HK1056160A - Transparent substrate provided with a silicon derivative layer - Google Patents

Description

Transparent substrate with silicon derivative layer

The present invention relates to a thin deposition layer on a transparent substrate to impart a special function thereto, i.e., a thin deposition layer having an interference thickness.

The transparent substrate may be an organic polymer, glass ceramic or preferably glass, for use in various glass plates, screens, mirrors, as will be described in more detail below.

A recurring problem with glass-based transparent substrates (or translucent substrates) is that they gradually break down and must be cleaned on a regular basis, which is tiresome. Another problem is that it causes undesirable condensation of water vapour when in contact with it, and in addition to simple water vapour, there are water droplets which obstruct the view.

At least partial solutions have been proposed: for example, fluoropolymer-based coatings are known, the surface of which is highly hydrophobic and which can remove water and reduce adherent fouling. It is also known that coatings having photocatalytic properties, such as coatings containing crystalline titanium oxide in anatase form, are effective in degrading at least organic fouling by oxidation.

These different types of coatings perform well, but are also relatively complex. In addition, neither can balance the above problems in an optimal way. For example, hydrophobic coatings do not prevent condensation, whereas photocatalytic coatings are only effective when exposed to ultraviolet radiation, and are therefore particularly useful outdoors rather than indoors.

The present invention therefore seeks to find a coating which is simple to use and which is suitable for making glass-type or similar substrates easier to clean and/or to reduce condensation of water vapour on their surface, or at least to avoid condensation, so that no water vapour or numerous droplets are present.

The object of the invention is a transparent substrate, in particular a glass substrate, provided on at least one of its surfaces with a layer of at least partially silicon oxide-based derivatives selected from silicon dioxide, silicon oxycarbide or oxynitride and exhibiting hydrophilic properties.

In the context of the present invention, the silicon derivative is in SiO₂In the case of (3), only the elements Si and O may be contained; in the case of oxynitrides, it is possible to contain only the elements Si, O and N, and in the case of oxycarbides, only Si, C and O. But the silicon derivatives of the invention also include materials containing minor amounts (by weight) of other materials than silicon, such as at least one metal, such as aluminum, zinc or zirconium. The addition of metal has three advantages: by active anodic sputtering, Si is targeted as an element to be incorporated into the additive, giving it a higher electrical conductivity, which makes the deposition more accelerated and easier. In addition, the addition of aluminum-based metals, regardless of the deposition method (e.g., pyrolytic deposition), can increase the durability of the material, particularly when there is little or no carbon/nitrogen. Finally, the addition of controlled amounts of these metals to the deposited layer enables the adjustment of the refractive index, in particular the increase of the refractive index (the refractive index of alumina is approximately 1.65, oxygenZinc oxide and zirconium oxide are both around 2).

Within the scope of the present invention, silicon derivatives also include those of the general formula SiO_xA substoichiometric oxygen (oxogene) of (a), where x is less than 2.

The present invention also finds a new feature of such substances, namely that they are unexpectedly endowed with certain hydrophilic characteristics: it is noted that substrates with such thin layers, preferably glass, are easier to clean than bare glass without thin layers (glass is cleaned with a rag with less friction and most of the dirt is easily removed by flushing). In addition, we have observed that the contamination can be delayed, which can reduce the frequency of cleaning, and the effect is more pronounced if the glass is exposed outdoors and in rain from time to time: in rain, rain water naturally carries a lot of dirt. The third surprising effect is that the condensation of water which can occur on the surface of the glass thus coated does not reduce at all or only very little the see-through properties of the glass: it appears that a uniform transparent liquid film appears on the glass, which can be seen through without the formation of droplets.

The same improvement is observed when glass to which a multilayer film comprising a thin layer of the present invention is attached and glass to which only a multilayer film is attached (e.g., a film having a function of controlling sunlight, a film having a low-emissivity function, a film having an optical function, which is constituted of a coating end chemically different from the present invention, such as a metal oxide layer, a metal nitride layer) are compared.

This beneficial effect can be tuned/amplified by tuning the chemical composition, surface characteristics, and deposition mode selected.

For example, this layer may have a thickness of about 1.45 (pure SiO)₂) Or a refractive index higher than 1.45, this being related to silicon suboxides or Si derivatives containing carbon or nitrogen. In the latter case, it is advantageous to adjust the refractive index to 1.45 to 1.80, in particular 1.50 to 1.75, or 1.55 to 1.68. In the sense of the present invention, we understand that "refractive index" can be in the general sense of refractive index, i.e. refractive indexThe refractive index, or the apparent average index (when the layer has a composition or index that varies across its thickness) across its thickness when the composition of the layer is uniform. An advantageous embodiment of the invention relates in fact to a layer whose refractive index decreases from the support of the substrate to the surface of the layer.

Choosing a refractive index that is not too high has two advantages:

on the one hand, when glass is used as substrate, the refractive index is very close to that of glass, thus avoiding the characteristic of giving reflection to glass;

on the other hand, the more the refractive index tends to increase, the higher the contents of C and N, against oxygen, it being clearly emphasized that the hydrophilic character of the thin layer increases with its oxygen content.

Another parameter that can affect the hydrophilic character of the layer is its surface roughness, which in certain embodiments of the invention is clearly higher than that of standard bare glass.

The layers of the invention may be deposited by various types of methods suitable for depositing such thin layers: this may involve methods of vacuum deposition such as methods of anodization (sputtering), particularly methods assisted by a magnetic field (such as for silicon targets optionally doped with boron or aluminum). To facilitate the formation of Si-OH groups on the surface which contribute to a high hydrophilicity, it is possible to use, for example, a composition which also contains O₂A pure oxidant-like compound, an active atmosphere containing a hydrogen compound, and/or the use of a compound containing both hydrogen and oxygen. Thus, in the production of silicon oxide, the active atmosphere may contain O₂/H₂、O₂/H₂O or H₂O₂A mixture of (a). If silicon deposition of the oxynitride is involved, reactive atmospheres like nitrogen-containing compounds and/or hydrogen-containing compounds, such as amines, imines, hydrazines, ammonia, can be used. SiO-based deposited by active anode sputtering₂The layers of (b) (optionally doped with small amounts of metal or boron) may have refractive indices that vary widely. According to the selected deposition parametersIn particular the pressure during atomization of the target, the refractive index of the thin layer (average value between 380 and 780 nm) can be between 1.4 and 1.5, resulting in a denser layer. It may be even lower, between 1.25 and 1.40, especially between 1.28 and 1.35, for example about 1.30(± 0.05 or so). In this case, the thin layer is less dense, while the surface has some porosity and/or roughness, which are advantageous for its hydrophilic properties.

Preference may be given to deposition by the sol-gel process or by pyrolysis, in particular vapor phase pyrolysis (known in the english as CVD process). In the case of deposition by the sol-gel route, the sol may contain a precursor based on Tetraethylorthosilicate (TEOS), deposited by a deposition mode known as impregnation (in english, "dipping"), spraying (in english, "spray-coating"), spin-coating (in english, "spin-coating"), or "flow-coating" in english. In the case of deposition by CVD, SiH in the form of silane may also be used₄A silicon precursor of type (iii). The silicon precursor may also be RSiX₃Type organosilanes, wherein X is a chlorine-like halogen and R is an alkyl group (linear or branched, having, for example, 1-10 or more carbon atoms). May relate to R_ySiX_4-yOrganosilanes of the type in which R and X have the same meaning, or compounds belonging to the ethoxysilanes class. Other precursors/gases may be added to the silicon precursor, such as ethylene, nitrogen-containing derivatives, such as ammonia or amines (particularly primary amines). Optionally an oxidizing agent (O) may be present₂、H₂O、H₂O₂Etc.).

It is also worth noting that some surface roughness in the layer contributes to the advantageous effects described above, in particular it can be controlled by the deposition parameters of the layer, suitably by the manufacturing process of the surface itself on which the deposition is to be performed.

The water contact angle measured on the coating of the invention is preferably less than 35 °, or less than or equal to 25 °, such as 15 to 25 °: this effectively indicates the hydrophilic character (in comparison to which the contact angle of standard bare glass is typically 40 °). The large hydrophilicity is not essential to bring about the advantageous effects of the present invention, and even moderate hydrophilicity stronger than that of bare glass is effective. It is not necessary to completely eliminate the condensation phenomenon, but to avoid the appearance of droplets (in fact, when the contact angle is less than 7-10 °, moisture is not visible, even if there is condensation).

According to certain embodiments, particularly for layers deposited by CVD, the contact angle may be less than 15 °, particularly less than 10 °.

The layer according to the invention may have a varying chemical composition over its different thicknesses. Advantageously, the oxygen content may be gradually increased towards the "outer" surface thereof (i.e. the surface further away from the substrate support) so as to obtain a layer of silicon oxycarbide or oxynitride having a C or N content more concentrated at the surface closest to the substrate thereof and 0 more concentrated near the outer surface thereof, until an almost pure SiO is formed thereon₂(thin) layer, but below a layer whose chemical composition is more rich in C or N, even almost pure Si or Si₃N₄. Such a concentration gradient of oxygen can be obtained by adjusting the deposition conditions or by surface oxidation after deposition, for example by heat treatment.

In fact, a high oxygen concentration at the surface of the layer is advantageous, enabling the formation of bonds with a high content of hydroxyl groups (Si-O-H) at the surface, which have hydrophilic properties.

The layer according to the invention preferably has a thickness of at least 5nm, in particular 5 to 100nm, for example 10 to 60 nm.

The layer of the present invention may be part of a multilayer thin layer, the last layer in a stack (or a layer to which a given multilayer thin layer is attached), i.e., the layer furthest from the substrate. This may involve, for example, antireflection layers (high refractive index layers alternating with low refractive index layers, such as TiO)₂/SiO₂/TiO₂The thin layer of the invention, TiO₂Can use Nb₂O₅、Si₃N₄、SnO₂Instead). It may also involve a layer of solar control type, such as an optional sublayer/TiN/layer of the type of the invention, or based on TIO₂Or iron, cobalt and chromium mixed oxides: the glasses thus coated are commercially available from Saint-Gobain Glass France under the trade names "Vision-Lite", "Star é lio" and "Ant lio", respectively. Multilayer structures which may also be mentioned include at least one silver-based layer whose function is to provide low-emissivity, or solar control (the Glass thus coated is commercially available from Saint-Gobain Glass France under the trade name "planotherm"), or low-emissivity multilayer structures whose functional layer is based on a layer of tin oxide doped with fluorine (the Glass thus coated is commercially available from Saint-Gobain Glass France under the trade name "EKO"), and also solar control multilayer structures whose functional layer is based on a layer of steel or a Ni/Cr alloy (the Glass thus coated is commercially available from Saint-Gobain Glass France under the trade name "Cool-Lite"). More detailed reports are found in patents EP-638528, EP-718250, EP-511901, EP-728712, WO 97/43224, EP-638527 and EP-573325.

When the substrate is glass, it may be subjected to bumping (bending) and/or dipping (trememperage) or annealing before or after deposition of these thin layers.

The object of the invention is also the use of the above-mentioned substrate for the manufacture of a glass that is "anti-condensation" and/or "anti-fouling" and/or simple to clean (in the sense of the present invention, "anti-condensation" means that condensation can occur, but that there is no or hardly any adverse effect on the vision through this glass). It may relate to glass for buildings, automotive glass, glass for mirrors and display screens particularly for bathroom mirrors, automotive rearview mirrors, shower glass, glass doors and interior partitions, urban utilities, billboards, television or computer display screens and the like.

The invention is described in more detail with the aid of the following figures and non-limiting examples:

FIGS. 1 to 3: a surface photograph of the layer in one of the examples was taken by a scanning electron Microscope (MEB).

In various embodiments, a thin 50nm layer of silicon oxycarbide is deposited by CVD (for example according to patent EP-518755) from SiH4, ethylene and optionally an oxidant compound on a transparent silica-soda-lime Glass of the "Plailux" type sold by Saint-Gobain Glass France, the precursor content, the deposition temperature being adjusted so that the refractive index of this thin layer is between about 1.58 and 1.75. This was confirmed to be the SiOC layer coated glass, which had the lowest refractive index, was the most hydrophilic and was most effective in reducing stains. This is also the most pronounced "anti-coagulation" effect of the glass, whose contact angle with water is not too small, about 15 to 30 °. It is to be noted that this layer with the lowest refractive index tends to be close to that of glass (index 1.52), and therefore there is a small change in the characteristics of the glass: other embodiments of the invention have a contact angle of less than 15 ° or 10 °.

Deposition by pyrolysis has the advantage of direct deposition on a continuous float line.

The coatings thus obtained generally have a significant durability.

Examples 1 to 4

Table 1 below summarizes the refractive indices i.r. of examples 1, 2, 3 and 4, each based on the oxycarbide of silicon thus obtained, the contact angle theta with water after cleaning and the test results, comprising storing the coated glass at 30 ℃ for 18 hours in an atmosphere with a relative humidity of 95%. "yes" means a "moisture resistant" effect in the sense that no visible water droplets appear on the layer, and "no" means visible water droplets. The cleaning was performed in two steps with surfactants, rinsing with tap water, final rinsing with deionized water after cleaning, and drying in a nitrogen stream.

TABLE 1

	i.r.	θ	Testing
				Example 1	1.58	14°	Is that
Example 2	1.68	23°	Is that
				Example 3	1.71	27°	Yes/no
Example 4	1.75	31°	Whether or not

From these data, it can be seen that the layer of most interest is the one with the smallest refractive index, i.e. below 1.70. These are also the most hydrophobic and oxygen-rich.

Examples 5 to 7

The glasses of these examples consist of Planilux, accompanied by a SiOC layer obtained as described above, with a thickness of 50 nm. For these examples, table 2 gives their refractive index i.r. (these glasses are cleaned before deposition of the layers described above).

TABLE 2

	i.r.
		Example 5	1.68
Example 6	1.58
		Example 7	1.71

FIGS. 1 to 3 are photographs of the thin layer according to example 5 taken with a scanning electron microscope at 3 different magnifications. Special surface porosity, irregular size bubbles and very flat tops can be noted. FIG. 3 shows the most magnified vesicle having a bottom of 60-80 nm to 100-110 nm in its largest dimension.

In comparison with comparative example 8 consisting of Planilux glass without this layer:

according to the laboratory test ("test lab") when stored in the atmosphere described in the scope of examples 1 to 4 for 1, 6 and 14 days: 30 ℃ and 95% relative humidity;

according to the test under exposure outside the industrial site ("test site construction"), storage is then carried out at 30 ℃ and 95% relative humidity for 1 day and 10 days.

The results (indicated as "yes" or "no" as in table 1) are shown in tables 3 and 4 below:

TABLE 3

	Laboratory testing
				1 day	6 days	14 days
	Example 5	Is that	Is that				Is that
Comparative example 8				Is that	Whether or not	Whether or not

TABLE 4

	Industrial site testing
			1 day	10 days
	Example 6	Is that			Is that
Example 7			Is that	Is that
	Comparative example 8	Is that			Whether or not

These results indicate that the thin layer of the present invention has a long lasting "moisture resistant" effect, when bare glass is only temporarily effective.

Some further tests were carried out in examples 6, 7 and comparative example 8: the haze of the bare glass according to the invention, with the thin-layer glass attached and the control 8, was measured after 10 days of outdoor storage in an industrial site (haze is the transmission of scattered light, generally expressed in percentage) in examples 6 and 7 according to the invention.

The results are as follows: examples 6 and 7 had limited haze after 10 days, below 1%, when comparative example 8 had greater haze (at least 5%) after 10 days due to the build up of dirt on the glass. This test demonstrates the stain retarding effect of the thin layer of the present invention.

Example 9

This example relates to solar control Glass marketed by Saint-Gobain Glass France under the trade name "Ant Li o Glass".

A6 mm thick Planikux glass with a layer of mixed oxides of Fe, Co and Cr, approximately 45nm thick, produced by the known vapor phase pyrolysis method, is concerned.

According to the invention, the SiO according to the invention obtained by the sol-gel process is deposited on a mixed oxide layer₂A base layer.

The sol was made from solvent, 2-propanol, 0.3N aqueous hydrochloric acid, and Tetraethylorthosilicate (TEOS).

The deposition and hardening of the thin layer is carried out in the usual manner. The resulting layer has a thickness of less than or equal to 20nm and a refractive index of 1.45.

The contact angle with water was measured and compared with comparative example 10 consisting of Ant lio glass plate/Fe, Co, Cr mixed oxide only.

Example 9 and comparative example 10 were successively subjected to the following treatments:

- (a) performing the cleaning, the ozone treatment and the ultraviolet ray treatment as described above to remove the carbonaceous matter adsorbed on the surface of the layer;

- (b) aging in the open air for 2 days;

- (c) ageing in the open air for 19 days

- (d) washing test as described above.

The contact angle with water was measured after each of these steps and the results are summarized in table 5 below.

TABLE 5

	Example 9	Comparative example 10
			θ(a)	17°	5°
θ(b)	32°	53.1°
			θ(c)	43°	79.3°
θ(d)	24°	71°

From these data, it can be seen that for comparative example 10, the contact angle θ rapidly increased outdoors and that standard cleaning was able to restore the contact angle to a smaller value. On the contrary, example 9 increases more slowly, even after a few weeks, the contact angle with water is still low, and especially after standard cleaning, the soil is removed quickly: such glass is easily recovered.

Example 11

This example relates to the deposition of a monolayer based on silicon oxide (optionally containing other elements, but only as a negligible amount of impurities). This layer was deposited on Planilux glass as in examples 1 to 4 by CVD from SiH4 and an oxidant compound, but without ethylene. A50 nm thick silicon oxide layer was obtained with a refractive index of 1.50. Its contact angle with water, as measured in examples 1-4, was small, below 10 ° (about 7 °). This layer had the same water vapour resistant effect as the layers described in examples 1 and 2.

Claims (12)

1. Transparent substrate, in particular made of glass, on at least one face of which is affixed a layer based on an at least partially oxidized silicon derivative chosen from silicon dioxide or a substoichiometric oxygen silicon dioxide, silicon oxycarbide or oxynitride, the thin layer having hydrophilic properties.

2. Substrate according to claim 1, characterized in that the silicon derivative-based layer has a refractive index of 1.45 to 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 a sol-gel method or a pyrogenic method, in particular by a vapour phase pyrolysis method, i.e. a CVD method.

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

5. Substrate according to one of the preceding claims, characterized in that the surface of the layer has a contact angle with water of less than 35 °, in particular less than 30 °, such as 15 to 25 ° or less than or equal to 10 °.

6. Substrate according to one of the preceding claims, characterized in that the oxygen content of the layer increases gradually towards the outer surface.

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

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

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

10. Substrate according to one of the preceding claims, characterized in that the substrate can be bent and/or impregnated or annealed before or after deposition of the thin layer.

11. Substrate according to one of the preceding claims, characterized in that the silicon derivative also contains at least one additive, in particular a metal such as aluminium, zinc or zirconium, in a minor amount corresponding to silicon.

12. Use of the substrate for the manufacture of glass articles, i.e. glass with an anti-condensation and/or anti-water vapour effect and/or glass with an anti-soiling effect and/or simple to clean, in particular for buildings, automobiles, mirror surfaces, in particular bathroom mirrors or automobile rearview mirrors, glass for shower cubicles, glass doors and partitions, urban infrastructure, advertising panels, display screens.