Process for replacing an initial outermost coating layer of a coated optical lens by a different coating layer

BACKGROUND OF THE INVENTION

0001The present invention concerns in general a process for replacing an initial outermost coating layer of a coated optical lens, in particular an ophthalmic lens, with or depositing thereon a layer of a new final coating having surface properties different of those of the initial outermost coating layer.

0002It has become more and more common in the manufacture of ophthalmic lenses to coat the lenses with one or several functional coating layers for imparting to the resulting ophthalmic lenses various properties such as impact resistance, scratch-resistance, anti-reflective and anti-soiling properties.

0003Thus, a typical ophthalmic lens may comprise a substrate made of an optically transparent material, such as mineral glass or organic glass, having at least one of its main surfaces coated, successively, with a primer coating layer, a scratch-resistant coating layer, an anti-reflective coating layer, and anti-soiling coating layer (hydrophobic and/or oleophobic top coat).

0004Typically, the outermost coating layer of an ophthalmic lens is the anti-soiling coating layer (or top coat).

0005In view of the fast development in the top coat technology, it would be of interest to be able to safely replace an initially deposited hydrophobic top coat by a new top coat having different or improved properties.

0006Of course, such a replacement of the outermost coating layer by an other one must be effective without adversely affecting the underneath coating layers and/or the substrate, in particular their optical properties.

0007In particular, the top coat is usually deposited onto an anti-reflective coating layer and the replacement process should not impair the properties of this anti-reflective coating layer.

0008Also, an ophthalmic lens results of a succession of molding and/or surfacing/polishing operations which determine the geometry of both convex and concave optical surfaces of the lens, and thereafter of appropriate surface treatment as indicated above. The last finition touch of an ophthalmic lens is the edging step which consists in machining the rim or periphery of the lens to conform it to required dimensions for adaptation of the lens into the spectacle mount in which it is intended to be placed.

0009Edging is generally done on a machine comprising diamond wheels which perform the above defined machining.

0010The lens is maintained, during this operation, by axial blocking means.

0011The relative movement of the lens with regard to the wheel is generally numerically controlled in order to obtained the desired shape.

0012It is thus absolutely necessary that the lens be firmly maintained during the movement.

0013To this end, before the edging operation a maintaining means is positioned onto the convex surface of the lens.

0014A maintaining pad, such as an adhesive wafer, for example a double face adhesive, is placed between the maintaining means and the convex surface of the lens.

0015The thus equipped lens is then positioned on one of the above mentioned axial blocking means, and the other axial blocking means exerts a pressure on the concave face of the lens, through an elastomeric stop.

0016During machining, a tangent torque is applied onto the lens which may induce a rotation of the lens relatively to the maintaining means if the lens is not sufficiently strongly maintained.

0017A good blocking of the lens principally depends upon a good adhesion at the interface between the maintaining pad and the convex surface of the lens.

0018As already mentioned, the outermost coating layer of an ophthalmic lens usually comprises a hydrophobic and/or oleophobic anti-soiling top coat generally formed onto an anti-reflective coating.

0019One problem associated with such top coats, is that, due to their surface properties, they do no permit to obtain a good adhesion of the interface between the maintaining pad and the convex surface of the lens, this lack of adhesion increasing with the increase of efficiency of the hydrophobic and/or oleophobic top coat.

0020Therefore, it will be of interest to produce ophthalmic lens with an outermost coating which results in a good adhesion with the maintaining pad for the edging operation and thereafter be able to replace this initial outermost coating by a more efficient or appropriate final coating layer depending on the intended final use.

0021The document <patcit id="pcit0001" dnum="WO0168384A"><text>WO 01/68384</text></patcit> discloses an apparatus and method for producing a high energy marking on a surface of an ophthalmic lens, such as a corona discharge, to increase the surface energy of the exposed area and obtain a resulting marking visible by fogging. Only a very small area of the lens surface is exposed and partial removal of the subjacent coating or substrate may be tolerated as it does not affect the optical properties of the lens.

0022Japanese unexamined patent application laid open <patcit id="pcit0002" dnum="JP2000308846A"><text>2000-308846</text></patcit> discloses forming an anti-fouling layer having excellent anti-fouling, scratch-resistance and solvent resistance by subjecting the surface of a base material, such as an optical part to a pre-treatment. Pre-treatment can be high frequency plasma, electron beam, ion beam, vapor deposition, sputtering, alkali, acid, corona discharge or atmospheric pressure glow discharge method.

0023The treated surface can be the outer surface of an anti-reflecting layer. It is further precised that the surface energy of anti-reflecting film is as high as 60 J/m². Therefore, due to the very high surface energy, the surface treated is the surface of a mineral layer, typically a SiO₂ layer of an anti-reflecting stack.

SUMMARY OF THE INVENTION

0024Thus, the aim of the present invention is to provide a process for replacing an initial outermost coating layer of a coated optical lens with a layer of a new final coating having surface properties different of those of the initial outermost coating without detrimentally affecting the properties, in particular the optical properties, of the subjacent functional layer and/or the lens substrate.

0025According to the invention, there is provided a process for replacing an initial outermost coating layer of a coated optical lens with or depositing on said initial outermost coating layer a layer of a new final coating having surfaces properties different from those of said initial outermost coating layer which comprises : <ul id="ul0001" list-style="dash" compact="compact"><li>(a) providing a coated optical lens having an initial outermost coating layer having a surface contact angle with water of at least 65°:</li><li>(b) subjecting the initial outermost coating layer to a treatment with activated chemical species at about atmospheric pressure and for less than one minute in order to obtain a treated surface having a contact angle with water of 10° or less;</li><li>(c) depositing on said treated surface a layer of a final coating having surface properties different from those of said initial outermost coating layer.</li></ul>

0026In another embodiment of the invention, the process comprises, before treatment step (b) or after treatment step (b) and before deposition step (c) of the final coating layer, an edging step of the lens.

DETAILED DESCRIPTION OF THE INVENTION

0027An essential step of the process of the invention is treatment step (b).

0028It shall be understood that, in treatment step (b), almost the entire surface of the lens and preferably the whole surface of the lens is treated.

0029Preferably, the duration of the treatment of the initial outermost coating layer with activated chemical species is 40 seconds or less and more preferably 30 seconds or less and even better is about 20 seconds, and preferably the treated surface has a contact angle with water of 10° or less, and even better 5° or less.

0030By definition, the duration of the treatment with activated chemical species is the time during which each point of the surface of the initial outermost coating layer is in contact with the activated chemical species.

0031If not mentioned, by surface contact angle with water, it is meant the stationary contact angle with water determined according to the liquid drop method in which a water drop having a diameter smaller than 2 mm is formed on the optical article and the contact angle is measured.

0032Essentially, the active chemical species are free radicals, and in particular oxygen free radicals.

0033In order to uniformize the action of the activated chemical species on the entire surface of the lens, it is recommended to blow air during treatment step (b).

0034A constant flow of air is blown between the two electrodes. It deflects the arc or plasma produced and causes it to spread on the surface of the material to treat. Three dimensional objects such as lenses can then be treated.

0035The preferred treatment with activated chemical species are corona discharge treatments and atmospheric pressure plasma treatments, in particular corona discharge treatments.

0036Typically, the power of the corona discharge treatment ranges from 10² to 2.10³ W, preferably 5.10² to 10.³ W.

0037For example, the corona discharge treatment may be effected using a corona discharge unit from 3DT, model Multidyne 800 Watts with a discharge of 12 KV per electrode.

0038The lower frequencies are preferred for reasons of safety, although higher frequencies, e.g. 2000 Hz, will provide good results.

0039The preferred atmospheric pressure plasma treatment is an oxygen plasma treatment.

0040Usually, the power of the plasma treatment ranges from 10² to 10³ W, and will generally be around 6.10² W.

0041An important feature of the treatment step (b) of the process of the invention is that it is performed at atmospheric pressure. By atmospheric pressure, it is meant a pressure ranging from 250 to 760 mm Hg, preferably 600 to 760 mm Hg.

0042Preferably, the initial outermost coating will have a surface energy of at least 13 mJ/m², more preferably at least 15 mJ/m² or better at least 20 mJ/m², but also preferably less than 35mJ/m² and even better less than 30 mJ/m², and a thickness of 1 to 100 nm, preferably 1 to 60nm, more preferably 10 to 60 nm. The initial outermost coating may also be as thin as 1 to 10 nm, preferably 1 to 10 nm, preferably 1 to 5 nm.

0043In the present invention, all surface energies are calculated according to the OWENS-WENDT method described in the following document: "<nplcit id="ncit0001" npl-type="s"><text>Estimation of the surface forces energy of polymers" OWENS D.K., WENDT R.G. (1969) J. APPL. POLYM, SCI., 13, 1741-1747</text></nplcit>.

0044The initial outermost coating layer may be any classical outer coating in the field of optical lenses and in particular an anti-soiling coating (hydrophobic and/or oleophobic top coat), an external surface portion of a scratch-resistant coating, or an outermost coating of an antireflective stack.

0045The initial outermost coating layer according to the invention is preferably of organic nature. By organic nature in the present invention, it is meant a layer which is comprised of at least 40% by weight, preferably at least 50% by weight of the total weight of the coating layer of organic materials.

0046A preferred initial outermost coating layer is a hydrophobic and/or oleophobic top coat, and preferably such a top coat made from a composition comprising at least one fluorinated compound.

0047Preferred fluoro compounds are silanes and silazanes bearing at least one group selected from fluorocarbons, polyfluorocarbons, fluoropolyethers and polyfluoropolyethers, in particular perfluoropolyethers.

0048Fluorocompounds are disclosed, among others, in <patcit id="pcit0003" dnum="US4410563A"><text>US-4,410,563</text></patcit>, <patcit id="pcit0004" dnum="EP0203730A"><text>EP-0 203 730</text></patcit>, <patcit id="pcit0005" dnum="EP749021A"><text>EP-749 021</text></patcit>, <patcit id="pcit0006" dnum="EP844265A"><text>EP-844 265</text></patcit> and <patcit id="pcit0007" dnum="EP933377A"><text>EP-933 377</text></patcit>.

0049Among fluorosilanes there may be cited the compounds of formulas: <chemistry id="chem0001" num="0001"><img file="EP1636616B1_D0001.tif" /></chemistry> n= 5, 7, 9 or 11 and R is an alkyl radical, typically a C₁-C₁₀ alkyl radical such as -CH₃, -C₂H₅ and -C₃H₇ ;         CF₃CH₂CH₂ SiCl₃; <chemistry id="chem0002" num="0002"><img file="EP1636616B1_D0002.tif" /></chemistry> and <chemistry id="chem0003" num="0003"><img file="EP1636616B1_D0003.tif" /></chemistry> n' = 7 or 9 and R is as defined above.

0050Compositions containing fluoro compounds also useful for making the top coat are disclosed in <patcit id="pcit0008" dnum="US6183872B"><text>US 6,183,872</text></patcit>.

0051The silicon-containing organic fluoropolymer of <patcit id="pcit0009" dnum="US6183872B"><text>US 6,183,872</text></patcit> is represented by the general formula and has a number average molecular weight of from 5x10² to 1x10⁵. <chemistry id="chem0004" num="0004"><img file="EP1636616B1_D0004.tif" /></chemistry><chemistry id="chem0005" num="0005"><img file="EP1636616B1_D0005.tif" /></chemistry> wherein Rf represents perfluoroalkyl ; Z represents fluoro or trifluoromethyl ; a, b, c, d and e each independently represent 0 or an integer of 1 or above, provided that a + b + c + d + e is not less than 1 and the order of the repeating units parenthesized by subscripts a, b, c, d and e occuring in the formula is not limited to that shown ; Y represents hydrogen or alkyl containing 1 to 4 carbon atoms ; X represents hydrogen, bromo or iodo ; R¹ represents hydroxy or a hydrolyzable substituent group ; R² represents hydrogen or a monovalent hydrocarbon group ; I represents 0, 1 or 2 ; m represents 1, 2 or 3 ; and n" represents an integer of 1 or above, preferably 2 or above.

0052An other class of preferred compositions for forming the initial top coat are those containing fluoropolyether groups, in particular polyfluoropolyether groups and in particular perfluoropolyether groups. A particular preferred class of compositions containing fluoropolyether groups is disclosed in <patcit id="pcit0010" dnum="US6277485B"><text>US-6,277,485</text></patcit>.

0053The anti-soiling top coats of <patcit id="pcit0011" dnum="US6277485B"><text>US-6,277,485</text></patcit> are at least partially cured coatings comprising a fluorinated siloxane prepared by applying a coating composition (typically in the form of a solution) comprising at least one fluorinated silane of the following formula :         R_f-[-R¹-SiY_3-xR²X]_y wherein : R_f is a monovalent or divalent polyfluoropolyether group, R¹ is a divalent alkylene group, arylene group, or combinations thereof, optionally containing one or more heteroatoms or functional groups and optionally substituted with halids, and preferably containing 2 to 16 carbon atoms ; R² is a lower alkyl group (i.e., a(C₁-C₄) alkyl group) ; Y is a halid, a lower alkoxy group (i.e., a(C₁-C₄) alkoxy group, preferably, a methoxy or ethoxy group), or a lower acyloxy group (i.e., -OC(O)R³ wherein R³ is a (C₁-C₄) alkyl group) ; x is O or 1 ; and y is 1 (R_f is monovalent) or 2 (R_f is divalent). Suitable compounds typically have a molecular weight (number average) of at least about 1000. Preferably, Y is a lower alkoxy group and R_f is a perfluoropolyether group.

0054A commercial composition for making the top coat is the composition KP 801M commercialized by SHINETSU.

0055Generally, the initial outermost coating layer of the coated lens has a thickness ranging from 1 to 100 nm, preferably 1 to 60 nm, more preferably 1 to 5 nm.

0056Preferably, the initial hydrophobic top coat of the coated lens is deposited on an anti-reflecting coating.

0057Anti-reflecting coatings and their methods of making are well known in the art. The anti-reflecting coating can be any layer or stack of layers which improve the anti-reflective properties of the finished lens.

0058The anti-reflecting coating may preferably consist of a mono or multilayer film of dielectric materials such as SiO, SiO₂, Si₃N₄, TiO₂, ZrO₂, La₂O₃, MgF₂ or Ta₂O₅ or mixtures thereof.

0059The anti-reflecting coating can be applied in particular by vacuum deposition according to one of the following techniques : <ol id="ol0001" compact="compact" ol-style=""><li>1. by evaporation, optionally ion beam assisted ;</li><li>2. by spraying using an ion beam ;</li><li>3. by cathode sputtering ; or</li><li>4. by plasma assisted vapor - phase chemical deposition.</li></ol>

0060In case where the film includes a single layer, its optical thickness must equal to λ/4 where λ is a wavelength of 450 to 650 nm.

0061Preferably, the anti-reflecting coating is a multilayer film comprising three or more dielectric material layers of alternatively high and low refractive indexes.

0062A preferred anti-reflecting coating comprises a stack of four layers formed by vacuum deposition, for example a first ZrO₂ layer having an optical thickness of about 35 to 75 nm, a second SiO₂ layer having an optical thickness of about 20 to 40 nm, a third ZrO₂ layer having an optical thickness of about 120 to 190 nm and a fourth SiO₂ layer having an optical thickness of about 100 to 160 nm (optical thickness are for a wavelength λ = 550 nm).

0063As already indicated, the coated lens preferably comprises a scratch-resistant coating layer, the anti-reflecting coating layer being typically deposited on the scratch-resistant coating layer.

0064Any know optical scratch-resistant coating composition can be used to form the scratch-resistant coating. Thus, the scratch-resistant coating composition can be a UV and/or a thermal curable composition.

0065By definition, a scratch-resistant coating is a coating which improves the abrasion resistance of the finished optical article as compared to a same optical article but without the scratch-resistant coating.

0066Preferred scratch-resistant coatings are those made by curing a precursor composition including epoxyalkoxysilanes or a hydrolyzate thereof and a curing catalyst. Preferably the scratch resistant coatings contain at least one inorganic filler such as SiO₂ and/or metal oxides colloïds. Examples of such compositions are disclosed in <patcit id="pcit0012" dnum="US4211823A"><text>US 4,211,823</text></patcit>, <patcit id="pcit0013" dnum="WO9410230A"><text>WO 94/10230</text></patcit>, <patcit id="pcit0014" dnum="US5015523A"><text>US 5,015,523</text></patcit>.

0067The most preferred scratch-resistant coating compositions are those comprising as the main constituents an epoxyalkoxysilane such as, for example, λ-glycidoxypropyltrimethoxysilane (GLYMO) and a dialkyldialkoxysilane such as, for example dimethyldiethoxysilane (DMDES), colloidal silica and a catalytic amount of a curing catalyst such as aluminum acetylacetonate or a hydrolyzate thereof, the remaining of the composition being essentially comprised of solvents typically used for formulating these compositions.

0068The scratch-resistant coating may comprise an effective amount of at least one coupling agent.

0069The preferred coupling agent is a pre-condensed solution of an epoxyalkoxysilane and an unsatured alkoxysilane, preferably comprising a terminal ethylenic double bond.

0070Examples of epoxyalkoxysilanes are γ-glycidoxypropyltermethoxysilane, γ-glycidoxyprolylpentamethyldisiloxane, γ-glycidoxypropylmethyldiisopropenoxysilane, (γ-glycidoxypropyl)-methyldiethoxysilane, γ-glycidoxypropylmethylethoxysilane, γ-glycidoxypropyldiisopropylethoxysilane and (γ-glycidoxypropyl)bis(trimethylsiloxy)methylsilane.

0071The preferred epoxyalkoxysilane is (γ-glycidoxypropyl)trimethoxysilane.

0072The unsatured alkoxysilane can be a vinylsilane, an allylsilane, an acrylic silane or a methacrylic silane.

0073Examples of vinylsilanes are vinyltri(2-methoxyethoxy)silane, vinyltrisisobutoxysilane, vinyltri-t-butoxysilane, vinyltriphenoxysilane, vinyltrimethoxysilane, vinyltriisopropoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinylmethyldiethoxysilane, vinylmethyldiacetoxysilane, vinylbis(trimethylsiloxy)silane and vinyldimethoxyethoxysilane.

0074Examples of allylsilanes are allyltrimethoxysilane, alkyltriethoxysilane and allyltris(trimethylsiloxy)silane.

0075Examples of acrylic silanes are 3-acryloxypropyltris (trimethylsiloxy)silane, 3-acryloxypropyltrimethoxysilane, acryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethylbis(trimethylsiloxy)silane, 3-acryloxypropyldimethylmethoxysilane, n-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane.

0076Examples of methacrylic silanes are 3-methacryloxypropyltris (vinyldimethoxysiloxy)silane, 3-methacryloxypropyltris (trimethylsiloxy)silane, 3-methacryloxypropyltris(methoxyethoxy)silane, 3-metacryloxypropyltrimethoxysilane, 3-methacryloxypropylpentamethyl disiloxane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxpropylmethyldiethoxysilane, 3-methacryloxypropyldimethyl methoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-methacryloxypropenyltrimethoxysilane and 3-methacryloxypropylbis (trimethylsiloxy)methylsilane.

0077The preferred silane is acryloxypropyltrimethoxysilane.

0078Preferably, the amounts of epoxyalkoxysilane(s) and unsaturated alkoxysilane(s) used for the coupling agent preparation are such that the weight ratio. <maths id="math0001" num=""><math display="block"><mi mathvariant="normal">R</mi><mo>=</mo><mfrac><mi>weight of epoxyalkoxysilane</mi><mi>weight of unsaturated alkoxysilane</mi></mfrac></math><img file="EP1636616B1_D0006.tif" /></maths> verifies the condition 0.8 ≤ R ≤ 1.2.

0079The coupling agent preferably comprises at least 50% by weight of solid material from the epoxyalkoxysilane(s) and unsaturated alkoxysilane(s) and more preferably at least 60% by weight.

0080The coupling agent preferably comprises less than 40% by weight of liquid water and/or organic solvent, more preferably less than 35% by weight.

0081The expression "weight of solid material from epoxyalkoxy silanes and unsaturated alkoxysilanes" means the theoretical dry extract from those silanes which is the calculated weight of unit Q_k Si O_(4-K)/2 Q_k Si O_(4K)/2 comes from Q_k Si R'O_(4-k) where Si R' reacts to form Si OH on hydrolysis.

0082k is an integer from 1 to 3 and is preferably equal to 1.

0083R' is preferably an alkoxy group such as OCH₃.

0084The water and organic solvents referred to above come from those which have been initially added in the coupling agent composition and the water and alcohol resulting from the hydrolysis and condensation of the alkoxysilanes present in the coupling agent composition.

0085Preferred preparation methods for the coupling agent comprises : <ol id="ol0002" compact="compact" ol-style=""><li>1) mixing the alkoxysilanes ;</li><li>2) hydrolysing the alkoxysilanes, preferably by addition of an acid, such as hydrochloric acid ;</li><li>3) stirring the mixture ;</li><li>4) optionally adding an organic solvent;</li><li>5) adding one or several catalyst(s) such as aluminum acetylacetonate ;</li><li>6) stirring (typical duration : overnight).</li></ol>

0086Typically the amount of coupling agent introduced in the scratch-resistant coating composition represents 0.1 to 15% by weight of the total composition weight, preferably 1 to 10% by weight.

0087The scratch-resistant coating composition can be applied using any classical method such as spin, dip or flow coating.

0088The scratch-resistant coating composition can be simply dried or optionally pre-cured before application of the subsequent anti-reflecting coating. Depending upon the nature of the scratch-resistant coating composition thermal curing, UV-curing or a combination of both can be added.

0089Thickness of the scratch-resistant coating, after curing, usually ranges from 1 to 15 µm, preferably from 1.5 to 6 µm.

0090The scratch-resistant coating composition may also comprise at least one hydrophobic surfactant.

0091By hydrophobic surfactant, there is meant a surfactant that increases the hydrophobic properties (for example decreasing the surface energy) of the cured scratch-resistant coating compared to the same cured coating without the surfactant.

0092Examples of surfactants are : <ul id="ul0002" list-style="none" compact="compact"><li>From Dow Corning : silicones, organosilanes, fluorosilane ;</li><li>From Witco : silicones, modified trisiloxane, acrylate, modified silicone copolymer.</li></ul>

0093Preferred surfactants are fluorinated compounds and in particular fluorinated silicon compounds, in particular the fluorinated silicon compounds disclosed above.

0094A preferred hydrophobic surfactant is Fluorad FC 430 commercialized by 3M, or EFKA-3034 from EFKA.

0095EFKA-3034 is a fluorocarbon containing organically modified polysiloxane.

0096Amount of surfactant typically ranges from 0.01 to 0.5 wt%.

0097The coated lens also preferably comprises a primer coating layer for improving adhesion of the scratch-resistant coating to the lens substrate and/or impact resistance of the lens.

0098The primer coating can be any coating typically used for improving impact resistance and/or adhesion of the scratch-resistant coating of a finished optical article.

0099By definition, an impact-resistant primer coating is a coating which improves the impact resistance of the finished optical article as compared with the same optical article but without the impact-resistant primer coating.

0100Typical primer coatings are (meth)acrylic based coatings and polyurethane based coatings.

0101(Meth)acrylic based coatings are, among others, disclosed in <patcit id="pcit0015" dnum="US5015523A"><text>US 5,015,523</text></patcit> whereas thermoplastic and crosslinked based polyurethane resin coatings are disclosed inter alia, in Japanese Patents <patcit id="pcit0016" dnum="JP63141001A"><text>63-141001</text></patcit> and <patcit id="pcit0017" dnum="JP63087223A"><text>63-87223</text></patcit>, <patcit id="pcit0018" dnum="EP0404111A"><text>EP 0 404 111</text></patcit> and <patcit id="pcit0019" dnum="US5316791A"><text>US 5,316,791</text></patcit>.

0102In particular, the primer coating according to the invention can be made from a latex composition such as a poly(meth)acrylic latex, a polyurethane latex or a polyester latex.

0103Among the preferred (meth)acrylic based primer coating compositions there can be cited polyethyleneglycol(meth)acrylate based compositions such as, for example, tetraethyleneglycoldiacrylate, polyethyleneglycol (200) diacrylate, polyethyleneglycol (400) diacrylate, polyethyleneglycol (600) di(meth)acrylate, as well as urethane (meth)acrylates and mixtures thereof.

0104Preferably, the primer coating has a glass transition temperature (Tg) of less than 30°C.

0105Among the preferred primer coating compositions, there may be cited the acrylic latex commercialized under the name ACRYLIC LATEX A-639 commercialized by ZENECA and polyurethane latex commercialised under the names of W-240 and W-234 by BAXENDEN.

0106In a preferred embodiment, the primer coating may also include an effective amount of a coupling agent in order to promote adhesion of the primer coating to the optical substrate and/or to the scratch-resistant coating.

0107The same coupling agents, in the same amounts, as for the scratch-resistant coating compositions can be used with the primer coating composition.

0108The primer coating composition can be applied using any classical method such as spin, dip, or flow coating.

0109Depending upon the nature of the impact-resistant primer coating composition, thermal curing, UV-curing or a combination of both can be used.

0110Thickness of the primer coating, after curing, typically ranges from 0.05 to 20 µm, preferably 0.5 to 10 µm and more particularly from 0.6 to 6 µm.

0111The lens substrate can be made from any material used in the optical field, such as mineral or organic glass, preferably an organic glass.

0112Examples of such lens substrates are : <ul id="ul0003" list-style="dash" compact="compact"><li>diethylene glycol bis(allylcarbonate) polymers and copolymers based substrates ;</li><li>(meth)acrylic polymers and copolymers based substrates, such as substrates comprising (meth)acrylic polymers and copolymers derived from bisphenol-A ;</li><li>thio(meth)acrylic polymers and copolymers based substrates ;</li><li>polythiourethane polymers and copolymers based substrates ;</li><li>epoxy and/or episulfide polymers and copolymers based substrates ; and</li><li>polycarbonate based substrates.</li></ul>

0113In an other embodiment of the invention, the initial outermost coating layer of the coated lens is comprised of an outer superficial portion of a scratch-resistant coating containing at least one hydrophobic surfactant.

0114The scratch-resistant coating can be any of the above described coating which includes at least one hydrophobic surfactant as disclosed above.

0115Preferably, the hydrophobic surfactant is a fluorinated compound and in particular silanes and silazanes bearing at least one fluorocarbon, polyfluorocarbon, fluoropolyether or polyfluoropolyether group as disclosed previously.

0116Typically, this outer superficial portion of the scratch-resistant coating has a thickness of 1 to 100 nm, preferably 1 to 30 nm, more preferably 1 to 10 nm, and even better 1 to 5 nm.

0117Otherwise, the treatment of the outer superficial portion of the scratch-resistant coating is the same as previously disclosed.

0118It is particularly surprising to see that, for low thicknesses (30 nm or less) of initial outermost coating layer containing fluorinated compound(s), it is possible to completely eliminate fluorine at the surface of the lens after step (b).

0119Indeed, no fluorine is detectable by X-ray photoelectron spectroscopy (XPS) Al Kalpha after the treatment of step (b).

0120In another embodiment, the initial outermost coating can be the outermost coating obtained by a sol/gel process, of an anti-reflective stack.

0121The thickness of such outermost coating is generally comprised between 60 nm and 120 nm, preferably between 70 and 100 nm and has a low refractive index value, generally less or equal than 1.45 (preferably from 1.38 to 1.44).

0122The outermost coating layer or coating is optically functional and contributes to the AR performances of the whole stack.

0123The outermost coating preferably comprises a hydrolyzate of a di, tri or tetraalkoxysilane, preferably an epoxysilane hydrolyzate and optionally low refractive index filler such as SiO₂.

0124Such outermost coatings are described in, for instance, the following patents: <ul id="ul0004" list-style="none" compact="compact"><li><patcit id="pcit0020" dnum="US4590117A"><text>US 4,590,117</text></patcit>, <patcit id="pcit0021" dnum="US5173368A"><text>US 5,173,368</text></patcit>, <patcit id="pcit0022" dnum="US5104692A"><text>US 5,104,692</text></patcit>, <patcit id="pcit0023" dnum="US4687707A"><text>US 4,687,707</text></patcit> and <patcit id="pcit0024" dnum="EP1279443A"><text>EP 1 279 443</text></patcit>.</li></ul>

0125In the two cited latter documents, a fluoroalkoxysilane component is used as a precursor of the final matrix constituting the initial outermost coating of the AR stack and lowering its index.

0126The last step of the process of the invention comprises the deposition on the treated surface obtained after step b) of a layer of a final coating having surface properties different from those of the initial outermost coating.

0127Preferably, the final coating has a contact angle with water of at least 100°.

0128Also preferably, the final coating has a surface energy of 25 mJ/m² or less, preferably of 22 mJ/m² or less and more preferably of 15 mJ/m² or less and even better of 12 mJ/m² or less.

0129Any coating typically used as anti-soil top coat can be used for the final coating provided it has surface properties different from those of the initial outermost coating, and in particular, improved hydrophobic properties, such as an increased contact angle with water or a lower surface energy, or a smaller hysteresis between advancing and receding contact angle of an aliphatic compound (squalene).

0130Preferred final coating may be any of the hydrophobic top coat disclosed hereabove, and in particular those disclosed in patent <patcit id="pcit0025" dnum="US6277485B"><text>US 6,277,485</text></patcit> and <patcit id="pcit0026" dnum="US6183872B"><text>US 6,183,872</text></patcit>. This final coating may be deposited by any know process, and in particular by vacuum, dip, spin, spray or stamping coating.

0131Generally, the final coating has a thickness of 1 to 100 nm, preferably 2 to 60 nm, more preferably 1 to 60 nm, and even better 2 to 5 nm.

0132The process of the invention may further comprise a step of edging the coated lens either before treatment step (b) with activated chemical species or after this step and before step (c) of deposition of the final coating, preferably before step (b).

0133Performing an edging step before treatment step (b) with activated chemical species requires that the initial outermost coating layer has a surface energy relatively high, typically of at least 15 mJ/m² in order to obtain a good adhesion to the maintaining pad during the edging operation.

0134Alternatively, a temporary coating may be deposited on top of the initial outermost coating prior to the edging operation, which coating is thereafter eliminated.

0135Such temporary coating may be mineral coating, in particular a coating comprised of a metal fluoride or a mixture of metal fluorides, and metal oxide or a mixture of metal oxides.

0136As fluorides, there may be cited MgF₂, LaF₃, AlF₃ or CF₃.

0137As metal oxides, there may be cited aluminum oxides, zirconium oxides and praseodymium oxides.

0138A preferred mixture is a mixture of alumina and praseodymium oxide. When made of mineral material, the thickness of the temporary layer is typically of 50 nm or less, generally of 1 to 50 nm, and preferably of 5 to 50 nm. The temporary coating may also be made of inks typically used for marking ophthalmic lenses or the resins making the binder of these inks.

0139In that case, it is possible to have coating of higher thicknesses than when pure mineral coatings are used. These thicknesses may range from 5 to 1.50 micrometers. Prefer resins are alkyde resins.

0140After the edging step, the temporary protective coating may be eliminated with a liquid medium or by dry sweeping or by combination of both.

0141Elimination with a liquid medium is preferably made with an acidic solution, in particular a solution of orthophosphoric acid with molarities ranging from 0.01 to 1 N.

0142The acidic solution may also include surfactants, anionic, cationic or amphotere.

0143After elimination of the temporary protective coating, the initial outermost coating layer of the coated lens may be subjected to the treatment with activated chemical species (b).

0144Subjecting the coated lens to an edging step before treatment with activated chemicals species (b) is preferred. However, it is also possible to edge the lenses after treatment (b). In this situation, no temporary coating will be required as treatment with activated chemical species typically results in an outer surface of the coated lens which has the required property of adhesion to the maintaining pad of the edging apparatus.

0145Thus, the edging step can be easily performed before step (b) and without the need of a temporary protective coating.

EXAMPLES 1 AND 2 AND COMPARATIVE EXAMPLES A TO C

0146Various coated lenses are treated using steps (a) and (b) of the process of the invention and for comparison using a vacuum oxygen plasma instead of the treatment step (b) of the invention.

0147The contact angles with water and the surface energy of the lens surface after treatment were measured and calculated and homogeneity was determined.

0148The compositions and structures of the coated lenses, the parameters of the treatments and the results are given below :

Coated lens n°1

0149The lens is coated, starting from the substrate, with a primer coating, a scratch-resistant coating, an anti-reflective stack and a hydrophobic top coat.

Substrate

:

0150<dl id="dl0001" compact="compact"><dt>Composition :</dt><dd>polymerized diethylene glycol diallyl carbonate (CR39^® - ORMA^® lens from ESSILOR)</dd></dl>

Primer coating :

0151<dl id="dl0002" compact="compact"><dt>Composition</dt><dd>: polyurethane latex W 234 from Baxenden.</dd><dt>Thickness</dt><dd>: about 1 µm.</dd><dt>Deposition process</dt><dd>: dip coating</dd></dl>

Scratch-resistant coating

0152<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="77mm" /><colspec colnum="2" colname="col2" colwidth="63mm" /><thead><row><entry align="center" valign="top"><b>Composition</b></entry><entry align="center" valign="top"><b>Parts by weight</b></entry></row></thead><tbody><row><entry align="center">γ-glycidoxypropyltrimethoxysilane</entry><entry align="center">224</entry></row><row><entry align="center">HCl 0.1N</entry><entry align="center">80.5</entry></row><row><entry align="center">Dimethyldiethoxy silane</entry><entry align="center">120</entry></row><row><entry align="center">Colloïdal silica (30% in methanol)</entry><entry align="center">718</entry></row><row><entry align="center">Aluminum acetylacetonate</entry><entry align="center">15</entry></row><row><entry align="center">Ethylcellosolve</entry><entry align="center">44</entry></row><row><entry align="center">Hydrophobic surfactant (FLUORAD FC430 from 3M)</entry><entry align="center">0,1 % of the total weight of the composition</entry></row></tbody></tgroup></table></tables><dl id="dl0003" compact="compact"><dt>Thickness</dt><dd>: about 3.5 µm</dd><dt>Deposition process</dt><dd>: dip coating</dd></dl>

Anti-reflective coating

0153Stack of 4 mineral layers comprising, starting from the layer closest to the substrate. <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="32mm" /><colspec colnum="2" colname="col2" colwidth="57mm" /><thead><row><entry align="center" valign="top"><b>Composition</b></entry><entry align="center" valign="top"><b>Optical thickness (nm) at λ = 550 nm</b></entry></row></thead><tbody><row><entry align="center">First layer: ZrO₂</entry><entry align="center">55</entry></row><row><entry align="center">Second layer: SiO₂</entry><entry align="center">30</entry></row><row><entry align="center">Third layer ZrO₂</entry><entry align="center">160</entry></row><row><entry align="center">Fourth layer: SiO₂</entry><entry align="center">120</entry></row></tbody></tgroup></table></tables>

0154The layers are vacuum deposited.

Hydrophobic top coat

0155<dl id="dl0004" compact="compact"><dt>Composition</dt><dd>: Fluorosilazane commercialized by SHIN ETSU under the name KP 801 M</dd><dt>Thickness</dt><dd>: 2 to 5 nm</dd><dt>Deposition process</dt><dd>: Evaporation</dd></dl>

TREATMENT N°1

0156This treatment is a corona discharge treatment at atmospheric pressure according to the invention having the following characteristics : <dl id="dl0005" compact="compact"><dt>Type of treatment</dt><dd>: Corona discharge</dd><dt>Pressure</dt><dd>: 750-760 mm Hg</dd><dt>Power</dt><dd>: 800 W</dd><dt>Active species</dt><dd>: Free radicals</dd><dt>Duration</dt><dd>: 10 seconds</dd></dl>

TREATMENT N°2

0157This treatment is the same as treatment n° 1 but with a duration of 20 seconds.

TREATMENT N°3

0158This treatment is an oxygen plasma treatment under vacuum which is outside the scope of the present invention having the following characteristics. <dl id="dl0006" compact="compact"><dt>Type of treatment</dt><dd>: oxygen plasma</dd><dt>Pressure</dt><dd>: 200 mbars</dd><dt>Power</dt><dd>: 600 W</dd><dt>Active species</dt><dd>: Ions</dd><dt>Duration</dt><dd>: 20 seconds</dd></dl>

TREATMENT N°4

0159This treatment is an oxygen plasma treatment under vacuum which is outside the scope of the present invention having the following characteristics. <dl id="dl0007" compact="compact"><dt>Type of treatment</dt><dd>: oxygen plasma</dd><dt>Pressure</dt><dd>: 200 mbars</dd><dt>Power</dt><dd>: 600 W</dd><dt>Active species</dt><dd>: Ions</dd><dt>Duration</dt><dd>: 10 seconds</dd></dl>

TREATMENT N°5

0160This treatment is an oxygen plasma treatment under vacuum which is outside the scope of the present invention having the following characteristics. <dl id="dl0008" compact="compact"><dt>Type of treatment</dt><dd>: oxygen plasma</dd><dt>Pressure</dt><dd>: 300 mbars</dd><dt>Power</dt><dd>: 300 W</dd><dt>Active species</dt><dd>: Ions</dd><dt>Duration</dt><dd>: 10 seconds</dd></dl><tables id="tabl0003" num="0003"><table frame="all"><title><b>TABLE I</b></title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="24mm" /><colspec colnum="2" colname="col2" colwidth="20mm" /><colspec colnum="3" colname="col3" colwidth="21mm" /><colspec colnum="4" colname="col4" colwidth="38mm" /><colspec colnum="5" colname="col5" colwidth="39mm" /><colspec colnum="6" colname="col6" colwidth="26mm" /><thead><row><entry align="center" valign="top"><b>Example n°</b></entry><entry align="center" valign="top"><b>Coated lens n°</b></entry><entry align="center" valign="top"><b>Treatment n°</b></entry><entry align="center" valign="top"><b>Surface Energy after treatment (mJ/m²)</b></entry><entry align="center" valign="top"><b>Contact angle with water after treatment</b></entry><entry align="center" valign="top"><b>Homogeneity</b></entry></row></thead><tbody><row><entry align="center">Comparative A</entry><entry align="center">1</entry><entry align="center">3</entry><entry align="center">> 70 to 50 (*)</entry><entry align="center">-</entry><entry align="center">0</entry></row><row><entry align="center">Comparative B</entry><entry align="center">1</entry><entry align="center">4</entry><entry align="center">> 70 to 50 (*)</entry><entry align="center">60°</entry><entry align="center">0</entry></row><row><entry align="center">Comparative C</entry><entry align="center">1</entry><entry align="center">5</entry><entry align="center">> 70 to 50 (*)</entry><entry align="center">-</entry><entry align="center">0</entry></row><row><entry align="center">1</entry><entry align="center">1</entry><entry align="center">1</entry><entry align="center">> 70</entry><entry align="center">< 5°</entry><entry align="center">+</entry></row><row><entry align="center">2</entry><entry align="center">1</entry><entry align="center">2</entry><entry align="center">> 70</entry><entry align="center">< 5°</entry><entry align="center">+</entry></row></tbody></tgroup><tgroup cols="6" rowsep="0"><colspec colnum="1" colname="col1" colwidth="24mm" /><colspec colnum="2" colname="col2" colwidth="20mm" /><colspec colnum="3" colname="col3" colwidth="21mm" /><colspec colnum="4" colname="col4" colwidth="38mm" /><colspec colnum="5" colname="col5" colwidth="39mm" /><colspec colnum="6" colname="col6" colwidth="26mm" /><tbody><row><entry namest="col1" nameend="col6" align="justify">(*) depending on the position of the measurements on the lens surface 0 = not good + = good</entry></row></tbody></tgroup></table></tables>

EXAMPLES 3 TO 5 AND COMPARATIVE EXAMPLE D TO F

0161Various coated lenses were treated according to the process of the invention. After the treatment with the active chemical species, the treated lenses were coated by dipping in a 0.1 weight % OPTOOL DSX solution in perfluorohexane and the lenses were heated in an oven at 50°C for 3 hours.

0162The obtained lenses are submitted to an adhesion test: Following is the protocole.

0163The lenses were then dipped a first time in perfluorohexane for 1 minute.

0164Contact angle with water of the lens surface was measured both before and after dipping in the solvent at 21°C +/- 1°C.

0165Ink test was also performed before and after dipping in solvent.

0166The lenses are thereafter dipped a second time for 2 minutes in the solvent. The resulting lenses are submitted to the ink test.

0167The characteristics of the coated lenses, if different from lens n°1, are given below.

0168For comparison, similar lenses which have not been treated according to the invention are submitted to the same dipping in the solvent (contact angles with water and ink test are measured and performed for these lenses).

0169If the ink test fails, it means that the hydrophobic coating OPTOOL DSX has eluted in the perfluorohexane solution, which demonstrates a bad adhesion.

0170Results are given in Table II.

Coated lens n°2

0171This lens comprises only a substrate and a scratch-resistant coating containing a hydrophobic surfactant. <dl id="dl0009" compact="compact"><dt>Substrate</dt><dd>: as in lens n°1 Scratch-resistant</dd><dt>Coating</dt><dd>: as in lens n°1.</dd></dl>

Coated lens n°3

0172Similar to coated lens n°2 but scratch-resistant coating does not include any hydrophobic surfactant. <tables id="tabl0004" num="0004"><table frame="all"><title><b>TABLE II</b></title><tgroup cols="9"><colspec colnum="1" colname="col1" colwidth="24mm" /><colspec colnum="2" colname="col2" colwidth="17mm" /><colspec colnum="3" colname="col3" colwidth="21mm" /><colspec colnum="4" colname="col4" colwidth="20mm" /><colspec colnum="5" colname="col5" colwidth="29mm" /><colspec colnum="6" colname="col6" colwidth="15mm" /><colspec colnum="7" colname="col7" colwidth="18mm" /><colspec colnum="8" colname="col8" colwidth="13mm" /><colspec colnum="9" colname="col9" colwidth="13mm" /><thead><row><entry align="center" valign="top"><b>Example n°</b></entry><entry align="center" valign="top"><b>Coated lens n°</b></entry><entry align="center" valign="top"><b>Treatment n°</b></entry><entry align="center" valign="top"><b>Contact angle with water before treatment</b></entry><entry align="center" valign="top"><b>Contact angle with water after deposition of OPTOOL DSX and before 1^st dip in solvent</b></entry><entry align="center" valign="top"><b>Ink test before 1^st dip</b></entry><entry align="center" valign="top"><b>Contact angle with water after 1^st dip</b></entry><entry align="center" valign="top"><b>Ink test after 1^st dip</b></entry><entry align="center" valign="top"><b>Ink test after 2^nd dip</b></entry></row></thead><tbody><row><entry align="center">3</entry><entry align="center">1</entry><entry align="center">2</entry><entry align="center">113°</entry><entry align="center">112.18°</entry><entry align="center">Pass</entry><entry align="center">116.6°</entry><entry align="center">Pass</entry><entry align="center">Pass</entry></row><row><entry align="center">Comparative D</entry><entry align="center">1</entry><entry align="center">No</entry><entry align="center">113°</entry><entry align="center">112.9°</entry><entry align="center">Pass</entry><entry align="center">-</entry><entry align="center">Fail</entry><entry align="center">Fail</entry></row><row><entry align="center">4</entry><entry align="center">2</entry><entry align="center">2</entry><entry align="center">70°</entry><entry align="center">112.9°</entry><entry align="center">Pass</entry><entry align="center">113.1°</entry><entry align="center">Pass</entry><entry align="center">Pass</entry></row><row><entry align="center">Comparative E</entry><entry align="center">2</entry><entry align="center">No</entry><entry align="center">70°</entry><entry align="center">111.3°</entry><entry align="center">Pass</entry><entry align="center">105.8°</entry><entry align="center">Pass</entry><entry align="center">Fail</entry></row><row><entry align="center">5</entry><entry align="center">3</entry><entry align="center">2</entry><entry align="center">64°</entry><entry align="center">109.9°</entry><entry align="center">Pass</entry><entry align="center">109.8°</entry><entry align="center">Pass</entry><entry align="center">Pass</entry></row><row><entry align="center">Comparative F</entry><entry align="center">3</entry><entry align="center">No</entry><entry align="center">64°</entry><entry align="center">106.6°</entry><entry align="center">Pass</entry><entry align="center">106.4°</entry><entry align="center">Pass</entry><entry align="center">Fail</entry></row></tbody></tgroup></table></tables><ul id="ul0005" list-style="none" compact="compact"><li>OPTOOL DSX : Compound comprising perfluoropropylene groups commercialized by DAIKIN</li></ul>

0173Contact angles with water was measured : <ul id="ul0006" list-style="none" compact="compact"><li>At ambiant temperature T° = 21 °C +/- 1°C</li><li>And relative humidity Rh = 55% +/- 5%</li><li>With a goniometer FTA 200 series from First Ten Angstroms.</li><li>The volume of the drop is 6 µl.</li></ul> Surface energy was calculated according to the model of OWENS-WENDT 2 components using the FTA 32 version 2.0 software or by using "the wetting tension tests kits" by Lectro treat following ASTM D-2578-67 procedure.

0174Ink test was effected by depositing a line of Magic ink n°500 from Teranishi Chemical Industries Ltd on the treated or coated surface of the lens.

0175If the Magic ink line forms discrete dots, the lens is said to pass the test and if the Magic ink line forms a continuous line, the lens is said to fail the test.

0176This test is a determination of the surface properties of the lens.

0177In order to show that there are significant different surface properties between the lenses having a coating replaced according to the invention and the initial lenses, i.e. before submitted to the process of the invention, several measurements are implemented using an apparatus FTA 200 series from First Ten Angstrom on lenses obtained in previous examples 3 and 4 and the initial lenses (coated lenses 1 and 2). The liquid used to measure the properties is an aliphatic compound : squalene. Between 4 to 5 µl of the desire chemical (squalene for those experiments) are deposited on the surface of each tested lens. The needle is left into drop and the pump is activated with the following program : <ul id="ul0007" list-style="bullet" compact="compact"><li>5 mL of squalene are added in 10s</li><li>the pump is stopped for 5s</li><li>5 mL of squalene are added for 10s</li><li>the pump is stopped for 5s (more than 10 mL of squalene are actually deposited due to the fact that the deposition still goes on a certain time after stopping the pump)</li><li>15 mL of squalene are removed in 10s</li><li>the pump is stopped for 5s</li><li>10 mL of squalene are added for 10s</li><li>the pump is stopped for 4s</li><li>15 mL of squalene are removed in 10s</li><li>the pump is stopped for 5s.</li></ul>

017880 images are recorded throughout this process and the contact angles for each of those images are measured.

0179This allowed us to draw the graph contact angle function of time. From this graph, it is then easy to measure the hysteresis. <tables id="tabl0005" num="0005"><table frame="all"><title><b>TABLE III</b></title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="37mm" /><colspec colnum="2" colname="col2" colwidth="35mm" /><colspec colnum="3" colname="col3" colwidth="38mm" /><thead><row><entry namest="col1" nameend="col3" align="center" valign="top"><b>Static contact angle and hysteresis of squalene on different substrates</b></entry></row><row><entry align="center" valign="top"><b>Substrate</b></entry><entry align="center" valign="top"><b>Static contact angle</b></entry><entry align="center" valign="top"><b>Hysteresis</b></entry></row></thead><tbody><row><entry align="center">Coated lens n°2</entry><entry align="center">50°</entry><entry align="center">13.6°</entry></row><row><entry align="center">Ex. 4</entry><entry align="center">70°</entry><entry align="center">7.2°</entry></row><row><entry align="center">Coated lens n°1</entry><entry align="center">80°</entry><entry align="center">14.8-16.8°</entry></row><row><entry align="center">Ex. 3</entry><entry align="center">70°</entry><entry align="center">8.3°</entry></row></tbody></tgroup></table></tables> Coated lens n°2 and 1 are initial lenses, before any treatment, and had been defined previously. It clearly appears that final lenses, after treatment n°2 and OPTOOL DSX deposition have a far better hysteresis compared to initial lenses.