Pair of electrodes for DBD plasma process

1. A device for the surface treatment of a substrate by dielectric barrier discharge that enables the generation of a cold filamentary plasma at atmospheric pressure, comprising: a reaction chamber;

rollers in the chamber for supporting and/or moving the substrate; and at least two electrodes arranged in parallel on either side of the substrate, of which a first electrode is connected to a high voltage power supply and a second electrode is a counter-electrode that is earthed, wherein the counter-electrode has a width (l ce ) and a length (L ce ) that are respectively smaller than a width (l e ) and a length (L e ) of the first electrode, and in that the counter-electrode is positioned so that it is enclosed in an orthogonal projection of the first electrode on a plane containing the counter-electrode,

wherein the device does not include any dielectric barrier and that allows an insulating substrate that itself alone forms the dielectric barrier to pass.

2. The device according to claim 1 , wherein the counter-electrode is positioned so that it is enclosed in a centered manner in the orthogonal projection of the first electrode on the plane containing the counter-electrode.

3. The device according to claim 1 , wherein the width of the counter-electrode (l ce ) is smaller than that of the first electrode (l e ) by at least 10 mm.

4. The device according to claim 1 , wherein the length of the counter-electrode (L ce ) is smaller than that of the first electrode (L e ) by at least 10 mm.

5. The device according to claim 1 , wherein a distance between the first electrode and the substrate is greater than 2 mm.

6. A process for the surface treatment of a substrate, which comprises the following:

providing a device according to claim 1 ;

feeding or passing a substrate into the reaction chamber;

putting into operation a power supply that is stabilised in amplitude and frequency comprising a very high-voltage (VHV) and high-frequency (HF) transformer comprising a secondary circuit, the at least two electrodes being connected to the terminals thereof;

generating in the secondary circuit of this transformer a stabilised high-frequency electric voltage of such a value that it causes the generation of a filamentary plasma in the reaction chamber between the at least two electrodes;

feeding into the reaction chamber a mixture, the composition of which is such that on contact with the plasma, it breaks down and generates substances able to react with the surface of the substrate;

keeping the substrate in the chamber for a sufficient period of time to achieve the desired treatment on at least one of its faces.

7. The process according to claim 6 , which is a process for depositing a layer onto a substrate.

8. The process according to claim 7 , wherein the mixture fed into the reaction chamber comprises an organic precursor of silicon, and that it generates a layer of SiO 2 .

9. A glass sheet coated with a layer of SiO 2 deposited by the process according to claim 8 .

10. The device according to claim 3 , wherein the width of the counter-electrode (l ce ) is smaller than that of the first electrode (l e ) by at least 20 mm.

11. The device according to claim 4 , wherein the length of the counter-electrode (L ce ) is smaller than that of the first electrode (L e ) by at least 20 mm.

12. The device according to claim 5 , wherein the distance between the first electrode and the substrate is greater than 3 mm.

13. The process according to claim 8 , wherein organic precursor of silicon is HMDSO.

14. A device for the surface treatment of a dielectric substrate by dielectric barrier discharge, comprising:

a reaction chamber;

a first electrode connected to a power supply; and

a counter electrode that is earthed,

wherein the first electrode and the counter electrode are parallel to one another and are separated by a space sufficient for passage of the substrate, and

wherein the counter-electrode has a width (l ce ) and a length (L ce ) that are respectively smaller than a width (l e ) and a length (L e ) of the first electrode,

wherein the device does not include any dielectric barrier other than the substrate, and

wherein during operation the device is configured to generate a cold filamentary plasma at atmospheric pressure.

15. The device according to claim 14 , wherein the counter-electrode is positioned so that it is enclosed in an orthogonal projection of the first electrode on a plane containing the counter-electrode.