JP2000063136A - Stepped glass plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stepped glass plate capable of inconsiderably standing a severe mechanical load applied to an end part by making the average surface compressive stress at a middle zone of a tempered glass plate larger than the value of a central zone. SOLUTION: Both the surfaces of a glass plate heated to a temperature close to a softening point is sprayed with a cooling medium in a jet flow state and quenched. A peripheral zone A, a central zone C and a difference in step at a boundary between the peripheral zone A and the central zone C are formed in such a way that the plate thickness of the peripheral zone A is thinner than that of the central zone C. A middle zone B having 5-30 mm width from the boundary between the peripheral zone A and the central zone B toward the inside of the glass plate is formed and the average surface compressive stress at the middle zone B is made 100-500 kg/cm2 higher than that at the central zone C. The value of the average surface compressive stress at the peripheral zone A can be 100-300 kg/cm2 higher than that at the central zone C and the value of the average surface compressive stress at the central zone C is 850-1,200 kg/cm2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepped glass plate, and more particularly to a stepped tempered glass plate used as a window glass plate on the side of an automobile.

[0002]

2. Description of the Related Art Conventionally, as a method of strengthening a glass sheet, cooling nozzles are arranged on the surface of the glass sheet in a lattice pattern or in a staggered pattern on both surfaces of the glass sheet heated to a temperature near the softening point of the glass. A method is known in which a jet-like cooling medium is blown to quench the material. In this strengthening method, the glass plate is strengthened by creating a residual compressive stress layer on the surface of the finally solidified glass plate by providing a temperature difference between the inside and the surface of the glass plate during cooling. .

If the glass plate has a constant plate thickness of infinite size and both sides thereof are uniformly cooled, the stress distribution in the plate thickness direction follows a so-called parabolic distribution. Then, the value of the surface compressive stress becomes equal to twice the tensile stress value at the inner center of the glass plate in the plate thickness direction, and the integrated value of the stress in the plate thickness direction is 0.
Becomes However, in reality, the glass plate has a finite size. The edge of the glass plate is usually chamfered from the viewpoint of preventing cracks during cooling and design.

When cooling such a glass plate,
Unlike the central region, where the edge effects are negligible, the cooling at the edges of the glass sheet acts on the entire chamfered portion and locally affects the total thickness of the edge of the glass sheet. As a result, a region having a width of 2 to 3 times the plate thickness at the outermost portion of the glass plate, in which the integrated average value of stress in the plate thickness direction shows compression, and the region on the inner peripheral side of the glass plate in a balanced manner An intermediate region in which the integrated average value of the stress in the plate thickness direction indicates tension is generated. This means that there is a region having a constant width and slightly vulnerable to an external impact on the inner peripheral side of the edge of the glass plate.

Here, with respect to the integrated mean value, the direction of the principal stress and the principal stress difference will be described. First, one plane (cross section of the glass plate) perpendicular to the glass plate surface is selected. The plane chosen can be at any angle to some straight line parallel to the plane of the glass sheet. Also, select one point in this plane. Since the stress value acting on this point in the direction perpendicular to the selected plane is different depending on the angle of the selected plane,
Among the angles, there are an angle that maximizes the stress value and an angle that minimizes the stress value. The direction of the stress showing the maximum value and the direction showing the minimum value orthogonal to this are the principal stress directions. Typically, the direction of the stress showing the maximum value is called the principal stress direction.

By the way, since the principal stress itself cannot be measured directly, in tempered glass, the principal stress is evaluated by the principal stress difference obtained by the photoelastic method. The main stress difference obtained by this photoelastic method is the value obtained by dividing the sum of the values obtained by subtracting the minimum value from the maximum value of stress at each point by the plate thickness for all points arranged in the plate thickness direction in tempered glass. It corresponds to (a value obtained by averaging the integrated value of values obtained by subtracting the minimum value of stress from the maximum value of stress by the plate thickness). Therefore,
Select a point on the glass plate surface, and from this point, the integrated average value of the values obtained by subtracting the minimum stress value from the maximum stress value at each point in the plate thickness direction is the principal stress difference at that point. (The principal stress direction at this time becomes the principal stress direction at that point). In this specification, the principal stress directions are all parallel to the glass plate surface.

By the way, as a window glass disposed on the side of an automobile, a stepped glass plate which is a kind of a window glass plate which eliminates a step from a body flange due to improvement of aerodynamic performance of the automobile and design needs is used. Being developed. FIG. 3 is a view showing an example of the end shape and arrangement state. In FIG.
Reference numeral 1 denotes a glass plate, and the peripheral edge of the glass plate is formed in a step shape as shown in the drawing. 2 is sash, 2 sash
The concave portion 3 is provided in the concave portion 3, and the peripheral edge of the glass plate 1 is fitted into the concave portion 3. This glass plate is an automobile glass plate having a thin portion with a constant width around a thick portion by subjecting an end of the glass plate to a stepped chamfer.

In particular, the stepped tempered glass sheet arranged on the side of the automobile is slid vertically or diagonally up and down, and is frequently performed. Therefore, a severe mechanical load is applied to the end portion of the glass plate. Then, the glass plate is required to have a strength capable of withstanding the load. However, regarding the stepped tempered glass plate as described above,
With a glass plate reinforced by a conventional method that makes the cooling rate uniform over the entire surface of the glass plate, the stress value of the compressive stress layer existing on the surface of the intermediate region becomes small, and it is difficult to give sufficient strength. Met.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in a stepped tempered glass plate used for a window glass plate for a side of an automobile and the like. An object of the present invention is to provide a stepped tempered glass sheet that can endure a severe mechanical load applied to its end portion without any problem.

[0010]

The present invention is directed to a peripheral area A
And a central region C and an intermediate region B between the peripheral region A and the central region C, wherein a step portion is provided at the boundary between the peripheral region A and the intermediate region B, and the peripheral region A In the stepped glass plate formed so that the plate thickness thereof is smaller than the plate thickness of the central region C, the glass plate is strengthened, and the average surface compressive stress in the intermediate region B is 1 compared to the average surface compressive stress in region C
Provided is a stepped glass plate having a large size of 0 to 500 kg / cm ² .

[0011]

1 and 2 are schematic views for explaining a stepped tempered glass sheet of the present invention, FIG. 1 is a plan view, and FIG.
2 is a sectional view taken along line ZZ in FIG. It is a relatively enlarged view from FIG. 1. A indicates a peripheral area. C indicates a central region, which corresponds to a thick portion. B is a peripheral portion of the central region C, and indicates an intermediate region between the central region C and the peripheral region A. The intermediate region B is a thick plate portion like the central region C. As shown in FIG. 1, the areas A, B, and C are areas defined when the glass plate is viewed in a plan view.

In the present invention, the stepped glass plate as described above is a glass plate that has been strengthened. And
The average surface compressive stress in the intermediate region B of this stepped glass plate is set to be 100 to 500 kg / cm ² larger than the average surface compressive stress in the central region C. This allows
Sufficient strength is imparted to the boundary region (that is, the intermediate region B) with the thin plate portion in the peripheral portion of the thick plate portion which is the intermediate region where the integrated average value of the stress in the plate thickness direction indicates tension. .

The average surface compressive stress in the intermediate area B is 100 kg compared to the average surface compressive stress in the central area C.
If the strength is larger than less than / cm ^{2, the} strength that can withstand the frequent vertical sliding when this glass plate is used for an automobile side window is insufficient. Therefore, the average surface compressive stress in the intermediate region B is 100 kg / cm ² larger than the average surface compressive stress in the central region C.

In the present invention, the intermediate region B preferably has a width of 5 to 30 mm from the boundary between the peripheral region A and the intermediate region B toward the inner circumference of the glass plate. As a result, the integrated average value of the stress in the plate thickness direction indicates the intermediate region B
However, a predetermined strength can be sufficiently ensured even when it extends over both the peripheral region A (thin plate thickness portion) and the central region C (thick plate thickness portion).

Further, in the present invention, it is preferable that the stepped tempered glass sheet has a characteristic point having a large principal stress difference in a portion having a high average surface compression stress as compared with a principal stress difference in the vicinity of the vicinity. And the closest to this feature point,
It is preferable that the distance between the second feature point having a large main stress difference as compared with the main stress difference in the vicinity and the feature point is in the range of 5 to 15 mm. By forming such a main stress difference, it is possible to suppress the generation of large fragments even when the glass plate is broken.

Further details will be described with reference to FIG. FIG. 4 is an enlarged conceptual view of the main part (P) of FIG. Intermediate area B
Are dotted with characteristic points b having a large difference in principal stress as compared with the vicinity. In this example, this feature point b
The principal stress direction at is perpendicular to the edge direction of the glass plate. On the other hand, in the peripheral area A, the characteristic points a having a large difference in main stress as compared with the peripheral area are provided in a scattered manner.
In this example, the principal stress directions of the characteristic points a of the adjacent characteristic points a are different from each other.
In this example, the point closest to the characteristic point b is the characteristic point a. The value of L shown by the dotted line in the figure is in the range of 5 to 10 mm. As a result, it is possible to prevent the generation of large fragments when the glass plate is crushed.

Thus, in the above example, the point closest to the characteristic point b is the characteristic point a in the peripheral area A. On the other hand, the point closest to a certain feature point b is not the feature point a but the intermediate region B.
In the case of another feature point b of, the L is between the feature points b in the intermediate region. In the central region C, there are other characteristic points having a large principal stress difference compared to the principal stress difference in the vicinity, and when this characteristic point is the closest distance from the characteristic point b, this distance corresponds to L. To do.

By the way, in the above example, a stepped step is formed at the boundary between the peripheral region A and the intermediate region B.
In addition, even when the boundary between the peripheral region A and the intermediate region B is formed smoothly, a step can be provided substantially at this boundary. In this case, as shown in FIG. 5, when the glass plate surface (the upper side in the drawing) on the side where the step is formed is traced from the intermediate region B to the peripheral region A from left to right, it projects downward. The curve is changed to a convex curve, that is, there is an inflection point between the peripheral region A and the intermediate region B.
This inflection point can be referred to as a boundary between the peripheral region A and the intermediate region B forming a substantial step. In the present invention, the width of the peripheral region A is 5 to 15 mm from the edge of the glass plate regardless of whether the stepped portion has a stepped shape (FIG. 2) or a smooth shape (FIG. 5). The range is preferable from the viewpoint of compatibility with the vehicle body.

As a concrete means for strengthening a glass plate satisfying the above conditions, a jet-like cooling medium is sprayed on both surfaces of the glass plate heated to a temperature near the softening point of the glass plate to quench the glass plate. It can be carried out by a method. As a preferable example thereof, the cooling device described in EP884286A can be used.

This cooling device has a wind box arranged opposite to each other on both sides of the glass plate and a plurality of nozzles mounted on the glass plate side of the wind box, and is directed toward the glass plate heated to a predetermined temperature. In a cooling device for a glass plate that blows cooling air ejected from each nozzle, the nozzle is a hollow tubular one having a convex curved surface type tip surface on the side facing the glass plate, and the tip surface is The cooling device is provided with a plurality of opening holes for blowing the cooling air supplied from the air box toward the glass plate.

In this cooling device, it is advantageous to use a nozzle having a plurality of openings on the tip surface thereof in the following points. That is, due to the sliding operation of the glass plate required during normal cooling, the collision between the glass plate and the nozzle that occurs when the nozzle is brought close to the glass plate in order to enhance the cooling capacity,
Can be avoided. Specifically, by using this nozzle, the pitch between the nozzles can be made small. By arranging the nozzles at a small pitch to reduce the sliding distance, it is possible to avoid collision between the glass plate and the nozzles, and there is a clear difference in cooling capacity at the boundary between the large cooling area and the small cooling area. Can be given. Further, by reducing the diameter of the opening hole, the sensitivity of the cooling ability to the distance between the glass and the nozzle can be increased. In this way, when the distance between the glass and the nozzle is changed in each region of the glass plate, it is possible to make a large difference in cooling ability between the thin plate portion and the thick plate portion even if the difference in the different distance is small. Yes, the stress distribution according to the invention is obtained.

That is, in the above cooling device, the distance between the glass and the nozzle in the intermediate region B, which is a region where a high average surface compressive stress is required, among the plurality of opening holes blown toward the glass plate in the plurality of nozzles is set to the central region. 100-500 compared to the average surface compressive stress in C
It is carried out by shortening the distance required to increase kg / cm ^{2 and} increasing the distance between the glass and the nozzle on the surface that does not require high average surface compression stress, and selectively changing the cooling capacity.

In the stepped glass plate, the plate thickness in the peripheral region A is smaller than the plate thickness in the central region C. Therefore, when the average surface compressive stress in the intermediate region B is increased by 100 to 500 kg / cm ^{2 as} compared with the average surface compressive stress in the central region C, the value of the average surface compressive stress in the peripheral region A is equal to that of the average surface compressive stress in the central region C. 100 to 3 compared to the value
Can be increased by 00 kg / cm ² . In order to obtain preferable strength under normal use conditions, the value of the average surface compressive stress in the central region C is preferably in the range of 850 to 1200 kg / cm ² .

As the cooling device which can be used in the present invention, in addition to the cooling device as described above, also in conventionally known cooling devices, devise such that the boundary between the portion having a large cooling capacity and the portion having a small cooling capacity appears clearly. Thus, it is possible to suppress the influence other than the necessary area. Furthermore, among the conventionally known cooling devices, the nozzles at the necessary locations may be used instead of the nozzles having a plurality of opening holes. In this way, a glass plate having a predetermined strength can be obtained even in the intermediate region B and the peripheral region A whose plate thickness is thinner than the plate thicknesses of the intermediate region B and the central region C.

The stepped glass plate having each of these preferable stress values is suitably used for a glass plate for an automobile side window that moves up and down. That is, in order to reduce the running aerodynamic resistance of an automobile and improve the design, it has been proposed to make the automobile sash and the ascending / descending automobile side window flush. On the other hand, between the side window and the sash, it is easy to become a target for inserting a theft tool. In order to make the sash and the side window flush with each other, the amount of biting of the side window into the sash becomes small. Therefore, it is difficult to prevent the theft tool from entering with the normal shape of the side window. When the stepped glass plate is used as a glass plate for a side window, a side window assembly structure in which it is difficult to insert a theft tool is obtained. Therefore, the stepped glass plate is
It is suitable for use in glass plates for automobile side windows that move up and down. Then, by setting each stress value in the stepped glass plate to each of the above preferable stress values, a stepped glass plate corresponding to the strength required for the automobile side window and the size of the fragments at the time of crushing can be obtained.

Glass plates for automobile side windows are often bent glass plates. On the other hand, in order to make the side window and the sash flush with each other, it is preferable to provide a step on the outer surface of the vehicle in terms of the structure for assembling the glass plate to the vehicle. Therefore, in the mounted state, it is preferable to provide the step portion on the convex portion on the outside of the glass plate on the vehicle side. Further, in this case, from the viewpoint of strength, it is preferable that the step portion is provided only on the convex surface of the glass plate, which is on the vehicle outer side.

The side window that moves up and down is connected to a lifting regulator provided inside the door of the automobile. In this case, the lower side of the side window glass plate in the attached state is connected to the lifting regulator. The connecting portion with the lifting regulator is a portion to which a severe mechanical load is applied because the lifting driving force is transmitted. Therefore, in the stepped glass plate of the present invention, it is preferable that the stepped part is formed in a portion of the entire circumference of the glass plate except the lower side. Further, the side edge of the glass plate engages with the side edge of the sash to guide the up and down movement of the side window.

From the viewpoint of improving the accuracy of the guide operation and the viewpoint of the mechanical load at the time of guiding, the stepped glass plate of the present invention has a portion (excluding the lower side and the side) of the entire circumference of the glass plate ( It is preferable to form a step on only the upper side).
On the other hand, the side window bite groove width of the car sash can be the same width as the upper side and the side of the sash.
It is superior in terms of ease of forming sash. From the viewpoint of forming superiority of the sash and the viewpoint that the sash and the side window can also be flushed to the side, the stepped portion is provided on the upper side and the side of the entire circumference of the stepped glass sheet of the present invention. It is preferable to provide.

In the present specification, the relevant parts of the upper side, the side side and the lower side in the state of being attached to the automobile can be explained with reference to FIG. The lower side in the state of being attached to the automobile is the lower side of the glass plate in FIG. The side edges in the state of being attached to the automobile are the left and right edges of the glass plate in FIG. The upper side in the state of being attached to the automobile is the upper side including the upper left inclined side of the glass plate in FIG. Figure 1
The stepped glass plate in 1 is an example in which a step portion is provided on the entire circumference of the glass plate. In the example in which the step is not provided only on the lower side, the cross-sectional shape of the upper side and the left and right sides of the glass plate in FIG. 1 is the shape shown in FIG. 2, and the cross-sectional thickness of the glass plate is uniform on the lower side. Equivalent to. The example in which the step portion is provided only on the upper side corresponds to an example in which the cross-sectional shape of the upper side of the glass plate in FIG. 1 is the shape shown in FIG. 2 and the cross-sectional thickness of the glass plate is uniform on the side and lower sides.

FIG. 7 shows a stepped glass plate having a convex portion on the outside of the vehicle, in which a step portion is provided on the upper side and a step portion is not provided on the lower side. FIG. 7 corresponds to a vertical cross-sectional view of the glass plate in a state where the glass plate is attached to an automobile. Although illustration of the state of the side is omitted, when the step is provided on the side,
The cross-sectional shape of the side is approximately the same as the cross-sectional shape of the upper side of FIG.
When no step is provided on the side, the cross-sectional shape of the side is substantially the same as the cross-sectional shape of the lower side of FIG.

The stepped glass plate of the present invention is a glass plate in which portions having different thicknesses are provided on one glass plate. That is, the stepped glass plate of the present invention is a glass plate in which the plate thickness of the peripheral region A of one glass plate is smaller than the plate thickness of the central region C. Therefore, it is not necessary to consider the bonding accuracy of the two glass plates unlike the laminated glass in which the two glass plates are bonded via the intermediate film.

Next, the method of measuring the stress value will be described. (A) Measurement of average surface compressive stress The surface compressive stress is measured according to JIS R3222. JIS R3222 relates to double strength glass. Since the specimen is a double-strength glass, the stepped tempered glass plate of the present invention is used as the specimen. Although there is a stipulation of the measurement point, when measuring the compressive stress of the stepped tempered glass sheet of the present invention, an appropriate plurality of points are measured without being restricted by this stipulation. afterwards,
The average value of the obtained surface compressive stresses at a plurality of points is calculated. As the measurement points, it is preferable to select the same number of points where the surface compressive stress value is expected to be close to the maximum value and the point where the surface compression stress value is expected to be close to the minimum value in each region. It should be noted that it is appropriate to consider that the surface compressive stress value becomes maximum at the intersection of the blowing direction line of the jet of cooling air for cooling the glass plate and the glass plate surface. It is appropriate to consider that the surface compressive stress value becomes the minimum value at the midpoint between two adjacent points at this intersection.

(B) Measurement of principal stress direction and principal stress difference FIG. 6 shows an apparatus for measuring principal stress direction and principal stress difference. Basically, the principal stress direction and the principal stress are measured by injecting a circularly polarized light beam into the tempered glass plate G and measuring the polarization state of the transmitted light that has become elliptically polarized light due to the strain of the stepped tempered glass plate G. Find the difference. The light beam emitted from the light source 4 passes through the polarizer 5 and becomes linearly polarized light. After that, the light is transmitted through the quarter-wave plate 6 to be circularly polarized light. An analyzer 7 is arranged behind the stepped tempered glass plate G. Stepped tempered glass plate G
Are arranged perpendicular to the incident light rays. The circularly polarized light beam incident on the stepped strengthened glass plate G passes through the stepped strengthened glass plate G and becomes elliptically polarized light according to the stress strain of the stepped strengthened glass plate G. The state of elliptically polarized light can be known by measuring the output of the photodetector 8 after passing the elliptically polarized light beam thus obtained through the rotating analyzer 7.

The principal stress direction and the principal stress difference can be obtained from the obtained elliptically polarized light state as follows. The principal stress directions θ ₁ and θ ₂ , and the phase difference corresponding to the principal stress difference is δ. The output I (φ) of the photodetector is given by the following equation (1). However, in the equation, k is a proportional constant and φ is a rotation angle of the analyzer. The ratio of the minimum value I _min and the maximum value I _max of the output of the photodetector is the ellipticity R. R and δ are connected by the following equation (2). However, δ> 0. Therefore, the phase difference δ and the principal stress directions θ ₁ and θ ₂ are expressed by the following equations (2) ′ to (4).
That is, the ellipticity R of elliptically polarized light and the rotation angle φ of the analyzer
The principal stress direction and the principal stress difference can be obtained by obtaining (the major axis angle of the ellipse when the maximum and minimum output values are obtained). The relationship between the principal stress difference Δρ and the corresponding δ is represented by equation (5). Here, c is the photoelastic constant (= 2.63 nm / cm / kg / cm ² ), t is the glass plate thickness of the measurement portion, λ is the wavelength of the light emitted from the light source 4, and in the present stress measurement device, λ = 623.8 nm.

[0035]

[Equation 1]

In this stress measuring device, the light source 4
A He-Ne laser was used for this. This is because the light beam can be focused on a minute point in order to detect a minute change such as uneven tempering of the tempered glass plate. As the polarizer 5, a Gram Thomson prism having a good polarization property is used. A glass plate 9 was arranged between the polarizer 5 and the quarter-wave plate 6 for taking out the reference light. In detecting this reference light, an interference filter 10 is arranged between the glass plate 9 and the reference light detector in order to reduce the influence of external light. The quarter-wave plate 6 used is one that polishes quartz to generate a phase difference of π / 2 with respect to a wavelength of 632.8 nm. The same element as the polarizer 5 was used for the rotation analyzer 7. As the photodetector 8, a solar cell in which an interference filter is arranged on the front surface is used in order to reduce the influence of external light as in the case of the reference light. Thus, the reference points a and b in the present invention can be determined by measuring the main stress difference and the main stress direction at a large number of points. Note that L can be determined by determining the reference points a and b.

[0037]

The present invention will be described in more detail based on the following examples, but it goes without saying that the present invention is not limited to the examples. In this example, the stepped glass plate as shown in FIGS. 1 and 2 was used. As shown in the figure, this stepped tempered glass sheet has a slightly cylindrical curved shape and is used as a window glass for a side door of an automobile mounted so as to be slid vertically or diagonally up and down.

As the cooling device, a cooling device obtained by improving the cooling device described in EP884286A was used. That is, it is a cooling device in which the nozzles of the cooling device are arranged at a small pitch to reduce the diameter of the nozzles. The small pitch arrangement of the nozzles makes it possible to reduce the required sliding distance and to give a clear difference in the cooling ability at the boundary between the portion having a large cooling ability and the portion having a small cooling ability. Further, by reducing the diameter of the nozzle, the sensitivity of the cooling capacity to the distance between the glass and the nozzle can be increased, and a large cooling capacity can be produced between the thin plate portion and the thick plate portion due to the small distance difference. It is possible and a stress distribution according to the invention is obtained.

The peripheral edge of the glass plate cut into a predetermined shape is chamfered. At this time, the chamfering process is performed by using a chamfering wheel for giving a step so that a predetermined portion of the peripheral portion is stepped. After that, the glass plate which was subjected to the step of heating and bending and subjected to the stepped chamfering was strengthened by using the improved cooling device. This stepped glass plate has an outer dimension of 110.
The glass plate is 0 × 500 mm, the central region C has a plate thickness of 6 mm, the peripheral region A has a plate thickness of 3 mm, and the peripheral region A has a width of 10 mm. The average surface compressive stress of each region was measured by measuring (A) the average surface compressive stress of the glass plate obtained by subjecting this stepped glass plate to the forming and strengthening treatment by the above-mentioned apparatus. 1100 kg / cm ^{2 in} central area C, 12 in peripheral area A
00 kg / cm ² , peripheral region B (20 mm toward the inner circumference of the glass plate from the boundary between the thick plate portion and the thin plate portion)
Width region) was 1300 kg / cm ² .

On the other hand, for the glass plate obtained above,
(B) Based on the measurement of the principal stress direction and the principal stress difference, the characteristic points having a larger principal stress difference compared to the vicinity of the vicinity were identified. As a result, the second feature point, which is closest to the first feature point in the intermediate region B and has a larger principal stress difference than that of the neighboring periphery, was in the peripheral region A. The distance between the first feature point and the second feature point was 10 mm. As a test for confirming the strength, a hammer test in which a 1.5-pound hammer is dropped from a height of 40 cm in this region, and a drop ball test in which a 227 g steel ball is dropped and broken to a height of 2 m or more Was carried out. This test corresponds to the automobile window glass test specified in JIS-R3212. The stepped tempered glass plate obtained as described above passed the test specified in JIS-R3212.

[0041]

According to the present invention, in the stepped glass plate, a large surface compressive stress is applied to the intermediate region B between the central region C and the peripheral region A having a small thickness, and the safety glass for automobiles is manufactured. An excellent effect that a plate or the like can be maintained with sufficient strength is obtained.

[Brief description of drawings]

FIG. 1 is a schematic front view illustrating an example of a stepped glass plate of the present invention.

FIG. 2 is a schematic sectional view illustrating an example of a stepped glass plate of the present invention.

FIG. 3 is a view showing an example of an arrangement state of stepped glass plates.

FIG. 4 is an enlarged conceptual view of a main part (P) of FIG.

FIG. 5 is a schematic cross-sectional view showing another example of the stepped glass plate of the present invention.

FIG. 6 is a conceptual diagram illustrating a method of measuring a principal stress direction and a principal stress difference.

FIG. 7 is a schematic sectional view illustrating an example of a stepped glass plate of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass plate 2 Sash 3 Recess A of sash 2 Peripheral region B Middle region C between the central region C and the peripheral region A at the peripheral region of the central region C Central region G Stepped glass plate

Claims (6)

[Claims] 1. A peripheral region A, a central region C, and a peripheral region A.
A glass plate having an intermediate region B between the central region C and a central region C, wherein a step portion is provided at the boundary between the peripheral region A and the intermediate region B, and the peripheral region A has a thickness equal to that of the central region C. In the stepped glass plate formed to be thinner than
The glass plate has been tempered and has an intermediate region B
The stepped glass plate is characterized in that the average surface compressive stress in (1) is larger than the average surface compressive stress in the central region (C) by 100 to 500 kg / cm ² . 2. The intermediate region B is 5 to 30 mm from the boundary between the peripheral region A and the intermediate region B toward the inner circumference of the glass plate.
The stepped glass sheet according to claim 1, having a width of. 3. The intermediate region B is scattered with first characteristic points having a large difference in principal stress as compared with those in the vicinity of the vicinity, and has a large difference in principal stress as compared with those in the vicinity of the vicinity, which is closest to the first characteristic point. The distance between the second feature point and the first feature point has 5 to 15 mm
The stepped glass plate according to claim 1 or 2. 4. The stepped glass according to claim 1, 2 or 3, wherein the glass sheet is a bent glass sheet for automobile windows, and the convex surface of the bent glass sheet is an outer surface of the automobile. Board. 5. The stepped glass sheet according to claim 4, wherein the stepped portion is a convex surface of a bent glass sheet and is formed on an upper side in a state of being attached to an automobile. 6. The stepped glass sheet according to claim 5, wherein the stepped portion is a convex surface of a bent glass sheet and is formed on an upper side and a side edge in a state of being attached to an automobile.