JP7044101B2 - Chemically tempered glass plate and its manufacturing method - Google Patents

Description

The present invention relates to a chemically strengthened glass plate and a method for manufacturing the same.

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. The 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.

Since the compressive stress formed on the main surface of the chemically strengthened glass plate is larger than that of the physically strengthened glass plate, it is resistant to sudden impacts. It has been done. 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

Chemically tempered glass plates are required to have good aesthetics in order to be used for various purposes such as building windows and vehicle windows. Here, the glass plate reflects the incident light on the front surface and the back surface. Therefore, a double image is generated by the light reflected on the front surface and the back surface, and the aesthetic appearance is deteriorated.

The present invention provides a chemically strengthened glass plate that is less likely to generate a double image due to light reflected on the front surface and the back surface and has a good appearance, and a method for manufacturing the same.

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. Is a chemically strengthened glass plate with a tensile stress formed inside.
The absolute value ΔR of the difference between the visible light reflectance R1 (unit:%) of the first main surface and the visible light reflectance R2 (unit:%) of the second main surface is 0.6% or more. ,
Of the first main surface and the second main surface, the main surface having the smaller visible light reflectance has an average surface roughness Ra of 0.4 nm or more.

The method for manufacturing a chemically strengthened glass plate of the present invention is a method for manufacturing a chemically strengthened glass plate for obtaining the above-mentioned chemically strengthened glass plate.
The glass plate manufacturing process for manufacturing glass plates and
It has a chemical strengthening treatment step of immersing the glass plate in a molten salt to form a compressive stress on the surface of the glass plate.
In the glass plate manufacturing process, a glass plate is manufactured by the float method.
^The mass of NO _2- of a 100 ml constant volume aqueous solution obtained by cooling the molten salt before immersing the glass plate in the chemical strengthening treatment step and dissolving 1 g of the molten salt in ion-exchanged water shall be 2500 μg or more. It is characterized by.

The chemically strengthened glass plate of the present invention is less likely to generate a double image due to the light reflected on the front surface and the back surface, and has a good appearance.

FIG. 1 shows a perspective view of a chemically strengthened glass plate according to an embodiment of the present invention. FIG. 2 shows a plan view of a chemically strengthened glass plate according to an embodiment of the present invention.

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, and FIG. 2 is a plan view of the 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 surface compressive stress is formed on the main surface 11b and tensile stress is formed inside, and the visible light reflectance R1 (unit:%) and the second main surface of the first main surface 11a. The absolute value ΔR of the difference between the surface 11b and the visible light reflectance R2 (unit:%) is 0.6% or more, and the visible light reflectance of the first main surface 11a and the second main surface 11b is It is characterized in that the average surface roughness Ra of the smaller main surface is 0.4 nm or more.

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 handrail material, a solar cell cover glass, and a vehicle window. Examples of architectural windows include windows of houses and buildings.

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, handrail materials, 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 are 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. Since the double glazing may generally have multiple reflections, it is preferable to use the chemically strengthened glass plate of the present invention.

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 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, 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 internal tensile stress is unlikely to become extremely high. Further, the chemically strengthened treatment step may be a short-time immersion in a high-temperature molten salt, 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. 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 30 μm or more, and most preferably 40 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 60 μm or less, and particularly preferably 50 μm or less.

Here, CS (surface compressive stress value) and DOL (depth in the plate thickness direction of the compressive stress layer) can be measured by a surface stress meter.

In the chemically strengthened glass plate 10 according to the embodiment of the present invention, compressive stress 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 compressive stress.

The chemically strengthened glass plate 10 according to the embodiment of the present invention has a visible light reflectance R1 (unit:%) of the first main surface 11a and a visible light reflectance R2 (unit:%) of the second main surface 11b. The absolute value ΔR of the difference from the above is 0.6% or more. Here, ΔR satisfies the following equation (1).

ΔR = | R1-R2 | Equation (1)

Further, the visible light reflectances R1 and R2 are visible light reflectances defined by ISO9050 (2003), and are measured by applying a black paint for antireflection to the surface facing the measurement surface. When ΔR is 0.6% or more, the reflected image of one surface of the front surface or the back surface is reflected more clearly than the reflected image of the other surface, so that a double image due to the light reflected on the front surface and the back surface is generated. It is difficult to do and has a good appearance. ΔR is preferably 0.8% or more, more preferably 0.9% or more, still more preferably 1.0% or more. Further, ΔR is typically 4% or less.

The chemically strengthened glass plate 10 according to the embodiment of the present invention has a visible light reflectance RS of the main surface having a smaller visible light reflectance among the first main surface 11a and the second main surface 11b. It is preferably 2% or less. If the RS is 4.2% or less, a reflected image is unlikely to occur and the appearance is good. RS is more preferably 4.0% or less, further preferably 3.8% or less, and particularly preferably 3.6% or less. Further, RS is typically 0.5% or more.

In the chemically strengthened glass plate 10 according to the embodiment of the present invention, the average surface roughness Ra of the first main surface 11a and the second main surface 11b, whichever has the smaller visible light reflectance, is 0. It is 4 nm or more. Here, the average surface roughness Ra is a value specified by JIS B 0601 (1994). When the average surface roughness Ra of the main surface having the smaller visible light reflectance is 0.4 nm or more, the refractive index of the surface is pseudo-reduced and the visible light reflectance can be lowered, so that the surface and the surface and the visible light reflectance can be lowered. The double image due to the light reflected on the back surface is unlikely to occur, and the appearance is good. The average surface roughness Ra of the main surface having the smaller visible light reflectance is preferably 0.5 nm or more, more preferably 0.6 nm or more, further preferably 0.7 nm or more, and particularly preferably 0.8 nm or more.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has an average surface roughness Ra of 20 nm or less on the first main surface 11a and the second main surface 11b. When the average surface roughness Ra of the first main surface 11a and the second main surface 11b is 20 nm or less, the haze is sufficiently low and the appearance is good. The average surface roughness Ra of the first main surface 11a and the second main surface 11b is more preferably 10 nm or less, further preferably 5 nm or less.

When the chemically strengthened glass plate 10 is used as laminated glass, the main surfaces having the larger visible light reflectance of the first main surface 11a and the second main surface 11b of the two chemically strengthened glass plates are combined. By using laminated glass, the visible light reflectance of both main surfaces of the laminated glass is lowered, and the reflected images of both main surfaces are difficult to see, and the appearance is good.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has a solar reflectance of 4.2% or less on the first main surface 11a and the second main surface 11b. The solar reflectance is the solar reflectance defined by ISO9050 (2003), and is measured by applying a black paint for antireflection to the surface facing the measurement surface.

When the solar reflectance is 4.2% or less, the power generation efficiency is good when the chemically strengthened glass plate 10 is used as a cover glass for a solar cell. The solar reflectance is more preferably 4.0% or less, further preferably 3.8% or less, and particularly preferably 3.6% or less. In addition, the solar reflectance is typically 0.5% or more.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has a haze of 0.4% or less. Here, haze is a value measured according to JIS K7136 (2000). If the haze is 0.4% or less, the appearance of the chemically strengthened glass plate 10 is good. The haze is more preferably 0.3% or less, still more preferably 0.2% or less. Further, the haze may be 0% or more, and may be 0.05% or more.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has an area of the first main surface 11a and the second main surface 11b of 0.5 m ² or more. When the area is 0.5 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 0.7 m ² or more, 1 m ² or more, 2 m ² or more, 3 m ² or more, 5 m ² or more. It may be 7 m ² or more, or 9 m ² or more.

On the other hand, the area of the first main surface 11a and the second main surface 11b is preferably 12 m ² or less. When the area is 12 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 10 m ² or less.

In the chemically strengthened glass plate 10 according to the embodiment of the present invention, it is preferable that the first main surface 11a and the second main surface 11b are rectangular. If it is rectangular, it can be easily installed as, for example, a building window, an outer wall, a handrail material, 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 depending on the measurement position is 0.3 for both the long side and the short side. Includes shapes that fit within% and have curvatures or notches at the corners.

When the chemically strengthened glass plate 10 according to the embodiment of the present invention is rectangular, the length b of the long side of the first main surface 11a and the second main surface 11b may be 700 mm or more. , 1000 mm or more, 1300 mm or more, 1500 mm or more, 1800 mm or more, 2100 mm or more, 2500 mm or more. The length b of the long side of the first main surface 11a and the second main surface 11b may be 5000 mm or less. Here, the length b of the long side is the shortest distance b between the two opposing short sides shown in FIG.

When the chemically strengthened glass plate 10 according to the embodiment of the present invention is rectangular, the length a of the short side of the first main surface 11a and the second main surface 11b may be 500 mm or more. , 700 mm or more, 800 mm or more, 1300 mm or more, 1500 mm or more, 1800 mm or more, 2100 mm or more. The length a of the short side of the first main surface 11a and the second main surface 11b may be 3000 mm or less. Here, the length a of the short side is the shortest distance a between the two opposing long sides shown in FIG.

The thickness of the chemically strengthened glass plate 10 according to the embodiment of the present invention may be 2 mm or more in terms of strength, handleability, and the like. The plate thickness may be 3 mm or more, 4 mm or more, 5 mm or more, or 6 mm or more. On the other hand, when the plate thickness is 25 mm or less, it is preferable because it is lightweight. The plate thickness is more preferably 22 mm or less, further preferably 19 mm or less.

The chemically strengthened glass plate 10 according to the embodiment of the present invention preferably has a weight of 1000 kg or less. When the weight is 1000 kg or less, it is preferable because it is lightweight. The weight is more preferably 500 kg or less. The weight is preferably 2 kg or more from the viewpoint of strength and the like. The weight is more preferably 5 kg or more, further preferably 10 kg or more.

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.

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. 540 ° C or higher is more preferable, and 550 ° C or higher is even more preferable.

The temperature T2 at which the viscosity of the chemically strengthened glass plate ¹⁰ according to the embodiment of the present invention is 102 dPa · s is preferably 1550 ° C. or lower, more preferably 1490 ° C. or lower.

The temperature T4 at which the viscosity of the chemically strengthened glass plate ¹⁰ according to the embodiment of the present invention is 104 dPa · s is preferably 1050 ° C. or lower.

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 it are included as a lower limit value and an upper limit value, and unless otherwise specified, "-" 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 the breaking strength become 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 suppress brittleness of the chemically strengthened glass plate and suppress chipping of the chemically strengthened glass plate during cutting and dicing. Young's modulus may be 85 GPa or less, or 80 GPa or less.

Here, in the chemically strengthened glass plate 10 according to the embodiment of the present invention, SiO ₂ is 56 to 75%, Al ₂ O ₃ is 0 to 20%, and Na ₂ O is 8 to 8 in the oxide-based molar percentage display. It preferably contains 22%, K2O 0-10%, MgO _0-14 %, ZrO2 0-5%, and CaO _2-12 %. 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 microstructure, 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, still 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.

Although Al ₂ O ₃ is not essential, it 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. 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. In addition, the refractive index is lowered and the reflectance is lowered. Further, when the content of Al ₂ O ₃ is 20% or less, the devitrification temperature does not increase 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.

The _total content of SiO ₂ and 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. In addition, the refractive index is lowered and the reflectance is lowered. It is more preferable that SiO ₂ + Al ₂ O ₃ is 70% or more. Further, the SiO ₂ + 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 more preferable, and 74% or less is further preferable.

Na ₂ O is a component that forms surface compressive stress 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, still more preferably 12% or more. The Na ₂ O content is preferably 22% or less, more preferably 16% or less, still more preferably 14% or less. When the Na ₂ O content is 8% or more, a desired surface compressive stress is likely to be formed by ion exchange. On the other hand, when the content of Na ₂ O 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 the amount of 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 K2O is ₁₀ % or less, sufficient CS can be obtained.

MgO is not essential, but is a component that stabilizes the glass. 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 content of MgO 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 content of MgO is 14% or less, the difficulty of devitrification is maintained and a sufficient ion exchange rate can be obtained.

ZrO ₂ is a component that increases the refractive index, and is preferably not contained substantially in order to lower the refractive index and lower the reflectance. 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. However, ZrO ₂ may be contained because it has an effect of increasing the CS of the chemically strengthened glass. When it is contained, it is preferably 5% or less, more preferably 3% or less, still 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, although not essential, for the purpose of lowering the high temperature viscosity of the glass and lowering the devitrification temperature. 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. When it is contained, the amount of BaO is preferably 3% or less, more preferably 2% or less, still more preferably 1% or less.

It is preferable that ZnO is not substantially contained because it is reduced by a float bath and becomes a product defect when the glass plate is formed by the float method.

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 schematically.

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.

Li ₂ O is a component that lowers the strain point to facilitate stress relaxation, and as a result, makes it impossible to obtain stable surface compressive stress. Therefore, it is preferable not to contain Li 2 O, and even if it is contained, it is contained. The amount 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 be melted, homogenized by defoaming, stirring, etc., molded into a plate shape by a float method, slowly cooled, and then desired. A glass plate is manufactured by cutting it to size.

In the method for manufacturing a chemically strengthened glass plate according to an embodiment of the present invention, a glass plate is manufactured by a float method. In the glass plate formed by the float method, one main surface of the glass plate is in contact with the molten tin surface (hereinafter, the main surface in contact with the molten tin surface is referred to as a B surface, and the other main surface is referred to as a T surface). ..

In the chemical strengthening treatment step described later, surface modification occurs when the glass plate is immersed in the molten salt, and the average surface roughness Ra of the T surface becomes large. As a result, the refractive index of the surface of the glass plate becomes low, and the visible light reflectance becomes low. Here, the visible light reflectance of the T surface is characterized by being lower than the visible light reflectance of the B surface.

Further, by using the glass plate formed by the float method, when the glass plate is immersed in the molten salt, the average surface roughness Ra of one main surface of the chemically strengthened glass plate becomes particularly large, and the visible light reflectance becomes large. Will be low.

Therefore, the absolute value ΔR of the difference between the visible light reflectance R1 (unit:%) of the first main surface 11a of the chemically strengthened glass plate 10 and the visible light reflectance R2 (unit:%) of the second main surface 11b. Is 0.6% or more, and double images due to light reflected on the front and back surfaces of the chemically strengthened glass plate are less likely to occur, and the appearance is good.

When the glass plate formed by the float method is irradiated with ultraviolet rays, the B surface has tin and therefore becomes cloudy due to fluorescent color development, and the T surface does not become cloudy. By irradiating and observing both main surfaces of the glass plate with ultraviolet rays, it is possible to determine whether the glass plate is formed by the float method.

In the chemical strengthening treatment step, the obtained glass plate is immersed in a molten salt to form a compressive stress having a desired surface compressive stress on the surface of the 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, for example, by 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. In order to prevent cracking due to thermal shock in the chemical strengthening process, it is advisable to hold the glass plate at the preheating temperature for a certain period of time after the temperature rise is completed. The 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.

In the chemical strengthening step, the preheated glass plate is immersed in a molten salt, for example, a heated potassium nitrate molten salt, and Na in the glass surface layer and K in the molten salt are ion-exchanged. In the present invention, the molten potassium nitrate includes KNO ₃ , KNO ₂ , and those containing 10% by mass or less of NaNO ₃ .

In the method for producing a chemically strengthened glass plate 10 according to an embodiment of the present invention, NO _2- of a 100 ml constant volume aqueous solution in which 1 g of the molten salt is dissolved in ion ^- exchanged water by cooling the molten salt before immersing the glass plate. (Hereinafter referred ^to as the mass of NO _2- in the aqueous solution) is 2500 μg or more. ^The mass of NO _2- in the aqueous solution is preferably 3000 μg or more, more preferably 3400 μg or more, particularly preferably 4000 μg or more, and most preferably 4500 μg or more.

When the mass of NO ₂ ⁻ in the aqueous solution is 2500 μg or more, the NO ₂ ⁻ concentration of the molten salt is large, the refractive index of the T surface of the glass plate formed by the float method is sufficiently lowered, and the visible light reflectance is sufficient. Therefore, the visible light reflectance of one main surface of the obtained chemically strengthened glass plate 10 becomes sufficiently low, and the visible light reflectance R1 (unit:%) of the first main surface 11a of the chemically strengthened glass plate 10 is obtained. ) And the visible light reflectance R2 (unit:%) of the second main surface 11b, the absolute value ΔR is 0.6% or more, and among the first main surface 11a and the second main surface 11b, The average surface roughness Ra of the main surface having the smaller visible light reflectance is 0.4 nm or more.

^The mass of NO _2- in the aqueous solution is preferably 10,000 μg or less. When the mass of NO ₂ ⁻ in the aqueous solution is 10,000 μg or less, the NO ₂ ⁻ concentration of the molten salt can be reduced, which is good for the environment. ^The mass of NO _2- in the aqueous solution is more preferably 8000 μg or less, further preferably 6000 μg or less. The mass of the nitrate ⁻ NO ₂ of the aqueous solution ⁻ can be adjusted by the amount of KNO ₃ , KNO ₂ and the like added, and the retention time of the molten salt at a high temperature.

In the method for producing a chemically strengthened glass plate 10 according to an embodiment of the present invention, the molten salt before immersing the glass plate is cooled and dissolved in ion-exchanged water to obtain a 10% by mass aqueous solution of hydrogen ions. The index (hereinafter referred to as pH of the aqueous solution) is preferably 8 to 11.

When the pH of the aqueous solution is 8 or more, the hydrogen ion index of the molten salt is large, the refractive index of the T surface of the glass plate formed by the float method is lowered, and the reflectance is lowered, so that the obtained chemically strengthened glass plate is obtained. The reflectance of one of the main surfaces of 10 becomes low. The pH of the aqueous solution is more preferably 9 or more.

Further, when the pH of the aqueous solution is 11 or less, the nitrite concentration of the molten salt can be kept low, which is good for the environment. The pH of the aqueous solution is more preferably 10 or less. The pH of the aqueous solution can be adjusted by the amount of KNO ₃ , KNO ₂ , etc. added, and the holding time of the molten salt at a high temperature.

The chemical strengthening treatment conditions for forming the desired surface compressive stress on the glass plate differ depending on the plate thickness of the glass plate and the like, but the glass plate is exposed to a molten salt such as a molten salt of potassium nitrate at 350 to 550 ° C for 2 to 50 hours. The conditions for immersing the glass are typical. From an economical point of view, the condition of immersing the glass plate at 350 to 500 ° C. for 2 to 40 hours is preferable, and the more preferable immersion time is 2 to 30 hours.

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 not slowly cooled immediately, but is kept 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.

The holding temperature preferably has a difference of 100 ° C. or less from the temperature of the molten salt, more preferably 50 ° C. or lower, further preferably 20 ° C. or lower, and particularly preferably 10 ° 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.

The glass plate taken out from the molten salt is preferably slowly cooled so that the slow cooling rate until the glass plate reaches 100 ° C. is 300 ° C./hour or less. The slow cooling rate is more preferably 200 ° C./hour or less, and even more preferably 100 ° C./hour or less.

In the method for producing a chemically strengthened glass plate 10 according to an embodiment of the present invention, before the glass plate is immersed in the molten salt on at least one of the first main surface 11a and the second main surface 11b. The absolute value RD of the difference between the visible light reflectance (visible light reflectance before immersion in the molten salt) and the visible light reflectance after immersing the glass plate in the molten salt (visible light reflectance after immersion in the molten salt) is It is preferably 0.3% or more. Here, RD satisfies the following equation (2).

RD = | (Visible light reflectance before soaking in molten salt)-(Visible light reflectance after soaking in molten salt) | Equation (2)

By immersing the glass plate in the molten salt, the RD increases. The higher the NO ₂ ^- concentration of the molten salt, the higher the RD. The RD is more preferably 0.4% or more, further preferably 0.6% or more, and particularly preferably 0.7% or more.

In the method for producing a chemically strengthened glass plate 10 according to an embodiment of the present invention, before the glass plate is immersed in the molten salt on at least one of the first main surface 11a and the second main surface 11b. It is preferable that the value ΔRa obtained by subtracting the average surface roughness Ra1 of the glass plate from the average surface roughness Ra2 of the glass plate after immersing the glass plate in the molten salt is 0.2 nm or more. Here, ΔRa is a value that satisfies the following equation (3).

ΔRa = Ra2-Ra1 equation (3)

By immersing the glass plate in the molten salt, the average surface roughness of the glass plate becomes large. The higher the concentration of NO ₂ ^- concentration of nitrate, the larger the ΔRa. ΔRa is more preferably 0.3 nm or more, and further preferably 0.4 nm or more.

In the method for producing a chemically strengthened glass plate 10 according to an embodiment of the present invention, the main surface having ΔRa of 0.2 nm or more may be the T surface.

In the chemically strengthened glass plate of the present embodiment described above, double images due to light reflected on the front surface and the back surface are less likely to occur, and the appearance is good.

The present invention is not limited to the above embodiment. Modifications and improvements 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 3 are examples, and example 4 is a comparative example.

Various glass raw materials such as silica sand are 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 is 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, Young's modulus (unit: GPa), visible light reflectance, and average surface roughness of the obtained glass plate are determined. It was measured. The results are shown in Table 1.

Next, the mass ^and pH of NO _2- of the aqueous solution were measured. The glass plate was placed in an electric furnace at 300 ° C., preheated for 30 minutes, and immersed in a molten salt of potassium nitrate at 500 ° C. for 6 hours. The glass plate was taken out from the molten salt and held at 300 ° C. for 10 minutes, and then taken out from the electric furnace and naturally cooled to obtain a chemically strengthened glass plate.

The visible light reflectances R1 and R2 of the obtained chemically strengthened glass plate were measured, and ΔR, RD, and RS were calculated. Moreover, the average surface roughness of the obtained chemically strengthened glass plate was measured, and ΔRa was calculated. Furthermore, the CS, DOL, haze, and T-plane solar reflectances of the obtained chemically strengthened glass plate were measured. The results are shown in Table 2.

In terms of average surface roughness, the average surface roughness Ra1 before being immersed in the molten salt and the average surface roughness Ra2 after being immersed in the molten salt on the main surface (T surface) having the lower visible light reflectance are shown.

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 glass lumps containing no bubbles were measured by the Archimedes method.

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

(Visible light reflectance, solar reflectance)
The measurement was performed using a spectrophotometer (Hitachi High-Tech Science Corporation: UH4150) according to the method specified in ISO 9050 (2003). Black paint [Sunday Paint Co., Ltd .: Acrylic lacquer spray (matte black)] was applied to the surface facing the measurement surface to prevent reflection on the back surface.

(Average surface roughness)
The measurement was carried out by an atomic force microscope (manufactured by Park Systems Co., Ltd .: XE-HDM) according to the method specified in JIS B 0601 (1994). PPP-NCHR (spring constant: 40 N / m) is used as the probe, NON-CONTACT mode, Source is Topography, Date Wide 256pxl, Date Height 128pxl, Scan rate 0.5 Hz, and the measurement field of view is 50 × 25 μm ² . It was measured.

(Haze)
It was measured by a turbidity meter (manufactured by Nippon Denshoku Kogyo Co., Ltd .: NDH7000SP) according to the method specified in JIS K 7136 (2000). The total light transmittance used for haze calculation was measured according to JIS K 7631-1 (1997).

(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].

⁽ Mass of NO _2- of aqueous solution)
^The mass of NO _2- in a 100 ml constant volume aqueous solution obtained by cooling the molten salt before immersing the glass plate and dissolving 1 g of the molten salt in ion-exchanged water was measured by ion chromatography (manufactured by Dionex Co., Ltd .: ICS1000).

(PH of aqueous solution)
The molten salt before immersing the glass plate was cooled, crushed in a mortar, diluted 10-fold with ion-exchanged water, and measured with a pH meter (manufactured by HORIBA, Ltd .: D-50).

As shown in Table 2, in the chemically strengthened glass plates of Examples 1 to 3 of Examples, since the mass of NO ₂ ⁻ of the aqueous solution is 2500 μg or more, the visible light reflectance of the T surface is lowered and ΔR is 0. The average surface roughness of the main surface of the main surface having a reflectance of 6.6% or more and a small visible light reflectance was 0.4 nm or more, and double images due to the light reflected on the front surface and the back surface were less likely to occur, and the appearance was good.

On the other hand, in the chemically strengthened glass plate of Example 4 which is a comparative example, since the mass of NO ₂ ⁻ of the aqueous solution is less than 2500 μg, the average surface of the main surface having a ΔR of less than 0.6% and a smaller visible light reflectance is obtained. The roughness was less than 0.4 nm, and double images due to the light reflected on the front surface and the back surface were likely to occur, and the appearance was poor.

Although the invention has been described in detail with reference to particular embodiments, it will be apparent to those skilled in the art that various modifications and modifications are possible without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on February 24, 2017 (Japanese Patent Application No. 2017-33812), which is incorporated by reference in its entirety. 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 handrail material, a solar cell cover glass, and a vehicle window.

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

Claims (8)

It has a first main surface and a second main surface facing the first main surface, surface compressive stress is formed on the first main surface and the second main surface, and tensile stress is generated inside. It is a chemically strengthened glass plate that is formed.
The absolute value ΔR of the difference between the visible light reflectance R1 (unit:%) of the first main surface and the visible light reflectance R2 (unit:%) of the second main surface is 0.6% or more. ,
Of the first main surface and the second main surface, the main surface having the smaller visible light reflectance has an average surface roughness Ra of 0.4 nm or more .
A chemically strengthened glass plate characterized in that the average surface roughness Ra of the first main surface and the second main surface is 20 nm or less . The chemically strengthened glass plate according to claim 1, wherein the haze is 0.4% or less. The chemically strengthened glass plate according to claim 1 or 2 , which contains 20% or less of Al ₂ O ₃ in terms of an oxide-based molar percentage and substantially does not contain ZrO ₂ . The chemically strengthened glass plate according to any one of claims 1 to 3 , wherein the CS 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 any one of claims 1 to 4 , wherein the DOL on at least one of the first main surface and the second main surface is 15 to 100 μm. A method for manufacturing a chemically strengthened glass plate for obtaining the chemically strengthened glass plate according to any one of claims 1 to 5 .
The glass plate manufacturing process for manufacturing glass plates and
It has a chemical strengthening treatment step of immersing the glass plate in a molten salt to form a compressive stress on the surface of the glass plate.
In the glass plate manufacturing process, a glass plate is manufactured by the float method.
^The mass of NO _2- of a 100 ml constant volume aqueous solution obtained by cooling the molten salt before immersing the glass plate in the chemical strengthening treatment step and dissolving 1 g of the molten salt in ion-exchanged water shall be 2500 μg or more. A method for manufacturing a chemically strengthened glass plate. The sixth aspect of claim 6 in which the hydrogen ion index (pH) of the aqueous solution is 8 to 11 when the molten salt before immersing the glass plate is cooled and dissolved in ion-exchanged water to prepare a 10% by mass aqueous solution. How to make a chemically strengthened glass plate. In the chemical strengthening treatment step
In at least one of the first main surface and the second main surface,
The value ΔRa obtained by subtracting the average surface roughness Ra1 of the glass plate before immersing the glass plate in the molten salt from the average surface roughness Ra2 of the glass plate after immersing the glass plate in the molten salt. The method for producing a chemically strengthened glass plate according to claim 6 or 7 , which has a diameter of 0.2 nm or more.

Images