Patent Description:
A glass panel unit has been known in the art as a structure, of which the thermal insulation properties are improved by providing an evacuated space between two glass panels facing each other. For example, Patent Literature <NUM> discloses a vacuum-insulated glass window unit, in which a space is provided between two glass substrates. Patent Literature <NUM> discloses an intermediate film bonding method to assemble a vacuum glass panel and a glass sheet.

There has been an increasing demand for glass panel units with further improved thermal insulation properties and mechanical strength.

An object of the present disclosure is to provide a method for manufacturing a multi-layer stack with excellent thermal insulation properties and mechanical strength.

The claimed method is defined by the features set forth in the appended independent claims. Particular embodiments are set forth in the dependent claims.

As shown in <FIG>, a method for manufacturing a multi-layer stack <NUM> according to a first embodiment of the present disclosure is designed to manufacture a multi-layer stack <NUM>. The multi-layer stack <NUM> includes a glass panel unit <NUM>, an intermediate film <NUM>, and a transparent plate <NUM>. The transparent plate <NUM> is attached via the intermediate film <NUM> to the glass panel unit <NUM>. The glass panel unit <NUM> includes a first glass panel <NUM>, a second glass panel <NUM>, and an evacuated space <NUM>. The evacuated space <NUM> is interposed between the first glass panel <NUM> and the second glass panel <NUM>. The method includes assembling the glass panel unit <NUM> and the transparent plate <NUM> together via the intermediate film <NUM> inside an evacuated chamber <NUM> (see <FIG>).

According to this manufacturing method, a glass panel unit <NUM> and a transparent plate <NUM> are assembled together, thus improving the thermal insulation properties and mechanical strength of the multi-layer stack <NUM>. In addition, while the glass panel unit <NUM> and the transparent plate <NUM> are being assembled together, the glass panel unit <NUM> is placed in an evacuated environment inside a chamber <NUM>. This allows the glass panel unit <NUM> and the transparent plate <NUM> to be assembled together with flexure (warpage) of the glass panel unit <NUM> due to the atmospheric pressure reduced. This enables manufacturing a multi-layer stack <NUM> with reduced flexure.

In a method for manufacturing a multi-layer stack <NUM> according to the first embodiment, a transparent plate <NUM> is attached to an outer surface <NUM>, <NUM> of at least one of a first glass panel <NUM> or a second glass panel <NUM> of a glass panel unit <NUM> with an intermediate film <NUM> interposed between the outer surface <NUM>, <NUM> and the transparent plate <NUM> as shown in <FIG> and 2A.

As used herein, the outer surface <NUM> of the first glass panel <NUM> is a surface, facing away from the second glass panel <NUM>, of the first glass panel <NUM> and is one surface with the first glass panel <NUM> of the glass panel unit <NUM>. Also, as used herein, the outer surface <NUM> of the second glass panel <NUM> is a surface, facing away from the first glass panel <NUM>, of the second glass panel <NUM> and is the other surface with the second glass panel <NUM> of the glass panel unit <NUM>.

The multi-layer stack <NUM> further includes a plurality of spacers <NUM>. The plurality of spacers <NUM> are provided, in the evacuated space <NUM>, between the first glass panel <NUM> and the second glass panel <NUM>. A pressure applied when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together is less than a compressive strength of the plurality of spacers <NUM>. As used herein, the "compressive strength" is a value representing, by force per unit area, the maximum load that a given structure can withstand before the structure is broken under the pressure (compression force).

In the multi-layer stack <NUM> obtained by the manufacturing method according to this embodiment, the transparent plate <NUM> is attached, via the intermediate film <NUM> (see <FIG>), to the glass panel unit <NUM> in which the evacuated space <NUM> is provided between the first glass panel <NUM> and the second glass panel <NUM> (see <FIG>). Thus, the multi-layer stack <NUM> has thermal insulation properties and mechanical strength superior to those of the glass panel unit <NUM>.

In addition, according to this embodiment, the pressure applied when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together is less than the compressive strength of the spacers <NUM>. This reduces the chances of the spacers <NUM> collapsing under pressure when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together.

If the spacers <NUM> collapsed under the pressure, then the evacuated space <NUM> would be compressed to cause a decline in the thermal insulation properties of the multi-layer stack <NUM>. In addition, if the spacers <NUM> collapsed under the pressure, the mechanical strength of the multi-layer stack <NUM> would decrease as well. Thus, avoiding the collapse of the spacers <NUM> under the pressure may reduce the chances of causing a decline in the thermal insulation properties and mechanical strength of the multi-layer stack <NUM>.

Suppose, for example, a situation where the spacers <NUM> are made of a metallic material such as stainless steel and have a compressive strength equal to or greater than the compressive strength of glass (i.e., a material for the first glass panel <NUM> or the second glass panel <NUM>). In that case, if the pressure for assembling the glass panel unit <NUM> and the transparent plate <NUM> goes beyond a required level, then the metallic spacers <NUM> might break the first glass panel <NUM> or the second glass panel <NUM>. According to this embodiment, however, the spacers <NUM> are made of a resin and the compressive strength of the spacers <NUM> is less than the compressive strength of glass. This reduces, even if the pressure for assembling the glass panel unit <NUM> and the transparent plate <NUM> together goes beyond a required level, the chances of the first glass panel <NUM> or the second glass panel <NUM> being broken under the excessive pressure. Note that the spacers <NUM> do not have to be made of a resin but may also be made of a ceramic or a metallic material.

The multi-layer stack <NUM> according to this embodiment includes the glass panel unit <NUM>, the transparent plate <NUM>, and the intermediate film <NUM> as shown in <FIG>. These constituent elements will be described one by one.

The glass panel unit <NUM> includes the first glass panel <NUM> and the second glass panel <NUM>, which face each other as shown in <FIG>. Thus, the first glass panel <NUM> and the second glass panel <NUM> are stacked one on top of the other.

The glass panel unit <NUM> further includes a sealant <NUM>. The sealant <NUM> is provided between the first glass panel <NUM> and the second glass panel <NUM>. The sealant <NUM> according to this embodiment has a frame shape and is used to hermetically bond the first glass panel <NUM> and the second glass panel <NUM> together. Thus, in this glass panel unit <NUM>, the first glass panel <NUM>, the sealant <NUM>, and the second glass panel <NUM> are stacked in this order one on top of another. The sealant <NUM> may be obtained by, for example, curing a hot glue to be described later.

In addition, the glass panel unit <NUM> also includes the evacuated space <NUM>. The evacuated space <NUM> is a space surrounded with the first glass panel <NUM>, the second glass panel <NUM>, and the sealant <NUM>.

The glass panel unit <NUM> further includes a plurality of spacers (pillars) <NUM>. The plurality of spacers <NUM> are provided, in the evacuated space <NUM>, between the first glass panel <NUM> and the second glass panel <NUM>. These spacers <NUM> may maintain a predetermined interval (gap distance) between the first glass panel <NUM> and the second glass panel <NUM>. Optionally, the plurality of spacers <NUM> may be omitted.

The glass panel unit <NUM> further includes a gas adsorbent <NUM>. The gas adsorbent <NUM> is provided in the evacuated space <NUM>. The gas adsorbent <NUM> may adsorb a gas in the evacuated space <NUM>. Optionally, the gas adsorbent <NUM> may be omitted.

Next, the first glass panel <NUM>, the second glass panel <NUM>, the sealant <NUM>, the evacuated space <NUM>, the spacers <NUM>, and the gas adsorbent <NUM> that form the glass panel unit <NUM> will be described in further detail.

The first glass panel <NUM> is a plate member of glass. The first glass panel <NUM> may have a rectangular shape in plan view. However, the planar shape of the first glass panel <NUM> does not have to be rectangular but may also be a triangular or any other polygonal shape, a circular shape, or an elliptical shape. The first glass panel <NUM> has an outer surface <NUM>, which is a surface exposed to the external environment outside of the glass panel unit <NUM>, and an inner surface <NUM> (see <FIG>), which is a surface facing the second glass panel <NUM>.

The first glass panel <NUM> may have a flat plate shape or may also have a curved plate shape. That is to say, the outer surface <NUM> of the first glass panel <NUM> may be either flat or curved, whichever is appropriate.

Examples of materials for the first glass panel <NUM> include soda lime glass, high strain point glass, chemically tempered glass, alkali-free glass, quartz glass, Neoceram, and thermally tempered glass. The thickness of the first glass panel <NUM> is not limited to any particular value but may fall within the range from <NUM> to <NUM>, for example.

Optionally, a low-emissivity film may be provided on the inner surface <NUM> of the first glass panel <NUM>. In that case, the low-emissivity film is located in the evacuated space <NUM>. The low-emissivity film is a film containing a metal with low emissivity. The low-emissivity film has the capability of reducing the transfer of heat by radiation, and therefore, may reduce the transfer (emission) of the heat, generated by light (radiation) irradiating the outer surface <NUM> of the first glass panel <NUM>, to the evacuated space <NUM>. Examples of metals having low emissivity include silver.

The second glass panel <NUM> is a plate member of glass. The second glass panel <NUM> has the same planar shape as the first glass panel <NUM>. The second glass panel <NUM> has an outer surface <NUM>, which is a surface exposed to the external environment outside of the glass panel unit <NUM>, and an inner surface <NUM> (see <FIG>), which is a surface facing the first glass panel <NUM>.

The second glass panel <NUM> may have a flat plate shape or may also have a curved plate shape. That is to say, the glass panel unit <NUM> may have a flat plate shape or a curved plate shape, whichever is appropriate. In other words, the outer surface <NUM> of the second glass panel <NUM> of the glass panel unit <NUM> may be either flat or curved, whichever is appropriate.

Examples of materials for the second glass panel <NUM> include soda lime glass, high strain point glass, chemically tempered glass, alkali-free glass, quartz glass, Neoceram, and thermally tempered glass. The material for the second glass panel <NUM> may be the same as, or different from, the material for the first glass panel <NUM>. The thickness of the second glass panel <NUM> is not limited to any particular value but may fall within the range from <NUM> to <NUM>, for example. The thickness of the second glass panel <NUM> may be the same as, or different from, the thickness of the first glass panel <NUM>.

The sealant <NUM> is a frame-shaped member (see <FIG>). In this embodiment, the first glass panel <NUM> and the second glass panel <NUM> have a rectangular shape in plan view, and therefore, the sealant <NUM> is also a rectangular frame shaped member. The sealant <NUM> is provided between the first glass panel <NUM> and the second glass panel <NUM> to hermetically bond the first glass panel <NUM> and the second glass panel <NUM> together.

The sealant <NUM> is made of a hot glue. As the hot glue, a glass frit such as a low-melting glass frit may be used, for example. Examples of the low-melting glass frit include a bismuth-based glass frit, a lead-based glass frit, and a vanadium-based glass frit. The sealant <NUM> may contain one or more types of low-melting glass frits selected from this group.

The evacuated space <NUM> is a space surrounded with the first glass panel <NUM>, the second glass panel <NUM>, and the sealant <NUM> (see <FIG>). More specifically, the evacuated space <NUM> is an evacuated space surrounded with the inner surface <NUM> of the first glass panel <NUM>, the inner surface <NUM> of the second glass panel <NUM>, and the sealant <NUM>.

The evacuated space <NUM> is suitably a vacuum space, for example. Specifically, the evacuated space <NUM> is suitably a space evacuated to a degree of vacuum of <NUM> Pa or less. This would improve the thermal insulation properties of the glass panel unit <NUM>.

A plurality of spacers <NUM> are provided in the evacuated space <NUM> as shown in <FIG>. That is to say, a plurality of spacers <NUM> are arranged between the first glass panel <NUM> and the second glass panel <NUM>. The plurality of spacers <NUM> may maintain a predetermined interval between the first glass panel <NUM> and the second glass panel <NUM>. This ensures a predetermined gap distance between the first glass panel <NUM> and the second glass panel <NUM> and also ensures that the thickness of the evacuated space <NUM> is kept constant.

Each of the spacers <NUM> is a circular columnar member. The height (i.e., the dimension in the thickness direction) of the spacers <NUM> may be set appropriately according to the gap distance between the first glass panel <NUM> and the second glass panel <NUM>. That is to say, the gap distance between the first glass panel <NUM> and the second glass panel <NUM> (i.e., the thickness of the evacuated space <NUM>) is defined by the height of the spacers <NUM>. The height of the spacers <NUM> may fall, for example, within the range from <NUM> to <NUM>. The diameter of the spacers <NUM> may fall, for example, within the range from <NUM> to <NUM>. For example, spacers <NUM> with a diameter of <NUM> and a height of <NUM> may be used. The shape of the spacers <NUM> does not have to be circular columnar but may also be a rectangular columnar shape or a spherical shape.

The spacers <NUM> are suitably transparent. This would make the spacers <NUM> much less conspicuous in the multi-layer stack <NUM> and thereby improve the appearance of the multi-layer stack <NUM>.

The spacers <NUM> according to this embodiment are made of a resin and are suitably made of a polyimide resin, for example. This would reduce the thermal conductivity of the spacers <NUM> and thereby reduce the transfer of heat between the first glass panel <NUM> and the second glass panel <NUM> that are in contact with the spacers <NUM>.

The gas adsorbent <NUM> has the capability of adsorbing gas molecules. The gas adsorbent <NUM> is placed in the evacuated space <NUM>. The gas adsorbent <NUM> may adsorb a gas in the evacuated space <NUM>, thus increasing the degree of vacuum in the evacuated space <NUM> and thereby improving the thermal insulation properties of the glass panel unit <NUM>.

The gas adsorbent <NUM> may contain, for example, a metallic getter material or a non-metallic getter material. The metallic getter material is a getter material having a metallic surface that may chemically adsorb gas molecules. Examples of the metallic getter materials include zirconium-based (such as Zr-Al and Zr-V-Fe) getter materials and titanium-based getter materials. Each of these metallic getter materials may adsorb molecules of a gas such as H<NUM>O, N<NUM>, O<NUM>, H<NUM>, or CO<NUM>. In addition, heating and activating any of these metallic getter materials may also cause the gas molecules, chemically adsorbed into the metallic surface of the metallic getter material, to diffuse inside the metallic getter material. Thus, the gas adsorbent <NUM> containing the metallic getter material may adsorb molecules of a gas such as H<NUM>O, N<NUM>, O<NUM>, H<NUM>, or CO<NUM> in the evacuated space <NUM>.

The non-metallic getter material is a getter material having a porous structure with the ability to adsorb gas molecules. Examples of the non-metallic getter materials include zeolite-based getter materials, active carbon, and magnesium oxide. The zeolite-based getter material may include ion-exchanged zeolite. In that case, examples of the ion exchange materials include K, NH<NUM>, Ba, Sr, Na, Ca, Fe, Al, Mg, Li, H, and Cu. Each of these non-metallic getter materials is able to adsorb molecules of a gas such as a hydrocarbon-based gas (such as CH<NUM> and C<NUM>H<NUM>) or ammonia (NH<NUM>) gas that a metallic getter material cannot adsorb. In addition, heating and activating any of these non-metallic getter materials may cause the gas molecules, which have been adsorbed into the porous structure of the non-metallic getter material, to be desorbed.

The glass panel unit <NUM> may be manufactured by, for example, the following method.

First, a hot glue is applied in a frame shape onto the inner surface <NUM> of the second glass panel <NUM>. Next, the first glass panel <NUM> is laid on top of the second glass panel <NUM> such that the frame-shaped hot glue is sandwiched between the first glass panel <NUM> and the second glass panel <NUM>. Then, the space surrounded with the first glass panel <NUM>, the second glass panel <NUM>, and the frame-shaped hot glue is heated. This process step may be performed by heating, in a heating furnace, the multi-layer assembly in which the first glass panel <NUM> and the second glass panel <NUM> are stacked one on top of the other with the hot glue interposed between themselves. In this manner, the sealant <NUM> is formed out of the frame-shaped hot glue. In addition, a gas is exhausted from the space surrounded with the first glass panel <NUM>, the second glass panel <NUM>, and the hot glue, thus creating the evacuated space <NUM>. In this manner, the glass panel unit <NUM> may be manufactured. Note that the plurality of spacers <NUM> and the gas adsorbent <NUM> are arranged along the inner surface <NUM> of the second glass panel <NUM> before the first glass panel <NUM> and the second glass panel <NUM> are laid one on top of the other with the hot glue interposed between themselves.

The transparent plate <NUM> shown in <FIG> is a transparent plate member with light-transmitting properties. The transparent plate <NUM> not only improves the mechanical strength, thermal insulation properties, and sound insulation of the multi-layer stack <NUM> but also imparts various functions to the multi-layer stack <NUM> according to the shape, capability, or any other parameter of the transparent plate <NUM>. The transparent plate <NUM> is provided for the outer surface <NUM>, <NUM> of at least one of the first glass panel <NUM> or the second glass panel <NUM> of the glass panel unit <NUM> as described above. In the multi-layer stack <NUM> according to this embodiment, the transparent plate <NUM> is provided for the outer surface <NUM> of the glass panel unit <NUM> as shown in <FIG>. Thus, the transparent plate <NUM> faces the glass panel unit <NUM>. In addition, the transparent plate <NUM> also faces the first glass panel <NUM>.

The planar shape of the transparent plate <NUM> may be the same as the planar shape of the glass panel unit <NUM>, for example. In the multi-layer stack <NUM> according to this embodiment, the transparent plate <NUM> has the same planar shape as the first glass panel <NUM>. The glass panel unit <NUM> may be flat or curved as described above. Accordingly, the transparent plate <NUM> may also be flat or curved, whichever is appropriate.

The thickness of the transparent plate <NUM> is not limited to any particular value but suitably falls, for example, within the range from <NUM> to <NUM>, and more suitably falls within the range from <NUM> to <NUM>. This may reduce the weight of the multi-layer stack <NUM> while ensuring sufficient mechanical strength for the multi-layer stack <NUM>.

The material for the transparent plate <NUM> is not limited to any particular one as long as the material has light-transmitting properties. For example, the transparent plate <NUM> is suitably made of polycarbonate. In other words, the transparent plate <NUM> is suitably a polycarbonate plate. This may reduce the weight of the transparent plate <NUM> and thereby reduce the overall weight of the multi-layer stack <NUM>.

The transparent plate <NUM> is suitably made of glass, for example. In other words, the transparent plate <NUM> is suitably a glass pane. This may increase the mechanical strength of the transparent plate <NUM> and eventually increase the mechanical strength of the multi-layer stack <NUM>. If the transparent plate <NUM> is made of glass, examples of materials for the transparent plate <NUM> include annealed glass, chemically tempered glass, and thermally tempered glass.

The intermediate film <NUM> is interposed between the glass panel unit <NUM> and the transparent plate <NUM> as described above. Thus, in the multi-layer stack <NUM> according to this embodiment, the intermediate film <NUM> is interposed between the first glass panel <NUM> and the transparent plate <NUM>.

In the multi-layer stack <NUM>, the glass panel unit <NUM> and the transparent plate <NUM> are bonded together via this intermediate film <NUM>. In the multi-layer stack <NUM> according to this embodiment, the first glass panel <NUM> and the transparent plate <NUM> are bonded together via the intermediate film <NUM>. Thus, the intermediate film <NUM> is suitably provided over not only the entire surface of the (first glass panel <NUM> of the) glass panel unit <NUM> but also the entire surface of the transparent plate <NUM>. The planar shape of the intermediate film <NUM> is suitably the same as not only that of the (first glass panel <NUM> of the) glass panel unit <NUM> but also that of the transparent plate <NUM> as well.

The thickness of the intermediate film <NUM> is not limited to any particular value as long as the intermediate film <NUM> may bond the (first glass panel <NUM> of the) glass panel unit <NUM> and the transparent plate <NUM> together but suitably falls, for example, within the range from <NUM> to <NUM> and more suitably falls within the range from <NUM> to <NUM>. This allows the glass panel unit <NUM> to hold the transparent plate <NUM> more easily and also facilitates maintaining the light-transmitting properties of the multi-layer stack <NUM>.

The material for the intermediate film <NUM> is not limited to any particular one as long as the intermediate film <NUM> may bond the (first glass panel <NUM> of the) glass panel unit <NUM> and the transparent plate <NUM> together and has light-transmitting properties. For example, the intermediate film <NUM> is suitably made of a sheet-shaped resin with light-transmitting properties and is more suitably a sheet of a thermoplastic resin. The intermediate film <NUM> may be configured as a single sheet of resin or a multi-layer stack made up of multiple sheets of resin. If the intermediate film <NUM> is configured as a multi-layer stack of multiple sheets of resin, some matter may be interposed between the multiple sheets of resin to improve its design and decorativeness. Examples of such interposed materials include a polyethylene terephthalate (PET) film, a sheet of metal foil, and a plant.

The intermediate film <NUM> is suitably made of a polyvinyl butyral (PVB) resin, for example. The PVB resin is suitable because the PVB resin not only is able to bond the glass panel unit <NUM> and the transparent plate <NUM> firmly but also has excellent transparency. In addition, the PVB resin may also increase the mechanical strength of the multi-layer stack <NUM>. Moreover, the PVB resin increases the anti-penetration ability of the multi-layer stack <NUM> as well. Thus, if the multi-layer stack <NUM> is required to have high mechanical strength, then the intermediate film <NUM> is suitably made of a PVB resin.

The intermediate film <NUM> is also suitably made of an ethylene vinyl acetate (EVA) copolymer resin (hereinafter referred to as an "EVA resin"). The EVA resin is suitable due to its excellent transparency and flexibility. In addition, the EVA resin also increases the anti-scattering ability of the multi-layer stack <NUM>. Furthermore, the EVA resin also allows the glass panel unit <NUM> and the transparent plate <NUM> to be bonded at a relatively low temperature via the intermediate film <NUM>. Moreover, the EVA resin increases the transportability of the multi-layer stack <NUM> as well. Thus, in this embodiment, the intermediate film <NUM> suitably includes at least one of the PVB resin or the EVA resin.

The intermediate film <NUM> is also suitably made of a liquid curable resin, for example. The liquid curable resin is suitably either a thermosetting resin or a UV curable resin. If the intermediate film <NUM> is made of a thermosetting resin, the intermediate film <NUM> suitably includes not only the thermosetting resin but also a curing agent as well. On the other hand, if the intermediate film <NUM> is made of a UV curable resin, then the intermediate film <NUM> suitably includes not only the UV curable resin but also a photopolymerization initiator as well. Examples of such curable resins include an acrylic resin. That is to say, the intermediate film <NUM> is suitably made of an acrylic resin as well.

The multi-layer stack <NUM> according to this embodiment may be manufactured by performing, for example, the following process steps. Note that the following method for manufacturing the multi-layer stack <NUM> is only an example and should not be construed as limiting.

First, the glass panel unit <NUM>, the transparent plate <NUM>, and the intermediate film <NUM> are provided. Next, the glass panel unit <NUM> and the transparent plate <NUM> are assembled together via the intermediate film <NUM> (see <FIG>). More specifically, the outer surface <NUM>, <NUM> of at least one of the first glass panel <NUM> or the second glass panel <NUM> of the glass panel unit <NUM> and the transparent plate <NUM> are assembled together via the intermediate film <NUM>.

In this embodiment, the outer surface <NUM> of the first glass panel <NUM> and the transparent plate <NUM> are assembled together via the intermediate film <NUM> made of a sheet of resin as shown in <FIG>. In this manner, the multi-layer stack <NUM> shown in <FIG> is obtained.

If the pressure applied when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together were too high, then the plurality of resin spacers <NUM> included in the glass panel unit <NUM> would collapse under the excessive pressure. In that case, this would cause damage to the glass panel unit <NUM> or cause a decline in the thermal insulation properties, the mechanical strength, or other properties of the glass panel unit <NUM>.

In this respect, in the manufacturing method according to this embodiment, the pressure applied when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together is, for example, <NUM> MPa or less, which is less than the compressive strength of the plurality of spacers <NUM>. This reduces the chances of the plurality of spacers <NUM> collapsing under the excessive pressure. As used herein, the "pressure applied for assembling the glass panel unit <NUM> and the transparent plate <NUM> together" refers to the pressure applied to the glass panel unit <NUM> and the transparent plate <NUM> when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together.

In this embodiment, the pressure applied when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together is suitably equal to or lower than <NUM> atmosphere [atm] (≃ <NUM> Mpa), and more suitably equal to or lower than <NUM> atm (≃ <NUM> Mpa). The lower limit value of the pressure applied for assembling is not limited to any particular value as long as the glass panel unit <NUM> and the transparent plate <NUM> may be assembled together, but is suitably equal to or greater than <NUM> atm (≃ <NUM> Mpa) and more suitably equal to or greater than <NUM> atm (≃ <NUM> Mpa). This may further reduce the chances of the plurality of resin spacers <NUM> collapsing under the excessive pressure, particularly when the spacers <NUM> are made of a polyimide resin. That is to say, the pressure applied for assembling suitably falls within the range from <NUM> atm to <NUM> atm and more suitably falls within the range from <NUM> atm to <NUM> atm. Note that the pressure applied for assembling the glass panel unit <NUM> and the transparent plate <NUM> together is not limited to any particular value.

In general, to bond the glass panel unit <NUM> and the transparent plate <NUM> together with the intermediate film <NUM> made of a PVB resin, heat and pressure need to be applied with an autoclave machine used. The pressure applied is usually <NUM> atm (≃ <NUM> Mpa), for example. Depending on the condition for applying heat and pressure, however, the spacers <NUM> included in the glass panel unit <NUM> would be deformed or the first glass panel <NUM>, the second glass panel <NUM>, or other members of the glass panel unit <NUM> would be damaged or deformed, for example.

In contrast, the PVB resin may bond the glass panel unit <NUM> and the transparent plate <NUM> only by heating, without using any autoclave machine, by reducing the moisture content thereof. This allows the glass panel unit <NUM> and the transparent plate <NUM> to be bonded together only by heating by drying the intermediate film <NUM> made of the PVB resin and then bonding the glass panel unit <NUM> and the transparent plate <NUM> via the intermediate film <NUM>.

According to an exemplary method for drying the intermediate film <NUM>, a vacuum pump may be connected to a large chamber in which a desiccant such as a silica gel is put, only the intermediate film <NUM> may be loaded, as either a roll or a flat film, into the large chamber, and then the inside of the large chamber may be evacuated with the vacuum pump to maintain a predetermined degree of vacuum. According to this method, the intermediate film <NUM> may be dried and may have its moisture content decreased. The dried intermediate film <NUM> made of the PVB resin is heated while being sandwiched between the glass panel unit <NUM> and the transparent plate <NUM>. In this manner, the glass panel unit <NUM> and the transparent plate <NUM> are bonded together via the intermediate film <NUM>.

Another method for drying the intermediate film <NUM> may be as follows, for example. According to this method, the intermediate film <NUM> is placed, for example, in a low-humidity environment (e.g., in a large chamber in which a desiccant such as a silica gel is put and to which a vacuum pump is connected) while being sandwiched between the glass panel unit <NUM> and the transparent plate <NUM>, and then the low-humidity environment is evacuated with the vacuum pump to maintain a predetermined degree of vacuum. According to this method, the intermediate film <NUM> made of the PVB resin, for example, may be dried and may have its moisture content decreased.

The condition for drying the intermediate film <NUM> by itself or the intermediate film <NUM> sandwiched between the glass panel unit <NUM> and the transparent plate <NUM> may be set as appropriate depending on the dimensions, the thickness, or any other parameter of the intermediate film <NUM>. For example, the intermediate film <NUM> is suitably dried for at least <NUM> hours (suitably <NUM> hours or more) with the pressure inside the chamber reduced to <NUM> atm (≃ <NUM> MPa) or less.

To accelerate drying the intermediate film <NUM> sandwiched between the glass panel unit <NUM> and the transparent plate <NUM>, a space is suitably provided between the transparent plate <NUM> (or the glass panel unit <NUM>) and a base on which the transparent plate <NUM> is mounted. In that case, plate-shaped spacers are suitably provided, for example, at the four corners of the transparent plate <NUM> (or the glass panel unit <NUM>). In addition, the thickness of these spacers is suitably equal to or greater than the thickness of the intermediate film <NUM>, for example. That is to say, the space between the transparent plate <NUM> (or the glass panel unit <NUM>) and the mount base is suitably at least as thick as the intermediate film <NUM>.

In this embodiment, before the glass panel unit <NUM> and the transparent plate <NUM> are assembled together, the intermediate film <NUM> is dried to a moisture content falling within the range from <NUM>% by weight to <NUM>% by weight and is suitably dried to a moisture content falling within the range from <NUM>% by weight to <NUM>% by weight. The glass panel unit <NUM> and the transparent plate <NUM> may be bonded together only by heating, without using any autoclave machine, by drying the intermediate film <NUM> and thereby decreasing its moisture content as described above. Thus, decreasing the moisture content of the intermediate film <NUM> to the range from <NUM>% by weight to <NUM>% by weight enables assembling the glass panel unit <NUM> and the transparent plate <NUM> together via the intermediate film <NUM> made of the PVB resin, while reducing the deformation of the spacers <NUM> and the damage and deformation of the first glass panel <NUM> and the second glass panel <NUM>.

Also, in a situation where the intermediate film <NUM> is made of the PVB resin, if the moisture content of the intermediate film <NUM> is less than <NUM>% by weight, then the bond strength would be so high as to cause a decline in the anti-penetration ability of the film. On the other hand, if the moisture content of the intermediate film <NUM> is greater than <NUM>% by weight, then the intermediate film <NUM> would lose its transparency or produce bubbles therein after going through the assembling process. Therefore, decreasing the moisture content of the intermediate film <NUM> made of the PVB resin sheet to the range from <NUM>% by weight to <NUM>% by weight, suitably to the range from <NUM>% by weight to <NUM>% by weight, may reduce the chances of causing a decline in the anti-penetration ability of the intermediate film <NUM>, loss of its transparency, and/or production of bubbles therein.

In addition, applying non-uniform pressure to the intermediate film <NUM> while assembling the glass panel unit <NUM> and the transparent plate <NUM> together via the intermediate film <NUM> made of the PVB resin is another cause of the loss of transparency of the intermediate film <NUM> and/or the production of bubbles therein. Thus, when assembled together, the glass panel unit <NUM> and the transparent plate <NUM> are suitably pressed so that pressure is applied uniformly to the intermediate film <NUM>.

In general, when the intermediate film <NUM> made of an EVA resin is used, then the glass panel unit <NUM> and the transparent plate <NUM> may be bonded together even at a lower heating temperature than the PVB resin. Thus, bonding the glass panel unit <NUM> and the transparent plate <NUM> together via the intermediate film <NUM> made of the EVA resin may reduce the chances of causing deformation of the spacers <NUM> included in the glass panel unit <NUM> and deformation, damage, and other inconveniences of the first glass panel <NUM> and second glass panel <NUM> thereof.

An air pressure difference is caused between the air pressure in the evacuated space <NUM> of the glass panel unit <NUM> and the atmospheric pressure in the external environment. For example, if a glass pane with a small thickness (e.g., equal to or less than <NUM>, or even <NUM> or less) is used as each of the first glass panel <NUM> and the second glass panel <NUM> of the glass panel unit <NUM>, then a phenomenon that the first glass panel <NUM> and the second glass panel <NUM> are flexed significantly as shown in <FIG> could be caused due to the air pressure difference. That is to say, a phenomenon that the first glass panel <NUM> and the second glass panel <NUM> are flexed and depressed toward the evacuated space <NUM> between the spacers <NUM> could be caused in some cases.

In addition, in the case of such a glass panel unit <NUM> of which the first glass panel <NUM> and the second glass panel <NUM> are flexed, a phenomenon that an image seen through the glass panel unit <NUM> (i.e., a transmitted image) and an image reflected from the glass panel unit <NUM> (i.e., a reflected image) look distorted is observed. Furthermore, if a multi-layer stack <NUM> is formed by attaching a transparent plate <NUM> to such a glass panel unit <NUM> of which the first glass panel <NUM> and the second glass panel <NUM> are flexed, then the intermediate film <NUM> thereof also becomes uneven due to the flexure of the first glass panel <NUM> and the second glass panel <NUM> of the glass panel unit <NUM>. In that case, even if the transparent plate <NUM> of the multi-layer stack <NUM> has a flat surface, both a transmitted image and a reflected image produced through the multi-layer stack <NUM> could look distorted due to the flexure of the first glass panel <NUM> and the second glass panel <NUM> and the unevenness of the intermediate film <NUM>.

Thus, according to this embodiment, the glass panel unit <NUM> and the transparent plate <NUM> are assembled together by, for example, the following assembling method using a vacuum chamber. According to the assembling method using a vacuum chamber, the process of assembling the glass panel unit <NUM> and the transparent plate <NUM> together is performed inside an evacuated chamber (vacuum chamber) <NUM>. Such an assembling method using a vacuum chamber enables assembling the glass panel unit <NUM> and the transparent plate <NUM> together via the intermediate film <NUM> with the first glass panel <NUM> and the second glass panel <NUM> either not flexed or hardly flexed between the spacers <NUM>. Note that the inside of the chamber <NUM> when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together needs to be evacuated to at least a pressure lower than the atmospheric pressure. Thus, the pressure inside the chamber <NUM> when the glass panel unit <NUM> and the transparent plate <NUM> are assembled together is not limited to any particular value.

The process using the vacuum chamber (hereinafter simply referred to as a "vacuum chamber process") may be performed, for example, by loading the glass panel unit <NUM>, the intermediate film <NUM>, and transparent plate <NUM> into the chamber <NUM> and assembling the glass panel unit <NUM> and the transparent plate <NUM> together via the intermediate film <NUM> while evacuating the chamber <NUM> as shown in <FIG>.

According to the vacuum chamber process as shown in <FIG>, the chamber <NUM> and a heater device <NUM> installed inside the chamber <NUM> are used. The heater device <NUM> includes a pair of heaters <NUM>, which are arranged to be spaced from each other in the upward/downward direction.

According to the vacuum chamber process as shown in <FIG>, first, a multi-layer assembly <NUM> including the glass panel unit <NUM>, the intermediate film <NUM>, and the transparent plate <NUM> is loaded into the chamber <NUM> as shown in <FIG>. At this time, the multi-layer assembly <NUM> is in a state where the glass panel unit <NUM> is stacked over the transparent plate <NUM> with the intermediate film <NUM> interposed between them.

Next, the chamber <NUM> is evacuated using a rotary pump, for example, thereby reducing the flexure of the first glass panel <NUM> and the second glass panel <NUM> as shown in <FIG>. In this case, the inside of the chamber <NUM> is evacuated to, for example, <NUM> atm (≃ <NUM> MPa).

Subsequently, as shown in <FIG>, the multi-layer assembly <NUM> is sandwiched between, and heated by, the pair of heaters <NUM> provided over and under the multi-layer assembly <NUM>, thus causing the intermediate film <NUM> to be melted and softened. In addition, the multi-layer assembly <NUM> is also compressed, thus exhausting air bubbles out of the intermediate film <NUM>. In this process step, the multi-layer assembly <NUM> is pressed by the pair of heaters <NUM> with force less than the compressive strength of the spacers <NUM> (e.g., force of <NUM> atm (≃ <NUM> MPa)).

Thereafter, with the multi-layer assembly <NUM> kept compressed by the pair of heaters <NUM>, the heaters <NUM> are powered OFF to stop heating the multi-layer assembly <NUM> and cool the multi-layer assembly <NUM>. This causes the temperature of the multi-layer assembly <NUM> to fall and the intermediate film <NUM> to be cured, thus forming a multi-layer stack <NUM> in which the glass panel unit <NUM> and the transparent plate <NUM> are bonded together via the intermediate film <NUM>.

Next, the pressure inside the chamber <NUM> is restored to the atmospheric pressure and the multi-layer stack <NUM> is unloaded from the chamber <NUM>. Note that the inside of the chamber <NUM> is kept evacuated at least until the intermediate film <NUM> is cured since the first glass panel <NUM> and the second glass panel <NUM> have had their flexure reduced. In addition, the means for heating the multi-layer assembly <NUM> does not have to be the heater device <NUM>. Alternatively, the multi-layer assembly <NUM> may also be heated by an infrared ray, for example.

The vacuum chamber process may be performed using the assembling apparatus <NUM> shown in <FIG>. The assembling apparatus <NUM> is installed in the chamber <NUM> that may be evacuated. The assembling apparatus <NUM> includes a press machine <NUM>. The press machine <NUM> is used to press the multi-layer assembly <NUM> (see <FIG>). The multi-layer assembly <NUM> includes the glass panel unit <NUM>, the transparent plate <NUM>, and the intermediate film <NUM> sandwiched between the glass panel unit <NUM> and the transparent plate <NUM>.

The press machine <NUM> includes a bearer <NUM> for supporting the multi-layer assembly <NUM> thereon and a press member <NUM> for sandwiching the multi-layer assembly <NUM> between the bearer <NUM> and itself by being brought up and down over the bearer <NUM>. The bearer <NUM> may be formed, for example, in the shape of a plate, and has a supporting surface <NUM> configured as a horizontal upper surface. The press member <NUM> may be formed, for example, in the shape of a plate, and has a pressing surface <NUM> configured as a horizontal lower surface.

The assembling apparatus <NUM> further includes an elevator device <NUM>. The elevator device <NUM> supports the glass panel unit <NUM> over the bearer <NUM> and brings the glass panel unit <NUM> up and down in that state. The elevator device <NUM> includes a pair of supporting members <NUM>. The pair of supporting members <NUM> are provided to be spaced from each other in the rightward/leftward direction. As used herein, the "rightward/leftward direction" is the direction parallel to the width of the transparent plate <NUM> in a state where the transparent plate <NUM> is supported by the bearer <NUM> as shown in <FIG>.

Each supporting member <NUM> includes a base <NUM> and a plurality of supporting portions <NUM> protruding from the base <NUM> toward the other supporting member <NUM>. Each supporting member <NUM> is movable in the upward/downward direction and the rightward/leftward direction. Each supporting member <NUM> is driven in the upward/downward direction and the rightward/leftward direction by, for example, a driving unit including a ball screw, a linear actuator, a motor, and other members.

In the press machine <NUM> shown in <FIG>, the press member <NUM> is elevated by motive power generated by a motor such as an electric motor. Each of the bearer <NUM> and the press member <NUM> includes a heater. The press machine <NUM> presses the multi-layer assembly <NUM> put on the supporting surface <NUM> of the bearer <NUM> with the bearer <NUM> and the press member <NUM> heated by their own heater.

The glass panel unit <NUM> and the transparent plate <NUM> may be assembled together using the assembling apparatus <NUM> in the following manner, for example. In the following description, a situation where an intermediate film <NUM> made of a PVB resin is used as the intermediate film <NUM> will be described.

First, as shown in <FIG>, the transparent plate <NUM> is mounted on the supporting surface <NUM> of the bearer <NUM> with one surface thereof in the thickness direction facing down, and the intermediate film <NUM> is put on the transparent plate <NUM> with one surface thereof in the thickness direction facing down. At this time, the respective supporting members <NUM> of the elevator device <NUM> are arranged at first positions where the supporting members <NUM> are located above the intermediate film <NUM> and outwardly spaced from the intermediate film <NUM> in the rightward/leftward directions.

Next, the respective supporting members <NUM> of the elevator device <NUM> are driven in the rightward/leftward directions and thereby placed at the second positions shown in <FIG>. When the respective supporting members <NUM> are placed at the second positions, the respective tip portions of the plurality of supporting portions <NUM> of each supporting member <NUM> are located above the intermediate film <NUM>.

Subsequently, as shown in <FIG>, the glass panel unit <NUM> is put on the respective tip portions of the plurality of supporting portions <NUM> of the supporting members <NUM> with one surface thereof in the thickness direction facing down. At this time, the lower surface of the glass panel unit <NUM>, which is either the outer surface <NUM> of the first glass panel <NUM> or the outer surface <NUM> of the second glass panel <NUM>, is located at a predetermined gap distance over the upper surface of the intermediate film <NUM>, thus leaving a gap <NUM> between the glass panel unit <NUM> and the intermediate film <NUM>. Evacuating the inside of the chamber <NUM> with such a gap <NUM> left accelerates drying the intermediate film <NUM>. Note that the predetermined gap distance preferably falls within the range from <NUM> to <NUM>, and more preferably falls within the range from <NUM> to <NUM>, to accelerate drying the intermediate film <NUM>. Also, the inside of the chamber <NUM> may have been evacuated before the gap <NUM> is created or may be evacuated after the gap <NUM> has been created. In any case, the inside of the chamber <NUM> will be kept evacuated at least until the intermediate film <NUM> is cured as will be described later.

After the intermediate film <NUM> has been dried as described above for a predetermined period of time, the respective supporting members <NUM> of the elevator device <NUM> are driven downward to be placed at the third positions shown in <FIG>. When the respective supporting members <NUM> are placed at the third positions, the respective tip portions of the plurality of supporting portions <NUM> of the supporting members <NUM> either come into contact with, or are located in the vicinity of, the upper surface of the intermediate film <NUM>. In this case, the glass panel unit <NUM> supported by the elevator device <NUM> is brought down to have the lower surface of the glass panel unit <NUM> brough either to the vicinity of, or into contact with, the upper surface of the intermediate film <NUM>.

Thereafter, the respective supporting members <NUM> of the elevator device <NUM> are driven in the rightward/leftward directions such that the respective supporting members <NUM> are placed at fourth positions where the supporting members <NUM> are located above the intermediate film <NUM> and outwardly spaced from the intermediate film <NUM> in the rightward/leftward directions as shown in <FIG>. As a result, the glass panel unit <NUM> comes to be supported only by the transparent plate <NUM> via the intermediate film <NUM>.

Next, the press member <NUM> of the press machine <NUM> is driven downward, thereby making the pressing surface <NUM> of the press member <NUM> and the supporting surface <NUM> of the bearer <NUM> press the multi-layer assembly <NUM> including the transparent plate <NUM>, the intermediate film <NUM>, and the glass panel unit <NUM> as shown in <FIG>. In the meantime, the press member <NUM> is heated by the heater built in the press member <NUM> itself. The bearer <NUM> is also heated by the heater built in the bearer <NUM> itself. That is to say, the multi-layer assembly <NUM> is pressed by the press member <NUM> and bearer <NUM> that are being heated. Thus, the intermediate film <NUM> is softened by the heat transferred from the press member <NUM> and the bearer <NUM> and the glass panel unit <NUM> and the transparent plate <NUM> are assembled together via the intermediate film <NUM> thus softened. Note that the intermediate film <NUM> softened may have been melted.

The press member <NUM> and the bearer <NUM> may start to be heated by their own heater either before or after the multi-layer assembly <NUM> starts to be pressed by the press machine <NUM>, whichever is appropriate. In addition, the thermal conductivity of the glass panel unit <NUM> is lower than the thermal conductivity of the transparent plate <NUM>. Thus, not both the press member <NUM> and the bearer <NUM> but only the bearer <NUM> may be heated by its own heater.

After the multi-layer assembly <NUM> has been pressed by the press machine <NUM> as described above, the press member <NUM> and the bearer <NUM> stop being heated by their own heater. This causes the intermediate film <NUM> to be cooled and cured, thus forming a multi-layer stack <NUM> in which the glass panel unit <NUM> and the transparent plate <NUM> are bonded together via the intermediate film <NUM>.

The vacuum chamber process as described above may reduce the air pressure difference between the evacuated space <NUM> of the glass panel unit <NUM> and the external environment during the assembling process, thus enabling reducing the flexure of the glass panel unit <NUM> during the assembling process.

In particular, this process is advantageous when the transparent plate <NUM> is a glass pane (such as float glass) having greater rigidity than at least the glass panel to which the transparent plate <NUM> is attached and which is either the first glass panel <NUM> or the second glass panel <NUM>. In that case, even if the multi-layer stack <NUM> is exposed to the air after the glass panel unit <NUM> and the transparent plate <NUM> have been assembled together, the glass panel unit <NUM> included in the multi-layer stack <NUM> may have its flexure between the spacers <NUM> reduced by the transparent plate <NUM> having the greater rigidity. Consequently, this may reduce the chances of causing the phenomenon that both a transmitted image and a reflected image look distorted through the multi-layer stack <NUM>. Optionally, the rigidity of the transparent plate <NUM> may be greater than both the rigidity of the first glass panel <NUM> and the rigidity of the second glass panel <NUM>. Alternatively, the transparent plate <NUM> may have as high rigidity as, or lower rigidity than, the first or second glass panel <NUM>, <NUM> to which the transparent plate <NUM> is attached.

In addition, the vacuum chamber process described above may also reduce the humidity in the chamber <NUM>. This may reduce the chances of the intermediate film <NUM> losing its transparency or producing air bubbles therein. Note that the intermediate film <NUM> may be dried either before or after the intermediate film <NUM> is loaded into the chamber <NUM>, whichever is appropriate.

When formed by the vacuum chamber process, the multi-layer stack <NUM> is heated in the chamber <NUM> at a reduced pressure, e.g., at a degree of vacuum equal to or less than <NUM> atm (≃ <NUM> MPa) and preferably at a degree of vacuum equal to or less than <NUM> atm (≃ <NUM> MPa).

Optionally, the intermediate film <NUM> may also be made of, for example, a UV curable resin. In that case, the multi-layer stack <NUM> may be formed with little flexure by irradiating, with an ultraviolet ray, the intermediate film <NUM> made of a UV curable resin and interposed between the glass panel unit <NUM> and the transparent plate <NUM> with the multi-layer assembly <NUM> loaded in the evacuated chamber <NUM>.

Optionally, after the glass panel unit <NUM> and the transparent plate <NUM> have been assembled together, the assembly may be subjected to autoclave curing at a low temperature.

The multi-layer stack <NUM> may be used in any field without limitation but is applicable to, for example, a field that requires high mechanical strength and excellent thermal insulation properties. Examples of uses of the multi-layer stack <NUM> include various types of moving vehicles such as automobiles, railway trains, watercrafts, spacecrafts, and space stations. For example, when applied to an automobile, the multi-layer stack <NUM> may be used in its front windshield, side windows, and rear windshield, for example.

Next, a method for manufacturing a multi-layer stack <NUM> according to a second embodiment will be described with reference to <FIG> and <FIG>. In the following description, description of a common feature between the first embodiment described above and the second embodiment to be described below will be omitted herein.

In the method for manufacturing a multi-layer stack <NUM> according to this embodiment, first, a multi-layer assembly <NUM> in which the glass panel unit <NUM> and the transparent plate <NUM> are assembled together via the intermediate film <NUM> is provided. Next, the multi-layer assembly <NUM> is heated inside an evacuated chamber <NUM> to soften the intermediate film <NUM>. Then, with the multi-layer assembly <NUM> left loaded inside the chamber <NUM>, the inside of the chamber <NUM> will be kept evacuated until the intermediate film <NUM> is cooled and cured.

The method for manufacturing the multi-layer stack <NUM> according to this embodiment is carried out by, for example, loading the multi-layer assembly <NUM> into the chamber <NUM> after the multi-layer assembly <NUM> has been brought into contact with rubber heaters of approximately the same size as the transparent plate <NUM> on both of the upper and lower surfaces thereof, starting heating the multi-layer assembly <NUM> with the rubber heaters turned ON, and evacuating the chamber <NUM>. At this time, if the pressure inside the chamber <NUM> is <NUM> atm (≃ <NUM> MPa), for example, then the degree of flexure around the spacers <NUM> may be approximately halved. In addition, the intermediate film <NUM> also softens to follow the surface shapes of the first glass panel <NUM> and the second glass panel <NUM>, which would halve the degree of the multi-layer stack <NUM> as well. Thereafter, with the pressure inside the chamber <NUM> maintained, the rubber heaters are turned OFF to cool the intermediate film <NUM>. This may reduce the flexure of the multi-layer stack <NUM>. After that, the pressure inside the chamber <NUM> is restored to the atmospheric pressure and the multi-layer stack <NUM> is unloaded.

A method for manufacturing the multi-layer stack <NUM> according to this embodiment includes the following first, second, and third process steps. The first process step includes providing a multi-layer assembly <NUM> including the glass panel unit <NUM>, the intermediate film <NUM>, and the transparent plate <NUM> attached to the glass panel unit <NUM> via the intermediate film <NUM> as shown in <FIG>. In this multi-layer assembly <NUM>, the glass panel unit <NUM> and the transparent plate <NUM> have been assembled together by a process other than the vacuum chamber process according to the first embodiment. For example, the multi-layer assembly <NUM> may be formed by a vacuum bag process using a bag.

According to the vacuum bag process, first, the glass panel unit <NUM>, the intermediate film <NUM>, and the transparent plate <NUM> are put into a bag. Next, the bag is evacuated, thus causing the bag to shrink. The bag thus shrunk presses the glass panel unit <NUM>, the intermediate film <NUM>, and the transparent plate <NUM> and assembles the glass panel unit <NUM> and the transparent plate <NUM> together via the intermediate film <NUM>, thereby forming the multi-layer assembly <NUM>. Optionally, the multi-layer assembly <NUM> provided in this first process step may be formed without using the bag. Alternatively, the multi-layer assembly <NUM> provided in the first process step may also be the multi-layer assembly <NUM> (multi-layer stack <NUM>) that has gone through the assembling process using the vacuum chamber according to the first embodiment.

The second process step is performed after the first process step. The second process step includes heating, inside the evacuated chamber <NUM>, the multi-layer assembly <NUM> that has been provided in the first step to cause the intermediate film <NUM> to be softened. For example, if the intermediate film <NUM> is made of a PVB resin, then the intermediate film <NUM> will be softened by being heated at a temperature equal to or higher than <NUM> for approximately <NUM> minutes. In the second process step, the inside of the chamber <NUM> is evacuated, thereby reducing the flexure of the first glass panel <NUM> and the second glass panel <NUM> of the multi-layer assembly <NUM> as shown in <FIG>.

The third process step is performed after the second process step. The third process step includes stopping heating the multi-layer assembly <NUM> with the multi-layer assembly <NUM> still loaded in the chamber <NUM>, thereby cooling the multi-layer assembly <NUM>. In this process step, the inside of the chamber <NUM> will be kept evacuated until the intermediate film <NUM> that has been softened in the second process step is cured. This allows the intermediate film <NUM> of the multi-layer assembly <NUM> to be cured with the flexure of the first glass panel <NUM> and the second glass panel <NUM> reduced. Consequently, the multi-layer assembly <NUM> turns into a multi-layer stack <NUM> with reduced flexure.

The method for manufacturing the multi-layer stack <NUM> according to this embodiment may be performed using, for example, the chamber <NUM> shown in <FIG> and the heater device <NUM> installed in the chamber <NUM>. The heater device <NUM> includes a pair of heaters <NUM>, which are arranged to be spaced from each other in the upward/downward direction. Each of these heaters <NUM> may be a rubber heater, for example.

The heater device <NUM> may be used, for example, in the following manner. First, as shown in <FIG>, the pair of heaters <NUM> are arranged inside the chamber <NUM> and the multi-layer assembly <NUM> is placed between the pair of heaters <NUM>. At this time, one heater <NUM> out of the pair of heaters <NUM> is brought into contact with one outer surface along the thickness of the multi-layer assembly <NUM> (i.e., the outer surface of the transparent plate <NUM>) and the other heater <NUM> is brought into contact with the other outer surface along the thickness of the multi-layer assembly <NUM> (i.e., either the outer surface <NUM> of the second glass panel <NUM> or the outer surface <NUM> of the first glass panel <NUM>).

Next, the inside of the chamber <NUM> is evacuated and the multi-layer assembly <NUM> will be kept heated in this state by the pair of heaters <NUM> until the intermediate film <NUM> is cured. This may reduce the flexure of the glass panel unit <NUM> due to the atmospheric pressure as shown in <FIG>. In addition, this may also reduce the flexure of the transparent plate <NUM> along the surface of the glass panel unit <NUM> accordingly.

After the flexure of the multi-layer assembly <NUM> has been reduced in this manner, the pair of heaters <NUM> stops heating the multi-layer assembly <NUM> to cool the multi-layer assembly <NUM>. The multi-layer assembly <NUM> will be cooled with the inside of the chamber <NUM> kept evacuated until the intermediate film <NUM> is cured. Curing the intermediate film <NUM> in this manner allows the glass panel unit <NUM> and the transparent plate <NUM> to be assembled together via the intermediate film <NUM> with their flexure reduced, thereby forming a multi-layer stack <NUM> with reduced flexure.

Next, a method for manufacturing a multi-layer stack <NUM> according to a third embodiment will be described. In this embodiment, the multi-layer stack <NUM> shown in <FIG> is manufactured. The multi-layer stack <NUM> includes the glass panel unit <NUM>, a first transparent plate <NUM>, a first intermediate film <NUM>, a second transparent plate <NUM>, and a second intermediate film <NUM>. In this embodiment, the multi-layer stack <NUM> is manufactured by the same vacuum chamber process as in the first embodiment. In the following description, description of a common feature between the first and third embodiments will be omitted herein.

The first transparent plate <NUM> is provided for the outer surface <NUM> of the first glass panel <NUM> of the glass panel unit <NUM>. The first intermediate film <NUM> is interposed between the first glass panel <NUM> and the first transparent plate <NUM>. That is to say, the first transparent plate <NUM> is provided along the outer surface <NUM> of the first glass panel <NUM> and the first intermediate film <NUM> is interposed between the first glass panel <NUM> and the first transparent plate <NUM>.

The second transparent plate <NUM> is provided for the outer surface <NUM> of the second glass panel <NUM> of the glass panel unit <NUM>. The second intermediate film <NUM> is interposed between the second glass panel <NUM> and the second transparent plate <NUM>. That is to say, the second transparent plate <NUM> is provided along the outer surface <NUM> of the second glass panel <NUM> and the second intermediate film <NUM> is interposed between the second glass panel <NUM> and the second transparent plate <NUM>.

In the multi-layer stack <NUM> according to this embodiment, the first transparent plate <NUM> and the second transparent plate <NUM> are respectively provided for the outer surface <NUM> of the first glass panel <NUM> and the outer surface <NUM> of the second glass panel <NUM>. This allows the multi-layer stack <NUM> to have improved mechanical strength, thermal insulation properties, and sound insulation compared to the glass panel unit <NUM> without any of these transparent plates <NUM>, <NUM>. In addition, this also makes the mechanical strength, thermal insulation properties, and sound insulation of this multi-layer stack <NUM> superior to those of the multi-layer stack <NUM> in which the transparent plate <NUM> is provided for only either the outer surface <NUM> of the first glass panel <NUM> or the outer surface <NUM> of the second glass panel <NUM>.

To manufacture the multi-layer stack <NUM> according to this embodiment, the outer surface <NUM> of the first glass panel <NUM> of the glass panel unit <NUM> and the first transparent plate <NUM> are assembled together via the first intermediate film <NUM> as shown in <FIG>. In addition, the outer surface <NUM> of the second glass panel <NUM> of the glass panel unit <NUM> and the second transparent plate <NUM> are also assembled together via the second intermediate film <NUM>. In this manner, a multi-layer stack <NUM> with excellent mechanical strength, thermal insulation properties, and sound insulation may be obtained.

Next, the multi-layer stack <NUM> according to the third embodiment and a method for manufacturing the same will be described in detail.

In the multi-layer stack <NUM> according to this embodiment, the transparent plate <NUM> includes the first transparent plate <NUM> and the second transparent plate <NUM> described above, and the intermediate film <NUM> includes the first intermediate film <NUM> and the second intermediate film <NUM> described above. These constituent elements will be described in detail. In the following description, any constituent element of the multi-layer stack <NUM> according to this third embodiment, having the same function as a counterpart of the multi-layer stack <NUM> according to the first embodiment described above, will be designated by the same reference numeral as that counterpart's, and description thereof will be sometimes omitted herein.

The glass panel unit <NUM> according to this embodiment has the same configuration as the glass panel unit <NUM> according to the first embodiment. Thus, the glass panel unit <NUM> includes: the first glass panel <NUM>; the second glass panel <NUM>; and the evacuated space <NUM> interposed between the first glass panel <NUM> and the second glass panel <NUM>. In addition, in the evacuated space <NUM>, the plurality of spacers <NUM> made of resin are provided between the first glass panel <NUM> and the second glass panel <NUM>.

The transparent plate <NUM> according to this embodiment includes the first transparent plate <NUM> and the second transparent plate <NUM> as described above.

The first transparent plate <NUM> is a plate member having light-transmitting properties. The material for the first transparent plate <NUM> may be the same as the material for the transparent plate <NUM> according to the first embodiment.

In the multi-layer stack <NUM> according to this embodiment, the first transparent plate <NUM> is provided for the outer surface <NUM> of the first glass panel <NUM> of the glass panel unit <NUM>. Thus, the first transparent plate <NUM> faces the glass panel unit <NUM>. In addition, the first transparent plate <NUM> also faces the first glass panel <NUM>.

The second transparent plate <NUM> is a plate member having light-transmitting properties. The material for the second transparent plate <NUM> may also be the same as the material for the transparent plate <NUM> according to the first embodiment. In this embodiment, the material for the first transparent plate <NUM> and the material for the second transparent plate <NUM> may be either the same as each other or different from each other, whichever is appropriate.

For example, the first transparent plate <NUM> and the second transparent plate <NUM> may be both made of polycarbonate. Alternatively, the first transparent plate <NUM> and the second transparent plate <NUM> may be both made of glass, for example. Still alternatively, one of the first transparent plate <NUM> or the second transparent plate <NUM> may be made of polycarbonate and the other may be made of glass.

That is to say, at least one of the first transparent plate <NUM> or the second transparent plate <NUM> suitably includes a glass pane. In addition, at least one of the first transparent plate <NUM> or the second transparent plate <NUM> suitably includes a polycarbonate plate.

In the multi-layer stack <NUM> according to this embodiment, the second transparent plate <NUM> is provided for the outer surface <NUM> of the second glass panel <NUM> of the glass panel unit <NUM>. Thus, the second transparent plate <NUM> faces the glass panel unit <NUM>. In addition, the second transparent plate <NUM> also faces the second glass panel <NUM>.

The intermediate film <NUM> according to this embodiment includes the first intermediate film <NUM> and the second intermediate film <NUM> as described above.

The first intermediate film <NUM> may have the same configuration as the intermediate film <NUM> according to the first embodiment. In the multi-layer stack <NUM> according to this embodiment, the first intermediate film <NUM> is interposed between the outer surface <NUM> of the first glass panel <NUM> of the glass panel unit <NUM> and the first transparent plate <NUM>. Thus, the first intermediate film <NUM> may be used to bond the glass panel unit <NUM> and the first transparent plate <NUM> together, and more specifically, bond the first glass panel <NUM> and the first transparent plate <NUM> together.

The second intermediate film <NUM> may have the same configuration as the intermediate film <NUM> according to the first embodiment. In the multi-layer stack <NUM> according to this embodiment, the second intermediate film <NUM> is interposed between the outer surface <NUM> of the second glass panel <NUM> of the glass panel unit <NUM> and the second transparent plate <NUM>. Thus, the second intermediate film <NUM> may be used to bond the glass panel unit <NUM> and the second transparent plate <NUM> together, and more specifically, bond the second glass panel <NUM> and the second transparent plate <NUM> together.

The first intermediate film <NUM> may have the same configuration as the intermediate film <NUM> according to the first embodiment as described above. Thus, the material for the first intermediate film <NUM> may be the same as the material for the intermediate film <NUM> according to the first embodiment.

Likewise, the second intermediate film <NUM> may have the same configuration as the intermediate film <NUM> according to the first embodiment. Thus, the material for the second intermediate film <NUM> may also be the same as the material for the intermediate film <NUM> according to the first embodiment.

In the multi-layer stack <NUM> according to this embodiment, the first intermediate film <NUM> and the second intermediate film <NUM> are suitably made of different materials. This makes it easier to enhance the performance of the multi-layer stack <NUM> while facilitating the manufacturing process thereof at the same time.

For example, at least one of the first intermediate film <NUM> or the second intermediate film <NUM> is suitably made of a PVB resin. This would ensure sufficient mechanical strength for the multi-layer stack <NUM>, to say the least. In addition, this would also increase the anti-penetration ability of the multi-layer stack <NUM>.

In addition, at least one of the first intermediate film <NUM> or the second intermediate film <NUM> is suitably made of an EVA resin. This would increase the anti-scattering ability of the multi-layer stack <NUM>. In addition, using the EVA resin allows the glass panel unit <NUM> and the transparent plate <NUM>, <NUM> to be bonded together at a relatively low temperature, thus facilitating the manufacturing process of the multi-layer stack <NUM> as well. This would also increase the handleability of the multi-layer stack <NUM>.

Furthermore, making the first intermediate film <NUM> and the second intermediate film <NUM> of two different materials would allow the multi-layer stack <NUM> to achieve both the advantages of the material for the first intermediate film <NUM> and the advantages of the material for the second intermediate film <NUM> alike.

For example, it is recommended that the first intermediate film <NUM> be made of the PVB resin and the second intermediate film <NUM> be made of the EVA resin. Alternatively, it is also recommended that the first intermediate film <NUM> be made of the EVA resin and the second intermediate film <NUM> be made of the PVB resin. In each of these cases, the manufacturing process of the multi-layer stack <NUM> may be facilitated with sufficient mechanical strength ensured for the multi-layer stack <NUM>. That is to say, the mechanical strength enhancement and simplified manufacturing process are achieved at the same time for the multi-layer stack <NUM>. In addition, the multi-layer stack <NUM> with each of these configurations may also have anti-penetration ability and anti-scattering ability at a time. For example, one of the first intermediate film <NUM> or the second intermediate film <NUM> which is required to have sufficient anti-penetration ability is suitably made of the PVB resin and the other intermediate film <NUM>, <NUM> required to have anti-scattering ability is suitably made of the EVA resin.

Alternatively, in this embodiment, the first intermediate film <NUM> and the second intermediate film <NUM> may also be made of the same material. In that case, the advantages of the material for the first intermediate film <NUM> and the second intermediate film <NUM> would be achieved particularly significantly.

For example, the first intermediate film <NUM> and the second intermediate film <NUM> are suitably both made of the PVB resin. This would increase the mechanical strength of the multi-layer stack <NUM> particularly significantly. In addition, this would also increase the anti-penetration ability of the multi-layer stack <NUM> particularly significantly. Alternatively, the first intermediate film <NUM> and the second intermediate film <NUM> are also suitably both made of the EVA resin. This would facilitate the manufacturing process of the multi-layer stack <NUM> particularly significantly. In addition, this would also increase the anti-scattering ability of the multi-layer stack <NUM> particularly significantly.

First, the glass panel unit <NUM>, the transparent plates <NUM>, and the intermediate films <NUM> are provided as shown in <FIG>. In the multi-layer stack <NUM> according to this embodiment, the transparent plates <NUM> include the first transparent plate <NUM> and the second transparent plate <NUM>, and the intermediate films <NUM> include the first intermediate film <NUM> and the second intermediate film <NUM>. Thus, the first transparent plate <NUM> and the second transparent plate <NUM> are provided as the transparent plates <NUM>, and the first intermediate film <NUM> and the second intermediate film <NUM> are provided as the intermediate films <NUM>.

Next, the glass panel unit <NUM> and the transparent plates <NUM> are assembled together via the intermediate films <NUM>. In this embodiment, the outer surface <NUM> of the first glass panel <NUM> of the glass panel unit <NUM> and the first transparent plate <NUM> are assembled together via the first intermediate film <NUM>. In addition, the outer surface <NUM> of the second glass panel <NUM> of the glass panel unit <NUM> and the second transparent plate <NUM> are assembled together via the second intermediate film <NUM>. In each of the process step of assembling the glass panel unit <NUM> and the first transparent plate <NUM> together and the process step of assembling the glass panel unit <NUM> and the second transparent plate <NUM> together, the pressure applied for assembling is less than the compressive strength of the plurality of resin spacers <NUM> included in the glass panel unit <NUM>. This reduces the chances of the plurality of resin spacers <NUM> included in the glass panel unit <NUM> collapsing under the pressure.

Assembling the glass panel unit <NUM> and the first transparent plate <NUM> and assembling the glass panel unit <NUM> and the second transparent plate <NUM> may be performed either two different processes or simultaneously, whichever is appropriate.

For example, if the first intermediate film <NUM> and the second intermediate film <NUM> are made of the same material, then assembling the glass panel unit <NUM> and the first transparent plate <NUM> and assembling the glass panel unit <NUM> and the second transparent plate <NUM> are suitably performed simultaneously. This enables manufacturing the multi-layer stack <NUM> efficiently.

For example, the first intermediate film <NUM> and the second intermediate film <NUM> are suitably both made of a PVB resin. In that case, the glass panel unit <NUM>, the first transparent plate <NUM>, and the second transparent plate <NUM> are suitably assembled together at a relative humidity of <NUM>% or less. This allows bonding the glass panel unit <NUM> and the first transparent plate <NUM> together only by heating and bonding the glass panel unit <NUM> and the second transparent plate <NUM> together only by heating. This may also reduce the chances of the first intermediate film <NUM> and the second intermediate film <NUM> made of the PVB resin losing transparency or producing bubbles therein. Alternatively, both the first intermediate film <NUM> and the second intermediate film <NUM> are suitably made of, for example, an EVA resin. Still alternatively, the first intermediate film <NUM> and the second intermediate film <NUM> may be both made of a thermosetting resin or both made of a UV curable resin.

Particularly when the first intermediate film <NUM> and the second intermediate film <NUM> are both made of the PVB resin, the glass panel unit <NUM> and the transparent plates <NUM> are laid one on top of another with the intermediate films <NUM> as sheets of resin interposed between themselves, and the glass panel unit <NUM>, the transparent plates <NUM>, and the intermediate films <NUM> are loaded into a chamber. Then, a negative pressure is produced inside the chamber by a vacuum pump connected to the chamber to dry the intermediate films <NUM>. This allows decreasing the moisture content of the intermediate films <NUM>. Specifically, the intermediate films <NUM> are suitably dried to a moisture content equal to or less than <NUM>% by weight. The glass panel unit <NUM> and the transparent plates <NUM>, <NUM> may be bonded together only by heating via the first intermediate film <NUM> and the second intermediate film <NUM> by decreasing the moisture content of the first intermediate film <NUM> and the second intermediate film <NUM> as described above. This reduces the chances of the intermediate films <NUM> losing its transparency and/or producing air bubbles therein while reducing the deformation of the spacers <NUM> included in the glass panel unit <NUM> and the damage and deformation of the first glass panel <NUM> and the second glass panel <NUM>.

According to this embodiment, assembling the glass panel unit <NUM> and the first transparent plate <NUM> and assembling the glass panel unit <NUM> and the first transparent plate <NUM> are performed by the method using the vacuum chamber as in the method for manufacturing the multi-layer stack <NUM> according to the first embodiment. Specifically, the glass panel unit <NUM>, the intermediate films <NUM>, and the transparent plates <NUM> are loaded into the chamber <NUM> and the glass panel unit <NUM> and the transparent plates <NUM> are assembled together via the intermediate films <NUM> with the inside of the chamber <NUM> evacuated.

Naturally, even when the first intermediate film <NUM> and the second intermediate film <NUM> are both made of an EVA resin, the glass panel unit <NUM>, the first transparent plate <NUM>, and the second transparent plate <NUM> may also be bonded together by the method using the vacuum chamber.

For example, if the first intermediate film <NUM> and the second intermediate film <NUM> are made of different materials, then assembling the glass panel unit <NUM> and the first transparent plate <NUM> by the method using the vacuum chamber and assembling the glass panel unit <NUM> and the second transparent plate <NUM> by the method using the vacuum chamber are preferably performed as two different processes. If the first intermediate film <NUM> and the second intermediate film <NUM> are made of different materials, then the heating temperature required for the bonding process using the first intermediate film <NUM> and the heating temperature required for the bonding process using the second intermediate film <NUM> may be different from each other. Thus, simultaneously heating the first intermediate film <NUM> and the second intermediate film <NUM> that are made of different materials would make the bond strength insufficient and/or deform the intermediate films <NUM> in some cases. In contrast, performing assembling the glass panel unit <NUM> and the first transparent plate <NUM> and assembling the glass panel unit <NUM> and the second transparent plate <NUM> as two different processes may reduce the chances of making the bond strength insufficient and/or causing deformation and other inconveniences to the intermediate films <NUM>.

Specifically, one of the first and second intermediate films <NUM>, <NUM> that requires the higher heating temperature for bonding than the other intermediate film <NUM>, <NUM> is preferably bonded earlier than the other intermediate film <NUM>, <NUM>. For example, if the first intermediate film <NUM> requires the higher heating temperature than the second intermediate film <NUM>, then it is recommended that the glass panel unit <NUM> and the first transparent plate <NUM> be assembled together via the first intermediate film <NUM> first and then the glass panel unit <NUM> and the second transparent plate <NUM> be assembled together via the second intermediate film <NUM>. On the other hand, if the second intermediate film <NUM> requires the higher heating temperature than the first intermediate film <NUM>, then it is recommended that the glass panel unit <NUM> and the second transparent plate <NUM> be assembled together via the second intermediate film <NUM> first and then the glass panel unit <NUM> and the first transparent plate <NUM> be assembled together via the first intermediate film <NUM>.

For example, if the first intermediate film <NUM> is made of a PVB resin and the second intermediate film <NUM> is made of an EVA resin, then the heating temperature required for the bonding process using the first intermediate film <NUM> made of the PVB resin may be higher than the heating temperature required for the bonding process using the second intermediate film <NUM> made of the EVA resin. In that case, it is recommended that the glass panel unit <NUM> and the first transparent plate <NUM> be assembled together via the first intermediate film <NUM> made of the PVB resin first and then the glass panel unit <NUM> and the second transparent plate <NUM> be assembled together via the second intermediate film <NUM> made of the EVA resin.

The vacuum chamber process according to this embodiment may be performed by using, for example, the chamber <NUM> shown in <FIG> and the heater device <NUM> installed in the chamber <NUM>. The heater device <NUM> includes a pair of heaters <NUM>, which are arranged to be spaced from each other in the upward/downward direction.

In the vacuum chamber process according to this embodiment, first, a multi-layer assembly <NUM> including the glass panel unit <NUM>, the intermediate films <NUM>, and the transparent plates <NUM> is loaded into the vacuum chamber <NUM> as shown in <FIG>. At this time, the multi-layer assembly <NUM> is in a state where the first transparent plate <NUM>, the first intermediate film <NUM>, the glass panel unit <NUM>, the second intermediate film <NUM>, and the second transparent plate <NUM> have been stacked one on top of another in this order.

Next, the vacuum chamber <NUM> is evacuated using a rotary pump, for example, thereby reducing the flexure of the first glass panel <NUM> and the second glass panel <NUM> as shown in <FIG>. Subsequently, as shown in <FIG>, the multi-layer assembly <NUM> is sandwiched between, and heated by, the pair of heaters <NUM> provided over and under the multi-layer assembly <NUM>, thus causing the intermediate films <NUM> to be melted and softened. In addition, the multi-layer assembly <NUM> is also compressed, thus exhausting air bubbles out of the intermediate films <NUM>. In this case, the multi-layer assembly <NUM> is pressed by the pair of heaters <NUM> with force less than the compressive strength of the spacers <NUM> (e.g., force of <NUM> atm (≃ <NUM> MPa)).

Thereafter, with the multi-layer assembly <NUM> kept compressed by the pair of heaters <NUM>, the heaters <NUM> are powered OFF to stop heating the multi-layer assembly <NUM> and cool the multi-layer assembly <NUM>. This causes the temperature of the multi-layer assembly <NUM> to fall and also causes the intermediate films <NUM> to be cured, thus forming a multi-layer stack <NUM> in which the glass panel unit <NUM>, the intermediate films <NUM>, and the transparent plates <NUM> are bonded together.

Next, the pressure inside the vacuum chamber <NUM> is restored to the atmospheric pressure and the multi-layer stack <NUM> is unloaded from the vacuum chamber <NUM>. Note that the inside of the chamber <NUM> will be kept evacuated at least until the intermediate films <NUM> are cured since the first glass panel <NUM> and the second glass panel <NUM> have had their flexure reduced.

Optionally, if assembling the glass panel unit <NUM> and the first transparent plate <NUM> and assembling the glass panel unit <NUM> and the second transparent plate <NUM> are performed as two different processes, then the assembling apparatus <NUM> shown in <FIG> may be used. That is to say, the glass panel unit <NUM> and the first transparent plate <NUM> may be assembled together by using the assembling apparatus <NUM> as in the first embodiment and the glass panel unit <NUM> and the second transparent plate <NUM> may be assembled together by using the assembling apparatus <NUM> as in the first embodiment.

Next, a method for manufacturing a multi-layer stack <NUM> according to a fourth embodiment will be described with reference to <FIG> and <FIG>. In this embodiment, a multi-layer stack <NUM> having the same configuration as the multi-layer stack <NUM> according to the third embodiment is manufactured. That is to say, the multi-layer stack <NUM> shown in <FIG> is manufactured.

In this embodiment, the multi-layer stack <NUM> is manufactured by the same manufacturing method as the one adopted in the second embodiment. Specifically, the multi-layer assembly <NUM> in which the glass panel unit <NUM> and the transparent plates <NUM> are assembled together via the intermediate films <NUM> is heated inside an evacuated chamber <NUM> to soften the intermediate films <NUM>. Then, with the multi-layer assembly <NUM> still loaded inside the chamber <NUM>, the inside of the chamber <NUM> will be kept evacuated until the intermediate films <NUM> are cooled and cured. Note that in the following description of the fourth embodiment, description of a common feature between the fourth embodiment and the second and third embodiments described above will be omitted herein.

Specifically, in the method for manufacturing a multi-layer stack <NUM> according to this embodiment, first, a first process step is performed. The first process step includes providing a multi-layer assembly <NUM>. The multi-layer assembly <NUM> includes the glass panel unit <NUM>, the first intermediate film <NUM>, the first transparent plate <NUM> attached to the glass panel unit <NUM> via the first intermediate film <NUM>, the second intermediate film <NUM>, and the second transparent plate <NUM> attached to the glass panel unit <NUM> via the second intermediate film <NUM>. In this multi-layer assembly <NUM>, the glass panel unit <NUM> and the first and second transparent plates <NUM>, <NUM> have been assembled together by a process other than the vacuum chamber process.

A second process step is performed after the first process step. The second process step includes heating, inside the evacuated chamber <NUM>, the multi-layer assembly <NUM> that has been provided in the first step to cause the first intermediate film <NUM> and the second intermediate film <NUM> to be softened. In the second process step, the inside of the chamber <NUM> is evacuated, thereby reducing the flexure of the first glass panel <NUM> and the second glass panel <NUM> of the multi-layer assembly <NUM>.

A third process step is performed after the second process step. The third process step includes stopping heating the multi-layer assembly <NUM> with the multi-layer assembly <NUM> still loaded inside the chamber <NUM>, thereby cooling the multi-layer assembly <NUM>. In this process step, the inside of the chamber <NUM> will be kept evacuated until the first intermediate film <NUM> and the second intermediate film <NUM> that have been softened in the second process step are cured. This allows the first intermediate film <NUM> and the second intermediate film <NUM> to be cured with the flexure of the first glass panel <NUM> and the second glass panel <NUM> reduced. Consequently, the multi-layer assembly <NUM> turns into a multi-layer stack <NUM> with reduced flexure.

The method for manufacturing the multi-layer stack <NUM> according to this embodiment may be performed by using, for example, the chamber <NUM> shown in <FIG> and the heater device <NUM> installed in the chamber <NUM>. The heater device <NUM> includes a pair of heaters <NUM>, which are arranged to be spaced from each other in the upward/downward direction. Each of these heaters <NUM> may be a rubber heater, for example.

The heater device <NUM> may be used, for example, in the following manner. First, as shown in <FIG>, the pair of heaters <NUM> are arranged inside the chamber <NUM> and the multi-layer assembly <NUM> is placed between the pair of heaters <NUM>. At this time, one heater <NUM> out of the pair of heaters <NUM> is brought into contact with one outer surface along the thickness of the multi-layer assembly <NUM> (i.e., the outer surface of the first transparent plate <NUM>) and the other heater <NUM> is brought into contact with the other outer surface along the thickness of the multi-layer assembly <NUM> (i.e., the outer surface of the second transparent plate <NUM>).

Next, the inside of the chamber <NUM> is evacuated and the multi-layer assembly <NUM> will be kept heated in this state by the pair of heaters <NUM> until the first intermediate film <NUM> and the second intermediate film <NUM> are cured. This may reduce the flexure of the glass panel unit <NUM> due to the atmospheric pressure as shown in <FIG>. In addition, this may also reduce the flexure of the first transparent plate <NUM> and the second transparent plate <NUM> along the surface of the glass panel unit <NUM> accordingly.

After the flexure of the multi-layer assembly <NUM> has been reduced in this manner, the pair of heaters <NUM> stops heating the multi-layer assembly <NUM> to cool the multi-layer assembly <NUM>. The multi-layer assembly <NUM> will be cooled with the inside of the chamber <NUM> kept evacuated until the intermediate films <NUM> are cured. Curing the intermediate films <NUM> in this manner allows a multi-layer stack <NUM> to be formed with reduced flexure.

As is clear from the foregoing description of the first and third embodiments, a method for manufacturing a multi-layer stack (<NUM>) according to a first aspect has the following feature. The multi-layer stack (<NUM>) includes a glass panel unit (<NUM>), an intermediate film (<NUM>), and a transparent plate (<NUM>) attached via the intermediate film (<NUM>) to the glass panel unit (<NUM>). The glass panel unit (<NUM>) includes a first glass panel (<NUM>), a second glass panel (<NUM>), and an evacuated space (<NUM>) interposed between the first glass panel (<NUM>) and the second glass panel (<NUM>). The method includes locating, into a chamber (<NUM>), a multi-layer assembly (<NUM>) where the glass panel unit (<NUM>) is stacked over the transparent plate (<NUM>) with the intermediate film (<NUM>) interposed between the transparent plate (<NUM>) and the glass panel unit (<NUM>); then evacuating the chamber (<NUM>); and then making the multi-layer assembly (<NUM>) be sandwiched between and heated by a pair of heaters (<NUM>) of a heating device (<NUM>) installed inside the chamber (<NUM>) to assemble the glass panel unit (<NUM>) and the transparent plate (<NUM>) together via the intermediate film (<NUM>) inside an evacuated chamber (<NUM>).

This aspect enables manufacturing a multi-layer stack (<NUM>) in which the transparent plate (<NUM>) is attached to the glass panel unit (<NUM>), and which has excellent thermal insulation properties and mechanical strength. In addition, while the glass panel unit (<NUM>) and the transparent plate (<NUM>) are being assembled together, the glass panel unit (<NUM>) is placed in an evacuated environment inside a chamber (<NUM>). This allows the glass panel unit (<NUM>) and the transparent plate (<NUM>) to be assembled together with flexure (warpage) of the glass panel unit (<NUM>) due to the atmospheric pressure reduced. This enables manufacturing a multi-layer stack (<NUM>) with reduced flexure.

A method for manufacturing a multi-layer stack (<NUM>) according to a second aspect may be implemented in conjunction with the first aspect. In the second aspect, the method includes assembling, inside the evacuated chamber (<NUM>), the glass panel unit (<NUM>) and the transparent plate (<NUM>) together via the intermediate film (<NUM>) that has been softened by heating; and then keeping the inside of the chamber (<NUM>) evacuated until the intermediate film (<NUM>) is cured while leaving the glass panel unit (<NUM>), the intermediate film (<NUM>), and the transparent plate (<NUM>) loaded inside the chamber (<NUM>).

This aspect may reduce the flexure of the glass panel unit (<NUM>) until the intermediate film (<NUM>) is cured since the glass panel unit (<NUM>) and the transparent plate (<NUM>) have been assembled together. This enables manufacturing a multi-layer stack (<NUM>) with further reduced flexure.

A method for manufacturing a multi-layer stack (<NUM>) according to a third aspect may be implemented in conjunction with the first or second aspect. In the third aspect, the transparent plate (<NUM>) has greater rigidity than at least one glass panel, to which the transparent plate (<NUM>) is attached via the intermediate film (<NUM>), out of two glass panels that are the first glass panel (<NUM>) and the second glass panel (<NUM>).

This aspect reduces the chances of the glass panel unit (<NUM>) being flexed after the glass panel unit (<NUM>) and the transparent plate (<NUM>) have been assembled together. This enables manufacturing a multi-layer stack (<NUM>) with further reduced flexure.

A method for manufacturing a multi-layer stack (<NUM>) according to a fourth aspect may be implemented in conjunction with any one of the first to third aspects. At least one glass panel, to which the transparent plate (<NUM>) is attached via the intermediate film (<NUM>), out of two glass panels that are the first glass panel (<NUM>) and the second glass panel (<NUM>) has a thickness equal to or less than <NUM>.

This aspect enables manufacturing a multi-layer stack (<NUM>), of which a glass panel has a thickness equal to or less than <NUM> and which has reduced flexure.

As is clear from the foregoing description of the second and fourth embodiments, a method for manufacturing a multi-layer stack (<NUM>) according to a fifth aspect has the following feature. The multi-layer stack (<NUM>) includes a glass panel unit (<NUM>), an intermediate film (<NUM>), and a transparent plate (<NUM>) attached via the intermediate film (<NUM>) to the glass panel unit (<NUM>). The glass panel unit (<NUM>) includes a first glass panel (<NUM>), a second glass panel (<NUM>), and an evacuated space (<NUM>) interposed between the first glass panel (<NUM>) and the second glass panel (<NUM>). The method includes: locating, into a chamber (<NUM>), a multi-layer assembly (<NUM>), the multi-layer assembly including the glass panel unit (<NUM>), the intermediate film (<NUM>), and the transparent plate (<NUM>) attached via the intermediate film (<NUM>) to the glass panel unit (<NUM>), ); then evacuating the chamber (<NUM>) and heating the multi-layer assembly (<NUM>) by a heater (<NUM>) installed inside the chamber (<NUM>), thereby heating the multi-layer assembly (<NUM>) inside the evacuated chamber (<NUM>) to soften the intermediate film (<NUM>); and then keeping the inside of the chamber (<NUM>) evacuated until the intermediate film (<NUM>) is cooled and cured while leaving the multi-layer assembly (<NUM>) loaded inside the chamber (<NUM>).

This aspect enables manufacturing a multi-layer stack (<NUM>) in which a transparent plate (<NUM>) is attached onto a glass panel unit (<NUM>), and which has excellent thermal insulation properties and mechanical strength. In addition, the multi-layer assembly (<NUM>) may have its flexure due to the atmospheric pressure reduced by having the chamber (<NUM>) evacuated and the intermediate film (<NUM>) is cured in such a state. This enables manufacturing a multi-layer stack (<NUM>) with reduced flexure.

A method for manufacturing a multi-layer stack (<NUM>) according to a sixth aspect may be implemented in conjunction with any one of the first to fifth aspects. In the sixth aspect, the glass panel unit (<NUM>) has a plurality of spacers (<NUM>). The plurality of spacers (<NUM>) are provided, in the evacuated space (<NUM>), between the first glass panel (<NUM>) and the second glass panel (<NUM>). A pressure applied when the glass panel unit (<NUM>) and the transparent plate (<NUM>) are assembled together is less than a compressive strength of the plurality of spacers (<NUM>).

This aspect may reduce the chances of the spacers (<NUM>) of the glass panel unit (<NUM>) collapsing under pressure while the glass panel unit (<NUM>) and the transparent plate (<NUM>) are being assembled together.

In a method for manufacturing a multi-layer stack (<NUM>) according to a seventh aspect, which may be implemented in conjunction with the sixth aspect, the pressure applied while the glass panel unit (<NUM>) and the transparent plate (<NUM>) are being assembled together is equal to or less than <NUM> atm (≃ <NUM> MPa).

This aspect may significantly reduce the chances of the spacers (<NUM>) of the glass panel unit (<NUM>) collapsing under the pressure.

In a method for manufacturing a multi-layer stack (<NUM>) according to an eighth aspect, which may be implemented in conjunction with any one of the first to seventh aspects, the intermediate film (<NUM>) contains at least one of a PVB resin or an EVA resin.

This aspect increases, if the intermediate film (<NUM>) is made of a PVB resin, the mechanical strength and anti-penetration ability of the multi-layer stack (<NUM>). On the other hand, if the intermediate film (<NUM>) is made of an EVA resin, this aspect increases the handleability and anti-scattering ability of the multi-layer stack (<NUM>).

In a method for manufacturing a multi-layer stack (<NUM>) according to a ninth aspect, which may be implemented in conjunction with the eighth aspect, the intermediate film (<NUM>) includes the PVB resin, and the intermediate film (<NUM>) is dried to a moisture content of <NUM>% by weight or less before the glass panel unit (<NUM>) and the transparent plate (<NUM>) are assembled together.

This aspect allows the glass panel unit (<NUM>) and the transparent plate (<NUM>) to be bonded together via the intermediate film (<NUM>) just by heating, thus reducing the chances of causing deformation and other inconveniences to the spacers (<NUM>) of the glass panel unit (<NUM>). In addition, this aspect also reduces the chances of the intermediate film (<NUM>) losing its transparency or producing air bubbles therein.

In a method for manufacturing a multi-layer stack (<NUM>) according to a tenth aspect, which may be implemented in conjunction with any one of the first to ninth aspects, the transparent plate (<NUM>) includes a first transparent plate (<NUM>) and a second transparent plate (<NUM>). The intermediate film (<NUM>) includes a first intermediate film (<NUM>) and a second intermediate film (<NUM>). The method includes assembling an outer surface (<NUM>) of the first glass panel (<NUM>) of the glass panel unit (<NUM>) and the first transparent plate (<NUM>) via the first intermediate film (<NUM>). In addition, the method also includes assembling an outer surface (<NUM>) of the second glass panel (<NUM>) and the second transparent plate (<NUM>) via the second intermediate film (<NUM>).

This aspect provides a multi-layer stack (<NUM>) with particularly excellent mechanical strength and thermal insulation properties.

In a method for manufacturing a multi-layer stack (<NUM>) according to an eleventh aspect, which may be implemented in conjunction with the tenth aspect, the first intermediate film (<NUM>) and the second intermediate film (<NUM>) are made of mutually different materials.

This aspect makes it easier to improve the performance of the multi-layer stack (<NUM>) while facilitating the manufacture process of the multi-layer stack (<NUM>) at the same time.

In a method for manufacturing a multi-layer stack (<NUM>) according to a twelfth aspect, which may be implemented in conjunction with the tenth or eleventh aspect, at least one of the first intermediate film (<NUM>) or the second intermediate film (<NUM>) is made of an EVA resin.

This aspect may improve the handleability and anti-scattering ability of the multi-layer stack (<NUM>).

In a method for manufacturing a multi-layer stack (<NUM>) according to a thirteenth aspect, which may be implemented in conjunction with any one of the tenth to twelfth aspects, at least one of the first transparent plate (<NUM>) or the second transparent plate (<NUM>) includes a glass pane.

This aspect may provide a multi-layer stack (<NUM>) with excellent mechanical strength and thermal insulation properties.

In a method for manufacturing a multi-layer stack (<NUM>) according to a fourteenth aspect, which may be implemented in conjunction with any one of the tenth to thirteenth aspects, at least one of the first transparent plate (<NUM>) or the second transparent plate (<NUM>) includes a polycarbonate plate.

Claim 1:
A method for manufacturing a multi-layer stack (<NUM>),
the multi-layer stack (<NUM>) including:
a glass panel unit (<NUM>);
an intermediate film (<NUM>); and
a transparent plate (<NUM>) attached via the intermediate film (<NUM>) to the glass panel unit (<NUM>),
the glass panel unit (<NUM>) including:
a first glass panel (<NUM>);
a second glass panel (<NUM>); and
an evacuated space (<NUM>) interposed between the first glass panel (<NUM>) and the second glass panel (<NUM>),
the method comprising:
locating, into a chamber (<NUM>), a multi-layer assembly (<NUM>) where the glass panel unit (<NUM>) is stacked over the transparent plate (<NUM>) with the intermediate film (<NUM>) interposed between the transparent plate (<NUM>) and the glass panel unit (<NUM>); then
evacuating the chamber (<NUM>); and then
making the multi-layer assembly (<NUM>) be sandwiched between and heated by a pair of heaters (<NUM>) of a heater device (<NUM>) installed inside the chamber (<NUM>) to assemble the glass panel unit (<NUM>) and the transparent plate (<NUM>) together via the intermediate film (<NUM>) inside the evacuated chamber (<NUM>).