阅读说明：本技术 非对称真空隔热玻璃窗单元 (Asymmetric vacuum insulated glazing unit ) 是由 A·本特拉德 M·王 于 2020-03-05 设计创作，主要内容包括：本发明涉及一种设置有第一红外反射涂层和第二红外反射涂层的真空隔热玻璃窗单元(10),所述玻璃窗单元包括：a.第一玻璃片(1),所述第一玻璃片具有厚度Z1、在其外片面(13)上承载有所述第一红外反射涂层,所述第一玻璃片具有能量吸收率EA1,以及b.第二玻璃片(2),所述第二玻璃片具有厚度Z2,所述经涂覆的第二玻璃片具有能量吸收率EA2；c.一组分立间隔件(3),所述组分立间隔件定位在所述第一玻璃片与所述第二玻璃片之间,保持所述第一玻璃片与所述第二玻璃片之间的距离,并且形成具有包含在10mm与35mm之间的间距λ的阵列；d.气密结合密封件(4),所述气密结合密封件在所述第一玻璃片和所述第二玻璃片的周边上密封所述第一玻璃片与所述第二玻璃片之间的距离；e.内部体积V,所述内部体积由所述第一玻璃片、所述第二玻璃片和所述组离散间隔件限定并且被所述气密结合密封件封闭,并且其中,存在绝对压力小于0.1mbar的真空,以及f.其中,所述第一玻璃片和所述第二玻璃片的内片面面向所述内部体积V；g.所述第二红外反射涂层被承载在面向所述内部体积的玻璃片面上,并且其特征在于,所述第一玻璃片比所述第二玻璃片厚(Z1>Z2),并且其特征在于,ΔEA≤0.0029ΔZ～(2)/mm～(2)-0.041ΔZ/mm+0.6375。(The present invention relates to a vacuum insulated glazing unit (10) provided with a first infrared reflective coating and a second infrared reflective coating, the glazing unit comprising: a. a first glass sheet (1) having a thickness Z1 carrying the first infrared-reflective coating on its outer face (13), the first glass sheet having an energy-absorbing rate EA1, and b. a second glass sheet (2) having a thickness Z2, the coated second glass sheet having an energy-absorbing rate EA 2; c. a set of discrete spacers (3) positioned between the first and second glass sheets, maintaining a distance between the first and second glass sheets, and forming an array having a pitch λ comprised between 10 and 35 mm; d. a hermetic bonding seal (4) that is hermetically bondedA seal sealing a distance between the first glass sheet and the second glass sheet on a perimeter of the first glass sheet and the second glass sheet; e. an interior volume V defined by the first glass sheet, the second glass sheet, and the set of discrete spacers and enclosed by the hermetic bond seal, and wherein a vacuum having an absolute pressure of less than 0.1mbar is present, and f, wherein inner sheet faces of the first and second glass sheets face the interior volume V; g. the second infrared-reflective coating is carried on a glass sheet side facing the interior volume, and is characterized in that the first glass sheet is thicker than the second glass sheet (Z1)>Z2), and is characterized by Δ EA ≦ 0.0029 Δ Z 2 /mm 2 ‑0.041ΔZ/mm+0.6375。)

1. A vacuum insulated glazing unit (10) provided with a first infrared-reflective coating and a second infrared-reflective coating, the vacuum insulated glazing unit having a length L of 300mm ≤ L ≤ 4000mm and a width W of 300mm ≤ W ≤ 1500mm, and comprising:

a. a first glass sheet (1) having an inner sheet side (12) and an outer sheet side (13) and having a thickness Z₁The first infrared-reflective coating is carried on the outer face of the first glass sheet, and the first glass sheet has energy absorption rate EA₁And an

b. A second glass sheet (2) having an inner sheet surface (22) and an outer sheet surface (23) and having a thickness Z₂Said coated second glass sheet having an energy absorption EA₂；

c. A set of discrete spacers (3) positioned between the first and second glass sheets, maintaining a distance between the first and second glass sheets, and forming an array having a pitch λ comprised between 10 and 35 mm;

d. a hermetic bond seal (4) sealing a distance between the first glass sheet and the second glass sheet on a perimeter of the first glass sheet and the second glass sheet;

e. an internal volume V defined by the first glass sheet, the second glass sheet, and the set of discrete spacers and enclosed by the hermetic bond seal, and wherein a vacuum having an absolute pressure of less than 0.1mbar is present, an

f. Wherein an inner sheet face of the first and second glass sheets faces the interior volume V;

g. the second infrared-reflective coating is carried on a side of the glass sheet facing the interior volume, an

h. Characterized in that the first glass sheet is thicker (Z) than the second glass sheet₁>Z₂) And is characterized in that Δ EA is not more than 0.0029 Δ Z²/mm²-0.041 Δ Z/mm + 0.6375; wherein Δ EA ═ EA₁-2*EA₂And is characterized by Z₁≥5mm，Z₂Not less than 3mm, and Δ Z ═ Z₁-Z₂) Not less than 1mm and is characterized in that lambda is not less than 10mm and not more than 35 mm.

2. The vacuum insulated glazing unit according to claim 1, wherein Z is when the following condition of a weighted difference in energy absorption rate of the first and second glass sheets is satisfied₂3mm and 10mm ≤ λ ≤ 25 mm: delta EA is less than or equal to 0.0073 Delta Z²/mm²-0.1355 Δ Z/mm + 0.573; wherein Δ EA ═ EA₁-2*EA₂L is more than or equal to 300mm and less than or equal to 3000mm, and W is more than or equal to 300mm and less than or equal to 1500 mm.

3. The vacuum insulated glazing unit of claim 1, wherein Z₂4mm and 10 mm. ltoreq. lambda. ltoreq.25 mm, and. DELTA.EA. ltoreq-0.0188. DELTA.Z/mm +0.4616, and 300 mm. ltoreq. L.ltoreq.3000 mm,300 mm. ltoreq. W.ltoreq.1500 mm.

4. The vacuum insulated glazing unit of claim 1, wherein Z₂5mm and 10mm ≦ λ ≦ 35mm, and Δ EA ≦ 0.0029 Δ Z²/mm²-0.041 Δ Z/mm +0.614, and L is more than or equal to 300mm and less than or equal to 3000mm, and W is more than or equal to 300mm and less than or equal to 1500 mm.

5. The vacuum insulated glazing unit of claim 1, wherein Z₂6mm and 10mm ≦ λ ≦ 35mm, and Δ EA ≦ 0.0029 Δ Z²/mm²-0.041 delta Z/mm +0.6375, L is more than or equal to 300mm and less than or equal to 3000mm, and W is more than or equal to 300mm and less than or equal to 1500 mm.

6. The vacuum insulated glazing unit of claim 1, wherein Z₂4mm and 25mm<Lambda is less than or equal to 30mm, delta EA is less than or equal to-0.027 delta Z/mm +0.4264, L is less than or equal to 300mm and less than or equal to 3000mm, and W is less than or equal to 300mm and less than or equal to 1500 mm.

7. A vacuum insulated glazing according to any preceding claim, wherein the second infrared reflective coating comprises a metal based functional low emissivity layer providing an emissivity of at most 0.04, preferably at most 0.02, and wherein the first infrared reflective coating comprises a functional low emissivity layer based on a transparent conductive oxide.

8. A vacuum insulated glazing unit according to any of the preceding claims, wherein at least one of the outer sheet faces (13; 23) of the first and second glass sheets is laminated to at least one glass sheet by at least one polymer interlayer, forming a laminated assembly.

9. A vacuum insulated glazing unit according to any of the preceding claims, wherein at least one of the outer sheet faces (13; 23) of the first and second panes of glass is coupled to a third pane of glass along the periphery of the vacuum insulated glazing unit via a peripheral spacer bar, thereby forming an insulating cavity sealed by a peripheral edge seal.

10. A partition defining an exterior space and an interior space, the partition comprising an opening closed by a vacuum insulated glazing unit according to any of the preceding claims, wherein the first glass sheet faces the exterior space.

11. Use of a vacuum insulated glazing unit according to any of claims 1 to 9 for closing the opening of a partition defining an exterior space and an interior space, wherein the first glass sheet faces the exterior space.

Technical Field

The present invention relates to a vacuum insulated glazing unit provided with a low emissivity coating and having high thermal strain resistance to negative and positive temperature differences.

Background

Vacuum insulated glass window units (VIGs) are recommended for their high insulating properties. Vacuum insulated glazing units are typically constructed from at least two glass sheets separated by an interior space in which a vacuum has been created. Generally, to achieve high thermal insulation performance, the heat transfer coefficient U is U<1.2W/m²K. The absolute pressure inside the glazing unit is typically 0.1mbar or lessLower, and typically at least one of the two glass sheets may be covered with a low emissivity coating. In order to obtain such a pressure inside the glazing unit, a hermetic joint seal is placed at the periphery of the two glass sheets and a vacuum is generated inside the glazing unit by means of a pump. To prevent the glazing unit from collapsing at atmospheric pressure (due to the pressure difference between the inside and outside of the glazing unit), a separate spacer is placed between the two sheets of glass.

A typical VIG unit is a symmetric VIG unit made of two sheets of glass having the same glass thickness. The high thermal insulation properties of vacuum insulated glazing, together with the inflexible hermetic bond seal, result in high thermal strains when there is a large temperature difference between the exterior and the interior of the building. Thus, JP 2001316137 a teaches configuring an asymmetric vacuum insulated glazing unit wherein the inner glass sheet disposed on the inside of the room is thicker than the outer glass sheet to achieve a lower level of thermal strain in intense sunlight than in a comparable symmetric VIG unit. While these asymmetric glazings have reduced distortion during summer conditions, they risk being subjected to higher stresses during winter conditions than comparable symmetric VIG units.

JP 2001316138A teaches an opposite asymmetric VIG configuration in which the outer glass sheet disposed outside the chamber is thicker than the inner glass sheet to improve impact resistance and acoustic performance.

US 2015/0354264 a1 teaches a pressure reducing double glazing panel having a low emissivity film having an emissivity of 0.067 or less on the second glass surface of the outside glass, i.e. the glass surface of the outside glass which is oriented to face the gap portion, to provide adequate thermal and heat shielding properties. The low-emissivity film is a stack of a lower dielectric layer, a metal layer, a sacrificial layer, and an upper dielectric layer, preferably formed by magnetron sputtering.

WO 2016/063007 a1 discloses a vacuum insulated glazing unit having a low emissivity coating on the outwardly facing surface thereof for anti-condensation properties.

EP 1630344 a1 teaches the provision of a low emissivity coating on the inner surface of a glass sheet of a vacuum insulated glazing unit which has an emissivity of less than 0.2. Examples of convenient low-e coatings are sputtered coating stacks of the dielectric/silver/sacrificial/dielectric type, or chemical vapor deposited coatings based on doped tin oxide layers. While the addition of coatings is also of interest to optimize the thermal insulation or solar control properties of VIGs, these coatings also alter the thermal stresses imposed on the VIG.

However, none of the prior art addresses the technical problem of improving resistance to thermal stresses induced in asymmetric VIG units, wherein one or more glass sheets carry a low emissivity solar control or thermal barrier coating and are subjected to temperature differentials from the external and internal environments. Furthermore, there is no prior art solution to the technical problem of atmospheric pressure induced stresses at the strut locations of such VIG units, let alone how to design vacuum insulated glazing units that exhibit improved resistance to such combined external stresses while maintaining high insulating performance.

In fact, none of the prior art addresses the technical problem of reducing the overall stress and the resulting risk of breakage of VIG units bearing infrared reflective coatings, both in summer conditions, where the interior is cooler than the exterior, and in winter conditions, where the exterior is cooler than the interior, particularly where winter conditions are more severe than summer conditions.

Disclosure of Invention

It is an object of the present invention to provide a vacuum insulated glazing bearing a first infrared reflective coating on the outer face of a first glass sheet and a second infrared reflective coating on the inner face of the first or second glass sheet facing the interior volume, and having a lower risk of damage associated with overall stress in the summer case, which is colder than the exterior internally, and in the winter case, which is colder than the interior externally, in particular in the case where winter conditions are worse than summer conditions. The infrared reflective coating in the present invention may be a thermal barrier coating or a solar control coating.

The inventors have surprisingly found that the combination of certain dimensions and thicknesses of the inner and outer glass sheets, together with the specific positioning of the spacing spacers and coatings and the energy properties of the glass sheets, significantly reduces the overall stress-related risk of breakage of vacuum insulated glazing exposed to both mild summer conditions, where the interior is cooler than the exterior, and harsh winter conditions, where the exterior is cooler than the interior. In the context of the present invention, an asymmetric VIG as a whole results in a stress reduction, in particular embodiments, to a level below its equivalent symmetric VIG under winter conditions. Their equivalent symmetrical VIGs are identical in all respects, except that the thickness of the first and second glass sheets is identical, particularly in terms of the external dimensions of length, width and overall thickness. Symmetric VIG has gained considerable commercial acceptance and naturally also becomes a reference for new developments in this field. It is known that they generally reach their highest combined induced stress level under winter conditions. The maximum combination of equivalent symmetric VIG's, achieved under both winter and summer conditions, causes stress levels to thus form useful reference values for comparison with asymmetric VIG's. In certain embodiments of the present invention, the overall induced stress values of asymmetric VIGs under both winter and summer conditions are lower than the maximum induced stress levels allowed by their equivalent symmetric VIGs under summer or winter conditions.

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

a. a first glass sheet having a thickness Z₁And energy absorption efficiency EA₁And an

b. Second glass sheetThe second glass sheet has a thickness Z₂And energy absorption efficiency EA₂，

c. Wherein Z is₁Equal to or greater than 5mm, and

d. wherein the thickness Z of the first glass sheet₁And the thickness Z of the second glass sheet₂Has a thickness difference Δ Z of 1mm or more (Δ Z ═ Z)₁-Z₂≥1mm)。

e. A set of discrete spacers positioned between the first glass sheet and the second glass sheet to maintain a distance between the first glass sheet and the second glass sheet and form an array having a pitch λ. The spacing lambda is comprised between 10mm and 35mm (10 mm. ltoreq. lambda. ltoreq.35 mm).

f. A hermetic bond seal (4) sealing a distance between the first glass sheet and the second glass sheet on a perimeter of the first glass sheet and the second glass sheet;

g. an internal volume V defined by the first glass sheet, the second glass sheet, and the set of discrete spacers and enclosed by the hermetic bond seal, and wherein there is a vacuum having an absolute pressure of less than 0.1 millibar [ mbar ]

h. A first infrared-reflective coating is carried on an outer face of the first glass sheet and a second infrared-reflective coating is carried on an inner face of the first glass sheet or the second glass sheet facing the interior volume.

Conventionally, to describe the location of the sheet surface in an insulated glazing unit, the surfaces of two or more sheets of glass are numbered, starting from the sheet surface facing outwards (position 1) towards the sheet surface facing inwards (position 4 in a double glazing). For purposes of the vacuum insulated glazing of the present invention, the sheet surface numbering of the VIG is maintained even in embodiments where the VIG is combined with additional glass sheets. Furthermore, the thickness is measured in a direction perpendicular to the plane P. For the purposes of the present invention, the glass thickness is rounded to millimeters.

The vacuum insulated glazing unit of the invention is in placeDevice 1 carries a first infrared-reflective coating and at position 2 or 3 (i.e. on the face of the first outer glass sheet or of the second inner glass sheet oriented towards the interior volume) a second infrared-reflective coating. When the weighted difference between the energy absorption rates of the outer and inner glass sheets, Δ EA, is at most 0.0029 Δ Z²/mm²-0.041ΔZ/mm+0.6375(ΔEA≤0.0029ΔZ²/mm²-0.041ΔZ/mm+0.6375；ΔEA＝EA₁-2*EA₂) Low overall stress can be achieved.

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

Drawings

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing exemplary embodiments of the invention.

FIG. 1 shows a cross-sectional view of an asymmetric vacuum insulated glazing unit according to one embodiment of the invention.

FIG. 2 illustrates a cross-sectional view of another asymmetric vacuum insulated glazing unit according to an embodiment of the present invention.

Detailed Description

It is an object of the present invention to provide a vacuum insulated glazing unit (hereinafter VIG) that exhibits low thermally induced stresses when exposed to high positive and negative temperature differences between the external and internal environments, provides insulating properties, is highly sustainable over its lifetime, and can be produced in an efficient and cost-effective manner.

In particular, it is an object of the present invention to provide a vacuum insulated glazing unit (hereinafter VIG) that exhibits high insulating performance or solar control and improved resistance to stresses caused by a combination of atmospheric pressure and temperature differences between the internal and external environments.

These objects are achieved by the present vacuum insulated glazing unit being asymmetric, i.e. wherein the first glass sheet is thicker than the second glass sheet (Z1> Z2) and is carefully dimensioned by specific dimensions, including a length (L) range and a width (W) range, a specific spacing (λ) between the spacers and a specific thickness (Z2) of the second glass sheet, and wherein the first infrared reflective coating is provided on the outer face of the first glass sheet and the second infrared reflective coating is provided on the inner face of the first glass sheet or of the second glass sheet facing the inner volume when the following conditions are met with respect to weighted differences in energy absorption rates of the first and second glass sheets:

ΔEA≤0.0029ΔZ²/mm²-0.041ΔZ/mm+0.6375；ΔEA＝EA₁-2*EA₁wherein L is more than or equal to 300mm and less than or equal to 4000mm,

300mm≤W≤1500mm，

Z₁≥5mm，Z₂≥3mm，

ΔZ＝Z₁-Z₂not less than 1mm, and

10mm≤λ≤35mm。

the first, thicker, glass sheet is intended to face the exterior of the building and the second, thinner, glass sheet is intended to face the interior of the building. Also in the case of a first infrared-reflective coating in position 1 and a second infrared-reflective coating in position 2 or 3, such a combination of different thicknesses improves the stresses associated with winter conditions. Surprisingly, also in summer, low induced stresses can be obtained on such an asymmetric VIG (bearing a first infrared-reflective coating on the outer face of the first glass sheet and a second infrared-reflective coating on the inner face of the first or second glass sheet facing the interior volume). To achieve this, in fact, it was found to be critical to adjust the energy absorption rate of the first and second glass sheets in view of the critical dimensions of the VIG.

The present invention relates to a vacuum insulated glazing unit generally comprising: a first glass sheet and a second glass sheet associated together by a set of discrete spacers that hold the glass sheets apart by a distance generally in the range between 50 μm and 1000 μm, preferably between 50 μm and 500 μm, and more preferably between 50 μm and 150 μm; and an interior space between the glass sheets, the interior space comprising at least one first cavity, wherein a vacuum of less than 0.1mbar absolute is present in the cavity, the space being closed by a peripheral gas-tight bond seal disposed on the periphery of the glass sheets around the interior space. For the purposes of the present invention, the pitch of the spacers is understood to be the shortest distance separating any given spacer from its nearest neighbor. Preferably, the spacers are spaced apart in a regular pattern, such as a square, hexagonal or triangular pattern.

As shown in fig. 1 and 2, the vacuum insulated glazing unit (10) extends along a plane P defined by a longitudinal axis X and a vertical axis Y. The VIG of the present invention comprises:

a. a first glass sheet (1) and a second glass sheet (2), the first glass sheet having an inner sheet side (12) and an outer sheet side (13) and having a thickness Z₁The second glass sheet has an inner sheet surface (22) and an outer sheet surface (23) and has a thickness Z₂. The thickness is measured in a direction perpendicular to the plane P (to the nearest mm).

b. A set of discrete spacers (3) positioned between the first and second glass sheets and maintaining a distance between the first and second glass sheets;

c. a hermetic bond seal (4) sealing a distance between the first glass sheet and the second glass sheet on a perimeter of the first glass sheet and the second glass sheet;

d. an internal volume V defined by the first glass sheet, the second glass sheet, and the set of discrete spacers and enclosed by the hermetic bond seal, and wherein a vacuum having an absolute pressure of less than 0.1mbar is present.

The vacuum insulated glazing unit of the present invention will be referred to hereinafter as an "asymmetric VIG".

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

As shown in fig. 1 and 2, the inner sheet face (12) of the first glass sheet (1) of the asymmetric VIG of the present invention is provided with an infrared reflective coating (hereinafter IR coating).

The IR coating (5, 5a, 5b) of the present invention has an emissivity of not more than 0.4, preferably less than 0.2. The IR coating (5a, 5b) in position 2 or 3 of the invention may have an emissivity, in particular, of less than 0.1, less than 0.05 or even less than 0.04. The IR coating of the present invention, particularly in position 2 or 3, may comprise a metal-based low-emissivity IR coating; these coatings are usually thin-layer systems comprising one or more (for example two, three or four) functional layers based on infrared radiation-reflecting materials and at least two dielectric coatings, wherein each functional layer is surrounded by a dielectric coating. The IR coating of the invention may in particular have an emissivity of at least 0.010. The functional layer is typically a silver layer with a thickness of a few nanometers, mostly about 5 to 20 nm. As regards the dielectric layers, they are transparent and each dielectric layer is conventionally made of one or more layers of metal oxides and/or nitrides. These different layers are deposited, for example, by means of vacuum deposition techniques such as magnetic field assisted cathode sputtering, more commonly known as "magnetron sputtering". Each functional layer, in addition to the dielectric layer, may be protected by a barrier layer or modified by deposition on a wetting layer.

The IR coating (5) in position 1 in the present invention can be in particular an IR coating based on a Transparent Conductive Oxide (TCO) with a functional low-emissivity layer based on fluorine-doped tin oxide, antimony-doped tin oxide or indium tin oxide. Such IR coatings include one or more anti-iridescent layers between the glass and the TCO based layer, sometimes the reflectivity reducing layer includes SiOx and/or a hydrophilic layer based on titanium oxide deposited on the TCO based IR coating.

The IR coating in the present invention may have solar control or solar control properties that may reduce the risk of overheating, for example, in enclosed spaces with large glazing surfaces, and thus reduce the power load to be considered for summer air conditioning. In this case, the glazing must allow as little total solar radiation as possible to pass through, i.e. must have as low a solar coefficient (SF or g) as possible. In general, it is highly desirable that glazing ensures a certain level of Light Transmission (LT) in order to provide a sufficient level of illumination for the interior of a building. These somewhat conflicting requirements express the desire to obtain glazing units with a high selectivity (S) defined by the ratio of light transmittance and solar coefficient. The IR coating in the present invention may also be a thermal barrier coating with low emissivity tuned to reduce heat loss from buildings by longer wavelength infrared radiation. They thus improve the thermal insulation of the glazing surface and reduce energy losses and heating costs during cold periods.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

It has been found that the following specific examples of combinations of sheet glass thickness, spacing range and size provide a combined induced stress level at both winter and summer conditions that is lower than the maximum combined stress level induced in an equivalent symmetrical vacuum insulated glazing of the same overall thickness at summer or winter conditions. EA₁And EA₂Indicating the energy absorption rate of the first glass sheet and the second glass sheet, respectively.

In particular, the strain resistance of the present invention under summer conditions was evaluated in comparison to its equivalent symmetric VIG. For the purposes of the present invention, the equivalent symmetric VIG of an asymmetric VIG is a VIG with all W, L, λ values, having the same overall thickness Z₁+Z₂In a VIG, but wherein the thickness of the first sheet is the same as the thickness of the second sheet, i.e., Z₁＝Z₂。

In particular, under both winter and summer conditions, for Z wherein₂A vacuum insulated glazing of 3mm and 10mm ≦ λ ≦ 25mm, the combination causing a stress level lower than a maximum combined stress level caused in an equivalent symmetric vacuum insulated glazing of the same overall thickness when the following conditions for weighted difference in energy absorption rate of the first glass sheet and the second glass sheet are satisfied: delta EA is less than or equal to 0.0073 Delta Z²/mm²-0.1355ΔZ/mm+0.573；ΔEA＝EA₁-2*EA₂Wherein，300mm≤L≤3000mm，300mm≤W≤1500mm，Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

In particular, under both winter and summer conditions, for Z wherein₂A vacuum insulated glazing of 4mm and 10mm ≦ λ ≦ 25mm, the combination causing a stress level lower than a maximum combined stress level caused in an equivalent symmetric vacuum insulated glazing of the same overall thickness when the following conditions for weighted difference in energy absorption rate of the first glass sheet and the second glass sheet are satisfied: delta EA is less than or equal to-0.0188 delta Z/mm + 0.4616; Δ EA ═ EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

In particular, under both winter and summer conditions, for Z wherein₂A vacuum insulated glazing of 5mm and 10mm ≦ λ ≦ 35mm, the combination causing a stress level lower than a maximum combined stress level caused in an equivalent symmetric vacuum insulated glazing of the same overall thickness when the following conditions for weighted difference in energy absorption rate of the first glass sheet and the second glass sheet are satisfied: delta EA is less than or equal to 0.0029 Delta Z²/mm²-0.041ΔZ/mm+0.614；ΔEA＝EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

In particular, under both winter and summer conditions, for Z wherein₂A vacuum insulated glazing of 6mm and 10mm ≦ λ ≦ 35mm, the combination causing a stress level lower than a maximum combined stress level caused in an equivalent symmetric vacuum insulated glazing of the same overall thickness when the following conditions for weighted difference in energy absorption rate of the first glass sheet and the second glass sheet are satisfied: delta EA is less than or equal to 0.0029 Delta Z²/mm²-0.041ΔZ/mm+0.6375；ΔEA＝EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

In particular, under both winter and summer conditions, for Z wherein₂4mm and 25mm<Lambda is less than or equal to 30mm, when satisfying(ii) the combination induces a stress level that is lower than a maximum combined stress level induced in an equivalent symmetrical vacuum insulated glazing of the same overall thickness when the following conditions of weighted difference in energy absorption rate of the first glass sheet and the second glass sheet; delta EA is less than or equal to-0.027 delta Z/mm + 0.4264; Δ EA ═ EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

In one embodiment of the invention, the thickness Z of the first glass sheet of the asymmetric VIG is₁May be equal to or greater than 5mm (Z)₁≧ 5mm), preferably may be equal to or greater than 6mm (Z)₁≥ 6mm), preferably equal to or greater than 8mm (Z)₁Not less than 8 mm). Typically, the thickness Z of the first glass sheet₁Will be no greater than 12mm, preferably no greater than 10 mm. In another embodiment, the thickness Z of the second glass sheet of the asymmetric VIG is₂May be generally equal to or greater than 3mm (Z)₂Not less than 3mm), preferably not less than 4mm (Z)₂Not less than 4mm), preferably not less than 5mm (Z)₂Not less than 5 mm). Typically, the thickness Z of the second glass sheet₂Will be no greater than 10mm, preferably no greater than 8 mm. However, to improve the mechanical resistance of the asymmetric VIG of the present invention, it is preferable to set the thickness Z of the second sheet₂Kept to a minimum.

In another embodiment of the invention, the invention is also applicable to any type of glazing unit comprising (two, three or more) glass sheets defining an insulated or non-insulated interior space (also referred to as multiple glazing units) provided that a partial vacuum is created in at least one of these interior spaces. Thus, in one embodiment, to improve the mechanical performance of the asymmetric VIG of the present invention, a third additional glass sheet may be coupled to at least one of the outer sheet faces (13 and/or 23) of the first and second glass sheets along the periphery of the VIG via a peripheral spacer bar, thereby forming an insulating cavity sealed by a peripheral edge seal. The peripheral spacer maintains a distance between the third glass sheet and at least one of the outer faces of one of the first and second glass sheets. Typically, the spacer comprises a desiccant and typically has a thickness comprised between 6mm and 20mm, preferably between 9mm and 15 mm. Typically, 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 combinations thereof. The predetermined gas is effective to prevent heat transfer and/or may be used to reduce sound transmission.

When an asymmetric VIG is used to close an opening in a partition separating an interior space and an exterior space, it is preferred that the third glass sheet faces the exterior space. It is further preferred that the third glass sheet is provided with at least one pyrolysed TCO-based coating on at least one of its surfaces. Such a specific glazing unit provides higher mechanical properties while improving emissivity properties and/or reducing condensate formation. In particular and for safety reasons, the outer face (23) of the second glass sheet facing the internal environment may be further laminated to at least one glass sheet by at least one polymer interlayer, thereby forming a laminated assembly.

In one embodiment of the invention, at least one of the outer sheet faces (13 and/or 23) of the first and second glass sheets may be further laminated to at least one additional glass sheet by at least one polymer interlayer for safety and reliability reasons, thereby forming a laminated assembly.

Within the laminated assembly, the at least one additional glass sheet preferably has a thickness Z_sThe thickness is equal to or greater than 0.5mm (Z)_sNot less than 0.5 mm). The thickness is measured in a direction perpendicular to the plane P. At least one polymer interlayer is a transparent or translucent polymer interlayer comprising a material selected from the group consisting of: ethylene Vinyl Acetate (EVA), Polyisobutylene (PIB), polyvinyl butyral (PVB), Polyurethane (PU), polyvinyl chloride (PVC), polyesters, copolyesters, assembled polyacetals, Cyclic Olefin Polymers (COP), ionomers, and/or uv-activated adhesives, as well as other materials known in the art of making glass laminates. Blended materials using any compatible combination of these materials may also be suitable.

Reinforced acoustical insulation with acoustically laminated glass is also compatible with the present concept to improve the performance of a window or door. In this case, the polymer interlayer comprises at least one additional sound insulating material interposed between two polyvinyl butyral films. Glass sheets having electrochromic, thermochromic, photochromic or photovoltaic elements are also compatible with the present invention.

The first and second glass sheets of asymmetric VGs according to the invention may be selected from the group consisting of float clear glass technology, ultra clear glass technology or coloured glass technology. The term "glass" is understood herein to mean any type of glass or equivalent transparent material, such as mineral glass or organic glass. The mineral glass used may be, independently, one or more of the known types of glass, such as soda-lime-silica glass, aluminosilicate glass or borosilicate glass, crystalline and polycrystalline glass. The glass sheet may be obtained by a float process, a drawing process, a rolling process, or any other process known to produce glass sheets starting from a molten glass composition. The glass sheet may optionally be edged. Edging turns the sharp edge into a smooth edge, which is much safer for someone who may touch the vacuum insulated glazing, especially the edges of the glazing. Preferably, the glass sheet according to the invention is a sheet of soda-lime-silica glass, aluminosilicate glass or borosilicate glass. More preferably and for reasons of lower production costs, the glass sheet according to the invention is a soda-lime-silica glass sheet. Typically, the first and second glass sheets of the present invention are annealed glass sheets. Preferably, the compositions of the first and second glass sheets of the asymmetric VIG of the present invention include the following components (table 1, component a) in weight percent expressed relative to the total weight of the glass. More preferably, the glass composition (table 1, component B) is a soda-lime-silica type glass, the base glass matrix of which comprises the following components in percentages by weight expressed with respect to the total weight of the glass.

TABLE 1

Other particular glass compositions of the first and second glass sheets of the asymmetric VIG of the present invention include the following components in table 2 in weight percent expressed relative to the total weight of the glass.

TABLE 2

Examples of the basic glass matrix of the composition according to the invention are described in particular in published PCT patent applications WO 2015/150207A 1, WO 2015/150403A 1, WO 2016/091672A 1, WO 2016/169823A 1 and WO 2018/001965A 1.

The second glass sheet and the first glass sheet may have the same dimensions or different dimensions and thereby form a stepped VIG. In a preferred embodiment of the invention, the first and second glass sheets comprise a first and second peripheral edge, respectively, and wherein the first peripheral edge is recessed from the second peripheral edge, or wherein the second peripheral edge is recessed from the first peripheral edge. This configuration allows for enhanced strength of the hermetic bond seal.

In one embodiment, it is contemplated that the first and/or second glass sheets of the present disclosure may be thermally or chemically pre-stressed in order to provide a VIG with higher mechanical properties and/or to further improve the safety of the VIG. In this case, both the first and second glass sheets need to be treated by the same pre-stressing treatment to provide the same resistance to thermally induced loads. Thus, if the glass sheets are pre-stressed, it is desirable that the first glass sheet and the second glass sheet are both thermally strengthened glass sheets, or that the first glass sheet and the second glass sheet are both chemically strengthened glass sheets.

Thermally treating the thermally strengthened glass using a controlled heating and cooling process that subjects the glass surface to compression and the glass core to tension. This heat treatment process provides glass having a flexural strength greater than annealed glass but less than thermally tempered safety glass.

Thermally treating thermally tempered safety glass using a controlled high temperature heating and rapid cooling process that subjects the glass surface to compression and the glass core to tension. Such stresses can cause the glass to break into small granular particles upon impact rather than breaking into jagged fragments. The granular particles are less likely to injure occupants or damage objects.

Chemical strengthening of glass articles is thermally induced ion exchange involving the replacement of smaller alkali sodium ions in the surface layers of the glass with larger ions (e.g., alkali potassium ions). Increased surface compressive stress occurs in the glass when larger ions "wedge" into small sites originally occupied by sodium ions. This chemical treatment is typically carried out by immersing the glass in an ion-exchange molten bath of a molten salt containing one or more larger ions, under precise control of temperature and time. Aluminosilicate-type Glass compositions are also known, such as the product line from Asahi Glass CoOr product line from Corning Inc (Corning Inc.)Those) are very efficient for chemical tempering.

As depicted in fig. 1 and 2, the vacuum insulated glazing unit of the present invention comprises a plurality of discrete spacers (3) (also referred to as pillars) sandwiched between first and second sheets of glass (1, 2) to maintain an internal volume V. According to the invention, discrete spacers are positioned between the first glass sheet and the second glass sheet, maintaining the distance between the first glass sheet and the second glass sheet, and forming an array having a pitch λ (10mm ≦ λ ≦ 35mm) comprised between 10mm and 35 mm. Pitch, which refers to the spacing between discrete spacers. In a preferred embodiment, the spacing is comprised between 20mm and 35mm (20 mm. ltoreq. lambda. ltoreq.35 mm). The array within the present invention is typically a regular array based on an equilateral triangular, square or hexagonal scheme, preferably a square scheme.

The discrete spacers may have different shapes, such as cylindrical, spherical, filiform, hourglass, C-shaped, cross-shaped, prismatic²Preferably equal to or less than 3mm²More preferably equal to or less than 1mm². These values may provide good mechanical resistance while being aesthetically discrete. The discrete spacers are typically made of a material having a strength that can withstand the pressure applied from the surface of the glass sheet, so as to be able to withstand high temperature processes such as burning and baking, and to emit little gas after the glass sheet is manufactured. Such a material is preferably a hard metallic material, quartz glass or a ceramic material, in particular a metallic material such as iron, tungsten, nickel, chromium, titanium, molybdenum, carbon steel, chromium steel, nickel steel, stainless steel, nickel chromium steel, manganese steel, chromium molybdenum steel, silicon steel, nickel chromium alloy, duralumin alloy or the like, or a ceramic material such as corundum, alumina, mullite, magnesia, yttria, aluminium nitride, silicon nitride or the like.

As shown in fig. 1 and 2, the internal volume V between the glass sheets (1, 2) of the vacuum insulated glazing (10) of the invention is closed with a hermetic joint seal (4) placed around the internal space on the periphery of the glass sheets. The hermetic bond seal is gas impermeable and rigid. As used herein and unless otherwise indicated, the term "gas impermeable" is understood to mean impermeable to air or to any other gas present in the atmosphere.

Various hermetic bond seal technologies exist. The first type of seal (most widely used) is a solder glass based seal having a melting point lower than the melting point of the glass sheets of the glazing unit. The use of this type of seal limits the choice of low-emissivity layer to one that is not degraded by the thermal cycles required to implement the solder glass, i.e. one that can withstand temperatures that may be as high as 250 ℃. In addition, because this type of solder glass-based seal is only very slightly deformable, the seal does not allow the differential expansion effect between the inside glass panel of the glazing unit and the outside glass panel of the glazing unit to be absorbed when the panels are subjected to large temperature differences. As a result, considerable stresses are generated at the periphery of the glazing unit and these stresses may cause cracking of the glass panels of the glazing unit.

A second type of seal comprises a metal seal, for example a metal strip of small thickness (<500 μm) which is soldered to the periphery of the glazing unit by a bonding primer at least partially covered with a layer of solderable material, such as a soft tin alloy solder. A significant advantage of the second type of seal with respect to the first type of seal is that it can be partially deformed so as to partially absorb the differential expansion formed between the two glass panels. Various types of bonding underlayers exist on the glass panels.

Patent application WO 2011/061208 a1 describes one exemplary embodiment of a second type of peripheral gas-tight seal for a vacuum insulated glazing unit. In this embodiment, the seal is a metal strip, for example made of copper, which is welded to an adhesive strip provided on the periphery of the glass sheet by means of a weldable material.

A vacuum having an absolute pressure of less than 0.1mbar, preferably less than 0.01mbar, is created within the interior volume V defined by the first and second glass sheets and the set of discrete spacers and enclosed by the hermetic bond seal within the asymmetric VIG of the present invention.

The internal volume of the asymmetric VIG of the present invention may include a gas such as, but not limited to, air, dry air, argon (Ar), krypton (Kr), xenon (Xe), sulfur hexafluoride (SF6), carbon dioxide, or combinations thereof. The energy transfer through the insulating panel with this conventional structure is reduced with respect to a single glass sheet due to the presence of gas in the internal volume.

The interior volume may also be evacuated of any gases, thus forming a vacuum glazing unit. The energy transfer through the vacuum insulated insulating glazing unit is greatly reduced by the vacuum. In order to generate a vacuum in the interior space of the glazing unit, a hollow glass tube which communicates the interior space with the outside is usually arranged on a main face of one of the glass sheets. Thus, a partial vacuum is created in the inner space by pumping out the gas present in the inner space by means of a pump connected to the outer end of the glass tube.

To maintain a given vacuum level for a duration in a vacuum insulated glazing unit, a getter may be used in the glazing panel. In particular, the inner surface of the glass sheets that make up the glazing panel may release gases previously absorbed in the glass over time, thereby increasing the internal pressure of the vacuum insulated glazing panel and thus reducing the vacuum performance. Typically, such getters consist of alloys of zirconium, vanadium, iron, cobalt, aluminium, etc., and are deposited in the form of thin layers (a few microns in thickness) or placed in the form of blocks between the glass sheets of the glazing panel so as not to be visible (for example, hidden by the external enamel or by a portion of the peripheral airtight seal). The getter forms a passivation layer on its surface at room temperature and therefore must be heated in order to make the passivation layer disappear and thus activate its alloy gettering properties. The getter is considered to be "heat activated".

TABLE 3

Examples of the invention

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

Since a vacuum is maintained between the two sheets of the VIG, atmospheric pressure causes permanent tensile stress on the outer surfaces of the glass sheets of the VIG at each post location. It is known to those skilled in the art that for small pillars, the tensile stress induced by the pillars at the outer surface of the glass sheet is independent of the size of its outer circumference. By small pillars it is generally meant that the contact surface of the pillars with the glass sheet, defined by the outer circumference of the pillars, is generally equal to or less than 5mm²Preferably equal to or less than 3mm²More preferably equal to or less than 1mm²。

In these cases, for regular arrays based on equilateral triangular, square or hexagonal schemes, this atmospheric pressure induced stress, also called tensile stress, can be calculated for the glass sheet by the following formula: sigma_p≤0.11xλ²/Z²[MPa]Wherein, λ [ m ]]And Z [ m ]]The spacing between the spacers and the glass sheet thickness, respectively. "pitch" is to be understood as the shortest distance separating any spacer from its adjacent spacers. In particular, for a regular array based on squares, the tensile stress is the greatest and therefore follows the following formula: sigma_p＝0.11xλ²/Z²[MPa]。

Calculating a maximum atmospheric pressure stress, σ, for each of a first glass sheet and a second glass sheet of a VIG_p1And σ_p2。

Once the first glass sheet (1, T)₁) With a second glass sheet (2, T)₂) There is a temperature difference between them that creates a thermally induced stress on the outer surface of the glass sheets of the VIG, and this thermally induced stress follows T₁And T₂The difference between them increases. The temperature difference (Delta T) is the average temperature T calculated for the first glass sheet (1)₁And the average temperature T calculated for the second glass sheet (2)₂The absolute difference between them. The average temperature of the glass sheet can be calculated, for example, by numerical simulations known to those skilled in the art. For the present invention, the temperature difference between the two glass sheets was calculated using the calculation software "Window 7.4" based on the product of the national door and Window thermal rating Commission NFRC andmethod according to ISO 15099. Under severe conditions, thermally induced stresses may lead to failure of the VIG when such absolute temperature differences between the glass sheets reach 30 ℃, even when the absolute temperature differences are above 40 ℃. The temperature of the internal environment is typically 20 ℃ to 25 ℃, while the temperature of the external environment can be extended from-20 ℃ in the winter to +35 ℃ in the summer. Thus, under severe conditions, the temperature difference between the internal environment and the external environment may reach above 40 ℃. Therefore, the average temperature T calculated for the first glass sheet (1) and the average temperature T calculated for the second glass sheet (2) are equal₂The temperature difference (Δ T) therebetween can also reach above 40 ℃. Numerical simulation was used to calculate the maximum thermal stress σ induced on the outer surface of each glass sheet of the VIG_T. Finite Element Analysis (FEA) models have been built by commercial software Abaqus2017 (formerly Abaqus) to simulate the behavior of VIGs when exposed to different temperature conditions. The calculation was achieved by meshing the glass sheet using C3D8R cells, which have 5 integration points in the thickness of the glass. The global grid size used was 1 cm. To achieve the Δ T of the present invention, an initial and uniform temperature is applied to both glass sheets, and then a uniform temperature change is applied to one of the glass sheets while the other glass sheet is maintained at the initial temperature. A mechanical coupling is applied between the two glass sheets to force the two contacting glass surfaces to have equal displacement. Other boundary conditions have been set to prevent rigid body motion of the assembly. The calculations were performed for all glazing with free, unconstrained edges.

For the purposes of the present invention, the severe winter temperature conditions used are: the outside air temperature was-20 deg.c and the inside air temperature was 20 deg.c, so that the maximum temperature difference between the outside and the inside was 40 deg.c.

The inventors have discovered that because of the simultaneous generation of heat-induced stresses and atmospheric pressure stresses in the glass sheet, combined stresses (σ) need to be considered in determining the dimensions of the VIG_c) I.e. a combination of thermally induced stresses and atmospheric pressure induced stresses. The term "combination induced stress" or "combination of induced stresses" is understood to mean thermally induced stress and largeSum of stresses (sigma) caused by gas pressure_c＝σ_p+σ_T). The combined stress may be for a selected winter condition σ_cwAnd selected summer conditions σ_csAnd (6) performing calculation.

It has been found that in an asymmetric VIG of the present invention having a thicker first glass sheet and a thinner second glass sheet, the highest combined winter stress σ is present under winter conditions_cwmaxA maximum combined winter stress (σ) of the first glass sheet_cw1＝σ_p1+σ_Tw1) Combined winter stress (σ) with a second glass sheet_cw2＝σ_p2+σ_Tw2) Highest value (σ) between_cwmax＝max(σ_cw1,σ_cw2). In particular, for asymmetric VIG, the following dimensional criteria are observed:

300mm≤L≤4000mm，

300mm≤W≤1500mm，

Z₁≥5mm，Z₂≥3mm，

ΔZ＝Z₁-Z₂not less than 1mm, and

10mm≤λ≤35mm，

the highest combined winter stress is lower than that of an equivalent symmetric VIG having the same overall thickness.

For the purposes of the present invention, the mild summer temperature conditions used are: the outside air temperature was 32 ℃, the inside air temperature was 24 ℃, and the solar flux was 783W/m²。

Highest combined summer stress sigma in summer conditions_csmaxIs the combined summer stress (σ) of the first glass sheet_cs1＝σ_p1+σ_Ts1) Combined summer stress (σ) with second glass sheet_cs2＝σ_p2+σ_Ts2) Highest value (σ) between_csmax＝max(σ_cs1,σ_cs2). It has been found that the highest combined summer stress σ in an asymmetric VIG under summer conditions_csmaxStress, i.e. σ, should be less than or equal to the maximum combination of its equivalent symmetric VIGs_cwmaxOr σ_csmaxIt is acceptable. When such aThe relationship is in line, then the risk of cracking of an asymmetric VIG due to combined atmospheric and heat induced stresses is never higher than its equivalent symmetric VIG under both severe winter and mild summer conditions.

It has been found that by balancing the energy absorption of the first and second glass sheets and their thicknesses for different sets of L, W and λ parameter ranges, an asymmetric VIG can be made that complies with the stress-induced limitations of such combinations.

In the following specific examples a to E of the present invention, the asymmetric VIG obeys the following relationship:

σ_cw2(asymmetric VIG)<σ_cw2(equivalently symmetrical VIG) and

σ_cs1(asymmetric VIG) is less than or equal to sigma_cw2(equivalent symmetry VIG)

Example A: an asymmetric VIG, wherein Z is Z when the following conditions are satisfied with respect to a weighted difference in energy absorption rates of the first glass sheet and the second glass sheet₂3mm and 10mm ≤ λ ≤ 25 mm: delta EA is less than or equal to 0.0073 Delta Z²/mm²-0.1355 Δ Z/mm + 0.573; wherein Δ EA ═ EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

Example B: an asymmetric VIG, wherein Z is Z when the following conditions are satisfied with respect to a weighted difference in energy absorption rates of the first glass sheet and the second glass sheet₂4mm and 10mm ≤ λ ≤ 25 mm: delta EA is less than or equal to-0.0188 delta Z/mm + 0.4616; wherein Δ EA ═ EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

Example C: an asymmetric VIG, wherein Z2 ≦ 5mm and 10mm ≦ λ ≦ 35mm when the following conditions are satisfied with respect to a weighted difference in energy absorption rates of the first glass sheet and the second glass sheet: wherein, delta EA is less than or equal to 0.0029 delta Z²/mm²-0.041ΔZ/mm+0.614；ΔEA＝EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

Example D: an asymmetric VIG, wherein Z2 ≦ 6mm and 10mm ≦ λ ≦ 35mm when the following conditions are satisfied with respect to a weighted difference in energy absorption rates of the first glass sheet and the second glass sheet: wherein, delta EA is less than or equal to 0.0029 delta Z²/mm²-0.041ΔZ/mm+0.6375；ΔEA＝EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

Example E: an asymmetric VIG, wherein Z is Z when the following conditions are satisfied with respect to a weighted difference in energy absorption rates of the first glass sheet and the second glass sheet₂4mm and 25mm<Lambda is less than or equal to 30 mm: wherein, delta EA is less than or equal to-0.027 delta Z/mm + 0.4264; Δ EA ═ EA₁-2*EA₂Wherein L is more than or equal to 300mm and less than or equal to 3000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，ΔZ＝Z₁-Z₂≥1mm。

In fact, it has been found that these limitations of energy absorption by the first and second glass sheets of an asymmetric VIG result in a temperature differential between the first and second glass sheets that causes the combined stress level to be below the desired limit.

For summer conditions, the inventors have found that there is a correlation between the energy absorption rate of the glass sheet and the temperature difference obtained. The following relationships were established based on the above example coatings positioned on the inner face of the first glass sheet of the VIG:

ΔT/℃＝42.635xΔEA+7.821；ΔEA＝EA₁-2*EA₂and Δ T ═ T₁-T₂. The energy absorption EA of the glass sheet when the glass sheet is in the VIG is determined according to ISO15099 standard reference EN410: 2011. For calculating EA, the struts are not considered.

These stress calculations are performed for a large number of glass sizes, thicknesses and infrared reflective coatings. In particular, the following infrared reflective coatings commercialized by the company Asahi Glass (AGC) were used: stopray Ultra 50(U50), I-plus Top 1.1(I +), and Planibel G Fast (PGF). All these coatings provide an emissivity < 0.4. For calculations, the glazing was considered free and unconstrained at all edges.

A soda lime transparent glass Planibel Clearlite (CL) was used for most glass sheets. Soda-lime ultra-clear low-iron glass Planibel Clearvision (CV) and dark grey glass (DG) have been used for some glass sheets.

The comparative example is labeled "c.ex.", and the example according to the present invention is labeled "ex.

In the examples and comparative examples, the space between the glass sheets was 100 μm, and the pillar array was a regular square array, and the size WxL was 1.5mx3 m.

TABLE 4

Table 5 below shows, for the examples and comparative examples of table 4 above, the maximum allowable Δ EA according to the present invention and the calculated Δ EA of each example or comparative example. The comparative examples present excessively high values of Δ EA, and therefore a higher risk of breakage, which are higher than the ones allowed according to the invention. Examples ex.1 to 19 in particular exhibit a lower risk of breakage than corresponding equivalent symmetrical vacuum insulated glazing.

TABLE 5

Table 6 below shows induced stresses obtained in the example and the comparative example under summer and winter conditions. The stress induced by pressure in the glass sheet above the pillars is denoted as σ_p1And σ_p2. Winter temperature stress is expressed as σ_Tw1And σ_Tw2The summer temperature stress is respectively expressed as sigma_Ts1And σ_Ts2. The combined summer stresses are respectively expressed as sigma_cs1(σ_cs1＝σ_p1+σ_Ts1) And σ_cs2(σ_cs2＝σ_p2+σ_Ts2) Combined winter stresses are respectively expressed as σ_cw1(σ_cw1＝σ_p1+σ_Tw1) And σ_cw2(σ_cw2＝σ_p2+σ_Tw2). The highest combined winter stress and the highest combined summer stress are respectively expressed as sigma_cwmax(σ_cwmax＝max(σ_cw1+σ_cw2))And σ_csmax(σ_cwmax＝max(σ_cs1+σ_cs2)). The highest combined induced stress generated under summer or winter conditions is denoted as σ_cmax. All stresses are measured in MPa. The maximum combined stress value for each example is underlined, and thus corresponds to σ_cmax。

As can be seen in table 6 below, in the symmetric VIG, the highest combined stress values were achieved on the second glass sheet under winter conditions, with a few exceptions. The maximum stress value reached under any condition is used as a reference point for comparing an asymmetric VIG with its equivalent symmetric VIG. Furthermore, it has been found that the highest combined winter stress σ is when the VIG is asymmetric, carrying a first glass sheet that is thicker and a second glass sheet that is thinner_cwmaxWill reduce, and in particular, for asymmetric VIGs that obey the following dimensional criteria: l is more than or equal to 300mm and less than or equal to 4000mm, W is more than or equal to 300mm and less than or equal to 1500mm, Z₁≥5mm，Z₂≥3mm，ΔZ＝Z₁-Z₂Not less than 1mm and not more than 10mm and not more than 35mm, the highest combined winter stress is lower than the equivalent symmetrical VIG with the same overall thickness.

It can also be seen from Table 6 below that the highest combined summer stress σ in the asymmetric VIG under summer conditions_csmaxHigher than its equivalent symmetric VIG. In a particular embodiment of the invention, i.e. in the example marked with an asterisk, it has been found that the highest combined summer stress σ in the example of the invention_csmaxIs acceptable, the highest combined summer stress σ_csmaxLess than or equal to the highest combined stress (winter or summer) of its equivalent symmetric VIG, i.e., the combined winter stress σ of the second glass sheet in its equivalent symmetric VIG_cw2。

TABLE 6