Method for curing polythionocarbamate-based substrate coupled to microstructured wafer

Abstract

The invention relates to a method for curing a cast substrate based on polythionocarbamate, comprising providing a first component A comprising a polythionocarbamate prepolymer A1 having isocyanate or isothiocyanate end groups of formula-NCX, where X is O or S, providing a second component B comprising a polythiourethane prepolymer B1 having thiol end groups or comprising at least one polythiol monomer B2, providing a microstructured sheet made of a thermoplastic material having an inner surface and an outer surface, the inner surface of the sheet bearing a microstructure, mixing together the first component A and the second component B and filling a mold cavity with the resulting mixture wherein the mold cavity is defined by the inner surface of the microstructured sheet and at least a portion of the mold part, curing the mixture and obtaining a polythionocarbamate-based substrate adhered to the microstructured sheet.

Description

[0001] The present invention relates to a method for manufacturing a polyurethane-based substrate, in particular an optical substrate such as an ophthalmic lens, which is joined to a thin sheet with microstructures, and these substrates typically have a medium or high refractive index of preferably at least 1.52, more preferably at least 1.54, more preferably at least 1.6, and even more preferably at least 1.67 within a short curing cycle.

[0002] Background Art and Summary of the Invention

[0003] Ophthalmic lenses made of polyurethane-based substrates are typically prepared by a method that includes mixing appropriate monomers (such as a mixture of polyisocyanates and polythiols) in a tank, adding catalysts and additives, filling a mold cavity with this liquid mixture of monomers, polymerizing the monomer mixture, and thereafter recovering the polymerized polyurethane-based substrate from the mold. Typically, the mixture is subjected to a heat cycle in an oven for a typical duration of 20 hours.

[0004] Application WO 00 / 26272 discloses a polymerizable composition for preparing a poly(thio)urethane resin, which polymerizable composition contains at least one poly(isothio)cyanate monomer, at least one polythiol monomer, and a salt catalyst system (typically a mixture of KSCN and a crown ether).

[0005] US2007 / 098999 discloses a method for obtaining a polyurethane polarizing article, which method includes positioning a polarizing polyvinyl alcohol film in the mold cavity of a two-piece mold assembly, pouring a polymerizable composition containing at least one poly(isothio)cyanate monomer and at least one polythiol; or a mixture of at least one liquid NCO- or NCS-terminated poly(thio)urethane prepolymer and at least one liquid SH-terminated poly(thio)urethane prepolymer into the mold cavity, curing the polymerizable composition, and removing the polyurethane polarizing article from the mold cavity.

[0006] Application EP 3640714 discloses a method for encapsulating microstructures (such as microlenses), which method includes forming a first optical member having an optical surface that defines a plurality of concave recesses or a plurality of convex protrusions, placing the first optical member in a two-piece mold assembly, introducing a moldable material into the mold cavity, and forming a second optical member such that the second optical member is joined to the first optical member and encapsulates the microstructures. Similar methods are described in EP 3640713 and EP 3910411. However, due to incompatibility problems, these methods cannot be used to make a thin sheet into a component of a polyurethane lens starting from monomers.

[0007] In fact, it has been found challenging to cast polyurethane lenses with functional sheets having microstructures. When using standard polyurethane monomers (such as polyisocyanates mixed with polythiols), the monomers diffuse from the surface of the sheet inside the sheet and may cause the sheet (which is typically a polycarbonate sheet) to swell, resulting in an opaque final lens and / or a change in the microstructure geometry.

[0008] Therefore, a technical solution is needed that brings about compatibility between the sheet and the mixture of polymerizable compounds forming the polyurethane matrix and follows the geometry of the microstructure.

[0009] US2003 / 125410 discloses a method for curing a transparent cast polyurethane substrate, the method comprising the steps of:

[0010] 1) providing a first component A comprising a polyurethane prepolymer having isocyanate or isothiocyanate end groups,

[0011] 2) providing a second component B comprising a polyurethane prepolymer having thiol end groups,

[0012] 3) mixing the first component A and the second component B together and filling the cavity of a mold assembly with the resulting mixture,

[0013] 4) curing the mixture to obtain a transparent solid substrate.

[0014] In applications EP 3916470 and EP 3919967, different methods were chosen to cure polyurethane optical materials, using monomers and prepolymers in combination in the presence of a polymerization catalyst, typically a basic catalyst. However, these methods have not been applied to the preparation of microstructured articles.

[0015] The object of the present invention is to provide a method for obtaining a cast substrate based on thermosetting polyurethane joined to a microstructured sheet, which method remedies the drawbacks observed at the interface between the sheet and the polymeric substrate in the prior art methods. The method for casting a thermosetting lens having a microstructure should preserve the design integrity of the microstructure.

[0016] Another object of the present invention is to provide a method for curing a cast substrate based on polyurethane, which substrates are substantially free of optical defects generated by the polymerization process, have high transmittance and clarity, and a low yellowness index.

[0017] The inventors have found that using a polyurethane prepolymer having isocyanate or isothiocyanate end groups instead of isocyanate or isothiocyanate monomers allows for improved compatibility and prevents swelling of the sheet that causes haze at the polymer interface, as well as a change in the microstructure geometry.

[0018] The present invention provides a method for curing a thiourethane-based casting substrate that can be used to manufacture optical articles such as ophthalmic lenses, the method comprising the following steps: 1), 2), 3), 4), 5) and 6) or 1'), 2'), 3), 4), 5) and 6):

[0019] 1) Providing a first component A comprising a thiourethane prepolymer A1 having isocyanate or isothiocyanate end groups of the formula -NCX, where X is O or S, said prepolymer A1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer,

[0020] 2) Providing a second component B comprising a thiourethane prepolymer B1 having thiol end groups, said prepolymer B1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer,

[0021] Or:

[0022] 1') Providing a first component A comprising a thiourethane prepolymer A1 having isocyanate or isothiocyanate end groups of the formula -NCX, where X is O or S, said prepolymer A1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer,

[0023] 2') Providing a second component B comprising at least one polythiol monomer B2,

[0024] 3) Providing a microstructured sheet made of a thermoplastic material, said microstructured sheet having an inner surface and an outer surface, wherein the inner surface of the sheet bears a microstructure,

[0025] 4) Mixing the first component A and the second component B together and filling a mold cavity with the resulting mixture, wherein the mold cavity is defined by the inner surface of the microstructured sheet and at least a portion of a mold part,

[0026] 5) Curing the mixture to obtain a thiourethane-based substrate, and

[0027] 6) Recovering the thiourethane-based substrate adhered to the microstructured sheet.

[0028] In addition to those mentioned above, the method of the present invention also offers several advantages.

[0029] In the method of the present invention, some monomers are first pre-reacted to form oligomers, which are then poured into a mold assembly that undergoes a short polymerization cycle (typically a few hours). By at least partially replacing the monomers with prepolymers (or oligomers), the time required to cure the polymerizable composition poured into the mold assembly is significantly shortened.

[0030] A rapid curing method is highly desirable as shorter residence times in the curing oven enable a significant increase in productivity, complex and demanding lens geometries can be obtained in higher yields due to the lower shrinkage rate of the final polymerizable mixture compared to mixtures obtained directly from monomers, there is better compatibility with the tape adhesives used for the mold components, and there is a reduction in energy consumption during the polymerization cycle.

[0031] If the viscosity is controlled, the batch mixing of such mixtures is inherently safer than the conventional methods of using monomer mixing, as a portion of the available bonding energy has been released during the formation of the oligomer (pre-polymerization), which limits the formation of local hot spots in the final polymerizable mixture. The use of pre-polymers allows for a stable and steady reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] When considered in conjunction with the accompanying drawings, the foregoing and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description, wherein Figure 1 and Figure 2 schematically represent different stages of the method of the present invention, namely steps 4) and 6, Figure 3 provide the haze values of three different optical articles prepared in the experimental section, and Figure 4 provide the transmittance (Tv) values of three different optical articles prepared in the experimental section. DETAILED DESCRIPTION

[0033] The substrate of the present invention is a plexiglass substrate made of a thermosetting resin. In some embodiments, the polymer matrix of the substrate is obtained from a material composition ("substrate composition") comprising at least one polymerizable prepolymer and at least two polymerizable prepolymers.

[0034] The substrate is preferably a substrate for an optical article, more preferably a substrate for an optical lens. The optical article is preferably an ophthalmic lens, such as a plastic spectacle lens.

[0035] In this specification, unless otherwise specified, when no significant contrast loss is perceived when observing an image through the substrate, i.e., when an image formed through the substrate is obtained without adversely affecting the quality of the image, the substrate is understood to be transparent. Unless otherwise specified, this definition of the term "transparent" can be applied to all objects so defined in this specification.

[0036] The term "ophthalmic lens" is used to mean a lens adapted to a spectacle frame to protect the eyes and / or correct vision. The lens may be selected from afocal, single-focus, bifocal, trifocal, progressive lenses and Fresnel lenses or any other type of lens having a discontinuous surface. Although ophthalmic optics is the preferred field of the present invention, it should be understood that the present invention may be applied to other types of optical elements, such as lenses for optical instruments, filters (especially filters for photography or astronomy), optical aiming lenses, eye protectors, optical devices of lighting systems, screens, glazed windows, etc.

[0037] If the optical article is an optical lens, it may be coated on its front principal surface, rear principal side or both sides with one or more functional coatings. As used herein, the rear of the substrate is intended to mean the face closest to the wearer's eyes when the article is in use. The rear is usually concave. In contrast, the front of the substrate is the face farthest from the wearer's eyes when the article is in use. The front is usually convex. The optical article may also be a plano article.

[0038] In the sense of the present invention, the substrate should be understood to mean an uncoated substrate and generally has two principal faces. The substrate may in particular be an optically transparent material having the shape of an optical article (such as an ophthalmic lens destined to be mounted in spectacles). In this context, the term "substrate" should be understood to mean the basic constituent material of an optical lens and more particularly an ophthalmic lens. Such a material may serve as a support for a stack of one or more coatings or layers.

[0039] The refractive index of the polyurethane-based substrate is preferably 1.52 or greater, more preferably 1.54 or greater, more preferably 1.56 or greater, more preferably 1.58 or greater, more preferably 1.60 or greater, and still more preferably 1.65 or greater, and it is preferably 1.80 or less, more preferably 1.70 or less, and still more preferably 1.67 or less. Unless otherwise specified, the refractive index mentioned in this application is expressed at 25 °C and a wavelength of 550 nm.

[0040] The rapidly curable polymerizable composition for producing a polyurethane-based material consists of two main components.

[0041] In a first embodiment which is a preferred embodiment of the present invention, the first component A consists of a polyurethane prepolymer A1 having isocyanate (NCO) or isothiocyanate (NCS) end groups; the second component B consists of a polyurethane prepolymer B1 having thiol (SH) end groups.

[0042] In step 1) of the first embodiment of the method of the present invention (and step 1' of the second embodiment of the method of the present invention), a first component A is provided which comprises a polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups, and this first component has been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, with the latter being used in excess. The first component A thus comprises oligomers and unpolymerized starting monomers.

[0043] In step 2) of the first embodiment of the method of the present invention, a second component B is provided which comprises a polythiourethane prepolymer B1 having thiol end groups, and this second component has been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, with the former being used in excess. The second component B thus comprises oligomers and unpolymerized starting monomers.

[0044] In the second embodiment of the present invention, the first component A consists of a polythiourethane prepolymer A1 having isocyanate (NCO) or isothiocyanate (NCS) end groups; the second component B consists of at least one polythiol monomer B2.

[0045] Compared with the prior art methods that use only is(thio)cyanate or thiol monomers, the present invention uses at least one prepolymer, in particular at least one polythiourethane prepolymer having isocyanate or isothiocyanate end groups.

[0046] A prepolymer means a polymer or oligomer containing prepolymer molecules. A prepolymer molecule means a macromolecule or oligomer molecule capable of undergoing further polymerization through reactive (polymerizable) groups and thus contributing more than one monomer unit to at least one chain of the final macromolecule. Prepolymer molecules are usually formed from two or more different monomers.

[0047] The polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups is prepared by reacting at least one polyisocyanate or polyisothiocyanate monomer with at least one polythiol monomer preferably in the absence of a catalyst in a ratio such that the molar ratio of isocyanate or isothiocyanate groups to thiol groups NCX / SH is preferably in the range of 3:1 to 30:1, where X is O or S.

[0048] The polythiourethane prepolymer B1 having thiol end groups is prepared by reacting at least one polyisocyanate or polyisothiocyanate monomer with at least one polythiol monomer preferably in the absence of a catalyst in a ratio such that the molar ratio of thiol groups to isocyanate or isothiocyanate groups SH / NCX is preferably in the range of 3:1 to 30:1, where X is O or S.

[0049] Polythiols and polyisocyanates or polyisothiocyanates used for preparing polythiourethane prepolymers A1 or B1 are considered monomers herein, even when they are oligomers.

[0050] Polyisocyanate means any compound containing at least two isocyanate groups, in other words, diisocyanates, triisocyanates, etc. Polyisocyanate prepolymers can be used. The polyisocyanate can be any suitable polyisocyanate having two or more, preferably two or three isocyanate functional groups.

[0051] The polyisocyanate can be selected from aliphatic, aromatic, alicyclic or heterocyclic polyisocyanates and mixtures thereof.

[0052] By replacing the "isocyanate" group with an "isothiocyanate" group, polyisothiocyanates are defined in the same manner as the above polyisocyanates.

[0053] Preferred polyisocyanate or isothiocyanate monomers are those having the following formula:

[0054]

[0055] wherein R 1 is independently H or a C1-C5 alkyl group, preferably CH3 or C2H5;

[0056] R 2 is H, a halogen, preferably Cl or Br, or a C1-C5 alkyl group, preferably CH3 or C2H5;

[0057] Z is -N=C=X, where X is O or S, preferably O;

[0058] a is an integer ranging from 1 to 4, b is an integer ranging from 2 to 4, and a + b ≤ 6; and

[0059] x is an integer from 1 to 10, preferably from 1 to 6.

[0060] The polyisocyanate of the present invention is preferably a diisocyanate. Among the available diisocyanates, there may be mentioned toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, biphenyl-diisocyanate, 3,3'-dimethyl-4,4'-diphenylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, 2,2,4-trimethylhexane-1,6-diisocyanate, lysine methyl ester diisocyanate, bis(isocyanatoethyl) fumarate, isophorone diisocyanate (IPDI), ethylene diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4-diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrophenylene-1,3-diisocyanate, hexahydrophenylene-1,4-diisocyanate, perhydrodiphenylmethane-2,4'-diisocyanate, perhydrodiphenylmethane-4,4'-diisocyanate (or bis-(4-isocyanatocyclohexyl)-methane or 4,4'-dicyclohexylmethane diisocyanate), bis(isocyanatomethyl) cyclohexane, dicyclohexylmethane diisocyanate, 2,5(or 2,6)-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, and mixtures thereof.

[0061] Other non-limiting examples of polyisocyanates are isocyanurates from isophorone diisocyanate and 1,6-hexamethylene diisocyanate, both of which are commercially available. Further polyisocyanates suitable for the present invention are described in detail in WO 98 / 37115, WO 2014 / 133111 or EP 1877839.

[0062] The polythiols that can be used in the present invention are defined as compounds containing at least two sulfhydryl (mercapto) groups, in other words, dithiols, trithiols, tetrathiols, etc. Polythiol prepolymers can be used. The polythiol can be any suitable polythiol having two or more, preferably two or three thiol functional groups. The polythiol can be used to prepare the polythiourethane prepolymers A1 or B1, but can also be directly used in component B in step 2') of the method of the present invention.

[0063] Among the preferred polythiol monomers and / or oligomers suitable according to the present invention, aliphatic polythiols can be cited, such as trimethylolpropane tris(2-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), trimethylolethane tris(2-mercaptoacetate), trimethylolethane tris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), bis(mercaptomethyl) sulfide, bis(mercaptomethyl) disulfide, bis(mercaptoethyl) sulfide, bis(mercaptoethyl) disulfide, bis(mercaptopropyl) sulfide, bis(mercaptopropyl) disulfide, 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol, 4,8(or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 2,5-dimercaptomethyl-1,4-dithiane and 2,5-bis[(2-mercaptoethyl)thiomethyl]-1,4-dithiane, 1-(1'-mercaptoethylthio)-2,3-dimercaptopropane, 1-(2'-mercaptopropylthio)-2,3-dimercaptopropane, 1-(3'-mercaptopropylthio)-2,3-dimercaptopropane, 1-(4'-mercaptobutylthio)-2,3-dimercaptopropane, 1-(5'-mercaptopentylthio)-2,3-dimercaptopropane, 1-(6'-mercaptohexylthio)-2,3-dimercaptopropane, 1,2-bis-(4'-mercaptobutylthio)-3-mercaptopropane, 1,2-bis-(5'-mercaptopentylthio)-3-mercaptopropane, 1,2-bis-(6'-mercaptohexylthio)-3-mercaptopropane, 1,2,3-tris(mercaptomethylthio)propane, 1,2,3-tris-(3'-mercaptopropylthio)propane, 1,2,3-tris-(2'-mercaptoethylthio)propane, 1,2,3-tris-(4'-mercaptobutylthio)propane, 1,2,3-tris-(6'-mercaptohexylthio)propane, methanedithiol, 1,2-ethanedithiol, 1,1-propanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 2,2-propanedithiol, 1,6-hexanedithiol-1,2,3-propanetrithiol, and 1,2-bis(2'-mercaptoethylthio)-3-mercaptopropane. Further examples of polythiols are shown in the following formula or can be found in WO 2014 / 133111, EP 394495, US 4775733 or EP1877839:

[0064]

[0065] C2H5C(CH2COOCH2CH2SH)3

[0066] Preferred embodiments are combinations of xylylene diisocyanate and pentaerythritol tetra(3-mercaptopropionate); combinations of xylylene diisocyanate and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; combinations of 2,5(or 2,6)-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, pentaerythritol tetra(3-mercaptopropionate) and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; combinations of xylylene diisocyanate and 4,8(or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane; combinations of dicyclohexylmethane diisocyanate and 4,8(or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane; or combinations of bis(2,3-epithiopropyl) disulfide and 4,8(or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane. The most preferred polythiol is 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol, as follows:

[0067]

[0068] Preferably, the polythiol has a viscosity at 25 °C of 1 Pa·s or less, more preferably 5·10 -1 Pa·s or less, more preferably 2.5·10 -1 Pa·s or less, more preferably 2·10 -1 Pa·s or less, more preferably 10 -1 Pa·s or less, and even more preferably 0.5·10 -1 Pa·s or less.

[0069] Specific examples of the polythiolurethane resin applicable to the present invention are those sold by Mitsui Chemicals company in the series, especially (refractive index: 1.67), (refractive index: 1.6) resin, (refractive index: 1.67). These optical materials and the monomers for their preparation are particularly described in patents US4,689,387, US 4,775,733, US 5,059,673, US 5,087,758 and US 5,191,055.

[0070] Depending on the embodiments of the present invention, components A and B are prepared by polymerizing a mixture of a required amount of at least one polyisocyanate and / or at least one polyisothiocyanate monomer and at least one polythiol monomer, and optionally a polyol monomer or a polyamine monomer. Typically, components A and B can be prepared by classical thermal polymerization including infrared heating.

[0071] In each case, preferably, the amounts of the polyisocyanate or polyisothiocyanate monomer and the polythiol monomer in the reaction medium are adjusted in such a way that the molar ratio of the NCX / SH groups of the mixture of the polyisocyanate or polyisothiocyanate monomer and the polythiol monomer for preparing the polythiourethane prepolymer A1 ranges from 3:1 to 30:1, preferably from 6:1 to 10:1, and / or the molar ratio of the SH / NCX groups of the mixture of the polyisocyanate or polyisothiocyanate monomer and the polythiol monomer for preparing the polythiourethane prepolymer B1 ranges from 3:1 to 30:1, preferably from 6:1 to 10:1, where X is O or S.

[0072] In one embodiment, both components A and B are prepared without using a catalyst system, which enables better control of the polymerization reaction and produces prepolymers with high stability over time. However, they can also be prepared using the catalysts described below.

[0073] Generally, in the first embodiment of the present invention, the prepolymer A1 and the prepolymer B1 are included in the mixture in such amounts that the molar ratio of NCX to SH groups is from 0.8 to 1.2, preferably 1.

[0074] Generally, in the second embodiment of the present invention, the prepolymer A1 and at least one polythiol monomer of component B are included in the mixture in such amounts that the molar ratio of NCX to SH groups is from 0.8 to 1.2, preferably 1.

[0075] The preparation of the prepolymer B1 having thiol end groups has been described in US 5908876. A similar method can be used to prepare component B of the present invention.

[0076] When component A of the present invention contains the polythiourethane prepolymer A1, it can be prepared in a similar manner but with the required ratio of polyisocyanate or polyisothiocyanate to polythiol monomer in order to obtain the polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups.

[0077] The polythiol / polyisothiocyanate mixture from which prepolymer A1 is obtained may comprise at most 90% by weight of at least one polyol. Preferably, the mixture may comprise at most 80%, 70%, 60%, 50%, 40%, 30%, 20% or 10% by weight of at least one polyol. More preferably, no polyol is used. Polyisothiocyanate means polyisocyanate or polyisothiocyanate.

[0078] The polythiol / polyisothiocyanate mixture from which prepolymer B1 is obtained may comprise at most 90% by weight of at least one polyol. Preferably, the mixture may comprise at most 80%, 70%, 60%, 50%, 40%, 30%, 20% or 10% by weight of at least one polyol. More preferably, no polyol is used.

[0079] The mixture of components A and B according to the invention may also comprise additives conventionally used in polymerizable compositions intended for the production of moulded optical articles, in particular ophthalmic lenses, in conventional proportions, namely inhibitors, dyes, photochromic agents, UV absorbers, fragrances, deodorants, antioxidants, resin modifiers, colour balance agents, chain extenders, crosslinking agents, free radical scavengers such as antioxidants or hindered amine light stabilizers (HALS), dyes, pigments, fillers, adhesion promoters, anti-yellowing agents and release agents.

[0080] In one embodiment, the additives are added to the first component A before mixing with the second component B.

[0081] UV absorbers are often incorporated into optical articles in order to reduce or prevent UV light from reaching the retina (especially in ophthalmic lens materials). The UV absorbers which can be used in the present invention preferably have the ability to at least partly block light having a wavelength shorter than 400 nm, but may also have an absorption spectrum extending into the visible blue light range (400 - 450 nm), in particular 420 - 450 nm, of the electromagnetic spectrum.

[0082] The UV absorber protects both the user's eyes from UV light and the substrate material itself, thus preventing it from weathering and becoming brittle and / or yellowing. The UV absorbers according to the invention may be, but are not limited to, benzophenone-based compounds, benzotriazole-based compounds or dibenzoylmethane-based compounds, preferably benzotriazole compounds. Suitable UV absorbers include, but are not limited to, 2-(2-hydroxyphenyl)-benzotriazoles such as 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole ( 703 / 326), or other allyl hydroxy methyl phenyl chlorobenzotriazole, 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol( 550), octyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl] propionate( 109), 2-(2-hydroxy-5-methoxyphenyl) benzotriazole, 2-(2-hydroxy-5-butoxyphenyl) benzotriazole and also those from BASF Preferred absorbers are from the benzotriazole family. Other examples of benzotriazole UV absorbers that protect against blue light can be found in WO 2017 / 137372.

[0083] The amount of the UV absorber compound according to the invention used herein is an amount sufficient to provide satisfactory protection against UV light, but not in excess to prevent precipitation. The UV absorber compound of the present invention is usually present in an amount ranging from 0.05% to 4% by weight, preferably from 0.1% to 3% by weight, more preferably from 0.1% to 2% by weight, based on the total weight of the optical material (or per 100 parts by weight of the polymerizable compound present in the mixture of components A and B or relative to the weight of the optical material composition).

[0084] Among the mold release agents that can be used in the present invention, there may be mentioned monoalkyl phosphates and dialkyl phosphates, alkyl phosphates, silicones, fluorinated hydrocarbons, fatty acids, and ammonium salts. Preferred mold release agents are monoalkyl phosphates and dialkyl phosphates, alkyl phosphates and mixtures thereof. Such mold release agents are disclosed in particular in US 4975 328 and EP 271839. Based on the total weight of the polymerizable compounds present in the mixture of components A and B, the mold release agent is preferably used in an amount of less than or equal to 1% by weight.

[0085] The polymerizable mixture of the present invention may contain a solvent for promoting catalyst dissolution, especially if the catalyst is in the form of a salt.

[0086] Any polar organic solvent can be used, such as acetonitrile, tetrahydrofuran, dioxane, ethanol, thioethanol, acetone, and 3-methyl-2-buten-1-ol. Based on the total weight of the polymerizable compounds present in the mixture of components A and B, the amount of the solvent is usually kept below 2% by weight, and preferably from 0% to 0.5% by weight, to avoid turbidity and bubbling. In one embodiment, the catalyst is used in the form of a solution in a compound such as 2-mercaptoethanol.

[0087] In the present invention, at least one catalyst can be used in the method before the curing step 5). In one embodiment, the resulting mixture of step 4) contains at least one catalyst.

[0088] The catalyst is a system used to accelerate the polymerization reaction. The catalyst can include one or more latent thermal catalysts.

[0089] The catalyst should be used in the polymerizable composition in an effective amount (i.e., an amount sufficient to promote the polymerization of the mixture). Generally, the at least one catalyst is used in a proportion of 0.01% to 5% by weight, more preferably 0.02% to 2% by weight, based on the total weight of the polymerizable compounds present in the mixture of components A and B.

[0090] The catalyst can be added at different stages of the method of the present invention.

[0091] In one embodiment, depending on the situation, the catalyst is added to the polythiol monomer B2 during the preparation of component B, or added to the polythiourethane prepolymer B1 having thiol end groups.

[0092] In one embodiment, the catalyst is added to the first component A obtained in step 1) or 1') before mixing with component B, or the catalyst is added to the second component B obtained in step 2) or 2') before mixing with component A. In this embodiment, depending on the situation, the catalyst can be added to these prepolymers after the preparation of prepolymers A1 and / or B1.

[0093] In another preferred embodiment, the catalyst is added to the mixture of components A and B in step 4) of the method of the present invention.

[0094] In one embodiment, the catalyst is an anionic catalyst. Preferred catalysts are transition metal-based catalysts and ammonium salts of acids, and these salts preferably satisfy the condition 0.5 ≤ pKa ≤ 14.

[0095] In one embodiment, the catalyst is a salt compound having the formula

[0096] where M p+ is a cation selected from the group consisting of: alkali metal cations, alkaline earth metal cations, transition metal cations, and ammonium groups having the formula NR + 4, where R is an alkyl group preferably having 1 to 10 carbon atoms, Y - is an anion such that the corresponding acid YH has a pKa satisfying the condition 0.5 ≤ pKa ≤ 14, p is the valence of the cation, and n = m × p.

[0097] Preferred metal cations of the salt are Li + , Na + , K + , R b+ , Mg 2+ , Ca 2+, Ba 2+ and Al 3+ . Particularly preferred metal cations are Li + , Na + and K + because they do not impart color and solubility in the composition. Transition metals are less preferred because their salts may result in a colored composition and thus a colored polymeric resin. In one embodiment, a tin-containing catalyst is not used in the process according to the invention.

[0098] Preferred NR + 4 groups are those in which R is a C1-C8 alkyl group and more preferably methyl, ethyl, propyl, butyl or hexyl.

[0099] Preferably, Y - is an anion such that the corresponding acid YH satisfies the condition 0.5 ≤ pKa ≤ 10, and more preferably 0.5 ≤ pKa ≤ 8.

[0100] Preferably, the anion Y - is selected from the group consisting of thiocyanate, carboxylate, thiocarboxylate, acetylacetonate, diketone anion, acetoacetate anion, malonate anion, cyanoacetate anion, ketonitrile anion and an anion having the formula RS - wherein R is a substituted or unsubstituted alkyl group preferably having 2 to 10 carbon atoms, or a phenyl group preferably having 6 to 12 carbon atoms.

[0101] Preferred anions Y - are SCN - , acetylacetonate, acetate, thioacetate, formate and benzoate. A preferred salt catalyst is KSCN.

[0102] Among the catalysts that can be used in the process according to the invention, amines such as tertiary amines (e.g. triethylamine or 3,5-dimethylpyridine) and organometallic compounds such as alkyl tin or alkyl tin oxide (especially dibutyltin dilaurate, dibutyltin dichloride and dimethyltin dichloride) can also be cited. Several catalysts according to the invention can be combined in the process according to the invention.

[0103] The electron donor compound can also be used in combination with a catalyst, preferably a salt catalyst, especially when the polymerizable composition contains poorly reactive thiols and / or isothiocyanates. Generally, the electron donor compound stabilizes the cation of the catalyst salt. Thus they contribute to the dissociation of the anion / cation pair and thus do increase the anionic reactivity in the polymerization medium and thus promote the polymerization reaction.

[0104] The electron donor compound is preferably selected from acetonitrile compounds such as malononitrile, amides, amines, imines, phosphines, sulfones, sulfoxides, trialkyl phosphites, triaryl phosphites, ethylene glycol ethers, crown ethers and cryptands. Preferred electron donor compounds are crown ethers, cryptands, trialkyl phosphites, triaryl phosphites and malononitrile.

[0105] Examples of acetonitrile compounds are:

[0106] N≡C-CH2-C≡N and where

[0107] R is an alkyl group, preferably a C1-C6 alkyl group such as methyl, ethyl, propyl, butyl.

[0108] The amide compound can be a primary, secondary or tertiary amide compound. The trialkyl phosphite and triaryl phosphite can be represented by the following formula:

[0109]

[0110] where R, R’, R”’ are alkyl groups (preferably C1-C6 alkyl groups), or preferably aryl groups having 6 to 12 carbon atoms (such as phenyl). Preferred is trialkyl phosphite, for example (C2H5O)​​3P.

[0111] The electron donor compound can also be selected from crown ethers and cryptands.

[0112] These cyclic molecules are usually selected to exhibit a good compromise between the heteroatom or metal size and the “cage” size, i.e., between the number and size of heteroatoms and the “cage” size, i.e., between the number of heteroatoms and the size of the ring.

[0113] Preferred crown ethers and cryptands can be represented by the following formula:

[0114]

[0115] where X 1 represents O, S or NH, x1 is an integer from 3 to 6, preferably from 3 to 4, n1 is 2 or 3,

[0116] X 2 、X 3 and X4 represent O, S, n2, n3, n4, y2, y3, y4 are 2 or 3, and x2, x3, x4 are 2 or 3.

[0117] Among the preferred crown ethers and cryptands, the following compounds can be listed:

[0118]

[0119] Examples of preferred crown ethers are 18-crown-6, 18-crown-7, 15-crown-5 and 15-crown-6.

[0120] These electron donor compounds are preferably present in an amount in the range from 0% to 5% by weight, preferably from 0% to 1% by weight, based on the total weight of the polymerizable compounds present in the mixture of components A and B.

[0121] In step 3) of the process according to the invention, there is provided a microstructured sheet made of a thermoplastic material having an inner (major) surface and an outer (major) surface. The inner surface of the sheet bears the microstructure.

[0122] In a further embodiment, the sheet has two major surfaces with the same or different microstructures, i.e. its outer surface also bears the microstructure.

[0123] The sheet or carrier is a thin support element made of a thermoplastic material. The sheet can comprise a variety of different configurations and materials. Such configurations include free-standing or non-laminated films, films with removable protective sheets, films with external permanent protective coatings or support plastic layers, and laminated films and sheets.

[0124] The sheet can be a preformed film or a stack of several coatings supported by a film. The coatings can be selected from, but are not limited to, anti-reflection coatings, anti-fouling top coatings, anti-wear and / or scratch-resistant coatings, impact-resistant coatings, polarization coatings, photochromic coatings, dye coatings, printed layers, antistatic coatings. The preparation of such coatings and coated sheets is described in WO 2008 / 015223 and U.S. 6,562,466, which are hereby incorporated herein by reference. These coatings are applied to the surface of the sheet in an order opposite to the desired order of the coating stack on the substrate.

[0125] Examples of thermoplastic (co)polymers which can be used to manufacture the sheets according to the invention are polysulphone, aliphatic poly(meth)acrylates such as poly(methyl methacrylate), polyethylene, polypropylene, polystyrene, SBM (styrene-butadiene-methyl methacrylate) block copolymers, polyphenylene sulphide, aryl polyoxides, polyimides, polyesters, polycarbonates such as bisphenol A polycarbonate, PVC, polyamides such as nylon, cellulose acetate butyrate, cellulose acetate and cellulose triacetate, other copolymers thereof, and mixtures thereof. The microstructured sheet is preferably made of polycarbonate. Preferably, the sheet is made of a non-elastomeric material.

[0126] If the curable composition used is thermally curable, the material of the sheet should be chosen to withstand the curing temperature.

[0127] Generally, the sheet has a thickness of from 0.25 to 5 mm, preferably from 0.5 to 4 mm, more preferably from 1 to 3 mm, even better from 1.5 to 2 mm.

[0128] The "inner surface of the sheet" means the major surface of the sheet which will be in contact with the curable composition for forming the polyurethane-based substrate during the process of the present invention.

[0129] The inner surface of the sheet including the microstructure can be a concave surface or a convex surface, depending on whether the sheet is overmolded on the concave or convex surface of the polyurethane-based substrate in the final optical article.

[0130] The working surface (inner surface) of the sheet has a relief organized according to a pattern (in other words, a microstructured surface), which gives the final optical article an optical surface with properties (such as preventing the development of myopia or hyperopia) imparted by the microstructure. Different techniques for obtaining microstructured mold parts are disclosed in WO 99 / 29494.

[0131] In one embodiment of the present invention, the microstructure includes a plurality of small lenses. The small lenses can form protrusions and / or depressions on the major surface on which they are arranged. The profile of the small lenses can be circular or polygonal, such as hexagonal.

[0132] In one embodiment, the inner surface of the sheet defines a plurality of concave recesses and / or a plurality of convex protrusions.

[0133] More particularly, the small lenses can be microlenses such that the microstructure includes a plurality of microlenses. The microlenses can be spherical, toric or have an aspherical shape, rotationally symmetric or not rotationally symmetric. The microlenses can have a single focal point, or a cylindrical power, or a non-focus point.

[0134] In a preferred embodiment, the small lenses or microlenses can be used to prevent the development of myopia or hyperopia. In this case, the resulting polyurethane-based substrate adhered to the microstructured sheet provides a refractive power for correcting myopia or hyperopia, and correspondingly, if the wearer is myopic, the microlenses or small lenses can provide a refractive power greater than that of the polyurethane-based substrate, or if the wearer is hyperopic, the microlenses or small lenses can provide a refractive power less than that of the polyurethane-based substrate.

[0135] In one embodiment, the inner surface of the sheet has at least one geometrically defined surface forming a Fresnel lens.

[0136] The small lens or microlens can also be a Fresnel structure, a diffractive structure defining each Fresnel structure, a permanent technical protrusion, or a phase shift element. The small lens can also be a refractive optical element such as a microprism and a light diffusing optical element such as a small protrusion or cavity, or any type of element that creates roughness on a substrate. It can also be a π-Fresnel microlens as described in US20211 / 09379, i.e., a Fresnel microlens in which the phase function has a π phase jump at the nominal wavelength, as opposed to a single-focus Fresnel lens with multiple values of 2π phase jumps. Such a small lens includes a structure with a discontinuous shape. In other words, the shape of such a structure can be described by a height function that exhibits discontinuity or whose derivative exhibits discontinuity in terms of the distance from the reference plane of the main surface of the optical article to which the small lens belongs.

[0137] The small lens can have an outer shape that can be inscribed within a circle with a diameter greater than or equal to 0.5 micrometers (μm) and less than or equal to 1.5 millimeters (mm).

[0138] The small lens can have a height measured in a direction perpendicular to the main surface on which it is disposed that is greater than or equal to 0.1 μm and less than or equal to 50 μm.

[0139] The inner surface of the sheet with the microstructure can be defined as the surface including the center points of each microstructure, and this surface can be a plane, a spherical surface, a spherocylindrical surface, or even a composite surface. When the microstructure is embedded in the lens, the main surface can be a virtual surface, or when the microstructure is not embedded, it is close to or the same as the physical outer surface of the lens. Then, a local axis perpendicular to this main surface can be used to determine the height of the microstructure, and for each point of the microstructure, the difference between the maximum positive deviation and the minimum negative deviation from the main surface along this axis is calculated.

[0140] The small lenses can have a periodic or pseudo-periodic layout, but can also have random positions. Exemplary layouts of the small lenses can be a grid with a constant grid step, a honeycomb layout, multiple concentric rings, contiguous (e.g., no space between the microstructures).

[0141] These structures can provide modification of the light wavefront in terms of intensity, curvature, or light deviation, where the intensity of the wavefront is configured such that the structure can be absorptive and can locally absorb the wavefront intensity in the range of 0% to 100%, the curvature is configured such that the structure can locally modify the wavefront curvature in the range of + / - 20 diopters, and the light deviation is configured such that the structure can locally scatter light at an angle in the range of + / - 1° to + / - 30°.

[0142] The distance between the structures can be in the range from 0 (contiguous) to 3 times that of the structure (separated microstructures).

[0143] Typically, microstructures, especially those for myopia control, include optical elements having a height of at least 0.1 μm or higher, and preferably the following values (in μm) or higher: 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1. If the microstructure is at the interface microstructure / air or at an internal interface located inside the optical element, it is measured at the surface of the lens.

[0144] The microstructure may include cylindrical annular refractive elements.

[0145] The sheet can be treated to improve its adhesion to the polyurethane-based material. The treatment includes mechanical roughening, physical cleaning, chemical surface modification, plasma activation.

[0146] The preferred treatment is a chemical treatment, which includes immersing the sheet in an alkaline or acidic solution (such as but not limited to NaOH, KOH, HCl, or HNO3 solution), rinsing, and drying. These acids or bases can be used at a normal concentration of at least 0.001 N or greater. Treatment with NaOH solution, typically 5% NaOH solution, is preferred.

[0147] The mixing of the first component A and the second component B in step 4) can be carried out by any known mixing technique (such as those mentioned in US5973098). Preferably, the components A and B to be mixed are added to a small reactor chamber and then mixed with a screw mixer. In one embodiment, the viscosity of the mixture of components A and B at 25 °C ranges from 0.01 Pa·s to 5 Pa·s, preferably from 0.05 Pa·s to 0.5 Pa·s, and even more preferably from 0.1 Pa·s to 0.3 Pa·s.

[0148] During step 4), the cavity of the mold assembly is filled with the mixture of the first component A and the second component B. The cavity is defined by the inner surface of the microstructured sheet and at least a part of the mold part (typically made of mineral glass). Both can be held together using an annular closure.

[0149] The mold assembly generally includes two mold parts that define two molding surfaces, which cooperate to form a cavity when moved from an open position to a closed position. Depending on the desired shape of the article, each of the molding surfaces can be concave, convex, or planar. The molding surface can be convex, for example, to form a concave substrate surface, or concave, for example, to form a convex substrate surface.

[0150] An annular closing member (such as a gasket or a tape) can be arranged around the peripheries of the two mold parts and attached thereto. A conventional way of filling such a two-piece mold is by flowing a (liquid) optical material composition through a casting opening provided in the closing member for this purpose against the wafer into the mold cavity. In at least a partially automated process, the mold cavity to be filled is vertically aligned with a filling device which is adapted to deliver a specific amount of molding material through a nozzle.

[0151] In a first embodiment, step 4) includes positioning the microstructured wafer in the mold cavity of the mold assembly such that the outer surface of the wafer contacts the surface of the mold assembly (i.e., the molding surface), wherein the mold assembly includes the mold part. In this embodiment, the wafer is placed into the cavity of the mold assembly which is typically a two-piece mold assembly, the first part of the mold assembly being the mold part and the second part of the mold assembly being a second mold part.

[0152] In a second embodiment, as Figure 1 shown, step 4) is carried out with a two-piece mold assembly, the first part of the two-piece mold assembly being the mold part 4 and the second part of the two-piece mold assembly being the microstructured wafer 1. In other words, in this embodiment, the microstructured wafer is used as a mold part. Figure 1 A tape 2 for holding together the two mold parts as well as the mixture 3 of the first component A and the second component B poured into the mold cavity is also shown.

[0153] In a third embodiment, step 4) includes positioning the microstructured wafer in the mold cavity of the mold assembly such that the outer surface of the wafer does not contact the surface of the mold assembly (i.e., the molding surface), wherein the mold assembly includes the mold part. In this embodiment, the wafer is placed into the cavity of the mold assembly which is typically a two-piece mold assembly, the first part of the mold assembly being the mold part and the second part of the mold assembly being a second mold part.

[0154] In this third embodiment of the invention, a first volume (first mold cavity) can be defined between the inner surface of the wafer with the microstructure and the first molding surface of the first mold part, and a second volume (second mold cavity) can be defined between the outer surface of the wafer and the second molding surface of the second mold part. These two volumes can be filled with the same or different mixtures of polymerizable compounds having the same or different refractive indices. Typically, the second volume is filled with the same mixture of the first component A and the second component B as the first volume. Thus, after curing, the wafer will be sandwiched between two substrates, the first substrate adhering to the microstructured (inner) side of the wafer and the second substrate adhering to the other (outer) side of the wafer, which second substrate can optionally carry a microstructure that is the same as or different from the microstructure on the inner side.

[0155] Depending on the desired characteristics of the resulting optical material, degassing may be carried out under reduced pressure and / or filtration may be carried out under increased or reduced pressure before injecting the optical material composition into the mold assembly.

[0156] After pouring the composition, the mold assembly, preferably a lens mold assembly, may be heated in an oven or heating device immersed in water according to a predetermined temperature program to cure the resin in the mold assembly. If desired, the resin molded product may be annealed.

[0157] The curing step 5) of the mixture of the polythiourethane-based substrate adhered to the microstructured sheet is carried out in the presence of a catalyst and may be carried out using any well-known polymerization technique and in particular thermal polymerization (including infrared heating) or radiation polymerization. The curing time of step 5) is preferably less than 10 or 5 hours, more preferably less than 4, 3 or 2 hours.

[0158] Due to the method of the present invention, the diffusion of the polymerizable compound into the sheet substrate is restricted, thus preserving the integrity of the microstructural design. Preferably, during steps 4) and 5), the compounds from the mixture prepared in step 4) do not diffuse into the microstructured sheet.

[0159] As previously explained, the use of monomers as in prior art methods to cast the sheet as part of the final polythiourethane-based substrate presents problems of incompatibility and causes swelling of the sheet, thus generating haze at the polymer interface.

[0160] Without wishing to be bound by any theory, the inventors believe that preventing the polythiourethane prepolymer having isocyanate or isothiocyanate end groups, which is a larger molecule than the corresponding isocyanate or isothiocyanate monomer, from entering the sheet network results in a transparent final product. The prepolymer (or oligomer) also reduces the shrinkage rate of the polythiourethane matrix compared to standard monomers, thus generating less stress on the sheet. Monomers having low molecular weight and aromaticity such as isocyanates or isothiocyanates are considered stress crack agents for the sheet substrate.

[0161] In step 6) of the method of the present invention, as Figure 2 shown, once the resin is molded onto the sheet, the cured polythiourethane-based substrate 5 adhered to the microstructured sheet 1 is recovered from the mold assembly. The overmolded substrate portion typically has a thickness greater than 2 mm, preferably greater than 3 mm.

[0162] The method of the present invention can be used to manufacture finished lenses having the desired geometry on both sides or semi-finished lenses (one side of which still needs to be surface-treated according to the desired geometry).

[0163] The article produced by the method of the present invention has satisfactory color characteristics, which can be quantified by the yellowness index Yi. The whiteness of the optical material of the present invention can be quantified by colorimetric measurement based on the CIE tristimulus values X, Y, Z as described in the standard ASTM E313 under the condition of light source C and observer 2°. The optical article according to the present invention preferably has a low yellowness index Yi, that is, less than 10, more preferably less than 8, and even better less than 6, as measured according to the above standard. The yellowness index Yi is calculated by the relationship Yi = (127.69X - 105.92Z)) / Y according to ASTM method E313, where X, Y and Z are the CIE tristimulus values.

[0164] As determined according to the standard ASTM D1003-00, the haze value of the polyurethane-based substrate with microstructured flakes adhered thereto is less than or equal to 6%, more preferably less than or equal to 5%, which indicates a high level of clarity. For a 2-mm thick sample, the haze is preferably measured.

[0165] The Tv factor, also known as the "light transmittance" of the system, is defined as in ISO standard 13666:1998 and measured according to standard ISO 8980-3. It is defined as the average value in the wavelength range of 380 - 780 nm, which is weighted according to the sensitivity of the eye at each wavelength in this range and is measured under D65 illumination conditions (daylight).

[0166] As determined according to the standard ISO 8980-3, the relative light transmittance factor Tv of the polyurethane-based substrate with microstructured flakes adhered thereto in the visible spectrum is higher than or equal to 74%, more preferably higher than or equal to 78% or 80%.

[0167] In some embodiments, the method does not include depositing the catalyst composition on the inner surface of the mold part and / or on at least one surface of the filter element positioned in the mold cavity thereafter.

[0168] In some embodiments, the method does not include depositing the catalyst composition on the surface of the microstructured flake.

[0169] In some embodiments, the method does not include depositing the catalyst composition on the inner surface of the microstructured flake.

[0170] In some embodiments, the method does not include depositing the catalyst composition on the outer surface of the microstructured flake.

[0171] In some embodiments, the method does not include depositing the catalyst composition in the mold cavity before adding the polymerizable composition in the mold cavity.

[0172] In some embodiments, the method does not include depositing a catalyst composition on the inner surface of at least one mold.

[0173] In some embodiments, the method does not include depositing a catalyst composition on at least one surface of a light filtering element.

[0174] In some embodiments, the method does not include depositing a catalyst composition on at least one surface of a light filtering element that is subsequently positioned within a mold assembly.

[0175] In one embodiment, the method according to the present invention does not include a method for manufacturing a rapidly curable transparent casting substrate useful for manufacturing optical articles such as ophthalmic lenses, the method comprising the steps of:

[0176] - providing a rapidly room temperature polymerizable composition;

[0177] - providing a catalyst composition;

[0178] - providing a mold assembly comprising two unsealed molds each having an inner surface and an outer surface; and optionally providing a light filtering element that is placed or configured to be placed between the two molds

[0179] - depositing the catalyst composition:

[0180] - on the inner surface of at least one of the molds; and / or

[0181] - on at least one surface of the light filtering element, which is subsequently positioned within the mold assembly;

[0182] - closing the mold assembly such that the inner surfaces of the molds together form a mold cavity;

[0183] - filling the mold cavity of the mold assembly with the rapidly room temperature polymerizable composition, the mold cavity already containing the catalyst composition deposited on the inner surface of at least one of the molds;

[0184] - curing the filled mold assembly to obtain a transparent solid substrate, the curing step comprising:

[0185] a) a first step of polymerizing the composition at room temperature to obtain a gel; and

[0186] b) a second step of post-curing the gel to obtain the transparent solid substrate; and

[0187] - recovering the transparent solid substrate from the mold assembly.

[0188] The following examples illustrate the invention in more detail but not by way of limitation. Unless otherwise indicated, all thicknesses disclosed in this application refer to physical thicknesses.

[0189] Example

[0190] Chemicals used

[0191] The optical material is prepared from a composition comprising a polymerizable monomer, Zelec (CAS 3896-11-5) and a catalyst solution comprising 8.5% by weight KSCN (CAS 333-20-0), 34.84% 18-crown-6 (CAS 17455-13-9) and 56.66% mercaptoethanol (CAS 60-24-2). The monomers used in the examples of the present invention are benzodimethylenediisocyanate (CAS 3634-83-1) and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol (CAS 131538-00-6) in order to produce a polythiourethane transparent matrix having a refractive index of 1.67.

[0192] Evaluation of the cured lens

[0193] The following test procedures were used to evaluate the optical articles prepared according to the present invention. Several samples were prepared for each system for measurement and the reported data were calculated as the average of different samples.

[0194] Taking into account the standard light source D65 and the standard observer 10°, in the transmission mode, for an angle of incidence of 0°, chromaticity measurements of the hue angle h, chromaticity C* and b* were carried out in the international chromaticity CIE (L*, a*, b*) space using a Zeiss spectrophotometer.

[0195] The light transmittance factor Tv in the visible spectrum was measured from the perspective of the wearer in transmission mode (angle of incidence: 0°) using a Cary 4000 spectrophotometer from Hunter, where the back (concave) side of the lens (2 mm thick at the center) faces the detector and the light enters on the front side of the lens. Tv was measured under D65 illumination conditions (daylight).

[0196] Haze was measured on a Hazeguard XL 211Plus apparatus from BYK-Gardner according to standard ASTM D1003-00 as disclosed in WO 2012 / 173596. Since haze is a measure of the percentage of transmitted light scattered more than 2.5° from the axis of the incident light, the lower the haze value, the lower the degree of turbidity.

[0197] The yellowness index Yi of the prepared lens is calculated as described above from the reflectance measurements by measuring the CIE tristimulus values X, Y, Z as described in standard ASTM E 313-05 on a white background with the above spectrophotometer, where the front (convex) side of the lens faces the detector and the light enters on the front side. From the observer's perspective, this way of measuring Yi is closest to the actual wearing situation.

[0198] Preparation of polythiourethane prepolymer A1 with isocyanate end groups (component A in Examples 1 and 3)

[0199] In a reactor equipped with a condenser, a thermal probe, and a stirrer, a determined amount of the polyisocyanate monomer xylylene diisocyanate (XDI) is charged and heated to 120 °C. Then, 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol is introduced and mixed with the polyisocyanate in an amount such that the molar ratio of isocyanate functional groups to thiol functional groups NCO / SH is 8:1 (89.7% polyisocyanate, 10.3% polysulfide). The mixture is heated for 3.5 hours. Then the resulting prepolymer A1 is cooled to about 35 °C and transferred to a suitable drum, purged with an inert gas (nitrogen or argon), and stored in a cold room. The final prepolymer with isocyanate end groups has a viscosity of about 0.1 Pa·s at 25 °C. Prepolymer A1 is prepared without using a catalyst.

[0200] Preparation of polythiourethane prepolymer B1 with mercapto end groups (component B in Examples 2 and 3)

[0201] In a reactor equipped with a condenser, a thermal probe, and a stirrer, a determined amount of the polythiol monomer 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol is charged and heated to 95 °C. Then, xylylene diisocyanate is introduced and mixed with the polythiol in an amount such that the molar ratio of thiol functional groups to isocyanate functional groups SH / NCO is 8:1. The mixture is heated for 3.5 hours. The end of the reaction is indicated by the temperature reaching a peak and returning to 95 °C (+ / - 2 °C). Then the resulting prepolymer B1 is cooled to about 35 °C and transferred to a suitable drum, purged with an inert gas (nitrogen or argon), and stored in a cold room. The final prepolymer with thiol end groups has a viscosity of about 0.5 Pa·s at 25 °C. Prepolymer B1 is prepared without using a catalyst.

[0202] Mold assembly

[0203] A two-piece mold assembly is assembled using tape to have a center thickness of 2 mm.

[0204] Figure 1Schematically shows a two-piece mold assembly. The first part (rear part) of the mold assembly is a mineral glass mold part with a diameter of 71 mm, and the second part (front part / top mold) of the mold assembly is a microstructured polycarbonate sheet (base 3.25, i.e., 76 mm, surface treated to a flat optical lens with a center thickness of 2 mm - 71 mm; front radius is 167.81 mm), with a microlens pattern on its rear side (concave side) for controlling myopia. Cleaned in advance with isopropanol to remove any dust or contaminants.

[0205] Place the sheet on top with its microstructured concave surface facing down. Place the glass mold part to be paired with the sheet in the bottom with its concave surface facing down.

[0206] Preparation of polythiourethane transparent casting substrate

[0207] Example 3

[0208] Prepare prepolymers A1 and B1 as described above. Mix a determined amount of cooled prepolymer A1 with a determined amount of Zelec Mix. Stir and degas the mixture at 15 °C for 1 hour and then degas for 15 minutes without stirring to form Component A. Mix a determined amount of prepolymer B1 with a determined amount of the above catalyst solution (KSCN, 18-crown-6, 2-mercaptoethanol). Stir and degas the mixture at 15 °C for 1 hour and then degas for 15 minutes without stirring to form Component B. Then mix Components A and B in a small reactor while stirring and degassing at room temperature for 5 minutes and then stirring and degassing at 15 °C for 2 minutes to prevent gelling. The resulting mixture has a viscosity at 25 °C of about 0.1 to 0.3 Pa·s. Once mixing is complete, fill the mold assembly with the aid of a clean syringe. Keep the assembled molds at room temperature for 10 minutes, after which insert them into a convection oven preheated to 120 °C. The mixture starts to gel in the mold assembly. The polymerization reaction is carried out by keeping these mold assemblies in the oven at 120 °C for 3 hours. Then, cool them to 65 °C.

[0209] In the context of the present invention, gel represents the reaction product of Components A and B, where the conversion rate of the reactive functional groups is very high. For example, the conversion rate ranges from 50% to 80%, and is preferably about 70%.

[0210] Then disassemble the mold assembly to obtain lenses with a center thickness of 2 mm of the overmolded body containing a polysulfururethane transparent thermosetting substrate, and anneal these lenses at 120 °C for 1 h. Clean the lenses by immersion and ultrasound in a surfactant solution, then rinse and dry. These lenses have a refractive index of 1.67 and have no optical defects such as streaks.

[0211] The polycarbonate sheet used as the front mold is now an integral part of the final lens and cannot be removed therefrom.

[0212] Example 1

[0213] The lens of Example 1 was prepared similarly to Example 3, except that Component B contained a defined amount of the polythiol monomer 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol and a defined amount of the above catalyst solution (KSCN, 18-crown-6, mercaptoethanol).

[0214] Comparative Example 2

[0215] The lens of Comparative Example 2 was prepared similarly to Example 3, except that Component A contained a defined amount of the polyisocyanate monomer isophthalylidene diisocyanate and a defined amount of Zelec

[0216]

[0217] Comparative Example 3

[0218] An attempt was made to prepare a mixture of at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer for injection into the mold assembly. However, the monomers reacted to form a gel within less than 10 minutes at room temperature, and this gel could not be introduced into the mold cavity.

[0219] Composition and results

[0220] The amounts (parts by weight) of the different compounds used and the results of the characterization are shown in Table 1:

[0221] Table 1

[0222]

[0223]

[0224] A comparison between Example 1 and Comparative Example 2 shows that when the prepolymer A1 with isocyanate or isothiocyanate end groups is used instead of the monomer A2 with isocyanate or isothiocyanate end groups, the transmittance (see Figure 4 ), yellowness index, and clarity (see Figure 3 ) are improved.

[0225] Lenses obtained by curing a composition comprising a prepolymer A1 having isocyanate or isothiocyanate end groups and a prepolymer B1 having thiol end groups (Example 3) or a monomer B2 having thiol end groups (Example 1) simultaneously have a satisfactory yellowness index, transmittance and clarity. The use of a mixture of two prepolymers in Example 3 allows for a further improvement in haze level, yellowness index and transmittance as compared to Example 1 using only one prepolymer or Comparative Example 2.

[0226] Without wishing to be bound by any theory, the inventors believe that casting a prepolymer A1 having isocyanate or isothiocyanate end groups allows for a significant reduction in the swelling of the sheet.

Claims

1. A method for curing a polyurethane-based casting substrate, the method comprising the following steps 1), 2), 3), 4), 5) and 6) or 1’), 2’), 3), 4), 5) and 6): 1) Providing a first component A comprising a polyurethane prepolymer A1 having isocyanate or isothiocyanate end groups of the formula -NCX, where X is O or S, the prepolymer A1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, 2) Providing a second component B comprising a polyurethane prepolymer B1 having thiol end groups, the prepolymer B1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, or: 1’) Providing a first component A comprising a polyurethane prepolymer A1 having isocyanate or isothiocyanate end groups of the formula -NCX, where X is O or S, the prepolymer A1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, 2’) Providing a second component B comprising at least one polythiol monomer B2, 3) Providing a microstructured sheet made of a thermoplastic material, the microstructured sheet having an inner surface and an outer surface, wherein the inner surface of the sheet bears a microstructure, 4) Mixing the first component A and the second component B together and filling a mold cavity with the resulting mixture, wherein the mold cavity is defined by the inner surface of the microstructured sheet and at least a part of a mold part, 5) Curing the mixture to obtain a polyurethane-based substrate, and 6) Recovering the polyurethane-based substrate adhered to the microstructured sheet.

2. The method according to claim 1, comprising the following steps 1) and 2): 1) Providing a first component A comprising a polyurethane prepolymer A1 having isocyanate or isothiocyanate end groups of the formula -NCX, where X is O or S, the prepolymer A1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, 2) Providing a second component B comprising a polyurethane prepolymer B1 having thiol end groups, the prepolymer B1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer.

3. The method according to any one of the preceding claims, wherein, The resulting mixture of step 4) comprises at least one catalyst.

4. The method according to any one of the preceding claims, wherein, The curing time of step 5) is less than 10 hours, preferably less than 5 hours.

5. The method according to any one of the preceding claims, wherein Adjusting the amounts of the polyisocyanate or polyisothiocyanate monomer and the polythiol monomer such that the molar ratio of the NCX / SH groups in the mixture of the polyisocyanate or polyisothiocyanate monomer and the polythiol monomer used for preparing the polyurethane prepolymer A1 ranges from 3:1 to 30:1, and / or the molar ratio of the SH / NCX groups in the mixture of the polyisocyanate or polyisothiocyanate monomer and the polythiol monomer used for preparing the polyurethane prepolymer B1 ranges from 3:1 to 30:1, X being O or S.

6. The method according to any one of the preceding claims, wherein, The substrate is an optical lens substrate.

7. The method according to any one of the preceding claims, wherein, The microstructure comprises a plurality of microlenses.

8. The method according to any one of the preceding claims, wherein, The inner surface of the sheet defines a plurality of concave recesses and / or a plurality of convex protrusions.

9. The method according to any one of the preceding claims, wherein The microstructured sheet is made of polycarbonate.

10. The method according to any one of the preceding claims, wherein The haze value of the polyurethane-based substrate to which the microstructured sheet is adhered is less than or equal to 6%, as determined according to the standard ASTM D1003-00.

11. The method according to any one of the preceding claims, wherein, The relative light transmittance factor Tv in the visible spectrum of the polyurethane-based substrate to which the microstructured sheet is adhered is higher than or equal to 74%, as determined according to the standard ISO 8980-3.

12. The method according to any one of the preceding claims, wherein, During steps 4) and 5), the compounds from the mixture prepared in step 4) do not diffuse into the microstructured sheet.

13. The method according to any one of the preceding claims, wherein, Step 4) includes positioning the microstructured sheet in the cavity of a mold assembly such that the outer surface of the sheet contacts the surface of the mold assembly, wherein the mold assembly includes the mold part.

14. The method according to any one of claims 1 to 12, wherein, Step 4) is carried out with a two-piece mold assembly, the first part of the two-piece mold assembly being the mold part and the second part of the two-piece mold assembly being the microstructured sheet.

15. The method according to any one of the preceding claims, wherein The method does not include depositing a catalyst composition on the inner surface of the mold part and / or on at least one surface of a filter element subsequently positioned in the cavity.

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