Easy-to-clean glass comprising an outer layer containing zinc and tin oxide

EASY TO CLEAN GLASS COMPRISING AN OUTER LAYER BASED ON TIN OXIDE AND ZINC

0002The invention relates to a glazing unit incorporating a glass substrate comprising on at least part of its surface a coating resistant to humidity and easy to clean.

0003The invention applies in particular to the field of interior furniture, more particularly when the substrate is intended to be arranged in a humid environment, in particular a bathroom, the substrate forming for example the glass wall of a shower enclosure or bath screen, or the front side of a mirror.

0004It is known that a humid environment induces corrosion of glass substrates until the visible appearance of white traces, and that in parallel these substrates get dirty quickly due to deposits of dirt, in particular limestone or soap.

0005In order not to interfere with viewing and for the sake of aesthetics and ease of cleaning, these glass substrates are, in known manner, mostly coated with hydrophobic layers of the silicone or fluorinated molecules type. Mention may in particular be made of the glass sold under the name Aquacontrol® of the company SAINT-GOBAIN.

0006In known manner, a hydrophobic coating allows the water deposited thereon to pearl in the form of drops. When the drops are large enough, they flow naturally by gravity on the vertical surface and therefore do not leave traces of lime when drying.

0007In the field of so-called hydrophobic glazing or coatings, a general distinction is made, in order to assess the interactions between glazing and water:

0008- the contact angle Θ, which makes it possible to assess the more or less hydrophobic nature of a surface placed in a horizontal position and - the sliding volume which more directly assesses the propensity of a drop to slide along the wall glazing in an inclined or vertical position, taking particular account of the surface condition thereof (in particular the roughness and the chemical uniformity of said surface).

0009By contact angle is meant the angle formed by the surface of the substrate and the tangent to the drop at the meeting point between the air, the drop and the substrate.

0010Organic coatings made of silicone or comprising fluorinated molecules have the best hydrophobic performance in the sense described above.

0011However, the hardness of such hydrophobic layers is inherently very low (organic compounds), while the bond between these layers and the glass substrate is often quite poor (particularly for silicones). As a result, they begin to degrade quickly (a few weeks to a few months), leaving parts of the surface hydrophilic while others remain hydrophobic. This chemical inhomogeneity tends to disadvantage the overall flow of the water drops along the glass wall. In addition, in the presence of water, the surface of the glass which is no longer protected gradually deteriorates (corrodes) due to the loss of the cations, in particular of the alkaline type, initially present in the glass material. Under the effect of this corrosion, the glass surface sees its roughness increase, which also harms the evacuation of water drops.

0012Furthermore, if outside the evacuation of water drops on a hydrophobic glazing is favored by the presence of an air flow such as wind (especially on automotive glazing), indoors it is not the case. Consequently, the small drops of water whose weight is not large enough will not flow, forming what is called "fogging", and will leave traces of limescale as they dry. Also, although a hydrophobic coating used on bathroom glazing is appreciable for easily removing dirt, it is highly recommended to wipe the glass with a squeegee to make it clean and dry after projection of water and formation of drops that are difficult to detach on their own.

0013If the residual lime can then be cleaned by products sold on the market as anti-limescale, the latter nevertheless attack the hydrophobic coating which thus deteriorates even more quickly over time.

0014Thus, when the use of cleaning products leads to the aggression of the hydrophobic coating, or even removes it, the glass which has no barrier layer corrodes very quickly over time, causing an increase in the roughness of its surface. The glass surface is thereafter more and more difficult to clean because of the incrustation of the limestone in the surface made rough.

0015Finally, the hydrophobic coatings are not hardenable, which makes it necessary to deposit them after the glazing toughening step, which aims to make the latter resistant to impact, and therefore after cutting the glass panels to final dimensions. This obviously involves an additional cost, and more often than not implies that the deposit is made at the glass processors when they are not necessarily equipped for this. In summary, the conventional hydrophobic coatings described above offer limited effectiveness in depositing dirt on the surface of the glass, have a relatively limited lifespan, varying between a few months and a few years, and ultimately involve limited corrosion protection. in time.

0016It is also necessary to deposit them separately on a glass substrate already previously tempered. In the end, such a hydrophobic coating is impractical for tempered glass substrates, such as those used in the bathroom, for which the drops of water are not always wiped after each spraying, and which are intended to be frequently cleaned with aggressive products.

0017Other bathroom glazing solutions are currently available. In particular, carbon like DLC layers (Diamond Like Carbon) have been advanced in applications WO2013184607A2 or WO2013003186A1 from the company Guardian industries.

0018Tempering glazing with a DLC layer is currently marketed under the reference Showerguard ®. This layer is said to facilitate cleaning of the glass and to make it resistant to lime. The hydrophobic DLC layer has an initial contact angle Θ of 70 ° and is indicated as being quenchable in the sense indicated above, that is to say it is no longer necessary to deposit this layer after the quenching step. of its glass support.

0019The first drawback of this DLC layer is related to quenching, which is made possible only by the addition of three layers on top of the DLC layer for its protection: a dense layer sensitive to acid attack, a dense barrier layer with oxygen and a scratch-resistant polymer layer. The plastic layer is removed manually just before the quenching step, and requires specific cutting tools. The two dense layers are removed after quenching thanks to a vinegar cleaning, which also requires specific tools. Obtaining the final monolayer product via an initial four-layer product therefore turns out to be a complex and costly process in the end. Another drawback of the layer seems to be its yellow coloring, due to the absorption by the DLC layer of part of the visible radiation. The invention therefore aims to provide a glazing which, during its transformation, its life and its use, does not have the aforementioned drawbacks, in particular the appearance of corrosion, the coloring of the glazing, the accumulation of limestone on its surface and the use of specific tools for processing, which is easily cleaned. The invention also proposes to provide a glazing whose manufacture is simple and inexpensive, incorporating a coating which can undergo the step of tempering its glass support without damage or significant degradation of its properties. More specifically, the invention relates to glazing for a humid environment comprising a glass substrate coated on at least part of its surface with an oxide layer, said layer being single or the last layer of a stack consisting of layers of dielectric materials, characterized in that said layer is a zinc and tin oxide.

0020By "layer of dielectric material" is conventionally meant a layer made of a material which does not conduct, or substantially does not conduct, the electric current, therefore excluding metallic layers.

0021By zinc and tin oxide is meant within the meaning of the present invention that the oxide essentially comprises cations of zinc and tin atoms, without however excluding that other cations, in particular other metal atoms such as Al, Ga, In, B, Y, La, Ge, Si, P, As, Sb, Bi, Ce, Ti, Zr, Nb and Ta, may be present in a very small amount compared to the sum of zinc and tin atoms, for example in an amount less than 10% of said sum, or even less than 5% of said sum. The insertion of such cations may in particular have the aim of promoting the deposition of the oxide layers on the substrate by magnetron techniques, as indicated in application WO 00/24686. According to one characteristic, the layer of tin and zinc oxide is deposited by sputtering assisted by magnetic field (magnetron) and consequently has a high density, in particular greater than 90% of the theoretical density of the solid material.

0022According to another characteristic, the zinc and tin oxide has a Sn / Zn molar ratio of between 30/70 and 70/30. Preferably, said Sn / Zn molar ratio is between 35/65 and 60/40 and very preferably said Sn / Zn molar ratio is between 40/60 and 50/50.

0023According to the invention, the layer of tin and zinc oxide has a thickness of between 5 and 100 nm. Preferably the layer has a thickness of between 10 and 50 nm. Very preferably, the layer has a thickness of less than 30 nm, or even less than 25 nm or even less than 20 nm. Preferably, said layer of tin and zinc oxide is unique and deposited directly on the glass substrate.

0024Thus, the layer according to the invention has several roles, it is easy to clean (“easy-to-clean” function according to the terms used in the field) and anti-corrosion (function of preventing corrosion of the substrate), without require any other layer to be associated with it. The layer is also hydrophobic.

0025In addition, the invention also relates to a glazing as described above and having undergone a toughening intended to make it mechanically resistant.

0026According to an advantageous embodiment, a toughened glazing according to the invention is obtained by heating-tempering a glazing as previously described, in which the layer of tin and zinc oxide is unique, so that the Sn ratio / Zn in said layer is between 99/1 and 75/25, preferably is between 98/2 and 80/20. The invention also relates to the use of glazing as described above arranged in a humid environment in which drops of water are intended to form on the glazing.

0027The glazing according to the invention may in particular be bathroom glazing, in particular shower cubicle glazing or a bath screen, or even a mirror. In other words, the glazing according to the invention can advantageously be configured to be used as bathroom glazing and very particularly as a shower cabin, a bath screen, or even a mirror.

0028The invention also relates to a process for obtaining glazing as described above. Said method makes it possible to obtain toughened and / or curved glazing comprising a glass substrate coated on at least part of its surface with an oxide layer comprising tin and zinc, said layer being single or the last layer of a stack of layers of dielectric materials. Said method comprises the steps which consist in depositing the layer stack or said layer on said substrate by a vacuum deposition technique such as sputtering assisted by magnetic field and in carrying out the heat treatment of quenching and / or bending on the substrate thus coated with the oxide layer comprising tin and zinc or with the stack comprising the latter. The inventors have unexpectedly highlighted the hydrophobic nature of the zinc oxide and tin layer (also noted Sn_xZn_yO in the following description) during its use when the latter is initially hydrophilic. Without this being considered as a well-established fact, the inventors believe that the impurities depositing on the layer of Sn_xZn_yO initially hydrophilic give it, after a short time of use, a hydrophobic property, with contact angles of the order of 60-70 °. Such a property makes it possible, unexpectedly, to envisage the use of such a layer, very advantageously, as a coating (or last layer of a coating) of a shower cubicle or more generally for any other use in which a glass , subject to splashing water, must quickly evacuate it.

0029The invention is now described using the following examples, which are only illustrative and in no way limit the scope of the invention.

0030The glazing units described in these examples incorporate a glass substrate comprising a single coating layer, known as an “easy-to-clean” layer, at least on a part of the surface, part intended to be exposed to a humid environment, such as in a room. -bath, and more particularly intended to receive water splashes. No other layer is deposited above or below the “easy-to-clean” layer.

0031The substrate is made of soda-lime glass, for example 2 mm thick, and sold under the reference PLANILUX® by the applicant company.

0032Conventionally, the oxide layer comprising tin and zinc is deposited on the glass substrate in a sputtering chamber assisted by a magnetic field (magnetron).

0033More specifically, two targets including one in SnO_x and the other in ZnO constitute cathodes and are co-pulverized by a plasma of argon and oxygen gas in the enclosure according to the conventional techniques well known in the field of the deposition of thin layers. The different molar ratios of the elements Sn and Zn in the final oxide layer as reported in Table 1 below are obtained by adjusting the respective powers applied to each of the two zinc and tin targets. More precisely, after the deposition and before any heat treatment, the Sn / Zn molar ratios present in the zinc and tin oxide (cf. table 1) are measured by conventional XPS techniques (X-ray photoelectron spectrometry ). For each of the embodiments, an 80 nm thick layer of zinc oxide and tin Sn_xZn_yO is filed.

0034The glass substrate thus coated is then tempered according to the usual techniques in the field.

0035Firstly, glazings according to the invention are produced and their performance is measured, for the respective respective zinc and tin contents.

0036The coloring of the various glazings thus obtained is first measured according to the international representation and standard CIE L^*at^*b^*. More specifically, the value b^* is measured, a large positive value indicating a marked undesirable yellow coloring. The measurements are carried out with a UV-visible spectrometer in transmission and in reflection on the layer side. The different measured values ​​are shown in Table 1 below.

0037The windows are then immersed for 8 hours in vinegar (a cleaning product commonly used for the shower cabin) to measure their resistance to corrosion. The difference in layer thickness between its initial value and its final value is shown in Table 1 below.

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0039Table 1 The results reported in Table 1 above show that high levels of zinc in the oxide lead to low resistance to corrosion. Conversely, high tin contents result in good chemical resistance of the layer but also in a marked yellow coloration of the glazing provided with its layer, in reflection.

0040The results reported in the previous table demonstrate that the best compromise is thus reached for initial molar ratio values ​​before quenching between 30/70 to 70/30, in particular between 35/65 to 60/40, and in particular included between 40/60 and 50/50.

0041Additional analyzes on the toughened glazing show that the compositions of the tin oxide layers after said toughening are significantly different from those of the layers after deposition: in particular, the Sn / Zn ratio in the layer after toughening increases appreciably, which seems to indicate that some of the zinc diffuses directly into the glass at high temperature.

0042Analysis by XPS of the composition of the layers after quenching shows that such samples, characterized by the presence of a single layer of tin oxide on the glass substrate, present the best compromise, in the sense described above, when the Sn / Zn molar ratio in said monolayer after quenching is between 99/1 and 75/25 and advantageously is between 98/2 and 80/20.

0043In a second series of examples, the quenchability of the layer and in particular its properties after the heat treatment of the glass substrate is also verified, in particular with respect to the other layers used today and described above for shower cabin glazing.

0044More specifically, a 10 nm thick layer of mixed zinc and tin oxide is deposited by magnetron sputtering techniques on a Diamant® glass substrate 8 mm thick, from an alloy target. metallic SnZn whose atomic ratio is 45/55 (ie a mass ratio 60/40), in an argon and oxygen plasma, introduced into the enclosure according to a volume ratio of the order of 1.8.

0045The glazing provided with the layer according to the invention is heated at 700 ° C for 3 minutes followed by quenching.

0046This glazing thus obtained according to the invention is compared to a first reference glazing, having a usual hydrophobic coating based on fluorinated silanes, in this case a glass sold under the brand Aquacontrol® by the applicant company, obtained thanks to a functional ization by ragging of a previously tempered glass substrate.

0047The glazing obtained according to the invention is also compared to a second reference glazing, comprising a hydrophobic coating based on DLC, in this case a toughened glazing currently marketed under the reference Showerguard®.

0048Finally, the performance of the three previous glazings is compared with that of the bare glass substrate.

0049The tests carried out on the various glazings to compare the performances reported in table 2 are described below:

0050The value of the light absorption is obtained with a UV-Visible spectrometer by measuring the transmission and the reflection of the sample on the layer side. The angle of contact with water Θ is measured with a drop of 2 μί deposited using a syringe on the horizontal surface of the substrate and using a suitable camera.

0051The sliding limit volume is defined as the limit value below which the drops no longer flow on the surface of a vertically held substrate, their weight no longer being sufficient to drive them down. If the contact angle Θ provides information on the hydrophobic nature of the layer, the sliding limit volume is more representative of the desired performance of the glazing during its use, in particular as a shower wall.

0052These two values ​​are obtained after exposure of the samples to the open air for 2 days, in order to simulate the real conditions of use where the glazing is not cleaned before use.

0053The High Humidity (HH) test consists in placing the samples in an enclosure heated to 50 ° C and in which a constant relative humidity of 95% prevails for 75 days, then in measuring the blurred appearance, the blurring being defined as the ratio between diffuse transmission and total transmission. This blurring is the result of the roughness of the substrate under the action of corrosion. This accelerated aging test appears very representative of the real conditions of use, over a long period, of the glazing in a hot and humid atmosphere such as a bathroom.

0054Measuring the coefficient of friction aims to assess the ease with which a squeegee can be used on the surface of the glazing to clean its surface. The coefficient of friction reported in table 2 is measured by means of a device comprising a squeegee 25 cm long, arranged on the surface of the glazing on the side covered by the coating. On the squeegee is placed a load of one kilogram. The force necessary for the squeegee to be moved at a speed of 4 m / min is measured using a dynamometer, in newtons.

0055The results obtained for the various tests and the various glazings studied are collated in Table 2 which follows:

0056No Sn_xZn_yO

0057Aquacontrol® Showerguard® layer

0058(Bare glass) (invention)

0059Absorption 5.1 5.1 6.6 5.1

0060θ 30 ° 105 ° 70 ° 60 °

0061Dragging vegetation 15 μΙ_ 27 μΙ_ 19 μΙ_

0062Coefficient of

00630.55 N 0.50 N 0.75 N 0.60 N friction

0064Blur after

006510% 0 2,4% 1 %

0066HH test

0067Table 2

0068The measurements carried out by the applicant company show that the glazing according to the invention differs from bare glass by a high resistance to corrosion, by an ability to cause drops of water to flow, as indicated by its very small volume of slip, close to that of the reference organic hydrophobic layer. Such a property makes it possible to limit the amount of water to be wiped on the glazing, but also to effectively limit the amount of drops of water remaining after each spraying on the surface of the wall and therefore the appearance of traces of lime. The measurements carried out by the applicant company on the reference product comprising a DLC layer show that this layer gives the coated glazing a coloration due to absorption in the visible. In addition, the DLC layer according to the prior art has a hydrolytic resistance (as measured by the HH test) lower than that of the coating according to the present invention. Also, the DLC layer according to the prior art has a lesser ability to cause the drops of water to flow and greater difficulty in removing these drops with a squeegee, as evidenced by the greater sliding volume and the coefficient of higher friction.

0069The layer according to the invention has properties fairly close to those of the hydrophobic comparative layer. It can also advantageously be deposited on a glass substrate to be toughened or toughenable. The present invention thus ultimately allows the production of glazing whose properties in use are similar to those of glazing comprising organic hydrophobic layers, with the additional advantages that the glass substrate can be quenched after depositing said layer of zinc oxide. and tin by conventional vacuum techniques, and that the properties, in particular the corrosion resistance, will last for several years.