1. FIELD OF THE INVENTION

The invention relates to a vacuum-insulated glazing unit wherein the glass panes are of different thicknesses.

2. BACKGROUND OF THE INVENTION

Vacuum-insulated glazing units are recommended because of their high-performance thermal insulation. A vacuum-insulated glazing unit is typically composed of at least two glass panes separated by an internal space in which a vacuum has been generated. In general, in order to achieve a high-performance thermal insulation (Thermal transmittance, U, being U<1.2 W/m2K) the absolute pressure inside the glazing unit is typically 0.1 mbar or less and generally at least one of the two glass panes is covered with a low-emissivity layer. To obtain such a pressure inside the glazing unit, a hermetically bonding seal is placed on the periphery of the two glass panes and the vacuum is generated inside the glazing unit by virtue of a pump. To prevent the glazing unit from caving in under atmospheric pressure (due to the pressure difference between the interior and exterior of the glazing unit), discrete spacers, are placed between the two glass panes.

Vacuum-insulated glazing units need to be carefully dimensioned to resist to different external stresses. Major external stresses to be considered in dimensioning specifically vacuum-insulated glazing units are the thermal stress induced by a temperature difference between exterior and interior environments and the atmospheric pressure induced stress.

The glass pane facing the interior environment, takes up a temperature similar to the temperature of the interior environment and the glass pane facing the exterior environment, takes up a temperature similar to the temperature of the exterior environment. In most stringent weather conditions, the difference between the interior and exterior temperatures can reach up to 40° C. and more. The temperature difference between the interior and exterior environments may cause an induced thermal stress inside the glass panes. In some severe cases, for instance, when the temperature difference is ≥40° C., the induced thermal stress may fracture the vacuum-insulated glazing unit. To resist this induced thermal stress, different solutions have been provided in the art such as increasing the thickness of both glass panes. Another solution is proposed in JP2001316137 which addresses how to improve vacuum-insulated glazing units so that no deformation or distortion occurs even if the glass panes are hit by strong sunlight. JP2001316137 teaches to design a glazing wherein the inner glass pane disposed on the indoor side is thicker than the outer glass pane. In contrast, JP2001316138 teaches the opposite VIG construction wherein the outer glass pane disposed on the outdoor side is thicker than the inner glass pane, for improved shock resistance and acoustic.

However, none of the art addresses the technical problem of improving the resistance to induced thermal stress in vacuum-insulated glazing units wherein glass panes are subjected to temperature difference between exterior and interior environments. Furthermore, none of the art addresses the technical problem of atmospheric pressure induced stress at the pillar locations and even less how to design a vacuum-insulated glazing unit demonstrating improved resistance to this combined external stresses while maintaining high performance thermal insulation.

3. SUMMARY OF THE INVENTION

The present invention relates to a vacuum insulating 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 of the vacuum insulating glazing unit, L, is equal to or greater than 800 mm, (L≥800 mm) and the width of the vacuum insulating glazing unit, W, is equal to or greater than 500 mm, (W≥500 mm). The vacuum insulating glazing unit comprises:

a) a first glass pane having a thickness Z1, and a second glass pane having a thickness, Z2, wherein Z1is greater than Z2(Z1>Z2) and wherein a thickness ratio, Z1/Z2, of the thickness of the first glass pane, Z1, to the thickness of the second glass pane, Z2, is equal to or greater than 1.10 (Z1/Z2≥1.10). The thicknesses are measured in the direction normal to the plane, P. The first glass pane and the second glass pane are float annealed glass panes.

b) a set of discrete spacers positioned between the first and second glass panes, maintaining a distance between the first and the second glass panes and forming an array having a pitch, λ. The pitch, λ, is comprised between 10 mm and 40 mm (10 mm≤λ≤40 mm).

c) a hermetically bonding seal (4) sealing the distance between the first and second glass panes over a perimeter thereof;

d) an internal volume, V, defined by the first and second glass panes and the set of discrete spacers and closed by the hermetically bonding seal and wherein there is a vacuum of absolute pressure of less than 0.1 mbar.

Within the vacuum insulting glazing unit of the present invention, the thickness of the second glass pane, Z2, is equal to or greater than 4 mm, (Z2≥4 mm) and equal to or greater than (λ−15 mm)/5(Z2≥(λ−15 mm)/5).

The present invention further relates to a partition separating a first space with a first temperature, Temp1, from a second space with a second temperature, Temp2, wherein Temp1is lower than Temp2. Said partition comprises an opening being closed by a vacuum insulating glazing unit according to the present invention, preferably wherein the first glass pane is facing the first space. The present invention further relates to the use of a vacuum insulated glazing unit according to the present invention to close the opening of such partition.

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.

