JPH11199257A - Tempered glass plate, cooling of glass plate, and cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sheet which can meet the safety standards from splinters for an automotive windshield by forming a plurality of belt-like regions which are formed with the compressive stresses of a specific numerical value on the surface and where the main stress directions thereof are approximately parallel at reference points where the main stress difference is larger than that of the periphery and belt-like regions which are held by these regions and where the main stress directions of the reference points vary from each other. SOLUTION: This tempered glass plate for the thin windshield having a sheet thickness of 2.3 to 3.5 mm desired to improve the fuel of automobiles is formed to have the average surface compressive stress of 1000 to 1300 kg/cm<2> . The belt-like regions A, B interspersed with the reference points (.mark) (a), (b) having the main stress difference larger than that of the periphery with respect to the jet collision points o marks of cold wind are alternately formed in parallel on the surface of the tempered glass plate. The reference point (a) is <=0 kg/cm<2> in the main stress difference and the main stress directions thereof are approximately parallel with each other. The width of the regions A is specified to a range of 10 to 30 nm. The reference points (b) have the main stress directions varying from each other from the adjacent reference points and the lines connecting these points are zigzag.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tempered glass sheet,
The present invention relates to a method and apparatus for cooling a glass sheet to obtain the tempered glass sheet. Particularly, a thin tempered glass sheet having a large area and a double curved surface such as a rear glass for automobiles,
The present invention relates to a cooling method and a cooling device for strengthening a thin glass plate.

[0002]

2. Description of the Related Art A tempered glass sheet is used for a window glass (excluding a windshield) of an automobile. In this case, in order to prevent a driver or a passenger from being injured, laws and regulations regarding cracking of the tempered glass sheet are set from the viewpoint of safety. Unless the performance stipulated by such regulations is satisfied, the glass cannot be used as a window glass of an automobile.

[0003] For example, in the regulations of tempered glass for automobile windows, there are regulations on the state of crushed pieces when a local impact is given to a tempered glass sheet. Specifically, the area where the number of particles of the crushed pieces of the glass plate broken by the impact is the smallest and the area where the number of the pieces of the crushed pieces are the largest are selected, and the minimum number of the pieces of the crushed pieces in these areas is selected. And the maximum number of particles falls within a certain allowable range.

[0004] The minimum allowable number of particles of the crushed pieces determines the maximum particle size of the particles generated by breaking the glass plate. The smaller the maximum particle size, the less the risk of tearing by large debris when the glass plate breaks. The maximum allowable particle number of the crushed pieces determines the minimum particle size of the crushed pieces generated by breaking the glass plate. Larger minimum particle sizes reduce the risk of glass particles entering the human body. The rules for the size of the crushed pieces when the glass plate is broken are in the ECE standard and JIS.

[0005] For example, the ECE standard (E6) requires that the number of crushed particles in a 5 cm x 5 cm square of a broken glass plate be at least 40 particles and at most 400 particles. Excludes a 20 mm wide strip from the edge and a 75 mm radius circle centered on the crack initiation point.) Hereinafter, the largest value among the above-mentioned crushed pieces is referred to as the largest number of particles, and the smallest value is referred to as the smallest number of particles. Also, when the glass plate breaks, the end is sharp or the length is 75 mm
There is a requirement that no long strips be contained at all. Another requirement is that the area of the fragments should not exceed 3 cm ² .

[0006] The tempered glass sheet is obtained by heating the glass sheet to a temperature near the softening point of the glass sheet (usually about 600 to 700 ° C) and then rapidly cooling it with cooling air. The cooling air is
It is sprayed toward the glass plate from a plurality of cooling nozzles arranged on both sides of the glass plate. In this way, the glass sheet is strengthened by providing a temperature difference between the glass sheet surface and the inside of the glass sheet during cooling and leaving a compressive stress layer on the finally solidified glass sheet surface.

By the way, recent automobiles are required to be reduced in weight in order to reduce fuel consumption. Accordingly, there is an increasing demand for reducing the thickness of the glass plate and reducing the weight. In the case of a glass sheet having a thickness of about 4 to 6 mm, a tempered glass sheet satisfying the above-mentioned standards can be obtained relatively easily by the above-described glass sheet tempering method. However, when the sheet thickness was reduced in accordance with the demand for weight reduction, it was difficult to obtain a tempered glass sheet satisfying each standard by the above-described tempering method. The reason is that a sufficient temperature difference cannot be provided between the glass plate surface and the inside of the glass plate due to the small thickness.

Conceptually, in order to provide a sufficient temperature difference between the glass plate surface and the inside of the glass plate, the pressure of the cooling air is increased, the nozzles are brought closer to the glass plate, and the distance (pitch) between the nozzles is increased. ) Can be shortened. However, it is difficult to increase the pressure of the cooling air due to mechanical limitations of the blower device and the compressor.

On the other hand, it is necessary for the cooling air colliding with the glass plate to have an escape route after colliding with the glass plate.
This is because if the cooling air after the collision remains on the spot, it will hinder the collision of the cooling air injected later on the glass plate, making it difficult to uniformly spray the glass plate surface. . If the above-mentioned nozzle pitch is shortened or the nozzle is brought close to the glass plate, it becomes impossible to secure an escape route after the collision with the glass plate.

In the strengthening process, the glass plate is swung when the cooling air is blown to make the surface of the glass plate evenly cooled. Therefore, when the nozzle is brought close to the glass plate, the swinging operation may be hindered by the nozzle. When the glass plate is bent so as to have a double curved surface, the interference between the nozzle and the glass plate is remarkable.

Therefore, in order to obtain a thin tempered glass sheet, it has been proposed to perform a tempering treatment with a special arrangement of nozzles. Specifically, it is intended to control the direction of crushing by providing regions having different main stresses on a glass plate.

Here, the main stress direction and the main stress difference will be described. First, one plane (cross section of the glass plate) perpendicular to the glass plate surface is to be selected. Depending on the choice, the plane can be at any angle to a straight line parallel to the plane of the glass sheet. When one point in this plane is selected, the stress value acting on this point in the direction perpendicular to the selected plane differs depending on the angle of the selected plane. And a minimum angle. The direction of the stress indicating the maximum value and the direction of the stress indicating the minimum value are the main stress directions. The two principal stress directions are orthogonal. In this specification, the direction of the stress showing the maximum value is called the principal stress direction in principle. The maximum value and the minimum value are the main stresses.

Since the main stress itself cannot be directly measured, the main stress of a tempered glass plate is evaluated by the main stress difference obtained by the photoelastic method. The main stress difference obtained by the photoelasticity method corresponds to the integrated average value of the sum of the differences between the maximum stress value and the minimum stress value at all points arranged in the thickness direction on the strengthened glass sheet. Therefore, select a point on the glass plate surface, take each point in the plate thickness direction from this point, and calculate the integrated average value of the difference between the maximum stress value and the minimum stress value of these points on the glass plate surface. The principal stress difference at the selected point and the principal stress direction at that time are evaluated as the principal stress direction at that point.

[0014]

A tempered glass sheet provided with regions having different principal stress directions is disclosed in U.S. Pat. No. 4,128,6.
No. 90, JP-A-55-104935 and JP-A-58-91042.

US Pat. No. 4,128,690 describes a tempered glass plate having a plate thickness of 2.5 to 3.5 mm. This tempered glass sheet has a maximum of 62 MN /
It has a center tensile stress of m ² (the maximum value of the surface compressive stress is 1
24MN / m ² ), the glass sheet has a distribution of areas having different main stresses acting in the plane of the glass sheet, and the maximum value of the main stress difference in the areas having different main stresses. Is 8 to 25 MN / m ² , and the distance between the sections showing the maximum value is in the range of 15 to 30 mm.

However, when a glass sheet having a thickness of 3.0 mm or less is actually manufactured as a tempered glass sheet having the above distribution,
The following problems occur. In the crushing test of E6, the difference between the maximum number of particles and the minimum number of particles is large. This is because, due to a slight change in the molding conditions of the strengthened glass sheet (for example, a change in the outside air temperature or the like), either the upper limit of the maximum number of particles or the lower limit of the minimum number of particles specified in E6 easily exceeds the limit. Indicates a state.

Further, in the tempered glass sheet having the different distribution of the main stress, elongated crushed pieces (small pieces) tend to be generated. Further, the maximum area of the crushed pieces generally tends to exceed 3 cm ² . This tendency is expected to be due to the above distribution being too sparse.

JP-A-55-104935 describes a tempered glass sheet having a sheet thickness of 2.5 to 3.5 mm. This tempered glass sheet is 850-1350 kg /
It has an average surface compressive stress of cm ² . Then, areas having different main stresses acting in the plane of the glass sheet are scattered and formed. In areas having different main stresses, the maximum value of the main stress difference is in the range of 50 to 300 kg / cm ² . The distance between the areas showing the maximum value is 5 mm or more and 15 m
m.

In this publication, there is described in Example 5 a tempered glass plate having a thickness of 2.5 mm. At this time, the distance between the sections showing the maximum value of the main stress difference is 7.1 to 9.0 mm. In other words, it is understood that if the thickness of the glass plate is small, it is difficult to obtain a strengthened glass plate that satisfies the regulations unless the above distance is short. If this distance is short, cracks generated in the strengthened glass plate during the crushing test are likely to stray. Straying is advantageous for obtaining fine fragments.

However, because of the stray, the progress of the crack is left to the end. That is, it becomes difficult to freely control the manner in which the crack proceeds. On the other hand, a slight change in the forming conditions of the strengthened glass sheet (for example, a change in the outside air temperature or the like) causes a slight change in the stress value of the obtained strengthened glass sheet and the distribution of different main stresses. In particular, thin glass plates are susceptible to this effect. For this reason, if the manner in which the crack progresses cannot be freely controlled, it is difficult to predict the obtained stress value and the above-mentioned distribution, and extraction of molding conditions and the like become complicated.

JP-A-58-91042 describes a tempered glass sheet having a sheet thickness of 2.4 to 3.5 mm. This tempered glass sheet has a maximum value of 13 on its surface.
And the surface compressive stress is high band region is 00kg / cm ² or less, the minimum value and the band-like region surface compressive stress is lower at 1020kg / cm ² or more, are formed alternately. The difference between the maximum value and the minimum value of the surface compressive stress is 80 to 220 k.
g / cm ² . In the belt-like region having a low surface compressive stress, the maximum value of the main stress difference is 80 kg / cm ² or more.

Of the tempered glass sheets disclosed in this publication, attention is focused on a glass sheet having a thickness of 2.4 mm. In this case, it is required to reduce the band width of the band-shaped region having a low surface compressive stress or to increase the main stress value of the band-shaped region having a low surface compressive stress. When the band width of the band-shaped region having a low surface compressive stress is reduced, the above-described crack strays easily occur. If the main stress value of the belt-shaped region having a low surface compressive stress is increased, the main stress difference is inherently a tensile stress, so that it may be difficult to obtain a practical strength of the strengthened glass sheet.

In particular, the following problems are expected in terms of practical strength. That is, the band-shaped region having a low surface compressive stress is a portion to which the cooling air jet does not hit during the strengthening process. Therefore, in the case of a glass plate having a thickness of 2.4 mm, the surface compressive stress of a portion of the glass plate where cooling air is not applied is set to 102 mm.
Making it 0 kg / cm ² or more is not feasible. Therefore, the surface compressive stress of this portion is expected to be actually about 900 kg / cm ² at most. In this case, the produced tempered glass sheet does not have a practical strength.

In the embodiment described in this publication, 2.4 is used.
The average surface compressive stress of a glass plate having a thickness of mm is disclosed. For example, the average surface compressive stress is 1100 kg / cm ²
There is an example of a tempered glass plate having a difference in height of surface compressive stress of 190 kg / cm ² . What is disclosed here is the average value of the large and small values of the compressive stress. Therefore, in this publication, the surface compressive stress of the band-like region of the surface compressive stress is actually 1020 kg / cm.
It does not show that a tempered glass plate of ² can be obtained.

As described above, a strengthened glass sheet in which a predetermined main stress distribution is formed on a glass sheet having a thickness of about 2.5 mm is known. However, in practice, with a sheet thickness of about 2.5 mm, it is difficult for these tempered glass sheets to satisfy the standards. Furthermore, in order to actually obtain a thin tempered glass sheet that satisfies these standards, there are many problems in equipment and it is not feasible. In particular, equipment problems are remarkable in a glass sheet bent into a double curved shape or a large-area glass sheet.

That is, conceptually, to make the distribution of the regions having different principal stresses denser is toward a direction satisfying the standard. However, for that purpose, means for bringing the nozzles closer to the glass plate, shortening the distance (pitch) between the nozzles, and the like are required. As a result, the problem that the escape route of the cooling air after colliding with the glass plate cannot be secured is as described above.

An object of the present invention is to provide a thin tempered glass sheet, and a method and apparatus for cooling a glass sheet for easily obtaining such a tempered glass sheet.

[0028]

According to the present invention, a sheet thickness of 2.3 is provided.
３3.5 mm, 1000 to 1300 kg / cm ²
A tempered glass sheet having an average surface compressive stress of not more than 120 kg / cm ² and having a main stress difference greater than the main stress difference in the vicinity of the vicinity. A plurality of reference points a whose principal stress directions are substantially parallel to each other, and there is no reference point a between adjacent reference points a, a having a principal stress difference greater than or equal to the principal stress difference between these reference points. A plurality of parallel belt-shaped regions A having a width in the range of 10 to 30 mm with the reference line formed by the group as the center line and being sandwiched between adjacent belt-shaped regions A, A are formed. And a plurality of reference points b having a main stress difference larger than the main stress difference in the vicinity of the vicinity are scattered in the band area B, and the main stress direction at the reference point b is Different from the main stress direction at the adjacent reference point b, Providing tempered glass plate, wherein the door.

In the present invention, the sheet thickness is 2.3 to 3.5 m.
m, and a tempered glass plate having an average surface compressive stress of 1000~1300kg / cm ² is formed, the glass plate surface is 120 kg / cm ² or less in size and the main stress difference near proximity Has a larger main stress difference than
A plurality of reference points a whose principal stress directions are substantially parallel to each other, and a point having a principal stress difference that is larger than the principal stress difference in the vicinity near the main stress direction that is different from the principal stress direction are adjacent reference points a. , A plurality of parallel belt-shaped areas A having a width in the range of 10 to 30 mm and a plurality of parallel belt-shaped areas A having a reference line formed by a group of reference points a not existing between A band-shaped region B sandwiched between A,
Are formed in the belt-shaped region B, a plurality of reference points b having a main stress difference larger than the main stress difference in the vicinity are scattered, and the main stress directions at the reference points b are adjacent to each other. The present invention provides a tempered glass sheet characterized by being different from the main stress direction in (1).

The present invention also provides a heated glass plate,
The glass sheet is conveyed between a pair of wind boxes having a plurality of nozzles arranged on both sides of the glass sheet, and the cooling air supplied from the wind box is blown from the plurality of nozzles to the glass sheet surface to strengthen the glass sheet. A method of cooling a glass plate, wherein each of the plurality of nozzles, which is arranged on at least one glass plate surface side, has a plurality of opening holes so as to simultaneously blow cooling air in a plurality of directions. It is provided to the glass plate so that the intersection of the spraying direction line of the cooling air jet from the opening hole of the nozzle toward the glass plate and the glass plate surface is almost uniformly aligned on the glass plate surface. To provide a method for cooling a glass sheet, characterized by blowing cooling air.

Further, according to the present invention, the heated glass sheet is transported between a pair of wind boxes having a plurality of nozzles arranged on both sides of the glass sheet, and the cooling air supplied from the wind box is supplied to the above-mentioned wind box. A method for cooling a glass sheet by strengthening the glass sheet by spraying the glass sheet from a plurality of nozzles, wherein a tip end surface on a side facing the glass sheet has a convex curved shape and is supplied from inside a wind box. A plurality of hollow tubular nozzles having a plurality of opening holes for blowing cooling air toward the glass plate are provided on at least one surface of the glass plate, and cooling is performed from these nozzles toward the glass plate. A method for cooling a glass sheet, characterized by blowing air.

Further, the present invention provides a glass box having at least a wind box disposed opposite to both sides of a glass plate and a plurality of nozzles mounted on the glass plate side of the wind box. In a cooling device for a glass plate, which blows cooling air jetted from each nozzle toward the plate, the nozzle is a hollow tubular member having a convex curved tip surface on a side facing the glass plate, A cooling device for a glass sheet, wherein a plurality of openings for blowing cooling air supplied from the inside of the wind box toward the glass sheet are provided on the surface.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a conceptual diagram showing an example of a tempered glass plate of the present invention, and FIG. 2 is an enlarged conceptual diagram of the tempered glass plate, for explaining main stresses formed in the tempered glass plate. The arrows in the figure indicate the principal stress direction at each reference point. A mark in the figure indicates a point at which a jet of cooling air, which will be described later, collides with the glass plate. The marks in the figure indicate each reference point.

The thickness of the tempered glass sheet 10 is 2.3 to 3.
It is in the range of 5 mm. In addition, in a special case where conditions such as the outside air temperature when the glass sheet is actually cooled are not sufficiently satisfied, the ability of the cooling air described below may be insufficient. Therefore, a preferable plate thickness that is more realistic and can effectively realize the present invention is 2.5 to 3.1 mm. The average value of the compressive stress formed on the surface of the tempered glass sheet 10 is in the range of 1000 to 1300 kg / cm ² . On the surface of the tempered glass sheet 10, band-shaped regions A and band-shaped regions B are alternately formed.

The band region A is the center line of the reference straight line T which is formed by a group of reference points a, the width L _a 10 to 30 m
It is a band-like area within the range of m. The reference point a is 12
This is a point having a main stress difference of 0 kg / cm ² or less and having a main stress difference larger than the main stress difference in the vicinity of the vicinity. The reference point a is a point selected so that there is no (a) point having a main stress difference equal to or larger than the main stress difference between the adjacent reference points a. Alternatively, the reference point “a” is located between the adjacent reference points “a” and “a”.
This point is selected so that there is no point having a main stress difference that is larger than the main stress difference in the vicinity, such as a direction that is different from the main stress direction in the above. The principal stress direction at the reference point a is
Each is substantially parallel to each other. The direction is the band-like area A
Is a direction substantially perpendicular to the longitudinal direction. In the figure, the sum of the distance L _c between the reference points a, a neighboring pair, reference points a neighboring other pair, and the distance L _d between a (L _c + L _d)
Is in the range of 40-60 mm.

In the belt-shaped region B, a plurality of reference points b having a main stress difference larger than the main stress difference around the vicinity are scattered. The reference point b has a main stress direction at that point different from the main stress direction at the adjacent reference point b.

In the tempered glass sheet 10 of the present embodiment, the line formed following the main stress direction at the reference point b in one band-shaped area B is meandering. The principal stress direction at a reference point b (hereinafter, this reference point is referred to as b _A ) near the boundary with the belt-shaped region A is substantially perpendicular to the principal stress direction at the reference point a.

In the tempered glass plate 10 of this embodiment,
The reference point b can be roughly divided into the following two groups. Reference point b
The first group of reference points is the reference point b _A and the reference point a
Have a main stress direction substantially perpendicular to the main stress direction. Then, in each of the band-shaped regions B, when viewed in the direction of the reference straight line (T), they are alternately arranged near the boundary with one adjacent band-shaped region A and near the boundary with the other adjacent band-shaped region A. Group. On the other hand, the second group of the reference points b is a reference point b _A near the boundary with the adjacent one of the strip-shaped areas A in the first group.
If, in a direction substantially coincides with the direction connecting the reference points b _A in the vicinity of the boundary between the other strip-like regions A adjacent to the reference point b _A having a principal stress direction. And the first of these two
Are arranged between the reference points b _A of the group of.

Incidentally, it has been described that the principal stress directions of the reference points a are substantially parallel to each other. The main stress direction at the reference point b _A has been described as being substantially perpendicular to the principal stress directions at the reference point a. This indicates that, in the present invention, “substantially parallel” and “substantially vertical” that describe the principal stress direction need not be strictly “parallel” and “vertical”. That is, in the present invention, "substantially parallel" and "substantially vertical"
Means that the glass sheet is "parallel" and "vertical" to such an extent that the glass sheet having a small thickness has a distribution of principal stress that can satisfy the regulations. This will be described in detail.

The tempered glass sheet in the present invention is obtained by blowing a cooling air to a heated glass sheet and rapidly cooling it. In this case, the distribution of the main stress can be obtained by scattering the points where the jet of the cooling wind collides with the glass plate on the glass plate surface. On the other hand, although the generation of the main stress difference depends on the degree of quenching, it is difficult to keep the degree of quenching constant at all times due to a difference in outside temperature or the like. Therefore, even if the cooling air is set so that the main stress direction is in a predetermined direction (parallel or vertical), it may not always be strictly in the predetermined direction (parallel or vertical). In consideration of such circumstances, the tempered glass sheet of the present invention includes a tempered glass sheet that satisfies the regulations even if the direction is slightly different from a predetermined direction (parallel or vertical). In addition, it is preferable that the main stress direction is strictly oriented in a predetermined direction (parallel, perpendicular) from the viewpoint of high control accuracy of the progress of the crack. For the same reason, it is assumed that a line slightly deviating from the strict “straight line” is also included in the “reference straight line (T)”.

The reason why the tempered glass sheet having such a distribution of the main stress can sufficiently satisfy the specifications even when the sheet thickness is small is as follows.
It is as follows. First, the tempered glass sheet of the present invention satisfies both the following properties (1) and (2). (1) 120 ≦ σ _a , preferably 40 ≦ σ _a ≦ 80 (unit kg / cm ² , σ _a ; main stress difference at reference point a). (2) 10 ≦ L _a ≦ 30 (unit: mm).

The tempered glass sheet of the present invention preferably satisfies at least one property selected from the following (3) to (6) in addition to the properties (1) and (2). (3) 10 ≦ L _b ≦ 30 (unit: mm). (4) 50 ≧ σ _b (kg / cm ² , σ _b ; reference point b)
Principal stress difference). (5) The line following the main stress direction at the reference point b is meandering, and the main stress direction at the reference point b near the band-shaped area A is substantially perpendicular to the main stress direction at the reference point a. (6) 40 ≦ L _c + L _d ≦ 60, preferably 20 ≦ L _c
≦ 30 and 20 ≦ L _d ≦ 30, more preferably 20 ≦ L
_c ≦ 30 and 20 ≦ L _d ≦ 30 and L _c > L _d . In addition,
Side with a reference point b _A near corresponds to L _c, the adjacent set of which corresponds to L _d.

On the other hand, the number and size of the crushed pieces in the crushing test depend on the behavior of crack propagation. In other words, as the cracks progress linearly, the crushed pieces tend to be elongated and smaller. Therefore, it is required that the crack does not proceed linearly as much as possible.

Basically, the presence of a large principal stress can prevent the crack from going straight. This is because the crack bends in a direction perpendicular to the main stress direction. And
After the crack bends and strikes another crack, splinters are formed. In the tempered glass sheet of the present invention, since the reference points b having different main stress directions are scattered in the band-shaped region B, the crack can travel from the band-shaped region A to the band-shaped region B. However, if the magnitude of σ _a is too large, even if the reference point b exists in the belt-shaped region B,
A crack traveling in the band-shaped region A cannot be directed to the band-shaped region B.

Therefore, by satisfying (1),
In the belt-shaped region A, it is possible to prevent a crack that progresses in parallel with the longitudinal direction of the region from continuing to advance (the main stress direction at the reference point a leads the crack in a direction that matches the direction in which the crack advances in this case). Is.). 40
If> σ _a, it is difficult to control the progress of cracks, and if 80 <σ _a , a slight restriction is likely to occur in the main stress difference and the main stress direction at the reference point b. Therefore, 40 ≦ σ _a
It is particularly preferred that ≦ 80.

Even if the condition (1) is satisfied, there is a case where the progress of the crack is hardly hindered. It is the case L _a is too large. That is, the principal stress at the reference point b plays a role in bending the traveling direction of the crack traveling in the belt-shaped region A. Therefore, in order to be easily affected by the main stress at the reference point b, L _a ≦ 30 is set. Conversely, when L _a is too small, it is difficult to bend the cracks that have progressed toward the band-like region A of a strip-shaped region B. Therefore, it is necessary to satisfy (2) while satisfying (1).

The reason why it is preferable to satisfy (3) is that
The reason for satisfying (2) is almost the same. On the other hand, in the tempered glass plate satisfying the condition (5), the crack traveling in the belt-shaped region B bends in a direction perpendicular to the main stress direction at the reference point b. Therefore, the crack can bend,
Even if the range slightly exceeds the range of (3), a desired progress of the crack can be realized.

On the contrary, in order to guide the progress of the crack in a desired direction, a tempered glass plate satisfying the condition (4) is preferable.
When σ _b <50, it is difficult to control the progress of the crack.

When the main stress direction at the reference point b _A is substantially perpendicular to the main stress direction at the reference point a, a crack traveling in the band-shaped region A is easily bent toward the band-shaped region B. Accordingly, it is possible to prevent a crack traveling in the belt-shaped region A from traveling in the longitudinal direction of the belt-shaped region A. When (6) is satisfied, the reason why L _c > L _d is particularly preferable is as follows. If the distance between adjacent reference points a is large, large fragments are likely to be generated at this point. Therefore, it is required to bend cracks that progress in the band-shaped region A toward the band-shaped region B to suppress generation of large fragments.
Therefore, in the vicinity of the reference point a neighboring provided at a distance apart, it is preferable that the reference point b _A is provided. Therefore, by setting L _c > L _d , a crack that progresses in the band-shaped region A can be bent toward the band-shaped region B, and large fragments in the band-shaped region A can be suppressed.

As described above, a plurality of factors influence each other on crack control. In particular, when the thickness of the glass plate is small, it is originally difficult to give a temperature difference between the glass plate surface and the inside of the glass plate. Therefore, crushing that satisfies the regulations cannot be obtained by simply controlling the progress of the crack. Therefore, the tempered glass sheet of the present invention is (1)
It has the main stress characteristic of (2), and further has (3)
It is preferable to have the main stress characteristics of (6) to (6).

Next, a method of measuring a stress value will be described. (A) Measurement of surface compressive stress Measurement of surface compressive stress is performed according to JIS R3222. JIS R3222 relates to a double strength glass plate. In this measurement, since the specimen is a double-strength glass plate, the measurement is performed using the tempered glass plate of the present invention as the specimen. Although there are regulations on measurement points, when measuring the compressive stress of the tempered glass sheet of the present invention, appropriate plural points are measured irrespective of the regulations. Thereafter, an average value of the obtained surface compressive stresses at a plurality of points is obtained.

As the measurement point, it is preferable to select a point within a circle having a radius of 50 mm from the center point of the glass plate. In particular, 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 compressive stress value is expected to be close to the minimum value. It is natural to consider that the surface compressive stress value becomes the maximum value at the intersection between the spraying direction line of the cooling air jet for cooling the glass sheet and the glass sheet surface. It is natural to think that the surface compressive stress value becomes a minimum value at an intermediate point between two adjacent points with respect to this intersection.

(B) Measurement of principal stress direction and principal stress difference FIG. 7 shows an apparatus for measuring principal stress direction and principal stress difference. Basically, the main stress direction and the main stress difference are determined by irradiating a circularly polarized light beam to the tempered glass plate 10 and measuring the polarization state of the transmitted light that has become elliptically polarized light due to the distortion of the tempered glass plate 10. Ask. The light emitted from the light source 41 is
2 and becomes linearly polarized light. After that, the light is transmitted through the 波長 wavelength plate 43 to be circularly polarized light. An analyzer 45 is arranged behind the tempered glass plate 10.

The tempered glass plate 10 is arranged perpendicular to the incident light beam. The circularly polarized light incident on the tempered glass plate 10 passes through the tempered glass plate 10 and
The light becomes elliptically polarized light in accordance with the stress strain. The state of the elliptically polarized light can be known by measuring the output of the photodetector 46 after passing the elliptically polarized light beam thus obtained through the rotating analyzer 45.

The principal stress direction and the principal stress difference are obtained from the obtained elliptically polarized light state as follows. The principal stress direction is θ
₁ , θ ₂ , and the phase difference corresponding to the main stress difference is δ. The output I (φ) of the photodetector is given by equation (1) (where
k is a proportionality constant, and φ is a rotation angle of the analyzer. ). The ratio between 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 in the relationship of Expression (2), that is, Expression (3) (assume δ> 0). Therefore, the phase difference δ,
The principal stress directions θ ₁ and θ ₂ are represented by equations (4) and (5).

That is, the principal stress difference and principal stress direction are determined by determining the ellipticity R of the elliptically polarized light and the rotation angle φ of the analyzer (the major axis angle of the ellipse when the maximum and minimum output values are obtained). be able to. Note that the relationship between the main stress difference Δσ and the corresponding δ is represented by Expression (6). Where c
Is the photoelastic constant (= 2.63 nm / cm / kg / cm)
² ), t is the thickness of the strengthened glass plate 10, λ is the wavelength of light emitted from the light source 41, and λ = 6 in the present stress measuring device.
23.8 nm.

[0057]

I (φ) = k {1−sin δ · sin 2 (θ−φ)} (1) R = I _min / I _max = (1−sin δ) / (1 + sin δ) (2) ^{) δ = sin -1 {(1} -R) / (1 + R)} ··· (3) θ 1 = φ + π / 4 ± nπ ··· (4) θ 2 = φ-π / 4 ± nπ ··· (5) Δσ = λδ / (360 ct) (6)

In this stress measuring device, the light source 4
1 was a He-Ne laser. This is because a light beam can be focused on a minute point in order to detect a minute change such as uneven reinforcement of the strengthened glass plate. For the polarizer 42, a Gram-Thompson prism having good polarization properties was used. A glass plate 47 was disposed between the polarizer 42 and the quarter-wave plate 43 for taking out reference light. In detecting this reference light, a glass plate 47 is used to reduce the influence of external light.
Filter 49 between the reference light detector 48
Was arranged. Quartz is polished on the 波長 wavelength plate 43 and 63
One that generates a phase difference of π / 2 with respect to a wavelength of 2.8 nm was used. The same element as the polarizer 42 was used for the rotation analyzer 45. As the photodetector 46, a solar cell having an interference filter on the front surface was used in order to reduce the influence of external light as in the case of the reference light.

By measuring the main stress difference and the main stress direction at many points in this manner, the reference points a and b in the present invention are obtained.
Can be determined. By determining the reference points a and b, L _a , L _b , L _c , and L _d can be determined.

A preferred method for producing the above tempered glass sheet of the present invention will be described below. FIG. 3 is a schematic sectional view showing an example of the glass plate cooling device of the present invention.
The cooling device for a glass plate according to the present invention includes wind boxes 11 and 11 ′ and wind boxes 11 and 11 ′ that are arranged on both sides of the glass sheet 1 to face each other.
And a plurality of nozzles 12 mounted on the glass plate 1 side as main constituent members.

The surface formed by each group of nozzles 12 mounted on the wind boxes 11 and 11 ′ substantially matches the shape of the glass plate 1. The glass sheet 1 heated to near the softening point in a heating furnace (not shown) and bent and formed as necessary is conveyed between the wind boxes 11 and 11 '. In this case, the glass plate 1 is held in a horizontal state by an appropriate transfer means such as a ring connected to a drive mechanism, and is transferred between the wind boxes 11 and 11 '. When the glass plate 1 is transported between the wind boxes 11 and 11 ′, a cooling air having a predetermined temperature and pressure is blown toward the glass plate 1 from each nozzle 12. In this way, the glass sheet 1 is rapidly cooled to obtain a desired tempered glass sheet.

FIG. 4 is a schematic perspective view (a) and a schematic top view (b) showing an example of a nozzle according to the present invention. The nozzle 12 has a hollow tubular shape, and its distal end surface 12a on the side facing the glass plate 1 has a partially spherical shape with the side facing the glass plate 1 as a convex side surface.

A plurality of opening holes 20 for blowing cooling air toward the glass plate 1 are provided in the tip end surface 12a.
These opening holes 20 are provided evenly on the entire front end surface 12 a so as to be scattered, for example, radially around the longitudinal center line of the nozzle 12. FIG. 5 is a schematic top view showing another example of the nozzle according to the present invention.

As described above, by making the shape of the tip end surface of the nozzle a convex curved surface and providing a plurality of opening holes in the tip end surface, the cooling air blown out from the nozzle is blown onto the glass plate. , And the number of jets colliding per unit area of the glass plate surface can be increased.

As shown in FIG. 6, the glass from the nozzle 12 is set so that the intersection point P between the spraying direction line of the jet flowing from the nozzle 12 toward the glass plate 1 and the surface of the glass plate 1 is almost uniformly aligned on the surface of the glass plate 1. Cooling air is blown toward the plate 1. In this case, it is preferable that the intersection point P be 30 points or more per 10 cm square on one surface of the glass plate, and for that purpose, the pitch of the nozzles, the distribution of the openings of the nozzles, and the distance between the nozzle tip and the glass plate surface Is adjusted appropriately.

In this adjustment, the angle between the spraying direction line and the glass plate surface is set to 45 ° or less, and the interval between the nozzle tip and the glass plate surface is set to about 4 to 6 times the opening diameter of the opening. It is preferable to obtain sufficient strength of the glass plate while obtaining predetermined fragments. As a result, the stress distribution in the direction of the glass sheet surface can be made dense (the distance between areas where the main stresses acting in the direction of the glass sheet are different) is reduced without lowering the cooling efficiency, and crushing when the glass sheet is broken Can be finely divided.

In particular, when the thickness of the glass plate is small, it is necessary to increase the cooling capacity of the cooling air in order to obtain the above-mentioned fine crushing. That is, in principle, if the cooling capacity is increased,
Even a thin glass plate having a thickness of, for example, about 2.3 to 3.5 mm can provide fine crushing when broken. However, when the cooling capacity is increased, the glass plate may be broken due to a tensile stress temporarily generated on the glass plate surface in the initial stage of cooling. More practically, as described above, it is difficult to blindly increase the cooling capacity due to the mechanical structure. For this reason, it has become possible to obtain a glass plate that is finely crushed at the time of breakage without particularly increasing the cooling capacity according to the present invention.

Further, a glass plate having a complicated shape (for example, a glass plate bent and formed so as to have a three-dimensionally curved surface,
In particular, when the arc of the curved surface is as large as about 20 mm), it becomes difficult to give a large swing required for uniform cooling of the glass plate. In view of this, since the openings are densely arranged by adopting the nozzle shape as described above, the swing stroke given to the glass plate between the wind boxes can be shortened.

The apparatus for cooling a glass sheet in the present invention is not limited to the above example. For example, the glass sheet may be held and transported between the wind boxes in a horizontal state, or may be held and transported in a vertical state. Good. Along with this, the wind boxes are not limited to those arranged vertically facing each other as shown in the figure, but can be arranged according to the holding of the glass plate in a vertical state.

The shape of the surface formed by the nozzle group can be appropriately set according to the shape of the glass plate. It is preferable that the distance from the tip surface of the nozzle to the glass plate be substantially equal in each nozzle, since a predetermined stress can be applied to the glass plate. Therefore, it is preferable that the shape of the surface formed by the nozzle group is substantially the same as the shape of the glass plate. In addition, by appropriately controlling the temperature, amount, pressure, and the like of the cooling air jetted from each nozzle by each nozzle, or by appropriately adjusting the pitch between the nozzles, the surface formed by the nozzle group is formed. The shape can be set without depending on the shape of the glass plate.

The cooling air supplied to the nozzles from the inside of the wind box is supplied from the blower device or the compressor connected to the wind box to the wind box. The inside of the wind box may be divided into a plurality of blocks, and cooling air may be supplied to each block from a blower device, a compressor, or the like.

Further, the shape, number, arrangement position and the like of the opening holes provided in each nozzle may be the same.
Each may be different. These are appropriately determined according to the stress distribution of the glass sheet to be provided.

The shape of the glass plate may be either a shape formed by bending to a predetermined curvature or a flat shape, and is not particularly limited. In view of the object of the present invention, the glass sheet cooling apparatus of the present invention is particularly effectively used when cooling a glass sheet bent into a complicated shape such as a bent shape having a double curved surface.

The temperature immediately before the cooling air is blown onto the glass plate is preferably a temperature near the softening point of the glass plate,
７００700 ° C. is exemplified. This is because the glass sheet for an automobile is usually heated to a temperature at which the glass sheet is bent and subjected to a strengthening treatment by a cooling step immediately after the bending step.

As the glass sheet to be strengthened so as to have a desired stress effectively by the glass sheet cooling apparatus of the present invention, a glass sheet having a thickness of 2.3 to 3.5 mm is preferably exemplified. You. This is because, in the case of a glass sheet having a small thickness, it is difficult to realize a strengthened glass sheet that can obtain fine crushing at the time of breakage without increasing the cooling capacity in the conventional apparatus, whereas the cooling apparatus for the glass sheet of the present invention is difficult. However, this is because a tempered glass plate that can obtain fine crushed pieces at the time of breakage without increasing the cooling capacity can be realized.

As described above, the dimensions of the glass sheet which can be obtained as a tempered glass sheet of the present invention or a desired and effective non-conventional tempered glass sheet by the method and apparatus for cooling a glass sheet of the present invention are as follows. (800-1500) × (5
A thickness of about 100 to 1000) mm is preferably exemplified. The arc depth of such a glass plate is 10
A preferred example is 30 mm.

[0077]

EXAMPLES Glass sheets having the shapes shown in Table 1 were subjected to tempering treatment under the cooling conditions shown in Table 1 to produce tempered glass sheets of Examples 1 to 10. In addition, the glass plate having the shape shown in Table 1 was simulated for the strengthening process under the cooling conditions shown in Table 1, and Example 11 was performed.
-The tempered glass plate model of Example 14 was produced. Examples 1 to 5
Then, the strengthening process was performed using the apparatus shown in FIGS.
In Examples 6 to 10, the strengthening treatment was performed using a conventional apparatus having a nozzle (nozzle pitch is large).

Note that “depth” (W) in Table 1 is the depth (unit: mm) of bending (arc) in the short side direction of the glass plate, and “temperature”.
Is the temperature of the glass plate at the start of cooling (unit: ° C), and "distance" is the distance from the tip of the nozzle to the glass plate surface (unit: mm)
It is. In addition, the thickness (t) and dimensions (x × y) of the glass plate
Is mm and the unit of wind pressure is mmAq. Refer to FIG. 8 for specification of dimensions and the like. The depth W is specified by considering the cross section so that the illustrated portion becomes the largest.

The tempered glass sheet thus obtained was a tempered glass sheet having the physical properties shown in Table 2. In Table 2, the maximum surface compressive stress sigma _max, the minimum surface compressive stress sigma _min, the principal stress difference sigma _a, sigma _b, a distance _{L a, L b, L c} , L d are respectively the above (A) surface compressive stress Measurement, (B) principal stress direction,
This was performed based on the measurement of the main stress difference. σ _max , σ _min , σ
The units of _a and σ _b are kg / cm ² , L _a , L _b ,
L _c, the unit of L _d is mm, respectively.

The glass sheet thus subjected to the tempering treatment was subjected to a test based on the crushing test of the tempered glass sheet specified in JIS R3212, and the results shown in Table 3 were obtained (“-” in Table 3 indicates that no measurement was made). ). Table 3 in "impact point" is the point of impact of the specimen of the double curved surfaces in the test of the JIS R3206, the minimum number of particles N _min is the fragments of tempered glass automotive safety glass of JIS R3211 state ( J
In Table 5) of IS R3211, crushing in the area selected so as to minimize the number of crushed pieces in the 50 × 50 mm square area around the impact point and more than 75 mm from the impact point The number of pieces, the maximum number of particles _Nmax is, among the above-mentioned pieces of crushed pieces, the number of pieces of crushed pieces in a 50 × 50 mm square area around the point of impact and more than 75 mm from the point of impact. The number of crushed pieces in the area selected to be the largest, the “number of pieces” is over 75 mm in length,
The number of elongated fragments of 150 mm or less is referred to as the "large fragment area".
Indicates the area of the largest crushed piece.

[0081]

[Table 1]

[0082]

[Table 2]

[0083]

[Table 3]

Comparison between Example 3 and Example 6 shows that in order to obtain a tempered glass sheet satisfying the standard for automotive safety glass,
In Example 3 (example using the method and apparatus of the present invention), 1400 m
It can be seen that cooling air with a wind pressure of mAq is sufficient, whereas cooling air with a wind pressure of 2300 mmAq is required in Example 6 (example using a conventional nozzle). Examples 6 to 10
Thus, the minimum number of particles is smaller than in Examples 1 to 5. In the conventional apparatus, it is difficult to arrange the nozzles densely in order to secure an escape path for the cooling air, so that it is understood that the crushed pieces are hard to be fine.

Examples 11 to 14 are tempered glass plate models obtained by simulations, and therefore, these models show the crushing tendency rather than the crushing state based on actual crushing. Comparing Example 1 and Example 11, sigma _a is unimpeded progress of cracks in the L small relative _a (L _a is too large enough not worth the sigma _a) a band-like region A, the strip It can be seen that this occurs. Comparison between Example 1 and Example 12 shows that L _b
Is too large to match L _c and L _d, it is not possible to realize crack intersecting in the band-shaped region B, and large fragments are generated. Comparison between Example 1 and Example 13 shows that L _c <L
If it is _d, the large pieces not to reduce the L _a is understood to occur. Comparing Example 1 with Example 14, it can be seen that large fragments are generated when σ _b is too small.

[0086]

According to the tempered glass sheet of the present invention,
By satisfying the main stress characteristics of (1) and (2), and more preferably one or more of the main stress characteristics of (3) to (6), cracks can be obtained so that crushing satisfying the regulations can be obtained. You can control the progress. As a result, even if the thickness of the glass sheet is particularly small, a tempered glass sheet satisfying the regulations can be obtained.

Further, according to the present invention, a nozzle having a plurality of opening holes for blowing cooling air supplied from the inside of the wind box toward the glass plate on the front end surface of the curved end surface is used. . As a result, for glass sheets having a small thickness that cannot be sufficiently strengthened by the conventional glass sheet strengthening method and apparatus, sufficient strengthening is required to satisfy the safety regulations for automotive window glass sheets. An excellent effect that a glass plate can be manufactured is obtained.

As described above, according to the present invention, compared with the conventional tempering method and apparatus applied to a thick glass sheet, the tempered glass sheet reinforced by the conventional tempering method and apparatus with a small air flow is used. An excellent effect that the same degree of reinforcement can be achieved is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a tempered glass plate of the present invention.

FIG. 2 is an enlarged conceptual diagram of FIG. 1;

FIG. 3 is a schematic cross-sectional view showing one example of a glass sheet cooling device of the present invention.

4A and 4B are a schematic perspective view and a schematic top view, respectively, showing an example of a nozzle according to the present invention.

FIG. 5 is a schematic top view showing another example of the nozzle according to the present invention.

FIG. 6 is a conceptual diagram showing an example of a state of blowing cooling air in the present invention.

FIG. 7 is a conceptual diagram of a measuring device used for obtaining a main stress direction and a main stress difference.

8A and 8B are a front view and a cross-sectional view for explaining dimensions and the like of a glass plate.

[Explanation of symbols]

 1: Glass plate 11, 11 ': Wind box 12: Nozzle 20: Opening hole

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Yoshida 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Asahi Glass Co., Ltd.

Claims (12)

[Claims] (1) a sheet thickness of 2.3 to 3.5 mm;
0～1300Kg / average surface compressive stress of cm ² is a tempered glass plate that is formed, the glass plate surface is larger than the principal stress difference is and close around a 120 kg / cm ² or less in size A plurality of reference points a having a main stress difference, and the main stress directions being substantially parallel to each other, and having a main stress difference between adjacent reference points a, which is equal to or greater than the main stress difference between these reference points. And a plurality of parallel belt-shaped regions A having a width in the range of 10 to 30 mm and a plurality of parallel belt-shaped regions A and A having a reference straight line formed by a group of reference points a where there is no And a plurality of reference points b having a main stress difference larger than the main stress difference in the vicinity of the vicinity are scattered in the band-shaped area B. b
Characterized in that the main stress direction is different from the main stress direction at the adjacent reference point b. 2. The method according to claim 1, wherein the sheet thickness is 2.3 to 3.5 mm,
0～1300Kg / average surface compressive stress of cm ² is a tempered glass plate that is formed, the glass plate surface is larger than the principal stress difference is and close around a 120 kg / cm ² or less in size A plurality of reference points a having a main stress difference, the main stress directions of which are substantially parallel to each other, and having a large main stress difference as compared with a main stress difference in a nearby vicinity which is directed in a direction different from the main stress direction. Has a center line of a reference straight line formed by a group of reference points a that are not present between adjacent reference points a and a, and has a width of 10 to 30 m.
m, a plurality of mutually parallel strip-shaped areas A,
A belt-like region B sandwiched between adjacent belt-like regions A, A is formed, and the band-like region B has a plurality of references having a main stress difference larger than the main stress difference in the vicinity. Point b is scattered and reference point b
Characterized in that the main stress direction is different from the main stress direction at the adjacent reference point b. 3. The tempered glass sheet according to claim 1, wherein the width of the band-shaped region B is in a range of 10 to 30 mm. 4. The main stress difference at a reference point a is 40 to 80 k.
g / cm ² .
3. The tempered glass plate according to any one of 3. 5. A main stress difference at a reference point b is 50 kg / c.
tempered glass plate according to any one of claims 1 to 4, characterized in that m ² or more. 6. The principal stress direction of the reference point b in each strip-shaped area B includes a direction substantially perpendicular to the principal stress direction of the reference point a, and the reference stress of the reference point b in each strip-shaped area B is included. The tempered glass sheet according to any one of claims 1 to 5, wherein the line formed along the main stress direction is meandering. 7. The reference point b is roughly divided into two groups, and the first group of the reference point b has a principal stress direction in a direction substantially perpendicular to the principal stress direction of the reference point a. And, in each of the band-shaped regions B, when viewed in the reference straight line direction, they are alternately arranged near the boundary with one adjacent band-shaped region A and near the boundary with the other adjacent band-shaped region A. The second group of the reference points b includes a reference point b near the boundary with one adjacent band-shaped area A in the first group, and a second group adjacent to the reference point b and the other. It has a principal stress direction in a direction substantially coincident with a direction connecting the reference point b near the boundary with the belt-shaped region A, and is disposed between the two reference points b. The tempered glass sheet according to claim 1. 8. A heated glass sheet is conveyed between a pair of wind boxes having a plurality of nozzles disposed on both sides of the glass sheet, and cooling air supplied from the wind box is sent from the plurality of nozzles. A method for cooling a glass sheet by strengthening the glass sheet by spraying the glass sheet surface, wherein each of the plurality of nozzles arranged on at least one of the glass sheet surfaces is simultaneously directed in a plurality of directions. A plurality of opening holes are provided so as to jet cooling air, and an intersection between a spraying direction line of a jet of cooling air flowing from the opening hole of the nozzle toward the glass plate and a glass plate surface is formed on the glass plate surface. A method of cooling a glass sheet, comprising blowing a cooling air toward the glass sheet so as to be almost uniformly arranged. 9. The method for cooling a glass sheet according to claim 8, wherein cooling air is blown toward the glass sheet so that the number of intersections on the glass sheet surface is 30 or more per 10 cm square. 10. A heated glass plate is transported between a pair of wind boxes having a plurality of nozzles disposed on both sides of the glass plate, and cooling air supplied from the wind box is sent from the plurality of nozzles. A method for cooling a glass sheet by strengthening the glass sheet by spraying the glass sheet surface, wherein a tip surface on a side facing the glass sheet has a convex curved shape, and cooling air supplied from the inside of the wind box is cooled by a glass. A plurality of hollow tubular nozzles in which a plurality of opening holes to be sprayed toward the plate are provided on the distal end surface are arranged on at least one surface side of the glass plate, and cooling air is blown from these nozzles toward the glass plate. A method for cooling a glass sheet. 11. A glass box having at least a wind box opposed to both sides of a glass plate and a plurality of nozzles mounted on the glass plate side of the wind box, and facing 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 member having a convex curved end surface on a side facing the glass plate, and the end surface includes: A cooling device for a glass plate, comprising a plurality of opening holes for blowing cooling air supplied from the inside of the wind box toward the glass plate. 12. The cooling device for a glass sheet according to claim 11, wherein a plurality of opening holes provided in a front end surface of said nozzle are provided evenly in said front end surface.