Soundproofing laminated window for vehicles

ABSTRACT

The invention relates to a soundproofing window in which an intermediate film provides for damping of vibrations transmitted in particular by structure-borne conduction.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DETAILED DESCRIPTION OF THE INVENTION

The window according to the invention is preferably designed to ensure soundproofing of a vehicle and in particular soundproofing against noises of structure-borne origin, and is made of a laminated window comprising at least one glass sheet and one intermediate film having a loss factor tan δ greater than 0.6 and a shear modulus G′ smaller than 2×107 N/cm2 in a temperature range between 10 and 60° C., in a frequency range between 50 and 10,000 Hz. These measurements of the dynamic characterization of the material are performed on a viscoanalyzer, for example a Metravib viscoanalyzer, under measurement conditions to be defined hereinafter.

The technique of the invention makes it possible to obtain a soundproofing window made of a laminated window in which the intermediate film brings about damping of the vibrations originating from the engine and transmitted in particular by the car body, to the effect that the radiation of vibrational modes of the window are attenuated so much that coupling with the vibrational modes of the passenger compartment no longer takes place, regardless of engine speed.

According to one embodiment of the invention, the intermediate film imparting damping properties is associated with at least one film of normal acoustic performances. Thus it is permissible to replace part of the thickness of an expensive acoustic film by a “normal” and inexpensive film without deterioration of the acoustic properties but with, for example, an appreciable improvement of the mechanical properties as well as with the entire range of additional properties that can be imparted to such a film: colors, anti-UV, light diffusion, etc.

According to another preferred embodiment of the invention, the intermediate film is a film of thermoplastic acrylic polymer 0.05 to 1.0 mm thick, and this film is joined to a glass sheet with interposition of a polyester film 0.01 to 0.1 mm thick and a layer of thermoplastic cement 0.3 to 0.8 mm thick. In accordance with the invention, a thin film of polyester, especially polyethylene terephthalate, is also interposed between the acrylic polymer film and the layer of thermoplastic cement.

It has been observed that a laminated window of this structure not only can be made without problems by means of standard assembly processes and thus be suitable for series production, but also can permit the exclusion of all the unfavorable influences of the acrylic polymer film by the addition of a thin film of PET between the acrylic polymer film and the layer of thermoplastic cement, which preferably is made of a film of polyvinylbutyral, which is standard for production of laminated windows. In fact, when the acrylic polymer film is in direct contact with the polyvinylbutyral film, particles of the plasticizer of the PVB film apparently diffuse into the acrylic polymer where they cause cloudiness effects as well as deterioration of the noise-damping properties. Surprisingly, the PET films, even if they have only a very thin thickness of less than 50 μm, represent a perfect barrier to diffusion of the plasticizer from the PVB film. In addition, by virtue of their surface properties, the PET films become joined both to the thermoplastic acrylate film and to the standard PVB films, to the effect that the laminated windows according to the invention satisfy all the requirements, even those concerning long-term strength and safety.

In its simplest embodiment, the laminated window according to the invention is made of two glass sheets between which there are interposed the above-mentioned films in the following sequence of layers: PVB-PET-acrylate-PET-PVB. Obviously the standard PVB films can also be replaced by thermoplastic cement films made of other materials, particularly such films made of appropriate thermoplastic polyurethanes.

According to another embodiment, the laminated window according to the invention consists of only one glass sheet which, in mounted condition, faces the outside, while the surface of the laminated window facing the passenger compartment is formed by a polymer layer having adequate abrasion resistance. Such windows of glass and synthetic material offer certain advantages as regards the weight and safety properties, and are known as such in different forms.

Films made of viscoelastic acrylic polymers having a shear modulus G′ between 106.5 Pa at 0° C. and 104.5 Pa at 60° C. as well as a loss factor tan δ between approximately 0.8 and 1 in a temperature range of 0 to 60° C. have proved particularly appropriate for the invention. They include, for example, the products of the 3M Corporation sold under the name “Scotchdamp Polymers”, the product brochures and MSD sheets thereof being incorporated herein by reference. These products comprise acrylic polymers that do not contain plasticizers and have damping properties covering a broad temperature range. The product type ISD 112, the damping properties of which are in the temperature range between 0 and 60° C., has proved particularly appropriate. The preparation of intermediate films meeting the characteristics described herein is within the skill of the ordinary artisan.

According to an advantageous embodiment of the invention, one of the layers of the laminated window, particularly a polyethylene terephthalate film, is provided with a layer that reflects infrared radiation.

The present invention also relates to the intermediate film that imparts damping properties with respect to vibrations, transmitted in particular by structure-borne conduction.

According to one embodiment of the invention, the laminated window contains two glass sheets of identical thickness. This common thickness is not limited, and may be equal to 2.2 mm. Thus the technique of the invention makes it possible to obtain a soundproofing window with relatively small total thickness.

According to a particular embodiment of the invention, the intermediate film imparting noise-damping properties is based on plasticizer and polyvinylacetal resins.

According to an advantageous embodiment of the invention, the shear modulus G′ of the intermediate film imparting noise-damping properties is between 106 and 2×107 N/m2.

The laminated window according to the invention is preferably used for acoustic attenuation of noises of structure-borne origin.

The windows according to the invention have the advantage that good insulation with respect to noises of structure-borne origin is achieved, as is also good insulation with respect to noises of aerodynamic origin and external noises.

The dynamic characterization of the intermediate film is performed on a viscoanalyzer of the Metravib viscoanalyzer type, under certain measurement conditions as listed hereinbelow:

sinusoidal loading,

double-shear test specimen, made of two rectangles of the following dimensions:

thickness=3.31 mm

width=10.38 mm

height=6.44 mm

dynamic amplitude: ±5 mm around rest position,

frequency range: 5 to 700 Hz

temperature range: −20 to +60° C.

By means of the viscoanalyzer, a material specimen can be subjected to deforming loads under precise temperature and frequency conditions, so that the entirety of the Theological variables characterizing the material can be measured and treated.

The raw data of the measurements of force, displacement and phase shift as a function of frequency at each temperature are processed according to techniques known to those of ordinary skill in the art in order to calculate, in particular, the following variables:

elastic component (or shear modulus) G′,

tangent of the loss angle (or loss factor) tan δ.

The master curves of G′ and tan δ are therefore plotted as a function of frequency at different temperatures by using the frequency/temperature equivalence law.

These master curves are processed to reveal the glass transition zones. The damping at the glass transition point is then calculated.

In fact, it is at the glass transition point that damping is best.

The technique according to the invention provides a laminated window for vehicles comprising an intermediate film having good damping of noises transmitted by solids. This damping can also satisfy the criteria of insulation against aerodynamic noises and external noises. Thus the window according to the invention makes it possible to achieve good general soundproofing.

DETAILED DESCRIPTION OF THE FIGURES AND EXAMPLES

FIG. 1 is a partial cross-sectional view of the structure of a laminated window such as used for windshields and also increasingly for the side windows and rear windows. Of course, it is also possible to use the same structure for windshields and rear windows of automobiles, possibly with silicate-glass sheets of slightly different thicknesses.

The laminated window is made of two silicate glass sheets , each 1.8 to 3 mm in thickness, two polyvinylbutyral layers , each 0.38 mm in thickness, two thin PET films , , and one film of viscoelastic acrylic polymer interposed between the PET films. The PET films , respectively have a thickness of 0.05 mm. The film consists of a film of Scotchdamp polymer of 0.05 mm thickness, of ISD 112 type, made by 3M. The different layers are juxtaposed in the manner that is standard for fabrication of laminated windows, and they are assembled at elevated temperature and under pressure.

The PET film or the PET film can be placed on one face of a system of layers that reflect infrared radiation. In addition to its noise-damping properties, such a window capable of reflecting infrared radiation ensures a greater thermally insulating effect with respect to incident thermal radiation. In addition, the laminated windows according to the invention have greater shattering resistance by virtue of the integration of PET films, and so automobile windows of very great comfort can be made in this way.

The laminated window shown in FIG. 2 comprises only one silicate-glass sheet . The silicate-glass sheet , with thickness of 4 mm, for example, is turned such that it faces toward the outside of the automobile when in installed condition. A PVB layer of 0.76 mm thickness is joined to the silicate-glass sheet . The PVB layer is followed by a PET film of 0.05 mm thickness, a Scotchdamp polymer film of ISD 112 type of 0.05 mm thickness, and a PET film of 0.1 mm thickness, which is provided on its free surface with an abrasion-resistant layer . As in the case of the first described embodiment, the PET film or the PET film can also be provided if necessary with a layer that reflects infrared radiation, for example a multiple layer applied by a vacuum process and comprising a functional layer of silver.

The diagram shown in FIG. 3 demonstrates the improvement of noise damping achieved by the invention. In this diagram, the noise damping expressed in dB is plotted as a function of frequency, both for a laminated window of standard structure (curve A) and for a laminated window with the structure described with reference to FIG. 1 (curve B). The measurements are performed on flat laminated windows with dimensions of 80×50 mm at 20° C. The thickness of the silicate-glass sheets in both cases is 2.1 mm. The comparison model exhibiting the damping profile of curve A has the following structure: 2.1 mm of glass, 0.76 mm of PVB, 2.1 mm of glass, while the model according to the invention has the following structure: 2.1 mm of glass, 0.38 mm of PVB, 0.05 mm of PET, 0.05 mm of acrylic polymer, 0.05 mm of PET, 0.38 mm of PVB, 2.1 mm of glass.

The results show that the degree of damping of the window according to the invention is superior to the degree of damping of the comparison window in by far the greater part of the frequency spectrum. Nevertheless, it is especially in the region approximately between 200 and 300 Hz and in the coincidence frequency region at approximately 3000 Hz, where the damping curves of the windows exhibit the greatest valleys in the case of the standard laminated window, that the measured degrees of noise damping are clearly higher, and so, on the whole, a considerable improvement of noise damping is achieved.

French Patent Application 96 14 404 and German Patent Application 197 05 586.3 are incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and characteristics of the invention will become apparent in the following description, provided with reference to the attached drawings, wherein:

FIG. 1 shows a first embodiment of the laminated window according to the invention,

FIG. 2 shows a second embodiment of the laminated window according to the invention; and

FIG. 3 shows the degree of damping as a function of the frequency of a standard laminated window and of the laminated window shown in FIG. .

CLAIMS

1. A laminated window comprising a glass sheet and an intermediate film, wherein said film has a loss factor tan δ greater than 0.6 and a shear modulus G′ smaller than 2×107 N/m2 in a temperature range between 10 and 60° C. and in a frequency range between 50 and 10,000 Hz, wherein said intermediate film is associated with at least one film of normal acoustic performance.

2. A laminated window comprising a glass sheet and an intermediate film, wherein said film has a loss factor tan δ greater than 0.6 and a shear modulus G′ smaller than 2×107 N/m2 in a temperature range between 10 and 60° C. and in a frequency range between 50 and 10,000 Hz, further comprising a thermoplastic cement film, a polyester film interposed between the thermoplastic cement film and the intermediate film, and a polyester film juxtaposed on the other face of the intermediate film and provided on its free surface with an abrasion-resistant layer.

3. A laminated window comprising a glass sheet and an intermediate film, wherein said film has a loss factor tan δ greater than 0.6 and a shear modulus G′ smaller than 2×107 N/m2 in a temperature range between 10 and 60° C. and in a frequency range between 50 and 10,000 Hz, wherein the intermediate film comprises viscoelastic polymer made of acrylic polymer without plasticizer having a shear modulus G′ between 104.5 Pa at 60° C. and 106.5 Pa at 0° C. as well as a loss factor tan δ between approximately 0.8 and 1 in a temperature range of 0 to 60° C.

4. A film designed to be used as an intermediate layer in a soundproofing laminated window, said film having a loss factor tan δ greater than 0.6 and a shear modulus G′ smaller than 2×107 N/m2 in a temperature range between 10 and 60° C. and in a frequency range between 50 and 10,000 Hz.

5. The film of claim 4, wherein said film is associated with at least one film of normal acoustic performance.

6. The film of claim 5, wherein said film is a thermoplastic acrylic polymer film 0.05 to 1.0 mm thick, and wherein said film is joined to at least one glass sheet with interposition of a polyester film 0.01 to 0.1 mm thick and a thermoplastic cement film 0.3 to 0.8 mm thick.

7. The film of claim 6, wherein the thermoplastic film comprises viscoelastic polymer made of acrylic polymer without plasticizer having a shear modulus G′ between 104.5 Pa at 60° C. and 106.5 Pa at 0 ° C., as well as a loss factor tan δ between approximately 0.8 and 1 in a temperature range of 0 to 60° C.

8. The film of claim 4, wherein said film comprises plasticizers and polyvinylacetal resins.

9. A film useful as an intermediate layer in a soundproofing laminated window, said film having a loss factor tan δ greater than 0.6 and a shear modulus G′ smaller than 2×107 N/m2 at a temperature of 20° C. and at a frequency of 50 Hz.

10. The film of claim 9, wherein said film is associated with at least one film of normal acoustic performance.

11. The film of claim 10, wherein said film is a thermoplastic acrylic polymer film 0.05 to 1.0 mm thick, and wherein said film is joined to at least one glass sheet with interposition of a polyester film 0.01 to 0.1 mm thick and a thermoplastic cement film 0.3 to 0.8 mm thick.

12. A laminated window comprising a glass sheet and the film of claim 9.

13. A laminated window comprising a glass sheet and the film of claim 10.

14. A laminated window comprising a glass sheet and the film of claim 11.

15. A laminated window comprising a glass sheet and the film of claim 9, wherein said film comprises plasticizers and polyvinylacetal resins.

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