EA041330B1 - ASYMMETRIC VACUUM INSULATED GLAZING UNIT - Google Patents

Description

Technical field

The invention relates to a vacuum insulating glazing unit provided with a low emissivity coating and having low voltage levels caused by the difference between negative and positive temperatures.

State of the art

Vacuum insulated glazing units (VIG) are recommended due to their high performance thermal insulation. A vacuum insulating glazing unit typically consists of at least two glass panels separated by an interior space in which a vacuum has been created. In general, in order to achieve high performance thermal insulation, the heat transfer coefficient U is U < 1.2 W/m ² K. The absolute pressure inside the glazing unit is usually 0.1 mbar or less, and usually at least one of the two glass panels can be coated with a low-emissivity coating. To obtain such a pressure inside the glazing unit, a hermetically connecting seal is placed on the periphery of two glass panels and a vacuum is created inside the glazing unit using a pump. Separate spacers are placed between the two glass panels to prevent the glazing unit from being pushed inward by atmospheric pressure due to the pressure difference inside and outside the glazing unit.

Typical VIG units are symmetrical VIG units made of two glass panels having the same glass thickness. The high insulating properties of vacuum insulated glazing, together with the inflexible hermetic seals, result in higher thermal stress when there is a large temperature difference between outside and inside the building. Therefore, JP 2001316137 A describes the configuration of an asymmetric vacuum insulated glazing unit in which the inner glass panel located on the inside is thicker than the outer glass panel in order to achieve thermal stress levels under strong sunlight that are lower than in a comparable symmetrical unit. VIG. Although these asymmetrical glazings reduce deformation in summer conditions, they risk being subjected to higher stress than comparable symmetrical VIG units in winter conditions.

JP 2001316138 A describes the opposite asymmetric VIG design in which the outer glass panel located on the outside is thicker than the inner glass panel for improved impact and acoustic performance.

US 2015/0354264 A1 describes a reduced pressure double glazed glass panel with a low emissivity film with an emissivity of 0.067 or less on the second glass surface of the outer glass, i. glass surface of the outer glass, which is oriented towards the part in the form of a gap to ensure sufficient heat-insulating and heat-shielding properties. The low emissivity film is a stack of a lower dielectric layer, a metal layer, a sacrificial layer and a top dielectric layer, preferably formed by magnetron sputtering.

WO 2016/063007 A1 discloses a vacuum insulating glazing unit with a low-e coating on the outward facing surface for anti-condensation properties.

EP 1630344 A1 describes the provision of a low emissivity coating with an emissivity of less than 0.2 on the inner surfaces of glass panels of a vacuum insulated glazing unit. Examples of convenient low emissivity coatings are dielectric/silver/sacrificial/dielectric sputter coating packages or chemical vapor deposition coatings based on doped tin oxide layers. Although the addition of coatings is also interesting for optimizing the insulating or sun protection properties of the VIG, these coatings, however, also change the thermal stress applied to the VIG.

However, there is no prior art solution to the technical problem of temperature induced stress reduction in asymmetric VIG units in which one or more glass panels have sunscreen or insulating low-emissivity coatings and are exposed to temperature differences between outdoor and indoor environments. In addition, there is no prior art solution to the technical problem of atmospheric pressure stress at the post locations of such VIG units, and even how to make such a vacuum insulated glazing unit exhibiting improved levels of combined temperature and pressure stress while maintaining thermal insulation with high performance.

Indeed, there is no solution in the prior art to the technical problem of reducing the combined induced stress and the resulting risk of failure of VIG blocks having infrared reflective coatings, both in summer conditions, when the inside is colder than the outside, and in winter conditions where the outside is colder than the inside, in particular in situations where winter conditions are more severe than summer conditions.

The essence of the invention

It is an object of the present invention to provide a vacuum insulating glazing having an infrared reflective coating on the inner surface of the second glass panel.

- 1 041330 radiation that faces the interior and has a low overall stress-related risk of failure in summer conditions, when the interior is colder than the exterior, and also in winter conditions, when the exterior is cooler than internal, in particular in situations where winter conditions are more severe than summer conditions. The infrared reflective coating in the present invention may be an insulating coating or a sun protection coating.

The present inventors have surprisingly found that the combination of specific dimensions and thicknesses of the inner and outer glass panels, together with specific spacer spacing, as well as specific coating arrangements and energy properties of the glass panels, resulted in a significant reduction in the overall risk of stress-related failure in vacuum insulated glazings. which are exposed to both moderate summer conditions, when the interior is colder than the exterior, and severe winter conditions, when the exterior is colder than the interior. In the present invention, the total induced stress of asymmetrical VIGs is reduced, in particular embodiments, winter stress is reduced to a level lower than that of their equivalent symmetrical VIGs. The equivalent symmetric VIGs are identical in all respects, in particular with respect to the external dimensions of length, width and overall thickness, except that the thicknesses of the first and second sheets of glass are the same. Symmetrical VIGs have proven themselves in the market and naturally form the starting point for new developments in the field. It is well known that they typically reach their highest levels of combined induced stress in winter conditions. Thus, the maximum level of combined induced voltage of equivalent symmetrical VIGs achievable in both winter and summer conditions provides a useful reference value for comparison with asymmetrical VIG. In certain specific embodiments of the present invention, the total induced stress values of the asymmetrical VIGs in both winter and summer conditions are lower than the maximum induced stress levels that their equivalent symmetrical VIGs withstand in summer or winter conditions.

The present invention relates to a vacuum insulating glazing unit extending along a plane P defined by a longitudinal X axis and a vertical Z axis, and having a width W measured along the longitudinal X axis and a length L measured along the vertical Z axis. The length L of the vacuum insulating glazing unit is in the range of 300 to 4000 mm (300 mm < L < 4000 mm), and the width W of the vacuum insulating glazing unit is in the range of 300 to 1500 mm (300 mm < W < 1500 mm). In certain preferred embodiments of the present invention, L is in the range of 300 to 3000 mm to further reduce stress. Vacuum insulating glazing unit contains:

a) a first glass panel having a thickness Z ₁ and an energy absorption index EA ₁ ,

b) a second glass panel having a thickness Z2 and an energy absorption index EA2,

c) while Z ₁ is equal to or greater than 5 mm, and

d) the difference in thickness AZ between the thickness Z ₁ of the first glass panel and the thickness Z2 of the second glass panel is equal to or greater than 1 mm (AZ = Z ₁ - Z2 > 1 mm),

e) a set of separate spacers located between the first and second glass panels, maintaining the distance between the first and second glass panels and forming an array with a step λ. The step λ is in the range from 10 to 35 mm (10 mm < λ < 35 mm),

f) a hermetically connecting seal (4) sealing the distance between the first and second glass panels along their perimeter,

g) an internal volume V formed by the first and second glass panels and a set of separate spacers and closed by a hermetically connecting seal, and while there is a vacuum with an absolute pressure of less than 0.1 mbar,

h) an infrared reflective coating having an emissivity of not more than 0.4 on the side facing the interior volume of the second glass panel.

Conventionally, to describe the position of a panel surface in an insulating glazing unit, the surfaces of two or more glass panels are numbered from the surface of the panel that faces the outside (position 1) to the surface of the panel that faces the inside (position 4 in double glazing). For the purposes of vacuum insulating glazings according to the present invention, the numbering of the surfaces of the VIG panel is retained even in embodiments in which this VIG is combined with additional glass panels. In addition, the thicknesses are measured in the direction perpendicular to the plane P. For the purposes of the present invention, glass thicknesses are rounded off to the nearest millimeter.

The vacuum insulating glazing unit of the present invention has an infrared reflective coating at position 3, which is on the surface of a second inner glass panel that is oriented towards the interior volume. A low total induced voltage is obtained when the weighted difference in the energy absorption rate between the outdoor

- 2 041330 glass panel and internal glass panel ΔΕΑ is not more than 0.0033 ΔΖ ² /μμ ² 0.0468 ΔΖ/μμ + 0.7702 (ΔΕΑ <0.0033 ΔΖ ² /μμ ² - 0.0468 ΔΖ/μμ + 0.7702; ΔΕΑ = EA1 - 2-EA2).

Other aspects and advantages of the embodiments will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate by way of example the principles of the described embodiments.

Brief description of graphic materials

This aspect and other aspects of the present invention will be described in more detail below with reference to the accompanying drawings, which show an exemplary embodiment of the invention.

The drawing shows a cross-sectional view of an asymmetric vacuum insulating glazing unit according to one embodiment of the present invention.

Description of Embodiments

It is an object of the present invention to provide a vacuum insulating glazing unit (hereinafter referred to as VIG) which exhibits low temperature-induced stress when subjected to a high positive and negative temperature difference between the external and internal environments, provides thermal insulation properties, is very stable over life and can be produced efficiently and cost-effectively.

In particular, it is an object of the present invention to provide a vacuum insulating glazing unit (hereinafter referred to as VIG) that exhibits high performance thermal insulation or sun protection and improved resistance to stress caused by a combination of temperature difference between indoor and outdoor environments and atmospheric pressure.

These objectives are realized by the vacuum insulating glazing unit according to the present invention, which is asymmetric, i.e. in which the first glass panel is thicker than the second glass panel (Z ₁ >Z ₂ ) and is carefully selected to a specific dimension, including a length range (L) and a width range (W), a specific spacer spacing (λ) and a specific thickness of the second glass panel (Z ₂ ), and in which the second glass panel has an infrared reflective coating on its inner surface facing the inner volume, when the following condition is met in relation to the weighted difference of the energy absorption index between the first and second glass panels:

ΔΕΑ <0.0033 ΔΖ ² /μμ ² - 0.0468 ΔΖ/μμ + 0.7702; ΔΕΑ=ΕΑ ₁ - 2 ΕΑι, while 300 mm < L <4000 mm,

300 mm < W < 1500 mm,

Z ₁ > 5 mm, Z ₂ > 3 mm,

ΔΖ=Z1 - Z ₂ > 1 mm, and mm < λ < 35 mm.

The thicker first glass panel is designed to face outside the building, the thinner second glass panel is designed to face the inside of the building. This combination of different thicknesses improves the voltage associated with winter conditions, also in the case of an infrared reflective coating in position 3. Surprisingly, also in summer conditions, low voltage can be obtained on such an asymmetric VIG having an infrared reflective coating, in position 3. In order to achieve this, it has, in fact, been found to be critical to adapt the energy absorption index levels of the first and second glass panels to the critical dimensions of the VIG.

The present invention relates to a vacuum insulating glazing unit typically comprising a first glass panel and a second glass panel connected to each other by means of a set of separate spacers that hold said panels at a certain distance from each other, typically in the range of 50 to 1000 µm, preferably from 50 to 500 µm, more preferably from 50 to 150 µm, and between said glass panels an internal space containing at least one first cavity in which there is an absolute vacuum with a pressure of less than 0.1 mbar, said space being closed by a peripheral hermetically connecting seal placed on the periphery of the glass panels around the specified interior space. In the present invention, the pitch of the struts should be understood as the shortest distance separating any given strut from its closest adjacent strut. Preferably the spacers are spaced apart from each other in a repeating pattern, such as a square, hexagon or triangle.

As illustrated in FIG. 1, the vacuum insulating glazing unit (10) extends along a plane P formed by the longitudinal axis X and the vertical axis Y. The VIG according to the present invention comprises:

a) a first glass panel (1) having an inner surface (12) of the panel and an outer surface (13) of the panel and having a thickness Z1, and a second glass panel (2) having an inner

- 3 041330 the surface (22) of the panel and the outer surface (23) of the panel and having a thickness Z ₂ . Thicknesses are measured to the nearest mm in the direction perpendicular to the plane P;

b) a set of separate spacers (3) located between the first and second glass panels and maintaining the distance between the first and second glass panels;

c) a hermetically connecting seal (4) sealing the distance between the first and second glass panels along their perimeter;

d) an internal volume V formed by the first and second glass panels and a set of separate spacers and closed with a hermetically bonding seal, and there is a vacuum with an absolute pressure of less than 0.1 mbar.

The vacuum insulating glazing unit according to the present invention is hereinafter referred to as asymmetric VIG.

In VIG, the first glass panel has an inner surface (12) of the panel and an outer surface (13) of the panel. The second glass panel has an inner surface (22) of the panel and an outer surface (23) of the panel. The inner surfaces of the panels face the inner volume V of the asymmetric VIG. For example, the outer surfaces of the panels face the exterior and interior of the building.

As illustrated in the drawing, the inner surface (12) of the panel of the first glass panel (1) of the asymmetric VIG according to the present invention is provided with an infrared reflective coating (hereinafter referred to as an IR reflective coating).

The IR reflective coating (5) according to the present invention has an emissivity of at most 0.4, preferably less than 0.2, in particular less than 0.1, less than 0.05 or even less than 0.04. The IR reflective coating according to the present invention may comprise a metal-based low-emissivity IR reflective coating; these coatings are usually a system of thin layers containing one or more, for example two, three or four, functional layers based on an infrared reflective material and at least two dielectric coatings, with each functional layer surrounded by dielectric coatings. The IR reflective coating according to the present invention may in particular have an emissivity of at least 0.010. The functional layers are typically silver layers a few nanometers thick, typically around 5-20 nm. As for the dielectric layers, they are transparent and traditionally each dielectric layer is made of one or more layers of metal oxides and/or nitrides. These different layers are deposited, for example, using vacuum sputtering techniques such as magnetic field cathode sputtering, more commonly known as magnetron sputtering. In addition to dielectric layers, each functional layer can be protected by barrier layers or enhanced by deposition on a wetting layer.

The IR reflective coatings of the present invention may have anti-solar or sun protection properties which may reduce the risk of overheating, for example in enclosed spaces with large glazed surfaces, and thus reduce the energy load that must be considered for air conditioning in the summer. . In this case, the glazing should transmit as little total solar energy radiation as possible, i.e. it should have as low a solar factor (SF or g) as possible. It is often highly desirable that the glazing guarantee a certain level of light transmission (LT) in order to provide a sufficient level of illumination within the building. These somewhat conflicting requirements reflect the desire for a glazing element with high selectivity (S), defined as the ratio of light transmission to solar factor. The IR reflective coatings of the present invention may also be low emissivity insulating coatings adapted to reduce building heat loss through longer wavelength infrared radiation. Thus, they improve the thermal insulation of glazed surfaces and reduce energy losses and heating costs during cold periods.

Specific Embodiments

The following specific embodiments of combinations of glass panel thicknesses, pitch ranges and sizes have been found to provide lower levels of combined induced stress in both winter and summer conditions than equivalent symmetrical vacuum insulating glazing of the same overall thickness. EA ₁ and EA2 denote the energy absorption values of the first and second glass panels, respectively.

In particular, the voltage resistance of the present invention in summer conditions is evaluated in comparison with its equivalent symmetrical VIG. For the purposes of the present invention, a symmetrical VIG equivalent to an asymmetric VIG is a VIG having all the values W, L, λ, having the same overall thickness Z1+Z2, but in which the thickness of the first panel is the same as that of the second panel, Z1 =Z ₂ .

In particular, for vacuum insulated glazing in both winter and summer conditions, lower levels of combined induced stress are achieved than the maximum level of combined stress induced in equivalent symmetrical vacuum insulating glazing of the same total thickness, while Z2 =3 mm, and 10 mm < λ < 25 mm, when the following condition is met with respect to the weighted difference in the energy absorption index between the first and second glass panels: AEA < 0.0084 ΔΖ ² /μμ ² - 0.1545 AZ/mm + 0 .6966; ΔΕΑ = EA1 -2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, AZ = Z1 - Z2 > 1 mm.

In particular, for vacuum insulated glazing in both winter and summer conditions, lower levels of combined induced stress are achieved than the maximum level of combined stress induced in an equivalent symmetrical vacuum insulating glazing of the same total thickness, with Z2=4 mm, and 10 mm < λ < 25 mm, when the following condition is met with respect to the weighted difference in the energy absorption index between the first and second glass panels: AEA < - 0.0214 AZ/mm + 0.5696; AEA = EA1 - 2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, AZ = Z1 - Z2 > 1 mm.

In particular, for vacuum insulated glazing in both winter and summer conditions, lower levels of combined induced stress are achieved than the maximum level of combined stress induced in an equivalent symmetrical vacuum insulating glazing of the same total thickness, with Z2=5 mm, and 10 mm < λ < 35 mm, when the following condition is met with respect to the weighted difference in the energy absorption index between the first and second glass panels: AEA < 0.0033 ΔΖ ² /μμ ² - 0.0468 AZ/mm + 0.7434; AEA = EA1 - 2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, AZ = Z1 - Z2 > 1 mm.

In particular, for vacuum insulated glazing in both winter and summer conditions, lower levels of combined induced stress are achieved than the maximum level of combined stress induced in an equivalent symmetrical vacuum insulating glazing of the same total thickness, with Z ₂ =6 mm , and 10 mm < λ < 35 mm, when the following condition is met in relation to the weighted difference in the energy absorption index between the first and second glass panels: AEA < 0.0033 ΔΖ ² /μ ² - 0.0468 AZ / mm + 0.7702; AEA = EA1 -2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, AZ = Z1 - Z2 > 1 mm.

In particular, for vacuum insulated glazing in both winter and summer conditions, lower levels of combined induced stress are achieved than the maximum level of combined stress induced in an equivalent symmetrical vacuum insulating glazing of the same total thickness, with Z ₂ =4 mm , and 25 mm < λ < 30 mm, when the following condition is met in relation to the weighted difference in the energy absorption index between the first and second glass panels: AEA < - 0.0308 AZ/mm + 0.5294; AEA = EA1 - 2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, AZ = Z1 - Z2 > 1 mm.

In one embodiment of the present invention, the thickness Z1 of the first glass panel of the asymmetric VIG may be equal to or greater than 5 mm (Z1 > 5 mm), preferably may be equal to or greater than 6 mm (Z1 > 6 mm), preferably equal to or greater than 8 mm (Z1 > 8 mm). Typically, the thickness Z1 of the first glass panel does not exceed 12 mm, preferably does not exceed 10 mm.

In another embodiment, the thickness Z2 of the second glass panel of the asymmetric VIG may typically be equal to or greater than 3 mm (Z ₂ > 3 mm), preferably may be equal to or greater than 4 mm (Z ₂ > 4 mm), preferably equal to or greater than 5 mm ( Z ₂ > 5 mm). Typically, the thickness Z ₂ of the second glass panel does not exceed 10 mm, preferably does not exceed 8 mm. However, in order to improve the mechanical resistance of the asymmetric VIG according to the present invention, it is preferable to keep the thickness Z ₂ of the second panel to a minimum. In another embodiment of the present invention, the present invention is also applicable to any type of glazing unit comprising glass panels (two, three or more) linking insulating or non-insulating interior spaces (also referred to as laminated glazing units), provided that the partial vacuum is applied at least measure in one of these internal spaces. Therefore, in one embodiment, to improve the mechanical performance of the asymmetric VIG according to the present invention, a third additional glass panel may be connected to at least one of the outer surfaces (13 and/or 23) of the panel of the first and second glass panels along the periphery of the VIG by means of a peripheral spacer. , creating an insulating cavity sealed with a peripheral edge seal. The specified peripheral spacer frame maintains a certain distance between the third glass panel and at least one of the outer surface of the panel of one of the first and second glass panels. Typically, said spacer contains a moisture absorber and typically has a thickness of 6 to 20 mm, preferably 9 to 15 mm. In general, said second internal volume is filled with a predetermined gas selected from the group consisting of air, dry air, argon (Ar), krypton (Kr), xenon (Xe), sulfur hexafluoride (SF6), carbon dioxide, or a combination thereof. Said target gas is effective in preventing heat transfer and/or may be used to reduce sound transmission.

- 5 041330

When an asymmetric VIG is used to close an opening within a partition separating the interior and exterior spaces, it is preferred that the third glass panel faces the exterior. It is also preferred that the third glass panel be provided with at least a TCO-based pyrolytic coating on at least one of its surfaces. Such a particular glazing unit provides higher mechanical performance while improving emissivity performance and/or reducing condensation. In particular and for safety reasons, at least one sheet of glass can be additionally layered on the outer surface (23) of the second glass panel facing the interior environment by means of at least one polymeric intermediate layer to form a multilayer assembly.

In one embodiment of the present invention, at least one of the outer surfaces (13 and/or 23) of the panel of the first and second glass panels can be further laminated with at least one additional sheet of glass by means of at least one polymeric interlayer to form a multilayer assembly. for security and reliability purposes.

In a multilayer assembly, at least one additional sheet of glass preferably has a thickness Z _s equal to or greater than 0.5 mm (Z _s > 0.5 mm). The thickness is measured in a direction perpendicular to plane P. At least one polymeric interlayer is a transparent or translucent polymeric interlayer containing a material selected from the group consisting of ethylene vinyl acetate (EVA), polyisobutylene (PIB), polyvinyl butyral (PVB), polyurethane ( PU), polyvinyl chlorides (PVC), polyesters, copolyesters, assembly polyacetals, cycloolefin polymers (COP), ionomer and/or UV-activated adhesive and others known in the laminated glass industry. Mixed materials using any compatible combination of these materials may also be suitable.

To improve the performance of a window or door, reinforced sound insulation with sound-absorbing laminated glass is also compatible with the concept of the present invention. In this case, the polymeric intermediate layer contains at least one additional sound-absorbing material placed between two polyvinyl butyral films. Glass panels with electrochromic, thermochromic, photochromic or photovoltaic cells are also compatible with the present invention.

The first and second asymmetric VG glass panels of the present invention may be selected from thermopolished sheet clear glass, extra clear glass, or colored glass technologies. The term glass in this document refers to any type of glass or equivalent transparent material such as mineral glass or organic glass. The mineral glasses used can independently be one or more known types of glass such as soda-lime silicate, aluminosilicate or borosilicate, crystalline and polycrystalline glasses. The glass panel can be produced by a float process, a drawing process, a rolling process, or any other known process for making a glass panel, starting from a molten glass composition. Glass panels may optionally have sanded edges. Edge grinding turns sharp edges into smooth edges that are much safer for people who may come into contact with vacuum insulated glazing, in particular the edge of the glazing. Preferably, the glass panel according to the present invention is a soda lime silicate glass, aluminosilicate glass or borosilicate glass panel. More preferably, and for reasons of lower manufacturing costs, the glass panel of the present invention is a soda lime silicate glass panel. Typically, the first and second glass panels according to the present invention are annealed glass panels. Preferably, the composition for the first and second asymmetric VIG glass panels according to the present invention contains the following components in weight percent, expressed relative to the total weight of the glass (Table 1, composition A). More preferably, the glass composition (Table 1, Composition B) is soda-lime silicate glass with a base glass matrix composition containing the following components in weight percent, expressed relative to the total weight of the glass.

- 6 041330

Composition A Composition B _SiO2 40 to 78% 60 to 78% A1 ₂ 0z 0 to 18% 0 to 8%, preferably 0 to 6% B ₂ O ₃ 0 to 18% 0 to 4%, preferably 0 to 1% _Na2O 0 to 20% 5 to 20%, preferably 10 to 20% Cao 0 to 15% 0 to 15%, preferably 5 to 15% MgO 0 to 10% 0 to 10%, preferably 0 to 8% K ₂ O 0 to 10% 0 to 10% VAO 0 to 5% 0 to 5%, preferably 0 to 1%.

Table 1

Other private glass compositions for the first and second asymmetric VIG glass panels according to the present invention contain the following components, presented in table. 2, in weight percent, expressed relative to the total weight of the glass.

_________________________________________________________ Table 2

Composition C Composition D Composition E 65 < SiO ₂ < 78 wt. % 60 < SiO ₂ < 78% 65 < SiO ₂ < 78 wt. % 5 < Na ₂ O < 20 wt. % 5 < Na ₂ O < 20% 5 < Na ₂ O < 20 wt. % 0 < K ₂ O < 5 wt. % 0.9 < K ₂ O < 12% 1 < K ₂ O < 8 wt. % 1 < A1 ₂ O ₃ < 6 wt. %, pred. 3 < A1 ₂ O ₃ < 5% 4.9 < A1 ₂ 0z < 8% 1 < A1 ₂ O ₃ < 6 wt. % 0 < CaO < 4.5 wt. % 0.4 < CaO < 2% 2 < CaO < 10 wt. % 4 < MgO < 12 wt. % 4 < MgO < 12% 0 < MgO < 8 wt. % (MgO/(MgO+CaO)) > 0.5, preferably 0.88 < [MgO/(MgO+CaO)] < 1 0.1 < K ₂ O/(K ₂ O+Na ₂ O) < 0.7

In particular, examples of basic glass matrices for the composition according to the present invention are described in PCT patent applications WO 2015/150207 Al, WO 2015/150403 A1, WO 2016/091672 Al, WO 2016/169823 A1 and WO 2018/001965 A1.

The second and first glass panels may have the same dimensions or different dimensions and thus form a stepped VIG. In a preferred embodiment of the present invention, the first and second glass panels comprise first and second peripheral edges, respectively, wherein the first peripheral edges are recessed relative to the second peripheral edges, or wherein the second peripheral edges are recessed relative to the first peripheral edges. This configuration allows the hermetically bonding seal to be reinforced.

In one embodiment, to provide the VIG with higher mechanical performance and/or to further improve the safety of the VIG, thermal or chemical prestressing of the first and/or second glass panels of the present invention may be provided. In this case, both the first and second glass panels are required to be subjected to the same prestressing treatment in order to provide the same resistance to temperature-induced stress. Therefore, if a prestressing treatment of glass panels occurs, then it requires that both of the first glass panel and the second glass panel are heat-strengthened glass panels, or that both of the first glass panel and the second glass panel are heat-strengthened glass panels, or that both of the first glass panel and the second glass panel were chemically strengthened glass panels.

Heat-strengthened glass is heat treated using a controlled heating and cooling process in which the surface of the glass is subjected to compression and the interior of the glass is subjected to tensile stress. This heat treatment method provides glass with a bending strength greater than annealed glass but less than thermally toughened impact glass.

Thermally toughened impact resistant glass is heat treated using a controlled high temperature heating and rapid cooling process in which the surface of the glass is subjected to compression and the interior of the glass is subjected to tensile stress. Such stresses cause the glass, when impacted, to break into small particles in the form of granules instead of shattering into sharp fragments. Granular particles are less likely to injure people or damage objects.

Chemical strengthening of a glass product is a heat-induced ion exchange that consists in replacing smaller sodium alkali ions with larger ions, such as potassium alkali ions, in the surface layer of the glass. An increase in surface compressive stress occurs in glass as larger ions are introduced into small areas previously occupied by sodium ions. Such chemical treatment is usually carried out by immersing the glass in a bath of ion-exchange melt containing one or more molten salts with larger ions, under precise control of temperature and time. Aluminosilicate-type glass compositions such as, for example, those derived from the DragonTrail® product line manufactured by Asahi Glass Co. or originating from Corning Inc.'s Gorilla® product line are also known for high chemical hardening performance.

As shown in the drawing, the vacuum insulating glazing unit according to the present invention comprises a plurality of individual spacers (3), also called struts, located between the first and second glass panels (1, 2) to maintain the internal volume V. According to the present invention, individual spacers are located between the first and the second glass panels, maintaining the distance between the first and second glass panels and forming an array with a step λ ranging from 10 to 35 mm (10 mm < λ < 35 mm). Pitch refers to the spacing between the individual spacers. In a preferred embodiment, the pitch is in the range of 20 to 35 mm (20 mm < λ < 35 mm). The array in the present invention is typically a uniform array based on an equilateral triangle, square, or hexagon pattern, preferably a square pattern. The individual spacers may have different shapes, such as cylindrical, spherical, thread-like, hourglass-shaped, C-shaped, cruciform, prismatic, etc. It is preferable to use small racks, i.e. posts having a common surface of contact with the glass panel formed by their outer circumference equal to or less than 5 mm ² , preferably equal to or less than 3 mm ² , more preferably equal to or less than 1 mm ² . These values can provide good mechanical resistance while being aesthetically abstract.

The individual spacers are generally made of a material having strength capable of withstanding the pressure exerted by the surfaces of the glass panels, capable of withstanding a high temperature process such as annealing and heat curing, and slightly outgassing after the glass panel is manufactured. Such a material is preferably a hard metal material, a quartz glass or a ceramic material, in particular a metal material such as iron, tungsten, nickel, chromium, titanium, molybdenum, carbon steel, chromium steel, nickel steel, stainless steel, nickel-chromium steel, manganese steel, chromium-manganese steel, chromium-molybdenum steel, silicon steel, nichrome, duralumin and the like, or a ceramic material such as corundum, alumina, mullite, magnesia, yttrium oxide, aluminum nitride, silicon nitride and the like.

As shown in the drawing, the internal volume V, limited between the glass panels (1, 2) of the vacuum insulating glazing (10), according to the present invention, is closed by a hermetically connecting seal (4) placed on the periphery of the glass panels around the said internal space. Said hermetically bonding seal is impermeable and solid. In the present description, unless otherwise indicated, the term impermeable means impervious to air or any other gas present in the atmosphere.

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There are various technologies for hermetically bonding sealing. The first type of seal (the most common) is a glass solder seal, which has a melting point lower than that of the glass panes of the glazing unit. The use of this type of seal limits the selection of low emissivity layers to those that do not decompose during the thermal cycle required for glass solder applications, i.e. those that can withstand temperatures that can reach 250°C. Additionally, since this type of seal based on glass solder can only be deformed to a small extent, it prevents the effects of absorbed relative expansion between the glass panel on the inside of the glazing unit and the glass panel on the outside of the glazing unit when these panels are subjected to large temperature differences. Consequently, sufficiently significant stresses are generated at the periphery of the glazing unit, and this can lead to the destruction of the glass panels of the glazing unit.

The second type of seal is a metal seal, e.g., a thin metal strip (<500 µm), soldered around the periphery of the glazing unit with a primer coated at least partially with a layer of solderable material, e.g., tin soft solder. One significant advantage of this second type of seal over the first type of seal is that it is able to partially deform to partially absorb the relative expansion created between the two glass panels. There are different types of undercoats on glass panel.

Patent application WO 2011/061208 A1 describes one exemplary embodiment of a second type of peripheral tight seal for a vacuum insulating glazing unit. In this embodiment, the seal is a metal strip, for example made of copper, which is soldered by means of a solderable material to an adhesive tape provided on the periphery of the glass panels.

A vacuum with an absolute pressure of less than 0.1 mbar, preferably less than 0.01 mbar, is created in the internal volume V, formed by the first and second glass panels and a set of separate spacers and closed by a hermetically connecting seal inside the asymmetric VIG of the present invention.

The internal volume of the asymmetric VIG of the present invention may contain a gas, for example, but not exclusively, air, dry air, argon (Ar), krypton (Kr), xenon (Xe), sulfur hexafluoride (SF 6 ), carbon dioxide, or a combination thereof. The transfer of energy through an insulating panel having this conventional structure is reduced due to the presence of gas in the interior relative to the single glass glass panel.

Any gas can also be evacuated from the internal volume, thereby creating a vacuum glazing unit. The energy transfer through the vacuum insulating glazing unit is greatly reduced by the vacuum. To create a vacuum in the interior of the glazing unit, a hollow glass tube is usually provided on the main surface of one of the glass panels to provide communication between the interior and the exterior. Thus, a partial vacuum is generated in the interior by pumping out the gases in the interior with a pump connected to the outer end of the glass tube.

To maintain a predetermined vacuum level in the vacuum insulating glazing unit for a certain time, the getter can be used in the glazing panel. In particular, the inner surfaces of the glass panels constituting the glazing panel may release, over time, the gases previously absorbed by the glass, thereby increasing the internal pressure in the vacuum insulating glazing panel and thus reducing the vacuum index. In general, such a getter consists of alloys of zirconium, vanadium, iron, cobalt, aluminum, etc. and is applied as a thin layer (several microns thick) or made as a bar placed between the glass panels of the glazing panel so that it is not visible (for example, hidden by outer enamel or part of a peripheral impermeable seal). The getter forms a passivation layer on its surface at room temperature, and therefore it must be heated to remove the passivation layer and thus activate the getter properties of its alloy. The getter is considered to be heat activated.

- 9 041330

Reference position Component 10 Vacuum Insulation Glazing Block 1 First glass panel 12 The inner surface of the panel of the first glass panel 13 The outer surface of the panel of the first glass panel 2 Second glass panel 22 The inner surface of the panel of the second glass panel 23 The outer surface of the panel of the second glass panel 3 Separate spacers 4 Hermetically sealing seal 5 Low emissivity coating V Internal volume

Table 3

Examples

To assess the risk of breakage, the combined stress resulting from the atmospheric pressure stress due to the vacuum in the internal volume V and the temperature-induced stress due to the temperature difference on both sides of the glazing was calculated.

Since a vacuum is maintained between the two VIG panels, atmospheric pressure induces a constant tensile stress on the outer surfaces of the VIG glass panels at each rack location. It is known to the person skilled in the art that for small studs, the tensile stress caused by the studs on the outer surfaces of the glass panels is independent of the size of their outer circumference. By small posts, as a rule, stands are meant having a contact surface with a glass panel, formed by their outer circumference, equal to or less than 5 mm ² , preferably equal to or less than 3 mm ² , more preferably equal to or less than 1 mm ² .

In such cases, and for uniform arrays based on an equilateral triangle, square, or hexagon pattern, such atmospheric pressure stress, also referred to as tensile stress, can be calculated for a glass panel using the following formula: p < 0.1 lx ² /Z ² [], where [w] and Z[m] are the spacing between the spacers and the thickness of the glass panel, respectively. A step should be understood as the shortest distance separating any spacer from its adjacent spacer. In particular, for uniform arrays based on a square, the tensile stress is maximum, and therefore the following formula is observed: p=0.1 lx ² /Z ² [].

The maximum stress from atmospheric pressure is calculated for each of the first and second sheets of glass VIG, σ _ρ1 and σ _ρ2 .

The temperature-induced tensile stress on the outer surface of the glass panel VIG occurs immediately after the appearance of a temperature difference between the first glass panel (1, Tt) and the second glass panel (2, T ₂ ) and increases as the difference between 11 and T ₂ increases. The temperature difference (ΔΤ) is the absolute difference between the average temperature _Tb calculated for the first glass panel (1) and the average temperature _T2 calculated for the second glass panel (2). The average temperature of the glass panel can, for example, be calculated based on numerical simulations known to the person skilled in the art. For the present invention, the temperature difference between two glass panels was calculated using the Window 7.4 calculation software, which is based on the method proposed by the National Window Distribution Rating Council of America NFRC, which complies with ISO 15099. Stress caused by temperature can lead to the destruction of the VIG, when such an absolute temperature difference between glass panels reaches 30°C, and even more when the absolute temperature difference is higher than 40°C under severe conditions. The temperature of the internal environment is usually between 20 and 25°C, while the temperature of the external environment can vary from -20°C in winter to +35°C in summer. Therefore, the temperature difference between the indoor environment and the outdoor environment can reach more than 40°C under harsh conditions. Therefore, the temperature difference (ΔΤ) between the average temperature _Tb calculated for the first glass panel (1) and the average temperature _T2 calculated for the second glass panel (2) can also reach more than 40°C. Numerical simulation is used to calculate the maximum thermal stress σ _τ induced on the outer surface of each glass panel VIG. The finite element (FEA) model of the commercially available software Abaqus2017 (formerly called ABAQUS) was developed to model the behavior of VIG

- 10041330 when exposed to different temperature conditions. Calculations were made for glass panels fitted with a grid using C3D8R elements with 5 integration points per glass thickness. The total mesh size used was 1 cm. To achieve the AT of the present invention, a reference and constant temperature was applied to both glass panels, then one of the glass panels was subjected to a constant temperature variation while the other glass panel was maintained at the reference temperature. A mechanical joint was placed between two glass panels to ensure equal displacement of the two touching glass surfaces. Other boundary conditions have been specified to prevent motion of the rigid body of the assembly. Calculations were carried out for all glazings with free, unlimited edges.

The severe winter temperature conditions used for the purposes of the present invention were an outside air temperature of -20°C, an inside air temperature of 20°C, resulting in a maximum temperature difference between outside and inside of 40°C.

The inventors have found that when temperature-induced stress and atmospheric pressure stress occur simultaneously in a glass panel, the combined stress (σ _ε ), which is the combination of temperature-induced stress and atmospheric pressure stress, must be taken into account when sizing VIG. The term combined induced stress or combination of induced stresses should be understood as the sum of the stress caused by temperature and the stress caused by atmospheric pressure (σ _ε = σ _p + σ _T ). The combined stress can be calculated for selected winter conditions σ _cw and for selected summer conditions σ _cs .

It was found that under winter conditions, when VIG is asymmetric with a thicker first glass panel and a thinner second glass panel, the highest combined winter stress σ _cwmax , which is the highest value among the combined winter stress of the first glass panel (σ _cw1 = σ _p1 + σ _Tw1 ) and the combined winter stress of the second glass panel (σ _cw2 = σ _p2 + σ _Tw2 ) σ _cwmax = max(σ _cw1 , σ _cw2 ), is reduced. In particular, for an asymmetric VIG, subject to the following size criteria:

300 mm < L < 4000 mm,

300 mm < W < 1500 mm,

Z ₁ > 5 mm, Z ₂ > 3 mm,

ΔZ = Z ₁ - Z ₂ > 1 mm and mm < λ < 35 mm, the highest combined winter stress is lower than the highest combined winter stress of an equivalent symmetrical VIG having the same overall thickness.

The moderate summer temperature conditions used for the purposes of the present invention were outdoor air temperature 32°C, indoor air temperature 24°C and solar flux 783 W/m ² .

In summer conditions, the highest combined summer stress σ _csmax is the highest value among the combined summer stress of the first glass panel (σ _cs1 = σ _p1 + σ _Ts1 ) and the combined summer stress of the second glass panel (σ _cs2 = σ _p2 + σ _Ts2 ) (σ _csmax = max(σ _cs1 , σ _cs2 ) It has been found that in summer conditions, in order to be acceptable, the highest combined summer stress σ _csmax in asymmetric VIG must be less than or equal to the maximum combined induced stress, which is either σ _cwmax , or σ _csmax , of its equivalent symmetrical VIG. With this ratio, the risk of failure due to combined atmospheric and temperature-induced stresses in both severe winter and moderate summer conditions for an asymmetric VIG never exceeds the risk for an equivalent symmetrical VIG. VIG.

It has been found that an asymmetric VIG subject to this combined induced stress limitation can be achieved by balancing the energy absorption rate of the first and second glass panels, as well as their thicknesses, for different sets of parameter ranges L, W, and λ.

In the following specific embodiments A to E according to the present invention, the asymmetric VIG respects the following relationships:

σ _cw2 (asymmetric VIG) < σ _cw2 (equivalent symmetric VIG) and σ _cs1 (asymmetric VIG) < σ _cw2 (equivalent symmetric VIG).

Embodiment A. Asymmetric VIG with Z ₂ =3 mm and 10 mm < λ < 25 mm when the following condition is met in relation to the weighted difference in the energy absorption index between the first and second glass panels: AEA < 0.0084 ΔΖ ² / μμ ² - 0.1545 ΔΖ / μμ + 0.6966; while ΔΕΑ=ΕΑ ₁ - 2-EA2, while 300 mm <L < 3000 mm, 300 mm < W < 1500 mm, Z ₁ > 5 mm, ΔΖ = Z ₁ - Z ₂ > 1 mm.

Embodiment B. Asymmetric VIG with Z ₂ =4 mm and 10 mm < λ < 25 mm when in

- 11 041330 in relation to the weighted difference in the energy absorption index between the first and second glass panels, the following condition is met: ΔΕΑ < - 0.0214 ΔΖ/μμ + 0.5696; while AEA=EA ₁ - 2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, ΔΖ = Z1 - Z ₂ > 1 mm.

Embodiment C. Asymmetric VIG, with Z ₂ =5 mm and 10 mm < λ < 35 mm, when the following condition is met in relation to the weighted difference in the energy absorption index between the first and second glass panels: ΔΕΑ < 0.0033 ΔΖ ² / μμ ² - 0.0468 ΔΖ / μμ + 0.7434; ΔΕΑ = EA1 - 2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, ΔΖ = Z1 - Z2 > 1 mm.

Embodiment D. Asymmetric VIG, with Z ₂ =6 mm and 10 mm < λ < 35 mm, when the following condition is met in relation to the weighted difference in the energy absorption index between the first and second glass panels: ΔΕΑ < 0.0033 ΔΖ ² / μμ ² - 0.0468 ΔΖ / μμ + 0.7702; ΔΕΑ = EA1 2-EA2, while 300 mm <L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, ΔΖ = Z1 - Z ₂ > 1 mm.

Embodiment E. Asymmetric VIG, with Z ₂ =4 mm, and 25 mm < λ < 30 mm, when the following condition is met in relation to the weighted difference in the energy absorption index between the first and second glass panels: ΔEA < - 0.0308 ΔΖ / µµ + 0.5294; ΔEA = EA1 - 2-EA2, while 300 mm < L < 3000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, ΔΖ = Z1 - Z ₂ > 1 mm.

Indeed, it has been found that these energy absorption limitations of the first and second asymmetrical VIG panels resulted in temperature differences in the first and second glass panels that kept the combined voltage levels below the required limits.

For summer conditions, the inventors found that there was a correlation between the energy absorption rates of the glass panels and the resulting temperature differences. The following ratio was established based on the exemplary coatings mentioned above located on the inner surface of the first VIG glass panel: ΔT/°C = 37.386 x ΔEA + 6.2068; ΔEA = EA1 2-EA2 and ΔΤ = T1-T2. The energy absorption values EA of glass panels are determined according to ISO15099, referring to EN410:2011, for glass panels when they are in VIG. Racks are not included in the EA calculation.

These stress calculations have been performed for a large number of glass sizes, thicknesses and infrared reflective coatings. In particular, the following infrared reflective coatings commercially produced by Asahi Glass Company (AGC) were used: Stopray Ultra 50 (U50), I-plus Top 1.1(I+). All of these coatings provide an emissivity <0.4. For calculations, glazing is considered free and unrestricted on all edges.

Planibel Clearlite (CL) soda-lime glass was used for most of the examples. For some examples, Dark Gray Glass (DG) was used.

Comparative examples are designated C.Ex., examples according to the present invention are designated Ex..

In the Examples and Comparative Examples, the space between the glass sheets is 100 µm, and the column array is an ordinary square array, and the WxL size is 1.5x3m.

Table 4

Composition V.I.G. Outdoor Internal glass panel Step glass panel Type thickness (mm) Coating on RH Type thickness (mm) (mm) Ex.1 CL 8 1+ CL 4 25 C. Ex.1 DG 8 1+ CL 4 25 Ex.2 CL 7 1+ CL 3 25 C.Ex.2 CL 5 1+ CL 5 25 Ex.3 CL 12 1+ CL 4 25 C.Ex.3 CL 8 1+ CL 8 25 C.Ex.4 DG eleven 1+ CL 5 25 C.Ex.5 DG 8 1+ CL 8 25 Ex.4 CL eleven 1+ CL 5 25 C.Ex.6 CL 8 1+ CL 8 25 C.Ex.7 DG 8 1+ CL 8 25

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Ex.5 CL 12 1-1- CL 6 25 C.Ex.8 DG 12 | + CL 6 25 C.Ex.9 DG 9 1+ CL 9 25 Ex.b CL 10 1+ CL 4 thirty C.Ex.10 CL 7 1+ CL 7 thirty Ex.7 CL eleven 1+ CL 5 thirty C.Ex.11 CL 8 | + CL 8 thirty C.Ex.12 DG eleven | + CL 5 thirty C.Ex.13 DG 8 1+ CL 8 thirty Ex.8 CL 12 1+ CL 6 thirty C.Ex.14 DG 12 | + CL 6 thirty C.Ex.15 DG 9 1+ CL 9 thirty Ex.9 CL eleven 1+ CL 5 35 C.Ex.16 CL 8 1+ CL 8 35 C.Ex.17 DG eleven 1+ CL 5 35 C.Ex.18 DG 8 1+ CL 8 35 Ex.10 CL 12 1+ CL 6 35 C.Ex.19 DG 12 1+ CL 6 35 C.Ex.2O DG 9 1+ CL 9 35

In table. 5 below are shown for examples and comparative examples of the table. 4 above, the maximum allowable ΔΕΑ according to the present invention and the calculated AEA of the corresponding example or comparative example. Comparative examples present too high AEA values, and therefore present a higher risk of failure, their AEA value is higher than the AEA value allowed according to the present invention. In particular, examples of Ex. 2-13 present a lower risk of breakage than the corresponding equivalent symmetrical vacuum insulating glazing.

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Table 5

Maximum allowable ΔΕΑ ΔΕΑ AT _summer (°C) lt _winter (°C) Ex.1 0.6358 0.6358 6.3 40 C.Ex.1 0.6358 0.6358 38.5 40 Ex.2 0.6358 0.213 6.2 40 C.Ex.2 3.6 40 Ex.3 0.607 0.3984 8.9 40 C.Ex.3 4.5 40 C.Ex.4 0.6082 0.5814 40 40 C.Ex.5 38.5 40 Ex.4 0.6082 0.5814 7.8 40 C.Ex.6 4.5 40 C.Ex.7 38.5 40 Ex.5 0.6082 0.6082 7.9 40 C.Ex.8 0.6082 0.6082 40.4 40 C.Ex.9 39.1 40 Ex.6 0.6082 0.3446 7.6 40 S.Ex.Yu 3.7 40 Ex.7 0.6082 0.5814 7.8 40 C.Ex.11 4.5 40 C.Ex.12 0.6082 0.5814 40 40 C.Ex.13 38.5 40 Ex.8 0.6082 0.6082 7.9 40 C.Ex.14 0.6082 0.6082 40.4 40 C.Ex.15 39.1 40 Ex.9 0.6082 0.5814 7.8 40 C.Ex.16 4.5 40 C.Ex.17 0.6082 0.5814 40 40 C.Ex.18 38.5 40 Ex.10 0.6082 0.6082 7.9 40 C.Ex.19 0.6082 0.6082 40.4 40 C.Ex.20 39.1 40

In table. 6 below shows the induced stresses obtained in the examples and comparative examples in summer and winter conditions. Pressure-induced stresses in the glass panel above the posts are denoted σ _p1 and σ _p2 , respectively. Stress at winter temperature is denoted by σ _Tw1 and σ _Tw2 , respectively, stress at summer temperature is denoted by σ _Ts1 and σ _Ts2 , respectively. The combined summer stress is denoted σ _cs1 (σ _cs1 = σ _p1 + σ _Ts1 ) and σ _cs2 (σ _cs2 = σ _p2 + σ _Ts2 ) respectively, the combined winter stress is denoted σ _cw1 (σ _cw1 = σ _p1 + σ _Tw1 ) and σ _cw2 (σ _cw2 = σ _p2 + σ _Tw2 ), respectively. The highest combined winter stress and the highest combined summer stress are denoted by σcwmaχ (σcwmaχ = max^ _W 1 + σcw2)) and σcsmaχ (σ<^^ = max(σcs1+σcs2)) respectively. The highest combined induced stress that occurs in either summer or winter conditions is denoted σ _cmax . The unit of measure for all stresses is MPa. The value of the maximum combined stress for each example is underlined and thus corresponds to σ _cmax .

As can be seen from Table. 6 below, in symmetrical VIGs, the highest combined voltage values, with a few exceptions, are achieved in winter conditions on the second glass panel. The maximum voltage value reached under any conditions serves as the starting point.

- 14 041330 to compare asymmetric VIG with its equivalent symmetrical VIG. In addition, it has been found that when the VIG is asymmetrical with a thicker first glass panel and a thinner second glass panel, the highest combined winter stress σ _cwmax is reduced, and in particular for an asymmetric VIG when the following size criteria are met: 300 mm < L < 4000 mm, 300 mm < W < 1500 mm, Z1 > 5 mm, Z2 > 3 mm, AZ = Z1 - Z2 > 1 mm, and 10 mm < λ < 35 mm, the highest combined winter stress is lower than for equivalent symmetrical VIG having the same overall thickness.

From Table. 6 below it can also be seen that under summer conditions the highest combined summer stress _σcsmax is higher in asymmetric VIG than in its equivalent symmetrical VIG. In specific embodiments of the present invention, i.e. in the examples marked with an asterisk, the highest combined summer stress σ _csmax in the examples of the present invention was found to be acceptable, with the highest combined summer stress σ _csmax less than or equal to the highest combined stress (winter or summer) of its equivalent symmetrical VIG, i.e. combined winter stress σ _cw2 of the second glass panel in its equivalent symmetrical VIG.

___________________________________________________________ Table 6

Tension of outer panel (MPa) Inner panel stress (MPa) O _T S1 O _T W1 σ _ρ ι ocsl ocwl Ots2 Otw2 Or2 ocs2 ocw2 Ex.1 1.84 0.04 1.07 2.92 1.11 1.63 4.09 4.30 5.93 8.38 C.Ex.1 11.27 0.04 1.07 12.34 1.11 9.98 4.09 4.30 14.28 8.38 Ex.2 1.79 1.66 1.40 3.20 3.07 2.18 2.08 7.64 9.82 9.72 C.Ex.2 0.84 9.14 2.75 3.59 11.89 0.82 9.36 2.75 3.57 12.11 Ex.3 2.36 0.00 0.48 2.84 0.48 2.41 1.71 4.30 6.71 6.01 C.Ex.3 1.03 0.89 1.07 2.10 1.97 0.10 9.15 1.07 1.17 10.22 C.Ex.4 11.43 0.00 0.57 11.99 0.57 7.87 4.41 2.75 10.62 7.16 C.Ex.5 8.80 0.89 1.07 9.88 1.97 0.86 9.15 1.07 1.93 10.22 Ex.4 2.23 0.00 0.57 2.80 0.57 1.53 4.41 2.75 4.28 7.16 C.Ex.6 1.03 0.89 1.07 2.10 1.97 0.10 9.15 1.07 1.17 10.22 C.Ex.7 8.80 0.89 1.07 9.88 1.97 0.86 9.15 1.07 1.93 10.22 Ex.5 2.25 0.00 0.48 2.73 0.48 1.11 5.51 1.91 3.02 7.42 C.Ex.8 11.53 0.00 0.48 12.00 0.48 5.66 5.51 1.91 7.57 7.42 C.Ex.9 8.83 0.00 0.85 9.68 0.85 0.00 9.03 0.85 0.85 9.88 Ex.6 2.15 0.00 0.99 3.14 0.99 2.01 2.78 6.19 8.20 8.97 C.Ex.10 0.86 2.73 2.02 2.88 4.75 0.25 9.25 2.02 2.27 11.27 Ex.7 2.23 0.00 0.82 3.05 0.82 1.53 4.41 3.96 5.49 8.37 C.Ex.11 1.03 0.89 1.55 2.58 2.44 0.10 9.15 1.55 1.65 10.69

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Claims (8)

C.Ex.12 11.43 0.00 0.82 12.24 0.82 7.87 4.41 3.96 11.83 8.37 C.Ex.13 8.80 0.89 1.55 10.35 2.44 0.86 9.15 1.55 2.41 10.69 Ex.8 2.25 0.00 0.69 2.94 0.69 1.11 5.51 2.75 3.86 8.26 C.Ex.14 11.53 0.00 0.69 12.21 0.69 5.66 5.51 2.75 8.41 8.26 C.Ex.15 8.83 0.00 1.22 10.05 1.22 0.00 9.03 1.22 1.22 10.26 Ex.9 2.23 0.00 1.11 3.34 1.11 1.53 4.41 5.39 6.92 9.80 C.Ex.16 1.03 0.89 2.11 3.13 3.00 0.10 9.15 2.11 2.21 11.25 C.Ex.17 11.43 0.00 1.11 12.54 1.11 7.87 4.41 5.39 13.26 9.80 C.Ex.18 8.80 0.89 2.11 10.91 3.00 0.86 9.15 2.11 2.97 11.25 Ex.10 2.25 0.00 0.94 3.19 0.94 1.11 5.51 3.74 4.85 9.25 C.Ex.19 11.53 0.00 0.94 12.46 0.94 5.66 5.51 3.74 9.40 9.25 C.Ex.20 8.83 0.00 1.66 10.49 1.66 0.00 9.03 1.66 1.66 10.70 CLAIM L Vacuum insulating glazing unit (10) provided with a single infrared reflective coating, having a length L, with 300 mm < L < 4000 mm, and a width W, with 300 mm < W < 1500 mm, and comprising: a) a first glass panel (1) having an inner surface (12) of the panel and an outer surface (13) of the panel having a thickness _Zb , wherein the first glass panel has an energy absorption index EA1, and b) a second glass panel (2) having an inner surface (22) of the panel and an outer surface (23) of the panel having a thickness Z ₂ and having an infrared reflective coating on its inner surface of the panel, the coated second glass panel having an index energy absorption EA ₂ ; c) a set of separate spacers (3) located between the first and second glass panels, maintaining the distance between the first and second glass panels and forming an array with a step λ, and the step λ is in the range from 10 to 35 mm; d) a hermetically connecting seal (4) sealing the distance between the first and second glass panels along their perimeter; e) an internal volume V formed by the first and second glass panels and a set of separate spacers and closed by a hermetically connecting seal, and while there is a vacuum with an absolute pressure of less than 0.1 mbar, and f) while the inner surfaces of the panels of the first and second glass panels facing the internal volume V; g) characterized in that the first glass panel is thicker than the second glass panel (Ζι>Ζ ₂ ), while ΔΕΑ < 0.0033 ΔΖ ² /µμ ² - 0.0468 ΔΖ/mm + 0.7702; moreover, ΔΕΑ=ΕΑι - 2·ΕΑ ₂ , while Ζι > 5 mm, Z ₂ > 3 mm, and ΔΖ = (Zj - Z ₂ ) > 1 mm, while 10 mm < λ < 35 mm. 2. Vacuum insulating glazing unit according to claim 1, characterized in that Ζ ₂ =3 mm and 10 mm < λ < 25 mm, when the following condition is met in relation to the weighted difference of the energy absorption index between the first and second glass panels: ΔΕΑ < 0 .0084 ΔΖ / mm ² - 0.1545 ΔΖ / mm + 0.6966; while ΔΕΑ = EA] - 2 EA ₂ and 300 mm < L < 3000 mm, 300 mm < W < 1500 mm. 3. Vacuum insulating glazing unit according to claim 1, characterized in that Z ₂ =4 mm and 10 mm < λ < 25 mm and ΔΕΑ < -0.0214 ΔΖ/mm + 0.5696 and 300 mm < L < 3000 mm, 300 mm < W < 1500 mm. 4. Vacuum insulating glazing unit according to claim 1, characterized in that Ζ ₂ =5 mm and 10 mm < λ < 35 mm and ΔΕΑ < 0.0033 ΔΖ ² /μμ ² - 0.0468 ΔΖ/mm + 0 .7434, and 300 mm < L < 3000 mm, 300 mm < W < 1500 mm. 5. Vacuum insulating glazing unit according to claim 1, characterized in that Ζ ₂ =6 mm and 10 mm < λ < 35 mm and ΔΕΑ < 0.0033 ΔΖ ² /μμ ² - 0.0468 ΔΖ/mm + 0 .7702, and 300 mm < L < 3000 mm, 300 mm < W < 1500 mm. 6. Vacuum insulating glazing unit according to claim 1, characterized in that Ζ ₂ =4 mm and 25 mm < λ < 30 mm and ΔΕΑ < -0.0308 ΔΖ/mm + 0.5294 and 300 mm < L < 3000 mm, 300 mm < W < 1500 mm. 7. Vacuum insulating glazing according to any of the preceding claims, characterized in that the infrared reflective coating comprises a metal-based functional low-emissivity layer providing an emissivity of at most 0.04, preferably at most 0.02. 8. Vacuum insulating glazing unit according to any of the preceding claims, characterized