EP2464610A1

EP2464610A1 - Method for manufacturing a substrate coated with mesoporous antistatic film, and use thereof in ophthalmic optics

Info

Publication number: EP2464610A1
Application number: EP10761052A
Authority: EP
Inventors: Mamonjy Cadet; Mathieu Feuillade
Original assignee: Essilor International Compagnie Generale dOptique SA
Current assignee: EssilorLuxottica SA
Priority date: 2009-08-13
Filing date: 2010-08-12
Publication date: 2012-06-20
Also published as: US9266772B2; US20120141770A1; FR2949111A1; CN102574734A; US20160145479A1; WO2011018590A1; FR2949111B1; US9534160B2; CN102574734B

Abstract

The present invention relates to an item containing a substrate having a main surface coated with a mesoporous antistatic coating, said coating having a refractive index less than or equal to 1.5, and moreover relates to a silica matrix functionalized by hydrophobic ammonium groups. Under certain conditions, the mesoporous antistatic coating consists of a single-layer anti-reflection coating or is part of a single-layer anti-reflection coating. The invention also relates to a method for producing said item and to the use of a mesoporous coating, having a silica matrix functionalized by ammonium groups, as an antistatic coating.

Description

METHOD FOR MANUFACTURING A MESOPOROUS ANTISTATIC FILM-COATED SUBSTRATE AND ITS APPLICATION IN OPTICAL OPTICS

The present invention generally relates to silica-based sol-gel mesoporous coatings having a low refractive index, which further have antistatic properties due to the presence of ammonium groups in their structure, and methods of preparation of these coatings. They are mainly intended to equip substrates made of organic or mineral glass, particularly in the field of ophthalmic optics.

More and more, it is sought to functionalize articles of organic or inorganic glass by depositing on their surface coatings of a few nanometers or micrometers thick intended to give them a particular property according to the intended application. Thus, there are layers with anti-reflective function, anti-abrasion, anti-scratch, shockproof, anti-fog, anti-fouling or antistatic.

It is well known that optics articles, which are composed of substantially insulating materials, tend to have their surface load easily into static electricity, particularly when they are cleaned under dry conditions by rubbing their surface by means of a cloth, a piece of synthetic foam or polyester (triboelectricity). The charges present on their surface create an electrostatic field capable of attracting and fixing objects of very low mass in the vicinity (a few centimeters), generally small particles such as dust, and during all the time the charge remains on the item.

In order to reduce or cancel the attraction of the particles, it is necessary to reduce the intensity of the electrostatic field, that is to say to reduce the number of static charges present on the surface of the article. This can be done by making the charges mobile, for example by introducing a layer of a material inducing a high mobility of "charge carriers". The materials inducing the highest mobility are the conductive materials. Thus, a high conductivity material makes it possible to dissipate the charges more quickly.

The state of the art reveals that an optical article can acquire antistatic properties by incorporating at its surface, in the stack of functional coatings, at least one electrically conductive layer, or "antistatic layer, "these two terms being used interchangeably.

This antistatic layer can most often constitute the outer layer of the stack of functional coatings, an intermediate layer (internal) or be deposited directly on the substrate of the optical article.

By "antistatic" is meant the property of not retaining and / or developing an appreciable electrostatic charge. An article is generally considered to have acceptable antistatic properties, when it does not attract and fix dust and small particles after one of its surfaces has been rubbed with a suitable cloth. It is able to quickly dissipate accumulated electrostatic charges, so that such an article seems more "clean" after wiping.

The ability of a glass to evacuate a static charge obtained after friction by a fabric or by any other method of generating an electrostatic charge (charge applied by corona ...) can be quantified by measuring the dissipation time of said charge. Generally, a glass can be considered antistatic when the discharge time is less than or equal to 500 milliseconds. In the present application, a glass is considered antistatic if its discharge time is less than or equal to 200 milliseconds.

Known antistatic coatings comprise at least one antistatic agent, which is generally an (optionally) doped (semi-) metal oxide, such as tin-doped indium oxide (ITO), tin oxide doped with antimony, vanadium pentoxide, or a conducting polymer with a conjugated structure.

A number of patent applications (US 2004/0209007, US 2002/01 14960 ...) describe articles provided with an antistatic layer based on conductive polymers deposited directly on the substrate of the article and independent of the antireflection coating . However, conductive polymers are much more expensive than conductive metal oxides. In addition, their presence increases the refractive index and the absorption of the coating.

Patents EP 0834092 and US Pat. No. 6,852,406 describe optic articles, in particular ophthalmic lenses, equipped with an anti-reflective stack of mineral nature, comprising a transparent antistatic layer of inorganic nature deposited under vacuum, based on tin-indium oxide. (ITO) or tin oxide. However, the antistatic layers based on ITO are not entirely satisfactory. They have the disadvantage of absorbing in the visible range in a significant way, so that their thickness must be relatively low so as not to affect the transparency properties of an optical article. In addition, these layers have high refractive indices, generally greater than 1.8.

It would be desirable to have antistatic coatings having lower refractive indices, especially less than 1.5.

The preparation of mesoporous silica-based matrix coatings having a low refractive index due to their high porosity is well known and has been described for example in WO 2006/021698, WO 2007/088312 and WO 2007/090983, on behalf of the applicant.

Japanese applications JP 2008-280193 and JP 2009-040967 describe structured mesoporous coatings with silica matrix functionalized with NH ₂ groups, obtained by co-hydrolysis of a tetraalkoxysilane precursor and an alkoxysilane precursor carrying at least one amino group, typically tetraethoxysilane and 3-aminopropyltriethoxysilane, in the presence of a base and a selected cationic porogen among surfactants having a quaternary ammonium group. The coating may optionally undergo a functionalization reaction of the amino groups before or after extraction of the pore-forming agent, by reaction with an organic compound carrying groups reactive with respect to amino groups such as vinyl, carboxy, epoxy or isocyanate. The coatings have a thickness of 50-150 nm, a low refractive index (1, 33-1, 36), and low conductivity.

Langmuir Publications 2002, 18, 972-974, J. Soi Gel Sci. Technol. 2007, 43, 305-31, J. Phys. Chem. B 2002, 106, 6652-6658, Chem. Mater. 2008, 20, 4661-4668, Chem. Common. 2003, 1,146-1,147 and Chem. Common. 2004, 1742-1743 describe the preparation of mesoporous matrix coatings based on silica or polysiloxane functionalized with ammonium groups. They are obtained by acidic condensation of a bridged tetraalkoxysilane or bis (trialkoxysilane) precursor (TEOS tetraethoxysilane or bis (triethoxysilyl) ethane BTSE) and an alkoxysilane precursor bearing at least one amino or ammonium group ( 3-aminopropyltriethoxysilane or N-trimethoxysilylpropyl-N, N, N-trimethylammonium chloride) and a blowing agent, followed by elimination by extraction or heat treatment of the blowing agent. When an alkoxysilane precursor carrying an amino group is used, it is important to use a sufficient amount of acid to protonate the amino group and thereby slow down the condensation reaction of the silanes forming the gel. The pore-forming agent is generally nonionic, of the copolymer type with ethylene oxide and propylene oxide or alkyl monoether polyethylene glycol, but it can also be ionic (cetyltrimethylammonium bromide). Both precursors are generally employed in 1 TEOS molar ratios: 0.05-0.667 organosilane bearing an ammonium group.

These mesoporous matrix-based silica coatings functionalized with amino or ammonium groups have the disadvantage of being sensitive to moisture, since water can easily be adsorbed in the pores of the material.

The present invention therefore aims to provide a transparent optical article, including an ophthalmic lens, having both antistatic properties and a low refractive index.

Another object of the invention is to obtain an optical article whose antistatic properties are stable over time, which is not subject to water absorption, which may have antireflection properties, good mechanical properties, and which retains excellent adhesion properties of the different coating layers to each other.

The Applicant has discovered that certain mesoporous silica-based matrix coatings can be used as antistatic coatings, but also as low refractive index layers of an antireflection coating. The present invention relates to the use of a mesoporous coating having an ammonium-functionalized silica-based matrix as an antistatic coating.

The present invention further relates to an article comprising a substrate having a major surface coated with a mesoporous antistatic coating, said coating having a refractive index of less than or equal to 1.45, better still less than or equal to 1.40, as well as an ammonium-functionalized silica-based matrix which is hydrophobic in nature.

The present invention finally relates to a method of manufacturing a substrate coated with a mesoporous antistatic film, comprising:

a) preparing a precursor soil of a mesoporous antistatic film comprising:

at least one inorganic precursor agent A chosen from the compounds of formula: Si (X) ₄ (I)

in which the X groups, which are identical or different, are hydrolyzable groups preferably chosen from alkoxy, acyloxy and halogen groups, preferably alkoxy, or a hydrolyzate of this precursor agent;

at least one precursor agent B chosen from organosilanes comprising:

α) a silicon atom bearing at least two hydrolyzable groups; and β) at least one ammonium group;

or a hydrolyzate of this precursor agent;

at least one organic solvent, at least one porogenic agent, water and optionally a group X hydrolysis catalyst;

the molar ratio compound B / compound A ranging from 0.1 to 0.8;

b) depositing a film of the precursor sol on a main surface of a substrate;

c) the consolidation of the deposited film;

d) removing the foaming agent from the film resulting from the previous step and recovering a mesoporous antistatic film having a refractive index of less than or equal to 1.5;

the method further comprising:

(i) a step of treating the film after step b) or if it exists, after step c), by at least one hydrophobic reactive compound bearing at least one hydrophobic group; and or

(ii) a step of introducing at least one hydrophobic precursor agent carrying at least one hydrophobic group into the precursor sol before the deposition step b) of the precursor sol film.

The invention will be described in more detail with reference to the appended drawing, in which FIG. 1 represents the evolution of the reflection coefficient of a coating according to the invention between 380 and 780 nm. In the present application, the mesoporous materials (coatings or films) are defined as solids comprising in their structure pores having a size ranging from 2 to 50 nm, called mesopores, that is to say that at least a portion of their structure includes mesopores. These preferentially have a size ranging from 3 to 30 nm. This pore size is intermediate between that of macropores (size> 50 nm) and that of micropores (size <2 nm, zeolite type materials). These definitions are consistent with those given by the IUPAC Compendium of Chemistry Terminology, 2 ^πd Ed., AD McNaught and A. Wilkinson, RSC, Cambridge, UK, 1997.

Mesopores can be empty, ie filled with air, or only partially empty.

Mesoporous materials and their preparation have been widely described in the literature, notably in Science 1983, 220, 365371 or The Journal of Chemical Society, Faraday Transactions 1985, 81, 545-548.

Mesoporous materials can be structured. Structured material is defined in the present application as a material having an organized structure, characterized more specifically by the existence of at least one diffraction peak in an X-ray or neutron diffraction pattern, which is associated with repetition a characteristic distance of the material, called the spatial repetition period of the structured system.

In the present application, a mesostructured material is defined as a structured material having a spatial repetition period ranging from 2 to 70 nm, preferably from 2 to 50 nm.

Structured mesoporous materials are a particular class of mesostructured materials. They are mesoporous materials with an organized spatial arrangement of the mesopores present in their structure, which results in a period of spatial repetition.

The conventional process for preparing mesoporous (optionally structured) films is the sol-gel process. It comprises the preparation of a low polymerized soil of an inorganic material obtained from one or more precursors co-hydrolyzed under generally acidic conditions in the presence of a pore-forming agent. This soil also contains water, a generally polar organic solvent such as ethanol, and optionally a hydrolysis and / or condensation catalyst.

A film of this precursor soil is then deposited on a main surface of a support, and the deposited film is thermally consolidated. The removal of the blowing agent, when it has been used in sufficient quantity, forms a mesoporous film.

When the blowing agent is an amphiphilic agent, for example a surfactant, it acts as a structuring agent and generally leads to structured materials.

The pore size in the final material depends on the size of the pore-forming agent that is trapped or encapsulated within the silica network. When a surfactant (surfactant) is When used, the pore size in the solid is relatively wide because the silica network is built around the micelles, that is to say the colloidal particles, formed by the surfactant. Inherently, the micelles are larger in size than their constituents, so that the use of a surfactant as a blowing agent generally produces a mesoporous material, if the surfactant is used in sufficient concentration.

When the blowing agent is not an amphiphilic agent, it generally does not form micelles under the reaction conditions and generally does not lead to structured materials.

Once the inorganic network has been formed around the mesopores containing the pore-forming agent, this pore-forming agent can be removed from the material, generally giving access to a mesoporous material. In the present application, a material may be described as mesoporous when the pore-producing agent used for its preparation has been at least partially removed from at least a part of this material, that is to say at least some of this material contains at least partially empty mesopores.

Mesoporous films which no longer contain pore-forming agents and whose pores have not been filled with other compounds have pores called "voids", that is to say filled with air, and possess the resulting properties, including a low refractive index.

The matrix constituting the mesoporous coating, comprising -Si-O-Si- chains, is a silica-based matrix, functionalized with ammonium groups.

By silica-based matrix is meant a matrix obtained from a composition comprising a precursor comprising at least one silicon atom bonded to 4 hydrolyzable (or hydroxyl) groups.

The matrix constituting the mesoporous coating is also generally a polysiloxane matrix, comprising hydrocarbon groups bonded to silicon atoms, said hydrocarbon groups carrying ammonium groups.

A sol available for use in the invention to form the ammonium functionalized mesoporous silica matrix comprises:

at least one inorganic precursor agent A of formula:

If (X) ₄ (I)

in which the X groups, which are identical or different, are hydrolyzable groups preferably chosen from alkoxy-OR groups, in particular C ₁ -C ₄ alkoxy, acyloxy-O-C (O) R, where R is an alkyl radical, preferentially C ₁ -C ₆ alkyl; preferably methyl or ethyl, and halogens such as Cl, Br and I and the combinations of these groups; or a hydrolyzate of this precursor agent;

at least one precursor agent B chosen from organosilanes comprising:

α) a silicon atom bearing at least two hydrolyzable groups; and β) at least one ammonium group, the molar ratio compound B / compound A ranging from 0.1 to 0.8; at least one organic solvent, at least one porogenic agent, water and optionally a group X hydrolysis catalyst.

Preferably, the groups X are alkoxy groups, and in particular methoxy or ethoxy, and better ethoxy.

The preferred compounds (I) are tetraalkyl orthosilicates. Among these, use is advantageously made of tetraethoxysilane (or tetraethyl orthosilicate) Si (OC ₂ H ₅ ) ₄ denoted by TEOS, tetramethoxysilane Si (OCH ₃ ) ₄ denoted TMOS, or tetraisopropoxysilane Si (OC ₃ H ₇ ) ₄ denoted TPOS, and preferably the TEOS.

The inorganic precursor agents of formula (I) present in the soil generally represent from 10 to 30% by weight relative to the total mass (including all the other compounds present in the precursor sol, in particular the solvent) of the precursor sol.

The precursor agent B, co-condensed in the presence of the inorganic precursor agent A, is an organosilane comprising a silicon atom bearing at least two hydrolyzable groups, preferably three hydrolysable groups, and at least one ammonium group.

By ammonium group is meant a group having a positively charged nitrogen atom bonded to carbon atoms and / or hydrogen.

In the context of the invention, any organosilane comprising a silicon atom bearing at least two hydrolyzable groups and at least one group generating an ammonium group under the working conditions is considered to be a precursor agent B.

A number of ammonium group precursor groups can effectively generate an ammonium group in situ. Groups capable of generating an ammonium group under working conditions, which are generally acidic conditions, are for example protonable nitrogen groups such as amino groups (NH ₂ ), secondary and tertiary primary amine groups, or groups 2 -pyridyl, 3-pyridyl or 4-pyridyl, which can generate pyridinium groups. The precursor group of a preferred ammonium group is the amino group. When such precursor groups are present in the B compounds, the precursor sol must include an amount of acid sufficient to fully protonate the ammonium group precursor groups.

The medium in which the precursor agents are found is generally an acid medium, the acidic nature of the medium being obtained by adding, for example, a mineral acid, typically HCl or an organic acid such as acetic acid, preferably HCI. This acid serves as a hydrolysis and condensation catalyst by catalyzing the hydrolysis of the hydrolyzable groups of the precursor agents, and also makes it possible to protonate the precursor groups of ammonium groups when they are present. A concentrated acidic solution will preferably be used to protonate these precursor groups.

The presence of ammonium groups in the B compounds is fundamental. Without wishing to be bound by theory, the inventors believe that the antistatic properties of the mesoporous coating of the invention result from the presence of charged groups in the matrix, in this case ammonium groups and their against ions, which allow to dissipate the electrostatic charges.

The method of the invention does not include treatment of the coating with a basic solution.

The ammonium group of compound B can be a quaternary, tertiary, secondary or primary ammonium group, preferably quaternary or primary, and ideally quaternary. The quaternary ammonium groups make it possible to have a stable charged species in the matrix and are not or not very sensitive to pH variations in the precursor soil.

Compound B is preferably a compound, or a hydrolyzate thereof, of the formula: R _n Y _m Si (X ') _4- _n- _m (H)

in which the groups Y, identical or different, are monovalent organic groups bonded to silicon by a carbon atom and containing at least one ammonium group, the X 'groups, which are identical or different, are hydrolyzable groups, R is an organic group monovalent bonded to silicon by a carbon atom, n and m being integers such that m = 1 or 2 with n + m = 1 or 2. Preferably m = 1. More preferably, n = 0.

The groups X 'may be chosen from the groups previously described for the hydrolysable groups X of the inorganic precursor agent A.

The group R is preferably a hydrocarbon group, saturated or unsaturated, preferably C ₁ -C ₁ 0 and better -C _4, for example an alkyl group such as methyl or ethyl, a vinyl group, an aryl group, phenyl example, optionally substituted, in particular with one or more dC ₄ alkyl groups, or represent the fluorinated or perfluorinated analogous groups of the abovementioned hydrocarbon groups, for example fluoroalkyl or perfluoroalkyl groups. Preferably R represents the methyl group.

The ammonium group is preferably located in the terminal position of the group Y. The group Y is preferably a group of formula

wherein z is an integer, preferably ranging from 2 to 20, more preferably from 2 to 5, most preferably

3, R ¹ , R ² and R ³ independently denote hydrogen atoms, aryl groups, aralkyl groups or linear or branched, preferably linear, alkyl groups preferably having from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and more preferably 1 to 4 carbon atoms, and W ^" is an anion.

W ^" may denote, without limitation, a halide anion or a hydroxide, triflate, hydrogen sulphonate, hydrogencarbonate, chlorate ion, a carboxylic acid anion such as the acetate ion, W ^" denotes a halide anion such as fluoride ion, chloride ion or bromide ion, ideally the chloride ion.

As explained above, the Y groups of formula (III) can be formed in situ, for example from a protonable precursor group. R ¹ , R ² and R ³ preferably independently denote alkyl groups such as methyl, ethyl propyl or butyl groups, or hydrogen atoms, ideally methyl groups.

Compounds B preferably have a molar mass of less than 500 g / mol, better still less than 300 g / mol.

According to a preferred embodiment, the precursor agent B comprises a trialkoxysilyl group such as a triethoxysilyl or trimethoxysilyl group, and preferably constitutes an N-trialkoxysilylpropyl-N, N, N-trialkylammonium halide or an N-trialkoxysilylpropylamine halohydrate. for example a 3-aminopropyltrialkoxysilane halohydrate.

Specific examples of compounds B are N-trimethoxysilylpropyl chloride.

N, N, N-trimethylammonium (TMAC), N-trimethoxysilylpropyl-N, N-didecyl-N-methylammonium chloride, N-trimethoxysilylpropyl-N, N-dimethyl-N-tetradecylammonium chloride, N-trimethoxysilylpropyl chloride N, N-dimethyl-N-octadecyl ammonium and the hydrochloride of 3-aminopropyl triethoxysilane (APTES). Such compounds are especially marketed by Gelest.

The precursor agents B carrying an ammonium group present in the soil generally represent from 1 to 15% by weight, preferably from 2 to 12% by weight, better still from 3 to 10% by weight relative to the total mass of the soil. precursor. The molar ratio compound B / compound A ranges from 0.1 to 0.8, preferably from 0.15 to 0.7. This means that the majority precursor of the matrix is the inorganic agent A of formula Si (X) ₄ .

The organic solvents or the mixture of organic solvents suitable for the preparation of the precursor sol according to the invention are all solvents conventionally used, and more particularly the polar solvents, in particular the alkanols such as methanol, ethanol, isopropanol, propylene glycol, and the like. isobutanol, n-butanol and mixtures thereof. Other solvents, preferably water-soluble, may be employed, such as 1,4-dioxane, tetrahydrofuran or acetonitrile. The preferred organic solvent is ethanol.

In general, the organic solvent represents from 40 to 90% by weight relative to the total mass of the precursor sol. The water present in the precursor sol is generally from 5 to 40% by weight, preferably from 10 to 30% by weight of the total mass of the precursor sol.

The pore-forming agent of the precursor sol may be an amphiphilic or non-amphiphilic porogen. Generally, it is an organic compound. It can be used alone or mixed with other blowing agents.

As non-amphiphilic pore-forming agents that can be used in the present invention, mention may be made of:

synthetic polymers such as ethylene polyoxides or their ethers, poly (alkylenoxy) alkyl ethers and especially poly (ethylenoxy) alkyl ethers, polyethylene glycols, diblock or triblock copolymers, preferably triblock, of ethylene oxide (PEO) and of propylene oxide (PPO),

gamma-cyclodextrin, lactic acid, and other biological materials such as proteins or sugars such as D-glucose or maltose.

The blowing agent is preferably an amphiphile of the surfactant type. An essential characteristic of such a compound is that it is able to form micelles in solution following the evaporation of the solvents which concentrate the solution, to lead to the formation of a mesostructured film.

The surfactant compounds may be nonionic, cationic, anionic or amphoteric. These surfactants are for the most part commercially available. The surfactant compounds that can be used in the present invention are those described in application WO 2007/088312.

The blowing agent is preferably nonionic. Preferably, the precursor sol of the mesoporous antistatic film does not comprise an ionic porogen, and in particular does not comprise cetyltrimethylammonium bromide (CTAB).

The preferred blowing agents are alkyl monoethers of polyethylene glycols and to a lesser extent triblock copolymers comprising two blocks of ethylene oxide and a central block of propylene oxide (PPO), called "poloxamers", marketed in particular under the name Pluronic ^® , for example Pluronic P-123 or Pluronic F-127.

The preferred polyethylene glycol monoethers pore alkyl ethers have the following formula:

H (OCH ₂ CH ₂ ) _n OR ¹ (IV)

wherein R ¹ is a linear or branched alkyl group, optionally substituted with one or more functional groups, and which may further comprise one or more double bonds, and n is an integer from 1 to 200, preferably from 2 to 150, more preferably 2 to 100 more preferably 4 to 20, and most preferably 8 to 12. R ¹ is preferably a linear alkyl group preferably comprising 10 to 20 carbon atoms, more preferably a saturated linear alkyl group. Nonlimiting examples of R ¹ groups that can be used are the dodecyl (Ci ₂ H ₂₅ ), cetyl (C ₁₆ H ₃₃ ), stearyl (C ₁₈ H ₃₇ ) and oleyl (C ₁₈ H ₃₅ ) groups.

n can in particular take the values 2, 4, 5, 10, 20, 23 or 100.

The blowing agents of formula (IV) preferably have a molar mass of 180 to 5000 g / mol, more preferably 300 to 1500 g / mol and more preferably 350 to 1000 g / mol.

The preferred blowing agent of formula (IV) is cetyl ether of polyoxyethylene (10) (n = 10, R ¹ = nC ₁₆ H ₃₃ ).

Compounds of formula (IV) usable in the present invention are marketed by ICI under the trademark Brij ^®, e.g. Brij ^® with the following numbers: 30, 35, 52, 56, 58, 76, 78, 92, 97, 98, 700. Among them, the Brij ^® 56 is preferred (compound of formula IV where n ~ 10 and R ¹ is nC ₁₆ H _33). In general, the pore-forming agent represents from 2 to 10% of the total mass of the precursor sol. Typically, the ratio of the number of moles of pore-producing agents used to the number of moles of precursor agents of formula (I) added to the precursor sol varies from 0.01 to 5, preferably from 0.05 to 1, more preferably from 0.05 to 0.25.

The step of depositing the precursor sol film on the main surface of the support may be by any conventional liquid process, for example dip coating, spray deposition or spin coating, preferably by centrifugation. This deposition step is preferably carried out in an atmosphere having a relative humidity (RH) ranging from 40 to 80%.

The step of consolidating the structure of the deposited precursor sol film consists in terminating the removal of the solvent or mixture of organic solvents from the precursor sol film and / or the possible excess of water and continuing the condensation of certain groups. residual silanol present in the soil, generally by heating said film. This step is preferably carried out by heating at a temperature of <150 ^° C., preferably <130 ^° C., better still <120 ^° C. and better still <10 ^° C.

The step of removing the blowing agent may be partial or total, preferably total. Preferably, this step eliminates at least 90% by weight of the total mass of pore-forming agent present in the film resulting from the preceding step, better at least 95% by weight and still more preferably at least 99% by mass. This removal is accomplished by any suitable method, for example by high-temperature calcination (heating at a temperature generally on the order of 400 ⁰ C), but is preferably accomplished through methods for working at low temperature, c that is to say at a temperature <150 ⁰ C, preferably <130 ⁰ C, better <120 ⁰ C and better still <1 10 ⁰ C. We can mention in particular the known methods of extraction by solvent or fluid to the supercritical state, ozone degradation, plasma treatment for example of oxygen or argon or corona discharge or photo-degradation by exposure to light radiation, especially UV.

Preferably, the removal of the pore-forming agent is by solvent extraction, which allows a greater respect of the matrix, a better control of the final thickness of the porous film than in the case of calcination, and which is better suited to polymer substrates.

Several successive extractions can be performed, so as to reach the desired level of extraction.

In one embodiment, the extraction is carried out using an organic solvent or a mixture of organic solvents by quenching the formed and consolidated film in a solvent or a mixture of preferably organic solvents brought to a temperature <150 ^° C. A non-toxic solvent such as acetone or ethanol is preferably used. It is also possible to carry out the extraction using an acidic solvent, for example a mixture of ethanol and hydrochloric acid. In a preferred embodiment, extraction with a solvent can also be effected efficiently at room temperature, with stirring, with the aid of ultrasound.

The various techniques for removing the porogenic agent and their implementation are described in more detail in the application WO 2007/090983.

The matrix of the mesoporous material of the invention has a hydrophobic character, which is preferably obtained by implementing at least one of the two following embodiments.

According to a first embodiment, a hydrophobic character can be conferred on the matrix by introducing at least one hydrophobic precursor agent carrying at least one hydrophobic group into the previously defined precursor sol before the deposition step b) of a film precursor soil.

By "hydrophobic" groups is meant, in the context of the present invention, combinations of atoms that are not likely to associate with water molecules, especially by hydrogen bonding. These are usually nonpolar organic groups, free of charged atoms. The alkyl, phenyl, fluoroalkyl, perfluoroalkyl, (poly) fluoroalkoxy [(poly) alkyleneoxy] alkyl, trialkylsilyloxy and hydrogen atom groups fall into this category. Alkyl groups are the preferred hydrophobic groups.

The hydrophobic precursor agents are preferably added to the precursor sol in the form of a solution in an organic solvent and are preferably chosen from the compounds and mixtures of the compounds of formulas (II) or (III) as described in the application WO 2007/090983 .

The preferred hydrophobic precursor agents are silanes, in particular alkoxysilanes, bearing at least one hydrophobic group directly in contact with the silicon atom. Among the alkoxysilanes that may be used, there may be mentioned alkyltrialkoxysilanes, such as methyltriethoxysilane (MTEOS, CH ₃ Si (OC ₂ H ₅ ) ₃ ), vinylalkoxysilanes, fluoroalkylalkoxysilanes, and arylalkoxysilanes. The most preferred hydrophobic precursor agent is methyltriethoxysilane (MTEOS).

When this first embodiment is used, the molar ratio of the hydrophobic precursor agent to the inorganic precursor agent of formula (I) ranges from 10/90 to 50/50, more preferably from 20/80 to 45/50. 55. Typically, the hydrophobic precursor agent carrying at least one hydrophobic group may represent from 1 to 50% by weight relative to the total mass of the precursor sol.

According to a second embodiment, which is the preferred embodiment, a hydrophobic character can be conferred on the silica-based matrix of the invention by treating the mesoporous film whose preparation is described above by at least one compound hydrophobic reagent carrying at least one hydrophobic group. The hydrophobic reactive compound is reactive with the silanol groups of the matrix and treatment with this compound leads to silica matrix of which at least a part of the silanol groups have been derivatized into hydrophobic groups.

The definition of the hydrophobic groups is the same as that used for the hydrophobic precursor agents defined above.

This additional processing step, called "post-synthetic grafting", is performed after the step of depositing a precursor sol film on a main surface of the support or after the step of consolidating the deposited film. It can be carried out during the step of removing the pore-forming agent, after the step of removing the pore-forming agent, or even before the step of removing the pore-forming agent.

The hydrophobic reactive compounds carrying at least one hydrophobic group that is particularly suitable for the present invention are compounds of a tetravalent metal or metalloid, preferentially silicon, comprising at least one function capable of reacting with the remaining hydroxyl groups in the film, especially a function Si-Cl, Si-

NH-, Si-OR where R is an alkyl group, preferably dC ₄ .

Preferably, said hydrophobic reactive compound is chosen from compounds and mixtures of compounds of formula (V):

(R ' ¹ ) ₃ (R' ² ) Si (V)

in which :

the groups R ' ¹ , which are identical or different, represent saturated or unsaturated hydrocarbon-based hydrophobic groups, preferably dC ₈ and better still dC ₄ , for example an alkyl group, such as methyl or ethyl, a vinyl group or an aryl group; , for example phenyl, optionally substituted, in particular with one or more dC ₄ alkyl groups, or represent the fluorinated or perfluorinated analogous groups of the abovementioned hydrocarbon groups, for example fluoroalkyl or perfluoroalkyl groups, or (poly) fluoro or perfluoro groups; alkoxy [(poly) alkyleneoxy] alkyl. Preferably, the group R ' ¹ is a methyl group,

the group R ' ² represents a hydrolyzable group, preferably chosen from the alkoxy-OR "groups, in particular the alkoxy groups in dC ₄ , the acyloxy -O-C (O) R" groups, where R "is an alkyl radical, preferably in the form of C ₁ -C ₆ preferably methyl or ethyl, amino optionally substituted by one or two functional groups, for example an alkyl or silane group, and halogens such as Cl, Br and I. These are preferably alkoxy groups, especially methoxy or ethoxy, chloro or -NHSiMe ₃ .

As the hydrophobic reactive compound, a fluoroalkyl chlorosilane, a fluoroalkyl-dialkyl chlorosilane, an alkylalkoxysilane, a fluoroalkylalkoxysilane, a fluoroalkyl-dialkylalkoxysilane, an alkylchlorosilane such as trimethylchlorosilane, a trialkylsilazane or a hexaalkyldisilazane can advantageously be used.

In a preferred embodiment, the hydrophobic reactive compound comprises a trialkylsilyl group, preferentially a trimethysilyl group, and a silazane group, particularly a disilazane group. The particularly preferred hydrophobic reactant compound is 1,1,1,3,3,3-hexamethyldisilazane (CH ₃ ) ₃ Si-NH-Si (CH ₃ ) 3, denoted HMDS.

This post-synthetic grafting step is described in more detail in the applications US 2003/15731 1 and WO 2007/088312. It can be carried out on a mesoporous coating whose matrix already has a hydrophobic character, since it was obtained from a sol comprising a hydrophobic precursor agent.

However, the coatings according to the invention preferably have a silica-based matrix prepared from a sol which does not contain a hydrophobic precursor agent carrying at least one hydrophobic group. According to this embodiment, the matrix of the mesoporous coating formed during the initial polymerization step is not a matrix having a hydrophobic character, but acquires this character following a hydrophobic post-treatment. In the context of the invention, an organosilane precursor agent carrying at least one ammonium group, at least one hydrophobic group and a silicon atom carrying at least two hydrolyzable groups is not considered. as a hydrophobic precursor agent carrying at least one hydrophobic group, but as a precursor agent B.

The mesoporous coatings of the invention, whose matrix has a hydrophobic character, demonstrate a better stability over time of their properties, in particular of their refractive index with respect to ambient humidity.

In their final state, the mesoporous films of the invention have a thickness which is not particularly limited, and which can be adapted according to the desired purpose. Generally, they have a maximum thickness of the order of 1 μm, and generally a thickness ranging from 50 nm to 1 μm, preferably from 50 to 500 nm and better still from 50 to 150 nm. It is possible to successively deposit several films so as to obtain a multilayer film of desired thickness.

The preparation of mesoporous silica-based matrix coatings is described in more detail in WO 2006/021698, WO 2007/088312 and WO 2007/090983 in the name of the applicant, which are incorporated by reference in the present application.

The porous coatings of the invention may be used to impart antistatic properties to various articles, whether transparent or not, such as, without limitation, lenses or optical lens blanks, preferably ophthalmic lenses or lens blanks, optical fibers, glazing used for example in the aeronautical field, in the field of building, transport (automobile ...), or in the field of interior design.

The support on which the porous films are deposited may consist of any solid material, transparent or non-transparent, such as mineral glass, a ceramic, a glass-ceramic, a metal or an organic glass, for example a thermoplastic or thermosetting plastic material. Preferably, the support is a glass substrate mineral or organic glass, preferably transparent. Better, the support is a substrate made of a transparent plastic material.

Among the thermoplastic materials suitable for substrates, described in more detail in the application WO 2007/090983, mention may be made of (co) polymers (thio) (meth) acrylic, polycarbonates (PC), poly (thio) urethanes, polyol allyl carbonates (co) polymers, ethylene / vinyl acetate thermoplastic copolymers, polyesters, polyepisulfides, polyepoxides, cycloolefin copolymers and combinations thereof. By (co) polymer is meant a copolymer or a polymer. By (meth) acrylate is meant an acrylate or a methacrylate.

Particularly recommended substrates are substrates obtained by

(Co) polymerization of bis allyl carbonate diethylene glycol, sold, for example, under the trade name CR-39 ^® by PPG Industries (lenses ORMA ^® ESSILOR).

The mesoporous films of the invention may be formed on at least a portion of the main surface of a bare (ie, uncoated) substrate (substrate), or already coated with one or more functional coatings.

The surface of the article on which the future anti-static mesoporous coating will be deposited may optionally undergo a pre-treatment intended to reinforce the adhesion of this coating. Among the pre-treatments that can be envisaged, mention may be made of corona treatment, vacuum plasma treatment, ion beam treatment, electron beam treatment, or acid or base treatment.

Preferably, the support of the invention is an ophthalmic lens substrate. In ophthalmic optics, it is well known to coat a main surface of a transparent organic material substrate, for example an ophthalmic lens, with one or more functional coatings to improve the optical and / or mechanical properties of the final lens. Also, the main surface of the support may be previously provided with a primer coating improving the impact resistance (shockproof primer) and / or the adhesion of subsequent layers in the final product, an abrasion-resistant coating and / or hard coat, anti-reflective coating, polarized coating, photochromic coating, antistatic coating, colored coating or stack of two or more of these coatings .

The mesoporous coating of the invention is preferably deposited on an anti-abrasion and / or anti-scratch coating, preferably having a high refractive index, typically from 1.55 to 1.65, more preferably from 1.55 to 1. 60. The mesoporous coating may optionally be coated with coatings making it possible to modify its surface properties, such as a hydrophobic and / or oleophobic layer (anti-fouling top coat).

Impact-resistant primer coatings, abrasion-resistant and / or scratch-resistant coatings and hydrophobic and / or oleophobic coatings may be selected from those described in WO 2007/088312. In a preferred embodiment, the mesoporous film of the invention constitutes a monolayer antireflection coating or is part of a multilayer antireflection coating, optionally coated with a hydrophobic and / or oleophobic layer, especially an antireflection coating comprising an alternation of layers. high refractive index (n≥ 1, 55) and low refractive index (n <1, 50).

The refractive index of the antistatic mesoporous coating of the invention is less than or equal to 1.45, more preferably less than or equal to 1.40. It therefore constitutes a low refractive index layer, following removal of the pore-forming agent within the mesopores. Such low refractive indices can not be achieved by antistatic coatings previously known.

When forming a monolayer antireflection coating, the antistatic mesoporous coating of the invention preferably has a thickness of 80 to 130 nm, preferably 90 to 120 nm, and a median thickness of 95 to 10 nm, to minimize reflection. for a wavelength of the order of 540 nm, at which the sensitivity of the eye is maximum. This embodiment is particularly interesting, since a single layer provides antistatic and antireflection properties to the stack.

It can in particular be the low refractive index layer of a bilayer antireflection coating, or even a Bragg mirror.

In a preferred embodiment of the invention, the mesoporous coating is formed on a layer of high refractive index previously deposited on the substrate, and thus forms a low refractive index layer of a bilayer antireflection coating.

Said layer of high refractive index is preferably obtained by curing a composition comprising a hydrolyzate of an alkoxysilane, in particular an epoxysilane, preferably an epoxytrialkoxysilane, and colloids of high refractive index (n≥ 1, 55 ) or precursors thereof. In particular, the colloids may be colloids of TiO ₂ , ZrO ₂ , Sb ₂ O ₅ , SnO ₂ , or WO ₃ . Its refractive index is preferably greater than 1, 7, better than 1, 8, and its thickness preferably varies from 10 to 200 nm.

Such a sol-gel antireflection coating has the advantage of being deposited by liquid, unlike conventional antireflection coatings based dielectric layers, which must be deposited by vacuum treatment.

Preferably, the average reflection factor in the visible range R _m (400-700 nm) and / or the average light reflection factor R _v (weighted average of the spectral reflection over the entire visible spectrum between 380 and 780 nm ) an article coated with a mesoporous coating according to the invention is (are) less than 2% per side, better (s) less than 1% per side and even better lower (s) to 0.75 % per face of the article. The means for achieving such values are well known to those skilled in the art. In the present application, the "average reflection factor" R _m and the "light reflection factor" R _v are as defined in ISO 13666: 1998, and measured in accordance with ISO 8980-4. Compared to known antistatic coatings based on metal oxides or conductive polymers, the antistatic coatings of the invention have the advantage of being much less absorbent.

Preferably, the optical article of the invention does not absorb in the visible or absorbs little in the visible, which means, in the sense of the present application, that its relative light transmission factor in the visible ( Tv) (for the whole article) is greater than 95%, better than 96%, and more preferably greater than 97%. The Tv factor meets a standardized international definition (ISO13666: 1998) and is measured in accordance with ISO8980-3. It is defined in the wavelength range from 380 to 780 nm.

The present invention also relates to the use of a mesoporous coating having an ammonium-functionalized silica-based matrix as an antistatic coating. Such a coating has a refractive index less than or equal to 1.5. Preferably, the matrix of the mesoporous coating has a hydrophobic character. This hydrophobic character can be imparted to it by implementing at least one of the two embodiments described above.

The examples below illustrate the present invention without limiting it. Unless otherwise indicated, all percentages are by mass. All the refractive indices are expressed at λ = 632.8 nm and T = 20-25 ^° C.

The dry extracts are determined or calculated before adding the blowing agent. In other words, the blowing agent is not taken into account for the calculation of the dry extract.

EXAMPLES

A) Reagents and material used to synthesize mesoporous films

TEOS, formula Si (OC ₂ H ₅₎ ₄ was used as inorganic agent precursor of formula (I), Brij ^® 56 has been used as the blowing agent surfactant and hexamethyldisilazane (HMDS ) has been used as a hydrophobic reactive compound. Two precursor agents of formula (II) have been employed: N-trimethoxysilylpropyl-N, N, N-trimethylammonium chloride (TMAC, in 50% solution in methanol, supplied by ABCR) and 3-aminopropyltriethoxysilane (APTES) . The latter is used in combination with an aqueous solution of 6M hydrochloric acid so that the amino group of the APTES is converted into an ammonium group.

The sols were prepared using absolute ethanol as the organic solvent and an aqueous hydrochloric acid solution diluted to 0.1 M (so as to obtain a pH = 1.25) as a hydrolysis catalyst.

The coatings were deposited on glasses comprising an ORMA ^® ESSILOR lens substrate (CR-39 ^® , 0.00 diopters, except for reflection measurements: -2.00 diopters), having a refractive index of 1, 50, 1.1 mm in thickness, a radius of curvature of 80 to 180 mm and a diameter of 65 to 70 mm. This substrate is coated with the anti-abrasion and anti-scratch coating disclosed in example 3 of patent EP 0614957 (with a refractive index equal to 1.48 and 3.5 μm in thickness), based on GLYMO, DMDES, colloidal silica and aluminum acetylacetonate.

B) Characterization of mesoporous coatings

Mesoporous coatings are characterized:

• By ellipsometry to determine their refractive index. For this, the coatings are deposited on polished silicon supports on both sides.

• Infrared spectroscopy to evaluate the efficiency of surfactant extraction and the efficiency of HMDS grafting. For this, the coatings are deposited on polished silicon supports on both sides.

• By reflection spectroscopy to evaluate the effectiveness of the antireflection coating, in the case where the mesoporous coating is sized to constitute an antireflection coating. For this, the coatings are deposited on the organic substrate CR-39 ^® described in § A). The average reflection (R _m ) over the entire visible spectrum is determined. The reflection obtained by considering the spectral sensitivity curve of the eye (R _v ) is also determined.

• By measuring the discharge time after applying an electrostatic charge to the glass surface according to the method described in the application WO 2008/015364. The measurements are performed under a controlled atmosphere to 22 ^<O and 50% humidity. For this, the coatings are deposited on the organic substrate CR-39 ^® described in § A). The glasses are considered antistatic since the discharge times are less than 200 ms.

• Coating thicknesses were measured with the Tencor ™ profilometer.

C) Preparation of mesoporous matrix-based silica coatings rendered hydrophilic by post-synthetic grafting

Example 1 (TEOS / TMAC Matrix)

The precursor sol was prepared by mixing reagents and solvents in the following molar proportions: 1 TEOS: 0.15 TMAC: 22 EtOH: 5.75 HCl (0.1 M): 1.21 MeOH.

The whole is heated for 1 h at 60 ⁰ C to hydrolyze the silanes. After cooling, the blowing agent is added to the mixture in a molar proportion of 1 TEOS: 0.0851 Brij ^®

56. The composition is diluted in ethanol to reach the final proportions 1 TEOS: 0.15 TMAC: 1.21 MeOH: 52.4 EtOH: 5.75 HCl (0.1 M) then allowed to stir overnight before deposition. It has a solids content of 5.13% by weight. The composition is then filtered through a 0.85 micron syringe filter and diluted by a factor of 2 (dry extract ~ 2.78%) before deposition by centrifugation on the substrate. Before deposition, the substrate has undergone a surface treatment of the corona treatment or oxygen plasma type to avoid any problem of adhesion.

The film then undergoes a heat treatment to advance the degree of polymerization of the network (consolidation). The substrate coated with the film obtained in paragraph 2 above is thermally consolidated in an oven at 75 ^° C. for 15 minutes and then at 100 ^° C. for 3 hours, then the blowing agent is removed by extraction by placing the substrate coated with the film. consolidated in the tank of an Elmasonic brand sonicator, containing isopropanol or acetone, at room temperature for 15 min.

The substrate coated with the mesoporous film is then introduced for 15 minutes into the tank of an Elmasonic brand ultrasound tank containing HMDS at room temperature.

The glasses are then rinsed with isopropyl alcohol to remove excess HMDS. This post-synthetic hydrophobation step is described in more detail in the WO application.

2007088312.

EXAMPLE 2 (TEOS / APTES Matrix) A silica sol was prepared by mixing reagents and solvents in the following molar proportions: 1 TEOS (45.8 g): 3.8 EtOH (39 g): 5 HCl (0.1 M) (19.9 g). The whole is heated for 1 h at 60 ⁰ C to hydrolyze the silanes. After cooling, 50 g of this solution are taken and introduced into a vessel, to which 34.7 g of ethanol, 42 g of water and 32 ml of 6M HCl are added, with stirring. The resulting composition is stirred at room temperature for 5 minutes and then cooled by placing the container in an ice bath. After about 15 minutes of stirring, the temperature of the composition reaches 1 -2 ^° C.

15.665 g of APTES are then added following a drop to slow taste, ensuring that the temperature of the mixture does not exceed ^{40 °} C., in order to limit the rate of condensation of the soil and therefore the appearance of a precipitate . After complete addition of the APTES, the stirring is continued for 5 min at 0-2 ^° C. and then for 15 min at room temperature. 8.91 g of Brij ^® 56 blowing agent are then added to the mixture and stirring is continued overnight at room temperature.

The final composition comprises the reagents and solvents in the following molar proportions: 1 TEOS: 0.67 APTES: 10.9 EtOH: 1, 82 HCI (6M): 27.1 H ₂ O: 0.124 Brij ^® 56. It has a dry matter content of 12.56% by mass.

The composition is then filtered through a 0.85 micron syringe filter and diluted with ethanol by a factor of 3 (dry extract ~ 4.68%), stirred for 15 minutes before deposition by centrifugation on the substrate (between 2000 and 2500 rpm). A layer having a high refractive index on the order of 1.5-1.51 is obtained because of the presence of the blowing agent in the mesopores. Before deposition, the substrate has undergone a surface treatment of the corona treatment or oxygen plasma type to avoid any problem of adhesion.

The consolidation of the film, the removal of the pore-forming agent by extraction and the post-synthetic grafting of the film with HMDS are then carried out as in Example 1.

Comparative Examples (TEOS / TMAC matrices, TEOS / APTES or TEOS)

The procedures followed for the preparation of the articles of the comparative examples are similar to those of Examples 1 and 2. The differences are indicated below.

The article of Comparative Example C1, comprising a non-porous coating, was obtained according to a procedure similar to that of Example 1, without using a pore-forming agent or carrying out a post-synthetic grafting with HMDS. The article of Comparative Example C1 1 differs from that of Example 1 in that no post-synthetic grafting with HMDS has been performed.

The article of Comparative Example C2, comprising a non-porous coating, was obtained according to a procedure similar to that of Example 2, without using a pore-forming agent or carrying out a post-synthetic grafting with HMDS. and using a dilution factor of 2 (solids content of the composition: 9.72% by weight) or without dilution (solids content of the composition: 4.86% by weight). The article of Comparative Example C22 differs from that of Example 2 in that no post-synthetic grafting by HMDS was performed.

The article of Comparative Example C3 differs from that of Examples 1 and 2 in that the only inorganic precursor agent used is TEOS. The precursor sol contained 14.36 g of TEOS, 79.42 g of ethanol, 6.2 g of 0.1 N hydrochloric acid, and 3.49 g of the blowing agent Brij ^® 56 (molar ratio TEOS 1 : 0.074 Brij ^® 56).

The article of Comparative Example C4, comprising a non-porous coating, was obtained according to a procedure similar to that of Example C3, without using a pore-forming agent or carrying out a post-synthetic grafting with HMDS.

The article of Comparative Example C5 differs from that of Comparative Example C3 in that no post-synthetic grafting by HMDS was performed.

D) Results

Table 1 compares the performance of the lenses of Examples 1, 2, and comparative examples in terms of refractive index and discharge time.

When several thicknesses are mentioned for the same example, they were obtained by slightly changing the solids of the solutions and / or the centrifugation rates. Table 1

E) Comment on the results of Table 1 1) Antistatic properties

A matrix based on TEOS (single precursor agent) does not have antistatic properties, whether porous or non-porous, whether or not it has undergone hydrophobic functionalization (examples C3-C5).

On the other hand, for thicknesses of the order of 100-200 nm, the matrices resulting from a mixture of TEOS precursors and TMAC or APTES (precursors comprising ammonium groups) all have antistatic properties, whether they are porous or not. porous, whether or not they have undergone hydrophobic functionalization (Examples 1, 2, C1, C1 1, C2, C22). In general, the greater the thickness of the antistatic layer, the lower the discharge times due to the increase in the total amount of ionic species, which can dissipate the electrostatic charges more quickly.

2) Effect of Hydrophobic Functionalization on the Refractive Index Without hydrophobic functionalization by HMDS, the refractive indices of the porous layers are higher. The IR spectra achieved show that removal of the blowing agent by solvent extraction was effective. The higher refractive indices are therefore not related to poor removal of the blowing agent but can be explained, without wishing to be bound by theory, by the condensation of moisture in the porosity. One way to avoid this condensation, and therefore to reduce the refractive index of the coating, is to hydrophobially functionalize the porous layer, as here with HMDS. 3) Effect of Hydrophobic Functionalization on Antistatic Properties

The post-processing of a matrix by the HMDS generally induces an increase of the discharge times. While not wishing to be bound by theory, the lower discharge times in the matrices observed for non-HMDS-functionalized matrices may be explained by the presence of moisture in the porosity that induces faster dissipation of electrostatic charges. The influence of moisture on the electrostatic properties of a coating is well known in the literature.

The hydrophobic functionalization of the system would therefore limit the presence of water in the porosity, which leads to an increase in discharge times.

In the case of Examples 1 and 2, the hydrophobic functionalization does not induce an increase in discharge times above 200 ms, so that the article retains antistatic properties.

In conclusion, the presence of charged species (ammonium + against ion) in the matrix of a mesoporous coating makes it possible to obtain a coating which simultaneously has a low refractive index (in this case less than 1, 4) and properties antistatic.

F) Study of the influence of the presence of ammonium groups in the matrix on the antistatic properties

An article prepared according to Example C22 but having a mesoporous coating of 400 nm thickness was immersed in an aqueous solution of 0.01 M sodium hydroxide for 30 minutes, in order to deprotonate the ammonium groups present in the matrix. Measurements of the discharge times before and after neutralization are shown in Table 2.

Table 2

Table 2 shows that the transformation of ammonium groups into amine groups

(not loaded) causes a significant increase in discharge time beyond 200 ms, that is, the disappearance of the antistatic properties. There is therefore an interest in using a charged species in the mesoporous matrix. G) Evaluation of antireflection properties

The optical properties of the coating of Example 1 (deposited on an organic substrate CR-39 ^® of refractive index 1, 5 equipped with an abrasion-resistant coating), having a thickness of 100 nm and a discharge time of 173 ms, are presented in Table 3. (Properties of a monolayer on one side of the substrate).

Table 3

Due to its relatively low visible average reflection factors Rm and Rv, this antistatic mesoporous coating is a high performance single-layer antireflection coating. It constitutes a coating of optical thickness λ / 4 for the wavelength λ = 548 nm.

The reflection curve of the sample between 380 and 780 nm is presented in FIG.

Claims

A method of manufacturing a substrate coated with a mesoporous antistatic film, comprising:

a) preparing a precursor soil of a mesoporous antistatic film comprising:

at least one inorganic precursor agent A chosen from compounds of formula:

If (X) ₄ (I)

at least one precursor agent B chosen from organosilanes comprising:

or a hydrolyzate of this precursor agent;

the molar ratio compound B / compound A ranging from 0.1 to 0.8;

b) depositing a film of the precursor sol on a main surface of a substrate;

c) the consolidation of the deposited film;

d) removing the foaming agent from the film resulting from the previous step and recovering a mesoporous antistatic film having a refractive index less than or equal to 1.45; the method further comprising:

(i) a step of treating the film after step b) or after step c), with at least one hydrophobic reactive compound bearing at least one hydrophobic group; and or

2. Method according to claim 1, characterized in that the precursor agent B is a compound, or a hydrolyzate thereof, of formula:

R _n YmSi (XVn-m (ll)

in which the groups Y, identical or different, are monovalent organic groups bonded to silicon by a carbon atom and containing at least one ammonium group, the X 'groups, which are identical or different, are hydrolyzable groups, R is an organic group monovalent bonded to silicon by a carbon atom, n and m being integers such that m = 1 or 2 with n + m = 1 or 2.

3. Method according to claim 2, characterized in that the ammonium group is located in the terminal position of the group Y.

4. Method according to claim 2, characterized in that the group Y is a group of formula: in which z is an integer, preferably ranging from 2 to 20, R ¹ , R ² and R ³ independently denote hydrogen atoms, aryl groups, aralkyl groups or linear or branched, preferably linear, alkyl groups, preferably having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and W ^" is an anion.

5. Method according to any one of the preceding claims, characterized in that the blowing agent is a polyethylene glycol alkyl monoether of formula:

H (OCH ₂ CH ₂ ) _n OR ¹ (IV)

wherein R ¹ is an alkyl group, linear or branched, optionally substituted with one or more functional groups, and may further comprise one or more double bonds, and n is an integer of 1 to 200.

6. Method according to any one of the preceding claims, characterized in that the precursor sol does not contain a hydrophobic precursor agent carrying at least one hydrophobic group.

7. Process according to any one of the preceding claims, characterized in that the hydrophobic reactive compound is chosen from compounds and mixtures of compounds of formula:

(R ' ¹ ) ₃ (R' ² ) Si (V)

in which :

the groups R ' ¹ , which are identical or different, represent hydrophobic hydrocarbon groups, saturated or unsaturated,

the group R ' ² represents a hydrolysable group.

8. Process according to claim 7, characterized in that the hydrophobic reactive compound is chosen from fluoroalkyl chlorosilanes, fluoroalkyl dialkyl chlorosilanes, alkylalkoxysilanes, fluoroalkylalkoxysilanes, fluoroalkyl dialkylalkoxysilanes, alkylchlorosilanes, trialkylsilazanes or hexaalkyldisilazanes.

An article comprising a substrate having a major surface coated with a mesoporous antistatic coating obtainable by the method of any one of claims 1 to 8, characterized in that said coating has a refractive index of less than or equal to at 1.45 as well as an ammonium-functionalized silica-based matrix which has a hydrophobic character.

An article according to claim 9, characterized in that the substrate is an optical lens substrate or an optical lens blank, preferably an ophthalmic lens or an ophthalmic lens blank.

1. Article according to claim 9 or 10, characterized in that the mesoporous coating has a thickness ranging from 50 nm to 1 μm, preferably from 50 to 150 nm.

12. Article according to any one of claims 9 to 11, characterized in that the mesoporous antistatic coating is a monolayer antireflection coating or is part of a multilayer antireflection coating.

13. Use of a mesoporous coating having an ammonium-functionalized silica-based matrix as an antistatic coating.

14. Use according to claim 13, characterized in that the silica-based matrix has a hydrophobic character.