MIRROR FOR A HUMID ENVIRONMENT

Abstract

A mirror to be tempered includes a glass substrate, a stack of thin layers deposited on one face of the substrate, the stack including a chromium-based or niobium-based metal layer, a coating layer above the stack of thin layers with reference to the glass substrate, in which the coating layer is a layer of mineral paint includes a mixture of an alkaline silicate and at least one white, colored or black pigment.

Claims

1. A mirror to be tempered or a temperable mirror, comprising: a. a glass substrate, b. a stack of thin layers deposited on one face of said substrate, said stack comprising a chromium-based or niobium-based metal layer, one or more underlayers made of dielectric materials, and one or more overlayers made of dielectric materials, said one or more underlayers and one or more overlayers being arranged, respectively, below and above the metal layer, with reference to the glass substrate, c. a coating layer above said stack of thin layers with reference to the glass substrate, in which said coating layer is a layer of mineral paint comprising a mixture of an alkaline silicate and at least one white, colored or black pigment.

2. The mirror as claimed in claim 1, in which the coating layer has an L* value of less than or equal to 50, in the CIE L*a*b* system.

3. The mirror as claimed in claim 1, in which the coating layer has an L* value of less than or equal to 30, in the CIE L*a*b* system.

4. The mirror as claimed in claim 1, in which the thickness of the chromium-based or niobium-based layer is between 10 and 100 nm.

5. The mirror as claimed in claim 1, in which the metal layer is based on chromium.

6. The mirror as claimed in claim 1, in which the metal layer is based on niobium.

7. The mirror as claimed in claim 1, in which the coating layer comprises between 5% and 15% by mass of sodium silicate, potassium silicate and/or lithium silicate.

8. The mirror as claimed in claim 1, in which the coating layer comprises between 5% and 50% by mass of pigment.

9. The mirror as claimed in claim 1, in which the coating layer comprises at least one pigment chosen from oxides or sulfides comprising at least one element chosen from iron, manganese, copper, aluminum, chromium, antimony or cobalt; titanium, silicon, copper, aluminum, chromium, cobalt, iron or manganese oxides or sulfides; zinc, cerium and/or cadmium sulfide; nickel and/or chromium titanates; or bismuth vanadate.

10. The mirror as claimed in claim 1, in which the coating layer comprises at least one pigment based on iron oxide, iron manganese oxide, iron titanium oxide, manganese oxide, chromium oxide, cobalt oxide, tin antimony oxide.

11. The mirror as claimed in claim 1, in which the coating layer also comprises a dispersant, an antifoam agent, a thickener, a stabilizer and/or a hardener.

12. The mirror as claimed in claim 11, in which said agents are present in an amount of between 0.01 and 5% by mass of the paint.

13. The mirror as claimed in claim 1, in which the coating layer comprises pigment particles less than 5 micrometers in size.

14. The mirror as claimed in claim 1, in which the coating layer has a thickness of at least 10 micrometers.

15. A mirror obtained by tempering a mirror to be tempered as claimed in claim 1.

16. A process for manufacturing a mirror to be tempered or a temperable mirror as claimed in claim 1, comprising: a. depositing onto a substrate, onto all or part of at least one face of a glass substrate, a stack of thin layers comprising at least one chromium-based or niobium-based metal layer, one or more underlayers made of dielectric materials, and one or more overlayers made of dielectric materials, said one or more layers of said stack being deposited via the techniques of vacuum cathodic sputtering, b. depositing a coating layer based on an aqueous solution of alkaline silicate and at least one pigment onto all or part of at least one of the faces of said substrate, over said stack, c. drying said coating, in a single step, at a temperature below 400 C.

17. A process for manufacturing a tempered mirror as claimed in claim 16, in which the mirror to be tempered or temperable is subjected to a heat treatment at a temperature above 600 C.

18. A method comprising manufacturing a kitchen backsplash panel with a tempered mirror as claimed in claim 17.

19. The mirror as claimed in claim 4, in which the thickness of the chromium-based or niobium-based layer is between 20 and 80 nm.

20. The mirror as claimed in claim 19, in which the thickness of the chromium-based or niobium-based layer is between 30 and 70 nm.

21. The mirror as claimed in claim 8, in which the coating layer comprises between 10% and 30% by mass of pigment.

22. The mirror as claimed in claim 12, in which said agents are present in an amount of between 0.01 and 1% by mass of the paint.

23. The mirror as claimed in claim 13, in which the coating layer comprises pigment particles less than 2 micrometers in size.

24. The mirror as claimed in claim 14, in which the coating layer has a thickness of at least 20 micrometers.

25. The mirror as claimed in claim 24, in which the coating layer has a thickness of at least 50 micrometers.

26. The process as claimed in claim 16, in which the temperature is below 300 C.

27. The process as claimed in claim 16, in which the vacuum cathodic sputtering is magnetron-assisted.

28. The process as claimed in claim 17, in which the heat treatment is a tempering treatment.

Description

EXAMPLE

[0076] According to the example according to the invention, a low light transmission glazing is manufactured according to the invention in accordance with the teaching of patent application EP962429. The layers of the stack are deposited via the standard magnetron techniques.

The glazing thus obtained may be described as follows:
Glass (Planiclear)/15 nm SiN.sub.x/35 nm Cr/15 nm SiN.sub.x/4 nm Ti.

[0077] The glazing coated with the stack of layers does not undergo any heat treatment, especially tempering, after deposition of the stack of thin layers.

[0078] Onto the stack comprising the chromium-based metal layer is deposited an additional coating layer using an aqueous solution comprising a potassium silicate and pigments, with a dry extract of 58.5% by weight. The aqueous solution deposited onto the glazing is a black mineral paint sold by the company Unikalo under the reference Kalium Silikat Finition Lisse Noire comprising a black pigment based on iron oxide.

[0079] After drying, the paint has the following colorimetric characteristics: L*=25; a*=0.6, b*=0.6.

[0080] The dry extract has the following mass composition of oxide, as measured by XPS (X-ray photoelectron spectrometry):

TABLE-US-00001 C Fe.sub.2O.sub.3 MnO CaO TiO.sub.2 K.sub.2O SiO.sub.2 Al.sub.2O.sub.3 Mg0 Na.sub.2O 15% 31% 0.6% 28% 0.3% 6% 15% 1% 3% 0.5%

[0081] The rheology of the paint is suitable for substantially uniform deposition onto the support with a slight dilution with a diluent product sold by the company Unikalo under the reference Kalium Silikat Diluant Fixatif. After dilution, the paint has a dry extract of about 50% by weight.

[0082] The aqueous composition is applied with a film spreader onto the precleaned glass substrate. The film is spread at a uniform speed, so that the wet thickness of the deposited film is about 150 micrometers. The coating layer is dried by a gradual rise up to 150 C. over a time of about 10 minutes.

[0083] The layer obtained has a final thickness of about 70 m. After drying, it visually appears black and particularly hard and resistant, with strong adhesion to the substrate even in the absence of a consolidating heat treatment.

[0084] The following tests were performed to characterize the properties of the mirror for tempering thus obtained:

1) Opacity test: the mirror is placed on a black support and then on a white support, the values L, a* and b*, according to the CIE L*a*b* international system, being measured through the mirror with a Minolta CM 2600d spectrometer for each support. The values L*; a*; b* are obtained by subtracting the value of the measurement on the black background from the reference value on the white background.
For example: L*=(L* on black background)(L* on white background).
The opacity of the mirror is calibrated by calculating the difference between the two measurements according to the standard formula:

E*={square root over ((L.sub.1L.sub.2).sup.2+(a.sub.1a.sub.2).sup.2+(b.sub.1b.sub.2).sup.2)}

The opacity is judged to be satisfactory for a mirror if the E value is less than 0.5%.
2) Adhesion test of the coating: The test, often referred to as the cross cut test, consists in producing a standardized grid using a cutter on the lacquer face. Using a reference table, a rating is defined which makes it possible to quantify the adhesion and thus to be able to make comparisons between the samples. The lower the rating, the greater the adhesion. The test conducted is performed in accordance with standard ISO 2409:2007.
A maximum rating of 1 is expected to ensure any degradation of the mirror especially during its storage or transportation.
3) Durability test under humid conditions. This test, often referred to as the high humidity test or HH test, is performed in accordance with the standard EN1036. It consists in placing the sample in an atmosphere containing 100% humidity for 7 or 21 days at 40 C. and then inspecting it visually to check the state of the coating. This test makes it possible to measure within a very short time the expected aging of the mirror under humid conditions, in particular in a kitchen or a bathroom. Absence of detachment of the coating is necessary to ensure any degradation of the mirror, during its use or even during its storage or transportation.
4) Durability test at elevated temperature. This test, often referred to as the high temperature test, is performed in accordance with the standard EN1036. It consists in placing the sample in an atmosphere whose humidity is not controlled for 7 days at 65 C. and then inspecting it visually to check the state of the coating. This test makes it possible to measure within a very short time the expected aging of the mirror under hot conditions, in particular such as in a kitchen. Absence of detachment of the coating is necessary to ensure any degradation of the mirror, during its use or even during its storage or transportation in countries with very strong sunshine.

[0085] A sample of a mirror in accordance with the present example, i.e. obtained under the same conditions as described previously, undergoes tempering at 700 C., followed by rapid cooling to room temperature.

[0086] The same tests as indicated previously are once again conducted on the tempered mirror.

[0087] The results obtained are all collated in Table 1 below:

TABLE-US-00002 TABLE 1 Durability Humidity test at Opacity Adhesion durability elevated test test test temperature Non-tempered E < 0.5 N = 1 No No mirror detachment detachment Tempered E < 0.5 N = 0 No No mirror detachment detachment

[0088] It is seen that the mirror before tempering, or even in the absence of any heating other than the drying of the coating layer, has adhesion and durability characteristics that are capable of preventing any problem during any storage or transportation, even in the absence of a consolidating heat treatment.

In addition, the results collated in the preceding table also show that the mirror after tempering has all the characteristics required for its use in humid and/or hot environments, such as on a backsplash panel of a kitchen or in a bathroom.