Asymmetric laminated glazing, associated manufacturing process

Abstract

Asymmetric laminated glazing, associated manufacturing method The invention relates to a laminated glazing comprising a first and a second glass sheet separated by an interlayer, the first glass sheet being thermally reinforced and having a thickness greater than 1.8 mm, the second glass sheet being free of toughening treatment and having a thickness less than 1.6 mm. Said glazing has at least a first bending curvature defining a bending depth between a surface arc and a chord supporting said arc, so as to be associated with a first bending ratio between the length of said chord and said bending depth. Furthermore, said glazing is shaped so that a flattening coefficient at least equal to said first bending ratio is greater than 250. Figure for abstract: Fig. 1

Description

Title of the invention: Asymmetric laminated glazing, associated manufacturing method Prior art

[0001] The present invention belongs to the general field of glazing production.

[0002] The invention relates more particularly to an asymmetric laminated glazing, as well as to a method for manufacturing such an asymmetric laminated glazing. The invention finds a particularly advantageous, although in no way limiting, application in the manufacture of laminated glazing for the automotive sector (roof, side window, windshield, rear window).

[0003] The technology for manufacturing glazing intended to equip motor vehicles has undergone major developments based on different design criteria.

[0004] Thus, automotive glazing, and in particular side glazing, was first designed monolithically and using thermal toughening treatments. This method of proceeding made it possible to achieve excellent resistance properties.

[0005] Subsequently, it was proposed to design laminated glazing in which the glass sheets used have identical thicknesses. Such laminated glazing also makes it possible to achieve very good resistance while proposing the addition of various functionalities, such as for example an acoustic attenuation function. In addition, the combination of this lamination principle with thermal tempering or semi-tempering operations of the glass sheets further reinforces the resistance of the manufactured glazing, in particular with regard to external impacts (in particular in the event of a break-in and possibly stone chipping) or internal impacts (laminated glass makes it possible to keep the occupants inside the passenger compartment in the event of an accident and the vehicle rolling over; they thus prevent irreparable injuries when an occupant is partially ejected from the vehicle).

[0006] Such laminated glazings are nevertheless not without drawbacks. In particular, they are particularly heavy and bulky elements. Design practices have therefore continued to evolve towards the production of laminated glazings whose weight and size are reduced. More recently, the production of so-called "asymmetric" laminated glazings has been proposed, i.e. laminated glazings in which the two assembled sheets of glass have different thicknesses. In practice, the glazing comprises a very thin sheet of glass, typically of the order of a millimeter, generally placed opposite an envi interior environment (e.g., the inside of the vehicle). The thicker glass sheet, on the other hand, is generally placed facing an external environment (e.g., the outside of the vehicle).

[0007] The fact that one of the glass sheets is much thinner than the other can lead to a reduction in rigidity, and therefore a fortiori a deterioration in impact resistance. To overcome this drawback, manufacturers have therefore systematically opted for the implementation of hardening treatments on the thinnest glass sheet, more particularly via the use of chemical toughening.

[0008] This method has a number of disadvantages. Indeed, chemical tempering is an expensive, long and complex process to implement because it requires maintaining the glass sheet at high temperature and for several hours in different baths of alkaline salts in order to obtain the right levels of surface stress. It gives rise to very poor yields with numerous breakages during handling, washing before or after chemical tempering and during the tempering operation itself. In addition, it constitutes a disadvantageous solution from an environmental point of view since the treated products are difficult to recycle.

[0009] It is important to note that although the preceding elements have been described in the application context of motor vehicles, they nonetheless remain valid in other application fields, such as, for example, the field of housing or even air, maritime or rail transport, etc. Statement of the invention

[0010] The present invention aims to overcome all or part of the drawbacks of the prior art, in particular those set out above, by proposing a solution which makes it possible to obtain asymmetric laminated glazings whose curved appearance is not very pronounced and whose production is simpler and more environmentally friendly than that of the asymmetric glazings of the state of the art.

[0011] To this end, and according to a first aspect, the invention relates to a laminated glazing comprising a first and a second glass sheet assembled by an interlayer, the first glass sheet being thermally reinforced and having a thickness greater than 1.8 mm, the second glass sheet being free of toughening treatment and having a thickness less than 1.6 mm, said glazing having at least a first bending curvature defining a bending depth between a surface arc and a chord supporting said arc, so as to be associated with a first bending ratio between the length of said chord and said bending depth, said glazing being further shaped so that a flattening coefficient at least equal to said first bending ratio is greater than 250.

[0012] In its general principle, the laminated glazing according to the invention corresponds to an asymmetrical laminated glazing and is configured so as to make it possible to circumvent the drawbacks inherent in the implementation of chemical toughening by relying on results obtained by the inventors after simulation and test campaigns.

[0013] More particularly, starting from the observation that more and more laminated glazings are manufactured so as to have a substantially flat geometry (this applies in particular, but not exclusively, in the automotive field), the inventors sought to characterize the acceptable curvatures for asymmetrical laminated glazings so that it is not necessary to impose a toughening treatment on all or part of the glass sheets used in their composition, while guaranteeing a low level of stress within the thinnest glass sheet (i.e. the second glass sheet in this case), and it being understood that the asymmetrical laminated glazing has, once assembled, excellent robustness (thanks to the sufficient level of stress within the thickest glass sheet and the presence of the interlayer).

[0014] The solution proposed by the invention therefore consists of an asymmetric laminated glazing in which the thinnest glass sheet is devoid of any tempering treatment. In other words, the second glass sheet has not undergone any thermal strengthening (semi-tempering or tempering), nor any chemical tempering, and is therefore directly formed from flat glass supplied at the output of a float glass production line (glass called "float" in the Anglo-Saxon literature).

[0015] Furthermore, to compensate for the absence of toughening treatment of the second sheet of glass, and to minimize the risk of breakage of the latter, the glazing according to the invention has a substantially flat geometry characterized by the values ​​which can be taken by said flattening coefficient.

[0016] This substantially flat geometry is produced within limits which advantageously allow it to acquire excellent robustness while avoiding the implementation of tempering treatments of the second glass sheet.

[0017] In particular embodiments, the laminated glazing may further comprise one or more of the following characteristics, taken individually or in all technically possible combinations.

[0018] In particular embodiments, the glazing has a second bending curvature in a direction essentially perpendicular to the first bending curvature, so as to be associated with a second bending ratio, said flattening coefficient being equal to the sum of said first and second bending ratios.

[0019] In particular embodiments, the flattening coefficient is greater than 500.

[0020] In particular embodiments, the thickness of the second glass sheet is less than 1.2 mm, for example less than 1 mm.

[0021] In particular embodiments, the thickness of the first glass sheet is greater than 2.1 mm, or greater than 2.6 mm, or greater than 2.85 mm, or greater than 3.15 mm, or greater than 3.5 mm or greater than 3.85 mm.

[0022] In particular embodiments, the interlayer comprises a polymer material comprising a polyvinyl butyral layer having a loss factor tan(δ) greater than 0.8 and a shear modulus G' less than 20 MPa at frequencies between 500 Hz and 5000 Hz at a temperature of 20°C.

[0023] In particular embodiments, the interlayer comprises a transparent adhesive material of the “OCA” type, such as for example a latex glue.

[0024] In particular embodiments, the interlayer is made of ethylene-vinyl acetate.

[0025] According to a second aspect, the invention relates to a use of a glazing according to the invention in a dwelling or means of road, air, sea or rail transport, preferably as window glazing in motor vehicles, in particular as windshield, rear glazing, side glazing or roof glazing.

[0026] According to a third aspect, the invention relates to a motor vehicle comprising glazing according to the invention.

[0027] According to a fourth aspect, the invention relates to a method of manufacturing a glazing unit according to the invention, said method comprising steps of: - obtaining the first glass sheet in a flat state as well as the second glass sheet in a flat state, - thermal bending of the first sheet of glass according to said flattening coefficient, - thermal reinforcement of the first sheet of glass, - assembly of the first and second glass sheets into a laminated glazing unit, the interlayer being placed between the first and second glass sheets, said assembly comprising cold bending of the second glass sheet against the first glass sheet, - extraction of air contained in the assembled laminated glazing.

[0028] The manufacturing method according to the invention is particularly advantageous in that it makes it possible to obtain a robust asymmetric laminated glazing, the production of which is simpler and more environmentally friendly than that of asymmetric glazing of the state of the art given the absence of toughening treatment of the thinnest glass sheet.

[0029] In particular embodiments, the manufacturing method may further include one or more of the following characteristics, taken individually or in all technically possible combinations.

[0030] In particular embodiments, the air extraction step is carried out by calendering the laminated glazing.

[0031] In particular embodiments, when the glazing comprises a PVB interlayer, in particular for example an acoustic PVB, said method further comprises, after the air extraction step, a step of autoclaving the assembled laminated glazing.

[0032] In particular embodiments, the assembly step comprises, after cold bending of the second glass sheet, holding in position the stack formed by the glass sheets and the interlayer. Brief description of the drawings

[0033] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character. In the figures:

[0034] - [Fig.l] schematically represents a particular embodiment of a asymmetric laminated glazing according to the invention;

[0035] - [Fig.2] schematically represents two bending curves of the glazing asymmetric laminate of [Fig.l];

[0036] - [Fig.3] is a table illustrating surface stress values ​​measured at level of the thinnest glass sheet belonging to the asymmetric laminated glazing of [Fig.l];

[0037] - [Fig.4] represents, in the form of a flowchart, the main stages of a method of manufacturing asymmetric laminated glazing according to the invention. Detailed description of the invention

[0038] [Fig.l] schematically represents a particular embodiment of a laminated glazing 100 according to the invention.

[0039] For the remainder of the description, it is considered in a non-limiting manner that the laminated glazing 100 is intended to equip a motor vehicle, such as for example a car. This is more specifically a side glazing of a car, but nothing of course excludes the possibility of considering a rear glazing, a windshield or even a roof glazing.

[0040] It is important to note, however, that considering such a type of glazing as well as such an application of the use of this glazing constitutes only a variant implementation of the invention. Generally speaking, no limitation is attached to the use that can be made of the glazing 100. For example, this use can be made in a home (separation of rooms, wall glazing, etc.) or still in all types of means of transport (road, air, sea or rail).

[0041] As illustrated by [Fig.l], the glazing 100 comprises a first glass sheet 110 and a second glass sheet 120 assembled by an interlayer 130.

[0042] By "glass sheet" is meant a plate formed from a transparent material. For example, the transparent material may be mineral glass, such as soda-lime, aluminosilicate, or borosilicate glass. Alternatively, the transparent material may be organic glass, such as stretched polymethyl methacrylate (stretched PMMA), unstretched polymethyl methacrylate, polycarbonate (PC), polyethylene terephthalate (PET), or polyurethane (PU). It should be noted that the two glass sheets 110, 120 may be made of different transparent materials.

[0043] Furthermore, one or both of the glass sheets 110, 120 may be tinted (A tinted glass is a glass comprising a desired inorganic pigment, such as iron oxide, cobalt oxide, chromium oxide, etc.). Here too, it should be noted that the two glass sheets 110, 120 may be of different tints.

[0044] The interlayer 130 is for example made of a polymer material, such as for example of the PVB (polyvinyl butyral) type. More specifically, in the present embodiment, this polymer material is of the “acoustic” type, that is to say having the function of reducing the sounds passing through the glazing 100. To be qualified as acoustic, such a polymer material comprises at least one layer of polymer material (generally made of PVB) having a loss factor tan(δ) greater than 0.8 and a shear modulus G' less than 20 MPa at frequencies between 500 Hz and 5000 Hz at a temperature of 20°C. These viscoelastic properties are for example evaluated by a person skilled in the art by means of a plane shear measurement according to the ISO 6721 standard (Determination of dynamic mechanical properties) using a viscoanalyzer of the Metravib OldB Metravib VA4000 type.

[0045] When such a layer of acoustic polymer material is implemented, it may constitute the only layer of the interlayer 130, or be juxtaposed with at least one other layer of polymer material. An interlayer 130 having acoustic properties may in particular be produced by assembling at least three layers of PVB, an inner layer being softer than two other layers which surround it. Generally, an acoustic polymer material causes a laminated glazing to lose a little rigidity, compared to a conventional polymer material. A conventional polymer material is therefore more suitable for a laminated glazing from which high rigidity is primarily expected. A conventional polymer material generally has a shear modulus G' greater than 100 MPa and a loss factor tan(δ) less than 0.4 at frequencies between 500 Hz and 5000 Hz at a temperature of 20°C.

[0046] It should also be noted that considering the sole presence of a PVB polymer material, in particular an acoustic polymer material, as an interlayer 130 constitutes only one variant of implementation of the invention. Thus, nothing precludes considering other embodiments in which, in combination or as an alternative with a PVB polymer material, the interlayer 130 comprises a transparent adhesive material of the “OCA” type (acronym for “Optical Clear Adhesive”), such as for example a latex glue, more particularly an acoustic latex glue (the thickness of the glue is for example less than 100 μm, ideally 30 μm). As an alternative to these modes, other modes can also be considered in which the interlayer 130 is made of EVA (ethylene-vinyl acetate).

[0047] The glazing 100 corresponds more particularly to an asymmetric laminated glazing. Consequently, the first and second glass sheets 110, 120 have different thicknesses. More particularly, in the present embodiment described with reference to [Fig. 1], the first glass sheet 110 has a thickness greater than 1.8 mm, the thickness of the second glass sheet 120 being less than 1.6 mm.

[0048] With regard to the use for which the glazing 100 is intended, the first sheet of glass 110 (more particularly the face 1 of the glazing 100, in accordance with the convention traditionally used in the field of glazing) is configured to be placed facing the environment outside the vehicle. The second sheet of glass 120 (more particularly the face 4 of the glazing 100) is configured to be placed facing the interior environment (i.e. the passenger compartment) of the vehicle.

[0049] It should be noted that the respective thickness values ​​of the first and second glass sheets 110, 120 considered in the present embodiment are not limiting of the invention. Thus, other modes can be envisaged in which the thickness of the second glass sheet 120 is less than 1.2 mm, for example less than 1 mm and / or the thickness of the first glass sheet 110 is greater than 2.1 mm, or greater than 2.6 mm, or greater than 2.85 mm, or greater than 3.15 mm, or greater than 3.5 mm or greater than 3.85 mm.

[0050] The first glass sheet 110, that is to say the thickest glass sheet among the two glass sheets of the glazing 100, is thermally reinforced. In other words, the first glass sheet 110 is semi-tempered or tempered.

[0051] The thermal strengthening operation by tempering is generally carried out just after bending the glass (by rapidly cooling the latter by blowing air on its two faces, from the bending temperature), as well as before assembly of the laminated glazing 100.

[0052] The manufacture of semi-tempered glass (also called "thermally toughened") is carried out on an installation identical to that of thermally toughened glass. Although the heating conditions are identical, the cooling air blowing power is lower.

[0053] In a known manner, very thin glass sheets, such as said second glass sheet 120, can be cold-bent during the manufacture of laminated glazing. Cold-bending is preferred for this type of glass sheet since thermal bending (i.e. hot bending) generally affects the optical quality of the latter.

[0054] By "cold bending", we conventionally refer to a deformation process occurring in the elastic range of the glass. Conversely, thermal bending refers to the hot bending of the glass at its deformation temperature, causing it to permanently deform after returning to room temperature. Thermal bending is more particularly carried out at a temperature above the glass transition temperature of the glass and generally at a temperature above 550°C.

[0055] Although preferred, cold bending has limitations in that it does not allow the glass to achieve significant curvatures without significantly increasing the risk of breakage. To limit this risk, it is apparent from the state of the art that the thin glass sheets used in the manufacture of asymmetric laminated glazing are systematically reinforced by chemical toughening.

[0056] The general principle of the present invention aims to circumvent the drawbacks inherent in the implementation of chemical quenching by relying on results obtained by the inventors after simulation and test campaigns.More particularly, starting from the observation that more and more laminated glazings are manufactured so as to have a substantially flat geometry (this applies in particular, but not exclusively, in the automotive field), the inventors sought to characterize the acceptable curvatures for asymmetrical laminated glazings so that it is not necessary to impose such a chemical toughening treatment on them while guaranteeing a low level of stress within the thinnest glass sheet, and it being understood that the asymmetrical laminated glazing has, once assembled, excellent robustness (thanks to the sufficient level of stress within the thickest glass sheet and the presence of the interlayer).

[0057] For these reasons, the second glass sheet 120, that is to say the thinnest glass sheet among the two glass sheets of the glazing 100, is devoid of any tempering treatment. In other words, the second glass sheet 120 has not undergone any thermal strengthening (semi-tempering or tempering), nor any chemical tempering, and is therefore directly formed from flat glass supplied at the outlet of a line of production of float glass (called “float” glass in Anglo-Saxon literature).

[0058] Furthermore, to compensate for the absence of toughening treatment of the second glass sheet 120, the glazing 100 has in the present embodiment two bending curvatures corresponding to characteristics which will now be described.

[0059] In a known manner, a glass sheet can be curved in one or more directions, each of these directions therefore being associated with a bending curvature (i.e. a radius of curvature). Each bending curvature makes it possible to define a bending depth between a surface arc (i.e. an arc running along the surface of the glass sheet) and a chord supporting said arc. To the extent that these characteristics apply in a similar manner to each of the glass sheets used in the composition of a laminated glazing unit, it is therefore possible to speak of the bending curvature of said laminated glazing unit in its entirety.

[0060] [Fig.2] schematically represents the two bending curves of the asymmetric laminated glazing 100 of [Fig.l].

[0061] As illustrated by [Fig.2], the glazing 100 has a first bending curvature (in this example corresponding to the most pronounced bending) associated with the bending depth of the longest arc ARC_F running across the surface of the glazing 100. This bending depth of the first bending curvature is also called “arrow F”, and corresponds more specifically to the segment having as ends the middle of said arc ARC_F and the middle of the chord C_F which subtends said arc ARC_F.

[0062] In the present embodiment, the glazing 100 also has a second bending curvature in a direction essentially perpendicular to the first bending curvature. This second bending curvature, also called double bending (“cross-bending” or “cross-curvature” in the English literature), is generally less pronounced than the first bending curvature. It is furthermore associated with the bending depth of the arc ARC_DB essentially perpendicular to the longest arc ARC_F. This bending depth of the second bending curvature is also called “double bending DB”, and corresponds more specifically to the segment having as ends the middle of said arc ARC_DB and the middle of the chord C_DB which subtends said arc ARC_DB.

[0063] It results from these provisions that the asymmetric laminated glazing 100 can be associated with: - a first bending ratio R_F between the length of said chord C_F and said bending depth F (ie R_F = C_F / F); - a second crowning ratio R_DB between the length of said chord C_DB and said crowning depth DB (i.e. R_DB = C_DB / DB).

[0064] As mentioned above, the asymmetric laminated glazing 100 has a substantially flat geometry, within limits advantageously allowing it to acquire excellent robustness while avoiding the implementation of toughening treatments of the second glass sheet 120. Concretely, in the present embodiment, the glazing 100 is shaped so that a flattening coefficient COEF_FLAT equal to the sum of the first bending ratio R_F and the second bending ratio R_DB is greater than 250.

[0065] [Fig. 3] is a table illustrating surface stress values ​​measured at the second glass sheet 120.

[0066] More particularly, to obtain the values ​​of the table in [Fig.3], an asymmetric laminated glazing 100 was considered in which the thickness of the first glass sheet 110 (respectively of the second glass sheet 120) is equal to 2.1 mm (respectively equal to 1.1 mm). The interlayer 130 is a PVB layer with a thickness equal to 0.76 mm.

[0067] In the table of [Fig. 3], the values ​​of the parameters C_F, F, R_F, C_DB, DB and R_DB are expressed in millimeters. The first column bearing the reference “%” corresponds to a flattening ratio of the glazing 100 with respect to a nominal configuration of said same glazing 100 (the flattening here refers to a reduction of the bending depths F and DB). Said nominal configuration corresponds in terms of curvature to the geometry which would typically be sought in the state of the art (i.e. if chemical treatment of the second glass sheet 120 is authorized), and is associated with values ​​F and DB respectively equal to 8.39 mm and 19.45 mm. This nominal configuration is indicated in the table in the 0% row. Thus, for illustration purposes, for the line corresponding to a flattening ratio of 20%, we have F = 8.39 x (1 - 20%) = 6.71 mm.

[0068] Furthermore, in the table of [Fig. 3], the column bearing the reference “CO_F4” includes the surface stress values ​​measured at the face 4 of the glazing 100 (i.e. the face of the second glass sheet 120 facing the interior of the vehicle). These values ​​are expressed in MPa, and are here all negative given the measurement convention chosen and the fact that these are compressive surface stresses (it is understood that positive stresses having the same values ​​can be measured symmetrically on face 3, these positive stresses therefore corresponding to extension surface stresses).

[0069] Conventionally, these surface stresses correspond to mechanical residual stresses resulting from the assembly of the asymmetric laminated glazing 100. In particular, these residual stresses result in particular from the thermal bending and thermal reinforcement of the first glass sheet 110, as well as from the cold bending of the second glass sheet 120. As regards the second glass sheet 120, said surface stresses are essentially located at the periphery, typically at the level of the edges of larger dimension.

[0070] In the context of the present application, a surface stress is measured by a device operating on the principle of polariscopy such as the Scalp-04 polariscope marketed by GlasStress Ltd, Tallin 10912 Estonia.

[0071] Also, as can be observed in the table of [Fig.3], the flattening coefficient COEFF_FLAT is greater than 250 for the flattening ratios 40%, 60% and 80%. This corresponds in particular to a surface stress lower (in absolute value) than 20 MPa, which corresponds to a stress level which makes it possible to very strongly limit the risk of breakage of the second glass sheet 120 as observed by the inventors.

[0072] In other words, by proposing to consider a geometry that is flatter than that of the state of the art (COEFF_FLAT > 250), it is possible to obtain a very robust asymmetric laminated glazing 100 in which it is not necessary to subject the second sheet of glass 120 to a toughening treatment.

[0073] The inventors were also able to measure that the asymmetric laminated glazing 100 considered in the example of [Fig. 3] has a surface stress level greater than 40 MPa or greater than 80 MPa at the first glass sheet 110 depending on whether the latter has undergone semi-tempering or thermal tempering respectively. Such a stress level at the first glass sheet 110 supports the conclusion that the glazing 100 thus obtained has excellent robustness.

[0074] The asymmetric laminated glazing 100 has been described up to now considering that the flattening coefficient COEFF_FLAT was at least greater than 250. However, nothing precludes considering, in more particular embodiments, a stronger constraint in terms of flattening, such as for example a flattening coefficient COEFF_FLAT at least greater than 500.

[0075] Furthermore, the asymmetric laminated glazing 100 has also been described by considering that the flattening coefficient COEFF_FLAT corresponds to the sum of the first bending ratio R_F and the second bending ratio R_DB. This way of proceeding only corresponds to a variant implementation of the invention, and nothing excludes the flattening coefficient COEFF_FLAT from being equal to only any one of the two bending ratios R_F, R_DB.

[0076] The invention also relates to a method for manufacturing the asymmetric laminated glazing 100 of [Fig. 1]. Said method is implemented using a shaping installation meeting characteristics known to those skilled in the art. Thus, said shaping installation typically comprises a device for heating glass sheets (e.g. an oven), a thermal bending device glass sheets, a device for cold bending glass sheets and a device for thermally reinforcing glass sheets. Steps of said manufacturing method are illustrated in [Fig.4], according to a particular mode of implementation.

[0077] As illustrated by [Fig.4], the manufacturing process begins with a step H10 obtaining the first glass sheet 110 in the flat state as well as the second glass sheet 120 in the flat state. Typically, the first and second glass sheets 110, 120 are cut from a ribbon of float glass. The first and second glass sheets 110, 120 may have the same contour before bending. They may further be shaped at their edges after being cut.

[0078] Generally speaking, the term "obtaining" can cover all or part of the intermediate stages of the production of glass sheets in the flat state (cutting, shaping, etc.), or else refer solely to the fact of obtaining glass sheets which have already undergone all the aforementioned production operations.

[0079] Once the first glass sheet 110 is obtained in the flat state, it is thermally curved during a step H20 of the manufacturing method. Said thermal curving is carried out as a function of said flattening coefficient COEFF_FLAT, that is to say so that the first glass sheet 110 has, once curved, a flattening coefficient at least greater than 250, or even at least greater than 500 as described previously.

[0080] The bending of the first glass sheet 110 therefore determines that of the asymmetric laminated glazing 100 once the latter is finalized. Bending methods suitable for a glass sheet are for example of the “bending on the move between two beds of rollers” type (as described in documents WO2005047198 or WO2004033381) or of the “bending by pressing” type (as described in documents WO0206170 or WO2017178733).

[0081] The first glass sheet 110 is then thermally reinforced (tempered or semi-tempered) during a step H30 of the manufacturing process.

[0082] The manufacturing method then comprises a step H40 of assembling the first and second glass sheets 110, 120 into said laminated glazing 100, the interlayer 130 being placed between the first and second glass sheets 110, 120. Said assembly notably comprises cold bending of the second glass sheet 120 against the first glass sheet 110.

[0083] In practice, the assembly of the asymmetric laminated glazing 100 from the first and second glass sheets 110, 120 and the interlayer 130 can be carried out according to any method known to those skilled in the art. In its general principle, this assembly comprises a pre-assembly in which the interlayer 130 is deposited on one of the faces of the first glass sheet 110 or the second glass sheet 120. More specifically, in the case where the intermediate layer 130 is made of PVB or EVA, it is typically deposited on the face 2 of the first glass sheet 110. If, on the other hand, the interlayer 130 comprises an OCA material, in particular a liquid OCA material, the latter is deposited on the face 3 of the second glass sheet 120. Subsequently, a suitable device bears against the face 4 of the second glass sheet 120, for example at a central zone of said second glass sheet 120, in order to deform it cold and press it against the first glass sheet 110. It should be noted that in the case where an OCA material, in particular a liquid OCA material, is used, the assembly step H40 may also include drying of the stack formed by the sheets 110, 120 and the interlayer 130.

[0084] In a more specific example of implementation, the assembly step H40 may also comprise, after the cold bending of the second glass sheet 120, holding in position the stack formed by the first and second glass sheets 110, 120 and the interlayer 130. Such holding in position advantageously makes it possible to stabilize said stack and thus minimize the risks of misalignment between the first glass sheet 110 and the second glass sheet 120. Said holding may be carried out according to any method known to those skilled in the art, for example by means of clamps or the creation of hot spots between the glass sheets 110, 120.

[0085] In the embodiment described with reference to [Fig. 4], the manufacturing method also comprises a step H50 of extracting air contained in the assembled asymmetric laminated glazing 100. This step H50 of extracting air or “deaerating” is for example carried out at the same time as the drying of the assembled asymmetric laminated glazing 100 when the interlayer 130 comprises an OCA material, in particular a liquid OCA material.

[0086] Said air extraction step H50 is for example carried out by calendering the assembled asymmetric laminated glazing 100.

[0087] However, the fact of considering calendering the assembled asymmetric laminated glazing 100 only constitutes a variant implementation of the invention. Generally speaking, any air extraction method known to those skilled in the art can be envisaged, such as for example a vacuum (the assembled glazing 100 being for example enclosed in a bag in which a vacuum is created).

[0088] It should be noted that when the asymmetric laminated glazing 100 comprises a PVB interlayer, in particular for example an acoustic PVB, the manufacturing method may also comprise, after the assembly step H40, an autoclaving step (not shown in [Fig.4]) of the assembled glazing 100.

Claims

Claims

1. Laminated glazing (100) comprising a first and a second glass sheet assembled by an interlayer (130), the first glass sheet (110) being thermally reinforced and having a thickness greater than 1.8 mm, the second glass sheet (120) being free of toughening treatment and having a thickness less than 1.6 mm, said glazing having at least a first bending curvature defining a bending depth (F, DB) between a surface arc (ARC_F, ARC_DB) and a chord (C_F, C_DB) supporting said arc, so as to be associated with a first bending ratio (R_F, R_DB) between the length of said chord and said bending depth, said glazing being further shaped so that a flattening coefficient (COEFF_FLAT) at least equal to said first bending ratio is greater than 250.

2. Glazing (100) according to claim 1, wherein the glazing has a second bending curvature in a direction essentially perpendicular to the first bending curvature, so as to be associated with a second bending ratio (R_F, R_DB), said flattening coefficient (COEFF_FLAT) being equal to the sum of said first and second bending ratios.

3. Glazing (100) according to any one of claims 1 to 2, in which the flattening coefficient (COEFF_FLAT) is greater than 500.

4. Glazing (100) according to any one of claims 1 to 3, wherein the thickness of the second glass sheet (120) is less than 1.2 mm, for example less than 1 mm.

5. Glazing (100) according to any one of claims 1 to 4, wherein the thickness of the first glass sheet (110) is greater than 2.1 mm, or greater than 2.6 mm, or greater than 2.85 mm, or greater than 3.15 mm, or greater than 3.5 mm or greater than 3.85 mm.

6. Glazing (100) according to any one of claims 1 to 5, in which the interlayer (130) comprises a polymer material comprising a layer of polyvinyl butyral having a loss factor tan(δ) greater than 0.8 and a shear modulus G' less than 20 MPa at frequencies between 500 Hz and 5000 Hz at a temperature of 20°C.

7. Glazing (100) according to any one of claims 1 to 6, in which the interlayer (130) comprises an adhesive material transparent “OCA” type, such as latex glue.

8. Glazing (100) according to any one of claims 1 to 5, in which the interlayer (130) is made of ethylene-vinyl acetate.

9. Use of a glazing (100) according to any one of claims 1 to 8 in a dwelling or means of road, air, sea or rail transport, preferably as window glazing in motor vehicles, in particular as windshield, rear glazing, side glazing or roof glazing.

10. Motor vehicle comprising glazing (100) according to any one of claims 1 to 8.

11. A method of manufacturing a glazing unit (100) according to any one of claims 1 to 8, said method comprising steps of: - obtaining (H10) the first glass sheet (110) in the flat state as well as the second glass sheet (120) in the flat state, - thermal bending (H20) of the first glass sheet as a function of said flattening coefficient (CEOFF_FLAT), - thermal strengthening (H30) of the first glass sheet, - assembling (H40) the first and second glass sheets into a laminated glazing unit, the interlayer (130) being placed between the first and second glass sheets, said assembly comprising cold bending of the second glass sheet against the first glass sheet, - extracting (H50) air contained in the assembled laminated glazing unit.

12. A method according to claim 11, wherein the air extraction step is carried out by calendering the laminated glazing.

13. A method according to any one of claims 11 to 12, wherein the laminated glazing to be manufactured is in accordance with any one of claims 6 to 7, said method further comprising, after the air extraction step, a step of autoclaving the assembled laminated glazing.

14. Method according to any one of claims 11 to 13, in which the assembly step comprises, after cold bending of the second glass sheet, holding in position the stack formed by the glass sheets and the interlayer.

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