JP2004091311A - Tempered glass sheet and method and apparatus for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tempered glass sheet having a thickness thinner than that of a conventional tempered glass sheet. <P>SOLUTION: The tempered glass sheet is constituted of residual compressive stress layers formed in the surfaces of the glass sheet and a residual compressive stress layer formed inside the glass sheet, and the strength of the glass sheet is increased by the balance of the residual stresses in these layers. The tempered glass sheet has in its front view a circular peripheral region including the peripheral edge parts and a central region (9) which occupies inner circle side of the peripheral region. The average surface compressive stress in the central region (9) is larger than that of the peripheral region. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tempered glass plate, a manufacturing method thereof, and a manufacturing apparatus.
[0002]
[Prior art]
In recent years, social interest in environmental issues has increased, and in the automobile industry, there has been a strong demand for fuel-saving automobiles, which requires measures such as reducing the weight of the vehicle body. Therefore, the weight reduction of automobile parts is required more than ever, and it is no exception to automobile window glass.
[0003]
In order to ensure the safety of passengers in automobile window glass, laminated glass is used for the windshield, and tempered glass plates are used for door glass, rear glass, etc., except for some vehicle types. Therefore, reducing the weight of the tempered glass plate, that is, reducing the thickness of the tempered glass plate leads to a reduction in the weight of the automobile.
[0004]
The tempered glass sheet for automobiles is generally manufactured by air cooling strengthening as described below. First, a glass plate is carried into a heating furnace and heated to near the softening point. The glass plate is taken out of the furnace after forming, or is formed after taking out of the furnace, and immediately cooled air is blown onto the surface of the glass plate for rapid cooling. The cooling air is blown toward the glass plate from a plurality of cooling nozzles disposed on both sides of the glass plate. At this time, since the temperature drop of the surface layer of the glass plate is faster than the inner layer, a temperature difference occurs between the inside and the surface in the cross-sectional direction, and as a result, in the direction of tension in the surface and compression in the inside. Thermal stress is generated. However, since glass has viscous flow when the temperature is near the softening point, the thermal stress relaxes and disappears due to the stress relaxation phenomenon, and there is a temperature difference between the inside and the surface in the cross-sectional direction of the glass plate. There will be no state.
[0005]
Since glass is elastic at room temperature, if cooling progresses and the glass plate finally reaches room temperature, the direction of force is reversed by the amount of thermal stress relaxed at high temperature, and a residual compressive stress layer is formed on the surface of the glass plate. A residual tensile stress layer is formed inside and a tempered glass plate is obtained.
[0006]
Since the tempered glass sheet is manufactured as described above, the magnitude of the residual stress of the tempered glass sheet depends on the state of occurrence of thermal stress due to the temperature distribution generated on the inside and the surface in the cross-sectional direction of the glass sheet during rapid cooling and its relaxation phenomenon. Depends on. Therefore, as the plate thickness of the glass plate is thinner, it is difficult to increase the temperature difference between the surface of the glass plate and the inside of the glass plate, and the residual stress is reduced. A harmful effect due to a decrease in the residual compressive stress on the surface of the glass plate is a decrease in the strength of the glass plate. The adverse effect of the decrease in the residual tensile stress inside the glass plate is that when the glass plate is broken, the number of fragments is reduced and the area of the fragments is increased. If the shards become large, the glass has sharp angles and is dangerous when broken.
[0007]
Therefore, the regulations on the tempered glass sheet for automobiles stipulate the provisions regarding the state of fragments when the tempered glass sheet is crushed by applying a local impact to the tempered glass sheet. That is, when the tempered glass sheet is crushed, select the region where the number of fragments in the square area of 50 × 50 mm is the maximum and the region where the number is the minimum, and the minimum and maximum values of the number of fragments in these regions are Those that do not meet this standard are not allowed to be used as tempered glass sheets for automobiles. In addition, strips (splines), which are elongated fragments, have a prescribed length that does not exceed 75 mm and the maximum allowable area of the fragments. Such regulations regarding the fragments when the tempered glass sheet for automobiles is crushed are in the ECE standard, JIS standard, and the like.
[0008]
In other words, since the number of fragments when the tempered glass sheet is crushed depends on the internal residual tensile stress, reducing the thickness of the glass sheet generates more residual stress than conventional tempered glass sheet manufacturing methods. If the manufacturing method to be used is not used, the residual stress required to satisfy the laws and regulations stipulated as tempered glass sheets for automobiles cannot be obtained.
[0009]
The current mainstream tempered glass sheet for automobiles has a thickness of about 2.8 to 5 mm. When reducing the weight of a tempered glass sheet for automobiles, it is necessary to make the sheet thickness thinner. As a method for strengthening the thin glass, in order to give a sufficient temperature difference between the inside and the surface in the cross-sectional direction of the glass plate, the cooling capacity (capability value for cooling the glass plate by the cooling means) is set to the current mainstream thickness (2. It can be considered that it is higher than that at the time of manufacturing a tempered glass plate of 8 to 5 mm. The thin glass here refers to a glass plate that is thinner than the thickness of a tempered glass plate for automobiles currently used.
[0010]
In the case of air cooling enhancement, in order to increase the cooling capacity, means such as increasing the wind pressure of the cooling air or bringing the nozzle tip close to the glass plate is required. However, in order to increase the wind pressure of the cooling air, it is necessary to increase the blower capacity, which is very expensive and has problems such as noise.
[0011]
Further, for example, as shown in the schematic cross-sectional view of the conventional tempered glass plate manufacturing apparatus in FIG. 11, bringing the nozzle tip 41b close to the glass plate 39 means that the cooling ring 42 collides with the nozzle tip 41b. There is a problem of interference with tools, etc., and there is a limit. Moreover, when manufacturing a tempered glass plate, it is necessary to slide the glass plate to prevent extreme spots (stress pattern) in the cooling state of the surface of the glass plate during rapid cooling, but it has a double curved surface. The glass plate cannot be slid by bringing the tip of the nozzle closer to the glass plate.
[0012]
As another method of strengthening the thin glass, it is conceivable to increase the temperature of the glass plate at the start of cooling. If the temperature of the glass plate rises, the temperature difference between the glass surface and the glass center can be increased during cooling, and sufficient residual stress can be obtained. However, since another problem of deterioration of optical quality occurs, there is a limit to increasing the temperature of the glass plate.
[0013]
As another method, a method using compressor air is known as a method for strengthening thin glass (see, for example, Patent Documents 1 and 2). In the method of Patent Document 1, the compressor air is added to the blower air blown to the glass plate at the time of rapid cooling, the shock wave of the compressor air is used to efficiently cool the glass plate with the blower air, and the surface of the glass plate and the glass plate This is a method of strengthening the thin glass by increasing the temperature difference at the center.
[0014]
In the method of Patent Document 2, the compressor air is partially added to the blower air, the compressor air is sprayed only on the “parts that are difficult to cool”, and the “parts that are difficult to cool” of the glass plate are cooled with a higher cooling capacity than the other parts. Then, the glass plate is uniformly cooled over the entire surface, and the equipment cost and the operation cost, which are the problems of the invention of Patent Document 1, can be reduced.
[0015]
[Patent Document 1]
Japanese Examined Patent Publication No. 6-24995 (Fig. 2-5)
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-26434 (Fig. 1-4)
[0016]
[Problems to be solved by the invention]
However, since the method of Patent Document 1 introduces a new compressor air, the current equipment must be significantly modified, and a large receiver tank or the like is required to supply a stable compressor air. As a result, the equipment will become excessive and the operating cost will increase.
[0017]
Moreover, when the glass plate heated to near the softening point is rapidly cooled, a thermal stress in the tensile direction is generated on the surface of the glass plate due to a temperature difference between the surface layer of the glass plate and the inner layer. Since the glass plate is in a viscous flow, the thermal stress relaxes and disappears due to the stress relaxation phenomenon, but because this method has too high cooling capacity, the thermal stress generated immediately after the start of cooling is too large, The relaxation rate cannot keep up with the generation rate of the thermal stress, and the thermal stress that cannot be completely relaxed on the surface of the glass plate is generated as a tensile stress. As a result, fine flaws existing on the surface of the glass plate develop, and a phenomenon called cooling cracking in which the glass plate is crushed may occur. For this reason, the problem that the tensile stress which generate | occur | produces on the surface of a glass plate immediately after the start of cooling will increase will become easy to generate | occur | produce a cooling crack compared with the past only by improving cooling capacity.
[0018]
Similarly, Patent Document 2 using compressor air also has a problem. The “part that is difficult to cool” in Patent Document 2 is the central part of the glass plate. However, there is no clear definition of the central portion of the glass plate, and the central portion described in the embodiment indicates a central band-like region from one side of the glass plate to the opposite side. That is, in the invention of Patent Document 2, since the edge with the most fine scratches on the glass plate is cooled by a high cooling ability such as compressor air, the tensile stress generated on the surface of the glass plate immediately after the start of cooling. There is a problem that the value increases, cracks develop from the edge, and cooling cracks occur.
[0019]
In addition, although the equipment cost and the operating cost can be reduced as compared with the invention of Patent Document 1, the current equipment must be remodeled significantly, and the equipment cost and the operating cost are higher than the current situation. In addition, compressor air has a problem of noise.
[0020]
As mentioned above, if the desired residual stress that satisfies the standard of tempered glass plate is formed on a glass plate with a plate thickness of 2.8 mm or less, strengthening with high cooling capacity will increase cooling cracking and equipment costs. Cause problems.
[0021]
Accordingly, an object of the present invention is to provide a tempered glass plate for automobiles that satisfies safety standards even when the glass plate is thinned, and to reduce cooling cracks due to the high cooling capacity accompanying the thinning of the glass plate. An object of the present invention is to provide a method of manufacturing a tempered glass sheet and a manufacturing apparatus that can keep equipment costs low.
[0022]
[Means for Solving the Problems]
Here, the principle of the present invention will be described.
When the tempered glass plate is crushed, an elastic wave is generated along with the generation of the crack, and propagates in all directions in the glass plate. This elastic wave propagates inside the tempered glass plate at a speed about twice as high as the crack progress rate (1.7 to 2.3 times), is reflected at the peripheral edge of the glass plate, and then proceeds with a delay. It collides with the tip of a crack that has come. As a result, the progress of the cracks branched, and the size of the fragments in the peripheral area of the tempered glass plate (the area outside the collision point between the elastic wave and the crack) is larger than the central area (the collision point between the elastic wave and the crack). Is smaller than the size of the fragments in the inner region. Therefore, in the strengthening process, a difference in the degree of strengthening can be provided between the central region and the peripheral region, that is, the cooling capability in the central region is preferably higher than the cooling capability in the peripheral region.
[0023]
Therefore, based on such a principle, the present invention solves the above-described problems of the prior art by using a residual compressive stress layer formed on the surface of the glass plate and a residual compressive stress formed inside the glass plate. A tempered glass sheet having a strength enhanced by a balance of residual stresses in these layers, the tempered glass sheet having an annular peripheral region in front view including the peripheral part, and the peripheral part And a central region occupying the inner peripheral side of the region, wherein the average surface compressive stress in the central region is larger than the average surface compressive stress in the peripheral region.
[0024]
Moreover, the one aspect | mode of the tempered glass board which concerns on this invention can take the following structures. That is, the average surface compressive stress in the peripheral region of the tempered glass sheet is preferably 90 MPa or more. Further, the boundary between the central region and the peripheral region is, when the tempered glass plate is crushed from the center of gravity, the tip of a crack that proceeds from the center of gravity toward the peripheral portion, and the crack, A point that is generated simultaneously and propagates through the tempered glass plate at a speed 1.7 to 2.3 times the progress speed of the crack, and collides with an elastic wave that is specularly reflected at the peripheral edge of the tempered glass plate. It is preferable to be defined by a line connecting the two.
[0025]
The average surface compressive stress in the central region is preferably 8 to 47% larger than the average surface compressive stress in the peripheral region. Further, the thickness of the tempered glass plate is 2.8 mm or less, the average surface compressive stress in the central region is preferably 100 MPa or more, and the average surface compressive stress in the peripheral region is preferably 90 MPa or more. .
[0026]
In the present invention, after heating the glass plate to near the softening point, the surface of the glass plate is cooled using a cooling means, thereby forming a residual compressive stress layer on the surface of the glass plate and A method for producing a tempered glass sheet for forming a residual tensile stress layer, wherein the tempered glass sheet comprises a ring-shaped peripheral region including a peripheral part thereof and a central region that occupies the inner peripheral side of the peripheral region. The cooling capacity of the first cooling means for cooling the central area is 16 to 78% higher than the cooling capacity of the second cooling means for cooling the peripheral area. A method for producing a tempered glass sheet is provided.
[0027]
Moreover, the one aspect | mode of the manufacturing method of the tempered glass board which concerns on this invention can take the following structures. That is, the boundary between the central region and the peripheral region is, when the tempered glass plate is crushed from the center of gravity, the tip of the crack that proceeds from the center of gravity toward the peripheral portion, and the crack A point that is generated simultaneously and propagates through the tempered glass plate at a speed 1.7 to 2.3 times the progress speed of the crack, and collides with an elastic wave that is specularly reflected at the peripheral edge of the tempered glass plate. It is preferable to be defined by a line connecting the two. The cooling capacity of the first cooling means is 520 W / cm. ² And the cooling capacity of the second cooling means is 350 W / cm. ² It is preferable that the temperature is not lower than ° C.
[0028]
The present invention also includes a heating furnace for heating the glass plate to near the softening point, and a cooling means having a plurality of nozzles for spraying a cooling medium on the surface of the glass plate, and the heated glass An apparatus for producing a tempered glass plate, wherein a residual compressive stress layer is formed on a surface of the glass plate by spraying the cooling medium on the surface of the plate, and a residual tensile stress layer is formed therein, the tempered glass plate Includes a peripheral edge region that includes the peripheral edge and is annular when viewed from the front, and a central area that occupies the inner peripheral side of the peripheral area, and the tip of the nozzle that cools the central area and the surface of the glass plate The distance between is 10 to 50 mm shorter than the distance between the tip of the nozzle that cools the peripheral region and the surface of the glass plate.
[0029]
Moreover, the one aspect | mode of the manufacturing apparatus of the tempered glass board which concerns on this invention can take the following structures. That is, the boundary between the central region and the peripheral region is, when the tempered glass plate is crushed from the center of gravity, the tip of the crack that proceeds from the center of gravity toward the peripheral portion, and the crack A point that is generated simultaneously and propagates through the tempered glass plate at a speed 1.7 to 2.3 times the progress speed of the crack, and collides with an elastic wave that is specularly reflected at the peripheral edge of the tempered glass plate. It is preferable to be defined by a line connecting the two.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. The first embodiment is an example of a tempered glass plate provided by the present invention, the second embodiment is an example of the manufacturing method of the present invention, and the third and fourth embodiments are examples of the manufacturing apparatus of the present invention. It is.
[0031]
(Embodiment 1)
FIG. 1 is a conceptual diagram showing the tempered glass plate of the first embodiment. The tempered glass plate 1 has a square shape, and has a peripheral region and a central region excluding this region in a front view. The central region is a region 9 near the center of the tempered glass plate 1 shown in FIG. 1, and the peripheral region is a region around the peripheral portion of the tempered glass plate 1 excluding the region 9.
[0032]
The region 9 will be described in detail below. The tempered glass plate has a compressive stress layer on the surface and a tensile stress layer inside. By applying a local impact to the tempered glass plate, cracks are generated on the surface. When the crack passes through the compressive stress layer and reaches the tensile stress layer, it proceeds in all directions of the glass plate due to the tensile stress, and the tempered glass plate is crushed. At that time, an elastic wave is generated and propagates toward the peripheral edge of the tempered glass sheet.
[0033]
The elastic wave is a transverse wave that is generated at the same time as the crack reaches the tensile stress layer and starts to progress in all directions of the glass plate and propagates concentrically from the generation point. The propagation speed of the elastic wave is faster than the progress speed of the crack. In the first embodiment, as shown in FIG. 1, assuming the case of crushing at the center of gravity A of the tempered glass plate 1, the size of the region 9 is determined by assuming that the elastic wave propagation speed is twice the crack propagation speed. ing.
[0034]
In FIG. 1, when the tempered glass plate 1 is crushed from the center of gravity A, the elastic wave propagated along the straight line 7 from the center of gravity A to the point B at the lower edge of the glass plate 1 is regularly reflected at the point B. , And propagate along the straight line 8. Therefore, the crack that has progressed along the straight line 6 from the center of gravity A toward the lower edge of the tempered glass plate 1 collides with the elastic wave propagating along the straight line 8 at the point C.
[0035]
A broken line 2 is a line connecting the collision point between the elastic wave that has been regularly reflected at the lower edge of the tempered glass plate 1 and the crack that has progressed toward the lower edge from the center of gravity A. Similarly, a line connecting the collision point between the elastic wave reflected regularly at the left edge of the tempered glass plate 1 and the crack proceeding toward the left edge side from the center of gravity A is a broken line 3. The line connecting the collision point between the elastic wave that has been regularly reflected at the upper edge and the crack that has progressed toward the upper edge from the center of gravity A is the broken line 4, and has been regularly reflected at the right edge of the tempered glass plate 1. A broken line 5 is a line connecting a collision point between the elastic wave and the center of gravity A and a crack that has progressed toward the right edge. A closed area formed by the broken lines 2 to 5 as a boundary line is an area 9 hatched with a diagonal line rising to the right.
[0036]
FIG. 2 shows the distribution of surface compressive stress along a straight line 10 passing through the center of gravity A of the tempered glass plate 1 of FIG. 1, the collision point E of elastic waves and cracks, and the point D at the lower edge of the tempered glass plate 1. It is a graph. The first embodiment is indicated by a solid line, and the conventional example is indicated by a broken line. In the region 9 of the first embodiment, the average value of the surface compressive stress is formed larger than the average value of the surface compressive stress in the peripheral region.
[0037]
As shown in FIG. 2, in the first embodiment, the surface compressive stress in the region 9 from the center of gravity A to the collision point E is formed to be 8 to 47% larger than the surface compressive stress in the peripheral region from the collision point E to the point D. Yes. In contrast, in the conventional example, the surface compressive stress is substantially constant over the entire surface of the glass plate. In practice, a tempered glass plate manufactured by blowing cooling air to a heated glass plate from the openings of a plurality of nozzles is a point where the jet of cooling air collides with the glass plate (hereinafter referred to as a direct point). Are scattered on the glass plate, and the surface compressive stress is different between the points immediately below each point, and the distribution of the surface compressive stress varies up and down to some extent.
[0038]
In the tempered glass sheet 1 of the first embodiment, the distribution of the surface compressive stress may vary as long as the average surface compressive stress in the region 9 is 8 to 47% greater than the average surface compressive stress in the peripheral region. Further, the surface compressive stress in the vicinity of the collision point E may change in a step shape, or may change from a surface compressive stress in the region 9 to a surface compressive stress in the peripheral region with a certain gradient, as described above. It does not matter if it fluctuates up and down.
[0039]
Next, a method for measuring the surface compressive stress will be described with reference to the drawings. For the measurement of the surface compressive stress, a Babinet type surface stress meter using a scattered light photoelasticity called a bias co-op method is used. FIG. 3 is a schematic sectional view showing the principle of the surface stress meter.
[0040]
The surface of the tempered glass plate 1 is covered with a liquid medium 17 having a higher refractive index than that, and linearly polarized light is incident from the medium 17 side through the prism 11 at a critical angle θ with an angle of polarization of 45 °. Part of the incident light 13 becomes surface propagation light 14 and travels along the vicinity of the surface inside the tempered glass plate 1. The surface propagation light 14 is refracted at each point of each path, and a part of the surface propagation light 14 is sent to the medium 17 side as the refracted emission light 15. Using this refracted light 15, the optical path difference of the surface propagation light 14 at each point of the path is measured.
[0041]
In general, since the incident light 13 and the reflected light 16 are much stronger than the surface propagation light 14, a shielding plate 12 is provided at the center of the prism 11 in order to block the incident light 13 and the reflected light 16 that hinder measurement. As the incident linearly polarized light propagates through the stressed surface, the optical path difference between the wave oscillating perpendicularly to the surface and the wave oscillating horizontally to the surface increases, and linearly polarized light-elliptical polarized light-circularly polarized light- This change is repeated as elliptically polarized light-linearly polarized light (incident light and polarization plane are orthogonal) -elliptical polarized light-circularly polarized light-elliptical polarized light-linearly polarized light (incident light and polarization plane are parallel). Since this change is reflected in the refracted light 15 as it is, when the refracted light 15 is observed through a polarizing filter, the path of the surface propagation light 14 appears to be repeated bright and dark.
[0042]
Accordingly, when a part of the refracted light 15 is observed through a Babinet corrector not shown in FIG. 3, the optical path difference does not change in the absence of surface compressive stress. Therefore, as shown in FIG. Interference fringes 18 on the instrument's quartz wedge are observed without tilting. In the state where there is a surface compressive stress, as shown in FIG. 4B, the interference fringe 18 on the quartz wedge of the Babinet corrector continuously moves to the right or left as the optical path difference increases. Is observed with an inclination.
[0043]
Here, if the path of the surface propagation light 14 projected onto the quartz wedge of the Babinet corrector is ΔL, and the optical path difference changed during that is ΔR, F: surface compressive stress, C: sensitivity constant of the device, Δn: optical path Difference (nm / cm), KC: Photoelastic constant (nm / cm / MPa)
Δn = ΔR / ΔL = tanφ
F = C · Δn / KC
It becomes. As described above, the surface compressive stress is obtained.
[0044]
Moreover, it is preferable to use a BTP-H surface stress meter manufactured by Orihara Seisakusho Co., Ltd. as an instrument for measuring the optical path difference. Further, it is preferable to use a prism having a size of 11 × 6 mm in contact with glass and a maximum measurement area of 5 × 6 mm. The photoelastic constant KC is preferably calculated as 2.68 nm / cm / MPa.
[0045]
As the measurement points, select the point where the surface compressive stress is expected to be close to the maximum value and the point where the surface compressive stress closest to the point is expected to be close to the minimum value. Measured in two directions, and the average value is the measured value at the point where the surface compressive stress measured previously is expected to be close to the maximum value.
[0046]
In the case of a tempered glass plate manufactured by blowing cooling air from a plurality of nozzle apertures to a heated glass plate, assuming that the nozzle apertures are in a staggered arrangement, the point immediately below the nozzle apertures has the highest surface compressive stress. It is a point that is expected to be close to the value, and is a triangle formed by the point immediately below the nozzle aperture and the two points that are closest to each other among the points directly below the other aperture The point of the center of gravity is the point where the surface compressive stress is expected to be close to the minimum value.
[0047]
Therefore, in the tempered glass plate of the first embodiment, the above-mentioned measurement points are measured from the center of gravity A to the point D along the straight line 10 in FIG. A near measurement point is measured along the straight line 10, and the average value of the surface compressive stress measured in the region 9 is 8 to 47% larger than the average value of the surface compressive stress measured in the peripheral region. In the conventional example, the average value of the surface compressive stress in the region 9 is less than 1.08 times the average value of the surface compressive stress in the peripheral region. In the first embodiment, the measurement points are selected along the straight line 10. However, as a reference for selecting the measurement points, the intervals between the points directly under measurement are arranged at substantially equal intervals, and the intervals are also narrowed. In order to obtain a measurement point, it is preferable to draw a straight line from the center of gravity A to the peripheral edge of the glass plate and select the measurement point along the straight line.
[0048]
Here, evaluation of the crushing test of Embodiment 1 will be described. As described above, a tempered glass plate used for an automobile window glass cannot be used unless it satisfies safety standards. Therefore, the evaluation of the crushing test is important. In the crushing test, the impact point at which the glass is broken into JIS R 3212 is determined from “Point 1” to “Point 4”, and the impact point at which the fragments are most rough is determined from the tests of the present inventors and empirical facts. Since it is known that it is “point 3”, which is almost the center point of the glass plate, in Embodiment 1, the crushing test at “point 3”, that is, the center of gravity A was compared with the conventional example.
[0049]
FIG. 5 shows the change in the number of pieces in a 50 × 50 mm square area (fracture number measurement area) when the tempered glass plate 1 is crushed with the center of gravity A as the starting point. 2 is a graph measured by shifting the center line A from the center of gravity A toward the point D so that the center line overlaps the straight line 10 in FIG. The first embodiment is indicated by a solid line, and the conventional example is indicated by a broken line. In the region 9, since the surface compressive stress of the first embodiment is larger than the surface compressive stress of the conventional example, the number of fragments increases. In the peripheral region, although the surface compressive stress of the first embodiment is smaller than the surface compressive stress of the conventional example, the number of fragments increases. This is because when the tempered glass plate 1 is crushed, the tip of the crack in progress is affected by the elastic wave reflected at the edge, so that the number of cracks traveling to the peripheral region increases and the surface of the conventional example Even if it is smaller than the compressive stress, the number of fragments in the peripheral region increases as compared with the conventional example.
[0050]
In other words, the progress of cracks in the tempered glass plate increases when energy increases due to the residual tensile stress inside the glass plate, and branches when reaching the speed of sound in the glass, but the tip of the crack is regularly reflected at the periphery of the glass plate. When the elastic wave collides with the elastic wave, the energy fluctuates and the crack also branches. Therefore, in the region where the crack proceeds after colliding with the elastic wave, the number of pieces to be measured in the 50 × 50 mm region increases. .
[0051]
Therefore, the tempered glass sheet that satisfies the safety standard has a value that satisfies the strength in the peripheral region if the residual stress in the central region is a value that can obtain the number of fractures that satisfies the safety standard of the tempered glass sheet for automobiles. If there is enough. The tempered glass plate having the stress distribution as in the first embodiment can be used as a tempered glass plate for automobiles that satisfies safety standards.
[0052]
In addition, although the tempered glass board 1 of Embodiment 1 was a square, even if the tempered glass board of this invention is another shape, the same effect is acquired.
[0053]
Moreover, when the plate | board thickness of the tempered glass board 1 of Embodiment 1 is 2.8 mm or less, from a test and empirical facts of the present inventors, the peripheral area in terms of strength is an average surface compression of 90 MPa or more. In order to obtain the number of fragments to be measured within a 50 × 50 mm region that satisfies the safety standards, the region 9 is preferably an average surface compressive stress of 100 MPa or more.
[0054]
Further, the region 9 may be enlarged to some extent or smaller. In the first embodiment, the region 9 is defined as the propagation speed of the elastic wave being twice the propagation speed of the crack, but the propagation speed of the elastic wave is 1.7 to 2.3 times the propagation speed of the crack. It has been confirmed from tests and empirical facts of the present inventors that the performance of the tempered glass sheet is not so different even if the region 9 is defined by changing it.
[0055]
That is, in FIG. 6, the broken line 2 connecting the collision points between the elastic wave regularly reflected on the lower side of the tempered glass plate 1 and the propagation of the crack propagated from the center of gravity A has a width as shown by the dotted lines 2a and 2b. Similarly, even if there is a broken line connecting the collision points between the elastic wave regularly reflected by the other side of the tempered glass plate 1 and the crack, and a width such as 3a and 3b, 4a and 4b, 5a and 5b, etc. Good. Therefore, the maximum size of the region 9 is a region hatched with a diagonal line rising to the right shown in FIG. 2, and the minimum size of the region 9 is a region hatched with a diagonal line rising to the left. The region 9 may be defined within the range of
[0056]
(Embodiment 2)
The second embodiment is a preferred method for manufacturing the tempered glass plate 1 of the first embodiment, and will be described below. In the second embodiment, the glass plate is heated to near the softening point, and the surface of the glass plate is cooled by using a cooling means, thereby forming a compressive stress layer on the surface of the glass plate, and a tensile stress layer inside. It is a manufacturing method of the tempered glass board which forms. The glass plate to be cooled has a central region and a peripheral region in front view. The central region is obtained by computer simulation in the same manner as the method for determining the region 9 shown in FIG.
[0057]
In the manufacturing method of the tempered glass plate of the second embodiment, the glass plate to be tempered is heated to near the softening point and cooled by the cooling means, but the cooling ability of the cooling means for cooling the central region of the glass plate is changed to the glass plate. The glass plate is cooled by 16 to 78% higher than the cooling ability of the cooling means for cooling the peripheral region of the glass plate. The cooling means for cooling the central area and the cooling means for cooling the peripheral area are separate from each other and may independently cool the central area and the peripheral area, respectively, or the cooling means for cooling the central area, and the peripheral edge The cooling means for the region may be the same, and the region may be adjusted to increase the cooling ability to the central region, or may be adjusted to reduce the cooling ability to the peripheral region.
[0058]
Thereby, the region 9 is cooled faster than the peripheral region, and the temperature difference between the inside and the surface in the cross-sectional direction of the glass plate being cooled becomes larger in the central region than in the peripheral region. Therefore, the residual stress formed in the central region becomes larger than the residual stress formed in the peripheral region, and the tempered glass plate 1 of Embodiment 1 can be manufactured.
[0059]
Moreover, the processed part which chamfered the peripheral part of the glass plate has many fine flaws, and a cooling crack often occurs because a crack advances from this part. According to the manufacturing method of the tempered glass sheet, the cooling capacity to the central area is large, but the cooling capacity of the peripheral area of the glass plate remains low and the peripheral area cools slower than the central area. The tensile stress which generate | occur | produces on the surface of a glass plate reduces, and the cooling crack from which a peripheral area | region starts can be reduced.
[0060]
The cooling means may be air cooling in which cooling air is blown onto the glass plate, mist cooling in which mist consisting of countless and innumerable water droplets is blown onto the glass plate, or contact that directly contacts the glass plate with the refrigerant. Cooling may be used.
[0061]
Further, when the glass plate is heated, the same tempered glass plate can be obtained by heating the central region to a temperature higher than that of the peripheral region and cooling the entire surface of the glass plate with substantially uniform cooling ability. In this case, since the peripheral region is substantially the same as the conventional temperature, the problem that the conveyance becomes difficult when the glass plate is heated to a high temperature is solved.
[0062]
(Embodiment 3)
An example of a preferable apparatus for carrying out the method for producing a tempered glass sheet of Embodiment 2 will be described below.
[0063]
Embodiment 3 has at least a wind box disposed opposite to both surfaces of a heated glass plate and a plurality of nozzles arranged on the glass plate side of the wind box, and is directed toward the heated glass plate. It is a manufacturing apparatus of the tempered glass board which blows the cooling wind ejected from a plurality of nozzles. A plurality of nozzles are arranged side by side so that the opening holes of the nozzles are oriented in a staggered arrangement perpendicularly to the glass plate and substantially match the shape of the glass plate, and are ejected from the opening holes to the entire surface of the glass plate. It is provided in the wind box so that cooling air can be blown.
[0064]
FIG. 7 is a schematic view showing the positional relationship between the central region of the glass plate 19 and the opening hole of the nozzle. The glass plate 19 shown in FIG. 7 has a square shape, and has a central region and a peripheral region in a front view.
[0065]
First, similarly to the method for determining the region 9 shown in FIG. 1, a computer simulation is performed to obtain the central region of the glass plate 19 to be strengthened. At this time, a central region within the range shown in FIG. 6 may be obtained. Next, when heating and cooling the glass plate 19, it is determined from which nozzle opening the cooling air for cooling the central region of the glass plate 19 is blown. The result of obtaining the positional relationship is shown in FIG.
[0066]
FIG. 7 shows a plurality of nozzles provided with a plurality of opening holes 24 disposed in a glass plate 19 for which lines 20 to 23 where cracks and elastic waves collide and a wind box used in the third embodiment are provided. FIG.
[0067]
A line 20 is a line connecting a collision point between a crack when crushing at the center of gravity of the glass plate 19 and an elastic wave reflected at the lower edge of the glass plate 19, and a line 21 is reflected at the left edge of the crack and the glass plate 19. The line 22 connects the crack and the collision point of the elastic wave reflected by the upper edge of the glass plate 19, and the line 23 connects the crack and the right edge of the glass plate 19. This is a line connecting the collision points with the elastic waves reflected by the. The result of FIG. 7 shows a region where the cooling capacity is increased, and the nozzle in this region is referred to as a central region nozzle.
[0068]
In the third embodiment, the cooling capacity in the central area is increased more than the cooling capacity in the peripheral area by extending the nozzle in the central area so that the distance between the opening hole and the glass plate 19 is closer than the nozzle in the peripheral area. FIG. 8 is a schematic perspective view of a wind box in which the nozzle 26 in the central region is extended. In the third embodiment, the nozzle 26 in the central region is extended by 10 to 50 mm from the nozzle 28 in the peripheral region. The distribution of the opening holes 27 in the central region is the same as the interval between the opening holes in the peripheral region in front view. By extending the nozzle in the central area, the cooling capacity in the central area is 16 to 78% higher than the cooling capacity in the peripheral area. In particular, when the glass plate 19 has a thickness of 2.8 mm or less and the cooling start temperature of the glass plate 19 is 640 ° C., the cooling capacity of the central region is 520 W / cm. ² It is preferable that the temperature is not lower than ° C., and the cooling capacity of the peripheral region is 350 W / cm. ² It is preferable that it becomes more than degreeC.
[0069]
FIG. 9 is a schematic side view showing an apparatus for manufacturing a tempered glass sheet according to the third embodiment using the air box shown in FIG. The apparatus for manufacturing a tempered glass plate according to the third embodiment includes an air box 30a, 30b disposed opposite to both surfaces of the glass plate 19, and a plurality of nozzles 26a disposed on the glass plate 19 side of the air box 30a, 30b. , 26b, 28a, and 28b, and the cooling air blown from the pipes 32a and 32b is blown from the opening holes of the plurality of nozzles 26a, 26b, 28a, and 28b toward the heated glass plate 19 It is a manufacturing apparatus of the tempered glass board of the form 3. In FIG. 9, the glass 19 is not bent and is not formed, but the glass plate 19 may be bent. In this case, the nozzle and the wind box are set so that the distance between the glass plate and the nozzle tip is constant. The shape may be matched to the curvature of the glass plate.
[0070]
The glass plate 19 heated to near the softening point in the heating furnace is conveyed between the air boxes 30a and 30b. In this case, the glass plate 19 is held between the wind boxes 30a and 30b while being held in a vertical state by the conveying means of the hanger 31 connected to the drive mechanism. When the glass plate 19 is conveyed between the air boxes 30a and 30b, cooling air is blown onto the glass plate 19 from the opening holes of the nozzles. In this way, by cooling the glass plate 19 with the cooling capacity of the central region higher than that of the peripheral region, in the apparatus of the third embodiment, the residual stress formed in the central region is formed in the peripheral region. The tempered glass plate of Embodiment 1 that is 8 to 47% larger than the residual stress can be manufactured.
[0071]
Moreover, since the cooling capacity to the central area of the glass plate 19 is high but the cooling capacity to the peripheral area remains low, the peripheral area cools slower than the central area, so that it occurs on the surface of the glass plate 19 immediately after the cooling of the peripheral area starts. The tensile stress to be reduced is reduced, and cooling cracks starting from the peripheral region can be reduced.
[0072]
Moreover, since the manufacturing apparatus of the tempered glass board of Embodiment 3 has only extended the nozzle, there is no big remodeling and expansion in the air-cooling strengthening apparatus itself, and expenses can be kept low.
[0073]
(Embodiment 4)
The apparatus for producing a tempered glass sheet according to the fourth embodiment, in which the glass sheet that is formed and bent is horizontally placed on the ring and cooled, instead of being suspended and cooled in the vertical direction according to the third embodiment. An example of this will be described below. FIG. 10 is a schematic cross-sectional view illustrating an example of a manufacturing apparatus for a tempered glass sheet according to the fourth embodiment. The tempered glass plate manufacturing apparatus of the fourth embodiment in FIG. 10 is disposed on the glass plate 33 side of the wind boxes 34a and 34b opposed to both surfaces of the glass plate 33 and the wind boxes 34a and 34b. It is an apparatus for manufacturing a tempered glass plate that has at least a plurality of nozzles and blows cooling air blown from the plurality of nozzles toward the heated glass plate 33.
[0074]
The plurality of nozzles are arranged side by side so that the opening holes of the nozzles are vertically oriented with respect to the glass plate 33 and are substantially coincident with the shape of the glass plate 33, and the opening holes are formed on the entire surface of the glass plate 38. It is provided in the wind boxes 34a and 34b so that the cooling air which blows off from can be blown. The tips of the plurality of nozzles are 35a, 35b, 36a, and 36b shown in FIG.
[0075]
The glass plate 33 has a shape used for a window glass of an automobile, and has a central region and a peripheral region in a front view. The central region is obtained by computer simulation in the same manner as the method for determining the region 9 shown in FIG.
[0076]
Further, in the conventional tempered glass plate manufacturing apparatus, as shown in FIG. 11, the distance between the glass plate 39 and the nozzle tips 41a and 41b is almost constant at any position on the glass plate. In the tempered glass plate manufacturing apparatus 4, the tips 36a, 36b of the nozzles 37a, 37b that cool the central region of the glass plate 33 are more glass plates 33 than the tips 35a, 35b of the nozzles that cool the peripheral region of the glass plate 33. 10-50mm close to the side.
[0077]
The glass plate 33 heated to near the softening point in the heating furnace and bent as necessary is conveyed between the air boxes 34a and 34b. In this case, the glass plate 33 is held in a horizontal state by appropriate conveying means such as a ring 38 connected to a driving mechanism, and is conveyed between the air boxes 34a and 34b.
[0078]
When the glass plate 33 is conveyed between the air boxes 34 a and 34 b, cooling air having a predetermined temperature and pressure is blown toward the glass plate 33 from the opening holes of the nozzles. Thus, the cooling ability of the central region is set to 16 from the peripheral region by bringing the tip 36a, 36b of the nozzle 37a, 37b sprayed to the central region closer to the glass plate 33 by 10-50 mm from the tip 35a, 35b of the nozzle spraying to the peripheral region. Since the glass plate is cooled by increasing it by ˜78%, it is possible to manufacture a tempered glass plate in which the residual stress formed in the central region is 8 to 47% larger than the residual stress formed in the peripheral region. In particular, when the glass plate 33 has a thickness of 2.8 mm or less and the cooling start temperature of the glass plate 33 is 640 ° C., the cooling capacity of the central region is 520 W / cm. ² It is preferable that the temperature is not lower than ° C., and the cooling capacity of the peripheral region is 350 W / cm. ² It is preferable that the temperature is not lower than ° C.
[0079]
Moreover, since the cooling ability to the center area | region of the glass plate 33 is high, but the cooling ability to a peripheral area remains low, since a peripheral area cools slower than a central area, it generate | occur | produces on the surface of the glass plate 33 immediately after the cooling start of a peripheral area | region. The tensile stress to be reduced is reduced, and cooling cracks starting from the peripheral region can be reduced.
[0080]
Further, when strengthening a glass plate having a shape having a double curved surface, as shown in FIG. 11, when the tips 41a and 41b of all the nozzles are brought close to the glass plate 39, the nozzle tip 41b and the glass plate 39 being rapidly cooled are used. Since there is a possibility that the cooling ring 42, which is a jig for holding the glass, comes into contact, the approach distance is limited and the glass plate 39 cannot slide in the horizontal direction. However, as shown in FIG. By bringing the nozzle tips 36a and 36b close to each other only, the problem of contact with the cooling ring 38 and slidability can be solved.
[0081]
Moreover, since the manufacturing apparatus of Embodiment 4 has only extended the front-end | tip of a nozzle, there is no big remodeling and expansion in the air-cooling strengthening apparatus itself, and can suppress cost low.
[0082]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained. The tempered glass sheet according to the present invention has an advantage that the average surface compressive stress in the central region is larger than that in the peripheral region, and therefore only the cooling ability in the central region needs to be increased. That is, the tip of the nozzle that injects the cooling medium can be moved away from the center region in the peripheral region, and the edge of the glass plate can be prevented from coming into contact with the tip of the nozzle when the glass plate is slid. .
[0083]
In addition, by setting the average surface compressive stress in the peripheral region to 90 MPa or more, or by increasing the average surface compressive stress in the central region by 8 to 47% larger than that in the peripheral region, a residual stress at a level that can satisfy safety regulations can be obtained. Formed.
[0084]
Moreover, in the manufacturing method of the tempered glass board of this invention, the cooling capacity of the cooling means which cools the center area | region of a tempered glass board at the time of rapid cooling is made 16-78% higher than the cooling capacity of the cooling means which cools a peripheral area | region. Thus, it is possible to manufacture a tempered glass plate in which the residual stress in the central region of the tempered glass plate is 8 to 47% larger than the residual stress in the peripheral region. In addition, the central region has a high cooling capacity, but the cooling capacity of the peripheral region remains low and cools slower than the central region, so that the tensile stress generated on the surface of the glass plate immediately after the cooling of the peripheral region can be reduced, and the cooling medium It is possible to prevent the glass plate from being broken when spraying.
[0085]
In the tempered glass plate manufacturing apparatus according to the present invention, the tempered glass is formed by extending the tip of the nozzle that cools the central region of the tempered glass plate during quenching by 10 to 50 mm from the tip of the nozzle that cools the peripheral region. The cooling capacity of the cooling means for cooling the central area of the plate is 16 to 78% higher than that of the cooling means for cooling the peripheral area, and the residual stress in the central area of the tempered glass sheet is 8% higher than the residual stress in the peripheral area. A tempered glass plate that is up to 47% larger can be produced and cooling cracks can be reduced. Furthermore, since the nozzle is only extended, the existing manufacturing apparatus can be easily implemented without major modifications or additions, and the cost can be kept low.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a central region and a peripheral region.
FIG. 2 is a graph showing a distribution of surface compressive stress in the first embodiment.
FIG. 3 is a schematic cross section showing the principle of a surface stress meter.
4A is a schematic diagram in the case of no stress when the emitted light 15 is observed, and FIG. 4B is a schematic diagram in the case of the stress when the emitted light 15 is observed.
FIG. 5 is a graph showing changes in the number of fragments in a 50 × 50 mm square region of the first embodiment.
FIG. 6 is a conceptual diagram for obtaining a central region in the first embodiment.
FIG. 7 is a schematic diagram showing a positional relationship between a central region of Embodiment 3 and an opening hole of a nozzle.
FIG. 8 is a schematic perspective view of an air outlet used in the third embodiment.
9 is a schematic side view showing an apparatus for producing a tempered glass plate used in Embodiment 3. FIG.
FIG. 10 is a schematic cross-sectional view of a tempered glass sheet manufacturing apparatus according to a fourth embodiment.
It is a graph.
FIG. 11 is a schematic cross-sectional view of a conventional tempered glass sheet manufacturing apparatus.
[Explanation of symbols]
A: Center of gravity
B: Peripheral portion of tempered glass plate 1
C: Collision point between crack and elastic wave
D: Peripheral portion of tempered glass plate 1
E: Collision point between crack and elastic wave
ΔL: Path of surface propagation light
ΔR: optical path difference changed during ΔL
θ: Critical refraction angle
φ: Angle of interference fringes
1: Tempered glass plate
2 to 5, 2a to 5a, 2b to 5b: lines connecting collision points of cracks and elastic waves
6: Progress of crack
7: Propagation of elastic waves
8: Propagation of specularly reflected elastic waves
9, 9a, 9b: Central region
10: Evaluation line
11: Prism
12: Shield version
13: Incident light
14: Surface propagation light
15: Refraction exit light
16: Reflected light
17: Medium of optical refractive index
18: Interference fringes
19: Glass plate
20-23: A line connecting the collision points of the crack and the elastic wave
24: Nozzle opening hole
25: Nozzle
26, 26a, 26b: extended nozzle
27: Extended nozzle opening hole
28, 28a, 28b: peripheral area nozzles
29: Nozzle opening hole in the peripheral area
30, 30a, 30b: wind box
31: Hanging tool
32a, 32b: piping
33: Glass plate
34a, 34b: wind box
35a, 35b: Nozzle tips in the peripheral area
36a, 36b: Nozzle tips in the central area
37a, 37b: Nozzle extension
38: Ring
39: Glass plate
40a, 40b: wind box
41a, 41b: nozzle tip
42: Ring

Claims (10)

This is a tempered glass plate composed of a residual compressive stress layer formed on the surface of the glass plate and a residual compressive stress layer formed inside the glass plate. There,
The tempered glass plate has an annular peripheral region in front view including the peripheral portion, and a central region that occupies the inner peripheral side of the peripheral region,
An average surface compressive stress in the central region is larger than an average surface compressive stress in the peripheral region. The tempered glass sheet according to claim 1, wherein an average surface compressive stress in a peripheral region of the tempered glass sheet is 90 MPa or more. The boundary between the central region and the peripheral region is
When the tempered glass plate is crushed starting from the center of gravity, the tip of the crack that proceeds from the center of gravity toward the peripheral edge,
An elastic wave that is generated at the same time as the crack and propagates through the tempered glass plate at a speed 1.7 to 2.3 times the progress speed of the crack, and is regularly reflected at the peripheral edge of the tempered glass plate. The tempered glass sheet according to claim 1 or 2, defined by a line connecting points of collision. The tempered glass sheet according to any one of claims 1 to 3, wherein an average surface compressive stress in the central region is 8 to 47% greater than an average surface compressive stress in the peripheral region. The tempered glass plate has a thickness of 2.8 mm or less,
The average surface compressive stress in the central region is 100 MPa or more,
The tempered glass sheet according to any one of claims 1 to 4, wherein an average surface compressive stress in the peripheral region is 90 MPa or more. After heating the glass plate to near the softening point, the surface of the glass plate is cooled using a cooling means, thereby forming a residual compressive stress layer on the surface of the glass plate and forming a residual tensile stress layer inside. A method of manufacturing a tempered glass sheet,
The tempered glass plate has an annular peripheral region in front view including the peripheral portion, and a central region that occupies the inner peripheral side of the peripheral region,
A tempered glass sheet characterized in that the cooling capacity of the first cooling means for cooling the central area is 16 to 78% higher than the cooling capacity of the second cooling means for cooling the peripheral area. Manufacturing method. The boundary between the central region and the peripheral region is
When the tempered glass plate is crushed starting from the center of gravity, the tip of the crack that proceeds from the center of gravity toward the peripheral portion,
An elastic wave that is generated at the same time as the crack and propagates through the tempered glass plate at a speed 1.7 to 2.3 times the progress speed of the crack, and is regularly reflected at the peripheral edge of the tempered glass plate. The manufacturing method of the tempered glass board of Claim 6 prescribed | regulated by the line | wire which connected the point which collides. The cooling capacity of the first cooling means is 520 W / cm ² ° C or higher,
The method for producing a tempered glass sheet according to any one of claims 6 and 7, wherein the cooling capacity of the second cooling means is 350 W / cm ² ° C or more. A heating furnace for heating the glass plate to near the softening point; and a cooling means having a plurality of nozzles for spraying a cooling medium on the surface of the glass plate, and the cooling on the surface of the heated glass plate By spraying the medium, a residual compressive stress layer is formed on the surface of the glass plate, and a residual tensile stress layer is formed inside, and an apparatus for producing a tempered glass plate,
The tempered glass plate includes a peripheral region that includes the peripheral portion and is annular in front view, and a central region that occupies the inner peripheral side of the peripheral region,
The distance between the tip of the nozzle that cools the central region and the surface of the glass plate is 10-50 mm shorter than the distance between the tip of the nozzle that cools the peripheral region and the surface of the glass plate Glass plate manufacturing equipment. The boundary between the central region and the peripheral region is
When the tempered glass plate is crushed starting from the center of gravity, the tip of the crack that proceeds from the center of gravity toward the peripheral portion,
An elastic wave that is generated at the same time as the crack and propagates through the tempered glass plate at a speed 1.7 to 2.3 times the progress speed of the crack, and is regularly reflected at the peripheral edge of the tempered glass plate. The tempered glass sheet manufacturing apparatus according to claim 9, wherein the tempered glass sheet manufacturing apparatus is defined by a line connecting points of collision.

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