Coated glass sheet

Abstract

The present invention concerns a process to increase the mechanical and chemical resistance of a hydrolyzable network-forming silica gel coating provided on the surface of a substrate. According to the invention, a coating composition comprising a hydrolyzable, network-forming silica gel doped with a precursor of bismuth or cerium oxide is applied on the surface of the substrate. The present invention concerns also the product obtained by the said process.

Claims

1. A process to increase the mechanical and chemical resistance of a hydrolyzable network-forming silica gel coating on a surface of a glass sheet, the process comprising: forming a low-e undercoating by PVD on the surface; applying a coating composition comprising a hydrolyzable, network-forming silica gel doped with a precursor of bismuth or cerium oxide to the surface comprising the undercoating, and subsequently heat treating the glass sheet at a temperature of from 530 C. to 730 C. or chemically tempering the glass sheet, wherein the hydrolyzable, network-forming silica gel doped with a precursor of bismuth or cerium oxide is a topmost coating throughout the heat treating.

2. The process according to claim 1, wherein the precursor of bismuth or cerium oxide is present between 0.4 to 5%, based on the percentage in weight of the coating.

3. The process according to claim 1, wherein the coating covers the entire or substantially the entire surface of the glass sheet.

4. The process according to claim 1, further comprising: heating the glass sheet after the glass is coated.

5. The process according to claim 1, wherein the coating composition comprising a hydrolyzable, network-forming, silica gel is doped with a precursor of bismuth oxide.

6. The process according to claim 1, comprising chemical tempering of the coated glass sheet.

7. A glass sheet, obtained by the process according to claim 1.

8. The glass sheet according to claim 7, wherein the glass sheet is heat treated.

9. The glass sheet according to claim 8, wherein the glass sheet is a tempered glass.

10. A shower door, table or display comprising the glass sheet according to claim 8.

11. A process for forming a coated glass sheet, comprising: forming a low-e PVD undercoating on the glass sheet; applying a coating composition comprising a hydrolyzable, network-forming silica gel doped with a precursor of bismuth oxide on the PVD undercoating, and subsequently heat treating the glass sheet at a temperature of from 530 C. to 730 C. or chemically tempering the glass sheet, wherein the precursor of bismuth is present between 0.4 to 5%, based on the percentage in weight of the coating.

12. The process according to claim 11, further comprising: heating the glass sheet after the glass is coated.

13. The process according to claim 11, comprising chemical tempering of the coated glass sheet.

14. The process according to claim 11, wherein the hydrolyzable, network-forming silica gel doped with a precursor of bismuth oxide is a topmost coating throughout the heat treating.

15. A glass sheet, obtained by the process according to claim 11.

16. The glass sheet according to claim 15, wherein the glass sheet is heat treated.

Description

EXAMPLES

Example 1: Preparation of a Bismuth Doped SiO2 Coating According to the Invention

(1) 0.058 g of bismuth nitrate, 1.00 g of acetyl acetone and 18 mL of 2-ethoxy-ethanol are stirred during 30 min. Bismuth nitrate used here is bismuth nitrate pentahydrate. 4.22 g of tetraethylorthesilicate is added and a diluted solution of 0.03 g of glacial acetic acid in 1.00 mL of water is added drop wisely. The resulting solution is kept stirred 18 hours at room temperature to allow hydrolysis and condensation reactions to form a sol-gel. Approximately 2 mL of the solution was then deposited by spin coating on a clean clear glass. The glass was then dried at 160 C. for 12 minutes and then thermally annealed under air for 3.5 min at 650 C.

Example 2: Preparation of a Cerium Doped SiO2 Coating According to the Invention

(2) 0.10 g of cerium (III) acetate hydrate is stirred in a mixture of 11.50 g of ethanol and 15.00 g of isopropanol during 30 min. 6.25 g of tetraethylorthosilicate was added. A solution of 0.02 g of nitric acid 1 M, 0.06 g of glacial acetic acid and 1.08 g of water was added drop wisely into the solution. The resulting solution was allowed to stay under stirring during 18 hours. Approximately 2 mL of the solution was then deposited by spin coating on a clean clear glass. The glass was then dried at 160 C. for 12 minutes and then thermally annealed under air for 3 min 30 at 650 C.

Example 3: Preparation of a Bismuth Doped SiO2 Coating According to the Invention and Application on a PVD Low-e Coated Glass Substrate

(3) 24.3 g of bismuth nitrate pentahydrate and 100.0 g of acetylacetone are stirred in 1800.0 g of 2-ethoxy-ethanol during 30 min. 422.0 g of tetraethylorthosilicate is added. A solution of 3.0 g of glacial acetic acid and 108.0 g of water is added drop wisely into the solution. The resulting solution is allowed to stay under stirring during 18 hours at room temperature. Approximately 2 mL of the solution is then deposited by spin coating at 1000 rotations per minute on a PVD low-e coated glass substrate (commercially available under the name Planibel AS from AGC). The substrate is then dried at 160 C. for 12 minutes and then thermally annealed under air for 4 min at 670 C.

Example 4: Preparation of a Bismuth Doped SiO2 Coating According to the Invention and Application on a PVD Low-e Coated Glass Substrate

(4) 0.81 g of bismuth nitrate pentahydrate and 0.33 g of acetylacetone are stirred in 200.27 g of 2-ethoxy-ethanol during 30 min. 46.87 g of tetraethylorthosilicate is added. A solution of 0.33 g of glacial acetic acid and 12.0 g of water is added drop wisely into the solution. The resulting solution is allowed to stay under stirring during 48 hours at room temperature. Approximately 2 mL of the solution is then deposited by spin coating at 2000 rotations per minute on a PVD low-e coated glass substrate (commercially available under the name Smart 51 from AGC). The substrate is then dried at 160 C. for 12 minutes and then thermally annealed under air for 5 min 30 at 650 C.

Example 5: Preparation of a Cerium Doped SiO2 Coating According to the Invention and Application on a PVD Low-e Coated Glass Substrate

(5) 0.074 g of cerium (III) nitrate hexahydrate and 0.066 g of ethylacetoacetate are stirred in 121.66 g of 2-ethoxy-ethanol during 30 min. 20.83 g of tetraethylorthosilicate is added. A solution of 0.018 g of nitric acid 65% wt and 7.20 g of water is added drop wisely into the solution. The resulting solution is allowed to stay under stirring during 48 hours at room temperature. Approximately 2 mL of the solution is then deposited by spin coating at 2000 rotations per minute on a PVD low-e coated glass substrate (commercially available under the name Smart 51 from AGC). The substrate is then dried at 160 C. for 12 minutes and then thermally annealed under air for 5 min 30 at 650 C.

Comparative Example 1: Preparation of a SiO2 Coating

(6) 46.8 g of tetraethylorthesilicate is stirred into 200 mL of 2-ethoxy-ethanol during 30 min. 0.33 g of glacial acetic acid in 20 mL of water is added drop wisely. The resulting solution was allowed to stay under stirring during 18 hours. Approximately 2 mL of the solution was then deposited by spin coating on a clean clear glass. The glass was then dried at 160 C. for 12 minutes and the thermally annealed under air for 3 min 30 at 650 C.

Comparative Example 2: Preparation of a SiO2 Coating on PVD Low-e Coated Glass Substrate

(7) The solution prepared in the Comparative example 1 is deposited by spin coating at 1000 rotations per minute on a PVD low-e coated glass substrate (commercially available under the name Planibel AS from AGC). The substrate is then dried at 160 C. for 12 minutes and then thermally annealed under air for 4 min at 670 C.

Comparative Example 3: Preparation of a SiO2 Coating

(8) 46.3 g of tetraethylorthosilicate is stirred into 200.2 mL of 2-ethoxy-ethanol during 30 min. 0.33 g of glacial acetic acid in 12 mL of water is added drop wisely. The resulting solution is allowed to stay under stirring during 24 hours at room temperature. Approximately 2 mL of the solution is then deposited by spin coating at 2000 rotations per minute on a PVD low-e coated glass substrate (commercially available under the name Smart 51 from AGC). The glass is then dried at 160 C. for 12 minutes and then thermally annealed under air for 5 min 30 at 650 C.

(9) Performance Regarding Mechanical Resistance of Tested Coatings

(10) The coatings prepared in examples 1 and 2 and in the comparative example 1 were subjected to an abrasion test performed with an Elcometer 1720 Abrasion and Washability Tester. The test consisted in scrubbing the coated glass for 500, 1000, 2000 or 3000 cycles with a nylon bristle brush as described in ASTM D2486 standard. The surface is examined in reflexion under lighting. If the appearance of the abraded area is distinguishable, the sample is considered as ko meaning not having good mechanical resistance. If there is no difference between the abraded area and the non-abraded area, the coating is considered as ok meaning having good mechanical resistance according to the invention. The test results are summarized in Table 1:

(11) TABLE-US-00001 TABLE 1 evaluation of abrasion resistance of various doped and non-doped SiO2 coating after n rubbing cycles % Dry extract Doping of 500 1000 2000 3000 Samples material doping material cycles cycles cycles cycles Ex. 1 Bi 0.11% ok ok ok ok Ex. 2 Ce 0.15% ok ok ok ok Comp. 0.00% ok ko ko ko Ex 1
Performance Regarding the Chemical Resistance of Tested Coatings

(12) Resistance to acid: the coatings prepared following examples 1 and 2 and in the comparative example 1 were subjected to chemical immersion at room temperature in a aqueous solution of HCl 0.1 mol/L. The samples are not completely immersed in the solution in order to have a non-immersed area used as reference. After immersion, the samples are rinsed with deionized water and let at room atmosphere for drying.

(13) Resistance to alkali: the coatings prepared following examples 1 and 2 and in the comparative example 1 were subjected to chemical immersion at room temperature in a aqueous solution of NaOH 0.1 mol/L. The sample are not completely immersed in the solution in order to have a non-immersed area used as reference. After immersion, the samples are rinsed with deionized water and let at room atmosphere for drying.

(14) For both tests (resistance to acid and resistance to alkali), the evaluation is done by observation of the sample under an artificial sky to determine whether discoloration/punctual delamination/defects can be observed on the sample. If the appearance of the immersed area is distinguishable from the non immersed area, the sample is considered as ko, meaning not having good resistance to the considered medium (acid or alkaline). If there is no difference between the immersed area and the non-immersed area, the coating is considered as ok, meaning having good resistance to the considered medium (acid or alkaline).

(15) TABLE-US-00002 % Dry extract of Immersion Immersion Immersion Immersion Immersion Immersion Doping doping HCl HCl HCl NaOH NaOH NaOH Samples material material 4 hours 24 hours 48 hours 4 hours 24 hours 48 hours Ex. 1 Bi 0.11% ok ok ok ok ok ok Ex. 2 Ce 0.10% ok ok ok ok ok ok Comp. 0.00% ok ko ko ko ko ko Ex 1
Performance Regarding the Humidity Resistance of Tested Coating

(16) The samples prepared following examples 1 and 2 and in the comparative example 3 were exposed to high humidity environment in a close humid chamber at 40 C. and 95% relative humidity following the standard EN1096-2.

(17) TABLE-US-00003 % Dry extract of Doping doping Exposure Exposure Exposure Exposure Exposure Samples material material 1 days 2 days 5 days 10 days 20 days Ex. 1 Bi 0.11% ok ok ok ok ok Ex. 2 Ce 0.10% ok ok ok ok ok Comp. 0.00% ok ko ko ko ko Ex1
Performance Regarding Mechanical Resistance of Tested Coatings on PVD Low-e Coated Glass Substrate

(18) The coatings prepared in examples 3, 4 and 5 and comparative examples 2 and 3 were subjected to an automatic wet rub test according to the standard EN1096: a flat circular teflon head covered with a cotton cloth is dragged on the coating with a constant, built-in load. The abrasion of the cotton over the coated surface will damage (remove) the coating after a certain number of cycles. The cotton should be kept wet with deionised water during the whole duration of the test. The speed should be adjusted between 60 and 90 full oscillations (back and forth)/minute. The evaluation is done by observation of the sample under an artificial sky to determine whether discoloration/scratches can be seen on the sample. If the appearance of the abraded area is significantly distinguishable, the sample is considered as ko meaning not having good mechanical resistance. If there is a slight difference in coloration without delamination of the coatings and without scratches on the coating, the coating is considered as acceptable, meaning having an improved mechanical resistance. If there is no difference between the abraded area and the non-abraded area, the coating is considered as ok meaning having good mechanical resistance according to the invention. The test results are summarized in Table 2 and 3:

(19) TABLE-US-00004 TABLE 2 evaluation of abrasion resistance of various SiO2 coatings on PVD low-e coated (Planibel AS) samples after n rubbing cycles % Dry extract Doping of 500 1000 Samples material doping material cycles cycles PVD low-e coated glass Bi 0.14% ok ok substrate coated with sol- gel coating of Ex. 3 PVD low-e coated glass ko ko substrate coated with sol- gel coating of Comp. Ex 2 PVD low-e coated glass ko ko substrate without sol-gel coating

(20) TABLE-US-00005 TABLE 3 evaluation of abrasion resistance of various SiO2 coatings on PVD low-e coated (Smart 51) samples after 1000 rubbing cycles % Dry extract Doping of 1000 Samples material doping material cycles PVD low-e coated glass substrate Bi 0.14% ok coated with sol-gel coating of Ex. 4 PVD low-e coated glass substrate Ce 0.49% acceptable coated with sol-gel coating of. Ex 5 PVD low-e coated glass substrate ko coated with sol-gel coating of Comp. Ex 3
The results in Tables 2 and 3 show the performances improvement obtained with coatings doped with cerium or bismuth. Table 3 further shows that the improvement is more significant with bismuth even when used at a lower content.