Solar control glazing

Abstract

A heat treatable solar control glazing showing low-emissivity properties, and possibly also anti-solar properties, and methods to manufacture such a glazing. The glazing comprises a transparent substrate coated with a stack of thin layers comprising n functional layer(s) reflecting infrared radiation and n+1 dielectric layers, with n1, each functional layer being surrounded by dielectric layers. At least one dielectric layer above a functional layer comprises a layer consisting essentially of silicon oxide deposited by PECVD, and the stack comprises a barrier layer based on zinc oxide above and in direct contact with any functional layer which has a silicon oxide layer in the dielectric layer directly above it.

Claims

1. A process of coating a transparent substrate with a stack of layers comprising n functional layer(s) reflecting infrared radiation and n+1 dielectric layers, with n1, each functional layer being surrounded by dielectric layers, comprising: depositing a layer consisting essentially of silicon oxide by plasma enhanced chemical vapour deposition (PECVD) as part of at least one dielectric layer above a functional layer and depositing a barrier layer based on zinc oxide above and in direct contact with any functional layer which has a silicon oxide layer in the dielectric directly above it.

2. The process according to claim 1, wherein the depositing of the layer consisting essentially of silicon oxide is made by low-pressure PECVD.

3. The process according to claim 1, wherein the depositing of the layer consisting essentially of silicon oxide is made by PECVD using a microwave source, a hollow cathode source or a dual beam plasma source.

4. The process according to claim 1, further comprising: depositing of layers of the stack other than the layer consisting essentially of silicon oxide by magnetron sputtering.

5. The process according to claim 1, wherein the layer consisting essentially of silicon oxide has a thickness of more than 10 nm.

6. The process according to claim 1, further comprising: depositing a barrier layer based on zinc oxide above and in direct contact with each functional layer.

7. The process according to claim 1, wherein the barrier layer(s) consists (consist) of zinc oxide, optionally doped with aluminium.

8. The process according to claim 1, wherein the barrier layer(s) has (have) a thickness of at most 35 nm.

9. The process according to claim 1, further comprising: depositing directly on the substrate a first dielectric layer comprising an oxide.

10. The process according to claim 9, wherein the dielectric layer comprising an oxide which is deposited directly on the substrate is a layer of zinc-tin mixed oxide or a layer of titanium oxide.

11. The process according to claim 9, wherein the dielectric layer comprising an oxide which is deposited directly on the substrate has a thickness of at least 10 nm.

12. The process according to claim 1, wherein the functional layer(s) reflecting infrared radiation is a (are) silver-based layer(s).

13. The process according to claim 1, wherein each dielectric layer under a functional layer comprises a layer based on zinc oxide, directly in contact with said functional layer.

14. The process according to claim 13, wherein the layer based on zinc oxide under a functional layer has a thickness of at most 15 nm.

15. The process according to claim 13, wherein the layer based on zinc oxide has a thickness of between 1 and 10 nm.

16. The process according to claim 1, wherein at least one dielectric layer above a functional layer comprises, between a barrier layer based on zinc oxide and a layer consisting essentially of silicon oxide, at least one layer of a metal oxide different from the barrier layer and from the layer consisting essentially of silicon oxide.

17. The process according to claim 1, further comprising: depositing a last dielectric layer between a barrier layer based on zinc oxide and a layer consisting essentially of silicon oxide, the last dielectric layer comprising at least one layer of zinc-tin mixed oxide or of titanium oxide.

18. The process according to claim 1, wherein the layer consisting essentially of silicon oxide has an extinction coefficient at a wavelength of 632 nm below 1E-4, a refractive index of at least 1.466 and a carbon content of at most 3%.

19. The process according to claim 1, wherein the barrier layer(s) has (have) a thickness of between 1 and 25 nm.

20. The process according to claim 1, wherein the depositing of the layer consisting essentially of silicon oxide is made by PECVD using a hollow cathode source.

Description

COMPARATIVE EXAMPLE 1

(1) The following stack of thin layers, not in accordance with the invention, has been deposited by magnetron sputtering on a glass substrate:

(2) TABLE-US-00004 glass ZnO:Al ZnSnO.sub.x ZnO Ag (2 Wt. %) ZnSnO.sub.x 32 5 13.3 15 41

(3) It corresponds to a coating stack according to the teaching of EP1140721. It shows a sheet resistance, before and after heat treatment, respectively of 3.342/ et 3.80/. Under examination with the naked eye, the heat-treated product shows inacceptable haze and spots.

(4) Compared to example 9, this demonstrates the advantage of having a silicon oxide layer in the second dielectric layer to minimise or avoid haze and spots after heat treatment.

COMPARATIVE EXAMPLES 2 AND 3

(5) The following stacks of thin layers, not in accordance with the invention, have been deposited by magnetron sputtering on a glass substrate:

(6) TABLE-US-00005 glass AlSiN ZnSnO.sub.x:Al TiO.sub.x ZnO:Al Ag ZnSnO.sub.x:Al ZnO AlN ZnSnO.sub.x c. ex. 2 43 4 0.9 7.7 8 7.7 1.3 50 12 glass AlSiN ZnSnO.sub.x:Al TiO.sub.x ZnO:Al Ag ZnSnO.sub.x:Al ZnO AlN ZnSnO.sub.x SiN c. ex. 3 43 4 0.9 7.7 8 7.7 1.3 50 12 20

(7) Before any heat treatment, they undergo a Cleveland test to measure their chemical durability. Results are bad: already after one day, discolouration is visible with the naked eye, and after 3 days, it is even more visible.

(8) By comparison, examples according to the present invention do not show any discolouration visible with the naked eye, after one day, nor 3 days, of Cleveland test. This demonstrates the advantage of having preferably and inter alia, a layer of an oxide in direct contact with the substrate, for a better chemical durability of the non heat-treated product.

COMPARATIVE EXAMPLES 4 TO 9

(9) Single silver and double silver coating stacks according to Table I, including a metallic titanium barrier, have been deposited on a glass substrate of 3 mm thickness. Silicon oxide layers have been deposited by Hollow Cathode PECVD, whilst other layers of the stack have been deposited by magnetron sputtering. These are coating stacks not in accordance with the invention.

(10) The score of Brush test (AB Brush), haze (AB Haze), emissivity (AB E) and sheet resistance (AB Rs [/]) on heat-treated samples (heat treatment was carried out at 730 C. during 3 min 15 s for single silver stacks and 4 min for double silver stacks) are given in the table. All comparative examples show at least one value for these properties which is unacceptable (underlined values in the table). By comparing c.ex.4 and c.ex.5 or c.ex.6 and c.ex.7, it can be seen, for example, that slightly increasing the thickness of the Ti barrier(s) improves the Brush score, but increases the haze.

(11) This shows that it is not possible to reach at the same time a low haze value and a good resistance to abrasion, for coating stacks incorporating a PECVD silicon oxide layer and having a metallic barrier layer.

(12) Moreover, by comparing the colour in reflection of the coatings according to c.ex.6-9 before and after heat treatment, we have noted that such stacks are far from being self-matchable, with Delta E* of more than 10.

EXAMPLES 1 TO 5 AND COMPARATIVE EXAMPLES 10 AND 11

(13) Single silver coating stacks according to Table II have been deposited on a glass substrate of 3 mm thickness. Silicon oxide layers in the examples 1 to 5 according to the invention have been deposited by Hollow Cathode PECVD, whilst silicon oxide layers in the comparative examples 10 and 11 not in accordance with the invention have been deposited by magnetron sputtering. Other layers of the stacks have been deposited by magnetron sputtering.

(14) The score of Brush test (AB Brush), haze (AB Haze), emissivity (AB E) and sheet resistance (AB Rs [/]) on heat-treated samples (heat treatment was carried out at 730 C. during 3 min 15 s) are given in the table, together with the Delta E* value in reflection on the coating side.

(15) All the examples according to the invention show good results in terms of resistance to abrasion, haze, emissivity and sheet resistance after heat treatment. They furthermore show good results in terms of self-matchability, with Delta E* of less than 5.0, preferably less than 3.0, more preferably less than 2.0. On the contrary, samples incorporating silicon oxide deposited by magnetron show at least one value for these properties which is unacceptable (underlined values in the table).

(16) In addition, the following properties were measured on example 1:

(17) TABLE-US-00006 Single glazing (SG) LT before | after heat treatment 86.5% | 90.4% LRc before | after heat treatment 4.7% | 4.9% LRg before | after heat treatment 5.1% | 5.2% Rs before | after heat treatment 3.8 / | 3.4 /

EXAMPLES 6 TO 8 AND COMPARATIVE EXAMPLES 12 AND 13

(18) Double silver coating stacks according to Table III have been deposited on a glass substrate of 3 mm thickness. Silicon oxide layers in the examples 6 to 8 according to the invention have been deposited by Hollow Cathode PECVD, whilst silicon oxide layers in the comparative examples 12 and 13 not in accordance with the invention have been deposited by magnetron sputtering. Other layers of the stacks have been deposited by magnetron sputtering.

(19) The score of Brush test (AB Brush), haze (AB Haze), emissivity (AB E) and sheet resistance (AB Rs [/]) on heat-treated samples (heat treatment was carried out at 730 C. during 4 min) are given in the table.

(20) All the examples according to the invention show good results in terms of resistance to abrasion, haze, emissivity and sheet resistance after heat treatment. On the contrary, samples incorporating silicon oxide deposited by magnetron show at least one value for these properties which is unacceptable (underlined values in the table).

(21) In addition, the following properties were measured on example 6:

(22) TABLE-US-00007 Single glazing (SG) LT before | after heat treatment 73% | 69.6% LRc before | after heat treatment 6.8% | 6.4% LRg before | after heat treatment 9% | 11.1% Rs before | after heat treatment 2.8 / | 2.4 /

(23) TABLE-US-00008 TABLE I ZSO5 ZnO:Al Ag Ti ZnO:Al SiO2 AB Brush AB Haze AB E AB Rs c. ex. 4 31.9 5 8.5 2.2 27 25.9 5 0.99 0.14 4.7 c. ex. 5 42.6 6.7 8.5 2.4 29.7 31.4 2 1.13 0.13 5.2 ZSO5 ZnO:Al Ag Ti SiO2 ZnO:Al Ag Ti ZnO:Al SiO2 AB Brush AB Haze AB E AB Rs c. ex. 6 30 5 9 1.8 90 20 10 2 30 5 1.17 0.06 2.2 c. ex. 7 30 5 9 3 90 20 10 3 30 1 2.50 0.08 2.2 c. ex. 8 30 5 9 2 90 20 10 2.5 20 20 5 1.67 0.06 2.0 c. ex. 9 30 5 9 1.8 90 20 10 2.2 20 20 5 0.49 0.06 2.1

(24) TABLE-US-00009 TABLE II ZSO5 ZnO:Al Ag AZO ZnO:Al SiO2 AB Brush AB Haze AB E AB Rs Delta E* ex. 1 32 5 8.5 15 17 26 1 0.11 0.08 3.4 1.4 ex. 2 32 5 8.5 15 17 50 2 0.12 0.08 3.0 2.7 c. ex. 10 32 5 8.5 15 17 26 4.5 0.47 0.09 3.6 5.0 c. ex. 11 32 5 8.5 15 17 50 4.5 0.25 0.08 3.4 8.3 ZSO5 ZnO:Al Ag AZO SiO2 AB Brush AB Haze AB E AB Rs Delta E* ex. 3 32 5 8.5 32 26 2 0.13 0.10 3.4 2.1 ex. 4 32 5 8.5 15 75 2.25 0.21 0.08 3.2 0.9 ex. 5 32 5 8.5 15 100 2 0.27 0.10 3.2 2.7

(25) TABLE-US-00010 TABLE III ZSO5 ZnO:Al Ag AZO ZnO:Al SiO2 ZnO:Al Ag AZO ZnO:Al ZSO5 AB Brush AB Haze AB E AB Rs ex. 6 30 5 8.5 15 15 75 20 10 5 19 19 2.25 0.10 0.06 2.4 ex. 7 30 5 8.5 5 10 125 10 10 5 19 19 2 0.28 0.09 3.0 c. ex. 12 30 5 8.5 15 15 75 20 10 5 19 19 4.5 1.09 0.03 3.1 c. ex. 13 30 5 8.5 7.5 125 20 10 5 19 19 4.75 0.57 0.07 3.5 ZSO5 ZnO:Al Ag AZO ZnO:Al SiO2 ZnO:Al Ag AZO ZnO:Al SiO2 AB Brush AB Haze AB E AB Rs ex. 8 30 5 8.5 15 15 75 20 10 15 17 50 2.25 0.37 0.06 2.2

EXAMPLE 9

(26) The following stacks of thin layers, in accordance with the invention, has been deposited on a glass substrate of 4 mm thickness:

(27) TABLE-US-00011 glass ZnO:Al ZSO5 (2 Wt. %) Ag AZO ZSO5 SiO2 42.5 3 7.9 3 32 20

(28) All the coatings have been deposited by magnetron sputtering, except the silicon oxide layer which has been deposited by microwave PECVD.

(29) The following properties were measured on example 9, before and after a heat treatment of 700 C. during 4 min. Moreover, under examination with the naked eye, the heat-treated product has showed no inacceptable haze or spots.

(30) TABLE-US-00012 Single glazing (SG) LT before | after heat treatment 89.8% | 89.7% before | after heat treatment 0.08 | 0.07 Colour in transmission L* 95.9 | 95.8 before | after heat treatment a* 1.1 | 0.8 b* 0.8 | 0.6 Colour in reflection coating side L* 24.8 | 26.5 before | after heat treatment a* 0.7 | 1.8 b* 0.4 | 0.1 Colour in reflection glass side L* 26.5 | 27.4 before | after heat treatment a* 1.1 | 1.9 b* 2.9 | 3.1

COMPARATIVE EXAMPLE 14

(31) A similar stack to example 9, but without SiO2 and thus not in accordance with the invention, has been deposited on a glass substrate of 4 mm thickness, by magnetron sputtering:

(32) TABLE-US-00013 glass ZnO:Al ZSO5 (2 Wt. %) Ag AZO ZSO5 40 3 7.5 3 38.3

(33) Performances to various tests (described hereunder) were compared between example 9 and comparative example 14, showing the advantageous effect of the PECVD SiO2 topcoat on coating hardness:

(34) TABLE-US-00014 Before heat-treatment After heat-treatment C. Ex. 14 Ex. 9 C. Ex. 14 Ex. 9 Washing test 1 1 1 Washing test 2 6 1 Taber test (dry) 6 2 2 1 Taber test (wet) 6 3 3 1

EXAMPLE 10

(35) The following stacks of thin layers, in accordance with the invention, has been deposited on a glass substrate of 4 mm thickness:

(36) TABLE-US-00015 glass ZnO:Al TiO2 (2 Wt. %) Ag AZO TiO2 SiO2 26.5 3 13.2 2 25 28

(37) All the coatings have been deposited by magnetron sputtering, except the silicon oxide layer which has been deposited by microwave PECVD.

COMPARATIVE EXAMPLE 15

(38) A similar stack to example 10, but without SiO2 and thus not in accordance with the invention, has been deposited on a glass substrate of 4 mm thickness, by magnetron sputtering:

(39) TABLE-US-00016 glass ZnO:Al TiO2 (2 Wt. %) Ag AZO TiO2 ZSO5 29.3 3 12.8 2 20 17

(40) Performances to AWRT test (described hereunder) were compared between example 10 and comparative example 15, showing again the advantageous effect of the PECVD SiO2 topcoat on coating hardness:

(41) TABLE-US-00017 C. Ex. 15 Ex. 10 AWRT (250) 7 8 AWRT (500) 5 9

(42) Finally samples according to example 10 and comparative example 15 were immersed into solutions of various pH during 5 minutes then dried. Colour was measured before and after immersion and drying, and a colour change E* was calculated, showing the advantageous effect of the PECVD SiO2 topcoat on coating chemical resistance:

(43) TABLE-US-00018 E* E* C. Ex. 15 Ex. 10 pH 2 2.1 0.1 pH 3.4 1.6 0.1 pH 5 0.4 0.1 pH 8 0.5 0.1 pH 12 0.7 0.1

(44) Brush Test

(45) The Brush test or Wet Brush test is used to evaluate the resistance of the coating to erosion caused by scrubbing. Full details of this test are set out in ASTM Standard D 2486-00. Samples of coated glass were submitted to Test Method A. The samples were scrubbed wet (with demineralized water), with a bristle brush, during 1000 cycles. Their degradation was then observed with the naked eye and compared. A score was assigned between 1 and 5, 1 meaning not degraded and 5 meaning very much degraded (entire coating removal).

(46) Washing Test

(47) The Washing test is used to evaluate the resistance of the coating to erosion caused by washing. A 4050 cm square sample is introduced into an industrial glass washing machine operating with demineralised water. While the sample is in contact with the rotating brushes, the forward movement is stopped for 60 s. In test 1, the brushes are switched off at the same time while in test 2 they continue rotating. In both cases the water keeps on running.

(48) The degradation is observed with the naked eye and compared. A score is assigned between 1 and 6, 1 meaning not degraded and 6 meaning very much degraded (entire coating removal).

(49) Taber Test

(50) The Taber test is another test used to evaluate the resistance of the coating to erosion caused by friction. A 1010 cm square sample is maintained on a steel plate rotating at a speed of 65 to 75 rpm. Each of two parallel weighted arms carries one specific abrasive small wheel rotating freely around a horizontal axis. The wheels are covered by a felt stripe (according to DIN 68861, supplied by Erichsen, attached to the wheels). Each wheel lies on the sample to be tested under the weight applied to each arm, which is a mass of 500 g. The samples may be scrubbed wet (with demineralized water) or dry. The combination of the abrasive wheels and the rotating supporting plate creates on the sample an abrasive crown, more or less pronounced according to the coating hardness. A score of 1 to 6 is given to each sample having being subjected to the test after a total of 500 rotations, 1 being the best score showing a highly resistant coating and 6 being the lowest score.

(51) AWRT

(52) The Automatic Web Rub Test (AWRT) is again a test used to evaluate the resistance of the coating to erosion. A piston covered with a cotton cloth (reference: CODE 40700004 supplied by ADSOL) is put in contact with the coating and oscillates over the surface. The piston carries a weight in order to have a force of 33N acting on a 17 mm diameter finger. The abrasion of the cotton over the coated surface will damage (remove) the coating after a certain number of cycles. The test is realised for 250 and 500 cycles, at separated distances over the sample. The sample is observed under an artificial sky to determine whether discoloration and/or scratches can be seen on the sample. The AWRT score is given on a scale from 1 to 10, 10 being the best score, indicating a highly resistant coating