Substrate having a functional coating and a temporary protection layer

Abstract

The invention relates to a substrate comprising two main faces defining two main surfaces separated by edges, said substrate bearing a functional coating deposited on at least one portion of one main surface and a temporary protective layer deposited on at least one portion of the functional coating. The temporary protective layer, cured by drying, by UV irradiation or by an electron beam, has a thickness of at least 1 micrometer and is not soluble in water. This temporary protective layer is obtained from a liquid composition comprising (meth)acrylate compounds selected from monomers, oligomers, prepolymers or polymers comprising at least one (meth)acrylate function.

Claims

1. A process for protecting an article with a glass substrate comprising two main faces that define two main surfaces separated by edges, said glass substrate to bear a functional coating to be deposited on at least one portion of at least one of the two main surfaces, said process comprising: depositing the functional coating on the at least one portion of at least one of the two main surfaces by magnetron sputtering; preparing a liquid composition comprising (meth)acrylate compounds selected from monomers, oligomers, prepolymers or polymers comprising at least one (meth)acrylate function; applying the composition to at least one portion of the functional coating over a thickness of at least 1 micrometer; crosslinking the composition so as to form a temporary protective layer, the temporary protective layer being directly in contact with the functional coating deposited by magnetron sputtering, and removing said temporary protective layer whenever deemed necessary by a heat treatment at a temperature of tempering, annealing or bending.

2. The process as claimed in claim 1, wherein the temperature is above 200 C.

3. The process as claimed in claim 2, wherein the temperature is above 300 C.

4. The process as claimed in claim 3, wherein the temperature is above 400 C.

5. The process as claimed in claim 1, further comprising, after said crosslinking, stacking said glass substrate with another glass substrate and then, after said stacking, removing said temporary protective layer.

6. The process as claimed in claim 1, wherein said temporary protective layer is removed during tempering of the glass substrate.

7. The process as claimed in claim 1, wherein said temporary protective layer is removed during annealing of the glass substrate.

8. The process as claimed in claim 1 wherein said temporary protective layer is removed during bending of the glass substrate.

9. The process as claimed in claim 1, wherein the (meth)acrylate compounds that have reacted together represent at least 90% by weight of a weight of the temporary protective layer.

10. The process as claimed in claim 1, wherein the functional coating comprises a thin-film multilayer successively comprising, starting from the substrate, an alternation of n functional metallic layers based on silver or on a metal alloy containing silver, and of (n+1) antireflection coatings, each antireflection coating comprising at least one dielectric layer, so that each functional metallic layer is positioned between two antireflection coatings.

11. The process as claimed in claim 1, wherein the functional coating comprises an upper layer selected from nitrides, oxides or oxynitrides of titanium, of zirconium and/or of hafnium.

12. The process as claimed in claim 11, wherein the upper layer is selected 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.

Description

EXAMPLES

(1) I. Materials Used

(2) 1. Substrates and Functional Layers

(3) The substrates used are flat glass substrates having a thickness of around 6 mm obtained by a float process that consists in pouring the molten glass onto a tin bath.

(4) Functional coatings that confer solar-control properties and that comprise a thin-film multilayer were deposited using a magnetron sputtering device.

(5) The first functional coating, referred to hereinbelow as Ag trilayer, successively comprises, starting from the substrate, an alternation of three silver layers (functional metallic layers) and of four antireflection coatings, each antireflection coating comprising at least one dielectric layer, so that each functional metallic layer is positioned between two antireflection coatings. The total thickness of this functional coating is between 200 and 250 nm.

(6) The second functional coating, referred to hereinbelow as Ag bilayer, comprises a thin-film multilayer that successively comprises, starting from the substrate, an alternation of two silver layers and of three antireflection coatings, each antireflection coating comprising several dielectric layers, so that each silver layer is positioned between two antireflection coatings. The total thickness of this functional coating is between 150 and 200 nm.

(7) The upper layer of the first and second functional coatings is selected from: OC1: a layer of titanium zirconium hafnium nitride obtained from targets of titanium metal, metal alloy of titanium and zirconium or metal alloy of titanium, zirconium and hafnium (TiZrHfNx) of 2 to 5 nm, OC2: a layer of titanium oxide obtained from a target of titanium metal or a sub-stoichiometric titanium oxide TiOx (x<2) of 2 to 5 nm or OC3: a layer of silicon nitride obtained from an optionally doped silicon target of 10 to 50 nm.
2. Temporary Protective Layer

(8) Liquid compositions were produced with mixtures of oligomers and monomers comprising at least one acrylate function sold by the company Sartomer: CN9276: tetrafunctional aliphatic urethane-acrylate oligomer, SR351: trimethylolpropane triacrylate, trifunctional acrylate monomer, SR833S: tricyclodecane dimethanol diacrylate, difunctional acrylate monomer.

(9) The presence of the urethane-acrylate oligomer makes it possible to adjust the hardness and flexibility properties of the temporary protective layer.

(10) The temporary protective layer is then cured either by drying or by UV crosslinking. A polymerization initiator is added and chosen as a function of the type of cross-linking. For example: for thermal crosslinking, the initiator is benzoyl peroxide, for UV crosslinking, the initiator may be selected from the photoinitiators sold by BASF under the name Irgacure such as Irgacure 500, by Lambson under the name Speedcure 500 or by Lamberti under the name Esacure HB.

(11) TABLE-US-00001 Compositions A B C D Main constituents: acrylate oligomer 40 40 60 36 difunctional acrylate 30 30 20 25 trifunctional acrylate 30 30 20 25 Initiator: Thermal 3 UV 5 5 5 Solvent: butyl acetate 9 Viscosity at 25 C. (Pa .Math. s) 0.71 0.50 1.08 0.15

(12) The compositions are defined in parts by weight.

(13) The main constituents consist of oligomers, monomers and optionally prepolymers.

(14) The liquid compositions are applied to the glass substrates by roll coating. Thicknesses between 10 and 20 m are obtained using speeds for the applicator roll of between around 15 and 25 m/min.

(15) The temporary layers A cured by drying are heated at 150 C. for 15 min and are thus perfectly dry and hard.

(16) The temporary layers D are pre-dried in an IR oven at a temperature of at least 120 C. but less than 170 C. before passing under UV for crosslinking.

(17) The temporary layers B, C or D cured by UV irradiation are crosslinked at a rate of 15 m/min by UV radiation provided by a mercury lamp having a power of 120 W. Under these conditions, the polymerization of the mixture of monomers and oligomers is obtained in the thickness range from 10 to 20 m.

(18) The temporary layers cured by UV irradiation may also be crosslinked using an LED UV crosslinking system.

(19) II. Evaluation of the Mechanical Properties

(20) These tests were carried out on glass substrates bearing: a silver trilayer functional coating, a temporary protective layer of type C.

(21) The thicknesses tested for the functional layer are respectively 13 and 20 m.

(22) The substrates are subjected to thermal tempering under the following conditions: 685-695 C. for 40-50 s/mm of glass. Next, an Erichsen scratch test (EST) and a high humidity (HH) test are carried out.

(23) The Erichsen test consists in reporting the value of the force needed, in newtons, to produce a scratch in the multilayer (van Laar tip, steel ball).

(24) The following assessment indicators were used: +++: no scratches, 0: non-continuous scratches, : many non-continuous scratches, : continuous scratches.

(25) The humidity (HH) test consists in storing samples for 8 days at 90% relative humidity and at 60 C. and in observing the possible presence of defects such as corrosion pitting. The following assessment indicators were used: +: no pitting, : much pitting.

(26) The tables below summarize the glazing units, the evaluation conditions and the assessment indicators. A reference substrate bearing a functional coating without a temporary protective layer is compared to two substrates bearing a functional coating and a temporary protective layer having a thickness of 13 m and 24 m. The test was carried out on two different locations of the surface of one and the same substrate. These examples clearly show the excellent scratch resistance and wet corrosion resistance of the substrates protected according to the invention.

(27) TABLE-US-00002 Erichsen test 0.1 0.5 0.7 1 3 5 7 10 Reference +++ +++ +++ 0 +++ +++ +++ 0 C-13 m +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ C-24 m +++ +++ +++ +++ +++ +++ 0 +++ +++ +++ +++ +++ +++ +++ HH test Assessment Reference C-13 m + C-24 m +

(28) The reference substrate according to the Erichsen test comprises, from 1 N, fine scratches and, at 10 N, numerous highly visible continuous scratches, uniform in thickness. A same substrate protected by a temporary protective layer according to the invention comprises far fewer scratches after tempering for applied forces of 7 to 10 N. Furthermore, the scratches are non-continuous.

(29) The substrates protected by a temporary protective layer according to the invention do not comprise corrosion pitting. These tests show that a substrate bearing a 13 m thick functional coating is effectively protected.

(30) III. Evaluation of the Properties After Tempering

(31) The tempering tests carried out show the total removal of the temporary protective layer without deterioration of the substrates bearing the functional coatings. This aspect was verified by measuring the colorimetric coordinates. Glass substrates bearing functional coatings which differ by the choice of the upper layer were tested. They comprise, respectively as upper layer, OC1 (TiZrHfNx) and OC2 (TiOx).

(32) Substrates referred to hereinbelow as OC1-Inv and OC2-Inv were protected by a temporary coating of C type and subjected to tempering. For comparison, reference substrates referred to hereinbelow as OC1-Ref and OC2-Ref were not protected and were subjected to tempering.

(33) The colorimetric color change upon heat treatment on the functional coating side, in reflection, induced by the tempering was calculated (E). For this: the colors in reflection L*, a* and b* in the LAB system measured according to the illuminant D65, on the layer side, are measured and the change is measured in the following manner:
E=(a*.sup.2+b*.sup.2+L*.sup.2).sup.1/2.

(34) Several measurements of E were made for each glass substrate covered with a functional coating. The table below summarizes the result of these tests.

(35) For the reference substrates, E represents the change between the L, a* and b* values obtained for an unprotected substrate before tempering and for a tempered unprotected substrate.

(36) For the substrates of the invention, E corresponds to the change between the L, a* and b* values obtained for an unprotected substrate before tempering and for a protected substrate, the protective layer of which has been removed following tempering.

(37) TABLE-US-00003 Substrate OC1-Inv OC1-Ref OC2-Inv OC2-Ref E 11.21 10.70 12.71 10.43 11.15 11.13 12.51 11.95 10.81 12.93

(38) These tests show that the presence of the temporary protective layer according to the invention does not modify the colorimetric changes that may be induced by a tempering type treatment. Indeed, the difference between the values of E are not significant between a substrate according to the invention and a reference substrate that are tempered with respect to an untempered substrate.

(39) Regardless of the nature of the upper layer, no colorimetric change is observed that can be attributed to the presence of the temporary protective layer. This means that the temporary protective layer does not induce a colorimetric modification in the substrate after heat treatment.

(40) IV. Influence of the Upper Layer

(41) Comparative tests for evaluating the influence of the upper layer on the appearance after tempering were carried out. Substrates bearing functional coatings of silver trilayer type with different upper layers were tested. Each of these substrates was covered with a temporary protective layer of C type then subjected to a heat treatment of tempering type.

(42) The observations of the surface after heat treatment, as a function of the nature of the upper layer, are the following: OC1 (TiZrHfNx): no defect, OC2 (TiOx): no defect, OC3 (Si.sub.3N.sub.4): no defect.

(43) Other upper layers were tested. These layers did not make it possible to obtain results as good as those obtained with the nitrides, oxides or oxynitrides of titanium, zirconium and/or hafnium. Functional coatings comprising upper layers based on titanium, zirconium and/or hafnium protected by temporary layers according to the invention show a better corrosion resistance and very low levels of haze.