WO2014084725A1

WO2014084725A1 - Glass laminate, adhesive layer and vehicle comprising such a glass laminate

Info

Publication number: WO2014084725A1
Application number: PCT/NL2013/050757
Authority: WO
Inventors: Jacob WIERSEMA; Joseph Gerardus Maria VAN BUSSEL
Original assignee: Aviation Glass & Technology B.V.
Priority date: 2012-10-26
Filing date: 2013-10-28
Publication date: 2014-06-05
Also published as: NL2009706C2

Abstract

Glass laminates comprising ultra-thin, chemically hardened glass sheets are known and have the advantage of being relatively light in weight and having a high impact resistance and sound-damping properties. The invention relates to a glass laminate. The invention also relates to an adhesive layer for use in such a glass laminate according to the invention. The invention further relates to a vehicle comprising such a glass laminate.

Description

Glass laminate, adhesive layer and vehicle comprising such a glass laminate

The invention relates to a glass laminate. The invention also relates to an adhesive layer for use in such a glass laminate according to the invention. The invention further relates to a vehicle comprising such a glass laminate.

Glass laminates comprising ultra-thin, chemically hardened glass sheets are known and have the advantage of being relatively light in weight and having a high impact resistance and sound-damping properties. Because of these advantageous properties such glass laminates are applied as windows and glazing in architectural structures and vehicles, including automobiles and aircraft. An ultra-thin glass sheet is understood to mean a glass sheet with a maximum thickness of 0.7 mm. These glass sheets are light in weight and moreover relatively flexible (bendable). Incorporating such ultra-thin, relatively fragile glass sheets into a glass laminate requires a production process differing from the case where conventional, thicker glass sheets are incorporated into a glass laminate. In the known glass laminate the ultra-thin glass sheets are fixed to each other by means of a thermoplastic intermediate layer. This intermediate layer, generally manufactured from polyvinyl butyral (PVB) or thermoplastic polyurethane (TPU), plays an important part in obtaining the desired high impact resistance, wherein, in the case of an impact on a glass sheet, shattering (decomposition) of the glass sheet and the glass laminate can be counteracted. A drawback of known thermoplastic intermediate layers in the production of glass laminate with ultra-thin glass sheets is however that they are only bendable to limited extent, which impedes the bending of the glass laminate into a desired shape after forming of the glass laminate. Small cracks moreover occur in the relatively rigid intermediate layer during deformation of the known glass laminate with ultra-thin glass sheets and these have an undesirable effect on the light refraction and thereby on the transparency and aesthetic properties (distortion, consistency) of the glass laminate. The adhesion of the known intermediate layer to the glass sheets is moreover limited as a result of the required rigidity of the material with a view to the desired relatively high impact resistance.

A first object of the invention is to provide an improved glass laminate. A second object of the invention is to provide a glass laminate comprising a relatively bendable adhesive layer.

A third object of the invention is to provide a glass laminate comprising an adhesive layer with an improved adhesive capacity.

A fourth object of the invention is to provide a glass laminate comprising an adhesive layer with an improved balance between impact resistance and adhesive capacity. At least one of the above stated objectives can be achieved by providing a glass laminate, comprising: at least one ultra-thin, chemically hardened first glass sheet with a maximum thickness of 0.7 mm; and at least one adhesive layer connected to a front side of the first glass sheet and comprising at least one polymer, wherein the adhesive layer is manufactured at least partially from an ionomer, wherein the thickness of the adhesive layer is less than or equal to 0.89 mm and preferably lies between 0.5 and 0.89 mm. Ionomers are polymer materials with hydrophobic organic chains to which a small number of ionic groups is bonded. Ionomers are mainly synthesized by

copolymerization of at least one functional monomer with at least one unsaturated monomer, after which some of the functional groups of the at least one functional monomer are neutralized by a metal cation, whereby highly polar salt groups are formed in the copolymer. These highly polar salt groups combine into small clusters which act as temporary, thermoreversible cross-links at room temperature but which soften sufficiently at increased temperature to enable thermoplastic processing. Due to the presence of the thermoreversible cross-links the elasticity of the ionomer will be considerably higher than the elasticity of the known prior art thermoplastics. Research into the mechanical properties and melt processability has moreover revealed that ionomers can have relatively good mechanical properties and a relatively high melt viscosity, depending on the composition of the ionomers, whereby a high impact resistance can be guaranteed and whereby the adhesive capacity of the adhesive layer for adhesion to glass can be considerably improved. Because the glass laminate according to the invention comprises an ultra-thin first glass sheet, the glass laminate will, in addition to being relatively reliable, structurally durable and impact-resistant, also be relatively light in weight and relatively elastic, which makes it possible to use the glass laminate according to the invention both in flat geometry and single or multiple curve geometry in numerous applications, particularly in the construction industry and transport sector, particularly in transport vehicles such as in automobiles, vessels (boats and ships) and aircraft. The thickness of the glass sheet is preferably less than 0.7 mm and can have a typical thickness of 0.3; 0.4; or 0.55 mm.

The thickness of the adhesive layer amounts to no more than 0.89 mm and preferably no less than 0.5 mm. Surprisingly, and counter to expectation, research has shown that an adhesive layer comprising an ionomer and having a thickness greater than 0.89 mm results in a less favourable stress distribution between the adhesive layer and an adjacent glass sheet, this having an adverse effect on the adhesion between the adhesive layer and the glass sheet, and thereby on the stability and durability of the glass laminate as such. This is because the common principle is that the further apart the outer layers of a laminate lie, the stronger it is. Research has however shown that this principle does not apply to the glass laminate according to the invention. The (ultra- thin) glass laminate according to the invention is loaded in different ways, by pure bending load as well as by point loads in a plane (for instance an elbow knocking against the window) and by impact load. In order to make it possible to absorb or counter all these loads, research has shown that the best results are obtained with a relatively thin glass sheet (between 0.1 and 0.7 mm and particularly between 0.2 and 0.5 mm) in combination with a relatively thin ionomer intermediate layer (between 0.3 and 0.9 mm, preferably between 0.5 and 0.89 mm). Tn the case of a thicker (so stiffer) laminate an impact load is more likely to result in breaking of the first (loaded) glass layer by shattering due to excessive local pressure. When a laminate is too thin or an adhesive layer too weak, the whole laminate deforms too much and breaks. With the stated dimensioning a unique balance is found between deformability and stiffness, whereby energy is absorbed highly efficiently. The relatively thin adhesive layer provides a number of additional advantages. The optical quality of the laminate remains optimal during the laminating process because of the small thickness of the adhesive layer. The flexibility (bendability) of the laminate moreover increases considerably when an adhesive layer is applied which is smaller than or equal to 0.90 mm, preferably 0.89 mm, this being particularly advantageous when the glass laminate is applied in curve geometry, for instance in a vehicle, vessel or aircraft. This also has the significant effect that the laminate deforms to some extent under impact load, whereby the impact energy is absorbed over a greater area. The relatively stiff material layer comprising ionomer, which is applied as adhesive layer in the glass laminate, helps transfer the energy effectively to a greater surface area. The excellent adhesion of the ionomer adhesive layer helps transfer the forces occurring here to glass sheets lying opposite each other (in the case that a plurality of glass sheets are applied in the laminate). In a broader sense this effect also helps damp acoustic energy effectively. Apart from the above stated advantageous effects, a further advantage of applying a relatively thin adhesive layer is that it reduces the weight of the glass laminate, this being particularly advantageous when the glass laminate is applied in a vehicle, vessel or aircraft. In order to make it possible to guarantee continued sufficient adhesion and stability it is nevertheless advantageous for the thickness of the adhesive layer to be greater than or equal to 0.3 mm, preferably greater than or equal to 0.5 mm.

Several advantageous embodiments of the glass laminate according to the invention will be described hereinbelow by way of illustration. Use is made in some embodiments of several inventive concepts. It is possible to envisage individual inventive concepts and technical measures being applied without all details of a determined embodiment also being applied therein.

It will be apparent that diverse modifications to the embodiments described below can be envisaged by a skilled person, wherein a skilled person can combine different inventive concepts and/or technical measures of different embodiments without departing from the inventive concept described in the appended claims.

The ionomer preferably comprises a copolymer of ethylene and a carboxylic acid chosen from the group consisting of: ν,Ξ-unsaturated carboxylic acids with 3-8 carbon atoms, wherein some of the acid groups are neutralized with at least one metal ion. It is particularly advantageous here for zinc ions to be used for neutralizing some of the acid groups of the at least one applied carboxylic acid. Research has shown that ionomers are to a certain extent of hydrophilic nature. However, the quantity of absorbed water is greatly dependent on the type of counter-ion. Compared to alkaline-earth or zinc ionomers, the alkali-neutralized ionomers absorb the most water. The zinc-based ionomers absorb the least water and are therefore generally recommended. An ionomer with an advantageous action is a semi-crystalline thermoplastic based on a random copolymer of ethylene and methacrylic acid which is partially neutralized to form a zinc or sodium salt.

An increase in the degree of neutralization of the ionomer results in an increase in the melt viscosity, tensile strength, hardness, impact resistance, and a decrease in the elongation at break and a decrease in the adhesive capacity of the ionomer. It is therefore important to find a balance in the degree of neutralization which on the one hand has to be sufficiently high to impart sufficient impact resistance and elasticity to the ionomer and which on the other is sufficiently low to guarantee a good adhesion and processability of the ionomer. This balance can be found when 15-45%, in particular 20-35%, of the acid groups are neutralized with at least one metal ion. A degree of neutralization greater than 45% makes the ionomer difficult to process, wherein it has moreover been found that the adhesive layer can then be adhered less easily and less well to the glass sheet. This is because in the case of an ionomer the adhesion of the adhesive layer to the glass sheet is determined mainly by the remaining acid groups in the copolymer. A degree of neutralization below 15% results in too few cross-links, this manifesting itself in a decreased elasticity, which is undesirable from a viewpoint of applicability. Particularly favourable properties are obtained when between about 20% and about 35% of the acid groups are neutralized.

The copolymer preferably comprises a percentage by weight of ethylene which lies within the range of 70-79% by weight. Too high a weight fraction of polyethylene (>79%) usually results in the structure of the adhesive layer being too brittle and not elastic enough. The crystallinity of the adhesive layer will moreover become too high here, which has an adverse effect on the light transmission of the adhesive layer. Too low a weight fraction of polyethylene (<79%) usually results in an adhesive layer which is too rubbery, and while this does enhance the elasticity it can make the processing of the adhesive layer considerably more difficult. The copolymer preferably comprises a percentage by weight of carboxylic acid which lies within the range of 21-30% by weight. The weight fraction (%) of the carboxylic acid generally amounts to 100% minus the weight fraction (%) of the polyethylene. It is however also possible to envisage one or more additives being added to the ionomer, thereby influencing the weight fraction of the carboxylic acid in particular. An example of such an additive are derivatives of methacrylic acid such as salts, esters and polymers of these derived monomers. Acrylic acid and methacrylic acid are generally most suitable as carboxylic acid for the intended application in a flexible glass laminate. As additives it is possible to envisage oil, such as paraffin oil (Sunpar 2280, Sunoco Holland B.V.) and/or fillers so as to enable manipulation of the mechanical properties. It is surmised that the relatively high impact resistance of the glass laminate as such is obtained because, before it is neutralized, the copolymer has a melt index (MI) lower than 60 grams/10 min at 190° Celsius, preferably lower than 55 grams/10 min, more preferably lower than 50 grams/10 min, particularly lower than 35 grams/10 min.

Following neutralization of the copolymer with one or more cations, preferably zinc, the MI is preferably lower than 2.5 grams/10 min and possibly lower than 1.5 grams/10 min.

The adhesive layer applied in the glass laminate according to the invention is preferably manufactured from a material with a Young's modulus (E -modulus) of at least 150 MPa, particularly at least 200 MPa, more particularly at least 250 MPa. The Young's modulus of the adhesive layer more preferably lies between 250 and 350 MPa, particularly between 290 and 310 MPa. This relatively high modulus has the advantage that the material is relatively stiff and strong, this enhancing the impact resistance.

The adhesive layer preferably has a transparency (light transmission) of at least 40%, more preferably at least 60%, more preferably at least 80%, in particular at least 95%.

The glass laminate according to the invention will generally be of flexible nature since each material layer of the glass laminate, including one or more ultra-thin, chemically hardened glass sheets applied, will also be flexible as such. Depending on the eventual application, the glass laminate can be applied in flat state or, conversely, in shaped (non-flat) state. When the glass laminate is for instance applied as glazing in a vehicle, such as automobile, vessel or aircraft, the glass laminate will usually be arranged in curved state in an enclosing bearing structure. The curvature of the glass laminate can be of simple or more complex nature here. It is for instance thus possible to envisage the glass laminate being provided with a more complex (multiple) curvature, wherein the glass laminate has different radii of curvature in different directions. A typical sunroof of an automobile with dimensions of 0.5 by 1 metre thus generally has for instance a radius of curvature of about 2-2.5 metres along the short axis and a radius of curvature of 4-5 m along the long axis.

In a preferred embodiment the glass laminate comprises at least one chemically hardened second glass sheet with a maximum thickness of 0.7 mm, which second glass sheet is positioned on a front side, remote from the first glass sheet, of the adhesive layer connected to the first glass sheet. A part of the adhesive layer left uncovered by the first glass sheet can be protected in fire-resistant and moisture-proof manner by applying an ultra-thin second glass sheet. The adhesive layer in fact functions here as intermediate layer. It is possible here to envisage the second glass sheet being directly connected to a front side, remote from the first glass sheet, of the adhesive layer connected to the first glass sheet. It is also possible to envisage the second glass sheet being indirectly connected to the adhesive layer, i.e. without interposing of one or more intermediate material layers. If the glass laminate were to consist only of the first glass sheet, the adhesive layer and the second glass sheet stacked in the manner of a sandwich and connected, the at least one end surface (peripheral side) of the adhesive layer would be uncovered, this generally being undesirable from a fire safety viewpoint since the ionomer adhesive layer is easily flammable and can moreover absorb moisture. At least a substantial part and preferably the whole of this end surface will therefore also be protected in the glass laminate according to the invention. Protection of the end surface of the adhesive layer can for instance take place by means of the first glass sheet and/or the second glass sheet. In a particular preferred embodiment the second glass sheet is connected to the first glass sheet such that the adhesive layer is substantially wholly enclosed by the second glass sheet and the first glass sheet. The first glass sheet and the second glass sheet are glued or fused to each other here, so enclosing and confining the intermediate adhesive layer.

Protection of the end surface of the adhesive layer so as to prevent absorption of moisture by the adhesive layer, whereby delamination (layer separation) of the glass laminate could occur, can also take place by arranging a separate sealing material such as silicone rubber. In a preferred embodiment the glass laminate comprises at least one fire-resistant and/or moisture-proof protective element connected to the first glass sheet and/or the adhesive layer for the purpose of substantially wholly protecting the easily flammable and moisture- sensitive adhesive layer from the environment. Owing to the polymeric character of the adhesive layer the advantageous, relatively high impact resistance of the glass laminate can as such be preserved. The fire resistance of the glass laminate is increased by protecting the flammable polymer adhesive layer as fully as possible from the environment, so preferably all the way round, so that the adhesive layer will not begin to burn immediately if a fire breaks out in the close vicinity.

Because the first glass sheet also has a naturally fire-resistant character and the first glass sheet already covers at least a part of the front side of the adhesive layer, the at least one protective element, not being the first glass sheet itself, will protect in fire- resistant manner the remaining surface of the adhesive layer not covered by the first glass sheet. The at least one protective element can here lie directly against said remaining surface, although it is also possible to envisage the at least one protective element lying a limited distance, generally in the order of magnitude of millimetres, from the adhesive layer. The at least one fire-resistant protective element is

manufactured here from a material which has a greater fire-resistant and/or fire- retardant capacity than the material comprising at least one polymer from which the adhesive layer is manufactured in order to improve the fire-resistance of the glass laminate as such. It is possible to envisage applying a moisture barrier element, such as silicone rubber, together with a (separate) fire barrier element in the glass laminate. The at least one protective element can optionally be provided with electronics and/or electric cables which could co-act with an electronic layer forming part of the glass laminate.

The at least one fire-resistant protective element applied in the glass laminate can be manufactured from diverse fire-resistant materials, can be shaped in diverse ways and can protect (parts left uncovered by the first glass sheet of) the adhesive layer from the environment in diverse ways.

In an alternative advantageous embodiment the glass laminate comprises a plurality of fire-resistant protective elements for protecting the adhesive layer from the

environment. The glass laminate more preferably comprises at least one first fire- resistant protective element for protecting at least a part of a front side, remote from the first glass sheet, of the adhesive layer connected to the first glass sheet, and wherein the glass laminate comprises at least one second fire-resistant protective element for protecting at least the at least one end surface of the adhesive layer. The production process can be simplified by having the different sides of the adhesive layer protected in fire-resistant manner by different protective elements, this also being advantageous from a financial viewpoint. Such a divided protection moreover makes it possible to optimize the design (shape, dimensioning, choice of material) of the protective elements for the purpose of protecting the specifics side(s) of the adhesive layer. It is possible here to envisage the first fire-resistant protective element being formed by the above mentioned second glass sheet. It is of course possible to envisage also manufacturing the second protective element from optionally ultra-thin glass. From a structural viewpoint however, the at least one second fire-resistant protective element is manufactured from metal, in particular aluminium, copper, stainless steel, silver, nickel or titanium. The protective element, optionally manufactured from a fire-resistant material, also contributes toward protection of the vulnerable edge of the glass laminate, at least of the one or more glass sheets forming part of the glass laminate, against impact. By applying a protective element such as a profile the edge is protected from damage and a force exerted on the edge, for instance as a result of an impact, is better distributed over the edge, whereby the notch effect and breakage at the edge can be considerably reduced. In order to make the peripheral side, also referred to as end surface or edge, of the at least one glass sheet less vulnerable, it is generally also advantageous for this peripheral side to be treated, in particular polished. Polishing of the peripheral sides can generally take place in chemical, thermal and/or mechanical manner.

By manufacturing the at least one second protective element from a metal a relatively strong framing can be provided to the glass laminate, which metal framing can also be mechanically fixed in relatively simple manner to a bearing structure such as a wall, a door/window frame or plating. It is therefore possible for the at least one second protective element to form a fire-resistant edge finish of the glass laminate. In a particular preferred embodiment the glass laminate comprises a plurality of second protective elements, wherein at least one inner second protective element protecting at least one end surface of the adhesive layer is enclosed by at least one other outer second protective element. Improved fire-resistant protection of the at least one end surface of the adhesive layer is possible by applying a plurality of second protective elements. Furthermore, this layered protection can considerably strengthen the construction of the glass laminate as such. This layered edge protection can in addition be advantageous in enabling subsequent mounting of the glass laminate in a surrounding bearing structure. It is advantageous here that at least one outer second protective element engages on a front side of the first glass sheet remote from the adhesive layer. The second protective element in this way forms a framing of the glass laminate which will generally considerably enhance the strength and form-retention of the glass laminate. The at least one outer protective element is preferably formed by a fire-resistant profile, in particular a fire-resistant extrusion profile. Aluminium and titanium are obvious choices here, since these materials are relatively strong and form-retaining, relatively inexpensive and moreover have a relatively low specific weight, this being particularly advantageous from a construction viewpoint.

In an advantageous embodiment of the glass laminate according to the invention a part of at least one protective element, in particular the second protective element, is positioned between the first glass layer and the adhesive layer. A relatively durable protection of the at least one end surface of the adhesive layer can be realized by partially confining the at least one protective element between the first glass sheet and the adhesive layer, wherein the chance of undesired release of the protective element from the adhesive layer and/or other parts of the glass laminate can be countered more effectively. It is a further advantage here for at least one protective element, in particular the second protective element, to enclose the adhesive layer on at least three sides. Not only will the at least one end surface of the adhesive layer be protected here in fire- resistant manner, at least a part of two front sides of the adhesive layer will also be covered in fire-resistant manner. This generally reduces the chance of gap formation in the seal, whereby the chance of the adhesive layer being exposed to the environment is minimized.

The adhesive layer will generally lie directly against the first glass sheet and be directly connected to the first glass sheet. It is however possible to envisage the adhesive layer being indirectly connected to the glass sheet via at least one intermediate material layer. This intermediate material layer can for instance be formed here by a light-reflecting layer, whereby the glass laminate can function as mirror. This light-reflecting layer can be vapour-deposited onto the first glass sheet here and is preferably manufactured from aluminium, silver or chromium. Although silver and chromium have a slightly lower oxidation speed than aluminium, the use of aluminium is generally recommended because of the relatively low specific mass and the relatively low cost price. When the glass laminate is used as a mirror the first glass sheet can also have a thickness (slightly) greater than 0.7 mm, such as for instance a thickness lying between 1.0 and 2.0 mm. Instead of or in addition to a light-reflecting layer it is also possible to apply other types of intermediate layer which are positioned between the first glass sheet and the adhesive layer, such as a coloured foil layer, a decorative foil layer and/or an electronic layer. An electronic layer is understood to mean a material layer able to visualize a video image (for users) or an interactive material layer, whereby the glass laminate can function as touchscreen. Physical contact between user and glass laminate need not be essential here in order to enable operation of the interactive material layer. Known interactive material layers are for instance resistive layers, capacitive layers, SAW layers (surface acoustic waves), APR layers (acoustic pulse recognition), infrared layers, NFI layers (near field imaging). The above stated non-limitative embodiments will be known to a skilled person in the field of interactive material layers.

It is also possible to envisage the glass laminate comprising at least one additional material layer positioned on a front side of the adhesive layer remote from the first glass sheet, wherein the at least one additional material layer is preferably chosen from the group consisting of: a decorative layer, a coloured layer, an additional adhesive layer, an electronic layer, a light-reflecting layer and an additional glass sheet. It is usually advantageous here for the additional material layer to take an at least partially transparent form.

The adhesive layer will generally be prefabricated as film before being incorporated into the glass laminate according to the invention. Since the glass laminate is generally applied as glazing, it is advantageous for the adhesive layer to be at least partially and preferably substantially wholly light- transmitting. It is otherwise possible to envisage the first glass sheet and/or the adhesive layer being provided with a colorant in order to give the glass laminate a colour.

The adhesive layer preferably has a Yellowness Index (YI) - in accordance with ASTM E313 - which is less than or equal to 1.5. Owing to the limited Yellowness Index of the applied adhesive layer, which is a factor of 4 to 8 lower than conventional adhesive layers, the adhesive layer as applied in the glass laminate according to the invention will generally be brightly transparent for a long time without the adhesive layer visibly discolouring (yellowing). This increases the predictability of the colour and brightness of the adhesive layer over the course of time. The glass laminate as such will in this way moreover also remain bright for a long time, particularly also because no separate additive such as a glue is necessary in order to manufacture the laminate.

The invention also relates to an adhesive layer for use in a glass laminate according to the invention, wherein the adhesive layer is at least partially manufactured from an ionomer. Advantages and embodiment variants are further elucidated in the remaining part of this specification.

The invention further relates to a vehicle comprising one or more glass laminates according to the invention. The glass laminates will generally serve here as glazing, mirror, as video screen, as touchscreen or combinations thereof. Vehicles are understood to mean, among others, motorbikes, automobiles, vessels and aircraft.

The invention will be elucidated on the basis of non-limitative exemplary embodiments shown in the following figures. Herein:

figure la shows an exploded cross-sectional view of a glass laminate according to the invention,

figure lb shows a cross-section of the glass laminate of figure l a in assembled state, figure 2 shows a cross-section of an alternative glass laminate according to the invention,

figure 3 shows a perspective view of another laminate according to the invention, figure 4 shows a perspective view of yet another laminate according to the invention, and

figure 5 shows a perspective view of a part of an aircraft comprising a glass laminate according to the invention. Figure la shows an exploded cross-sectional view of a fireproof (fire-resistant) glass laminate 1 according to the invention. Glass laminate 1 comprises a first ultra-thin, chemically hardened glass sheet 2 with a thickness of a maximum of 0.7 mm, a second ultra-thin, chemically hardened glass sheet 3 with a thickness of a maximum of 0.7 mm, which glass sheets 2, 3 are separated and mutually connected by an ionomeric intermediate layer 4 (adhesive layer). The thickness of intermediate layer 4 lies between 0.5 and 1.8 mm and has in particular a typical thickness of 0.89 mm in this exemplary embodiment. In order to reduce the flammability of glass laminate 1 it is advantageous to protect the flammable component, i.e. intermediate layer 4, from the immediate environment. The front sides 4a of intermediate layer 4 are already covered - in the assembled state as shown in figure lb - by the two glass sheets 2, 3. Depending on the geometry, intermediate layer 4 will have one or more end surfaces 4b. In this exemplary embodiment these end surfaces 4b are covered by one or more fire-resistant inner protective elements 5 which are in fact folded around end surfaces 4b such that the inner protective elements 5 are enclosed between intermediate layer 4 on one side and respective glass sheets 2, 3 on the other, whereby an adequate, reliable and durable protection of end surfaces 4b of intermediate layer 4 is obtained. The inner protective elements 5 are manufactured in this embodiment from aluminium or copper. A further protection of end surfaces 4b of intermediate layer 4 is realized by an additional protective element 6 which surrounds glass laminate 1 and the inner protective element 5 and engages on sides of the two glass sheets 2, 3 remote from intermediate layer 4. Protective element 6 can further be engaged by a further protective element 7 which is formed particularly by a construction element such as a profile of for instance a wall, door/window frame or plating. The two additional protective elements 6, 7 are also manufactured from a fire-resistant material, preferably aluminium or copper. The two additional protective elements 6, 7 are deemed in this context to be two different outer protective elements. The construction of glass laminate 1 is symmetrical, whereby the edge finish formed by protective elements 5, 6, 7 is present all the way round glass laminate 1. In assembled state the intermediate adhesive layer 4 is fused with glass sheets 2, 3 and with the one or more inner protective elements 5, whereby a strong but flexible structure is created. The eventual shape is determined by the shape of the outer protective elements 7. The ultra-thin glass sheets 2, 3 can have numerous and mutually differing compositions. Stated only by way of example is that glass sheets 2, 3 can be manufactured from: 64-68 mol.% Si0₂; 12- 16 mol.% Na₂0 ; 8-12 mol.% A1₂0₃; 0-3 mol.% B₂0 3; 2-5 mol.% K₂0 ; 4-6 mol.% MgO; and 0-5 mol.% CaO, wherein: 66 mol.% < Si0₂ + B₂0₃ + CaO < 69 mol.%; Na₂0 + K₂0 + B2O3+ MgO + CaO + SrO > 10 mol.%; 5mol.% < MgO + CaO + SrO < 8 mol.%; (Na₂0 + B2O3) - A1₂0₃ < 2 mol.%; 2 mol.% < Na₂0 - AI2O3 < 6 mol.%; and 4 mol.% < (Na₂0 + K₂0) - A1₂0₃ < 10 mol.%. A preferred embodiment of the composition of soda-lime glass to be used is shown in the following table:

The glass is chemically hardened in order to make the glass particularly strong. The (unhardened) glass is preferably immersed here in a bath of molten potassium nitrate at a temperature of about 400°C. This results in chemical exchange of K⁺ ions from the bath with the Na⁺ ions from the glass. The K⁺ ions (size 2.66 A) take the place of the Na⁺ ions (size 1.96 A). Since they have larger dimensions they induce compressive stresses at the surface of the glass, which can thus provide more resistance. The duration of immersion determines the finally obtained stress level. The stress distribution does not take the same form as in the case of thermally hardened glass and results in considerably stronger glass than if unhardened glass were to be hardened in thermal manner. It is noted in this respect that chemically hardened glass generally has a much higher compressive stress at the surface of the glass sheet which decreases relatively quickly just beneath the surface, wherein there is a limited tensile stress in the centre (half depth) of the glass sheet, resulting in a block-shaped stress profile. Thermally hardened glass generally has a considerably lower compressive stress at the surface of the glass sheet, wherein a relatively high tensile stress is present in the centre of the glass sheet, resulting in a parabolic stress profile. Intermediate layer 4 is manufactured in this exemplary embodiment from a copolymer consisting of 81% ethylene, 19% methacrylic acid, wherein 37% of the acid groups are neutralized with sodium or zinc. The Young's modulus of such an ionomer amounts to about 361 MPa. Figure 2 shows a cross-section of an alternative glass laminate 21 according to the invention. Glass laminate 21 comprises a first ultra-thin, chemically hardened glass sheet 22 with a thickness of 0.5 mm, a second ultra-thin, chemically hardened glass sheet 23 with a thickness of a maximum of 0.5 mm, which glass sheets 22, 23 are separated and mutually connected by an ionomeric intermediate layer 24 (adhesive layer). The thickness of intermediate layer 24 lies between 0.3 and 1.5 m, preferably between 0.5 and 1 mm, more preferably between 0.5 and 0.9 mm in this exemplary embodiment, hi order to reduce the flammability of glass laminate 21 it is advantageous to protect the flammable component, i.e. intermediate layer 24, from the immediate environment. The front sides of intermediate layer 24 are already covered by the two glass sheets 22, 23. Depending on the geometry, intermediate layer 24 will have one or more end surfaces. Tn this exemplary embodiment these end surfaces are protected by one or more fire-resistant inner protective elements 25 which are in fact folded around the end surfaces such that the inner protective elements 25 are enclosed between intermediate layer 24 on one side and respective glass sheets 22, 23 on the other, whereby a reliable and durable protection of the end surfaces of intermediate layer 24 is obtained. The inner protective elements 25 are manufactured in this embodiment from aluminium or copper. One or more fire-resistant outer protective elements 26 are also applied to make the sealing more durable. These outer protective elements 26 generally also function as fixing element for fixing glass laminate 21 to an adjacent structure. The outer protective elements 26 are generally manufactured from a profile, in particular an aluminium extrusion profile. The ionomer intermediate layer is formed by a copolymer comprising 21.5% methacrylic acid and 78.5% ethylene, wherein 14.1% of the acid groups are neutralized. Figure 3 shows a perspective view of another glass laminate 31 according to the invention. Glass laminate 31 comprises a first ultra-thin, chemically hardened glass sheet 32 with a thickness of 0.3 mm, a second ultra-thin, chemically hardened glass sheet 33 with a maximum thickness of 0.5 mm, these glass sheets 32, 33 being partially separated and mutually connected by an ionomeric intermediate layer 34 (adhesive layer). The thickness of intermediate layer 34 amounts to 0.89 mm in this exemplary embodiment. In order to reduce the flammability of glass laminate 31 the flammable component, i.e. intermediate layer 34, is protected from the immediate environment by giving glass sheets 32, 33 slightly larger dimensions than intermediate layer 34, whereby peripheral edges 32a, 33a of glass sheets 32, 33 protrude relative to

intermediate layer 34. By mutually connecting the glass peripheral edges 32a, 33b during the production process, for instance by fusing thereof, adhesive layer 4 can be substantially wholly protected from the immediate environment, this enhancing the fire- resistance of glass laminate 31 as such. The composition of adhesive layer 34 can correspond to the adhesive layers 4, 24 described in figures 1 and 2.

Figure 4 shows a perspective view of yet another laminate 41 according to the invention. Glass laminate 41 comprises a plurality of layers 41a-41f which are stacked onto each other and mutually connected, wherein the formed peripheral edge of the stacked material layers 41a-41f is protected by a fire-resistant metal frame 42. Material layers 41 a-41f which form part of the shown laminate are successively an ultra-thin, chemically hardened glass sheet (41a), an ionomeric adhesive layer (41b), an interactive electronic layer (41c), a light-reflecting layer (mirror layer) (41d), an ionomeric adhesive layer (41e) and a rear glass sheet (4 If). The rear glass sheet 4 If can optionally take an ultra-thin form (thickness < 0.7 mm) and can optionally be thermally and/or chemically hardened. The composition of adhesive layer 41 can correspond to the adhesive layers 4, 24 described in figures 1 and 2.

Figure 5 shows a perspective view of a part of an aircraft 51 comprising a glass laminate 52 according to the invention. The glass laminate will take a curved form here. In addition to being light in weight and having a relatively high impact resistance, additional advantages of the applied glass laminate according to the invention are having a relatively homogeneous light-transmission, the high degree of scratch- resistance and having a uniform thickness, whereby the light refraction is likewise relatively uniform.

It will be apparent that the invention is not limited to the exemplary embodiments shown and described here, but that within the scope of the appended claims numerous variants are possible which will be self-evident to the skilled person in this field.

Claims

1. Glass laminate, comprising:

at least one ultra- thin, chemically hardened first glass sheet with a maximum thickness of 0.7 mm;

at least one adhesive layer connected to a front side of the first glass sheet and comprising at least one polymer, wherein the adhesive layer is manufactured at least partially from an ionomer, wherein the thickness of the adhesive layer lies between 0.5 and 0.89 mm.

2. Glass laminate as claimed in claim 1, wherein the ionomer comprises a copolymer of ethylene and a carboxyhc acid chosen from the group consisting of ν,Ξ- unsaturated carboxyhc acids with 3-8 carbon atoms, wherein some of the acid groups are neutralized with at least one metal ion.

3. Glass laminate as claimed in claim 2, wherein the at least one metal ion is formed by a zinc ion.

4. Glass laminate as claimed in claim 2 or 3, wherein 15-45%, in particular 20- 35%, of the acid groups are neutralized with at least one metal ion.

5. Glass laminate as claimed in any of the claims 2-4, wherein the copolymer comprises a percentage by weight of ethylene which lies within the range of 70-79% by weight.

6. Glass laminate as claimed in any of the claims 2-5, wherein the copolymer comprises a percentage by weight of carboxyhc acid which lies within the range of 21 - 30% by weight.

7. Glass laminate as claimed in any of the claims 2-6, wherein the carboxyhc acid is formed by acrylic acid and/or methacrylic acid.

8. Glass laminate as claimed in any of the foregoing claims, wherein the adhesive layer has a melt index (MI) of about 60 g/10 min or less before neutralization, determined at a temperature of 190° C.

9. Glass laminate as claimed in any of the foregoing claims, wherein the adhesive layer is manufactured from a material with a Young's modulus of at least 150 MPa, particularly at least 200 MPa, more particularly at least 250 MPa.

10. Glass laminate as claimed in claim 9, wherein the Young's modulus of the adhesive layer lies between 250 and 350 MPa, particularly between 290 and 310 MPa.

11. Glass laminate as claimed in any of the foregoing claims, wherein the adhesive layer is substantially transparent.

12. Glass laminate as claimed in any of the foregoing claims, wherein the

Yellowness Index (YI) of the adhesive layer is less than or equal to 1.5.

13. Glass laminate as claimed in any of the foregoing claims, wherein the glass laminate comprises at least one chemically hardened second glass sheet with a maximum thickness of 0.7 mm, which second glass sheet is positioned on a front side, remote from the first glass sheet, of the adhesive layer connected to the first glass sheet.

14. Glass laminate as claimed in claim 13, wherein the second glass sheet is directly connected to a front side, remote from the first glass sheet, of the adhesive layer connected to the first glass sheet.

15. Glass laminate as claimed in claim 13 or 14, wherein the second glass sheet is connected to the first glass sheet such that the adhesive layer is substantially wholly enclosed by the second glass sheet and the first glass sheet.

16. Glass laminate as claimed in any of the foregoing claims, wherein the glass laminate is bendable.

17. Glass laminate as claimed in any of the foregoing claims, wherein the glass laminate has a curved geometry.

18. Glass laminate as claimed in any of the foregoing claims, wherein the glass laminate comprises at least one fire-resistant protective element connected to the first glass sheet and/or the adhesive layer for the purpose of substantially wholly protecting the adhesive layer from the environment.

19. Glass laminate as claimed in claim 18, wherein the at least one protective element is manufactured from a material which has a greater fire-resistant capacity than the material comprising at least one polymer from which the adhesive layer is manufactured.

20. Glass laminate as claimed in any of the claims 18-19, wherein the glass laminate comprises a plurality of fire-resistant protective elements for protecting the adhesive layer from the environment.

21. Glass laminate as claimed in claim 20, wherein the glass laminate comprises at least one first fire-resistant protective element for protecting at least a part of a front side, remote from the first glass sheet, of the adhesive layer connected to the first glass sheet, and wherein the glass laminate comprises at least one second fire-resistant protective element for protecting at least the end surfaces of the adhesive layer.

22. Glass laminate as claimed in any of the claims 13-15 and claim 21, wherein the first fire-resistant protective element is formed by the second glass sheet.

23. Glass laminate as claimed in claim 21 or 22, wherein the glass laminate comprises a plurality of second protective elements, wherein at least one inner second protective element protecting at least one end surface of the adhesive layer is enclosed by at least one other outer second protective element.

24. Glass laminate as claimed in claim 23, wherein the at least one outer second protective element engages on a front side of the first glass sheet remote from the adhesive layer.

25. Glass laminate as claimed in claim 23 or 24, wherein at least one outer protective element is formed by a fire-resistant profile, in particular a fire-resistant extrusion profile.

26. Glass laminate as claimed in any of the claims 18-25, wherein at least one fire- resistant protective element is manufactured from metal, in particular aluminium.

27. Glass laminate as claimed in any of the claims 18-26, wherein at least one protective element forms at least a part of an edge finish of the glass laminate.

28. Glass laminate as claimed in any of the claims 18-27, wherein a part of at least one protective element, in particular the second protective element, is positioned between the first glass layer and the adhesive layer.

29. Glass laminate as claimed in any of the claims 18-28, wherein the protective element, in particular the second protective element, encloses the adhesive layer on at least three sides.

30. Glass laminate as claimed in any of the foregoing claims, wherein the glass laminate comprises at least one intermediate material layer which is positioned between the first glass sheet and the adhesive layer.

31. Glass laminate as claimed in claim 30, wherein the intermediate material layer is formed by a light-reflecting layer.

32. Glass laminate as claimed in any of the foregoing claims, wherein the glass laminate comprises at least one additional material layer positioned on a front side of the adhesive layer remote from the first glass sheet, wherein the at least one additional material layer is chosen from the group consisting of: a decorative layer, a coloured layer, an additional adhesive layer, an electronic layer, a reflective layer and an additional glass sheet.

33. Glass laminate as claimed in claim 32, wherein the additional material layer is at least partially transparent.

34. Glass laminate as claimed in any of the foregoing claims, wherein at least a part of an end surface of at least one glass sheet is polished.

35. Adhesive layer for use in a glass laminate as claimed in any of the foregoing claims, wherein the adhesive layer is at least partially manufactured from an ionomer.

36. Motor vehicle comprising a glass laminate as claimed in any of the claims 1-34.

37. Aircraft comprising a glass laminate as claimed in any of the claims 1-34.

38. Vessel comprising a glass laminate as claimed in any of the claims 1-34.