EP1758830A1

EP1758830A1 - Method for producing a hydrophobic coating, device for implementing said method and support provided with a hydrophobic coating

Info

Publication number: EP1758830A1
Application number: EP05762552A
Authority: EP
Inventors: Alfred Horichter; Hervé MONTIGAUD; Jean-Christophe Giron
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2004-05-26
Filing date: 2005-05-26
Publication date: 2007-03-07
Also published as: CN1976880A; DE102004026344A1; DE102004026344B4; US20090297863A1; US8282997B2; JP2008500256A; WO2005118501A1

Abstract

The invention concerns a method for producing a coating on a support, in particular a glass support, wherein a thin-film metal oxide is deposited on the support, said thin film being subjected to an etching process to roughen its surface, a second coating capable of adhering to the first metal oxide film is then applied on the roughened surface. The invention is characterized in that it consists in depositing a first doped metal oxide or metal oxynitride doped with at least a second metal oxide or metal oxynitride, the second metal oxide or metal oxynitride being distributed in the deposited film. During the etching process, a plasma-activated gas is used which removes at least a second metal oxide or metal oxynitride less than the first metal oxide or metal oxynitride so as to form, after the etching process, on the surface raised irregularities consisting of at least a second metal oxide or metal oxynitride.

Description

Method for producing a hydrophobic coating, device for carrying out the method and support provided with a hydrophobic coating

The invention relates to a method for producing a hydrophobic coating which has the characteristics of the preamble of claim 1, a device for carrying out the method and supports provided with a hydrophobic coating.

Coatings which have hydrophobic properties, in particular for window panes, have been worked and studied intensively for a long time and which on the one hand improve the vision through these window panes in the event of moisture condensation. , and which on the other hand must simplify the cleaning of window panes.

As a measure of the wettability of a surface or boundary surfaces with another phase, the so-called contact angle is frequently used. It is the angle formed by a tangent to the outline of the drop at the meeting point of the three phases on the surface of the solid body. The wetting is all the worse when the contact angle is large.

A hydrophobic coating on the window surface decreases the adhesion of the water drops on the coated surface by bringing said contact angle beyond 90 ° if possible.

A fundamental problem with these coatings is their relatively reduced resistance to mechanical stresses (abrasion by particles of dust or fouling which come to settle there, wiping). For example, this has long deteriorated the long-term reliability of hydrophobic coatings on vehicle windshields that are stressed at the same time. by the particles which strike them during driving and also by the wipers (and in the latter case, especially when the wipers are running dry).

Document EP 0 866 037 B1 discloses a method for forming a multilayer water repellant coating which has a first layer of metal oxide and a second layer of water repellency on a glass support. , in which the metal oxide layer is formed from a slightly rough surface, the second layer being applied to this rough surface and then being heated in a range between 100 and 300 ° C. The second layer is produced by a sol-gel process from a mixture of fluoroalkylsilanes, tin oxide particles doped with antimony oxide, a compound of silicon, water and an organic solvent.

This booklet presents on the same subject numerous patent publications which have already disclosed successions of layers of metal oxides (for example SiO ₂ ) and hydrophobic compounds of fluorine (for example perfluoroalkylsilanes).

Document JP-A 4 124 047 thus also discloses a process in which a first layer of metal oxide undergoes an etching operation after having been deposited on a support, to make its surface slightly rough, a hydrophobic layer then being applied to this roughened surface.

Document JP-A 6 116 430 describes a process in which a layer of Si0 ₂ deposited on a support undergoes a plasma etching operation to make its surface slightly rough, a monomolecular layer of chemical absorption which contains fluorine being then applied on this roughened surface. Document EP 0 476 510 A1 discloses a similar process by which a layer of metal oxide applied to a glass surface by a sol-gel process is treated with an acid or a plasma to make it rough, after which it is applied to this surface a layer of fluorine or silicone.

According to the EP-B1 patent mentioned above, these methods must be considered to be complicated, and other solutions are being sought to obtain the increased resistance to mechanical stresses of a hydrophobic coating, the "wiper" stress being claimed. explicitly and being evaluated in the coating test.

The document EP 0 545 201 B1 describes yet another relevant process in which a layer of sol-gel consisting of a silicon oxide mixed with other mineral oxides is applied to a glass support as a base layer or a adhesion enhancing agent. Although no special surface treatment of the type mentioned several times above is carried out, the primer can be applied to glass surfaces even before a bending and / or prestressing heat treatment and therefore is sufficiently resistant to high temperatures.

The problem underlying the invention is to propose another method for producing a hydrophobic coating in which a layer system is created which withstands all the stresses exerted on the surface of the support which is exposed in the assembled state. .

According to the invention, this problem is solved with the features of claim 1. The features of the dependent claims give advantageous developments of the present invention. The invention also relates to a device for the implementation of a method according to the invention and to the products which can be produced with this device.

It has been found that a plasma etching operation or an etching operation with a plasma activated gas can have different effects on different materials contained in a layer system; it is therefore possible to carry out selective etching.

The invention takes advantage of this by producing the layer applied to the support from at least two different metal oxides or metal oxynitrides. When in the following, and in a simplified manner, we speak only of metal oxides, we do not exclude the equivalent use of oxynitrides.

The plasma, the plasma-activated gas and the appropriate treatment plant are regulated and controlled so that one of these metal oxides is deposited much less than the other (matrix material). This result can be achieved in particular by not simultaneously passing all the materials of the layer into the gas phase under the same plasma or etching conditions.

In this way, a roughness is formed in the surface of the layer, the irregularity of which obviously depends on the distribution of the second metal oxide or metal doping oxide in the material of the matrix. This irregular surface of the layer must be functionally considered as a basecoat or as an adhesion-strengthening layer for the hydrophobic coating which will be applied later. In addition, hydrophobic coating particles will preferably accumulate in the "valleys" of the irregular surface and can no longer be removed without problem, even by mechanical action.

Due to the roughness of the surface, the treated layer also has a modified low reflection coefficient.

According to the invention, the doped metal oxide coating can be deposited preferably by sputtering under vacuum supported by a magnetic field (which is called in the following "spraying"). Other deposition techniques, for example CVD, plasma-reinforced DVD, vaporization, are however also and obviously envisaged.

As matrix material, Si0 _{2 is} mainly considered, because on the one hand it adheres very well to glass surfaces and on the other hand it has a high proportion of free OH bonds which for their part ensure good adhesion of the hydrophobic coating that will be applied later; we will expand further on this.

Silicon can also be deposited at high flow rates in spraying facilities. An Si0 ₂ target that has an eight percent aluminum content has been found to be well suited in testing. However, other doping elements are also envisaged, for example carbon, titanium, zirconium, zinc and boron, Rb, Cs, K, Na, Li, Ba, Sr, Mg as well as alkali and alkaline metals - earthy and rare earths, and it is absolutely possible to also use layers of mixed oxides or mixed ternary oxynitrides, provided that they meet the requirements in terms of light transmission.

Basically, in addition to SiO _x (with x <2), one can also use other matrix materials, for example SiOC, SiON, SiOCN, to which hydrogen can possibly still be combined (general formula

SiO _x C _y H _z N _u ).

The entire composition of the lower coating which will be deposited on the support directly or optionally after a blocking layer, and therefore in particular the second metal oxide (or oxynitride), is selected as a priority according to the particular condition that the glass pane thus coated must still be bent and possibly prestressed before the application of the hydrophobic coating. The deposited coating must therefore be able to withstand temperatures above 650 ° C without damage. Without damage here also means, independently of the maintenance of the adhesion and the absence of cracks (quality of the layer), the respect (or the obtaining, at least after the heat treatment) of a sufficient (total) transmission visible light, in the range of more than 70%, and for windshield windows even at least 75%, which means that an individual layer must have an even higher transmittance than the values mentioned.

It is conceivable to incorporate further into the process an activation step after the plasma etching (or to carry out the activation at the same time as the etching) in order to obtain in known manner an (improved) adhesion of the hydrophobic layer even further. on the metal oxide layer.

As soon as the first layer is applied, the operating parameters are adjusted so that the layer receives a relatively rough surface. This can be achieved, for example, by a relatively high spray pressure and / or by the use of lower spray energies.

In known manner, the metal oxides can be deposited in a reactive working gas atmosphere

(which contains oxygen) from metal targets or in an inert atmosphere (argon) from oxide targets. Optionally, targets may contain the mixture of materials from the start

(the alloys) desired, which makes it possible to dispense with the use in parallel of several targets made up of the various constituent materials of the layer.

On glass supports, the final composition of the layer before the etching operation can also be influenced by intermediate steps, for example heat treatments such as bending and prestressing. In particular due to diffusion processes, this can lead to an enrichment of the layer with atoms, in particular with alkali metal atoms which come from the glass.

If these transitions by diffusion are undesirable, a blocking layer can be provided between the support and the base layer of metal oxide or oxynitride. These blocking layers which oppose the diffusion of alkaline elements or other elements which come from the glass are known per se, so that it is not necessary to extend it further here.

The treated glass pane can then be assembled or transformed to obtain ready-to-use products (windshield panes, front glazing, shower stalls, refrigerator doors, etc.).

The plasma etching operation or the etching operation using a plasma activated gas can be carried out in different installations. What is important is the presence of a reagent which acts selectively only on the material of the doped metal oxide layer, this reagent being fluorine in the preferred example. The plasma operation can be conducted so as to selectively attack the doped and treated metal oxide layer. In the example of a layer of silicon oxide doped with aluminum, a gaseous phase of SiF ₄ (volatile) is formed in the plasma which makes it possible to remove the silicon, while the fluoride compounds aluminum are not gaseous at the same time and thus remain on the support or in the layer.

One can for example use a capacitive RF reactor with parallel planes.

Another system that can be used has a vacuum chamber in which the support to be engraved is located. This chamber is crossed by one or more tubes of non-conductive material (ceramic, A1 ₂ 0 ₃ ), quartz) in which there is an electrical conductor which is connected on both sides to a respective microwave generator (magnetron).

Inside the tube there is an atmospheric pressure. Therefore, the formation of a plasma inside the tube is hindered, but the electric field of the conductor crosses the wall of the tube and a homogeneous plasma can ignite at the periphery of the tube. By adjusting the power supplied on both sides, one can also act on the plasma locally so as to form a denser plasma at the ends of the tube.

Said tubes can even reach four meters in length, so that these installations make it possible to prestress float glass of the usual width of 3.2, and then to engrave them for coating.

Finally, the treatment can be carried out in a closed chamber, for example in a large steel chamber, the activation of the plasma taking place outside of this chamber and the plasma-activated etching gas being supplied by a distribution device on the coated support. Such a device will be described further below by way of example of embodiment.

As etching gases, the etching gases known in the industry and in the art are considered, for example SF ₆ , CF, C ₂ F ₆ , CHF ₃ or in general

C _X F _Y H _Z , mostly mixed with 0 ₂ . We select a gas whose state activated by the plasma is maintained as long as possible and therefore a gas whose radicals have a particularly long lifespan.

The contribution of the working or etching gas, via the site, the quantity, the pressure, the activation energy, etc., offers other possibilities of acting on the result of the 'engraving operation.

It turned out that before the plasma operation, the distribution of Al according to the thickness of the layer is relatively homogeneous, whereas after the plasma operation, it has a sharp point in the range of about 20 nm. This can be explained by the fact that following the tearing off of the Si0 ₂ matrix in the outer zone of the layer, Al is densified on the surface at higher concentrations, which provides said peaks. At the same time, the presence of silicon in the upper border area of the layer in contact with air decreases markedly.

This can also be proven for other doping elements than aluminum.

In the doped metal oxide coating applied or deposited on the glass, it is also possible to detect other alkali metal atoms after the heat treatment of the glass support. At high temperatures, these atoms diffuse out of the glass (usually silicate glass) to enter the coating. It has also been found that the position of the alkali metal atoms depending on the thickness of the layer changes during or because of the plasma treatment, so that traces of the treatment can be detected on the product.

The hydrophobic layer or coating is preferably represented by the general formula:

CF ₃ - (CF ₂ ) _n - (CH ₂ ) ₂ -Si (R ⁴ ) ₃

n being in the range between 7 and 11 and R ⁴ representing a low residual alkyl content.

For a specific hydrophobization treatment, a mixture of 90% propanol-2 and 10% 0.3 N HCl in water can be used. C ₈ Fi7 (CH ₂ ) ₂ Si (OEt) _{3 is added to it} in a proportion of 2%. In this formula, "Et" represents an ethyl.

Typical methods of applying this hydrophobization layer are, for example, rubbing, spraying, vacuum spraying, etc.

The concrete examples above do not, however, exclude the use of other hydrophobization compositions in the context of the present invention, provided that their good adhesion to the bottom layer and their compatibility with the latter are guaranteed.

Other details and advantages of the subject of the invention appear from the drawing of an exemplary embodiment and from its detailed description given below. In the drawing:

FIG. 1 shows schematically and not to scale an embodiment of a plasma treatment reactor for coated supports,

FIG. 2 represents a diagram of the distribution of the quantities (SIMS depth profile) of aluminum and aluminum oxide in the metal oxide coating according to the invention before and after plasma etching and

FIG. 3 represents a diagram of the distribution of the quantities of silicon (silicon oxide) in the metal oxide coating according to the invention before and after plasma etching.

In FIG. 1, a treatment device 1 (also called a plasma reactor) comprises a vacuum chamber 2 in addition to a pumping device 2P, a receptacle 3 with support only sketched, on which a support 4 has been placed (or possibly can also move), a device 5 for distributing gas and a plasma chamber 7 which is connected to the latter by a conduit 6, for the activation of a working or etching gas of the indicated type at the beginning, which is brought by a gas intake 8.

During the operation, the gas is brought into the plasma chamber 7 by the inlet 8 and is activated there by an intense electromagnetic field, that is to say brought into a state of chemical activity and etching potential. increased. Via the conduit 6, it reaches the distribution device 5 which distributes it in the vacuum chamber 2 in a sufficiently large and regular manner so that the entire surface of the support therein is in as homogeneous contact as possible with the gas. of engraving. Due to the fact that gas particles are constantly evacuated by the pumping 2P out of the vacuum chamber 2, the introduced gas is immediately evacuated with the volatile particles torn from the coating of the support.

It should be pointed out explicitly that in this configuration of the installation, the plasma can be spatially restricted to the "prechamber" 7, while the working gas passes through the latter. Only the working gas activated by the plasma goes into the chamber 2 under vacuum or proper treatment provided for the coated support. This has the advantage that the plasma is only ignited in the plasma chamber 7 of relatively small volume and can be maintained there, which would require significantly more processing in the larger vacuum chamber. Thus, again, the working or etching gas retains its activated state at least long enough to be in sufficiently prolonged contact with the surface of the support or of the layer to be etched.

FIG. 2 and FIG. 3 represent the selective action of the etching operation carried out according to the invention on the main components of the metal oxide layer, each time using a measurement curve B (line consisting of squares) before engraving and an A curve after engraving (line of diamonds). On the Y axis, we have reported the signal intensities of the SIMS device which allow conclusions to be drawn about the proportions of the particular material detected in the layer.

In the two figures, the two curves are aligned with respect to each other along the x-axis (distance along the depth of the layer, in nanometers nm) so that the surface of the support or glass is located at the same value of x (approximately

120 nm). We therefore see in the two curves A a decrease of a few nanometers in thickness total layer. While the curves B start at 0 nm and therefore at the initial surface of the layer, even when it is rough, the measurement values of the curves A do not start until around 20 nm, due to displacement or normalization mentioned (e) of the two curves with respect to the position of the glass surface.

In FIG. 2, it is clearly seen that before the etching, a relatively regular Si density is measured in a range of 0 to 50 nm, while after the selective etching (which targets only silicon), it is greatly reduced and does not resume its old value until around 30 nm. From this penetration depth, the etching operation carried out on a trial basis no longer has any effect on the proportion of Si.

On the other hand, FIG. 3 represents the large relative decrease in the proportions of Al in the layer. Whereas before the etching (curve B), the Ai is distributed relatively evenly to a depth of about 60 to 70 nm, after the etching (curve A), there is a sharp increase on the surface ( relative) of the Al signal which only regains its initial value of approximately 30 to 40 nm. This relative enrichment of Al on the etched surface results from the selective removal of the silicon matrix material (or silicon oxide) and also causes an even greater irregularity of the surface of the layer.

After this treatment, a hydrophobization coating of the type already mentioned above is applied in a manner known per se. This treatment can be expected to have a very durable hydrophobization which even resists mechanical attack (for example by wipers which work dry). The increase in resistance of the coating to mechanical wear can be easily proven by measurement techniques.

Claims

1. A method of producing a coating on a support, in particular on a glass surface, in which a first metal oxide is deposited in a thin layer on the support, this thin layer is subjected to a plasma etching operation or a plasma-activated etching operation to make its surface rough and a second coating capable of adhering to the layer of said first metal oxide is then applied to the roughened surface, characterized in that the first metal oxide or metal oxynitride is deposited with at least a second metal oxide or metal oxynitride, the second metal oxide or metal oxynitride being distributed in the deposited layer, and in that in the etching operation, a plasma activated gas is used which removes at least a second metal oxide or metal oxynitride less than the first metal oxide or metal oxynitride for, after etching, forming relief irregularities on the surface consisting of at least one second metal oxide or metal oxynitride.

2. Method according to claim 1, characterized in that the layer of metallic oxide or metallic oxynitride is deposited by spraying on the support, controlling the spraying pressure and / or the spraying energy creating a roughness controlled from the surface.

3. Method according to claim 1, characterized in that the metal oxide or metallic oxynitride layer is applied by a method such as CVD or vaporization.

4. Method according to claims 1, 2 or 3, characterized in that the metal oxide layer or of metallic oxynitride contains a silicon compound doped with an aluminum compound, in particular with an aluminum proportion of 8%.

5. Method according to one of the preceding claims, characterized in that as the silicon compound, SiO _x (with x <2), SiO _x C _y , SiO _x N _y , SiOyCyN _z , optionally with the addition of hydrogen, is used .

6. Method according to one of the preceding claims, characterized in that, as doping elements, Na, K, B, Rb, Cs, K, Li, Ba, Sr, Mg, Ca, La, Ti, Zr are used, alkali metals, alkaline earth metals or rare earths.

7. Method according to one of the preceding claims, characterized in that the metal oxide or metal oxynitride layer is selected so that it withstands without damage the temperatures necessary for the bending of glass supports and in that that at the latest after said heat treatment, it has in particular a light transmittance of at least 75%.

8. Method according to one of the preceding claims, characterized in that the metal oxide or metal oxynitride layer is heat treated so that atoms of the glass diffuse there.

9. Method according to one of claims 1 to 7, characterized in that is deposited on the support a diffusion blocking layer before the layer of metal oxide or metal oxynitride.

10. Method according to one of the preceding claims, characterized in that for the etching, a gas is used which contains fluorine and which is activated by plasma to form by attack of the coated support by the activated gas, gaseous compounds of silicon and fluorine which can be evacuated outside the treatment installation.

11. The method of claim 10, in which SF ₆ , CF, C ₂ F ₆ , CHF ₃ or generally C _X F _Y H _Z + 0 ₂ are used as the etching gas.

12. Method according to one of the preceding claims, characterized in that the support (4) is treated in a chamber (2) by an etching gas activated by plasma outside this chamber.

13. Method according to claim 12, characterized in that the plasma-activated etching gas is supplied to the coated support by a distribution device.

14. Method according to claims 12 or 13, characterized in that the support (4) is held stationary during the etching treatment.

15. Method according to claims 12 or 13, characterized in that the support (4) passes through the vacuum chamber (2) during the etching treatment.

16. Method according to one of the preceding claims, characterized in that the layer made rough by the etching operation has a low reflection coefficient.

17. Method according to one of the preceding claims, in which a fluorine compound of the CF ₃ - (CF ₂ ) _n - (CH ₂ ) 2 ~ Si (R ⁴ ) ₃ type is used for the application of said second coating. n being in the range from 7 to 11 and R ⁴ representing a low residual alkyl content.

18. Device (1) for the implementation of a method according to one of the preceding claims, characterized in that it comprises a vacuum chamber (2) for the treatment of the coated support (4), a device (5) for distributing gas provided in this chamber (2) and a plasma chamber (7) connected to the gas distribution device (5), a plasma being created therein to activate a working or etching gas which is introduced therein.

19. Device according to claim 18, characterized in that a pumping device (2P) is provided for the evacuation of volatile particles from the coating treated by etching during the etching operation.

20. Device according to claims 18 or 19, characterized in that the support (4) is kept stationary during the etching treatment.

21. Device according to claims 18 or 19, characterized in that it comprises a transport device which transports the support (4) through the vacuum chamber (2) during the etching treatment.

22. Support, in particular glass pane, provided with a hydrophobic coating which has been produced by a method according to the preceding process claims and / or in a device according to claim 18.