Heating glazing unit

Abstract

A laminated automotive glazing unit including two glass sheets joined by a thermoplastic interlayer sheet, a system of conductive layers applied to one of the sheets, and including on an edge of the same sheet a substantially opaque masking strip, making contact with the glass sheet, the system of conductive layers covering at least partially the masking strip. The glazing unit further includes busbars for supplying electrical power, the busbars making contact with the layer system in the portion covering the masking strip. The masking strip includes a set of layers that absorb visible radiation, the layers being formed by cathodic sputtering.

Claims

1. A laminated motor vehicle glass panel comprising: first and second glass sheets united by a thermoplastic interlayer sheet; a system of conductive layers applied to a first face of the first glass sheet, wherein the first glass sheet has a reflection which is not greater than 8% on a second side of the first glass sheet opposite the first side of the first glass sheet when the first glass sheet is 4 mm thick; an opaque masking strip, in contact with the first glass sheet on an edge of the first glass sheet, forming an interference optical system for at least partially neutralizing overall reflection on the first side of the first glass sheet, the opaque masking strip including an assembly of layers including (a) a first absorbent/reflective layer, (b) a second absorbent/reflective layer located between the first face of the first glass sheet and the first absorbent/reflective layer, and (c) plural dielectric layers, wherein at least part of the opaque masking strip is covered by the system of conductive layers, and wherein a thickness of the second absorbent/reflective layer is between a third and a tenth of a thickness of the first absorbent/reflective layer; and electrical supply busbars in contact with the system of conductive layers where the at least part of the opaque masking strip is covered by the system of conductive layers, wherein the assembly of layers of the opaque masking strip absorb visible radiation and is formed by cathode sputtering such that visible light transmission through the opaque masking strip is at most 1%, wherein the second absorbent/reflective layer is made of metal or based on a metal compound, and the second absorbent/reflective layer comprises (1) a metal from a selected metal group, the selected metal group consisting of: W, Cr, Ta, Nb, Zr, Ti, Nb, Mo, V, Hf and NiCr, CoCr, ZrCr, NbCr and NiCrW, and stainless steels, (2) an alloy of metals from the selected metal group, (3) a partially nitrided compound of at least one metal from the selected metal group, (4) a completely nitrided compound of metal from the selected metal group, (5) a partially nitrided compound of at least one alloy including a metal from the selected metal group, or (6) a completely nitrided compound of at least one alloy including a metal from the selected metal group.

2. The glass panel according to claim 1, wherein the opaque masking strip is applied to a 4 mm thick clear glass sheet.

3. The glass panel according to claim 1, wherein the assembly of layers of the opaque masking strip has a total thickness which is not greater than 4000 .

4. The glass panel according to claim 1, wherein the first absorbent/reflective layer is made of metal or based on a metal compound, and the first absorbent/reflective layer comprises (1) a metal from an extended metal group consisting of the selected metal group, Al and Cu, (2) an alloy of metals from the extended metal group, (3) a partially nitrided compound of at least one metal from the extended metal group, (4) a completely nitrided compound of metal from the extended metal group, (5) a partially nitrided compound of at least one alloy including a metal from the extended metal group, or (6) a completely nitrided compound of at least one alloy including a metal from the extended metal group.

5. The glass panel according to claim 4, wherein the first absorbent/reflective layer has an extinction coefficient k, which is an average of coefficients over a visible wavelength range, 350-750 nm, which is not less than 2.5.

6. The glass panel according to claim 4, wherein the first absorbent/reflective layer has a thickness which is not less than 300 .

7. The glass panel according to claim 6, wherein the first absorbent/reflective metal has a thickness which is not greater than 1000 .

8. The glass panel according to claim 1, wherein the second absorbent/reflective layer is such that a product (kne) of a refractive index (n) of a material of the second absorbent/reflective layer, (2) a value of an extinction coefficient (k), which is an average of coefficients over a visible wavelength range, 350-750 nm, and (3) a thickness (e) of the second absorbent/reflective layer expressed in Angstroms is at least 300.

9. The glass panel according to claim 1, wherein the plural dielectric layers are transparent.

10. The glass panel according to claim 9, wherein a first dielectric layer of the plural dielectric layers is directly applied to the first glass sheet and has a refractive index of greater than 1.5.

11. The glass panel according to claim 9, wherein the plural dielectric layers are Si.sub.3N.sub.4, SiO.sub.xN.sub.y, AlN layers.

12. The glass panel according to claim 1, wherein the opaque masking strip has a structure G/D.sub.1/M.sub.2/D.sub.2/M.sub.1/D.sub.3, wherein M.sub.1 and M.sub.2 are respectively the first and second absorbent/reflective layers, and D.sub.1, D.sub.2, D.sub.3 are dielectric layers of the plural dielectric layers, the layer D.sub.3 essentially having a role of mechanically and/or chemically protecting the underlying layers.

13. The glass panel according to claim 1, wherein the first absorbent/reflective layer is a layer formed of an alloy that comprises, by weight, at least 40% of tungsten.

14. The glass panel according to claim 13, wherein the first absorbent/reflective layer further comprises chromium.

15. The glass panel according to claim 13, wherein the second absorbent/reflective layer is of a same nature as that of the first absorbent/reflective layer.

16. The glass panel according to claim 1, wherein the system of conductive layers is formed by cathode sputtering and comprises an assembly of metal layers and of dielectric layers, the assembly of metal layers and of dielectric layers having a thickness which is not greater than 4000 .

17. The glass panel according to claim 1, wherein the opaque masking strip has a visible light transmission through the opaque masking strip of at most 0.5%.

18. The glass panel according to claim 1, wherein the opaque masking strip has a visible light transmission through the opaque masking strip of at most 0.1%.

Description

(1) The invention is described in detail subsequently with reference to the figures, in which:

(2) FIG. 1 illustrates the arrangement on one of the glass sheets of the elements occurring in a glass panel comprising a system of heated layers;

(3) FIG. 2 illustrates the edge of a heated laminated glass panel.

(4) In these figures, the ratio of the dimensions is not respected for convenience of interpretation.

(5) FIG. 1 shows the arrangement of the components of a layered heating assembly on a glass sheet of a glass panel such as a windshield.

(6) The glass sheet 1 comprises a masking strip 4 located on the edge of the sheet. This strip is intended to hide the unattractive elements, in particular the busbars 6 powering a system of conductive layers 5 that extends both over the masking strip and directly over the glass sheet.

(7) FIG. 2 presents a laminated glass panel that incorporates a glass sheet and the functional components borne by the sheet as represented in FIG. 1.

(8) The glass panel comprises two glass sheets 1, 2 assembled by means of a thermoplastic interlayer sheet 3 of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) type. The elements of the heating system are all applied to the face of the glass sheet directed toward the interlayer sheet. The glass sheet 1 is the one in contact with the outside atmosphere. This arrangement is preferred insofar as the heated layer is in immediate contact with the sheet that is directly exposed to the atmospheric hazards. Considering the low thermal conductivity of the various glass and interlayer sheets, the transmission of heat in this arrangement takes place under the best possible conditions.

(9) In addition to the masking strip 4, the sheet 1 bears the system of heated layers 5 and a supply collector (busbar) 6. The glass/masking strip/heated layer/busbar sequence is controlled by the role of each of these elements. The system of layers 5 is necessarily in contact with the busbar 6, and this busbar must be masked by the strip 4. In this arrangement, the heated layers applied to the masking strip extend the portion of this layer that is directly in contact with the glass sheet 1. Passing from the masking strip 4 to the glass sheet 1, the layer must cross the edge of the masking strip without discontinuity or lack of homogeneity to enable the highest possible transmission of the electrical power communicated by means of the busbar 6.

(10) In the conventional mode, the differences in thickness between that of the conductive layers 5 and of the enameled masking strip 4 compromise the continuity of the conductive layers along this threshold.

(11) The choice of forming the masking strip 4 from layers having a thickness which is of the order of magnitude of that of the conductive layers significantly reduces the defects observed with the enamel strips.

(12) A comparison is carried out between a glass panel, the masking strips of which are produced by screen printing of enamel in a conventional manner, and a glass panel, the masking strip of which is obtained by cathode sputtering according to the invention.

(13) In both cases, the support is formed of a clear glass sheet with a thickness of 2.1 mm. The conductive layers are as described in the publication WO 2011/147875. They comprise three silver layers. The total thickness of the layers varies slightly depending on the assemblies proposed, remaining of the order of 4000 . As a general rule, the total thickness of the systems of conductive layers is not greater than 0.6.

(14) Under the conditions of the test, the measurement of the resistance of the layer on the glass alone becomes established at 0.80/. On the enamel masking strip produced by conventional screen printing, this resistance is measured at 320/, and that of the conductive layer applied to the enamel strip is of the order of 4 /.

(15) The conduction of the layers applied to the enamel strips is therefore substantially impaired due in particular to the considerable roughness of the enamel layers. This difficulty is nevertheless much less detrimental than that corresponding to the passage of the conductive layers from the enamel strip to the glass sheet. The resistance measurement at the threshold of the enamel strip is at best not less than 5/, but in places may rise without limit when the conductive layers are broken along this threshold.

(16) In a first test according to the invention, a masking strip formed of the following successive layers is formed, the thicknesses between parentheses are expressed in ngstrms.

(17) Glass/Si.sub.3N.sub.4 (563)/NiCrW (72)/Si.sub.3N.sub.4 (500)/NiCrW (500)/Si.sub.3N.sub.4 (500)

(18) This system is applied by magnetron cathode sputtering under conventional conditions using metal cathodes, in an argon atmosphere for the metal layers and in a nitrogen atmosphere for the formation of the silicon nitrides.

(19) The total thickness of the system of layers of the masking system is 2135 , i.e. 0.2135, in comparison with the customary thicknesses of the screen-printed enamel layers which are of the order of 20 to 150. The masking strip obtained by cathode sputtering has a thickness comparable to that of the system of conductive layers. The threshold at the boundary of this masking strip is quite unlike the threshold corresponding to conventional enamels. The continuity of the conductive layers is better ensured. In this case, the measurement of the resistance of the conductive layers is substantially the same whether it is measured on the masking strip, on the glass sheet or else on a portion forming the transition between the masking strip and the portion without this strip. The measurement in all cases is 0.78/, analogous to that measured in the previous case as regards the resistance of the conductive layer on the glass.

(20) The glass panel coated with the masking strip furthermore offers a practically neutral black appearance, a transmission at this strip which is less than 0.5% and a reflection on the glass side of 4.3%. The colorimetric indices are a* 0.1 and b* 0.3.

(21) In the absence of the de-reflective layer M2, the optical results are substantially modified. The measurements are carried out on the following system of absorbent layers:

(22) Glass/Si.sub.3N.sub.4 (50)/NiCrW (500)/Si.sub.3N.sub.4 (500)

(23) For this assembly the transmission is slightly higher. It becomes established at 2.2%. But above all the reflection in the absence of the second metal layer increases significantly, R.sub.g rises to 25.5%, and at the same time the reflection is less neutral, a* 3.1 and b* 0.8.

(24) Various tests are undertaken by varying the nature of the layers, their thicknesses and the structure of these assemblies.

(25) 1. In the G/D1/M2/D2/M1/D3 structure, the nature of M1 is varied.

(26) TABLE-US-00001 G D1 M2 D2 M1 D3 T.sub.L R.sub.g a* b* k (M1) 1 G Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 4.3 0 0.3 3 564 71 502 638 500 2 G Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.24 32 0.3 10.5 3 300 566 476 83 446 3 G Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 Al Si.sub.3N.sub.4 0.2 4.4 0.1 0.1 6.6 588 87 523 340 500 4 G Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 Ti Si.sub.3N.sub.4 0.2 4.3 0 0.3 2.6 564 69 564 940 564 5 G Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 CrN Si.sub.3N.sub.4 0.2 4.3 0 0.45 1.8 553 59 496 1315 500

(27) For tests 1, 3, 4, the desired properties are satisfied: very low transmission, limited reflection and neutrality of color. Depending on the value of the extinction coefficient, the thickness of M1 is greater or smaller. The higher k is, the thinner M1 is.

(28) Example 2 shows the importance of the relative position of M1 and M2. In this test, the thickest absorbent/reflective layer is closest to the glass sheet. It is observed that if the absorption remains very high, the reflection is not suitably attenuated on the glass sheet side. Conversely, on the layer side, the reflection not indicated in the table remains low, of the order of 4%.

(29) Starting from the preceding observation, if the reflection should be low both on the glass side and on the layer side, a structure comprising three absorbent layers may be used which corresponds to:

(30) G/D1/M2/D2/M2/D3/M3/D4

(31) By way of example, the following assembly is prepared:

(32) G/Si.sub.3N.sub.4(567)/NiCrW(72)/Si.sub.3N.sub.4(508)/NiCrW(434)/Si.sub.3N.sub.4(448)/NiCrW(84)/Si.sub.3N.sub.4(483)

(33) For this assembly, the reflection properties are those obtained previously, separately in examples 1 and 2.

(34) Example 5 involves a material (CrN) of conductive nature but that has a reduced conduction with respect to a metal or metal alloy. The extinction coefficient of this material is markedly lower (1.8) than for metals and alloys. To achieve comparable performances, it is necessary to substantially increase the thickness of the corresponding layer.

(35) 2. In these tests, the nature of M2 is varied.

(36) TABLE-US-00002 G D1 M2 D2 M1 D3 T.sub.L R.sub.g a* b* k (M2) 6 G Si.sub.3N.sub.4 W Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 4.3 0 0.3 3.6 559 90 395 646 500 7 G Si.sub.3N.sub.4 Ti Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 4.4 0.1 0.1 2.6 497 145 609 648 500 8 G Si.sub.3N.sub.4 Al Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.4 10.6 4.2 1.7 6.1 479 34 819 668 500 9 G Si.sub.3N.sub.4 Cu Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.3 13.5 11.8 5 3.2 408 95 785 691 500 10 G Si.sub.3N.sub.4 Cr Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 4.5 0 0.2 3.6 501 101 684 655 500 11 G Si.sub.3N.sub.4 CrN Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 4.3 0 0.22 1.8 467 159 274 659 500 12 G Si.sub.3N.sub.4 TiN Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 4.9 0.4 0.2 1.2 450 291 374 646 500 13 G Si.sub.3N.sub.4 AZO Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 8.85 0.8 0.28 0.2 557 1609 1264 707 500 14 G Si.sub.3N.sub.4 ZrN NiCrW Si.sub.3N.sub.4 0.26 6 0 0.5 0.5 398 250 755 500 15 G Si.sub.3N.sub.4 TaN Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.21 5.3 0.98 0.5 1.1 510 79 99 774 500

(37) For the low k coefficients, the thickness of M2 should be increased in order to try to re-establish the preferred conditions according to the invention. This is also the result expressed by the product n.Math.k.Math.e that appears on the next table. If this product is too small, the reflection is relatively high. This is the case for example for aluminum (8) or copper (9). The significant increase in the thickness may compensate for the very low extinction coefficients like for AZO (14).

(38) TABLE-US-00003 n k e n.k.e 8 0.9 6.1 34 182 7 1.9 2.6 145 740 9 0.9 3.2 95 280 12 2.1 1.4 291 848 14 2.7 0.2 1609 809 10 1.8 3.6 101 662 11 3.1 1.8 159 877 16 5.2 1.1 79 458 6 3.5 2.7 90 830 15 3.2 0.5 250 385

(39) 3. Impact of D1.

(40) TABLE-US-00004 G D1 M2 D2 M1 D3 T.sub.L R.sub.g a* b* n (D1) 16 G TiO.sub.2 NiCrW Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.18 4.9 0.3 0.15 2.5 436 104 578 615 500 17 G NiCrW Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.35 6.7 5.9 0.47 51 494 597 500 18 G SiON NiCrW Si.sub.3N.sub.4 NiCrW Si.sub.3N.sub.4 0.2 5 2.6 0.2 1.75 693 41 514 675 500

(41) The absence of layer D1 leads to an increased reflection.

(42) 4. Impact of the index of D2.

(43) TABLE-US-00005 G D1 M2 D2 M1 D3 T.sub.L R.sub.g a* b* n (D2) 19 G Si.sub.3N.sub.4 NiCrW TiO.sub.2 NiCrW Si.sub.3N.sub.4 0.2 4.6 0.3 0.1 2.5 569 58 374 684 500 20 G TiO.sub.2 NiCrW TiO.sub.2 NiCrW Si.sub.3N.sub.4 0.2 4.7 0.1 0.2 2.5 422 99 405 644 500 21 G Si.sub.3N.sub.4 NiCrW SiO.sub.2 NiCrW Si.sub.3N.sub.4 0.2 4.3 0 0.35 1.5 543 82 801 556 500

(44) The play in the thickness and in the index makes it possible to achieve the interference conditions that result in the desired conditions with various materials.

(45) Example 15 from the previous table shows that in particular combinations of material M2, in this case of ZrN, the absence of specific dielectric layer does not stand in the way of obtaining satisfactory results.

(46) The examples presented show the great diversity of the combinations forming systems of layers that are capable of forming appropriate masking strips. The choice of a system under these conditions is a function of additional considerations such as the ease of production of these layers.

(47) The formation of the masking strips only coats a small portion of the surface of the glass panels. The cathode sputtering techniques necessitate masking the portions of the glass panel that should not be coated. Solid masks may be applied to the glass sheets during the deposition of the opacifying strips. The preparation of the glass panels in question preferably goes through the application of protective films to the zones that should not be coated, which films are then removed for the application of the conductive layers A technique of this type is described for example in the publication WO 03/080528.