Transparent textured substrate and methods for obtaining same

Translation of description of equivalent WO 0202472 A1

SUBSTRATE TRANSPARENT TEXTURE AND METHODS FOR OBTAINING

The present invention relates to a transparent substrate to which is searched the best optical properties required for a window at present, whether it be a vehicle glazing for transportation or building. In addition to optical properties presented to the highest degree, the substrate is designed to introduce additional properties residing in the modification of the substrate wettability behavior in a behavior that can be described as super hydrophobic / oleophobic or super-hydrophilic / oleophilic in anti-fouling, anti-reflection, electrical conductivity, antistatic.

The property of hydrophobicity / oleophobicity of a substrate is that the contact angles between a liquid and this substrate are high, for example of the order of 120 ° for water. The liquid then tends to flow easily in the form of drops on the substrate, by gravity if the substrate is tilted or under the effect of aerodynamic forces in the case of a moving vehicle. This is the expression of an anti-rain effect. The drops are on the other hand, could result in runoff of dust, insects or dirt more or less fat of all kinds whose presence would result in an unattractive appearance or, where appropriate, impaired vision through the substrate. In this measurement, the substrate hydrophobic / oleophobic also has an antifouling property.

Hydrophobic agents / oleophobic coatings are known, for example, fluorinated chorosilanes, fluorinated alkylsilanes such as described in patent application EP-A1-0 675 087. They are applied in a known manner using conventional deposition methods with or without heating .

On the contrary, the property dTiydrophilie / oleophilic character of a substrate is reflected in low contact angles between a liquid and the substrate, for example between 0 and 5 ° and preferably well below 5 ° for water on clean glass. This property favors the formation of liquid films transparent purposes, at the expense of fog or frost up of tiny droplets impairing visibility through a transparent substrate. These anti-fog and anti-frost effects observed a hydrophilic / oleophilic substrate are well known.

Many hydrophilic agents including hydroxylated, such as poly ((meth) acrylates ydroxyalkyle Td) are used for this purpose, in known manner, for transparent substrates. Some compounds, called photocatalytic such as TiO 2, are furthermore used, especially in combination with glass substrates not only to their hydrophilic character after exposure to light, but also for their ability to degrade by a process radical oxidation, dirt of organic origin; the hydrophilic properties / oleophilic and antifouling are then obtained simultaneously. It is known to deposit coatings photocatalytic TiO 2 comprising from at least one titanium precursor, optionally in solution, by liquid phase pyrolysis, by a sol-gel technique or by vapor phase pyrolysis.

In accordance with the foregoing, the property dTrydrophobie / oil repellency will appreciate quantitatively by measuring the contact angle formed, usually by a water drop on a given substrate. If no further indication, this contact angle is measured for a horizontal substrate. In fact, as already mentioned above, the liquid drops of dynamic behavior that is subject to the conferring hydrophobicity to a substrate. This applies both to substantially vertical static substrates such as exterior glazing for buildings, glazing shower for the glazing of vehicles. However, in the case of a drop of liquid on an inclined substrate relative to the horizontal, two different contact angles are observed: the advancing angle and the receding contact angle, determined in the front, respectively at the rear of the drop, relative to the direction of its movement. These angles are values ​​reached the limit of the offset of the drop. hysteresis called the difference between advancing angle and the receding contact angle. A drop of water having high hysteresis or a small receding contact angle will struggle to pass on a substrate. Thus, it is understandable that effective hydrophobicity is conditioned both by high advanced angle and low hysteresis. Finally, in known manner, the size of the drop affects the angles of advanced and retracted.

The invention makes now available a transparent substrate capable of exacerbating the hydrophobic / oleophobic or hydrophilic / oleophilic intrinsic substrate material, which can be obtained in excellent industrial conditions, in particular continuously, at all glazing dimensions requested and used by the public, and having optical properties at the best level of those of existing glazing. This substrate may be, as appropriate, superhydrophobic / oleophobic (characterized as an indication of a minimum advance angle of 160 ° and a minimum receding contact angle of 120 ° for a drop of water) or super-hydrophilic / oleophilic (angle contacting less than 5 °, approaching 0 ° to water). It can also be made simply hydrophobic / oleophobic or hydrophilic / oleophilic a perfectly controlled manner. Examples may be obtained according to the invention hydrophobic substrates / oleophobic for having a drop angles of forward / backward by 160 ° / 110 °, 140 ° / 130 ° ... (angles measured by growth and decay drop pipette).

When the substrate is hydrophilic / oleophilic and photocatalytic, exacerbation of hydrophilic / oleophilic goes along with that of the antifouling character. To this end, the invention relates to a substrate having at least a portion of the outer surface has the geometry of a sheet having protuberances having, for at least 80% of them, heights between 40 and 250 nm, average diameters between 1 and 500 nm, at least 80% of the distance between two neighboring protrusions being between 1 and 500 nm.

Although the transparency of the substrate permits to assess specific benefits related to its optical properties, the substrate of the invention may also be not transparent.

The minimum of 80% set by the invention is not absolutely imperative and in some cases this minimum may be less than 80%, for example of the order of 70%. However, such a reduction is at the expense of the optical qualities so that in reality it will be almost all growths, particularly at least 90%, preferably at least 95% growths that satisfy the required criteria.

The invention therefore provides a process industrially advantageous in many ways as we will see later in a transparent substrate superhydrophobic / oleophobic or superhydrophilic / oleophilic for all shapes and currently requested glazing dimensions, with the best optical qualities to glazing. substrates made according to the invention have also presented remarkable durability and resistance to abrasion and erosion.

Moreover, thanks to the invention, additional functions such as anti-reflection, electrical conductivity, anti-static may be imparted to the substrate by an equally advantageous fabrication process.

According to other characteristics of the invention:

- At least 80% of the protuberances have heights at least equal to 60 nm, in particular at least equal to 80 nm; - At least 80% of the protuberances have heights at most equal to 190 nm, in particular at most equal to 170 nm;

- At least 80% of the protuberances substantially constitute cones or truncated cones straight axes perpendicular to the main plane of the substrate and half-angles at the apex between 0 and 60 °, in particular between 0 and 30 °, this definition designating also, in the limiting case, the cylinders;

- At least 80% of the protuberances have average diameters of 40 to 380 nm, the average diameter may for example be considered as that of the truncated cone at mid-height. Of course many outgrowths of the invention have geometries deviating more or less from those of a cone, truncated cone or cylinder which are only approximations frequently obtained forms. Be mentioned more, growths in columns perpendicular to the main plane of the substrate sections regular or irregular, but defined by two Orthogonal axes corresponding to a larger, respectively a smaller both dimensions in the range of 1 to 500 nm, that is to say the area average diameters defined in accordance with the invention. Include a ratio of said largest to said smallest dimension advantageously between 1 and 4.

Are also part of the invention the substrates which knobs, in general different sections from one another, include growths section having a partially concave periphery.

The invention encompasses the other substrates in which growths aforementioned geometries were formed in negative, that is to say hollow. In this regard include cavities with diameters between 0, 1 and 500 nm in the case of an applicable substrate as chemical or biochemical microreactor.

In preferred embodiments, the required geometry of at least part of the outer surface of the substrate is given by a layer of a material containing one or more oxidation products or nitriding such as SiO 2, Si3N4, AlN, Al2O3 , SnO 2, ZnO x with x> 0, and / or formed by a vacuum technique, especially by sputtering assisted by magnetic field, magnetron plasma, plasma CVD, atmospheric CVD, pyrolysis of powder and liquid, by a process of polymerization and / or crosslinking, by a technique of the sol-gel type. These compounds and methods are in fact well suited to forming the seed layer in which are formed the projections defined above, to obtain a high optical quality product.

This layer gives the desired geometry to the outer surface of the substrate can be itself outside, or covered with a coating almost none modifying the surface geometry, such as a functional coating, or other hydrophobic monomolecular of few nanometers thick. The substrate of the invention may be composed exclusively of this layer provided if necessary of its monomolecular coating, or laminate thereof with a sheet of glass or transparent plastic material underneath, with possible interposition of an electroconductive layer. Can be used a soda lime glass, including float glass as used for transportation vehicles, for building or other application of flat glass, or a type of glass bottle or flask, a borosilicate Pyrex type, a phosphate glass used as prosthesis or optical glass, lead glass (crystal), an aluminosilicate such as a ceramic, or an amorphous solid material free of silica. All suitable transparent plastics among which can be cited the polyvinylburyral, polyurethane, polycarbonate, polymethyl methacrylate, ionomer resin, etc. subject to their compatibility with the operating conditions (temperature, pressure ...) successive stages of the substrate formation. On the other hand several sheets of glass and / or plastic can be laminated in the substrate of the invention: for example, two glass sheets connected to one another by an intermediate adhesive layer polyvinylburyral, a sheet of glass and a sheet of polyurethane having energy absorption properties ...

The advantage of the interposition of an electroconductive layer between the sheet of glass or plastics and the growths layer is explained below in connection with one of the methods of manufacture of the substrate of the invention. Examples for this electroconductive layer, may be mentioned metal oxides substoichiometric and / or doped known from patent application FR-2695117, in particular indium oxide doped with tin (ITO) oxide zinc doped with indium (ZnO: in), fluorine (ZnO: F), aluminum (ZnO: Al) or with tin (ZnO: Sn) and the fluorine-doped tin oxide ( SnO 2: F) or antimony (tetravalent or pentavalent) (SnO 2: Sb). In addition to their electrically conductive properties, these materials are described as having reflection properties in the infrared, in particular of poultry-emissivity.

In this regard, any known association of functional layers of low-emissivity type sunscreen, anti-reflective, decorative (matted with acid, screen-printed, painted, glazed, textured by rolling through rollers or other equivalent methods) with the substrate in a glazing monolithic or laminated is encompassed in the invention. as an example we quote:

- A reflective layer deposited on PET film itself embedded in the interlayer adhesive PVB in a laminated windshield - a multiple glazing or laminated with a thin layer of solar control (for example of the type sold by Saint - Gobain glass under one of STARELIO marks COOL-LITE) on face 2 and a dimpled substrate of the invention the inner side of the multiple glazing, in contact with the atmosphere of the enclosure protected, - or a double glazing, the outer sheet of glass is a clear glass sold under the brand PLANILUX by the company SAINT-Gobain glass, which has an outer face with growths of the invention and an inner side, facing the air gap, provided with a thin layer of SnO 2: F deposited by CVD (product marketed under the trademark EKO and EKO PLUS by Saint-Gobain Glass) or layer to the money deposited by vacuum sputtering (product sold by the Saint-Gobain Glass under the brand PLANITHERM), each layer having a high reflection in the field of infrared radiation of long wavelength (low-e) which greatly reduces heat loss and provides the double glazing insulation heat strengthened to a high light transmission,

- Textured layer (side 1) / Planilux / sunscreen layer: COOL-LITE, STARELIO (face 2) - textured layer (the face) / Planilux / air rare gas / emissive layer flip-SnO 2: F (EKO) or silver (PLANITHERM) (face 3) / Planilux / textured layer / Planilux / reflective layers (mirror substrate is always transparent, it is the layer that is reflective) - texturing / glass / screen printing (SERALIT, trademark by Saint-Gobain Glass).

The substrate of the invention can achieve a remarkable optical quality. It has thus advantageously a light transmission of at least 80%, especially at least 85%, most preferably at least equal to 90% and a haze of at most 5%, in particular at most equal to 2% and most preferably at most equal to 1%.

According to a major variant of the invention, the substrate is hydrophobic / oleophobic. In known manner the creation of irregularities on a surface increases the hydrophobic or hydrophilic character. As indicated above, an appropriate choice of geometry of protrusions allows to control the hydrophobic nature. for example converting a planar surface characterized by angles of forward / backward by 100 ° / 80 ° in a dimpled surface of angles 160 ° / 120 °.

In this case, the substrate is formed at its outer surface, at least in part a) of the compounds obtained in particular by a vacuum technique, by evaporation, sputtering, sol-gel, CVD or the like; b) silicones; and / or c) compounds of the formulas:

F3C (CF2) m (CH2) p-nSiX3 (I)

RP <img id="imgf000009_0001" he="6" wi="94" file="imgf000009_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" /> in which :

- M = 0 to 15;

- N ≈ 1 to 5;

- P = 0, 1 or 2;

- R is a linear or branched alkyl group or a hydrogen atom; - X is a hydrolyzable group such as halogen, alkoxy, acetoxy, acyloxy, amino, NCO;

- Ρ = 0, 1, 2 or 3.

The above techniques for obtaining are advantageous in that they allow to incorporate hydrophobic compounds in a layer which is not hydrophobic without this incorporation. We can therefore use for this purpose an additional precursor in order to obtain an organic / inorganic composite. However, it is also possible to implement one precursor capable of giving the dliydrophobie property. Exemplary mention is the implementation of a plasma CVD process, from at least one precursor selected from:

- A silane such as tetramethylsilane, hexamethyldisilane, an alkoxysilane such a alkoxytrialkylsilane, in which the alkyl group is methyl, ethyl, propyl, methyl being preferred;

- A fluorinated silane, including a perfluoroalkylalkyltrialkoxysilane or perfluoroalkylalkyltrihalogénosilane;

- A siloxane such quTiexaméthyldisiloxane; - A silazane such quliexaméthyldisilazane.

Using, for example hexamethyldisiloxane a flat surface layer is obtained, that is to say prior to forming protrusions, static contact angle for a drop of water of 105 °.

This outer surface of the substrate consists at least partly of one or more of the above compounds, consists either of the layer giving the required geometry Studded described above, or in a coating applied to this layer, thin enough not to change essentially geometry. As mentioned above, it may be a graft monomolecular film. According to another variant, the substrate is hydrophilic / oleophilic in that it comprises a suitable agent. Hydrophilic agent / oleophilic mention may be made, as final product or precursor, the polyacid (meth) acrylic acid as such or at least partially salified with sodium, potassium, cesium ..., nonionic surfactants, cellulose esters such that hydroxypropylcellulose, chitosan derivatives and chitin, polymethacrylates, poly (vinyl alcohols) and poly (vinyl acetate), polypyrrole, polyaniline, polyacrylamide, poly (N, N-dimethylacrylamide), poly (N-isopropylacrylamide), polyethylene glycol, polypropylene glycol, polyoxyethylene hydroxy or methoxy terminal groups, polyallylamine hydrochloride, polysaccharide, dextran (branched), pullulan (linear polysaccharide), polyacid styrènecarboxylique and salt thereof, polyacid sryrènesulfonique, sodium polystyrenesulfonate, polyvinylburyral, polyiodide 2-vinyl-N - methyl pyridinium, polyiodide 4-vinyl-N-methyl-pyridinium poly (2- vinyl pyridine), polybromide of 2-vinyl-pyridinium, polyvinylpyrrolidone, copolymers obtained from monomers from different aforementioned polymers, including block copolymers, some titanium compounds such as titanium tetraisopropyl or titanium tetraisobutyl, optionally stabilized, eg acetylacetonate, titanium tetrachloride ...

As the hydrophobic / oleophobic agents, hydrophilic / oleophilic agents can be incorporated especially in the layer constituting the growths itself, or be applied to this layer into a thin film.

The dT properties ydrophobie and dliydrophilie is annoying each other, the substrate of the invention generally comprises one or more hydrophobic / oleophobic agents or one or more hydrophilic agents / oleophilic. However, the invention allows the coexistence of the two types of agents, including a variant in which the outer surface of the substrate comprises hydrophobic growths and a low level between the protrusions which is hydrophilic (below it will be understood how the manufacturing process the substrate of the invention allows easy implementation of such a product). In this variant, the major part of a liquid when in contact with the substrate flows over the hydrophobic growths, and only a small part of this liquid comes into contact with the hydrophilic low level and forms a transparent uniform film.

Advantageously, the substrate of the invention exhibits antifouling properties. These may result in part, as has been seen above, properties (super) hydrophobic / oleophobic or (super-) hydrophilic / oleophilic. These properties can also be directly linked to the nature of certain constituents of the substrate. And as already mentioned, from hydrophilic agents / oleophilic certain titanium compounds, for example TiO 2, have the ability to decompose photocatalytically organic residues.

The invention provides a substantial progress in the control of the disposal of liquid on the substrate, removing droplets, fog, frost formed from the residual liquid, that is to say not evacuated to degradation of soil contained in the residual liquid, so that the substrate can be kept clean without any cleaning.

According to a preferred embodiment, the substrate of the invention exhibits anti-reflection properties. Conventionally, an anti-reflective substrate is obtained by combining a first outer thin layer, that is to say in contact with the atmosphere, of relatively low refractive index, with a second thin layer immediately below the first and higher refractive index then possibly with other layers of indices alternately strong and weak. According to the present invention the preparation of protuberances can control the solid fraction relative to the fraction of air. Thus in the corresponding thickness of the substrate, the refractive index is a function of the index of the material and the index of air, equal to 1, that is to say a minimum. This index is less than that which would be a solid layer of the same material and may be lowered tending to 1, in that it decreases the solid fraction in a controlled manner.

Thus an anti-reflection effect due to the fact that the outer layer comprises an outer portion corresponding to the protrusions and full inner fraction. According to another variant, the outer layer does not contain such full inner fraction. Alternatively or additionally, the anti-reflective properties can result from a treatment in the form of a stack of interferential thin layers, generally consisting of alternating layers based on a dielectric material with high and low refractive indices or in the form of a layer having a refractive index gradient in its thickness, as described in document EP-1 013 622. such a coating deposited on a transparent substrate has the function of reducing the light reflection, so to increase light transmission. It was emphasized that such stacks or layers may be formed in particular by vacuum techniques of plasma CVD, CVD not assisted by a plasma sputtering in particular assisted by a magnetic field, reactive sputtering, that is, -dire techniques that can be easily integrated in a continuous process with those forming excrescences, developed in the following.

In outer surface of an automotive windshield, the anti-reflection effect results in improving the visual comfort of the driver and passengers. According to an advantageous embodiment, the substrate is electrically conductive. This may be the case of a constituent layer of the substrate, in contact or not with the ambient atmosphere, or the entire substrate. Examples of materials used are metal oxides substoichiometric and / or doped mentioned above. The ability of the substrate to conduct electricity is here antistatic function, ie the ability to dissipate electrostatic charges and to avoid the accumulation locally, as well as the constitution of heating films, including the demisting and defrosting windows. Other useful electrically conductive materials are a material comprising eg SiB or CH4 as precursor to form metallic bonds of the Si-Si or DC or metal salts such copper qu'acérylacétonate. The interest of avoiding local accumulations of electrostatic charges appear in applications such as aircraft windshields, in which it is important instead of evacuating these charges by conduction. charge accumulations indeed constitute a source of cracking and destruction of any stacked functional layers, as well as the structure of the substrate, particularly when it is laminated.

Another object of the invention resides in a method of etching a layer of a glass, silica (quartz) or a polymer substrate, a reactive plasma through a mask in a suitable material and dimensions , so as to form the protuberances are as defined above.

It was indeed overview surprisingly, and without the reasons are still well known that etching had virtually no place in the absence of mask, if it is a drink that is meant to burn.

In addition to the benefits of this process reside in the qualities of the products obtained as ultrahydrophobicity, superhydrophilicity, optical properties in the case of a transparent substrate, durability, over large areas, the process currently seems promising because it can be achieved by techniques including vacuum that perform treatments of the substrate in particular to the equipping of increasingly numerous functions required for glazing, continuously and by a single apparatus. Adequate etching method is reactive ion etching.

The layer to be etched (which, in the following, include both the layer, glass, silica or polymer substrate etching) may be transparent or not; in the latter case it may in some cases be then converted into transparent layer (for example oxidation of Ti or Al or TiO 2 transparent Al2O3).

According to advantageous features of the process:

- The mask is made of an electrically conductive material, such as metal, in particular a noble metal such as Au, Ag, Pt, Pd, a metal alloy, a conductive oxide as obtained by doping, including SnO 2: F , SnO 2: In and the like, a ceramic or a polymer;

- The mask is used in contact with the layer to be etched; in this regard include a training mode type mask inkjet, among many other possibilities;

- On the contrary, the mask is used without contact with the layer to be etched; the mask may for example consist of a metal grid positioned parallel and at a short distance therefrom;

- Said mask is used in the form supported on a sheet, particularly made of plastic, which is especially convenient, the mask being in particular obtained from a product in rolls; in this embodiment, good results can be obtained, that the mask is located on the side of said facing sheet layer to be etched, or on its other face. For the substrate of the invention by this process, the etching is anisotropic and oriented along the normal to the substrate. To do this, five variants are preferred.

According to the first, the layer to be etched is laminated to an electrically conductive layer thereunder which is polarized with a generator Radiofrequency during burning. The nature of the electrically conductive layer has been specified above.

According to the second variant, the substrate is placed on an electrically conductive support connected to a radiofrequency generator during burning.

According to the other three variants:

- The layer to be etched itself is electrically conductive; it is for example of SnO 2: F or a metal layer such as Ti or Al which will eventually, after etching, oxidized to TiO 2 or transparent Al2O3; - The layer etching is laminated to an electrically conductive glass sheet;

- The layer to be etched is laminated to a sheet of glass provided on its opposite side to an electrically conductive layer such as SnO 2: F.

According to other features of the method: - using one or more of the CF4 plasma-generating gas, C3F2, SFβ,

C2F4, CHF3 to perform the engraving;

- The mask consists of nodules comprising at least one of Ag, Au, Pd, Pt, Cu, Al, Zn, Sn, Sb, Ti, Zr, W, Mb, Ta, Ir A layer of. one or more of these elements is easily subjected to dewetting for nodules in excellent reproducibility conditions, the required dimensions comparable to less than the wavelength of visible light in order to minimize blurring over relatively surfaces larger sizes (such as greater than 1 m²) And with a fast focus speed; - The method comprises a step of removing or transforming into the compounds transparent portion of said mask consisting of nodules remaining after performing the etching. It is specified that the metal nodules can also be attacked during etching, it does not always rest at the end of it. A removal process may consist, in the case of Ag nodules for example, to immerse the substrates etched in an acidic aqueous solution, for example HNO3. One may also consider a mechanical removal, in particular using a brush. An example of transformation in transparent compounds is the oxidation of Al Al2O3 by passage of the flame on etched substrate;

- The method comprises a step of forming a coating on the substrate after performing the etching and then, if necessary, removed or transformed fraction of said mask remaining after performing the etching. One example is the vacuum grafting of a monomolecular layer of a hydrophobic or hydrophilic agent.

According to a second method of manufacturing the transparent substrate described above, nodulates dimensions and geometry required for said excrescences, is rendered transparent if required, and a coating is formed such that the vacuum grafting a functional monomolecular layer.

The invention secondly relates to a glazing comprising the substrate described above, this glazing being intended for a land transport vehicle, sea or air, particularly an automobile, building (window, door, sanitary furniture unit or else such as shower, table, tablet ...), with an interior decorative element such as an aquarium or outdoor, street furniture (bus shelters ...), domestic appliances (door oven, refrigerator shelf ...). Outside the frame members or frame of such a glazing may essentially consist of a substrate according to the invention, or comprise one or more such substrates associated with one or more sheets of glass or plastic or laminated transparent structures in a multiple glazing unit in which all the constituents are separated in pairs by an air knife or the like. Other objects and advantageous applications of the invention are:

- A lenticular screen or a microprism substrate obtained according to one of the above described processes comprising dimensions of surface irregularities in the principal plane in the range from 1 .mu.m to 1 mm; include regular rows and adjoining protruding, from 8 to 14 microns in height, 300 to 400 microns of pitch (distance peak to peak between two adjacent rows) formed in order to obtain a display system in three dimensions;

- A glass substrate etched to lamp or display obtained according to a the above described processes comprising dimensions of surface irregularities in the principal plane in the range of 0 1 to 10 microns;

- The application of a substrate according to the invention having cavities with diameters between 0.1 and 500 nm as chemical or biochemical micro reactors.

The invention is now described on the basis of an exemplary embodiment.

EXAMPLE 1

A sheet of clear glass float 0.7 mm thick sold under the trade name "Planilux" by Saint-Gobain Company GLASS

France was provided with an indium oxide coating doped with tin (ITO) 110 nm thick according to any deposition technique known for this purpose, then a SiO 2 layer of 100 nm thickness by any suitable technique (magnetron plasma, pyrolysis, plasma CVD, sol-gel ...).

An Ag layer of 15 nm thick is vacuum deposited by magnetron sputtering. It is then proceeded to dewetting of this Ag layer by heat treatment at 300 ° C under a vacuum of 9 mTorr for 30 min. Of Ag nodules are thus formed on the SiO 2 layer.

Subjecting the resulting substrate to a reactive ion etching under the following operating conditions. The cathode is supplied with direct current, the conductive undercoat DTTOs being polarized by being connected to a radiofrequency generator set to 13.56 MHz. SFβ is used as plasma gas and a pressure of 75 mTorr. The power is 0, 106 W / cm² and the treatment time of 250 s.

An overnight immersion in an aqueous solution of 1 molar HNO3 at room temperature has the effect of removing the portion of Ag nodules that had not been attacked the previous etching step.

The resulting substrate seen at an angle of 15 ° with a magnification of 50000 with a scanning electron microscope is shown in the single appended. It is observed growths of training, 80% have at least heights between 70 and 200 nm, the mean diameters between 50 and 400 nm, at least 80% of the distance between two neighboring protrusions being between 1 and

500 nm. These growths can be defined as axes rights truncated cones perpendicular to the main plane of the substrate and half angles at low peak, less than 20 °.

vacuum vapor is grafted on the substrate a monolayer of perfluorooctyléthyltrichlorosilane CιoFi7H4SiCl3.

The advancing and receding contact angles measured by growth, respectively decrease of a drop of water by means of a pipette are 165 ° or 122 °, corresponding to a superhydrophobic behavior.

One more measure a light transmission of 92.8% and a haze of less than 4% using a Hazegard XL 211 machine.

Example 2 A sheet of glass differing from that of the previous example in that it contains neither coating ITO or SiO 2 layer, is subject to the same dewetting money than previously, and the subsequent operations described in Example previous, being simply placed on an electrically conductive support connected to the same radiofrequency generator, other conditions being equal.

The cylindrical protrusions (axes perpendicular to the plane of the sheet) formed are characterized in their almost entirely by a height of about 100 nm, a diameter of 80 to 100 nm, and a distance between the axes of two neighboring cylinders between 130 and 150 nm. The etch rate measured perpendicular to the substrate surface is 5 to 8 nm / min; in the absence of the mask consisting of silver nodules, this speed is zero.

Thus, the invention allows it to combine on a large substrate surface tension functionality, outstanding optical quality and an opportunity to provide additional functions, in excellent industrial implementation conditions, including many if by performing the different treatment continuously in one apparatus.