EP1874534A1

EP1874534A1 - Fireproof glazing

Info

Publication number: EP1874534A1
Application number: EP06725756A
Authority: EP
Inventors: Bertrand GLAVERBEL - Centre R & D DURY; Etienne GLAVERBEL - Centre R & D DEGAND
Original assignee: AGC Glass Europe SA
Current assignee: AGC Glass Europe SA
Priority date: 2005-04-15
Filing date: 2006-04-13
Publication date: 2008-01-09
Also published as: RU2007141982A; WO2006108873A1; BE1016494A3; RU2417173C2

Abstract

The invention concerns fireproof glazings. The inventive glazings comprise at least one hydrated alkaline silicate-based intumescent layer sandwiched between glass sheets one of which at least is coated with a thin layer filtering ultraviolet rays to which the glazing is exposed, the ultraviolet radiation filtering layer not transmitting more than 35 % of the rays of wavelengths not more than 345 nm. The resulting glazings are highly resistant to aging.

Description

Fire-resistant glazing

The present invention relates to fireproof glazing comprising a layer of intumescent material based on hydrated alkali silicate.

Fireproof glazing comprising in addition to glass sheets, one or more sheets of intumescent material are widely used in the trade. They have various fire resistance qualities depending on their constitution. Apart from their quality of fire resistance they must also ensure a certain mechanical resistance. These two properties can be obtained also by a suitable choice of structure including in particular several sheets of glass associated with several sheets of intumescent material.

For satisfactory use the products in question must be free from defects, and in particular from defects which impair their transparency. It is known that among the possible defects for this type of product, the most common are the formation of bubbles eVou sail ("haze"). These defects appear most often to the test of aging. To be perfectly satisfactory it is appropriate that these products retain their optical quality for at least a period of not less than 10 years.

A recognized factor promoting accelerated aging is exposure to ultraviolet light. Given that the products in question are very often exposed to ultraviolet-rich radiation, especially to solar radiation, the preservation of optical qualities requires the implementation of specific provisions.

Various means have been proposed to prevent the alteration of the optical properties of the glazings comprising layers based on hydrated alkali silicates, it being understood that the traditional clear glass sheets which envelop these layers, obviously do not constitute a sufficient barrier to ultraviolet rays.

Among the proposed means in particular is the use of a sheet known to constitute an effective UV filter, and which is also commonly used in the constitution of laminated glazing for their confer impact resistance properties. Polyvinyl butyral sheets are particularly suitable. In particular, it is known that even at a relatively small thickness, of about 0.38 mm, more than 95% of the UV rays are stopped. However, the use of polymer sheets in fireproof glazing is not always appropriate. The presence of organic materials is preferably avoided in this type of products because of their fire behavior. Moreover, the implementation imposes a well-defined provision of this sheet on the path of the incident radiation so that it actually prevents UV rays before they reach the sensitive layer to be protected.

Other proposals have been made which include using a thin layer of titanium oxide deposited on the glass sheet at least on the side of the incident light. The studies of the inventors have shown that the presence of a layer of this type in terms of UV protection is insufficient to prevent the degradation of the intumescent layer (while keeping a sufficient light transmission).

The object of the invention is therefore to provide fire-resistant glazings comprising intumescent layers based on alkaline silicates protected against the alterations resulting from exposure to ultraviolet rays.

According to the invention, in glazings of this type at least one glass sheet comprises a layer, or a set of layers, whose transmission of ultraviolet rays of wavelength less than 345 nm, is not greater than 35% preferably not more than 25% and particularly preferably not more than 20%. For the most efficient UV filtering layers do not transmit more than 10% and even less than 10% of wavelengths less than 345 nm. The layer or layers in question also offer a transmission in the visible which is not less than 80% and preferably not less than 85%.

The transmissions in question here are those specific to the layer or the layer system, it being understood that in the glazing necessarily intervenes between the intumescent layer to be protected and the source of radiation, not only the protective layer but at least the glass sheet carrying this layer. As it is recalled later the presence of the glass sheet further reduces the transmission, even if this reduction is limited, it is not indifferent, and varies for the same glass depending on the thickness of the sheet.

To be perfectly satisfactory, the products according to the invention must be substantially "neutral" in coloring or slightly gray or bluish.

The elements concerning the optical parameters used in the definition of the invention follow the following standard forms:

- the total light transmission (TL). This total transmission is the result of the integration between the 380 and 780 nm wavelengths of the expression:

Σ Tχ.Eχ.Sχ / Σ Eχ.Sχ, where Tχ is the transmission at the wavelength λ, Eχ is the spectral distribution of the illuminant and Sχ is the sensitivity of the normal human eye according to the wavelength λ;

- the total transmission in the ultraviolet (TUV). This total transmission is the result of the integration between 280 and 380 nm of the expression: Σ Tχ.Uχ / Σ Uχ. where Uχ is the spectral distribution of ultraviolet radiation having passed through the atmosphere, as determined in DIN 67507.

For traditional products in which the intumescent layer is based on hydrated alkali silicates, it has been found in the experiment that the degradation was mainly due to wavelengths below 345 nm. Degradation at longer wavelengths is not perceptible in the duration of the aging tests. Similarly, the measures taken by the inventors made it possible to determine the quantitative threshold beyond which UV rays of wavelength less than 345 nm could lead to the appearance of defects within the time limits compatible with use. normal.

The inventors have also established that the UV sensitivity of the intumescent layer depends in part on the nature of this layer. The appearance of defects of the "bubble" or "veil" type seems all the more marked as the water content of this layer is higher. In this sense the sodium silicates hydrate which are the most common products are particularly sensitive.

Depending on the tests, and depending on the nature of the silicates, the value of 20% of the UV rays (percentages actually reaching the layer intumescent by the combined filtering effects of the layer and the glass sheet with this layer) for the wavelength of 345 nm of sunlight appears as the highest threshold that can be supported without risk of occurrence of defects . Preferably this value is at most 15%, or even 10%, and advantageously is as low as possible. In other words, a UV filtration which does not make it possible to fall below this proportion, does not improve the UV resistance sufficiently for any hydrous alkali silicate product.

The fire-resistant glazings according to the invention comprise one or more layers, or sets of thin layers, of which at least one layer chosen from the group of materials comprising zinc oxide or a zinc-based alloy, the oxides mixed tin and zinc, cerium oxide.

The thicknesses used are chosen according to this ability to hinder the transmission of UV. The choice still takes into account the visible transmission of the layers in question. But other factors, in particular the convenience of producing these layers, are also decisive in the choice made. For all of these reasons, a preferred layer according to the invention is based on zinc oxide. Zinc oxide layers are relatively easy to deposit, and are relatively inexpensive.

For a layer of zinc oxide alone, the thickness is not less than 50 nm. It is advantageously at least 100 nm, and preferably at least 150 nm. For smaller thicknesses the fraction of UV of less than 345 nm wavelength effectively filtered is not sufficient to ensure the desired longevity of the products when they are exposed to solar radiation.

In determining the necessary thickness of the UV filtering layer, it is also necessary to take into account other elements involved in the composition of the glazing, which can reduce the UV transmission. As an indication, even the glass sheets have an impact on this transmission. For plain clear glass sheets the UV transmission according to the thickness of the sheet (s) is of the order indicated in the following table.

In the determination of the UV transmission as indicated above, the range considered has a significant share greater than the selected threshold of 345 nm. The effective influence of the glass sheet takes into account this spectral distribution. In other words, it is a little less than the preceding table suggests, which expresses the transmission over an extended range of wavelengths.

Fire-resistant glazings have on their faces glass sheets which are usually 3 or 4 mm thick. The UV that reaches the first intumescent layer are already reduced by about a third. This proportion for thicker, less usual glass sheets can go down to less than half. The UV filtering layers according to the invention can be adapted accordingly. In particular their thickness may be less if the outer glass sheet on which this layer is disposed is relatively thick.

If for the filter layer a minimum thickness is required, there is in principle no upper limit not to exceed outside that leading to an excessive decrease in the visible light transmission that could result. For layers based on zinc oxide it is not desirable to use layers having a thickness of more than 300 nm. Beyond the gain in terms of UV filtration is no longer significant, but the increase in the thickness of the layer results in a possible reduction of the transmission in the visible.

An additional factor leads to limiting the thicknesses of the UV filtering layers. This is the structure of these layers. Given their mode of production the UV filtering layers, and particularly the layers based on zinc oxide can develop under structures more or less sensitive to the corrosive action of the alkali silicate layers. The formation of these layers can lead either to relatively "compact" shapes or, conversely, to structures having points facilitating the alteration of these layers.

The layers based on zinc oxide are deposited in a traditional, especially in techniques using vacuum deposition by sputtering under magnetic field ("magnetron sputtering"). These layers can easily be brought to the required thicknesses. The layers in question can also advantageously be deposited by pyrolysis, the latter generally having the advantage of a lower production cost and a better compactness.

Thin layers based on zinc oxide often comprise another metal in small proportions. This is particularly the case of aluminum which is introduced at percentages of the order of 2 to 4% for reasons related to the process of formation of these layers. The presence of aluminum, especially in sputtering techniques, makes it possible to stabilize the operation of the metal cathode formed of this alloy. This avoids the irregularities in the layer from a certain instability of the system.

Whatever its method of preparation, but particularly when the zinc oxide-based layer is formed by sputtering, if the thickness exceeds a few tens of nanometers, the layer tends to take a structure described as "columnar". This type of structure as its name suggests leads to clusters of oxide separated by interfaces conducive to the penetration of corrosive agents. To limit this mechanism, it is preferable according to the invention to limit the thickness of each oxide layer so that the deposit does not develop, or little, this type of structure.

When the layers are of such a thickness that it is difficult to prevent the appearance of this type of columnar structure, it is advantageous according to the invention to divide the layer so as to reduce the thickness of each at the level where such structure does not manifest itself or in a limited way. In this case, the divided layers are separated by an intermediate layer of another material, which is advantageously of the type indicated below to protect the UV filtering layers.

The hydrated alkali silicates constituting the intumescent layers are relatively aggressive. These are highly basic products. Direct contact of the anti-UV layer with the intumescent material may cause alteration of the layer. It is preferable according to the invention to protect the layer by interposing a perfectly inert barrier vis-à- silicate screw.

Advantageously, the protection of the layer based on zinc oxide is obtained by interposition of a thin layer resistant to pH greater than 11 and having a visible light transmission of at least 80%. Thin layers of this type are for example based on tin oxide, oxide, nitride or aluminum oxy-nitride, titanium or zirconium. This protective layer is of limited thickness which is strictly necessary for the protective role of the UV filter layer. Ordinarily, this layer has no thickness less than 10 nm and, as far as possible, this thickness remains less than 70 nm, and preferably less than 50 nm, to minimize its influence on the light transmission.

The protective layer is optionally a layer of an organic polymer resistant to the indicated alkaline conditions and sufficiently transparent. They are, for example, polyurethane films, polyethylene glycol terephthalate (PET), AAE, or silicone layer.

The organic layers are substantially thicker than the mineral layers indicated above. Typically their thickness is between 5 and 70 μ, and most often between 10 and 30 μ.

The corrosive nature of the intumescent layer varies according to its composition. It is even more marked that the water content is higher. It also varies according to the additives contained in the layer and which can influence its more or less caustic nature. This is the case for example strongly basic additives, especially urea. As a result, the protective barrier of the UV-resistant layer may also be more or less important to adapt to the nature of the silicate used to form the intumescent layer.

The introduction of an anti-UV filter is justified only in those uses in which the layer of silicates is effectively subjected to radiation that may alter the transparency of the glazing. In this sense, if only one side of the glazing is exposed to such radiation, the UV filter may be limited to the side corresponding to the incidence of this radiation. In the opposite hypothesis, namely where the UV radiation can come indifferently on one side or the other of the glazing, it will be necessary to have a UV filter on each side of the intumescent layer.

In glazings comprising a plurality of glass sheets and intumescent layers, it goes without saying that the protection of the layers must be performed on the faces exposed first UV. For layers or faces located deeper in the glazing, they automatically benefit from the protection of previous layers.

The fireproof glazing as described above can also be assembled in the form of double glazing. As before, it suffices to guarantee the optical properties that the incident radiation is filtered before reaching the intumescent layer. If the first sheet of the double glazing is not of the fire-resistant type, it may be advantageous to deposit the filtering layer thereon so that it is not in contact with the alkali silicates, it does not require the presence a protective layer.

The invention is described in more detail with reference to the drawings in which:

- Figure 1 is a schematic sectional view showing a basic structure of an anti-fire glazing;

FIG. 2, similar to the previous one, shows a fireproof glazing according to the invention, whose intumescent layer is protected against UV damage;

FIG. 3, similar to FIG. 2, is an embodiment in which the UV filter is isolated from the intumescent layer;

FIG. 4 shows another embodiment of the invention comprising an anti-UV assembly on each side of the intumescent layer;

FIG. 5 shows an embodiment according to the invention in which a glass sheet is replaced by a laminated assembly;

FIG. 6 illustrates the implementation of an anti-fire glazing unit in a double glazing structure;

FIG. 7 is a graph showing transmission variations different glazings depending on the wavelength considered;

FIG. 8 shows the incidence of the thickness of an anti-UV layer based on zinc oxide;

FIG. 9 illustrates the influence of the thickness of the glass sheet for two identical anti-UV layers;

FIG. 10 shows the transmission variation for an anti-UV layer based on zinc oxide protected by a tin oxide layer.

The type of glazing concerned by the invention is shown in section in FIG. 1. The fireproof glazing in its most basic configuration comprises two sheets of glass (1 and 2) joined together by means of a sheet of intumescent material. (3) consisting of hydrated alkali silicate.

The glass sheets are either of conventional "float" glass or, where appropriate, of low borosilicate type thermal expansion glass.

The structures of commercial fire-resistant glazing can assemble several sheets of intumescent materials and a corresponding number of glass sheets. Similarly, the thickness of the glass sheets and that of the or sheets of intumescent material, vary depending on the production methods and applications envisaged. The thicker structures, and those consisting of multiple sheets of glass and intumescent material normally leading to the most fire resistant glazing.

Whatever the chosen structure, the question of transparency, and more specifically of the absence of appearance of bubbles or veil over time, remains attached to the presence of these sheets of intumescent material exposed to UV rays. To a certain extent, the greater the total thickness of the intumescent material, the more the defects related to aging alter the transparency of the glazing, and therefore it is necessary to ensure that the appearance of these defects is avoided.

In the form presented the glass sheets are "Simple". In some embodiments, one or more "monolithic" glass sheets may be replaced by one or more laminated sheets consisting for example of two glass sheets joined by means of a polyvinyl butyral (PVB), vinyl acetate-type thermoplastic interlayer sheet. ethylene (EVA) etc. The use of sheets of this type is generally intended to improve the mechanical properties of the glazing. The properties of the constituent materials of these spacers, however, have a number of disadvantages when they are subjected to the test of fire, especially because they lead to a release of fumes from their decomposition. When they are present in a glazing, efforts are made to arrange them so that these disadvantages are minimized. In particular, they are preferably placed on the side of the windows least likely to be exposed to fire or, in more complex structures with more than two glass sheets, they are located possibly in the center of these structures.

As indicated above, the PVB sheets incidentally constitute a very powerful filter against UV rays. The systematic use of these sheets as a protection against the degradation of the intumescent layers is, however, not generally desirable because of the difficulties mentioned above with respect to the fire resistance of these materials, also because of their As a result of an increase in the total thickness of the glazing, because of their cost, the PVB sheets constitute an important element of the cost of the whole.

The intumescent materials in question are of various natures. Their composition based on hydrated alkali silicates is distinguished, in particular by the nature of the silicates used. The most common are sodium silicates, but potassium silicates are also often used optionally mixed with sodium silicates. The choice of one or other of these alkalis also influences the proportions of the other constituents and in particular the water content.

Intumescent materials are further characterized by the relative proportions of Si and alkali present in the composition. This report defines what is usually presented as reflecting the more or less "refractory" nature of these materials. Another significant feature of these materials is their water content, which is sometimes presented indirectly by the "loss on fire" of the product, designating the percentage by weight of what is removed when the material is calcined. The water present in the intumescent material, releasing under the effect of heat, is responsible for the formation of the foam on which the fire-resistant quality depends.

Other constituents participate in the composition of these materials. These are various elements that either contribute to the improvement of the fireproof properties, or contribute to the stability of the product over time, or facilitate the production of these glazings. Among the most commonly used elements include polyol compounds and in particular glycerine which promotes in particular a certain plasticity of the intumescent material.

The nature and properties of the materials in question are the subject of many previous publications. As an indication, reference may in particular be made to patent publications: EP 1 027 404, FR 2 607 491 and FR 2 399 513.

In a first step, the inventors have sought exposure conditions liable to lead to the appearance of defects when the glazing is subjected to aging under accelerated conditions. They were able to determine the characteristics of the radiation responsible for the formation of these defects. For this, they submitted identical glazing samples to the same radiation but by filtering this radiation by means of known filters making it possible to eliminate wavelengths below specific values.

For these tests, the glazing consists of two sheets of ordinary clear glass 2.85 mm thick, joined by means of a layer of sodium silicate hydrated 1 mm thick. The glass is of traditional silico-soda-lime type. Its light transmission at a thickness of 4mm is 90%. The UV transmission for the same thickness is 57%. The sodium silicate layer has an SiO ₂ / alkali oxide ratio of 3.3. The water content is 20% by weight, and the glycerin content is of the order of 5% by weight of the layer.

Thus in the experiment it appeared that wavelengths greater than 345 nm practically did not lead to the appearance of any defects, in particular bubbles after exposure equivalent to 10 years under natural conditions of use. The same aging test has been reproduced with constituent elements of the fireproof glazing itself. In particular it has been verified that a glazing unit comprising a laminated assembly consisting of two 1.6 mm thick glass sheets, joined by a 0.38 mm PVB sheet, was effectively protected against harmful radiation to the longevity of the product. . In this configuration after the 1000 hours of test corresponding to the 10 years of natural aging, the product was not substantially altered by the appearance of bubbles or "haze" when the irradiation was performed on the side comprising the PVB.

Figure 2 illustrates the principle of the invention. In the structure presented in addition to the two sheets of glass (1, 2) and the intumescent layer (3) of FIG. 1, a layer (4) acting as a UV filter is arranged on the sheet (1) on the side exposed to UV radiation, so that the intumescent layer is downstream in the path of the radiation.

FIG. 3, which is analogous to the previous one, additionally comprises a layer or coating 5, the function of which is to avoid the contact of the UV filter and the intumescent layer, when their characteristics make the silicate of the intumescent layer likely to Corrode the UV filter.

FIG. 4 shows a glazing unit comprising an anti-UV filter and its protective layer on each side of the intumescent layer. The presence of two anti-UV layers is made necessary when both sides of the glazing can be exposed to UV.

FIG. 5 shows a glazing unit comprising a laminated assembly formed of two glass sheets (1, 1 ') and a PVB type interlayer (6). The other glass sheet (2) is simple. The presence of the PVB sheet which constitutes a powerful UV filter makes it superfluous to provide an additional filter on the laminate side. Conversely, the opposite face which does not include a laminate must be subject to specific UV protection by means of the layers (4,5) if it is exposed to UV.

FIG. 6 illustrates an embodiment of a double glazing unit comprising an anti-fire element (1, 2, 3) of the type shown in FIG. 1. The glass sheet 7 associated with the fireproof element is separated from the latter by a spacing (8) ordinarily confined and isolated from the surrounding atmosphere. In the case where the incident radiation first encounters the sheet (7), it is advantageous to arrange the anti-UV filter on the inner face of this sheet. first sheet. This prevents contact with the silicate and the need to protect the filter against the corrosive effect of the silicate. The filter layer can also, of course, be located on the outer face of this first sheet, provided that it resists claws and external aggression. It can finally be located on the face of the fireproof element exposed first to UV radiation. The implementation is nevertheless more delicate because of the increased risks of alterations, especially mechanical alterations that accompany the formation of this fireproof element. Conversely, the production, storage and implementation of a single sheet carrying an anti-UV layer such as those proposed according to the invention correspond to common operations, well controlled.

The combinations indicated above are only some of the possibilities offered to constitute fire-resistant glazings according to the invention which can cover multiple variants. In particular, the fireproof glazings presented have only an intumescent layer. The invention covers, of course, glazings comprising several layers of this type.

The determination of the light transmission for different configurations of the prior art is the subject of FIG. 7. On the graph, the light transmission is plotted as a function of the wavelength.

In this graph, the curve I is that corresponding to a clear "float" glass sheet only, 2.85 mm thick. It is found that wavelengths below 345 nm are widely transmitted. Total elimination is progressively achieved only for wavelengths below about 310 nm. A significant part of the UV rays responsible for the alteration of the intumescent layer is therefore transmitted to it. In practice this leads to the appearance of troublesome defects, after only the equivalent of one year of exposure under natural conditions.

Curve II is given as an indication of the influence of the glass itself on the transmission at various wavelengths. In this case, the clear glass sheet has a thickness of 4.85 mm.

Overall the profile of the transmission curve is similar to the previous one with a shift towards slightly longer wavelengths. The complete disappearance of the transmission starts at about 320 nm. The maximum transmission for both low wavelengths as well as for the visible is lowered. However, it is found that the fraction transmitted, whose wavelength is less than 345 nm, remains very significant. Increasing the thickness of the glass sheet protecting the intumescent layer does not adequately protect it against aging-related deterioration. As previously after a year of exposure to natural conditions, the layer has bubbles in undesirable amount.

Curve III is obtained by using for "filter" a laminate consisting of two glass sheets each 1.6 mm thick, and a PVB interlayer 0.38 mm thick. The laminated assembly, unlike the previous cases, is a particularly effective filter for all wavelengths less than about 380 nm. This explains the very good behavior of the intumescent layer protected by the presence of the PVB sheet. After a year of natural exposure virtually no change is detectable for the optical properties of the intumescent layer and glazing with this layer.

Curve IV corresponds to the transmission of a sheet of glass of the same type as that which is the subject of curve I, but this time a layer of titanium oxide of 100 nm thickness is added over the entire surface of the leaf, as previously proposed. It can be seen that the presence of the titanium oxide layer substantially modifies the transmission spectrum. However, in wavelengths below 345 nm, the proportion of transmitted UV remains significant. At 345 nm it is still around 30%. The filter is insufficient for intumescent layers sensitive to UV. In addition, the TL in the visible wavelengths is strongly affected by this titanium oxide layer: the curve I corresponds to a TL of 90% whereas this value drops to 68% for the curve IV.

Figure 8 shows the transmission spectra of 6 mm thick glass sheets coated with zinc oxide layers.

The layers are deposited by magnetron sputtering conventionally from a Zn cathode by reactive deposition in an oxygen-rich atmosphere (80%).

Three thicknesses of layers are tested to determine the influence of this thickness on the transmission. The thicknesses are respectively 50 (V), 100 (VI) and 150 nm (VII). The presence of the layers slightly modifies the overall light transmission in the visible. The graph does not make it possible to account for this small variation, the contribution to this transmission being essentially between 400 and 800 nm. In total the presence of the layer reduces this transmission by about 1 to 2%.

With these layers of zinc oxide it is found that below about 360 nm, the transmission falls to sufficiently low levels that the intumescent material is suitably protected by this filter, for all the thicknesses tested. UV transmissions below the 345 nm threshold show decay as the thickness increases. The influence of the thickness diminishes beyond 100 nm. An increase no longer significantly modifies UV transmission. The increase in thickness results in a reduction of the transmission in the visible. For this reason, if it is desirable to have a thickness sufficient to reduce UV transmission to levels that effectively protect the intumescent layers, it is preferable not to increase the thickness too much to substantially reduce transmission. light.

As a comparison of the different structures, it is convenient to measure their UV transmission rate at 345 nm. For previous structures, the transmission values are:

clear glass 2.85 mm 75%

clear glass 4.85 mm 65%

laminated with PVB -0%

2.85mm clear glass and ZnO layer 170 nm 2%

The role of the glass thickness, which appears to be significant, is in fact relatively moderate when a layer is introduced effectively blocking the transmission of UV. FIG. 9 shows the spectrum obtained for the same layer of zinc oxide 170 nm thick, respectively on a glass sheet 2.85 mm thick (VIII), and on a sheet of 5.85 mm (IX). It can be seen in the wavelengths less than 370 nm that the curves are practically merged.

To protect the UV filter layer when it can be sensitive to contact with the intumescent layer of silicate, interposed for example a complementary protective layer. FIG. 10 illustrates the transmission spectrum of a 2.85 mm thick glass sheet coated with a 150 nm thick zinc oxide layer (X), and that corresponding to the analogous sample to the above, and wherein the zinc oxide layer is covered with a protective layer of tin oxide 50 nm thick.

It can be seen from this graph that UV behavior is essentially the same in both cases. The presence of the protective layer slightly reduces the transmission in the visible wavelengths. For this reason the protective layer is advantageously as small as possible while ensuring sufficient protection of the zinc oxide layer.

Claims

1. Fire-resistant glazing comprising at least one intumescent layer based on hydrated alkali silicate comprised between glass sheets, at least one of which is coated with a thin layer filtering the ultraviolet rays to which the glazing is exposed, the ultraviolet filtering layer not transmitting more than 35%, wavelengths equal to or less than 345nm.

2. Glazing according to claim 1 wherein the ultraviolet filter layer transmits no more than 25%, rays of wavelengths equal to and less than 345 nm.

3. Glazing according to one of the preceding claims wherein the ultraviolet filter layer has a light transmission of not less than 70%.

4. Glazing according to one of the preceding claims wherein the transmission of UV due to the filter layer but also the other elements upstream of the intumescent layer in the path of the radiation, including glass sheets, this transmission does not is not more than 20% of incident UV wavelengths greater than 345 nm when they reach the intumescent layer.

5. Glazing according to one of the preceding claims wherein the transmission of UV due to the filter layer but also the other elements upstream of the intumescent layer in the path of the radiation, and in particular glass sheets, this transmission n ' is not more than 10% of incident UV wavelengths greater than 345 nm when they reach the intumescent layer.

6. Glazing according to one of the preceding claims wherein the ultraviolet filter layer is based on one of the constituents of the group comprising: zinc oxide or a zinc-based alloy, mixed oxides of tin and zinc, cerium oxide.

7. Glazing according to claim 6 wherein the UV filter layer has a thickness of not less than 50 nm.

8. Glazing according to claim 6 or claim 7 wherein the UV filter layer has a thickness of not greater than 300 nm.

9. Glazing according to one of the preceding claims wherein the anti-UV filter is constituted by zinc oxide.

10. Glazing according to one of the preceding claims wherein the anti-UV layer is disposed between two sheets of glass enclosing an intumescent layer.

11. Glazing according to claim 10 wherein the anti-UV layer is separated from the intumescent layer by interposing an inert layer with hydrated alkali silicates.

12. Glazing according to claim 11 wherein the hydrated alkali silicate inert layer is a tin oxide layer, a layer of oxide, nitride or oxynitride aluminum, titanium or zirconium.

13. Glazing according to claim 11 wherein the hydrated alkali silicate inert layer has a thickness of not more than 50 nm.

14. Glazing according to claim 10 wherein the hydrated alkali silicate inert layer is an organic layer of the epoxy resin type, polyurethane, polyethylene glycol terephthalate (PET), AAE or silicones.

15. Glazing according to claim 13 wherein the hydrated alkali silicate inert layer has a thickness of not more than 50 μ.

16. Glazing according to one of the preceding claims constituting a double glazing, one of the elements thereof consisting of at least two sheets of glass and an intumescent layer of hydrated alkali silicate, the other element having a thin layer filtering the ultraviolet rays to which the glazing is exposed, the ultraviolet filter layer transmitting not more than 35%, wavelengths equal to and less than 345 nm.

17. Glazing according to one of the preceding claims constituting a double glazing, one of the elements thereof consisting of at least two sheets of glass and an intumescent layer of hydrated alkali silicate, the other element having a layer thin film filtering the ultraviolet radiation to which the glazing is exposed, the ultraviolet filter layer transmitting no more than 25%, wavelengths equal to and less than 345 nm.