Method for making a water-based Anti-abrasion hard coat composition

Abstract

The invention relates to a method for making a water-based anti-abrasion hard coat. The method comprises steps of (a) hydrolyzing a tetraalkoxysilane compound with an amount of HCl solution having a concentration from 0.025 to 0.05 mol·L⁻¹, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition; (b) adding a hydrolysable epoxysilane compound to the first composition; (c) stirring the composition obtained from step (b); (d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCl concentration to less than 0.025 mol.L-1; and (e) adding a chelate aluminum catalyst under stirring.

Description

METHOD FOR MAKING A WATER-BASED ANTI-ABRASION HARD COAT COMPOSITIONTechnical field

[0001] The present invention relates to a method for making a water-based hard coat composition having good anti-abrasion properties, the related water-based hard coat composition and the optical article containing said hard coat layer. This water-based hard coat composition is intended to be applied on optical articles, in particular on optical substrates such as ophthalmic lenses.Background information and prior art

[0002] Over the past years, optical articles made of polymer materials have become standard over traditional glass-made products. They present advantages such as being lightweight, impact-resistant, and easily molded or colored through the use of several types of dyes. Nevertheless, they also have several drawbacks, notably their tendency to be easily marred and scratched when exposed to abrasives such as dust, cleaning equipment or ordinary weathering. Such exposure leads to transparency reduction, hence impairing the vision of the person using such optical article.

[0003] To overcome such drawbacks, optical materials are coated with one or more layers of hard coat composition(s) at their surface. The hard coat layer is formed after the composition is dried and cured. Generally, most hard coat compositions comprise organic solvents. These organic solvents are required to ensure the coating solution can form a uniform and homogenous layer on the substrate surface and that this uniformity is maintained during the curing process.

[0004] For health and environment purposes, it is desirable to replace organic solvent-based hard coat compositions with water-based compositions. However, the quality of a hard coat composition relies on its mechanical properties (scratch and / or abrasion resistance) and on its optical properties, especially transparency. The solvent plays a crucial role in ensuring optimal stability of the ingredients contained in the hard coat composition. It also influences the surface tension, which impacts the wetting properties of the composition on the surface of the optical article and the cracking behavior of the hard coat during the curing process. For example, if aggregates form in the hard coat composition applied on the substrate, transparency will be reduced due to visible light diffusion. The same effect can occur if the deposited layer of hard coat cracks due to the higher thickness. Therefore, the objective of replacing organic solvents with water is quite challenging.

[0005] In most water-based hard coat composition, the addition of other organic solvents is still necessary. In order to produce a hard coat composition with the minimum amount of organic solvent possible, some polymerizable composition were elaborated with a process in which some solvents are generated during an acidic hydrolysis step.

[0006] Patent application WO2021 / 214198 A1 discloses a water-based anti-abrasion hard coat composition used for the preparation of anti-abrasion coatings on ophthalmic lenses. The composition comprises the product of hydrolysis of an epoxyalkoxysilane SiXYs, wherein X represents a monovalent organic group linked to the silicon atom through a carbon atom and containing at least one epoxy function, and Y represents an alkoxy group; cationic nanoparticles comprising silica, wherein a water sol of said cationic particles is stable at acidic pH; an inorganic non-hydrogen Lewis acid; a surfactant, and less than 0.5 wt% of a water- miscible organic solvent less volatile than water. Moreover, the composition contains no organic solvents other than said water miscible organic solvent that are a product of hydrolysis of the epoxyalkoxysilane.

[0007] 0rganoaluminum compounds are widely used in polymerizable compositions for the manufacturing of optical material due to their catalytic properties. However, according to the teachings of WO2021 / 214198 A1 , during the process of making the hard coat composition and due to the organic nature of ligands complexing the metal ion, when a organoaluminum compound, such as aluminum acetylacetonate (Al(acac)3) is employed in the hard coat composition instead of an inorganic non hydrogen Lewis acid, unsatisfactory results are obtained due to the lack of solubility in the liquid compositions.

[0008] It is therefore an object of the invention to provide a method for making a water-based anti-abrasion hard coat composition that remains stable for a long period when stored at low temperature, while maintaining optimal mechanical and optical properties remain optimal over time once applied to the surface of an optical article. A further objective is to obtain hard coat composition using water as the main solvent. The only organic solvents permitted are those generated by-product from the hydrolysis of alkoxy-, or epoxy- silane compounds present in the composition and in sufficient quantity to enable the use of a chelate aluminum as a catalyst. In addition, the hydrolysis of tetraalkoxysilane compound with specific concentration of HCI solution improves the stability of the obtained hard coat composition.Summary

[0009] The present invention therefore relates to a method for making a water-based antiabrasion hard coat composition comprising steps of:(a) hydrolyzing a tetraalkoxysilane compound with an amount of HCI solution having a concentration from 0.025 to 0.05 mol-L"1, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition;(b) adding a hydrolysable epoxysilane compound to the first composition;(c) stirring the composition obtained from step (b);(d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCI concentration to less than 0.025 mol.L’1; and(e) adding a chelate aluminum catalyst under stirring.The composition can be optionally filtered in an additional step.

[0010] According to another aspect of the invention, the method also comprises the following features alone or in combination:- the water-based anti-abrasion hard coat composition does not contain any colloids;- the amount of HCI solution is in a range from 55% to 96.5% of the stoichiometric amount required to react with the tetraalkoxysilane compound;- the step of hydrolyzing the tetraalkoxysilane compound with the HCI solution is carried out for a period of 50 to 180 minutes, preferably from 50 to 90 minutes;- the tetraalkoxysilane compound is tetraethoxysilane;- the epoxysilane compound is (y-glycidoxypropyl)trimethoxysilane;- optionally, a polyether-modified siloxane wetting agent is added to the mixture during step (d);- the chelate aluminum catalyst is aluminium acetylacetonate (Al(acac)3).

[0011] In another embodiment, the invention also relates to a water-based anti-abrasion hard coat composition obtained by the aforementioned method. This composition presents good stability even when stored for several months.

[0012] According to another aspect of the invention, the water-based anti-abrasion hard coat composition comprises one or more of the following features:- the composition further comprises a polyether-modified siloxane wetting agent in an amount ranging from 0.05 to 5% wt of the composition;- the composition comprises aluminium acetylacetonate (Al(acac)3) as a chelate aluminum catalyst in an amount ranging from 0.5 to 0.6% wt of the composition;- the composition comprises water in an amount higher than 20% wt of the compostion;- a ratio of organic solvent to water is lower than 1.8 after the hydrolysis of both tetraalkoxysilane compound and epoxysilane compound.

[0013] In another embodiment, the invention also relates to an optical article which comprises an anti-abrasion hard coat layer made by curing the water-based anti-abrasion hard coatcomposition obtained from the aforementioned method. This hard coat layer presents good anti-abrasion properties which can remain intact for several months.

[0014] According to another aspect of the invention, the optical article further comprises the following feature:- the anti-abrasion hard coat layer has a thickness of less than 2 pm, preferably 1.5 pm.Detailed description of embodiments

[0015] The terms “comprise” (and any grammatical variation thereof, such as “comprises” and “comprising”), “have” (and any grammatical variation thereof, such as “has” and “having”), “contain” (and any grammatical variation thereof, such as “contains” and “containing”), and “include” (and any grammatical variation thereof, such as “includes” and “including”) are open- ended linking verbs. They are used to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps or components or groups thereof. As a result, a method, or a step in a method, that “comprises,” “has,” “contains,” “includes,” or “consisting of” one or more steps or elements possesses those one or more steps or elements but is not limited to possessing only those one or more steps or elements.

[0016] The term "lens" means an organic or inorganic glass lens, preferably an organic lens, comprising a lens substrate having one or more surfaces which may be coated with one or more coatings of various natures.

[0017] The phrase "organic solvent" means any hydrocarbon-based liquid miscible in water for use in the current embodiments. Exemplary organic solvents comprise methanol, ethanol, butanol.

[0018] In the present description, unless otherwise specified, an optical article / material is understood to be transparent when the observation of an image through said optical article is perceived with no significant loss of contrast, that is, when the formation of an image through said optical article is obtained without adversely affecting the quality of the image. This definition of the term “transparent” can be applied to all objects qualified as such in the description, unless otherwise specified.

[0019] The present invention is a method for making a water-based anti-abrasion hard coat composition, which would be applied on the surface of optical material as an anti-abrasion hard coat. The hard coat composition obtained from the method according the present invention shows optimal mechanical and optical properties, which are preserved over time when applied on substrate surfaces.

[0020] In one embodiment of this invention, this invention relates to a method for making a water-based anti-abrasion hard coat composition comprises steps of:(a) hydrolyzing a tetraalkoxysilane compound with an amount of HCI solution having a concentration from 0.025 to 0.05 mol-L"1, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition;(b) adding a hydrolysable epoxysilane compound to the first composition;(c) stirring the composition obtained from step (b);(d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCI concentration to less than 0.025 mol.L-1; and(e) adding a chelate aluminum catalyst under stirring.The mixture is homogenized to obtain a water-based anti-abrasion hard coat composition. The composition can then be applied to a surface of optical substrate, and cured to obtain an antiabrasion hard coat layer on the surface of optical substrate.

[0021] The use of alkoxysilane compound is known in the field of coatings for optical material, since they provide good anti-abrasion properties. The mixture of the alkoxysilane compounds with HCI solution results in the hydrolysis of the Si-OR bonds (R being an alkyl group). The hydrolysis leads to the formation of the corresponding alcohol.

[0022] A concentration of HCI solution in the range of 0.025 to 0.05 mol.L-1favors a controllable hydrolysis of the alkoxysilane compound, ensuring the stability of the final hard coat composition. As the HCI acts as a catalyst in the hydrolysis reaction, if the concentration of the HCI solution is lower than 0.025 mol.L-1, the hydrolysis reaction will be dramatically slowed and can even be suppressed. On the other hand, if the concentration of the HCI solution exceeds 0.05 mol.L-1, the hydrolysis reaction becomes too fast, generating a high concentration of silanol groups (Si-OH) in a short time. This accelerates the formation of polymer network of Si-O-Si, leading to gel formation within few days and reducing stability of the hard coat composition during the storage. Preferably, the concentration of HCI solution from 0.025 to 0.03 mol.L-1to ensure a controllable hydrolysis reaction and maintain the stability of the obtained hard coat composition. Additionally, it also avoids the use of high amounts of alkoxy silane compounds which generally leads to cracks in the coating with normal thickness (2-3 pm).

[0023] Additionally, the amount of HCI solution is controlled within a range of greater than 50% and up to 100% of the stoichiometric amount required to react with the tetraalkoxysilane compound. This range ensures both stability and the desired anti-abrasion properties of the final hard coat composition. Within this range, the hard coat composition can remain stable for several months at low temperature (approximately 5 to 10 °C). If 50% or less of the stoichiometric amount is used, the obtained composition tends to form a gel within a few hours due to too many non-hydrolysis species. Preferably, the amount is 50.1 % or more, 50.5% or more, 51% or more, 52% or more, 53% or more, 54% or more, or 55% or more of thestoichiometric amount. On the other hand, if more than 100% of the stoichiometric amount is used, the anti-abrasion properties of the composition will decrease much when stored at approximately 5 °C. More preferably, the amount of HCI solution is controlled within the range of 55% to 96.5% of stoichiometric amount of HCI solution required to react with the alkoxysilane compound.

[0024] The alkoxysilane compound selected to prepare the water-based anti-abrasion hard coat composition according to the present invention may be a tetraalkoxysilane compound represented by a compound (I) below:Si(OR)<where R represents alkyl group having at least one carbon atom.

[0025] The tetraalkoxysilane compound may be selected from tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetraisopropyl orthosilicate or tetrabutyl orthosilicate. Other polyalkoxysilanes compounds may also be employed. Preferably, the tetraalkoxysilane compound is tetraethyl orthosilicate (TEOS).

[0026] In addition to the stoichiometric amount of HCI solution, the hydrolysis time is another parameter for obtaining a partially hydrolyzed tetraalkoxysilane compound, thereby ensuring the stability of the obtained hard coat composition. In step (a), the hydrolysis of tetraalkoxysilane compound with HCI solution may be carried out for 50 to 180 minutes. The tetraalkoxysilane compound in step (a) should not be fully hydrolyzed in order to ensure both the stability of the composition and the desired anti-abrasion properties of the hard coat layer. If the hydrolysis time is less than 50 minutes, such as 30 to 40 minutes, the composition remains hazy, which leads to poor anti-abrasion properties and a high haze value of the resulting coating layer. On the other hand, if the hydrolysis time exceeds 180 minutes, the tetraalkoxysilane compound is fully hydrolyzed to silanol species (Si(OH)4), which then start to crosslink with each other. Preferably, the hydrolysis time is from 50 to 90 minutes. The controlled conditions lead to the formation of specific intermediate species, as described below.

[0027] Under such controlled hydrolysis conditions in step (a) (e.g. greater than 50% and up to 100% of stoichiometric amount of HCI solution for 50 to 180 minutes), tetraalkoxysilane compound is not fully hydrolyzed to silanol. Instead, it forms intermediate structures such as species represented by compounds (II), (III) and / or (IV) below, which help moderate the rate of formation of Si-O-Si network during step (b). This moderation is key to achieving good storage stability of the obtained hard coat composition.

[0028] where R represents alkyl group having at least one carbon atom.

[0029] After obtaining the first composition from step (a) (hydrolysis reaction), in step (b), an epoxysilane compound is added to the first composition. The mixture is then stirred to be homogenized (step (C)). According to the present invention, the epoxysilane compound may contain at least 2 alkoxy groups, preferably 3 alkoxy groups such as methoxy (-OCH3) or ethoxy (-OCH2CH3) groups or combination thereof. Examples of suitable epoxysilane compound include y-(glycidoxypropyl)trimethoxysilane (GLYMO), y- (glycidoxypropyl)triethoxysilane (GLYEO), (3,4-epoxycyclohexyl)ethyltrimethoxysilane, (3,4- epoxycyclohexyl)ethyltriethoxysilane, and 3-Glycidoxypropylmethyldiethoxysilane. These examples are not limiting, and other epoxysilane compounds may also be used in the method according to the present invention. Preferably, the epoxysilane compound is y- (glycidoxypropyl)trimethoxysilane (GLYMO) or y- (glycidoxypropyl)triethoxysilane (GLYEO), and more preferably y-(glycidoxypropyl)trimethoxysilane (GLYMO).

[0030] In step (d), an excess amount of water is added to lowering the HOI concentration less than 0.025 mol.L'1(under stirring) thereby minimizing crosslinking of the hydrolyzed tetraalkoxysilane compound at low temperature (approximately 5 to 10 °C). The excess amount of water may be at least 10% wt over the total amount of the hard coat composition. The addition of water promotes the hydrolysis of the epoxysilane compound which contributes to the formation of polar and protic solvent that improve the solubility of the aluminum chelate catalyst in the system and form the corresponding epoxysilanol. This also contributes to controlling the coating thickness to less than 2 pm.

[0031] To promote the polymerization of the epoxysilane compound, in step (e), a Lewis acidbased catalyst may be added to the mixture under stirring to generate the formation of ether bonds via opening of the epoxy rings. Typically, the catalyst employed is an inorganic, non- hydrogen-based Lewis acid, such as an inorganic salt of a multivalent metal. Aluminum saltssuch as aluminum (III) perchlorate (AI(CIC>4)3) can be used for epoxide ring opening synthesis, but such strong acids may reduce the stability of the obtained composition. Preferably, the catalyst used for the method according to the present invention is an aluminum chelate catalyst, wherein the ligands may have a structure represented by (V) or (VI).M1OCCH2COM2(V)M3OCCH2COOM4(V|)wherein M1 , M2, M3 and M4 are independently selected from alkyl groups having 1 to 10 carbon atoms. The aluminum chelate catalyst may be selected from aluminum acetylacetonate, aluminum ethylacetoacetate bisacetylacetonate, aluminum bisethylacetoacetate acetylacetonate, aluminum di-n-butoxide monoethylacetoacetate and aluminum dipropoxide monomethylacetoacetate. Preferably, the aluminum chelate catalyst is aluminum acetylacetonate (Al(acac)3). These examples are provided for illustration and do not limit the choice of catalyst that may be used in the method according to the present invention. Moreover, the aluminum chelate catalyst is added to the mixture in an amount ranging from 0.5 to 0.6% wt of the composition.

[0032] The efficiency of the catalyst depends on the amount of organic solvent generated during the hydrolysis of both the tetraalkoxysilane compound and the epoxysilane compound. Since metal-organic ligands tend to have limited solubility in water-based solution, the inventors determined that the ratio of the total amount of solvent generated during hydrolysis to the total amount of residual water left should be lower than 1 .8 and greater than 0.2.

[0033] In an examplary embodiment, the method for making a water-based anti-abrasion hard coat composition according to the present invention does not require the use of cationic particles. Generally, most hard coat compositions contain cationic particles to provide a stable acidic pH in the composition while also ensuring their compatibility with the other components of the hard coat composition. To avoid a use of any particles that may be incompatible with the composition, the selection of aluminum chelate catalyst and controlled amount of Lewis acid (aluminum chelate catalyst) used for the polymerization provide an effective alternative to ensure the stability of the obtained hard coat composition. This allows an increase of antiabrasion properties due to the high degree of cross-linking of the hydrolyzed alkoxysilane. Furthermore, it also has additional advantage of significantly reducing the manufacturing cost of hard coat composition.

[0034] In addition, during step (d), the method according to the present invention may further comprise the step of adding a polyether-modified siloxane wetting agent to the mixture in an amount ranging from 0.05 to 5% wt of the composition to promote easier spreading of the coating composition on the optical substrate. Preferably, the amount of polyether-modified siloxane wetting agent is in the range from 0.1 to 0.2% wt of the composition. Severalcommercially available wetting agents or surfactants can be used such as BYK347, BYK348 and BYK3455 provided by BYK, Borchi Gol LA50 by OMG Borchers, Capstone FS35 by DuPont and Megaface F477 by DIC. These examples are provided for illustration and do not limit the choice of wetting agent that may be used in the method according to the present invention.

[0035] In another embodiment, the invention also relates to a water-based anti-abrasion hard coat composition obtained from a method comprising steps of:(a) hydrolyzing a tetraalkoxysilane compound with an amount of HCI solution having a concentration from 0.025 to 0.05 mol-L"1, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition;(b) adding a hydrolysable epoxysilane compound to the first composition;(c) stirring the composition obtained from step (b);(d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCI concentration to less than 0.025 mol.L’1; and(e) adding a chelate aluminum catalyst under stirring.The composition comprises the products obtained from the hydrolysis of the tetraalkoxysilane compound and epoxysilane compound, namely the corresponding silanol and epoxysilanol. Upon curing, the epoxysilanol generates a polymer network which primarily constitutes the hard coat layer.

[0036] The composition may comprise organic solvents, such as alcohols, generated during the hydrolysis of the alkoxysilane compound and the epoxysilane compound, together with water. The amount of organic solvent generated should be sufficient to allow the solubilization of the chelate aluminum catalyst. The ratio of the total amount of organic solvent generated during the hydrolysis to the total amount of residual water left should be lower than 1 .8 and greater than 0.2. This ratio ensure adequate solubility of the chelate aluminum catalyst to effectively catalyze the polymerization reaction. In an exemplary embodiment, the amount of water in the hard coat composition should be higher than 20% wt of the composition.

[0037] As described above, the water-based anti-abrasion hard coat composition according to the present invention may contain the chelate aluminum catalyst in an amount ranging from 0.5 to 0.6% wt of the composition, to catalyze the polymerization of the epoxysilane monomer. Examples of suitable chelate aluminum catalysts are described above.

[0038] Also, the water-based anti-abrasion hard coat composition may further comprise a polyether-modified siloxane wetting agent as an additive, in an amount ranging from 0.05 to 5% wt of the composition, preferably from 0.1 to 0.2% wt of the composition. Examples of suitable polyether-modified siloxane wetting agents are described above.

[0039] In another embodiment, the invention also relates to an optical article comprising an anti-abrasion hard coat layer made from a water-based anti-abrasion hard coat composition obtained from a method comprising steps of:(a) hydrolyzing a tetraalkoxysilane compound with an amount of HCI solution having a concentration from 0.025 to 0.05 mol-L"1, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition;(b) adding a hydrolysable epoxysilane compound to the first composition;(c) stirring the composition obtained from step (b);(d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCI concentration to less than 0.025 mol.L’1; and adding a chelate aluminum catalyst under stirring.

[0040] The optical article may be, for example, an optical lens — including ophthalmic lenses, spectacle lenses, camera lenses, and binocular lenses — or other transparent or translucent substrates such as protective screens, display panels, or windows requiring improved abrasion resistance. Preferably, the optical article is an optical lens, particularly ophthalmic lenses and / or spectacle lenses.

[0041] The inventors have discovered that, when applied to the optical substrate, a hard coat layer having a thickness of less than 2 pm, preferably 1.5 pm provides anti-abrasion properties equivalent to or better than those of other available hard coats, which typically exhibit effective anti-abrasion performance at usual applied thicknesses of 2.5 to 3.5 pm. Furthermore, the solid content of the hard coat composition according to the present invention applied on the optical article is approximately 25% wt of the composition, enabling the formation of a hard coat layer with a thickness between 1 and 2 pm, preferably 1.5 pm.

[0042] In an exemplary embodiment, the optical substrate may be coated with one or more functional coatings prior to depositing the water-based anti-abrasion hard coat composition of the present invention. Such functional coatings, commonly used in optics, may include, for example an impact-resistant primer layer, a polarizing coating, a photochromic coating, a myopia controlled red light emission coating or a tinted coating. On the other hand, additional functional coatings may also be further deposited on the anti-abrasion hard coat layer of the present invention such as interferential coatings (antireflective or mirror coatings). These functional layers may be applied depending on the end use of the optical article, whether it is a spectacle lens, an architectural window, an automotive windshield, or an electronic display screen.Example

[0043] It should be understood that the examples of the invention described hereinafter are provided solely for purpose of illustration and as exemplary embodiments of the present invention. Accordingly, the scope of the present invention is defined solely by the appended claims and any equivalents thereof arising from this disclosure.Chemicals used

[0044] A water-based anti-abrasion hard coat composition according to the present invention was prepared using tetraethyl orthosilicate (TEOS, CAS No.: 78-10-4) as the tetraalkylsilane compound, hydrochloric acid (HCI, CAS No.: 7647-01-0), y-(glycidoxypropyl)trimethoxysilane (GLYMO, CAS No.: 2530-83-8) as the epoxysilane compound, (BYK 348) as the polyether- modified siloxane wetting agent, aluminum acetylacetonate (Al(acac)3, CAS No.: 13963-57-0) as the an aluminum chelate catalyst, and deionized (DI) water.Preparation process:

[0045] Approximately 12 g of TEOS were introduced into a conical flask equipped with a water bath on a hotplate. An HCI solution either approximately 0.03 mol.L-1or approximately 0.1 mol.L-1in concentration was added in an amount corresponding to approximately 2.076 g to approximately 4.15 g (covering approximately 50% to 100% of the stoichiometric amount for hydrolyzing TEOS). The mixture was stirred at 700 rpm for 50, 60, 90, 180 minutes and 24 hours at ambient temperature. Next, 7.34 g of GLYMO were introduced into the flask and the mixture was stirred at ambient temperature for 30 minutes. Then, 10 g of DI water were added dropwise over 5 minutes into the flask under stirring. After 30 minutes of additional stirring, 0.54 g of BYK 348 and 0.18 g of Al(acac)3 were added into the flask, followed by stirring for another 30 minutes. The resulting composition was filtered through a 3 pm filter and stored at 5°C for test and application.Viscosity of the composition

[0046] Samples of the prepared compositions were performed viscosity test in order to investigate stability of the hard coat composition. The test was performed by Brookfield viscometer using ULA spindle with 60 rpm at 25 °C.Coating application and testing methods:

[0047] ORMA® lenses samples were coated with each obtained hard coat composition to test the stability at 5°C. Each sample was coated one day after the composition was prepared. The hard coat composition was then stored at 5°C for a month and applied on another lens sample. The process was then repeated for a second month. Coating was applied at the following speed rate: 700 rpm for 3 seconds, 1000 rpm for 5 seconds and 1800 rpm for 15 seconds. The coated samples were pre-cured at 75°C for 15 minutes and post-cured at 100°C for 3 hours.Abrasion resistance (“Bayer sand test”)

[0048] The coated lens was subjected to abrasion in an oscillating abrasive box using sand (about 500 g) for 1 cycle of 300 forward-and-back motions. The degree of abrasion was measured as the change in haze of the article (measured with a hazemeter by Hazegard). Performance were expressed as the Bayer value, calculated as the ratio of the haze of a reference lens to the haze of the tested lens, (Bayer value = haze of the standard I haze of the sample).Scratch resistance (“Hand steel Wool test hereafter” HSW)

[0049] The HSW test was performed on the convex side of the lens only, after post-curing and a 24-hour condition. When an anti-reflective coating was present, the test was conducted after 24-hour conditioning period after the deposition of said anti-reflective coating.

[0050] Lens was manually abraded with extra fine (000#) steel wool, performing 5 back-and- forth strokes (4 to 5 cm amplitude) under constant pressure on the steel wool with the index finger. The applied pressurewas estimated using a balance: the lens was fixed on the balance plate with adhesive tape and pressed with the index finger with the same force as during test. The pressure was approximately 5 kg during forward stokes and approximately 2.5 kg during backward strokes. The obtained lens was visually inspected and assigned an HSW value according to the evaluation table. A higher HSW value indicated greater abrasion of the lens.Properties of the obtained hard coat compositions

[0051] When approximately 50% of the stoichiometric amount of HCI solution (approximately 2.076 g) is used to hydrolyze TEOS, the inventors observed that the composition appearedhazy during hydrolysis and the obtained hard coat composition formed a gel in a few hours. On the other hand, when using at least 55% of the stoichiometric amount of HCI solution (approximately 2.28 g) to hydrolyze TEOS, clear compositions could be obtained. This was observed for both low-concentration HCI solutions (0.03 N) and higher-concentration HCI solutions (0.1 N). Table 1 below shows properties of the obtained hard coat compositions at different hydrolysis conditions.Table 1

[0052] From Table 1 , it can be seen that, except Sample 1 (50% of stoichiometric amount of 0.03 mol.L-1HCI for 60 minutes) and Sample 8 (55% of stoichiometric amount of 0.03 mol.L-1HCI for 24 hours), the obtained hard coat compositions exhibit good anti-abrasion properties. In case of Sample 8, the aggregation of the formed intermediate structures of (II) or (III) makes the further hydrolysis and crosslink in later steps difficult, even at high curing temperature, which nevertheless indicates improved stability of the hard coat composition.

[0053] When the viscosity of the first composition obtained from step (a) (hydrolyzed TEOS composition) is considered (as shown in Table 2), it can be seen that at 100% of the stoichiometric amount of HCI solution (both 0.03 mol.L-1and 0.1 mol.L-1), the first compositionbecame solid within 144 hours. In contrast, at approximately 55% of the stoichiometric amount, the first composition remained stable for at least 312 hours. These results indicated the preferred amount of HCI solution in step (a) is approximately 55% or more and 96.5% or less of the stoichiometric amount of HCI solution having a concentration from 0.025 mol.L-1to 0.05 mol.L-1to hydrolyze TEOS for 50 to 180 minutes. This range facilitates the formation of intermediate structures of (II) or (III) and makes a hard coat composition with both good stability and anti-abrasion properties.Table 2

[0054] As described above, the partial hydrolysis of TEOS in step (a), under specific hydrolysis condition, forms intermediate structures such as the aforementioned species (II), (III) and / or (IV), which help moderate the rate of formation of Si-O-Si network during step (b) (introduction of GLYMO into the mixture). This moderation is key to achieving good storage stability of the obtained hard coat composition.

[0055] Among the tested samples, Sample 4 (96.4% of stoichiometric amount of 0.03 mol.L-1HCI for 60 minutes) showed better anti-abrasion properties compared to other samples. The inventors therefore selected Sample 4 for further testing to compare the properties of the hard coat composition with those of a commercially available hard coat. Table 3 below shows the performance of the hard coat composition Sample 4 stored at 5°C over time, in comparison with a commercially available hard coat (HC-1), and a hard coat composition disclosed in patent application WO2021214198.

[0056] ORMA® lenses samples were also coated with HC-1 and with the hard coat composition disclosed in patent application WO2021214198 as comparative examples. HC-1 is a commercially available hard coat composition disclosed in example 3 of patent EP 0614957 (having a refractive index of 1.47 and a thickness of 3.5 pm). It is based on ahydrolyzate of GLYMO and DMDES (dimethyl diethoxysilane), colloidal silica and aluminium acetylacetonate, followed by deposition of an anti-reflection multilayer interference coating.

[0057] Sand bayer and HSW tests were performed on both comparative hard coat samples and on Sample 4. Table 3

[0058] From Table 3, several points can be observed when analyzing the results. For the water-based anti-abrasion hard coat composition of the present invention, the data show that even after 2 months of storage at 5 °C, the anti-abrasion properties remain well preserved, as indicated by the consistently high Sand Bayer values. The thickness of the coating layer obtained from the water-based hard coat of the present invention increases slightly over time, due to a small increase in viscosity after storage.

[0059] When comparing the water-based anti-abrasion hard coat composition of the present invention with comparative examples, the Sand Bayer values for the inventive hard coat are higher, even with a coating layer of approximately 1 pm thickness, whereas the comparative examples achieve similar results only with significantly thicker layers applied on the lens substrate.

Claims

CLAIMS1 . A method for making a water-based anti-abrasion hard coat composition comprising steps of:(a) hydrolyzing a tetraalkoxysilane compound with an amount of HCI solution having a concentration from 0.025 to 0.05 mol-L"1, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition;(b) adding a hydrolysable epoxysilane compound to the first composition;(c) stirring the composition obtained from step (b);(d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCI concentration to less than 0.025 mol.L’1; and(e) adding a chelate aluminum catalyst under stirring.

2. The method according to claim 1 , wherein the water-based anti-abrasion hard coat composition does not contain any colloids.

3. The method according to claim 1 or 2, wherein the amount of HCI solution is in a range from 55% to 96.5% of the stoichiometric amount required to react with the tetraalkoxysilane compound.

4. The method according to any one of claims 1 to 3, wherein step (a) comprises hydrolyzing the tetraalkoxysilane compound with the HCI solution for a period of 50 to 180 minutes, preferably from 50 to 90 minutes.

5. The method according to any one of claims 1 to 4, wherein the tetraalkoxysilane compound in step (a) is tetraethoxysilane.

6. The method according to any one of claims 1 to 5, wherein the epoxy silane compound instep (b) is (y-glycidoxypropyl)trimethoxysilane.

7. The method according to any one of claims 1 to 6, wherein the method further comprises a step of adding a polyether-modified siloxane wetting agent into the mixture during step (d).

8. The method according to any one of claims 1 to 7, wherein the chelate aluminum catalyst is aluminium acetylacetonate (Al(acac)3).

9. A water-based anti-abrasion hard coat composition obtained from a method comprising steps of:(a) hydrolyzing a tetraalkoxysilane compound with an amount of HCI solution having a concentration from 0.025 to 0.05 mol-L-1, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition;(b) adding a hydrolysable epoxysilane compound to the first composition;(c) stirring the composition obtained from step (b);(d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCI concentration to less than 0.025 mol.L’1; and(e) adding a chelate aluminum catalyst under stirring.

10. The water-based anti-abrasion hard coat composition according to claim 9 further comprising a polyether-modified siloxane wetting agent in an amount ranging from 0.05 to 5% wt of the composition.

11. The water-based anti-abrasion hard coat composition according to claim 9 or 10, wherein the chelate aluminum catalyst is aluminium acetylacetonate (Al(acac)3) in an amount ranging from 0.5 to 0.6% wt of the composition.

12. The water-based anti-abrasion hard coat composition according to any one of claims 9 to 11 , wherein the water-based anti-abrasion hard coat composition comprises water in an amount higher than 20% wt of the composition.

13. The water-based anti-abrasion hard coat composition according to any one of claims 9 to 12, wherein a ratio of organic solvent to water is lower than 1.8 after the hydrolysis of both tetraalkoxysilane compound and epoxysilane compound.

14. An optical article comprising an anti-abrasion hard coat layer made from a waterbased anti-abrasion hard coat composition obtained from a method comprising steps of:(a) hydrolyzing a tetraalkoxysilane compound with an amount of HCI solution having a concentration from 0.025 to 0.05 mol-L-1, the amount corresponding to greater than 50% and up to 100% of the stoichiometric amount, to obtain a first composition;(b) adding a hydrolysable epoxysilane compound to the first composition;(c) stirring the composition obtained from step (b);(d) adding an excess amount of water to hydrolyze the epoxysilane compound, and to lower the HCI concentration to less than 0.025 mol.L’1; and(e) adding a chelate aluminum catalyst under stirring.

15. The optical article according to claim 14, wherein the anti-abrasion hard coat layer has a thickness of less than 2 pm, preferably 1.5 pm.

Images