FIELD

[0001] The present invention relates to a method of manufacturing a vacuum-insulated glazing unit.

[0002] The present invention has particular application in the field of commercial production of vacuum insulated glazing units, and it will be convenient to describe the invention herein in this exemplary context. It will be appreciated, however, that the invention is not limited to this particular application, but may also be employed in domestic or industrial applications or in the production of other glass-based containment devices.

BACKGROUND

[0003] Vacuum insulated glazing (VIG) units are typically constructed from two flat float glass panels or panes that are paired, separated by an evacuated gap or cavity and hermetically sealed at their edges. A pump-out tube is also fitted to one of the panels. Through this tube the gap between the glass panes is evacuated to a pressure of 0.001 Torr (0.1 Pa) or lower. To maintain a well-defined distance between the panes, and minimise the stresses resulting from atmospheric pressure, a regular array of small spacers (typically disk shaped, 0.5 mm in diameter and 0.2 mm in height) is placed between the panes. The primary aim of current manufacturing processes is to form a hermetic edge seal, which is possible using a solder glass material (or glass frit paste that melts at high temperatures). This step in forming the seal requires the VIG unit to be placed in a furnace and heated to temperatures ranging from 300-500°C depending on the solder glass material. Including the heating and cooling times, the complete heat cycle is a 2-4 hr process. Furthermore, the manufacturing process includes a step to place spacers and to outgas the glass surfaces as a matter of cleaning the glass (this latter process is a 1-3 hr step during evacuation of the internal gap). Accordingly, current manufacturing processes are time consuming and require significant energy use in running the furnaces. SUMMARY OF INVENTION

[0004] It is an object of the present invention to substantially overcome, or at least ameliorate, one or more of the above disadvantages.

[0005] A method of manufacturing a vacuum insulated glazing unit, the method including steps of:

providing a first pane and a second pane, wherein each pane has an inner side and an outer side, and wherein a surface region is defined along a periphery of each of the inner sides of the panes, the surface region bounding an interior region of the inner side of each of the panes; depositing a sealing medium on each of the surface regions of each of the panes;

tempering each of the panes to strengthen the panes and to cause the sealing medium to bond to the surface regions of each of the panes;

pairing the panes to define a cavity therebetween; and

forming an edge seal between the surface regions of each of the inner sides to seal the cavity.

[0006] In one or more embodiments, the cavity is evacuated to a pressure of about 0.001 Torr (0.1 Pa) or below vacuum during the step of forming the edge seal.

[0007] In one or more embodiments, the sealing medium is comprised of solder glass.

[0008] In one or more embodiments, the step of pairing the panes includes:

subjecting the panes to a temperature which is lower than a temperature to which the panes are subjected during the step of tempering the panes; and

subjecting the panes to a pressure which is lower than a pressure to which the panes are subjected during the step of tempering the panes.

[0009] In one or more embodiments, the temperature of the panes during the step of pairing the panes is in the range of about 25°C - 400°C and the pressure during the step of pairing the panes is about 0.001 Torr (0.1 Pa).

[0010] In one or more embodiments, the method further includes steps of:

bonding a gasket of metal or glass to at least a portion of the solder glass during the step of tempering each of the panes; and bonding at least a portion of each of the gaskets to each other during the step of forming the edge seal.

[0011] In one or more embodiments, the step of forming the edge seal occurs during the step of pairing the panes such that the temperature to which the panes are subjected causes non-bonded portions of the solder glass of each pane to fuse together thereby sealing the cavity.

[0012] In one or more embodiments, the steps of tempering each of the panes and pairing the panes includes conveying each of the panes through an in-line furnace.

[0013] In one or more embodiments, the method further includes a step of outgassing each of the panes to clean the panes.

[0014] In one or more embodiments, the step of outgassing each of the panes occurs during the step of tempering the panes.

[0015] In one or more embodiments, the step of outgassing each of the panes occurs during the step of pairing the panes.

[0016] In one or more embodiments, the step of outgassing each of the panes includes inducing a plasma within the cavity.

[0017] In one or more embodiments, the method further includes a step of arranging a spacer assembly on at least one of the interior regions of the panes to maintain the cavity between the interior regions of the panes, wherein the step of arranging the spacer assembly occurs prior to or during the step of tempering the panes.

[0018] In one or more embodiments, the spacer assembly includes an array of support spacers.

[0019] In one or more embodiments, the step of arranging the spacer assembly includes screen printing the array of support spacers.

BRIEF DESCRIPTION OF DRAWINGS [0020] For a more complete understanding of the present invention, exemplary embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawing figures, in which like reference signs designate like parts and in which:

[0021] FIG. 1 is a flowchart that schematically illustrates steps associated with a method of manufacturing a vacuum insulated glazing unit according to a preferred embodiment.

[0022] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate particular embodiments of the invention and together with the description serve to explain the principles of the invention. Other embodiments of the invention and many of the attendant advantages of the invention will be readily appreciated as they become better understood with reference to the following detailed description.

[0023] It will be appreciated that common and/or well understood elements that may be useful or necessary in a commercially feasible embodiment are not necessarily depicted in order to facilitate a more abstracted view of the embodiments. The elements of the drawings are not necessarily illustrated to scale relative to each other. It will also be understood that certain actions and/or steps in an embodiment of a method may be described or depicted in a particular order of occurrences while those skilled in the art will understand that such specificity with respect to sequence is not actually required.

DESCRIPTION OF EMBODIMENTS

[0024] Referring to the flowchart of FIG. 1, steps associated with a method of manufacturing a vacuum insulated glazing (VIG) unit according to a preferred embodiment are illustrated.

[0025] In an initial step 100, a pair of glass panes are provided and prepared. Each glass pane has an inner side and an outer side. An edge surface region is defined along a perimeter or periphery of each of the inner sides of the glass panes and bounds an interior region of the inner side of each of the glass panes. In the preferred embodiment, the glass panes are cut to be the same size. In the preferred embodiment, a hole is drilled near one corner of one of the glass panes in order to accommodate a pump-out tube for evacuating a cavity between the interior regions when the glass panes are paired in a later step 140. The glass panes are then washed and dried. It will be appreciated, however, that a pump-out tube may not be required in other embodiments. For example, in one or more embodiments, the glass panes may be paired in a vacuum chamber. In one or more embodiments, the edges of the glass panes may be held apart whilst the cavity is evacuated and an edge seal is formed.

[0026] In a next step 110, a sealing medium comprised of solder glass is deposited or pre-coated onto each of the surface regions of each of the glass panes. The solder glass may be pre-coated using screen printing, or with an automated dispenser. The region surrounding the hole for the pump-out tube may also be pre-coated with solder glass at this stage. It will be appreciated that the pump-out tube may also be installed during this step 110. The solder glass is formulated such that its coefficient of thermal expansion is a good match to that of the underlying glass pane with respect to the strain change during the cooling stage from the temperature point of softening, which reduces mechanical stresses in the structure during manufacture. In particular, the solder glass is formulated to withstand high temperatures and not crystallize during the subsequent tempering step 130 which may reach temperature conditions of about 700-800°C. The aim of using pre-coated tempered glass is to take advantage of the softening point temperature of the solder glass. As an example, for a solder glass at 420-460°C sealing temperature, the softening point would be about 350-380°C. When two panes of pre-coated glass are paired, the edge seal can be formed, with an acceptable rigidity and strength, by only raising the unit temperature to the softening point of the pre-coated solder glass. Solder glass inherently has a much lower softening temperature than soda-lime float glass. Therefore, it is reasonable to expect that solder glass to solder glass should fuse at lower temperatures than solder glass to soda-lime float glass. The step of tempering in the subsequent step 130 will ensure that the solder glass to soda-lime glass bond is strong.

[0027] As an optional intermediate step 120, a spacer assembly having an array of support spacers is arranged on one of the glass panes. The array of support spacers will be positioned between the interior regions of the glass panes during pairing in a later step 140 in order to maintain the separation of the glass panes under the action of atmospheric pressure; which is about ten tonnes per square meter. The spacers can be produced from a high strength material, such as alloy steel, ceramics, and specific glassy materials. The spacers can be printed or laser etched onto the interior region of one of the glass panes. The design (size and shape) of the spacer and the spacing of the array should be optimised to prevent stresses and strains reaching levels that cause failure of the spacer and/or glass. To reduce the heat flow through the spacer assembly fewer and/or smaller spacers would be needed. In contrast, to limit the amount of mechanical stresses in the glass panes, and in the spacers themselves, to tolerable levels, requires more and/or larger spacers. The design compromise between the two competing constraints results in a VIG unit of defined thermal conductance and acceptable levels of stress in the glass and spacers for a service life of +25yrs. The optimisation according to a preferred embodiment is based on the use of 3 mm thick glass, spacers at 0.5 mm in diameter and 0.2 mm in height, which results in an optimised array separation of 25 mm, and a U-value (winter conditions defined by the ASTM 1991 standard) of 0.8 W m ² K ¹ (a lowE coating of emissivity 0.04 has been used). Preferably, this optimised design option is used so as to not exceed the Australian Standards AS 1288“long-term loading of float glass” limit of 8 MPa.

[0028] After the glass panes are pre-coated with the solder glass (and the spacer assembly arranged), the glass panes are conveyed through a thermal tempering furnace or“in-line” furnace; that is, a furnace that has a well-defined and environmentally (temperature and pressure and gas composition) controlled volume. Here, the glass panes are tempered as a next step 130. This step 130 marks the start of a continuous production line. During this step 130, the solder glass melts and fuses or bonds with the surface region of each of the glass panes. The solder glass should remain in a vitreous state during a cooling stage after tempering, as the solder glass needs to be re-melted in the next step 140.

[0029] In a following step 140, once the tempering is complete, the glass panes are conveyed through a closed continuous furnace that will progress the glass panes through as the pressure is lowered to about 0.1 Pa. The temperature may be maintained at about 300°C or other desired temperature. Before the glass panes enter the continuous furnace, the evacuation system is attached to the glass pane. An all-metal cup may be attached over the pump-out tube and used to evacuate the cavity. A metal gasket may first be installed before the placement of the cup. The all-metal evacuation cup is connected to a pumping system that moves with the glass panes as it is transported through the production line. The outer annular region of the all-metal cup is evacuated to prevent it from moving on the surface of the glass pane. Other evacuation means, such as a glass tube, may also be used. Such a tube requires a ring of solder glass to seal it to the glass pane. In this case, an electrically activated tip-off coil would be positioned around the pump-out tube prior to the installation of the tube. The evacuation tube is also connected to a pumping system that moves with the sample as it is transported through the furnace. [0030] At a point when the pressure is lowest, the glass panes are paired by lowering one of the glass panes on top of the other. Even though the glass panes have a pre-coat of the solder glass, there may be benefit from the deposition of a small bead of additional solder glass around the edges of one of the glass panes. Depending on the design of pump-out tube, the components for the pump-out tube may rather be installed at this step 140 of the method. The glass panes are paired so that the interior regions of each of the inner sides of the glass panes are generally aligned and opposite each other to define the cavity therebetween and so that non-bonded portions of the solder glass are generally aligned and opposite each other.

[0031] In the continuous furnace, the temperature of the glass panes is increased. This increase can be quite rapid, because the tempered glass used in the glass panes can withstand much larger transient stresses due to lateral temperature non-uniformities than annealed glass. The temperature is increased to the point at which the non-bonded portions of the pre-coated solder glass around the edges of the glass panes melts and fuses together to form the edge seal. If a glass tube is used to evacuate the unit, a solder glass seal must be made at this point between the tube and the outer surface of the glass. The tip-off coil that surrounds the pump-out tube may be energized in this process to raise the local temperature of region of the glass pane around the tube, thus assisting in the formation of this seal. The temperature of the entire assembly is then reduced, by only a small amount, prior to the commencement of the evacuation process.

[0032] During formation of the edge seal, steps of outgassing each of the panes and evacuating the cavity are simultaneously performed. It will be appreciated, however, that the step of outgassing each of the panes may occur during the tempering step 130 by virtue of the temperature of the tempering oven which may desorb most if not all contaminants off the surfaces of the glass panes. During formation of the edge seal, a factor in determining the optimum temperature is establishing an edge seal that is of the correct thickness, and thus, reducing the stresses at the edge seal. The cavity is then partially evacuated to an optimum pressure for plasma cleaning. Within the continuous furnace, the glass panes pass through a section where a conductive plate is positioned just above or in contact with the glass pane. With the conveyor at a potential of ground, and the conductive plate at a high voltage, a plasma is induced within the cavity of the unit. The time required for the plasma cleaning will be short compared to the other steps in the manufacturing process. The plasma is then turned off, and the cavity is evacuated to the required pressure, preferably about 0.1 Pa. The use of a plasma treatment to clean the glass panes will reduce significantly the time and heating required to outgas the glass surface, and thus, ensure that the vacuum will be stable over long periods of service.

[0033] Once the inner sides of the glass panes are sufficiently outgassed, the temperature of the unit is reduced and the end of the pump-out tube is melted and sealed off. The temperature at which the pump-out tube is sealed is preferably somewhat lower than the highest temperature at which the unit is pumped in order that any outgassing that occurs after the tube is sealed should not excessively degrade the internal vacuum of the unit. The unit is then cooled towards room temperature. The rate of decrease of the temperature of the unit can be quite large because of the ability of the tempered glass panes to withstand significant transient mechanical stresses.

[0034] To complete the edge seal, one or the other of two main steps described below could be implemented, with each having potential variations/combinations:

[0035] When the glass panes are prepared with solder glass at the edge, a gasket of metal or glass could be placed on top, where this gasket extends some distance out from the edge of the glass. During the tempering process the gasket would bond well with the solder glass edge due to the high temperatures. Once the glass panes are paired, the gasket from both glass panes would align and the edge of the gaskets would then be“welded” together to form a hermetic seal. Various methods could be used to“weld” the gasket edges together: such as direct linear welding, ultrasonic welding, and combinations.

[0036] Alternatively, after the tempering process and at the step of glass pairing a gasket of metal or glass would be placed between the glass panes, between the solidified solder glass layers, at a width that is less than the solder glass layer. At the appropriate time using inductive heating, capacitive heating or direct electrical current, the metal glass would be heated rapidly to melt only the surface contact of the solder glass to form a bond to the gasket.

[0037] The method according to the embodiment described above permits the manufacture of VIG units using tempered glass. It also results in a very substantial reduction in the time necessary to manufacture VIG units compared with the existing single-step batch manufacturing process. The described embodiment retains all of the advantages of the single-step process of enabling tight controls to be maintained on the thickness of the solder glass in the edge seal region. Although the embodiment has been described in the context of in-line manufacture, the principles inherent in the method should be equally applicable to a batch manufacturing process. [0038] Although specific embodiments of the invention are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternative and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are examples only and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0039] It will also be appreciated that in this document the terms "comprise", "comprising", "include", "including", "contain", "containing", "have", "having", and any variations thereof, are intended to be understood in an inclusive (i.e. non-exclusive) sense, such that the process, method, device, apparatus or system described herein is not limited to those features or parts or elements or steps recited but may include other elements, features, parts or steps not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "a" and "an" used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms "first", "second", etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects.