Article with a Hydrophobic Surface Coated with a Temporary Super-Hydrophobic Film Providing Antirain Functionality and Process for Obtaining Same

Abstract

The present invention relates to an article having a surface coated with a nanostructured temporary super-hydrophobic film having a static contact angle with water of at least 140°, preferably exhibiting multiple length scales of roughness and comprising nanoparticles functionalized with a hydrophobic agent, wherein the functionalization of the nanoparticles with the hydrophobic agent has been performed before said nanostructured temporary super-hydrophobic film is coated on said surface. The surface of the article exhibits a static contact angle with water of at least 60° before being coated with the nanostructured temporary super-hydrophobic film. The treatment according to the invention can be used to provide an antirain function to optical articles having a hydrophobic surface.

Claims

1.-15. (canceled)

16. An article having at least one surface that is at least partially coated with a nanostructured temporary super-hydrophobic film: having a static contact angle with water of at least 140°; comprising nanoparticles functionalized with at least one hydrophobic agent, wherein the functionalization of the nanoparticles with said at least one hydrophobic agent has been performed before said nanostructured temporary super-hydrophobic film is coated on said surface; said surface exhibits a static contact angle with water of at least 60° before being at least partially coated with said nanostructured temporary super-hydrophobic film.

17. The article of claim 16, wherein the hydrophobic agent is an organosilane comprising at least one fluorinated group connected to the silicon atom through a carbon atom and at least one silicon atom bearing at least one hydrolyzable group.

18. The article of claim 17, wherein the fluorinated group is a perfluoropolyether group.

19. The article of claim 16, wherein the functionalized nanoparticles are bound by at least one binder.

20. The article of claim 16, wherein the nanoparticles have a double-scale of roughness.

21. The article of claim 16, wherein the temporary super-hydrophobic film comprises at least two nanoparticle populations of different size ranges, a first one having an average diameter ranging from 40 to 100 nm, and a second one having an average diameter ranging from 5 to less than 40 nm.

22. The article of claim 16, wherein the nanoparticles comprise a core nanoparticle having an average diameter D1 and nanoparticles having an average diameter D2 and adhering to said core nanoparticle, with D2<D1.

23. The article of claim 22, wherein the nanoparticles having an average diameter D2 adhere by grafting to the core nanoparticle.

24. The article of claim 16, wherein the nanoparticles are made of at least one metal, at least one metal oxide, at least one metal nitride, at least one metal fluoride, or at least one polymer.

25. The article of claim 16, wherein the nanostructured temporary super-hydrophobic film exhibits a static contact angle with water of at least 145°.

26. The article of claim 16, wherein said surface exhibits a static contact angle with water of at least 100° before being at least partially coated with said nanostructured temporary super-hydrophobic film.

27. The article of claim 16, wherein said surface is the surface of a coating obtained by applying a composition comprising at least one fluorinated organosilane, having a chain functionalized at only one end or at both ends thereof by a group comprising at least one silicon atom carrying at least one hydrolyzable group.

28. The article of claim 27, wherein said fluorinated organosilane is a perfluorinated organosilane.

29. The article of claim 16, further defined as an optical lens.

30. The article of claim 16, further defined as an ophthalmic lens.

31. The article of claim 16, wherein the temporary super-hydrophobic film can be removed by wiping with a cloth.

32. The article of claim 31, wherein the cloth is a dry cloth.

33. The article of claim 16, wherein the article has a haze value of 1.5% or less, as determined by the standard ASTM D1003-00.

34. A method of forming the article of claim 16, comprising: providing an article having at least one a surface exhibiting a static contact angle with water of at least 60°; and applying on said surface a coating composition comprising nanoparticles functionalized with at least one hydrophobic agent so that said surface is at least partially coated with a nanostructured temporary super-hydrophobic film having a static contact angle with water of at least 140°.

Description

EXAMPLES

[0226] 1. Materials

[0227] The articles employed in the examples comprise a 65 mm-diameter ORMA® lens substrate (polymer obtained by polymerization of diethylene glycol bis (allyl carbonate) from Essilor based on CR-39® monomer, refractive index=1.5), or a polythiourethane MR8® lens substrate (from Mitsui Toatsu Chemicals Inc., refractive index=1.59) with a power of −2.00 diopters and a thickness of 1.2 mm, coated on its convex face with the impact resistant primer coating based on a W234™ polyurethane material disclosed in the experimental part of WO 2010/109154 modified to have a refractive index of 1.6 by addition of high refractive index colloids and the abrasion- and scratch-resistant coating (hard coat) disclosed in example 3 of EP 0614957 (modified to have a refractive index of 1.6 rather than 1.5 by adding high refractive index colloids), both deposited by dip coating, the antireflective coating of example 6 of the patent application WO 2008/107325 and with an antifouling coating deposited by evaporation under vacuum.

[0228] Said antireflection coating was deposited by evaporation under vacuum, and comprised a 150 nm thick SiO.sub.2 sub-layer and the stack ZrO.sub.2/SiO.sub.2/ZrO.sub.2/ITO/SiO.sub.2 (respective thicknesses of the layers: 29, 23, 68, 7 and 85 nm). An ITO layer is an electrically conductive layer of indium oxide doped with tin (In.sub.2O.sub.3:Sn).

[0229] The antifouling coating (hydrophobic and oleophobic coating) was either made of the Optool DSX® composition marketed by Daikin Industries or the KY-130® composition commercialized by Shin-Etsu Chemical (thickness: from 2 to 5 nm).

[0230] In examples 1, 4 and 7, the substrate was MR8® and the lens did not comprise any antireflection coating and antifouling coating. Its outer coating was the above described hard coat.

[0231] The treating machine was a 1200 DLF from Satis, or a BAK2-F or BAK4 machine from Balzers equipped with an electron gun for the evaporation of the precursor materials, a thermal evaporator, and a KRI EH 1000 F ion gun (from Kaufman & Robinson Inc.) for use in the preliminary phase of preparation of the surface of the substrate by argon ion bombardment (IPC) and in the ion-assisted deposition (IAD) of layers.

[0232] 2. Synthesis of Raspberry Nanoparticle Suspensions

[0233] Raspberry nanoparticles were synthesized based on large silica particles (50 nm) onto which a chemical group was grafted (-NCO). These nanoparticles were then contacted with smaller silica particles (15 nm).

[0234] Spherical nanoparticles of silica having an average diameter of 50 nm (“NP50”) were functionalized to obtain isocyanate (-NCO) groups on their surface, as disclosed in the experimental part of WO 2015/177229, using the adhesion agent 3-(triethoxysilyl)propyl isocyanate. “NP50-NCO” nanoparticles were produced.

[0235] Spherical nanoparticles of silica having an average diameter of 15 nm (“NP15”), which naturally comprise hydroxyl (—OH) groups on their surface, were used as received. A suspension of “NP15-OH” nanoparticles in methoxypropyl acetate was produced.

[0236] Then, thanks to their complementary reactive groups, the NP15-OH nanoparticles were covalently grafted onto NP5O-NCO nanoparticles in methoxypropyl acetate solvent (CAS n° 108-65-6), by introducing the NP5O-NCO nanoparticles in a suspension of NP15-OH nanoparticles. The reaction mixture was heated at 120° C. overnight. The smaller NP15-OH nanoparticles were used in excess (ration 30:1) to be sure to cover the surface of the NP50-NCO nanoparticles, to yield a stable suspension in methoxypropyl acetate of raspberry nanoparticles called “NPF80” nanoparticles, with a particle concentration of 50 g/L.

[0237] The methoxypropyl acetate solvent was replaced by a hydrofluoroolefin solvent (Vertrel Suprion from Chemours, comprising methoxytridecafluoroheptene isomers) following several series of centrifugation/removal of supernatant solvent/addition of hydrofluoroolefin steps.

[0238] 3. Preparation of a Suspension of Raspberry Nanoparticles Functionalized with a Hydrophobic Agent

[0239] After the solvent exchange step, a fluorinated silane hydrophobic agent was added to the raspberry nanoparticles NPF80 suspension in hydrofluoroolefin, in excess ratio, and the suspension was stirred for 24h at 110° C. The excess of hydrophobic agent that has not reacted with the nanoparticles was eliminated from the suspension by successive centrifugation/solvent removal/washing with butyl acetate/addition of pure hydrofluoroolefin solvent steps, leading to a stable suspension of functionalized raspberry nanoparticles with a particle concentration of about 50 g/L.

[0240] Then, the suspension in hydrofluoroolefin was diluted with an adequate mixture of hydrofluoroolefin and isopropanol (provided by Fisher Scientific) to obtain a final suspension of raspberry nanoparticles in 95/5 hydrofluoroolefin/isopropanol, with a particle concentration of 5 g/L, ready for deposition onto surfaces.

[0241] In examples 4-6, a binder (tetraethoxysilane, CAS N° 78-10-4) was added in the form of a solution in isopropanol to get a concentration of 10 mM of binder.

[0242] In examples 7-9, the compound SP-02-001 provided by Specific Polymers (CAS N° 155881-89-3, triethoxysilane content: 2.3 meq/g) was added in the coating composition as a hydrophobic binder in the form of a solution in hydrofluoroolefin to get a concentration of 2.5 mM of binder. It is a mixture comprising 15.5 mol % of the difunctional fluoro alkyl bis(triethoxysilane) of formula (IIb) (H.sub.5C.sub.2O).sub.3Si—C.sub.2H.sub.4—C.sub.6F.sub.12—C.sub.2H.sub.4—Si(OC.sub.2H.sub.5).sub.4, 47.5 mol % of the corresponding monofunctional fluoro alkyl triethoxysilane of formula (Ic) CH.sub.3—CH═CF—C.sub.5F.sub.10—C.sub.2H.sub.4—Si(OC.sub.2H.sub.5).sub.3 and .sub.37.1 mol % of the compound CH.sub.3—CH═CF—C.sub.4F.sub.8—CF═CH—CH.sub.3.

[0243] The following fluorinated silane was used as hydrophobic agent to functionalize the raspberry nanoparticles. This trimethoxysilane perfluoropolyether of formula Ib was provided by Surfactis Technologies (MW=989 g/mol):

##STR00010##

[0244] 4. Deposition of the Nanostructured Temporary Super-Hydrophobic Film

[0245] Each lens (having an antifouling coating or a hard coat as outer coating) was subjected to the following washing procedure before deposition of the liquid coating composition containing the functionalized nanoparticles. The lens was rinsed with soapy water using a sponge (4 rotations convex face, 4 rotations concave face), thoroughly rinsed with tap water, dipped in a beaker of deionized water 3 or 4 times, dried with a cloth (Selvyt), rubbed (circular wiping) with a Cémoi™ fabric soaked in isopropyl alcohol and wiped with a clean and dry Cémoi™ fabric. The Cémoi™ fabric denotes a microfiber fabric (manufacturer KB SEIREN—distributor: Facol, reference Microfibre M8405 30×40).

[0246] The liquid coating composition was applied on the surface to be treated at least five minutes after it was washed, by means of a 50 mL sprayer (simple water mister) with two successive sprayings without intermediate drying. This allows the deposition of a wet film on the whole surface of the lens and to a homogeneous drying (drying was carried out at room temperature for 1 minute). The amount of liquid composition used to treat a lens was about 0.5 mL.

[0247] 5. Removal and Reapplication of the Nanostructured Temporary Super-Hydrophobic Film

[0248] The temporary film was removed by dry wiping with a disposable Wypall™ cloth or CEMOI™ cloth, by applying a mild pressure and circular movements on the lenses. A measure of contact and sliding angles after wiping allows the determination of whether the temporary film was successfully removed.

[0249] It can be reapplied on the wiped lens by the same process as the initial application (same spraying composition and deposition conditions).

[0250] 6. Testing Methods

[0251] The following test procedures were used to evaluate the optical articles prepared according to the present invention.

[0252] The thickness of the layers was controlled by means of a quartz microbalance.

[0253] The haze value H (diffusion rate) of both the reference and the tested optical article were measured by light transmission as disclosed in WO 2012/173596 utilizing the Haze-Guard Plus haze meter from BYK-Gardner (a color difference meter) according to the method of ASTM D1003-00 before and after the test has been performed. As haze is a measurement of the percentage of transmitted light scattered more than 2.5° from the axis of the incident light, the smaller the haze value, the lower the degree of cloudiness. Generally, for optical articles described herein, a haze value of less than or equal to 1.5% is acceptable, more preferably of less than or equal to 1%.

[0254] The static contact angles with water of the surfaces were determined at 25° C. according to the liquid drop method, according to which three deionized water drops having a diameter of less than 2 mm (typically 20 μL for hydrophobic surfaces and 4 μL for super-hydrophobic surfaces) were deposited gently on a cleaned and dried planar lens surface, one on the center thereof and the two others 20 mm away from the latter. The angle at the interface between the liquid and the solid surface was measured with a Dataphysics SCA20. Water had a conductivity of between 0.3 μS and 1 μS at 25° C. Sliding angles, i.e., tilt angles at which a water droplet begins to slide, were determined with the same apparatus with 20 μL or 4 μL deionized water drops in two points of the lens.

[0255] The durability of the super-hydrophobic treatment was evaluated by immersing the lenses for 30 seconds in deionized water. Other durability tests were performed to investigate resistance to water impacts of the super-hydrophobic treatment. In the water jet test, a focused jet (ØÆ2 mm) was sprayed onto the surface of the lenses at a distance of 10 cm. A jet represents a volume of water of 1 mL and exerts a force of 0.1 N. 15 sprays were applied on the same zone of the coated lens. In the dripping test, the lenses were placed at an angle of 45° with the horizontal under a 250 mL introduction funnel delivering deionized water drop by drop. The water fell on the lens surface from a height of 70 cm. The test lasts about 20 minutes.

[0256] The durability tests are successful (“pass”) if the super-hydrophobic properties of the lens are maintained after each test, i.e., if the static contact angle with water of the temporary super-hydrophobic film is maintained at 140° or above and the sliding angle is maintained at 10° or lower.

[0257] 7. Results

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 Surface Hard coat Optool KY-130 ™ Hard coat Optool KY-130 ™ treated DSX ™ DSX ™ Binder — — — TEOS TEOS TEOS 10 mM 10 mM 10 mM Hydrophobic Compound Compound Compound Compound Compound Compound agent Ia Ia Ia Ia Ia Ia Initial water 75° +/− 4° 114.5° +/− 1° .sup.   109° +/− 1°  75° +/− 4° 114.5° +/− 1° .sup.   109° +/− 1°  contact angle Initial sliding 36° +/− 5° 13° +/− 3° 23° +/− 6°  36° +/− 5° 13° +/− 3° 23° +/− 6° angle Initial haze  0.13% +/− 0.04%  0.06% +/− 0.02% 0.06% +/− 0.03%  0.13% +/− 0.04%  0.06% +/− 0.02%  0.06% +/− 0.03% Initial Tv 90.4% +/− 0.3% 96.2% +/− 0.2% 95.9% +/− 0.2%  90.4% +/− 0.3% 96.2% +/− 0.2% 95.9% +/− 0.2% Water contact >150° >150° >150° >150° >150° >150° angle after film deposition Sliding angle  <10°  <10°  <10°  <10°  <10°  <10° after film deposition Haze after  0.9% +/− 0.3%  1.3% +/− 0.3% 1.0% +/− 0.1%  1.1% +/− 0.5%  1.1% +/− 0.2%  1.0% +/− 0.2% film deposition Tv after film 93.2% +/− 0.7% 95.3% +/− 0.3% 95.2% 93.0% +/− 0.7% 95.7% +/− 0.2% 95.6% +/− 0.2% deposition Immersion Pass Pass Pass Pass Pass Pass test Water contact 72° +/− 2° 115.4° +/− 0.5°  110.1° +/− 0.4°  75.8° +/− 0.7° 112.7° +/− 0.1°  110.0° +/− 0.7°  angle after (a) film removal Example 7 8 9 Surface treated Hard coat Optool DSX ™ KY-130 ™ Binder SP-02-001 2.5 mM SP-02-001 2.5 mM SP-02-001 2.5 mM Hydrophobic agent Compound Ia Compound Ia Compound Ia Initial water contact 75° +/− 4° 114.5° +/− 1° .sup.   109° +/− 1°  angle Initial sliding angle 36° +/− 5° 13° +/− 3° 23° +/− 6° Initial haze  0.13% +/− 0.04%  0.06% +/− 0.02%  0.06% +/− 0.03% Initial Tv 90.4% +/− 0.3% 96.2% +/− 0.2% 95.9% +/− 0.2% Water contact >150° >150° >150° angle after film deposition Sliding angle after  <10°  <10°  <10° film deposition Haze after film  1.4% +/− 0.2%  1.8% +/− 0.4%  1.9% +/− 0.1% deposition Tv after film 93.3% +/− 0.2% 95.2% +/− 0.2% 95.0% +/− 0.1% deposition Immersion test Pass Pass Pass Water contact 76.5° +/− 4°.sup.  114.0° +/− 1.4°   108° angle after film removal (a) same results obtained if wiped with Cemoi ™ cloth or Cemoi ™ IPA)

[0258] Table 1 indicates for the ophthalmic lenses treated the surface properties displayed: [0259] before deposition of a nanostructured temporary super-hydrophobic film (“initial properties”), [0260] after deposition of a nanostructured temporary super-hydrophobic film, [0261] after removal of the nanostructured temporary super-hydrophobic film.

[0262] After deposition of a nanostructured temporary film according to the invention, the lens is imparted super-hydrophobic properties (water contact angle≥150°, sliding angle≤10°) with a low level of haze, whatever the kind of surface treated having an initial static contact angle with water of at least 60°. Although the treatment brings about some haze increase, the level of haze obtained is acceptable for the user (<1.5%), and the transmission factor Tv is hardly not affected, which offers clarity of vision under rain.

[0263] The lenses were subjected to several tests to evaluate the mechanical resistance of the treatment to water. Super-hydrophobic properties were neither impacted by water immersion, nor by the dripping test performed consecutively.

[0264] The super-hydrophobic coating passed the water immersion test described above, which makes it compatible with a use under rain. It has also been observed that the film had a very good resistance to water impacts. The super-hydrophobic properties were maintained after the dripping test described above, consisting in making 250 mL of deionized water fall drop-by-drop on one point of the lens from height of 70 cm, or after the water jet test described above. Visually, water drops bounce off the surface of treated lenses, so there are no droplets remaining to disturb the vision.

[0265] The temporary film can be easily removed from the surface of the coated lenses without leaving residues. After wiping, the initial transparency, haze values and colorimetric features of the lenses are recovered. The water contact angle after removal of the film is close to the initial water contact angle of the treated surface.

[0266] It has also been checked that after removal of a first temporary film, a new temporary film could be applied on the lens using the same application process and provided the same super-hydrophobic properties to the lens, with the same haze level.