Corrosion resistant coated glass

Abstract

The present invention concerns a glass pane comprising at least one glass sheet and having a first major surface and a second major surface bearing at least on part of the first major surface a coating comprising a first layer comprising silicon oxide and a second layer comprising a mixed oxide of silicon and zirconium.

Description

DescriptionCorrosion resistant coated glassFIELD OF THE INVENTION

[0001] This invention relates to glass products that are useful in any application where the glass surface is submitted to weathering and / or chemical strain and in particular when frequent cleaning is performed. The applications comprise for example furniture applications such as table tops or shelving, in particular garden furniture, structural applications such as balustrades and partition walls and also certain windows, glass doors, shower walls and shower doors. This invention relates in particular to glass products submitted to high humidity environments such as bathrooms, swimming pools and greenhouses for example. In all these applications it is usually desired for the glass transmission and reflection to be as color neutral as possible.BACKGROUND OF THE INVENTION

[0002] While a large part of dirt collected on glass surfaces can in principle be removed by glass cleaning sprays and a soft cloth, in reality most glass surfaces are cleaned by sponge and squeegee techniques, where a sponge or cloth covered device, dipped into a cleaning solution, is used to scrub the glass and a squeegee is then used to sluice the dirt and water mixture from the glass. While this is efficient, it also submits the glass surface to considerable mechanical strain and may lead to visible mechanical deterioration of the glass, in particular of glass for use in humid environments bearing corrosion protection coatings.

[0003] At the same time it is desirable to provide glass corrosion protection coatings which do not significantly the optical properties of the glass in particular regarding reflectance / transmittance levels and colors.

[0004] Corrosion protection coatings having a high refractive are known that may protect the glass surface against corrosion and provide hydrophilic properties, for example TiCh, or hydrophobic properties, for example TixZryOz. Such coatings however tend to increase the reflectance of the glass and local thickness variations due to abrasion tend to be very visible.

[0005] While SiCh coatings may be deposited in higher thicknesses without overlyaffecting the optical properties of the glass, the inventors found that its mechanical durability, in particular in combination with humidity exposure could still be improved.SUMMARY OF THE INVENTION

[0006] In the present invention, the following conventions are used: a. The luminous transmission (LT) is the percentage of incident luminous flux, of llluminant D65 / 2°, transmitted by the glazing. b. The luminous reflection (LR) is the percentage of incident luminous flux, of llluminant D65 / 2°, reflected by the glazing. It can be measured on coating side (LRc) or substrate side (LRg). c. CIELAB 1976 values (L*a*b*) are used to define colors for transmission, reflectance on coating side and reflectance on substrate side. They are measured with llluminant D65 / 100. d. colors in transmittance are the more neutral the closer a* and b* are to 0. e. When values are said to be "comprised between a and b", they may also be equal to a or b.

[0007] In an embodiment of this invention, a coating for glass substrates is provided that increases the chemical resistance of the glass to weathering and chemical strain, while at the same time maintaining suitably neutral optical properties concerning the color of transmitted light.

[0008] In an embodiment of this invention, a coating for glass substrates is provided that increases the chemical resistance of the glass to weathering, mechanical and chemical strain, while at the same time maintaining suitably neutral optical properties concerning the color of transmitted and / or reflected light.Detailed description of the invention

[0009] The present invention concerns a glass pane comprising at least one glass sheet and having a first major surface and a second major surface bearing at least on part of the first major surface a coating comprising a first layer comprising silicon oxide and a second layer comprising a mixed oxide of silicon and zirconium.

[0010] In an embodiment of the present invention the first layer comprises SiCh or aluminum doped silicon oxide (SiO2:AI) having a Al / Si weight ratio ranging from 4 to 10%.

[0011] In an embodiment of the present invention the thickness of the first layer ranges from 22 to 32nm.

[0012] In an embodiment of the present invention the first layer is in direct contact with the first major glass surface.

[0013] In an embodiment of the present invention the second layer comprises a mixed oxide of silicon and zirconium (SiZrOx) having a Zr / Si atomic ratio ranging from 10% to 50%. It was found that within these ranges, mechanical resistance is increased while the refractive index increase compared to the first layer is limited. In an embodiment of the present invention the thickness of the second layer ranges from 1 .5 to 4.5nm. It was found that within these ranges the mechanical resistance could be increased while limiting the reflectance increase due to this second layer.

[0014] In an embodiment of the present invention, the second layer is in direct contact with the first layer.

[0015] In an embodiment of the present invention, the coating is devoid of any organic coatings, in particular of any hydrophobic organic coatings. It was found that such coatings generally show low mechanical durability and need to be refreshed at regular intervals.

[0016] Advantageously the color coordinates a* and b* in reflectance of the coated major surface differ by less than 20%, more advantageously by less than 10%, less than 5% even less than 2% from the color in reflectance of the uncoated glass pane.

[0017] Advantageously the coatings of the present invention may provide the glass substrate with a color in reflectance on the coated major surface are such that a* and b* range from -1 to 1 , before and / or after heat treatment.

[0018] The first and second layers of the coating may in particular be prepared by magnetron sputtering. Alternately plasma enhance chemical vapor deposition may be used.

[0019] According to an embodiment of the present invention the glass pane comprisesa single glass sheet or comprises at least two glass sheets united by a thermoplastic intercalating sheet. Typical thermoplastic intercalating sheets are of polyvinylbutyral (PVB) or ethyl vinyl acetate (EVA).

[0020] According to the invention, the glass substrate may be any glass substrate that may be subjected to weathering and / or chemical strain. Preferably the glass sheets are colored, normal clear or extra-clear soda lime glass substrates, advantageously having a thickness comprised between 2 mm and 25 mm. Uncoated soda lime glass is known to be sensitive to weathering and chemical strain and the resulting degradation becomes visible with the appearance of haze.

[0021] In certain example embodiments of the invention, the glass sheets are normal clear or extra-clear soda-lime glass sheets advantageously having a thickness comprised between 2 mm and 12 mm.

[0022] Normal clear and extra-clear glass sheets have been found to be particularly prone to show color changes in reflection and / or transmission when a coating is added on one or more major surfaces.

[0023] Normal clear glass is glass having an content of iron, expressed as Fe2O3, comprised between 0.04 % and 0.4 % by weight. In extra-clear glass the iron content, expressed as Fe2O3, is less than 0.04 % by weight, preferably less than 0.02 % by weight and the redox ratio, measured as the ratio of iron in the ferrous state (expressed as FeO) to the total amount of iron (expressed as Fe2Os) is more than 0.4. Extra-clear glass is particularly advantageous as it has low visible light absorption, which leads to particularly bright edges.

[0024] In certain embodiments of the invention, the coated glass sheets are heat treated, for example annealed or tempered and / or bended. In an embodiment of the present invention the coated glass sheets present a pleasant edge color both before and after heat treatment. Typically this involves heating the coated sheet in a furnace to a temperature of at least 580 °C, more preferably of at least about 600 °C and still more preferably of at least 620 °C before rapidly cooling down the glass substrate. An example heat treating furnace temperature is from 600 to 700 °C. This tempering and / or bending can take place for a period of at least 4 minutes, at least 5 minutes, or more in different situations.Examples

[0025] The coating of comparative example 1 (CEx1 ) was a single 32nm thick aluminum doped Si02 layer deposited on a normal clear soda lime glass sheet of 4mm by magnetron sputtering from a metallic SiAl target having a Al / Si weight ratio of 8%.

[0026] The coating of example 1 (Ex1 ) according to the present invention was a first layer of 27nm thickness of aluminum doped SiO2 layer deposited by magnetron sputtering from a metallic SiAl target having a Al / Si atomic ratio of 8% followed by a second layer of 3nm thickness of SiZrOx on a normal clear soda lime glass sheets of 6mm thickness.

[0027] All layers were deposited by magnetron sputtering. Aluminum doped SiO2 was deposited from a SiAl target, with a Al / Si weight ratio of 8%. The same Al / Si weight ratio is present in the coating. SiZrOx was deposited from a mixed target of Si and ZrO2 having a Si / ZrCh weight ratio of 65 / 35. Typically impurities such as Y may be present in such targets. The resulting SiZrOx layer is preferably fully oxidized and has Zr / Si atomic ratio in this example of 11 / 89. SiO2:AI and SiZrOx layers are typically deposited in a mixed Ar / O2 atmosphere with a Ar / O2 flow rate ratio in range from 0.6 to 1.0.

[0028] Table 1 shows the optical properties obtained before and after thermal treatment (HT)

[0029] Heat treatment conditions were adapted according to the different glass thicknesses. For CEx1 the heat treatment was performed at 670°C for 4 minutes. For Ex1 the heat treatment was performed at 670°C for 6 minutes.

[0030] Optical measurements were performed according to standard EN410 using ilium inant D65, 2° observer angle for transmittance (TL), reflectance on the uncoated side (RLg), and reflectance on the coated side (RLg) and using illuminant D65, 10° observer angle for the colors (a*, b*) in transmittance and reflectance.

[0031] As can be seen from table 1 above, CEx1 has no significant impact on the optical properties of the glass substrate and also Ex1 according to the present invention has only a minimal impact on the optical properties, both before and after heat treatment.

[0032] Two different chemical tests and one combined mechanical and chemical test were used for evaluating the samples. After exposure to each type of test, the samples were evaluated by measuring the haze level, as described in standard ASTM D 1003-61. This standard defines the haze as the percentage of transmitted light, which, while passing through the sample, deviates from the incident beam by an angle of more than 2.5°.

[0033] Both CEx1 and Ex1 show excellent results in condensation resistance, acid resistance neutral salt spray and abrasion resistance tests performed in accordance with standard EN 1096-2012, qualifying as class A coatings.

[0034] with no or very little degradation for a test duration of 21 days, both heat treated and not heat treated.

[0035] To simulate damage to the coated surfaces before heat treatment, the samples were submitted to the abrasion test of EN 1096-2012 mentioned above, followed by heat treatment, followed by exposure for 21 days to humidity in a climatic chamber at a temperature in between 45 and 55°C and a relative humidity of 97%.

[0036] While both CEx1 and Ex1 show no damage with 3 minute and 6 minute abrasion durations, with 30 minute abrasion durations, CEx1 shows 10% more corroded surface than Ex1 .

[0037] A similarly improvement is observed when the abrasion test is performed after heat treatment, to simulate frequent cleaning of coated tempered glass sheets. Here also, CEx1 shows 10% more corroded surface than Ex1.

Claims

ClaimsClaim 1 . Glass pane comprising at least one glass sheet and having a first major surface and a second major surface bearing at least on part of the first major surface a coating comprising a first layer comprising silicon oxide and a second layer comprising a mixed oxide of silicon and zirconium.Claim 2. Glass pane according to claim 1 characterized in that the first layer comprises SiO2 or aluminum doped silicon oxide (SiO2: Al) having a Al / Si weight ratio ranging from 4 to 10%.Claim 3. Glass pane according to any one preceding claim characterized in that the thickness of the first layer ranges from 22 to 32nm.Claim 4. Glass pane according to any one preceding claim characterized in that the first layer is in direct contact with the first major glass surface.Claim 5. Glass pane according to any one preceding claim characterized in that the second layer comprises a mixed oxide of silicon and zirconium (SiZrOx) having a Zr / Si atomic ratio ranging from 10% to 50%.Claim 6. Glass pane according to any one preceding claim characterized in that the thickness of the second layer ranges from 1.5 to 4.5nm.Claim 7. Glass pane according to any one preceding claim characterized in that the second layer is in direct contact with the first layer.Claim 8. Glass pane according to any one preceding claim characterized in that the coating is devoid of any organic coatings.Claim 9. Glass pane according to any one preceding claim characterized in that the color coordinates a* and b* in reflectance of the coated major surface differ by less than 20%, or by less than 10% from the color in reflectance of the uncoated glass pane.Claim 10. Glass pane according to any one preceding claim characterized in that the color in reflectance on the coated major surface are such that a* and b* range from -1 to 1 , before and / or after heat treatment.Claim 11 . Glass pane according to any one preceding claim characterized in that the first and second layers of the coating are magnetron sputtered layers.Claim 12. Glass pane according to any one preceding claim characterized in that the glass pane comprises a single glass sheet or at least two glass sheets united by a thermoplastic intercalating sheet.Claim 13. Glass pane according to any one preceding claim characterized in that the glass sheets are colored, normal clear or extra-clear soda lime glass sheets.Claim 14. Glass pane according to any one preceding claim characterized in that the glass sheets are heat treated, for example annealed or tempered and / or bended.

Images