GREENHOUSE GLAZING

Abstract

A greenhouse glazing, including a glass substrate with a first surface containing a first coating and a second surface containing a second coating. The first surface is an air-side face of the glass substrate and the second surface is a tin-side face of the glass substrate, and the second surface is textured prior to a deposition of the second coating in such a way that a roughness parameter Rsm is at most 155 m. The first coating on the first surface contains a nano-porous silica layer having a thickness between 80 and 150 nm and a transparent conductive oxide located between the nano-porous silica layer and the first surface of the glass substrate. The second coating on the second surface contains a nano-porous silica layer having a thickness between 80 and 180 nm.

Claims

1: A greenhouse glazing, comprising: a glass substrate with a first surface comprising a first coating and a second surface comprising a second coating, wherein, the first surface is an air-side face of the glass substrate and the second surface is a tin-side face of the glass substrate, and the second surface is textured prior to a deposition of the second coating in such a way that a roughness parameter Rsm is at most 155 m, the first coating on the first surface comprises a nano-porous silica layer having a thickness between 80 and 150 nm and a transparent conductive oxide located between the nano-porous silica layer and the first surface of the glass substrate, the second coating on the second surface comprises a nano-porous silica layer having a thickness between 80 and 180 nm.

2: The greenhouse glazing of claim 1, wherein a first dielectric layer is deposited on the first surface between the transparent conductive oxide and the first surface.

3: The greenhouse glazing of claim 2, wherein the first dielectric layer is a titanium oxide layer and has a thickness between 5 and 25 nm.

4: The greenhouse glazing of claim 1, wherein a first dielectric coating laver and a second dielectric coating layer are deposited between the first surface of the glass substrate and the transparent conductive oxide, and the first dielectric layer is deposited directly on the first surface.

5: The greenhouse glazing of claim 4, wherein the first dielectric layer is a titanium oxide layer and has a thickness between 5 and 25 nm, and the second dielectric layer is deposited over the first dielectric layer and has a thickness between 10 and 40 nm.

6: The greenhouse glazing of claim 1, wherein the transparent conductive oxide is a doped tin oxide, the doping agent being fluor or antimony.

7: The greenhouse glazing of claim 1, wherein the transparent conductive oxide has a thickness between 150 and 500 nm.

8: The greenhouse glazing of claim 1, wherein a roughness of the second surface is characterized by a parameter Sa being at least 0.05 m.

9: The greenhouse glazing of claim 1, wherein a roughness of the second surface is characterized by a parameter Sz being at least 1 m.

10: The greenhouse glazing of claim 1, wherein a roughness of the second surface is characterized by the roughness parameter Rsm being 50 m.

11: The greenhouse glazing of claim 1, wherein each of the nano-porous silica layers deposited on the first surface or the second surface of the glass substrate has a refractive index of at most 1.5.

12: The greenhouse glazing of claim 1, wherein an emissivity is smaller than 0.20.

13: The greenhouse glazing of claim 1, having a durability of a class A glazing conform to a norm EN1096-2 2012E.

14: The greenhouse glazing of claim 1, wherein each of the nano-porous silica layers deposited on the first surface or the second surface of the glass substrate has a thickness between 100 and 120 nm.

15: The greenhouse glazing of claim 4, wherein the first dielectric layer is a titanium oxide layer having a thickness between 8 and 15 nm, the second dielectric layer is deposited over the first dielectric layer, and the second dielectric layer is a silicon oxide layer having a thickness between 10 and 40 nm.

16: The greenhouse glazing of claim 1, wherein the transparent conductive oxide has a thickness between 170 and 360 nm.

17: The greenhouse glazing of claim 1, wherein a roughness of the second surface is characterized by a parameter Sa being 0.10-10 m.

18: The greenhouse glazing of claim 1, wherein a roughness of the second surface is characterized by a parameter Sz being 2-12 m.

19: The greenhouse glazing of claim 1, wherein a roughness of the second surface is characterized by a roughness parameter Rsm being 55 m to 140 m.

20: The greenhouse glazing of claim 1, wherein an emissivity is smaller than 0.16.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings and by showing various exemplifying embodiments of the invention.

[0034] FIG. 1 shows 2 preferred embodiments of the invention: FIG. 1a illustrates a glazing of the invention without hortiscatter and FIG. 1b illustrates a glazing of the invention with hortiscatter

[0035] FIG. 2 shows the impact of the antireflective coating on transmittance (FIG. 2a) and reflectance (FIG. 2b). In both graphs, the solid line correspond to the greenhouse glazing of the invention (with antireflective coating on each side) and the dashed line correspond to the same glazing without antireflective coating.

[0036] FIG. 3 shows the angular transmission of the textured glass with 2 antireflective coating and a hortiscatter of 30%.

DESCRIPTION

[0037] The features of our invention are the consequence of a combination of glass quality, glass surface treatment (or not depending the desired hortiscatter) and both low-e and antireflective coatings. Each of those characteristics will now be described with more details.

Definitions

[0038] When a specific range is given for a particular characteristic, we consider the limits of this range is part of it. [0039] PAR meaning is Photosynthetically active radiation and comprises wavelength between 400 to 700 nm, based on NEN 2675+C1:2018. This is the main part of natural light responsible for photosynthetic activities of plants. [0040] Within the context of horticulture, Hortiscatter is the integral value of geometrical distribution of light intensity by bi-directional transmittance (or reflectance) distribution function BTDF under a given angle of incidence of incoming light beam (3D data), defined by Wageningen University and Research (WUR) in the standard NEN 2675+C1:2018. [0041] Hemispherical light transmission (T.sub.hem) is measured following the standard NEN 2675+C1:2018. The hemispherical light transmission is a measure of light transmission at different angles from the point of light incidence. [0042] The refractive index n is calculated from the light spectrum wavelength at 550 nm. [0043] When roughness is considered, the latter is characterized through the Sa, Sz and Rsm values (expressed in micrometers). The roughness parameters were measured by confocal microscopy. The surface parameters (Sa and Sz) according to ISO 25178 standard (part 2 and part 3, 2012F), and the profile parameter (Rsm) by isolating a 2D profile which then gives access to the parameters defined in the ISO 4287-1997 standard. Alternatively, one can use a 3D profilometer for the surface parameters (according to the ISO 25178 standard, part 2 and part 3, 2012F) and a 2D profilometer for the profile parameters (according to the ISO 4287-1997 standard). The texture/roughness is a consequence of the existence of surface irregularities/patterns. These irregularities consist of bumps called peaks and cavities called valleys. On a section perpendicular to the etched surface, the peaks and valleys are distributed on either side of a center line (algebraic average) also called mean line. In a profile and for a measurement along a fixed length (called evaluation length). [0044] Sa (arithmetic mean height) expresses, as an absolute value, the difference in height of each point compared to the arithmetical mean of the surface, the Sa parameter is characterized by a standard deviation of 0.1 m; [0045] Sz (maximum height) is defined as the sum of the largest peak height value and the largest pit depth value within the defined area, the Sz parameter is characterized by a standard deviation of 0.6 m; [0046] Rsm (spacing value, sometimes also called Sm) is the average distance between two successive passages of the profile through the mean line; and this gives the average distance between the peaks and therefore the average value of the widths of the patterns, the Rsm parameter is characterized by a standard deviation of 1.0 m. [0047] The water contact angle is the angle made between the tangent to a water drop and the surface of the support. The measure is made following the standard method ASTM C 813-75 (1989)

[0048] Preferably, the glass used for the invention is a clear glass or an extra clear glass. The clear glass has a composition characterized by an iron content expressed in weight percent of Fe.sub.2O.sub.3 which is at most 0.1%. This value drops to at most 0.015% for the extra clear glass. The glass substrate of the invention has a thickness that is greater than 1 mm, preferably greater than 1.5 mm and more preferably greater than 2 mm. The thickness of the glass substrate is at most 20 mm, preferably at most 15 mm and more preferably at most 10 mm. Advantageously the thickness of the glass substrate is comprised between 3 and 6 mm. A 4 mm glass substrate with the extra clear composition has a light transmission of about 91.7%. Air-side or tin-side referred to the surface of the glass being in contact with the tin bath or the face in air contact during the float process.

[0049] The low-e stack with the transparent conductive oxide is deposited on the air-side of the glass surface during the float manufacturing process. This is a very known process and more particularly the process is performed as it is described in EP1877350B1.

[0050] One surface of the glass can be textured through a mechanical or a chemical process, by methods well known from the man skilled in the art.

[0051] For example, texturing may be obtained by means of a controlled chemical attack with an aqueous solution based on hydrofluoric acid, carried out one or more times. Generally, the aqueous acidic solutions used for this purpose have a pH between 0 and 5 and they can comprise, in addition to the hydrofluoric acid itself, salts of this acid, other acids, such as HCl, H.sub.2SO.sub.4, HNO.sub.3, CH.sub.3CO.sub.2H, H.sub.3PO.sub.4 and/or their salts (for example, Na.sub.2SO.sub.4, K.sub.2SO.sub.4, (NH.sub.4).sub.2SO.sub.4, BaSO.sub.4, and the like), and also other adjuvants in minor proportions. Alkali metal and ammonium salts are generally preferred, such as, for example, sodium, potassium and ammonium bifluoride. The acid etching stage according to the invention can advantageously be carried out by controlled acid attack, for a time which can vary as a function of the acid solution used and of the expected result. Specific textured surface are achieved and are responsible for various level of Hortiscatter.

[0052] In all cases, the glazing is coated with a nano-porous silica layer on both glass surfaces.

[0053] The nano-porous silica layer may be deposited by any known mean. In a preferred embodiment the nano-porous silica layer is a SiO, nano-porous layer deposited as described in EP1679291B1 and in DE10159907A1, both incorporated here by reference. The nano-porous SiO, film will get its final optical and mechanical properties in a two-step production. At first, in the as-deposited state the thin film is coated by a PECVD process and results in high carbon content SiO.sub.xC, coating, the layer comprises 5 to 30 at. % of Silicon, 20 to 60 at. % of Oxygen, 2 to 30 at. % of carbon and 2 to 30 at. % of hydrogen.

[0054] In order to get the final optical and mechanical properties one needs to bake the glass and the film. The carbon is desorbed during the tempering process leaving increased porosity, pores having a mean diameter greater than 5 nm. Increasing porosity results in a smaller refractive index, responsible for the antireflective performance. Preferably, after tempering the refractive index of the SiO.sub.x layer is at most 1.5, preferably at most 1.4 and more preferably at most 1.38. Temperatures for any heat strengthened glass are between 650 C.-680 C. During this tempering process the organic parts will desorb from the coating and leave a porous SiO.sub.2 film. Advantageously, the final refractive index is 1.37.

[0055] Advantageously, the thickness of the heat treated nano-porous silica layer is at least 80 nm, preferably at least 90 nm and more preferably at least 100 nm. The thickness of the silicon oxide based layer is at most 180 nm, preferably at most 140 nm and more preferably at most 120. Advantageously, the film thickness after bake is around 110 nm (5 nm).

[0056] Based on the special plasma process the surface of the glass together with the coating will be densified. The chemical bond between the Si group in the coating and the Si group on the surface of the glass at the interface of coating-glass surface is the main reason on the better mechanical durability performances at least on the tin side. Furthermore regarding the mechanical behaviour, the coating after bake is harder than the uncoated float glass for both sides.

[0057] The existence of the Hortiscatter is due to the presence of special microstructure implemented by texturing the glass surface while the nano-porosity of the anti-reflective coating is only improving the hemispherical light transmission. Moreover the nano-porous silica layer is also protecting the textured surface from corrosion by acting as diffusion barrier for volatile species inside the core glass, giving enhanced chemical and mechanical durability which enable the longer performance with the minimized deterioration rate, being in line with class A coating based on the norm EN 1096-2 (2012-E).

DESCRIPTION OF EMBODIMENTS/EXAMPLES

[0058] The following examples have been made in accordance with the invention.

[0059] Example 1. A first layer of TiO.sub.2 with a thickness of 8.1 nm has been deposited on a ribbon of 4 mm thick extra-clear glass sheet by CVD. The precursor used was titanium tetraisopropoxide (TTIP) and the layer was deposited in the float tank where the glass has a temperature comprised between 660 and 700 C. A second layer of silicon oxide with a thickness of 27.4 nm was deposited on the first layer also by CVD. The precursors used are silane, oxygen and nitrogen as carrier gas. This second layer has been deposited in the float bath when the glass ribbon is at a temperature comprised between 640 and 660 C. A third layer of tin oxide doped with fluorine having a thickness of 320.6 nm was finally deposited above the SiO.sub.2 layer. The precursor used was monobutyl-tin-trichloride (MBTC) combined with trifluoroacetic acid (TFA). The annealed glass sheet, after cooling and cutting process, was transferred to a coating line where a SiO.sub.xC, layer was deposited by a PECVD method as described in EP1679291B1 on both glass sides. Basic coating material is an HMDSO which is heated up in an evaporator outside the line to transfer the chemical fluid from liquid to the gas phase in combination with an plasma in vacuum atmosphere comprising oxygen and forming an amorphous SiO, film with high organically content on the glass surface. Each SiO, layer was heat treated at a temperature between 650 C. and 680 C. during about 4 minutes. After bake the film thickness of the nano-porous silica layer deposited on the tin side of the glass was 118.9 nm and the film thickness of the nano-porous silica layer deposited above the CVD low-e stack, on the air side of the glass was 115.8 nm.

[0060] Example 2. The example 1 is repeated but after the CVD deposition and after the glazing has been cut, the resulted annealed coated glass has been washed with deionized water and then dried. An acid etching solution, composed by volume of 50% NH.sub.4HF.sub.2, 25% water, 6% concentrated H.sub.2SO.sub.4, 6% of a 50% by weight aqueous HF solution, 10% K.sub.2SO.sub.4 and 3% (NH.sub.4).sub.2SO.sub.4, at 20-25 C., was allowed to contact the glass surface for 1.5 minutes on the uncoated side. After removal of the acid solution, the glass surface was rinsed with water and washed again and the resulted textured glass sheet was then transferred to a coating line where a SiO.sub.xC, layer was deposited by a PECVD method on both glass sides in the same way as in example 1. The PECVD coated glass is then sent to a tempering furnace where it is submitted at a temperature between 650 C. and 680 C. during about 4 minutes.

[0061] The performances of the coated glazing of the examples 1 and 2 have been measured after tempering of the coated glass. Results are given in the tables 4 and 5.

TABLE-US-00004 TABLE 4 Measurements on the coated glazing of the example 1 (without hortiscatter). Glazing of the Glazing of the example without example with the the nano-porous nano-porous silica layers silica layers Normal emissivity (%) 13 13 T.sub.hem (%) 75.45 86.6 PAR transmission (%) 82.6 92.6

TABLE-US-00005 TABLE 5 Measurements on the coated glazing of the example 2 Glazing of the example with the nano-porous silica layers Roughness Sa 0.86 m parameters Sz 6.2 m Rsm 80 m Normal emissivity 0.13 T.sub.hem (%) 77.6 PAR transmission (%) 82.3 Water contact angle () <30 Hortiscatter (%) 30

[0062] The durability of the glazing for both example 1 and example 2 has been evaluated through Class A coating testing following EN 1096-2 (Class A) and coating for both examples successfully fulfil the norm.