Article comprising a functional coating and a temporary protective layer made of polyfuranic resin

Abstract

An article includes a substrate with two main faces defining two main surfaces separated by edges, the substrate carrying a functional coating deposited over at least a portion of a main surface and a temporary protective layer deposited over at least a portion of the coating. The temporary protective layer has a thickness of at least 1 micrometer. The temporary protective layer made of polyfuran resin is obtained from a liquid composition comprising furfuryl alcohol.

Claims

1. An article comprising a substrate comprising two main faces defining two main surfaces separated by edges, said substrate carrying: a functional coating deposited over at least a portion of a main surface and a temporary protective layer deposited over at least a portion of the functional coating, wherein: the temporary protective layer has a thickness of greater than 1 micrometer, the temporary protective layer comprises or consists essentially of a poly(furfuryl alcohol) resin, wherein the functional coating comprises a stack of thin layers successively comprising, starting from the substrate, an alternation of n functional metal layers based on silver or on silver-containing metal alloy, and (n+1) antireflective coatings, each antireflective coating comprising at least one dielectric layer, so that each functional metal layer is positioned between two antireflective coatings.

2. The article comprising a substrate as claimed in claim 1, wherein the substrate carrying the functional coating has not been subjected to heat treatment at a temperature of greater than 400° C.

3. The article comprising a substrate as claimed in claim 1, wherein the products of the polymerization of the furfuryl alcohol represent at least 90% by weight of the weight of the temporary protective layer.

4. The article comprising a substrate as claimed in claim 1, wherein the temporary protective layer is deposited: over each of the main surfaces of the substrate and/or over at least one edge of the substrate and/or over each of the edges of the substrate.

5. The article comprising a substrate as claimed in claim 1, wherein the temporary protective layer is directly in contact with the functional coating.

6. The article as claimed in claim 1, wherein said substrate is made of glass, of glass-ceramic, of ceramic, of steel or of a metal having a melting point of greater than 250° C.

7. The article as claimed in claim 1, wherein said substrate is made of glass.

8. The article comprising a substrate as claimed in claim 1, wherein the thickness of the temporary protective layer is less than 100 micrometers.

9. An article comprising a substrate comprising two main faces defining two main surfaces separated by edges, said substrate carrying: a functional coating deposited over at least a portion of a main surface and a temporary protective layer deposited over at least a portion of the functional coating, wherein: the temporary protective layer has a thickness of greater than 1 micrometer, the temporary protective layer comprises or consists essentially of a poly(furfuryl alcohol) resin, and the functional coating comprises an upper layer chosen from a metal nitride, a metal oxide or a metal oxynitride and the metal is one or more selected from the group consisting of titanium, zirconium and hafnium.

10. The article comprising a substrate as claimed in claim 9, wherein the upper layer is chosen from a layer: of titanium nitride; of zirconium nitride; of hafnium nitride; of titanium zirconium nitride; of titanium zirconium hafnium nitride, of titanium oxide; of zirconium oxide; of hafnium oxide; of titanium zirconium oxide; of titanium zirconium hafnium oxide.

11. A process for the protection of an article comprising a substrate comprising two main faces defining two main surfaces separated by edges, said substrate carrying a functional coating deposited over at least a portion of a main surface, said protection process comprising the following stages: preparing a liquid composition comprising furfuryl alcohol, applying the composition to at least a portion of the functional coating over a thickness of at least 1 micrometer, polymerizing the composition so as to form a temporary protective layer a poly(furfuryl alcohol) resin, wherein the functional coating comprises a stack of thin layers successively comprising, starting from the substrate, an alternation of n functional metal layers based on silver or on silver-containing metal alloy, and (n+1) antireflective coatings, each antireflective coating comprising at least one dielectric layer, so that each functional metal layer is positioned between two antireflective coatings.

12. The process for the protection of an article as claimed in claim 6, wherein the liquid composition comprises an acid catalyst of the polymerization reaction.

13. The process for the protection of an article as claimed in claim 6, wherein the liquid composition comprises a wetting agent or surfactant.

14. The process for the protection of an article as claimed in claim 11, wherein the substrate is a glass substrate.

15. The process for the protection of an article as claimed in claim 11, further comprising removing said temporary protective layer.

16. The process for the protection of an article as claimed in claim 15, wherein the substrate is a glass substrate.

17. The process for the protection of an article as claimed in claim 15, wherein the temporary protective layer is removed by a heat treatment at a temperature of greater than 300° C.

18. The process for the protection of an article as claimed in claim 17, wherein the temporary protective layer is removed by tempering, annealing and/or bending.

Description

EXAMPLES

(1) I. Materials Used

(2) 1. Substrates and Functional Layers

(3) The substrates used are flat glass substrates with a thickness of approximately 6 mm obtained by a float glass process which consists in pouring the molten glass over a bath of tin.

(4) Functional coatings conferring solar control properties comprising a stack of thin layers were deposited by virtue of a magnetic-field-assisted (magnetron) cathode sputtering device.

(5) The functional coating, known below as Ag trilayers (Cool-Lite Xtrem® 70/33 II sold by the applicant company), successively comprises, starting from the substrate, an alternation of three silver layers (functional metal layers) and of four antireflective coatings, each antireflective coating comprising at least one dielectric layer, so that each functional metal layer is positioned between two antireflective coatings. The total thickness of this functional coating is of the order of 200 nm.

(6) 2. Temporary Protective Layer

(7) Liquid compositions are produced with the BioRez™ polyfuran (or poly(furfuryl alcohol)) resin sold by TransFurans Chemicals, Belgium. The resin is obtained by polycondensation of furfuryl alcohol in the presence of an acid catalyst. It exhibits an acid pH of approximately 5, a low content of residual furfuryl alcohol (less than 1%) and a viscosity at 25° C. of less than 1000 mPa.Math.s. 0.17% by weight of Tego® Wet 250 wetting agent from Evonik (siloxane polyether copolymer) is added to the resin. The mixture is subsequently deposited using a Meyer rod over the functional coating deposited beforehand over the substrate.

(8) Once deposited over the glass, the coating is hardened by a heat treatment at 200° C. for 15 minutes.

(9) These tests were carried out on two samples produced as described above but in which a different amount of the polyfuran resin was deposited. After drying, the thicknesses for the temporary protective layer are 13 and 20 μm for the two samples, respectively C1 and C2.

(10) The main characteristics of the samples C1 and C2 and of the process for obtaining them are given in table 1 below:

(11) TABLE-US-00001 TABLE 1 C1 C2 Wet thickness (μm) 24 40 Curing time 200° C. 15 min 15 min Curing type oven oven Homogeneous deposition after curing Yes Yes Coating thickness (μm) after curing 13 20
II. Evaluation of the Mechanical Properties

(12) The substrates are subjected to thermal tempering under the following conditions: 730° C. for 240 seconds. Then an Erichsen scratch test (EST) is carried out.

(13) The Erichsen test consists in giving the value of the force necessary, in newtons, to produce a scratch in the stack (Van Laar tip, steel ball).

(14) The following assessment indicators were used:

(15) “+”: no scratch,

(16) “0”: noncontinuous scratches,

(17) “−”: continuous scratches.

(18) A reference substrate carrying a functional coating without a temporary protective layer is compared with the two substrates carrying a functional coating and a temporary protective layer with a thickness of 13 and 20 micrometers (μm). The test was carried out on different places of the surface of one and the same substrate. These examples clearly show the excellent scratch resistance of the protected articles according to the invention, as given in table 2 which follows.

(19) TABLE-US-00002 TABLE 2 Erichsen test 0.1 0.5 0.7 1 4 7 Reference + + + 0 − − C1-13 μm + + + + + 0 C1-20 μm + + + + + +

(20) The reference substrate or article comprises, from 1N, according to the Erichsen test, fine scratches and, at 4N, numerous continuous scratches which are very visible and homogeneous in thickness. One and the same substrate protected by a temporary protective layer according to the invention comprises very few scratches after tempering for forces applied up to at least 7N. Furthermore, the scratches are noncontinuous.

(21) These tests show that an article carrying a protective layer with a thickness of 13 μm can be regarded as effectively protected.

(22) III. Evaluation of the Properties after Tempering

(23) The colorimetric variation ΔE brought about by the tempering on the side of the functional coating, in reflection, was calculated. For this: the colors in reflection L*, a* and b* in the LAB system, measured according to the illuminant D65, layers side, are measured before the deposition of the protective layer and after the tempering, and the variation is measured in the following way: ΔE=(Δa*.sup.2+Δb*.sup.2+ΔL*.sup.2).sup.1/2.

(24) No colorimetric variation attributable to the presence of the temporary protective layer is observed, the ΔE measured on the samples C1 and C2 being substantially equal to that measured on the reference sample.

(25) This means that the deposition and the removal of the temporary protective layer does not bring about a modification to the properties of the protected stack.