TECHNICAL FIELD

[0001] The present invention is in the general field of multiple glazing units and more

5 particularly the field multiple glazing units providing protection against vandalism and burglary attempts. It relates to a multiple glazing unit with a reduced overall glass weight over traditional multiple glazing units and guaranteeing resistance to impacts including vandalism or burglary attempts while maintaining mechanical performances of the whole glazing unit. The present invention further relates to a window comprising said multiple glazing unit and0 to the use of such a window to satisfy sound protection performances.

BACKGROUND OF THE INVENTION

[0002] Windows are typically composed by one or more glazed structure coupled to a fixed frame mounted in an opening of an enclosure such as a wall or similar. The glazed structure comprises at least one glazing unit. The glazing unit may be a single glazing unit or a multiple glazing unit. Single glazing units consist of a monolithic glass sheet while multiple glazing units conventionally consist of at least two glass panes, separated by a gap, also designated as cavity, containing a gas, often an insulating gas. The glazing unit can be a framed glazing unit or a frameless glazing unit.

[0003] Nowadays, the multiple glazing units are widely used for their functional performances0 such as thermal insulation, sound protection, interactive performances or a combination thereof, and must meet security and/or safety requirements. In particular, in terms of security performances, more and more efforts are being made to increase their resistance to impacts. In this sense, the multiple glazing unit that is used in building constructions must offer all guarantees against the risks associated to impacts including vandalism or burglary attempts5 from the outer environment.

[0004] In order to ensure security performance, it is known to use multiple glazing units designed with at least a laminated glass pane facing the outer environment. Traditionally, the laminated glass pane comprises two monolithic glass sheets of similar thickness bounded by a polymer interlayer resulting in a symmetric laminate configuration. For multiple glazing units comprising three glass panes, the laminated glass pane is typically facing the outer environment to achieve security performances and its overall glass thickness is designed to

5 achieve required mechanical performances for a given surface area of glazing. By mechanical performances, it is understood resistance to external loads, i.e. wind load, and to climatic loads such as thermal and pressure loads. Because the laminated glass pane is the thickest glass pane of the unit, climatic loads are transferred to the thinner glass panes of the multiple glazing unit, i.e. the inner glass pane of the triple glazing unit and the glass pane facing the0 inner environment. Therefore, the inner glass pane and the glass pane facing the inner environment are typically dimensioned with significant thicknesses to overcome the deformations caused by said transferred climatic loads. The security performances resulting from this multiple glazing unit design are thus guaranteed from the outer environment in terms of resistance to impacts and allows maintaining mechanical performances of the whole glazing unit. However, such a security multiple glazing unit design has the disadvantage to lead to a significant overall glass thickness resulting in a significant overall glass weight. Furthermore, this multiple glazing unit with significant overall glass weight is not easy to handle and their use in building structures as well in new construction and renovation of existing windows is not facilitated. 0 [0005] A multiple glazing unit is for example disclosed in EP231 8206 describing a triple glazing unit having a laminated glass panel facing the inner environment and intended to increase safety performances. Safety performances ensure people protection from defenestration and from broken glass. The laminated glass panel is designed to achieve a glass thickness similar to the one of a monolithic glass sheet. However, EP231 8206 does not5 consider the overall glass weight of the multiple glazing unit and does not specifically consider the security performances.

[0006] A double glazing unit is disclosed in W020201 5241 6 comprising a specific laminated glass pane having a reduced thickness of glass to reduce its glass weight. The security performance is guaranteed thanks to the polymer interlayer of the laminated glass pane which is specifically designed in terms of surface weight. This document does also not consider the overall glass weight of the multiple glazing unit and does not consider the mechanical performances of the multiple glazing.

[0007] So, none of the arts addresses the technical problem of configuring a multiple glazing

5 unit having at least three glass panes intended to provide anti-vandalism and anti-burglary performances with a reduced overall glass weight over a traditional security multiple glazing unit having similar dimensions and similar mechanical performances and while maintaining mechanical performances of the whole glazing unit.

SUMMARY OF THE INVENTION

[0008] Against this background, the present invention provides a multiple glazing unit according to claim 1 bringing at least partly a solution to the above mentioned disadvantages . The invention also provides a window according to claims 1 2 or 1 3 comprising the multiple glazing unit, and the use of the window comprising the multiple glazing unit for acoustic performances according to claim 14. 5 [0009] Preferred embodiments are defined in the dependent claims.

[0010] It is noted that the invention relates to all possible combinations of features recited in the claims or in the described embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 : shows a cross-sectional view of a multiple glazing unit according to one0 embodiment of the present invention wherein the inner glass pane is a laminated glass pane and the first and the second outermost glass panes are monolithic glass sheets.

Figure 2 : shows a cross-sectional view of a multiple glazing unit according to another embodiment of the present invention wherein the multiple glazing unit comprises a first functional and a second functional coating deposited on the outermost glass panes. 5 Figure 3 : shows a cross-sectional view of a multiple glazing unit according to yet another embodiment of the present invention wherein the multiple glazing unit comprises a first functional coating and a second functional coating deposited on the inner glass pane. Figure 4a: shows a cross-sectional view of a multiple glazing unit according to yet another embodiment of the present invention wherein the inner glass pane is a laminated glass pane comprising a first and second monolithic glass sheets, a first and second polymer interlayers and a polymer sheet.

5 Figure 4b: shows an enlargement of a portion of the inner glass pane of Figure 4a.

DETAILED DESCRIPTION OF THE INVENTION

[0011] The object of the present invention is a multiple glazing unit comprising:

(a) a first outermost glass pane facing an outer environment and having a thickness Z1 ,and

(b) a second outermost glass pane facing an inner environment and having a thickness, Z2,0 and

(c) an inner glass pane located between the first and second outermost glass panes wherein the three glass panes

• are held apart by a first and a second peripheral spacers positioned between each of the outermost glass panes and the inner glass pane,

• are separated by a first gap defined within the first outermost glass pane, the inner glass pane and the first peripheral spacer, and a second gap defined within the second outermost glass pane, the inner glass pane and the second peripheral spacer, wherein the first and the second outermost glass panes are monolithic glass sheets, and 0 the inner glass pane is a laminated glass pane comprising

• a first monolithic glass sheet having a thickness Z31 , a second monolithic glass sheet having a thickness Z32, the first and second monolithic glass sheets having a total thickness, Tglal , equal to the sum of Z31 and Z32,

• a first polymer interlayer having a thickness Z41 and positioned between the first (1031 )5 and second glass sheets, and wherein

• at least one of the thickness Z31 and the thickness Z32 is at least 3 mm and preferably is at least 4 mm, and • the total thickness, Tglal , is at most twice the thickness Z1 of the first outermost glass pane and at most twice the thickness Z2 of the second outermost glass pane.

[0012] The multiple glazing unit according to the invention is a multiple glazing unit comprising at least three glass panes, two outermost glass panes and an inner glass pane, the

5 inner glass pane being a laminated glass pane.

[0013] Within the present invention, the term “a" means one or more.

[0014] The expression glass pane is understood in the present invention to mean a monolithic sheet of glass or a laminated glass pane which is an assembly of monolithic glass sheets and polymer interlayers, especially two glass sheets, joined together by one polymer interlayer. 0 [0015] By first outermost glass pane is meant the glass pane of the multiple glazing unit facing an outer environment.

[0016] By second outermost glass pane is meant the glass pane of the multiple glazing unit facing an inner environment.

[0017] Outer and inner environments herein mean respectively the environment outside of the concerned room or space and inside of the concerned room or space. The outer environment typically refers to the exterior of a building.

[0018] The inner glass pane is an internal glass pane of the multiple glazing unit located between the first and second outermost glass panes.

[0019] The first and the second outermost glass panes are monolithic glass sheets while the0 inner glass pane is a laminated glass pane. The term monolithic glass sheet denotes a single sheet of glass and the term laminated glass pane denotes an assembly comprising a first monolithic glass sheet and a second monolithic glass sheet between which a first polymer interlayer is laminated.

[0020] The three glass panes, i.e. the two outermost and the inner glass panes, are held apart5 by a first and a second peripheral spacers positioned between each of the outermost glass panes and the inner glass pane. In other words, the first outermost glass pane is held apart from the inner glass pane by a first peripheral spacer and the inner glass pane is held apart from the second outermost glass pane by a second peripheral spacer. It follows that the three glass panes are separated by a first and a second gap. The first gap is defined within the first outermost glass pane, the inner glass pane and the first peripheral spacer, and the second gap is defined within the second outermost glass pane, the inner glass pane and the second

5 peripheral spacer.

[0021] In the present invention, the outermost glass panes, which are monolithic glass sheets, have a thickness Z1 and Z2, respectively. The first and second monolithic glass sheets of the inner glass pane have a thickness Z31 and Z32 respectively, so that the total thickness of the monolithic glass sheets of the inner glass pane is equal to the sum of Z31 and Z32 and is0 referred to as Tglal . The first polymer interlayer of the inner glass pane has a thickness Z41 .

[0022] Throughout the description, it shall be noted that the numeric values given for monolithic glass sheets thicknesses are considered with a +/- 5% degree of uncertainty corresponding typically to the tolerance on the thicknesses obtained on the production lines.

[0023] In the present invention at least one of the first and second monolithic glass sheet of the inner glass pane has a thickness of at least 3 mm, preferably at least 4 mm. In other words, at least one of Z31 and Z32 is equal to at least 3 mm and preferably to at least 4 mm.

[0024] In the present invention, the total thickness, Tglal , is at most twice the thickness Z1 and is at most twice the thickness Z2. In other words, the total thickness, Tglal is at the same time lower or equal to twice the thickness Z1 of the first outermost glass pane and lower or0 equal to twice the thickness Z2 of the second outermost glass pane (Tglal <2*Z1 and Tglal <2*Z2).

[0025] As it will be detailed, the present invention goes against the general practices established in the field of multiple glazing units providing protection against vandalism and burglary attempts. A conventional triple glazing unit providing anti-vandalism and anti¬5 burglary protection typically comprises at least a first outermost glass pane that is a laminated glass pane complying with anti-vandalism and anti-burglary according to standard EN356. This laminated glass pane comprises two monolithic glass sheets of similar thickness bounded by a polymer interlayer. Furthermore, to guarantee the required mechanical performances of the whole glazing unit, the second outermost glass pane and inner glass pane have typically a significant thickness to overcome the deformations caused by said transferred climatic loads. By mechanical performances, it is understood resistance to external loads, i.e. wind load, and to climatic loads such as thermal and pressure loads.

5 [0026] In the present invention, the design of the inner glass pane allows to provide antivandalism and anti-burglary protection according to EN356 and to maintain mechanical performances together with an overall glass weight reduction of the multiple glazing unit in comparison to a conventional triple glazing unit as described above and having similar dimensions and similar mechanical performances. By overall glass weight is meant the sum of0 the weight of each of the monolithic glass sheets of the multiple glazing unit.

[0027] The presence of at least one monolithic glass sheet with a thickness of at least 3 mm in the inner glass pane participates to anti-vandalism and anti-burglary performance.

[0028] The inner position of the laminated glass pane leads to a more homogeneous repartition of the climatic loads in the glazing unit and advantageously allows for an overall glass thickness reduction and hence an overall glass weight reduction.

[0029] Reduction of the overall glass weight of the multiple glazing unit leads to reduction of costs thanks to material savings and to a more cost-effective production process, which leads to reduction of carbon footprint. The multiple glazing unit with reduced overall glass weight is more appropriate for handling. Reduction of the overall glass thickness further leads to0 better transparency of the multiple glazing unit as required by the market.

[0030] These and other advantages are described in more details in the following sections.

Outermost glass panes

[0031] The first and the second outermost glass panes in the invention are monolithic glass sheets. The term “glass” is herein understood to mean any type of mineral or organic glass. 5 The mineral glasses used may be one or more known types of glass such as soda-lime-silica, aluminosilicate or borosilicate, crystalline and polycrystalline glasses. The mineral monolithic glass sheets can be obtained by a floating process, a drawing process, a rolling process or any other process known for manufacturing a glass sheet starting from a molten glass composition. Some non-exhaustive examples of organic glasses comprise polycarbonate and poly(methyl methacrylate).

[0032] Preferably, the outermost glass panes according to the invention are mineral monolithic glass sheets, more preferably made of soda-lime-silica glass, aluminosilicate glass

5 or borosilicate glass, most preferably made of soda-lime-silica glass. Monolithic glass sheets can be made of float clear, extra-clear or coloured glass. In particular and for aesthetic purposes, the first and second outermost glass panes can be a decorative monolithic glass sheets such as a painted or enamelled or etched or sand-blasted glass sheets or a combination thereof. 0 [0033] Each of the first and the second outermost glass pane has preferably a thickness, Z1 , Z2, of at least 3 mm, preferably at least 4 mm, and more preferably at least 5 mm. The thicknesses Z1 and Z2 can be the same or different. The thicknesses have to be adjusted as known by the skilled person, for instance they need to be increased with increasing glazing surface areas, S, to sustain external loads.

Peripheral spacers

[0034] The peripheral spacers can either be independent elements or they can be linked together by a linking element to form a peripheral element. In this peripheral element, the first and second peripheral spacers protrude out of the linking element towards the first and second gaps of the glazing unit, respectively. The peripheral element is typically U-shaped0 wherein the groove of the “U” aims at receiving the inner glass pane.

[0035] The peripheral spacers have a surrounding shape which spaces apart the glass panes on their periphery. Typically, the peripheral spacers are hold between the glass panes by means of butyl strips or silicone. The peripheral spacers can be solid or hollow. Hollow peripheral spacers are able to receive drying materials also designated as a desiccant. 5 [0036] The peripheral spacers are made of any material known by the skilled person such as metal, polymer, a composite material reinforced by glass fibers or a mix of several of these materials. Use of warm-edge peripheral spacers, often made of plastics reinforced with a metallic foil, are preferred to reduce thermal fluxes at the periphery of the glass panes. [0037] The peripheral spacers have typically a thickness ranging from 4 to 32 mm. In standard glazing units, the thickness ranges from 9 to 1 8 mm. The first and a second peripheral spacers of the multiple glazing unit may have the same thickness or different thicknesses. They have preferably the same thickness which advantageously limits climatic constraints towards the

5 inner glass pane. The peripheral spacers thickness may be adapted for specific multiple glazing units. For instance, devices may be placed inside of at least one of the gaps, the thickness of the corresponding peripheral spacer(s) may in this case range from 1 8 and 32 mm. Examples of such devices are for instance blinds for thermal insulation and/or light occultation, LED for light illumination, or a combination thereof. 0 [0038] The gaps of the multiple glazing unit of the invention can also be referred to as interspaces or cavities. In general, the gap is filled with an insulating gas which is generally selected from air, dry air, argon (Ar), krypton (Kr), xenon (Xe), carbon dioxide or a combination thereof. Said gases are effective for preventing heat transfer and/or may be used to reduce sound transmission.

Inner glass pane

[0039] The inner glass pane in the invention is a laminated glass pane comprising a first and a second monolithic glass sheet with a first polymer interlayer positioned in between. The laminated inner glass pane guarantees security performances, in terms of resistance to impacts including vandalism or burglary attempts. 0 [0040] The first and second monolithic glass sheets of the inner glass pane are as described supra with reference to the outermost glass panes. They are preferably made of mineral glass, more preferably made of soda-lime-silica glass, aluminosilicate glass or borosilicate glass, most preferably of soda-lime-silica glass. In particular, at least one of the monolithic glass sheet of the inner glass pane is an extra-clear glass, which advantageously limits the5 temperature increase of the inner glass pane.

[0041] The polymer interlayer to be used in the present invention typically comprises polymers known in the art of manufacturing glass laminates and are different from the polymers known as organic glass such as polycarbonate and poly(methyl methacrylate). Examples of polymers that are suitable as interlayer in a glass laminate are ethylene vinyl acetate (EVA), polyvinyl butyral (PVB), polyurethanes (PU), polyvinyl chloride (PVC), polyesters, co-polyesters, polyacetals, cyclo olefin polymers (COP), ionomers and/or an radiation activated adhesives. Radiation activated adhesives are typically obtained by polymerization of precursors bearing

5 acrylate or methacrylate functions, another class of such precursors bear cyclic epoxides. The polymerization is initiated by exposition to radiations such as UV radiations or electron beam. Such precursors may be known as radiation curable compounds. An example of commercial radiation curable compounds is the Uvekol range commercialized by Allnex. Blended materials using any compatible combination of these materials can be suitable as well. In0 particular, the polymer interlayer comprises a material selected from the group consisting of ethylene vinyl acetate, and/or polyvinyl butyral, more preferably polyvinyl butyral. In an embodiment of the present invention detailed later, polyurethane is also a preferred material of the polymer interlayer. The polymer interlayer is also designated as a “bonding interlayer” since the polymer interlayer and the glass sheet form a bond that results in adhesion between the glass sheet and the polymer interlayer. The polymer interlayer may consist of one or several polymer films, typically one or several films of PVB or EVA.

[0042] In particular, the polymer interlayer to be used in the present invention is a transparent or translucent polymer interlayer. However, for decorative applications, the polymer interlayer may be colored or patterned. 0 [0043] Typical thicknesses for the polymer interlayer is from 0.3 mm to 3.5 mm. A commercially available polymer interlayer is for instance polyvinyl butyral (PVB) of 0.38 mm, 0.76 mm, 1 .52 mm, 2.28 mm and 3.04mm. According to an embodiment of the present invention, the thickness, Z41 , of the first polymer interlayer of the inner glass pane is at least 0.3 mm, preferably at least 0.7 mm, more preferably at least 1 .5 mm. 5 [0044] To form the laminated glass pane of the multiple glazing unit of the present invention, the first polymer interlayer is preferably a polyvinyl butyral polymer interlayer. Polyvinyl butyral (or PVB) is a resin known for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. [0045] The polymer interlayer provides the following contribution to the multiple glazing unit: firstly, the polymer interlayer distributes impact forces across a greater area of the monolithic glass sheets, thus increasing the impact resistance of the glass pane. Secondly, the polymer interlayer binds the resulting shards if the monolithic glass sheet(s) is/are ultimately broken

5 and remains an obstacle to intrusion after impact. Thirdly, the polymer interlayer undergoes plastic deformation during impact and under static loads after impact, absorbing energy and reducing penetration by the impacting object as well as reducing the energy of the impact that is transmitted to impacted object.

[0046] In the present invention, the inner glass pane of the multiple glazing comprises a first0 monolithic glass sheet having a thickness Z31 and a second monolithic glass sheet having a thickness Z32 which are bonded by a first polymer interlayer having a thickness Z41 . The first and the second monolithic glass sheets have a total thickness, Tglal , equal to the sum of their thicknesses Z31 and Z32 (Tglal = Z31 +Z32). It has been found that, at least one of the thickness Z31 and the thickness Z32 of the monolithic glass sheets of the inner glass pane of at least 3 mm (Z31 >3 mm and/or Z32 >3 mm) allows to comply with standard EN356. In particular, for achieving high levels of security performances according to standard EN 356 and/or for larger surface area of the multiple glazing unit, it is preferred that at least one of the thickness Z31 and the thickness Z32 of the monolithic glass sheets of the inner glass pane of the multiple glazing unit is at least 4 mm (Z31 >4 mm and/or Z32 >4 mm). 0 [0047] In the present invention, Tglal is at most twice the thickness of each of the outermost glass panes (Tglal < 2*Z1 and Tglal < 2*Z2).

[0048] The inner glass pane is the glass pane of the multiple glazing unit which is generally subjected to the least climatic loads. By choosing to laminate this inner glass pane, it allows the production of a thinner laminated glass pane in comparison to a conventional triple glazing5 unit of similar dimensions and mechanical performances providing anti-vandalism and antiburglary protection which typically comprises a laminated glass pane as first outermost glass pane. In addition, this inner position of the laminated glass pane leads to a more homogeneous repartition of the climatic loads in the glazing unit and advantageously allows for an overall glass thickness reduction and hence an overall glass weight reduction. Consequently, the multiple glazing unit having a Tglal which is at most twice the thickness of each of the outermost glass panes allows to achieve security performances with reduced overall glass thickness and then reduced overall glass weight while maintaining the mechanical performances required to sustain external loads.

5 [0049] For further reduction of glass thickness, it is further advantageous that the total thickness, Tglal , sum of the first and second monolithic glass sheets thickness of the inner glass pane (Tglal = Z31 +Z32) is lower than twice the thickness of each of the outermost glass panes (Tglal < 2*Z1 and Tglal < 2*Z2).

[0050] The monolithic glass sheet thickness Z31 and monolithic glass sheet thickness Z32 of0 the inner glass pane may be the same or different resulting in symmetric or asymmetric laminated glass plane configurations.

[0051] According to an embodiment of the present invention, the total thickness, Tglal is at most 1 0 mm, preferably is at most 9 mm and more preferably is at most 8 mm for achieving security performances of the multiple glazing unit with reduced overall glass thickness and 5 then reduced overall glass weight while maintaining the mechanical performances required to sustain external loads.

[0052] According to another embodiment, the total thickness, Tglal ranges from 4 mm to 10 mm, preferably ranges from 4 mm to 9 mm, more preferably ranges from 4 mm to 8 mm for achieving security performances of the multiple glazing unit with reduced overall glass0 thickness and then reduced overall glass weight while maintaining the mechanical performances required to sustain external loads.

[0053] It has been found in the present invention that the thicker the first and second outermost glass panes, the higher the overall glass weight reduction. For the sake of clarity, when thick first and second outermost glass panes are required (amongst other in case of5 large size glazing, large multiples glazing gaps, high external loads), the inner laminated glass pane can be slimmer than the laminated glass pane of a conventional triple glazing unit having similar dimensions and mechanical performances and having its laminated glass pane facing the outer environment. [0054] It has also been found that the thinner the laminated inner glass pane can be while maintaining the mechanical performances of the multiple glazing unit required to sustain external loads and climatic loads, the higher the overall glass weight reduction. A thin laminated glass pane is suitable amongst other when pressure within the gaps is balanced. In

5 such cases, the load on the inner glass pane is limited and its thickness may be low.

[0055] In a particular embodiment of the invention, the multiple glazing unit comprises a communication means between the first and second gaps. The presence of the communication means allows to reach a pressure equilibrium between the gaps and advantageously contributes to reduce the stresses on the inner glass pane. Indeed, in the absence of a0 communication means, temperature variations as well as pressure differences between the first and second gaps may lead to stresses on the internal glass pane. Thanks to the communication means, the inner glass pane is subjected to less stresses and the glass sheet thicknesses of the inner glass pane can be minimized leading to an improved reduced overall glass weight of the multiple glazing unit. 5 [0056] Non exhaustive examples of communication means between the gaps are a through hole in the inner glass pane, an edge cutting or a corner cutting in the inner glass pane and the like. In the particular case of peripheral spacers linked together by a linking element to form a peripheral element, equilibration of the pressure between the gaps of the multiple glazing unit may also be achieved. The linking element may link the peripheral spacer while0 allowing communication between the gaps.

[0057] In addition to the communication means, the stresses on the outermost glass panes can be reduced thanks to a pressure balance device between one of the gaps of the multiple glazing unit and the atmospheric pressure. Pressure balance devices are known to the skilled man. The outermost glass panes being subjected to less stresses, their thicknesses can be5 minimized leading to an improved reduced overall glass weight of the multiple glazing unit.

[0058] In a particular embodiment of the present invention, enhanced security performances may be achieved. In order to achieve enhanced security protection such as against burglary attempts in compliance with standard EN 356 and even against firearms and explosions in compliance with Standards EN 1063 and EN 1 3541 respectively, it is conventional that laminated glass panes are designed with a number of glass sheets combined with polymer sheets, often of different thicknesses, assembled with several PVB and/or polyurethane polymer interlayers. Polyurethane may typically be a thermoplastic polyurethane (TPU). Generally, such a laminated glass pane in a multiple glazing unit is facing the outer and/or

5 the inner environment.

[0059] In the particular embodiment of the invention, enhanced security performances may be achieved when the inner glass pane of the security multiple glazing unit further comprises a polymer sheet having a thickness Z33 and a second polymer interlayer having a thickness Z42. The polymer of the polymer sheet is different from the polymer of the polymer interlayer. 0 It is typically a transparent polymer known as an organic glass such as polycarbonate or poly(methyl methacrylate), preferably polycarbonate. In this embodiment, the second polymer interlayer is positioned between the first or the second monolithic glass sheet and the polymer sheet of the inner glass pane. The polymer interlayer again acts as a “bonding interlayer”.

[0060] In order to achieve an improved reduced overall glass weight combined with enhanced 5 security protection while maintaining mechanical performances of the whole glazing unit, it is advantageous that the polymer sheet has a thickness Z33 of at most 4 mm, preferably at most 3 mm, more preferably at most 2 mm. In particular and for cost reductions, it is preferred that the polymer sheet is a polycarbonate sheet having a thickness of at most 4 mm, preferably at most 3 mm, more preferably at most 2 mm. In order to be in compliance with Standard EN3560 and further EN1063 or EN 1 3541 , the first and second polymer interlayers are PVB or polyurethane (typically TPU) polymer interlayers having each a thickness of at least 0.76 mm (Z41 >0.76mm and Z42>0.76mm ).

[0061] The multiple glazing unit according to the invention can be further configured to achieve one or more additional performances such as: 5 sound protection performances, safety performances, thermal insulation performances, increased transparent see-through area, interactive performances, a couple of which will be described.

[0062] The multiple glazing unit of the invention has sound protection performances thanks to the presence of the laminated inner glass pane. It is advantageous according to a preferred

5 embodiment of the invention that the thickness Z31 of the first monolithic glass sheet of the inner glass pane is different from the thickness Z32 of the second monolithic glass sheet of the inner glass pane (Z31 Z32), which allows improving the sound protection performances.

[0063] Reinforced acoustic insulation can be provided by using a polymer interlayer with specific acoustic performance, such as specific PVBs, e.g. Saflex® acoustic PVB interlayer from0 Eastman or Trosifol® acoustic PVB layer from Kuraray.

[0064] The multiple glazing unit of the present invention can further be configured to achieve safety performances. Safety performances relate to people protection from defenestration and from broken glass pieces.

[0065] The multiple glazing unit of the invention, thanks to the presence of the laminated 5 inner glass pane provides protection from defenestration. In a particular embodiment of the invention, to provide protection from broken glass pieces, the first and/or the second outermost glass panes is a pre-stressed glass. Preferably the first and the second outermost glass panes are pre-stressed glass panes. By pre-stressed glass pane, it means a heat strengthened glass pane or a thermally toughened glass pane. 0 [0066] Heat strengthened glass is heat treated using a method of controlled heating and cooling which places each surface of the glass pane under compression or under tension. This heat treatment method delivers a glass with a bending strength greater than annealed glass but less than thermally toughened safety glass. Thermally toughened safety glass is heat treated using a method of controlled heating and cooling which puts also each surface of the5 glass pane under compression or under tension. Such stresses cause the glass pane, when impacted, to break into small granular particles instead of splintering into jagged shards. The granular particles are less likely to injure occupants or damage objects.

[0067] In particular, for further sustaining resistance to external loads combined with increasing surface area, S, when the outermost glass pane is a pre-stressed glass pane, it is preferred that such glass pane has a thickness of at least 3 mm, preferably of at least 4 mm, and more preferably of at least 5 mm.

[0068] The multiple glazing unit of the present invention can also be configured to achieve

5 thermal insulation performances.

[0069] The multiple glazing unit of the present invention is preferably highly energy efficient. For this reason, it is preferred that the multiple glazing unit has a thermal transmittance coefficient, Ug, of not more than 1 .0 W / m ² K, preferably of not more than 0.7 W / m ² K, more preferably of not more than 0.5 W / m ² K. To achieve such values, the multiple glazing unit0 of the present invention may comprise at least one functional coating on at least one of the glass panes sides, i.e. on at least one side of any of the outermost glass panes or inner glass pane. The at least first functional coating is preferably located on a glass pane side facing the first or the second gap of the multiple glazing unit.

[0070] Functional coatings are known by the skilled person and can be heat insulating with 5 low-emissivity (Low E) coatings, solar control coatings, anti-reflective coatings or a combination thereof. For the purpose of the description of the present invention, functional coatings that are able to act on solar radiation and/or long-wavelength infrared radiations are named insulating coatings. For instance, such an insulating coating, usually a metal-based insulating coating, generally comprises one or more individual layers that are deposited in a0 sequence on a glass pane. Herein, a film, for instance a dielectric film or a protective film, may comprise a single layer or a group of two or more layers, with the layers of this film fulfilling at least one common function or purpose of this film.

[0071] For better thermal insulation performances, it is advantageous that the multiple glazing unit comprises a first functional coating and a second functional coating. Each of the5 first functional coating and the second functional coating is located on a glass pane side facing the first or second gap of the multiple glazing unit, and preferably the first functional coating is located on a glass pane side facing the first gap and the second functional coating is located on a glass pane side facing the second gap.

[0072] The multiple glazing unit of the invention can be a framed glazing unit or a frameless glazing unit. By framed glazing unit is understood a glazing unit with a traditional external peripheral frame in contact with the sides of the outermost glass panes facing the outer and inner environments. By frameless glazing unit, it is meant a glazing unit with no traditional external peripheral frame in contact with the side of at least one of the outermost glass panes,

5 facing the outer and inner environments. A frameless glazing unit is typically a multiple glazing unit wherein the traditional external peripheral frame may be replaced by an inner peripheral frame encased between the outermost glass panes. Frameless glazing units are generally characterized by larger transparent see-through areas than corresponding glazing units of same dimensions provided with a traditional external frame. The see-through area of0 a glazing unit is the transparent area of the glazing.

[0073] According to an embodiment of the invention, the multiple glazing unit is a frameless multiple glazing unit.

[0074] In order to hide the peripheral spacers and enclosed inner peripheral frame, if any, the first and second outermost glass panes of the frameless multiple glazing unit comprise a peripheral region having a reduced visible light transmission. The peripheral regions have a visible light transmission, TL, at least 50% lower than the first and the second outermost glass panes, respectively, outside of their respective peripheral region, and is preferably opaque. For example, the peripheral region can be enamelled, or etched or sand-blasted to create a texture yielding a translucent peripheral region. The peripheral region can also be made0 opaque or translucent by applying a film. The peripheral region can also comprise decorative patterns. To increase the transparent see-through area of the frameless multiple glazing, the height of the peripheral region, measured from an edge toward the centre of a glazing unit is preferably comprised between 1 0 and 1 00 mm, more preferably between 1 5 and 80 mm, most preferably, between 20 and 60 mm. 5 [0075] In order to further increase the transparent see-through area, it might be advantageous that the peripheral spacers are made of a transparent material so that the height of the peripheral regions having a reduced visible light transmission can be further decreased. The transparent material of the peripheral spacers may be glass, pre-stressed glass or a transparent organic material such as poly(methyl methacrylate), polycarbonate and the like. In this case, the peripheral spacers may ideally be attached to the glass panes by transparent adhesives or seals placed between each of the glass panes and the peripheral spacers.

Window

[0076] Another object of the present invention is a window comprising at least one multiple

5 glazing unit of the invention as described in details supra. Any of the possible configurations of multiple glazing units described is suitable to be used in a window.

[0077] Windows are typically composed of a glazed structure coupled to a fixed frame mounted in an opening of a wall or similar. The fixed frame is preferably highly performant in terms of insulation performances. In particular, heat transfer coefficient, Uf, of the fixed frame0 is typically not more than 2.0 W / m ² K, preferably not more than 1 .6 W / m ² K, more preferably not more than 1 .2 W / m ² K and most preferably not more than 0.7 W / m ² K. The fixed frame can for instance be made of aluminium with thermal break element(s) for achieving insulating properties, or they can be made of an insulating material, such as wood or some polymers or fibre reinforced polymer composite materials or a combination thereof. It may happen that a cover plate is coupled to the fixed frame and covers portion of the fixed frame which is exposed to the outer environment.

[0078] Windows are not completely resistant to a forced entry. However, depending on their structure and type of used components, it is possible to determine whether they meet requirements of European standards and to determine the class/level of burglary-resistance0 with the relevant classification. The windows are classified according to EN 1627 including six classes of burglary-resistance: from RC1 to RC6 determining the extent to which a window can resist attempts to a force entry using different sets of tools and various forces. In the case of RC1 resistance class, the window characterized by mushroom-shaped elements on wing and fittings around perimeter of the window provides basic protection against impacts5 including vandalism or burglary attempts, e.g by breaking the window with force, kicking or pushing the bar. There is no specific requirement of resistance class of glazing according to European standard EN 356 but national provisioned may be followed. In the case of RC2 antiburglary protection class according to European standard EN 1627, the window must meet all the requirements of the basic protection level RC1 resistance class and needs to have increased number of fittings around perimeter of the window, handle with a key with anti-piercing sheet, additional locking points for window corners and tempered glass - the so-called safe glass. Such windows provide effective protection against burglary attempts with usage of simple

5 tools such as screwdriver, pliers, wedge. To comply with RC2 class, the glazing unit requires at least the P4A level according to European standard EN356.

[0079] The window of the present invention comprising at least one multiple glazing unit of the invention complies with RC1 resistance class according to European standard EN1627 and provides basic protection against break-in attempts. In a preferred embodiment, the window0 comprises at least one multiple glazing unit according to the invention wherein the first and the second outermost glass panes are pre-stressed glass panes and the thickness, Z41 , of the first polymer interlayer of the inner glass pane is more than 0.7 mm. Such a multiple glazing unit may reach the P4A level according to European standard EN356 by the appropriate selection of the glass panes and of polymer interlayer and the window comprising said multiple glazing unit reaches the RC2 resistance class according to European standard EN1627.

Use

[0080] The present invention further relates to the use of the window of the invention to provide a weighted sound reduction index, Rw, of at least 33 dB according to ISO 71 7-1 .0 [0081] Windows with sound protection performances are characterized by a weighted sound reduction index, Rw. The weighted sound seduction index is a number used to rate the effectiveness of a soundproofing system or material. Increasing the Rw by one translates into a reduction of approximately I db in noise level. Therefore, high Rw numbers mean better sound insulation. 5 DRAWINGS

[0082] The invention will now be further illustrated by way of drawings that are provided for illustrative purposes only and which in no way limit the scope of the invention. The drawings are schematic representations and are not drawn to scale.

[0083] Figure 1 shows a cross-sectional view of a multiple glazing unit (10) according to one embodiment of the present invention wherein the inner glass pane (103) is a laminated glass pane and the first (1 01 ) and the second (1 02) outermost glass panes are monolithic glass sheets of thicknesses Z1 and Z2, respectively. The glass panes (101 ,1 02,1 03) are held apart by a first (1 1 1 ) and a second (1 1 2) peripheral spacers and separated by a first (1 21 ) and a

5 second (122) gaps. The peripheral spacers (1 1 1 ,1 12) are hold between the glass panes by means of butyl strips or silicone. The inner glass pane (103) is composed of a first (1031 ) and a second (1032) monolithic glass sheets of thicknesses Z31 and Z32, respectively. A first polymer interlayer (1 31 ) of thickness Z41 is positioned between the first (1 031 ) and the second (1 032) monolithic glass sheets. The inner glass pane (103) guarantees security0 performances, in terms of resistance to impacts including vandalism or burglary attempts. In figure 1 , Z31 is equal to Z32 and Tglal is lower than Z1 and lower than Z2.

[0084] Figure 2 shows a cross-sectional view of a multiple glazing unit (10) according to another embodiment of the present invention. The figure represents the same elements as Figure 1 and in addition, the outermost glass panes (101 , 102) of the glazing unit bear a 5 functional coating (141 , 142) on the sides facing the intermediate gaps (121 , 122). In this configuration, the sides of the inner glass pane (1 03) does not bear functional coatings so that production costs can be reduced.

[0085] Figure 3 shows a cross-sectional view of a multiple glazing unit (10) according to another embodiment of the present invention. The figure represents the same elements as0 Figure 2 but the functional coatings (141 ,142) are deposited on the inner glass pane (1 03) and are facing the first and second gap (121 ,122) respectively. In this configuration, one of the monolithic glass sheet (1031 , 1032) of the inner glass pane is an extra-clear glass. Furthermore, the outermost glass panes do not bear insulating coatings so that other coatings can be applied, such as for example enamels, electrochromic, anti-fog or thermochromic5 coatings.

[0086] Figure 4a and 4b show respectively a cross-sectional view of a multiple glazing unit (10) according to another embodiment of the present invention and an enlargement of a portion of the inner glass pane (1 03). Figure 4a and 4b represent the same elements as in Figure 1 and in addition, the inner glass pane (1 03) comprises a polymer sheet (1033) having a thickness Z33 and a second polymer interlayer (1 32) having a thickness Z42. The second polymer interlayer (1 32) is positioned between the second monolithic glass sheet (1032) and the polymer sheet (1 033) of the inner glass pane. The polymer of the polymer sheet (1033) is different from the polymer of the polymer interlayers (1 31 ,1 32).