Method for obtaining a substrate provided with a coating comprising a discontinuous thin metal layer

Abstract

A process for obtaining a material includes a substrate coated on at least one portion of at least one of its faces with a coating including at least one discontinuous metallic thin layer based on silver, on gold, or on any alloy thereof, the or each discontinuous metallic thin layer being encapsulated between at least two dielectric thin layers, and the or each discontinuous metallic thin layer being in the form of periodic geometric patterns, the process including a deposition step then a step wherein the substrate thus coated is made to run opposite at least one laser device emitting a laser radiation focused on the coating in the form of at least one line, the power of the radiation being adapted in order to render the or each metallic thin layer discontinuous by dewetting.

Claims

1. A process for obtaining a material comprising a substrate coated on at least one portion of at least one of its faces with a coating comprising at least one discontinuous metallic thin layer based on silver, on gold, or on any alloy thereof, the or each discontinuous metallic thin layer being encapsulated between at least two dielectric thin layers, and the or each discontinuous metallic thin layer being in the form of periodic geometric patterns, said process comprising: depositing a coating on at least one portion of at least one face of said substrate, the coating comprising at least one continuous metallic thin layer based on silver, on gold, or on any alloy thereof, the or each continuous metallic thin layer being encapsulated between at least two dielectric thin layers, then making the substrate thus coated run opposite at least one laser device emitting a laser radiation focused on said coating in the form of at least one line, a power of said radiation being adapted in order to render the or each metallic thin layer discontinuous by dewetting.

2. The process as claimed in claim 1, wherein the periodic geometric patterns have a period within a range extending from 0.1 to 10 micrometers.

3. The process as claimed in claim 1, wherein the geometric patterns obtained are lines extending in the run direction of the substrate.

4. The process as claimed in claim 1, wherein the periodic patterns have a periodicity along at least two axes that are not parallel to one another.

5. The process as claimed in claim 1, wherein a physical thickness of the or each continuous metallic thin layer is within a range extending from 2 to 20 nm.

6. The process as claimed in claim 1, wherein a wavelength of the laser radiation is within a range extending from 200 to 2000 nm.

7. The process as claimed in claim 1, wherein the laser radiation is continuous.

8. The process as claimed in claim 1, wherein the substrate is made of glass, of glass-ceramic or of a polymeric organic material.

9. The process as claimed claim 1, wherein the coating comprises, starting from the substrate, a first coating comprising at least a first dielectric layer, at least a metallic thin layer, optionally an overblocker layer and a second coating comprising at least a second dielectric layer.

10. The process as claimed in claim 9, wherein the first and/or second dielectric layer is an oxide, or a nitride.

11. The process as claimed in claim 1, wherein the substrate has at least one dimension of at least 1 m.

12. The process as claimed in claim 1, wherein the coating is deposited by sputtering.

13. The process as claimed in claim 2, wherein the period is within a range extending from 0.3 to 5 micrometers.

14. The process as claimed in claim 6, wherein the wavelength of the laser radiation is within a range extending from 500 to 1500 nm.

15. The process as claimed in claim 10, wherein the oxide is tin oxide or titanium oxide, and the nitride is silicon nitride.

16. The process as claimed in claim 11, wherein the at least one dimension is at least 2 m.

17. The process as claimed in claim 16, wherein the at least one dimension is at least 3 m.

Description

(1) The invention is illustrated with the aid of the following nonlimiting figures and exemplary embodiments.

(2) FIGS. 1 and 2 are scanning electron microscopy images of materials according to the invention.

(3) FIGS. 3a and 3b are transmission and absorption spectra of materials according to the invention.

(4) The following multilayer stack was deposited in a known manner by magnetron sputtering onto a 4 mm thick clear glass substrate:

(5) Glass/Si.sub.3N.sub.4 (26)/TiO.sub.2 (7)/ZnO (6)/Ag (11)/TiO.sub.x (1)/ZnO (6)/Si.sub.3N.sub.4 (35)/TiO.sub.2 (2).

(6) The numbers between parentheses correspond to the physical thicknesses, expressed in nanometers. All the layers are continuous.

(7) The formulae given do not predict the exact stoichiometry of the compounds forming the layers, or a possible doping. In this case, the layers of silicon nitride (referred to as Si.sub.3N.sub.4) also contain aluminum because the target used contains it.

(8) The coated substrate then runs under a laser line positioned perpendicular to the run direction in order to treat the coating and dewet the silver. The line is formed using high-power laser diodes. The linear power density of the laser is 490 W/cm.

(9) The width of the laser line is around 48 micrometers. The wavelengths used are 913 and 980 nm.

(10) When the run speed is too high (above 13 meters per minute), the silver layer remains continuous.

(11) By decreasing the run speed (below 13 meters per minute, in particular around 11.5 to 12.5 meters per minute), the silver layer begins to be dewetted and forms lines. FIG. 1 illustrates this embodiment. On the scanning electron microscopy image, the light lines correspond to the silver layer, which has become discontinuous and in the form of lines, extending in the run direction of the substrate, perpendicular to the laser line. The lines have a width of around 1 m, and are regularly distributed, the period being of the order of 2 m, therefore the order of double the wavelength of the laser.

(12) When the run speed is further reduced (to 11 meters per minute and below), the silver lines begin to be dewetted, until drops are formed. FIG. 2 illustrates this embodiment. The drops have a substantially identical shape, similar to an ellipse, and are distributed periodically. The major axis of the ellipse has a size of around 1 m. The periodic patterns (drops) have a periodicity along several axes that are not parallel to one another. Each of these drops is the center of a hexagon, the vertices of which are the six drops closest to the drop in question.

(13) For an even lower run speed, an ablation of the coating, and even of the surface layers of the glass, is observed.

(14) The polarization properties of the material comprising lines as periodic patterns, represented in FIG. 1, were tested in the following manner. Using a spectrophotometer, the transmission spectrum and reflection spectrum were measured for each polarization (s and p). The absorption spectrum was calculated from these two spectra.

(15) FIGS. 3a and 3b respectively represent the transmission spectrum and the absorption spectrum. As is customary, the wavelength (expressed in nm) is plotted on the x-axis and the transmission or absorption value (expressed in percent) is plotted on the y-axis.

(16) The transmission spectrum shows that, for a wavelength of around 1800 nm and for one polarization (in this case the polarization p, taking into account the orientation of the material) is transmitted while the other (here the polarization s) is transmitted very little. The absorption spectrum shows that the absorption does not depend on the polarization: the polarization s is therefore reflected.