Patent Description:
Document <CIT> relates to a vacuum glass including pillars having different arrangement distances to minimize stress applied to the vacuum glass, and a method of manufacturing the same. Patent Literature <NUM> discloses a multi-pane glazing. The multi-pane glazing disclosed in Patent Literature <NUM> includes, as illustrated in <FIG>, a first panel <NUM> including a first glass plate <NUM>, a second panel <NUM> including a second glass plate <NUM> and arrange to face the first panel <NUM>, and a seal <NUM> hermetically bonding the first panel <NUM> and the second panel <NUM> together. The multi-pane glazing further includes multiple pillars (spacers) <NUM> arranged in an internal space <NUM>, which forms a reduced-pressure space when hermetically enclosed by the first panel <NUM>, the second panel <NUM>, and the seal <NUM>, so as to be in contact with the first panel <NUM> and the second panel <NUM>.

When exposed to the atmospheric pressure, the first panel <NUM> and the second panel <NUM> attempt to flex themselves toward each other (i.e., in a direction in which these panels come closer to each other). Meanwhile, the spacers <NUM> are into contact with, and support, both of the first panel <NUM> and the second panel <NUM> that are going to flex themselves, thus maintaining the internal space <NUM>.

When an impact force acts on a plate surface (a plate surface of the first glass plate <NUM>) of the multi-pane glazing of Patent Literature <NUM>, the first panel <NUM> attempts to flex toward the second panel <NUM> according to the impact force acting thereon. In this context, if the impact force acts on the first panel <NUM> from a falling steel ball <NUM> at a position where one of the pillars <NUM> is arranged, as shown in <FIG>, the first panel <NUM> is less likely to be flexed. The first panel <NUM> is thus less likely to make contact with the second panel <NUM>, which can reduce the probability that the first panel <NUM> or the second panel <NUM> be damaged due to the contact of the first panel <NUM> against the second panel <NUM>.

However, if the impact force acts on the first panel <NUM> at an intermediate position between pillars <NUM>, as shown in <FIG>, the first panel <NUM> tends to flex toward the second panel <NUM> to make contact with the second panel <NUM>, leading to the damage of the first panel <NUM> or the second panel <NUM> caused by the contact between the first panel <NUM> and the second panel <NUM>.

It is therefore an object of the present invention to provide a glass panel unit and a glass window, which has a reduced probability of the first panel and the second panel making contact with each other even when an impact force acts thereon, and a method for manufacturing the glass panel unit.

First to third embodiments each generally relate to glass panel units (the third embodiment further relates to a glass window), and more particularly relate to a glass panel unit including a first panel, a second panel, a seal hermetically bonding the first panel and the second panel, and a pillar arranged in an internal space hermetically enclosed by the first panel, the second panel and the seal so as to be in contact with the first panel and the second panel.

<FIG> and <FIG> illustrate a glass panel unit (a completed product of a glass panel unit) <NUM> according to the first embodiment. The glass panel unit <NUM> of the first embodiment is implemented as a vacuum insulating glass panel unit. The vacuum insulating glass panel unit is a type of multi-pane glazing including at least one pair of glass panels, and includes a vacuum space between the pair of glass panels.

The glass panel unit <NUM> of the first embodiment includes a first panel <NUM>, a second panel <NUM>, a seal <NUM>, a vacuum space <NUM>, a gas adsorbent <NUM>, multiple pillars <NUM>, and an occluding member <NUM>.

The glass panel unit (completed product) <NUM> is obtained by subjecting a temporary assembly <NUM> shown in <FIG> and <FIG> to a predetermined process.

The temporary assembly <NUM> includes the first panel <NUM>, the second panel <NUM>, a frame <NUM>, an internal space <NUM>, a partition <NUM>, a gas passage <NUM>, an outlet <NUM>, the gas adsorbent <NUM>, and the multiple pillars <NUM> made of resin.

The first panel <NUM> includes a first glass plate <NUM> determining a plan shape of the first panel <NUM>, and a coating <NUM>.

The first glass plate <NUM> is a rectangular flat plate and includes a first face (lower face in <FIG>) and a second face (upper face in <FIG>), which are parallel to each other, on both sides in a direction of a thickness t1 (see <FIG>) thereof. Each of the first face and the second face of the first glass plate <NUM> is a flat face. Examples of material of the first glass plate <NUM> may include soda lime glass, high strain point glass, chemically strengthened glass, non-alkaline glass, quartz glass, neoceram, and physically strengthened glass.

The coating <NUM> is formed on the first face of the first glass plate <NUM>. The coating <NUM> is an infrared reflective film. Note that, the coating <NUM> is not limited to such an infrared reflective film but may be a film with desired physical properties. Alternatively, the first panel <NUM> may include the first glass plate <NUM> alone. In short, the first panel <NUM> includes at least the first glass plate <NUM>.

The second panel <NUM> includes a second glass plate <NUM> determining a plan shape of the second panel <NUM>. The second glass plate <NUM> is a rectangular flat plate and includes a first face (upper face in <FIG>) and a second face (lower face in <FIG>), which are parallel to each other, on both sides in a direction of a thickness t2 (see <FIG>) thereof. Each of the first face and the second face of the second glass plate <NUM> is a flat face.

The second glass plate <NUM> has the same plan shape and plan size as the first glass plate <NUM> (in other words, the second panel <NUM> has the same plan shape as the first panel <NUM>). Further, the second glass plate <NUM> has the thickness t2, which is a thickness t same as the thickness t1 of the first glass plate <NUM>, for example (i.e., t=t1=t2). Examples of material of the second glass plate <NUM> may include soda lime glass, high strain point glass, chemically strengthened glass, non-alkaline glass, quartz glass, neoceram, and physically strengthened glass.

The second panel <NUM> includes the second glass plate <NUM> alone. In other words, the second glass plate <NUM> forms the second panel <NUM> by itself. Alternatively, the second panel <NUM> may further include a coating provided at either or both faces thereof. The coating may be a film with desired physical properties such as an infrared reflective film. In this case, the second panel <NUM> includes the second glass plate <NUM> and the coating. In short, the second panel <NUM> includes at least the second glass plate <NUM>.

The second panel <NUM> is placed to face the first panel <NUM>. In more detail, the first panel <NUM> and the second panel <NUM> are arranged so that the first face of the first glass plate <NUM> and the first face of the second glass plate <NUM> face and parallel to each other.

The frame <NUM> is placed between the first panel <NUM> and the second panel <NUM> to hermetically bond the first panel <NUM> and the second panel <NUM> together. Thereby, the internal space <NUM> enclosed by the frame <NUM>, the first panel <NUM>, and the second panel <NUM> is formed.

The frame <NUM> is formed of thermal adhesive (first thermal adhesive with a first softening point). Examples of the first thermal adhesive may include glass frit. Examples of the glass frit may include low-melting-point glass frit. Examples of the low-melting-point glass frit may include bismuth-based glass frit, lead-based glass frit, and vanadium-based glass frit.

The frame <NUM> has a rectangular frame shape. The frame <NUM> has the same plan shape as each of the first glass plate <NUM> and the second glass plate <NUM>, but the frame <NUM> has a smaller plan size than each of the first glass plate <NUM> and the second glass plate <NUM>. The frame <NUM> is formed to extend along an outer periphery of an upper face of the second panel <NUM> (the first face of the second glass plate31). In other words, the frame <NUM> is formed to surrounds an almost entire region on the upper face of the second panel <NUM>.

The first panel <NUM> and the second panel <NUM> are hermetically bonded with the frame <NUM> by once melting the first thermal adhesive of the frame <NUM> at a predetermined temperature (first melting temperature) Tm1 (see <FIG>) equal to or higher than the first softening point.

The partition <NUM> is placed inside the internal space <NUM>. The partition <NUM> divides the internal space <NUM> into a first space <NUM> and a second space <NUM>. The first space <NUM> is a space to be hermetically enclosed to form a vacuum space <NUM> while the glass panel unit <NUM> is produced, namely is a hermetically enclosed space. The second space <NUM> is a space communicated with the outlet <NUM>, namely is an evacuation space. The partition <NUM> is formed between a first end (right end in <FIG>) and a center of the second panel <NUM> in a lengthwise direction (left/right direction in <FIG>) of the second panel <NUM> so that the first space <NUM> is larger than the second space <NUM>.

The partition <NUM> is formed of thermal adhesive (second thermal adhesive with a second softening point). Examples of the second thermal adhesive may include glass frit. Examples of the glass frit may include low-melting-point glass frit. Examples of the low-melting-point glass frit may include bismuth-based glass frit, lead-based glass frit, and vanadium-based glass frit. The second thermal adhesive may be same as the first thermal adhesive, and the second softening point may be equal to the first softening point.

The outlet <NUM> is a hole interconnecting the second space <NUM> and an outside. The outlet <NUM> is used for evacuating the first space <NUM> by way of the second space <NUM> and the gas passage <NUM>. The outlet <NUM> is formed in the second panel <NUM> to interconnect the second space <NUM> and the outside. In more detail, the outlet <NUM> is positioned in a corner of the second panel <NUM>. The outlet <NUM> is formed in the second panel <NUM> in the first embodiment, but is not limited thereto. Alternatively, an outlet <NUM> may be formed in the first panel <NUM>, or in each of the first panel <NUM> and the second panel <NUM>.

The gas adsorbent <NUM> is placed inside the first space <NUM>. In more detail, the gas adsorbent <NUM> has an elongated shape, and is formed on a second end (left end in <FIG>) in the lengthwise direction of the second panel <NUM> to extend along the width direction of the second panel <NUM>. In summary, the gas adsorbent <NUM> is placed on one end of the first space <NUM> (the vacuum space <NUM>). According to this arrangement, the gas adsorbent <NUM> can be unlikely to be perceived. Further, the gas adsorbent <NUM> is positioned away from the partition <NUM> and the gas passage <NUM>. Hence, it is possible to lower a probability that the gas adsorbent <NUM> prevents evacuation of the first space <NUM>.

The gas adsorbent <NUM> is used to adsorb unnecessary gas (for example, residual gas). The unnecessary gas may include gas emitted from the frame <NUM> and the partition <NUM> when heated.

The gas adsorbent <NUM> includes a getter. The getter is a substance having properties of adsorbing molecules smaller than a predetermined size. The getter may be an evaporative getter. The evaporative getter has properties of desorbing adsorbed molecules when having a temperature equal to or higher than a predetermined temperature (activation temperature). Therefore, even if the adsorbability of the evaporative getter has been decreased, the adsorbability of the evaporative getter can be recovered by heating the evaporative getter to a temperature equal to or higher than the activation temperature. Examples of the evaporative getter may include zeolite and ion-exchanged zeolite (for example, copper ion-exchanged zeolite).

The gas adsorbent <NUM> includes a powder of this getter. In more detail, the gas adsorbent <NUM> may be formed by applying a liquid containing a dispersed powder of the getter. In this case, the gas adsorbent <NUM> can be downsized. Therefore, the gas adsorbent <NUM> can be placed even if the vacuum space <NUM> is small.

The multiple pillars <NUM> are used to keep an interval between the first panel <NUM> and the second panel <NUM> at a predetermined interval h (see <FIG>). In other words, the multiple pillars <NUM> serve as spacers to keep a distance between the first panel <NUM> and the second panel <NUM> to a desired value.

The multiple pillars <NUM> are arranged inside the first space <NUM>. In more detail, the multiple pillars <NUM> are arranged at individual intersections of a square or rectangular lattice of constant lattice intervals including a pitch p (see <FIG>). In the first embodiment, the multiple pillars <NUM> are arranged at individual intersections of a square lattice having longitudinal intervals and lateral intervals equal to the pitch p. Alternatively, the lateral intervals of the lattice may be longer than or shorter than the pitch p while the longitudinal intervals be equal to the pitch p. Further alternatively, the longitudinal intervals may be longer than or shorter than the pitch p while the lateral intervals be equal to the pitch p.

Each pillar <NUM> is made of light-transmissive material. Note that, each pillar <NUM> may be made of opaque material, providing that it is sufficiently small. Material of the pillars <NUM> is selected so that deformation of the pillars <NUM> does not occur during a first melting step, an evacuating step, and a second melting step which are described later. For example, the material of the pillars <NUM> is selected to have a softening point (softening temperature) higher than the first softening point of the first thermal adhesive and the second softening point of the second thermal adhesive.

The first embodiment is characterized in the intervals of the pillars <NUM>, which is described hereinafter.

As shown in <FIG>, the pillars <NUM> are placed at individual intersections of a square or rectangular lattice having a pitch p (m). Let consider a case where four pillars <NUM>, which are respectively placed at four vertexes of a center square whose length of each side equals to the pitch p, are to be broken. In this case, further providing that four sides of a square <NUM> (length of each side a=<NUM>·p) defined by twelve pillars <NUM> surrounding the above four pillars <NUM> are fixed, either the first panel <NUM> or the second panel <NUM> has a distortion δ (m) at its center (a position where the symbol "×" is drawn in the figure), which is expressed by a (formula <NUM>) below.

Where P (N) denotes a load, D (N·m) denotes flexural rigidity of each of the first panel <NUM> and the second panel <NUM>, and α is a coefficient depending on a condition of the load.

The flexural rigidity D is expressed by a (formula <NUM>) below.

Where Eg (Pa) denotes Young's modulus of each of the first panel <NUM> and the second panel <NUM>, t (m) denotes the thickness of each of the first panel <NUM> and the second panel <NUM> described above, v denotes Poisson's ratio of each of the first panel <NUM> and the second panel <NUM>.

In a case where the load is a concentric load, α=α<NUM>(=<NUM>), and the distortion δ<NUM> is expressed by a (formula <NUM>) below.

In a case where the load is an uniformly distributed load, α=α<NUM>(=<NUM>), and the load P is expressed by a (formula <NUM>) below.

Where w (Pa) denotes the pressure (atmospheric pressure). The distortion δ<NUM> caused by the uniformly distributed load is expressed by a (formula <NUM>) below.

In this context, a total distortion δ (m), which is a sum of the distortion of the first panel <NUM> and the distortion of the second panel <NUM>, is expressed by a (formula <NUM>) below.

Because the concentric load acts on the first panel <NUM> only, and the uniformly distributed load from the atmospheric pressure acts on both of the first panel <NUM> and the second panel <NUM>, solely the distortion δ<NUM> is multiplied by "<NUM>" in the (formula <NUM>).

Substitute the (formula <NUM>) and the (formula <NUM>) in the (formula <NUM>) to obtain a (formula <NUM>).

Let denote P<NUM> (N) as a real load loading compression fracture, which is defined as a margin per one pillar <NUM> until the load acting on the pillar <NUM> reaches a load loading compression fracture, P<NUM> can be expressed by a (formula <NUM>) below, where P<NUM> (N) denotes a load loading compression fracture per one pillar <NUM>, and w·p<NUM> expresses the atmospheric pressure acting on one pillar <NUM>.

Substitute the above mentioned formula a=<NUM>·p in the (formula <NUM>) and assume that the concentric load P acting the first panel <NUM> alone equals to the real load loading compression fracture P<NUM> acting on the four pillars <NUM> to obtain an (formula <NUM>), which expresses the distortion δ of the glass panel unit when the glass panel unit receives a theoretical minimum concentric load causing the breakage of the four pillars <NUM>, which is theoretically determined minimum concentric load that can cause the breakage of the four pillars <NUM>.

Rearrange the (formula <NUM>) to obtain a (formula <NUM>) below.

Substitute the equations α<NUM>=<NUM> and α<NUM>=<NUM> in the (formula <NUM>) to obtain a (formula <NUM>) below.

In case a relation <NUM>·P<NUM>>><NUM>·w·p<NUM> is satisfied and thus the term <NUM>·w· p<NUM> can be substantially ignored, the (formula <NUM>) can be approximated to a (formula <NUM>) below.

The (formula <NUM>) is a model formula of an ideal case where each length of four sides of the rectangle are fixed to a (m), but in an actual glass panel unit the pillars <NUM> are disposed discretely. Thus the (formula <NUM>) is corrected by a correction coefficient K to obtain a (formula <NUM>) below.

The correction coefficient K satisfies the relation <NUM>≤K≤<NUM>, which is determined according to some experiments. Substitute the equation K=<NUM> in this formula to obtain a (formula <NUM>) below.

Providing that the total distortion δ, obtained by adding the distortion of the first panel <NUM> and the distortion of the second panel <NUM>, is smaller than an interval h between the first panel <NUM> and the second panel <NUM>, then the first panel <NUM> does not make contact with the second panel <NUM>. Therefore, providing that the glass panel unit satisfies a (formula <NUM>) below, the first panel <NUM> and the second panel <NUM> do not make contact with each other even when the glass panel unit receives the theoretical minimum concentric load causing the breakage of the four pillars <NUM>.

That is, the glass panel unit satisfying the (formula <NUM>) can reduce the probability of damaging the first panel <NUM> or the second panel <NUM>, because the first panel <NUM> and the second panel <NUM> are less likely to make contact with each other even when the glass panel unit receives the theoretical minimum concentric load causing the breakage of the four pillars <NUM>.

Experiments <NUM> to <NUM> were performed in order to confirm the validity of the (formula <NUM>).

In the experiments <NUM> to <NUM>, a steel ball <NUM> having a weight of <NUM> (g) was fallen on the first panel <NUM> at an intermediate positon between two pillars <NUM>, and it was measured a minimum height (hereinafter, referred to as a "breaking ball height") of the steel ball <NUM> at which at least one of the first panel <NUM> and the second panel <NUM> was broken. An average value of the breaking ball height was used for evaluation. It can be understood that a higher breaking ball height indicates a better resistance to the impact.

Table <NUM> shows experimental conditions, a breaking ball height, and a value obtained by a discriminating expression, according to each of the experiment <NUM> and comparative experiments <NUM> to <NUM>.

Note that the discriminating expression is expressed by the left member of the (formula <NUM>).

Further, the height of the pillar <NUM> equals to the interval h between the first panel <NUM> and the second panel <NUM>.

The first panel <NUM> and the second panel <NUM> are assumed to have same physical quantities, and the "Glass Panel" in the table indicates each of the first panel <NUM> and the second panel <NUM>.

According to the glass panel unit for the experiment <NUM>, the value obtained by the discriminating expression was <NUM> which was significantly beyond <NUM>, and the breaking ball height was <NUM> (cm), concluded to be excellent.

The value obtained by the discriminating expression according to the glass panel unit for each of the comparative experiment <NUM>, the comparative experiment <NUM> and the comparative experiment <NUM> was negative and thus these glass panel units did not satisfy the (formula <NUM>). Furthermore, the breaking ball heights of them were far inferior to that (<NUM> (cm)) of the experiment <NUM>. According to the glass panel unit for the comparative experiment <NUM>, the value obtained by the discriminating expression was <NUM>, which was slightly larger than <NUM>, but the breaking ball height thereof was <NUM> (cm), which was far inferior to that of the experiment <NUM>. According to the glass panel unit for the comparative experiment <NUM>, the value obtained by the discriminating expression was <NUM>, which was significantly beyond <NUM>, but the breaking ball height thereof was <NUM> (cm), which was far inferior to that of the experiment <NUM>.

The glass panel units for the comparative experiments <NUM> to <NUM> include pillars <NUM> made of SUS304. According to the comparative experiments <NUM> to <NUM>, it was found that the first panel <NUM> and/or the second panel <NUM> was broken at a position where the pillar <NUM> is provided. This can be considered that the glass panel unit according to these comparative experiments was broken due to a mechanism different from the contact between the first panel <NUM> and the second panel <NUM>. According to these results, it can be concluded that the (formula <NUM>) may be valid for the glass panel including the pillars <NUM> made of resin, rather than the glass panel including the pillars <NUM> made of SUS304.

Table <NUM> shows experimental conditions, a breaking ball height, and a value obtained by the discriminating expression, according to each of the experiment <NUM> and comparative experiments <NUM> to <NUM>.

The value obtained by the discriminating expression according to the glass panel unit for each of the comparative experiment <NUM> and the comparative experiment <NUM> was negative and thus these glass panel units did not satisfy the (formula <NUM>). Furthermore, the breaking ball heights of them were far inferior to that (<NUM> (cm)) of the experiment <NUM>. According to the glass panel unit for the comparative experiment <NUM>, the value obtained by the discriminating expression was <NUM>, which was slightly larger than <NUM>, but the breaking ball height thereof was far inferior to that (<NUM> (cm)) of the experiment <NUM>.

The aforementioned temporary assembly <NUM> is subjected to the above predetermined process to obtain the completed assembly <NUM>.

The above predetermined process includes converting the first space <NUM> into the vacuum space <NUM> by evacuating the first space <NUM> by way of an evacuation passage capable of evacuating gas to an outside at a predetermined temperature (an evacuation temperature) Te. The evacuation passage includes the gas passage <NUM>, the second space <NUM>, and the outlet <NUM>. The evacuation temperature Te is higher than the activation temperature of the getter of the gas adsorbent <NUM>. Consequently, evacuation of the first space <NUM> and recovery of the adsorbability of the getter can be performed simultaneously.

The above predetermined process further includes forming the seal <NUM> enclosing the vacuum space <NUM> by forming a separator <NUM> for closing the gas passage <NUM> by changing a shape of the partition <NUM>, as shown in <FIG>. The partition <NUM> includes the second thermal adhesive. Therefore, the separator <NUM> can be formed by changing the shape of the partition <NUM> by once melting the second thermal adhesive at a predetermined temperature (a second melting temperature) Tm2 (see <FIG>) equal to or higher than the second softening point. Note that, the first melting temperature Tm1 is lower than the second melting temperature Tm2. Consequently, it is possible to prevent the gas passage <NUM> from being closed due to deformation of the partition <NUM> in bonding the first panel <NUM> and the second panel <NUM> with the frame <NUM>.

The partition <NUM> is changed in shape so that the second gas passage <NUM> is closed as shown in <FIG>. The separator <NUM>, which is obtained by changing the shape of the partition <NUM>, separates (spatially) the vacuum space <NUM> from the second space <NUM>. The separator (second part) <NUM> and part (first part) <NUM> of the frame <NUM> corresponding to the vacuum space <NUM> constitute the seal <NUM> enclosing the vacuum space <NUM>.

The glass panel unit (completed product) <NUM> obtained in the aforementioned manner includes, as shown in <FIG>, the first panel <NUM>, the second panel <NUM>, the seal <NUM>, the vacuum space <NUM>, the second space <NUM>, the gas adsorbent <NUM>, the multiple pillars <NUM>, and the occluding member <NUM>.

The vacuum space <NUM> is obtained by evacuating the first space <NUM> by way of the second space <NUM> and the outlet <NUM> as described above. In other words, the vacuum space <NUM> is defined as the first space <NUM> with a degree of vacuum equal to or lower than a predetermined value. The predetermined value may be <NUM> Pa, for example. The vacuum space <NUM> is hermetically enclosed by the first panel <NUM>, the second panel <NUM>, and the seal <NUM> completely and thus is separated from the second space <NUM> and the outlet <NUM>.

The seal <NUM> encloses the vacuum space <NUM> completely and bonds the first panel <NUM> and the second panel <NUM> to each other hermetically. The seal <NUM> has a frame shape, and includes the first part <NUM> and the second part <NUM>. The first part <NUM> is part of the frame <NUM> corresponding to the vacuum space <NUM>. In other words, the first part <NUM> is part of the frame <NUM> facing the vacuum space <NUM>. The second part <NUM> is a separator formed by changing the shape of the partition <NUM>.

The occluding member <NUM> lowers the probability of foreign objects such as dusts entering the second space <NUM> through the outlet <NUM>. In the first embodiment, the occluding member <NUM> includes a cover <NUM> provided on a front side of the outlet <NUM> formed in the first panel <NUM> or the second panel <NUM>.

Such an occluding member <NUM> provided to the outlet <NUM> can prevent the foreign objects such as the dust from entering the second space <NUM> through the outlet <NUM>. This can prevent the visual quality of the glass panel unit <NUM> from being deteriorated due to the foreign object entering the second space <NUM> through the outlet <NUM>. Note that the occluding member <NUM> may be an optional element and may be omitted.

Hereinafter, a method for manufacturing the glass panel unit <NUM> of the first embodiment is described with reference to <FIG>.

The method for manufacturing the glass panel unit <NUM> of the first embodiment includes a preparation step, an assembling step, a hermetically enclosing step, and a removing step. Note that, the preparation step can be omitted.

The preparation step is a step of forming the first panel <NUM>, the second panel <NUM>, the frame <NUM>, the partition <NUM>, the internal space <NUM>, the gas passage <NUM>, the outlet <NUM>, and the gas adsorbent <NUM>, for the purpose of producing the temporary assembly <NUM>. The preparation step includes first to sixth steps. Note that, the order of the second to sixth steps may be modified.

The first step is a step (substrate formation step) of forming the first panel <NUM> and the second panel <NUM>. For example, in the first step, the first panel <NUM> and the second panel <NUM> are produced. The first step may include cleaning the first panel <NUM> and the second panel <NUM> if necessary.

The second step is a step of forming the outlet <NUM>. In the second step, the outlet <NUM> is formed in the second panel <NUM>. Further, in the second step, the second panel <NUM> is cleaned if necessary.

The third step is a step (sealing material formation step) of forming the frame <NUM> and the partition <NUM>. In the third step, the material (the first thermal adhesive) of the frame <NUM> and the material (the second thermal adhesive) of the partition <NUM> are applied on to the second panel <NUM> (the first face of the second glass plate <NUM>) with a dispenser or the like.

The material of the frame <NUM> and the material of the partition <NUM> are dried and calcined. For example, the second panel <NUM> where the material of the frame <NUM> and the material of the partition <NUM> are applied is heated. Note that, the first panel <NUM> may be heated together with the second panel <NUM>. In other words, the first panel <NUM> may be heated under the same condition as the second panel <NUM>. By doing so, it is possible to reduce a difference in degree of warp between the first panel <NUM> and the second panel <NUM>.

The fourth step is a step (pillar formation step) of forming the pillars <NUM>. The fourth step may include placing the multiple pillars <NUM> in individual predetermined locations on the second panel <NUM> with a chip mounter. Note that, the multiple pillars <NUM> are formed in advance. Alternatively, the multiple pillars <NUM> may be formed by use of photolithography techniques and etching techniques. In this case, the multiple pillars <NUM> may be made of photocurable material or the like. Alternatively, the multiple pillars <NUM> may be formed by use of known thin film formation techniques.

In the pillar formation step, the multiple pillars <NUM> are arranged to satisfy the above (formula <NUM>). As mentioned above, the (formula <NUM>) is obtained without consideration with the elastic deformation of the pillars <NUM>.

The fifth step is a step (gas adsorbent formation step) of forming the gas adsorbent <NUM>. In the fifth step, a solution where a power of the getter is dispersed is applied to a predetermined location on the second panel <NUM> and then dried to thereby form the gas adsorbent <NUM>.

When a process from the first step to the fifth step is completed, the second panel <NUM> is obtained, on which the frame <NUM>, the partition <NUM>, the gas passage <NUM>, the outlet <NUM>, the gas adsorbent <NUM>, and the multiple pillars <NUM> are formed as shown in <FIG>.

The sixth step is a step (placing step) of placing the first panel <NUM> and the second panel <NUM>. In the sixth step, the first panel <NUM> and the second panel <NUM> are placed so that the first face of the first glass plate <NUM> and the first face of the second glass plate <NUM> face and are parallel to each other.

The assembling step is a step of preparing the temporary assembly <NUM>. In more detail, in the assembling step, the temporary assembly <NUM> is prepared by bonding the first panel <NUM> and the second panel <NUM> together. In other words, the assembling step may be referred to as a step (first melting step) of hermetically bonding the first panel <NUM> and the second panel <NUM> together with the frame <NUM>.

In the first melting step, the first thermal adhesive is melted once at the predetermined temperature (the first melting temperature) Tm1 equal to or higher than the first softening point and thereby the first panel <NUM> and the second panel <NUM> are hermetically bonded together. In more detail, the first panel <NUM> and the second panel <NUM> are placed in a furnace and heated at the first melting temperature Tm1 for a predetermined time (the first melting time) tm1, as shown in <FIG>.

The first melting temperature Tm1 and the first melting time tm1 are selected so that the first panel <NUM> and the second panel <NUM> are hermetically bonded together with the thermal adhesive of the frame <NUM> but the gas passage <NUM> is not closed by the partition <NUM>. In other words, a lower limit of the first melting temperature Tm1 is equal to the first softening point, and an upper limit of the first melting temperature Tm1 is however selected so as not to cause the partition <NUM> to close the gas passage <NUM>. For example, when the first softening point and the second softening point are <NUM>, the first melting temperature Tm1 is set to <NUM>. Further, the first melting time tm1 may be <NUM> minutes, for example. Note that, in the first melting step, the frame <NUM> may emit gas. However such gas can be adsorbed by the gas adsorbent <NUM>.

Through the aforementioned assembling step (the first melting step), the temporary assembly <NUM> shown in <FIG> can be produced.

The hermetically enclosing step is a step of subjecting the temporary assembly <NUM> to the above predetermined process to obtain the glass panel unit (completed product) <NUM>. The hermetically enclosing step includes the evacuating step and a melting step (the second melting step). In other words, the evacuating step and the second melting step constitute the above predetermined process.

The evacuating step is a step of converting the first space <NUM> into the vacuum space <NUM> by evacuating it by way of the gas passage <NUM>, the second space <NUM>, and the outlet <NUM> at the predetermined temperature (the evacuation temperature) Te.

Evacuation can be done by a vacuum pump, for example. As shown in <FIG>, the vacuum pump is connected to the temporary assembly <NUM> with the evacuation pipe <NUM> and a sealing head <NUM>. The evacuation pipe <NUM> is bonded to the second panel <NUM> so that an inside of the evacuation pipe <NUM> is connected to the outlet <NUM>, for example. The sealing head <NUM> is attached to the evacuation pipe <NUM>, and thereby an inlet of the vacuum pump is connected to the outlet <NUM>.

The first melting step, the evacuating step, and the second melting step are performed with the first panel <NUM> and the second panel <NUM> (the second panel <NUM> where the frame <NUM>, the partition <NUM>, the gas passage <NUM>, the outlet <NUM>, the gas adsorbent <NUM>, and the multiple pillars <NUM> are formed) being left in the furnace. Therefore, the evacuation pipe <NUM> is bonded to the second panel <NUM> before the first melting step at the latest.

In the evacuating step, the first space <NUM> is evacuated by way of the gas passage <NUM>, the second space <NUM>, and the outlet <NUM> at the evacuation temperature Te for a predetermined time (evacuation time) te (see <FIG>).

The evacuation temperature Te is set to be higher than the activation temperature (for example, <NUM>) of the getter of the gas adsorbent <NUM>, and also is set to be lower than the first softening point and the second softening point (for example, <NUM>). For example, the evacuation temperature Te is <NUM>.

According to the above settings, deformation of the frame <NUM> and the partition <NUM> is unlikely to occur. Further, the getter of the gas adsorbent <NUM> is activated, and thus molecules (gas) adsorbed on the getter are desorbed from the getter. Such molecules (that is, gas) desorbed from the getter are discarded through the first space <NUM>, the gas passage <NUM>, the second space <NUM>, and the outlet <NUM>. Therefore, in the evacuating step, the adsorbability of the gas adsorbent <NUM> is recovered.

The evacuation time te is set to obtain the vacuum space <NUM> having a desired degree of vacuum (for example, a degree of vacuum equal to or lower than <NUM> Pa). For example, the evacuation time te is set to <NUM> minutes.

Note that the degree of vacuum of the vacuum space <NUM> is not limited particularly. It may be possible that the glass panel unit includes a reduced-pressure space with a pressure smaller than <NUM> atm, such as <NUM> atm or the like, in place of the vacuum space <NUM>.

The second melting step is a step of forming the seal <NUM> enclosing the vacuum space <NUM> by changing the shape of the partition <NUM> to form the separator <NUM> closing the gas passage <NUM>. In the second melting step, the second thermal adhesive is melted once at the predetermined temperature (the second melting temperature) Tm2 equal to or higher than the second softening point, and thereby the partition <NUM> is changed in shape to form the separator <NUM>. In more detail, the first panel <NUM> and the second panel <NUM> are heated at the second melting temperature Tm2 for the predetermined time (the second melting time) tm2 in the furnace (see <FIG>).

The second melting temperature Tm2 and the second melting time tm2 are set to allow the second thermal adhesive to soften to form the separator <NUM> closing the gas passage <NUM>. A lower limit of the second melting temperature Tm2 is equal to the second softening point (<NUM>). Note that, differently from the first melting step, the purpose of the second melting step is to change the shape of the partition <NUM>, and consequently the second melting temperature Tm2 is set to be higher than the first melting temperature (<NUM>) Tm1. For example, the second melting temperature Tm2 is set to <NUM>. Additionally, the second melting time tm2 is <NUM> minutes, for example.

In the first embodiment, evacuation may be performed during the evacuating step only, before the second melting step. Alternatively, the evacuation may be performed during the second melting step.

Additionally, in the second melting step, evacuation of the first space <NUM> through the gas passage <NUM>, the second space <NUM>, and the outlet <NUM> is continued from the evacuating step. In other words, in the second melting step, the separator <NUM> closing the gas passage <NUM> is formed by changing the shape of the partition <NUM> at the second melting temperature Tm2 while the first space <NUM> is evacuated through the gas passage <NUM>, the second space <NUM>, and the outlet <NUM>. By doing so, it is possible to more lower a probability that the degree of vacuum of the vacuum space <NUM> decreases during the second melting step. Note that, the second melting step does not necessarily include evacuating the first space <NUM> through the gas passage <NUM>, the second space <NUM>, and the outlet <NUM>.

Through the aforementioned preparation step, assembling step, hermetically enclosing step, and removing step, the glass panel unit <NUM> is produced.

According to the glass panel unit <NUM> of the first embodiment, the pillars <NUM> are arranged so as to satisfy a discriminant of the above (formula <NUM>). As mentioned above, the (formula <NUM>) is a discriminant obtained without consideration with the elastic deformation of the pillars <NUM>.

Since components of the glass panel unit <NUM> satisfy the discriminant, the first panel <NUM> and the second panel <NUM> are less likely to be damaged, because the first panel <NUM> is less likely to collide against the second panel <NUM> even when the glass panel unit <NUM> receives the theoretical minimum concentric load causing the breakage of the four pillars <NUM>.

A glass panel unit <NUM> of a second embodiment is described with reference to <FIG> and <FIG>. The glass panel unit <NUM> according to the second embodiment includes additional components, as well as components of the first embodiment.

The glass panel unit <NUM> of the second embodiment includes a third panel <NUM> arranged to face a second panel <NUM>. The third panel <NUM> faces the second panel <NUM> in the second embodiment, but alternatively, may face a first panel <NUM>.

The third panel <NUM> includes a third glass plate <NUM>. The third glass plate <NUM> of the third panel <NUM> has a flat surface and a predetermined thickness. In the second embodiment, the third panel <NUM> includes the third glass plate <NUM> alone.

Alternatively, the third panel <NUM> may further include a coating provided at either or both faces thereof. The coating may be a film with desired physical property such as an infrared reflective film. In this case, the third panel <NUM> includes the third glass plate <NUM> and the coating. In short, the third panel <NUM> includes at least the third glass plate <NUM>.

The glass panel unit <NUM> further includes a second seal <NUM>, which is placed between the second panel <NUM> and the third panel <NUM> to hermetically bond the second panel <NUM> and the third panel <NUM> together. In this case, a seal <NUM> may be a first seal. The second seal <NUM> is arranged in a ring between the respective peripheral portions of the second panel <NUM> and the third panel <NUM>. The second seal <NUM> may be made of material same as or different from that of the seal <NUM> without limitation.

The glass panel unit <NUM> includes a second internal space <NUM> which is hermetically enclosed by the second panel <NUM>, the third panel <NUM> and the second seal <NUM> and which contains a dry gas airtightly. Examples of the dry gas include a dry rare gas such as an argon gas and dry air, without limitation.

In addition, a hollow frame member <NUM> is arranged in a ring inside of the second seal <NUM> provided between the respective peripheral portions of the second panel <NUM> and the third panel <NUM>. A through hole <NUM> interconnecting an inside space of the frame member <NUM> and the second internal space <NUM> is cut in the frame member <NUM>. A desiccant <NUM> such as a silica gel is introduced in the inside space of the frame member <NUM>.

The second panel <NUM> and the third panel <NUM> may be bonded together in almost the same way as the first panel <NUM> and the second panel <NUM>. Hereinafter, an exemplary method thereof is described.

Firstly, prepared are a component which later constitutes the third panel <NUM>, and an assembly (the glass panel unit <NUM> of the first embodiment) including the first panel <NUM> and the second panel <NUM>.

Arranged is a second thermal adhesive, which later constitutes the second seal <NUM>, on the peripheral portion of the face of either the third panel <NUM> or the second panel <NUM> in a frame shape (second thermal adhesive arranging step). Material of the thermal adhesive may be same as or different from material of thermal adhesive (first thermal adhesive) which later constitutes a frame <NUM> without limitation. Further, a through hole interconnecting the second internal space <NUM> and an outside is formed in the thermal adhesive during this step to form a gas passage (second gas passage).

The third panel <NUM> and the second panel <NUM> are disposed to face each other (third panel opposite disposition step).

Thereafter, the thermal adhesive is melted once at temperature sufficient to melt the thermal adhesive constituting the second seal <NUM> and thereby the second panel <NUM> and the third panel <NUM> are hermitically bonded together with the second seal <NUM> (bonding step). Note that the melting is done so that the second gas passage is not completely closed during this step.

The dry gas is introduced into the second internal space <NUM> through the second gas passage (dry gas introducing step). According to this step, the second internal space <NUM> may be filled with the dry gas alone, or may further include residual air without limitation.

The second seal <NUM> is then heated to close the second gas passage, and thereby the second internal space <NUM> is airtightly closed (second space closing step).

The glass panel unit <NUM> is formed according the above mentioned method. The glass panel unit <NUM> of the second embodiment achieves an even higher degree of thermal insulation properties.

Hereinafter, a third embodiment is described with reference to <FIG>. Note that the third embodiment is directed to a glass window <NUM> including the glass panel unit <NUM> of the first embodiment or the second embodiment.

The glass window <NUM> of the third embodiment includes the glass panel unit <NUM> of any one the first embodiment and the second embodiment, and a window frame <NUM> with a U-cross section is fitted onto the outer peripheral portion of this glass panel unit <NUM>.

The glass window <NUM> of the third embodiment achieves an even higher degree of thermal insulation properties.

In the above embodiments (which means any of the first embodiment to the third embodiment, same meanings are applied to the following description), the glass panel unit <NUM> is rectangular, but the glass panel unit <NUM> may have a desired shape such as a circular shape and a polygonal shape. In other words, each of the first panel <NUM>, the second panel <NUM>, and the seal <NUM> may not be rectangular and may have a desired shape such as a circular shape and a polygonal shape. Note that, the shapes of the first panel <NUM>, the second panel <NUM>, the frame <NUM>, and the separator <NUM> may not be limited to the shapes described in the explanation of the above embodiments, and may have such shapes that the glass panel unit <NUM> can have a desired shape. Note that, the shape and size of the glass panel unit <NUM> may be determined in consideration of application of the glass panel unit <NUM>.

The first face and the second face, of the first glass plate <NUM> of the first panel <NUM> may not be limited to flat faces. Similarly, the first face and the second face, of the second glass plate <NUM> of the second panel <NUM> may not be limited to flat faces.

The first glass plate <NUM> of the first panel <NUM> and the second glass plate <NUM> of the second panel <NUM> may not have the same plan shape and plan size. Further, the first glass plate <NUM> and the second glass plate <NUM> may not have the same thickness. Furthermore, the first glass plate <NUM> and the second glass plate <NUM> may not be made of the same material. Similarly, the first glass plate <NUM> of the first panel <NUM> and the second glass plate <NUM> of the second panel <NUM> may not have the same plan shape and plan size. Further, the first glass plate <NUM> and the second glass plate <NUM> may not have the same thickness. Furthermore, the first glass plate <NUM> and the second glass plate <NUM> may not be made of the same material.

The seal <NUM> may not have the same plan shape with the first panel <NUM> and the second panel <NUM>. Similarly, the frame <NUM> may not have the same plan shape with the first panel <NUM> and the second panel <NUM>.

The first panel <NUM> may include a coating which has desired physical properties and is formed on the second face of the first glass plate <NUM>. The first panel <NUM> may not include the coating <NUM>. In other words, the first panel <NUM> may include the first glass plate <NUM> alone.

The second panel <NUM> may include a coating with desired physical properties. For example, the coating may include at least one of thin films formed on the first face and the second face of the second glass plate <NUM> respectively. Examples of the coating may include a film reflective for light with a specified wavelength, such as an infrared reflective film or an ultraviolet reflective film.

In the above embodiments, the frame <NUM> is made of the first thermal adhesive. However, the frame <NUM> may include other component such as a core, in addition to the first thermal adhesive. In other words, it is sufficient that the frame <NUM> includes the first thermal adhesive. In the above embodiment, the frame <NUM> is formed to surround an almost entire region on the second panel <NUM>. However, it is sufficient that the frame <NUM> is formed to surround a predetermined region on the second panel <NUM>. In other words, there is no need to form the frame <NUM> so as to surround an almost entire region on the second panel <NUM>.

In the above embodiments, the partition <NUM> is made of the second thermal adhesive. However, the partition <NUM> may include other component such as a core, in addition to the second thermal adhesive. In other words, it is sufficient that the partition <NUM> includes the second thermal adhesive.

In the above embodiments, the internal space <NUM> is divided into one first space <NUM> and one second space <NUM>. Note that, the internal space <NUM> may be divided into one or more first spaces <NUM> and one or more second spaces <NUM>.

In the above embodiments, the second thermal adhesive is identical to the first thermal adhesive, and the second softening point is equal to the first softening point. However, the second thermal adhesive may be different material from the first thermal adhesive. For example, the second thermal adhesive may have the second softening point different from the first softening point of the first thermal adhesive. In such a case, the second softening point may be preferably higher than the first softening point. In this case, the first melting temperature Tm1 can be set to be equal to or higher than the first softening point and lower than the second softening point. By doing so, it is possible to suppress undesired deformation of the partition <NUM> in the first melting step.

Additionally, each of the first thermal adhesive and the second thermal adhesive may not be limited to glass frit, but may be selected from low-melting-point metal, hot-melt adhesive, and the like, for example.

In the above embodiments, a furnace is used to heat the frame <NUM>, the gas adsorbent <NUM>, and the partition <NUM>. However, such heating can be done with appropriate heating means. Examples of the heating means may include a laser and a thermally conductive plate connected to a heat source.

In the above embodiment, the outlet <NUM> is formed in the second panel <NUM>. However, the outlet <NUM> may be formed in the first glass plate <NUM> of the first panel <NUM> or may be formed in the frame <NUM>.

As obviously derived from the aforementioned first to third embodiments and the like, a glass panel unit <NUM> of the first aspect according to the present disclosure includes a first panel <NUM> including at least a first glass plate <NUM>; and a second panel <NUM> including at least a second glass plate <NUM>. The second panel <NUM> is arranged to face the first panel <NUM> with a predetermined interval h left with respect to the first panel <NUM>.

The glass panel unit <NUM> includes: a seal <NUM> arranged between the first panel <NUM> and the second panel <NUM> to hermetically bond the first panel <NUM> and the second panel <NUM> together; and an internal space <NUM> configured to form a reduced-pressure space by being hermetically enclosed by the first panel <NUM>, the second panel <NUM>, and the seal <NUM>.

The glass panel unit <NUM> includes multiple pillars <NUM> made of resin. The multiple pillars <NUM> are arranged in the internal space <NUM> at individual intersections of a square or rectangular lattice of constant lattice intervals, including a predetermined pitch p, so as to be in contact with the first panel <NUM> and the second panel <NUM>.

The predetermined pitch p of the multiple pillars <NUM> is determined such that a distortion δ of the first panel <NUM> and second panel <NUM> is smaller than the predetermined interval h between the first panel <NUM> and the second panel <NUM>. The distortion δ is calculated based on the predetermined pitch p, load loading compression fracture P<NUM> per one pillar of the multiple pillars, Young's moduli Eg of the first panel <NUM> and the second panel <NUM>, thicknesses t of the first panel <NUM> and the second panel <NUM>, and Poisson's ratios v of the first panel <NUM> and the second panel <NUM>.

According to the glass panel unit <NUM> of the first aspect, the first panel <NUM> and the second panel <NUM> are less likely to be damaged because the first panel <NUM> and the second panel <NUM> are less likely to make contact with each other.

The glass panel unit <NUM> of the second aspect according to the present disclosure would be realized in combination with the first aspect. In the second aspect, the predetermined pitch p of the multiple pillars <NUM> is determined such that the distortion δ of the first panel <NUM> and second panel <NUM> is smaller than the predetermined interval h between the first panel <NUM> and the second panel <NUM>. The distortion δ is calculated further based on Young's modulus Esp of each pillar <NUM>, and a cross-section area S of each pillar <NUM>, in addition to the predetermined pitch p, the predetermined interval h between the first panel <NUM> and the second panel <NUM>, the load loading compression fracture P<NUM> per one pillar of the multiple pillars <NUM>, the Young's moduli Eg of the first panel <NUM> and the second panel <NUM>, the thicknesses t of the first panel <NUM> and the second panel <NUM>, and the Poisson's ratios v of the first panel <NUM> and the second panel <NUM>.

According to the glass panel unit <NUM> of the second aspect, the first panel <NUM> and the second panel <NUM> are further less likely to be damaged because the first panel <NUM> and the second panel <NUM> are further less likely to make contact with each other.

The glass panel unit <NUM> of the third aspect according to the present disclosure would be realized in combination with the first aspect. In the third aspect, the multiple pillars <NUM> are arranged so as to satisfy a formula below: <MAT> where p (m) denotes the predetermined pitch, h (m) denotes the predetermined interval between the first panel <NUM> and the second panel <NUM>, P<NUM> (N) denotes the load loading compression fracture per one pillar of the multiple pillars <NUM>, Eg (Pa) denotes the Young's modulus of each of the first panel <NUM> and the second panel <NUM>, t (m) denotes the thickness of each of the first panel <NUM> and the second panel <NUM>, and v denotes the Poisson's ratio of each of the first panel <NUM> and the second panel <NUM>.

According to the glass panel unit <NUM> of the third aspect, the first panel <NUM> and the second panel <NUM> are further less likely to be damaged because the first panel <NUM> and the second panel <NUM> are further less likely to make contact with each other.

The glass panel unit <NUM> of the fifth aspect according to the present disclosure would be realized in combination with any one of the first to fourth aspects. In the fifth aspect, the glass panel unit <NUM> includes a third panel <NUM> including at least a third glass plate <NUM> and arranged to face the second panel <NUM>.

The glass panel unit <NUM> further includes a second seal <NUM> arranged between the second panel <NUM> and the third panel <NUM> to hermetically bond the second panel <NUM> and the third panel <NUM> together.

The glass panel unit <NUM> further includes a second internal space <NUM> hermetically enclosed by the second panel <NUM>, the third panel <NUM>, and the second seal <NUM> and containing a dry gas airtightly.

The glass panel unit <NUM> of the fifth aspect can achieve an even higher degree of thermal insulation properties.

A glass window <NUM> of the sixth aspect according to the present disclosure includes the glass panel unit <NUM> of any one of the first to fifth aspects, and a window frame <NUM> fitted onto a peripheral portion of the glass panel unit <NUM>.

The glass window <NUM> of the fourth aspect can achieve an even higher degree of thermal insulation properties.

A method for manufacturing glass panel unit <NUM> of a seventh aspect according to the present disclosure includes an adhesive disposing step, a pillar arranging step, an opposite disposition step, an internal space forming step, a pressure reducing step, and a reduced-pressure space forming step.

The adhesive disposing step includes disposing a thermal adhesive in a frame on a first panel <NUM> including at least a first glass plate <NUM>.

The pillar arranging step includes disposing multiple pillars <NUM> made of resin on the first panel <NUM> so as to be arranged at individual intersections of a square or rectangular lattice of constant lattice intervals, including a predetermined pitch p.

The opposite disposition step includes disposing a second panel <NUM> including at least a second glass plate <NUM> to face the first panel <NUM>.

The internal space forming step includes heating a glass composite including the first panel <NUM>, the second panel <NUM>, and the thermal adhesive to melt the thermal adhesive to form an internal space <NUM> enclosed by the first panel <NUM>, the second panel <NUM> and a melted substance of the thermal adhesive with an evacuation passage left opened to an outside, the evacuation passage being capable of evacuating gas to the outside.

The pressure reducing step includes removing gas in the internal space <NUM> to reduce a pressure of the internal space <NUM>.

The reduced-pressure space forming step includes hermetically enclosing the internal space <NUM> while keeping the internal space <NUM> in a pressure-reduced state to form a reduced-pressure space enclosed hermetically.

The predetermined pitch p of the multiple pillars <NUM> are determined such that a distortion δ of the first panel <NUM> and second panel <NUM> is smaller than an interval h between the first panel <NUM> and the second panel <NUM>. The distortion δ is calculated based on the predetermined pitch p, load loading compression fracture P<NUM> per one pillar of the multiple pillars, Young's moduli Eg of the first panel <NUM> and the second panel <NUM>, thicknesses t of the first panel <NUM> and the second panel <NUM>, and Poisson's ratios v of the first panel <NUM> and the second panel <NUM>.

According to the glass panel unit <NUM> of the seventh aspect, the first panel <NUM> and the second panel <NUM> are less likely to be damaged because the first panel <NUM> and the second panel <NUM> are less likely to make contact with each other.

The glass panel unit <NUM> of the eighth aspect according to the present disclosure would be realized in combination with the seventh aspect. In the eighth aspect, the predetermined pitch p of the multiple pillars <NUM> is determined such that the distortion δ of the first panel <NUM> and second panel <NUM> is smaller than the interval h between the first panel <NUM> and the second panel <NUM>. The distortion δ is calculated further based on Young's modulus Esp of each pillar <NUM>, and a cross-section area S of each pillar <NUM>, in addition to the predetermined pitch p, the interval h between the first panel <NUM> and the second panel <NUM>, the load loading compression fracture P<NUM> per one pillar of the multiple pillars, the Young's moduli Eg of the first panel <NUM> and the second panel <NUM>, the thicknesses t of the first panel <NUM> and the second panel <NUM>, and the Poisson's ratios v of the first panel <NUM> and the second panel <NUM>.

According to the glass panel unit <NUM> of the eighth aspect, the first panel <NUM> and the second panel <NUM> are less likely to be damaged because the first panel <NUM> and the second panel <NUM> are less likely to make contact with each other.

The glass panel unit <NUM> of the ninth aspect according to the present disclosure would be realized in combination with the seventh aspect. In the ninth aspect, the multiple pillars <NUM> are arranged so as to satisfy a formula below: <MAT> where p (m) denotes the predetermined pitch, h (m) denotes the interval between the first panel <NUM> and the second panel <NUM>, P<NUM> (N) denotes the load loading compression fracture per one pillar of the multiple pillars <NUM>, Eg (Pa) denotes the Young's modulus of each of the first panel <NUM> and the second panel <NUM>, t (m) denotes the thickness of each of the first panel <NUM> and the second panel <NUM>, and v denotes the Poisson's ratio of each of the first panel <NUM> and the second panel <NUM>.

Claim 1:
A glass panel unit (<NUM>), comprising:
a first panel (<NUM>) including at least a first glass plate (<NUM>);
a second panel (<NUM>) including at least a second glass plate (<NUM>), the second panel (<NUM>) being arranged to face the first panel (<NUM>) with a predetermined interval left with respect to the first panel (<NUM>);
a seal (<NUM>) arranged between the first panel (<NUM>) and the second panel (<NUM>) to hermetically bond the first panel (<NUM>) and the second panel (<NUM>) together;
an internal space (<NUM>) configured to form a reduced-pressure space by being hermetically enclosed by the first panel (<NUM>), the second panel (<NUM>), and the seal (<NUM>); and
multiple pillars (<NUM>) made of resin, the multiple pillars (<NUM>) being arranged in the internal space (<NUM>) at individual intersections of a square or rectangular lattice of constant lattice intervals, including a predetermined pitch, so as to be in contact with the first panel (<NUM>) and the second panel (<NUM>),
wherein
the multiple pillars (<NUM>) are arranged so as to satisfy a formula below. <MAT>
where p (m) denotes the predetermined pitch, h (m) denotes the predetermined interval between the first panel (<NUM>) and the second panel (<NUM>), P<NUM> (N) denotes the load loading compression fracture per one pillar (<NUM>) of the multiple pillars, Eg (Pa) denotes the Young's modulus of each of the first panel (<NUM>) and the second panel (<NUM>), t (m) denotes the thickness of each of the first panel (<NUM>) and the second panel (<NUM>), and v denotes the Poisson's ratio of each of the first panel (<NUM>) and the second panel (<NUM>).