Item protected by a rough temporary protective cover

Abstract

An article includes a glass substrate including two main faces defining two main surfaces separated by edges and a temporary protective layer comprising an organic polymer matrix deposited on at least one portion of a main surface of the glass substrate, wherein the temporary protective layer has a rough surface defined by a surface roughness parameter Sa, corresponding to the arithmetic mean height of the profile of the surface, of greater than 0.2 μm.

Claims

1. An article comprising a glass substrate comprising two main faces defining two main surfaces separated by edges and a temporary protective layer comprising an organic polymer matrix deposited on at least one portion of a main surface of the glass substrate, wherein the temporary protective layer is obtained from a polymerizable composition comprising (meth)acrylate compounds and has a rough surface defined by a surface roughness parameter Sa, corresponding to the arithmetic mean height of the profile of the surface, of greater than 0.2 μm and less than 5.0 μm.

2. The article as claimed in claim 1, wherein the rough surface has a surface roughness parameter Sz, corresponding to the maximum height of the profile of the surface, of greater than 1.0 μm.

3. The article as claimed in claim 1, wherein the rough surface has a roughness parameter Rsm, corresponding to a mean width of the elements of the profile, of greater than 0.5 mm.

4. The article as claimed in claim 1, wherein the surface roughness parameter Sa, corresponding to the arithmetic mean height of the profile of the surface, represents at least 1% of a mean thickness of the temporary protective layer.

5. The article as claimed in claim 1, wherein the surface roughness parameter Sz, corresponding to the maximum height of the surface, represents at least 10% of a mean thickness of the temporary protective layer.

6. The article as claimed in claim 1, wherein the substrate is coated with a functional coating deposited on at least one portion of a main surface and the temporary protective layer is deposited on at least one portion of the functional coating.

7. The article as claimed in claim 1, wherein the functional coating comprises a stack of thin layers 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.

8. The article as claimed in claim 1, wherein the roughness is in a form of wavelets.

9. The article as claimed in claim 8, wherein said wavelets are formed by a deposition roll and the wavelets are parallel to an axis of rotation of the deposition roll.

10. The article as claimed in claim 1, wherein the roughness is formed by stamping the polymerizable composition with a stamp having a predetermined pattern.

11. The article as claimed in claim 1, wherein the glass substrate has at least one dimension of greater than 3 m.

12. The article as claimed in claim 11, wherein the at least one dimension is greater than 6 m.

13. The article as claimed in claim 1, wherein the glass substrate has at least two dimensions of greater than 3 m, or even one dimension of greater than 3 m and one dimension of greater than 6 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a thickness measurement by a profilometer,

(2) FIG. 2 illustrates two-dimensional profiles of the surface before correction (left image) and after correction (right image), and

(3) FIG. 3 illustrates an adhesion test.

EXAMPLES

(4) I. Materials Used

(5) 1. Substrates Coated with the Functional Coating

(6) The substrates used are flat glass substrates having a thickness of around 6 mm obtained by a float process.

(7) The functional coatings comprise a stack of thin layers deposited by means of a magnetron sputtering device.

(8) The stack of thin layers successively comprises, starting from the substrate, an alternation of three dielectric coatings and of two silver layers (functional metallic layers), each dielectric coating comprising at least one dielectric layer, so that each functional metallic layer is positioned between two dielectric coatings. The layer of the functional coating furthest from the substrate is a 1 to 5 nm layer of titanium zirconium nitride. The total thickness of this functional coating is between 150 and 200 nm.

(9) 2. Preparation of the Polymerizable Compositions

(10) The polymerizable compositions were prepared. These compositions comprise the constituents of the polymer matrix, polymerization initiators and optionally additives.

(11) The constituents of the polymer matrix comprise oligomers, monomers and optionally prepolymers. A mixture of oligomers and monomers comprising at least one acrylate function sold by Sartomer was used with, in particular: CN9276: tetrafunctional aliphatic urethane-acrylate oligomer, SR351: trimethylolpropane triacrylate, trifunctional acrylate monomer, SR833S: tricyclodecane dimethanol diacrylate, difunctional acrylate monomer.

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

(13) The polymerization initiator used in these examples is Irgacure® 500 or Irgacure® 184, sold by BASF.

(14) The various constituents and additives are mixed by ultrasonic mixing.

(15) The compositions tested are defined in the table below in parts by weight.

(16) TABLE-US-00001 Parts by Composition weight Viscosity Polymer matrix: acrylate oligomer   60 5.8 Pa.s difunctional acrylate   20 140 mPa.s trifunctional acrylate   20 110 mPa.s UV initiator +10 —

(17) The viscosity of the polymerizable composition is measured using an Anton Parr viscometer or the no. 5 Ford cup. The polymerizable composition has a viscosity at 20° C. of 0.8±0.1 Pa.Math.s

(18) 3. Preparation of the Articles Tested

(19) TABLE-US-00002 Articles F E R1 R2 Substrate + Functional coating Yes Yes Yes Yes Polymerizable composition No E E E

(20) The article E corresponds to an article as described in application WO 2015/019022. This article does not have the roughness as claimed. The polymerizable composition is applied to the glass substrate coated with the functional coating by roll coating. The applicator roll rotates at a speed between 15 and 25 m/min. The run speed of the substrate is also between 15 and 25 m/min. The temporary layer is crosslinked by UV radiation. The thicknesses of polymerizable compositions deposited are between 10 and 20 μm.

(21) The article R1 corresponds to an article according to the invention. The polymerizable composition is applied to the glass substrate coated with a functional coating by roll coating. The applicator roll rotates at a speed of around 40 m/min. The run speed of the substrate is also 40 m/min. The temporary layer is immediately crosslinked by UV radiation. The article R1 according to the invention has a roughness as claimed. The thickness of polymerizable composition deposited corresponds to the thickness of the temporary protective layer and is between 10 and 20 μm.

(22) The temporary protective layers are obtained by crosslinking by UV radiation provided by a mercury lamp having a power of 120 W.

(23) The article R2 corresponds to an article according to the invention. The polymerizable composition would have been applied to the glass substrate coated with the functional coating by spin coating. The surface roughness is obtained by the process as described in application FR 2990384. A pattern is printed on the surface using a polydimethylsiloxane PDMS stamp. The process of printing the pattern comprises the following steps: applying the stamp to the surface of the layer of polymerizable composition, introducing the article coated with the polymerizable composition and the stamp into a pouch made of an impermeable material, introducing the pouch and its contents into a hermetic chamber, placing the chamber under vacuum, sealing the pouch before reintroducing air into the chamber, UV crosslinking separating the article and the stamp.

(24) The surface roughness of the stamp is defined by the following parameters: Sa: 0.7 μm, Sz: 7 μm Rsm: 7 μm.
II. Characterization
1. Thicknesses

(25) The thicknesses can be measured using a Dektak profilometer. Two scratches spaced around 2 cm apart are used to correct the baseline and position the substrate at 0 μm, as shown in FIG. 1. The thickness is obtained by taking the mean value of the profile between the two scratches.

(26) In the case of the article R1, the roughness corresponds to flatness defects in the form of wavelets. The profile is produced perpendicular to these wavelets.

(27) The thicknesses of the temporary protective layers obtained under these conditions are from 10 to 20 μm.

(28) 2. Determination of the Surface Roughness

(29) The surface roughness was determined using a Newview® interference profilometer from Zygo. FIG. 2 illustrates two-dimensional profiles of the surface before correction (left image) and after correction (right image).

(30) The 2D profile is produced at 3 different positions for each sample with a magnification of ×0.5 using an image A of 14.49×10.87 mm.sup.2. On the images presented, a roughness in the form of wavelets is clearly seen.

(31) The data are then processed using the MountainsMap® software. In a first step, the background is rectified by subtracting a plane (cf. FIG. 2, right image). The roughness parameters are calculated, on the corrected image, according to the standard ISO 25178, by using an analysis length of the profile of around 15 mm combined with a low-pass Gaussian filter of 2.5 mm (ISO 13565-1 for the profiles). These parameters are judiciously selected in order to distinguish the waviness parameters from the roughness parameters. Sa and Sq correspond to the arithmetic mean height of the profile and the quadratic mean height of the profile of the surface. Sz corresponds to the maximum height of the profile of the surface.

(32) The image is then broken down into 480 horizontal profiles, i.e. profiles perpendicular to the roughness. The software calculates the mean period Rsm and its standard deviation for each profile.

(33) TABLE-US-00003 Articles E R1 R2 Thicknesses (e) 15 μm 15 μm 15 μm Roughness parameter: Sa 0.10 ± 0.05 μm 0.68 ± 0.05 μm 0.53 ± 0.05 μm Sz 0.53 ± 1 μm    7.2 ± 1 μm    5.8 ± 1 μm   Sq 0.13 ± 0.05 μm 0.86 ± 0.05 μm 0.66 ± 0.05 μm Rsm  1.5 ± 0.1 mm  1.1 ± 0.1 mm  1.1 ± 0.1 mm (Sa/(e))*100 0.67% 4.5% 3.5% (Sz/(e))*100  3.5%  48%   39% 

(34) The protected articles R1 and R2 each have: a surface roughness parameter Sa, representing at least 3% of the mean thickness of the temporary protective layer, a surface roughness parameter Sz, corresponding to the maximum height of the surface, representing at least 30% of the mean thickness of the temporary protective layer.
3. Adhesion Test

(35) Small sheets measuring 10 cm×10 cm were bought into contact on a flat glass substrate measuring 30 cm×30 cm that had been washed with water then dried (hereinbelow large sheet): a sheet of Article F (comparative) fastened with 4 pieces of adhesive tape, a sheet of Article F (comparative) fastened with a clip, a sheet of Article E (comparative) fastened with 4 pieces of adhesive tape, a sheet of Article E (comparative) fastened with a clip, a sheet of Article R1 (invention) fastened with 4 pieces of adhesive tape, a sheet of Article R1 (invention) fastened with a clip.

(36) FIG. 3 illustrates this test.

(37) The assembly is then wetted with tap water and dried rapidly with compressed air. Water remains trapped between the sheets and the glass substrate. Then the assembly is left to dry for 4 days. After 4 days, the clips and the adhesive tape are removed.

(38) The two sheets of article F not comprising the temporary protective layer adhere to the large sheet. They cannot be detached from the large glass sheet. Nor is it possible to move the sheets F in translation relative to the large sheet.

(39) The two sheets of article E comprising a temporary protective layer as described in application WO 2015/019022 adhere to the large sheet. They cannot be detached from the large glass sheet. Nor is it possible to move the sheets E in translation relative to the large sheet.

(40) The two sheets of article R1 according to the invention do not adhere to the large sheet. They can easily be moved and detached from the large glass sheet.