UV-curable composition for optical lens by jetting printing

Abstract

The invention relates to a UV-curable, inkjet transparent composition comprising at least one free-radical photoinitiator, at least one surfactant and a polymerizable composition containing at least a mixture of : - 40 to 60 weight % of a first polymerizable component - 40 to 60 weight % of a second polymerizable component with the weight percentage wt% based on the total weight of the polymerizable composition and, wherein, • The first polymerizable component is of formula (I), (II), or (III) • The second polymerizable component is of formula (IV).

Description

[0001] UV-CURABLE COMPOSITION FOR OPTICAL LENS BY JETTING PRINTING

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a curable composition for inkjet printing comprising at least two different monomeric components, a surfactant and a photoinitiator for the manufacture of optical articles, especially ophthalmic articles. The present invention also relates to a method of manufacturing a three-dimensional (3D) printed optical article from the curable composition.

[0004] BACKGROUND OF THE INVENTION

[0005] It is known to use an additive manufacturing technology to manufacture an optical article such as a lens.

[0006] For example, additive manufacturing methods comprise three dimensions (3D)-printing processes that build objects layer by layer based on a digital model. These methods encompass various technologies such as inkjet printing or stereolithography and their variants.

[0007] For example, a lens may be produced by successively depositing droplets of liquid composition and curing them forming layers of composition. This method, commonly referred as inkjet printing, generally controls the shape of the layers by controlling the position and volume of the deposited droplets whereas the curing step is usually global. Other additive manufacturing method may also be used such as stereolithography and its variants.

[0008] A complete optical lens or at least the substrate of an optical lens can be manufactured layer by layer by additive manufacturing. Alternatively, additive manufacturing, in particular 3D printing can be used to manufacture an optical element only. In that case, said optical element or complementary optical member is adjoined by additive manufacturing to a starting optical member for example by using a technology called “build over technology”. Such a build over technology is disclosed for instance in international applications W02015004383A1 and W02020115061A1.

[0009] To be suitable for inkjet printing, the composition must have certain physical properties. For example, the composition must have a Z number comprised between 1 and 10 or a viscosity compatible with the inkjet printhead used in the inkjet printing method. In fact, most inkjet printers require inks with viscosities in the range of 2-20 cP. Consequently, inkjet inks are quite limited in the amount of polymerizable components.

[0010] The Z number is a theoretical value calculated from the physico-chemical properties of the composition and the projected drop size. It is used to predict the suitability of the composition for inkjet printing. An ink composition for inkjet printing has these physical properties and is therefore a composition that can be used in an inkjet printing method.

[0011] Regardless of the manufacturing method, the optical article must also meet certain optical and physical criteria such as a relative light transmission factor in the visible spectrum (Tv) higher or equal to 80 %, an Abbe number greater than 38, for example, a Yellowness Index less than 1.5 for a thickness of 2 mm, or a storage modulus higher than or equal to 1 ,5GPa at 23°C.

[0012] US2023 / 0122021 discloses a surfactant-free curable composition comprising two different monomeric components and a photoinitiator suitable for inkjet printing. However, it does not disclose a printed article with suitable optical properties.

[0013] Thus, there is a need in the art to develop a composition with good physical properties compatible with a printhead and inkjet printing and resulting in a polymer with mechanical and / or optical properties suitable for optical products.

[0014] INVENTION SUMMARY

[0015] A first object of the present invention is a UV-curable, inkjet transparent composition comprising at least one free-radical photoinitiator, at least one surfactant and a polymerizable composition containing at least a mixture of:

[0016] - 40 to 60 weight % of a first polymerizable component

[0017] - 40 to 60 weight % of a second polymerizable component with the weight percentage wt% based on the total weight of the polymerizable composition and, wherein,

[0018] • The first polymerizable component is of formula (I), (II), or (III):

[0019] Wherein

[0020] Ri, R2, R3, R4, Rs, Re, R7, Rs, R9, R10, R11 and R12, identical or different, are independently a hydrogen or an alkyl;

[0021] A is an alkylene, an alkoxylene, an alkyleneoxy, a poly(alkylene), a poly(alkoxylene) or a poly(alkyleneoxy), wherein the alkylene, the alkoxylene, the alkyleneoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkyleneoxy) is optionally substituted for example by at least one hydroxyl (-OH) or an alkyl;

[0022] • The second polymerizable component is of formula (IV): Wherein

[0023] R13, R14, R15, R16, R17 and Ris identical or different, are independently hydrogen or an alkyl;

[0024] Ai and A2, identical or different, are independently an alkylene, an alkoxylene, an alkyleneoxy, a poly(alkylene), a poly(alkoxylene) or a poly(alkyleneoxy), wherein the alkylene, the alkoxylene, the alkyleneoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkyleneoxy) is optionally substituted, for example by at least one hydroxyl, and / or one acryloxy and / or one methacryloxy group;

[0025] B is a non-aromatic carbocycle or non-aromatic heterocycle and is optionally substituted by at least one alkyl and / or at least one acryloxy and / or one methacryloxy group.

[0026] In particular, an object of the present invention is a UV-curable, inkjet transparent composition suitable for optical use comprising at least one free-radical photoinitiator, at least one surfactant and a polymerizable composition containing at least a mixture of:

[0027] - 40 to 60 weight % of a first polymerizable component

[0028] - 40 to 60 weight % of a second polymerizable component with the weight percentage wt% based on the total weight of the polymerizable composition and, wherein,

[0029] • The first polymerizable component is of formula (I), (II), or (III):

[0030] Wherein

[0031] R1, R2, R3, R4, Rs, Re, R7, Rs, R9, R10, R11 and R12, identical or different, are independently a hydrogen or an alkyl;

[0032] A is an alkylene, an alkoxylene, an alkyleneoxy, a poly(alkylene), a poly(alkoxylene) or a poly(alkyleneoxy), wherein the alkylene, the alkoxylene, the alkyleneoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkyleneoxy) is optionally substituted for example by at least one hydroxyl (-OH) or an alkyl;

[0033] • The second polymerizable component is of formula (IV):

[0034] Wherein

[0035] R13, R14, R15, Ri6, R17 and Ris identical or different, are independently hydrogen or an alkyl;

[0036] Ai and A2, identical or different, are independently an alkylene, an alkoxylene, an alkyleneoxy, a poly(alkylene), a poly(alkoxylene) or a poly(alkyleneoxy), wherein the alkylene, the alkoxylene, the alkyleneoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkyleneoxy) is optionally substituted, for example by at least one hydroxyl, and / or one acryloxy and / or one methacryloxy group;

[0037] B is a non-aromatic carbocycle or non-aromatic heterocycle and is optionally substituted by at least one alkyl and / or at least one acryloxy and / or one methacryloxy group. A second object of the present invention is an optical material obtained by the curing of the said composition.

[0038] A third object of the present invention is a method for the manufacturing of an optical element comprising the UV polymerization of the said composition and the optical element obtained thereof.

[0039] The invention is also directed to an ophthalmic lens comprising at least one said optical element.

[0040] This UV-curable transparent ink composition exhibits excellent stability over time (physical and optical properties), making it suitable for inkjet printing. This UV-curable transparent ink composition enables to form a transparent material or article with excellent optical and mechanical performances.

[0041] Another advantage of the present invention is that the composition is free of carcinogenic, mutagenic or reprotoxic compounds (CMR compounds).

[0042] DETAILED DESCRIPTION OF THE INVENTION

[0043] In the present disclosure, the term “UV-curable composition” refers to Ultra Violet curable composition. More specifically, it means that said composition is a product in which monomers, oligomers, etc. are solidified, hardened through a polymerization reaction by ultraviolet rays. The terms “cure” and “harden” can be used interchangeably.

[0044] In the present disclosure, unless otherwise specified, an optical article / material is understood to be transparent when the observation of an image through said optical article is perceived with no significant loss of contrast, that is, when the formation of an image through said optical article is obtained without adversely affecting the quality of the image. This definition of the term “transparent” can be applied to all objects qualified as such in the description, unless otherwise specified.

[0045] The term “inkjet ink” means an ink suitable for digital manufacturing technology, and especially an ink or composition suitable for inkjet printing. As used herein, the terms “inkjet printing”, “jetting printing” and “material jetting” can be used interchangeably.

[0046] In the present disclosure, unless specified otherwise, the term “alkyl” refers to a linear or branched chain monovalent saturated aliphatic hydrocarbon radical of 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably of 1 to 4 carbon atoms.

[0047] For example, the term “linear or branched saturated alkyl” refers to methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl or and t-butyl, preferably methyl (-CH3) and ethyl (- CH2-CH3). In the present disclosure, the term “alkylene” represents any divalent radical of a linear or branched hydrocarbon chain comprising 1 to 12 carbon atoms. Examples of C1-C12 alkylene groups include C1-C4 alkylene groups such as -CH2-, -(CH2)2-, -(CH2)3-, -(CH2)4- , -CH(CH3)-, -CH(CH3)-CH2-, -CH2-CH(CH3)-, -(CH2)2-CH(CH3)-, -CH2-CH(CH3)-CH2- or - CH(CH3)-(CH2)2- as well as -(CH2)5- -(CH2)6- -(CH2)2-CH(CH3)-(CH2)2-, -(CH2)3- CH(CH3)- CH2-, -(CH2)7-, -(CH2)S- -(CH2)9-, -(CH2)IO-, -(CH2)H-, -(CH2)i2-.

[0048] In the present disclosure, the term “alkoxylene” refers to -O(alkylene) group, wherein the alkylene is as defined above.

[0049] In the present disclosure, the term “alkyleneoxy” represents a radical of formula -O(R'O) R wherein R' is a C1C12 alkylene, R is a C1C12 alkyl. Examples of (C1-C12 alkylenoxy) groups include OCFWCH The term “polyalkyleneoxy” represents a radical of formula -O(R'O)mR wherein R' is a C1C12 alkylene, R is a C1C12 alkyl and m is an integer from 1 to 12. Examples of (C1-C12 alkylenoxy) groups include OCH2 CFWCH

[0050] As used herein, the term “acryloxy” or “acryloxy group” means -O(CO)-CH2=CH2.

[0051] As used herein, the term “methacryloxy” or “methacryloxy group” means -O(CO)- CH2=CHCH3.

[0052] In the present disclosure, the term “cycle” or “ring” corresponds to a compound in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, for example 5 or 6 atoms and include examples where all the atoms are carbon (i.e., are carbocycles), or where both carbon and non-carbon atoms are present (heterocyclic compounds). More precisely, a “heterocyclic compound or ring structure” is a cyclic compound that has atoms of at least two different elements as members of its ring(s).

[0053] As used herein, the term “non-aromatic carbocycle” refers to a divalent monocyclic hydrocarbon ring or fused polycyclic hydrocarbon rings, which may comprise one or more unsaturations. In one variant, the non-aromatic carbocycle does not show any unsaturation but is a saturated ring. Examples of non-aromatic carbocycle include cycloalkylene. The expression "cycloalkylene" represents any divalent radical of a monocyclic or polycyclic 3 to 12 membered carbocycle. Examples of C3-Ci2 alkylene groups include cyclopropylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclodecylene and decahydronaphthylene. The non-aromatic carbocycle can also be for example a fused polycyclic ring such as a tricyclodecane derivative. The non-aromatic carbocycle can be substituted, for example by a linear or branched alkyl.

[0054] In the present disclosure, the term “non-aromatic heterocycle” refers to a divalent monocyclic ring or fused polycyclic rings, which comprise at least one heteroatom being oxygen atom, nitrogen atom or sulfur atom and which may comprise one or more unsaturations. When the heterocycle comprises more than one heteroatom, each heteroatom is, identically or differently of each other, oxygen atom, nitrogen atom or sulfur atom. For example, the heterocycle comprises between 1 to 3 heteroatoms.

[0055] For example, non-aromatic heterocycle includes, but is not limited to, heterocycloalkylene. The non-aromatic heterocycle as used herein can form for example a dioxane, a trioxane, a tetrahydrofuran, a thiane, a pyrrolidine etc.

[0056] Unless mentioned otherwise, the groups and radicals defined hereinabove may be unsubstituted or substituted by one or more substituents.

[0057] The term “substituted” refers to the specified group or moiety bearing one or more substituents, for example by a hydroxyl group (-OH) and / or an akyl group. The term “optionally substituted” refers to the specified group or moiety being unsubstituted or substituted by one or more substituents.

[0058] «UV-curable Composition »

[0059] The UV-curable, inkjet transparent composition of the present disclosure is particularly suitable for optical use. In particular, the UV-curable composition may be for the manufacture of an optical element.

[0060] The UV-curable composition of the present disclosure comprises a polymerizable composition containing at least a mixture of two polymerizable components: a first polymerizable component and a second polymerizable component.

[0061] The term “difunctional” in e.g. difunctional polymerizable compound means that the polymerizable compound includes two polymerizable groups.

[0062] The term “polyfunctional” in e.g. polyfunctional polymerizable compound means that the polymerizable compound includes more than two polymerizable groups.

[0063] Preferably, the first polymerizable component and second polymerizable component comprise at least two (meth)acrylates groups. The first polymerizable component and second polymerizable component are preferably difunctional (meth)acrylates or polyfunctional (meth)acrylates. Such polymerizable acrylates components enable to get a composition, an ink with a good stability over time (stable physical and chemical properties) and a low viscosity.

[0064] Moreover, these specific di or poly(meth)acrylates enable to form a cross-linked polymer exhibiting good mechanical properties. Advantageously the first polymerizable component has a linear backbone to get a flexible UV-curable composition with low viscosity.

[0065] The first polymerizable component is typically of formula (I), (II), or (III): Wherein

[0066] Ri, R2, R3, R4, Rs, Re, R7, Rs, R9, R10, R11 and R12, identical or different, are independently a hydrogen or a linear or branched saturated alkyl having 1 to 4 carbon atoms, preferably independently a hydrogen or -CH3; A is an alkylene, an alkoxylene, an alkyleneoxy, a poly(alkylene), a poly(alkoxylene) or a poly(alkyleneoxy), wherein the alkylene, the alkoxylene and the alkylenoxy are linear or branched, saturated and having 1 to 20 carbon atoms, preferably 2 to 15 atoms and wherein the alkylene, the alkoxylene, the alkyleneoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkyleneoxy) is optionally substituted for example by at least one hydroxyl (-OH) or a linear or branched saturated alkyl.

[0067] Examples of the first polymerizable component include, but are not limited to, di(ethylene glycol) diacrylate, 2-hydroxy 3-methacryl propyl acrylate, propoxylated(3)trimethylolpropane triacrylate, 3-methyl-1,5-pentanediol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triethylene glycol dimethacrylate, hexandiol diacrylate, poly(ethylene glycol) diacrylate, pentaerythritol tetraacrylate, a mixture of pentaerythritol tetraacrylate, pentaerythritol triacrylate and trimethylolpropane triacrylate, neopentyl glycol diacrylate, trimethylolpropane ethoxylate triacrylate, dipropylene glycol diacrylate, 1 ,10-decamethylene glycol diacrylate, 1,4- butanediol dimethacrylate, glycerol 1,3-di methacrylate and 1-(Acryloyloxy)-3-

[0068] (methacryloyloxy)-2-propanol.

[0069] In a preferred embodiment, the first polymerizable component is of formula (I) with Ri, R2, R3, R4, Rs and Re, independently a hydrogen or -CHs.

[0070] The first polymerizable component may be advantageously selected from the group consisting of dipropylene glycol diacrylate, 1 ,10-Decamethylene glycol diacrylate, 1,4- Butanediol dimethacrylate, glycerol 1,3-di methacrylate and 1-(Acryloyloxy)-3- (methacryloyloxy)-2-propanol, more preferably is dipropylene glycol diacrylate or 1 ,10- Decamethylene glycol diacrylate, still more preferably is dipropylene glycol diacrylate.

[0071] The second polymerizable component may be regarded as the rigid monomer of the polymerizable composition, the monomer enabling to get a resulting polymer with a relatively high glass transition temperature (Tg) and a good storage modulus.

[0072] The second polymerizable component is typically of formula (IV): Wherein

[0073] R13, R14, R15, Ri6, R17 and Ris identical or different, are independently hydrogen (-H) or a linear or branched saturated alkyl having 1 to 4 carbon atoms, preferably independently is hydrogen or methyl (-CH3);

[0074] A1 and A2, identical or different, are independently an alkylene, an alkoxylene, analkylenoxy, a poly(alkylene), a poly(alkoxylene) or a poly(alkyleneoxy), wherein the alkylene, the alkoxylene and the alkylenoxy are linear or branched, saturated and having 1 to 10 carbon atoms and wherein the alkylene, the alkoxylene, the alkylenoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkylenoxy) is optionally substituted, for example by at least one hydroxyl (-OH), and / or one acryloxy and / or one methacryloxy group;

[0075] B is a non-aromatic carbocycle or non-aromatic heterocycle wherein the cycle comprising 3 to 20 atoms, preferably 3 to 12 atoms, more preferably 3 to 8 atoms and still more preferably 3 to 6 atoms and is optionally substituted by at least one linear or branched saturated alkyl having 1 to 10 carbon atoms and / or at least one acryloxy and / or one methacryloxy group.

[0076] In particular, the second polymerizable component is preferably tricyclo[5.2.1.02’6]decanedimethanol diacrylate or 2-[5-[(Acryloyloxy)methyl]-5-ethyl-1 ,3- dioxan-2-yl]-2-methylpropyl Acrylate, more preferably tricyclo[5.2.1.02’6]decanedimethanol diacrylate.

[0077] The proportion of the first polymerizable component (monomeric or oligomeric component) and second polymerizable component (monomeric or oligomeric component) may be adjusted to tune the strength and / or flexibility of the resulting crosslinked polymer. By increasing the amount of the first polymerizable component, a more flexible polymer may be obtained, while increasing the amount of the second polymerizable component, a tougher polymer may be obtained.

[0078] Advantageously the polymerizable composition contains at least a mixture of:

[0079] - 40 to 60 weight % of the first polymerizable component

[0080] - 40 to 60 weight % of the second polymerizable component, with the weight percentage wt% based on the total weight of the polymerizable composition.

[0081] In one preferred variant of the present invention, the polymerizable composition comprises, preferably is constituted of, between 45 to 55 wt% of the first polymerizable component and between 45 to 55 wt% of the second polymerizable component, the weight percentage wt% being based on the total weight of the polymerizable composition. According to such variant of the present invention, the polymerizable composition can comprise, preferably is constituted of, between 45 to 55 wt% of dipropylene glycol diacrylate or 1 ,10- Decamethylene glycol diacrylate and between 45 to 55 wt% of tricyclo[5.2.1.02’6]decanedimethanol diacrylate, the weight percentage wt% being based on the total weight of the polymerizable composition.

[0082] In another preferred variant of the present invention, the polymerizable composition comprises, preferably is constituted of, between 50 to 60 wt% of the first polymerizable component and between 40 to 50 wt% of the second polymerizable component, the weight percentage wt% being based on the total weight of the polymerizable composition. According to such variant of the present invention, the polymerizable composition can comprise, preferably is constituted of, between 50 to 60 wt% of dipropylene glycol diacrylate or 1 ,10-Decamethylene glycol diacrylate and between 40 to 50 wt% of 2-[5- [(Acryloyloxy)methyl]-5-ethyl-1 ,3-dioxan-2-yl]-2-methylpropyl Acrylate, the weight percentage wt% being based on the total weight of the polymerizable composition.

[0083] The polymerizable composition of the present invention may also comprise a third polymerizable component, preferably 0.1 to 20 weight%, more preferably 1 to 10 wt%, the weight percentage wt% being based on the total weight of the polymerizable composition. Examples of the third polymerizable component include, but are not limited to, a (meth)acrylic acid ester monomer or oligomer, an urethane-acrylate monomer or oligomer, a thio-acrylate monomer or oligomer, an urethane monomer or oligomer, an epoxy acrylate monomer or oligomer or polyester acrylate oligomer.

[0084] <PoJY.nierizable. initiatory

[0085] The UV-curable composition of the present invention preferably includes at least one polymerization initiator, more precisely at least one photopolymerization initiator.

[0086] The term “photopolymerization initiator” and “photoinitiator” can be used interchangeably. Said photo initiator is preferably a free-radical photoinitiator. Specific examples of free- radical initiator suitable for the present invention include, but are not limited to, bis(2,4,6- trimethyl benzoyl)phenylphosphine oxide (IRGACURE® 819), 2,4,6-trimethylbenzoyl diphenyl phosphine (TPO), 2-hydroxy-2-methy 1-1-pheny 1-1-propane (DAROCUR® 1173) or benzophenone (BP). Among them, bis(2,4,6-trimethyl benzoyl)phenylphosphine oxide (IRGACURE® 819) is particularly preferred because it enables to limit the Yellowness index (Yl) of the cured composition. Since the (meth)acrylate composition of the present invention is cured under air, the concentration of the free-radical photoinitiator is preferably equal or greater than 0.1 % by weight of the total weight of the UV-curable composition and equal or less than 10% by weight of the total weight of the UV-curable composition, preferentially equal or greater than 1% by weight of the total weight of the UV-curable composition and equal or less than 10% by weight of the total weight of the UV-curable composition, more preferentially equal or greater than 2% by weight of the total weight of the UV-curable composition and equal or less than 5% by weight of the total weight of the UV-curable composition.

[0087] The concentration of the free-radical photoinitiator is for example between 1% and 10%, more preferably between 2% and 5% by weight of the total weight of the UV-curable composition.

[0088] In addition to the photoinitiator, a polymerization accelerator (sensitizer) such as a thermal polymerization initiator can be used in combination.

[0089] It is known by those skilled in the art that in order to consistently eject ink from an inkjet print head, the physical properties of the inkjet ink are constrained by certain physical parameters namely the liquid density, liquid viscosity, liquid surface tension and a characteristic dimension of the print head device namely the diameter of the print head nozzle orifice. Su.rfactant>

[0090] The UV-curable composition of the present invention preferably includes at least one surfactant, preferably a fluoro-free and / or a non-ionic surfactant.

[0091] The surfactant is preferably a silicone based or polyacrylate based surfactant. Commercially available examples of silicone based surfactants suitable for the present invention include, but are not limited to, Borchi® gol LA2, BYK® 349, CoatOTSil™ 77 and BYK® 3455. Commercially available examples of acrylate based surfactants suitable for the present invention include, but are not limited to the polyacrylate based levelling agent sold by Evonik under the name TEGO®Flow and BYK® 381. Among them, Borchi® gol LA2 is particularly preferable.

[0092] The concentration of the surfactant is preferably equal or greater than 0.1% by weight of the total weight of the UV-curable composition and equal or less than 3% by weight of the total weight of the UV-curable composition, more preferably equal or greater than 0.1 % by weight of the total weight of the UV-curable composition and equal or less than 1%, by weight of the total weight of the UV-curable composition, and still more preferentially is equal to 0.3% by weight of the total weight of the UV-curable composition.

[0093] Thanks to the surfactant, the static surface tension of the UV-curable composition decreases. Preferably, the UV-curable composition may have a low static surface tension, in other words, a static surface tension of between 20 to 50 mN / m, more preferably of between 25 to 50 mN / m, still more preferably of 25 mN / m. As a result, orange-peel effect can be avoided. This orange-peel effect is observed when the deposit of a composition has a granular aspect. .Q.ther.compp.ne nts >

[0094] The UV-curable composition may comprise other known additives, other components which are conventionally employed in polymerizable compositions intended for manufacturing optical articles, in particular ophthalmic lenses, in conventional proportions such as solvents, dyes, non-reactive light absorbers, leveling agents, adhesion additives, wetting agents, rheology additives, oxygen scavenger, defoamers and air release additives. These additives and their amounts are selected according to the desired application. For example, these additives can be added to compensate the Yellowness index, to colour the optical article or to control the viscosity of the UV-curable composition.

[0095] The UV-curable composition is preferably solvent-free, preferably free of organic solvent. “Free of” a solvent means that no solvent is substantially contained. The content thereof is preferably less than 0.1 wt% of the total weight of the UV-curable composition.

[0096] The viscosity of the UV-curable composition of the present invention (Brookfield viscosity) has no particular limit because it can be adjusted depending on the purpose and application devices. However since an ejecting device that ejects the UV-curable composition is employed, the UV-curable composition may preferably have a viscosity at 25°C in range of 1 to 150 centipoises (cP), more preferably 1 to 100 cP, still more preferably 1 to 70 cP and / or preferably a viscosity at 45°C in range of 2 to 30 cP, more preferably 5 to 30 cP, still more preferably 5 to 20 cP, more preferably 8 to 12 cP. The viscosity is typically measured with Brookfield Viscometer, SC4-18 modulus.

[0097] The UV-curable composition of the present invention has typically a dimensionless inverse Ohnesorge number, also known as the Z number, of between 1 to 10.

[0098] < < The optical, materi al . obtai ned by . cu ri ng. said com p.os i ti n > >

[0099] The present invention also relates to the material obtained by curing the UV-curable composition, said material exhibiting good optical and good mechanical performances. The curing of the UV-curable composition comprises the UV irradiation of UV-curable composition. This UV irradiation enables the polymerization of the at least two polymerizable components detailed above. The curing of the UV-curable composition may advantageously be followed by a thermal treatment. The optical material according to the present invention preferably has a glass transition temperature (Tg) higher than or equal to 80°C, preferably higher than or equal to 85°C, more preferably higher than 90°C, even more preferably higher than 100°C. The Tg measure is typically carried out by dynamic mechanical analysis (DMA) on a planar 5.2 cm*1 cm*2 mm (thickness) sample.

[0100] The optical material according to the present invention preferably has a coefficient of linear thermal expansion (GET) equal to or less than about 120 pm / (m.°C), more preferably equal to or less than about 80 pm / (m.°C), still more preferably of about 80 pm / (m.°C). The GET is typically measured by ThermoMechanical Analyser (TMA) in accordance with ASTM E831.

[0101] In the present disclosure, the term “about” is defined as the measurement incertitude.

[0102] The optical material according to the present invention preferably has a storage modulus of higher than 1 .5 GPa at 23°C, more preferably equal or higher than 2 GPa, at 23°C and still preferably of higher than 0.5 GPa at 100°C, still more preferably equal or greater than 1 GPa at 100°C. The storage modulus measure is typically carried out by dynamic mechanical analysis (DMA) on a planar 5.2 cm*1 cm*2 mm (thickness) sample.

[0103] The optical material preferably has a refractive index at 550 nm of about 1 .5 and preferably an Abbe number (Ve) of higher or equal to 38 when it is measured using the green line (e) of a mercury lamp at A=546.1 nm. Unless otherwise specified, the refractive indexes referred to in the present application are expressed at 25°C at a wavelength of 550 nm.

[0104] The optical material according to the present invention preferably has a relative light transmission factor in the visible spectrum (Tv) of higher or equal 80 % when the optical material has 3 mm of thickness or when the optical material has 2 mm of thickness preferably equal or greater than 80%, more preferably equal or greater than 85% when the UV-curable composition is dye-free, and still more preferably equal or greater than 89% when the UV-curable composition is dye-free. The Tv factor, also called “luminous transmission" of the system, is such as defined in ISO standard 13666:1998 and is measured according to the standard ISO 8980-3. It is defined as the average transmission in the 380-780 nm wavelength range that is weighted according to the sensitivity of the eye at each wavelength of the range and measured under D65 illumination conditions (daylight). Transmissions are expressed for 2 mm thick optical articles, measured at the center of the optical article and at a normal incidence of the light beam (0° from the normal). The optical material according to the present invention preferably has a Yellowness index (Yi) of lower than 4, more preferably equal or lower than 1.5. The yellowness index is measured according to ASTM E313.

[0105] The UV-curable composition of the present invention is therefore particularly suitable for the manufacture of optical article, especially ophthalmic article, by 3D printing, by inkjet printing. .Q.P.tica Ophthal mic fields>>

[0106] The optical material of the invention can be used for the manufacturing of an optical element. The optical element can be the bulk material, the substrate of an optical article, preferably an optical lens or lens blank, more preferably an ophthalmic lens or lens blank, such as a plastic eyeglass lens. The optical element can also be used as a coating or as a complementary optical member which is adjoined by additive manufacturing to a starting optical member, for example to a substrate. Said optical element can be manufactured by using, for example, the technology disclosed in international applications W02015004383A1 and W02020115061 A1.

[0107] A substrate, in the sense of the present invention, should be understood to mean an uncoated substrate, and generally has two main faces. The substrate may in particular be made of the present optical material having the shape of an optical article, for example an ophthalmic lens destined to be mounted in glasses. In this context, the term “substrate” is understood to mean the base constituent material of the optical article and more particularly of the optical lens. This material may act as support for a stack of one or more coatings or layers.

[0108] When the UV-curable composition is used in the so-called build over technology, the UV- curable composition preferably comprises an adhesion additive. Such adhesion additive enables to promote adhesion on the substrate, and to promote adhesion of the subsequent coating deposited on the top surface of the cured UV-curable composition. This adhesion additive is preferably an acrylate based, silane based or polyether-based adhesion additive. It is, for example selected from the group consisting of 2-Hydroxyethyl methacrylate, 2-Phenoxyethyl acrylate, 2-(2-Ethoxyethoxy)ethyl acrylate and Trimethoxy[3-(methylamino)propyl]silane. Preferably, the adhesion additive is acrylate based to get good compatibility and good reactivity with the UV-curable composition.

[0109] In such embodiment (using the build over technology), the optical substrate can be made of polycarbonate, polyamide, polyimide, polysulfone, copolymer of polyethylene terephthalate and polycarbonate, polyolefin such as polynorbornene, resin resulting from polymerization or (co)polymerization of alkylene glycol bis allyl carbonate such as polymers and copolymers of diethylene glycol bis(allylcarbonate) (marketed, for instance, under the trade name CR 39® by PPG), polycarbonate such as those derived from bisphenol-A, (meth)acrylic or thio(meth)acrylic polymer and copolymer such as poly methyl methacrylate (PMMA), urethane and thiourethane polymer and copolymer, epoxy polymer and copolymer, episulfide polymer and copolymer.

[0110] In particular, the optical substrate preferably is a diethylene glycol bis(allyl carbonate), such as CR39®, in particular with a refractive index of 1.5, sold by PPG Industries, allylic and (meth)acrylic copolymer, having a refractive index between 1.54 and 1.58, a polythiourethane, such as MR series provided by Mitsui Chemicals: MR6®, MR7®, MR8®, MR10®, MR1.74®, or even Polycarbonate.

[0111] Although ophthalmic optics is a preferred field of the invention, it will be understood that this invention can be applied to optical articles of other types, such as, for example, lenses for optical instruments, in photography or astronomy, optical sighting lenses, ocular visors, optics of lighting systems, screens, glazing, windshields, sport masks, face shields, goggles, optical coatings or adhesives, etc.

[0112] In the present disclosure, the term of “ophthalmic lens” is used to mean a lens adapted to a spectacle frame to protect the eye and / or correct the sight. Said lens can be chosen from afocal, unifocal, bifocal, trifocal, progressive, piano, solar and Fresnel lenses or any other kind of lenses having a discontinuous surface.

[0113] If the optical article is an optical lens or an ophthalmic lens, it may be coated on its front main surface, rear main side, or both sides with one or more functional coatings. As used herein, the rear face of the substrate is intended to mean the face which, when using the article, is the nearest from the wearer's eye. It is generally a concave face. On the contrary, the front face of the substrate is the face which, when using the article, is the most distant from the wearer's eye. It is generally a convex face. The optical article can also be a piano article.

[0114] The ophthalmic lens of the invention may comprise functional coatings classically used in optics such as an impact-resistant and / or adhesion primer, an abrasion-resistant and / or scratch-resistant coating, an anti-reflection coating, an antistatic coating, an anti-soiling coating, an anti-smudge coating, an anti-dust coating, an anti-fog coating, a water repellent coating, an interferential filter, a tinted coating, a mirror coating, and a combination of any of preceding compatible coatings, especially an impact-resistant primer coating coated with an abrasion and / or scratch-resistant coating. 55 Me th od for. the man uf actu rj ng of. an. optical, elements >

[0115] The present invention also relates to a method for the manufacturing of an optical element, said method comprising the UV polymerization of the UV-curable composition defined above.

[0116] The method for the manufacturing of the optical element of the present disclosure preferably comprises: a step A of depositing with a jetting system a predetermined volume of the UV- curable composition defined above on a substrate; a step B of inducing partial polymerization of the polymerizable components at least until the gel point of the UV-curable composition is reached; optionally repeating several times step A and step B; a final step C of completing polymerization of the polymerizable components to form said optical element.

[0117] According to the invention, and as it is well known by one skilled in the art, the “gel point” corresponds to an abrupt change in the viscosity of the liquid mixture of polymerizable compounds. At the gel point, the liquid mixture undergoes gelation as reflected in a loss in fluidity. This definition can also be found in the IUPAC Goldbook according to which the gel point is the point of incipient network formation in a process forming a chemical or physical polymer network (htps: / / qoldbook.iupac.Org / html / G / GT07535.html).

[0118] The predetermined volume is preferably a droplet or a layer.

[0119] The steps A and B are preferably repeated several times before performing final step C, to build a 3D material.

[0120] The final step C of completing polymerization is preferably carried out by applying UV and / or thermal treatment.

[0121] Another object of the present invention is the optical element obtained according to said method.

[0122] The optical element is a part of an optical article. It can be the substrate of an optical article or another layer of the stack constituting an optical article.

[0123] The optical element according to the present invention is preferably an ophthalmic element.

[0124] A further object of the present invention is the ophthalmic lens comprising the ophthalmic element. In one variant, the ophthalmic element is the substrate of an ophthalmic lens. EXAMPLES

[0125] Hereinafter, the present disclosure will be described by way of examples. However, the present disclosure should not be construed as being limited to these examples.

[0126] Compositions Materials listed in Table 1 below were used in the corresponding amounts presented in the table and were mixed together.

[0127] Table 1

[0128] Characterizations of the compositions

[0129] The viscosity at 45°C of each composition was measured with Brookfield Viscometer, SC4-18 modulus. The results are given in Table 2.

[0130] The dynamic surface tension of each composition was measured with KRUSS DSA100 (Drop Shape Analyzer) by pendant drop analysis according to Laplace method. The results are given in Table 2.

[0131] The Z number was measured using the following formula: with p the viscosity of the composition, p the density of the composition, o the dynamic surface tension of the composition, L the characteristic length scale of the drop and Z the reciprocal of the Oh. For these examples, L corresponds to the nozzle diameter of KM1024iSHE inkjet printhead (Konica Minolta) and is equal to 23pm. The results are shown in Table 2.

[0132] The static surface tension of the compositions was measured at about 25mN / m with KRUSS DSA100 (Drop Shape Analyzer) by pendant drop analysis according to Young- Laplace method.

[0133] This result shows that a low static surface tension is achieved due to the presence of the surfactant. This allows the composition to spread properly over a substrate. In other words, the deposit of the composition on a substrate has a smooth and not granular aspect. The orange-peel effect is therefore avoided.

[0134] Table 2

[0135] The results show that each composition achieves high dynamic surface tension with a Z number greater than 1 and less than 10. Therefore, these compositions can be stable during the jetting.

[0136] Moreover, each composition has a viscosity between 8 and 12 cP at 45°C and is therefore compatible with an inkjet printhead such as KM1024iSHE inkjet printhead (Konica Minolta).

[0137] Drop formation

[0138] The suitability to an inkjet printing method of the compositions was tested. The composition obtained in Example 1 is introduced in an inkjet printhead (Konica Minolta, KM1024iSHE). The drop formation speed was 5.07m / s and the drop volume was 8.37 pL. No satellites were observed and the drops were formed with good speed and good volume. This result shows that the composition of example 1 conducts to stable drops and is therefore suitable for inkjet printing.

[0139] Polymerization of the compositions

[0140] Each composition of Examples 1 to 4 was poured into a mold and polymerized under UV irradiation at 365 nm. The final polymerized object has a thickness of 3 mm.

[0141] Optical properties

[0142] Optical properties of the polymerized objects were characterized. The results are given in Table 3.

[0143] The refraction index of each object at 550 nm was determined using Metricon instrument. The Abbe number (Ve) of each object was determined using the Metricon instrument and the following formula (II) : ; with Nethe refraction index of the green line

[0144] (e) of a mercury lamp at A=546.1 nm, NF’ the refraction index of the cadmium at A=480.0 nm and Nc the refraction index of the cadium at A=643.8nm.

[0145] For each object, the relative light transmission factor in the visible spectrum (Tv), also called luminous transmittance, was characterized in compliance with the standard ISO 8980-3 using a spectrometer Cary 50 (Agilent). The Tv is defined in the standard ISO

[0146] 13666:1998 with the following formula

[0147] The Yellowness index (Yi) was determined according to ASTM E313 with a spectrometer Cary 50 (Agilent) and Essilor Transcalc calculation software. Indeed, the yellowness index was determined from the CIE tristimulus values X, Y, Z through the relation of formula (IV)

[0148] Table 3

[0149] Relative light transmission factor and Yellowness Index results for a 3mm thickness suggest that relative light transmission factor in the visible spectrum of over 89% and Yellowness Index of less than 4, and preferably less than 1.5, are achieved when the polymer is 2 mm thick.

[0150] These results show that the polymer obtained from the compositions of Example 1 to 4 shows suitable optical properties for an optical article.

[0151] Mechanical properties

[0152] Mechanical properties of the polymerized materials were characterized. The results are given in Table 4.

[0153] The Coefficients of thermal expansion (CET) were determined using 0400 Thermomechanical Analyzer (TA instruments) according to the ASTM E831 standard.

[0154] The Glass Transition Temperatures measure of each polymerized object was carried out by dynamic mechanical analysis with Dynamic Mechanical Analyzer (TA instruments), on a planar 60mmx10mmx2mm sample.

[0155] The Storage Modulus (G’) of each polymerized material was determined using with Dynamic Mechanical Analyzer (TA instruments) on a planar 60mmx10mmx2mm sample.

[0156] Table 4

[0157] The results show that these polymers have a high Tg (Tg > 85°C) and a high storage modulus (at 25°C G’>1.5GPa) with a low CET value (CET < 120pm / (m.°C)). These polymers can be processed after polymerization, a necessary step in the production of optical objects by additive manufacturing. These polymers have mechanical properties that are compatible with those of an optical article such as a lens.

[0158] Based on these results, it can be concluded that the composition of Example 1 to 4 are CMR-free compositions with good physical properties compatible with inkjet printing and resulting in a polymer with mechanical and / or optical properties suitable for optical articles.

[0159] Comparative compositions

[0160] Materials listed in Table 5 below were used in the corresponding amounts presented in the table and were mixed together.

[0161] Table 5

[0162] Characterizations of the comparative compositions

[0163] The viscosity at 45°C, the dynamic surface tension and the Z number of each comparative composition Comp 1 to Comp 3 were determined as for the compositions of examples 1 to 4 according to the invention. The results are given in Table 6 below.

[0164] Table 6

[0165] These results, represented in Table 6, show that Comp 2 and Comp 3 have a viscosity higher than 12 cP and higher than 20 cP at 45°C. Comp 2 and Comp 3 are therefore incompatible with an inkjet printhead and especially incompatible with an inkjet printhead such as KM1024iSHE inkjet printhead (Konica Minolta).

[0166] These results also show that Comp 1 has a viscosity at 45°C less than 8 cP which means that Comp 1 is probably incompatible with the KM1024iSHE inkjet printhead (Konica Minolta).

[0167] Polymerization of the comparative compositions

[0168] Each comparative composition Comp 1 to Comp 5 was polymerized as for the compositions of examples 1 to 4 according to the invention. In particular, each composition Comp 1 to 5 was poured into a mold and polymerized under UV irradiation at 365 nm. The final polymerized object has a thickness of 3 mm.

[0169] Mechanical properties

[0170] Then, the Glass Transition Temperatures (Tg) and the Storage Modulus (G’) of each polymerized material obtained by the polymerization of compositions Comp 1 to 5 were determined as for the polymerized material obtained by the polymerization of compositions of example 1 to 4 according to the invention. The results are given in Table 7 below.

[0171] Table 7

[0172] These results, given in Table 7, show that the polymers obtained by the polymerization of the comparative compositions Comp 1 , Comp 4 and Comp 5 do not have the mechanical properties that are compatible with those of an optical article such as a lens, notably the storage modulus at 25°C of each polymer is far too low.

[0173] These results given in Table 6 and 7 show that:

[0174] 1) the curable composition has to comprise a mixture of a first polymerizable component of formula (I), (II) or (III) and a second polymerizable component of formula (IV); and

[0175] 2) the weight amount of the first and second polymerizable component has to be in range of 40 to 60 weight %; in order to obtain a curable composition that can be used in an inkjet printing method and to obtain a polymer having mechanical properties suitable for optical products.

Claims

CLAIMS1. A UV-curable, inkjet transparent composition suitable for optical use comprising at least one free-radical photoinitiator, at least one surfactant and a polymerizable composition containing at least a mixture of:- 40 to 60 weight % of a first polymerizable component- 40 to 60 weight % of a second polymerizable component with the weight percentage wt% based on the total weight of the polymerizable composition and, wherein,• The first polymerizable component is of formula (I), (II), or (III):WhereinRi, R2, R3, R4, Rs, Re, R7, Rs, R9, R10, R11 and R12, identical or different, are independently a hydrogen or a linear or branched saturated alkyl having 1 to 4 carbon atoms, preferably independently a hydrogen or -CH3;A is an alkylene, an alkoxylene, an alkyleneoxy, a poly(alkylene), a poly(alkoxylene) or a poly(alkyleneoxy), wherein the alkylene, the alkoxylene, the alkyleneoxy are linear or branched, saturated and having 1 to 20 carbon atoms, preferably 2 to 15 atoms and wherein the alkylene, the alkoxylene, the alkyleneoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkyleneoxy) is optionally substituted for example by at least one hydroxyl or a linear or branched saturated alkyl;• The second polymerizable component is of formula (IV):WhereinR13, R14, R15, R16, R17 and Ris identical or different, are independently hydrogen or a linear or branched saturated alkyl having 1 to 4 carbon atoms, preferably independently a hydrogen or -CH3;A1 and A2, identical or different, are independently an alkylene, an alkoxylene, an alkyleneoxy, a poly(alkylene) or a poly(alkoxylene) or a poly(alkyleneoxy), wherein thealkylene and the alkoxylene and the alkylenoxy are linear or branched, saturated and having 1 to 10 carbon atoms and wherein the alkylene, the alkoxylene, the alkylenoxy, the poly(alkylene), the poly(alkoxylene) or the poly(alkylenoxy) is optionally substituted, for example by at least one hydroxyl, and / or one acryloxy and / or one methacryloxy group;B is a non-aromatic carbocycle or non-aromatic heterocycle wherein the cycle comprising 3 to 20 atoms and is optionally substituted by at least one linear or branched saturated alkyl having 1 to 10 carbon atoms and / or at least one acryloxy and / or one methacryloxy group.

2. The UV-curable composition according to claim 1 , wherein the first polymerizable component is di(ethylene glycol) diacrylate, 2-hydroxy 3-methacryl propyl acrylate, propoxylated(3)trimethylolpropane triacrylate, 3-methyl-1 ,5-pentanediol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triethylene glycol dimethacrylate, hexandiol diacrylate, poly(ethylene glycol) diacrylate, pentaerythritol tetraacrylate, a mixture of pentaerythritol tetraacrylate, pentaerythritol triacrylate and trimethylolpropane triacrylate, neopentyl glycol diacrylate, trimethylolpropane ethoxylate triacrylate, dipropylene glycol diacrylate, 1 ,10-decamethylene glycol diacrylate, 1 ,4- butanediol dimethacrylate, glycerol 1 ,3-dimethacrylate or 1-(Acryloyloxy)-3- (methacryloyloxy)-2-propanol.

3. The UV-curable composition according to any one of the preceding claims, wherein the first polymerizable component is of formula (I) with Ri, R2, R3, R4, Rs and Re, independently a hydrogen or -CH3.

4. The UV-curable composition according to any one of the preceding claims, wherein the first polymerizable component is dipropylene glycol diacrylate, 1 , 10-Decamethylene glycol diacrylate, 1 ,4-Butanediol dimethacrylate, glycerol 1 ,3-dimethacrylate or l-(Acryloyloxy)- 3-(methacryloyloxy)-2-propanol, preferably dipropylene glycol diacrylate or 1 ,10- Decamethylene glycol diacrylate.

5. The UV-curable composition according to any one of the preceding claims, wherein the second polymerizable component is tricyclo[5.2.1.02’6]decanedimethanol diacrylate or 2- [5-[(Acryloyloxy)methyl]-5-ethyl-1 ,3-dioxan-2-yl]-2-methylpropyl Acrylate.

6. The UV-curable composition according to any one of the preceding claims, wherein the polymerizable composition further comprises a third polymerizable component, preferably 0.1 to 20 weight%, more preferably 1 to 10 wt% based on the total weight of the polymerizable composition.

7. The UV-curable composition to the preceding claim, wherein the third polymerizable component is a (meth)acrylic acid ester monomer or oligomer, an urethane-acrylate monomer or oligomer, a thio-acrylate monomer or oligomer, an urethane monomer or oligomer, an epoxy acrylate monomer or oligomer or polyester acrylate oligomer.

8. The UV-curable composition according to any one of the preceding claims, wherein the surfactant is a silicone based or polyacrylate based surfactant.

9. The UV-curable composition according to any one of the preceding claims, wherein the composition further comprises at least one adhesion additive, preferably an acrylate based, silane based or polyether based adhesion additive, for example selected from the group consisting of 2-Hydroxyethyl methacrylate, 2-Phenoxyethyl acrylate, 2-(2- Ethoxyethoxy)ethyl acrylate and Trimethoxy[3-(methylamino)propyl]silane.

10. A method for the manufacturing of an optical element, said method comprising the UV polymerization of the UV-curable composition according to any one of the preceding claims.

11. The method according to claim 10, comprising a printing method, said method comprising:- a step A of depositing with a jetting system a predetermined volume of the UV-curable composition according to any one of the preceding claims on a substrate;- a step B of inducing partial polymerization of the polymerizable components at least until the gel point of the UV-curable composition is reached;- optionally repeating several times step A and step B;- a final step C of completing polymerization of the polymerizable components to form said optical element.

12. An optical element obtained according to the method defined in anyone of the preceding claims.

13. The optical element obtained according to claim 12, further defined as a part of an optical article and further defined as an ophthalmic element.

14. An ophthalmic lens comprising the ophthalmic element as claimed in claim 13.

15. The ophthalmic element as defined in claim 13 or 14, further defined as the substrate of an ophthalmic lens.

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