JP6965881B2 - Chemically tempered glass plate - Google Patents

Description

The present invention relates to a chemically strengthened glass plate.

In order to improve the strength of a glass plate, a tempered glass plate in which a compressive stress is formed on the main surface of the glass plate and a tensile stress is formed inside is known. Tempered glass includes physically tempered glass obtained by heating the glass plate and then quenching it to form a temperature difference between the main surface and the inside, and immersing the glass plate in molten salt to have a small ion radius on the main surface side. There is chemically tempered glass by ion exchange between ions and ions with a large ion radius on the molten salt side.

Chemically tempered glass plates can have a larger compressive stress value formed on the main surface than physically tempered glass plates. Has been used in. Further, Patent Document 1 proposes a chemically strengthened glass plate used as a building window, an outer wall, a solar cell cover glass, and a vehicle window.

International Publication No. 2014/168246

However, in a chemically strengthened glass plate having a large area, distribution tends to occur in the thickness in the plate thickness direction of the layer in the plate thickness direction having the surface compressive stress value and the compressive stress (hereinafter referred to as the compressive stress layer). Therefore, a portion having a weak strength is locally generated in the main surface of the chemically strengthened glass plate, and the chemically strengthened glass plate may be cracked by the impact.

Further, in order to increase the strength of the glass plate so that a locally weak portion does not occur, the glass plate must be immersed in a molten salt for a long time to make the surface compressive stress layer excessively thick. ..

Therefore, an object of the present invention is to provide a chemically strengthened glass plate having a large area that is not easily broken by impact without forming a compressive stress layer to an excessive thickness.

The chemically strengthened glass plate of the present invention has a first main surface and a second main surface facing the first main surface, and surface compressive stress is applied to the first main surface and the second main surface. However, it is a chemically strengthened glass plate in which tensile stress is formed, and the areas of ^{the first main surface and the second main surface are 1 m 2} or more, and the first main surface and the second main surface are present. in at least one major surface of the face, Ri thickness direction of the thickness of der plane distribution is 15% or less of the compressive stress layer, in both the main surfaces of the first major surface and a second major surface The in-plane distribution of the surface compressive stress value is 12% or less, the thickness of the chemically strengthened glass plate is 2 mm or more, and the Al ₂ O ₃ content of the chemically strengthened glass plate is 3 mol% or less. It is a feature.

According to the present invention, a chemically strengthened glass plate having a large area that is not easily broken by impact can be obtained by immersing in a molten salt for a short time.

FIG. 1 is a perspective view of a chemically strengthened glass plate according to an embodiment of the present invention. FIG. 2 is a plan view of a chemically strengthened glass plate according to an embodiment of the present invention. FIG. 3 is a plan view of a chemically strengthened glass plate for explaining the warp measurement position of the embodiment.

Hereinafter, the chemically strengthened glass plate according to the embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a chemically strengthened glass plate according to an embodiment of the present invention.

The chemically strengthened glass plate 10 according to an embodiment of the present invention has a first main surface 11a and a second main surface 11b facing the first main surface 11a, and has a first main surface 11a and a second main surface 11a. A chemically strengthened glass plate in which a surface compressive stress is formed on the main surface 11b and a tensile stress is formed inside, and the areas of the first main surface 11a and the second main surface 11b are 1 m ² or more, and the first On at least one of the main surface 11a and the second main surface 11b, the in-plane distribution of the surface compressive stress value is 15% or less, and the in-plane distribution of the thickness of the compressive stress layer in the plate thickness direction is It is characterized by being 15% or less.

The chemically strengthened glass plate 10 according to the embodiment of the present invention is suitably used as, for example, a building window, an outer wall, a solar cell cover glass, and a vehicle window. Examples of architectural windows include windows of houses, buildings, and the like.

The chemically strengthened glass plate 10 according to the embodiment of the present invention has an area of the first main surface 11a and the second main surface 11b of 1 m ² or more. When the area is 1 m ² or more, it is suitably used for various applications such as building windows, outer walls, solar cell cover glass, and vehicle windows. The area of the chemically strengthened glass plate 10 may be 2 m ² or more, 3 m ² or more, 5 m ² or more, ^{or 7 m 2} or more.

On the other hand, the area of the first main surface 11a and the second main surface 11b ^{is preferably 10 m 2} or less. When the area is 10 m ² or less, the chemically strengthened glass plate can be easily handled, and for example, damage due to contact with peripheral members when the chemically strengthened glass plate is installed can be suppressed. The area may be 9 m ² or less, ^{or 8 m 2} or less.

The shape of the chemically strengthened glass plate 10 according to the embodiment of the present invention is preferably rectangular. If it is rectangular, it can be easily installed as, for example, a building window, an outer wall, or a solar cell cover glass. Here, the rectangle is a substantially right-angled quadrilateral, and when the distance from any one side to the opposite side is measured, the error due to the measurement position is 0.3 for both the long side and the short side. Includes shapes that fit within% and have curvatures and notches at the corners.

When the chemically strengthened glass plate 10 according to the embodiment of the present invention is rectangular, the lengths of the long sides of the first main surface 11a and the second main surface 11b may be 1300 mm or more and 1500 mm. It may be 1800 mm or more, 2100 mm or more, or 2500 mm or more.

When the chemically strengthened glass plate 10 according to the embodiment of the present invention is rectangular, the lengths of the short sides of the first main surface 11a and the second main surface 11b may be 800 mm or more and 1300 mm. It may be 1500 mm or more, 1800 mm or more, or 2100 mm or more.

The thickness of the chemically strengthened glass plate 10 according to the embodiment of the present invention is preferably 2 mm or more from the viewpoint of strength and handleability. The plate thickness is more preferably 4 mm or more, further preferably 5 mm or more, and particularly preferably 6 mm or more. On the other hand, if the thickness is 20 mm or less, it is preferable because it is lightweight. The plate thickness is more preferably 15 mm or less, and even more preferably 13 mm or less.

In the chemically strengthened glass plate 10 according to the embodiment of the present invention, surface compressive stress is formed on the main surfaces 11a and 11b.

The chemically strengthened glass plate according to the embodiment of the present invention can be used as a single glass for various purposes such as building windows, outer walls, solar cell cover glass, and vehicle windows. Further, in another embodiment, it can be used as a laminated glass in which two or more glass plates are laminated with an intermediate layer film.

In yet another embodiment, two or more glass plates can be arranged at intervals and used as double glazing. In yet another embodiment, the surface of the glass plate can be coated and used. In the configuration of laminated glass or double glazing, the chemically strengthened glass plate of the present invention can be used for at least one sheet.

The chemically strengthened glass plate 10 according to the embodiment of the present invention has an in-plane surface compressive stress value (hereinafter referred to as CS) on at least one of the first main surface 11a and the second main surface 11b. The distribution is 15% or less, and the in-plane distribution of the thickness of the compressive stress layer in the plate thickness direction (hereinafter referred to as DOL) is 15% or less. Here, the in-plane distribution is defined as follows.

FIG. 2 is a plan view of the chemically strengthened glass plate 10.

When the main surfaces 11a and 11b of the chemically strengthened glass plate are rectangular, in the rectangular ABCD obtained by drawing a line segment at a position where the distance L from the end sides of the main surfaces 11a and 11b is 30 mm, the long side AB and Three straight lines E, F, and G that are orthogonal to the CD and divide the long sides AB and CD into four equal parts, and one straight line H that is orthogonal to the short sides AC and BD and divide the short sides AC and BD into two equal parts. At each of the CS and DOL of the 15 intersections P1 to P15 with the line segments AB, CD, AC, and BD, the value obtained by dividing the difference between the maximum value and the minimum value by the average value and expressing it as a percentage is within the plane of the present invention. Let it be a distribution.

When the main surfaces 11a and 11b of the chemically strengthened glass plate are other than a rectangle, 15 rectangles are inscribed in the edges of the main surfaces 11a and 11b so as to have the maximum area, as in the case of the above-mentioned rectangle. By determining the intersection points P1 to P15, the in-plane distribution of CS and DOL is calculated.

The chemically strengthened glass plate 10 according to the embodiment of the present invention has an in-plane distribution of CS of 15% or less on at least one of the first main surface 11a and the second main surface 11b. On the main surface where the in-plane distribution of CS is 15% or less, a portion where CS is locally small does not occur, and it is difficult to crack due to impact. The in-plane distribution of CS is preferably 12% or less, more preferably 10% or less, further preferably 8% or less, particularly preferably 6% or less, and most preferably 4% or less.

The chemically strengthened glass plate 10 according to the embodiment of the present invention has an in-plane distribution of DOL of 15% or less on at least one of the first main surface 11a and the second main surface 11b. On the main surface where the in-plane distribution of DOL is 15% or less, it is difficult to crack due to impact. The in-plane distribution of DOL is preferably 11% or less, more preferably 9% or less, further preferably 7% or less, particularly preferably 4% or less, and most preferably 2% or less.

Here, CS and DOL can be measured by a surface stress meter.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has a CS of 250 MPa or more on at least one of the first main surface 11a and the second main surface 11b. When CS is 250 MPa or more, the mechanical strength of the chemically strengthened glass plate is high. The CS is more preferably 300 MPa or more, further preferably 350 MPa or more, and particularly preferably 380 MPa or more.

On the other hand, the CS is preferably 500 MPa or less on at least one of the first main surface 11a and the second main surface 11b. When CS is 500 MPa or less, the stress distribution can be kept small. Further, the internal tensile stress is unlikely to become extremely high. Further, it may be immersed in a high-temperature molten salt for a short time, and it is easy to obtain the chemically strengthened glass plate 10. Further, when cutting the chemically strengthened glass plate 10, it becomes easy to form a cut line by a wheel cutter. The CS is more preferably 480 MPa or less, further preferably 460 MPa or less.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has a DOL of 15 μm or more on at least one of the first main surface 11a and the second main surface 11b. When the DOL is 15 μm or more, sufficient strength can be obtained and the impact can be withstood. The DOL is more preferably 20 μm or more, further preferably 25 μm or more, particularly preferably 28 μm or more, and most preferably 30 μm or more.

On the other hand, the DOL is preferably 100 μm or less. When the DOL is 100 μm or less, the immersion in the molten salt may be short, and it is easy to obtain the chemically strengthened glass plate 10. The DOL is more preferably 80 μm or less, further preferably 50 μm or less, and particularly preferably 40 μm or less.

When the chemically strengthened glass plate 10 according to the embodiment of the present invention is used for, for example, a building window, an outer wall, a solar cell cover glass, or a vehicle window, the in-plane distribution of CS is 15% of the main surfaces 11a and 11b. It is preferable that the main surface having the in-plane distribution of DOL of 15% or less is arranged outdoors because it can withstand an impact.

In the chemically strengthened glass plate 10 according to the embodiment of the present invention, the in-plane distribution of CS on both the first main surface 11a and the second main surface 11b is 15% or less, and the in-plane distribution of DOL is 15. % Or less is preferable because both sides can withstand impact.

Further, the chemically strengthened glass plate 10 according to the embodiment of the present invention forms a functional film such as a heat ray reflecting film or an antifouling film on one or both of the first main surface 11a and the second main surface 11b. You may.

In the chemically strengthened glass plate 10 according to the embodiment of the present invention, a compressive stress layer may be formed not only on the main surfaces 11a and 11b but also on the end surface 12. When the glass plate is cut into a desired shape after chemical strengthening, the end face 12 may not have a compressive stress layer.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has a warp of 0.5% or less as defined by JIS R3206 (2003). When the warp is 0.5% or less, it is possible to prevent delayed fracture of the glass due to local stress generated on the chemically strengthened glass plate 10 when the chemically strengthened glass plate 10 is used as a building window, for example. The warp is more preferably 0.4% or less, further preferably 0.3% or less, particularly preferably 0.2% or less, and most preferably 0.1% or less.

The glass transition point Tg of the chemically strengthened glass plate 10 according to the embodiment of the present invention is preferably 530 ° C. or higher. As a result, relaxation of the surface compressive stress during ion exchange can be suppressed. Tg is more preferably 540 ° C. or higher, further preferably 550 ° C. or higher.

Temperature T2 at which the viscosity becomes ¹⁰ 2 dPa · s of chemically strengthened glass sheet 10 according to an embodiment of the present invention is preferably 1550 ° C. or less, more preferably 1490 ° C. or less.

Temperature T4 at which the viscosity of the chemically strengthened glass sheet 10 according to an embodiment of the present invention is ¹⁰ 4 dPa · s is preferably 1050 ° C. or less.

The specific gravity of the chemically strengthened glass plate 10 according to the embodiment of the present invention is preferably 2.45 to 2.55.

The above-mentioned "~" indicating a numerical range is used to mean that the numerical values described before and after the above are included as the lower limit value and the upper limit value, and unless otherwise specified, the "~" in the present specification is the same. It is used with the meaning of.

The Young's modulus of the chemically strengthened glass plate 10 according to the embodiment of the present invention is preferably 65 GPa or more. As a result, the rigidity and breaking strength are sufficient. Young's modulus may be 70 GPa or more. On the other hand, when Young's modulus is 90 GPa or less, it is possible to prevent the chemically strengthened glass plate from becoming brittle, and to suppress chipping during cutting and dicing of the chemically strengthened glass plate. Young's modulus may be 85 GPa or less, or 80 GPa or less.

Here, the chemically strengthened glass plate 10 according to the embodiment of the present invention contains 56 to 75% _{of SiO 2} , 0 to 20% of _{Al 2} O ₃ , and 8 to 8 of _{Na 2 O in terms of oxide-based molar percentage.} 22%, the _{K 2} O 0% to MgO 0 to 14% of ZrO ₂ 0 to 5% preferably contains 2 to 12% of CaO. Hereinafter, the percentage display indicates the molar percentage display content based on the oxide unless otherwise specified.

The reason why the glass composition is limited to the above range in the chemically strengthened glass plate 10 according to the embodiment of the present invention will be described below.

SiO ₂ is a component that forms a network structure in the glass fine structure, and is a main component that constitutes glass. The content of SiO ₂ is preferably 56% or more, more preferably 63% or more, further preferably 66% or more, and particularly preferably 68% or more. The content of SiO ₂ is preferably 75% or less, more preferably 73% or less, and even more preferably 72% or less. When _{the content of SiO 2} is 56% or more, it is superior in terms of stability and weather resistance as glass. On the other hand, when _{the content of SiO 2} is 75% or less, it is superior in terms of meltability and moldability.

Al ₂ O ₃ is not essential, but may be contained because it has an effect of improving the ion exchange performance in chemical strengthening and particularly has a large effect of increasing CS. It also improves the weather resistance of the glass. Further, it has an effect of suppressing the infiltration of tin from the bottom surface during float molding. When Al ₂ O ₃ is contained, 0.4% or more is preferable, 0.6% or more is more preferable, and 0.8% or more is further preferable. Further, when _{the content of Al 2} O ₃ is 20% or less, the devitrification temperature does not rise significantly even when the viscosity of the glass is high, which is advantageous in terms of melting and molding in the soda lime glass production line. .. The content of Al ₂ O ₃ is more preferably 10% or less, further preferably 5% or less, particularly preferably 3% or less, and most preferably 2% or less.

Total _SiO 2 + _Al 2 _{O 3} content of SiO ₂ and _Al 2 _{O 3} is preferably 80% or less. If it is 80% or less, the viscosity of the glass at high temperature decreases, and melting becomes easy. 76% or less is preferable, and 74% or less is more preferable. Further, SiO ₂ + Al ₂ O ₃ is preferably 68% or more. When it is 68% or more, the crack resistance at the time of indentation is improved, and more preferably 70% or more.

Na ₂ O is a component that forms a surface compressive stress layer by ion exchange, and has the effect of deepening DOL. It is also a component that lowers the high-temperature viscosity and devitrification temperature of glass and improves the meltability and moldability of glass. The Na ₂ O content is preferably 8% or more, more preferably 10% or more, and even more preferably 12% or more. The Na ₂ O content is preferably 22% or less, more preferably 16% or less, and even more preferably 14% or less. When the Na ₂ O content is 8% or more, a desired surface compressive stress layer is likely to be formed by ion exchange. On the other hand, when the Na ₂ O content is 22% or less, sufficient weather resistance can be obtained.

K ₂ O may be contained because it has the effect of increasing the ion exchange rate and deepening the DOL. On the other hand, if K ₂ O is too large, sufficient CS cannot be obtained. When K ₂ O is contained, it is preferably 10% or less, more preferably 2% or less, still more preferably 1% or less. When the content of K ₂ O is 10% or less, sufficient CS is obtained.

MgO is a component that stabilizes the glass, although it is not essential. When MgO is contained, 2% or more is preferable, 4% or more is more preferable, and 6% or more is further preferable. The MgO content is preferably 14% or less, more preferably 10% or less, and even more preferably 8% or less. When the MgO content is 2% or more, the chemical resistance of the glass becomes good. Meltability at high temperature is improved, and devitrification is less likely to occur. On the other hand, when the MgO content is 14% or less, the difficulty of devitrification is maintained and a sufficient ion exchange rate can be obtained.

ZrO ₂ has the effect of increasing CS in chemical fortification. However, even if a small amount of ZrO ₂ is contained, the effect is not great for the cost increase. Therefore, any proportion of ZrO ₂ can be contained as the cost allows. When it is contained, it is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

CaO is a component that stabilizes glass. Since CaO tends to inhibit the exchange of alkaline ions, it is preferable to reduce the content, especially when it is desired to increase the DOL. On the other hand, in order to improve the chemical resistance, the CaO content is preferably 2% or more, more preferably 5% or more, still more preferably 7% or more. When CaO is contained, the amount is preferably 12% or less, more preferably 10% or less, still more preferably 9% or less. When the CaO content is 12% or less, a sufficient ion exchange rate is maintained and a desired DOL can be obtained.

Although not essential, SrO may be contained for the purpose of lowering the high temperature viscosity of the glass and lowering the devitrification temperature. Since SrO has an effect of lowering the ion exchange efficiency, it is preferable not to contain SrO especially when it is desired to increase the DOL. When contained, the amount of SrO is preferably 3% or less, more preferably 2% or less, still more preferably 1% or less.

BaO may be contained for the purpose of lowering the high temperature viscosity of the glass and lowering the devitrification temperature, although it is not essential. Since BaO has an effect of increasing the specific gravity of the glass, it is preferable not to contain it when the weight is intended to be reduced. The amount of BaO when contained is preferably 3% or less, more preferably 2% or less, still more preferably 1% or less.

In addition, sulfate, chloride, fluoride and the like may be appropriately contained as a clarifying agent for melting glass.

The glass of the present invention is essentially composed of the components described above, but may contain other components as long as the object of the present invention is not impaired. When such components are contained, the total content of these components is preferably 5% or less, more preferably 3% or less, and typically 1% or less. Hereinafter, the above other components will be described exemplarily.

ZnO may be contained, for example, up to 2% in order to improve the meltability of the glass at a high temperature. However, when it is produced by the float method, it is preferably not contained because it is reduced by the float bath and becomes a product defect.

B ₂ O ₃ may be contained in the range of less than 1% in order to improve the meltability at high temperature or the glass strength. In general, if the alkaline component of _{Na 2} O or K _{2 O and B 2} O ₃ are contained at the same time, volatilization becomes intense and the bricks are significantly eroded. Therefore, _{it is preferable that B 2} O ₃ is not substantially contained. In addition, in this specification, "substantially not contained" means that it is not contained other than unavoidable impurities mixed from raw materials and the like, that is, it is not intentionally contained.

Li ₂ O is a component that lowers the strain point to facilitate stress relaxation, and as a result, makes it impossible to obtain a stable surface compressive stress layer. Therefore, it is preferable not to contain Li 2 O, and even if it is contained, it is not contained. The content is preferably 1% or less, more preferably 0.05% or less, and particularly preferably 0.01% or less.

Next, a method for manufacturing the chemically strengthened glass plate 10 according to the embodiment of the present invention will be described.

When the chemically strengthened glass plate 10 according to the embodiment of the present invention is manufactured, it goes through a glass plate manufacturing step and a chemically strengthened treatment step.

In the glass plate manufacturing process, for example, various raw materials are mixed in appropriate amounts, heated to about 1400 to 1800 ° C. to melt, homogenized by defoaming, stirring, etc., and then homogenized by a well-known float method, down draw method, rollout method, press. A glass plate is manufactured by molding it into a plate shape by a method or the like, slowly cooling it, and then cutting it into a desired size.

In the chemical strengthening treatment step, a compressive stress layer having a desired surface compressive stress is formed on the obtained glass plate. The chemical strengthening treatment step goes through a preheating step, a chemical strengthening step, and a slow cooling step.

In the preheating step, the glass plate is preheated before the chemical strengthening treatment is performed. Preheating is performed by, for example, placing a glass plate in an electric furnace at room temperature, raising the temperature of the electric furnace to the preheating temperature, and holding the electric furnace for a certain period of time. If the process immediately shifts to the chemical strengthening step after the temperature rise is completed, the temperature distribution in the main surface of the glass plate is chemically strengthened, so that the in-plane distribution of CS and DOL tends to be large.

In order to reduce the in-plane distribution of CS and DOL, it is preferable to hold the glass plate at the preheating temperature for a certain period of time after the temperature rise is completed. This holding time is preferably 10 minutes or more, more preferably 20 minutes or more, further preferably 30 minutes or more, and particularly preferably 40 minutes or more. By sufficiently preheating the glass plate in this way, the temperature distribution in the main surface of the glass plate is suppressed, and the in-plane distribution of CS and DOL of the glass plate tends to be small in the chemical strengthening step.

The preheating temperature is preferably (TE-100) ° C. or higher, where TE is the temperature of the molten salt for performing the chemical strengthening treatment. When the preheating temperature is (TE-100) ° C. or higher, cracking due to thermal shock in the chemical strengthening step is suppressed, the temperature of the molten salt when immersing the glass plate in the molten salt in the chemical strengthening step does not easily decrease, and the glass The desired strength can be given to the plate. The preheating temperature is more preferably (TE-50) ° C. or higher, further preferably (TE-20) ° C. or higher, and particularly preferably (TE-10) ° C. or higher.

In the chemical strengthening step, the preheated glass plate is immersed in, for example, a heated potassium nitrate molten salt, and Na on the glass surface layer and K in the molten salt are ion-exchanged. Any method may be used as long as Na and K can be ion-exchanged. Incidentally, potassium nitrate molten salt, or potassium nitrate salts in the present invention, other KNO _3, including those containing KNO ₃ and 10 wt% or less of NaNO _3.

The chemical strengthening treatment conditions for forming a compressive stress layer having a desired surface compressive stress on the glass plate vary depending on the thickness of the glass plate and the like, but the glass is immersed in a molten potassium nitrate salt at 350 to 550 ° C. for 2 to 50 hours. It is typical to immerse the board. From an economical point of view, it is preferable to immerse at 350 to 500 ° C. for 2 to 40 hours, and a more preferable immersing time is 2 to 30 hours.

In the chemical strengthening step, it is preferable to arrange the glass plate in the molten salt in the vertical direction. By arranging the glass plate in the molten salt in the vertical direction, the thermal convection of the molten salt is less likely to be hindered, the in-plane temperature distribution of the glass plate becomes small, and the in-plane distribution of CS and DOL of the glass plate tends to become small.

In the slow cooling step, the glass plate taken out from the molten salt is slowly cooled. It is preferable that the glass plate taken out from the molten salt is held at a uniform temperature for a certain period of time in order to prevent a temperature distribution from occurring on the main surface of the glass plate, instead of immediately slowly cooling the glass plate. The holding temperature is preferably 100 ° C. or lower, more preferably 50 ° C. or lower, further preferably 20 ° C. or lower, and particularly preferably 10 ° C. or lower, with a difference from the temperature of the molten salt being 100 ° C. or lower. The holding time is preferably 10 minutes or longer, more preferably 20 minutes or longer, and even more preferably 30 minutes or longer.

Since the temperature distribution of the atmosphere in the slow cooling step is larger than the temperature distribution of the molten salt at the time of ion exchange in the chemical strengthening step, it tends to affect the in-plane distribution of CS and DOL.

In order to reduce the in-plane distribution of CS and DOL, the glass plate taken out from the molten salt may be slowly cooled so that the slow cooling rate until the glass plate reaches 100 ° C. is 300 ° C./hour or less. preferable. The slow cooling rate is more preferably 200 ° C./hour or less, and even more preferably 100 ° C./hour or less.

In the chemically strengthened glass plate of the present embodiment described above, the areas of the first main surface and the second main surface are 1 m ² or more, and at least one of the first main surface and the second main surface On one main surface, the in-plane distribution of CS is 15% or less, and the in-plane distribution of DOL is 15% or less, so that it is not easily cracked by impact.

The present invention is not limited to the above embodiment. Modifications, improvements, and the like to the extent that the object of the present invention can be achieved are included in the present invention.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Examples 1 to 6 are examples, and example 7 is a comparative example.

Various glass raw materials such as silica sand were mixed so as to have the glass composition shown in Table 1, melted at a temperature of 1400 to 1500 ° C., and the obtained molten glass was formed into a plate shape by a float method, and Table 2 shows. A rectangular glass plate of the size shown was obtained. The glass transition points Tg (unit: ° C.), T2 (unit: ° C.), T4 (unit: ° C.), specific gravity, and Young's modulus (unit: GPa) of the obtained glass plate were measured and shown in Table 1.

Next, in Examples 1 to 6, the obtained glass plate was heated at a rate of 100 ° C./hour or less, held at 400 ° C. for 30 minutes after the temperature rise, and then added to a molten potassium nitrate salt at 450 ° C. for 30 minutes. After being immersed for a time and taken out from the molten salt, it was held at 400 ° C. for 30 minutes and slowly cooled at a slow cooling rate of 100 ° C./hour or less to obtain a chemically strengthened glass plate.

In Example 7, the obtained glass plate was heated at a rate of 100 ° C./hour or less, and after the temperature was raised, it was immediately immersed in a molten potassium nitrate at 450 ° C. for 30 hours and taken out from the molten salt. After that, the mixture was slowly cooled without maintaining the temperature to obtain a chemically strengthened glass plate.

Table 3 shows the results of measuring CS and DOL at the above-mentioned 15 points on the obtained chemically strengthened glass plate. The results of measuring the warpage are shown in Table 4.

The measurement method of each physical property is shown below.

(Glass transition point Tg)
Measurements were made using TMA according to the method specified in JIS R3103-3 (2001).

(T ₂ )
The viscosity was measured using a rotational viscometer, and the temperature T2 (° C.) at ^{10 2 d · Pa · s was measured.}

(T ₄ )
The viscosity was measured using a rotational viscometer, and the temperature T4 (° C.) at ^{10 4 d · Pa · s was measured.}

(specific gravity)
About 20 g of foam-free glass lumps were measured by the Archimedes method.

(Young's modulus)
It was measured by the ultrasonic pulse method.

(Distortion point)
The measurement was performed according to the method specified in JIS R3103-2 (2001).

(CS, DOL)
It was calculated from the number of interference fringes observed using a surface stress meter (manufactured by Orihara Seisakusho: FSM-7000H) and their intervals. In the calculation, the refractive index of the chemically strengthened glass plate was 1.518, and the optical elastic constant was 27.1 [(nm / cm) / MPa]. In addition, the in-plane distribution of CS and DOL was determined by the above method.

(warp)
FIG. 3 is a plan view illustrating the measurement position of the warp of the obtained chemically strengthened glass plate. The warp at the position along the side connecting the vertices RS, TU, RT, SU, RU, and ST was measured according to the method specified in JIS R3206 (2003). The warp (unit:%) was obtained by dividing the measured warp (unit: mm) by the length of the measured side (mm).

As shown in Tables 3 and 4, the chemically strengthened glass plates of the present invention of Examples 1 to 6 have a small temperature distribution after temperature rise and during slow cooling, and the in-plane distribution of CS and DOL is 15% or less, and impact. It is hard to break. On the other hand, the chemically strengthened glass plate of Example 7, which is a comparative example, has a large temperature distribution after heating and during slow cooling, and the in-plane distribution of CS and DOL is more than 15%, and CS and DOL are higher than the others. There is a small part, and the glass plate may break due to impact.

Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Japanese Patent Application No. 2016-130231) filed on June 30, 2016, and the entire application is incorporated by reference. Also, all references cited here are taken in as a whole.

The chemically strengthened glass plate of the present invention is suitably used, for example, as a building window, an outer wall, a solar cell cover glass, and a vehicle window.

10 Chemically tempered glass plate 11a First main surface 11b Second main surface 12 End surface

Claims (4)

A surface compressive stress is formed on the first main surface and the second main surface facing the first main surface and a tensile stress is formed inside the first main surface and the second main surface. It is a chemically strengthened glass plate
The area of the first main surface and the second main surface is 1 m ² or more.
In at least one major surface of said first main surface and the second main surface state, and are the thickness direction of the thickness of the in-plane distribution of the compressive stress layer 15% or less,
The in-plane distribution of the surface compressive stress values is 12% or less on both the first main surface and the second main surface.
The thickness of the chemically strengthened glass plate is 2 mm or more.
A chemically strengthened glass plate characterized in that _{the content of Al 2} O ₃ of the chemically strengthened glass plate is 3 mol% or less. The chemically strengthened glass plate according to claim 1, wherein the surface compressive stress value of at least one of the first main surface and the second main surface is 250 to 500 MPa. The chemically strengthened glass plate according to claim 1 or 2 , wherein the thickness of the compressive stress layer on at least one of the first main surface and the second main surface in the plate thickness direction is 15 to 100 μm. The chemically strengthened glass plate according to any one of claims 1 to 3 , wherein the warp specified in JIS R3206 (2003) is 0.5% or less.

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