Patent Publication Number: US-2023141217-A1

Title: Depressurized multilayered glass panel

Description:
TECHNICAL FIELD 
     The present invention relates to a depressurized multilayer glass panel. 
     BACKGROUND ART 
     A depressurized multilayer glass panel includes a pair of glass plates and a plurality of columns disposed between the pair of glass plates and is configured such that an air gap portion in which the columns are disposed is provided between the pair of glass plates and kept in a depressurized state. When a temperature difference occurs between the pair of glass plates, part of the heat is transferred from one of the glass plates to the other of the glass plates through the columns. Such heat transfer is preferably as small as possible in terms of enhancing the thermal insulation performance in the depressurized multilayer glass panel. That is, in the depressurized multilayer glass panel, the lower the heat transfer rate (U-value), the more preferable. The heat transfer rate of the depressurized multilayer glass panel is proportional to the contact area between the pair of glass plates and the columns. 
     Patent Literature 1 discloses a configuration of a vacuum multilayer glass panel using cylinders with a diameter of 600 μm or less as columns. In this way, with the vacuum multilayer glass panel in which the diameter of the columns is small, the heat transfer rate can be made low. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2016-531081 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In a depressurized multilayer glass panel, when one of glass plates is subjected to an external force such as an impact, it may be deformed toward the other of the glass plates, and when the external force is large, there is a possibility of damage to the glass plate. In order to suppress the deformation of the glass plate due to the external force, it is conceivable to take measures to increase the area of the columns in contact with the glass plate, but, in this case, the heat transfer rate is increased due to the increase in contact area between the pair of glass plates and the columns. While the vacuum multilayer glass panel of Patent Literature 1 is able to make the heat transfer rate low by the small diameter of the columns, there is a possibility that the strength against an external force such as an impact is not sufficient. In addition, in the vacuum multilayer glass panel of Patent Literature 1, the columns are each the cylinder, and therefore, when the glass plate is deformed, the deformed glass plate comes in contact with a peripheral corner being a boundary between a top or bottom surface and a side surface of the column. An angle formed by the corner is 90 degrees, and therefore, when the corner of the column is pressed against the glass plate deformed by the external force, the stress of the deformed glass plate is concentrated on a portion where the corner is pressed, so that the deformed glass plate subjected to the external force is susceptible to damage. 
     In view of the circumstances described above, a depressurized multilayer glass panel is required that can suppress damage to a glass plate subjected to an external force while keeping the heat transfer rate low. 
     Solution to Problem 
     A characteristic configuration of a depressurized multilayer glass panel according to the present invention resides in that the depressurized multilayer glass panel includes a first glass plate; a second glass plate disposed to face the first glass plate; a sealing portion provided around respective entire outer peripheries of the first glass plate and the second glass plate to form an air gap portion between the first glass plate and the second glass plate, the air gap portion sealed in a depressurized state; and a plurality of columns disposed between the first glass plate and the second glass plate, each column including contact surfaces in contact with respective facing surfaces of the first glass plate and the second glass plate, and a non-contact portion provided around the contact surface and spaced apart from the facing surface of the first glass plate or the second glass plate, wherein the non-contact portion is configured such that when the facing first glass plate or second glass plate is deformed by being subjected to a first external force, at least a part of the non-contact portion is contactable with the deformed first glass plate or second glass plate. 
     According to this configuration, the column has the contact surfaces in contact with the facing surfaces of the first glass plate and the second glass plate, and the non-contact portion provided around the contact surface. Consequently, it is possible to reduce the contact area of the column with the first glass plate and the second glass plate. As a result, the heat transfer rate can be made low in the depressurized multilayer glass panel. 
     Further, the non-contact portion of the column is spaced apart from the facing surface of the first glass plate or the second glass plate, and is configured such that at least a part of the non-contact portion is contactable with the first glass plate or the second glass plate deformed by being subjected to the first external force. Herein, the first external force refers to an external force that can deform the first glass plate or the second glass plate to come in contact with the non-contact portion of the column. Consequently, the glass plate deformed by being subjected to the first external force comes in contact with the non-contact portion around the contact surface of the column, and therefore, the stress that acts on the glass plate is distributed. As a result, the depressurized multilayer glass panel is able to enhance the impact strength and thus suppress damage to the glass plate. 
     Another characteristic configuration resides in that the non-contact portion being configured to be contactable refers to a configuration such that when the first glass plate or the second glass plate is deformed by being subjected to a second external force, the deformed first glass plate or second glass plate comes in contact with the non-contact portion before the deformed first glass plate or second glass plate comes in contact with the facing first glass plate or second glass plate. 
     According to this configuration, the first glass plate or the second glass plate deformed by being subjected to the second external force comes in contact with the non-contact portion of the column before coming in contact with the facing first glass plate or second glass plate. Herein, the second external force refers to an external force that can deform the first glass plate or the second glass plate to come in contact with the facing first glass plate or second glass plate. Consequently, the glass plate deformed by being subjected to the second external force securely comes in contact with the non-contact portion before coming in contact with the facing glass plate, and thus can be supported while distributing the stress. As a result, the depressurized multilayer glass panel is able to suppress damage to the glass plate. 
     Another characteristic configuration resides in that the columns each further includes a non-contact surface extending outward continuously from a periphery of the contact surface and spaced gradually farther apart from the facing surface of the first glass plate or the second glass plate toward an outer periphery of the column, and that the non-contact portion is on the non-contact surface. 
     According to this configuration, the glass plate deformed by being subjected to the external force comes in contact with the non-contact portion on the non-contact surface extending continuously from the periphery of the contact surface of the column so that the acting stress is distributed. As a result, the depressurized multilayer glass panel is able to enhance the impact strength and thus suppress damage to the glass plate. 
     Another characteristic configuration resides in that the column further includes a non-contact surface extending outward continuously from a periphery of the contact surface and spaced gradually farther apart from the facing surface of the first glass plate or the second glass plate toward an outer periphery of the column, and that the non-contact portion is a part of the non-contact surface. 
     According to this configuration, the glass plate deformed by being subjected to the external force comes in contact with the non-contact portion being a part of the non-contact surface extending continuously from the periphery of the contact surface of the column so that the acting stress is distributed. As a result, the depressurized multilayer glass panel is able to enhance the impact strength and thus suppress damage to the glass plate. 
     Another characteristic configuration resides in that the columns each have a gradient angle between the facing surface of the first glass plate or the second glass plate and the non-contact surface, the gradient angle being such that when the first glass plate or the second glass plate is deformed by being subjected to the first external force, at least a part of the non-contact surface is contactable with the deformed first glass plate or second glass plate. 
     According to this configuration, the columns each have a gradient angle between the facing surface of the first glass plate or the second glass plate and the non-contact surface, the gradient angle being such that at least a part of the non-contact surface is contactable with the deformed first glass plate or second glass plate. Therefore, it is possible to make the deformed glass plate properly come in contact with the non-contact surface of the column. 
     As another characteristic configuration, it is preferable that the gradient angle of the column be set to less than 65 degrees. 
     When the first glass plate or the second glass plate is deformed by being subjected to the first external force, a deformed portion of the glass plate is deformed at an acute angle from the facing surface before the deformation in the glass plate while being supported by the column. Therefore, like this configuration, by setting the gradient angle of the column formed between the facing surface of the first glass plate or the second glass plate and the non-contact surface to less than 65 degrees, it is possible to make the deformed glass plate come in contact with the non-contact surface of the column. 
     As another characteristic configuration, it is preferable that the gradient angle of the column be set to 0.4 degrees or more. 
     The minimum angle of the gradient angle of the column formed between the facing surface of the first glass plate or the second glass plate and the non-contact surface is set based on a gradient angle in a normal resting state that is formed between the facing surface of the glass plate in contact with the column and the facing surface of the glass plate around the column when only the atmospheric pressure is applied to the first glass plate or the second glass plate. While affected by the material or thickness of the glass plate, the material, size, or shape of the column, or the like, the initial gradient angle generally becomes less than 0.4 degrees. Therefore, in this configuration, the gradient angle formed between the facing surface of the first glass plate or the second glass plate and the non-contact surface is set to 0.4 degrees or more. Consequently, it is possible to make the first glass plate or the second glass plate come in contact with the non-contact surface when deformed by being subjected to the first external force. 
     As another characteristic configuration, it is preferable that the contact surface of the column be in a shape of a spherical cap. 
     Like this configuration, when the contact surface of the column is in a shape of the spherical cap, since a pressing force by the contact surface on the facing surface of the first glass plate or the second glass plate is increased, the column is restrained from moving from the position where the column is disposed between the first glass plate and the second glass plate. 
     As another characteristic configuration, it is preferable that the contact surface of the column be planar. 
     Like this configuration, when the contact surface of the column is planar, the contact surface is in uniform surface contact with the facing surface of the first glass plate or the second glass plate, and therefore, the column hardly falls so that its posture is easily held between the first glass plate and the second glass plate. 
     As another characteristic configuration, it is preferable that the non-contact portion of the column be formed straight toward the outer periphery. 
     Like this configuration, when the non-contact portion of the column is formed straight toward the outer periphery, the inclination (gradient angle) for the deformed first glass plate or second glass plate to come in contact with the non-contact surface of the column can be easily set. 
     As another characteristic configuration, it is preferable that the contact surface and the non-contact portion of the column be in a shape of a spherical cap with a constant radius as a whole. 
     Like this configuration, when the contact surface and the non-contact portion of the column are in a shape of the spherical cap with the constant radius as a whole, since the contact surface and the non-contact portion are smoothly continuous with each other, the non-contact portion easily comes in contact with the deformed first glass plate or second glass plate therealong. Further, when, for example, the column is formed using a mold, it is easy to withdraw a spherical cap-shaped portion of the column from the mold. Therefore, it is also possible to form the column at low cost. 
     As another characteristic configuration, it is preferable that a radius of curvature of the contact surface and the non-contact portion be 0.3 mm or more and 20 mm or less. 
     According to this configuration, the radius of curvature of the contact surface and the non-contact portion is set within the predetermined range, and therefore, the contact surface and the non-contact portion can be easily formed in the column. 
     As another characteristic configuration, it is preferable that, in a falling ball test in which the columns each having the contact surface with a diameter of 0.2 mm and each having a height of 0.2 mm are disposed at an interval of 20 mm between the first glass plate and the second glass plate each being 350 mm×350 mm and having a plate thickness of 3.1 mm, and a ball of 1 kg is dropped at a central position of the first glass plate and at a middle position between the adjacent columns from above the first glass plate, the first external force be a force when the ball has an upper limit height of 100 mm within which the ball does not damage the first glass plate. 
     According to this configuration, it is possible to configure the vacuum multilayer glass panel with high impact strength. 
     As another characteristic configuration, it is preferable that a heat transfer rate be equal to or less than 1.5 W/m2K. 
     Like this configuration, when the heat transfer rate is equal to or less than 1.5 W/m2K, it is possible to obtain the vacuum multilayer glass panel with high thermal insulation. 
     As another characteristic configuration, it is preferable that a maximum diameter of regions of the column facing the first glass plate and the second glass plate be 100 μm or more and 1000 μm or less. 
     Even if the contact surfaces of the column with the first glass plate and the second glass plate are made small, when the maximum diameter of the regions facing the first glass plate and the second glass plate is increased, the amount of heat that can be stored in the column is increased so that the heat flow rate between the glass plates and the column is increased. Therefore, in this configuration, the maximum diameter of the regions facing the first glass plate and the second glass plate is set to 100 μm or more and 1000 μm or less. Consequently, the column is miniaturized as a whole, and therefore, it is possible to suppress the increase in heat flow rate between the glass plates and the column. 
     As another characteristic configuration, it is preferable that a maximum diameter of the contact surface be greater than 100 μm. 
     Like this configuration, when the maximum diameter of the contact surface is greater than 100 μm, the contact area of the column with the first glass plate and the second glass plate is ensured. Consequently, it is possible to stably hold the column between the first glass plate and the second glass plate. 
     As another characteristic configuration, it is preferable that a length of the column in a direction perpendicular to plate surfaces of the first glass plate and the second glass plate be 50 μm or more and 500 μm or less. 
     Like this configuration, when the length of the column in the direction perpendicular to the plate surfaces of the first glass plate and the second glass plate is 50 μm or more and 500 μm or less, since the column is miniaturized, it is possible to suppress the increase in heat flow rate between the glass plates and the column. 
     As another characteristic configuration, it is preferable that a compressive strength of the column be equal to or more than 200 MPa. 
     Like this configuration, when the compressive strength of the column is equal to or more than 200 MPa, the column is able to securely keep the interval between the first glass plate and the second glass plate without being compressively deformed. 
     As another characteristic configuration, it is preferable that the columns each contain zirconia. 
     Like this configuration, when the columns each contain the zirconia, it is possible to easily enhance the lower thermal conductivity, the heat resistance, and the strength in the column. 
     As another characteristic configuration, it is preferable that a shape of the column as viewed in a direction perpendicular to the plate surfaces of the first glass plate and the second glass plate be any of a circular shape including an ellipse and an elongated circle, a rectangular shape, a triangular shape, and a polygonal shape with five or more corners. 
     According to this configuration, since the column can be formed by various shapes, the shape of the column can be freely selected in consideration of the type of glass plate, visibility of the vacuum multilayer glass panel from the outside, and so forth. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an exploded perspective view illustrating a depressurized multilayer glass panel of a first embodiment. 
         FIG.  2    is a longitudinal sectional view of the depressurized multilayer glass panel. 
         FIG.  3    is a plan view of a column. 
         FIG.  4    is a side view of the column. 
         FIG.  5    is a main part longitudinal sectional view of the depressurized multilayer glass panel. 
         FIG.  6    is a main part longitudinal sectional view illustrating a state when the depressurized multilayer glass panel is subjected to an external force. 
         FIG.  7    is a diagram for explaining a gradient angle of the column. 
         FIG.  8    is a longitudinal sectional view of a column of a second embodiment. 
         FIG.  9    is a main part longitudinal sectional view of a depressurized multilayer glass panel of the second embodiment. 
         FIG.  10    is a partial longitudinal sectional view of a depressurized multilayer glass panel for a falling ball test. 
         FIG.  11    is a partial plan view of the depressurized multilayer glass panel for the falling ball test. 
         FIG.  12    is a main part longitudinal sectional view of a depressurized multilayer glass panel of another embodiment. 
         FIG.  13    is a plan view of a column of another embodiment. 
         FIG.  14    is a plan view of a column of another embodiment. 
         FIG.  15    is a plan view of a column of another embodiment. 
         FIG.  16    is a plan view of a column of another embodiment. 
         FIG.  17    is a main part longitudinal sectional view of a depressurized multilayer glass panel of another embodiment. 
         FIG.  18    is a main part longitudinal sectional view of a depressurized multilayer glass panel of another embodiment. 
         FIG.  19    is a main part longitudinal sectional view of a depressurized multilayer glass panel of another embodiment. 
         FIG.  20    is a main part longitudinal sectional view of a depressurized multilayer glass panel of another embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Hereinafter, a depressurized multilayer glass panel according to the present invention will be described with reference to the drawings. 
     As illustrated in  FIGS.  1  and  2   , a vacuum multilayer glass panel  10  includes a first glass plate  11 , a second glass plate  12  disposed to face the first glass plate  11 , a sealing portion  14  provided around the respective entire outer peripheries of the first glass plate  11  and the second glass plate  12 , and a plurality of columns  16  disposed between the first glass plate  11  and the second glass plate  12 . The vacuum multilayer glass panel  10  (hereinafter abbreviated as a “glass panel”) is one example of a depressurized multilayer glass panel. 
     The glass panel  10  is configured such that an air gap portion  13  with a predetermined space is formed between the first glass plate  11  and the second glass plate  12 , and that the air gap portion  13  is sealed in a vacuum state by the sealing portion  14 . In order to form the air gap portion  13 , the sealing portion  14  is formed around the entire outer peripheries of the glass plates  11 ,  12  in a state where a predetermined space is kept between facing surfaces  17 ,  18  of the glass plates  11 ,  12  by disposing the columns  16  between the facing surfaces  17 ,  18 . The sealing portion  14  is made of a sealing material or the like. In order to place the air gap portion  13  in a vacuum state, the outer peripheral portion of the air gap portion  13  is sealed by the sealing portion  14  and then the air gap portion  13  is evacuated through a suction port (not illustrated) provided, for example, in the first glass plate  11 . After the evacuation, the suction port is sealed by fusion of low melting point glass or the like. Note that, in the depressurized multilayer glass panel, the air gap portion  13  is sealed in a depressurized state lower than the atmospheric pressure. 
     As illustrated in  FIGS.  3  and  4   , when viewed along the central axis X, the column  16  has, in each of a top surface and a bottom surface, a circular contact surface  21  with the central axis X at its center, and an annular non-contact portion  23  provided around the contact surface  21 . In this embodiment, the non-contact portion  23  is formed by a non-contact surface  22 . Both the contact surfaces  21 ,  21  of the column  16  are respectively in contact with the facing surfaces  17 ,  18  of the glass plates  11 ,  12 . The non-contact surfaces  22  (the non-contact portions  23 ) are respectively spaced apart from the facing surfaces  17 ,  18  of the first glass plate  11  and the second glass plate  12 . The non-contact surfaces  22  (the non-contact portions  23 ) each extend outward continuously from the periphery of the contact surface  21  and are each spaced gradually farther apart from the facing first glass plate  11  or second glass plate  12  toward an outer periphery  19  of the column  16 . 
     The non-contact surfaces  22  are each integrally connected to the contact surface  21  around the entire circumference of the column  16  about the central axis X so that the column  16  is formed in a disk shape. In this way, since the column  16  has the non-contact surfaces  22  each located around the periphery of the contact surface  21 , contact regions R 1  of the contact surfaces  21  can be made small. Consequently, the heat transfer rate can be made low in the glass panel  10 . 
     In this embodiment, the column  16  is configured such that the contact surface  21  and the non-contact surface  22  facing each of the first glass plate  11  and the second glass plate  12  are in a shape of a spherical cap with a constant radius as a whole. When the contact surfaces  21  of the column  16  are each in a shape of the spherical cap, since pressing forces by the contact surfaces  21  on the facing surfaces  17 ,  18  of the first glass plate  11  and the second glass plate  12  are increased, the column  16  is easily held in position between the first glass plate  11  and the second glass plate  12 . Further, when the contact surface  21  and the non-contact surface  22  are in a shape of the spherical cap with the constant radius as a whole, the non-contact surface  22  easily comes in contact with the deformed first glass plate  11  or second glass plate  12  therealong. Further, when, for example, the column  16  is formed using a mold, it is easy to withdraw spherical cap-shaped portions of the column  16  from the mold. Therefore, it is also possible to form the column  16  at low cost. In the column  16 , the contact surface  21  and the non-contact surface  22  (the non-contact portion  23 ) have a shape of a spherical cap with a radius of curvature of 0.3 mm or more and 20 mm or less. In this way, by setting the radius of curvature of the contact surface  21  and the non-contact surface  22  (the non-contact portion  23 ) within the predetermined range, the contact surface  21  and the non-contact surface  22  (the non-contact portion  23 ) can be easily formed in the column  16 . 
     In the glass panel  10 , the heat transfer rate (U-value) is equal to or less than 1.5 W/m2K. When the heat transfer rate of the glass panel  10  is equal to or less than 1.5 W/m2K, the glass panel  10  has sufficient thermal insulation. Herein, “the heat transfer rate (U-value)” is a value measured in accordance with “ISO 19916-1:2018 Glass in building—Vacuum insulating glass—Part 1”. 
     The glass panel  10  illustrated in  FIG.  5    is in a normal state where only the contact surfaces  21  (contact regions R 1 ) of the column  16  are in contact with the facing surfaces  17 ,  18  of the first glass plate  11  and the second glass plate  12 . Since the Young&#39;s modulus of the column  16  is higher than that of the first glass plate  11  and the second glass plate  12 , when the column  16  is pressed against them, the facing surfaces  17 ,  18  of the first glass plate  11  and the second glass plate  12  are deformed to dent. 
     The glass panel  10  illustrated in  FIG.  6    is in a state where the first glass plate  11  is subjected to an external force so that the facing surface  17  in contact with the column  16  is deformed. When the first glass plate  11  is deformed in this way, the column  16  comes in contact with the facing surface  17  not only at the contact surface  21  but also at an inner side surface  22 A being a part of the non-contact surface  22  so that the contact region R 1  is expanded to a contact region R 2 . Consequently, only an outer side surface  22 B of the non-contact surface  22  other than the inner side surface  22 A is in non-contact with the facing surface  17 . Specifically, the contact region R 1  is expanded to the contact region R 2  so that bending occurring on the facing surface  17  of the first glass plate  11  is supported by the contact surface  21  and the inner side surface  22 A of the non-contact surface  22 . 
     In this way, the non-contact surface  22  (the non-contact portion  23 ) is configured such that when the facing first glass plate  11  or second glass plate  12  is deformed by being subjected to a first external force, at least a part of the non-contact surface  22  (the non-contact portion  23 ) is able to come in contact with the deformed first glass plate  11  or second glass plate  12 . Herein, the first external force refers to an external force that can deform the first glass plate  11  or the second glass plate  12  to come in contact with the non-contact surface  22  (the non-contact portion  23 ) of the column  16 . 
     The non-contact surface  22  (the non-contact portion  23 ) being configured such that at least a part of it is able to come in contact with the deformed first glass plate  11  or second glass plate  12  refers to a configuration such that when the first glass plate  11  or the second glass plate  12  is deformed by being subjected to a second external force, the deformed first glass plate  11  or second glass plate  12  comes in contact with the non-contact surface  22  (the non-contact portion  23 ) before the deformed first glass plate  11  or second glass plate  12  comes in contact with the facing first glass plate  11  or second glass plate  12 . Herein, the second external force refers to an external force that can deform the first glass plate  11  or the second glass plate  12  to come in contact with the facing first glass plate  11  or second glass plate  12 . 
     In this way, the first glass plate  11  deformed by being subjected to the first external force or the second external force comes in contact with the non-contact surface  22  extending continuously from the periphery of the contact surface  21  of the column  16 , and therefore, the contact area is increased and there is no occurrence of the pressing of the corner as in the invention of Patent Literature 1, so that the stress that acts on the first glass plate  11  is distributed. As a result, the glass panel  10  is able to enhance the impact strength and thus suppress damage to the first glass plate  11  subjected to an external force such as an impact. 
     The column  16  is configured such that a gradient angle α 1  is set between the facing surface  17 ,  18  of the first glass plate  11  or the second glass plate  12  and the non-contact surface  22 . The gradient angle α 1  is an angle such that when the first glass plate  11  or the second glass plate  12  facing the non-contact surface  22  is deformed by being subjected to the first external force, at least a part of the non-contact surface  22  is able to come in contact with the deformed first glass plate  11  or second glass plate  12 , and is an angle formed by a tangent line passing through a boundary between the contact surface  21  and the non-contact surface  22  and the facing surface  17  or the facing surface  18 . By properly setting the gradient angle α 1  in the column  16 , it is possible to make the deformed first glass plate  11  or second glass plate  12  come in contact with the non-contact surface  22  of the column  16 . 
     The gradient angle α 1  is set based on a gradient angle α shown in  FIG.  7   .  FIG.  7    illustrates, by way of example, a state where the first glass plate  11  is deformed with respect to a cylindrical column  31 . In this case, the gradient angle α is an angle that is formed between a facing surface  17 A after the deformation and a facing surface  17 B before the deformation in the first glass plate  11  when the first glass plate  11  is subjected to the first external force. In  FIG.  7   , the facing surface  17 B before the deformation is illustrated by a two-dot chain line, and the facing surface  17 A after the deformation is illustrated by a solid line. The gradient angle α can be increased to an extent where the first glass plate  11  is broken. The maximum value of the gradient angle α changes according to the material or thickness of the first glass plate  11  and the second glass plate  12 , the material, size, or shape of the column  16 , or the like. When, for example, the maximum value of the gradient angle α is set to 65 degrees, the gradient angle α 1  is set to less than 65 degrees, preferably less than 55 degrees, and more preferably less than 40 degrees. By setting the gradient angle α 1  of the column  16  to less than 65 degrees, it is possible to make the deformed glass plate  11 ,  12  come in contact with the non-contact surface  22  of the column  16 . 
     The minimum angle of the gradient angle α 1  is set based on a gradient angle α 0  in a normal resting state that is formed between the facing surface  17  of the first glass plate  11  in contact with the column  16  and the facing surface  17  of the first glass plate  11  around the column  16  when only the atmospheric pressure is applied to the first glass plate  11  illustrated in  FIG.  7   . While affected by the material or thickness of the first glass plate  11  and the second glass plate  12 , the material, size, or shape of the column  16 , or the like, the gradient angle α 0  generally becomes less than 0.4 degrees. Therefore, the gradient angle α 1  can be set to 0.4 degrees or more. Consequently, it is possible to make the glass plate  11 ,  12  come in contact with the non-contact surface  22  when deformed by being subjected to the first external force. 
     The column  16  is made of ceramic such as alumina or zirconia, or the like. The column  16  may contain a nanoparticle filler such as zirconia. When the column  16  contains the zirconia, it is possible to easily enhance the lower thermal conductivity, the heat resistance, and the strength in the column  16 . As examples of the material of the column  16 , there can be cited ceramic nanoparticles (Al2O3, SiO2, ZrO2, SiC, Si3N4, and combinations thereof), ceramic precursors such as SSQ and polysilazane, sintered ceramics (Al2O3, SiO2, ZrO2, SiC, Si3N4, zircon, steatite, cordierite, aluminum titanate, etc.), glasses (silica, soda lime, borosilicate, etc.), glass ceramics (crystallized glass), glass frits, glass beads or glass bubbles, metals (SUS304, SUS430, SUS410, iron, nickel, etc.), resins (polyimide, polyamide, PEEK, PTFE, etc.), and combinations thereof. The column  16  of this embodiment is made of a material with a strength greater than that of the glass plates  11 ,  12 . Therefore, even when the glass plates  11 ,  12  are deformed, the column  16  is able to keep its shape constant. 
     In the column  16 , a maximum diameter W 1  ( FIG.  3   ) of regions facing the facing surfaces  17 ,  18  of the first glass plate  11  and the second glass plate  12  is set to 100 μm or more and 1000 μm or less. Even if the contact surfaces  21  of the column  16  with the first glass plate  11  and the second glass plate  12  are made small, when the maximum diameter W 1  of the regions facing the first glass plate  11  and the second glass plate  12  is increased, the amount of heat that can be stored in the column  16  is increased so that the heat flow rate between the glass plates  11 ,  12  and the column  16  is increased. By setting the maximum diameter W 1  of the column  16  to 100 μm or more and 1000 μm or less, the column  16  is miniaturized as a whole, and therefore, it is possible to suppress the increase in heat flow rate between the glass plates  11 ,  12  and the column  16 . Note that, in terms of stably supporting the first glass plate  11  and the second glass plate  12 , a maximum diameter W 2  of the contact surfaces  21  is preferably greater than 100 μm. 
     In the column  16 , a total height (thickness) H 1  being the length in a direction perpendicular to the facing surfaces  17 ,  18  (plate surfaces) of the first glass plate  11  and the second glass plate  12  is set to 50 μm or more and 500 μm or less. A height (thickness) H 2  of the outer periphery  19  of the column  16  is set as appropriate based on the gradient angle cd. 
     The compressive strength of the column  16  is equal to or more than 200 MPa. Consequently, the column  16  is able to securely keep the interval between the first glass plate  11  and the second glass plate  12  without being compressively deformed in the glass panel  10 . 
     Second Embodiment 
     A second embodiment of a glass panel  10  will be described with reference to  FIGS.  8  and  9   . The same numerals are given to elements similar to those in the first embodiment, and a description thereof is omitted herein. 
     In this embodiment, as illustrated in  FIG.  8   , a column  16  includes contact surfaces  21  each being planar, and non-contact portions  23  each formed straight toward an outer periphery  19  of the column  16  from the periphery of the contact surface  21 . In this embodiment, the non-contact portion  23  is formed by a non-contact surface  22 . As illustrated in  FIG.  9   , in the glass panel  10 , the column  16  is disposed between the first glass plate  11  and the second glass plate  12 . 
     When the contact surfaces  21  of the column  16  are planar, the contact surfaces  21  are in uniform surface contact with the facing surfaces  17 ,  18  of the first glass plate  11  and the second glass plate  12 . Therefore, the column  16  hardly falls so that its posture is easily held between the first glass plate  11  and the second glass plate  12 . Further, when the non-contact surfaces  22  (the non-contact portions  23 ) are formed straight toward the outer periphery  19  in the column  16 , it is easy to set a gradient angle α 2  of the column  16 . Note that a boundary portion  24  between the planar contact surface  21  and the straight non-contact surface  22  serves as a corner so that there is a possibility of concentration of the stress of the glass plate  11 ,  12  deformed at the corner. Therefore, the boundary portion  24  is preferably rounded. 
     As illustrated in  FIG.  8   , a predetermined gradient angle α 2  is set for the column  16 . The column  16  illustrated in  FIGS.  8  and  9    has a shape in which the non-contact surface  22  on the first glass plate  11  side and the non-contact surface  22  on the second glass plate  12  side cross each other at the outer periphery  19 . That is, the outer periphery  19  has no thickness (corresponding to the thickness H 2  in the first embodiment) in the column  16 . Therefore, assuming that a maximum diameter W 2  of the contact surfaces  21  is equal to that in the first embodiment, the gradient angle α 2  becomes greater than the gradient angle α 2  in the first embodiment. In the glass panel  10  illustrated in  FIG.  9   , the column  16  is configured such that when, for example, the first glass plate  11  is deformed by being subjected to an impact, it is possible to make the deformed first glass plate  11  come in contact with the non-contact surface  22 . Specifically, bending occurring on the facing surface  17  of the first glass plate  11  can be supported also by the non-contact surface  22 . Consequently, the non-contact surface  22  can absorb the impact to which the first glass plate  11  is subjected, while distributing the impact. As a result, it is possible to enhance the impact strength in the glass panel  10 . 
     [Falling Ball Test] 
     With respect to glass panels of Examples 1 and 2 and Comparative Examples 1 and 2 given below, the following falling ball test was performed to confirm the impact strength. The falling ball test was performed using a method in which columns  16 ′ each having a height of 0.2 mm were disposed at intervals of 20 mm between a first glass plate  11  and a second glass plate  12  (each being 350 mm×350 mm and having a plate thickness of 3.1 mm) to place the first glass plate  11  and the second glass plate  12  in a positional relationship illustrated in  FIG.  10   , and a ball of 1 kg was dropped at a central position of the first glass plate  11  and at middle positions S (see  FIG.  11   ) between the adjacent columns  16 ′ from above the first glass plate  11 . In Examples 1 and 2 and Comparative Examples 1 and 2, the glass plates  11 ,  12  are common, and only columns differ from each other. Out of the glass plates  11 ,  12 , the first glass plate  11  is Low-E glass, and Low-E films, not illustrated, are laminated on the entirety of a second surface (a surface facing the second glass plate  12 ) of the first glass plate  11 .  FIGS.  10  and  11    are diagrams for explaining the outline of the falling ball test, wherein the cylindrical column  16 ′ is illustrated as one example of a column. Note that the shape of a column of Comparative Example 1 given below is the same as that of the column  16 ′ illustrated in  FIGS.  10  and  11   . 
     Example 1 
     In a glass panel of Example 1, columns  16  below are disposed between the first glass plate  11  and the second glass plate  12 . The column  16  used in Example has the same shape as that of the column  16  illustrated in  FIGS.  3  and  4   , wherein the total diameter (maximum diameter W 1 ) is 0.5 mm, the diameter (maximum diameter W 2 ) of the contact surface  21  is 0.2 mm, and the non-contact surface  22  exists in a width of 0.15 mm around the contact surface  21 . The height H 1  of the column  16  is 0.2 mm, and the height (thickness) H 2  of the outer periphery  19  of the column  16  is 0.16 mm. The radius of curvature of the contact surface  21  and the non-contact surface  22  is 1.2 mm, and the gradient angle α 1  is 5 degrees. 
     Example 2 
     In a glass panel of Example 2, columns  16  below are disposed between the first glass plate  11  and the second glass plate  12 . The column  16  used in Example 2 has the same shape as that of the column  16  illustrated in  FIG.  8   , wherein the total diameter (maximum diameter W 1 ) is 0.5 mm, and the diameter (maximum diameter W 2 ) of the contact surface  21  is 0.42 mm. The height (thickness) H 1  of the column  16  is 0.2 mm. In the column of Example 2, the gradient angle α 2  formed between the facing surface  17 ,  18  of the first glass plate  11  or the second glass plate  12  and the non-contact surface  22  is 52 degrees. 
     Comparative Example 1 
     In a glass panel of Comparative Example 1, columns below are disposed between the first glass plate  11  and the second glass plate  12 . The column (column  16 ′) used in Comparative Example 1 is a cylinder with a diameter of 0.2 mm and with a thickness (height) of 0.2 mm That is, in the column of Comparative Example 1, contact surfaces in contact with the first glass plate  11  and the second glass plate  12  are of the same size as that in Example 1. In Comparative Example 1, since the column  16 ′ is the cylinder, the gradient angle is 90 degrees. 
     Comparative Example 2 
     In a glass panel of Comparative Example 2, columns below are disposed between the first glass plate  11  and the second glass plate  12 . The column used in Comparative Example 2 has a shape similar to that of the column  16  illustrated in  FIG.  8   , wherein the gradient angle differs from that of the column of Example 2. In the column of Comparative Example 2, the gradient angle α 2  is 68 degrees. Therefore, the diameter of a contact surface of the column of Comparative Example 2 is 0.42 mm equal to that in Example 2, and the total diameter is also approximately equal (about 0.5 mm) to that of the column of Example 2. The height (thickness) of the column  16  is 0.2 mm 
     [Result 1 of Falling Ball Test] 
     In the falling ball test, the upper limit height of a ball that does not damage the first glass plate  11  is defined as a falling ball clear height. The falling ball clear heights are compared with respect to Example 1 and Comparative Example 1 where the diameters of the contact surfaces are both 0.2 mm Herein, the average value of 15-times falling ball tests was used as a falling ball clear height for comparison. In Example 1, the maximum value of the falling ball clear height was 203 mm, the minimum value of the falling ball clear height was 109 mm, and the falling ball clear height (average value) was 152 mm. In Example 1, while the variation in falling ball clear height was close to 100 mm, the falling ball clear heights were 100 mm or more in all the falling ball tests. On the other hand, in Comparative Example 1, the maximum value of the falling ball clear height was 58 mm, the minimum value of the falling ball clear height was 32 mm, and the falling ball clear height (average value) was 44 mm. In Comparative Example 1, while the variation in falling ball clear height was less than 30 mm, the falling ball clear heights were much less than 100 mm in all the falling ball tests. 
     In this way, it was proved that the impact strength was high in the glass panel of Example 1 with the column having the non-contact surface  22 , as compared to the glass panel of Comparative Example 1 with the column having no non-contact surface  22 . 
     [Result 2 of Falling Ball Test] 
     The falling ball clear heights are compared with respect to Example 2 and Comparative Example 2 where the diameters of the contact surfaces are both 0.42 mm. Also herein, the average value of 15-times falling ball tests was used as a falling ball clear height for comparison. In Example 2, the maximum value of the falling ball clear height was 312 mm, the minimum value of the falling ball clear height was 185 mm, and the falling ball clear height (average value) was 230 mm. In Example 2, while the variation in falling ball clear height was close to 130 mm, the falling ball clear heights were 100 mm or more in all the falling ball tests. On the other hand, in Comparative Example 2, the maximum value of the falling ball clear height was 292 mm, the minimum value of the falling ball clear height was 73 mm, and the falling ball clear height (average value) was 203 mm. In Comparative Example 2, the variation in falling ball clear height was as large as 219 mm, and there were cases where the falling ball clear height was less than 100 mm in the falling ball test. 
     In this way, it was proved that the impact strength was high in the glass panel of Example 2 with the gradient angle α 2  of the column being set to less than 65 degrees, as compared to the glass panel of Comparative Example 2 with the gradient angle of the column being set to greater than 65 degrees. 
     Herein, assuming that the first external force is a force when the falling ball clear height is 100 mm in the falling ball test, the glass panels  10  of the first embodiment and the second embodiment are each able to make the falling ball clear height 100 mm or more in the falling ball test by setting the gradient angles cd, α 2  to proper angles. Consequently, it is possible to configure the glass panels  10  with the high impact strength. 
     The heat transfer rates (U-values) of the glass panels of Examples 1 and 2 and Comparative Examples 1 and 2 were measured, and as a result, the U-values were 0.5 W/m2K in Example 1 and Comparative Example 1, and the U-values were 0.9 W/m2K in Example 2 and Comparative Example 2. Herein, the diameters of the contact surfaces  21  of the columns  16 ,  16 ′ are 0.2 mm in in Example 1 and Comparative Example 1, and the diameters of the contact surfaces  21  of the columns  16 ,  16 ′ are 0.42 mm in Example 2 and Comparative Example 2. From the above, it can be understood that the heat transfer rates (U-values) of the glass panels are increased in proportion to the diameters (areas) of the contact surfaces  21  of the columns  16 ,  16 ′. 
     OTHER EMBODIMENTS 
     In the glass panel  10 , the column  16  is not limited to the shape shown in each of the embodiments described above, and may have the following shape. 
     (1) As illustrated in  FIGS.  12  to  16   , a column  16  may be provided with protruding non-contact portions  23  on non-contact surfaces  22 . As illustrated in  FIG.  13   , the protruding non-contact portion  23  may be provided around the entire circumference about the central axis X on the non-contact surface  22 . As illustrated in  FIGS.  14  to  16   , a plurality of protruding non-contact portions  23  may be dispersedly arranged about the central axis X on the non-contact surface  22 . In  FIG.  14   , four protruding non-contact portions  23  are arranged in four directions, and  FIGS.  15  and  16   , eight protruding non-contact portions  23  are arranged in eight directions. The number of the protruding non-contact portions  23  arranged on the non-contact surface  22  is not particularly limited and may be one or two or more. As illustrated in  FIGS.  14  and  15   , the protruding non-contact portions  23  may each have a circular shape in plan view of the column  16 , or as illustrated in  FIG.  16   , the protruding non-contact portions  23  may each have a linear shape or the like extending radially. In this way, by providing the non-contact portions  23  on part of the non-contact surfaces  22 , it is possible to reduce the total volume of the column  16 . The heat transfer rate (U-value) in the column  16  is proportional to the volume of the column  16 . Therefore, by shaping the column  16  as illustrated in  FIGS.  12  to  16   , the column  16  is able to suppress the heat transfer rate (U-value). Further, by reducing the volume of the column  16 , it is also possible to suppress the material cost of the column  16 . 
     (2) In the first embodiment described above, an example has been given where, in the column  16 , the contact surfaces  21  and the non-contact surfaces  22  are in a shape of the spherical cap, and the side surfaces perpendicular to the facing surfaces  17 ,  18  of the first glass plate  11  and the second glass plate  12  are formed by the flat surfaces. As illustrated in  FIG.  17   , a column  16  may be formed by a curved surface in its entirety including not only contact surfaces  21  and non-contact surfaces  22 , but also side surfaces. Consequently, since the column  16  has no flat surface at the side surface, the column  16  is not held in a posture where the side surface is in contact with the first glass plate  11  or the second glass plate  12 . Therefore, it is easy to dispose the column  16  between the first glass plate  11  and the second glass plate  12 . With respect to the column  16  illustrated in  FIG.  17   , an example has been given where protruding non-contact portions  23  are provided on the non-contact surface  22 , but the non-contact surface  22  may be a non-contact portion  23  in its entirety with no protruding non-contact portion  23 . 
     As illustrated in  FIG.  18   , a column  16  may be formed with groove portions  25  in non-contact surfaces  22 , and may have a shape in which contact surfaces  21  and non-contact portions  23  are provided with the groove portions  25  interposed therebetween. In this way, by providing the groove portions  25  in the non-contact surfaces  22 , it is possible to reduce the total volume of the column  16 . Consequently, the column  16  is able to suppress the heat transfer rate (U-value), and it is also possible to suppress the material cost of the column  16 . As illustrated in  FIG.  19   , in a column  16 , non-contact portions  23  may be formed by flat surfaces along the facing surfaces  17 ,  18  of the glass plates  11 ,  12  in non-contact surfaces  22 . When the non-contact portions  23  are the flat surfaces, the deformed glass plate  11 ,  12  is supported by the flat surface of the non-contact portion  23 , and therefore, it is possible to enhance the impact strength of the glass panel  10 . Further, as illustrated in  FIG.  20   , in a column  16 , non-contact portions  23  may each be formed by a projection disposed on the outer peripheral side of a non-contact surface  22  and projecting toward the facing surface  17 ,  18  of the glass plate  11 ,  12 . 
     (3) In the embodiments described above, an example has been given where the shape of the column  16  in plan view (view in a direction perpendicular to the plate surfaces (the facing surfaces  17 ,  18 ) of the first glass plate  11  and the second glass plate  12 ) is a circular shape or an octagonal shape. The shape of the column  16  in plan view may be any of another circular shape including an ellipse and an elongated circle, a rectangular shape, a triangular shape, and a polygonal shape with five or more corners (e.g., an octagonal shape illustrated in  FIG.  16   ). 
     (4) In the embodiments described above, an example has been given where the column  16  is provided with the non-contact surfaces  22  facing the first glass plate  11  and the second glass plate  12 . However, the column  16  may be configured such that the contact surface  21  and the non-contact surface  22  face one of the first glass plate  11  and the second glass plate  12 , and that only the contact surface  21  faces the other of the first glass plate  11  and the second glass plate  12 . Further, in the embodiments described above, an example has been given where, in the column  16 , the non-contact portions  23  facing the first glass plate  11  and the second glass plate  12  are provided on the non-contact surfaces  22  or on part of the non-contact surfaces  22 . However, the non-contact portions  23  may be provided on only one of the non-contact surfaces  22  facing the first glass plate  11  and the second glass plate  12 . 
     (5) In the first embodiment, an example has been given where the column  16  has the thickness region (thickness H 2 ) at the outer periphery  19 , and in the second embodiment, an example has been given where the column  16  has no thickness region at the outer periphery  19 . Instead of this, the column  16  of the first embodiment may be configured such that there is no thickness region at the outer periphery  19 , and the column  16  of the second embodiment may be configured such that there is a thickness region at the outer periphery  19 . 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to various depressurized multilayer glass panels. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10 : vacuum multilayer glass panel (depressurized multilayer glass panel) 
               11 : first glass plate 
               12 : second glass plate 
               13 : air gap portion 
               14 : sealing portion 
               16 : column 
               17 ,  18 : facing surface 
               19 : outer periphery 
               21 : contact surface 
               22 : non-contact surface 
               22 A 1 : inner side surface 
               22 A 2 : outer side surface 
               23 : non-contact portion 
             W 1 : maximum diameter of column 
             W 2 : maximum diameter of contact surface 
             H 1 : total height 
             H 2 : height of outer periphery 
             X: central axis 
             α, α 1 , α 2 : gradient angle