LAMINATED GLAZING REFLECTING INFRARED

Abstract

A laminated glazing includes an outer sheet of clear glass and an inner sheet of clear glass, which are joined to one another by an interlayer of plastic, includes the succession of the following elements, from the inside to the outside of the glazing: the inner sheet of clear glass, a stack of layers reflecting infrared radiation between 780 nm and 2500 nm, the interlayer including successively a) a first thin sheet including a layer of a polymer compound or of a varnish, the polymer compound or the varnish including a dye, the dye absorbing substantially all of the light within the visible region and being substantially transparent to the infrared, b) a second thin sheet of an untinted plastic, the outer sheet of clear glass.

Claims

1. A laminated glazing comprising an outer sheet of clear glass and an inner sheet of clear glass, which are bonded to one another by means of an interlayer, comprising the succession of the following elements, from an inside to an outside of said laminated glazing: said inner sheet of clear glass, a stack of layers reflecting infrared radiation between 780 nm and 2500 nm, said interlayer comprising: a) a first thin sheet comprising or consisting of a layer of a polymer compound or of a varnish, said polymer compound or said varnish comprising a dye, said dye absorbing substantially all of the light within the visible region between 380 and 780 nm and being substantially transparent to infrared radiation, b) a second thin sheet of a plastic that is not bulk-tinted, said outer sheet of clear glass.

2. The laminated glazing as claimed in claim 1, wherein said dye has, as measured with a Perkin-Elmer lambda 900 spectrophotometer, an absorption spectrum between 380 and 2000 nm, at a concentration of 0.5 wt % in a layer with a thickness of 0.25 millimeters of said polymer compound or of said varnish, an averaged absorbance between 800 and 2000 nm at least 5 times lower than the averaged absorbance between 380 and 780 nm.

3. The laminated glazing as claimed in claim 1, wherein said dye has, in a matrix of said polymer compound and at 25° C., an average molar extinction coefficient between 780 nm and 2000 nm at least 5 times less than the average molar extinction coefficient between 380 nm and 780 nm.

4. The laminated glazing as claimed in claim 1, wherein the stack of layers reflecting infrared radiation is a stack comprising at least two functional layers based on silver separated by layers of dielectric materials.

5. The laminated glazing as claimed in claim 1, wherein the polymer compound of the first thin sheet is selected from monomers, oligomers, or polymers comprising at least one methacrylate function, epoxides, varnish comprising dispersed particles of PVB, latex, polyurethane or acrylate.

6. The laminated glazing as claimed in claim 1, wherein the dye is selected from Sudan Black B® (CAS 4197-25-5) or Nigrosine Solvent black 5 (CAS 11099-03-9).

7. The laminated glazing as claimed in claim 1, wherein the dye represents between 0.1 and 10 wt % of the first thin sheet.

8. The laminated glazing as claimed in claim 1, wherein the second thin sheet of an undyed plastic is of polyvinyl butyral (PVB), ethylene/vinyl acetate copolymers (EVA), polyurethane (PU) or polyvinyl chloride (PVC).

9. The laminated glazing as claimed in claim 1, wherein the second thin sheet consists of two sheets of polyvinyl butyral with a sheet of poly(ethylene terephthalate) disposed between them.

10. The laminated glazing as claimed in claim 1, wherein the inner and outer sheets of clear glass have a thickness between 0.7 mm and 5 mm.

11. The laminated glazing as claimed in claim 1, wherein the stack of layers is a system of thin layers with thicknesses between 0.5 and 100 nm which comprises one or more layers based on silver.

12. The laminated glazing as claimed in claim 1, wherein the interlayer comprises successively, with reference to the inner sheet of clear glass: said first thin sheet comprising or consisting of a layer of a polymer compound or of a varnish, then said polymer compound or said varnish comprising a dye, and then said second thin sheet of a plastic that is not bulk-tinted.

13. The laminated glazing as claimed in claim 1, wherein the interlayer comprises successively, with reference to the inner sheet of clear glass: said second thin sheet of a plastic that is not bulk-tinted, then said first thin sheet comprising or consisting of a layer of a polymer compound or of a varnish and then said polymer compound or said varnish comprising a dye.

14. A method comprising forming a roof, side window, or back window of a motor vehicle with a laminated glazing as claimed in claim 1.

15. A method of manufacturing the laminated glazing as claimed in claim 1, comprising at least one first glass sheet and one second glass sheet, the first and second glass sheets being bonded together by a thermoplastic interlayer, the method comprising: depositing a stack of layers reflecting infrared radiation between 780 nm and 2500 nm on an inner face of the first glass sheet, depositing, on said stack of layers, a colored polymer layer or a varnish comprising a dye, said dye absorbing substantially all of the light within the visible region and being substantially transparent to the infrared, drying and/or optionally hardening the polymer layer or varnish comprising the dye, assembling the first glass sheet covered with the stack of layers and the colored polymer layer with an undyed transparent thermoplastic interlayer, and with the second glass sheet, in such a way that the colored polymer layer is in direct contact with said interlayer, degassing, during which air trapped between the first and second glass sheets and the thermoplastic interlayer is eliminated, and heat treating the laminated glazing under pressure and/or under vacuum at a temperature between 100 and 200° C., during which assembly of the laminated glazing is effected.

16. The laminated glazing as claimed in claim 1, wherein said dye is substantially transparent to wavelength between 800 and 2000 nm.

17. The laminated glazing as claimed in claim 1, wherein the second thin sheet is made of thermoplastic.

18. The laminated glazing as claimed in claim 1, wherein the second thin sheet is made of clear PVB.

19. The laminated glazing as claimed in claim 2, wherein the averaged absorbance between 800 and 2000 nm is at least 10 times lower than the averaged absorbance between 380 and 780 nm.

20. The laminated glazing as claimed in claim 3, wherein the average molar extinction coefficient between 780 nm and 2000 nm is at least 10 times less than the average molar extinction coefficient between 380 nm and 780 nm.

Description

[0098] An embodiment example of glazing according to the invention is given hereunder: [0099] A—Manufacture of a laminated structure according to the invention:

[0100] A specimen A, of a laminated structure as described above in connection with FIG. 1, with dimensions 10×10 cm.sup.2, is prepared.

[0101] Specimen A is obtained as follows: [0102] A stack of layers is deposited by the techniques of magnetron-assisted cathode sputtering on a first clear glass with a thickness of 2.1 mm marketed by the applicant company under the reference Planiclear® (T.sub.L of about 90%, undyed). The stack comprises three layers of silver and is described in example 14 of the publication WO2005051858. Its sheet resistance is 1.0 ohm/square, as measured using a type SRM-14T instrument from Nagy Mess Systems). [0103] A liquid composition comprising an acrylate oligomer of the Sartomer CN9002 type (bifunctional aliphatic urethane-acrylate oligomer) and SR 410 monomer (monofunctional aromatic acrylic monomer), prepared at a 50/50 weight ratio, is deposited on this first clear glass. A dye of the Black Sudan B type is added to the acrylate formulation at the rate of a proportion of 0.5 wt % relative to the total weight of the initial composition as well as an amount of a Speedcure 73 photoinitiator equal to 2 wt % of the mixture obtained, is added to induce polymerization.

[0104] The liquid composition thus obtained is deposited with a Mayer bar on the glass substrate covered with the stack and above the latter to obtain a wet layer with a thickness of about 20 micrometers. The layer thus obtained is hardened by UV irradiation (UVB dose of about 280 mJ/cm.sup.2, travel speed of 16 m/min). The thickness of the dry colored layer is about 10-15 μm.

[0105] A thin sheet of clear PVB with a thickness of 0.76 mm, marketed under the reference Saflex RK11 ® by the Eastman company, is placed on the first glass sheet coated with the colored layer and a second clear glass sheet identical to the first is affixed to the interlayer so as to close the laminated glazing. The assembly is autoclaved for 30 minutes, at 130° C. at a pressure of 12 bar. In the course of this autoclaving step, we may optionally observe diffusion of the dye inside the PVB, which tends to homogenize the surface density of the dye. [0106] B—Characterization of the laminated structure according to the invention:

[0107] The optical characterizations of the glazing as described above are carried out with a Lambda900 spectrophotometer from the company Perkin Elmer.

[0108] The accompanying FIG. 3 shows the spectra of transmission (curve 1) and of reflection of the laminated glazing obtained according to the preceding example. The reflection spectra are measured both on the outer face of the glazing (external glass side, curve 3) and on the inner face of the glazing (internal glass side, curve 2).

[0109] It can be seen that the reflection of the near infrared lengths, in the wavelength region between 650 and 900 nm, is almost identical whatever face of the glazing is measured (inner or outer). This characteristic illustrates absence of absorption of the Black Sudan B dye used in the near infrared region.

[0110] Furthermore, reflection of visible light on the outer face is low (R.sub.L<10%). Moreover, the color observed with the naked eye is not very pronounced and is substantially neutral.

[0111] Table 1 below gives the main colorimetry data of the laminated glazing according to the invention:

TABLE-US-00001 TABLE 1 Color in Color in external internal Value Transmission reflection reflection L* 50 25 34.3 a* −1.3 0.4 −4.7 b* −1.8 −1.2 −2.6

[0112] The light transmission T.sub.L is, moreover, reduced efficiently by the colored layer based on acrylate, the T.sub.L integrated from the spectrum in FIG. 3 being measured at 18%. Visually, the laminated glazing obtained looks dark gray in transmission.

[0113] The TTS measured according to standard ISO 13837 convention A, AM1.5 from the spectrum in FIG. 3 is 26%, very close to the values obtained for the configurations of the prior art described above and based on the use of PVB and/or of colored glass.

[0114] According to the invention, it seems possible for the light transmission and the total energy transmission of the glazing to be reduced further by acting on the concentration of dye, to levels that may be up to TLs of the order of 5% and a TTS of the order of 15%. [0115] C—Choice of the dye according to the invention:

[0116] FIG. 2 below shows: [0117] the absorption spectrum of a thin sheet of 0.38 mm of bulk-dyed PVB, commercial RB17 (curve shown with solid line), [0118] the absorption spectrum of a thin sheet of 0.25 mm of an acrylate thin sheet as described above and comprising 0.5 wt % of the dye Black Sudan B (curve shown with dotted line).

[0119] Comparison of the two spectra clearly shows that the thin sheet containing the black dye Sudan B absorbs strongly in the visible region, the dye absorbing almost all of the visible and very little in the near infrared region, notably between 800 and 2000 nm. More particularly, FIG. 2 shows that the average absorption of the acrylate thin sheet between 800 and 2000 nm is lower by a ratio of at least 5, or even of at least 7 or even of at least 10 relative to its average absorption in the visible region (380-780 nm).

[0120] In contrast, the thin sheet comprising colored PVB, commercial RB17, absorbs a substantial part of the IR radiation, notably between 800 and 2000 nm.

[0121] This property of the thin sheet (or of the layer) comprising the dye and its specific positioning in glazing according to the invention, between the incident solar radiation and the stack of IR-reflective layers, thus makes it possible to prevent heating of the glazing, notably under strong insolation, while preserving its selectivity.

[0122] In a preferred embodiment, the laminated glazing according to the invention reflects more than 50%, or even more than 70% of the IR portion of the incident solar radiation to the outside. According to another advantage of the present invention, when viewed from outside, the laminated glazing may have a dark appearance or else a (partial) mirror effect without particular, notable visible and undesirable coloration. In particular, any colored effect of the glazing viewed from the outside is avoided, which is usually due to the presence of the stack of reflective layers in the glazing, which more often has a very colored appearance in reflection. Advantageously, according to the embodiments of the invention, the presence, in the interlayer, of the dye between the stack of layers and the exterior makes it possible to attenuate the initial color resulting from reflection of the solar radiation on the stack, to levels that are imperceptible or barely perceptible to the human eye.

[0123] The laminated glazing according to the invention is particularly suitable for use in roof glasses, but also side glasses or rear glasses of vehicles, for example by adapting the concentration of the dye in the interlayer. The laminated glazing gives an enhanced sensation of thermal comfort as well as a certain luminosity inside the vehicle, the enhanced thermal comfort being obtained by means of high selectivity in terms of transmission of light and transmission of energy.