EP1230186A1

EP1230186A1 - Transparent substrate provided with a silicon derivative layer

Info

Publication number: EP1230186A1
Application number: EP00974617A
Authority: EP
Inventors: Xavier Talpaert; Michel Simonet; Marie-José Azzopardi; Anne Durandeau
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: 1999-11-05
Filing date: 2000-10-31
Publication date: 2002-08-14
Also published as: AU776987B2; CA2389707A1; ZA200203387B; CZ20021568A3; MXPA02004454A; US6818309B1; EE200200243A; NO20022104L; UA75877C2; RU2269494C2; KR100735763B1; PL193515B1; JP2003512997A; AU1285101A; CN1269759C; SK6352002A3; FR2800731B1; PL355571A1; CN1420853A; WO2001032578A1

Abstract

The invention concerns a transparent substrate, in particular made of glass, provided on at least one of its surfaces a layer based on a silicon derivative at least partially oxidised selected among silicon dioxide or oxides hypostoichiometric in silicon oxygen, silicon oxycarbide or oxynitride, and having hydrophile properties.

Description

TRANSPARENT SUBSTRATE HAVING A SILICON-DERIVED LAYER

The invention relates to the deposition of thin layers, that is to say layers of interference thickness, on transparent substrates in order to give them a particular functionality.

The transparent substrates can be made of organic polymer, glass-ceramic or, preferably, glass, in various applications of the glazing, screen, mirror type detailed below.

The recurring problem of transparent substrates of the glass (or semi-transparent) type is that of their progressive fouling requiring tedious periodic cleaning. Another problem is the phenomenon of condensation when it causes annoying fogging on contact with water vapor, and beyond a simple fogging, an accumulation of water droplets preventing vision. Solutions, at least partial, have already been proposed: thus, coatings based on fluoropolymer are known whose highly hydrophobic surface allows evacuation of water and less clogging of dirt. There are also known coatings with photocatalytic properties, for example comprising anatase crystallized titanium oxide, effective for degrading at least organic dirt by oxidation. These different types of coating are efficient but relatively complex. Furthermore, none of them responds optimally to all of the problems raised above. Thus, hydrophobic coatings do not prevent the phenomenon of condensation, on the contrary, and photocatalytic coatings are only really effective when exposed to ultraviolet radiation and therefore usable rather outside than inside a habitat.

The invention therefore aims to find coatings that are simple to use and able to facilitate the cleaning of glass or similar substrates and / or to reduce the phenomenon of condensation of water vapor on their surface or at least prevent condensation from resulting in the appearance of mist or a multitude of droplets.

The subject of the invention is a transparent substrate, in particular made of glass, provided on at least one of its faces with a layer based on an at least partially oxidized derivative of silicon chosen from silicon dioxide, oxycarbide or oxynitride. of silicon and having a hydrophilic character.

Within the meaning of the invention, the silicon derivative may comprise only the elements Si, 0, in the case of Si0 ₂ , the elements Si, 0, N in the case of an oxynitride and the elements Si, 0, C in the case of an oxycarbide. However, the silicon derivative according to the invention also comprises materials containing in addition, in a minority with respect to silicon (by weight), at least one metal such as aluminum, zinc or zirconium. The addition of a metal can have three advantages: by reactive sputtering, this amounts to "doping" the Si target to make it more conductive, which accelerates / facilitates deposition. In addition, whatever the mode of deposition (by pyrolysis for example), the addition of an aluminum type metal can increase the durability of the material, especially in the case where it is little or not carbon / nitrogen. Finally, the addition in a controlled amount of this type of metal in the layer makes it possible to modulate its refractive index, in particular to increase it (aluminum oxide has an index of about 1.65 , the oxides of zinc and zirconium have an index of about 2). Within the meaning of the invention, the silicon derivative also includes the sub-stoichiometric silicon oxides in oxygen of formula SiOx, with x less than

2.

The invention has thus discovered a new characteristic of this type of material, namely a certain hydrophilicity conferring on it unexpected properties: it has been observed that the substrate, preferably glass, provided with this type of layer is cleaned much more easily than a bare glass (less friction to clean the glass with a cloth, the majority of dirt being removed effortlessly by spraying water). In addition, a delay in fouling was observed, allowing the frequency of cleaning to be reduced, an effect all the more marked if the glass is outside and exposed from time to time to rain: by runoff, the rainwater naturally stains the glass. The third unexpected effect is that a possible phenomenon of water condensation on the surface of the glass thus coated does not reduce the visibility of the glazing at all or little: it seems that the water appears in the form of a liquid, homogeneous and transparent film. , invisibly and no longer in the form of droplets.

The same improvements are observed by comparing a glass provided with a stack of layers surmounted by the layer according to the invention with a glass provided only with the stack of layers (for example a stack with a solar control function, of low emissivity , with an optical function, ending in a layer chemically different from that of the invention, for example a layer of metal oxide, of metal nitride).

These advantageous effects can be adjusted / amplified by modulating the chemical composition, the surface appearance, the mode of deposition chosen.

Thus, the layer may have a refractive index of approximately 1.45 (pure Si0 ₂ ) or greater than 1.45 if it is a silicon sub-oxide or if the derivative contains carbon or nitrogen. Advantageously, in these latter cases, the refractive index is adjusted between 1.45 and 1.80, in particular between 1.50 and 1.75 or between 1.55 and 1.68. In the sense of the invention, the term “refractive index” is understood to mean its refractive index in the usual sense of the term when the layer is homogeneous in composition and index in its thickness, that is to say its average index, apparent when the layer has a composition, an index which vary in its thickness. An advantageous embodiment of the invention in fact relates to layers in which the refractive index decreases from the carrier substrate to the outer surface of the layer.

There are two advantages to choosing a low refractive index:

•> •• on the one hand, it approaches that of glass when it is the substrate in question, thus avoiding giving a reflective appearance to glass,

• “* •• on the other hand, the more the refractive index tends to rise, the more the proportion of C or N increases at the expense of oxygen, and it turns out that the hydrophilicity of the layer by increasing its oxygen level.

Another parameter which can influence the hydrophilic nature of the layer is its surface roughness, which, in certain embodiments of the invention, is much higher than that of a standard bare glass.

The layer according to the invention can be deposited by any type of process capable of depositing thin layers of this type: it can be vacuum processes such as sputtering, in particular assisted by magnetic field (for example starting from a silicon target possibly doped with boron or aluminum). To promote the formation on the surface of Si-OH groups favorable to high hydrophilicity, it is possible to use a reactive atmosphere containing for example, in addition to a purely oxidizing compound type O ₂ , a hydrogenated compound and / or to use a compound containing both hydrogen and oxygen. The reactive atmosphere can thus contain a mixture of 0 ₂ / H ₂ , 0 ₂ / H ₂ 0 or H ₂ 0 ₂ when a silicon oxide is produced. If it is a question of depositing a silicon oxynitride, it is possible to use reactive atmospheres using as nitrogenous and / hydrogenated compounds for example an amine, an imine, hydrazine, ammonia. The SiO2-based layers (possibly doped with a small amount of a metal or boron) deposited by reactive sputtering can have fairly variable refractive indices. Depending on the deposit parameters chosen, in particular the pressure during the spraying of the target, the refractive index (average between 380 and 780 nm) of the layers can thus be around 1, 4 to 1, 5, reflecting fairly dense layers. It can also be lower on the order of

1.25 to 1.40, in particular 1.28 to 1.35, for example around 1.30 (to within ± 0.05). In this case, there are then less dense layers, with a certain porosity and / or surface roughness which can promote their hydrophilicity.

It may preferably be a deposit by sol-gel route or by pyrolysis, in particular by vapor phase pyrolysis (CVD or "Chemical Vapor").

Deposition "in English). In the case of a deposition by the sol-gel route, the soil may contain a precursor based on TEET orthosilicate orthosilicate, and be deposited by known techniques such as dipping. , spraying ("spray-coating" in English), centrifugation ("spin-coating" in English or the mode of deposition designated by the English term "flow-coating". In the case of deposition by CVD , it is thus possible to use a silicon precursor in the form of a silane of the SiH type. The silicon precursor can also be an organosilane, of the RsiX ₃ type with X a halide of the chlorine type and R an alkyl (linear or branched , having for example from 1 to 10 carbons or more). These may include organo-silane-type RySiX _4. _y, with the same conventions for R and X, or a compound belonging to the family of ethoxysilanes Other precursors / gases can be added to the silicon precursor (s), such as ethyl not, a derivative containing nitrogen such as ammonia or an amine (especially primary). An oxidizing agent may also be present (0 ₂ , H ₂ 0, H ₂ 0 ₂ , ...).

It has also been noted that a certain surface roughness in the layer promotes the beneficial effects described above, certain roughness which can be controlled in particular by the deposition parameters of the layer, and by the very preparation of the surface. on which the actual deposit is made.

The contact angle with water measured on the coatings according to the invention is advantageously less than 35 °, or less than or equal to 25 °, for example between 15 and 25 °: this effectively denotes a hydrophilic character (with compare to the contact angle on standard bare glass which is generally 40 °). It is not necessarily a very significant hydrophilicity which brings about the beneficial effects of the invention, even a modest hydrophilicity, but accentuated compared to that of bare glass, is effective. We do not necessarily eliminate the phenomenon of condensation, but we avoid that it causes the appearance of drops (in fact, when the contact angle is less than 7 or 10 °, the fog becomes invisible, even if we always has condensation).

According to certain embodiments, and in particular for layers deposited by CVD, the contact angle can be less than 15 °, and in particular be less than 10 °.

The layer according to the invention can have a variable chemical composition in its thickness. Advantageously, it can have an increasing oxygen concentration towards its "external" surface (that is to say its surface furthest from the carrier substrate). It is thus possible to have a layer of silicon oxycarbide or oxynitride which is markedly richer in C or N near its surface closest to the substrate, and richer in O near its outer surface, even forming a (thin) layer of almost pure Si0 ₂ over a layer with a chemical composition richer in C or N, or even in Si or in Si ₃ N almost pure. This oxygen concentration gradient can be obtained by adjusting the deposition conditions or by surface oxidation after deposition, for example by heat treatment.

A high concentration of oxygen at the surface of the layer is indeed favorable, in the sense that it makes it possible to have a high rate of hydroxyl bonds Si-O-H at the surface, which makes it hydrophilic. The layer according to the invention preferably has a thickness of at least 5 nm, in particular between 5 and 100 nm, for example between 10 and 60 nm.

The layer of the invention can be part of a stack of thin layers, being the last layer of the stack (or an additional layer to a given stack), the one which is the farthest from the substrate. It may for example be an anti-reflection stack (alternating layers with high refractive index and basic refractive index, such as

Tiθ ₂ / Si0 ₂ / Ti0 ₂ / layer according to the invention, the Ti0 ₂ can be substituted by

Nb ₂ Os, Si ₃ N ₄ , Sn0 ₂ , ...). It can also be a stack of the solar control type, such as a stack of the optional sublayer / TiN / layer type according to the invention or a solar control layer based on Ti0 ₂ or mixed iron oxide. , cobalt and chromium: glazing thus coated is marketed by Saint-Gobain Glass France under the names of

"Vision-Lite", "Starélio" and "Antélio" respectively. It may also be a stack of layers comprising at least one silver-based layer with a low-emissivity or solar control function, (glazing thus coated being sold by Saint-Gobain Glass France under the name of " Planitherm "), or low-emissive stacks whose functional layer is based on tin oxide doped with fluorine (glazing thus coated being marketed by Saint-Gobain Glass France under the name of glazing" EKO "), or solar control stacks whose functional layer is based on steel or Ni / Cr alloy (glazing thus coated being sold by Saint-Gobain Vitrage under the name of "Cool-Lite" glazing). For more details, see the patents EP-638 528, EP-718 250, EP-511 901, EP-728 712, WO97 / 43224, EP-638 527 and EP-573 325. When the substrate is made of glass , it can be curved and / or hardened or annealed before or after deposition of the layer (s).

The subject of the invention is also the application of the substrates described above to the manufacture of glazing with "anti-condensation" effect and / or with "anti-fouling" effect and / or simple to clean (within the meaning of the invention , "anti-condensation" means that there may be condensation, but with little or no negative effect on visibility through the glazing). It can be glazing for buildings, for vehicles, for mirrors, and in particular for bathroom mirrors, rear view mirrors, shower cabin glass, glass doors and interior partitions, urban furniture, display panels, display screens of the television or computer screen type. The invention will be described in more detail using nonlimiting examples, using the following figures:

*** - Figures 1 to 3: photographs obtained by scanning electron microscopy (SEM) of the surface of a layer according to one of the examples. In all the examples, on a clear silica-soda-lime glass of the "Planilux" type sold by Saint-Gobain Glass France, layers of silicon oxycarbide of 50 nm by CVD (for example according to patent EP-518

755) from SiH ₄ , ethylene and optionally an oxidizing compound, by modulating the levels of precursors, the deposition temperatures so that the layers have refractive indices of the order of 1.58 at 1.75. It has been confirmed that it is the glasses coated with SiOC layers having the lowest refractive indices which are the most hydrophilic and the most effective in terms of slowing down of fouling. These glasses also have the most marked “anti-condensation” effect, although they have a contact angle with water which is not very small, and which is around 15 to 30 °. Note that the lower index layers tend to approach the glass (index 1.52) and therefore only slightly modify the appearance of the glass: other examples according to the invention have contact angles below 15 or 10 °.

Pyrolysis deposits offer the advantage of continuous deposit directly on the float line.

The coatings thus obtained are generally remarkably durable. EXAMPLES 1 to 4

Table 1 below groups together for Examples 1, 2, 3 and 4 the refractive indices ir of four layers based on silicon oxycarbide thus obtained, as well as the values angle of contact angle with water after cleaning, and the result of a test consisting in storing the glasses coated with the layer for 18 hours at 30 ° C. in an atmosphere at 95% relative humidity. ("YES" means that there is an "anti-fog" effect, in the sense that there is no appearance of visible water droplets on the layer, "NO" means that there is such droplets visible to the naked eye). Cleaning is done with a surfactant in two stages, with rinsing with tap water, cleaning ending with a final rinsing with deionized water and then drying under nitrogen flow.

From these data, we can see that the most interesting layers are those with the lowest refractive index, less than 1.70. They are also the most hydrophilic and the richest in oxygen. EXAMPLES 5 to 7

They consist of a Planilux glass surmounted by a layer of SiOC obtained as above and of 50 nm. Table 2 below indicates for these examples their refractive indices i.r. (the glasses were cleaned before depositing the layers as before).

Figures 1 to 3 are pictures obtained by SEM of the layer according to Example 5, according to three different enlargements. One can notice a particular porosity of surface, with sorts of small blisters of rather irregular sizes and rather flat tops. Figure 3 showing the largest enlargement shows "blisters" whose base, in its largest dimension, is in the 60-80 to 100-110 nm range.

We compare them to a comparative example 8 made of Planilux glass without a layer: • *** • - according to a laboratory test ("laboratory test"), where they are stored for 1, 6 and 14 days in the atmosphere described in the context of examples 1 to 4: 30 ° C, 95% of relative humidity,

• *** • according to an outdoor exposure test on an industrial site ("industrial site test"), where they are stored for 1 and 10 days in the atmosphere at 30 ° C and 95% relative humidity.

The results (expressed in "YES" or "NO" as in Table 1) are shown in Tables 3 and 4 below:

These results show that the layers according to the invention have a lasting "anti-fog" effect, while bare glass has it only very temporarily.

Another test was carried out on examples 6, 7 and comparative example 8: the blurring of the glasses provided with the layers according to examples 6 and 7 and of the bare glass of comparative example 8 was measured, after 10 days of outdoor storage on an industrial site (blur is the diffuse light transmission, expressed as a percentage in a known manner).

The results are as follows: examples 6 and 7 show after 10 days a limited blurring (which is less than 1%), while comparative example 8 shows after 10 days a significant blurring (of at least 5%) due an accumulation of dirt on the glass. This test confirms the effect of delaying the fouling of the layers according to the invention. EXAMPLE 9

This example concerns a solar control glass marketed under the name "Clear Antelio" by Saint-Gobain Glass France.

It is a 6 mm thick Planilux glass surmounted by a layer of mixed Fe, Co, Cr oxide of approximately 45 nm deposited by pyrolysis in the liquid phase in a known manner.

According to the invention, a thin layer based on Si0 ₂ according to the invention is deposited on the mixed oxide layer by the sol-gel route.

The sol is made of a solvent, propanol-2, 0.3 N HCl in H ₂ 0 and tetra ethyl orthosilicate TEOS.

The deposition and hardening of the layer is done conventionally. The layer obtained has a thickness less than or equal to 20 nm, and a refractive index of approximately 1.45.

Contact angle measurements were made in comparison with a comparative example consisting of the single Antélio glazing glass / mixed oxide Fe, Co, Cr.

The following treatments are successively subjected to comparative examples 9 and 10:

* » ^• (a) - cleaning as before, ozone and UN treatment. to eliminate the carbonaceous species adsorbed on the surface of the layer, • - ** • ^• (b) - 2 days of aging outdoors,

- "* ^• (c) - 19 days of aging outdoors,

^• - ** ^• (d) - cleaning test as before.

We measure between the angles of contact with water after each of these steps. The results are collated in Table 5 below:

TABLE 5 It can be noted from these data that for comparative example 10, the contact angle θ increases quickly outdoors, and that a standard cleaning fails to restore a small contact angle. On the other hand, example 9 gets dirty much less quickly, its contact angle with water remains relatively low even after several weeks, and, above all, the dirt leaves much faster after a standard cleaning: the glazing becomes clean again easily.

EXAMPLE 11

This example relates to the deposition of a layer based solely on silicon and oxygen (possibly containing other elements, but as impurities of negligible quantities). The layer is deposited on a “Planilux” glass as in Examples 1 to 4, by CVD from SiH and an oxidizing compound, but without ethylene. A layer of silicon oxide of 50 nm and of index 1.50 is obtained. Its contact angle with water, measured as in Examples 1 to 4, is low, less than 10 ° (of the order of 7 °). The layer has the same anti-fog effect as the layers of Examples 1 and 2.

Claims

1. Transparent substrate, in particular made of glass, provided on at least one of its faces with a layer based on an at least partially oxidized derivative of silicon chosen from silicon dioxide or sub-stoeochiometric oxides of silicon oxygen, the oxycarbide or oxynitride of silicon, and having a hydrophilic character.

2. Substrate according to claim 1, characterized in that the refractive index of the layer based on the silicon derivative is between 1.45 and 1.80, in particular 1.50 to 1.75, preferably 1, 55 to 1.68.

3. Substrate according to one of the preceding claims, characterized in that the layer is deposited by sol-gel or by pyrolysis, in particular by CVD gas phase pyrolysis.

4. Substrate according to one of the preceding claims, characterized in that the layer is rough on the outer surface.

5. Substrate according to one of the preceding claims, characterized in that the contact angle with water of the surface of the layer is less than 35 °, in particular less than or equal to 30 °, for example between 15 and 25 ° or less than or equal to 10 °.

6. Substrate according to one of the preceding claims, characterized in that the layer has an increasing oxygen concentration towards its outer surface.

7. Substrate according to one of the preceding claims, characterized in that the layer has a high rate of hydroxyl bond Si-O-H on the outer surface.

8. Substrate according to one of the preceding claims, characterized in that the layer has a thickness of at least 5 nm, in particular between 10 nm and 60 nm.

9. Substrate according to one of the preceding claims, characterized in that the layer is the last of a stack of thin layers, in particular of an anti-reflection stack, of a solar control stack, of a low stack -emissive.

10. Glass substrate according to one of the preceding claims, characterized in that it is curved and / or toughened, or annealed before or after deposition of the layer.

11. Glass substrate according to one of the preceding claims, characterized in that the silicon derivative also contains, in a minority with respect to silicon, at least one additive, in particular a metal such as aluminum, zinc or zirconium .

12. Application of the substrate to the production of glazing with an “anti-condensation” and / or “anti-fogging” effect and / or with an “anti-fouling” effect and / or simple to clean, in particular glazing for the building industry, for vehicles , for mirrors, in particular bathroom mirrors or rear view mirrors, shower cabin glasses, glass doors and interior partitions, street furniture, display panels, display screens.