Glazing with a thermoplastic viscoelastic interlayer for vibration and acoustic damping

Description

[0001] The invention relates to a viscoelastic plastic interlayer intended to be incorporated between two sheets of glass to form a laminated glazing having vibro-acoustic damping properties, intended in particular for means of locomotion, especially a motor vehicle.

[0002] Among all the qualities contributing to comfort in modern means of transport such as trains and automobiles, silence has become crucial.

[0003] Acoustic comfort has been improved for several years now by addressing noises, such as engine, rolling or suspension noise, at their origin or during their propagation through the air or in solids, using, for example, absorbent coatings or elastomer connecting pieces.

[0004] The shapes of the vehicles have also been modified to improve air penetration and reduce turbulence, which is itself a source of noise.

[0005] And in recent years, research has focused on the role that glazing can play in improving acoustic comfort, particularly laminated glazing with interlayer plastic films. Laminated glazing also offers other advantages, such as eliminating the risk of shards flying in the event of sudden breakage and acting as a burglar deterrent.

[0006] It has been shown that the use of standard plastic films in laminated glazing is unsuitable for improving acoustic comfort. Specific plastic films have therefore been developed that offer damping properties enabling improved acoustic comfort.

[0007] Furthermore, in existing windshields, the thickness of the glass pane facing outwards is generally 2.1 mm, and the thickness of the glass pane facing inwards is generally 1.6 mm. However, the trend is towards making motor vehicles lighter in order to reduce their fuel consumption and the resulting CO2 emissions. One way to achieve this is to offer lighter automotive glazing. One solution to reduce the weight of glazing is to decrease the thickness of the glass panes. However, this reduction in thickness leads to a degradation of the acoustic properties of laminated glass. US 2012 / 094084 A1 describes an interlayer for incorporation into laminated glass that makes it possible to obtain thinner and more economical glazing that also possesses the durability and soundproofing properties associated with thicker and heavier glazing.

[0008] Furthermore, it is also important to respect the privacy of people inside a vehicle or to protect the driver of a vehicle from glare in sunlight or simply for an aesthetic effect.

[0009] There is therefore a need for a viscoelastic plastic interlayer intended to be incorporated between two sheets of glass to form a laminated glazing with vibro-acoustic damping properties, which allows a reduction in the thickness of the glass sheets without degradation of the vibro-acoustic damping properties, while ensuring respect for the privacy of people inside a vehicle or protection of the driver of a vehicle against glare in sunlight or simply for an aesthetic effect.

[0010] To this end, the invention proposes a glazing as described in claim 1. Dependent claims 2 to 6 describe preferred embodiments.

[0011] The invention also relates to a motor vehicle comprising glazing as described above, the glass sheet with a thickness between 0.5 mm and 2.6 mm being turned towards the outside of the vehicle and the glass sheet with a thickness between 0.5 mm and 1.6 mm being turned towards the inside of the vehicle.

[0012] The invention also relates to a use of the glazing described above as a windshield for a motor vehicle.

[0013] According to another feature, the glazing is used as a front side window, rear side window, rear window or quarter window of a motor vehicle.

[0014] Other features and advantages of the invention will now be described with reference to the drawings on which: Therefigure 1 represents a curve of sound insulation as a function of frequency, measured on three windshields; The figure 2 represents a cross-sectional view of a glazing according to the invention.

[0015] The invention relates to a viscoelastic plastic interlayer intended to be incorporated between two sheets of glass to form laminated glazing having vibro-acoustic damping properties. The interlayer comprises at least one layer of viscoelastic plastic material with vibro-acoustic damping properties.

[0016] The spacer is such that the resonance frequency f2 of the second resonance mode of a 25 mm x 300 mm surface laminated glazing bar composed of two 2.1 mm thick glass sheets between which the spacer is incorporated, determined by a mechanical impedance measurement (MIM) at 20°C according to ISO 16940 (with only one difference concerning the thickness of the glass sheets of the bar which is 2.1 mm instead of 4 mm), is between 760 Hz and 1000 Hz and the loss factor η2 of the second resonance mode of the same bar, determined by MIM under the same conditions, is greater than or equal to 0.25.

[0017] In addition, the interlayer is dyed throughout at least part of its surface, which allows, in the case of tinting over the whole surface, to respect the privacy of people inside a vehicle or simply for an aesthetic effect, or, in the case of tinting the upper part of a windshield, to protect the driver of a vehicle against glare from sunlight.

[0018] The inventors have demonstrated, as will be seen later, that an interlayer including these characteristics makes it possible to obtain a thinned laminated glazing with acoustic performance equivalent to, or even superior to, that of a laminated glazing with conventional glass thicknesses incorporating a known interlayer with improved acoustic properties.

[0019] The interlayer is intended to be incorporated between two sheets of glass to form laminated glazing according to the invention.

[0020] There figure 2 represents a cross-sectional view of a glazing according to the invention.

[0021] The glazing comprises two sheets of glass 1, 2 between which the spacer is inserted.

[0022] The interlayer is bonded to the glass sheets by known means, for example by stacking the glass sheets and the interlayer and passing the assembly through an autoclave.

[0023] Glass pane 1 of the glazing is designed to face outwards from the vehicle, while glass pane 2 is designed to face inwards. Glass pane 1 is preferably thicker than glass pane 2 so that the glazing provides better protection against external elements (weather, gravel impacts, etc.). Indeed, the thicker the glass, the more mechanically resistant it is. However, the thicker the glass, the heavier it is. A compromise must therefore be found between mechanical resistance and the weight of the glazing. Thus, the thickness of glass pane 1 is, for example, between 0.5 mm and 2.6 mm, preferably between 1.4 mm and 2.0 mm, and the thickness of glass pane 2 is, for example, between 0.5 mm and 1.6 mm, preferably between 1.1 mm and 1.5 mm.

[0024] In existing glazing, the thickness of glass sheet 1 is generally 2.1 mm and the thickness of glass sheet 2 is generally 1.6 mm, for a total glass thickness of 3.7 mm.

[0025] The glazing according to the present invention comprises a total glass thickness strictly less than 3.7 mm, preferably less than or equal to 3.2 mm.

[0026] Preferably, according to the invention, the thickness of glass sheet 1 is 1.8 mm and the thickness of glass sheet 2 is 1.4 mm in order to limit the weight of the glazing, thereby reducing the fuel consumption of a vehicle equipped with such glazing. This also makes the glazing easier to handle and saves material.

[0027] The glazing according to the invention can also have a glass sheet 1 of thickness 1.6 mm and a glass sheet 2 of thickness 1.2 mm, or a glass sheet 1 of thickness 1.4 mm and a glass sheet 2 of thickness 1.1 mm.

[0028] The interlayer consists of at least one layer 3 of viscoelastic plastic with vibro-acoustic damping properties. It is based on polyvinyl butyral and a plasticizer. The amount and type of plasticizer and the degree of acetalization of the polyvinyl butyral allow for known adjustments to the stiffness of a component based on polyvinyl butyral and plasticizer.

[0029] The interlayer also includes two layers 4, 5, called outer layers, between which layer 3 is inserted.

[0030] The outer layers 4 and 5 are made of standard PVB. Layer 3 is less rigid than outer layers 4 and 5 to allow for proper vibration and ensure the desired acoustic damping.

[0031] Alternatively, the interlayer may comprise at least two layers of viscoelastic plastic with vibro-acoustic damping properties, surrounded or not by layers of standard PVB.

[0032] The acoustic characteristics of the spacer are determined by measuring the mechanical impedance (MIM) at 20°C according to ISO 16940 of a 25 mm x 300 mm surface laminated glazing bar composed of two sheets of glass 2.1 mm thick (and not 4 mm as recommended in ISO 16940) each between which is incorporated a spacer according to the invention, i.e. a spacer comprising at least one layer of viscoelastic plastic with vibro-acoustic damping properties.

[0033] MIM allows the determination of resonance frequencies and loss factors of the different resonance modes of the laminated glazing bar.

[0034] The glazing is according to the invention if the interlayer is such that the resonance frequency f 2 of the second resonance mode of the laminated glazing bar determined by MIM is between 760 Hz and 1000 Hz and the loss factor η 2 of the second resonance mode of the laminated glazing bar determined by MIM is greater than or equal to 0.25.

[0035] Preferably, the resonance frequency f2 is between 800 Hz and 900 Hz, which allows for improved acoustic performance by minimizing the degradation of the attenuation level of the laminated glass before the critical frequency. Even more preferably, the resonance frequency f2 is between 800 Hz and 850 Hz, which allows for further improved acoustic performance by minimizing the degradation of the attenuation level of the laminated glass before the critical frequency.

[0036] Preferably, the loss factor η2 is greater than 0.30, which allows for improved acoustic performance by enhancing acoustic damping.

[0037] Mechanical impedance measurement (MIM) is preferably carried out at least one month after the laminated glass bar is assembled, the laminated glass bar itself having been assembled at least one month after the spacer was manufactured. This ensures that the spacer and the laminated glass have reached stable states and therefore allows for the determination of reliable values.

[0038] There figure 1 This represents a curve of sound insulation as a function of frequency, measured on three windshields. The sound insulation of a windshield reflects the acoustic performance that can be observed on a vehicle equipped with that windshield.

[0039] Thus, the first windshield (21-16 known) includes: two sheets of glass with respective thicknesses of 2.1 mm and 1.6 mm, and an interlayer comprising two outer layers of standard PVB and a central layer of viscoelastic plastic with vibro-acoustic damping properties, the interlayer having a resonance frequency f 2 of 675 Hz (± 15 Hz) and a loss factor η 2 equal to 0.35 (± 0.03).

[0040] The first windshield corresponds to a classic windshield with an interlayer with known acoustic damping properties.

[0041] The sound insulation curve (represented by diamonds) of the first windshield shows a dip around 6500 Hz.

[0042] A second windshield (18-14 known) includes: two sheets of glass with respective thicknesses of 1.8 mm and 1.4 mm, and an interlayer comprising two outer layers of standard PVB and a central layer of viscoelastic plastic with vibro-acoustic damping properties, the interlayer having a resonance frequency f 2 of 675 Hz (± 15 Hz) and a loss factor η 2 equal to 0.35 (± 0.03).

[0043] The second windshield is a thinner windshield with an interlayer identical to that of the first windshield.

[0044] The sound insulation curve (represented by squares) of the second windshield shows similar behavior to that of the first windshield up to around 5000 Hz, but a dip shifted towards higher frequencies, around 8000 Hz. This shift in the dip is very problematic because it means that this windshield allows airborne noise at high frequencies, which are unpleasant for the human ear, to pass through.

[0045] A third windshield (18-14 invention) comprises: two sheets of glass with respective thicknesses of 1.8 mm and 1.4 mm, and an interlayer comprising two outer layers of standard PVB and a central layer of viscoelastic plastic with vibro-acoustic damping properties, the interlayer having a resonance frequency f 2 of 800 Hz (± 15 Hz) and a loss factor η 2 equal to 0.30 (± 0.03).

[0046] The third windshield corresponds to a thinned windshield with an interlayer to form glazing according to the invention.

[0047] The sound insulation curve (represented by triangles) of the third windshield shows a behavior similar to that of the first windshield, with a dip recentered around 6500 Hz and sound insulation values ​​similar to those of the first windshield.

[0048] The windshield with an interlayer to form glazing according to the invention therefore makes it possible to compensate for the acoustic degradation linked to the thinning of the glazing.

[0049] The laminated glass according to the invention can be used as a windshield for motor vehicles. In this case, it naturally meets all the requirements of United Nations Regulation No. 43 (Regulation R43) for resistance to severe impacts to ensure its mechanical strength. To this end, in the case of an interlayer comprising two outer layers of standard PVB, the thickness of these outer layers 4, 5 is, for example, adapted in a manner known, for example, by patent application FR 09 52567.

[0050] Furthermore, the interlayer is tinted throughout, at least on part of its surface. When tinted only on the upper portion of a windshield, it protects the driver from glare in sunlight. When tinted across its entire surface, it can provide privacy for occupants. A light tint is purely for aesthetic purposes. If the light transmission is too low compared to existing standards for windshields or front side windows, it can be used in a rear side window, rear window, or quarter window of a motor vehicle.

Claims

1. Glazing comprising: - a glass sheet (1) between 0.5 mm and 2.6 mm thick, - a glass sheet (2) between 0.5 mm and 1.6 mm thick, - an interlayer, the interlayer being between the glass sheets (1, 2), in which the total thickness of the glass sheets (1, 2) is strictly less than 3.7 mm, the interlayer being a viscoelastic plastic interlayer intended to be incorporated between two glass sheets to form a laminated glazing with vibro-acoustic damping properties, the interlayer comprising at least one layer (3) made of viscoelastic plastic with vibro-acoustic damping properties and two outer layers (4, 5) made of standard PVB, the layer (3) being between the two outer layers (4, 5), the layer (3) being based on polyvinyl butyral and plasticizer, and the interlayer being tinted in the bulk at least on a part of its surface, the interlayer being such that the resonant frequency f2 of the second resonance mode of a laminated glazing bar with a surface area of 25 mm × 300 mm composed of two glass sheets each 2.1 mm thick, between which is incorporated the interlayer, determined by measuring the mechanical impedance (MIM) at 20°C according to standard ISO 16940, is between 760 Hz and 1000 Hz and the loss factor η2 of the second resonance mode of the same bar, determined by MIM under the same conditions, is greater than or equal to 0.25.

2. Glazing according to Claim 1, in which the resonant frequency f2 is between 800 and 900 Hz and preferably between 800 Hz and 850 Hz.

3. Glazing according to Claim 1 or 2, in which the loss factor n2 is greater than 0.30.

4. Glazing according to one of Claims 1 to 3, in which the measurement of the mechanical impedance is performed at least one month after assembly of the laminated glazing bar, the laminated glazing bar having itself been assembled at least one month after the manufacture of the interlayer.

5. Glazing according to one of Claims 1 to 4, in which the interlayer is tinted only in its upper part.

6. Glazing according to one of Claims 1 to 5, in which the interlayer is tinted over its entire surface.

7. Motor vehicle comprising glazing according to one of Claims 1 to 6, the glass sheet (1) between 0.5 mm and 2.6 mm thick being turned facing the exterior of the vehicle and the glass sheet (2) between 0.5 mm and 1.6 mm thick being turned facing the interior of the vehicle.

8. Use of the glazing according to one of Claims 1 to 6 as a motor vehicle windscreen.

9. Use of the glazing according to one of Claims 1 to 6 as a windscreen, a front side window, a rear side window, a rear window or a quarter glass of a motor vehicle.