JP2023137438A - Manufacturing method of strengthened glass, and strengthened glass - Google Patents

Abstract

To provide manufacturing method of strengthened glass that dissolves deformation defects caused by ion exchange in strengthened glass of thin thickness and thereby improves the shape of the strengthened glass.SOLUTION: A manufacturing method of strengthened glass for obtaining strengthened glass having a compressive stress layer on the surface layer, includes a preparation step for preparing tabular or film-like chemically strengthened glass of a thickness of 0.2 mm or less as glass to be processed, and an adjustment step for bringing the surface of the glass to be processed into contact with a molten salt for adjustment containing a polyvalent metal ion.SELECTED DRAWING: Figure 1

Description

The present invention relates to tempered glass, particularly thin chemically strengthened glass.

In recent years, chemically strengthened glass with a thickness of about 0.4 to 1.0 mm has been widely used as cover glass for various electronic terminals and display devices. 2. Description of the Related Art Devices such as so-called foldable smartphones and tablet PCs whose display surfaces are foldable have been developed. In order to make the cover glass used in such a device bendable, the thickness of the cover glass is thinner than before.For example, in the technique of Patent Document 1, it is being considered to make the cover glass extremely thin to 0.5 mm or less.

Special table 2016-508954 publication

However, the ultra-thin glass described above is more easily deformed than conventional glass, which is relatively thick, so when chemically strengthened using molten salt, the glass surface deforms in a wavy manner. In some cases, wrinkle-like defects or wrinkle-like defects may occur. Such defects are caused, for example, by variations in the degree of ion exchange due to variations in the state of adhesion of molten salt to the glass surface, and variations in the ion concentration distribution and stress distribution in the direction of the main surface of the glass. it is conceivable that.

The present invention provides a method for manufacturing tempered glass that eliminates deformation defects caused by ion exchange in thin tempered glass and improves the shape of the tempered glass, and provides an improved tempered glass by the method. The purpose is to

In the method for manufacturing tempered glass of the present invention, a chemically strengthened glass in the form of a plate or film with a thickness of 0.2 mm or less is prepared as glass for processing, in which a tempered glass having a compressive stress layer on the surface layer is obtained. and, after the preparation step, a conditioning step of bringing the surface of the glass for treatment into contact with a conditioning molten salt containing polyvalent metal ions.

In the method for manufacturing tempered glass of the present invention, it is preferable that the stress distribution in the direction along the main surface of the glass for treatment is adjusted in the adjustment step.

In the method for producing tempered glass of the present invention, the molten salt for adjustment used in the adjustment step contains an alkaline earth metal nitrate, and the total amount of the alkaline earth metal nitrate in the molten salt for adjustment is R(NO ₃ ) ₂ The concentration of is preferably 0.1 to 100% by mass.

According to such a configuration, unnecessary ion exchange of the processing glass can be suppressed, and fluctuations in the stress characteristics of the tempered glass in the adjustment process can be suitably suppressed.

In the method for producing tempered glass of the present invention, it is preferable that the thickness of the glass for treatment is 0.06 mm or less.

According to such a configuration, it is possible to obtain tempered glass particularly suitable for foldable devices.

In the method for producing tempered glass of the present invention, in the conditioning step, it is preferable that the immersion time of the glass for treatment in the molten salt for conditioning is 10 to 600 seconds.

According to such a configuration, it is possible to prevent the processing time of the adjustment step from being too short and deformation defects are not eliminated, or the processing time of the adjustment step being too long and causing the stress characteristics of the tempered glass to deteriorate.

In the method for producing tempered glass of the present invention, it is preferable that the temperature of the molten salt for adjustment is 350 to 565°C.

According to such a configuration, it is possible to suppress the occurrence of defects due to undissolved adjustment molten salt in the adjustment step, and the decomposition of the molten salt and the generation of gas due to excessive heating.

In the method for manufacturing tempered glass of the present invention, the molten salt for adjustment used in the adjustment step contains 0.5 to 45% by mass of Ca(NO ₃ ) ₂ , KNO ₃ +NaNO ₃ (KNO ₃ and NaNO _{3 )} . It is preferable that the total amount is 55 to 99.5%.

According to such a configuration, the molten salt for adjustment can be obtained using easily managed and low-cost materials.

In the tempered glass manufacturing method of the present invention, it is preferable that the content of LiNO ₃ in the molten salt for adjustment used in the adjustment step is less than 5% by mass.

According to such a configuration, excessive release of alkali metal ions from the processing glass can be suppressed, and fluctuations in the stress characteristics of the tempered glass in the adjustment process can be suitably suppressed.

The method for producing tempered glass of the present invention is characterized in that the compressive stress value CS of the outermost surface of the compressive stress layer of the tempered glass after the adjustment step is compared to the compressive stress value CS ₁ of the outermost surface of the compressive stress layer of the processing glass before the adjustment step. It is preferable to adjust the adjustment step so that the ratio CS ₂ /CS ₁ of ₂ is 0.8 to 1.

According to such a configuration, fluctuations in stress characteristics before and after the adjustment process can be suppressed to a small level.

In the method for manufacturing tempered glass of the present invention, it is preferable that the adjusting step is adjusted so that the compressive stress value CS ₂ of the outermost surface of the compressive stress layer of the tempered glass after the adjusting step is 400 MPa or more.

According to such a configuration, the strength characteristics required for a cover glass of a device such as a smartphone or a tablet PC can be obtained in the obtained tempered glass.

The method for manufacturing tempered glass of the present invention is characterized in that the ratio DOL 2 of the stress depth DOL ₂ of the compressive stress layer of the tempered glass after the adjustment step to the stress depth DOL ₁ of the compressive stress layer of the processing glass before the adjustment step is DOL ₂ / Preferably, the adjustment process is adjusted so that DOL ₁ is 0.9 to 1.2.

According to such a configuration, fluctuations in stress characteristics before and after the adjustment process can be suppressed to a small level.

In the tempered glass manufacturing method of the present invention, when the thickness of the tempered glass after the adjustment step is _t2 , the stress depth _DOL2 of the compressive stress layer of the tempered glass is 0.1· _t2 or more. Preferably, the adjustment step is adjusted accordingly.

According to such a configuration, the strength characteristics required as a cover glass for smartphones, touch panel devices, etc. can be obtained in the obtained tempered glass.

In the method for manufacturing tempered glass of the present invention, it is preferable that the tempered glass after the adjustment step has a warpage of 0.2 mm or less.

According to such a configuration, the resulting tempered glass can have the flatness required as a cover glass for smartphones, touch panel devices, and the like.

In the method for manufacturing tempered glass of the present invention, the tempered glass after the adjustment step has a glass composition of 50 to 80% SiO ₂ , 5 to 25% Al ₂ O ₃ , and 0 to 15% B ₂ O ₃ in mol%. , Li ₂ O 0 to 15%, Na ₂ O 1 to 20%, and K ₂ O 0 to 10%.

Another aspect of the method for manufacturing tempered glass of the present invention is a method for manufacturing tempered glass for obtaining a tempered glass having a compressive stress layer on the surface, the method comprising forming a plate-shaped glass having a thickness of 0.2 mm or less into which alkali ions are introduced. Alternatively, it includes a preparation step of preparing a film-like chemically strengthened glass as a processing glass, and an adjustment step of immersing the processing glass in a molten salt for adjustment after the preparation step, and the molten salt for adjustment has a composition of % by mass. It is characterized by containing 0.5-60% of Ca(NO ₃ ) ₂ and 40-99.5% of KNO ₃ +NaNO ₃ .

The tempered glass of the present invention is a plate-like or film-like tempered glass having a compressive stress layer on the surface layer and having a thickness of 0.2 mm or less, and the compressive stress value CS ₂ of the outermost surface of the compressive stress layer is 400 MPa or more. , the Ca ion concentration at the surface is higher than that inside. Here, the "surface portion" refers to a portion within 3 μm from the surface of the tempered glass.

According to the present invention, it is possible to correct shape defects in tempered glass caused by ion exchange, and it is possible to improve productivity of tempered glass.

1 is a flow diagram showing a method for manufacturing tempered glass according to an embodiment of the present invention. Example No. It is an image obtained by observing the shape of the main surface of the tempered glass according to No. 12 using a scanning white interference microscope. Example No. 5 is an image obtained by observing the shape of the main surface of the tempered glass according to No. 5 using a scanning white interference microscope. Comparative example no. It is an image obtained by observing the shape of the main surface of the tempered glass according to No. 14 using a scanning white interference microscope.

Hereinafter, a method for manufacturing tempered glass according to an embodiment of the present invention will be described.

<Method for manufacturing tempered glass>

FIG. 1 is a flow diagram showing a method for manufacturing tempered glass according to an embodiment of the present invention. As shown in FIG. 1, the method for manufacturing tempered glass of the present invention includes a preparation step S1, a first inspection step S2, an adjustment step S3, a cleaning/drying step S4, a second inspection step S5, and a packaging/drying step S5. A shipping step S6 is provided.

The tempered glass according to the present invention is obtained by performing a conditioning step S3 in which the glass for treatment is brought into contact with a polyvalent metal molten salt.

First, in the preparation step S1, glass for processing is prepared. The glass for processing is chemically strengthened glass in the form of a plate or film having a uniform thickness of 0.2 mm or less, which has been chemically strengthened in advance by ion exchange. Here, film-like glass refers to glass that is thin enough to be flexible enough to be rolled or bent, for example.

In the preparation step S1, the glass for treatment is prepared as a plate-like or film-like glass containing an alkali metal oxide as a composition (hereinafter referred to as chemically strengthened glass), and subjected to chemical strengthening treatment to this chemically strengthened glass. Manufactured by

In this embodiment, the preparation step S1 includes a molding step S11 and a chemical strengthening step S12.

The molding step 11 is a step in which chemically strengthened glass is molded and processed as necessary. In the forming step S11, the chemically strengthened glass is obtained by cutting a plate-like or film-like mother glass obtained by a forming method such as an overflow down-draw method, a slot down-draw method, a float method, or a redraw method into small glass pieces, Obtained by processing. In order to obtain a smooth surface, it is preferable to use an overflow down-draw method as the molding method.

It is preferable that the end face of the chemically strengthened glass be chamfered or treated to improve strength by polishing, heat treatment, etching, or the like. The main surface of chemically strengthened glass may be polished, but for example, if the main surface is previously formed smooth by the overflow down-draw method, or if it is formed to have a uniform thickness and high precision, The main surface may be used without polishing, that is, as a non-polished surface. In addition, when it is formed by the overflow down-draw method and is not polished, the main surface of the chemically strengthened glass becomes a fire-making surface. The chemically strengthened glass may be further subjected to a slimming process to reduce its thickness by etching. In the present invention, the main surface refers to the front and back surfaces of the entire plate-shaped or sheet-shaped glass surface excluding the end surfaces.

It is preferable that the glass for chemical strengthening is formed so that the glass for processing has the shape described below. The shape of the chemically strengthened glass is, for example, a rectangular shape (rectangular shape) having a thickness of 0.2 mm or less and having long sides and short sides in a plan view.

The chemically strengthened glass has a glass composition of 50 to 80% SiO ₂ , 5 to 25% Al ₂ O ₃ , 0 to 15% B ₂ O ₃ , 0 to 15% Li ₂ O, and Na ₂ O in terms of mol%. It is preferable to contain 1 to 20% of K ₂ O and 0 to 10% of K 2 O.

The reason why the above composition is preferable is shown below. In addition, in the description of the content range of each component, % indication refers to mol% unless otherwise specified.

SiO ₂ is a component that forms the glass network. If the content of SiO ₂ is too low, it becomes difficult to vitrify, and the coefficient of thermal expansion becomes too high, making it easy to reduce thermal shock resistance. Therefore, the preferable lower limit range of SiO ₂ is 50% or more, 55% or more, 57% or more, 59% or more, especially 61% or more. On the other hand, if the content of SiO ₂ is too large, meltability and moldability tend to decrease, and the coefficient of thermal expansion becomes too low, making it difficult to match the coefficient of thermal expansion of surrounding materials. Therefore, the preferable upper limit range of SiO ₂ is 80% or less, 75% or less, 70% or less, 68% or less, 67.5% or less, particularly 67% or less.

Al ₂ O ₃ is a component that improves ion exchange performance, and is also a component that increases strain point, Young's modulus, fracture toughness, and Vickers hardness. Therefore, the preferable lower limit ranges of Al ₂ O ₃ are 5% or more, 8% or more, 10% or more, 11% or more, and 11.2% or more. On the other hand, if the content of Al ₂ O ₃ is too large, the high temperature viscosity will increase and the meltability and moldability will tend to decrease. Furthermore, devitrification crystals tend to precipitate in the glass, making it difficult to form it into a plate shape using an overflow down-draw method or the like. In particular, when a glass plate is formed by an overflow down-draw method using an alumina-based refractory as the molded refractory, spinel devitrification crystals tend to precipitate at the interface with the alumina-based refractory. Furthermore, the acid resistance also decreases, making it difficult to apply to acid treatment steps. Therefore, the preferable upper limit range of Al ₂ O ₃ is 25% or less, 21% or less, 20.5% or less, 20% or less, 19.9% or less, 19.5% or less, 19.0% or less, especially 18 .9% or less. By setting the content of Al ₂ O ₃ , which has a large influence on ion exchange performance, within a suitable range, it becomes easy to design a high CS/DOL value even in 0.2 mm glass.

B ₂ O ₃ is a component that reduces high-temperature viscosity and density, stabilizes the glass, makes it difficult for crystals to precipitate, and lowers the liquidus temperature. It is also a component that suppresses Young's modulus and increases bending strength and crack resistance. However, if the content of B ₂ O ₃ is too high, chemical strengthening treatment tends to cause surface discoloration called discoloration, decrease in water resistance, and decrease in the compressive stress value of the compressive stress layer. There is. Therefore, the preferable lower limit range of B ₂ O ₃ is 0% or more, 0.01% or more, 0.02% or more, 0.1% or more, 0.3% or more, and the preferable upper limit range is 35% or more. % or less, 30% or less, 25% or less, 22% or less, 20% or less, especially 15% or less. In addition, from the viewpoint of giving priority to increasing CS, the content of B ₂ O ₃ can be more preferably set to 0.2 to 5% and 0.3 to 1%. In addition, from the viewpoint of improving chemical durability for the purpose of suppressing defects during etching processing, the upper limit range of the B ₂ O ₃ content is preferably 1% or more, 1.5% or more, and 2% or more. The lower limit range can be 5% or less, 4.5% or less, 4% or less, or 3% or less. On the other hand, from the viewpoint of giving priority to suppressing Young's modulus, the content of B ₂ O ₃ can be more preferably 10 to 25%, 15 to 23%, and 18 to 22%.

Li ₂ O is an ion exchange component, and in particular is a component that ion exchanges Li ions contained in the glass with K ions in the molten salt to obtain a high surface compressive stress value. Moreover, Li ₂ O is a component that lowers high temperature viscosity and improves meltability and moldability. Therefore, the preferred lower limit ranges of Li ₂ O are 0% or more, 0.01% or more, 0.5% or more, 1% or more, 3% or more, 4% or more, 4.2% or more, 5% or more, It is 5.5% or more, 6.5% or more, 7% or more, 7.3% or more, 7.5% or more, 7.8% or more, especially 8% or more. Therefore, the preferred upper limit range of Li ₂ O is 20% or less, 15% or less, 13% or less, 12% or less, 11.5% or less, 11% or less, 10.5% or less, less than 10%, especially 9. 9% or less, 9% or less, 8.9% or less.

Na ₂ O is an ion exchange component, and also a component that lowers high temperature viscosity and improves meltability and moldability. Moreover, Na ₂ O is also a component that improves devitrification resistance and reaction devitrification with molded refractories, especially alumina refractories. If the content of Na ₂ O is too low, the meltability will be reduced, the coefficient of thermal expansion will be too low, and the ion exchange rate will be likely to be reduced. Therefore, the preferred lower limit ranges for Na ₂ O are 5% or more, 7% or more, 8% or more, 8.5% or more, 9% or more, 9.5% or more, 10% or more, 11% or more, and 12%. or more, especially 12.5% or more. On the other hand, if the content of Na ₂ O is too large, the viscosity at which phase separation occurs and the acid resistance tend to decrease. In addition, the glass composition may lack component balance, and the devitrification resistance may be reduced on the contrary. Therefore, the preferred upper limit ranges of Na ₂ O are 20% or less, 19.5% or less, 19% or less, 18% or less, 17% or less, 16.5% or less, 16% or less, 15.5% or less, especially It is 15% or less.

K ₂ O is a component that lowers high temperature viscosity and improves meltability and moldability. Furthermore, it is a component that improves devitrification resistance and increases Vickers hardness. However, if the content of K ₂ O is too large, the viscosity at which phase separation occurs and the acid resistance tend to decrease. In addition, the glass composition may lack component balance, and the devitrification resistance may be reduced on the contrary. Therefore, the preferable lower limit ranges for K ₂ O are 0% or more, 0.01% or more, 0.02% or more, 0.1% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, especially 3.5% or more, and the preferable upper limit range is 10% or less, 5.5% or less, 5% or less, especially less than 4.5%. .

Both Li ₂ O and Na ₂ O are components that undergo ion exchange with K ions in the molten salt to obtain a high surface compressive stress value. Therefore, the preferred lower limit ranges of Li ₂ O + Na ₂ O are 1% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, and 10% in mol%. 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 16% or more, 17% or more, 18% or more, especially 18.5% or more. On the other hand, if the content of Li ₂ O + Na ₂ O is too large, the coefficient of thermal expansion becomes too high and the thermal shock resistance tends to decrease. Moreover, the component balance of the glass composition may be disrupted, and the devitrification resistance may be reduced on the contrary. Therefore, a preferable upper limit range of Li ₂ O+Na ₂ O is 20% or less, particularly 19% or less.

In addition to the above components, the chemically strengthened glass may contain, for example, the following components as a glass composition.

MgO is a component that lowers high-temperature viscosity and increases meltability, moldability, strain point, and Young's modulus, and among alkaline earth metal oxides, it is a component that has a large effect on improving ion exchange performance. However, if the content of MgO is too large, the density and coefficient of thermal expansion tend to increase, and the glass tends to devitrify. Therefore, the preferable upper limit range of MgO is 12% or less, 10% or less, 8% or less, 6% or less, particularly 5% or less. In addition, when introducing MgO into the glass composition, the preferable lower limit range of MgO is 0.1% or more, 0.5% or more, 1% or more, particularly 2% or more.

Compared to other components, CaO is highly effective in lowering high temperature viscosity and increasing meltability, moldability, strain point, and Young's modulus without reducing devitrification resistance. The content of CaO is preferably 0 to 10%. However, if the content of CaO is too large, the density and coefficient of thermal expansion will increase, and the component balance of the glass composition will be lost, making the devitrification resistance and ion exchange performance of the glass more likely to deteriorate. Therefore, the preferred content of CaO is 0 to 5%, 0.01 to 4%, 0.1 to 3%, particularly 1 to 2.5%.

SrO is a component that lowers high-temperature viscosity and increases meltability, moldability, strain point, and Young's modulus without reducing devitrification resistance. However, if the content of SrO is too large, the density and coefficient of thermal expansion will increase, the ion exchange performance will decrease, and the component balance of the glass composition will be lacking, making the glass more likely to devitrify. The preferred content range of SrO is 0 to 5%, 0 to 3%, 0 to 1%, particularly 0 to less than 0.1%.

BaO is a component that lowers high-temperature viscosity and increases meltability, moldability, strain point, and Young's modulus without reducing devitrification resistance. However, if the content of BaO is too large, the density and coefficient of thermal expansion will increase, the ion exchange performance will decrease, and the component balance of the glass composition will be lacking, making the glass more likely to devitrify. The preferred content range of BaO is 0 to 5%, 0 to 3%, 0 to 1%, particularly 0 to less than 0.1%.

ZnO is a component that enhances ion exchange performance, and is particularly effective in increasing compressive stress values. It is also a component that reduces high temperature viscosity without reducing low temperature viscosity. However, if the ZnO content is too large, the glass tends to undergo phase separation, the devitrification resistance decreases, the density increases, and the stress depth of the compressive stress layer decreases. Therefore, the ZnO content is preferably 0 to 6%, 0 to 5%, 0 to 1%, 0 to 0.5%, particularly 0 to less than 0.1%.

ZrO ₂ is a component that significantly improves ion exchange performance, as well as a component that increases viscosity near the liquidus viscosity and strain point, but if its content is too large, there is a risk that devitrification resistance will decrease significantly. However, there is a risk that the density may become too high. Therefore, the preferred upper limit range of ZrO ₂ is 10% or less, 8% or less, 6% or less, particularly 5% or less. In addition, when it is desired to improve the ion exchange performance, it is preferable to introduce ZrO ₂ into the glass composition. In that case, the preferable lower limit range of ZrO ₂ is 0.001% or more, 0.01% or more, 0.5% , especially 1% or more.

P ₂ O ₅ is a component that enhances ion exchange performance, and particularly increases the stress depth of the compressive stress layer. It is also a component that suppresses Young's modulus to a low level. However, if the content of P ₂ O ₅ is too large, the glass tends to undergo phase separation. Therefore, the content of P ₂ O ₅ is 0 to 10%, 0 to 8%, 0 to 6%, 0 to 4%, 0 to 2%, 0 to 1%, especially less than 0 to 0.1%. It is preferable that there be.

As a clarifier, one or more selected from the group of As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , F, Cl, and SO ₃ (preferably the group of SnO ₂ , Cl, and SO ₃ ) is used in an amount of 0 to 2 or more. 30000 ppm (3%) may be introduced. The content of SnO ₂ +SO ₃ +Cl is preferably 0 to 10,000 ppm, 50 to 5,000 ppm, 80 to 4,000 ppm, 100 to 3,000 ppm, particularly 300 to 3,000 ppm, from the viewpoint of accurately enjoying the clarification effect. Here, “SnO ₂ +SO ₃ +Cl” refers to the total amount of SnO ₂ , SO ₃ and Cl.

The preferred content range of SnO ₂ is 0 to 10,000 ppm, 0 to 7,000 ppm, particularly 50 to 6,000 ppm. The preferred content range of Cl is 0 to 1500 ppm, 0 to 1200 ppm, 0 to 800 ppm, 0 to 500 ppm, particularly 50 to 300 ppm. The preferred content range of SO ₃ is 0 to 1000 ppm, 0 to 800 ppm, particularly 10 to 500 ppm.

Rare earth oxides such as Nd ₂ O ₃ and La ₂ O ₃ are components that increase Young's modulus, and when a complementary color is added, they are decolored and can control the color of the glass. However, the cost of the raw material itself is high, and if a large amount is introduced, the devitrification resistance tends to decrease. Therefore, the content of the rare earth oxide is preferably 0 to 4%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.5%.

In the present invention, from environmental considerations, it is preferable that substantially no As ₂ O ₃ , F, PbO, or Bi ₂ O ₃ be contained. Here, "substantially does not contain As ₂ O ₃ " means that although As ₂ O ₃ is not actively added as a glass component, it is allowed to be mixed in at an impurity level, and specifically, , indicates that the content of As ₂ O ₃ is less than 500 ppm. "Substantially no F" means that although F is not actively added as a glass component, it is allowed to be mixed in at an impurity level. Specifically, it means that the F content is less than 500 ppm. refers to something. "Substantially no PbO" means that although PbO is not actively added as a glass component, it may be mixed in at an impurity level. Specifically, if the PbO content is less than 500 ppm, refers to something. "Substantially not containing Bi ₂ O ₃ " means that although Bi ₂ O ₃ is not actively added as a glass component, it is allowed to be mixed in at an impurity level, and specifically, Bi ₂ O 3 is not actively added as a glass component. It means that the content of O ₃ is less than 500 ppm.

As an example, the chemically strengthened glass may not contain B ₂ O ₃ or may contain only a small amount of B 2 O 3 to limit its content. That is, the chemically strengthened glass has a glass composition, in terms of mol%, of SiO ₂ 50-80%, Al ₂ O ₃ 5-25%, B ₂ O ₃ 0-1%, Li ₂ O 0-20%, Na ₂ It may contain 1 to 20% of O and 0 to 10% of K ₂ O.

As another example, the chemically strengthened glass may include B ₂ O ₃ as an essential component in the glass composition. That is, the chemically strengthened glass has a glass composition of 50 to 80% SiO ₂ , 5 to 25% Al ₂ O _{3 ,} 1 to 5% B ₂ O ₃ , 0 to 20% Li ₂ O , and Na. It may contain 1 to 20% of ₂ O and 0 to 10% of K ₂ O.

In addition, if chemically strengthened glass contains B ₂ O ₃ as an essential component, there is a concern that the formability of the glass will decrease, so in order to maintain balance, other components such as Al ₂ O ₃ are added The amount may be limited. That is, the chemically strengthened glass has a glass composition of 50 to 80% SiO ₂ , 5 to 10% Al ₂ O _{3 ,} 1 to 5% B ₂ O ₃ , 0 to 20% Li ₂ O , and Na. It may contain 1 to 20% of ₂ O and 0 to 10% of K ₂ O.

The composition of the chemically strengthened glass described above is an example, and if chemically strengthened by ion exchange is possible, a chemically strengthened glass having a known composition may be used. In addition, the treated glass obtained by chemically strengthening the above-mentioned glass for chemical strengthening (i.e., chemical strengthening step S12) and the tempered glass obtained after the conditioning step S3 are chemically strengthened before the chemical strengthening treatment in the areas that have not been ion-exchanged. The composition is similar to that of tempered glass.

The chemically strengthened glass obtained in the forming step S11 is chemically strengthened in a chemically strengthened step S12. The chemical strengthening step S12 is a step of chemically strengthening the glass for chemical strengthening by immersing it in an alkali molten salt. In this embodiment, a case where chemically strengthened glass is chemically strengthened by one chemical strengthening process will be exemplified.

The alkali molten salt is a salt containing alkali metal ions that can be ion-exchanged with components in the chemically strengthened glass, and is typically an alkali nitrate. Examples of the alkali nitrates include NaNO ₃ , KNO ₃ , LiNO ₃ , and the like, and each of these can be used alone (at 100% by mass) or in a mixture of multiple types. When mixing multiple types of alkali nitrates, the mixing ratio may be determined arbitrarily, but for example, NaNO ₃ 5-95%, KNO ₃ 5-95%, preferably _NaNO 30-80%, KNO ₃ in mass %. The content can be 20-70%, more preferably 50-70% NaNO ₃ and 30-50% KNO ₃ .

Conditions such as the temperature and immersion time of the molten salt in the chemical strengthening treatment may be set according to the composition etc. within a range that can obtain the above stress characteristics. are 355°C to 470°C, 360°C to 450°C, 365°C to 430°C, and 370°C to 410°C. The immersion time is, for example, 3 to 300 minutes, preferably 5 to 120 minutes, and more preferably 7 to 100 minutes.

Note that the glass for chemical strengthening to be immersed in the molten alkali salt may be preheated to the temperature of the molten salt for strengthening in the chemical strengthening step S12, or it may be strengthened at room temperature (for example, 1°C to 40°C). It may also be immersed in molten salt.

Glass for processing is obtained through the above-mentioned chemical strengthening step S12. After the chemical strengthening step S12 described above, the glass for treatment is preferably washed and dried. By performing cleaning, deposits that have adhered to the processing glass can be removed. Furthermore, by drying the glass for treatment after washing, it is possible to prevent alkali metal ions from flowing out into the attached moisture.

Note that the contents of the preparation step S1 for the processing glass are merely an example, and may be modified as follows, for example. Specifically, a pre-shaped ion exchange glass may be obtained, that is, the forming step S11 may be omitted, and the glass may be treated in the chemical strengthening step S12. Alternatively, by obtaining processing glass that has been processed (formed and ion-exchanged) to have the above-mentioned composition and characteristics in advance, the processing glass may be prepared by omitting the forming step S11 and chemical strengthening step S12. good.

The processing glass prepared in the preparation step S1 is inspected in the first inspection step S2.

The first inspection step S2 is a step of inspecting the quality of the shape of the processing glass prepared in the preparation step S1. Specifically, whether or not the glass to be processed has deformation defects such as wavy or wrinkled shapes is inspected visually by an operator or using an image inspection device. If a deformation defect is found in the processing glass in the first inspection step S2, the next adjustment step S3 is performed on the processing glass. On the other hand, if no deformation defects are found and the glass meets other product standards, the processing glass is subjected to a packing and shipping step S5 as a tempered glass product without performing the adjustment step S3.

The adjustment step S3 is a step of correcting the deformation of the processing glass whose deformation defects were found in the first inspection step S2, and flattening the shape of the glass. Specifically, the glass for treatment is treated by immersing it in a molten salt for adjustment containing polyvalent metal ions, and the stress distribution in the direction along the main surface is adjusted.

The polyvalent metal salt contains a component that inhibits the introduction of alkali metal ions to the surface of the glass for treatment. On the surface of the glass for processing that has deformation defects, there are areas in which the alkali metal ions introduced by chemical strengthening are excessive and areas in which they are deficient. By performing the adjustment step S3 in which the glass for treatment is brought into contact with a polyvalent metal molten salt, excess alkali metal ions are exchanged with polyvalent metal ions, and alkali metal ions are replenished into the alkali metal ion-deficient portion. Therefore, a tempered glass in which the stress distribution in the direction along the main surface is adjusted can be obtained.

Polyvalent metal salts are typically alkaline earth nitrates. Examples of alkaline earth nitrates include Ca(NO ₃ ) ₂ , Mg(NO ₃ ) ₂ , Sr(NO ₃ ) ₂ , Ba(NO ₃ ) ₂ , and these may be used alone or in a mixture of multiple types. It can be used as The preferred lower limit range of the concentration of the total amount R(NO ₃ ) ₂ of alkaline earth metal nitrates in the molten salt for adjustment is 0.1% or more, 0.5% or more, 1% or more, 3% by mass. % or more, especially 5% or more. Suitable upper limit ranges are 100% or less, 90% or less, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, especially 40% or less. It is. If the concentration of R(NO ₃ ) ₂ is too high, the melting point will become too high and melting will become difficult. On the other hand, if the concentration of R(NO ₃ ) ₂ is too low, the effect of inhibiting the introduction of alkali metal ions to the surface of the glass for treatment cannot be obtained.

Note that from the viewpoint of reducing the raw material cost of the molten salt and preventing the generation of nitrogen oxide gas and precipitation due to thermal decomposition, it is particularly preferable to use Ca(NO ₃ ) ₂ as the polyvalent metal salt. . The preferred lower limit range of the concentration of Ca(NO ₃ ) ₂ in the molten salt for adjustment is 0.1% or more, 0.5% or more, 1% or more, 3% or more, especially 5% or more in mass%. be. Suitable upper limit ranges are 100% or less, 90% or less, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, especially 40% or less. It is. If the concentration of Ca(NO ₃ ) ₂ in the molten salt for adjustment is too low, it will be difficult to obtain the effect of inhibiting the introduction of alkali metal ions to the surface of the glass for treatment. On the other hand, if the concentration of Ca(NO ₃ ) ₂ in the molten salt for adjustment is too high, the melting point will become too high and melting will become difficult, and the undissolved Ca(NO ₃ ) ₂ will adhere to the tempered glass and cause defects. There is a possibility that it may cause. In addition, thermal decomposition of Ca(NO ₃ ) ₂ occurs, causing health hazards due to inhalation of the generated nitrogen oxide gas, and CaO precipitation formed in the molten salt may adhere to the tempered glass and cause defects. There is.

The balance other than the polyvalent metal salt in the molten salt for adjustment is preferably an alkali nitrate. Examples of the alkali nitrate include NaNO ₃ , KNO ₃ , LiNO ₃ and the like. In particular, when using NaNO ₃ and KNO ₃ , the preferable lower limit range of the concentration of NaNO ₃ +KNO ₃ is 0% or more, 10% or more, 20% or more, 30% or more, 40% or more, 45% or more, 50%. This is 55% or more, particularly 60% or more. Suitable upper limit ranges are 99.9% or less, 99.5% or less, 99% or less, 97% or less, 95% or less, 90% or less, 80% or less, especially 70% or less. If the concentration of NaNO ₃ +KNO ₃ is too low, the melting point will be too high and melting will be difficult. On the other hand, if the concentration of NaNO ₃ +KNO ₃ is too high, ion exchange of alkali metal ions will proceed, which may cause the stress characteristics of the tempered glass to vary and deviate from the desired range. In addition, in order to prevent an increase in the raw material cost of the molten salt and excessive release of the alkali metal ions introduced into the glass for treatment in the chemical strengthening step S12, the concentration of LiNO ₃ in the molten salt for adjustment is determined by the mass %, preferably 0 to less than 5%, 0 to 3%, particularly 0 to 1%.

The preferable lower limit range of the temperature of the molten salt for adjustment in the adjustment step S3 is 350°C or higher, 355°C, 360°C or higher, 365°C or higher, particularly 370°C or higher. Preferred upper limit ranges are 565°C or less, 550°C or less, 530°C or less, 520°C or less, 500°C or less, 480°C or less, 460°C or less, especially 440°C or less. If the temperature of the molten salt for adjustment is too low, it becomes difficult to melt the polyvalent metal salt, and there is a possibility that the undissolved polyvalent metal salt may adhere to the tempered glass and cause defects. On the other hand, if the temperature of the molten salt for adjustment is too high, the polyvalent metal salt will thermally decompose, producing nitrogen oxide gas and precipitation of polyvalent metal oxides, which may adhere to the tempered glass and cause defects. There is.

The preferable lower limit range of the immersion time in the molten salt for adjustment is 10 seconds or more, 15 seconds or more, 20 seconds or more, 25 seconds or more, particularly 30 seconds or more. Preferred upper limit ranges are 600 seconds or less, 500 seconds or less, 400 seconds or less, 300 seconds or less, 240 seconds or less, 180 seconds or less, particularly 120 seconds or less. If the immersion time in the molten salt for adjustment is too short, the effect of inhibiting the introduction of alkali metal ions to the surface of the glass for treatment cannot be obtained. If the immersion time in the molten salt for adjustment is too long, the ion exchange of alkali metal ions will proceed, causing the stress characteristics of the tempered glass to fluctuate and possibly deviate from the desired range. Moreover, there is a possibility that the warpage of the tempered glass will worsen.

Note that the glass for treatment to be immersed in the molten salt for adjustment may be preheated to the temperature of the molten salt for adjustment in the adjustment step S3, or may be immersed in the molten salt for adjustment while remaining at room temperature (for example, 1° C. to 40° C.). It may also be immersed in molten salt.

Further, the tempered glass may be further subjected to a polishing treatment after the adjustment step S3. If the dimensions, shape, and surface condition of the tempered glass change due to chemical strengthening and immersion in a polyvalent metal salt, these can be corrected by performing a polishing treatment. On the other hand, since it is possible that unnecessary microcracks may increase due to the polishing process, as mentioned above, the glass for chemical strengthening is an unpolished product formed by the overflow down-draw method, etc. If the main surface of the glass or the main surface of the tempered glass after the adjustment step S3 is also a smooth non-polished surface (fired surface), it is preferable not to perform the polishing treatment. In addition, when the glass for chemical strengthening, the glass for processing, and the tempered glass are each molded by the overflow down-draw method, they each have a molding convergence surface inside.

Furthermore, the tempered glass may be subjected to an etching treatment after the adjustment step S3. Specifically, the entire tempered glass is immersed in a liquid etching medium, and the entire surface of the tempered glass is wet-etched. According to such a process, the entire glass can be uniformly etched, so that it is possible to suppress the occurrence of variations in thickness due to the etching process. When such an etching process is performed, the surface of the tempered glass is composed of an etched surface.

As the etching medium, an acidic or alkaline aqueous solution capable of etching glass can be used. As the acidic etching medium, for example, an acidic aqueous solution containing HF can be used. Further, as the alkaline etching medium, for example, an alkaline aqueous solution containing NaOH or KOH can be used.

It is preferable to perform etching using the above-mentioned etching medium so that the etching amount (thickness reduction due to etching) on one surface of the tempered glass is, for example, 0.25 μm to 3 μm. By setting the etching amount within such a range, the amount of variation in the compressive stress on the outermost surface and the compressive stress depth before and after etching can be reduced and easily controlled.

According to the tempered glass shown above, by appropriately controlling its stress characteristics and thickness dimensions, and further reducing surface defects through etching, it is possible to achieve high bending performance, bending strength, and suppression of shattering at the time of breakage. It is.

The tempered glass that has undergone the adjustment step S3 is preferably washed and dried in a washing and drying step S4. By cleaning, deposits that have adhered to the tempered glass can be removed. Furthermore, by drying the tempered glass after washing, it is possible to prevent alkali metal ions from flowing out into the attached moisture.

The tempered glass that has undergone the cleaning and drying step S4 is inspected again for quality (presence of foreign matter defects, presence of deformation defects such as unevenness, etc.) in a second inspection step S5. Specifically, whether or not the tempered glass has defects and whether it conforms to standards as a product is inspected visually by an operator or using an image inspection device. If no defects are found and the glass meets other product standards, the processing glass is processed as a product and undergoes a packing and shipping step S5. Note that if the tempered glass has any defects or does not meet product standards, it is preferable to crush it and discard it or reuse it as a raw material for chemically strengthened glass.

It is preferable that the tempered glass is protected by attaching a protective film in the packing/shipping step S5. As the protective film, it is preferable to use a self-adhesive type protective film or a protective film provided with a slightly adhesive adhesive so that there is no adhesive residue after peeling and high surface cleanliness is obtained.

<Glass for processing>

The processing glass according to the embodiment of the present invention obtained through the above-mentioned preparation step S1 has the following characteristics.

The preferred upper limit range of the thickness t ₁ of the glass for processing is 0.2 mm or less, 0.15 mm or less, 0.1 mm or less, 0.08 mm or less, 0.06 mm or less, particularly 0.05 mm or less, and a suitable The lower limit range is 0.02 mm or more, 0.025 mm or more, particularly 0.03 mm or more. If the glass for processing is too thick, there is a risk that the glass for processing may be damaged when it is bent. In addition, if the glass for processing is too thin, it will be difficult to ensure strength, and if the glass is made too thin, it will be difficult to increase the compressive stress value on the surface, which may actually reduce flexibility. be.

According to the present invention, the processing glass preferably has a rectangular shape (rectangular shape) having long sides and short sides in plan view. The size of the tempered glass may be determined arbitrarily, but the length of the long side is 40 to 550 mm, 50 to 500 mm, 60 to 450 mm, 65 to 400 mm, 70 to 300 mm, 75 to 200 mm, especially 80 to 160 mm. It is preferable that there be. The length of the short side of the tempered glass is preferably 30 to 400 mm, 40 to 350 mm, 45 to 300 mm, 50 to 200 mm, 55 to 120 mm, particularly 60 to 80 mm.

The glass for processing has a compressive stress layer on the surface and a tensile stress layer inside. A preferable lower limit range of the compressive stress CS ₁ on the outermost surface of the compressive stress layer (compressive stress layer before the adjustment step) of the processing glass is 400 MPa or more, 450 MPa or more, 500 MPa or more, 550 MPa or more, particularly 600 MPa or more. Suitable upper limit ranges are 1100 MPa or less, 1000 MPa or less, 950 MPa or less, 900 MPa or less, especially 880 MPa or less. The larger the compressive stress _CS1 on the outermost surface of the processing glass, the easier it is to prevent damage caused by tensile stress generated at the bent portion of the cover glass when the flexible display is bent. On the other hand, if an extremely large compressive stress is formed on the surface, the tensile stress inherent in the tempered glass will become extremely high, leading to increased dimensional changes before and after chemical strengthening treatment, and explosive scattering when broken. There is a possibility. Therefore, the preferable upper limit of the compressive stress CS ₁ on the outermost surface of the glass for processing is 1300 MPa or less, 1100 MPa or less, 900 MPa or less, particularly 800 MPa or less.

The depth DOL ₁ of the compressive stress layer (compressive stress layer before the adjustment process) of the processing glass is _t1 , and the preferable lower limit range of DOL ₁ is 0.1·t. ₁ or more, 0.12·t ₁ or more, 0.15·t ₁ or more, 0.18·t ₁ or more, especially 0.2·t ₁ or more. The larger the depth DOL ₁ of the compressive stress layer of the processing glass, the more difficult the processing glass and tempered glass will be to break even if the processing glass and tempered glass are deeply scratched, and the smaller the variation in mechanical strength will be. . On the other hand, if the depth DOL ₁ of the compressive stress layer of the processing glass is too large, there is a possibility that dimensional changes before and after the chemical strengthening treatment will become large. Therefore, there is a possibility that the dimensional change before and after the chemical strengthening treatment becomes large. Suitable upper limit ranges for DOL ₁ are 0.5·t ₁ or less, 0.45·t ₁ or less, 0.4·t ₁ or less, especially 0.35·t ₁ or less.

The tensile stress CT ₁ inside the processing glass is, for example, 10 to 1000 MPa.

In the present invention, numerical values related to stress such as the compressive stress of the outermost surface (CS ₁ , CS ₂ ), the depth of the compressive stress layer (DOL ₁ , DOL ₂ ), and the tensile stress value (CT ₁ , CT ₂ ) are, for example, It can be measured using a measuring device such as FSM-6000 or SLP-1000 manufactured by Orihara Seisakusho.

In addition, when the glass for processing is chemically strengthened glass strengthened by one-step ion exchange, the approximate value of the internal tensile stress can also be calculated using the following equation (1).

CT ₁ = (CS ₁ × DOL ₁ )/(t ₁ −2 × DOL ₁ )…(1)

<Tempered glass>

The tempered glass according to the embodiment of the present invention obtained through the adjustment step S3 has the following characteristics.

The preferable upper limit range of the thickness _t2 of the tempered glass is 0.2 mm or less, 0.15 mm or less, 0.1 mm or less, 0.08 mm or less, 0.06 mm or less, especially 0.05 mm or less, and a preferable lower limit The range is 0.02 mm or more, 0.025 mm or more, especially 0.03 mm or more. If the tempered glass is too thick, there is a risk that it will break when the processing glass is bent. Moreover, if the tempered glass is too thin, it will be difficult to ensure strength, and if the glass is made too thin, there is a possibility that it will be difficult to increase the compressive stress value on the surface.

The dimensions of the tempered glass according to the present invention are approximately the same as the dimensions of the processing glass used to obtain the tempered glass, and the preferred size range is also the same as the above-mentioned dimensions of the processing glass. That is, although the shape of the processing glass due to the deformation defect changes before and after the adjustment step S3, the dimensions of the obtained tempered glass itself do not vary greatly from the processing glass. The rate of change in the long sides and short sides of the glass before and after the adjustment step S3 is, for example, 5% or less.

The preferable lower limit range of the compressive stress CS ₂ on the outermost surface of the compressive stress layer of the tempered glass (the compressive stress layer after the adjustment step S3) is 400 MPa or more, 450 MPa or more, 500 MPa or more, 550 MPa or more, particularly 600 MPa or more. The larger the compressive stress CS ₂ on the outermost surface of the processing glass, the easier it is to prevent damage caused by tensile stress generated at the bent portion of the cover glass when the flexible display is bent. On the other hand, if an extremely large compressive stress is formed on the surface, the tensile stress inherent in the tempered glass will become extremely high, and there is a possibility that dimensional changes before and after the chemical strengthening treatment will become large. Therefore, the preferable upper limit range of the compressive stress CS ₂ on the outermost surface of the glass for processing is 1100 MPa or less, 1000 MPa or less, 950 MPa or less, 900 MPa or less, particularly 880 MPa or less.

The depth DOL ₂ of the compressive stress layer of the tempered glass (the compressive stress layer after the adjustment step S3) is t ₂ when the thickness of the tempered glass is t 2 , and the preferable lower limit range of DOL ₂ is 0.1·t ₂ Above, 0.12·t ₂ or more, 0.15·t ₂ or more, 0.18·t ₂ or more, especially 0.2·t ₂ or more. The larger the depth DOL ₂ of the compressive stress layer of the tempered glass, the more difficult the tempered glass will be to break even if the tempered glass is deeply scratched, and the less variation in mechanical strength will occur. On the other hand, if the depth DOL ₂ of the compressive stress layer of the tempered glass is too large, there is a possibility that dimensional changes before and after the chemical strengthening treatment will become large. Therefore, there is a possibility that the dimensional change before and after the chemical strengthening treatment becomes large. Suitable upper limit ranges are 0.5·t ₂ or less, 0.45·t ₂ or less, 0.4·t ₂ or less, especially 0.35·t ₂ or less.

The tensile stress CT ₂ inside the tempered glass is, for example, 10 to 1000 MPa. Note that the tensile stress value CT ₂ is obtained by replacing the compressive stress CS ₁ with CS ₂ , the depth of the compressive stress layer DOL ₁ with DOL ₂ , and the glass thickness t ₁ with t ₂ in the above equation (1). An approximate value can also be calculated by the formula.

Ratio of the compressive stress value CS ₂ of the outermost surface of the compressive stress layer of the tempered glass after the adjusting step S3 to the compressive stress value CS 1 of the outermost surface of the compressive stress layer of the processing glass before the adjusting step _{S3 CS 2 /} CS ₁ is preferably 0.8-1, 0.85-1, 0.9-1, particularly 0.95-1. If CS ₂ /CS ₁ is too small, there is a possibility that the bending strength of the tempered glass will be lower than that of the glass for processing.

The preferred lower limit range of the ratio DOL ₂ /DOL ₁ of the stress depth DOL ₂ of the compressive stress layer of the tempered glass after the adjustment step to the stress depth DOL ₁ of the compressive stress layer of the processing glass before the adjustment step S3 is as follows: It is 0.9 or more, 0.92 or more, especially 0.95 or more. A preferred upper limit range is 1.2 or less, 1.15 or less, particularly 1.1 or less. If DOL ₂ /DOL ₁ is too small, there is a possibility that the bending strength of the tempered glass will be lower than that of the processing glass. On the other hand, if DOL ₂ /DOL ₁ is too large, CS ₂ on the surface may decrease as ion diffusion progresses, and in this case, the bending strength of the tempered glass may be lower than that of the treated glass. .

The ratio CT ₂ /CT _{1 of the tensile stress value CT 2 inside} the tempered glass after the adjustment step S3 to the tensile stress value CT ₁ inside the processing glass before the adjustment step S3 is, for example, 0.9 to 1.2. It is. If CT ₂ /CT ₁ is too large, there is a risk that the tempered glass will explode into pieces when broken.

The warpage of the tempered glass is preferably 0 to 0.3 mm, 0 to 0.2 mm, particularly 0 to 0.15 mm. Note that the warpage of the tempered glass is determined by placing the tempered glass on a horizontal surface such as a surface plate with the convex side facing down, and measuring the maximum height of the tempered glass from the horizontal surface.

It is preferable that the alkaline earth metal concentration, particularly the Ca concentration, in the surface portion of the tempered glass is higher than that in the inside of the tempered glass. By increasing the alkaline earth metal concentration in the surface portion, a tempered glass in which the stress distribution in the direction along the main surface is sufficiently adjusted can be obtained.

(Modified example)
In each of the above embodiments, the shape of the chemically strengthened glass, the treated glass, and the tempered glass is rectangular in plan view, but the present invention is not limited to this. The shape of the glass in plan view can be, for example, square, circular, oval, or the like.

Further, in each of the above embodiments, the case where the chemically strengthened glass, the treated glass, and the tempered glass as a whole have a thin thickness of 0.2 mm or less is illustrated, but the present invention is not limited to this. , processing glass, and tempered glass may have a thick portion in part. If the thick portion is used as the touch surface of the foldable device, the touch surface can be protected when the foldable device is folded.

In the method for manufacturing tempered glass of the present invention, the case where the chemically strengthened glass, the glass for treatment, and the tempered glass are flat plate shapes has been exemplified; however, the method for manufacturing tempered glass of the present invention is not limited to this. Glass, processing glass, and tempered glass may be given a three-dimensional shape by three-dimensional bending, if necessary. For example, by performing a three-dimensional bending process on the glass for chemical strengthening in whole or in part in advance, a three-dimensional bent shape can be given to the glass for processing and the tempered glass after the adjustment step S3.

In the above embodiment, the glass for treatment is subjected to chemical strengthening treatment once in the chemical strengthening step S12, but in the method for manufacturing tempered glass of the present invention, the glass for treatment is subjected to chemical strengthening treatment twice, Alternatively, it may be subjected to chemical strengthening treatment three or more times. Further, heat treatment may be performed before and after ion exchange. By performing heat treatment, stress can be relaxed and ion diffusion can be promoted to control the depth of the compressive stress layer and the like.

In the tempered glass manufacturing method of the present invention, the adjustment step S3 may be performed without the inspection step S2. That is, all of the glass prepared in the preparation step S1 may be used as processing glass in the steps after the adjustment step S3.

In the method for manufacturing tempered glass of the present invention, when an alkaline earth nitrate is used as the molten salt for adjustment, the adjustment step S3 may be performed after the chemical strengthening step S12 without washing and drying the glass for treatment.

In the method for manufacturing tempered glass of the present invention, the cleaning/drying step S4, the second inspection step S5, and the packing/shipping step S6 may be omitted.

In the method for manufacturing tempered glass of the present invention, tempered glass may be laminated with any plate-shaped or sheet-shaped resin material, metal material, glass, or other transparent material via an adhesive, and used as a laminate. good.

EMBODIMENT OF THE INVENTION Hereinafter, the manufacturing method of the tempered glass based on this invention, and a tempered glass are demonstrated based on an Example. Note that the following examples are merely illustrative, and the present invention is not limited to the following examples in any way.

A sample was prepared as follows. First, the glass composition in mol% is SiO ₂ 66.3%, Al ₂ O ₃ 11.4%, B ₂ O ₃ 0.5%, K ₂ O 1.4%, Na ₂ O 15.2%, Li. A chemically strengthened glass containing 0.2% of _2O , 4.8% of MgO, and 0.2% of _SnO2 was prepared.

Specifically, glass raw materials were prepared to have the above composition, and melted at 1600° C. for 21 hours using a platinum pot. Thereafter, the obtained molten glass was flow-molded from a refractory molded body using an overflow down-draw method, and was molded and processed into the dimensions shown in Table 1 to obtain a chemically strengthened glass.

Next, the glass for chemical strengthening was immersed for 600 seconds in a molten salt for strengthening containing 100% KNO ₃ at 430° C. to obtain a glass for treatment.

Furthermore, No. The treated glasses Nos. 1 to 3 and 5 to 13 were immersed in the molten salt for conditioning under the treatment conditions (molten salt composition, temperature, time) listed in Table 1 to obtain tempered glasses.

In Table 1, No. Nos. 1 to 3 and 5 to 13 are examples of the present invention. 4 and 14 are comparative examples.

The compressive stress at the outermost surface (CS ₁ , CS ₂ ) and the depth of compressive stress (DOL ₁ , DOL ₂ ) in Table 1 were calculated using a surface stress meter FSM-6000LE manufactured by Orihara Seisakusho Co., Ltd. This is the value measured at . More specifically, DOL is DOL_zero measured using FSM-6000LE. Moreover, the tensile stress values (CT ₁ , CT ₂ ) are values calculated using the above-mentioned calculation formula.

The surface shape was evaluated in the following manner.
First, the shape z(x,y) of the main surface of each sample was measured using a scanning white interference microscope (VertScan, manufactured by Ryoka System Co., Ltd.). The measurement was performed in WAVE mode using a 530 nm white filter and an objective lens with a magnification of 2.5 times, with a measurement area of 5409.70 μm×7208.58 μm set to a resolution of 640 pixels×480 pixels. Visual field synthesis was performed on the obtained measurement images using analysis software VS-Viewer. The measurement area after visual field synthesis is 10007.95 μm×25590.47 μm. In order to remove the long-period waviness of the measurement sample, the data after synthesis was corrected using VS-Viewer, and those with a periodic length λ of surface irregularities of 0.2 mm < λ < 1.0 mm were extracted. Band decomposition processing was performed. The shape z(x,y) of the main surface was obtained from the image after band decomposition.

Next, an image showing the surface shape of the tempered glass obtained as described above was evaluated in three ranks: a, b, and c. Specifically, rank A indicates that no deformation defects are observed on the surface, rank B indicates that deformation defects are observed in a relatively narrow range of the surface (occupying less than 10% of the observation area), and rank C. indicates that deformation defects are observed over a relatively wide range of the surface (occupying 10% or more of the observation area). Examples of surface shape images for each evaluation are shown in FIGS. 2 to 4. Specifically, FIG. 2 shows Example No. 2 as an example of glass evaluated as A rank. 12 shows the surface shape of the glass. FIG. 3 shows Example No. 3 as an example of glass evaluated as B rank. The surface shape of the glass No. 5 is shown. FIG. 4 shows Comparative Example No. 4 as an example of glass evaluated as C rank. The surface shape of No. 14 glass is shown. Note that a deformation defect refers to a portion where the relevant portion is shown in a darker color than the surrounding area.

The warpage of each sample was determined by placing the sample on a horizontal surface such as a surface plate with the convex side facing down, and measuring the maximum height of the tempered glass from the horizontal surface.

Furthermore, the surface Ca ion concentration and the internal Ca ion concentration were measured in the following manner.

Regarding chemically strengthened glass, Ca concentration was measured using an electron probe micro analyzer (EPMA). The sample was cut perpendicularly to the main surface, and measurements were taken on the main surface of the glass plate and the center of the thickness of the cut surface. For the measurement, JXA-8100 manufactured by JEOL Ltd. was used, and a profile of characteristic X-ray counts of Ca was obtained using an accelerating voltage of 15 kV, a probe current of 500 nA, and a spectroscopic crystal PETH (Ca Kα ray, peak position: 107.57 mm).

According to the results of the above surface shape evaluation, No. In No. 1 to 3 and No. 5 to No. 13, the surface condition of the sample was changed from that of No. 3, which was not immersed, by being immersed in the molten salt for adjustment containing Ca(NO ₃ ) ₂ . It was confirmed that this was improved compared to 4 and 14. Also, No. In Nos. 1 to 3, higher improvement effects were obtained when the temperature of the molten salt for adjustment was higher. Furthermore, No. In No. 5 to No. 12, the higher the concentration of Ca(NO ₃ ) ₂ in the molten salt for adjustment, the higher the improvement effect was obtained.

Furthermore, No. Although Ca ions were not detected from inside the tempered glass No. 12, it was confirmed that Ca ions were detected from the surface. Therefore, it was found that Ca ion concentration was introduced into the surface of the tempered glass subjected to the adjustment step S3.

The tempered glass of the present invention can be used for, for example, smartphones, mobile phones, tablet computers, personal computers, digital cameras, touch panel displays, cover glasses for other display devices, in-vehicle display devices, in-vehicle panels, and the like.

S1 Preparation process S11 Molding process S12 Chemical strengthening process S2 First inspection process S3 Adjustment process S4 Cleaning/drying process S5 Second inspection process S6 Packing/shipping process

Claims (15)

In a method for manufacturing tempered glass to obtain tempered glass having a compressive stress layer on the surface layer,
A preparation step of preparing chemically strengthened glass in the form of a plate or film with a thickness of 0.2 mm or less as processing glass;
A method for manufacturing tempered glass, comprising, after the preparation step, a conditioning step of bringing the surface of the glass for treatment into contact with a conditioning molten salt containing polyvalent metal ions. The method for manufacturing tempered glass according to claim 1, wherein in the adjusting step, stress distribution in a direction along the main surface of the processing glass is adjusted. The molten salt for adjustment used in the adjustment step contains an alkaline earth metal nitrate,
The method for producing tempered glass according to claim 1 or 2, wherein the concentration of the total amount R(NO ₃ ) ₂ of alkaline earth metal nitrates in the molten salt for adjustment is 0.1 to 100% by mass. The method for producing tempered glass according to any one of claims 1 to 3, wherein the thickness of the glass for processing is 0.06 mm or less. The method for producing tempered glass according to any one of claims 1 to 4, wherein in the conditioning step, the treatment glass is immersed in the conditioning molten salt for 10 to 600 seconds. The method for producing tempered glass according to any one of claims 1 to 5, wherein the temperature of the molten salt for adjustment is 350 to 565°C. The tempered glass according to any one of claims 1 to 6, wherein the molten salt for adjustment contains 0.5 to 45% of Ca(NO ₃ ) ₂ and 55 to 99.5% of KNO ₃ +NaNO ₃ in mass %. manufacturing method. The method for producing tempered glass according to any one of claims 1 to 7, wherein the content of LiNO ₃ in the molten salt for adjustment is less than 5% by mass. Ratio of the compressive _stress value CS ₂ of the outermost surface of the compressive stress layer of the tempered glass after the adjustment step to the compressive stress value CS 1 of the outermost surface of the compressive stress layer of the tempered glass before the adjustment step CS ₂ / The method for manufacturing tempered glass according to any one of claims 1 to 8, wherein the adjusting step is adjusted so that CS ₁ is 0.8 to 1. The tempered glass according to any one of claims 1 to 9, wherein the adjusting step is adjusted so that the compressive stress value CS ₂ of the outermost surface of the compressive stress layer of the tempered glass after the adjusting step is 400 MPa or more. Production method. The ratio DOL ₂ /DOL ₁ of the stress depth DOL ₂ of the compressive stress layer of the tempered glass after the adjustment step to the stress depth DOL ₁ of the compressive stress layer of the processing glass before the adjustment step is 0. The method for manufacturing tempered glass according to any one of claims 1 to 10, wherein the adjusting step is adjusted so that the ratio is 9 to 1.2. When the thickness of the tempered glass after the adjustment step is t ₂ , the adjustment step is adjusted so that the stress depth DOL ₂ of the compressive stress layer of the tempered glass is 0.1·t ₂ or more. A method for producing tempered glass according to any one of claims 1 to 11. The method for manufacturing tempered glass according to any one of claims 1 to 12, wherein the tempered glass has a warpage of 0.2 mm or less after the adjusting step. The tempered glass after the adjustment step has a glass composition, in terms of mol%, of SiO ₂ 50-80%, Al ₂ O ₃ 5-25%, B ₂ O ₃ 0-15%, Li ₂ O 0-15%. , 1 to 20% of Na ₂ O, and 0 to 10% of K ₂ O, the method for producing tempered glass according to any one of claims 1 to 13. A plate-shaped or film-shaped tempered glass with a thickness of 0.2 mm or less having a compressive stress layer on the surface layer,
The compressive stress value _CS2 of the outermost surface of the compressive stress layer is 400 MPa or more,
A tempered glass characterized by a higher Ca ion concentration on the surface than on the inside.