrile), benzoyl peroxide, 2,2-bis(tert-butylperoxy)butane, 1 ,1 - bis(tert-butylperoxy)cyclohexane, 2,2'-azobisisobutyronitrile (AIBN), 2,5-bis(tert- butylperoxy)-2,5-dimethylhexane, 2,5-bis(tert-Butylperoxy)- 2,5 -dimethyl-3 -hexyne, bis(1 -(tert-butylperoxy)- 1 -methylethyl)benzene, 1 ,1 -bis(tert-butylperoxy)-3,3,5- trimethylcyclohexane, tert-butyl hydroperoxide, tert-butyl peracetate, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxy isopropyl carbonate, bumene hydroperoxide, byclohexanone peroxide, bicumyl peroxide, lauroyl peroxide, 2,4- pentanedione peroxide, peracetic acid, potassium persulfate, 2-lsopropylthioxanthone or 2-Hydroxy-4'- (2-hydroxyethoxy)-2-methylpropiophenone or 2-Benzyl-2-(dimethylamino)-1 -(4- morpholinophenyl)butan-1 -one, or cationic initiators, such as sulfonium hexafluoroantimonate.

[0200] The silane group is capable of achieving cross-linking to a carbon-carbon double bond, such as a vinyl or allyl group) of an adjacent siloxane polymer chains upon hydrosilylation, preferably in the presence of a suitable catalyst, such as a platinum (Pt) - based catalyst such as the Speier catalyst (H2PtCle.H2O), Karstedt’s catalyst (Pt(O)-1 ,3- divinyl-1 ,1 ,3,3-tetramethyldisiloxane complex solution) or a rhodium (Rh)-based catalyst such as Tris(triphenylphosphine)rhodium (I) chloride.

[0201] None of the initiators or the catalysts preferably comprise fluorine atoms.

[0202] In one embodiment the siloxane polymer (C-1 ) preferably comprises an epoxy group containing siloxane resin. Suitable siloxane polymers are e.g. disclosed in US 9,617,449 B2, US 9,994,731 B2, US 10,246,606 B2 and US 10,337,919 B2.

[0203] In another embodiment the siloxane polymer (C-1 ) preferably comprises monomer units selected from at least two different silane monomers, wherein at least one of the silane monomers includes an active group capable of achieving cross-linking to adjacent siloxane polymer chains, and wherein the adjacent siloxane polymer chains are crosslinked by means of said an active groups. Said active groups capable of achieving cross-linking to adjacent siloxane polymer chains are preferably as described above. The siloxane polymer (C-1 ) can comprise monomer units selected from 2 to 10, such as from 2 to 6, preferably from 2 to 4 different silane monomers. “Different” in this connection means that the silane monomers differ in at least one chemical moiety.

[0204] In one embodiment, the molar ratio between monomers containing a first active group, e.g. selected from epoxy, alicyclic epoxy groups (e. g. glycidyl), and vinyl and allyl groups, to monomers containing a second active group, e.g. selected from acrylate and methacrylate;groups, varies in the range of 1 :100 to 100:1 , in particular 1 :10 to 1 0:1 , for example 5:1 to 1 :2 or 3:1 to 1 :1 .

[0205] In some embodiments, the components containing the second active group also be selected from acrylate and metacrylate containing compounds other than silane monomers, such as tetraethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ditrimethylo propane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate and combinations thereof.

[0206] In some embodiments, the active group or active groups will be present in a concentration of about 1 to 35 % based on the molar portion of monomers.

[0207] Suitable silane monomers are preferably represented by formula (VI) R9aSiX4-a(VI) wherein

[0208] R9is selected from hydrogen and a group comprising linear and branched alkyl, cycloalkyl, alkenyl, alkynyl, (alk)acrylate, epoxy, allyl, vinyl and alkoxy and aryl having 1 to 6 rings, and wherein the group is substituted or unsubstituted;

[0209] X is a hydrolysable group or a hydrocarbon residue; and a is an integer 1 to 3.

[0210] Neither R1nor X in formula (I) comprises fluorine atoms.

[0211] The hydrolysable group is in particular an alkoxy group (cf. formula VII).

[0212] The alkoxy groups of R9and / or the hydrolysable group X can be identical or different and preferably selected from the group of radicals having the formula

[0213] -O-R10(VII) wherein

[0214] R10stands for a linear or branched alkyl group having 1 to 10, preferably 1 to 6 carbon atoms, and optionally exhibiting one or two substituents selected from the group of halogen, hydroxyl, vinyl, epoxy and allyl. Most preferred are methoxy and ethoxy groups.

[0215] 10 does not comprise fluorine atoms.

[0216] Especially preferred are di-, tri- or tetraalkoxysilanes comprising alkoxy groups according to formula (VII).

[0217] Particularly suitable silane monomers are selected from the group of tetraethoxysilane (TEOS), tetramethoxysilane (TMS), methyltriethoxysilane (MTEOS), methyltrimethoxysilane (MTMS), dimethyldiethoxysilane (DMDEOS), dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPDMS), 3- (Trimethoxysilyl)propylmethacrylate (MEMO), 3-(Triethoxysilyl)propylmethacrylate, 5- (Bicycloheptenyl)triethoxysilane (BCHTEOS), (3-Glycidoxypropyl)triethoxysilane, (3- Glycidoxypropyl)trimethoxysilane (GPTMS), allyltrimethoxysilane (allylTMS), allyltriethoxysilane (allylTEOS), vinyltrimethoxysilane, vinyltriethoxysilane, (3- Glycidopropyl)dimethoxymethylsilane (Me-GPTMS), methacryloxypropylmethyldimethoxysilane (Me-MEMO), phenylmethyldimethoxysilane (PMDMS) or mixtures thereof.

[0218] Preferred are silane monomers are selected from the group of phenylmethyldimethoxysilane (PMDMS), 3-(Trimethoxysilyl)propylmethacrylate (MEMO) and (3-Glycidoxypropyl)trimethoxysilane (GPTMS).

[0219] Said silane monomers are preferably present in the in the siloxane polymer in a molar amount of 50 to 100 mol%, preferably of 50 to 99 mol%, still more preferably of 65 to 97 mol%.

[0220] In one embodiment the at least two different silane monomers of the siloxane polymer (C-1 ) comprise at least one bi-silane.

[0221] Suitable bi-silanes are preferably represented by formula (VIII)

[0222] (R11)3Si-Y-Si(R12)3, (VIII) wherein R11and R12are independently selected from hydrogen and a group consisting of linear or branched alkyl, cycloalkyl, alkenyl, alkynyl, (al k) acrylate, epoxy, allyl, vinyl, alkoxy and aryl having 1 to 6 rings, and wherein the group is substituted or unsubstitued; and Y is a linking group selected from bivalent unsubstituted or substituted aliphatic and aromatic groups, such as alkylene, arylene, -O-alkylene-O-; -O-arylene-O-; alkylene-O- alkylene, arylene-O-arylene; alkylene-Z1C(=O)Z2-alkylene, arylene-Z1C(=O)Z2-arylene and -O-alkylene-Z1C(=O)Z2-alkylene-O-; -O-arylene-Z1C(=O)Z2-arylene-O-, wherein Z1and Z2are each selected from a direct bond or -O-.

[0223] None of R11, R12and Y in formula (VIII) comprises fluorine atoms.

[0224] In the bivalent “alkylene” groups and other similar aliphatic groups, the alkyl residue (or residue derived from an alkyl moiety) stands for 1 to 10, preferably 1 to 8, or 1 to 6 or even 1 to 4, more preferably 1 or 2 carbon atoms, examples include ethylene and methylene and propylene.

[0225] “Arylene” stands for an aromatic bivalent group containing typically 1 to 3 aromatic rings, and 6 to 18 carbon atoms. Such groups are exemplified by phenylene (e.g. 1 ,4- phenylene and 1 ,3-phenylene groups) and biphenylene groups as well as naphthylene or anthracenylene groups.

[0226] The alkylene and arylene groups can optionally be substituted with 1 to 5 substituents selected from hydroxy, halo, vinyl, epoxy and allyl groups as well as alkyl, aryl and aralkyl groups. The halo group thereby does not include fluorine atoms.

[0227] Preferred alkoxy groups contain 1 to 4 carbon atoms. Examples are methoxy and ethoxy.

[0228] The term “phenyl” includes substituted phenyls such as phenyltrialkoxy, in particular phenyltrimethoxy or phenyltriethoxy. The phenyl as well as other aromatic or alicyclic groups can be coupled directly to a silicon atom, or they can be coupled to a silicon atom via a methylene or ethylene bridge.

[0229] Exemplary bi-silanes include 1 ,2-Bis(triethoxysilyl)ethane (BTESE), 1 ,2- Bis(trimethoxysilyl)ethane (BTMSE) and mixtures thereof. It is preferable to have the bi-silane present in the siloxane polymer in a molar amount of 0 to 50 mol%, preferably of 1 to 50 mol%, still more preferably of 3 to 35 mol%.

[0230] It is especially preferred that the at least two silane monomers are selected from mixture of two or more of the group of 1 ,2-Bis(triethoxysilyl)ethane (BTESE), phenylmethyldimethoxysilane (PMDMS), 3-(Trimethoxysilyl)propylmethacrylate (MEMO) and (3-Glycidoxypropyl)trimethoxysilane (GPTMS).

[0231] The composition comprising a siloxane polymer (C-1 ) is preferably formed by a method comprising the steps of

[0232] • Admixing the at least two different silane monomers, preferably as described above or below, in a first solvent to form a mixture;

[0233] • Subjecting the mixture to an at least partial hydrolysis of the monomers in the presence of a catalyst, whereby the hydrolysed monomers are at least partially polymerized and cross-linked;

[0234] • Optionally changing the first solvent to a second solvent;

[0235] • Optionally subjecting the mixture to further crosslinking by hydrosilylation, thermal or radiation initiation or radical polymerization.

[0236] It is preferred that the composition comprising a siloxane polymer (C-1 ) does not comprise a component which comprises fluorine atoms.

[0237] The first solvent is preferably selected from the group of acetone, tetrahydrofuran (THF), toluene, 1 -propanol, 2-propanol, methanol, ethanol, water (H2O), cyclopentanone, acetonitrile, propylene glycol propyl ether, methyl-tert-butylether (MTBE), propylene glycol monomethylether acetate (PGMEA), methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethylether (PGME) and propylene glycol propyl ether (PnP). It is preferred that the first solvent does not include fluorine atoms.

[0238] The at least two different silane monomers can be admixed in the first solvent at any suitable temperature for solving the silane monomers. Usually, room temperature suffices. In the next method step the mixture is subjected to an at least partial hydrolysis in the presence of a catalyst.

[0239] Suitable catalysts are acidic catalysts, basic catalysts, or other catalysts.

[0240] Acidic catalysts are preferably selected from nitric acid (HNO3), sulfuric acid (H2SO4), formic acid (HCOOH), hydrochloric acid (HCI), sulfonic acid, hydrogen fluoride (HF), acetic acid (CH3COOH), trifluoromethanesulfonic acid or p-toluene sulfonic acid. Especially preferred acidic catalysts are nitric acid (HNO3) hydrochloric acid (HCI) and formic acid (HCOOH).

[0241] Basic catalysts are preferably selected from triethylamine (TEA), ammonium hydroxide (NH4OH), tetraethylammonium hydroxide (TEAH), tetramethylammonium hydroxide (TMEA), 1 ,4-diazabicyclo[2.2.2]octane, imidazole and diethylenetriamine.

[0242] Other catalysts are preferably selected from 2,2,3,3,4,4,5,5-octafluoropentylacrylate, polyethylene glycol) 200, polyethylene glycol) 300 and n-butylated melamine formaldehyde resin.

[0243] Preferably the catalyst does not comprise fluorine atoms.

[0244] The hydrolysis step is preferably performed at a temperature of from 20 to 80°C for 1 to 24 hours, such as at room temperature overnight.

[0245] During the hydrolysis step the silane monomers are at least partially hydrolysed. Said at least partially hydrolysed silane monomers then are at least partially polymerized, preferably by condensation polymerization and crosslinked to form a siloxane polymer. Said polysiloxane usually has a relatively low molecular weight in range of about 500 to 2000 g / mol.

[0246] According to a preferable embodiment the subjecting the mixture to an at least partial hydrolysis includes refluxing. A typical refluxing time is 2 h.

[0247] The first solvent can be changed to a second solvent in an optional further method step after the hydrolysis step. The optional solvent change is advantageous, since it assists the removal of water and alcohols formed during hydrolysis of the silane monomers. In addition, it improves the properties of the final siloxane polymer solution when used as coating layer(s) on the substrate. Especially, when using a fluorine-comprising component, such as a fluorine comprising first solvent, catalyst or additive, solvent change to a second solvent is conducted.

[0248] The second solvent is preferably selected from the group of propylene glycol methyl ether (PGME), propylene glycol methyl ether acetate (PGMEA), 1 -ethanol, 2-ethanol (IPA), acrylonitrile diacetone alcohol (DAA), propylene glycol n-propyl ether (PnP), methyl isobutyl ketone, methyl ethyl ketone or mixtures thereof.

[0249] The second solvent does not comprise fluorine atoms.

[0250] The mixture comprising the siloxane polymer can be further subjected to a crosslinking step after the hydrolysis step. Thereby, the siloxane polymer (C-1 ) is preferably at least partially crosslinked by hydrosilylation, thermal, radiation or photo initiation or radical polymerization.

[0251] In the present context, the term “partially crosslinked” means that the polymer is capable of further crosslinking at conditions conducive to cross-linking. In practice, the polymer still contains at least some reactive, crosslinking groups after the first polymerisation step. The further crosslinking, which typically takes place after deposition of the partially crosslinked composition on a substrate, will be described below.

[0252] The siloxane polymer (C-1 ) is preferably at least partially crosslinked by hydrosilylation, thermal, radiation or photo initiation using catalysts as described above.

[0253] Thereby, thermal crosslinking is preferably conducted at temperatures in the range of about 30 to 200 °C.

[0254] Typically cross-linking is carried out at refluxing conditions of the solvent.

[0255] To improve resolution of the material when applied to photolithography, the siloxane polymer can be optionally partially cross-linked during polymerization, in particular during or immediately after condensation polymerization. Various methods can be used for achieving cross-linking. For example, cross-linking method where two chains are joined via reactive groups not affecting any of the active groups intended for the UV photolithography can be employed. To mention an example, hydrosilylation for example using a proton on one chain reacting with a double bond on another chain will achieve cross-linking of desired kind. Another example is cross-linking through double bonds or epoxy groups. Different active groups are preferably used for cross-linking and for photolithography. Thus, the cross-linking of the siloxane polymer can be achieved with an active group having double bonds or epoxy groups or both, such as epoxy, vinyl or allyl or methacrylate group using radiation or initiators and photoacid generators.

[0256] Epoxy groups can be employed for UV-lithography and vice versa. The proportion of active groups required for cross-linking is generally smaller than for UV lithography, e.g. about 0.1 to 10 mol%, based on the monomers, for cross-linking and about 5 to 50 mol%, based on the monomers, for UV lithography.

[0257] The amount of the initiator added to the reaction mixture / solution is generally about 0.1 to 10 wt%, preferably about 0.5 to 5 wt%, calculated from the total weight of the siloxane polymer.

[0258] As a result of the partial cross-linking, the molecular weight will typically be 2- to 1 fl- folded. Thus from a molecular weight in the range of about 500 to 2000 g / mol, the crosslinking will increase it above 3000, preferably to 4000 to 20000 g / mol.

[0259] Optionally, resulting free Si-OH groups present in backbone of the siloxane polymer can be protected by an end-capping. For end capping, the free Si-OH groups are reacted with silanes such as methyldichlorofluorosilane (C^FSiCHs, 3- chloropropyltrimethoxysilane (CI(CH2)3Si(OMe)3), ethyltrimethoxysilane (ETMS), or trimethylchlorosilane (CISiMes) in presence of a catalyst such as triethylaluminium (TEA) or imidazole. The amount of catalyst varies from 1 .5 to 2 wt% of total solid. The reaction time varies from 40 to 45 min.

[0260] The silanes and catalysts do not comprise fluorine atoms.

[0261] Other additives typically introduced into the first composition comprising a siloxane polymer (B-1 ) include chemicals that can further modify the final surface properties of coated and cured film or improve wettability / adhesion properties of the coating layer (B) to the substrate layer (A) or the other coating layer (C) or improve coating drying and packing behavior during deposition and drying to reach good visual quality.

[0262] These additives can be surfactants, defoamers, antifouling agents, wetting agents etc. Examples of such additives include: BYK-301 , BYK-306, BYK-307, BYK-308, BYK-333, BYK-051 , BYK-036, BYK-028, BYK-057A, BYK-011 , BYK-055, BYK-036, BYK-067A, BYK-088, BYK-302, BYK-310, BYK-322, BYK-323, BYK-331 , BYK-333, BYK-341 , BYK- 345, BYK-348, BYK-370, BYK-377, BYK-378, BYK-381 , BYK-390, BYK-3700, BYK- 3720, all commercially available from BYK Chemie GmbH.

[0263] The additives preferably do not comprise fluorine atoms.

[0264] The additives are preferably present in an amount of 0.01 -5 wt% by weight, more preferably 0.1 to 1 wt% of the total weight of the solids.

[0265] Before further condensation the excess of water is preferably removed from the material and at this stage it is possible to make a solvent exchange to another synthesis solvent if desired. This other synthesis solvent may function as the final or one of the final processing solvents of the siloxane polymer. The residual water and alcohols and other by-products may be removed after the further condensation step is finalized. Additional processing solvent(s) may be added during the formulation step to form the final processing solvent combination. Additives such as thermal initiators, radiation sensitive initiators, photo initiators, sensitizers, surfactants, and other additives may be added prior to final filtration of the siloxane polymer. After the formulation of the composition, the polymer is ready for processing in, for example, roll-to-roll film deposition or in a lithographic process.

[0266] By adjusting the hydrolysis and condensation conditions it is possible to control the concentration / content of the group capable of being deprotonated (e. g. an OH-group) and any residual leaving groups from the silane precursors (e. g. alkoxy groups) of the siloxane polymer composition and also to control the final molecular weight of the siloxane polymer. This greatly affects dissolution of the siloxane polymer material into the aqueous based developer solution. Furthermore, the molecular weight of the polymer also greatly effects on the dissolution properties of the siloxane polymer into developer solutions.

[0267] Thus, for example, it has been found that when the final siloxane polymer has a high content of hydroxyl groups remaining and a low content of alkoxy (e.g. ethoxy) groups, the final siloxane polymer can be dissolved into an alkaline-water developer solution (egg. tetra methyl ammonium hydroxide; TMAH, or potassium hydroxide; KOH). On the other hand, if the remaining alkoxy-group content of the final siloxane polymer is high and it contains hardly any OH-groups, the final siloxane polymer has a very low solubility in an alkaline-water developer of the above kind. The OH-groups or other functional groups, such as amino (NH2), thiol (SH), carboxyl, phenol or similar that result in solubility to the alkaline developer systems, can be attached directly to the silicon atoms of the siloxane polymer backbone or optionally attached to organic functionalities attached into the siloxane polymer backbone to fi1 rther facilitate and control the alkaline developer solubility.

[0268] After synthesis, the siloxane polymer composition can be diluted using a proper solvent or solvent combination to give a solid content which in film deposition will yield the preselected film thickness.

[0269] Usually, a further amount of an initiator molecule compound is added to the siloxane composition after synthesis. The initiator, which can be optionally similar to the one added during polymerization, is used for creating a species that can initiate the polymerization of the “active” functional group in the UV curing step. Thus, in case of an epoxy group, cationic or anionic initiators can be used. In case of a group with double bonds as “active” functional group in the synthesized material, radical initiators can be employed. Also thermal initiators (working according to the radical, cationic or anionic mechanism) can be used to facilitate the crosslinking of the “active” functional groups. The choice of a proper combination of the photo-initiators and sensitizers also depends on the used exposure source (wavelength). Furthermore, the selection of the used sensitizer depends on the selected initiator type.

[0270] The concentration of the thermal, radiation or photo initiator and sensitizers in the composition is generally about 0.1 to 10 %, preferably about 0.5 to 5 %, calculated from the mass of the siloxane polymer.

[0271] The composition as described above may comprise solid nanoparticles or other compounds in an amount of between 1 and 50 wt-% of the composition. The nanoparticles (or similar nano-, or microscale rods, crystals, spheres, dots, buds etc.) are in particular selected from the group of light scattering, light absorbing, light emitting and / or conductive pigments, dyes, organic and inorganic phosphors, oxides, quantum dots, polymers or metals.

[0272] Preferably, none of the solid nanoparticles or other compounds comprise fluorine atoms.

[0273] The composition comprising the siloxane polymer (C-1 ) is then deposited onto the at least one surface of the substrate layer (A) or on the outer surface of an already deposited inner coating layer (C) to form an inner coating layer (C).

[0274] It is preferred that the inner coating layer (C) is in adherent contact with the at least one surface of the substrate or the outer surface layer of another inner coating layer (C).

[0275] Suitable deposition methods include spin-on, clip, spray, ink-jet, roll-to-roll, gravure, reverse gravure, bar coating, slot, flexo-graphic, curtain, screen printing coating methods, extrusion coating, dip coating, flow coating or slit coating.

[0276] The deposited composition comprising the siloxane polymer (C-1 ) forms the inner coating layer (C) on at least one surface of the substrate (A) or the outer surface of an already deposited inner coating layer (C). Typically, after deposition, or during the deposition step, the solvent is evaporated and the inner coating layer (C) dried, preferably by thermal drying or optionally by vacuum and / or thermal drying combined. This step is also referred to as pre-curing.

[0277] In a second, subsequent step the inner coating layer (C) is cured to final hardness by using thermal curing at elevated temperature or UV exposure followed by thermal curing at elevated temperature.

[0278] In one embodiment, the pre-curing and the final curing steps are combined by carrying out heating by using an increasing heating gradient. In addition to the thermal cure only process, the curing can be performed in three steps, the process comprising thermal pre-cure and UV-cure followed by final thermal cure. It is also possible to apply a two steps curing process where thermal pre-cure is followed by UV-cure. In such a case no final thermal cure is preferably applied after UV-cure).

[0279] According to a particular embodiment the method further includes developing the deposited film. In one embodiment, developing comprises exposing (full area or selective exposure using photomask or reticle or laser direct imaging) the deposited first siloxane polymer composition to UV light. The step of developing is typically carried out after any pre-curing step and before a final curing step.

[0280] Thus, in one embodiment the method comprises the steps of pre-curing or drying the inner coating layer (C) deposited on the substrate (A); optionally exposing the thus obtained inner coating layer (C); optionally developing the thus obtained inner coating layer (C); and curing the inner coating layer (C), optionally repeating these steps with a further inner coating layer (C) deposited on the outer surface of the inner coating layer (C).

[0281] According to a particular embodiment the method further includes curing the composition comprising the siloxane polymer (C-1 ).

[0282] The thickness of each inner coating layer (C) (i.e. the film thickness) may independently range from 5 nm to 100 pm, preferably of 7 nm to 50 pm, more preferably 10 nm to 30 pm.

[0283] The inner coating layer (C) preferably is a flexible hard coat layer.

[0284] It is preferred that the hardness of the inner coating layer (C) is greater than 3H, over 4H, over 5H, over 6H or even over 7H as determined by ASTM D3363-00, Elcometer tester.

[0285] Preferably the inner coating layer (C) has an adhesion of 4B-5B, as tested by ASTM D3359-09, Crosshatch tester.

[0286] Further, the inner coating layer (C) preferably has a scratch resistance as evidenced by no visual scratches on a Taber linear abrasion test (Using Linear Abraser from Taber Industries) carried out at up to 2000 linear cycles with BonStar steel wool #0000, at 500g weight, 2x2 cm head size, 2.0-inch stroke length, 60 cycles / min.

[0287] Layered structure

[0288] The layered structure according to the present invention preferably comprises the substrate layer (A) and the outer coating layer (B), and optionally one or more inner coating layer(s) (C). The outer coating layer (B) is the outermost layer of the layered structure.

[0289] In one preferred embodiment the layered structure consists of the substrate layer (A) and the outer coating layer (B). In said embodiment the layered structure is a layered structure with a monolayer coating.

[0290] In another preferred embodiment the layered structure consists of the substrate layer (A), one or more, such as one to three, preferably one or two, inner coating layers (C) and the outer coating layer (B). Thereby, the one or more inner coating layers (C) are sandwiched between the substrate layer (A) and the outer coating layer (B) in the configuration (A)-(C)X-(B), with x being the number of inner coating layers (C). In said embodiment the layered structure is a layered structure with a multi-layered coating. In the presence of a single inner coating layer (C) in the configuration (A)-(C)-(B), the layered structure is a layered structure with a two-layer coating.

[0291] In the presence of two inner coating layers (C1 ) and (C2) in the configuration (A)-(C1 )- (C2)-(B), the layered structure is a layered structure with a three-layer coating.

[0292] It is preferred that the layered structure does not comprise any additional coating layers, with exception of the outer coating layer (B) and optionally the one or more inner coating layer(s) (C).

[0293] It is further preferred that the layered structure does not comprise any adhesive layers, such as between the substrate layer (A) and the outer coating layer (B) or optionally the inner coating layers (C), optionally between different inner coating layers (C) and optionally between the inner coating layer (C) and the outer coating layer (B).

[0294] It is preferred that the layered structure comprises a fluorine free hard coating on the substrate layer (A).

[0295] The layered structure shows a good balance of properties of adhesion of the different layers to each other, high hardness, high water contact angle, low abrasion, high transmittance and low haze. Further the layered structure preferably shows an adhesion of the inner coating layer (C) to the outer coating layer (B) of 4-6B.

[0296] The layered structure preferably shows pencil hardness of 5B-H.

[0297] Further, the layered structure preferably shows an initial water contact angle of at least 90°, preferably at least 95°.

[0298] Still further the layered structure preferably shows a scratch resistance corresponding to a visual quality of 0 to 3 on a Taber linear abrasion test (Using Linear Abraser from Taber Industries) carried out at up to 400 linear cycles with BonStar steel wool #0000, at 1 kg load, 2x2 cm head size, 2.0-inch stroke length, 60 cycles / min.

[0299] Further, the layered structure preferably shows a water contact angle of at least 50°, more preferably at least 55° on a Taber linear abrasion test (Using Linear Abraser from Taber Industries) carried out at up to 400 linear cycles with BonStar steel wool #0000, at 1 kg load, 2x2 cm head size, 2.0-inch stroke length, 60 cycles / min.

[0300] Still further the layered structure preferably shows a haze of not more than 5.0%, preferably not more than 45%, when measured on a coated PET substrate.

[0301] Further, the layered structure preferably shows a transmittance at 550 nm of at least 85.0%, preferably at least 87.5%, when measured on a coated PET substrate.

[0302] The layered structure according to the present invention is suitable for flexible electronics applications, including displays, optical lens, transparent boards, and automotive industries especially as a lightweight alternative to glass.

[0303] The present invention is further characterized by the following non-limiting examples:

[0304] Examples

[0305] 1. Determination methods

[0306] Molecular weight: the polymers were characterized by gel permeation chromatography. The chromatographic system consisted of a GPC apparatus equipped with an isocratic HPLC pump and a refractive index detector. The polysiloxanes (0,20 g; 50% solid content) were dissolved in THF (HPLC-grade; 2,30 g). The analyte injection volume was 100 pL, the flow was 0,70 mL / min, and the column temperature was set to 40 °C. Four polysterene exclusion-based columns were used. The mobile phase was THF (HPLC grade). Number-average molecular weight (Mn) and the weight-average molecular weight (Mw) of the polymers were determined using internal standards, e.g. two series of polystyrenes (Serie A: 5 polystyrenes with Mw= 120.000 g / mol, 42.400 g / mol, 10.700 g / mol, 2.640 g / mol, 474 g / mol and Serie B: 4 polymers with Mw= 193.000 g / mol, 16.700 g / mol, 6.540 g / mol, 890 g / mol).

[0307] Solid contents: The solid content of the polymers was determined using a Mettler Toledo HB43 instrument. The polymeric solution (0.9 - 1 .1 g) to analyzed was placed in a measuring tray (disposable weighing / drying pan in aluminum). The aluminum pan was then heated by a halogen lamp for 10 min from room temperature to T = 160 °C. The mass of solid polymer present in the analyzed polymeric solution was determined after evaporation of the solvents.

[0308] Film thickness and refractive index (Rl): the film thickness and refractive index were measured using Ellipsometer UVISEL-VASE Horiba Jobin-Yvon. Measurements are performed using Gorilla Glass 4 or silicon wafer (diameter: 150 mm, Type / Dopant: P / Bor, Orientation: <1 -0-0>, Resistivity: 1 -30 Q.cm, thickness: 675 + / - 25 pm, TTV: < 5 pm, particle: < 20 @ 0,2 pm, Front surface: polished; back surface: etched; Flat 1 SEMI standard) or other suitable substrates.

[0309] Transmission (T%) and haze (H%): A Konica Minolta spectrophotometer CM-3700A (Specta Magic NX software) was used to measure transmittance and haze.

[0310] Pencil hardness (PEHA): the pencil hardness was determined according to ASTM standard D3363-00 using a Elcometer pencil hardness tester.

[0311] Water contact angle (WCA): the static contact angle measurement was performed by optical tensiometer using distilled water, 4 pL droplet size, three measurement points average was recorded as the measurement result value and Young-Laplace equation was used as the numerical method to describe the contour of the drop (tool: attention theta optical tensiometer).

[0312] Abrasion:

[0313] Abrasion testing was carried out using Bon star steel wool #0000, 1 kg load, 2 x 2 cm head, 2-inch stroke, 60 cycles I minute using taber linear abraser 5750. Abrasion test evaluation criteria: Initial water contact angle, water contact angle measurement at 400 cycle intervals (up to 2500 cycles) and visual inspection for surface damage I visual scratch inspection at 400 cycle intervals (up to 2500 cycles).

[0314] Visual quality (VQ): the visual inspection can be observed with bear eyes, under microscope using a green or red-light quality lamp inspection. The visual quality can be scored between 0 (best) to 3 (worse).

[0315] Adhesion: the adhesion was determined according to ASTM standard D3359-D9 using a Elcometer cross-hatch tester and Elcometer tape test.

[0316] 2. List of components used in the examples: a) Silane Monomers:

[0317] GPTMS = (3-Glycidoxypropyl)trimethoxysilane, Sigma-Aldrich

[0318] PMDMS = phenyl methyl dimethoxy silane, Sigma-Aldrich

[0319] BTESE = 1 ,2-Bis(triethoxysilyl)ethane, Momentive Performance Materials

[0320] MEMO = 3-(Trimethoxysilyl)propylmethacrylate, ABCR b) Polysiloxanes

[0321] BYK 310 = polyester-modified polydimethylsiloxane, BYK Chemie GmbH

[0322] BYK 067A = polysiloxane-based defoamer, BYK Chemie GmbH

[0323] BYK 3720 = solution of polyether-modified, hydroxy-functional polydimethylsiloxane in methoxypropanol, BYK Chemie GmbH

[0324] BYK 3701 = epoxy-functionalized polysiloxane, BYK Chemie GmbH DMS-E09 = vinyl-functionalized polydimethylsiloxane, Gelest DMS-V05 = epoxy-functionalized polydimethylsiloxane, Gelest

[0325] HTHC = homopolymer of tetraethoxysilane (TEOS), CAS number: 11099-06-2, endcapped with chlorotrimethyl silane c) Solvents:

[0326] EtOH = ethanol, Altia VWR

[0327] PGME = 1 -methoxy-2-propanol, Ultra Pure Solutions Inc.

[0328] IPA = 2-propanol, Merck

[0329] EG = ethylene glycol, Sigma-Aldrich

[0330] Acetone, Brenntag d) Catalysts:

[0331] Formic acid, Sigma-Aldrich

[0332] HNO3 = nitric acid, Merck e) Photoinitiator:

[0333] UVI Speed Cure 976 = (sulfanediyldibenzene-4,1 -diyl)bis(diphenylsulfonium), Lambson Irgacure 369 = 2-Benzyl-2-(dimethylamino)-1 -(4-morpholinophenyl)butan-1 -one, BASF f) End-capping agents

[0334] Chlorotrimethyl silane, Sigma-Aldrich

[0335] 3. Preparation examples a) Preparation Examples for inner coating layer (C)

[0336] The compositions C-1 or C-2 for the first coating layer are adapted to the PET as substrate especially in regard of the curing and baking conditions.

[0337] Composition C-1

[0338] Root polymer:

[0339] In a 500 mL round bottom flask, BTESE (21 .15 g; 0.06 mol), GPTMS (91 g; 0.3875 mol), MEMO (37 g; 0.149 mol) are mixed in acetone (112.4 g). HNO3 (0.1 M; 35.47 g) is added dropwise over 15 min and the reaction mixture is stirred at room temperature overnight. PGME (90 g) is added and solvent exchange procedure from acetone to PGME was performed. Additional PGME is added to have a final solid content of 41 .85%.

[0340] Formulation: The root polymer was further diluted to 30 % solid content with IPA and the additives Speed Cure 976 (1 .2 % of solid material), BYK 067A (1 .0 % of solid material) and BYK 310 (0.7 % of solid material).

[0341] Composition C-2

[0342] Root polymer:

[0343] In a 500 mL round bottom flask, BTESE (21 .15 g; 0.06 mol), GPTMS (91 g; 0.3875 mol), MEMO (37 g; 0.149 mol) are mixed in acetone (112.4 g). HNO3 (0.1 M; 35.47 g) is added dropwise over 15 min and the reaction mixture is stirred at room temperature overnight. PGME (90 g) is added and solvent exchange procedure from acetone to PGME was performed. Additional PGME is added to have a final solid content of 41 .85%.

[0344] Formulation:

[0345] The root polymer was further diluted to 30 % solid content with IPA and the additives Irgacure 369 (1 .5 % of solid material), BYK 067A (1 .0% of solid material) and BYK 310 (0.7 % of solid material). b) Preparation Examples for the outer coating layer (B) Composition B-1

[0346] Root polymer:

[0347] In a 50 mL round bottom flask, bis(methyldimethoxysilyl)ethane (10 g; 0.0419 mol), phenyl methyl dimethoxy silane (3.8 g; 0.0209 mol) and 3- glycidoxypropyltrimethoxysilane (1 .65 g; 0.0069 mol) were mixed in ethanol (15.45 g). HCOOH (0.1 M aqueous solution; 8.28 g) was added dropwise and the reaction mixture was refluxed for 2 h. After cooling to room temperature, PGME (15 g) was added and solvent exchange procedure from MeOH / EtOH / H2O to PGME was performed under reduced pressure. The final solid content was adjusted to 10% by addition of PGME (1 g)-

[0348] Stock solution:

[0349] A stock solution was made from BYK 3720 (0.5175 g), IPA (418,12 g), EG (20.86 g) and PGME (395.15 g).

[0350] Formulation:

[0351] The root polymer (15.02 g; 10% in PGME) was mixed with the stock solution (185.02 g). Composition B-2

[0352] Root polymer:

[0353] DMS-E09

[0354] Stock solution:

[0355] A stock solution was made from BYK 3720 (0.52 g), IPA (418.15 g), EG (20.88 g) and

[0356] PGME (395.08 g).

[0357] Formulation:

[0358] The root polymer (1 .5058 g) was mixed with the stock solution (198.58 g). B-3:

[0359] DMS-V05

[0360] Stock solution:

[0361] A stock solution was made from BYK 3720 (0.5125 g), IPA (417.95 g), EG (20.85 g) and

[0362] PGME (395.62 g).

[0363] Formulation:

[0364] The root polymer (1 .5113 g) was mixed with the stock solution (198.53 g).

[0365] B-4

[0366] Root polymer:

[0367] In a 500 mL round bottom flask, BTESE (21 .15 g; 0.06 mol), GPTMS (91 g; 0.3875 mol), MEMO (37 g; 0.149 mol) are mixed in acetone (112.4 g). HNO3 (0.1 M; 35.47 g) is added dropwise over 15 min and the reaction mixture is stirred at room temperature overnight. PGME (90 g) is added and solvent exchange procedure from acetone to PGME was performed. Additional PGME is added to have a final solid content of 41 .85%.

[0368] Formulation:

[0369] The root polymer was further diluted to 21 % solid content with IPA and PGME, the additives Speed Cure 976 (1 .2 % of solid material), BYK 067A (1 .0 % of solid material) and BYK 310 (0.7 % of solid material), HTHC (1 .0 % of solid material).

[0370] Composition B-5

[0371] Root polymer: In a 500 mL round bottom flask, BTESE (21 .15 g; 0.06 mol), GPTMS (91 g; 0.3875 mol), MEMO (37 g; 0.149 mol) are mixed in acetone (112.4 g). HNO3 (0.1 M; 35.47 g) is added dropwise over 15 min and the reaction mixture is stirred at room temperature overnight. PGME (90 g) is added and solvent exchange procedure from acetone to PGME was performed. Additional PGME is added to have a final solid content of 41 .85%.

[0372] In a 50 mL round bottom flask, the root polymer prepared above (20 g; 41 .85% solid content in PGME) and Chlorotrimethyl silane (0.25 g) were mixed and stirred at 80° C for 1 hour. After allowing the mixture to cool to room temperature, the solid content was measured and found to remain at 42%.

[0373] Formulation:

[0374] The root polymer was further diluted to 30 % solid content with IPA, the additives Speed Cure 976 (1 .0 % of solid material), and BYK 3701 (1 .0 % of solid material).

[0375] 4. Preparation and properties of the coatings a) Two-layer coating on PET substrate

[0376] Inner Layer (C)

[0377] The naked PET plastic substrate was first treated by O2 plasma at 300W for 6 min.

[0378] Then, coating composition (C-1 or C-2) was coated onto the plasma treated surface of the substrate. The coating process was performed using sheet to sheet technique, bar coating procedure (bar #3 or #4 to get a target coating thickness of 2-5 pm), a pre-bake temperature of T = 120 °C for 90s, a UV power of 90 W / cm2, and a post bake temperature of T = 120 C for 10 minutes.

[0379] Alternatively, when coated with coating composition (C-1 ) the naked PET substrate can also be plasma treated with a mixture of N2 and O2 plasma at 300 W for 1 min.

[0380] Outer Layer (B)

[0381] The PET substrate coated with the inner layer (C) was firstly O2 plasma treated at 150 W for 12 seconds (when coated with composition (C-1 )) or 300 W for 1 min (when coated with composition (C-2)). Then, the coating composition (B-1 , B-2 or B-3) was coated on the inner layer (C) on the substrate using bar coating technique (bar #2 to get a target coating thickness of 40-60 nm). After thermal curing (T = 120 °C for 30 minutes), the coating properties were evaluated. 5. Properties of the examples

[0382] The properties of the coating are listed in Table 1 and Table 2 below.

[0383] In Table 1 ,the coating compositions of example 1 are C-1 and B-1 , of example 2 are C-1 and B-2, of example 3 are C-1 and B-3, of example 4 are C-1 and B-4 and of example 5 are C-1 and B-5. Thereby, for the inner layer (C) bar coating procedure #4 has been used.

[0384] Table 1 : coating properties ND = not determined

[0385] In Table 2, the coating composition of example 6 are B-2 and C-3 and bar 3 to prepare the first layer, of example 7 are B-2 and C-3 and bar 4 to prepare the first layer. Table 2: coating properties

Claims

Claims1 . A layered structure comprising(A) a substrate layer; and(B) an outer coating layer coated on at least one surface of the substrate layer (A), wherein the outer coating layer (B) comprises a first siloxane polymer (B-1 ), wherein the first siloxane polymer (B-1 ) comprises monomer units selected from at least two different silane monomers, wherein at least one, such as one to five, preferably one to four, more preferably one or two first silane monomers independently have the general structure according to formula (I)R1aSi(OR2)4-a (I), wherein R1is independently selected from substituted or non-substituted linear, branched or cyclic Ci to C20 alkyl groups and substituted or non-substituted C& to C20 aryl groups, whereby the substituents are selected from linear, branched or cyclic Ci to C20 alkyl groups, which optionally include heteroatoms selected from Si, O and / or N;R2is independently selected from linear, branched or cyclic Ci to C20 alkyl groups; and a is a number selected from 1 to 3, preferably 1 or 2; and at least one, such as one to five, preferably one to four, more preferably one or two second silane monomers, which independently include an active group capable of achieving cross-linking to adjacent siloxane polymer chains; characterized in that none of the coating layers of the layered structure comprises fluorine atoms.

2. The layered structure according to claim 1 , wherein the active group capable of achieving cross-linking to adjacent siloxane polymer chains in the at least one second silane monomer is selected from epoxy, alicyclic epoxy groups (e.g. glycidyl), vinyl, allyl, acrylate, methacrylate, silane, silanol, and primary hydroxy, carbinol, and anhydrate groups and combinations thereof.

3. The layered structure according to any one of the preceding claims, wherein the outer coating layer (B) comprises a second siloxane polymer (B-2), preferably a polydimethylsiloxane elastomer, which comprises functional groups, which are capable of at least partially crosslinking with the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers and polymer chains of the first siloxane polymer (B-1 ) and of the second siloxane polymer (B-2) are crosslinked via a covalent bond between the active group capable of achieving cross-linking to adjacent siloxane polymer chains of the at least one second silane monomers and the functional groups, which are capable of at least partially crosslinking with the active group capable of achieving crosslinking to adjacent siloxane polymer chains of the at least one second silane monomers.

4. The layered structure according to any one of the preceding claims, wherein the outer coating layer (B) has a thickness of 5 nm to 60 pm, preferably of 7 nm to 50 pm, more preferably 10 nm to 30 pm and / or the substrate layer (A) has a thickness of 10 to 5000 pm, preferably 20 to 4000 pm.

5. The layered structure according to any one of the preceding claims being a layered structure with a monolayer coating.

6. The layered structure according to any one of the preceding claims further comprising one or more inner coating layer(s) (C) situated between the substrate layer (A) and the outer coating layer (B), which comprises a second siloxane polymer (C-1 ).

7. The layered structure according to claim 6, wherein the second siloxane polymer (C-1 ) comprises monomer units selected from at least two different silane monomers, wherein at least one of the silane monomers includes an active group capable of achieving cross-linking to adjacent siloxane polymer chains, and wherein the adjacent siloxane polymer chains are crosslinked by means of said an active groups.

8. The layered structure according to claims 6 or 7, wherein the at least one inner coating layer (C) independently has a thickness of 5 nm to 100 pm, preferably of 7 nm to 50 pm, more preferably 10 nm to 30 pm.

9. The layered structure according to any one of the preceding claims, wherein the material of the substrate layer (A) is selected from the group of glass, quartz, silicon, silicon nitride, polymers, metals and plastics and combinations thereof, wherein the plastics are preferably selected from thermoplastic polymers, such as polyolefins, polyesters, polyamides, polyimides, acrylic polymers, such as poly(methylmethacrylate), and Custom Design polymers.

10. A method for producing a layered structure according to any one of the preceding claims comprising the following steps:• Preparing a composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) comprising the steps of: a) Admixing the at least two different silane monomers in a first solvent to form a mixture; b) Subjecting the mixture to an at least partial hydrolysis of the monomers in the presence of a catalyst, whereby the hydrolysed monomers are at least partially polymerized and cross-linked to obtain the first siloxane polymer (B-1 ); c) Optionally mixing the first siloxane polymer (B-1 ) with a second siloxane polymer (B-2); d) Optionally changing the first solvent to a second solvent; e) Optionally subjecting the composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) to further crosslinking by hydrosilylation, thermal or radiation initiation or radical polymerization;• Providing a substrate (A);• Depositing the composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) onto at least one surface of substrate (A) to form the outer coating layer (B);• Curing the composition of the outer coating layer (B).11 . The method according to claim 10, further comprising the following steps:• Providing a composition comprising a siloxane polymer (C-1 )• Depositing the composition comprising a siloxane polymer (C-1 ) onto at least one surface of the substrate (A) to form an inner coating layer (C) in adherent contact with the at least one surface of the substrate (A);• Cross-linking the siloxane polymer chains of the inner coating layer (C) as to obtain a first coating layer (C) comprising a cross-linked siloxane polymer in adherent contact with the at least one surface of the substrate (A);• Depositing the composition comprising the first siloxane polymer (B-1 ) and optionally a second siloxane polymer (B-2) onto at least one outer surface of inner coating layer (C) to form the outer coating layer (B);• Curing the composition of the outer coating layer (B).

12. The method according to claim 11 , wherein the composition comprising the siloxane polymer (C-1 ) is formed by a method comprising the steps of:• Admixing the at least two different silane monomers in a first solvent to form a mixture;• Subjecting the mixture to an at least partial hydrolysis of the monomers in the presence of a catalyst, whereby the hydrolysed monomers are at least partially polymerized and cross-linked;• Optionally changing the first solvent to a second solvent;• Optionally subjecting the mixture to further crosslinking by hydrosilylation, thermal or radiation initiation or radical polymerization.

13. The method according to any one of claims 10 to 12, wherein the first and / or second composition is deposited by spin-on, clip, spray, ink-jet, roll-to-roll, gravure, reverse gravure, bar coating, slot, flexo-graphic, curtain, screen printing coating methods, extrusion coating, dip coating, flow coating or slit coating.

14. Use of the layered structure according to any one of claims 1 to 13 for flexible electronics applications, including displays, optical lens, transparent boards, and automotive industries especially as a lightweight alternative to glass.

15. Use of the outer coating layer (B) in the layered structure according to any one of claims 1 to 13 in a fluorine-free hard coating.

Images