ASYMMETRIC LAMINATED GLASS PANEL

Description

TECHNICAL FIELD

[0001] The invention relates to the field of laminated glazing for vehicles, particularly automobiles, in particular side windows, i.e. glazing fitting the doors of motor vehicles that can be mounted or lowered in the door. TECHNICAL BACKGROUND

[0002] Traditionally, automotive side windows are monolithic and tempered. To improve break-in resistance, these side windows can advantageously be laminated. To maintain good resistance to external impacts (particularly in the event of a break-in and potentially from stone chips) or internal impacts (laminated side windows help keep occupants inside the passenger compartment in the event of an accident and vehicle rollover; they thus prevent irreparable injuries when an occupant is partially ejected from the vehicle), the glass sheets composing the laminated glazing are toughened, that is to say, tempered or semi-tempered. It has already been proposed to produce laminated glazing by bonding a very thin sheet of glass, less than 1 mm thick, possibly cold-formed, with a thicker sheet of glass.However, the very thinness of the laminated sheet necessitates chemical tempering as a hardening treatment, which is an expensive technique. Furthermore, the aim is to produce the lightest possible glass panes, with a weight and thickness no greater than that of standard monolithic glass. Moreover, since these laminated side windows are primarily intended for high-end vehicles, they are expected to offer acoustic insulation and be compatible with frameless doors, meaning doors without an upper frame. In this case, the glass must be sufficiently rigid so that its upper edge fits perfectly into the groove provided for this purpose in the bodywork at the top of the door opening when the window is raised.Indeed, it was observed that when the vehicle is moving at high speed, it could be difficult to fully raise a window that is not rigid enough, because of a pressure differential between the inside and outside of the vehicle causing a significant deformation of this window.

[0003] WO 2020 / 020937 A1 discloses a laminated vehicle glazing comprising a first sheet of soda-lime silico-mineral glass of a thickness e1 of between 1.5 mm and 2.5 mm, a second sheet of mineral glass and a lamination interlayer, the first and second sheets of mineral glass being bonded together adhesively by means of the lamination interlayer, said laminated glazing being characterized in that the second sheet of mineral glass is a soda-lime silico-mineral glass having a thickness e2 of between 0.4 and 1.1 mm; said second sheet of soda-lime silico-mineral glass is chemically hardened; and the surface compressive stress of said second sheet of soda-lime silico-mineral glass is between 350 MPa and 550 MPa. The lamination interlayer is preferably made of PVB, with a thickness in the range of 0.05 to 4 mm. SUMMARY OF THE INVENTION

[0004] The invention addresses the aforementioned problems and enables the production, at a reasonable cost, of laminated glazing with an exceptional compromise of properties. The invention stems from the desire to use glass sheets thick enough to be thermally strengthened without the need for chemical tempering. To achieve this, and based on current state-of-the-art technology, it is estimated that these sheets must have a thickness of at least 1 mm.

[0005] For the same glass thickness, laminated glass has a lower flexural modulus than monolithic glass. Indeed, according to plate mechanics theory, the flexural modulus R (representing the capacity to resist imposed bending forces) of a sheet of glass is proportional to its thickness T cubed, according to the formula: R = K E μ ⋅ T 3 in which K is a proportionality coefficient depending on the elastic modulus E of the material and its Poisson's ratio µ. This is why, when comparing the flexural stiffness Rm of a monolithic glass with a thickness between 2.85 and 4.85 mm and that Rf of a laminate of two glasses whose individual thicknesses are between 1.6 mm and 2.6 mm, we find that the stiffness of the monolithic glass is much greater: R m = K ⋅ 2 , 85 à 4,85 3 ≫ R f = K ⋅ 1 , 6 à 2,6 3 + 1 , 6 à 2,6 3

[0006] It should be noted that in the Rf formula above, the contribution of the thermoplastic interlayer has been eliminated, which, for temperatures above -10°C, is always very clearly negligible.

[0007] According to the invention, an asymmetrical glazing system is created, meaning that it comprises two sheets of glass of different thicknesses: a glass sheet V1 of thickness E1, and a glass sheet V2 of thickness E2, E1 being greater than E2. V1 is referred to as the thick glass and V2 as the thin glass. Generally, the thin glass is placed on the interior side of the vehicle and can be called the "inner glass." Its outer surface, facing the interior of the vehicle, is generally concave in a vertical direction. Generally, the thick glass is placed on the exterior side of the vehicle and can be called the "outer glass." Its outer surface, facing the exterior of the vehicle, is generally convex in a vertical direction.

[0008] According to the invention, the asymmetry ratio is moderate, such that 0.34 ≤ E2 / E1 ≤ 0.9, and the thin glass is at least 1.1 mm thick. Indeed, the use of very thin glass sheets is avoided due to the following negative observations: Very thin sheets of glass (i.e., less than 1 mm, typically 0.7 or 0.55 mm) are extremely fragile and give rise to numerous breakages at many stages of the process: cutting, shaping, washing before or after forming, possible chemical tempering, assembly, palletizing, etc.; cold bending, possible with very thin sheets (i.e., less than 1 mm, typically 0.7 or 0.55 mm), has proven disappointing for two reasons: 1) a limitation of the geometric complexity achievable by this technique because it affects the optical quality of the edges or the joinability of the two sheets of glass - because the very thin inner sheet of glass tends to form folds at the periphery of the glazing, and 2) it is necessary to strengthen the mechanical properties of the inner sheet of glass by chemical tempering;The chemical tempering operation, necessary to strengthen very thin sheets, has proven to be very poorly suited to the production of automotive products: 1) this operation is too long because it requires maintaining the glass sheet at high temperature for several hours in different baths of alkaline salts in order to obtain the correct levels of surface stress, 2) it results in very poor yields with numerous breakages during handling, washing before or after chemical tempering and during the tempering operation itself, 3) batch work, by nature discontinuous and requiring intermediate stocks, is very disruptive in production workshops.

[0009] Therefore, the invention was designed based on the following principles: 1) use glass sheets with a thickness of 1.1 mm or more, 2) form the two glass sheets using conventional thermal bending (not "cold") and lamination processes, and 3) use thermal (not chemical) strengthening by rapid air cooling to semi-temper or possibly temper each glass sheet; 4) take into account the thickness of the polymer interlayer; indeed, it has been observed that the thicker the interlayer, the more it reduces the rigidity of the laminated glazing.

[0010] The term thermal bending refers to the hot bending of glass at its deformation temperature, resulting in permanent deformation after it returns to room temperature. It is therefore not a cold bending occurring within the elastic range of glass. This thermal bending takes place at a temperature above the glass transition temperature and generally above 550°C.

[0011] Thus, the invention relates firstly to a curved laminated glazing for vehicles comprising two sheets of glass of different thicknesses separated by an interlayer made of polymer material, characterized in that the thickness E1 of the thick glass V1 is such that 1.4 mm ≤ E1 ≤ 3.9 mm, the thickness E2 of the thin glass V2 is such that 1.1 mm ≤ E2 ≤ 2.6 mm, the thickness E3 of the polymer material M is such that 0.3 mm ≤ E3 ≤ 1.2 mm, the total glass thickness EV is such that 2.5 mm ≤ EV ≤ 5.7 mm, the ratio of thicknesses E2 / E1 is such that 0.34 ≤ E2 / E1 ≤ 0.9.

[0012] The polymer material referred to as M is generally of the PVB (polyvinyl butyral) type. This polymer material may be of the "acoustic" type, meaning it has the function of reducing sound passing through the glazing. To be classified as acoustic, such a polymer material must comprise at least one layer of polymer material (generally PVB) with 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 evaluated by a person skilled in the art using a plane shear measurement according to ISO 6721 (Determination of dynamic mechanical properties) with a Metravib 01dB or Metravib VA4000 viscoanalyzer.

[0013] This layer of acoustic polymer material can be the sole layer of the interlayer, or it can be juxtaposed with at least one other layer of polymer material. An interlayer with acoustic properties can, in particular, be made by assembling at least three layers of PVB, with an inner layer being softer than the two surrounding layers. Generally, an acoustic polymer material reduces the rigidity of laminated glass somewhat compared to a conventional polymer material. A conventional polymer material is therefore better suited to laminated glass where high rigidity is the primary requirement. A conventional polymer material 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.

[0014] In particular, we have laminated glazing which offers a good compromise between rigidity and acoustics with 0.45 ≤ E2 / E1 ≤ 0.62.

[0015] The more glass the laminated glazing contains, the better its rigidity. Therefore, advantageously, the total thickness EV of glass (EV=E1+E2) in the laminated glazing is such that 3 mm ≤ EV ≤ 5.7 mm, and preferably such that 3.5 mm ≤ EV ≤ 5.7 mm (note that "x ≤ y" means "x less than or equal to y" and that "x ≥ y" means "x greater than or equal to y").

[0016] For a constant total glass thickness (constant EV), as the asymmetry increases, the rigidity also increases, as a consequence of the fact that the rigidity of a glass increases with the cube of its thickness, as explained above. Therefore, if rigidity is a very important criterion, it is advantageous to combine the following: E2 / E1 ≤ 0.88 and preferably E2 / E1 ≤ 0.74 and preferably E2 / E1 ≤ 0.62, and 1.8 mm ≤ E1 and preferably 2.1 mm ≤ E1; where appropriate in combination with the previously mentioned preference for total glass thickness favoring rigidity, i.e. 3 mm ≤ EV ≤ 5.7 mm, and even 3.5 mm ≤ EV ≤ 5.7 mm, and where appropriate in combination with the use of a conventional polymer material (generally PVB) between V1 and V2. Within the framework With this combination, an acoustic polymer (usually including acoustic PVB) can also be placed between the two sheets of glass, if one accepts losing some rigidity in the final glazing.

[0017] If high acoustic performance is required for laminated glass, an acoustic polymer, as described above, is preferably used as the interlayer. However, at equal thicknesses of V1, V2, and M, this generally reduces the rigidity of the laminated glass. To compensate for this loss of rigidity, one might have thought it advisable to significantly increase the thickness asymmetry between the two panes. While this high asymmetry does indeed increase rigidity, it was unexpectedly observed that acoustic performance was degraded. It was therefore ultimately determined that the asymmetry between the two panes should be present but relatively moderate in order to achieve an excellent compromise between acoustic performance and rigidity.

[0018] If acoustics is a very important criterion, then a combination is advantageous: 0.36 ≤ E2 / E1 and preferably 0.39 ≤ E2 / E1 and preferably 0.42 ≤ E2 / E1 and preferably 0.45 ≤ E2 / E1, and 1.4 mm ≤ E2 and preferably 1.6 mm ≤ E2, where appropriate in combination with the already mentioned preference on the total glass thickness favoring rigidity, i.e. 3 mm ≤ EV ≤ 5.7 mm, and even 3.5 mm ≤ EV ≤ 5.7 mm, and preferably in combination with the use of an interlayer comprising an acoustic polymer material, generally an acoustic PVB.

[0019] The two glass sheets can have the same outline before curving. Both glass sheets are curved to the same shape, i.e., the shape of the final glazing unit before assembly into laminated glass. Suitable curving processes for both glass sheets include, for example, "curving between two roller beds" (as in WO2005047198 or WO2004033381) or "pressing" (as in WO0206170 or WO2017178733). The sheets are preferably curved individually, not stacked.

[0020] At least one sheet of glass may be made of soda-lime glass, aluminosilicate glass, or borosilicate glass. Both sheets of glass may be made of soda-lime glass, aluminosilicate glass, or borosilicate glass. The two sheets of glass may be of different types; for example, one may be soda-lime glass while the other is aluminosilicate or borosilicate glass.

[0021] At least one sheet of glass can be tinted. Both sheets of glass can be tinted. Tinted glass is glass containing the desired inorganic pigment (iron oxide, cobalt oxide, chromium oxide, etc.). Specifically, the two sheets of glass can be of different compositions and tints.

[0022] Generally, glass sheets are thermally strengthened, i.e., semi-tempered or tempered, before being assembled into laminated glass. For the purposes of this application, surface stress is measured using a polariscopy instrument such as the Scalp-04 polariscope, marketed by GlasStress Ltd, Tallinn 10912 Estonia. The stress values ​​provided are absolute values, as those skilled in the art can also express them with a negative sign.

[0023] Within the framework of this application, an edge stress is measured by photoelasticity using the Sharples Edge Stress Meter Ref (S-67) from Sharples Stress Engineers LTD, Preston United Kingdom.

[0024] Thermally tempered glass results in a surface stress greater than 90 MPa, typically between 90 and 200 MPa. Thermally toughened (or semi-toughened) glass has a surface stress in the range of 15 to 90 MPa, more commonly in the range of 20 to 60 MPa.

[0025] The glazing according to the invention can be automotive glazing, in particular frameless door glazing.

[0026] The production of semi-tempered (also called "thermally toughened") glass is carried out on the same equipment as that used for thermally tempered glass. The heating conditions are identical, but the cooling airflow is lower, which reduces convective heat exchange with the main glass surfaces. Consequently, the cycle time is longer because it takes more time for the cooling process to eliminate residual stresses in the glass.

[0027] The invention also relates to a method for manufacturing glazing according to the invention, comprising thermal curvature followed by thermal reinforcement by air blowing of two sheets of glass; the assembly of the two sheets of glass into a laminated glazing, a sheet of polymer material being placed between the two sheets of glass and adhering to them.

[0028] Thermal bending of the sheets can be performed on each individual glass sheet. Preferably, both glass sheets are bent to identical shapes, although slight variations in shape are acceptable as long as they remain within the tolerance range of the manufacturing process designed to produce identical shapes. Ideally, both sheets are bent using the same type of bending process. This is because using the same process offers the advantage of producing the most similar shapes possible for different sheets, even if they are of different thicknesses. By "identical process," we mean that both glass sheets are bent using the same principle, that is, both by pressing, both by gravity, or both by conforming as they pass between roller beds.Even if both sheets of glass are curved by the same type of curving process, each may be curved during a different campaign than the one during which the other sheet is curved.

[0029] In cases where each sheet of glass (outer and inner) is formed individually (i.e., not stacked), it is advantageous to circulate them through the furnace and form them one after the other. This allows for a continuous feed to the assembly process immediately after the forming stage. However, when the two sheets of glass are too different, for example in terms of color and / or thickness, it can be difficult to ensure a similar geometry for both types of glass sheets if they are formed immediately after each other during the same production run. For example, a thin, heavily tinted sheet of glass will heat up more quickly than a thick, clear sheet of glass.If these two types of glass sheets follow one another in the same production, it is very likely that the curvature will result in two significantly different families of geometry (one corresponding to thin and tinted glass and the other to clear and thick glass).

[0030] Therefore, if the two glass sheets are too different from each other, it is preferable to form them in batches. A first batch of glass sheets (corresponding, for example, to the outer pane) can be curved, and then, during a second batch, a second batch of glass sheets (corresponding to the inner pane) can be formed. The assembly operation, combining sheets from two separate forming batches, can then be carried out simultaneously with the second forming batch. Thermal curving can thus be performed on both glass sheets individually, using the same process for both sheets, and during two separate production runs for each of these glass sheets.

[0031] Preferably, at least one sheet of glass is thermally strengthened, and preferably both sheets of glass are thermally strengthened. The thermal strengthening is carried out immediately after bending by rapidly cooling the glass by blowing air onto both sides, starting from the bending temperature.

[0032] The assembly of laminated glazing from the glass sheets and the interlayer can be carried out according to methods known to those skilled in the art, generally involving autoclaving. BRIEF DESCRIPTION OF THE FIGURES

[0033] there figure 1 is a perspective view that partially depicts a motor vehicle with an open door and illustrates the example of a so-called "frameless" door; the figure 2 is a schematic representation that depicts the technique used to measure the rigidity of a monolithic or laminated glass; the figure 3 represents a nomogram of the evolution of the rigidity of laminated glazing relative to the rigidity of a monolithic glazing 4.2 mm thick, and this as a function of the thickness ratio of the two sheets of glass contained in said laminated glazing; there figure 4 represents the airborne sound insulation (or STL) as a function of its frequency for different glazing units including a 0.81 mm thick acoustic PVB; the figure 5 represents the evolution of relative stiffness (decreasing curve) and minimum relative acoustic attenuation (increasing curve) as a function of the thickness ratio of the two sheets in laminated glazing equipped with the same acoustic PVB as that of the figures 3 And 4 and under the same temperature conditions (namely 20°C), each curve having the same total glass thickness, i.e. 4.2mm; the figure 6 graphically represents the evolution of the product (in the sense of a multiplication): (relative stiffness - 104%) x (relative decrease of the minimum of STL - 94%) as a function of the thickness ratio of the two sheets of glass, and this, at the same total glass thickness, i.e. in the example 4.2 mm. DETAILED DESCRIPTION

[0034] There figure 1 Figure 1 represents a motor vehicle with an open door 2. This door includes a frameless window 3, meaning that the door does not frame it at its upper edge. It is important that this window be sufficiently rigid so that its upper edge 4 fits snugly into the groove 5 in the bodywork when it is fully closed. The structure of the window 3 conforms to the invention and is shown in the magnified view. It is a laminated glass unit comprising a sheet of glass V1 of thickness E1 and a sheet of glass V2 of thickness E2, these two sheets being bonded together on either side of a sheet M of polymer material of thickness E3, with E1 > E2. The thicker sheet V1 is on the outside of the vehicle and the thinner sheet V2 is on the inside of the vehicle. The concave face of the glass unit is on the inside of the vehicle.

[0035] There figure 2 This represents the technique used in this application to measure the stiffness of monolithic or laminated glass. A rectangular pane of glass 1 (laminated or monolithic), with dimensions similar to those of a car door window, is held fixedly by an edge 2, and a known bending force F is applied to the edge 4 opposite the fixed edge. A fixed bar 6 holds the bottom of the pane in position. The displacement caused by the force F is measured by a sensor 5. The ratio of the force to the displacement is considered a measure of stiffness. Given that, for a given glass thickness, stiffness increases as asymmetry increases, a symmetrical pane of glass with a constant total glass thickness is taken as the reference. The following examples provide relative stiffness values.This method of measuring stiffness can be simulated using a finite element numerical model, taking into account the contribution of the polymer interlayer as a function of temperature, and whose results have been correlated with experimental data. These simulations were used to establish the curves. figures 3 And 5 Note that for these simulations, we considered a 0.81 mm thick Sekisui brand acoustic PVB, reference RZN 12 SAF, meeting the conditions indicated above for acoustic PVB, at a temperature of 20°C. Of course, we verified at a representative number of points that the simulations accurately reflected reality.

[0036] There figure 3 This represents a nomogram showing the evolution of the rigidity of laminated glass relative to the rigidity of a 4.2 mm thick monolithic pane, as a function of the thickness ratio of the two glass sheets contained in the laminated glass. Each curve assumes a constant total glass thickness, which varies from 2.85 to 5.6 mm. Points on the y-axis (with a ratio of 0) therefore correspond to monolithic glass, and those with a ratio of 1 correspond to symmetrical laminated glass (both glass sheets having the same thickness). All the curves show the same trend: monolithic glass has a significantly higher rigidity than any laminated glass containing the same amount of glass. Furthermore, for laminated glass, the closer the thickness ratio of the sheets approaches 1 (with a constant quantity of glass), the lower the rigidity.

[0037] There figure 4 This represents the airborne sound transmission loss (STL) as a function of frequency for different glazing units containing 0.81 mm thick Sekisui brand acoustic PVB, reference RZN 12 SAF, meeting the conditions specified above for acoustic PVB. Airborne sound transmission losses were determined from measurements carried out according to EN ISO 10140 on 500 mm x 800 mm glazing units at a temperature of 20°C (+ / - 3°C). For comparison, the same measurements were taken on 4.85 mm thick tempered glass. The 2000-5000 Hz frequency range is particularly important for two reasons. First, this is the frequency range in which the human ear has the greatest sensitivity.Furthermore, the critical frequency for a person skilled in the art for this type of glazing, with a total glass thickness of 2.5 to 6 mm, lies within the 2000-5000 Hz frequency range due to the presence of minimal acoustic attenuation. Therefore, for simplicity, we refer to this frequency range as the "critical frequency range." This is particularly important because, in the case of car doors, the passengers' ears are located in close proximity to the side windows and thus to their acoustic radiation, linked to acoustic excitations in this frequency range, such as turbulence from rearview mirrors. Analysis of the various curves in this spectral range highlights the presence of coincidence frequencies for different glazing types that have a detrimental impact on airborne noise reduction.The composition exhibiting the best level of airborne sound insulation in the 2 kHz - 5 kHz band corresponds to symmetrical glazing of 2.6 / 2.6 mm. Tempered glass exhibits the lowest level of sound insulation, with a coincidence frequency of 2500 Hz. Under the conditions of these tests, the sound attenuation in the critical frequency range shows a difference of approximately +9 dB in favor of symmetrical laminated glazing compared to tempered monolithic glass, with a similar total glass quantity (less than 10% difference). Continuing this analysis, for asymmetrical laminated glazing with a similar total glass quantity, a difference in favor of symmetrical laminated glazing of +2 dB and +3.5 dB is observed compared to glazing with an inner-to-outer glass thickness ratio (E2 / E1) of 0.46 and 0.29, respectively.

[0038] There figure 5 represents the evolution of relative stiffness (decreasing curve) and minimum relative acoustic attenuation (increasing curve) as a function of the thickness ratio of the two sheets in laminated glazing equipped with the same acoustic PVB as that mentioned for the figures 3 And 4 and under the same temperature conditions (namely 20°C), each curve being at the same total glass thickness, i.e. 4.2mm.

[0039] Regarding stiffness values, the reference used is 2.1 / 2.1mm laminated glass. In the figure, for each thickness ratio point, the percentage of the intrinsic stiffness of each simulation relative to the stiffness of the previously defined reference glass is plotted.

[0040] The acoustic values ​​were determined by taking the minimum of STL at the critical frequency (or first frequency of coincidence in the 2000 to 5000 Hz band defined previously as illustrated by the figure 4 ), for each thickness ratio and for the same total glass thickness (4.2 mm). Next, the relative evolution of the minimum STL in the critical frequency range was determined with respect to the same reference values ​​as for the stiffness curve (2.1 / 2.1 mm symmetrical laminated glass). To do this, for each thickness ratio considered, each of these values ​​(minimum STL) was subtracted from the corresponding value of the reference glazing, the result was then divided by the value of the reference glazing, and the result was then converted to a percentage by multiplying by 100. The thickness ratio range of 0.34 to 0.9 can be considered to allow for the production of laminated glass with an excellent compromise between acoustic properties and stiffness.

[0041] These curves of the figure 5 These values ​​demonstrate that there exists a range of thickness ratios within which the rigidity of a glazing unit is increased by at least 4% (i.e., 104% of the reference value) compared to that of a symmetrical glazing unit of equal total glass thickness, while maintaining a minimum sound loss of at least 94% of that of a symmetrical laminated glazing unit of equal total glass thickness. These values ​​are chosen based on known applications of automotive glazing and correspond to the perception threshold for vehicle occupants. For example, in the case of acoustic performance, a 2.1 / 2.1 mm symmetrical laminated glazing unit incorporating a 0.81 mm thick Acoustic PVB (defined above) exhibits a minimum STL (Sound Level Limit) in the critical frequency range of 2-5 kHz of approximately 38 dB.Therefore, a change of -6% (100-94%) corresponds to a decrease in the minimum STL of the order of 3 dB when rounded up to the nearest whole number, even though a person skilled in the art considers the threshold of perception of the human ear to be 3dB.

[0042] Having defined that, the figure 6 graphically represents the evolution of the product (in the sense of a multiplication): (relative stiffness - 104%) x (relative decrease in the minimum STL - 94%) as a function of the thickness ratio of the two glass sheets, assuming a constant total glass thickness, i.e., 4.2 mm in our example. Seeking glass combinations that provide both good stiffness and minimal degradation of the minimum STL in the critical frequency range, with a constant total glass thickness, we preferentially look for asymmetric laminated glazing that allows the product defined above to be positive. For the figure 6 (total glass thickness = 4.2 mm), this range corresponds to a thickness ratio between the panes of glass ranging from 0.34 to 0.9. In all cases, a good compromise between rigidity and acoustics exists for a thickness ratio within the range of 0.45 to 0.62. A maximum is observed, demonstrating the existence of a compromise that simultaneously optimizes acoustic and rigidity performance. In this example of the figure 6 , the optimum ratio of the thicknesses of the two sheets of glass is 0.5.

Claims

1. A formed laminated glazing (3) for a vehicle (1), comprising two sheets of glass (V1, V2) of different thicknesses separated by an interlayer (M) made of polymer material, characterized in that - the thickness E1 of the thick glass V1 is such that 1.4 mm ≤ E1 ≤ 3.9 mm, - the thickness E2 of the thin glass V2 is such that 1.1 mm ≤ E2 ≤ 2.6 mm, - the thickness E3 of the polymer material M is such that 0.3 mm ≤ E3 ≤ 1.2 mm, - the total glass thickness EV is such that 2.5 mm ≤ EV ≤ 5.7 mm, - the ratio of the thicknesses E2 / E1 is such that 0.34 ≤ E2 / E1 ≤ 0.9.

2. The glazing according to the preceding claim, characterized in that the total glass thickness EV is such that 3 mm ≤ EV ≤ 5.7 mm, and preferably such that 3.5 mm ≤ EV ≤ 5.7 mm.

3. The glazing according to one of the preceding claims, characterized in that the polymer material comprises a PVB having a tan(δ) loss factor of greater than 0.8 and a shear modulus G' of less than 20 MPa at frequencies of between 500 Hz and 5000 Hz at the temperature of 20°C, these parameters being measured in accordance with ISO 6721, referred to as acoustic PVB.

4. The glazing according to the preceding claim, characterized in that - 0.36 ≤ E2 / E1 and preferably 0.39 ≤ E2 / E1 and preferably 0.42 ≤ E2 / E1 and preferably 0.45 ≤ E2 / E1, and 1.4 mm ≤ E 2 .

5. The glazing according to the preceding claim, characterized in that 1.6 mm ≤ E2.

6. The glazing according to one of claims 1 to 3, characterized in that - E21E1 ≤ 0.88 and preferably E21E1 ≤ 0.74 and preferably E21E1 ≤ 0.62, and 1.8 mm ≤ E 1 .

7. The glazing according to the preceding claim, characterized in that 2.1 mm ≤ E1.

8. The glazing according to one of the preceding claims, characterized in that 0.45 ≤ E2 / E1 ≤ 0.62.

9. The glazing according to one of the preceding claims, characterized in that at least one sheet of glass is thermally reinforced and preferably in that the two sheets of glass are thermally reinforced.

10. The glazing according to one of the preceding claims, characterized in that the two sheets of glass are of different composition and hue.

11. The glazing according to one of the preceding claims, characterized in that it is a motor vehicle glazing, particularly for a frameless door.

12. A vehicle (1) comprising the glazing (3) of one of the preceding claims.

13. The vehicle according to the preceding claim, characterized in that the glazing is mounted in a frameless door (2).

14. A method for manufacturing a glazing of one of the preceding glazing claims, comprising - hot forming followed by thermal reinforcement by blowing air for the two sheets of glass, then, - assembling the two sheets of glass into a laminated glazing, one sheet of polymer material being placed between the two sheets of glass and adhering to them.

15. The method according to the preceding claim, characterized in that the hot forming gives the two sheets of glass identical shapes.

16. The method according to one of the preceding process claims, characterized in that the hot forming is carried out on each sheet in the individual state, the same type of forming process being used for forming the two sheets of glass.

17. The method according to the preceding claim, characterized in that the hot forming is carried out over two separate production runs for each of these sheets of glass.