WO2018155456A1

WO2018155456A1 - Chemically tempered glass plate and production method therefor

Info

Publication number: WO2018155456A1
Application number: PCT/JP2018/006076
Authority: WO
Inventors: 幹通川上; 準一郎加瀬; 石田　光
Original assignee: Ａｇｃ株式会社
Priority date: 2017-02-24
Filing date: 2018-02-20
Publication date: 2018-08-30
Also published as: JPWO2018155456A1; JP7044101B2

Abstract

The present invention provides a chemically tempered glass plate which has a good appearance and in which light reflected by the front surface and the back surface is less likely to form a double reflection image. This chemically tempered glass plate (10) has a first main surface (11a) and a second main surface (11b) facing the first main surface (11a), and has a surface compression stress formed at the first main surface (11a) and the second main surface (11b) and a tensile stress at the interior thereof. The chemically tempered glass plate (10) is characterized in that: the absolute value ∆R of the difference between the visible light reflectance R1 (%) of the first main surface (11a) and the visible light reflectance R2 (%) of the second main surface (11b) is 0.6% or more; and a main surface having a smaller visible light reflectance among the first main surface (11a) and the second main surface (11b) has an average surface roughness Ra of 0.4 nm or more.

Description

Chemically tempered glass plate and manufacturing method thereof

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

In order to improve the strength of the 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. In tempered glass, the glass plate is heated and then rapidly cooled to form a temperature difference between the main surface and the inside, and a physically tempered glass obtained by immersing the glass plate in molten salt to reduce the ionic radius on the main surface side There is chemically strengthened glass by ion exchange between ions and ions having a large ion radius on the molten salt side.

Chemically tempered glass plates have a greater compressive stress on the main surface than physical tempered glass plates, so they are resistant to sudden impacts. It has been. Patent Document 1 proposes a chemically strengthened glass plate used as an architectural window, an outer wall, a solar cell cover glass, and a vehicle window.

International Publication No. 2014/168246

A chemically tempered glass plate is required to have a beautiful appearance in order to be used for various purposes such as architectural windows and vehicle windows. Here, the glass plate reflects incident light on the front surface and the back surface. Therefore, a double image is generated by light reflected from the front and back surfaces, 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 from the front and back surfaces and has a good appearance, and a method for producing the same.

The chemically strengthened glass plate of the present invention has a first main surface and a second main surface opposite to 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 in which a tensile stress is 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, an average surface roughness Ra of a main surface having a smaller visible light reflectance is 0.4 nm or more.

The method for producing a chemically strengthened glass plate of the present invention is a method for producing a chemically strengthened glass plate to obtain the above chemically strengthened glass plate,
A glass plate manufacturing process for manufacturing a glass plate;
A chemical strengthening treatment step of immersing the glass plate in a molten salt and forming a compressive stress on the surface of the glass plate;
In the glass plate manufacturing process, a glass plate is manufactured by a float method,
The mass of NO ₂ ⁻ in 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 is 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 light reflected from the front and back surfaces, and has a good appearance.

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

Hereinafter, a chemically strengthened glass plate according to an 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 sheet according to an embodiment of the present invention, and FIG. 2 is a plan view of the chemically strengthened glass sheet according to an embodiment of the present invention.

The chemically strengthened glass plate 10 according to one embodiment of the present invention has a first main surface 11a and a second main surface 11b facing the first main surface 11a, and the first main surface 11a and the second main surface 11b. A chemically tempered glass plate in which a surface compressive stress is formed on the main surface 11b and a tensile stress is formed therein, and the visible light reflectance R1 (unit:%) of the first main surface 11a and the second main surface 11b The absolute value ΔR of the difference from the visible light reflectivity R2 (unit:%) of the surface 11b is 0.6% or more, and the visible light reflectivity is the first main surface 11a and the second main surface 11b. The average surface roughness Ra of the smaller main surface is 0.4 nm or more.

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

The chemically strengthened glass plate according to an embodiment of the present invention can be used as a single plate glass for various uses such as architectural windows, outer walls, handrail materials, solar cell cover glasses, vehicle windows, and the like. Moreover, in another embodiment, it can be used as a laminated glass which bonded together the 2 or more glass plate with the intermediate | middle layer film.

In still another embodiment, two or more glass plates can be arranged at intervals to be used as a double-layer glass. In yet another embodiment, the glass plate surface can be coated and used.

In the configuration of laminated glass or multilayer glass, the chemically strengthened glass plate of the present invention can be used for at least one sheet. Since the multilayer glass may generally undergo 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 one embodiment of the present invention, surface compressive stress is formed on the main surfaces 11a and 11b.

In the chemically strengthened glass plate 10 according to an embodiment of the present invention, CS is preferably 250 MPa or more on at least one main surface of the first main surface 11a and the second main surface 11b. If CS is 250 MPa or more, the mechanical strength of the chemically strengthened glass plate is high. CS is preferably 300 MPa or more, more 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. If CS is 500 MPa or less, the internal tensile stress is unlikely to become extremely high. Further, the chemical strengthening treatment step may be short-time immersion in a high-temperature molten salt, and it is easy to obtain the chemically strengthened glass plate 10. Further, when the chemically strengthened glass plate 10 is cut, it is easy to form a cut line by a wheel cutter. CS is preferably 480 MPa or less, and more preferably 460 MPa or less.

The chemically strengthened glass plate 10 according to an embodiment of the present invention preferably has a DOL of 15 μm or more on at least one main surface of the first main surface 11a and the second main surface 11b. If the DOL is 15 μm or more, sufficient strength can be obtained and it can withstand impact. 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. If DOL is 100 micrometers or less, the immersion to molten salt may be a short time, and it is easy to obtain the chemically strengthened glass plate 10. FIG. 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 thickness direction of the compressive stress layer) can be measured by a surface stress meter.

In the chemically strengthened glass plate 10 according to an embodiment of the present invention, compressive stress may be formed on the end surface 12 together with the main surfaces 11a and 11b. 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 one 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 is 0.6% or more. Here, ΔR satisfies the following formula (1).

ΔR = | R1-R2 | Formula (1)

Further, the visible light reflectances R1 and R2 are visible light reflectances defined by ISO 9050 (2003), and are measured by applying a black paint for preventing reflection to the surface facing the measurement surface. If ΔR is 0.6% or more, the reflected image on one surface of the front or back surface is more clearly reflected than the reflected image on the other surface, so a double image is generated by the light reflected on the front and back surfaces. Difficult to do and good aesthetics. ΔR is preferably 0.8% or more, more preferably 0.9% or more, and further preferably 1.0% or more. ΔR is typically 4% or less.

In the chemically strengthened glass plate 10 according to an embodiment of the present invention, the visible light reflectance RS of the principal surface having the smaller visible light reflectance of the first principal surface 11a and the second principal surface 11b is 4. It is preferable that it is 2% or less. If the RS is 4.2% or less, a reflected image is less likely to occur and the aesthetic appearance is good. The RS is more preferably 4.0% or less, still more preferably 3.8% or less, and particularly preferably 3.6% or less. RS is typically 0.5% or more.

In the chemically strengthened glass plate 10 according to one embodiment of the present invention, the average surface roughness Ra of the principal surface having the smaller visible light reflectance of the first principal surface 11a and the second principal surface 11b is 0.00. 4 nm or more. Here, the average surface roughness Ra is a value defined by JIS B 0601 (1994). If 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 lowered in a pseudo manner, and the visible light reflectance can be lowered. A double image due to the light reflected from the back surface hardly occurs, and the appearance is good. The average surface roughness Ra of the main surface having a 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.

In the chemically strengthened glass plate 10 according to an embodiment of the present invention, the average surface roughness Ra of the first main surface 11a and the second main surface 11b is preferably 20 nm or less. If average surface roughness Ra of the 1st main surface 11a and the 2nd main surface 11b is 20 nm or less, haze will become low enough and aesthetics will be 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, and further preferably 5 nm or less.

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

In the chemically strengthened glass plate 10 according to an embodiment of the present invention, the solar reflectance of the first main surface 11a and the second main surface 11b is preferably 4.2% or less. The solar reflectance is a solar reflectance defined by ISO 9050 (2003), and is measured by applying a black paint for preventing reflection to the surface facing the measurement surface.

If 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 solar cell cover glass. The solar reflectance is more preferably 4.0% or less, further preferably 3.8% or less, and particularly preferably 3.6% or less. Also, the solar reflectance is typically 0.5% or more.

The chemically tempered glass plate 10 according to an 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 aesthetic appearance of the chemically strengthened glass plate 10 is good. The haze is more preferably 0.3% or less, and further preferably 0.2% or less. Further, the haze may be 0% or more, and may be 0.05% or more.

In the chemically strengthened glass plate 10 according to one embodiment of the present invention, the area of the first main surface 11a and the second main surface 11b is preferably 0.5 m ² or more. If the area is 0.5 m ² or more, it is suitably used for various applications such as architectural windows, outer walls, solar cell cover glass, vehicle windows and the like. 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, or 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. If an area is 12 m < ² > or less, handling of a chemically strengthened glass plate will become easy, for example, the damage by the contact with the peripheral member at the time of installation of a chemically strengthened glass plate can be suppressed. The area may be 10 m ² or less.

In the chemically strengthened glass plate 10 according to an embodiment of the present invention, the first main surface 11a and the second main surface 11b are preferably rectangular. If it is a rectangle, it is easy to install as, for example, an architectural window, an outer wall, a handrail material, or a solar cell cover glass. Here, the rectangle is a substantially right-angled quadrilateral, and when measuring the distance from any one side to the opposite side, the error due to the measurement position is 0.3 for each of the long side and the short side. Including shapes with curvature and notches in the corners.

When the chemically strengthened glass plate 10 according to an embodiment of the present invention is rectangular, the length b of the long sides 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, or 2500 mm or more. The long side length b 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 two opposing short sides shown in FIG.

When the chemically strengthened glass plate 10 according to an embodiment of the present invention is rectangular, the length a of the short sides 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, or 2100 mm or more. The length a of the short sides 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 two opposing long sides shown in FIG.

The thickness of the chemically strengthened glass plate 10 according to an embodiment of the present invention may be 2 mm or more from the viewpoint of strength and handling properties. 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, if 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, and further preferably 19 mm or less.

The chemically strengthened glass plate 10 according to an embodiment of the present invention preferably has a weight of 1000 kg or less. A weight of 1000 kg or less is preferable because it is lightweight. The weight is more preferably 500 kg or less. Further, 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, and further preferably 10 kg or more.

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

The glass transition point Tg of the chemically strengthened glass plate 10 according to an embodiment of the present invention is preferably 530 ° C. or higher. Thereby, 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 more preferable.

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

The temperature T4 at which the viscosity of the chemically strengthened glass plate 10 according to an embodiment of the present invention is 10 ⁴ dPa · s is preferably 1050 ° C. or lower.

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

The term “to” indicating the above numerical range is used in the sense that the numerical values described before and after it are used as the lower limit value and the upper limit value, and unless otherwise specified, “to” is the same in the following specification. Used with meaning.

The Young's modulus of the chemically strengthened glass plate 10 according to an embodiment of the present invention is preferably 65 GPa or more. Thereby, rigidity and breaking strength are sufficient. The Young's modulus may be 70 GPa or more. On the other hand, if the Young's modulus is 90 GPa or less, the chemically strengthened glass plate can be prevented from becoming brittle, and chipping during cutting and dicing of the chemically strengthened glass plate can be suppressed. The Young's modulus may be 85 GPa or less, or 80 GPa or less.

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

The reason for limiting the glass composition to the above range in the chemically strengthened glass plate 10 according to an 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, still more preferably 66% or more, and particularly preferably 68% or more. Further, the content of SiO ₂ is preferably 75% or less, more preferably 73% or less, and further preferably 72% or less. When the content of SiO ₂ is 56% or more, it is advantageous 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 advantageous in terms of meltability and moldability.

Al ₂ O ₃ is not essential, but has an effect of improving ion exchange performance in chemical strengthening, and may be contained because it has a particularly large effect of increasing CS. Moreover, the weather resistance of glass is improved. When it contains Al ₂ O ₃ , 0.4% or more is preferable, 0.6% or more is more preferable, and 0.8% or more is more preferable. Further, 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 greatly even when the viscosity of the glass is high, and this 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.

68% or more of the total SiO ₂ + Al ₂ O ₃ content of SiO ₂ and Al ₂ O ₃ is preferable. If it is 68% or more, the crack resistance when indentation is applied is improved. Further, the refractive index is lowered and the reflectance is lowered. SiO ₂ + _Al 2 _{O 3} is more preferably 70% or more. _Further, SiO 2 + _Al 2 _{O 3} is preferably 80% or less. If it is 80% or less, the viscosity of the glass at a high temperature is lowered and melting becomes easy. 76% or less is more preferable, and 74% or less is more preferable.

Na ₂ O is a component that forms surface compressive stress by ion exchange, and has the effect of deepening DOL. Moreover, it is a component which 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. Further, the content of Na ₂ O is preferably 22% or less, more preferably 16% or less, and still more preferably 14% or less. When the content of Na ₂ O is 8% or more, a desired surface compressive stress is easily 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 excessive, sufficient CS cannot be obtained. When it contains K ₂ O, it is preferably 10% or less, more preferably 2% or less, and even more preferably 1% or less. When the content of K ₂ O is 10% or less, sufficient CS can be obtained.

MgO is not essential, but is a component that stabilizes the glass. When it contains MgO, 2% or more is preferable, 4% or more is more preferable, and 6% or more is further more 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. The meltability at high temperature becomes good and devitrification hardly occurs. 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 is obtained.

ZrO ₂ is a component that increases the refractive index, and is preferably not substantially contained in order to lower the refractive index and decrease the reflectance. In the present specification, “substantially does not contain” means that it is not contained other than inevitable impurities mixed from raw materials or the like, that is, it is not intentionally contained. However, ZrO ₂ may be contained because it has the effect of increasing the CS of the chemically strengthened glass. When it contains, 5% or less is preferable, 3% or less is more preferable, and 1% or less is further more preferable.

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

SrO is not essential, but may be contained for the purpose of lowering the high temperature viscosity of the glass and lowering the devitrification temperature. Since SrO has the effect of lowering the ion exchange efficiency, it is preferable not to contain it 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, and even more preferably 1% or less.

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

ZnO is preferably not substantially contained because it is reduced by a float bath and becomes a product defect when a glass plate is formed by the float process.

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

The glass of the present invention consists essentially 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 other components will be described as an example.

B ₂ O ₃ may be contained in a range of less than 1% in order to improve the meltability at high temperature or the glass strength. In general, when an alkali 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 brick is remarkably eroded. Therefore, it is preferable that B ₂ O ₃ is not substantially contained.

Li ₂ O is a component that makes it easy to cause stress relaxation by lowering the strain point and, as a result, makes it impossible to obtain a stable surface compressive stress. The amount is preferably 1% or less, more preferably 0.05% or less, and particularly preferably 0.01% or less.

Next, the manufacturing method of the chemically strengthened glass plate 10 which concerns on one Embodiment of this invention is demonstrated.

When manufacturing the chemically strengthened glass plate 10 which concerns on one Embodiment of this invention, it passes through a glass plate manufacturing process and a chemical strengthening process process.

In the glass plate manufacturing process, for example, appropriate amounts of various raw materials are prepared, heated to about 1400 to 1800 ° C. and melted, homogenized by defoaming, stirring, etc., formed into a plate shape by the float process, and then slowly cooled to a desired shape. A glass plate is manufactured by cutting into sizes.

In the method for producing a chemically strengthened glass plate according to an embodiment of the present invention, a glass plate is produced by a float process. In the glass plate formed by the float process, 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 B surface, and the other main surface is referred to as 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 plane increases. Thereby, the refractive index of the surface of a glass plate becomes low, and a visible light reflectance becomes low. Here, the visible light reflectance of the T plane is lower than that of the B plane.

Further, by using a glass plate formed by the float process, 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 is particularly increased, and the visible light reflectance is increased. Becomes lower.

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 it is difficult to generate a double image due to light reflected from the front and back surfaces of the chemically strengthened glass plate, and the appearance is good.

Note that when the glass plate formed by the float method is irradiated with ultraviolet rays, the B surface has tin because it has tin, 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 has been 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 process goes through a preheating process, a chemical strengthening process, and a slow cooling process.

In the preheating process, the glass plate is preheated before the chemical strengthening treatment. Preheating is performed, for example, by placing a glass plate in a normal temperature electric furnace, raising the temperature of the electric furnace to a preheating temperature, and holding the electric furnace for a predetermined time. In order to prevent cracking due to thermal shock in the chemical strengthening process, it is preferable to hold the glass plate at a 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.

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. Incidentally, potassium nitrate molten salt in the present _invention, other KNO 3, KNO _2, including those containing NaNO ₃ of 10 wt% or less.

In the method for producing a chemically strengthened glass sheet 10 according to an embodiment of the present invention, a molten salt before dipping the glass sheet is cooled, and NO ₂ ⁻ in a 100 ml constant volume aqueous solution in which 1 g of the molten salt is dissolved in ion-exchanged water. mass (hereinafter, NO ₂ of an aqueous solution ^- of the mass) is not less than 2500 g. 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 plane 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 chemically strengthened glass plate 10 obtained is sufficiently low, and the visible light reflectance R1 (unit:%) of the first main surface 11a of the chemically strengthened glass plate 10 is reduced. ) And the visible light reflectance R2 (unit:%) of the second principal surface 11b is 0.6% or more in absolute value, and the first principal surface 11a and the second principal surface 11b, The average surface roughness Ra of the main surface with 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. If the mass of NO ₂ ^{− in} the aqueous solution is 10000 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, and even more preferably 6000 μg or less. NO ₂ in aqueous solution ^- ^- nitrate mass _can be adjusted KNO 3, KNO amount of such _2, and the holding time at high temperature molten salt.

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 mass% aqueous solution hydrogen ion. The index (hereinafter referred to as the pH of the aqueous solution) is preferably 8-11.

If 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-plane of the glass plate formed by the float method is lowered, and the reflectance is lowered. The reflectance of one main surface of 10 becomes low. The pH of the aqueous solution is more preferably 9 or more.

Moreover, if pH of aqueous solution is 11 or less, the nitrous acid density | concentration of molten salt can be restrained low and it is good for an environment. The pH of the aqueous solution is more preferably 10 or less. The pH of the aqueous solution can be adjusted by the addition amount of KNO ₃ , KNO _{2 and the} like 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 vary depending on the thickness of the glass plate, but the glass plate is heated in a molten salt such as potassium nitrate molten salt at 350 to 550 ° C. for 2 to 50 hours. The conditions for soaking are typical. From an economical point of view, conditions of immersing the glass plate at 350 to 500 ° C. for 2 to 40 hours are preferable, and a more preferable immersing time is 2 to 30 hours.

In the slow cooling step, the glass plate taken out from the molten salt is slowly cooled. The glass plate taken out from the molten salt is not immediately cooled slowly, but is preferably maintained at a uniform temperature for a certain time in order to make it difficult for temperature distribution to occur on the main surface of the glass plate.

The difference between the holding temperature and the temperature of the molten salt is preferably 100 ° C. or less, more preferably 50 ° C. or less, further preferably 20 ° C. or less, and particularly preferably 10 ° C. or less. The holding time is preferably 10 minutes or more, more preferably 20 minutes or more, and further preferably 30 minutes or more.

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 further preferably 100 ° C./hour or less.

In the manufacturing method of the chemically strengthened glass plate 10 which concerns on one Embodiment of this invention, before immersing a glass plate in molten salt in at least one main surface among the 1st main surface 11a and the 2nd main surface 11b. The absolute value RD of the difference between the visible light reflectance (visible light reflectance before immersion of molten salt) and the visible light reflectance after immersion of the glass plate in molten salt (visible light reflectance after immersion of molten salt) is It is preferable that it is 0.3% or more. Here, RD satisfies the following formula (2).

RD = | (Visible light reflectance before immersion of molten salt) − (Visible light reflectance after immersion of molten salt) | Equation (2)

RD becomes large when a glass plate is immersed in molten salt. The higher the NO ₂ ⁻ concentration of the molten salt, the greater the RD. RD is more preferably 0.4% or more, further preferably 0.6% or more, and particularly preferably 0.7% or more.

In the manufacturing method of the chemically strengthened glass plate 10 which concerns on one Embodiment of this invention, before immersing a glass plate in molten salt in at least one main surface among the 1st main surface 11a and the 2nd main surface 11b. A 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 preferably 0.2 nm or more. Here, ΔRa is a value that satisfies the following formula (3).

ΔRa = Ra2-Ra1 Equation (3)

When the glass plate is immersed in the molten salt, the average surface roughness of the glass plate is increased. The higher the NO ₂ ⁻ concentration in nitrate, the greater ΔRa. ΔRa is more preferably 0.3 nm or more, and further preferably 0.4 nm or more.

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

In the chemically strengthened glass plate of the present embodiment described above, a double image due to light reflected on the front surface and the back surface hardly occurs, and the appearance is good.

The present invention is not limited to the above embodiment. The present invention includes modifications and improvements as long as the object of the present invention can be achieved.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this 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 were prepared so as to have the glass composition shown in Table 1, melted at a temperature of 1400-1500 ° C., and the obtained molten glass was formed into a plate shape by a float process. A rectangular glass plate having the size shown was obtained. The glass transition point 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 It was measured. The results are shown in Table 1.

Then, NO ₂ in aqueous solution ^- to measure the mass and the pH of the. The glass plate was placed in an electric furnace at 300 ° C., preheated for 30 minutes, and immersed in 500 ° C. potassium nitrate molten salt 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. Further, the solar reflectance of CS, DOL, haze, and T-plane of the obtained chemically strengthened glass plate was measured. The results are shown in Table 2.

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

The measurement method of each physical property is shown below.

(Glass transition point Tg)
Measurement was performed using TMA according to the method defined in JIS R3103-3 (2001).

(T ₂ )
The viscosity was measured using a rotational viscometer, and the temperature T2 (° C.) when it reached 10 ² d · Pa · s was measured.

_(T 4)
The viscosity was measured using a rotational viscometer, and the temperature T4 (° C.) when it reached 10 ⁴ d · Pa · s was measured.

(specific gravity)
About 20 g of glass lump containing no foam was measured by the Archimedes method.

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

(Visible light reflectance, solar reflectance)
According to the method prescribed | regulated to ISO 9050 (2003), it measured using the spectrophotometer (The Hitachi High-Tech Science company make: UH4150). A black paint [manufactured by 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)
According to the method defined in JIS B 0601 (1994), the measurement was performed with an atomic force microscope (manufactured by Park Systems: XE-HDM). Using PPP-NCHR (spring constant: 40 N / m) as a probe, NON-CONTACT mode, Source is Topography, Date Width 256 pxl, Date Height 128 pxl, Scan rate 0.5 Hz, and measurement field is 50 × 25 μm ² It was measured.

(Haze)
According to the method prescribed | regulated to JISK7136 (2000), it measured with the turbidimeter (Nippon Denshoku Industries Co., Ltd. product: NDH7000SP). The total light transmittance used for haze calculation was measured according to JIS K 7361-1 (1997).

(CS, DOL)
The number was calculated from the number of interference fringes observed using a surface stress meter (manufactured by Orihara Seisakusho: FSM-7000H) and the interval therebetween. 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 NO ₂ aqueous solution)
The molten salt before immersing the glass plate was cooled, and the mass of NO ₂ ⁻ in a 100 ml constant volume aqueous solution in which 1 g of the molten salt was dissolved in ion-exchanged water was measured by ion chromatography (manufactured by Dionex: ICS1000).

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

As shown in Table 2, chemically strengthened glass plate Examples 1-3 are examples, NO ₂ of an aqueous solution ^- for mass is not less than 2500 g, the visible light reflectance of T surface is decreased, [Delta] R is 0 The average surface roughness of the main surface with a visible light reflectance of less than .6% or more was 0.4 nm or more, and a double image due to light reflected on the front and back surfaces was hardly generated, and the appearance was good.

On the other hand, the chemically strengthened glass plate of Example 4, which is a comparative example, has an NO ₂ ⁻ mass of less than 2500 μg in the aqueous solution, so that the average surface of the main surface with the smaller ΔR of less than 0.6% and the smaller visible light reflectance The roughness was less than 0.4 nm, and a double image was easily generated due to light reflected on the front and back surfaces, and the aesthetic appearance was poor.

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 changes 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. 2017-33812) filed on Feb. 24, 2017, which is incorporated by reference in its entirety. Also, all references cited herein are incorporated as a whole.

The chemically tempered glass plate of the present invention is suitably used as, for example, an architectural window, an outer wall, a handrail material, a solar cell cover glass, or a vehicle window.

10 chemically strengthened glass plate 11a first main surface 11b second main surface

Claims

A first main surface and a second main surface opposite to the first main surface; surface compressive stress is formed on the first main surface and the second main surface; A formed chemically strengthened glass plate,
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. ,
The chemically strengthened glass sheet, wherein an average surface roughness Ra of a main surface having a smaller visible light reflectance is 0.4 nm or more among the first main surface and the second main surface.
The chemically strengthened glass sheet according to claim 1, wherein the haze is 0.4% or less.
The chemically strengthened glass sheet according to claim 1 or 2, wherein an average surface roughness Ra of the first main surface and the second main surface is 20 nm or less.
The chemically strengthened glass sheet according to any one of claims 1 to 3, which contains 20% or less of Al 2 O 3 in terms of an oxide-based mole percentage and substantially does not contain ZrO 2 .
The chemically strengthened glass sheet according to any one of claims 1 to 4, wherein CS of at least one main surface of the first main surface and the second main surface is 250 to 500 MPa.
The chemically strengthened glass sheet according to any one of claims 1 to 5, wherein a DOL on at least one main surface of the first main surface and the second main surface is 15 to 100 µm.
A method for producing a chemically strengthened glass sheet to obtain the chemically strengthened glass sheet according to any one of claims 1 to 6,
A glass plate manufacturing process for manufacturing a glass plate;
A chemical strengthening treatment step of immersing the glass plate in a molten salt and forming a compressive stress on the surface of the glass plate;
In the glass plate manufacturing process, a glass plate is manufactured by a float method,
The mass of NO 2 − in 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 is 2500 μg or more. A method for producing a chemically strengthened glass sheet.
The hydrogen ion exponent (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 obtain a 10% by mass aqueous solution. Manufacturing method of chemically strengthened glass plate.
In the chemical strengthening treatment step,
In at least one main surface of the first main surface and the second main surface,
A 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 is It is 0.2 nm or more, The manufacturing method of the chemically strengthened glass plate of Claim 7 or 8.