Method for producing a transparent substrate comprising a coating

0001Description

0002Title: Process for manufacturing a transparent substrate comprising a coating

0003[001] The subject of the present invention is a method of manufacturing a coated substrate, as well as the material comprising the coated substrate and its application in the field of glazing.

0004[002] It is of interest to treat the surface of a substrate such as glass to modify its properties or provide new functionality. One of the means used to treat the substrate surface is the liquid deposition technique (also called wet coating) to form a deposited coating. In particular, we seek to be able to deposit a transparent film coating having good optical properties.

0005[003] Coatings obtained using liquid deposition methods may, however, present certain defects such as homogeneity defects. In the majority of cases, we put up with these lack of homogeneity. These defects do not necessarily have a significant impact on the desired properties. This is particularly the case for opaque coatings or coatings with low light transmission, or coatings deposited on small surfaces. However, certain applications are more demanding, whether for technical or aesthetic reasons. These homogeneity defects can in fact affect the particularly optical properties of the coating, generating for example, more or less locally, moiré, wave, magnifying glass effects, etc.

0006[004] We are therefore seeking to have a liquid deposition method making it possible to obtain coatings having improved optical quality.

0007[005] It has been discovered that the use of particular surfactants as defined below in the aqueous coating composition used for liquid deposition makes it possible to improve the optical qualities of the coating obtained.

0008[006] The subject of the invention is therefore a method of manufacturing a material comprising a substrate coated with a coating, preferably transparent, on at least one of its faces, said method comprising a step of application to said face said substrate of an aqueous composition (called aqueous coating composition) containing at least one coating precursor and at least one surfactant, characterized in that the surfactant is chosen from:

0009- surfactants having an absorption time greater than or equal to 1 s; Or

0010- surfactants having a critical micellar concentration less than or equal to 0.1 mM. [007] The invention also relates to a material comprising a substrate coated with a coating on at least one of its faces, capable of being obtained according to the method described above. Such a material has in particular a blur less than or equal to 2%, or even less than or equal to 1.5% or even less than or equal to 1%, and/or a clarity greater than or equal to 99%.

0011[008] Substrate

0012[009] The substrate is preferably glass, or a polymeric organic material. It is preferably transparent, colorless (it can then be a clear or extra-clear glass) or colored, for example blue, green, gray or bronze. The glass is preferably of the soda-lime-silico type, but it can also be of the borosilicate or alumino-borosilicate type glass, particularly for high temperature applications (oven doors, fireplace inserts, fire-resistant glazing). Preferred polymeric organic materials are polycarbonate (PC), polymethyl methacrylate (PMMA) or polyethylene terephthalate (PET). The substrate advantageously has at least one dimension greater than or equal to 20 cm, or even 1 m or even 2 m. The thickness of the substrate generally ranges from 0.01 mm to 19 mm, preferably from 0.02 to 15 mm. The substrate can be rigid, in particular planar or curved, or flexible. In the case of a rigid substrate (in particular a sheet of glass, PMMA, or PC), this generally has a thickness of 0.4 to 12 mm, preferably 1 to 6 mm. In the case of a flexible substrate (in particular a polymer film), this generally has a thickness of 0.02 to 1 mm.

0013The substrate is preferably a sheet of glass.

0014[0011] Surfactant

0015The surfactant used in the manufacturing process according to the invention can be:

0016- a surfactant having an absorption time greater than or equal to 1 s; Or

0017- a surfactant having a critical micellar concentration less than or equal to 0.1 mM. The CMC or Critical Micellar Concentration is the concentration at which a surfactant added to water begins to aggregate and form micelles. Below the CMC, the surfactant is in the free state. Above the CMC, the surfactant forms micelles.

0018[0013] The CMC can be measured in a known manner using the bubble method. The measurement is carried out at a temperature of 23°C.

0019[0014] A TRACKER optical blood pressure monitor from the company TECLIS is used and a curved needle previously rinsed with ethanol then deionized water and then dried.

0020The needle is placed in a container filled with the aqueous solution of the surfactant to be evaluated at a concentration of 1 g/l so as to form a rising bubble. We first form 2 rising bubbles, then we form a new bubble to carry out the measurements. [0016] When the bubble is formed, its surface is free of surfactants. During the adsorption of surfactants on the surface, the surface tension varies with time, which leads to deformation of the bubble (this deformation is controlled by the balance between gravity and surface tension). We thus measure the dynamic surface tension which varies as a function of time.

0021[0017] When the dynamic surface tension reaches a plateau (the bubble reaches an equilibrium), measuring the surface tension makes it possible to determine the equilibrium surface tension of the aqueous solution.

0022The surface tension at equilibrium is measured for different concentrations of the surfactant in water and then the curve of the surface tension at equilibrium is plotted as a function of the surfactant concentration. This curve generally presents two sections of different slopes: one of the sections corresponds to a zone of concentrations of the surfactant for which the surfactant is in the free state in the water; the other section corresponds to a zone of concentrations of the surfactant for which the surfactant forms micelles. The inflection point of the curve (crossing of the slopes) corresponds to the critical micellar concentration.

0023According to one embodiment of the invention, the surfactant has an adsorption time greater than or equal to 1 s, in particular 2 to 20 s, or even 5.6 to 15 s, or 6.0 at 10 s.

0024[0020] The adsorption time of the surfactant can be measured according to the method described in the article by H. Ritacco “Dynamic surface tension of aqueous solutions of ionic surfactants: role of electrostatics”, Langmuir, 2011, 27(3), pp. 1009-1014.

0025To determine this adsorption time, the dynamic surface tension is measured over the time of bubble formation, at 4 different concentrations of the surfactant in water at 0.1 CMC, 1 CMC , 10 CMC and 100 CMC. Then we establish the curve of the variation of the dynamic surface tension over time. We thus have a curve for each concentration tested.

0026The curves obtained are fitted by an exponential adsorption model using the following function: f —

0027Y = Yeq + Ay ■ Ta in which: t is the time expressed in sy is the surface tension expressed in mN/m, y_eq is the equilibrium surface tension expressed in mN/m, Ay is the amplitude of the decrease in surface tension expressed in mN/m, T_has is the characteristic adsorption time expressed in s. [0023] The curve with exponential adjustment corresponds to the variation of (y - y_ec/)/Ay as a function of t/T_has.

0028[0024] We can thus deduce from this curve the value of the characteristic adsorption time T_has of the surfactant (value which is independent of the concentration of the surfactant).

0029Advantageously, the surfactant is chosen from anionic or non-ionic surfactants.

0030As a surfactant having an adsorption time greater than or equal to 1 s, mention may be made of the surfactants of formula [Chem. 1]<img file="WO2023198912A1_D0001.tif" /> in which R¹ and R² are each independently selected from hydrogen, linear or branched C1-C16 alkyl or aryl, and each X is independently selected from hydrogen, sodium or potassium.

0031[0027] An example of such a surfactant is in particular the surfactant of formula [Chem 2] sold under the trade name “Dowfax® 2 A1” by the company Dow Chemical.<img file="WO2023198912A1_D0002.tif" />

0032This surfactant has an adsorption time of 5.5 s.

0033As a surfactant having a critical micellar concentration of less than 0.1 mM, mention may be made of dodecanol pentaethylene glycol ether, also called C12E5, which has a CMC of 0.07 mM, and polyoxyethylene monooleate (20 OE) sorbitan, sold in particular under the name “Tween 80” by the company Sigma Aldrich, which has a CMC of 0.01 mM.

0034[0029] In a particular embodiment, the surfactant can be chosen from the surfactant of formula [Chem 2] above, dodecanol and pentaethylene glycol ether and polyoxyethylene (20 EO) sorbitan monooleate [0030] The particular surfactant as defined above may be present in the aqueous coating composition in a content ranging from 0.001 to 10% by weight, relative to the total weight of the aqueous composition, preferably ranging from 0.01 to 1% by weight. Alternatively, the concentration of surfactant in the aqueous composition is generally 1 to 10 CMC.

0035[0031] Precursor

0036The coating precursors present in the aqueous coating composition can be chosen from inorganic or metal-organic precursors, such as sol-gel precursors or alkali silicates, organic precursors, such as film-forming polymers, generally in aqueous dispersion form, or polymerizable monomers or oligomers and mixtures thereof.

0037The aqueous coating composition may comprise at least 10% by weight, preferably at least 20% by weight, of coating precursors relative to the total weight of dry matter of the composition.

0038[0034] The coating precursor may be a sol-gel precursor chosen from the precursors of silica, titanium dioxide, zinc oxide, aluminum oxide, tin oxide, aluminum oxide. indium and yttrium oxide.

0039The sol-gel precursor can be chosen from metal alkoxides, in particular alkoxides of titanium, silicon, aluminum, zinc, tin or indium. Examples of alkoxides are chosen from alkoxides of formula R_notM, M being a metal chosen from titanium, silicon, aluminum, zinc, tin or indium, preferably titanium or silicon, n being an integer equal to the valence of the metal and each R being independently chosen from a C1-C4 alkyloxy, in particular methoxy, ethoxy or isopropoxy. The metal alkoxides are preferably chosen from titanium or silicon alkoxides, in particular tetramethoxysilane, tetraethoxysilane, titanium(IV) tetraethoxide, titanium(IV) tetraisopropoxide.

0040As precursor of yttrium oxide, mention may be made of yttrium nitrate or yttrium chloride (as described in the article by R. Melado-Vasquez “Sol-gel synthesis and antioxidant properties of yttrium oxide nanocrystallites incorporating P-123", Materials (Basel). 2014 Sep; 7(9): 6768-6778) or even yttrium acetate.

0041The sol-gel precursor can also be chosen from silicon halides, in particular silicon chloride.

0042[0038] The sol-gel precursor can also be silicic acid, for example as described in WO2010/103236.

0043The sol-gel precursor can also be a precursor of an organometallic nature. This organometallic precursor can be an organosilane, such as that of formula 3 below: R¹ has_hasR^2bSiX (.4,-a_ohb.) (^v3) ⁷

00441 2 1 in which R represents a non-hydrolyzable radical, R, different from R, represents a radical carrying an epoxy or amino group, equal to 0, 1, 2 or 3, (a+b) is equal to 1, 2 or 3, or an oligomer derived from this silane.

0045[0041] In formula 3, the radical R¹ is preferably an alkyl radical, advantageously C1-C6, an alkenyl radical, advantageously C2-C6, for example vinyl, propenyl or butenyl, an alkynyl radical, advantageously C2-C6, for example acetynyl or propargyl, or a radical aryl, advantageously C6-C10, for example phenyl or naphthyl.

00462

0047The functional group carried by the radical R is linked to the silicon atom by an alkylene, alkenylene or alkynylene radical, optionally containing divalent groups such as O, S and/or NH. Advantageously, the radical R contains 1 to 8 carbon atoms.

0048Preferably, a is equal to 0, 1 or 2, b is equal to 1 or 2 and the sum (a+b) is equal to 1 or 2.

0049Examples of organosilane of formula 3 are glycidoxypropyltrimethyoxysilane (GLYMO), methyltriethoxysilane (MTEOS) and (3-aminopropyl)triethoxysilane (APTES). We can also use those described in US7857905.

0050The use of an organometallic sol-gel precursor, alone or in combination with other sol-gel precursors, in particular metal alkoxides, makes it possible to obtain a coating of inorganic-organic nature, also called hybrid.

0051The sol-gel precursor may be present in the aqueous coating composition in a content of 10% to 90% by weight, relative to the total weight of dry matter of the composition, and preferably from 20 to 80% by weight. weight.

0052The coating precursor may be an alkali silicate.

0053The alkali silicate can be chosen from sodium silicate, potassium silicate, lithium silicate, and mixtures thereof. Preferably, the alkali silicate is sodium or potassium silicate.

0054The alkali silicate may be present in the aqueous coating composition in a content of at least 20% by weight, relative to the total weight of dry matter of the composition, and preferably at least 35%. by weight, and typically up to 99% by weight, or even up to 90% or up to 80% by weight. The coating precursor may be a film-forming polymer, preferably in aqueous dispersion (or latex). By “film-forming polymer” is meant a polymer capable of forming a film when applied to the surface of the substrate.

0055The film-forming polymer may be a polyurethane, an acrylic polymer, an alkyd polymer, or a polyester.

0056The film-forming polymer may be present in the aqueous coating composition in a content of at least 20% by weight, relative to the total weight of dry matter of the composition, and preferably at least 30% by weight. , and typically up to 90%, even up to 80% or even up to 60% by weight.

0057The coating precursor may be a polymerizable monomer or oligomer chosen from polyfunctional monomers or oligomers, for example with alcohol, isocyanate, cyclic ethers (in particular epoxy or oxetane) or acrylate functions. These can be crosslinked after deposition of the coating composition, for example by UV irradiation. Alternatively or cumulatively, they can crosslink by reaction with reactive functions of other precursors of identical or different nature, in particular organosilanes.

0058[0054] The coating composition may comprise mixtures of precursors of different natures, in particular at least one inorganic or metal-organic precursor, such as sol-gel precursors or alkali silicates, and at least one organic precursor, such as as film-forming polymers or polymerizable monomers or oligomers. Such coating compositions make it possible to obtain hybrid organic-inorganic coatings.

0059When the precursor is an inorganic or metal-organic precursor, in particular a sol-gel precursor, the aqueous composition may also comprise a pore-forming agent. The pore-forming agent is preferably solid, the choice of its size making it possible to vary the size of the pores. The pore-forming agent is preferably particulate, in particular of substantially spherical shape, for example in the form of hollow or solid balls. The blowing agent is preferably organic in nature. By way of example, the blowing agent comprises polymeric beads, in particular of a polymer chosen from polymethyl methacrylate (PMMA), methyl (meth) acrylate/(meth) acrylic acid copolymers, polycarbonates, polyesters. , polystyrene. The blowing agent may be a non-film-forming polymer latex.

0060[0056] The coating composition may comprise other additives well known to those skilled in the art such as dyes, pigments, metal particles, metal salts, anti-UV agents, anti-oxidant agents, flame retardants, intumescent agents, stabilizing agents, plasticizers such as polyethylene glycol, pH adjusters such as tertiary amines and N-alkylalkanolamine, reinforcing agents such as inorganic particles, in particular silica particles. These additives are generally present in a content of at most 30% by weight relative to the total dry matter, preferably from 1 to 20% by weight.

0061The aqueous composition may further comprise an organic solvent such as ethanol, isopropanol, propanol, acetone, and mixtures thereof. The organic solvent may be present in a content ranging from 0.1 to 20% by weight, relative to the total weight of the aqueous composition.

0062[0058] In one embodiment of the process according to the invention, the aqueous composition does not comprise any organic solvent.

0063The aqueous composition typically has a dry matter content of 1 to 80% by weight, preferably 2 to 60% by weight.

0064Advantageously, when the aqueous composition comprises a sol-gel precursor as described above, the aqueous composition has a dry matter content of 1 to 50% by weight.

0065Advantageously, when the aqueous composition comprises an alkali silicate precursor as described above, the aqueous composition has a dry matter content of 10 to 60% by weight.

0066Advantageously, when the aqueous composition comprises a film-forming polymer precursor as described above, the aqueous composition has a dry matter content of 10 to 80% by weight.

0067[0063] Deposition methods

0068[0064] The application of the aqueous solution to the substrate can be carried out by any technique known to those skilled in the art, such as for example wet deposition techniques such as by spray coating, by curtain application (curtain coating), by spraying (flow coating), by roller application (roller coating), by laminar flow through a slot (slot die), by dipping or casting (dip coating), by blade (blade coating) , by screen printing or inkjet.

0069The application of the aqueous composition is preferably carried out by coating using at least one roller, and which makes it possible to precisely control the quantity of solution deposited as well as the spatial homogeneity of the deposit. According to this technique, the substrate (in particular glass) is preferably passed under a metering roller and an applicator roller in almost contact with each other and rotating in the same direction or in the opposite direction, the applicator roller being in contact with the face of the substrate to be coated, and the solution to be applied being poured from above between these two rollers. The solution, passing between the metering roller and the applicator roller, is deposited on the surface of the latter, then is transferred to the surface to be coated.

0070When the aqueous composition comprises a sol-gel precursor, before being deposited on the substrate, the precursor solution undergoes a pre-condensation step, typically for 20 min to 48 hours to obtain a coating composition. This pre-condensation step may include heating the precursor solution to a temperature of 30 to 100°C. The coating composition is then deposited on the substrate and dried.

0071The wet layer of aqueous composition deposited on the surface of the substrate may have a thickness of 0.5 to 500 μm, preferably of 1 to 200 μm.

0072[0068] Drying step

0073[0069] Immediately after the application step, the method according to the invention preferably comprises a drying step. This step is intended to accelerate the evaporation of the water, and where appropriate the organic solvent, contained in the wet layer deposited in order to obtain a coating. It can be implemented by any known means. The drying may be thermal drying, for example at a temperature between 20 and 200°C, or vacuum drying. Vacuum drying can be advantageous in combination with the composition according to the invention to improve the optical quality of the coatings obtained. Vacuum drying can be carried out at a pressure below 100 Pa, preferably 1 to 30 Pa.

0074The drying time is preferably between 30 s and 24 hours, preferably 1 min to 30 min. In the case of vacuum drying, the drying time is preferably 30 s to 10 min.

0075[0071] After the drying step, the coating thus obtained typically has a thickness of 20 nm to 400 pm.

0076Advantageously, when the coating is obtained from metal-organic sol-gel precursors as described above, the coating obtained after drying can have a thickness ranging from 20 nm to 10 pm.

0077Advantageously, when the coating is obtained from organometallic sol-gel precursors as described above, the coating obtained after drying can have a thickness ranging from 50 nm to 300 pm.

0078Advantageously, when the coating is obtained from alkali silicates as described above, the coating obtained after drying can have a thickness ranging from 20 nm to 200 pm.

0079Advantageously, when the coating is obtained from film-forming polymer precursors or polymerizable monometers or oligomers as described above, the coating obtained after drying can have a thickness ranging from 300 nm to 400 pm.

0080[0076] Optional heating step

0081[0077] When the substrate is a glass substrate and the coating is at least partly inorganic, the method according to the invention may comprise, after the drying step, a heat treatment step. The heat treatment can be carried out at a temperature of at least 400°C, in particular 500°C.

0082[0078] The heat treatment is preferably a glass tempering treatment. Glass tempering involves heating the glass to a temperature generally above 600°C and then rapidly cooling it, usually using nozzles emitting cold air. This rapid cooling creates compressive stresses on the surface of the glass substrate, and therefore reinforces its mechanical and impact resistance.

0083[0079] This treatment step can make it possible in particular to eliminate any pore-forming agents possibly present in the coating obtained after the drying step, thus creating porosity within the coating and thus making it possible to lower its refractive index.

0084[0080] In the application of the substrate of the invention as glazing (based on transparent plastic material or glass), one or more thin layers can be interposed between the substrate surface and the coating according to the invention. These may include, in particular, layers with an antistatic, thermal (heating by providing current supply, low-emissive, anti-solar, etc.), optical (reducing light reflection and/or making it more neutral) functions. the color in reflection of the substrate...), a stack of anti-reflection layers... With regard to such functional layers applied in a known manner to the glazing, possibly in the form of stacks, mention will be made of applications WO 97/10186, WO 02/02472, WO2012/072915, WO2019/008282.

0085[0081] The invention also relates to a material comprising a substrate coated with a coating on at least one of its faces capable of being obtained according to the method described above. Such a material has in particular a blur less than or equal to 2%, or even less than or equal to 1.5% or even less than or equal to 1%, and/or a clarity greater than or equal to 99%. The coating according to the invention is preferably a transparent coating typically having a light transmission greater than 30%, or even greater than 50%, or even greater than 70%, or even greater than 80%.

0086[0082] The blur, measured according to the ASTM D1003 standard with an illuminant D65, corresponds to the ratio Td/Tt, Td being the diffuse transmission at an angle of more than 2.5° and Tt the total transmission. The clarity measured under the same conditions corresponds to T n/(T p+T n), Tn being the diffuse transmission at an angle less than 2.5° and Tp the direct transmission. Light transmission is measured according to the ISO 9050:2003 standard with a D65 illuminant and a 2° observer.

0087[0083] The present invention also relates to glazing for a land, air or water transport vehicle, for buildings, urban furniture (bus shelters, display screens, etc.), furnishings (furniture, tablets, etc.). .), interior design (aquarium, shower cabin, etc.), household appliances (refrigerator shelf, radiator, etc.), electronics (TV screen, computer screen, etc.).

0088Another object of the invention is the use of the material described above as glazing for a land, air or water transport vehicle, for buildings, urban furniture (bus shelters, display screens, etc.), furnishings (furniture, tablet, etc.), interior design (aquarium, shower cabin, etc.), household appliances (refrigerator shelf, radiator, etc.), electronics (TV screen, etc.). 'computer ...).