Method for producing a coated substrate

Abstract

The subject of the invention is a process for obtaining a substrate provided on at least one portion of at least one of its sides with a coating, comprising a step of depositing said coating on said substrate, then a step of heat treatment of said coating using a pulsed or continuous laser radiation focused on said coating in the form of at least one laser line, the wavelength of which is within a range extending from 400 to 1500 nm, said heat treatment being such that a relative displacement movement is created between the substrate and the or each laser line, the speed of which is at least 3 meters per minute, the or each laser line having a beam quality factor (BPP) of at most 3 mm.Math.mrad and, measured at the place where the or each laser line is focused on said coating, a linear power density divided by the square root of the duty cycle of at least 200 W/cm, a length of at least 20 mm and a width distribution along the or each line such that the mean width is at least 30 micrometers and the difference between the largest width and the smallest width is at most 15% of the value of the mean width.

Claims

1. A process for obtaining a substrate provided, on at least one portion of at least one side, with a heat-treated coating, the process comprising: heat treating a coating provided on at least one portion of at least one side of said substrate with a pulsed or continuous laser radiation focused on said coating as a laser line provided by a plurality of lasers positioned to form the laser line having a cumulative laser length, wherein, in the heat treating, said substrate is substantially horizontal and travels on a conveyor facing the laser line, wherein the heat treating substantially homogeneously treats the substrate while tolerating a variation in distance to the laser focal spot due to vibrations of the substrate while the speed of travel of the substrate is at least 3 meters per minute, wherein, in the heat treating, the laser line has a combination of a wavelength within a range of 400 to 1500 nm, a beam parameter product (BPP) of at most 3 mm.Math.mrad, measured at a place where the laser line is focused on said coating, a linear power density divided by the square root of a duty cycle within a range from 200 W/cm to 1000 W/cm, a length within a range of 20 cm to 100 cm, a mean width within a range of 40 to 100 micrometers, wherein a width of the laser line remains essentially constant throughout said heat treating such that a difference between a largest width and a smallest width of the laser line is at most 10% of the mean width when the displacement distance from the coating to the focal plane of the laser varies between 1 mm, and wherein the temperature reached by said coating at each point during said heat treating does not vary by more than 10% in relative terms compared to the targeted temperature when the displacement distance from the coating to the focal plane of the laser varies between 1 mm.

2. The process as claimed in claim 1, wherein the laser line is fixed and positioned substantially perpendicular to a direction of travel.

3. The process as claimed in claim 1, wherein the wavelength of the radiation of the laser line is within a range of from 800 to 1000 nm.

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

5. The process as claimed in claim 1, wherein the linear power density divided by the square root of the duty cycle is within a range of 400 to 500 W/cm.

6. The process as claimed in claim 1, wherein the mean width of the laser line is within a range of 50 to 53 micrometers.

7. The process as claimed in claim 1, wherein the length of the laser line is at least 20 cm.

8. The process as claimed in claim 1, wherein an energy density provided to the coating divided by the square root of the duty cycle is at least 20 J/cm.sup.2.

9. The process as claimed in claim 1, wherein the substrate comprises glass or a polymeric organic material.

10. The process as claimed in claim 1, wherein the substrate has at least one dimension greater than 1 m.

11. The process as claimed in claim 1, wherein the coating comprises a metallic layer, a titanium oxide layer, a transparent electrically conductive layer, or any combination thereof.

12. The process as claimed in claim 1, wherein the heat treating is at a temperature of at least 300 C.

13. The process as claimed in claim 1, wherein a temperature of a side of the substrate opposite a side treated by the laser radiation does not exceed 100 C. during the heat treatment.

14. The process of claim 11, wherein the coating comprises a silver or molybdenum layer as a metallic layer.

15. The process as claimed in claim 1, wherein the laser line has a beam parameter product (BPP) of at most 2.6 mm.Math.mrad.

16. The process as claimed in claim 1, wherein the laser line has a beam parameter product (BPP) of at most 2 mm.Math.mrad, the difference between the largest width and the smallest width of the laser line is at most 10% of the mean width, and the temperature reached by said coating at each point during said heat treating does not vary by more than 10% in relative terms.

17. The process as claimed in claim 1, wherein the laser line has a beam parameter product (BPP) of at most 1.5 mm.Math.mrad, the difference between the largest width and the smallest width of the laser line is at most 5% of the mean width, and the temperature reached by said coating at each point during said heat treating does not vary by more than 5% in relative terms.

18. The process as claimed in claim 1, wherein the laser line has a beam parameter product (BPP) of at most 1 mm.Math.mrad.

19. The process as claimed in claim 1, wherein the laser line has a beam parameter product (BPP) of at most 0.7 mm.Math.mrad.

20. The process as claimed in claim 1, wherein the targeted temperature is at least 300 C.

21. A process for obtaining a substrate provided, on at least one portion of at least one side, with a heat-treated coating, the process comprising: heat treating a coating provided on at least one portion of at least one side of said substrate with a pulsed or continuous laser radiation focused on said coating as a laser line provided by a plurality of lasers positioned to form the laser line having a cumulative laser length, wherein, in the heat treating, said substrate is substantially horizontal and travels on a conveyor facing the laser line, wherein the heat treating substantially homogeneously treats the substrate while tolerating, relative displacement distance between the coating and the focal plane of the laser line varies based on a variation in distance to the laser focal spot due to vibrations of the substrate while the speed of travel of the substrate is at least 3 meters per minute, wherein, in the heat treating, the laser line has a combination of a wavelength of 915 or 980 nm, a beam parameter product (BPP) of 2.5 mm.Math.mrad, measured at a place where the laser line is focused on said coating, a linear power density divided by the square root of a duty cycle is 400 W/cm, a length within a range of approximately 30 cm, a mean width is 53 micrometers, wherein the homogeneous treatment is such that a width of the laser line remains essentially constant throughout said heat treating such that a difference between a largest width and a smallest width of the laser line is at most 10% of the mean width when the displacement distance from the coating to the focal plane of the laser varies between 0.5 mm, and wherein the homogeneous treatment is such that the sheet resistance of the coating decreases from 18% to 21% at any point of the coating.

22. A process for obtaining a substrate provided, on at least one portion of at least one side, with a heat-treated coating, the process comprising: heat treating a coating provided on at least one portion of at least one side of said substrate with a pulsed or continuous laser radiation focused on said coating as a laser line provided by a plurality of lasers positioned to form the laser line having a cumulative laser length, wherein, in the heat treating, said substrate is substantially horizontal and travels on a conveyor facing the laser line, wherein the heat treating substantially homogeneously treats the substrate while tolerating, relative displacement distance between the coating and the focal plane of the laser line varies based on a variation in distance to the laser focal spot due to vibrations of the substrate while the speed of travel of the substrate is at least 3 meters per minute, wherein, in the heat treating, the laser line has a combination of a wavelength of 915 or 980 nm, a beam parameter product (BPP) of 1.1 mm.Math.mrad, measured at a place where the laser line is focused on said coating, a linear power density divided by the square root of a duty cycle of 500 W/cm, a length of approximately 22 cm, a mean width of 50 micrometers, wherein the homogeneous treatment is such that a width of the laser line remains essentially constant throughout said heat treating such that a difference between a largest width and a smallest width of the laser line is at most 10% of the mean width when the displacement distance from the coating to the focal plane of the laser varies between 1 mm.

Description

EXAMPLE 1

(1) A low-emissivity multilayer stack containing a silver layer is deposited by magnetron sputtering on a 4 mm thick clear glass substrate, the surface area of which is 6003210 cm.sup.2.

(2) Table 1 below indicates the physical thickness of each of the layers of the multilayer stack, expressed in nm. The first line corresponds to the layer furthest from the substrate, in contact with the open air.

(3) TABLE-US-00001 TABLE 1 ZnSnSbO.sub.x 2 Si.sub.3N.sub.4:Al 43 ZnO:Al 5 Ti 0.5 Ag 15 ZnO:Al 5 TiO.sub.2 11 Si.sub.3N.sub.4:Al 14

(4) Table 2 below summarizes the deposition parameters used for the various layers.

(5) TABLE-US-00002 TABLE 2 Deposition Layer Target used pressure Gas Si.sub.3N.sub.4 Si:Al at 92:8 wt % 1.5 10.sup.3 mbar Ar/(Ar + N.sub.2) at 45% TiO.sub.2 TiO.sub.x with x of 1.5 10.sup.3 mbar Ar/(Ar + O.sub.2) the order of 1.9 at 95% ZnSnSbO.sub.x SnZn:Sb at 2 10.sup.3 mbar Ar/(Ar + O.sub.2) 34:65:1 wt % at 58% ZnO:Al Zn:Al at 98:2 wt % 2 10.sup.3 mbar Ar/(Ar + O.sub.2) at 52% Ti Ti 2 10.sup.3 mbar Ar Ag Ag 2 10.sup.3 mbar Ar at 100%

(6) The substrate is then heat-treated using eleven laser lines having a length of 30 cm, positioned so that the entire width of the substrate is treated. The laser sources are laser diodes that emit a continuous radiation, the wavelength of which is 915 nm or 980 nm, in the form of a line focused on the coating.

(7) The substrate coated with its multilayer stack is positioned on a roller conveyor, level with the focal plane of each laser line, and runs under each laser line at a speed of 5 m/min, the speed not varying by more than 1% in relative terms.

(8) During operation, the linear power density of each laser line is 400 W/cm, the mean width of each line is 53 micrometers, and the beam quality factor (beam parameter product) is 2.5 mm.Math.mrad.

(9) In this way, the width of each laser line varies by at most 10% in relative terms when the distance from the coating to the focal plane of the laser varies by 0.5 mm.

(10) Moreover, the width of each line is homogeneous over the length of each of the lines so that, for each line, the difference between the largest width and the smallest width is equal to 3% of the mean value (i.e. 1.5 micrometers).

(11) The coating is treated very homogeneously, the sheet resistance of the coating decreasing from 18% to 21% in relative terms at any point of the coating, without generation of optical defects.

EXAMPLE 2

(12) This example differs from example 1 in that use is made of fifteen laser lines having a length of 22 cm, juxtaposed so as to form a single line having a length of 3.3 m. The linear power density of each laser line is 500 W/cm, the mean width of each line is 50 micrometers, and the beam quality factor is 1.1 mm.Math.mrad. In this way, the width of each laser line varies by at most 10% in relative terms when the distance from the coating to the focal plane of the laser varies by 1 mm. Here too the treatment is again very homogeneous, the coating not having any optical defect.

COMPARATIVE EXAMPLE 1

(13) This comparative example differs from example 1 in that the beam quality factor is 6.2 mm.Math.mrad.

(14) In this case, the width of each laser line varies by around 50% in relative terms when the distance from the coating to the focal plane of the laser varies by 0.5 mm.

(15) After treatment it is observed that the loss of sheet resistance is not homogeneous over the entire surface of the substrate. Although at certain locations it reaches 20% to 21%, it is only 3% in certain zones of the substrate due to variations in the distance between the substrate and the focal plane generated by the flatness defects of the substrate and the conveying thereof at high speed.

COMPARATIVE EXAMPLE 2

(16) This example differs from example 2 in that the beam quality factor is 4 mm.Math.mrad.

(17) In this case, the width of each laser line varies by around 90% in relative terms when the distance from the coating to the focal plane of the laser varies by 1 mm.

(18) As for comparative example 1, the loss of sheet resistance is not homogeneous.

COMPARATIVE EXAMPLE 3

(19) This example differs from example 1 in that the linear power density is 180 W/cm. In this case, the loss of sheet resistance due to the treatment is too low since the coating does not reach the appropriate temperatures that enable the crystallization thereof.

(20) In order to be able to reach the desired temperatures, it is necessary to reduce the mean width of each line to 11 micrometers. In this case however, the width of each laser line varies by a factor of 10 when the distance from the coating to the focal plane of the laser varies by 0.5 mm. Taking into account the flatness defects of the large-sized substrate, the conveying thereof, and vibrations, the treatment is then not homogeneous, the loss of sheet resistance varying significantly as a function of the zones of the surface of the substrate.

COMPARATIVE EXAMPLE 4

(21) This example differs from example 2 in that the linear power density is 180 W/cm. In this case too, the loss of sheet resistance due to the treatment is too low since the coating does not reach the appropriate temperatures that enable the crystallization thereof.

(22) In order to be able to reach the desired temperatures, it is necessary to reduce the mean width of each line to 7 micrometers. In this case however, the width of each laser line varies by a factor of 22 when the distance from the coating to the focal plane of the laser varies by 1 mm. Taking into account the flatness defects of the large-sized substrate, the conveying thereof, and vibrations, the treatment is then not homogeneous, the loss of sheet resistance varying significantly as a function of the zones of the surface of the substrate.

COMPARATIVE EXAMPLE 5

(23) This example differs from example 1 in that each line is not homogeneous in terms of width. Although the mean width is still 53 micrometers, the width distribution is such that the difference between the largest width and the smallest width is equal to 13 micrometers, i.e. 25% of the mean value. The treatment is then heterogeneous: the layer is locally degraded due to an over-intensity of the laser treatment (in the zones where the width of the line is smallest), leading both to the appearance of isolated optical defects that are visually unacceptable, and an overall loss of sheet resistance of only 13% to 14% in relative terms.