Vacuum glass and method for manufacturing the same

Abstract

A high-strength vacuum glass is provided. The vacuum glass includes a first glass sheet that has been tempered by air cooling, a second glass sheet that has also been tempered by air cooling and faces the first glass sheet with a reduced pressure layer interposed therebetween, and a peripheral seal portion that joins the peripheral edges of the first glass sheet and the second glass sheet together so as to seal the reduced pressure layer. The peripheral seal portion includes solder.

Description

Technical Field

[0001] The present invention relates to a vacuum glass and a method for manufacturing the same.

Background Art

[0002] A multilayer glass in which a pressure-reduced layer is formed between two glass plates is also called a vacuum glass and has excellent heat insulation properties. In the manufacturing process of the vacuum glass, the outer peripheral edges of the two glass plates are sealed to ensure the pressure-reduced layer. The sealing material used at this time is typically glass frit as shown in Patent Document 1. The sealing of the outer peripheral edge is performed by applying the melted glass frit along the outer peripheral edges of the two glass plates and then re-solidifying it.

[0003] By the way, one of the manufacturing methods of a high-strength glass plate called tempered glass is the air-cooling strengthening method. As shown in Patent Document 2, the air-cooling strengthening method is a method of heating a glass plate to a high temperature of about 600°C to 700°C and then blowing air onto its surface for rapid cooling. At this time, the strength of the glass plate is increased by forming a compressive layer on the surface of the glass plate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors considered manufacturing a vacuum glass using an air-cooled strengthened glass sheet. However, at this time, when attempting to seal the outer peripheral edges of two air-cooled strengthened glass sheets with glass frit, the strength of the glass sheet increased by air-cooled strengthening decreased. This is because the melting point of the glass frit was still high even if it was called a low-melting glass frit, and when sealing the outer peripheral edge, the glass sheet was reheated to a high temperature by the heat during the melting of the glass frit. Therefore, even when using an air-cooled strengthened glass sheet, it is ultimately difficult to manufacture a vacuum glass with high strength.

[0006] An object of the present invention is to provide a vacuum glass with high strength.

Means for Solving the Problems

[0007] The vacuum glass according to the first aspect of the present invention includes an air-cooled strengthened first glass sheet, an air-cooled strengthened second glass sheet facing the first glass sheet with a pressure-reduced layer therebetween, and an outer peripheral seal portion that joins the outer peripheral edge of the first glass sheet and the outer peripheral edge of the second glass sheet so as to seal the pressure-reduced layer. The outer peripheral seal portion includes solder.

[0008] The vacuum glass according to the second aspect of the present invention is the vacuum glass according to the first aspect, wherein the first glass sheet and the second glass sheet are arranged such that the areas of the main surfaces are substantially the same and the edge surfaces extending in the thickness direction are substantially flush.

[0009] The vacuum glass according to the third aspect of the present invention is the vacuum glass according to the first aspect or the second aspect, wherein the solder is lead-free solder.

[0010] The vacuum glass according to the fourth aspect of the present invention is the vacuum glass according to any one of the first to third aspects, wherein the first glass plate and the second glass plate each have a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface. In a state where no external force is applied, the first glass plate and the second glass plate are warped in the same direction at both ends in the second direction when viewed from the first direction.

[0011] The vacuum glass according to the fifth aspect of the present invention is the vacuum glass according to any one of the first to third aspects, wherein the first glass plate and the second glass plate each have a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface. In a state where no external force is applied, the first glass plate and the second glass plate are warped so as to be separated from each other toward the outside in the second direction at both ends in the second direction when viewed from the first direction.

[0012] The vacuum glass according to the sixth aspect of the present invention is the vacuum glass according to any one of the first to third aspects, wherein the first glass plate and the second glass plate each have a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface. In a state where no external force is applied, the first glass plate and the second glass plate are warped so as to approach each other toward the outside in the second direction at both ends in the second direction when viewed from the first direction.

[0013] The method for manufacturing a vacuum glass according to the seventh aspect of the present invention includes the following steps. (1) A step of preparing a first glass plate and a second glass plate (2) A step of air-cooling and strengthening the first glass plate and the second glass plate respectively (3) After the air-cooling strengthening, a step of facing the first glass plate and the second glass plate so that a space is formed therebetween (4) Joining the outer peripheral edge of the first glass plate and the outer peripheral edge of the second glass plate with solder so as to seal the space between the first glass plate and the second glass plate (5) Reducing the pressure of the space between the first glass plate and the second glass plate by evacuation

[0014] The method for manufacturing a vacuum glass according to the eighth aspect of the present invention is the method for manufacturing a vacuum glass according to the seventh aspect, wherein the first glass plate and the second glass plate each have a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface. The first glass plate and the second glass plate faced in the facing step are warped in the same direction at both ends in the second direction when viewed from the first direction in a state where no external force is applied.

[0015] The method for manufacturing a vacuum glass according to the ninth aspect of the present invention is the method for manufacturing a vacuum glass according to the seventh aspect, wherein the first glass plate and the second glass plate each have a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface. The first glass plate and the second glass plate faced in the facing step are warped so as to be separated from each other toward the outside of the second direction at both ends in the second direction when viewed from the first direction in a state where no external force is applied.

[0016] The method for manufacturing a vacuum glass according to the tenth aspect of the present invention is the method for manufacturing a vacuum glass according to the seventh aspect, wherein the first glass plate and the second glass plate each have a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface. The first glass plate and the second glass plate faced in the facing step are warped so as to approach each other toward the outside of the second direction at both ends in the second direction when viewed from the first direction in a state where no external force is applied.

Advantages of the Invention

[0017] According to the above viewpoints of the present invention, the outer peripheral edges of two air-cooled strengthened glass plates are sealed with solder. Thereby, the outer peripheral edges of the glass plates can be sealed in a low-temperature environment, and the air-cooled strengthened glass plates are not excessively reheated. Therefore, the decrease in the strength of the air-cooled strengthened glass plates is suppressed, and a vacuum glass with high strength is provided.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 7C

Figure 8

Figure 9A

Figure 9B

Figure 10A

Figure 10B

Figure 11A

Figure 11B

Embodiments for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, a vacuum glass and a manufacturing method thereof according to an embodiment of the present invention will be described.

[0020] <1. Overall Configuration of Vacuum Glass> FIG. 1 shows a front view of a vacuum glass 1 according to an embodiment of the present invention, and FIG. 2 shows a side cross-sectional view thereof. The use of the vacuum glass 1 is not particularly limited, but in this embodiment, it is for building materials and is used as window glass or door glass of a building. As shown in these figures, the vacuum glass 1 is a glass structure including two glass plates 10 and 20. The glass plates 10 and 20 face each other via a decompression layer 3 and are arranged such that their main surfaces are parallel to each other. Hereinafter, the side surface (main surface) facing the outside of the glass plate 10 (hereinafter sometimes referred to as the first glass plate 10) is called the first surface T1, and the side surface (main surface) facing the inside of the first glass plate 10 (the decompression layer 3 side) is called the second surface T2. Also, the side surface (main surface) facing the inside of the glass plate 20 (hereinafter sometimes referred to as the second glass plate 20) is called the third surface T3, and the side surface (main surface) facing the outside of the second glass plate 20 is called the fourth surface T4. Note that, although not limited thereto, when installed in a building, the first glass plate 10 is arranged on the outdoor side and the second glass plate 20 is arranged on the indoor side.

[0021] The first glass plate 10 and the second glass plate 20 are substantially rectangular in shape, having two sides extending in the first direction D1 and two sides extending in the second direction D2 orthogonal thereto when viewed from the front. "Viewed from the front" means viewing the glass plates 10 and 20 from a direction orthogonal to their respective main surfaces. The first direction D1 corresponds to the left-right direction in FIG. 1, and the second direction D2 corresponds to the up-down direction in FIG. 1.

[0022] The first glass plate 10 and the second glass plate 20 are arranged such that the areas of their main surfaces are substantially the same, and their respective edge surfaces 10a and 20a extending in the thickness direction D3 are substantially flush. The thickness direction D3 is the direction orthogonal to the main surfaces T1 to T4 of the glass plates 10 and 20 (the horizontal direction in FIG. 2). The edge surface 10a is a surface extending between and connecting the outer peripheral edges of the first surface T1 and the second surface T2, and the edge surface 20a is a surface extending between and connecting the outer peripheral edges of the third surface T3 and the fourth surface T4.

[0023] Between the first glass plate 10 and the second glass plate 20, a large number of spacers 30 having substantially the same thickness are arranged on the second surface T2 and the third surface T3, which are the surfaces facing the inside of both. The spacers 30 are arranged at regular intervals in the first direction D1 and the second direction D2, at positions corresponding to the vertices of the lattice when viewed from the front. The arrangement interval of the spacers 30 is preferably 5 to 100 mm, more preferably 5 to 80 mm, and even more preferably 5 to 60 mm. And by these spacers 30, a pressure-reduced layer 3 having a certain thickness corresponding to the thickness of the spacers 30 is secured between the second surface T2 of the first glass plate 10 (more precisely, the low-emissivity film 11 described later) and the third surface T3 of the second glass plate 20. The pressure-reduced layer 3 is reduced in pressure from the standard atmospheric pressure and is typically 1.33 Pa or less, and is also called a vacuum layer. Such a substantially vacuum state pressure-reduced layer 3 suppresses heat conduction and convection between the outdoor side and the indoor side of the vacuum glass 1, thereby preventing the indoor heat from escaping to the outdoor side and imparting high heat insulation performance to the vacuum glass 1.

[0024] The first glass plate 10 of this embodiment is a Low-E glass, and a low-emissivity film (Low-E film) 11 is laminated substantially over the entire surface on the second surface T2. The low-emissivity film 11 suppresses heat radiation and contributes to further improving the heat insulation performance of the vacuum glass 1. Considering the high performance of the low-emissivity film 11 to be formed, the sputtering method is preferably selected as the film formation method of the low-emissivity film 11, but it is not limited thereto. For example, the CVD (chemical vapor deposition) method can also be selected.

[0025] Further, an outer peripheral seal portion 31 is disposed between the first glass plate 10 and the second glass plate 20 over the entire circumference along the outer peripheral edge portions of both glass plates 10 and 20. The outer peripheral seal portion 31 is a member for ensuring a substantially vacuum state of the decompression layer 3, and joins the outer peripheral edge portion of the first glass plate 10 and the outer peripheral edge portion of the second glass plate 20 so as to seal the decompression layer 3 between both glass plates 10 and 20. The outer peripheral seal portion 31 is mainly made of solder and is metallic. The liquidus temperature of the solder used here is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. Here, the liquidus temperature indicates the temperature at which the solder is completely melted and can be measured by, for example, differential scanning calorimetry (DSC).

[0026] The outer peripheral seal portion 31 of the present embodiment contains solder as described above. The outer peripheral seal portion 31 can further include a protective film for protecting the solder. The protective film is, for example, made of resin. The solder is preferably lead-free solder. For example, lead-free solder containing Sn and Zn can be used. Further, the lead-free solder preferably contains at least one of Ag, Ti, and Al. The content of Sn is preferably 90.0% or more. The content of Zn is preferably 0.001 to 10%. Also, the content of Ag is preferably 0 to 6.0%, more preferably 0 to 3.5%. The content of Ti is preferably 0 to 3.0%. The content of Al is preferably 0 to 3.0%, more preferably 0 to 1.0%. The lead-free solder preferably contains at least one of Bi, Si, and Sb in a total range of 10% or less. Also, the content of Si is preferably 0 to 1.0%, more preferably 0 to 0.1%. Also, the lead-free solder preferably contains In. The lead-free solder preferably contains at least one of Fe, Ni, Co, Ga, Ge, and P, and the total content thereof is preferably 1.0% or less.

[0027] Both the first glass plate 10 and the second glass plate 20 are tempered glass that has been air-cooled and strengthened. In the present embodiment, a float glass plate is air-cooled and strengthened. That is, the glass plates 10 and 20 are manufactured by heating a float glass plate to a high temperature of about 600°C to 700°C and then blowing air onto its surface for rapid cooling. As a result, a compressive force is generated on the surfaces of the glass plates 10 and 20, and a tensile force is generated inside, enhancing the strength of the glass plates 10 and 20. Although not limited thereto, typically, when a crushing test is performed based on JIS (Japanese Industrial Standard) R3206, a glass plate in which the number of fragments within a 50×50 mm square area is 40 or more can be called tempered glass.

[0028] Figures 9A and 9B show the results of a crushing test on samples of an air-cooled tempered glass sheet (TP3) manufactured by Nippon Sheet Glass Co., Ltd. that were heat-treated at two different temperatures. The heat treatment at this time was such that the space where the samples were placed was heated starting from room temperature at a rate of 10 °C / min until the temperature reached T °C, and the temperature was maintained for 30 minutes at that point, and then cooled to return to room temperature. The size of the samples was 300 mm × 300 mm × 3 mm. Figure 9A shows the results for T = 300 °C, and Figure 9B shows the results for T = 350 °C. From Figures 9A and 9B, it was found that the degree of relaxation of the strengthening when the air-cooled tempered glass sheet was heated to 300 °C was very small compared to when it was heated to 350 °C.

[0029] Figures 10A and 10B are graphs published in the paper by Novotny.V and Kavka.J. ("Stress relaxation in toughened glass", "Glass Technology", Vol. 18, No. 5, pp. 148 - 151, October 1977). However, the line along 0.1 on the horizontal axis was added by the applicant for the purpose of explanation. Figures 10A and 10B are graphs showing the progress of relaxation of strengthening for tempered glass sheets with thicknesses of 4.6 mm and 9.5 mm, respectively, for various heating temperatures. The horizontal axis represents the heating time (hours), and the vertical axis represents the ratio of the current stress to the initial stress (hereinafter referred to as the stress ratio). The smaller the value of the stress ratio on the vertical axis, the more the strengthening has been relaxed. These graphs show that, for example, if the heating time is about 0.1 hour, relaxation of strengthening does not occur when the heating temperature is 300 °C or lower. On the other hand, even if the heating time is about 0.1 hour, relaxation of strengthening can occur if the heating temperature is 500 °C or higher, such as the melting point of a conventional sealing material that seals the outer peripheral edge of the glass sheet.

[0030] From the above, it was confirmed that the liquidus temperature of the solder used for the outer peripheral seal portion 31 is preferably 300°C or lower. In this case, the outer peripheral edges of the glass plates 10 and 20 can be sealed at 300°C or lower, the glass plates 10 and 20 are not excessively reheated, and a decrease in the strength of the air-cooled reinforced glass plates 10 and 20 can be effectively suppressed.

[0031] Let the thicknesses (average thickness when there are variations) of the first glass plate 10, the second glass plate 20, the pressure-reducing layer 3, and the low-emissivity film 11 be d1, d2, d3, and d4, respectively. The values of d1 to d4 can be appropriately selected according to the application, but preferably 0.3 mm ≤ d1 ≤ 15 mm, more preferably 0.5 mm ≤ d1 ≤ 12 mm, and even more preferably 1 mm ≤ d1 ≤ 10 mm. The same applies to d2, and d1 and d2 can be the same value or different values. Also, preferably 0.03 mm ≤ d3 ≤ 1 mm, more preferably 0.05 mm ≤ d3 ≤ 0.5 mm, and even more preferably 0.1 mm ≤ d3 ≤ 0.3 mm. Also, preferably 50 nm ≤ d4 ≤ 600 nm, more preferably 50 nm ≤ d4 ≤ 500 nm, and even more preferably 50 nm ≤ d4 ≤ 400 nm. When d1 to d4 satisfy the above numerical ranges, while reducing the thickness of the vacuum glass 1, the heat insulation performance can be easily enhanced.

[0032] As shown in FIG. 1, a through hole 15 is formed near one corner of the second glass plate 20. The through hole 15 is sealed with a sealing material. The through hole 15 is used for evacuating the space between the glass plates 10 and 20 to form the pressure-reducing layer 3 and is then sealed. As the sealing material for sealing the through hole 15, for example, solder can be used, and in this case, it is preferable to use lead-free solder. Note that the through hole 15 may be formed in the first glass plate 10.

[0033] <2. Manufacturing method> Next, a method for manufacturing the vacuum glass 1 will be described. First, a float glass sheet 2 cut into a predetermined shape, which will ultimately be processed into the first glass sheet 10 and the second glass sheet 20, is prepared. Here, two types of float glass sheets 2 are prepared. One float glass sheet 2 (hereinafter sometimes referred to as 2a) has a low-emissivity film 11 formed on one main surface and will ultimately become the first glass sheet 10. The other float glass sheet 2 (hereinafter sometimes referred to as 2b) does not have a low-emissivity film 11 formed thereon, and the surface of the glass is exposed, and it will ultimately become the second glass sheet 20. Further, through holes 15 for evacuation are formed in the float glass sheet 2b.

[0034] Next, these float glass sheets 2 are air-cooled and strengthened. FIG. 3 is a schematic diagram of equipment for performing air-cooling strengthening. The float glass sheet 2 is conveyed on a roller conveyor 40 including a number of rollers 40a. At this time, the float glass sheet 2a is placed on the roller conveyor 40 with the low-emissivity film 11 facing upward. The float glass sheet 2 is first placed on the roller conveyor 40 and introduced into the heating furnace 45, where it is exposed to a high-temperature environment for a predetermined time and heated to about 600°C to 700°C. Then, the float glass sheet 2 thus heated to a high temperature is placed on the roller conveyor 40 and introduced into the cooling furnace 46. In the cooling furnace 46, air is blown onto the surface of the float glass sheet 2 on the roller conveyor 40 from above and below through nozzles 48 for a predetermined time, and the float glass sheet 2 is rapidly cooled. As a result, a compressive force is generated on the surface of the float glass sheet 2, while a tensile force is generated inside, and as a result, the strength of the float glass sheet 2 is increased. In this embodiment, the roller conveyor 40 reciprocates the float glass sheet 2 in the heating furnace 45 and the cooling furnace 46 during the heating and cooling of the float glass sheet 2, respectively.

[0035] As shown in FIG. 2, the glass plates 10 and 20 included in the vacuum glass 1 are both substantially flat. However, as described above, the float glass plate 2 strengthened by air cooling, in a state where no external force is applied, has a shape in which both ends in the second direction D2 are warped when viewed from the first direction D1, as shown in FIGS. 4A and 4B. That is, through the processes of heating and rapid cooling, warping occurs at both ends of the glass plate 2. When air cooling strengthening is performed with the equipment as described above, the directionality of the warping depends on the conveyance direction of the roller conveyor 40, the direction parallel to the conveyance direction becomes the second direction D2, and the first direction D1 is orthogonal to the conveyance direction.

[0036] Also, when air cooling strengthening is performed with the equipment as described above, the surface of the float glass plate 2 that is not in contact with the roller 40a (the upper surface in FIG. 3) is less likely to be contaminated than the surface in contact with the roller 40a (the lower surface in FIG. 3). The contamination referred to here is typically organic contamination such as oil. In FIGS. 4A and 4B, the surface indicated by the dotted line of the float glass plate 2 is the surface that is not in contact with the roller 40a. According to the research of the inventors, the glass plate 2 tends to warp in the same direction mainly at both ends in the second direction D2. In FIG. 4A, when the surface not in contact with the roller 40a is taken as the upper surface, both ends in the second direction D2 are warped upward, and in FIG. 4B, when the surface not in contact with the roller 40a is taken as the upper surface, both ends in the second direction D2 are warped downward. Which type of glass plate 2 is manufactured tends to depend on the specifications of the glass plate 2 and the air cooling strengthening equipment (for example, the size of the glass plate 2, and the size and interval of the rollers 40a), etc.

[0037] The inventors confirmed the above tendency through experiments. The inventors manufactured 10 float glass plates strengthened by air cooling by the above-described method in the same air-cooling strengthening facility, and measured the warpage shapes at both ends of these glass plates. The measurement of the warpage shapes at both ends was performed as follows. FIG. 5 is a diagram for explaining the method of measuring the warpage shapes at both ends. The glass plate was placed on a metal surface plate with the surface not in contact with the roller facing upward. Then, rails were installed along two sides extending in the second direction D2 of the glass plate, and a laser displacement meter (LK-G30 manufactured by Keyence Corporation) was scanned parallel to the two sides along these rails. The origin of the measurement and the scanning direction are shown in FIG. 5. The origin was aligned with the edge of the glass plate in the scanning direction, and for the direction perpendicular to the scanning direction, since a measurement error would occur if it was on the edge, it was set to 5 mm inside from the edge of the glass plate to avoid this. The length of the glass plate in the second direction D2 was 900 mm. The measurement pitch was 20 mm, and the measurement points were located at positions 5 mm, 25 mm, 45 mm, ···, 865 mm, 885 mm, 895 mm from the origin. The scanning by the laser displacement meter was performed from above the glass plate. The distance d0 between the metal surface plate and the displacement meter at the origin was measured, and further, while moving the laser displacement meter, the distance d from the laser displacement meter to the upper surface of the glass plate was measured at each measurement point. Separately, the thickness h of the glass plate was measured. The thickness h was measured at the plate thicknesses at the four corners of the glass plate and taken as the average value. And the displacement amount (the distance between the metal surface plate and the lower surface of the glass plate) d g was calculated as d g = d0 - (h + d).

[0038] The measurement results of the warpage shapes at both ends based on the displacement amount d g are shown in FIGS. 6A and 6B. FIG. 6A is a graph showing the measurement of the displacement amount d g of one side (long side 1 in FIG. 5) along the second direction D2 of the glass plate having 10 Low-E films, and FIG. 6B is a graph showing the displacement amount d gIt is a graph obtained by measurement. From 10 glass plates corresponding to FIGS. 6A and 6B, it was confirmed that both ends in the second direction D2 tend to warp upward, which is the type shown in FIG. 4A. The inventors also confirmed that a warping tendency as shown in FIG. 4B appears depending on the conditions of air-cooling strengthening. Here, although it was verified with a glass plate having a Low-E film, it was also confirmed that a warping tendency as shown in FIGS. 4A and 4B appears similarly even in a normal float glass plate without a Low-E film.

[0039] FIG. 11A shows the results of measuring the warpage amount d1 at the ends of five tempered glass plates G1 to G5 without a Low-E film, and FIG. 11B shows the results of measuring the warpage amount d1 at the ends of two tempered glass plates H1 and H2 with a Low-E film. The tempered glass plates G1 to G5, H1, and H2 are all float glass plates, heated at 700° C. for 5 minutes, and air-cooled and strengthened. The Low-E films of the tempered glass plates H1 and H2 were formed to be about 85 nm. The sizes of the tempered glass plates G1 to G5 and H1 and H2 were as follows. [Table 1]

[0040] In the experiments of FIGS. 11A and 11B, in addition to the warpage amount d1 at the end of the glass plate, the warpage start position d2 from the end of the glass plate was also measured. FIGS. 11A and 11B are graphs plotting the relationship between the warpage amount d1 and the warpage start position d2. d1 and d2 are defined as shown in FIGS. 4A and 4B and were measured using the measuring device described with reference to FIG. 5. More specifically, the glass plate was placed on a metal surface plate, a rail extending in the second direction D2 was prepared, and while moving a laser displacement meter (LK-G30 manufactured by Keyence Corporation) along this rail in the second direction D2, with a measurement pitch of 20 mm, the distance d from the laser displacement meter to the upper surface of the glass plate was measured at each measurement point. However, the measurement pitch in the second direction D2 was 2 mm from the edge of the glass plate to the first measurement point and the fourth measurement point. Further, the above scanning along the second direction D2 was repeated while leaving a 20 mm interval in the first direction D1. As a result, the distance d was measured in a grid pattern at 20 mm × 20 mm intervals on the glass plate. Also, regarding the first direction D1, scanning along the edge of the glass plate was not performed. Scanning was performed in the second direction D2 from 5 mm inside the edge of the glass plate in the first direction D1, and then the scanning in the second direction D2 was repeated while leaving a 20 mm interval in the D1 direction. The scanning by the laser displacement meter was performed from above the glass plate.

[0041] Then, while sequentially checking the values of a series of distances d measured during each scan along the second direction D2 in the scan direction, the position where the change amount of the value of the distance d first becomes 0, the position where the value of the distance d first changes from increasing to decreasing, or the position where the value of the distance d first changes from decreasing to increasing was defined as the warpage start position d2. For example, along the second direction D2, assume that from the first measurement point to the measurement point 60 mm away, the distance d increases monotonically, but at the measurement point 80 mm away from the first measurement point, the distance d first changes from increasing to decreasing for the first time. In this case, the warpage start position d2 = 80 mm. On the other hand, the warpage amount d1 is defined as the difference between the distance d measured at the edge and the distance d measured at the warpage start position d2.

[0042] From the results of FIGS. 11A and 11B, it was confirmed that warping can occur at the edges of the tempered glass plate regardless of the presence or absence of the Low-E film. However, it was confirmed that the warping amount d1 at the edge of the glass plate is larger when there is no Low-E film, and the warping ratio d1 / d2 at the edge of the glass plate is larger when there is a Low-E film. Also, it was found that the warping amount d1 is generally within 0.6 mm even considering the variation at the measurement points.

[0043] Also, in the experiments of FIGS. 11A and 11B, the outer peripheral seal portions were formed on the tempered glass plates G1 to G5, H1, and H2 using solder. When the surface compressive stress values (average) of the tempered glass plates G1 to G5, H1, and H2 were measured before and after this heating, there was no change before and after heating, and they were 99 MPa, 100 MPa, 80 MPa, 90 MPa, 98 MPa, 98 MPa, and 99 MPa, respectively. Therefore, it was also confirmed that the tempering of the tempered glass plate is not relaxed by heating with solder.

[0044] Returning to the description of the manufacturing method, after air-cooling tempering, the float glass plate 2a that will become the first glass plate 10 and the float glass plate 2b that will become the second glass plate 20 are faced so that a space that will finally become a reduced-pressure layer is formed between them. Specifically, the glass plate 2a is placed on the workbench 54 shown in FIG. 8 with the low-emissivity film 11 facing upward, and the spacers 30 are arranged in a predetermined pattern on the upper surface of the glass plate 2a. Then, the glass plate 2b is placed on top of it. As preferable modes of the pattern for facing the glass plates 2, three patterns of FIGS. 7A to 7C can be considered. Also, in FIGS. 7A to 7C, similar to FIGS. 4A and 4B, the surface indicated by the dotted line of the float glass plate 2 is the surface that does not contact the roller 40a in the air-cooling tempering process.

[0045] FIG. 7A shows a pattern (hereinafter referred to as Pattern 1) in which the float glass plate 2 is warped in the same direction at both ends in its second direction D2. FIG. 7B shows a pattern (hereinafter referred to as Pattern 2) in which the float glass plate 2 is warped at both ends in its second direction D2 so as to be farther apart from each other toward the outside of the second direction D2. FIG. 7C shows a pattern (hereinafter referred to as Pattern 3) in which the float glass plate 2 is warped at both ends in its second direction D2 so as to approach each other toward the outside of the second direction D2. Note that the warpage of the glass plate 2 shown in FIGS. 4A, 4B, and 7A to 7C is described with emphasis for easy understanding of the explanation. However, the amount of warpage with respect to the thickness of the glass plate 2 is actually smaller than these figures, and it can be said that the glass plate 2 is substantially flat visually. Therefore, which pattern the glass plate 2 belongs to can be determined as follows.

[0046] First, in the same measurement method as described with reference to FIG. 5, the displacement amount d of the glass plate is measured at a measurement pitch of 20 mm along the second direction D2 from the origin. g And within the graph regions as shown in FIGS. 6A and 6B, these displacement amounts d gDraw a line graph passing through the measurement points. Then, identify the first minimum or maximum point (hereinafter referred to as the extreme point) that appears on the line graph along the second direction D2 from the origin. If the extreme point is within 100 mm from the origin, determine whether the line graph is going upward or downward as it goes outward in the section from the origin to the extreme point. If it is going upward, it is determined that the end on the origin side is warped upward along the second direction of the glass plate. If it is going downward, it is determined that the end is warped downward. On the other hand, if the extreme point is not within 100 mm from the origin, determine whether the line graph is going upward or downward as it goes outward in the section of 100 mm from the origin. If it is going upward, it is determined that the end on the origin side is warped upward along the second direction of the glass plate. If it is going downward, it is determined that the end is warped downward. Here, the extreme point is a point where the positive and negative of the slope of the line graph are interchanged before and after it. Also, at the end of the glass plate on the side opposite to the origin along the second direction, similarly, pay attention to the section of 100 mm from the end of the line graph, and determine whether the end is warped upward or downward. Then, as described above, identify the warping directions of both ends of the glass plate along the second direction, and based on this, identify the warping pattern.

[0047] In Pattern 1 of FIG. 7A, the upper glass plate 2 in the figure is the glass plate 2a on which the low-emissivity film 11 is formed. That is, since the low-emissivity film 11 is finally arranged to face the decompression layer 3, it is arranged to face the inside. In Pattern 1, since both ends in the second direction D2 are bent in the same direction, the distance between the glass plates 2a and 2b is generally constant at these ends. Therefore, in the soldering process described later, it is easy to insert a solder introduction plate between the two glass plates 2, and the process becomes easy. As a result, stable adhesive strength can be obtained.

[0048] However, when the amount of warpage at the edge of the glass plate increases, the adhesive strength may decrease. Therefore, in Pattern 1 of FIG. 7A, from the perspective of facilitating the insertion of the solder introduction plate and ensuring stable adhesive strength, the amount of warpage is preferably 0.1 mm or more and 0.6 mm or less. Note that the amount of warpage referred to here is the displacement amount d g measured as described above.

[0049] Also, in the form of Pattern 1 of FIG. 7A, a vacuum glass having a Low-E film formed only on one glass plate may be manufactured. In this case, as described above, when there is a Low-E film, the amount of warpage at the edge of the glass plate becomes small, so it is easy to insert the solder introduction plate between the glass plates, and stable adhesive strength can be ensured.

[0050] In Pattern 2 of FIG. 7B, either of the glass plates 2 may be the glass plate 2a. In Pattern 2, the space between the glass plates 2a and 2b is open at both ends in the second direction D2. Therefore, in the soldering process described later, it is easy to insert the solder introduction plate between the two glass plates 2, and the process becomes easier. In view of this effect, Pattern 2 can be preferably adopted when the vacuum glass 1 is composed of the glass plates 2a and 2b that do not have a Low-E film, that is, the amount of warpage at the edge is large (see the results in FIG. 11A). Also, in the example of FIG. 7B, since the surfaces with less dirt adhesion (the surfaces not in contact with the roller 40a) of the glass plates 2a and 2b both face inward, there is no dirt that hinders the evacuation process described later, and the control of the process becomes easy. However, in either or both of the glass plates 2a and 2b, the surface not in contact with the roller 40a in the air-cooling strengthening process may face outward. Even in this case, in the soldering process, it is easy to insert the solder introduction plate between the two glass plates 2, and the process becomes easier.

[0051] As described above, when the amount of warping at the end of the glass plate increases, the adhesive strength may decrease. Therefore, in Pattern 2 of FIG. 7B, from the viewpoint of facilitating the insertion of the solder introduction plate and ensuring stable adhesive strength, the amount of warping is preferably 0.1 mm or more and 0.6 mm or less. Note that the amount of warping referred to here can also be measured as the displacement amount d g described above.

[0052] In the form of Pattern 2 of FIG. 7B, a vacuum glass having a Low-E film formed only on one glass plate may be manufactured. In this case, as described above, when there is a Low-E film, the amount of warping at the end of the glass plate is reduced, so that it is easy to insert the solder introduction plate and stable adhesive strength can be ensured. Particularly from the viewpoint of ensuring adhesive strength, such a vacuum glass is superior to the case where there is no Low-E film on both glass plates.

[0053] In Pattern 3 of FIG. 7C, either of the glass plates 2 may be the glass plate 2a. In Pattern 3, the space between the glass plates 2a and 2b is closed at both ends in the second direction D2. Therefore, in the soldering process described later, it is excellent in that the outer peripheral seal portion 31 of the solder formed between the glass plates 2a and 2b is difficult to peel off. In view of this effect, Pattern 3 can be preferably adopted when the vacuum glass 1 is composed of the glass plates 2a and 2b having a Low-E film, that is, when the ratio d1 / d2 of the warping at the end increases (see the results of FIG. 11B). Further, in the example of FIG. 7C, since the surfaces with less dirt adhesion (the surfaces not in contact with the roller 40a) of the glass plates 2a and 2b both face inward, there is no dirt that inhibits the same process in the evacuation process described later, and the control of the same process becomes easy. However, in either or both of the glass plates 2a and 2b, the surface not in contact with the roller 40a in the air-cooling strengthening process may face outward. Even in this case, it is excellent in that the outer peripheral seal portion 31 is difficult to peel off. Note that in the form of Pattern 3, if the amount of warping at the end of the glass plate becomes too large and the ends of the glass plates may interfere with each other, the thickness of the decompression layer may be adjusted and set to a value that can avoid such a situation.

[0054] After arranging the glass plates 2a and 2b to face each other, the outer peripheral edges of the glass plates 2a and 2b are joined by solder so as to seal the space between the glass plates 2a and 2b. At this time, a solder supply device 50 as shown in FIG. 8 is used. The solder supply device 50 includes a storage container 51 for storing molten solder, and a discharge pipe 52 that communicates with a hole formed in the bottom surface of the storage container 51 and discharges the molten solder from the hole. The storage container 51 is provided with a heater 51a for maintaining the molten state of the solder. The tip of the discharge pipe 52 is aligned with the space between the glass plates 2a and 2b at the outer peripheral edges of the glass plates 2a and 2b, and an introduction plate 53 is inserted inside the tip of the discharge pipe 52. The introduction plate 53 is a member for guiding and introducing the solder between the glass plates 2a and 2b. The introduction plate 53 protrudes from the discharge pipe 52, and the protruding portion is inserted into the space between the glass plates 2a and 2b. Note that the tip of the introduction plate 53 can be formed in a deformable bellows shape. In this case, soldering can be performed while rubbing the surfaces of the glass plates 2a and 2b with the tip of the introduction plate 53, and the joining strength can be increased. Therefore, when the thickness of the tip of the introduction plate 53 is d5, d5>d3 (the thickness of the reduced pressure layer 3) may be satisfied. The housing 55 that supports the storage container 51 and the discharge pipe 52 is also placed on the workbench 54 on which the glass plates 2a and 2b are placed, and moves along the outer peripheral edges of the glass plates 2a and 2b on the workbench 54. To assist this movement, a rail 56 corresponding to a groove provided in the lower part of the housing 55 is provided on the workbench 54.

[0055] Subsequently, the space between the glass plates 2a and 2b is evacuated to reduce the pressure. More specifically, an exhaust cup is attached onto the glass plate 2a so as to cover the through-hole 15 of the glass plate 2a. Then, gas molecules within the space between the glass plates 2a and 2b are suctioned through the through-hole 15 by a pump such as a rotary pump or a turbo molecular pump connected to this exhaust cup. Thereafter, solder as a sealing material is dropped onto the through-hole 15 to bond the surface of the glass plate 2a near the through-hole 15 and the solder. Thereby, the through-hole 15 is sealed, and a reduced-pressure layer 3 is formed between the glass plates 2a and 2b.

[0056] The warpage of the glass plates 2a and 2b is eliminated or alleviated through the evacuation process, and substantially flat first glass plate 10 and second glass plate 20 are formed. Thus, the vacuum glass 1 having a pair of air-cooling enhanced glass plates 10 and 20 is manufactured.

[0057] As described above, one embodiment of the present invention has been explained. However, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit thereof.

[0058] For example, in the above embodiment, the glass plate 10 is a glass plate having a Low-E film, but it may be an ordinary float glass plate without a Low-E film.

Explanation of Reference Numerals

[0059] 1 Vacuum glass 2 Float glass plate 10 First glass plate 10a Edge surface 20 Second glass plate 20a Edge surface 3 Reduced-pressure layer 30 Spacer 31 Outer peripheral seal portion D1 First direction D2 Second direction T1 First surface (main surface) T2 Second surface (main surface) T3 Third surface (main surface) T4 Side 4 (Main Side)

Claims

1. A first glass plate with enhanced air cooling, A second glass plate with enhanced air cooling, facing the first glass plate with a decompression layer in between, An outer peripheral seal part that joins the outer peripheral edge of the first glass plate and the outer peripheral edge of the second glass plate so as to seal the decompression layer, The outer peripheral seal part contains solder, The first glass plate and the second glass plate, Each has a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface, In a state where no external force is applied, when viewed from the first direction, at both ends in the second direction, it is warped so as to be separated from each other toward the outside in the second direction, A vacuum glass in which the warpage amounts of the first glass plate and the second glass plate in the second direction are 0.1 mm or more and 0.6 mm or less.

2. The vacuum glass according to claim 1, wherein the first glass plate and the second glass plate are arranged such that the areas of the main surfaces are substantially the same and the edge surfaces extending in the thickness direction are substantially flush.

3. The vacuum glass according to claim 1 or 2, wherein the solder is lead-free solder.

4. A method for manufacturing a vacuum glass, comprising: Preparing a first glass plate and a second glass plate; Air-cooling and strengthening the first glass plate and the second glass plate respectively; After the air-cooling strengthening, facing the first glass plate and the second glass plate so that a space is formed between them; Joining the outer peripheral edge of the first glass plate and the outer peripheral edge of the second glass plate with molten solder so as to seal the space between the first glass plate and the second glass plate; Including the step of decompressing the space between the first glass plate and the second glass plate by evacuation; The first glass plate and the second glass plate each have a substantially rectangular shape having two sides extending in a first direction and two sides extending in a second direction orthogonal to the first direction when viewed from a direction orthogonal to the main surface; The first glass plate and the second glass plate faced in the facing step are warped so as to be separated from each other toward the outside in the second direction at both ends in the second direction when viewed from the first direction in a state where no external force is applied. A method for manufacturing a vacuum glass, wherein the warpage amount of the first glass plate and the second glass plate in the second direction is 0.1 mm or more and 0.6 mm or less.

Images