HEATING DEVICE, IN PARTICULAR A SEMI-TRANSPARENT HEATING DEVICE

Abstract

The present invention relates to a heating device comprising: a base substrate; an electrically conductive layer, referred to as the heating layer, carried by the substrate, formed from at least one percolating network of nano-objects comprising metal nanowires; and a thermal diffusion layer made from aluminum nitride, covering all or part of the heating layer. The invention also concerns a method for preparing such a heating device.

Claims

1. A heating device comprising: a base substrate; an electrically conducting layer, referred to as heating layer, carried by the substrate, formed of at least a percolating network of nano-objects comprising metal nanowires; and a thermal diffusion layer based on aluminum nitride, covering all or part of the heating layer.

2. The device as claimed in claim 1, in which the heating layer exhibits a transmittance, over the whole of the visible spectrum, of greater than or equal to 50%.

3. The device as claimed in claim 1, in which the heating layer exhibits a sheet resistance of less than or equal to 500 ohm/square.

4. The device as claimed in claim 1, in which the metal nanowires represent at least 40% by weight, of the total weight of the nano-objects of said heating layer.

5. The device as claimed in claim 1, in which the metal nanowires are chosen from silver, gold and/or copper nanowires.

6. The device as claimed in claim 1, in which the heating layer comprises, besides the metal nanowires, carbon nanotubes and/or graphene, or their derivatives.

7. The device as claimed in claim 1, in which the percolating network of nano-objects of the heating layer exhibits a density of nano-objects of between 100 μg/m.sup.2 and 500 mg/m.sup.2.

8. The device as claimed in claim 1, in which the heating layer is provided in the form of a single layer formed of a percolating network of nano-objects.

9. The device as claimed in claim 1, in which the heating layer exhibits a multilayer percolating network formed of at least two sublayers of nano-objects having distinct compositions, at least one of the sublayers comprising, indeed even being formed of, metal nanowires.

10. The device as claimed in claim 1, in which the heating layer exhibits a thickness of between 1 nm and 10 μm.

11. The device as claimed in claim 1, in which the thermal diffusion layer exhibits a thermal conductivity of greater than or equal to 20 W.Math.K.sup.−1.Math.m.sup.−1.

12. The device as claimed in claim 1, in which the thermal diffusion layer exhibits a thickness of between 50 nm and 5 μm.

13. The device as claimed in claim 1, in which the thermal diffusion layer covers all of the heating layer.

14. The device as claimed in claim 1, in which the base substrate is a transparent or semitransparent substrate.

15. The device as claimed in claim 1, which is semitransparent or transparent, in which: the base substrate is semitransparent or transparent, in particular as defined in claim 14; and the heating layer exhibits a transmittance, over the whole of the visible spectrum, of greater than or equal to 50%.

16. The device as claimed in claim 15, characterized in that it exhibits an overall transmittance, over the whole of the visible spectrum, of at least 50%.

17. A process for the preparation of a heating device, comprising at least the stages consisting in: (i) having available a base substrate, one of the faces of which is covered at least in part with an electrically conducting layer, known as heating layer, formed of at least a percolating network of nano-objects comprising metal nanowires; and (ii) forming, over all or part of the exposed surface of said heating layer, the thermal diffusion layer based on aluminum nitride by high power pulsed or direct current magnetron cathode sputtering, at a temperature of strictly less than 280° C.

18. The process as claimed in claim 17, in which the thermal diffusion layer is formed in stage (ii) at a temperature of less than or equal to 250° C.

19. The process as claimed in claim 17, in which the heating layer carried by the substrate of stage (i) is formed beforehand by spray coating one or more suspensions of the nano-objects in a solvent medium, followed by the evaporation of the solvent or solvents.

20. A heating and/or demisting system, comprising a heating device as defined according to claim 1.

21. The system as claimed in claim 20, comprising a transparent or semitransparent heating device as defined in claim 15, said system being employed for a glazing, a shower panel, a mirror industry element, a visor, a mask, spectacles, a radiator, a heating element of an optoelectronic device or a transparent food container.

22. The device as claimed in claim 1, in which the metal nanowires represent at least 60% of the total weight of the nano-objects of said heating layer.

23. The device as claimed in claim 1, in which the heating layer is provided in the form of a percolating network of metal nano wires.

24. The device as claimed in claim 1, in which the heating layer exhibits a thickness of between 5 nm and 800 nm.

25. The device as claimed in claim 1, in which the base substrate is made of glass or of transparent polymers, selected from polycarbonate, polyolefins, polyethersulfone, polysulfone, phenolic resins, epoxy resins, polyester resins, polyimide resins, polyetherester resins, polyetheramide resins, poly(vinyl acetate), cellulose nitrate, cellulose acetate, polystyrene, polyurethanes, polyacrylonitrile, polytetrafluoroethylene, polyacrylates, selected from polymethyl methacrylate, polyarylate, polyetherimides, polyetherketones, polyetheretherketones, polyvinylidene fluoride, polyesters, selected from polyethylene terephthalate or polyethylene naphthalate, polyamides, zirconia or their derivatives.

Description

FIGURES

[0129] FIG. 1: Diagrammatic representation, in a vertical sectional plane, of the structure of a heating device (1) in accordance with the invention.

[0130] FIG. 2: Diagrammatic view of the application of a voltage using a voltage generator (22) to the contact pads of a device (1) in accordance with the invention, as carried out in examples 1 to 4.

[0131] It should be noted that, for reasons of clarity, the different elements visible in the figures are not represented to scale, the true dimensions of the different parts not being observed.

EXAMPLES

[0132] Measurement Methods

[0133] The total transmittance is measured using an integrating sphere on a Varian Cary 5000 spectrometer.

[0134] The transmittance over the visible spectrum corresponds to the transmittance for wavelengths of between 350 and 800 nm. The transmittance is measured every 2 nm.

[0135] The electrical sheet resistance is measured with a 4-point resistivity meter of Loresta EP type.

Example 1

[0136] Formation of the Heating Layer (12)

[0137] In a first step, silver nanowires are synthesized and purified according to the process described in the document Nanotechnology, 2013, 24, 215501 [4].

[0138] These nanowires are deposited on Eagle XG™ glass (Corning) (substrate (11)) according to a spray coating process.

[0139] The material thus deposited, constituting the heating layer (12), exhibits a sheet resistance of 28 ohm/square.

[0140] Electrical contact pads (21) are produced on two opposite edges by use of a silver lacquer or of a deposition of metal film, for example by CVD or PVD.

[0141] Formation of the Thermal Diffusion Layer (13)

[0142] The aluminum nitride (AlN) is deposited on this heating layer (12) by direct current magnetron sputtering. During this deposition, the electrical contact pads are protected in order to be subsequently used in order to apply a potential to the device.

[0143] The deposition by direct current magnetron sputtering is carried out starting from a pure aluminum target and from an argon and nitrogen plasma under high vacuum (pressure of between 2 and 3 mTorr) and at low temperature (T=200° C.). The power used is 175 W. The ratio of the amounts of nitrogen and argon AN.sub.2/(AN.sub.2+AAr) is 25%.

[0144] Under these conditions, the rate of deposition is approximately 40 nm/min, which makes possible precise control of the thickness of the AlN layer deposited.

[0145] The deposition is carried out for 5 minutes, which makes it possible to obtain a layer (13) of 200 nm.

[0146] On applying a voltage of 5 V to the contact pads, a temperature of 35° C. is achieved in less than one minute, homogeneously over the whole of the surface of the heating device (1).

[0147] This heating device (1) has an overall transmittance, measured using an integrating sphere on a Varian Cary 5000 spectrometer, of a minimum of 85% over the whole of the visible spectrum.

[0148] On applying a voltage of 7 V to the contact pads, a temperature of 51° C. is achieved in less than one minute, homogeneously over the whole of the surface of the heating device.

Example 2

[0149] Formation of the Heating Layer (12)

[0150] In a first step, carbon nanotubes (CSP3 type from Carbon Solution) are dispersed in NMP (N-MethylPyrrolidone) and deposited on Eagle XG™ glass (Corning) according to a spray coating process. The transmittance of the deposited layer, over the whole of the visible spectrum, is 99.2%.

[0151] Silver nanowires are synthesized and purified according to the process described in the document Nanotechnology, 2013, 24, 215501. These nanowires are deposited on the layer of carbon nanotubes.

[0152] The “hybrid” heating layer (12), composed of the two sublayers of nanomaterials of different natures, thus formed exhibits a sheet resistance of 20 ohm/square.

[0153] Electrical contact pads (21) are produced on two opposite edges by use of a silver lacquer or of deposition of metal film, for example by CVD.

[0154] Formation of the Thermal Diffusion Layer (13)

[0155] The aluminum nitride (AlN) is deposited on this heating layer as described in example 1.

[0156] On applying a voltage of 5 V to the contact pads (21), a temperature of 45° C. is achieved in less than one minute, homogeneously over the whole of the surface of the heating device (1).

[0157] This device (1) has an overall transmittance of a minimum of 88% over the whole of the visible spectrum.

Example 3

[0158] A heating device (1) similar to that described in example 1 is produced, employing, in place of the silver nanowires, copper nanowires manufactured according to the process described in the publication Nano Research, 2014, pp 315-324 [5].

[0159] The heating layer (12) thus produced exhibits a sheet resistance of 53 ohm/square.

[0160] The deposition of AlN is carried out as described in example 1.

[0161] On applying a voltage of 9 V to the contact pads, a temperature of 63° C. is achieved in less than one minute, homogeneously over the whole of the surface of the heating device.

[0162] This device has an overall transmittance of a minimum of 82% over the whole of the visible spectrum.

Example 4

[0163] A heating device (1) similar to that described in example 1 is produced, employing, in place of the glass substrate, a substrate (11) made of polyethylene naphthalate with a thickness of 125 μm.

[0164] The heating layer (12) thus produced exhibits a sheet resistance of 19 ohm/square.

[0165] The deposition of AlN is carried out as described in example 1.

[0166] On applying a voltage of 9 V to the contact pads, a temperature of 71° C. is achieved under stationary conditions, homogeneously over the whole of the surface of the heating device.

[0167] This device has an overall transmittance of a minimum of 90% over the whole of the visible spectrum.

REFERENCES

[0168] [1] Celle et al., “Highly Flexible Transparent Film Heaters Based on Random Networks of Silver Nanowires”, Nano Research (2012), 5(6), 427-433; [0169] [2] Kim et al., “Transparent flexible heater based on hybrid of carbon nanotubes and silver nanowires”, Carbon, 63 (2013), 530-536; [0170] [3] Zhang et al., “Large-size graphene microsheets as a protective layer for transparent conductive silver nanowire film heaters”, Carbon, 69 (2014), 437-443; [0171] [4] Nanotechnology, 2013, 24, 215501; [0172] [5] Nano Research, 2014, pp 315-324; [0173] [6] Belkerk et al., “Structural-dependent thermal conductivity of aluminum nitride produced by reactive direct current magnetron sputtering”, Appl. Phys. Lett., 101, 151908 (2012); [0174] [7] Duquenne et al., Appl. Phys. Lett., 93, 052905 (2008).